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Synchronization
Kinds of Synchronization Terms modified by Synchronization Selected AbstractsCooling Abolishes Neuronal Network Synchronization in Rat Hippocampal SlicesEPILEPSIA, Issue 6 2002Sam P. Javedan Summary: ,Purpose: We sought to determine whether cooling brain tissue from 34 to 21°C could abolish tetany-induced neuronal network synchronization (gamma oscillations) without blocking normal synaptic transmission. Methods: Intracellular and extracellular electrodes recorded activity in transverse hippocampal slices (450,500 ,m) from Sprague,Dawley male rats, maintained in an air,fluid interface chamber. Gamma oscillations were evoked by afferent stimulation at 100 Hz for 200 ms. Baseline temperature in the recording chamber was 34°C, reduced to 21°C within 20 min. Results: Suprathreshold tetanic stimuli evoked membrane potential oscillations in the 40-Hz frequency range (n = 21). Gamma oscillations induced by tetanic stimulation were blocked by bicuculline, a ,-aminobutyric acid (GABA)A -receptor antagonist. Cooling from 34 to 21°C reversibly abolished gamma oscillations in all slices tested. Short, low-frequency discharges persisted after cooling in six of 14 slices. Single-pulse,evoked potentials, however, were preserved after cooling in all cases. Latency between stimulus and onset of gamma oscillation was increased with cooling. Frequency of oscillation was correlated with chamber cooling temperature (r = 0.77). Tetanic stimulation at high intensity elicited not only gamma oscillation, but also epileptiform bursts. Cooling dramatically attenuated gamma oscillation and abolished epileptiform bursts in a reversible manner. Conclusions: Tetany-induced neuronal network synchronization by GABAA -sensitive gamma oscillations is abolished reversibly by cooling to temperatures that do not block excitatory synaptic transmission. Cooling also suppresses transition from gamma oscillation to ictal bursting at higher stimulus intensities. These findings suggest that cooling may disrupt network synchrony necessary for epileptiform activity. [source] Nursing Synchronization and Milk Ejection Failure as Maternal Strategies to Reduce Allosuckling in Pair-Housed Sows (Sus scrofa domestica)ETHOLOGY, Issue 7 2005Gudrun Illmann Non-offspring nursing (allosuckling) is costly for lactating females. It is reasonable to assume, therefore, that mechanisms have evolved to control the frequency of allosuckling. It is suggested that the synchronization of nursing between females could be such a mechanism. The aim of this study was to investigate whether nursing synchronization is related to the timing of nursing behaviour of paired sows and the behaviour of alien piglets in relation to allosuckling. Specifically, we predicted that: (i) nursing synchronization will increase if there is a real risk of allosuckling compared with a situation where there is none, (ii) nursing synchronization indeed reduces allosuckling and, therefore, those nursings with allosuckling attempts will be less closely synchronized than those without allosuckling attempts and (iii) in non-synchronized nursings, the sows will more often employ another strategy to reduce allosuckling, namely, they will make the nursings non-nutritive by not releasing milk. Ten pairs of sows and their litters were used in this study. For each pair, the two sows were housed individually until their litters were weaned; however, their litters had access to both sows from day 11 post-partum. The behaviour of the 10 pairs of sows with their litters was videotaped for 6 h on days 10, 11, 17 and 24 post-partum. The frequency of allosuckling attempts, non-nutritive nursings and allosuckling during milk ejection was analysed for every pair for every day of observation. The observed frequency of nursing synchronization was high. The median interval between the start of a nursing within one pair of sows was 32 s. The first prediction was supported as synchronization became significantly tighter when piglets were given the possibility to allosuckle on day 11 [Cochran,Mantel,Haenszel (CMH) statistics, p < 0.0001]. The second prediction was also supported; the nursings were less closely synchronized when there were allosuckling attempts (CMH statistics, p < 0.05). Of all nursings, 36% had an allosuckling attempt; however, only 17% resulted in real allosuckling. Evidence in favour of the third prediction was also found as non-nutritive nursings were more frequent in non-synchronized nursings (CMH statistics, p < 0.05). Finally, real allosuckling during milk ejection was unrelated to the degree of nursing synchronization, as in less synchronized nursings, the sows responded to allosuckling attempts by not releasing milk. Our results suggest that sows are not able to completely suppress allosuckling; however, they can reduce its frequency through nursing synchronization and non-nutritive nursings. [source] High-frequency gamma oscillations coexist with low-frequency gamma oscillations in the rat visual cortex in vitroEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 8 2010Olaleke O. Oke Abstract Synchronization of neuronal activity in the visual cortex at low (30,70 Hz) and high gamma band frequencies (> 70 Hz) has been associated with distinct visual processes, but mechanisms underlying high-frequency gamma oscillations remain unknown. In rat visual cortex slices, kainate and carbachol induce high-frequency gamma oscillations (fast-,; peak frequency , 80 Hz at 37°C) that can coexist with low-frequency gamma oscillations (slow-,; peak frequency , 50 Hz at 37°C) in the same column. Current-source density analysis showed that fast-, was associated with rhythmic current sink-source sequences in layer III and slow-, with rhythmic current sink-source sequences in layer V. Fast-, and slow-, were not phase-locked. Slow-, power fluctuations were unrelated to fast-, power fluctuations, but were modulated by the phase of theta (3,8 Hz) oscillations generated in the deep layers. Fast-, was spatially less coherent than slow-,. Fast-, and slow-, were dependent on ,-aminobutyric acid (GABA)A receptors, ,-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors and gap-junctions, their frequencies were reduced by thiopental and were weakly dependent on cycle amplitude. Fast-, and slow-, power were differentially modulated by thiopental and adenosine A1 receptor blockade, and their frequencies were differentially modulated by N -methyl- d -aspartate (NMDA) receptors, GluK1 subunit-containing receptors and persistent sodium currents. Our data indicate that fast-, and slow-, both depend on and are paced by recurrent inhibition, but have distinct pharmacological modulation profiles. The independent co-existence of fast-, and slow-, allows parallel processing of distinct aspects of vision and visual perception. The visual cortex slice provides a novel in vitro model to study cortical high-frequency gamma oscillations. [source] Dealing with Timing and Synchronization in Opportunities for Joint Activity ParticipationGEOGRAPHICAL ANALYSIS, Issue 3 2010Tijs Neutens The ability of people to access opportunities offered by the built environment is circumscribed by various sets of space,time constraints, including the requirements to meet other persons at particular times and places to undertake activities together. While models of space,time accessibility recognize that joint activities may constrain the performance of activities in space and time, their specifications do not explicitly acknowledge the opportunities that individuals of a group have for joint activity participation. Therefore, this article focuses on joint activity participation and argues that collective activity decisions are the outcome of a complex process involving various aspects of timing, synchronization, and social hierarchy. The utility-theoretic model proposed here quantifies the extent to which opportunities can be jointly accessed by a particular group of people within a specific time period. Central to the approach are three key variables: the attractiveness of an opportunity, the time available for activity participation, and the travel time to an activity location. Because of the multiperson character of joint activities, the determination of these variables is subject to individual preferences, privileges, and power differentials within a group. Specific attention is given to how time-of-day and synchronization effects influence the opportunities accessible to a group of individuals. The impact of these factors on joint accessibility is illustrated by a real-world example of an everyday rendezvous scenario. The outcomes of a simulation exercise suggest that time-of-day and synchronization effects significantly affect the benefits that can be gained from opportunities for joint activities. La capacidad de acceso a las oportunidades que los entornos construidos (como las ciudades) ofrecen a las personas, está limitada por un conjunto diverso de restricciones espacio-temporales. Entre ellas se incluyen los requisitos para coincidir y encontrarse con otras personas en determinados momentos y lugares con el fin de realizar actividades conjuntas. Los modelos de accesibilidad comunes reconocen que las actividades conjuntas pueden limitar el ejercicio de actividades en el espacio y el tiempo. Sin embargo, sus especificaciones no reconocen explícitamente las oportunidades disponibles a todos los individuos de un grupo para participar de una actividad conjunta. Es en este contexto y dadas las limitaciones descritas que este artículo se centra en la participación de individuos en actividades conjuntas y propone el argumento que la toma de decisiones relacionadas con dichas actividades son el resultado de un proceso complejo que involucra varios aspectos de temporización (programación temporal), sincronización, y jerarquía social. El modelo teórico de utilidad que se propone aquí cuantifica el grado en que las oportunidades pueden ser evaluadas en forma conjunta por un grupo de personas particular dentro de un período de tiempo específico. El marco general propuesto por los autores se basa en tres variables fundamentales: el atractivo de una oportunidad, el tiempo disponible para la participación de la actividad, y el tiempo de desplazamiento al lugar donde se lleva a cabo actividad. Debido al carácter particular de estas actividades (que involucran múltiples participantes), la determinación de estas variables está sujeta a preferencias individuales, a privilegios y a diferencias de poder dentro de un grupo. El presente estudio además presta atención especial a la forma en la que la hora del día y los efectos de sincronización pueden influenciar la disponibilidad de oportunidades para un grupo determinado de individuos. El impacto de estos factores sobre la accesibilidad agregada de actividades conjuntas es ejemplificado por los autores mediante un caso del mundo real que utiliza escenarios de encuentros diarios entre personas. Los resultados de este ejercicio de simulación sugieren que los efectos de la hora del día y la sincronización afectan significativamente los beneficios que se pueden obtener a partir las oportunidades disponibles para acceder a y realizar actividades conjuntas. [source] Synchronization among neighbouring RNCs in a TD-CDMA mobile networkINTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 5 2007Yin-Fu Huang Abstract In the paper, we use zone concepts, and also consider multiple-bunch in a TD-CDMA mobile network. In the multiple-bunch environment, we need a synchronization mechanism to avoid inter-RNC interferences. Here, we use an Informed-of message to transmit local resource allocation results to other neighbouring RNCs through a high-speed network. Thus, inter-RNC interferences can be avoided and the global resource allocation can be made with the message passing. Within the resource allocation algorithm, we also find maximal compatible cliques to achieve the best resource utilization, using the graph algorithm finding maximal cliques in graph theory. Through the simulation, we found that the SRU classification using Conservative strategy matching the SRU allocation using Aggressive strategy has the best performance among all combinations. Copyright © 2006 John Wiley & Sons, Ltd. [source] Improved artifact correction for combined electroencephalography/functional MRI by means of synchronization and use of vectorcardiogram recordingsJOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 3 2008Karen J. Mullinger BSc Abstract Purpose To demonstrate that two methodological developments (synchronization of the MR scanner and electroencephalography [EEG] clocks and use of the scanner's vectorcardiogram [VCG]) improve the quality of EEG data recorded in combined EEG/functional MRI experiments in vivo. Materials and Methods EEG data were recorded using a 32-channel system, during simultaneous multislice EPI acquisition carried out on a 3 Tesla scanner. Recordings were made on three subjects in the resting state and on five subjects using a block paradigm involving visual stimulation with a 10-Hz flashing checkerboard. Results Gradient artifacts were significantly reduced in the EEG data recorded in vivo when synchronization and a TR equal to a multiple of the EEG clock period were used. This was evident from the greater attenuation of the signal at multiples of the slice acquisition frequency. Pulse artifact correction based on R-peak markers derived from the VCG was shown to offer a robust alternative to the conventionally used ECG-based method. Driven EEG responses at frequencies of up to 60 Hz due to the visual stimulus could be more readily detected in data recorded with EEG and MR scanner clock synchronization. Conclusion Synchronization of the scanner and EEG clocks, along with VCG-based R-peak detection is advantageous in removing gradient and pulse artifacts in combined EEG/fMRI recordings. This approach is shown to allow the robust detection of high frequency driven activity in the EEG data. J. Magn. Reson. Imaging 2008;27:607,616. © 2008 Wiley-Liss, Inc. [source] Melatonin Implants Disrupt Developmental Synchrony Regulated By Flexible Interval TimersJOURNAL OF NEUROENDOCRINOLOGY, Issue 11 2003M. R. Gorman Abstract Siberian hamsters born into short daylengths near the end of the breeding season are reproductively inhibited from birth and delay gonadal maturation until the following spring. This vernal transition to a reproductive phenotype coincides with an abrupt increase in body weight, and both processes are triggered by an interval timing mechanism that becomes insensitive, or refractory, to short-day inhibition. It was previously demonstrated that hamsters born into simulated natural photoperiods in early August became photorefractory at later ages than hamsters born into September photoperiods. As a consequence of flexibility in the duration programmed by the interval timer, development of seasonal birth cohorts was synchronous with respect to the calendar date simulated by laboratory photoperiod. In the present study, hamsters were born into simulated August or September photoperiods. Hamsters from each cohort were given removable constant release melatonin implants to reversibly obscure the neuroendocrine representation of daylength between 3 and 9 weeks or 9,15 weeks of age. When control hamsters were given beeswax capsules throughout, August-born males were approximately 6 weeks older than September males at the onset of photorefractoriness as assessed by accelerated increases in body weight and testicular size. Females exhibited the same pattern in body weight. These measures were synchronized with respect to calendar date. Synchronization of cohorts was disrupted by melatonin capsules from 3,9 weeks of age but not by later implants. Melatonin implants altered synchronization by influencing the developmental trajectory of September-born hamsters without influencing the August cohort. These results demonstrate that the function of the interval timer underlying photorefractoriness is influenced by photoperiod and by melatonin. The endogenous pattern of melatonin signals adjusts the duration measured by the interval timer to insure that developmental milestones of seasonal cohorts are synchronized with environmental conditions. [source] Measuring Synchronization and Convergence of Business Cycles for the Euro area, UK and US,OXFORD BULLETIN OF ECONOMICS & STATISTICS, Issue 1 2008Siem Jan Koopman Abstract This paper investigates business cycle relations among different economies in the Euro area. Cyclical dynamics are explicitly modelled as part of a time series model. We introduce mechanisms that allow for increasing or diminishing phase shifts and for time-varying association patterns in different cycles. Standard Kalman filter techniques are used to estimate the parameters simultaneously by maximum likelihood. The empirical illustrations are based on gross domestic product (GDP) series of seven European countries that are compared with the GDP series of the Euro area and that of the US. The original integrated time series are band-pass filtered. We find that there is an increasing resemblance between the business cycle fluctuations of the European countries analysed and those of the Euro area, although with varying patterns. [source] Synchronization of strongly interacting overdamped Josephson junctionsPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 6 2005Alexander Grib Abstract The high frequency approximation is applied for the description of phase locking in the chain of two junctions loaded by the arbitrary resonance system providing strong coupling. The derived equation of synchronization describes phase locking for junctions which McCumber parameters of an order of magnitude larger than those described in ranges of the slowly varying amplitude approximation. The developed method is applied to the chain of junctions loaded by a resonant transmission line. Obtained values of the voltage locking interval and the maximal tolerant spread of critical currents are in agreement with numerical calculations. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Ultrasonographic and Endocrine Evaluation of Three Regimes for Oestrus and Ovulation Synchronization for Sheep in the SubtropicsREPRODUCTION IN DOMESTIC ANIMALS, Issue 6 2009A Ali Contents This study aimed to evaluate three regimes for oestrus and ovulation synchronization in Farafra ewes in the subtropics. During autumn, 43 ewes were assigned to (i) controlled internal drug releasing (CIDR)-eCG group, treated with CIDR for 12 days and eCG at insert withdrawal, n = 13; (ii) PGF2,-PGF2, group, treated with two PGF2, injections at 11 days interval, n = 14; and (iii) GnRH-PGF2,-GnRH group, treated with GnRH, followed 5 days later with PGF2, and 24 h later with a second GnRH, n = 16. Oestrus-mating detection was carried out at 4 h intervals starting on day 0 [the day of CIDR withdrawal (CIDR-eCG group), the day of second PGF2, treatment (PGF2,-PGF2, group) and the day of PGF2, treatment (GnRH-PGF2,-GnRH group)]. Ovarian dynamics was monitored by ultrasound every 12 h beginning on day 0 and continued for 4 days. Blood samples were obtained daily for progesterone (P4) and oestradiol 17, (E2) estimation starting on day 0 and continued for 4 days. The obtained results showed that, oestrus expression, ovulation and conception were greater (p < 0.05) in CIDR-eCG and PGF2,-PGF2, groups than in GnRH-PGF2,-GnRH group. All ewes of PGF2,-PGF2, group presented, on day of second PGF2, injection with mature CL (P4 > 2.0 ng/ml), compared to 42.9% in GnRH-PGF2,-GnRH group (p = 0.01). The peak of oestrus occurred 32,52, 48,60 and 28,96 h after the end of treatment in CIDR-eCG, PGF2,-PGF2, and GnRH-PGF2,-GnRH groups, respectively. Ovulation started 48 h after treatment in all groups and extended for 24, 36 and 48 h for CIDR-eCG, PGF2,-PGF2, and GnRH-PGF2,-GnRH groups, respectively. Results demonstrated that oestrus and ovulation synchronization could be efficiently achieved in Farafra ewes using either CIDR-eCG or PGF2,-PGF2, regimes; however, the GnRH-PGF2,-GnRH treatment induced a more spread oestrus and ovulation that may make the protocol inadequate for timed artificial insemination. [source] Inhibitory Effect of Selenium Supplementation on the Reproductive Performance in Synchronized Merino Sheep at Range Conditions in a Selenium-deficient AreaREPRODUCTION IN DOMESTIC ANIMALS, Issue 3 2008J Sánchez Contents The effect of selenium (Se) supplementation on the reproductive performance of Merino ewes mated out of the normal breeding season was studied in a 2 (no Se supplementation vs Se supplementation) × 2 (ewes mated at natural oestrus vs synchronized oestrus) factorial design with 50 ewes per treatment combination. Synchronization of oestrus was achieved by intravaginal insertion of 40 mg cronolone sponges for 14 days and administration of 440 IU PMSG at sponge withdrawal. Se supplementation was by the addition to the concentrate with 0.5 mg/kg of Se in the form of selenomethionin, for the 3 months prior to the mating and during gestation. Ewes were kept under range conditions in south-west Spain, and exposed to Merino rams at a female: male ratio of 4 : 1 from 2 days following sponge withdrawal, or the equivalent time, for 21 days. Se supplementation alone did not improve significantly ewe fertility or lamb birth weight, but there was a positive effect of synchronizing ewes mated out of the breeding season as more of these ewes lambed and produced more lambs than those not synchronized. However, a strong interaction was found between synchronization and Se supplementation, causing a deleterious effect on the reproductive performance of ewes. This negative effect, presumably related to high embrionary mortality caused by Se toxicity, should be taken into account for oestrus synchronizing in Se-deficient areas. The supplementation with Se, for the prevention of nutritional myodystrophy degeneration in lambs, should be conducted in a fashion which does not generate high levels of Se in the ewes around the mating period. [source] Preovulatory Follicle Development in Goats Following Oestrous Synchronization with Progestagens or ProstaglandinsREPRODUCTION IN DOMESTIC ANIMALS, Issue 1 2008D Fernandez-Moro Contents The study reports on differences in the dynamics of growth and functionality of preovulatory follicles in response to oestrous synchronization, either by the administration of two doses of prostaglandin or by an intravaginal progestagen sponge, in goats. The progestagen-treated group (n = 8) showed more follicles of preovulatory size (,5.5 mm) than the cloprostenol group (n = 8) during the follicular phase (4.5 ± 0.6 vs 1.9 ± 0.2, p < 0.01). The diameters of the largest follicles (LF1, LF2 and LF3) were also larger in the progestagen group (LF1, 7.8 ± 0.3 vs 7.0 ± 0.2 mm, p < 0.05; LF2, 6.7 ± 0.2 vs 5.6 ± 0.2 mm, p < 0.01; LF3, 5.5 ± 0.3 vs 4.2 ± 0.2 mm, p < 0.01). The study of the preovulatory follicles showed that 27.2% (3/11) of the follicles were in the static phase in the cloprostenol group, whilst 71.4% (10/14) were static in progestagen group (p < 0.05). Higher plasma oestradiol levels were recorded in the progestagen-treated goats during the 48 h prior to cloprostenol injection or progestagen withdrawal (4.2 ± 0.4 vs 3.0 ± 0.2 pg/ml, p < 0.05). In conclusion, goats with oestrus synchronized by progestagen showed a higher number of preovulatory-sized follicles, but a decreased oestradiol secretion when compared with does with oestrus synchronized by using prostaglandin analogues. These would support the development of alternative protocols for assisted reproduction. [source] Second Oestrus Synchronization and Precocious Embryo Viability after Puberty Induction in Gilts by the Use of Gonadotrophin TreatmentREPRODUCTION IN DOMESTIC ANIMALS, Issue 2 2005V Do Lago Contents The use of exogenous gonadotrophins in puberty inducement and ovulation synchronization is a technique that has a positive influence on the management of swine. The purpose of this study was to verify the effects of a second gonadotrophin treatment [equine chorionic gonadotrophin (eCG) and luteinizing hormone (LH), intramuscularly (i.m.)] upon the second oestrus synchronization and fertility in gilts. Seventy-one NAIMA® (Pen Ar Lan) gilts had their first oestrus (puberty inducement) induced by a hormonal treatment (eCG and LH). Then, they were randomly distributed into two treatments, with (T1) and without (C) gonadotrophin treatment at the second oestrus. The animals were fed with a single ration (16% of crude protein and 3286.73 kcal ME/kg), and timed artificial insemination performed at the second oestrus. Gilts were slaughtered for embryo recovery and ovary examination about 5 days after insemination. There was no evidence of a difference in the percentage of the second oestrus expression (T1 , 90.90% and C , 86.84%), the duration of the oestrus cycle (T1 , 19.62 ± 0.82 days and C , 19.67 ± 4.14 days), the percentage of follicular cysts (T1 , 15.15% and C , 18.42%) and number of ovulations (T1 , 14.60 ± 5.7 and C , 13.23 ± 4.8) between treatments (p > 0.05). However, the hormonal treatment (T1) showed minor oestrus dispersion and embryo viability (T1 , 8.4 ± 5.6 and C , 11.2 ± 4.6) (p < 0.05). These results indicate that the better synchronization and expression of the second oestrus when using gonadotrophins (eCG and LH) is followed by a lower embryo viability, which is probably the consequence of the heterogeneous follicle recruitment during the injection of eCG. [source] Synchronization of enteric neuronal firing during the murine colonic MMCTHE JOURNAL OF PHYSIOLOGY, Issue 3 2005Nick J. Spencer DiI (1,1,didodecyl-3,3,3,,3,-tetramethylindocarbecyanine perchlorate) retrograde labelling and intracellular electrophysiological techniques were used to investigate the mechanisms underlying the generation of spontaneously occurring colonic migrating myoelectric complexes (colonic MMCs) in mice. In isolated, intact, whole colonic preparations, simultaneous intracellular electrical recordings were made from pairs of circular muscle (CM) cells during colonic MMC activity in the presence of nifedipine (1,2 ,m). During the intervals between colonic MMCs, spontaneous inhibitory junction potentials (IJPs) were always present. The amplitudes of spontaneous IJPs were highly variable (range 1,20 mV) and occurred asynchronously in the two CM cells, when separated by 1 mm in the longitudinal axis. Colonic MMCs occurred every 151 ± 7 s in the CM and consisted of a repetitive discharge of cholinergic rapid oscillations in membrane potential (range: 1,20 mV) that were superimposed on a slow membrane depolarization (mean amplitude: 9.6 ± 0.5 mV; half-duration: 25.9 ± 0.7 s). During the rising (depolarizing) phase of each colonic MMC, cholinergic rapid oscillations occurred simultaneously in both CM cells, even when the two electrodes were separated by up to 15 mm along the longitudinal axis of the colon. Smaller amplitude oscillations (< 5 mV) showed poor temporal correlation between two CM cells, even at short electrode separation distances (i.e. < 1 mm in the longitudinal axis). When the two electrodes were separated by 20 mm, all cholinergic rapid oscillations and IJPs in the CM (regardless of amplitude) were rarely, if ever, coordinated in time during the colonic MMC. Cholinergic rapid oscillations were blocked by atropine (1 ,m) or tetrodotoxin (1 ,m). Slow waves were never recorded from any CM cells. DiI labelling showed that the maximum projection length of CM motor neurones and interneurones along the bowel was 2.8 mm and 13 mm, respectively. When recordings were made adjacent to either oral or anal cut ends of the colon, the inhibitory or excitatory phases of the colonic MMC were absent, respectively. In summary, during the colonic MMC, cholinergic rapid oscillations of similar amplitudes occur simultaneously in two CM cells separated by large distances (up to 15 mm). As this distance was found to be far greater than the projection length of any single CM motor neurone, we suggest that the generation of each discrete cholinergic rapid oscillation represents a discreet cholinergic excitatory junction potential (EJP) that involves the synaptic activation of many cholinergic motor neurones simultaneously, by synchronous firing in many myenteric interneurones. Our data also suggest that ascending excitatory and descending inhibitory nerve pathways interact and reinforce each other. [source] Influence of cell cycle on ecdysteroid receptor in CHO-K1 cellsARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY (ELECTRONIC), Issue 3 2009Katarzyna Betanska Abstract CHO-K1 cells are routinely used for characterization of ecdysone receptor (EcR) function, because these vertebrate cells are devoid of endogenous ecdysone receptor protein. Moreover, the endogenous expression of RXR, the vertebrate orthologue of Ultraspiracle (Usp), the most important heterodimerization partner, is neglectable. In contrast to insect cells, there is also no influence of moulting hormone on CHO-K1 cells on cell proliferation either in the absence or presence of transiently expressed EcR. In contrast to Usp, which is exclusively found in nuclei, EcR is heterogeneously distributed between cytoplasm and nuclei in non-synchronized cells. Synchronization of CHO-K1 cells by nocodazole revealed that the cell cycle influences receptor concentration with lowest amounts in late S-phase and G2/M phase and intracellular distribution of the receptor protein showing a minimum of receptors present in nuclei during S-phase. EcR, but not Usp reduces cyclin D1 expression and cyclin D1 concentration is impaired by cyclin D1. Coimmunoprecipitation studies reveal physical interaction of EcR and cyclin D1. © 2009 Wiley Periodicals, Inc. [source] Synchronization of the Fungal and the Plant Circadian Clock by LightCHEMBIOCHEM, Issue 16 2008László Kozma-Bognár Abstract Circadian clocks are endogenous time keeping devices that provide temporal control of physiology in accordance with predicted daily changes in the environment. Photoentrainment is the process that synchronizes circadian clocks-and thereby clock-controlled gene expression and physiology-to the environmental day/night cycles. Light is primarily detected by specialized photoreceptors that are coupled,directly or through other signaling components,to the rhythm-generating oscillator. As a consequence, the expression, the activity or the stability of oscillator components are altered, resulting in a change of phase and/or pace of the oscillator. In this review our present knowledge about light absorption/transduction and light-induced modifications of oscillator components in Neurospora crassa and Arabidopsis thaliana is summarized. These systems provide a basis for understanding the molecular mechanisms of entrainment in the fungal and plant circadian systems. [source] Spontaneous electrical and Ca2+ signals in the mouse renal pelvis that drive pyeloureteric peristalsisCLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 4 2010Richard J Lang Summary 1.,Peristalsis in the smooth muscle cell (SMC) wall of the pyeloureteric system is unique in physiology in that the primary pacemaker resides in a population of atypical SMCs situated near the border of the renal papilla. 2.,Atypical SMCs display high-frequency Ca2+ transients upon the spontaneous release of Ca2+ from inositol 1,4,5-trisphosphate (IP3)-dependent stores that trigger cation-selective spontaneous transient depolarizations (STDs). In the presence of nifedipine, these Ca2+ transients and STDs seldom propagate > 100 ,m. Synchronization of STDs in neighbouring atypical SMCs into an electrical signal that can trigger action potential discharge and contraction in the typical SMC layer involves a coupled oscillator mechanism dependent on Ca2+ entry through L-type voltage-operated Ca2+ channels. 3.,A population of spindle- or stellate-shaped cells, immunopositive for the tyrosine receptor kinase kit, is sparsely distributed throughout the pyeloureteric system. In addition, Ca2+ transients and action potentials of long duration occurring at low frequencies have been recorded in a population of fusiform cells, which we have termed interstitial cells of Cajal (ICC)-like cells. 4.,The electrical and Ca2+ signals in ICC-like cells are abolished upon blockade of Ca2+ release from either IP3 - or ryanodine-dependent Ca2+ stores. However, the spontaneous Ca2+ signals in atypical SMCs or ICC-like cells are little affected in W/W,v transgenic mice, which have extensive lesions of their intestinal ICC networks. 5.,In summary, we have developed a model of pyeloureteric pacemaking in which atypical SMCs are indeed the primary pacemakers, but the function of ICC-like cells has yet to be determined. [source] Theorizing Flow and Media Enjoyment as Cognitive Synchronization of Attentional and Reward NetworksCOMMUNICATION THEORY, Issue 4 2009René Weber This article reconceptualizes the psychological concept of "flow" as it pertains to media entertainment. Our goal is to advance flow theory in ways that highlight the necessity of reliable and valid operationalization. We posit flow as a discrete, energetically optimized, and gratifying experience resulting from a cognitive synchronization of specific attentional and reward networks under condition of balance between challenge and skill. We identify video-game play as a context in which flow is likely to occur, and where we can observe our neurophysiological conceptualization of flow using measurement techniques (functional magnetic resonance imaging [fMRI]) without disrupting the experiential state. After presenting preliminary evidence consistent with our synchronization theory of flow, we suggest ways to advance this research. [source] Visualizing massively multithreaded applications with ThreadScopeCONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 1 2010Kyle B. Wheeler Abstract As highly parallel multicore machines become commonplace, programs must exhibit more concurrency to exploit the available hardware. Many multithreaded programming models already encourage programmers to create hundreds or thousands of short-lived threads that interact in complex ways. Programmers need to be able to analyze, tune, and troubleshoot these large-scale multithreaded programs. To address this problem, we present ThreadScope: a tool for tracing, visualizing, and analyzing massively multithreaded programs. ThreadScope extracts the machine-independent program structure from execution trace data from a variety of tracing tools and displays it as a graph of dependent execution blocks and memory objects, enabling identification of synchronization and structural problems, even if they did not occur in the traced run. It also uses graph-based analysis to identify potential problems. We demonstrate the use of ThreadScope to view program structure, memory access patterns, and synchronization problems in three programming environments and seven applications. Copyright © 2009 John Wiley & Sons, Ltd. [source] Clock synchronization in Cell/B.E. tracesCONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 14 2009M. Biberstein Abstract Cell/B.E. is a heterogeneous multicore processor that was designed for the efficient execution of parallel and vectorizable applications with high computation and memory requirements. The transition to multicores introduces the challenge of providing tools that help programmers tune the code running on these architectures. Tracing tools, in particular, often help locate performance problems related to thread and process communication. A major impediment to implementing tracing on Cell is the absence of a common clock that can be accessed at low cost from all cores. The OS clock is costly to access from the auxiliary cores and the hardware timers cannot be simultaneously set on all the cores. In this paper, we describe an offline trace analysis algorithm that assigns wall-clock time to trace records based on their thread-local time stamps and event order. Our experiments on several Cell SDK workloads show that the indeterminism in assigning wall-clock time to events is low, on average 20,40 clock ticks (translating into 1.4,2.8,µs on the system used in our experiments). We also show how various practical problems, such as the imprecision of time measurement, can be overcome. Copyright © 2009 John Wiley & Sons, Ltd. [source] Structural testing criteria for message-passing parallel programsCONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 16 2008S. R. S. Souza Abstract Parallel programs present some features such as concurrency, communication and synchronization that make the test a challenging activity. Because of these characteristics, the direct application of traditional testing is not always possible and adequate testing criteria and tools are necessary. In this paper we investigate the challenges of validating message-passing parallel programs and present a set of specific testing criteria. We introduce a family of structural testing criteria based on a test model. The model captures control and data flow of the message-passing programs, by considering their sequential and parallel aspects. The criteria provide a coverage measure that can be used for evaluating the progress of the testing activity and also provide guidelines for the generation of test data. We also describe a tool, called ValiPar, which supports the application of the proposed testing criteria. Currently, ValiPar is configured for parallel virtual machine (PVM) and message-passing interface (MPI). Results of the application of the proposed criteria to MPI programs are also presented and analyzed. Copyright © 2008 John Wiley & Sons, Ltd. [source] Parallel tiled QR factorization for multicore architecturesCONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 13 2008Alfredo Buttari Abstract As multicore systems continue to gain ground in the high-performance computing world, linear algebra algorithms have to be reformulated or new algorithms have to be developed in order to take advantage of the architectural features on these new processors. Fine-grain parallelism becomes a major requirement and introduces the necessity of loose synchronization in the parallel execution of an operation. This paper presents an algorithm for the QR factorization where the operations can be represented as a sequence of small tasks that operate on square blocks of data (referred to as ,tiles'). These tasks can be dynamically scheduled for execution based on the dependencies among them and on the availability of computational resources. This may result in an out-of-order execution of the tasks that will completely hide the presence of intrinsically sequential tasks in the factorization. Performance comparisons are presented with the LAPACK algorithm for QR factorization where parallelism can be exploited only at the level of the BLAS operations and with vendor implementations. Copyright © 2008 John Wiley & Sons, Ltd. [source] The effect of uncontrolled concurrency on model checkingCONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 12 2008Donna M. Carter Abstract Correctness of concurrent software is usually checked by techniques such as peer code reviews or code walkthroughs and testing. These techniques, however, are subject to human error, and thus do not achieve an in-depth verification of correctness. Model-checking techniques, which can systematically identify and verify every state that a system can enter, are a powerful alternative method for verifying concurrent systems. However, the usefulness of model checking is limited because the number of states for concurrent models grows exponentially with the number of processes in the system. This is often referred to as the ,state explosion problem.' Some processes are a central part of the software operation and must be included in the model. However, we have found that some exponential complexity results due to uncontrolled concurrency introduced by the programmer rather than due to the intrinsic characteristics of the software being modeled. We have performed tests on multimedia synchronization to show the effect of abstraction as well as uncontrolled concurrency using the Promela/SPIN model checker. We begin with a sequential model not expected to have exponential complexity but that results in exponential complexity. In this paper, we provide alternative designs and explain how uncontrolled concurrency can be removed from the code. Copyright © 2007 John Wiley & Sons, Ltd. [source] A robust monitor construct with runtime fault detection,CONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 5 2006Jiannong Cao Abstract The monitor concept provides a structured and flexible high-level programming construct to control concurrent accesses to shared resources. It has been widely used in a concurrent programming environment for implicitly ensuring mutual exclusion and explicitly achieving process synchronization. This paper proposes an extension to the monitor construct for detecting runtime errors in monitor operations. Monitors are studied and classified according to their functional characteristics. A taxonomy of concurrency control faults over a monitor is then defined. The concepts of a monitor event sequence and a monitor state sequence provide a uniform approach to history information recording and fault detection. Rules for detecting various types of faults are defined. Based on these rules, fault-detection algorithms are developed. A prototypical implementation of the proposed monitor construct with runtime fault detection mechanisms has been developed in Java. We shall briefly report our experience with and the evaluation of the robust monitor prototype. Copyright © 2005 John Wiley & Sons, Ltd. [source] JAC: declarative Java concurrencyCONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 5 2006Max Haustein Abstract The Java programming language has a low-level concurrency model which is hard to use and does not blend well with inheritance. JAC is an extension of Java that introduces a higher level of concurrency, hiding threads and separating thread synchronization from application logic in a declarative fashion. The emphasis is on limiting the differences between sequential and concurrent code, thus furthering code reuse, and on avoiding inheritance anomalies. This is achieved by taking a middle road between concurrent code on the one hand and complete separation of sequential application logic from concurrency mechanisms on the other. An extensive comparison with related approaches is given for motivating our design decisions. Copyright © 2005 John Wiley & Sons, Ltd. [source] Simulation of resource synchronization in a dynamic real-time distributed computing environmentCONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 14 2004Chen Zhang Abstract Today, more and more distributed computer applications are being modeled and constructed using real-time principles and concepts. In 1989, the Object Management Group (OMG) formed a Real-Time Special Interest Group (RT SIG) with the goal of extending the Common Object Request Broker Architecture (CORBA) standard to include real-time specifications. This group's most recent efforts have focused on the requirements of dynamic distributed real-time systems. One open problem in this area is resource access synchronization for tasks employing dynamic priority scheduling. This paper presents two resource synchronization protocols that the authors have developed which meet the requirements of dynamic distributed real-time systems as specified by Dynamic Scheduling Real-Time CORBA (DSRT CORBA). The proposed protocols can be applied to both Earliest Deadline First (EDF) and Least Laxity First (LLF) dynamic scheduling algorithms, allow distributed nested critical sections, and avoid unnecessary runtime overhead. In order to evaluate the performance of the proposed protocols, we analyzed each protocol's schedulability. Since the schedulability of the system is affected by numerous system configuration parameters, we have designed simulation experiments to isolate and illustrate the impact of each individual system parameter. Simulation experiments show the proposed protocols have better performance than one would realize by applying a schema that utilizes dynamic priority ceiling update. Copyright © 2004 John Wiley & Sons, Ltd. [source] An order-based algorithm for implementing multiparty synchronizationCONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 12 2004José A. Pérez Abstract Multiparty interactions are a powerful mechanism for coordinating several entities that need to cooperate in order to achieve a common goal. In this paper, we present an algorithm for implementing them that improves on previous results in that it does not require the whole set of entities or interactions to be known at compile- or run-time, and it can deal with both terminating and non-terminating systems. We also present a comprehensive simulation analysis that shows how sensitive to changes our algorithm is, and compare the results with well-known proposals by other authors. This study proves that our algorithm still performs comparably to other proposals in which the set of entities and interactions is known beforehand, but outperforms them in some situations that are clearly identified. In addition, these results prove that our algorithm can be combined with a technique called synchrony loosening without having an effect on efficiency. Copyright © 2004 John Wiley & Sons, Ltd. [source] Effect of Wax Epilation Before Hair Removal With a Long-Pulsed Alexandrite Laser: A Pilot StudyDERMATOLOGIC SURGERY, Issue 2 2003Michael S. Lehrer MD Background. Recent reports indicate that laser hair removal is most effective on anagen hairs. However, no published trials have examined laser epilation after hair cycle synchronization. Objective. To evaluate the potential for enhanced laser hair removal after the induction of telogen hairs into anagen by wax epilation. Methods. We identified four 2.5-cm square areas with equivalent hair length and density on the backs of 13 dark-haired white men. To induce typically telogen hairs into anagen, two areas on each patient were wax epilated. Two weeks later, one waxed area and one unwaxed area were treated with a long-pulsed alexandrite laser. One month after laser treatment, a subjective comparison was made based on hair density, length, and thickness. Results. In 12 of 13 patients, lasered areas that had been pretreated with wax epilation were clearer of hair as compared with areas that had been pretreated by shaving (P=0.0034). No significant difference was noted between waxed and unwaxed control areas that had not been laser treated (P=1.0). Conclusion. Wax epilation 2 weeks before laser hair removal improves cosmetic outcomes at 1 month. This effect may be secondary to the recruitment and heightened sensitivity of early anagen hairs. [source] Modeling the model organism Dictyostelium discoideumDEVELOPMENT GROWTH & DIFFERENTIATION, Issue 6 2000Seido Nagano The cellular slime mold Dictyostelium discoideum is a fascinating organism, not only for biologists, but also for physicists. Since the Belousov,Zhabotinskii reaction pattern, a well-known non-linear phenomenon in chemistry, was observed during aggregation of Dictyostelium amoebae, Dictyostelium has been one of the major subjects of non-linear dynamics studies. Macroscopic theory, such as continuous cell density approximation, has been a common approach to studying pattern formation since the pioneering work of Turing. Recently, promising microscopic approaches, such as the cellular dynamics method, have emerged. They have shown that Dictyostelium is useful as a model system in biology. The synchronization mechanism of oscillatory production of cyclic adenosine 3,,5,-monophosphate in Dictyostelium is discussed in detail to show how it is a universal feature that can explain synchronization in other organisms. [source] Vibration signals from the FT joint can induce phase transitions in both directions in motoneuron pools of the stick insect walking systemDEVELOPMENTAL NEUROBIOLOGY, Issue 2 2003Ulrich Bässler Abstract The influence of vibratory signals from the femoral chordotonal organ fCO on the activities of muscles and motoneurons in the three main leg joints of the stick insect leg, i.e., the thoraco,coxal (TC) joint, the coxa,trochanteral (CT) joint, and the femur,tibia (FT) joint, was investigated when the animal was in the active behavioral state. Vibration stimuli induced a switch in motor activity (phase transition), for example, in the FT joint motor activity switched from flexor tibiae to extensor tibiae or vice versa. Similarly, fCO vibration induced phase transitions in both directions between the motoneuron pools of the TC joint and the CT joint. There was no correlation between the directions of phase transition in different joints. Vibration stimuli presented during simultaneous fCO elongation terminated the reflex reversal motor pattern in the FT joint prematurely by activating extensor and inactivating flexor tibiae motoneurons. In legs with freely moving tibia, fCO vibration promoted phase transitions in tibial movement. Furthermore, ground vibration promoted stance,swing transitions as long as the leg was not close to its anterior extreme position during stepping. Our results provide evidence that, in the active behavioral state of the stick insect, vibration signals can access the rhythm generating or bistable networks of the three main leg joints and can promote phase transitions in motor activity in both directions. The results substantiate earlier findings on the modular structure of the single-leg walking pattern generator and indicate a new mechanism of how sensory influence can contribute to the synchronization of phase transitions in adjacent leg joints independent of the walking direction. © 2003 Wiley Periodicals, Inc. J Neurobiol 56: 125,138, 2003 [source] | |||||||||||||||||||||||||||||||||||||