3,886 research outputs found
Photon-induced vanishing of magnetoconductance in 2D electrons on liquid He
We report on a novel transport phenomenon realized by optical pumping in
surface state electrons on helium subjected to perpendicular magnetic fields.
The electron dynamics is governed by the photon-induced excitation and
scattering-mediated transitions between electric subbands. In a range of
magnetic fields, we observe vanishing longitudinal conductivity sigma_xx. Our
result suggests the existence of radiation-induced zero-resistance states in
the nondegenerate 2D electron system.Comment: 4 pages, 5 figure
Bistability and Hysteresis of Intersubband Absorption in Strongly Interacting Electrons on Liquid Helium
We study nonlinear inter-subband microwave absorption of electrons bound to
the liquid helium surface. Already for a comparatively low radiation intensity,
resonant absorption due to transitions between the two lowest subbands is
accompanied by electron overheating. The overheating results in a significant
population of higher subbands. The Coulomb interaction between electrons causes
a shift of the resonant frequency, which depends on the population of the
excited states and thus on the electron temperature . The latter is
determined experimentally from the electron photoconductivity. The
experimentally established relationship between the frequency shift and
is in reasonable agreement with the theory. The dependence of the shift on the
radiation intensity introduces nonlinearity into the rate of the inter-subband
absorption resulting in bistability and hysteresis of the resonant response.
The hysteresis of the response explains the behavior in the regime of frequency
modulation, which we observe for electrons on liquid He and which was
previously seen for electrons on liquid He
Microwave absorption saturation and decay heating of surface electrons on liquid helium
The microwave (MW) resonance absorption and decay heating of surface electrons (SEs) on liquid ⁴He
are theoretically studied for the vapor atom scattering regime. The decay heating is shown to be an essential
occurrence of a MW resonance experiment appearing even at low excitation rates. It strongly affects the occupancies
of surface levels and the broadening of resonance lines long before the absorption suturation condition
is reached. Contrary to the model of cold SEs usually used for description of the MW resonance, the
new theory leads to MW absorption saturation when only a very small fraction of electrons (less than 10%) is
left on the ground and the first excited levels
Angle-resolved photoemission spectroscopy with an tunable magnetic field
Angle-resolved photoemission spectroscopy (ARPES) is a powerful tool for
probing the momentum-resolved single-particle spectral function of materials.
Historically, magnetic fields have been carefully avoided as
they are detrimental to the control of photoelectron trajectory during the
photoelectron detection process. However, magnetic field is an important
experimental knob for both probing and tuning symmetry-breaking phases and
electronic topology in quantum materials. In this paper, we introduce an easily
implementable method for realizing an tunable magnetic field
at the sample position in an ARPES experiment and analyze magnetic field
induced artifacts in ARPES data. Specifically, we identified and quantified
three distinct extrinsic effects of a magnetic field: Fermi surface rotation,
momentum shrinking, and momentum broadening. We examined these effects in three
prototypical quantum materials, i.e., a topological insulator (BiSe),
an iron-based superconductor (LiFeAs), and a cuprate superconductor
(BiSrCaCuO), and demonstrate the feasibility of ARPES
measurements in the presence of a controllable magnetic field. Our studies lay
the foundation for the future development of the technique and interpretation
of ARPES measurements of field-tunable quantum phases.Comment: 23 pages, 6 figure
Distinct cell proliferation, myogenic differentiation, and gene expression in skeletal muscle myoblasts of layer and broiler chickens
Myoblasts play a central role during skeletal muscle formation and growth. Precise understanding of myoblast properties is thus indispensable for meat production. Herein, we report the cellular characteristics and gene expression profiles of primary-cultured myoblasts of layer and broiler chickens. Broiler myoblasts actively proliferated and promptly differentiated into myotubes compared to layer myoblasts, which corresponds well with the muscle phenotype of broilers. Transcriptomes of layer and broiler myoblasts during differentiation were quantified by RNA sequencing. Ontology analyses of the differentially expressed genes (DEGs) provided a series of extracellular proteins as putative markers for characterization of chicken myogenic cells. Another ontology analyses demonstrated that broiler myogenic cells are rich in cell cycle factors and muscle components. Independent of these semantic studies, principal component analysis (PCA) statistically defined two gene sets: one governing myogenic differentiation and the other segregating layers and broilers. Thirteen candidate genes were identified with a combined study of the DEGs and PCA that potentially contribute to proliferation or differentiation of chicken myoblasts. We experimentally proved that one of the candidates, enkephalin, an opioid peptide, suppresses myoblast growth. Our results present a new perspective that the opioids present in feeds may influence muscle development of domestic animals.Articlejournal articl
Excitonic condensation in a symmetric electron-hole bilayer
Using Diffusion Monte Carlo simulations we have investigated the ground state
of a symmetric electron-hole bilayer and determined its phase diagram at T=0.
We find clear evidence of an excitonic condensate, whose stability however is
affected by in-layer electronic correlation. This stabilizes the electron-hole
plasma at large values of the density or inter-layer distance, and the Wigner
crystal at low density and large distance. We have also estimated pair
correlation functions and low order density matrices, to give a microscopic
characterization of correlations, as well as to try and estimate the condensate
fraction.Comment: 4 pages, 3 figures, 2 table
Interaction potential between dynamic dipoles: polarized excitons in strong magnetic fields
The interaction potential of a two-dimensional system of excitons with
spatially separated electron-hole layers is considered in the strong magnetic
field limit. The excitons are assumed to have free dynamics in the -
plane, while being constrained or `polarized' in the direction. The model
simulates semiconductor double layer systems under strong magnetic field normal
to the layers. The {\em residual} interaction between excitons exhibits
interesting features, arising from the coupling of the center-of-mass and
internal degrees of freedom of the exciton in the magnetic field. This coupling
induces a dynamical dipole moment proportional to the center-of-mass magnetic
moment of the exciton. We show the explicit dependence of the inter-exciton
potential matrix elements, and discuss the underlying physics. The unusual
features of the interaction potential would be reflected in the collective
response and non-equilibrium properties of such system.Comment: REVTEX - 11 pages - 1 fi
Development of pericardial fat count images using a combination of three different deep-learning models
Rationale and Objectives: Pericardial fat (PF), the thoracic visceral fat
surrounding the heart, promotes the development of coronary artery disease by
inducing inflammation of the coronary arteries. For evaluating PF, this study
aimed to generate pericardial fat count images (PFCIs) from chest radiographs
(CXRs) using a dedicated deep-learning model.
Materials and Methods: The data of 269 consecutive patients who underwent
coronary computed tomography (CT) were reviewed. Patients with metal implants,
pleural effusion, history of thoracic surgery, or that of malignancy were
excluded. Thus, the data of 191 patients were used. PFCIs were generated from
the projection of three-dimensional CT images, where fat accumulation was
represented by a high pixel value. Three different deep-learning models,
including CycleGAN, were combined in the proposed method to generate PFCIs from
CXRs. A single CycleGAN-based model was used to generate PFCIs from CXRs for
comparison with the proposed method. To evaluate the image quality of the
generated PFCIs, structural similarity index measure (SSIM), mean squared error
(MSE), and mean absolute error (MAE) of (i) the PFCI generated using the
proposed method and (ii) the PFCI generated using the single model were
compared.
Results: The mean SSIM, MSE, and MAE were as follows: 0.856, 0.0128, and
0.0357, respectively, for the proposed model; and 0.762, 0.0198, and 0.0504,
respectively, for the single CycleGAN-based model.
Conclusion: PFCIs generated from CXRs with the proposed model showed better
performance than those with the single model. PFCI evaluation without CT may be
possible with the proposed method
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