Effect of support foot placement on football instep kick performance

Although the support foot plays an important role in kicking a football, there has been a paucity of research exploring the effect of the placement of the support foot on kicking performance. To investigate the kick performance under different support foot positions, ten male footballers were recruited to participate in two experiments: one determining the maximum ball speed and the second determining accuracy. The participants were instructed to plant their support foot on one of nine different spots marked in the form of a 3 × 3 shape on a piece of artificial grass and asked to kick the ball. In the first (maximum speed) test, the participants tried their best to kick the ball at the maximum ball speed from nine different support foot positions. In the second (accuracy) test, the participants kicked the ball toward the target area without restricting the support foot position. The ball speed, as well as the success rate, were recorded from each support foot position. Significantly higher ball speed and accuracy were obtained at medial positions than was the case at lateral positions from the nine spots. It was concluded that although footballers may choose different positions for support foot placement, the maximum ball speed and better accuracy could be expected when the support foot was next to or slightly in front of the ball centre without too much side-by-side separation (27-37 cm).

Biomechanical fidelity of athletic training using virtual reality head-mounted display: the case of preplanned and unplanned sidestepping

Virtual reality has recently been recognised as an effective tool for investigating visual-perceptual tasks. To develop a sport-specific virtual environment with realistic locomotion, it is crucial to examine the effect of using virtual reality devices on athletes performing intense and complex movements. Twelve collegiate football players were instructed to perform pre-planned and unplanned sidestepping in both environments with the same dimension and experimental setup in the virtual environment as in the real one. Analysis of the performance and knee biomechanical parameters showed that movements performed in the two environments were generally comparable. Consistent changes in approach velocity and knee angle/moment under unplanned conditions (compared with preplanned conditions) were also found in the virtual environment as in the real one, except for the significantly larger peak flexion angle (p < .05) observed in the virtual environment. Interestingly, half of the participants changed from producing abduction to adduction moment at the weight acceptance phase in the preplanned condition (p < .05). These findings suggested that while it is generally feasible to use virtual reality head-mounted displays for designated experiments and training, the effect of wearing virtual reality devices could be somewhat subject-specific.

Control of a virtual vehicle influences postural activity and motion sickness in pre-adolescent children

Among adults, persons in control of a vehicle (i.e., drivers) are less likely to experience motion sickness compared to persons in the same vehicle who do not control it (i.e., passengers). This "driver-passenger effect" is well-known in adults, but has not been evaluated in children. Using a yoked-control design with seated pre-adolescent children, we exposed dyads to a driving video game. In each dyad, one child (the driver) drove the virtual vehicle. Their performance was recorded, and later shown to the other child (the passenger). Thus, visual motion stimuli were identical for the members of each dyad. During exposure to the video game, we monitored the quantitative kinematics of head and torso movements. Participants were instructed to discontinue participation immediately if they experienced any symptoms of motion sickness, however mild. Accordingly, the movements that we recorded preceded the onset of motion sickness. Results revealed that Passengers (73.08%) were more likely than Drivers (42.31%) to state that they were motion sick. Drivers tended to move more than passengers, and with a greater degree of multifractality. The magnitude of movement was greater among participants who later reported motion sickness than among those who did not. In addition, for the multifractality of movement a statistically significant interaction revealed that postural precursors of motion sickness differed qualitatively between Drivers and Passengers. Overall, the results reveal that control of a virtual vehicle reduces the risk of motion sickness among pre-adolescent children.

Protective parenting behavior buffers the impact of racial discrimination on depression among Black youth

The adverse impact of racial discrimination on youth, and particularly its impact on the development of depressive symptoms, has prompted attention regarding the potential for family processes to protect youth from these erosive effects. Evidence from non-experimental studies indicates that protective parenting behavior (PPB) which occurs naturally in many Black families can buffer youth from the negative impact of racial discrimination. Of interest is whether "constructed resilience" developed through family-centered prevention programming can add to this protective buffering. The current paper examines the impact of constructed resilience in the form of increased protective parenting using 295 families randomly assigned either to a control condition or to the Protecting Strong African American Families (ProSAAF) program, a family-based prevention program previously shown to enhance protective parenting. We found that baseline racial discrimination was predictive of change in youths' depressive symptoms across the pre-post study period. Second, we found that parents participating in ProSAAF, relative to those randomly assigned to the control group, significantly improved in their use of an intervention targeting PPB. Third, we found a significant effect of change in PPB on the association of discrimination with change in depressive symptoms. Finally, we found that ProSAAF participation buffered the impact of racial discrimination on change in depressive symptoms through change in PPB. Results provide experimental support for constructed resilience in the form of change in PPB and call for increased attention to the development of family-based intervention programs to protect Black youth from the pernicious effects of racial discrimination. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Effects of physical driving experience on body movement and motion sickness among passengers in a virtual vehicle

Virtual vehicles (e.g., driving video games) can give rise to visually induced motion sickness. Typically, people drive virtual vehicles. In the present study, we investigated motion sickness among participants who were exposed to virtual vehicles as passengers; that is, they observed vehicle motion, but did not control it. We also asked how motion sickness and the postural precursors of motion sickness might be influenced by participants' previous experience of driving physical vehicles. Participants viewed a recording of a virtual automobile in a driving video game. Drivers were young adults with several years of experience driving physical automobiles, while non-drivers were individuals in the same age group who did not have a driver's license and had never driven an automobile. During exposure to the virtual vehicle, we monitored movement of the head and torso. The independent measures included the incidence and severity of motion sickness. After exposure to the virtual vehicle, the incidence and severity of motion sickness did not differ between Drivers and Non-Drivers. By contrast, postural movement differed between participants who later became motion sick and those who did not. In addition, during exposure to the virtual vehicle, physical driving experience was related to patterns of postural activity that preceded motion sickness. The results are consistent with the postural instability theory of motion sickness, and illuminate relations between the control of physical and virtual vehicles.

The effect of early discrimination on accelerated aging among African Americans

OBJECTIVE

This study examined the role of depressive symptoms in mediating the relationship between early life experiences of racial discrimination and accelerated aging in adulthood for African Americans (i.e., prediction over a 19-year period, from ages 10 to 29) after adjusting for gender and health behaviors.

METHOD

Longitudinal self-report data over 7 waves of data collection from the Family and Community Health Study were utilized. The sample included 368 African Americans with usable gene expression data to compute accelerated aging, as well as complete data on all self-report variables including racial discrimination (Schedule of Racist Events) and depression (Diagnostic Interview Schedule for Children-Version 4). Blood was collected by antecubital blood draws from participants at age 29. The proposed model was tested by path analysis.

RESULTS

Findings revealed that high discrimination at ages 10-15 was associated with depression at ages 20-29 (β = .19, p = .001), controlling for depression at ages 10-15, which, in turn, was related to accelerated cellular-level aging (β = .11, p = .048) after controlling for gender, alcohol consumption, and cigarette use. The indirect effect of racial discrimination on aging through depression at ages 20-29 was significant (β = .021, 95% confidence interval [.001, .057]), accounting for 32.3% of the total variance.

CONCLUSION

These findings support research conceptualizations that early life stress due to racial discrimination lead to sustained negative affective states continuing into young adulthood that confer risk for accelerated aging and possibly premature disease and mortality in African Americans. These findings advance knowledge of potential underlying mechanisms that influence racial health disparities. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Perceived relationship support moderates the association of contextual stress with inflammation among African Americans

We followed 402 African American young adults from ages 24 to 29, a period of emerging committed relationships, to examine the association of contextual stress (CS), for example, experiences of financial strain, victimization, and racial discrimination, with inflammation, and to test predictions that greater perceived relationship warmth and support (PRWS) at age 29 would moderate the association between earlier CS and inflammation, using a multiplex assessment of cytokines to construct an index of the ratio between predominantly proinflammatory cytokines versus predominantly anti-inflammatory cytokines. CS experienced at age 24 was associated with greater inflammation at age 29 in the full sample (b = .112, p = .004). PRWS at age 29 moderated the association of earlier CS with inflammation (b = -.114, p = .011), but there was no significant main effect of PRWS (b = -.053, p = .265). Finally, using an internal moderator approach, we compared the association of CS with inflammation among those not in a committed relationship to those in more or less supportive relationships, showing a significant and stronger association of CS with inflammation for those with low PRWS (-1 SD; b = .182, p < .001), a weaker and nonsignificant association of CS with inflammation among those with higher PRWS (+1 SD; b = -.002, p = .975), and an intermediate and nonsignificant association of CS with inflammation among those with no committed romantic relationship (b = .077, p = .227). Results were robust to number of cytokines included in the inflammation index. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Polymer Surface Textured with Nanowire Bundles to Repel High-Speed Water Drops

Water drops impacting windshields of high-speed trains and aircraft as well as blades in steam turbine power generators obliquely and at high speeds are difficult to repel. Impacting drops penetrate the void regions of nanotextured and microtextured superhydrophobic coatings, with this pinning resulting in the loss of drop mobility. In order to repel high-speed water drops, we nanotextured polymer surfaces with nanowire bundles separated from their neighbors by microscale void regions, with the nanowires in a bundle separated from their neighbors by nanoscale void regions. Water drops with speeds below a critical speed rebound completely. Water drops with speeds exceeding a critical speed rebound partially, but residual droplets that begin to be pinned undergo a spontaneous dewetting process and slide off. The natural oscillations of residual droplets drive this dewetting process in the interbundle void regions, resulting in a transition from the sticky Wenzel state to the slippery Cassie state without external stimuli.

MTHFR methylation moderates the impact of smoking on DNA methylation at AHRR for African American young adults

Smoking has been shown to have a large, reliable, and rapid effect on demethylation of AHRR, particularly at cg05575921, suggesting that methylation may be used as an index of cigarette consumption. Because the availability of methyl donors may also influence the degree of demethylation in response to smoking, factors that affect the activity of methylene tetrahydrofolate reductase (MTHFR), a key regulator of methyl group availability, may be of interest. In the current investigation, we examined the extent to which individual differences in methylation of MTHFR moderated the association between smoking and demethylation at cg05575921 as well as at other loci on AHRR associated with a main effect of smoking. Using a discovery sample (AIM, N = 293), and a confirmatory sample (SHAPE, N = 368) of young adult African Americans, degree of methylation of loci in the first exon of MTHFR was associated with amplification of the association between smoking and AHRR demethylation at cg05575921. However, genetic variation at a commonly studied MTHFR variant, C677T, did not influence cg05575921 methylation. The significant interaction between MTHFR methylation and the smoking-induced response at cg05575921 suggests a role for individual differences in methyl cycle regulation in understanding the effects of cigarette consumption on genome wide DNA methylation.

Decreasing Substance use Risk among African American Youth: Parent-based Mechanisms of Change

African American couples (N = 139; 67.7 % married; with children between the ages of 9 and 14) were randomly assigned to (a) a culturally sensitive, couple- and parenting-focused program designed to prevent stress-spillover (n = 70) or (b) an information-only control condition in which couples received self-help materials (n = 69). Eight months after baseline, youth whose parents participated in the program, compared with control youth, reported increased parental monitoring, positive racial socialization, and positive self-concept, as well as decreased conduct problems and self-reported substance use. Changes in youth-reported parenting behavior partially mediated the effect of the intervention on conduct problems and fully mediated its impact on positive self-concept, but did not mediate effects on lifetime substance use initiation. Results suggest the potential for a culturally sensitive family-based intervention targeting adults' couple and parenting processes to enhance multiple parenting behaviors as well as decrease youths' substance use onset and vulnerability.

Economic hardship and biological weathering: The epigenetics of aging in a U.S. sample of black women

BACKGROUND

Past research has linked low socio-economic status (SES) to inflammation, metabolic dysregulation, and various chronic and age-related diseases such as type 2 diabetes, coronary heart disease, stroke, and dementia. These studies suggest that the challenges and adversities associated with low SES may result in premature aging and increased risk of morbidity and mortality.

OBJECTIVE

Building upon this research, the present study investigates various avenues whereby low income might accelerate biological aging.

METHODS

Structural equation modeling and longitudinal data from a sample of 100 Black, middle-aged women residing in the United States was used to investigate the effect of income on a recently developed epigenetic measure of biological aging. This measure can be used as a "biological clock" to assess, at any point during adulthood, the extent to which an individual is experiencing accelerated or decelerated biological aging.

RESULTS

Low income displayed a robust association with accelerated aging that was unaffected after controlling for other SES-related factors such as education, marital status, and childhood adversity. Further, our analyses indicated that the association between income and biological aging was not explained by health-related behaviors such as diet, exercise, smoking, alcohol consumption, or having health insurance. Rather, in large measure, it was financial pressure (difficulty paying bills, buying necessities, or meeting daily expenses) that accounted for the association between low income and accelerated aging.

CONCLUSIONS

These findings support the view that chronic financial pressures associated with low income exert a weathering effect that results in premature aging.

Constructing Confidence Intervals for Effect Size Measures of an Indirect Effect

Confidence intervals for an effect size can provide the information about the magnitude of an effect and its precision as well as the binary decision about the existence of an effect. In this study, the performances of five different methods for constructing confidence intervals for ratio effect size measures of an indirect effect were compared in terms of power, coverage rates, Type I error rates, and widths of confidence intervals. The five methods include the percentile bootstrap method, the bias-corrected and accelerated (BCa) bootstrap method, the delta method, the Fieller method, and the Monte Carlo method. The results were discussed with respect to the adequacy of the distributional assumptions and the nature of ratio quantity. The confidence intervals from the five methods showed similar results for samples of more than 500, whereas, for samples of less than 500, the confidence intervals were sufficiently narrow to convey the information about the population effect sizes only when the effect sizes of regression coefficients defining the indirect effect are large.

Higher levels of protective parenting are associated with better young adult health: exploration of mediation through epigenetic influences on pro-inflammatory processes

The current investigation was designed to examine the association of parenting during late childhood and early adolescence, a time of rapid physical development, with biological propensity for inflammation. Based on life course theory, it was hypothesized that parenting during this period of rapid growth and development would be associated with biological outcomes and self-reported health assessed in young adulthood. It was expected that association of parenting with health would be mediated either by effects on methylation of a key inflammatory factor, Tumor necrosis factor (TNF), or else by association with a pro-inflammatory shift in the distribution of mononuclear blood cells. Supporting expectations, in a sample of 398 African American youth residing in rural Georgia, followed from age 11 to age 19, parenting at ages 11-13 was associated with youth reports of better health at age 19. We found that parenting was associated with changes in TNF methylation as well as with changes in cell-type composition. However, whereas methylation of TNF was a significant mediator of the association of parenting with young adult health, variation in mononuclear white blood cell types was not a significant mediator of the association of parenting with young adult health. The current research suggests the potential value of examining the health-related effects of parenting in late childhood and early adolescence. Further examination of protection against pro-inflammatory tendencies conferred by parenting appears warranted.

The effect of communication change on long-term reductions in child exposure to conflict: impact of the promoting strong African American families (ProSAAF) program

African American couples (n = 331) with children, 89% of whom were married, were assigned to either (a) a culturally sensitive couple- and parenting-enhancement program (ProSAAF) or (b) an information-only control condition in which couples received self-help materials. Husbands averaged 41 years of age and wives averaged 39 years. We found significant effects of program participation in the short term on couple communication, which was targeted by the intervention, as well as over the long term, on self-reported arguing in front of children. Long-term parenting outcomes were fully mediated by changes in communication for wives, but not for husbands. For husbands, positive change depended on amount of wife reported change. We conclude that wives' changes in communication from baseline to posttest may be more pivotal for the couples' long-term experience of decreased arguing in front of children than are husbands' changes, with wives' changes leading to changes in both partners' reports of arguments in front of children.

Nonsupportive parenting affects telomere length in young adulthood among African Americans: mediation through substance use

Telomere length (TL) is an indicator of age-related changes at the cellular level associated with heightened mortality risk. The effect of nonsupportive parenting (NSP) during late adolescence and young adulthood on TL 5 years later was examined in a sample of N = 183 young adult African Americans to determine if effects of NSP on TL were mediated by substance use. Results indicated that the effect of caregiver reported NSP on diminished TL was mediated by escalation of drinking and smoking in young adulthood, even after controlling effects of socioeconomic status risk, gender, BMI, young adult stress, and intervention status. Results suggest that prevention of NSP may influence later physical health consequences by influencing substance use trajectory.

Genetic Moderation of the Impact of Parenting on Hostility toward Romantic Partners

Although GxE studies are typically based on the assumption that some individuals possess genetic variants that enhance their vulnerability to environmental adversity, the differential susceptibility model posits that these individuals are simply more sensitive to social context, whether that context be adverse or supportive. Thus those persons most vulnerable to adversity are the same ones who reap the most benefit from support. This idea was tested using longitudinal data from a sample of several hundred African Americans. Findings indicated that relatively common variants of the GABRA2 gene interact with parenting to predict hostility toward romantic partners in a manner consonant with the differential susceptibility hypothesis. Individuals with these genetic variants displayed more aggression toward their partner than those with other genotypes when they had been subjected to harsh parenting, but exhibited less aggression toward their partner than other genotypes if their parents avoided harsh parenting practices.

Impact of child sex abuse on adult psychopathology: a genetically and epigenetically informed investigation

Genetic, environmental, and epigenetic influences and their transactions were examined in a sample of 155 women from the Iowa adoptee sample who had been removed from their biological parents shortly after birth and assessed when participants were an average of 41.10 years old. We observed an interactive effect of child sex abuse (CSA) and biological parent psychopathology (i.e., genetic load) on substance abuse as well as a main effect of CSA on substance abuse in adulthood. We also observed main effects of CSA and genetic load on depression and on antisocial characteristics. As predicted, CSA, but not genetic load or later substance abuse, was associated with epigenetic change. In addition, the interaction between genetic load and CSA predicted epigenetic change, indicating a potential genetic basis for a differential impact of CSA on epigenetic change. Finally, epigenetic change partially mediated the effect of CSA on antisocial characteristics. The results suggest the relevance of genetic and epigenetic processes for future theorizing regarding marital and family precursors of several forms of adult psychopathology. Implications for preventive intervention are discussed.

Relational schemas, hostile romantic relationships, and beliefs about marriage among young African American adults

The present study tests a developmental model designed to explain the romantic relationship difficulties and reluctance to marry often reported for African Americans. Using longitudinal data from a sample of approximately 400 African American young adults, we examine the manner in which race-related adverse experiences during late childhood and early adolescence give rise to the cynical view of romantic partners and marriage held by many young African Americans. Our results indicate that adverse circumstances disproportionately suffered by African American youth (viz., harsh parenting, family instability, discrimination, criminal victimization, and financial hardship) promote distrustful relational schemas that lead to troubled dating relationships, and that these negative relationship experiences, in turn, encourage a less positive view of marriage.

Genetic moderation of contextual effects on negative arousal and parenting in African-American parents

A three-stage context amplification model was tested with a sample of 345 African-American parent-child dyads. The model combined the conceptual structure of stress generation with recent findings regarding genetic susceptibility. Because the 7R + allele of the dopamine transporter (DRD4) has the potential to enhance contextual priming and arousal, this allele was examined as a potential moderator of each stage of the amplification process. Particular attention was given to the hypothesized influence of parental negative arousal on valence of parent-child interactions. The literature on genetic susceptibility led to the hypothesis that DRD4 would moderate each stage of the model in a "for better or for worse" manner. The model was partially supported. DRD4 moderated effects at all three stages of the model and, as hypothesized, DRD4 moderated contextual effects on negative arousal in a "for better or for worse" manner. Effects on parent-child interaction, however, were moderated in a "for worse" manner only. These results indicate that parenting interactions may amplify the effects of positive and negative contexts in a stress-generating manner, and that a susceptibility framework captures the way in which DRD4 moderates the impact of context on negative arousal.

SOCIAL ADVERSITY, GENETIC VARIATION, STREET CODE, AND AGGRESSION: A GENETICLLY INFORMED MODEL OF VIOLENT BEHAVIOR

Elijah Anderson (1997, 1999) argues that exposure to extreme community disadvantage, residing in "street" families, and persistent discrimination encourage many African Americans to develop an oppositional culture that he labels the "code of the street." Importantly, while the adverse conditions described by Anderson increase the probability of adopting the code of the street, most of those exposed to these adverse conditions do not do so. The present study examines the extent to which genetic variation accounts for these differences. Although the diathesis-stress model guides most genetically informed behavior science, the present study investigates hypotheses derived from the differential susceptibility perspective (Belsky & Pluess, 2009). This model posits that some people are genetically predisposed to be more susceptible to environmental influence than others. An important implication of the model is that those persons most vulnerable to adverse social environments are the same ones who reap the most benefit from environmental support. Using longitudinal data from a sample of several hundred African American males, we examined the manner in which variants in three genes - 5-HTT, DRD4, and MAOA - modulate the effect of community and family adversity on adoption of the street code and aggression. We found strong support for the differential susceptibility perspective. When the social environment was adverse, individuals with these genetic variants manifested more commitment to the street code and aggression than those with other genotypes, whereas when adversity was low they demonstrated less commitment to the street code and aggression than those with other genotypes.

Social Environmental Variation, Plasticity Genes, and Aggression: Evidence for the Differential Susceptibility Hypothesis

Although G×E studies are typically based on the assumption that some individuals possess genetic variants that enhance their vulnerability to environmental adversity, the differential susceptibility perspective posits that these individuals are simply more susceptible to environmental influence than others. An important implication of this model is that those persons most vulnerable to adverse social environments are the same ones who reap the most benefit from environmental support. The present study tested several implications of this proposition. Using longitudinal data from a sample of several hundred African Americans, we found that relatively common variants of the dopamine receptor gene and the serotonin transporter gene interact with social environmental conditions to predict aggression in a manner consonant with differential susceptibility. When the social environment was adverse, individuals with these genetic variants manifested more aggression than other genotypes, whereas when the environment was supportive they demonstrated less aggression than other genotypes. Further, we found that these genetic variants interact with environmental conditions to foster various cognitive schemas and emotions in a manner consistent with differential susceptibility and that a latent construct formed by these schemas and emotions mediated the effect of gene by environment interaction on aggression.

Measurements of coating density using ultrasonic reflection coefficient phase spectrum

A nondestructive method to determine the density of coating has been proposed in this paper based on the ultrasonic reflection coefficient phase spectrum (URCPS). A model was set up first to represent the ultrasonic waves reflected from a coating system at normal incident, and the relation between the extremum of URCPS and the coating density was established to provide the principle of determining the density. The ultrasonic method was validated on a series of ZrO2-7wt.%Y2O3 (YSZ) coatings with various density. The specimens were prepared by electric beam physical vapor deposit (EB-PVD). After deposition, the specimens were irradiated using high-intensity pulsed ion beam (HIPIB) at different ion current density of 100 and 200A/cm2 to change coating density. The coating densities of as-deposited and post irradiation by HIPIB were derived to be 4940-5030, 5200-5320 and 5390-5470kg/m3, respectively. The relative error between the coating density measured by the ultrasonic method and Archimedean principle ranging from 2.53% to 6.11%, indicates that the proposed ultrasonic quantification method provides a reliable nondestructive way to determine coating density.

Oxidation and corrosion behaviors of Mg-based nanoparticles

Various Mg-based nanoparticles were prepared by evaporating bulk magnesium in the atmospheres of Ar, Ar+N2 and CH4, respectively. The formations, phases, morphologies, thermal properties and corrosion behaviors of these kinds of nanocomposite particles were investigated by means of X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), thermogravimetric-differential thermal analysis (TG/DTA) and potentiodynamic polarisation scan (PPS). It is shown that the Mg-based nanoparticles produced in Ar and Ar+N2 atmospheres have hexangular crystal habits with particles' sizes ranging from 50 to 400 nm, while the nanoparticles produced in CH4 atmosphere have amorphous carbon out layers with particles' sizes among 20-100 nm. TG/DTA results show that two-steps oxidation process can be confirmed for all samples, which may be attributed to the oxidations of out layer and core of nanoparticle. The CH4 atmosphere-prepared nanoparticles exhibit better corrosion resistance properties due to its peculiar carbon doping.

Change in caregiver depression in response to parent training: genetic moderation of intervention effects

A previous report in the Journal of Family Psychology (S. R. H. Beach et al., 2008) described the results of a randomized prevention trial contrasting families who participated in the Strong African American Families Program (SAAF, a preventive intervention for rural African American parents and their 11-year-olds) with control families. This brief report examines a novel contextual variable, child's genetic risk status for negative affect and poor self-control, as a moderator of treatment effects on caregiver's depression. Genetic data were obtained from (N = 109) youths' saliva samples. The primary study hypothesis of differential program impact on caregiver depression as a function of youth genetic risk was confirmed. Among caregivers with initially elevated scores on the Center for Epidemiologic Studies--Depression Scale (L. S. Radloff, 1977), SAAF participation was associated with greater impact on depressive symptoms among those whose children were at genetic risk, suggesting that effect size estimates based on full samples may underestimate the impact of prevention programs on at-risk subgroups, whose response is particularly important to understand and to target.

Lifetime of anode polymer in magnetically insulated ion diodes for high-intensity pulsed ion beam generation

Generation of high-intensity pulsed ion beam (HIPIB) has been studied experimentally using polyethylene as the anode polymer in magnetically insulated ion diodes (MIDs) with an external magnetic field. The HIPIB is extracted from the anode plasma produced during the surface discharging process on polyethylene under the electrical and magnetic fields in MIDs, i.e., high-voltage surface breakdown (flashover) with bombardments by electrons. The surface morphology and the microstructure of the anode polymer are characterized using scanning electron microscopy and differential scanning calorimetry, respectively. The surface roughening of the anode polymer results from the explosive release of trapped gases or newly formed gases under the high-voltage discharging, leaving fractured surfaces with bubble formation. The polyethylene in the surface layer degrades into low-molecular-weight polymers such as polyethylene wax and paraffin under the discharging process. Both the surface roughness and the fraction of low molecular polymers apparently increase as the discharging times are prolonged for multipulse HIPIB generation. The changes in the surface morphology and the composition of anode polymer lead to a noticeable decrease in the output of ion beam intensity, i.e., ion current density and diode voltage, accompanied with an increase in instability of the parameters with the prolonged discharge times. The diode voltage (or surface breakdown voltage of polymer) mainly depends on the surface morphology (or roughness) of anode polymers, and the ion current density on the composition of anode polymers, which account for the two stages of anode polymer degradation observed experimentally, i.e., stage I which has a steady decrease of the two parameters and stage II which shows a slow decrease, but with an enhanced fluctuation of the two parameters with increasing pulses of HIPIB generation.