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  • Other Sources  (139)
  • Taylor & Francis  (78)
  • Univ. Köln  (61)
  • MDPI Publishing
  • 2020-2023  (5)
  • 2010-2014  (134)
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  • 1
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    Snapshot of the Carbon Dioxide Removal certification and standards ecosystem (2021–2022) (2022)
    Taylor & Francis
    Details
    Publication Date: 2022-09-23
    Description: Carbon Dioxide Removal (CDR) will be necessary to fulfil the hundreds of pledges to reach net-zero by 2050. As with any industry, standard methodologies and certification are crucial to guarantee successful and reliable activities. However, buyers and policymakers currently face challenges in evaluating the ecosystem of CDR certification. The issue is not with CDR, nor with individual certifications – some of which may be very robust – but with the lack of transparency in the overall ecosystem. To bring some clarity, we present a snapshot of the CDR certification and standards ecosystem for the year 2021–2022. We find a complex ecosystem with at least 30 standard developing organizations proposing at least 125 standard methodologies for carbon removal from 23 different CDR activities and selling 27 different versions of certification instruments in voluntary and compliance markets. This exercise reveals many more existing standards for nature-based than for engineering-based activities and more diversity from standards serving the voluntary rather than the compliance market. It also highlights a proliferation of standards for the same activity, and a plethora of activities without standards. The process revealed ambiguity on what constitutes carbon removal, with many standards certifying activities that remove CO2 already in the environment as well as activities that avoid or reduce new emissions by sequestering the carbon into reservoirs. This mapping highlights key gaps and potential starting points for reforms to strengthen the CDR certification industry; it also underscores the need for independent oversight.
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  • 2
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    Sea ice conditions and navigability through the Northeast Passage in the past 40 years based on remote-sensing data (2021)
    Taylor & Francis
    In:  International Journal of Digital Earth, 14 (5). pp. 555-574.
    Details
    Publication Date: 2022-01-07
    Description: Sea ice conditions and navigability along four typical routes of the Northeast Passage (NEP) are analysed using remote-sensing data from 1979 to 2019. The influence of air temperature (Tair) and surface wind on the sea ice concentration (SIC) and the navigability of routes is determined. It is found that the annually averaged SICs of the different routes have decreased over the past 41 years. The fastest rate of decrease occurred in the Kara Sea (∼−1% per year), while the slowest rates of decrease occurred in the Laptev/East Siberian Sea (∼−0.42% per year). The number of navigable days for the Kara Sea has become ∼1–2 months longer than the Laptev/East Siberian Sea route as a result. The effect of Tair on SIC, quantified by ΔSIC/ΔTair in the routes through the eastern Kara Sea and Laptev/East Siberian Sea in 2010s was ∼−0.04/°C, two to three times that seen during the 1980s. Air temperature is becoming a significant driving force of melting ice in these routes. Surface winds are also a crucial factor for the navigability of the Vilkitsky Strait and Long Strait, as they drive ice drift, and affect the navigability of the Kara Strait by introducing warm air.
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  • 3
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    Carbon accounting for negative emissions technologies (2021)
    Taylor & Francis
    In:  Climate Policy . pp. 1-19.
    Details
    Publication Date: 2022-01-07
    Description: Negative emissions technologies (NETs) are an essential part of most scenarios for achieving the Paris Agreement goal of limiting warming to below 2°C and for all scenarios that limit warming to 1.5 °C. The deployment of these technologies requires carbon accounting methods for a range of different purposes, such as determining the effectiveness of specific technologies or incentivising NETs. Although the need for carbon accounting methods is discussed within the literature on NETs, there does not appear to be a clear understanding of the range of different accounting challenges. Based on a systematic literature review this study identifies five distinct accounting issues related to NETs: 1. estimating total system-wide change in emissions/removals; 2. non-permanence; 3. non-equivalence of ‘no overshoot’ and ‘overshoot and removal’; 4. accounting for incentives for NETs; and 5. the temporal distribution of emissions/removals. Solutions to these accounting challenges are proposed, or alternatively, areas for further research and the development of solutions are highlighted. One key recommendation is that carbon accounting methods should follow a ‘reality principle’ to report emissions and removals when and where they actually occur, and an important overall conclusion is that it is essential to use the correct accounting method for its appropriate purpose. For example, consequential methods that take account of total system-wide changes in emissions/removals should be used if the purpose is to inform decisions on the deployment or incentivisation of NETs. Attributional methods, however, should be used if the purpose is to construct static descriptions of possible net zero worlds.
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  • 4
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    User-specific touch interfaces: a viable solution for an aging society? (2021)
    Taylor & Francis
    Details
    Publication Date: 2022-02-23
    Description: Touch interaction has established a dominating role in the realisation of Human–Machine Interfaces. However, to be able to use touch effectively and efficiently, users have to comply with particular prerequisites. Due to age-related changes, such as the decline of tactile accuracy and speed, especially elderly users often struggle with the touch modality. Interfaces that adapt to specific user characteristics could be a promising solution to overcome this problem. Notwithstanding the advantages of adaptive systems, perceived changes in the user interface can reduce the system's predictability and transparency. The present study compares three approaches concerning the adaptation of touch button sizes: no adaptation and adaptation with visible and invisible feedback. Results show that especially elderly users substantially benefit from an adaptive approach. Furthermore, data shows that the type of adaptation supports different usage goals. While adaption with visual feedback enables a higher interaction speed, invisible adaptation leads to a higher degree of accuracy.
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  • 5
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    Beyond crystal mushes: evidence for uptake of high-T pyroxene antecrysts from mid- to upper crustal andesites into tephras from the Central Plateau, New Zealand (2021)
    Taylor & Francis
    Details
    Publication Date: 2022-02-25
    Description: Pyroxene crystals from recent Central Plateau tephras are used to deduce their formation conditions through two-pyroxene thermobarometry. Crystals return pseudo-pressures and pseudo-temperatures that are artefacts of uptake of antecrysts formed at a range of crustal levels by isobaric cooling of previously intruded magmas. MELTS modelling of tephra glass compositions shows that pseudo-PT conditions are reproduced at oxygen fugacities above the nickel-nickel oxide buffer (NNO+1, NNO+2), mid- to upper crustal pressures (100–400 MPa), and temperatures between c. 900°C and 〉1100°C. Modelled crystals from the deep crust (800 MPa) are restricted to clinopyroxenes. However, these display chemical equilibrium with shallow orthopyroxenes at higher pseudo-PT conditions than observed in Central Plateau pyroxenes. The data indicate uptake of high-temperature pyroxenes at mid- to shallow crustal levels into ascending andesitic melts and thus preclude the presence of long-lived crustal mush zones (〈1000°C) as a source for the crystal cargo of the Central Plateau tephras studied here. Further, the apparent absence of deep crustal pyroxene antecrysts does not preclude models of arc andesite genesis without a ‘deep crustal hot zone’ beneath the Central Plateau. Generation and ascent of primary andesites from a heterogeneous mantle wedge is therefore a possible scenario at the southern Hikurangi margin.
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  • 6
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    Predictive modelling of gold potential with the integration of multisource information based on random forest: a case study on the Rodalquilar area, Southern Spain (2014)
    Taylor & Francis
    In:  International Journal of Geographical Information Science, 28 (7). pp. 1336-1354.
    Details
    Publication Date: 2020-07-28
    Description: Mineral exploration activities require robust predictive models that result in accurate mapping of the probability that mineral deposits can be found at a certain location. Random forest (RF) is a powerful machine data-driven predictive method that is unknown in mineral potential mapping. In this paper, performance of RF regression for the likelihood of gold deposits in the Rodalquilar mining district is explored. The RF model was developed using a comprehensive exploration GIS database composed of: gravimetric and magnetic survey, a lithogeochemical survey of 59 elements, lithology and fracture maps, a Landsat 5 Thematic Mapper image and gold occurrence locations. The results of this study indicate that the use of RF for the integration of large multisource data sets used in mineral exploration and for prediction of mineral deposit occurrences offers several advantages over existing methods. Key advantages of RF include: (1) the simplicity of parameter setting; (2) an internal unbiased estimate of the prediction error; (3) the ability to handle complex data of different statistical distributions, responding to nonlinear relationships between variables; (4) the capability to use categorical predictors; and (5) the capability to determine variable importance. Additionally, variables that RF identified as most important coincide with well-known geologic expectations. To validate and assess the effectiveness of the RF method. Statistical measures of map quality indicate that the RF method performs better than LR, with mean square errors equal to 0.12 and 0.19, respectively. The efficiency of RF is also better, achieving an optimum success rate when half of the area predicted by LR is considered.
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  • 7
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    Evaluating decadal predictions of northern hemispheric cyclone frequencies (2014)
    Taylor & Francis
    In:  Tellus A: Dynamic meteorology and oceanography, 66 . p. 22830.
    Details
    Publication Date: 2015-11-25
    Description: Mid-latitudinal cyclones are a key factor for understanding regional anomalies in primary meteorological parameters such as temperature or precipitation. Extreme cyclones can produce notable impacts on human society and economy, for example, by causing enormous economic losses through wind damage. Based on 41 annually initialised (1961–2001) hindcast ensembles, this study evaluates the ability of a single-model decadal forecast system (MPI-ESM-LR) to provide skilful probabilistic three-category forecasts (enhanced, normal or decreased) of winter (ONDJFM) extra-tropical cyclone frequency over the Northern Hemisphere with lead times from 1 yr up to a decade. It is shown that these predictions exhibit some significant skill, mainly for lead times of 2–5 yr, especially over the North Atlantic and Pacific. Skill for intense cyclones is generally higher than for all detected systems. A comparison of decadal hindcasts from two different initialisation techniques indicates that initialising from reanalysis fields yields slightly better results for the first forecast winter (month 10–15), while initialisation based on an assimilation experiment provides better skill for lead times between 2 and 5 yr. The reasons and mechanisms behind this predictive skill are subject to future work. Preliminary analyses suggest a strong relationship of the model’s skill over the North Atlantic with the ability to predict upper ocean temperatures modulating lower troposphere baroclinicity for the respective area and time scales.
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  • 8
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    Intertidal foraminiferal fauna and the distribution of Elphidiidae at Chupa Inlet, western White Sea (2014)
    Taylor & Francis
    In:  Marine Biology Research, 10 (2). pp. 153-166.
    Details
    Publication Date: 2015-04-21
    Description: The bright colouration of the cytoplasm in intertidal rotaliid foraminifera and their particle-gathering activity reliably reveals live specimens in fresh samples, without any fixatives or dyes applied. Using this approach, we demonstrate that live representatives of three rotaliid species, all belonging to the genus Elphidium, were common on intertidal mud and sand beaches. Two species, E. excavatum clavatum and E. albiumbilicatum, lived close to freshwater outflows, whereas E. williamsoni occupied beaches bathed by waters with normal salinity (surface 26–27‰ in the western White Sea). A least 13 species were found alive in the intertidal zone. Among non-calcareous foraminifera, Miliammina fusca, Ammotium cassis and Ovammina opaca were the most numerous.
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  • 9
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    Recommendations on reintroduction of crustaceans and fish, use of fish stocks, and improvement of the state of Lake Drūkšiai (2014)
    Taylor & Francis
    In:  Zoology and Ecology, 24 (2). pp. 185-186.
    Details
    Publication Date: 2020-04-20
    Description: According to historical data, the glacial relict higher crustaceans, Mysis relicta and Pallaseopsis quadrispinosa, as well as a plankton crustacean Limnocalanus macrurus had earlier been recorded in Lake Drüksiai. Our data and investigations of other authors evidence that these crustaceans no longer inhabit the lake. What are the prospects for the recovery of these crustaceans after restoring the natural thermal regime in Lake Drüksiai? One of the possibilities is to reintroduce these species after restoring the natural thermal regime in the lake and improving dissolved oxygen level in the hypolimnion, which would provide conditions for long-term survival and recovery of populations of these crustaceans. As reintroduction of relict species is rather costly, it is necessary to assess effectiveness of such works.
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  • 10
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    Enhanced calcite dissolution in the presence of the Aerobic Methanotroph Methylosinus trichosporium (2014)
    Taylor & Francis
    In:  Geomicrobiology Journal, 31 (4). pp. 325-337.
    Details
    Publication Date: 2017-09-28
    Description: Microbial aerobic methane oxidation (MOx) is intrinsically coupled to the production of carbon dioxide, favoring carbonate dissolution. Recently, microbial organic polymers were shown to be able to induce carbonate dissolution. To discriminate between different mechanisms causing calcite dissolution, experiments were conducted in the presence of solid calcite with (1) actively growing cells (2) starving cells, and (4) dead cells of the methanotrophic bacterium Methylosinus trichosporium under brackish conditions (salinity 10) near calcite saturation (saturation state (Ω) 1.76 to 2.22). Total alkalinity and the amount of dissolved calcium markedly increased in all experiments containing M. trichosporium cells. After initial system equilibration, similar calcite dissolution rates, ranging between 14.9 (dead cells) and 29.6 μmol l−1 d−1 (actively growing cells), were observed. While concentrations of transparent exopolymer particles declined with time in the presence of actively growing and starving cells, they increased in experiments with dead cells. Scanning electron microscopy images of calcite crystals revealed visible surface corrosion after exposure to live and dead M. trichosporium cells. The results of this study indicate a strong potential for microbial MOx to affect calcite stability negatively, facilitating calcite dissolution. In addition to CO2 production by methanotrophically active cells, we suggest that the release of acidic or Ca2+-chelating organic carbon compounds from dead cells could also enhance calcite dissolution.
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  • 11
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    Herbivore-induced defence response in the brown seaweed Fucus vesiculosus (Phaeophyceae): temporal pattern and gene expression (2014)
    Taylor & Francis
    In:  European Journal of Phycology, 49 (3). pp. 356-369.
    Details
    Publication Date: 2019-09-23
    Description: This study aimed to reveal the dynamics of inducible anti-herbivory traits in the brown seaweed Fucus vesiculosus, in response to grazing by the isopod Idotea baltica. As the molecular basis of defence induction in seaweeds is poorly understood, a transcriptomic approach was used to gain insight into cellular processes underlying defence induction and thus promote the mechanistic understanding of anti-herbivory responses in seaweeds. In a 27 day feeding-assayed induction experiment, temporal patterns of the induced anti-herbivory resistance of F. vesiculosus were assessed under laboratory conditions. Feeding assays were performed at three day intervals, using fresh and reconstituted food. Microarray hybridizations investigating the expression of genes 3 days before, as well as at the same time as, feeding assays revealed a decreased palatability of previously grazed F. vesiculosus pieces compared with non-grazed control pieces. Despite permanent exposure to grazers, F. vesiculosus palatability varied over time. Non-grazed F. vesiculosus pieces were significantly preferred to grazed pieces after 18 and again after 27 days of previous grazing, while their relative palatability for isopods was comparable at all other times during the experiment. Relative to controls, 562/402 genes were ≥ 1.5-fold up-/down-regulated in seaweed pieces that were grazed for 18 days, i.e. when induction of defences was detected in feeding assays. Massive reprogramming of the regulatory expression orchestra (translation, transcription) as well as up-regulation of genes involved in lipid and carbohydrate metabolism, intracellular trafficking, defence and stress response was found. At the same time, down-regulation of photosynthesis was observed in grazed seaweed pieces. This study suggests a high level of temporal variability in induced anti-herbivory traits of F. vesiculosus and reveals increased expression of genes with putative defensive functions in conjunction with the reallocation of resources from primary to secondary metabolism.
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  • 12
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    Impact of saltwater inflows on phosphorus cycling and eutrophication in the Baltic Sea: a 3D model study (2014)
    Taylor & Francis
    In:  Tellus A: Dynamic meteorology and oceanography, 66 . p. 23985.
    Details
    Publication Date: 2019-09-23
    Description: The impact of dense saltwater inflows on the phosphorus dynamics in the Baltic Sea is studied from tracer experiments with a three-dimensional physical model. Model simulations showed that the coasts of the North West Gotland Basin and the Gulf of Finland, the Estonian coast in the East Gotland Basin are regions where tracers from below the halocline are primarily lifted up above the halocline. After 1 yr tracers are accumulated at the surface along the Swedish east coast and at the western and southern sides of Gotland. Elevated concentrations are also found east and southeast of Gotland, in the northern Bornholm Basin and in the central parts of the East Gotland Basin. The annual supplies of phosphorus from the deeper waters to the productive surface layers are estimated to be of the same order of magnitude as the waterborne inputs of phosphorus to the entire Baltic Sea. The model results suggest that regionally the impact of these nutrients may be quite large, and the largest regional increases in surface concentrations are found after large inflows. However, the overall direct impact of major Baltic inflows on the annual uplift of nutrients from below the halocline to the surface waters is small because vertical transports are comparably large also during periods without major inflows. Our model results suggest that phosphorus released from the sediments between 60 and 100 m depth in the East Gotland Basin contributes to the eutrophication, especially in the coastal regions of the eastern Baltic Proper.
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  • 13
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    Smectite Reduction by Shewanella Species as Facilitated by Cystine and Cysteine (2014)
    Taylor & Francis
    In:  Geomicrobiology Journal, 31 (1). pp. 53-63.
    Details
    Publication Date: 2019-08-06
    Description: Exogenous electron transfer mediators employed by Fe(III)-reducing bacteria are believed to govern the kinetics and equilibrium of bioreduction of Fe(III) in solid phase. In contrast to a large number of studies on humic substances and analog anthraquinone-2,6-disulfonate (AQDS), our knowledge of other potential electron shuttles involved in Fe(III) reduction is limited. The purpose of the present study was to understand the role of cystine and cysteine in reduction of iron-rich smectite (nontronite, NAu-2) by Shewanella species. A series of abiotic and biotic experiments were conducted in nongrowth media (bicarbonate buffered, pH = 7.0). Fe(II) and cysteine concentrations were monitored over the course of the bioreduction experiments with wet chemistry, and the unreduced and reduced nontronites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results indicated that all Shewanella species tested here were capable of reducing cystine to cysteine. Either cystine or cysteine amendments significantly stimulated the Fe(III) bioreduction rate and extent. The initial reduction rate was linearly correlated with cystine or cysteine concentration. The reduction extent (18.7–22.3%) calculated from bioreactor with cystine or cysteine was slightly lower than those with AQDS (26.3%). Mineralogical analysis demonstrated that cystine or cysteine facilitated the reaction of smectite to illite as a result of Fe(III) bioreduction. Thus, we concluded that, in our experiments, cystine and cysteine functioned as electron carrier in the smectite reduction systems, and were favorable factors influencing smectite illitization.
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  • 14
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    Anabaena flos-aquae (2014)
    Taylor & Francis
    In:  Critical Reviews in Environmental Science and Technology, 44 (18). pp. 1995-2037.
    Details
    Publication Date: 2020-07-29
    Description: Cyanobacteria (blue-green algae) are the most primitive prokaryotic photosynthetic organisms, that have survived and flourished on the planet for more than 3 billion years and produced the oxygen that enabled aerobic metabolism. Anabaena is a genus of filamentous cyanobacteria, known for its nitrogen fixing abilities and is one of cyanobacterial genera that produce toxins. Because of plasmid DNA, the nontoxic strain of Anabaena flos-aquae, transformed into a toxic strain that producing neuro-toxins. The major toxins those were produced by this species are anatoxin-a, homoanatoxin-a, and anatoxin-a(s). Presence of these toxins in the source of fresh water makes water toxic and every year so many reports on death of animals were documented. Several studies have been done over this toxic cyanobacterium and showed that under controlled environment this species is very useful for human being. However, presence of this alga in the water sources makes environment toxic. Several analytical methods were reported for the detection of these toxins. This review is be focused on the detailed literature survey on fresh water cyanobacterium, Anabaena flos-aquae, with respect to its importance and cure.
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  • 15
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    Regeneration and clonality in Metazoa. The price to pay for evolving complexity (2014)
    Taylor & Francis
    In:  Invertebrate Reproduction & Development, 58 (1). pp. 1-8.
    Details
    Publication Date: 2016-11-25
    Description: Explaining the high variability of regenerative ability across metazoan taxa is one of the major challenges in modern biology. Although common and widespread, regeneration shows a heterogeneous distribution and most authors consider regeneration capacity to be an ancestral trait that has been restricted or completely lost over the course of metazoan evolution. Basal Metazoans show the highest capacity for regeneration. By contrast, this feature is highly variable within bilaterians, with many taxa limited in their capacity for regeneration or not regenerating at all. The causes of the loss and/or maintenance of regeneration remain poorly understood, with most explanations invoking adaptive mechanisms. In the present study Metazoan regeneration is discussed with reference to stem cell biology, tissue plasticity, evolution of tissue complexity, cell turnover and lifespan. The presence or absence of regenerative ability cannot be seen only as an adaptation to a particular environment but can also be a consequence of body plan and developmental constraints such as may arise from the evolution of an adaptive immune system.
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  • 16
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    Mini-review: Impact and dynamics of surface fouling by solitary and compound ascidians (2014)
    Taylor & Francis
    In:  Biofouling, 30 (3). pp. 259-270.
    Details
    Publication Date: 2016-11-25
    Description: Globally, ascidians are a significant contributor to benthic marine fouling communities, but have remained poorly studied in this context. In some cases, such as in shellfish and finfish aquaculture, ascidians are the most problematic of all fouling organisms. The disproportionate impact of ascidian fouling in some specific geographic locations has been related directly to anthropogenic translocation of these organisms around the globe. In the case of ascidians, therefore, the economic issue of biofouling and the ecological ramifications of invasion are inextricably linked. This mini-review briefly discusses the introduction of non-native ascidians to areas where they have subsequently proven to be a significant fouling pest. The elements of ascidian reproductive ecology that support their aggressive fouling character are discussed and the scant information pertaining to their adhesion and adhesives is presented. Finally, strategies for mitigating ascidian fouling are examined. It is suggested that sufficient working knowledge currently exists to support the inclusion of one or more common ascidian species as ‘standard’ test organisms used for evaluation of novel fouling-resistant surfaces.
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  • 17
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    Pelopuradazole, a new imidazole derivative alkaloid from the marine bacteria Pelomonas puraquae sp. nov. (2014)
    Taylor & Francis
    In:  Natural Product Research, 28 (9). pp. 680-682.
    Details
    Publication Date: 2021-01-11
    Description: One new imidazole derivative alkaloid pelopuradazole (1), together with three known alkaloids as in 3H-imidazole-4-carboxylic acid (2), 1H-pyrrole-2-carboxylic acid (3) and 2-methyl-3H-imidazole-4-carboxylic acid (4) and two known cyclo-dipeptides pelopurin A (5) and pelopurin B (6), has been isolated from the marine bacterium Pelomonas puraquae sp. nov. Pelopuradazole (1) was a new imidazole derivative alkaloid, while compounds 2, 3, 5 and 6 were firstly obtained as natural products. Compounds 1–6 were isolated from P. puraquae sp. nov. for the first time.
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  • 18
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    Anabaena flos-aquae (2014)
    Taylor & Francis
    In:  Critical Reviews in Environmental Science and Technology, 44 (18). pp. 1995-2037.
    Details
    Publication Date: 2018-09-06
    Description: Cyanobacteria (blue-green algae) are the most primitive prokaryotic photosynthetic organisms, that have survived and flourished on the planet for more than 3 billion years and produced the oxygen that enabled aerobic metabolism. Anabaena is a genus of filamentous cyanobacteria, known for its nitrogen fixing abilities and is one of cyanobacterial genera that produce toxins. Because of plasmid DNA, the nontoxic strain of Anabaena flos-aquae, transformed into a toxic strain that producing neuro-toxins. The major toxins those were produced by this species are anatoxin-a, homoanatoxin-a, and anatoxin-a(s). Presence of these toxins in the source of fresh water makes water toxic and every year so many reports on death of animals were documented. Several studies have been done over this toxic cyanobacterium and showed that under controlled environment this species is very useful for human being. However, presence of this alga in the water sources makes environment toxic. Several analytical methods were reported for the detection of these toxins. This review is be focused on the detailed literature survey on fresh water cyanobacterium, Anabaena flos-aquae, with respect to its importance and cure.
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  • 19
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    PTP1B: a simple enzyme for a complex world (2013)
    Taylor & Francis
    In:  Critical Reviews in Biochemistry and Molecular Biology, 48 (5). pp. 430-445.
    Details
    Publication Date: 2020-07-29
    Description: Our understanding of the fundamental regulatory roles that tyrosine phosphatases play within cells has advanced significantly in the last two decades. Out-dated ideas that tyrosine phosphatases acts solely as the “off” switch counterbalancing the action of tyrosine kinases has proved to be flawed. PTP1B is the most characterized of all the tyrosine phosphatases and it acts as a critical negative and positive regulator of numerous signaling cascades. PTP1B’s direct regulation of the insulin and the leptin receptors makes it an ideal therapeutic target for type II diabetes and obesity. Moreover, the last decade has also seen several reports establishing PTP1B as key player in cancer serving as both tumor suppressor and tumor promoter depending on the cellular context. Despite many key advances in these fields one largely ignored area is what role PTP1B may play in the modulation of immune signaling. The important recognition that PTP1B is a major negative regulator of Janus kinase – signal transducer and activator of transcription (JAK-STAT) signaling throughout evolution places it as a key link between metabolic diseases and inflammation, as well as a unique regulator between immune response and cancer. This review looks at the emergence of PTP1B through evolution, and then explore at the cell and systemic levels how it is controlled physiologically. The second half of the review will focus on the role(s) PTP1B can play in disease and in particular its involvement in metabolic syndromes and cancer. Finally we will briefly examine several novel directions in the development of PTP1B pharmacological inhibitors.
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  • 20
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    A review: carbon dioxide capture: biomass-derived-biochar and its applications (2013)
    Taylor & Francis
    In:  Journal of Dispersion Science and Technology, 34 (7). pp. 974-984.
    Details
    Publication Date: 2017-09-25
    Description: The changes in global temperatures as a result of carbon dioxide (CO2) emissions has suggested that cumulative CO2 emissions will continue to increase over time. Many countries are looking for ways to reduce or alter the amount of CO2 harming our environment; therefore, this review is a compilation of CO2 adsorption on biomass-derived-biochar (BDB). This suggests that effective measures to mitigate the risk of dangerous climate change will need to limit cumulative emissions of CO2. Further, if cumulative CO2 emissions overshoot acceptable limits, it will become necessary to remove CO2 from the air, that is, the so-called “negative emissions.” In this review, we discuss the definitions and classes of technologies for capturing CO2 from the air and the application of biochar in the improvement of soil fertility. We also discuss the economic tradeoff between biochar and bio-oil, agricultural nutrient leaching, the novel magnetic property of biochar and its durability.
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    Improving lignocellulolytic enzyme production with Penicillium: from strain screening to systems biology (2013)
    Taylor & Francis
    In:  Biofuels, 4 (5). pp. 523-534.
    Details
    Publication Date: 2020-06-19
    Description: Many Penicillium species produce enzyme systems with good performances in lignocellulose degradation. In our laboratory, lignocellulolytic enzyme-producing Penicillium oxalicum (formerly classified as Penicillium decumbens) strains have been studied for more than 30 years. High cellulase-producing mutants have been obtained through random mutagenesis and genetic engineering, and the components in the enzyme systems have been elucidated using systems biology tools. The effects of different carbon sources on the production level of lignocellulolytic enzymes have been studied, and the related molecular mechanisms have been investigated. When compared with the widely used cellulase producer Trichoderma reesei, some unique features have been found in P. oxalicum, including higher β-glucosidase activity, higher numbers of lignocellulolytic enzyme gene, and different response of cellulase gene expression to some disaccharides. To boost the economic potential of the biorefineries using lignocellulosic biomass, P. oxalicum strains need to be further improved regarding the performance and production level of the enzyme systems.
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    Cytochrome P450-mediated metabolism in brain: functional roles and their implications (2013)
    Taylor & Francis
    In:  Expert Opinion on Drug Metabolism & Toxicology, 9 (5). pp. 551-558.
    Details
    Publication Date: 2020-07-31
    Description: Cytochromes P450 (P450) and associated monooxygenases are a family of heme proteins involved in metabolism of endogenous compounds (arachidonic acid, eicosanoids and prostaglandins) as also xenobiotics including drugs and environmental chemicals. Liver is the major organ involved in P450-mediated metabolism and hepatic enzymes have been characterized. Extrahepatic organs, such as lung, kidney and brain have the capability for biotransformation through P450 enzymes. Brain, including human brain, expresses P450 enzymes that metabolize xenobiotics and endogenous compounds. AREAS COVERED: An overview of P450-mediated metabolism in brain is presented focusing on distinct differences seen in expression of P450 enzymes, generation of unique P450 enzymes in brain through alternate splicing and their consequences in terms of metabolism of psychoactive drugs and inflammatory prompts, such as leukotrienes, thus modulating inflammatory response. EXPERT OPINION: The brain possesses unique P450s that metabolize drugs and endogenous compounds through pathways that are markedly different from that seen in liver indicating that extrapolation directly from liver to brain is not appropriate. It is therefore necessary to characterize the unique brain P450s and their ability to metabolize xenobiotics and endogenous compounds to better understand the functions of this important class of enzymes in brain, especially human brain.
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    Seasonal variation in the antifouling defence of the temperate brown alga Fucus vesiculosus (2013)
    Taylor & Francis
    In:  Biofouling, 29 (6). pp. 661-668.
    Details
    Publication Date: 2019-09-23
    Description: The important role of marine epibiotic biofilms in the interactions of the host with its environment has been acknowledged recently. Previous studies with the temperate brown macroalga Fucus vesiculosus have identified polar and non-polar compounds recovered from the algal surface that have the potential to control such biofilms. Furthermore, both the fouling pressure and the composition of the epibiotic bacterial communities on this macroalga varied seasonally. The extent to which this reflects a seasonal fluctuation of the fouling control mechanisms of the host is, however, unexplored in an ecological context. The present study investigated seasonal variation in the anti-settlement activity of surface extracts of F. vesiculosus against eight biofilm-forming bacteria isolated from rockweed-dominated habitats, including replication of two populations from two geographically distant sites. The anti-settlement activity at both sites was found to vary temporally, reaching a peak in summer/autumn. Anti-settlement activity also showed a consistent and strong difference between sites throughout the year. This study is the first to report temporal variation of antifouling defence originating from ecologically relevant surface-associated compounds.
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    Definition of species groups of Oncaeidae (Copepoda: Cyclopoida) as basis for a worldwide identification key (2013)
    Taylor & Francis
    In:  Journal of Natural History, 47 (5-12). pp. 265-288.
    Details
    Publication Date: 2019-03-13
    Description: The copepod family Oncaeidae is widely distributed in the world's oceans and includes many small and abundant species. Due to their small size and the existence of sister and sibling species in different parts of the ocean, species identification is very difficult. Quantitative studies on copepod communities usually consider oncaeids at the family level only, or present uncertain species names, when based on regional identification keys not established for the study area. This paper aims to develop the basis for an improved taxonomic resolution of oncaeids in ecological studies. It summarizes the most relevant morphological elements to characterize the seven presently known genera and to define in addition 16 species groups within the paraphyletic taxon Oncaea s.l. On this basis, a worldwide identification key for oncaeids is presently being developed, restricted to genera and species groups, with species included as far as the state of knowledge allows.
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  • 25
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    Phylogenetic analysis and antibiotic activity of bacteria isolated from the surface of two co-occurring macroalgae from the Baltic Sea (2013)
    Taylor & Francis
    In:  European Journal of Phycology, 48 (1). pp. 47-60.
    Details
    Publication Date: 2019-09-23
    Description: Bacteria associated with Fucus vesiculosus and Delesseria sanguinea, two macroalgae from the Kiel Fjord were investigated seasonally over two years by cultivation-based methods. A total of 166 bacterial strains were isolated from the macroalgae, affiliated to seven classes of bacteria (Actinobacteria, Bacilli, Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria, Cytophagia and Flavobacteria). According to 16S rRNA gene sequence similarities they were arranged in 82 phylotypes of〉99.0% sequence identity. Assuming that chemical factors rule the bacteriamacroalga and bacteriabacteria interactions on algal surfaces, we tested the antibiotic activity of the bacterial isolates not only against a panel of four standard test organisms (Bacillus subtilis, Candida glabrata, Escherichia coli and Staphylococcus lentus) but also four macroalga-associated microorganisms: Algicola bacteriolytica and Pseudoalteromonas elyakovii (macroalgal pathogens), and Bacillus algicola and Formosa algae (strains associated with algal surfaces). Organic extracts of more than 51% of the isolates from the two macroalgae inhibited the growth of at least one of the tested microorganisms. As much as 46% and 45% of the isolates derived from F. vesiculosus and D. sanguinea, respectively, showed antimicrobial activity against the set of macroalga-associated bacteria, compared with 13 and 19% against a standard set of microorganisms. High antibacterial activity against macroalgal pathogens and bacterial competitors support the assumption that complex chemical interactions shape the relationships of bacteria associated with macroalgae and suggest that these bacteria are a rich source of antimicrobial metabolites.
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    Depth structuring of pelagic copepod biodiversity in waters adjacent to an Eastern Indian Ocean coral reef (2013)
    Taylor & Francis
    In:  Journal of Natural History, 47 . pp. 639-665.
    Details
    Publication Date: 2019-03-14
    Description: We compared pelagic copepod communities at three (400+ m) stations adjacent to Scott Reef (14°S), a shelf-break reef in Australia's Indian Ocean territory, with those within the shallow (c.50 m) atoll lagoon. The metazooplankton assemblage sampled by our 100-μm multinet system was dominated by small (〈 1.0 mm) copepods. We identified over 220 copepod species, belonging to five of the nine orders. Of these, 68 (31%) are new records for Australian waters and at least 14 are likely to be undescribed. Redundancy analysis indicated that depth stratum was the most important determinant of community structure: distinct communities were associated with the epipelagic (within which the atoll lagoon community was further distinguished by reef-associated copepods), the chlorophyll maximum/thermocline, the upper mesopelagic and the hyper-benthos. The family Oncaeidae was highly speciose (〉 52 taxa) and progressively more important with increasing depth.
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    Improving Statistical Downscaling of General Circulation Models (2013)
    Taylor & Francis
    In:  Atmosphere-Ocean, 51 (2). pp. 213-225.
    Details
    Publication Date: 2019-09-23
    Description: We present a new method for the statistical downscaling of coarse-resolution General Circulation Model (GCM) fields to predict local climate change. Most atmospheric variables have strong seasonal cycles. We show that the prediction of the non-seasonal variability of maximum and minimum daily surface temperature is improved if the seasonal cycle is removed prior to the statistical analysis. The new method consists of three major steps. First, the average seasonal cycles of both predictands and predictors are removed. Second, a principal component-based multiple linear regression model between the deseasonalized predictands and predictors is developed and validated. Finally, the regression is used to make projections of future changes in maximum and minimum daily surface temperature at Shearwater, Nova Scotia. This projection is made using the local grid-scale variables of the Canadian General Circulation Model Version 3 (CGCM3) climate model as predictors. Our statistical downscaling method indicates significant skill in predicting the observed distribution of temperature using GCM predictors. Projections suggest minimum and maximum temperatures at Shearwater will be up to about five degrees warmer by 2100 under the current “business-as-usual” scenario. RÉSUMÉ [Traduit par la rédaction] Nous présentons une nouvelle méthode pour la réduction d'échelle statistique des champs des modèles de circulation générale (MCG) à faible résolution pour prévoir les changements du climat local. La plupart des variables atmosphériques ont des cycles saisonniers bien marqués. Nous démontrons que la prédiction de la variabilité non saisonnière de la température de surface quotidienne minimum et maximum est meilleure si on retranche le cycle saisonnier avant de procéder à l'analyse statistique. Voici les trois grandes étapes de cette nouvelle méthode. D'abord, nous retirons les cycles saisonniers moyens des prédictants et des prédicteurs. Ensuite, nous concevons et validons un modèle de régression linéaire multiple sur composantes principales entre les prédictants et les prédicteurs désaisonnalisés. Enfin, nous nous servons de la régression afin d'établir des projections pour les changements à venir dans la température de surface quotidienne minimum et maximum à Shearwater en Nouvelle-Écosse. Cette projection est établie au moyen des variables locales à l'échelle du maillage de la troisième version du modèle canadien de circulation générale (MCCG3). Notre méthode de réduction d'échelle statistique se révèle très efficace pour prédire la répartition observée de la température au moyen des prédicteurs du MCG. D'après les projections, les températures minimum et maximum à Shearwater connaîtront une augmentation d'environ cinq degrés d'ici 2100 dans le scénario actuel de type « statu quo ».
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    Deep-sea Fe-Mn Crusts from the Northeast Atlantic Ocean: Composition and Resource Considerations (2013)
    Taylor & Francis
    In:  Marine Georesources & Geotechnology, 31 (1). pp. 40-70.
    Details
    Publication Date: 2019-09-23
    Description: Eighteen deep-sea ferromanganese crusts (Fe-Mn crusts) from 10 seamounts in the northeast Atlantic were studied. Samples were recovered from water depths of 1,200 to 4,600 m from seamounts near Madeira, the Canary and Azores islands, and one sample from the western Mediterranean Sea. The mineralogical and chemical compositions of the samples indicate that the crusts are typical continental margin, hydrogenetic Fe-Mn crusts. The Fe-Mn crusts exhibit a Co + Cu + Ni maximum of 0.96 wt%. Platinum-group element contents analyzed for five samples showed Pt contents from 153 to 512 ppb. The resource potential of Fe-Mn crusts within and adjacent to the Portuguese Exclusive Economic Zone (EEZ) is evaluated to be comparable to that of crusts in the central Pacific, indicating that these Atlantic deposits may be an important future resource.
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    A new species of the dentipes-subgroup of Triconia and a redescription of T. giesbrechti and T. elongata (Copepoda: Cyclopoida: Oncaeidae) from the tropical Pacific and the Korea Strait (2013)
    Taylor & Francis
    In:  Journal of Natural History, 47 (25-28). pp. 1707-1743.
    Details
    Publication Date: 2019-04-18
    Description: A new species of Triconia in the family Oncaeidae, Triconia pacifica sp. nov., and a new form variant each of Triconia giesbrechti Bottger-Schnack and Triconia elongata Bottger-Schnack are described from two sites in the Pacific. Triconia pacifica can be distinguished from its sibling Triconia dentipes (Giesbrecht) by (1) morphometric characters, including the proportional lengths of distal endopod spines of swimming leg 4, and the relative length of the outer basal seta on P5, and by (2) a number of micro-structures on the appendages. The Pacific specimens of T.elongata and T.giesbrechti resemble the typical forms in morphometric characters, with some minor differences in proportional spine lengths on the swimming legs, and differ in a few micro-structures. The hitherto unknown male of T.giesbrechti is newly described. For all species/forms described, the intraspecific variability of proportional spine lengths on the endopods of P2-P4 is examined and discussed
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    Spectral effects of atmospheric dust and clouds on estimation of chlorophyll-aconcentration from radiation measurements (2013)
    Taylor & Francis
    In:  Remote Sensing Letters, 4 (8). pp. 774-782.
    Details
    Publication Date: 2020-06-04
    Description: Atmospheric dust and clouds modify the spectral distribution of the incident solar radiation. The influence of these spectral effects on the determination of chlorophyll-a concentration from the sea surface and remotely sensed radiation measurements made from ships, aircrafts or satellites was studied in the region off Northwest Africa in the Atlantic Ocean. The chlorophyll-a algorithms that are typically used in ocean colour community are based on ratios of reflectance values of different wavelengths. This fact, together with the wavelength dependent effect of atmospheric dust and clouds, causes uncertainties in the estimation of chlorophyll-a concentration. The most frequently used Morel, OC4v4 and OC3M chlorophyll-a algorithms were included in the investigation. The highest and the smallest uncertainties were found for the Morel and the OC3M algorithms, respectively. For the first time, sky conditions with dust and clouds together in the atmosphere were studied. Overestimations of the chlorophyll-a concentration of up to 8.8% were observed in the case of dusty skies without clouds. The concentration was also overestimated between 7.6% and 14.3% for skies with mixtures of dust and clouds increasing the solar irradiance. Underestimations of up to 24.1% and overestimations of up to 12.2% were found for skies with mixtures of dust and clouds decreasing the solar irradiance. Compensations of the influences of spectral effects were observed at special ratios of clouds to dust. Earlier results in relation to the impact of clouds on the estimation of chlorophyll-a concentration were verified. The spectral effects of cloudy skies cannot be neglected because it may result in an error of up to 40% of the estimated value.
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    Green energy from marine algae: biogas production and composition from the anaerobic digestion of Irish seaweed species (2013)
    Taylor & Francis
    In:  Environmental Technology, 34 (15). pp. 2277-2283.
    Details
    Publication Date: 2021-07-12
    Description: Marine algae have emerged as an alternative feedstock for the production of a number of renewable fuels, including biogas. In addition to energy potential, other characteristics make them attractive as an energy source, including their ability to absorb carbon dioxide (CO2), higher productivity rates than land-based crops and the lack of water use or land competition. For Ireland, biofuels from marine algae can play an important role by reducing imports of fossil fuels as well as providing the necessary energy in rural communities. In this study, five potential seaweed species common in Irish waters, Saccorhiza polyschides, Ulva sp., Laminaria digitata, Fucus serratus and Saccharina latissima, were co-digested individually with bovine slurry. Batch reactors of 120 ml and 1000 ml were set up and incubated at 35°C to investigate their suitability for production of biogas. Digesters fed with S. latissima produced the maximum methane yield (335 ml g volatile solids−1 (gVS−1)) followed by S. polyschides with 255 ml gVS−1. L. digitata produced 246 ml gVS−1 and the lowest yields were from the green seaweed Ulva sp. 191 ml gVS−1. The methane and CO2 percentages ranged between 50–72% and 10–45%, respectively. The results demonstrated that the seaweed species investigated are good feedstocks candidates for the production of biogas and methane as a source of energy. Their use on a large-scale process will require further investigation to increase yields and reduce production costs.
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    Evaluation of Phytase Production by Fish Gut Bacterium, Bacillus subtilis , for Processing of Ipomea aquatica Leaves as Probable Aquafeed Ingredient (2013)
    Taylor & Francis
    In:  Journal of Aquatic Food Product Technology, 22 (5). pp. 508-519.
    Details
    Publication Date: 2020-09-03
    Description: Extracellular phytase production by Bacillus subtilis isolated from the gut of a minor carp, Labeo bata, has been investigated under solid-state fermentation using leaves from four low cost aquatic weeds (Ipomea aquatica, Pistia stratiotes, Lemna major, and Eichhornia crassipes) as substrates. Water spinach, I. aquatica, leaf meal supported maximum phytase activity (15.31 ± 0.38 U/g) and phytate degradation (66.79%). Incubation for 8 days at pH 7 and 35°C temperature revealed optimum phytase production. Maximum phytase production complied with 3.0-mL inoculum size (12.38 ± 0.05 U/g) and 60% initial moisture content (13.46 ± 0.08 U/g). Glucose (10 g/L) and ammonium sulfate (20.0 g/L) supplementation as additional carbon and nitrogen sources yielded maximum phytase production (12.24 ± 0.09 and 17.35 ± 0.06 U/g, respectively). Analysis of fermented leaf meal revealed that there was marginal increase (t-value significant at p 〈 0.05) in the contents of crude protein, lipid, minerals (Na, K, Ca, Mg, Zn, Fe, Cu, P), free amino acids, and fatty acids; along with reduction in the contents of the antinutritional factors—e.g., crude fiber, tannins, phytic acid, and trypsin inhibitor. The results indicate that there is ample scope for further research to appraise potential application of gut bacteria for sustainable utilization of aquatic weeds as aquafeed ingredients.
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    Computer-aided identification of coelacanths, Latimeria chalumnae, using scale patterns (2012)
    Taylor & Francis
    In:  Marine Biology Research, 8 (3). pp. 300-306.
    Details
    Publication Date: 2017-06-20
    Description: Despite coelacanths, Latimeria chalumnae, being listed as either endangered by CITES or critically endangered by the IUCN, their population size within South Africa is unknown and still needs to be estimated. Their conservation status unfortunately excludes the use of conventional tagging to mark individual animals for a possible mark–recapture experiment. This study shows that because coelacanths have a unique spot patterning it is possible to quickly and accurately identify specific individuals photographically using computer-aided identification software. Without any manual intervention by an operator, the software accurately identified between 56 and 92% of the individuals. Indentification success increased to 100% if the operator could also manually select from other potential matching photographs. It was also shown that fish exhibiting a yaw angle not exceeding 60° could be accurately identified in photographs, although the percentage of fish correctly identified without operator-intervention decreased rapidly with increasing yaw angle. Computer-aided identification should therefore facilitate future coelacanth research as it is both efficient and accurate while also reducing potential stress on the animals observed.
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    Robustness of random forests for regression (2012)
    Taylor & Francis
    In:  Journal of Nonparametric Statistics, 24 (4). pp. 993-1006.
    Details
    Publication Date: 2018-03-26
    Description: In this paper, we empirically investigate the robustness of random forests for regression problems. We also investigate the performance of six variations of the original random forest method, all aimed at improving robustness. These variations are based on three main ideas: (1) robustify the aggregation method, (2) robustify the splitting criterion and (3) taking a robust transformation of the response. More precisely, with the first idea, we use the median (or weighted median), instead of the mean, to combine the predictions from the individual trees. With the second idea, we use least-absolute deviations from the median, instead of least-squares, as splitting criterion. With the third idea, we build the trees using the ranks of the response instead of the original values. The competing methods are compared via a simulation study with artificial data using two different types of contaminations and also with 13 real data sets. Our results show that all three ideas improve the robustness of the original random forest algorithm. However, a robust aggregation of the individual trees is generally more profitable than a robust splitting criterion.
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    Influence of positional accuracy, sample size and scale on modelling species distributions: a review (2012)
    Taylor & Francis
    In:  International Journal of Geographical Information Science, 26 (11). pp. 2083-2095.
    Details
    Publication Date: 2020-07-28
    Description: Species distribution models (SDMs) are an important tool in biogeography and ecology and are widely used for both fundamental and applied research purposes. SDMs require spatially explicit information about species occurrence and environmental covariates to produce a set of rules that identify and scale the environmental space where the species was observed and that can further be used to predict the suitability of a site for the species. More spatially accurate data are increasingly available, and the number of publications on the influence of spatial inaccuracies on the performance of modelling procedures is growing exponentially. Three main sources of uncertainty are associated with the three elements of a predictive function: the dependent variable, the explanatory variables and the algorithm or function used to relate these two variables. In this study, we review how spatial uncertainties influence model accuracy and we propose some methodological issues in the application of SDMs with regard to the modelling of fundamental and realized niches of species. We distinguish two cases suitable for different types of spatial data accuracy. For modelling the realized distribution of a species, particularly for management and conservation purposes, we suggest using only accurate species occurrence data and large sample sizes. Appropriate data filtering and examination of the spatial autocorrelation in predictors should be a routine procedure to minimize the possible influence of positional uncertainty in species occurrence data. However, if the data are sparse, models of the potential distribution of species can be created using a relatively small sample size, and this can provide a generalized indication of the main regional drivers of the distribution patterns. By this means, field surveys can be targeted to discover unknown populations and species in poorly surveyed regions in order to improve the robustness of the data for later modelling of the realized distributions. Based on this review, we conclude that (1) with data that are currently available, studies performed at a resolution of 1–100 km2 are useful for hypothesizing about the environmental conditions that limit the distribution of a species and (2) incorporating coarse resolution species occurrence data in a model, despite an increase in sample size, lowers model performance.
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    Rediscovery of Cereopsis studeri Koch, 1891, a forgotten Mediterranean soft coral species, and its inclusion in the genus Nidalia Gray, 1835 (Octocorallia, Alcyonacea, Nidaliidae) (2012)
    Taylor & Francis
    In:  Marine Biology Research, 8 (7). pp. 594-604.
    Details
    Publication Date: 2017-06-20
    Description: Cereopsis studeri was described by G. von Koch in 1891 with material from Naples. However, it was subsequently synonymized, erroneously identified, and overlooked in subsequent soft coral literature of the twentieth century. After the original description, this species was not recorded or correctly described for 120 years. The study of newly collected material from the North Western Mediterranean permits the re-description of this forgotten species and its assignation to the genus Nidalia in the family Nidaliidae. The main features of Nidalia studeri com. nov. are: colony torch-like, a capitulum light orange in colour, not laterally flattened, dome-shaped and not distinctly projecting beyond the stalk, introvert with sclerites transversally placed in two longitudinal rows per interseptal space, anthocodial crown with 28–38 sclerite rows, points separated from polyps distally, formed by 6–9 pairs of sclerites, and the presence of intermediate points (secondary points) between principal (interseptal) ones. Nidalia studeri is here compared with its closest congeners, especially with the Indonesian species N. simpsoni, species from the West Indian Region N. dissidens, N.occidentalis, N. deichmannae, and the recently described Nidalia aurantia from the Mid-Atlantic Ocean. This is the first time that the genus Nidalia and the family Nidaliidae have been reported with certainty for the Mediterranean Sea.
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    Three new compounds from the marine-derived fungusTrichoderma atrovirideG20-12 (2012)
    Taylor & Francis
    In:  Journal of Asian Natural Products Research, 14 (7). pp. 647-651.
    Details
    Publication Date: 2018-01-24
    Description: Three new compounds, 4′-(4,5-dimethyl-1,3-dioxolan-2-yl)methyl-phenol (1), (3′-hydroxybutan-2′-yl)5-oxopyrrolidine-2-carboxylate (2), and atroviridetide (3), have been isolated from the marine-derived fungus Trichoderma atroviride G 20-12. Their structures were determined on the basis of chemical and spectroscopic methods.
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    Bias-corrected random forests in regression (2012)
    Taylor & Francis
    In:  Journal of Applied Statistics, 39 (1). pp. 151-160.
    Details
    Publication Date: 2018-07-13
    Description: It is well known that random forests reduce the variance of the regression predictors compared to a single tree, while leaving the bias unchanged. In many situations, the dominating component in the risk turns out to be the squared bias, which leads to the necessity of bias correction. In this paper, random forests are used to estimate the regression function. Five different methods for estimating bias are proposed and discussed. Simulated and real data are used to study the performance of these methods. Our proposed methods are significantly effective in reducing bias in regression context.
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    Reproductive biology of the shore crabCarcinus maenas(Decapoda, Portunidae): a macroscopic and histological view (2012)
    Taylor & Francis
    In:  Invertebrate Reproduction & Development, 56 (2). pp. 144-156.
    Details
    Publication Date: 2018-04-11
    Description: A histological study of the reproductive cycle of male and female shore crabs, Carcinus maenas (Linnaeus), was performed monthly on the South West coast of Ireland (from December 2006 to July 2008). The calculated sex ratio deviated from equality, 1:0.53, revealing a strong male bias. A system was devised, based on screening of tissue sections, to describe and stage gametogenic development. Histological examinations revealed that ovarian development occurred biannually, with a primary winter cycle in which the larger crabs reproduced and a secondary summer cycle, when smaller crabs reproduced. An association was observed where more of the larger specimens were caught in the summer months and the smaller specimens in the winter months, which inversely correlated with the segregated breeding cycles. There was strong evidence that mature male crabs could potentially copulate year round since all mature specimens, collected throughout the year, contained viable spermatozoa. Developmental stages of oogenesis and spermatogenesis were described to develop a practical gonadal index for this portunid crab, providing information on the biology of this species, which will be of benefit for fisheries management.
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    Temporal and spatial patterns in the abundance of jellyfish in the northern Benguela upwelling ecosystem and their link to thwarted pelagic fishery recovery (2012)
    Taylor & Francis
    In:  African Journal of Marine Science, 34 (1). pp. 131-146.
    Details
    Publication Date: 2018-01-16
    Description: There has been debate in the literature about whether jellyfish abundance has increased in the northern Benguela upwelling system, or not, over the past five decades and what impact they are having on pelagic fish. Here we review old expedition literature as well as more recent spatial and temporal patterns in distribution of jellyfish off Namibia at a number of different scales, using both published and previously unpublished data. Specifically, we have used data from fishery-dependent sources of both the demersal (359 638 trawls) and pelagic fisheries (11 324 purse-seine sets) that cover the period 1992–2006, supported by data from fishery-independent demersal (6 109 trawls) and pelagic trawls (1 817 trawls) from 1996 to 2006. Using frequency of capture as an index of abundance, it is clear that jellyfish are not randomly distributed within the northern Benguela ecosystem, but show specific areas of concentration that broadly reflect regional oceanography and the distribution of other zooplankton. Although jellyfish are present throughout the year, peaks in abundance are shown that often coincide with peaks in the spawning activity of fish of commercial importance. Interannual changes in jellyfish abundance observed from all sources do not agree, with some showing increases, others declines, and still others showing no change, which suggests caution should be exercised in their interpretation. Based on the multiple lines of evidence synthesised here, we conclude that jellyfish abundance has increased concomitant with a decline of pelagic fish stocks. We conclude that future recovery of the pelagic fishery off Namibia is likely to be considerably challenged because of significant overlaps in space and time between fish and jellyfish, and through the effects of competition and predation effects of jellyfish on fish.
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    Drained behaviour of cemented sand in high pressure triaxial compression tests (2012)
    Taylor & Francis
    In:  Geomechanics and Geoengineering, 7 (3). pp. 159-174.
    Details
    Publication Date: 2018-04-17
    Description: In this paper, drained behaviour of cemented sand under high pressure is studied. A recently developed high pressure triaxial apparatus is used. The test results indicate the significance of degree of cementation and confining pressure on the isotropic compression, volumetric change, stress-strain behaviour and stress-dilatancy relationship of cemented sand at high confining pressures. The results suggest that the influence of cementation is greater at low confining stresses and it reduces with increasing confining stress where the effect of the confining pressure becomes dominant. A Scanning Electron Microscope analysis has also been included in the paper. It revealed that the particle and cement bonding breakage at high pressure is dependent on the stress level and the cement content. The higher the confining pressure the more significant particle and cement bonding breakage is observed. The higher the cement content the fewer sand particles and cement bonds are broken.
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    Dimethylsulphopropionate (DMSP) and proline from the surface of the brown alga Fucus vesiculosus inhibit bacterial attachment (2012)
    Taylor & Francis
    In:  Biofouling, 28 (6). pp. 593-604.
    Details
    Publication Date: 2019-09-23
    Description: It was demonstrated previously that polar and non-polar surface extracts of the brown alga Fucus vesiculosus collected during winter from the Kiel Bight (Germany) inhibited bacterial attachment at natural concentrations. The present study describes the bioassay-guided identification of the active metabolites from the polar fraction. Chromatographic separation on a size-exclusion liquid chromatography column and bioassays identified an active fraction that was further investigated using nuclear magnetic resonance spectroscopy and mass spectrometry. This fraction contained the metabolites dimethylsulphopropionate (DMSP), proline and alanine. DMSP and proline caused the anti-attachment activity. The metabolites were further quantified on the algal surface together with its associated boundary layer. DMSP and proline were detected in the range 0.12–1.08 ng cm−2 and 0.09–0.59 ng cm−2, respectively. These metabolites were tested in the concentration range from 0.1 to 1000 ng cm−2 against the attachment of five bacterial strains isolated from algae and sediment co-occurring with F. vesiculosus. The surface concentrations for 50% inhibition of attachment of these strains were always 〈0.38 ng cm−2 for DMSP and in four cases 〈0.1 ng cm−2 for proline, while one strain required 1.66 ng cm−2 of proline for 50% inhibition. Two further bacterial strains that had been directly isolated from F. vesiculosus were also tested, but proved to be the least sensitive. This study shows that DMSP and proline have an ecologically relevant role as surface inhibitors against bacterial attachment on F. vesiculosus.
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    Paleocene MORB and OIB from the Resolution Ridge, Tasman Sea (2012)
    Taylor & Francis
    In:  Australian Journal of Earth Sciences, 59 (6). pp. 953-964.
    Details
    Publication Date: 2018-06-08
    Description: Altered lavas have been dredged from three locations on the Resolution Ridge, west of New Zealand's South Island. On the basis of whole-rock geochemistry, Sr, Nd and Pb isotope data and Ar–Ar ages, they can be divided into two suites: 62–60 Ma enriched mid-ocean ridge basalt (E-MORB), and 57 Ma trachybasalt and trachyandesite of ocean island basalt (OIB) affinity. The E-MORBs from the Resolution Ridge are only the second place from which Tasman Sea abyssal oceanic crust has ever been sampled, they have Indian MORB-like isotope compositions, and their ages support a recent interpretation of a 100 km sinistral offset of the southern part of the Tasman Sea spreading ridge. The slightly younger OIB suite erupted shortly after oceanic crust formation and has FOZO to HIMU source characteristics similar to the well-known SW Pacific Diffuse Alkaline Magmatic Province (DAMP). The close occurrence and isotopic mixing relationships of both Paleocene volcanic suites on the Resolution Ridge may be explained by a heterogeneous upper mantle in which the more fertile OIB component was extracted during a later melting event away from the spreading ridge. The dredged lavas predate formation of Southeast Tasman oceanic crust that borders the Resolution Ridge to the south.
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    Impacts of Saharan dust and clouds on photosynthetically available radiation in the area off Northwest Africa (2012)
    Taylor & Francis
    In:  Tellus B: Chemical and physical meteorology, 64 . p. 17160.
    Details
    Publication Date: 2019-09-23
    Description: Radiation measurements in the area off Northwest Africa (research cruise, February 2008) and at Mindelo (Cape Verde Islands, May 2009) were used to investigate the impacts of Saharan dust and clouds on solar irradiance and on photosynthetically available radiation, to derive a relationship between dust aerosol optical depth (AOD) and photosynthetically available radiation and to determine the annual variations of photosynthetically available radiation. Three different kinds of atmospheric conditions were considered: cloudy skies, which decreased or increased the irradiance and dusty skies. The reduction by clouds was up to 67.2% at 400 nm and up to 84.4% at 700 nm. Enhancements of up to 21.9% at 400 nm and 34.0% at 700 nm were observed. The decrease by dust was up to 19.7% at 400 nm and up to 4.1% at 700 nm. Clouds decreased or increased the photosynthetically available radiation by up to 79.9% or up to 31.2%. The reduction by dust depended on the dust AOD and was between 3.6% and 12.3%. A linear relationship confirmed a decrease of photosynthetically available radiation of 1.2% by an increase of dust AOD of 0.1.
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    Bacteria associations with co-occurring macroalgae: Host, epiphyte and environmental factors (2012)
    Taylor & Francis
    In:  European Journal of Phycology, 46 (sup1). pp. 45-50.
    Details
    Publication Date: 2017-01-04
    Description: Bacteria associated with 2 macroalgae growing in the Kiel Fjord (Baltic Sea) were investigated seasonally over two years by scanning electron microscopy and cultivation methods. Seasonal variations and significant differences between both macroalgal species with respect to the associated bacteria were observed. 166 bacterial strains were isolated from the macroalgae and classified by phylogenetic analysis of 16S rRNA gene sequences. The strains formed 82 phylotypes according to sequence similarities of499.0%. Samples from Fucus vesiculosus revealed 43 and from Delesseria sanguinea 57 bacterial phylotypes. They affiliated to Actinobacteria, Alphaproteobacteria, Bacilli, Betaproteobacteria, Flavobacteria, Gammaproteobacteria, and Sphingobacteria. Following the assumption that chemical interactions rule the bacteria-macroalga associations, we tested the biological activity of both macroalgae and isolated bacterial strains against a panel comprising standard and ecologically relevant microorganisms (Gram-positive and Gram-negative bacteria, including macroalgal pathogens and surface associated strains, and a yeast). Both macroalgae presented inhibitory activity against at least one microorganism, but overall the inhibitory activities were low. In contrast, all extracts stimulated growth of many of the tested bacteria. While growth stimulation was common concerning bacteria associated with macroalgae, no stimulation was shown for the standard set of bacteria (with exception of one case of stimulation of the plant pathogen Erwinia amylovora). Regarding the potential biological activity of microorganisms associated with macroalgae, more than 60% of the bacterial phylotypes inhibited the growth of at least one microorganism. A higher proportion of strains showed antimicrobial activity against the set of bacteria associated with macroalgae as compared to standard set of microorganisms. Certain phylotypes are consistently found as epiphytes, suggesting their specific association with macroalgae. The presented positive and negative effects of macroalgal extracts on growth of macroalga-associated bacteria, significant bacterial activity against macroalgal pathogens and competitors, and potential degradative capabilities support the assumption that complex chemical interactions shape the bacteria-macroalga relationships.
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    HOAPS precipitation validation with ship-borne rain gauge measurements over the Baltic Sea (2012)
    Taylor & Francis
    In:  Tellus A: Dynamic meteorology and oceanography, 64 (18486).
    Details
    Publication Date: 2016-06-14
    Description: Global ocean precipitation is an important part of the water cycle in the climate system. A number of efforts have been undertaken to acquire reliable estimates of precipitation over the oceans based on remote sensing and reanalysis modelling. However, validation of these data is still a challenging task, mainly due to a lack of suitable in situ measurements of precipitation over the oceans. In this study, validation of the satellite-based Hamburg Ocean Atmosphere Parameters and fluxes from Satellite data (HOAPS) climatology was conducted with in situ measurements by ship rain gauges over the Baltic Sea from 1995 to 1997. The ship rain gauge data are point-to-area collocated against the HOAPS data. By choosing suitable collocation parameters, a detection rate of up to about 70% is achieved. Investigation of the influence of the synoptic situation on the detectability shows that HOAPS performs better for stratiform than for convective precipitation. The number of collocated data is not sufficient to validate precipitation rates. Thus, precipitation rates were analysed by applying an interpolation scheme based on the Kriging method to both data sets. It was found that HOAPS underestimates precipitation by about 10%, taking into account that precipitation rates below 0.3 mm h−1 cannot be detected from satellite information.
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    Disruption-free imaging by Raman spectroscopy reveals a chemical sphere with antifouling metabolites around macroalgae (2012)
    Taylor & Francis
    In:  Biofouling, 28 (7). pp. 687-696.
    Details
    Publication Date: 2020-06-19
    Description: Investigations of the surface chemistry of marine organisms are essential to understand their chemically mediated interactions with fouling organisms. In this context, the concentration of natural products in the immediate vicinity of algal surfaccs, as well as their biological activity, are of particular importance. Howevcr, due to lack of appropriate methods, the distribution of Compounds within the Chemical sphere around marine algae is unknown. This study demonstrates the suitability of confocal resonance Raman microspcctroscopy for the determination of metabolites around algal surfaces with a micrometer resolution.
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    Impacts of Saharan dust on downward irradiance and photosynthetically available radiation in the water column (2012)
    Taylor & Francis
    In:  Advances in Oceanography and Limnology, 3 (2). pp. 99-131.
    Details
    Publication Date: 2020-04-23
    Description: A semi-empirical approach was used to quantify the modification of the underwater light field in amplitude (magnitude effect) and spectral distribution (spectral effect) by different atmospheric conditions altering the incident light. The approach based on an optical model in connection with radiation measurements in the area off Northwest Africa. Key inputs of the model were parameterized magnitude and spectral effects. Various atmospheric conditions were considered: clear sky, dusty sky without clouds, cloudy sky without dust and skies with different ratios of dust and clouds. Their impacts were investigated concerning the modification of the downward irradiance and photosynthetically available radiation in the water column. The impact on downward irradiance depended on the wavelength, the water depth, the optical water properties, the dust and cloud properties, and the ratio of clouds to dust. The influence of clouds on the amplitude can be much higher than that of dust. Saharan dust reduced the photosynthetically available radiation in the water column. Ocean regions were more influenced than coastal areas. Compensations of the magnitude and spectral effects were observed at special water depths in ocean regions and at atmospheric conditions with definite cloud to dust ratios
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    Light scintillation in oceanic turbulence (2012)
    Taylor & Francis
    In:  Waves in Random and Complex Media, 22 (2). pp. 260-266.
    Details
    Publication Date: 2019-12-02
    Description: The scintillation index of plane and spherical light waves as well as of a Gaussian beam, propagating in the clear-water weakly turbulent ocean, is revealed. The results are of utmost importance for underwater optical communications and sensing. An analysis of the threshold between the weak and strong regimes of oceanic turbulence is made, with the accent on the contribution from salinity-induced turbulence. It is found that strong oceanic turbulence can occur at distances as short as several meters, in striking contrast with atmospheric studies for which the typical distances are on the order of a kilometer.
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    Structure of the reproductive system and hectocotylus in males of lesser flying squid Todaropsis eblanae (Cephalopoda: Ommastrephidae) (2012)
    Taylor & Francis
    In:  Journal of Natural History, 46 (29-30). pp. 1761-1778.
    Details
    Publication Date: 2021-08-20
    Description: This paper introduces new data on Todaropsis eblanae morphology, morphometry and functional aspects of the male reproductive system and hectocotylus. Spermatophores differ in specimens from the Atlantic Ocean (average length, 18.28 ± 1.45 mm, 15.63 ± 0.8% of mantle length; weight, 2.0–12.0 mg) and the Indian Ocean (average length, 24.8 ± 2.85 mm, 16.9 ± 2.1% of mantle length; weight, 35.0–39.6 mg) (t = 3.14; p 〈 0.01 for absolute sizes and t = 0.711; p 〉 001 for relative sizes). An additional important distinctive trait is the form of connection of the cement body with the ejaculatory tube. In recent years, T. eblanae has been regularly caught in the Barents Sea, meaning its range has extended to subarctic waters. The morphology and morphometry of the spermatophoric complex of organs did not vary in investigated parts of its range. Hectocotylus patterns and some important spermatophore traits distinguish Todaropsis from other Ommastrephidae.
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    Amelioration of free copper by hydrothermal vent microbes as a response to high copper concentrations (2012)
    Taylor & Francis
    In:  Chemistry and Ecology, 28 (5). pp. 405-420.
    Details
    Publication Date: 2021-11-04
    Description: We examined the effect of increased copper concentrations (0-10 mu M) on hydrothermal vent microorganisms and the production of copper (Cu)-binding ligands as a response. Hydrothermal vent microbes originated from diffuse fluids at the Lilliput mussel field and the Irina II site in the Logatchev hydrothermal vent field, both on the Mid-Atlantic Ridge. Parallel studies were also conducted with amino acids supplemented to the incubations in order to verify whether dissolved amino acids, present in hydrothermal fluids, can buffer the bioavailable copper and reduce the active production of Cu-binding ligands. In all incubations, ligand concentrations increased with rising copper concentrations, but microbial cell numbers remained constant. This study shows that microbes were able to cope with as much as 10 mu M dissolved copper by buffering the free copper concentration. The presence of amino acids had no significant influence on the active ligand production. Our results imply that mediation of chemical speciation by vent microbes may have an important impact on hydrothermal trace metal fluxes into the ocean.
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    A new compound, jolynamine, from marine brown alga Jolyna laminarioides (2011)
    Taylor & Francis
    In:  Natural Product Research, 25 (9). pp. 898-904.
    Details
    Publication Date: 2018-01-24
    Description: A new compound, jolynamine (1), was isolated from the marine brown alga Jolyna laminarioides collected from the coast of Karachi, Pakistan. In addition, four known compounds, namely saringosterol (2), loliolide (3), methyl-4-hydroxybenzoate (4) and propyl-4-hydroxybenzoate (5), were isolated for the first time from the marine brown alga Iyengaria stellata, and two known compounds, namely 3,4,5-trimethylaniline (6) and harmine (7), were isolated for the first time from the marine brown alga Melanothamnus afaqhusainii. Compound 6 is synthetically known but was isolated for the first time from a natural source. The structures of these compounds were elucidated with the help of powerful spectroscopic techniques. Furthermore, the methanolic extracts of both algae showed anti-microbial activities against various bacteria and fungi.
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    Sialic acid as a potential approach for the protection and targeting of nanocarriers (2011)
    Taylor & Francis
    In:  Expert Opinion on Drug Delivery, 8 (7). pp. 921-937.
    Details
    Publication Date: 2017-05-22
    Description: Introduction: Nanocarriers are considered to be one of the most innovative drug delivery systems, owing to their high potential in drug protection, delivery and targeting to the diseased site. Unfortunately, their applicability is hampered mainly by their uptake, due to macrophagic recognition and lack of specificity, if not properly engineered. Areas covered: Sialic acid (SA) and its derivatives have recently been studied in order to govern their stealthness as carriers and their effectiveness as targeting moieties. In this review, the most outstanding research (in vitro and in vivo) dealing with the use of SA or its derivatives to modify the surface carriers, in order to achieve targeted or stealth nanosystems, is summarized. Moreover, the application of SA or its derivatives as modifiers in cancer targeting and therapy, and in recognition purposes, is considered. Expert opinion: The application of SA-based strategies for nanocarrier engineering represents one of the most stimulating challenges in drug delivery and drug targeting. Both in vivo and in vitro results on stealth or targeted nanocarriers, modified with different kinds of SA or SA derivative, have highlighted the great potential of this approach. These studies have drawn attention to both the advantages (stealth properties, targeting ability, cancer inhibition, viral and inflammation recognition, brain targeting) and the possible disadvantages (i.e., presence of possible multi-target side effect outputs) of this strategy, and overall suggests that further investigations on this strategy are required.
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    Background concentrations of gold in different rock types (2011)
    Taylor & Francis
    In:  Applied Earth Science, 120 (1). pp. 31-38.
    Details
    Publication Date: 2018-04-24
    Description: The abundance of gold in crustal rocks is an important constraint on the formation of gold deposits. Gold concentrations in unmineralised igneous, sedimentary and metamorphic rocks range from 0.05 to 20 ppb with average concentrations commonly between 0.5 and 5 ppb. Analytical methods with ultra-low detection limits are required to observe the full range of concentrations. Gold concentrations in igneous rocks are strongly controlled by the behaviour of sulphur. Higher gold concentrations occur in sulphur-undersaturated rocks compared to sulphur saturated igneous rocks. Mid ocean ridge basalt has lower gold concentration than ocean-island and volcanic-arc basalt, due mainly to lower oxygen fugacity at MOR settings that causes sulphur saturation. Gold concentrations in sedimentary rocks increase with increasing abundance of diagenetic sulphide minerals and organic matter. Gold concentrations in metamorphic rocks decrease systematically with increasing metamorphic grade. Amphibolite facies rocks commonly contain between 50 and 80% less gold than their unmetamorphosed protolith rocks.
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    Underwater bottom topography in coastal areas from TerraSAR-X data (2011)
    Taylor & Francis
    In:  International Journal of Remote Sensing, 32 (16). pp. 4527-4543.
    Details
    Publication Date: 2017-07-18
    Description: In this article, wave refraction and shoaling in coastal areas were investigated and used to derive the bathymetry. With its high spatial resolution, which can achieve up to 1 m in SpotLight mode, and its low cut-off wavelength, the TerraSAR-X satellite provides images that are particularly suitable for the observation of wave behaviour in transient and shallow waters. By computing the two-dimensional (2D) spectra, shoaling waves were tracked from the open sea to the shoreline. The observed wave refraction and shoaling were compared with wave refraction laws and first-order wave theory (Airy theory). The retrieved bathymetry was compared against depth data from other sources such as ETOPO1, the US Coastal Relief Model and sea charts from the British Admiralty. A further aim of this article was the investigation of breaking waves showing up as near-shore image patterns. A theory is presented of how to derive the height of breaking waves by use of this pattern. Synthetic aperture radar (SAR) images with azimuth as well as range travelling waves were investigated. As test sites, we chose the entrance of Port Phillip near Melbourne (Australia) and the Duck Research Pier in North Carolina (USA).
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    High radar-backscatter regions on Antarctic sea-ice and their relation to sea-ice and snow properties and meteorological conditions (2011)
    Taylor & Francis
    In:  International Journal of Remote Sensing, 32 (14). pp. 3967-3984.
    Details
    Publication Date: 2014-12-09
    Description: The temporal and spatial variability of sea-ice radar signatures in the Southern Ocean during late winter, spring and early summer from QuikSCAT data is presented. We observe a circumpolar and broad band of sea-ice close to the marginal ice zone that is characterized by very high radar backscatter. This feature is explained through detailed in situ observations of snow and sea-ice properties as well as in relation to meteorological conditions, which were derived from US National Center for Environmental Prediction (NCEP)/National Center for Atmospheric Research (NCAR) reanalysis data. Our results indicate that high backscatter regions are caused by metamorphous snow, which forms through re-freezing after short-term melt events. This process is connected with the episodic passes of low-pressure systems entraining warmer air from the north. South of the Antarctic Circumpolar Trough, sea-ice is not affected by this influence and shows spatially homogenous microwave signatures with low backscatter.
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    Optimising settlement assays of pediveligers and plantigrades ofMytilus galloprovincialis (2011)
    Taylor & Francis
    In:  Biofouling, 27 (8). pp. 859-868.
    Details
    Publication Date: 2015-09-10
    Description: The mussel Mytilus galloprovincialis is a common aquaculture species, and also a major fouling organism that has negative economic impacts. There are no standard assay conditions for this important species and therefore, this study quantified the effect of key factors on the settlement of pediveligers and plantigrades. Density dependent settlement did not occur for either pediveligers or plantigrades. Settlement increased in drop assays in a 12 h light:12 h dark cycle, while bottom shade had no effect of any magnitude. In addition, settlement was significantly enhanced by storing pediveligers for between 4 and 24 days at 4 °C. Overall, these data provide the template to optimise and standardise static laboratory settlement assays for mussels in order to develop materials that either enhance settlement for the aquaculture industry, or deter settlement for antifouling applications. Furthermore, simple mechanisms such as storage at 4 °C can enhance settlement beyond current methods used in aquaculture hatcheries.
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    A practical indicator for surface ocean heat and freshwater buoyancy fluxes and its application to the NCEP reanalysis data (2011)
    Taylor & Francis
    In:  Tellus A: Dynamic meteorology and oceanography, 63 . pp. 338-347.
    Details
    Publication Date: 2019-09-23
    Description: The buoyancy flux at the air/sea interface plays a key role in water mass transformation and mixing as it modifies surface water density and in turn drives overturning and enhances stratification. It is the interplay of these two independent heat and freshwater buoyancy flux components that is of central importance when analysing mechanisms of the ocean/atmosphere interaction. Here, a diagnostic quantity (ΘB) is presented that allows to capture the relative contribution of both components on the buoyancy flux in one single quantity. Using NCEP reanalysis of heat and freshwater fluxes (1948–2009) demonstrates that ΘB is a convenient tool to analyse both the temporal and spatial variability of their corresponding buoyancy fluxes. For the global ocean the areal extent of buoyancy gain and loss regions changed by 10%, with the largest extent of buoyancy gain during the 1970–1990 period. In the subpolar North Atlantic, and likewise in the South Pacific, decadal variability in freshwater flux is pronounced and, for the latter region, takes control over the total buoyancy flux since the 1980s. Some of the areal extent time series show a significant correlation with large-scale climate indices.
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    Surface-associated fucoxanthin mediates settlement of bacterial epiphytes on the rockweed Fucus vesiculosus (2011)
    Taylor & Francis
    In:  Biofouling, 27 (4). pp. 423-433.
    Details
    Publication Date: 2019-09-23
    Description: The chemical defence against microfouling in the brown seaweed Fucus vesiculosus was investigated and an inhibitor of bacterial settlement was isolated by bioassay-guided fractionation of non-polar surface extracts. UV-vis and mass spectrometry were used to identify the compound as the carotenoid fucoxanthin. The metabolite was tested at the natural concentration (in a surface volume based assay) against the settlement of four bacterial strains isolated from F. vesiculosus and 11 strains isolated from co-occurring algae and marine sediment. Surface concentrations between 1.4 and 6 μg cm-2 resulted in 50% inhibition of four of these isolates, which were studied in more detail using a surface area-based assay, while a fifth isolate proved to be less sensitive. The presence of fucoxanthin on the surface of F. vesiculosus was demonstrated with two different surface extraction methods. Fucoxanthin was detected at concentrations between 0.7 and 9 μg cm-2 on the algal surface. Fucoxanthin was still present at the algal surface after removal of associated diatoms through mechanical cleaning and germanium dioxide treatment and was thus mainly produced by F. vesiculosus rather than by diatoms. Thus, the photosynthetic pigment fucoxanthin appears to be ecologically relevant as a surface-associated antimicrobial agent, acting against the settlement of bacteria on the surface of the macroalga F. vesiculosus.
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    Parasites of shore crabs in the genusHemigrapsus(Decapoda: Brachyura: Varunidae) and their status in crabs geographically displaced: a review (2011)
    Taylor & Francis
    In:  Journal of Natural History, 45 (39-40). pp. 2419-2441.
    Details
    Publication Date: 2016-08-30
    Description: Two brachyurans of the varunid genus Hemigrapsus from the northwestern Pacific Ocean have invaded coastal regions of the north Atlantic – Hemigrapsus takanoi (sibling species of Hemigrapsus penicillatus) and Hemigrapsus sanguineus in Europe and the latter in the USA. Parasites are known from these crabs in their native habitats, but except for an undescribed larval nematode, none has been found in those examined from their new locations. These parasites include metacercariae of eight species of microphallid trematode, the rhizocephalan barnacles Polyascus polygenea, Sacculina nigra and Sacculina senta, and the obligate gut-inhabiting mesomycetozoan Enteromyces callianassae (potential parasite). The following have been identified in four of the other eight Pacific crabs within the genus (Hemigrapsus nudus and Hemigrapsus oregonensis, northern hemisphere; Hemigrapsus crenulatus and Hemigrapsus sexdentatus, southern hemisphere), none of which have been geographically displaced: metacercariae of two microphallid trematodes; cystacanths of three acanthocephalans Profilicollis antarcticus, Profilicollis botulus and Profilicollis novaezelandensis; larval nematode Ascarophis sp.; nematomorph Nectonema zealandica; entoniscid isopod Portunion conformis; mesomycetozoan Taeniella carcini; and nemertean egg predator Carcinonemertes epialti. The likelihood of the displaced species of shore crabs being rejoined with their native parasites or their susceptibility to becoming infected by similar parasites in their new locations is discussed. In future global displacements of parasitized Hemigrapsus species it is possible that their most serious parasites, rhizocephalans and entoniscid isopods, may infect previously uninfected species. For example, the two eastern Pacific species of Hemigrapsus (H. nudus and H. oregonensis) may be vulnerable to the rhizocephalans and may in turn be a source of entoniscids transported elsewhere.
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    A comparative study on the removability of different ozone-produced oxidants by activated carbon filtration (2011)
    Taylor & Francis
    In:  Ozone: Science & Engineering, 33 (3). pp. 224-231.
    Details
    Publication Date: 2019-09-23
    Description: A comparative study about the removability of four potentially harmful ozone-produced oxidants (free bromine, bromamines, free chlorine and chloramines) by activated carbon filtration was performed under identical conditions in small-scale filter experiments. Removability was high and similar among the oxidants with the exception of chloramines which showed the least removability. Results proved activated carbon filtration to be very efficient in removing the dominating brominated oxides formed during the ozonation of natural and most artificial seawaters. In contrast, removability of chloramines, sometimes present in ozonated bromide-free artificial saltwater, was shown to be significantly lower. To improve removal of persistent chloramines by activated carbon filtration, a comparative evaluation of 3 different activated carbon types was conducted. Granulated activated carbon on coal basis was suggested to be the most cost-effective carbon for removing chloramines as it possessed highest removal capacity, while being the cheapest of the carbons tested.
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    Visual sensitivity, coloration and morphology of red-tailed tropicbirds Phaethon rubricauda breeding on the Kermadec Islands (2011)
    Taylor & Francis
    In:  New Zealand Journal of Zoology, 38 (1). pp. 29-42.
    Details
    Publication Date: 2020-06-22
    Description: Subtle sexual dimorphism and its perception in apparently monomorphic bird species warrant assessment of how birds identify the sex of conspecifics, particularly of prospective mates. Visual sensitivity and its potential co-variation with cryptic sexual dichromatism are still uninvestigated in most avian taxa. Using molecular sexing, reflectance spectrometry and perceptual modelling based on the sequencing of short wavelength visual pigments, we assessed the sex-specificity of coloration and colour perception in the red-tailed tropicbird Phaethon rubricauda. We also measured morphological dimorphism at a previously unstudied breeding locality for this species. Our data are in line with both physical and avian-perceived monochromatism with a potential indication of achromatic sex differences in plumage reflectance. The moderate extent of size dimorphism is consistent with reports from other Pacific breeding populations, and morphological measurements from live specimens in this study are in line with reports on museum specimens from the same sample location. Potential differences between individuals of the same sex in size and coloration warrant the assessment of sexual dimorphism in larger sample sizes of this species.
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    Impact of increasing resolution and a warmer climate on extreme weather from Northern Hemisphere extratropical cyclones (2011)
    Taylor & Francis
    In:  Tellus A: Dynamic meteorology and oceanography, 63 (5). pp. 893-906.
    Details
    Publication Date: 2016-06-15
    Description: The effect of a warmer climate on the properties of extratropical cyclones is investigated using simulations of the ECHAM5 global climate model at resolutions of T213 (60 km) and T319 (40 km). Two periods representative of the end of the 20th and 21st centuries are investigated using the IPCC A1B scenario. The focus of the paper is on precipitation for the NH summer and winter seasons, however results from vorticity and winds are also presented. Similar number of events are identified at both resolutions. There are, however, a greater number of extreme precipitation events in the higher resolution run. The difference between maximum intensity distributions is shown to be statistically significant using a Kolmogorov–Smirnov test. A generalized Pareto distribution is used to analyse changes in extreme precipitation and wind events. In both resolutions, there is an increase in the number of extreme precipitation events in a warmer climate for all seasons, together with a reduction in return period. This is not associated with any increased vertical velocity, or with any increase in wind intensity in the winter and spring. However, there is an increase in wind extremes in the summer and autumn associated with tropical cyclones migrating into the extratropics
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    Solar radiative transfer simulations in Saharan dust plumes: particle shapes and 3-D effect (2011)
    Taylor & Francis
    In:  Tellus B: Chemical and physical meteorology, 63 (4). pp. 770-780.
    Details
    Publication Date: 2019-01-24
    Description: Radiative fields of three-dimensional inhomogeneous Saharan dust clouds have been calculated at solar wavelength (0.6 μm) by means of a Monte Carlo radiative transfer model. Scattering properties are taken from measurements in the SAMUM campaigns, from light scattering calculations for spheroids based on the MIESCHKA code, from Mie theory for spheres and from the geometric optics method assuming irregular shaped particles. Optical properties of different projected area equivalent shapes are compared. Large differences in optical properties are found especially in the phase functions. Results of radiative transfer calculations based on the Monte Carlo method are shown exemplarily for one dust cloud simulated by the cloud resolving atmospheric circulation model LM-MUSCAT-DES. Shape-induced differences in the radiation fluxes are pronounced, for example, the domain averaged normalized radiance is about 30% lower in the case of a dust plume consisting of spheroids or irregular particles compared to spheres. The effect of net horizontal photon transport (3-D effect) on the reflected radiance fields is only notable at the largest gradients in optical thickness. For example, the reflectance at low sun position differs locally about 15% when horizontal photon transport is accounted for. ‘Sharp edges' due to 1-D calculations are smoothed out in the 3-D case.
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    Secondary metabolites of Pyrenochaeta sp. B36, an endophytic fungus from Annona squamosa L. (2011)
    Taylor & Francis
    In:  Natural Product Research, 25 (10). pp. 1008-1013.
    Details
    Publication Date: 2020-06-19
    Description: Four new metabolites, named pyrenochaetamide A (1), pyrenochaetolide A (2), pyrenochaetoxy A (3) and pyrenochaetolide B (4), together with five known compounds (5–9), were isolated from strain Pyrenochaeta sp. B36, an endophytic fungus of Annona squamosa L. Their structures were elucidated by spectroscopic analyses including 1D- and 2D-NMR (HMQC, HMBC, 1H–1H COSY and NOESY) and HRFT-MS. The cytotoxic activities of these compounds were evaluated and some of them showed substantial effect.
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    The changing atmospheric water cycle in Polar Regions in a warmer climate (2011)
    Taylor & Francis
    In:  Tellus A: Dynamic meteorology and oceanography, 63 (5). pp. 907-920.
    Details
    Publication Date: 2016-06-14
    Description: We have examined the atmospheric water cycle of both Polar Regions, polewards of 60°N and 60°S, using the ERA-Interim reanalysis and high-resolution simulations with the ECHAM5 model for both the present and future climate based on the IPCC, A1B scenario. The annual precipitation in ERA-Interim amounts to ∼17000 km3 and is more or less the same in the Arctic and the Antarctic, but it is composed differently. In the Arctic the annual evaporation is ∼8000 km3 but ∼3000 km3 less in the Antarctica where the net horizontal transport is correspondingly larger. The net water transport of the model is more intense than in ERA-Interim, in the Arctic the difference is 2.5% and in the Antarctic it is 6.2%. Precipitation and net horizontal transport in the Arctic has a maximum in August and September. Evaporation peaks in June and July. The seasonal cycle is similar in Antarctica with the highest precipitation in the austral autumn. The largest net transport occurs at the end of the major extra-tropical storm tracks in the Northern Hemisphere such as the eastern Pacific and eastern north Atlantic. The variability of the model is virtually identical to that of the re-analysis and there are no changes in variability between the present climate and the climate at the end of the 21st century when normalized with the higher level of moisture. The changes from year to year are substantial with the 20- and 30-year records being generally too short to identify robust trends in the hydrological cycle. In the A1B climate scenario the strength of the water cycle increases by some 25% in the Arctic and by 19% in the Antarctica, as measured by annual precipitation. The increase in the net horizontal transport is 29% and 22%, respectively, and the increase in evaporation correspondingly less. The net transport follows closely the Clausius–Clapeyron relation. There is a minor change in the annual cycle of the Arctic atmospheric water cycle with the maximum transport and precipitation occurring later in the year. There is a small imbalance of some 4–6% between the net transport and precipitation minus evaporation. We suggest that this is mainly due to the fact that the transport is calculated from instantaneous six hourly data while precipitation and evaporation is accumulated over a 6-h period. The residual difference is proportionally similar for all experiments and hardly varies from year to year.
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    A new lineage in Pucciniomycotina: class Tritirachiomycetes, order Tritirachiales, family Tritirachiaceae (2011)
    Taylor & Francis
    In:  Mycologia, 103 (6). pp. 1331-1340.
    Details
    Publication Date: 2018-10-25
    Description: Based on multiple gene analyses (nuclear large subunit, nuclear small subunit, internal transcribed spacer region including the 5.8 s subunit rDNA, and translation elongation factor 1α) and septal pore ultrastructure we describe a new lineage of Pucciniomycotina consisting of a new class, Tritirachiomycetes, new order, Tritirachiales, and new family, Tritirachiaceae. Tritirachium dependens, T. oryzae, T. roseum (reintroduced), T. cinnamomeum and two unidentified species are recognized. Phylogenetic analyses do not support existing morphological circumscription of some species, and the available evidence suggests that morphological evaluation alone is not adequate for species identification.
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    Masses of small bodies (2010)
    Univ. Köln
    Details
    Publication Date: 2020-10-07
    Description: The Radio Science technique enables to estimate the mass and other gravitational parameters of a solar system body from spacecraft observations very precisely. It uses the radio link between ground station and spacecraft. The frequency shift of the radio signal is proportional to the relative velocity change between spacecraft and ground station. If a spacecraft performs a close flyby at a solar system body, the velocity of the spacecraft is changed by the gravitational attraction of the body. If all other contributions on the radio signal are known, the remaining frequency change is solely due to the gravitational attraction. A least square fit can be performed on the frequency residuals to derive from it gravitational parameters. Within this thesis models were developed and merged into a software package with which it is possible to determine the orbit of a spacecraft precisely and to predict accurately the frequency to be observed at a ground station. Models for extracting the frequency shift caused by the propagation of the radio signal through the ionosphere and troposphere of the Earth were incorporated...
    Description: thesis
    Keywords: 522 ; TBC 000 ; TGL 000 ; Radioastronomie ; Interplanetare Materie {Astronomie}
    Language: English
    Type: monograph , publishedVersion
    Format: 151 S.
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    Properties of quasistellar objects and their progenitors in the radio and mm wavelength regimes in the context of ULIRG-to-QSO evolution (2010)
    Univ. Köln
    Details
    Publication Date: 2020-10-07
    Description: The thesis at hand presents the results of a study of galaxies with active galactic nuclei (AGN) carried out in the radio and mm wavelength regimes at low and high angular resolutions. The studied objects cover a broad range of mechanisms responsible for powering the engines of the respective galaxies: ULIRGs (UltraLuminous Infrared Galaxies), a product of mergers between galaxies that are supposedly powered by starbursts, AGN or a mixture of the two, and QSOs (quasi-stellar objects) which are powered by AGN. Since ULIRGs and QSOs show similar properties (especially the infrared luminosities), it was proposed that they form the early and late phase of an evolutionary sequence where supposedly ULIRGs are the dust enshrouded progenitors of QSOs. As a prototypical ULIRG, Arp 220 represents an early-to-intermediate phase object in the scheme of the ULIRG-to-QSO evolution. For this object observations at multiple mm wavelengths and angular resolutions with the IRAM Plateau de Bure Interferometer (PdBI) are presented and analyzed. Arp 220 as a whole is studied in CO emission of the more extended structure. Furthermore, Arp 220-East is analyzed in more detail in the CO gas. Indications for emission ~10" towards the south, as well as to the north and to the west of the two nuclei, were found in the low resolution CO(1-0) maps ...
    Description: Zsfassung in dt. und engl. Sprache
    Description: thesis
    Keywords: 523 ; TBC 000 ; TIE 900 ; Radioastronomie ; Sonstige Sternensysteme {Astronomie}
    Language: English
    Type: monograph , publishedVersion
    Format: 152 S.
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    Multi-telescope studies of neutron stars (2010)
    Univ. Köln
    Details
    Publication Date: 2021-03-29
    Description: Neutron stars are unique stellar remnants with extreme properties, as their density and magnetic field. Their study can be the key to a number of unanswered problems in fundamental physics and astronomy, ranging from stellar evolution to strong field gravity. One of the best ways of studying these objects is with observations at radio wavelengths, the efficiency of which can be vastly improved with the combination of data from multiple radiotelescopes. In this thesis, we use the largest European radiotelescopes for performing high quality studies of the properties of objects belonging into two separate categories of neutron stars, millisecond pulsars and magnetars. In the first part of this thesis, a complete description of the observing systems and calibration procedures for the multiple telescopes used is presented. Specifically, all observations were made with the European Pulsar Timing Array (EPTA) telescopes, which are the Effelsberg 100m radiotelescope in Germany, the Lovell 76m radiotelescope in UK, the Westerbork 94m equivalent synthesis radiotelescope in the Netherlands and the Nanc cay 94m equivalent decimetric radiotelescope in France...
    Description: Zsfassung in dt. und engl. Sprache
    Description: thesis
    Keywords: 523 ; THU 400 ; THK 000 ; TBC 000 ; Pulsare, Neutronensterne {Astronomie} ; Spektren und Spektroskopie von Sternen {Astronomie} ; Radioastronomie
    Language: English
    Type: monograph , publishedVersion
    Format: 152 S.
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    The fate of singularities in quantum cosmology and the application of generalized effective equations to constrained quantum systems (2010)
    Univ. Köln
    Details
    Publication Date: 2020-10-07
    Description: The first part of the thesis is concerned with the fate of singularities in quantum cosmology. The second part addresses the derivation of predictions from quantum cosmology. In the first part, two classes of cosmological models were studied. In the first class of models, the universe evolves to or emerges from a big-rip singularity. Here, energy density, pressure and scale factor diverge after a finite amount of time. This type of singularity arises rather generically in cosmological models with phantom dark energy. For each of these phantom-field models, the corresponding scenario with ordinary scalar field was studied. The scalar field induced a big-bang singularity. The second class of models studied was dominated by a big-brake singularity. At the big brake, the universe evolution comes to a halt due to an infinite deceleration. The motivation behind this choice of models was the occurrence of a singularity at large scale factor. The major question pursued was whether these types of singularity were resolved on the quantum level. If such singularities were resolved in quantum cosmology, this would imply that quantum gravitational effects can occur in the macroscopic universe. After devising classical models that contain the respective singularity, I subjected these models to quantization which was carried out in the geometrodynamical approach. The governing equation is then the WheelerDeWitt equation ...
    Description: Zsfassung in dt. und engl. Sprache
    Description: thesis
    Keywords: 523 ; TEC 800 ; Quantenkosmologie {Astronomie: Kosmologie}
    Language: English
    Type: monograph , publishedVersion
    Format: 228 S.
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    Star-disc encounters in young star clusters (2010)
    Univ. Köln
    Details
    Publication Date: 2021-03-29
    Description: According to current knowledge, star formation occurs preferentially in clustered environments. As a byproduct of the star formation process young stars are found to be surrounded by accretion discs that are potential birth places of planets and planetary systems. Located in the hosting cluster, these protoplanetary discs are potentially subject to stellar interactions. These interactions give rise to a fundamental question of clustered star formation: How far does the cluster environment affect the evolution of protoplanetary discs and the formation of planets? The question is addressed in the present investigation in terms of the effect of stellar encounters on stars and their disc in young clusters by combining numerical simulations of isolated star-disc encounters and stellar dynamics of young star clusters. The investigation is composed of three key aspects. First, simulations of a dynamical model of the Orion Nebula Cluster (ONC) show that disc destruction is dominated by encounters with high-mass stars that act as gravitational foci for the lower mass stars in the cluster centre. The massive stars are thus subject to repeated encounters which can lead to a total disc destruction ...
    Description: thesis
    Keywords: 523 ; THX 000 ; TIC 000 ; Extrasolare Planetensysteme {Astronomie: Sterne} ; Sternhaufen {Astronomie}
    Language: English
    Type: monograph , publishedVersion
    Format: 137 S.
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  • 73
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    The LRS double prism assembly to be flown on the James Webb Space Telescope and host galaxies of active galactic nuclei in the near infrared (2010)
    Univ. Köln
    Details
    Publication Date: 2021-03-29
    Description: The work presented in my thesis covers two aspects of modern astronomy: Observations and instrumentation. Part I of this thesis addresses the design, the development and the qualification of the Low Resolution Spectroscopy Double Prism Assembly (LRSDPA). From an instrumentational point of view, the purpose of the LRSDPA is to make an integration of two prisms, made of Germanium and Zincsulfide, into the imaging module of the mid infrared instrument of the James Webb Space Telescope possible. My design of the LRSDPA answers to several challenging specifications, joining together available envelope, mechanical, thermal, optical and alignment aspects. Both prisms are mounted separately onto a holder via a semi-kinematic interface. The Aluminium components of the demonstration, qualification and flight model all have been manufactured at the mechanical workshop of the 1st Institute of Physics. As it is demanded of all space equipment, the function and performance of the LRSDPA has to be thoroughly demonstrated. The qualification campaign that was conducted in collaboration with the Centre Spatial de Liège, has just been brought to a successful finish. A brief introduction to the James Webb Space Telescope and its mid infrared instrument are given in Chapters 1 and 2. Chapter 3 then describes in detail the scientific capabilities, the design and the qualification of the LRSDPA. The low resolution spectroscopy mode will provide prism slit spectroscopy at a resolution of R=100 and cover the wavelength range from 5æm-10æm. This mode is particularly aiming at spectroscopic analyses of very low surface brightness objects, such as the first light-emitting galaxies that re-ionized the universe shortly after the big bang ...
    Description: thesis
    Keywords: 522 ; TCE 230 ; TIE 400 ; TBG 000 ; TCE 380 ; Weltraumbasierte UV-, Optische und Infrarotteleskope {Astronomische Instrumente} ; Spektren und Leuchtkraft von Sternsystemen {Astronomie} ; Infrarot-Astronomie ; CCD, Photodetektoren {Astronomische Instrumente}
    Language: English
    Type: monograph , publishedVersion
    Format: 146 S.
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    Periodic variability in active galactic nuclei (2010)
    Univ. Köln
    Details
    Publication Date: 2021-03-29
    Description: In this doctoral thesis, multi-frequency very long baseline interferometry observations together with multi-frequency total flux-density variability data of compact relativistic jets in active galactic nuclei are presented and analyzed. The main goal of the thesis is to investigate the physical mechanisms in relativistic jets responsible for such phenomena as the co-existence of moving and stationary jet components, jet wiggling and precession. We also aim to study the connection between the structural changes in the relativistic jets and flares in the total flux-density light curves and to find observational evidences for the appearance of a primary perturbation in the base of the jet and its further propagation. In this thesis we also investigate which physical mechanisms are responsible for periodical total flux-density variability and to search for periodicities as a sign of jet precession. In order to study the jet physics we used the multi-frequency very long baseline interferometry technique which gives the highest possible in astronomy resolution. We also compared jet structural changes with single-dish multi-frequency observations spanning more than 30 years together with optical and gamma-ray data. In particular, analysis of the long-term kinematics of two active galactic nuclei S5 1803+784 and 0605-085 shows evidence for jet precession ...
    Description: thesis
    Keywords: 523 ; TBC 000 ; TIE 500 ; Radioastronomie ; Aufbau und Struktur von Sternsystemen {Astronomie}
    Language: English
    Type: monograph , publishedVersion
    Format: 201 S.
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  • 75
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    Star formation conditions in nearby galaxies (2010)
    Univ. Köln
    Details
    Publication Date: 2021-03-29
    Description: The understanding of gravitational stability of galactic disks against star formation, the interplay of atomic and molecular components of the interstellar medium in a galaxy and its physical conditions, namely temperature and density, are important to gain a deeper insight into star formation. Nearby galaxies like the spiral galaxy M51 or the southern starburst galaxies NGC4945 and Circinus offer excellent opportunities to investigate these topics over a complete galactic disk or parts of the galaxy. A suitable tracer to study the molecular part of the gaseous component of galaxies is the CO molecule. It is the second most abundant molecule after H2 in the interstellar medium, its lower lying transition are excited at typical conditions of molecular clouds and the rotational transitions lie in the radio window. Thus, CO emission can penetrate throughout galactic disks and is observable from the ground. Apart from complementary data from the literature, we use observations of 12CO 21, 12CO 4--3, and 13CO 2--1 in this thesis. Additionally, the [CI] 3P1-3P0 fine structure line was observed to study the physical conditions in the central regions of galaxies. In the first part of this thesis, the nearby spiral galaxy M51 is used as a sample source to investigate the onset of star formation. CO, HI, radio-continuum, dust, and stellar maps of M51 are combined to study star formation rate, the H2/HI transition, the gas-to-dust ratios, the stability of the disk against gravitational collapse, and properties of the giant molecular clouds. Parts of the results have been published in Astronomy and Astrophysics (461,143) in 2007 and are submitted to Astronomy and Astrophysics, 2008 for publication. We use the first complete 12CO 2--1 map of M51 including the companion galaxy NGC5195 observed with HERA at the IRAM-30m telescope to trace the molecular gas. Complementary HI VLA data is used to study the atomic gas distribution and the combined total gas surface density ...
    Description: thesis
    Keywords: 523 ; TEG 000 ; Kosmogonie {Astronomie}
    Language: English
    Type: monograph , publishedVersion
    Format: 180 S.
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    LINC-NIRVANA piston control and near-infrared polarization images of the Orion proplyds (2010)
    Univ. Köln
    Details
    Publication Date: 2021-03-29
    Description: This thesis is focussed on the development of optimized techniques to overcome limitations of astrophysical observations. The goal is an optimal signal estimation in noisy measurements by the consideration of underlying physical processes. This principle was applied to two different fields in astrophysics: intrumental design and analysis of polarimetric observations. In the observational part of this thesis near-infrared images of young stellar objects in the Orion constellation are studied. Limitations in resolution and sensitivity of current astronomical instruments prohibit the detailed analysis of interesting proto-stellar sources to improve theories of star formation. Radiation from the astronomical targets is not only characterized by its spectral energy, but also by polarization properties. The modeling of typical configurations of star-disk systems and the simulation of their polarization patterns helped to understand and interprete features, that were found in observations. For the case of a proto-stellar systems with both a disk and an envelope analysis techniques were developed, which are based on polarimetric effects of the scattering of light by dust. These techniques substantially improve the sensitivity and resolution and are reliable under different observing conditions. Although the obtained data did not allow investigations of substructures of the circumstellar material, the techniques are suitable to obtain constraints on star formation processes ...
    Description: thesis
    Keywords: 523 ; THK 000 ; Spektren und Spektroskopie von Sternen {Astronomie}
    Language: English
    Type: monograph , publishedVersion
    Format: 168 S.
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    Entwicklung und Aufbau eines BWO-basierten 1,9-THz-Lokaloszillatoren für den Heterodynempfänger GREAT (2010)
    Univ. Köln
    Details
    Publication Date: 2021-03-29
    Description: Astronomische Beobachtungen im Bereich der THz-Frequenzen geben Aufschluss über die Entwicklung der interstellaren Materie in unserem Universum. Als wichtigste Kühllinie dichter Molekülwolken ist die Detektion des Feinstrukturübergangs von einfach-ionisiertem atomarem Kohlenstoff CII bei der Frequenz von 1,9 THz von fundamentaler Bedeutung. Wünschenswert ist das Studium astronomischer Quellen hinsichtlich ihrer Dynamik, Temperatur und Dichte mit möglichst hoher sowohl räumlicher als auch spektraler Auflösung. Heterodynempfänger sind für diese Aufgabe am besten geeignet. Bei dieser Technologie wird das astronomische Signal mittels eines Lokaloszillatoren (LO) auf eine Zwischenfrequenz von wenigen GHz umgesetzt und dann rauscharm weiterverstärkt. Gegenstand der vorliegenden Arbeit ist die Entwicklung und der Aufbau des LOs für den 1,9 THz Frequenzkanal des Mehrkanalheterodynempfängers German REceiver for Astronomy at THz-Frequencies (GREAT) der auf dem Flugzeugobservatorium Stratospheric Observatory For Infrared Astronomy (SOFIA) zum Einsatz kommen wird. Für den Aufbau des LOs wurde auf eine Kombination zweier THz-Strahlungsquellen bestehend aus einem Rückwärtswellenoszillator (Backward-Wave Oscillator, BWO) und einem Frequenzverdreifacher zurückgegriffen. Dieser Ansatz erforderte die Entwicklung einer astigmatisch-abbildenden Submillimeteroptik, um die Leistungsankopplung zwischen BWO und Frequenzverdreifacher zu verbessern...
    Description: thesis
    Keywords: 522 ; 550 ; TBG 000 ; Infrarot-Astronomie
    Language: German
    Type: monograph , publishedVersion
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    The central parsec of the milky way at 3.8 micrometer (2010)
    Univ. Köln
    Details
    Publication Date: 2021-03-29
    Description: The central part of the Milky Way is a unique environment where an interplay of different astrophysical phenomena can be studied, starting from the physics of the interstellar medium, stellar physics and star formation, to high energetic processes associated with the accretion onto the supermassive black hole Sgr A*. In this thesis I focus onto the central parsec of the Milky Way, observed at 3.8 micrometer (L'-band) during several epochs from 2002 to 2007. This particular wavelength is interesting because one can observe the (very dense) Galactic stellar nuclear cluster, as well as the thermal component of the interstellar medium which is not visible at shorter near-infrared wavelengths. Our images revealed a high number of very narrow filamentary structures associated with the streamers of gas and dust (called mini-spiral), and sometimes also with stars. We also detected several stellar sources that are barely observable at shorter wavelengths, but well defined in the dust-dominated L'-band. The goal of this thesis was to use multi-epoch observations in order to measure motions of filamentary structures, as well as of those very red stars. The proper motion analysis allows us to come a step further in understanding the real nature of these enigmatic sources. The high-resolution observations were obtained with the NAOS/CONICA Adaptive Optics system at the ESO Very Large Telescope at Paranal, Chile. The first part of the thesis deals with the narrow dust filaments. The analysis of their morphology and proper motions shows that they are (i) probably not due to a projectional effect and (ii) are influenced by other forces than just the gravitational force of the central black hole...
    Description: thesis
    Keywords: 523 ; 550 ; TIE 662 ; Struktur der Milchstrasse {Astronomie}
    Language: German
    Type: monograph , publishedVersion
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    The near infrared activity of Sagittarius A* (2010)
    Univ. Köln
    Details
    Publication Date: 2021-03-29
    Description: The meaning of my thesis was to obtain new insights about the supermassive Black Hole in the center of our Milky Way and its accretion flow. The non-thermal radio, X-ray, and near-infrared source Sagittarius A* (Sgr A*) is the electro-magnetic manifestation of the Black Hole. Sgr A* is a unique source to study the accretion onto a very massive compact object as it is the closest galactic nucleus. For this work I conducted observations as well as theoretical computations. The near-infrared camera CONICA in combination with the adaptive optics device NAOS at ESO's Very Large Telescope in Chile were used for the observations. The goal of our group was in particular to find further evidence for a quasi-periodic signal of ~17 minutes in radiation outbursts from Sgr A* that has been reported for the first time in 2003. The radiation outbursts - most often termed `flares' - are periods of ~50 - 130 minutes in which the flux of Sgr A* in the near-infrared rises up to a factor of ten. The quasi-periodic sub-structure thereby manifests itself as sub-flares with a constant separation superimposed on the larger, underlying flare. In 2005 and 2006 we were able to detect a significant periodicity, hence the previous findings are supported ...
    Description: thesis
    Keywords: 522 ; TBG 000 ; THK 000 ; Infrarot-Astronomie ; Spektren und Spektroskopie von Sternen {Astronomie}
    Language: English
    Type: monograph , publishedVersion
    Format: 125 S.
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    Broadband IF circuits for superconductor isolator superconductor (SIS) mixers for the Heterodyne Instrument for the far infrared on the Herschel Space Observatory and for sideband separating mixers (2010)
    Univ. Köln
    Details
    Publication Date: 2021-03-29
    Description: This thesis describes the development and manufacturing of the IF circuits for two different heterodyne receivers used for sub-mm radio astronomy. The first project is the broadband 4-8 GHz IF circuitry for the mixer units for band 2 of the Heterodyne Instrument for the Far Infrared (HIFI). This instrument will be operating onboard of ESA’s Herschel space observatory. The band 2 mixer units for HIFI, built by KOSMA, implement low noise SIS mixers in a very compact, modular design. The complete IF path in the mixer units consist of the mixer block (with the SIS mixer chip) and the bias-T, which is needed to apply a bias voltage to the SIS-junction and to extract the IF signal. The detailed investigation of the IF performance of the mixer block must consider the geometric capacitances of the SIS-junction and the tuning structure as well as the inductance of the bond wires used to establish the contact between the mixer chip and the SMA output connector. The calculations presented in this thesis show that the design can be used for IF frequencies up to 12 GHz. The bias-T, which is implemented in the mixer unit, is a dedicated, new development with high performance and high reliability complying with the special requirements for a spaceborne instrument. These include the survival under high mechanical stress such as vibration during the launch and extensive thermal cycling to cryogenic temperatures during the tests of the mixer unit and the instrument.
    Description: thesis
    Keywords: 522 ; 550 ; TBC 000 ; TCE 230 ; Radioastronomie ; Weltraumbasierte UV-, Optische und Infrarotteleskope {Astronomische Instrumente}
    Language: English
    Type: monograph , publishedVersion
    Format: 173 S.
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    Studying martian dust devils by applying pattern recognition algorithms to multi-mission camera images (2010)
    Univ. Köln
    Details
    Publication Date: 2021-03-29
    Description: A pattern recognition and classification software was developed to detect dust devils automatically in surface images from Mars. The amount of images taken by spacecraft orbiting Mars is increasing continuously and the expenditure of time is too high to search every image for spatially and temporally highly variable features like dust devils. The pattern recognition method was therefore used to conduct a completely new kind of search for dust devils. Images from the three different Mars missions Viking, Mars Global Surveyor and Mars Express can be processed and for the first time automatically scanned for the desired objects. Viking images including dust devils were used as the database to filter unique dust devil features and the derived parameters built the feature vector. Various Classification methods have been tested resulting in a two-layer perceptron (neural network) as the best classifier. Necessary adjustments and increments complete the software so that it can be applied to Mars Global Surveyor Mars Orbiter Camera (MOC), Mars Express High Resolution Stereo Camera (HRSC) and probably coming images from future missions. It was shown that the standard dust devil is filtered and correctly classified. The two main features, the bright spot representing the dust column and the shadow, must be filterable from the background. Crater rims and hills are the most false-positive objects...
    Description: thesis
    Keywords: 523 ; TGG 545 ; TGG 515 ; TCM 000 ; TCE 380 ; Marsoberfläche {Astronomie} ; Marsbeobachtung, Raumflüge zum Mars {Astronomie} ; Mathematische und EDV-Verfahren {Astronomie} ; CCD, Photodetektoren {Astronomische Instrumente}
    Language: English
    Type: monograph , publishedVersion
    Format: 158 S.
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    Dissecting the host galaxies of active galactic nuclei at high angular resolution (2010)
    Univ. Köln
    Details
    Publication Date: 2021-03-29
    Description: The work presented here is concerned with issues related to the interplay of galaxy structure and the accretion phenomenon onto supermassive black holes (SMBH), i.e. active galactic nuclei (AGN). There is statistical evidence for a coevolution of SMBHs and the galaxy bulges they reside in. The detailed knowledge of the involved physical processes, however, is still far from being satisfactory. In order to test and improve theoretical models of how this coevolution is arising, high angular resolution observations of the host galaxies of AGN are necessary. Imaging and spectroscopy of the innermost region of galaxies have the power to reveal information on the structure, the chemical composition, and the dynamics of stars and gas in the presence of an SMBH, and allow us to separate energetic signatures related either to star formation or to the accretion onto the SMBH. Considering such observations over cosmological distances (redshifts) -- i.e. looking into the past because of the finite light-travel time -- we are also able to assess evolutionary effects on the beforementioned properties ...
    Description: thesis
    Keywords: 523 ; TIE 400 ; Spektren und Leuchtkraft von Sternsystemen {Astronomie}
    Language: English
    Type: monograph , publishedVersion
    Format: 174 S.
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    Cophasing LINC-NIRVANA and molecular gas in low-luminosity QSO host and cluster galaxies (2010)
    Univ. Köln
    Details
    Publication Date: 2021-03-29
    Description: This thesis consists of two parts. The first part reports on the development of a fringe tracking system for LINC-NIRVANA, the near-infrared homothetic imaging camera for the Large Binocular Telescope (LBT). LINC-NIRVANA allows for a coherent combination of the light entering the two primary mirrors. The fringe pattern in the focal plane is required to be stable in time to preserve the high spatial frequency information in long exposure images. Atmospheric differential piston causes the position of the fringes to change with time. A fringe tracker is a servo system that measures and corrects for atmospheric differential piston in real-time. In the first part, numerical simulations of atmospheric turbulence are used to investigate the problem of angular anisoplanatism of differential piston. The fringe tracking concept and the top-level requirements are introduced, followed by a presentation of the mechanical design of the system. This design includes a solution for a device that is capable of positioning a detector with high precision within a cryogenic environment. A fitting algorithm determines the amount of differential piston in the point-spread function of a reference target. The performance of this algorithm under different signal-to-noise conditions is investigated. First polychromatic fringes obtained with a testbed interferometer conclude the first part ...
    Description: thesis
    Keywords: 523 ; TII 500 ; Emissionsnebel {Astronomie: Interstellare Materie}
    Language: English
    Type: monograph , publishedVersion
    Format: 186 S.
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    Near- and mid-infrared studies of the galactic center and Sagittarius A* (2010)
    Univ. Köln
    Details
    Publication Date: 2021-03-29
    Description: The focus of this thesis lies on the analysis and interpretation of near- and mid-infrared images of the Galactic center, with a view to improving the understanding of this region, especially at longer wavelengths. Multi-band (H, K, L and M, i.e. 1.6, 2.1, 3.78 and 4.66æm) photometry of images with a large field of view results in a new L-band calibration which eliminates anomalous color effects found in previous surveys of the Galactic center stellar cluster. The color data obtained indicates that the average extinction toward the region containing the Northern Arm and Sgr A* is lower than previously assumed, confirming the findings of Scoville et al. (2003). The stellar population of the inner few arcseconds is compared to that situated up to approximately 0.5 arcminutes out from the position of Sgr A*, revealing that the extinction does not increase significantly over the entire field of view of the ISAAC instrument (i.e. 70" x 70"). Using the large number of sources (over 500), the M-band extinction is calculated from the average L-M colors, resulting in a higher value than that of the "standard" extinction law of Rieke & Lebofsky (1985). The L-M color is shown to be a useful diagnostic tool in distinguishing hot and cool stars, when more precise methods (e.g. spectroscopy) are not available. The unusual morphology of the bright mid-infrared source IRS 3 is also discussed...
    Description: thesis
    Keywords: 522.683 ; 550 ; TBG 000 ; TIE 400 ; Infrarot-Astronomie ; Spektren und Leuchtkraft von Sternsystemen {Astronomie}
    Language: English
    Type: monograph , publishedVersion
    Format: 117 S.
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    Waveguide heterodyne mixers at THz-frequencies (2010)
    Univ. Köln
    Details
    Publication Date: 2021-03-29
    Description: Design and performance of waveguide mixers at 1.4 THz and 1.9 THz based on NbTiN phonon-cooled hot electron bolometers (HEB) fabricated on a 2 æm thick Si_3N_4 membrane. The membrane is bonded to a silicon frame in the mixer block using a flip chip process. Simulated RF coupling is compared with experimental results, showing good agreement. Receiver noise temperature measurements show uncorrected values of 1600 K at 1.4 THz and 2100 K at 1.9 THz, both at 1.5 GHz intermediate frequency. Device cooling on the membrane seems not to be problematic. The mixers are used in receivers for SOFIA (GREAT & CONDOR) and APEX (CONDOR).
    Description: thesis
    Keywords: 523 ; TBG 000 ; Infrarot-Astronomie
    Language: German
    Type: monograph , publishedVersion
    Format: 153 S.
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    Aufbau, Optimierung und Charakterisierung der THz-Optik für GREAT auf SOFIA (2010)
    Univ. Köln
    Details
    Publication Date: 2021-03-29
    Description: Sternentstehung findet im dichten Teil der Molekülwolken des interstellaren Mediums statt. In diesen Gebieten werden die ablaufenden physikalischen und chemischen Prozesse maßgeblich von der Wechselwirkung zwischen der Materie und dem Strahlungsfeld eingebetteter junger Sterne bestimmt. Konsequenz der Bestrahlung mit FUV-Photonen (6eV〈E〈13.6eV) ist die Aufheizung des Staubes und des atomaren bzw. molekularen Gases. Dabei fÓhrt die auf StaubkÒrnern umgesetzte Photonenenergie zur Emission von IR-Kontinuumsstrahlung, wohingegen die vom atomaren bzw. molekularen Gas aufgenommene Energie zu einer Anregung charakteristischer ÃbergÑnge im submm-Bereich fÓhrt. Beobachtbar sind astronomisch relevante Linien wie z.B. CO-RotationsÓbergÑnge, aber auch starke Linienemissionen von HyperfeinstrukturÓbergÑngen von z.B. [OI] und [CII], die im THz-Bereich liegen. Die Verteilung und die IntensitÑten lassen sich mit gÑngigen Modellen Óber so genannte Photonen-dominierte Regionen beschreiben und liefern wichtige Informationen fÓr unser VerstÑndnis Óber z.B. Sternentstehungsgebiete. Mit dem German REceiver for Astronomy at THz-Frequencies (GREAT), einem Einpixel-HeterodynempfÑnger fÓr zwei Frequenzen, wird der Wissenschaft der Zugang zu diesen Linien spektral hochaufgelÒst (R〉10^6) ermÒglicht. Dabei ist zu beachten, dass Frequenzen im Bereich von 1-10THz erdgebunden aufgrund der Absorption des atmosphÑrischen Wassersdampfs nicht beobachtbar sind.
    Description: thesis
    Keywords: 522 ; TJI 000 ; TBG 000 ; Werkstofforschung und Verfahrenstechnik im Weltraum ; Infrarot-Astronomie
    Language: German
    Type: monograph , publishedVersion
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    Entwicklung eines Laser-Seitenband-Spektrometers für extrem breitbandige Frequenzanalyse (2010)
    Univ. Köln
    Details
    Publication Date: 2021-03-29
    Description: Sowohl in der Radioastronomie als auch in der Atmosphärenforschung gibt es einen Bedarf für breitbandige Spektrometer mit einer Bandbreite von bis zu 10 GHz und einer moderaten Auflösung. In der Radioastronomie wurde durch die stete Weiterentwicklung der Heterodynempfangssysteme der THz-Bereich für die Beobachtung zugänglich. Dies erfordert bei zahlreichen Beobachtungen, z.B. des galaktischen Zentrums, breitbandige Spektrometer, da die Geschwindigkeitsverteilung von Molekül- und Atomlinien in diesen turbulenten Gebieten sehr hoch ist. Die Auflösung des Spektrometers kann dabei in einen Bereich von 50-100 MHz liegen. Auch in der Atmosphärenforschung werden breitbandige Spektrometer benötigt, um die vollständige Information aus den Flügeln der druckverbreiterten Linienprofile zu gewinnen. Ziel dieser Arbeit war es daher ein Spektrometer zu entwickeln, das die Möglichkeit einer breitbandigen Frequenzanalyse bietet. Dies wird durch die Modulation eines Lasers mit einem externen Phasenmodulator möglich. Der Phasenmodulator kann das Laserlicht mit Frequenzen über 10 GHz modulieren. Zur Frequenzanalyse der so erzeugten Seitenbänder dient ein Fabry-Perot Etalon. Durch die Ausleuchtung des Etalons mit einer Zylinderlinse konnte erreicht werden, dass das vom Etalon erzeugte Ringsystem auf eine Zeile transformiert wird. Dies ermöglicht eine effiziente Ausnutzung des Signallichts. Um die Eigenschaften des in dieser Arbeit entwickelten Spektrometers zu charakterisieren und die Ausleuchtung des Etalons zu optimieren wurde ein Simulationsprogramm entwickelt. Mit Hilfe der Simulation ist es möglich eine Aussage über die Mindestgröße der Apertur des Etalons zu treffen, um die "walk-off" Verluste zu reduzieren. Es konnte zudem an Hand der Simulation gezeigt werden, welchen Einfluss die Ausleuchtung des Etalons auf die Auflösung und Intensitätsverteilung über das gesamte Band hat.
    Description: thesis
    Keywords: 523 ; TCE 320 ; TUD 000 ; Photometer, Polarimeter, spektroskopische Instrumente {Astronomische Instrumente} ; Meteorologische Instrumente
    Language: German
    Type: monograph , publishedVersion
    Format: 97 S.
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    Astrophysical phenomena related to supermassive black holes (2010)
    Univ. Köln
    Details
    Publication Date: 2021-03-29
    Description: All projects aim at pushing the limits of our knowledge about the interaction between a galaxy and a supermassive black hole (SMBH) at its center. The development of a new instrument can be as valuable as combining different datasets. I follow both approaches and developed projects which deal with new instrumentation and telescope technology, combine datasets from different wavelengths and resolutions, and incorporate recent theoretical models and predictions, which can be verified empirically. The first two of the six chapters compile astrophysical and technical background of the individual projects, which are presented in the following four chapters. While the first project (Chapter 3) deals with observations of the innermost parsec of our Galaxy, Chapter 4 presents data of the inner kpc of an active galaxy. The subjects of Chapters 5 and 6 are very luminous AGN/host systems, so-called QSOs. Whereas Chapter 5 presents global, spatially unresolved properties of SMBH/host systems, the radio jet, analyzed in the final Chapter 6, combines all size scales. It is investigated from close to its origin out to several kpc. The accretion onto the black hole of the Milky Way (Chapter 3) is extremely inefficient and the SMBH possibly interacts dominantly via tidal forces only. The next discussed system (Chapter 4) is the prototype of moderately luminous Seyfert 2 AGN, NGC 1068. Here a strong local influence of the nuclear X-ray radiation is observed. Chapter 5 deals with the possible global importance of radiative interaction between highly luminous QSO AGN and the host. The radio jet in Chapte 6 definitely shows signs of interaction with the matter of its host several kpc away from the nucleus. Chapters 3-6 include a dedicated introductory and a conclusive section, which put the results obtained in the larger astrophysical context of the observation ...
    Description: thesis
    Keywords: 523 ; TEG 440 ; TIE 662 ; Schwarze Löcher {Astronomie: Kosmogonie} ; Struktur der Milchstrasse {Astronomie}
    Language: English
    Type: monograph , publishedVersion
    Format: 147 S.
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    Time varying interaction of Europa's atmosphere ionosphere and its conducting ocean with the Jovian magnetosphere (2010)
    Univ. Köln
    Details
    Publication Date: 2021-03-29
    Description: A time-dependent 3D magnetohydrodynamic (MHD) model has been developed to investigate the temporal periodic interaction between Europa and the Jovian magnetosphere. The temporal variations are caused by the periodic variations of the magnetospheric plasma at Europa. As a new feature compared to existing stationary models, periodic induced magnetic fields, caused by electromagnetic induction in a potential subsurface ocean, are included. The MHD-flow problem and the internal induction problem are solved simultaneously by making use of the periodicity and the quasi-stationarity of the problem. The ideal MHD equations have been extended in order to account for the effects of Europa's neutral atmosphere and the internal periodic induced magnetic fields on the plasma interaction. At the beginning of this work, Galileo magnetometer data acquired on four passes by Europa were used to investigate whether a fixed permanent dipole moment is present in the interior of the moon in addition to the induced dipole moment previously identified. We thereby confirm the presence of an inductive response and find that the dipole coefficients of the constant intrinsic field contribute at best in a very minor way to the magnetic field. The induced magnetic fields caused by the time variable plasma interaction are calculated in an interactive process...
    Description: thesis
    Keywords: 523.45 ; 550 ; TGG 605 ; Jupitermonde {Astronomie}
    Language: English
    Type: monograph , publishedVersion
    Format: 161 S.
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    Superconducting hot electron bolometers on silicon nitride membranes for terahertz waveguide mixers (2010)
    Univ. Köln
    Details
    Publication Date: 2021-03-29
    Description: The topic of this work is the development of Hot Electron Bolometer (HEB) mixers on freestanding membrane substrates for terahertz high resolution heterodyne receiver systems. The radio astronomy in the THz frequency spectrum is still in the beginning. At present much effort is put into the development of novel telescopes as well as in detector technologies. This work focuses on the development of THz waveguide detectors with superconducting Hot Electron Bolometer (HEB) mixers. These are primarily aimed for the use in the airborne Stratospheric Observatory For Infrared Astronomy (SOFIA) (1.9 THz) and the Atacama Pathfinder EXperiment (APEX) telescope (1.4 THz) in northern Chile ...
    Description: thesis
    Keywords: 523 ; TBC 000 ; Radioastronomie
    Language: English
    Type: monograph , publishedVersion
    Format: 169 S.
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    Palaeodiversity, palaeobiology and palaeoecology of middle devonian crinoids from the Eifel type region (2010)
    Univ. Köln
    Details
    Publication Date: 2021-03-29
    Description: This doctoral thesis deals with crinoids from the Middle Devonian (U. Eifelian to L. Givetian) of the Eifel Synclines (western Rhenish Massif, Germany) and secondary with U. Eifelian to U. Givetian crinoids of the eastern Rhenish Massif. The study focuses on new recovered material and on material deposit in historical collections. Since the classic monographs of the early 19th century, crinoids are nearly unstudied in modern view. They are only periphery mentioned within the standard works Treatise on Invertebrate Paleontology and Fossil Crinoids. The Eifel has to be characterised as the global hotspot of Middle Devonian crinoids. Because of the high diversity, selected groups of each of the four occurring Palaeozoic subclasses are studied in the course of this work: 1. The subfamily Cupressocrininae (subclass Cladida); 2. the family Hexacrinitidae (subclass Camerata); 3. the genus Stylocrinus (subclass Disparida); 4. the genus Ammonicrinus (subclass Flexibilia). Altogether, four families, eight genera and 66 species are described taxonomically. 10 new species are erected newly. Based on the excellent three-dimensional preservation of the partly autochthon conserved skeletons and their ecological-/facial response, the Eifel crinoids gave important information about the palaeodiversity, palaeobiology and palaeoecology: Regeneration processes in cupressocrinitids and hexacrinitids correspond with that features defined for recent echinoderms. Because of their important functions, the regeneration of injured arms is more perfect than those of affected cups. Hexacrinites contra balanced the general smallness of the regenerative arms by an increased pinnulated surface ...
    Description: thesis
    Keywords: 560 ; VZB 121 ; VWG 600 ; VXR 000 ; Rheinisches Schiefergebirge {Paläontologie} ; Devon {Stratigraphische Paläontologie} ; Echinodermata {Paläozoologie}
    Language: German
    Type: monograph , publishedVersion
    Format: 263 S.
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    Ein temperaturabhängiges thermodynamisches Modell für das System H+ - NH_hn+4 - Na+ - SO2 -4 - NO-1hn3 - Cl- - H2O (2010)
    Univ. Köln
    Details
    Publication Date: 2017-06-09
    Description: Atmosphärische Aerosolpartikel spielen eine bedeutende Rolle in verschiedenen Fragestellungen der Luftreinhaltung. Einen wesentlichen Bestandteil ihrer Masse bilden anorganische Komponenten wie Sulfat, Ammonium und Nitrat, die in der maritimen planetaren Grenzschicht u.a. durch Natrium und Chlorid ergänzt werden. Die Wirkung eines Aerosols ist vom Phasenzustand der Partikel, ihrem Wassergehalt und der Partitionierung flüchtiger Komponenten zwischen Gas- und Partikelphase abhängig. Zur Bestimmung dieser Eigenschaften wird ein thermodynamisches Modell ...
    Description: thesis
    Keywords: VJH 200 ; Thermodynamische Prozesse, Verteilungskoeffizienten {Physikalische Geochemie}
    Language: German
    Type: monograph , publishedVersion
    Format: 282 S.
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    Die Bildung SiO2-reicher Phasen im frühen Sonnensystem (2010)
    Univ. Köln
    Details
    Publication Date: 2021-03-29
    Description: In meiner Arbeit untersuche ich die Bildung SiO2-reicher Objekte (SRO) in chondritischen Meteoriten (--〉 Chondrite). Diese Phasen werden nach den heutigen Modellen des frühen Sonnsystems nicht in diesen erwartet. Trotzdem enthalten einige kohlige Chondrite darunter insbesondere die CH-Chondrite und einige gewöhnliche Chondrite Objekte mit freiem SiO2. Die SRO habe ich mit der Elektronenstrahl-Mikrosonde und dem Sekundärionen-Massenspektrometer zur Bestimmung der chemischen Zusammensetzung, sowie mit dem Mikro-Raman Spektrometer und dem Transmissionselektronen-Mikroskop zur Bestimmung der SiO2-Polymorphie untersucht. In den kohligen Chondriten treten die SRO fast nur in den CH- und CR-Chondriten auf. Deren Population in den CH-Chondriten beträgt ~0.1 Vol.%. Die Paragenese besteht fast ausschließlich aus SiO2 und einem etwa Pyroxen-normativen Silikat. Diese beiden Phasen zeigen oftmals Entmischungsstrukturen. Diese SRO sind meist an den refraktären Elementen Ca, Al und Ti verarmt, bis zu 0.015 x CI. In gleichem Maße sind die Seltenen Erd-Elemente (SEE) verarmt und zeigen unfraktionierte, flache Muster. Das Si/Mg-Verhältnis ist stark fraktioniert, mit 3 4 x CI. Die SRO sind außerdem verarmt an volatilen Elementen, jedoch haben zwei SRO-Chondren sehr hohe Mn-Konzentrationen, und das, obwohl die CH-Chondrite die Mn-ärmsten Gesamt-Zusammensetzungen aller Chondrite haben. Eine dieser Mn-reichen Chondren enthält Pyroxen mit den höchsten, je aus einem Meteoriten berichteten Mn-Konzentrationen von 6.68 Gew.%. Das SiO2 tritt in den SRO hauptsächlich als Glas und in seinen Hoch- und Mitteltemperatur-Polymorphen Cristobalit und Tridymit auf. Die Bildung dieser SRO kann über einen zweistufigen Mechanismus verstanden werden, bei dem zuerst eine fraktionierte Kondensation die Precursor der SRO bildete, die anschließend im zweiten Schritt zu Temperaturen 〉1968 K wieder aufgeheizt wurden und danach rasch abkühlten ...
    Description: thesis
    Keywords: 523 ; TGL 600 ; TJM 000 ; VJG 221 ; Meteorite {Astronomie} ; Kosmochemie {Weltraumforschung} ; Geochemie der Chondrite
    Language: German
    Type: monograph , publishedVersion
    Format: 137 S.
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    Prozessbasierte und räumlich verteilte Modellierung der Bodenstickstoffflüsse zur Abschätzung der Auswirkungen des Klimawandels auf Stickstoffverfügbarkeit und Nitratauswaschung im Einzugsgebiet der Oberen Donau (2010)
    Univ. Köln
    Details
    Publication Date: 2021-03-29
    Description: Vor dem Hintergrund des Globalen Wandels sind räumliche und zeitliche Informationen über die Stickstoffverfügbarkeit im Boden und die Nitratauswaschung von entscheidender Bedeutung für die Entwicklung von Maßnahmen zur integrierten Bewirtschaftung der (Grund-)Wasserressourcen. Im Rahmen des Projekts GLOWA-Danube untersucht diese Arbeit die Reaktionen des Bodenstickstoffhaushalts auf Klimaänderungen im Einzugsgebiet der Oberen Donau. Als Komponente des integrativen Entscheidungsunterstützungssystems DANUBIA wurde das objektorientierte und prozessbasierte Bodenstickstoffmodell SNT auf der Grundlage des Modells CERES Maize 2.0 entwickelt. SNT bildet die wichtigsten Prozesse (Mineralisierung/Immobilisierung, Denitrifizierung, Nitrifizierung, Harnstoffhydrolyse und Nitratverlagerung) und die Dynamik von zwei mineralischen (Nitrat und Ammonium) sowie zwei organischen (frische Biomasse und Humus) Stickstoffreserven im Boden ab. Die Validierung des Modells erfolgte durch einen multikriteriellen und skalenübergreifenden Vergleich mit Messreihen, die ein breites Spektrum pedologischer und meteorologischer Bedingungen in Deutschland abdeckten. In einer Sensitivitätsanalyse wurde die Reaktivität des Modells gegenüber Eingabedaten und physikochemischen Bodenparametern bestimmt ...
    Description: thesis
    Keywords: 577.22 ; 577.145 ; VJI 000 ; VOBB 400 ; VPB 200 ; Geochemische Kreislaufmodelle ; Anorganische Bodenchemie, Anorganische Bodenbestandteile ; Deutschland {Bodenkunde}
    Language: German
    Type: monograph , publishedVersion
    Format: 216 S.
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  • 95
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    Late Quaternary environmental history of Taylor Valley, southern Victoria Land, Antarctica, reconstructed by a multidisciplinary study of lake sediments (2010)
    Univ. Köln
    Details
    Publication Date: 2021-03-29
    Description: In the unglaciated areas of Antarctica, lake sediments act as archives of the regional environmental and climatic history. In most cases, the records are restricted to the Holocene. Amongst the few exceptions are lakes in the McMurdo Dry Valleys, southern Victoria Land, which are known to have remained mostly ice-free during the Last Glacial Maximum. Within the scope of an U.S.-American-German expedition in austral summer 2002/2003, several sediment cores were recovered from the three major lakes in the Taylor Valley: lakes Fryxell, Hoare, and Bonney. In order to reconstruct the late Quaternary regional environmental and climate history, sedimentological, biogeochemical, mineralogical, and chronological investigations were conducted on the sediment sequences recovered from Lake Hoare (core Lz1020) and East Lake Bonney (core Lz1023) within the scope of this thesis. Sediment cores from Lake Hoare with a maximum length of 2.3 m mainly consist of coarse-grained material and penetrate back into the late Weichselian, when Taylor Valley was occupied by the large proglacial Lake Washburn. This lake was dammed by the advanced Ross Sea ice sheet at the valley outlet and was mainly fed by meltwater of the ice sheet. During the Pleistocene-Holocene transition, enhanced evaporation led to a significant lake level drop of Lake Washburn ...
    Description: thesis
    Keywords: 551 ; 550 ; TWC 500 ; VDI 200 ; VAU 000 ; VEY 200 ; VBN 500 ; VBL 500 ; Klimaschwankungen und Klimaänderungen im Quartär ; Quartär ; Paläolimnologie {Geologie} ; Antarktis {Geologie} ; Geochronologie einzelner Regionen im allgemeinen ; Geologische Bohrungen in einzelnen Regionen
    Language: English
    Type: monograph , publishedVersion
    Format: 121 S.
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  • 96
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    The late Quaternary environmental and climatic history of North-East Greenland, inferred from coastal lakes (2010)
    Univ. Köln
    Details
    Publication Date: 2021-03-29
    Description: Eleven lakes and ponds and three lacustrine sediment sequences from coastal East and North-East Greenland were studied for recent hydrological and phytoplankton characteristics and for palaeolimnology, respectively. The limnological survey of lakes and ponds from Store Koldewey in summer 2003 revealed cold, monomictic, thermally unstratified, alkaline and likely oligotrophic water bodies. The diatom phytoplankton, present in six lakes and dominated by four species, varied distinctly between the lakes. The results give information about the recent status of the ecology of these High Arctic freshwater bodies. The sediment sequences were investigated for their chronology, changes in physical and biogeochemical properties, macro- and microfossils, grain-size distribution and in the case of one sequence for its elemental profiles using XRF. The palaeolimnological studies address different time intervals at various temporal resolutions with particular attention to the latitudinal differences of late Quaternary climatic and environmental changes along the coast of East and North-East Greenland. The results include information about the Late Weichselian ice-front environments on southern Store Koldewey with information about the temporal and spatial evolution of the Greenland Ice Sheet margin west of the island ...
    Description: thesis
    Keywords: 551 ; 550 ; TWC 500 ; VDI 200 ; VAU 000 ; VEY 110 ; VBN 500 ; VBL 500 ; Klimaschwankungen und Klimaänderungen im Quartär ; Quartär ; Paläolimnologie {Geologie} ; Grönland {Geologie} ; Geochronologie einzelner Regionen im allgemeinen ; Geologische Bohrungen in einzelnen Regionen
    Language: English
    Type: monograph , publishedVersion
    Format: 148 S.
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  • 97
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    Karbonat- und Lignitzyklen im Ptolemais-Becken: orbitale Steuerung und suborbitale Variabilität (Spätneogen, NW-Griechenland) (2010)
    Univ. Köln
    Details
    Publication Date: 2021-03-29
    Description: Die mio-pliozänen Ablagerungen im NNW SSE streichenden Monastir-Florina-Ptolemais-Kozani/Servia-Graben beherbergen das größte zusammenhängende Braunkohlevorkommen in Bereich des Balkans. Das Becken erstreckt sich von Monastir (F.Y.R.O.M.) im Norden bis hin zur Region von Elassona im Süden (Makedonien/GR). Es umfasst eine Gesamtfläche von ca. 120 kmø. Mittlerweile werden ca. 71 % des elektrischen Energiebedarfs der Hauptstadt Athen durch die Energiegewinnung aus dem MFPK/S-G gedeckt. Diese rhythmisch entwickelten Lignitvorkommen zeigen, neben den bedeutenden wirtschaftlichen Aspekten, ein großes Potential für eine Paläoklima-Analyse des nordöstlichen mediterranen Raums. Das Neogen zeigt einen multiplen Wechsel von Kalt- und Warmzeiten mit vereinzelt deutlich höheren Temperaturen als heute an (Bradley, 1999). Die Ursachen hierfür können u.a. auf Variationen der Erdbahnparameter zurückgeführt werden, welche Schwankungen in der Insolation verursachen und somit das atmosphärisch-ozeanische System steuern. Zeitreihenanalysen belegten bereits in den 70er bis späten 90er Jahren des letzten Jahrhunderts diese Variationen innerhalb mariner (Hays et al., 1976; Imbrie & Imbrie, 1980) und kontinentaler Ablagerungen (Santarelli et al., 1988, van Vugt et al., 1998. Die Ursachen und Steuerungsprozesse dieser Variationen sind von Milankovitch (1920, 1930, 1941) eingehenst diskutiert worden ...
    Description: thesis
    Keywords: 551.69 ; 551 ; 550 ; TSF 300 ; TOT 310 ; VEF 300 ; VKB 372 ; VKB 376 ; VKB 326 ; VDI 110 ; Griechenland und griechische Inseln {Geophysik} ; Gesteinsmagnetismus {Geophysik} ; Griechenland und griechische Inseln {Geologie} ; Karbonatische Sedimentgesteine ; Organogene Sedimentgesteine ; Magnetische Stratigraphie {Sedimentologie} ; Paläogen
    Language: German
    Type: monograph , publishedVersion
    Format: 131 S.
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  • 98
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    Ozon- und Wasserdampfverteilung im polaren Strahlstrom über dem Nordatlantik (2010)
    Univ. Köln
    Details
    Publication Date: 2021-03-29
    Description: thesis
    Keywords: 551.5 ; 550 ; TVK 900 ; TYZ 100 ; Vertikale Komponenten der Luftbewegung {Meteorologie} ; Atlantischer Ozean {Meteorologie und Klimatologie}
    Language: German
    Type: monograph , publishedVersion
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  • 99
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    Geomorphometrische Analysen zur Rekonstruktion holozäner Nutzungspotentiale ausgewählter Standorte in der Western Desert (Ägypten) (2010)
    Univ. Köln
    Details
    Publication Date: 2021-03-29
    Description: Die hyperaride und weitgehend vom Menschen unveränderte Western Desert Ägyptens ist ein Hauptuntersuchungsgebiet des interdisziplinär angelegten Sonderforschungsbereichs 389 (ACACIA) und bietet somit ein ideales Feld zur Entwicklung und Prüfung neuer Methoden. In dieser Arbeit wurden erstmalig flächenhafte digitale Höheninformationen in hoher Auflösung für das Untersuchungsgebiet abgeleitet, aufbereitet und hinsichtlich ihrer Qualität und Einsatzmöglichkeiten untersucht. Dabei konnten über die Fragestellung der Arbeit hinaus weitere Einsatzmöglichkeiten zur Beantwortung geomorphologischer und geoarchäologischer Fragestellung herausgearbeitet werden. Beide Höhenmodelle (ASTER / SRTM-3) zeigen für die jeweilige Auflösung geringe Höhenfehler, sie unterscheiden sich jedoch hinsichtlich ihres nutzbaren Maßstabsbereiches. Hier konnte eine Trennung im Bereich von ca. 1:100.000 festgelegt werden. Während die SRTM-3-Daten durch ihre flächenhafte Verfügbarkeit für großräumige Fragestellungen geeignet sind, fallen die ASTER-Höhendaten in die chorische Maßstabsebene und eignen sich besonders zur Beantwortung regionaler Fragestellungen. Die abgeleiteten methodischen Ergebnisse zum Einsatz und der Überprüfung der Höhendaten können problemlos auf andere aride Räume übertragen werden. Zur Ableitung holozäner Nutzungspotentiale wurde ein offenes Modell entwickelt, das die spezielle Fragestellung aufgreift, jedoch ebenfalls mit anderen Datensets und in anderen Regionen nutzbar ist. Es beinhaltet die Verknüpfung geomorphometrischer mit anderen raumbezogenen Daten in einem statistischen Verfahren. Die kanonische Korrespondenzanalyse wurde dabei als geeignete statistische Methode vorgestellt, um ein solches Datenset zu analysieren und einen Mehrwert an Information aus den Daten abzuleiten. Für das holozäne Nutzungspotential der Western Desert konnten durch die Untersuchung zweier archäologischer Fundregionen verschiedene Erkenntnisse gewonnen werden ...
    Description: thesis
    Keywords: 910
    Language: German
    Type: monograph , publishedVersion
    Format: 197 S.
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  • 100
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    Sedimentologische und geochronologische Untersuchungen zur jungquartären Klima- und Reliefgeschichte im südlichen Kaokoland (NW-Namibia) (2010)
    Univ. Köln
    Details
    Publication Date: 2021-03-29
    Description: Mit dem Ziel der Rekonstruktion des jungquartären Klimawandels im südlichen Kaokoland (NW-Namibia) und einer daraus resultierend zu erstellenden regionalen Klimastratigraphie wurden sedimentologische und geochronologische Untersuchungen von äolischen Sandablagerungen und fluvial/aquatisch abgelagerten Beckensedimenten durchgeführt. Das Untersuchungsgebiet im nordwestlichen Namibia ist durch ein arides Klima gekennzeichnet, kann aber aufgrund der geologisch bedingten Kleinkammerung seines Reliefs in klimatische Gunst- und Ungunsträume für menschliche Besiedlung gegliedert werden. Die bislang vorliegenden Rekonstruktionen der Klimageschichte dieser Region gehen von einer seit dem Tertiär andauernden Aridität aus. Die quartäre Klimaentwicklung ist durch hygrische Fluktuationen geringer Ausprägung gekennzeichnet. Anhand der sedimentologischen und geochronologischen Ergebnisse wurde eine bis 16 700 Jahre vor heute zurückreichende Stratigraphie erarbeitet, in der Änderungen des Klimas dokumentiert sind. So sind um 8000 und um 4500 Jahre vor heute zwei feuchtere Phasen nachweisbar. Die Ergebnisse der Untersuchungen äolischer Sande belegen für die Folgezeit die seit mindestens 2000 Jahren vor heute andauernde Trockenheit mit ausgeprägter äolischer Dynamik. Die fluvial/aquatische Ablagerung der Beckensedimente endet im südlichen Kaokoland um 15 500 Jahre vor heute. Die nachfolgend einsetzende Phase äolischer Aktivität kann mit dem Aufbau der Wüstenlösse’ im nördlichen Kaokoland korreliert werden. Weiterhin wurde gezeigt, dass die feuchteren Phasen am Namib-Rand nicht die Intensität und Dauer aufweisen, wie sie östlich des Untersuchungsgebietes festgestellt wurden. Nicht zuletzt wird anhand der sedimentologischen Ergebnisse der untersuchten Dünen eine bisher nicht beschriebene Genese von Pseudoechodünen’ aus Sandrampen aufgezeigt.
    Description: thesis
    Keywords: 551.79 ; 551
    Language: German
    Type: monograph , publishedVersion
    Format: 176 S.
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