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Irradiation Time (irradiation + time)
Selected AbstractsPt immobilization on TiO2 -embedded carbon nanofibers using photodepositionCRYSTAL RESEARCH AND TECHNOLOGY, Issue 10 2010S. Kim Abstract Currently, the use of fuel cell electrodes containing Pt catalysts has been limited due to technological problems in this system, primarily the system's high cost. The improvement of Pt catalyst use has been achieved by changes in the Pt immobilization method. In this study, we have studied Pt immobilization on carbon nanofiber composites using the photodeposition method. First, we prepared the carbon nanofibers, which were homogeneously embedded TiO2 using the electrospinning technology. These TiO2 -embedded carbon nanofiber composites (TiO2/CNFs) were then immersed in a Pt precursor solution and irradiated with UV light. The obtained Pt-deposited TiO2/CNFs contained Pt that was immobilized on the carbon nanofibers, and the Pt particle size was 2-5 nm. The XPS spectra showed that the amount of Pt increased with an increasing UV irradiation time. The current densities and total charge also increased with an increase in the UV irradiation time, possibly due to an increase of active specific area by finely dispersed Pt nanoparticles. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Open-tubular capillary columns with a porous layer of monolithic polymer for highly efficient and fast separations in electrochromatographyELECTROPHORESIS, Issue 21 2006Sebastiaan Eeltink Abstract Open-tubular columns for CEC separations having inner-wall coated with a thin layer of porous monolithic polymer have been studied. A two-step process including (i),UV-initiated polymerization leading to a layer of porous poly(butyl methacrylate- co -ethylene dimethacrylate), and (ii),UV-initiated grafting of ionizable monomers appear to be well suited for the preparation of these columns. The thickness of the porous polymer layer is controlled by the percentage of monomers in the polymerization mixture and/or length of the irradiation time. The layer thickness significantly affects retention, efficiency, and resolution in open-tubular CEC. Under optimized conditions, column efficiencies up to 400,000 plates/m can be achieved. Use of higher temperature and application of pressure enables a significant acceleration of the open-tubular CEC separations. [source] Automated ultrasound-assisted method for the determination of the oxidative stability of virgin olive oilEUROPEAN JOURNAL OF LIPID SCIENCE AND TECHNOLOGY, Issue 2 2007José Platero-López Abstract A fast and automated method is proposed for determining the oxidative stability of virgin olive oil by using ultrasound. The ultrasound microprobe (3,mm in diameter) was directly immersed into the olive oil sample contained in a test tube. The most influential variables in the oxidation process, namely pulse amplitude, duty cycle, irradiation time, and sample amount, were optimized. The oil absorbance at 270,nm was continuously monitored by oil recirculation through a 0.1-mm path length flow cell connected to a fiber optic microspectrometer. This short path length allowed the direct monitoring of absorbance without needing any sample dilution. The ultrasound energy was applied during 35,min, and the resulting increase in absorbance was continuously monitored. The difference between the final and the initial absorbance at 270,nm of a set of virgin olive oil samples was closely correlated with their oxidative stability calculated by the Rancimat method (R2,=,0.9915). The resulting equation enabled the prediction of the oxidative stability of virgin olive oil in a short period of time (35,min), by using a simple, inexpensive, automatic and easy-to-use system. [source] Influence of whitening on the degree of conversion of dental adhesives on dentinEUROPEAN JOURNAL OF ORAL SCIENCES, Issue 3 2006Milena Cadenaro The aim of this study was to analyze the extent of polymerization of different adhesive systems on whitened dentin. One adhesive of each class was investigated: Adper Scotchbond Multi Purpose (3M ESPE); One-Step (Bisco); Clearfil Protect Bond (Kuraray); and Xeno III (Dentsply DeTrey). Dentin disks were treated with Opalescence Xtra Boost (Ultradent) for 30 min and bonded immediately after 24 h or after 14 d of storage in 100% humidity at 37°C. Unbleached dentin disks were prepared as controls. The extent of polymerization of bonded interfaces was obtained with differential scanning calorimetry (DSC) at 20, 40 and 60 s, and the data were statistically analyzed. The extent of polymerization obtained from DSC exotherms of adhesives applied immediately after whitening was significantly lower compared with controls. An increased extent of polymerization after storage was confirmed for all adhesives, and no difference with controls was found after 14 d. A prolonged irradiation time increased the curing rate for all the tested adhesives. This study supports the hypothesis that polymerization of the adhesive is reduced after dentin whitening and that delayed adhesive application reverses the polymerization inhibition. Prolonged polymerization intervals may counteract the inhibition of polymerization caused by the whitening procedure. Nevertheless, further in vivo studies should validate this issue. [source] Generation Mechanism and in situ Growth Behavior of ,-Iron Nanocrystals by Electron Beam Induced Deposition,ADVANCED ENGINEERING MATERIALS, Issue 8 2006W. Zhang Amorphous iron-containing deposits were formed on carbon films by electron beam induced deposition with a precursor of iron pentacarbonyl and alpha-Fe nanocrystals were grown around the target tip deposits when the electron beam irradiation time was longer than 1000,s. [source] Multicolor Tunable Emission from Organogels Containing Tetraphenylethene, Perylenediimide, and Spiropyran DerivativesADVANCED FUNCTIONAL MATERIALS, Issue 19 2010Qun Chen Abstract A dendron-substituted tetraphenylethene low molecular weight gelator (LMWG)compound, LMWG1, is designed and investigated. Gelation-induced fluorescence enhancement is observed for the gel based on LMWG1 and its fluorescence can be reversibly tuned by varying the temperature of the ensemble. The photoinduced energy-transfer can occur between LMWG1 and PI2 (perylene diimide) in the gel phase, but it cannot occur in the corresponding solution. The emission color of the gel of LMWG1 and PI2 can be tuned from cyan, yellow, to red by varying the concentration of PI2. By taking advantage of the photochromic transformation of spiropyran, the emission color of the organogels based on LMWG1 and SP3 can be switched by alternating UV and visible-light irradiations. The emission color can also be tuned by varying the irradiation time. In this way, organogels based on LMWG1 with multiemission color can be achieved in the presence of SP3 after light irradiations. [source] Rewritable Holographic Structures Formed in Organic,Inorganic Hybrid Materials by Photothermal ProcessingADVANCED FUNCTIONAL MATERIALS, Issue 16 2009Hiroshi Kakiuchida Abstract Holographic and direct-written structures are fabricated in tin-doped silicophosphite thin plates containing rhodamine 6G dye by a photothermal process based on the principle of glass softening/frozen-in behavior. To be highly processable by photothermal treatment and stable at room temperature after processing, the intrinsic viscoelastic property is improved by increasing the crosslinking density of the network structure, and the photothermal conditions for efficient transfer of the irradiated photons to thermal phonons are explored. Then, the excellent rewritability and reliability of the fine processed structure are found by examining the writing/erasing repetition. Furthermore, the origins of the changes in refractive index due to photothermal treatment are classified into density change and photobleaching, and the dynamics of the formation process of holographic gratings are studied by measuring refractive index changes as functions of irradiation time and wavelength. As a result, it is found that the holographic structure consists of spatial modulation of the refractive index and the refractive index change results primarily from the change in the frozen structure, although there is a slight influence by photobleaching. [source] In vitro Studies of Functionalized Mesoporous Silica Nanoparticles for Photodynamic TherapyADVANCED MATERIALS, Issue 2 2009Hsiung-Lin Tu A versatile platform for photodynamic therapy (PDT), mesoporous silica nanoparticles functionalized with protoporphyrin IX (PpIX-MSNs), has been developed. In vitro studies on HeLa cells show high uptake efficiency. Phototoxicity results give both irradiation time- and dosage-dependent cell death events. Because of the ease of incorporating other biomedical functional groups, we believe MSNs would be an ideal platform for biomedical applications. [source] Fading of artificial hair colour and its prevention by photofiltersINTERNATIONAL JOURNAL OF COSMETIC SCIENCE, Issue 3 2006B. Locke Fading of artificial hair colour has been investigated by simulating actual usage conditions through exposure to artificial radiation in a weatherometer, with 0.35 mW (m2nm),1 at 340 nm, for 16,48 h, and by periodical washing. Hair colour was produced by using commercial two-part, permanent hair dyes with light auburn, medium auburn and dark auburn shades. Formulations based on red couplers, such as 4-amino-2-hydroxytoluene and 1-naphthol, as well as primary intermediates, such as 1-hydroxyethyl-4,5-diamino pyrazole sulphate, were employed. Results indicate that the extent of fading, as measured by the total colour change parameter, dE, is greatest for coloured hair subjected to both irradiation and shampooing, and significantly smaller for hair undergoing only irradiation or washing. Colour loss has been also found to be dependent upon the hair type employed, with coloured natural white and bleached hair undergoing much greater change than coloured brown hair. It has been also shown that hair colour based on pyrazole intermediates displayed the deepest fading as a result of shampooing (dE 4,6 after 10 shampooings) and irradiation per shampooing (dE 14,16 after 32 h of light exposure and four shampooings). The contribution of UV light (UVB + UVA) to the artificial hair-colour loss was found experimentally to be dependent upon the irradiation dose and varied from 63% at 16 h of irradiation time to 27% at 48 h of light exposure. The theoretical extent of photoprotection by a formulation was assessed by calculating the percentage of UV light it attenuates in the wavelength range from 290 to 400 nm. The results indicate that UVB photofilters, such as octyl methoxy cinnamate, absorb <25% of the total UV irradiation at concentrations as high as 30 mg (g hair),1. UVA absorbers were found to be more effective, with benzophenone-3 and benzophenone-4 absorbing about 40% of UV at the same concentration. Corresponding experimental data were in reasonable agreement with the theoretical predictions. The data are also presented for colour protection with treatments containing two photo-absorbers: benzophenone-3,ZnO; benzophenone-4,ZnO; octyl methoxy cinnamate,ZnO; and dimethylpabaimidopropyl laurdimonium tosylate-benzophenone-3. [source] Study on bulk polymerization of methyl methacrylate initiated by low intensity ultrasonic irradiationJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2010Sude Ma Abstract Methyl methacrylate (MMA) was polymerized in bulk solutions using low intensity ultrasonic radiation of 0.25 W/cm2. The polymerization occurred after 1 h of irradiation time was applied. The polymerization rate was greatly accelerated either by increasing the amount of poly (methyl methacrylate) (PMMA) granular added into the system or by elongating the irradiation time. However, it was found that the reaction rate increased with the decreasing of the ultrasonic frequencies when the exposure time of the polymerization under the irradiation was less than 3 h. Experimental results verified that the polymerization was initiated by free radicals, which were mainly generated from the degradation of PMMA macromolecular chains, the friction between the polymer macromolecular chains and the solvent monomer. These findings were obviously different from those obtained when high intensity ultrasonic irradiation was used. The polymers fabricated in this study by using ultrasound irradiation have a narrower molecular weight distribution compared to those obtained from the polymerizations induced by the conventional initiators. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Photografting of acrylic acid and methacrylic acid onto polyolefines initiated by formaldehyde in aqueous solutionsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2009Jianmei Han Abstract Formaldehyde aqueous solution can act as an effective photoinitiating system for water-borne photografting. The photografting of acrylic acid (AA) and methacrylic acid (MAA) onto high-density polyethylene (HDPE), low-density polyethylene (LDPE) and polypropylene (PP) initiated by formaldehyde aqueous solutions has been reported. The effects of formaldehyde content and monomer concentration on grafting varied with the polymeric substrates and monomers used. For the grafting of AA onto HDPE, the extent of grafting increased with increasing formaldehyde content in the solution, monomer concentration had a little effect on grafting. Whereas for the grafting of MAA onto HDPE, the grafting performed in 8% formaldehyde aqueous solution lead to the highest extent of grafting, the extent of grafting increased with monomer concentration till 2.5 mol/L. MAA was easier to be grafted onto the polyolefins than AA. The easiness of grafting occurring on the polyolefins was in a decreasing order of LDPE > HDPE > PP. Qualitative and semi-quantitative Fourier transform infrared (FTIR) characterizations of the grafted samples were performed. For both grafted LDPE and PP samples, at the same irradiation time, the carbonyl index of the samples grafted with MAA was higher than that grafted with AA. The FTIR results are in accord with the results obtained by gravimetric method. The water absorbency of the grafted samples increased almost linearly with the extent of grafting. The PE films grafted with AA adsorbed more water than those grafted with MAA. This study had broadened the water-borne initiating system for photografting. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 [source] Biodegradable poly(vinyl alcohol)- graft - poly(,-caprolactone) comb-like polyester: Microwave synthesis and its characterizationJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2007Zhaoju Yu Abstract Poly(vinyl alcohol)-initiated microwave-assisted ring opening polymerization of ,-caprolactone in bulk was investigated, and a series of poly(vinyl alcohol)- graft -poly(,-caprolactone) (PVA- g -PCL) copolymers were prepared, with the degree of polymerization (DP) of PCL side chains and the degree of substitution (DS) of PVA by PCL being in the range of 3,24 and 0.35,0.89, respectively. The resultant comb-like PVA- g -PCL copolymers were confirmed by means of FTIR, 1H NMR, and viscometry measurement. The introduction of hydrophilic backbone resulted in the decrease in both melting point and crystallization property of the PVA- g -PCL copolymers comparing with linear PCL. With higher microwave power, the DP of PCL side chains and DS of PVA backbone were higher, and the polymerization reaction proceeded more rapidly. Both the DP and monomer conversion increased with irradiation time, while the DS increased first and then remained constant. With initiator in low concentration, the DP and DS were higher, while the monomer was converted more slowly. Microwaves dramatically improved the polymerization reaction in comparison of conventional heating method. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104, 3973,3979, 2007 [source] Photografting of unable-to-be-irradiated surfaces.JOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2007Abstract In this article, a batch liquid-phase process was reported, by which the photo-initiated grafting polymerization could be carried out on the dark surfaces that were not directly irradiated by UV light. In the reaction system, an aluminum foil was placed horizontally to reflect UV light back and form a dark area underneath where the grafting polymerization took place. The occurrence of the polymerization was demonstrated by gravitational analyses and XPS spectra. The factors affecting the grafting reaction have been studied and the results showed that increasing irradiation time, reaction temperature, and benzophenone concentration and decreasing distance (D) between the light area and the place where grafting reaction took place were beneficial to the grafting reaction. The highest grafting density was obtained at a acrylic acid concentration of 15 vol %. Moreover, some further investigations were also made. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 118,124, 2007 [source] Photocatalytic degradation of methyl tert -butyl ether (MTBE) in contaminated water by ZnO nanoparticlesJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 11 2008Akbar Eslami Abstract BACKGROUND: Over the past several decades methyl tert -butyl ether (MTBE) as additive to gasoline, intended to either boost ratings of fuel or to reduce air pollution, has been accepted worldwide. Since MTBE has high water solubility, the occurrence of fuel spills or leaks from underground storage tanks or transferring pipeline has led to the contamination of natural waters. In this study the degradation of aqueous MTBE at relatively high concentrations was investigated by a UV-visible/ZnO/H2O2 photocatalytic process. The effects of important operational parameters such as pH, amount of H2O2, catalyst loading and irradiation time were also investigated. Concentration of MTBE and intermediates such as tert -butyl formate and tert -butyl alcohol were measured. RESULTS: Time required for complete degradation increased from 20 to 150 min when the initial concentration was increased from 10 to 500 mg L,1. The first-order rate constants for degradation of MTBE were estimated to be 0.183,0.022 min,1 as the concentration increased from 10 to 500 mg L,1. Study of the overall mineralization monitored by total organic carbon analysis showed that at an initial concentration of 100 mg L,1 MTBE complete mineralization was obtained after 100 min under UV-visible/ZnO/H2O2 photocatalysis. CONCLUSION: The data presented in this paper clearly indicated that UV-visible/ZnO/O2 as an advanced oxidation process provides an efficient treatment alternative for the remediation of MTBE-contaminated waters. Copyright © 2008 Society of Chemical Industry [source] The Application of Ultraviolet Irradiation to Exogenous Sources of DNA in Plasticware and Water for the Amplification of Low Copy Number DNAJOURNAL OF FORENSIC SCIENCES, Issue 4 2006Jeannie Tamariz B.S. ABSTRACT: Using high sensitivity forensic STR polymerase chain reaction (PCR) typing procedures, we have found low concentrations of DNA contamination in plasticware and water assumed to be sterile, which is not detected by standard DNA procedures. One technique commonly used to eliminate the presence of DNA is ultraviolet (UV) irradiation; we optimized such a protocol used in the treatment of water, tubes, plates, and tips for low copy number DNA (LCN) amplification. UV light from a Stratalinker® 2400 was administered to 0.2, 1.5 mL tubes, and PCR plates contaminated with up to 500 pg of DNA. They were subsequently quantified with an ALU-based real-time PCR method using the Rotorgene 3000. Overall, there was a decrease in concentration of DNA recovered as the duration of treatment increased. Nonetheless, following 45 min of irradiating a PCR plate with 500 pg of DNA, nearly 6 pg were still detected. However, when the plate was raised within an inch of the UV source, less than 0.2 pg of DNA was detected. Additionally, lining the area around the samples with aluminum foil further reduced the amount of time necessary for irradiation, as only 30 min eliminated the presence DNA in the raised PCR plate. Similar experiments were conducted using tubes filled with a solution of DNA and water in equivalent concentrations for 50, 15, and 1.5 mL tubes with comparative results. It is plausible that the aluminum foil increased the amount of reflection in the area thereby enhancing penetration of UV rays through the walls of the plasticware. This protocol was tested for the possibility of inhibitors produced from irradiation of plastic tubes. As our protocols require less irradiation time than previous studies, PCR sensitivity was not affected. Moreover, the lifespan of the UV lamps was extended. Our findings demonstrate that this method is useful as an additional precautionary measure to prevent amplification of extraneous DNA from plasticware and water without compromising the sensitivity of LCN DNA amplifications. [source] Rapid contrasting of ultrathin sections using microwave irradiation with heat dissipationJOURNAL OF MICROSCOPY, Issue 2 2001F. Hernández-Chavarría The use of microwave irradiation (MWI) to accelerate fixation, dehydration and contrasting (staining) for electron microscopy has been applied to the development of rapid methods to process biological samples in electron microscopy. A simple explanation is that the reduced time in those procedures is due to heating. In this paper we propose a contrasting method for thin sections that avoids the thermal effects of MWI. Grids with thin sections of mouse kidney, the dinoflagellate Alexandrium monilatum, spermatophores of the fly Archicepsis diversiformis, the bacteria Acinetobacter calcoaceticum and Enterobacter cloacae were placed into Beem capsules and stained with uranyl acetate and lead citrate, while immersed in an ice-water bath, and irradiated for periods ranging from 30 s to 2 min. After each contrasting procedure, the Beem capsule was filled with distilled water to wash the grids under MWI with the same irradiation time as used to contrast. Good results were obtained on irradiating for 1 min and the temperature of the Beem capsule was maintained around 5 °C. [source] Phase behavior and photo-responsive studies of photoactive liquid crystalline hyperbranched polyethers containing benzylidene moietyJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 11 2009V. Srinivasa Rao Abstract Two sets of hyperbranched polyether epoxies were synthesized to study the effect of substituent, rigidity, and nature of photoactive unit on the thermal and photoresponsive properties. Each set was comprised of one molecule with an acyclic moiety in the repeating unit, and two molecules with a cyclic moiety of varying rigidity (cycle size) in the repeating unit. Two substituents on aromatic rings in the repeating unit were present in one set, and other set was without a substituent. The mesogenic and photoresponsive properties were studied and correlated to the varied structural parameters. The effects of varied molecular structural parameters on phase behavior and photoresponsive properties were very prominent. Out of six monomeric diols, only four have exhibited liquid crystalline phase while the polymers corresponding to all monomeric diols revealed mesophase. The findings in photoresponsive properties were further supported by molecular modeling studies. The changes in refractive index, photoviscosity, and fluorescence intensity with irradiation time substantiated the spectral pattern observed in UV-Vis spectroscopy. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2774,2786, 2009 [source] Synthesis of azobenzene-containing polymers via RAFT polymerization and investigation on intense fluorescence from aggregates of azobenzene-containing amphiphilic diblock copolymersJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 16 2008Jie Xu Abstract The well-defined azobenzene-containing homopolymers, poly{6-(4-phenylazophenoxy)hexyl methacrylate (AHMA)} (PAHMA), were synthesized via reversible addition fragmentation chain transfer polymerization (RAFT) in anisole solution using 2-cyanoprop-2-yl 1-dithionaphthalate (CPDN) as the RAFT agent and 2,2,-azobisisobutyronitrile (AIBN) as the initiator. The first-order kinetic plot of the polymerization and the linear dependence of molecular weights of the homopolymers with the relatively low polydispersity index values (PDIs , 1.25) on the monomer conversions were observed. Furthermore, the amphiphilic diblock copolymer, poly{6-(4-phenylazophenoxy)hexyl methacrylate (AHMA)}- b -poly{2-(dimethylamino)ethyl methacrylate (DMAEMA)} (PAHMA- b -PDMAEMA), was prepared with the obtained PAHMA as the macro-RAFT agent. The structures and properties of the polymers were characterized by 1H NMR and GPC, respectively. Interestingly, the amphiphilic diblock copolymers in chloroform (CHCl3) solution (PAHMA23 - b -PDMAEMA97 (4 × 10,5 M, Mn(GPC) = 18,400 g/mol, PDI = 1.48) and PAHMA28 - b -PDMAEMA117 (6 × 10,5 M, Mn(GPC) = 19,300 g/mol, PDI = 1.51) exhibited the intense fluorescence emission at ambient temperature. Moreover, the fluorescent intensity of PAHMA- b -PDMAEMA in CHCl3 was sensitive to the ultraviolet irradiation at 365 nm, which increased within the first 10 min and later decreased when irradiation time was prolonged to 30 min or longer. The well distributed, self-assembled micelles composed of azobenzene-containing amphiphilic diblock copolymers, (PAHMA- b -QPDMAEMA)s (QPDMAEMA is quaternized PDMAEMA), in the mixed N,N -dimethyl formamide (DMF)/H2O solutions were prepared. Their fluorescent intensities decreased with the increasing amount of water. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5652,5662, 2008 [source] Crosslinking of PVC formulations treated with UV lightJOURNAL OF VINYL & ADDITIVE TECHNOLOGY, Issue 2 2006G. Arias Typical wire and cable formulations of plasticized Poly(vinyl chloride) were prepared with three different stabilizer systems: Ca/Zn (2:1 or 1:1) and dibasic lead phthalate. The mixtures contained trimethylolpropane trimethacrylate (TMPTMA) as crosslinking agent and a UV photoinitiator (Irgacure 819). Mixtures were dry-blended, then roll-milled and to finally hot-pressed at 180°C to obtain sheets of 1 and 1.5 mm thickness. Small specimens (3 × 3 cm) were irradiated with UV light for up to 10 days while monitoring changes at different time intervals. The presence of TMPTMA in the samples, as expected, influenced the storage modulus (E,) and gel content percentage, specifically for the thinner samples. These results indicated that UV irradiation produced surface crosslinking. The samples with crosslinking agent also reached higher carbonyl index values. The Ca/Zn formulations showed higher mechanical properties with respect to the Pb ones, thus suggesting that during the stabilization period of the Ca/Zn mixtures, an effective crosslinking was promoted. Irregular behavior was observed during the last days of treatment for both types of formulations, thereby suggesting an optimum irradiation time for this procedure. J. VINYL. ADDIT. TECHNOL. 12:49,54, 2006. © 2006 Society of Plastics Engineers. [source] Targeting of the retinal pigment epithelium (RPE) by means of a rapidly scanned continuous wave (CW) laser beamLASERS IN SURGERY AND MEDICINE, Issue 4 2003Ralf Brinkmann Abstract Background and Objectives Selective treatment of the retinal pigment epithelium (RPE) by repetitively applying green ,s-laser pulses is a new method for retinal diseases associated with a degradation of the RPE, which spares the neural retina. We investigated an alternative approach to realize repetitive ,s-laser exposure by rapidly scanning a continuous wave (CW)-laser beam across the RPE. Study Design/Materials and Methods An Ar+ laser beam (514 nm) with a diameter of 18.75 ,m was repetitively scanned across porcine RPE samples in vitro providing an irradiation time of 1.6 ,s per point on the central scan axis. RPE cell damage was investigated by means of the fluorescence viability assay Calcein-AM. Results The ED50 cell damage is 305 mJ/cm2 when applying 10 scans with a repetition rate of 500 Hz. The threshold decreases with the number of scans, a saturation was found at 135 mJ/cm2 with more than 500 exposures applied. The depth of focus in beam direction is 350 ,m, defined by an increase of the threshold radiant exposure by 20%. Conclusions Targeting of pigmented cells with high local resolution has been proved with a laser-scanning device. Looking ahead selective RPE-treatment, the adaptation of a laser-scanning device on a slit-lamp or into a modified retina angiograph seems to be an attractive alternative to the pulsed ,s laser device. Lasers Surg. Med. 32:252,264, 2003. © 2003 Wiley-Liss, Inc. [source] Synthesis of PLLA-MPEG Diblock Copolymers by Microwave-Assisted Copolymerization of L -Lactide and Methoxy Poly(ethylene glycol)MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 10 2007Chao Zhang Abstract PLLA-MPEG diblock copolymers with a controlled number-average molar mass ranging from 7,330 to 117,610 g,·,mol,1 and an L -lactide conversion ranging from 65.1 to 97.3% were synthesized effectively in 20 min at 100,°C by MPEG-initiated ROP of L -lactide under microwave irradiation. Prolonged microwave irradiation time led to the degradation of the copolymers because the ROP reaction and the thermal degradation reaction occurred simultaneously at the later stage of the reaction process. The differential scanning calorimetric and thermogravimetric study indicated that higher melting temperatures and thermal stability were obtained for PLLA-MPEG diblock copolymers with longer PLLA segments. [source] Photophysics and Photochemistry of z -Chlorprothixene in Acetonitrile,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 4 2009Luis E. Piñero Chlorprothixene (CPTX, Taractan®) is a low potency antipsychotic mainly used for the treatment of psychotic disorders (e.g. schizophrenia) and acute mania occurring as part of bipolar disorders. As in the case of other numerous drugs used in the treatment of psychiatric disorders, CPTX presents geometric isomerism. Therefore, in vitro irradiation induces a rapid Z/E isomerization, which can affect its pharmacokinetic properties. This photoisomerization is not dependent on the oxygen concentration. The Z/E quantum yields determined for zCPTX in acetonitrile are 0.22 and 0.21 in anaerobic and aerobic environments, respectively. In the presence of water, both isomers decompose to produce 2-chlorothioxanthone (CTX) after prolonged irradiation. This process strongly depends on the water concentration and the irradiation time, i.e. it is autocatalyzed by the CTX through a triplet-energy transfer mechanism. The protonation state of the terminal amino group, on the other hand, has no effect on the isomerization process, but inhibits the formation of CTX. These results indicate that the phototoxicity of zCPTX is somehow affected by the formation of CTX. [source] Photosensitized Oxidation of Hypoxanthine and Xanthine by Aluminum Phthalocyanine Tetrasulfonate.PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 6 20084-benzoquinone, 5-Dichloro-diaziridinyl-, Role of the Alkylating Quinone Photoirradiation of nitrogen-saturated aqueous solutions containing aluminum phthalocyanine tetrasulfonate (AlPcS4) at 675 nm in the presence of 2,5-dichloro-diaziridinyl-1,4-benzoquinone (AZDClQ) and hypoxanthine (HX) produces the oxidized HX derivatives, xanthine (X) and uric acid (UA). Concentrations of the AZDClQ semiquinone, X and UA increase at the expense of HX with an increase in irradiation time. Almost negligible decomposition of HX, as well as very low amounts of X, are detected if photolysis occurs under identical conditions but in the absence of AZDClQ. Addition of calf-thymus DNA produces quinone-DNA covalent adducts after photolysis of anaerobic samples containing quinone, DNA and AlPcS4, in the presence or absence of HX and at pH 5.5. However, larger amounts of quinone-DNA adducts are detected if HX is present. The results presented here could have applications in the photodynamic treatment of hypoxic tissues such as solid tumors, under conditions of high HX concentration, where Type-I pathways could be more important than singlet oxygen generation. [source] Nitridation and reoxidation of high- k metal oxide thin films using argon excimer sourcesPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 3 2006J. J. Yu Abstract We report for the first time the nitridation and reoxidation of metal oxide films with the active nitrogen and oxygen species produced by argon excimer sources. Preliminary results on 9 nm Ta2O5 films using this method exhibited excellent electrical properties with the leakage current density being up to 3 orders of magnitude lower than the as-deposited films. Breakdown fields were found to be greater than 13 MV/cm. Accumulation capacitance with the nitrided film increased by 25% compared with the as-deposited film. Optical transmittance was as high as 99% in the visible region and more than 74% in the UV region. The refractive index at 632.8 nm was high up to 2.2. The Ar excimer source emitted energetic VUV photons which could break nitrogen triple bonds to produce active nitrogen species and photodissociate O2 to form strong oxidant O3 and highly reactive O (1S) atoms, leading to the nitridation and reoxidation of Ta2O5 without the need for the use of H2O, NH3 and high temperature substrate heating. The nitridation process for a specific film thickness can be optimised by adjusting the VUV irradiation time to achieve increased accumulation capacitance and improved leakage property simultaneously. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Microwave-assisted extraction of total bioactive saponin fraction from Gymnema sylvestre with reference to gymnemagenin: a potential biomarkerPHYTOCHEMICAL ANALYSIS, Issue 6 2009Vivekananda Mandal Abstract Objective , To develop a fast and ecofriendly microwave assisted extraction (MAE) technique for the effective and exhaustive extraction of gymnemagenin as an indicative biomarker for the quality control of Gymnema sylvestre. Methodology , Several extraction parameters such as microwave power, extraction time, solvent composition, pre-leaching time, loading ratio and extraction cycle were studied for the determination of the optimum extraction condition. Scanning electron micrographs were obtained to elucidate the mechanism of extraction Results , The final optimum extraction conditions as obtained from the study were: 40% microwave power, 6,min irradiation time, 85% v/v methanol as the extraction solvent, 15,min pre-leaching time and 25,:,1 (mL/g) as the solvent-to-material loading ratio. The proposed extraction technique produced a maximum yield of 4.3% w/w gymnemagenin in 6,min which was 1.3, 2.5 and 1.95 times more efficient than 6,h of heat reflux, 24,h of maceration and stirring extraction, respectively. A synergistic heat and mass transfer theory was also proposed to support the extraction mechanism Conclusion , Comparison with conventional extraction methods revealed that MAE could save considerable amounts of time and energy, whilst the reduction of volume of organic solvent consumed provides an ecofriendly feature. Copyright © 2009 John Wiley & Sons, Ltd. [source] Preparation of temperature-sensitive polymer films by surface photografting techniquesPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 3-4 2002Bin Li Abstract In this paper, poly(N-isopropylacrylamide) has been successfully grafted on polypropylene (PP) films by pre-dipping photografting and dormant radical photografting techniques. It was found that higher grafting yield was achieved by the dormant radical photografting method. An optimum concentration of N-isopropylacrylamide monomer existed both for the pre-dipping photografting and for the dormant radical photografting methods. The grafting yield was improved by increasing the UV irradiation time for both methods. Water absorbency of grafted PP films prepared by the two methods was similar and increased nearly linearly with the improvement of grafting yield. At constant temperature and humidity, the grafted PP films lost the absorbed water continually before the water absorbency reached an equilibrium value at this temperature. Copyright © 2002 John Wiley & Sons, Ltd. [source] Microwave-assisted specific chemical digestion for rapid protein identificationPROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 2 2006Lin Hua Abstract We have developed a rapid microwave-assisted protein digestion technique based on classic acid hydrolysis reaction with 2% formic acid solution. In this mild chemical environment, proteins are hydrolyzed to peptides, which can be directly analyzed by MALDI-MS or ESI-MS without prior sample purification. Dilute formic acid cleaves proteins specifically at the C-terminal of aspartyl (Asp) residues within 10,min of exposure to microwave irradiation. By adjusting the irradiation time, we found that the extent of protein fragmentation can be controlled, as shown by the single fragmentation of myoglobin at the C-terminal of any of the Asp residues. The efficacy and simplicity of this technique for protein identification are demonstrated by the peptide mass maps of in-gel digested myoglobin and BSA, as well as proteins isolated from Escherichia coli,K12 cells. [source] Toxicity reduction of metal pyrithiones by near ultraviolet irradiationENVIRONMENTAL TOXICOLOGY, Issue 4 2006Hideo Okamura Abstract Zinc pyrithione (ZnPT) or copper pyrithione (CuPT) have been effectively used as ship-antifouling agents, as an alternative to organotin compounds. Because of their instability in light and a lack of suitable analytical procedures, there is little data on their residue levels in environmental matrices. It is possible to investigate the fate of such compounds by toxicity alteration with certain treatments. The purpose of this study was to evaluate the degradation of pyrithiones through toxicity reduction by near ultraviolet (UV-A) irradiation. Metal pyrithiones dissolved in acetonitrile were irradiated with a UV-A lamp for 0, 0.5, 1, and 2 h, and were subjected to UV spectral measurement and toxicity evaluation using both sea urchin and freshwater rotifer bioassays. For the bioassays, photolyzed samples were dissolved in dimethyl sulfoxide after evaporation of the acetonitrile. The changes in UV spectra of photolyzed ZnPT or CuPT showed a time-dependent degradation, and the UV spectra at 2 h irradiation suggested substantial decomposition. Toxicities of ZnPT and CuPT were 12 and 5 ,g/L as 24 h LC50 to the survival of rotifers and 10,6 ng/L and 2.3 ng/L as 27 h EC50 to normal pluteus formation, respectively. By evaporation of the acetonitrile, the EC50 of ZnPT was 2.2 ng/L, which was the same as that of CuPT. The EC50s of ZnPT or CuPT for both species increased with longer irradiation times. Photolyzed ZnPT or CuPT demonstrated substantial degradation in the UV spectra, but possessed marked toxicity, which is probably due to toxic degradation products. One reason why photolyzed CuPT was toxic to rotifers was explained by the high toxicity of copper ions formed by UV-A irradiation. © 2006 Wiley Periodicals, Inc. Environ Toxicol 21: 305,309, 2006. [source] Chemical modification and surface reactions on carbon fibers studied by SERSJOURNAL OF RAMAN SPECTROSCOPY, Issue 12 2006Bing Xu Abstract Carbon fibers were modified by reacting with maleic anhydride (MA) and oxidation in nitric acid to alter their inert nature. Bismaleimide, acting as a model compound of polyimide, was chosen to react with the surface-active carbon fibers. Surface-enhanced Raman scattering was performed by chemically depositing Ag colloids on different carbon fiber samples, including raw, modified and post-reaction materials. The obtained enhanced Raman spectra explained the surface chemistry of the different carbon fiber samples and their further interaction with bismaleimide. The results could serve as a guide for the design of functional groups on carbon fibers and the manufacture of the carbon-fiber-reinforced polyimide matrix composites. Moreover, the effect of different laser powers and laser irradiation times on the carbon fiber surface was studied and is discussed. Copyright © 2006 John Wiley & Sons, Ltd. [source] | ||||||||||||||||||||||||||||||||||