Specific Heat of the Ca-Intercalated Graphite Superconductor CaC6_6

The superconducting state of Ca-intercalated graphite CaC6 has been investigated by specific heat measurements. The characteristic anomaly at the superconducting transition (Tc = 11.4 K) indicates clearly the bulk nature of the superconductivity. The temperature and magnetic field dependence of the electronic specific heat are consistent with a fully-gapped superconducting order parameter. The estimated electron-phonon coupling constant is lambda = 0.60 - 0.74 suggesting that the relatively high Tc of CaC6 can be explained within the weak-coupling BCS approach.Comment: 4 pages, 4 figs, submitted to Phys. Rev. Let

Superconductivity in Heavy Alkaline-Earths Intercalated Graphites

We report the discovery of superconductivity below 1.65(6) K in Sr-intercalated graphite SrC6, by susceptibility and specific heat (Cp) measurements. In comparison with CaC6, we found that the anisotropy of the upper critical fields for SrC6 is much reduced. The Cp anomaly at Tc is smaller than the BCS prediction indicating an anisotropic superconducting gap for SrC6 similar to CaC6. The significantly lower Tc of SrC6 as compared to CaC6 can be understood in terms of "negative" pressure effects, which decreases the electron-phonon coupling for both in-plane intercalant and the out-of-plane C phonon modes. We observed no superconductivity for BaC6 down to 0.3 K.Comment: 4 pages, 4 figures, submitted to Phys. Rev. Let

A non-adiabatic approach to entanglement distribution over long distances

Entanglement distribution between trapped-atom quantum memories, viz. single atoms in optical cavities, is addressed. In most scenarios, the rate of entanglement distribution depends on the efficiency with which the state of traveling single photons can be transferred to trapped atoms. This loading efficiency is analytically studied for two-level, $V$-level, $\Lambda$-level, and double-$\Lambda$-level atomic configurations by means of a system-reservoir approach. An off-resonant non-adiabatic approach to loading $\Lambda$-level trapped-atom memories is proposed, and the ensuing trade-offs between the atom-light coupling rate and input photon bandwidth for achieving a high loading probability are identified. The non-adiabatic approach allows a broad class of optical sources to be used, and in some cases it provides a higher system throughput than what can be achieved by adiabatic loading mechanisms. The analysis is extended to the case of two double-$\Lambda$ trapped-atom memories illuminated by a polarization-entangled biphoton.Comment: 15 pages, 15 figure

Effect of Pressure on Superconducting Ca-intercalated Graphite CaC6_6

The pressure effect on the superconducting transition temperature ($T_c$) of the newly-discovered Ca-intercalated graphite compound CaC$_6$ has been investigated up to $\sim$ 16 kbar. $T_c$ is found to increase under pressure with a large relative ratio $\Delta$$T_c$/$T_c$ of $\approx$ +0.4 %/kbar. Using first-principles calculations, we show that the large and positive effect of pressure on $T_c$ can be explained in the scope of electron-phonon theory due to the presence of a soft phonon branch associated to in-plane vibrations of Ca atoms. Implications of the present findings on the current debate about the superconducting mechanism in graphite intercalation compounds are discussed.Comment: 6 pages, 5 figs, final PRB versio

Ferulone A and ferulone B: two new coumarin esters from Ferula orientalis L. roots, Natural Products Research

Ferula orientalis (Apiaceae) is a well known perennial herb growing wild in Iran used in traditional medicine. To perform phytochemical studies, dried ground roots of F. orientalis were sequentially Soxhlet-extracted using n-hexane, dichloromethane and methanol. A combination of vacuum liquid chromatography and preparative thin layer chromatographic analyses were performed to isolate coumarin esters. The structures of the isolated compounds were elucidated by spectroscopic means, and in vitro free-radical-scavenging property was determined by the DPPH assay.Two new coumarin esters, 7-O-(4,8,12,16-tetrahydroxy-4,8,12,16-tetramethyl-heptadecanoyl)-coumarinand 7-O-(4-hydroxy-4,8,12-trimethyl-trideca- 7,11-dienoyl)-coumarin, named ferulone A and ferulone B, respectively, were isolated from the n-hexane extract of the roots of F. orientalis. Both compounds showed a low level of free-radical-scavenging property with the RC50 values of 0.252 and 0.556mg/mL for compounds 1 and 2, respectively, as opposed to that of the positive control (quercetin) 0.004 mg/mL. This is the first report on the purification of coumarin esters from the genus Ferula

Measurement-device-independent quantum key distribution with nitrogen vacancy centers in diamond

Memory-assisted measurement-device-independent quantum key distribution (MA-MDI-QKD) has recently been proposed as a possible intermediate step towards the realization of quantum repeaters. Despite its relaxing some of the requirements on quantum memories, the choice of memory in relation to the layout of the setup and the protocol has a stark effect on our ability to beat existing no-memory systems. Here, we investigate the suitability of nitrogen vacancy (NV) centers, as quantum memories, in MA-MDI-QKD. We particularly show that moderate cavity enhancement is required for NV centers if we want to outperform no-memory QKD systems. Using system parameters mostly achievable by today's state of the art, we then anticipate some total key rate advantage in the distance range between 300 and 500 km for cavity-enhanced NV centers. Our analysis accounts for major sources of error including the dark current, the channel loss, and the decoherence of the quantum memories

Communication skills training in oncology: a position paper based on a consensus meeting among European experts in 2009

Background: Communication in cancer care has become a major topic of interest. Since there is evidence that ineffective communication affects both patients and oncology clinicians (physicians and nurses), so-called communication skills trainings (CSTs) have been developed over the last decade. While these trainings have been demonstrated to be effective, there is an important heterogeneity with regard to implementation and with regard to evidence of different aspects of CST. Methods: In order to review and discuss the scientific literature on CST in oncology and to formulate recommendations, the Swiss Cancer League has organised a consensus meeting with European opinion leaders and experts in the field of CST, as well as oncology clinicians, representatives of oncology societies and patient organisations. On the basis of a systematic review and a meta-analysis, recommendations have been developed and agreed upon. Results: Recommendations address (i) the setting, objectives and participants of CST, (ii) its content and pedagogic tools, (iii) organisational aspects, (iv) outcome and (v) future directions and research. Conclusion: This consensus meeting, on the basis of European expert opinions and a systematic review and meta-analysis, defines key elements for the current provision and future development and evaluation of CST in oncolog