Acellular comet assay: a tool for assessing variables influencing the alkaline comet assay

In this study, an acellular modification to the alkaline comet assay to further evaluate key variables within the assay that may influence the outcome of genotoxicity studies is described. This acellular comet assay can detect differences of 0.2 Gy of (60)Co gamma-ray radiation between 0 and 1 Gy and differences of 1 Gy between 0 and 8 Gy; thus, this assay is applicable for a wide range of DNA damage levels. It is also shown that DNA damage from different radiation energies was not significantly different from (60)Co gamma-ray. This assay displayed a statistical increase in DNA damage due to uncontrolled exposure to natural light; however, the slope of the dose-response curve for light-exposed samples was similar to that for samples protected from light. A comparison of the alkaline comet assay with the acellular comet assay allowed for the intrinsic repair capacity of the alkaline comet assay to be quantified.     

Enhancement of wettability and antibiotic loading/release of hydroxyapatite thin film modified by 100 MeV Ag ion irradiation

The effect of swift heavy 100 MeV Ag⁷⁺ ions irradiation was studied on hydroxyapatite (HAp) thin film prepared by pulsed laser deposition technique (PLD). The GIXRD analysis confirmed the absence of any phase in the HAp phase due to irradiation. In addition, there was a considerable decrease in crystallinity and crystallite size on irradiation. There was no significant variation in the stoichiometry of the irradiated films. Irradiation seemed to decrease the optical band gap energy of HAp thin films. The surface roughness, wettability and bioactivity were improved on irradiation of the samples. Amount of amoxicillin loading/release increased (10%) in ion beam irradiated (1 × 10¹² ions cm⁻²) sample. Irradiated sample showed fast rate of amoxicillin (AMX) release than the pristine. Bactericidal effect was found to increase on irradiation. Surface modified and antibiotics incorporated HAp coated titanium implants may be used to prevent post-surgical infections and to promote bone-bonding of orthopedic devices.     

Solid-state charge-based device for control of catalytic carbon monoxide oxidation on platinum nanofilms using external bias and light

Using a Pt/Si catalytic nanodiode, we externally control the rate of CO oxidation on a Pt nanofilm. The catalytic reaction can be turned on and off by alternating between bias states of the device. Additionally, the reaction rate is sensitive to photocurrent induced by visible light. The effects of both bias and light show that negative charge on the Pt increases catalytic activity, while positive charge on the Pt decreases catalytic activity for CO oxidation.     

Characterizing the geometry of InAs nanowires using mirror electron microscopy

Mirror electron microscopy (MEM) imaging of InAs nanowires is a non-destructive electron microscopy technique where the electrons are reflected via an applied electric field before they reach the specimen surface. However strong caustic features are observed that can be non-intuitive and difficult to relate to nanowire geometry and composition. Utilizing caustic imaging theory we can understand and interpret MEM image contrast, relating caustic image features to the properties and parameters of the nanowire. This is applied to obtain quantitative information, including the nanowire width via a through-focus series of MEM images.     

Conditional same-different discrimination by pigeons: Acquisition and generalization to novel and few-item displays.

The authors explored whether pigeons can learn to discriminate simultaneously presented arrays of 16 identical (Same) visual items from arrays of 16 nonidentical (Different) visual items, when the correct choice was conditional on the presence of another cue: the color of the background. In one experiment, pigeons rapidly learned this task and, after training with arrays created from a 72-icon set, they exhibited nearly perfect transfer to novel testing arrays. In a second experiment, pigeons’ accuracy to 24-, 20-, 12-, and 8-icon arrays during later testing remained as high as accuracy to training arrays; although accuracy declined with 4- and 2-icon arrays, it was still significantly above chance. In both experiments, pigeons’ choice reaction time scores nicely complemented their choice accuracy scores. These results suggest that the conditional discrimination procedure is well suited to disclose same-different discrimination in pigeons and to elucidate the interaction between perception and abstraction in conceptual learning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Modulation of field emission properties of znO nanorods during arc discharge

Zinc oxide (ZnO) nanorods have been synthesized via the arc discharge method. Different oxygen partial pressures were applied in the arc discharge chamber to modulate the field emission properties of the as-synthesized ZnO nanorods. Scanning electron microscopy (SEM) was carried out to analyze the morphology of the ZnO nanorods. The ion beam analysis technique of proton induced X-ray emission (PIXE) was performed to probe the impurities in ZnO nanorods. SEM images clearly revealed the formation of randomly oriented ZnO nanorods with diameters between 10-50 nm. It was found that the morphology and the electrical properties of the ZnO nanorods were dependent on the oxygen partial pressure during arc discharge. In addition enhanced UV-sensitive photoconductivity was found for ZnO nanorods synthesized at high oxygen partial pressure during arc discharge. The field emission properties of the nanorods were studied. The turn-on field, which is defined at a current density of 10 microA cm(-2), was about 3 V microm(-1) for ZnO nanorods synthesized at 99% oxygen partial pressure during arc discharge. The turn-on field for ZnO nanorods increased with the decrease of oxygen partial pressure during arc discharge. The simplicity of the synthesis route coupled with the modulation of field emission properties due to the arc discharge method make the ZnO nanorods a promising candidate for a low cost and compact cold cathode material.     

Flux-assisted spreading of an Al–7 wt%Si alloy on TiC

The effect of a K–Al–F-based flux was investigated on the wettability of TiC by an Al–7 wt%Si alloy in the interval of temperatures between 660 and 900 °C in Ar and in atmospheric air. Null spreading was observed without flux whereas perfect wetting was enabled by the flux in both atmospheres. The liquid flux, which provides a locally protective atmosphere by spreading on the surfaces of the substrate and eventually on the Al alloy, dissolves the aluminium oxide covering the molten alloy enabling thus direct contact between the liquid alloy and the TiC substrate. The low tensions for the solid/flux and liquid metal/flux interfaces facilitate spontaneous spreading and instantaneous wetting. Meanwhile, the flux is displaced to the lateral periphery of the substrate and to the surface of the liquid. Under the resolution of the scanning electron microscope, microstructural examination of the interfaces did not reveal reaction products. Rapid infiltration of the alloy into TiC/flux compacts, at low temperatures, correlated well with the flux-assisted spreading kinetics observed.     

Long-term effects of the family bereavement program on multiple indicators of grief in parentally bereaved children and adolescents.

Objectives: This article reports on results from a randomized experimental trial of the effects of the Family Bereavement Program (FBP) on multiple measures of grief experienced by parentally bereaved children and adolescents over a 6-year period. Method: Participants were 244 youths (ages 8–16, mean age = 11.4 years) from 156 families that had experienced the death of a parent. The sample consisted of 53% boys and 47% girls; ethnicity was 67% non-Hispanic White and 33% ethnic minority. Families were randomly assigned to the FBP (N = 135) or a literature control condition (N = 109). Two grief measures, the Texas Revised Inventory of Grief and the Intrusive Grief Thoughts Scale (IGTS) were administered at 4 times over 6 years: pretest, posttest, and 11-month and 6-year follow-ups. A 3rd measure, an adaptation of the Inventory of Traumatic Grief (ITG) was administered only at the 6-year follow-up. Results: Compared with the control group, the FBP group showed a greater reduction in their level of problematic grief (IGTS) at posttest and 6-year follow-up and in the percentage at clinical levels of problematic grief at the posttest. The FBP also reduced scores on a dimension of the ITG, Social Detachment/Insecurity, at 6-year follow-up for 3 subgroups: those who experienced lower levels of grief at program entry, older youths, and boys. Conclusion: These are the first findings from a randomized trial with long-term follow-up of the effects of a program to reduce problematic levels of grief of parentally bereaved youths. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Computer simulation of a biomass gasification-solid oxide fuel cell power system using Aspen Plus

The operation and performance of a SOFC (solid oxide fuel cell) stack on biomass syn-gas from a biomass gasification CHP (combined heat and power) plant is investigated. The objective of this work is to develop a model of a biomass-SOFC system capable of predicting performance under diverse operating conditions. The tubular SOFC technology is selected. The SOFC stack model, equilibrium type based on Gibbs free energy minimisation, is developed using Aspen Plus. The model performs heat and mass balances and considers ohmic, activation and concentration losses for the voltage calculation. The model is validated against data available in the literature for operation on natural gas. Operating parameters are varied; parameters such as fuel utilisation factor (U_f), current density (j) and STCR (steam to carbon ratio) have significant influence. The results indicate that there must be a trade-off between voltage, efficiency and power with respect to j and the stack should be operated at low STCR and high U_f. Operation on biomass syn-gas is compared to natural gas operation and as expected performance degrades. The realistic design operating conditions with regard to performance are identified. High efficiencies are predicted making these systems very attractive.     

Characteristics of feed efficiency within and across lactation in dairy cows and the effect of genetic selection

The objective of the present study was to investigate the phenotypic inter- and intra-relationships within and among alternative feed efficiency metrics across different stages of lactation and parities; the expected effect of genetic selection for feed efficiency on the resulting phenotypic lactation profiles was also quantified. A total of 8,199 net energy intake (NE_I) test-day records from 2,505 lactations on 1,290 cows were used. Derived efficiency traits were either ratio based or residual based; the latter were derived from least squares regression models. Residual energy intake (REI) was defined as NE_I minus predicted energy requirements based on lactation performance; residual energy production (REP) was defined as net energy for lactation minus predicted energy requirements based on lactation performance. Energy conversion efficiency was defined as net energy for lactation divided by NE_I. Pearson phenotypic correlations among traits were computed across lactation stages and parities, and the significance of the differences was determined using the Fisher r-to-z transformation. Sources of variation in the feed efficiency metrics were investigated using linear mixed models, which included the fixed effects of contemporary group, breed, parity, stage of lactation, and the 2-way interaction of parity by stage of lactation. With the exception of REI, parity was associated with all efficiency and production traits. Stage of lactation, as well as the 2-way interaction of parity by stage of lactation, were associated with all efficiency and production traits. Phenotypic correlations among the efficiency and production traits differed not only by stage of lactation but also by parity. For example, the strong phenotypic correlation between REI and energy balance (EB; 0.89) for cows in parity 3 or greater and early lactation was weaker for parity 1 cows at the same lactation stage (0.81), suggesting primiparous cows use the ingested energy for both milk production and growth. Nonetheless, these strong phenotypic correlations between REI and EB suggested negative REI animals (i.e., more efficient) are also in more negative EB. These correlations were further supported when assessing the effect on phenotypic performance of animals genetically divergent for feed intake and efficiency based on parental average. Animals genetically selected to have lower REI resulted in cows who consumed less NE_I but were also in negative EB throughout the entire lactation. Nonetheless, such repercussions of negative EB do not imply that selection for negative REI (as defined here) should not be practiced, but instead should be undertaken within the framework of a balanced breeding objective, which includes traits such as reproduction and health.