1,590 research outputs found
-degeneration and -lemma
For a double complex , we show that if it satisfies the
-lemma and the spectral sequence induced by does
not degenerate at , then it degenerates at . We apply this result to
prove the degeneration at of a Hodge-de Rham spectral sequence on compact
bi-generalized Hermitian manifolds that satisfy a version of -lemma
Solitons and excitations in the duality-based matrix model
We analyse a specific, duality-based generalization of the hermitean matrix
model. The existence of two collective fields enables us to describe specific
excitations of the hermitean matrix model. By using these two fields, we
construct topologically non-trivial solutions (BPS solitons) of the model. We
find the low-energy spectrum of quantum fluctuations around the uniform
solution. Furthermore, we construct the wave functional of the ground state and
obtain the corresponding Green function.Comment: 13 pages,v2: new solutions constructed, title changed accordingl
Literature Survey on the Dynamics of Plate and Shell Structures
The aim of this report is to outline and summarize the study that has been done in the area of vibration of plate and shell structures. A brief description of vibration of grids is also made. The Rayleigh-Ritz method appears to be the most useful method for finding a reasonable approximate solution for natural frequencies of vibration of thin elastic plates and shells. This literature survey will serve the first step towardthe complete comprehension of the vibration problems in plate and shell structures; it will be very beneficial in future investigations of this problem.Civil Engineerin
The ΛS-Householder matrices
AbstractLet A,S∈Mn(C) be given. Suppose that S is nonsingular and Hermitian. Then A is ΛS-orthogonal if A∗SA=S. Let u∈Cn be such that u∗Su≠0. The ΛS-Householder matrix of u is Su≡I-tuu∗S, where t=2u∗Su. We show that det Su=-1, so that products of ΛS-Householder matrices have determinant ±1. Let n⩾2 and let k be positive integers with k⩽n. Set Lk≡Ik⊕-In-k. We show that every ΛLk-orthogonal matrix having determinant ±1 can be written as a product of at most 2n+2 ΛLk-Householder matrices. We also determine the possible Jordan Canonical Forms of products of two ΛLk-Householder matrices
Regional variations in ex-vivo diffusion tensor anisotropy are associated with cardiomyocyte remodeling in rats after left ventricular pressure overload
Background
Pressure overload left ventricular (LV) hypertrophy is characterized by increased cardiomyocyte width and ventricle wall thickness, however the regional variation of this remodeling is unclear. Cardiovascular magnetic resonance (CMR) diffusion tensor imaging (DTI) may provide a non-invasive, comprehensive, and geometrically accurate method to detect regional differences in structural remodeling in hypertrophy. We hypothesized that DTI parameters, such as fractional and planar anisotropy, would reflect myocyte remodeling due to pressure overload in a regionally-dependent manner.
Methods
We investigated the regional distributions of myocyte remodeling in rats with or without transverse aortic constriction (TAC) via direct measurement of myocyte dimensions with confocal imaging of thick tissue sections, and correlated myocyte cross-sectional area and other geometric features with parameters of diffusivity from ex-vivo DTI in the same regions of the same hearts.
Results
We observed regional differences in several parameters from DTI between TAC hearts and SHAM controls. Consistent with previous studies, helix angles from DTI correlated strongly with those measured directly from histological sections (p < 0.001, R2 = 0.71). There was a transmural gradient in myocyte cross-sectional area in SHAM hearts that was diminished in the TAC group. We also found several regions of significantly altered DTI parameters in TAC LV compared to SHAM, especially in myocyte sheet angle dispersion and planar anisotropy. Among others, these parameters correlated significantly with directly measured myocyte aspect ratios.
Conclusions
These results show that structural remodeling in pressure overload LV hypertrophy is regionally heterogeneous, especially transmurally, with a greater degree of remodeling in the sub-endocardium compared to the sub-epicardium. Additionally, several parameters derived from DTI correlated significantly with measurements of myocyte geometry from direct measurement in histological sections. We suggest that DTI may provide a non-invasive, comprehensive method to detect regional structural myocyte LV remodeling during disease
Overcoming data scarcity of Twitter: using tweets as bootstrap with application to autism-related topic content analysis
Notwithstanding recent work which has demonstrated the potential of using
Twitter messages for content-specific data mining and analysis, the depth of
such analysis is inherently limited by the scarcity of data imposed by the 140
character tweet limit. In this paper we describe a novel approach for targeted
knowledge exploration which uses tweet content analysis as a preliminary step.
This step is used to bootstrap more sophisticated data collection from directly
related but much richer content sources. In particular we demonstrate that
valuable information can be collected by following URLs included in tweets. We
automatically extract content from the corresponding web pages and treating
each web page as a document linked to the original tweet show how a temporal
topic model based on a hierarchical Dirichlet process can be used to track the
evolution of a complex topic structure of a Twitter community. Using
autism-related tweets we demonstrate that our method is capable of capturing a
much more meaningful picture of information exchange than user-chosen hashtags.Comment: IEEE/ACM International Conference on Advances in Social Networks
Analysis and Mining, 201
HbA2 levels in β-thalassaemia carriers with the Filipino β0-deletion: are the levels higher than what is found with non-deletional forms of β0-thalassaemia?
AIMS: Classical carriers of β-thalassaemia are identified by a raised HbA2 level. Earlier studies indicated that the Filipino β-deletion has high raised HbA2 levels. The introduction of automated high performance liquid chromatography (HPLC) for thalassaemia screening is an important advance in technology for haematology laboratories. The BioRad Variant II Hb analyser is a common instrument used to quantify HbA2 levels in thalassaemia screening. This study aimed to determine HbA2 levels in carriers of Filipino β-mutation using the BioRad Variant II Hb analyser.
METHODS: The Filipino β-deletion was identified using gap-polymerase chain reaction (PCR) in the parents of transfusion dependent β-thalassaemia patients who were homozygous for the Filipino β-deletion in the indigenous population of Sabah, Malaysia. Hb subtypes were quantified on the BioRad Variant II Hb analyser. Concurrent α-thalassaemia was identified by multiplex gap-PCR for deletions and amplification refractory mutation system (ARMS)-PCR for non-deletional mutations.
RESULTS: The mean HbA2 level for Filipino β-thalassaemia trait was 5.9 ± 0.47 and with coinheritance of α-thalassaemia was 6.3 ± 0.44 (-α heterozygous) and 6.7 ± 0.36 (-α homozygous). The HbA2 levels were all >4% in keeping with the findings of classical β-thalassaemia trait and significantly higher than levels seen in non-deletional forms of β-thalassaemia.
CONCLUSION: The HbA2 level measured on the BioRad Variant II Hb analyser was lower than the level in the first description of the Filipino β-thalassaemia. β-thalassaemia trait with coinheritance of α-thalassaemia (-α) is associated with significantly higher HbA2 level
Decay and coherence of two-photon excited yellow ortho-excitons in Cu2O
Photoluminescence excitation spectroscopy has revealed a novel, highly
efficient two-photon excitation method to produce a cold, uniformly distributed
high density excitonic gas in bulk cuprous oxide. A study of the time evolution
of the density, temperature and chemical potential of the exciton gas shows
that the so called quantum saturation effect that prevents Bose-Einstein
condensation of the ortho-exciton gas originates from an unfavorable ratio
between the cooling and recombination rates. Oscillations observed in the
temporal decay of the ortho-excitonic luminescence intensity are discussed in
terms of polaritonic beating. We present the semiclassical description of
polaritonic oscillations in linear and non-linear optical processes.Comment: 14 pages, 12 figure
Potent and Stable Attenuation of Live-HIV-1 by Gain of a Proteolysis-resistant Inhibitor of NF-κB (IκB-αS32/36A) and the Implications for Vaccine Development *
Live-attenuated human immunodeficiency viruses (HIVs) are candidates for Acquired Immunodeficiency Syndrome (AIDS) vaccine. Based on the simian immunodeficiency virus (SIV) model for AIDS, loss-of-function (e.g. deletion of accessory genes such as nef) has been forwarded as a primary approach for creating enfeebled, but replication-competent, HIV-1/SIV. Regrettably, recent evidence suggests that loss-of-function alone is not always sufficient to prevent the emergence of virulent mutants. New strategies that attenuate via mechanisms distinct from loss-of-function are needed for enhancing the safety phenotype of viral genome. Here, we propose gain-of-function to be used simultaneously with loss-of-function as a novel approach for attenuating HIV-1. We have constructed an HIV-1 genome carrying the cDNA of a proteolysis-resistant nuclear factor-kappaB inhibitor (IkappaB-alphaS32/36A) in the nef region. HIV-1 expressing IkappaB-alphaS32/36A down-regulates viral expression and is highly attenuated in both Jurkat and peripheral blood mononuclear cells. We provide formal proof that the phenotypic and attenuating characteristics of IkappaB-alphaS32/36A permit its stable maintenance in a live, replicating HIV-1 despite 180 days of forced ex vivo passaging in tissue culture. As compared with other open-reading frames embedded into HIV/SIV genome, this degree of stability is unprecedented. Thus, IkappaB-alphaS32/36A offers proof-of-principle that artifactually gained functions, when used to attenuate the replication of live HIV-1, can be stable. These findings illustrate gain-of-function as a feasible strategy for developing safer live-attenuated HIVs to be tested as candidates for AIDS vaccine
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