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We have developed a continuous theory for grinding of solids in batch and continuous mills which includes only a few parameters, the values of which can be obtained directly from data on a laboratory scale batch mill. This allows an easy scale-up from a laboratory-scale batch mill to an industrial continuous mill. Furthermore, the analysis presented indicates that a characteristic material parameter, the “ critical volume ”, plays an important role on the grinding process in general, and it is the only parameter which is affected by the additives. The performance of industrial mills is due to the influence that additives may have on the value of the critical volume.

We have developed a simple model to address the melting of corundum (Al2O3). For this simple model, a critical volume representative for the melting point was determined, and by employing the relat ...

Purpose: To incorporate the effects of repair into a model for normal tissue complication probability (NTCP) in the spinal cord. Methods and Materials: We used an existing model of NTCP for the spinal cord, based on a critical volume concept, into which we incorporated an incomplete repair (IR) scheme. Values for the repair half time were taken from existing experimental data. Repair corrections were expanded to account for the possibility of biphasic repair, namely the existence of long and short components of repair. Results: We found that the model predicts complete repair to occur at approximately 15 hours, consistent with experimental data. The dependence of the model on the value of the dose per fraction was also studied. It was found that there is a sparing effect as the dose per fraction is decreased below 2 Gy. Surface plots of the NTCP as a function of both the interfraction interval (IFI) and the dose per fraction were generated. We investigated “iso-NTCP” curves, which may allow freedom in choice of treatment plans in terms of the optimal IFI and dose per fraction. As for biphasic repair, as the relative weights of the long and short components of repair were varied, the NTCP changed as well. The model showed little difference between mono- and bi-exponential repair in the time to complete repair, due to a dominance of the long component at long IFIs. Conclusions: Incorporating IR into NTCP modeling of the spinal cord is consistent with current experimental data. The concept of iso-NTCP curves is an approach which may be clinically useful.

A recently introduced predictive scheme is used to calculate the permeability of various types of heterogeneous polymer blends, which are characterized by the ratio of the permeability of constituents in the range 10-10,000. The scheme combines a two-parameter equivalent box model and the data on the continuity of constituting phases acquired by modifying equations proposed by the percolation theory; it takes into account the permeability of components and the interval of phase duality (co-continuity) delimited by the critical volume fractions of components ν 1cr and ν 2cr The scheme can be used in two ways: (i) permeability of blends predicted by using the theoretical value of parameters ν 1cr = ν 2cr = 0.16 should be regarded as a first approximation which may not well approximate experimental data due to the fact that real ν 1cr and ν 2cr are affected by relative viscosities of the components, interfacial energy, conditions of blend mixing, phase structure coarsening, etc.; (ii) conversely, by fitting experimental data, it is possible to determine ν 1cr and ν 2cr for the studied system; thus the scheme can be alternatively viewed as an efficient tool for phase structure analysis of polymer blends.

Liquid–vapor critical-point properties of molecular liquids will first be contrasted with properties of fluid alkali metals. In the latter case, some insight into (limited) phase transitions can be gained from the one-component plasma model. This insight can be transferred to understand an empirical relation between critical temperature and critical volume for the alkalis, which is quite different from that characterizing molecular fluids. Attention will then be focused on “unconventional” critical points, with the dominant examples being (i) a “structural phase transformation” in C solely within the liquid state, between sp3 hybridization at high density and sp hydridization in the low-density liquid as suggested by Ferraz and March (1979), as is evidenced in the recent atomistic simulations of Glosli and Ree (1999) and (ii) a so-called plasma phase transition in fluid hydrogen. © 2000 John Wiley & Sons, Inc. Int J Quant Chem 80: 692–700, 2000

The transition of the structural and electronic properties of expanded Se due to its volume increase is investigated by the density functional method. It is shown that, when the volume is expanded to a critical volume, the fragmentation of Se chains occurs as a result of disruption of some bonds, which is accompanied by a discontinuous decrease of bond lengths. The breaking of some bonds triggers the reduction of the splitting between the bonding, σ , and anti-bonding, σ ∗ , states corresponding to broken bonds, which induces a discontinuous nonmetal-to-metal transition.

The equation proposed for non-associated liquids describes a new functional dependence of the sound velocity in these liquids on their physico-chemical characteristics (critical volume, surface tension, density and molecular mass). It is shown that this equation can be used for the adequate calculation of the sound velocity at different temperature.

We have developed an endoscopic instrument that will allow a surgeon to safely, dependably and accurately place intramuscular (IM) electrodes in the diaphragm. This instrument has been used to implant 28 IM electrodes in the diaphragms of eleven acute and four chronic dogs. All electrodes achieved full activation of the diaphragm muscle, producing tidal volumes up to 130% V/sub TCRIT/, the critical volume necessary for basal ventilatory support, with unilateral stimulation. The surgeon is able to control the angle of the IM electrode insertion needle, which enables the needle to approach the diaphragm at an angle that is parallel to the surface of the muscle. This insures good control over the depth of needle penetration into the muscle, which greatly reduces the risk of accidentally passing the needle through the diaphragm and entering the thorax. Endoscopic placement of IM electrodes into the diaphragm opens opportunities to provide cost effective negative pressure ventilation to patients who are unable to effect sufficient ventilation by central nervous system (CNS) control of respiration.

Ge nanocrystalline islands grown at 650°C on Si(001) are square-base pyramids bounded by {105} facets when they are small and transform to multifaceted, octagonal-base domes when they exceed a critical volume. This letter presents the first demonstration that the transition between the two island shapes is reversible, showing that the pyramids are stable, rather than kinetically limited transition structures. Alloying between a Ge island and the Si substrate during annealing at 650°C reduces the strain in an initially dome-shaped nanocrystal. Consequently, the island shape can change from a dome back to a pyramid, even though the island size increases substantially. Stress-enhanced diffusion of Si into Ge likely aids the unexpectedly rapid alloying.

Sturzstroms are giant landslides that travel kilometers within minutes. Data from terrestrial examples of 0.001–10 km3 suggest that their runout lengths increase in proportion to the square root of their volume. This trend is investigated assuming that runout is controlled by fragmental flow. The results indicate that runout lengths depend on the potential energy available for motion after initial collapse (itself a function of the dimensions of the collapse zone), on the degree of rock fragmentation, and on the rate of momentum loss by fragment collisions in a basal boundary layer, assumed to thicken with time by diffusion. A dependence on initial conditions during collapse would explain claims that a minimum volume is required for sturzstroms to form: Beneath a critical volume, insufficient energy is available to initiate fragmental flow, and so the unstable mass slumps downslope. The drop height (H) is often similar to the vertical extent of the collapse zone and so is linked by geometry to sturzstrom volume. The ratio of H to L (the horizontal distance of effective transport), normally interpreted as a measure of frictional resistance, is thus reinterpreted as an inverse measure of the energy available for runout after collapse. By providing a physical basis for observed trends, the analysis justifies use of empirical limits for forecasting the runout lengths of major landslides.

A predictive equation, based on the Stokes–Einstein equation, was developed for the determination of infinite-dilution molecular diffusion coefficients in supercritical and high-temperature liquid solvents ( T r ≥0.7). An extensive database on diffusion was collected through the literature in order to evaluate the proposed equation and to determine the accuracy of the predictions with no additional parameter adjustment. The predictions were good, with an average absolute deviation 8.2% for 113 binary systems and 1332 data points. The input data required for the correlations are the solute molecular weight, temperature and density, and the solvent basic properties (molecular weight, critical temperature and critical volume).

Formation and subsequent evolution of gas bubbles in blood and tissues of subjects exposed to decompression are casual processes in their nature. Such character of bubbling processes in a body predetermines probabilistic character of decompression sickness (DCS) incidence in divers, aviators and astronauts. Our original probabilistic theory of decompression safety is based on stochastic models of these processes and on the concept of critical volume of a free gas phase in body tissues. From positions of this theory, the probability of DCS incidence during single-stage decompressions and during hypobaric decompressions under EVA in particular, is defined by the distribution of possible values of nucleation efficiency in “pain” tissues and by its critical significance depended on the parameters of a concrete decompression. In the present study the following is shown: 1) the dimensionless index of critical nucleation efficiency for “pain” body tissues is a more adequate index of decompression stress in comparison with Tissue Ratio, TR; 2) a priory the decompression under EVA performed according to the Russian protocol is more safe than decompression under EVA performed in accordance with the U.S. protocol; 3) the Russian space suit operated at a higher pressure and having a higher “rigidity” induces a stronger inhibition of mechanisms of cavitation and gas bubbles formation in tissues of a subject located in it, and by that provides a more considerable reduction of the DCS risk during real EVA performance.

A new method is proposed in this paper to predict the critical pressures of hydrocarbon mixtures by reversely using the Riedel equation which is used for calculating vaporization heat. The parameters used in the calculation are boiling temperature, critical temperature, critical volume and vaporization heat of the pure substances. The reliability of the method is discussed on the basis of the results obtained by predicting the critical pressures of many binary hydrocarbon–hydrocarbon and hydrocarbon–non-hydrocarbon mixtures. The proposed method is rather simple and can be used for rapid estimation of the critical pressures of hydrocarbon mixtures.

Based on the free-volume-type diffusion model, new correlations are developed to estimate the tracer diffusion coefficients of liquid and solid solutes in supercritical solvents. The correlations are tested to predict various solute–solvent systems with good results. The input data required for the correlations are the solute molecular weight, temperature, density and the solvent basic properties (molecular weight, critical temperature, critical volume and critical pressure).

New correlations, based on the rough hard-sphere theory and an extensive literature database, were developed for the determination of the binary diffusion coefficients of liquid and solid solutes in supercritical solvents. The correlations were tested to predict 107 solute-solvent systems with good results. The input data required for the correlations are the solute molecular weight, temperature, density and the solvent basic properties (molecular weight, critical volume, and critical pressure).

Based on the hard-sphere theory and an extensive literature database, new correlations are developed to estimate the binary diffusion coefficients of liquid and solid solutes in supercritical solvents. The correlations can predict the behavior of the binary diffusion coefficients in a range of the reduced solvent density larger than 0.21, with an average absolute error of 7.8% for 107 systems and 1167 data points. The input data required for the correlations are the solute molecular weight, temperature, and density and the solvent basic properties (molecular weight, critical volume, and critical pressure).

A new method based on atomic and structural contributions is proposed for estimating the critical volumes of organic liquids. The proposed method gives more accurate values compared with the methods of Lydersen, Joback and Somayajulu, the average absolute deviations being 2.3%, 3.2%, 3.1.% and 2.7% respectively for these four methods when tested against the experimental data for 279 organic liquids. The methods of Ambrose and Fedors recommended by the API technical data book for hydrocarbons and the AIChE data prediction manual for non-hydrocarbons gave overall average deviations of the same order as those for the Lydersen et al. method. The proposed constants can also be used to calculate the volume of liquids at the normal boiling point, with accuracies better than or comparable to those of the existing methods.

The occurrence of harmful algal blooms has been increasing significantly around the world. In order to ensure the safety of drinking water, procedures to screen potential materials as effective algicides are needed, and predictive methods which save both the labor and time compared with traditional experimental approaches, are particularly desirable. In this study, data from previous studies on the algal-growth inhibitory action of two kinds of compounds, namely, the action of fatty acids and thiazolidinediones on the harmful algae Heterosigma akashiwo and Chattonella marina, were modeled using multiple linear regression (MLR) based on quantitative structure-activity relationships (QSAR). The models were shown to have highly predictive ability and stability, and provided insight into the inhibitory mechanisms of congeneric compounds. The main descriptors in the fatty-acid models were the Connolly accessible area and the number of rotatable bonds, illustrating that molecular surface area and shape are important in their algicidal actions. In the thiazolidinedione models, the critical volume, octanol-water partition coefficient (LogP), and Connolly solvent-excluded volume were found to be significant, indicating that hydrophobicity, substituent group size, and mode of action are mechanistically important. Our results showed the algicidal activity of a series of compounds on different algae could be modeled, and each model is efficacious for compounds that fall into the application domain of the QSAR model. This work demonstrates how reliable predictions of the algicidal activity of novel compounds and explanations of their inhibitory mechanisms can be obtained.

We report an experimental investigation of the fragmentation process of a heavy drop falling in a lighter miscible fluid. For fixed liquid composition and for different drop sizes, we observe that the fragmentation cascade stops after a few breakups, once each individual droplet has reduced below a critical volume for further splitting. Since each fragmentation is the outcome of a hydrodynamic instability, we expect fluctuations in the size of the fragmented droplets. The main experimental outcomes are the following: ~1! the first breakup time scales with the size separation from the critical volume in a universal way independent of the fluid composition; ~2! in the region intermediate between the first and the last fragmentation, the droplet sizes display multifractal properties, with the average dimension D0 decreasing to a minimum and then increasing again once diffusion prevails; and ~3! the droplet height scales with time with an exponent independent of the drop volume and composition. @S1063-651X~96!00607-1#

We study the class of collapsed Riemanniann-manifolds with bounded sectional curvature and diameter. Our main result asserts that there is a constant,δ(n, d)>0, such that if a compactn-manifold has bounded curvature,\(|K_{M^n } | \leqslant 1\), bounded diameter, diam (Mn)≤d and sufficiently small volume, Vol(Mn)≤δ(n, d), then it admits a mixed polarized F-structure. As a consequence, infg Vol(Mn,g)=0, where the infimum is taken over all metrics with\(|K_{(M^n ,g)} | \leqslant 1\). This assertion can be viewed as a weakened version of Gromov's “critical volume” conjecture.

Prediction of fast transient voltage-induced breakdown in quasi-homogeneous field geometries requires compounding the breakdown probability over time, while taking into account the field-dependent probability of electron detachment. In this paper, a breakdown probability model has been developed to predict the impulse breakdown under quasi-uniform fields, as this is the fundamental condition, the knowledge of which facilitates computation of breakdown probability under more complex conditions. The model will facilitate computation of breakdown probability under more complex conditions. It accounts for the effect of the streamer formation length on the critical volume and the probability of initial electron production by electron detachment from negative ions. The proposed model has been verified through comparison with the measured impulse breakdown probabilities. The predicted breakdown probabilities are in good agreement (/spl plusmn/10%) with those measured.

We study electromigration in copper lines encapsulated in an organosilicate glass. A line fails when a void near the upstream via grows to a critical volume. We calculate the void volume as a function of time. The statistical distribution of the critical volume (DCV) is taken to be independent of testing variables, such as line length and electric current density. By contrast, the distribution of the lifetime (DLT) strongly depends on these testing variables. We deduce the DCV from the experimentally measured DLT. Once deduced, the DCV can predict the DLT under untested conditions.

In the present paper, author will attempt to point out empirically that if alcohol is used in moderation up to a certain critical volume, then this will have a positive impact on human life expectancy, but beyond that critical volume life expectancy will be reduced. The sample covers all industrial world. Data are taken from OECD. The elaboration of these panel data is made feasible by means of the Eviews software package.

Experimental results and interpretations on time lags in pure SF6 at 1 bar are reported. Positive impulse voltages (1.2/50 μs and 6/5 000 μs) were applied to a quasi-homogeneous configuration: a 4 cm long sphere-plan gap. An ageing effect is observed: as the number of shots increases, the breakdown probability decreases and the time lags become longer. After a few hundreds of shots, a stabilization occurs. This effect is due mainly to some changes in the gas state and is fairly well reproducible. For a stabilized gas, the time lag distributions were recorded under different impulse shapes and voltage levels. The results are presented as Von Laue plots and interpreted in terms of the critical volume concept. Different sources of seeds must be supposed, namely direct electron production by cosmic rays or natural radioactivity and electron detachment from negative ions. To confirm this hypothesis, some additional experiments were made, as irradiating the cathode and/or applying a permanent drift.

In order to study the trade-off between improved lean combustion and reduced NO x emissions under a locally stratified charge mixture, this paper examines the effects of the rich mixture volume on combustion duration and the NO x emissions under the same total equivalence ratio in a combustion vessel. The rich methane-air mixture in a soap bubble was ignited at the center of the bubble by a pulsed YAG laser. As a result, it was found that the magnitude of the NO x emissions does not increase as the rich mixture volume increases up to a critical volume, but the combustion duration at that time shortens remarkably. The same tendency was also obtained by means of computer simulation using a 4-cylinder lean burn engine.

Geometric volume has been used for correlating ten molecular and thermodynamic properties of a particular category of halomethane refrigerants. The properties have been selected such that their conformity to certain specified norms qualify a compound as a good refrigerant. Based on the developed correlations, these properties have been predicted for the entire range of halomethanes belonging to the same category. A number of new halomethanes have emerged as potentially capable refrigerants. Existing refrigerants are mostly low geometric volume compounds. However, for some of the properties, namely, critical volume, critical density, density of saturated vapour pressure at boiling point and thermal conductivity, higher geometric volume compounds are as efficient as the lower volume members.

Previous studies have demonstrated that bone morphological properties are a significant determinant of orthopaedic fastener fixation strength. The authors previously tested a new design of unthreaded expandable fastener (UEF) prototype against screws and demonstrated a significant increase in pull-out strength. However the effect of bone morphology on the pull-out strength of the UEF and expandable fasteners in general is unknown. This study assessed the correlation between failure force and maximum force against five microstructural parameters. The failure force of the UEF was correlated to the trabecular bone volume fraction, as with screws. Unlike screws, however, the maximum force of the UEF has an inverse relationship with cortical volume. No correlation was found between failure force and the Structural Model Index (SMI). Additionally the critical volume of interest (VOI) for the UEF is around the bottom of the fastener where the expansion occurs, whereas for the screw a full height VOI is critical. Furthermore, we observed that screw mechanical performance may be affected more by bone morphological parameters that are associated with poorer quality bone. Therefore the UEF may perform better than screws in low quality osteoporotic bone.

Geological processes, such as burial, can lead to remagnetization in rocks due to neoformed magnetic minerals that have passed a critical volume, called blocking volume. In this study, we designed a heating experiment for claystones obtained from the Paris Basin (France), in the 50-130°C temperature range, in order to simulate 20 nm and ∼20 nm minerals respectively. This result led us to propose a conceptual model of nucleation-and-growth process of magnetite during low grade burial from ∼2 to ∼4 km depth. Ultrafine magnetite (≤20 nm) was predominant over single domain magnetite (>20 nm) for

Рассматривается проблема разрушения конструктивных систем при техногенных воздействиях. Приводится решение задачи определения размеров аварийной зоны, вызывающей лавинообразное разрушение систем. The problem of destruction of structural systems under man-caused impact is considered. The solution of the problem of dimensioning of a disaster zone, causing avalanching destruction of systems is given. Ивашенко Юлий Алексеевич, доктор технческих наук, профессор кафедры «Строительные конструкции и инженерные сооружения», Южно-Уральский государственный университет. Область научных интересов: теория расчета конструктивных систем из железобетона. Тел.: 8 (351) 2679373. IVASHENKO Yuliy Alexeevich is a Doctor of Science (Engineering), a professor of Building Constructions and Engineering Structures Department of South Ural State University. Research interests: calculation of armed concrete structural systems theory.Tel.:8 (351) 2679373.

International audience; Geological processes, such as burial, can lead to remagnetization in rocks due to neoformed magnetic minerals that have passed a critical volume, called blocking volume. In this study, we designed a heating experiment for claystones obtained from the Paris Basin (France), in the 50-130°C temperature range, in order to simulate 20 nm and ∼20 nm minerals respectively. This result led us to propose a conceptual model of nucleation-and-growth process of magnetite during low grade burial from ∼2 to ∼4 km depth. Ultrafine magnetite (≤20 nm) was predominant over single domain magnetite (>20 nm) for

Radiation induced normal tissue complication probability is calculated for three different organs: brain, liver and kidney. The model applied is a reliability model where the volume effect of the tissue is described by the structural parameter, k, which reflects the architecture of the functional subunits of the organ. The complication probability depends on k, the inactivation probability of the functional subunits (p) and the irradiated volume fraction (n). For partial, homogeneous irradiation of the brain, a k-value close to unity was found, and the respective values for liver and kidney were 0.92 and 0.77. An extension of the reliability model to account for individual inactivation probability of the subunits allows calculation of complication probability for inhomogeneous dose distributions. For the brain, intercomparison of a three-field and a two-field technique demonstrated a small reduction in complication probability for the former at low total doses. At high total doses a minimum complication probability was achieved applying a three-field technique, being three times less than that associated with the two-field technique.

Molecular discreteness is apparent in small-volume chemical systems, such as biological cells, leading to stochastic kinetics. Here we present a theoretical framework to understand the effects of discreteness on the steady state of a monostable chemical reaction network. We consider independent realizations of the same chemical system in compartments of different volumes. Rate equations ignore molecular discreteness and predict the same average steady-state concentrations in all compartments. However, our theory predicts that the average steady state of the system varies with volume: if a species is more abundant than another for large volumes, then the reverse occurs for volumes below a critical value, leading to a concentration inversion effect. The addition of extrinsic noise increases the size of the critical volume. We theoretically predict the critical volumes and verify, by exact stochastic simulations, that rate equations are qualitatively incorrect in sub-critical volumes. The kinetics of chemical reactions occurring within confined volumes is relevant to a range of systems, including biological cells. This study examines the kinetics of reaction networks, and finds that below a critical volume there may be pairs of species whose relative concentrations invert.

In situ acoustic emission monitoring is shown to capture the initiation of shear bands in metallic glasses. A model picture is inferred from stick-slip flow in granular media such that the origin of acoustic emission is attributed to a mechanism of structural dilatation. By employing a quantitative approach, the critical volume change associated with shear-band initiation in a metallic glass is estimated to be a few percent only. This result agrees with typical values of excess free volume found in the supercooled liquid regime near the glass transition temperature.

In order to optimize pedestrian signal cycle, queuing theory and probability theory were used to build delay model of pedestrian-vehicle system, and then put forward the calculation method of conversion coefficient of pedestrian crowd and vehicles. The delays of pedestrian and vehicle were calculated by equilibrium phase delay formula. The critical volume curves of pedestrian signal for pedestrian signal by comparing the delay with or without traffic signal, then obtained the minimum signal cycle and minimum green light time with the object of transportation efficiency. Finally, pedestrian signal cycle was optimized by constraints of minimum pedestrians crossing time and pedestrian maximum bearable waiting time.

International audience; In this article, artificial neural network group contribution (ANN-GC) method is applied to calculate and estimate critical properties including the critical pressure, temperature, and volume and acentric factors of pure compounds. About 1700 chemical compounds from various chemical families have been investigated to propose a comprehensive and predictive model. Using this dedicated model, we obtain satisfactory results quantified by the following absolute average deviations of the calculated and estimated properties from existing experimental values: 1.1 % for critical pressure, 0.9 % for critical temperature, 1.4 % for critical volume, and 3.7 % for acentric factor.

Hollow glass microspheres/epoxy foams of different densities were prepared by stir casting process in order to investigate their mechanical properties. The effect of hollow spheres content and wall thickness of the microspheres on the mechanical response of these foams is studied extensively through a series of quasi-static uni-axial compression tests performed at a constant strain rate of 0.001s-1. It is found that strength of these foams decreases linearly from 105MPa (for the pure resin) to 25MPa (for foam reinforced with 60vol.% hollow microspheres) with increase in hollow spheres content. However, foams prepared using hollow spheres with a higher density possess higher strength than those prepared with a lower one. The energy absorption capacity increases till a critical volume fraction (40vol.% of the hollow microspheres content) and then decreases. Failure and fracture of these materials occur through shear yielding of the matrix followed by axial splitting beyond a critical volume fraction. � 2011 Elsevier Ltd.

The theory of the double dilution method is shortly described. Critical volume of the liquid specimen has been determined. Optimal specimen concentration ratios of the sample in a given diluent have been examined. The validity and precision of the method have also been investigated. The usefulness of the method has been confirmed by analyzing a typical coin of Thailand. Good agreement with atomic absorption spectrometry (AAS) is obtained.

A continuum model of shape transitions in strained heteroepitaxial islands predicts that small islands are hut shaped, while larger islands are domed. The volume of a stable hut can exceed that of a stable dome, however, indicating that the stability of hut-shaped islands plays an important role in shape transition, in addition to energy changes associated with the transition. A hut-shaped island loses stability upon reaching a critical volume, which depends on the anisotropy in surface energy. Impingement between islands reduces the critical volume by nucleating new facets at the base of a hut, which subsequently trigger a shape transition.

In this chapter, we briefly review recent advances in modelling permeability behaviour of nanoplatelet-reinforced polymer nanocomposites, with a special focus on tortuosity-based models, aspect ratio-controlled percolation, and estimations of critical volume fractions and exponents. Also discussed is the influence of large-scale morphology and disorder of nano-additives in polymer nanocomposites on their physical properties.

We discuss a phase field model for the numerical simulation of contact angle hysteresis phenomena in wetting. The performance of the model is assessed by comparing its predictions with experimental data on the critical size of drops that can stick on a vertical glass plate.

A basic theory of nonspecific toxicity has been developed using bioconcentration as a basis and applying kinetic relationships developed in previous work. This approach has involved calculation of the critical volume fraction and critical concentration in lipid tissue of fish for a variety of organic compounds at the lethal level. Corrections to previous data sets for time period of exposure and inclusion of biodegradable compounds did not make a significant improvement in the values obtained. A new data base with compounds containing a wide range of Kow values gave results for critical volume and concentration similar to previous work. The influence of experimental procedures and methods for data development are considered. The basic theoretical derivation developed was found to provide a basis for predicting the approximate nonspecific toxicity of nondegradable lipophilic organic compounds at different exposure time periods. This requires a knowledge of the Kow value and the clearance rate constant (k2) which can be calculated from the Kow value.

An empirical method to predict critical volume fractions for conduction in conductor-filled polymers is presented, based on the idea that a conductive composite can be thought of as a conductive skeleton with its packing geometry determined by the char acteristics of the conductive filler alone. Trends in critical volume fractions can thus be predicted based on the packing behavior of the filler, provided that the filler is well dis persed in the polymer. Critical volume fractions are generally —0.05 below the specific packing fraction for a given filler. All specific rules governing powder packing in general can therefore be applied to conductive composites.

Extending the critical volume (separated phase) hypothesis in time integral form to repetitive decompressions, we show that reduced gradients following repetitive exposures are necessary in time, in any model, to maintain the separated nitrogen in tissue (bubbles) below a limit point. A realistic bubble model is then discussed, systematized, and applied to some marginal decompression profiles. The focus is permissible bubble excess, not dissolved gas per se, though reductions affect all compartments, fast and slow, requiring a systematic lowering of repetitive tensions. Deep repetitive and shallower multi-day exposures are impacted by the procedure. Within nucleation theory, deeper- than-first exposures are also treated. A set of exposure fractions, @x, accounting for micronuclei excitation and regeneration, reduced bubble elimination in repetitive activity and coupled effects on tissue tension is discussed, with @x representing a set of multiplicative factors (less than one) reducing critical parameters controlling exposures. These factors penalize repetitive activity between short time spans, deeper-than-previous and continuous multi-day activities,compared to standard algorithms using a fixed slow compartment. Within the approach, fast compartments, controlling deeper exposures, are impacted the most, but slow compartments are also affected.

Conference: 27th Spring Meeting on Fatigue and Plasticity Paris, FRANCE, 2008; International audience; This paper shows that fatigue strength of notched specimens under cyclic loading can be simply and accurately estimated by using elastic-plastic computations and averaging stress over a critical volume obtained by an optimisation process minimizing the dispersion between experiments and simulations. The Dang Van high cycle fatigue criterion is considered. Fatigue tests (tension-compression, bending and torsion) carried out by the Cetim, are used to calibrate the critical volume.