409 resultados para Chern-Simons
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Welsch (Projektarbeiter): Gesetzentwurf auf Aufhebung der Paragraphen 151 bis 155 des Preußischen Allgemeinen Landrechts ('Erweckung von Unzufriedenheit gegen die Regierung durch frechen Tadel oder Verspottung der Landesgesetze') und Vorschlag ihrer Neufassung in folgender Form: Wer durch Reden oder Schriften wissentlich Unwahrheiten verbreitet, welche geeignet sind, Haß oder Verachtung dem Staat gegenüber hervorzurufen, wird mit Freiheitsstrafe bis zu sechs Monaten bestraft
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Human land use may detrimentally affect biodiversity, yet long-term stability of species communities is vital for maintaining ecosystem functioning. Community stability can be achieved by higher species diversity (portfolio effect), higher asynchrony across species (insurance hypothesis) and higher abundance of populations. However, the relative importance of these stabilizing pathways and whether they interact with land use in real-world ecosystems is unknown. We monitored inter-annual fluctuations of 2,671 plant, arthropod, bird and bat species in 300 sites from three regions. Arthropods show 2.0-fold and birds 3.7-fold higher community fluctuations in grasslands than in forests, suggesting a negative impact of forest conversion. Land-use intensity in forests has a negative net impact on stability of bats and in grasslands on birds. Our findings demonstrate that asynchrony across species—much more than species diversity alone—is the main driver of variation in stability across sites and requires more attention in sustainable management.
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The purpose of this study was to determine, for penetrating injuries (gunshot, stab) of the chest/abdomen, the impact on fatality of treatment in trauma centers and shock trauma units compared with general hospitals. Medical records of all cases of penetrating injury limited to chest/abdomen and admitted to and discharged from 7 study facilities in Baltimore city 1979-1980 (n = 581) were studied: 4 general hospitals (n = 241), 2 area-wide trauma centers (n = 298), and a shock trauma unit (n = 42). Emergency center and transferred cases were not studied. Anatomical injury severity, measured by modified Injury Severity Score (mISS), was a significant prognostic factor for death, as were cardiovascular shock (SBP $\le$ 70), injury type (gunshot vs stab), and ambulance/helicopter (vs other) transport. All deaths occurred in cases with two or more prognostic factors. Unadjusted relative risks of death compared with general hospitals were 4.3 (95% confidence interval = 2.2, 8.4) for shock trauma and 0.8 (0.4, 1.7) for trauma centers. Controlling for prognostic factors by logistic regression resulted in these relative risks: shock trauma 4.0 (0.7, 22.2), and trauma centers 0.8 (0.2, 3.2). Factors significantly associated with increased risk had the following relative risks by multiple logistic regression: SBP $\le$ 70 (RR = 40.7 (11.0, 148.7)), highest mISS (42 (7.7, 227)), gunshot (8.4 (2.1, 32.6)), and ambulance/helicopter transport (17.2 (1.3, 228.1)). Controlling for age, race, and gender did not alter results significantly. Actual deaths compared with deaths predicted from a multivariable model of general-hospital cases showed 3.7 more than predicted deaths in shock trauma (SMR = 1.6 (0.8, 2.9)) and 0.7 more than predicted deaths in area-wide trauma centers (SMR = 1.05 (0.6, 1.7)). Selection bias due to exclusion of transfers and emergency center cases, and residual confounding due to insufficient injury information, may account for persistence of adjusted high case fatality in shock trauma. Studying all cases prospectively, including emergency center and transferred cases, is needed. ^
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Ice-wedge polygon (IWP) mires in the Arctic and Subarctic are extremely vulnerable to climatic and environmental change. We present the results of a multidisciplinary paleoenvironmental study on IWPs in the northern Yukon, Canada. High-resolution laboratory analyses were carried out on a permafrost core and the overlying seasonally thawed (active) layer, from a low-centered IWP located in a drained lake basin on Herschel Island. In relation to 14 Accelerator Mass Spectrometry (AMS) radiocarbon dates spanning the last 5000 years, we report sedimentary data including grain size distribution and biogeochemical parameters (organic carbon, nitrogen, C/N ratio, d13C), stable water isotopes (d18O, dD), as well as fossil pollen, plant macrofossil and diatom assemblages. Three sediment units (SUs) correspond to the main stages of deposition (1) in a thermokarst lake (SU1: 4950 to 3950 cal yrs BP), (2) during transition from lacustrine to palustrine conditions after lake drainage (SU2: 3950 to 3120 cal yrs BP), and (3) in palustrine conditions in the IWP field that developed after drainage (SU3: 3120 cal yrs BP to AD 2012). The lacustrine phase (pre 3950 cal yrs BP) is characterized by planktonic-benthic and pioneer diatoms species indicating circumneutral waters, and very few plant macrofossils. The pollen record has captured a regional signal of relatively stable vegetation composition and climate for the lacustrine stage of the record until 3950 cal yrs BP. Palustrine conditions with benthic and acidophilic species characterize the peaty shallow-water environments of the low-centered IWP. The transition from lacustrine to palustrine conditions was accompanied by acidification and rapid revegetation of the lake bottom within about 100 years. Since the palustrine phase we consider the pollen record as a local vegetation proxy dominated by the plant communities growing in the IWP. Ice-wedge cracking in water-saturated sediments started immediately after lake drainage at about 3950 cal yrs BP and led to the formation of an IWP mire. Permafrost aggradation through downward closed-system freezing of the lake talik is indicated by the stable water isotope record. The originally submerged IWP center underwent gradual drying during the past 2000 years. This study highlights the sensitivity of permafrost landscapes to climate and environmental change throughout the Holocene.
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The notion of a differential invariant for systems of second-order differential equations on a manifold M with respect to the group of vertical automorphisms of the projection is de?ned and the Chern connection attached to a SODE allows one to determine a basis for second-order differential invariants of a SODE.
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We have investigated the relationships between the apical sorting mechanism using lipid rafts and the soluble N-ethyl maleimide-sensitive factor attachment protein receptor (SNARE) machinery, which is involved in membrane docking and fusion. We first confirmed that anti-alpha-SNAP antibodies inhibit the apical pathway in Madin– Darby canine kidney (MDCK) cells; in addition, we report that a recombinant SNAP protein stimulates the apical transport whereas a SNAP mutant inhibits this transport step. Based on t-SNARE overexpression experiments and the effect of botulinum neurotoxin E, syntaxin 3 and SNAP-23 have been implicated in apical membrane trafficking. Here, we show in permeabilized MDCK cells that antisyntaxin 3 and anti-SNAP-23 antibodies lower surface delivery of an apical reporter protein. Moreover, using a similar approach, we show that tetanus toxin-insensitive, vesicle-associated membrane protein (TI-VAMP; also called VAMP7), a recently described apical v-SNARE, is involved. Furthermore, we show the presence of syntaxin 3 and TI-VAMP in isolated apical carriers. Polarized apical sorting has been postulated to be mediated by the clustering of apical proteins into dynamic sphingolipid-cholesterol rafts. We provide evidence that syntaxin 3 and TI-VAMP are raft-associated. These data support a raft-based mechanism for the sorting of not only apically destined cargo but also of SNAREs having functions in apical membrane-docking and fusion events.
Phalangeal curvature and positional behavior in extinct sloth lemurs (Primates, Palaeopropithecidae)
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Recent paleontological discoveries in Madagascar document the existence of a diverse clade of palaeopropithecids or “sloth lemurs”: Mesopropithecus (three species), Babakotia (one species), Palaeopropithecus (three species), and Archaeoindris (one species). This mini-radiation of now extinct (“subfossil”) lemurs is most closely related to the living indrids (Indri, Propithecus, and Avahi). Whereas the extant indrids are known for their leaping acrobatics, the palaeopropithecids (except perhaps for the poorly known giant Archaeoindris) exhibit numerous skeletal design features for antipronograde or suspensory positional behaviors (e.g., high intermembral indices and mobile joints). Here we analyze the curvature of the proximal phalanges of the hands and feet. Computed as the included angle (θ), phalangeal curvature develops in response to mechanical use and is known to be correlated in primates with hand and foot function in different habitats; terrestrial species have straighter phalanges than their arboreal counterparts, and highly suspensory forms such as the orangutan possess the most curved phalanges. Sloth lemurs as a group are characterized by very curved proximal phalanges, exceeding those seen in spider monkeys and siamangs, and approaching that of orangutans. Indrids have curvatures roughly half that of sloth lemurs, and the more terrestrial, subfossil Archaeolemur possesses the least curved phalanges of all the indroids. Taken together with many other derived aspects of their postcranial anatomy, phalangeal curvature indicates that the sloth lemurs are one of the most suspensory clades of mammals ever to evolve.
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Tarsiers and extinct tarsier-like primates have played a central role in views of primate phylogeny and evolution for more than a century. Because of the importance of tarsiers in so many primatological problems, there has been particular interest in questions about the origin of tarsier specializations and the biogeography of early tarsioid radiations. We report on a new fossil of rare Afrotarsius that shows near identity to modern Tarsius in unique specializations of the leg, which provides information about the locomotor behavior and clarifies the phylogenetic position of this previously controversial primate. These specializations constitute evidence that Afrotarsius is a tarsiid, closely related to extant Tarsius; hence, it is now excluded from being a generalized sister taxon to Anthropoidea.
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Recent discovery of crania, dentitions, and postcrania of a primitive anthropoidean primate, Proteopithecus sylviae, at the late Eocene L-4l quarry in the Fayum, Egypt, provides evidence of a new taxonomic family of early African higher primates, the Proteopithecidae. This family could be part of the basal radiation that produced the New World platyrrhine primates, or it could be unrelated to any subsequent lineages. Although no larger than a small callitrichid or a dwarf lemur, this tiny primate already possessed many of the derived features of later anthropoids and was a diurnal and probably dimorphic species. In dental formula and other dental proportions, as well as in known postcranial features, Proteopithecus more nearly resembles platyrrhines than does any other Old World higher primate. The small size of the Proteopithecus cranium demonstrates that the defining cranial characteristics of Anthropoidea did not arise as a consequence of an increase in size during derivation from earlier prosimians.
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Exogenous application of gangliosides to cells affects many cellular functions. We asked whether these effects could be attributed to the influence of gangliosides on the properties of sphingolipid–cholesterol microdomains on the plasma membrane, also termed rafts. The latter are envisaged as lateral assemblies of sphingolipids (including gangliosides), cholesterol, and a specific set of proteins. Rafts have been implicated in processes such as membrane trafficking, signal transduction, and cell adhesion. Recently, using a chemical cross-linking approach with Madin-Darby canine kidney (MDCK) cells permanently expressing a GPI-anchored form of growth hormone decay accelerating factor (GH-DAF) as a model system, we could show that GPI-anchored proteins are clustered in rafts in living cells. Moreover, this clustering was dependent on the level of cholesterol in the cell. Here we show that incubation of MDCK cells with gangliosides abolished subsequent chemical cross-linking of GH-DAF. Furthermore, insertion of gangliosides into the plasma membrane of MDCK GH-DAF cells renders GH-DAF soluble when subjected to extraction with Triton X-114 at 4°C. Our data suggest that exogenous application of gangliosides displaces GPI-anchored proteins from sphingolipid–cholesterol microdomains in living cells.
The phylogeny of closely related species as revealed by the genealogy of a speciation gene, Odysseus
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Molecular differentiation between races or closely related species is often incongruent with the reproductive divergence of the taxa of interest. Shared ancient polymorphism and/or introgression during secondary contact may be responsible for the incongruence. At loci contributing to speciation, these two complications should be minimized (1, 2); hence, their variation may more faithfully reflect the history of the species' reproductive differentiation. In this study, we analyzed DNA polymorphism at the Odysseus (OdsH) locus of hybrid sterility between Drosophila mauritiana and Drosophila simulans and were able to verify such a prediction. Interestingly, DNA variation only a short distance away (1.8 kb) appears not to be influenced by the forces that shape the recent evolution of the OdsH coding region. This locus thus may represent a test case of inferring phylogeny of very closely related species.
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Two very small late Eocene anthropoid primates, Catopithecus browni and Proteopithecus sylviae, from Fayum, Egypt show evidence of substantial sexual dimorphism in canine teeth. The degree of dimorphism suggests that these early anthropoids lived in social groups with a polygynous mating system and intense male–male competition. Catopithecus and Proteopithecus are smaller in estimated body size than any living primates showing canine dimorphism. The origin of canine dimorphism and polygyny in anthropoids was not associated with the evolution of large body size.
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Apical proteins are sorted and delivered from the trans-Golgi network to the plasma membrane by a mechanism involving sphingolipid–cholesterol rafts. In this paper, we report the effects of changing the levels of VIP17/MAL, a tetraspan membrane protein localized to post-Golgi transport containers and the apical cell surface in MDCK cells. Overexpression of VIP17/MAL disturbed the morphology of the MDCK cell layers by increasing apical delivery and seemingly expanding the apical cell surface domains. On the other hand, expression of antisense RNA directed against VIP17/MAL caused accumulation in the Golgi and/or impaired apical transport of different apical protein markers, i.e., influenza virus hemagglutinin, the secretory protein clusterin (gp80), the transmembrane protein gp114, and a glycosylphosphatidylinositol-anchored protein. However, antisense RNA expression did not affect the distribution of E-cadherin to the basolateral surface. Because VIP17/MAL associates with sphingolipid–cholesterol rafts, these data provide functional evidence that this protein is involved in apical transport and might be a component of the machinery clustering lipid rafts with apical cargo to form apical transport carriers.