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At least 919 records · Page 51Linked to original sources
PubMed2005

Extraction of phenol in wastewater with annular centrifugal contactors.

Solvent extraction is an effective way to treat and recover the phenolic compounds from the high content phenolic wastewater at present. The experimental study on treating the wastewater containing phenol has been carried out with QH-1extractant (the amine mixture) and annular centrifugal contactors. The distribution ratio of phenol was 108.6 for QH-1-phenol system. The mass-transfer process of phenol for the system was mainly controlled by diffusion. When the flow ratio (aqueous/organic) was changed from 1/1 to 4/1, the rotor speed was changed from 2500 to 4000 r/min, and the total flow of two phases was changed from 20 to 70 mL/min, the mass-transfer efficiency E of the single-stage centrifugal contactor was more than 95%. When the flow ratio was changed from 4.4/1 to 4.9/1, the rotor speed was 3000 r/min, and the total flow of two phases was changed from 43.0 to 47.0 mL/min, the extraction rate rho of the three-stage cascade was more than 99%. When 15% NaOH was used for stripping of phenol in QH-1, the stripping efficiency of the three-stage cascade was also more than 99% under the experimental conditions.

Centrifugation↗
PubMed2005

Concentration by centrifugation for gas exchange EPR oximetry measurements with loop-gap resonators.

Measurement of the bimolecular collision rate between a spin label and oxygen is conveniently carried out using a gas permeable plastic sample tube of small diameter that fits a loop-gap resonator. It is often desirable to concentrate the sample by centrifugation in order to improve the signal-to-noise ratio (SNR), but the deformable nature of small plastic sample tubes presents technical problems. Solutions to these problems are described. Two geometries were considered: (i) a methylpentene polymer, TPX, from Mitsui Chemicals, at X-band and (ii) Teflon tubing with 0.075 mm wall thickness at Q-band. Sample holders were fabricated from Delrin that fit the Eppendorf microcentrifuge tubes and support the sample capillaries. For TPX, pressure of the sealant at the end of the sample tube against the Delrin sample holder provided an adequate seal. For Teflon, the holder permitted introduction of water around the tube in order to equalize pressures across the sealant during centrifugation. Typically, the SNR was improved by a factor of five to eight. Oxygen accessibility applications in site-directed spin labeling studies are discussed.

Centrifugation↗
PubMed2005

Purification, potency and immunogenicity analysis of Vero cell culture-derived rabies vaccine: a comparative study of single-step column chromatography and zonal centrifuge purification.

Continuous Vero cell lines are more suitable for large-scale production of rabies vaccine. The purification of Vero cell-derived rabies vaccine is critical because of the residual cellular DNA and serum proteins. The perfection of techniques using column chromatography with different matrix material, gel filtration and zonal centrifugation is of paramount importance for the optimal purification of rabies vaccine, leaving minimal residual cellular DNA, below the permissible level of 100 pg per dose and serum protein content of 1 ppm. In this study the potency, immunogenicity and safety of Vero cell-derived rabies vaccines were compared following purification by densely or loosely packed DEAE-sepharose CL-6B columns with different bed heights or by zonal centrifugation. The optimal virus recovery and maximum removal of substrate DNA and serum proteins were achieved only when the sepharose CL-6B column bed height was maintained at a thickness of 2-2.5 cm. The rabies virus material was purified by layering over the matrix without applying pressure. DEAE-sepharose CL-6B column purification using a simplified, cost effective technique as described in this study enhances the antigen yield by 50% in comparison with zonal purification.

Animals↗
PubMed2006

Reactivation and growth of non-culturable indicator bacteria in anaerobically digested biosolids after centrifuge dewatering.

Recent literature has reported that high concentrations of indicator bacteria such as fecal coliforms (FCs) were measured in anaerobically digested sludges immediately after dewatering even though low concentrations were measured prior to dewatering. This research hypothesized that the indicator bacteria can enter a non-culturable state during digestion, and are reactivated during centrifuge dewatering. Reactivation is defined as restoration of culturability. To examine this hypothesis, a quantitative polymerase chain reaction (qPCR) method was developed to enumerate Escherichia coli, a member of the FC group, during different phases of digestion and dewatering. For thermophilic digestion, the density of E. coli measured by qPCR could be five orders of magnitude greater than the density measured by standard culturing methods (SCMs), which is indicative of non-culturable bacteria. For mesophilic digestion, qPCR enumerated up to about one order of magnitude more E. coli than the SCMs. After centrifuge dewatering, the non-culturable organisms could be reactivated such that they are enumerated by SCMs, and the conditions in the cake allowed rapid growth of FCs and E. coli during cake storage.

Anaerobiosis↗
PubMed2003

Isolation of a caveolae-enriched fraction from rat lung by affinity partitioning and sucrose gradient centrifugation.

Caveolae were isolated from rat lungs by a combination of affinity partitioning and sucrose gradient centrifugation. After homogenization of the lungs directly in a polyethylene glycol-dextran two-phase system and conventional phase partitioning, the polyethylene glycol-rich top phase was affinity partitioned with fresh bottom phase containing dextran-linked wheat-germ agglutinin. The lectin selectively attracted plasma membranes to the bottom phase. The isolated plasma membrane fraction was treated with Triton X-100 or, alternatively, sonicated before centrifugation in a stepwise sucrose gradient. Caveolin-enriched material collected at the 5/24% sucrose boundary. This material also contained 5'-nucleotidase activity and actin. Electron microscopy showed the material to consist of a homogeneous population of 50- to 100-nm vesicles. This purification protocol should allow the facile purification of caveolae also from other tissues, facilitating structural and functional studies.

Actins↗
PubMed1992

Purification of mucin glycoproteins by density gradient centrifugation in cesium trifluoroacetate.

A procedure for the rapid isolation of mucin glycoprotein by density gradient centrifugation in cesium trifluoroacetate (CsTFA) is described. The separation of mixtures of rat tracheobronchial mucin, DNA, hyaluronic acid, and bovine serum albumin in CsTFA gradients was superior to that in cesium bromide gradients. Inclusion of guanidinium chloride or urea in the gradient had no influence on the separation obtained. The mucins isolated from sputum samples of cystic fibrosis patients by this procedure are largely free of nucleic acid, nonglycosylated proteins, and glycosaminoglycans. The results of the use of CsTFA gradient centrifugation for the isolation of mucin from extracts of bovine submaxillary gland are also presented. The CsTFA method is particularly suitable for the high-yield isolation of mucin from individual samples which are available in limited quantities.

Animals↗
PubMed1968

Transport phenomena in zonal centrifuge rotors. I. Velocity and shear-stress distributions of fluid during acceleration.

An analysis is presented for the evaluation of velocity components and shear-stress distributions of fluid in zonal centrifuge rotors during acceleration. Analytical expressions for the distribution of tangential and radial velocity components and the tangential shear-stress and the radial shear-stress distributions of fluid are obtained for the transient case. Characteristics of each distribution for a typical density gradient liquid in a zonal centrifuge rotor are computed from the relations derived, and are presented as figures. An unusual phenomenon-the tangential velocity of the gradient exceeding the velocity of the rotor during a particular period of acceleration-is demonstrated.

Centrifugation, Zonal↗
PubMed1969

Transport phenomena in zonal centrifuge rotors. II. A mathematical analysis of the areas of isodensity surfaces in reorienting gradient systems.

Zonal centrifuges may be loaded during rotation (dynamically) or at rest (statically). In the latter case, the shearing forces occurring in a liquid confined in a closed cylinder, during the transition from rest to a stable orientation in a high centrifugal force field, were examined qualitatively by evaluating the change of surfaces in each isodense layer. Analytical expressions for isodense surfaces at various levels were obtained as a function of the rotational speeds. Characteristics of the changes of each isodense layer were computed from the formula derived and are presented, in a graphical form, as figures. From these results, an optimal sample-loading location and an ideal control of acceleration or deceleration in a reorienting gradient rotor are concluded.

Centrifugation, Zonal↗
PubMed1976

Distribution of bacteria in the velocity gradient centrifuge.

Cells in different parts of the cell cycle can be separated by brief centrifugation in a density stabilized gradient: the Mitchison-Vincent technique. The position of a cell in the tube depends upon its size, shape, and density, upon the gradients of density, viscosity, and centrifugal force through which it sediments, and upon time. A program to compute the velocities and integrate the velocity profile for particles of a particular size class is presented. Because enteric bacteria are a form intermediate between right cylinders and prolate ellipsoids of revolution, the program uses values for the frictional coefficient intermediate between those calculated for ellipsoids and for cylinders. The formula f=6pietab(a/b)1/2 possesses this property and because of its simplicity greatly speeds the calculations. A second program computes the distribution of masses and then of sedimentation constants for a bacterial population, expressed either as a frequency distribution or as total mass per s-class. The effect of the known variation in cell size at division is included in these calculations, which apply to organisms undergoing balanced, asynchronous growth in which mass increase is proportional to cell size. The two programs in conjunction compute the mass or cell-number profile in an arbitrary gradient. The programs have been used to design gradients to maximize the resolution of the technique.

Bacterial Physiological Phenomena↗
PubMed1983

Separation of human X- and Y-bearing sperm using percoll density gradient centrifugation.

Human X- and Y-bearing sperm, which were detected by the quinacrine mustard fluorescent staining method, were separated in density gradient centrifugation using Percoll (Pharmacia Fine Chemicals, Uppsala, Sweden). The apparent percentages of Y-bearing sperm in normo- and oligospermia were 46.7% +/- 3.4% (n = 13) and 46.6% +/- 1.2% (n = 10), respectively. The separation was observed to some extent in Ficoll Paque (Pharmacia Fine Chemicals); then it was further achieved using Percoll. After centrifugation, sperm were distributed widely on various interfaces of the discontinuous Percoll density gradient (1.06 to 1.11 gm/ml). The content of Y-bearing sperm in the fraction lighter than 1.06 gm/ml was 73.1% +/- 3.3% and was reduced gradually along the density increment. Finally, it was found to be 27.4% +/- 3.4% in the sediment (more than 1.11 gm/ml).

Adult↗
PubMed1998

Preparation by differential gradient centrifugation is better than swim-up in selecting sperm with normal morphology (strict criteria).

OBJECTIVE: To evaluate two commonly used methods of sperm preparation with respect to their effects on sperm morphology (strict criteria). DESIGN: Auto-controlled, split sample study performed on the semen of 74 male partners of couples enrolled for IVF. SETTING: In vitro fertilization and andrology laboratories at a tertiary care, major teaching hospital. PATIENT(S): Seventy-four male partners of couples who were scheduled to undergo IVF. INTERVENTION(S): Equal halves of the same semen sample were evaluated for strict criteria sperm morphology before and after preparation by differential gradient centrifugation using Percoll (Pacific Andrology, Montrose, CA) and by the standard swim-up method. MAIN OUTCOME MEASURE(S): The percentage of morphologically normal sperm was assessed using strict criteria before and after the two methods of sperm preparation. Specific parameters studied were individual abnormalities of the head, midpiece, and tail. RESULT(S): Sperm preparation using differential gradient centrifugation with Percoll produced a significantly greater number of specimens with normal sperm morphology and also showed higher absolute quantitative improvement over the swim-up method. The two methods were comparable in regard to their effects on specific sperm abnormalities (i.e., head, midpiece, and tail defects). CONCLUSION(S): The differential gradient sperm separation method using Percoll is superior to the swim-up method for selecting sperm with normal morphology as assessed by strict criteria. Because sperm morphology as assessed by strict criteria is a good predictor of oocyte fertilization, this method can be recommended as the method of choice for assisted reproductive technology laboratories. Use of this method may help improve outcome by increasing fertilization rates.

Centrifugation, Density Gradient↗
PubMed1976

Separation of free and protein-bound ligands in the radioimmunoassay by gel filtration-centrifugation.

The application of gel filtration-centrifugation to the separation of free and protein-bound ligands in radioimmunoassay is described. The method is simple and rapid. A large number of samples can be handled simultaneously and the bount radioactivity is directly transferred to the scintillation vial. Using a 9 X 36 mm column of Sephadex G-50 (coarse), 400 mul of the reaction mixture can be separated during 2 min centrifugation.

Animals↗
PubMed1988

Preliminary applications of cross-axis synchronous flow-through coil planet centrifuge for large-scale preparative counter-current chromatography.

The cross-axis synchronous flow-through coil planet centrifuge with a 20-cm revolutional radius and a total capacity of 1600 ml was successfully applied to preparative counter-current chromatography of various biological samples, which include sea buckthorn extract, steroid reaction mixture, indole plant hormones, and dinitrophenylamino acids. The present system offers advantages of stable balance of the centrifuge, a large column capacity, and high resolution.

Amino Acids↗
PubMed1983

Rapid preparation and purification of alkaline phosphatase and 125I-labeled antibody by minicolumn gel centrifugation chromatography.

Gel centrifugation chromatography was used for the preparation, purification and concentration of enzyme and 125I-labeled antibody. Low-molecular-weight reactants were rapidly and efficiently removed from either 125I-labeled antibody or enzyme-antibody conjugates by centrifugation of the reaction mixture through a minicolumn of Sephadex. Further purification of both radiolabeled and enzyme labeled antibodies were possible by the application and elution of each labeled antibody through a minicolumn of Protein A Sepharose. Minicolumns were constructed from readily available inexpensive components and allowed the rapid preparation and purification of antibody of high specific enzyme, and radioactivity. No difference between the 125I, or enzyme labeled antibody detection limit could be detected by a direct solid-phase immunoassay.

Alkaline Phosphatase↗
PubMed1986

New angle rotor coil planet centrifuge for counter-current chromatography. I. Analysis of acceleration.

Simple mathematical analysis has been performed on a new type of synchronous planetary motion to elucidate the acceleration field. Using generalized formulae derived from the above analysis, distribution of the centrifugal force vectors produced by all types of the synchronous planetary motion is computed and expressed in the same format to facilitate comparative studies. The results of the above analysis predict high performance of the new angle rotor coil planet centrifuge in counter-current chromatography.

Centrifugation↗
PubMed1986

New angle rotor coil planet centrifuge for counter-current chromatography. II. Design of the apparatus and studies on phase retention and partition capability.

A new angle rotor coil planet centrifuge (psi = 25 degrees), which produces a Type J-L synchronous planetary motion, has been constructed to examine its capability in terms of stationary phase retention and solute partitioning. Studies on phase distribution diagrams obtained from various two-phase solvent systems indicated that the present system can be adapted to a wide variety of solvent systems by adjusting the centrifugal conditions. Excellent partition capability of the apparatus was successfully demonstrated in separations of dinitrophenyl amino acid samples with chloroform-acetic acid-0.1 N hydrochloric acid (2:2:1).

Amino Acids↗
PubMed1991

Cross-axis synchronous flow-through coil planet centrifuge (type XLL). II. Speculation on the hydrodynamic mechanism in stationary phase retention.

The hydrodynamic mechanism involved in the retention of stationary phase in the present x-axis coil planet centrifuge system is discussed. A statistical treatment of the retention data disclosed important clues such as the effect of the inward-outward elution mode, the close correlation between the planetary motion and the head-tail elution mode, and the superior retention capacity of the left-handed coils. The combined effects of the radial and lateral centrifugal force field derived from the mathematical analysis of acceleration acting on the coil provide an explanation for the phenomena.

Centrifugation↗
PubMed1999

Biomembrane-affinity centrifugal analyses of solute interactions with membrane proteins.

We have developed a rapid centrifugal method for analyzing solute interactions with membrane proteins in cytoskeleton-depleted membrane vesicles or proteoliposomes sterically immobilized in Superdex 200 gel beads. The size and density of the gel beads allow fast sedimentation in a bench-top centrifuge. Biospecific interactions of cytochalasin B and D-glucose with the human red cell glucose transporter, Glut1, were analyzed. The binding constants and the molar ratio of inhibitor sites per protein monomer agreed well with recent results obtained by frontal affinity chromatography.

Cell Membrane↗