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Notes: We have used x-ray photoelectron spectroscopy (XPS) to measure the dependence of the InAs/GaSb valence band offset on both interface composition and growth order. Molecular beam epitaxy was used to grow InAs-on-GaSb and GaSb-on-InAs interfaces with both InSb-like and GaAs-like interface compositions. Analysis of XPS core level separations showed no dependence of the valence band offset on interface composition; however, a 90 meV increase in the valence band offset was observed for InAs grown on GaSb compared to GaSb grown on InAs. This difference is attributed to the extended nature of the InAs-on-GaSb interface. Results from analysis of an intentionally extended GaSb-on-InAs interface were consistent with this conclusion. © 1995 American Institute of Physics.

Notes: Effect of a nitrogen electron-cyclotron-resonance (ECR) microwave plasma on near-surface composition, crystal structure, and morphology of the As-stabilized GaAs (100) surface is investigated with the use of digitally image-processed in situ reflection high energy electron diffraction. Nitridation is performed on molecular beam epitaxially (MBE) grown GaAs surfaces near 600 °C under typical conditions for ECR microwave plasma-assisted MBE growth of GaN films on GaAs. Brief plasma exposures (≈3–5 s) are shown to result in a specular, coherently strained, relatively stable, GaN film approximately one monolayer in thickness, which can be commensurately overgrown with GaAs while longer exposures (up to 1 min) result in incommensurate zincblende epitaxial GaN island structures. Specular and nonspecular film formations are explained in terms of N-for-As surface and subsurface anion exchange reactions, respectively. Commensurate growth of ultrathin buried GaN layers in GaAs is achieved. © 1995 American Institute of Physics.

Notes: We compare low-temperature, excimer-laser-induced etching of GaAs, GaSb, InAs, and InSb surfaces covered with 1–2 monolayers of condensed Cl2. The etch properties and a relative etch rate of GaAs∼GaSb〈InAs〈InSb are obtained. In addition, the etch rate of GaSb is characterized as a function of various system parameters, i.e., substrate temperature, chlorine pressure, and laser fluence. Spatially well resolved, anisotropic etching of 0.5 μm features has been achieved. © 1995 American Institute of Physics.

Notes: Abstract The unique sol/gel behavior of an organic/inorganic hybrid material synthesized from 3-aminopropyl-triethoxysilane (3AS) and tetramethoxysilane (TMOS) is discussed and examined. The addition of H2O to a mixture of a basic (3AS) and an acidic (TMOS) alkoxide leads to rapid gel formation. This wet gel reverses to a sol upon heating which is attributed to the dissolution of siloxane bonds between the surfaces of colloidal particles in the gel. The reversed sol dries to an optically transparent solid which is water soluble. The water solubility and the stability of these colloidal particles are described by their aminopropyl/silanol surface and the electrostatic interactions between them using DLVO theory.

Notes: Abstract The marked advantages and merit of pre-term and particularly pre-labor (PTPL) cesarean section (C-section) in the avoidance, and indeed, virtual elimination of severely disabling gastroschisis (GS) complications in infants diagnosed prior to birth by ultrasound has unfortunately remained controversial in the 10 to 12 years since it was first reported and strongly recommended by numerous authors. During this period, GS has remained one of the four major causes of the short-gut syndrome (SGS) in infancy and childhood and a major cause of prolonged, costly, complicated, and hazardous neonatal intensive care unit stays with requirements for total parenteral nutrition (TPN). The most serious and frequent complications of GS in infants born without PTPL C-section are the occurrence of the “peel”, which greatly enlarges and rigidifies the eviscerated gut, and of “complicated GS” (intestinal atresia/s, stenosis, necrosis, perforations) (CGS). The “peel” occurs in 100% of these cases and CGS in approximately 20%. “Peel” enlargement and rigidification of eviscerated intestine in the presence of a reduced peritoneal cavity causes great difficulty in covering the eviscerated, enlarged, and rigidified gut with abdominal wall, skin, a prosthesis, etc., and frequently produces gut ischemia from excessive pressure, which may lead to necrotizing enterocolitis (NEC) and SGS as well as prolonged hospital stays. The presence of a “peel” greatly complicates the hazards of dealing with cases of CGS, as resection and anastomosis are virtually impossible in the presence of a “peel.” The authors report personal experience with 77 cases of GS dating as far back as 1951; 44 of the infants were born after the onset of labor by vaginal or C-section delivery and all had some degree of “peel” formation. Of 320 cases from the literature (including some of the cases reported here), 61 (19.1%) involved CGS. Of the 33 cases born PT, and especially PL, there were no cases of “peel” and only 1 case of CGS (3.0%). This infant had a single atresia associated with a very small (1 cm) defect in the abdominal wall and no labor-induced “peel,” which was easily and successfully repaired by resection and anastomosis. The 6.4-fold reduction in the occurrence of CGS by PTPL C-section (3.0% vs 19.1%) was statistically significant by the chi-square test (P 〈 0.05), as was the 100% elimination of the disabling “peel.” If the single case of CGS associated with a very small defect and no labor or labor-associated “peel” is eliminated, the incidence of CGS in the remaining PTPL group of 32 cases falls to 0 (0% versus 19.1%, P 〈 0.007). PT and especially PL C-section may be expected to virtually eliminate “peel” formation and CGS and to remove GS as one of the four major causes of SGS. The findings of this report that PT labor prior to PT C-section may result in both “peel” formation and CGS further solidifies the role of labor in the production of both the “peel” and the equally disabling CGS. Failure to appreciate the central role of labor in GS complications has doubtless contributed to the persistent controversy concerning the value and importance of PTPL C-section for gastroschisis diagnosed in utero. The pediatric surgeon has an important responsibility with the obstetrician to monitor the possible occurrence of occult labor in the waning weeks of pregnancy and be prepared to do a prompt C-section if it occurs and there is adequate lung maturity. The achievement of “peel”- and CGS-free gut would greatly facilitate the use of the new Bianchi technique of gut reduction without anesthesia. The combination of the use of epidural anesthesia for the elective PTPL C-section with the Bianchi approach would spare both mother and baby any untoward effects of general anesthesia and present the potential for massive reductions in hospital costs with minimal patient manipulation and disturbance. For infants born with labor-associated “peel,” re-evaluation of the suitability and effectiveness of surgical “peel” decortication from involved gut is strongly urged.

Notes: [Auszug] Although conventional proton magnetic resonance imaging has increased our ability to detect brain tumors, it has not enhanced to nearly the same degree our ability to diagnose tumor type1. Proton magnetic resonance spectroscopy is a safe, noninvasive means of performing biochemical analyses in ...

Notes: [Auszug] SIR — Although hypervariable DNA markers have revolutionized the study of kinship patterns and mating systems in the wild1'2, these techniques have largely been restricted to species that can be easily captured and handled. Where handling is either unsafe or impracticable, DNA must be ...

Notes: [Auszug] Olive baboons at Gombe have been studied continuously since 19578 13 jjie National Park consists of a series of steep valleys that run down the rift escarpment to the shore of Lake Tanganyika14. The valley floors are filled with semi-evergreen forest, and the slopes and ridgetops are covered by ...