Particle-in-cell simulations of rf breakdown

Breakdown voltages of a capacitively coupled radio frequency argon discharge at 27 MHz are studied. We use a one-dimensional electrostatic PIC code to investigate the effect of changing the secondary emission properties of the electrodes on the breakdown voltage, particularly at low pd values. Simulation results are compared with the available experimental results and a satisfactory agreement is found.Comment: 12th International Congress on Plasma Physics, 25-29 October 2004, Nice (France

Nociceptive Cortical Activity Is Dissociated from Nociceptive Behavior in Newborn Human Infants under Stress.

Newborn infants display strong nociceptive behavior in response to tissue damaging stimuli, and this is accompanied by nociceptive activity generated in subcortical and cortical areas of the brain [1, 2]. In the absence of verbal report, these nociceptive responses are used as measures of pain sensation in newborn humans, as they are in animals [3, 4]. However, many infants are raised in a physiologically stressful environment, and little is known about the effect of background levels of stress upon their pain responses. In adults, acute physiological stress causes hyperalgesia [5-7], and increased background stress increases pain [8-10], but these data cannot necessarily be extrapolated to infants. Here we have simultaneously measured nociceptive behavior, brain activity, and levels of physiological stress in a sample of 56 newborn human infants aged 36-42 weeks. Salivary cortisol (hypothalamic pituitary axis), heart rate variability (sympathetic adrenal medullary system), EEG event-related potentials (nociceptive cortical activity), and facial expression (behavior) were acquired in individual infants following a clinically required heel lance. We show that infants with higher levels of stress exhibit larger amplitude cortical nociceptive responses, but this is not reflected in their behavior. Furthermore, while nociceptive behavior and cortical activity are normally correlated, this relationship is disrupted in infants with high levels of physiological stress. Brain activity evoked by noxious stimulation is therefore enhanced by stress, but this cannot be deduced from observation of pain behavior. This may be important in the prevention of adverse effects of early repetitive pain on brain development

Teleological Essentialism

Placeholder essentialism is the view that there is a causal essence that holds category members together, though we may not know what the essence is. Sometimes the placeholder can be filled in by scientific essences, such as when we acquire scientific knowledge that the atomic weight of gold is 79. We challenge the view that placeholders are elaborated by scientific essences. On our view, if placeholders are elaborated, they are elaborated Aristotelian essences, a telos. Utilizing the same kinds of experiments used by traditional essentialists—involving superficial change (study 1), transformation of insides (study 2), acquired traits (study 3) and inferences about offspring (study 4)—we find support for the view that essences are elaborated by a telos. And we find evidence (study 5) that teleological essences may generate category judgments

Breakdown in hydrogen and deuterium gases in static and radio-frequency fields

We report the results of a combined experimental and modeling study of the electrical breakdown of hydrogen and deuterium in static (DC) and radio-frequency (RF) (13.56 MHz) electric fields. For the simulations of the breakdown events, simplified models are used and only electrons are traced by Monte Carlo simulation. The experimental DC Paschen curve of hydrogen is used for the determination of the effective secondary electron emission coefficient. A very good agreement between the experimental and the calculated RF breakdown characteristics for hydrogen is found. For deuterium, on the other hand, presently available cross section sets do not allow a reproduction of RF breakdown characteristics

The impact of parental contact upon cortical noxious-related activity in human neonates

BACKGROUND: Neonates display strong behavioural, physiological and cortical responses to tissue-damaging procedures. Parental contact can successfully regulate general behavioural and physiological reactivity of the infant, but it is not known whether it can influence noxious-related activity in the brain. Brain activity is highly dependent upon maternal presence in animal models, and therefore this could be an important contextual factor in human infant pain-related brain activity. METHODS: Global topographic analysis was used to identify the presence and inter-group differences in noxious-related activity in three separate parental contexts. EEG was recorded during a clinically required heel lance in three age and sex-matched groups of neonates (a) while held by a parent in skin-to-skin (n = 9), (b) while held by a parent with clothing (n = 9) or (c) not held at all, but in individualized care (n = 9). RESULTS: The lance elicited a sequence of 4-5 event-related potentials (ERPs), including the noxious ERP (nERP), which was smallest for infants held skin-to-skin and largest for infants held with clothing (p=0.016). The nERP was then followed by additional and divergent long-latency ERPs (> 750 ms post-lance), not previously described, in each of the groups, suggesting the engagement of different higher level cortical processes depending on parental contact. CONCLUSIONS: These results show the importance of considering contextual factors in determining infant brain activity and reveal the powerful influence of parental contact upon noxious-related activity across the developing human brain. SIGNIFICANCE: This observational study found that the way in which the neonatal brain processes a noxious stimulus is altered by the type of contact the infant has with their mother. Specifically, being held in skin-to-skin reduces the magnitude of noxious-related cortical activity. This work has also shown that different neural mechanisms are engaged depending on the mother/infant context, suggesting maternal contact can change how a baby's brain processes a noxious stimulus

Fronto-central slow cortical activity is attenuated during phasic events in rapid eye movement sleep at full-term birth

Delta and theta power across fronto-central regions is lower during phasic (saccadic eye movements) than tonic rapid eye movement (active) sleep in full-term infants (n = 15). This indicates that the behavioural-electrophysiological pillars of rapid eye movement sleep micro-architecture are in place at birth

Equipping learners to evaluate online health care resources: Longitudinal study of learning design strategies in a health care Massive Open Online Course

Background: The digital revolution has led to a boom in the number of available online health care resources. To navigate these resources successfully, digital literacy education is required. Learners who can evaluate the reliability and validity of online health care information are likely to be more effective at avoiding potentially dangerous misinformation. In addition to providing health care education, massive open online courses (MOOCs) are well positioned to play a role in providing digital literacy education in this context. Objective: This study focused on learners enrolled in a MOOC on cancer genomics. The aim of this study was to evaluate the efficacy of a series of digital literacy-related activities within this course. This was an iterative study, with changes made to digital literacy-related activities in 4 of the 8 runs of the course. Methods: This mixed methods study focused on learner engagement with the digital literacy-related activities, including the final course written assignment. Quantitative data including the number of references listed in each written assignment were compared between successive runs. Qualitative data in the form of learner comments on discussion forums for digital literacy-related tasks were evaluated to determine the impact of these educational activities. Results: Using the number of references included for each final course assignment as an indicator of digital literacy skills, the digital literacy-related activities in the final 2 runs were judged to be the most successful. We found a statistically significant increase in the number of references cited by learners in their final written assignments. The average number of references cited in Run 8 was significantly higher (3.5) than in Run 1 (1.8) of the MOOC (P=.001). Learner comments in Runs 7 and 8 showed that a poll in which learners were asked to select which of 4 online resources was reliable was effective in stimulating learner discussion about how to evaluate resource reliability. Conclusions: Similar to many health care MOOCs, the course studied here had a heterogeneous group of learners, including patients (and their families), the public, health care students, and practitioners. Carefully designing a range of digital literacy-related activities that would be beneficial to this heterogenous group of learners enabled learners to become more effective at evaluating and citing appropriate online resources within their written assignments