Fabrication and Characterization of Electrostatic Quantum Dots in a Si/SiGe 2D Electron Gas, Including an Integrated Read-out Channel

A new fabrication technique is used to produce quantum dots with read-out channels in silicon/silicon-germanium two-dimensional electron gases. The technique utilizes Schottky gates, placed on the sides of a shallow etched quantum dot, to control the electronic transport process. An adjacent quantum point contact gate is integrated to the side gates to define a read-out channel and thus allow for noninvasive detection of the electronic occupation of the quantum dot. Reproducible and stable Coulomb oscillations and the corresponding jumps in the read-out channel resistance are observed at low temperatures. The fabricated dot combined with the read-out channel represent a step towards the spin-based quantum bit in Si/SiGe heterostructures.Comment: 3 pages, 4 fig

Coherent back-scattering near the two-dimensional metal-insulator transition

We have studied corrections to conductivity due to the coherent backscattering in low-disordered two-dimensional electron systems in silicon for a range of electron densities including the vicinity of the metal-insulator transition, where the dramatic increase of the spin susceptibility has been observed earlier. We show that the corrections, which exist deeper in the metallic phase, weaken upon approaching to the transition and practically vanish at the critical density, thus suggesting that the localization is suppressed near and at the transition even in zero field.Comment: to appear in PR

Cytomegalovirus infection of the upper gastrointestinal tract following liver transplantation—incidence, location, and severity in cyclosporine- and FK506-treated patients

One hundred and forty randomly selected liver transplant recipients were studied before and after primary orthotopic liver transplantation for the presence or absence of CMV enteritis. Following OLTx, 65 patients were treated with cyclosporine A and 75 were treated with FK506. The two groups were similar with regard to the incidence, location, and outcome of their upper gastrointestinal CMV infection. Prior to OLTx, only one patient had evidence of enteric CMV infection. The incidence of CMV enteritis post-OLTx was 27.7% in the CsA-treated group and 20% in the FK-treated group. During the first posttransplant month, no patient in the FK-treated group developed CMV enteritis, compared with 11.5% of the patients who were treated with CsA (P<0.05). Gastric CMV was found in over 80% of those positive for any organ in either group. In addition to CMV infection of the upper gastrointestinal tract, clinically evident CMV disease involved more nonenteric organs in the CsA-treated group than in the FK-treated group. In the CsA-treated group, CMV-negative patients had a statistically higher 1-year survival rate (100%) than CMV-positive patients (77.8%) (P<0.05). In the FK-treated group, no difference in survival was observed between CMV-positive or CMV-negative cases at 1 year. Of the patients on CsA, 20% received OKT3 for persistent rejection, as compared with 13% in the FK-treated group. The patients receiving both CsA and OKT3 had a higher rate of upper gastrointestinal CMV infection than did FK-treated patients who also received OKT3 therapy (38.5% versus 20%, respectively). Based upon these data, it can be concluded that (1) patients receiving FK have a lower incidence of enteric CMV infection; (2) following OLTx, upper gastrointestinal CMV infection presents later in FK-treated patients; (3) the stomach is the most frequently involved organ in the UGIT; (4) FK-treated liver recipients have less severe enteric CMV infection than do CsA-treated patients; (5) enteric CMV is not a major cause of mortality in liver trans lant recipients; and (6) in patients receiving FK, those who require OKT3 therapy do not appear to be at a greater risk for the development of CMV enteritis than those who do not. © 1992 by Williams & Wilkins

Effect of Different Factors on the Service Life of Concrete Structures in Chloride Environments: A Parametric Study – Part One

This paper presents a comprehensive parametric study to determine the effect of different factors on the service life of reinforced concrete structures in chloride-laden environment. A model for corrosion initiation is selected and solved numerically by Finite Element Method for one-dimensional diffusion problem. It has been found that increase in water to cement ratio by 12.5%-50% in range of 0.20-0.40reduces the service life by 8%-35%, and by 7.35%-30.5% for the range 0.40-0.60. Also, the increase in concrete cover in the range of 20-35 mm by 14%-42%increases the service life by 8.1%-25.8%, and in the range of 35-60 mm by 7.7%-21.8%.Regarding mineral admixtures, the addition of fly ash and blast-furnace slag resulted in enhances the service life by 8%-70.7% due to increase of age factor by 25%-200%. Moreover,the addition of silica fume by 5%-15% increases the service life by 25.5%-80.6%.Finally, the rise of temperature by 25%-75% reduces the service life by 6.45%-18.7%, and the reduction of relative humidity by 25%-50% increases the life by 21.2%-89%. These values are based on a conservative approach and tend to guide the practice engineer on how these parameters affect service life of concrete structures

Effect of Different Factors on the Service Life of Concrete Structures in Chloride Environment: A Parametric Study - Part Two

In this paper, the effect of different factors on the service life of reinforced concrete structures in marine environments is investigated through a parametric study. The considered case for the study was the two- dimensional diffusion problem. By solving the selected model for corrosion initiation by Finite Element Method, it has been concluded that, corrosion initiates at corner bars before side bars. Also, concrete elements subjected to two-dimensional diffusion are more susceptible to corrosion initiation than elements subjected to one-dimensional diffusion. Moreover, increase in water to cement ratio by 12.5%-50% in range 0.20-0.40 reduces the service life by 6.2%-31%, and by 5.3%-16.9% for the range 0.40-0.60. And, the increase in concrete cover in the range of 20-40 mm by 12.5% - 50% increases the service life by 5.1%-18.8%, and in the range of 35-60 mm by 2.9%-10.3%. The addition of fly ash and blast-furnace slag increased the service life by 6.35%-69.7% due to increase of age factor by 25%-200%. Furthermore, the addition of silica fume by 5%-15% increases the service life by 21.7%-81.2%. Regarding the environmental factors, increasing of temperature by 25%-75% reduces service life by 4.7%-12.75%, and reducing of relative humidity by 25%-50% increases the life by 17.5%-90.4%.are also given

Pauli spin susceptibility of a strongly correlated two-dimensional electron liquid

Thermodynamic measurements reveal that the Pauli spin susceptibility of strongly correlated two-dimensional electrons in silicon grows critically at low electron densities - behavior that is characteristic of the existence of a phase transition.Comment: As publishe

Survival or Sustainability? Contributions of Innovatively-Managed News Ventures to the Future of Egyptian Journalism

In the repressive political climate prevailing in Egypt in 2013-15, news ventures aspiring to high standards of reporting were forced to innovate. This paper analyses three Egyptian start-ups that experimented with novel revenue streams and news services during that period, to gain insights into their approaches to managing journalism. In the process it compares different criteria for assessing sustainability and concludes that, in adverse political environments, narrow economic measures of profitability and survival may give a misleading picture as to the sustainability of the kind of journalism conducive to democratic practice. Operating collaboratively, transparently and ethically may slow productivity and profitability in the short term while laying stronger foundations for durable relations among media teams, as well as with readers and advertisers, in the long run

Effect of FK 506 chronic administration on bromosulphthalein hepatic excretion in rats

There are several reports dealing with the hepatic effect of FK 506,1–4 some of which are beneficial while others are adverse. Because the liver is a major target organ that is often the site of drug toxicity, studies directed at determining whether FK 506 affects specific hepatic function and/or its histologic appearance are important. Therefore, the present study was undertaken to examine bromosulphthalein (BSP) elimination kinetics in rats as a sensitive index of hepatic excretory function under the influence of FK 506 in the rat