500 Kilovolt Cathode Rays

The high potential x-ray tube at the California Institute has been modified so as to permit either x-rays or cathode rays to be produced. Electron currents up to 35 microamperes have been obtained through an aluminum window. A typical magnetic velocity spectrum of the high speed electrons passing out of an aluminum window is presented. The high velocity limit corresponds to about 500 kilovolts when the transformer voltage is 600 kilovolts peak. The velocity spectrum appears to be continuous and no absorption anomalies due to aluminum and lead foil are evident. The time required to obtain a velocity spectrum was reduced to a few minutes by allowing the electrons after being magnetically deflected, to pass through a copper foil into the air. The outside of the foil is coated with calcium tungstate and the photographic plate is placed in contact with the tungstate. It is noted that part of the photographic action of the high speed electrons is due to fluorescence of the glass backing of the photographic plates

500 Kilovolt Cathode Rays

The high potential x-ray tube at the California Institute has been modified so as to permit either x-rays or cathode rays to be produced. Electron currents up to 35 microamperes have been obtained through an aluminum window. A typical magnetic velocity spectrum of the high speed electrons passing out of an aluminum window is presented. The high velocity limit corresponds to about 500 kilovolts when the transformer voltage is 600 kilovolts peak. The velocity spectrum appears to be continuous and no absorption anomalies due to aluminum and lead foil are evident. The time required to obtain a velocity spectrum was reduced to a few minutes by allowing the electrons after being magnetically deflected, to pass through a copper foil into the air. The outside of the foil is coated with calcium tungstate and the photographic plate is placed in contact with the tungstate. It is noted that part of the photographic action of the high speed electrons is due to fluorescence of the glass backing of the photographic plates

Prediction of posttraumatic stress in fathers of children with chronic diseases or unintentional injuries: a six-months follow-up study

<p>Abstract</p> <p>Background</p> <p>While fathers were neglected for a long time in research investigating families of pediatric patients, there are now a few studies available on fathers' posttraumatic stress symptoms (PTSS) and posttraumatic stress disorder (PTSD). However, little is known about the course of PTSS and PTSD in fathers of pediatric patients. The present study aimed to compare the prevalence and course of PTSS and PTSD in fathers of children with different chronic and acute conditions and to identify factors that contribute to fathers' PTSS.</p> <p>Methods</p> <p>Sixty-nine fathers of children newly diagnosed with either cancer, type I diabetes mellitus, or epilepsy and 70 fathers of children suffering from an unintentional injury completed questionnaires at 4–6 weeks (Time 1) and six months (Time 2) after diagnosis or injury.</p> <p>Results</p> <p>Noticeable PTSD rates were found in fathers of children with a chronic disease (26% at Time 1 and 21% at Time 2, respectively). These rates were significantly higher than rates found in fathers of children with unintentional injuries (12% at Time 1 and 6% at Time 2, respectively). Within six months after the child's diagnosis or accident a decrease in severity of PTSS was observed in both groups. Significant predictors of PTSS at Time 2 were the father's initial level of PTSS, the child's medical condition (injuries vs. chronic diseases) and functional status, the father's use of dysfunctional coping strategies, and father's level of neuroticism.</p> <p>Conclusion</p> <p>Our findings suggest that fathers with initially high PTSS levels are at greater risk to experience PTSS at follow-up, particularly fathers of children with a chronic disease. Sensitizing health care professionals to the identification of PTSS symptoms but also to indicators of neuroticism and the use of specific coping strategies early in the treatment course is essential for the planning and implementation of adequate intervention strategies.</p

Bee Threat Elicits Alarm Call in African Elephants

Unlike the smaller and more vulnerable mammals, African elephants have relatively few predators that threaten their survival. The sound of disturbed African honeybees Apis meliffera scutellata causes African elephants Loxodonta africana to retreat and produce warning vocalizations that lead other elephants to join the flight. In our first experiment, audio playbacks of bee sounds induced elephants to retreat and elicited more head-shaking and dusting, reactive behaviors that may prevent bee stings, compared to white noise control playbacks. Most importantly, elephants produced distinctive “rumble” vocalizations in response to bee sounds. These rumbles exhibited an upward shift in the second formant location, which implies active vocal tract modulation, compared to rumbles made in response to white noise playbacks. In a second experiment, audio playbacks of these rumbles produced in response to bees elicited increased headshaking, and further and faster retreat behavior in other elephants, compared to control rumble playbacks with lower second formant frequencies. These responses to the bee rumble stimuli occurred in the absence of any bees or bee sounds. This suggests that these elephant rumbles may function as referential signals, in which a formant frequency shift alerts nearby elephants about an external threat, in this case, the threat of bees

Hierarchical Chain Model of Spider Capture Silk Elasticity

Spider capture silk is a biomaterial with both high strength and high elasticity, but the structural design principle underlying these remarkable properties is still unknown. It was revealed recently by atomic force microscopy that, an exponential force--extension relationship holds both for capture silk mesostructures and for intact capture silk fibers [N. Becker et al., Nature Materials 2, 278 (2003)]. In this Letter a simple hierarchical chain model was proposed to understand and reproduce this striking observation. In the hierarchical chain model, a polymer is composed of many structural motifs which organize into structural modules and supra-modules in a hierarchical manner. Each module in this hierarchy has its own characteristic force. The repetitive patterns in the amino acid sequence of the major flagelliform protein of spider capture silk is in support of this model.Comment: 4 pages, 3 figures. Will be formally published in PR

Trajectories of Maternal Mental Health: A Prospective Study of Mothers of Infants With Congenital Heart Defects From Pregnancy to 36 Months Postpartum

Objective To chart mothers' trajectories of mental health from pregnancy to 36 months postpartum in order to investigate the association between infants' congenital heart defects (CHD) and compromised maternal mental health. Methods Mothers of infants with mild, moderate, or severe CHD (n = 141) and mothers (n = 36,437) enrolled in the Norwegian Mother and Child Cohort Study were assessed at regular intervals from pregnancy up to 36 months postpartum, including measurements at 6 and 18 months, using an 8-item version of the Hopkins Symptom Checklist-25. Results Mean score trajectories of SCL-8 for mothers of infants with severe CHD deviated significantly from cohort controls 6, 18, and 36 months postpartum, indicating heightened symptoms of depression and anxiety. Conclusions Mothers of infants with severe CHD are at risk of compromised mental health from delivery to 36 months postpartum. Strain due to CHD-related interventions is identified as a possible partial mediator of the distres

Relationship Satisfaction Among Mothers of Children With Congenital Heart Defects: A Prospective Case-Cohort Study

Objective To assess the level of partner relationship satisfaction among mothers of children with different severity of congenital heart defects (CHD) compared with mothers in the cohort. Methods Mothers of children with mild, moderate, or severe CHD (n = 182) and a cohort of mothers of children without CHD (n = 46,782) from the Norwegian Mother and Child Cohort Study were assessed at 5 time points from pregnancy to 36 months postpartum. A 5-item version of the Relationship Satisfaction scale was used, and relevant covariates were explored. Results The trajectories of relationship satisfaction among mothers of children with varying CHD severity did not differ from the trajectories in the cohort. All women in the cohort experienced decreasing relationship satisfaction from 18 months after delivery up to 36 months after delivery. Conclusions Having a child with CHD, regardless of severity, does not appear to exacerbate the decline in relationship satisfactio

Menstrual cycle phase modulates emotional conflict processing in women with and without premenstrual syndrome (PMS): A pilot study

Background Premenstrual syndrome (PMS) is characterized by a cluster of psychological and somatic symptoms during the late luteal phase of the menstrual cycle that disappear after the onset of menses. Behavioral differences in emotional and cognitive processing have been reported in women with PMS, and it is of particular interest whether PMS affects the parallel execution of emotional and cognitive processing. Related to this is the question of how the performance of women with PMS relates to stress levels compared to women without PMS. Cortisol has been shown to affect emotional processing in general and it has also been shown that women with severe PMS have a particular cortisol profile. Methods We measured performance in an emotional conflict task and stress levels in women with PMS (n = 15) and women without PMS (n = 15) throughout their menstrual cycle. Results We found a significant increase (p = 0.001) in the mean reaction time for resolving emotional conflict from the follicular to the luteal cycle phase in all subjects. Only women with PMS demonstrated an increase in physiological and subjective stress measures during the luteal menstrual cycle phase. Conclusions Our findings suggest that the menstrual cycle modulates the integration of emotional and cognitive processing in all women. Preliminary data are supportive of the secondary hypothesis that stress levels are mediated by the menstrual cycle phase only in women with PMS. The presented evidence for menstrual cycle-specific differences in integrating emotional and cognitive information highlights the importance of controlling for menstrual cycle phase in studies that aim to elucidate the interplay of emotion and cognition