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Asynchrony
Kinds of Asynchrony Selected AbstractsVentricular Mechanical Asynchrony in Patients with Different Degrees of Systolic Dysfunction: Results from AVE Registry by the Italian Society of Cardiovascular Echography (SIEC)ECHOCARDIOGRAPHY, Issue 2 2010Scipione Carerj M.D. Objective: The aim of the study was to compare the prevalence of interventricular and intraventricular asynchrony in patients with different degrees of left ventricular (LV) dysfunction. Methods: We enrolled 182 patients (male 79%, mean age 64 ± 11 years) with LV ejection fraction (EF) < 50% and identified two groups: Group A (n = 79) with mild-to-moderate LV dysfunction (EF between 36% and 49%) and Group B (n = 103) with severe dysfunction (EF , 35%). An echocardiogram was performed in all patients and a delay longer than 40 msec in the time difference between the aortic and pulmonary preejection intervals was considered as an index of interventricular asynchrony. The electromechanical delays were assessed by pulsed tissue Doppler technique. A time difference between the earliest and the latest segment greater than 40 msec was considered the cutoff for intraventricular asynchrony. The sum of asynchrony was calculated by adding to the LV intraventricular delay the delay between the lateral basal right ventricular segment and the most delayed LV basal segment. Results: The prevalence of interventricular asynchrony was lower among Group A patients (19.8% vs. 37.9%; P = 0.007) while the prevalence of intraventricular asynchrony did not differ between groups (32.9% vs. 44% in Group A and Group B respectively; P = 0.18). The sum of asynchrony (cutoff >102 msec) did not differ between groups either (29.9% vs. 35.9%; P = 0.39). Conclusions: The prevalence of intraventricular asynchrony is independent of the LV systolic dysfunction severity. This could indicate the potential role of cardiac resynchronization therapy in patients with mild-moderate systolic dysfunction. (ECHOCARDIOGRAPHY 2010;27:110-116) [source] Asynchrony of the early maturation of white matter bundles in healthy infants: Quantitative landmarks revealed noninvasively by diffusion tensor imagingHUMAN BRAIN MAPPING, Issue 1 2008Jessica Dubois Abstract Normal cognitive development in infants follows a well-known temporal sequence, which is assumed to be correlated with the structural maturation of underlying functional networks. Postmortem studies and, more recently, structural MR imaging studies have described qualitatively the heterogeneous spatiotemporal progression of white matter myelination. However, in vivo quantification of the maturation phases of fiber bundles is still lacking. We used noninvasive diffusion tensor MR imaging and tractography in twenty-three 1,4-month-old healthy infants to quantify the early maturation of the main cerebral fascicles. A specific maturation model, based on the respective roles of different maturational processes on the diffusion phenomena, was designed to highlight asynchronous maturation across bundles by evaluating the time-course of mean diffusivity and anisotropy changes over the considered developmental period. Using an original approach, a progression of maturation in four relative stages was determined in each tract by estimating the maturation state and speed, from the diffusion indices over the infants group compared with an adults group on one hand, and in each tract compared with the average over bundles on the other hand. Results were coherent with, and extended previous findings in 8 of 11 bundles, showing the anterior limb of the internal capsule and cingulum as the most immature, followed by the optic radiations, arcuate and inferior longitudinal fascicles, then the spinothalamic tract and fornix, and finally the corticospinal tract as the most mature bundle. Thus, this approach provides new quantitative landmarks for further noninvasive research on brain-behavior relationships during normal and abnormal development. Hum Brain Mapp, 2008. © 2007 Wiley-Liss, Inc. [source] The Temporal Asynchrony of Planktonic Cladocerans Population at Different Environments of the Upper Paraná River FloodplainINTERNATIONAL REVIEW OF HYDROBIOLOGY, Issue 6 2008Erica Mayumi Takahashi Abstract The aim of this study was to investigate the existence of synchronic fluctuation patterns in cladoceran populations of the Upper Paraná River floodplain. The following hypothesis were tested: (i) the populations of a given species present the same fluctuation pattern in abundance for different environments and (ii) synchrony is higher when we consider subsets of neighboring environments or those belonging to the same category (e.g., lagoons, rivers). Samplings were performed every three months from February 2000 to November 2002 at 11 sites. To evaluate spatial synchrony, the intraclass correlation coefficient was used. The results showed no significant correlation for the most abundant species, meaning that fluctuation patterns of planktonic cladocerans were asynchronous. Asynchrony indicated that the influence of floods and regional climatic factors was not strong enough to synchronize the populations, suggesting that local factors were more important than regional effects in determining zooplankton abundance patterns. The implications of these results are that the observations from a single environment cannot be extrapolated to other environments in a manner that would allow its use as a sentinel site. This means that a monitoring program for floodplain systems, or at least for the Paraná River floodplain, has to comprise greater spatial extents. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Morphological characterization of the testicular cells and seminiferous epithelium cycle in six species of Neotropical batsJOURNAL OF MORPHOLOGY, Issue 8 2009Mateus R. Beguelini Abstract We know little about the process of spermatogenesis in bats, a great and diverse clade of mammals that presents different reproductive strategies. In the present study, spermatogenesis in six species of Neotropical bats was investigated by light microscopy. On the basis of chromatin condensation, nuclear morphology, relative position to the basal membrane and formation of the flagellum, three types of spermatogonia were recognized: dark type A (Ad), pale type A (Ap), and type B; the development of spermatids was divided into seven steps. With the exception of Myotis nigricans, the seminiferous epithelium cycle of the other five species studied was similar to those of other mammals, showing gradual stages by the tubular morphology method. Asynchrony was observed in the seminiferous epithelium cycle of M. nigricans, shown by overlapping stages and undefined cycles. The frequencies found in the three phases of the cycle were variable with the greatest frequency occurring in the postmeiotic phase (>50%) and the least in the meiotic phase (<10%). The similarities observed in the five species of Phyllostomidae appeared to be related to their phylogenetic relationship and shorter divergence times, whereas the differences in M. nigricans appeared to be related to its greater phylogenetic distance because the Vespertilionidae family diverged earlier. J. Morphol., 2009. © 2009 Wiley-Liss, Inc. [source] Relationship between group sunspot numbers and Wolf sunspot numbersASTRONOMISCHE NACHRICHTEN, Issue 7 2010K.J. Li Abstract Continuous wavelet transform and cross-wavelet transform have been used to investigate the phase periodicity and synchrony of the monthly mean Wolf (Rz) and group (Rg) sunspot numbers during the period of June 1795 to December 1995. The Schwabe cycle is the only one common period in Rg and Rz, but it is not well-defined in case of cycles 5,7 of Rg and in case of cycles 5 and 6 of Rz. In fact, the Schwabe period is slightly different in Rg and Rz before cycle 12, but from cycle 12 onwards it is almost the same for the two time series. Asynchrony of the two time series is more obviously seen in cycles 5 and 6 than in the following cycles, and usually more obviously seen around the maximum time of a cycle than during the rest of the cycle. Rg is found to fit Rz better in both amplitudes and peak epoch during the minimum time time of a solar cycle than during the maximum time of the cycle, which should be caused by their different definition, and around the maximum time of a cycle, Rg is usually less than Rz. Asynchrony of Rg and Rz should somewhat agree with different sunspot cycle characteristics exhibited by themselves (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Fast, but Error-Prone, Responses During Acute Alcohol Intoxication: Effects of Stimulus-Response Mapping ComplexityALCOHOLISM, Issue 4 2004Tom A. Schweizer Abstract: Background: Although moderate doses of alcohol can impair performance on tasks that require information processing, little is known about the locus of the alcohol effects within the processing stream. This study used a psychological refractory period paradigm to investigate the effect of alcohol on the central, cognitive stage of information processing when task complexity is manipulated by altering stimulus-response compatibility. Methods: Thirty-four healthy male social drinkers were assigned to one of two groups (n= 17) that performed two tasks. Each trial consisted of a task 1 stimulus (tone) followed by a task 2 stimulus (letter) that was presented after one of four stimulus onset asynchronies (50, 200, 500, or 1100 msec). A baseline test of performance was obtained before the groups received a beverage containing either 0.0 g/kg (placebo) or 0.65 g/kg alcohol. Both groups were retested when blood alcohol concentration (BAC) was increasing and was decreasing. Results: The alcohol group made significantly more errors in task 1 compared with their drug-free baseline measure during the ascending phase of the BAC curve, and error rates increased to a greater extent for the more complex arbitrary stimulus-response mapping condition. Moreover, this increase in errors continued unabated during the descending phase of the BAC curve. Increasing BACs also slowed performance (longer reaction time), but unlike errors, reaction time returned to drug-free baseline levels when BAC was decreasing. Conclusions: The results provide evidence that an acute dose of alcohol can impair one aspect of the central, cognitive stages of information processing. The possibility that errors in information processing remain during decreasing BACs even after processing speed has returned to drug-free levels has important practical implications relating to the detrimental consequences of acute alcohol intoxication. [source] Backward masking and visual mismatch negativity: Electrophysiological evidence for memory-based detection of deviant stimuliPSYCHOPHYSIOLOGY, Issue 4 2007István Czigler Abstract Sequences composed of two different colored checkerboard patterns (standard and deviant) were presented to adults. Each pattern was followed by a mask with stimulus onset asynchronies (SOAs) varying between 14 and 174 ms. ERPs were recorded to the deviant and standard stimuli while the participants detected changes of a cross, which was continuously present at the center of the screen. In further experiments, the participants performed a Go-NoGo task detecting the deviant checkerboards. Deviant stimuli elicited an occipital negative component with 124,132 ms mean latency (the visual mismatch negativity, vMMN) at test (standard or deviant)-to-mask SOAs longer than 27 ms. No vMMN amplitude increase was observed beyond 40 ms test-to-mask intervals, whereas detection of deviant checkerboard patterns improved up to 174-ms SOA. Therefore the processes underlying vMMN elicitation cannot fully explain the overt detection of visual deviance. [source] The relationship between prepulse detection and prepulse inhibition of the acoustic startle reflexPSYCHOPHYSIOLOGY, Issue 3 2001Peggy Postma Prepulse inhibition (PPI) of the startle reflex is defined as the attenuation of the startle response to a startling stimulus (pulse), when such a stimulus is briefly preceded by a stimulus of subthreshold intensity (prepulse). PPI is thought to be neither learned nor due to conscious response inhibition, as it occurs at stimulus onset asynchronies (SOAs) too short to enable the activation of a volitional response. The present study explored the latter of these assertions by investigating (a) the degree to which human subjects are able to detect prepulses at SOAs of 30, 60 and 120 ms, and (b) whether such detection is related to inhibition. Startle eyeblink reflex and detection were measured in 39 participants subjected to an acoustic startle paradigm. Results revealed a significant trend in prepulse detection according to SOA, with highest detection rates at the 120-ms SOA (75%). However, trials on which detection occurred did not differ from trials without detection on measures of startle inhibition. This suggests that PPI is independent of awareness of the prepulse. [source] Orienting of visual attention among persons with autism spectrum disorders: reading versus responding to symbolic cuesTHE JOURNAL OF CHILD PSYCHOLOGY AND PSYCHIATRY AND ALLIED DISCIPLINES, Issue 7 2009Oriane Landry Background:, Are persons with autism spectrum disorders (ASD) slower than typically developing individuals to read the meaning of a symbolic cue in a visual orienting paradigm? Methods:, Participants with ASD (n = 18) and performance mental age (PMA) matched typically developing children (n = 16) completed two endogenous orienting conditions in which the cue exposure time and response preparation time were manipulated within a consistent series of cue-target stimulus onset asynchronies (SOAs). Results:, Participants with ASD displayed facilitation effects at all SOAs, whereas typically developing children displayed facilitation effects only at shorter SOAs. The magnitude of the facilitation effect was greater for the group with ASD at 400ms SOA. Both groups showed similar effects of condition, with similar patterns of facilitation in both conditions. Conclusion:, Persons with ASD were not slower to read the symbolic cue, as the effect was elicited by brief cues within longer SOAs before target onset. The participants with ASD were also less efficient in using the predictability of the cues to guide responding. The difficulties of participants with ASD on endogenous orienting occur at the response selection level, not the perceptual level. [source] An architecture for exploiting multi-core processors to parallelize network intrusion preventionCONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 10 2009Robin Sommer Abstract It is becoming increasingly difficult to implement effective systems for preventing network attacks, due to the combination of the rising sophistication of attacks requiring more complex analyses to detect; the relentless growth in the volume of network traffic that we must analyze; and, critically, the failure in recent years for uniprocessor performance to sustain the exponential gains that for so many years CPUs have enjoyed. For commodity hardware, tomorrow's performance gains will instead come from multi-core architectures in which a whole set of CPUs executes concurrently. Taking advantage of the full power of multi-core processors for network intrusion prevention requires an in-depth approach. In this work we frame an architecture customized for parallel execution of network attack analysis. At the lowest layer of the architecture is an ,Active Network Interface', a custom device based on an inexpensive FPGA platform. The analysis itself is structured as an event-based system, which allows us to find many opportunities for concurrent execution, since events introduce a natural asynchrony into the analysis while still maintaining good cache locality. A preliminary evaluation demonstrates the potential of this architecture. Copyright © 2009 John Wiley & Sons, Ltd. [source] Time reproduction in finger tapping tasks by children with attention-deficit hyperactivity disorder and/or dyslexiaDYSLEXIA, Issue 4 2004Margaret C. Tiffin-Richards Abstract Aim: Deficits in timing and sequencing behaviour in children with dyslexia and with attention-deficit hyperactivity disorder have already been identified. However many studies have not controlled for comorbidity between dyslexia and ADHD. This study investigated timing performance of children with either dyslexia or ADHD, or ADHD + dyslexia or unaffected children using a finger-tapping paradigm. Method: Four groups of children (ADHD × Dyslexia) with a total of 68 children were compared using a four factorial design with two between-subject factors (ADHD (yes/no), dyslexia (yes/no)) and two within-subject factors, inter-stimulus interval (263, 500, 625, 750, 875 and 1000 ms) and tapping condition (free tapping, synchronous tapping, and unpaced tapping). In addition the complexity of rhythm reproduction pattern (unpaced tapping) was varied (simple/complex). Results: No significant differences were found either in the ability of the ADHD or the dyslexia groups to sustain a self-chosen free tapping rate or to generate a stable inter-response interval either by synchronising to a signal or in reproducing a given interval without the previous pacing signal. Response averages showed the expected asynchrony and variability. In rhythm pattern reproduction the groups did not differ significantly in their ability to reproduce rhythms. However, a significant two way interaction effect between dyslexia and complexity was apparent indicating that the difference in levels of performance for simple versus complex rhythms was more pronounced for dyslexia than for the two other groups. Conclusion: The results indicate that motor timing ability in the millisecond range below 1000 ms in children with ADHD and/or dyslexia is intact. The performance of the comorbid group was revealed to be similar to the performance of the single disorder groups, but both the dyslexic groups were relatively worse than either the ADHD-only or the unimpaired group at reproducing complex versus simple rhythms. Copyright © 2004 John Wiley & Sons, Ltd. [source] Ventricular Asynchrony of Time-to-Peak Systolic Velocity in Structurally Normal Heart by Tissue Doppler ImagingECHOCARDIOGRAPHY, Issue 7 2010Hakimeh Sadeghian M.D. Background: Echocardiographic measurements of time-to-peak systolic velocities (Ts) are helpful for assessing the degree of cardiac asynchrony. We assessed the degree of ventricular asynchrony in structurally normal heart according to Ts by tissue Doppler imaging. Methods: We performed conventional echocardiography and tissue velocity imaging for 65 healthy adult volunteers to measure the Ts of 12 left ventricular segments in the mid and basal levels delay of Ts and standard deviation (SD) of Ts in all and basal segments. Six frequently used markers of dyssynchrony were measured and were also compared between men and women. Data are presented as median (25th and 75th percentile). Results: Septal-lateral and anteroseptal-posterior delays were 50 (20, 90) and 20 (0, 55) ms. The delay between the longest and the shortest Ts in basal and all segments were 100 (80, 120) and 110 (83, 128) ms, respectively. SD of Ts was 39 (24, 52) ms for basal and 41 (28, 51) ms for all segments. Overall, 76.9% of cases had at least one marker of dyssynchrony. Frequencies of dyssynchrony markers were almost significantly higher in women compared to men. The most frequently observed dyssynchrony marker was SD of Ts of all segments (70.8%) and the lowest was anteroseptal-posterior delay (21.5%). Conclusions: Normal population almost had dyssynchrony by previously described markers and many of these markers were more frequent in women. Conducting more studies on normal population by other tissue Doppler modalities may give better description of cardiac synchronicity. (Echocardiography 2010;27:823-830) [source] Ventricular Mechanical Asynchrony in Patients with Different Degrees of Systolic Dysfunction: Results from AVE Registry by the Italian Society of Cardiovascular Echography (SIEC)ECHOCARDIOGRAPHY, Issue 2 2010Scipione Carerj M.D. Objective: The aim of the study was to compare the prevalence of interventricular and intraventricular asynchrony in patients with different degrees of left ventricular (LV) dysfunction. Methods: We enrolled 182 patients (male 79%, mean age 64 ± 11 years) with LV ejection fraction (EF) < 50% and identified two groups: Group A (n = 79) with mild-to-moderate LV dysfunction (EF between 36% and 49%) and Group B (n = 103) with severe dysfunction (EF , 35%). An echocardiogram was performed in all patients and a delay longer than 40 msec in the time difference between the aortic and pulmonary preejection intervals was considered as an index of interventricular asynchrony. The electromechanical delays were assessed by pulsed tissue Doppler technique. A time difference between the earliest and the latest segment greater than 40 msec was considered the cutoff for intraventricular asynchrony. The sum of asynchrony was calculated by adding to the LV intraventricular delay the delay between the lateral basal right ventricular segment and the most delayed LV basal segment. Results: The prevalence of interventricular asynchrony was lower among Group A patients (19.8% vs. 37.9%; P = 0.007) while the prevalence of intraventricular asynchrony did not differ between groups (32.9% vs. 44% in Group A and Group B respectively; P = 0.18). The sum of asynchrony (cutoff >102 msec) did not differ between groups either (29.9% vs. 35.9%; P = 0.39). Conclusions: The prevalence of intraventricular asynchrony is independent of the LV systolic dysfunction severity. This could indicate the potential role of cardiac resynchronization therapy in patients with mild-moderate systolic dysfunction. (ECHOCARDIOGRAPHY 2010;27:110-116) [source] Climate change and phenological asynchronyECOLOGICAL ENTOMOLOGY, Issue 3 2003A. F. G. Dixon No abstract is available for this article. [source] Effects of the estrogen agonist 17,-estradiol and antagonist tamoxifen in a partial life-cycle assay with zebrafish (Danio rerio)ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 1 2007Leo T. M. van der Ven Abstract A partial life-cycle assay (PLC) with zebrafish (Danio rerio) was conducted to identify endocrine-disrupting effects of 17,-estradiol (E2) and tamoxifen (TMX) as reference for estrogen agonist and antagonist activity. Adult zebrafish were exposed for 21 d and offspring for another 42 d, allowing differentiation of gonads in control animals. The assessed end points included reproductive variables (egg production, fertilization, and hatching), gonad differentiation of juveniles, histopathology, and vitellogenin (VTG) expression. With E2, the most sensitive end points were feminization of offspring (at 0.1 nM) and increased VTG production in males (at 0.32 nM). At 1 nM, decreased F1 survival, increased F1 body length and weight, VTG-related edema and kidney lesions, and inhibited spermatogenesis were observed. Oocyte atresia occurred at even higher concentrations. Exposure to TMX resulted in specific effects at an intermediate test concentration (87 nM), including oocyte atresia with granulosa cell transformation and disturbed spermatogenesis (asynchrony within cysts). In F1, decreased hatching, survival, and body weight and length as well as decreased feminization were observed. Decreased vitellogenesis and egg production in females and clustering of Leydig cells in males occurred at higher concentrations. Toxicological profiles of estrogen agonists and antagonists are complex and specific; a valid and refined characterization of endocrine activity of field samples therefore can be obtained only by using a varied set of end points, including histology, as applied in the presented PLC. Evaluation of only a single end point can easily produce under- or overestimation of the actual hazard. [source] Ontogenetic selection on hatchery salmon in the wild: natural selection on artificial phenotypesEVOLUTIONARY APPLICATIONS (ELECTRONIC), Issue 4 2010Michael M. Bailey Abstract Captive rearing often alters the phenotypes of organisms that are destined for release into the wild. Natural selection on these unnatural phenotypes could have important consequences for the utility of captive rearing as a restoration approach. We show that normal hatchery practices significantly advance the development of endangered Atlantic salmon (Salmo salar) fry by 30+ days. As a result, hatchery fry might be expected to face strong natural selection resulting from their developmental asynchrony. We investigated patterns of ontogenetic selection acting on hatchery produced salmon fry by experimentally manipulating fry development stage at stocking. Contrary to simple predictions, we found evidence for strong stabilizing selection on the ontogeny of unfed hatchery fry, with weaker evidence for positive directional selection on the ontogeny of fed fry. These selection patterns suggest a seasonally independent tradeoff between abiotic or biotic selection favoring advanced development and physiological selection linked to risk of starvation in unfed fry. We show, through a heuristic exercise, how such selection on ontogeny may exacerbate problems in restoration efforts by impairing fry productivity and reducing effective population sizes by 13,81%. [source] Cross-sample entropy statistic as a measure of complexity and regularity of renal sympathetic nerve activity in the ratEXPERIMENTAL PHYSIOLOGY, Issue 4 2007Tao Zhang In this study, we employed both power spectral analysis and cross-sample entropy measurement to assess the relationship between two time series, arterial blood pressure (ABP) and renal sympathetic nerve activity (RSNA), during a mild haemorrhage in anaesthetized Wistar rats. Removal of 1 ml of venous blood decreased BP (by 7.1 ± 0.7 mmHg) and increased RSNA (by 25.9 ± 2.4%). During these changes, the power in the RSNA signal at heart rate frequency was reduced but coherence between the spectra at heart rate frequency in RSNA and ABP remained unchanged. Cross-sample entropy was significantly increased (by 10%) by haemorrhage, revealing that there was greater asynchrony between ABP and the RSNA time series. Intrathecal administration of the glutamate receptor antagonist kynurenic acid (2 mm) almost halved (P < 0.01) the reflex increase in RSNA. Also during kynurenic acid block, haemorrhage failed to change total power, power at heart rate frequency, coherence at heart rate frequency, or the cross-sample entropy measurements. We conclude that the increase in asynchrony between ABP and RSNA during the reflex increase in RSNA was a consequence of an increase in synaptic input to the spinal renal neurones. The data show that the cross-sample entropy calculations can characterize the non-linearities of neural mechanisms underlying cardiovascular control and have a potential to reveal how some aspects of homeostatic regulation of kidney function is achieved by the autonomic nervous system. [source] A metapopulation perspective for salmon and other anadromous fishFISH AND FISHERIES, Issue 4 2007Nicolas Schtickzelle Abstract Salmonids are an important component of biodiversity, culture and economy in several regions, particularly the North Pacific Rim. Given this importance, they have been intensively studied for about a century, and the pioneering scientists recognized the critical link between population structure and conservation. Spatial structure is indeed of prime importance for salmon conservation and management. At first glance, the essence of the metapopulation concept, i.e. a population of populations, widely used on other organisms like butterflies, seems to be particularly relevant to salmon, and more generally to anadromous fish. Nevertheless, the concept is rarely used, and barely tested. Here, we present a metapopulation perspective for anadromous fish, assessing in terms of processes rather than of patterns the set of necessary conditions for metapopulation dynamics to exist. Salmon, and particularly sockeye salmon in Alaska, are used as an illustrative case study. A review of life history traits indicates that the three basic conditions are likely to be fulfilled by anadromous salmon: (i) the spawning habitat is discrete and populations are spatially separated by unsuitable habitat; (ii) some asynchrony is present in the dynamics of more or less distant populations and (iii) dispersal links populations because some salmon stray from their natal population. The implications of some peculiarities of salmon life history traits, unusual in classical metapopulations, are also discussed. Deeper understanding of the population structure of anadromous fish will be advanced by future studies on specific topics: (i) criteria must be defined for the delineation of suitable habitats that are based on features of the biotope and not on the presence of fish; (ii) the collection of long-term data and the development of improved methods to determine age structure are essential for correctly estimating levels of asynchrony between populations and (iii) several key aspects of dispersal are still poorly understood and need to be examined in detail: the spatial and temporal scales of dispersal movements, the origin and destination populations instead of simple straying rates, and the relative reproductive success of immigrants and residents. [source] Offspring performance and the adaptive benefits of prolonged pregnancy: experimental tests in a viviparous lizardFUNCTIONAL ECOLOGY, Issue 4 2009Geoffrey M While Summary 1Offspring locomotor performance has been shown to influence fitness related traits in a wide range of taxa. One potential mechanism by which viviparous animals can increase the performance (e.g. sprint speed) of their offspring is by prolonging pregnancy (beyond that required for complete development). However, to date studies examining this potentially important maternal effect have been largely descriptive. 2The skink Egernia whitii is an ideal candidate species to examine the consequences of delayed parturition on the performance of offspring as it routinely gives birth asynchronously despite synchronous offspring development. 3Using correlative data from a natural population and experimental manipulations of birthing asynchrony, we tested the prediction that, within litters, last born offspring have a better locomotor performance than first born offspring. 4We show that prolonged pregnancy does significantly influence average offspring locomotor performance; however, contrary to predictions, the direction of this effect is dependent on gestation length and thus offspring date of birth. Last born offspring had significantly poorer performance than first born offspring in litters early in the season with this pattern reversed late in the season. 5These results do not support the hypothesis that prolonged retention of fully formed offspring consistently increases offspring performance; however, they may help us understand the asymmetries in offspring competitive ability generated by birthing asynchrony. [source] LATE-GLACIAL GLACIER EVENTS IN SOUTHERNMOST SOUTH AMERICA: A BLEND OF ,NORTHERN' AND 'SOUTHERN' HEMISPHERIC CLIMATIC SIGNALS?GEOGRAFISKA ANNALER SERIES A: PHYSICAL GEOGRAPHY, Issue 2 2005D.E. SUGDEN ABSTRACT. This paper examines new geomorphological, chronological and modelling data on glacier fluctuations in southernmost South America in latitudes 46,55°S during the last glacial,interglacial transition. Establishing leads and lags between the northern and southern hemispheres and between southern mid-latitudes and Antarctica is key to an appreciation of the mechanisms and resilience of global climate. This is particularly important in the southern hemisphere where there is a paucity of empirical data. The overall structure of the last glacial cycle in Patagonia has a northern hemisphere signal. Glaciers reached or approached their Last Glacial Maxima on two or more occasions at 25,23 ka (calendar) and there was a third less extensive advance at 17.5 ka. Deglaciation occurred in two steps at 17.5 ka and at 11.4 ka. This structure is the same as that recognized in the northern hemisphere and taking place in spite of glacier advances occurring at a time of high southern hemisphere summer insolation and deglaciation at a time of decreasing summer insolation. The implication is that at orbital time scales the,northern' signal dominates any southern hemisphere signal. During deglaciation, at a millennial scale, the glacier fluctuations mirror an antiphase 'southern' climatic signal as revealed in Antarctic ice cores. There is a glacier advance coincident with the Antarctic Cold Reversal at 15.3,12.2 ka. Furthermore, deglaciation begins in the middle of the Younger Dryas. The implication is that, during the last glacial,interglacial transition, southernmost South America was under the influence of sea surface temperatures, sea ice and southern westerlies responding to conditions in the 'southern' Antarctic domain. Such asynchrony may reflect a situation whereby, during deglaciation, the world is more sensitized to fluctuations in the oceanic thermohaline circulation, perhaps related to the bipolar seesaw, than at orbital timescales. [source] Influences of species, latitudes and methodologies on estimates of phenological response to global warmingGLOBAL CHANGE BIOLOGY, Issue 9 2007CAMILLE PARMESANArticle first published online: 14 AUG 200 Abstract New analyses are presented addressing the global impacts of recent climate change on phenology of plant and animal species. A meta-analysis spanning 203 species was conducted on published datasets from the northern hemisphere. Phenological response was examined with respect to two factors: distribution of species across latitudes and taxonomic affiliation or functional grouping of target species. Amphibians had a significantly stronger shift toward earlier breeding than all other taxonomic/functional groups, advancing more than twice as fast as trees, birds and butterflies. In turn, butterfly emergence or migratory arrival showed three times stronger advancement than the first flowering of herbs, perhaps portending increasing asynchrony in insect,plant interactions. Response was significantly stronger at higher latitudes where warming has been stronger, but latitude explained < 4% of the variation. Despite expectation, latitude was not yet an important predictor of climate change impacts on phenology. The only two previously published estimates of the magnitude of global response are quite different: 2.3 and 5.1 days decade,1 advancement. The scientific community has assumed this difference to be real and has attempted to explain it in terms of biologically relevant phenomena: specifically, differences in distribution of data across latitudes, taxa or time periods. Here, these and other possibilities are explored. All analyses indicate that the difference in estimated response is primarily due to differences between the studies in criteria for incorporating data. It is a clear and automatic consequence of the exclusion by one study of data on ,stable' (nonresponsive) species. Once this is accounted for, the two studies support each other, generating similar conclusions despite analyzing substantially nonoverlapping datasets. Analyses here on a new expanded dataset estimate an overall spring advancement across the northern hemisphere of 2.8 days decade,1. This is the first quantitative analysis showing that data-sampling methodologies significantly impact global (synthetic) estimates of magnitude of global warming response. [source] Differences in egg size, shell thickness, pore density, pore diameter and water vapour conductance between first and second eggs of Snares Penguins Eudyptes robustus and their influence on hatching asynchronyIBIS, Issue 2 2005MELANIE MASSARO Brood reduction in birds is frequently induced by hatching asynchrony. Crested penguins (genus Eudyptes) are obligate brood reducers, but in contrast to most other birds, first-laid eggs are considerably smaller in size than second-laid eggs; furthermore, first-laid eggs hatch after their siblings. The mechanisms underlying this reversal in size and hatching order remain unclear. In this study, we tested whether the second-laid eggs of Snares Penguins Eudyptes robustus have a higher eggshell porosity allowing them to maintain a higher metabolic rate throughout incubation and to hatch before their first-laid siblings. We investigated differences in egg size, shell thickness, pore density, pore diameter and water vapour conductance between first and second eggs within clutches and examined the influence of these shell characteristics on hatching asynchrony. First-laid eggs of Snares Penguins were approximately 78% of the size of the larger second eggs. Second-laid eggs had considerably thicker shells and more pores per cm2 than first eggs, whereas pore diameter did not differ between eggs. Water vapour conductance was greater in second- (16.8 mg/day/torr) than in first-laid eggs (14.9 mg/day/torr). The difference in water vapour conductance between first- and second-laid eggs within clutches was related to hatching patterns. In nests where second eggs hatched before first-laid eggs, second eggs had a considerably greater water conductance than their sibling, whereas in nests where both eggs hatched on the same day, the difference in water conductance between eggs was very small, and in a few nests where small first eggs hatched before their larger sibling, they had a greater water conductance than their larger second-laid nestmate. Surprisingly few studies have investigated differences in shell characteristics between eggs within clutches and associated effects on hatching asynchrony. This study has demonstrated that such differences exist between eggs within clutches and that they can influence hatching patterns. [source] Cortical Indexes of Saccade Planning Following Covert Orienting in 20-Week-Old InfantsINFANCY, Issue 2 2001John E. Richards This study examined scalp-recorded, event-related potential (ERP) indexes of saccade planning in 20-week-old infants. A spatial cuing procedure was used in which the infants were presented with a central fixation stimulus and a peripheral cue. A peripheral target followed the cue on the ipsilateral or contralateral side of the cue. The procedure resulted in covert orienting of attention in these participants, reflected in behavioral (e.g., response facilitation or inhibition of return depending on cue-target stimulus-onset asynchrony) and ERP (P1 facilitation to ipsilateral target) indexes of covert orienting of attention. A presaccadic ERP that occurred over the frontal cortex about 50 msec before the saccade onset was largest when the saccade was to a target in a cued location. A presaccadic ERP potential that occurred about 300 msec before the saccade onset was largest for the saccades toward the cued location whether the target was present or not. These results suggest that saccade planning occurs in infants at this age and that infant saccade planning is controlled by cortical systems. [source] Patterns of emotional availability among young mothers and their infants: A dydaic, contextual analysisINFANT MENTAL HEALTH JOURNAL, Issue 4 2005M. Ann Easterbrooks The aim of this study was to examine patterns of emotional availability among 80 young mothers (under 21 years at their child's birth) and their infants, and to identify contextual and individual factors associated with different patterns of emotional availability. To operationalize the dyadic aspect of emotional availability, cluster analysis of the Emotional Availability Scales, third edition (EAS; Biringen, Robinson, & Emde, 1998) was conducted on mother and infant scales simultaneously. Four distinct groups of emotional availability patterns emerged, reflecting synchrony and asynchrony between maternal and child behavior: (a) low-functioning dyads, (b) average dyads, (c) average parenting/disengaged infants, and (d) high-functioning dyads. Further analyses revealed that mothers in different clusters differed on outcomes such as depressive symptomatology, social support, and relationships with their own mothers. The clusters and the variables related to them demonstrate the various challenges in integrating the dual tasks of adolescent and parenting development among young mothers. The clinical implications of these patterns of emotional availability and live context are discussed. [source] Classification of a traumatic brain injury: the Glasgow Coma scale is not enoughACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 6 2010A. CHIEREGATO Background: Classifying the severity of a traumatic brain injury (TBI) solely by means of the Glasgow Coma scale (GCS) is under scrutiny, because it overlooks other important clinical signs. Clinicians treating patients with acute TBI are well placed to suggest which variables, in addition to the GCS, should concur in a new classification of TBI. Methods: In Italy, acute TBI patients are treated by anaesthetists, and so we asked them, in a questionnaire survey, to rate the weight they give to the GCS and to other clinical variables in their approach to TBI. Because sedation may underestimate GCS scores, we also inquired whether anaesthetists select sedatives that allow drug-free GCS scores. The questionnaire was distributed to 1334 anaesthetists attending courses on neurotrauma; the response rate was 63%. Results: Two thirds of the respondents believe that the definition of severe TBI should include, in addition to GCS scores, pupil reactivity to light and computer tomogram (CT) findings, the variables that guide Italian anaesthetists in TBI management. Most respondents (68.2%) administer sedation which allows prompt neurological evaluation and reliable GCS scoring. A minority of respondents (9.3%) withhold or antagonize sedation, delay tracheal intubation or allow patient,ventilator asynchrony. Conclusions: Italian anaesthetists would welcome a definition of TBI severity that includes CT findings and pupil reactivity in addition to the GCS. [source] Constituent-morpheme priming: Implications from the morphology of two-kanji compound wordsJAPANESE PSYCHOLOGICAL RESEARCH, Issue 2 2002Terry Joyce Abstract: The diversity in the morphological structure of two-kanji compound words is a matter of special concern for models of the Japanese mental lexicon. This study discusses two proposals for models of the Japanese mental lexicon ,Hirose's (1992, 1994, 1996) hypotheses and a Japanese lemma-unit version of the multilevel interactive-activation framework , in terms of their ability to cope with this diversity. As the proposals make different predictions concerning constituent-morpheme priming, patterns of facilitation were examined in two experiments with five word-formation principles as experimental conditions. Experiment 1, using the long stimulus onset asynchrony (SOA) of 3000 ms employed by Hirose (1992), only found significant differences between the first- and second-element conditions in one of the word-formation conditions. Experiment 2, using a short SOA of 250 ms, confirmed the pattern of priming obtained in Experiment 1. These results are more consistent with the prediction from the Japanese lemma-unit model. [source] Temperature and life history: experimental heating leads female tree swallows to modulate egg temperature and incubation behaviourJOURNAL OF ANIMAL ECOLOGY, Issue 1 2009Daniel R. Ardia Summary 1Life-history decisions are strongly affected by environmental conditions. In birds, incubation is energetically expensive and affected significantly by ambient temperature. We reduced energetic constraints for female tree swallows (Tachycineta bicolor) by experimentally heating nests during incubation by an average of 6·9 °C to test for changes in incubation behaviour. 2Females in heated boxes (hereafter ,heated females') increased time spent incubating and maintained higher on-bout and off-bout egg temperatures. This indicates that female energetic constraints, not maximizing developmental conditions of offspring, determine incubation investment. Furthermore, this result suggests that embryonic developmental conditions in unmanipulated nests are suboptimal. 3We found individual variation in how females responded to experimental heating. Early-laying (i.e. higher phenotypic quality) females with heated nests increased egg temperatures and maintained incubation constancy, while later-laying (lower quality) heated females increased incubation constancy. Changes in egg temperature were due to changes in female behaviour and not due directly to increases in internal nest-box temperatures. 4Behaviour during the incubation period affected hatching asynchrony. Decreased variation in egg temperature led to lower levels of hatching asynchrony, which was also generally lower in heated nests. 5Our study finds strong support for the prediction that intermittent incubators set their incubation investment at levels dictated by energetic constraints. Furthermore, females incubating in heated boxes allocated conserved energy primarily to increased egg temperature and increased incubation attentiveness. These results indicate that studies investigating the role of energetics in driving reproductive investment in intermittent incubators should consider egg temperature and individual variation more explicitly. [source] Reproductive asynchrony in natural butterfly populations and its consequences for female matelessnessJOURNAL OF ANIMAL ECOLOGY, Issue 4 2008Justin M. Calabrese Summary 1Reproductive asynchrony, where individuals in a population are short-lived relative to the population-level reproductive period, has been identified recently as a theoretical mechanism of the Allee effect that could operate in diverse plant and insect species. The degree to which this effect impinges on the growth potential of natural populations is not yet well understood. 2Building on previous models of reproductive timing, we develop a general framework that allows a detailed, quantitative examination of the reproductive potential lost to asynchrony in small natural populations. 3Our framework includes a range of biologically plausible submodels that allow details of mating biology of different species to be incorporated into the basic reproductive timing model. 4We tailor the parameter estimation methods of the full model (basic model plus mating biology submodels) to take full advantage of data from detailed field studies of two species of Parnassius butterflies whose mating status may be assessed easily in the field. 5We demonstrate that for both species, a substantial portion of the female population (6·5,18·6%) is expected to die unmated. These analyses provide the first direct, quantitative evidence of female reproductive failure due to asynchrony in small natural populations, and suggest that reproductive asynchrony exerts a strong and largely unappreciated influence on the population dynamics of these butterflies and other species with similarly asynchronous reproductive phenology. [source] Should males come first?JOURNAL OF AVIAN BIOLOGY, Issue 6 2005The relationship between offspring hatching order, sex in the black-headed gull Larus ridibundus In birds with hatching asynchrony and sexual size dimorphism, chicks hatched earlier and later in the laying sequence usually suffer different mortalities due to uneven abilities to compete for food, especially in poor years. If sexes differ in vulnerability to environmental conditions, e.g., by having different food requirements due to differential growth rates, mothers can increase fitness by allocating sex according to the laying order, producing less vulnerable sex later rather than early in the clutch. By analysing variation in primary sex ratio using a PCR-based DNA technique, we tested this prediction in black-headed gull Larus ridibundus chicks where males may be the less viable sex under adverse conditions. The overall primary sex ratio of the population did not depart from parity. However, first hatched chicks were more likely to be males whereas last hatched chicks were more likely to be females. Both egg volume and hatchling body mass decreased with laying order irrespective of sex. Time of breeding had no effect on offspring sex or hatchling sex ratios. [source] Hatching asynchrony and maternal androgens in egg yolks of House WrensJOURNAL OF AVIAN BIOLOGY, Issue 1 2001Lisa A. Ellis Synchronously and asynchronously hatching clutches of House Wrens Troglodytesaedon usually do not differ in reproductive success. Thus late-hatching nestlings in asynchronously hatching clutches somehow overcome any age- and size-related disadvantages of hatching after their nest-mates. One possible way for them to do this is for female House Wrens to add maternal androgens to the yolk of late-hatching eggs. We tested this hypothesis in a wild population of House Wrens that produces both asynchronously and synchronously hatching clutches. Yolks of eggs from both types of clutches were biopsied and the eggs returned to their nests to hatch. Radioimmunoassays revealed that total androgen levels in the yolk varied within and among clutches. However, total androgen levels in yolks did not vary predictably with egg position in either synchronously or asynchronously hatching clutches. Thus, deposition of androgens in yolk did not follow the expected pattern based on the potential for sibling competition in House Wrens. [source] | ||||||||||||||||||||||||||||||||||