2,315 research outputs found
Kondo Spin Screening Cloud in Two-dimensional Electron Gas with Spin-orbit Couplings
A spin-1/2 Anderson impurity in a semiconductor quantum well with Rashba and
Dresselhaus spin-orbit couplings is studied by using a variational wave
function method. The local magnetic moment is found to be quenched at low
temperatures. The spin-spin correlations of the impurity and the conduction
electron density show anisotropy in both spatial and spin spaces, which
interpolates the Kondo spin screenings of a conventional metal and of a surface
of three-dimensional topological insulators.Comment: accepted by the Journal of Physics: Condensed Matte
Exact solution of gyration radius of individual's trajectory for a simplified human mobility model
Gyration radius of individual's trajectory plays a key role in quantifying
human mobility patterns. Of particular interests, empirical analyses suggest
that the growth of gyration radius is slow versus time except the very early
stage and may eventually arrive to a steady value. However, up to now, the
underlying mechanism leading to such a possibly steady value has not been well
understood. In this Letter, we propose a simplified human mobility model to
simulate individual's daily travel with three sequential activities: commuting
to workplace, going to do leisure activities and returning home. With the
assumption that individual has constant travel speed and inferior limit of time
at home and work, we prove that the daily moving area of an individual is an
ellipse, and finally get an exact solution of the gyration radius. The
analytical solution well captures the empirical observation reported in [M. C.
Gonz`alez et al., Nature, 453 (2008) 779]. We also find that, in spite of the
heterogeneous displacement distribution in the population level, individuals in
our model have characteristic displacements, indicating a completely different
mechanism to the one proposed by Song et al. [Nat. Phys. 6 (2010) 818].Comment: 4 pages, 4 figure
A General Theorem Relating the Bulk Topological Number to Edge States in Two-dimensional Insulators
We prove a general theorem on the relation between the bulk topological
quantum number and the edge states in two dimensional insulators. It is shown
that whenever there is a topological order in bulk, characterized by a
non-vanishing Chern number, even if it is defined for a non-conserved quantity
such as spin in the case of the spin Hall effect, one can always infer the
existence of gapless edge states under certain twisted boundary conditions that
allow tunneling between edges. This relation is robust against disorder and
interactions, and it provides a unified topological classification of both the
quantum (charge) Hall effect and the quantum spin Hall effect. In addition, it
reconciles the apparent conflict between the stability of bulk topological
order and the instability of gapless edge states in systems with open
boundaries (as known happening in the spin Hall case). The consequences of time
reversal invariance for bulk topological order and edge state dynamics are
further studied in the present framework.Comment: A mistake corrected in reference
Hybrid quantum device based on NV centers in diamond nanomechanical resonators plus superconducting waveguide cavities
We propose and analyze a hybrid device by integrating a microscale diamond
beam with a single built-in nitrogen-vacancy (NV) center spin to a
superconducting coplanar waveguide (CPW) cavity. We find that under an ac
electric field the quantized motion of the diamond beam can strongly couple to
the single cavity photons via dielectric interaction. Together with the strong
spin-motion interaction via a large magnetic field gradient, it provides a
hybrid quantum device where the dia- mond resonator can strongly couple both to
the single microwave cavity photons and to the single NV center spin. This
enables coherent information transfer and effective coupling between the NV
spin and the CPW cavity via mechanically dark polaritons. This hybrid
spin-electromechanical de- vice, with tunable couplings by external fields,
offers a realistic platform for implementing quantum information with single NV
spins, diamond mechanical resonators, and single microwave photons.Comment: Accepted by Phys. Rev. Applie
Effects of dietary supplementation with peony pollen on growth, immune-related gene expression, and antioxidant status of Cyprinus carpio
Peony (Paeonia suffruticosa Andr.) is both ornamental flower and Chinese herbal medicine in China. This study was conducted to investigate the effects of dietary peony pollen on growth performance and immune status of common carp (Cyprinus carpio). Five different diets with 0% (control group), 1%, 2%, 3% and 4 % of peony pollen were designed to feed the fish for 6 weeks. The results indicated that the dietary peony pollen has beneficial effects on growth performance of common carp. In addition, evaluation of the liver antioxidant enzymes activity of total antioxidant capacity (T-AOC), glutathione peroxidase (GPX), superoxide dismutase (SOD) and catalase (CAT) in 3% peony pollen group, showed significant increase in carps fed peony pollen (P < 0.05), except the malondialdehyde (MDA) activity. The genes expression levels of tumor necrosis factor-α (TNF-α), transforming growth factor-β (TGF-β) and interleukin-1-β (IL1β) in the carps fed peony pollen were obviously decreased compared to the control group (P < 0.05). The expression levels of heat shock protein-70 (Hsp70) were up-regulated significantly in carps fed peony pollen (P < 0.05). Our observations suggest that peony pollen supplementation in the diets has the potential to improve the immune response by activating carp's cellular antioxidant activity and regulating the expression of immune -related genes, which may lead to increased carp tolerance to adverse conditions. Further research is needed on the use of peony pollen to improve disease resistance in fisheries
Renormalization of the Cabibbo-Kobayashi-Maskawa Quark Mixing Matrix
We have investigated the present renormalization prescriptions of
Cabibbo-Kobayashi-Maskawa (CKM) matrix. When considering the prescription which
is formulated with reference to the case of zero mixing we find it doesn't
satisfy the unitary condition of the bare CKM matrix. After added a delicate
patch this problem can be solved at one-loop level. In this paper We generalize
this prescription to all loop levels and keep the unitarity of the bare CKM
matrix, simultaneously make the amplitude of an arbitrary physical process
involving quark mixing convergent and gauge independent. We also find that in
order to keep the CKM counterterms gauge independent the unitarity of the bare
CKM matrix must be preserved.Comment: has been revised, 8 pages, 1 figur
Effect of the momentum dependence of nuclear symmetry potential on the transverse and elliptic flows
In the framework of the isospin-dependent Boltzmann-Uehling-Uhlenbeck
transport model, effect of the momentum dependence of nuclear symmetry
potential on nuclear transverse and elliptic flows in the neutron-rich reaction
Sn+Sn at a beam energy of 400 MeV/nucleon is studied. We find
that the momentum dependence of nuclear symmetry potential affects the rapidity
distribution of the free neutron to proton ratio, the neutron and the proton
transverse flows as a function of rapidity. The momentum dependence of nuclear
symmetry potential affects the neutron-proton differential transverse flow more
evidently than the difference of neutron and proton transverse flows as well as
the difference of proton and neutron elliptic flows. It is thus better to probe
the symmetry energy by using the difference of neutron and proton flows since
the momentum dependence of nuclear symmetry potential is still an open
question. And it is better to probe the momentum dependence of nuclear symmetry
potential by using the neutron-proton differential transverse flow and the
rapidity distribution of the free neutron to proton ratio.Comment: 6 pages, 6 figures, to be published by EPJ
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
Energy-momentum for Randall-Sundrum models
We investigate the conservation law of energy-momentum for Randall-Sundrum
models by the general displacement transform. The energy-momentum current has a
superpotential and are therefore identically conserved. It is shown that for
Randall-Sundrum solution, the momentum vanishes and most of the bulk energy is
localized near the Planck brane. The energy density is .Comment: 13 pages, no figures, v4: introduction and new conclusion added, v5:
11 pages, title changed and references added, accepted by Mod. Phys. Lett.
- …