bluuebunny/crossref_metadata_2025_split huggingface dataset:
Growth and threshold weaning weights among captive rhesus macaques
Authors: Bowman J. E. , Lee P. C. 
Published: August 2005

AbstractInterspecific analyses of infant growth and the time to maternal reconception (or weaning) demonstrate a consistent threshold for weaning weight at close to four times neonate weight, irrespective of the duration of lactation (Lee et al., [1991] J. Zool. Lond.225:99–114). Intraspecific variation in the attainment of a threshold weaning weight was determined in a sample of 31 captive infant rhesus macaques, where growth between birth and subsequent parturition was measured along with information on maternal size, weight, and social characteristics. A threshold weaning weight was found, with infants attaining approximately 1,335 g at the time of reconception. Birth weights of the infants were influenced by maternal physical and social variables in that larger mothers, and alpha ranking mothers, produced larger neonates. Postnatal growth rate, which determined the attainment of the threshold weight, was independent of maternal size or condition, but was influenced by offspring sex and the probability of reconception. Future reproductive status of mothers was specifically related to differences in patterns of growth among the infants. Mothers who conceived again at 30 weeks had infants who grew more slowly after the first 12 weeks of life, especially if these infants were sons. Mothers in this colony appeared to make decisions about the need to sustain their infants' growth in relation to their ability to invest in current offspring, which may compromise their subsequent reproduction. © 1995 Wiley‐Liss, Inc.
Faunal assemblage seriation of southern African Pliocene and Pleistocene fossil deposits
Authors: McKee Jeffrey K. , Thackeray J. Francis , Berger Lee R. 
Published: August 2005

AbstractFossil assemblages from the Pliocene and Pleistocene of southern Africa were seriated in order to give a better idea of their relative chronology. Time‐sensitive mammals were selected for calculation of the Faunal Resemblance Index among 17 site units. On the basis of a logistical seriation and subsequent site analysis, the following sequence of sites was deemed most probable: Makapansgat Member 3, Makapansgat Member 4, Taung Dart deposits, Sterkfontein Member 4 and Taung Hrdlička deposits, Sterkfontein Member 5 (in part) and Kromdraai B, Kromdraai A and Swartkrans Member 1, Swartkrans Member 2, Swartkrans Member 3, Plovers Lake, Cornelia, Elandsfontein Main Site, Cave of Hearths Acheulian levels, Florisbad and Equus Cave and Klasies River Mouth. © 1995 Wiley‐Liss, Inc.
Electrospray ionization suppression, a physical or a chemical phenomenon?
Authors: Beaudry Francis , Vachon Pascal 
Published: August 2005

AbstractMass spectrometry is a powerful qualitative and quantitative analytical technique that has been introduced in many bioanalytical and research laboratories in the last 10 years. The combination of HPLC with tandem MS yields a particularly powerful tool and it is now the method of choice for the analysis drugs, metabolites, biomarkers and proteins. However, HPLC‐MS methods are not completely without problems that can compromise the quality of the results. An important phenomenon that can affect the quantitative performance of a mass detector is ion suppression. In this study, we measured the influence of the observed current (I) vs signal intensity and the variation of the observed current (I) when analyzing biological samples. Our experiment suggests that, despite the fact that it is possible for other chemicals to compete for protons in the droplets, the increase in the observed current (I) during the signal suppression is important and indicates that the conductivity of the liquid increases significantly. The salts and the charged species influence the conductivity and the surface tension of the droplets and modify the equilibrium between the two main forces involved during the electrospray process, resulting in an erratic spray behavior. Copyright © 2005 John Wiley & Sons, Ltd.
Mass transfer area in different gas‐liquid reactors as a function of liquid properties
Authors: Sedelies Reinhold , Steiff Artur , Weinspach Paul‐Michael 
Published: August 2005

AbstractUsing pilot‐scale test plant, the interfacial area per unit volume was investigated in different gasliquid reactors, i.e. packed column, bubble column and free jet reactor. The interfacial area was studied as a function of liquid viscosity and of operating parameters. As a rule, identical test conditions were maintained in all the measurements, in order to obtain comparable results. The interfacial area was determined by chemical means using the sulphite system (a solution of sodium sulphite in water as model liquid and air as gaseous medium). The viscosity of the solution can be increased by adding carboxymethyl cellulose without significantly affecting the reaction kinetics. The addition of a surfactant to the sulphite system allowed comparative measurements at reduced surface tension. Based on a large number of measurements, the correlations of the interfacial area are expressed as power laws. The inclusion of experiments with a jet tube reactor and a stirring vessel allows an extensive comparison of all reactors. All tests were carried out with the same material system and the same method was used to determine the interfacial area per unit volume. Therefore, a comparison with respect to mass transfer is possible.
Liquid channelling on trays and its effect on plate efficiency
Authors: Stichlmair Johann , Ulbrich Siegmund 
Published: August 2005

AbstractAll the present experiments confirm that there is some liquid channelling on trays. Liquid channelling is extensive on trays of large diameters. It largely depends on the tilting of the plate, modifications of the inlet weirs and on non‐uniform bubble cap spacing. Consequences of liquid channelling for plate efficiency are clear; the higher the degree of liquid channelling the lower the plate efficiency. However, own experimental and theoretical investigations indicate that plate efficiency never falls below the value of point efficiency. Therefore, liquid channelling only affects the crossflow on trays. Liquid channelling reduces the mass transfer performance to a similar extent as does the backmixing of liquid. Consequently, plate efficiency is not very sensitive to liquid channelling. Since the liquid is completely mixed in the downcomer, the effects of liquid channelling are restricted to a single tray. The behaviour of tray columns completely differs from that of packed columns, where the effects of liquid channelling are cumulative over the packed height. Consequently, trays represent a suitable design for columns of large diameters.
Local energy dissipation in agitated turbulent fluids and its significance for the design of stirring equipment
Authors: Laufhütte Hans Dietrich , Mersmann Alfons 
Published: August 2005

AbstractIdeal flow conditions are generally assumed for the reactor design. If stoichiometry, reaction mechanism and kinetics are known, the balance equations for the ideal flow tube, the ideal steady‐state continuous stirred tank reactor or the ideal, completely mixed stirred batch reactor are often applied. In many cases, formal kinetics, which forms the basis of reaction modelling, is so uncertain that the idealization of the flow field can be accepted. In practice, however, deviations from the ideally calculated conversions, yields and product qualities, often occur. In these cases, it is necessary to consider the real flow conditions. In general, a distinction is made between macroand micromixing processes.
Advances in gas permeability measurements
Authors: Igwe Godwin J. I. , Allen Terence 
Published: August 2005

AbstractThe Carman‐Arnell equation relates the rate of flow of a fluid through a packed bed to the pressure drop across the bed. This equation is the basis for surface area determination by permeametry. It is found that the surface area measured at sub‐atmospheric pressure varies with the bed porosity, so a porosity was selected where the rate of change was at a minimum. The study suggests that, at reduced pressures, the gas flow rate is a linear function of the mean pressure.
Calculation of primary bubble volume in gravitational and centrifugal fields
Authors: Voit Harald , Zeppenfeld Rolf , Mersmann Alfons 
Published: August 2005

AbstractA one‐stage model of the formation of primary bubbles is presented in which the bubble volume is deduced from an equilibrium of buoyancy, viscosity, inertia and surface tension forces. In contrast to the two‐stage model, presented by Kumar and Kuloor, it was not assumed that the drag coefficient in bubble expansion can be described by the same constants as in the steady‐state bubble ascent. The constants were adapted in such a way that the introduction of an additional bubble volume was not necessary. It was demonstrated that this model describes the bubble formation in gravitational and centrifugal fields equally well and, furthermore, is also applicable to structurally viscous liquids, provided that the effective shear gradient

is calculated from the equilibrium of shearing and buoyancy forces. The model is based on the assumption of a constant volumetric flow rate during bubble formation and, for this reason, a minimum Froude number is necessary in analogy to the weeping limit for sieve plates. The normalized presentation permits simple operation. The possibility of applying the model to drop formation was confirmed by comparison of experimental values with those, predicted by the model.
Influence of electrolytes on the absorption of nitrogen oxide components N2O4 and N2O3 in aqueous absorbents
Authors: Weisweiler Werner , Deiß Karl‐Heinz 
Published: August 2005

AbstractThe influence of electrolytes, which are dissolved in the aqueous absorbent and do not react with nitrogen oxides, on the absorption kinetics of both these components was investigated experimentally. In addition to demineralized water, various salt solutions of different concentrations as well as sodium hydroxide solution were used as absorbents. The term H \documentclass{article}\pagestyle{empty}\begin{document}$ H\sqrt {k_1 D} $\end{document} for N2O4 and N2O3, which is important for the design of industrial absorbers, was determined as a function of composition and concentration of the absorbents. In the case of N2O4, the chosen measuring and evaluation methods permitted a separate determination of the rate constant k of the pseudo first order reaction and of the solubility H. The diffusion coefficient D of the gas in the absorbent can be obtained only by calculation. Experimental results showed that \documentclass{article}\pagestyle{empty}\begin{document}$(H\sqrt {k_1 D} )\,_{{\rm N}_{\rm 2} {\rm O}_{\rm 4} } $\end{document} decreases with increasing ionic strength I, however, without a clear indication of any ion‐specific effects. This decrease does not appear to be caused simply by a reduction in solubility (salting out effect), or in diffusion coefficient, but at least, to the same extent, through a decrease of the rate constant k with increasing electrolyte content in the absorbent. The measurements permitted the determination of the gas‐based salting out parameter for N2O4. The investigations on the absorption of N2O3 in water and in an Na2SO4 solution showed no experimentally detectable influence of dissolved salts on \documentclass{article}\pagestyle{empty}\begin{document}$(H\sqrt {k_1 D} )\,_{{\rm N}_{\rm 2} {\rm O}_{\rm 3} } $\end{document}. The numerical value of \documentclass{article}\pagestyle{empty}\begin{document}$(H\sqrt {k_1 D} )\,_{{\rm N}_{\rm 2} {\rm O}_{\rm 3} } $\end{document} is six times that of \documentclass{article}\pagestyle{empty}\begin{document}$(H\sqrt {k_1 D} )\,_{{\rm N}_{\rm 2} {\rm O}_{\rm 4} } $\end{document}.
New equipment for the determination of virial coefficients of pure substances and binary mixtures
Authors: Spiske Jürgen , Gaube Johann 
Published: August 2005

AbstractA new equipment for the measurement of virial coefficients of pure substances and binary mixtures is described. It consists of an improved modification of the set‐up proposed by Eucken and Meyer in 1929. The development is based on a critical review of the existing methods particularly with respect to adsorption effects. In order to reduce the influence of adsorption on the accuracy of virial coefficients, an optimum range for gas density is recommended. The accuracy of the virial coefficients is better than 20 cm3mol−1. The set‐up was employed for the measurement of virial coefficients of acetone and hexane in the range from 352.95 to 393.85 K. The results are in excellent agreement with data published in literature. Furthermore, cross‐virial coefficients of the binary system acetone/hexane were measured and interpreted.
Fluid dynamics and mass transfer in a bubble column with suspended particles
Authors: Sauer Thomas , Hempel Dietmar‐Christian 
Published: August 2005

AbstractSlurry bubble columns are widely used in biotechnology. Therefore, the effects of solid particles on fluidization characteristics, gas hold‐up and volumetric liquid‐side mass transfer coefficient were measured in a slurry bubble column (i.d. 0.14 m). The density and diameter of the suspended particles were similar to those applied in biotechnology with immobilized bacteria. Based on models of turbulence and of liquid circulation induced by rising gas bubbles, equations for critical gas velocity, gas hold‐up and volumetric liquid‐side mass transfer coefficient were obtained by dimensional analysis.
Investigation of entrainment in tray columns
Authors: Puppich Peter , Goedecke Ralf 
Published: August 2005

AbstractThis paper describes a pilot plant for entrainment measurements on various types of column trays. The data obtained from different trays differ by up to a factor of 10. The measurements were compared with the theoretical model of Stichlmair. The Stichlmair entrainment diagram permits a fairly accurate prediction for most types of trays if the height of the two‐phase layer is known. Prediction of the height and relative liquid hold‐up in this two‐phase system should be modified by a term reflecting the vapour flow profile, which requires further testing. These tests should examine the effect of tray spacing, fractional free area and, in particular, the influence of different media.
Heat transfer in boiling of multicomponent mixtures
Authors: Schmitt Dieter W. 
Published: August 2005

AbstractPool boiling data of multicomponent mixtures show that the heat transfer coefficients can be considerably lower than those of a corresponding pure fluid with the same physical properties as the mixture. The proposed model, which assumes maximum mass transfer resistance in the liquid boundary layer, is confirmed by the comparison between calculated and experimental data. The model allows the prediction of heat transfer coefficients in pool boiling of mixtures using only single component properties and vapour‐liquid equilibrium data. Judging by experience with a number of different systems, the method should be sufficiently accurate for most practical applications.
Pressure pulsations in the piping of reciprocating pumps
Authors: Vetter Gerhard , Schweinfurther Friedrich 
Published: August 2005

AbstractPressure pulsations in hydraulic systems, generated by reciprocating pumps, can cause serious problems with regard to plant safety and reliability. In particular, fatigue problems arise in high‐pressure piping systems. The available knowledge is not sufficient for an accurate computation of pressure peaks in the piping of reciprocating pumps. A number of calculation models are available which, however, neglect both fluid compressibility and friction. This contribution presents a calculation method which allows a precise modelling of various pump installations. Comparison of calculated and experimental data shows a good agreement and provides a validation of the computational model.
Influence of temperature and properties of solids on the size and growth of bubbles in gas fluidized beds
Authors: Hilligardt Klaus , Werther Joachim 
Published: August 2005

AbstractIn the present paper, models are developed for the description of coalescence and splitting of bubbles in gas fluidized beds. The distinction between slow and fast bubbles, which originates from the Davidson model of gas flow in and around a rising bubble, was found to be decisive for the modelling of coalescence processes. On the basis of the respective models, it is shown that a change in bed temperature does influence the mechanisms of both bubble coalescence and splitting. In cases of both slow and fast bubbles undergoing splitting, the theory predicts a decrease of bubble size with temperature whereas in the case of a non‐splitting system with fast bubbles, typically encountered with Geldart type B particles, no significant temperature effect on bubble size is expected. The theoretical predictions are shown to be in agreement with own measurements as well as with the results of other workers.
Particle velocity in a stratified two‐phase flow between inclined parallel plates
Authors: Meon Walter , Blass Eckhart 
Published: August 2005

AbstractFundamental investigations of coalescence processes in settlers with plate packages for the separation of liquid‐liquid dispersions prompted an analysis of the drop motion on the interface of a stratified two‐phase flow. Therefore, a physical model was developed, which permits the calculation of drop velocity along the interface of an inclined trickling film. Starting from a balance of forces around a single particle, the model provides the equation of motion for a steady motion of single particles in a stratified two‐phase flow. Several assumptions and considerations were necessary to solve this equation, such as taking into account the influence of the wall and of flow resistance. The model calculation assumes Newtonian liquids and laminar, smooth trickling films. A comparison with experimental results confirms that the drop motion behaviour is well reproduced.
Rheology and flow of phosphate slurries (mine tailings) in pipes
Authors: Fam Doudou , Dodds John , Scrivener Olivier 
Published: August 2005

AbstractAn experimental study of the flow of phosphate mine tailings was carried out in order to characterize these suspensions of fine particles for pipeline transport. Rheological measurements with a rotating cylinder viscometer indicate a viscoplastic behaviour which can be represented by a Herschell‐Bulkley or by a Casson model. The variation of the parameters of these models with solids concentration reveals a change in the behaviour at a concentration of 10 to 15%. The pressure drops were measured during flow in capillary tubes, in both laminar and turbulent regimes. The variation of the pressure drop coefficient (Fanning friction factor) as a function of the generalized Reynolds number confirms the validity of the employed rheological models. The results are in good agreement with measurements made in pipes of industrial size. The velocity profiles measured with a novel ultrasonic velocimeter demonstrate the influence of the rheological behaviour on the yield and wall stresses.
Dynamics of distillation with high product purities
Authors: Wozny Günter , Witt Werner , Jeromin Lutz 
Published: August 2005

AbstractFor the simulation of steady‐ and non‐steady‐state behaiour of separation columns, a simulation program was developed and employed for the calculation and optimization of methanol‐water separation. The demand for increasingly higher purities and energy‐saving optimization of plants results in complex column configurations and thus in complex control schemes. The number of possible control schemes was reduced on the basis of heuristic rules. By simulating the process, the optimum control and manipulative variables and measuring points were determined from the reduced number of control concepts. A control scheme was introduced. The model was verified by simulation of the dynamic behaviour of the process. The investigation included the effects of computing technique, time interval, model reduction and tray hold‐up on the results. Thus, various effects and interactions were verified theoretically with respect to the robustness of the model. This was followed by a simulation of the non‐ontrolled and controlled column. By implementing the controllers in the existing column program, the computer can predict the control parameters. These parameters were checked and corrected when the metahnol‐ater column was put in operation. In the start‐up phase, major problems were caused by the sensitivity and failure rate of density, throughput and pump measuring sensors. Feed impurities were another source of problems. Operation with high product purities is possible, with a side stream to discharge impurities.
Bubble flow in pressurized gas/solid fluidized beds
Authors: Schweinzer Jürgen , Molerus Otto 
Published: August 2005

AbstractThis contribution presents the measurements of bubble behaviour in presence of A, B and D powders in a semi‐industrial scale pressurized fluidized bed. Local measurements were taken at static pressures of 0.2, 1.0 and 2.5 MPa, using capacitance probes. Quartz sand with mean particle diameter of 157 μm was fluidized in small “two‐dimensional” transparent equipment with Frigen R 115. In addition, pressure fluctuations in the bulk of the fluidized bed with inner diameter of 0.4 m were studied experimentally.
Vapour‐liquid and vapour‐liquid‐liquid equilibria in ternary and quaternary systems of n‐hexadecane, benzene, water and hydrogen, at elevated temperatures and pressures
Authors: Dohrn Ralf , Brunner Gerd 
Published: August 2005

AbstractPhase equilibria in the n‐hexadecane‐water‐hydrogen and n‐hexadecane‐benzene‐water‐hydrogen systems were determined experimentally at temperatures between 200 and 350°C and pressures between 100 and 300 bar. At high water concentrations, three‐phase equilibria were observed. Two‐phase regions could be correlated with a modified Redlich‐Kwong equation of state. The influence of interaction parameters on the calculated miscibility gaps was investigated. On application of mean interaction parameters, it is possible to calculate phase equilibria at different pressures or temperatures with the same set of parameters. In the ternary system, the three‐phase regions could be calculated from the correlated binodal curves of two‐phase regions. In the quaternary system, cross‐sections through the vapour‐liquid miscibility gap could be successfully correlated.
Scale‐up of power consumption in agitated ball mills
Authors: Weit Herbert , Schwedes Jörg 
Published: August 2005

AbstractPrevious investigations have shown that the specific energy input is the overall parameter of influence on product size during communition in agitated ball mills, from laboratory up to industrial scale. The specific energy input is the introduced energy related to the amount of comminuted material. This parameter can be used for mill scale‐up. Consequently, a method had to be found of introducing power into the mill so as to obtain a given specific energy input. For this purpose, stirring tests with purely Newtonian liquids were carried out in absence of solids and hence, without comminution. Mathematical models are presented which describe the power consumption in agitated ball mills in absence of grinding beads. In addition, tests with grinding beads filling were also performed, leading to scale‐up guidelines with respect to power consumption. Finally, the influence of size and material of grinding beads was investigated.