Electrochemically deposited sol-gel-derived silicate films as a viable alternative in thin-film design

Sol-gel-derived silicate films were electrochemically deposited on conducting surfaces from a sol consisting of tetramethoxysilane (TMOS). In this method, a sufficiently negative potential is applied to the electrode surface to reduce oxygen to hydroxyl ions, which serves as the catalyst for the hydrolysis and condensation of TMOS. The electrodeposition process was followed by the electrochemical quartz crystal microbalance and cyclic voltammetry. The electrodeposited films were characterized for their surface morphology, porosity, and film thickness using atomic force microscopy, electrochemical probe techniques, surface area and pore size analysis, and profilometry. The electrodeposited films were found to have a completely different surface structure and to be significantly rougher relative to spin-coated films. This is likely due in part to the separation of the gelation and evaporation stages of film formation. The electrodeposited films were found to be permeable to simple redox molecules, such as ruthenium(III) hexaammine and ferrocene methanol. Film thickness can be easily varied from < 75 nm to > 15 microm by varying the electrode potential from -600 mV to more than -1000 mV, respectively. The electrodeposition process was further applied for the electroencapsulation of redox molecules and organic dyes within the silicate network. Cyclic voltammograms for the gel-entrapped ferrocene methanol (FcCH2OH) and ruthenium(II) tris(bipyridine) (Ru(bpy)3(2+)) exhibited the characteristic redox behavior of the molecules. The electroencapsulation of organic dyes in their "native" form proved to be more difficult because these species typically contain reducible functionalities that change the structure of the dye.     

Diffusion of redox probes in hydrated sol-gel-derived glasses. Effect of gel structure

The diffusion coefficients of redox probes entrapped in a silica matrix prepared by the sol-gel process were measured using a combination of cyclic voltammetry and chronoamperometry at an ultramicroelectrode. In this study, the porosities of the gels were varied to assess the importance of constrained environments vs intermolecular interactions on the translational mobility of guests entrapped in this solid host matrix. The average pore diameter of the gels was varied from 40 to 400 A by utilizing different catalysts (HCl, NH3, NaF) or different silicon precursors (tetramethoxysilane or Ludox colloidal silica). The diffusion coefficients of cobalt(II) tris(bipyridine), ferrocenemethyltrimethylammonium ion, and dicyanobis(phenanthroline)iron(II) and their rate of change as the gel dried were found to be nearly identical for gels prepared from TMOS and catalyzed with either HCl, NH3, or NaF. When trapped in gels prepared from Ludox, ferrocenemethanol and potassium ferricyanide diffused at rates identical to that measured in solution. In contrast, Dapp for ferrocenemethyl(trimethylammonium) dropped 1 order of magnitude over a 30-day drying period. These results attest to the importance of intermolecular interactions in governing diffusion in sol-gel-derived materials.     

Sex differences in left-handedness: A meta-analysis of 144 studies.

Human handedness, a marker for language lateralization in the brain, continues to attract great research interest. A widely reported but not universal finding is a greater male tendency toward left-handedness. Here the authors present a meta-analysis of k = 144 studies, totaling N = 1,787,629 participants, the results of which demonstrate that the sex difference is both significant and robust. The overall best estimate for the male to female odds ratio was 1.23 (95% confidence interval = 1.19, 1.27). The widespread observation of this sex difference is consistent with it being related to innate characteristics of sexual differentiation, and its observed magnitude places an important constraint on current theories of handedness. In addition, the size of the sex difference was significantly moderated by the way in which handedness was assessed (by writing hand or by other means), the location of testing, and the year of publication of the study, implicating additional influences on its development. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

VALIDATING A MODEL FOR THE PREDICTION OF DUST GENERATION

Modifications were made to a bench-top dustiness tester to allow for the simultaneous collection of dust generation and separation force data. Tests were performed on limestone, glass beads, titanium dioxide, and lactose, and their results compared to data from a previous study for a large-scale tester. The results of tests on these and four additional materials (instant tea mix, copier toner, baby powder, fly ash) were then compared to a model by Plinke et al. (1995) for predicting the amount and size distribution of dust generation. All of the test materials except glass beads followed the trends in dust generation of the previous study. The results of these tests were then compared to the proposed model. Titanium dioxide and limestone both followed the model very well with 91% and 86% of the data within one standard error of the model respectively. Glass beads and lactose did not perform as well as the other materials each having 45% of their data within one standard error. Overall, 67% of the tests fell within one standard error. Of the four additional materials used to verify the model, only data for the instant tea mix was not within one standard error of the model. These results provide independent confirmation for the ability of the model by Plinke et al. (1995) to predict the amount and size distribution of dust produced by material handling operations.     

Neuropsychological functioning in posttraumatic stress disorder and alcohol abuse.

Studies have shown differences in neuropsychological functioning between groups with posttraumatic stress disorder (PTSD) and control participants. Because individuals with PTSD often have a history of comorbid alcohol abuse, the extent to which an alcohol confound is responsible for these differences remains a concern. The current study compares neuropsychological testing scores in 4 groups of veterans with and without PTSD (PTSD+ and PTSD-, respectively) and with and without a history of alcohol abuse (ETOH+ and ETOH-, respectively): n for PTSD+/ETOH- = 30, n for PTSD+/ETOH- = 37, n for PTSD-/ETOH+ = 30, and n for PTSD-/ETOH- = 31. Results showed that PTSD, when alcohol, educational level, vocabulary, and depression are controlled for, was associated with decreased verbal memory, attention, and processing speed performance. Alcohol abuse history was associated with decreased visual memory performance. By controlling for alcohol and depression, the authors can more conclusively demonstrate that verbal memory and attention differences are associated with PTSD. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Visual sharpness contingency in recognition memory for orientation: Mnemonic illusion suppressed by sensory signature.

A striking finding about human memory is that people's level of accuracy in remembering the orientation of heads on coins is often not simply at the chance level but significantly below it. However, S. W. Kelly, A. M. Burton, T. Kato, and S. Akamatsu (2001) reported that this is not so when two-alternative forced-choice visual recognition is employed. The Kelly et al. result could not be replicated here with a copy of their stimuli. However, the result was successfully replicated with newly created stimuli. A series of experiments provided converging evidence that the mnemonic illusion is suppressed when recognition alternatives possess sharp visual detail. The role of a sensory signature in suppressing the mnemonic illusion and in modulating visual recognition performance in general is delineated. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Forgetting sexual trauma: What does it mean when 38% forget?

L. M. Williams (1994) has shown that many women who were sexually abused as children do not report the abuse when questioned 2 decades later. These findings do not support certain freely made claims about memory, but they do support other claims. The findings do not provide cogent support for the claim that a long stream of childhood sexual traumas is routinely banished from conscious awareness and then can be reliably recovered later. The findings do support the claim that many children can forget about a sexually abusive experience from their past. Extreme claims such as "if you were raped, you'd remember" are disproven by these findings. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Aeromonas species in foods

Aeromonas species have been recognized as potential or emerging foodborne pathogens for more than 20 years. Aeromonads are estuarine bacteria and are ubiquitous in fresh water, fish and shellfish, meats, and fresh vegetables. Actual sourced foodborne outbreaks are few, but epidemiological evidence suggests that the bacterium can cause self-limiting diarrhea, with children being the most susceptible population. Most aeromonads are psychrotrophic and can grow in foods during cold storage. Aeromonads are not resistant to food processing regimes and are readily killed by heat treatment. A host of virulence factors are present, but the exact role of each in human disease has not been fully elucidated.     

Effect of food matrix and cell growth on PCR-based detection of Escherichia coli O157:H7 in ground beef

The purpose of this work was (i) to investigate the feasibility of a previously reported upstream processing method for PCR template preparation to facilitate the detection of Escherichia coli O157:H7 from ground beef and (ii) to assess the impact of cell growth (no growth in the matrix versus growth in the matrix) on molecular detection limits. Two food matrices (autoclaved and raw ground beef) were evaluated in all studies. For no-growth experiments, 10-g meat samples were inoculated with 10(2) to 10(7) CFU/g E. coli O157:H7 and then homogenized. The homogenates were processed to remove large particulates and inhibitors using a two-phase upstream processing method consisting of two sequential centrifugation steps, the second of which used titanous hydroxide to facilitate bacterial immobilization. After upstream processing, sample concentrates were extracted for DNA isolation and amplified by PCR. For growth experiments, 10-g meat samples were inoculated at 1 CFU of E. coli O157:H7 per gram, allowed to grow to 10(2) to 10(7) CFU/g, and then processed for PCR assay. Cell recoveries after upstream processing ranged from 15.9 to 77.6% and were not facilitated by the use of titanous hydroxide, as compared with a saline control (P > 0.05). Bacterial cell recovery and PCR detection limits were similar when comparing autoclaved ground beef and raw ground beef, but cell recoveries were highly variable for raw ground beef samples in which E. coli O157:H7 cells were allowed to grow before processing for detection. Overall, PCR detection limits approximated 10(3) CFU/g of ground beef for all treatments. These results indicate that use of model food systems may not always provide an accurate replication of real-world conditions when evaluating PCR detection limits.