SLS Booster Development

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The Psychology of Two-Part Tariffs

This paper investigates preferences for two-part tariff pricing plans which require consumers to pay a flat fee plus a per unit surcharge for usage beyond an allowance. People have difficulty estimating the effective cost of a two-part tariff, so they apply heuristics to the most salient attributes. Compared to a normative benchmark of expected cost, these heuristics lead people to excessively choose plans with smaller flat fees, larger usage allowances, and lower overage rates. When these attributes are in conflict, people assign greater importance to comparisons of the two attributes that provide upside protection against overage charges: the usage allowance and the overage rate. The presence of usage uncertainty heightens the reliance on these comparisons, and calculating a cost does not appear to reduce them

KINEMATIC AND KINETIC PATTERNS IN OLYMPIC WEIGHTLIFTING

The purpose of this study was to identify lower extremity kinematic and kinetic patterns during weightlifting movements and to compare them across different external loads. Subjects completed multiple sets of the clean exercise at various percentage loads. Principal component analysis (PCA) was used to extract kinematic and kinetics patterns of the hip, knee, and ankle joint across the loads. These patterns were then compared across joint and percentage load. Results indicate that lower extremity kinematics and kinetics can be characterized through combinations of PCA-derived patterns. Patterns differed predominantly between joints, but not across percentage loads. The results point to joint-specific lower extremity function during Olympic weightlifting and quantified important technical aspects

How to estimate the measurement error variance associated with ancestry proportion estimates

To show how the variance of the measurement error (ME) associated with individual ancestry proportion estimates can be estimated, especially when the number of ancestral populations (k) is greater than 2. We extend existing internal consistency measures to estimate the ME variance, and we compare these estimates with the ME variance estimated by use of the repeated measurement (RM) approach. Both approaches work by dividing the genotyped markers into subsets. We examine the effect of the number of subsets and of the allocation of markers to each subset on the performance of each approach. We used simulated data for all comparisons. Independently of the value of k, the measures of internal reliability provided less biased and more precise estimates of the ME variance than did those obtained with the RM approach. Both methods tend to perform better when a large number of subsets of markers with similar sizes are considered. Our results will facilitate the use of ME correction methods to address the ME problem in individual ancestry proportion estimates. Our method will improve the ability to control for type I error inflation and loss of power in association tests and other genomic research involving ancestry estimates

Crecimiento en función de la densidad de poliquetos Diopatra aciculata

Effects of intraspecific density on growth of the tube-building polychaete Diopatra aciculata (Onuphidae) were examined over a three-month period within a marine worm aquaculture facility. Three polychaete densities (500, 1000 and 2000 worms/m2) were represented within triplicate 0.30 m2 boxes containing late juvenile D. aciculata, sandy sediment and recirculating seawater. Daily food ration per worm was held constant across all density levels. Total length, weight and number of segments were recorded for 20 polychaetes randomly removed from each of nine treatment boxes at weeks 1, 7 and 14. Mean daily growth was higher during weeks 1-7 than during weeks 7-14 for all growth variables at each density level. Polychaetes at the highest density level exhibited lower rates of growth and more broken and/or regenerating posterior segments than those at low density. High D. aciculata density was also associated with reduced dissolved oxygen concentrations and high polychaete mortality (20%). At medium polychaete density (1000/m2), D. aciculata exhibited low levels of apparent stress and high biomass return per unit area, both of which are important considerations in the aquaculture rearing of this species. We suggest that further studies focus on age- and size-related factors contributing to density effects on polychaete growth.Durante un período de más de tres meses se examinaron en instalaciones de acuicultura de gusanos marinos los efectos de la densidad interespecífica en el crecimiento del poliqueto tubícola Diopatra aciculata (Onuphidae). Se utilizaron tres niveles de densidad de poliquetos (aproximadamente 500, 1000 y 2000 gusanos/m2) en cajas experimentales de 0,30 m2 replicadas, conteniendo ejemplares juveniles avanzados de D. aciculata y sedimento arenoso, todo ello con recirculación de agua marina. La ración diaria de alimento por gusano se mantuvo constante en todos los niveles de densidad. Se registró la longitud total, el peso, y el número de segmentos en 20 poliquetos extraídos aleatoriamente para cada tratamiento durante las semanas 1, 7, y 14. Para cada uno de los niveles de densidad estudiados, el crecimiento diario promedio durante el período entre la semana 1 y la 7 fue mayor que durante el período entre la semana 7 y la 14 en todas las variables de crecimiento. Los poliquetos cultivados a mayores densidades poblacionales exhibieron menores tasas de crecimiento y un mayor número de segmentos posteriores fragmentados y/o regenerados que aquellos cultivados a menores densidades de población. Asimismo, la alta densidad de D. aciculata provocó menores concentraciones de oxígeno disuelto y un mayor índice de mortalidad de poliquetos (20% promedio). Al nivel medio de densidad de poliquetos (1000/m2), los ejemplares de D. aciculata presentaron un bajo nivel de estrés aparente y una elevada producción de biomasa por unidad de área, dos factores importantes en la crianza mediante técnicas de acuicultura de esta especie. Para posteriores estudios, se propone concentrarse en los efectos de la densidad en el comportamiento interactivo y en la competencia por el alimento. &nbsp

Predictors of Comorbid Eating Disorders and Association with Other Obsessive-Compulsive Spectrum Disorders in Trichotillomania

Trichotillomania (TTM) and eating disorders (ED) share many phenomenological similarities, including ritualized compulsive behaviors. Given this, and that comorbid EDs may represent additional functional burden to hair pullers, we sought to identify factors that predict diagnosis of an ED in a TTM population. Subjects included 555 adult females (age range 18–65) with DSM-IV-TR TTM or chronic hair pullers recruited from multiple sites. 7.2% (N = 40) of our TTM subjects met criteria for an ED in their lifetime. In univariable regression analysis, obsessive-compulsive disorder (OCD), Yale-Brown Obsessive Compulsive Scale (Y-BOCS) worst-ever compulsion and total scores, certain obsessive-compulsive spectrum disorders, anxiety disorder, attention-deficit/hyperactivity disorder (ADHD), and substance disorder all met the pre-specified criteria for inclusion in the multivariable analysis. In the final multivariable model, diagnosis of OCD (OR: 5.68, 95% CI: 2.2–15.0) and diagnosis of an additional body-focused repetitive behavior disorder (BFRB) (OR: 2.69, 95% CI: 1.1–6.8) were both associated with increased risk of ED in TTM. Overall, our results provide further support of the relatedness between ED and TTM. This finding highlights the importance of assessing for comorbid OCD and additional BFRBs in those with TTM. Future research is needed to identify additional predictors of comorbid disorders and to better understand the complex relationships between BFRBs, OCD and EDs

Most Published Research Findings Are False—But a Little Replication Goes a Long Way

While the authors agree with John Ioannidis that "most research findings are false," here they show that replication of research findings enhances the positive predictive value of research findings being true

Striatal abnormalities in trichotillomania: a multi-site MRI analysis.

Trichotillomania (hair-pulling disorder) is characterized by the repetitive pulling out of one's own hair, and is classified as an Obsessive-Compulsive Related Disorder. Abnormalities of the ventral and dorsal striatum have been implicated in disease models of trichotillomania, based on translational research, but direct evidence is lacking. The aim of this study was to elucidate subcortical morphometric abnormalities, including localized curvature changes, in trichotillomania. De-identified MRI scans were pooled by contacting authors of previous peer-reviewed studies that examined brain structure in adult patients with trichotillomania, following an extensive literature search. Group differences on subcortical volumes of interest were explored (t-tests) and localized differences in subcortical structure morphology were quantified using permutation testing. The pooled sample comprised N=68 individuals with trichotillomania and N=41 healthy controls. Groups were well-matched in terms of age, gender, and educational levels. Significant volumetric reductions were found in trichotillomania patients versus controls in right amygdala and left putamen. Localized shape deformities were found in bilateral nucleus accumbens, bilateral amygdala, right caudate and right putamen. Structural abnormalities of subcortical regions involved in affect regulation, inhibitory control, and habit generation, play a key role in the pathophysiology of trichotillomania. Trichotillomania may constitute a useful model through which to better understand other compulsive symptoms. These findings may account for why certain medications appear effective for trichotillomania, namely those modulating subcortical dopamine and glutamatergic function. Future work should study the state versus trait nature of these changes, and the impact of treatment

Latent traits of impulsivity and compulsivity: towards dimensional psychiatry

Background: The concepts of impulsivity and compulsivity are commonly used in psychiatry. Little is known about whether different manifest measures of impulsivity and compulsivity (behavior, personality, and cognition) map onto underlying latent traits; and if so, their inter-relationship. Methods: 576 adults were recruited using media advertisements. Psychopathological, personality, and cognitive measures of impulsivity and compulsivity were completed. Confirmatory Factor Analysis was used to identify the optimal model. Results: The data were best explained by a two factor model, corresponding to latent traits of impulsivity and compulsivity respectively, which were positively correlated with each other. This model was statistically superior to the alternative models of their being one underlying factor (“disinhibition”) or two anti-correlated factors. Higher scores on the impulsive and compulsive latent factors were each significantly associated with worse quality of life (both p<0.0001). Conclusions: This study supports the existence of latent functionally impairing dimensional forms of impulsivity and compulsivity, which are positively correlated. Future work should examine the neurobiological and neurochemical underpinnings of these latent traits; and explore whether they can be used as candidate treatment targets. The findings have implications for diagnostic classification systems, suggesting that combining categorical and dimensional approaches may be valuable and clinically relevant