Distribution by Scientific Domains
Distribution within Chemistry

Kinds of Irradiation

  • adjuvant irradiation
  • b irradiation
  • beam irradiation
  • body irradiation
  • breast irradiation
  • cranial irradiation
  • e-beam irradiation
  • electron beam irradiation
  • electron irradiation
  • electron-beam irradiation
  • external beam irradiation
  • external irradiation
  • final irradiation
  • food irradiation
  • gamma irradiation
  • infrared irradiation
  • ion irradiation
  • laser irradiation
  • light irradiation
  • local irradiation
  • low-energy laser irradiation
  • low-level laser irradiation
  • microwave irradiation
  • mw irradiation
  • neck irradiation
  • off-resonance irradiation
  • orbital irradiation
  • partial breast irradiation
  • pelvic irradiation
  • postoperative irradiation
  • prophylactic cranial irradiation
  • proton irradiation
  • ray irradiation
  • solar irradiation
  • total body irradiation
  • ultrasonic irradiation
  • ultrasound irradiation
  • ultraviolet b irradiation
  • ultraviolet irradiation
  • uv irradiation
  • uv light irradiation
  • uv-b irradiation
  • uva irradiation
  • uvb irradiation
  • uvc irradiation
  • visible light irradiation
  • visible-light irradiation
  • white light irradiation
  • x-ray irradiation
  • yag laser irradiation

  • Terms modified by Irradiation

  • irradiation alone
  • irradiation condition
  • irradiation dose
  • irradiation effects
  • irradiation exposure
  • irradiation lead
  • irradiation parameter
  • irradiation process
  • irradiation protocol
  • irradiation source
  • irradiation therapy
  • irradiation time
  • irradiation treatment

  • Selected Abstracts


    ABSTRACT We determined the dose distribution within a tray of highbush blueberries (Vaccinium corymbosum L.) exposed to electron beam irradiation at medium levels (1.0,3.2 kGy) using Monte Carlo and computer tomography scanning technology. We also evaluated the quality of irradiated and nonirradiated (control) fruits stored at 5C and 70% relative humidity during 14 days by a series of chemical analyses. Blueberries packed in plastic clamshell containers (trays) were irradiated using a 10-MeV linear accelerator with single-beam fixture (top only). Irradiation of blueberries at 1.1 kGy had no significant (P > 0.05) effect on the fruit quality with the exception of ascorbic acid, which decreased by 17% by the end of storage. Irradiation had an enhancing effect on the total phenolic and tannin content of all the irradiated fruits (10,20% increases). The calculated dose distribution in a pack of blueberries confirmed that the dose is not uniformly distributed within the pack because of density inhomogeneities (flesh, skin air). Dose levels at the bottom of the trays were 18 (±8%) higher than at the top. These results suggest that careful dose distribution examination must be conducted prior to setting up of an irradiation run for the packed fruits. Excellent agreement was found between measured and calculated doses at different electron beam conveyor speeds. PRACTICAL APPLICATIONS Little information is available on how electron beam irradiation penetrates a complex medium such as packed blueberries. This study presents unique results from a dose distribution calculation method using Monte Carlo simulation and computed tomography scanning techniques, which can be an effective tool for the development of proper irradiation treatment planning of packed fruits and other fresh produce. The suitability of using electron beam technology to preserve the quality characteristics and shelf life of packed blueberries was verified. [source]


    ABSTRACT We determined the optimum irradiation treatment for decontamination of physiologically mature fresh "Tommy Atkins" mangoes, without detriment to the fruits' sensory and chemical properties. Mangoes were irradiated at 1.0, 1.5 and 3.1 kGy using a 10-MeV linear accelerator (14-kW LINAC, double beam mode). Mangoes were stored for 21 days at 12C and 62.7% relative humidity with nonirradiated fruits as controls. Dose distribution within the fruit was determined using Monte Carlo techniques. Irradiation did not affect the overall sensory quality of mangoes at doses up to 1.5 kGy. Only fruits irradiated at 3.1 kGy were unacceptable by the panelists. Irradiation at 3.1 kGy enhanced the fruit's aroma characteristics. Irradiation at all levels caused a significant (P , 0.05) decrease (,50,70%) in ascorbic acid content by the end of storage. Mangoes irradiated at 1.5 and 3.1 kGy had slightly higher levels of phenolics than the control (27.4 and 18.3%, respectively). E-beam irradiation of Tommy Atkins mangoes up to 3.0 kGy causes no detriment to the fruit's overall sensory and chemical quality. [source]


    V.K.G. ABREU
    ABSTRACT The objective of this work was to evaluate the effects of , irradiation (0, 2, 4 and 6 kGy doses), applied on frozen and packaged headed shrimps, on pathogenic Vibrio cholerae O1 and Salmonella enteritidis bacteria, as well as on some of the physical and sensory characteristics of this kind of food. The 6 kGy dose was highly efficient in inhibiting V. cholerae O1 and S. enteritidis and in decreasing lipid oxidation in shrimps compared with the nonirradiated product. Shrimp texture was not affected by any of the irradiation doses studied, but the lightness of the surface color increased in shrimps irradiated with 6 kGy compared with those irradiated with 2 kGy. Shrimps irradiated with 6 kGy showed lower overall acceptability than those irradiated with 2 kGy or were nonirradiated. The application of , irradiation in doses up to 6 kGy on frozen and packaged headed shrimps could improve the microbiological quality of this commodity. PRACTICAL APPLICATIONS The use of , irradiation has the potential to ensure safety effectively by inactivating bacteria, increasing shelf life and maintaining food quality without significant chemical changes in the food matrix. Besides, this process can be applied to frozen and packaged products. Thus, irradiation of frozen and packaged shrimps could benefit the local processing industry, which could offer the international market a high-quality product, with an additional safety treatment. [source]


    JOURNAL OF FOOD SAFETY, Issue 3 2006
    ABSTRACT Ninety random grain samples were collected and analyzed for mycotoxins, and the effect of gamma irradiation on the production of mycotoxins in grains was studied. Aspergillus, Penicillium, Mucor, Rhizopus, Fusarium, Alternaria, Scopulariopsis and Cladosporium were the most common fungal genera isolated from grains. Aspergillus flavus, Aspergillus niger, Aspergillus candidus, Aspergillus ochraceus, Penicillium citrinum, Penicillium expansum, Penicillium citreonigrum, Penicillium purpurogenum, Penicillium griseofulvum and Penicillium verrucosumwere the most common Aspergillus and Penicillium species in grains. Out of 120 Aspergillus and Penicillium isolates, 80 were mycotoxin producers. Analysis of grains revealed the occurrence of aflatoxin B1 ochratoxin A, cycolopiazonic acid and citrinin. Of the 90 samples, 67 were positive for one or more mycotoxin. Irradiation of grains at dose of 2.0 and 4.0 kGy decreased significantly the total fungal counts compared with unirradiated controls. After 100 days of storage at room temperature, the unirradiated grains were contaminated with high concentrations of mycotoxins as compared with irradiated 4.0-kGy samples. Mycotoxin production in grains decreased with increasing irradiation doses and was not detected at 6.0 kGy over 100 days of storage. [source]

    Differential Long-Term Stimulation of Type I versus Type III Collagen After Infrared Irradiation

    BACKGROUND The dermis is composed primarily of type I (soft) and type III (rigid scar-like) collagen. Collagen degradation is considered the primary cause of skin aging. Studies have proved the efficacy of infrared irradiation on collagen stimulation but have not investigated the differential long-term effects of infrared irradiation on type I and type III collagen. OBJECTIVE To determine differential long-term stimulation of type I and type III collagen after infrared (1,100,1,800 nm) irradiation. METHODS AND MATERIALS In vivo rat tissue was irradiated using the infrared device. Histology samples were analyzed for type I and III collagen stimulation, visual changes from baseline, and treatment safety up to 90 days post-treatment. RESULTS Infrared irradiation provided long-term stimulation of type I collagen and temporary stimulation of type III collagen. Treatment also created long-term smoothing of the epidermis, with no observed complications. CONCLUSIONS Infrared irradiation provides safe, consistent, long-term stimulation of type I collagen but only short-term stimulation in the more rigid type III collagen. This is preferential for cosmetic patients looking for improvement in laxity and wrinkles while seeking smoother, more youthful skin. [source]

    Near Painless, Nonablative, Immediate Skin Contraction Induced by Low-Fluence Irradiation with New Infrared Device: A Report of 25 Patients

    BACKGROUND Nonablative radiofrequency (NARF) has been the only method for producing noninvasive skin tightening. Nevertheless, significant pain during the procedure is an important downside of this technology. A new nonablative medical device, Titan (Cutera, Inc., Brisbane, CA, USA), capable of fluences much lower than those possible with NARF, was tested as a less painful alternative. OBJECTIVES To produce skin contraction leading to lifting of eyebrows and/or improvement of lower face and neck skin laxity using fluences below pain levels. PATIENTS AND METHODS Twenty-five patients were treated. Standardized photographs were obtained preoperatively, after a few days, a few weeks, and up to 12 months after the procedure. RESULTS Immediate changes were obtained in 22 of 25 patients. Examination of photographs revealed that the initial improvement was maintained throughout the follow-up period. CONCLUSION Immediate true skin contraction persisting through the immediate, intermediate, and long-term follow-up was found in the vast majority of patients in this group. Edema as an artifact simulating immediate improvement was excluded by serial photographs taken during the follow-up period. Skin contraction occurred at low fluences, below the threshold of pain. This, to the best of our knowledge, has not been previously described in the medical literature. [source]

    Collagen Remodeling After 585-nm Pulsed Dye Laser Irradiation: An Ultrasonographic Analysis

    Brent R. Moody MD
    Background and Objectives. Nonablative dermal remodeling is an evolving technology that has generated great interest among both laser surgeons and patients. Evidence indicates that dermal collagen formation is the key mechanism of action for the nonablative techniques. We studied, with ultrasound, new collagen formation after nonablative laser irradiation. Methods. Ten patients with facial rhytids underwent a single treatment with a 585-nm pulsed dye laser. The patients were all female, ranging in age from 47 to 67, and were Fitzpatrick skin types I,III. Laser parameters were as follows: an energy fluence of 2.4 to 3.0 J/cm2, a pulse duration of 350 ,sec, and a spot size of 5 mm with no overlap. Ultrasonographic assessments of dermal collagen were taken at baseline and at 30 and 90 days after treatment. Results. Ultrasonography demonstrated an increase in dermal collagen after a single treatment with the 585-nm pulsed dye laser. The greatest degree of neocollagenesis occurred periocularly. Conclusion. A single treatment with a 585-nm pulsed dye laser appears to increase dermal collagen. This increase in dermal collagen can be assessed with noninvasive cutaneous ultrasound. [source]

    Mutation spectrum in UVB-exposed skin epidermis of Xpa -knockout mice: Frequent recovery of triplet mutations

    Hironobu Ikehata
    Abstract Knockout mutations in both alleles of the Xpa gene give rise to a complete deficiency in nucleotide excision repair (NER) in mammalian cells. We used transgenic mice harboring the ,-phage-based lacZ mutational reporter gene to study the effect of Xpa null mutation (Xpa,/,) on damage induction, repair, and mutagenesis in mouse skin epidermis after UVB irradiation. UVB induced equal amounts of cyclobutane pyrimidine dimers (CPDs) and pyrimidine(6-4)pyrimidone photoproducts (64PPs) in mouse skin epidermis of Xpa,/, and wild-type mice. Neither photolesion was removed in the Xpa,/, epidermis by 12 hr after irradiation whereas removal of 64PPs was observed in the epidermis of wild-type mice. Irradiation with 200 and 300 J/m2 UVB increased the lacZ mutant frequency in the epidermis of Xpa,/, mice, but the induced mutant frequencies were not significantly different from those previously determined for wild-type mice. One-hundred lacZ mutants isolated from the UVB-exposed epidermis of Xpa,/, mice were analyzed and compared with mutant sequences previously determined for irradiated wild-type mice. The distribution of the mutations along the lacZ transgene and the preferred dipyrimidine context of the UV-specific mutations were similar in mutants from the Xpa,/, and wild-type mice. The spectra of the mutations in the two genotypes were both highly UV-specific and similar in a dominance of C , T transitions at dipyrimidine sites; however, Xpa,/, mice had a higher frequency than wild-type mice of two-base tandem substitutions, including CC , TT mutations, three-base tandem mutations and double base substitutions that were separated by one unchanged base in a three-base sequence (alternating mutations). These tandem/alternating mutations included a remarkably large number of triplet mutations, a recently reported, novel type of UV-specific mutation, characterized by multiple base substitutions or frameshifts within a three-nucleotide sequence containing a dipyrimidine. We conclude that the triplet mutation is a UV-specific mutation that preferably occurs in NER-deficient genetic backgrounds. Environ. Mol. Mutagen., 2007. © 2006 Wiley-Liss, Inc. [source]

    Evaluation of the radioprotective effect of Liv 52 in mice

    Ganesh C. Jagetia
    Abstract Liv 52 is a mixture of botanicals that is used clinically to treat various hepatic disorders. In this study, the radioprotective activity of Liv 52 was evaluated in mice given whole-body exposure to different doses of ,-radiation. In addition, a series of studies was conducted to explore the mechanism of radioprotection. Radioprotection was evaluated by the ability of Liv 52 to reduce both the frequency of bone marrow micronucleated erythrocytes and the lethality produced by 60Co ,-radiation. Mice were treated by oral gavage once daily for seven consecutive days with 500 mg/kg body weight Liv 52 or carboxymethylcellulose vehicle prior to radiation. Micronucleated polychromatic erythrocytes (MPCEs), micronucleated normochromatic erythrocytes (MNCEs), and the PCE/NCE ratio were measured at 0.25,14 days after exposure to whole-body radiation doses of 0, 0.5, 1.5, 3.0, or 4.5 Gy; animal survival was monitored after doses of 7, 8, 9, 10, 11, or 12 Gy. Pretreatment of mice with Liv 52 significantly reduced the frequency of radiation-induced MPCEs and MNCEs. Irradiation reduced the PCE/NCE ratio in a dose-related manner for up to 7 days following irradiation; Liv 52 pretreatment significantly mitigated against these reductions. Liv 52 treatment also reduced the symptoms of radiation sickness and increased mouse survival 10 and 30 days after irradiation. Liv 52 pretreatment elevated the levels of reduced glutathione (GSH), increased the activities of glutathione transferase, GSH peroxidase, GSH reductase, superoxide dismutase, and catalase, and lowered lipid peroxidation (LPx) and the activities of alanine amino transferase and aspartate aminotransferase 30 min after exposure to 7 Gy of ,-radiation. Liv 52 pretreatment also reduced radiation-induced LPx and increased GSH concentration 31 days following the exposure. The results of this study indicate that pretreatment with Liv 52 reduces the genotoxic and lethal effects of ,-irradiation in mice and suggest that this radioprotection may be afforded by reducing the toxic effects of the oxidative products of irradiation. Environ Mol. Mutagen., 2006. © 2006 Wiley-Liss, Inc. [source]

    Effect of mangiferin on radiation-induced micronucleus formation in cultured human peripheral blood lymphocytes

    Ganesh Chandra Jagetia
    Abstract Irradiation causes a variety of lesions in important biomolecules of the cell through generation of free radicals leading to genomic instability. DNA strand breaks, acentric fragments, or defective kinetochores are manifested as micronuclei after the first cell division. Chemicals that can trap free radicals may reduce the deleterious effects of ionizing radiation. Mangiferin (MGN), a glucosylxanthone derived from Mangifera indica (mango), was investigated for its ability to reduce the frequency of radiation-induced micronucleated binucleate cells (MNBNCs) in cultured human peripheral blood lymphocytes (HPBLs). HPBL cultures were pretreated with 0, 5, 10, 20, 50, and 100 ,g/ml of MGN for 30 min before exposure to 3 Gy of 60Co ,-radiation. The maximum decline in radiation-induced micronuclei was observed at a concentration of 50 ,g/ml MGN; thereafter, a nonsignificant elevation in MNBNC frequency was observed at 100 ,g/ml MGN. Since the lowest MNBNC frequency was observed for 50 ,g/ml MGN, dose-response studies were undertaken using this concentration. Irradiation of HPBLs with 0, 1, 2, 3, or 4 Gy of ,-radiation caused a dose-dependent elevation in the MNBNC frequency, while treatment of HPBLs with 50 ,g/ml MGN 30 min before radiation resulted in significant declines in these frequencies. MGN alone did not alter the proliferation index. Irradiation caused a dose-dependent decline in the proliferation index, while treatment of HPBLs with 50 ,/ml MGN significantly elevated the proliferation index in irradiated cells. MGN treatment reduced hydrogen peroxide-induced lipid peroxidation in HPBLs in a concentration-dependent fashion. In cell-free studies, MGN inhibited the induction of ·OH (hydroxyl), O2·, (superoxide), DPPH (1,1-diphenyl-2-picrylhydrazyl), and ABTS·+ (2,2-azino-bis-3-ethyl benzothiazoline-6-sulphonic acid) radicals in a dose-dependent manner. The results of this study indicate that MGN possesses radioprotective properties by suppressing the effects of free radicals. Environ. Mol. Mutagen. 45:000,000, 2005. © 2005 Wiley-Liss, Inc. [source]

    Cytotoxic Rhodium(III) Polypyridyl Complexes Containing the Tris(pyrazolyl)methane Coligand: Synthesis, DNA Binding Properties and Structure,Activity Relationships

    Ruth Bieda
    Abstract The RhIII complexes of the type [RhCl(pp)(tpm)]2+ [pp = bpy, bpm, phen, tap, dpq, dppz] 4,9 have been prepared by stepwise treatment of RhCl3·3H2O or mer,cis -[RhCl3(DMSO-,S)2(DMSO-,O)] with the appropriate polypyridyl ligand (pp) followed by the tripodal ligand tris(pyrazolyl)methane (tpm). Intermediates of the type [RhCl3(CH3OH)(pp)] 1,3 with pp = bpy, phen, dpq were also characterized but exhibit either low (3) or no (1, 2) cytotoxicity. X-ray structural analyses of [RhCl(bpy)(tpm)][PF6]24 and [RhCl(phen)(tpm)][PF6]26 were performed, and the interaction of complexes 4,9 with DNA was investigated by CD and UV/Vis spectroscopy and by gel electrophoresis. CD and viscosity studies confirm strong intercalation of dppz complex 9 into DNA. Complexes 8 and particularly 9 (IC50 = 0.43, 0.37 ,M) are potent cytotoxic agents towards the human cancer cell lines MCF-7 and HT-29, whereas respectively little (complex 6) or no activity (complexes 4, 5, 7) is observed for the other members of the series. Our findings indicate that the cytotoxicity is dependent on the hydrophobicity of both the polypyridyl and the facial coligand in these and other half-sandwich RhIII complexes. Irradiation of bpy compound 4 in the presence of plasmid pBR322 for 30 min at 311 nm at a molar ratio of r = 0.1 leads to total conversion of the supercoiled form into the nicked version. Although dppz complex 9 also functions as a photonuclease under these conditions, the degree of cleavage is much lower. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]

    Highly Efficient Visible-Light-Induced Photocleavage of DNA by a Ruthenium-Substituted Fluorinated Porphyrin

    Michelle Cunningham
    Abstract A new porphyrin, meso -5-(pentafluorophenyl)-10,15,20-tris(4-pyridyl)porphyrin, has been synthesized. Coordination of two [Ru(bipy)2Cl]+ moieties (where bipy = 2,2,-bipyridine) to the pyridyl nitrogen atoms in the 10,15-positions gives the target complex. Electronic transitions associated with the ruthenium,porphyrin include an intense Soret band and four less intense Q-bands in the visible region of the spectrum. An intense ,,,* transition in the UV region associated with the bipyridyl groups and a metal-to-ligand charge-transfer (MLCT) band appearing as a shoulder to the Soret band are also observed. Electrochemical properties associated with the complex include a redox couple in the cathodic region with E1/2 = ,0.84 V vs. Ag/AgCl attributed to the porphyrin and a redox couple in the anodic region at E1/2 = 0.79 V vs. Ag/AgCl due to the RuIII/II couple. DNA titrations and ethidium bromide displacement experiments indicate the ruthenium porphyrin interacts with DNA potentially through a partial intercalation mechanism. Irradiation of aqueous solutions of the ruthenated complex and supercoiled DNA at a 100:1 base pair/complex ratio with visible light above 400 nm indicates that the complex causes double-strand breaks of the DNA.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]

    Effect of irradiation type (LED or QTH) on photo-activated composite shrinkage strain kinetics, temperature rise, and hardness

    Norbert Hofmann
    This study compares commercially available light-emitting diode (LED) lights with a quartz tungsten halogen (QTH) unit for photo-activating resin-based composites (RBC). Shrinkage strain kinetics and temperature within the RBC were measured simultaneously using the ,deflecting disc technique' and a thermocouple. Surface hardness (Knoop) at the bottom of 1.5-mm thick RBC specimens was measured 24 h after irradiation to indicate degree of cure. Irradiation was performed for 40 s using either the continuous or the ramp-curing mode of a QTH and a LED light (800 mW cm,2 and 320 mW cm,2, respectively) or the continuous mode of a lower intensity LED light (160,mW cm,2). For Herculite XRV and Filtek Z250 (both containing only camphoroquinone as a photo-initiator) the QTH and the stronger LED light produced similar hardness, while in the case of Definite (containing an additional photo-activator absorbing at lower wavelength) lower hardness was observed after LED irradiation. The temperature rise during polymerization and heating from radiation were lower with LED compared to QTH curing. The fastest increase of polymerization contraction was observed after QTH continuous irradiation, followed by the stronger and the weaker LED light in the continuous mode. Ramp curing decreased contraction speed even more. Shrinkage strain after 60 min was greater following QTH irradiation compared with both LED units (Herculite, Definite) or with the weaker LED light (Z250). [source]

    Photochemistry of Salicylaldoxime in Solid Argon: An Experimental and Theoretical Study

    Joanna Grzegorzek
    Abstract The photochemistry of salicylaldoxime in solid argon has been investigated by FTIR spectroscopy and DFT calculations. The salicylaldoxime molecule trapped in the matrix from the vapor above the solid sample has the most stable syn1 conformation with an intramolecular hydrogen bond. Irradiation (, > 320 nm) leads to conversion of the syn1 conformer into the syn3 one, in which the C(H)NOH and (C)OH groups are rotated around the C,C and C,O bonds, respectively, and the intramolecular hydrogen bond is broken. The photochemistry of syn3 involves three possible routes: (i) conversion of syn3 into anti2 conformer, this process requires rearrangement of the NOH group with respect to the C=N bond; (ii) photodissociation of salicylaldoxime into 2-cyanophenol and water, which form a hydrogen-bonded complex; and (iii) regeneration of the syn1 conformer. The third route is a very small contribution to the overall process. The study performed with [D2]salicylaldoxime indicates that the dehydration reaction of salicylaldoxime involves cleavage of the N,O bond and formation of OH and Ph(OH)C(H)N radicals in the first step. Then, the OH radical abstracts a hydrogen atom from the CH group to form 2-cyanophenol and water molecules. When the sample is exposed to the full output of the mercury lamp the 2-cyanophenol complex with water becomes the dominating product. [source]

    Solid-Phase Reactive Chromatography (SPRC): A New Methodology for Wittig and Horner,Emmons Reactions on a Column under Microwave Irradiation

    Saada C. Dakdouki
    Abstract A new methodology named solid-phase reactive chromatography (SPRC), which combines reaction, separation, and purification into a single unit for the preparation of small samples, is described. This method was illustrated in the synthesis of some natural bioactive compounds, namely, methoxylated analogues of resveratrol, alkylresorcinols, and 5-aryl-2,4-pentadienoates, over a column of alumina-KF under microwave irradiation by using the Wittig and Horner,Emmons reactions. This approach permitted the preparation of the target olefins with high purity and good to excellent yields in short reaction times. [source]

    Synthesis and Property Studies of Cyclotrisazobenzenes

    Raphael Reuter
    Abstract Azobenzenophanes are fascinating macrocycles, which are of special interest due to their unique photochromic behavior. Cyclotrisazobenzenes 2 (R = H, Br, tBu) were prepared to probe how much strain the photoisomerization of the azobenzene motive can tolerate. The macrocycles were synthesized in an overall yield of 10,20,% from ortho -phenylenediamine (6). Solid-state structures of cyclotrisazobenzenes 2a and 2b were obtained. Irradiation under various conditions did not induce any isomerization.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]

    Novel Photochemical Reactions of Phosphonium-Iodonium Ylides: Synthesis of Phosphonium-Substituted Oxazoles

    Elena D. Matveeva
    Abstract Irradiation of the mixed phosphonium-iodonium ylides 4,6 in the presence of acetonitrile, propionitrile, and benzonitrile yielded the oxazole derivatives 9a,9c, 10a,10c, and 11a,11c in 30,%,50,% yields. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]

    On the Synthesis of Carbon Nanofibers and Nanotubes by Microwave Irradiation: Parameters, Catalysts, and Substrates

    Tamara Druzhinina
    Abstract The microwave (MW)-assisted synthesis of one dimensional carbon systems is introduced as a promising approach to improve the speed and cost-effectiveness of the fabrication process. Improved reaction conditions are generated by direct MW heating and synthesis under advanced reaction conditions. The influence of the reaction conditions is investigated and the importance of individual process parameters on the synthesis is discussed. Temperature and pressure data recorded during the irradiation process are analyzed in detail and allow the determination of essential process parameters. This leads to improved reaction conditions, better control of the one-dimensional carbon nanosystems by tuning the catalyst materials, and allows expanding this approach to initiate the synthesis on a variety of different substrates, such as quartz glass and mica. [source]

    Densification of Oxide Nanoparticle Thin Films by Irradiation with Visible Light

    Massimo F. Bertino
    Abstract A technique is presented that allows for altering of the physical characteristics of films of TiO2 nanoparticles by exposure to visible light. In this technique, dye-sensitized oxide nanoparticles are deposited on a substrate by dip-coating. Photodissociation of the organic ligand layer leads to cross-linking of the nanoparticles. Consequently, irradiated films have a decreased porosity, an increased index of refraction and an increased hydrophobicity. Films irradiated with green light are compared to films irradiated with UV light. Within experimental error, visible- and UV-illumination induces the same changes in the films. The mechanism of surfactant elimination in dye-sensitized oxide particles is discussed, patterning is demonstrated, and prospective applications of the technique are considered. [source]

    Spontaneous Formation of Complex Periodic Superstructures under High Interferential Illumination of Small-Molecule-Based Photochromic Materials

    Eléna Ishow
    Abstract A series of push-pull azo compounds containing bulky substituents are synthesized, yielding fully amorphous materials with glass-transition temperatures above 200,°C. Thin films are subjected to holographic illumination and show superior bulk photomigration in terms of speed and efficiency compared to materials exhibiting similar electronic and photochromic properties in the solid state. The reported results give evidence that a microscopic consideration of the free volume rather than macroscopic parameters like the glass-transition temperature should to be adopted to interpret the matrix stiffness and its deformation ability. Irradiation performed at higher laser intensity produces periodic superstructures whose height is five to six times as high as the initial film thickness. The surface tension and instability effects are put forward to interpret the growth of such superstructures. [source]

    Tuning and Enhancing Photoluminescence of Light-Emitting Polymer Nanotubes through Electron-Beam Irradiation

    Young Ki Hong
    A new method for the tuning and enhancing photoluminescence (PL) characteristics of light emitting poly (3-methylthiopnehe) (P3MT) nanotubes through E-beam irradiation under atmospheric environments is reported. An E-beam generated from a linear electron accelerator (1 MeV, 1.6,×,1013,8.0,×,1016 electrons cm,2) is irradiated onto P3MT nanotubes including an Al2O3 template. From laser confocal microscope (LCM) PL experiments, significant enhancements in the PL intensity,up to about 90 times of an isolated single strand of the E-beam irradiated P3MT nanotubes,are observed. The luminescent color of the P3MT nanotubes changes from green to red color depending on the variation of E-beam dosage. These results might originate from the de-doping effect and the conformational modification through E-beam irradiations. Conformational changes of the E-beam irradiated P3MT nanotubes are confirmed by LCM single Raman and ultraviolet-visible (UV/Vis) absorption spectra. From UV/Vis absorption spectra, it is observed that the ,,,* transition peak and the doping induced bipolaron peaks of the P3MT nanotubes dramatically vary with E-beam irradiating conditions. [source]

    The Influence of UV Irradiation on Ketonic Defect Emission in Fluorene-Based Copolymers,

    Horst Scheiber
    Abstract The influence of UV irradiation in inert atmosphere on the emission spectrum of fluorenone containing poly[9,9-bis(2-ethyl)hexylfluorene] (PF2/6) has been investigated by means of optical absorption, photoluminescence (PL) and Fourier transform infrared (FTIR) spectroscopy. It is shown that a substantial reduction of green emission arising from ketonic defect sites can be achieved by irradiation of thin films with UV light. This is found to be accompanied by partial cross-linking of the films. FTIR measurements show no reduction of the C=O stretching mode upon irradiation, and, moreover, the degree of cross-linking does not scale with the relative fluorenone content (0.1, 0.5, and 5%). Therefore, the reduced emission intensity in the green spectral region is rather associated with the occurrence of interruptions in the polymer backbone, which reduce the effective conjugation length and subsequently inhibit the energy transfer onto the ketonic defect sites. The found results enabled us to build organic light emitting devices (OLEDs) that can be structured by selective illumination of the emitting layer with an intense UV light source. This method allows for the fabrication of rather efficient (2000,cd,m,2 at 7,V) two-color OLEDs. [source]

    Strong Carbon-Nanotube,Polymer Bonding by Microwave Irradiation,

    Y. Wang
    Abstract The vigorous response of multiwalled carbon nanotubes (MWNTs) to microwave irradiation, leading to the release of a large amount of heat, is used to locally melt a plastic matrix adjacent to the nanotubes within a period of seconds. This results in the intercalation of the MWNTs into the polymer matrix at room temperature without any physical damage to the polymer. The so-called "microwave welding" approach creates a new paradigm for the formation of very strong MWNT,polymer bonds without the use of any adhesive, and represents a significant step forward for the fabrication of functional nanotube composites. Here, we demonstrate the implications of the anisotropic alignment of MWNTs in polymers, patterned conductors/resistors for soft electronics, and high-strength composites, where the MWNTs are ,soldered' to flexible polymer substrates. [source]

    Definitive radiotherapy in the management of chemodectomas arising in the temporal bone, carotid body, and glomus vagale

    Russell W. Hinerman MD
    Abstract Purpose To evaluate the results of treatment for 71 patients with 80 chemodectomas of the temporal bone, carotid body, or glomus vagale who were treated with radiation therapy (RT) alone (72 tumors in 71 patients) or subtotal resection and RT (8 tumors) at the University of Florida between 1968 and 1998. Methods and Materials Sixty-six lesions were previously untreated, whereas 14 had undergone prior treatment (surgery, 11 lesions; RT, 1 lesion; or both, 2 lesions) and were treated for locally recurrent disease. All three patients who received prior RT had been treated at other institutions. Patients had minimum follow-up times as follows: 2 years, 66 patients (93%); 5 years, 53 patients (75%); 10 years, 37 patients (52%); 15 years, 29 patients (41%); 20 years, 18 patients (25%); 25 years, 12 patients (17%); and 30 years, 4 patients (6%). Results There were five local recurrences at 2.6 years, 4.6 years, 5.3 years, 8.3 years, and 18.8 years, respectively. Four were in glomus jugulare tumors and one was a carotid body tumor. Two of the four patients with glomus jugulare failures were salvaged, one with stereotactic radiosurgery and one with surgery and postoperative RT at another institution. Two of the five recurrences had been treated previously at other institutions with RT and/or surgery. Treatment for a third recurrence was discontinued, against medical advice, before receiving the prescribed dose. There were, therefore, only 2 failures in 65 previously untreated lesions receiving the prescribed course of RT. The overall crude local control rate for all 80 lesions was 94%, with an ultimate local control rate of 96% after salvage treatment. The incidence of treatment-related complications was low. Conclusions Irradiation offers a high probability of tumor control with relatively minimal risks for patients with chemodectomas of the temporal bone and neck. There were no severe treatment complications. © 2001 John Wiley & Sons, Inc. Head Neck 23: 363,371, 2001. [source]

    Formation of Nanoislands on Conducting Poly(3,4-ethylenedioxythiophene) Films by High-Energy - Ion Irradiation: Applications as Field Emitters and Capacitor Electrodes,

    J. Joo
    Abstract Nanoislands have been fabricated on the surface of conducting poly(3,4-ethylenedioxythiophene) (PEDOT) films doped with poly(4-styrenesulfonate) (PSS) using high-energy (,,1,3,MeV) Cl2+ ion irradiation. Scanning electron microscopy and atomic force microscopy confirm the direct formation of nanoislands with diameters ranging from 50,to 300,nm and heights ranging from 40,to 120,nm. From our analysis, we propose that the formation of nanoislands might be due to micelle formation of the polymeric stabilizer poly(sodium 4-styrenesulfonate) (PSS-Na) surrounding the nuclei in the PEDOT/PSS via the high-energy-ion irradiation. We observe similar results for high-energy-ion irradiated polyaniline doped with PSS-Na. On using the nanoislands as nanotip emitters of a field-emission display, an increase in the current density of about five orders of magnitude is observed. Cyclic voltammetry of the PEDOT/PSS electrode with the nanoislands as the electrode shows enhanced capacitance compared with that of the PEDOT/PSS film that contains no nanostructure. [source]

    2-(2,4-Dinitrobenzyl)pyridine (DNBP): A Potential Light-Activated Proton Shuttle

    Catrin Goeschen
    Abstract The well-known photochromic tautomerism of 2-(2,4-dinitrobenzyl)pyridine (1; CH; Scheme,1) was re-investigated by flash photolysis in aqueous solution in view of its potential application as a light-activated proton pump. Irradiation of 1 yields the enamine tautomer NH (,max=520,nm) that rapidly equilibrates with its conjugate base CNO, (,max=420,nm). The pH,rate profile for the first-order decay of NH and CNO, provides a direct determination of the acidity constant of NH, pK=5.94±0.12 (I=0.1M) and serves to clarify the mechanisms of proton transfer prevailing in aqueous solutions. The acidity constant of protonated 1 (CHNH+), pK=4.18±0.02, was determined by spectrophotometric titration. [source]

    Formal Synthesis of Olivacine via Indolylborate

    Minoru Ishikura
    Abstract Palladium-catalyzed tandem cyclization,cross-coupling reaction of indolylborate 2 and vinyl bromide 5 was successfully applied in a short formal synthesis of olivacine. The reaction of 2 with 5 in the presence of Pd(OAc)2 readily afforded three kinds of products, triene derivative 6 and vinylindole derivative 7, along with a small amount of the piperidine derivative 8 (Scheme,2). On the other hand, the reactions of 2 with bromide 10 or 15 were also examined (Schemes,4 and 5), and their outcome markedly depended on the relative ease of ring closure as a function of ring size. Irradiation of 6 with a high-pressure mercury lamp (,9; Scheme,2), followed by removal of the N -[(benzyloxy)carbonyl] group and subsequent oxidation afforded, after deprotection, pyridocarbazole 23, and the conversion of 23 to olivacine is known (Scheme,6). [source]

    Photogeneration of High Pretilt Angles of Nematic Liquid Crystals by Non-Polarized Light Irradiation of Azobenzene-Containing Polymer Films,

    S. Furumi
    Abstract A vertical-alignment (VA) cell of nematic liquid crystals (LCs) was prepared using photoirradiated thin films of a poly(methacrylate) with mesogenic moieties of 4-trifluoromethoxyazobenzene as the side chains. Optical anisotropy was generated by oblique irradiation of the azobenzene-containing polymer films with non-polarized UV light, followed by annealing treatment to enhance the photodichroism, which displayed thermal stability. The combination of oblique exposure to non-polarized UV light and subsequent annealing treatment brought about high pretilt angles of nematic LCs so that a photoaligned VA LC cell was fabricated. The photopatterned LC cell exhibited electro-optical properties with excellent optical quality when a voltage was applied even after heating at 100,°C for several hours. [source]

    Symmetric Wrinkling Patterns: Diffusion-Controlled, Self-Organized Growth of Symmetric Wrinkling Patterns (Adv. Mater.

    ADVANCED MATERIALS, Issue 13 2009
    Irradiation of thin polystyrene films leads to the formation of a stiff skin layer, which can dynamically wrinkle under osmotic swelling of a small molecule penetrant from localized defects in the film. As shown by Christopher Stafford and co-workers on p. 1358, these wrinkled surfaces display a rich diversity of pattern symmetries that are not readily accessible by any other route. [source]

    Dominant-negative Rac increases both inherent and ionizing radiation-induced cell migration in C6 rat glioma cells

    So-Young Hwang
    Abstract Rho-like GTPases, including Cdc42, Rac1 and RhoA, regulate distinct actin cytoskeleton changes required for cell adhesion, migration and invasion. In the present study, we examined the role of Rac signaling in inherent migration, as well as radiation-induced migration, of rat glioma cells. Stable overexpression of dominant-negative Rac1N17 in a C6 rat glioma cell line (C6-RacN17) promoted cell migration, and ionizing radiation further increased this migration. Migration was accompanied by decreased expression of the focal adhesion molecules FAK and paxillin. Focal contacts and actin stress fibers were also reduced in C6-RacN17 cells. Downstream effectors of Rac include JNK and p38 MAP kinases. Irradiation transiently activated p38, JNK and ERK1/2 MAP kinases in C6-RacN17 cells, while p38 and JNK were constitutively activated in C6 control cells. Blocking JNK activity with JNK inhibitor SP600125 inhibited migration, suggesting that the JNK pathway may regulate radiation-induced, as well as inherent, migration of C6-RacN17 cells. Additionally, the radiation-induced migration increase was also inhibited by SB203580, a specific inhibitor of p38 MAP kinase. However, PD98059, a MEK kinase 1 inhibitor, failed to influence migration. This is the first evidence that suppression of Rac signaling may be involved in invasion or metastasis of glioma cells before and/or after radiotherapy. These data further suggest that radiotherapy for malignant glioma needs to be used with caution because of the potential for therapy-induced cell migration or invasion and that pharmacological inhibition of cell migration and invasion through targeting the Rac signaling pathway may represent a new approach for improving the therapeutic efficacy of radiotherapy for malignant glioma. © 2005 Wiley-Liss, Inc. [source]