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Two-step

Distribution by Scientific Domains
Chemistry40%
Polymers and Materials Science20%
Life Sciences15%
Medical Sciences13%
Earth and Environmental Science6%
Distribution within Chemistry
Organic Chemistry32%
Chemical Engineering15%
General & Introductory Chemistry10%

Terms modified by Two-step

  • two-step approach
  • two-step mechanism
  • two-step method
    		•
  • two-step polymerization
  • two-step procedure
  • two-step process
    		•
  • two-step protocol
  • two-step reaction
  • two-step route
    		•
  • two-step synthesis

    • Selected Abstracts

    ChemInform Abstract: A Two-Step, Formal [4 + 2] Approach Toward Piperidin-4-ones via Au Catalysis.

    CHEMINFORM, Issue 45 2009
    Li Cui
    Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

    A Simple, Two-Step, Site-Specific Preparation of Fluorinated Naphthalene and Phenanthrene Derivatives from Fluorobromo-Substituted Alkenes.

    CHEMINFORM, Issue 5 2007
    Yi Wang
    Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source]

    A Survey of Acid Catalysis and Oxidation Conditions in the Two-Step, One-Flask Synthesis of Meso-Substituted Corroles via Dipyrromethanedicarbinols and Pyrrole.

    CHEMINFORM, Issue 41 2004
    G. Richard III Geier
    Abstract For Abstract see ChemInform Abstract in Full Text. [source]

    ChemInform Abstract: A Two-Step, One-Pot Synthesis of Diverse N-Pyruvoyl Amino Acid Derivatives Using the Ugi Reaction.

    CHEMINFORM, Issue 12 2001
    Masayuki Nakamura
    Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

    One-pot preparation of 3-miktoarm star terpolymers via click [3 + 2] reaction

    JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 16 2007
    Ozcan Altintas
    Abstract The preparation of 3-miktoarm star terpolymers using nitroxide mediated radical polymerization (NMP), ring opening polymerization (ROP), and click reaction [3 + 2] are carried out by applying two types of one-pot technique. In the first one-pot technique, NMP of styrene (St), ROP of ,-caprolactone (,-CL), and [3 + 2] click reaction (between azide end-functionalized poly(ethylene glycol) (PEG-N3)/or azide end-functionalized poly(methyl methacrylate) (PMMA-N3) and alkyne) are carried out in the presence of 2-(hydroxymethyl)-2-methyl-3-oxo-3-(2-phenyl-2-(2,2,6,6-tetramethylpiperidin-1-yloxy)ethoxy) propyl pent-4-ynoate, 2, as an initiator for 48 h at 125 °C (one-pot/one-step). As a second technique, NMP of St and ROP of ,-CL were conducted using 2 as an initiator for 20 h at 125 °C, and subsequently PEG-N3 or azide end-functionalized poly(tert -butyl acrylate (PtBA-N3) was added to the polymerization mixture, followed by a click reaction [3 + 2] for 24 h at room temperature (one-pot/two-step). The 3-miktoarm star terpolymers, PEG-poly(,-caprolactone)(PCL)-PS, PtBA-PCL-PS and PMMA-PCL-PS, were recovered by a simple precipitation in methanol without further purification. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3588,3598, 2007 [source]

    Transthoracic Doppler Echocardiographic Coronary Flow Imaging in Identification of Left Anterior Descending Coronary Artery Stenosis in Patients with Left Bundle Branch Block

    ECHOCARDIOGRAPHY, Issue 10 2008
    Ozer Soylu M.D.
    Background: Conventional noninvasive methods have well-known limitations for the detection of coronary artery disease (CAD) in patients with left bundle branch block (LBBB). However, advancements in Doppler echocardiography permit transthoracic imaging of coronary flow velocities (CFV) and measurement of coronary flow reserve (CFR). Our aim was to evaluate the diagnostic value of transthoracic CFR measurements for detection of significant left anterior descending (LAD) stenosis in patients with LBBB and compare it to that of myocardial perfusion scintigraphy (MPS). Methods: Simultaneous transthoracic CFR measurements and MPS were analyzed in 44 consecutive patients with suspected CAD and permanent LBBB. Typical diastolic predominant phasic CFV Doppler spectra of distal LAD were obtained at rest and during a two-step (0.56,0.84 mg/kg) dipyridamole infusion protocol. CFR was defined as the ratio of peak hyperemic velocities to the baseline values. A reversible perfusion defect at LAD territory was accepted as a positive scintigraphy finding for significant LAD stenosis. A coronary angiography was performed within 5 days of the CFR studies. Results: The hyperemic diastolic peak velocity (44 ± 9 cm/sec vs 62 ± 2 cm/sec; P=0.01) and diastolic CFR (1.38 ± 0.17 vs 1.93 ± 0.3; P=0.001) were significantly lower in patients with LAD stenosis compared to those without LAD stenosis. The diastolic CFR values of <1.6 yielded a sensitivity of 100% and a specificity of 94% in the identification of significant LAD stenosis. In comparison, MPS detected LAD stenosis with a sensitivity of 100% and a specificity of 29%. Conclusions: CFR measurement by transthoracic Doppler echocardiography is an accurate method that may improve noninvasive identification of LAD stenosis in patients with LBBB. [source]

    Multiple displacement amplification as a pre-polymerase chain reaction (pre-PCR) to process difficult to amplify samples and low copy number sequences from natural environments

    ENVIRONMENTAL MICROBIOLOGY, Issue 7 2005
    Juan M. Gonzalez
    Summary Microbial assessment of natural biodiversity is usually achieved through polymerase chain reaction (PCR) amplification. Deoxyribonucleic acid (DNA) sequences from natural samples are often difficult to amplify because of the presence of PCR inhibitors or to the low number of copies of specific sequences. In this study, we propose a non-specific preamplification procedure to overcome the presence of inhibitors and to increase the number of copies prior to carrying out standard amplification by PCR. The pre-PCR step is carried out through a multiple displacement amplification (MDA) technique using random hexamers as priming oligonucleotides and ,29 DNA polymerase in an isothermal, whole-genome amplification reaction. Polymerase chain reaction amplification using specific priming oligonucleotides allows the selection of the sequences of interest after a preamplification reaction from complex environmental samples. The procedure (MDA-PCR) has been tested on a natural microbial community from a hypogean environment and laboratory assemblages of known bacterial species, in both cases targeting the small subunit ribosomal RNA gene sequences. Results from the natural community showed successful amplifications using the two steps protocol proposed in this study while standard, direct PCR amplification resulted in no amplification product. Amplifications from a laboratory assemblage by the two-step proposed protocol were successful at bacterial concentrations ,,10-fold lower than standard PCR. Amplifications carried out in the presence of different concentrations of fulvic acids (a soil humic fraction) by the MDA-PCR protocol generated PCR products at concentrations of fulvic acids over 10-fold higher than standard PCR amplifications. The proposed procedure (MDA-PCR) opens the possibility of detecting sequences represented at very low copy numbers, to work with minute samples, as well as to reduce the negative effects on PCR amplifications of some inhibitory substances commonly found in environmental samples. [source]

    Effects of estimates from different geochemical models on metal fate predicted by coupled speciation-fate models,

    ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 5 2008
    Satyendra P. Bhavsar
    Abstract Coupled metal speciation-fate models are an improvement over stand-alone fate-transport models for accurately assessing metal fate and transport. These coupled models estimate fate-controlling partition coefficients using geochemical speciation/complexation models. Commercially available geochemical models are practical options for a two-step, loose coupling with fate-transport models. These models differ in their partitioning estimates because of differences in assumptions, databases, and so on. The present study examines the effects of differences in estimates from geochemical models on estimates of cationic metal fate using two geochemical models: the Windermere humic aqueous model (WHAM) and the minicomputer equilibrium+ model (MINEQL+). The results from each geochemical model were used as input to the fate module of TRANSPEC (a general, coupled metal transport and speciation model). The two versions of the TRANSPEC model were then used to assess the fate of five cationic metals (Cd, Cu, Ni, Pb, and Zn) in Ross Lake (Flin Flon, MB, Canada; alkaline, eutrophic, mine impacted), Kelly Lake (Sudbury, ON, Canada; circumneutral, mesotrophic, mine influenced), and Lake Tantaré (Quebec City, QC, Canada; acidic, oligotrophic, pristine). For relatively soluble metals (Cd, Ni, and Zn), the WHAM and MINEQL+ estimates of speciation/complexation were similar for Ross and Kelly lakes but differed for Lake Tantaré. These differences, however, did not result in significant differences in overall fate estimates. Marked differences were observed between the WHAM and MINEQL+ estimates of partition coefficient, Kd, for more particle-reactive Cu and Pb that translated into the greatest impact on fate in mesotrophic Kelly Lake, in which particle movement is important for fate. [source]

    Micro-shear bond strengths and etching efficacy of a two-step self-etching adhesive system to fluorosed and non-fluorosed enamel

    EUROPEAN JOURNAL OF ORAL SCIENCES, Issue 2 2009
    Kanako Shida
    The purpose of this study was to evaluate the micro-shear bond strengths and the etching efficacy of a two-step self-etching adhesive system to fluorosed and non-fluorosed enamel. The extracted teeth, obtained from Australian and Japanese patients, were classified according to the severity of fluorosis, using the Thylstrup & Fejerskov index (TFI). Australian teeth were classified as mildly fluorosed (TFI = 1,3), whereas Japanese teeth were classified as non-fluorosed (TFI = 0). Resin composite was bonded to 20 enamel samples using Clearfil SE bond. The bonded samples were stressed at a crosshead speed of 1 mm min,1 to determine the micro-shear bond strength. To examine the etching efficacy of primer on fluorosed and non-fluorosed enamel, the enamel-surface pH values were directly measured using a micro pH sensor. The non-fluorosed enamel showed significantly higher bond strengths compared with the fluorosed enamel. There was a statistical difference between fluorosed and non-fluorosed enamel regarding the surface pH change before and after application of the Clearfil SE bond primer. The results from this study suggest that water fluoridation has an effect on the acid resistance of enamel surfaces when treated with a two-step self-etching adhesive system and that this effect leads to reduced bond strengths. [source]

    A Convenient Synthesis of Functionalised 1-Aryl-1,3-alkadiynes

    EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 5 2005
    Irina A. Balova
    Abstract A two-step, one-pot synthesis of functionalised 1-arylalka-1,3-diynes is described. A key feature in this approach is exploitation of the "acetylene zipper" reaction to obtain terminal 1,3-alkadiynes 3 from internal isomers 1. Without isolation, but after protonation, the 1,3-alkadiynes 3 are subjected to subsequent Pd/Cu-catalyzed Sonogashira cross-couplings with aryl iodides having both electron-withdrawing and electron-donating groups. The whole sequence takes place under mild reaction conditions to afford functionalised 1-arylalka-1,3-diynes 21,35 in high yields. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source]

    Self-Propagating Domino-like Reactions in Oxidized Graphite

    ADVANCED FUNCTIONAL MATERIALS, Issue 17 2010
    Franklin Kim
    Abstract Graphite oxide (GO) has received extensive interest as a precursor for the bulk production of graphene-based materials. Here, the highly energetic nature of GO, noted from the self-propagating thermal deoxygenating reaction observed in solid state, is explored. Although the resulting graphene product is quite stable against combustion even in a natural gas flame, its thermal stability is significantly reduced when contaminated with potassium salt by-products left from GO synthesis. In particular, the contaminated GO becomes highly flammable. A gentle touch with a hot soldering iron can trigger violent, catastrophic, total combustion of such GO films, which poses a serious fire hazard. This highlights the need for efficient sample purification methods. Typically, purification of GO is hindered by its tendency to gelate as the pH value increases during rinsing. A two-step, acid,acetone washing procedure is found to be effective for suppressing gelation and thus facilitating purification. Salt-induced flammability is alarming for the fire safety of large-scale manufacturing, processing, and storage of GO materials. However, the energy released from the deoxygenation of GO can also be harnessed to drive new reactions for creating graphene-based hybrid materials. Through such domino-like reactions, graphene sheets decorated with metal and metal oxide particles are synthesized using GO as the in situ power source. Enhanced electrochemical capacitance is observed for graphene sheets loaded with RuO2 nanoparticles. [source]

    Self-Propagating Domino-like Reactions in Oxidized Graphite

    ADVANCED FUNCTIONAL MATERIALS, Issue 17 2010
    Franklin Kim
    Abstract Graphite oxide (GO) has received extensive interest as a precursor for the bulk production of graphene-based materials. Here, the highly energetic nature of GO, noted from the self-propagating thermal deoxygenating reaction observed in solid state, is explored. Although the resulting graphene product is quite stable against combustion even in a natural gas flame, its thermal stability is significantly reduced when contaminated with potassium salt by-products left from GO synthesis. In particular, the contaminated GO becomes highly flammable. A gentle touch with a hot soldering iron can trigger violent, catastrophic, total combustion of such GO films, which poses a serious fire hazard. This highlights the need for efficient sample purification methods. Typically, purification of GO is hindered by its tendency to gelate as the pH value increases during rinsing. A two-step, acid,acetone washing procedure is found to be effective for suppressing gelation and thus facilitating purification. Salt-induced flammability is alarming for the fire safety of large-scale manufacturing, processing, and storage of GO materials. However, the energy released from the deoxygenation of GO can also be harnessed to drive new reactions for creating graphene-based hybrid materials. Through such domino-like reactions, graphene sheets decorated with metal and metal oxide particles are synthesized using GO as the in situ power source. Enhanced electrochemical capacitance is observed for graphene sheets loaded with RuO2 nanoparticles. [source]

    Enhancement of Interconnectivity in the Channels of Pentacene Thin-Film Transistors and Its Effect on Field-Effect Mobility,

    ADVANCED FUNCTIONAL MATERIALS, Issue 14 2006
    S. Lee
    Abstract With the aim of improving the field-effect mobility of transistors by promoting the interconnectivity of the grains in pentacene thin films, deposition conditions of the pentacene molecules using one-step (total thickness of layer 50,nm: 0.1,Å,s,1) and two-step (first layer 10,nm: 0.1,Å,s,1, second layer 40,nm: 4.0,Å,s,1) depositions are controlled. Significantly, it is found that the continuities of the pentacene thin films vary with the deposition conditions of the pentacene molecules. Specifically, a smaller number of voids is observed at the interface for the two-step deposition, which results in field-effect mobilities as high as 1.2,cm2,V,1,s,1; these are higher by more than a factor of two than those of the pentacene films deposited in one step. This remarkable increase in field-effect mobility is due in particular to the interconnectivity of the pentacene grains near the insulator substrate. [source]

    Do Medicaid Wage Pass-through Payments Increase Nursing Home Staffing?

    HEALTH SERVICES RESEARCH, Issue 3 2010
    Zhanlian Feng
    Objective. To assess the impact of state Medicaid wage pass-through policy on direct-care staffing levels in U.S. nursing homes. Data Sources. Online Survey Certification and Reporting (OSCAR) data, and state Medicaid nursing home reimbursement policies over the period 1996,2004. Study Design. A fixed-effects panel model with two-step feasible-generalized least squares estimates is used to examine the effect of pass-through adoption on direct-care staff hours per resident day (HPRD) in nursing homes. Data Collection/Extraction Methods. A panel data file tracking annual OSCAR surveys per facility over the study period is linked with annual information on state Medicaid wage pass-through and related policies. Principal Findings. Among the states introducing wage pass-through over the study period, the policy is associated with between 3.0 and 4.0 percent net increases in certified nurse aide (CNA) HPRD in the years following adoption. No discernable pass-through effect is observed on either registered nurse or licensed practical nurse HPRD. Conclusions. State Medicaid wage pass-through programs offer a potentially effective policy tool to boost direct-care CNA staffing in nursing homes, at least in the short term. [source]

    A Modular Approach to ,-Arylated Carbonyl Compounds via Indium Tris(bistriflylamide)-Catalyzed Regioselective Addition of ,-Ketoesters to 1,3-Diynes

    ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 11-13 2005
    Masaharu Nakamura
    Abstract A modular synthesis of ,-arylated carbonyl compounds has been achieved by the combination of an indium-catalyzed regioselective addition of ,-keto esters to conjugated diynes and a palladium-catalyzed benzannulation reaction. Indium tris(bistriflylamide), In(NTf2)3, was found to be an efficient catalyst for the first addition reaction of ,-keto esters to diynes. The reaction proceeds with perfect regioselectivity to give conjugated enynes in high yield. The second palladium-catalyzed benzannulation proceeds in high to excellent yield and with high regioselectivity for a variety of diynes. This two-step ,-arylation of carbonyl compounds thus proceeds in a catalytic manner without loss of elements in the starting materials. The reaction may be performed in a single pot without isolation of the product of the first step. [source]

    Influence of melt drawing on the morphology of one- and two-step processed LDPE/thermoplastic starch blends

    ADVANCES IN POLYMER TECHNOLOGY, Issue 4 2003
    F. J. Rodriguez-Gonzalez
    Abstract In this study the morphology of LDPE/TPS blends prepared by a one-step extrusion process is compared to that obtained by reprocessing of the original blends. The influence of composition and melt drawing is examined. A novel methodology based on the form factor of the dispersed particle was used to estimate the equivalent spherical particle size of dispersed thermoplastic starch (TPS). This approach allows for the quantitative comparison of average dispersed phase particles regardless of their shape. Blends prepared in the one-step extrusion process show increased levels of anisotropy as a consequence of a combination of coalescence and particle deformation during melt drawing. Reprocessed materials demonstrate morphologies that are highly stable to a wide range of hot stretch ratio conditions. The TPS particles of reprocessed blends show no coalescence and a low degree of deformation. This phenomenon is explained by plasticizer evaporation resulting from the second processing step. The TPS is transformed from a highly deformable phase to one resembling a partially cross-linked material. These data indicate that the one-step processing of LDPE/TPS blends can be used to generate a wide range of highly elongated morphological structures. A two-step approach, analogous to typical compounding and shaping operations and involving controlled glycerol removal in the second step can be used to prepare a wide range of highly stable, more isotropic, dispersed particle morphologies. © 2003 Wiley Periodicals, Inc. Adv Polym Techn 22: 297,305, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.10057 [source]

    Evaluation of the effect of four self-etching adhesives ondentin permeability

    JOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 1 2009
    Hasan Orucoglu
    Abstract Objective: The aim of this study was to evaluate the effect of two two-step and two single-step self-etching adhesives on dentin permeability using a computerized fluid filtration (CFF) test method. Methodology: Forty recently extracted sound human molar teeth were sectioned at the mid level of the crown to obtain dentin discs of 1 ± 0.2 mm. A total of 40 discs were obtained and randomly divided into four groups (n = 10). The permeability of the discs was measured using the CFF test method before and after application of the following self-etching adhesives: Hybrid Bond, G-Bond, AdheSE, and Protect Bond. Fluid movement measurements were made at 2-min intervals for 8 min, and a mean of the values obtained was calculated for each specimen. Results: The in vitro fluid conductance of dentin discs treated with Hybrid Bond and AdheSE were lower than the dentin discs treated with G-Bond and Protect Bond (p < 0.05). Conclusion: 1-Treating dentin discs with self-etching adhesives caused significant reduction of dentin permeability. 2-All self-etching adhesives allowed diffusion of distilled water. However, AdheSE and Hybrid Bond showed the lowest permeability. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2009 [source]

    Bioactive and mechanically strong Bioglass®-poly(D,L -lactic acid) composite coatings on surgical sutures

    JOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 2 2006
    Q. Z. Chen
    Abstract New coating processes have been investigated for degradable (Vicryl®) and nondegradable (Mersilk®) sutures with the aim to develop Bioglass® coated polymer fibers for wound healing and tissue engineering scaffold applications. First, the aqueous phase of a Bioglass® particle slurry was replaced with a poly(D,L -lactic acid) (PDLLA) polymer dissolved in solvent dimethyle carbonate (DMC) to act as third phase. SEM observations indicated that this alteration significantly improved the homogeneity of the coatings. Second, a new coating strategy involving two steps was developed: the sutures were first coated with a Bioglass®,PDLLA composite film followed by a second PDLLA coating. This two-step process of coating has addressed the problem of poor adherence of Bioglass® particles on suture surfaces. The coated sutures were knotted to determine qualitatively the mechanical integrity of the coatings. The results indicated that adhesion strength of coatings obtained by the two-step method was remarkably enhanced. A comparative assessment of the bioactivity of one-step and two-step produced coatings was carried out in vitro using acellular simulated body fluid (SBF) for up to 28 days. Coatings produced by the two-step process were found to have similar bioactivity as the one-step produced coatings. The novel Bioglass®/PDLLA/Vicryl® and Bioglass®/PDLLA/Mersilk® composite sutures are promising bioactive materials for wound healing and tissue engineering applications. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2006 [source]

    Lipase-catalyzed production of biodiesel from rice bran oil

    JOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 3 2005
    Chao-Chin Lai
    Abstract Biodiesel has attracted considerable attention as an alternative fuel during the past decades. The main hurdle to the commercialization of biodiesel is the cost of the raw material. Use of an inexpensive raw material such as rice bran oil is an attractive option to lower the cost of biodiesel. Two commercially available immobilized lipases, Novozym 435 and IM 60, were employed as catalyst for the reaction of rice bran oil and methanol. Novozym 435 was found to be more effective in catalyzing the methanolysis of rice bran oil. Methanolysis of refined rice bran oil and fatty acids (derived from rice bran oil) catalyzed by Novozym 435 (5% based on oil weight) can reach a conversion of over 98% in 6 h and 1 h, respectively. Methanolysis of rice bran oil with a free fatty acid content higher than 18% resulted in lower conversions (<68%). A two-step lipase-catalyzed methanolysis of rice bran oil was developed for the efficient conversion of both free fatty acid and acylglycerides into fatty acid methyl ester. More than 98% conversion can be obtained in 4,6 h depending on the relative proportion of free fatty acid and acylglycerides in the rice bran oil. Inactivation of lipase by phospholipids and other minor components was observed during the methanolysis of crude rice bran oil. Simultaneous dewaxing/degumming proved to be efficient in removing phospholipids and other minor components that inhibit lipase activity from crude rice bran oil. Copyright © 2005 Society of Chemical Industry [source]

    Genetic polymorphism of CYP2C8 in three Malaysian ethnics: CYP2C8*2 and CYP2C8*3 are found in Malaysian Indians

    JOURNAL OF CLINICAL PHARMACY & THERAPEUTICS, Issue 5 2005
    Y. D. Muthiah PhD candidate
    Summary Background:,CYP2C8 is genetically polymorphic. Four variants, CYP2C8*2, CYP2C8*3, CYP2C8*4 and CYP2C8*5, which contain mutations in the coding regions have been reported to exhibit different enzyme activity as compared with CYP2C8*1. Objective:, To determine the allele frequency of three codon-changing variants (CYP2C8*2, CYP2C8*3 and CYP2C8*4) in the Malaysian population. Method:, Healthy unrelated volunteers from three major races in Malaysia were recruited. The study was approved by the local Research Ethics Committee. DNA was extracted using a standard protocol. A two-step multiplex PCR method was developed to detect three alleles of CYP2C8. PCR results were confirmed by subsequent direct DNA sequencing. Result:, Only the Indians showed CYP2C8 polymorphism with allele frequency of 98% for CYP2C8*1, 0·8% for CYP2C8*2 and 1·2% for CYP2C8*3. CYP2C8*4 was not detected in any of the ethnic groups. Conclusion:, To the best of our knowledge, the current study described, for the first time polymorphisms of CYP2C8 in Malaysian Indians. [source]

    Experimental susceptibility of different life-stages of the giant freshwater prawn, Macrobrachium rosenbergii (de Man), to white spot syndrome virus (WSSV)

    JOURNAL OF FISH DISEASES, Issue 4 2002
    R B Pramod Kiran
    Studies were conducted by injecting/feeding white spot syndrome virus (WSSV) derived from infected shrimp, Penaeus monodon (Fabricius), to different life-stages, namely post-larvae, juveniles, sub-adults and adults of Macrobrachium rosenbergii (de Man). The disease was also induced in brood stock, and the eggs and larvae derived from these animals were subsequently tested for WSSV infection. All the stages except egg used for the experiment were found WSSV positive in histopathology, cross infection bioassay and polymerase chain reaction (PCR) analysis. Experimentally infected post-larvae and juveniles showed a high percentage of mortality and an increased rate of cannibalism. The cumulative mortality in post-larvae was up to 28%; with 28,40% cannibalism resulting in a maximum loss of up to 68%. In juveniles, observed mortality and cannibalism were 10,20% and 6.7,30.0%, respectively, and the maximum loss recorded was 50%. In sub-adults, mortality ranged from 2.8 to 6.7%, cannibalism was up to 20% and the total loss was up to 26.7%. Sub-adults and adults were found to be more tolerant to the infection as evidenced by the mortality pattern. A nested (two-step) PCR resulted in a 570-bp product specific to WSSV in all stages, except the eggs. [source]

    Development of a sensitive diagnostic assay for fish nervous necrosis virus based on RT-PCR plus nested PCR

    JOURNAL OF FISH DISEASES, Issue 5 2000
    L Dalla Valle
    A polymerase chain reaction (PCR)-based assay to detect nervous necrosis virus (NNV) in fish was developed by using two sets of primers designed on a highly conserved region of the coat protein gene encoded by RNA2 of NNV. The first pair of primers amplified a fragment of 605 bp by one-step reverse-transcription (RT)-PCR, while the second pair amplified an internal segment of 255 bp by nested PCR. Addition of nested PCR increased the assay sensitivity 100-fold when carried out in a separate tube (two-step assay) and 10-fold when performed in the same tube (one-step assay). The sensitivity of the two-step assay was 104 times higher than that of virus cultivation. Nested PCR served also to confirm the specificity of the first amplification, as verified also by Southern hybridization analysis and direct sequencing. In species known to be susceptible to infection, such as European sea bass, Dicentrarchus labrax, and gilthead seabream, Sparus aurata, NNV was often detectable in brain tissue by RT-PCR alone but only by the two-step assay in blood, sperm, ovarian tissue or larvae. The same was true for sperm and ovarian tissue of shi drum, Umbrina cirrosa. NNV was also detected in the brains of Japanese red seabream, Pagrus major and brown meagre, Sciaena umbra, suggesting that these species can also be infected. No NNV was detected in samples of Artemia salina nauplii and rotifers obtained from a fish farm with an NNV outbreak. The inclusion of nested PCR in the assay appears to be necessary to screen out NNV-positive broodfish by blood sampling and testing of their larval progeny. [source]

    Substitution-reduction: an alternative process for the [18F]N -(2-fluoroethylation) of anilines

    JOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 4 2004
    Emmanuelle Briard
    Abstract Substitution of a halo atom (chloro or bromo) in easily prepared N -haloacetyl-anilines with no-carrier added (NCA) cyclotron-produced [18F]fluoride ion (18F, t1/2= 109.8 min; ,+=96.9%), followed by reduction with borane,tetrahydrofuran (BH3,THF), provides an alternative route to NCA [18F]N -(2-fluoroethyl)-anilines. This two-step and one-pot process is rapid (,50 min) and moderately high yielding (,40% decay-corrected radiochemical yield (RCY) overall). In the nucleophilic substitution reaction, 18-crown-6 is preferred to Kryptofix® 222 as complexing agent for the solubilization of the counter-ion (K+), derived from an added metal salt, in acetonitrile. Weakly basic potassium bicarbonate is preferred as the added metal salt. Inclusion of a small amount of water, equating to 4,5 molar equivalents relative to 18-crown-6, base or precursor (held in equimolar ratio), is beneficial in preventing the adsorption of radioactivity onto the wall of the glass reaction vessel and for achieving high RCY in the nucleophilic substitution reaction. BH3,THF is effective for the rapid reduction of the generated [18F]N -fluoroacetyl-aniline to the [18F]N -(2-fluoroethyl)-aniline. Copyright © 2004 John Wiley & Sons, Ltd. [source]

    Design of a two-step pulsed pressure-swing adsorption-based oxygen concentrator

    AICHE JOURNAL, Issue 2 2010
    V. Rama Rao
    Abstract A two-step pulsed pressure-swing adsorption (PPSA) process has been modeled to assess the extent to which an oxygen concentrator might be miniaturized for medical applications. The process consists of a single bed of packed adsorbent particles that is alternately pressurized and depressurized at the feed end. An enriched oxygen product is withdrawn at ambient pressure from the product end when the bed is pressurized at the feed end. The product end remains closed during depressurization. The model development addresses the manner in which axial dispersion enters into the describing equations and the formulation of proper boundary conditions, both of which have not been handled rigorously in some prior modeling studies. The describing equations are solved using COMSOL® Multiphysics software. The effect on the performance of the adsorption time, desorption time, bed length, particle diameter, and imposed pressure drop across the bed have been investigated. An interesting novel result is that for a chosen particle size, bed length, and applied pressure drop, there is an optimum combination of adsorption and desorption times that maximizes the product purity. The results suggest that there are operating windows for both 5A and partially Ag-exchanged Li-substituted 13X zeolite adsorbents wherein the product oxygen purity is greater than 90%. At a given product flow rate within this operating window, the extent of miniaturization is limited by the (maximum) cycling frequency that is practically achievable. Sizing of an oxygen concentrator for personal medical applications is also discussed. A principal conclusion is that a compact oxygen concentrator capable of producing a highly oxygen-enriched product is possible using commercially available adsorbents and implementable operating conditions. © 2009 American Institute of Chemical Engineers AIChE J, 2010 [source]

    Synthesis and characterization of conjugated triblock copolymers

    JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 12 2007
    Xing Xiao
    Abstract A series of conjugated triblock copolymers containing hole-transporting polycarbazole segments, electron-transporting polyoxadiazole segments, and blue-light-emitting polyfluorene segments were prepared with a two-step palladium-catalyzed Suzuki polycondensation (SPC). First dibromo-terminated polymer precursors (polyfluorenes and polyoxadiazoles) were synthesized as the central buildingblocks. Then, the dibromo-terminated polymer precursors were further polymerized with AB-type monomers [2-bromo-7-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-9-octylcarbazole, 3-bromo-6-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-9-octylcarbazole, and 2-bromo-7-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-9,9-dioctylfluorene] to achieve the target triblock copolymers under SPC conditions. The formation of the triblock copolymers was confirmed by gel permeation chromatography and NMR spectroscopy. The triblock copolymers exhibited good thermal stability. An investigation of the photophysical properties indicated that efficient, photoinduced through-bond energy transfer occurred in such triblock copolymer systems. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2410,2424, 2007 [source]

    Synthesis of a novel block copolymer containing aromatic polyamide and fluoroethylene segments

    JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 18 2003
    Arata Korematsu
    A novel block copolymer containing aromatic polyamide (aramid) and fluoroethylene segments was synthesized by a two-step, low-temperature solution polycondensation. In the first step, a telechelic diamine was prepared by the reaction of 3,4,-diaminodiphenylether and tetrafluorosuccinic acid in the presence of 1,3-dicyclohexylcarbodiimide as a condensing agent. Next, the block copolymer was synthesized by the polycondensation of the telechelic diamine and isophthaloyl chloride. The number-average molecular weight of this polymer, according to gel permeation chromatography, was over 1.7 × 104. Incorporating fluoroethylene segments improved the solubility of the resulting polymer with respect to conventional aramids. [source]

    Participation of cysteine protease cathepsin L in the gel disintegration of red bulleye (Priacanthus macracanthus) surimi gel paste

    JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 3 2010
    Yaqin Hu
    Abstract BACKGROUND: Endogenous proteases, among them cysteine-type proteases, are reported to contribute to gel disintegration, resulting in kamaboko of poor quality. Severe gel disintegration occurs in red bulleye surimi gel paste. The objective of this study was to clarify the participation of cysteine protease cathepsin L in the gel disintegration of red bulleye surimi. The surimi was made into kamaboko with and without cathepsin L inhibitors. To confirm its hydrolysis action, crude cathepsin L was also extracted and added to the surimi to make kamaboko. RESULTS: The gel strength of kamaboko obtained by both one-step (50 °C, 2 h) and two-step (50 °C, 2 h + 80 °C, 20 min) heating was very low in the absence of inhibitors. Protease inhibitors E-64 and leupeptin were found to enhance the gel strength considerably. Sodium dodecyl sulfate polyacrylamide gel electrophoresis revealed that the hydrolysis of kamaboko was promoted by crude cathepsin L and inhibited by E-64 and leupeptin. The gel strength of two-step heated kamaboko was increased from 12 to 110 and 130 g cm,2 by E-64 and leupeptin respectively at a concentration of 0.2 g kg,1 surimi. CONCLUSION: Endogenous cathepsin L of red bulleye surimi participates in gel disintegration during kamaboko processing. It does so by degrading the myosin heavy chain of actomyosin and consequently hindering the gelation of red bulleye surimi. Copyright © 2009 Society of Chemical Industry [source]

    Fabrication of Chemically Tethered Binary Polymer-Brush Pattern through Two-Step Surface-Initiated Atomic-Transfer Radical Polymerization

    MACROMOLECULAR RAPID COMMUNICATIONS, Issue 23 2004
    Feng Zhou
    Abstract Summary: The communication provides a novel and alternative route to generate chemically tethered binary polymer-brush pattern through two-step surface-initiated atomic-transfer radical polymerization (SI-ATRP). Polymer brush-1 was prepared by SI-ATRP, passivated by a reaction with NaN3, and etched with UV irradiation through a transmission electron microscopy grid to create exposed sites for the subsequently attached initiator on which polymer brush-2 was grown. Schematic representation of the resultant binary polymer brush patterns. [source]

    A host species-informative internal control for molecular assessment of African swine fever virus infection rates in the African sylvatic cycle Ornithodoros vector

    MEDICAL AND VETERINARY ENTOMOLOGY, Issue 4 2009
    A. D. S. BASTOS
    Abstract African swine fever virus (ASFV) infection in adult Ornithodoros porcinus (Murry 1877, sensuWalton 1979) ticks collected from warthog burrows in southern and East Africa was assessed using a duplex genomic amplification approach that is informative with respect to the invertebrate host species and infecting sylvatic cycle virus. DNA extracted from individual ticks was used as template for the simultaneous amplification of a C-terminal 478-bp ASFV p72 gene region and a ,313-bp fragment of the tick mitochondrial 16S rRNA gene, under optimized reaction conditions. Within-warthog burrow infection rates ranged from 0% to 43% using this approach, and phylogenetic analysis of 16S gene sequences revealed the presence of three geographically discrete O. porcinus lineages, but no support for subspecies recognition. False negatives are precluded by the inclusion of host species-informative primers that ensure the DNA integrity of cytoplasmically located genome extracts. In addition, infection rate estimates are further improved as false positives arising from carry-over contamination when performing a two-step nested polymerase chain reaction are negated by the one-step approach. Phylogenetic comparison of full-length virus gene sequences with the partial C-terminal p72 gene target confirmed the epidemiological utility of the latter in a sylvatic setting. The method is therefore of particular value in studies assessing the prevalence and diversity of ASFV in relation to the African sylvatic tick vector and holds potential for investigating the role of alternative tick species in virus maintenance and transmission. [source]

    Identification of the intermediate hosts of Habronema microstoma and Habronema muscae under field conditions

    MEDICAL AND VETERINARY ENTOMOLOGY, Issue 3 2008
    D. TRAVERSA
    Abstract A polymerase chain reaction (PCR)-based assay was used for the specific detection of Habronema microstoma and Habronema muscae (Nematoda, Spirurida) in order to identify the intermediate hosts of both nematode species under field conditions. A total of 1087 netted and 165 laboratory-bred flies were tested. Flies were identified as Musca domestica Linnaeus 1758, Musca autumnalis De Geer 1776, Haematobia irritans (Linnaeus 1758), Haematobia titillans (De Geer 1907) and Stomoxys calcitrans (Linnaeus 1758) (Muscidae). Genomic DNA was extracted from pools of fly heads, thoraces and abdomens, and 703 samples were subjected to a duplex two-step semi-nested PCR assay to specifically detect diagnostic regions within the ribosomal ITS2 sequence of both H. microstoma and H. muscae. Stomoxys calcitrans specimens were positive for H. microstoma DNA and M. domestica specimens were positive for H. muscae DNA. In particular, PCR-positive samples derived from both farm-netted and laboratory-bred flies. The present study represents the first evidence of the vectorial competence of different fly species as intermediate hosts of Habronema stomachworms under field conditions. We discuss the roles of S. calcitrans and M. domestica in transmitting H. microstoma and H. muscae. [source]