Soft X-ray spectroscopy of oxide-embedded and functionalized silicon nanocrystals

An X-ray absorption spectroscopic investigation into the electronic and optical properties of silicon nanocrystals (Si-NCs) derived from the thermal processing of hydrogen silsesquioxane (HSQ) is presented. Hydrofluoric (HF) acid etching and subsequent photochemical hydrosilylation with styrene liberates the as-synthesized oxide-embedded Si-NCs from their matrix and renders them solution dispersible through the formation of surface Si–C bonds. The impact of this process on the photoluminescence behavior exhibited by these materials has been studied through near edge X-ray absorption fine structure (NEXAFS) and X-ray excited optical luminescence (XEOL) spectroscopies.     

Effectiveness of multidimensional family therapy with higher severity substance-abusing adolescents: Report from two randomized controlled trials.

Objective: We used growth mixture modeling to examine heterogeneity in treatment response in a secondary analysis of 2 randomized controlled trials testing multidimensional family therapy (MDFT), an established evidence-based therapy for adolescent drug abuse and delinquency. Method: The first study compared 2 evidence-based adolescent substance abuse treatments: individually focused cognitive–behavioral therapy and MDFT in a sample of 224 urban, low-income, ethnic minority youths (average age = 15 years, 81% male, 72% African American). The second compared a cross-systems version of MDFT (MDFT—detention to community) with enhanced services as usual for 154 youths, also primarily urban and ethnic minority (average age = 15 years, 83% male, 61% African American, 22% Latino), who were incarcerated in detention facilities. Results: In both studies, the analyses supported the distinctiveness of 2 classes of substance use severity, characterized primarily by adolescents with higher and lower initial severity; the higher severity class also had greater psychiatric comorbidity. In each study, the 2 treatments showed similar effects in the classes with lower severity/frequency of substance use and fewer comorbid diagnoses. Further, in both studies, MDFT was more effective for the classes with greater overall substance use severity and frequency and more comorbid diagnoses. Conclusions: Results indicate that for youths with more severe drug use and greater psychiatric comorbidity, MDFT produced superior treatment outcomes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Iodide Residues in Milk Vary between Iodine‐Based Teat Disinfectants

Majority of iodine found in dairy milk comes from the diet and teat disinfection products used during milking process. The objective of this study was to evaluate the effects of 4 iodine‐based teat dips on milk iodide concentrations varying in iodine level (0.25% vs. 0.5%, w/w), normal low viscosity dip versus barrier dip, and application method (dip vs. spray) to ensure safe iodine levels in dairy milk when these products are used. The iodine exposure study was performed during a 2‐wk period. The trial farm was purged of all iodine‐based disinfection products for 21 d during a prestudy “washout period,” which resulted in baseline milk iodide range of 145 to 182 ppb. During the experiment, iodine‐based teat dips were used as post‐milking teat disinfectants and compared to a non‐iodine control disinfectant. Milk iodide residue levels for each treatment was evaluated from composited group samples. Introduction of different iodine‐based teat disinfectants increased iodide residue content in milk relative to the control by between 8 and 29 μg/L when averaged across the full trial period. However, residues levels for any treatment remained well below the consumable limit of 500 μg/L. The 0.5% iodine disinfectant increased milk iodide levels by 20 μg/L more compared to the 0.25% iodine. Compared to dip‐cup application, spray application significantly increased milk iodide residue by 21 μg/L and utilized approximately 23% more teat dip. This carefully controlled study demonstrated an increase in milk iodide concentrations from iodine disinfectants, but increases were small and within acceptable limits.     

Book Review

The evaluation of pressure vessel integrity affected by pressurized thermal shock (PTS) events caused by emergency cooling due to a small leak break is being addressed. Comprehensive numerical and experimental investigations were performed at MPA Stuttgart and the HDR plant.

During cold water feeding necessary to maintain core cooling under accident conditions, high temperature gradients arise which cause thermal stresses in the walls near the inner surface of the reactor pressure vessel (RPV). Supposing there are flaws in the inner wall the thermal stresses can increase the stress intensity considerably compared with the stresses caused by internal pressuse. st the same time, the fract/fre toughness of the ferritic reactor pressure vessel matenalls reduced through the coolmg process. Therefore, the possibility of stable or unstable crack growth cannot be ruled out.

This paper describes numerical and experimental investigations with large-scale heavy section specimens with circumferential and semi-elliptical cracks. The whole range of material toughness relevant for RPV integrity studies was tested. A full-scale vessel test at the HDR plant is reported, too. The experimental results were evaluated for validation of the analytical and numerical methods. Results from these investigations contribute to resolving a generic issue in the area of reactor pressure vessel integrity.     

Measure of morphological and performance properties in polymeric silicone foams by X-ray tomography

In the absence of nuclear weapons testing, assuring comparable material performance for replacement of no-longer-available material with modern formulations is difficult. The replacement material must completely replicate the performance of the original. Quantification of morphological characteristics in three dimensions by micro X-ray computed tomography (μCT) lends statistics and property values not otherwise achieved. This allows for the measurement of lot-to-lot, synthesis formula variations, as well as pre- and post-experimental structural changes that would be invisible to qualitative image comparison techniques. Owing to the unavailability of the original material, several novel formulations of poly(dimethylsiloxane) (PDMS) foams were imaged and quantitatively compared to aid in choosing a replacement material. In this study, bulk properties were measured with μCT including, percent void volume, average void equivalent diameter and others, and were collected for four different formulations of PDMS foams from pristine, return for service, as well as samples that were aged by gamma ray exposure. Performance characteristics (e.g., Poisson ratio) were measured and compared. From this study, we will be able to provide more information for the selection of the material that most closely matches the performance of the original material.     

Preliminary design of the ITER ECH Upper Launcher

The design of the ITER electron cyclotron launchers recently reached the preliminary design level - the last major milestone before design finalization. The ITER ECH system contains 24 installed gyrotrons providing a maximum ECH injected power of 20 MW through transmission lines towards the tokamak. There are two EC launcher types both using a front steering mirror; one equatorial launcher (EL) for plasma heating and four upper launchers (UL) for plasma mode stabilization (neoclassical tearing modes and the sawtooth instability). A wide steering angle range of the ULs allows focusing of the beam on magnetic islands which are expected on the rational magnetic flux surfaces q = 1 (sawtooth instability), q = 3/2 and q = 2 (NTMs).In this paper the preliminary design of the ITER ECH UL is presented, including the optical system and the structural components. Highlights of the design include the torus CVD-diamond windows, the frictionless, front steering mechanism and the plasma facing blanket shield module (BSM). Numerical simulations as well as prototype tests are used to verify the design     

Impedimetric Measurements for Monitoring Avidin-Biotin Interaction on Self-Assembled Monolayer

Avidin-biotin has been controllable immobilized on the surface of gold electrodes using mercaptopropionic acid as self-assembled monolayer. Electrochemical impedance spectroscopy (EIS) was employed to investigate the changes that appear at the electrode surface in the presence of a redox mediator, K₃[Fe(CN)₆]. An electrical model more complex than that in other studies was used to interpret the EIS measurements (Randles circuit). This model is very useful because it takes into consideration both the transfer of electrons at the electrode/electrolyte interface and the diffusion of redox species through the double layer. The model allowed us to determine some important parameters like solution resistance R_sol, charge-transfer resistance R_ct, double-layer capacitance C_dl, Warburg resistance R_W, and the diffusion time constant τ. The EIS results proved that immobilization of avidin-biotin increased the charge-transfer resistance R_ct, due to the insulating character of these molecules.     

Investigation of tin-based alternatives for cadmium in optoelectronic thin-film materials

Increasing legislation has steadily been introduced throughout the world to restrict the use of heavy metals, particularly cadmium (Cd) and lead (Pb) in high temperature pigments, ceramics, and optoelectronic material applications. Removal of cadmium from thin-film optical and semiconductor device applications has been hampered by the absence of viable alternatives that exhibit similar properties with stability and durability. We describe a range of tin-based compounds that have been deposited and characterized in terms of their optical and mechanical properties and compare them with existing cadmium-based films that currently find widespread use in the optoelectronic and semiconductor industries.     

Activin B is produced early in antral follicular development and suppresses thecal androgen production

Little is known about the role of activin B during folliculogenesis. This study investigated the expression levels of activin/inhibin subunits (βA, βB, and α), steroid enzyme, and gonadotrophin receptors in theca (TC) and granulosa cells (GC) by QPCR and activin A and B and inhibin A protein levels in follicular fluid (FF) of developing sheep follicles during estrus and anestrus. The effect of activin B on androgen production from primary TC cultures in vitro was also assessed. During folliculogenesis, in anestrus and estrus, FF activin B concentrations and thecal and GC activin βB mRNA levels decreased as follicle diameter increased from 1-3 to >6 mm regardless of estrogenic status. Estrogenic preovulatory follicles had reduced concentrations of FF activins B and A, and TC and GCs expressed higher levels of activin βA mRNA at 3-4 mm, and TCs more inhibin α mRNA at >4 mm stages of development compared with nonestrogenic follicles. Activin B decreased androstenedione production from primary TCs in vitro, an effect blocked by inhibin A. Thus, sheep follicles 1-3 mm in diameter contained high FF levels of activin B, which decreased as the follicle size increased, and, like activin A, suppressed thecal androgen production in vitro, an effect blocked by inhibin. Furthermore, the theca of large estrogenic follicles expressed high levels of inhibin α and activin βA mRNA suggesting local thecal derived inhibin A production. This would inhibit the negative effects of thecal activins B and A ensuring maximum androgen production for enhanced estradiol production by the preovulatory follicle(s).     

No emotional “pop-out” effect in natural scene viewing.

It has been shown that attention is drawn toward emotional stimuli. In particular, eye movement research suggests that gaze is attracted toward emotional stimuli in an unconscious, automated manner. We addressed whether this effect remains when emotional targets are embedded within complex real-world scenes. Eye movements were recorded while participants memorized natural images. Each image contained an item that was either neutral, such as a bag, or emotional, such as a snake or a couple hugging. We found no latency difference for the first target fixation between the emotional and neutral conditions, suggesting no extrafoveal “pop-out” effect of emotional targets. However, once detected, emotional targets held attention for a longer time than neutral targets. The failure of emotional items to attract attention seems to contradict previous eye-movement research using emotional stimuli. However, our results are consistent with studies examining semantic drive of overt attention in natural scenes. Interpretations of the results in terms of perceptual and attentional load are provided. (PsycINFO Database Record (c) 2011 APA, all rights reserved)