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Fusion fast ignition (FI) initiated by a laser-driven particle beam promises a path to high-yield and high-gain for inertial fusion energy. FI can readily leverage the proven capability of inertial confinement fusion (ICF) drivers, such as the National Ignition Facility, to assemble DT fusion fuel at the relevant high densities. FI provides a truly alternate route to ignition, independent of the difficulties with achieving the ignition hot spot in conventional ICF. FI by laser-driven ion beams provides attractive alternatives that sidestep the present difficulties with laser-driven electron-beam FI, while leveraging the extensive recent progress in generating ion beams with high-power density on existing laser facilities. Whichever the ion species, the ignition requirements are similar: delivering a power density ≈1022 W cm−3 (∼10 kJ in ≈20 ps within a volume of linear dimension ≈20 µm), to the DT fuel compressed to ∼400 g cm−3 with areal density ∼2 g cm−2. High-current, laser-driven beams of many ion species are promising candidates to deliver such high-power densities. The reason is that high energy, high-power laser drivers can deliver high-power fluxes that can efficiently make ion beams that are born neutralized in ∼fs–ps timescales, making them immune to the charge and current limits of conventional beams. In summary, we find that there are many possible paths to success with FI based on laser-driven ion beams. Although many ion species could be used for ignition, we concentrate here on either protons or C ions, which are technologically convenient species. We review the work to date on FI design studies with those species. We also review the tremendous recent progress in discovering, characterizing and developing many ion-acceleration mechanisms relevant to FI. We also summarize key recent technological advances and methods underwriting that progress. Based on the design studies and on the increased understanding of the physics of laser-driven ion acceleration, we provide laser and ion-generation laser-target design points based on several distinct ion-acceleration mechanisms.

Yeast TAF90p is a component of at least two transcription regulatory complexes, the general transcription factor TFIID and the Spt-Ada-Gcn5 histone acetyltransferase complex (SAGA). Broad transcription defects have been observed in mutants of other TAF(II)s shared by TFIID and SAGA but not in the only two TAF90 mutants isolated to date. Given that the numbers of mutants analyzed thus far are small, we isolated and characterized 11 temperature-sensitive mutants of TAF90 and analyzed their effects on transcription and integrity of the TFIID and SAGA complexes. We found that the mutants displayed a variety of allele-specific defects in their ability to support transcription and maintain the structure of the TFIID and SAGA complexes. Sequencing of the alleles revealed that all have mutations corresponding to the C terminus of the protein, with most clustering within the conserved WD40 repeats; thus, the C terminus of TAF90p is required for its incorporation into TFIID and function in SAGA. Significantly, inactivation of one allele, taf90-20, caused the dramatic reduction in the levels of total mRNA and most specific transcripts analyzed. Analysis of the structure and/or activity of both TAF90p-containing complexes revealed that this allele is the most disruptive of all. Our analysis defines the requirement for the WD40 repeats in preserving TFIID and SAGA function, demonstrates that the defects associated with distinct mutations in TAF90 vary considerably, and indicates that TAF90 can be classified as a gene required for the transcription of a large number of genes.

The direct simulation Monte Carlo method of modeling fluids requires sampling one or more random variables every time step for each particle. In this paper a "quiet Monte Carlo" technique is proposed that eliminates the random sampling and the noise it produces by deterministically generating a small number of computational particles. The technique is applied to particle equations of motion appropriate for modeling an Eulerian fluid. Results indicate that strong one- and two-dimensional shocks with large dynamic ranges are accurately represented with only a few particles per cell.

Four different methods for methylating conjugated linoleic acid (CLA) were compared. The HCl/MeOH and BF3/MeOH methods were tested under different time and temperature combinations. Increasing temperature and/or incubation time for either method decreased the cis-9,trans-11 and trans-10,cis-12 isomers, but trans-9,trans-11/trans-10,trans-12 isomers and artifacts (allylic methoxide) were increased. In addition, the triacylglyceride form of CLA was tested using the above methods and NaOMe at various temperatures for 20 min. The NaOMe did not generate methoxy artifacts. However, there were impurities in GC after methylation with NaOMe as well as with BF3/MeOH. The (trimethylsilyl)diazomethane method, which is a mild and easy alternative, was tested. Free forms of fatty acids were easily, but not completely, methylated by this method. Also, the method generated artifacts (trimethylsilyl CLA esters) and impurities (trimethylsilyl) that would interfere with short-chain fatty-acid analysis by GC. Keywords: Conju...

This is the first report of the isolation and characterization of a fish virus from the Philippines. The virus was isolated using snakehead spleen cells (SHS) from severely lesioned epizootic ulcerative syndrome (EUS)-affected snakehead Ophicephalus striatus from Laguna de Bay, in January 1991. The virus induced cytopathic effects (CPE) in SHS cells yielding a titer of 3.02 x 10(6) TCID50 ml(-1) at 25 degrees C within 2 to 3 d. Other susceptible cell lines included bluegill fry (BF-2), catfish spleen (CFS) and channel catfish ovary (CCO) cells. Replication in chinook salmon embryo cells (CHSE-214) was minimal while Epithelioma papulosum cyprini cells (EPC) and rainbow trout gonad cells (RTG-2) were refractory. Temperatures of 15 to 25 degrees C were optimum for virus replication but the virus did not replicate at 37 degrees C. The virus can be stored at -10 and 8 degrees C for 30 and 10 d, respectively, without significant loss of infectivity. Viral replication was logarithmic with a 2 h lag phase; viral assembly in the host cells occurred in 4 h and release of virus occurred 8 h after viral infection. A 1-log difference in TCID50 titer between the cell-free virus and the total virus was noted. Freezing and thawing the virus caused a half-log drop in titer. Viral exposure to chloroform or heating to 56 degrees C for 30 min inactivated the virus. Exposure to pH 3 medium for 30 min resulted in a more than 100-fold loss of viral infectivity. The 5-iododeoxyuridine (IUdR) did not affect virus replication, indicating a RNA genome. Neutralization tests using the Philippine virus, the ulcerative disease rhabdovirus (UDRV) and the infectious hematopoietic necrosis virus (IHNV) polyvalent antisera showed slight cross-reaction between the Philippine virus antiserum and UDRV but established no serological relationship with SHRV and IHN virus. Transmission electron microscopy (TEM) of SHS cells infected with the virus showed virus particles with typical bullet morphology and an estimated size of 65 x 175 nm. The Philippine virus was therefore a rhabdovirus, but the present study did not establish its role in the epizootiology of EUS.

Two experiments were conducted to determine the conjugated linoleic acid (CLA) content of milk from cows offered diets rich in linoleic and linolenic acid. In experiment 1, 36 cows were assigned to a control and five treatment groups. Cows in the control group received a diet containing 51% forage and 49% grain on a dry matter basis. In the treatment group, grain was partly replaced by either 18% raw cracked soybeans, 18% roasted cracked soybeans, 3.6% soybean oil, 2.2% linseed oil, or 4.4% linseed oil. Experimental diets were fed for 5 wk. Average CLA contents in milk fat from wk 2 through 5 were 0.39% in control and 0.37, 0.77, 2.10, 1.58, and 1.63% of total fatty acids in the raw soybean, roasted soybeans, soybean oil, 2.2% linseed oil, and 4.4% linseed oil treatments, respectively. In experiment 2, 36 cows were assigned to a control and 5 treatment groups. Cows in the control group received a diet containing 55% forage and 45% grain. In the treatment groups, grain was partly replaced by soybean oil at 0.5, 1.0, 2.0, 4.0, or by linseed oil at 1.0% of the dietary dry matter. Experimental diets were fed for 5 wk. Average CLA contents in milk fat from wk 2 through 5 were 0.50% in control and 0.75, 0.76, 1.45, 2.08, and 0.73% of total fatty acids in 0.5, 1.0, 2.0, 4.0 soybean oil and 1.0% linseed oil treatments, respectively. Diets rich in linoleic or linolenic acid can increase CLA content of milk when dietary oil is accessible to the rumen microorganisms.

Adults, preadults, and chalimus larvae of Lepeophtheirus cuneifer were recovered from rainbow trout, Oncorhynchus mykiss, and Atlantic salmon, Salmo salar, cultured in seawater in the southern Strait of Georgia, British Columbia. This species has not been reported previously from these hosts or in Canadian waters. It was found only in low abundance and is not an economically important parasite of farmed salmonids in British Columbia.

To evaluate the association between smoking and the occurrence of low-grade cervical cytological abnormalities.We conducted a population-based cross-sectional study of smoking and other exposures in reproductive-age women with normal and abnormal cytology results (Class 1-4 Pap tests). Participants (n = 2,448) were enrollees of the Group Health Cooperative of Puget Sound, a health maintenance organization (HMO) in Washington state, USA. Non-pregnant women were selected monthly from the HMO's cytology database during 1995-6, with over-sampling of women with low-grade abnormalities. All participants completed a structured telephone-administered survey.Of the 2,448 participants, 19% (n = 465) had Class 2 Pap results, and 5% (n = 117) had Class 3-4 results. Forty percent of the sample (n = 975) reported ever smoking. Women reporting current/recent smoking (n = 514, 21%) had an increased likelihood of cervical abnormalities (adjusted odds ratio (OR) 1.4, 95% confidence interval (CI 1.1-1.8). Women who had never smoked but who reported recent passive smoking exposure also had a greater likelihood of abnormal test results (OR 1.4, 95% CI 1.0-2.0). Prior smoking was not associated with cytology status.Our results, examining low-grade cervical abnormalities, are compatible with those from studies of more severe cervical lesions, lending added support to the hypothesis that smoking predisposes to development of a spectrum of cervical abnormalities. Thus, even cytologic screening visits represent an opportunity to counsel women smokers about their health risks, particularly the more proximal risks of cervical abnormalities and cancer.

We investigated the effects of conjugated linoleic acid (CLA) preparations, which were enriched for the cis-9,trans-11 CLA isomer or the trans-10,cis-12 CLA isomer, on body composition in mice. Body composition changes (reduced body fat, enhanced body water, enhanced body protein, and enhanced body ash) were associated with feeding the trans-10,cis-12 CLA isomer. In cultured 3T3-L1 adipocytes, the trans-10,cis-12 isomer reduced lipoprotein lipase activity, intracellular triacylglycerol and glycerol, and enhanced glycerol release into the medium. By contrast, the cis-9,trans-11 and trans-9,trans-11 CLA isomers did not affect these biochemical activities. We conclude that CLA-associated body composition change results from feeding the trans-10,cis-12 isomer.

Recent innovations in large-scale 3-D kinetic simulations along with advanced visualization techniques are facilitating new scientific discoveries into the basic physics of collisionless magnetic reconnection. Present supercomputers are now fully capable of exploring the dynamics of large-scale electron-positron plasmas, whereas the next generation will extend this capability to allow first-principle simulations of magnetic reconnection in electron-proton plasmas.

Intrastromal injection of mice with antigens from the parasitic helminth that causes river blindness (Onchocerca volvulus) induces eosinophil recruitment to the corneal stroma at the time of maximum corneal opacification and neovascularization. The present study was conducted to examine the role of eosinophils and neutrophils in onchocercal keratitis in control C57Bl/6 mice and in interleukin-5 gene knockout (IL-5(-/-)) mice.C57Bl/6 and IL-5(-/-) mice were immunized subcutaneously and injected intrastromally with soluble O. volvulus antigens. Mice were killed at various times thereafter. Development of keratitis was assessed by slit lamp examination, and inflammatory cells in the cornea were identified by immunohistochemistry.A biphasic recruitment of inflammatory cells was observed in C57Bl/6 mice; neutrophils predominated during the first 72 hours after intrastromal injection and subsequently declined, whereas eosinophil recruitment increased as time elapsed and comprised the majority (90%) of cells in the cornea by day 7. In contrast, neutrophils were the predominant inflammatory cells in IL-5(-/-) mice at early and late time points and were associated with extensive stromal damage and corneal opacification and neovascularization. Eosinophils were not detected in these mice at any time.In the absence of eosinophils, neutrophils can mediate keratitis induced by helminth antigens. Together with the early neutrophilic infiltrate in control animals, these observations indicate that neutrophils have an important role in onchocercal keratitis.

The ultimate fate of the expanded pool of osteoblasts formed following a typical bone injury is unclear. Since necrosis has not been described in the latter stages of bone healing, there must be some other mechanism by which obsolete osteoblasts are cleared from an injury site. We therefore evaluated the possibility that their removal is pre-programmed, by investigating the occurrence of apoptosis in rats that received a standardized bone injury. Histological evidence identical to that found in tissues known to exhibit apoptosis was obtained, thereby showing that programmed cell death was a normal concomitant of fracture healing. The concentration of apoptotic bodies reached its maximum after the differentiative response had peaked, suggesting that the two processes were coordinated. The same result was found in a second group of rats that received the same bone injury plus a simultaneous standardized soft-tissue injury. The combined injuries resulted in more osteoblasts and more apoptotic bodies, but an identical temporal relationship between the peak responses in the two parameters. The results suggested that osteoblasts were removed from the injury site via apoptosis, and that the process was coordinately regulated with differentiation. Since the number of apoptotic bodies per osteoblast varied during healing, it is likely that apoptosis was associated with healing and not merely with osteoblast concentration.

Recent work by Molvig et al. [Phys. Rev. Lett. 109, 095001 (2012)] examined how fusion reactivity may be reduced from losses of fast ions in finite assemblies of fuel. In this paper, this problem is revisited with the addition of an asymptotic boundary-layer treatment of ion kinetic losses. This boundary solution, reminiscent of the classical Milne problem from linear transport theory, obtains a free-streaming limit of fast ion losses near the boundary, where the diffusion approximation is invalid. Thermonuclear reaction rates have been obtained for the ion distribution functions predicted by this improved model. It is found that while Molvig's “Knudsen distribution function” bounds from above the magnitude of the reactivity reduction, this more accurate treatment leads to less dramatic losses of tail ions and associated reduction of thermonuclear reaction rates for finite fuel volumes.

The proper selection of a wheelchair requires making several critical decisions, not the least of which is what type of wheelchair is appropriate. The International Organization for Standards (ISO) continues to develop and refine wheelchair standards. Standards allow the objective comparison of products from various sources, permitting consumers or clinicians to assess wheelchairs with which they are not familiar by comparing test results. This study consisted of three components: 1) the comparison of fatigue test results with a planar ANSI/RESNA test dummy to a HERL contoured test dummy; 2) the comparison of fatigue test results for common depot versus common rehabilitation manual wheelchairs; and 3) the comparison of fatigue test results for manual rehabilitation wheelchairs with solid 8-inch casters versus those with pneumatic 8-inch casters. Rehabilitation wheelchairs lasted on average 13.2 times longer than the depot wheelchairs. Both types, tested with the standard ISO-ANSI/RESNA dummy, lasted on average 2.1 times longer than those wheelchairs tested using the contoured dummy. The three rehabilitation wheelchairs equipped with 8-inch pneumatic casters lasted on average 3.2 times longer than the 6 rehabilitation wheelchairs equipped with solid 8-inch casters. The depot wheelchairs cost about 3.4 times as much to operate per cycle or per meter than the rehabilitation wheelchairs. The rehabilitation wheelchairs tended to experience component failures, while the depot wheelchairs tended to experience frame failures. Our testing indicates that the tests in the ISO-ANSI/RESNA standards can relate design features to fatigue test results and durability. Rehabilitation wheelchairs tend to use higher quality materials and better manufacturing practices, and they provide greater mobility for wheelchair users. Purchasers and prescribers of wheelchairs should consider the life-cycle cost and not just the purchase price for wheelchairs.

Nonlinear physics governing the kinetic behavior of stimulated Raman scattering (SRS) in multi-speckled laser beams has been identified in the trapping regime over a wide range of kλD values (here k is the wave number of the electron plasma waves and λD is the Debye length) in homogeneous and inhomogeneous plasmas. Hot electrons from intense speckles, both forward and side-loss hot electrons produced during SRS daughter electron plasma wave bowing and filamentation, seed and enhance the growth of SRS in neighboring speckles by reducing Landau damping. Trapping-enhanced speckle interaction through transport of hot electrons, backscatter, and sidescatter SRS light waves enable the system of speckles to self-organize and exhibit coherent, sub-ps SRS bursts with more than 100% instantaneous reflectivity, resulting in an SRS transverse coherence width much larger than a speckle width and a SRS spectrum that peaks outside the incident laser cone. SRS reflectivity is found to saturate above a threshold laser intensity at a level of reflectivity that depends on kλD: higher kλD leads to lower SRS and the reflectivity scales as ∼(kλD)−4. As kλD and Landau damping increase, speckle interaction via sidescattered light and side-loss hot electrons decreases and the occurrence of self-organized events becomes infrequent, leading to the reduction of time-averaged SRS reflectivity. It is found that the inclusion of a moderately strong magnetic field in the laser direction can effectively control SRS by suppressing transverse speckle interaction via hot electron transport.

The range of a power wheelchair depends on many factors including: battery type, battery state, wheelchair/rider weight, terrain, the efficiency of the drive train, and driving behavior. The purpose of this study was to evaluate the feasibility of three methods of estimating power wheelchair range. Another significant purpose was to compare the current draw on pavement to current draw on an International Standards Organization (ISO) Double Drum tester at one m/sec. Tests were performed on seven different power wheelchairs unloaded, and loaded with an ISO 100 kg test dummy. Each chair was configured according to the manufacturer's specifications, and tires were properly inflated. Experienced test technicians were used for the tennis court tests, and treadmill tests. An ISO 100 kg test dummy was used for the ISO Double Drum test. Energy consumption was measured over a distance of 1500 m for each of the three test conditions. The rolling surface was level in all cases. Repeated measure analysis of variance (ANOVA) revealed a significant difference (p = 0.0001) between the predicted range at maximum speed for the three tests. Post hoc analysis demonstrated a significant difference (p0.01) in estimated range at maximum speed between the Double Drum test and the treadmill test, as well as between the Double Drum test and the tennis court test. Our results indicate no significant difference (p0.05) between the predicted range at maximal speed between the treadmill and tennis court tests. A simple relationship does not exist between the results of range testing with the Double Drum tester and the tennis court. An alternative would be to permit the use of a treadmill for range testing as simple relationships between all pertinent treadmill and tennis court range data were found. For the Double Drum tester used, the current demand is higher than under normal usage. This presents a problem as current is related to load torque in a power wheelchair. Hence, the Double Drum tester friction must be reduced. The predicted range for the tennis court test at maximum speed ranges from a low of 23.6 km to a high of 57.7 km. The range of the power wheelchair can be improved by the use of wet lead acid batteries in place of gel lead acid batteries.

Dynamic measurements are a required part of any fatigue test. Two frequently measured parameters are applied load and testpiece strain. Load cells and extensometers are frequently used to make those measurements, respectively. Detailed standards for static calibrations of these devices have been available for many years. These standards provide a method for calibrating a transducer, with traceability to national and international standards.

In inertial confinement fusion experiments, stimulated Raman scattering (SRS) occurs when electron density fluctuations are amplified resonantly by the incident laser beams and scattered light. These beams comprise several thousands of individual laser speckles. We have found in single-speckle studies that electron trapping lowers the threshold intensity for SRS onset to a value below that from linear theory and enhances scattering. The trapping-induced plasma-wave frequency shift leads to wave-front bowing and filamentation processes that saturate SRS and limit scattering within a speckle. With large-scale simulations, we have now examined how laser speckles interact with one another through three-dimensional (3D) particle-in-cell (PIC) simulations of two interacting speckles and 2D PIC simulations of ensembles of laser speckles (hundreds of speckles). Our work shows that kinetic trapping physics also governs the onset and saturation of SRS in ensembles of speckles. Speckles interact in a manner that is ...

We studied the effect of conjugated linoleic acid (CLA) on rat development and growth. Primigravid female Fischer rats were fed control or CLA-supplemented (0.25% or 0.5% CLA) diets during gestation and/or lactation. Conjugated linoleic acid was incorporated into milk fat and tissue lipids proportional to the level of CLA fed and the duration of CLA feeding. Conjugated linoleic acid was incorporated into fetal and neonatal tissues; it did not affect litter size nor induce apparent abnormalities. To the contrary, feeding CLA to the dams during gestation and lactation improved the postnatal body weight gain of pups (P0.05), measured on d 10 of lactation. Pups that continued to receive the CLA-supplemented diet after weaning had significantly greater body weight gain and improved feed efficiency relative to control animals (P0.05).

Research on fusion fast ignition (FI) initiated by laser-driven ion beams has made substantial progress in the last years. Compared with electrons, FI based on a beam of quasi-monoenergetic ions has the advantage of a more localized energy deposition, and stiffer particle transport, bringing the required total beam energy close to the theoretical minimum. Due to short pulse laser drive, the ion beam can easily deliver the 200 TW power required to ignite the compressed D–T fuel. In integrated calculations we recently simulated ion-based FI targets with high fusion gain targets and a proof of principle experiment [1]. These simulations identify three key requirements for the success of ion-driven fast ignition (IFI): (1) the generation of a sufficiently high-energetic ion beam (≈400–500 MeV for C), with (2) less than 20% energy spread at (3) more than 10% conversion efficiency of laser to beam energy. Here we present for the first time new experimental results, demonstrating all three parameters in separate experiments. Using diamond nanotargets and ultrahigh contrast laser pulses we were able to demonstrate >500 MeV carbon ions, as well as carbon pulses with ΔE/E < 20%. The first measurements put the total conversion efficiency of laser light into high energy carbon ions on the order of 10%.

Kinetic simulations of break-out-afterburner (BOA) ion acceleration from nm-scale targets are examined in a longer pulse length regime than studied previously. It is shown that when the target becomes relativistically transparent to the laser, an epoch of dramatic acceleration of ions occurs that lasts until the electron density in the expanding target reduces to the critical density in the non-relativistic limit. For given laser parameters, the optimal target thickness yielding the highest maximum ion energy is one in which this time window for ion acceleration overlaps with the intensity peak of the laser pulse. A simple analytic model of relativistically induced transparency is presented for plasma expansion at the time-evolving sound speed, from which these times may be estimated. The maximum ion energy attainable is controlled by the finite acceleration volume and time over which the BOA acts.

A double-foil target is proposed for laser ion acceleration with thin targets to take advantage of high efficiency of such targets while avoiding beam degradation in late stage of acceleration. Laser heating of electrons co-moving with the ion beam is stopped by the second foil. It is found that the second foil can also modify and substantially improve the spectral and spatial properties of the ion beam and reduce the temperature of the co-moving electrons, leading to better preservation of the beam quality. Details of the dynamics are studied with particle-in-cell simulations.

In recent experiments at the Trident laser facility, quasi-monoenergetic ion beams have been obtained from the interaction of an ultraintense, circularly polarized laser with a diamond-like carbon target of nm-scale thickness under conditions of ultrahigh laser pulse contrast. Kinetic simulations of this experiment under realistic laser and plasma conditions show that relativistic transparency occurs before significant radiation pressure acceleration and that the main ion acceleration occurs after the onset of relativistic transparency. Associated with this transition are a period of intense ion acceleration and the generation of a new class of ion solitons that naturally give rise to quasi-monoenergetic ion beams. An analytic theory has been derived for the properties of these solitons that reproduces the behavior observed in kinetic simulations and the experiments.

A novel ion wide angle spectrometer (iWASP) has been developed, which is capable of measuring angularly resolved energy distributions of protons and a second ion species, such as carbon C(6 +), simultaneously. The energy resolution for protons and carbon ions is better than 10% at ∼50 MeV/nucleon and thus suitable for the study of novel laser-ion acceleration schemes aiming for ultrahigh particle energies. A wedged magnet design enables an acceptance angle of 30°(∼524 mrad) and high angular accuracy in the μrad range. First, results obtained at the LANL Trident laser facility are presented demonstrating high energy and angular resolution of this novel iWASP.

The influence of binary Coulomb collisions on trapped particle nonlinearities related to stimulated Raman scatter (SRS) in a single laser speckle is examined using one-dimensional particle-in-cell simulations. Binary Coulomb collisions are incorporated using a numerical particle-pairing algorithm that reproduces a collision integral of the Landau form. The onset of nonlinearly enhanced levels of SRS reflectivity is shown to coincide with electron trapping in the daughter plasma wave and is sensitive to the collisional scattering rate. Relaxation of trapping-induced perturbations to the electron velocity distribution via collisional velocity space diffusion is predicted to have the largest effect on the onset of SRS when the amplitude of the daughter plasma wave is smallest, and trapping-induced perturbations to the electron velocity distribution function are also small. In the absence of higher dimensional detrapping mechanisms (e.g., electron side-loss), it is shown that the onset threshold for enhanced ...

Here, we report on the development of a novel high resolution and high dispersion Thomson parabola for simultaneously resolving protons and low-Z ions of more than 100 MeV/nucleon necessary to explore novel laser ion acceleration schemes. High electric and magnetic fields enable energy resolutions of ΔE/E < 5% at 100 MeV/nucleon and impede premature merging of different ion species at low energies on the detector plane. First results from laser driven ion acceleration experiments performed at the Trident Laser Facility demonstrate high resolution and superior species and charge state separation of this novel Thomson parabola for ion energies of more than 30 MeV/nucleon.

Densitometric analysis of images obtained by digital subtraction angiography (DSA) allows for more reproducible and less operator-dependent quantitation of ventricular function. Conventional DSA uses temporal subtraction but is limited by misregistration artifacts. Dual-energy digital subtraction angiography (DE-DSA) is immune to such misregistration artifacts. The ability of DE-DSA to quantitate changes in regional ventricular volume resulting from ischemia was tested. Densitometric analysis of both phase-matched and ejection fraction DE-DSA images was used to quantitate regional left ventricular systolic function during four levels of ischemia ranging from mild to severe in open-chest dogs (n = 10). DE-DSA left ventriculograms were obtained by means of central venous injections of iodinated contrast medium. Ischemia was graded according to percentage of systolic wall thickening as measured by sonomicrometry. Phase-matched end-systolic images were obtained at each of four levels of ischemia by subtracting an end-systolic control image from each end-systolic ischemic image. Ejection fraction images were obtained at the control level and at each level of ischemia by subtracting an end-systolic image from an end-diastolic image of the same cardiac cycle. The resulting wall motion difference signals represent the changes in regional ventricular volumes and were quantitated by densitometry. Densitometry was able to detect the effect of all levels of ischemia on regional function, even the mildest. Densitometric analysis of both phase-matched and ejection fraction DE-DSA images provides a sensitive technique for detecting and quantitating the changes in regional left ventricular systolic volume that occur with ischemia.

A simple model has been derived for expansion of a thin (up to 100s of nm thickness) target initially of solid density irradiated by an ultraintense laser. In this regime, ion acceleration mechanisms, such as the Break-Out Afterburner (BOA) [1], emerge with the potential for dramatically improved energy, efficiency, and energy spread. Ion beams have been proposed [2] as drivers for fast ignition inertial confinement fusion [3]. Analysis of kinetic simulations of the BOA shows the period of enhanced acceleration occurs between times t1, when the target becomes relativistically transparent to the laser, and t2, when the target becomes classically underdense and the enhanced acceleration terminates. A simple model for target expansion has been derived that contains early, one-dimensional (1D) expansion of the target and three-dimensional (3D) expansion at late times. The model assumes expansion is slab-like at the instantaneous ion sound speed and requires as input target composition, laser intensity, laser spot area, and the efficiency of laser absorption into electron thermal energy.

The influence of Coulomb collisions on the dynamics of driven magnetic reconnection in geometry mimicking the Magnetic Reconnection eXperiment (MRX) [M. Yamada et al., Phys. Plasmas 4, 1936 (1997)] is investigated using two-dimensional (2D) fully kinetic simulations with a Monte Carlo treatment of the collision operator. For values of collisionality typical of MRX, the reconnection mechanism is shown to be a combination of collisionless effects, represented by off-diagonal terms in the electron stress tensor, and collisional momentum exchange between electrons and ions. The ratio of the reconnection electric field ER to the critical runaway field Ecrit provides a convenient measure of the relative importance of these two mechanisms. The structure of electron-scale reconnection layers in the presence of collisions is investigated in light of the previously reported [S. Dorfman et al., Phys. Plasmas 15, 102107 (2008)] discrepancy in the width of the electron reconnection layers between collisionless simulat...

Fully electromagnetic particle in cell simulations of nonlinear waves propagation and interaction are performed in two-dimensional plane geometry in magnetized plasma in ion cyclotron frequency range. A spectrum of fast magnetosonic wave modes with wave numbers parallel and perpendicular to the uniform equilibrium magnetic field is launched into plasma and the nonlinear dynamics of these waves is analyzed. Results show that the wave magnetic energy spectrum cascades to smaller scales. In the low frequency in the magnetohydrodynamic regime, the cascade is basically isotropic. Once entering the high frequency kinetic regime the cascade exhibits strong anisotropy, it extends to much smaller scales in direction perpendicular to the equilibrium magnetic field. The shape of the cascade is established after a few ion cyclotron periods and most of the energy in the cascade stays in the fast wave oscillations. Collisionless damping on electrons is the main dissipation channel in these results.

The influence of Coulomb collisions on the structure of reconnection layers is examined in neutral sheet geometry using fully kinetic simulations with a Monte Carlo treatment of the Fokker–Planck operator. The algorithm is first carefully benchmarked against key predictions from transport theory, including the parallel and perpendicular resistivities as well as the thermal force. The results demonstrate that the collisionality is accurately specified, thus allowing the initial Lundquist number to be chosen as desired. For modest Lundquist numbers S≲1000, the classic Sweet–Parker solution is recovered. Furthermore, a distinct transition to a faster kinetic regime is observed when the thickness of the resistive layer δSP falls below the ion inertial length di. For higher Lundquist numbers S≳1000, plasmoids (secondary islands) are observed within the elongated resistive layers. These plasmoids give rise to a measurable increase in the reconnection rate and for certain cases induce a transition to kinetic reg...

VPIC [1], a first-principles 3d electromagnetic charge-conserving relativistic kinetic particle-in-cell code, was recently adapted to run on Los Alamos's Roadrunner [2], the first supercomputer to break a petaflop (1015 floating point operations per second) in the TOP500 supercomputer performance rankings. [3] We summarize VPIC's modeling capabilities, VPIC's optimization techniques and Roadrunner's computational characteristics. We then discuss three applications enabled by VPIC's unprecedented performance on Roadrunner: modeling laser plasma interaction in upcoming inertial confinement fusion experiments at the National Ignition Facility, modeling short-pulse laser GeV ion acceleration and modeling reconnection in space and laboratory plasmas.

Fusion fast ignition (FI) initiated by laser-driven ion beams is a promising concept examined in this paper. FI based on a beam of quasi-monoenergetic ions (protons or heavier ions) has the advantage of a more localized energy deposition, which minimizes the required total beam energy, bringing it close to the ≈10 kJ minimum required for fuel densities ∼500 g cm−3. High-current, laser-driven ion beams are most promising for this purpose. Because they are born neutralized in picosecond timescales, these beams may deliver the power density required to ignite the compressed DT fuel, ∼10 kJ/10 ps into a spot 20 µm in diameter. Our modelling of ion-based FI include high fusion gain targets and a proof of principle experiment. That modelling indicates the concept is feasible, and provides confirmation of our understanding of the operative physics, a firmer foundation for the requirements, and a better understanding of the optimization trade space. An important benefit of the scheme is that such a high-energy, quasi-monoenergetic ignitor beam could be generated far from the capsule (⩾1 cm away), eliminating the need for a reentrant cone in the capsule to protect the ion-generation laser target, a tremendous practical benefit. This paper summarizes the ion-based FI concept, the integrated ion-driven FI modelling, the requirements on the ignitor beam derived from that modelling, and the progress in developing a suitable laser-driven ignitor ion beam.

Fully electromagnetic particle-in-cell simulations of tearing modes in two-dimensional plane geometry in a force-free reversed field pinch (RFP)-like plasma equilibrium are performed to study possible kinetic effects on these modes in RFPs. Linear tearing modes are compared in the kinetic and two fluid models. The results showed that the growth rates and the profiles of magnetic field components in the two models are very similar, indicating that the kinetic effects on the studied tearing modes are weak such that the two fluid approximation is rather accurate for modeling these instabilities in RFPs. During the nonlinear evolution of the tearing mode in this geometry, small scale secondary instabilities located near the internal layer of the primary tearing instability are excited. These secondary instabilities appear to be driven by the nonlinearly induced local pressure gradient in the regions of unfavorable curvature of the nonlinearly evolved magnetic field. They could also appear in a realistic RFP g...

The amidase activity of human alpha-thrombin has been studied at steady state in the pH range 6-10, as a function of NaCl concentration from 1 mM to 1 M and temperature from 10 to 40 degrees C. The Michaelis-Menten constant, Km, shows a bell-shaped dependence over this pH range with a minimum around pH 7.5 in the presence of 0.1 M NaCl at 25 degrees C. The catalytic constant, kcat, also has a bell-shaped pH dependence with multiple inflection points that are more evident at low NaCl concentrations and a maximum around pH 8.2 in the presence of 0.1 M NaCl at 25 degrees C. A detailed analysis of the results in terms of a general linkage scheme has allowed a thorough characterization of the linkage between proton and substrate binding and its dependence on NaCl concentration, as well as the relevant entropic and enthalpic contributions to binding and catalytic events. Formulation of detailed partition functions for each enzyme intermediate involved in the catalytic cycle suggests that (at least) three groups are responsible for the control of thrombin amidase activity as a function of pH. One group is to be identified with the active site His, due to its pK values in the free enzyme and the adduct and its enthalpy of ionization. The effect of NaCl concentration on amidase activity seems to be extremely specific. Comparative steady-state measurements carried out in the presence of NaCl, NaBr, NaI, KCl, and MgCl2 show that human alpha-thrombin is capable of discriminating among different cations and anions. This suggests that small ions participate as allosteric effectors in the regulation of thrombin activity. The linkage with NaCl is strongly pH dependent and increases with decreasing pH. The present results provide information on the basic aspects of human alpha-thrombin activity and regulation and enable a rigorous thermodynamic approach to other important regulatory interactions in human alpha-thrombin and its structurally perturbed derivatives.

Conjugated dienoic derivatives of linoleic acid (referred to by the acronym CLA) constitute a newly recognized class of anticarcinogenic fatty acids. Of the eight major CIA isomere, the cis-9, trans-11 isomer alone is incorporated into phospholipid and may to be the most biologically relevant isomer. CLA exhibits potent antioxidant activity; evidence is presented indicating that CLA acts both as an in vitro and in vivo antioxidant. The formation of CLA in foods, and its possible biological significance in cell membranes, is discussed.

Digital subtraction angiography (DSA) allows quantitative analysis of ventricular function via densitometric and parametric imaging techniques. However, DSA is limited by the artifacts in temporal subtraction images that result from patient and cardiac motion. Dual-energy subtraction imaging is insensitive to motion. This study evaluated the initial application of dual-energy subtraction in cardiac patients. The image quality of dual-energy subtraction left ventriculograms obtained from a pulmonary artery injection of contrast was assessed in 13 patients, ranging in weight from 54 to 100 kg. The dual-energy images were compared with left ventricular images obtained using standard left ventricular injection cine angiography. End-systolic and end-diastolic ventricular volumes calculated from the cine (C) and dual-energy (DE) images using the Area-Length method were compared. The resulting regression line was DE = 0.98 C+ 7.0 ml, and the r value was 0.987. Dual-energy subtraction provided good left ventricular visualization, free from misregistration artifacts, even during patient motion.

Ion-driven fast ignition (IFI) may have significant advantages over electron-driven FI due to the potentially large reduction in the amount of energy required for the ignition beam and the laser driver. Recent experiments at the Los Alamos National Laboratory’s Trident facility employing novel Au flat-top cone targets have produced a fourfold increase in laser-energy to ion-energy efficiency, a 13-fold increase in the number of ions above 10MeV, and a few times increase in the maximum ion energy compared to Au flat-foil targets. Compared to recently published scaling laws, these gains are even greater. If the efficiency scales with intensity in accordance to flat-foil scaling, then, with little modification, these targets can be used to generate the pulse of ions needed to ignite thermonuclear fusion in the fast ignitor scheme. A proton energy of at least 30MeV was measured from the flat-top cone targets, and particle-in-cell (PIC) simulations show that the maximum cutoff energy may be as high as 40–45MeV...

Ion fast ignition (FI) is an approach to fast ignition inertial confinement fusion (ICF) where an energetic ion beam is used to heat a hot spot in a compressed ICF capsule to ignition conditions. Recent work at LANL and elsewhere suggests that ion beams with Z > 1 may be produced with characteristics suitable for FI. Indeed, fast ignition using mid-Z ions may have advantages over protons FI in terms of number of ions required for ignition, robustness of the ion beam to beam-plasma instabilities, sharpness of Bragg peak, and ability to locate the ion source far from the ignition capsule. In this paper, simple preliminary capsule designs for mid-Z ion fast ignition are assessed. These designs comprise a DT gas pocket, a DT ice fuel layer, and a low-Z ablator subject to a drive achievable on facilities such as the NIF and LMJ. Dependence of capsule gain with various beam parameters are obtained.

Parametric coupling involving stimulated Raman and Brillouin scattering (SRS and SBS) of Trident short-pulse laser in a single-hot-spot [Kline J L et al. 2007 Investigation of stimulated Raman scattering using a short-pulse single-hot-spot at the Trident laser facility J. Phys.: Conf. Series in press] is examined using Particle-In-Cell simulations in the kinetic regime. The scaling of SRS reflectivity versus laser intensity at kλD = 0.35 is obtained from two-dimensional simulations in which SRS saturation level is in quantitative agreement with that in the experiments. At this high laser intensity regime (> 1016 W/cm2), it is found that SRS saturation is caused by electron plasma wavefront bowing and self-focusing from trapped particle modulational instability [Rose H A 2005 Phys. Plasmas 12 12318]; ion acoustic wave bowing also contributes to the SBS saturation. These results are consistent with our findings for long laser pulse at lower intensities [Yin L, Albright B J, Bowers K J, Daughton W and Rose H A 2007 Phys. Rev. Lett. 99 265004]. A frequency chirp in a short-pulse laser leads to significant reduction of the SBS reflectivity.

Research at Los Alamos on fusion fast ignition (FI) [1] initiated by laser-driven ion beams heavier than protons has produced encouraging results. The minimum requirements for FI are relatively well understood [2]. Based on simple considerations and on those requirements, it is shown that FI of the compressed DT fuel using laser-driven heavy ion beams has advantages compared to laser-driven proton or electron beams, along with different risks compared to those approaches. Using a technologically convenient light-ion species such as Carbon, ~ 100-fold fewer ions may deliver the energy necessary to ignite, simplifying target fabrication. Key requirements for success include the generation of a monoenergetic beam (energy spread ≤ ~ 10%), a sufficiently high ion kinetic energy (~ 450 MeV for C), and a sufficiently high conversion efficiency of laser to beam energy. An important benefit of this scheme is that such a high-energy, quasi-monoenergetic beam may be generated far from the capsule (~ 1 cm away), eliminating the need for a reentrant cone in the capsule, a tremendous practical benefit. This paper summarizes our progress in meeting those requirements, and the results of an integrated 2D design for a proof of principle FI experiment based on this concept.

A new short-pulse version of the single-hot-spot configuration has been implemented to enhance the performance of experiments to understand Stimulated Raman Scattering. The laser pulse length was reduced from ~200 to ~3 ps. The reduced pulse length improves the experiment by minimizing effects such as plasma hydrodynamic evolution and ponderomotive filamentation of the interaction beam. In addition, the shortened laser pulses allow full length 2D particle-in-cell simulations of the experiments. Using the improved single-hot-spot configuration, a series of experiments to investigate kλD scaling of SRS has been performed. Details of the experimental setup and initial results will be presented.

Backward stimulated Raman and Brillouin scattering (SRS and SBS) of laser are examined in the kinetic regime using particle-in-cell simulations. The SRS reflectivity measured as a function of the laser intensity in a single hot spot from two-dimensional (2D) simulations shows a sharp onset at a threshold laser intensity and a saturated level at higher intensities, as obtained previously in Trident experiments [D. S. Montgomery et al., Phys. Plasmas 9, 2311 (2002)]. In these simulations, wavefront bowing of electron plasma waves (ion acoustic waves) due to the trapped particle nonlinear frequency shift, which increases with laser intensity, is observed in the SRS (SBS) regime for the first time. Self-focusing from trapped particle modulational instability (TPMI) [H. A. Rose, Phys. Plasmas 12, 12318 (2005)] is shown to occur in both two- and three-dimensional SRS simulations. The key physics underlying nonlinear saturation of SRS is identified as a combination of wavefront bowing, TPMI, and self-focusing of...

A new laser-driven ion acceleration mechanism has been identified in particle-in-cell simulations of high-contrast-ratio ultraintense lasers with very thin (10s of nm) solid targets [Yin et al., Laser and Particle Beams 24, 291 (2006); Yin et al., Phys. Plasmas 13, 072701 (2007)]. After a brief period of target normal sheath acceleration (TNSA), “enhanced” TNSA follows. In this stage, the laser rapidly heats all the electrons in the target as the target thickness becomes comparable to the skin depth and enhanced acceleration of the ions results. Then, concomitant with the laser penetrating the target, a large accelerating longitudinal electric field is generated that co-moves with the ions. This last phase has been termed the laser “breakout afterburner” (BOA). Earlier work suggested that the BOA was associated with the Buneman instability that efficiently converts energy from the drift of the electrons into the ions. In this Brief Communication, this conjecture is found to be consistent with particle-in-...

A new laser-driven ion acceleration mechanism using ultrathin targets has been identified from particle-in-cell simulations. After a brief period of target normal sheath acceleration (TNSA) [S. P. Hatchett et al., Phys. Plasmas 7, 2076 (2000)], two distinct stages follow: first, a period of enhanced TNSA during which the cold electron background converts entirely to hot electrons, and second, the “laser breakout afterburner” (BOA) when the laser penetrates to the rear of the target where a localized longitudinal electric field is generated with the location of the peak field co-moving with the ions. During this process, a relativistic electron beam is produced by the ponderomotive drive of the laser. This beam is unstable to a relativistic Buneman instability, which rapidly converts the electron energy into ion energy. This mechanism accelerates ions to much higher energies using laser intensities comparable to earlier TNSA experiments. At a laser intensity of 1021W∕cm2, the carbon ions accelerate as a quasimonoenergetic bunch to 100s of MeV in the early stages of the BOA with conversion efficiency of order a few percent. Both are an order of magnitude higher than those realized from TNSA in recent experiments [Hegelich et al., Nature 441, 439 (2006)]. The laser-plasma interaction then evolves to produce a quasithermal energy distribution with maximum energy of ∼2GeV.