Detection, isolation and enumeration of Yersinia enterocolitica from raw pork

The methods available for the isolation of Yersinia enterocolitica from foods are generally considered to be less than optimal, and methods for estimation of numbers are lacking. Such methods are needed to understand better the significance of foodborne yersiniosis and to provide data for exposure assessment. We describe a method for the detection and enumeration of Y. enterocolitica containing the pYV virulence plasmid (YeP+) in samples from pork surfaces. The method uses a multiplex PCR targeting the ail and virF genes to detect Y. enterocolitica after incubation of surface swabs in Yersinia enrichment broth according to Ossmer. Enumeration was achieved by adapting the enrichment to a most probable number (MPN) method format. A presumptive result was available within 24 h of sample receipt, and YeP+ isolates were confirmed within four days. The presence/absence and MPN methods were evaluated in a pilot survey of 34 packs of raw pork meat purchased from retail outlets in Christchurch, New Zealand. YeP+ was detected by PCR on meat from 32% of the packs, and YeP+ isolates were obtained from 18% of the samples. YeP+ were present at numbers ranging from 0.30 to 5.42 MPN/cm(2). This improved method for the detection and enumeration of YeP+ from meat samples can be used for microbiological surveys to obtain data for assessments of consumer exposure to virulent Y. enterocolitica, and in outbreak investigations.     

Sulfate addition increases methylmercury production in an experimental wetland

Atmospheric mercury is the dominant Hg source to fish in northern Minnesota and elsewhere. However, atmospherically derived Hg must be methylated prior to accumulating in fish. Sulfate-reducing bacteria are thought to be the primary methylators of Hg in the environment. Previous laboratory and field mesocosm studies have demonstrated an increase in methylmercury (MeHg) levels in sediment and peatland porewaters following additions of sulfate. In the current ecosystem-scale study, sulfate was added to half of an experimental wetland at the Marcell Experimental Forest located in northeastern Minnesota, increasing annual sulfate load by approximately four times relative to the control half of the wetland. Sulfate was added on four separate occasions during 2002 and delivered via a sprinkler system constructed on the southeast half (1.0 ha) of the S6 experimental wetland. MeHg levels were monitored in porewater and in outflow from the wetland. Prior to the first sulfate addition, MeHg concentrations (filtered, 0.7 microm) were not statistically different between the control (0.47 +/- 0.10 ng L(-1), n = 12; mean +/- one standard error) and experimental 0.52 +/- 0.05 ng L(-1), n = 18) halves. Following the first addition in May 2002, MeHg porewater concentrations increased to 1.63 +/- 0.27 ng L(-1) two weeks after the addition, a 3-fold increase. Subsequent additions in July and September 2002 did not raise porewater MeHg, but the applied sulfate was not observed in porewaters 24 h after addition. MeHg concentrations in outflow from the wetland also increased leading to an estimated 2.4x increase of MeHg flux from the wetland. Our results demonstrate enhanced methylation and increased MeHg concentrations within the wetland and in outflow from the wetland suggesting that decreasing sulfate deposition rates would lower MeHg export from wetlands.     

Protein separation by electrophoretic-electroosmotic focusing on supported lipid bilayers

An electrophoretic-electroosmotic focusing (EEF) method was developed and used to separate membrane-bound proteins and charged lipids based on their charge-to-size ratio from an initially homogeneous mixture. EEF uses opposing electrophoretic and electroosmotic forces to focus and separate proteins and lipids into narrow bands on supported lipid bilayers (SLBs). Membrane-associated species were focused into specific positions within the SLB in a highly repeatable fashion. The steady-state focusing positions of the proteins could be predicted and controlled by tuning experimental conditions, such as buffer pH, ionic strength, electric field, and temperature. Careful tuning of the variables should enable one to separate mixtures of membrane proteins with only subtle differences. The EEF technique was found to be an effective way to separate protein mixtures with low initial concentrations, and it overcame diffusive peak broadening to allow four bands to be separated simultaneously within a 380 μm wide isolated supported membrane patch.     

Cognitive–behavioral therapy for PTSD and depression symptoms reduces risk for future intimate partner violence among interpersonal trauma survivors.

Objective: Women who develop symptoms of posttraumatic stress disorder (PTSD) and depression subsequent to interpersonal trauma are at heightened risk for future intimate partner violence (IPV) victimization. Cognitive–behavioral therapy (CBT) is effective in reducing PTSD and depression symptoms, yet limited research has investigated the effectiveness of CBT in reducing risk for future IPV among interpersonal trauma survivors. Method: This study examined the effect of CBT for PTSD and depressive symptoms on the risk of future IPV victimization in a sample of women survivors of interpersonal violence. The current sample included 150 women diagnosed with PTSD secondary to an array of interpersonal traumatic events; they were participating in a randomized clinical trial of different forms of cognitive processing therapy for the treatment of PTSD. Participants were assessed at 9 time points as part of the larger trial: pretreatment, 6 times during treatment, posttreatment, and 6-month follow-up. Results: As hypothesized, reductions in PTSD and in depressive symptoms during treatment were associated with a decreased likelihood of IPV victimization at a 6-month follow-up even after controlling for recent IPV (i.e., IPV from a current partner within the year prior to beginning the study) and prior interpersonal traumas. Conclusions: These findings highlight the importance of identifying and treating PTSD and depressive symptoms among interpersonal trauma survivors as a method for reducing risk for future IPV. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Improving nanoparticle dispersion and charge transfer in cadmium telluride tetrapod and conjugated polymer blends

The dispersion of CdTe tetrapods in a conducting polymer and the resulting charge transfer is studied using a combination of confocal fluorescence microscopy and atomic force microscopy (AFM). The results of this work show that both the tetrapod dispersion and charge transfer between the CdTe and conducting polymer (P3HT) are greatly enhanced by exchanging the ligands on the surface of the CdTe and by choosing proper solvent mixtures. The ability to experimentally probe the relationship between particle dispersion and charge transfer through the combination of AFM and fluorescence microscopy provides another avenue to assess the performance of polymer/semiconductor nanoparticle composites.     

"Social–Cognitive influences on change in aggression over time": Erratum.

Reports an error in the original article by S. K. Egan et al (Developmental Psychology, 1998 [Sep], Vol 34[5], 996–1006). On pages 1004–1005, the last sentence of the article should read as follows: "Given that we speculated that the effects of aversive treatment hinge crucially on factors such as timing and whether successful counterattacks occur, such observations, especially if supplemented with measures of social cognitions, might greatly enrich our understanding of how cognition and behavior jointly contribute to social development." The first line of text in the right-hand column on page 1005 should be deleted. (The following abstract of this article originally appeared in record 1998-10846-016.) This study examined whether social cognitions that have been assumed to influence aggression actually forecast change in aggressive habits over time. Participants were 189 3rd- through 7th-grade boys and girls; data on social cognitions and social behaviors were collected in the fall and spring of the school year. Aggression-encouraging cognitions assessed in the fall indeed promoted aggression over the school year, but such developments hinged critically on child sex and on initial (fall) levels of aggression and victimization. Results illustrate the principle that cognitions affect behavioral development mainly when the child's transactions with the social environment support the use of the cognitions as guides for behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Lifetime enhancement of ultrasmall fluorescent liquid polymeric film based optodes by diffusion-induced self-recovery after photobleaching

The major concern with optodes, especially miniaturized ones, has been their photobleaching limited lifetime. Liquid polymer [highly plasticized poly(vinyl chloride)] films are commonly used to prepare fluorescent optical fiber sensors. A major advantage is the ease of their fabrication. It is demonstrated here that, with proper choice of excitation power and illumination time, the sensor will completely recover itself from photobleaching after each measurement. This self-recovery is demonstrated on single-mode optical fibers with 80 microns diameter (3.1 microns active region) and on near-field scanning optical microscope pulled fiber tips with submicrometer diameter (250 nm active region). The single-mode optode can be used for 30,000 measurements with only a 5% signal loss at a signal/noise of > 66. This opens the way for prolonged ratiometric application of such optodes.     

Char oxidation at elevated pressures

Approximately 100 char oxidation experiments were performed at atmospheric and elevated pressures, with two sizes (70 and 40 μm) of Utah and Pittsburgh bituminous coal chars at 1, 5, 10, and 15 atm total pressure. Reactor temperatures were varied between 1000 and 1500 K with 5% to 21% oxygen in the bulk gas, resulting in average particle temperatures ranging from 1400 to 2100 K and burnoff from 15% to 96% (daf). Independently determined particle temperature and overall reaction rate allowed an internal check on the data consistency and provided insight into the products of combustion. The chars burned in a reducing density and reducing diameter mode in an intermediate regime between the kinetic and pore diffusion zones, irrespective of total pressure. Significant surface CO₂ formation occurred at particle temperatures below about 1800 K over the entire pressure range. Particle temperatures were strongly dependent on the oxygen and total pressures; increasing oxygen pressure at constant total pressure resulted in substantial increases in particle temperature, while increasing the total pressure at constant oxygen pressure led to substantial decreases in particle temperature. Increasing total pressure from 1 to 5 atm in an environment of constant gas composition led to modest increases in the reaction rate; the rate decreased with further increases in pressure. Results indicate that ambient pressure global model kinetic parameters cannot be accurately extrapolated to elevated pressures. The apparent reaction rate coefficients (based on the partial pressure form of the nth-order rate equation) showed significant pressure dependence, since both the activation energy and frequency factor decreased with increasing pressure. This suggests that the empirical nth-order rate equation is not valid over the range of pressures encountered in the experiments. However, simulations indicate that the global model can be used to model elevated pressure char oxidation provided pressure-dependent kinetic parameters are used.     

Influence of carbon chain length on the synthesis and yield of fatty amine-coated iron-platinum nanoparticles

Iron oxide nanoparticles are among the most widely used and characterized magnetic nanoparticles. However, metal alloys such as superparamagnetic iron-platinum particles (SIPPs), which have better magnetic properties, are receiving increased attention. Scalable techniques to routinely synthesize SIPPs in bulk need further study. Here, we focus on the role played by the fatty amine ligand in the formation of the bimetallic FePt nanocrystal. More specifically, we compare the effect of varying lengths of fatty amine ligands on the shape, structure, uniformity, composition, and magnetic properties of the SIPPs. We synthesized SIPPs by employing a ‘green’ thermal decomposition reaction using fatty amine ligands containing 12 to 18 carbons in length. Greater fatty amine chain length increased the polydispersity, particle concentration, iron concentration, and the stability of the SIPPs. Additionally, longer reflux times increased the diameter of the particles, but decreased the iron concentration, suggesting that shorter reaction times are preferable. Fourier transform infrared spectroscopy of the SIPPs indicates that the ligands are successfully bound to the FePt cores through the amine group. Superconducting quantum interference device magnetometry measurements suggest that all of the SIPPs were superparamagnetic at room temperature and that SIPPs synthesized using tetradecylamine had the highest saturation magnetization. Our findings indicate that the octadecylamine ligand, which is currently used for the routine synthesis of SIPPs, may not be optimal. Overall, we found that using tetradecylamine and a 30-min reflux reaction resulted in optimal particles with the highest degree of monodispersity, iron content, stability, and saturation magnetization.

PACS

81.07.-b; 75.75.Fk; 61.46.Df     

Mass profile monitoring in trace analysis by gas chromatography/mass spectrometry.

The advantages of gas chromatography/mass spectrometry (GC/MS) selected-ion monitoring (SIM) in the mass profile (MP) mode at medium mass resolving power were investigated for analyses requiring detection of low-picogram quantities of analytes in complex mixtures. The mass profile monitoring provides a certainty at least 10 times greater than that achieved by conventional GC/MS-SIM in the peak-top monitoring mode, and it can be operated at lower mass resolving power to compensate for the loss of sensitivity in the MP mode. The examination of mass profile peak shape, central mass shift, and sequential changes during GC elution not only reveals the presence of interfering compounds but also results in accurate mass measurement for those interferences. The latter feature takes the MP mode beyond the target mass analysis that GC/MS-SIM was originally designed for. This additional dimension of information is particularly useful for those complex and incompletely characterized matrices that are frequently encountered in environmental and biological sample analyses.