1,308 research outputs found
Winter habitat use of New Zealand falcons (Falco novaeseelandiae ferox) in an intensively managed pine plantation, central North Island, New Zealand
Copyright and source must be acknowledgedPublishe
Engrailed, a homeodomain protein, can repress in vitro transcription by competition with the TATA box-binding protein transcription factor IID.
MOF phosphorylation by ATM regulates 53BP1-mediated double-strand break repair pathway choice
Genome-wide distribution of histone H4 Lysine 16 acetylation sites and their relationship to gene expression
BACKGROUND: Histone post-translational modifications are critical determinants of chromatin structure and function, impacting multiple biological processes including DNA transcription, replication, and repair. The post-translational acetylation of histone H4 at lysine 16 (H4K16ac) was initially identified in association with dosage compensation of the Drosophila male X chromosome. However, in mammalian cells, H4K16ac is not associated with dosage compensation and the genomic distribution of H4K16ac is not precisely known. Therefore, we have mapped the genome-wide H4K16ac distribution in human cells. RESULTS: We performed H4K16ac chromatin immunoprecipitation from human embryonic kidney 293 (HEK293) cells followed by hybridization to whole-genome tiling arrays and identified 25,893 DNA regions (false discovery rate <0.005) with average length of 692 nucleotides. Interestingly, although a majority of H4K16ac sites localized within genes, only a relatively small fraction (~10%) was found near promoters, in contrast to the distribution of the acetyltransferase, MOF, responsible for acetylation at K16 of H4. Using differential gene expression profiling data, 73 genes (> ±1.5-fold) were identified as potential H4K16ac-regulated genes. Seventeen transcription factor-binding sites were significantly associated with H4K16ac occupancy (p < 0.0005). In addition, a consensus 12-nucleotide guanine-rich sequence motif was identified in more than 55% of the H4K16ac peaks. CONCLUSIONS: The results suggest that H4K16 acetylation has a limited effect on transcription regulation in HEK293 cells, whereas H4K16ac has been demonstrated to have critical roles in regulating transcription in mouse embryonic stem cells. Thus, H4K16ac-dependent transcription regulation is likely a cell type specific process
Measurement of the cosmic-ray antiproton spectrum at solar minimum with a long-duration balloon flight over Antarctica
The energy spectrum of cosmic-ray antiprotons from 0.17 to 3.5 GeV has been
measured using 7886 antiprotons detected by BESS-Polar II during a
long-duration flight over Antarctica near solar minimum in December 2007 and
January 2008. This shows good consistency with secondary antiproton
calculations. Cosmologically primary antiprotons have been investigated by
comparing measured and calculated antiproton spectra. BESS-Polar II data show
no evidence of primary antiprotons from evaporation of primordial black holes.Comment: 4 pages, 4 figures, submitted to Physical Review Letter
Conformational Polymorphism of cRNA of T-Cell-Receptor Genes as a Clone-Specific Molecular Marker for Cutaneous Lymphoma
A novel molecular assay for the detection and characterization of monoclonal lymphoid populations in clinical specimens was developed. The assay is based on the principle that upon non-denaturing polyacrylamide gel electrophoresis RNA molecules separate into several metastable conformational forms. These conformational polymorphisms strictly depend on the nucleotide sequence of the individual molecule. Using DNA from formalin-fixed, paraffin-embedded tissue of patients with mycosis fungoides, highly variable junctional sequences of rearranged T-cell receptor gamma genes were amplified by polymerase chain reaction. Subsequently, the polymerase chain reactions products were transcribed into complementary RNA and analyzed by non-denaturing polyacrylamide gel electrophoresis. In clinical specimens with a monoclonal lymphoid population, a clone-specific pattern of bands was identified representing conformational polymorphisms of cRNA molecules of rearranged T-cell receptor gamma genes of the predominant lymphoid clone. Three biopsies from one patient taken from different sites of the body over 3 years yielded an identical pattern of bands. This methodology provides a novel and rapid tool for the molecular identification and characterization of clonal lymphoid populations in clinical specimens. It is likely to be of special value for studies on the clonal evolution of lymphoid disorders of the skin
Exploring the Thermodynamics of a Universal Fermi Gas
From sand piles to electrons in metals, one of the greatest challenges in
modern physics is to understand the behavior of an ensemble of strongly
interacting particles. A class of quantum many-body systems such as neutron
matter and cold Fermi gases share the same universal thermodynamic properties
when interactions reach the maximum effective value allowed by quantum
mechanics, the so-called unitary limit [1,2]. It is then possible to simulate
some astrophysical phenomena inside the highly controlled environment of an
atomic physics laboratory. Previous work on the thermodynamics of a
two-component Fermi gas led to thermodynamic quantities averaged over the trap
[3-5], making it difficult to compare with many-body theories developed for
uniform gases. Here we develop a general method that provides for the first
time the equation of state of a uniform gas, as well as a detailed comparison
with existing theories [6,14]. The precision of our equation of state leads to
new physical insights on the unitary gas. For the unpolarized gas, we prove
that the low-temperature thermodynamics of the strongly interacting normal
phase is well described by Fermi liquid theory and we localize the superfluid
transition. For a spin-polarized system, our equation of state at zero
temperature has a 2% accuracy and it extends the work of [15] on the phase
diagram to a new regime of precision. We show in particular that, despite
strong correlations, the normal phase behaves as a mixture of two ideal gases:
a Fermi gas of bare majority atoms and a non-interacting gas of dressed
quasi-particles, the fermionic polarons [10,16-18].Comment: 8 pages, 5 figure
Feynman diagrams versus Fermi-gas Feynman emulator
Precise understanding of strongly interacting fermions, from electrons in
modern materials to nuclear matter, presents a major goal in modern physics.
However, the theoretical description of interacting Fermi systems is usually
plagued by the intricate quantum statistics at play. Here we present a
cross-validation between a new theoretical approach, Bold Diagrammatic Monte
Carlo (BDMC), and precision experiments on ultra-cold atoms. Specifically, we
compute and measure with unprecedented accuracy the normal-state equation of
state of the unitary gas, a prototypical example of a strongly correlated
fermionic system. Excellent agreement demonstrates that a series of Feynman
diagrams can be controllably resummed in a non-perturbative regime using BDMC.
This opens the door to the solution of some of the most challenging problems
across many areas of physics
Pair excitations and parameters of state of imbalanced Fermi gases at finite temperatures
The spectra of low-lying pair excitations for an imbalanced two-component
superfluid Fermi gas are analytically derived within the path-integral
formalism taking into account Gaussian fluctuations about the saddle point. The
spectra are obtained for nonzero temperatures, both with and without imbalance,
and for arbitrary interaction strength. On the basis of the pair excitation
spectrum, we have calculated the thermodynamic parameters of state of cold
fermions and the first and second sound velocities. The parameters of pair
excitations show a remarkable agreement with the Monte Carlo data and with
experiment.Comment: 14 pages, 5 figure
- …