Gold traps in 〈100〉 silicon-silicon dioxide interfaces

The effects of gold on the trapping states at the silicon-silicon dioxide interface have been studied. A theory is presented which allows the ‘static’ low frequency C-V characteristic of a MOS capacitor, with arbitrary interface trap distribution, to be determined. The quasi-static technique of Kuhn, which measures the displacement current response to a slowly varying linear voltage, is subsequently used to obtain experimental curves which are correlated with theory. It is found that at low temperatures (? 230°K) the technique resolves pronounced structure in the interfacial trap distribution that is not apparent at room temperature.To assess the effects of varying amounts of gold, various diffusion times at 900°C were used on n-type silicon wafers of (100) orientation. It was found that interface trap density increased with extended diffusion time, but the energy distribution remained essentially the same, exhibiting pronounced maxima at energies E_v + 0.36 eV and E_v + 0.63 eV. As well as producing peaks in the distribution, the gold diffusions resulted in an increase in interface state density by approximately a factor of 5 from the control devices.     

Effects of temperature on norepinephrine-induced sinus acceleration and overdrive suppression in the isolated dog atrium

Using an isolated, blood-perfused atrium preparation, the effects of temperature on SA nodal pacemaker activity were investigated in 9 preparations. The PP interval decreased as temperature was raised. Regular sinus rhythm and atrial contraction were maintained above approximately 26 degrees C. Below 26 degrees C, sinus depolarization still showed a regular rate, although atrial contractions had ceased. At about 24 degrees C, atrial rhythm became irregular. Below 20 degrees C, atrial depolarization disappeared. Chronotropic responses to norepinephrine were suppressed at decreased temperatures, not only with respect to maximum PP shortening but also to the threshold dose for inducing sinus acceleration. Overdrive suppression was not influenced significantly by decreasing temperature. These results indicate that a temperature decrease causes suppression of SA nodal pacemaker activity, although the SA node continues to function regularly until about 25 degrees C.     

Sulfur coating of urea treated with attapulgite clay

A commercial attapulgite-type gelling clay was added as a conditioning-hardening agent to urea which was then tested as a substrate for sulfur coating. The coating tests were made in bench-scale batch equipment. The total coating weights and the 7-day dissolution rates of the sulfur-coated products were determined and compared with those from similar tests of previously made sulfur-coated urea products containing calcium lignosulfonate or formaldehyde. Compared with urea substrates containing formaldehyde, the urea containing attapulgite clay required about one-third less sulfur coating to attain the same 7-day dissolution rate. The urea containing attapulgite clay and the urea containing calcium lignosulfonate were about equally effective as substrates for sulfur coating.     

High-level expression of a novel epitope of CD59 identifies a subset of CD34+ bone marrow cells highly enriched for pluripotent stem cells

To further define the hierarchy of human hematopoietic progenitor cells, we have attempted to identify antibodies to cell-surface molecules expressed on CD34+ progenitor cell subsets. Herein we describe the utility of a new monoclonal antibody, HCC-1, which binds to a novel epitope of CD59 differentially expressed among CD34+ progenitor cells. HCC-1 subdivides the adult marrow CD34+ population into HCC-1high and HCC-1low/- fractions of approximately equal size. Cobblestone area-forming cells (CAFC) in long-term bone marrow culture were enriched 10-30-fold in CD34+HCC-1high cells compared with CD34+HCC1-low/- cells and two-fold compared with CD34+ cells. When injected into fetal human bone fragments implanted in SCID mice, the CD34+HCC-1high population showed potent engrafting activity leading to the production of myeloid, lymphoid, and erythroid elements, as well as the retention of progenitor cell phenotype. These studies demonstrate that the CD34+HCC-1high population contains primitive pluripotent hematopoietic stem cells. No hematopoietic engrafting activity was detected in the CD34+HCC-1low/- population. Consistent with this finding, simultaneous five-color flow cytometric analysis revealed that HCC-1high cells include virtually all CD34+Thy-1+Lin- cells, a cell population previously characterized as highly enriched for primitive pluripotent hematopoietic stem cells. The ability of CD34+ cells divided into subsets by HCC-1 to produce T cells was assessed by transplantation of sorted cells into human fetal thymus implanted into SCID mice. A higher frequency of thymus-engrafting activity was observed in the CD34+HCC-1high than in the CD34+HCC-1low/- population. Consistent with the limited ability to engraft in the SCID-hu thymus model, the CD34+HCC-1low/- population was shown to contain a low frequency of CD34+CD10+ lymphoid progenitor cells. We conclude that the HCC-1 epitope is expressed at high levels on a subset of CD34+ cells that contain virtually all primitive pluripotent hematopoietic stem cells and that the population of CD59 molecules expressed on CD34+ cells is not homogeneous.     

Granulocyte colony-stimulating factor (G-CSF) dose-dependent efficacy in peripheral blood stem cell mobilization in patients who had failed initial mobilization with chemotherapy and G-CSF

For 10 consecutive patients in our unit who did not show a significant rise in blood progenitor cells within 14 days following chemotherapy and G-CSF, we increased the G-CSF dose from 5 to 10 microg/kg/day (n = 9) or from 10 to 15 microg/kg/day (n = 1). As a result, there were significant increases in total yield as well as yield per apheresis of mononuclear cells, CD34+ cells and CFU-GM (P < 0.025, <0.01 and <0.005, respectively). After G-CSF dose escalation, six of the 10 patients had sufficient CD34+ cells for performing transplantation. These results demonstrate a dose-dependent response of progenitor cell mobilization by G-CSF when used in combination with chemotherapy. Moreover, increasing the dose of G-CSF as late as the third week of mobilization may still provide sufficient cell yield even with patients who did not show a significant mobilization with conventional doses of G-CSF.     

Hazard assessment techniques used in the chemical industry and their possible uses elsewhere

The traditional methods used for the identification and assessment of hazards in the chemical industry are based on experience, but increased economic and environmental restrictions on its operations have required the development of other methods to ensure that an acceptable level of safety is maintained. The present paper briefly reviews the traditional methods, describes in mire detail the basis of the newer methods, namely hazard and operability studies and hazard analysis, and considers how they might be more widely used in assessing fire hazards.     

Single myosin molecule mechanics: piconewton forces and nanometre steps

A new in vitro assay using a feedback enhanced laser trap system allows direct measurement of force and displacement that results from the interaction of a single myosin molecule with a single suspended actin filament. Discrete stepwise movements averaging 11 nm were seen under conditions of low load, and single force transients averaging 3-4 pN were measured under isometric conditions. The magnitudes of the single forces and displacements are consistent with predictions of the conventional swinging-crossbridge model of muscle contraction.     

APA accreditation: A status report.

Outlines the evolution of the procedures and mechanisms of American Psychological Association (APA) accreditation (ACR) between 1966 and 1971. Under the present system, APA accredits professional programs as units rather than singling out individual specialities, programs put on probation are so identified in lists of approved programs, a provisional ACR category has been added, and greater emphasis has been placed on the advisory and consulting functions of the ACR process. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A p-channel BICFET in the InGaAs/InAlAs material system

The bipolar inversion-channel field-effect transistor (BICFET) relies on a field-effect mechanism to induce and modulate an inversion layer placed at the heterojunction interface. The device was fabricated using molecular beam epitaxy. A current gain of ~15 has been achieved at a current density J of ~8×10³ A/cm² at 300 K. At 77 K, the gain rises to 40 with J=2×10⁴ A/cm². This gain, which follows theoretical predictions, continuously increases with collector current and is limited only by the amount of heat generated in a large-area device. Because of its potential for ballistic transport in the collector, the InGaAs/InAlAs BICFET should be very attractive for high-speed applications     

Direct measurement of FM noise in 80 GHz solid-state oscillators

A technique for the measurement of FM noise in W-band oscillators is described. The method is `direct?, since it makes use of a tuned frequency discriminator operating at the fundamental oscillator frequency. The equipment is compared with other types of noise measurement systems, and the important factors affecting sensitivity are noted. Measurements of the FM noise performance of oscillators utilising GaAs TEOs and Si impatts are presented.