8,883 research outputs found
Fermion Pairing across a Dipolar Interaction Induced Resonance
It is known from the solution of the two-body problem that an anisotropic
dipolar interaction can give rise to s-wave scattering resonances, which are
named as dipolar interaction induced resonaces (DIIR). In this letter, we study
zero-temperature many-body physics of a two-component Fermi gas across a DIIR.
In the low-density regime, it is very striking that the resulting pairing order
parameter is a nearly isotropic singlet pairing and the physics can be well
described by an s-wave resonant interaction potential with finite range
corrections, despite of the anisotropic nature of dipolar interaction. The
pairing energy is as strong as a unitary Fermi gas nearby a magnetic Feshbach
resonance. In the high density regime, the anisotropic effect plays an
important role. We find phase transitions from singlet pairing to a state with
mixed singlet and triplet pairing, and then from mixed pairing to pure triplet
pairing. The state with mixed pairing spontaneously breaks the time-reversal
symmetry.Comment: 4.5 pages, 4 figures, figures updated, minor changes in tex
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Investigation of the Viscoelastic Effect on Optical- Fiber Sensing and Its Solution for 3D-Printed Sensor Packages
Viscoelasticity is an effect seen in a wide range of materials and it affects the reliability of static measurements made using Fiber Bragg Grating-based sensors, because either the target structure, the adhesive used, or the fiber itself could be viscoelastic. The effect of viscoelasticity on FBG-based sensing has been comprehensively researched through theoretical analysis and simulation using a finite-element approach and a further data processing method to reconstruct the graphical data has been developed. An integrated sensor package comprising of an FBG-based sensor in a polymer host and manufactured by using three-dimensional printing was investigated and examined through tensile testing to validate the approach. The application of the 3D-printed FBG-based sensor package, coupled to the data process method has been explored to monitor the height of a railway pantograph, a critical measurement requirement to monitor elongation, employing a method that can be used in the presence of electromagnetic interference. The results show that the effect of viscoelasticity can be effectively eliminated, and the graphical system response allows results that are sufficiently precise for field use to be generated
Precision microwave dielectric and magnetic susceptibility measurements of correlated electronic materials using superconducting cavities
We analyze microwave cavity perturbation methods, and show that the technique
is an excellent, precision method to study the dynamic magnetic and dielectric
response in the frequency range. Using superconducting cavities, we
obtain exceptionally high precision and sensitivity for measurements of
relative changes. A dynamic electromagnetic susceptibility
is introduced, which
is obtained from the measured parameters: the shift of cavity resonant
frequency and quality factor . We focus on the case of a
spherical sample placed at the center of a cylindrical cavity resonant in the
mode. Depending on the sample characteristics, the magnetic
permeability , the dielectric permittivity and
the complex conductivity can be extracted from
. A full spherical wave analysis of the cavity perturbation
is given. This analysis has led to the observation of new phenomena in novel
low dimensional materials.Comment: 16 pages, 5 figure
Double-Layer Bose-Einstein Condensates with Large Number of Vortices
In this paper we systematically study the double layer vortex lattice model,
which is proposed to illustrate the interplay between the physics of a fast
rotating Bose-Einstein condensate and the macroscopic quantum tunnelling. The
phase diagram of the system is obtained. We find that under certain conditions
the system will exhibit one novel phase transition, which is consequence of
competition between inter-layer coherent hopping and inter-layer
density-density interaction. In one phase the vortices in one layer coincide
with those in the other layer. And in another phase two sets of vortex lattices
are staggered, and as a result the quantum tunnelling between two layers is
suppressed. To obtain the phase diagram we use two kinds of mean field theories
which are quantum Hall mean field and Thomas-Fermi mean field. Two different
criteria for the transition taking place are obtained respectively, which
reveals some fundamental differences between these two mean field states. The
sliding mode excitation is also discussed.Comment: 12 pages, 8 figure
An Integrated Computational and Experimental Approach to Identifying Inhibitors for SARS-CoV-2 3CL Protease
The newly evolved SARS-CoV-2 has caused the COVID-19 pandemic, and the SARS-CoV-2 main protease 3CLpro is essential for the rapid replication of the virus. Inhibiting this protease may open an alternative avenue toward therapeutic intervention. In this work, a computational docking approach was developed to identify potential small-molecule inhibitors for SARS-CoV-2 3CLpro. Totally 288 potential hits were identified from a half-million bioactive chemicals via a protein-ligand docking protocol. To further evaluate the docking results, a quantitative structure activity relationship (QSAR) model of 3CLpro inhibitors was developed based on existing small molecule inhibitors of the 3CLproSARS– CoV– 1 and their corresponding IC50 data. The QSAR model assesses the physicochemical properties of identified compounds and estimates their inhibitory effects on 3CLproSARS– CoV– 2. Seventy-one potential inhibitors of 3CLpro were selected through these computational approaches and further evaluated via an enzyme activity assay. The results show that two chemicals, i.e., 5-((1-([1,1′-biphenyl]-4-yl)-2,5-dimethyl-1H-pyrrol-3-yl)methylene)pyrimidine-2,4,6(1H,3H,5H)-trione and N-(4-((3-(4-chlorophenylsulfonamido)quinoxalin-2-yl)amino)phenyl)acetamide, effectively inhibited 3CLpro SARS-CoV-2 with IC50’s of 19 ± 3 μM and 38 ± 3 μM, respectively. The compounds contain two basic structures, pyrimidinetrione and quinoxaline, which were newly found in 3CLpro inhibitor structures and are of high interest for lead optimization. The findings from this work, such as 3CLpro inhibitor candidates and the QSAR model, will be helpful to accelerate the discovery of inhibitors for related coronaviruses that may carry proteases with similar structures to SARS-CoV-2 3CLpro
Abdominal obesity and the prevalence of diabetes and intermediate hyperglycaemia in Chinese adults
Objective: To assess the association of indicators of general and abdominal obesity with the prevalence of type 2 diabetes (T2DM) and intermediate hyperglycaemia (IHG) in the Chinese population. Methods: We used data of 50 905 adults aged 18¿79 years in the 2002 China National Nutrition and Health Survey. Recommended Chinese cut-off values were used for BMI (24 kg/m2) and waist circumference (WC; 85 cm in men, 80 cm in women). Optimal cut-offs for waist:height ratio (WHtR) were determined from analyses of receiver-operating characteristic (ROC) curves. Results: The prevalence of T2DM and IHG was 2?6% and 1?9% respectively. ROC curve analyses indicated 0?5 as the optimal cut-off value for WHtR in both sexes. High BMI, WC and WHtR were all associated with the prevalence of glucose tolerance abnormalities, with the highest prevalence ratio (PR) for high WHtR (men: PR52?85, 95% CI 2?54, 3?21; women: PR53?10, 95% CI 2?74, 3?51). When combining BMI and WHtR, in men either a high BMI or a high WHtR alone was associated with increased risk. Among women, a high BMI without a concomitant high WHtR was not associated with increased glucose tolerance abnormalities risk, whereas a high WHtR was associated with risk irrespective of BMI. Conclusions: Among the Chinese adult population measures of central obesity are better predictors of glucose tolerance abnormalities prevalence than BMI. AWHtR cutoff point of 0?5 for both men and women can be considered as optimum for predicting (pre-) diabetes and may be a useful tool for screening and health education
Synergistic Effect of Chlorogenic Acid and Caffeic Acid with Fosfomycin on Growth Inhibition of a Resistant Listeria monocytogenes Strain
Listeria monocytogenes, a human foodborne pathogen that causes listeriosis with high-rate mortality, has been reported to be resistant to commonly used antibiotics. New antibiotics or cocktails of existing antibiotics with synergistic compounds are in high demand for treating this multi-drug-resistant pathogen. Fosfomycin is one of the novel and promising therapeutic antibiotics for the treatment of listeriosis. However, some L. monocytogenes strains with the FosX gene were recently reported to survive from the fosfomycin treatment. This work aims to identify FosX inhibitors that can revive fosfomycin in treating resistant L. monocytogenes. Since structures and activities of the FosX protein in L. monocytogenes have been well studied, we used an integrated computational and experimental approach to identify FosX inhibitors that show synergistic effect with fosfomycin in treating resistant L. monocytogenes. Specifically, automated ligand docking was implemented to perform virtual screening of the Indofine natural-product database and FDA-approved drugs to identify potential inhibitors. An in vitro bacterial growth inhibition test was then utilized to verify the effectiveness of identified compounds combined with fosfomycin in inhibiting the resistant L. monocytogenes strains. Two phenolic acids, i.e., caffeic acid and chlorogenic acid, were predicted as high-affinity FosX inhibitors from the ligand-docking platform. Experiments with these compounds indicated that the cocktail of either caffeic acid (1.5 mg/mL) or chlorogenic acid (3 mg/mL) with fosfomycin (50 mg/L) was able to significantly inhibit the growth of the pathogen. The finding of this work implies that the combination of fosfomycin with either caffeic acid or chlorogenic acid is of potential to be used in the clinical treatment of Listeria infections
Spin-filtering and charge- and spin-switching effects in a quantum wire with periodically attached stubs
Spin-dependent electron transport in a periodically stubbed quantum wire in
the presence of Rashba spin-orbit interaction (SOI) is studied via the
nonequilibrium Green's function method combined with the Landauer-Buttiker
formalism. The coexistence of spin filtering, charge and spin switching are
found in the considered system. The mechanism of these transport properties is
revealed by analyzing the total charge density and spin-polarized density
distributions in the stubbed quantum wire. Furthermore, periodic spin-density
islands with high polarization are also found inside the stubs, owing to the
interaction between the charge density islands and the Rashba SOI-induced
effective magnetic field. The proposed nanostructure may be utilized to devise
an all-electrical multifunctional spintronic device.Comment: 4 pages, 4 figure
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