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Showing papers on "Ultraviolet light published in 1993"


PatentDOI
01 Mar 1993
TL;DR: In this paper, the authors described a crosslinked macromer consisting of hydrophilic oligomers having biodegradable monomeric or oligomeric extensions, which are terminated on free ends with end cap monomers or oligomers capable of polymerization and cross linking.
Abstract: Hydrogels of polymerized and crosslinked macromers comprising hydrophilic oligomers having biodegradable monomeric or oligomeric extensions, which biodegradable extensions are terminated on free ends with end cap monomers or oligomers capable of polymerization and cross linking are described. The hydrophilic core itself may be degradable, thus combining the core and extension functions. Macromers are polymerized using free radical initiators under the influence of long wavelength ultraviolet light, visible light excitation or thermal energy. Biodegradation occurs at the linkages within the extension oligomers and results in fragments which are non-toxic and easily removed from the body. Preferred applications for the hydrogels include prevention of adhesion formation after surgical procedures, controlled release of drugs and other bioactive species, temporary protection or separation of tissue surfaces, adhering of sealing tissues together, and preventing the attachment of cells to tissue surfaces.

979 citations


Journal ArticleDOI
10 Sep 1993-Science
TL;DR: Enucleated cells are fully responsive to UV both in NF-kappa B induction and in activation of another key signaling event, suggesting that the UV response does not require a signal generated in the nucleus and is likely to be initiated at or near the plasma membrane.
Abstract: Exposure of mammalian cells to radiation triggers the ultraviolet (UV) response, which includes activation of activator protein-1 (AP-1) and nuclear factor kappa B (NF-kappa B). This was postulated to occur by induction of a nuclear signaling cascade by damaged DNA. Recently, induction of AP-1 by UV was shown to be mediated by a pathway involving Src tyrosine kinases and the Ha-Ras small guanosine triphosphate-binding protein, proteins located at the plasma membrane. It is demonstrated here that the same pathway mediates induction of NF-kappa B by UV. Because inactive NF-kappa B is stored in the cytosol, analysis of its activation directly tests the involvement of a nuclear-initiated signaling cascade. Enucleated cells are fully responsive to UV both in NF-kappa B induction and in activation of another key signaling event. Therefore, the UV response does not require a signal generated in the nucleus and is likely to be initiated at or near the plasma membrane.

635 citations


Journal ArticleDOI
TL;DR: In this paper, the authors present an overview of recent studies carried out both independently and jointly in the authors' laboratories focusing upon the remarkably rich, but relatively unexplored, photochemical and photophysical properties of various tetra-and hexanuclear d[sup 10] and s[sup 2] metal ion clusters in solution.
Abstract: Relatively little attention has been paid to metal ions with the nd[sup 10] and nd[sup 10](n+1)s[sup 2] (i.e., [open quotes]s[sup 2][close quotes]) configurations. In combination with various anionic and neutral ligands, these metal ions form a wide variety of cluster compounds, some of which have been known to be luminescent when irradiated with ultraviolet light. Prominent examples of this family are cuprous iodide clusters such as Cu[sub 4]I[sub 4]-(py)[sub 4] (1, py = pyridine), which shows [open quotes]luminescence thermochromism[close quotes]; that is, they display bright emissions with colors markedly dependent on the temperature. Here the authors present an overview of recent studies carried out both independently and jointly in the authors' laboratories focusing upon the remarkably rich, but relatively unexplored, photochemical and photophysical properties of various tetra-and hexanuclear d[sup 10] and s[sup 2] metal ion clusters in solution. 74 refs., 4 figs., 2 tabs.

493 citations


Journal ArticleDOI
TL;DR: The formation of collagen I is significantly decreased in photodamaged human skin, and this process is partly restored by treatment with tretinoin.
Abstract: Background Topical tretinoin (retinoic acid) modifies fine wrinkles and certain other features of human skin damaged by exposure to the sun (photodamage), but histologic changes do not account for this improvement. In mice with photodamage induced by ultraviolet light, effacement of fine wrinkles by tretinoin is correlated with dermal collagen synthesis but not with histologic changes. We investigated whether collagen synthesis was reduced in photodamaged human skin and, if so, whether it could be restored by treatment with topical tretinoin. Methods Biopsies of photodamaged skin from the extensor aspect of the forearm and skin from the buttocks, which had been protected from the sun, were performed on 26 healthy subjects. In addition, 29 patients with photodamaged skin were treated for 10 to 12 months with a daily application of 0.1 percent tretinoin cream (15 patients) or vehicle cream (14 patients). Skin-biopsy specimens obtained at base line and after treatment were assessed immunohistologically for e...

442 citations


Journal ArticleDOI
TL;DR: Human epithelial cell lines were examined for p53 mutations in exons 4-9 which include the evolutionarily conserved regions and wild type p53 was found in human bronchial, esophageal and hepatic epithelial cells immortalized by SV40 T antigen gene and human renal epithelial Cells immortalization by adenovirus 5.
Abstract: Although rodent cells have been immortalized following transfection with a mutant p53 gene, the role of p53 in the immortalization of human cells is unknown. Therefore, human epithelial cell lines were examined for p53 mutations in exons 4-9 which include the evolutionarily conserved regions. A spontaneously immortalized skin keratinocyte cell line, HaCat, and three ras-transfected clones, have a p53 mutational spectrum that is typical of ultraviolet light induced mutations. A normal finite lifespan cell strain (184) and two benzo[a]pyrene immortalized mammary epithelial cell lines derived from 184 (184A1 and 184B5) contain wild type p53 sequences in exons 4-9, although elevated levels of nuclear p53 indicate an alteration in the stability of the normally transient protein. Wild type p53 was found in human bronchial, esophageal and hepatic epithelial cells immortalized by SV40 T antigen gene and human renal epithelial cells immortalized by adenovirus 5. BEAS-2B, an SV40 T antigen immortalized bronchial epithelial cell line and two subclones, have a germline polymorphism at codon 47. Inactivation of p53 by mechanisms such as mutation or complexing with proteins of DNA tumor viruses appears to be important in the immortalization of human epithelial cells.

436 citations


Journal ArticleDOI
TL;DR: Because the reduction in total ascorbate and catalase was much more severe in epidermis than dermis, it can be concluded that UV light is more damaging to the antioxidant defenses in the epidermi than in the dermis.

348 citations


Journal ArticleDOI
TL;DR: The application status and potential of three chemical oxidation treatment methods which generate powerful oxidants (hydroxyl radicals): ultraviolet light (UV)/hydrogen peroxide (H2O2) process, Fenton's reagent treatment, and titanium dioxide (TiO2)-assisted photocatalytic degradation, are described and discussed in this paper.
Abstract: The application status and potential of three chemical oxidation treatment methods which generate powerful oxidants (hydroxyl radicals): ultraviolet light (UV)/hydrogen peroxide (H2O2) process, Fenton's reagent treatment, and titanium dioxide (TiO2)-assisted photocatalytic degradation, are described and discussed. These oxidation methods are known to effectively degrade and, in several cases, mineralize contaminants ranging from inorganic compounds (such as cyanides) to chlorinated aliphatic compounds and complex aromatic compounds in reaction times on the order of a few minutes to a few hours. Of the three oxidation systems discussed, the technology for the UV/H2O2 process is the most advanced, with numerous successful full-scale treatment units already in existence. Applications of both the Fenton's reagent and TiO2-assisted photodegradation processes are currently being developed, with the concepts proven in numerous laboratory-scale studies for a wide range of contaminants. However, both of t...

321 citations


Journal ArticleDOI
TL;DR: In this article, the authors used strand specific probes to study the effect of the hereditary disease Cockayne's syndrome (CS) on the repair of lesions in active genes in normal cells.
Abstract: Removal of ultraviolet light induced cyclobutane pyrimidine dimers (CPD) from active and inactive genes was analyzed in cells derived from patients suffering from the hereditary disease Cockayne's syndrome (CS) using strand specific probes. The results indicate that the defect in CS cells affects two levels of repair of lesions in active genes. Firstly, CS cells are deficient in selective repair of the transcribed strand of active genes. In these cells the rate and efficiency of repair of CPD are equal for the transcribed and the nontranscribed strand of the active ADA and DHFR genes. In normal cells on the other hand, the transcribed strand of these genes is repaired faster than the nontranscribed strand. However, the nontranscribed strand is still repaired more efficiently than the inactive 754 gene and the gene coding for coagulation factor IX. Secondly, the repair level of active genes in CS cells exceeds that of inactive loci but is slower than the nontranscribed strand of active genes in normal cells. Our results support the model that CS cells lack a factor which is involved in targeting repair enzymes specifically towards DNA damage located in (potentially) active DNA.

295 citations


Journal ArticleDOI
28 Jan 1993-Nature
TL;DR: It is reported here that an enzyme that catalyses the light-dependent repair of (6–4)photoproduct exists in Drosophila melanogaster, the first report of such photoreactivating activity specific for (6-4) photographers in any organism.
Abstract: Cyclobutane pyrimidine dimers (CPDs) and pyrimidine (6-4) pyrimidone photoproducts ((6-4)photoproducts) are the two major classes of cytotoxic, mutagenic and carcinogenic DNA photoproducts produced by ultraviolet light irradiation of cells. The phenomenon of photoreactivation, the reduction of the lethal and mutagenic effects of ultraviolet radiation by simultaneous or subsequent irradiation with near ultraviolet or visible light, has been identified in several organisms and in some cases the enzymes that catalyse this process have been characterized in sufficient detail. CPDs are the only known substrate for the photoreactivating enzymes so far analysed and enzymatic photoreactivation of (6-4)photoproducts has not yet been reported. We report here that an enzyme that catalyses the light-dependent repair of (6-4)photoproduct exists in Drosophila melanogaster. This is, to our knowledge, the first report of such photoreactivating activity specific for (6-4)photoproducts in any organism.

289 citations


Journal ArticleDOI
TL;DR: Signals elicited from different primary sites merge prior to or at the level of activation of Raf‐1 kinase, indicating obligatory involvement of identical components in cytoplasmic signal transduction.
Abstract: Irradiation of cells with ultraviolet light (UV) leads to modifications of c-Jun resembling those elicited by phorbol esters or oncogenes, and to enhanced transcription of AP-1-dependent genes The UV-induced signal also triggers activation of Raf-1 and MAP-2 kinases A dominant-negative Raf-1 kinase mutant strongly interferes with both phorbol ester and UV-induced AP-1 activation, indicating obligatory involvement of identical components in cytoplasmic signal transduction Thus, from a presumably nuclear site of energy absorption, a signal needs to be transmitted to the cytoplasm in order to achieve activation of a nuclear transcription factor Further, signals elicited from different primary sites merge prior to or at the level of activation of Raf-1 kinase

250 citations


Journal ArticleDOI
TL;DR: Clinical reports indicate that retention is similar for second- and third-generation systems, but longer clinical evaluations are necessary, and the addition of fluoride to sealants is a recent innovation.
Abstract: The first sealant clinical trials used cyanoacrylate-based materials. These were replaced by dimethacrylate-based products which were marketed. A major difference between marketed sealants is their method of polymerization. First-generation sealants were initiated by ultraviolet light, second-generation sealants are autopolymerized, and third-generation sealants use visible light. Over time, clinical retention was found to be greater for second generation as compared with first-generation sealants. Five to 7 years after initial application the pits and fissures of approximately one third of teeth treated with first-generation sealants were fully protected as compared with two thirds of the teeth treated with second-generation sealants. First-generation, ultraviolet light initiated, sealants are no longer marketed. Clinical reports indicate that retention is similar for second- and third-generation systems, but longer clinical evaluations are necessary. A recent innovation is the addition of fluoride to sealants. Fluoride release to the saliva from a fluoride sealant system is rapid, but clinical studies are needed to determine if the fluoride addition improves caries inhibition.

Journal ArticleDOI
13 May 1993-Nature
TL;DR: In this paper, frog and human complementary DNAs that encode proteins resembling RAD2, a protein involved in this pathway in yeast, were identified and aligned with two other RAD2 related proteins, revealing that their conserved sequences are largely confined to two regions.
Abstract: Defects in human DNA repair proteins can give rise to the autosomal recessive disorders xeroderma pigmentosum (XP) and Cockayne's syndrome (CS), sometimes even together. Seven XP and three CS complementation groups have been identified that are thought to be due to mutations in genes from the nucleotide excision repair pathway. Here we isolate frog and human complementary DNAs that encode proteins resembling RAD2, a protein involved in this pathway in yeast. Alignment of these three polypeptides, together with two other RAD2 related proteins, reveals that their conserved sequences are largely confined to two regions. Expression of the human cDNA in vivo restores to normal the sensitivity to ultraviolet light and unscheduled DNA synthesis of lymphoblastoid cells from XP group G, but not CS group A. The XP-G correcting protein XPGC is generated from a messenger RNA of approximately 4 kilobases that is present in normal amounts in the XP-G cell line.

Journal ArticleDOI
TL;DR: The overproduction and purification of RecG is described and the overlap extends to the biochemistry and it is suggested that RecG and RuvAB provide alternative activities than can promote branch migration of Holliday junctions in recombination and DNA repair.
Abstract: The RecG protein of Escherichia coli is needed for normal levels of recombination and for repair of DNA damaged by ultraviolet light, mitomycin C and ionizing radiation The true extent of its involvement in these processes is masked to a large degree by what appears to be a functional overlap with the products of the three ruv genes RuvA and RuvB act together to promote branch migration of Holliday junctions, while RuvC catalyses the resolution of these recombination intermediates into viable products by endonuclease cleavage In this paper, we describe the overproduction and purification of RecG and demonstrate that the overlap extends to the biochemistry We show that the 76 kDa RecG protein is a DNA-dependent ATPase, like RuvB Using gel retardation assays we demonstrate that it binds specifically to a synthetic Holliday junction, like RuvA and RuvC Finally, we show that in the presence of ATP and Mg2+, RecG dissociates these junctions to duplex products, like RuvAB We suggest that RecG and RuvAB provide alternative activities than can promote branch migration of Holliday junctions in recombination and DNA repair


Journal ArticleDOI
S. Karrasch1, M. Dolder1, F. Schabert1, Jeremy J. Ramsden1, Andreas Engel1 
TL;DR: A method to achieve the covalent binding of biological samples to glass surfaces by squeezing between derivatized coverslips and then cross-linked to the glass surface by irradiation with ultraviolet light is described.

Journal ArticleDOI
04 Jun 1993-Science
TL;DR: In situ hybridization analyses reveal that mitochondrial large ribosomal RNA is enriched in germ plasm and is tightly associated with polar granules, the distinctive organelles of germ Plasm, which supports the idea that mtlrRNA functions in pole cell formation.
Abstract: Mitochondrial large ribosomal RNA (mtlrRNA) has been identified as a cytoplasmic factor that induces pole cell formation in embryos whose ability to form a germ line has been abolished by treatment with ultraviolet light. In situ hybridization analyses reveal that mtlrRNA is enriched in germ plasm and is tightly associated with polar granules, the distinctive organelles of germ plasm, which supports the idea that mtlrRNA functions in pole cell formation. This suggests that a product from the mitochondrial genome, along with nuclear products, participates in a key event in embryonic development: determination of the germ line.

Patent
25 May 1993
TL;DR: In a photo-CVD system, ultraviolet light is introduced into a reaction chamber from light emitting elements of ultraviolet light sources, through transparent bulb surfaces thereof, and through elongated light pipes in a sealed wall bounding the reaction chamber as discussed by the authors.
Abstract: In a photo-CVD system, ultraviolet light is introduced into a reaction chamber from light emitting elements of ultraviolet light sources, through transparent bulb surfaces thereof, and through elongated light pipes in a sealed wall bounding the reaction chamber. This prevents molecules of reactant gas in the reaction chamber from reaching and being deposited on the transparent bulb surfaces, and thereby prevents buildup of such reactant molecules from occurring and impeding flow of ultraviolet light into the reaction chamber.

Journal ArticleDOI
TL;DR: UV-C treated tomatoes were firmer in texture and less red in color than the control tomatoes, indicating a delay in ripening, and resistance to storage rots of tomatoes are probably related.

Journal ArticleDOI
TL;DR: It is suggested that epiboly is driven, at least partially, by motors that use microtubules radiating from the yolk syncytial layer into the yull cytoplasmic layer, and a two-force model of epibolic is proposed.
Abstract: Early morphogenesis of the teleost embryo is characterized by three orchestrated cell movements. Epiboly leads to spreading of the blastoderm over an uncleaved yolk cell while involution around the blastoderm margin and convergence movements towards the dorsal side generate the mes-endodermal inner cell sheet and the axis rudiment, respectively. Irradiation of zebrafish zygotes with ultraviolet light selectively impairs epiboly resulting in embryos with open blastopores but well-formed anterior axes. Gastrulation movements are only marginally affected by ultraviolet irradiation. Involution of marginal cells in epiboly-retarded embryos takes place prior to 50% epiboly and thus appears independent of epiboly. Expression of dorsal and anterior marker genes is unaffected by ultraviolet irradiation. The ultraviolet light effect is not restricted to the zygote stage as irradiation of later embryonic stages also impairs epiboly. The ultraviolet-sensitive targets may thus be maternally encoded components of the machinery driving epiboly. These targets appear to be microtubules: firstly, irradiated embryos show disorganized and less microtubules in the cytoplasmic layer of the yolk sphere; secondly, the ultraviolet light effect can be mimicked by the microtubule-depolymerizing agent nocodazole. We suggest that epiboly is driven, at least partially, by motors that use microtubules radiating from the yolk syncytial layer into the yolk cytoplasmic layer. Together with an observed constrictive behaviour of the blastoderm margin, we propose a two-force model of epiboly: epiboly is initiated and driven by a pulling force dependent on microtubules in the yolk cytoplasmic layer; contraction at the margin operates in addition to aid closure of the blastopore.

Patent
24 Sep 1993
TL;DR: An all-polymeric cold mirror which reflects visible wavelengths while transmitting a substantial portion of infrared wavelengths is provided in this paper, which includes a sufficient number of alternating layers of at least first and second diverse polymeric materials such that at least 50% of peak reflecting visible light of a wavelength of between about 380-680 nm incident on the mirror is reflected and at least half of infrared light between about 680-2000 nm is transmitted or absorbed.
Abstract: An all-polymeric cold mirror which reflects visible wavelengths while transmitting a substantial portion of infrared wavelengths is provided. The mirror includes a sufficient number of alternating layers of at least first and second diverse polymeric materials such that at least 50% of peak reflecting visible light of a wavelength of between about 380-680 nm incident on the mirror is reflected and at least 50% of infrared light between about 680-2000 nm is transmitted or absorbed. The mirror may be designed so that it either reflects or absorbs ultraviolet light.

Patent
03 May 1993
TL;DR: In this article, an erasable-programmable-read-only-memory (EPROM) package is provided, where the EPROM chip is mounted on the circuit carrying substrate, and the pad electrodes on the chip are connected to pads on the conductive patterns of the substrate by wire bonds or other means.
Abstract: A shielded, erasable-programmable-read-only-memory (EPROM) package is provided. A circuit carrying substrate (10), contains an area for mounting an EPROM chip (16), having conductive interconnecting patterns (12) adjacent to the chip mounting area. The EPROM chip is mounted on the circuit carrying substrate, and the pad electrodes on the EPROM chip are connected to pads on the conductive patterns of the substrate by wire bonds (17) or other means. An ultraviolet (UV) light transmitting resin (18) is transfer molded onto the circuit carrying substrate, covering the EPROM chip (16) and the wire bonds (17) so as to provide an optical path through the material to the top surface of the EPROM chip, and sealing the EPROM chip from the exterior of the package. An adherent metal coating (19) is sputtered over the transfer molded resin, and the metal coating is coated with a protective organic resin (15). Both the metal coating and the organic resin are at least partially transparent to ultraviolet light.

Journal ArticleDOI
TL;DR: The results of an anatomic investigation performed in 40 fresh cadaver specimens and 80 consecutive clinical cases of the posterior interosseous reverse forearm flap are reported, and it is observed that there is a choke anastomosis between the recurrent dorsal branch of the anterior interOSseous artery and the posteriorInterosseus artery at the level of the middle third ofThe posterior forearm.
Abstract: The results of an anatomic investigation performed in 40 fresh cadaver specimens and 80 consecutive clinical cases of the posterior interosseous reverse forearm flap are reported. It was observed that there is a choke anastomosis between the recurrent dorsal branch of the anterior interosseous artery and the posterior interosseous artery at the level of the middle third of the posterior forearm. Ink injections through a catheter placed in the distal part of the anterior interosseous artery stained the distal and middle thirds of the posterior forearm, but the proximal third remained unstained; this secondary territory cannot be captured through the choke anastomosis between the anterior interosseous artery and the posterior interosseous artery. Intravital fluorescein injection into the distal arterior interosseous artery revealed (under ultraviolet light) that the distal third of the posterior forearm is irrigated by direct flow through the recurrent branch of the arterior interosseous artery (the traditionally called distal anastomosis of the interosseous arteries). Therefore, we can assume that the blood flow is not reversed when the so-called posterior interosseous reverse forearm flap is raised. From this point of view, this flap could be renamed as the recurrent dorsal anterior interosseous direct flap; however, the classical name is maintained for practical purposes. From the venous standpoint, the cutaneous area included in this flap belongs to an oscillating type of venous territory and is connected to the deep system through an interconnecting venous perforator that accompanies a medial cutaneous arterial branch located at 1 to 2 cm distal to the middle point of the forearm.(ABSTRACT TRUNCATED AT 250 WORDS)

Journal Article
TL;DR: It is demonstrated that macrophage-derived NO synthesis can contribute to the antitumor immune response in vivo.
Abstract: The role of macrophages in the host immune response against cancers remains uncertain. Since nitric oxide synthesis represents a significant macrophage antitumor mechanism in vitro , we evaluated whether NO was synthesized during the immune response to growing murine skin cancers. NO synthesis was readily detectable in enzymatically dissociated tumors (RD-995 and LR-298) and was inhibited by N ω -monomethyl-l-arginine (MLA) and by macrophage depletion. Nitrosylation of iron-sulfur and heme complexes was observed in these tumors using electron paramagnetic resonance spectroscopy. NO production in the presence of increasing concentrations of MLA correlated inversely with tumor cell proliferation in vitro . To elucidate the role of NO during in vivo tumor progression, tumor-bearing mice were treated with continuous infusions of the nitric oxide synthase inhibitor MLA. MLA-treated mice demonstrated increased growth and delayed rejection of the highly antigenic UV radiation-induced regressor tumor LR-298. These experiments demonstrate that macrophage-derived NO synthesis can contribute to the antitumor immune response in vivo .

Journal ArticleDOI
13 May 1993-Nature
TL;DR: It is reported that the DNA repair deficiency of XP-G cell extracts can be corrected by addition of protein fractions from normal cells, and activity can be restored with an XP- G/group 5 complementing fraction.
Abstract: HUMANS with the complementation group G form of the inherited syndrome xeroderma pigmentosum (XP) are hypersensitive to solar ultraviolet light because of a defect in nucleotide-excision repair of DNA1–4. Some individuals are also affected with Cockayne's syndrome, and have neurological abnormalities. Here we report that the DNA repair deficiency of XP-G cell extracts can be corrected by addition of protein fractions from normal cells. Repair proficiency can also be restored by mixing XP-G cell extracts with extracts from different repair-defective cell lines, with one excep-tion. Extracts from cells representing group 5 of a set of ultraviolet-sensitive rodent mutants fail to complement XP-G extracts. XP-G and group 5 correcting activities co-elute after ∼1,000-fold purification from HeLa cells. An antibody directed against a recombinant fragment of the XP-G complementing protein (XPGC) inhibits excision repair by normal cell extracts, and activity can be restored with an XP-G/group 5 complementing fraction. These data strongly suggest that the XPGC and group 5 correcting (ERCC5) proteins are identical.

Journal ArticleDOI
TL;DR: It is demonstrated that photolyase expression in plants is light induced, thus providing good evidence for the adaptation of plants to their environment in order to diminish the harmful effects of sunlight.
Abstract: Photolyases are thought to be critical components of the defense of plants against damage to DNA by solar ultraviolet light, but nothing is known about their molecular or enzymatic nature. The molecular cloning of a photolyase from mustard (Sinapis alba) described here is intended to increase the knowledge about this important repair mechanism in plant species at a molecular level. The gene encodes a polypeptide of 501 amino acids with a predicted molecular mass of 57 kDa. There is a strong sequence similarity to bacterial and yeast photolyases, with a close relationship to enzymes with a deazaflavin chromophor. The plant photolyase is shown to be functional in Escherichia coli which also indicates conservation of photolyases during evolution. It is demonstrated that photolyase expression in plants is light induced, thus providing good evidence for the adaptation of plants to their environment in order to diminish the harmful effects of sunlight.

Journal ArticleDOI
TL;DR: In this article, the photochromic effect of thin amorphous WO3 films, i.e., the coloration upon exposing the sample to ultraviolet light, has been investigated by means of optically excited surface plasmons.
Abstract: The photochromic effect of thin amorphous WO3 films, i.e., the coloration upon exposing the sample to ultraviolet light, has been investigated by means of optically excited surface plasmons. Due to the high sensitivity of this technique, it was possible to investigate the dynamics of this effect on a scale as short as seconds. Our results demonstrate the dominant role of oxygen during the coloration and bleaching processes. We found clear evidence of an oxygen exchange between the sample and the ambient atmosphere during the photochromic process, which is at variance with the widely accepted double charge injection model. The coloration rate shows the same wavelength dependence as that of the creation rate of electron‐hole pairs formed by optical excitation. The results can be explained by the light‐induced decomposition of the incorporated water.

Patent
29 Mar 1993
TL;DR: In this paper, a sprayable coating composition is formulated using one or more acrylates and photoinitiators which act to polymerize the composition when exposed to ultraviolet light.
Abstract: A sprayable coating composition is formulated using one or more acrylates and one or more photoinitiators which act to polymerize the composition when exposed to ultraviolet light. Because of the use of low molecular weight monomers or oligomers, the composition is essentially free of volatile organic solvents and therefore evaporative emissions in curing are substantially eliminated.

Journal ArticleDOI
TL;DR: In this article, the formation of the porous layer was dependent on the wavelength of the incident light, and the simultaneous irradiation of an ultraviolet light did not form the porous layers.
Abstract: Photosynthesis of porous silicon is reported for the first time with visible‐light irradiation in a hydrofluoric acid solution, which does not need any electrodes for anodization. The photosynthesized porous layer consisted of microparticles, and the photoluminescence spectra were very close to those of anodized porous silicons. The formation of the porous layer was dependent on the wavelength of the incident light, and the simultaneous irradiation of an ultraviolet light did not form the porous layer. The mechanism is discussed with the quantum confinement model of the porous layer.

Journal ArticleDOI
TL;DR: Structural data are presented which demonstrate tissue-specific, quantitative differences in the high order complexes containing apoB mRNA editing activity and RNA-binding proteins and suggest that differences in both the pre-editosomal assembly state of editing factors and their abundance may be mechanistically important for tissue- specific differences in editing efficiency.

Patent
02 Jun 1993
TL;DR: In this paper, a photoacid is formed upon irradiation of a nitro-substituted aromatic aldehyde with ultraviolet light and wherein proton transfer to a dye causes the dye to undergo a visible color change.
Abstract: Photochemical systems for the direct visualization of exposure to ultraviolet radiation that effect visible color changes involving a process in which a photoacid is formed upon irradiation of a nitro-substituted aromatic aldehyde with ultraviolet light and wherein proton transfer to a dye causes the dye to undergo a visible color change. The system undergoes such color change to an extent directly proportional to the cumulative amount of ultraviolet incident thereupon.