1,466 research outputs found
Effect of picosecond strain pulses on thin layers of the ferromagnetic semiconductor (Ga,Mn)(As,P)
The effect of picosecond acoustic strain pulses (ps-ASP) on a thin layer of
(Ga,Mn)As co-doped with phosphorus was probed using magneto-optical Kerr effect
(MOKE). A transient MOKE signal followed by low amplitude oscillations was
evidenced, with a strong dependence on applied magnetic field, temperature and
ps-ASP amplitude. Careful interferometric measurement of the layer's thickness
variation induced by the ps-ASP allowed us to model very accurately the
resulting signal, and interpret it as the strain modulated reflectivity
(differing for probe polarizations), independently from dynamic
magnetization effects.Comment: 6 pages, 5 figure
A hybrid metal/semiconductor electron pump for quantum metrology
Electron pumps capable of delivering a current higher than 100pA with
sufficient accuracy are likely to become the direct mise en pratique of the
possible new quantum definition of the ampere. Furthermore, they are essential
for closing the quantum metrological triangle experiment which tests for
possible corrections to the quantum relations linking e and h, the electron
charge and the Planck constant, to voltage, resistance and current. We present
here single-island hybrid metal/semiconductor transistor pumps which combine
the simplicity and efficiency of Coulomb blockade in metals with the
unsurpassed performances of silicon switches. Robust and simple pumping at
650MHz and 0.5K is demonstrated. The pumped current obtained over a voltage
bias range of 1.4mV corresponds to a relative deviation of 5e-4 from the
calculated value, well within the 1.5e-3 uncertainty of the measurement setup.
Multi-charge pumping can be performed. The simple design fully integrated in an
industrial CMOS process makes it an ideal candidate for national measurement
institutes to realize and share a future quantum ampere
Probably Safe or Live
This paper presents a formal characterisation of safety and liveness
properties \`a la Alpern and Schneider for fully probabilistic systems. As for
the classical setting, it is established that any (probabilistic tree) property
is equivalent to a conjunction of a safety and liveness property. A simple
algorithm is provided to obtain such property decomposition for flat
probabilistic CTL (PCTL). A safe fragment of PCTL is identified that provides a
sound and complete characterisation of safety properties. For liveness
properties, we provide two PCTL fragments, a sound and a complete one. We show
that safety properties only have finite counterexamples, whereas liveness
properties have none. We compare our characterisation for qualitative
properties with the one for branching time properties by Manolios and Trefler,
and present sound and complete PCTL fragments for characterising the notions of
strong safety and absolute liveness coined by Sistla
Bacillus subtilis and Bacillus velezensis population dynamic and quantification of spores after inoculation on ornamental plants
Abstract: Bacillus subtilis and Bacillus velezensis are used in organic agriculture as an alternative to chemical pesticides to fight against phytopathogen organisms. These Gram-positive soil-dwelling bacteria are able to resist harsh conditions and survive by differentiating into endospores. Few studies have examined how bacterial populations change on plants over time, and if they remain active or enter a dormant state. Nonetheless, these characteristics are strikingly important to determine the usage of B. subtilis and B. velezensis and their efficacy in environmental conditions. Here, we investigate the population dynamic on plants of B. subtilis NCIB3610 and B. velezensis QST713 when applied as spores on different ornamental plants. We report that on all plants studied (Echinacea purpurea cv. Salsa red, Echinacea purpurea cv. Fatal attraction and Lavandula angustifolia cv. Hidecote blue) spores rapidly germinated and colonized the rhizoplane, maintaining a relatively low proportion of spores in the population over time, whereas bacterial population on leaves rapidly declined. Bacteria in the surrounding soil did not germinate and persisted as spores. Taken together, these results suggest that only cells found at the rhizosphere remain metabolically active to allow the formation of a lasting relationship with the plant, making possible beneficial effects from the inoculated bacteria.Bacillus subtilis et Bacillus velezensis sont utilisées en agriculture biologique comme alternative aux pesticides chimiques. Ces bactéries Gram-positives vivant dans le sol sont capables de résister à des conditions difficiles et de survivre en se différenciant en endospores. Peu d'études ont examiné comment les bactéries persistent sur les plantes, si elles demeurent actives ou entrent en dormance. Néanmoins, ces caractéristiques sont importantes pour déterminer leur utilisation et leur efficacité dans des conditions environnementales. Nous avons étudié la dynamique de population de B. subtilis NCIB3610 et de B. velezensis QST713 lorsqu'appliquées comme spores sur différentes plantes ornementales. Nous montrons que sur toutes les plantes étudiées (Echinacea purpurea cv. Salsa red, Echinacea purpurea cv. Fatal attraction et Lavandula angustifolia cv. Hidecote blue) les spores ont rapidement germées et colonisées la rhizoplane, maintenant une proportion relativement faible de spores dans la population, alors que la population sur les feuilles a rapidement diminué. Les bactéries présentes dans le sol environnant n'ont pas germé et ont persisté sous forme de spores. Ces résultats suggÚrent que seules les bactéries trouvées au niveau des racines restent métaboliquement actives pour permettre la formation d'une relation durable avec la plante, rendant possible les effets bénéfiques des bactéries inoculées
Coherent Control of Isotope Separation in HD+ Photodissociation by Strong Fields
The photodissociation of the HD+ molecular ion in intense short- pulsed
linearly polarized laser fields is studied using a time- dependent wave-packet
approach where molecular rotation is fully included. We show that applying a
coherent superposition of the fundamental radiation with its second harmonic
can lead to asymmetries in the fragment angular distributions, with significant
differences between the hydrogen and deuterium distributions in the long
wavelength domain where the permanent dipole is most efficient. This effect is
used to induce an appreciable isotope separation.Comment: Physical Review Letters, 1995 (in press). 4 pages in revtex format, 3
uuencoded figures. Full postcript version available at:
http://chemphys.weizmann.ac.il/~charron/prl.ps or
ftp://scipion.ppm.u-psud.fr/coherent.control/prl.p
Theoretical study of a cold atom beam splitter
A theoretical model is presented for the study of the dynamics of a cold
atomic cloud falling in the gravity field in the presence of two crossing
dipole guides. The cloud is split between the two branches of this laser guide,
and we compare experimental measurements of the splitting efficiency with
semiclassical simulations. We then explore the possibilities of optimization of
this beam splitter. Our numerical study also gives access to detailed
information, such as the atom temperature after the splitting
Bose-Einstein condensation in dark power-law laser traps
We investigate theoretically an original route to achieve Bose-Einstein
condensation using dark power-law laser traps. We propose to create such traps
with two crossing blue-detuned Laguerre-Gaussian optical beams. Controlling
their azimuthal order allows for the exploration of a multitude of
power-law trapping situations in one, two and three dimensions, ranging from
the usual harmonic trap to an almost square-well potential, in which a
quasi-homogeneous Bose gas can be formed. The usual cigar-shaped and
disk-shaped Bose-Einstein condensates obtained in a 1D or 2D harmonic trap take
the generic form of a "finger" or of a "hockey puck" in such Laguerre-Gaussian
traps. In addition, for a fixed atom number, higher transition temperatures are
obtained in such configurations when compared with a harmonic trap of same
volume. This effect, which results in a substantial acceleration of the
condensation dynamics, requires a better but still reasonable focusing of the
Laguerre-Gaussian beams
Crystallization and preliminary X-ray diffraction studies of D-glyceraldehyde-3-phosphate dehydrogenase from the hyperthermophilic archaeon Methanothermus fervidus.
Journal ArticleThe homotetrameric holo-D-glyceraldehyde-3-phosphate dehydrogenase from the hyperthermophilic archaeon Methanothermus fervidus has been crystallized in the presence of NADP+ using the hanging-drop vapour-diffusion method. Crystals grew from a solution containing 2-methyl-2,4-pentanediol and magnesium acetate. A native data set has been collected to 2.1 A using synchrotron radiation and cryocooling. Diffraction data have been processed in the orthorhombic system (space group P21212) with unit-cell dimensions a = 136.7, b = 153.3, c = 74.9 A and one tetramer per asymmetric unit
Monitoring Partially Synchronous Distributed Systems using SMT Solvers
In this paper, we discuss the feasibility of monitoring partially synchronous
distributed systems to detect latent bugs, i.e., errors caused by concurrency
and race conditions among concurrent processes. We present a monitoring
framework where we model both system constraints and latent bugs as
Satisfiability Modulo Theories (SMT) formulas, and we detect the presence of
latent bugs using an SMT solver. We demonstrate the feasibility of our
framework using both synthetic applications where latent bugs occur at any time
with random probability and an application involving exclusive access to a
shared resource with a subtle timing bug. We illustrate how the time required
for verification is affected by parameters such as communication frequency,
latency, and clock skew. Our results show that our framework can be used for
real-life applications, and because our framework uses SMT solvers, the range
of appropriate applications will increase as these solvers become more
efficient over time.Comment: Technical Report corresponding to the paper accepted at Runtime
Verification (RV) 201
Maintenance of GLUT4 expression in smooth muscle prevents hypertensionâinduced changes in vascular reactivity
Previous studies have shown that expression of GLUT4 is decreased in arterial smooth muscle of hypertensive rats and mice and that total body overexpression of GLUT4 in mice prevents enhanced arterial reactivity in hypertension. To demonstrate that the effect of GLUT4 overexpression on vascular responses is dependent on vascular smooth muscle GLUT4 rather than on some systemic effect we developed and tested smoothâmuscleâspecific GLUT4 transgenic mice (SMG4). When made hypertensive with angiotensin II, both wildâtype and SMG4 mice exhibited similarly increased systolic blood pressure. Responsiveness to phenylephrine, serotonin, and prostaglandin F2α was significantly increased in endotheliumâintact aortic rings from hypertensive wildâtype mice but not in aortae of SMG4 mice. Inhibition of Rhoâkinase equally reduced serotoninâstimulated contractility in aortae of hypertensive wildâtype and SMG4âmice. In addition, acetylcholineâstimulated relaxation was significantly decreased in aortic rings of hypertensive wildâtype mice, but not in rings of SMG4 mice. Inhibition of either prostacylin receptors or cyclooxygenaseâ2 reduced relaxation in rings of hypertensive SMG4 mice. Inhibition of cyclooxygenaseâ2 had no effect on relaxation in rings of hypertensive wildâtype mice. Cyclooxygenaseâ2 protein expression was decreased in hypertensive wildâtype aortae but not in hypertensive SMG4 aortae compared to nonhypertensive controls. Our results demonstrate that smooth muscle expression of GLUT4 exerts a major effect on smooth muscle contractile responses and endotheliumâdependent vasorelaxation and that normal expression of GLUT4 in vascular smooth muscle is required for appropriate smooth muscle and endothelial responses.e12299In the smooth muscle of aortae of hypertensive mice, expression of GLUT4 is decreased. Maintenance of aortic smooth muscle GLUT4 expression prevents hypertensionâmediated changes in vasomotor response. These effects include decreasing/preventing endothelial dysfunction.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/110755/1/phy212299.pd
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