Intense lasers interacting with dense targets accelerate relativistic electron beams, which transport part of the laser energy into the target depth. However, the overall laser-to-target energy ...coupling efficiency is impaired by the large divergence of the electron beam, intrinsic to the laser-plasma interaction. Here we demonstrate that an efficient guiding of MeV electrons with about 30 MA current in solid matter is obtained by imposing a laser-driven longitudinal magnetostatic field of 600 T. In the magnetized conditions the transported energy density and the peak background electron temperature at the 60-μm-thick target's rear surface rise by about a factor of five, as unfolded from benchmarked simulations. Such an improvement of energy-density flux through dense matter paves the ground for advances in laser-driven intense sources of energetic particles and radiation, driving matter to extreme temperatures, reaching states relevant for planetary or stellar science as yet inaccessible at the laboratory scale and achieving high-gain laser-driven thermonuclear fusion.
The central challenge in building a quantum computer is error correction. Unlike classical bits, which are susceptible to only one type of error, quantum bits (qubits) are susceptible to two types of ...error, corresponding to flips of the qubit state about the X and Z directions. Although the Heisenberg uncertainty principle precludes simultaneous monitoring of X- and Z-flips on a single qubit, it is possible to encode quantum information in large arrays of entangled qubits that enable accurate monitoring of all errors in the system, provided that the error rate is low
. Another crucial requirement is that errors cannot be correlated. Here we characterize a superconducting multiqubit circuit and find that charge noise in the chip is highly correlated on a length scale over 600 micrometres; moreover, discrete charge jumps are accompanied by a strong transient reduction of qubit energy relaxation time across the millimetre-scale chip. The resulting correlated errors are explained in terms of the charging event and phonon-mediated quasiparticle generation associated with absorption of γ-rays and cosmic-ray muons in the qubit substrate. Robust quantum error correction will require the development of mitigation strategies to protect multiqubit arrays from correlated errors due to particle impacts.
Dehydration of glycerol solution and further oxidation have been investigated with different mixed oxide catalysts. Among them, iron phosphates were found to be highly active and selective toward ...acrolein. Glycerol conversion was nearly complete and acrolein yields reach 80–90% after 5
h of test. Fresh and used catalysts were also characterized by different techniques (XRD, SEM, BET and TGA-DSC). Pure and well-defined structures were found more stable than relatively poor crystalline phase. Distribution of products changes during the deactivation of the catalyst, leading to by-products such as acetol, propanal and coke deposit on the surface of the catalyst, indicating a modification of the mechanism.
Introducing some oxygen in the feed allowed decreasing the amount of those by-products, but oxidation products appeared such as acetic acid or CO
x
on detriment of the yield in acrolein. Using appropriate mixed oxide catalysts such as molybdenum/tungsten vanadium based catalysts showed interesting performances to obtain acrylic acid directly from glycerol.
Target charging in short-pulse-laser-plasma experiments Dubois, J-L; Lubrano-Lavaderci, F; Raffestin, D ...
Physical review. E, Statistical, nonlinear, and soft matter physics,
01/2014, Letnik:
89, Številka:
1
Journal Article
Recenzirano
Interaction of high-intensity laser pulses with solid targets results in generation of large quantities of energetic electrons that are the origin of various effects such as intense x-ray emission, ...ion acceleration, and so on. Some of these electrons are escaping the target, leaving behind a significant positive electric charge and creating a strong electromagnetic pulse long after the end of the laser pulse. We propose here a detailed model of the target electric polarization induced by a short and intense laser pulse and an escaping electron bunch. A specially designed experiment provides direct measurements of the target polarization and the discharge current in the function of the laser energy, pulse duration, and target size. Large-scale numerical simulations describe the energetic electron generation and their emission from the target. The model, experiment, and numerical simulations demonstrate that the hot-electron ejection may continue long after the laser pulse ends, enhancing significantly the polarization charge.
Systematic review on cashew nut allergy van der Valk, J. P. M.; J. Dubois, A. E.; Gerth van Wijk, R. ...
Allergy,
June 2014, Letnik:
69, Številka:
6
Journal Article
Recenzirano
Odprti dostop
Recent studies on cashew nut allergy suggest that the prevalence of cashew nut allergy is increasing. Cashew nut consumption by allergic patients can cause severe reactions, including anaphylaxis. ...This review summarizes current knowledge on cashew nut allergy to facilitate timely clinical recognition and to promote awareness of this emerging food allergy amongst clinicians. The goal of this study is to present a systematic review focused on the clinical aspects of allergy to cashew nut including the characteristics of cashew nut, the prevalence, allergenic components, cross‐reactivity, diagnosis and management of cashew nut allergy. The literature search yielded 255 articles of which 40 met our selection criteria and were considered to be relevant for this review. The 40 articles included one prospective study, six retrospective studies and seven case reports. The remaining 26 papers were not directly related to cashew nut allergy. The literature suggests that the prevalence of cashew nut allergy is increasing, although the level of evidence for this is low. A minimal amount of cashew nut allergen may cause a severe allergic reaction, suggesting high potency comparable with other tree nuts and peanuts. Cashew allergy is clearly an underestimated important healthcare problem, especially in children.
The on-demand generation of pure quantum excitations is important for the operation of quantum systems, but it is particularly difficult for a system of fermions. This is because any perturbation ...affects all states below the Fermi energy, resulting in a complex superposition of particle and hole excitations. However, it was predicted nearly 20 years ago that a Lorentzian time-dependent potential with quantized flux generates a minimal excitation with only one particle and no hole. Here we report that such quasiparticles (hereafter termed levitons) can be generated on demand in a conductor by applying voltage pulses to a contact. Partitioning the excitations with an electronic beam splitter generates a current noise that we use to measure their number. Minimal-excitation states are observed for Lorentzian pulses, whereas for other pulse shapes there are significant contributions from holes. Further identification of levitons is provided in the energy domain with shot-noise spectroscopy, and in the time domain with electronic Hong-Ou-Mandel noise correlations. The latter, obtained by colliding synchronized levitons on a beam splitter, exemplifies the potential use of levitons for quantum information: using linear electron quantum optics in ballistic conductors, it is possible to imagine flying-qubit operation in which the Fermi statistics are exploited to entangle synchronized electrons emitted by distinct sources. Compared with electron sources based on quantum dots, the generation of levitons does not require delicate nanolithography, considerably simplifying the circuitry for scalability. Levitons are not limited to carrying a single charge, and so in a broader context n-particle levitons could find application in the study of full electron counting statistics. But they can also carry a fraction of charge if they are implemented in Luttinger liquids or in fractional quantum Hall edge channels; this allows the study of Abelian and non-Abelian quasiparticles in the time domain. Finally, the generation technique could be applied to cold atomic gases, leading to the possibility of atomic levitons.
Résumé
L’identification des cellules souches cancéreuses (CSC) cette dernière décennie a permis l’émergence de nouveaux espoirs. Néanmoins, leur caractérisation a mis en évidence une certaine ...résistance aux traitements anticancéreux tels que la radiothérapie. De plus, il a récemment été montré que certaines cellules non-CSC pouvaient réacquérir le phénotype de cellules souches cancéreuses sous l’effet de traitement anticancéreux, enrichissant d’autant la population résistante. Nous proposons dans cette revue de faire un tour d’horizon des différentes propriétés des CSC et tout particulièrement des mécanismes de radiorésistance, de reprogrammation et des approches thérapeutiques envisagées pour outrepasser ces résistances.
Oscillations are ubiquitous in electrical recordings of brain activity. While the amplitude of ongoing oscillatory activity is known to correlate with various aspects of perception, the influence of ...oscillatory phase on perception remains unknown. In particular, since phase varies on a much faster timescale than the more sluggish amplitude fluctuations, phase effects could reveal the fine-grained neural mechanisms underlying perception. We presented brief flashes of light at the individual luminance threshold while EEG was recorded. Although the stimulus on each trial was identical, subjects detected approximately half of the flashes (hits) and entirely missed the other half (misses). Phase distributions across trials were compared between hits and misses. We found that shortly before stimulus onset, each of the two distributions exhibited significant phase concentration, but at different phase angles. This effect was strongest in the theta and alpha frequency bands. In this time-frequency range, oscillatory phase accounted for at least 16% of variability in detection performance and allowed the prediction of performance on the single-trial level. This finding indicates that the visual detection threshold fluctuates over time along with the phase of ongoing EEG activity. The results support the notion that ongoing oscillations shape our perception, possibly by providing a temporal reference frame for neural codes that rely on precise spike timing.
We have used Ramsey tomography to characterize charge noise in a weakly charge-sensitive superconducting qubit. We find a charge noise that scales with frequency as 1/fα over five decades with α=1.93 ...and a magnitude Sq(1Hz)=2.9×10−4e2/Hz. The noise exponent and magnitude of the low-frequency noise are much larger than those seen in prior work on single electron transistors, yet are consistent with reports of frequency noise in other superconducting qubits. Moreover, we observe frequent large-amplitude jumps in offset charge exceeding 0.1e; these large discrete charge jumps are incompatible with a picture of localized dipolelike two-level fluctuators. The data reveal an unexpected dependence of charge noise on device scale and suggest models involving either charge drift or fluctuating patch potentials.
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