Good Efficiency (good + efficiency)

Distribution by Scientific Domains

Selected Abstracts

Influence of microemulsion chirality on chromatographic figures of merit in EKC: Results with novel three-chiral-component microemulsions and comparison with one- and two-chiral-component microemulsions

Kimberly A. Kahle
Abstract Novel microemulsion formulations containing all chiral components are described for the enantioseparation of six pairs of pharmaceutical enantiomers (atenolol, ephedrine, metoprolol, N -methyl ephedrine, pseudoephedrine, and synephrine). The chiral surfactant dodecoxycarbonylvaline (DDCV, R - and S -), the chiral cosurfactant S -2-hexanol, and the chiral oil diethyl tartrate (R - and S -) were combined to create four different chiral microemulsions, three of which were stable. Results obtained for enantioselectivity, efficiency, and resolution were compared for the triple-chirality systems and the single-chirality system that contained chiral surfactant only. Improvements in enantioselectivity and resolution were achieved by simultaneously incorporating three chiral components into the aggregate. The one-chiral-component microemulsion provided better efficiencies. Enantioselective synergies were identified for the three-chiral-component nanodroplets using a thermodynamic model. Additionally, two types of dual-chirality systems, chiral surfactant/chiral cosurfactant and chiral surfactant/chiral oil, were examined in terms of chromatographic figures of merit, with the former providing much better resolution. The two varieties of two-chiral-component microemulsions gave similar values for enantioselectivity and efficiency. Lastly, the microemulsion formulations were divided into categories based on the number of chiral microemulsion reagents and the average results for each pair of enantiomers were analyzed for trends. In general, enantioselectivity and resolution were enhanced while efficiency was decreased as more chiral components were used to create the pseudostationary phase (PSP). [source]

Synthesis, growth and characterization of single crystals of pure and thiourea doped L-glutamic acid hydrochloride

R. Sathyalakshmi
Abstract L(+)Glutamic acid hydrochloride [HOOC (CH2)2CH(NH2) COOH·HCl], a monoamino dicarboxylic acid salt of L-Glutamic acid was synthesized and the synthesis was confirmed by FTIR analysis. Solubility of the material in water was determined. Pure and Thiourea doped L-Glutamic acid hydrochloride crystals were grown by low temperature solution growth using solvent evaporation technique. XRD, UV-Vis-NIR analyses were carried out for both pure and thiourea doped crystals. The crystals were qualitatively analyzed by EDAX analysis and the presence of thiourea was confirmed. The cell parameters of L-Glutamic acid hydrochloride have been determined as a = 5.151 Å, b = 11.79 Å, c = 13.35 Å by X-ray diffraction analysis and it crystallizes in orthorhombic space group P212121. UV-Vis-NIR spectra analysis showed good optical transmission in the entire visible region for both pure and doped crystals. Micro hardness of both pure and doped crystals has been determined using Vickers micro hardness tester. The SHG efficiencies of both pure and doped crystals were determined using Kurtz powder test and pure L-Glutamic acid hydrochloride crystal was found to possess better efficiency than thiourea doped L-Glutamic acid hydrochloride crystals. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Habit modification and improvement in properties of potassium hydrogen phthalate (KAP) crystals doped with metal ions

S. K. Geetha
Abstract Potassium hydrogen phthalate (KAP) single crystals were grown by slow evaporation and slow cooling techniques. The growth procedure like temperature cooling rate, evaporation rate, solution pH, concentration of the solute, supersaturation ratio etc., has been varied to have optically transparent crystals. Efforts were made to dope the KAP crystals with rubidium, sodium and lithium ions. The dopant concentration has been varied from 0.01 to 10 mole percent. Good quality single crystals were grown with different concentrations of dopants in the mother phase. Depending on the concentration of the dopants and the solution pH value, there is modification of habit. Rubidium ions very much improve the growth on the prismatic faces. The transparency of the crystals is improved with rubidium and sodium doping. The role of the dopants on the non-linear optical performance of KAP indicates better efficiency for doped crystals. The grown crystals were characterized with XRD, FT-IR, chemical etching, Vickers microhardness and SHG measurements. The influence of the dopants on the optical, chemical, structural, mechanical and other properties of the KAP crystals was analysed. © 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim [source]

Conformational effects on the performance and selectivity of a polymeric pseudostationary phase in electrokinetic chromatography

Jonathan P. McCarney
Abstract The effect of the conformation of a polymeric pseudostationary phase on performance and selectivity in electrokinetic chromatography was studied using an amphiphilic pH-responsive polymer that forms compact intramolecular aggregates (unimer micelles) at low pH and a more open conformation at high pH. The change in conformation was found to affect the electrophoretic mobility, retention, selectivity, and separation efficiency. The low-pH conformer has higher electrophoretic mobility and greater affinity for most solutes. The unimer micelle conformation was also found to provide a solvation environment more like that of micelles and other amphiphilic self-associative polymers studied previously. It was not possible to fully characterize the effect of conformation on efficiency, but very hydrophobic solutes with long alkyl chains appeared to migrate with better efficiency when the unimer micelle conformation was employed. The results imply that polymers with a carefully optimized lipophilic-hydrophilic balance that allow self-association will perform better as pseudostationary phases. In addition, the results show that electrokinetic chromatography is a useful method for determining the changes in solvation environment provided by stimuli-responsive polymers with changes in the conditions. [source]

A new distributed approximation algorithm for constructing minimum connected dominating set in wireless ad hoc networks

Bo Gao
Abstract In recent years, constructing a virtual backbone by nodes in a connected dominating set (CDS) has been proposed to improve the performance of ad hoc wireless networks. In general, a dominating set satisfies that every vertex in the graph is either in the set or adjacent to a vertex in the set. A CDS is a dominating set that also induces a connected sub-graph. However, finding the minimum connected dominating set (MCDS) is a well-known NP-hard problem in graph theory. Approximation algorithms for MCDS have been proposed in the literature. Most of these algorithms suffer from a poor approximation ratio, and from high time complexity and message complexity. In this paper, we present a new distributed approximation algorithm that constructs a MCDS for wireless ad hoc networks based on a maximal independent set (MIS). Our algorithm, which is fully localized, has a constant approximation ratio, and O(n) time and O(n) message complexity. In this algorithm, each node only requires the knowledge of its one-hop neighbours and there is only one shortest path connecting two dominators that are at most three hops away. We not only give theoretical performance analysis for our algorithm, but also conduct extensive simulation to compare our algorithm with other algorithms in the literature. Simulation results and theoretical analysis show that our algorithm has better efficiency and performance than others. Copyright © 2005 John Wiley & Sons, Ltd. [source]

Optimization of enzymatic extraction of ferulic acid from wheat bran, using response surface methodology, and characterization of the resulting fractions

Hélène Barberousse
Abstract BACKGROUND: The agro-industries generate thousands of tons of by-products, such as bran or pulps, each year. They are, at best, used for cattle feeding. Through biocracking, this biomass may constitute a renewable source for various molecules of interest for the industry. For instance, ferulic acid, a compound showing antioxidant ability, is found in abundance in cereal bran. Its release depends mainly on the breaking of its ester linkage to other constitutive elements of the cell wall, such as arabinoxylans. Response surface methodology was used to evaluate the effects of ferulic acid esterase (FAE) and xylanase activities, as well as incubation time and temperature, on ferulic acid extraction yield from wheat bran. Under optimized conditions, the composition of the hydrolysate and of residual bran were compared to native bran. RESULTS: Experiments carried out under the predicted optimal conditions (FAE amount, 27 U g,1; xylanase amount, 304 U g,1; incubation time, 2 h; and temperature, 65 °C) led to an extraction yield of 52.8%, agreeing with the expected value (51.0%). The crude ferulic acid fraction was purified with Amberlite XAD16, leading to a final concentration of 125 µg mL,1 of ferulic acid in ethanol. The antioxidant capacity of this purified fraction was evaluated by the DPPH· scavenging method: it exhibited better efficiency (EC50 = 10.6 µmol L,1 in ferulic acid) than the ferulic acid standard (EC50 = 13.7 µmol L,1). CONCLUSION: These results confirm the potential of wheat bran valorization in the field of natural antioxidant extraction, possibly viable in an industrial scheme. Copyright © 2009 Society of Chemical Industry [source]

Polycyclic aromatic hydrocarbons (PAHs) adsorption on solid surfaces applied to waste lubricant oils recovery process

José Lima Assunção Filho
Abstract Lubricant oils undergo degradation increasing polycyclic aromatic hydrocarbons (PAHs) concentration. In this work, PAHs adsorption onto activated carbon, powder silica, and powder chitosan surfaces was estimated, with their concentrations in organic solvents (ethanol, 2-propanol, 1-butanol, and terc -butanol) monitored by UV-visible absorption. Equilibrium concentration was attained after 72,h and the isotherms presented characteristic of multilayer formation. The greater surface density was determined for the chitosan, but the system containing activated carbon and 1-butanol presented better efficiency for PAHs removal. Results indicated that the adsorption evaluated in this work can be a potential stage in the waste lubricant oils global recovery process. Les huiles de lubrification subissent une dégradation augmentant la concentration d'hydrocarbures aromatiques polycycliques (HAP). Dans ce travail, on a estimé l'adsorption de HAPs sur du carbone activé, de la silice en poudre et des surfaces de chitosane en poudre, leurs concentrations dans des solvants organiques (éthanol, 2-propanol, 1-butanol et terc -butanol) étant suivies par absorption UV et dans le domaine visible. Une concentration d'équilibre a été atteinte après 72,h et les isothermes présentaient des caractéristiques de formation de couches multiples. La densité de surface la plus importante a été déterminée pour le chitosane mais le système contenant du carbone activé et du 1-butanol présentait une meilleure efficience en matière de retrait des HAPs. Les résultats indiquaient que l'adsorption évaluée dans ce travail pourrait constituer une étape potentielle du processus global de récupération des résidus d'huiles de lubrification. [source]

Petri nets based FPGA controller of PDP sustainer with half-voltage energy recovery circuit,

Jian-Long Kuo
Abstract This paper proposes a FPGA controller design of a driver circuit based Petri nets for the Plasma Display Panel (PDP). In such a driver circuit, complicated control logic is required in the PDP sustainer circuit to implement the sustaining voltage waveform. The control logic has the zero-switching behaviour for the driver circuit to provide better efficiency for the driving circuit. Conventionally, the VHDL programmer does not have a systematic way to program the control logic. Time delay problem of logic components in logic controller may occur under high frequency operation. With the help of the proposed Petri nets approach, the VHDL programming for the PDP driver circuit can be easier in a systematic way. Also, this paper illustrates three types of sustainers with Petri nets based FPGA controller. The basic full-bridge and full-voltage sustainers are used to compare the performance with the proposed half-voltage sustainer. Details of the circuit operation are described. From the experimental results, the performance such as efficiency, luminance, and gamma curve are assessed to show the effectiveness of the proposed half-voltage sustainer. It is believed that the proposed Petri nets based control circuit is very powerful for the practical application of the PDP sustainer circuit. Copyright © 2010 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society [source]

Use of a Standardized Order Set for Achieving Target Temperature in the Implementation of Therapeutic Hypothermia after Cardiac Arrest: A Feasibility Study

J. Hope Kilgannon MD
Abstract Objectives:, Induced hypothermia (HT) after cardiac arrest improved outcomes in randomized trials. Current post,cardiac arrest treatment guidelines advocate HT; however, utilization in practice remains low. One reported barrier to adoption is clinician concern over potential technical difficulty of HT. We hypothesized that using a standardized order set, clinicians could achieve HT target temperature in routine practice with equal or better efficiency than that observed in randomized trials. Methods:, After a multidisciplinary HT education program, we implemented a standardized order set for HT induction and maintenance including sedation and paralysis, intravenous cold saline infusion, and an external cooling apparatus, with a target temperature range of 33,34°C. We performed a retrospective analysis of a prospectively compiled and maintained registry of cardiac arrest patients with HT attempted (intent-to-treat) over the first year of implementation. The primary outcome measures were defined a priori by extrapolating treatment arm data from the largest and most efficacious randomized trial: 1) successful achievement of target temperature for ,85% of patients in the cohort and 2) median time from return of spontaneous circulation (ROSC) to achieving target temperature <8 hours. Results:, Clinicians attempted HT on 23 post,cardiac arrest patients (arrest location: 78% out-of-hospital, 22% in-hospital; initial rhythm: 26% ventricular fibrillation/tachycardia, 70% pulseless electrical activity or asystole) and achieved the target temperature in 22/23 (96%) cases. Median time from ROSC to target temperature was 4.4 (interquartile range 2.8,7.2) hours. Complication rates were low. Conclusions:, Using a standardized order set, clinicians can achieve HT target temperature in routine practice. [source]

Separation and determination of carnosine-related peptides using capillary electrophoresis with laser-induced fluorescence detection

Ying Huang
Abstract A capillary electrophoresis (CE) method with laser-induced fluorescence (LIF) detection was developed for the separation and detection of carnosine-related peptides (carnosine, anserine, and homocarnosine). A sensitive and fluorogenic regent, 3-(4-carboxybenzoyl) quinoline-2-carboxaldehyde (CBQCA) was selected as a precapillary labeling reagent for imidazole dipeptides to form isoindole derivatives. The optimized molar ratio between CBQCA and peptide was found to be 75:1, and 50 mmol/L borate buffer (pH 9.2) was used for the derivatization in order to achieve good efficiency. Three imidazole dipeptides were baseline-separated within 20 min by using 112 mmol/L sodium borate (pH 10.4,10.8) as running buffer. Concentration detection limits (signal-to-noise ratios) for carnosine, anserine, and homocarnosine were 4.73, 4.37, and 3.94 nmol/L, respectively. This method has been applied to the analysis of human cerebrospinal fluid (CSF) and meat dry powder of pig and sheep. Recoveries were in the range of 82.9,104.8% for homocarnosine in CSF. For carnosine and anserine, the recoveries are 98.3% and 80.2% in meat dry powder of pig and 111.2% and 112.8% in meat dry powder of sheep, respectively. [source]

Phosphorescent OLEDs: Synthesis and Characterization of Red-Emitting Iridium(III) Complexes for Solution-Processable Phosphorescent Organic Light-Emitting Diodes (Adv. Funct.

On page 2205, S.H. Jin and co-workers report on the development of red-emitting iridium(III) complexes for solution-processable phosphorescent organic light-emitting diodes (PhOLEDs). This frontispiece image shows the fabrication of full-color PhOLEDs by an inkjet printing method. The combination of good efficiency and color purity identifies this material as a promising candidate for red phosphorescent doping of PhOLEDs. Structure-property relationships for improving the performance of such devices are also investigated. [source]

Meshfree weak,strong (MWS) form method and its application to incompressible flow problems

G. R. Liu
Abstract A meshfree weak,strong (MWS) form method has been proposed by the authors' group for linear solid mechanics problems based on a combined weak and strong form of governing equations. This paper formulates the MWS method for the incompressible Navier,Stokes equations that is non-linear in nature. In this method, the meshfree collocation method based on strong form equations is applied to the interior nodes and the nodes on the essential boundaries; the local Petrov,Galerkin weak form is applied only to the nodes on the natural boundaries of the problem domain. The MWS method is then applied to simulate the steady problem of natural convection in an enclosed domain and the unsteady problem of viscous flow around a circular cylinder using both regular and irregular nodal distributions. The simulation results are validated by comparing with those of other numerical methods as well as experimental data. It is demonstrated that the MWS method has very good efficiency and accuracy for fluid flow problems. It works perfectly well for irregular nodes using only local quadrature cells for nodes on the natural boundary, which can be generated without any difficulty. Copyright © 2004 John Wiley & Sons, Ltd. [source]

Nonwoven as heat barrier: Modeling of the efficiency of Carbtex fibers

Serge Bourbigot
Abstract In this work, we examine the use of nonwoven (NW) as heat barrier to protect a metallic substrate. Carbtex fibers consisting in a thermoplastic core inside an oxidized outer shell (polyacrylonitrile or PAN fibers) are selected to make the NW. Measuring temperature profiles in a heat radiator test; it is revealed that Carbtex NW is an efficient heat barrier. A macroscopic model is then developed to simulate heat transfer in NW (considered as a porous medium) used as a protective heat barrier on aluminum plate. The model is validated comparing experimental results obtained by the heat radiator test and predicted values. The efficiency of NW layer is simulated varying different parameters characteristic of the NW (porosity and heat conductivity) and of the design (thickness of the layer). It is revealed to get good efficiency of the NW heat barrier that heat conductivity of the fibers is crucial to get superior performance as well as high porosity (higher than 0.5) associated with a reasonable thickness of NW (5,7 mm). © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source]

Midpoint CD34 measurement as a predictor of PBPC product yield in pediatric patients undergoing high-dose chemotherapy ,

Rameshwar S. Sidhu
Abstract High-dose chemo/radiotherapy of sensitive tumors requires PBPC rescue doses of >3×106 CD34/kg (range: 3,20×106 CD34/kg). Because of the diversity of stem cell treatment protocols and clinical presentation of patients at the time of peripheral blood progenitor cell (PBPC) harvest, the use of the mid-point CD34 positive cell measurement was initiated to predict the final CD34-positive cell product yield/stem cell harvest. The measurement of CD34-positive cells at the mid-point of the initial setting of 5 total blood volumes (TBV) allows for the extension, shortening, or no change in the TBV processing to achieve a maximum goal of CD34-positive cells/kg body weight required for stem cell transplantation. The estimation of mid-point CD34-positive cells guided our center to extend 22 procedures, shorten 26 procedures, and leave 20 procedures unchanged. This investigation addresses three aspects of PBPC collection in pediatric patients: (1) the processing of large blood volumes (more than the defined 3 TBV and maximum up to 13 TBV in one session) to achieve good efficiency of the procedure; (2) the use of the mid-point CD34 measurement at 2.5 of 5 TBV initially set to predict the maximum goal of CD34 cells /kg needed on the same day of PBPC collection; and (3) PBPC collection in pediatric patients <10 kg body weight (as low as 5.8 kg body weight). J. Clin. Apheresis 2006. © 2006 Wiley-Liss, Inc. [source]


ABSTRACT Egg white contains high-quality proteins. Some processes using eggs produce egg white as by-product. These egg white proteins may be recovered for use as additive in food products. In the first part of this study, a new polymeric material was developed and used in the chromatographic separation of ovalbumin at preparative scale. Ovalbumin is the major component of egg white and thus, it has the greatest weight in terms of its functional effects. An application of the purified ovalbumin was subsequently studied in the elaboration of yogurt mousse. The results obtained showed that the poly(glycidil methacrylate-co-ethylene dimethacrylate) resin that was manufactured enabled the separation of ovalbumin with good efficiency. This study also showed that the formulation obtained from the yogurt mousse with ovalbumin had a greater yield in volume than the commercial product used as a benchmark, improving the majority of its organoleptic qualities without appreciably affecting its stability and organoleptic properties. [source]

Evaluation of glycosylation and malonylation patterns in flavonoid glycosides during LC/MS/MS metabolite profiling

P. Kachlicki
Abstract Flavonoid conjugates constitute several classes of plant phenolic secondary metabolites including many isomeric compounds differing in the hydroxylation pattern and substitution of their rings with different groups such as alkyls, acyls or sugars. These compounds occur in plant tissues mainly as glycosides and in many cases it is necessary to have reliable and detailed information concerning the structure of these natural products. Our results were obtained using leaf extracts of Arabidopsis thaliana and Lupinus angustifolius in which different glycosides of flavones, flavonols and isoflavones are present. Analysis of collision-induced dissociation (CID)/MS/MS spectra of protonated [M + H]+, sodiated [M + Na]+ or deprotonated [M , H], molecules recorded during HPLC runs may bring needed information in this respect. However, registration of mass spectra of [M + Na]+ ions with a good efficiency is possible only after post-column addition of a sodium acetate solution to the LC column eluate. The retention of sodium cation on the saccharidic parts of the molecule is observed after the CID fragmentation. In many cases, the location of this cation on the glycan attached to C-3 hydroxyl group of flavonol led to assignment of its structure. Additionally, the determination of the structure of the aglycone and of the sequence of the glycan part was made possible through the CID data obtained from the [M + H]+ and [M , H], ions. CID spectra show a different order of sugar elimination from hydroxyl groups at C-3 and C-7 in flavonol glycosides isolated from A. thaliana leaves and give sufficient information to discriminate flavonoid O-diglycosides from flavonoid di-O-glycosides. Copyright © 2007 John Wiley & Sons, Ltd. [source]

Synthesis of biodegradable copolymers with low-toxicity zirconium compounds.


Abstract The aim of this article is to show a new method of copolymerizing glycolide and caprolactone with the low-toxicity zirconium(IV) acetylacetonate and zirconium(IV) chloride as initiators. Such initiators enabled us to obtain copolymers with very good efficiency and good mechanical properties. The reactivity of the initiators was defined, and the chain-propagation process was examined. On the basis of an NMR examination and differential scanning calorimetry thermograms, we found that the samples obtained at 100 °C with the initiators were characterized by a segmental chain microstructure, which provided good mechanical properties. When the synthesis was carried out at 150 °C, a more randomized structure was obtained, which caused crucial changes in the properties of the copolymers and decreases in the mechanical properties. Because of their properties, the obtained copolymers could be successfully applied as degradable surgical implants or drug carriers. The results show that the copolymers obtained with zirconium(IV) acetylacetonate and chloride could successfully replace ones obtained in the presence of tin compounds as far as medical applications are concerned. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1379,1394, 2002 [source]

High-energy X-ray diffraction using the Pixium 4700 flat-panel detector

J. E. Daniels
The Pixium 4700 detector represents a significant step forward in detector technology for high-energy X-ray diffraction. The detector design is based on digital flat-panel technology, combining an amorphous Si panel with a CsI scintillator. The detector has a useful pixel array of 1910 × 2480 pixels with a pixel size of 154,µm × 154,µm, and thus it covers an effective area of 294,mm × 379,mm. Designed for medical imaging, the detector has good efficiency at high X-ray energies. Furthermore, it is capable of acquiring sequences of images at 7.5 frames per second in full image mode, and up to 60 frames per second in binned region of interest modes. Here, the basic properties of this detector applied to high-energy X-ray diffraction are presented. Quantitative comparisons with a widespread high-energy detector, the MAR345 image plate scanner, are shown. Other properties of the Pixium 4700 detector, including a narrow point-spread function and distortion-free image, allows for the acquisition of high-quality diffraction data at high X-ray energies. In addition, high frame rates and shutterless operation open new experimental possibilities. Also provided are the necessary data for the correction of images collected using the Pixium 4700 for diffraction purposes. [source]

A highly efficient class-F power amplifier for wideband linear power amplifier applications

Jangheon Kim
Abstract In this letter, a highly efficient class-F power amplifier (PA) is developed as a new main block of the wideband base-station linear power amplifier. The class-F PA is implemented using Eudyna EGN010MK GaN HEMT with a 10-W peak envelop power. The nonlinearity and memory effects of class-F PA are explored to apply the wideband application. The maximum power-added efficiency of the implemented PA is 68% at a saturated output power of 40 dBm for the 2.14-GHz CW signal. The PA delivers a good efficiency of 35% at an average output power of 32.3 dBm for wide-band code division multiple access 3FA signal with 15-MHz bandwidth, and the linearity can be improved to about ,48 dBc using the digital feedback predistortion linearization technique. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2323,2326, 2009; Published online in Wiley InterScience ( DOI 10.1002/mop.24631 [source]