Interplay between Superconductivity and Antiferromagnetism in a Multi-layered System

Based on a microscopic model, we study the interplay between superconductivity and antiferromagnetism in a multi-layered system, where two superconductors are separated by an antiferromagnetic region. Within a self-consistent mean-field theory, this system is solved numerically. We find that the antiferromagnetism in the middle layers profoundly affects the supercurrent flowing across the junction, while the phase difference across the junction influences the development of antiferromagnetism in the middle layers. This study may not only shed new light on the mechanism for high-$T_{c}$ superconductors, but also bring important insights to building Josephson-junction-based quantum devices, such as SQUID and superconducting qubit.Comment: 4+ pages, 5 figures, Accepted for publication in Phys. Rev.

Quantum-Classical Transition of Photon-Carnot Engine Induced by Quantum Decoherence

We study the physical implementation of the Photon Carnot engine (PCE) based on the cavity QED system [M. Scully et al, Science, \textbf{299}, 862 (2003)]. Here, we analyze two decoherence mechanisms for the more practical systems of PCE, the dissipation of photon field and the pure dephasing of the input atoms. As a result we find that (I) the PCE can work well to some extent even in the existence of the cavity loss (photon dissipation); and (II) the short-time atomic dephasing, which can destroy the PCE, is a fatal problem to be overcome.Comment: 6 pages, 3 figure

Smectic order, pinning, and phase transition in a smectic liquid crystal cell with a random substrate

We study smectic-liquid-crystal order in a cell with a heterogeneous substrate imposing surface random positional and orientational pinnings. Proposing a minimal random elastic model, we demonstrate that, for a thick cell, the smectic state without a rubbed substrate is always unstable at long scales and, for weak random pinning, is replaced by a smectic glass state. We compute the statistics of the associated substrate-driven distortions and the characteristic smectic domain size on the heterogeneous substrate and in the bulk. We find that for weak disorder, the system exhibits a three-dimensional temperature-controlled phase transition between a weakly and strongly pinned smectic glass states akin to the Cardy-Ostlund phase transition. We explore experimental implications of the predicted phenomenology and suggest that it provides a plausible explanation for the experimental observations on polarized light microscopy and x-ray scattering.Comment: 30 pages, 11 figures, Published in PRE, with minor typos correcte

Stability and distortions of liquid crystal order in a cell with a heterogeneous substrate

We study stability and distortions of liquid crystal nematic order in a cell with a random heterogeneous substrate. Modeling this system as a bulk xy model with quenched disorder confined to a surface, we find that nematic order is marginally unstable to such surface pinning. We compute the length scale beyond which nematic distortions become large and calculate orientational correlation functions using the functional renormalization-group and matching methods, finding universal logarithmic and double-logarithmic distortions in two and three dimensions, respectively. We extend these results to a finite-thickness liquid crystal cell with a second homogeneous substrate, detailing crossovers as a function of random pinning strength and cell thickness. We conclude with analysis of experimental signatures of these distortions in a conventional crossed-polarizer-analyzer light microscopy.Comment: 27 pages, 15 figures, Published in PRE, with minor typos correcte

Isolation of Unknown Genes from Human Bone Marrow by Differental Screening and Single-Pass cDNA Sequences Determination

A cDNA sequencing project was initiated to characterize gene expression in human bone marrow and develop strategies to isolate novel genes. Forty-eight random cDNAs from total human bone marrow were subjected to single-pass DNA sequence analysis to determine a limited complexity of mRNAs expressed in the bone marrow. Overall, 8 cDNAs (17%) showed no similarity to known sequences. Information from DNA sequence analysis was used to develop a differential prescreen to subtract unwanted cDNAs and to enrich for unknown cDNAs. Forty-eight cDNAs that were negative with a complex probe were subject to single-pass DNA sequence determination. Of these prescreened cDNAs, the number of unknown sequences increased to 23 (48%). Unknown cDNAs were also characterized by RNA expression analysis using 25 different human leukemic cell lines. Of 13 unknown cDNAs tested, 10 were expressed in all cell types tested and 3 revealed a hematopoietic lineage-restricted expression pattern. Interestingly, while a total of only 96 bone marrow cDNAs were sequenced, 31 of these cDNAs represent sequences from unknown genes and 12 showed significant similarities to sequences in the data bases. One cDNA revealed a significant similarity to a serine/threonine-protein kinase at the amino acid level (56% identity for 123 amino acids) and may represent a previously unknown kinase. Differential screening techniques coupled with single-pass cDNA sequence analysis may prove to be a powerful and simple technique to examine developmental gene expression

Quantum signature scheme with single photons

Quantum digital signature combines quantum theory with classical digital signature. The main goal of this field is to take advantage of quantum effects to provide unconditionally secure signature. We present a quantum signature scheme with message recovery without using entangle effect. The most important property of the proposed scheme is that it is not necessary for the scheme to use Greenberger-Horne-Zeilinger states. The present scheme utilizes single photons to achieve the aim of signature and verification. The security of the scheme relies on the quantum one-time pad and quantum key distribution. The efficiency analysis shows that the proposed scheme is an efficient scheme