11,991 research outputs found
Mitochondrial DNA Copy Number Is Associated with Breast Cancer Risk
Mitochondrial DNA (mtDNA) copy number in peripheral blood is associated with increased risk of several cancers. However, data from prospective studies on mtDNA copy number and breast cancer risk are lacking. We evaluated the association between mtDNA copy number in peripheral blood and breast cancer risk in a nested case-control study of 183 breast cancer cases with pre-diagnostic blood samples and 529 individually matched controls among participants of the Singapore Chinese Health Study. The mtDNA copy number was measured using real time PCR. Conditional logistic regression analyses showed that there was an overall positive association between mtDNA copy number and breast cancer risk (Ptrend = 0.01). The elevated risk for higher mtDNA copy numbers was primarily seen for women with <3 years between blood draw and cancer diagnosis; ORs (95% CIs) for 2nd, 3rd, 4th, and 5th quintile of mtDNA copy number were 1.52 (0.61, 3.82), 2.52 (1.03, 6.12), 3.12 (1.31, 7.43), and 3.06 (1.25, 7.47), respectively, compared with the 1st quintile (Ptrend = 0.004). There was no association between mtDNA copy number and breast cancer risk among women who donated a blood sample ≥3 years before breast cancer diagnosis (Ptrend = 0.41). This study supports a prospective association between increased mtDNA copy number and breast cancer risk that is dependent on the time interval between blood collection and breast cancer diagnosis. Future studies are warranted to confirm these findings and to elucidate the biological role of mtDNA copy number in breast cancer risk. © 2013 Thyagarajan et al
Study of the effectiveness of outrigger system for high-rise composite buildings for cyclonic region
The demands of taller structures are becoming imperative almost everywhere in the world in addition to the challenges of material and labor cost, project time line etc. This paper conducted a study keeping in view the challenging nature of high-rise construction with no generic rules for deflection minimizations and frequency control. The effects of cyclonic wind and provision of outriggers on 28-storey, 42-storey and 57-storey are examined in this paper and certain conclusions are made which would pave way for researchers to conduct further study in this particular area of civil engineering. The results show that plan dimensions have vital impacts on structural heights. Increase of height while keeping the plan dimensions same, leads to the reduction in the lateral rigidity. To achieve required stiffness increase of bracings sizes as well as introduction of additional lateral resisting system such as belt truss and outriggers is required
Strong Converse and Second-Order Asymptotics of Channel Resolvability
We study the problem of channel resolvability for fixed i.i.d. input
distributions and discrete memoryless channels (DMCs), and derive the strong
converse theorem for any DMCs that are not necessarily full rank. We also
derive the optimal second-order rate under a condition. Furthermore, under the
condition that a DMC has the unique capacity achieving input distribution, we
derive the optimal second-order rate of channel resolvability for the worst
input distribution.Comment: 7 pages, a shorter version will appear in ISIT 2014, this version
includes the proofs of technical lemmas in appendice
Circuit models and SPICE macro-models for quantum Hall effect devices
Quantum Hall effect (QHE) devices are a pillar of modern quantum electrical
metrology. Electrical networks including one or more QHE elements can be used
as quantum resistance and impedance standards. The analysis of these networks
allows metrologists to evaluate the effect of the inevitable parasitic
parameters on their performance as standards. This paper presents a systematic
analysis of the various circuit models for QHE elements proposed in the
literature, and the development of a new model. This last model is particularly
suited to be employed with the analogue electronic circuit simulator SPICE. The
SPICE macro-model and examples of SPICE simulations, validated by comparison
with the corresponding analytical solution and/or experimental data, are
provided
Measuring valley polarization in two-dimensional materials with second-harmonic spectroscopy
A population imbalance at different valleys of an electronic system lowers
its effective rotational symmetry. We introduce a technique to measure such
imbalance - a valley polarization - that exploits the unique fingerprints of
this symmetry reduction in the polarization-dependent second-harmonic
generation (SHG). We present the principle and detection scheme in the context
of hexagonal two-dimensional crystals, which include graphene-based systems and
the family of transition metal dichalcogenides, and provide a direct
experimental demonstration using a 2H-MoSe monolayer at room temperature.
We deliberately use the simplest possible setup, where a single pulsed laser
beam simultaneously controls the valley imbalance and tracks the SHG process.
We further developed a model of the transient population dynamics which
analytically describes the valley-induced SHG rotation in very good agreement
with the experiment. In addition to providing the first experimental
demonstration of the effect, this work establishes a conceptually simple,
com-pact and transferable way of measuring instantaneous valley polarization,
with direct applicability in the nascent field of valleytronics
Science Requirements and Conceptual Design for a Polarized Medium Energy Electron-Ion Collider at Jefferson Lab
This report presents a brief summary of the science opportunities and program
of a polarized medium energy electron-ion collider at Jefferson Lab and a
comprehensive description of the conceptual design of such a collider based on
the CEBAF electron accelerator facility.Comment: 160 pages, ~93 figures This work was supported by the U.S. Department
of Energy, Office of Nuclear Physics, under Contract No. DE-AC05-06OR23177,
DE-AC02-06CH11357, DE-AC05-060R23177, and DESC0005823. The U.S. Government
retains a non-exclusive, paid-up, irrevocable, world-wide license to publish
or reproduce this manuscript for U.S. Government purpose
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The chronology of the 2002-2003 SARS mini pandemic.
Severe acute respiratory syndrome (SARS) was a new human disease in the autumn of 2002. It first occurred in Southern China in November 2002 and was transported to Hong Kong on February 21, 2003 by an infected and ill patient. Ten secondary cases spread the infection to two hospitals in Hong Kong and to Singapore, Toronto and Hanoi. In March 2003 a novel coronavirus (SARS-CoV) was found to be the causative agent. Within 11 weeks from the first SARS case in Hong Kong it had spread to an additional 27 countries or special administrative regions. The mini pandemic peaked during the last week of May 2003 and the last new probable case was on July 13, 2003. There were a total of 8096 probable cases and 774 deaths. Sixty-six per cent of the cases occurred in China, 22% in Hong Kong, 4% in Taiwan and 3% in both Singapore and Canada. Twenty-one per cent of all cases occurred in healthcare workers
Observation and absolute frequency measurements of the 1S0 - 3P0 optical clock transition in ytterbium
We report the direct excitation of the highly forbidden (6s^2) 1S0 - (6s6p)
3P0 optical transition in two odd isotopes of ytterbium. As the excitation
laser frequency is scanned, absorption is detected by monitoring the depletion
from an atomic cloud at ~70 uK in a magneto-optical trap. The measured
frequency in 171Yb (F=1/2) is 518,295,836,593.2 +/- 4.4 kHz. The measured
frequency in 173Yb (F=5/2) is 518,294,576,850.0 +/- 4.4 kHz. Measurements are
made with a femtosecond-laser frequency comb calibrated by the NIST cesium
fountain clock and represent nearly a million-fold reduction in uncertainty.
The natural linewidth of these J=0 to J=0 transitions is calculated to be ~10
mHz, making them well-suited to support a new generation of optical atomic
clocks based on confinement in an optical lattice.Comment: 4 pages, 3 figure
Wrapping of ellipsoidal nano-particles by fluid membranes
Membrane budding and wrapping of particles, such as viruses and
nano-particles, play a key role in intracellular transport and have been
studied for a variety of biological and soft matter systems. We study
nano-particle wrapping by numerical minimization of bending, surface tension,
and adhesion energies. We calculate deformation and adhesion energies as a
function of membrane elastic parameters and adhesion strength to obtain
wrapping diagrams. We predict unwrapped, partially-wrapped, and
completely-wrapped states for prolate and oblate ellipsoids for various aspect
ratios and particle sizes. In contrast to spherical particles, where
partially-wrapped states exist only for finite surface tensions,
partially-wrapped states for ellipsoids occur already for tensionless
membranes. In addition, the partially-wrapped states are long-lived, because of
an increased energy cost for wrapping of the highly-curved tips. Our results
suggest a lower uptake rate of ellipsoidal particles by cells and thereby a
higher virulence of tubular viruses compared with icosahedral viruses, as well
as co-operative budding of ellipsoidal particles on membranes.Comment: 10 pages, 11 figure
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