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  • Wiley-Blackwell  (80,603)
  • 2005-2009  (46)
  • 1980-1984  (43,083)
  • 1965-1969  (26,891)
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  • 1
    Publication Date: 2021-06-22
    Description: In this work, we analyse continuous measurements of microseisms to assess the reliability of the fundamental resonance frequency estimated by means of the horizontal-to-vertical (H/V) spectral ratio within the 0.1–1 Hz frequency range, using short-period sensors (natural period of 1 s). We apply the H/V technique to recordings of stations installed in two alluvial basins with different sedimentary cover thicknesses—the Lower Rhine Embayment (Germany) and the Gubbio Plain (Central Italy). The spectral ratios are estimated over the time–frequency domain, and we discuss the reliability of the results considering both the variability of the microseism activity and the amplitude of the instrumental noise. We show that microseisms measured by short period sensors allow the retrieval of fundamental resonance frequencies greater than about 0.1–0.2 Hz, with this lower frequency bound depending on the relative amplitude of themicroseism signal and the self-noise of the instruments. In particular,we show an examplewhere the considered short-period sensor is connected to instruments characterized by an instrumental noise level which allows detecting only fundamental frequencies greater than about 0.4 Hz. Since the frequency at which the peak of the H/V spectral ratio is biased depends upon the seismic signal-to-instrument noise ratio, the power spectral amplitude of instrumental self-noise should be always considered when interpreting the frequency of the peak as the fundamental resonance frequency of the investigated site.
    Description: Published
    Description: 175-184
    Description: 4.1. Metodologie sismologiche per l'ingegneria sismica
    Description: JCR Journal
    Description: open
    Keywords: site effects ; fourier analysis ; 04. Solid Earth::04.06. Seismology::04.06.01. Earthquake faults: properties and evolution
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 2
    Publication Date: 2017-04-04
    Description: Geochemical investigations have shown that there is a considerable inflow of gas into both crater lakes of Monticchio, Southern Italy. These lakes are located in two maars that formed 140 000 years ago during Mt. Vulture volcano s last eruptive activity. Isotopic analyses suggest that CO2 and helium are of magmatic origin; the latter displays 3He ⁄ 4He isotope ratios similar to those measured in olivines of the maar ejecta. In spite of the fact that the amount of dissolved gases in the water is less than that found in Lake Nyos (Cameroon), both the results obtained and the historical reports studied indicate that these crater lakes could be highly hazardous sites, even though they are located in a region currently considered inactive. This could be of special significance in very popular tourist areas such as the Monticchio lakes, which are visited by about 30 000 people throughout the summer, for the most part on Sundays.
    Description: Published
    Description: 83-87
    Description: 2.4. TTC - Laboratori di geochimica dei fluidi
    Description: JCR Journal
    Description: reserved
    Keywords: volcanic gases ; gas hazard ; crater lakes ; 04. Solid Earth::04.04. Geology::04.04.12. Fluid Geochemistry ; 04. Solid Earth::04.08. Volcanology::04.08.01. Gases ; 04. Solid Earth::04.08. Volcanology::04.08.08. Volcanic risk
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 3
    Publication Date: 2017-04-04
    Description: On 2009 April 6, the Central Apennines were hit by an Mw = 6.3 earthquake. The region had been shaken since 2008 October by seismic activity that culminated in two foreshocks with Mw 〉 4, 1 week and a few hours before the main shock. We computed seismic moment tensors for 26 events with Mw between 3.9 and 6.3, using the Regional Centroid Moment Tensor (RCMT) scheme. Most of these source parameters have been computed within 1 hr after the earthquake and rapidly revised successively. The focal mechanisms are all extensional, with a variable and sometimes significant strike-slip component. This geometry agrees with the NE–SW extensional deformation of the Apennines, known from previous seismic and geodetic observations. Events group into three clusters. Those located in the southern area have larger centroid depths and a wider distribution of T-axis directions. These differences suggest that towards south a different fault systemwas activated with respect to the SW-dipping normal faults beneath L’Aquila and more to the north.
    Description: In press
    Description: 1.1. TTC - Monitoraggio sismico del territorio nazionale
    Description: JCR Journal
    Description: open
    Keywords: moment tensor ; seismotectonics ; L'Aquila ; 04. Solid Earth::04.07. Tectonophysics::04.07.04. Plate boundaries, motion, and tectonics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 4
    Publication Date: 2017-04-04
    Description: The strong motion data of 2009 April 6 L’Aquila (Central Italy) earthquake (Mw = 6.3) and of 12 aftershocks (4.1 ≤ Mw ≤ 5.6) recorded by 56 stations of the Italian strong motion network are spectrally analysed to estimate the source parameters, the seismic attenuation, and the site amplification effects. The obtained source spectra for S wave have stress drop values ranging from 2.4 to 16.8 MPa, being the stress drop of the main shock equal to 9.2 MPa. The spectral curves describing the attenuation with distance show the presence of shoulders and bumps, mainly around 50 and 150 km, as consequence of significant reflected and refracted arrivals from crustal interfaces. The attenuation in the first 50 km is well described by a quality factor equal to Q( f ) = 59 f 0.56 obtained by fixing the geometrical spreading exponent to 1. Finally, the horizontal-to-vertical spectral ratio provides unreliable estimates of local site effects for those stations showing large amplifications over the vertical component of motion.
    Description: Published
    Description: 1573–1579
    Description: 4.1. Metodologie sismologiche per l'ingegneria sismica
    Description: JCR Journal
    Description: open
    Keywords: Generalized inversion ; strong-motion ; 04. Solid Earth::04.06. Seismology::04.06.04. Ground motion
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 5
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    Wiley-Blackwell
    In:  Journal of Zoology, 179 (3). pp. 291-295.
    Publication Date: 2020-07-17
    Description: The cartilaginous tubercles of the mantle of the squid Cranchia scabra have been examined with the scanning electron microscope. Some tubercles are small, simple nodules whereas others are large with a complex Maltese cross form. The varying shapes and sizes probably represent a developmental sequence. The possible role of the tubercles is discussed.
    Type: Article , PeerReviewed
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  • 6
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    Wiley-Blackwell
    In:  Journal of Quaternary Science, 23 (1). pp. 3-20.
    Publication Date: 2017-04-06
    Description: Investigations indicate that the Iceland Ice Sheet was reduced in size during MIS 3 but readvanced to the shelf break at the LGM. Retreat occurred very rapidly around 15 k–16 k cal. yr BP. By contrast, the margin of the ice sheet on the East Greenland shelf, north of the Denmark Strait, was at or close to the shelf break during MIS 3 and 2 and retreat starting ∼17 k cal. yr BP. Quantitative X-ray diffraction analysis of the 〈2 mm sediment fraction was undertaken on 161 samples from Iceland and East Greenland diamictons, and from cores on the slopes and margins of the Denmark Strait. Weight% mineralogical data are used in a principal component analysis to differentiate sediments derived from the two margins. The first two PC axes explain 52% of the variance. These associations are used to characterise sediments as being affiliated with (a) Iceland, (b) East Greenland or (c) mixed. The contribution from Iceland becomes prominent during MIS 2. The extensive outcrop of early Tertiary basalts on East Greenland between 68° and 71° N is an alternative source for basaltic clasts and North Atlantic sediments with εNd(0) values close to ±0.
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  • 7
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    Wiley-Blackwell
    In:  Journal of Quaternary Science, 25 (5). pp. 633-650.
    Publication Date: 2017-12-19
    Description: Two cores were recovered in the southeastern part of Lake Shkodra (Montenegro and Albania) and sampled for identification of tephra layers. The first core (SK13, 7.8 m long) was recovered from a water depth of 7 m, while the second core (SK19, 5.8 m long) was recovered close to the present-day shoreline (water depth of 2 m). Magnetic susceptibility investigations show generally low values with some peaks that in some cases are related to tephra layers. Naked-eye inspection of the cores allowed the identification of four tephra layers in core SK13 and five tephra layers in core SK19. Major element analyses on glass shards and mineral phases allowed correlation of the tephra layers between the two cores, and their attribution to six different Holocene explosive eruptions of southern Italy volcanoes. Two tephra layers have under-saturated composition of glass shards (foiditic and phonolitic) and were correlated to the AD 472 and the Avellino (ca. 3.9 cal. ka BP) eruptions of Somma-Vesuvius. One tephra layer has benmoreitic composition and was correlated to the FL eruption of Mount Etna (ca. 3.4 cal. ka BP). The other three tephra layers have trachytic composition and were correlated to Astroni (ca. 4.2 cal. ka BP), Agnano Monte Spina (ca. 4.5 cal. ka BP) and Agnano Pomici Principali (ca. 12.3 cal. ka BP) eruptions of Campi Flegrei. The ages of tephra layers are in broad agreement with eight 14C accelerator mass spectrometric measurements carried out on plant remains and charcoal from the lake sediments at different depths along the two cores. The recognition of distal tephra layers from Italian volcanoes allowed the physical link of the Holocene archive of Lake Shkodra to other archives located in the central Mediterranean area and the Balkans (i.e. Lake Ohrid). Five of the recognised tephra layers were recognised for the first time in the Balkans area, and this has relevance for volcanic hazard assessment and for ash dispersal forecasting in case of renewed explosive activity from some of the southern Italy volcanoes. Copyright © 2009 John Wiley & Sons, Ltd.
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  • 8
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    Wiley-Blackwell
    In:  Journal of Quaternary Science, 24 (5). pp. 437-449.
    Publication Date: 2018-05-15
    Description: This paper presents a temperature reconstruction of the past 1000 years for Central Europe, based on chronological records. The advantages and limitations of this hermeneutic, text-based approach are discussed and the statistic methodology is introduced. Historical documents represent direct observation of weather and atmospheric conditions with highest temporal resolution available and precise dating. A major advantage of these extensive data is that they allow the reconstruction of large numbers of variables such as winter temperature, precipitation, pressure patterns or climate extremes as well as floods or storms. Within this hermeneutic climatological research approach, even human impacts and social dimensions of climate development can be examined. In order to quantify the historical information, statistical methods are applied, based on an index approach.
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  • 9
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    Wiley-Blackwell
    In:  Journal of Zoology, 170 (4). pp. 451-462.
    Publication Date: 2020-07-17
    Description: The dry weight and the crest length of the upper and lower beak, the length of the radula ribbon, the average width of the base of the six proximal and distal rachidian teeth as well as the total number of these teeth have all been related to the live body weight of octopuses between 1.1 and 4440 g. From any one of these parameters it is possible to estimate the size and approximate age of the animal.
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  • 10
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    Wiley-Blackwell
    In:  Journal of Zoology, 181 (4). pp. 527-559.
    Publication Date: 2020-07-17
    Description: Features of the brain of this oceanic squid have been investigated and related, as far as possible, to its habits and mode of life. The body and arms are much vacuolated for buoyancy and the animal probably lives with the head upwards. The very long whip-like tentacles are not vacuolated and perhaps hang downwards. They are covered by numerous minute pedunculated suckers, perhaps providing a sticky surface. A special nerve running outside the brain carries signals from the arms and tentacles to the magnocellular lobe, which is very large and of complex structure. However, there are no giant cells and the mantle is weak. Propulsion is mainly by the large fins, which are controlled from the magnocellular lobe, presumably using the information from the arms and tentacles.
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  • 11
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    Wiley-Blackwell
    In:  Marine Ecology, 28 (1). pp. 152-159.
    Publication Date: 2020-07-14
    Description: Meiobenthos densities and higher taxon composition were studied in an active gas seepage area at depths from 182 to 252 m in the submarine Dnieper Canyon located in the northwestern part of the Black Sea. The meiobenthos was represented by Ciliata, Foraminifera, Nematoda, Polychaeta, Bivalvia, Gastropoda, Amphipoda, and Acarina. Also present in the sediment samples were juvenile stages of Copepoda and Cladocera which may be of planktonic origin. Nematoda and Foraminifera were the dominant groups. The abundance of the meiobenthos varied between 2397 and 52,593 ind.·m−2. Maximum densities of Nematoda and Foraminifera were recorded in the upper sediment layer of a permanent H2S zone at depths from 220 to 250 m. This dense concentration of meiobenthos was found in an area where intense methane seeps were covered by methane-oxidizing microbial mats. Results suggest that methane and its microbial oxidation products are the factors responsible for the presence of a highly sulfidic and biologically productive zone characterized by specially adapted benthic groups. At the same time, an inverse correlation was found between meiofauna densities and methane concentrations in the uppermost sediment layers. The hypothesis is that the concentration of Nematoda and Foraminifera within the areas enriched with methane is an ecological compromise between the food requirements of these organisms and their adaptations to the toxic H2S.
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  • 12
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    Wiley-Blackwell
    In:  Journal of Zoology, 158 (4). pp. 475-483.
    Publication Date: 2020-07-17
    Description: An automatic food dispenser was designed for use with Octopus vulgaris Lamarck. One live crab was delivered each time the octopus pulled a white shape attached to the dispenser. The apparatus provided a continuous record of the time and frequency of feeding over periods of up to 15 days.
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  • 13
    Publication Date: 2017-12-19
    Description: This paper presents an event stratigraphy based on data documenting the history of vegetation cover, lake-level changes and fire frequency, as well as volcanic eruptions, over the Last Glacial–early Holocene transition from a terrestrial sediment sequence recovered at Lake Accesa in Tuscany (north-central Italy). On the basis of an age–depth model inferred from 13 radiocarbon dates and six tephra horizons, the Oldest Dryas–Bølling warming event was dated to ca. 14 560 cal. yr BP and the Younger Dryas event to ca. 12 700–11 650 cal. yr BP. Four sub-millennial scale cooling phases were recognised from pollen data at ca. 14 300–14 200, 13 900–13 700, 13 400–13 100 and 11 350–11 150 cal. yr BP. The last three may be Mediterranean equivalents to the Older Dryas (GI-1d), Intra-Allerød (GI-1b) and Preboreal Oscillation (PBO) cooling events defined from the GRIP ice-core and indicate strong climatic linkages between the North Atlantic and Mediterranean areas during the last Termination. The first may correspond to Intra-Bølling cold oscillations registered by various palaeoclimatic records in the North Atlantic region. The lake-level record shows that the sub-millennial scale climatic oscillations which punctuated the last deglaciation were associated in central Italy with different successive patterns of hydrological changes from the Bølling warming to the 8.2 ka cold reversal. Copyright © 2006 John Wiley & Sons, Ltd.
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  • 14
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    Wiley-Blackwell
    In:  Journal of Zoology, 188 (1). pp. 53-67.
    Publication Date: 2020-07-17
    Description: The movements of the isolated buccal mass of Octopus vulgaris have been investigated. The beaks undergo rhythmic cycles of activity in the absence of applied stimulation and after electrical stimulation of the inter-buccal connective. Initial opening, closing, retraction and re-opening phases of movement are described. This cycle of movements is taken to resemble those in the intact animal. Anatomical and electrical evidence identifies the superior mandibular muscle as being partly responsible for the closing and retraction phases of movement. The inferior buccal ganglion determines the sequence of these buccal movements, but modification by sensory feed-back from the musculature is also implied. The preparation will allow a closer comparison of the control of movement in cephalopods and gastropods.
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  • 15
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    Wiley-Blackwell
    In:  Journal of Zoology, 179 (1). pp. 19-83.
    Publication Date: 2020-07-17
    Description: Taonius megalops is a neutrally buoyant oceanic squid, very different in form when young and old. The young, has a round, sac-like mantle and relatively long tentacles, while the adult has an elongated cone-like mantle and relatively short tentacles. The transition in shape and form is gradual and has been followed in animals of between 3 and 180 mm dorsal mantle length. Statistical tests on various parameters investigated, both external and internal, revealed good correlation with the dorsal mantle length and confirmed the descriptions of the development of the chromatophores and subocular light organs with growth. It was concluded that these animals, captured in the Atlantic Ocean, all belonged to the species T. megalops Prosch 1849. This study has permitted us to suggest a tentative outline of the life cycle, although no adults were present in the material available.
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  • 16
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    Wiley-Blackwell
    In:  Journal of Zoology, 202 (3). pp. 441-447.
    Publication Date: 2020-07-17
    Description: A crab which has been captured and paralysed by an octopus but retrieved 1 1/2 min later cannot at first be pulled apart by the experimenter: 27 min later it can be dismembered easily. This demonstrates that there is external digestion when Octopus vulgaris feeds upon crabs. However, it is strictly limited at this stage to the arthrodial membrane and the musculo-skeletal attachment mechanisms as the exoskeleton separates at the joints allowing the muscles to be drawn out of the appendages. And yet, two hours after capture, pieces of crab meat are still recognizable in the octopus's stomach. The process of paralysing and cleaning a crab was noticeably slowed after the surgical removal of the radula, salivary papilla or the lateral buccal palps.
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  • 17
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    Wiley-Blackwell
    In:  Journal of Zoology, 150 (1). pp. 1-9.
    Publication Date: 2020-07-17
    Description: The changes in body weight of 12 octopuses, fed on fish or crabs, were followed under laboratory conditions for periods of 1 to 7 1/2 months. The food intake was estimated and compared with the changes in body weight of the octopuses; 25 to 55% of the total intake of food appeared to be incorporated. The range of the average increase in weight over the whole observation period of each of the animals was 1.9 to 7.7g per day (1 to 7 1/2 months); the mean value was 4.8g per day. The effect of changing the diet of small octopuses (fish or crab)was followed for four weeks but there was no evidence that alteration of the diet affected the rate of changes in body weight of animals of more than 47g initial body weight.
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  • 18
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    Wiley-Blackwell
    In:  Magnetic Resonance in Chemistry, 45 (12). pp. 1072-1075.
    Publication Date: 2020-07-15
    Description: Diosmetin, 5,7,3′-trihydroxy-4′-methoxyflavone shows chemopreventive, antimutagenic, and antiallergic effects. On the other hand, chrysoeriol, 5,7,4′-trihydroxy-3′-methoxyflavone induced nodABC-lacZ in Rhizobium meliloti. Both of them belong to hydroxymethoxy- flavones. One major difference between diosmetin and chrysoeriol is the substituted position of hydroxyl and methoxyl groups. In order to elucidate the relationships between their structures and activity, one of the first things to be done is the determination of their structures. However, most flavones occur widely in nature, and thus it is difficult to obtain in sufficient amounts from natural sources to identify their structures. Assignments of NMR data of several hydroxymethoxyflavones may help us to identify novel flavonoid compounds isolated from natural sources based on their NMR experiments. Therefore, we report here the complete assignments of 1H and 13C NMR data of 13 hydroxymethoxyflavones.
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  • 19
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    Wiley-Blackwell
    In:  Journal of Zoology, 186 (1). pp. 95-108.
    Publication Date: 2020-07-17
    Description: Reproductive mechanisms in the seven species of the thecosomatous pteropod genus Limacina are described and compared. All species are protandrous hermaphrodites. Five species–L. bulimoides, L. helicina, L. lesueuri, L. retroversa and L. trochiformis–have a similar reproductive anatomy in which the gonoduct leading from the gonad to the common genital pore functions as a seminal vesicle in the male and is elaborated into mucous and albumen glands in the female. The male system consists of a prostate gland and penis connected to the common genital pore by an external ciliary tract. All five species have a free-swimming veliger stage which hatches from free-floating egg masses. Limacina helicoides has the same reproductive anatomy but is ovoviviparous, with embryos retained in capsules in the mucous gland until they are juveniles of 50 mm in shell diameter. Limacina inflata lacks mucous and albumen glands and a penis; a spermatophore formed by the prostate gland is used in aphallic sperm transfer. This species exhibits brood protection with un-encapsulated embryos retained in the mantle cavity until they are released as veligers measuring 0067 mm in diameter. L. inflata is the most abundant of the seven species despite lowered fecundity; reasons for its ecological success are discussed.
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  • 20
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    Wiley-Blackwell
    In:  In: Biofouling. , ed. by Dürr, S. and Thomason, J. Wiley-Blackwell, Weinheim, pp. 73-86. ISBN 978-1-4051-6926-4
    Publication Date: 2012-02-23
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  • 21
    Publication Date: 2020-07-24
    Description: Myrionecta rubra, a ubiquitous planktonic ciliate, has received much attention due to its wide distribution, occurrence as a red tide organism, and unusual cryptophyte endosymbiont. Although well studied in coastal waters, M. rubra is poorly examined in the open ocean. In the Irminger Basin, North Atlantic, the abundance of M. rubra was 0–5 cells/ml, which is low compared with that found in coastal areas. Distinct patchiness (100 km) was revealed by geostatistical analysis. Multiple regression indicated there was little relationship between M. rubra abundance and a number of environmental factors, with the exception of temperature and phytoplankton biomass, which influenced abundance in the spring. We also improve on studies that indicate distinct size classes of M. rubra; we statistically recognise four significantly distinct width classes (5–16, 12–23, 18–27, 21–33 μm), which decrease in abundance with increasing size. A multinomial logistic regression revealed the main variable correlated with this size distribution was ambient nitrate concentration. Finally, we propose a hypothesis for the distribution of sizes, involving nutrients, feeding, and dividing of the endosymbiont.
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  • 22
    Publication Date: 2015-10-06
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  • 23
    Publication Date: 2020-07-27
    Description: Understanding the influence of growth temperature and carbon dioxide (CO2) on seed quality in terms of seed composition, subsequent seedling emergence and early seedling vigour is important under present and future climates. The objective of this study was to determine the combined effects of elevated temperature and CO2 during seed-filling of parent plants on seed composition, subsequent seedling emergence and seedling vigour of red kidney bean (Phaseolus vulgaris). Plants of cultivar ‘Montcalm’, were grown at daytime maximum/nighttime minimum sinusoidal temperature regimes of 28/18 and 34/24 °C at ambient CO2 (350 μmol mol−1) and at elevated CO2 (700 μmol mol−1) from emergence to maturity. Seed size and seed composition at maturity and subsequent per cent emergence, early seedling vigour (rate of development) and seedling dry matter production were measured. Elevated CO2 did not influence seed composition, emergence, or seedling vigour of seeds produced either at 28/18 or 34/24 °C. Seed produced at 34/24 °C had smaller seed size, decreased glucose concentration, but significantly increased concentrations of sucrose and raffinose compared to 28/18 °C. Elevated growth temperatures during seed production decreased the subsequent per cent emergence and seedling vigour of the seeds and seedling dry matter production of seed produced either at ambient or elevated CO2.
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  • 24
    Publication Date: 2015-09-01
    Description: Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) is a high spatial resolution analytical method which has been applied to the analysis of silicic tephras. With current instrumentation, around 30 trace elements can be determined from single glass shards as small as ∼ 40 µm, separated from tephra deposits. As a result of element fractionation during the ablation process using a 266 nm laser, a relatively complex calibration strategy is required. Nonetheless, such a strategy gives analyses which are accurate (typically within ±5%) and have an analytical precision which varies from ∼ ±2% at 100 ppm, to ∼ ±15% at 1 ppm. Detection limits for elements used in correlation and discrimination studies are well below 1 ppm. Examples of the application of trace element analysis by LA-ICP-MS in tephra studies are presented from the USA, New Zealand and the Mediterranean. Improvements in instrumental sensitivity in recent years have the potential to lower detection limits and improve analytical precision, thus allowing the analysis of smaller glass shards from more distal tephras. Laser systems operating at shorter wavelengths (e.g. 193 nm) are now more widely available, and produce a much more controllable ablation in glasses than 266 nm lasers. Crater sizes of 〈10 µm are easily achieved, and at 193 nm many of the elemental fractionation issues which mar longer wavelengths are overcome. By coupling a short wavelength laser to a modern ICP-MS it should be possible to determine the trace element composition of glass shards as small as 20 µm and, providing sample preparation issues can be overcome, the determination of the more abundant trace elements in glass shards as small as 10 µm is within instrumental capabilities. This will make it possible to chemically fingerprint tephra deposits which are far from their sources, and will greatly extend the range over which geochemical correlation of tephras can be undertaken.
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  • 25
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    Wiley-Blackwell
    In:  Journal of Fish Biology, 75 (5). pp. 960-996.
    Publication Date: 2015-09-14
    Description: Absolute barriers to dispersal are not common in marine systems, and the prevalence of planktonic larvae in marine taxa provides potential for gene flow across large geographic distances. These observations raise the fundamental question in marine evolutionary biology as to whether geographic and oceanographic barriers alone can account for the high levels of species diversity observed in marine environments such as coral reefs, or whether marine speciation also operates in the presence of gene flow between diverging populations. In this respect, the ecological hypothesis of speciation, in which reproductive isolation results from divergent or disruptive natural selection, is of particular interest because it may operate in the presence of gene flow. Although important insights into the process of ecological speciation in aquatic environments have been provided by the study of freshwater fishes, comparatively little is known about the possibility of ecological speciation in marine teleosts. In this study, the evidence consistent with different aspects of the ecological hypothesis of speciation is evaluated in marine fishes. Molecular approaches have played a critical role in the development of speciation hypotheses in marine fishes, with a role of ecology suggested by the occurrence of sister clades separated by ecological factors, rapid cladogenesis or the persistence of genetically and ecologically differentiated species in the presence of gene flow. Yet, ecological speciation research in marine fishes is still largely at an exploratory stage. Cases where the major ingredients of ecological speciation, namely a source of natural divergent or disruptive selection, a mechanism of reproductive isolation and a link between the two have been explicitly documented are few. Even in these cases, specific predictions of the ecological hypothesis of speciation remain largely untested. Recent developments in the study of freshwater fishes illustrate the potential for molecular approaches to address specific questions related to the ecological hypothesis of speciation such as the nature of the genes underlying key ecological traits, the magnitude of their effect on phenotype and the mechanisms underlying their differential expression in different ecological contexts. The potential provided by molecular studies is fully realized when they are complemented with alternative (e.g. ecological, theoretical) approaches.
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  • 26
    Publication Date: 2020-04-28
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  • 27
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    In:  Geofluids, 6 . pp. 241-250. Date online first: 2006
    Publication Date: 2017-08-02
    Description: Groundwater seeps are known to occur in Eckernförde Bay, Baltic Sea. Their discharge rate and dispersion were investigated with a new schlieren technique application, which is able to visualize heterogeneous water parcels with density anomalies down to Drt ¼ 0.049 on the scale of millimeters. With the use of an inverted funnel, discharged fluids can be captured and the outflow velocity can be determined. Overall, 46 stations could be categorized by three different cases: active vent sites, seep-influenced sites, and non-seep sites. New seep locations were discovered, even at shallow near-shore sites, lacking prominent sediment depression, which indicate submarine springs. The detection of numerous seeps was possible and the groundwater-influenced area was defined to be approximately 6.3 km2. Flow rates of between 0.05 and 0.71 l m)2 min)1 were measured. A single focused fluid plume, which was not disturbed by the funnel was recorded and revealed a flux of 59.6 ± 20 ml cm)2 min)1 and it was calculated that this single focused plume would be strong enough to produce a flow rate through the funnel of 1.32 ± 0.44 l m)2 min)1. The effect of different seep-meter funnel sizes is discussed.
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  • 28
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    In:  In: Biofouling. , ed. by Dürr, S. and Thomason, J. Wiley-Blackwell, Weinheim, pp. 100-108. ISBN 978-1-4051-6926-4
    Publication Date: 2012-02-23
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  • 29
    Publication Date: 2017-01-31
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  • 30
    Publication Date: 2016-06-29
    Description: Quantitative X-ray diffraction analysis of the 〈2mm sediment fraction was carried out on 1257 samples (from the seafloor and 16 cores) from the Iceland shelf west of 188 W. All but one core (B997-347PC) were from transects along troughs on theNW to N-central shelf, an area that in modern and historic times has been affected by drift ice. The paper focuses on the non-clay mineralogy of the sediments (excluding calcite and volcanic glass). Quartz and potassium feldspars occupy similar positions in an R-mode principal component analysis, and oligoclase feldspar tracks quartz; these minerals are used as a proxy for ice-rafted detritus (IRD). Accordingly, the sum of these largely foreign minerals (Q&K) (to Icelandic bedrock) is used as a proxy for drift ice. A stacked, equi-spaced 100 a record is developed which shows both low-frequency trends and higher-frequency events. The detrended stacked record compares well with the flux of quartz (mg cm-2 a-1) at MD99-2269 off N Iceland. The multi-taper method indicated that there are three significant frequencies at the 95% confidence level with periods of ca. 2500, 445 and 304 a. Regime shift analysis pinpoints intervals when there was a statistically significant shift in the average Q&K weight %, and identifies four IRDrich events separated by intervals with lower inputs. There is some association between peaks of IRD input, less dense surface waters (from d18O data on planktonic foraminifera) and intervals of moraine building.
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  • 31
    Publication Date: 2017-09-14
    Description: An experimental study was performed to disentangle parental and environmental effects on the growth of Atlantic cod Gadus morhua larvae and juveniles. Eggs were collected during the spawning season from spawning pairs (families) kept separately in specially designed spawning compartments. Newly hatched larvae were released simultaneously into two mesocosms of 2500 and 4400 m3. Larval growth was monitored by sampling over a 10 week period, after which juveniles were transferred to on-growing tanks, where they were tagged and kept for up to 2 years. Maternal origin was determined by individual microsatellite genotyping of the larvae (n = 3949, 24 families) and juveniles (n = 600). The results showed significant positive correlations between egg size and larval size during the whole mesocosm period. Correlations, however, weakened with time and were no longer significant at the first tank-rearing sampling at an age of 9 months. Significant family-specific differences in growth were observed. The coefficient of variation (c.v.) was calculated in order to examine variation in standard length of larvae during the mesocosm period. Inter-family c.v. was on average 69% of intra-family c.v. Differences in zooplankton densities between the two mesocosms were reflected in larval growth, condition factor and c.v. Low food abundance appeared to reduce c.v. and favour growth of larvae that showed relatively slow growth at high food abundance. It is suggested that genetically determined variation in growth potential is maintained by environmental variability.
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  • 32
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    In:  International Journal of Climatology, 29 (12). pp. 1731-1744.
    Publication Date: 2020-03-19
    Description: The annual cycle of extreme 1-day precipitation events across the UK is investigated by developing a statistical model and fitting it to data from 689 rain gauges. A generalized extreme-value distribution (GEV) is fit to the time series of monthly maxima, across all months of the year simultaneously, by approximating the annual cycles of the location and scale parameters by harmonic functions, while keeping the shape parameter constant throughout the year. We average the shape parameter of neighbouring rain gauges to decrease parameter uncertainties, and also interpolate values of all model parameters to give complete coverage of the UK. The model reveals distinct spatial patterns for the estimated parameters. The annual mean of the location and scale parameter is highly correlated with orography. The annual cycle of the location parameter is strong in the northwest UK (peaking in late autumn or winter) and in East Anglia (where it peaks in late summer), and low in the Midlands. The annual cycle of the scale parameter exhibits a similar pattern with strongest amplitudes in East Anglia. The spatial patterns of the annual cycle phase suggest that they are linked to the dominance of frontal precipitation for generating extreme precipitation in the west and convective precipitation in the southeast of the UK. The shape parameter shows a gradient from positive values in the east to negative values in some areas of the west. We also estimate 10-year and 100-year return levels at each rain gauge, and interpolated across the UK.
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  • 33
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    In:  Journal of Zoology, 210 (1). pp. 137-147.
    Publication Date: 2020-07-17
    Description: Epipelagic pterotracheid heteropods and young cranchiid squids rely primarily on transparency for concealment; yet they have opaque structures, the eyes and visceral organs that compose the visceral nuclei, which can only be camouflaged in other ways. These two groups have achieved convergent solutions to this problem. The visceral nucleus has a narrow and conical shape and a covering layer of iridophores that lies parallel to the surface of the organ. The eyes also have iridophore layers and tapered shapes. A minimal ventral silhouette results when the long axes of the visceral nucleus and eyes are oriented vertically, with the narrowest ends directed downward. In pterotracheids, this is actively achieved by tilting the nucleus and eyes and flexing the body and proboscis. In cranchiids, tilting of the organs alone suffices and adjustments are accomplished much more rapidly than in the pterotracheids.
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  • 34
    Publication Date: 2016-07-28
    Description: Coccoliths were studied from the ODP Hole 1002C and core PL07-39PC in the Cariaco Basin. Increases in Emiliania huxleyi are synchronous with decreases of Gephyrocapsa oceanica and vice versa. A new index (GEX) based on the relative abundances of these two taxa is proposed, and correlates with various other proxies. It is shown that GEX can serve as upwelling proxy. This confirms that the Intertropical Convergence Zone shifted north during the Bølling/Allerød, south during the Younger Dryas and back north during the Preboreal. The upwelling proxy shows few discrepancies with the terrigenous record.
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  • 35
    Publication Date: 2016-05-27
    Description: A visible tephra horizon in the NGRIP ice core has been identified by geochemical analysis as the Fugloyarbanki Tephra, a widespread marker horizon in marine cores from the Faroe Islands area and the northern North Atlantic. An age of 26 740 ± 390 yr b2k (1s uncertainty) is derived for this tephra according to the new Greenland Ice Core Chronology (GICC05) based on multiparameter counting of annual layers. Detection of this tephra for the first time within the NGRIP ice core provides a key tie-point between marine and ice-core records during the transition between MIS 3 and 2. Identification of this volcanic event within the Greenland records demonstrates the future potential of using tephrochronology to precisely correlate palaeoarchives in widely separated localities that span the last glacial period, as well as providing a potential method for examining the extent of the radiocarbon marine reservoir effect at this time.
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  • 36
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    In:  Journal of Zoology, 207 (4). pp. 511-519.
    Publication Date: 2020-07-17
    Description: A study of the diet of Sepia officinalis and S. elegans in the Ria de Vigo has shown that crustaceans are the most abundant prey in both species, followed by fish. Changes in the food composition of both species occur with growth. The type of prey eaten by the two sexes of these species is very similar. The possibility of trophic competition between juveniles of S. qficinalis and S. elegans is discussed.
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  • 37
    Publication Date: 2017-10-05
    Description: Natural communities are constantly changing due to a variety of interacting external processes and the temporal occurrence and intensity of these processes can have important implications for the diversity and structure of marine sessile assemblages. In this study, we investigated the effects of temporal variation in a disturbance regime, as well as the specific timing of events within different regimes, on the composition and diversity of marine subtidal fouling assemblages. We did this in a multi-factorial experiment using artificial settlement tiles deployed at two sites on the North East coast of England. We found that although there were significant effects of disturbances on the composition of assemblages, there were no effects of either the variation in the disturbance regime or the specific timing of events on the diversity or assemblage composition at either site. In contrast to recent implications we conclude that in marine fouling assemblages, the variability in disturbance regimes (as a driving force) is unimportant, while disturbance itself is an important force for structuring robust ecosystems.
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  • 38
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    In:  In: Microbial Ecology of the Oceans. Wiley-Blackwell, Hoboken, NJ, pp. 383-441. 2. Edition ISBN 978-0-470-04344-8
    Publication Date: 2019-12-06
    Type: Book chapter , NonPeerReviewed
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  • 39
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    In:  Fish and Fisheries, 9 (4). pp. 450-461.
    Publication Date: 2016-12-13
    Description: Archived scales and otoliths constitute a unique source of DNA that potentially enables extension of the temporal scale of genetic studies of fish populations by decades and even centuries. We review recent insights into fish population and conservation genetics obtained using analysis of DNA from archived samples. This involves both new knowledge about demographic parameters and population structure in wild populations and insights into consequences of anthropogenic pressure resulting from over-harvesting, habitat degradation and stocking. We show that the latter category of studies have led to significant changes of management practices. Ongoing improvement of genetic methods will undoubtedly further expand the ability to utilize historical DNA samples. We envisage that temporal comparisons of large numbers of coding genes will lead to novel insights into selective responses of fish populations to anthropogenic challenges, particularly fisheries-induced selection and global warming. However, both acquisition and storage of historical DNA samples can be hurdles to temporal genetic analyses, while degradation and low copy number in historical DNA samples render genetic data from such sources prone to technical artefacts. We summarize recommendations for storage of samples and DNA extraction and provide checklists for validation of genotyping results. Finally, we stress that validation procedures also involve documentation of the time and population of origin of historical samples, and the inferences drawn should account for the technical and statistical uncertainties associated with historical DNA analysis.
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  • 40
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    In:  Journal of Quaternary Science, 21 (6). pp. 645-675.
    Publication Date: 2018-10-22
    Description: Intra‐plate volcanism in western Europe shows statistically significant episodicity during the Quaternary period. By comparing the known ages for eruptions in France and Germany, which are compiled here, with a composite oxygen isotope record, we have investigated the link between this episodic volcanism and the climate record over the last two million years. We show that increased volcanism between 415–400 ka and 17–5 ka correlates with warming phases at the end of the last Weichselian (Devensian) and earlier Elsterian (Anglian) glacial stages. The three significant caldera explosions in the eastern Eifel, Germany, are all associated with warming phases at the onset of interglacials. The growth and decay of nearby ice sheets suggest that surface changes in continental mass distribution during glacial Milankovich cycles could provide a mechanism for this correlation by means of the distal effects of flexural loading on the lithosphere.
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  • 41
    Publication Date: 2017-09-14
    Description: An analysis of mass (M) and standard length (LS) data for larval, juvenile and adult sprat (Sprattus sprattus; Clupeidae) revealed marked changes in the allometric scaling factor (b in inline image). For sprat 〈44 mm LS, b was 5·0, whereas in larger juveniles and adults, b was c. 3·4 indicating a relatively protracted metamorphic period for this species.
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  • 42
    Publication Date: 2019-09-11
    Description: To investigate and disentangle the role of major histocompatibility complex (MHC)‐based ‘good genes' and ‘compatible genes' in mate choice, three‐spined sticklebacks Gasterosteus aculeatus with specific MHC IIB genotypes were allowed to reproduce in an outdoor enclosure system. Here, fish were protected from predators but encountered their natural parasites. Mate choice for an intermediate genetic distance between parental MHC genotypes was observed, which would result in intermediate diversity in the offspring, but no mate choice based on good genes was found under the current semi‐natural conditions. Investigation of immunological variables revealed that the less‐specific innate immune system was more active in individuals with a genetically more divergent MHC allele repertoire. This suggests the need to compensate for an MHC‐diminished T‐cell repertoire and potentially explains the observed mate choice for intermediate MHC genetic distance. The present findings support a general pattern of mate choice for intermediate MHC diversity (i.e. compatible genes). In addition, the potentially dynamic role of MHC good genes in mate choice under different parasite pressures is discussed in the light of present and previous results.
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  • 43
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    In:  Journal of Fish Biology, 75 . pp. 290-294.
    Publication Date: 2017-09-14
    Description: Individual behaviour of Atlantic cod Gadus morhua in the presence of hypoxic water was measured in situ in the vertically stratified Bornholm Basin of the Baltic Sea. Considering all recaptured individuals, the use of hypoxic habitat was comparable to data derived by traditional survey data, but some G. morhua had migrated towards the centre of the c.100 m deep basin and spent about a third of their time at oxygen saturation 〈50%, possibly to forage on zoobenthos. Maximal residence time per visit in such hypoxic water was limited to a few hours, allowing for the digestion of consumed prey items in waters with sufficient dissolved oxygen.
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  • 44
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    In:  Journal of Fish Biology, 67 . pp. 1585-1602.
    Publication Date: 2017-09-14
    Description: The seasonal growth trajectories of wild Atlantic salmon Salmo salar juveniles by age group within the Margaree River, Canada, are described. Circuli counts from scales were used to infer growth rates at different ages and these were used to predict the proportions of age 2‐ and 3‐year old smolts from different portions of the watershed. In the wild Atlantic salmon juveniles from the Margaree River, there was no bimodality in fork length frequencies and no 1 year old smolts were produced. Water temperature differences during the growing season were insufficient to explain the differences in growth rates and size at age among the sites sampled. There was a positive association between the growth rate in the first year and the subsequent age at smoltification. In the Margaree River, differences in tributary specific growth rates and size at age were expected to produce important differences in the relative ages at smoltification.
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  • 45
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    In:  Oikos, 117 (5). pp. 754-762.
    Publication Date: 2019-09-23
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  • 46
    Publication Date: 2020-03-20
    Description: Speciation and the maintenance of recently diverged species has been subject of intense research in evolutionary biology for decades. Although the concept of ecological speciation has been accepted, its mechanisms and genetic bases are still under investigation. Here, we present a mechanism for speciation that is orchestrated and strengthened by parasite communities acting on polymorphic genes of the immune system. In vertebrates, these genes have a pleiotropic role with regard to parasite resistance and mate choice. In contrasting niches, parasite communities differ and thus the pools of alleles of the adapted major histocompatibility complex (MHC) also differ between niches. Mate choice for the best‐adapted MHC genotype will favour local adaptations and will accelerate separation of both populations: thus immune genes act as pleiotropic speciation genes –‘magic traits’. This mechanism should operate not only in sympatric populations but also under allopatry or parapatry. Each individual has a small subset of the many MHC alleles present in the population. If all individuals could have all MHC alleles from the pool, MHC‐based adaptation is neither necessary nor possible. However, the typically small optimal individual number of MHC loci thus enables MHC‐based speciation. Furthermore, we propose a new mechanism selecting against species hybrids. Hybrids are expected to have super‐optimal individual MHC diversity and should therefore suffer more from parasites in all habitats.
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  • 47
    Publication Date: 2017-01-31
    Description: Human activities have differentially altered biogeochemical cycling at local, regional and global scales. We propose that a stoichiometric approach, examining the fluxes of multiple elements and the ratio between them, may be a useful tool for better understanding human effects on ecosystem processes and services. The different scale of impacts of the elements carbon, nitrogen and phosphorus and the different nature of their biogeochemical cycles, imply a large variation of their stoichiometric ratios in space and time and thus divergent impacts on biota. In this paper, we examine the effects of anthropogenic perturbations on nutrient ratios in ecosystems in two examples and one case study. Altered stoichiometry in agricultural systems (example 1) can affect not only crop yield and quality but also the interactions between plants and their pollinators, pests and pathogens. Human activities have also altered stoichiometry in coastal ecosystems (example 2). Increased N loading has especially lead to increased N:P and reduced Si:N ratios, with detrimental effects on ecosystem services derived from coastal pelagic food webs, such as fish yield and water quality. The terrestrial–aquatic linkage in stoichiometric alterations is illustrated with a case study, the Mississippi River watershed, where anthropogenic activities have caused stoichiometric changes that have propagated through the watershed into the northern Gulf of Mexico. Coupled with altered stoichiometric nutrient inputs are the inherent differences in variation and sensitivity of different ecosystems to anthropogenic disturbance. Furthermore, the connections among the components of a watershed may result in downstream cascades of disrupted functioning. Applying a multiple element perspective to understanding and addressing societal needs is a new direction for both ecological stoichiometry and sustainability.
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  • 48
    Electronic Resource
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 11 (1965), S. 2-177 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 49
    Electronic Resource
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    AIChE Journal 11 (1965), S. 3-3 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 50
    Electronic Resource
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    AIChE Journal 11 (1965), S. 18-25 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A theoretical model for interstitial liquid flow in a stationary or moving foam was devised by relating the physical structure of the foam to the physical properties of the surfactant and the foam movement. This was accomplished through a differential momentum balance within a typical capillary (Plateau border) of noncircular cross section with finite surface viscosity at its boundaries. Velocity profiles were then calculated and integrated numerically for the randomly oriented capillaries so as to obtain the overall liquid flow through the foam in terms of the pertinent variables. Results are presented in a form suitable for estimating concentrations and flow rates of product and waste streams in foam fractionation.
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  • 51
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    AIChE Journal 11 (1965), S. 145-151 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Terminal velocity drag coefficients CD were determined for cylinders, prisms, disks, and spheres in air and water at NRe from 1,000 to 300,000, the regime where particles rotate and/or oscillate. These and other similar data show that CD is a function of particle and fluid densities ρp and ρf, as well as shape and NRe.By considering CD a function of particle moment of inertia and the rotational moment generated by circulation (or alternatively the field force and the lift), one can deduce that \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm C}_{\rm D} = {\rm f}\left({\frac{{\rho {\rm p}}}{{\rho {\rm p}}}\,{\rm or}\,\frac{{\rho {\rm p} - \rho {\rm f}}}{{\rho {\rm f}}},\hbox{a length ratio, N}_{{\rm RE}}} \right) $\end{document}. This relationship correlates the data for ρp = 1.2 to 8.3 and ρf = 0.1 to 1.3 g./cc. to within ± 10%.
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  • 52
    Electronic Resource
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    AIChE Journal 11 (1965), S. 151-154 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In an earlier paper (1), three general methods of approaching the moving-boundary problems were developed. In the present work, these three methods are applied in detail to the solution of the problem of evaporation from a flat surface into a vapor phase of infinite depth. While this particular problem has been solved before (2,3), it has been chosen as an example here because all three methods apply directly.
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  • 53
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    AIChE Journal 11 (1965), S. 155-158 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The reduced thermal pressure-temperature ratio has been used to relate residual viscosity modulus for argon, krypton, and xenon into a unique relationship applicable for the dense gaseous and liquid regions. For these monatomic substances the critical compressibility factor is zc = 0.291. Values of (∂PR/∂TR)pR vs. (μ  - μ*)ζ on log-log coordinates produced a linear relationship. For these simple substances, this relationship was used to predict viscosities with an average deviation of 3.0% for fifty eight experimental values. This relationship was also applied for the prediction of viscosities for nitrogen, oxygen and carbon dioxide.The approach developed in this study merits further examination with several additional substances. The lack of adequate thermal pressures in the dense gaseous and liquid regions of substances other than argon limits the use of this study to substances having critical compressibility factors zc = 0.291.
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  • 54
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    AIChE Journal 11 (1965), S. 723-727 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Stirred tank reactor yields are successfully described by the following model. The impeller is considered to act as a local micro-mixer that perfectly mixes the recirculating stream down to the molecular level. All other portions of the vessel act as a large volume macro-mixer, throughout which the impeller discharge stream remains completely segregated. Changes in overall conversion due to variations in mean residence time, impeller size, and rev./min. as predicted by this micro- and macro-mixer model agree with Worrell's data for a relatively slow, second-order, irreversible reaction.
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  • 55
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    AIChE Journal 11 (1965), S. 678-685 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A method for the determination of the plate efficiencies for existing conventional and complex columns is presented. Information, such as any combination of product distributions, plate temperatures, and plate compositions, which is in addition to that required to solve a problem for a fixed column is used to determine efficiencies.
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  • 56
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    AIChE Journal 11 (1965), S. 686-689 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A method is developed for the treatment of data obtained from flow systems whose performance is unsteady and periodic. Experimental results from a study of axial dispersion in pulsating turbulent flow in an open, round pipe are presented; they show that pulsations can greatly increase axial mixing.
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  • 57
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    AIChE Journal 11 (1965), S. 690-695 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Sufficiently accurate values of first twenty eigenvalues, eigenfunctions Rn (1), and the coefficients for series expansion, as well as asymptotic expressions for these quantities, have been obtained for heat (or mass) transfer to fully developed laminar flow inside a round tube with uniform wall heat (or mass) flux. The first ten eigenfunctions are shown graphically for the radius range 0 ≤ r/ro ≤ 1.These quantities are used to calculate the Nusselt numbers for sinusoidal wall heat flux distribution and are compared with the corresponding slug flow Nusselt numbers.
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    AIChE Journal 11 (1965), S. 695-701 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A method is proposed for achieving the optimum design, in the sense of minimum plates, for conventional and complex distillation columns for any set of specifications directly dependent on product purity which might be imposed by the designer. The method uses the calculational procedure of Theiele and Geddes, the θ-method of convergence, and sequential-search procedures. Illustrative examples chosen from a large number of design problems solved by this method are presented.
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    AIChE Journal 11 (1965), S. 706-712 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The problem of isothermal diffusion in a variable molecular-weight binary gas mixture is considered for the case when the process occurs in a laminar boundary layer. Viscosity and diffusion coefficient are assumed constant. Solutions are given for both forced and free convection at large Schmidt numbers and large mass transfer rates toward the surface. Use of the molar average velocity considerably simplifies the results. These results suggest that the constant density solution in terms of mole fractions, evaluated at free stream conditions, may be a good approximation for variable density. This technique, improved by an approximate correction derived herein, is shown to agree reasonably well with the results of exact numerical solutions of the boundary layer equations.
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    AIChE Journal 11 (1965), S. 747-758 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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    AIChE Journal 11 (1965), S. 748-759 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 62
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    Keywords: Chemistry ; Chemical Engineering
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    Notes: The mathematical relation for the retention volume for elution chromatography has been extended to include the case of a multicomponent elution gas mixture in which all the components are adsorbed appreciably on the adsorbent. The total adsorption, component adsorption, and the K values or the ratio of the gas-phase concentration to the adsorbed-phase concentration for each component are related to the retention volume for the components as measured by a technique which distinguishes the molecules in the elution gas from those in the perturbing sample. Radioactively traced hydrocarbons are used in the application to obtain the retention volumes appropriate for the theory.The relations derived were applied in studying the adsorption of methane-propane mixtures on silica gel up to a pressure of 1,000 lb./sq. in. abs. The internal consistency of the propane adsorption data with the propane infinite dilution data and the methane data with the pure methane adsorption data obtained by a gravimetric method is demonstrated.
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    Notes: Alternating current voltage (60 cycles/sec.) was found to increase boiling heat transfer rates and prevent film boiling for deionized water under forced convection at essentially ambient pressure. Steam was used to supply heat to the interior wall of a 0.292-in. thick annulus, and voltages up to 5,000 v. were impressed across the region of vapor formation. The highest heat transfer rates reached were approximately twice the normal nucleate boiling peak. The application of voltage increased the boiling heat transfer over the entire range tested - mass flow rates up to 5.2 × 105 lb./hr.-sq.ft. and exit qualities up to 4% by weight vapor. Data obtained from tests in which the external wall of the flow annulus was heated indicated an increase in heat flux up to 2,000 v., followed by a decrease in heat flux at voltages above 2,000 v.
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    AIChE Journal 11 (1965), S. 279-287 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An experimental study with fixed and fluidized beds in the isomerization of cyclopropane on a silica alumina catalyst is reported for a temperature range of 150° to 250°C. and of 5 to 150 W/F (g-catalyst, hr./g.-mole). The effects of various cylindrical screen packing, 0.2-, 0.4-, and 1.0-in. diameter, and 1.0-in. diameter pall ring, on final conversion were determined. Reactor scale effects were also considered with reactors of 0.9-, 1.8-, and 6.0-in. diameter and bed heights 1.8 to 11.0 in.Overall conversions were higher in a fluidized bed with packing than in a normal fluidized bed but were less than in a fixed bed, though approaching it in some cases. Rate data from the fixed bed closely followed first-order kinetics. When the same catalyst was tested in a normal fluidized bed, the rate was dependent on linear gas velocity and catalyst bed height. With packing present in the fluidized bed, this dependency was much less, but packing size and shape had some effect.Several previously proposed reactor models were considered for correlating the data.
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    AIChE Journal 11 (1965), S. 294-303 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The major types of instabilities which can alter a given two-phase flow pattern or lead to the breakup of a liquid film are delineated, and their physical mechanisms are discussed. Existing stability criteria are correlated to these basic types, and their application and limitations with respect to actual problems are indicated. Basic areas requiring further study are outlined.A criterion for determining the breakup length of a liquid film is developed which gives an indication of whether a given instability will lead to low frequency and high amplitude pressure and inventory pulsations. Such phenomena may be undesirable.Two new aspects of importance to the problem of film instability are introduced which have not been previously studied. These are rotation of the fluids and large disturbances in the flow. Their possible influence on the problem is discussed.
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    AIChE Journal 11 (1965), S. 304-310 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A detailed study has been made of the excess viscosity of dense-phase aragon, deuterium, helium-3, helium-4, para and normal hydrogen, neon, and nitrogen and of the excess thermal conductivity of normal hydrogen. A definite temperature dependence for the excess viscosity vs. density has been shown to exist for argon, helium-4, hydrogen, and nitrogen and to be indicated for deuterium. The existing thermal conductivity data for hydrogen have been examined. A theoretical analysis for the qualitative behavior of excess thermal conductivity is given. The critical point viscosity values for all the species are given. Graphs, together with references to 1-atm. data, are presented for computation of the transport properties.
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    AIChE Journal 11 (1965), S. 311-318 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The vertical upflow of air-water mixtures in the dispersed-annular flow regime has been studied in a ¼ × 3-in. rectangular channel. Dye injection into the wall film was used to determine film and gas core properties along with the rate of droplet interchange between the core and the film. Visual observations demonstrated that the most important characteristic of this flow regime is the surface waves generated by the gas flow over the liquid film. Despite the surface waves, these data indicate that the liquid film approximately follows the generalized u+  -  y+ relationship for turbulent pipe flow. The droplet motion is discussed in terms of transverse diffusion and momentum transfer.
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    AIChE Journal 11 (1965), S. 324-330 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A major problem in the analysis of complex flows of viscoelastic fluids lies in the development of a suitable constitutive equation relating stresses to the kinematics of deformation. In this paper an equation is developed from successive approximations to a very general theory of viscoelasticity. This equation, which predicts both a non-Newtonian viscosity coefficient and normal stress effects in simple laminar shearing flows, appears to reflect a reasonable compromise between simplicity and useful applicability to real materials.The use of this equation is illustrated by means of a study of rapid flows about submerged objects. The results of this study are compared with the usual boundary-layer theory for Newtonian fluids, and the implications of this comparison are discussed in some detail.
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    AIChE Journal 11 (1965), S. 319-324 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The foam separation process uses differences in surface activity to separate components of a solution. Stable foams can flow upward countercurrent to liquid to give countercurrent differential separations with stripping, enrichment, or scrubbing similar to solvent extraction.Six- and 24-in. I.D. foam columns were operated with sodium dodecylbenzenesulfonate solutions to measure height of transfer unit (HTU) values and foam densities and to develop satisfactory gas spargers, liquid feed distributors, foam drainage conditions, and foam condensation equipment. The HTU values for stripping of Sr-89 were about 1 cm. for the best conditions of uniform foams, liquid flows of 100 gal./sq.ft.hr. or less, and uniform liquid feed distribution with low inlet velocities. Variations of countercurrent column lengths within 10 to 28 cm. caused little variation in HTU values. The foams were condensed, with four types of pneumatic or mechanical foam breakers used. A pilot plant was designed for decontamination of a low level radioactive waste.
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    AIChE Journal 11 (1965), S. 331-333 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Generalized equations for vapor pressure and PVT behavior are used to develop a functional relationship between latent heat of vaporization and reduced temperature and pressure. This function leads to a graphical correlation which utilizes the slope M of the vapor-pressure curve at the critical point. The correlation gives the latent heat of vaporization at any temperature in the two-phase region for any substance for which the critical point and one vapor-pressure point are known. The correlation is particularly useful for prediction of latent heat of vaporization near the critical point by the use of information for removed from the critical. Included in the study are polar, nonpolar, organic, inorganic, and metallic substances. General predictions of latent heat as a function of temperature are within a few percent wherever comparisons can be made with experimental data.
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    AIChE Journal 11 (1965), S. 334-339 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
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    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The Lydersen-Greenkorn-Hougen (L-G-H) charts correlating the isothermal pressure effects on enthalpy for pure compounds based on a modified corresponding states principle have been improved with the aid of reliable literature data. To facilitate machine computations, the improved charts, divided into the superheated vapor region, the subcooled liquid region, the saturated vapor, and the saturated liquid lines, have been expressed in analytical forms. This correlation reproduces the literature enthalpy data including those in the critical region for pure compounds with an average deviation of about 5 B.t.u./lb. It can also be used for the estimation of enthalpies of nonpolar mixtures with satisfactory results.
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    AIChE Journal 11 (1965), S. 339-350 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Three models of a catalyst particle are examined for existence of multiple steady states depending upon whether intraparticle heat conduction or diffusion is important. The particle with constant temperature but with intraparticle diffusion is examined in detail and a necessary and sufficient condition for the stability of the steady state is obtained. Calculations are made for a particle with both intraparticle diffusion and conduction and it is shown that there may be multiple steady states some of which are unstable to small perturbations.
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    AIChE Journal 11 (1965), S. 351-355 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The great utility of the effectiveness factor concept to account for intraparticle diffusion lies in its simplicity of application. Unfortunately, the standard formulation leads to a separate relationship for each type of reaction rate form, which greatly complicates practical computations.A general asymptotic solution is given here which leads to the definition of a general modulus somewhat different in form from the standard one. The use of this general modulus tends to approximately bring together all of the various curves.To illustrate its use, a few new exact solutions for simple order reactions are derived and combined with existing solutions for both simple order and adsorption reaction rate forms. It is seen that all of the curves lie within a relatively narrow range. Thus the general modulus permits one to estimate the effectiveness factor for any arbitrary reaction from the existing curves.
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    AIChE Journal 11 (1965), S. 364-365 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
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    AIChE Journal 11 (1965), S. 365-366 
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    Keywords: Chemistry ; Chemical Engineering
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    AIChE Journal 11 (1965), S. 356-363 
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    Keywords: Chemistry ; Chemical Engineering
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    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An efficient gas absorption device has been developed based on a stable aqueous foam moving in a horizontal duct, with a gas-liquid interaction that causes only negligible pressure drops.The study of a liquid-phase and a mostly gas-phase-controlled system has indicated that their mass transfer performance can be predicted. This is based on hydrodynamic data for flowing foams, obtained in a preliminary study published elsewhere.The influence of geometry, foaming solution properties, and surfactant-caused interfacial resistance are included in the analysis.
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    AIChE Journal 11 (1965), S. 367-368 
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    AIChE Journal 11 (1965), S. 369-369 
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    AIChE Journal 11 (1965), S. 369-373 
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    AIChE Journal 11 (1965), S. 370-374 
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    AIChE Journal 11 (1965), S. 370-384 
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    AIChE Journal 11 (1965), S. 381-381 
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    AIChE Journal 11 (1965), S. 386-563 
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    AIChE Journal 11 (1965), S. 563-563 
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    Keywords: Chemistry ; Chemical Engineering
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    Notes: The local and the average rates of forced convection through laminar boundary layers on a flat plate were shown to be markedly increased by locating small cylinders near the outer edge of the boundary layer. The local rate of forced convection was strongly peaked directly beneath each cylinder; the magnitude of the effect depended upon the free stream velocity, the spacing between cylinders, and the gap between the cylinders and the plate. Under optimum conditions, local values of the rate of forced convection were increased as much as 340%, while the average values were increased by over 190%.
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    AIChE Journal 11 (1965), S. 853-858 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
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    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The equations normally used to predict velocity distribution and eddy viscosity in single-phase flow systems can be adapted to fit gas-solids flow systems by including a term to account for the quantity of solid matter carried by the gas stream. This solids loading is expressed as pounds of solid per pound of gas. These modified equations can then be used to calculate the pressure drop of a solids-laden gas stream flowing in a pipe by means of a two-phase friction factor. Comparison of this approach with available pressure drop data is used to check its validity and to evaluate the constants in the equations.
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    AIChE Journal 11 (1965), S. 395-402 
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    Keywords: Chemistry ; Chemical Engineering
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    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Experimental measurements have been performed for pulsed perforated-plate columns of different sizes and geometry to obtain longitudinal dispersion coefficients for continuous and dispersed phases and size and holdup of liquid droplets dispersed in the columns. These quantities are correlated with operating conditions and column design, including the data published by different authors. Longitudinal dispersion coefficients for the continuous phase are shown to follow the backflow model. A superficial number of stages in series in each compartment is shown to come from inherent instability of fluid motion in the compartment. The longitudinal dispersion coefficient of the dispersed phase approaches that of the continuous phase with increasing pulse velocity. Holdup and mean size of droplets are correlated mainly on the basis of the rate of energy dissipation in the column fluid. Inclusion of dispersed-phase viscosity is shown to correlate the holdup data successfully for different liquid-liquid systems.
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    AIChE Journal 11 (1965), S. 866-873 
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    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The absorption of ammonia and oxygen in horizontal cocurrent gas-liquid froth flow in a 1-in. I.D. pipe has been investigated. At superficial liquid rates between 2 × 106 and 3.2 × 106 lb./(hr.)(sq.ft.) and superficial gas rates between 5 × 103 and 18 × 103 lb./(hr.)(sq.ft.), the length of a transfer unit in both systems was between 0.5 and 4.0 ft. The effects of distance and temperature were also investigated.With the use of James and Silberman's data on bubble size and distribution in froth flow to estimate average bubble sizes, the gas-phase-controlled ammonia absorption data could be explained by the model of unsteady state transfer from a stagnant sphere. With the use of an interfacial-area estimate from the ammonia results, the liquid-phase-controlled oxygen absorption data were correlated by a Sherwood number characterizing the transfer from the bubbles, a Reynolds number characterizing the turbulence within the system, and the void fraction.
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    AIChE Journal 11 (1965), S. 873-885 
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    Keywords: Chemistry ; Chemical Engineering
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    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An analytical study of the interaction of mixing, radiation attenuation, and chemical kinetics in isothermal photoreactors is presented. For a particular chain reaction mechanism in the presence of stationary state kinetics and low conversion, the conditions required for the existence of mixing effects are formally stated, and the direction of change of conversion and quantum yield resulting from the introduction of mixing is established. Calculated results are presented for monoenergetic, unidirectional sources. Factors considered include mode of chain termination, radiation attenuation law, photoreactor geometry, state of mixing, and reactor optical thickness. Chemical and mixing time scale considerations are discussed.
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    AIChE Journal 12 (1966), S. 530-534 
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    Keywords: Chemistry ; Chemical Engineering
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    Notes: A mass transfer model for vigorously oscillating single liquid drops moving in a liquid field has been developed with the concepts of interfacial stretch and internal droplet mixing. The model takes into account both amplitude and frequency of drop oscillations. Experimental values of fraction extracted were predicted with an average deviation of 15%. Oscillations break up internal circulation streamlines and a type of turbulent internal mixing is achieved.
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    AIChE Journal 12 (1966), S. 534-540 
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    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The effect of product recycle and temperature on the maximum yield of product for several different autocatalytic reactions taking place in a tubular reactor is studied.A generalized version of the maximum principle is used to determine the maximum conversion and optimal temperature profile for each of the reactions considered. The fraction of product recycled, which affects the concentration of autocatalytic agent entering the reactor, is investigated to determine its effect on the maximum conversion.
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    AIChE Journal 12 (1966), S. 548-552 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Measurements of the diffusion coefficients of hydrogen and methane in strong aqueous electrolytes have been made with the use of the diaphragm cell method. The variation of the diffusion coefficients with electrolyte concentration, type of ion, and temperature has been studied over the electrolyte concentration range zero to saturated, and for temperatures in the range 25° to 65°C.The results have been interpreted with the Eyring rate theory. The presence of ions in water increases the activation energy for diffusion which results in a decrease in the diffusion coefficient. The increase in activation energy is represented by terms that are additive for the ions involved. The influence of ions on the diffusion coefficient increases rapidly with ionic charge, but seems to be little affected by temperature or solute for the systems studied.
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  • 94
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 12 (1966), S. 541-548 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Carbon dioxide was absorbed from mixtures with nitrogen by countercurrent contact with water in an experimental packed tower. Radial and axial gas concentration profiles were determined from measurements made within the packing. Substantial gas phase channeling was observed. Characterizing the gas flow regime by both piston flow and axial diffusion models yielded mass transfer data and computed axial gas concentration profiles. Differences between the mass transfer results for the two models allowed the influence of axial dispersion to be assessed. Comparison of the piston flow and axially dispersed profiles with the experimental profiles enabled conclusions to be drawn regarding the applicability of the axial diffusion model and the accuracy of available dispersion parameter values.The axial diffusion model appears to be a satisfactory representation of the process. The dispersion coefficients used were found to be too high, which emphasizes shortcomings in the transient response experiments yielding dispersion coefficients. The influence of dispersion on the performance was found to be only moderately adverse. The effect increases with increasing liquid rate, decreasing gas rate, and decreasing packing height. It is improbable that the effect is large enough to account for the difference between industrial scale performance and that predicted from available mass transfer correlations.
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  • 95
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 12 (1966), S. 553-559 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A new experimental technique has been developed for study of transport from drops. Large single drops are heated dielectrically while suspended motionless in an unheated continuous phase. Direct measurements of temperature distributions within drops are presented both for circulating drops and for drops in which surface-active materials retard circulation. The results of the measurements will be useful in assessing the validity of the various proposed models.
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  • 96
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 12 (1966), S. 559-562 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Measurements of the thermal conductivity and viscosity of n-heptane and n-octane in the gas phase were made at temperatures of 100° and 160°F. and at pressures below 1 atm. In addition, measurements of the viscosity and thermal conductivity of binary gas mixtures of nitrogen and n-heptane were made at 160°F. at pressures below 1 atm.
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  • 97
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 12 (1966), S. 571-576 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The rate of growth of bubbles forming on a wall from a liquid initially uniformly supersaturated with a dissolved gas was investigated. Attention was directed to the effect of the contact angle.Theoretical predictions for the growth rate of a spherical bubble tangent to a wall were carried out with a digital computer. The predictions included the diffusion equation and the continuity equation. The energy equation was neglected; viscosity and surface tension were assumed nil. The results are compared with existing predictions for a 90-deg. contact angle. For extremely slow growth, the theoretical growth coefficient is about 30% smaller for a bubble with zero contact angle compared to one with a 90-deg. contact angle. For fast growth the difference is much less.Experimental growth rates were determined photographically for bubbles of carbon dioxide coming out of solution from water at an artifical nucleation site. Different contact angles from 15 to 89 deg. were obtained by coating the wall with various nonwetting agents. Every bubble showed changes in its contact angle during growth. No effect of contact angle on the growth rate could be detected.
    Additional Material: 4 Ill.
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  • 98
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 12 (1966), S. 577-580 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The coefficients of the Benedict-Webb-Rubin equation of state have been developed for argon. By employing these coefficients, the volumetric behavior of argon has been predicted with an average deviation of 0.241% for five hundred ninety-seven smoothed and experimental data points in the superheated region.At temperatures below the critical, two sets of Co's, one for the liquid and one for the vapor, were needed to relate the vapor pressure to the densities of saturated argon. However, consistent fugacities for the saturated vapor and liquid argon could not be predicted with these Co values. Therefore, another set of Co's was developed by equating the pure component vapor and liquid fugacities along the vapor pressure curve. These values were used to test the applicability of the equation of state to predict derived thermodynamic properties.The original BWR expression for calculating isothermal pressure effects on enthalpy was modified to include explicitly the temperature dependence of the coefficient Co. Vapor-liquid equilibrium relations for the argon-nitrogen system predicted by the standard BWR procedure were compared with experimental data.
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  • 99
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 12 (1966), S. 563-571 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A free, vertical jet of liquid plunging into a uiescent surface of the same liquid entrains the surrounding gas into the receiving liquid to form bubbles. The entrainment characteristics of such jets of Newtonian liquids of varying physical properties have been investigated by means of high-speed photography.Although both laminar and turbulent jets entrain gas bubbles, the mechanisms governing the entrainment process of the two types of jets are clearly different. Entrainment by turbulent jets results from the disturbances on the free surface caused by the jet instability; entrainment by laminar jets is accomplished by the formation of a thin shell of gas around the jet at the point of entrance, by the development of oscillations in the shell, and by its subsequent breakup into bubbles.Entrainment occurs only when the average jet velocity exceeds a certain critical value termed minimum entrainment velocity. For a laminar jet having a flat velocity profile at the point of entrance, the following correlation permits prediction of the minimum entrainment velocity: \documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm Weber\;number} = 10\left({{\rm Reynolds\;number}} \right)^{0.74} $$\end{document} where the dimensionless numbers are based on the liquid properties and the jet diameter at the point where the jet meets the surface of the receiving liquid.
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  • 100
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 11 (1965), S. 937-937 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 3 Ill.
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