High-temperature superconducting quantum interference device with cooled LC resonant circuit for measuring alternating magnetic fields with improved signal-to-noise ratio

Certain applications of superconducting quantum interference devices (SQUIDs) require a magnetic field measurement only in a very narrow frequency range. In order to selectively improve the alternating-current (ac) magnetic field sensitivity of a high-temperature superconductor SQUID for a distinct frequency, a single-coil LC resonant circuit has been used. Within the liquid nitrogen bath, the coil surrounds the SQUID and couples to it inductively. Copper coils with different numbers of windings were used to cover the frequency range from <1 to nearly 100 kHz. A superconducting coil made of YBa(2)Cu(3)O(7-delta) tape conductor was also tested. With the LC circuit, the signal-to-noise ratio of measurements could be improved typically by one order of magnitude or more in a narrow frequency band around the resonance frequency exceeding a few kilohertz. The best attained equivalent magnetic field resolution was 2.5 fT/radicalHz at 88 kHz. The experimental findings are in good agreement with mathematical analysis of the circuit with copper coil.     

Photoderivatized polymer thin films at quartz crystal microbalance surfaces: sensors for carbohydrate-protein interactions

Photoderivatized polymer-coated gold surfaces have been developed following a perfluorophenylazide-based double ligation strategy. Gold-plated quartz crystal microbalance (QCM) crystals were initially covalently functionalized with a monolayer of poly(ethylene glycol) (PEG), using photo- or thermolytic nitrene formation and insertion. The polymer surfaces were subsequently used as substrates for photoinsertion of carbohydrate-derivatized photoprobes, yielding different recognition motifs for selective protein binding. The resulting robust and biocompatible sensor surfaces were applied to a flow-through QCM instrument for monitoring lectin-carbohydrate interactions in real time. The results clearly show the predicted lectin selectivity, demonstrating the applicability of the approach.     

Light-emitting diodes with 17% external quantum efficiency at 622Mb/s for high-bandwidth parallel short-distance optical interconnects

We report on nonresonant cavity light-emitting diodes (NRC-LED) with large quantum efficiencies and high speed. A maximum quantum efficiency of 31% is measured for a device with an active layer thickness of 120 nm, and 18.7% for a device having an active layer of 30 nm. Further, we report on optical rise and fall times of NRC-LEDs. Even when switched to current levels below 4 mA, at which the external quantum efficiency exceeds 17%, our NRC-LEDs have 10%-90% rise and fall times of less than 2 ns. As a result, eye diagrams taken at this current level at 622 Mb/s are wide open. This demonstrates the suitability of high-efficiency NRC-LEDs for optical interconnects. Finally, from a system's viewpoint it is important to note that the optical output power of NRC-LEDs decreases by only 0.36%/°C     

Continuous epoxidation of soybean oil: operational analysis and process development

Continuous epoxidation of soybean oil: operational analysis and process development The epoxidation of refined soybean oil with peracetic acid is examined having special regard to the mass and heat transfer phenomena as well as to distribution coefficients depending on conversion and temperature. The process is described by a mathematic mechanistic model based on the cooled continuously stirred two-phase tank reactor. The process is limited by hydrodynamics and chemical kinetics. The main operation parameters feed temperature of coolant, volumetric rate of the lipoid phase, and residence time are optimized with respect to the space-time-yield. The two-stage countercurrent cascade of tank reactors leads to higher space-time-yields as well as higher epoxide yields.     

Synthesis and stereochemistry of bis(dithiacrown ether) and dodecylthio substituted (E)-thiodesaurines

Reductive dimerization of dodecylthio substituted 1,2-dithiole-3-thiones 6a–b and trithion-dithiacrown ethers 10a–c with triethyl phosphite furnished bis- and tetrakis (dodecylthio), and bis(dithiacrown ether) substituted thiodesaurines (E)- 11a–b and (E)- 12a–c . The stereochemistry of bis(dithia[15]crown-5)-thiodesaurine (E)- 12b has been determined by X-ray crystallographic analysis.     

Synthesis of 2-Substituted 2-Arylmalonates via Tricarbonylchromium Complexes

Tricarbonylchromium complexes 1 react with monosubstituted malonic acid esters 2 in DMSO at room temperature in the presence of KOtBu to give the complexes 3 . After oxidative demetalation, the appropriate aryl derivatives 4 are obtained in moderate to good overall yields. Diastereoselective arylations of chirally modified malonates such as 5a–c were studied. The stereoselectivity was highest for the products 6c/6c ′ (80:20) with (−)-8-phenylmenthol as alcohol component in the malonate 5 .     

Distribution of chiral PCBs in selected tissues in the laboratory rat

The enantiomeric enrichment of polychlorinated biphenyl (PCB) atropisomers has been reported in both wildlife and in humans. The biological processes causing this enrichment are only poorly investigated, a fact that limits the use of enantiomeric fractions (EFs) as a tool to study various processes of environmental relevance. To further understand these enantioselective processes, this study investigates the tissue distribution and EFs of some PCB atropisomers after administration of PCB mixtures to immature male Sprague-Dawley rats. The mixtures selected for this study, Aroclor 1254 and an environmental mixture extracted from Chlorofen-contaminated soil, are qualitatively different and are known to induce different groups of hepatic enzymes. Animals were sacrificed 6 days after dosing, PCBs were extracted, and, whenever possible, the EFs of PCBs 84, 91, 95, 149, 174, and 176 were determined by chiral gas chromatography. The EFs of PCB 95 (adipose tissue, liver, and skin) and PCB 149 (adipose tissue, liver, skin, and blood) in tissues from Aroclor 1254-treated animals differed significantly from EFs in the Aroclor standard, while only EFs of PCB 95 (blood) and PCB 174 (adipose tissue) in tissues from soil-extract-treated animals were different from those of the Chlorofen soil extract. PCB 149 in tissues from soil-extract-treated animals underwent no statistically significant enantiomeric enrichment. These differences in the EFs clearly suggest that the enantioselective enrichment of PCB atropisomers may correlate with exposure history, and with the induction of hepatic enzymes, and that EFs may be useful chemical markers of physiologic and biochemical changes following exposure to PCBs.     

Validation of recent Geant4 physics models for application in carbon ion therapy

Cancer treatment with energetic carbon ions has distinct advantages over proton or photon irradiation. In this paper we present a simulation model integrated into the Geant4 Monte Carlo toolkit (version 9.3) which enables the use of ICRU 73 stopping powers for ion transport calculations. For a few materials, revised ICRU 73 stopping power tables recently published by ICRU (P. Sigmund, A. Schinner, H. Paul, Errata and Addenda: ICRU Report 73 (Stopping of Ions Heavier than Helium), International Commission on Radiation Units and Measurements, 2009) were incorporated into Geant4, also covering media like water which are of importance in radiotherapeutical applications. We examine, with particular attention paid to the recent developments, the accuracy of current Geant4 models for simulating Bragg peak profiles of ¹²C ions incident on water and polyethylene targets. Simulated dose distributions are validated against experimental data available in the literature, where the focus is on beam energies relevant to ion therapy applications (90-400 MeV/u). A quantitative analysis is performed which addresses the precision of the Bragg peak position and proportional features of the dose distribution. It is shown that experimental peak positions can be reproduced within 0.2% of the particle range in the case of water, and within 0.9% in the case of polyethylene. The comparisons also demonstrate that the simulations accurately render the full width at half maximum (FWHM) of the measured Bragg peaks in water. For polyethylene slight deviations from experimental peak widths are partly attributed to systematic effects due to a simplified geometry model adopted in the simulation setup.