Formation of lithium niobate-tantalate waveguides

Low loss diffused lithium niobate-tantalate waveguides exhibiting strong electrooptic coefficients have been made by a simple processing procedure. The formation of these waveguides takes place by the conversion of a Nb metal film to Nb oxide at a low temperature, followed by diffusion of Nb into the LiTaO₃ substrate at about 1100°C. The diffused layer has a Gaussxan composition profile. Its measured refractive index is consistent with that calculated by interpolation between the indices of LiNbO₃, and LiTaO₃. The research reported in this paper was jointly sponsored by the Office of Naval Research, Arlington, Virginia and RCA Laboratories, Princeton, New Jersey. This paper is based on a presentation at the Conference on Preparation and Properties of Electronic Materials, Boston, Massachusetts, September 1974.     

Life cycle management

Life Cycle Management of electronic computer/communications systems is maturing after thirty years of experimentation and some false starts. This holistic concept provides an improved framework for planning, implementation and control of electronic hardware or software systems. It effects of symbiosis between users and suppliers who are both concerned with reliability of hardware and software, cost-effectiveness of applications, and the impacts of a rapidly changing technology. Improved cooperation between hardware/software vendors and users will undoubtedly result in significantly better product designs and services as well as their more intelligent use by sophisticated and concerned management.     

Rapid Annealing in Silicon Transistors

Rapid annealing data after a pulse of reactor neutrons for seven NPN planar transistors at room temperature and the 2N1613 at various temperatures down to dry ice were interpreted in terms of the motion of a single type of mobile defect. An equation was derived for the recombination of the defect with fixed defects in a spherical cluster and the subsequent diffusion of the defect outside the cluster. This treatment leads to an identification of two stages of annealing, with a transition time between stages at room temperature of a few milliseconds. The variation in the transition time with temperature for the 2N1613 is used to derive an activation energy of (0.28 ± 0.02) eV, which agrees, within error, with that for the vacancy in p-type silicon. A calculation of the cluster radius is in reasonable agreement with one-half the primary recoil range.     

Quasimonochromatic x-ray backlighting on the COrnell Beam Research Accelerator (COBRA) pulsed power generator

Monochromatic x-ray backlighting has been employed with great success for imaging of plasmas with strong self-emission such as x-pinches and wire array z-pinches. However, implementation of a monochromatic backlighting system typically requires extremely high quality spherically bent crystals which are difficult to manufacture and can be prohibitively expensive. Furthermore, the crystal must have a direct line of sight to the object, which typically emits copious amounts of radiation and debris. We present a quasimonochromatic x-ray backlighting system which employs an elliptically bent mica crystal as the dispersive element. In this scheme a narrow band of continuum radiation is selected for imaging, instead of line radiation in the case of monochromatic imaging. The flat piece of mica is bent using a simple four-point bending apparatus that allows the curvature of the crystal to be adjusted in situ for imaging in the desired wavelength band. This system has the advantage that it is very cost effective, has a large aperture, and is extremely flexible. The principles of operation of the system are discussed and its performance is analyzed.     

搭载人类自体干细胞的纤维支架及其在软组织再生中的应用

文章介绍了搭载人类自体干细胞的纤维支架技术及其在软组织再生中的应用优势。选用藻酸盐材料结合人体干细胞搭载关键技术制成的纤维支架,同时具有促进血管再生和触发成脂分化的能力。     

Calibration and analysis of spatially resolved x-ray absorption spectra from a nonuniform plasma

We report here the calibration and analysis techniques used to obtain spatially resolved density and temperature measurements of a pair of imploding aluminum wires from x-ray absorption spectra. A step wedge is used to measure backlighter fluence at the film, allowing transmission through the sample to be measured with an accuracy of ±14% or better. A genetic algorithm is used to search the allowed plasma parameter space and fit synthetic spectra with 20?μm spatial resolution to the measured spectra, taking into account that the object plasma nonuniformity must be physically reasonable. The inferred plasma conditions must be allowed to vary along the absorption path in order to obtain a fit to the spectral data. The temperature is estimated to be accurate to within ±25% and the density to within a factor of two. This information is used to construct two-dimensional maps of the density and temperature of the object plasma.     

Transgenic mice expressing human ApoB95 and ApoB97. Evidence that sequences within the carboxyl-terminal portion of human apoB100 are important for the assembly of lipoprotein

The structural features of apolipoprotein (apo) B that are important for its covalent linkage to apo(a) to form lipoprotein(a) (Lp(a)) are incompletely understood. Although apoB100 cysteine 4326 is required for the disulfide linkage with apo(a), other structural features, aside from a single free cysteine residue, must be important for apoB's initial interaction with apo(a) and for facilitating the formation of the disulfide bond. To determine if sequences carboxyl-terminal to cysteine 4326 affect the efficiency of Lp(a) formation, we used "pop-in, pop-out" gene targeting in a human apoB yeast artificial chromosome to introduce nonsense mutations into exon 29 of the apoB gene. The mutant yeast artificial chromosomes, which coded for the truncated versions of human apoB, apoB95, and apoB97, were then used to express these mutant forms of apoB in transgenic mice. As judged by in vitro assays of Lp(a) formation, apoB95 (4330 amino acids) formed a small amount of Lp(a) but did so slowly. In contrast, apoB97 (4397 amino acids) formed Lp(a) rapidly, although not quite as rapidly as the full-length apoB100 (4536 amino acids). These results were supported by an analysis of double-transgenic mice expressing both human apo(a) and either apoB95 or apoB97. In mice expressing both apoB95 and apo(a), there was only a trace amount of Lp(a) in the plasma, and most of the apo(a) was free, whereas in mice expressing both apoB97 and apo(a), virtually all of the apo(a) was bound to apoB97 in the form of Lp(a). These results show that sequences carboxyl-terminal to apoB95 (amino acids 4331-4536) are not absolutely required for Lp(a) formation, but this segment of the apoB molecule, particularly residues 4331-4397, is necessary for the efficient assembly of Lp(a).     

Intraocular laser surgical probe for membrane disruption by laser-induced breakdown

A fiber probe has been designed as a surgical aid to cut intraocular membranes with laser-induced breakdown as the mechanism. The design of the intraocular laser surgical probe is discussed. A preliminary retinal damage distance has been calculated with breakdown threshold, spot size, and shielding measurements. Collateral mechanical-damage effects caused by shock wave and cavitation are discussed.