Comparison of quasistatic to impact mechanical properties of multiwall carbon nanotube/polycarbonate composites

We report the quasistatic tensile and impact penetration properties (falling dart test) of injection-molded polycarbonate samples, as a function of multiwall carbon nanotube (MWNT) concentration (0.0-2.5%). The MWNT were incorporated by dilution of a commercial MWNT/polycarbonate masterbatch. The stiffness and quasistatic yield strength of the composites increased approximately linearly with MWNT concentration in all measurements. The energy absorbed in fracture was, however, a negative function of the MWNT concentration, and exhibited different dependencies in quasistatic and impact tests. Small-angle x-ray scattering (SAXS) showed that the dispersion of the MWNT was similar at all concentrations. The negative effects on energy absorption are attributed to agglomerates remaining in the samples, which were observed in optical microscopy and SAXS. Overall, there was a good correspondence between static and dynamic energy absorptio

On the generalized Davenport constant and the Noether number

Known results on the generalized Davenport constant related to zero-sum sequences over a finite abelian group are extended to the generalized Noether number related to the rings of polynomial invariants of an arbitrary finite group. An improved general upper bound is given on the degrees of polynomial invariants of a non-cyclic finite group which cut out the zero vector.Comment: 14 page

Psychological Flexibility Is Key for Reducing the Severity and Impact of Fibromyalgia

Fibromyalgia has a significant impact on the lives of patients; symptoms are influenced by psychological factors, such as psychological flexibility and catastrophizing. The objective of this study was to determine the importance of these variables in moderating the association between the severity and impact of fibromyalgia symptoms. A total of 187 patients from a general hospital population were evaluated using the Combined Index of Severity of Fibromyalgia (ICAF), the Fibromyalgia Impact Questionnaire (FIQ), the Acceptance and Action Questionnaire-II (AAQ-II), and the Pain Catastrophizing Scale (PCS). A series of multiple regression analyses were carried out using the PROCESS macro and decision tree analysis. The results show that psychological flexibility modulates the relation between severity and the impact of fibromyalgia symptoms. Catastrophism has residual importance and depends on the interaction with psychological flexibility. Interaction occurs if the severity of the disease is in transition from a mild to a moderate level and accounts for 40.1% of the variance in the sample. These aspects should be considered for evaluation and early intervention in fibromyalgia patients

Impaired Punishment Learning in Conduct Disorder

Objective: Conduct disorder (CD) has been associated with deficits in the use of punishment to guide reinforcement learning (RL) and decision making. This may explain the poorly planned and often impulsive antisocial and aggressive behavior in affected youths. Here, we used a computational modeling approach to examine differences in RL abilities between CD youths and typically developing controls (TDCs). Specifically, we tested 2 competing hypotheses that RL deficits in CD reflect either reward dominance (also known as reward hypersensitivity) or punishment insensitivity (also known as punishment hyposensitivity). Method: The study included 92 CD youths and 130 TDCs (aged 9-18 years, 48% girls) who completed a probabilistic RL task with reward, punishment, and neutral contingencies. Using computational modeling, we investigated the extent to which the 2 groups differed in their learning abilities to obtain reward and/or to avoid punishment. Results: RL model comparisons showed that a model with separate learning rates per contingency explained behavioral performance best. Importantly, CD youths showed lower learning rates than TDCs specifically for punishment, whereas learning rates for reward and neutral contingencies did not differ. Moreover, callous-unemotional (CU) traits did not correlate with learning rates in CD. Conclusion: CD youths have a highly selective impairment in probabilistic punishment learning, regardless of their CU traits, whereas reward learning appears to be intact. In summary, our data suggest punishment insensitivity rather than reward dominance in CD. Clinically, the use of punishment-based intervention techniques to achieve effective discipline in patients with CD may be a less helpful strategy than reward-based techniques.</p

Impaired Punishment Learning in Conduct Disorder

Objective: Conduct disorder (CD) has been associated with deficits in the use of punishment to guide reinforcement learning (RL) and decision making. This may explain the poorly planned and often impulsive antisocial and aggressive behavior in affected youths. Here, we used a computational modeling approach to examine differences in RL abilities between CD youths and typically developing controls (TDCs). Specifically, we tested 2 competing hypotheses that RL deficits in CD reflect either reward dominance (also known as reward hypersensitivity) or punishment insensitivity (also known as punishment hyposensitivity). Method: The study included 92 CD youths and 130 TDCs (aged 9-18 years, 48% girls) who completed a probabilistic RL task with reward, punishment, and neutral contingencies. Using computational modeling, we investigated the extent to which the 2 groups differed in their learning abilities to obtain reward and/or to avoid punishment. Results: RL model comparisons showed that a model with separate learning rates per contingency explained behavioral performance best. Importantly, CD youths showed lower learning rates than TDCs specifically for punishment, whereas learning rates for reward and neutral contingencies did not differ. Moreover, callous-unemotional (CU) traits did not correlate with learning rates in CD. Conclusion: CD youths have a highly selective impairment in probabilistic punishment learning, regardless of their CU traits, whereas reward learning appears to be intact. In summary, our data suggest punishment insensitivity rather than reward dominance in CD. Clinically, the use of punishment-based intervention techniques to achieve effective discipline in patients with CD may be a less helpful strategy than reward-based techniques.</p

Reward processing in autism: a thematic series

This thematic series presents theoretical and empirical papers focused on understanding autism from the perspective of reward processing deficits. Although the core symptoms of autism have not traditionally been conceptualized with respect to altered reward-based processes, it is clear that brain reward circuitry plays a critical role in guiding social and nonsocial learning and behavior throughout development. Additionally, brain reward circuitry may respond to social sources of information in ways that are similar to responses to primary rewards, and recent clinical data consistently suggest abnormal behavioral and neurobiologic responses to rewards in autism. This thematic series presents empirical data and review papers that highlight the utility of considering autism from the perspective of reward processing deficits. Our hope is that this novel framework may further elucidate autism pathophysiology, with the ultimate goal of yielding novel insights with potential therapeutic implications

Screening for affective dysregulation in school-aged children: relationship with comprehensive measures of affective dysregulation and related mental disorders

Affective dysregulation (AD) is characterized by irritability, severe temper outbursts, anger, and unpredictable mood swings, and is typically classified as a transdiagnostic entity. A reliable and valid measure is needed to adequately identify children at risk of AD. This study sought to validate a parent-rated screening questionnaire, which is part of the comprehensive Diagnostic Tool for Affective Dysregulation in Children (DADYS-Screen), by analyzing relationships with comprehensive measures of AD and related mental disorders in a community sample of children with and without AD. The sample comprised 1114 children aged 8–12 years and their parents. We used clinical, parent, and child ratings for our analyses. Across all raters, the DADYS-Screen showed large correlations with comprehensive measures of AD. As expected, correlations were stronger for measures of externalizing symptoms than for measures of internalizing symptoms. Moreover, we found negative associations with emotion regulation strategies and health-related quality of life. In receiver operating characteristic (ROC) analyses, the DADYS-Screen adequately identified children with AD and provided an optimal cut-off. We conclude that the DADYS-Screen appears to be a reliable and valid measure to identify school-aged children at risk of AD

Gratitude mediates quality of life differences between fibromyalgia patients and healthy controls

Purpose: Despite a growing literature on the benefits of gratitude for adjustment to chronic illness, little is known about gratitude in medical populations compared to healthy populations, or the degree to which potential deficits in gratitude might impact quality of life. The purpose of the present study was to (1) examine levels of gratitude and quality of life in fibromyalgia patients and healthy controls and (2) consider the role of gratitude in explaining quality of life differences between fibromyalgia patients and healthy controls. Methods: Participants were 173 fibromyalgia patients and 81 healthy controls. All participants completed measures of gratitude, quality of life, and socio-demographics. Results: Although gratitude was positively associated with quality of life, levels of gratitude and quality of life were lower in the fibromyalgia sample relative to the healthy controls. This difference in gratitude partially mediated differences in quality of life between the two groups after controlling for socio-demographic variables. Conclusions: Our findings suggest that gratitude is a valuable positive psychological trait for quality of life in people with fibromyalgia. Interventions to improve gratitude in this patient population may also bring enhancement in quality of life

Identifying cortical structure markers of resilience to adversity in young people using surface-based morphometry

Previous research on the neurobiological bases of resilience in youth has largely used categorical definitions of resilience and voxel-based morphometry methods that assess gray matter volume. However, it is important to consider brain structure more broadly as different cortical properties have distinct developmental trajectories. To address these limitations, we used surface-based morphometry and data-driven, continuous resilience scores to examine associations between resilience and cortical structure. Structural MRI data from 286 youths (Mage = 13.6 years, 51% female) who took part in the European multi-site FemNAT-CD study were pre-processed and analyzed using surface-based morphometry. Continuous resilience scores were derived for each participant based on adversity exposure and levels of psychopathology using the residual regression method. Vertex-wise analyses assessed for correlations between resilience scores and cortical thickness, surface area, gyrification and volume. Resilience scores were positively associated with right lateral occipital surface area and right superior frontal gyrification and negatively correlated with left inferior temporal surface area. Moreover, sex-by-resilience interactions were observed for gyrification in frontal and temporal regions. Our findings extend previous research by revealing that resilience is related to surface area and gyrification in frontal, occipital and temporal regions that are implicated in emotion regulation and face or object recognition