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Significant Enhancement (significant + enhancement)
Selected AbstractsEffects of Chain Length and N-Methylation on a Cation,, Interaction in a ,-Hairpin PeptideCHEMISTRY - A EUROPEAN JOURNAL, Issue 20 2007Robert Abstract The effects of N-methylation and chain length on a cation,, interaction have been investigated within the context of a ,-hairpin peptide. Significant enhancement of the interaction and structural stabilization of the hairpin have been observed upon Lys methylation. Thermodynamic analysis indicates an increased entropic driving force for folding upon methylation of Lys residues. Comparison of lysine to analogues ornithine (Orn) and diaminobutyric acid (Dab) indicates that lysine provides the strongest cation,, interaction and also provides the most stable ,-hairpin due to a combination of side chain,side chain interactions and ,-sheet propensities. These studies have significance for the recognition of methylated lysine in histone proteins. [source] How Do the Different Defect Structures and Element Substitutions Affect the Nonlinear Optical Properties of Lacunary Keggin Polyoxometalates?EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 20 2006A DFT Study Abstract Systematic DFT calculations have been carried out on the lacunary ,-Keggin polyoxometalate derivatives [PW11O39]7,, [XW9O34]n, (X = AlIII, SiIV, GeIV, PV, AsV, and SbV), [XW9M2O39]n,, and [XW9M3O40]n, (X = PV and SiIV, M = MoVI, VV, NbV, and TaV) to investigate the geometric structure and element substitution effects on the molecular nonlinear optical response. Analysis of the computed static second-order polarizability (,0) predicts that the molecular nonlinear optical activity of lacunary Keggin polyoxometalate derivatives can be modified by replacing the central heteroatom and the addenda metal atom. Substitution of the central Al atom or the addenda V atom causes significant enhancement in the molecular nonlinearity. Moreover, the ,0 values are substantially dependent on the defect structures. This class of inorganic complexes possesses remarkably large molecular optical nonlinearity, especially for the partial substitution complex [SiW9Nb2O39]10, (IIIc), which has a computed ,0 value of 2071.0 a.u. Thus, lacunary Keggin polyoxometalates could become excellent candidates in the field of second-order NLO. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Acute and long-term changes in the mesolimbic dopamine pathway after systemic or local single nicotine injectionsEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 11 2002R. Ferrari Abstract We have examined several neurochemical and behavioural parameters related to the function of the mesolimbic dopamine (DA) pathway in animals treated with nicotine following three modes of drug administration, i.e. systemic intraperitoneal injection, intra-accumbens (Acb) infusion or intraventral tegmental area (intra-VTA) microinjection. The present modes of systemic, intra-Acb and intra-VTA nicotine administration elicited comparable acute increases in dialysate DA levels from the Acb. The increase in extracellular DA levels was paralleled by a significant enhancement of locomotion in a habituated environment in the case of systemic or intra-VTA nicotine administration, whereas unilateral or bilateral intra-Acb nicotine infusion was ineffective, showing that accumbal DA increase is not sufficient to elicit locomotion in this experimental paradigm. Intra-VTA, but not systemic or intra-Acb, nicotine administration caused a long-term (at least 24-h) increase in basal dialysate DA levels from the Acb. In addition, significant increases in tyrosine hydroxylase (TH) and GluR1 (but not dopamine transporter or NR1) mRNA levels in the VTA were detected 24 h after intra-VTA nicotine administration. Systemic nicotine injection caused only an increase in TH mRNA levels while intra-Acb infusion did not modify any of the mRNAs tested. The long-term increase in basal DA levels in the Acb and TH, and GluR1 mRNA levels in the VTA upon intra-VTA nicotine microinjection indicates that even a single nicotine injection can induce plastic changes of the mesolimbic DA pathway. [source] Time-dependent enhancement of inhibitory avoidance retention and MAPK activation by post-training infusion of nerve growth factor into CA1 region of hippocampus of adult ratsEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 6 2000Roger Walz Abstract Several studies have demonstrated that chronic intracerebroventricular nerve growth factor (NGF) infusion has a beneficial effect on cognitive performance of lesioned as well as old and developing animals. Here we investigate: (i) the effect of post-training infusion of NGF into the CA1 region of hippocampus on inhibitory avoidance (IA) retention in rats; (ii) the extension of the effect, in time and space, of NGF infusion into CA1 on the activity of mitogen-activated protein kinase (MAPK, syn: ERK1/2, p42/p44 MAPK). NGF was bilaterally injected into the CA1 regions of the dorsal hippocampus (0.05, 0.5 or 5.0 ng diluted in 0.5 ,L of saline per side ) at 0, 120 or 360 min after IA training in rats. Retention testing was carried out 24 h after training. The injection of 5.0 and 0.5, but not 0.05, ng per side of NGF at 0 and 120 min after IA training enhanced IA retention. The highest dose used was ineffective when injected 360 min after training. The infusion of 0.5 ,L of NGF (5.0 ng) induced a significant enhancement of MAPK activity in hippocampal microslices; this enhancement was restricted to a volume with 0.8 mm radius at 30 min after injection. The MAPK activation was still seen 180 min after NGF infusion, although this value showed only a tendency. In conclusion, localized infusion of NGF into the CA1 region enhanced MAPK activity, restricted in time and space, and enhanced IA retention in a time- and dose-dependent manner. [source] Enhanced Electrical Switching and Electrochromic Properties of Poly(p-phenylenebenzobisthiazole) Thin Films Embedded with Nano-WO3ADVANCED FUNCTIONAL MATERIALS, Issue 18 2010Jiahua Zhu Abstract The electrical switching and electrochromic phenomena of a novel nanocomposite comprising poly(p-phenylenebenzobisthiazole) (PBZT) and tungsten oxide (WO3) nanoparticles are investigated as a function of the nanoparticle loading. Both dissolving PBZT and doping PBZT backbone structure with acid are achieved by one simple step. Chlorosulfonic acid (CSA) is used as a solvent and spontaneously transformed to sulfuric acid upon exposure to moisture. The formed sulfuric acid serves as doping agent to improve the electrical conductivity of PBZT. The most significant enhancement of electrical switching is observed in the nanocomposites with low weight fraction (5%). The electrical conductivity of 5% WO3/PBZT nanocomposite thin film is increased by about 200 times and 2 times, respectively, as compared to those of the as-received PBZT and PBZT/CSA thin films. As the nanoparticle loading increases to 20% and 30%, the nanocomposites follow an ohmic conduction mechanism. Stable electrical conductivity switching is observed before and after applying a bias on the pristine PBZT and WO3/PBZT nanocomposite thin films. Electrochromic phenomena of both PBZT and WO3/PBZT nanocomposite thin films with high contrast ratio are observed after applying a bias (3 V). The mechanisms of the nanoparticles in enhancing the electrical switching and electrochromic properties are proposed. [source] Enhancement of Carrier Mobilities of Organic Semiconductors on Sol,Gel Dielectrics: Investigations of Molecular Organization and Interfacial Chemistry EffectsADVANCED FUNCTIONAL MATERIALS, Issue 3 2009Tommy Cahyadi Abstract The dielectric-semiconductor interfacial interactions critically influence the morphology and molecular ordering of the organic semiconductor molecules, and hence have a profound influence on mobility, threshold voltage, and other vital device characteristics of organic field-effect transistors. In this study, p-channel small molecule/polymer (evaporated pentacene and spin-coated poly(3,3,;-didodecylquarterthiophene) , PQT) and n-channel fullerene derivative ({6}-1-(3-(2-thienylethoxycarbonyl)-propyl)-{5}-1-phenyl-[5,6]-C61 , TEPP-C61) show a significant enhancement in device mobilities ranging from ,6 to ,45 times higher for all classes of semiconductors deposited on sol,gel silica gate-dielectric than on pristine/octyltrichlorosilane (OTS)-treated thermally grown silica. Atomic force microscopy, synchrotron X-ray diffraction, photoluminescence/absorption, and Raman spectroscopy studies provide comprehensive evidences that sol,gel silica dielectrics-induced enhancement in both p- and n-channel organic semiconductors is attributable to better molecular ordering/packing, and hence reduced charge trapping centers due to lesser structural defects at the dielectric-semiconductor interface. [source] Critical heat flux enhancement in pool boiling using alumina nanofluidsHEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 5 2010Ramakrishna Hegde Abstract The pool boiling characteristics of dilute dispersions of alumina nanoparticles in water were studied. Consistent with other nanofluid studies, it was found that a significant enhancement in critical heat flux (CHF) can be achieved at modest nanoparticle concentrations (<0.1% by volume). During experimentation and subsequent inspection, formation of a porous layer of nanoparticles on the heater surface occurred during nucleate boiling. This layer significantly changes surface texture of the heater wire surface which could be the reason for improvement in the CHF value. © 2010 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20301 [source] Fluid flow and heat transfer characteristics of cone orifice jet (effects of cone angle)HEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 4 2009Mizuki Kito Abstract The use of a jet from an orifice nozzle with a saddle-backed-shape velocity profile and a contracted flow at the nozzle exit may improve the heat transfer characteristics on an impingement plate because of its larger centerline velocity. However, it requires more power to operate than a common nozzle because of its higher flow resistance. We therefore initially considered the use of a cone orifice nozzle to obtain better heat transfer performance as well as to decrease the flow resistance. We examined the effects of the cone angle , on the cone orifice free jet flow and heat transfer characteristics of the impinging jet. We compared two nozzles: a pipe nozzle and a quadrant nozzle. The first one provides a velocity profile of a fully developed turbulent pipe flow, and the second has a uniform velocity profile at the nozzle exit. We observed a significant enhancement of the heat transfer characteristics of the cone orifice jets at Re=1.5×104. Using the cone orifice impinging jets enhanced the heat transfer rates as compared to the quadrant jet, even when the jets were supplied with the same operational power as the pipe jet. For instance, a maximum enhancement up to approximately 22% at r/do,0.5 is observed for ,=15°. In addition, an increase of approximately 7% is attained as compared to when the pipe jet was used. © 2009 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20243 [source] Prediction of turbulent flow and heat transfer within rotating U-shaped passagesHEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 6 2006Liu Chuan Kai Abstract Numerical predictions of three-dimensional flow and heat transfer are presented for rotating serpentine passages with and without rib turbulators. The coolant air is pressurized and its operating conditions are selected closely to match actual turbine operating parameters. Two different arrangements of rib turbulators were studied: (1) transverse ribs on the leading and trailing walls and (2) transverse ribs on all four walls. The rib height-to-hydraulic diameter ratio (e/Dh) is 0.143; the rib pitch-to-height ratio (s/e) is 7. Results for the rib-roughened serpentine passages were compared with those of smooth ones calculated in the literature. It was shown that a significant enhancement is achieved by means of rib turbulators in a serpentine passage at a stationary state as well as in a rotating state. In the radially-outward flow passages, the effect of rotation on heat transfer is relatively prominent. The secondary flows induced by the Coriolis forces are most intensive in the channel with four ribbed surfaces. The heat transfer after a 180° sharp turn in the smooth channel is influenced more by the sharp-turn-induced flow than the rib-roughened ones. © 2006 Wiley Periodicals, Inc. Heat Trans Asian Res, 35(6): 410,420, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20125 [source] The effects of the glutamate antagonist memantine on brain activation to an auditory perception taskHUMAN BRAIN MAPPING, Issue 11 2009Heidi van Wageningen Abstract Glutamate is critically involved in the regulation of cognitive functions in humans. There is, however, sparse evidence regarding how blocking glutamate action at the receptor site during a cognitive task affects brain activation. In the current study, the effects of the glutamate antagonist memantine were examined with functional magnetic resonance imaging (fMRI). Thirty-one healthy adults were scanned twice in a counter-balanced design, either in a no-drug session or after administration of memantine for 21 days. The subjects performed a simple auditory perception task with consonant-vowel stimuli. Group-level spatial independent component analysis (ICA) was used to decompose the data and to extract task-related activations. The focus was on four task-related ICA components with frontotemporal localization. The results showed that glutamate-blockage resulted in a significant enhancement in one component, with no significant effect in the other three components. The enhanced effect of memantine was in the middle temporal gyrus, superior frontal gyrus, and middle frontal gyrus. It is suggested that the results reflect effects of glutamatergic processes primarily through non- N -methyl- D -aspartate (NMDA) receptor pathways. Moreover, the results demonstrate that memantine can be used as a probe which allows for studying the effect of excitatory neurotransmission on neuronal activation. Hum Brain Mapp, 2009. © 2009 Wiley-Liss, Inc. [source] Modulation of the intraseasonal rainfall over tropical Brazil by the Madden,Julian oscillationINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 13 2006Everaldo B. De Souza Abstract Fifteen years (1987,2001) of rain gauge-based data are used to describe the intraseasonal rainfall variability over tropical Brazil and its associated dynamical structure. Wavelet analysis performed on rainfall time series showed significant peaks centered roughly in periods of 30,70 days, particularly in the eastern southeastern Amazon and northern northeast Brazil. A significant enhancement of precipitation with maximum anomalies in a northeastward oriented band over tropical Brazil is evidenced from empirical orthogonal function (EOF) analysis of 30,70-day filtered rainfall anomalies during rainy season (January to May). Lagged/lead composites revealed that, on a global scale, the Madden,Julian oscillation (MJO) is the main atmospheric-mechanism modulator of the pluviometric variations on intraseasonal timescale in the eastern Amazon and northeast Brazil. A coherent northward expansion of rainfall across tropical Brazil is evident during the passage of MJO over South America. Regionally, the establishment of a quasi-stationary deep convection band triggered by the simultaneous manifestation of south Atlantic convergence zone (SACZ) and intertropical convergence zone (ITCZ) explains the intensified rainfall over these regions. Such regional mechanisms are dynamically embedded within the eastward-propagating MJO-related large-scale convective envelope along tropical South America/the Atlantic Ocean. These features occur in association with a significant intraseasonal evolution of the lower-level wind and sea-surface temperature (SST) patterns, particularly in the Atlantic Ocean, including a coherent dynamical connection with atmospheric circulation, deep convective activity over South America and rainfall over tropical Brazil. Copyright © 2006 Royal Meteorological Society [source] Investigation of multi-layered-gate electrode workfunction engineered recessed channel (MLGEWE-RC) sub-50,nm MOSFET: A novel designINTERNATIONAL JOURNAL OF NUMERICAL MODELLING: ELECTRONIC NETWORKS, DEVICES AND FIELDS, Issue 3 2009Rishu Chaujar Abstract In this paper, a two-dimensional (2D) analytical sub-threshold model for a novel sub-50,nm multi-layered-gate electrode workfunction engineered recessed channel (MLGEWE-RC) MOSFET is presented and investigated using ATLAS device simulator to counteract the large gate leakage current and increased standby power consumption that arise due to continued scaling of SiO2 -based gate dielectrics. The model includes the evaluation of surface potential, electric field along the channel, threshold voltage, drain-induced barrier lowering, sub-threshold drain current and sub-threshold swing. Results reveal that MLGEWE-RC MOSFET design exhibits significant enhancement in terms of improved hot carrier effect immunity, carrier transport efficiency and reduced short channel effects proving its efficacy for high-speed integration circuits and analog design. Copyright © 2008 John Wiley & Sons, Ltd. [source] Assessment of Growth, Physiological and Biochemical Parameters and Activities of Antioxidative Enzymes in Salinity Tolerant and Sensitive Basmati Rice VarietiesJOURNAL OF AGRONOMY AND CROP SCIENCE, Issue 6 2007M. P. Singh Abstract This investigation was undertaken to compare the level of salinity tolerance of the newly bred CSR-30 basmati rice variety with that of the salinity sensitive HBC-19 and Pokkali rice varieties. Twenty-one-day-old hydroponically raised seedlings at 6 and 12 dS m,1 were investigated for growth, photosynthetic rate, chlorophyll content, ribulose-1,5-bisphosphate carboxylase-oxygenase (Rubisco) activity, relative water content (RWC), membrane stability index (MSI), lipid peroxidation, Na/K ratio and activities and gene expression of various isoforms of antioxidative enzymes. Salinity stress led to reduction in shoot length, leaf area, dry weight, RWC, MSI, rate of photosynthesis, chlorophyll content and Rubisco activity in all the three rice varieties. The levels of reduction in these parameters were maximal in HBC-19 followed by those in CSR-30 and Pokkali respectively. Cumulative superoxide dismutase (SOD) activity increased in Pokkali and CSR-30 in consonance with increase in salinity stress while it decreased in HBC-19. The Mn-SOD activity however, was enhanced in all three varieties in the presence of salinity stress while the activities of Fe-SOD, Cu/Zn-SOD and ascorbate peroxidase were decreased in HBC-19 when compared with CSR-30 and Pokkali. The activity of catalase (CAT) was higher in HBC-19 when compared with its activity in CSR-30 and Pokkali. The levels of gene expressions of the three isoforms of SOD ascertained by reverse transcriptase polymerase chain reaction were not necessarily indicative of the activities of the corresponding enzymes. Thus, despite the maximal enhancement in gene expression of Fe-SOD in HBC-19 in response to salinity stress, the activity of this enzyme in HBC-19 remained low. Similarly, despite a marginal increase in gene expression of Cu-Zn SOD in the three varieties, its activity was significantly higher in Pokkali and CSR-30 when compared with that in HBC-19. A significant enhancement in the activity of CAT at 12 dS m,1 in HBC-19 when compared with CSR-30 and Pokkali might confer a degree of tolerance to H2O2 stress in this variety in the presence of higher levels of NaCl at the seedling stage. [source] Identification of some optimal parameters to achieve higher laminate quality through tape placement processADVANCES IN POLYMER TECHNOLOGY, Issue 2 2010Muhammad Amir Khan Abstract Investigations of the tape placement process are still underway to achieve the laminate quality comparable with other highly developed composite manufacturing methods, such as autoclave-based processes. The evaluation of the products and the mechanical properties of the material has revealed regions where some upgrading could bring significant enhancement in performance. This study is concerned with issues related to the characterization of material properties, interlaminar bond development, and ways of optimizing process parameters. These include heating, layup velocity, tool temperature, and consolidation force, which were studied to determine their effects on the mechanical strength of the composites produced. The bonding degree of the laminates was simulated taking into account a combination of process parameters, comparing the predictions with the actual test results. The thermal stability of the polyether ether ketone matrix, in relation to the processing conditions used in the manufacture, and their effects on the interlaminar bonding stability were also investigated and explained. © 2010 Wiley Periodicals, Inc. Adv Polym Techn 29:98,111, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20177 [source] Efficient utilization of plastic waste through product design and process adaptation: A case study on stiffness enhancement of beams produced from plastic lumberADVANCES IN POLYMER TECHNOLOGY, Issue 3 2008Cristian Pio Abstract The aim of the present work is the development of a method for structural reinforcement of beams obtained by in-mold extrusion of plastics from solid urban waste. The beams obtained by in-mold extrusion are commonly used for outdoor furniture and structures. The material used for such applications is mainly composed of low-density polyethylene derived from bags and films, with small amounts of high density polyethylene and polypropylene, as well as traces of polyethylene terephthalate. This material is usually referred to as "plastic lumber." Plastic lumber products have a low stiffness, which results in high deflections under flexural loads, particularly under creep loading. In this study, reinforcing rods of high aspect ratio were incorporated into plastic lumber beams in specific positions with respect to the cross section of the beam. The reinforcement of the plastic lumber beams with fine rods is introduced in the typical intrusion process used for the production of unreinforced beams. Glass fiber reinforced pultruded rods were chosen for this purpose from a preliminary evaluation of different materials. Different diameter glass fiber reinforced pultruded rods, including surface-abraded systems to increase the roughness, were used for the reinforcement of plastic lumber beams. The reinforced beams were tested in terms of flexural stiffness, creep resistance, and pullout resistance of the embedded rods. The results obtained from the mechanical tests showed a significant enhancement of flexural stiffness and creep resistance behavior. The performance at higher stress levels was shown to be significantly dependent on the interfacial adhesion between rods and polymer matrix. © 2009 Wiley Periodicals, Inc. Adv Polym Techn 27:133,142, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20131 [source] Synthesis and characterization of a cured epoxy resin with a benzoxazine monomer containing allyl groupsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2010Shiao-Wei Kuo Abstract Vinyl-terminated benzoxazine (VB-a), which can be polymerized through ring-opening polymerization, was synthesized through the Mannich condensation of bisphenol A, formaldehyde, and allylamine. This VB-a monomer was then blended with epoxy resin and then concurrently thermally cured to form an epoxy/VB-a copolymer network. To understand the curing kinetics of this epoxy/VB-a copolymer, dynamic differential scanning calorimetry measurements were performed by the Kissinger and Flynn,Wall,Ozawa methods. Fourier transform infrared (FTIR) analyses revealed the presence of thermal curing reactions and hydrogen-bonding interactions of the epoxy/VB-a copolymers. Meanwhile, a significant enhancement of the ring-opening and allyl polymerizations of the epoxy was observed. For these interpenetrating polymer networks, dynamic mechanical analysis and thermogravimetric analysis results indicate that the thermal properties increased with increasing VB-a content in the epoxy/VB-a copolymers. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Intermittent watt-level ultrasonication facilitates vancomycin release from therapeutic acrylic bone cementJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 1 2009Xun-Zi Cai Abstract Ultrasound holds promise for enhancing the vancomycin release from cement though the length of time when local drug level exceeded the minimum inhibitory concentration (T>MIC) was not prolonged by the previous protocol of milliwatt-level ultrasonication. Here vancomycin-loaded cements were subjected to continuous watt-level ultrasonication (CUG), intermittent watt-level ultrasonication (IUG) or no ultrasonication (NUG) for 14 d during immersion in 40-ml phosphate buffered saline (PBS) for 28 d. The T>MIC for IUG was more than three times that for NUG. In contrast, T>MIC for CUG was slightly shortened. The subtherapeutic release of vancomycin between 15 d and 28 d for IUG was one-ninth that for NUG. The fitting equations indicated a significant enhancement on the burst release and the slow release for IUG; however, the continuous ultrasonication hampered the slow release. SEM images exhibited denser craters and pores with larger diameters and less residual drug in specimens from IUG relative to those from both CUG and NUG. Intermittent watt-level ultrasonication improved the ultrasound-enhanced vancomycin release from cement in view of the prolonged T>MIC and the inhibited subtherapeutic release compared with continuous ultrasonication. The mechanisms may be associated with the distinctive effects of detaching forces and pushing forces by acoustic microstreams. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2009 [source] Combining microwave and ultrasound irradiation for rapid synthesis of nanowires: a case study on Pb(OH)BrJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 12 2009Xiao-Fang Shen Abstract BACKGROUND: One-dimensional (1D) nanostructures such as wires, tubes and belts have attracted much attention in recent years because of their fascinating properties and promising applications, and various methods have been developed to prepare 1D nanostructures. Microwave and ultrasound, two methodologies for rapid synthesis, have both been applied to fabricate nanostructures. This paper reports on combining microwave and ultrasound irradiation as a new strategy for rapid synthesis of nanowires. Using Pb(OH)Br as a study case, nanowires were rapidly synthesized under the combined irradiation. The use of the ionic liquid 1-butyl-3-methylimidazolium bromide as a structure-directing agent and microwave absorbent significantly simplified the preparation procedure. RESULTS: Combined microwave,ultrasound irradiation at (50 W,50 W) greatly reduced the reaction time (10 min) and significantly increased the product yield (45.0%) in comparison with conventional heating (24 h reaction time, 23.0% yield). Combined microwave,ultrasound irradiation at (50 W,50 W) also changed the resultant wires from 20,30 µm diameter and 2,3 mm long to 80,800 nm and 50,100 µm, respectively. Further increase in power of the combined irradiation (250 W,50 W) led to a dramatic reduction in the reaction time (80 s) with a slightly increased yield of 48.2%. CONCLUSIONS: The obvious advantages of combined microwave,ultrasound irradiation are marked improvement of the product yield, significant enhancement of reaction rate and increased aspect ratio of the 1D structure. Copyright © 2009 Society of Chemical Industry [source] Non-specific immune response of turbot, Scophthalmus maximus (L.), experimentally infected with a pathogenic Vibrio pelagiusJOURNAL OF FISH DISEASES, Issue 6 2003L Villamil Abstract The effect of a pathogenic Vibrio pelagius, isolated during a mass mortality of turbot larvae, on the non-specific immune response of turbot, Scophthalmus maximus (L.), macrophages was studied both in vitro and in vivo. The in vitro treatment of head kidney (HK) macrophages with viable V. pelagius caused a significant inhibition of the chemiluminescence (CL) response in comparison with untreated macrophages, while incubation with heat-killed bacteria did not affect this response. In vivo, the intraperitoneal injection of V. pelagius resulted in a significant inhibition of the CL response in infected fish at days 1 and 4 post-infection compared with the control fish response. The HK macrophage nitric oxide (NO) production was enhanced by in vitro incubation with intermediate doses of viable V. pelagius (5 × 103 and 5 × 104 bacteria mL,1) and higher doses of the heat-killed bacteria (5 × 104,5 × 106 bacteria mL,1). In both cases, the NO inhibitorN- , -nitro-L-arginine was capable of down-regulating the specific NO induction caused by incubation with the bacterial treatments. In contrast, incubation with ECPs at higher doses caused a reduction in NO production. In vivo, a significant enhancement in NO production was also observed in macrophage supernatants at day 10 post-infection. Lysozyme concentration in the serum was also significantly increased in the experimentally infected fish at days 4 and 10 post-injection. In addition, viable V. pelagius and its ECPs significantly reduced HK macrophage viability in vitro, whereas no significant differences in viability were observed during the incubation with heat-killed bacteria. As NO production was enhanced in the experimentally infected fish, the inhibitory effect of the NO donor, S-nitroso-acetyl-penicillamine (SNAP), was tested in vitro in a cell-free assay. The results showed that growth of V. pelagius was significantly inhibited using SNAP at a high concentration (1 mm). [source] Lead Induced Changes in the Growth and Antioxidant Metabolism of the Lead Accumulating and Non-accumulating Ecotypes of Sedum alfrediiJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 2 2008Dan Liu Abstract The phytotoxicity and antioxidative adaptations of lead (Pb) accumulating ecotype (AE) and non-accumulating ecotype (NAE) of Sedum alfredii Hance were investigated under different Pb treatments involving 0, 0.02 mmol/L Pb, 0.1 mmol/L Pb and 0.1 mmol/L Pb/0.1 mmol/L ethylenediaminetetraacetic acid (EDTA) for 6 days. With the increasing Pb level, the Pb concentration in the shoots of AE plants enhanced accordingly, and EDTA supply helped 51% of Pb translocation to shoots of AE compared with those treated with 0.1 mmol/L Pb alone. Moreover, the presence of EDTA alleviated Pb phytotoxicity through changes in plant biomass, root morphology and chlorophyll contents. Lead toxicity induced hydrogen peroxide (H2O2) accumulation and lipid peroxidation in both ecotypes of S. alfredii. The activities of superoxide dismutase (SOD), guaiacol peroxidase (G-POD), ascorbate peroxidase, and dehydroascorbate reductase elevated in both leaves and roots of AE as well as in leaves of NAE with the increasing Pb levels, but SOD and G-POD declined in roots of NAE. Enhancement in glutathione reductase activity was only detected in roots of NAE while a depression in catalase activity was recorded in the leaves of NAE. A significant enhancement in glutathione and ascorbic acid (AsA)levels occurred in both ecotypes exposed to Pb and Pb/EDTA treatment compared with the control, however, the differences between these two treatments were insignificant. The dehydroascorbate (DHA) contents in roots of both ecotypes were 1.41 to 11.22-fold higher than those in leaves, whereas the ratios of AsA to DHA (1.38 to 6.84) in leaves altering more to the reduced AsA form were much higher than those in roots. These results suggested that antioxidative enzymes and antioxidants play an important role in counteracting Pb stress in S. alfredii. [source] Cytotoxicity and apoptosis enhancement in brain tumor cells upon coadministration of paclitaxel and ceramide in nanoemulsion formulationsJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 7 2008Ankita Desai Abstract The objective of this study was to examine augmentation of therapeutic activity in human glioblastoma cells with combination of paclitaxel (PTX) and the apoptotic signaling molecule, C6 -ceramide (CER), when administered in novel oil-in-water nanoemulsions. The nanoemulsions were formulated with pine-nut oil, which has high concentrations of essential polyunsaturated fatty acid (PUFA). Drug-containing nanoemulsions were characterized for particle size, surface charge, and the particle morphology was examined with transmission electron microscopy (TEM). Epi-fluorescent microscopy was used to analyze nanoemulsion-encapsulated rhodamine-labeled PTX and NBD-labeled CER uptake and distribution in U-118 human glioblastoma cells. Cell viability was assessed with the MTS (formazan) assay, while apoptotic activity of PTX and CER was evaluated with caspase-3/7 activation and flow cytometry. Nanoemulsion formulations with the oil droplet size of approximately 200 nm in diameter were prepared with PTX, CER, and combination of the two agents. When administered to U-118 cells, significant enhancement in cytotoxicity was observed with combination of PTX and CER as compared to administration of individual agents. The increase in cytotoxicity correlated with enhancement in apoptotic activity in cells treated with combination of PTX and CER. The results of these studies show that oil-in-water nanoemulsions can be designed with combination therapy for enhancement of cytotoxic effect in brain tumor cells. In addition, PTX and CER can be used together to augment therapeutic activity, especially in aggressive tumor models such as glioblastoma. © 2007 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 97:2745,2756, 2008 [source] Transport of levovirin prodrugs in the human intestinal Caco-2 cell lineJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 6 2006Fujun Li Abstract The transport of 10 amino acid ester prodrugs of levovirin (LVV) was investigated in the human intestinal Caco-2 cell line in order to overcome the poor oral bioavailability of LVV, an investigational drug for the treatment of hepatitis C infection. The prodrugs were designed to improve the permeability of LVV across the intestinal epithelium by targeting the di/tri-peptide carrier, PepT1. Caco-2 cell monolayers were employed to study the transport and hydrolysis properties of the prodrugs. Among all mono amino acid ester prodrugs studied, the LVV-5,-(L)-valine prodrug (R1518) exhibited the maximum increase (48-fold) in permeability with nearly complete conversion to LVV within 1 h. Di-amino acid esters did not offer significant enhancement in permeability comparing with mono amino acid esters and exhibited slower conversion to LVV in Caco2 cell monolayers. Pharmacokinetic screening studies of the prodrugs in rats yielded the highest fold increase (6.9-fold) of AUC with R1518 and in general displayed a similar trend to that observed in increases of permeability in Caco-2 cells. Mechanisms involved in the Caco-2 cell transport of R1518 were also investigated. Results of bi-directional transport studies support the involvement of carrier-mediated transport mechanisms for R1518, but not for the LVV-5,-(D)-valine prodrug or LVV. Moreover, the permeability of R1518 was found to be proton dependent. PepT1-mediated transport of R1518 was supported by results of competitive transport studies of R1518 with the PepT1 substrates enalapril, Gly-Sar, valganciclovir, and cephalexin. R1518 was also found to inhibit the permeability of valganciclovir and cephalexin. These results suggest that R1518 is a PepT1 substrate as well as an inhibitor. © 2006 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 95:1318,1325, 2006 [source] Effect of lipid bilayer alteration on transdermal delivery of a high-molecular-weight and lipophilic drug: Studies with paclitaxelJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 9 2004Ramesh Panchagnula Abstract Skin forms an excellent barrier against drug permeation, due to the rigid lamellar structure of the stratum corneum (SC) lipids. Poor permeability of drugs can be enhanced through alteration in partition and diffusion coefficients, or concentration gradient of drug with an appropriate choice of solvent system, along with penetration enhancers. The aim of the current investigation was to assess applicability of lipid bilayer alteration by fatty acids and terpenes toward the permeation enhancement of a high-molecular-weight, lipophilic drug, paclitaxel (PCL) through rat skin. From among the fatty acids studied using ethanol/isopropyl myristate (1:1) vehicle, no significant enhancement in flux of PCL was observed (p,>,0.05). In the case of cis mono and polyunsaturated fatty acids lag time was found to be similar to control (p,>,0.05). This suggests that the permeation of a high-molecular-weight, lipophilic drug may not be enhanced by the alteration of the lipid bilayer, or the main barrier to permeation could lie in lower hydrophilic layers of skin. A significant increase in lag time was observed with trans unsaturated fatty acids unlike the cis isomers, and this was explained on the basis of conformation and preferential partitioning of fatty acids into skin. From among the terpenes, flux of PCL with cineole was significantly different from other studied terpenes and controls, and after treatment with menthol and menthone permeability was found to be reduced. Menthol and menthone cause loosening of the SC lipid bilayer due to breaking of hydrogen bonding between ceramides, resulting in penetration of water into the lipids of the SC lipid bilayer that leads to creation of new aqueous channels and is responsible for increased hydrophilicity of SC. This increased hydrophilicity of the SC bilayer might have resulted in unfavorable conditions for ethanol/isopropyl myristate (1:1) along with PCL to penetrate into skin, therefore permeability was reduced. The findings of this study suggest that the permeation of a high-molecular-weight and lipophilic drug cannot be enhanced through bilayer alteration by penetration enhancers, and alteration in partitioning of drug into skin could be a feasible mode to enhance the permeation of drug. © 2004 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 93:2177,2183, 2004 [source] Confirmation of the anxiolytic-like effect of dihydrohonokiol following behavioural and biochemical assessmentsJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 5 2001Yuji Maruyama Previous studies in this laboratory revealed that dihydrohonokiol-B (DHH-B; 3,-(2 propenyl)-5-propyl-(1,1,-biphenyl)-2,4,-diol), a partially reduced derivative of honokiol, was an effective anxiolytic-like agent in mice at an oral dose of 0.04 mg kg,1, and at higher doses, when evaluated by the elevated plus-maze test. The aim of this study was to further confirm the anxiolytic-like effect of DHH-B using an additional behavioural procedure (Vogel's conflict test in mice) and a biochemical assessment (in-vitro determination of muscimol-stimulated 36Cl, uptake into mouse cortical synaptoneurosomes). As in earlier experiments, DHH-B (0.04,1 mg kg,1, p.o.) was shown to prolong the time spent in the open-sided arms of the elevated plus-maze in a dose-dependent manner. Moreover, in the Vogel's conflict test, DHH-B (5 mg kg,1, p.o.) significantly increased punished water intake. In tests with mouse cerebral cortical synaptoneurosomes, 10 and 30 ,m of DHH-B significantly increased 36Cl, influx in the absence of muscimol. In the presence of 25 ,m muscimol, the addition of 1 ,m DHH-B led to significant enhancement of 36Cl, uptake, while 30 ,m DHH-B was required to further stimulate the 36Cl, uptake induced by 250 ,m muscimol. The results of these studies confirm that DHH-B is a potent anxiolytic-like agent and that GABAA receptor-gated Cl, -channel complex is involved in the anxiolytic-like efficacy of DHH-B. [source] Solving the loss of orthogonality during the polyaddition of ,-azide-,-alkyne monomers catalyzed by Cu(PPh3)3Br: Application to the synthesis of high-molar mass polytriazolesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 11 2010Sandra Binauld Abstract Polyaddition of an ,-azide-,-alkyne monomer by Cu(PPh3)3Br catalyzed 1,3-dipolar cycloaddition was thoroughly studied as a model system to investigate the orthogonality of this click chemistry process. Indeed, loss of chain-end functionality and occurrence of side reactions have a tremendous impact on the molar mass of polymers obtained by step growth polymerization. Particularly, SEC, 1H, and 31P NMR experiments have highlighted the occurrence of a Staudinger side-reaction between azide chain-ends and PPh3 from the copper(I) catalyst that dramatically alters Mn of the resulting polytriazoles. A significant enhancement of Mn could be achieved by using an alternative catalyst and optimized experimental conditions, that is, dilution and reaction time. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2470,2476, 2010 [source] pH-responsive ampholytic terpolymers of acrylamide, sodium 3-acrylamido-3-methylbutanoate, and (3-acrylamidopropyl)trimethylammonium chloride.JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 13 2004Abstract The solution properties of low-charge-density ampholytic terpolymers of acrylamide, sodium 3-acrylamido-3-methylbutanoate, and (3-acrylamidopropyl)trimethylammonium chloride were studied as functions of the solution pH, ionic strength, and polymer concentration. Terpolymers with low charge densities, large charge asymmetries, or both exhibited excellent solubility in deionized (DI) water, and higher charge density terpolymers were readily dispersible in DI water; however, the higher charge density terpolymer solutions separated into polymer-rich and polymer-poor phases upon standing over time. Charge-balanced terpolymers exhibited antipolyelectrolyte behavior at pH values greater than or equal to the ambient pH (6.5 ± 0.2); the same terpolymers behaved increasingly as cationic polyelectrolytes with decreasing solution pH because of the protonation of the 3-acrylamido-3-methylbutanoate (AMB) repeat units. Unbalanced terpolymers generally exhibited polyelectrolyte behavior, although the effects of intramolecular electrostatic attractions (i.e., polyampholyte effects) on the hydrodynamic volume of the unbalanced terpolymer coils were evident at certain values of the solution pH and salt concentration. The dilute-solution behavior of the terpolymers correlated well with the behavior predicted by several polyampholyte solution theories. In the semidilute regime, solution viscosities increased with increasing terpolymer charge density, and this indicated a significant enhancement of the solution viscosity by intermolecular electrostatic associations. Upon the addition of NaCl, semidilute-solution viscosities tended to decrease because of the disruption of the intermolecular electrostatic associations. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3252,3270, 2004 [source] Surface-enhanced Raman scattering from gold-coated germanium oxide nanowiresJOURNAL OF RAMAN SPECTROSCOPY, Issue 7 2008Muhammad A. Khan Abstract We utilized bulk-synthesized nanowires (NWs) of germanium dioxide as nanoscale structures that can be coated with noble metals to allow the excitation of surface plasmons over a broad frequency range. The NWs were synthesized on substrates of silicon using gold-catalyst-assisted vapor,liquid,solid (VLS) growth mechanism in a simple quartz tube furnace setup. The resulting NWs have diameters of ,100,200 nm, with lengths averaging ,10,40 µm and randomly distributed on the substrate. The NWs are subsequently coated with thin films of gold, which provide a surface-plasmon-active surface. Surface-enhanced Raman scattering (SERS) studies with near-infrared (NIR) excitation at 785 nm show significant enhancement (average enhancement > 106) with good uniformity to detect submonolayer concentrations of 4-methylbenzenethiol (4-MBT), trans -1,2-bis(4-pyridyl)ethylene (BPE), and 1,2-benzendithiol (1,2-BDT) probe molecules. We also observed an intense, broad continuum in the Raman spectrum of NWs after metal coating, which tended to diminish with the analyte monolayer formation. Copyright © 2008 John Wiley & Sons, Ltd. [source] A Polymorphism in the ,4 Nicotinic Receptor Gene (Chrna4) Modulates Enhancement of Nicotinic Receptor Function by EthanolALCOHOLISM, Issue 5 2003Christopher M. Butt Background: Several studies indicate that ethanol enhances the activity of ,4,2 nicotinic acetylcholine receptors (nAChR). Our laboratory has identified a polymorphism in the ,4 gene that results in the substitution of an alanine (A) for threonine (T) at amino acid position 529 in the second intracellular loop of the ,4 protein. Mouse strains expressing the A variant have, in general, greater nAChR-mediated 86Rb+ efflux in response to nicotine than strains with the T variant. However, the possibility of the polymorphism modulating the effects of ethanol on the 86Rb+ efflux response has not been investigated. Methods: We have used the 86Rb+ efflux method to study the acute effects of ethanol on the function of the ,4,2 nAChR in the thalamus in six different mouse strains. Experiments were also performed on tissue samples taken from F2 intercross animals. The F2 animals were derived from A/J mice crossed with a substrain of C57BL/6J mice that carried a null mutation for the gene encoding the ,2 nAChR subunit. Results: In strains carrying the A polymorphism (A/J, AKR/J, C3H/Ibg), coapplication of ethanol (10,100 mM) with nicotine (0.03,300 ,M) increased maximal ion flux when compared with nicotine alone with no effect on agonist potency. In contrast, ethanol had little effect on the nicotine concentration-response curve in tissue prepared from strains carrying the T polymorphism (Balb/Ibg, C57BL/6J, C58/J). Experiments with the F2 hybrids demonstrated that one copy of the A polymorphism was sufficient to produce a significant enhancement of nAChR function by ethanol (50 mM) in animals that were also ,2 +/+. Ethanol had no effect on nicotine concentration-response curves in T/T ,2 +/+ animals. Conclusions: The results suggest that the A/T polymorphism influences the initial sensitivity of the ,4,2 nAChR to ethanol. [source] Determination of propafenone hydrochloride by flow-injection analysis coupled with resonance light scattering detectionLUMINESCENCE: THE JOURNAL OF BIOLOGICAL AND CHEMICAL LUMINESCENCE, Issue 2 2009Xiaoli Hu Abstract A simple, sensitive and rapid flow injection analysis (FIA) method with resonance light scattering (RLS) was described for the determination of propafenone (PPF). The method was based on the ion-association reaction of 12-tungstophosphoric acid (TP) with propafenone. In pH 1.0 acidic medium, TP reacted with PPF to form an ion-associate complex, which resulted in a significant enhancement of RLS intensity. The maximum scattering peak was located at 340 nm, the RLS intensity was proportional to the concentration of PPF in the range 0.003,9.0 µg/mL, and the detection limit (3,) of 1.0 ng/mL was obtained at a sampling rate of 60 samples/h. The feasible reaction conditions and FIA parameters for the system were optimized. The method proposed in this paper shows satisfactory reproducibility with a relative standard deviation (RSD) of 2.1% for 10 successive determinations of 2.0 µg/mL PPF. The present method had been successfully applied to the determination of PPF in serum samples and pharmaceutical samples. The results obtained were in agreement with the method used in the Chinese Pharmacopoeia. Copyright © 2008 John Wiley & Sons, Ltd. [source] Resonance Rayleigh scattering method for the determination of chitosan with some anionic surfactantsLUMINESCENCE: THE JOURNAL OF BIOLOGICAL AND CHEMICAL LUMINESCENCE, Issue 3 2008Yu-Wei Wang Abstract In weak acidic buffer medium, chitosan binding with an anionic surfactant, such as sodium dodecyl benzene sulphonate (SDBS), sodium lauryl sulphate (SLS) or sodium dodecyl sulphonate (SDS), can result in a significant enhancement of resonance Rayleigh scattering (RRS) intensity. The results showed that under optimum conditions the enhanced RRS intensity is proportional to the concentration of chitosan in the range 0.10,20.0 µg/mL for SDBS, 0.27,15.0 µg/mL for SLS and 0.20,15.0 µg/mL for SDS. Among these, the sensitivity of SDBS is the highest and its detection limit for chitosan is 29 ng/mL, while those of SLS and SDS are 83 and 61 ng/mL, respectively. The method has good selectivity and was applied to the determination of trace amounts of chitosan in practical samples with satisfactory results. Therefore, a simple and convenient method with high sensitivity and selectivity for the determination of chitosan was established. Copyright © 2008 John Wiley & Sons, Ltd. [source] | ||||||||||||||||||||||||||||||||||||||||