Home About us Contact
|
Home About us Contact | ||
|
|
||
Rate Increases (rate + increase)
Kinds of Rate Increases Selected AbstractsChanges in Left Ventricular Repolarization and Ion Channel Currents Following a Transient Rate Increase Superimposed on Bradycardia in Anesthetized DogsJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 6 2000MICHAEL RUBART M.D. Electrical Remodeling of the Heart due to Rate. Introduction: We previously demonstrated in dogs that a transient rate increase superimposed on bradycardia causes prolongation of ventricular refractoriness that persists for hours after resumption of bradycardia. In this study, we examined changes in membrane currents that are associated with this phenomenon. Methods and Results: The whole cell, patch clamp technique was used to record transmembrane voltages and currents, respectively, in single mid-myocardial left ventricular myocytes from dogs with 1 week of complete AV block; dogs either underwent 1 hour of left ventricular pacing at 120 beats/min or did not undergo pacing. Pacing significantly heightened mean phase 1 and peak plateau amplitudes by ,6 and ,3 mV, respectively (P < 0.02). and prolonged action potential duration at 90% repolarization from 235 ± 8 msec to 278 ± 8 msec (1 Hz; P = 0.02). Rapid pacing-induced changes in transmembrane ionic currents included (1) a more pronounced cumulative inactivation of the 4-aminopyridine-sensitive transient outward K+ current, I to over the range of physiologic frequencies, resulting from a ,30% decrease in the population of quickly reactivating channels; (2) increases in peak density of L-type Ca2+ currents, Ica.I.' by 15% to 35% between +10 and +60 mV; and (3) increases in peak density of the Ca2+ -activated chloride current, ICl.Ca' by 30% to 120% between +30 and +50 mV. Conclusion: Frequency-dependent reduction in Ito combined with enhanced ICa.I. causes an increase in net inward current that may he responsible for the observed changes in ventricular repolarization. This augmentation of net cation influx is partially antagonized by an increase in outward ICa.Cl. [source] Do Small Farmers Borrow Less When the Lending Rate Increases?ASIAN ECONOMIC JOURNAL, Issue 4 2009Interest Rate Elasticity of Rice Farmers in the Philippines O160; O180; Q140 The new generation of credit programs directed at small borrowers emphasizes financial sustainability. Based on anecdotal information, proponents of cost recovery claim that raising formal lending rates would have a minimal impact on borrowing. However, rigorous evidence for this conjecture is sparse. The present study conducts an econometric test of this conjecture using data from a survey of small rice farmers from the Philippines. Alternative regression techniques tend to reject the conjecture; in particular, a regression that controls for selection effects shows a unitary elastic response of formal borrowing to the lending rate. [source] An ecological law and its macroecological consequences as revealed by studies of relationships between host densities and parasite prevalenceECOGRAPHY, Issue 3 2001Per ArnebergArticle first published online: 30 JUN 200 Epidemiological models predict a positive relationship between host population density and abundance of macroparasites. Here I test these by a comparative study. I used data on communities of four groups of parasites inhabiting the gastrointestinal tract of mammals, nematodes of the orders Oxyurida, Ascarida, Enoplida and Spirurida, respectively. The data came from 44 mammalian species and represent examination of 16 886 individual hosts. I studied average prevalence of all nematodes within an order in a host species, a measure of community level abundance, and considered the potential confounding effects of host body weight, fecundity, age at maturity and diet. Host population density was positively correlated with parasite prevalence within the order Oxyurida, where all species have direct life cycles. Considering the effects of other variables did not change this. This supports the assumption that parasite transmission rate generally is a positive function of host population density. It also strengthens the hypothesis that host densities generally act as important determinants of species richness among directly transmitted parasites and suggests that negative influence of such parasites on host population growth rate increase with increasing host population density among host species. Within the other three nematode orders, where a substantial number of the species have indirect life cycles, no relationships between prevalence and host population density were seen. Again, considering the effects of other variables did not affect this conclusion. This suggests that host population density is a poor predictor of species richness of indirectly transmitted parasites and that effects of such parasites on host population dynamics do not scale with host densities among species of hosts. [source] Unintentional drug overdose death trends in New Mexico, USA, 1990,2005: combinations of heroin, cocaine, prescription opioids and alcoholADDICTION, Issue 1 2008Nina G. Shah ABSTRACT Aims To determine the contribution of heroin, prescription opioids, cocaine and alcohol/drug combinations to the total overdose death rate and identify changes in drug overdose patterns among New Mexico subpopulations. Design We analyzed medical examiner data for all unintentional drug overdose deaths in New Mexico during 1990,2005. Age-adjusted drug overdose death rates were calculated by sex and race/ethnicity; we modeled overall drug overdose death adjusting for age and region. Findings The total unintentional drug overdose death rate in New Mexico increased from 5.6 per 100 000 in 1990 to 15.5 per 100 000 in 2005. Deaths caused by heroin, prescription opioids, cocaine and alcohol/drug combinations together ranged from 89% to 98% of the total. Heroin caused the most deaths during 1990,2005, with a notable rate increase in prescription opioid overdose death during 1998,2005 (58%). During 1990,2005, the 196% increase in single drug category overdose death was driven by prescription opioids alone and heroin alone; the 148% increase in multi-drug category overdose death was driven by heroin/alcohol and heroin/cocaine. Hispanic males had the highest overdose death rate, followed by white males, white females, Hispanic females and American Indians. The most common categories causing death were heroin alone and heroin/alcohol among Hispanic males, heroin/alcohol among American Indian males and prescription opioids alone among white males and all female subpopulations. Conclusions Interventions to prevent drug overdose death should be targeted according to use patterns among at-risk subpopulations. A comprehensive approach addressing both illicit and prescription drug users, and people who use these drugs concurrently, is needed to reduce overdose death. [source] Heart Rate Changes and ECG Abnormalities During Epileptic Seizures: Prevalence and Definition of an Objective Clinical SignEPILEPSIA, Issue 8 2002Maeike Zijlmans Summary: ,Purpose: To determine the prevalence of heart rate changes and ECG abnormalities during epileptic seizures and to determine the timing of heart rate changes compared to the first electrographic and clinical signs. To assess the risk factors for the occurrence of ECG abnormalities. Methods: We analyzed retrospectively 281 seizures in 81 patients with intractable epilepsy who had prolonged video-EEG and two-channel ECG. The nature and timing of heart rate changes compared to the electrographic and clinical seizure onset was determined. The ictal period (including one minute preictally and three minutes postictally) was analyzed for cardiac arrhythmias, conduction and repolarization abnormalities. Risk factors for cardiac abnormalities were investigated using parametric and non-parametric statistics. Results: There was an increase in heart rate of at least 10 beats/minute in 73% of seizures (93% of patients) and this occurred most often around seizure onset. In 23% of seizures (49% of patients) the rate increase preceded both the electrographic and the clinical onset. ECG abnormalities were found in 26% of seizures (44% of patients). One patient had an asystole for 30 seconds. Long seizure duration increased the occurrence of ECG abnormalities. No other risk factor was found. Conclusions: Heart rate changes occur frequently and occur around the time or even before the earliest electrographic or clinical change. The change can clarify the timing of seizure onset and the specific rate pattern may be useful for seizure diagnosis and for automatic seizure detection. ECG abnormalities occur often and repeatedly in several seizures of the same patient. [source] Hydrolysis of Toxic Natural Glucosides Catalyzed by Cyclodextrin DicyanohydrinsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 4 2008Jeannette Bjerre Abstract The hydrolysis of toxic 7-hydroxycoumarin glucosides and other aryl and alkyl glucosides, catalyzed by modified ,- and ,-cyclodextrin dicyanohydrins, was investigated using different UV, redox, or HPAEC detection assays. The catalyzed reactions all followed Michaelis,Menten kinetics, and an impressive rate increase of up to 7569 (kcat/kuncat) was found for the hydroxycoumarin glucoside substrate 4-MUGP. Good and moderate degrees of catalysis (kcat/kuncat) of up to 1259 were found for the natural glucosides phloridzin and skimmin. By using a newly developed catechol detection UV-assay, a weak degree of catalysis was also found for the toxic hydroxycoumarin esculin. A novel synthesized diaminomethyl ,-cyclodextrin showed a weak catalysis of p -nitrophenyl ,- D -glucopyranoside hydrolysis. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Growth-enhanced fish can be competitive in the wildFUNCTIONAL ECOLOGY, Issue 5 2001J. I. Johnsson Summary 1,The widespread commercial interest in producing growth-enhanced organisms has raised concerns about ecological consequences, emphasizing the need to understand the costs and benefits associated with accelerated growth in nature. Here, sustained-release growth hormone (GH) implants were used to estimate the competitive ability of growth-enhanced fish in the wild. Growth rate, movements and survival over winter were compared between GH-implanted and control Brown Trout in a natural stream. The study was repeated over two consecutive years. 2,GH treatment had no effect on recapture rates, indicating that mortality rates did not differ between GH-treated and control fish. More GH-treated trout (63%) than control fish (41%) were recaptured within their 10 m section of release. Thus, GH-treated fish were more stationary than control fish over winter. 3,GH-treated fish grew about 20% faster than control fish. This was mainly because of a three-fold growth rate increase in GH-treated fish in late summer, whereas growth rates over winter did not differ significantly between treatment groups. These results were consistent over both replicate years. 4,This first study of growth-enhanced fish in the wild shows that they can survive well and therefore may out-compete normal fish with lower growth rates. Although selection against rapid growth may be more intense at other life-history stages and/or during periods of extreme climate conditions, our findings raise concerns that released or escaped growth-enhanced salmonids may compete successfully with resident fish. It is clear that the potential ecological risks associated with growth-enhanced fish should not be ignored. [source] Changes in Left Ventricular Repolarization and Ion Channel Currents Following a Transient Rate Increase Superimposed on Bradycardia in Anesthetized DogsJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 6 2000MICHAEL RUBART M.D. Electrical Remodeling of the Heart due to Rate. Introduction: We previously demonstrated in dogs that a transient rate increase superimposed on bradycardia causes prolongation of ventricular refractoriness that persists for hours after resumption of bradycardia. In this study, we examined changes in membrane currents that are associated with this phenomenon. Methods and Results: The whole cell, patch clamp technique was used to record transmembrane voltages and currents, respectively, in single mid-myocardial left ventricular myocytes from dogs with 1 week of complete AV block; dogs either underwent 1 hour of left ventricular pacing at 120 beats/min or did not undergo pacing. Pacing significantly heightened mean phase 1 and peak plateau amplitudes by ,6 and ,3 mV, respectively (P < 0.02). and prolonged action potential duration at 90% repolarization from 235 ± 8 msec to 278 ± 8 msec (1 Hz; P = 0.02). Rapid pacing-induced changes in transmembrane ionic currents included (1) a more pronounced cumulative inactivation of the 4-aminopyridine-sensitive transient outward K+ current, I to over the range of physiologic frequencies, resulting from a ,30% decrease in the population of quickly reactivating channels; (2) increases in peak density of L-type Ca2+ currents, Ica.I.' by 15% to 35% between +10 and +60 mV; and (3) increases in peak density of the Ca2+ -activated chloride current, ICl.Ca' by 30% to 120% between +30 and +50 mV. Conclusion: Frequency-dependent reduction in Ito combined with enhanced ICa.I. causes an increase in net inward current that may he responsible for the observed changes in ventricular repolarization. This augmentation of net cation influx is partially antagonized by an increase in outward ICa.Cl. [source] Metallocene-Catalyzed Gas-Phase Ethylene Copolymerization: Kinetics and Polymer PropertiesMACROMOLECULAR REACTION ENGINEERING, Issue 8 2009Michiel F. Bergstra Abstract The influence of 1-hexene is examined on the kinetics of ethylene copolymerization with a metallocene catalyst in gas phase. A model is derived, which is able to describe a large reaction rate increase due to a small amount of incorporated comonomer. This complexation model describes the measured reaction rates for ethylene and 1-hexene, and the co-monomer incorporation. Polymer properties were analyzed, such as comonomer weight fraction. The density, melting point, and molecular weight of the produced polymer decreased with increase in 1-hexene gas concentration. The in situ 1-hexene sorption is estimated and follows Henry's law, but seems much higher than reported in the literature. [source] RUN/EDIT information processing mode and phasic cardiac accelerationPSYCHOPHYSIOLOGY, Issue 6 2008Tytus Sosnowski Abstract Our previous research showed that tasks demanding running of ready-to-use programs (RUN tasks) caused a greater tonic heart rate increase than did tasks that require problem solving (EDIT tasks). We found also a similar though not so consistent effect in the analysis of phasic cardiac acceleration. The aim of the present study was to replicate the last finding using new experimental tasks. Fifty-four male secondary school pupils were divided randomly into three experimental groups. Each group performed a different version of a nonsignaled reaction time (RT) task: simple RT, sensory choice RT, and semantic choice RT. Participants had to respond within an established time limit, but this limit was continuously modified in such a way that each participant was given positive feedback in approximately 50% of trials. According to expectations, the simple RT task evoked greater phasic cardiac acceleration than did the choice RT tasks. [source] Process improvement evaluation approach using flow diagramsQUALITY ASSURANCE JOURNAL, Issue 3 2006Paul C. Constant Jr. Abstract Maintaining company processes will afford optimum operation and enhance the company's quality management system. A vital part of maintaining processes is their periodic evaluation. An important part of the monitoring and evaluation process is the flow diagram. A detailed flow diagram is an important tool that affords ease in visualizing the total process and is an aid in locating problem areas. The evaluation of a process is broken down into 15 steps. These steps cover gathering pertinent information, such as problem symptoms from knowledgeable sources and carrying these through their route to potential problem areas to the problems, potential causes, and the root cause of the problem. Knowing the problems brings about the need to assess their impact on the process operation as well as what changes to the process are needed and what impact these changes will have on the product , its improved quality and cost , and other vital information, such as, production rate increase, competition status, and company image. With this information, the appropriate changes are made according to a process change action plan. The plan is executed, and the process is continuously monitored according to a monitoring and evaluation plan. The paper ends with conclusions. Copyright © 2006 John Wiley & Sons, Ltd. [source] Postnatal development of synaptic transmission in local networks of L5A pyramidal neurons in rat somatosensory cortexTHE JOURNAL OF PHYSIOLOGY, Issue 1 2007Andreas Frick The probability of synaptic transmitter release determines the spread of excitation and the possible range of computations at unitary connections. To investigate whether synaptic properties between neocortical pyramidal neurons change during the assembly period of cortical circuits, whole-cell voltage recordings were made simultaneously from two layer 5A (L5A) pyramidal neurons within the cortical columns of rat barrel cortex. We found that synaptic transmission between L5A pyramidal neurons is very reliable between 2 and 3 weeks of postnatal development with a mean unitary EPSP amplitude of ,1.2 mV, but becomes less efficient and fails more frequently in the more mature cortex of ,4 weeks of age with a mean unitary EPSP amplitude of 0.65 mV. Coefficient of variation and failure rate increase as the unitary EPSP amplitude decreases during development. The paired-pulse ratio (PPR) of synaptic efficacy at 10 Hz changes from 0.7 to 1.04. Despite the overall increase in PPR, short-term plasticity displays a large variability at 4 weeks, ranging from strong depression to strong facilitation (PPR, range 0.6,2.1), suggesting the potential for use-dependent modifications at this intracortical synapse. In conclusion, the transmitter release probability at the L5A,L5A connection is developmentally regulated in such a way that in juvenile animals excitation by single action potentials is efficiently transmitted, whereas in the more mature cortex synapses might be endowed with a diversity of filtering characteristics. [source] Gas-Phase and Surface Kinetics of Epitaxial Silicon Carbide Growth Involving Chlorine-Containing Species,CHEMICAL VAPOR DEPOSITION, Issue 8-9 2006A. Veneroni Abstract A detailed chemical mechanism for the silicon carbide epitaxial growth using light hydrocarbons, silane, and either chlorosilanes and/or HCl as the chlorine source is presented. The mechanism involves 153,gas-phase and 76 surface reactions among 47,gas-phase and 9 surface species, respectively. A comparison with the performances of the standard process using silane-hydrocarbons is presented, and the observed growth rate increase and the disappearing of the homogeneous silicon droplets in gas phase is explained. [source] Improving exercise capacity, 6 wk training tends to reduce circulating endothelin after heart transplantationCLINICAL TRANSPLANTATION, Issue 6 2004Stčphane Doutreleau Abstract:, Short-term survival is no longer the pivotal issue after heart transplantation but, most heart-transplant (Htx) patients still present with increased circulating endothelin-1 (ET) and reduced exercise capacity. ET-1 limits both exercise-induced vasodilation and blood flow redistribution toward acting muscles and might be accessible to training. This study was performed to investigate the effect of training on ET-1 and whether an eventual training-induced improvement in exercise capacity may be related to reduced baseline or exercise circulating ET-1 in Htx patients. Five Htx patients performed a maximal bicycle exercise test and an endurance exercise test before and after a training program of 18 exercises sessions during 6 wk. ET-1 was determined by radioimmunoassay at rest, end endurance exercise and 30 min recovery, before and after training. Training improved significantly Htx's maximal oxygen uptake (+13.1 ± 4.8%; p < 0.05) and also reduced significantly the endurance exercise-induced heart rate increase. Resting ET-1 was increased in Htx (5.98 ± 1.88 vs. 1.61 ± 0.25 pmol/L in controls; p < 0.01) but although ET-1 modulation might participate in training-induced beneficial effects, training failed to modulate either resting or exercise ET-1 plasma level. Training-induced improvement in exercise capacity might not mainly due to decreased ET-1 after heart transplantation. Further supporting the usefulness of training, these preliminary data suggest that improved exercise capacity may not be mainly due to decreased ET-1 in Htx patients. Further, larger scale studies will be needed to investigate whether an impaired nitric oxide pathway stimulation might explain such results and whether a longer training program can reduce local ET-1, arising from working muscles after heart transplantation. [source] The influence of groundwater on surface flow erosion processes during a rainstormEARTH SURFACE PROCESSES AND LANDFORMS, Issue 5 2002D. L. RockwellArticle first published online: 27 MAY 200 Abstract Surface erosion rates on a disturbed natural soil in a 10 m indoor flume increased by an order of magnitude when a water table developed at a 10 cm depth during simulated rainstorms. Erosion rate increases did not correlate well with surface hydraulic flow conditions, and all significant erosion increases began before the full soil depth was saturated, before the water table reached the soil surface, and before seepage was possible. Groundwater influenced erosion processes primarily by increasing unsaturated pore-water pressures and decreasing soil shear strength in surface rainflow, rather than through the direct entrainment of soil particles by seepage flow. There was no unique morphologic expression of the influence of groundwater during a rainstorm. Subsurface processes influencing surface erosion were detected only by appropriate subsurface instrumentation, which included micropiezometers, tensiometers and time domain reflectometry. Erosion rate increases occurred all along the slope, and were not concentrated at the base of slope due to a seepage zone. Soil depth was crucial to determining surface erosion increase. It is likely that confusing trends in surface flow erosion rates in past studies have occurred due to unrecorded groundwater development or an emphasis on seepage effects. Groundwater must be monitored along hillslopes under all moisture and soil conditions in order to avoid misleading and inconsistent conclusions derived solely from surface flow or seepage data. Copyright © 2002 John Wiley & Sons, Ltd. [source] Intraspecific variation in the strength of density dependence in aphid populationsECOLOGICAL ENTOMOLOGY, Issue 5 2004Anurag A. Agrawal Abstract., 1. Experimental evidence is presented for positive, negative, and no density dependence from 32 independent density manipulations of milkweed aphids (Aphis nerii) in laboratory and field experiments. This substantial variation in intraspecific density dependence is associated with temperature and host-plant species. 2. It is reported that as population growth rate increases, density dependence becomes more strongly negative, suggesting that the monotonic definition of density dependence used in many common population models is appropriate for these aphids, and that population growth rate and carrying capacity are not directly proportional. 3. For populations that conform to these assumptions, population growth rate may be widely applicable as a predictor of the strength of density dependence. [source] Interbank Lending, Liquidity and Banking CrisesECONOMIC NOTES, Issue 3 2002Paola Brighi In this paper, we show that abandoning the Diamond and Dybvig hypothesis of a unique bank representing the entire banking system gives rise to the possibility of endogenizing the interbank exchanges. In a system characterized by uncertainty regarding the moment of withdrawal of deposits, access to interbank liquidity decreases the bank risk of failure and bank runs. The possibility, moreover, to invest excess liquidity in the interbank market at a positive interest rate increases expected bank profits. (J.E.L.: E52, G21). [source] Effect of deposition temperature on the properties of thin polymer films deposited by plasma-enhanced CVD using cyclo-hexa-hydrocarbons as monomersELECTRONICS & COMMUNICATIONS IN JAPAN, Issue 4 2010Kazunori Moriki Abstract Plasma CVD is a candidate technology for the fabrication of optical polymer waveguides. It can deposit a film on any surface geometry and any substrate material at a temperature under 200 °C in a vacuum process. It also provides good thickness controllability and uniformity of the deposition film. In the present study, the effects of the deposition temperature on film properties, specifically the refractive index, deposition rate, and molecular structure, are discussed. The refractive index decreases as the deposition temperature rises. The logarithm of the deposition rate increases with the reciprocal of the temperature and the gradient of the deposition rate depends on the relative abundance of double bonds in the monomer source. The gradient does not change when CF4 is used instead of Ar as the gas mixed into the plasma, although the deposition rate increases by a factor of about five. We speculate that the deposition rate increases due to the increase in the abundance precursors produced by the presence of CF4 in the plasma and due to an increased abundance of dangling bonds on the surface of the deposition film caused by F radicals. We further speculate that the precursors incorporated into the polymer are selected on the substrate by the density of adsorption sites and the adsorption energy. © 2010 Wiley Periodicals, Inc. Electron Comm Jpn, 93(4): 27,35, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecj.10171 [source] A research on used quantity of ground resistance reduction agent for ground systemsEUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 4 2010Li-Hsiung Chen Abstract The ground resistance reduction agent can be used to decrease ground resistance for high soil resistivity. The ground resistance decreases and the ground resistance reduction rate increases with increasing quantity of ground resistance reduction agent used. However, the ground resistance reduction effect will display the saturation phenomenon when the quantity of ground resistance reduction agent used increases to a certain level. This research discusses the quantity of ground resistance reduction agent used for ground rod. The used quantity of ground resistance reduction agent should be avoided in saturated areas to maximize the efficiency of ground resistance reduction agent use. Copyright © 2009 John Wiley & Sons, Ltd. [source] The sex-peptide DUP99B is expressed in the male ejaculatory duct and in the cardia of both sexesFEBS JOURNAL, Issue 21 2003Albana Rexhepaj Mating elicits two postmating responses in many insect females: the egg laying rate increases and sexual receptivity is reduced. In Drosophila melanogaster, two peptides of the male genital tract, sex-peptide and DUP99B, elicit these postmating responses when injected into virgin females. Here we show that the gene encoding DUP99B is expressed in the male ejaculatory duct and in the cardia of both sexes. The DUP99B that is synthesized in the ejaculatory duct is transferred, during mating, into the female genital tract. Expression of the gene is first seen in a late pupal stage. Males containing an intact ejaculatory duct, but lacking accessory glands, initiate the two postmating responses in their female partners [Xue, L. & Noll, M. (2000) Proc. Natl Acad. Sci. USA97, 3272,3275]. Although such males synthesize DUP99B in wild-type quantities, they elicit only weak postmating responses in their mating partners. Males lacking the Dup99B gene elicit the two postmating responses to the same extent as wild-type males. These results suggest that both sex-peptide and DUP99B can elicit both responses in vivo. However, sex-peptide seems to play the major role in eliciting the postmating responses, while DUP99B may have specialized for other, as yet unknown, functions. [source] Melting of a vertical ice cylinder inside a rotating cylindrical cavity filled with binary aqueous solutionHEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 6 2008Yoshimi Komatsu Abstract The melting of a vertical ice cylinder into a homogeneous calcium chloride aqueous solution inside a rotating cylindrical cavity with several rotating speeds is considered experimentally. The melting mass and temperature are measured on four initial conditions of the solution and four rotating speeds of the cavity. The temperature of the liquid layer becomes uniform by the mixing effect resulting from cavity rotation and it enhances the melting rate of the ice cylinder. As the cavity-rotating speed increases, the melting rate increases. The dimensionless melting mass is related to the Fourier number and the rotating Reynolds number in each initial condition, therefore an experimental equation that is able to quantitatively calculate the dimensionless melting mass is presented. It is seen that the melting Nusselt numbers increase again in the middle of the melting process. The ice cylinder continues to melt in spite of the small temperature difference between the ice cylinder and the solution. © 2008 Wiley Periodicals, Inc. Heat Trans Asian Res, 37(6): 359,373, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20211 [source] A learning rule for place fields in a cortical model: Theta phase precession as a network effectHIPPOCAMPUS, Issue 7 2005Silvia Scarpetta Abstract We show that a model of the hippocampus introduced recently by Scarpetta et al. (2002, Neural Computation 14(10):2371,2396) explains the theta phase precession phenomena. In our model, the theta phase precession comes out as a consequence of the associative-memory-like network dynamics, i.e., the network's ability to imprint and recall oscillatory patterns, coded both by phases and amplitudes of oscillation. The learning rule used to imprint the oscillatory states is a natural generalization of that used for static patterns in the Hopfield model, and is based on the spike-time-dependent synaptic plasticity, experimentally observed. In agreement with experimental findings, the place cells' activity appears at consistently earlier phases of subsequent cycles of the ongoing theta rhythm during a pass through the place field, while the oscillation amplitude of the place cells' firing rate increases as the animal approaches the center of the place field and decreases as the animal leaves the center. The total phase precession of the place cell is lower than 360°, in agreement with experiments. As the animal enters a receptive field, the place cells' activity comes slightly less than 180° after the phase of maximal pyramidal cell population activity, in agreement with the findings of Skaggs et al. (1996, Hippocampus 6:149,172). Our model predicts that the theta phase is much better correlated with location than with time spent in the receptive field. Finally, in agreement with the recent experimental findings of Zugaro et al. (2005, Nature Neuroscience 9(1):67,71), our model predicts that theta phase precession persists after transient intrahippocampal perturbation. © 2005 Wiley-Liss, Inc. [source] Physiological costs of the hearing due to noise exposure, additional physical stress, and combined exposure to alcohol and cigarette smokeHUMAN FACTORS AND ERGONOMICS IN MANUFACTURING & SERVICE INDUSTRIES, Issue 3 2002H. Strasser In 2 studies, each with 5 test series, physiological costs of the hearing due to legally tolerable noise exposures of 94 dB (A) for 1 hr have been measured audiometrically. The temporary threshold shifts (TTS) and their restitution time, as well as cardiovascular responses in work-related heart rate increases, of 10 and 8 subjects (Ss), respectively, could be shown to be modulated by additional physical stress and combined exposure to alcohol (Study 1) and cigarette smoke (Study 2). Moderate dynamic muscle work (50 W) administered via a bicycle ergometer either immediately after noise, or simultaneous to the noise exposure, significantly reduced restitution time as well as the integrated restitution temporary threshold shift (IRTTS). A physical stress to 100 W,which exceeded the endurance level when demanded simultaneously to the noise exposure,did not show any favorable effects. However, if the same physical stress succeeded the noise exposure, and when it was interrupted several times for the audiometric measurements, it also brought about significant accelerations of the restitution processes. Some reductions in physiological costs of the hearing were found due to an intervening alcohol consumption (blood alcohol concentration , 0.08%) prior to the noise exposure and a simultaneous physical load of 50 W. Smoking 10 cigarettes instead of the consumption of alcohol was associated with a reduced TTS, but a prolonged restitution time. IRTTS as total physiological costs of the most unfavorable combination of noise, simultaneous high physical workload, and preceding smoke exposure was increased. The results of the test series with cigarette smoke,probably due to the small group of just 8 Ss and the counteracting effects of the agents carbon monoxide (CO) and nicotine,were not statistically significant, but these exposures were associated with a substantial activation of the cardiovascular system. Significant heart rate increases are evidence that CO and nicotine must not be neglected as influential factors in the context of physiological costs that the organism, and especially the hearing, has to pay for noise exposures. © 2002 Wiley Periodicals, Inc. [source] Infiltration, runoff and sediment production in blanket peat catchments: implications of field rainfall simulation experimentsHYDROLOGICAL PROCESSES, Issue 13 2002J. Holden Abstract Blanket peat covers the headwaters of many major European rivers. Runoff production in upland blanket peat catchments is flashy with large flood peaks and short lag times; there is minimal baseflow. Little is known about the exact processes of infiltration and runoff generation within these upland headwaters. This paper presents results from a set of rainfall simulation experiments performed on the blanket peat moorland of the North Pennines, UK. Rainfall was simulated at low intensities (3,12 mm h,1), typical of natural rainfall, on bare and vegetated peat surfaces. Runoff response shows that infiltration rate increases with rainfall intensity; the use of low-intensity rainfall therefore allows a more realistic evaluation of infiltration rates and flow processes than previous studies. Overland flow is shown to be common on both vegetated and bare peat surfaces although surface cover does exert some control. Most runoff is produced within the top few centimetres of the peat and runoff response decreases rapidly with depth. Little vertical percolation takes place to depths greater than 10 cm owing to the saturation of the peat mass. This study provides evidence that the quickflow response of upland blanket peat catchments is a result of saturation-excess overland flow generation. Rainfall,runoff response from small plots varies with season. Following warm, dry weather, rainfall tends to infiltrate more readily into blanket peat, not just initially but to the extent that steady-state surface runoff rates are reduced and more flow takes place within the peat, albeit at shallow depth. Sediment erosion from bare peat plots tends to be supply limited. Seasonal weather conditions may affect this in that after a warm, dry spell, surface desiccation allows sediment erosion to become transport limited. Copyright © 2002 John Wiley & Sons, Ltd. [source] Different methods for modelling the areal infiltration of a grass field under heavy precipitationHYDROLOGICAL PROCESSES, Issue 7 2002Bruno Merz Abstract The areal infiltration behaviour of a grass field is studied using a data set of 78 sprinkler infiltration experiments. The analysis of the experimental data shows a distinct event dependency: once runoff begins, the final infiltration rate increases with increasing rainfall intensity. This behaviour is attributed to the effects of small-scale variability. Increasing rainfall intensity increases the ponded area and therefore the portion of the plot which infiltrates at maximum rate. To describe the areal infiltration behaviour of the grass field the study uses two different model structures and investigates different approaches for consideration of subgrid variability. It is found that the effective parameter approach is not suited for this purpose. A good representation of the observed behaviour is obtained by using a distribution function approach or a parameterization approach. However, it is not clear how the parameters can be derived for these two approaches without a large measurement campaign. The data analysis and the simulations show the great importance of considering the effects of spatial variability for the infiltration process. This may be significant even at a small scale for a comparatively homogeneous area. The consideration of heterogeneity seems to be more important than the choice of the model type. Furthermore, similar results may be obtained with different modelling approaches. Even the relatively detailed data set does not seem to permit a clear model choice. In view of these results it is questionable to use very complex and detailed simulation models given the approximate nature of the problem. Although the principle processes may be well understood there is a lack of models that represent these processes and, more importantly, there is a lack of techniques to measure and parameterize them. Copyright © 2002 John Wiley & Sons, Ltd. [source] Numerical investigation of the effect of inlet condition on self-excited oscillation of wet steam flow in a supersonic turbine cascade,INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 12 2009Wu Xiaoming Abstract Self-excited oscillation can be induced due to the interaction between condensation process and local transonic condition in condensing flow, which is an important problem in wet steam turbine. With an Eulerian/Eulerian numerical model, the self-excited oscillation of wet steam flow is investigated in a supersonic turbine cascade. Owing to supercritical heat addition to the subsonic flow in the convergent part of the cascade, the oscillation frequency decreases with increased inlet supercooling. Mass flow rate increases in the oscillating flow due to the greater supersaturation in condensation process, while the increase will be suppressed with the flow oscillation. Higher inlet supercooling leads to the fact that the condensation process moves upstream and the loss increases. Moreover, some predictions of oscillation effects on outflow angle and aerodynamic force are also presented. Finally, heterogeneous condensations with inlet wetness and periodic inlet conditions, as a result of the interference between stator and rotor, are discussed. Copyright © 2008 John Wiley & Sons, Ltd. [source] The silver(I)-catalyzed exchange of coordinated cyanide in hexacyanoferrate(II) by phenylhydrazine in aqueous mediumINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 8 2007R. M. Naik The [Ag]+ -catalyzed exchange of coordinated cyanide in [Fe(CN)6]4, by phenylhydrazine (PhNHNH2) has been studied spectrophotometrically at 488 nm by monitoring increase in the absorbance for the formation of cherry red colored complex [Fe(CN)5PhNHNH2]3,. The other reaction conditions were pH 2.80±,0.02, temperature = 30.0 ± 0.1°C, and ionic strength (I) = 0.02 M (KNO3). The reaction was followed as a function of pH, ionic strength, temperature, [Fe(CN)4,6], [PhNHNH2], [Ag+] by varying one variable at a time. The initial rates were evaluated for each variation using the plane mirror method. The initial rates evaluated as a function of [Fe(CN)4,6] clearly indicate that the initial rate increases with the increase in [Fe(CN)4,6] and finally reaches to a limiting value when [Fe(CN)4,6]/[AgNO3] , 1000. It indicates the formation of a strong adduct between [Fe(CN)6]4, and AgNO3 prior to the abstraction of CN,. The variation in initial rates with [PhNHNH2] also showed limiting values at [Fe(CN)4,6]/[PhNHNH2] , 8.30. The complex behavior due to pH and [Ag+] variations on the rate has been explained in detail. The composition of the final reaction product [Fe(CN)5PhNHNH2] formed during the course of reaction has been found to be 1:1 using the mole ratio method. The evaluated values of activation parameters for the catalyzed reaction are Ea = 53.85 kJ mol,1, , H,, = 51.33 kJ mol,1, and , S, = ,134.63 J K,1 mol,1, which suggest an interchange dissociative mechanism. A most plausible mechanistic scheme has been proposed based on the experimental observations. © 2007 Wiley Periodicals, Inc. Int J Chem Kinet 39: 447,456, 2007 [source] The prevalence of psychiatric symptoms and behavioural disturbances and the use of psychotropic drugs in Norwegian nursing homes,INTERNATIONAL JOURNAL OF GERIATRIC PSYCHIATRY, Issue 9 2007Geir Selbęk Abstract Background Psychiatric and behavioural symptoms in dementia are associated with a range of negative outcomes, including institutional placement and the widespread use of psychotropic drugs in spite of limited evidence for their efficacy. Aims To determine the prevalence of psychiatric and behavioural symptoms and the pattern of psychotropic drug prescription in patients with various degrees of dementia. Methods A sample of 1,163 non-selected nursing home patients were assessed by means of the Neuropsychiatric Inventory, the Clinical Dementia Rating scale and Lawton's activities of daily living scale. In addition, information was collected from the patients' records. Results Dementia was found in 81% of the patients and 72% of them had clinically significant psychiatric and behavioural symptoms. The frequencies of symptoms increased with the severity of the dementia. Psychotropic medication was being prescribed to 75% of patients with dementia. There was a significant relationship between the type of drug and the symptom for which it had been dispensed. Conclusion Psychiatric and behavioural symptoms are frequent in nursing homes and the rate increases with the progression of the dementia. Systematic programmes are needed for disseminating skills and providing guidance regarding the evaluation and treatment of these symptoms in nursing homes. Copyright © 2006 John Wiley & Sons, Ltd. [source] Unusual low-intensity regime in laser-induced molecular photodissociationINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 14 2009R. Lefebvre Abstract Previous investigations of laser-induced photodissociation of a diatomic molecule (Atabek et al., Phys Rev A 2006, 74, 063412 and Atabek and Lefebvre, Phys Rev A 2008, 78, 043419) have shown that some of the Floquet eigenstates have the property that at some critical intensities their width is vanishing. These intensities are wavelength dependent. We exploit further this property by showing that by a proper choice of the wavelength, the critical intensity for a Floquet state originating from a given field-free vibrational state can be made vanishingly small. In such a case, the rate increases with intensity in an abnormally slow way. The wavelengths, which are required to reach this regime, can be derived accurately from the semiclassical criterion to obtain a zero-width resonance. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2009 [source] Deterioration of Organization in the First Minutes of Atrial Fibrillation: A Beat-to-Beat Analysis of Cycle Length and Wave SimilarityJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 1 2007FLAVIA RAVELLI Ph.D. Introduction: It has been recently suggested that many episodes of atrial fibrillation (AF) may be partially organized at the onset and thus more suitable for antitachycardia pacing therapy. Nevertheless, the time course of organization in the first minutes of AF has not been quantified yet. Methods and Results: Twenty episodes of paroxysmal AF were studied. Electrograms were recorded from the right atrium (RA), distal (CSd), and proximal coronary sinus (CSp). The time course of AF cycle length (AFCL) and the regularity of wave morphology (similarity index S) were beat-to-beat measured at each recording site during the first 7 minutes of AF. AFCL and S showed a decreasing trend after the onset of AF. AFCL decreased from 208 ± 31 to 171 ± 21 msec (P < 0.001), from 206 ± 40 to 169 ± 23 msec (P < 0.001) and from 190 ± 42 to 152 ± 18 msec (P < 0.05), respectively, in RA, CSd, and CSp. Similarly, the similarity index decreased in CSd from 0.37 ± 0.27 to 0.12 ± 0.09 (P < 0.01) and in RA from 0.40 ± 0.18 to 0.17 ± 0.16 (P < 0.001). The 80% of the decrease occurred during the first 3 minutes of the arrhythmia, while after this time both cycle length and similarity index did not change significantly anymore. Conversely, the electrical activity in CSp was highly disorganized (S = 0.05 ± 0.03) even in the first minute of AF, and no decreasing temporal trend was observed. Conclusion: Higher levels of organization and longer fibrillation intervals exist at the onset of AF. The degree of organization of the electrical activity decays within less than 3 minutes. Since antitachycardia pacing success rate increases with high levels of organization, these results suggest an early delivery of pacing treatment. [source] | ||||||||||||||||||||||||||||||||||||||||