Surface Analysis of OFE-Copper X-Band Accelerating Structures and Possible Correlation to RF Breakdown Events

X-band accelerator structures meeting the Next Linear Collider (NLC) design requirements have been found to suffer vacuum surface damage caused by radio frequency (RF) breakdown, when processed to high electric-field gradients. Improved understanding of these breakdown events is desirable for the development of structure designs, fabrication procedures, and processing techniques that minimize structure damage. RF reflected wave analysis and acoustic sensor pickup have provided breakdowns localization in RF structures. Particle contaminations found following clean autopsy of four RF-processed travelling wave structures, have been catalogued and analyzed. Their influence on RF breakdown, as well as that of several other material-based properties, will be discussed.Comment: 21 pages, 8 figures, 4 tables, Submitted to JVST A as a proceeding of the 50th AVS conference (Baltimore, MD, 2-7 Nov 2003

Влияние электрического поля на адгезионные характеристики системы полихлоропрен-шунгит

The effect of temperature and external electric field on the adhesion characteristics in the polychloroprene-schungite system was investigated. It is shown that an increase in temperature and orientation of macromolecules of polychloroprene in an external electric field significantly increase the bond strength between the studied components. The detected effects are explained from the viewpoint of the possibility of direct chemical interaction ofshungite with polychloroprene macromolecules oriented in a certain way in the region of an adhesive compound formation. This is facilitated by the structural features of schungite (the presence of paramagnetic centers, fullerene-like structures, metal oxides) and polychloroprene in shungite, as well as by the creation of the most optimal modes for implementing this interaction. To assess the strength of the interaction between polychloroprene and the surface of shungite we used a method for determining the stress of exfoliation of a polymer film from the surface of a shungite plate. It was established that the greatest effect in strengthening the bond between polychloroprene and the surface of shungite is achieved when a polymer film is formed from a solution in carbon tetrachloride on a negative electrode (cathode). The strength of the bond between shungite and the polychloroprene film formed on the cathode is more than two times higher than this parameter when forming the same film on the anode. The energy expended during the peeling of a film formed on the cathode is twice the energy of exfoliation from the shungite plate of the film formed on the anode. The analysis of the change in the supramolecular structure of polychloroprene in the polychloroprene-shungite system as a result of the orientational influence of an external electrostatic field was carried out using the temperature dependence of the tangent of the dielectric loss angle of the systems under study. It is shown that a polychloroprene film formed in an electrostatic field has a more ordered structure compared to a similar sample formed without a field. This fact is evidenced by the shift of the maxima toward higher temperatures in the relaxation spectra of the dipole polarization for the system formed without the field, and the system formed on the cathode. The polychloroprene film containing finely dispersed shungite as a filler and formed on the cathode is characterized by an increased value of the tangent of dielectric loss angle and an increased number of peaks of dipole relaxation in the temperature range studied.Исследовано влияние температуры и внешнего электрического поля на адгезионные характеристики в системе полихлоропрен-шунгит. Показано, что повышение температуры и ориентация макромолекул полихлоропрена во внешнем электрическом поле существенно увеличивают прочность связи между исследованными компонентами. Обнаруженные эффекты, объяснены с точки зрения возможности непосредственного химического взаимодействия шунгита с ориентированными определенным образом макромолекулами полихлоропрена в области формирования адгезионного соединения. Этому способствуют особенности строения шунгита (наличие в шунгите парамагнитных центров, фуллереноподобных структур, оксидов металлов) и полихлоропрена, являющегося полярным эластомером, а также создание оптимальных режимов для реализации такого взаимодействия. Для оценки прочности взаимодействия между полихлоропреном и поверхностью шунгита в работе использован метод определения напряжения отслаивания полимерной пленки от поверхности шунгитовой пластинки. Установлено, что наибольший эффект в упрочнении связи между полихлоропреном и поверхностью шунгита достигается при формировании полимерной пленки из раствора в четыреххлористом углероде на отрицательном электроде (катоде). Прочность связи шунгита с полихлоропреновой пленкой, сформированной на катоде, более, чем в два раза превышает этот параметр при формировании такой же пленки на аноде. Анализ изменения надмолекулярной структуры полихлоропрена в системе полихлоропрен-шунгит в результате ориентационного воздействия внешнего электростатического поля произведен с помощью температурной зависимости тангенса угла диэлектрических потерь исследуемых систем. Показано, что пленка полихлоропрена, сформированная в электростатическом поле, имеет более упорядоченную структуру по сравнению с аналогичным образцом, но сформированном без поля. Об этом факте свидетельствует сдвиг максимумов в сторону больших температур в спектрах релаксации дипольной поляризации для системы, сформированной без воздействия поля, и системы, сформированной на катоде. Пленка полихлоропрена, содержащая в качестве наполнителя мелкодисперсный шунгит и сформированная на катоде, характеризуется повышенным значением тангенса угла диэлектрических потерь и увеличенным количеством пиков дипольной релаксации в исследованной температурной области

Theory of Interaction of Memory Patterns in Layered Associative Networks

A synfire chain is a network that can generate repeated spike patterns with millisecond precision. Although synfire chains with only one activity propagation mode have been intensively analyzed with several neuron models, those with several stable propagation modes have not been thoroughly investigated. By using the leaky integrate-and-fire neuron model, we constructed a layered associative network embedded with memory patterns. We analyzed the network dynamics with the Fokker-Planck equation. First, we addressed the stability of one memory pattern as a propagating spike volley. We showed that memory patterns propagate as pulse packets. Second, we investigated the activity when we activated two different memory patterns. Simultaneous activation of two memory patterns with the same strength led the propagating pattern to a mixed state. In contrast, when the activations had different strengths, the pulse packet converged to a two-peak state. Finally, we studied the effect of the preceding pulse packet on the following pulse packet. The following pulse packet was modified from its original activated memory pattern, and it converged to a two-peak state, mixed state or non-spike state depending on the time interval

Dose-effect study of Gelsemium sempervirens in high dilutions on anxiety-related responses in mice

Introduction This study was designed to investigate the putative anxiolytic-like activity of ultra-low doses of Gelsemium sempervirens (G. sempervirens), produced according to the homeopathic pharmacopeia. Methods Five different centesimal (C) dilutions of G. sempervirens (4C, 5C, 7C, 9C and 30C), the drug buspirone (5 mg/kg) and solvent vehicle were delivered intraperitoneally to groups of ICR-CD1 mice over a period of 9 days. The behavioral effects were assessed in the open-field (OF) and light\u2013dark (LD) tests in blind and randomized fashion. Results Most G. sempervirens dilutions did not affect the total distance traveled in the OF (only the 5C had an almost significant stimulatory effect on this parameter), indicating that the medicine caused no sedation effects or unspecific changes in locomotor activity. In the same test, buspirone induced a slight but statistically significant decrease in locomotion. G. sempervirens showed little stimulatory activity on the time spent and distance traveled in the central zone of the OF, but this effect was not statistically significant. In the LD test, G. sempervirens increased the % time spent in the light compartment, an indicator of anxiolytic-like activity, with a statistically significant effect using the 5C, 9C and 30C dilutions. These effects were comparable to those of buspirone. The number of transitions between the compartments of the LD test markedly increased with G. sempervirens 5C, 9C and 30C dilutions. Conclusion The overall pattern of results provides evidence that G. sempervirens acts on the emotional reactivity of mice, and that its anxiolytic-like effects are apparent, with a non-linear relationship, even at high dilutions

Long-Term Effects of the Periconception Period on Embryo Epigenetic Profile and Phenotype: The Role of Stress and How This Effect Is Mediated

Stress represents an unavoidable aspect of human life, and pathologies associated with dysregulation of stress mechanisms - particularly psychiatric disorders - represent a significant global health problem. While it has long been observed that levels of stress experienced in the periconception period may greatly affect the offspring's risk of psychiatric disorders, the mechanisms underlying these associations are not yet comprehensively understood. In order to address this question, this chapter will take a 'top-down' approach, by first defining stress and associated concepts, before exploring the mechanistic basis of the stress response in the form of the hypothalamic-pituitary-adrenal (HPA) axis, and how dysregulation of the HPA axis can impede our mental and physical health, primarily via imbalances in glucocorticoids (GCs) and their corresponding receptors (GRs) in the brain. The current extent of knowledge pertaining to the impact of stress on developmental programming and epigenetic inheritance is then extensively discussed, including the role of chromatin remodelling associated with specific HPA axis-related genes and the possible role of regulatory RNAs as messengers of environmental stress both in the intrauterine environment and across the germ line. Furthering our understanding of the role of stress on embryonic development is crucial if we are to increase our predictive power of disease risk and devise-effective treatments and intervention strategies

Cannabigerol is a novel, well-tolerated appetite stimulant in pre-satiated rats

Rationale The appetite-stimulating properties of cannabis are well documented and have been predominantly attributed to the hyperphagic activity of the psychoactive phytocannabinoid, ∆9-tetrahydrocannabinol (∆9-THC). However, we have previously shown that a cannabis extract devoid of ∆9-THC still stimulates appetite, indicating that other phytocannabinoids also elicit hyperphagia. One possible candidate is the non-psychoactive phytocannabinoid cannabigerol (CBG), which has affinity for several molecular targets with known involvement in the regulation of feeding behaviour. Objectives The objective of the study was to assess the effects of CBG on food intake and feeding pattern microstructure. Methods Male Lister hooded rats were administered CBG (30–120 mg/kg, per ora (p.o.)) or placebo and assessed in open field, static beam and grip strength tests to determine a neuromotor tolerability profile for this cannabinoid. Subsequently, CBG (at 30–240 mg/kg, p.o.) or placebo was administered to a further group of pre-satiated rats, and hourly intake and meal pattern data were recorded over 2 h. Results CBG produced no adverse effects on any parameter in the neuromotor tolerability test battery. In the feeding assay, 120–240 mg/kg CBG more than doubled total food intake and increased the number of meals consumed, and at 240 mg/kg reduced latency to feed. However, the sizes or durations of individual meals were not significantly increased. Conclusions Here, we demonstrate for the first time that CBG elicits hyperphagia, by reducing latency to feed and increasing meal frequency, without producing negative neuromotor side effects. Investigation of the therapeutic potential of CBG for conditions such as cachexia and other disorders of eating and body weight regulation is thus warranted

Spike Timing Dependent Plasticity Finds the Start of Repeating Patterns in Continuous Spike Trains

Experimental studies have observed Long Term synaptic Potentiation (LTP) when a presynaptic neuron fires shortly before a postsynaptic neuron, and Long Term Depression (LTD) when the presynaptic neuron fires shortly after, a phenomenon known as Spike Timing Dependant Plasticity (STDP). When a neuron is presented successively with discrete volleys of input spikes STDP has been shown to learn ‘early spike patterns’, that is to concentrate synaptic weights on afferents that consistently fire early, with the result that the postsynaptic spike latency decreases, until it reaches a minimal and stable value. Here, we show that these results still stand in a continuous regime where afferents fire continuously with a constant population rate. As such, STDP is able to solve a very difficult computational problem: to localize a repeating spatio-temporal spike pattern embedded in equally dense ‘distractor’ spike trains. STDP thus enables some form of temporal coding, even in the absence of an explicit time reference. Given that the mechanism exposed here is simple and cheap it is hard to believe that the brain did not evolve to use it