2,366 research outputs found
Late Pleistocene-Holocene History of Chaco-Pampa Sediments in Argentina and Paraguay
Eine erheblich verbesserte Rekonstruktion der spĂ€tpleistozĂ€nen/holozĂ€nen morphologischen und geologischen Geschichte des paraguayischen Chaco und der argentinischen Pampa Ebene wird vorgestellt. Wegen der groĂen Ausdehnung des Gebietes waren Satellitenbilder der SchlĂŒssel, um frĂŒhere und neue interdisziplinĂ€re geowissenschaftliche Ergebnisse zu einem verlĂ€sslicheren Bild zusammenzufĂŒhren. FĂŒr diesen synoptischen Ăberblick wurde die Interpretation von Fernerkundungsdaten durch GelĂ€ndeuntersuchungen und physikalische Altersbestimmungen ergĂ€nzt. Viele Lumineszenzalter (75 IRSL und 12 TL) von LöĂ, löĂĂ€hnlichen Sedimenten und Sanden wurden bestimmt, die bei der Rekonstruktion der Klimageschichte des Untersuchungsgebiets im Marinen Isotopen Stadium 3 bis 1 (MIS 3â1) beitragen. LöĂablagerungen ĂŒberwiegen in der Zeit vor MIS 2. Die numerische Alter von lakustrinen und alluvialen Sedimenten, im Löà zwischengelagert, belegen wechselnde feuchte und trockene Perioden in der Chaco/Pampa-Ebene im MIS 2 und MIS 1. Ăberwiegend trockene Bedingungen herrschten von 8.5 bis 3.5 ka BP (mittleres MIS 1), als Sande in Form von DĂŒnen oder in PalĂ€oflussbetten abgelagert wurden. Zeitlich begrenzte Phasen extrem verstĂ€rkter PalĂ€oflussaktivitĂ€t im MittelholozĂ€n wurden auf sporadische Starkregenereignisse in den Anden zuruÌckgefĂŒhrt. Die Ursprungsgebiete des LöĂ, der löĂartigen Sedimente und der sandigen Ablagerungen wurden in der sĂŒdwestlichen Pampa, den benachbarten AndenabhĂ€ngen und im Altiplano lokalisiert. Diese Sedimente wurden von dort nach Osten und spĂ€ter nach Nordosten transportiert, wie sich aus den morphologischen Mustern als Zeugnisse frĂŒherer Ă€olischer AktivitĂ€t rekonstruieren lieĂ.researc
The fate of porcine sperm CRISP2 from the perinuclear theca before and after in vitro fertilization
In a previous study, we reported that porcine sperm cysteine-rich secretory protein 2 (CRISP2) is localized in the post-acrosomal sheath-perinuclear theca (PT) as reduction-sensitive oligomers. In the current study, the decondensation and removal of CRISP2 was investigated during in vitro sperm capacitation, after both the induction of the acrosome reaction and in vitro fertilization. Confocal immunofluorescent imaging revealed that additional CRISP2 fluorescence appeared on the apical ridge and on the equatorial segment (EqS) of the sperm head following capacitation, likely due to cholesterol removal. After an ionophore A23187-induced acrosome reaction, CRISP2 immunofluorescence disappeared from the apical ridge and the EqS area partly not only owing to the removal of the acrosomal shroud vesicles, but to its presence in a subdomain of EqS. The fate of sperm head CRISP2 was further examined post-fertilization. In vitro matured porcine oocytes were co-incubated with boar sperm cells for 6-8 h and the zygotes were processed for CRISP2 immunofluorescent staining. Notably, decondensation of CRISP2, and thus of the sperm PT, occurred while the sperm nucleus was still fully condensed. CRISP2 was no longer detectable in fertilized oocytes in which sperm nuclear decondensation and paternal pronucleus formation were apparent. This rapid dispersal of CRISP2 in the PT is likely regulated by redox reactions for which its cysteine-rich domain is sensitive. Reduction of disulfide bridges within CRISP2 oligomers may be instrumental for PT dispersal and elimination
Mechanisms of Hemolysis-Associated Platelet Activation
Background
Intravascular hemolysis occurs after blood transfusion, in hemolytic anemias, and in other conditions, and is associated with hypercoagulable states. Hemolysis has been shown to potently activate platelets in vitro and in vivo, and several mechanisms have been suggested to account for this, including: (i) direct activation by hemoglobin (Hb); (ii) increase in reactive oxygen species (ROS); (iii) scavenging of nitric oxide (NO) by released Hb; and (iv) release of intraerythrocytic ADP. Objective
To elucidate the mechanism of hemolysis-mediated platelet activation. Methods
We used flow cytometry to detect PAC-1 binding to activated platelets for in vitro experiments, and a Siemens\u27 Advia 120 hematology system to assess platelet aggregation by using platelet counts from in vivo experiments in a rodent model. Results
We found that Hb did not directly activate platelets. However, ADP bound to Hb could cause platelet activation. Furthermore, platelet activation caused by shearing of red blood cells (RBCs) was reduced in the presence of apyrase, which metabolizes ADP to AMP. The use of ROS scavengers did not affect platelet activation. We also found that cell-free Hb enhanced platelet activation by abrogating the inhibitory effect of NO on platelet activation. In vivo infusions of ADP and purified (ADP-free) Hb, as well as hemolysate, resulted in platelet aggregation, as shown by decreased platelet counts. Conclusion
Two primary mechanisms account for RBC hemolysis-associated platelet activation: ADP release, which activates platelets; and cell-free Hb release, which enhances platelet activation by lowering NO bioavailability
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Theories of behaviour change synthesised into a set of theoretical groupings: Introducing a thematic series on the Theoretical Domains Framework
Behaviour change is key to increasing the uptake of evidence into healthcare practice. Designing behaviour-change interventions first requires problem analysis, ideally informed by theory. Yet the large number of partly overlapping theories of behaviour makes it difficult to select the most appropriate theory. The need for an overarching theoretical framework of behaviour change was addressed in research in which 128 explanatory constructs from 33 theories of behaviour were identified and grouped. The resulting Theoretical Domains Framework (TDF) appears to be a helpful basis for investigating implementation problems. Research groups in several countries have conducted TDF-based studies. It seems timely to bring together the experience of these teams in a thematic series to demonstrate further applications and to report key developments. This overview article describes the TDF, provides a brief critique of the framework, and introduces this thematic series.
In a brief review to assess the extent of TDF-based research, we identified 133 papers that cite the framework. Of these, 17 used the TDF as the basis for empirical studies to explore health professionalsâ behaviour. The identified papers provide evidence of the impact of the TDF on implementation research. Two major strengths of the framework are its theoretical coverage and its capacity to elicit beliefs that could signify key mediators of behaviour change. The TDF provides a useful conceptual basis for assessing implementation problems, designing interventions to enhance healthcare practice, and understanding behaviour-change processes. We discuss limitations and research challenges and introduce papers in this series
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Carbon stable isotope analysis of cereal remains as a way to reconstruct water availability: preliminary results
Reconstructing past water availability, both as rainfall and irrigation, is important to answer questions about the way society reacts to climate and its changes and the role of irrigation in the development of social complexity. Carbon stable isotope analysis of archaeobotanical remains is a potentially valuable method for reconstructing water availability. To further define the relationship between water availability and plant carbon isotope composition and to set up baseline values for the Southern Levant, grains of experimentally grown barley and sorghum were studied. The cereal crops were grown at three stations under five different irrigation regimes in Jordan. Results indicate that a positive but weak relationship exists between irrigation regime and total water input of barley grains, but no relationship was found for sorghum. The relationship for barley is site-specific and inter-annual variation was present at Deir âAlla, but not at Ramtha and Khirbet as-Samra
Structure and oxidation kinetics of the Si(100)-SiO2 interface
We present first-principles calculations of the structural and electronic
properties of Si(001)-SiO2 interfaces. We first arrive at reasonable structures
for the c-Si/a-SiO2 interface via a Monte-Carlo simulated annealing applied to
an empirical interatomic potential, and then relax these structures using
first-principles calculations within the framework of density-functional
theory. We find a transition region at the interface, having a thickness on the
order of 20\AA, in which there is some oxygen deficiency and a corresponding
presence of sub-oxide Si species (mostly Si^+2 and Si^+3). Distributions of
bond lengths and bond angles, and the nature of the electronic states at the
interface, are investigated and discussed. The behavior of atomic oxygen in
a-SiO2 is also investigated. The peroxyl linkage configuration is found to be
lower in energy than interstitial or threefold configurations. Based on these
results, we suggest a possible mechanism for oxygen diffusion in a-SiO2 that
may be relevant to the oxidation process.Comment: 7 pages, two-column style with 6 postscript figures embedded. Uses
REVTEX and epsf macros. Also available at
http://www.physics.rutgers.edu/~dhv/preprints/index.html#ng_sio
Drawing the Line: How African, Caribbean and White British Women Live Out Psychologically Abusive Experiences
The final, definitive version of this paper has been published in Violence Against Women, 19 (9):1104-32, Sept 2013 by SAGE Publications Ltd, All rights reserved. © The Author(s) 2013.
The online version of this article can be found at: http://vaw.sagepub.com/content/19/9/110
Improved Visibility of the Subthalamic Nucleus on High-Resolution Stereotactic MR Imaging by Added Susceptibility (T2*) Contrast Using Multiple Gradient Echoes
The Target Silicon Detector for the FOCUS Spectrometer
We describe a silicon microstrip detector interleaved with segments of a
beryllium oxide target which was used in the FOCUS photoproduction experiment
at Fermilab. The detector was designed to improve the vertex resolution and to
enhance the reconstruction efficiency of short-lived charm particles.Comment: 18 pages, 14 figure
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