3,322 research outputs found
Computational investigation of static multipole polarizabilities and sum rules for ground-state hydrogen-like ions
High precision multipole polarizabilities, for
of the ground state of the hydrogen isoelectronic series are obtained from
the Dirac equation using the B-spline method with Notre Dame boundary
conditions. Compact analytic expressions for the polarizabilities as a function
of with a relative accuracy of 10 up to are determined by
fitting to the calculated polarizabilities. The oscillator strengths satisfy
the sum rules for all multipoles from
to . The dispersion coefficients for the long-range H-H and H-He
interactions are given.Comment: 8 figures, 8 table
Deciphering hierarchical organization of topologically associated domains through change-point testing.
BACKGROUND: The nucleus of eukaryotic cells spatially packages chromosomes into a hierarchical and distinct segregation that plays critical roles in maintaining transcription regulation. High-throughput methods of chromosome conformation capture, such as Hi-C, have revealed topologically associating domains (TADs) that are defined by biased chromatin interactions within them.
RESULTS: We introduce a novel method, HiCKey, to decipher hierarchical TAD structures in Hi-C data and compare them across samples. We first derive a generalized likelihood-ratio (GLR) test for detecting change-points in an interaction matrix that follows a negative binomial distribution or general mixture distribution. We then employ several optimal search strategies to decipher hierarchical TADs with p values calculated by the GLR test. Large-scale validations of simulation data show that HiCKey has good precision in recalling known TADs and is robust against random collisions of chromatin interactions. By applying HiCKey to Hi-C data of seven human cell lines, we identified multiple layers of TAD organization among them, but the vast majority had no more than four layers. In particular, we found that TAD boundaries are significantly enriched in active chromosomal regions compared to repressed regions.
CONCLUSIONS: HiCKey is optimized for processing large matrices constructed from high-resolution Hi-C experiments. The method and theoretical result of the GLR test provide a general framework for significance testing of similar experimental chromatin interaction data that may not fully follow negative binomial distributions but rather more general mixture distributions
A note on modular forms and generalized anomaly cancellation formulas
By studying modular invariance properties of some characteristic forms, we
prove some new anomaly cancellation formulas which generalize the Han-Zhang and
Han-Liu-Zhang anomaly cancellation formula
Sulforaphane induces adipocyte browning and promotes glucose and lipid utilization
Scope: Obesity is closely related to the imbalance of white adipose tissue storing excess calories, and brown adipose tissue dissipating energy to produce heat in mammals. Recent studies revealed that acquisition of brown characteristics by white adipocytes, termed “browning,” may positively contribute to cellular bioenergetics and metabolism homeostasis. The goal was to investigate the putative effects of natural antioxidant sulforaphane (1-isothiocyanate-4-methyl-sulfonyl butane; SFN) on browning of white adipocytes. Methods and Results: 3T3-L1 mature white adipocytes were treated with SFN for 48 h, and then the mitochondrial content, function, and energy utilization were assessed. SFN was found to induce 3T3-L1 adipocytes browning based on the increased mitochondrial content and activity of respiratory chain enzymes, whereas the mechanism involved the upregulation of nuclear factor E2-related factor 2/ sirtuin1/ peroxisome proliferator-activated receptor gamma coactivator 1 alpha signaling. SFN enhanced uncoupling protein 1 expression, a marker for brown adipocyte, leading to the decrease in cellular ATP. SFN also enhanced glucose uptake and oxidative utilization, lipolysis and fatty acid oxidation in 3T3-L1 adipocytes. Conclusion: SFN-induced browning of white adipocytes enhanced the utilization of cellular fuel, and the application of SFN is a promising strategy to combat obesity and obesity-related metabolic disorder
Quantum transport through a double Aharonov-Bohm-interferometer in the presence of Andreev reflection
Quantum transport through a double Aharonov-Bohm-interferometer in the
presence of Andreev reflection is investigated in terms of the nonequilibrium
Green function method with which the reflection current is obtained. Tunable
Andreev reflection probabilities depending on the interdot coupling strength
and magnetic flux as well are analysised in detail. It is found that the
oscillation period of the reflection probability with respect to the magnetic
flux for the double interferometer depends linearly on the ratio of two parts
magnetic fluxes n, i.e. 2(n+1)pi, while that of a single interferometer is 2pi.
The coupling strength not only affects the height and the linewidth of Andreev
reflection current peaks vs gate votage but also shifts the peak positions. It
is furthermore demonstrated that the Andreev reflection current peaks can be
tuned by the magnetic fluxes.Comment: 13 pages, 12 figur
Label Transfer from APOGEE to LAMOST: Precise Stellar Parameters for 450,000 LAMOST Giants
In this era of large-scale stellar spectroscopic surveys, measurements of
stellar attributes ("labels," i.e. parameters and abundances) must be made
precise and consistent across surveys. Here, we demonstrate that this can be
achieved by a data-driven approach to spectral modeling. With The Cannon, we
transfer information from the APOGEE survey to determine precise Teff, log g,
[Fe/H], and [/M] from the spectra of 450,000 LAMOST giants. The Cannon
fits a predictive model for LAMOST spectra using 9952 stars observed in common
between the two surveys, taking five labels from APOGEE DR12 as ground truth:
Teff, log g, [Fe/H], [\alpha/M], and K-band extinction . The model is then
used to infer Teff, log g, [Fe/H], and [/M] for 454,180 giants, 20% of
the LAMOST DR2 stellar sample. These are the first [/M] values for the
full set of LAMOST giants, and the largest catalog of [/M] for giant
stars to date. Furthermore, these labels are by construction on the APOGEE
label scale; for spectra with S/N > 50, cross-validation of the model yields
typical uncertainties of 70K in Teff, 0.1 in log g, 0.1 in [Fe/H], and 0.04 in
[/M], values comparable to the broadly stated, conservative APOGEE DR12
uncertainties. Thus, by using "label transfer" to tie low-resolution (LAMOST R
1800) spectra to the label scale of a much higher-resolution (APOGEE R
22,500) survey, we substantially reduce the inconsistencies between
labels measured by the individual survey pipelines. This demonstrates that
label transfer with The Cannon can successfully bring different surveys onto
the same physical scale.Comment: 27 pages, 14 figures. Accepted by ApJ on 16 Dec 2016, implementing
suggestions from the referee reports. Associated code available at
https://github.com/annayqho/TheCanno
Pretensioned centrifugal spun high-strength concrete piles reinforced with steel strands: flexural performances
Resonant peak splitting for ballistic conductance in magnetic superlattices
We investigate theoretically the resonant splitting of ballistic conductance
peaks in magnetic superlattices. It is found that, for magnetic superlattices
with periodically arranged identical magnetic-barriers, there exists a
general -fold resonant peak splitting rule for ballistic conductance,
which is the analogy of the -fold resonant splitting for transmission in
-barrier electric superlattices (R. Tsu and L. Esaki, Appl. Phys. Lett. {\bf
22}, 562 (1973)).Comment: 9 pages, 3 figures, latex forma
Joint Beamforming for RIS-Assisted Integrated Sensing and Communication Systems
Integrated sensing and communications (ISAC) is an emerging critical
technique for the next generation of communication systems. However, due to
multiple performance metrics used for communication and sensing, the limited
degrees-of-freedom (DoF) in optimizing ISAC systems poses a challenge.
Reconfigurable intelligent surfaces (RIS) can introduce new DoF for beamforming
in ISAC systems, thereby enhancing the performance of communication and sensing
simultaneously. In this paper, we propose two optimization techniques for
beamforming in RIS-assisted ISAC systems. The first technique is an alternating
optimization (AO) algorithm based on the semidefinite relaxation (SDR) method
and a one-dimension iterative (ODI) algorithm, which can maximize the radar
mutual information (MI) while imposing constraints on the communication rates.
The second technique is an AO algorithm based on the Riemannian gradient (RG)
method, which can maximize the weighted ISAC performance metrics. Simulation
results verify the effectiveness of the proposed schemes. The AO-SDR-ODI method
is shown to achieve better communication and sensing performance, than the
AO-RG method, at a higher complexity. It is also shown that the
mean-squared-error (MSE) of the estimates of the sensing parameters decreases
as the radar MI increases.Comment: 30 pages, 8 figures. This paper has been submitted to IEEE
Transactions on Communication
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