NMR Characterization of Sulphur Substitution Effects in the K(x)Fe(2-y)Se(2-z)S(z) high Tc Superconductor

We present an NMR study of the effect of S substitution in the high Tc superconductor K(x)Fe(2-y)Se(2-z)S(z) in a temperature range up to 250 K. We present NMR Knight shift and nuclear spin-lattice relaxation rate 1/T1 data, and compare our results to that of the non-substituted system K(x)Fe(2-y)Se(2).Comment: Typos fixed, figure replace

Experimental study on Gaussian-modulated coherent states quantum key distribution over standard telecom fiber

In this paper, we present a fully fiber-based one-way Quantum Key Distribution (QKD) system implementing the Gaussian-Modulated Coherent States (GMCS) protocol. The system employs a double Mach-Zehnder Interferometer (MZI) configuration in which the weak quantum signal and the strong Local Oscillator (LO) go through the same fiber between Alice and Bob, and are separated into two paths inside Bob's terminal. To suppress the LO leakage into the signal path, which is an important contribution to the excess noise, we implemented a novel scheme combining polarization and frequency multiplexing, achieving an extinction ratio of 70dB. To further minimize the system excess noise due to phase drift of the double MZI, we propose that, instead of employing phase feedback control, one simply let Alice remap her data by performing a rotation operation. We further present noise analysis both theoretically and experimentally. Our calculation shows that the combined polarization and frequency multiplexing scheme can achieve better stability in practice than the time-multiplexing scheme, because it allows one to use matched fiber lengths for the signal and the LO paths on both sides of the double MZI, greatly reducing the phase instability caused by unmatched fiber lengths. Our experimental noise analysis quantifies the three main contributions to the excess noise, which will be instructive to future studies of the GMCS QKD systems. Finally, we demonstrate, under the "realistic model" in which Eve cannot control the system within Bob's terminal, a secure key rate of 0.3bit/pulse over a 5km fiber link. This key rate is about two orders of magnitude higher than that of a practical BB84 QKD system.Comment: 21 pages, 9 figure

Glassy Dynamics in a Frustrated Spin System: Role of Defects

In an effort to understand the glass transition, the kinetics of a spin model with frustration but no quenched randomness has been analyzed. The phenomenology of the spin model is remarkably similiar to that of structural glasses. Analysis of the model suggests that defects play a major role in dictating the dynamics as the glass transition is approached.Comment: 9 pages, 5 figures, accepted in J. Phys.: Condensed Matter, proceedings of the Trieste workshop on "Unifying Concepts in Glass Physics

77Se NMR Investigation of the K(x)Fe(2-y)Se(2) High Tc Superconductor (Tc=33K)

We report a comprehensive 77Se NMR study of the structural, magnetic, and superconducting properties of a single crystalline sample of the newly discovered FeSe-based high temperature superconductor K(x)Fe(2-y)Se(2) (Tc=33K) in a broad temperature range up to 290 K. We will compare our results with those reported for FeSe (Tc=9K) and FeAs-based high Tc systems.Comment: Final versio

The Catalytic and Non-catalytic Functions of the Brahma Chromatin-Remodeling Protein Collaborate to Fine-Tune Circadian Transcription in Drosophila.

Daily rhythms in gene expression play a critical role in the progression of circadian clocks, and are under regulation by transcription factor binding, histone modifications, RNA polymerase II (RNAPII) recruitment and elongation, and post-transcriptional mechanisms. Although previous studies have shown that clock-controlled genes exhibit rhythmic chromatin modifications, less is known about the functions performed by chromatin remodelers in animal clockwork. Here we have identified the Brahma (Brm) complex as a regulator of the Drosophila clock. In Drosophila, CLOCK (CLK) is the master transcriptional activator driving cyclical gene expression by participating in an auto-inhibitory feedback loop that involves stimulating the expression of the main negative regulators, period (per) and timeless (tim). BRM functions catalytically to increase nucleosome density at the promoters of per and tim, creating an overall restrictive chromatin landscape to limit transcriptional output during the active phase of cycling gene expression. In addition, the non-catalytic function of BRM regulates the level and binding of CLK to target promoters and maintains transient RNAPII stalling at the per promoter, likely by recruiting repressive and pausing factors. By disentangling its catalytic versus non-catalytic functions at the promoters of CLK target genes, we uncovered a multi-leveled mechanism in which BRM fine-tunes circadian transcription

A systematic study on the binding energy of Λ\Lambda hypernuclei

In this paper, we calculated the binding energy per baryon of the $\Lambda$ hypernuclei systemically, using the relativistic mean field theory (RMF) in a statistic frame. Some resemble properties are found among most of the hypernuclei found in experiments. The data show that a $\Lambda$ hypernucleus will be more stable, if it is composed of a $\Lambda$ hyperon adding to a stable normal nuclear core, or a $\Lambda$ hyperon replacing a neutron in a stable normal nuclear core. According to our calculations, existences of some new $\Lambda$ hypernuclei are predicted under the frame of RMF.Comment: 8 pages, 6 figures, 3 table

Development of hot drawing process for nitinol tube

In recent years, Nitinol, near-equiatomic nickel-titanium alloys, have found growing applications in medical technology and joining technology, due to their special characteristics such as shape memory, superplasticity and biocompatibility. The production of Nitinol tube cost-effectively remains a technical challenge. In this paper, we describe a hot drawing process for Nitinol tube production. A Nitinol tube blank and a metal core are assembled together. The assembly is hot drawn for several passes to a final diameter. The metal core is then plastically stretched to reduce its diameter and removed from the tube. Hot drawing process has been applied to Ni50.7Ti and Ni47Ti44Nb9 alloys. Nitinol tubes of 13.6 mm outer diameter and 1 mm wall thickness have been successfully produced from a tube blank of 20 mm outer diameter and 3.5 mm thickness