210 research outputs found
Anisotropic de Gennes narrowing in confined fluids
The collective diffusion of dense fluids in spatial confinement was studied
by combining high-energy (21 keV) x-ray photon correlation spectroscopy and
small-angle x-ray scattering from colloid-filled microfluidic channels. We
found the structural relaxation in confinement to be slower compared to bulk.
The collective dynamics is wave vector dependent, akin to de Gennes narrowing
typically observed in bulk fluids. However, in stark contrast to bulk, the
structure factor and de Gennes narrowing in confinement are anisotropic. These
experimental observations are essential in order to develop a microscopic
theoretical description of collective diffusion of dense fluids in confined
geometries.Comment: 5 pages, 2 figures, accepted for publication in Phys Rev Let
Transport and Strong-Correlation Phenomena in Carbon Nanotube Quantum Dots in a Magnetic Field
Transport through carbon nanotube (CNT) quantum dots (QDs) in a magnetic
field is discussed. The evolution of the system from the ultraviolet to the
infrared is analyzed; the strongly correlated (SC) states arising in the
infrared are investigated. Experimental consequences of the physics are
presented -- the SC states arising at various fillings are shown to be
drastically different, with distinct signatures in the conductance and, in
particular, the noise. Besides CNT QDs, our results are also relevant to double
QD systems.Comment: 5 pages, 5 figure
Major Determinants of Serum Homocysteine Concentrations in a Korean Population
The objective of this study was to identify the factors that determine serum homocysteine concentrations in Korean population. In a community-based study, 871 participants completed detailed questionnaires and physical examination. We found that increased age, male sex, family history of stroke, deficiencies of serum folate and vitamin B12, and elevated serum creatinine significantly increased the risk of hyperhomocysteinemia. However, hormonal and behavioral factors (smoking, alcohol drinking, coffee consumption, and sedentary time) were not associated with the risk of hyperhomocysteinemia. The risk of hyperhomocysteinemia was steeply increased in subjects with two or more risk factors among four selected risk factors (deficiencies of serum folate and vitamin B12, elevated creatinine, and family history of stroke) compared to subjects who did not have any risk factors, especially subjects over the age of 65 yr (odds ratio [OR], 33.5; 95% confidence interval [CI], 3.71-302.0 in men; OR, 39.2; 95% CI, 7.95-193.2 in women). In conclusion, increased age, male sex, family history of stroke, deficiencies of serum folate and vitamin B12, and elevated serum creatinine are important determinants of serum homocysteine concentrations with interaction effects between these factors
Intrinsic Coulomb blockade in multi-wall carbon nanotubes
Carbon nanotubes provide a new class of molecular wires that display new and
exciting mesoscopic transport properties. We provide a detailed theoretical
description for transport in multi-wall nanotubes, where both disorder and
strong interactions are important. The interplay of both aspects leads to a
particularly effective intrinsic Coulomb blockade for tunneling. The relation
to recent experiments is discussed.Comment: 13 pages, incl 2 figs, for: Special issue "Transport in Molecular
Wires" in Chemical Physics, ed. by P. Hanggi, M. Ratner, S. Yalirak
Thermopower of Aharonov-Bohm Interferometer with a Quantum Dot
We report on the thermopower of an Aharonov-Bohm interferometer (AB) with a
quantum dot in the Kondo limit. The thermopower is anomalously enhanced due to
the Kondo effect as in heavy fermion systems. In contrast to the bulk systems,
the sign of the thermopower can be changed by adjusting the energy level scheme
or the particle-hole asymmetry of a dot with the gate voltage. Further the
magnitude and even the sign of the thermopower in the AB ring can be changed at
will with varying either magnetic fields or the gate voltages.Comment: 4 pages, 3 figures, accepted for publication in Physical Review
Letter
Thermoelectric effects of an Aharonov-Bohm interferometer with an embedded quantum dot in the Kondo regime
Thermoelectric effects are studied in an Aharonov-Bohm (AB) interferometer
with an embedded quantum dot in the Kondo regime. The AB flux-dependent
transmission probability has an asymmetrical shape arising from the Fano
interference between the direct tunneling path and the Kondo-resonant tunneling
path through a quantum dot. The sign and magnitude of thermopower can be
modulated by the AB flux and the direct tunneling amplitude. In addition, the
thermopower is anomalously enhanced by the Kondo correlation in the quantum dot
near the Kondo temperature (). The Kondo correlation in the quantum dot
also leads to crossover behavior in diagonal transport coefficients as a
function of temperature. The amplitude of an AB oscillation in electric and
thermal conductances is small at temperatures far above , but becomes
enhanced as the system is cooled below . The AB oscillation is strong in
the thermopower and Lorenz number within the crossover region near the Kondo
temperature.Comment: 16 pages, 10 figure
Suppression of current in transport through parallel double quantum dots
We report our study of the I-V curves in the transport through the quantum
dot when an additional quantum dot lying in the Kondo regime is side-connected
to it. Due to the Kondo scattering off the effective spin on a side-connected
quantum dot the conductance is suppressed at low temperatures and at low
source-drain bias voltages. This zero-bias anomaly is understood as enhanced
Kondo scattering with decreasing temperature.Comment: 14 pages, 8 figure
A study of alternative splicing in the pig
<p>Abstract</p> <p>Background</p> <p>Since at least half of the genes in mammalian genomes are subjected to alternative splicing, alternative pre-mRNA splicing plays an important contribution to the complexity of the mammalian proteome. Expressed sequence tags (ESTs) provide evidence of a great number of possible alternative isoforms. With the EST resource for the domestic pig now containing more than one million porcine ESTs, it is possible to identify alternative splice forms of the individual transcripts in this species from the EST data with some confidence.</p> <p>Results</p> <p>The pig EST data generated by the Sino-Danish Pig Genome project has been assembled with publicly available ESTs and made available in the PigEST database. Using the Distiller package 2,515 EST clusters with candidate alternative isoforms were identified in the EST data with high confidence. In agreement with general observations in human and mouse, we find putative splice variants in about 30% of the contigs with more than 50 ESTs. Based on the criteria that a minimum of two EST sequences confirmed each splice event, a list of 100 genes with the most distinct tissue-specific alternative splice events was generated from the list of candidates. To confirm the tissue specificity of the splice events, 10 genes with functional annotation were randomly selected from which 16 individual splice events were chosen for experimental verification by quantitative PCR (qPCR). Six genes were shown to have tissue specific alternatively spliced transcripts with expression patterns matching those of the EST data. The remaining four genes had tissue-restricted expression of alternative spliced transcripts. Five out of the 16 splice events that were experimentally verified were found to be putative pig specific.</p> <p>Conclusions</p> <p>In accordance with human and rodent studies we estimate that approximately 30% of the porcine genes undergo alternative splicing. We found a good correlation between EST predicted tissue-specificity and experimentally validated splice events in different porcine tissue. This study indicates that a cluster size of around 50 ESTs is optimal for <it>in silico </it>detection of alternative splicing. Although based on a limited number of splice events, the study supports the notion that alternative splicing could have an important impact on species differentiation since 31% of the splice events studied appears to be species specific.</p
Evaluation of Potential Reference Genes for Relative Quantification by RT-qPCR in Different Porcine Tissues Derived from Feeding Studies
Five potential reference genes for RT-qPCR application, namely histone H3, beta-actin, GAPDH, ubiquitin and 18S rRNA, were evaluated for normalization of gene expression in four selected tissues (liver, kidney, thyroid and abdominal fat). Tissues were derived from fattening pigs exposed to different amounts and type of dietary iodine. Two software applications (geNorm and NormFinder) were used to evaluate the stability of the potential reference genes. All studied genes displayed high expression stability but different stability patterns between the investigated tissues. The results suggest GAPDH and 18S rRNA as reference genes applicable in all tissues investigated. Beta-actin and histone H3 are suitable reference genes for all tissues investigated except fat. In contrast, ubiquitin should be excluded from use as a reference gene in the porcine tissues analyzed due to variations in expression levels, despite the good expression stability
Historical analysis of the Brazilian cervical cancer screening program from 2006 to 2013: a time for reflection
BACKGROUND: The Cervical Cancer Database of the Brazilian National Health Service (SISCOLO) contains information regarding all cervical cytological tests and, if properly explored, can be used as a tool for monitoring and managing the cervical cancer screening program. The aim of this study was to perform a historical analysis of the cervical cancer screening program in Brazil from 2006 to 2013.
MATERIAL AND METHODS: The data necessary to calculate quality indicators were obtained from the SISCOLO, a Brazilian health system tool. Joinpoint analysis was used to calculate the annual percentage change.
RESULTS: We observed important trends showing decreased rates of low-grade squamous intraepithelial lesions (LSIL) and high-grade squamous intraepithelial lesions (HSIL) and an increased rate of rejected exams from 2009 to 2013. The index of positivity was maintained at levels below those indicated by international standards; very low frequencies of unsatisfactory cases were observed over the study period, which partially contradicts the low rate of positive cases. The number of positive cytological diagnoses was below that expected, considering that developed countries with low frequencies of cervical cancer detect more lesions annually.
CONCLUSIONS: The evolution of indicators from 2006 to 2013 suggests that actions must be taken to improve the effectiveness of cervical cancer control in Brazil
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