Showing papers on "Ultraviolet light published in 2014"
TL;DR: In this article, the first organolead halide perovskite based broadband photodetector is demonstrated, with CH3NH3PbI3 film deposited on flexible ITO coated substrate.
Abstract: Organolead halide perovskites have attracted extensive attentions as light harvesting materials for solar cells recently, because of its high charge-carrier mobilities, high photoconversion efficiencies, low energy cost, ease of deposition, and so on. Herein, with CH3NH3PbI3 film deposited on flexible ITO coated substrate, the first organolead halide perovskite based broadband photodetector is demonstrated. The organolead halide perovskite photodetector is sensitive to a broadband wavelength from the ultraviolet light to entire visible light, showing a photo-responsivity of 3.49 A W−1, 0.0367 A W−1, an external quantum efficiency of 1.19×103%, 5.84% at 365 nm and 780 nm with a voltage bias of 3 V, respectively. Additionally, the as-fabricated photodetector exhibit excellent flexibility and robustness with no obvious variation of photocurrent after bending for several times. The organolead halide perovskite photodetector with high sensitivity, high speed and broad spectrum photoresponse is promising for further practical applications. And this platform creates new opportunities for the development of low-cost, solution-processed and high-efficiency photodetectors.
756 citations
TL;DR: The identification of a TiO2 anatase surface phase with a bandgap in the visible and high chemical reactivity has important implications for solar energy conversion, photocatalysis, and artificial photosynthesis.
Abstract: TiO2 anatase plays a central role in energy and environmental research. A major bottleneck toward developing artificial photosynthesis with TiO2 is that it only absorbs ultraviolet light, owing to its large bandgap of 3.2 eV. If one could reduce the bandgap of anatase to the visible region, TiO2-based photocatalysis could become a competitive clean energy source. Here, using scanning tunneling microscopy and spectroscopy in conjunction with density functional theory calculations, we report the discovery of a highly reactive titanium-terminated anatase surface with a reduced bandgap of less than 2 eV, stretching into the red portion of the solar spectrum. By tuning the surface preparation conditions, we can reversibly switch between the standard anatase surface and the newly discovered low bandgap surface phase. The identification of a TiO2 anatase surface phase with a bandgap in the visible and high chemical reactivity has important implications for solar energy conversion, photocatalysis, and artificial photosynthesis.
503 citations
TL;DR: Comparing typical doses for practical applications ozonation proved to be more efficient for abatement of sulfamethoxazole, while removal of benzotriazole and iomeprol was comparatively more efficient with activated carbon and DOC-normalized doses were also applied to PAC and correlated better to relative OMP removal than volume proportional PAC addition.
285 citations
TL;DR: In this article, a series of CaTiO3 phosphors doped with trivalent europium (Eu3+) and codoped with potassium (K+) ions were prepared by the solid state reaction method and X-ray diffraction results revealed that the obtained powder phosphors consisted out of a single-phase orthorhombic structure and it also indicated that the incorporation of the dopants/co-dopants did not affect the crystal structure.
Abstract: This paper reports on the defect correlated self-quenching and spectroscopic investigation of calcium titanate (CaTiO3) phosphors. A series of CaTiO3 phosphors doped with trivalent europium (Eu3+) and codoped with potassium (K+) ions were prepared by the solid state reaction method. The X-ray diffraction results revealed that the obtained powder phosphors consisted out of a single-phase orthorhombic structure and it also indicated that the incorporation of the dopants/co-dopants did not affect the crystal structure. The scanning electron microscopy images revealed the irregular morphology of the prepared phosphors consisting out of μm sized diameter particles. The Eu3+ doped phosphors illuminated with ultraviolet light showed the characteristic red luminescence corresponding to the 5D0→7FJ transitions of Eu3+. As a charge compensator, K+ ions were incorporated into the CaTiO3:Eu3+ phosphors, which enhanced the photoluminescence (PL) intensities depending on the doping concentration of K+. The concentration quenching of Eu3+ in this host is discussed in the light of ion-ion interaction, electron phonon coupling, and defect to ion energy transfer. The spectral characteristics and the Eu-O ligand behaviour were determined using the Judd-Ofelt theory from the PL spectra instead of the absorption spectra. The CIE (International Commission on Illumination) parameters were calculated using spectral energy distribution functions and McCamy's empirical formula. Photometric characterization indicated the suitability of K+ compensated the CaTiO3:Eu3+ phosphor for pure red emission in light-emitting diode applications.
236 citations
Patent•
20 Feb 2014TL;DR: In this article, a method of fabricating a light emitting diode, which includes an n-type contact layer and a light generating structure adjacent to the n type contact layer, is provided.
Abstract: A method of fabricating a light emitting diode, which includes an n-type contact layer and a light generating structure adjacent to the n-type contact layer, is provided. The light generating structure includes a set of quantum wells. The contact layer and light generating structure can be configured so that a difference between an energy of the n-type contact layer and an electron ground state energy of a quantum well is greater than an energy of a polar optical phonon in a material of the light generating structure. Additionally, the light generating structure can be configured so that its width is comparable to a mean free path for emission of a polar optical phonon by an electron injected into the light generating structure.
236 citations
TL;DR: It is proposed that this novel SETD2-dependent role provides a chromatin bookmarking instrument that facilitates signaling and repair of DSBs and may afford an alternative mechanism for the inactivation of the p53-mediated checkpoint without the need for additional genetic mutations in TP53.
Abstract: Normal wear and tear, exposure to chemicals, and ultraviolet light can all damage DNA, so cells rely on a range of sensors and mechanisms to detect and repair damaged DNA. Cells also package DNA molecules inside structures called histones to protect them against damage. Double-strand breaks—one of the most serious forms of DNA damage—are detected by an enzyme called ATM, and can be repaired in two ways. Bringing the broken strands back together is an obvious method, but it is also error prone. Using templates to generate new DNA to repair the damage is less prone to error, but it can only happen at certain times of the cell cycle. Some cancers are linked to the faulty repair of double-strand breaks. Moreover, a type of kidney cancer called clear cell renal carcinoma is linked to a lack of activity by a protein called p53, even in individuals who don't have mutations in the gene for this protein. However, many people with this type of cancer have mutations in the gene for a protein called SETD2. To investigate the links between SETD2 and DNA repair, Carvalho et al. compared cells with and without mutations in the gene for SETD2. It emerged that SETD2 must be present for DNA repair to take place: the SETD2 modifies the histones so that they can recruit the enzymes that repair the DNA via the template approach (which is relatively error free). SETD2 may be particularly important for repairing damage to genes without introducing errors. Carvalho et al. also show that mutations in SETD2 are sufficient to inactivate p53. The gene for this protein, which impedes the proliferation of cells with genomic aberrations, such as double-strand breaks, is mutated in most cancers. Overall the results help to illustrate how histone modifications and the DNA damage repair mechanisms and checkpoints work in concert to suppress cancer.
215 citations
TL;DR: It was concluded that eyelid malignancies (BCC and SCC), photokeratitis, CDK, pterygium, and cortical cataract are strongly associated with UVR exposure.
Abstract: The objective of this study is to review the association between ultraviolet (UV) light and ocular diseases. The data are sourced from the literature search of Medline up to Nov 2012, and the extracted data from original articles, review papers, and book chapters were reviewed. There is a strong evidence that ultraviolet radiation (UVR) exposure is associated with the formation of eyelid malignancies [basal cell carcinoma (BCC) and squamous cell carcinoma (SCC)], photokeratitis, climatic droplet keratopathy (CDK), pterygium, and cortical cataract. However, the evidence of the association between UV exposure and development of pinguecula, nuclear and posterior subcapsular cataract, ocular surface squamous neoplasia (OSSN), and ocular melanoma remained limited. There is insufficient evidence to determine whether age-related macular degeneration (AMD) is related to UV exposure. It is now suggested that AMD is probably related to visible radiation especially blue light, rather than UV exposure. From the results, it was concluded that eyelid malignancies (BCC and SCC), photokeratitis, CDK, pterygium, and cortical cataract are strongly associated with UVR exposure. Evidence of the association between UV exposure and development of pinguecula, nuclear and posterior subcapsular cataract, OSSN, and ocular melanoma remained limited. There is insufficient evidence to determine whether AMD is related to UV exposure. Simple behaviural changes, appropriate clothing, wearing hats, and UV blocking spectacles, sunglasses or contact lens are effective measures for UV protection.
213 citations
TL;DR: In this article, a series of uniform ZnO nanospheres and reduced graphene oxide nanocomposites (ZnO-RGO NCs) with different weight addition ratios of RGO are successfully synthesized via a facile yet efficient method.
Abstract: A series of uniform ZnO nanospheres–reduced graphene oxide nanocomposites (ZnO–RGO NCs) with different weight addition ratios of RGO are successfully synthesized via a facile yet efficient method by intimately coating ZnO nanospheres (NSs) with RGO, which is afforded by electrostatic attraction between positively charged ZnO NSs and negatively charged graphene oxide (GO) in an aqueous medium at room temperature. The photocatalytic test of degradation of Rhodamine B shows that the optimal ZnO–10% RGO NCs exhibit a 5-fold enhancement of photoactivity than bare ZnO NSs, which is ascribed to the integrative synergetic effect of enhanced adsorption capacity, the decreased recombination of the electron–hole pairs and the enhanced ultraviolet light absorption intensity. Significantly, the recycled photoactivity tests show that, for ZnO–RGO NCs, the anti-photocorrosion of ZnO NSs is improved remarkably which is attributed to the effective hybridization of ZnO NSs with the RGO sheet via intimate surface coating. Such a significant photoactivity enhancement and anti-photocorrosion phenomenon can not be obtained by simply integrating RGO with ZnO NSs that are not subject to surface charge modification, which thus indicates the importance of intimate surface coating of ZnO with RGO toward the efficiency of enhancement of photoactivity and particularly the anti-photocorrosion of ZnO.
208 citations
TL;DR: It was demonstrated that with an appropriate tuning of the activator content the Y2O2S:Eu(3+)/Dy(3+) phosphors can exhibit a great potential to act as single-emitting component phosphors for white light emission in solid state lighting technology.
Abstract: This paper reports on the structural, optical and photometric characterization of an Eu3+/Dy3+ doped yttrium oxysulfide phosphor (Y2O2S:Eu3+/Dy3+) for near white emission in solid state lighting. A series of Y2O2S phosphors doped with Eu3+/Dy3+ were prepared by the hydrothermal method. The microstructures of the as-synthesized phosphors were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The XRD results reveal that the obtained powder phosphors have a single-phase hexagonal structure and also indicate that the incorporation of the dopants/co-dopants did not affect the crystal structure. The SEM images reveal the morphology of the prepared phosphors as an intense interpenetrating network of interconnected micro-fibers with a diameter of about 0.15 μm. The band gap of the phosphors was calculated from diffuse reflectance spectra using the Kubelka–Munk function. The Eu3+, Dy3+ doped and Eu3+/Dy3+ co-doped phosphors illuminated with ultraviolet light showed characteristic red luminescence corresponding to the 5D0→7FJ transitions of Eu3+ and characteristic blue and yellow luminescence corresponding to the 4F9/2→6H15/2 or 4F9/2→6H13/2 transitions of Dy3+. The luminescence spectra, the energy transfer efficiency and the decay curves of the phosphors indicated that there exists a strong energy transfer from Dy3+ to Eu3+ and this was demonstrated to be a resonant type via a dipole–quadrupole reaction. Furthermore, the critical distance of the Eu3+ and Dy3+ ions have also been calculated. By utilizing the principle of energy transfer it was also demonstrated that with an appropriate tuning of the activator content the Y2O2S:Eu3+/Dy3+ phosphors can exhibit a great potential to act as single-emitting component phosphors for white light emission in solid state lighting technology.
198 citations
TL;DR: In this article, the advancement in visible light induced initiating systems using free radical, cationic, and hybrid photoinitiators is reviewed, and the characteristics and limitations of some visible light initiating systems are compared and discussed in terms of the initiating efficiency, excitation wavelength, material cost and safety.
180 citations
TL;DR: The discovery of vitamin A by McCollum and Davis in 1913 ushered in the era of accessory food substances culminating in the achievement of that goal of a healthy skeleton and beyond.
Abstract: Before the twentieth century, it was not possible to describe the essentials of a diet that could support life, growth and reproduction of higher animals. The discovery of vitamin A by McCollum and Davis in 1913 ushered in the era of accessory food substances culminating in the achievement of that goal. It included the discovery of vitamin D and its production in skin caused by ultraviolet light. This was followed by a description of its actions at the physiological level that resulted in a healthy skeleton and beyond. To carry out these functions, vitamin D is converted to a hormone that acts through a nuclear receptor. The findings leading to this concept and their importance to biology and medicine are presented.
TL;DR: In vivo analysis in a subcutaneous Wistar rat model at 1, 4 and 12 weeks showed superior implant integration and adipogenesis in the MCS-based composites, with allogenic ASCs promoting cell infiltration, angiogenesis and ultimately, fat formation.
TL;DR: The fabrication of a rewritable paper based on colour switching of commercial redox dyes using titanium oxide-assisted photocatalytic reactions is reported, which is believed to represent an attractive alternative to regular paper in meeting the increasing global needs for sustainability and environmental protection.
Abstract: The invention of paper as writing materials has greatly contributed to the development and spread of civilization. However, its large-scale production and usage have also brought significant environment and sustainability problems to modern society. To reduce paper production and consumption, it is highly desirable to develop alternative rewritable media that can be used multiple times. Herein we report the fabrication of a rewritable paper based on colour switching of commercial redox dyes using titanium oxide-assisted photocatalytic reactions. The resulting paper does not require additional inks and can be efficiently printed using ultraviolet light and erased by heating over 20 cycles without significant loss in contrast and resolution. The legibility of prints can retain over several days. We believe this rewritable paper represents an attractive alternative to regular paper in meeting the increasing global needs for sustainability and environmental protection.
TL;DR: In this article, the external quantum efficiency of AlGaN deep ultraviolet (DUV) light-emitting diodes (LEDs) on sapphire substrates is analyzed.
Abstract: We present the analysis of the external quantum efficiency in AlGaN deep ultraviolet (DUV) light-emitting diodes (LEDs) on sapphire substrates and discuss factors affecting the output power of DUV LEDs. Performance of the LED is related to optimization of the device structure design and improvements of the epitaxial material quality.
TL;DR: A drug-eluting contact lens designed for prolonged delivery of latanoprost for the treatment of glaucoma and as a platform for other ocular drug delivery applications is developed.
TL;DR: Although CTVT has acquired a massive number of genomic alterations, including hundreds of times more somatic mutations than are normally found in human cancers, the tumor cell genome has remained diploid and stable.
Abstract: Canine transmissible venereal tumor (CTVT) is the oldest known somatic cell lineage. It is a transmissible cancer that propagates naturally in dogs. We sequenced the genomes of two CTVT tumors and found that CTVT has acquired 1.9 million somatic substitution mutations and bears evidence of exposure to ultraviolet light. CTVT is remarkably stable and lacks subclonal heterogeneity despite thousands of rearrangements, copy-number changes, and retrotransposon insertions. More than 10,000 genes carry nonsynonymous variants, and 646 genes have been lost. CTVT first arose in a dog with low genomic heterozygosity that may have lived about 11,000 years ago. The cancer spawned by this individual dispersed across continents about 500 years ago. Our results provide a genetic identikit of an ancient dog and demonstrate the robustness of mammalian somatic cells to survive for millennia despite a massive mutation burden.
TL;DR: The vitamin D story thus started as inert molecule but gained an essential role for calcium and bone homeostasis in terrestrial animals to cope with the challenge of higher gravity and calcium-poor environment.
Abstract: Vitamin D3 is already found early in the evolution of life but essentially as inactive end products of the photochemical reaction of 7-dehydrocholestol with ultraviolet light B. A full vitamin D (refers to vitamin D2 and D3) endocrine system, characterized by a specific VDR (vitamin D receptor, member of the nuclear receptor family), specific vitamin D metabolizing CYP450 enzymes regulated by calciotropic hormones and a dedicated plasma transport-protein is only found in vertebrates. In the earliest vertebrates (lamprey), vitamin D metabolism and VDR may well have originated from a duplication of a common PRX/VDR ancestor gene as part of a xenobiotic detoxification pathway. The vitamin D endocrine system, however, subsequently became an important regulator of calcium supply for an extensive calcified skeleton. Vitamin D is essential for normal calcium and bone homeostasis as shown by rickets in vitamin D-deficient growing amphibians, reptiles, birds and mammals. From amphibians onward, bone is gradually more dynamic with regulated bone resorption, mainly by combined action of PTH and 1α,25-dihydroxyvitamin D3 (1,25(OH)2D3) on the generation and function of multinucleated osteoclasts. Therefore, bone functions as a large internal calcium reservoir, under the control of osteoclasts. Osteocytes also display a remarkable spectrum of activities, including mechanical sensing and regulating mineral homeostasis, but also have an important role in global nutritional and energy homeostasis. Mineralization from reptiles onward is under the control of well-regulated SIBLING proteins and associated enzymes, nearly all under the control of 1,25(OH)2D3. The vitamin D story thus started as inert molecule but gained an essential role for calcium and bone homeostasis in terrestrial animals to cope with the challenge of higher gravity and calcium-poor environment.
TL;DR: This review surveys critical factors that determine UV microbial resistance and assess the effects of such factors on the inactivation mechanism and repair pathway efficiency and suggests the combination of UV light with mild heating or oxidant compounds could offer promising treatments to enhance the safety and stability of minimally processed foods.
Abstract: The potential to commercialize nonthermal ultraviolet (UV) light technologies as new methods for preserving food products has caught the attention of a food industry that wishes to fulfill consumers' demands for fresh products. Numerous investigations have demonstrated UV light's ability to inactivate a wide range of microorganisms. However, the lack of UV sensitivity data from pathogenic and spoilage bacteria is evident. In addition, the main factors associated with UV light in terms of microbial lethality remain unclear. This review surveys critical factors (process, microbial, and environmental parameters) that determine UV microbial resistance and assess the effects of such factors on the inactivation mechanism and repair pathway efficiency. The effects of some of these factors, such as prior sublethal stresses and post-recovery conditions of UV treatments, may extensively improve the damage repair capacity and thus microbial survivability. Further research is needed to establish adequate control measures pre- and post-UV treatments. Furthermore, the possibility of combining UV light with conventional preservatives and other nonthermal technologies was assessed. The combination of UV light with mild heating or oxidant compounds could offer promising treatments to enhance the safety and stability of minimally processed foods.
TL;DR: In this article, the upconverted co-luminance of three rare-earth Yb3+ ions was observed in the ultraviolet (UV) region under near-infrared (NIR) excitation.
Abstract: Cooperative luminescence (CL) occurs in spectral regions in which single ions do not have energy levels. It was first observed more than 40 years ago, and all results reported so far are from a pair of ions. In this work, upconverted CL of three Yb3+ ions was observed in the ultraviolet (UV) region under near-infrared (NIR) excitation. The UV CL intensity showed a cubic dependence on the NIR pump power, whereas the luminescence lifetime was nearly one-third the luminescence lifetime of single Yb3+ ions. The triplet CL (TCL) has a clear spectral structure, in which most emission peaks are consistent with the self-convoluted spectra from single Yb3+ ions. Blue shifts were observed for certain peaks, indicating complex interactions among the excited Yb3+ ions. The probability of the TCL process versus the average distances among three Yb3+ ions was derived via the first- and second-order corrections to the wave functions of lanthanide ions, indicating that the formation of Yb3+ clusters containing closely spaced ions favors the occurrence of the multi-ion interaction processes. Furthermore, the cooperative sensitization of one Gd3+ ion by four excited Yb3+ ions (Yb3+-tetramer) was demonstrated experimentally, which exhibited a novel upconversion mechanism—cluster sensitization. Our results are intriguing for further exploring quantum transitions that simultaneously involve multiple ions. Scientists in China have observed ultraviolet light emission from a cluster of rare-earth Yb3+ ions in a CaF2 matrix. Zhen-Yu Liu and co-workers from Jilin University excited the polycrystalline powders with 978 nm near-infrared laser light. The resulting up-converted emission in the ultraviolet is believed to be due to a phenomenon called co-operative luminescence, whereby multiple Yb3+ ions emit a single shorter-wavelength photon by simultaneous depopulation from their excited states. In this particular case, three Yb3+ ions are thought to be involved — a hypothesis confirmed by low-temperature laser spectroscopy of the sample. This process is interesting because it could lead to light emission at wavelengths that lie outside the absorption and emission bands of single ions.
TL;DR: In this article, a transparent luminescent downshifting (DS) YVO4:Eu3+ nano-phosphor layer was used to mitigate ultra-violet degradation in TiO2-based perovskite solar cells.
Abstract: We report a simple method to mitigate ultra-violet (UV) degradation in TiO2 based perovskite solar cells (PSC) using a transparent luminescent down-shifting (DS) YVO4:Eu3+ nano-phosphor layer. The PSC coated with DS phosphor showed an improvement in stability under prolonged illumination retaining more than 50% of its initial efficiency, whereas PSC without the phosphor layer degraded to ∼35% of its initial value. The phosphor layer also provided ∼8.5% enhancement in photocurrent due to DS of incident UV photons into additional red photons. YVO4:Eu3+ layer thus served a bi-functional role in PSC by reducing photo-degradation as well as enhancing energy conversion efficiency.
TL;DR: In this paper, the feasibility of using the UV/S2O82− process to treat TMAH was investigated and the effects of various operational parameters, including pH conditions, dosages of persulfate, UV intensities, and system temperatures were evaluated.
TL;DR: In this article, the photoactivity of new rare earth metal-containing TiO 2 nanocomposites using sol-gel route and their photoactivity under visible and ultraviolet light is reported.
TL;DR: The findings contribute to elucidation of the factors involved in the toxicity of these nanoparticles, as well as to the establishment of protocols for risk assessments of nanotechnology.
TL;DR: The results showed that the degradation of the 6 EDCs during all the three oxidation processes fitted well with pseudo-first-order kinetics, and indicate that the sludge matrix plays an important role in the degrading of EDCs.
TL;DR: A method of observing grain boundary distribution of monolayer TMdCs by a selective oxidation that paves the way toward the investigation of transport properties engineered by defects and grain boundaries.
Abstract: Two-dimensional monolayer transition metal dichalcogenides (TMdCs), driven by graphene science, revisit optical and electronic properties, which are markedly different from bulk characteristics. These properties are easily modified due to accessibility of all the atoms viable to ambient gases, and therefore, there is no guarantee that impurities and defects such as vacancies, grain boundaries, and wrinkles behave as those of ideal bulk. On the other hand, this could be advantageous in engineering such defects. Here, we report a method of observing grain boundary distribution of monolayer TMdCs by a selective oxidation. This was implemented by exposing directly the TMdC layer grown on sapphire without transfer to ultraviolet light irradiation under moisture-rich conditions. The generated oxygen and hydroxyl radicals selectively functionalized defective grain boundaries in TMdCs to provoke morphological changes at the boundary, where the grain boundary distribution was observed by atomic force microscopy an...
TL;DR: In this paper, a chemical precipitation method was used to synthesize ZnS nanoparticles, which were characterized by X-ray diffraction, scanning electron microscope, high resolution transmission electron microscope and ultraviolet-visible and photoluminescence spectrometer.
TL;DR: In this paper, a carbon/TiO2/carbon nanotube (CTCNT) composite featuring a TiO2 nanotubes sandwiched between two thin tubes of carbon with graphitic characteristics is presented.
Abstract: As one of the most promising photocatalysts, TiO2 suffers from disadvantages of a wide band gap energy and especially the ultrafast recombination of photoinduced-charges, which limit its practical application for efficient solar water splitting. Here we show a hitherto unreported carbon/TiO2/carbon nanotube (CTCNT) composite featuring a TiO2 nanotube sandwiched between two thin tubes of carbon with graphitic characteristics. The carbon layer is only about 1 nm thick covering the surface of TiO2 nanotubes. The minimum bandgap between the edges of band tails for the CTCNTs can conjecturally be narrowed to 0.88 eV, and the measured apparent quantum efficiency of CTCNT in the ultraviolet light region is even close to 100%, indicating it can greatly enhance the utilization of sunlight and extremely suppress charge recombination. As a consequence, under illumination of one AM 1.5G sunlight, CTCNT can give a super-high solar-driven hydrogen production rate (37.6 mmol h−1 g−1), which is much greater than the best yields ever reported for TiO2-based photocatalysts. We anticipate this work may open up new insights into the architectural design of nanostructured photocatalysts for effective capture and conversion of sunlight.
TL;DR: In this article, the effects of dynamic loading and environmental conditions on the bond between carbon fiber reinforced polymer (CFRP) and steel are investigated. And the combined effect of applied loading and environment conditions is also included.
Abstract: Carbon fiber reinforced polymer (CFRP) has great potential in strengthening steel structures and the bond between CFRP and steel is a critical issue in the strengthening technique. State-of-the-art reviews have been reported in the literature on the bond behavior between CFRP and steel under static loading at ambient temperature. However, steel structures are often subjected to dynamic loading and harsh environment conditions, and the bond between CFRP and steel may be affected by these conditions. This paper presents a state-of-the-art review on the effects of dynamic loading (e.g., fatigue, impact, and earthquake) and environmental conditions (e.g., subzero temperatures, elevated temperatures, sea water, and ultraviolet light) on the bond between CFRP and steel. The combined effect of applied loading and environmental conditions is also included. Directions for future research are indicated and a comprehensive reference list is provided.
TL;DR: In this paper, a new approach to the catalysis of alkane fluorination employing ultraviolet light and a photosensitizer, 1,2,4,5-tetracyanobenzene (TCB), was presented.
Abstract: We disclose a new approach to the catalysis of alkane fluorination employing ultraviolet light and a photosensitizer, 1,2,4,5-tetracyanobenzene (TCB). The process is efficient, mild, and operationally straightforward. We demonstrate reaction utility on a variety of substrates, from simple hydrocarbons to complex natural products. In a showcase example, we establish that the well-known photochemical rearrangement of α-santonin can be supplanted by a highly selective catalyzed fluorination.
09 Feb 2014
TL;DR: Coque et al. as mentioned in this paper presented a list of enterococcal plasmids recently compiled by one of the authors (Teresa M Coque) to provide a perspective that is relevant to bacterial-human-human interaction interaction.
Abstract: Extrachromosomal elements are ubiquitous in the prokaryotic world and play important roles in the adaptation and survival of cell populations, especially in changing environments Plasmids are readily found in enterococci, and it is not unusual for clinical and commensal strains (eg Enterococcus faecalis and Enterococcus faecium) to harbor a number of such elements Indeed, plasmid-free isolates are only infrequently identified Enterococcal plasmids commonly encode: i) resistance to one or more antibiotics; ii) elevated resistance to ultraviolet light; iii) virulence factors, such as cytolysin and aggregation substance; and iv) bacteriocins In addition, intercellular transmissibility is frequently a plasmid-determined trait As in many bacterial species, plasmids generally range in size from 3–4 kb to well over 100 kb and may be present at relatively low copy number (1–2 copies) or up to 20 or more per cell Table 1 presents a list of enterococcal plasmids recently compiled by one of the authors (Teresa M Coque)Conjugation is a primary means for intercellular DNA mobility in enterococci—natural transformation has never been reported, and information is only beginning to be reported with regard to transduction involving a bacteriophage (see Enterococcal bacteriophages and genome defense) Some conjugative plasmids transfer efficiently from donor to recipient in broth, whereas others transfer well only on solid surfaces In the case of E faecalis, peptide sex pheromones secreted by recipient cells induce conjugation-related mating functions, determined by certain plasmids (eg pAD1, pCF10, and a host of others) Another group of plasmids, such as pMG1 and related elements identified mainly in E faecium, are also able to transfer efficiently in broth, but do not appear to make use of sex pheromones A group of plasmids exemplified by pAMβ1 do not transfer well in broth, but are able to move if the cells are on a solid surface Nonconjugative plasmids are also commonly present in enterococci, and some are readily mobilized by conjugative elements in trans or move via co-integration in some cases Representatives of some of the above-noted elements have been sequenced, and studies relating to their transfer mechanisms have been published In addition, reports relating to replication and partitioning provide significant information on the ways in which certain transmissible elements are maintained in their hostOther types of transmissible elements common in enterococci are the so-called conjugative transposons, which are exemplified by the Tn916 family Usually found integrated in the chromosome, their movement involves an excision event that results in a non-replicative circular intermediate that is able to transfer conjugatively, followed by insertion into the genome of a recipient cell Originally identified in E faecalis, these elements, which commonly encode antibiotic resistance traits, have a broad host range and are widespread among numerous bacterial genera In a similar vein and as found to be the case for many species of bacteria in recent years, enterococci have been shown to carry a plethora of “genomic islands,” some of which are mobile and called “integrative conjugative elements” (ICEs) Some of these represent “pathogenicity islands” that confer significant virulence traits and even antibiotic resistanceRapidly accumulating genomic sequencing data are facilitating identification of the enterococcal “mobilome,” which includes not only transmissible elements, but also insertion sequences, transposons, and integrons that move intracellularly Studies based on functionality, including replication and maintenance, complement this rapidly expanding picture, and the significant extent to which enterococci have participated in horizontal transfer within the bacterial world is becoming readily apparent Below we attempt to summarize recent developments in various aspects of mobile genetic elements (MGEs) in enterococci and try to provide a perspective that is relevant to bacterial-human interaction