Progress in direct-drive inertial confinement fusion research at the laboratory for laser energetics

Direct-drive inertial confinement fusion (ICF) is expected to demonstrate high gain on the National Ignition Facility (NIF) in the next decade and is a leading candidate for inertial fusion energy production. The demonstration of high areal densities in hydrodynamically scaled cryogenic DT or D₂ implosions with neutron yields that are a significant fraction of the “clean” 1-D predictions will validate the ignition-equivalent direct-drive target performance on the OMEGA laser at the Laboratory for Laser Energetics (LLE). This paper highlights the recent experimental and theoretical progress leading toward achieving this validation in the next few years. The NIF will initially be configured for X-ray drive and with no beams placed at the target equator to provide a symmetric irradiation of a direct-drive capsule. LLE is developing the “polar-direct-drive” (PDD) approach that repoints beams toward the target equator. Initial 2-D simulations have shown ignition. A unique “Saturn-like” plastic ring around the equator refracts the laser light incident near the equator toward the target, improving the drive uniformity. LLE is currently constructing the multibeam, 2.6-kJ/beam, petawatt laser system OMEGA EP. Integrated fast-ignition experiments, combining the OMEGA EP and OMEGA Laser Systems, will begin in FY08.     

移动WiMAX竞技于边缘市场

经过多年的酝酿,移动WiMAX终于成为一种为网络运营商提供高速数据传输服务的可行方式。近几个月来,一些运营商开始部署这种技术,但是语音服务的欠缺很可能会降低移动WiMAX短期内对客户的吸引力。另外,一些长期性问题依旧悬而未决。例如,运营商将怎样在移动语音技术环境下提供基于移动WiMAX的数据服务?发展     

Combinatorial synthesis and characterization of a ternary epitaxial film of Co and Mn doped Ge (0 0 1)

We report combinatorial molecular beam epitaxy synthesis and properties of a ternary epitaxial film of Co and Mn co-doped Ge grown on Ge (0 0 1) substrate. Structural effects were examined in situ by reflection high-energy electron diffraction and ex situ by microbeam X-ray diffraction techniques, and magnetic properties were probed by using magnetooptic Kerr effect. Ternary epitaxial phase diagrams have been studied for total doping concentrations up to 30 at.%, where regions of coherent epitaxy and rough disordered growth and those of near room temperature ferromagnetic ordering have been identified.     

Diffusion of 111Cd probes in Ga7Pt3 studied via nuclear quadrupole relaxation

Diffusion of ¹¹¹In/Cd impurity atoms was studied in Ga₇Pt₃ at the atomic level using the method of perturbed angular correlation of gamma rays (PAC). As in previous measurements on Ga₇Pd₃, probes were observed to occupy two inequivalent Ga-sublattices. Quadrupole interaction perturbation functions for each site exhibited damping at elevated temperatures that is attributed to nuclear relaxation caused by stochastic jumps of the probe atoms accompanied by reorientation of axes of the electric field gradient tensor. Fitted relaxation frequencies, proportional to mean jump frequencies of the probe, were thermally activated. Arrhenius plots revealed jump-frequency activation enthalpies of 0.94 (8) and 0.67 (4) eV for the two sites and frequency prefactors close to 1 THz. Results were similar to those found previously for Ga₇Pd₃, although jump frequencies are about 100 times lower in Ga₇Pt₃.     

Band‐Offset Engineering for Enhanced Open‐Circuit Voltage in Polymer–Oxide Hybrid Solar Cells

The power conversion efficiency of organic and hybrid solar cells is commonly reduced by a low open‐circuit voltage (V_OC). In these cases, the V_OC is significantly less than the energy of the lowest energy absorbed photon, divided by the elementary charge q. The low photovoltage originates from characteristically large band offsets between the electron donor and acceptor species. Here a simple method is reported to systematically tune the band offset in a π‐conjugated polymer–metal oxide hybrid donor–acceptor system in order to maximize the V_OC. It is demonstrated that substitution of magnesium into a zinc oxide acceptor (ZnMgO) reduces the band offset and results in a substantial increase in the V_OC of poly(3‐hexylthiophene) (P3HT)–ZnMgO planar devices. The V_OC is seen to increase from 500 mV at x = 0 up to values in excess of 900 mV for x = 0.35. A concomitant increase in overall device efficiency is seen as x is increased from 0 to 0.25, with a maximum power‐conversion efficiency of 0.5 % obtained at x = 0.25, beyond which the efficiency decreases because of increased series resistance in the device. This work provides a new tool for understanding the role of the donor–acceptor band offset in hybrid photovoltaics and for maximizing the photovoltage and power‐conversion efficiency in such devices.     

Capsosomes with Multilayered Subcompartments: Assembly and Loading with Hydrophobic Cargo

Therapeutic artificial cells or organelles are nanoengineered vehicles that are expected to substitute for missing or lost cellular function. The creation of capsosomes, polymer carrier capsules containing liposomal subcompartments, is a promising approach towards constructing such therapeutic devices using the layer‐by‐layer assembly method. Herein, the assembly of intact, nonaggregated capsosomes containing multiple liposome layers is reported. It is also further demonstrated that thiocoraline, a hydrophobic model peptide with antitumor activity, can be efficiently loaded into the membrane of the liposomal subcompartments of the capsosomes. Cell viability assays verify the activity of the trapped antitumor cargo. It is also shown that pristine capsosomes do not display inherent cytotoxic effects. The ability to tune the number of liposome layers and hence the drug loading in capsosomes as well as their noncytotoxicity provide new opportunities for the creation of therapeutic artificial cells and organelles.     

NEUROTOXICITY OF TETRAPHENYLPORPHINESULFONATE TPPS4 and ITS RELATION TO PHOTODYNAMIC THERAPY*

Abstract Tetraphenylporphinesulfonate (TPPS₄) is a synthetic porphyrin that localizes in certain tumors to a higher absolute concentration and with more favorable tumor to other tissue ratios than any other porphyrin yet studied. Its utilization for photodynamic therapy and other applications has been inhibited by reported neurotoxicity. We injected TPPS₄ over a broad dose range of 5-150 mg kg^?1 and observed the effects on peripheral nerve in groups of animals sacrificed 35, 70 and 140 days later. No immediate deaths or phototoxic manifestations were seen. Light and electron microscopy, however, revealed cytoskeletal abnormalities and nerve fiber degeneration affecting both myelinated and unmyelinated fibers in all the time and dose groups. These findings have similarities to those of other experimental toxic neuropathies, and may also be related to the preponderance of autonomic manifestations in patients with porphyric neuropathy. The morphological changes consisted of tangles of fibrillar material in the myelinated fibers and loss of neurotubules in the unmyelinated fibers. Our studies indicate a direct interaction of TPPS₄ with tubulin. This biological mechanism may be involved in the selective distribution of certain parenterally administered porphyrins.     

An Integrating Wide Dynamic-Range Image Sensor With a Logarithmic Response

An integrating CMOS image sensor with a wide dynamic range is described. The dynamic range of these pixels is controlled by a user-defined reference voltage that creates a photocurrent-dependent effective integration time. The operation of these pixels and a method of obtaining a well-controlled logarithmic response are both described. Furthermore, described are the results of two alternative methods of correcting the fixed pattern noise in these pixels and measurements of the temporal noise from individual pixels. These results show that with these pixels, it is possible to match the contrast sensitivity of the human visual system.     

Vladimir Evgen’evich Dmitrienko (On the occasion of his 60th birthday)

Crystallography Reports -