1,036 research outputs found
The replacement histone H2A.Z in a hyperacetylated form is a feature of active genes in the chicken
The replacement histone H2A.Z is variously reported
as being linked to gene expression and preventing the
spread of heterochromatin in yeast, or concentrated
at heterochromatin in mammals. To resolve this
apparent dichotomy, affinity-purified antibodies
against the N-terminal region of H2A.Z, in both a triacetylatedandnon-
acetylatedstate, areusedin native
chromatin immmuno-precipitation experiments with
mononucleosomes from three chicken cell types. The
hyperacetylated species concentrates at the 50 end of
active genes, both tissue specific and housekeeping
but is absent from inactive genes, while the
unacetylated form is absent from both active and
inactive genes. A concentration of H2A.Z is also
found at insulators under circumstances implying a
link to barrier activity but not to enhancer blocking.
Although acetylated H2A.Z is widespread throughout
the interphase genome, at mitosis its acetylation is
erased, the unmodified form remaining. Thus,
although H2A.Z may operate as an epigenetic marker
for active genes, its N-terminal acetylation does not
The replacement histone H2A.Z in a hyperacetylated form is a feature of active genes in the chicken
The replacement histone H2A.Z is variously reported
as being linked to gene expression and preventing the
spread of heterochromatin in yeast, or concentrated
at heterochromatin in mammals. To resolve this
apparent dichotomy, affinity-purified antibodies
against the N-terminal region of H2A.Z, in both a triacetylatedandnon-
acetylatedstate, areusedin native
chromatin immmuno-precipitation experiments with
mononucleosomes from three chicken cell types. The
hyperacetylated species concentrates at the 50 end of
active genes, both tissue specific and housekeeping
but is absent from inactive genes, while the
unacetylated form is absent from both active and
inactive genes. A concentration of H2A.Z is also
found at insulators under circumstances implying a
link to barrier activity but not to enhancer blocking.
Although acetylated H2A.Z is widespread throughout
the interphase genome, at mitosis its acetylation is
erased, the unmodified form remaining. Thus,
although H2A.Z may operate as an epigenetic marker
for active genes, its N-terminal acetylation does not
Transitions between lifetime alcohol use, regular use and remission: Results from the 2004 South African Stress and Health Survey
Background. Hazardous alcohol consumption presents a serious threat to the health and wellbeing of all people and is linked to chronic and acute health problems.Objectives. To: (i) estimate the prevalence of alcohol use disorders and remission from alcohol abuse and dependence in the South African (SA) population; and (ii) determine whether age of onset, education, sex and level of cohort alcohol use are associated with commencement of use, regularity of use, and transitions to and remission from more harmful levels of use.Methods. The study was a nationally representative sample of 4 315 individuals aged ≥18 years. In a multistage, area probability sample of adults, data were collected from 4 311 alcohol users using the World Mental Health Survey Initiative version of the Composite International Diagnostic Interview version 3.0. All analyses were carried out using SAS version 9.4.Results. Of the respondents, 40.6% indicated lifetime use of alcohol, 35.3% reported regular use, and 8.8% met diagnostic criteria for alcohol abuse and 2.7% for alcohol dependence. The prevalence of remission from lifetime abuse without dependence was 55.9%. The median age of onset of alcohol use was 20 years, with transition from use to regular use occurring within ~1 - 3 years. The results suggest that males, students (compared with those who had completed a high level of education) and greater alcohol use in the respondent’s birth cohort were all associated with increased odds of commencing alcohol use. For transitions from use to regular use, increased odds were associated with males, greater birth cohort alcohol use, low education and later (>21 years) onset of first alcohol use.Conclusions. Our findings suggest that cohort alcohol use is associated with transition to commencement of use and from use to regular use in the general SA population. The study further highlighted the need for interventions among males and university students, given that hazardous alcohol consumption seems to be the most prevalent public health issue encountered by university students and males
Graviton Propagators on Fuzzy G/H
We describe closed string modes by open Wilson lines in noncommutative (NC)
gauge theories on compact fuzzy G/H in IIB matrix model. In this construction
the world sheet cut-off is related to the spacetime cut-off since the string
bit of the symmetric traced Wilson line carries the minimum momentum on G/H. We
show that the two point correlation functions of graviton type Wilson lines in
4 dimensional NC gauge theories behave as 1/(momentum)^2. This result suggests
that graviton is localized on D3-brane, so we can naturally interpret D3-branes
as our universe. Our result is not limited to D3-brane system, and we
generalize our analysis to other dimensions and even to any topology of D-brane
worldvolume within fuzzy G/H.Comment: 22 pages, 1 figure. minor correction
The Origin of the Wigner Energy
Surfaces of experimental masses of even-even and odd-odd nuclei exhibit a
sharp slope discontinuity at N=Z. This cusp (Wigner energy), reflecting an
additional binding in nuclei with neutrons and protons occupying the same shell
model orbitals, is usually attributed to neutron-proton pairing correlations. A
method is developed to extract the Wigner term from experimental data. Both
empirical arguments and shell-model calculations suggest that the Wigner term
can be traced back to the isospin T=0 part of nuclear interaction. Our
calculations reveal the rather complex mechanism responsible for the nuclear
binding around the N=Z line. In particular, we find that the Wigner term cannot
be solely explained in terms of correlations between the neutron-proton J=1,
T=0 (deuteron-like) pairs.Comment: 10 RevTeX pages, 3 Postscript figures include
An efficient hardware architecture for a neural network activation function generator
This paper proposes an efficient hardware architecture for a function generator suitable for an artificial neural network (ANN). A spline-based approximation function is designed that provides a good trade-off between accuracy and silicon area, whilst also being inherently scalable and adaptable for numerous activation functions. This has been achieved by using a minimax polynomial and through optimal placement of the approximating polynomials based on the results of a genetic algorithm. The approximation error of the proposed method compares favourably to all related research in this field. Efficient hardware multiplication circuitry is used in the implementation, which reduces the area overhead and increases the throughput
Branes as Stable Holomorphic Line Bundles On the Non-Commutative Torus
It was recently suggested by A. Kapustin that turning on a -field, and
allowing some discrepancy between the left and and right-moving complex
structures, must induce an identification of B-branes with holomorphic line
bundles on a non-commutative complex torus. We translate the stability
condition for the branes into this language and identify the stable topological
branes with previously proposed non-commutative instanton equations. This
involves certain topological identities whose derivation has become familiar in
non-commutative field theory. It is crucial for these identities that the
instantons are localized. We therefore explore the case of non-constant field
strength, whose non-linearities are dealt with thanks to the rank-one
Seiberg--Witten map.Comment: 12 pages, LaTe
Assessment and Optimization of Medical Risks using the Integrated Medical Model
ObjectiveDevelop an evidence-based, probabilistic risk forecasting model that can help guide mission planning, requirements development, and align science with engineering technology development
The High Redshift Integrated Sachs-Wolfe Effect
In this paper we rely on the quasar (QSO) catalog of the Sloan Digital Sky
Survey Data Release Six (SDSS DR6) of about one million photometrically
selected QSOs to compute the Integrated Sachs-Wolfe (ISW) effect at high
redshift, aiming at constraining the behavior of the expansion rate and thus
the behaviour of dark energy at those epochs. This unique sample significantly
extends previous catalogs to higher redshifts while retaining high efficiency
in the selection algorithm. We compute the auto-correlation function (ACF) of
QSO number density from which we extract the bias and the stellar
contamination. We then calculate the cross-correlation function (CCF) between
QSO number density and Cosmic Microwave Background (CMB) temperature
fluctuations in different subsamples: at high z>1.5 and low z<1.5 redshifts and
for two different choices of QSO in a conservative and in a more speculative
analysis. We find an overall evidence for a cross-correlation different from
zero at the 2.7\sigma level, while this evidence drops to 1.5\sigma at z>1.5.
We focus on the capabilities of the ISW to constrain the behaviour of the dark
energy component at high redshift both in the \LambdaCDM and Early Dark Energy
cosmologies, when the dark energy is substantially unconstrained by
observations. At present, the inclusion of the ISW data results in a poor
improvement compared to the obtained constraints from other cosmological
datasets. We study the capabilities of future high-redshift QSO survey and find
that the ISW signal can improve the constraints on the most important
cosmological parameters derived from Planck CMB data, including the high
redshift dark energy abundance, by a factor \sim 1.5.Comment: 20 pages, 18 figures, and 7 table
Stringy Derivation of Nahm Construction of Monopoles
We derive the Nahm construction of monopoles from exact tachyon condensation
on unstable D-branes. The Dirac operator used in the Nahm construction is
identified with the tachyon profile in our D-brane approach, and we provide
physical interpretation of the procedures Nahm gave. Crucial is the
introduction of infinite number of brane-antibranes from which arbitrary
D-brane can be constrcuted, exhibitting a unified view of various D-branes. We
explicitly show the equivalence of the D3-brane boundary state with the
monopole profile and the D1-brane boundary state with the Nahm data as
transverse scalars.Comment: 18 pages, 4 eps figures, JHEP style, comments about low energy limits
added, references adde
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