1,003 research outputs found
Flux quench in a system of interacting spinless fermions in one dimension
We study a quantum quench in a one-dimensional spinless fermion model
(equivalent to the XXZ spin chain), where a magnetic flux is suddenly switched
off. This quench is equivalent to imposing a pulse of electric field and
therefore generates an initial particle current. This current is not a
conserved quantity in presence of a lattice and interactions and we investigate
numerically its time-evolution after the quench, using the infinite
time-evolving block decimation method. For repulsive interactions or large
initial flux, we find oscillations that are governed by excitations deep inside
the Fermi sea. At long times we observe that the current remains non-vanishing
in the gapless cases, whereas it decays to zero in the gapped cases. Although
the linear response theory (valid for a weak flux) predicts the same long-time
limit of the current for repulsive and attractive interactions (relation with
the zero-temperature Drude weight), larger nonlinearities are observed in the
case of repulsive interactions compared with that of the attractive case.Comment: 10 pages, 10 figures; v2: Added references. Figures are refined and
animations are added. Corrected typos. Published versio
Irreducible Hamiltonian BRST-anti-BRST symmetry for reducible systems
An irreducible Hamiltonian BRST-anti-BRST treatment of reducible first-class
systems based on homological arguments is proposed. The general formalism is
exemplified on the Freedman-Townsend model.Comment: LaTeX 2.09, 35 page
Quantitative MRFM characterization of the autonomous and forced dynamics in a spin transfer nano-oscillator
Using a magnetic resonance force microscope (MRFM), the power emitted by a
spin transfer nano-oscillator consisting of a normally magnetized PyCuPy
circular nanopillar is measured both in the autonomous and forced regimes. From
the power behavior in the subcritical region of the autonomous dynamics, one
obtains a quantitative measurement of the threshold current and of the noise
level. Their field dependence directly yields both the spin torque efficiency
acting on the thin layer and the nature of the mode which first
auto-oscillates: the lowest energy, spatially most uniform spin-wave mode. From
the MRFM behavior in the forced dynamics, it is then demonstrated that in order
to phase-lock this auto-oscillating mode, the external source must have the
same spatial symmetry as the mode profile, i.e., a uniform microwave field must
be used rather than a microwave current flowing through the nanopillar
Machine Learning of Molecular Electronic Properties in Chemical Compound Space
The combination of modern scientific computing with electronic structure
theory can lead to an unprecedented amount of data amenable to intelligent data
analysis for the identification of meaningful, novel, and predictive
structure-property relationships. Such relationships enable high-throughput
screening for relevant properties in an exponentially growing pool of virtual
compounds that are synthetically accessible. Here, we present a machine
learning (ML) model, trained on a data base of \textit{ab initio} calculation
results for thousands of organic molecules, that simultaneously predicts
multiple electronic ground- and excited-state properties. The properties
include atomization energy, polarizability, frontier orbital eigenvalues,
ionization potential, electron affinity, and excitation energies. The ML model
is based on a deep multi-task artificial neural network, exploiting underlying
correlations between various molecular properties. The input is identical to
\emph{ab initio} methods, \emph{i.e.} nuclear charges and Cartesian coordinates
of all atoms. For small organic molecules the accuracy of such a "Quantum
Machine" is similar, and sometimes superior, to modern quantum-chemical
methods---at negligible computational cost
A Frequency-Controlled Magnetic Vortex Memory
Using the ultra low damping NiMnSb half-Heusler alloy patterned into
vortex-state magnetic nano-dots, we demonstrate a new concept of non-volatile
memory controlled by the frequency. A perpendicular bias magnetic field is used
to split the frequency of the vortex core gyrotropic rotation into two distinct
frequencies, depending on the sign of the vortex core polarity inside
the dot. A magnetic resonance force microscope and microwave pulses applied at
one of these two resonant frequencies allow for local and deterministic
addressing of binary information (core polarity)
A consistent methodology for the derivation and calibration of a macroscopic turbulence model for flows in porous media
This work aims to model turbulent flows in media laden with solid structures according to porous media approach. A complete set of macroscopic transport equations is derived by spatially averaging the Reynolds averaged governing equations. A two-scale analysis highlights energy transfers between macroscopic and sub-filter kinetic energies (dispersive and turbulent kinetic energies). Additional terms coming from the averaging procedure and representing solids/fluid interactions and turbulent contributions are modeled. Connections between turbulence modeling and dispersion modeling are presented. Other closure expressions are determined using physical considerations and spatial averaging of microscopic computations. A special care is given to the calibration methodology for the phenomenological coefficients. Results of the present model are successfully compared to volume-averaged reference results coming from fine scale computations and show significant improvements with respect to previous macroscopic models
GraphKKE: graph Kernel Koopman embedding for human microbiome analysis
More and more diseases have been found to be strongly correlated with disturbances in the microbiome constitution, e.g., obesity, diabetes, or some cancer types. Thanks to modern high-throughput omics technologies, it becomes possible to directly analyze human microbiome and its influence on the health status. Microbial communities are monitored over long periods of time and the associations between their members are explored. These relationships can be described by a time-evolving graph. In order to understand responses of the microbial community members to a distinct range of perturbations such as antibiotics exposure or diseases and general dynamical properties, the time-evolving graph of the human microbial communities has to be analyzed. This becomes especially challenging due to dozens of complex interactions among microbes and metastable dynamics. The key to solving this problem is the representation of the time-evolving graphs as fixed-length feature vectors preserving the original dynamics. We propose a method for learning the embedding of the time-evolving graph that is based on the spectral analysis of transfer operators and graph kernels. We demonstrate that our method can capture temporary changes in the time-evolving graph on both synthetic data and real-world data. Our experiments demonstrate the efficacy of the method. Furthermore, we show that our method can be applied to human microbiome data to study dynamic processes
Sexual and relationship intimacy among women with provoked vestibulodynia and their partners : associations with sexual satisfaction, sexual function, and pain self-efficacy
Introduction
Provoked vestibulodynia (PVD) is the most frequent subtype of vulvodynia. Women report negative consequences of PVD on their sexual and romantic relationships. Researchers have recently highlighted the importance of examining interpersonal factors such as intimacy, and of including both women and their partners in study designs.
Aim
The aim of this study was to investigate sexual and relationship intimacy as defined by the Interpersonal Process Model of Intimacy and their associations with sexual satisfaction, sexual function, pain self-efficacy, and pain intensity among women with PVD and their partners.
Methods
Ninety-one heterosexual women (M age = 27.38, SD = 6.04) diagnosed with PVD and their partners (M age = 29.37, SD = 7.79) completed measures of sexual and relationship intimacy, sexual satisfaction, sexual function, pain self-efficacy, and pain intensity.
Main Outcome Measures
Dependent measures were the (i) Global Measure of Sexual Satisfaction Scale; (ii) Female Sexual Function Index; (iii) Painful Intercourse Self-Efficacy Scale; and (iv) visual analog scale of pain intensity during intercourse.
Results
After controlling for women's age, women's greater sexual intimacy (β = 0.49, P < 0.001) was associated with women's greater sexual satisfaction and higher pain self-efficacy (β = 0.39, P = 0.001), beyond the effects of partners’ sexual intimacy. Also, women's greater sexual intimacy (β = 0.24, P = 0.05) and women's greater relationship intimacy (β = 0.54, P = 0.003) were associated with greater women's sexual function, beyond the effects of partners’ sexual and relationship intimacy.
Conclusions
Women's self-reported sexual and relationship intimacy in the couple relationship may promote higher sexual satisfaction, sexual function, and pain self-efficacy, as well as possibly foster greater sexual well-being among women with PVD. The authors discuss implications for the inclusion of emotional and interpersonal aspects of the couple's dynamic in clinical interventions and future research in PVD
Elastic turbulence in shear banding wormlike micelles
We study the dynamics of the Taylor-Couette flow of shear banding wormlike
micelles. We focus on the high shear rate branch of the flow curve and show
that for sufficiently high Weissenberg numbers, this branch becomes unstable.
This instability is strongly sub-critical and is associated with a shear stress
jump. We find that this increase of the flow resistance is related to the
nucleation of turbulence. The flow pattern shows similarities with the elastic
turbulence, so far only observed for polymer solutions. The unstable character
of this branch led us to propose a scenario that could account for the recent
observations of Taylor-like vortices during the shear banding flow of wormlike
micelles
Dysfunctional endometres in Libreville: 20 years retrospective study
Background: The objectives of this work were to inventory the different morphological entities, to alert the medical class to the need for multidisciplinary care; to sensitize the health authorities on this pathology having a considerable influence on the fertility of the woman and a possible evolution towards cancerous disease.Methods: A retrospective study was carried out over 20 years from January 1983 to December 2002 at the laboratory of anatomy pathology of the faculty of health sciences in Libreville. The revealing clinical signs were the couple's bleeding and infertility. Curettage, endometrial biopsy, and subtotal or total hysterectomy were fixed with 10% buffered formalin or Bouin's fluid. After staining, histological study was carried out by the pathologist.Results: The histological images of the endometrial polyps were the most representative (73 cases or 17.68%), followed by prolonged proliferative endometers (70 cases, or 16.95%), glandulo-cystic hyperplasia (66 cases, or 15.98%) and persistent proliferative endometers (58 cases, or 14.04%). More than half of the numbers concerned women under 35 (225/413 cases); in those over 45 years of age, the predominantly endometrial carcinoma was found. The most affected province was Woleu-Ntem (24%), followed by Haut-Ogooué (18%).Conclusions: The different dysfunctional endometers are also described in the different regions of the continent. The management of these aims to be multidisciplinary and urgently requires a frank collaboration between clinician and morphologist, especially for country where a birth policy is clearly expressed by governing bodies.
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