Home About us Contact
|
Home About us Contact | ||
|
|
||
Signals
Kinds of Signals Terms modified by Signals Selected AbstractsSEX CHROMOSOME LINKAGE OF MATE PREFERENCE AND COLOR SIGNAL MAINTAINS ASSORTATIVE MATING BETWEEN INTERBREEDING FINCH MORPHSEVOLUTION, Issue 5 2010Sarah R. Pryke Assortative mating is a key aspect in the speciation process because it is important for both initial divergence and maintenance of distinct species. However, it remains a challenge to explain how assortative mating evolves when diverging populations are undergoing gene flow (e.g., during hybridization). Here I experimentally test how assortative mating is maintained with frequent gene flow between diverged head-color morphs of the Gouldian finch (Erythrura gouldiae). Contrary to the predominant view on the development of sexual preferences in birds, cross-fostered offspring did not imprint on the phenotype of their conspecific (red or black morphs) or heterospecific (Bengalese finch) foster parents. Instead, the mating preferences of F1 and F2 intermorph-hybrids are consistent with inheritance on the Z chromosomes, which are also the location for genes controlling color expression and the genes causing low fitness of intermorph-hybrids. Genetic associations between color signal and preference loci on the sex chromosomes may prevent recombination from breaking down these associations when the morphs interbreed, helping to maintain assortative mating in the face of gene flow. Although sex linkage of reproductively isolating traits is theoretically expected to promote speciation, social and ecological constraints may enforce frequent interbreeding between the morphs, thus preventing complete reproductive isolation. [source] Can macroinvertebrate rapid bioassessment methods be used to assess river health during drought in south eastern Australian streams?FRESHWATER BIOLOGY, Issue 12 2008PETER ROSE Summary 1Despite significant concern about drought impacts in Australia, there have been no broad-scale studies of drought effects on river health. A severe and prolonged drought has been acting on many streams in south eastern Australia over the past decade. EPA Victoria has undertaken rapid bioassessment (RBA) of over 250 stream reference sites since 1990, providing an opportunity for a before-after-control-impact investigation of drought related changes to macroinvertebrate indices and water quality. This study uses data from 1990 to 2004 to critically evaluate the effectiveness of using RBA methods and indices, which were designed for assessment of human impacts, for monitoring streams during drought. 2Reference stream sites across Victoria (those with minimal anthropogenic disturbances and repeatedly sampled) were classified as being ,in drought' or ,not in drought' using the Bureau of Meteorology's rainfall deficiency definition. Four biological indices (SIGNAL, EPT, Family Richness and AUSRIVAS) were calculated for combined autumn and spring samples for edge and riffle habitats for the selected sites. 3General linear models and paired t -tests were used to detect drought related changes to index and water quality values at state-wide and bioregional scales. Changes in taxa constancy were examined to determine which taxa were sensitive to or benefited from drought conditions. Frequency of site failure against biological objectives specified in the State Environment Protection Policy (Waters of Victoria) (herein termed ,SEPP WoV') before and during drought was also examined to detect changes in a management context. 4Few significant changes in index values were detected for riffle habitat samples. Rates of failure against biological objectives were similar before and during drought for riffle samples. In contrast, edge habitat AUSRIVAS and SIGNAL scores were significantly reduced at the state-wide scale and most indices showed significant declines in the lower altitude forests, and foothills and coastal plains bioregions. 5Generally, more pollution tolerant, lentic taxa replaced sensitive and flow-requiring taxa in edge samples during drought. In contrast, there were few reductions in the taxa of riffle samples during drought. However, many pool preferring, but pollution sensitive taxa occurred more frequently in riffle areas. Hence, the riffle community began to resemble that of pools and edges. This was attributed to decreased flow and increased ,lentic' habitat opportunities in riffles. 6Detection of a drought effect was confined to the edge habitat and site failure could be assigned to drought and anthropogenic impacts, in conjunction or alone. The riffle sampling protocol was resistant to detection of drought effects as samples were only taken when sufficient water was present within this habitat. Therefore, biological changes at sites not meeting policy objectives for riffle habitats can be attributed to anthropogenic rather than drought impacts. [source] THE RELIABILITY OF NAĎVE ASSESSORS IN SENSORY EVALUATION VISUALIZED BY PRAGMATICAL MULTIVARIATE ANALYSISJOURNAL OF FOOD QUALITY, Issue 5 2002M.G. O'SULLIVAN The first part of this paper demonstrates a simple graphical way to visualize estimated variances, in terms of a plot of the total initial variance ("SIGNAL") versus residual variance ("NOISE"), as a pragmatic alternative to tables of F-tests. The recently developed Procrustes rotation in the bilinear "jack-knifing" form is then presented as a method for simplifying the comparison of PLS Regression models from different data sets. These methods are applied to sensory data in order to study if naďve (untrained) sensory panelists can produce reliable descriptions of systematic differences between various test meals. The results confirm that three panels of 15 naďve assessors each could give repeatable intersubjective description of the most dominant sensory variation dimensions. [source] AN ORGANIZED SIGNAL IN SNOWMELT RUNOFF OVER THE WESTERN UNITED STATES,JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 2 2000D. H. Peterson ABSTRACT: Daily-to-weekly discharge during the snowmelt season is highly correlated among river basins in the upper elevations of the central and southern Sierra Nevada (Carson, Walker, Tuolumne, Merced, San Joaquin, Kings, and Kern Rivers). In many cases, the upper Sierra Nevada watershed operates in a single mode (with varying catchment amplitudes). In some years, with appropriate lags, this mode extends to distant mountains. A reason for this coherence is the broad scale nature of synoptic features in atmospheric circulation, which provide anomalous insolation and temperature forcing that span a large region, sometimes the entire western U.S. These correlations may fall off dramatically, however, in dry years when the snowpack is spatially patchy. [source] WARNING SIGNALS OR DANGEROUS OPPORTUNITIES?EDUCATIONAL THEORY, Issue 4 2000AND EDUCATIONAL POLICY SHIFTS, GENDER, GLOBALIZATION First page of article [source] EVOLUTION OF BIRD SONG AFFECTS SIGNAL EFFICACY: AN EXPERIMENTAL TEST USING HISTORICAL AND CURRENT SIGNALSEVOLUTION, Issue 8 2007Elizabeth P. Derryberry Mating signals act as behavioral barriers to gene flow in many animal taxa, yet little is known about how signal evolution within populations contributes to the formation of these barriers. Although variation in mating signals among populations is known to affect mating behavior, there is no direct evidence that the evolution of mating signals changes signal effectiveness within a natural population. Making use of historical recordings of bird song, I found that both male and female white-crowned sparrows (Zonotrichia leucophrys) respond more strongly to current than to historical songs, indicating that historical songs are less effective as signals in the current contexts of both mate choice and male,male competition. Finding that historical signals are less effective suggests that signal evolution within populations may ultimately contribute to the formation of behavioral barriers to gene flow between populations. [source] HABITAT-DEPENDENT SONG DIVERGENCE IN THE LITTLE GREENBUL: AN ANALYSIS OF ENVIRONMENTAL SELECTION PRESSURES ON ACOUSTIC SIGNALSEVOLUTION, Issue 9 2002Hans Slabbekoorn Abstract., Bird song is a sexual trait important in mate choice and known to be shaped by environmental selection. Here we investigate the ecological factors shaping song variation across a rainforest gradient in central Africa. We show that the little greenbul (Andropadus virens), previously shown to vary morphologically across the gradient in fitness-related characters, also varies with respect to song characteristics. Acoustic features, including minimum and maximum frequency, and delivery rate of song notes showed significant differences between habitats. In contrast, we found dialectal variation independent of habitat in population-typical songtype sequences. This pattern is consistent with ongoing gene flow across habitats and in line with the view that song variation in the order in which songtypes are produced is not dependent on habitat characteristics in the same way physical song characteristics are. Sound transmission characteristics of the two habitats did not vary significantly, but analyses of ambient noise spectra revealed dramatic and consistent habitat-dependent differences. Matching between low ambient noise levels for low frequencies in the rainforest and lower minimal frequencies in greenbul songs in this habitat suggests that part of the song divergence may be driven by habitat-dependent ambient noise patterns. These results suggest that habitat-dependent selection may act simultaneously on traits of ecological importance and those important in prezygotic isolation, leading to an association between morphological and acoustic divergence. Such an association may promote assortative mating and may be a mechanism driving reproductive divergence across ecological gradients. [source] EVOLUTION OF REPRODUCTIVE STRATEGIES IN THE SEXUALLY DECEPTIVE ORCHID OPHRYS SPHEGODES: HOW DOES FLOWER-SPECIFIC VARIATION OF ODOR SIGNALS INFLUENCE REPRODUCTIVE SUCCESS?EVOLUTION, Issue 6 2000Manfred Ayasse Abstract The orchid Ophrys sphegodes Miller is pollinated by sexually excited males of the solitary bee Andrena nigroaenea, which are lured to the flowers by visual cues and volatile semiochemicals. In O. sphegodes, visits by pollinators are rare. Because of this low frequency of pollination, one would expect the evolution of strategies that increase the chance that males will visit more than one flower on the same plant; this would increase the number of pollination events on a plant and therefore the number of seeds produced. Using gas chromatography-mass spectrometry (GC-MS) analyses, we identified more than 100 compounds in the odor bouquets of labellum extracts from O. sphegodes; 24 compounds were found to be biologically active in male olfactory receptors based on gas chromatography with electroantennographic detection (GC-EAD). Gas chromatography (GC) analyses of odors from individual flowers showed less intraspecific variation in the odor bouquets of the biologically active compounds as compared to nonactive compounds. This can be explained by a higher selective pressure on the pollinator-attracting communication signal. Furthermore, we found a characteristic variation in the GC-EAD active esters and aldehydes among flowers of different stem positions within an inflorescence and in the n-alkanes and n-alkenes among plants from different populations. In our behavioral field tests, we showed that male bees learn the odor bouquets of individual flowers during mating attempts and recognize them in later encounters. Bees thereby avoid trying to mate with flowers they have visited previously, but do not avoid other flowers either of a different or the same plant. By varying the relative proportions of saturated esters and aldehydes between flowers of different stem positions, we demonstrated that a plant may take advantage of the learning abilities of the pollinators and influence flower visitation behavior. Sixty-seven percent of the males that visited one flower in an inflorescence returned to visit a second flower of the same inflorescence. However, geitonogamy is prevented and the likelihood of cross-fertilization is enhanced by the time required for the pollinium deposited on the pollinator to complete its bending movement, which is necessary for pollination to occur. Cross-fertilization is furthermore enhanced by the high degree of odor variation between plants. This variation minimizes learned avoidance of the flowers and increases the likelihood that a given pollinator would visit several to many different plants within a population. [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] FOREIGN DIRECT INVESTMENT IN SUB-SAHARAN AFRICA: CHANGING LOCATION-SPECIFIC ADVANTAGES AS SIGNALS OF COMPETITIVENESSTHE DEVELOPING ECONOMIES, Issue 3 2009Frank L. BARTELS F21; R3; P42; F23 This paper uses longitudinal factor analysis of location-specific advantages that are relevant to the foreign direct investment decisions of multinational enterprises (MNEs) in sub-Saharan Africa (SSA) to signal changes in location competitiveness. A total of 1,216 responses by MNEs to a survey in 15 SSA countries are analyzed. We find that, first, over a three-year period (2002,5), MNEs perceive a positive change in the market-servicing environment in SSA. Second, MNEs find negative changes in SSA regarding the availability of input factors and characteristics of market demand. [source] EPIGALLOCATECHIN-3-GALLATE ATTENUATES CARDIAC HYPERTROPHY IN HYPERTENSIVE RATS IN PART BY MODULATION OF MITOGEN-ACTIVATED PROTEIN KINASE SIGNALSCLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 9 2009Dan-Dan Chen SUMMARY 1It has been demonstrated that epigallocatechin-3-gallate (EGCG) inhibits cardiac hypertrophy through its antihypertensive and anti-oxidant effects. However, the underlying molecular mechanism is not clear. 2In the present study, we tested the hypothesis that EGCG attenuates transaortic abdominal aortic constriction (TAC)-induced ventricular hypertrophy by regulating mitogen-activated protein kinase (MAPK) signal pathways in hypertensive rats. Four groups of rats were used: (i) a sham-operated control group; (ii) an EGCG-treated (50 mg/kg per day, i.p., for 21 days) sham-operated group; (iii) a TAC group; and (iv) an EGCG-treated TAC group. Histological analysis of whole hearts and biochemical analyses of left ventricular (LV) tissue were used to investigate the effects of EGCG. 3The results showed that the LV myocyte diameter and the expression of atrial natriuretic peptide, brain natriuretic peptide and ,-myocardial heavy chain were significantly decreased in the EGCG-treated (50 mg/kg per day, i.p.) TAC group. Levels of reactive oxygen species and malondialdehyde in the lV were significantly reduced by EGCG in the TAC group. Total superoxide dismutase, catalase and glutathione peroxidase activities were decreased in the TAC group, and this decrease was significantly restored by EGCG treatment. Phosphorylation of extracellular signal-regulated kinase 2, p38 and c-Jun N-terminal kinase 1 was significantly reversed in the LV of EGCG-treated TAC rats (40%, 53% and 52%vs TAC, respectively), accompanied by significant inhibition of nuclear factor-,B and activator protein-1. Transaortic abdominal aortic constriction significantly upregulated LV expression of matrix metalloproteinase-9 from 32 ± 6 to 100 ± 12% and this increase was inhibited by EGCG treatment (from 100 ± 12 to 50 ± 15%). In addition, TAC decreased mitochondrial DNA copy number and the activity of respiratory chain complexes I (from 100 ± 7 to 68 ± 5%), III (from 100 ± 4 to 2 ± 5%) and IV (from 766 ± 2 to 100 ± 5%); this decrease was reversed by EGCG treatment to levels seen in sham-operated rats. 4In conclusion, EGCG attenuates TAC-induced ventricular hypertrophy in hypertensive rats in part by suppression of anti-oxidant enzymes and regulation of MAPK signals. [source] INVOLVEMENT OF N -METHYL- d -ASPARTATE RECEPTORS and NITRIC OXIDE IN THE ROSTRAL VENTROMEDIAL MEDULLA IN MODULATING MORPHINE PAIN-INHIBITORY SIGNALS FROM THE PERIAQUEDUCTAL GREY MATTER IN RATSCLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 7 2005Kazem Javanmardi SUMMARY 1.,Supraspinal opioid antinociception is mediated, in part, by connections between the periaqueductal grey (PAG) and the rostral ventromedial medulla (RVM). Morphine antinociception from the PAG is decreased by serotonin, N -methyl- d -aspartate (NMDA) and opioid receptor antagonists administered into the RVM. Because the brain isoform of nitric oxide synthase (NOS) is also prominent in the RVM, the present study was designed to evaluate the effects of microinjection of the non-selective NOS inhibitor NG -nitro- l -arginine methyl ester (l -NAME) and the non-competitive NMDA receptor antagonist MK-801 into the RVM on PAG morphine antinociception and their potential interactions, as measured by the tail-flick test. 2.,Rats were anaesthetized with sodium pentobarbital and then special cannulas were inserted stereotaxically into the RVM and PAG. After 1 week recovery, the effects of microinjection of MK-801 and l -NAME into the RVM and their interactions in altering PAG morphine (2.5 µg) antinociception elicited from the PAG were assessed. 3.,Mesencephalic morphine antinociception was significantly reduced after pretreatment with l -NAME (0.6,1.3 µmol) or MK-801 (0.8 nmol). The reduction in mesencephalic morphine antinociception when MK-801 (0.8 nmol) and l -NAME (1 µmol) were microinjected sequentially into the RVM was not significantly different from the effects of MK-801 (0.8 nmol) or l -NAME (1 µmol) administered alone. 4.,These data imply that NMDA receptors and nitric oxide production in the RVM modulate the transmission of opioid pain-inhibitory signals from the PAG. [source] Signal de-noising in magnetic resonance spectroscopy using wavelet transformsCONCEPTS IN MAGNETIC RESONANCE, Issue 6 2002Hector F. Cancino-De-Greiff Abstract Computer signal processing is used for quantitative data analysis (QDA) in magnetic resonance spectroscopy (MRS). The main difficulty in QDA is that MRS signals appear to be contaminated with random noise. Noise reduction can be achieved by coherent averaging, but it is not always possible to average many MRS waveforms. Wavelet shrinkage de-noising (WSD) is a technique that can be employed in this case. The potentialities of WSD in MRS, alone and combined with the Cadzow algorithm, are analyzed through computer simulations. The results can facilitate an appropriate application of WSD, as well as a deeper understanding of this technique. © 2002 Wiley Periodicals, Inc. Concepts Magn Reson 14: 388,401, 2002 [source] Expressional changes of ganglioside GM3 during ovarian maturation and early embryonic development in db/db miceDEVELOPMENT GROWTH & DIFFERENTIATION, Issue 1 2003Dong Hoon Kwak Diabetes and obesity cause abnormal development of reproductive processes in a variety of species, but the mechanisms that underlie this effect have not been fully elucidated. This study examined the expressional changes of ganglioside GM3 during ovarian maturation, in vitro fertilization (IVF) and early embryonic development in diabetic/obese db/db mice. In high-performance thin-layer chromatography studies, GM3 expression was conspicuously low in the ovaries of db/db mice compared to non-diabetic db/+ mice. Signal detected by anti-GM3 monoclonal antibody was greatly reduced in the primary, secondary and graffian follicles of db/db mice compared to control mice. Results from IVF with ova and sperm from db/db mice showed that GM3 expression during early embryonic development was obviously decreased compared to db/+ mice. This study also elucidated the effects of high glucose (20 and 30 mm) on early embryonic development in ICR strain mice. High glucose caused a decrease in GM3 expression during early embryonic development. Taken together, the results of this study indicate decreased GM3 expression during ovarian maturation and embryonic development of db/db mice, suggesting that alteration of ganglioside expression induced by the diabetic condition may be implicated in the abnormal follicular embryonic development. [source] Novel, Sensitive Voltammetric Methods for Titanium Determination Using Chromotropic Acid and Azo-Compounds as Complexing AgentsELECTROANALYSIS, Issue 12 2003Marcin Gawrys Abstract Voltammetric behavior of titanium(IV) complexes with chromotropic acid, its azo-derivatives: 2-(4-sulfophenylazo)-1,8-dihydroxy-3,6-naphthalenedisulfonic acid (SPANDS), chromotrope 2B, sulfonazo III and other azo-compounds: calmagite, tropeoline O and kalces was investigated at a hanging mercury drop electrode. These complexes strongly adsorb onto the electrode, thus can be determined by an adsorptive stripping voltammetry (optimal pH about 6). At pH about 3 reduction current enhancement for Ti-kalces complex was observed in the presence of chlorate ions. It is a rare example of a catalytic process with azo-compound as a complexing agent. Signal for Fe-calmagite complex reduction was also observed. Influence of foreign ions and the optimal conditions for titanium determination are described in detail. Additionally, a connection between obtained results and a structure of titanium complexes is discussed. [source] Electrochemical Biosensor for the Detection of Interaction Between Arsenic Trioxide and DNA Based on Guanine SignalELECTROANALYSIS, Issue 7 2003Mehmet Ozsoz Abstract The interaction of arsenic trioxide (As2O3) with calf thymus double-stranded DNA (dsDNA), calf thymus single-stranded DNA (ssDNA) and also 17-mer short oligonucleotide (Probe,A) was studied electrochemically by using differential pulse voltammetry (DPV) with carbon paste electrode (CPE) at the surface and also in solution. Potentiometric stripping analysis (PSA) was employed to monitor the interaction of As2O3 with dsDNA in solution phase by using a renewable pencil graphite electrode (PGE). The changes in the experimental parameters such as the concentration of As2O3, and the accumulation time of As2O3 were studied by using DPV; in addition, the reproducibility data for the interaction between DNA and As2O3 was determined by using both electrochemical techniques. After the interaction of As2O3 with dsDNA, the DPV signal of guanine was found to be decreasing when the accumulation time and the concentration of As2O3 were increased. Similar DPV results were also found with ssDNA and oligonucleotide. PSA results observed at a low DNA concentration such as 1,ppm and a different working electrode such as PGE showed that there could be damage to guanine bases. The partition coefficients of As2O3 after interaction with dsDNA and ssDNA in solution by using CPE were calculated. Similarly, the partition coefficients (PC) of As2O3 after interaction with dsDNA in solution was also calculated by PSA at PGE. The features of this proposed method for the detection of DNA damage by As2O3 are discussed and compared with those methods previously reported for the other type of DNA targeted agents in the literature. [source] Design and testing of ,genome-proxy' microarrays to profile marine microbial communitiesENVIRONMENTAL MICROBIOLOGY, Issue 2 2008Virginia I. Rich Summary Microarrays are useful tools for detecting and quantifying specific functional and phylogenetic genes in natural microbial communities. In order to track uncultivated microbial genotypes and their close relatives in an environmental context, we designed and implemented a ,genome-proxy' microarray that targets microbial genome fragments recovered directly from the environment. Fragments consisted of sequenced clones from large-insert genomic libraries from microbial communities in Monterey Bay, the Hawaii Ocean Time-series station ALOHA, and Antarctic coastal waters. In a prototype array, we designed probe sets to 13 of the sequenced genome fragments and to genomic regions of the cultivated cyanobacterium Prochlorococcus MED4. Each probe set consisted of multiple 70-mers, each targeting an individual open reading frame, and distributed along each ,40,160 kbp contiguous genomic region. The targeted organisms or clones, and close relatives, were hybridized to the array both as pure DNA mixtures and as additions of cells to a background of coastal seawater. This prototype array correctly identified the presence or absence of the target organisms and their relatives in laboratory mixes, with negligible cross-hybridization to organisms having , ,75% genomic identity. In addition, the array correctly identified target cells added to a background of environmental DNA, with a limit of detection of ,0.1% of the community, corresponding to ,103 cells ml,1 in these samples. Signal correlated to cell concentration with an R2 of 1.0 across six orders of magnitude. In addition, the array could track a related strain (at 86% genomic identity to that targeted) with a linearity of R2 = 0.9999 and a limit of detection of ,1% of the community. Closely related genotypes were distinguishable by differing hybridization patterns across each probe set. This array's multiple-probe, ,genome-proxy' approach and consequent ability to track both target genotypes and their close relatives is important for the array's environmental application given the recent discoveries of considerable intrapopulation diversity within marine microbial communities. [source] Intra-Patriline Variability in the Performance of the Vibration Signal and Waggle Dance in the Honey Bee, Apis melliferaETHOLOGY, Issue 7 2008Nhi Duong We examined intra-patriline behavioral plasticity in communication behavior by generating lifetime behavioral profiles for the performance of the vibration signal and waggle dance in workers which were the progeny of three unrelated queens, each inseminated with the semen of a single, different drone. We found pronounced variability within each patriline for the tendency to produce each signal, the ontogeny of signal performance, and the persistence with which individual workers performed the signals throughout their lifetimes. Within each patriline, the number of workers that performed each signal and the distribution of onset ages for each signal were significantly different. In each patriline, workers of all ages could perform vibration signals; vibration signal production began 3,5 d before waggle dancing; and some workers began performing waggle dances at ages typically associated with precocious foraging. Most workers vibrated and waggled only 1,2 d during their lifetimes, although each patriline contained some workers that performed the signal persistently for up to 8 or 9 d. We also found marked variability in signal performance among the three worker lineages examined. Because the vibration signal and waggle dance influence task performance, variability in signaling behavior within and between subfamilies may help to organize information flow and collective labor in honey bee colonies. Inter-patriline variability may influence the total number of workers from different partrilines that perform the signals, whereas intra-patriline variability may further fine-tune signal performance and the allocation of labor to a given set of circumstances. Although intra-patriline behavioral variability is assumed to be widespread in the social insects, our study is the first to document the extent of this variability for honey bee communication signals. [source] The Importance of Visual Cues for Nocturnal Species: Eagle Owl Fledglings Signal with White Mouth FeathersETHOLOGY, Issue 10 2007Vincenzo Penteriani Complex begging display by bird offspring has predominantly been investigated in diurnal species, which have conspicuous gape colours or plumage features. In nocturnal species, in contrast, such visual communication has received little attention because the assumption is that they exclusively rely on vocal communication. Here, we use a field experiment to investigate whether eagle owls, Bubo bubo, communicate through visual signals at night. We artificially decreased the brightness of the white feathers surrounding fledgling eagle owls' mouths during the post-fledging dependence period, and investigated the effect of this treatment by comparing the condition of these birds to that of birds who received a control treatment. Several physiological parameters considered in our analyses indicate that control owlets were in better condition than owlets with brightness-reduced mouth feathers, which suggests that they received more or better food from feeding parents who discriminated between those young. Brightness-dependent reactions of parent owls suggest that visual signalling may be more widely employed than previously thought, and studying birds at night may reveal sophisticated strategies of animal communication. [source] Sudden Worsening of Cluster Headache: A Signal of Aneurysmal Thrombosis and EnlargementHEADACHE, Issue 8 2000Juanita G. McBeath MD We report a 55-year-old man presenting with symptoms of cluster headache, including throbbing pain behind the left eye, tearing, and rhinorrhea. Magnetic resonance imaging and magnetic resonance angiography revealed no abnormalities. Two days of intravenous dihydroergotamine resolved his pain. His headaches were somewhat relieved with a treatment regimen of 100 mg of imipramine each night, 40 mg of propranolol twice a day, 250 mg of divalproex three times a day, and dihydroergotamine nasal spray for breakthrough headaches. Two months later, the severity of his pain increased dramatically. Repeat imaging revealed a large thrombosed left posterior communicating artery aneurysm. Following obliterative surgery, his headaches are infrequent and mild and resemble tension headaches. Dramatic changes in headache characteristics can be an indicator of aneurysmal enlargement and thrombosis. This case illustrates the importance of repeat imaging when a patient's headache significantly worsens. [source] Different activation dynamics in multiple neural systems during simulated drivingHUMAN BRAIN MAPPING, Issue 3 2002Vince D. Calhoun Abstract Driving is a complex behavior that recruits multiple cognitive elements. We report on an imaging study of simulated driving that reveals multiple neural systems, each of which have different activation dynamics. The neural correlates of driving behavior are identified with fMRI and their modulation with speed is investigated. We decompose the activation into interpretable pieces using a novel, generally applicable approach, based upon independent component analysis. Some regions turn on or off, others exhibit a gradual decay, and yet others turn on transiently when starting or stopping driving. Signal in the anterior cingulate cortex, an area often associated with error monitoring and inhibition, decreases exponentially with a rate proportional to driving speed, whereas decreases in frontoparietal regions, implicated in vigilance, correlate with speed. Increases in cerebellar and occipital areas, presumably related to complex visuomotor integration, are activated during driving but not associated with driving speed. Hum. Brain Mapping 16:158,167, 2002. © 2002 Wiley-Liss, Inc. [source] Finding the Signal by Adding Noise: The Role of Noncontrastive Phonetic Variability in Early Word LearningINFANCY, Issue 6 2010Gwyneth C. Rost It is well attested that 14-month-olds have difficulty learning similar sounding words (e.g., bih/dih), despite their excellent phonetic discrimination abilities. By contrast, Rost and McMurray (2009) recently demonstrated that 14-month-olds' minimal-pair learning can be improved by the presentation of words by multiple talkers. This study investigates which components of the variability found in multitalker input improved infants' processing, assessing both the phonologically contrastive aspects of the speech stream and phonologically irrelevant indexical and suprasegmental aspects. In the first two experiments, speaker was held constant while cues to word-initial voicing were systematically manipulated. Infants failed in both cases. The third experiment introduced variability in speaker, but voicing cues were invariant within each category. Infants in this condition learned the words. We conclude that aspects of the speech signal that have been typically thought of as noise are in fact valuable information,signal,for the young word learner. [source] Design, implementation and verification through a real-time test-bed of a multi-rate CDMA adaptive interference mitigation receiver for satellite communicationINTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, Issue 1 2003Luca Fanucci Abstract This paper presents the design, the implementation, and the main performance results of a multi-rate code division multiple access (CDMA) interference mitigation receiver for satellite communication. Such activity was performed within a research project supported by the European Space Agency (ESA), whose aim was to demonstrate the suitability of the linear adaptive interference mitigation detector (IMD) named extended complex-valued blind anchored interference-mitigating detector (EC-BAID) for single-user detection of a CDMA signal in third-generation (3G) satellite networks. Such a detector, which exhibits a remarkable robustness to multiple access interference, operates in a blind mode, i.e. it only requires knowledge of the timing of the wanted user's signature code, and is therefore very well suited for integration into handheld user terminals. Experimental results in terms of bit error rate with respect to the theoretical behaviour were derived through a specifically developed test bed. Signal plus multiple access interference generation is performed via a computer-controlled arbitrary waveform generator, followed by frequency up-conversion to the standard intermediate frequency of 70 MHz. Additive white Gaussian noise is then injected with the aid of a precision noise generator. The core of the test bed is a flexible digital receiver prototype featuring the EC-BAID detector plus all functions ancillary to IMD (multi-rate front-end, automatic gain control, code acquisition and tracking, carrier synchronization, etc.). Those functions were implemented through careful mixing of different technologies: field programmable gate arrays (FPGAs) for computing-intensive signal processing functions, digital signal processor (DSP) for housekeeping and monitoring, and application specific integrated circuit (ASIC) for adaptive IMD. The adopted design flow also allows an easy re-use of the prototype architecture to come to an overall integration of the receiver into a single ASIC with modest complexity and power consumption increase with respect to a conventional detector. Copyright © 2003 John Wiley & Sons, Ltd. [source] Crying as a Sign, a Symptom and a SignalJOURNAL OF APPLIED RESEARCH IN INTELLECTUAL DISABILITIES, Issue 1 2002Pippa Mundy [source] Distinguishing Far-Field Appendage from Local Pulmonary Vein Signal in the Left Upper Pulmonary Vein During Atrial TachycardiaJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 4 2010EDWARD DUNCAN Ph.D. First page of article [source] In vivo magnetic resonance imaging of iron oxide,labeled, arterially-injected mesenchymal stem cells in kidneys of rats with acute ischemic kidney injury: Detection and monitoring at 3TJOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 6 2007Harald Ittrich MD Abstract Purpose To evaluate MRI for a qualitative and quantitative in vivo tracking of intraaortal injected iron oxide,labeled mesenchymal stem cells (MSC) into rats with acute kidney injury (AKI). Materials and Methods In vitro MRI and R2* measurement of nonlabeled and superparamagnetic iron oxide (SPIO)-labeled MSC (MSCSPIO) was performed in correlation to cellular iron content and cytological examination (Prussian blue, electron microscopy). In vivo MRI and R2* evaluation were performed before and after ischemic/reperfusion AKI (N = 14) and intraaortal injection of 1.5 × 106 MSCSPIO (N = 7), fetal calf serum (FCS) (medium, N = 6), and SPIO alone (N = 1) up to 14 days using a clinical 3T scanner. Signal to noise ratios (SNR), R2* of kidneys, liver, spleen, and bone marrow, renal function (creatinine [CREA], blood urea nitrogen [BUN]), and kidney volume were measured and tested for statistical significance (Student's t -test, P < 0.05) in comparison histology (hematoxylin and eosin [H&E], Prussian blue, periodic acid-Schiff [PAS], CD68). Results In vitro, MSCSPIO showed a reduction of SNR and T2* with R2* , number of MSCSPIO (R2 = 0.98). In vivo MSCSPIO administration resulted in a SNR decrease (35 ± 15%) and R2* increase (101 ± 18.3%) in renal cortex caused by MSCSPIO accumulation in contrast to control animals (P < 0.01). Liver, spleen, and bone marrow (MSCSPIO) showed a delayed SNR decline/R2* increase (P < 0.05) resulting from MSCSPIO migration. The increase of kidney volume and the decrease in renal function (P < 0.05) was reduced in MSC-treated animals. Conclusion Qualitative and quantitative in vivo cell-tracking and monitoring of organ distribution of intraaortal injected MSCSPIO in AKI is feasible in MRI at 3T. J. Magn. Reson. Imaging 2007;25:1179,1191. © 2007 Wiley-Liss, Inc. [source] Acute Ethanol Inhibits Extracellular Signal,Regulated Kinase, Protein Kinase B, and Adenosine 3,:5,-Cyclic Monophosphate Response Element Binding Protein Activity in an Age- and Brain Region,Specific MannerALCOHOLISM, Issue 4 2005L Judson Chandler Background: As little as a single episode of exposure of the developing brain to ethanol can result in developmental neuropathology and mental retardation. Extracellular signal,regulated kinases (ERKs), protein kinase B (PKB), and adenosine 3,:5,-cyclic monophosphate response element binding protein (CREB) are messenger molecules that play important roles in neuronal plasticity and survival. This study was undertaken to examine the effects of acute ethanol on ERK, PKB, and CREB activation in the brain. Methods: Immunoblot analysis was used to determine the effects of a 1-hr exposure of ethanol on levels of phospho-ERC in primary cortical cultures and in the cerebral cortex, hippocampus, and cerebellum of postnatal day 5 (PN5), postnatal day 21 (PN21), and adult rats. Results: In cortical cultures, ethanol (100 mM) significantly reduced activity-dependent activation of phospho-ERK, phospho-PKB, and phospho-CREB by approximately 50%. In PN5 rats, ethanol (3.5 g/kg) inhibited both phospho-ERK and phospho-PKB in the cerebral cortex and hippocampus but was without effect in the cerebellum. A similar brain region,specific inhibition of phospho-ERK was observed in PN21 rats, whereas in adult rats, ethanol inhibited phospho-ERK in all three brain regions. In contrast, ethanol had no effect on phospho-PKB in either PN21 or adult rats. Without exception, ethanol inhibited phospho-CREB in an identical brain region, and age-dependent manner as was observed for phospho-ERK. Finally, administration of the NMDA antagonist MK-801 (0.5 mg/kg) to PN5 rats had no effect on phospho-ERK or phospho-PKB levels in any brain region. Conclusion: The results demonstrate that acute ethanol inhibits ERK/PKB/CREB signaling in brain. This inhibition occurs in an age- and brain region,specific manner, with inhibition of PKB restricted to a time during the brain growth-spurt period. Furthermore, the lack of effect of MK-801 suggests that inhibition of NMDA receptors is unlikely to play a major role in binge ethanol inhibition of ERK/PKB/CREB signaling in vivo. [source] Effects of Abstinence From Alcohol on the Broad Phospholipid Signal in Human Brain: An In Vivo 31P Magnetic Resonance Spectroscopy StudyALCOHOLISM, Issue 8 2001M. R. Estilaei Background: In vivo phosphorus magnetic resonance spectroscopy (31P MRS) at a magnetic field strength of 1.5 T allows measurement of fairly mobile membrane phospholipids in the human brain. We previously showed that subjects who are heavy drinkers had a smaller signal and a shorter transverse relaxation time (T2) of white matter phospholipids than light drinkers, which suggested lower concentrations and molecular mobility of phospholipids in heavy drinkers. The purpose of the present study was to measure if such chronic alcohol-induced white matter tissue changes are persistent in long-term abstinent alcoholics. Methods: Fourteen abstinent alcoholics (mean age 45 years, seven men and seven women) were studied by localized 31P MRS in the centrum semiovale and were compared with 13 male, alcohol-dependent, heavy drinkers and 23 nondependent light drinkers (17 men, 6 women) of similar age. Methods for measurements of the broad membrane phospholipid signal and its relaxation time were described previously. Results: Phospholipid concentrations and relaxation times in alcoholics abstinent for an average of 31 months were not significantly different from those measured in light drinkers. The contribution of fast and slowly relaxing signal components to the broad phospholipid signal, however, was still different in abstinent alcoholics compared with light drinkers. No effects of sex or of family history of alcoholism were noted on any of our spectroscopic measures within the light-drinking or abstinent groups. Conclusions: Most of our results suggest at least partial recovery of chronic alcohol-induced white matter phospholipid damage with long-term abstinence. They offer myelination changes and/or dendritic rearborization as a possible mechanism for the commonly observed white matter volume gain with prolonged abstinence. But the results also suggest a persistent abnormality in the nature and/or physical properties of white matter phospholipids in long-term abstinent alcoholics. [source] Weighted Estimation of Harmonic Components in a Musical Sound SignalJOURNAL OF TIME SERIES ANALYSIS, Issue 1 2002RAFAEL A. IRIZARRY The study of musical sound has become a popular research field. Harmonic regression signal plus noise statistical models have been used to analyze sound signals. However, it is common to give estimates of harmonic parameters without indications of their uncertainties. Least squares estimates for harmonic models have been studied and asymptotic variance expression have been developed. In practice, window-based estimates are used. This paper studies the statistical properties of such estimates; in particular, we use asymptotic variance expressions to develop standard errors and construct confidence intervals. We present applications and examples of the statistical techniques to musical sound signal analysis. [source] A Price Is a Signal: on Intrinsic Motivation, Crowding-out, and Crowding-inKYKLOS INTERNATIONAL REVIEW OF SOCIAL SCIENCES, Issue 1 2010Friedel Bolle SUMMARY If a previously unpaid activity (e.g. donating blood) is paid, then we often observe that this activity is reduced. In this paper, it is hypothesized that the price offered is taken as a proxy for the "value" of the activity. Depending on how the actor valued the activity previously, crowding-out or crowding-in is implied, an effect with or without persistence after stopping the payment. The model can be adapted to a number of similar situations, including those where a high price signals high costs instead of high values. Our "naďve" explanation is confronted with Bčnabou and Tirole's (2003) Principal-Agent model. A questionnaire study supports our basic hypothesis as well as some of the derived consequences, and contradicts Bčnabou and Tirole's model. [source] | |||||||||||||||||||||||||||||||||||||||||||||||||