Single-Electron Transistor in Strained Si/SiGe Heterostructures

A split gate technique is used to form a lateral quantum dot in a two-dimensional electron gas of a modulation-doped silicon/silicon-germanium heterostructure. e-beam lithography was employed to produce split gates. By applying negative voltages to these gates the underlying electron gas is depleted and a lateral quantum dot is formed, the size of which can be adjusted by the gate voltage. We observe single-electron operation with Coulomb blockade behavior below 1K. Gate leakage currents are well controlled, indicating that the recently encountered problems with Schottky gates for this type of application are not an inherent limitation of modulation-doped Si/SiGe heterostructures, as had been speculated.Comment: 3 page

Ultra-steep side facets in multi-faceted SiGe/Si(001) Stranski-Krastanow islands

For the prototypical Ge/Si(001) system, we show that at high growth temperature a new type of Stranski-Krastanow islands is formed with side facets steeper than {111} and high aspect ratio. Nano-goniometric analysis of the island shapes reveals the presence of six new facet groups in addition to those previously found for dome or barn-shaped islands. Due to the highly multi-faceted island shape and high aspect ratio, the new island types are named "cupola" islands and their steepest {12 5 3} side facet is inclined by 68°to the substrate surface. Assessing the relative stability of the new facets from surface area analysis, we find that their stability is similar to that of {113} and {15 3 23} facets of dome islands. The comparison of the different island shapes shows that they form a hierarchical class of geometrical structures, in which the lower aspect ratio islands of barns, domes and pyramids are directly derived from the cupola islands by successive truncation of the pedestal bases without facet rearrangements. The results underline the key role of surface faceting in the process of island formation, which is as crucial for understanding the island's growth evolution as it is important for device applications

Ultra-steep side facets in multi-faceted SiGe/Si(001) Stranski-Krastanow islands

<p>Abstract</p> <p>For the prototypical Ge/Si(001) system, we show that at high growth temperature a new type of Stranski-Krastanow islands is formed with side facets steeper than {111} and high aspect ratio. Nano-goniometric analysis of the island shapes reveals the presence of six new facet groups in addition to those previously found for dome or barn-shaped islands. Due to the highly multi-faceted island shape and high aspect ratio, the new island types are named "cupola" islands and their steepest {12 5 3} side facet is inclined by 68&#176;to the substrate surface. Assessing the relative stability of the new facets from surface area analysis, we find that their stability is similar to that of {113} and {15 3 23} facets of dome islands. The comparison of the different island shapes shows that they form a hierarchical class of geometrical structures, in which the lower aspect ratio islands of barns, domes and pyramids are directly derived from the cupola islands by successive truncation of the pedestal bases without facet rearrangements. The results underline the key role of surface faceting in the process of island formation, which is as crucial for understanding the island's growth evolution as it is important for device applications.</p

Bile Acids Improve the Antimicrobial Effect of Rifaximin▿ †

Diarrhea is one of the most common infirmities affecting international travelers, occurring in 20 to 50% of persons from industrialized countries visiting developing regions. Enterotoxigenic Escherichia coli (ETEC) is the most common causative agent and is isolated from approximately half of the cases of traveler's diarrhea. Rifaximin, a largely water-insoluble, nonabsorbable (<0.4%) antibiotic that inhibits bacterial RNA synthesis, is approved for use for the treatment of traveler's diarrhea caused by diarrheagenic E. coli. However, the drug has minimal effect on the bacterial flora or the infecting E. coli strain in the aqueous environment of the colon. The purpose of the present study was to evaluate the antimicrobial effect and bioavailability of rifaximin in aqueous solution in the presence and absence of physiologic concentrations of bile acids. The methods used included growth measurement of ETEC (strain H10407), rifaximin solubility measurements, total bacterial protein determination, and assessment of the functional activity of rifaximin by monitoring inhibition of bacterial β-galactosidase expression. Solubility studies showed rifaximin to be 70- to 120-fold more soluble in bile acids (approximately 30% in 4 mM bile acids) than in aqueous solution. Addition of both purified bile acids and human bile to rifaximin at subinhibitory and inhibitory concentrations significantly improved the drug's anti-ETEC effect by 71% and 73%, respectively, after 4 h. This observation was confirmed by showing a decrease in the overall amount of total bacterial protein expressed during incubation of rifaximin plus bile acids. Rifaximin-treated samples containing bile acids inhibited the expression of ETEC β-galactosidase at a higher magnitude than samples that did not contain bile acids. The study provides data showing that bile acids solubilize rifaximin on a dose-response basis, increasing the drug's bioavailability and antimicrobial effect. These observations suggest that rifaximin may be more effective in the treatment of infections in the small intestine, due to the higher concentration of bile in this region of the gastrointestinal tract than in the colon. The water insolubility of rifaximin is the likely explanation for the drug's minimal effects on colonic flora and fecal pathogens, despite in vitro susceptibility

Das Europäische Parlament

In einem jahrzehntelangen Prozess hat sich das Europäische Parlament von einer beratenden Einrichtung zu einem Mitgestalter europäischer Politik entwickelt. Heute besitzt es sowohl innerhalb der Union als auch als globaler Akteur politisches Gewicht. Diese Erfolgsgeschichte wird von den europäischen Bürgerinnen und Bürgern nur beschränkt wahrgenommen, wie die geringe Beteiligung an den Wahlen zum Europäischen Parlament zeigt. Das vorliegende Buch beantwortet zentrale Fragen: Wie funktioniert diese demokratisch legitimierte Institution? Was bedeutet ihr Machtzuwachs konkret? Welche weiteren Entwicklungen können erwartet werden?In May 2014 the 8th European elections take place. 751 Members of Parliament form 28 different countries are directly elected for a five-year term form an electorate of 383 Mio citizens. The European Parliament is a dynamic, truly supranational and since Lisbon a more and more powerful actor. It negotiates on eye-level with the Council of Ministers, holds the European Commission effectively accountable, represents the aggregated interests, ideas and concerns of the Union's citizens, and supervises the development of the EU together with the national parliaments. As a global player the European Parliament deals with members of parliaments of third countries, negotiates international agreements and watches over the protection of human rights and democracy. The authors - MEPs, officials, stakeholders and experts - gibe a deep practical and academic insight into all functions of the European Parliament. The different articles take into account the specific conditions of the EU's only directly legitimized institution. For academics and practitioners alike, Dialer, Neisser and Lichtenberger offer a superb "guide" for any serious understanding of the world's only elected transnational parliament