Constant Energy Input Research Articles

Pulsed electric field treatment of Saccharomyces cerevisiae suspensions: A mechanistic approach coupling energy transfer, mass transfer and hydrodynamics

Pulsed electric field (PEF) treatment is a promising sterilization technique because of its nonthermal characteristics. It is well known that PEF applied at field values about 30 × 10 5 V m −1 promotes cell disruption, internal component leakage, and subsequent death. Classically, lethality is only related to electric and biological parameters. However, it is conceivable that hydrodynamic or process parameters are also involved. The goal of this work was therefore to understand the synergetic effects between electric energy transfer and hydrodynamics, based on trials carried out with a model biomass composed of Saccharomyces cerevisiae yeast treated in an experimental set-up. This work demonstrates that survival rates can be drastically decreased at constant electric energy input, by strong mixing between each pulse. Taking into account the cell permeabilization, leakage phenomena were considered through internal component diffusion and convection from the biologic cell to the surrounding medium. A new approach was therefore proposed in which the survival rate was associated with a modified Sherwood number. For the first time with PEF treatment, this approach integrated all kinds of parameters: biological (mainly through the cell radius), electrical (through the electric field and electrical resistance), and hydraulic (through the Reynolds number and number of recyclings). Finally, this study contributes to optimizing the specific energy consumption, making the PEF sterilization process more efficient.

Elimination of Carbon Monoxide in the Gas Streams by Dielectric Barrier Discharge Systems with Mn Catalyst

Elimination of CO in air stream using the plasma catalytic reactors was investigated. Two plasma catalytic systems were evaluated in this study, one consisting of a catalyst-bed packed in plasma zone of a dielectric barrier discharge (DBD) reactor directly (CID reactor), and the other (CAD reactor) consisting of a catalyst-bed after a DBD reactor. The examined operating parameters in this study included applied voltage, discharge power, the lengths of plasma zone and catalyst-bed, and inlet CO concentration. It was found that the glass packed DBD reactor without catalyst cannot eliminate CO in air stream effectively. When MnO x catalyst applied to DBD reactors, the removal of 1000 ppm CO can achieve to 97% by both type reactors. Under constant energy input condition, the CO removal of a CID reactor increased with the decrease of the initial CO concentration and the increase of the length of catalyst beds. In addition, the operating energy consumption of CID system was lower than that of CAD system.

Study of the Comminution Characteristics of Coal by Single Particle Breakage Test Device

ABSTRACT Single-particle breakage tests of South Blackwater and Ensham coal from the Bowen Basin area in Queensland were conducted by a computer-monitored twin-pendulum device to measure the energy utilization pattern of the breakage particles. Three particle sizes (−16.0 + 13.2 mm, −13.2 + 11.2 mm, −11.2 + 9.5 mm) of each coal were tested by a pendulum device at five input energy levels to measure the specific comminution energy. When particles were tested at constant input energy, the variation of comminution energy between the same size broken particles of Ensham coal was minimal, because Ensham coal is a softer and higher friability coal, which absorbs more input energy than harder coal during breakage tests. For different particle sizes, the specific comminution energy increases linearly with the input energy and the fineness of the breakage products increases with the specific comminution energy.The size distribution graphs are curved but approach linearity in the finer region. At a constant input energy, the twin pendulum breakage product results show that the fineness of the products increases with decrease in particle size and South Blackwater coal produced finer products than the Ensham coal. The t-curves are the family of size distribution curves, which can describe the product size distribution of the breakage particles during single-particle breakage tests.

Melting dynamics of finite clusters in dusty plasmas

The nonequilibrium melting dynamics of finite two-dimensional dust clusters is investigated experimentally. Nonequilibrium melting is induced by placing a single particle in the layer below the actual cluster which leads to unstable oscillations of the lower particle. The dynamic and thermodynamic properties during the two-step melting process have been investigated. Using the novel technique of singular value decomposition, the driving modes have been unambiguously related to the unstable oscillation. These modes are not accessible by normal mode analysis. Further it has been observed that angular melting occurred prior to the radial melting. Also, clusters with smaller number of particles revealed stronger heating than larger. This behavior is attributed to constant energy input by the unstable oscillation. Finally, clusters consisting of smaller particles are found to be more susceptible to fluctuations of the plasma parameters leading to a less pronounced two-step melting.

Vibration mill results in the light of stress intensity and number of stressing events

Vibration mills work with free moving grinding media as it is with stirred media mills. Investigations on stirred media mills showed that for constant energy input there is an optimum concerning fineness in dependence on specific energy exchange per stressing event. It is the aim of this paper to compare the knowledge about stirred media mills with vibration mill results. In comparison to stirred media mills it is possible to determine the absolute number of stressing events of the mill filling. So, the specific energy exchange of the total mill filling for one stressing event can be calculated from measured energy input. It is a means to decide whether energy input is not sufficient for comminution or whether energy input is too high, as results with stirred ball mills tell us. The results indicate that vibration mills work outside the energetic optimum.

Modelling the Control of Energy Partitioning During Sub-Maintenance Feeding in Cattle

In ruminants, the profile of nutrients available for absorption generally differ largely from that present in the ingested feed. The type and amount of feed nutrients absorbed can significantly affect the amount and composition of products. A simulation model was developed to examine the effect that a constant input of energy at four different levels had on the concentration of blood metabolites and the partition of energy in intermediary metabolism. In addition, the effect of changing the proportion of acetic acid and propionic acid on the energy expenditure for maintenance and heat production was examined.The model shows that during nutritional restriction tissues are differentially mobilized and that the greatest losses occur in the liver and small intestine. Also, model analysis indicate that the utilization of absorbed energy is unlikely to be affected by the proportion of absorbed volatile fatty acids (VFA).

Residence Time Optimization in Continuous Crystallizers

The production rate of a given crystallizer is defined, in part, by the residence time provided by the crystallizer vessel. Typically, this parameter is based on small-scale tests, which exaggerate the effects of secondary nucleation. Scale-up of crystallization equipment should allow for lower secondary nucleation, and this may, on occasion, allow for lower residence time than that used in pilot testing. In scale-up, the attrition rate decreases with the square of the vessel size increase, at constant specific energy input, and crystal−crystal contact is more dependent on crystal size, than crystal number. To determine the results of increasing production (lowering the crystal residence time), one needs to consider specific characteristics of the crystal shape, hardness, brittleness, sources of attrition, stresses on the crystal structure, supersaturation, and type of equipment in use. A reduction in residence time is not necessarily going to bring about poorer crystal quality.

Bulk flow velocities in the solar corona at solar maximum

We present velocity estimates of bulk motions seen in the solar corona by the Large Angle Spectrometric Coronagraph (LASCO) onboard the Solar and Heliospheric Observatory (SOHO) spacecraft. These estimates reflect the mass-weighted mean outflow of all coronal mass ejections (CMEs) seen during a 1-yr period on the approach to solar maximum. The particular period of interest spans 1999 March 6 to 2000 March 5 and velocities are compared with those obtained previously during an epoch of minimum activity. We use a correlation analysis and we address issues concerned with qualifying this method with regard to its possible limitations. Our method allows us to determine objectively velocity estimates at altitudes from 2 to 30 R⊙ at all latitudes. This represents an increased range over what was possible at solar minimum, and the high number of events has also allowed for much improved statistical accuracy in our estimates. At all latitudes we find outflow speed profiles that are similar in form to those seen in the equatorial region at solar minimum, although overall they are slightly faster. We do not see the large-scale latitudinal dependence of velocity evolution that was apparent at solar minimum and we associate this with the much reduced strength of the solar magnetic dipole relative to higher-order multipoles. We find that a typical kilogram of ejected plasma enters the C2 field at a speed of around 50 km s−1. The typical kilogram of plasma accelerates at a reasonably uniform rate of about 5 m s−2 and eventually reaches the edge of the C3 field with a velocity of ∼450 km s−1. To maintain this trajectory we find that the ejected plasma requires a remarkably constant input of energy, at a rate of around 2.2×106 W kg-1, throughout its entire evolution. In total, we find that a typical kilogram of plasma takes approximately 24 h to traverse the combined field of the LASCO white-light coronagraphs. This is somewhat slower than typically quoted CME speeds and highlights how the velocity associated with the leading edge of an event does not always accurately reflect the motion associated with the bulk of the mass of an event. We compare our velocity profiles with a basic model describing the expansion of an isothermal solar wind and find strong similarities in the flow speed. We suggest that at altitudes as low as 5 R⊙ in the corona the motion of the mass-dominant class of CMEs is governed by their immersion in the surrounding wind flow. We discuss the relaxing of the internal energy requirements of the CME phenomenon associated with their being carried through the lower corona by the solar wind and provide what we believe to be the most reasonably parametrized velocity profiles to be met by models of CME eruption.

The Effect of Gaseous Diluents on Ozone Generation from Oxygen

Ozone generation in a negative corona discharge has been experimentally investigated using both a pure oxygen and in binary mixtures of oxygen with several gases. The concentration of ozone (O3) in such mixtures is found to be dependent both on the input energy density η, dissipated in unit volume of gas mixture and on the type and the concentration of the additives. The experimentally measured dependencies of ozone concentration on the input energy density (O3) = f(η) have been fitted using the Vasiliev–Kobozev–Eremin formula and the specific rate coefficients for ozone formation Kf and ozone decomposition Kd have been calculated. Using Ar, N2 or CO2 as admixtures, an increase in the specific rate coefficient for ozone generation was observed for increasing concentrations of added gaseous impurity into oxygen. In contrast, admixtures with SF6 or CCl2F2 caused a substantial reduction of Kf values. The absolute values of ozone concentration at constant input energy density were observed to decrease with decreasing concentrations of oxygen in all mixtures.

Experimental investigations and modelling studies of ozone producing corona discharges

The ozone generation by negative corona discharge in coaxial cylindrical system of electrodes have been studied experimentally in Ar+O2 and N2+O2 mixtures. Both in argon and nitrogen mixtures with oxygen the monotonous decrease in ozone concentration [O3] was observed at decreasing oxygen content in mixtures and the constant input energy density η. The rate coefficients for the ozone generation and ozone decomposition were obtained by fitting experimentally measured data [O3]=f(η) with Vasiljev-Eremin formula. The calculated rate coefficient for ozone generation in N2+O2 mixtures at low content of oxygen (below 20%) was found considerably higher than that in Ar+O2 mixtures. Increase in the rate coefficients for ozone generation and decomposition was observed with decreasing content of oxygen in both mixtures. The experimental results are in qualitative agreement with the simple model incorporating five main chemical processes in mechanism of ozone generation.

H2S and NH3 Removal by Silent Discharge Plasma and Ozone Combo-System

Treatment of H2S and NH3 using the non-thermal plasma (NTP) methods was investigated. Two NTP systems were used in this study, one consisting of a multi-cell plate-to-wire reactor (PTW), and the other consisting of an ozonization chamber and the multi-cell PTW reactor. Each cell of the PTW reactor had a sheet of copper foil embedded in dielectric layers as its high voltage electrode and a wired rack as its gounded electrode. Use of the wired rack type electrode allowed large flow throughput, and promoted intense local electric fields. The experiments showed that under constant energy input, the decomposition efficiency of H2S or NH3 decreased with increasing initial concentration of the gas, and increased with increasing injected ozone and relative humidity. Injection of NH3 into H2S stream did not improve the H2S decomposition efficiency but was necessary for removal of sulfite-containing compounds in the discharge air.

Modeling of Electron Temperature in H- Ion Source

The equation of electron temperature is included in a two point numerical code for a high power hydrogen negative ion source. The calculated results of the electron temperature are in good agreement with Japan Atomic Energy Research Institute (JAERI)'s experimental results. The scaling law of electron temperature is estimated as a function of input power and gas pressure. Energy input by arc discharge, energy loss by ionization, dissociation and loss on the wall are considered in the electron energy equation. The leak width on the wall at the cusp magnet is also calculated numerically. Energy loss on the wall is dominant, and is larger than the ionization loss. In a similarly enlarged JAERI's Kamaboko source, electron density increases and electron temperature decreases under a constant energy input per unit volume. In this situation, H- extraction current increases despite the decrease in H- density because of the enlargement of the H- extraction area.

H [CSC]i[/CSC] Shells in the Large Magellanic Cloud

A recent high-resolution H I survey of the Large Magellanic Cloud (LMC) shows that the structure of the neutral atomic interstellar gas is dominated by numerous shells and holes, as well as complex filamentary and spiral-type structure. We present an up-to-date catalog of candidate H I supergiant and giant shells in the LMC. The candidates are visually selected from the H I data cube using selection and classification criteria that are described. Twenty-three supergiant shells, defined as those regions whose extent is much larger than the H I scale height, are cataloged; 103 giant shells (radii less than the scale height of the H I gas) are cataloged. We further classify the H I shells into five different types, based on the comparison of the H I with their associated Hα emission. For this purpose, we obtained new wide-field Hα images of the LMC with a CCD camera mounted on a 16 inch (0.41 m) telescope at Siding Spring Observatory. The pixel size of 20'' and the field of view of 12° are well matched to the H I survey. The size distribution of H I shells follows a crude power law, N(log R) ∝ R-1.5. For constant energy input to the H I shells and a constant shell creation rate, a shell luminosity spectrum of the form (L) ∝ L-β, where β = 1.75 ± 0.2, is obtained. This agrees well with the observed H II region luminosity spectrum for the LMC of Kennicut, Edgar, & Hodge, which has β = 1.75 ± 0.15. H I shells containing H II regions and OB associations seem to expand more rapidly than those without, providing direct evidence for substantial input of mechanical energy from regions of star formation.

Numerical investigation of 3D shock focusing effects on the basis of the Euler equation

In the present paper, we investigate the influence of the initial condition of a three-dimensional (3D) shock focusing problem on its solution. We search for an optimum combination of initial values to produce a maximum pressure amplification under the condition that the total energy input in the system is constant for each parameter combination. The flow problem consists of a spherical high-pressure gas volume, which is released at an initial time, t=0, within a cubical cavity with rigid walls. The developing shock wave is reflected on the walls and focuses in the centre of the cube, leading to a strong local increase of pressure and temperature. Optimum conditions can be found to reach a maximum amplification of pressure and temperature with constant energy input in the system. To investigate this flow problem, we use a Total Variational Diminishing-upwind method to solve the Euler equations of gas dynamics. The time integration is carried out explicitly by a multi-step method. The extension to three spatial dimensions is based on the Strang-type operator splitting. The implementation of the algorithm on a parallel computer (Fujitsu VPP-300/4) in the domain decomposition approach is discussed.

Stem water storage and diurnal patterns of water use in tropical forest canopy trees

Stem water storage capacity and diurnal patterns of water use were studied in five canopy trees of a seasonal tropical forest in Panama. Sap flow was measured simultaneously at the top and at the base of each tree using constant energy input thermal probes inserted in the sapwood. The daily stem storage capacity was calculated by comparing the diurnal patterns of basal and crown sap flow. The amount of water withdrawn from storage and subsequently replaced daily ranged from 4 kg d–1 in a 0·20‐m‐diameter individual of Cecropia longipes to 54 kg d–1 in a 1·02‐m‐diameter individual of Anacardium excelsum, representing 9–15% of the total daily water loss, respectively. Ficus insipida, Luehea seemannii and Spondias mombin had intermediate diurnal water storage capacities. Trees with greater storage capacity maintained maximum rates of transpiration for a substantially longer fraction of the day than trees with smaller water storage capacity. All five trees conformed to a common linear relationship between diurnal storage capacity and basal sapwood area, suggesting that this relationship was species‐independent and size‐specific for trees at the study site. According to this relationship there was an increment of 10 kg of diurnal water storage capacity for every 0·1 m2 increase in basal sapwood area. The diurnal withdrawal of water from, and refill of, internal stores was a dynamic process, tightly coupled to fluctuations in environmental conditions. The variations in basal and crown sap flow were more synchronized after 1100 h when internal reserves were mostly depleted. Stem water storage may partially compensate for increases in axial hydraulic resistance with tree size and thus play an important role in regulating the water status of leaves exposed to the large diurnal variations in evaporative demand that occur in the upper canopy of seasonal lowland tropical forests.

On the dynamics of mechanical milling in a vibratory mill

The dynamics of mechanical milling in a vibratory mill have been studied by means of mechanical vibration, shock measurements, computer simulation and microstructural evolution measurements. Two distinct modes of ball motion during milling, periodic and chaotic vibration, were observed. Mill operation in the regime of periodic vibration, in which each collision provides a constant energy input to milled powders, enabled a quantitative description of the effect of process parameters on system dynamics. An investigation of the effect of process parameters on microstructural development in an austenitic stainless steel showed that the impact force associated with collision events is an important process parameter for characterizing microstructural evolution.

Local fluctuations in a fluidized granular medium

Molecular dynamics simulations have been carried out on a two-dimensional model granular material made up of inelastically colliding discs subjected to gravity. The granular system is fluidized by a constant energy input from a vibrating base, and a stationary non-equilibrium state is achieved. Density and granular temperature profiles are determined; while the former goes through a maximum at intermediate altitudes, the latter exhibits a minimum at a higher altitude, beyond which the granular temperature is found to increase. Local density fluctuations are characterized by the time-displaced density autocorrelation function. Longitudinal compression (sound) waves propagating in the horizontal direction are found to be strongly damped, while they are overdamped in the vertical direction at the longest accessible wavelength.

Analysis of solid propellant combustion behavior under electrothermal plasma injection for ETC launchers

Enhanced burn rates of solid propellants through plasma erosion has been studied showing evidence of increased burn rate with injection of electrothermal plasmas into the propellant. These experiments are designed to evaluate the effectiveness of maximizing energy versus momentum transport, and the influence of geometry on the burn rates of the JA-2 solid granular propellant. A series of experiments has shown evidence of enhanced burn rate at pressures between 55 and 90 MPa (8,000 and 12,000 psi, respectively) over 400 ps pulse length. A 20 to 40% enhancement in the burn rates has been observed when plasma is injected parallel to the surface of the propellant. When plasma is injected normal to the surface, the burn rate increases by about a factor of three. A set of experiments has been designed to measure the burn rates when the electrothermal plasma is injected at various angles, from 0/spl deg/ to 90/spl deg/, to the surface of the propellant. Experiments were conducted at a constant input energy of 5 kJ/spl plusmn/2% to the electrothermal plasma source and constant base pressure of 15 Torr, which provides a 12,300 psi plasma pressure at the source exit close to the surface of the propellant. Results indicate increased burn rates with increased angle of injection. Optical emission spectroscopy measurements revealed a decrease in plasma temperature, at the plasma-propellant interface, with increased angle of injection.

An Analytical Model for Fluted Sunspots and a New Interpretation of Evershed Flow and X-Ray Anemones

view Abstract Citations (19) References (33) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS An Analytical Model for Fluted Sunspots and a New Interpretation of Evershed Flow and X-Ray Anemones Martens, Petrus C. H. ; Hurlburt, Neal E. ; Title, Alan M. ; Acton, Loren W. Abstract We present a force-free constant-α model for the magnetic field in and above so-called "fluted" sunspots. This model is motivated by recent high-resolution observations of Title et al. at the Swedish Solar Observatory in La Palma. They observed that the inclination angle of the magnetic field in the penumbra of sunspots oscillates rapidly with azimuth, with a period of about 60 and an amplitude of about 18°. They further find that there is little variation in the radial direction and in absolute field strength. The resulting phenomenon of interlocking high- and low-inclination field lines was called "flutedness. In our model, the parameters are chosen to reproduce the La Palma magnetograms, and an analytical expression is obtained for the three-dimensional magnetic field emanating from the sunspot's umbra and penumbra. The model correctly reproduces the azimuthal variation in inclination angle, as well as the mean constancy of the magnetic field strength, and the appearance of a highly corrugated neutral line on the limb side of off-center sunspots. We find that the "flutedness" results in a highly complex topology in a boundary layer extending from the photo sphere into the chromosphere, while the coronal field is uniform. Title et al. demonstrated that the Evershed flow occurs in regions of nearly horizontal magnetic field, and tacitly assumed, as is done in most of the literature, that the dark filaments in which the flow is observed form individual magnetic flux tubes. Our magnetic field solution suggests that the regions of nearly horizontal field at the photo spheric boundary may not form individual magnetic flux tubes, but rather a series of short horizontal loops bridging a neutral line that is stretched in the radial direction along the penumbra, up to the outer penumbral boundary. Hence, the Evershed flow could not be a simple siphon flow in the radial direction, but would consist of phase-coordinated flows along the many short loops bridging the neutral line. However, the assumption of a force-free field breaks down in this region of the atmosphere, and the topology suggested by it may not materialize in reality. We further demonstrate that there are large variations in the photospheric cross sections of coronal loops, due to the complexity of the field near their photospheric footpoints. Under the assumption of constant energy input per unit surface area into these loops, the variation in cross section is qualitatively consistent with the variation in X-ray brightness of loops in penumbral "anemones" observed by Yohkoh. Publication: The Astrophysical Journal Pub Date: May 1996 DOI: 10.1086/177251 Bibcode: 1996ApJ...463..372M Keywords: MAGNETOHYDRODYNAMICS: MHD; SUN: MAGNETIC FIELDS; SUN: X-RAYS; GAMMA RAYS; SUN: SUNSPOTS full text sources ADS |

A new science of health: salutology and the evolutionary perspective.

Traditional medical science is primarily concerned with pathological processes; with understanding disease, illness and sickness; and the causes and management of dysfunction. The starting point is a healthy organism, and medicine seeks to explicate departures from this state of harmony. Thus disease is usually conceptualized and classified in terms of the causes of pathological process—neoplasia, infection, trauma and so on. Yet, while this has proved a valid and fruitful viewpoint, the pathological perspective misrepresents the human situation in important respects. To the eye of an evolutionary biologist it is health, not disease, which requires explanation. The arrangements of matter associated with disease are much more probable than those associated with health— there are more ways of being dead than alive. Life and health require a high degree of adaptation and organization, and a constant input of energy. Health represents a triumph against the odds. The human organism is formed and develops by complex and fallible processes through a sequence of embryonic and fetal stages to a slowly maturing existence of relative autonomy and self-regulated homoeostasis, all the while being assaulted by endemic hazards, only to undergo eventual senescence, death and disintegration.