Dielectric behavior of Copper Tantalum Oxide

A thorough investigation of the dielectric properties of Cu2Ta4O12, a material crystallizing in a pseudo-cubic, perovskite-derived structure is presented. We measured the dielectric constant and conductivity of single crystals in an exceptionally broad frequency range up to GHz frequencies and at temperatures from 25 - 500 K. The detected dielectric constant is unusually high (reaching values up to 105) and almost constant in a broad frequency and temperature range. Cu2Ta4O12 possesses a crystal structure similar to CaCu3Ti4O12, the compound for which such an unusually high dielectric constant was first observed. An analysis of the results using a simple equivalent circuit and measurements with different types of contact revealed that extrinsic interfacial polarization effects, derived from surface barrier capacitors are the origin of the observed giant dielectric constants. The intrinsic properties of Cu2Ta4O12 are characterized by a (still relatively high) dielectric constant in the order of 100 and by charge transport via hopping conduction of Anderson-localized charge carriers.Comment: 18 pages, 6 figures, submitted to Jouranl of Physical Chemestr

Pregnancy Anxiety and Prenatal Cortisol Trajectories

Pregnancy anxiety is a potent predictor of adverse birth and infant outcomes. The goal of the current study was to examine one potential mechanism whereby these effects may occur by testing associations between pregnancy anxiety and maternal salivary cortisol on 4 occasions during pregnancy in a sample of 448 women. Higher mean levels of pregnancy anxiety over the course of pregnancy predicted steeper increases in cortisol trajectories compared to lower pregnancy anxiety. Significant differences between cortisol trajectories emerged between 30 to 31 weeks of gestation. Results remained significant when adjusted for state anxiety and perceived stress. Neither changes in pregnancy anxiety over gestation, nor pregnancy anxiety specific to only a particular time in pregnancy predicted cortisol. These findings provide support for one way in which pregnancy anxiety may influence maternal physiology and contribute to a growing literature on the complex biological pathways linking pregnancy anxiety to birth and infant outcomes

Single Dose of a Dopamine Agonist Impairs Reinforcement Learning in Humans: Evidence from Event-related Potentials and Computational Modeling of Striatal-Cortical Function

Animal findings have highlighted the modulatory role of phasic dopamine (DA) signaling in incentive learning, particularly in the acquisition of reward-related behavior. In humans, these processes remain largely unknown. In a recent study, we demonstrated that a single low dose of a D2/D3 agonist (pramipexole) - assumed to activate DA autoreceptors and thus reduce phasic DA bursts - impaired reward learning in healthy subjects performing a probabilistic reward task. The purpose of this study was to extend these behavioral findings using event-related potentials and computational modeling. Compared with the placebo group, participants receiving pramipexole showed increased feedback-related negativity to probabilistic rewards and decreased activation in dorsal anterior cingulate regions previously implicated in integrating reinforcement history over time. Additionally, findings of blunted reward learning in participants receiving pramipexole were simulated by reduced presynaptic DA signaling in response to reward in a neural network model of striatal-cortical function. These preliminary findings offer important insights on the role of phasic DA signals on reinforcement learning in humans and provide initial evidence regarding the spatiotemporal dynamics of brain mechanisms underlying these processes.Psycholog

Elevated Corticotropin-Releasing Hormone in Human Pregnancy Increases the Risk of Postpartum Depressive Symptoms

Postpartum depression (PPD) is common and has serious implications for the mother and her newborn. A possible link between placental corticotropin-releasing hormone (pCRH) and PPD incidence has been discussed, but there is a lack of empirical evidence

Prenatal Beta-Endorphin as an Early Predictor of Postpartum Depressive Symptoms in Euthymic Women

After delivery, many women experience symptoms of postpartum depression (PPD), and early identification of women at risk is therefore important. The opioid peptide [beta]-endorphin has been implicated in non-puerperal depression but its role in the development of PPD is unknown

Single Dose of a Dopamine Agonist Impairs Reinforcement Learning in Humans: Behavioral Evidence from a Laboratory-based Measure of Reward Responsiveness

Rationale. The dopaminergic system, particularly D2-like dopamine receptors, has been strongly implicated in reward processing. Animal studies have emphasized the role of phasic dopamine (DA) signaling in reward-related learning, but these processes remain largely unexplored in humans. Objectives. To evaluate the effect of a single, low dose of a D2/D3 agonist-pramipexole-on reinforcement learning in healthy adults. Based on prior evidence indicating that low doses of DA agonists decrease phasic DA release through autoreceptor stimulation, we hypothesized that 0.5 mg of pramipexole would impair reward learning due to presynaptic mechanisms. Materials and methods. Using a double-blind design, a single 0.5-mg dose of pramipexole or placebo was administered to 32 healthy volunteers, who performed a probabilistic reward task involving a differential reinforcement schedule as well as various control tasks. Results. As hypothesized, response bias toward the more frequently rewarded stimulus was impaired in the pramipexole group, even after adjusting for transient adverse effects. In addition, the pramipexole group showed reaction time and motor speed slowing and increased negative affect; however, when adverse physical side effects were considered, group differences in motor speed and negative affect disappeared. Conclusions. These findings show that a single low dose of pramipexole impaired the acquisition of reward-related behavior in healthy participants, and they are consistent with prior evidence suggesting that phasic DA signaling is required to reinforce actions leading to reward. The potential implications of the present findings to psychiatric conditions, including depression and impulse control disorders related to addiction, are discussed.Psycholog

Timing of Fetal Exposure to Stress Hormones: Effects on Newborn Physical and Neuromuscular Maturation

The purpose of the study was to determine the specific periods during pregnancy in which human fetal exposure to stress hormones affects newborn physical and neuromuscular maturation. Blood was collected from 158 women at 15, 19, 25, and 31 weeks\u27 gestation. Levels of placental corticotropin-releasing hormone (CRH) and maternal cortisol were determined from plasma. Newborns were evaluated with the New Ballard Maturation Score. Results indicated that increases in maternal cortisol at 15, 19, and 25 weeks and increases in placental CRH at 31 weeks were significantly associated with decreases in infant maturation among mates (even after con trolling for length of gestation). Results also suggested that increases in maternal cortisol at 31 weeks were associated with increases in infant maturation among females, although these results were not significant after controlling for length of gestation. Findings suggest that stress hormones have effects on human fetal neurodevelopment that are independent of birth outcome

Preconception Maternal Posttraumatic Stress and Child Negative Affectivity: Prospectively Evaluating the Intergenerational Impact of Trauma

The developmental origins of psychopathology begin before birth and perhaps even prior to conception. Understanding the intergenerational transmission of psychopathological risk is critical to identify sensitive windows for prevention and early intervention. Prior research demonstrates that maternal trauma history, typically assessed retrospectively, has adverse consequences for child socioemotional development. However, very few prospective studies of preconception trauma exist, and the role of preconception symptoms of posttraumatic stress disorder (PTSD) remains unknown. The current study prospectively evaluates whether maternal preconception PTSD symptoms predict early childhood negative affectivity, a key dimension of temperament and predictor of later psychopathology. One hundred and eighteen women were recruited following a birth and prior to conception of the study child and were followed until the study child was 3–5 years old. Higher maternal PTSD symptoms prior to conception predicted greater child negative affectivity, adjusting for concurrent maternal depressive symptoms and sociodemographic covariates. In exploratory analyses, we found that neither maternal prenatal nor postpartum depressive symptoms or perceived stress mediated this association. These findings add to a limited prospective literature, highlighting the importance of assessing the mental health of women prior to conception and providing interventions that can disrupt the intergenerational sequelae of trauma

A new polymorph of N-(prop-2-yn­yl)tricyclo­[3.3.1.13,7]decane-1-carbox­amide

The alkynyl bond of the title compound, C14H19NO, has a length of 1.170 (5) Å. The amide function shows a trans conformation with respect to the carbonyl group characterized by the torsion angle O—C—N—H of −176 (2)°. There is an inter­molecular N—H⋯O hydrogen bond between the amide function and the carbonyl group. In addition, weak inter­molecular hydrogen bonds stabilize the crystal structure. A comparison with a polymorphic structure shows conformational differences with regard to the orientation of the carbonyl groups with respect to the adamantyl group [O—C—C—C = 96.2 (3)° in the title compound and 123.7 (2)° in the polymorph] and the orientations of the propargyl groups in relation to the carbonyl groups [O—C—C—C = −87.7 (3) and −58.7 (2)°, respectively]