Biological Water Treatment by a Hybrid Fluidized-Bed Bioreactor: Theoretical Study

A hybrid fluidized-bed bioreactor for water purification was proposed and analyzed. It is a novel type of bioreactor characterized by hitherto unknown stationary and dynamic features. Steady-state characteristics of this hybrid bioreactor with external liquid circulation are presented. A quantitative analysis of steady-state properties of the bioreactor was performed with the aid of an original mathematical model developed for a double-substrate aerobic microbiological process. A steady-state analysis of aerobic processes characterized by different oxygen demand was performed. The effect of essential parameters was evaluated, including carbonaceous substrate concentration in the feed stream to the apparatus, aeration intensity, total residence time of a liquid in the bioreactor, and height of the bed of fine carrier particles.     

Men, medicine and machines

PURPOSE: To examine the management and possible causes of primary valve malfunction of the Krupin eye valve with disk. METHODS: The authors reviewed the results of 113 patients undergoing implantation of the Krupin eye valve with disk and identified eight patients with primary valve malfunction requiring surgical revision. RESULTS: Valve revision involved manipulation (n = 1 case), explantation of the malfunctioning valve and implantation of a new valve (n = 2), and amputation of the valve (n = 5). Six of eight patients had final intraocular pressures of < 21 mmHg on one or no medications at a mean interval of 15.9 months (range 5-36) after surgical revision. Transient postoperative hypotony was noted in three patients and chronic hypotony with loss of light perception in one patient. One explanted valve was examined and found to have partially fused leaflets. CONCLUSIONS: Surgical revision in cases of primary valve malfunction of the Krupin eye valve with disk may be accomplished relatively safely with an acceptable level of postoperative complications. The etiology of primary valve malfunction may be related to the sterilization process and prolonged storage before implantation.     

Contacting modes and behaviour classification of gas—solid and other two-phase suspensions

An attempt is made to extend schemes for classifying the behaviour of gas—solid contacting modes and other two-phase systems. The regime diagram approach of Reh (1971) is modified and extended to cover the operating regions of common reactors and contactors where a gas flows upwards through a bed of solids including fixed and moving packed beds, conventional fluidized beds, circulating beds, spouted beds, and pneumatically conveyed suspensions. New boundaries are proposed between groups A and B and between groups B and D of the Geldart (1972, 1973) powder classification scheme. These boundaries reflect more recent data and allow the classification scheme to be used for gases other than air and for temperatures and pressures other than atmospheric.     

Solubilization and biochemical characterization of the melatonin deacetylase from Xenopus laevis retina

Melatonin deacetylase, an enzyme activity recently discovered in the Xenopus laevis retina, regulates local melatonin levels. The deacetylase occurs in retina, retinal pigment epithelium, and skin, all sites of melatonin action, and is widely distributed among vertebrates. We have solubilized the enzyme from Xenopus retina and pigment epithelium using nonionic detergents, and have developed a specific enzyme assay. We have characterized the enzyme and now report that the deacetylase is relatively specific for melatonin and is inhibited by the melatonin precursor N-acetylserotonin and the product of the deacetylase, 5-methoxytryptamine. Inhibition of deacetylase activity by eserine (physostigmine) suggests a relationship between deacetylase and cholinesterase activities. However, among a variety of cholinesterase inhibitors tested, only eserine inhibits the deacetylase. Furthermore, eserine is much less potent as an inhibitor of the deacetylase than the cholinesterases, and purified cholinesterases failed to deacetylate melatonin. We also show that melatonin deacetylase and aryl acylamidase (an enzyme related to cholinesterases) activities are differentially extractable from Xenopus ocular tissues, and that they exhibit different pH optima and inhibition profiles. Our results provide an initial characterization of the Xenopus retinal melatonin deacetylase, and indicate that deacetylase activity is distinct from cholinesterase and aryl acylamidase activities.     

Dye coupling between rat striatal neurons recorded in vivo: compartmental organization and modulation by dopamine

1. The presence of dye coupling between striatal neurons was investigated using in vivo intracellular recording and dye injection in adult rats. In 17% of the cases in which a single striatal neuron was injected with Lucifer yellow, more than one labeled neuron was recovered. In control rats, this dye coupling was observed only between single pairs of medium spiny neurons and only when the neuron injected exhibited the Type II response profile as defined by paired-pulse stimulation of corticostriatal afferents. 2. After intravenous administration of the D1/D2 agonist apomorphine at a behaviorally effective dose (i.e., 0.1-0.3 mg/kg), an increase in the incidence (from 17% to 82% of injected cells) and extent (from 2 cells to 3-7 cells labeled per injection) of dye coupling was observed. This effect was mediated by D2 receptor stimulation because administration of the D2 agonist quinpirole caused similar alterations in the incidence and extent of dye coupling (66% coupled). In contrast, administration of the D1 agonist SKF 38393 or the D1 antagonist SCH 23390 did not result in any significant alteration in dye coupling. 3. In control rats, the entire somatodendritic regions of dye-coupled neurons were found to be localized within single matrix compartments of the striatum. However, after intravenous administration of apomorphine or quinpirole, clusters of dye-coupled neurons were found to extend across the patch/matrix boundary. Moreover, dye coupling was observed after injecting cells exhibiting either the Type I or the Type II response profile. 4. In response to D2 receptor stimulation, both the extent and the pattern of coupling between striatal neurons is altered, resulting in direct coupling between neurons that are otherwise functionally and anatomically segregated in the control animal.     

Distributed channel assignment strategies using coexistenceetiquettes for land based radio environment

The performance of two distributed channel assignment algorithms which use coexistence etiquettes for point to point links are considered by the authors. It has been found that selecting channels prior to transmission at the transmitter as opposed to the receiver, supports greater offered traffic with the additional advantage of a less complex protocol     

Metabolism of lysophosphatidylcholine by swine platelets

Incubation of intact platelets from Sinclair(S-1) miniature swine with³²P-labeled lysophosphatidylcholine (lyso PC) indicated the presence of an active lysophospholipase with a pH optimum of 8.0 for hydrolysis of the substrate. However, lyso PC was incorporated into the membrane phosphatidylcholines by the acyltransferase pathway upon addition of ATP, Mg⁺⁺ and CoA to the platelet suspension. These results suggest that intact platelets are able to resist the cytotoxic effects of lyso PC in plasma, and the phospholipids in platelet membranes are not readily affected by the lipid environment of the plasma. The acyltransfer reaction apparently is saturated with endogenous free fatty acids since arachidonic acid added exogenously did not further enhance the incorporation activity. Neither the acyltransferase nor the lysophospholipase activity was affected by Ca⁺⁺, but divalent metal ions such as Zn⁺⁺ inhibited the lysophospholipase activity. Cholesterol but not cholesteryl esters elicited a biphasic effect on both enzymes, stimulating at low concentration but inhibiting at a cholesterol to lyso PC ratio greater than 1. Serum albumin inhibited the lysophospholipase but gave a small biphasic effect to the acyltransferase.     

Modelling and Simulation of Batch and Continuous Fluidized Bed Dryers

The performance of batch and continuous fluidized solids dryers has been modeled, with allowance for diffusional moisture transport in the dense phase particles and for interstitial gas-to-particle mass transfer within the dense phase, as well as for interphase exchange resistance between gas bubbles and the dense phase. Two types of boundary conditions are employed. Variations of the bed temperature and product moisture content in the bed with time are predicted numerically under various batch drying conditions. Exit product moisture contents, bed temperatures and outlet air humidities are also predicted for continuous drying at various mean residence times. The model can be used for homogeneous as well as bubbling fluidized bed drying. It can be used for a wide range of materials, including cereal grains and granular synthetic polymeric materials.