782 research outputs found
Effect of Peierls transition in armchair carbon nanotube on dynamical behaviour of encapsulated fullerene
The changes of dynamical behaviour of a single fullerene molecule inside an
armchair carbon nanotube caused by the structural Peierls transition in the
nanotube are considered. The structures of the smallest C20 and Fe@C20
fullerenes are computed using the spin-polarized density functional theory.
Significant changes of the barriers for motion along the nanotube axis and
rotation of these fullerenes inside the (8,8) nanotube are found at the Peierls
transition. It is shown that the coefficients of translational and rotational
diffusions of these fullerenes inside the nanotube change by several orders of
magnitude. The possibility of inverse orientational melting, i.e. with a
decrease of temperature, for the systems under consideration is predicted.Comment: 9 pages, 6 figures, 1 tabl
RNA polymerase II stalling promotes nucleosome occlusion and pTEFb recruitment to drive immortalization by Epstein-Barr virus
Epstein-Barr virus (EBV) immortalizes resting B-cells and is a key etiologic agent in the development of numerous cancers. The essential EBV-encoded protein EBNA 2 activates the viral C promoter (Cp) producing a message of ~120 kb that is differentially spliced to encode all EBNAs required for immortalization. We have previously shown that EBNA 2-activated transcription is dependent on the activity of the RNA polymerase II (pol II) C-terminal domain (CTD) kinase pTEFb (CDK9/cyclin T1). We now demonstrate that Cp, in contrast to two shorter EBNA 2-activated viral genes (LMP 1 and 2A), displays high levels of promoter-proximally stalled pol II despite being constitutively active. Consistent with pol II stalling, we detect considerable pausing complex (NELF/DSIF) association with Cp. Significantly, we observe substantial Cp-specific pTEFb recruitment that stimulates high-level pol II CTD serine 2 phosphorylation at distal regions (up to +75 kb), promoting elongation. We reveal that Cp-specific pol II accumulation is directed by DNA sequences unfavourable for nucleosome assembly that increase TBP access and pol II recruitment. Stalled pol II then maintains Cp nucleosome depletion. Our data indicate that pTEFb is recruited to Cp by the bromodomain protein Brd4, with polymerase stalling facilitating stable association of pTEFb. The Brd4 inhibitor JQ1 and the pTEFb inhibitors DRB and Flavopiridol significantly reduce Cp, but not LMP1 transcript production indicating that Brd4 and pTEFb are required for Cp transcription. Taken together our data indicate that pol II stalling at Cp promotes transcription of essential immortalizing genes during EBV infection by (i) preventing promoter-proximal nucleosome assembly and ii) necessitating the recruitment of pTEFb thereby maintaining serine 2 CTD phosphorylation at distal regions
Three Dimensional Visualization and Fractal Analysis of Mosaic Patches in Rat Chimeras: Cell Assortment in Liver, Adrenal Cortex and Cornea
The production of organ parenchyma in a rapid and reproducible manner is critical to normal development. In chimeras produced by the combination of genetically distinguishable tissues, mosaic patterns of cells derived from the combined genotypes can be visualized. These patterns comprise patches of contiguously similar genotypes and are different in different organs but similar in a given organ from individual to individual. Thus, the processes that produce the patterns are regulated and conserved. We have previously established that mosaic patches in multiple tissues are fractal, consistent with an iterative, recursive growth model with simple stereotypical division rules. Fractal dimensions of various tissues are consistent with algorithmic models in which changing a single variable (e.g. daughter cell placement after division) switches the mosaic pattern from islands to stripes of cells. Here we show that the spiral pattern previously observed in mouse cornea can also be visualized in rat chimeras. While it is generally held that the pattern is induced by stem cell division dynamics, there is an unexplained discrepancy in the speed of cellular migration and the emergence of the pattern. We demonstrate in chimeric rat corneas both island and striped patterns exist depending on the age of the animal. The patches that comprise the pattern are fractal, and the fractal dimension changes with the age of the animal and indicates the constraint in patch complexity as the spiral pattern emerges. The spiral patterns are consistent with a loxodrome. Such data are likely to be relevant to growth and cell division in organ systems and will help in understanding how organ parenchyma are generated and maintained from multipotent stem cell populations located in specific topographical locations within the organ. Ultimately, understanding algorithmic growth is likely to be essential in achieving organ regeneration in vivo or in vitro from stem cell populations
A La Autoantigen Homologue Is Required for the Internal Ribosome Entry Site Mediated Translation of Giardiavirus
Translation of Giardiavirus (GLV) mRNA is initiated at an internal ribosome entry site (IRES) in the viral transcript. The IRES localizes to a downstream portion of 5′ untranslated region (UTR) and a part of the early downstream coding region of the transcript. Recent studies indicated that the IRES does not require a pre-initiation complex to initiate translation but may directly recruit the small ribosome subunit with the help of a number of trans-activating protein factors. A La autoantigen homologue in the viral host Giardia lamblia, GlLa, was proposed as one of the potential trans-activating factors based on its specific binding to GLV-IRES in vitro. In this study, we further elucidated the functional role of GlLa in GLV-IRES mediated translation in Giardia by knocking down GlLa with antisense morpholino oligo, which resulted in a reduction of GLV-IRES activity by 40%. An over-expression of GlLa in Giardia moderately stimulated GLV-IRES activity by 20%. A yeast inhibitory RNA (IRNA), known to bind mammalian and yeast La autoantigen and inhibit Poliovirus and Hepatitis C virus IRES activities in vitro and in vivo, was also found to bind to GlLa protein in vitro and inhibited GLV-IRES function in vivo. The C-terminal domain of La autoantigen interferes with the dimerization of La and inhibits its function. An over-expression of the C-terminal domain (200–348aa) of GlLa in Giardia showed a dominant-negative effect on GLV-IRES activity, suggesting a potential inhibition of GlLa dimerization. HA tagged GlLa protein was detected mainly in the cytoplasm of Giardia, thus supporting a primary role of GlLa in translation initiation in Giardiavirus
Geochemical detection of carbon dioxide in dilute aquifers
<p>Abstract</p> <p>Background</p> <p>Carbon storage in deep saline reservoirs has the potential to lower the amount of CO<sub>2 </sub>emitted to the atmosphere and to mitigate global warming. Leakage back to the atmosphere through abandoned wells and along faults would reduce the efficiency of carbon storage, possibly leading to health and ecological hazards at the ground surface, and possibly impacting water quality of near-surface dilute aquifers. We use static equilibrium and reactive transport simulations to test the hypothesis that perturbations in water chemistry associated with a CO<sub>2 </sub>gas leak into dilute groundwater are important measures for the potential release of CO<sub>2 </sub>to the atmosphere. Simulation parameters are constrained by groundwater chemistry, flow, and lithology from the High Plains aquifer. The High Plains aquifer is used to represent a typical sedimentary aquifer overlying a deep CO<sub>2 </sub>storage reservoir. Specifically, we address the relationships between CO<sub>2 </sub>flux, groundwater flow, detection time and distance. The CO<sub>2 </sub>flux ranges from 10<sup>3 </sup>to 2 × 10<sup>6 </sup>t/yr (0.63 to 1250 t/m<sup>2</sup>/yr) to assess chemical perturbations resulting from relatively small leaks that may compromise long-term storage, water quality, and surface ecology, and larger leaks characteristic of short-term well failure.</p> <p>Results</p> <p>For the scenarios we studied, our simulations show pH and carbonate chemistry are good indicators for leakage of stored CO<sub>2 </sub>into an overlying aquifer because elevated CO<sub>2 </sub>yields a more acid pH than the ambient groundwater. CO<sub>2 </sub>leakage into a dilute groundwater creates a slightly acid plume that can be detected at some distance from the leak source due to groundwater flow and CO<sub>2 </sub>buoyancy. pH breakthrough curves demonstrate that CO<sub>2 </sub>leaks can be easily detected for CO<sub>2 </sub>flux ≥ 10<sup>4 </sup>t/yr within a 15-month time period at a monitoring well screened within a permeable layer 500 m downstream from the vertical gas trace. At lower flux rates, the CO<sub>2 </sub>dissolves in the aqueous phase in the lower most permeable unit and does not reach the monitoring well. Sustained pumping in a developed aquifer mixes the CO<sub>2</sub>-affected water with the ambient water and enhances pH signal for small leaks (10<sup>3 </sup>t/yr) and reduces pH signal for larger leaks (≥ 10<sup>4</sup>t/yr).</p> <p>Conclusion</p> <p>The ability to detect CO<sub>2 </sub>leakage from a storage reservoir to overlying dilute groundwater is dependent on CO<sub>2 </sub>solubility, leak flux, CO<sub>2 </sub>buoyancy, and groundwater flow. Our simulations show that the most likely places to detect CO<sub>2 </sub>are at the base of the confining layer near the water table where CO<sub>2 </sub>gas accumulates and is transported laterally in all directions, and downstream of the vertical gas trace where groundwater flow is great enough to transport dissolved CO<sub>2 </sub>laterally. Our simulations show that CO<sub>2 </sub>may not rise high enough in the aquifer to be detected because aqueous solubility and lateral groundwater transport within the lower aquifer unit exceeds gas pressure build-up and buoyancy needed to drive the CO<sub>2 </sub>gas upwards.</p
Neue linguistische Methoden und arbeitstechnische Verfahren in der Erschliessung der ägyptischen Grammatik
15 páginas, 1 tabla, 6 figuras.Does diversity beget diversity? Diversity
includes a diversity of concepts because it is linked to
variability in and of life and can be applied to multiple
levels. The connections between multiple levels of
diversity are poorly understood. Here, we investigated
the relationships between genetic, bacterial, and
chemical diversity of the endangered Atlanto-Mediterranean sponge Spongia lamella. These levels of
diversity are intrinsically related to sponge evolution
and could have strong conservation implications. We
used microsatellite markers, denaturing gel gradient
electrophoresis and quantitative polymerase chain
reaction, and high performance liquid chromatography to quantify genetic, bacterial, and chemical
diversity of nine sponge populations. We then used
correlations to test whether these diversity levels
covaried. We found that sponge populations differed
significantly in genetic, bacterial, and chemical
diversity. We also found a strong geographic pattern
of increasing genetic, bacterial, and chemical dissimilarity with increasing geographic distance between
populations. However, we failed to detect significant
correlations between the three levels of diversity
investigated in our study. Our results suggest that
diversity fails to beget diversity within a single species
and indicates that a diversity of factors regulates a
diversity of diversities, which highlights the complex
nature of the mechanisms behind diversityResearch funded by grants from the Agence Nationale de la
Recherche (ECIMAR), from the Spanish Ministry of Science
and Technology SOLID (CTM2010-17755) and Benthomics
(CTM2010-22218-C02-01) and the BIOCAPITAL project
(MRTN-CT-2004-512301) of the European Union. This is a
contribution of the Consolidated Research Group ‘‘Grupo de
Ecologı´a Bento´nica,’’ SGR2009-655.Peer reviewe
Search for new phenomena in final states with an energetic jet and large missing transverse momentum in pp collisions at √ s = 8 TeV with the ATLAS detector
Results of a search for new phenomena in final states with an energetic jet and large missing transverse momentum are reported. The search uses 20.3 fb−1 of √ s = 8 TeV data collected in 2012 with the ATLAS detector at the LHC. Events are required to have at least one jet with pT > 120 GeV and no leptons. Nine signal regions are considered with increasing missing transverse momentum requirements between Emiss T > 150 GeV and Emiss T > 700 GeV. Good agreement is observed between the number of events in data and Standard Model expectations. The results are translated into exclusion limits on models with either large extra spatial dimensions, pair production of weakly interacting dark matter candidates, or production of very light gravitinos in a gauge-mediated supersymmetric model. In addition, limits on the production of an invisibly decaying Higgs-like boson leading to similar topologies in the final state are presente
Enhancing Electron Coherence via Quantum Phonon Confinement in Atomically Thin Nb3SiTe6
The extraordinary properties of two dimensional (2D) materials, such as the
extremely high carrier mobility in graphene and the large direct band gaps in
transition metal dichalcogenides MX2 (M = Mo or W, X = S, Se) monolayers,
highlight the crucial role quantum confinement can have in producing a wide
spectrum of technologically important electronic properties. Currently one of
the highest priorities in the field is to search for new 2D crystalline systems
with structural and electronic properties that can be exploited for device
development. In this letter, we report on the unusual quantum transport
properties of the 2D ternary transition metal chalcogenide - Nb3SiTe6. We show
that the micaceous nature of Nb3SiTe6 allows it to be thinned down to
one-unit-cell thick 2D crystals using microexfoliation technique. When the
thickness of Nb3SiTe6 crystal is reduced below a few unit-cells thickness, we
observed an unexpected, enhanced weak-antilocalization signature in
magnetotransport. This finding provides solid evidence for the long-predicted
suppression of electron-phonon interaction caused by the crossover of phonon
spectrum from 3D to 2D.Comment: Accepted by Nature Physic
Th1-Th17 Cells Mediate Protective Adaptive Immunity against Staphylococcus aureus and Candida albicans Infection in Mice
We sought to define protective mechanisms of immunity to Staphylococcus aureus and Candida albicans bloodstream infections in mice immunized with the recombinant N-terminus of Als3p (rAls3p-N) vaccine plus aluminum hydroxide (Al(OH3) adjuvant, or adjuvant controls. Deficiency of IFN-γ but not IL-17A enhanced susceptibility of control mice to both infections. However, vaccine-induced protective immunity against both infections required CD4+ T-cell-derived IFN-γ and IL-17A, and functional phagocytic effectors. Vaccination primed Th1, Th17, and Th1/17 lymphocytes, which produced pro-inflammatory cytokines that enhanced phagocytic killing of both organisms. Vaccinated, infected mice had increased IFN-γ, IL-17, and KC, increased neutrophil influx, and decreased organism burden in tissues. In summary, rAls3p-N vaccination induced a Th1/Th17 response, resulting in recruitment and activation of phagocytes at sites of infection, and more effective clearance of S. aureus and C. albicans from tissues. Thus, vaccine-mediated adaptive immunity can protect against both infections by targeting microbes for destruction by innate effectors
A Natural Combination Extract of Viscum album L. Containing Both Triterpene Acids and Lectins Is Highly Effective against AML In Vivo
Aqueous Viscum album L. extracts are widely used in complementary cancer
medicine. Hydrophobic triterpene acids also possess anti-cancer properties,
but due to their low solubility they do not occur in significant amounts in
aqueous extracts. Using cyclodextrins we solubilised mistletoe triterpenes
(mainly oleanolic acid) and investigated the effect of a mistletoe whole plant
extract on human acute myeloid leukaemia cells in vitro, ex vivo and in vivo.
Single Viscum album L. extracts containing only solubilised triterpene acids
(TT) or lectins (viscum) inhibited cell proliferation and induced apoptosis in
a dose-dependent manner in vitro and ex vivo. The combination of viscum and TT
extracts (viscumTT) enhanced the induction of apoptosis synergistically. The
experiments demonstrated that all three extracts are able to induce apoptosis
via caspase-8 and -9 dependent pathways with down-regulation of members of the
inhibitor of apoptosis and Bcl-2 families of proteins. Finally, the acute
myeloid leukaemia mouse model experiment confirmed the therapeutic
effectiveness of viscumTT-treatment resulting in significant tumour weight
reduction, comparable to the effect in cytarabine-treated mice. These results
suggest that the combination viscumTT may have a potential therapeutic value
for the treatment AML
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