Resonance Raman spectroscopy of carbon nanotubes: pressure effects on G-mode

We use 488 and 568 nm laser Raman spectroscopy under high pressure to selectively follow evolution of Raman G-mode signals of single-walled carbon nanotubes (SWCNTs) of selected diameters and chiralities ((6, 5) and (6, 4)). The G-mode pressure coefficients of tubes from our previous work are consistent with the thick-wall tube model. Here we report the observation of well-resolved G-minus peaks in the Raman spectrum of SWCNTs in a diamond-anvil cell. The pressure coefficients of these identified tubes in water, however, are unexpected, having the high value of over 9 cm^?1 GPa^?1 for the G-plus and the G-minus, and surprisingly the shift rates of the same tubes in hexane have clearly lower values. We also report an abrupt increase of G-minus peak width at about 4 GPa superposed on a continuous peak broadening with pressure.     

CFD investigation of dense phase pneumatic conveying at a pipeline enlargement

The practice of stepping a conveying line is not new and there are many examples in industry; however, the details of the flow behaviour at the step have not been extensively studied. Three step geometries were modelled: an ‘abrupt’ step and two ‘gradual’ step-up geometries from a pipe bore of 75–100 mm. The flow behaviour of a single plug of material passing through these geometries was investigated using the ‘Eulerian’ CFD model from Fluent. Solids volume fractions were recorded at 0.01 s time steps at several point locations, and visualised throughout the pipe.     

Use of modelling to inform public health policy: a case study on the blood-borne transmission of variant-CJD

Since the identification of variant Creutzfeldt–Jacob Disease in the late 1980s, the possibility that this disease might be passed on via blood transfusion has presented challenging policy questions for Government and blood services in the UK. This paper discusses the use of mathematical modelling to inform policy in this area of health protection. We focus on the use of a relatively simple analytical model to explore how many such infections might eventually be expected to result in clinical cases under a range of alternative scenarios of interest to policy, and on the potential impact of possible additional counter measures. We comment on the value of triangulating between findings generated using distinct modelling approaches and observational data.     

Focus on quadrupole ion traps

Editorial

Focus on quadrupole ion traps     

Screening for testosterone, methyltestosterone, 19-nortestosterone residues and their metabolites in bovine urine with enzyme-linked immunosorbent assay (ELISA)

This work reports on the development of rapid enzyme-linked immunosorbent assay for testosterone, methyltestosterone, 19-nortestosterone and their metabolites in real samples of bovine urine. The assays were based on the competition between an immobilised testosterone-BSA conjugate and the analyte for corresponding antibodies, followed by the use of secondary anti-species (α-IgG-HRP) to determine the degree of competition. Urine samples were analysed after 10-fold dilution with the buffer, omitting extraction and hydrolysis. The limits of detection calculated for the original sample were ca. 74, 266 and 131 pg ml⁻¹ (ppt) for testosterone, methyltestosterone and 19-nortestosterone, respectively. In particular, testosterone and methyltestosterone assays offer the advantage to pick up both parent compounds and their major metabolites due to the high cross-reactivity pattern with corresponding antibody used in each assay. The concentration in bovine urine detected by developed method does indicate 19-nortestosterone administration to heifers. The developed assays were applied to urine samples of heifers treated with above androgens.     

Design and fabrication of 0.5 micron GaAs Schottky barrier diodes for low-noise terahertz receiver applications

Recent technological advances have made possible the development of heterodyne receivers with high sensitivity and high spectral resolution for frequencies in the range 1,000–3,000 GHz (1–3 THz). These receivers rely on GaAs Schottky barrier mixer diodes to translate the high-frequency signal to a lower frequency where amplification and signal processing are possible. At these frequencies, the diode quality is a major limitation to the performance of the receiver. The design, fabrication and DC evaluation of a diode for this frequency range is presented. A figure-of-merit cut-off frequency of over 10 THz is achieved with a record low zero biased capacitance of 0.5 fF. Results from RF tests are also given.This work has been supported in part by the National Science Foundation under contract ECS-8720850 and the US Army.