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  • 1
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    In:  EPIC3Marine Animal Forests, Marine Animal Forests, Switzerland, Springer, 35 p., ISBN: 978-3-319-17001-5
    Publication Date: 2017-09-26
    Description: The Chilean fjord region, situated between 42 and 56 °S, forms one of the most ragged shorelines and belongs to the ecologically and biogeographically least understood marine regions of the world. A labyrinth of fjords, channels, and islands extends over 240,000 km2 and creates a coastline of more than 80,000 km. Due to strong abiotic gradients, numerous habitats are created, which are further diversified by temporal dynamics (tidal cycle, seasonal changes in precipitation, temperature, radiation, etc.). The region is a biodiversity hotspot hosting unique and fragile ecosystems. Among the species living here, several are species forming habitats in the ecosystem. These organisms can reach high densities conforming the so-called marine animal forests. Examples are marine animal forests dominated by cold-water stony corals, gorgonians, hydrocorals, brachiopods, polychaetes, giant barnacles, sponges, and ascidians. Many of these communities have been discov- ered only recently. There is also a singular characteristic in this area: exceptionally low pH levels of the waters of Patagonian fjords provide the opportunity to study calcifying organisms in an environment with pH conditions in the same range as the ones predicted by the IPCC for the world oceans in 2100. Despite the scarce ecological and biogeographical knowledge of this area, it encounters an unparalleled economic development including high-impact industry-scale salmonid farming, ambitious infrastructure and industrialization projects, and increasing extractive activities. Baseline research on the abiotic and biotic environment of the region is needed to reach sustainability in the use of the marine resources. Management plans including the establishment of marine protected areas to preserve benthic diversity and ecosystem services are urgently needed.
    Repository Name: EPIC Alfred Wegener Institut
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  • 2
    Publication Date: 2016-10-24
    Description: Marine microbial biogeography has been studied intensively; however few studies address community variation across temporal and spatial scales simultaneously so far. Here we present a yearlong study investigating the dynamics of the free-living and particle-attached bacterioplankton community across a 100 km transect in the German Bight reaching from the Elbe estuary towards the open North Sea. Community composition was assessed using automated ribosomal intergenic spacer analysis and linked to environmental parameters applying multivariate statistical techniques. Results suggest that the spatial variation of the bacterioplankton community is defined by hydrographic current conditions, which separate the inner German Bight from the open North Sea and lead to pronounced differences in the coastal and offshore bacterioplankton community. However this spatial variation is overwhelmed by a strong temporal variation which is triggered by temperature as the main driving force throughout the whole transect. Variation in the free-living community was predominantly driven by temperature, whereas the particle-attached community exhibited stronger spatial variation patterns.
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  • 3
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    In:  EPIC3Marine Animal Forests: The Ecology of Benthic Biodiversity Hotspots, Marine Animal Forests: The Ecology of Benthic Biodiversity Hotspots, Switzerland, Springer
    Publication Date: 2017-01-23
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  • 4
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    In:  EPIC3Marine Animal Forests: The Ecology of Benthic Biodiversity Hotspots, Marine Animal Forests: The Ecology of Benthic Biodiversity Hotspots, Switzerland, Springer
    Publication Date: 2017-01-23
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  • 5
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    In:  EPIC3Springer
    Publication Date: 2017-03-06
    Repository Name: EPIC Alfred Wegener Institut
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  • 6
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    In:  EPIC3Biology and Ecology of Antactic Krill, Advances in Polar Ecology, Springer, 30 p., pp. 145-174, ISBN: 978-3-319-29277-9
    Publication Date: 2016-09-23
    Description: Since the 1920s, E. superba is one of the best studied species in the Southern Ocean in terms of their general biology. The main driver for this research focus has been the fisheries’ requirements for stock forecasting and conservation measures. Nowadays this is joined by concerns over climate change effects and the requirement to take a more holistic over view to understand food web structures. So far, however, we do not have a clear understanding of the physiological response of krill and hence their adaptability to cope with ongoing environmental changes, caused by the anthropogenic carbon emissions. This is due to the extreme lack of intense studies on krill physiology, especially of their larval stages in relation to their seasonal environment. A major aim of this book chapter is on the one hand to summaries how physiological functions such as lipid accumulation and utilisation, metabolic activity and growth change with ontogeny and season and to demonstrate which environmental factors are the main drivers for seasonal variability of these functions in adult and larval krill. On the other hand, we draw the attention to the importance of photoperiod (day length) as an entrainment cue for endogenous rhythms and clocks in the life cycle of krill. Furthermore, we give an overview of the current knowledge on the impact of elevated seawater temperature and ocean acidification on krill.
    Repository Name: EPIC Alfred Wegener Institut
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  • 7
    Publication Date: 2019-10-01
    Description: Over the last decade, our understanding of cli- mate sensitivity has improved considerably. The climate system shows variability on many timescales, is subject to non-stationary forcing and it is most likely out of equi- librium with the changes in the radiative forcing. Slow and fast feedbacks complicate the interpretation of geolog- ical records as feedback strengths vary over time. In the geological past, the forcing timescales were different than at present, suggesting that the response may have behaved differently. Do these insights constrain the climate sensitiv- ity relevant for the present day? In this paper, we review the progress made in theoretical understanding of climate sensitivity and on the estimation of climate sensitivity from proxy records. Particular focus lies on the background state dependence of feedback processes and on the impact of tipping points on the climate system. We suggest how to further use palaeo data to advance our understanding of the currently ongoing climate change.
    Repository Name: EPIC Alfred Wegener Institut
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  • 8
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    In:  EPIC3Handbook of the Protists, Handbook of the Protists, Springer, pp. 1-61, ISBN: 978-3-319-32669-6
    Publication Date: 2016-11-17
    Description: Haptophyta are predominantly planktonic and phototrophic organisms that have their main distribution in marine environments worldwide. They are a major component of the microbial ecosystem, some form massive blooms and some are toxic. Haptophytes are significant players in the global carbonate cycle through photosynthesis and calcification. They are characterized by the haptonema, a third appendage used for attachment and food handling, two similar flagella, two golden-brown chloroplasts, and organic body scales that serve in species identification. Coccolithophores have calcified scales termed coccoliths. Phylogenetically Haptophyta form a well-defined group and are divided into two classes Pavlovophyceae and Coccolithophyceae (Prymnesiophyceae). Currently, about 330 species are described. Environmental DNA sequencing shows high haptophyte diversity in the marine pico- and nanoplankton, of which many likely represent novel species and lineages. Haptophyte diversity is believed to have peaked in the past and their presence is documented in the fossil record back to the Triassic, approximately 225 million years ago. Some biomolecules of haptophyte origin are extraordinarily resistant to decay and are thus used by geologists as sedimentary proxies of past climatic conditions.
    Repository Name: EPIC Alfred Wegener Institut
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  • 9
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    In:  EPIC3Encyclopedia of Marine Geosciences, Encyclopedia of Marine Geosciences, Heidelberg, Springer, 2 p., pp. 792-792, ISBN: 978-94-007-6237-4
    Publication Date: 2016-12-04
    Repository Name: EPIC Alfred Wegener Institut
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  • 10
    Publication Date: 2016-04-07
    Description: The maintenance of ion and pH homeostasis despite changes in ambient temperature is crucial for ectothermic organisms. Thermal sensitivity of Na+/K+ ATPase mRNA expression, protein expression and activity was determined in gills of North Sea cod (NC) and Northeastern Arctic cod (NEAC), acclimated for 6 weeks at 4 and 10 °C and compared to field samples of North Sea cod (sNC), acclimatized to early spring (4 °C) and summer (18 °C) conditions. The same analyses were conducted in gills of the confamiliar whiting, acclimated at 4 and 10 °C. Branchial Na+/K+ ATPase capacities remained uncompensated at functional and protein levels in NC and NEAC at both acclimation temperatures. Na+/K+ ATPase mRNA expression in NEAC acclimated at 10 °C was about twofold higher compared to NC, indicating some population-specific differentiation at this level. Lower Na+/K+ ATPase capacities in gills of warm-acclimatized sNC at common assay temperatures indicate thermal compensation between seasonal extremes, and post-translational modifications contributed to this mitigation at high assay temperature. Together, cod compensates Na+/K+ ATPase capacities on the warm edge of the thermal window and below 4 °C, respectively. In contrast, whiting Na+/K+ ATPase capacities were cold compensated at 4 °C, supported by 1.5-fold higher mRNA and protein expression. Besides, capacities were lower in whiting compared to NC and NEAC at optimum temperature, which may be advantageous in terms of reduced maintenance cost, but at temperatures ≤4 °C, compensation may represent an energy trade-off to maintain homeostasis. The species-specific response of gadid Na+/K+ ATPase indicates certain threshold temperatures beyond which compensation of the pump is elicited, possibly related to the different biogeography of these species.
    Repository Name: EPIC Alfred Wegener Institut
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  • 11
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    In:  EPIC3Listening in the Ocean, New York, Springer, pp. 257-308
    Publication Date: 2018-02-13
    Description: New developments and applications of autonomous Passive Acoustic Monitoring (PAM) technology in polar regions have come at time of increased interest in the Arctic and Antarctic due to predictions of global climate change. Information gained with autonomous PAM systems has provided new information on polar pinniped communication, mating systems, distribution, and the relationships between these species and their environment. Although new discoveries continue to be made, there is still much that remains to be learned about these species. This chapter is organized into a review of species specifi c information known prior to 2000, case studies describing new knowledge gained through the use of autonomous PAM systems since 2000, and future projection on how autonomous PAM systems can be used to address and fi ll data gaps related to polar pinnipeds.
    Repository Name: EPIC Alfred Wegener Institut
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  • 12
    Publication Date: 2016-09-19
    Description: The key role of the South Atlantic Anticyclone (SAA) on the seasonal cycle of the tropical Atlantic is investigated with a regionally coupled atmosphere–ocean model for two different coupled domains. Both domains include the equatorial Atlantic and a large portion of the northern tropical Atlantic, but one extends southward, and the other northwestward. The SAA is simulated as internal model variability in the former, and is prescribed as external forcing in the latter. In the first case, the model shows significant warm biases in sea surface temperature (SST) in the Angola-Benguela front zone. If the SAA is externally prescribed, these biases are substantially reduced. The biases are both of oceanic and atmospheric origin, and are influenced by ocean–atmosphere interactions in coupled runs. The strong SST austral summer biases are associated with a weaker SAA, which weakens the winds over the southeastern tropical Atlantic, deepens the thermocline and prevents the local coastal upwelling of colder water. The biases in the basins interior in this season could be related to the advection and eddy transport of the coastal warm anomalies. In winter, the deeper thermocline and atmospheric fluxes are probably the main biases sources. Biases in incoming solar radiation and thus cloudiness seem to be a secondary effect only observed in austral winter. We conclude that the external prescription of the SAA south of 20°S improves the simulation of the seasonal cycle over the tropical Atlantic, revealing the fundamental role of this anticyclone in shaping the climate over this region.
    Repository Name: EPIC Alfred Wegener Institut
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  • 13
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    In:  EPIC3Encyclopedia of Marine Geosciences, Encyclopedia of Marine Geosciences, Heidelberg, Springer, 2 p., pp. 746-747, ISBN: 978-94-007-6237-4
    Publication Date: 2016-12-04
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  • 14
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    In:  EPIC3Encyclopedia of Marine Geosciences, Encyclopedia of Marine Geosciences, Heidelberg, Springer, 7 p., pp. 87-93, ISBN: 978-94-007-6237-4
    Publication Date: 2016-12-04
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  • 15
    Publication Date: 2017-04-04
    Description: A complex system of electric currents flowing in the ionosphere and magnetosphere originates from the interaction of the solar wind and the Interplanetary Magnetic Field (IMF) with the Earth’s magnetic field. These electric currents generate magnetic fields contributing themselves to those measured by both ground observatories and satellites. Here, low-resolution (1 Hz) magnetic vector data recorded between 1 March 2014 and 31 May 2015 by the recently launched Swarm constellation are considered. The core and crustal magnetic fields and part of that originating in the magnetosphere are removed from Swarm measurements using CHAOS-5 model. Low- and mid-latitude residuals of the geomagnetic field representing the ionospheric and the unmodelled magnetospheric contributions are investigated, in the Solar Magnetic frame, according to the polarity of IMF B y (azimuthal) and B z (north–south) components and to different geomagnetic activity levels. The proposed approach makes it possible to investigate the features of unmodelled contributions due to the external sources of the geomagnetic field. Results show, on one side, the existence of a relation between the analysed residuals and IMF components B y and B z , possibly due to the long distance effect of high-latitude field-aligned currents. On the other side, they suggest the presence of a contribution due to the partial ring current that is activated during the main phase of geomagnetic storms. The perturbation observed on residuals is also compatible with the effect of the net field-aligned currents. Moreover, we have quantitatively estimated the effect of these current systems on computed residuals.
    Description: Published
    Description: 108
    Description: 1A. Geomagnetismo e Paleomagnetismo
    Description: JCR Journal
    Description: open
    Keywords: Swarm magnetic vector data ; Interplanetary Magnetic Field ; Magnetic models ; Field-aligned currents ; Partial ring current ; 01. Atmosphere::01.03. Magnetosphere::01.03.99. General or miscellaneous ; 01. Atmosphere::01.03. Magnetosphere::01.03.02. Magnetic storms ; 04. Solid Earth::04.05. Geomagnetism::04.05.03. Global and regional models ; 05. General::05.07. Space and Planetary sciences::05.07.01. Solar-terrestrial interaction
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 16
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    In:  EPIC3Parallel Processing and Applied Mathematics, Parallel Processing and Applied Mathematics, Switzerland, Springer, 10 p., pp. 570-580, ISBN: 978-3-319-32151-6
    Publication Date: 2016-06-14
    Description: eVolutus is a new software platform designed for modeling evolutionary and population dynamics of living organisms. Single-celled eukaryotes, foraminifera, are selected as model organisms that have occupied the marine realm for at least 500 Ma and left an extraordinary fossil record preserved in microscopic shells. This makes them ideal objects for testing general evolutionary hypotheses based on studying multiscale genotypic, phenotypic, ecologic and macroevolutionary patterns. Our platform provides a highly configurable environment for conducting evolutionary experiments at various spatiotemporal scales.
    Repository Name: EPIC Alfred Wegener Institut
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  • 17
    Publication Date: 2017-01-12
    Description: During the austral summer expedition PS81, ANT-XXIX/3 with the German research ice breaker Polarstern in 2013, research was carried out to investigate the role of environmental factors on the distribution of benthic communities and marine mammal and krill densities around the northern tip of the Antarctic Peninsula. For these studies collated in this special issue and studies in this area, we present a collection of environmental parameters with probable influence on the marine ecosystems around the Antarctic Peninsula.
    Repository Name: EPIC Alfred Wegener Institut
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  • 18
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    In:  EPIC3Marine Animal Forests, Marine Animal Forests, Switzerland, Springer, 26 p., pp. 1-26, ISBN: 978-3-319-17001-5
    Publication Date: 2017-01-27
    Description: Cold-water coral ecosystems differ from each other greatly in structure, faunal makeup, and ecological function. Attributes such as substrate type, 3-D complexity, biological community, and nutrient supply also change over small temporal and spatial scales. In this chapter, we present an overview of food gathering strategies employed by a range of cold-water corals. Furthermore, the importance of corals as habitat providers for associated fauna and thus biodiversity is discussed. The coral habitats support ecosystems at various spatial scales ranging from local exposed skeleton patches on gorgonian branches to the various zones on a reef. Comparison is made between many types of animal forests made up by cold-water corals, including several types of coral gardens and coastal and offshore reefs from a wide range of environmental settings. The trophic ecology of reef types is compared, and the variation in feeding behavior across particular reefs is also discussed.
    Repository Name: EPIC Alfred Wegener Institut
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  • 19
    Publication Date: 2016-06-16
    Description: A comprehensive expert consultation was conducted in order to assess the status, trends and the most important drivers of change in the abundance and geographical distribution of kelp forests in European waters. This consultation included an on-line questionnaire, results from a workshop and data provided by a selected group of experts working on kelp forest mapping and eco-evolutionary research. Differences in status and trends according to geographical areas, species identity and small-scale variations within the same habitat where shown by assembling and mapping kelp distribution and trend data. Significant data gaps for some geographical regions, like the Mediterranean and the southern Iberian Peninsula, were also identified. The data used for this study confirmed a general trend with decreasing abundance of some native kelp species at their southern distributional range limits and increasing abundance in other parts of their distribution (Saccharina latissima and Saccorhiza polyschides). The expansion of the introduced species Undaria pinnatifida was also registered. Drivers of observed changes in kelp forests distribution and abundance were assessed using experts’ opinions. Multiple possible drivers were identified, including global warming, sea urchin grazing, harvesting, pollution and fishing pressure, and their impact varied between geographical areas. Overall, the results highlight major threats for these ecosystems but also opportunities for conservation. Major requirements to ensure adequate protection of coastal kelp ecosystems along European coastlines are discussed, based on the local to regional gaps detected in the study.
    Repository Name: EPIC Alfred Wegener Institut
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  • 20
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    In:  EPIC3Geodynamic Evolution of the Southernmost Andes Connections with the Scotia Arc, Springer Earth System Sciences, Springer, pp. 75-108, ISBN: 978-3-319-39725-2
    Publication Date: 2019-07-17
    Description: Study of the tectonic development of the Scotia Sea region started with basic lithological and structural studies of outcrop geology in Tierra del Fuego and the Antarctic Peninsula. To nineteenth- and early twentieth-century geologists, the results of these studies suggested the presence of a submerged orocline running around the margins of the Scotia Sea. Subsequent increases in detailed knowledge about the fragmentary outcrop geology from islands distributed around the margins of the Scotia Sea, and later their interpretation in the light of the plate tectonic paradigm led to large modifications in the hypothesis such that by the present day the concept of oroclinal bending in the region persists only in vestigial form. Of the early comparative lithostratigraphic work in the region, only the likenesses between Jurassic–Cretaceous basin floor and fill sequences in South Georgia and Tierra del Fuego are regarded as strong enough to be useful in plate kinematic reconstruction by permitting the interpretation of those regions’ contiguity in mid-Mesozoic times. Marine and satellite geophysical data sets reveal features of the remaining, submerged, 98 % of the Scotia Sea region between the outcrops. These data enable a more detailed and quantitative approach to the region’s plate kinematics. In contrast to long-used interpretations of the outcrop geology, these data do not prescribe the proximity of South Georgia to Tierra del Fuego in any past period. It is, however, possible to reinterpret the geology of those two regions in terms of the plate kinematic history that the seafloor has preserved.
    Repository Name: EPIC Alfred Wegener Institut
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  • 21
    Publication Date: 2017-06-05
    Description: In the Kongsfjorden–Krossfjorden system (Spitsbergen), increasing temperatures enhance glacier melting and concomitant intrusion of freshwater. These altered conditions affect the timing, intensity, and composition of the phytoplankton spring bloom in Kongsfjorden; yet, the effects on prokaryotes (bacteria and archaea) are not well understood. The aim of this study was to examine springtime prokaryote communities in both fjords as a function of hydrographic and phytoplankton variability. Prokaryote community composition was studied in two consecutive years by molecular fingerprinting of the 16S rRNA gene. In addition, we measured bacterial abundance, productivity (3H-Leucine uptake), and single-cell activity using catalyzed reporter deposition fluorescence in situ hybridization combined with microautoradiography. Differences in bacterial and archaeal communities were found etween Kongsfjorden and Krossfjorden. Furthermore, an increase in productivity, abundance, and proportion of active bacterial cells was observed during the course of spring. Bacteroidetes were the most abundant bacterial group among the assessed taxa in both Kongsfjorden and Krossfjorden. Multivariate analysis of the microbial community fingerprints revealed a strong temporal shaping of both the bacterial and archaeal communities in addition to a spatial separation between the two fjords. A significant part of the observed bacterial variation could be explained by cyanobacterial biomass, as deduced from pigment analysis, and by phosphate concentration. Archaea were mainly controlled by abiotic factors. We speculate that the bacterial response to hydrographic changes and glacier meltwater is mediated through shifts in phytoplankton abundance and composition, whereas archaea are directly influenced by abiotic environmental variables.
    Repository Name: EPIC Alfred Wegener Institut
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  • 22
    Publication Date: 2022-05-25
    Description: © The Author(s), 2015. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Theoretical Ecology 8 (2015): 449-465, doi:10.1007/s12080-015-0261-0.
    Description: Breaking the core assumption of ecological equivalence in Hubbell’s “neutral theory of biodiversity” requires a theory of species differences. In one framework for characterizing differences between competing species, non-neutral interactions are said to involve both niche differences, which promote stable coexistence, and relative fitness differences, which promote competitive exclusion. We include both in a stochastic community model in order to determine if relative fitness differences compensate for changes in community structure and dynamics induced by niche differences, possibly explaining neutral theory’s apparent success. We show that species abundance distributions are sensitive to both niche and relative fitness differences, but that certain combinations of differences result in abundance distributions that are indistinguishable from the neutral case. In contrast, the distribution of species’ lifetimes, or the time between speciation and extinction, differs under all combinations of niche and relative fitness differences. The results from our model experiment are inconsistent with the hypothesis of “emergent neutrality” and support instead a hypothesis that relative fitness differences counteract effects of niche differences on distributions of abundance. However, an even more developed theory of interspecific variation appears necessary to explain the diversity and structure of non-neutral communities.
    Description: The research was funded by NSF grant ECCS-0835847 and a postdoctoral scholarship from the Woods Hole Oceanographic Institution.
    Keywords: Neutral theory ; Niche difference ; Relative fitness difference ; Demographic stochasticity ; Species abundance distribution
    Repository Name: Woods Hole Open Access Server
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  • 23
    Publication Date: 2022-05-25
    Description: © The Author(s), 2016. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Science China Life Sciences 59 (2016): 811-824, doi:10.1007/s11427-016-5094-6.
    Description: In order to develop a novel method of visualizing possible Ca2+ signaling during the early differentiation of hESCs into cardiomyocytes and avoid some of the inherent problems associated with using fluorescent reporters, we expressed the bioluminescent Ca2+ reporter, apo-aequorin, in HES2 cells and then reconstituted active holo-aequorin by incubation with f-coelenterazine. The temporal nature of the Ca2+ signals generated by the holo-f-aequorin-expressing HES2 cells during the earliest stages of differentiation into cardiomyocytes was then investigated. Our data show that no endogenous Ca2+ transients (generated by release from intracellular stores) were detected in 1–12-day-old cardiospheres but transients were generated in cardiospheres following stimulation with KCl or CaCl2, indicating that holo-f-aequorin was functional in these cells. Furthermore, following the addition of exogenous ATP, an inositol trisphosphate receptor (IP3R) agonist, small Ca2+ transients were generated from day 1 onward. That ATP was inducing Ca2+ release from functional IP3Rs was demonstrated by treatment with 2-APB, a known IP3R antagonist. In contrast, following treatment with caffeine, a ryanodine receptor (RyR) agonist, a minimal Ca2+ response was observed at day 8 of differentiation only. Thus, our data indicate that unlike RyRs, IP3Rs are present and continually functional at these early stages of cardiomyocyte differentiation.
    Description: This work was supported by the Hong Kong Theme-based Research Scheme award (T13-706/11-1), the Hong Kong Research Grants Council (RGC) General Research Fund awards (662113, 16101714, 16100115), the ANR/RGC joint research scheme award (A-HKUST601/13), and the Innovation and Technology Commission (ITCPD/17-9). HYSC was supported by a Hong Kong University Grants Council post-graduate studentship (T13-706/11- 11PG).
    Keywords: Ca2+ signaling ; Apo-aequorin expression ; Bioluminescence ; HES2 human embryonic stem cells ; hESC-derived cardiospheres ; IP3 and ryanodine receptors
    Repository Name: Woods Hole Open Access Server
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  • 24
    Publication Date: 2022-05-25
    Description: © The Author(s), 2016. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Applied Microbiology and Biotechnology 100 (2016): 8315–8324, doi:10.1007/s00253-016-7777-0.
    Description: Endozoicomonas bacteria are emerging as extremely diverse and flexible symbionts of numerous marine hosts inhabiting oceans worldwide. Their hosts range from simple invertebrate species, such as sponges and corals, to complex vertebrates, such as fish. Although widely distributed, the functional role of Endozoicomonas within their host microenvironment is not well understood. In this review, we provide a summary of the currently recognized hosts of Endozoicomonas and their global distribution. Next, the potential functional roles of Endozoicomonas, particularly in light of recent microscopic, genomic, and genetic analyses, are discussed. These analyses suggest that Endozoicomonas typically reside in aggregates within host tissues, have a free-living stage due to their large genome sizes, show signs of host and local adaptation, participate in host-associated protein and carbohydrate transport and cycling, and harbour a high degree of genomic plasticity due to the large proportion of transposable elements residing in their genomes. This review will finish with a discussion on the methodological tools currently employed to study Endozoicomonas and host interactions and review future avenues for studying complex host-microbial symbioses.
    Description: This work was supported by a KAUST-WHOI Post-doctoral Partnership Award to MJN and a KAUST-WHOI Special Academic Partnership Funding Reserve Award to CRV and AA. Research in this study was further supported by baseline research funds to CRV by KAUST and NSF award OCE-1233612 to AA.
    Keywords: Endozoicomonas ; Symbiosis ; Marine ; Coral reefs
    Repository Name: Woods Hole Open Access Server
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  • 25
    Publication Date: 2022-08-12
    Description: Arctic lowland landscapes have been modified by thermokarst lake processes throughout the Holocene. Thermokarst lakes form as a result of ice-rich permafrost degradation, and they may expand over time through thermal and mechanical shoreline erosion. We studied proximal and distal sedimentary records from a thermokarst lake located on the Arctic Coastal Plain of northern Alaska to reconstruct the impact of catchment dynamics and morphology on the lacustrine depositional environment and to quantify carbon accumulation in thermokarst lake sediments. Short cores were collected for analysis of pollen, sedimentological, and geochemical proxies. Radiocarbon and 210Pb/137Cs dating, as well as extrapolation of measured historic lake expansion rates, were applied to estimate a minimum lake age of ~1400 calendar years BP. The pollen record is in agreement with the young lake age as it does not include evidence of the “alder high” that occurred in the region ~4000 cal yr BP. The lake most likely initiated from a remnant pond in a drained thermokarst lake basin (DTLB) and deepened rapidly as evidenced by accumulation of laminated sediments. Increasing oxygenation of the water column as shown by higher Fe/Ti and Fe/S ratios in the sediment indicate shifts in ice regime with increasing water depth. More recently, the sediment source changed as the thermokarst lake expanded through lateral permafrost degradation, alternating from redeposited DTLB sediments, to increased amounts of sediment from eroding, older upland deposits, followed by a more balanced combination of both DTLB and upland sources. The characterizing shifts in sediment sources and depositional regimes in expanding thermokarst lakes were, therefore, archived in the thermokarst lake sedimentary record. This study also highlights the potential for Arctic lakes to recycle old carbon from thawing permafrost and thermokarst processes.
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  • 26
    Publication Date: 2022-05-26
    Description: © The Author(s), 2016. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Marine Biology 163 (2016): 112, doi:10.1007/s00227-016-2892-0.
    Description: A temporal change in the stable isotope (SI) composition of jellyfish in the Kiel Fjord, Western Baltic Sea, was documented by analyzing δ13C, δ15N and δ34S of bell tissue of Aurelia aurita and Cyanea capillata in the period between June and October 2011. A strong and significant temporal change in all SI values of A. aurita was found, including an increase of ~3 ‰ in δ13C, a decrease of ~4 ‰ in δ15N and sharp decline of ~7 ‰ in δ34S. While knowledge gaps in jellyfish isotope ecology, in particular the lack of reliable trophic enrichment factors, call for a conservative interpretation of our data, observed changes in particular in δ34S, as indicated by means of a MixSIR mixing model, would be consistent with a temporal dietary shift in A. aurita from mesozooplankton (〉150 µm) to microplankton and small re-suspended particles (0.8–20 µm) from the benthos. Presence of a hitherto unidentified food source not included in the model could also contribute to the shift. During the 2-month occurrence of C. capillata, its isotope composition remained stable and was consistent with a mainly mesozooplanktonic diet. Mixing model output, mainly driven by δ34S values, indicated a lower proportion of A. aurita in the diet of C. capillata than previously reported, and thus to a potentially lesser importance of intraguild predation among jellyfish in the Kiel Fjord. Overall, our results clearly highlighted the potential for substantial intraspecific isotopic seasonal variation in jellyfish, which should be taken into account in future feeding ecology studies on this group.
    Description: This project was funded by the German Research Foundation (DFG, JA2008/1-1). JD received financial support from the Cluster of Excellence “The Future Ocean” and the BONUS project BIO-C3, funded jointly by the EU and the BMBF (Grant No. 03F0682A).
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  • 27
    Publication Date: 2022-05-26
    Description: This paper is not subject to U.S. copyright. The definitive version was published in Estuaries and Coasts 39 (2016): 916-934, doi:10.1007/s12237-015-0057-x.
    Description: Assessments of coupled barrier island-estuary storm response are rare. Hurricane Sandy made landfall during an investigation in Barnegat Bay-Little Egg Harbor estuary that included water quality monitoring, geomorphologic characterization, and numerical modeling; this provided an opportunity to characterize the storm response of the barrier island-estuary system. Barrier island morphologic response was characterized by significant changes in shoreline position, dune elevation, and beach volume; morphologic changes within the estuary were less dramatic with a net gain of only 200,000 m3 of sediment. When observed, estuarine deposition was adjacent to the back-barrier shoreline or collocated with maximum estuary depths. Estuarine sedimentologic changes correlated well with bed shear stresses derived from numerically simulated storm conditions, suggesting that change is linked to winnowing from elevated storm-related wave-current interactions rather than deposition. Rapid storm-related changes in estuarine water level, turbidity, and salinity were coincident with minima in island and estuarine widths, which may have influenced the location of two barrier island breaches. Barrier-estuary connectivity, or the transport of sediment from barrier island to estuary, was influenced by barrier island land use and width. Coupled assessments like this one provide critical information about storm-related coastal and estuarine sediment transport that may not be evident from investigations that consider only one component of the coastal system.
    Description: Funding for this project was provided by the New Jersey Department of Environmental Protection and the US Geological Survey (USGS) Coastal and Marine Geology Program.
    Keywords: Barnegat Bay ; Hurricane Sandy ; Coastal change ; Water quality ; Geomorphology ; Sediments ; Numerical modeling
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    Publication Date: 2022-05-26
    Description: © The Author(s), 2015. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Estuaries and Coasts 39 (2016): 311-332, doi:10.1007/s12237-015-0011-y.
    Description: Numerical modeling has emerged over the last several decades as a widely accepted tool for investigations in environmental sciences. In estuarine research, hydrodynamic and ecological models have moved along parallel tracks with regard to complexity, refinement, computational power, and incorporation of uncertainty. Coupled hydrodynamic-ecological models have been used to assess ecosystem processes and interactions, simulate future scenarios, and evaluate remedial actions in response to eutrophication, habitat loss, and freshwater diversion. The need to couple hydrodynamic and ecological models to address research and management questions is clear because dynamic feedbacks between biotic and physical processes are critical interactions within ecosystems. In this review, we present historical and modern perspectives on estuarine hydrodynamic and ecological modeling, consider model limitations, and address aspects of model linkage, skill assessment, and complexity. We discuss the balance between spatial and temporal resolution and present examples using different spatiotemporal scales. Finally, we recommend future lines of inquiry, approaches to balance complexity and uncertainty, and model transparency and utility. It is idealistic to think we can pursue a “theory of everything” for estuarine models, but recent advances suggest that models for both scientific investigations and management applications will continue to improve in terms of realism, precision, and accuracy.
    Description: NKG, ALA, and RPS acknowledge support from the USGS Coastal and Marine Geology Program. DKR gratefully acknowledges support from NSF (OCE-1314642) and NIEHS (1P50-ES021923-01). MJB and JMPV gratefully acknowledge support from NOAA NOS NCCOS (NA05NOS4781201 and NA11NOS4780043). MJB and SJL gratefully acknowledge support from the Strategic Environmental Research and Development Program—Defense Coastal/Estuarine Research Program (RC-1413 and RC-2245).
    Keywords: Numerical modeling ; Hydrodynamics ; Ecological modeling ; Ecosystem modeling ; Skill assessment
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  • 29
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    In:  EPIC3Encyclopedia of Marine Geosciences, (Encyclopedia of Earth Sciences Series), Dordrecht, Springer, pp. 721-731, ISBN: 978-94-007-6644-0
    Publication Date: 2023-06-21
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    In:  Water Resources Development and Management
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    Bulletin of mathematical biology 38 (1976), S. 205-207 
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    Bulletin of mathematical biology 38 (1976), S. 161-192 
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    Notes: Abstract In order to evaluate the effect of anatomic asymmetries on the gas concentration distribution in the pulmonary airways, a Monte Carlo simulation of combined bulk flow and molecular diffusion was carried out in a realistic distal airway model (Parkeret al., 1971). This airway model, composed of branches distal to the 0.5-ram diameter airways, contained an upper symmetric segment consisting of four generations of conducting airways and a lower asymmetric segment of alveolar ducts and sacs arranged in five transport paths of varying lengths. In accounting for the volume increases of these ducts and sacs occurring during normal respiration, uniform alveolar filling rates and a fixed length-to-diameter ratio of all airways were assumed. For a pulse injection of inert tracer gas, the simulation was employed to determine the longitudinal concentration profiles in the conducting airways. In the alveolated airways, not only were the longitudinal profiles determined along each path, but radial transport from the core to the periphery of the airways was considered. The results of the simulations indicate that geometric asymmetries alone contribute substantially to regional concentration variations in the distal airways. For example, when a gas bolus is injected at mid*inspiration, there are concentration differences as great as 40% between two points along different transport paths located equi-distant from the proximal end of the model. As viewed from the terminal end of the model (acinus), average concentration differences as large as 6-to-1 exist between the longest and shortest transport paths respectively for gas boli introduced near the end of inspiration. The results further indicate because of large radial diffusion rates, no significant concentration differences exist between the periphery a-ld the central core of alveolated airways. Simulation of the expired concentration profiles indicate that boll injected very late during inspiration exhibit a sloping tail, unlike the earlier injected boll whose tails are virtually horizontal. Through the use of superposition teehniqnes, it was found that these sloping tails correspond to an alveolar slope of 1.5 vol% between 750 and 1250 ml expired for a continuous washing of tracer. This result is in disagreement with other transport analyses which did not directly account for the effect of geometric asymmetries.
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    Notes: Abstract Assuming a spherical geometry for the left ventricle, passive elastic stiffness-stress relations have been obtained on the basis of linear elasticity theory and large deformation theory. Employing pressure-volume aata taken from rat hearts of various age groups, it is shown that young rat heart muscle (1 month) is stiffer than either adult (7 months) or old rat heart muscle (17 months). Although the qualitative results are similar for both elasticity theories, the large deformation theory gave results in closer agreement with those obtained from papillary muscle studies. These results imply that stiffness of muscleper se can be assessed from left ventricular pressure-volume data.
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    Bulletin of mathematical biology 38 (1976), S. 277-293 
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    Notes: Abstract Deliberate evaluation of the quantum theory of nerve excitation is made by comparing it with Hill's theory in fitting the experimental data on threshold-frequency relation, optimum frequency (v0) for nerve excitation and strength-duration relation. Decrease of v0 and increase of all the time constants (Hill's λ andk, Wei'sT 2 and spike durationw) with decreasing temperature are interpreted on the basis of the dipole relaxation timeT 2 but inexplicable from Hill's theory or any other existing theory. The closeness ofk,T 2 andw values is explained. A variety of experimental results obtained by others is discussed. Finally, a comparison is made between the Hodgkin-Huxley equations and the quantum theory. Most of the facts (electrical and non-electrical) tend to support the thesis that nerve excitation is a macroscopic expression of quantum transitions of dipoles between energy states.
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    Bulletin of mathematical biology 38 (1976), S. 317-319 
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    Notes: Abstract In the periodic Leslie model the asymptotic period of total population is a divisor of the asymptotic period of the population vector. Under reasonable circumstances these periods are identical.
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    Bulletin of mathematical biology 38 (1976), S. 305-315 
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    Notes: Abstract A number of biological branching systems, such as the bronchial and pulmonary arterial trees, are being investigated in an ongoing study in order to define their physiological properties. The technique involves the description of branching trees by the use of hierarchical systems of ordering, especially those described by Horsfield and by Strahler. During this work some mathematical properties of branching trees were demonstrated and these are described in this paper.
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    Bulletin of mathematical biology 38 (1976), S. 323-324 
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  • 38
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    Bulletin of mathematical biology 38 (1976), S. 209-217 
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    Bulletin of mathematical biology 38 (1976), S. 387-400 
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    Notes: Abstract Luteinizing hormone (LH) is secreted continuously from the anterior pituitary gland. The concentration in the blood of this gonadotropic hormone plays a regulatory role in the development of puberty in both sexes, in the induction of ovulation in females, and in the production of testosterone in males. The secretion of LH is in turn controlled by luteinizing hormone releasing hormone (LHRH) secreted by the hypothalamus. LH and LHRH are removed from the blood by degradation and excretion. This hormonal system is modelled by a system of ordinary differential equations based upon specific physiological and biochemical assumptions current among experimentalists in this field. The one exception is the assumption that LHRH may bind reversibly to a serum protein; an analysis of the data shows that this or a similar mechanism is a crucial specification. Data on the serum levels of LH and LHRH in two human subjects were fitted using the model. The data consist of the transients and subsequent decays created by a bolus intravenous injection of LHRH.
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    Bulletin of mathematical biology 38 (1976), S. 401-413 
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    Notes: Abstract A thick-wall incompressible, elastic sphere was used as a model for the diastolic rat left ventricle. A model for myocardial nonhomogeneity was derived assuming that fiber (circumferential) stress was independent of position in the ventricular wall. The theoretical implications of the resulting constitutive relations together with the spherical model were analyzed in the context of large deformation elasticity theory. It was found that muscle stiffness at a given level of uniaxial stress increased monotonically from the endocardium to the epicardium. In addition, fiber stress was found to be essentially a linear function of transmural pressure above a pressure of 6 g/cm2. It was also shown theoretically that neglecting the nonhomogeneity of the myocardium resulted in a state of stress which differed significantly from that predicted by the nonhomogeneous model. For example, at a transmural pressure of 14 g/cm2, fiber stress in the nonhomogenous model was equal to 17 g/cm2 while fiber stress in the homogeneous model varied between 100 g/cm2 at the endocardial surface and 2 g/cm2 at the epicardial surface. The change in muscle stiffness with position which characterized the nonhomogeneous model also tended to linearize the highly curvilinear radial stress distribution predicted by the homogeneous model at a given transmural pressure.
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    Bulletin of mathematical biology 38 (1976), S. 435-444 
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    Notes: Abstract The phenomenon of axonal transport has been well documented (Ochs, 971; Lasek, 1970; and Grafstein, 1967). In a previous paper, we showed how diffusion alone could not account for this process. In this report we show that convection or convection with diffusion can account for the observed build-up of material. By including a first-order catabolic sequestration term, we are able to offer an understanding of the several apparent rates of transport with the same underlying velocity and variable sequestration.
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    Bulletin of mathematical biology 38 (1976), S. 459-465 
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    Notes: Abstract It is known that the Lotka-Volterra coupled nonlinear differential equations for a two-species prey-predator ecosystem possess a periodic solution, although its exact form is not yet obtained analytically. The conventional linearization approximation for solving these nonlinear equations leads to a harmonic oscillator whose frequency depends only on the intraspecific coefficients. We propose here a prescription for obtaining nonlinear correction to the linear frequency by using the Hamilton-Jacobi canonical formalism of classical mechanics. It is found that the first-order correction, which also involves interspecific parameters, exhibits the basic qualitative features of the nonlinearity.
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    Bulletin of mathematical biology 38 (1976), S. 467-478 
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    Notes: Abstract Environmental safety testing typically requires procedures for extrapolating from the relatively high experimental to the very low use doses of potentially harmful substances. In the present paper, a stochastic mammillary compartmental model for environmental safety testing is proposed and extrapolation procedures based on its dose-response relationship are developed. The proposed model is a direct generalization of one of the basic safety models, the one-hit model, in that a harmful reaction is assumed to occur if at any time any of the peripheral compartments attains a specified threshold of particles. Consideration of a closed model yields an upper bound on the probability of attaining a certain threshold level, thus providing a conservative procedure for extrapolating to a low dose, while a lower bound obtained from a related open model provides a useful monitoring device as to the sharpness of the upper, bound. The extrapolation procedure is illustrated with simulated data and approximations for initial values are developed.
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    Bulletin of mathematical biology 38 (1976), S. 505-516 
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    Notes: Abstract By using chromosome images as a framework, algorithms for finding most dissimilar images are presented and illustrated by examples. In terms of angles, a chromosome image consists of two exterior biangles and two interior biangles. Biangles are defined and classified into 180° biangles, 〉180° biangles and 〈180° biangles. The dissimilarity of biangles and its geometric interpretation together with various properties of biangles are also presented. The results may have useful applications in pattern recognition, scene analysis, information storage and retrieval, artificial intelligence and fuzzy set theory.
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    Bulletin of mathematical biology 38 (1976), S. 517-526 
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    Notes: Abstract The Volterra equations which represent competitions between two species are utilized to examine the phenomenon of boundary formation between two species of plants. The set of stable stationary points for these equations is determined and is illustrated in a product space of parameters and dynamical variables. The stages of boundary appearance and succession are visualized by considering slow changes of the parameters as functions of time and space.
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    Bulletin of mathematical biology 38 (1976), S. 95-96 
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    Bulletin of mathematical biology 38 (1976), S. 119-133 
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    Notes: Abstract A method, based on symmetry, is suggested for determining the information content of systems. A comparison has been made between the information for symmetry, topology, and chemical composition. The new information measure increases when the asymmetry of the molecules and the number of atoms in the latter increases. It can distinguish between different molecular conformations, and give a linear correlation with the absolute entropy for homologous series of chemical compounds.
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    Bulletin of mathematical biology 38 (1976), S. 135-159 
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    Notes: Abstract The micromorphic theory of Eringen is applied to study the tube flow of blood. The blood is considered to be a deformable suspension, with constitutive relations of the form of those of simple microfluids. By means of energy consideration, a relation is established between the local concentration parameter and the measure of rotationality involving both macro-and micromotions. The tube flow problem is then solved with some analyses on viscosity coefficients and boundary conditions. The results obtained indicate an integrated explanation of various important physical phenomena associated with blood flow, such as the tube size dependence of the apparent viscosity and the non-uniform concentration distribution over a tube cross section.
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    Bulletin of mathematical biology 38 (1976), S. 193-197 
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    Notes: Abstract By observing that the n-tuple of rate functionsQ(c) is orthogonal to the c-space gradients of each of the (n - 1) constants of the motion Φ v (c), a generic canonical expression for the rate functions is given in terms of the exterior product of the gradients of the (n - 1) Φ v 's. For models withQ so prescribed from the outset, an analytical general solution is obtainable directly for the system of autonomous ordinary differential equations dc/dt =Q(c). Thus, the generic canonical expression for the rate functions can be utilized to construct analytically solvable models for interacting biological species, as ilIus~rated by examples here.
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    Bulletin of mathematical biology 38 (1976), S. 39-57 
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    Notes: Abstract A model for the extraocular plant of the human visual eye tracking mechanisms is discussed. Its sensitivity to variation of controller signal nervous activity is studied in order to determine the type of activity that yields realistic simulations characteristic of typical saccadic eye movements.
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    Bulletin of mathematical biology 38 (1976), S. 359-368 
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    Notes: Abstract Mathematical models of predator-prey systems in which the prey species has a three-stage life cycle are studied. Certain stages of the prey life history are allowed to use younger stages as food. It is shown that sufficiently restricted cannibalism can result in an increase in the numbers of adult prey on a sustained basis when cannibalism decreases the vulnerability of a stage subject to predation or increases overall productivity.
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    Bulletin of mathematical biology 38 (1976), S. 369-386 
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    Notes: Abstract A general analysis is presented for the thermal behavior of a biological tissue. Energy transport by the circulatory system is assumed to be represented by a modified Fick's law. General boundary conditions are assumed for the two-dimensional model and solutions are obtained for rectangular, cylindrical, and spherical geometries. The effects of blood perfusion rate, metabolic rate, arterial temperature and heat exchange with the environment are considered. Results indicate a region of almost constant temperature in the deeper layers of the tissue and reaffirm the important role which blood flow plays in maintaining homeostasis.
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    Bulletin of mathematical biology 38 (1976), S. 351-358 
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    Notes: Abstract The oscillatory aspect in a system having two steady states is studied theoretically using a model of excitable nerve membrane. The condition for the occurrence of oscillatory instability is discussed on the basis of the kinetic picture of nerve excitation in consideration of the non-Markoffian effect caused by ion transport in the system. Small oscillations around a steady state as well as a giant fluctuation between two states are obtained. Results are compared with experiments carried out with squid giant axons perfused intracellularly.
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    Bulletin of mathematical biology 38 (1976), S. 415-423 
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    Notes: Abstract An expression for the variance in birth volumes during balanced growth of a cell population is derived. The requirement of this expression being positive and finite allows a discussion of some of the requirements imposed on the mechanisms of growth and division.
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    Bulletin of mathematical biology 38 (1976), S. 425-433 
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    Notes: Abstract The phenomenon of axonal transport of material has been well documented (Ochs, 1971; Lasek, 1970; and Grafstein, 1967). This report seeks to establish the role of diffusion—if any—in such a transport process. We report that diffusion cannot account for the observed build-up of material as reported in the literature.
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    Bulletin of mathematical biology 38 (1976), S. 445-452 
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    Notes: Abstract The question of how to fit a general cubic model of a multicomponent, interactive growth system to observed data is addressed. A multidimensional-polynomial type of regression analysis is used, with a least-squares criterion. By testing the scheme on a problem with known solution, the way in which the accuracy of the results varies with the number of datum points used is investigated in an heuristic manner.
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    Bulletin of mathematical biology 38 (1976), S. 453-458 
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    Notes: Abstract The describing function method is used as a guide to the behaviour of the solutions of the equations of Danziger and Elmergreen, proposed as a model of periodic catatonia. The method suggests that whenever the equilibrium point is unstable it is surrounded by a stable closed periodic orbit. This is confirmed in specific cases by computation.
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    Bulletin of mathematical biology 38 (1976), S. 497-504 
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    Notes: Abstract A theory of ambiguous pattern perception is formulated. This theory proposes a feature selector (field of attention) based on the time-sequential discrete property of the attention, a short-term memory for storage of the selected features, and a displayer (perception) to display the consecutively stored features. Since the selected features continuously enter, and since the features can only be stored in the short-term memory for a short period, the features which can be displayed in the displayer vary with time. When all the essential features belonging to one pattern happen to be in the displayer, the picture is perceived to be that pattern; when all the essential features belonging to another pattern happen to be in the displayer, then the picture is perceived to be the other pattern. Thus the picture appears to vary with time and alternate between two patterns. A numerical calculation is presented.
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    Bulletin of mathematical biology 38 (1976), S. 479-496 
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    Notes: Abstract The thermodynamics of irreversible processes is derived from the principles of dynamical field theory independently of all elements of thermostatics, in particular the assumption of local equilibrium. Field thermodynamics proceeds from the premise that all driving forces experienced by the molecules in a continuum are conservative and arise from scalar potential functions. Dynamically the temperature potentialT is no different from the pressure potentialp. A field is converted to a force upon multiplication by a scale factor. A potential is converted to potential energy by the same scale factor. To scale the field −∇p to the force per mole of molecular speciesk, the partial molar, volume $$\bar V_k $$ is the scale factor. Similarly the partial molar entropy, $$\bar S_k $$ , scales the temperature field. The transition from the scale factors (which are physical parameters) to the systemic variables, for example $$\bar S_k \to s\left( {x,y,z;t} \right)$$ , is not trivial. From the dynamics and the structure of the derived potential energy function are inducted the conjugate variables such as (p, V I) and (T, s). The meta-mechanical properties of the thermal variables (T, s) are discovered via the local First Law of Thermodynamics, which relates internal energy, thermal flux, and work, and from the local Second Law, which prescribes, the possible partitions of internal energy between kinetic, potential, and thermal energies. From the form of the potential energy come Maxwell's relationships. From the energy partition comes the equation of continuity for entropy, with its important source term. In contrast to earlier theories of irreversible thermodynamics, the dissipation function does not include the stress tensor, a constitutive parameter.
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    Bulletin of mathematical biology 38 (1976), S. 527-534 
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    Notes: Abstract The transfer of solute through a membrane separating two aqueous solutions is studied with the time-dependent diffusion equation for composite media. By introducing new independent and dependent variables it is shown that the differential equations and boundary conditions can be transformed into a dimensionless form which does not explicitly depend on the diffusivities of the media. Laplace transforms are used to derive explicit solutions for the solute concentration as a function of position and time. It is shown that at large time the concentration approaches the equilibrium distribution exponentially. Explicit results are given for the decay time as a function of the parameters of the system. In addition, an accurate and simplified expression is derived for the decay time for the case of small membrane permeability. The accuracy of the analytic solutions for the concentration profiles is tested by comparing them with numerical results obtained by solving the diffusion equations by the method of finite differences. Excellent agreement is found.
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    Bulletin of mathematical biology 38 (1976), S. 679-693 
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    Notes: Abstract Physiological systems are often modelled by a set of compartments. Alternatively they can be described by the diffusion-convection-reaction equations governing distributed systems. The problem considered here is that of identifying a continuously changing input of some metabolite )tracee), endogenous to the system and hence inaccessible, when a nonlinear or time-varying component is also introduced into the loss parameter, as for example through feedback mechanisms. A tracer is used to determine the steady-state impulse response under time-invariant, linear conditions. A known input of tracer is also administered when the system is driven out of steady state. The integral equations developed utilize the predetermined impulse response, the measured concentrations of both tracer and tracee (output) in some region of the system to estimate the changing loss parameter and the unknown input in a continuous fashion.
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    Bulletin of mathematical biology 38 (1976), S. 597-622 
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    Notes: Abstract The equilibrium distribution for a generalQth-order multivariate reaction system is studied. The state transition intensity matrix is developed and examples are given for small numbers of reaction components. A closed-form expression for the equilibrium distribution for systems which are symmetric with respect to the order of component reactions is presented. Numerical examples for three component systems are discussed.
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    Bulletin of mathematical biology 38 (1976), S. 623-631 
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    Notes: Abstract The model recently proposed by Dreitlein and Smoes for oscillatory kinetic systems is studied. Diffusion of the oscillating species is taken into account, and bounds on the total number of individuals of each species are determined for both two- and three-dimensional finite regions with various boundary conditons applied. It is found that in general the effect of diffusion on the system behavior is to reduce the maximum possible radius of limit cycles. In particular, in some cases global limit cycle behavior is precluded.
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    Bulletin of mathematical biology 38 (1976), S. 671-677 
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    Notes: Abstract The Kedem-Katchalsky equations for fluid flux across membranes may not be adequate for large solvent flows. In particular, for an example of two membranes in series, it is argued that they would predict physically unreasonable behavior. An alternate equation for solute flow is proposed for a simple sieving membrane. For the same example, this equation predicts more physically reasonable results.
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    Bulletin of mathematical biology 38 (1976), S. 1-13 
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    Notes: Abstract The paper introduces a basic mathematical form, which is characteristic of a number of linear one-dimensional diffusion equations with coefficients being represented as simple polynomials in the spatial coordinate. A number of particular diffusion equations are introduced and their corresponding exact mathematical solutions are obtained.
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    Bulletin of mathematical biology 38 (1976), S. 15-28 
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    Notes: Abstract In this paper we examine a set of nonlinear rate equations (devised by M. Eigen (1971)) which describe the process of selection in a collection of self-reproducing, macromolecular information carriers. We construct exact solutions to the equations for the case of constant rate parameters and constant error distributions. The solutions allow the direct assessment of the effect of mutations on the “selective value” parameters discussed by Eigen as well as the distribution of the molecular species selected in steady state. In addition we show that the selection process may be characterized by an extremal principle.
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    Bulletin of mathematical biology 38 (1976), S. 29-38 
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    Notes: Abstract The electromagnetic molecular electronic resonance (EMER) frequencies of the molecular chains of α-chymotrypsin are calculated. The chain length relations and coupling positions suggest a possible energy transfer, at the EMER frequencies, from one chain to the other. Photon enzyme activation data indicate that the energy corresponding to the EMER frequencies of its molecular chains is used by α-chymotrypsin for its enzyme function.
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    Bulletin of mathematical biology 38 (1976), S. 59-70 
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    Notes: Abstract Based on Wei's dipole flip-flop model and with the assumption that the dipole is coupled to the membrane matrix, the cathode-make-excitation, the anode-break-excitation and the cathode-gap-excitation can be explained in a systematic way. The istrength-duration relations for these three processes are derived.
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    Bulletin of mathematical biology 38 (1976), S. 93-94 
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    Bulletin of mathematical biology 38 (1976), S. 87-92 
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    Notes: Abstract It is usually stated that only systems with multiple steady states can exhibit hysteresis. For protein conformations, this would violate the idea that, in fixed environments, primary structure uniquely determines tertiary structure. It is shown that hysteresis-like phenomena can be exhibited by systems possessing only a single steady-state configuration. This property is placed in a more general theoretical setting of recognition and classification systems, and some implications for processes such as memory, learning and pattern generation (morphogenesis) are discussed.
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    Bulletin of mathematical biology 38 (1976), S. 97-109 
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    Notes: Abstract The natural historical literature contains a considerable body of work which indicates that harvesting (or predation) can alleviate competitive instabilities. In order to arrive at an understanding of this, the appropriate bifurcation structure for a rather general family of two-dimensional competitive systems is here investigated. The results of this analysis suggest that, in more complicated ecosystems with many competing species, (1) there is a good chance that harvesting at moderate rates will increase species diversity if one species is dominant in the unharvested system, while an increase in diversity is not likely to result from harvesting from a system with no dominant species, (2) whenever harvesting does increase species diversity, maximal diversity will occur at moderate harvesting rates, with less diversity at both very high and very low harvesting rates.
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    Bulletin of mathematical biology 38 (1976), S. 111-118 
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    Notes: Abstract The Weber-Fechner law (response of an organism is a linear function of log of stimulus) has been widely used for description of physiological and psychological data for many years. It is shown here that the Weber-Fechner law is derivable in a simple way from the Elovich equation (−dx/dt=m exp(nx), which is observed experimentally in numerous physiological and biochemical systems, and which has a simple derivation from solid state charge transport across interfaces in these systems. It therefore seems reasonable to interpret data conforming to the Webner-Fechner law to imply that the observed phenomenon is rate-limited by interfacial charge transport in the cell. By a similar analysis, the Loewenstein equation, which may be considered an exact form of the Weber-Fechner law applicable to data over a wider range of values of the variables, is derived from a more exact form of the Elovich equation.
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    Bulletin of mathematical biology 38 (1976), S. 199-203 
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    Notes: Abstract A simple similarity transformation of the Leslie matrix renders certain properties obvious. In particular the characteristic polynomial, characteristic vectors and principal vectors can be explicitly written out. Bounds for the dominant root are given.
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    Bulletin of mathematical biology 38 (1976), S. 659-669 
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    Notes: Abstract A mathematical description of the process of adherence to glass of the rat thymus lymphocytes is presented. It is based on the result of previous work in which the process was studied in the course of the flow of the51Cr labelled cell suspension through the glass-bead column. The concentration of cell suspension, flow velocity and medium temperature were constant; the experiments were performed with different lengths of the bead bed. The amount of cells captured on the glass beads' surface was calculated as a function of time. Two approaches to the mathematical description of the process are presented. The first one is based on the linear equation of kinetics of cell retention on the elementary thin layer and on the transport equation of the flow of the suspension through the column. In the second one, the differential equation of the adhesion, derived from the experimental data, is discussed.
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    Bulletin of mathematical biology 38 (1976), S. 83-86 
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    Notes: Abstract Complementary variational principles are derived for the pressure boundary value problems in Weinbaum's (1965) model of the human eye. These principles can be used to obtain accurate solutions for the pressure.
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    Bulletin of mathematical biology 38 (1976), S. 71-82 
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    Notes: Abstract The bat wing is used as an experimental preparation and as a self-contained vascular bed. The number, dimensions, and distribution of the vessels of the real vascular bed are included into an analyzable, representative geometric configuration. Based on theoretical analysis and experimental data, equations are developed and utilized to characterize the pressure-flow relationships for each branching order of the vascular field. The geometric configuration and associated describing equations are used to determine the resistance distribution of the microvascular bed. The predicted values are compared with experimentally determined quantities in normal and hypertensive animals.
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    Bulletin of mathematical biology 38 (1976), S. 219-237 
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    Notes: Abstract The geometry of the human bronchial tree has been described as a network formed by successive dichotomous branching with constant branching angles and geometrically decaying branch lengths. Models having these properties and with randomly distributed branching planes are constructed. The distribution of the end points of the model networks are described by computing the variance of the distributions in the direction of the axis of the network and in the transverse directions. It is found that, for a given decay ratio, there is a branching angle for which the volume filled by the end points is a maximum. The advantages of the network with the decay ratio and branching angle of the human bronchial tree are discussed.
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    Bulletin of mathematical biology 38 (1976), S. 269-275 
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    Notes: Abstract The steady state distribution of oxygen tension in thein vivo cornea is estimated in the present study by using a nonlinear oxygen consumption rate equation of the Michaelis-Menten type. Such a rate expression is more accurate than the previous simplified versions in predicting the oxygen consumption rate. It is found that for an open eye with or without contact lens, the oxygen tensions predicted previously are in good agreement with these predicted in the present work. However, for a closed eye with or without contact lens, the previous predictions underestimate the oxygen tension.
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    Notes: Abstract The dual reciprocal and antagonistic organization of B- and D-neurons of the afferent visual system is obtained using differentiation and integration as mathematical equivalents of visual information processing by an impulse frequency code. The spatial and temporal derivatives lead to the transient responses. A constant and a time-dependent term proportional to the luminance distribution describe the sustained response components and the shift-effect of retinal on- and off-center ganglion cells. Receptive field properties of lateral geniculate cells and their antagonistic shift-effect are obtained by passing the retinal output, i.e. the difference between B- and D-neurons' activity, once again through the same operations. However, the factor of proportionality is applied to the retina alone. The surprisingly small difference between retinal and geniculate receptive field properties on the one hand and the dramatic change from a synergistic to an antagonistic shift-effect on the other hand are thereby explained. The theory offers an understanding of a a possible functional significance of the shift-effect as a mechanism of transientrestoration of visual information, which prevents the system from total fading by means of shifts of the retinal image, normally produced by eye movements.
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    Bulletin of mathematical biology 38 (1976), S. 295-304 
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    Notes: Abstract Applications of randomly connected networks are reviewed briefly. The connectivity of a random network has been defined in a variety of ways including output connectivity, total or network connectivity, connectance, expected path length and radius. One or more of these definitions may prove more convenient in a given experimental system. Interrelations among these definitions are derived and displayed and asymptotic results provided in the form of two theorems. Computer simulations were used to explore the range of application of these asymptotic approximations. The results were used to determine the output connectivity of the neurons of the brain.
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    Bulletin of mathematical biology 38 (1976), S. 321-322 
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    Bulletin of mathematical biology 38 (1976), S. 325-350 
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    Bulletin of mathematical biology 38 (1976), S. 547-563 
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    Notes: Abstract In order to recognize the realizability of inputs with different physical natures through a component, Yoneda's Lemma is applied. The major utility of this Lemma is when the components produce only energy. From this, it is assumed that a new material input must exist which was not recognized in the original developments in biological systems representation. Moreover, simple transfers of energy, between objects, components, and among both objects and components are developed under the generic name; energetical evolution. Thus, energetical evolution appears as anew element in the abstract representation of biological systems. These new concepts are incorporated into a new abstract diagram and a newM β category.
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    Bulletin of mathematical biology 38 (1976), S. 569-571 
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    Bulletin of mathematical biology 38 (1976), S. 573-596 
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    Notes: Abstract The question of efficiency in performing biological functions is raised in the context of peristaltic fluid transport. To deal with this problem a complete solution for peristaltic flow in a pipe and in a channel, assuming a given time mean flow, is developed, by a double expansion in terms of the Reynolds number and the square of the wave number. This solution is valid for arbitrary waveshapes. We resolve a long-standing problem and show that quite generally the pressure rise per wave length is constant on a cross section. We also show that for a sinusoidal wave (and others) the interaction of Reynolds number and wave number is a third-order effect for this pressure rise. Plow-type waves, nipple-type waves and the sinusoidal wave are compared for maximum efficiency and for minimum energy usage. It is found that large plows are best from mechanical efficiency considerations, but large nipples use the least energy. The biological implications of these results are discussed.
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    Bulletin of mathematical biology 38 (1976), S. 633-642 
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    Notes: Abstract A theoretical analysis of the transient temperature responses of a heated thermocouple and its surroundingin vivo tissue is described. The model includes the effects of local blood perfusion, metabolic heat generation and blood pooling. The solutions presented are generalized for pulsed heating in the probe region. Inspection of these solutions reveals that for accurate experimental results precise knowledge of the tissue's thermal conductivity is necessary but that blood pooling around the probe may sometimes be regarded as an insignificant parameter.
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    Bulletin of mathematical biology 38 (1976), S. 643-658 
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    Notes: Abstract Analytic and numerical solutions to two coupled nonlinear diffusion equations are studied. They are the modified equations of Volterra and Lotka for the spatially stratified predatorprey population model. In a bounded domain with the reflecting boundary, equilibrium, stability, and transition to time-periodic solutions are analyzed. For a wide class of initial states, the solutions to the initial boundary-value problem evolve into their corresponding stable, space-homogeneous, periodic oscillations. In an unbounded domain, a family of traveling wave solutions is found for certain exponential, initial distributions in the limit as the diffusion coefficientv 1 of the prey tends to zero. In the presence of both diffusions, the results of a numerical simulation to an initial-value problem showed the rapid formation of the Pursuit-Evasion Waves whose speed of propagation and amplitudes increase with the diffusion coefficientv 1.
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    Bulletin of mathematical biology 38 (1976), S. 535-546 
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    Notes: Abstract Time-integration of the master equation governing the birth-and-death model of the Volterra-Lotka reaction is carried out for three different initial conditions, with the results: (i) Fluctuations destroy the deterministic steady state in a manner quantitatively predicted from a cumulant expansion; (ii) The sustained oscillatory behavior predicted by the deterministic model degenerated after 1/4 cycle in the stochastic model; (iii) It is possible to select initial distributions such that the asymptotic distribution is a spike at the origin of the plane of reactants.
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    Bulletin of mathematical biology 38 (1976), S. 565-568 
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    Bulletin of mathematical biology 38 (1976), S. 701-712 
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    Notes: Abstract This study is concerned with the application of a possible form of a strain-energy function suitable for soft biological tissues. Two problems considered here are related to simultaneous extension and inflation of cylindrical arteries, and inflation of the left ventricle under a given internal pressure. The values of the material constants are obtained via comparison of theoretical results with experimental findings. Some details concerning the wall stresses and the elastic stiffness are also given in the paper. For each case, it is seen that experiment and theory are in good agreement.
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    Bulletin of mathematical biology 38 (1976), S. 723-738 
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    Notes: Abstract We give a stochastic foundation to the Volterra prey-predator population in the following case. We take Volterra's predator equations and let a free host birth and death process support the evolution of the predator population. The purpose of this article is to present a rigorous population sample path construction of this interacted predator process and study the properties of this interacted process. The constructions yields a strong Markov process. The existence of steady-state distribution for the interacted predator process means the existence of equilibrium population level. We find a necessary and sufficient condition for the existence of a steady-state distribution. Next we see that if the host process possesses a steady-state distribution, so does the interacted predator process and this distribution satisfies a difference equation. For special choices of the auto death and interaction parametersa andb of the predator, whenever the host process visits the particular statea *=a/b the predator takes rest (saturates) from its evolution. We find the probability of asymptotic saturating of the predator.
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    Bulletin of mathematical biology 38 (1976), S. 695-700 
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    Notes: Abstract This paper deals with stochasticm-compartmental systems with continuous time-dependent infusions into all compartments and reversible time-independent flows between any two compartments. A methodology for the first two moments of the distribution of the number of units in the different compartments at any point in time is outlined without resorting to the usual techniques of generating functions and inverse Laplace transforms. A possible application to a systems analysis of the kidney transplant system is discussed.
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    Bulletin of mathematical biology 38 (1976), S. 713-721 
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    Notes: Abstract The kinetics of cellular depositon from a stagnant solution to a surface are studied, taking into account the combined effect of an interaction field between the cells and the surface and of an external field. Since the forces involved in the adhesion of cells to a surface are short ranged, the cells are conveyed to the vicinity of the surface only by the external field. The equations developed are general, in the sense that they are independent of any particular form of the potential energy function, provided that it presents an appreciable potential barrier between the cells and the deposition surface. The characteristic shape of the curve representing the decay of the fraction of cells in solution with time is shown to be affected by the value ofPt *, consisting of the probability per unit time,P, for the escape over the potential barrier, and the sedimentation time,t *. A simple inspection procedure of this curve can disclose the relative significance of the external field and of the potential barrier in the overall kinetics of deposition. In addition, such an inspection can reveal the existence of alterations in the cellular adhesiveness with increasing coverage of the deposition surface. By matching the equation obtained to experimental results, the cellular adhesiveness, in term ofP, and the sedimentation rate (in the case of very slow sedimentation) can be evaluated.
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    Bulletin of mathematical biology 38 (1976), S. 739-743 
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    Notes: Abstract The analysis of a previous paper obtaining bounds on the total population number of species (chemical or biological) described by the recently proposed Dreitlein-Smoes model of oscillatory kinetic systems, including diffusion, is extended to generalized models of the Dreitlein-Smoes type, describing a system ofS components withS〉2. The results for such generalized models are analogous to those of the previous case. It is found that the effects of diffusion serve to restrict the region in the concentration space available to limitcycle type oscillations.
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    The Geneva risk and insurance review 2 (1976), S. 3-4 
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    Topics: Economics
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    The Geneva risk and insurance review 2 (1976), S. 5-9 
    ISSN: 1554-9658
    Source: Springer Online Journal Archives 1860-2000
    Topics: Economics
    Type of Medium: Electronic Resource
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  • 97
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    The Geneva risk and insurance review 2 (1976), S. 10-13 
    ISSN: 1554-9658
    Source: Springer Online Journal Archives 1860-2000
    Topics: Economics
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  • 98
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    The Geneva risk and insurance review 2 (1976), S. 16-26 
    ISSN: 1554-9658
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    Topics: Economics
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  • 99
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    The Geneva risk and insurance review 2 (1976), S. 27-55 
    ISSN: 1554-9658
    Source: Springer Online Journal Archives 1860-2000
    Topics: Economics
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    The Geneva risk and insurance review 3 (1976), S. 5-6 
    ISSN: 1554-9658
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    Topics: Economics
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