Coherent forward stimulated Brillouin scattering of a spatially incoherent laser beam in a plasma and its effect on beam spray

A statistical model for forward stimulated Brillouin scattering (FSBS) is developed for a spatially incoherent, monochromatic, laser beam propagating in a plasma. A threshold for the average power in a speckle is found, well below the self-focusing one, above which the laser beam spatial incoherence can not prevent the coherent growth of FSBS. Three-dimensional simulations confirm its existence and reveal the onset of beam spray above it. From these results, we propose a new figure of merit for the control of the propagation through a plasma of a spatially incoherent laser beam.Comment: submitted to PR

Adiabatic Theorems for Generators of Contracting Evolutions

We develop an adiabatic theory for generators of contracting evolution on Banach spaces. This provides a uniform framework for a host of adiabatic theorems ranging from unitary quantum evolutions through quantum evolutions of open systems generated by Lindbladians all the way to classically driven stochastic systems. In all these cases the adiabatic evolution approximates, to lowest order, the natural notion of parallel transport in the manifold of instantaneous stationary states. The dynamics in the manifold of instantaneous stationary states and transversal to it have distinct characteristics: The former is irreversible and the latter is transient in a sense that we explain. Both the gapped and gapless cases are considered. Some applications are discusse

Optimal parametrizations of adiabatic paths

The parametrization of adiabatic paths is optimal when tunneling is minimized. Hamiltonian evolutions do not have unique optimizers. However, dephasing Lindblad evolutions do. The optimizers are simply characterized by an Euler-Lagrange equation and have a constant tunneling rate along the path irrespective of the gap. Application to quantum search algorithms recovers the Grover result for appropriate scaling of the dephasing. Dephasing rates that beat Grover imply hidden resources in Lindblad operators.Comment: 4 pages, 2 figures; To prevent from misunderstanding, we clarified the discussion of an apparent speedup in the Grover algorithm; figures improved + minor change

Quantum response of dephasing open systems

We develop a theory of adiabatic response for open systems governed by Lindblad evolutions. The theory determines the dependence of the response coefficients on the dephasing rates and allows for residual dissipation even when the ground state is protected by a spectral gap. We give quantum response a geometric interpretation in terms of Hilbert space projections: For a two level system and, more generally, for systems with suitable functional form of the dephasing, the dissipative and non-dissipative parts of the response are linked to a metric and to a symplectic form. The metric is the Fubini-Study metric and the symplectic form is the adiabatic curvature. When the metric and symplectic structures are compatible the non-dissipative part of the inverse matrix of response coefficients turns out to be immune to dephasing. We give three examples of physical systems whose quantum states induce compatible metric and symplectic structures on control space: The qubit, coherent states and a model of the integer quantum Hall effect.Comment: Article rewritten, two appendices added. 16 pages, 2 figure

High-quality ion beams by irradiating a nano-structured target with a petawatt laser pulse

We present a novel laser based ion acceleration scheme, where a petawatt circularly polarized laser pulse is shot on an ultra-thin (nano-scale) double-layer target. Our scheme allows the production of high-quality light ion beams with both energy and angular dispersion controllable by the target properties. We show that extraction of all electrons from the target by radiation pressure can lead to a very effective two step acceleration process for light ions if the target is designed correctly. Relativistic protons should be obtainable with pulse powers of a few petawatt. Careful analytical modeling yields estimates for characteristic beam parameters and requirements on the laser pulse quality, in excellent agreement with one and two-dimensional Particle-in Cell simulations.Comment: 18 pages, 7 figures, accepted in New. J. Phy

The influence of anti-asthma drugs on the transcriptional regulation of chemokine receptor 3 (CCR3)

Introduction: Chemokine receptor 3 (CCR3), the major chemokine receptor expressed on eosinophils, binds promiscuously to several ligands, mainly the eotaxin family of chemokines which are up-regulated in inflammatory response. CCR3 expression in airway epithelial cells, has been reported to be upregulated in asthma, and has been proposed to play an important role in airway inflammation by amplifying the expression of chemokine transcripts. The promoter region of CCR3 gene has recently been characterized in the literature and contains promoter elements which include a TATA box and motifs for transcription factors such as NF-κB, AP-1 and GATA-1. Aim: The aim of this study was to investigate the effects of transcription modifier anti-asthma drugs on the transcriptional regulation of the CCR3 promoter. Methodology: pGL3E luciferase-based reporter deletion constructs were generated for the 1.6kb CCR3 promoter region, using standard cloning approaches in DH5α E.Coli cells. Each promoter construct was transfected to A549 cells in microwell plate format and stimulated with dexamethasone, cortisol, and theophylline, in a dose dependent manner. Results: A CCR3 promoter tri-phasic response (i.e. activation at low concentration 10-8M, repression at medium concentration 10-7M, and activation at high concentration 10- 6 M) to dexamethasone was observed, indicating a complex transcriptional regulatory mechanism. Unlike dexamethasone, cortisol did not activate CCR3 promoter activity at any of the concentrations investigated, but rather showed significant transcriptional repression at concentrations of 10-6M and 10-7M. Theophylline showed significant transcriptional repression at all three concentrations investigated (10-4M, 10-5M and 10-6M). Conclusions: Dexamethasone-induced transcriptional regulation of the CCR3 promoter in A549 cells appears to occur in a complex dose-dependent manner, potentially involving additional mechanisms besides the established NF-κB and AP-1 transcriptional pathways. Changes in CCR3 promoter activity in response to cortisol were different from those observed for dexamethasone, and can be explained by doserelated increases in transcriptional repression. Our results have also shown that theophylline significantly represses CCR3 promoter activity in the absence of glucocorticoids, suggesting that this may be another mechanism by which theophylline exerts its pharmacological effects.peer-reviewe

Investigation into the genetic and functional relevance of the association of rS12477314 with pulmonary function

Introduction: Recent Genome-Wide Association Study (GWAS) metaanalyses have identified a number of significant association signals for pulmonary function, one of which maps to a locus (rs12477314) in an intergenic region on 2q37.3 flanked by two oppositely transcribed genes - HDAC4 and Twist2, and a lincRNA (FLJ43879). Aim: The aim of this study is to investigate the genetic and functional relevance of the association of single nucleotide polymorphism (SNP) rs12477314 with pulmonary function.peer-reviewe

Checking Whether an Automaton Is Monotonic Is NP-complete

An automaton is monotonic if its states can be arranged in a linear order that is preserved by the action of every letter. We prove that the problem of deciding whether a given automaton is monotonic is NP-complete. The same result is obtained for oriented automata, whose states can be arranged in a cyclic order. Moreover, both problems remain hard under the restriction to binary input alphabets.Comment: 13 pages, 4 figures. CIAA 2015. The final publication is available at http://link.springer.com/chapter/10.1007/978-3-319-22360-5_2

Temperature dependence, accuracy, and repeatability of T-1 and T-2 relaxation times for the ISMRM/NIST system phantom measured using MR fingerprinting

Purpose Before MR fingerprinting (MRF) can be adopted clinically, the derived quantitative values must be proven accurate and repeatable over a range of T1 and T2 values and temperatures. Correct assessment of accuracy and precision as well as comparison between measurements can only be performed when temperature is either controlled or corrected for. The purpose of this study was to investigate the temperature dependence of T1 and T2 MRF values and evaluate the accuracy and repeatability of temperature-corrected relaxation values derived from a B1-corrected MRF–fast imaging with steady-state precession implementation using 2 different dictionary sizes. Methods The International Society of MR in Medicine/National Institute of Standards and Technology phantom was scanned using an MRF sequence of 2 different lengths, a variable flip angle T1, and a multi-echo spin echo T2 at 14 temperatures ranging from 15°C to 28°C and investigated with a linear regression model. Temperature-corrected accuracy was evaluated by correlating T1 and T2 times from each MRF dictionary with reference values. Repeatability was assessed using the coefficient of variation, with measurements taken over 30 separate sessions. Results There was a statistically significant fit of the model for MRF-derived T1 and T2 and temperature (p 500 ms. Both MRF methods showed a strong linear correlation with reference values for T1 (R2 = 0.996) and T2 (R2 = 0.982). MRF repeatability for T1 values was ≤1.4% and for T2 values was ≤3.4%. Conclusion MRF demonstrated relaxation times with a temperature dependence similar to that of conventional mapping methods. Temperature-corrected T1 and T2 values from both dictionaries showed adequate accuracy and excellent repeatability in this phantom study