10,542 research outputs found
Complex Curve of the Two Matrix Model and its Tau-function
We study the hermitean and normal two matrix models in planar approximation
for an arbitrary number of eigenvalue supports. Its planar graph interpretation
is given. The study reveals a general structure of the underlying analytic
complex curve, different from the hyperelliptic curve of the one matrix model.
The matrix model quantities are expressed through the periods of meromorphic
generating differential on this curve and the partition function of the
multiple support solution, as a function of filling numbers and coefficients of
the matrix potential, is shown to be the quasiclassical tau-function. The
relation to softly broken N=1 supersymmetric Yang-Mills theories is discussed.
A general class of solvable multimatrix models with tree-like interactions is
considered.Comment: 36 pages, 10 figures, TeX; final version appeared in special issue of
J.Phys. A on Random Matrix Theor
Insulin promoter DNA methylation correlates negatively with insulin gene expression and positively with HbA1c levels in human pancreatic islets
Aims/hypothesis: Although recent studies propose that epigenetic factors influence insulin expression, the regulation of the insulin gene in type 2 diabetic islets is still not fully understood. Here, we examined DNA methylation of the insulin gene promoter in pancreatic islets from patients with type 2 diabetes and non-diabetic human donors and related it to insulin expression, HbA levels, BMI and age. Methods: DNA methylation was analysed in 25 CpG sites of the insulin promoter and insulin mRNA expression was analysed using quantitative RT-PCR in pancreatic islets from nine donors with type 2 diabetes and 48 non-diabetic donors. Results: Insulin mRNA expression (p = 0.002), insulin content (p = 0.004) and glucose-stimulated insulin secretion (p = 0.04) were reduced in pancreatic islets from patients with type 2 diabetes compared with non-diabetic donors. Moreover, four CpG sites located 234 bp, 180 and 102 bp upstream and 63 bp downstream of the transcription start site (CpG -234, -180, -102 and +63, respectively), showed increased DNA methylation in type 2 diabetic compared with non-diabetic islets (7.8%, p = 0.03; 7.1%, p = 0.02; 4.4%, p = 0.03 and 9.3%, p = 0.03, respectively). While insulin mRNA expression correlated negatively (p < 1 × 10), the level of HbA correlated positively (p ≤ 0.01) with the degree of DNA methylation for CpG -234, -180 and +63. Furthermore, DNA methylation for nine additional CpG sites correlated negatively with insulin mRNA expression (p ≤ 0.01). Also, exposure to hyperglycaemia for 72 h increased insulin promoter DNA methylation in clonal rat beta cells (p = 0.005). Conclusions/interpretations: This study demonstrates that DNA methylation of the insulin promoter is increased in patients with type 2 diabetes and correlates negatively with insulin gene expression in human pancreatic islets
The Burst and Transient Source Experiment Earth Occultation Technique
An Earth orbiting detector sensitive to gamma ray photons will see step-like
occultation features in its counting rate when a gamma ray point source crosses
the Earth's limb. This is due to the change in atmospheric attenuation of the
gamma rays along the line of sight. In an uncollimated detector, these
occultation features can be used to locate and monitor astrophysical sources
provided their signals can be individually separated from the detector
background. We show that the Earth occultation technique applied to the Burst
and Transient Source Experiment (BATSE) on the Compton Gamma Ray Observatory
(CGRO) is a viable and flexible all-sky monitor in the low energy gamma ray and
hard X-ray energy range (20 keV - 1 MeV). The method is an alternative to more
sophisticated photon imaging devices for astronomy, and can serve well as a
cost-effective science capability for monitoring the high energy sky.
Here we describe the Earth occultation technique for locating new sources and
for measuring source intensity and spectra without the use of complex
background models. Examples of transform imaging, step searches, spectra, and
light curves are presented. Systematic uncertainties due to source confusion,
detector response, and contamination from rapid background fluctuations are
discussed and analyzed for their effect on intensity measurements. A sky
location-dependent average systematic error is derived as a function of
galactic coordinates. The sensitivity of the technique is derived as a function
of incident photon energy and also as a function of angle between the source
and the normal to the detector entrance window. Occultations of the Crab Nebula
by the Moon are used to calibrate Earth occultation flux measurements
independent of possible atmospheric scattering effects.Comment: 39 pages, 24 figures. Accepted for publication in the Astrophysical
Journal Supplement
Geometric observation for the Bures fidelity between two states of a qubit
In this Brief Report, we present a geometric observation for the Bures
fidelity between two states of a qubit.Comment: 4 pages, 1 figure, RevTex, Accepted by Phys. Rev.
Correlation Function of Superclusters of Galaxies
We present a study of the two-point correlation function of superclusters of
galaxies. The largest catalogs are used. The results show negligible
correlation less than 0.1-0.2 for separations up to 500-600 h^{-1} Mpc. Small
correlations are obtained using various estimates and samples. Seemingly there
are no structures of superclusters of galaxies.Comment: 19 pages, 3 figures, 4 tables. To appear in 1998 ApJ, 506, No. 2 (Oct
20
A Graph Theoretic Approach for Object Shape Representation in Compositional Hierarchies Using a Hybrid Generative-Descriptive Model
A graph theoretic approach is proposed for object shape representation in a
hierarchical compositional architecture called Compositional Hierarchy of Parts
(CHOP). In the proposed approach, vocabulary learning is performed using a
hybrid generative-descriptive model. First, statistical relationships between
parts are learned using a Minimum Conditional Entropy Clustering algorithm.
Then, selection of descriptive parts is defined as a frequent subgraph
discovery problem, and solved using a Minimum Description Length (MDL)
principle. Finally, part compositions are constructed by compressing the
internal data representation with discovered substructures. Shape
representation and computational complexity properties of the proposed approach
and algorithms are examined using six benchmark two-dimensional shape image
datasets. Experiments show that CHOP can employ part shareability and indexing
mechanisms for fast inference of part compositions using learned shape
vocabularies. Additionally, CHOP provides better shape retrieval performance
than the state-of-the-art shape retrieval methods.Comment: Paper : 17 pages. 13th European Conference on Computer Vision (ECCV
2014), Zurich, Switzerland, September 6-12, 2014, Proceedings, Part III, pp
566-581. Supplementary material can be downloaded from
http://link.springer.com/content/esm/chp:10.1007/978-3-319-10578-9_37/file/MediaObjects/978-3-319-10578-9_37_MOESM1_ESM.pd
Area Spectrum of Near Extremal Black Branes from Quasi-normal Modes
Motivated by the recent interest in quantization of black hole area spectrum,
we consider the area spectrum of near extremal black branes. Based on the
proposal by Bekenstein and others that the black hole area spectrum is discrete
and equally spaced, we implement Kunstatter's method to derive the area
spectrum for the near extremal black branes. The result for the area of
event horizon although discrete, is not equally spaced.Comment: 8 pages, no figures, accepted for publication in IJT
Quantum Gravity, the Origin of Time and Time's Arrow
The local Lorentz and diffeomorphism symmetries of Einstein's gravitational
theory are spontaneously broken by a Higgs mechanism by invoking a phase
transition in the early Universe, at a critical temperature below which
the symmetry is restored. The spontaneous breakdown of the vacuum state
generates an external time and the wave function of the Universe satisfies a
time dependent Schrodinger equation, which reduces to the Wheeler-deWitt
equation in the classical regime for , allowing a semi-classical WKB
approximation to the wave function. The conservation of energy is spontaneously
violated for and matter is created fractions of seconds after the big
bang, generating the matter in the Universe. The time direction of the vacuum
expectation value of the scalar Higgs field generates a time asymmetry, which
defines the cosmological arrow of time and the direction of increasing entropy
as the Lorentz symmetry is restored at low temperatures.Comment: 37 page
Stabilnost amlodipin besilata i atenolola u jednoslojnim i dvoslojnim tabletama
Multi-drug tablets of amlodipine besylate and atenolol were prepared as either mono-layer (mixed matrix) or bi-layer tablets containing each drug in a separate layer by using similar excipients and processing. Each tablet batch was packed in strip and blister packs and kept under accelerated temperature and humidity conditions. The stability of two tablet and packaging types was compared by HPLC analysis after 0, 1, 3 and 4.5 months and expressed as the content of intact amlodipine and atenolol.
The content of atenolol did not decline regardless of tablet and packaging type. Amlodipine content in bi-layer tablets decreased to about 95 and 88% when packed in strips and blisters, respectively. When prepared as mono-layer tablets, the content decreased to 72 and 32%, respectively.
The study revealed that the bi-layer tablet formulation was more stable than the mono-layer type. Further, the stability was increased when the tablets were packed in aluminium strips as compared to PVC blisters.Tablete s amlodipinom i atenololom pripremljene su ili u obliku jednoslojne tablete (miješani matriks) ili kao dvoslojne tablete (lijekovi u zasebnim slojevima) koristeći slične pomoćne tvari i uvjete tabletiranja. Tablete su pakirane u dvije vrste pakiranja, aluminijske folije (strip) ili PVC (blister) i čuvane u uvjetima ubrzanog starenja. Stabilnost je određivana pomoću HPLC metode nakon 0, 1, 2, 3 i 4,5 mjeseci i izražena kao sadržaj intaktnog lijeka.
Sadržaj atenolola nije se značajno promijenio bez obzira na tip tablete ili pakiranje. Sadržaj amlodipina u dvoslojnim tabletama smanjio se na 95 % (tablete u strip pakiranju) i 88 % (tablete u blister pakiranju). Istodobno, u jednoslojnom tipu kombiniranih tableta sadržaj se smanjio na 72 % (strip pakiranje) i 32 % (blister pakiranje).
Rezultati pokazuju da su dvoslojne tablete s amlodipinom i atenololom stabilnije od jednoslojnih. Štoviše, pakiranje tableta u aluminijsku foliju u obliku strip pakiranja povećava njihovu stabilnost u usporedbi s PVC pakirnim materijalom (blister)
Progress in the physics of massive neutrinos
The current status of the physics of massive neutrinos is reviewed with a
forward-looking emphasis. The article begins with the general phenomenology of
neutrino oscillations in vacuum and matter and documents the experimental
evidence for oscillations of solar, reactor, atmospheric and accelerator
neutrinos. Both active and sterile oscillation possibilities are considered.
The impact of cosmology (BBN, CMB, leptogenesis) and astrophysics (supernovae,
highest energy cosmic rays) on neutrino observables and vice versa, is
evaluated. The predictions of grand unified, radiative and other models of
neutrino mass are discussed. Ways of determining the unknown parameters of
three-neutrino oscillations are assessed, taking into account eight-fold
degeneracies in parameters that yield the same oscillation probabilities, as
well as ways to determine the absolute neutrino mass scale (from beta-decay,
neutrinoless double-beta decay, large scale structure and Z-bursts). Critical
unknowns at present are the amplitude of \nu_\mu to \nu_e oscillations and the
hierarchy of the neutrino mass spectrum; the detection of CP violation in the
neutrino sector depends on these and on an unknown phase. The estimated
neutrino parameter sensitivities at future facilities (reactors, superbeams,
neutrino factories) are given. The overall agenda of a future neutrino physics
program to construct a bottom-up understanding of the lepton sector is
presented.Comment: 111 pages, 35 figures. Update
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