Specific Dynamic Effect Research Articles

A novel mechanism for ramping bursts based on slow negative feedback in model respiratory neurons.

Recordings from pre-Bötzinger complex neurons responsible for the inspiratory phase of the respiratory rhythm reveal a ramping burst pattern, starting around the time that the transition from expiration to inspiration begins, in which the spike rate gradually rises until a transition into a high-frequency burst occurs. The spike rate increase along the burst is accompanied by a gradual depolarization of the plateau potential that underlies the spikes. These effects may be functionally important for inducing the onset of inspiration and hence maintaining effective respiration; however, most mathematical models for inspiratory bursting do not capture this activity pattern. Here, we study how the modulation of spike height and afterhyperpolarization via the slow inactivation of an inward current can support various activity patterns including ramping bursts. We use dynamical systems methods designed for multiple timescale systems, such as bifurcation analysis based on timescale decomposition and averaging over fast oscillations, to generate an understanding of and predictions about the specific dynamic effects that lead to ramping bursts. We also analyze how transitions between ramping and other activity patterns may occur with parameter changes, which could be associated with experimental manipulations, environmental conditions, and/or development.

Dimerization dynamics of carboxylic acids in helium nanodroplets.

The dimerization of molecules in helium nanodroplets is known to preferentially yield structures of higher energy than the global energy minimum structure for a number of quite different monomers. Here, we explore dimerization in this environment using an atomistic model within statistically converged molecular dynamics (MD) trajectories, treating the solvent implicitly through the use of a thermostat, or more explicitly by embedding one monomer in a He100 cluster. The focus is on the two simplest carboxylic acids, formic and acetic, both of which have been studied experimentally. While the global minimum structure, which comprises two CO⋯HO hydrogen bonds, is predicted to be the most abundant dimer in the absence of the helium solvent, this is no longer the case once helium atoms are included. The simulations confirm the importance of kinetic trapping effects and also shed light on the occurrence of specific dynamical effects, leading to the occasional formation of high-energy structures away from minima, such as saddle configurations. Theoretically predicted infrared spectra, based on the MD statistics, are in good agreement with the experimental spectra.

Accurate Modeling of Infrared Multiple Photon Dissociation Spectra: The Dynamical Role of Anharmonicities

The dynamical response of a molecular system to a macropulse typically produced by a free-electron laser is theoretically modeled over experimentally long times, within a realistic kinetic Monte Carlo framework that incorporates absorption, stimulated emission, spontaneous emission, and dissociation events. The simulation relies on an anharmonic potential energy surface obtained from quantum chemistry calculations. Application to cationic naphthalene yields a better agreement with measurements than the anharmonic linear absorption spectrum, thus emphasizing the importance of specific dynamical effects on the spectral properties.

FORMATION OF DESIGN SOLUTIONS AND DYNAMIC TESTING SPANS PEDESTRIAN BRIDGE NEW TYPE

Purpose. To improving the reliability of the bearing capacity of structures under dynamic loading steel- reinforced concrete bridge spans a new type of pedestrian bridges that are based on the operation and development of methods to streamline and control their parameters. Methodology. To achieve the research was used new design ofpedestrian bridges span structures, theoretical models that simulate the stress-strain state of the bridge span specific dynamic effects and conducted experimental and theoretical studies of the proposed design. Findinfs. Analysis of the studies suggests that the natural period of oscillation structure misses the Forbidden for pedestrian bridges range0,45...0,6, and as a result, load-bearing capacity of the system is sufficient for the perception of the design loads. Originality. Further developed principles and criteria that predict rational topology span pedestrian bridge in the form of spatial rod system with a reinforced concrete slab of the upper belt (flooring) and enhanced the formation ofa set of sequences and procedures for finite element modeling of the stress -strain state of composite superstructures pedestrian bridges , including accounting for nonlinearity of deformation of structural materials , which have increased the share of resource constructive going on perception payload. Practical value. The technique of designingcomposite superstructures pedestrian bridges, technical and economic indicators which are highly competitive.

Dynamics of Patterns

Over the past few years, the focus has shifted to situations where neither bifurcation theory nor the amplitude-equation formalism can give enough insight into the formation and the dynamics of patterns. Examples are the dynamical selection of patterns, extracting and describing transient dynamics, the nonlinear stability of patterns in unbounded domains, and the development of efficient numerical techniques to capture specific dynamical effects and behaviours. This workshop brought together researchers who work on these questions from different perspectives and with different techniques, ranging from dynamical systems theory, qualitative analysis of partial differential equations, and bifurcation theory to spectral analysis and numerical methods for patterns.

Solitons in the Tonks–Girardeau gas with dipolar interactions

The existence of bright solitons in the model of the Tonks–Girardeau (TG) gas with dipole–dipole (DD) interactions is reported. The governing equation is taken as the quintic nonlinear Schrödinger equation (NLSE) with the nonlocal cubic term accounting for the DD attraction. In different regions of the parameter space (the dipole moment and atom number), matter-wave solitons feature flat-top or compacton-like shapes. For the flat-top states, the NLSE with the local cubic-quintic (CQ) nonlinearity is shown to be a good approximation. Specific dynamical effects are studied assuming that the strength of the DD interactions is ramped up or drops to zero. Generation of dark-soliton pairs in the gas shrinking under the action of the intensifying DD attraction is observed. Dark solitons exhibit particle-like collision behaviour. Peculiarities of dipole solitons in the TG gas are highlighted by comparison with the NLSE including the local CQ terms. Collisions between the bright solitons are also studied. In many cases, the collisions result in the merger of the solitons into a breather, due to a strong attraction between them.

PROBING NUCLEAR DYNAMICS IN REAL-PHOTON EXPERIMENTS

Experimental results on the reactions γd → π0d, γd → pn, γ3 He → ppn, and γ3 He → pd obtained in Hall B at Jefferson Lab at photon energies between 0.3 and 3.0 GeV are discussed. The goal of the measurements is to study the transition between long- and short-range nuclear dynamics, as well as more specific dynamical effects, such as manifestations of three-body mechanisms. Conventional nuclear models can describe the data up to a momentum transfer of ~ 1 ( GeV /c)2. All the studied reactions on deuterium clearly show scaling properties consistent with the predictions of the Constituent Counting Rules. The data on 3 He suggest that the favorable energy range for the study of three-body mechanisms is 0.6 - 0.8 GeV .

Multiple time scale method for atomistic simulations

A novel multiple time scale approach is proposed which combines dynamic and static atomistic methods in one numerical simulation. The method is especially effective for modeling processes that consist of two distinct phases: the slow phase when atomic equilibrium positions barely change and the fast phase associated with a rapid change of the system’s configuration. In this case, the slow phase can be effectively modeled using static energy minimization while molecular dynamics (MD) can be applied when specific dynamic effects have to be captured. Compared to direct MD simulations, the new method allows for computational cost savings, and eventually simulation timescale extension, since the major part of the simulation can be modeled as static, without the need to follow vibrations of individual atoms and comply with the critical time step requirement of molecular dynamics. As a result, this approach may allow for modeling loading velocities and strain rates that are more realistic than those currently attainable through direct MD simulations. The fundamental issues in developing this method include the correlation between the MD time scale and quasi-static step-like procedure as well as finding effective criteria for switching between the static and dynamic regimes. The method was inspired by and is applied to simulations of atomic-scale stick-slip friction. Possible applications of the new method to other nano-mechanical problems are also discussed.

Shape memory training for smart fabrics

Recent advances in shape memory alloys (SMAs) and shape memory polymers (SMPs) have inspired researchers to create intelligent textiles as self-regulating shape-changing structures responding to environmental variation, contributing to a new field in the scientific frontier of smart materials. This paper shows how appropriate shape memory training can engineer fabric designs to enhance their performance and their aesthetic appeal. Main technologies include the training procedure of shape memory effect (SME) in SMAs and SMPs, the regulation of phase transformation temperatures in SMAs, the manufacture of SMP yarns and SMP coating on fabrics for specific requirements of fabric design. Further attention is also paid to the combination of SMPs or SMAs with textile design of different fabric yarn for promoting specific dynamic aesthetic effects.

Dynamic response for motion capture animation

Human motion capture embeds rich detail and style which is difficult to generate with competing animation synthesis technologies. However, such recorded data requires principled means for creating responses in unpredicted situations, for example reactions immediately following impact. This paper introduces a novel technique for incorporating unexpected impacts into a motion capture-driven animation system through the combination of a physical simulation which responds to contact forces and a specialized search routine which determines the best plausible re-entry into motion library playback following the impact. Using an actuated dynamic model, our system generates a physics-based response while connecting motion capture segments. Our method allows characters to respond to unexpected changes in the environment based on the specific dynamic effects of a given contact while also taking advantage of the realistic movement made available through motion capture. We show the results of our system under various conditions and with varying responses using martial arts motion capture as a testbed.

Specific Dynamic Action of Food and Energy Metabolism of Fishes under Experimental and Natural Conditions

Based on literature and original experimental (aquarium) and natural (the Mediterranean Sea) data, the author’s point of view on the nature of the specific dynamic food effect (SDA) in fishes is substantiated. It is concluded that, in fishes the SDA exists constantly because this effect is supported by continuously proceeding digestion of food. The intensity and duration of the SDA as an energy metabolic process depend on the ratios of chemical components in food.

Time of feeding and possible associated thermoregulatory benefits in bronze mannikins Lonchura cucullata

Birds with a small body size have a high surface area to volume ratio, and this means that they have a high rate of heat loss to the environment. Birds may employ behavioural strategies in order to counter this heat loss. The adjustment of feeding patterns in the short term is probably the least documented of all of these strategies. Feeding results in the specific dynamic effect (SDE) which increases the metabolic rate of animals after a feeding bout. This increase in metabolic rate has been reported to possibly substitute for thermoregulatory costs in a variety of endotherms, including house wrens ( Troglodytes aedon) and a variety of finch species. The thermoneutral zone was described for bronze mannikins, Lonchura cucullata ( T lc=33.7°C), and the bronze mannikins’ post-absorptive physiology was described within this thermoneutral zone. Bronze mannikin mean basal metabolic rate (0.043±0.0038 S.E. ml O 2 min −1 g −1), daytime resting metabolic rates (0.0549±0.0088 S.E. ml O 2 min −1 g −1), and diurnal metabolic responses were described. The SDE in bronze mannikins was demonstrated within the thermoneutral zone, and was quantified. The mean magnitude of the SDE was 26.42% of mean total metabolism of post-absorptive birds. The magnitude of this SDE was independent of meal size and bird body mass. Assuming a 100% substitution, the presence of the SDE may afford bronze mannikins a maximum thermoregulatory energy saving of approximately 71.76 J g −1 over a 300-min period.

Oxygen Requirement and the Affecting Factors in the Baikal Seal Pusa sibirica

In 13 Baikal seals Pusa sibirica (the body mass of 11–73 kg) on the empty stomach and at free swimming in a reservoir, gas exchange parameters were studied. In 5 of these individuals, the gas exchange was assessed in satiated and hungry animals. The numerical correlations are presented between the oxygen requirement of these both groups of animals and their body mass. The data obtained show that the basal metabolism of seals corresponds to that of terrestrial mammals and in the seals with the body mass of 40 kg and more, the temperature of the lake habitat is close to thermoneutral. The specific dynamic effect of food (fish) in the seals in the thermoneutral zone is 22–93%.

Heat increment as affected by protein and amino acid nutrition

The activity of feeding and the metabolism caused by digestion and assimilation of food increase an animal's heat production. This increased heat production has been referred to as specific dynamic effect, specific dynamic action or heat increment (HI). HI is much larger when protein is a source of energy than when carbohydrate or fat are the sources of energy. HI for protein is much greater when the animal's ambient temperature is high than when it is low. Metabolisable energy is used more efficiently, thus having less HI, for maintenance than for production. A suggested explanation is that heat resulting from digestion and assimilation of food can substitute for the heat production in fasting when food provides energy equal to, or less than, maintenance requirements. When energy intake is large enough to support production, HI from anabolic processes becomes a waste product that cannot substitute for a fasting or maintenance function. The same rationale can be applied to the observation that dietary protein has a greater HI when an animal is at high temperatures. At low temperatures protein would be used for maintenance. At high temperatures the same amount of energy from protein would be enough to support production. As a result, HI of the protein would be increased at high temperatures. The high HI of protein or amino acids when at a high level in the diet can be at least partially explained. Protein synthesis requires a large amount of energy. Some energy is required to excrete nitrogenous waste. In addition, dietary protein stimulates protein turnover. Research findings have suggested that HI should be lowered by decreasing dietary protein. For non-ruminant animals this could be accomplished by discovering the essential amino acid requirements for an ideal protein. The ideal protein should result in a minimum HI. Research to date generally fails to document improved feed efficiency as a result of feeding an ideal protein.

Specific Dynamic Effect in the Horned Frog Ceratophrys cranwelli

Animals exhibit an increase in resting metabolic rate after feeding while they process the ingested food, a response that has been termed the specific dynamic effect. This postprandial rise in metabolism is due in part to the cost of processing absorbed nutrients, especially amino acids, and is particularly pronounced in animals such as large snakes that consume large prey on an infrequent basis. To increase our understanding of the specific dynamic effect in amphibians, we measured the metabolic rates of horned frogs, Ceratophrys cranwelli, before and after they consumed mice or an amino acid solution. After the frogs consumed mice at 20, 25, and 30 C, their oxygen consumption increased within 48 h to a peak that was twoto fivefold greater than the fasting level. The total energy expended depended on the mass of the mice consumed and was not significantly related to variation in frog mass or temperature. Of the energy ingested, 9-15% was expended during the processing of the food. These frogs were as efficient in processing a meal as other vertebrates. After the frogs consumed an amino acid solution, their excess postprandial energy expenditure was less than 25% of the value when they consumed mice of the equivalent amino acid composition. The cost of processing absorbed amino acids cannot be responsible for the majority of the specific dynamic effect in these frogs.

The interactive effects of feeding and exercise on oxygen consumption, swimming performance and protein usage in juvenile rainbow trout (Oncorhynchus mykiss)

The impacts of feeding on the rate of O2 consumption (O2), aerobic swimming performance, nitrogenous waste excretion (ammonia-N and urea-N) and protein utilization as an aerobic fuel were investigated in juvenile rainbow trout. Feeding trout to satiation (in groups of 120) resulted in rapid growth and elevated routine O2 by 68% relative to fasted fish and by 30% relative to trout fed a maintenance ration of 1% of body mass daily. This in-tank O2 of satiation-fed trout was approximately 70% of the O2max observed at the critical swimming speed (UCrit) when trials were performed on individual trout in swimming respirometers. Feeding increased O2 at all swimming speeds; the absolute elevation (specific dynamic action or SDA effect) was dependent on ration but independent of swimming velocity. There was no difference in O2max at UCrit amongst different ration treatments, but UCrit was significantly reduced by 15% in satiation-fed fish relative to fasted fish. These results suggest that the irreducible SDA load reduces swimming performance and that O2max is limited by the capacity to take up O2 at the gills and/or to deliver O2 through the circulatory system rather than by the capacity to consume O2 at the tissues. Ammonia-N and urea-N excretion increased with protein intake, resulting in a 6.5-fold elevation in absolute protein use and a fourfold elevation in percentage use of protein as an aerobic fuel for routine metabolism in satiation-fed trout (50-70%) relative to fasted fish (15%). Urea-N excretion increased greatly with swimming speed in all treatments, but remained a minor component of overall nitrogen excretion. However, even in satiation-fed fish, ammonia-N excretion remained constant as swimming speed increased, and protein did not become more important as a fuel source during exercise. These results suggest that the reliance on protein as a fuel is greatly dependent on feeding quantity (protein intake) and that protein is not a primary fuel for exercise as suggested by some previous studies.

Energy budget for postlarvae and juveniles of the malaysian prawn Macrobrachium rosenbergii De Man (Crustacea: Palaemonidae)

An experiment was conducted to determine the energy budget of postlarvae and juveniles of Macrobrachium rosenbergii fed with Bovilac Prawn and Purina Trout Chow. The specific dynamic effect was 4% and 7% greater for postlarvae and juveniles fed Purina. The values calculated for the scope for growth obtained for postlarval and juvenile prawns were 11.62% and 18.66% for organisms fed Purina Trout Chow (P < 0.05). Indicators of energetic substrate such as respiratory quotient, O:N atomic ratio and the rate of metabolic substrate, showed that the main substrates oxidized by the prawns were carbohydrates, followed by lipids and in less amount proteins. Since both prawn developmental stages used carbohydrates as the main substrate to meet their metabolic requirements, we can conclude that the highest percentage of proteins supplied by Purina Trout Chow was channelled into growth.

Effect of sleep and circadian cycle on sleep period energy expenditure.

Energy expenditure is lower during sleep than relaxed wakefulness. However, there is disagreement as to the particular metabolic changes that produce the difference. The present study assessed the contribution of sleep, circadian cycle, and the specific dynamic action effect of the evening meal to the sleep period fall in metabolic rate. Five subjects were tested for a total of nine nights under three conditions in a repeated-measures design. Subjects were confined to bed throughout their usual sleep period but were instructed to go to sleep 0, 3, or 6 h after their usual time for lights out. O2 consumption was measured in all conditions for the 0.5 h before and after each of the times for lights out and then throughout the sleep period after lights out. The results demonstrated that changes in energy expenditure during the sleep period are a function of both sleep and circadian cycle. In this study, the contribution of the two components was approximately equal. However, the effect of sleep was rapid asymptoting within 15 min of sleep onset, whereas that of circadian cycle was constant over the assessment period.

Heat transfer in subsonic high-temperature gas flow through three-dimensional curved channels

The heat transfer in subsonic high-temperature (T⋆ ∼ 2000°K) gas flow through a curved channel of rectangular cross section has been experimentally investigated. The local heat flow into the channel wall was measured by the modified gradient method, which consists in subdividing the walls by means of thin annular thermally-insulating partitions, measuring the temperature in the upper (gas) and lower (coolant) sections of the modules thus formed, and using these measurements to determine the local heat flux qw on the assumption that the thermal field in the module is homogeneous. The soundness of this method has been demonstrated theoretically and experimentally and the expediency of using it in the intensive wall cooling regime has been confirmed. The method is employed to find the local heat flux fields over the- entire surface of the channel. The integrated fluxes qw coincide to within 5% with the independently determined total increase in the enthalpy of the water in the cooling channels. A distinguishing feature of the investigation is the high relative curvature of the bend in the channel, which leads to the formation of a zone of intense separation on the convex (inner) wall. Three types of channel are examined. These differ with respect to the section beyond the bend which is either long or short or short with a contraction. A close correlation between the characteristics of the qw fields and the hydrodynamic effects is detected and explained. These effects comprise: separation and reattachment of the flow, secondary effects in the bend, the formation of an unclosed separation zone in the short outlet section, the localization of this zone when the outlet section includes a contraction, and specific gas dynamic effects near the intersection of the surfaces.

Physiological energetics of the intertidal sea anemone Anthopleura elegantissima

Energy budgets were calculated for individuals of the sea anemone Anthopleura elegantissima (Brandt), collected in 1981 and 1982 from Bodega Harbor, California, USA. Rates of ammonium excretion were measured in high-and low-intertidal, symbiotic and aposymbiotic sea anemones within 24 h of collection. Among symbiotic and aposymbiotic individuals, no differences in excretion rate were found on the basis of intertidal height. However, rates of ammonium excretion in aposymbiotic anemones (2.14 μmol NH + 4 g-1 h-1) were significantly higher than in symbiotic ones (0.288 μmol NH + 4 g-1 h-1). Rates of excretion were used with estimated rates of oxygen uptake to calculate nitrogen quotients (NQ). NQ and RQ values from the literature were used to calculate an oxyenthalpic equivalent [501 kJ (mol O2)-1 for R+U], and mass proportions of protein (54%), carbohydrate (44%) and lipid (2%) catabolized during routine metabolism in this species 24 h after feeding. Integrated energy budgets of these experimental anemones were calculated from data on ingestion, absorption and growth, and estimates of translocated energy from the symbiotic algae. Contribution of zooxanthellae to animal respiration based on translocation=90% and RQ=0.97 are 41 and 79% in high-and low-intertidal anemones, respectively. Calculated scope for growth is greater than directly measured growth in both high-and low-intertidal individuals. The deficit, estimated as 30% of assimilated energy in high-intertidal anemones, is attributed to unmeasured costs (specific dynamic effect) or production (mucus). Low-intertidal anemones lost mass during the experiment, implying that the magnitude of the deficit was greater in these anemones than in upper intertidal individuals. Anemones from both shore levels lost zooxanthellae during the experiment, which contributed to energy loss since the contribution of the zooxanthellae is greater in low-intertidal anemones. Scope for growth is preserved in high-intertidal anemones (29% of assimilated energy) because metabolic demands are lower due to aerial exposure, and prey capture rate is higher compared to lowshore anemones. Although possibly underestimated, lower scope for growth in low-shore anemones may result from continuous feeding and digestion processes that are less efficient than those of periodically feeding high-intertidal anemones.