1,108 research outputs found
Device-dependent and device-independent quantum key distribution without a shared reference frame
Standard quantum key distribution (QKD) protocols typically assume that the
distant parties share a common reference frame. In practice, however,
establishing and maintaining a good alignment between distant observers is
rarely a trivial issue, which may significantly restrain the implementation of
long-distance quantum communication protocols. Here we propose simple QKD
protocols that do not require the parties to share any reference frame, and
study their security and feasibility in both the usual device-dependent
case--in which the two parties use well characterized measurement devices--as
well as in the device-independent case--in which the measurement devices can be
untrusted, and the security relies on the violation of a Bell inequality. To
illustrate the practical relevance of these ideas, we present a
proof-of-principle demonstration of our protocols using polarization entangled
photons distributed over a coiled 10-km-long optical fiber. We consider two
situations, in which either the fiber spool freely drifts, or randomly chosen
polarization transformations are applied. The correlations obtained from
measurements allow, with high probability, to generate positive asymptotic
secret key rates in both the device-dependent and device-independent scenarios
(under the fair-sampling assumption for the latter case).Comment: 12 pages, 11 figure
New Bauer Flydrill System Drilling Monopiles at Barrow Offshore Wind Farm, UK
With an output capacity of 90 MW of renewable electricity, Barrow OSWF is an offshore wind farm constructed in UK coastal waters. The site is located approximately 7 km south of Walney Island near Barrow-in-Furness, Cumbria, in the East Irish Sea. Steel monopiles with an outer diameter of 4750 mm and a wall thickness of between 45 mm and 80 mm provide the wind turbines foundations and vary in length between 49.5 m and 61.2 m weighing up to 452 tonnes. Installation of the monopile foundations with a penetration into the seabed of between 30.2 m and 40.7 m was carried out by a process of driving and drilling. The geology of the area beneath the wind farm site comprises sequences of medium dense to very dense sands, firm to stiff and very stiff to hard clays and weathered mudstone/siltstones. Specialist pile driving company IHC Hydrohammer BV of Holland used its 1200 tonnes hydrohammer to drive the monopiles into the subsea soil formations, whilst specialty foundation equipment manufacturer Bauer Maschinen GmbH of Germany, employed its Flydrill BFD 5500 for drilling out the core inside the monopiles to reduce frictional resistance. Main contractor for the project was Marine Projects International Ltd of Middlesbrough, UK. All construction operations were carried out from MPI\u27s jack-up vessel MV Resolution
A single ion as a three-body reaction center in an ultracold atomic gas
We report on three-body recombination of a single trapped Rb^+ ion and two
neutral Rb atoms in an ultracold atom cloud. We observe that the corresponding
rate coefficient K_3 depends on collision energy and is about a factor of 1000
larger than for three colliding neutral Rb atoms. In the three-body
recombination process large energies up to several 0.1eV are released leading
to an ejection of the ion from the atom cloud. It is sympathetically recooled
back into the cloud via elastic binary collisions with cold atoms. Further, we
find that the final ionic product of the three-body processes is again an
atomic Rb^+ ion suggesting that the ion merely acts as a catalyzer, possibly in
the formation of deeply bound Rb_2 molecules.Comment: 5 pages, 4 figure
Zyklische Levelzeichnungen gerichteter Graphen
The Sugiyama framework proposed in the seminal paper of 1981 is one of the most important algorithms in graph drawing and is widely used for visualizing directed graphs. In its common version, it draws graphs hierarchically and, hence, maps the topological direction to a geometric direction. However, such a hierarchical layout is not possible if the graph contains cycles, which have to be destroyed in a preceding step. In certain application and problem settings, e.g., bio sciences or periodic scheduling problems, it is important that the cyclic structure of the input graph is preserved and clearly visible in drawings. Sugiyama et al. also suggested apart from the nowadays standard horizontal algorithm a cyclic version they called recurrent hierarchies. However, this cyclic drawing style has not received much attention since. In this thesis we consider such cyclic drawings and investigate the Sugiyama framework for this new scenario. As our goal is to visualize cycles directly, the first phase of the Sugiyama framework, which is concerned with removing such cycles, can be neglected. The cyclic structure of the graph leads to new problems in the remaining phases, however, for which solutions are proposed in this thesis. The aim is a complete adaption of the Sugiyama framework for cyclic drawings. To complement our adaption of the Sugiyama framework, we also treat the problem of cyclic level planarity and present a linear time cyclic level planarity testing and embedding algorithm for strongly connected graphs
Tachyon Condensation on the Elliptic Curve
We use the framework of matrix factorizations to study topological B-type
D-branes on the cubic curve. Specifically, we elucidate how the brane RR
charges are encoded in the matrix factors, by analyzing their structure in
terms of sections of vector bundles in conjunction with equivariant R-symmetry.
One particular advantage of matrix factorizations is that explicit moduli
dependence is built in, thus giving us full control over the open-string moduli
space. It allows one to study phenomena like discontinuous jumps of the
cohomology over the moduli space, as well as formation of bound states at
threshold. One interesting aspect is that certain gauge symmetries inherent to
the matrix formulation lead to a non-trivial global structure of the moduli
space. We also investigate topological tachyon condensation, which enables us
to construct, in a systematic fashion, higher-dimensional matrix factorizations
out of smaller ones; this amounts to obtaining branes with higher RR charges as
composites of ones with minimal charges. As an application, we explicitly
construct all rank-two matrix factorizations.Comment: 69p, 6 figs, harvmac; v2: minor change
Comparable Analysis of Acute Changes in Vascular Tone after Coffee versus Energy Drink Consumption
Caffeinated beverages are popular throughout the world, especially due to their stimulating effects on body physiology. However, short- and long-term outcome studies have shown variable results on general health. In this pilot study, we exposed a cohort of 23 healthy individuals to 240 mg of caffeine either in the form of coffee or energy drinks and performed repetitive pulse wave analyses. This experimental approach was chosen to investigate the acute effects of caffeine consumption on vascular tone depending on the form of caffeine intake. Our data indicate that energy drinks, in contrast to coffee, might negatively impact systolic blood pressure and pulse wave velocity. This issue needs special attention in the light of cardiovascular health as the observed effects have been associated with an increased risk of cardiovascular events upon persistent exposure
Therapeutic benefits of increasing natriuretic peptide levels
Natriuretic peptides play an important role in water and salt homeostasis and in the regulation of the cardiovascular system. In recent years, exogenous administration of natriuretic peptides has primarily been used to improve our understanding of the role of natriuretic peptides. Also, it became evident that natriuretic peptides may be used therapeutically. Because of their peptide character, they cannot be administered orally and, therefore, may be used for short-term intravenous therapy only. In recent years, inhibitors of neutral endopeptidase, which degrades natriuretic peptides to inactive metabolites, have been investigated. This review focuses on the potential benefits of increasing natriuretic peptide levels, either through exogenous administration or inhibiting the degradation of endogenous natriuretic peptide
Effect of intracellular Ca2+ concentration on endothelin-1 secretion
AbstractThe role of intracellular free Ca2+ concentration ([Ca2+]i in cellular regulation of endothelin-(ET-1) secretion was investigated in cultured porcine aortic endothelial cells of first passage. Intracellular Ca2+ concentration were adjusted between 50 nM and 1 μM using EGTA and thapsigargin, respectively. ET-1 secretion was maximal at [Ca2+]i of 190–470 nM, and reduced at low (50 and 110 nM) and high (470 nM) [Ca2+]i. The Ca2+ ionophores A23187 and ionomycin (each 1 μM), both of which raise [Ca2+]i above 1 μM, also potently inhibited ET-1 secretion under basal and stimulated conditions. The A23187-induced reduction in ET-1 secretion was not affected by NG-nitro-l-arginine (0.1 mM). Our results provide evidence that basal ET-1 secretion is regulated by Ca2+ and that Ca2+ ionophores reduce ET-1 secretion due to the inhibitory effect of high [Ca2+]i
O-28: Molecular basis for the insurmountable AT-1 receptor antagonism of telmisartan
In vitro studies have shown that telmisartan is an insurmountable angiotensin II AT-1 receptor antagonist. In this study we have investigated the molecular basis of this insurmountable antagonism. The association and dissociation kinetics of telmisartan to angiotensin AT-1 receptors were measured using an in vitro radio-receptor binding assay. These radioligand binding studies were conducted either directly on rat vascular (aorta) smooth muscle cells (RVSMC) expressing solely the AT-1 receptor or on membrane preparation obtained from the same cells. The specific binding of3H-telmisartan to the surface of living RVSMC or membranes was saturable. From these data, a Kd value of 1.7 nM was estimated. Scatchard analysis of the3H-telmisartan binding on RVSMC indicated the existence of a single class of binding sites. The affinity of telmisartan for AT-1 receptor is only poorly affected by the presence of proteins (0.4% of rat plasma proteins) in the binding buffer, indicating that no great competition between telmisartan binding to its specific AT-1 receptor and to non-specific proteins binding sites occurs. In association experiments, the specific binding of3H-telmisartan increases quickly and reaches equilibrium within less than 1 hour, with an association rate constant calculated to be 0.006 min-1nM-1. Telmisartan dissociates very slowly from the AT-1 receptor, either in RVSMC membrane preparation or in living cells with a dissociation rate constant of ca. 0.01 min-1 resulting in a dissociation half-life (t1/2) of about 60 min, which is comparable to the previously published data for candesartan in bovine adrenal cortical membranes and almost 5 times slower than that of 125I-angiotensin II binding (t1/2=12 min). In contrast to candesartan that has been shown to re-associate with the AT-1 receptor, telmisartan does not appear to re-associate. Indeed, when the dissociation of labeled-telmisartan from AT-1 receptors was induced by washing the cells with cold-binding buffer, followed by addition of fresh binding buffer containing either cold telmisartan, Ang II or losartan, or nothing, no difference were observed in the dissociation rate constants measured with telmisartan whatever the composition of the binding buffer after removal of labeled-telmisartan. In conclusion, these results suggest that the insurmountable antagonism of telmisartan is due mainly to its very slow dissociation from angiotensin AT-1 receptor
Qualitätssicherungsverfahren, Prozess- und Ergebnisqualität an Schulen in Berlin und Brandenburg
Im Mittelpunkt des Berichts des Instituts für Schulqualität der Länder Berlin
und Brandenburg (ISQ) stehen die Eckpunkte der Bildungssysteme, wichtige
Faktoren der Qualitätssicherung von schulischen Prozessen sowie zentrale
Bildungsergebnisse im Verlauf der Schülerkarriere in Berlin und Brandenburg.
Dabei präsentiert der Schulqualitätsbericht für Berlin und Brandenburg eine
problemorientierte Analyse der Bildungssituation in der Region.
Problemorientierung heißt, zentrale Entwicklungen im Bildungswesen für Politik
und Öffentlichkeit erkennbar zu machen und möglichen Handlungsbedarf
aufzuzeigen, ohne jedoch Wertungen vorzunehmen oder politische Empfehlungen
abzugeben. Der vorliegende Bericht verfolgt dasselbe Ziel wie seine Vorgänger
(wenn auch in thematisch engerem Rahmen): In der Zusammenstellung relevanter
und empirisch gesicherter Daten und Informationen soll ein Beitrag geleistet
werden, Diskussionen und Entscheidungen im Bildungsbereich durch die
Bereitstellung von (zusätzlichen) Fakten anzureichern
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