Benchmarking headtail with electron cloud instabilities observed in the LHC

After a successful scrubbing run in the beginning of 2011, the LHC can be presently operated with high intensity proton beams with 50 ns bunch spacing. However, strong electron cloud effects were observed during machine studies with the nominal beam with 25 ns bunch spacing. In particular, fast transverse instabilities were observed when attempting to inject trains of 48 bunches into the LHC for the first time. An analysis of the turn-by-turn bunch-bybunch data from the transverse damper pick-ups during these injection studies is presented, showing a clear signature of the electron cloud effect. These experimental observations are reproduced using numerical simulations: the electron distribution before each bunch passage is generated with PyECLOUD and used as input for a set of HEADTAIL simulations. This paper describes the simulation method as well as the sensitivity of the results to the initial conditions for the electron build-up. The potential of this type of simulations and their clear limitations on the other hand are discussed.Comment: 7 pages, contribution to the Joint INFN-CERN-EuCARD-AccNet Workshop on Electron-Cloud Effects: ECLOUD'12; 5-9 Jun 2012, La Biodola, Isola d'Elba, Ital

A intera??o dos beb?s na creche: o que dizem as pesquisas

This study aims to systematize and discuss the educational implications of the theses and dissertations defended in postgraduate programs in Brazil regard to the expressions and characteristics of the interactions between pairs of infants up to two years of age at the nursery. This is a bibliographical research, in which a survey of theses and dissertations was carried out at sites ?IBICT ? and ?CAPES?, having as search terms "interaction between babies" and "babyinteractions". There were 18 papers related to the subject, but only five related specifically to relations between peers. The analysis of the abstracts of these five studies showed that babies interact with each other and use strategies to communicate, like look, babbling, vocalizations, offer, smiles, movements, gestures, invitations, cries, laughter and facial expressions. They are behaviors full of meanings, a set of actions and communications that differ from spoken language. Imitation is an effective non-verbal communicative resource for babies who do not have developed oral language and the jokes constitute privileged and indispensable situations to provide these interactions.Este estudo teve como objetivo sistematizar e discutir as implica??es educacionais dos achados de teses e disserta??es defendidas em programas de p?s-gradua??o no Brasil, no que se refere ?s express?es e caracter?sticas das intera??es entre pares de beb?s de at? dois anos, em ambientes de creche. Trata-se de uma pesquisa bibliogr?fica, na qual foi efetuado um levantamento de teses e disserta??es, nos sites IBICT e CAPES, tendo como termos de busca ?intera??o entre beb?s? e ?intera??es-beb??. Foram encontrados 18 trabalhos relacionados com o tema, 18 mas apenas cinco se referiam especificamente ?s rela??es entre coet?neos. A an?lise dos resumos desses cinco trabalhos mostrou que os beb?s interagem entre si e que utilizam estrat?gias para se comunicarem, como o olhar, balbucios, vocaliza??es, oferta, sorrisos, movimentos, gestos, convites, choros, risos, express?es faciais. S?o comportamentos repletos de significados, um conjunto de a??es e comunica??es que diferem da linguagem falada. A imita??o ? um recurso comunicativo n?o verbal eficaz para beb?s que n?o possuem linguagem oral desenvolvida e as brincadeiras se constituem em situa??es privilegiadas e indispens?veis para proporcionarem essas intera??es

Experimental Investigation of the Effect Of Zeolite Coating Thickness on the Performance of a Novel Zeolite-Water Adsorption Heat Pump Module

A novel zeolite-water absorption heat pump module comprising an adsorber, an evaporator and a condenser heat exchanger as well as a module non-return valve in a hermetically sealed vessel is introduced. The investigated adsorber heat exchanger is an extruded aluminum finned-tube heat exchanger coated with AQSOA-Z02 zeolite of Mitsubishi Plastics Incorporation (MPI). The effect of the Zeolite layer thickness (300 and 500 micrometers) on the performance of the heat pump module has been experimentally investigated under different operating conditions related to floor heating systems in Middle Europe. A coefficient of performance (COP) of 1.18 has been measured with the 300 micrometers coated adsorber at a return temperature of 35 C, increasing 1.23 at a return temperature of 25 C. With the 500 micrometer coated adsorber, the measured COPs have been enhanced to 1.27 and 1.35, respectively. This enhancement has been attributed to the increase of the ration between zeolite and heat exchanger heat capacities

Correlation of compressive stress with spalling of plasma sprayed ceramic materials

Ceramics on metal substrates for potential use as high temperature seals or other applications are exposed to forces originating from differences in thermal expansion between the ceramic and the metal substrate. This report develops a relationship between the difference in expansion of the ceramic and the substrate, defines conditions under which shear between the ceramic and the substrate occurs, and those under which bending forces are produced in the ceramic. The off-axis effect of compression forces resulting from high temperature plastic flow of the ceramic producing buckling of the ceramic is developed. Shear is associated with the edge or boundary stresses on the component while bending is associated with the distortion of an interior region. Both modes are significant in predicting life of the ceramic

Regional cerebral blood flow changes as a function of delta and spindle activity during slow wave sleep in humans

In the present study, we investigated changes in regional cerebral blood flow (rCBF) in humans during the progression from relaxed wakefulness through slow wave sleep (SWS). These changes were examined as a function of spindle (12-15 Hz) and delta (1.5-4.0 Hz) electroencephalographic (EEG) activity of SWS. rCBF was studied with positron emission tomography (PET) using the H215O bolus method. A maximum of six 60 sec scans were performed per subject during periods of wakefulness and stages 1-4 of SWS, as determined by on-line EEG monitoring. Spectral analysis was performed off-line on the EEG epochs corresponding to the scans for computation of activity in specific frequency bands. The relationship between EEG frequency band activity and normalized rCBF was determined by means of a voxel-by-voxel analysis of covariance. delta activity covaried negatively with rCBF most markedly in the thalamus and also in the brainstem reticular formation, cerebellum, anterior cingulate, and orbitofrontal cortex. After the effect of delta was removed, a significant negative covariation between spindle activity and the residual rCBF was evident in the medial thalamus. These negative covariations may reflect the disfacilitation and active inhibition of thalamocortical relay neurons in association with delta and spindles, as well as the neural substrates underlying the progressive attenuation of sensory awareness, motor responsiveness, and arousal that occur during SWS. delta activity covaried positively with rCBF in the visual and auditory cortex, possibly reflecting processes of dream-like mentation purported to occur during SW

Divergence in Gene Regulation Contributes to Sympatric Speciation of \u3ci\u3eShewanella baltica\u3c/i\u3e Strains

Niche partitioning and sequence evolution drive genomic and phenotypic divergence, which ultimately leads to bacterial diversification. This study investigated the genomic composition of two Shewanella baltica clades previously identified through multilocus sequencing typing and recovered from the redox transition zone in the central Baltic Sea. Comparative genomic analysis revealed significantly higher interclade than intraclade genomic dissimilarity and that a subset of genes present in clade A were associated with potential adaptation to respiration of sulfur compounds present in the redox transition zone. The transcriptomic divergence between two representative strains of clades A and D, OS185 and OS195, was also characterized and revealed marked regulatory differences. We found that both the transcriptional divergence of shared genes and expression of strain-specific genes led to differences in regulatory patterns between strains that correlate with environmental redox niches. For instance, under anoxic conditions of respiratory nitrate ammonification, OS185—the strain isolated from a nitrate-rich environment—upregulated nearly twice the number of shared genes upregulated by OS195—the strain isolated from an H2S-containing anoxic environment. Conversely, OS195 showed stronger induction of strain-specific genes, especially those associated with sulfur compound respiration, under thiosulfate-reducing conditions. A positive association between the level of transcriptional divergence and the level of sequence divergence for shared genes was also noted. Our results provide further support for the hypothesis that genomic changes impacting transcriptional regulation play an important role in the diversification of ecologically distinct populations

Mathematical Models of Feedback Systems for Control of Intra-Bunch Instabilities Driven by E-Clouds and TMCI

The feedback control of intra-bunch instabilities driven by electron-clouds or strong head-tail coupling (transverse mode coupled instabilities TMCI) requires bandwidth sufficient to sense the vertical position and apply correction fields to multiple sections of a nanosecond-scale bunch. These requirements impose challenges and limits in the design and implementation of the feedback control channel. This paper presents different models for the feedback subsystems: receiver, processing channel, amplifier and kicker, that take into account their frequency response and limits. These models are included in reduced mathematical models of the bunch dynamics and multi-particle simulation codes (WARP / C-MAD / HEADTAIL) to evaluate the impact of the subsystem limitations in the bunch stabilization and emittance improvement. With this realistic model of the hardware, it is possible to analyze and design the feedback system. This research is crucial to evaluate the boundary in the performance of the feedback control system due to technological limitations. Additionally, these models define the impact of parameter variations or mismatching and the effect of spurious perturbation and noise in the performance of the feedback system