Joule-class THz pulses from microchannel targets.

Inference of joule-class THz radiation sources from microchannel targets driven with hundreds of joule, picosecond lasers is reported. THz sources of this magnitude are useful for nonlinear pumping of matter and for charged-particle acceleration and manipulation. Microchannel targets demonstrate increased laser-THz conversion efficiency compared to planar foil targets, with laser energy to THz energy conversion up to ∼0.9% in the best cases.

Space-Time Structured Plasma Waves.

Electrostatic waves play a critical role in nearly every branch of plasma physics from fusion to advanced accelerators, to astro, solar, and ionospheric physics. The properties of planar electrostatic waves are fully determined by the plasma conditions, such as density, temperature, ionization state, or details of the distribution functions. Here we demonstrate that electrostatic wave packets structured with space-time correlations can have properties that are independent of the plasma conditions. For instance, an appropriately structured electrostatic wave packet can travel at any group velocity, even backward with respect to its phase fronts, while maintaining a localized energy density. These linear, propagation-invariant wave packets can be constructed with or without orbital angular momentum by superposing natural modes of the plasma and can be ponderomotively excited by space-time structured laser pulses like the flying focus.

Nonlinear Thomson scattering with ponderomotive control.

In nonlinear Thomson scattering, a relativistic electron reradiates the photons of a laser pulse, converting optical light to x rays or beyond. While this extreme frequency conversion offers a promising source for probing high-energy-density materials and driving uncharted regimes of nonlinear quantum electrodynamics, conventional nonlinear Thomson scattering has inherent trade-offs in its scaling with laser intensity. Here we discover that the ponderomotive control afforded by spatiotemporal pulse shaping enables regimes of nonlinear Thomson scattering that substantially enhance the scaling of the radiated power, emission angle, and frequency with laser intensity. By appropriately setting the velocity of the intensity peak, a spatiotemporally shaped pulse can increase the power radiated by orders of magnitude. The enhanced scaling with laser intensity allows for operation at significantly lower electron energies or intensities.

Generation of focusing ion beams by magnetized electron sheath acceleration.

We present the first 3D fully kinetic simulations of laser driven sheath-based ion acceleration with a kilotesla-level applied magnetic field. The application of a strong magnetic field significantly and beneficially alters sheath based ion acceleration and creates two distinct stages in the acceleration process associated with the time-evolving magnetization of the hot electron sheath. The first stage delivers dramatically enhanced acceleration, and the second reverses the typical outward-directed topology of the sheath electric field into a focusing configuration. The net result is a focusing, magnetic field-directed ion source of multiple species with strongly enhanced energy and number. The predicted improvements in ion source characteristics are desirable for applications and suggest a route to experimentally confirm magnetization-related effects in the high energy density regime. We additionally perform a comparison between 2D and 3D simulation geometry, on which basis we predict the feasibility of observing magnetic field effects under experimentally relevant conditions.

Generation of megatesla magnetic fields by intense-laser-driven microtube implosions.

A microtube implosion driven by ultraintense laser pulses is used to produce ultrahigh magnetic fields. Due to the laser-produced hot electrons with energies of mega-electron volts, cold ions in the inner wall surface implode towards the central axis. By pre-seeding uniform magnetic fields on the kilotesla order, the Lorenz force induces the Larmor gyromotion of the imploding ions and electrons. Due to the resultant collective motion of relativistic charged particles around the central axis, strong spin current densities of [Formula: see text] peta-ampere/[Formula: see text] are produced with a few tens of nm size, generating megatesla-order magnetic fields. The underlying physics and important scaling are revealed by particle simulations and a simple analytical model. The concept holds promise to open new frontiers in many branches of fundamental physics and applications in terms of ultrahigh magnetic fields.

Clinical and molecular characteristics of patients with non-amyloid light chain deposition disorders, and outcome following treatment with high-dose melphalan and autologous stem cell transplantation.

Light chain deposition disease (LCDD) is caused by a clonal plasma cell disorder in which fragments of monoclonal immunoglobulin light chains form non-fibrillary deposits in various tissues resulting in organ dysfunction. Crystal storing histiocytosis (CSH) is another light chain deposition disorder in which monoclonal light chains form intracytoplasmic crystals. Both are uncommon diseases for which there is limited treatment experience. Between 2003 and 2005, five patients with LCDD and one with CSH were treated at Boston University Medical Center with high-dose melphalan and autologous peripheral blood stem cell transplantation (HDM/SCT). Five of the six patients had predominantly renal involvement, and one patient with LCDD had biopsy-proven deposits in the myocardium. Molecular characterization revealed that the pathologic light chains were kappa in four of the six patients, and sequence analysis revealed unusual germline donor genes and high rates of amino-acid substitutions. One light chain sequence encoded a new potential N-linked glycosylation site, and another showed evidence of antigen selection. All patients are alive and five of the six patients are in complete hematologic remission at a median follow-up of 12 months (range 4-29 months) after HDM/SCT. In our experience, HDM/SCT is a feasible and effective treatment approach for these disorders.

Phenotypic variation in a genetically identical population of mice.

The parental alleles of an imprinted gene acquire their distinctive methylation patterns at different times in development. For the imprinted RSVIgmyc transgene, methylation of the maternal allele is established in the oocyte and invariably transmitted to the embryo. In contrast, the methylation of the paternal allele originates during embryogenesis. Here, we show that the paternal methylation pattern among mice with identical genetic backgrounds is subject to extensive variation. In addition to this nongenetic variation, the process underlying RSVIgmyc methylation in the embryo is also subject to considerable genetic regulation. The paternal transgene allele is highly methylated in an inbred C57BL/6J strain, whereas it is relatively undermethylated in an inbred FVB/N strain. Individual methylation patterns of paternal alleles, and therefore all of the variation (nongenetic and genetic) in methylation patterns within an RSVIgmyc transgenic line, are established in early embryogenesis. For each mouse, the paternal RSVIgmyc allele is unmethylated at the day-3.5 blastocyst stage, and the final, adult methylation pattern is found no later than day 8.5 of embryogenesis. Because of the strong relationship between RSVIgmyc methylation and expression, the variation in methylation is also manifest as variation in transgene expression. These results identify embryonic de novo methylation as an important source of both genetic and nongenetic contributions to phenotypic variation and, as such, further our understanding of the developmental origin of imprinted genes.