136 research outputs found
Excitation of atoms in an optical lattice driven by polychromatic amplitude modulation
We investigate the mutiphoton process between different Bloch states in an
amplitude modulated optical lattice. In the experiment, we perform the
modulation with more than one frequency components, which includes a high
degree of freedom and provides a flexible way to coherently control quantum
states. Based on the study of single frequency modulation, we investigate the
collaborative effect of different frequency components in two aspects. Through
double frequency modulations, the spectrums of excitation rates for different
lattice depths are measured. Moreover, interference between two separated
excitation paths is shown, emphasizing the influence of modulation phases when
two modulation frequencies are commensurate. Finally, we demonstrate the
application of the double frequency modulation to design a
large-momentum-transfer beam splitter. The beam splitter is easy in practice
and would not introduce phase shift between two arms.Comment: 11pages, 7 figure
Atomic Ramsey interferometry with S- and D-band in a triangular optical lattice
Ramsey interferometers have wide applications in science and engineering.
Compared with the traditional interferometer based on internal states, the
interferometer with external quantum states has advantages in some applications
for quantum simulation and precision measurement. Here, we develop a Ramsey
interferometry with Bloch states in S- and D-band of a triangular optical
lattice for the first time. The key to realizing this interferometer in
two-dimensionally coupled lattice is that we use the shortcut method to
construct pulse. We observe clear Ramsey fringes and analyze the
decoherence mechanism of fringes. Further, we design an echo pulse
between S- and D-band, which significantly improves the coherence time. This
Ramsey interferometer in the dimensionally coupled lattice has potential
applications in the quantum simulations of topological physics, frustrated
effects, and motional qubits manipulation
Associations between gut microbiota and sleep: a two-sample, bidirectional Mendelian randomization study
IntroductionPrevious research has reported that the gut microbiota performs an essential role in sleep through the microbiome–gut–brain axis. However, the causal association between gut microbiota and sleep remains undetermined.MethodsWe performed a two-sample, bidirectional Mendelian randomization (MR) analysis using genome-wide association study summary data of gut microbiota and self-reported sleep traits from the MiBioGen consortium and UK Biobank to investigate causal relationships between 119 bacterial genera and seven sleep-associated traits. We calculated effect estimates by using the inverse-variance weighted (as the main method), maximum likelihood, simple model, weighted model, weighted median, and MR-Egger methods, whereas heterogeneity and pleiotropy were detected and measured by the MR pleiotropy residual sum and outlier method, Cochran’s Q statistics, and MR-Egger regression.ResultsIn forward MR analysis, inverse-variance weighted estimates concluded that the genetic forecasts of relative abundance of 42 bacterial genera had causal effects on sleep-associated traits. In the reverse MR analysis, sleep-associated traits had a causal effect on 39 bacterial genera, 13 of which overlapped with the bacterial genera in the forward MR analysis.DiscussionIn conclusion, our research indicates that gut microbiota may be involved in the regulation of sleep, and conversely, changes in sleep-associated traits may also alter the abundance of gut microbiota. These findings suggest an underlying reciprocal causal association between gut microbiota and sleep
Precisely controlled resorcinol-formaldehyde resin coating for fabricating core-shell, hollow, and yolk-shell carbon nanostructures
MOST of China [2011CB932403, 2009CB930703]; NSFC [21131005, 21021061, 20925103, 20923004]; Fok Ying Tung Education Foundation [121011]This work provides a facile one-step sol-gel route to synthesize high-quality resorcinol-formaldehyde (RF) resin coated nanocomposites that can be further used to fabricate desired carbon nanostructures. Colloidal particles with different morphologies and sizes can be coated with high-quality RF resin shells by the proposed cationic surfactant assisted RF resin coating strategy. The as-synthesized RF resin coated nanocomposites are ideal candidates for selective synthesis of core-shell, hollow, and yolk-shell carbon nanostructures. Based on the carboxylic functional RF resin coating, graphitic carbon nanostructures can also be synthesized by employing the graphitization catalyst. The as-synthesized carbon nanostructures show the advantageous performances in several applications. Hollow carbon spheres are potential electrode materials for lithium-sulfur batteries. Hollow graphitic spheres are promising catalyst supports for oxygen reduction reaction. And yolk-shell structured Au@HCS nanoreactors with ultrathin shells exhibit high catalytic activity and recyclability in confined catalysis
Retrospective evaluation of whole exome and genome mutation calls in 746 cancer samples
Funder: NCI U24CA211006Abstract: The Cancer Genome Atlas (TCGA) and International Cancer Genome Consortium (ICGC) curated consensus somatic mutation calls using whole exome sequencing (WES) and whole genome sequencing (WGS), respectively. Here, as part of the ICGC/TCGA Pan-Cancer Analysis of Whole Genomes (PCAWG) Consortium, which aggregated whole genome sequencing data from 2,658 cancers across 38 tumour types, we compare WES and WGS side-by-side from 746 TCGA samples, finding that ~80% of mutations overlap in covered exonic regions. We estimate that low variant allele fraction (VAF < 15%) and clonal heterogeneity contribute up to 68% of private WGS mutations and 71% of private WES mutations. We observe that ~30% of private WGS mutations trace to mutations identified by a single variant caller in WES consensus efforts. WGS captures both ~50% more variation in exonic regions and un-observed mutations in loci with variable GC-content. Together, our analysis highlights technological divergences between two reproducible somatic variant detection efforts
A Normalized Rich-Club Connectivity-Based Strategy for Keyword Selection in Social Media Analysis
In this paper, we present a study on keyword selection behavior in social media analysis that is focused on particular topics, and propose a new effective strategy that considers the co-occurrence relationships between keywords and uses graph-based techniques. In particular, we used the normalized rich-club connectivity considering the weighted degree, closeness centrality, betweenness centrality and PageRank values to measure a subgroup of highly connected “rich keywords” in a keyword co-occurrence network. Community detection is subsequently applied to identify several keyword combinations that are able to accurately and comprehensively represent the researched topic. The empirical results based on four topics and comparing four existing models confirm the performance of our proposed strategy in promoting the quantity and ensuing the quality of data related to particular topics collected from social media. Overall, our findings are expected to offer useful guidelines on how to select keywords for social media-based studies and thus further increase the reliability and validity of their respective conclusions
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