High speed p-type SiGe modulation-doped field-effect transistors

We report on the fabrication and characterization of high-speed p-type modulation-doped field-effect transistors (MODFETs) with 0.7-μm and 1-μm gate-lengths having unity current-gain cut-off frequencies (f_T) of 9.5 GHz and 5.3 GHz, respectively. The devices were fabricated on a high hole mobility SiGe heterostructure grown by ultra-high-vacuum chemical vapor deposition (UHV-CVD). The dc maximum extrinsic transconductance (g_m) is 105 mS/mm (205 mS/mm) at room temperature (77 K) for the 0.7-μm gate length devices. The fabricated devices show good pinch-off characteristics and have a very low gate leakage current of a few μA/mm at room temperature and a few nA/mm at 77 K     

Effect of superconducting fluctuations on the nmr relaxation rate of high-T c superconductors

The effect of superconducting order parameter fluctuations on the nuclear-spin relaxation rate, 1/T ₁, is studied for clean two-dimensional systems by calculating the three Maki-Thomson-type diagrams which represent the lowest-order fluctuation contributions to the transverse susceptibility. For Gaussian fluctuations and for temperatures near the mean field transition temperature,T _c0, we employ a weak-coupling theory in which the pair-fluctuation propagator can also include pair-breaking effects. We also go beyond the Gaussian theory and take into account the interactions between Cooper-pair fluctuations corresponding to the fourth-order Ginzburg-Landau fluctuation terms. We compare our results with previous results in the dirty limit and in 3D. We obtain a pronounced peak in 1/T₁ atT _c and briefly discuss possible reasons why this peak is not observed.     

Functional analysis of the amino- and carboxyl-termini of streptokinase

1. The classical ATP sensitive K+ (K(ATP)) channels are composed of a sulphonylurea receptor (SUR) and an inward rectifying K+ channel subunit (BIR/Kir6.2). They are the targets of vasorelaxant agents called K+ channel openers, such as pinacidil and nicorandil. 2. In order to examine the tissue selectivity of pinacidil and nicorandil, in vitro, we compared the effects of these agents on cardiac type (SUR2A/Kir6.2) and vascular smooth muscle type (SUR2B/Kir6.2) of the K(ATP) channels heterologously expressed in HEK293T cells, a human embryonic kidney cell line, by using the patch-clamp method. 3. In the cell-attached recordings (145 mM K+ in the pipette), pinacidil and nicorandil activated a weakly inwardly-rectifying, glibenclamide-sensitive 80 pS K+ channel in both the transfected cells. 4. In the whole-cell configuration, pinacidil showed a similar potency in activating the SUR2B/Kir6.2 and SUR2A/Kir6.2 channels (EC50 of approximately 2 and approximately 10 microM, respectively). On the other hand, nicorandil activated the SUR2B/Kir6.2 channel > 100 times more potently than the SUR2A/Kir6.2 (EC50 of approximately 10 microM and > 500 microM, respectively). 5. Thus, nicorandil, but not pinacidil, preferentially activates the K(ATP) channels containing SUR2B. Because SUR2A and SUR2B are diverse only in 42 amino acids at their C-terminal ends, it is strongly suggested that this short part of SUR2B may play a critical role in the action of nicorandil on the vascular type classical K(ATP) channel.     

The Joint Evaluation Procedure for Active Substances contained in Plant Protection Products within the European Community – 10?Years of the ECCO-Project

Pflanzenschutzmittel müssen seit 1993 in den Mitgliedstaaten der Europ?ischen Gemeinschaft nach der Richtlinie 91/414/EWG des Rates bewertet und zugelassen werden. Das Programm zur Bewertung von alten Wirkstoffen (welche vor Juli 1993 auf dem Markt waren) beinhaltet mehrere Schritte und Stufen, die früher über einen Zeitraum von bis zu 10 Jahren zu bew?ltigen waren; heute sind dafür jedoch 15 Jahre vorgesehen. Das Programm wurde seit 1996 von der Europ?ischen Kommission mit Unterstützung des ECCO-Teams(European Community Co-Ordination) koordiniert. Das ECCO-Team bestand aus zwei Gruppen: eine im Pesticides Safety Directorate – PSD in York (Gro?britannien) und eine im Bundesamt für Verbraucherschutz und Lebensmittelsicherheit (BVL) bzw. vor November 2002 in der Biologischen Bundesanstalt für Land- und Forstwirtschaft in Braunschweig. Sie unterstüzten das Programm zur Bewertung von Wirkstoffen im Namen der Kommission in technischer und administrativer Hinsicht und zeichneten sich insbesondere für das ECCO Peer Review Programm (Expertenprüfungen) verantwortlich. Im November 2003 übernahm die Europ?ische Beh?rde für Lebensmittelsicherheit (EFSA) die Verantwortung für die wissenschaftliche überprüfung der von den Mitgliedstaaten erstellten Bewertungen durch Experten. Das ECCO-Team leistete jedoch weiterhin der Europ?ischen Kommission Unterstützung bei der Durchführung anderer Verfahrensaspekte, vor allem im Bereich der Managementaufgaben der Europ?ischen Kommission. Insgesamt war das Programm au?erordentlich erfolgreich. Es wurden für 162 Wirkstoffen zwischen 1996 und 2003 der Inhalt der von den Mitgliedstaaten erstellten Bewertungsberichte durch eine Expertengruppe diskutiert und füberprüft, was ma?geblich eine Entscheidungsfindung zur Akzeptabilitf?t dieser Wirkstoffe auf Gemeinschaftsebene erm?glicht hat.     

Protecting biodegradable coatings releasing antimicrobial agents

This article describes the synthesis and in vitro analysis of poly(ester anhydride) antimicrobial protection coatings. Poly(ester anhydride)s composed of ricinoleic acid, sebacic acid, terephthalic acid, and isophthalic acid were used in this study. The polymers were compatible with various fillers commonly used in paint preparation. The in vitro experiments showed that the polymers are able to release diuron, an antimicrobial agent, for months. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Prospects for the incorporation of cobalt into α-Fe2O3 nanorods during hydrothermal synthesis

A feasibility study on the incorporation of cobalt into α-Fe₂O₃ nanorods (NRs) during hydrothermal synthesis (HS) is presented as a function of FeCl₃ and CoCl₂ concentration, phosphate surfactant concentration and pH value, with samples assessed using X-ray diffractometry, transmission electron microscopy, selected area electron diffraction and energy dispersive X-ray analysis. No evidence was found for the incorporation of cobalt into α-Fe₂O₃ NRs at low pH, whilst synthesis at intermediate and high pH values favoured the formation of CoFe₂O₄ NPs. The critical role of pH value over the precipitation, size and phase purity of the nanostructured reaction products is emphasised. At pH ~2, large, well crystalline α-Fe₂O₃ nanoparticles (NPs) and NRs were grown from FeCl₃ solution in the absence and presence of phosphate, respectively, whilst no evidence was found for Co precipitation or incorporation in α-Fe₂O₃ following HS in the presence of CoCl₂. At pH ~8, smaller α-Fe₂O₃ NPs, as well as Co₃O₄ and CoFe₂O₄ NPs were synthesised from FeCl₃, CoCl₂, or a mixture thereof. HS at pH ~12 produced a mixture of larger CoFe₂O₄ NPs and α-Fe₂O₃ NPs depending on the Fe:Co molar ratio. The formation of intermediate metastable (oxy)hydroxide phases is considered pH dependent, providing for a variety of different reaction pathways. Further, inclusion of preformed Co₃O₄ and CoFe₂O₄ NPs to the FeCl₃ solution at pH ~2 in the presence of phosphate surfactant resulted in the synthesis of α-Fe₂O₃ NRs with residual Co₃O₄ and CoFe₂O₄ NPs attached to their surfaces. The CoFe₂O₄ NPs encouraged local dissolution leading to the formation of α-Fe₂O₃ NR surface corrugations.     

Micro/nanometric investigations of the effects of laser ablation in the generation of micro-tools from solid CVD diamond structures

Using pulsed laser ablation, a novel method has been successfully developed for the generation of micro-features in diamond thus enabling the production of precision abrasive like micro-cutting elements into solid diamond micro-grinding tools. This paper examines the effects of the laser ablation on the generation of abrasive micro-features in diamond by using electron energy loss spectroscopy (EELS) and transmission electron microscopy (TEM). Site specific specimen preparation by a focus ion beam (FIB) material removal process has been made possible by the application of platinum and tungsten protective layers, providing the necessary specimen surface stability during the ion beam milling and lift-out operations. The prepared thin section orientated orthogonally to the cutting edge of a laser generated abrasive feature, has allowed the identification of the graphite and diamond allotropes across the ablated interface using EELS. A sequence of TEM images has revealed the extent of surface graphitisation and the high integrity of the diamond substructure. TEM examinations at nanometric resolutions have allowed the visualisation of the diamond and graphite allotropes at molecular level while depicting the abrupt graphite to diamond transition resulting in a highly defined boundary, thereby endorsing the capabilities of the laser ablation process to generate cutting edges with minimal structural damage.     

Performance dependence of InGaP/InGaAs/GaAs pHEMTs on gatemetallization

The performance of InGaP-based pHEMTs as a function of gate metallization is examined for Mo/Au, Ti/Au, and Pt/Au gates. DC and microwave performance of pHEMT's with 0.7-μm gate lengths is evaluated. Transconductance, threshold voltage, f_t, and f_max are found to depend strongly on gate metallization. High-speed performance is achieved, with f_t of 41.3 GHz and f _max of 101 GHz using Mo/Au gates. The difference in performance between devices with different gate metallizations is postulated to be due to a combination of the difference in Schottky barrier heights and different gate-to-channel spacings due to penetration of the gate metal into the InGaP barrier layer