Energy Liberation Research Articles

Rheological aspects of red blood cell aggregation

The rheological aspects of red blood cell aggregation include molecular phenomena, cell viscoelasticity, and bulk flow rheology. At the molecular level, rates at which bonds are formed and broken, the chemical energy liberation from bond formation, the elasticity of the cross-bridges and lateral mobility of cross-linking molecules must all be considered for a complete description of bond formation and distribution. Lateral migration of binding molecules occurs due to diffusion in the surface of the membrane but may also be influenced by the stresses in the membrane during separation of adhering cells. In red blood cell disaggregation, fluorescent probes have shown concentration of ligands in the region of contact close to the line of separation. The chemical potential decrement that occurs when a bond is formed provides the energy source that may deform red blood cells in the process of aggregation. The degree of aggregation and the extent of cell deformation depends on the viscoelastic properties of the cell as well as the dynamics of bond formation and repulsive potential of surface charges present, which is governed by an equation representing a balance of these energies. In flowing blood, the hydrodynamic forces applied by the plasma and surrounding cells must be added to the bond forces and elastic response of the cell. Under sufficiently strong aggregation, plug flow or large aggregates may result. At high shear rates, aggregation may be prevented due to the small contact time and high shear stresses so that no effects of aggregation may be observed. At intermediate shear stresses, transitory contact, adhesion and disaggregation may occur between neighboring cells. Such phenomena have not been analyzed in detail, but simplified models suggest that plug-like flow can occur due to hydrodynamic cell-cell interaction even when cells are not aggregated.

ヒト骨格筋の機械インピーダンス調節機構の解析

Mechanochemical constants (elastic coefficients of the series and parallel elastic components, heat constants and rate constants of energy liberation) were estimated in human thumb muscles (flexor pollicis longus and extensor pollicis longus muscles). These constants were determined by comparing model responses with measured force caused by stretching or shortening of the thumb, over the interval when the contractile force was maintained constant; the interval was from the onset of length perturbation to 47ms after that onset. Close agreement between measured responses and calculated model responses was obtained. Some of the estimated mechanochemical constants depended on the contractile force, and changes in the constants were almost the same in the flexor and extensor muscles. (1) Both series and parallel elastic coefficients increased almost linearly with the contractile force. (2) The heat constant and the rate constant of energy liberation were constant, not dependent on the contractile force. This implied that the viscous coefficient increased almost linearly with the contractile force. An experimental setup was devised to measure the mechanical characteristics around the distal joint of the thumb. The displacement of the thumb in response to the sudden change in load was smaller and of higher frequency, when both flexor and extensor muscles generated larger contractile forces. A mathematical model consisting of both flexor and extensor muscles was presented, based on the above-mentioned muscle properties. Computer simulation showed the same characteristics as the experimental ones.

Antifriction coatings on aluminum and its alloys formed by electric spark alloying from powder materials

The effectiveness of the method of ESA with powder materials for the reinforcement of aluminum and its alloys may be linked with several factors. First, powder particles introduced into the electrode gap (EG) initiate discharges at a greater distance between the electrodes, and increasing the EG brings about a redistribution of the discharge energy in the anode-EG-cathode system such that the proportion of energy liberated on the electrodes decreases, while that liberated in the EG increases [5]. Secondly, the presence of powder particles in the EG results in the formation of a multichannel electric discharge structure [6], which divides a single erosion crater into a multitude of small craters. With the simultaneous decrease in energy liberation on the electrodes, the powder particles entering the discharge channel experience comminution with rapid melting and evaporation pulses, so that material transport to the basis is effected in the vapor, liquid, and solid phases. Relief forms mainly with the participation of the liquid phase because solid-phase particles seldom attach themselves firmly to the cathode surface. An electron microscopical examination of the microrelief on an aluminum cathode revealed long streaks of molten powder material and spreading of the liquid phase over the surface (Fig. i). Under these conditions the erosion of both electrodes was considerably reduced, with the anode being practically unconsumed and the volume erosion of the cathode being much smaller than the volume of the coating-forming powder material transported onto it. The effectiveness of the process of ESA of aluminum and its alloys was assessed in rubbing tests on coatings. A study was made of the effect of composition of the powder mixtures on the structure, thickness, hardness, and wear resistance of coatings. In these tests copper,

Methodological errors in in-reactor temperature measurements

The requirement of increased reliability and economy of atomic power stations necessitates high accuracy of in-reactor measurements of the fuel-element temperatures. Thermoelectric converters are mainly used as the primary temperature converters for this purpose [i]. In most cases, they are positioned along the fuel-element axis, where the temperature gradients are least. Accordingly, there are longitudinal holes in the fuel element, into which the thermoelectric converter is introduced directly or as part of a thermometric assembly, where the converter is placed in a technological (protective) sleeve [2]. The changes in thermoemf observed over time suggest [3] that one cause of such changes, in addition to integral effects [i], may be the presence of methodological errors ATqv due to radiational energy liberation in the constructional materials of thermoelectric converters and the technological sleeve. Variation in the contact thermal resistance between the working junction of the converter and the fuel leads to oscillation of the methodological errors. Theoretical estimates of these oscillations do not ensure that the basic modifying factors are taken adequately into account: the initial deviation of the geometric dimensions of the constructional elements from the specification, the actual heattransfer conditions in the gas gaps, their variation on account of change in the geometric parameters of the elements under the action of the medium, the temperature, and radiation in the course of operation, and the thermophysical characteristics of the constructional materials in the given conditions. Thus, it is necessary to develop a theoretical-experimental method of finding the methodological error directly in the operating conditions of the thermoelectric converters, ensuring that the complex of factors determining the contact thermal resistance between the working junction and the object being studied is taken into account.

Variation in the normalized tetanic force of single frog muscle fibres.

1. The forces produced in maximal fixed-end tetani of single fibres isolated from the anterior tibialis muscle of the frog Rana temporaria have been measured at sarcomere lengths of 2.2 microns and temperatures near 0 and 10 degrees C. 2. When normalized by either cross-sectional area or dry weight per unit length at a sarcomere length of 2.2 microns, the forces vary over a twofold range. 3. The normalized force is not significantly correlated with the velocity of unloaded shortening or the twitch characteristics of the fibres. Lack of variability of these two quantities (together with histochemical evidence) suggest that only one fibre type is present in the experimental sample. 4. The steady rate of energy liberation (stable, heart rate) of the fibres during isometric tetani is positively correlated with the normalized force, indicating that extra ATP splitting is required to produce higher forces. 5. Fibres with a higher ratio of dry weight per unit length to cross-sectional area ('dry density') show a higher force when normalized by area, but not when normalized by dry weight per unit length. 6. Fibres with a more circular cross-sectional profile produce more force when normalized by either cross-sectional area or dry weight per unit length. The significance of this correlation is unclear. 7. The contribution of various sources to the total overall variation in normalized force is assessed. It is suggested that a diffusible substance or substances may be involved in modulating fibre force.

Testing of compton-emission type detectors of neutrons and of triaxial fission chambers in a pulsed reactor

Compton-emission type neutron detectors with an emitter containing hafnium or gadolinium and small triaxial fission chambers are promising detectors for monitoring the energy liberation in nuclear reactors. By contrast to the B-emission type neutron detectors which are widely employed in power reactors and have an emitter of rhodium, silver, or vanadium [1-3], the Compton-emission type neutron detectors with an emitter containing hafnium or gadolinium are almost without the inertia 14, 5] which is characteristic of fission detectors. Therefore the Compton-emission type neutron detectors and the fission chambers are preferably employed in automatic monitoring and controlling systems and in safety systems of reactors where the detectors must meet increased requirements in regard to fast response. A technology which is used in analogy in the manufacture of coaxial and triaxial cables with magnesia insulation is used in the manufacture of Compton emission type neutron detectors and fission chambers. We tested three Compton-emiss~on type neutron detectors in cable form with a hafniumcontaining emitter, three Compton-emission type neutron detectors of the same form with a gadolinium-containing emitter, and four triaxial small-scale KtV fission chambers [6]. In regard to their design, the Compton-emission type neutron detectors resembled the previously tested G-emission type neutron detectors with a silver emitter [7]. Measurements which were made during the manufacture of the Compton-emission type neutron detectors and during their operation in a research reactor have shown that the mean-square spread of the emitter diameters of these detectors and of their initial sensitivity amount to about 1.5%. The sensie tive element of the Compton-emission type neutron detector with the hafnium-containing emitter has an outer diameter of 3.0 m~n and a length of 0.83 m; the detector with the gadolinium-containing emitter has an outer diameter of 3.4 mm and a length of 0.85 m. Thedesign of the fission chambers hardly differs from that described in [8]. The characteristics of the small axial fission chambers with an outer diameter of 6.0 mm and one to two 50-mm-long sensitive elements were studied. In the case of two sensitive elements, the collecting electrode of one of them was without a fissile cover, i.e., it was used to monitor the dose rate of the y radiation. The gap between the collecting electrode and the housing of the fission chamber was about 0.7 mmwide. The operative volume of the chamber was filled with argon ofanalysis-type purity under a pressure of 0.101 MPa (760 mm Hg) at a temperature of 20~ The operating voltage applied to the electrodes of the triaxial chamber was changed from 200 to 300 V; this is much higher than in the operation and testing of the chambers in power reactors and research reactors [6]. The increased operating voltage results from the irradiation intensity which in the pulsed graphite reactor is higher than in the reactors indicated above. Magnesium oxide powder of analysis-type purity corresponding to GOST 452675 was the insulation of the Compton-emission type neutron detectors; magnesium oxide powder

A self-induced translation model of myosin head motion in contracting muscle. I. Force-velocity relation and energy liberation.

In our previous model, it was assumed that the two heads of myosin act co-operatively in producing force for the sliding of actin filaments relative to myosin filaments. We eliminate the assumption of co-operativity in the present model, following the conclusion by Harada and co-workers that a co-operative interaction between the two heads of myosin is not essential in producing actin filament movement. We assume that (1) a myosin head activated by ATP hydrolysis binds to the thin filament at a definite angle and does not do the power stroke, i.e. does not change its orientation during attachment, (2) a potential of force acting on the myosin head is induced around the thin filament when an ATP-activated myosin head binds to an actin molecule in the thin filament, and (3) the potential remains for a while after detachment of the myosin head and statistically controls the direction of thermal motion of the myosin head, so that the myosin head translates toward the Z-line as a statistical average. We did calculations on these assumptions with a mean tension approximation and got the following results. (a) The calculated force-velocity relation in muscle contraction is in fairly good agreement with experimental observation, including the give phenomenon that lengthening velocity becomes very large for a force about twice the isometric tension. (b) The calculated rate of energy liberation during muscle contraction as a function of load on muscle is in good agreement with experimental results. (c) The calculated distance over which a myosin molecule moves along the thin filament during one ATP hydrolysis can be more than 60 nm under unloaded conditions.

Heat transfer in triangular lattice with liquid-metal coolant in the case of variable energy liberation

1. The results of calculating the local heat-transfer characteriztics in a triangular lattice with liquid-metal coolant are given. Expanded bundles are considered, when 5·103≤Re≤5·106, Pr=0.005, 0≤K0≤400, h≥1.3. 2. Values of Nu∞ as a function of K0=(1/f) (∂f/dZ) have been obtained, where f(Z) is the distribution function of the energy liberation along the Z axis. The parameter K0 varies from 0 to 400. 3. Satisfactory agreement is seen between the present results and the data obtained elsewhere when K0=0. 4. The data obtained in [3] on the strong influence of nonuniformity of energy liberation on the Nusselt number have been confirmed. Thus, for expanded bundles with K0=400 and Re=1.5·106, the ratio of the asymptotic Nusselt number to the stabilized value when f=const is 28. 5. With increase in K0, the stabilization length of the Nusselt number decreases, and when K0=100 it is no more than 0.1R (Re=4.1·104). 6. The results obtained are convenient for use in calculating the heat transfer in steam generators with liquid-metal coolant in the case of a variable thermal load.

Microwave heating characteristics of selected minerals and compounds

Naturally occurring minerals and reagent-grade compounds were tested to determine their receptivity to microwave heating. The maximum temperature achieved for the samples and the time required to reach temperature are reported. A description of the microwave oven and a thermocouple technique that accurately measures and continuously records the temperature of samples during irradiation are reported. Extractive applications using the generated microwave data were investigated. Stress fracturing at mineral grain boundaries in a gangue matrix was shown. This should significantly affect grinding energy requirements and liberation properties. A method to produce a magnetic phase on pyrite surfaces, a method of using microwave heating to retort cinnabar concentrate, and a roast-leaching microwave treatment of chalcopyrite ore are described.

Basic parameters of a radionuclide thermoelectric generator

A one-dimensional model of an RTG is presented, allowing its basic parameters to be determined in terms of the characteristic values of the radius and specific energy liberation of the RTG.

Kinetics of energy liberation during thermal decomposition of nitrates in shock waves

Kinetics of energy liberation during thermal decomposition of nitrates in shock waves

A non-linear boundary value problem of ignition by radiation

Existence and non-existence conditions are obtained for stationary solutions in the model problem of laser macrokinetics which describes the heating of a semi-infinite sample by a spatially inhomogeneous beam of radiation with a power approximation of the energy liberation at the surface of the sample. The modes of localization and peaking of the heat field in the substance at the high-temperature stage of heating are examined.

The kinetics of heat production in response to active shortening in frog skeletal muscle.

1. Tension and heat production were measured at 0 degree C in sartorius muscles from Rana temporaria in response to two extents of shortening at five velocities. Shortening was from approximately 2.4 to 2.2 microns, 2.4 to 2.3 microns and 2.3 to 2.2 micron at velocities per half-sarcomere from 0.2 to 1.56 micron s-1. 2. Tension became approximately constant at all velocities. Records of heat rate obtained by differentiating traces from which thermoelastic heat had been subtracted became negative early in shortening and then rose. Heat rate became constant during shortening only at the lowest velocity and was still rising at the end of shortening at higher velocities. The highest heat rate occurred at the end of shortening at the two highest velocities. At the end of shortening at all velocities heat rate gradually approached the isometric level measured at the short length, the half-time for decline being largest following the slowest larger shortening. 3. Heat produced as a consequence of shortening but not associated with tension recovery was determined by subtracting shortening heat measured in response to two extents of shortening to the same muscle length. The differences in shortening heat continued to increase after shortening ended, and more of the extra heat produced in response to shortening appeared after the end of rapid shortening than during shortening itself. 4. Shortening heat coefficients calculated in different ways were similar to coefficients determined in previous studies. Coefficients calculated from measurements that excluded heat produced by tension recovery and allowed for continued production of heat by processes initiated by shortening were found to increase linearly with the force maintained during shortening. 5. The results show that the kinetics of heat production during and after shortening are very sensitive to the speed of shortening and that steady rates of energy liberation are not attained during shortening of less than or equal to 10% of muscle length at velocities greater than or equal to 12% of maximum velocity.

Muscle enthalpy production and its relationship to actomyosin ATPase.

During a maintained tetanus most of the energy liberated is produced by ATP hydrolysis at the cross-bridge. The energy produced by ATP hydrolysis by the sarcoplasmic reticulum is, however, a significant fraction (0.35) of the total. The energy liberation rate depends on a variety of factors (including the shortening velocity, sarcomere length, temperature, fiber type, and duration of contraction) and is, for the most part, consistent with current cross-bridge models. At the beginning of tetanic stimulation, a significant amount of heat (approximately 30 mJ/g) is produced by calcium binding reactions in the sarcoplasm. In the transition from an isometric to a shortening contraction, the cross-bridge cycling rate increases, and as much as 6 mJ/g of unexplained heat is produced. This unexplained heat appears to involve enthalpy changes accompanying a redistribution of cross-bridge intermediates, and it is reversed by high-energy phosphate splitting after the cessation of shortening. The mechanistic significance of these enthalpy changes remains to be elucidated.

Least-squares calculation of the contribution of fissile nuclides to the general energy liberation in irradiated nuclear fuel

The authors consider the possibility of estimating the contribution of each fissile nuclide to the total energy liberation on account of the difference in product yields in the burnup of different nuclides. The total number of nuclei of each fission product is determined by the relation between the numbers of fissions of /sup 235/U, /sup 239/Pu, /sup 241/Pu, and /sup 238/U and the yields of each fission product in the fission of these nuclei. Solving a system of several related equations by the least squares method results in a quantitative estimation of the energy spectra of each of the fissile nuclides. The sensitivity and accuracy of the equations are tested against measured data for three-year service of WWER-440 reactor fuel with the following fission products: Sr 89, Zr 92, 93, and 94, Mo 97, 98, and 100, Ba 138, La 139, Ce 140 and 142, and Nd 145, 146, 148, and 150.

Temperature dependence of the crossbridge cycle during unloaded shortening and maximum isometric tetanus in frog skeletal muscle.

The primary objective of this study was to determine if the rate limiting step in the crossbridge cycle was the same during maximum rate of shortening and during maintenance of maximum tension in an isometric contraction. To this end the temperature dependence, Q10, of the crossbridge cycle was estimated during unloaded shortening and maximum isometric tetanus. Isolated semitendinosus muscles from the frog were studied at 0 and 10 degrees C. Crossbridge cycling during unloaded shortening was determined from the velocity of unloaded shortening estimated by the slack step technique. Crossbridge cycling during maintained isometric tetanus was determined from the steady rate of energy liberation during the tetanus after allowance for energy liberation due to Ca2+ cycling. The Q10 of the velocity of unloaded shortening was 2.5 and that of the steady rate of energy liberation was 4.6. After correction for the temperature dependence of energy liberation associated with Ca2+ cycling (5.7), the estimated Q10 of the steady rate of energy liberation became 3.9. These estimates of the Q10 of the crossbridge cycle are significantly different. These results support the conclusion that the rate limiting steps during unloaded shortening and maximum isometric force maintenance occur at different steps in the crossbridge cycle. Further the high Q10 of the energy liberation due to Ca2+ cycling may relate to the high concentration of parvalbumin in frog muscle. A second objective of this study was to document in the same muscle the variation of Q10s of mechanical and energetic properties of contraction. Over this temperature range the Q10s ranged from 1.1 to 5.7.

Energetics and mechanics of frog skeletal muscle in hypotonic solution.

Hypotonic solutions are known to potentiate muscle force production and increase actomyosin ATPase activity in solution. As such, both the rate and amount of ATP hydrolysis should increase during contraction. This was tested indirectly by measuring force and energy liberation in Rana pipiens semitendinosus muscles at 0 degrees C in hypotonic solution. Force and the amount and rate of energy liberation increased. This increase is consistent with the interpretation that the rate of ATP hydrolysis is increased in hypotonic solution. Muscles, stretched to beyond myofilament overlap, liberate a substantial fraction of the energy liberated at maximal myofilament overlap. This energy liberation, the activation heat, is thought to reflect the energy utilized to cycle Ca2+. Hypotonic solution decreased the amplitude and the rate of the activation heat, suggesting that the amount and rate of Ca2+ cycled by the sarcoplasmic reticulum is reduced. Thus in hypotonic solution, force production and the rate of ATP hydrolysis by the cross bridges are potentiated despite an apparent decrease in Ca2+ cycling.

Estimating the impact safety of rocks from their energy liberation

In the present work, the authors attempt to use the acoustic-emission (AE) method of estimating the impact safety of rocks from their response to load. The AE method is based on the liberation of elastic energy with dynamic variation in the structure in a loaded sample. Rocks that are widespread in nature and distinguished by their mechanical properties and tendency to brittle failure are investigated. AE laws for marble and granite are investigated for uniaxial compression. A diagram of the measuring system used to record the AE is shown. In regard to the impact safety of rocks, the results allow the conclusions that with the increase in the energy which a material is able to accumulate in the course of deformation without microfailure the dynamic effects in the concluding stages of microfailure become larger, and that an increase in the proportion of elastic energy that is released on a large scale is accompanied by decrease in impact safety of the material.

Optical waves inside corundum particles in the spectral range of CO2-laser radiation

The authors present the results of calculating the optical field inside corundum particles in the wavelength range of a carbon dioxide laser (the IR region of the spectrum). The possibility of controlling the magnitude and position of the maximum of energy liberation in the particle as a result of slight change in wavelength is also shown. The authors' investigations of the spectral dependence of heat liberation in a particle show that when using corundum particles and a tunable carbon dioxide laser, the intensity and position of the heat-liberation maximum in the particles may be varied, achieving uniform heat liberation in the particle volume (wavelength = 9.6-9.8 ..mu..m) or predominant heating of the illuminated (wavelength = 10.0-11.2 ..mu..m) or dark (wavelength = 9.1-9.5 ..mu..m) hemispheres of the particles.

Calculation of the field of energy liberation in the RBMK-1000 reactor

Calculation of the field of energy liberation in the RBMK-1000 reactor