Extremal Quantum Correlations and Cryptographic Security

We investigate a fundamental property of device independent security in quantum cryptography by characterizing probability distributions which are necessarily independent of the measurement results of any eavesdropper. We show that probability distributions that are secure in this sense are exactly the extremal quantum probability distributions. This allows us to give a characterization of security in algebraic terms. We apply the method to common examples for two-party as well as multi-party setups and present a scheme for verifying security of probability distributions with two parties, two measurement settings, and two outcomes.Comment: 7 pages, 2 figures, revised version, accepted for publication in Phys. Rev. Let

Evidence for complex order parameter in La_{1.83}Sr_{0.17}CuO_4

The in-plane magnetic field penetration depth (\lambda_{ab}) in single-crystal La_{1.83}Sr_{0.17}CuO_4 was investigated by means of the muon-spin rotation (\muSR) technique. The temperature dependence of \lambda^{-2}_{ab} has an inflection point around 10-15K, suggesting the presence of two superconducting gaps: a large gap (\Delta_1^d) with d-wave and a small gap (\Delta_2^s) with s-wave symmetry. The zero-temperature values of the gaps at \mu_0H=0.02T were found to be \Delta_1^d(0)=8.2(2)meV and \Delta_2^s(0)=1.57(8)meV.Comment: 5 pages, 3 figure

Universal observation of multiple order parameters in cuprate superconductors

The temperature dependence of the London penetration depth \lambda was measured for an untwined single crystal of YBa_2Cu_3O_{7-\delta} along the three principal crystallographic directions (a, b, and c). Both in-plane components (\lambda_a and \lambda_b) show an inflection point in their temperature dependence which is absent in the component along the c-direction (\lambda_c). The data provide convincing evidence that the in-plane superconducting order parameter is a mixture of s+d-wave symmetry whereas it is exclusively s-wave along the c-direction. In conjunction with previous results it is concluded that coupled s+d-order parameters are universal and intrinsic to cuprate superconductors.Comment: 5 pages, 3 figure

Präoperative Nüchternzeiten: Sicht der Patienten

Zusammenfassung: Hintergrund: Mit dem Ziel der subjektiven perioperativen Qualitätsverbesserung scheint es wünschenswert, die präoperativen Nüchternzeiten im Rahmen der als sicher geltenden Grenzen so kurz als möglich zu halten. Diese Maßnahmen sollten mit einer messbaren Verminderung von präoperativem Hunger und Durst einhergehen und v.a. in einer Verbesserung der präoperativen Befindlichkeit resultieren. Welchen Einfluss Durst und Hunger aus Patientensicht auf den präoperativen Komfort haben, ist jedoch weit gehend unbekannt. Ziel dieser Studie war es, das Ausmaß der Beeinträchtigung der Patienten durch eine traditionelle Nüchternheitsregelung abzuschätzen. Patienten und Methoden: Ein Kollektiv von 412Patienten der "American-Society-of-Anesthesiologists"- (ASA-)RisikoklassenI und II, das sich einem kleineren chirurgischen Eingriff unterzog, wurde mithilfe eines Fragebogens zum Ausmaß und Stellenwert von präoperativem Durst und Hunger befragt. Ergebnisse: Es hatten 33% der Patienten mäßigen oder starken Durst, 19% mäßigen bis starken Hunger. Von den Befragten möchten 47% vor der Operation noch trinken, 72% hätten gern noch ein leichtes Frühstück eingenommen. Die mittlere Nüchternzeit war 12,8±3,4h für Flüssigkeiten und 15,5±4,4h für Essen. Durst wurde von 3,3% und Hunger von 0,8% der Patienten als Hauptgrund für die Beeinträchtigung des präoperativen Wohlbefindens genannt. Das lange Warten (8,5%), Nervosität (6,5%) und Angst (4,8%) wurden am häufigsten genannt. Die Antworten waren unabhängig von der Zeitdauer der präoperativen Nüchternheit. Schlussfolgerung: Der Patientenkomfort ist durch eine traditionelle Nüchternheitsregelung beeinträchtigt, und Minimierung der präoperativen Nüchternzeiten wird von den Patienten gewünscht. Anstrengungen mit dem Ziel der Reduktion von präoperativer Angst und Nervosität bergen jedoch zusätzliches großes Potenzial für eine Steigerung der perioperativen Behandlungsqualität aus Sicht der Patiente

Q-dependence of the inelastic neutron scattering cross section for molecular spin clusters with high molecular symmetry

For powder samples of polynuclear metal complexes the dependence of the inelastic neutron scattering intensity on the momentum transfer Q is known to be described by a combination of so called interference terms. They reflect the interplay between the geometrical structure of the compound and the spatial properties of the wave functions involved in the transition. In this work, it is shown that the Q-dependence is strongly interrelated with the molecular symmetry of molecular nanomagnets, and, if the molecular symmetry is high enough, is actually completely determined by it. A general formalism connecting spatial symmetry and interference terms is developed. The arguments are detailed for cyclic spin clusters, as experimentally realized by e.g. the octanuclear molecular wheel Cr8, and the star like tetranuclear cluster Fe4.Comment: 8 pages, 1 figures, REVTEX

Finite-size and pressure effects in YBa_2Cu_4O_8 probed by magnetic field penetration depth measurements

We explore the combined pressure and finite-size effects on the in-plane penetration depth \lambda_{ab} in YBa_2Cu_4O_8. Even though this cuprate is stoichiometric the finite-size scaling analysis of \lambda_{ab}^{-2}(T) uncovers the granular nature and reveals domains with nanoscale size L_{c} along the c-axis. L_{c} ranges from 33.2 Angstrom to 28.9 Angstrom at pressures from 0.5 to 11.5 kbar. These observations raise serious doubts on the existence of a phase coherent macroscopic superconducting state in cuprate superconductors.Comment: 7 pages, 6 figure

Attenuated increase in maximal force of rat medial gastrocnemius muscle after concurrent peak power and endurance training

Improvement of muscle peak power and oxidative capacity are generally presumed to be mutually exclusive. However, this may not be valid by using fibre type-specific recruitment. Since rat medial gastrocnemius muscle (GM) is composed of high and low oxidative compartments which are recruited task specifically, we hypothesised that the adaptive responses to peak power training were unaffected by additional endurance training. Thirty rats were subjected to either no training (control), peak power training (PT), or both peak power and endurance training (PET), which was performed on a treadmill 5 days per week for 6 weeks. Maximal running velocity increased 13.5% throughout the training and was similar in both training groups. Only after PT, GM maximal force was 10% higher than that of the control group. In the low oxidative compartment, mRNA levels of myostatin and MuRF-1 were higher after PT as compared to those of control and PET groups, respectively. Phospho-S6 ribosomal protein levels remained unchanged, suggesting that the elevated myostatin levels after PT did not inhibit mTOR signalling. In conclusion, even by using task-specific recruitment of the compartmentalized rat GM, additional endurance training interfered with the adaptive response of peak power training and attenuated the increase in maximal force after power training

Effects of concurrent training on oxidative capacity in rat gastrocnemius muscle

PURPOSE: Training for improvement of oxidative capacity of muscle fibers may be attenuated when concurrently training for peak power. However, because of fiber type-specific recruitment, such attenuation may only account for high-oxidative muscle fibers. Here, we investigate the effects of concurrent training on oxidative capacity (as measured by succinate dehydrogenase (SDH) activity) by using task-specific recruitment of the high- and low-oxidative compartment of rat medial gastrocnemius muscle (GM). METHODS: Forty rats were subjected to 6 wk of peak power training (PT, n = 10), endurance training (ET, n = 10), concurrent peak power and endurance training (PET, n = 10), or no training (control, n = 10). SDH activity, mRNA expression of SDH, peroxisome proliferator-activated receptor-γ coactivator 1α (PGC-1α), receptor-interacting protein 140, and BCL2/adenovirus E1B 19 kDa-interacting protein 3 as well as PGC-1α protein levels were analyzed in the low- and high-oxidative region of the GM. RESULTS: In the low-oxidative compartment, PT and PET induced a 30% decrease in SDH activity of Type IIB fibers compared with controls and ET (P < 0.001) without changes in mRNA or protein levels. In the high-oxidative compartment, after ET, SDH mRNA levels were 42% higher and RIP140 mRNA levels 33% lower compared with controls, which did not result in changes in SDH activity. CONCLUSION: These results indicate that in compartmentalized rat GM, peak power on top of endurance training attenuated transcription of mRNA for mitochondrial proteins in high-oxidative muscle fibers. In low-oxidative Type IIB fibers, peak power training substantially decreased SDH activity, which was not related to lower SDH mRNA levels. It is concluded that PT and PET enhanced mitochondrial degradation in the low-oxidative compartment of rat GM. Copyright © 2013 by the American College of Sports Medicine

Heisenberg Dimer Single Molecule Magnets in a Strong Magnetic Field

We calculate the static and dynamic properties of single crystal, single molecule magnets consisting of equal spin $S=1/2$ or 5/2 dimers. The spins in each dimer interact with each other via the Heisenberg exchange interaction and with the magnetic induction ${\bf B}$ via the Zeeman interaction, and interdimer interactions are negligible. For antiferromagnetic couplings, the static magnetization and specific heat exhibit interesting low temperature $T$ and strong ${\bf B}$ quantum effects. We calculate the frequency spectrum of the Fourier transform of the real part of the time autocorrelation function ${\cal C}_{11}(t)$ for arbitrary $T, {\bf B}$, and compare our results with those obtained for classical spins. We also calculate the inelastic neutron magnetic dynamical structure factor $S({\bf q},\omega)$ at arbitrary $T, {\bf B}$.Comment: 11 pages, 14 figures, submitted to Phys. Rev.