Production of ultracollimated bunches of multi-MeV electrons by 35 fs laser pulses propagating in exploding-foil plasmas

Very collimated bunches of high energy electrons have been produced by focusing super-intense femtosecond laser pulses in submillimeter under-dense plasmas. The density of the plasma, preformed with the laser exploding-foil technique, was mapped using Nomarski interferometry. The electron beam was fully characterized: up to 10(9) electrons per shot were accelerated, most of which in a beam of aperture below 10(-3) sterad, with energies up to 40 MeV. These measurements, which are well modeled by three-dimensional numerical simulations, validate a reliable method to generate ultrashort and ultracollimated electron bunches. (C) 2002 American Institute of Physics.

Relativistic laser interactions with preformed plasma channels and gamma-ray measurements

The propagation of a 1-ps laser pulse at intensities exceeding 10(19) Wcm(-2) in a low-density plasma channel was experimentally tested. The channel was produced by a lower intensity preceding pulse of the same duration. Plasma electrons were accelerated during the propagation of the main pulse, and high energy gamma -ray detectors were used to detect their bremsstrahlung emission. The gamma -ray yield was studied for different channel conditions, by varying the delay between the channel forming pulse and the high intensity pulse. These results are correlated with the interferograms of the propagation region into the plasma.

FASCIOLA-HEPATICA - ULTRASTRUCTURAL-CHANGES TO THE TEGUMENT OF JUVENILE FLUKES FOLLOWING INCUBATION IN-VITRO WITH THE DEACETYLATED (AMINE) METABOLITE OF DIAMPHENETHIDE

Ultrastructural changes to the tegument of 5-week-old, 3-week-old and freshly-excysted Fasciola hepatica following in vitro incubation with the deacetylated (amine) metabolite of diamphenethide (DAMD, 10 mu gml(-1)) were examined by transmission electron microscopy, A similar sequence of tegumental changes occurred in all three age groups of fluke, although, with increasing fluke age, the time before onset increased and the damage became more extensive. The 5-week-old flukes showed an initial stress response after 3 h, typified by blebbing of the apical plasma membrane, formation of microvilli and an accumulation and accelerated release of secretory bodies at the tegumental apex, as well as swelling of the basal infolds, The swelling increased in extent with progressively longer periods of incubation in DAMD, leading to extreme edema and sloughing of the tegument after 9 h. The 3-week-old flukes showed a stress response and swelling of the basal infolds after only 1.5 h, although sloughing of the tegument did not occur until after 9 h. In the freshly-excysted metacercaria, a stress response and some sloughing of the tegument were evident after only 0.5 h. At all stages of development, the ventral tegument was more severely affected than the dorsal, Changes also occurred to the tegumental cells which were indicative of a disruption in the synthesis and release of tegumental secretory bodies: the amount of GER became reduced, the cisternae became swollen and their ribosomal covering decreased, the Golgi complexes disappeared from the cells and the numbers of secretory bodies in the cells also decreased, The heterochromatin content of the nuclei increased and eventually the tegumental cells began to break down, Again, the changes became apparent more rapidly at the earlier stages of development. The ultrastructural changes to the tegument are linked to a possible mode of action for diamphenethide as an inhibitor of protein synthesis. In turn, the results may help to explain the drug's high efficacy against juvenile stages of F. hepatica.

Dominance of Radiation Pressure in Ion Acceleration with Linearly Polarized Pulses at Intensities of 10(21) W cm(-2)

A novel regime is proposed where, by employing linearly polarized laser pulses at intensities 10(21) W cm(-2) (2 orders of magnitude lower than discussed in previous work [T. Esirkepov et al., Phys. Rev. Lett. 92, 175003 (2004)]), ions are dominantly accelerated from ultrathin foils by the radiation pressure and have monoenergetic spectra. In this regime, ions accelerated from the hole-boring process quickly catch up with the ions accelerated by target normal sheath acceleration, and they then join in a single bunch, undergoing a hybrid light-sail-target normal sheath acceleration. Under an appropriate coupling condition between foil thickness, laser intensity, and pulse duration, laser radiation pressure can be dominant in this hybrid acceleration. Two-dimensional particle-in-cell simulations show that 1.26 GeV quasimonoenergetic C6+ beams are obtained by linearly polarized laser pulses at intensities of 10(21) W cm(-2).

Effects of front surface plasma expansion on proton acceleration in ultraintense laser irradiation of foil targets

The properties of beams of high energy protons accelerated during ultraintense, picosecond laser-irradiation of thin foil targets are investigated as a function of preplasma expansion at the target front surface. Significant enhancement in the maximum proton energy and laser-to-proton energy conversion efficiency is observed at optimum preplasma density gradients due, to self-focusing Of the incident laser pulse. For very long preplasma expansion, the propagating laser pulse is observed to filament, resulting in highly uniform proton beams, but with reduced flux and maximum energy.

Effect of laser intensity on fast-electron-beam divergence in solid-density plasmas

Metal foil targets were irradiated with 1 mu m wavelength (lambda) laser pulses of 5 ps duration and focused intensities (I) of up to 4x10(19) W cm(-2), giving values of both I lambda(2) and pulse duration comparable to those required for fast ignition inertial fusion. The divergence of the electrons accelerated into the target was determined from spatially resolved measurements of x-ray K-alpha emission and from transverse probing of the plasma formed on the back of the foils. Comparison of the divergence with other published data shows that it increases with I lambda(2) and is independent of pulse duration. Two-dimensional particle-in-cell simulations reproduce these results, indicating that it is a fundamental property of the laser-plasma interaction.

Scaling of proton acceleration driven by petawatt-laser-plasma interactions

The possibility of using high-power lasers to generate high-quality beams of energetic ions is attracting large global interest. The prospect of using laser-accelerated protons in medicine attracts particular interest, as these schemes may lead to compact and relatively low-cost sources. Among the challenges remaining before these sources can be used in medicine is to increase the numbers and energies of the ions accelerated. Here, we extend the energy and intensity range over which proton scaling is experimentally investigated, up to 400 J and 6 x 10(20) W cm(-2) respectively, and find a slower proton scaling than previously predicted. With the aid of plasma-expansion simulation tools, our results suggest the importance of time-dependent and multidimensional effects in predicting the maximum proton energy in this ultrahigh-intensity regime. The implications of our new understanding of proton scaling for potential medical applications are discussed.

MeV negative ion source from ultra-intense laser-matter interaction

Experimental demonstration of negative ion acceleration to MeV energies from sub-micron size droplets of water spray irradiated by ultra-intense laser pulses is presented. Thanks to the specific target configuration and laser parameters, more than 109 negative ions per steradian solid angle in 5% energy bandwidth are accelerated in a stable and reliable manner. To our knowledge, by virtue of the ultra-short duration of the emission, this is by far the brightest negative ion source reported. The data also indicate the existence of beams of neutrals with at least similar numbers and energies.

Selective block in erythropoietin-induced differentiation of growth factor-independent retrovirally-infected TF-1 cells

The erythroleukaemic cell line TF-1, infected with either the pBabe neo retrovirus or the retrovirus bearing the human erythropoietin (hEpo) gene, developed three growth factor-independent clones. Erythropoietin (Epo), interleukin-3 (IL-3) and granulocyte-macrophage colony stimulating factor (GM-CSF) accelerated the proliferation of these clones. Autonomous growth of the clones was independent of Epo because it was not altered by Epo anti-sense oligonucleotides, nor was Epo detectable in culture supernatants. Cells from the mutant clones could not be induced by Epo to express glycophorin A and haemoglobin synthesis was markedly reduced. Haemin reversed the block in Epo-induced haemoglobin synthesis. Acquisition of growth factor-independence appears to be linked with the selective loss of differentiation capacity. These cells may provide a useful model for the study of the mechanisms involved in leukaemic transformation.

A probabilistic modelling scheme for analysis of long-term failure of cemented femoral joint replacements

Reliable prediction of long-term medical device performance using computer simulation requires consideration of variability in surgical procedure, as well as patient-specific factors. However, even deterministic simulation of long-term failure processes for such devices is time and resource consuming so that including variability can lead to excessive time to achieve useful predictions. This study investigates the use of an accelerated probabilistic framework for predicting the likely performance envelope of a device and applies it to femoral prosthesis loosening in cemented hip arthroplasty.
A creep and fatigue damage failure model for bone cement, in conjunction with an interfacial fatigue model for the implant–cement interface, was used to simulate loosening of a prosthesis within a cement mantle. A deterministic set of trial simulations was used to account for variability of a set of surgical and patient factors, and a response surface method was used to perform and accelerate a Monte Carlo simulation to achieve an estimate of the likely range of prosthesis loosening. The proposed framework was used to conceptually investigate the influence of prosthesis selection and surgical placement on prosthesis migration.
Results demonstrate that the response surface method is capable of dramatically reducing the time to achieve convergence in mean and variance of predicted response variables. A critical requirement for realistic predictions is the size and quality of the initial training dataset used to generate the response surface and further work is required to determine the recommendations for a minimum number of initial trials. Results of this conceptual application predicted that loosening was sensitive to the implant size and femoral width. Furthermore, different rankings of implant performance were predicted when only individual simulations (e.g. an average condition) were used to rank implants, compared with when stochastic simulations were used. In conclusion, the proposed framework provides a viable approach to predicting realistic ranges of loosening behaviour for orthopaedic implants in reduced timeframes compared with conventional Monte Carlo simulations.

Activation of extracellular signal-regulated kinase in proliferative glomerulonephritis in rats

Multiple extracellular mitogens are involved in the pathogenesis of proliferative forms of glomerulonephritis (GN), In vitro studies demonstrate the pivotal role of extracellular signal-regulated kinase (ERK) in the regulation of cellular proliferation in response to extracellular mitogens. In this study, we examined whether this kinase, as a convergence point of mitogenic stimuli, is activated in proliferative GN in vivo, Two different proliferative forms of anti-glomerular basal membrane (GEM) GN in rats were induced and whole cortical tissue as well as isolated glomeruli examined using kinase activity assays and Western blot analysis, Administration of rabbit anti-rat GEM serum to rats, preimmunized with rabbit IgG, induced an accelerated crescentic anti-GEM GN. A significant increase in cortical, and more dramatically glomerular ERK activity was detected at 1, 3, and 7 d after induction of GN, Immunization of Wistar-Kyoto rats with bovine GEM also induced a crescentic anti-GBM GN with an increase of renal cortical ERK activity after 4, 6, and 8 wk, ERK is phosphorylated and activated by the MAP kinase/ERK kinase (MEK), We detected a significant increase in the expression of glomerular MEK in the accelerated form of anti-GEM CN, providing a possible mechanism of long-term activation of ERK in this disease model, In contrast to ERK, activation of stress-activated protein kinase was only detectable at early stages of proliferative GN, indicating these related kinases to serve distinct roles in the pathogenesis of GN, Our observations point to ERK as a putative mediator of the proliferative response to immune injury in GN and suggest that upregulation of MEK is involved in the long-term regulation of ERK in vivo.

An efficient particle filter for color-based tracking in complex scenes

In this paper, we introduce an efficient method for particle selection in tracking objects in complex scenes. Firstly, we improve the proposal distribution function of the tracking algorithm, including current observation, reducing the cost of evaluating particles with a very low likelihood. In addition, we use a partitioned sampling approach to decompose the dynamic state in several stages. It enables to deal with high-dimensional states without an excessive computational cost. To represent the color distribution, the appearance of the tracked object is modelled by sampled pixels. Based on this representation, the probability of any observation is estimated using non-parametric techniques in color space. As a result, we obtain a Probability color Density Image (PDI) where each pixel points its membership to the target color model. In this way, the evaluation of all particles is accelerated by computing the likelihood p(z|x) using the Integral Image of the PDI.

Tobramycin Inhalation Powder™:a novel drug delivery system for treating chronic Pseudomonas aeruginosa infection in cystic fibrosis

Lung disease in cystic fibrosis (CF) is typified by the development of chronic airways infection culminating in bronchiectasis and progression to end-stage respiratory disease. Pseudomonas aeruginosa, a ubiquitous gram-negative bacteria, is the archetypical CF pathogen and is associated with an accelerated clinical decline. The development and widespread use of chronic suppressive aerosolized antibacterial therapies, in particular Tobramycin Inhalation Solution (TIS), in CF has contributed to reduced lung function decline and improved survival. However, the requirement for the aerosolization of these agents through nebulizers has been associated with increased treatment burden, reduced quality of life and remain a barrier to broader uptake. Tobramycin Inhalation Powder (TIP™) has been developed by Novartis with the express purpose of delivering the same benefits as TIS in a time-effective manner. Administered via the T-326™ (Novartis) Inhaler in four individual 28-mg capsules, TIP can be administered in a quarter of the time of traditional nebulizers and is inherently portable. In clinical studies, TIP has been shown to be safe, result in equivalent or superior reductions in P. aeruginosa sputum density and produce similar improvements in pulmonary function. TIP offers significant advantages in time saving, portability and convenience over traditional nebulized TIS with comparable clinical outcomes for individuals with CF.

Ethanol (C2H5OH) spray of sub-micron droplets for laser driven negative ion source

Liquid ethanol (C₂H₅OH) was used to generate a spray of sub-micron droplets. Sprays with different nozzle geometries have been tested and characterised using Mie scattering to find scaling properties and to generate droplets with different diameters within the spray. Nozzles having throat diameters of 470 µm and 560 µm showed generation of ethanol spray with droplet diameters of (180 ± 10) nm and (140 ± 10) nm, respectively. These investigations were motivated by the observation of copious negative ions from these target systems, e.g., negative oxygen and carbon ions measured from water and ethanol sprays irradiated with ultra-intense (5 × 1019 W/cm2), ultra short (40 fs) laser pulses. It is shown that the droplet diameter and the average atomic density of the spray have a significant effect on the numbers and energies of accelerated ions, both positive and negative. These targets open new possibilities for the creation of efficient and compact sources of different negative ion species.

Generation of a quasi-monoergetic proton beam from laser-irradiated sub-micron droplets

Proton bursts with a narrow spectrum at an energy of (2.8 +/- 0.3 MeV) are accelerated from sub-micron water spray droplets irradiated by high-intensity (similar to 5 x 10(19)W/cm(2)), high-contrast (similar to 10(10)), ultra-short (40 fs) laser pulses. The acceleration is preferentially in the laser propagation direction. The explosion dynamics is governed by a residual ps-scale laser pulse pedestal which "mildly" preheats the droplet and changes its density profile before the arrival of the high intensity laser pulse peak. As a result, the energetic electrons extracted from the modified target by the high-intensity part of the laser pulse establish an anisotropic electrostatic field which results in anisotropic Coulomb explosion and proton acceleration predominantly in the forward direction. Hydrodynamic simulations of the target pre-expansion and 3D particle-in-cell simulations of the measured energy and anisotropy of the proton emission have confirmed the proposed acceleration scenario. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4731712]