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At least 865 records · Page 48Linked to original sources

PubMed2005

Optimizing double emulsion process to decrease the burst release of protein from biodegradable polymer microspheres.

The process parameters such as the compositions of inner and outer aqueous phase and emulsification technique of the primary emulsion were optimized to decrease the burst release of BSA from biodegradable polymer microspheres in double emulsion method. It was found that diminished burst release of -14% was achieved for the microspheres produced by formulations, where no phosphate was present in the inner water phase (non-buffered system). Primary emulsion made by probe sonication rather than homogenization or mechanical stirring led to microspheres with insignificant burst effect. Microspheres obtained using 0.1% aqueous Tween 80 solution as the outer aqueous phase, frequently exhibit reduced burst effect of 2.7%. Low microsphere yield (52.1%), however, was observed. Microsphere yield was, therefore, enhanced by addition of additive such as sodium chloride, glucose or mannitol into the outer aqueous phase. Decrease in BSA entrapment was observed in the presence of sodium chloride, but reduction in entrapment efficiency was observed in the case of glucose. Burst release increased from 2.7% to 9.5% or 3.4% as 2.5% sodium chloride or 7.5% glucose was added into the outer aqueous phase respectively. Marked burst release (>20%) was observed in the presence of additive of higher concentration independent of sodium chloride or glucose. As far as surfactant type was concerned, diminished burst was found when PVP or Tween 80 rather than PVA was utilized as the surfactant during microsphere preparation. In addition to PLGA, the copolymers of L-lactide (LLA) and dimethyl trimethylene carbonate (DTC) or trimethylene carbonate (TMC) were also evaluated. Insignificant burst effect was found for the microspheres composed of DTC or TMC copolymers.

Animals↗

PubMed2005

Optimization of Fenton process for the treatment of landfill leachate.

The treatment of landfill leachate by Fenton process was carried out in a batch reactor. The effect of operating conditions such as reaction time, pH, H2O2 to Fe(II) molar ratio, Fenton's reagent dosage, initial COD strength, feeding mode, the type of polymer, and temperature on the efficacy of Fenton process was investigated. It is demonstrated that Fenton's reagent can effectively degrade leachate organics. Fenton process was so fast that it was complete in 30 min. The oxidation of organic materials in the leachate was pH dependent and the optimal pH was 2.5. The favorable H2O2 to Fe(II) molar ratio was 1.5, and organic removal increased as dosage increased at the favorable H2O2 to Fe(II) molar ratio. The efficacy of Fenton process was improved by adding Fenton's reagent in multiple steps than that in a single step. Furthermore, the stepwise addition of both hydrogen peroxide and ferrous iron was more effective than that of hydrogen peroxide only. Sludge settling characteristics were much improved with the addition of the proper polymer. Temperature gave a positive effect on organic removal.

Environmental Pollutants↗

PubMed2003

Information processing and movement optimization during development: kinematics of cyclical pointing in 5- to 11-year-old children.

The authors studied the development of movement control in speed-accuracy tradeoff conditions in children aged 5-11 years and in adults performing cyclical pointings. Twelve difficulty levels (IDs), ranging from 2 to 6.58 bits, were defined (P. M. Fitts, 1954). Peak and time to peak velocity, acceleration, and deceleration, and acceleration profiles as a function of hand position (Hooke's portraits) were analyzed. Movement time decreased with age and was less affected by ID. Peak velocity and acceleration increased, acceleration and deceleration were decreasingly time consuming, and movement profiles turned to increased harmonicity with age and task easiness. Nevertheless, the developmental trends differed between parameters. Gain in velocity seemed chiefly dependent on improved muscular cooperation patterns before 7 years of age and on improved information processing from age 7 onward; achievement of an optimized strategy in the speed-accuracy tradeoff occurred at age 11 years.

Acceleration↗

PubMed2005

A post-processing method for optimizing synthesis strategy for oligonucleotide microarrays.

The broad applicability of gene expression profiling to genomic analyses has generated huge demand for mass production of microarrays and hence for improving the cost effectiveness of microarray fabrication. We developed a post-processing method for deriving a good synthesis strategy. In this paper, we assessed all the known efficient methods and our post-processing method for reducing the number of synthesis cycles for manufacturing a DNA-chip of a given set of oligos. Our experimental results on both simulated and 52 real datasets show that no single method consistently gives the best synthesis strategy, and post-processing an existing strategy is necessary as it often reduces the number of synthesis cycles further.

Algorithms↗

PubMed2003

Scale-up and optimization of an evaporative drying process applied to aqueous dispersions of solid lipid nanoparticles.

An apparatus to dry aqueous dispersions of solid lipid nanoparticles (SLNs) was designed. Optimal running conditions were evaluated to obtain minimum process time and produce dried SLNs characterized by small size variation. To achieve process optimization, SLN average diameter, SLNs polydispersity index, and drying time were related to three operative variables: process temperature, SLN concentration in the original aqueous dispersions, and nitrogen flow rate as the physical means of the drying process. An experimental design procedure and a multicriteria optimization method, targeting desirability functions, enabled us to obtain the optimal conditions for all responses. Drying time, average diameter, and polydispersity index of dried SLN batches were more favorable than those obtained by freeze-drying identical SLN aqueous dispersions with the same initial nanoparticle concentration.

Freeze Drying↗

PubMed2002

Thalamocortical [correction of Thalamcortical] optimization of tactile processing according to behavioral state.

We propose a conceptual model that describes the operation of the main thalamocortical loop of the rat somatosensory system. According to this model, the asynchronous convergence of ascending and descending projections dynamically alters the physiological properties of thalamic neurons in the ventral posterior medial (VPM) nucleus as rats shift between three behavioral states. Two of these states are characterized by distinct modes of rhythmic whisker movements. We posit that these simultaneous shifts in exploratory behavioral strategy and in the physiological properties of VPM neurons allow rats to either (i) optimize the detection of stimuli that are novel or difficult to sense or (ii) process complex patterns of multi-whisker stimulation.

Afferent Pathways↗

PubMed2006

Controlled release of a self-emulsifying formulation from a tablet dosage form: stability assessment and optimization of some processing parameters.

The objective of this study was to evaluate the effect of some processing parameters on the release of lipid formulation from a tablet dosage form. A 17-run, face-centered cubic design was employed to evaluate the effect of colloidal silicates (X(1)), magnesium stearate mixing time (X(2)), and compression force (X(3)) on flow, hardness, and dissolution of Coenzyme Q(10) (CoQ(10)) lipid formulation from a tablet dosage form. The optimized formulation was subsequently subjected to a short-term accelerated stability study. All preparations had a flowability index values ranging from 77 to 90. The cumulative percent of CoQ(10) released within 8h (Y(5)) ranged from 40.6% to 90% and was expressed by the following polynomial equation: Y(5)=49.78-16.36X(1)+2.90X(2)-3.11X(3)-0.37X(1)X(2)+1.06X(1)X(3)-1.02X(2)X(3)+11.98X(1)(2)+10.63X(2)(2)-7.10X(3)(2). When stored at 4 degrees C, dissolution rates were retained for up to 3 months. Storage at higher temperatures, however, accelerated lipid release and caused leakage, and loss of hardness. Processing parameters have a profound effect on the release of lipid formulations from their solid carriers. While optimized controlled release formulations could be attained, further considerations should be made to prepare "liquisolids" that are physically stable at higher storage temperatures.

Coenzymes↗

PubMed2004

Optimization of enrichment processes of pentachlorophenol (PCP) from water samples.

The method of enriching PCP(pentachlorophenol) from aquatic environment by solid phase extraction(SPE) was studied. Several factors affecting the recoveries of PCP, including sample pH, eluting solvent, eluting volume and flow rate of water sample, were optimized by orthogonal array design(OAD). The optimized results were sample pH 4; eluting solvent, 100% methanol; eluting solvent volume, 2 ml and flow rate of water sample, 4 ml/min. A comparison is made between SPE and liquid-liquid extraction(LLE) method. The recoveries of PCP were in the range of 87.6%-133.6% and 79%-120.3% for SPE and LLE, respectively. Important advantages of the SPE compared with the LLE include the short extraction time and reduced consumption of organic solvents. SPE can replace LLE for isolating and concentrating PCP from water samples.

Environmental Pollutants↗

PubMed1998

Simultaneous optimization of wet granulation process involving factor of drug content dependency on granule size.

Computer optimization technique was applied to the simultaneous optimization of wet granulation process by a high-speed mixer granulator. Four pharmaceutical properties, including yield, drug content uniformity, geometrical mean diameter of granules, and uniformity of granule size, were selected to evaluate the quality of the granules. In particular, dependence of drug content uniformity on granule size was investigated using two model drugs, ascorbic acid and ethenzamide. An appreciable dependence of ascorbic acid content on granule size was not observed in model formulations. On the other hand, ethenzamide was contained more in small-size granules, and its content was decreased with an increase in amounts of hydroxypropyl cellulose (HPC-L; used as a binder) and binder solution. These observations suggested that drug content uniformity is influenced not only by drug solubility in the binder solution, but also by the use of HPC-L. A simultaneous optimal point incorporating four pharmaceutical properties was obtained using the generalized distance function. The experimental values of the four response variables obtained in newly prepared granules were found to correspond well with the predicted values of both granules containing ascorbic acid and ethenzamide. These results suggested that computer optimization would benefit the wet granulation process even if drug content segregation was involved in the process. Further, data obtained from computer optimization, in particular the contour diagram, will be valuable in the process validation.

Ascorbic Acid↗

PubMed2004

Nixtamalized flour from quality protein maize (Zea mays L). optimization of alkaline processing.

Quality of maize proteins is poor, they are deficient in the essential amino acids lysine and tryptophan. Recently, in Mexico were successfully developed nutritionally improved 26 new hybrids and cultivars called quality protein maize (QPM) which contain greater amounts of lysine and tryptophan. Alkaline cooking of maize with lime (nixtamalization) is the first step for producing several maize products (masa, tortillas, flours, snacks). Processors adjust nixtamalization variables based on experience. The objective of this work was to determine the best combination of nixtamalization process variables for producing nixtamalized maize flour (NMF) from QPM V-537 variety. Nixtamalization conditions were selected from factorial combinations of process variables: nixtamalization time (NT, 20-85 min), lime concentration (LC, 3.3-6.7 g Ca(OH)2/l, in distilled water), and steep time (ST, 8-16 hours). Nixtamalization temperature and ratio of grain to cooking medium were 85 degrees C and 1:3 (w/v), respectively. At the end of each cooking treatment the steeping started for the required time. Steeping was finished by draining the cooking liquor (nejayote). Nixtamal (alkaline-cooked maize kernels) was washed with running tap water. Wet nixtamal was dried (24 hours, 55 degrees C) and milled to pass through 80-US mesh screen to obtain NMF. Response surface methodology (RSM) was applied as optimization technique, over four response variables: In vitro protein digestibility (PD), total color difference (deltaE), water absorption index (WAI), and pH. Predictive models for response variables were developed as a function of process variables. Conventional graphical method was applied to obtain maximum PD, WAI and minimum deltaE, pH. Contour plots of each of the response variables were utilized applying superposition surface methodology, to obtain three contour plots for observation and selection of best combination of NT (31 min), LC (5.4 g Ca(OH)2/l), and ST (8.1 hours) for producing optimized NMF from QPM.

Calcium Compounds↗

PubMed2006

Phytochemical characterization of defatted rice bran and optimization of a process for their extraction and enrichment.

The aim of this study was to characterize the defatted rice bran (DRB) employing HPLC for identifying the major phytochemicals in DRB and to examine its commercial potential as a source of bioactive phytochemicals leading to value addition of DRB otherwise used as cattle feed. Various solvent extracts showed the presence of oryzanols, tocols, and ferulic acid. Methanol was the most effective extractant under the optimized conditions of a material-solvent ratio of 1:15 (wt./vol.) and a time of extraction of 10h. The yields of total phenols, oryzanols and ferulic acid from DRB with methanol were 2204, 316, and 233 ppm, respectively. Enrichment of antioxidants in the crude methanolic extract (CME) was achieved by sequential extraction and fractionation, resulting in three enriched fractions, viz., acetone extract (AE), acetone extract-lipophilic fraction (AE-LP) and acetone extract-polar fraction (AE-PP). While AE-LP was enriched in oryzanols and tocols by about 65 times, AE-PP was enriched in ferulic acid by 70 times as compared to their contents in DRB.

Animal Feed↗

PubMed1977

[Principles for optimizing and guaging several processes in the technology of vaccine production. I. Several problems in guaging and optimizing thermal sterilization of fluids].

Thermal sterilization of fluids--one of the widespread operations in microbiological laboratories and in vaccine production--solves two tasks: provides sterility and maximal preservation of biological value of the sterilized fluid. A possibility and expediency of using some indices for the quantitative assessment of the efficacy of the sterilization regimens, including measurement of the sterilization processes is considered in this work. A possible way of the regimen optimization on the basis of known values of the activation energies of the processes of decomposition of thermolabile components and inactivation of foreign microbial flora is assessed.

Hot Temperature↗

PubMed2006

Caspase-9 holoenzyme is a specific and optimal procaspase-3 processing machine.

Caspase-9 activation is critical for intrinsic cell death. The activity of caspase-9 is increased dramatically upon association with the apoptosome, and the apoptosome bound caspase-9 is the caspase-9 holoenzyme (C9Holo). In this study, we use quantitative enzymatic assays to fully characterize C9Holo and a leucine-zipper-linked dimeric caspase-9 (LZ-C9). We surprisingly show that LZ-C9 is more active than C9Holo for the optimal caspase-9 peptide substrate LEHD-AFC but is much less active than C9Holo for the physiological substrate procaspase-3. The measured Km values of C9Holo and LZ-C9 for LEHD-AFC are similar, demonstrating that dimerization is sufficient for catalytic activation of caspase-9. The lower activity of C9Holo against LEHD-AFC may be attributed to incomplete C9Holo assembly. However, the measured Km of C9Holo for procaspase-3 is much lower than that of LZ-C9. Therefore, in addition to dimerization, the apoptosome activates caspase-9 by enhancing its affinity for procaspase-3, which is important for procaspase-3 activation at the physiological concentration.

Animals↗

PubMed2003

Neural networks for process control and optimization: two industrial applications.

The two most widely used neural models, multilayer perceptron (MLP) and radial basis function network (RBFN), are presented in the framework of system identification and control. The main steps for building such nonlinear black box models are regressor choice, selection of internal architecture, and parameter estimation. The advantages of neural network models are summarized: universal approximation capabilities, flexibility, and parsimony. Two applications are described in steel industry and water treatment, respectively, the control of alloying process in a hot dipped galvanizing line and the control of a coagulation process in a drinking water treatment plant. These examples highlight the interest of neural techniques, when complex nonlinear phenomena are involved, but the empirical knowledge of control operators can be learned.

Algorithms↗

PubMed2005

Microfocal X-ray computed tomography post-processing operations for optimizing reconstruction volumes of stented arteries during 3D computational fluid dynamics modeling.

Restenosis caused by neointimal hyperplasia (NH) remains an important clinical problem after stent implantation. Restenosis varies with stent geometry, and idealized computational fluid dynamics (CFD) models have indicated that geometric properties of the implanted stent may differentially influence NH. However, 3D studies capturing the in vivo flow domain within stented vessels have not been conducted at a resolution sufficient to detect subtle alterations in vascular geometry caused by the stent and the subsequent temporal development of NH. We present the details and limitations of a series of post-processing operations used in conjunction with microfocal X-ray CT imaging and reconstruction to generate geometrically accurate flow domains within the localized region of a stent several weeks after implantation. Microfocal X-ray CT reconstruction volumes were subjected to an automated program to perform arterial thresholding, spatial orientation, and surface smoothing of stented and unstented rabbit iliac arteries several weeks after antegrade implantation. A transfer function was obtained for the current post-processing methodology containing reconstructed 16 mm stents implanted into rabbit iliac arteries for up to 21 days after implantation and resolved at circumferential and axial resolutions of 32 and 50 microm, respectively. The results indicate that the techniques presented are sufficient to resolve distributions of WSS with 80% accuracy in segments containing 16 surface perturbations over a 16 mm stented region. These methods will be used to test the hypothesis that reductions in normalized wall shear stress (WSS) and increases in the spatial disparity of WSS immediately after stent implantation may spatially correlate with the temporal development of NH within the stented region.

Angiography↗

PubMed1992

Optimization of a process for the production of (R)-2-hydroxy-4-phenylbutyric acid--an intermediate for inhibitors of angiotensin converting enzyme.

(R)-2-Hydroxy-4-phenylbutyric acid, an intermediate in the manufacture of inhibitors of angiotensin converting enzyme, can be produced continuously in an enzyme membrane reactor by enzymatic reduction of its corresponding alpha-keto acid. D-Lactate dehydrogenase (D-LDH) from Staphylococcus epidermidis was chosen as the most appropriate enzyme to carry out the NADH-dependent reduction. Formate dehydrogenase (FDH) was used for NADH regeneration. Detailed kinetic measurements and a mathematical model for the coupled enzyme reactions were applied to calculate the optimal conditions for continuous production of the alpha-hydroxy acid. A mass of 1 kg [corrected] (R)-2-hydroxy-4-phenylbutyric acid was synthesized in a 220 ml enzyme membrane reactor over a period of 4 weeks. A mean space-time-yield of 165 g l-1 d-1 was achieved at low enzyme consumptions of 150 U kg-1 alpha-hydroxy acid for FDH and D-LDH.

Angiotensin-Converting Enzyme Inhibitors↗

PubMed1993

Optimizing the biolistic process for different biological applications.

The biolistic process is still rapidly evolving. We do not anticipate further major improvements in biolistic apparatus. There will probably still be further major improvements in particles, DNA coating, and vectors, as well as significant further advances in understanding of biological determinants of cell penetration and survival. The technology has currently reached the point at which it can be readily and reliably used for a wide range of applications. Given the information presented in this chapter, new applications can be optimized fairly readily.

Animals↗

PubMed2002

Optimal methods for processing mineralized tissues for Fourier transform infrared microspectroscopy.

Fourier transform infrared microspectroscopy (FTIRM) and infrared imaging (FTIRI) are techniques utilized in the analysis of bone mineral and matrix properties in health and disease. Since the spatial arrangement of bone tissue is conserved using FTIRM and FTIRI, quantitative data can be obtained on bone mineral (hydroxyapatite) crystalline size and composition, and on matrix structure and composition at discrete anatomic locations with a spatial resolution from approximately 7 mm (FTIRI) to 10 mm (FTIRM). To section bone for FTIRM and FTIRI, it must be preserved ("fixed") to maintain its properties, and embedded in a hard supportive material. Since most of the embedding media have components that spectrally overlap the components of mineralized tissues, it is critical to define optimal embedding and fixation protocols that have the least effect on mineral and matrix spectra. In the current study, the spectra of mouse calvaria in seven different fixatives and six different commonly used embedding media were assessed by FTIRM and FTIRI. The fixatives evaluated were absolute ethanol, 70% ethanol, glycerol, formaldehyde, EM fixative, and formalin in cacodylate or phosphate-buffered saline. The embedding media tested were Araldite, Epon, JB-4, LR White, PMMA, and Spurr. Comparisons were made to FTIR spectra obtained from unprocessed ground calvaria and to spectra of cryosections of unfixed tissue, fast-frozen in polyvinyl alcohol (5% PVA). Non-aqueous fixatives and embedding in LR White, Spurr, Araldite, and PMMA had the least effect on the spectral parameters measured (mineral to matrix ratio, mineral crystallinity, and collagen maturity) compared with cryo-sectioned calvaria and non-fixed, non-embedded calvaria in KBr pellets.

Animals↗