830 research outputs found
Correcting the quantum clock: conditional sojourn times
Can the quantum-mechanical sojourn time be clocked without the clock
affecting the sojourn time? Here we re-examine the previously proposed
non-unitary clock, involving absorption/amplification by an added infinitesimal
imaginary potential(), and find it {\it not} to preserve, in general,
the positivity of the sojourn time, conditional on eventual reflection or
transmission. The sojourn time is found to be affected by the scattering
concomitant with the mismatch, however small, due to the very clock
potential() introduced for the purpose, as also by any prompt
scattering involving partial waves that have not traversed the region of
interest. We propose a formal procedure whereby the sojourn time so clocked can
be corrected for these spurious scattering effects. The resulting conditional
sojourn times are then positive definite for an arbitrary potential, and have
the proper high- and low-energy limits.Comment: Corrected and rewritten, RevTeX, 4 pages, 2 figures (ps files)
include
Learning 3D Human Pose from Structure and Motion
3D human pose estimation from a single image is a challenging problem,
especially for in-the-wild settings due to the lack of 3D annotated data. We
propose two anatomically inspired loss functions and use them with a
weakly-supervised learning framework to jointly learn from large-scale
in-the-wild 2D and indoor/synthetic 3D data. We also present a simple temporal
network that exploits temporal and structural cues present in predicted pose
sequences to temporally harmonize the pose estimations. We carefully analyze
the proposed contributions through loss surface visualizations and sensitivity
analysis to facilitate deeper understanding of their working mechanism. Our
complete pipeline improves the state-of-the-art by 11.8% and 12% on Human3.6M
and MPI-INF-3DHP, respectively, and runs at 30 FPS on a commodity graphics
card.Comment: ECCV 2018. Project page: https://www.cse.iitb.ac.in/~rdabral/3DPose
Optimal control theory for unitary transformations
The dynamics of a quantum system driven by an external field is well
described by a unitary transformation generated by a time dependent
Hamiltonian. The inverse problem of finding the field that generates a specific
unitary transformation is the subject of study. The unitary transformation
which can represent an algorithm in a quantum computation is imposed on a
subset of quantum states embedded in a larger Hilbert space. Optimal control
theory (OCT) is used to solve the inversion problem irrespective of the initial
input state. A unified formalism, based on the Krotov method is developed
leading to a new scheme. The schemes are compared for the inversion of a
two-qubit Fourier transform using as registers the vibrational levels of the
electronic state of Na. Raman-like transitions through the
electronic state induce the transitions. Light fields are found
that are able to implement the Fourier transform within a picosecond time
scale. Such fields can be obtained by pulse-shaping techniques of a femtosecond
pulse. Out of the schemes studied the square modulus scheme converges fastest.
A study of the implementation of the qubit Fourier transform in the Na
molecule was carried out for up to 5 qubits. The classical computation effort
required to obtain the algorithm with a given fidelity is estimated to scale
exponentially with the number of levels. The observed moderate scaling of the
pulse intensity with the number of qubits in the transformation is
rationalized.Comment: 32 pages, 6 figure
Super-reflection of light from a random amplifying medium with disorder in the complex refractive index : Statistics of fluctuations
The probability distribution of the reflection coefficient for light
reflected from a one-dimensional random amplifying medium with {\it
cross-correlated} spatial disorder in the real and the imaginary parts of the
refractive index is derived using the method of invariant imbedding. The
statistics of fluctuations have been obtained for both the correlated telegraph
noise and the Gaussian white-noise models for the disorder. In both cases, an
enhanced backscattering (super-reflection with reflection coefficient greater
than unity) results because of coherent feedback due to Anderson localization
and coherent amplification in the medium. The results show that the effect of
randomness in the imaginary part of the refractive index on localization and
super-reflection is qualitatively different.Comment: RevTex 6 pages, 3 figures in ps file
Contributions of spontaneous phase slippage to linear and non-linear conduction near the Peierls transition in thin samples of o-TaS_3
In the Peierls state very thin samples of TaS_3 (cross-section area \sim
10^{-3} mkm^2) are found to demonstrate smearing of the I-V curves near the
threshold field. With approaching the Peierls transition temperature, T_P, the
smearing evolves into smooth growth of conductance from zero voltage
interpreted by us as the contribution of fluctuations to the non--linear
conductance. We identify independently the fluctuation contribution to the
linear conductance near T_P. Both linear and non-linear contributions depend on
temperature with close activation energies \sim (2 - 4) x 10^3 K and apparently
reveal the same process. We reject creep of the {\it continuous} charge-density
waves (CDWs) as the origin of this effect and show that it is spontaneous phase
slippage that results in creep of the CDW. A model is proposed accounting for
both the linear and non-linear parts of the fluctuation conduction up to T_P.Comment: 6 pages, 5 Postscript figure, RevTeX, accepted for publication in PR
Analysis of the Mitogen-activated protein kinase kinase 4 (MAP2K4) tumor suppressor gene in ovarian cancer
<p>Abstract</p> <p>Background</p> <p><it>MAP2K4 </it>is a putative tumor and metastasis suppressor gene frequently found to be deleted in various cancer types. We aimed to conduct a comprehensive analysis of this gene to assess its involvement in ovarian cancer.</p> <p>Methods</p> <p>We screened for mutations in <it>MAP2K4 </it>using High Resolution Melt analysis of 149 primary ovarian tumors and methylation at the promoter using Methylation-Specific Single-Stranded Conformation Polymorphism analysis of 39 tumors. We also considered the clinical impact of changes in <it>MAP2K4 </it>using publicly available expression and copy number array data. Finally, we used siRNA to measure the effect of reducing <it>MAP2K4 </it>expression in cell lines.</p> <p>Results</p> <p>In addition to 4 previously detected homozygous deletions, we identified a homozygous 16 bp truncating deletion and a heterozygous 4 bp deletion, each in one ovarian tumor. No promoter methylation was detected. The frequency of <it>MAP2K4 </it>homozygous inactivation was 5.6% overall, and 9.8% in high-grade serous cases. Hemizygous deletion of <it>MAP2K4 </it>was observed in 38% of samples. There were significant correlations of copy number and expression in three microarray data sets. There was a significant correlation between <it>MAP2K4 </it>expression and overall survival in one expression array data set, but this was not confirmed in an independent set. Treatment of JAM and HOSE6.3 cell lines with <it>MAP2K4 </it>siRNA showed some reduction in proliferation.</p> <p>Conclusions</p> <p><it>MAP2K4 </it>is targeted by genetic inactivation in ovarian cancer and restricted to high grade serous and endometrioid carcinomas in our cohort.</p
Development of genome-specific primers for homoeologous genes in allopolyploid species: the waxy and starch synthase II genes in allohexaploid wheat (Triticum aestivum L.) as examples
<p>Abstract</p> <p>Background</p> <p>In allopolypoid crops, homoeologous genes in different genomes exhibit a very high sequence similarity, especially in the coding regions of genes. This makes it difficult to design genome-specific primers to amplify individual genes from different genomes. Development of genome-specific primers for agronomically important genes in allopolypoid crops is very important and useful not only for the study of sequence diversity and association mapping of genes in natural populations, but also for the development of gene-based functional markers for marker-assisted breeding. Here we report on a useful approach for the development of genome-specific primers in allohexaploid wheat.</p> <p>Findings</p> <p>In the present study, three genome-specific primer sets for the <it>waxy </it>(<it>Wx</it>) genes and four genome-specific primer sets for the <it>starch synthase II </it>(<it>SSII</it>) genes were developed mainly from single nucleotide polymorphisms (SNPs) and/or insertions or deletions (Indels) in introns and intron-exon junctions. The size of a single PCR product ranged from 750 bp to 1657 bp. The total length of amplified PCR products by these genome-specific primer sets accounted for 72.6%-87.0% of the <it>Wx </it>genes and 59.5%-61.6% of the <it>SSII </it>genes. Five genome-specific primer sets for the <it>Wx </it>genes (one for Wx-7A, three for Wx-4A and one for Wx-7D) could distinguish the wild type wheat and partial waxy wheat lines. These genome-specific primer sets for the <it>Wx </it>and <it>SSII </it>genes produced amplifications in hexaploid wheat, cultivated durum wheat, and <it>Aegilops tauschii </it>accessions, but failed to generate amplification in the majority of wild diploid and tetraploid accessions.</p> <p>Conclusions</p> <p>For the first time, we report on the development of genome-specific primers from three homoeologous <it>Wx </it>and <it>SSII </it>genes covering the majority of the genes in allohexaploid wheat. These genome-specific primers are being used for the study of sequence diversity and association mapping of the three homoeologous <it>Wx </it>and <it>SSII </it>genes in natural populations of both hexaploid wheat and cultivated tetraploid wheat. The strategies used in this paper can be used to develop genome-specific primers for homoeologous genes in any allopolypoid species. They may be also suitable for (i) the development of gene-specific primers for duplicated paralogous genes in any diploid species, and (ii) the development of allele-specific primers at the same gene locus.</p
Characterisation of Inactivation Domains and Evolutionary Strata in Human X Chromosome through Markov Segmentation
Markov segmentation is a method of identifying compositionally different subsequences in a given symbolic sequence. We have applied this technique to the DNA sequence of the human X chromosome to analyze its compositional structure. The human X chromosome is known to have acquired DNA through distinct evolutionary events and is believed to be composed of five evolutionary strata. In addition, in female mammals all copies of X chromosome in excess of one are transcriptionally inactivated. The location of a gene is correlated with its ability to undergo inactivation, but correlations between evolutionary strata and inactivation domains are less clear. Our analysis provides an accurate estimate of the location of stratum boundaries and gives a high–resolution map of compositionally different regions on the X chromosome. This leads to the identification of a novel stratum, as well as segments wherein a group of genes either undergo inactivation or escape inactivation in toto. We identify oligomers that appear to be unique to inactivation domains alone
Transformational Plasmon Optics
Transformation optics has recently attracted extensive interest, since it
provides a novel design methodology for manipulating light at will. Although
transformation optics in principle embraces all forms of electromagnetic
phenomena on all length scales, so far, much less efforts have been devoted to
near-field optical waves, such as surface plasmon polaritons (SPPs). Due to the
tight confinement and strong field enhancement, SPPs are widely used for
various purposes at the subwavelength scale. Taking advantage of transformation
optics, here we demonstrate that the confinement as well as propagation of SPPs
can be managed in a prescribed manner by careful control of the dielectric
material properties adjacent to a metal. Since the metal properties are
completely unaltered, it provides a straightforward way for practical
realizations. We show that our approach can assist to tightly bound SPPs over a
broad wavelength band at uneven and curved surfaces, where SPPs would normally
suffer significant scattering losses. In addition, a plasmonic waveguide bend
and a plasmonic Luneburg lens with practical designs are proposed. It is
expected that merging the unprecedented design flexibility based on
transformation optics with the unique optical properties of surface modes will
lead to a host of fascinating near-field optical phenomena and devices.Comment: 17 pages, 6 figure
Effects of Layer Stacking on the Combination Raman modes in Graphene
We have observed new combination modes in the range from 1650 - 2300 cm-1 in
single-(SLG), bi-, few-layer and incommensurate bilayer graphene (IBLG) on
silicon dioxide substrates. The M band at ~1750 cm-1 is suppressed for both SLG
and IBLG. A peak at ~1860 cm-1 (iTALO-) is observed due to a combination of the
iTA and LO phonons. The intensity of this peak decreases with increasing number
of layers and this peak is absent in bulk graphite. Two previously unidentified
modes at ~1880 cm-1 (iTALO+) and ~2220 cm-1 (iTOTA) in SLG are tentatively
assigned as combination modes around the K point of the graphene Brillouin
zone. The peak frequencies of the iTALO+ (iTOTA) modes are observed to increase
(decrease) linearly with increasing graphene layers.Comment: 11 Pages, 4 Figure
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