Enhanced power conversion efficiency of organic solar cells by embedding Ag nanoparticles in exciton blocking layer

We demonstrate the power conversion efficiency of bulk heterojunction organic solar cells can be enhanced by introducing Ag nanoparticles into organic exciton blocking layer. The Ag nanoparticles were incorporated into the exciton blocking layer by thermal evaporation. Compared with the conventional cathode contact materials such as Al, LiF/Al, devices with Ag nanoparticles incorporated in the exciton blocking layer showed lower series resistances and higher fill factors, leading to a 3.2% power conversion efficiency with a 60 nm active layer; whereas, the conventional devices have only 2.0–2.3% power conversion efficiency. Localized surface plasmon resonances by the Ag nanoparticles and their contribution to photocurrent were also discussed by simulating optical absorptions using a FDTD (finite-difference-time-domain) method.     

Evaluation of the boron tolerant grass, Puccinellia distans, as an initial vegetative cover for the Phytorestoration of a boron-contaminated mining site in Southern California

Land damaged by boron (B) mining should be restored to its natural state with a zero net impact on biodiversity. In an earlier study (Environ. Sci. Technol.2010,44, 7089-7095), we characterized a Turkish ecotype of the grass, Puccinellia distans, which exhibited extreme tolerance to B. Here we evaluated the use of a US ecotype of P. distans as an initial vegetative cover for the phytorestoration of a B mine in southern California. Hydroponic studies revealed that this P. distans ecotype tolerated B concentrations >100 mg B/L and could be germinated and grown in B-contaminated soils taken from the sites to be restored. P. distans grew well in moderately B-contaminated soil (～88 mg B/L saturated extract) amended with added organic matter (peat moss); other soil treatments such as gypsum addition or pH correction were not needed. P. distans also grew in severely B-contaminated soil (～1506 mg B/L) provided that toxic levels of soil B were diluted by the addition of sand and/or organic matter. Our results provide evidence in support of the concept of using the US ecotype of P. distans as an initial vegetative cover for the phytorestoration of B-contaminated soil.     

Direct detection of biologically significant thiols and disulfides with manganese(IV) chemiluminescence

The quantification of low-molecular mass thiols and disulfides involved in cellular redox processes is hindered by oxidation or degradation of analytes during conventional sample preparation steps (including deproteinization and derivatization). Researchers therefore seek techniques that minimize sample handling and permit direct detection of thiols and disulfides within a single chromatographic separation. We demonstrate a new HPLC procedure for these biologically important analytes that incorporates direct chemiluminescence detection with a manganese(IV) reagent. A mixture of seven thiols and disulfides (cysteine, N-acetylcysteine, homocysteine, glutathione (GSH), glutathione disulfide (GSSG), cystine, and homocystine) in their native forms were separated using a C18 column within 20 min. Detection limits for these analytes ranged from 5 × 10(-8) to 1 × 10(-7) M, and the precision for retention times and peak areas was excellent, with relative standard deviations of less than 0.3% and 2%, respectively. This approach was employed to determine two key biomarkers of oxidative stress, GSH and GSSG, in whole blood taken from 12 healthy volunteers. Samples were deproteinized, centrifuged, and diluted prior to analysis using a simple procedure that was shown to avoid significant artificial oxidation of GSH.     

The relationship of parental warm responsiveness and negativity to emerging behavior problems following traumatic brain injury in young children.

Parenting behaviors play a critical role in the child's behavioral development, particularly for children with neurological deficits. This study examined the relationship of parental warm responsiveness and negativity to changes in behavior following traumatic brain injury (TBI) in young children relative to an age-matched cohort of children with orthopedic injuries (OI). It was hypothesized that responsive parenting would buffer the adverse effects of TBI on child behavior, whereas parental negativity would exacerbate these effects. Children, ages 3–7 years, hospitalized for TBI (n = 80) or OI (n = 113), were seen acutely and again 6 months later. Parent–child dyads were videotaped during free play. Parents completed behavior ratings (Child Behavior Checklist; T. M. Achenbach & L. A. Rescorla, 2001) at both visits, with baseline ratings reflecting preinjury behavior. Hypotheses were tested using multiple regression, with preinjury behavior ratings, race, income, child IQ, family functioning, and acute parental distress serving as covariates. Parental responsiveness and negativity had stronger associations with emerging externalizing behaviors and attention-deficit/hyperactivity disorder symptoms among children with severe TBI. Findings suggest that parenting quality may facilitate or impede behavioral recovery following early TBI. Interventions that increase positive parenting may partially ameliorate emerging behavior problems. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Executive functions and social competence in young children 6 months following traumatic brain injury.

Objective: This study examined the impact of traumatic brain injury (TBI) in young children on executive functions and social competence, and particularly on the role of executive functions as a predictor of social competence. Method: Data were drawn from a prospective, longitudinal study. Participants were children between the ages of 3 years 0 months and 6 years 11 months at time of injury. The initial sample included 23 with severe TBI, 64 with moderate TBI, and 119 with orthopedic injuries (OI). All participants were assessed at 3 and 6 months postinjury. Executive functions were assessed using neuropsychological tests (Delayed Alternation task and Shape School) and parent ratings on the Behavior Rating Inventory of Executive Function and Child Behavior Questionnaire. Parents rated children's social competence on the Adaptive Behavior Assessment System, Preschool and Kindergarten Behavior Scales, and Home and Community Social Behavior Scales. Results: Children with severe TBI displayed more negative outcomes than children with OI on neuropsychological tests, ratings of executive functions, and ratings of social competence (η2 ranged from .03 to .11). Neuropsychological tests of executive functions had significant but weak relationships with behavioral ratings of executive functions (ΔR2 ranged from .06 to .08). Behavioral ratings of executive functions were strongly related to social competence (ΔR2 ranged from .32 to .42), although shared rater and method variance likely contributed to these associations. Conclusions: Severe TBI in young children negatively impacts executive functions and social competence. Executive functions may be an important determinant of social competence following TBI. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Life Guard: Evaluation of an ACT-based workshop to facilitate reintegration of OIF/OEF veterans.

Over 2 million soldiers have been deployed to Iraq and Afghanistan since 2001. Evidence suggests that they confront significant difficulties postdeployment, including psychosocial problems such as depression, PTSD, substance abuse, and family distress. Few programs to promote healthy reintegration exist that are evidence-based and designed for those not in formal mental health care. In response to this need, a 2-hour workshop, Life Guard, was developed for the Arkansas National Guard. The workshop is based upon Acceptance and Commitment Therapy (ACT; Hayes & Strosahl, 2004) and emphasizes skill development to promote resiliency and successful postdeployment reintegration. The purposes of this pilot study were to describe the deployment experiences of OIF/OEF veterans and evaluate the effectiveness of the workshop. The sample included 144 veterans (63 intervention and 81 control) in a quasi-experimental, pre-post design (interim 2 months) with a delayed intervention control group. Both groups were largely young, male, Caucasian, and married. Control participants were significantly older, and more educated. Symptoms of a variety of psychological disorders and social adjustment were assessed at baseline and follow-up. Participants reported high levels of exposure to traumatic events, physical injury, and symptoms of psychosocial distress. In contrast to control participants, intervention participants reported significant declines in symptoms of depression, anxiety, and PTSD, and increases in relationship satisfaction. Only effects for depression and relationship satisfaction remained significant in between-group comparisons. Further work is needed to evaluate Life Guard, but results suggest it is a promising workshop to assist with reintegration and resiliency. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

An update on thoron exposure in Canada with simultaneous ²²²Rn and ²²⁰Rn measurements in Fredericton and Halifax

Naturally occurring isotopes of radon in indoor air are identified as the second leading cause of lung cancer after tobacco smoking. Radon-222 (radon gas) and radon-220 (thoron gas) are the most common isotopes of radon. While extensive radon surveys have been conducted, indoor thoron data are very limited. To better assess thoron exposure in Canada, radon/thoron discriminating detectors were deployed in 45 homes in Fredericton and 65 homes in Halifax for a period of 3 months. In this study, radon concentrations ranged from 16 to 1374 Bq m(-3) with a geometric mean (GM) of 82 Bq m(-3) and a geometric standard deviation (GSD) of 2.56 in Fredericton, and from 4 to 2341 Bq m(-3) with a GM of 107 Bq m(-3) and a GSD of 3.67 in Halifax. It is estimated that 18 % of Fredericton homes and 32 % of Halifax homes could have radon concentrations above the Canadian indoor radon guideline of 200 Bq m(-3). This conclusion is significantly higher than the previous estimates made 30 y ago with short-term radon measurements. Thoron concentrations were below the detection limit in 62 % of homes in both cities. Among the homes with detectable thoron concentrations, the values varied from 12 to 1977 Bq m(-3) in Fredericton and from 6 to 206 Bq m(-3) in Halifax. The GM and GSD were 86 Bq m(-3) and 3.19 for Fredericton, and 35 Bq m(-3) and 2.35 for Halifax, respectively. On the basis of these results, together with previous measurements in Ottawa, Winnipeg and the Mont-Laurier region of Quebec, it is estimated that thoron contributes ～8 % of the radiation dose due to indoor radon exposure in Canada.     

End-group functionalization of poly(3-hexylthiophene) as an efficient route to photosensitize nanocrystalline TiO2 films for photovoltaic applications

Bulk heterojunction (BHJ) and dye-sensitized solar cells (DSSCs) have seen increased popularity over recent years and each technology has experienced tremendous improvements in power conversion efficiencies (PCEs), reaching 8 and 12%, respectively. The two technologies have been on independent improvement pathways, and this work establishes a link between them by using the archetypical hole conductor (poly-3-hexylthiophene, P3HT) in BHJs as a sensitizer on TiO(2) for DSSC applications. Three polymers were synthesized and examined as potential TiO(2) sensitizers in DSSCs under AM1.5 solar radiation. Using Grignard metathesis, regioregular P3HT was synthesized then functionalized with either one or two cyanoacrylic acid linker moieties to bind to the TiO(2) surface. End-group modification resulted in minimal changes to the optical and electronic properties as compared to pristine P3HT. Cyclic voltammetry (CV) experiments at anodic potentials of adsorbed sensitizer quantified the amount of alkylthiophene adsorbed on the TiO(2), whereas under reductive sweeps, cyanoacrylic acid end-group binding was determined. CVs of each polymer indicated that loading was drastically different as compared to pristine P3HT with the lowest loading on TiO(2) and monofunctionalized P3HT exhibited the highest loading. The DSSCs showed power conversion efficiencies (PCEs) of 0.1%, 0.2 and 2.2% for the polymer-sensitized TiO(2) of the unfunctionalized, monofunctionalized and difunctionalized polymers, respectively. DSSCs were then subjected to electrochemical impedance spectroscopy (EIS) in the dark and under monochromatic light radiation. The large variance in performance for the functionalized-P3HT sensitizers is attributed to differences in the adsorption modes of sensitizer on the TiO(2) surface, which in the difunctionalized case limits electrolyte recombination and favors forward charge transfer reactions.     

Fat substitutes promote weight gain in rats consuming high-fat diets.

The use of food products designed to mimic the sensory properties of sweet and fat while providing fewer calories has been promoted as a method for reducing food intake and body weight. However, such products may interfere with a learned relationship between the sensory properties of food and the caloric consequences of consuming those foods. In the present experiment, we examined whether use of the fat substitute, olestra, affect energy balance by comparing the effects of consuming high-fat, high-calorie potato chips to the effects of consuming potato chips that sometimes signaled high calories (using high-fat potato chips) and that sometimes signaled lower calories (using nonfat potato chips manufactured with the fat substitute olestra). Food intake, body weight gain and adiposity were greater for rats that consumed both the high-calorie chips and the low-calorie chips with olestra compared to rats that consumed consuming only the high-calorie chips, but only if animals were also consuming a chow diet that was high in fat and calories. However, rats previously exposed to both the high- and low-calorie chips exhibited increased body weight gain, food intake and adiposity when they were subsequently provided with a high fat, high calorie chow diet suggesting that experience with the chips containing olestra affected the ability to predict high calories based on the sensory properties of fat. These results extend the generality of previous findings that interfering with a predictive relationship between sensory properties of foods and calories may contribute to dysregulation of energy balance, overweight and obesity. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

In Situ Carbon Nanotube Formation in Templated Pores of Polymer‐Derived Ceramics

Multi‐walled carbon nanotubes (MWCNTs) have been formed in situ in porous, polymer derived ceramics, using polystyrene (PS) microbeads as pore formers. The microbeads were coated with nickel acetate, as a transition metal catalyst precursor, and then introduced into the preceramic polymer methylphenylpolysiloxane (PMPS). The PMPS served as a precursor for the ceramic matrix and as carbon source for CNT formation. The PS microbead burnout was observed between 200 and 400 °C, leaving behind nickel nanoparticles at the surface of the templated pore walls. Thermal conversion of the precursor to ceramic was carried out in the temperature range between 500 and 1 200 °C. MWCNTs were formed in the templated pores during the pyrolysis step by converting the carbon from the decomposition of PMPS. The oxidation resistance of these composites has been studied and an interesting catalytic oxidation phenomenon was observed that may be quite important for the oxidation of carbon nanotubes.