Mechanical alignment of quasi-one-dimensional nanoparticles

Randomly oriented rod or rope-like nanoparticles on the surface of an elastomeric substrate are aligned along one direction simply by stretching the substrate. The technique is demonstrated here using single-walled carbon nanotube ropes, and the degree of alignment is assessed by polarized Raman spectroscopy. The alignment is preserved after the particles are removed from the substrate surface, showing that the aligned nanoparticles can be stamped in patterns onto another surface.     

Further results from a trial comparing a hidden speed camera programme with visible camera operation

As described in a previous paper [Accident Anal. Prev., 33 (2001) 277], the hidden camera programme was found to be associated with significant net falls in speeds, crashes and casualties both in ‘speed camera areas’ (specific signed sites to which camera operation is restricted) and on 100 km/h speed limit roads generally. These changes in speeds, crashes and casualties were identified in the trial area in comparison with a control area where generally highly visible speed camera enforcement continued to be used (and was used in the trial area prior to the commencement of the trial). There were initial changes in public attitudes associated with the trial that later largely reverted to pre-trial levels. Analysis of 2 years’ data of the trial showed that falls in crash and casualty rates and speeds associated with the hidden camera programme were being sustained. It is not possible to separate out the effects of the concealment of the cameras from other aspects of the hidden speed camera programme, such as the four-fold increase in ticketing. This increase in speed camera tickets issued was an expected consequence of hiding the cameras and as such, an integral part of the hidden camera programme being evaluated.     

Exercise training-induced changes in sensitivity to endothelin-1 and aortic and cerebellum lipid profile in rats

The purpose of this work was to study whether exercise training induces changes in the lipid profile of rat aorta and nervous system and in the in vitro intrinsic responsiveness of these tissues to endothelin-1 (ET-1) treatment. The exercise program performed successfully produced the characteristic metabolic alterations of the trained state. Exercise training induced a large and significant increase in the levels of both aortic ethanolamine plasmalogens (PlasEtn) and glucosylceramides. In contrast, a decrease of aortic ceramide and cholesterol levels was evoked by exercise training. ET-1 increased PlasEtn content only in sedentary animals. An exercise-induced increase in cerebellum levels of ceramides and ceramide monohexosides was found. The cerebellum ceramide content was increased by FT-1 more noticeably in sedentary rats than in trained animals. In contrast, cerebral cortex was observed to be largely insensitive to both exercise training and ET-1 treatment. It was concluded that exercise training (i) induces changes in both vascular and cerebellar lipid profiles, the former being much more pronounced than the latter, and (ii) diminishes the aortic and cerebellar sensitivity to ET-1 action.     

多能源综合利用型溴化锂吸收式冷温水机的开发应用

介绍一种新型的可以单独或同时利用多种能源的溴化锂吸收式冷温水机,并对其实际应用进行系统的说明。     

Plastic microchip electrophoresis with analyte velocity modulation. Application to fluorescence background rejection

Fluorescence background interference from the device is inherent in plastic microchips, particularly with blue or UV excitation. Conventionally, microchip background has been reduced with confocal optics or circumvented with specialized long-wavelength fluorophores. We show that microchip background can be rejected with analyte velocity modulation. In this scheme, the driving voltage is modulated at low frequency, typically in the range of 7-20 Hz. Consequently, migration velocities and analyte signals are modulated at the same frequency. Microchip fluorescence is unmodulated, so that lock-in detection (synchronous demodulation) easily separates the analyte signal from background. The technique does not require a laser source. In our implementation, a blue (485 nm) LED is the light source. Simple optics are used to shape the source and focus it to a spot approximately 50 microns in diameter inside a microchip. Photomultiplier detection is employed, and a lock-in amplifier is used to demodulate the signal. Apertures in the system generate a derivative response, which can be converted to conventional bands by integration. Fluorescence rejection provided by our current system lowers detection limits by approximately 1 order of magnitude compared to dc measurements with the same optical train.     

Measurement of dilute 29Si species in solution using a large volume coil and DEFT NMR

A large-sample-volume nuclear magnetic resonance (NMR) spectroscopy probehead has been developed for the detection and characterization of low concentrations of 29Si species in aqueous solution. The approach described entails the use of a large-diameter radio frequency solenoid coil that permits substantially larger sample volumes to be investigated at moderate magnetic field strengths, compared with conventional NMR probehead configurations. In addition, difficulties presented by long 29Si T1 relaxation times have been circumvented by using the DEFT NMR pulse sequence, which permits more rapid signal averaging. Through a combination of these hardware and methodological improvements, high-resolution 29Si NMR spectra have been obtained at 4.2 T (29Si resonance frequency = 36.8 MHz) for an 800 microM solution of 96% 29Si-enriched silicic acid, H4SiO4 (pH approximately 8), with a signal-to-noise ratio of 16 and a line width of 31 Hz after 3 h of total measurement time.     

Graphite microparticles as coatings for quartz crystal microbalance-based gas sensors

The use of graphite particles (1-2 microm) as coatings on quartz crystal microbalances (QCMs) for detection and monitoring of toluene and other volatile organic compounds (VOCs) is described. Unlike the more commonly used polymeric coatings with low glass transition temperatures (Tg), particulate graphitic coatings are not as susceptible to loss of acoustic energy when coating thickness or operational temperature increases. This situation enables the use of relatively thick coatings, which increases the absolute amount of vapor sorbed in the coating and, consequently, lowers the level of detection and enhances operation over a wide temperature range. The use of small size particles also results in a coating with a more porous structure, which facilitates uptake and release of VOCs in comparison to coatings made from high Tg polymers, which have a lower porosity. These attributes, coupled with the inherent stability of graphitic materials, make particulate graphite coatings especially suitable for applications at high temperatures. The advantages of using particulate graphite as a coating on QCMs are demonstrated by comparison to the performance of a few low-Tg polymers [i.e., poly(isobutylene) and poly(diphenoxyphosphazene)] and high-Tg polymers (i.e., polystyrene).     

Objective quantification of the motion of soft tissues in the orbit

Orbital soft-tissue motion analysis aids in the localization and diagnosis of orbital disorders. A technique has been developed to objectively quantify and visualize motion in the orbit during gaze. T1-weighted MR volume sequences are acquired during gaze and soft-tissue motion is quantified using optical flow techniques. The flow field is visualized using color-coding: orientation of the flow vector is coded by hue and magnitude by saturation of the pixel. Current clinical circumstances limit MR image acquisition to short sequences and short acquisition times. The effect of these limitations on the performance of optical flow computation has been studied for four representative optical flow algorithms: on short (nine frames) and long (21 frames) simulated sequences of rotation of a magnetic resonance (MR) imaged object, on short measured MR sequences of controlled rotation of the same object and on short MR sequences of motion in the orbit. On the short simulated and motion-controlled sequences, the Lucas and Kanade algorithm showed the best performance with respect to both accuracy and robustness. These motion estimates were accurate to within 20%. Motion in the orbit ranged between 0.05 and 0.25 mm/degree gaze. Color-coding was found to be attractive as a visualization technique, because it shows both magnitude and orientation of all flow vectors without cluttering.     

The effect of formulation on radioiodide thyroid uptake in the hyperthyroid cat

This investigation was designed to compare in vitro dissolution profiles from sodium iodide capsules with radioiodide thyroid uptake in hyperthyroid cats using sodium iodide capsules prepared with a formulation exhibiting a complete release of radioiodide (I-123) in vitro and a formulation with an incomplete release of radioiodide. In vitro dissolution profiles for I-123 sodium iodide capsules with two different formulations were determined using the USP XXIII dissolution test. The two formulations studied in vitro were sodium phosphate dibasic powder with 1% magnesium stearate and calcium phosphate dibasic powder with 3% magnesium stearate. By 20 min after initiation of the dissolution test, over 95% of the I-123 was released from capsules of sodium phosphate dibasic powder. The capsules of calcium phosphate dibasic powder reached 75% at 65 min, with no further release occurring thereafter. There was a statistically significant difference in the dissolution profiles of the two formulations. The thyroid uptake of I-123 from capsules exhibiting complete release and incomplete release of radioiodide was determined in hyperthyroid cats. At 4 hr, the mean percentage thyroid uptake value for sodium phosphate dibasic powder with 1% magnesium stearate (complete release formulation) was 12.0% compared to 9.4% for calcium phosphate dibasic powder with 3% magnesium stearate (incomplete release formulation); at 24 hr, the values were 34.4% compared to 23.7%. The data suggest that the incomplete dissolution profile observed in vitro may correlate with a reduction in the bioavailability of the radioiodide in vivo. However, using the Wilcoxon signed rank test, statistically significant differences did not occur between the complete release formulation and incomplete release formulation at either 4 hr or 24 hr (p > .05). The results of the in vivo study with five hyperthyroid cats were not conclusive due to the variability in response between individual cats.