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Selected AbstractsVoltammetry as an Alternative Tool for Trace Metal Detection in Peloid Marine SedimentsELECTROANALYSIS, Issue 13 2007Irena Ciglene Abstract Here was demonstrated for the first time a possible application of abrasive stripping voltammetry in the direct measurement of trace metals in anoxic, sulfidic marine sediments (peloid mud) from a small and shallow (0.2,1,m) marine lagoon in Central Dalmatia, Croatia. Trace amounts of sample compounds are transferred to the graphite electrode surface and electrochemical reduction or oxidation processes are followed by the cyclic voltammetry in seawater or 0.55,M NaCl as electrolyte. After a preelectrolysis at potentials ranging from ,1.0 to ,1.5,V (vs. SCE) a well-defined anodic stripping peak corresponding to the oxidation of metal deposits generated at deposition potentials is obtained around ,0.74,V (vs. SCE). The same samples were studied by anodic stripping voltammetry at the Hg electrode and inductively coupled plasma-mass spectrometer (ICP-MS). ICP-MS showed higher concentrations of trace metals such as Al, Fe, Mo, Mn. A relatively high concentration of reduced sulfur species (RSS) (10,3 M) is determined electrochemically in porewater of the peloid mud, indicating that the magnitude of metal enrichment in the sediments is probably controlled by precipitation with sulfide. [source] Adsorptive Stripping Voltammetric Detection of Single-Stranded DNA at Electrochemically Modified Glassy Carbon ElectrodeELECTROANALYSIS, Issue 23 2002Huai-Sheng Wang Abstract Electrochemically modified glassy carbon electrode (GCE) was used to study the electrochemical oxidation and detection of denatured single-stranded (ss) DNA by means of adsorptive stripping voltammetry. The modification of GCE, by electrochemical oxidation at +1.75,V (vs.SCE) for 10,min and cyclic sweep between +0.3,V and ,1.3,V for 20,cycles in pH,5.0 phosphate buffer, results in 100-fold improvement in sensitivity for ssDNA detection. We speculated that the modified GCE has a high affinity to single-stranded DNA through hydrogen bond (specific static adsorption). Single-stranded DNA can accumulate at the GCE surface at open circuit and produce a well-defined oxidation peak corresponding to the guanine residues at about +0.80,V in pH,5.0 phosphate buffer, while the native DNA gives no signal under the same condition. The peak currents are proportional to the ssDNA concentration in the range of 0,18.0,,g,mL,1. The detection limit of denatured ssDNA is ca. 0.2,,g mL,1 when the accumulation time is 8,min at open circuit. The accumulation mechanism of ssDNA on the modified GCE was discussed. [source] Chitosan Hydrogel-Capped Porous SiO2 as a pH Responsive Nano-Valve for Triggered Release of InsulinADVANCED FUNCTIONAL MATERIALS, Issue 5 2009Jianmin Wu Abstract A pH responsive, chitosan-based hydrogel film is used to cap the pores of a porous SiO2 layer. The porous SiO2 layer is prepared by thermal oxidation of an electrochemically etched Si wafer, and the hydrogel film is prepared by reaction of chitosan with glycidoxypropyltrimethoxysilane (GPTMS). Optical reflectivity spectroscopy and scanning electron microscopy (SEM) confirm that the bio-polymer only partially infiltrates the porous SiO2 film, generating a double layer structure. The optical reflectivity spectrum displays Fabry,Pérot interference fringes characteristic of a double layer, which is characterized using reflective interferometric Fourier transform spectroscopy (RIFTS). Monitoring the position of the RIFTS peak corresponding to the hydrogel layer allows direct, real-time observation of the reversible volume phase transition of the hydrogel upon cycling of pH in the range 6.0,7.4. The swelling ratio and response time are controlled by the relative amount of GPTMS in the hydrogel. The pH-dependent volume phase transition can be used to release insulin trapped in the porous SiO2 layer underneath the hydrogel film. At pH 7.4, the gel in the top layer effectively blocks insulin release, while at pH 6.0 insulin penetrates the swollen hydrogel layer, resulting in a steady release into solution. [source] Purification of Matrix Gla Protein From a Marine Teleost Fish, Argyrosomus regius: Calcified Cartilage and Not Bone as the Primary Site of MGP Accumulation in Fish,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 2 2003DC Simes Abstract Matrix Gla protein (MGP) belongs to the family of vitamin K-dependent, Gla-containing proteins, and in mammals, birds, and Xenopus, its mRNA was previously detected in extracts of bone, cartilage, and soft tissues (mainly heart and kidney), whereas the protein was found to accumulate mainly in bone. However, at that time, it was not evaluated if this accumulation originated from protein synthesized in cartilage or in bone cells because both coexist in skeletal structures of higher vertebrates and Xenopus. Later reports showed that MGP also accumulated in costal calcified cartilage as well as at sites of heart valves and arterial calcification. Interestingly, MGP was also found to accumulate in vertebra of shark, a cartilaginous fish. However, to date, no information is available on sites of MGP expression or accumulation in teleost fishes, the ancestors of terrestrial vertebrates, who have in their skeleton mineralized structures with both bone and calcified cartilage. To analyze MGP structure and function in bony fish, MGP was acid-extracted from the mineralized matrix of either bone tissue (vertebra) or calcified cartilage (branchial arches) from the bony fish, Argyrosomus regius,, separated from the mineral phase by dialysis, and purified by Sephacryl S-100 chromatography. No MGP was recovered from bone tissue, whereas a protein peak corresponding to the MGP position in this type of gel filtration was obtained from an extract of branchial arches, rich in calcified cartilage. MGP was identified by N-terminal amino acid sequence analysis, and the resulting protein sequence was used to design specific oligonucleotides suitable to amplify the corresponding DNA by a mixture of reverse transcription-polymerase chain reaction (RT-PCR) and 5,rapid amplification of cDNA (RACE)-PCR. In parallel, ArBGP (bone Gla protein, osteocalcin) was also identified in the same fish, and its complementary DNA cloned by an identical procedure. Tissue distribution/accumulation was analyzed by Northern blot, in situ hybridization, and immunohistochemistry. In mineralized tissues, the MGP gene was predominantly expressed in cartilage from branchial arches, with no expression detected in the different types of bone analyzed, whereas BGP mRNA was located in bone tissue as expected. Accordingly, the MGP protein was found to accumulate, by immunohistochemical analysis, mainly in the extracellular matrix of calcified cartilage. In soft tissues, MGP mRNA was mainly expressed in heart but in situ hybridization, indicated that cells expressing the MGP gene were located in the bulbus arteriosus and aortic wall, rich in smooth muscle and endothelial cells, whereas no expression was detected in the striated muscle myocardial fibers of the ventricle. These results show that in marine teleost fish, as in mammals, the MGP gene is expressed in cartilage, heart, and kidney tissues, but in contrast with results obtained in Xenopus and higher vertebrates, the protein does not accumulate in vertebra of non-osteocytic teleost fish, but only in calcified cartilage. In addition, our results also indicate that the presence of MGP mRNA in heart tissue is due, at least in fish, to the expression of the MGP gene in only two specific cell types, smooth muscle and endothelial cells, whereas no expression was found in the striated muscle fibers of the ventricle. In light of these results and recent information on expression of MGP gene in these same cell types in mammalian aorta, it is likely that the levels of MGP mRNA previously detected in Xenopus, birds, and mammalian heart tissue may be restricted toregions rich in smooth muscle and endothelial cells. Our results also emphasize the need to re-evaluate which cell types are involved in MGP gene expression in other soft tissues and bring further evidence that fish are a valuable model system to study MGP gene expression and regulation. [source] Non-invasive monitoring of commonly used intraocular drugs against endophthalmitis by raman spectroscopyLASERS IN SURGERY AND MEDICINE, Issue 4 2003K. Hosseini MD Abstract Purpose To develop a non-contact and non-invasive method for quantification of the local concentration of certain antibiotic and antifungal drugs in the eye. Study Design/Materials and Methods An integrated CCD-based Raman spectroscopic system designed specifically for ophthalmic applications was used to non-invasively detect the presence of ceftazidime and amphotericin B in ocular media. Specific Raman signatures of the above named drugs were determined for various concentrations that were injected through a needle in the aqueous humor of rabbit eyes in vivo. Raman spectra were subsequently acquired by focusing an argon laser beam within the anterior chamber of the eye. Results Compared to ocular tissue, unique spectral features of ceftazidime appeared near 1,028, 1,506, 1,586, and 1,641 cm,1. Amphotericin B exhibited its characteristic peaks at 1,156.5 and 1,556 cm,1. The amplitude of the spectral peak corresponding to these drugs (acquired by 1 second exposure time and 25 mW of laser power) were determined to be linearly dependent on their local concentration in the anterior chamber of the eye. Conclusions Raman spectroscopy may offer an effective tool to non-invasively assess the local concentration of the delivered drugs within the ocular media. This technique potentially could be used to investigate the pharmacokinetics of intraocular drugs in vivo either from a releasing implant or a direct injection. Lasers Surg. Med. 32:265,270, 2003. © 2003 Wiley-Liss, Inc. [source] Electronic structure of RCoxGe2 (R=Ce, Pr, Gd) compoundsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 1 2006B. Penc Abstract The electronic structure of the RCoxGe2 (R=Ce, Pr, Gd) compounds with the orthorhombic crystal structure of CeNiSi2 -type was studied by X-ray photoemission spectroscopy. The valence bands of CeCo0.86Ge2 and PrCo0.85Ge2 compounds have the similar character. Near the Fermi level the broad peak corresponding to the Co 3d and R 4f and 5d6s states is observed. In the case of GdCo0.64Ge2, the strong intensity peak at 8.7 eV corresponding to Gd 4f states is observed. The analysis of the XPS spectra of Ce and Pr 3d5/2 and 3d3/2 in the Gunnarson-Schönhammer model give the information on the hybridization of the f orbital with the conduction band. The hybridization energy equal 93 eV for R=Ce and 143 eV for R=Pr, respectively indicate stability of the shell in these compounds. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Electrical conductivity and optical properties of poly(3-thiophene boronic acid) organic semiconductorPOLYMER ENGINEERING & SCIENCE, Issue 4 2009Fahrettin Yakuphanoglu Electrical conductivity and optical properties of the poly(3-thiophene boronic acid) have been investigated. The room temperature electrical conductivity and activation energy of the poly(3-thiophene boronic acid) were 2.0 × 10,9 S/cm and 0.17 eV, respectively. In the semiconductor region of the polymer, the charge transport mechanism is taking place by the hopping process in the localized states. The direct optical band gap value of the poly(3-thiophene boronic acid) was found to be 1.92 eV via optical absorption method. The width of localized states for the polymer was determined to be 0.36 eV. The refractive index dispersion curve of the polymer obeys the single oscillator model. The refractive index dispersion parameter Eo/So for the poly(3-thiophene boronic acid) was determined to be 9.82 × 1012 eV m2. The optical dielectric constants of the polymer were determined. The real part of the dielectric constant of the polymer is higher than that of imaginary part of the dielectric constant. The imaginary part shows a peak corresponding to the absorption edge. It is evaluated that the electrical and optical results of the poly(3-thiophene boronic acid) indicate that it is an organic semiconductor with electrical and optical parameters. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers [source] Physicochemical properties of the thermal gel of water-washed meat in the presence of the more soluble fraction of porcine sarcoplasmic proteinANIMAL SCIENCE JOURNAL, Issue 1 2007Yuji MIYAGUCHI ABSTRACT We investigated the physicochemical properties of the thermal gel of water-washed pork meat (WWM) in the presence of the soluble fraction of porcine sarcoplasmic protein (SP) obtained with ammonium sulfate at 75 percent saturation. Two precipitated fractions of SP were obtained at 0,50 percent and 50,75 percent saturation, named SP-f1 and SP-f2, respectively, and the soluble fraction obtained at 75 percent saturation, SP-f3, was used. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed that SP-f3 contained mainly glyceraldehyde-3-phosphate dehydrogenase (GAPDH), while SP-f1 and SP-f2 had other SPs such as phosphorylase b, enolase, actin and phosphoglycerate mutase. The gel strength of WWM was greater when SP-f3 rather than one of various animal proteins such as bovine plasma (BP), egg white, or whey protein isolates (WPI), was added and SP-f3 had a gel-enhancing effect as good as that of polyphosphate (PP). The gel strength of WWM with added SP-f3 increased significantly with NaCl at 0.15 mol/L or more, but not in the absence of NaCl (0 mol/L). The effect of SP-f3 was evident at neutral pH and maximum gel strength was obtained at a pH above 6.0. Differential scanning calorimetric (DSC) analysis showed that an endothermic peak corresponding to myosin heads in WWM shifted to a lower temperature with the addition of SP-f3, as in the case of PP, though there was no such shift in the presence of other animal proteins (BP, egg white and WPI), suggesting that SP-f3 increases the gel strength of WWM through the dissociation of actomyosin similar to PP. Scanning electron microscopy (SEM) revealed wall-like structures among the protein strands in the WWM gel matrix in the presence of SP-f3. The results of DSC and SEM indicated that the formation of a gel network in meat products is reinforced with GAPDH in SP after the interaction between GAPDH and myofibrillar protein. [source] A Method for the Rapid Discovery of Naturally Occurring Products by Proteins Immobilized on Magnetic Beads and Reverse Affinity ChromatographyCHEMISTRY - AN ASIAN JOURNAL, Issue 12 2009Midori Abstract A highly efficient screening method for naturally occurring products that bind to a specific target protein was demonstrated by using hVDR magnetic beads. The native ligand 1,,25(OH)2 VD3 (1) was selectively bound by hVDR magnetic beads when present in a mixture of natural compounds. Furthermore, this method was shown to be applicable to the identification of natural products that interact with a specific protein immobilized on the beads from an extract of a natural resource. Two new natural compounds were isolated by this method. This approach will be helpful for the discovery of novel, naturally occurring products that bind to specific target proteins. This method has the further advantages that it can identify the HPLC peak corresponding to the target compound for isolation, as well as provide important UV, CD, or MS profile information. [source] Highly selective single nucleotide polymorphism recogniton by a chiral (5S) PNA beacon,CHIRALITY, Issue 1 2009Filbert Totsingan Abstract A chiral peptide nucleic acid (PNA) beacon containing a C-5 modified monomer based on L-lysine was synthesized. The terminal amino group of the lysine side chain was linked to a spacer for future applications on surfaces. The PNA beacon bears a carboxyfluorescein fluorophore and a dabcyl quencher at opposite ends. The DNA binding properties were compared with those of a homologous PNA beacon containing only achiral monomers. Both beacons underwent a fluorescence increase in the presence of complementary DNA, with higher efficiency and higher selectivity (evaluated using single mismatched DNA sequences) observed for the chiral monomer containing PNA. Ion exchange (IE) HPLC with fluorimetric detection was used in combination with the beacon for the selective detection of complementary DNA. A fluorescent peak corresponding to the PNA beacon:DNA duplex was observed at a very low detection limit (1 nM). The discriminating capacity of the chiral PNA beacon for a single mismatch was found to be superior to those observed with the unmodified one, thus confirming the potency of chirality for increasing the affinity and specificity of DNA recognition. Chirality, 2009. © 2008 Wiley-Liss, Inc. [source] Sonochemical synthesis and characterization of ZnO nanorod/Ag nanoparticle compositesCRYSTAL RESEARCH AND TECHNOLOGY, Issue 11 2009Fei Li Abstract A simple sonochemical route for the synthesis of Ag nanoparticles on ZnO nanorods is reported. Ultrasonic irradiation of a mixture of ZnO nanorods, Ag(NH3)2+, and formaldehyde in an aqueous medium yields ZnO nanorod/Ag nanoparticle composites. The powder X-ray diffraction of the ZnO/Ag composites shows additional diffraction peaks corresponding to the face-center-cubic structured Ag crystalline, apart from the signals from the ZnO nanorods. Scanning electron microscopy and transmission electron microscopy images of the ZnO/Ag composites reveal that the ZnO nanorods are coated with Ag nanoparticles with a mean size of several tens nanometer. The absorption band of ZnO/Ag composites is distinctly broadened and red-shifted, indicating the strong interfacial interaction between ZnO nanorods and Ag nanoparticles. This sonochemical method is simple, mild and readily scaled up, affording a simple way for synthesis of other composites. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Thermal and mechanical properties of uncrosslinked and chemically crosslinked polyethylene/ethylene vinyl acetate copolymer blendsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2007H. A. Khonakdar Abstract Uncrosslinked and chemically crosslinked binary blends of low- and high-density polyethylene (PE), with ethylene vinyl acetate copolymer (EVA), were prepared by a melt-mixing process using 0,3 wt % tert -butyl cumyl peroxide (BCUP). The uncrosslinked blends revealed two distinct unchanged melting peaks corresponding to the individual components of the blends, but with a reduced overall degree of crystallinity. The crosslinking further reduced crystallinity, but enhanced compatibility between EVA and polyethylene, with LDPE being more compatible than HDPE. Blended with 20 wt % EVA, the EVA melting peak was almost disappeared after the addition of BCUP, and only the corresponding PE melting point was observed at a lowered temperature. But blended with 40% EVA, two peaks still existed with a slight shift toward lower temperatures. Changes of mechanical properties with blending ratio, crosslinking, and temperature had been dominated by the extent of crystallinity, crosslinking degree, and morphology of the blend. A good correlation was observed between elongation-at-break and morphological properties. The blends with higher level of compatibility showed less deviation from the additive rule of mixtures. The deviation became more pronounced for HDPE/EVA blends in the phase inversion region, while an opposite trend was observed for LDPE/EVA blends with co-continuous morphology. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3261,3270, 2007 [source] Synthesis of Mo,W carbide via propane carburization of the precursor sulfide: Kinetic analysisJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 3 2004Tuan-Huy Nguyen Abstract Thermogravimetric analysis (TGA) has been used to investigate the carburization kinetics of Mo,W sulfide using an H2:C3H8 feed mixture. The effect of heating rate over the range 1,10 K min,1 showed that up to four different carburized products may be formed but the critical (peak) temperature for formation of these species and the amount (peak height) of each species formed are highly dependent on the heating rate employed. The critical temperature increased linearly with heating rate for each of the four products. The four TGA peaks corresponding to the four phase transformation species are consistent with XRD identifiable species, namely; ,-Mo2C, ,-Mo2C, W and MoC1,x. Isothermal conversion,time data at three different temperatures are described by a reaction-controlled shrinking core model implicating a first-order dependency on the H2:C3H8 ratio. The reaction exhibited fractional order dependence on the metal sulfide concentration, the associated global activation energy estimated as 227 kJ mol,1 is representative of a non-catalytic gas,solid reaction. Copyright © 2004 Society of Chemical Industry [source] Cefuroxime axetil solid dispersions prepared using solution enhanced dispersion by supercritical fluidsJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 12 2005Seoung Wook Jun Cefuroxime axetil (CA) solid dispersions with HPMC 2910/PVP K-30 were prepared using solution enhanced dispersion by supercritical fluids (SEDS) in an effort to increase the dissolution rate of poorly water-soluble drugs. Their physicochemical properties in solid state were characterized by differential scanning calorimeter (DSC), powder X-ray diffraction (PXRD), Fourier transform infrared spectrometry (FT-IR) and scanning electron microscopy. No endothermic and characteristic diffraction peaks corresponding to CA were observed for the solid dispersions in DSC and PXRD. FTIR analysis demonstrated the presence of intermolecular hydrogen bonds between CA and HPMC 2910/PVP K-30 in solid dispersions, resulting in the formation of amorphous or non-crystalline CA. Dissolution studies indicated that the dissolution rates were remarkably increased in solid dispersions compared with those in the physical mixture and drug alone. In conclusion, an amorphous or non-crystalline CA solid dispersion prepared using SEDS could be very useful for the formulation of solid dosage forms. [source] Carbon Nanotubes Functionalized in Oxygen and Water Low Pressure Discharges used as Reinforcement of Polyurethane CompositesPLASMA PROCESSES AND POLYMERS, Issue S1 2009Lenka Zají, ková Abstract The functionalization of multi-walled CNTs in O2/Ar and H2O/Ar low pressure capacitive discharges was studied by XPS and FT-IR. The pristine and functionalized CNTs were used as fillers in polyurethane paints. Successful plasma functionalization was confirmed by changes in atomic composition and chemical shift of the XPS atomic signals. The functionalization was indicated also by the shift of IR absorption peaks corresponding to the motion of carbon skeleton, especially the peak at about 1,560,cm,1. The presence of carbonyl was confirmed by IR absorption peak at 1,723,cm,1 only for O2/Ar plasma. The plasma functionalized CNTs increased significantly the universal and plastic hardness of the CNTs reinforced polyurethane as compared to the composites with pristine CNTs. 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