Continuous Steady State Research Articles

The direction of Wolf-Rayet stars in a very powerful far-infrared galaxy - Direct evidence for a starburst

Spectra covering the wavelength range 4476-7610 A are presented for the powerful far-infrared galaxy IRAS 01003-2238. The broad emission band centered at a rest wavelength of roughly 4660 A, and other broad weaker features are interpreted, as arising from the combined effect of approximately 100,000 late Wolf-Rayet stars of the WN subtype. This represents perhaps the most direct evidence to date for the presence of a large number of hot massive stars in the nucleus of a very powerful far-infrared galaxy. The high number of Wolf-Rayet stars in relation to the number of O-type stars may be interpreted as arguing against continuous steady state star formation in 01003-2238, in favor of a recent burst of star formation occurring approximately 100 million yrs ago.

The Influence of Acidosis on the Distribution of Lidocaine and Bupivacaine into the Myocardium and Brain of the Sheep

To test the hypothesis that acidosis can increase the toxicity of bupivacaine more than that of lidocaine by increasing the distribution into the brain, myocardium, or both, studies were performed to measure the in vivo tissue:blood partition coefficients during continuous steady state intravenous infusions of these agents in anesthetized sheep during normal acid-base status and during combined respiratory-metabolic acidosis. Acidosis decreased the partition coefficient of both agents into the myocardium and that of bupivacaine into the brain but did not systematically change that of either agent into skeletal muscle or fat. Total body and hepatic drug clearances were not affected systematically, but plasma binding of both agents was decreased. Thus predictions based on the pH partition hypothesis about the effects of acidosis on myocardial:blood partition coefficients being a basis for explaining the relative toxicity of these agents were not supported.

Line Width Narrowing with 14N Nuclear Quadrupole Resonance Lines at 296 K and 77 K Using a High Powered Pulsed Spectrometer

The dependence of the NQR line width on the RF pulse intensity and period using a continuous steady state pulse train for polycrystalline 14N compounds shows a dependence on the asymmetry parameter η, the temperature, and the crystal structure.

Continuous culture growth of photoautotrophic cell suspensions from Chenopodium rubrum

The construction and operation of a continuous culture system for the propagation of cell suspensions from Chenopodium rubrum under photoautotrophic conditions has been described. A dilution rate of 0.16/day gave an equilibrium culture density of 1,100,000 cells/ml and a mean doubling time of 150 hours. During continuous culture steady state conditions with respect to nutrient uptake, cell protein and chlorophyll content, starch accumulation, in vitro activities of enzymes related to different metabolic pathways could be established. Photosynthetic CO2 assimilation of steady state cells was about 100 mol CO2/mg chlorophyll x hour. Dark CO2 fixation was 3% of the light values.

A Model for Drying on Adiabatic Saturation Lines

A model is developed to simulate continuous steady state evaporation. The process is one that proceeds along adiabatic saturation curves. Aerodynamic effects of dryer air and circulation flow flux are combined with dryer temperature and humidity to compute evaporation rates. The calculation method requires several iteration loops and a computer program to do the work is described. Curves are presented of evaporation rates as affected by temperature, humidity, nozzle heat transfer efficiency and circulation flow quantity. Optimization of process cost and energy are discussed.

Radiosensitivity of Continuous Cultures: II. Continuous γ-Ray Exposure

Continuous cultures of diploid yeast were continuously exposed to60 Co γ-rays. It was found that even under continuous irradiation steady state could be maintained if the dose rate was sufficiently low. Critical dose rate levels depend on the chemostat turnover, i.e., the dilution rate. With higher dilution rates only lower dose rates can be tolerated. In any case, the tolerable dose rates were less than anticipated on the basis of assuming complete recovery from sublethal damage. It is suggested that under conditions of substrate limitation recovery may be reduced due to the shortage of essential nutrients.

Orthophosphate influx and efflux rates of Chlorella fusca measured in a continuous turbidostat culture with 32P under various conditions.

The main objective of the experiments with Chlorella fusca strain 211-8b was to measure, with adequate time resolution, the unidirectional influx rates of phosphate into non-phosphate-starved algae under different steady state conditions (light, temperature, 3-phosphoglycerate influence) or following the addition of several photosynthesis and phosphate transport inhibitors (phenylmercuric acetate, p-chloromercuribenzoate, arsenate). the algae were cultivated in a phosphate rich medium in a continuous turbidostat culture. The phosphate exchange experiments with carrier-free 32PO 4 3- were performed directly in the continuous culture. The sampling intervals after the tracer addition were 15 s. For a continuous steady state culture grown in the light (25° C) the unidirectional influx rate measured with 32P is 260 times higher than the net uptake rate (=influx minus efflux rate) calculated from the mass balance using the data of this culture. In all experiments, except the control experiment with trichloroacetic acid killed cells, the specific activity of the intracellular inorganic orthophosphate compartment oscillates around a constant mean value which never reaches the specific activity of the nutrient medium within the duration of the short-term experiments (7.5 min). The inhibitors strongly affect the characteristics of the oscillations. The unidirectional influx rates are constant. Oscillating flushing rates with unlabelled phosphate from a storage compartment have been postulates to explain the oscillations. Oscillating rates from the individual cells are apparently synchronized by an unknown mechanism.

Theory of T1 relaxation measurements in pure nuclear quadrupole resonance for spins / = 1

A quantitative analysis of the effect of spin lattice relaxation rates on pure quadrupole resonance pulse experiments for spins with I = 1 is given. A model is presented in which the three dimensional relaxation problem is reduced to a two dimensional one. In this model any possible population distribution of the energy levels corresponds to a point in a plane, the ``ν plane.'' The response of the system to spin-lattice relaxation effects and to rf pulses are described as translations of points in this plane. The experimental signal intensities are directly related to the coordinates of those points. The following cases are treated quantitatively: (i) CW saturation, (ii) CW saturation followed by a 90° pulse, (iii) two-pulse sequences, and (iv) continuous steady state pulse sequences. For each case explicit equations for the signal intensity as function of the experimental parameters are given. The analysis is made for both single crystals and powders.

Kinetics studies in a continuous steady state hollow fiber membrane enzyme reactor.

AbstractPorous hollow cellulose fibers have been used to separate a nonflowing enzyme solution of alkaline phosphatase from a continuous flow of substrate. The porosity of the hollow fiber membrane allows the substrate and product to diffuse freely through the membrane while restricting the permeation of the enzyme. The resulting “immobilized” enzyme system has been shown to behave as a continuous reactor—converting p‐nitrophenylphosphate to p‐nitrophenol. By varying the concentrations, flow rate, etc., either diffusion or enzyme kinetics can be studied. The continual influx of product and removal of substrate at steady state allows the study of kinetics of relatively short half‐life enzymes and unstable systems.

A model for continuous enzymatic saccharification of cellulose with simultaneous removal of glucose syrup

AbstractCellulase of Trichoderma viride was concentrated in various molecular cutoff membranes, and flux rates and retention of activity were studied under ultra‐filtration conditions. Little or no Cellulase was discharged through the membranes tested. The concentrated (5–8‐fold) enzymes were used to saccharify finely ground substrate (Solka Floe) in stirred tank (STR) and membrane reactors (MR). A pressure filtration vessel provided with a membrane for simultaneous removal of low molecular weight products (glucose) from the reacting system (Cellulose‐Cellulase) is designated as a membrane reactor. Continuous digestion of dense cellulose suspension in the membrane reactor was achieved. Using PM‐30 (Amicon) membrane reasonably high mass flux values (9.7–23.3 gals/ft2—day) were obtained in separating glucose from a digest of 30% cellulose suspension. Abcor membrane (HFA 300) was equally effective and necessitated less care in handling. Nearly 14% glucose concentration has been achieved in less than 50 hrs in STR by digesting a 30% cellulose suspension. Based on experimental data a model system is proposed for the continuous steady state Saccharification of ground substrate in which there is continuous removal of concentrated glucose syrup, and a feedback of enzyme.

Action of urea on the activity of dehydrogenases and alpha glucosidase in Aerobacter aerogenes grown in continous culture.

THE inhibition of enzymes by relatively high concentrations of urea and the protection afforded by various substances has been reported in some detail1. In particular Sachar and Sadoff2 have investigated the effect of glucose on the inactivation caused by 8 M urea on glucose dehydrogenase (EC 1.1.1.47 β-D-glucose : NAD(P) oxido-reductase) isolated from spores of Bacillus cereus. We have studied the action of urea on the activity of various dehydrogenases in intact cells of Aerobacter aerogenes grown in the chemostat. In this technique one of the constituents of the medium is kept in such short supply that the rate at which it is added controls the growth rate. If then the source of carbon is chosen as the limiting nutrient its protective action can be studied at low concentrations. Furthermore, in continuous culture true steady state levels of cellular properties are eventually obtained. The α-glucosidase (EC 3.2.1.20-α-D-glucoside glucohydrolase) activity has also been studied.

On the stability of flow-formed inter-faces, and a diffusion-gravity controlled enzyme-substrate reaction

A kind of “competitive diffusion” and the normal force of gravity can interact, leading to a microconvectional instability called “droplet sedimentation.” This type of phenomenon is demonstrated in an initially stably layered flow-system, and used to transport lysozyme rapidly into its physically separated substrate. In this manner a continuous steady state enzyme-substrate reaction is brought under the complete control of gravity and the diffusion coefficients of inert components of the system. If such a mechanism should play a role in any biological function, then in the “weightless” condition the function would be altered or removed.