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At least 739 records · Page 41Linked to original sources
PubMed2004

[Recovery of CO from an ammonia plant tail gas with pressure swing adsorption process].

Ammonia plant tail gas is an important CO source for C1 chemistry if an efficient separation/purification technology is available. Presented is pressure swing adsorption using a home made catalyst PU1 for recovery of CO from ammonia plant tail gas. A performance comparison of PU1 with a commercial zeolite was also presented. The pilot plant experiments were carried out in an intermission one-bed PSA unit with ammonia plant tail gas and a feed flow rate of 0.2-0.8 m3/h. The purity and recovery of CO was studied under various operating conditions. The operating conditions for the process were optimized and an optimum cyclic sequence of operation steps was proposed. A good performance of PU1 in the process was experimentally demonstrated. Product gas with a CO purity over 98% could be produced at a CO recovery of 75% for a feed gas CO concentration of 30% and gas pressure of 0.3 MPa.

Adsorption↗
PubMed2002

Enzymatic cleaning of inorganic ultrafiltration membranes fouled by whey proteins.

The aim of this work was to study the cleaning of inorganic membranes fouled with whey protein solutions using the enzymatic formulation Alcalase (Novo Nordisk A/S). Hydraulic and chemical methods were considered to characterize the cleanliness of the membranes. Cleaning efficiency was observed to be a function of the operating conditions. The operating conditions tested were the following: recycling versus non-recycling of permeate, pH of the cleaning solution, addition of alkali to regulate the pH, enzymatic agent concentration, and cleaning time. The best conditions to perform the cleaning were related to the best conditions to hydrolyze whey proteins in a discontinuous reactor using the same enzyme preparations. Very high cleaning efficiencies (>90%) were achieved in short operating times (20 min). However, residual matter was observed on the membrane surface.

Equipment Contamination↗
PubMed2002

Eye movement training and recording in alert macaque monkeys: 1. Operant visual conditioning; 2. Magnetic search coil and head restraint surgical implantation; 3. Calibration and recording.

PURPOSE: To describe current methodology used to: a) train alert adult macaque monkeys to perform visual fixation tasks, b) implant binocular magnetic scleral search coils and attach a head restraint, and c) precisely record their fixation and pursuit eye movements. METHODS: Animals are trained to sit in a primate chair and manipulate a lever. The animal turns on a laser spot (< 1 degree of arc) by pulling the lever. The spot dims after a variable, randomized period of time (luminance decrement 30-80%) and if the monkey releases the lever within 150-500 msec of dimming, a small bolus of juice is squirted via a servo into the monkey's mouth as a reward. The small size of the spot, the difficulty of detecting the dimming, and the short reaction time required for reward act in concert to assure attentive foveal fixation. After training, a search coil is implanted subconjunctivally in each eye and a polycarbonate head restraint device is attached to the skull. With the animal at the center of magnetic field coils, eye position is then calibrated precisely by requiring the animal to perform the dimming task at known positions of gaze. Fixation, vergence and pursuit eye movements are recorded by rewarding the animal for positioning the fovea of the eye within a small fixation 'window' encompassing the position of a stationary or moving target. A cover test of binocular eye alignment is performed by having the animal view through liquid crystal shutters that can be switched instantaneously from transparent to opaque. These methods have been used to train and to record eye movements in over 20 monkeys, and a representative sample of our experience in eight animals is reported in the Results. RESULTS: Normal monkeys, and monkeys who had strabismus or amblyopia, required an average of 53 days to learn to fixate steadily for a minimum of 5 sec with a dimming-detection performance of at least 75% correct. Implanted coils provided good signals for durations ranging from 4 months to longer than 3 years (average greater than 1 year) before signs of breakage or extrusion. Head restraints under daily use have lasted an average of 11 months (range 5 months to greater than 2 years) before spontaneous detachment. CONCLUSION: The training and surgical techniques described provide an efficient, straightforward method for recording precise binocular eye movements in awake monkeys.

Animals↗
PubMed1963

Free-operant avoidance conditioning in individual and paired human subjects.

Male, medical and graduate students were subjected to a non-discriminated avoidance regimen with shock-shock and response-shock intervals of 10 sec. Using a yoked-chair procedure it was found that acquisition of the button-pressing avoidance response was influenced by the social environment in which the conditioning occurred. There was a significantly greater number of "learners" among subjects conditioned individually than among those exposed to the conditioning procedures in the presence of a second person.

Avoidance Learning↗
PubMed2000

Enantioseparation of 1-phenyl-1-propanol by simulated moving bed under linear and nonlinear conditions.

Approximately optimum operating conditions needed to separate 1-phenyl-1-propanol (PP) enantiomers by simulated moving bed (SMB) were determined using the "safety margin" approach in the linear case and the "triangle theory" in the nonlinear case. Previous results showed the adsorption isotherm data to fit well to the competitive Langmuir model. This allowed the use of the triangle theory approach that applies straightforwardly to Langmuir systems. Experimentally, the operating conditions under nonlinear isotherm behavior were determined for a feed solution with a total concentration of 5 g/l. The purity of the products exceeded 98% for the raffinate and 95% for the extract. Failing to reach complete purity while the experimental conditions were chosen inside the separation zone is explained by the nonideality of the system used, which violates one of the triangle theory assumptions. The computed overall daily production rate was 11.6 g of racemic PP processed per day per kg of stationary phase, a result that compares favorably with previous ones.

Adsorption↗
PubMed2005

Conversion of food waste into hydrogen by thermophilic acidogenesis.

Conversion of food waste into hydrogen by thermophilic acidogenesis was investigated as a function of organic loading rate (OLR), hydraulic retention time (HRT) and pH in a continuous stirred tank reactor. In order to identify hydrogen-producing microorganisms, denaturing gradient gel electrophoresis (DGGE) of the polymerase chain reaction (PCR)--amplified V3 region of 16S rDNA analysis was conducted at each tested pH. The conversion of food waste into hydrogen was strongly influenced by the operational conditions. The hydrogen production was increased as OLR increased up to 8 gVSl(-1) d(-1), but drastically decreased at 10 gVSl(-1) d(-1). The yield of hydrogen was decreased from 2.2 to 1.0 mol-H2/mol-hexose consumed as HRT decreased from 5 to 2 days. More carbohydrates in the food waste were decomposed at longer HRT, 76-90%, at HRT of 2-5 days. The hydrogen production peaked at pH 5.5+/-0.1 and significantly decreased at pH 5.0+/-0.1. The biogas produced was composed of hydrogen and carbon dioxide, but no methane was detected at all tested conditions. The hydrogen contents in the gas produced were more than 55% (v/v) and not sensitive to all tested conditions. The optimum operational condition for continuous hydrogen production from the food waste was obtained at 8 gVSl(-1)d(-1), 5 days HRT and pH 5.5+/-0.1 where the hydrogen production rate, content, yield and the efficiency of carbohydrate decomposition were 1.01 H2/l-d, 60.5% (v/v), 2.2 mol-H2/mol-hexose consumed and 90%, respectively. The hydrogen production was related with the concentration of total organic acids (TOA) which was strongly dependent on that of butyrate indicating that the reaction was mainly butyrate fermentation. The hydrogen-producing microorganism of Thermoanaerobacterium thermosaccharolyticum that involved in acetate/butyrate fermentation, was detected with strong intensity at all tested pHs by denaturing gradient gel electrophoresis (DGGE) of the polymerase chain reaction (PCR)--amplified V3 region of 16S rDNA analysis and sensitive to the tested pHs. The experimental results indicated that effective hydrogen production from the food waste could be obtained continuously by thermophilic acidogenesis at proper operational condition.

Acids↗