Indirect-drive hohlraum experiments at the National Ignition Facility have demonstrated symmetric capsule implosions at unprecedented laser drive energies of 0.7 megajoule. One hundred and ninety-two ...simultaneously fired laser beams heat ignition-emulate hohlraums to radiation temperatures of 3.3 million kelvin, compressing 1.8-millimeter-diameter capsules by the soft x-rays produced by the hohlraum. Self-generated plasma optics gratings on either end of the hohlraum tune the laser power distribution in the hohlraum, which produces a symmetric x-ray drive as inferred from the shape of the capsule self-emission. These experiments indicate that the conditions are suitable for compressing deuterium-tritium-filled capsules, with the goal of achieving burning fusion plasmas and energy gain in the laboratory.
Morphological, spectroscopic, and scattering studies of the self-assembly and aggregation of mixtures of RF4 and PRF4 peptides (where R = arginine; F = phenylalanine; P = proline), in solution and ...as hydrogels, were performed to obtain information about polymorphism. CD data confirmed a β-sheet secondary structure in aqueous solution, and TEM images revealed nanofibers with diameters of ∼10 nm and micrometer lengths. SAXS curves were fitted using a mass fractal-component and a long cylinder shell form factor for the liquid samples, and only a long cylinder shell form factor for the gels. Increasing the PRF4 content in the systems leads to a reduction in cylinder radius and core scattering density, suggesting an increase in packing of the peptide molecules; however, the opposite effect is observed for the gels, where the scattering density is higher in the shell for the systems containing higher PRF4 content. These compounds show potential as catalysts in the asymmetric aldol reactions, with cyclohexanone and p-nitrobenzaldehyde in aqueous media. A moderate conversion (36.9%) and a good stereoselectivity (69:31) were observed for the system containing only RF4. With increasing PRF4 content, a considerable decrease of the conversion was observed, suggesting differences in the self-assembly and packing factor. Rheological measurements were performed to determine the shear moduli for the soft gels.
Morphological, spectroscopic and scattering studies of the self-assembly and aggregation process of hybrids containing gold nanoparticles (AuNPs) and the amyloid peptides RF
4
and PRF
4
(where R = ...arginine; F = phenylalanine; P = proline) in aqueous solution were performed. Two methodologies were tested for the AuNP nucleation, using sodium borohydride (NaBH
4
) or epigallocatechin gallate (EGCG) as a reducing agent. This led to remarkable distinct modes of assembly, AuNP decorated fibrils with NaBH
4
reduction or isolated AuNPs with EGCG reduction. For both methodologies, the presence of spherical AuNPs was observed by plasmonic resonance bands in absorption spectra at ∼520 nm. Zeta potential measurements confirmed stable systems, with a similar aggregation state. Circular dichroism spectra revealed an antiparallel β-sheet conformation of the peptides. The transmission electron microscopy (TEM) images showed the coexistence of nanometer fibers and globular nanoparticles with 20 nm size. The small-angle X-ray scattering (SAXS) results show that the NaBH
4
systems presented large cylindrical structures, while with increasing PRF
4
content, a decrease in radius was observed. However, the EGCG-AuNPs were characterized by spherical particles, with a radius of 10-20 nm. Also, the colorimetric efficiency of the hybrids in the capture of Cu
2+
ions in solution was monitored. Raman spectroscopy data confirmed the conformation/structure of self-assembled samples. Moreover, there are indications for a surface-enhanced Raman spectroscopy (SERS) effect for Cu
2+
sites. The set of results indicates that these systems could act as a promising sensitive metal concentration probes.
We show that arginine/phenylalanine based peptides can be used to control the aggregation of gold nanoparticles in different ways. The arrangement provides a colorimetric approach to detect Cu
2+
ions in water.
The self-assembly of model PRWG lipopeptides (P:
l
-proline, R:
l
-arginine, W:
l
-tryptophan, G:
l
-glycine), containing one or two aliphatic octadecyl (C
18
) chains in water and ...cyclohexanone/water solutions was examined. The self-assembly of mixtures of these RWG and PRWG lipopeptides was also investigated. These materials presented a similar critical aggregation concentration of ∼4.0 × 10
−4
wt% and were characterized by unordered secondary structures with some β-sheet content. TEM and cryo-TEM revealed the presence of mainly nanotape structures with micelles observed for systems rich in
PRWG(C
18
H
37
)
. Analysis of detailed SAXS form factor measurements revealed the presence of bilayers 3-4 nm thick while the
PRWG(C
18
H
37
)
micelles have a core radius of approximately 3 nm, and a shell thickness of 2 nm. For the cyclohexanone/water systems polymorphs containing cluster aggregates (with radius of 0.25 nm to 0.50 nm) and some elongated structures (with radius of 5.7 nm to 26.1 nm) were seen. Longer structures were formed with the increase of the proline-containing lipopeptide content. The catalytic activity of these peptides was assessed using a model nitro-aldol reaction. The concentration of water in the reaction system influenced the conversion, higher content promoted better efficiency for the water systems, but the opposite was observed for the cyclohexanone/water samples.
The self-assembly of model PRWG lipopeptides (P:
l
-proline, R:
l
-arginine, W:
l
-tryptophan, G:
l
-glycine), containing one or two aliphatic octadecyl (C
18
) chains in water and cyclohexanone/water solutions was examined. The enantiomeric selectivity was found to be related to the assembly of catalyst molecules.
Influenza virus causes a spectrum of illness in transplant recipients with a high rate of lower respiratory disease. Seasonal influenza vaccination is an important public health measure recommended ...for transplant recipients and their close contacts. Vaccine has been shown to be safe and generally well tolerated in both adult and pediatric transplant recipients. However, responses to vaccine are variable and are dependent on various factors including time from transplantation and specific immunosuppressive medication. Seasonal influenza vaccine has demonstrated safety and no conclusive evidence exists for a link between vaccination and allograft dysfunction. Annually updated trivalent inactivated influenza vaccines have been available and routinely used for several decades, although newer influenza vaccination formulations including high‐dose vaccine, adjuvanted vaccine, quadrivalent inactivated vaccine and vaccine by intradermal delivery system are now available or will be available in the near future. Safety and immunogenicity data of these new formulations in transplant recipients requires investigation. In this document, we review the current state of knowledge on influenza vaccines in transplant recipients and make recommendations on the use of vaccine in both adult and pediatric organ transplant recipients.
This article on influenza vaccination after organ transplantation discusses specific evidence‐based recommendations for immunization including timing, vaccine type, and the effect of immunosuppressive medication on vaccine response rates. See accompanying general guidelines from the CDC on page 2250.
Indirect drive experiments at the National Ignition Facility are designed to achieve fusion by imploding a fuel capsule with x rays from a laser-driven hohlraum. Previous experiments have been unable ...to determine whether a deficit in measured ablator implosion velocity relative to simulations is due to inadequate models of the hohlraum or ablator physics. ViewFactor experiments allow for the first time a direct measure of the x-ray drive from the capsule point of view. The experiments show a 15%-25% deficit relative to simulations and thus explain nearly all of the disagreement with the velocity data. In addition, the data from this open geometry provide much greater constraints on a predictive model of laser-driven hohlraum performance than the nominal ignition target.
Mixing of plastic ablator material, doped with Cu and Ge dopants, deep into the hot spot of ignition-scale inertial confinement fusion implosions by hydrodynamic instabilities is diagnosed with x-ray ...spectroscopy on the National Ignition Facility. The amount of hot-spot mix mass is determined from the absolute brightness of the emergent Cu and Ge K-shell emission. The Cu and Ge dopants placed at different radial locations in the plastic ablator show the ablation-front hydrodynamic instability is primarily responsible for hot-spot mix. Low neutron yields and hot-spot mix mass between 34(-13,+50) ng and 4000(-2970,+17 160) ng are observed.
In hohlraums for inertial confinement fusion (ICF) implosions on the National Ignition Facility, suprathermal hot electrons, generated by laser plasma instabilities early in the laser pulse ...("picket") while blowing down the laser entrance hole (LEH) windows, can preheat the capsule fuel. Hard x-ray imaging of a Bi capsule surrogate and of the hohlraum emissions, in conjunction with the measurement of time-resolved bremsstrahlung spectra, allows us to uncover for the first time the directionality of these hot electrons and infer the capsule preheat. Data and Monte Carlo calculations indicate that for most experiments the hot electrons are emitted nearly isotropically from the LEH. However, we have found cases where a significant fraction of the generated electrons are emitted in a collimated beam directly towards the capsule poles, where their local energy deposition is up to 10× higher than the average preheat value and acceptable levels for ICF implosions. The observed "beaming" is consistent with a recently unveiled multibeam stimulated Raman scattering model P. Michel et al., Phys. Rev. Lett. 115, 055003 (2015), where laser beams in a cone drive a common plasma wave on axis. Finally, we demonstrate that we can control the amount of generated hot electrons by changing the laser pulse shape and hohlraum plasma.
Laser redirection by cross-beam power transfer in a plasma is an important example of a nonlinear optics process which uses laser-plasma instabilities to one's advantage. We have demonstrated this in ...a hohlraum plasma at the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory. A four-wave mixing process causes laser power in multiple beams to change direction and add to the laser power of a selected beam. The process is controlled by setting the wavelength separation of the interacting laser beams. This technique provides a method to remotely re-point or combine high-powered laser beams without the need of local optical apparatus. PUBLICATION ABSTRACT
Fire activity has varied globally and continuously since the last glacial maximum (LGM) in response to long-term changes in global climate and shorter-term regional changes in climate, vegetation, ...and human land use. We have synthesized sedimentary charcoal records of biomass burning since the LGM and present global maps showing changes in fire activity for time slices during the past 21,000 years (as differences in charcoal accumulation values compared to pre-industrial). There is strong broad-scale coherence in fire activity after the LGM, but spatial heterogeneity in the signals increases thereafter. In North America, Europe and southern South America, charcoal records indicate less-than-present fire activity during the deglacial period, from 21,000 to ~11,000 cal yr BP. In contrast, the tropical latitudes of South America and Africa show greater-than-present fire activity from ~19,000 to ~17,000 cal yr BP and most sites from Indochina and Australia show greater-than-present fire activity from 16,000 to ~13,000 cal yr BP. Many sites indicate greater-than-present or near-present activity during the Holocene with the exception of eastern North America and eastern Asia from 8,000 to ~3,000 cal yr BP, Indonesia and Australia from 11,000 to 4,000 cal yr BP, and southern South America from 6,000 to 3,000 cal yr BP where fire activity was less than present. Regional coherence in the patterns of change in fire activity was evident throughout the post-glacial period. These complex patterns can largely be explained in terms of large-scale climate controls modulated by local changes in vegetation and fuel load.
PDF
