Ochratoxin A in dried vine fruit: method development and survey

A method is described for the determination of concentrations of the mycotoxin ochratoxin A in dried vine fruits (currants, raisins and sultanas) using acidic methanolic extraction,immunoaffinity chromatography clean-up and HPLC determination. The limit of detection was estimated as 0.2mug/kg, and recoveries of 63-77% were achieved at 5mug/kg. HPLC-mass spectrometric confirmation of the identity of ochratoxin was obtained. Ochratoxin A and aflatoxins were determined in 60 samples of retail dried vine fruits purchased in the United Kingdom. Ochratoxin A was found in excess of 0.2mug/kg in 19 of 20 currant, 17 of 20 sultana and 17 of 20 raisin samples examined, an overall incidence of 88% . The maximum level found was 53.6mug/kg. No aflatoxin was found in any sample analysed, using a method with a detection limit of 0.2mug/kg for each of aflatoxin B1, B2, G1 and G2.     

Electrical Percolation Behavior in Silver Nanowire–Polystyrene Composites: Simulation and Experiment

The design and preparation of isotropic silver nanowire‐polystyrene composites is described, in which the nanowires have finite L/D (< 35) and narrow L/D distribution. These model composites allow the L/D dependence of the electrical percolation threshold, ?_c, to be isolated for finite‐L/D particles. Experimental ?_c values decrease with increasing L/D, as predicted qualitatively by analytical percolation models. However, quantitative agreement between experimental data and both soft‐core and core–shell analytical models is not achieved, because both models are strictly accurate only in the infinite‐L/D limit. To address this analytical limitation, a soft‐core simulation method to calculate ?_c and network conductivity for cylinders with finite L/D are developed. Our simulated ?_c results agree strongly with our experimental data, suggesting i) that the infinite‐aspect‐ratio assumption cannot safely be made for experimental networks of particles with L/D < 35 and ii) in predicting ?_c, the soft‐core model makes a less significant assumption than the infinite‐L/D models do. The demonstrated capability of the simulations to predict ?_c in the finite‐L/D regime will allow researchers to optimize the electrical properties of polymer nanocomposites of finite‐L/D particles.     

Highly Accurate Quasi-Static Modeling of Coupled Interconnects in CMOS Technology

A new analytic model is presented (the model is based on the induced current density distribution inside silicon substrate) to calculate frequency dependent mutual inductance and resistance per unit length of coupled on-chip interconnects in CMOS technology. The validity of the proposed model has been checked by a comparison with a quasi-TEM spectral domain numerical simulation and equivalent-circuit modeling procedure. It is found that the silicon semiconducting substrate skin effect must be considered for the accurate prediction of the high-frequency characteristics of VLSI interconnects.     

The Effect of Nanotube Content and Orientation on the Mechanical Properties of Polymer–Nanotube Composite Fibers: Separating Intrinsic Reinforcement from Orientational Effects

We have measured the mechanical properties of coagulation‐spun polymer–nanotube composite fibers. Both the fiber modulus, Y, and strength, σ_B, scale linearly with volume fraction, V_f, up to V_f ～10%, after which these properties remain constant. We measured dY/dV_f = 254 GPa and dσ_B/dV_f = 2.8 GPa in the linear region. By drawing fibers with V_f < 10% to a draw ratio of ～60%, we can increase these values to dY/dV_f = 600 GPa and dσ_B/dV_f = 7 GPa. Raman measurements show the Herman's orientation parameter, S, to increase with drawing, indicating that significant nanotube alignment occurs. Raman spectroscopy also shows that the nanotube effective modulus, Y_Eff, also increases with drawing. We have calculated an empirical relationship between the nanotube orientation efficiency factor, η_o, and S. This allows us to fit the data for Y_Eff versus η_o, showing that the fiber modulus scales linearly with η_o, as predicted theoretically by Krenchel. From the fit, we estimate the nanotube modulus to be; Y_NT = 480 GPa. Finally, we show that the fiber strength also scales linearly with η_o, giving an effective interfacial stress transfer of τ = 40 MPa and a nanotube critical length of l_c=1250 nm. This work demonstrates the validity of the Cox‐Krenchel rule of mixtures and shows that continuum theory still applies at the near‐molecular level.     

3D Printed Anatomical Nerve Regeneration Pathways

A 3D printing methodology for the design, optimization, and fabrication of a custom nerve repair technology for the regeneration of complex peripheral nerve injuries containing bifurcating sensory and motor nerve pathways is introduced. The custom scaffolds are deterministically fabricated via a microextrusion printing principle using 3D models, which are reverse engineered from patient anatomies by 3D scanning. The bifurcating pathways are augmented with 3D printed biomimetic physical cues (microgrooves) and path‐specific biochemical cues (spatially controlled multicomponent gradients). In vitro studies reveal that 3D printed physical and biochemical cues provide axonal guidance and chemotractant/chemokinetic functionality. In vivo studies examining the regeneration of bifurcated injuries across a 10 mm complex nerve gap in rats showed that the 3D printed scaffolds achieved successful regeneration of complex nerve injuries, resulting in enhanced functional return of the regenerated nerve. This approach suggests the potential of 3D printing toward advancing tissue regeneration in terms of: (1) the customization of scaffold geometries to match inherent tissue anatomies; (2) the integration of biomanufacturing approaches with computational modeling for design, analysis, and optimization; and (3) the enhancement of device properties with spatially controlled physical and biochemical functionalities, all enabled by the same 3D printing process.     

Injectable Collagen–Genipin Gel for the Treatment of Spinal Cord Injury: In Vitro Studies

Spinal cord injury (SCI) often results in a cavitary lesion, contained within the dura, which involves only a portion of the cord. Injectable biopolymers are an attractive treatment option for SCI to re‐establish cell migratory pathways within the lesion while minimizing the collateral damage attendant to an open surgical procedure. In this study we evaluate a thermoresponsive soluble collagen gel incorporating genipin, an amine reactive covalent cross‐linker with low cytotoxicity and fluorogenic attributes. Unlike previous studies, genipin is being investigated as an in situ covalent cross‐linker that will continue to act on the gel after injection. Physical characterization studies show that the addition of genipin provides control over the mechanical and degradative behavior of the gel, to meet design specifications of an injectable material for neural tissues. Additionally, an improved in situ assay to predict the extent of cross‐linking reaction is investigated. Encapsulation of mesenchymal stem cells (MSCs) in collagen–genipin gels show the gels support cell viability and proliferation, and thus serve as a cell delivery vehicle. Neural stem cells are found to be more sensitive to genipin, with respect to toxicity, as compared to MSCs. From our studies, 0.25‐0.5 mM is an appropriate genipin concentration to use for an in situ forming scaffold capable of delivering cells and therapeutic agents.     

BM3D frames and variational image deblurring

A family of the block matching 3-D (BM3D) algorithms for various imaging problems has been recently proposed within the framework of nonlocal patchwise image modeling , . In this paper, we construct analysis and synthesis frames, formalizing BM3D image modeling, and use these frames to develop novel iterative deblurring algorithms. We consider two different formulations of the deblurring problem, i.e., one given by the minimization of the single-objective function and another based on the generalized Nash equilibrium (GNE) balance of two objective functions. The latter results in the algorithm where deblurring and denoising operations are decoupled. The convergence of the developed algorithms is proved. Simulation experiments show that the decoupled algorithm derived from the GNE formulation demonstrates the best numerical and visual results and shows superiority with respect to the state of the art in the field, confirming a valuable potential of BM3D-frames as an advanced image modeling tool.     

通过可重配置手机对付移动电话盗窃

在英国现在每3分钟就有一部移动电话被盗。这一现象并不仅局限于英国,而是一个全球问题,并且数量在不断上升。例如,在澳大利亚的新南威尔士,1999年10月至2000年9月间约有4万部移动电话被偷或被抢,比前一年增长了100%。     

Assessment of degradation pathways in an aquifer with mixed chlorinated hydrocarbon contamination using stable isotope analysis

The demonstration of monitored natural attenuation (MNA) of chlorinated hydrocarbons in groundwater is typically conducted through the evaluation of concentration trends and parent-daughter product relationships along prevailing groundwater flow paths. Unfortunately, at sites contaminated by mixtures of chlorinated ethenes, ethanes, and methanes, the evaluation of MNA by using solely concentration data and parent-daughter relationships can result in erroneous conclusions regarding the degradation mechanisms that are truly active at the site, since many of the daughter products can be derived from multiple parent compounds. Stable carbon isotope analysis was used, in conjunction with concentration data, to clarify and confirm the active degradation pathways at a former waste solvent disposal site where at least 14 different chlorinated hydrocarbons have been detected in the groundwater. The isotope data indicate that TCE, initially believed to be present as a disposed product and/or a PCE dechlorination intermediate, is attributable to dehydrochlorination of 1,1,2,2-PCA. The isotope data further support that vinyl chloride and ethene in the site groundwater result from dichloroelimination of 1,1,2-trichlorethane and 1,2-dichloroethane, respectively, rather than from reductive dechlorination of the chlorinated ethenes PCE, TCE, or 1,2-DCE. The isotope data confirm that the chlorinated ethanes and chlorinated methanes are undergoing significant intrinsic degradation, whereas degradation of the chlorinated ethenes may be limited. In addition to the classical trend of enriched isotope values of the parent compounds with increasing distance associated to biodegradation, shifts of isotope ratios of degradation byproduct in the opposite direction due to mixing of isotopically light byproducts of biodegradation with compounds from the source are shown to be of high diagnostic value. These data underline the value of stable isotope analysis in confirming transformation processes at sites with complex mixtures of chlorinated compounds.     

Comparison of a real-time PCR and an IMS/culture method to detect Escherichia coli O26 and O111 in minced beef in the Republic of Ireland

This study compared an immuno-magnetic separation (IMS)/culture method and a real-time PCR method to detect Verocytotoxigenic Escherichia coli (VTEC) serovar O26 and/or O111 in minced beef. A total of 65 samples were examined, 40 of which were frozen beef samples previously established as containing E. coli O157, and 25 were samples of fresh minced beef, purchased from butcher shops in the Dublin area. After selective enrichment, all samples were (a) subjected to IMS, plated on differential media and identified as E. coli O26 or O111 using biochemical and immuno-logical methods; and (b) subjected to DNA extraction and real-time PCR analysis using primers and probes against E. coli O111 and O26 serovar specific genes, and verotoxin genes. Overall, from the 65 minced beef samples collected, three were positive for E. coli O26 by real-time PCR, with only one of these samples positive for E. coli O26 by the culture method. One sample was positive for E. coli O111 by both real-time PCR and the culture method. The two samples found positive for E. coli O26 by real-time PCR method but not by culture method belonged to the group of frozen beef samples, indicating that the previously developed culture method for the detection of E. coli O26 may not be suitable for the detection of freeze injured cells. In conclusion, this study highlights the role of beef meat in the transmission of non-O157 VTEC. The results of the study emphasize that the analyses for emergent pathogens should be included in food safety surveillance systems and that the development of standard methods for the detection of E. coli O26 and O111 in routine food testing is needed in order to reduce the consumer exposure to contaminated food.