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We conducted signal detection analyses to test for curvilinear, U-shaped relations between early experiences of adversity and heightened physiological responses to challenge, as proposed by biological sensitivity to context theory. Based on analysis of an ethnically diverse sample of 338 kindergarten children (4–6 years old) and their families, we identified levels and types of adversity that, singly and interactively, predicted high (top 25%) and low (bottom 25%) rates of stress reactivity. The results offered support for the hypothesized U-shaped curve and conceptually replicated and extended the work of Ellis, Essex, and Boyce (2005). Across both sympathetic and adrenocortical systems, a disproportionate number of children growing up under conditions characterized by either low or high adversity (as indexed by restrictive parenting, family stress, and family economic condition) displayed heightened stress reactivity, compared with peers growing up under conditions of moderate adversity. Finally, as hypothesized by the adaptive calibration model, a disproportionate number of children who experienced exceptionally stressful family conditions displayed blunted cortisol reactivity to stress.
Classrooms are key social settings that impact children's mental health, though individual differences in physiological reactivity may render children more or less susceptible to classroom environments. In a diverse sample of children from 19 kindergarten classrooms (N = 338, 48% female, M age = 5.32 years), we examined whether children's parasympathetic reactivity moderated the association between classroom climate and externalizing symptoms. Independent observers coded teachers’ use of child-centered and teacher-directed instructional practices across classroom social and management domains. Children's respiratory sinus arrhythmia reactivity to challenge tasks was assessed in fall and a multi-informant measure of externalizing was collected in fall and spring. Both the social and the management domains of classroom climate significantly interacted with children's respiratory sinus arrhythmia reactivity to predict spring externalizing symptoms, controlling for fall symptoms. For more reactive children, as classrooms shifted toward greater proportional use of child-centered methods, externalizing symptoms declined, whereas greater use of teacher-dominated practices was associated with increased symptoms. Conversely, among less reactive children, exposure to more teacher-dominated classroom management practices was associated with lower externalizing. Consistent with the theory of biological sensitivity to context, considering variability in children's physiological reactivity aids understanding of the salience of the classroom environment for children's mental health.
Harsh and restrictive parenting are well-established contributors to the development of oppositional defiant disorder (ODD) among children. However, few studies have explored whether interpersonal relationships that develop outside the family environment attenuate the risk for ODD that is associated with harsh parenting. The current study tested multireporter measures of teacher–child closeness and peer acceptance as moderators of the association between harsh parenting and children's ODD as children's social worlds widen during the kindergarten year (N = 338 children, 48% girls, M age = 5.32 years). Harsh parenting interacted with peer nominations of peer acceptance and children's report of teacher–child closeness to predict children's ODD symptoms in the spring, adjusting for fall symptoms. Children exposed to harsh parenting exhibited greater symptom increases when they were less liked/accepted playmates and in the context of lower teacher–child closeness. However, harsh parenting was not associated with symptom change among children with higher levels of peer-nominated acceptance and those who reported closer relationships with teachers. There were no significant interactions using teacher's report of peer acceptance or teacher's report of teacher–child closeness. Findings highlight positive peer and teacher relationships as promising targets of intervention among children exposed to harsh parenting and support the importance of assessing multiple perspectives of children's social functioning.
Entry into kindergarten is a developmental milestone that children may differentially experience as stressful, with implications for variability in neurobiological functioning. Guided by the goodness-of-fit framework, this study tested the hypothesis that kindergarten children's (N = 338) daily cortisol would be affected by the “match” or “mismatch” between children's temperament and qualities of the classroom relational context. The robustness of these associations was also explored among a separate sample of children in third grade (N = 165). Results among kindergarten children showed negative affectivity and overcontrolled temperament were positively related to cortisol expression within classrooms characterized by lower levels of teacher motivational support, but there was no relation between temperament and cortisol when motivational support was higher. Among third-grade children, negative affectivity was marginally positively related to cortisol at lower levels of teacher–child closeness and unrelated at higher levels of teacher–child closeness. Findings suggest children's cortisol expression depends on the extent to which specific temperamental characteristics “fit” within the relational and contextual qualities of the classroom environment, particularly as children navigate the new roles and relationships that emerge during the transition to formal schooling. Developmentally informed neurobiological research in classrooms may contribute to tailored programmatic efforts to support children's school adjustment.
We examined the prospective associations of objective and subjective measures of stress during pregnancy with infant stress reactivity and regulation, an early-life predictor of psychopathology. In a racially and ethnically diverse low-income sample of 151 mother–infant dyads, maternal reports of stressful life events (SLE) and perceived stress (PS) were collected serially over gestation and the early postpartum period. Infant reactivity and regulation at 6 months of age was assessed via maternal report of temperament (negativity, surgency, and regulation) and infant parasympathetic nervous system physiology (respiratory sinus arrhythmia [RSA]) during the Still Face Paradigm. Regression models predicting infant temperament showed higher maternal prenatal PS predicted lower surgency and self-regulation but not negativity. Regression models predicting infant physiology showed higher numbers of SLE during gestation predicted greater RSA reactivity and weaker recovery. Tests of interactions revealed SLE predicted RSA reactivity only at moderate to high levels of PS. Thus, findings suggest objective and subjective measures of maternal prenatal stress uniquely predict infant behavior and physiology, adjusting for key pre- and postnatal covariates, and advance the limited evidence for such prenatal programming within high-risk populations. Assessing multiple levels of maternal stress and offspring stress reactivity and regulation provides a richer picture of intergenerational transmission of adversity.
A paleoecological record from Lake Palotoa (1370 m elevation) in the Andean foothills of Peru spans the last 3800 years. Lake Palotoa lies near the modern cloud base in a location sensitive to changes in atmospheric moisture. In many areas, these forests have been destroyed, but Lake Palotoa shows no sign of human occupation today or in the past. The modern forest surrounding the lake is dominated by the Andean palm, Dictyocaryum lamarckianum, which is also the most abundant taxon in the fossil pollen record. Fossil pollen data show the vegetation assemblages have not experienced strong compositional changes in the late Holocene. Global-scale climatic events such as the Medieval Climate Anomaly (MCA) and the Little Ice Age (LIA) are identified within the record, though the vegetation responses are subtle. Hedyosmum and Sloanea pollen percentages increase near the onset of the MCA and may reflect decreased seasonality. The LIA coincides with increased Hedyosmum pollen percentages, and increases in Clethra and Begonia, two elements that tend to occupy forests now found at higher elevations. Our findings demonstrate the stability of montane forest systems to natural Holocene climate change.
Magnetohydrodynamic (MHD) oscillations are observed in the solar photosphere with the Michelson Doppler Imager (MDI). The absorption of acoustic waves by sunspots (Braun et al., 1988) and the possible conversion of acoustic waves into MHD waves (Spruit et al., 1992) provide a plausible basis for the existence of MHD waves in the solar atmosphere and motivate this attempt at observation.
Cognitive deficits are predictors of functional outcome in patients with psychosis. While conventional antipsychotics are relatively effective on positive symptoms, their impact on negative and cognitive symptoms is limited. Recent studies have established a link between oxidative stress and neurocognitive deficits in psychosis. N-acetylcysteine (NAC), a glutathione precursor with glutamatergic properties, has shown efficacy on negative symptoms and functioning in patients with schizophrenia and bipolar disorder, respectively. However, there are few evidence-based approaches for managing cognitive impairment in psychosis. The present study aims to examine the cognitive effects of adjunctive NAC treatment in a pooled subgroup of participants with psychosis who completed neuropsychological assessment in two trials of both schizophrenia and bipolar disorder.
A sample of 58 participants were randomized in a double fashion to receive 2 g/day of NAC (n = 27) or placebo (n = 31) for 24 weeks. Attention, working memory and executive function domains were assessed. Differences between cognitive performance at baseline and end point were examined using Wilcoxon's test. The Mann–Whitney test was used to examine the differences between the NAC and placebo groups at the end point.
Participants treated with NAC had significantly higher working memory performance at week 24 compared with placebo (U = 98.5, p = 0.027).
NAC may have an impact on cognitive performance in psychosis, as a significant improvement in working memory was observed in the NAC-treated group compared with placebo; however, these preliminary data require replication. Glutamatergic compounds such as NAC may constitute a step towards the development of useful therapies for cognitive impairment in psychosis.
Twenty Small Tailed Han (STH) and 20 Ujumqin (UJU) ewes naturally infected with gastrointestinal nematodes were randomly assigned to one of four treatments arranged in a 2 × 2 factorial design, receiving anthelmintic treatment (AT) or non-anthelmintic treatment (NonAT) prior to lambing. After lambing, the effects of AT on feed intake, digestion and milk yield in ewes, and the growth rates of lambs fed their mother's milk were assessed for 28 days. Faecal samples were collected to determine faecal egg counts (FECs), milk was collected to measure milk yield and ewes and lambs were weighed to quantify daily body weight change. The results showed that AT significantly increased ewe dry matter intake (2411 g/d for AT and 2209 g/d for NonAT) and decreased FECs (50 eggs/g for AT and 2655 eggs/g for NonAT). All ewes lost weight after lambing, but body weight loss in the AT (43 g/d) was significantly less than in NonAT (84 g/d), and STH ewes (70 g/d) lost more weight than UJU ewes (58 g/d). Anthelmintic-treated ewes produced more milk for their lambs to consume. However, the extent of these positive effects of AT differed between STH and UJU ewes. The average daily body weight gain of lambs in AT was higher than those in NonAT. In conclusion, effective AT in ewes before lambing benefits subsequent lactation in ewes and growth rate in lambs.
The SoHO/MDI experiment generates a continous record of the solar limb brightness using 1.96″ pixels. Because there is no atmospheric blurring, these data allow measurements of solar limb brightness and shape changes with a precision that has not been achieved from the ground. The first results of a 1 month astrometric timeseries from the MDI solar structure program will be described here.
The Medium-l Program of the Michelson Doppler Imager (MDI) instrument on board SOHO provides continuous observations of oscillation modes of angular degree, l, from 0 to ∼ 300. The initial results show that the noise in the Medium-l oscillation power spectrum is substantially lower than in ground-based measurements. This enables us to detect lower amplitude modes and, thus, to extend the range of measured mode frequencies. The MDI observations also reveal the asymmetry of oscillation spectral lines. The line asymmetries agree with the theory of mode excitation by acoustic sources localized in the upper convective boundary layer. The sound-speed profile inferred from the mean frequencies gives evidence for a sharp variation at the edge of the energy-generating core. In a thin layer just beneath the convection zone, helium appears to be less abundant than predicted by theory. Inverting the multiplet frequency splittings from MDI, we detect significant rotational shear in this thin layer.
Is the Solar Radius a constant? Ground experiments show evidence of possible variations in the visual solar semi diameter that are correlated with the solar activity. Those measurements are limited by the Earth's atmospheric turbulance. It is importance to accurately determine the solar radius variations because of their implication for stellar structure and possible relation to the terrestrial climate. Here we report on data from a space experiment (MDI-SOHO) used to detect solar diameter fluctuations. We stabilish a superior limit for changes in the solar radius.
The study of ancient biodiversity trends is confounded by biases of the paleontologic record, but standardizing sampling intensity among time intervals can ameliorate sample-size biases. We show that several existing standardization methods are intimately linked to the spatial components of diversity (alpha, the within-assemblage diversity; and beta, the between-assemblage diversity). The subsampling curves generated by these methods can also be generated by various manipulations of alpha and beta, so that one can predict the responses of the methods to specific changes in alpha or beta diversity. The responses of the subsampling methods to changes in total diversity depend on whether measured alpha or measured beta diversity changed. Like biodiversity, sampling consists of a within-sample component (the number of specimens collected per locality) and a between-sample component (the number of localities). Several subsampling methods (rarefaction, OW, O2W) attempt to standardize sampling effort at both levels, although they use no direct information on the former. Instead, they alter sampling intensity at the beta level to compensate for perceived biases at the alpha level. We show that alpha and beta diversity are not so easily interchangeable and that the accuracy of the subsampling methods depends critically on the spatial characteristics of diversity in a data set. Current methods are calibrated only to the abundance-richness characteristics of individual collections, but the amount of beta diversity and the degree to which the rareness/commonness of taxa correlates among samples also strongly affect the accuracy of the subsampling methods. We offer new calibrations based on empirical data sets that account for these factors. Our findings do not support Alroy et al.'s (2001) tentative claim that the taxonomic radiation in the Cenozoic marine realm is an artifact of biased sampling intensity. Their diversity curves that most strongly contradict Sepkoski's traditional Phanerozoic curve are based on a method that overcorrects for local sample-size biases, whereas the remaining curves are either consistent with the traditional curve or ambiguous because of the limited temporal and taxonomic coverage of the analysis. Other factors may bias Sepkoski's curve, but there is insufficient evidence to claim that variations in sampling intensity are the major determinant of its long-term trajectory.
Continental deposits of the Early Jurassic East Berlin Formation in Holyoke, Massachusetts, have yielded an exceptional occurrence of the ichnogenus Treptichnus. Here, burrows are preserved in full relief within thin mud laminae between layers of fine-grained, cross-bedded sandstone. We studied these burrows to evaluate whether earlier explanations of burrow morphology are applicable to all Treptichnus. Our research focused on three questions. (1) Do the Holyoke Treptichnus have significant vertical relief? (2) Does the lack of projections in some of the Holyoke Treptichnus result from stratinomic sectioning through the bottom of the burrow? (3) Do expanded, bulbous ends of burrow segments result from sediment compaction? While addressing these questions, the Holyoke fossils were compared to syntype and topotype material of Treptichnus from the Carboniferous of Indiana. The Holyoke Treptichnus did not exhibit significant vertical relief, and the presence and absence of projections is explained by the positioning of new segments at different points along older ones. The bulbous ends of burrow segments resulted from trace-maker behavior, not sediment compaction. Drawing on the analysis of the Holyoke material, a new reconstruction is proposed that presents continental Treptichnus as a shallow mole-tunnel-like burrow produced just below the sediment surface. This reconstruction is consistent with the morphology of Recent Treptichnus-like burrows produced by fly (dipteran) larvae, which are considered the most likely makers of the Holyoke Treptichnus.
We have developed a simple, rapid method to screen carbonates for survey applications, which provides radiocarbon dates with decreased precision at lower cost. The method is based on previous work by Longworth et al. (2011) and involves mixing pulverized CaCO3 with Fe powder, followed by pressing into aluminum target holders for direct 14C accelerator mass spectrometry (AMS) measurements. An optimum beam current averaging ∼10% of those produced by >0.7 mg C graphite targets was obtained for carbonate samples of 0.3–0.5 mg (0.04–0.06 mg C). The precision of the method was evaluated by measuring triplicates of 14C reference materials, as well as by comparing results from this rapid method with results from high-precision AMS measurements on graphite (typically 0.2–0.3%). Measurement reproducibility was ∼1.8% (1σ) for samples <10 ka BP, and it increased drastically for older samples. However, t tests on paired samples resulted in p values greater than 0.05, indicating a good correlation between this survey method and the conventional one. An average blank (calcite) of 0.0075 Fm (∼39 ka BP) was achieved. The simplicity of the technique allowed us to process and measure 72 deep-sea coral samples in less than 25 hr.
Ergot alkaloids in endophyte-infected (Neotyphodium coenophialum) tall fescue (Lolium arundinaceum) have been shown to cause a reduction in blood flow to the rumen epithelium as well as a decrease in volatile fatty acids (VFA) absorption from the washed rumen of steers. Previous data also indicates that incubating an extract of endophyte-infected tall fescue seed causes an increase in the amount of VFA absorbed per unit of blood flow, which could result from an alteration in the absorptive or barrier function of the rumen epithelium. An experiment was conducted to determine the acute effects of an endophyte-infected tall fescue seed extract (EXT) on total, passive or facilitated acetate and butyrate flux across the isolated bovine rumen as well as the barrier function measured by inulin flux and tissue conductance (Gt). Flux of ergovaline across the rumen epithelium was also evaluated. Rumen tissue from the caudal dorsal sac of Holstein steers (n=6), fed a common diet, was collected and isolated shortly after slaughter and mounted between two halves of Ussing chambers. In vitro treatments included vehicle control (80% methanol, 0.5% of total volume), Low EXT (50 ng ergovaline/ml) and High EXT (250 ng ergovaline/ml). Results indicate that there is no effect of acute exposure to ergot alkaloids on total, passive or facilitated flux of acetate or butyrate across the isolate bovine rumen epithelium (P>0.51). Inulin flux (P=0.16) and Gt (P>0.17) were not affected by EXT treatment, indicating no alteration in barrier function due to acute ergot alkaloid exposure. Ergovaline was detected in the serosal buffer of the High EXT treatment indicating that the flux rate is ~0.25 to 0.44 ng/cm2 per hour. Data indicate that specific pathways for VFA absorption and barrier function of the rumen epithelium are not affected by acute exposure to ergot alkaloids from tall fescue at the concentrations tested. Ergovaline has the potential to be absorbed from the rumen of cattle that could contribute to reduced blood flow and motility and lead to reduced growth rates of cattle.
We present the results of a theoretical investigation of droplets walking on a rotating vibrating fluid bath. The droplet’s trajectory is described in terms of an integro-differential equation that incorporates the influence of its propulsive wave force. Predictions for the dependence of the orbital radius on the bath’s rotation rate compare favourably with experimental data and capture the progression from continuous to quantized orbits as the vibrational acceleration is increased. The orbital quantization is rationalized by assessing the stability of the orbital solutions, and may be understood as resulting directly from the dynamic constraint imposed on the drop by its monochromatic guiding wave. The stability analysis also predicts the existence of wobbling orbital states reported in recent experiments, and the absence of stable orbits in the limit of large vibrational forcing.