Electromagnetically induced transparency in multi-level cascade scheme of cold rubidium atoms

We report an experimental investigation of electromagnetically induced transparency in a multi-level cascade system of cold atoms. The absorption spectral profiles of the probe light in the multi-level cascade system were observed in cold Rb-85 atoms confined in a magneto-optical trap, and the dependence of the spectral profile on the intensity of the coupling laser was investigated. The experimental measurements agree with the theoretical calculations based on the density matrix equations of the rubidium cascade system.Comment: 9 pages, 5 figure

The quantum cryptographic switch

We illustrate using a quantum system the principle of a cryptographic switch, in which a third party (Charlie) can control to a continuously varying degree the amount of information the receiver (Bob) receives, after the sender (Alice) has sent her information. Suppose Charlie transmits a Bell state to Alice and Bob. Alice uses dense coding to transmit two bits to Bob. Only if the 2-bit information corresponding to choice of Bell state is made available by Charlie to Bob can the latter recover Alice's information. By varying the information he gives, Charlie can continuously vary the information recovered by Bob. The performance of the protocol subjected to the squeezed generalized amplitude damping channel is considered. We also present a number of practical situations where a cryptographic switch would be of use.Comment: 7 pages, 4 Figure

Indications of coherence-incoherence crossover in layered transport

For many layered metals the temperature dependence of the interlayer resistance has a different behavior than the intralayer resistance. In order to better understand interlayer transport we consider a concrete model which exhibits this behavior. A small polaron model is used to illustrate how the interlayer transport is related to the coherence of quasi-particles within the layers. Explicit results are given for the electron spectral function, interlayer optical conductivity and the interlayer magnetoresistance. All these quantities have two contributions: one coherent (dominant at low temperatures) and one incoherent (dominant at high temperatures).Comment: 6 pages, 4 figures, REVTEX

Patients with refractory cytomegalovirus (CMV) infection following allogeneic haematopoietic stem cell transplantation are at high risk for CMV disease and non-relapse mortality

AbstractPre-emptive therapy is an effective approach for cytomegalovirus (CMV) control; however, refractory CMV still occurs in a considerable group of recipients after allogeneic haematopoietic stem cell transplantation (allo-HSCT). Until now, hardly any data have been available about the clinical characteristics and risk factors of refractory CMV, or its potential harmful impact on the clinical outcome following allo-HSCT. We studied transplant factors affecting refractory CMV in the 100 days after allo-HSCT, and the impact of refractory CMV on the risk of CMV disease and non-relapse mortality (NRM). We retrospectively studied 488 consecutive patients with CMV infection after allo-HSCT. Patients with refractory CMV in the 100 days after allo-HSCT had a higher incidence of CMV disease and NRM than those without refractory CMV (11.9% vs. 0.8% and 17.1% vs. 8.3%, respectively). Multivariate analysis showed that refractory CMV infection in the 100 days after allo-HSCT was an independent risk factor for CMV disease (hazard ratio (HR) 10.539, 95% CI 2.467–45.015, p 0.001), and that refractory CMV infection within 60–100 days after allo-HSCT was an independent risk factor for NRM (HR 8.435, 95% CI 1.511–47.099, p 0.015). Clinical factors impacting on the risk of refractory CMV infection included receiving transplants from human leukocyte antigen-mismatched family donors (HR 2.012, 95% CI 1.603–2.546, p <0.001) and acute graft-versus-host disease (HR 1.905, 95% CI 1.352–2.686, p <0.001). We conclude that patients with refractory CMV infection during the early stage after allo-HSCT are at high risk for both CMV disease and NRM

Extended calculations of energy levels, radiative properties, AJ , BJ hyperfine interaction constants, and Landé gJ-factors for nitrogen-like Ge XXVI

Employing two state-of-the-art methods, multiconfiguration Dirac–Hartree–Fock and second-order many-body perturbation theory, highly accurate calculations are performed for the lowest 272 fine-structure levels arising from the 2s22p3, 2s2p4, 2p5, 2s22p23l (l = s, p, d), 2s2p33l (l = s, p, d), and 2p43l (l = s, p, d) configurations in nitrogen-like Ge XXVI. Complete and consistent atomic data, including excitation energies, lifetimes, wavelengths, hyperfine structures, Landé gJ-factors, and E1, E2, M1, M2 line strengths, oscillator strengths, and transition rates among these 272 levels are provided. Comparisons are made between the present two data sets, as well as with other available experimental and theoretical values. The present data are accurate enough for identification and deblending of emission lines involving the n=3 levels, and are also useful for modeling and diagnosing fusion plasmas

Long-distant contribution and χc1\chi_{c1} radiative decays to light vector meson

The discrepancy between the PQCD calculation and the CLEO data for $\chi_{c1}\to \gamma V$ ($V=\rho^0,\,\omega,\,\phi$) stimulates our interest in exploring extra mechanism of $\chi_{c1}$ decay. In this work, we apply an important non-perturbative QCD effect, i.e., hadronic loop mechanism, to study $\chi_{c1}\to \gamma V$ radiative decay. Our numerical result shows that the theoretical results including the hadronic loop contribution and the PQCD calculation of $\chi_{c1}\to \gamma V$ are consistent with the corresponding CLEO data of $\chi_{c1}\to \gamma V$. We expect further experimental measurement of $\chi_{c1}\to \gamma V$ at BES-III, which will be helpful to test the hadronic loop effect on $\chi_{c1}$ decay.Comment: 7 pages, 2 figures. Accepted for publication in Eur. Phys. J.

The Periodic Instability of Diameter of ZnO Nanowires via a Self-oscillatory Mechanism

ZnO nanowires with a periodic instability of diameter were successfully prepared by a thermal physical vapor deposition method. The morphology of ZnO nanowires was investigated by SEM. SEM shows ZnO possess periodic bead-like structure. The instability only appears when the diameter of ZnO nanowires is small. The kinetics and mechanism of Instability was discussed at length. The appearance of the instability is due to negative feed-back mechanism under certain experimental conditions (crystallization temperature, vapor supersaturation, etc)

Nonleptonic Weak Decays of Bottom Baryons

Cabibbo-allowed two-body hadronic weak decays of bottom baryons are analyzed. Contrary to the charmed baryon sector, many channels of bottom baryon decays proceed only through the external or internal W-emission diagrams. Moreover, W-exchange is likely to be suppressed in the bottom baryon sector. Consequently, the factorization approach suffices to describe most of the Cabibbo-allowed bottom baryon decays. We use the nonrelativistic quark model to evaluate heavy-to-heavy and heavy-to-light baryon form factors at zero recoil. When applied to the heavy quark limit, the quark model results do satisfy all the constraints imposed by heavy quark symmetry. The decay rates and up-down asymmetries for bottom baryons decaying into $(1/2)^++P(V)$ and $(3/2)^++P(V)$ are calculated. It is found that the up-down asymmetry is negative except for $\Omega_b \to (1/2)^++P(V)$ decay and for decay modes with $\psi'$ in the final state. The prediction $B(\Lambda_b \to J/\psi\Lambda)=1.6 \times 10^{-4}$ for $|V_{cb}|=0.038$ is consistent with the recent CDF measurement. We also present estimates for $\Omega_c \to (3/2)^++P(V)$ decays and compare with various model calculations.Comment: 24 pages, to appear in Phys. Rev. Uncertainties with form factor q^2 dependence are discusse

Extended calculations with spectroscopic accuracy : energy levels and radiative rates for O-like ions between Ar XI and Cr XVII

Using the multiconfiguration Dirac–Hartree–Fock and the relativistic configuration interaction methods, a consistent set of transition energies and radiative transition data for the main states of the 2s22p4, 2s2p5, 2p6, 2s22p33s, 2s22p33p, 2s22p33d, 2s2p43s, 2s2p43p, and 2s2p43d configurations in O-like Ions between Ar XI (Z=18) and Cr XVII (Z=24) is provided. Our data set is compared with the NIST compiled values and previous calculations. The data are accurate enough for identification and deblending of new emission lines from hot astrophysical and laboratory plasmas. The amount of data of high accuracy is significantly increased for the n=3 states of several O-like ions, where experimental data are very scarce

Mass measurements of neutron-deficient Y, Zr, and Nb isotopes and their impact on rp and νp nucleosynthesis processes

© 2018 The Authors. Published by Elsevier B.V. This manuscript is made available under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International licence (CC BY-NC-ND 4.0). For further details please see: https://creativecommons.org/licenses/by-nc-nd/4.0/Using isochronous mass spectrometry at the experimental storage ring CSRe in Lanzhou, the masses of 82Zr and 84Nb were measured for the first time with an uncertainty of ∼10 keV, and the masses of 79Y, 81Zr, and 83Nb were re-determined with a higher precision. The latter are significantly less bound than their literature values. Our new and accurate masses remove the irregularities of the mass surface in this region of the nuclear chart. Our results do not support the predicted island of pronounced low α separation energies for neutron-deficient Mo and Tc isotopes, making the formation of Zr–Nb cycle in the rp-process unlikely. The new proton separation energy of 83Nb was determined to be 490(400) keV smaller than that in the Atomic Mass Evaluation 2012. This partly removes the overproduction of the p-nucleus 84Sr relative to the neutron-deficient molybdenum isotopes in the previous νp-process simulations.Peer reviewe