CW and pulsed electrically detected magnetic resonance spectroscopy at 263 GHz/12 T on operating amorphous silicon solar cells

Here we describe a new high frequency/high field continuous wave and pulsed electrically detected magnetic resonance (CW EDMR and pEDMR) setup, operating at 263 GHz and resonance fields between 0 and 12 T. Spin dependent transport in illuminated hydrogenated amorphous silicon p-i-n solar cells at 5 K and 90 K was studied by in operando 263 GHz CW and pEDMR alongside with complementary X-band CW EDMR. Benefiting from the superior resolution at 263 GHz, we were able to better resolve EDMR signals originating from spin dependent hopping and recombination processes. 5 K EDMR spectra were found to be dominated by conduction and valence band tale states involved in spin dependent hopping, with additional contributions from triplet exciton states. 90 K EDMR spectra could be assigned to spin pair recombination involving conduction band tail states and dangling bonds as dominating spin dependent transport process, with additional contributions from valence band tail and triplet exciton states.Comment: 8 pages, 4 figure

Performance Pay and Multidimensional Sorting - Productivity, Preferences and Gender

This paper studies the impact of incentives on worker self-selection in a controlled laboratory experiment. Subjects face the choice between a fixed and a variable payment scheme. Depending on the treatment, the variable payment is a piece rate, a tournament or a revenue-sharing scheme. We find that output is higher in the variable pay schemes (piece rate, tournament, and revenue sharing) compared to the fixed payment scheme. This difference is largely driven by productivity sorting. In addition personal attitudes such as willingness to take risks and relative self-assessment as well as gender affect the sorting decision in a systematic way. Moreover, self-reported effort is significantly higher in all variable pay conditions than in the fixed wage condition. Our lab findings are supported by an additional analysis using data from a large and representative sample. In sum, our findings underline the importance of multi-dimensional sorting, i.e., the tendency for different incentive schemes to systematically attract people with different individual characteristics

Pretend Play and Creativity in Preschool-Aged Children: Associations and Brief Intervention

Cognitive and affective processes in play have related to measures of creativity in school-aged children. In a previous examination of these play processes in preschool-aged children with the Affect in Play Scale-Preschool version, cognitive and affective play processes related to divergent thinking. One goal of the current study was to replicate this finding and examine the relationship between pretend play and storytelling creativity in preschoolers. A second goal was to test the effectiveness of a brief play intervention. Adult-led play interventions have effectively improved play skills and related developmental skills for children with documented play deficits. However, there is a need for an empirically-based, brief play intervention for typically developing preschool-aged children. A pilot study found medium to large effect sizes for increased play skills for an intervention with preschool-aged children and their parents. The current study aimed to examine the effectiveness of the intervention without parent involvement. Forty-one typically developing children (ages 4-6 years) participated. Pretend play, divergent thinking, and creative storytelling were assessed at baseline and outcome. Children were randomly assigned to the play skills intervention, which received three 20-30 minute individual play sessions, or the active control. At baseline, results were that cognitive and affective play processes related to divergent thinking and creative storytelling. The play intervention did not significantly improve pretend play skills or creativity in the intervention group compared to the control group. Reasons for the nonsignfiicant findings for the intervention, suggestions for future refinement of the intervention, and implications for childhood development are discussed

Role of Solvent in Excited-State Proton Transfer in Hypericin

The excited-state proton transfer of hypericin is monitored by the rise time (-6-1 2 ps in the solvents investigated) of the component of stimulated emission corresponding to the formation of the long-lived (-5 ns) fluorescent tautomer. The assignment of this excited-state process to proton transfer has been verified by noting that a hypericin analog (mesonaphthobianthrone) lacking labile protons is not fluorescent unless its carbonyl groups are protonated. Recent experimental studies on other systems have suggested that three solvent properties play important roles in excited-state proton transfer: viscosity, hydrogen-bonding character, and dynamic solvation. We find that for hypericin, in a range of protic, aprotic, hydrogen-bonding, and non-hydrogen-bonding solvents in which the viscosity changes by a factor of 60 and the average solvation time changes by a factor of 100, the excited-state proton-transfer rate of hypericin is uncorrelated with these properties and varies not more than a factor of 2 (- 6-1 2 ps) at room temperature. The relative contribution of the bulk solvent polarity is considered, and the role of intramolecular vibrations of hypericin on the proton-transfer rate is discussed

Observation of Excited-State Tautomerization in the Antiviral Agent Hypericin and Identification of Its Fluorescent Species

The absorption spectra, fluorescence spectra, and fluorescence lifetimes of hypericin, an analog lacking hydroxyl groups, mesonaphthobianthrone, and hexamethylhypericin are obtained in aprotic and protic solvents. In aprotic solvents, mesonaphtobianthrone is nonfluorescent. In strong acids such as sulfuric or triflic acids, it becomes fluorescent. Furthermore, its spectrum is very similar to that of hypericin. Similarly, only in sulfuric acid does hexamethylhypericin afford absorption and emission spectra resembling those of hypericin. We therefore conclude that the fluorescent species of hypericin has one or both of its carbonyl groups protonated. The protonation equilibrium in both the ground and the excited state is discussed. The first detailed measurements of the primary processes in the antiviral agent, hypericin, are performed with picosecond resolution and a white-light continuum. Transient absorption measurements of hypericin with - 1-ps resolution indicate that upon optical excitation a new species is created that absorbs in the range of roughly 580-640 nm. This species exhibits a 6-1 2-ps decay, depending on the solvent. It is also observed that the stimulated emission signal, which arises from the fluorescent state, grows in with a time constant of 6-12 ps. Based upon the identification of the fluorescent species as hypericin with one or both carbonyl groups protonated, the rise time for the appearance of the stimulated emission signal is attributed to excited-state tautomerization

Research Notes: Performance of lines from four generations of a backcrossing program involving Glycine max and G. soja

We are interested in the possibility of using Glycine soja as a source of genes for improving cultivars of Glycine max. However, some characteristics in G. soja , such as low yield, vining, l odging, shattering, non-defoliation at maturity, poor seed quality, and non-yellow seed coat color are not acceptable in a cultivar. The purpose of our study is to explore the performance of these characters in lines derived from a backcrossing program in which G. soja is the donor parent

Revealed preferences in a sequential prisoners' dilemma: a horse-race between five utility functions

We experimentally investigate behavior and beliefs in a sequential prisoner’s dilemma. Each subject had to choose an action as first-mover and a conditional action as second-mover. All subjects also had to state their beliefs about others’ second-mover choices. We find that subjects’ beliefs about others’ choices are fairly accurate on average. Using the elicited beliefs, we compare the explanatory power of a few current models of social and moral preferences. The data show clear differences in explanatory power between the preference models, both without and with control for the number of free parameters. The best-performing models explain about 80% of observed behavior. We use the estimated preference parameters to identify biases in subjects’ expectations. We find a consensus bias (whereby subjects believe others behave like themselves) and a certain optimism (whereby subjects overestimate probabilities for favorable outcomes), the former being about twice as strong as the second