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Gutenberg Open Science: Variation of stable silicon isotopes: Analytical developments and applications in Precambrian geochemistry

Gutenberg Open Science: Variation of stable silicon isotopes: Analytical developments and applications in Precambrian geochemistry

First investigations of stable silicon isotopes can be dated back to the 1950s (Reynold and Verhoogen, 1953; Allenby, 1954). However, due to the severity of Si purification methods and the poor analytical precision and accuracy accomplishable at that time, the reliability of these first results is doubtful. In subsequent studies, analytical precision was improved by the introduction of new analysis methods e.g. using isotope ratio mass spectrometry (IRMS, Tilles, 1961; Douthitt, 1982; Molini-Velsko et al., 1986; De La Rocha et al., 1996), culminating in the onset of MC-ICP-MS in the mid 1990s (for details see Chapter 4.2.). Until now more than 100 articles on Si stable isotopes were published, whereby the majority of these articles emerged in last years, illustrating the increased interest on this research field on the basis of the ability to determine smaller isotope variations. Whereby, the two most comprehensive and most frequently referred studies are the publication of Douthitt (1982) and a book of Ding (1996). However, most articles cover analytical methods and fractionation in natural systems and only few publications about experimental or theoretical approaches on the dimension of isotope fractionation exist (Georg et al. 2007b; Méheut et al., 2007, 2009).
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Understanding trophic interactions in host-parasite associations using stable isotopes of carbon and nitrogen

Understanding trophic interactions in host-parasite associations using stable isotopes of carbon and nitrogen

Overall, the parasite’s taxonomy in combination with its way of nutrient uptake determines its trophic position with respect to the host. Although there are no data available regarding stable isotope composition of acan- thocephalans, the results of the present study were in line with some other groups of parasites, which share a similar absorptive feeding strategy. For example, ces- todes were reported to be depleted in δ 15 N and δ 13 C [14, 17, 20]. These findings were also opposed to a predator–prey relationship, that defines parasites as con- sumers, which feed on their hosts [29]. Cestodes as well as acanthocephalans take up nutrients through the body surface (tegument) and assimilate compounds, which were previously processed by the host. These metabolites (pep- tides, amino acids, carbohydrates mono-oligosaccharides) are depleted in heavier stable isotopes, as due to the kinetic isotope effect, lighter isotopes are favored in biochemical reactions [30]. Parasites, in general, face limitations in metabolism and energy utilization under anaerobic conditions and various macromolecules have to be assimilated via the tegument [31]. It is also known that endoparasites are not able to synthetize several complex molecules such as purine nucleotides, fatty acids, sterols, and some amino acids de novo. The only source for these molecules remains the host’s me- tabolism [31, 32]. Ammonia to be excreted by the host,
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Using stable isotopes to follow excreta N dynamics and N2O emissions in animal production systems

Using stable isotopes to follow excreta N dynamics and N2O emissions in animal production systems

reduces the chances of measuring robust 29 R and 30 R ratios. Fractionation results from the differential responses of stable isotopes in either kinetic reactions, where lighter isotopes tend to react faster, or exchange reactions, where heavy isotopes concentrate where bonds are strongest (Fry, 2006). The result is that products have a lighter isotopic composition owing to the fractionation process. The degree of fractionation can be calculated as a fractionation factor. Detailed discussion of fractionation factors is beyond the scope of this article and the reader is directed to other arti- cles (Fry, 2006; Sharp, 2007). It has been experimentally shown that the isotopic fractionation during the production of N 2 O via denitrification may vary with the 15 N enrichment
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Middle to Late Pleistocene environments based on stable organic carbon and nitrogen isotopes of loess‐palaeosol sequences from the Carpathian Basin

Middle to Late Pleistocene environments based on stable organic carbon and nitrogen isotopes of loess‐palaeosol sequences from the Carpathian Basin

Stable organic carbon and nitrogen isotopes can be used to interpret past vegetation patterns and ecosystem qualities. Here we present these proxies for two loess-palaeosol sequences from the southern Carpathian Basin to reconstruct the palaeoenvironment during the past 350 ka and establish regional commonalities and differences. Before now, isotopic studies on loess sequences from this region were only conducted on deposits from the last glacial cycle. We conducted methodological tests involving the complete decalcification of the samples prior to stable isotope analyses. Two decalcification methods (fumigation method and wet chemical acidification), different treatment times, and the reproducibility of carbon isotope analyses were tested. Obtained results indicate that the choice of the decalcification method is important for organic carbon stable isotope analyses of loess-palaeosol sequences because ratios vary by more than 10 & between thewet chemical and fumigation methods, due to incomplete carbonate removalbythe latter. Therefore, we suggest avoiding the fumigation method for studies on loess-palaeosol sequences. In addition, our data show that samples with TOC content <0.2% bear increased potential for misinterpretation of their carbon isotope ratios. For our sites, C 3 -vegetation is predominant and no palaeoenvironmental shifts leading to a change of the dominant photosynthesis pathway can be detected during the Middle to Late Pleistocene. Furthermore, the importance of further stable nitrogen isotope studies is highlighted, since this proxy seems to reflect past precipitation patterns and reveals favourable conditions in the southern Carpathian Basin, especially during interstadials. Stephan P €otter (stephan.poetter@geo.rwth-aachen.de), Arndt Schmitz, Philipp Schulte and Frank Lehmkuhl, Department of Geography, RWTH Aachen University, W €ullnerstraße 5b, Aachen 52064, Germany; Andreas L€ucke and Holger Wissel, Institute of Bio- and Geosciences, Agrosphere (IBG-3), Forschungszentrum J€ulich GmbH, Wilhelm- Johnen-Stra ße, J€ulich 52428, Germany; Igor Obreht, Organic Geochemistry Group, MARUM-Center for Marine Environmental Sciences and Department of Geosciences, University of Bremen, Leobener Str. 8, Bremen 28359, Germany; Michael Zech, Institute of Geography, Technical University of Dresden, Helmholtzstra ße 10, Dresden 01069, Germany; Slobodan B. Markovi c, Chairof Physical Geography, Universityof Novi Sad, Trg Dositeja Obradovica 3, Novi Sad 21000, Serbia; received 16th April 2020, accepted 17th July 2020.
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Cadmium, copper and zinc stable isotopes as analytical tool to trace sources and processes in agricultural systems

Cadmium, copper and zinc stable isotopes as analytical tool to trace sources and processes in agricultural systems

Furthermore, stable metal isotopes of the soil and all inputs and outputs were (Cd) and will be (Cu & Zn) determined. Cd mass balances showed losses for wheat cultivation (-0.01 to -0.35 g ha -1 y -1 ) and accumulations for barley cultivation (0.18 to 0.71 g ha -1 y -1 ). Isotopic ratios in wheat (? 114/110 Cd straw-grain = -0.34 to -0.38‰) and barley plants (-0.44 to -0.82‰) revealed that uptake and retranslocation of Cd in the plants is driven by physiological processes to reduce toxic Cd impacts. Cu and Zn mass balances showed that manure application is by far the most important Cu (146-340 g ha -1 y -1 ) and Zn (947-1’742 g ha -1 y -1 ) input. Inputs with bulk deposition and through parent material weathering were by 1-2 orders of magnitude smaller. Beside the Cu and Zn budgets, stable isotope data (not yet analysed) will be presented and discussed to assess the biogeochemical processes and redistribution of (anthropogenic) Cu and Zn in agricultural systems.
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Stable water isotopes in the global water cycle: Atmospheric model simulations and application to proxy data

Stable water isotopes in the global water cycle: Atmospheric model simulations and application to proxy data

differ starkly from the present (e.g., Lee et al. , 2008 ). Stable water isotopes have been included in the hydrological cycle of various global atmospheric models, namely, GISS ( Jouzel et al. , 1987 ), ECHAM ( Hoffmann et al. , 1998 ), MUGCM ( Noone and Simmonds , 2002 ), CAM2.0 ( Lee et al. , 2007 ), LMDZ ( Bony et al. , 2008 ), CAM3.0 ( Noone and Sturm , 2010 ) and the atmosphere-ocean coupled model HadCM3 ( Tin- dall et al. , 2009 ). These models have been successfully used for simulating the present and paleoclimatic distributions of the stable isotopes in the global hydrological cycle. Charles et al. ( 1994 ) find that changes in moisture transport and source regions for Greenland at the LGM may have produced an isotopic response independently of temperature changes. A similar result has also been found for shorter (millennial- scale) climate variations ( Liu et al. , 2012 ). Masson-Delmotte et al. ( 2006 ) show that a major part of Greenland and Antarctic coolings of the GCM simulations is caused by the prescribed local elevation increase due to ice sheets at the LGM. Werner et al. ( 2000 ) find an increased seasonality in the annual cycle of precipitation over Green- land during the LGM, but not over Antarctica. Conventionally, the spatial slope over a region (the relationship between δ 18 O precip and temperature over a region) was as-
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Modelling Stable Isotopes in the Eemian and Holocene Hydrological Cycles

Modelling Stable Isotopes in the Eemian and Holocene Hydrological Cycles

The climate of the younger part of the Quaternary 1 is characterised by frequent North- ern Hemisphere glaciation, interrupted by warm periods. These interglacial stages are also called interstadials due to their short duration and their transient character compared to the glacial/stadial times. The most prominent Quaternary climate variation is the 100 ka glacial-interglacial cycle that appeared in the records after the mid-pleistocene transition from a 40 ka cycle at about 0.8 million years before present. The last 450 thousand years (kiloyears=ka) have been characterised by a prominent series of four glacial-interglacial cy- cles with a short (less than 10 ka) warm period and a longer (100 ka) gradual cooling and a glacial period each of which ended with an abrupt warming (Augustin et al., 2004). The peak of the warm period at the end of the penultimate cycle is called Eemian and dates back to 124 ka before present (BP). The existence of a 100 ka cycle is often referred to as the 100 ka paradox or the 100 ka problem, since the external (i.e. orbital) forcing is weak in this frequency band, while the climatic response is strong (e.g. Paillard, 2001). This suggests that the variations in insolation are rather a trigger instead of forcing (Claussen et al., 2007). Nonlinear amplification by internal components of the climate system, such as ice sheets or the deep ocean circulation is necessary to explain the glacial-interglacial cycles.
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Minor element composition and stable oxygen isotopes of calcareous shells of the dinoflagellate Thoracosphaera heimii

Minor element composition and stable oxygen isotopes of calcareous shells of the dinoflagellate Thoracosphaera heimii

As a last possible environmental influence we need to consider the living depth of T. heimii. We observed that the correlation between temperature and the  18 O composition of T. heimii shells from surface sediment samples in the Atlantic Ocean slightly increases when we consider temperatures at mixed layer depth (MLD) instead of sea surface temperatures or temperatures averaged over 200m water depth. The lower limit of the surface mixed layer is characterized by an abrupt density change (pycnocline) or temperature change (thermocline). And these gradients are often co-located with a maximum in chlorophyll-a concentration. The upper part of the photic zone and the area immediately above the deep chlorophyll maximum (DCM) is supposedly the living depth of T. heimii (Kohn & Zonneveld, 2010). Therefore we used the MLD from the Monterey & Levitus (1997) database as a measure for the depth of the DCM. It should be noted however, that the MLD is not a constant or permanent phenomenon. Temporal variabilities of the MLD can range from diurnally to interannually, including seasonally and interseasonally. Also the spatial variability of the MLD is very large. The MLD can be less than 20 m in the summer hemisphere, while reaching more than 500 m in the winter hemisphere (de Boyer Montégut et al., 2004 with all references therein). Unfortunately, so far no information is available on how these seasonal variabilities of the MLD or DCM effect the isotopic composition of T. heimii. But since we assume a year-round production of T. heimii shells (see discussion above), the use of annually averaged MLDs can be justified.
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A change in coral extension rates and stable isotopes after El Niño-induced coral bleaching and regional stress events

A change in coral extension rates and stable isotopes after El Niño-induced coral bleaching and regional stress events

with sampling problems, as sampling off the central axis of the thecal walls in P. strigosa should also result in more positive δ 18 O and δ 13 C values, and larger Sr/Ca ratios (see Giry et al. 18 , their Fig. 5). We also researched other possible explanations for this baseline shift. For example, cloud cover data do not show significant changes after 1998 (Fig. 3). Thus, a change in light levels/solar irradiance, that could potentially influence photosynthesis, is ruled out. Observations from the MNP, west of the study site, suggest additional influence from other stressors on coastal Venezuelan reefs starting in the mid-1990s: A mortality event in early 1996 in the MNP was described as one of the greatest massive die-offs reported in Venezuela. It has been attrib- uted to an abnormal upwelling and expansion of cold (< 20 °C) and nutrient-rich water along the central-west coast, combined with a lack of winds that produced a plankton bloom leading to anoxic conditions on the sea- floor 14 . Detailed surveys in the MNP revealed that corals suffered mortalities from 60 to 98%, depending on the
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Stable isotopes in loess-paleosol-sequences from the Carpathian Basin : methodological challenges and paleoenvironmental implications

Stable isotopes in loess-paleosol-sequences from the Carpathian Basin : methodological challenges and paleoenvironmental implications

Germany; 3 Institute of Geography, Technical University of Dresden, Germany; 4 Organic Geochemistry Group, MARUM-Center for Marine Environmental Sciences and Department of Geosciences[r]

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Variations in surface and thermocline conditions of the Western Pacific Warm Pool : Insights from Mg/Ca and stable isotopes in foraminifera tests

Variations in surface and thermocline conditions of the Western Pacific Warm Pool : Insights from Mg/Ca and stable isotopes in foraminifera tests

controls the spatial distribution of precipitation and the meridional transport of heat and energy within the atmosphere [e.g. Donohoe et al., 2013]. It is basically driven by meridional temperature gradients between tropics and subtropics. Exceptional warm temperatures across the equator cause ascend of air. Near the tropopause, the rising air diverges into a northern and a southern branch that flow poleward, descend in the subtropics and then flow back within easterly trades towards the equator, where the branches converge creating a trough of deep atmospheric convection and heavy rainfall, known as the ITCZ. The ITCZ is thus mainly allocated with the ascending branch of the Hadley circulation. The atmospheric near surface flow is characterized by warm and moist easterly trades that also feed the ITCZ [e.g. Schneider et al., 2014]. The position of the ascending branch of the Hadley cells and the ITCZ mainly depends on the thermal conditions near the surface which are primarily modulated by insolation and ocean currents that transport huge amounts of heat. In accordance with this, the rising Hadley branch and the ITCZ seasonally migrate between the hemispheres [e.g. Schneider et al., 2014]. During boreal summer (austral winter), the rising Hadley branch, the ITCZ and therewith maximal precipitation are located to the north of the equator (over the northern WPWP) and southeasterly trade winds prevail. During boreal winter (austral summer), the rising Hadley branch and the ITCZ shift to the south, maximal rainfall is located to the south of the equator (over the southern WPWP) and northeasterly winds prevail (Figure 2.2).
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Unveiling community patterns and trophic niches of tropical and temperate ants using an integrative framework of field data, stable isotopes and fatty acids

Unveiling community patterns and trophic niches of tropical and temperate ants using an integrative framework of field data, stable isotopes and fatty acids

Similarities in resource use were correlated between Brazil and Germany ( Fig. 1 , Mantel test, rho = 0.63, p = 0.03). In both communities, large prey was set apart from the other resources, being used less frequently and by fewer species. Seeds and melezitose changed positions between communities. In Germany, all ants used both sugars indiscriminately, while in Brazil several species used more sucrose (e.g., Camponotus zenon, Gnamptogenys striatula, Pachycondyla striata, Odontomachus chelifer, Solenopsis sp.6) and others used more melezitose (e.g., Pheidole aper, Solenopsis sp.8, Wasmannia affinis) ( Table 2 ). Both modularity (Q BR = 0.16, Q GE = 0.14) and network specialization (H 2 ′ BR = 0.13, H 2 ′ GE = 0.12) were relatively low and similar between sites. Species used resources in different ways and a few were more specialized (see below), but there were no clear links between particular resources and species or groups of species.
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Gutenberg Open Science: Exploring physical processes related to past climate proxies: lake sediments and stable water isotopes

Gutenberg Open Science: Exploring physical processes related to past climate proxies: lake sediments and stable water isotopes

In future research, two main issues will have to be addressed in order to establish an appropriate description of the dependence of the non-equilibrium fractionation factor k on wind velocity (or, alternatively, to show in a more definite way that this dependence is negligible). First, more measurements of isotope ratios in atmospheric water vapor should be made available that al- low to test newly developed parameterizations of k. As isotope ratios in the evaporation flux cannot be measured directly, complex models, which include processes like the advection of water vapor (e.g. GCMs or the Lagrangian approach used here) have to be applied to compare theoretical predictions from a Craig-Gordon model with measurements. Second, more recent parameterizations of water evaporation from the ocean (see e.g. Fairall et al., 2003) might pro- vide the theoretical basis for the description of k. These parameterizations have the advantage that they are grounded on measurement data in a much stronger way than the mostly theoretical Brutsaert model applied by MJ79. However, they usually do not contain an explicit formulation of molecular diffusion, but subsume the properties of the diffusive surface layer in a parameter called moisture roughness length, which is then parameterized with an empirical equation. Ba- sically, the moisture roughness length can also be expressed in terms of a diffusion coefficient or Schmidt number (and thus calculated for the different water isotopes) (cf. Liu et al., 1979; Brutsaert, 1982). But, owing to its empirical formulation, it is not straightforward to employ these more recent parameterizations of evaporation for the deduction of the isotope fractionation factor. In our opinion, this issue will have to be addressed with the help of a comprehensive ex- perimental (e.g. wind tunnel) study analyzing the dependence of the moisture roughness length on the Schmidt number, extending the work of Merlivat (1978a).
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Emission and dynamics of halocarbons from seagrass meadows traced by stable carbon isotopes

Emission and dynamics of halocarbons from seagrass meadows traced by stable carbon isotopes

methane fluxes with the height of the water table from a brackish coastal lake in Japan (Yamamoto et al., 2009). The authors of this study did not present a conclusive explanation for the elevated fluxes, but suggested either lateral transport in the sediment in combination with salinity gradients affecting the source strength and/or enhanced gas ebullition due to increased pressure from the water column to be responsible for the enhanced emissions during high tide. A correlation between bubble ebullition and pressure change has been reported in some previous studies (Chanton et al., 1989; Baird et al., 2004; Glaser et al., 2004). However, the only study carried out in a tidally influenced system we are aware of suggests an inverse correlation between tidal height and bubble ebullition (Chanton et al., 1989). Due to a negligible inflow of freshwater, the Ria Formosa has a fairly constant salinity close to that of the open ocean. Thus, significant salinity driven lateral changes in methanogenesis and benthic respiration as suggested by Yamamoto et al. (2009) are implausible. Nevertheless, spatial variations in the source strength may occur due to variations in the benthic communities and in the supply of substrate by litter production and root exudates. The benthic vegetation around the sampling site consisted almost exclusively of Z. noltii and was quite homogeneous with variations in the above ground biomass being clearly below a factor of 2 and thus, do not support a change in the source strength by a factor of 6 as observed for methane during tidal immersion.
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Novel methodological approaches in loess research – interrogating biomarkers and compound-specific stable isotopes

Novel methodological approaches in loess research – interrogating biomarkers and compound-specific stable isotopes

The authors gratefully acknowledge the support provided by the many cooperation partners world-wide during the last few years. M. Zech and B. Buggle thank all members of the Soil Physics Department, University of Bayreuth, for the familial working atmosphere, A. Mergner and K Jeschke for laboratory assistance, PD Dr. M. Fuchs, Dr. U. Hambach and Dr. G. Wiesenberg for valuable discussions and Prof. B. Glaser, Prof. G. Gebauer, Prof. B. Huwe and Prof. S. Markovic for logistic support. B. Buggle appreci- ates the financial support given by the German Research Foundation (DFG GL 327/8–2) and M. Zech expresses grati- tude for the financial support given by the Alexander von Humboldt-Foundation and the German Research Founda- tion (DFG ZE 844/1–1). R. Zech was supported by an SNF fellowship, and gratefully acknowledges the supervision and training by Prof. Y. Huang and his team at the Brown University over the last two years. We also thank Prof. M. Frechen for the editorial handling and proof-reading of our manuscript and an anonymous reviewer for valuable com- ments and suggestions.
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In-situ Studies of Microbial CH4 Oxidation Efficiency in  Arctic Wetland Soils – Application of Stable Carbon Isotopes

In-situ Studies of Microbial CH4 Oxidation Efficiency in Arctic Wetland Soils – Application of Stable Carbon Isotopes

My gratitude goes to staff of the Alfred-Wegener-Institute, Research Unit Potsdam, whose logistical, technical and administrative support during the joint Russian-German expeditions Lena 2009 and 2010 made life pleasant as it was on Samoylov Island, especially to Waldemar Schneider and Günther ‘Molo’ Stoof. These expeditions were the highlights of this project, and my warmest thanks go to all participants, particularly to Anna Urban, Antonina Chetverova, Christian Wille, Hanno Meyer Juliane Bischoff, Konstanze Piel, Moritz Langer, Thomas Opel, Silke Höfle and Janet Rethemeyer. Special thanks I owe to Susanne Liebner for conjoint O 2 profile measurements and always encouraging words and to Svetlana Evgrafova,
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Detection of Localized Hepatocellular Amino Acid Kinetics by using Mass Spectrometry Imaging of Stable Isotopes

Detection of Localized Hepatocellular Amino Acid Kinetics by using Mass Spectrometry Imaging of Stable Isotopes

Martijn Arts + , Zita Soons + ,* Shane R. Ellis, Keely A. Pierzchalski, Benjamin Balluff, Gert B. Eijkel, Ludwig J. Dubois, Natasja G. Lieuwes, Stijn M. Agten, Tilman M. Hackeng, Luc J. C. van Loon, Ron M. A. Heeren, and Steven W. M. Olde Damink Abstract: Mass spectrometry imaging (MSI) simultaneously detects and identifies the spatial distribution of numerous molecules throughout tissues. Currently, MSI is limited to providing a static and ex vivo snapshot of highly dynamic systems in which molecules are constantly synthesized and consumed. Herein, we demonstrate an innovative MSI meth- odology to study dynamic molecular changes of amino acids within biological tissues by measuring the dilution and conversion of stable isotopes in a mouse model. We evaluate the method specifically on hepatocellular metabolism of the essential amino acid l-phenylalanine, associated with liver diseases. Crucially, the method reveals the localized dynamics of l-phenylalanine metabolism, including its in vivo hydrox- ylation to l-tyrosine and co-localization with other liver metabolites in a time course of samples from different animals. This method thus enables the dynamics of localized biochem- ical synthesis to be studied directly from biological tissues.
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Systematics of the Electric Dipole Response in Stable Tin Isotopes

Systematics of the Electric Dipole Response in Stable Tin Isotopes

The electric dipole response is a fundamental observable to understand properties of nuclei. In Fig. 1.1 a schematic overview of a typical dipole response in medium and heavy mass nu- clei near shell closure is shown. Up to the neutron threshold discrete states are excited and distinct peaks in the energy excitation spectrum can be observed. First collective phenomena emerge already at an excitation energy of a few MeV, namely a two-phonon state, which can be interpreted as the coupling of collective surface vibrations [1]. Around the neutron thresh- old one encounters the pygmy dipole resonance (PDR) [2], which is usually thought of as an oscillation of the neutron skin against an isospin saturated core. However, the true nature of the PDR is still under discussion [3, 4]. At even higher energies the electric dipole response is dominated by the giant dipole resonance (GDR) [5], which is described as an oscillation of neutrons against protons. Traditionally, the low-energy region below the neutron threshold is investigated via nuclear resonance fluorescence experiments (NRF), while the high-energy region above the neutron threshold can be accessed by photoabsorption experiments. In this work, inelastic proton scattering experiments under small scattering angles including 0° are used [6, 7]. Inelastic proton scattering has a great advantage as it can cover both, the PDR and the GDR regions at the same time, so that these excitation modes can be measured simulta- neously in one experimental campaign. Furthermore, the PDR and GDR are measured with comparable uncertainties.
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Pup vibrissae stable isotopes reveal geographic differences in adult female southern sea lion habitat use during gestation

Pup vibrissae stable isotopes reveal geographic differences in adult female southern sea lion habitat use during gestation

Elucidating marine predator habitat use is an important challenge in behavioural ecology because it underpins species management and conservation, and has potentially important the- oretical and far reaching ecological implications [ 1 , 2 ]. However, knowledge of habitat use remains rudimentary for many marine predators. Although biologging tags enable marine predator habitat use to be directly assessed, financial and logistical constraints and ethical con- siderations associated with capture and tagging [ 3 ] often limit the number of individuals that can be tracked, which may not be representative. This is particularly problematic for central place foraging marine predators, as these often exhibit individual foraging specialization, forag- ing site fidelity and colony partitioning of foraging areas [ 4 – 8 ]. Under such circumstances, it would be desirable to study as many individuals from as many breeding colonies as possible in order to obtain an accurate representation of habitat use for a given species. Fortunately, bio- geochemical markers provide powerful tools to study marine predator habitat use, in part because sample sizes large enough to assess population-level variation can be efficiently and economically gathered either remotely (for example through biopsy sampling) or from nutri- tionally dependant offspring that are a proxy for adults, but often easier to sample [ 9 , 10 ].
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Characterizing hydrological processes within kettle holes using stable water isotopes in the Uckermark of northern Brandenburg, Germany

Characterizing hydrological processes within kettle holes using stable water isotopes in the Uckermark of northern Brandenburg, Germany

implemented in the “Hydrocalculator” programme was employed. Results indicated that isotopic composition of kettle holes has fluctu- ated both spatially and temporally, thereby representing distinct phases of dilution and enrichment being attributed to hydrological inflows of shallow groundwater, snow, rainfall, and evaporative loss. Moreover, findings revealed that evaporation/inflow (E/I) ratios chan- ged annually, which may arise from the impacts of meteorological conditions on the depth of shallow groundwater. We identified that puddle-type kettle holes exhibited the highest E/I in comparison with the other kinds of the studied kettle holes. This might be associated with intimately interlocked linkage between puddle-type kettle holes and the shallow groundwater system, which per se is highly depen- dent upon the precipitation in terms of wet and dry spell periods. The obtained results demonstrated that water loss over Uckermark in 2017 can change from 26.00% to 28.10%. Moreover, based on the obtained results of this study and the system understanding gained from the applied approaches to kettle holes of the prairie region, a simplified but informative conceptual model was developed. The model illustrates that across the highest altitudes, the recharging ket- tle holes are dominant, where a lower ratio of E/I as well as a lower electrical conductivity is seen. Conversely, the lowest topographical depressions represent the discharge kettle holes, where a higher ratio of E/I and electrical conductivity can be observed. The kettle holes that exist in between, that is, the highest and lowest altitudes, are cat- egorized as flow-through kettle holes in which the recharge takes place from one side and discharge from the other, depending upon the regional groundwater head gradient.
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