Two-dimensional localization with a single diffuse ultrasound field excitation

Traditional ultrasound imaging methods rely on the bandwidth and center frequency of transduction to achieve axial and radial image resolution, respectively. In this study, a new modality for spatially localizing scattering targets in a two-dimensional field is presented. In this method, the bandwidth of field excitation is high, and the center frequency is lowered such that the corresponding wavelengths are substantially larger than the target profiles. Furthermore, full two-dimensional field measurements are obtained with single send-receive sequences, demonstrating a substantial simplification of the traditional scanning techniques. Field reconstruction is based on temporal-spectral cross-correlations between measured backscatter data and a library of region of interest (ROI) backscatter data measured a priori. The transducer design is based upon a wedge-shaped geometry, which was shown to yield spatially frequency-separated bandwidths of up to 156% with center frequencies of 1.38 MHz. Initial results with these send-and-receive transducer parameters and cylindrical reflection targets in a 10-mm x 10-mm ROI demonstrate two-dimensional target localization to within 0.5 mm. Spatial localization of point scatterers is demonstrated for single and multiple scattering sites.     

Revising the machine smoking regime for cigarette emissions: implications for tobacco control policy

Background

The WHO Framework Convenion on Tobacco Control includes provisions for testing and regulating cigarette emissions. However, the current international standard for generating cigarette emissions—the ISO machine smoking regime—is widely acknowledged to be inappropriate for purposes of setting regulatory restrictions.

Objective

To review alternatives to the ISO machine smoking regime and the extent to which they: 1) Represent human smoking behaviour, 2) Reduce the potential for industry exploitation, particularly in the area of risk communication, and 3) Serve as suitable measures for product regulation.

Methods

Emissions data from 238 Canadian cigarette brands tested under the ISO and “Canadian Intense” machine smoking regimes.

Results

None of the alternative smoking regimes, including the Canadian Intense method, are more “representative” of human smoking behaviour and none provide better predictors of human exposure.

Conclusions

Given that alternatives such as the Canadian Intense regime are subject to the same fundamental limitations as the ISO regime, key questions need to be addressed before any smoking regime should be used to set regulatory limits on smoke emissions. In the meantime, regulators should remove quantitative emission values from cigarette packages and more work should be done on alternative machine smoking methods.The issue of how to test and regulate conventional cigarettes represents a critical challenge for tobacco control. To date, the primary means of testing cigarette toxicity has been to machine smoke the cigarettes according to a standard puffing regime and to measure the chemical emissions in the mainstream smoke. In many jurisdictions, these cigarette “yields” are printed on packages and represent the only source of information on constituents or toxicity available to consumers. Cigarette emissions also serve as a regulatory standard in several of jurisdictions, including the European Union, where brands that generate emissions >10 mg of tar, 1 mg of nicotine or 10 ppm of carbon monoxide are prohibited. The puffing regime used to machine smoke the cigarettes—the International Organization for Standardization (ISO) regime¹—is widely recognised to be inadequate for the purposes of product regulation or consumer information. The ISO regime constitutes a set of puffing parameters that systematically underestimate smoking behaviour in humans.^2,3,4 Tobacco manufacturers have also designed cigarette brands to perform one way under the machine smoking conditions, but to deliver much greater smoke constituents to humans.^5,6 As a result, the emissions generated under the ISO smoking regime have little relationship with actual measures of human exposure, and exaggerate the differences between brands in a manner that has proved deceptive to both consumers and regulators.^7,8,9 Overall, the emissions from the ISO regime have served as more of an industry marketing tool to falsely reassure health‐concerned smokers, rather than as a valid measure of cigarette toxicity.^2,10,11,12There is a growing movement to develop a more meaningful machine testing method. The World Health Organization''s Framework Convention on Tobacco Control (FCTC)—the world''s first international public health treaty—includes provisions for testing and regulating cigarette emissions under Article 9.¹³ These provisions will need to be specified now that the FCTC has come into force. After discussions with the WHO, the ISO convened a working group (ISO TC 126 WG9) to develop recommendations for “…a robust and practical smoking regime that as far as possible is representative of smokers'' behaviour”. Meanwhile, the World Health Organization''s Study Group on Tobacco Product Regulations (WHO TobReg) has developed its own set of recommendations, which were under consideration by the ISO Working Group.¹⁴ There are also concerns that the ISO committee structure responsible for setting tobacco standards is dominated by the tobacco industry.¹²Before any new testing regime is implemented, it is critical to ensure that the new standards will serve the interests of public health rather than the tobacco industry. The purpose of this paper is to review the smoking regimes that are under consideration by the ISO Working Group, and to examine the implications for tobacco control policy and product regulation. In particular, we examine the extent to which the proposed regimes will: (1) succeed in “representing” smoking behaviour in humans and generate better predictors of human exposure; (2) reduce the potential for industry exploitation, particularly in the field of risk communication; and (3) help to establish more effective regulatory limits on cigarette toxicity.     

Supercritical carbon dioxide extraction of lipids from Pythium irregulare

Lipids that contain polyunsaturated fatty acids (PUFA) have therapeutic value. PUFA, however, degrade in high-temperature, oxygen-rich conditions typical of conventional hot solvent-extraction and distillation methods. Supercritical CO₂ extraction was chosen as an alternative method to recover these valuable compounds from the lower fungus, Pythium irregulare. Freeze-dried biomass was subjected to an aqueous phase and placed into a flow-through extraction apparatus. Extraction of oil from this biomass showed some success for moisture contents as high as 30% (wet basis). The addition of a novel CO₂-philic surfactant to the wet biomass with moisture contents as high as 95% (wet basis) increased the extraction rate of fungal oil by more than an order of magnitude. For tests with extraction times of 5 to 6 h, data for the diffusion-controlled region were modeled with an analytical solution to Fick’s second law. Equilibrium data were also obtained for the fungal oil at two isotherms (40 and 60°C) over a pressure range of 13.7 to 27.5 MPa.     

Physical and chemical properties of polypyrrole–carbon fiber interphases formed by aqueous electrosynthesis

The properties of carbon fibers modified by aqueous electrochemical synthesis of pyrrole has been determined by using the dynamic contact angle analyzer (DCA), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR). Electrochemical process parameters such as the initial pyrrole concentration, electrolyte concentration, applied voltage, electrolyte type, and reaction time were systematically varied, and their impact on the polypyrrole–carbon fiber interphases surface free energy and morphology was ascertained. The surface free energies of the polypyrrole–carbon fiber interphases were obtained by using single fiber filaments. SEM analysis of the interphases revealed several distinct surface structures, including smooth, porous, granular, microspheroidal, and leafoidal morphologies. The noncoated but commercially surface oxidized carbon fibers have smooth surface morphology with occasional longitudinal striations. FTIR analysis of the polypyrrole interphases confirmed that the counterions derived from the electrolytes were incorporated into the film. The surface free energies of the electrochemically formed polypyrrole–carbon fiber interphases equivalent to 60–75 dynes/cm, was determined to be up to 40% higher than that for the surface oxidized but unsized carbon fibers equivalent to 50 dynes/cm. This improvement in the surface free energies of the polypyrrole–carbon fiber interphases suggests easy wettability by polymer matrices such as epoxy resin, γ ˜ 47 dynes/cm and, polyimide matrix, γ ˜ 45 dynes/cm. © 1996 John Wiley & Sons, Inc.     

The DMACA–HCl Protocol and the Threshold Proanthocyanidin Content for Bloat Safety in Forage Legumes

A protocol using HCl-acidified 4-dimethylaminocinnamaldehyde (DMACA) was developed for screening proanthocyanidins (PA) in plants. Individual PA-containing cells could be observed following staining of decolourised leaves with DMACA. The quantitative assay using DMACA-HCl to detect soluble PA and butanol–HCl to detect insoluble PA could detect PA content lower than 0·4 mg g⁻¹ dry matter (DM). The DMACA–HCl protocol is recommended for PA detection in low-PA plants because of its higher sensitivity than vanillin–acid protocols. Twenty-two forage legume species, most of which had been reported free of leaf PA but bloat-safe, were re-examined using the DMACA–HCl protocol. PA-positive cells were observed in leaves of 15 species. Measurable amounts of PA were detected in leaves of seven species, with the PA content ranging from 0·6 to 11 mg g⁻¹ DM. White clover ( Trifolium repens L), red clover ( T pratense L) and lucerne ( Medicago sativa L) were also found to have PA-positive leaf trichomes. By analysis of these data and the literature, the threshold PA content for bloat safety in forage legumes was estimated to be 1–5 mg PA g⁻¹ DM.     

PXI平台采用新的商业化标准

PXI平台已发展了七年,它已成为测量和自动化最为成功的工业标准平台之一.PXI不仅能在行业最为萧条的时期快速地发展,而且使用PXI的用户也迅猛增长,在2004年PXI的增长率超过分析家的预测值,达到40%以上.商业化标准促进了PXI在测试到控制的应用中快速地增长,基于PCI Express技术的PXI未来革新将扩大该平台的应用,同时保持向后的兼容性.     

Bead-assisted displacement immunoassay for staphylococcal enterotoxin B on a microchip

A microchip-based, displacement immunoassay for the sensitive laser-induced fluorescence detection of staphylococcal enterotoxin B is presented. The glass microchip device consists of a microchannel that contains a double weir structure for supporting antibody-functionalized microbeads. After a 30-min sample preparation step, the displacement assay was performed without user intervention and produced quantitative results in an additional 20 min. Linear detection responses were observed over 6 orders of magnitude and provided detection limits down to 1 fM (28.5 fg/mL). The surprisingly low detection limits are hypothesized to arise from field-based enrichment analogous to field-amplified stacking, chromatographic effects, and limited diffusion lengths in the microbead bed. The assay was challenged with bovine serum albumin, casein, and milk sample matrixes. This system has the potential to provide highly sensitive detection capabilities for target biomolecules.     

Deconvolution of axisymmetric flame properties using Tikhonov regularization

We present a method based on Tikhonov regularization for solving one-dimensional inverse tomography problems that arise in combustion applications. In this technique, Tikhonov regularization transforms the ill-conditioned set of equations generated by onion-peeling deconvolution into a well-conditioned set that is less susceptible to measurement errors that arise in experimental settings. The performance of this method is compared to that of onion-peeling and Abel three-point deconvolution by solving for a known field variable distribution from projected data contaminated with an artificially generated error. The results show that Tikhonov deconvolution provides a more accurate field distribution than onion-peeling and Abel three-point deconvolution and is more stable than the other two methods as the distance between projected data points decreases.     

Aptamer-based detection and quantitative analysis of ricin using affinity probe capillary electrophoresis

The ability to detect sub-nanomolar concentrations of ricin using fluorescently tagged RNA aptamers is demonstrated. Aptamers rival the specificity of antibodies and have the power to simplify immunoassays using capillary electrophoresis. Under nonequilibrium conditions, a dissociation constant, Kd, of 134 nM has been monitored between the RNA aptamer and ricin A-chain. With use of this free-solution assay, the detection of 500 pM (approximately 14 ng/mL) or 7.1 amol of ricin is demonstrated. The presence of interfering proteins such as bovine serum albumin and casein do not inhibit this interaction at sub-nanomolar concentrations. When spiked with RNAse A, ricin can still be detected down to 1 nM concentrations despite severe aptamer degradation. This approach offers a promising method for the rapid, selective, and sensitive detection of biowarfare agents.