455 research outputs found
Upper Cretaceous, K/T boundary, and Paleocene agglutinated foraminifers from Hole 959D (CĂŽte d'Ivoire-Ghana Transform Margin)
Upper Cretaceous agglutinated foraminifer assemblages from Hole 959D of Ocean Drilling Program (ODP) Leg 159, CĂŽte dâIvoire-Ghana Transform Margin, reflect the subsidence history and paleoceanography of the widening equatorial Atlantic gateway. Five benthic foraminifer assemblage types are recognized: (1) Santonian and the lowermost Campanian assemblages (Cores 159-959D-65R and 64R) are characterized by the occurrence of bathyal calcareous benthic foraminifers with an increasing proportion of agglutinated foraminifers. The disappearance of calcareous foraminifers and assemblages exclusively composed of organically cemented agglutinated forms in Section 159-959D-65R-3 reflects the subsidence of the seafloor below the calcite compensation depth (CCD); (2) lower Campanian "biofacies B" assemblages (Cores 159-959D-63R through 61R) are exclusively composed of low-diversity agglutinated foraminifers, accompanied by abundant and occasionally well-preserved radiolarian assemblages; (3) middle Campanian to upper Maastrichtian deposits (Cores 159-959D-59R through 49R) contain an exclusively agglutinated Rzehakina epigona biofacies, which is well-known from middle to deep bathyal sites along the North Atlantic margins; (4) a change in agglutinated foraminifer assemblage composition toward morphologies commonly observed in present infaunal habitats and the common occurrence of the presumably infaunal genus Spiroplectammina are observed in Core 159-959D-48R. This change in agglutinated foraminifer assemblages corresponds to the Tethyan early Paleocene "Spiroplectammina event;" (5) a diversified Paleocene "Lizard Springs type" assemblage is characterized by several diverse Rzehakina, Saccamina, and Haplophragmoides species. Assemblages from Cores 159-959D-48R through 44R display high species diversity and reflect the deepest (lower bathyal to upper abyssal) paleobathymetry.
Ranges of agglutinated foraminifer marker species and occurrences of paleoceanographic events within this biostratigraphic framework are almost identical to those observed in the North Atlantic, in the Western Tethys, and along the conjugate Brazilian margin. These observations lead us to confirm that a deep-water circulation system common to the North and South Atlantic has been active at least since the Santonian
Revisiting ligand-to-ligand charge transfer phosphorescence emission from zinc(II) diimine bis-thiolate complexes: it is actually thermally activated delayed fluorescence
In this work we revisit and re-evaluate the photophysical behavior of the prototypical complex [Zn(SC6H4-4-R)2(phen)] as the most in-depth studied type of Zn(II)-based triplet state emitters. Previous reports suggest population of ligand-to-ligand charge transfer (LLCT) states via phenanthroline localized ÏÏ* states, with an energy barrier between the 3ÏÏ* and the bk;1/3LLCT states requiring thermal activation. Besides very weak prompt fluorescence, the dominant radiative mechanism was attributed to phosphorescence. Our photophysical studies, including temperature-dependent quantum yield determination and time-resolved luminescence measurements, reveal a high radiative rate constant kr=3.5Ă105â
sâ1 at room temperature and suggest thermally activated luminescence as the major emission path. High-level DFT/MRCI calculations confirm this assignment and provide deeper insight into the excited-state kinetics, including rate constants for the (reverse) intersystem crossing processes. Thus, our study demonstrates that further optimization of the photophysical properties of this type of Zn(II) triplet exciton emitter bears great potential for future application in devices
High content of long-chain n-3 polyunsaturated fatty acids in red blood cells of Kenyan Maasai despite low dietary intake
<p>Abstract</p> <p>Background</p> <p>Increasing land restrictions and a reduced livestock-to-human ratio during the 20th century led the Maasai to lead a more sedentary, market-orientated lifestyle. Although plant-derived food nowadays contributes substantially to their diet, dairy products being high in saturated fatty acids (SFA) and low in polyunsaturated fatty acids (PUFA) still are an important energy source. Since reliable data regarding the Maasai diet date back to the 1980s, the study objective was to document current diet practices in a Kenyan Maasai community and to investigate the fatty acid distribution in diet and red blood cells.</p> <p>Methods</p> <p>A cross-sectional study was conducted among 26 Maasai (20 women, 6 men) from Loodokilani, Kajiado District, Kenya. Food intake was described by the subjects via 24-h recall, and both food and blood samples were analysed.</p> <p>Results</p> <p>Two main foods - milk and <it>ugali </it>- constituted the Maasai diet in this region. A total of 0.9 L of milk and 0.6 kg of <it>ugali </it>were consumed per person and day to yield an energy intake of 7.6 MJ/d per person. A major proportion of ingested food contributing 58.3% to the total dietary energy (en%) was plant-derived, followed by dairy products representing 41.1 en%. Fat consumed (30.5 en%) was high in SFA (63.8%) and low in PUFA (9.2%). Long-chain n-3 PUFA (EPA, DPA and DHA) made up only 0.15% of the ingested fatty acids, but 5.9% of red blood cell fatty acids.</p> <p>Conclusion</p> <p>The study indicates the Maasai diet is rich in SFA and low in PUFA. Nevertheless, red blood cells are composed of comparable proportions of long-chain n-3 PUFA to populations consuming higher amounts of this fatty acid group.</p
Outlier detection for multivariate categorical data
This is an Accepted Manuscript of an article published by Taylor & Francis in â Quality and Reliability Engineering International â on 06th June 2018, available online: https://onlinelibrary.wiley.com/doi/abs/10.1002/qre.2339The detection of outlying rows in a contingency table is tackled from a Bayesian perspective, by adapting the framework adopted by Box and Tiao for normal models to multinomial models with random effects. The solution assumes a 2âcomponent mixture model of 2 multinomial continuous mixtures for them, one for the nonoutlier rows and the second one for the outlier rows. The method starts by estimating the distributional characteristics of nonoutlier rows, and then it does cluster analysis to identify which rows belong to the outlier group and which do not. The method applies to any type of contingency table, and in particular, it could be used on the analysis of multivariate categorical control charts. Here, the use of the method is illustrated through a simulated example and by applying it to help identify heterogeneities of style among the acts in the plays of the First Folio edition of Shakespeare dramaPeer ReviewedPostprint (author's final draft
Records of past mid-depth ventilation: Cretaceous ocean anoxic event 2 vs. Recent oxygen minimum zones
Present day oceans are well ventilated, with the exception of mid-depth oxygen minimum zones (OMZs) under high surface water productivity, regions of sluggish circulation, and restricted marginal basins. In the Mesozoic, however, entire oceanic basins transiently became dysoxic or anoxic. The Cretaceous ocean anoxic events (OAEs) were characterised by laminated organic-carbon rich shales and low-oxygen indicating trace fossils preserved in the sedimentary record. Yet assessments of the intensity and extent of Cretaceous near-bottom water oxygenation have been hampered by deep or long-term diagenesis and the evolution of marine biota serving as oxygen indicators in today's ocean. Sedimentary features similar to those found in Cretaceous strata were observed in deposits underlying Recent OMZs, where bottom-water oxygen levels, the flux of organic matter, and benthic life have been studied thoroughly. Their implications for constraining past bottom-water oxygenation are addressed in this review. We compared OMZ sediments from the Peruvian upwelling with deposits of the late Cenomanian OAE 2 from the north-west African shelf. Holocene laminated sediments are encountered at bottom-water oxygen levels of 10 ÎŒmol kgâ1 showed an inverse exponential relationship of bottom-water oxygen levels and organic carbon accumulation depicting enhanced bioirrigation and decomposition of organic matter with increased oxygen supply. In the absence of seasonal laminations and under conditions of low burial diagenesis, this relationship may facilitate quantitative estimates of palaeo-oxygenation. Similarities and differences between Cretaceous OAEs and late Quaternary OMZs have to be further explored to improve our understanding of sedimentary systems under hypoxic conditions
Specific Heat Study of 1D and 2D Excitations in the Layered Frustrated Quantum Antiferromagnets CsCuClBr
We report an experimental and theoretical study of the low-temperature
specific heat and magnetic susceptibility of the layered anisotropic
triangular-lattice spin-1/2 Heisenberg antiferromagnets
CsCuClBr with = 0, 1, 2, and 4. We find that the ratio
of the exchange couplings ranges from 0.32 to , implying a
change (crossover or quantum phase transition) in the materials' magnetic
properties from one-dimensional (1D) behavior for to
two-dimensional (2D) behavior for behavior. For , realized for = 0, 1, and 4, we find a magnetic contribution to the
low-temperature specific heat, , consistent with spinon
excitations in 1D spin-1/2 Heisenberg antiferromagnets. Remarkably, for =
2, where implies a 2D magnatic character, we also observe
. This finding, which contrasts the prediction of made by standard spin-wave theories, shows that Fermi-like
statistics also plays a significant role for the magnetic excitations in
frustrated spin-1/2 2D antiferromagnets
Fertility Ideals of Women and Men Across the Life Course
This paper explores the stability of womenâs and menâs fertility preferences across the life course. The data come from the first six waves of the German Family Panel (pairfam), which span the period from 2008/2009 until 2013/2014. In our analysis, fertility preferences are measured using the following question: âUnder ideal circumstances, how many children would you like to have?â The average number cited by both women and men is 2.2. With rising age, this number declines modestly. Relying on fixed-effects modelling, we find that neither partnership status nor economic circumstances have any causal effect on fertility preferences. However, as the number of children a respondent has increases, his or her ideal number of children is also likely to grow. Thus, fertility ideals appear to undergo changes over time, and are adjusted in line with the size of the respondentâs own family
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