Showing papers on "Ultraviolet light published in 2009"

Gold nanocages covered by smart polymers for controlled release with near-infrared light

Abstract: Photosensitive caged compounds have enhanced our ability to address the complexity of biological systems by generating effectors with remarkable spatial/temporal resolutions. The caging effect is typically removed by photolysis with ultraviolet light to liberate the bioactive species. Although this technique has been successfully applied to many biological problems, it suffers from a number of intrinsic drawbacks. For example, it requires dedicated efforts to design and synthesize a precursor compound for each effector. The ultraviolet light may cause damage to biological samples and is suitable only for in vitro studies because of its quick attenuation in tissue. Here we address these issues by developing a platform based on the photothermal effect of gold nanocages. Gold nanocages represent a class of nanostructures with hollow interiors and porous walls. They can have strong absorption (for the photothermal effect) in the near-infrared while maintaining a compact size. When the surface of a gold nanocage is covered with a smart polymer, the pre-loaded effector can be released in a controllable fashion using a near-infrared laser. This system works well with various effectors without involving sophisticated syntheses, and is well suited for in vivo studies owing to the high transparency of soft tissue in the near-infrared region.

DNA Excited-State Dynamics: From Single Bases to the Double Helix

Abstract: Ultraviolet light is strongly absorbed by DNA, producing excited electronic states that sometimes initiate damaging photochemical reactions. Fully mapping the reactive and nonreactive decay pathways available to excited electronic states in DNA is a decades-old quest. Progress toward this goal has accelerated rapidly in recent years, in large measure because of ultrafast laser experiments. Here we review recent discoveries and controversies concerning the nature and dynamics of excited states in DNA model systems in solution. Nonradiative decay by single, solvated nucleotides occurs primarily on the subpicosecond timescale. Surprisingly, excess electronic energy relaxes one or two orders of magnitude more slowly in DNA oligo- and polynucleotides. Highly efficient nonradiative decay pathways guarantee that most excited states do not lead to deleterious reactions but instead relax back to the electronic ground state. Understanding how the spatial organization of the bases controls the relaxation of excess electronic energy in the double helix and in alternative structures is currently one of the most exciting challenges in the field.

Self-Repairing Oxetane-Substituted Chitosan Polyurethane Networks

Abstract: Polyurethanes have many properties that qualify them as high-performance polymeric materials, but they still suffer from mechanical damage. We report the development of polyurethane networks that exhibit self-repairing characteristics upon exposure to ultraviolet light. The network consists of an oxetane-substituted chitosan precursor incorporated into a two-component polyurethane. Upon mechanical damage of the network, four-member oxetane rings open to create two reactive ends. When exposed to ultraviolet light, chitosan chain scission occurs, which forms crosslinks with the reactive oxetane ends, thus repairing the network. These materials are capable of repairing themselves in less than an hour and can be used in many coatings applications, ranging from transportation to packaging or fashion and biomedical industries.

Single-Crystalline ZnS Nanobelts as Ultraviolet-Light Sensors

Abstract: [*] Dr. X. S. Fang, Prof. Y. Bando, Dr. U. K. Gautam, Dr. C. Y. Zhi, Dr. B. D. Liu, Dr. T. Y. Zhai, Prof. D. Golberg International Center for Young Scientists (ICYS) and World Premier International Center for Materials Nanoarchitectonics (MANA) National Institute for Materials Science (NIMS) Namiki 1-1, Tsukuba, Ibaraki 305-0044 (Japan) E-mail: fang.xiaosheng@nims.go.jp; xshfang@yahoo.cn Dr. M. Y. Liao, Prof. Y. Koide Sensor Materials Center, NIMS Namiki 1-1, Tsukuba, Ibaraki 305-0044 (Japan)

Advances in Ultraviolet Light Technology for Non-thermal Processing of Liquid Foods

Abstract: A negative, public reaction is growing over the addition of chemical preservatives to liquid foods and beverages to extend their shelf life and to protect against foodborne pathogens. As a physical method, ultraviolet light (UV) irradiation has a positive consumer image and is of interest to the food industry as a low cost non-thermal method of preservation. Recent advances in the science and engineering of UV light irradiation have demonstrated that this technology holds considerable promise as an alternative to traditional thermal pasteurization for liquid foods and ingredients, fresh juices, soft drinks, and beverages. However, its use for treating foods is still limited due to low UV transmittance of liquid foods. The goal of this review is to provide a summary of the basic principles of UV light generation and propagation with emphasis on its applications for liquid food processing. The review includes information on critical product and process factors that affect UV light inactivation and consequently the delivery of a required scheduled process in liquids foods; measuring and modeling of UV inactivation, and the important effects of UV light on overall quality and nutritional value of liquid foods. The commercially available UV light sources and UV reactor designs that were used for liquid foods treatment are reviewed. The research priorities and challenges that need to be addressed for the successful development of UV technology for liquid foods treatment are discussed.

Guidelines of Care for the Management of Psoriasis and Psoriatic Arthritis. Section 3. Guidelines of Care for the Management and Treatment of Psoriasis With Topical Therapies

Abstract: Psoriasis is a common, chronic, inflammatory, multi-system disease with predominantly skin and joint manifestations affecting approximately 2% of the population. In this third of 6 sections of the guidelines of care for psoriasis, we discuss the use of topical medications for the treatment of psoriasis. The majority of patients with psoriasis have limited disease (<5% body surface area involvement) and can be treated with topical agents, which generally provide a high efficacy-to-safety ratio. Topical agents may also be used adjunctively for patients with more extensive psoriasis undergoing therapy with either ultraviolet light, systemic or biologic medications. However, the use of topical agents as monotherapy in the setting of extensive disease or in the setting of limited, but recalcitrant, disease is not routinely recommended. Treatment should be tailored to meet individual patients' needs. We will discuss the efficacy and safety of as well as offer recommendations for the use of topical corticosteroids, vitamin D analogues, tazarotene, tacrolimus, pimecrolimus, emollients, salicylic acid, anthralin, coal tar, as well as combination therapy.

The Grapevine R2R3-MYB Transcription Factor VvMYBF1 Regulates Flavonol Synthesis in Developing Grape Berries

Abstract: Flavonols are important ultraviolet light protectants in many plants and contribute substantially to the quality and health-promoting effects of fruits and derived plant products. To study the regulation of flavonol synthesis in fruit, we isolated and characterized the grapevine (Vitis vinifera 'Shiraz') R2R3-MYB transcription factor VvMYBF1. Transient reporter assays established VvMYBF1 to be a specific activator of flavonol synthase1 (VvFLS1) and several other promoters of grapevine and Arabidopsis (Arabidopsis thaliana) genes involved in flavonol synthesis. Expression of VvMYBF1 in the Arabidopsis mutant myb12 resulted in complementation of its flavonol-deficient phenotype and confirmed the function of VvMYBF1 as a transcriptional regulator of flavonol synthesis. Transcript analysis of VvMYBF1 throughout grape berry development revealed its expression during flowering and in skins of ripening berries, which correlates with the accumulation of flavonols and expression of VvFLS1. In addition to its developmental regulation, VvMYBF1 expression was light inducible, implicating VvMYBF1 in the control of VvFLS1 transcription. Sequence analysis of VvMYBF1 and VvFLS1 indicated conserved putative light regulatory units in promoters of both genes from different cultivars. By analysis of the VvMYBF1 amino acid sequence, we identified the previously described SG7 domain and an additional sequence motif conserved in several plant MYB factors. The described motifs have been used to identify MYB transcription factors from other plant species putatively involved in the regulation of flavonol biosynthesis. To our knowledge, this is the first functional characterization of a light-inducible MYB transcription factor controlling flavonol synthesis in fruit.

Band gap narrowing of titanium oxide semiconductors by noncompensated anion-cation codoping for enhanced visible-light photoactivity.

Abstract: Titanium dioxide (TiO2) is widely recognized as one of the most promising photocatalysts for solar energy utilization and environmental cleanup, but because of its wide bandgap, pure TiO2 can only absorbs ultraviolet light, which represents 4% of the solar spectrum1-6. Here we establish a conceptually novel approach, termed non-compensated n-p codoping, to narrow the bandgap of TiO2 and shift the optical response into the visible spectral range where a much larger fraction of the solar spectrum can be captured. The concept embodies two key ingredients: The electrostatic attraction within the n-p dopant pair enhances the thermodynamic and kinetic solubility in substitutional doping, and the non-compensated nature ensures the creation of broadened intermediate electronic states that effectively narrow the bandgap. The concept is demonstrated quantitatively within first-principles density functional theory. The experimental evidence for bandgap narrowing is obtained in the forms of direct measurements of the density of states by scanning tunneling spectroscopy, dramatically redshifted and increased optical absorbance, and enhanced photoactivity manifested by efficient hole-electron separation in the visible spectral region. These findings represent the first crucial steps toward development of a new class of titania-based photocatalysts with greatly enhanced efficiency of solar energy conversion facilitating environmentally friendly applications ofrenewablemore » energy.« less

Cellular mechanisms regulating human melanogenesis

Abstract: The major differentiated function of melanocytes is the synthesis of melanin, a pigmented heteropolymer that is synthesized in specialized cellular organelles termed melanosomes. Mature melanosomes are transferred to neighboring keratinocytes and are arranged in a supranuclear cap, protecting the DNA against incident ultraviolet light (UV) irradiation. The synthesis and distribution of melanin in the epidermis involves several steps: transcription of melanogenic proteins, melanosome biogenesis, sorting of melanogenic proteins into the melanosomes, transport of melanosomes to the tips of melanocyte dendrites and finally transfer into keratinocytes. These events are tightly regulated by a variety of paracrine and autocrine factors in response to endogenous and exogenous stimuli, principally UV irradiation.

ZnO and ZnS Nanostructures: Ultraviolet-Light Emitters, Lasers, and Sensors

Abstract: ZnO and ZnS, well-known direct bandgap II–VI semiconductors, are promising materials for photonic, optical, and electronic devices. Nanostructured materials have lent a leading edge to the next generation technology due to their distinguished performance and efficiency for device fabrication. As two of the most suitable materials with size- and dimensionality-dependent functional properties, wide bandgap semiconducting ZnO and ZnS nanostructures have attracted particular attention in recent years. For example, both materials have been assembled into nanometer-scale visible-light-blind ultraviolet (UV) light sensors with high sensitivity and selectivity, in addition to other applications such as field emitters and lasers. Their high-performance characteristics are particularly due to the high surface-to-volume ratios (SVR) and rationally designed surfaces. This article provides a comprehensive review of the state-of-the-art research activities in ZnO and ZnS nanostructures, including their syntheses and po...

Athletic performance and vitamin D.

Abstract: CANNELL, J. J., B. W. HOLLIS, M. B. SORENSON, T. N. TAFT, and J. J. ANDERSON. Athletic Performance and Vitamin D. Med. Sci. Sports Exerc., Vol. 41, No. 5, pp. 1102–1110, 2009. Purpose: Activated vitamin D (calcitriol) is a pluripotent pleiotropic secosteroid hormone. As a steroid hormone, which regulates more than 1000 vitamin D–responsive human genes, calcitriol may influence athletic performance. Recent research indicates that intracellular calcitriol levels in numerous human tissues, including nerve and muscle tissue, are increased when inputs of its substrate, the prehormone vitamin D, are increased. Methods: We reviewed the world’s literature for evidence that vitamin D affects physical and athletic performance. Results: Numerous studies, particularly in the German literature in the 1950s, show vitamin D–producing ultraviolet light improves athletic performance. Furthermore, a consistent literature indicates physical and athletic performance is seasonal; it peaks when 25-hydroxy-vitamin D [25(OH)D] levels peak, declines as they decline, and reaches its nadir when 25(OH)D levels are at their lowest. Vitamin D also increases the size and number of Type II (fast twitch) muscle fibers. Most cross-sectional studies show that 25(OH)D levels are directly associated with musculoskeletal performance in older individuals. Most randomized controlled trials, again mostly in older individuals, show that vitamin D improves physical performance. Conclusions: Vitamin D may improve athletic performance in vitamin D–deficient athletes. Peak athletic performance may occur when 25(OH)D levels approach those obtained by natural, full-body, summer sun exposure, which is at least 50 ngImL j1 . Such 25(OH)D levels may also protect the athlete from several acute and chronic medical

High-performance blue/ultraviolet-light-sensitive ZnSe-nanobelt photodetectors

Abstract: Single-crystalline zinc selenide (ZnSe) nanobelts were fabricated via the ethylenediamine (en)-assisted ternary solution technique and subsequent thermal treatment. Individual ZnSe nanobelts were assembled into nanoscale devices, showing a high spectral selectivity and photocurrent/immediate-decay ratio and a fast time response, justifying effective utilization of the ZnSe nanobelts as blue/UV-light-sensitive photodetectors.

How DNA lesions are turned into powerful killing structures: insights from UV-induced apoptosis.

Abstract: Mammalian cells treated with ultraviolet (UV) light provide one of the best-known experimental systems for depicting the biological consequences of DNA damage. UV irradiation induces the formation of DNA photoproducts, mainly cyclobutane pyrimidine dimers (CPDs) and (6-4) pyrimidine-pyrimidone photoproducts [(6-4)PPs], that drastically impairs DNA metabolism, culminating in the induction of cell death by apoptosis. While CPDs are the most important apoptosis-inducing lesions in DNA repair proficient cells, recent data indicates that (6-4)PPs also signals for apoptosis in DNA repair deficient cells. The toxic effects of these unrepaired DNA lesions are commonly associated with transcription blockage, but there is increasing evidence supporting a role for replication blockage as an apoptosis-inducing signal. This is supported by the observations that DNA double-strand breaks (DSBs) arise at the sites of stalled replication forks, that these DSBs are potent inducers of apoptosis and that inhibition of S phase progression diminishes the apoptotic response. Reactive oxygen species, generated after exposure of mammalian cells to longer UV wavelengths, may also induce apoptotic responses. In this regard, emphasis is given to the formation of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-OxoG), but indirect induced lesions such as lipoperoxide DNA adducts also deserve attention. ATR is the main established sensor molecule for UV-induced DNA damage. However, there is evidence that ATM as well as the MAPK pathway also play a role in the UV response by activating either the death receptor or the mitochondrial damage pathway. Adding more complexity to the subject, cells under stress suffer other types of processes that may result in cell death. Autophagy is one of these processes, with extensive cross-talks with apoptosis. No matter the mechanisms, cell death avoids cells to perpetuate mutations induced by genotoxic lesions. The understanding of such death responses may provide the means for the development of strategies for the prevention and treatment of cancer.

Ultraviolet Light in Food Technology: Principles and Applications

Abstract: Principles and Applications of UV Technology Basic Principles of UV Light Technology Propagation of UV Light Application Guidance in Food Processing Current Status of US and International Regulations Sources of UV Light Introduction Mercury-Emission Lamps Amalgam UV Lamps Special Lamp Technologies Guidelines for Choice of Lamp Technology Characterization of Foods in Relation to UV Treatment Terms and Definitions Analytical Measurements Absorptive and Physicochemical Properties of Liquid Foods Food Solids and Surfaces Conclusions Microbial Inactivation by UV Light Mechanisms of Microbial Inactivation by UV Light UV Sensitivity of Pathogenic and Spoilage Food-Borne Microorganisms UV Sensitivity of Waterborne Pathogens UV Sensitivity of Food-Borne Pathogens UV Inactivation Kinetics and Competitive Effects in Foods: Absorbance, pH, Solids, and Other Components Methods to Measure, Quantify, and Mathematically Model UV Inactivation Efficacy of Low-Pressure, High-Intensity Lamp for Inactivation of Food Pathogen Conclusions UV Processing Effects on Quality of Foods Basic Considerations Chemistry of the Photodegradation of Organic Compounds Shelf Life and Quality Changes in Fresh Juices Effects of UV Light on Degradation of Essential Vitamins Effect of UV Processing on Milk Quality Shelf Life and Quality Changes in Fresh Produce Degradation and Formation of Chemical Compounds in Foods Conclusions Transport Phenomena in UV Processing UV Irradiance in Liquid Foods General Hydraulic Condition UV Process Calculations for Food Applications Establishment of Specifications for Preservation Delivery of the Scheduled Process Measurement of UV Dose Delivery Conclusions Reactor Designs for the UV Treatment of Liquid Foods Laminar Flow in Concentric Cylinders Turbulent Flow in Concentric Cylinders Taylor-Couette Flow in Concentric Cylinders Comparison of Disinfection in Concentric Cylinders Turbulent Channel Flow Dean Flow Reactor Evaluation of UV Reactor Design UDF Source C Codes Principles of Validation of UV Light Pasteurization Validation Concept Validation at Different Phases of Process Development-Scale-Up Process Key Components of Validation Procedures Conclusions Pulsed-Light Treatment: Principles and Applications Description of Pulsed-Light Treatment Inactivation of Microorganisms by Pulsed-Light Treatment Applications of Pulsed-Light Treatment Future Prospects of Pulsed-Light Treatment in the Food Industry References appear at the end of each chapter.

Ultraviolet light-emitting diodes in water disinfection

Abstract: The novel system of ultraviolet light-emitting diodes (UV LEDs) was studied in water disinfection. Conventional UV lamps, like mercury vapor lamp, consume much energy and are considered to be problem waste after use. UV LEDs are energy efficient and free of toxicants. This study showed the suitability of LEDs in disinfection and provided information of the effect of two emitted wavelengths and different test mediums to Escherichia coli destruction. Common laboratory strain of E. coli (K12) was used and the effects of two emitted wavelengths (269 and 276 nm) were investigated with two photolytic batch reactors both including ten LEDs. The effects of test medium were examined with ultrapure water, nutrient and water, and nutrient and water with humic acids. Efficiency of reactors was almost the same even though the one emitting higher wavelength had doubled optical power compared to the other. Therefore, the effect of wavelength was evident and the radiation emitted at 269 nm was more powerful. Also, the impact of background was studied and noticed to have only slight deteriorating effect. In the 5-min experiment, the bacterial reduction of three to four log colony-forming units (CFU) per cubic centimeter was achieved, in all cases. When turbidity of the test medium was greater, part of the UV radiation was spent on the absorption and reactions with extra substances on liquid. Humic acids can also coat the bacteria reducing the sensitivity of the cells to UV light. The lower wavelength was distinctly more efficient when the optical power is considered, even though the difference of wavelengths was small. The reason presumably is the greater absorption of DNA causing more efficient bacterial breakage. UV LEDs were efficient in E. coli destruction, even if LEDs were considered to have rather low optical power. The effect of wavelengths was noticeable but the test medium did not have much impact. This study found UV LEDs to be an optimal method for bacterial disinfection. The emitted wavelength was found to be an essential factor when using LEDs; thus, care should be taken in selecting the proper LED for maximum disinfection.

Ultraviolet light curves of supernovae with the swift ultraviolet/optical telescope

Abstract: We present ultraviolet (UV) observations of supernovae (SNe) obtained with the UltraViolet/Optical Telescope (UVOT) on board the Swift spacecraft. This is the largest sample of UV light curves from any single instrument and covers all major SN types and most subtypes. The UV light curves of SNe Ia are fairly homogenous, while SNe Ib/c and IIP show more variety in their light-curve shapes. The UV-optical colors clearly differentiate SNe Ia and IIP, particularly at early times. The color evolution of SNe IIP, however, makes their colors similar to SNe Ia at about 20 days after explosion. SNe Ib/c are shown to have varied UV-optical colors. The use of UV colors to help type SNe will be important for high-redshift SNe discovered in optical observations. These data can be added to ground-based optical and near infrared data to create bolometric light curves of individual objects and as checks on generic bolometric corrections used in the absence of UV data. This sample can also be compared with rest-frame UV observations of high-redshift SNe observed at optical wavelengths.

The missing link--light-induced (280-1,600 nm) free radical formation in human skin.

Abstract: The recent European recommendation on the efficacy of sunscreen products requests now a minimum ratio of UVA/UVB protection. However, the visible and the infrared (IR) parts of the sun spectrum have r

Upper-Room Ultraviolet Light and Negative Air Ionization to Prevent Tuberculosis Transmission

Abstract: Background Institutional tuberculosis (TB) transmission is an important public health problem highlighted by the HIV/AIDS pandemic and the emergence of multidrug- and extensively drug-resistant TB. Effective TB infection control measures are urgently needed. We evaluated the efficacy of upperroom ultraviolet (UV) lights and negative air ionization for preventing airborne TB transmission using a guinea pig air-sampling model to measure the TB infectiousness of ward air.

RNA under attack: cellular handling of RNA damage.

Abstract: Damage to RNA from ultraviolet light, oxidation, chlorination, nitration, and akylation can include chemical modifications to nucleobases as well as RNA-RNA and RNA-protein crosslinking. In vitro studies have described a range of possible damage products, some of which are supported as physiologically relevant by in vivo observations in normal growth, stress conditions, or disease states. Damage to both messenger RNA and noncoding RNA may have functional consequences, and work has begun to elucidate the role of RNA turnover pathways and specific damage recognition pathways in clearing cells of these damaged RNAs.

Semiconductor disk lasers for the generation of visible and ultraviolet radiation

Abstract: Recent developments in semiconductor disk lasers (SDLs) generating visible or ultraviolet light are reviewed. After an introduction on potential applications, we discuss how the combination of vertical-emitting semiconductor GaAs-based structures and intra-cavity nonlinear conversion techniques can be successfully exploited to uniquely meet demands for continuous-wave radiation in the visible and ultraviolet spectral range. To do so, an overview of the device operating princi- ples and performance is presented highlighting the underlying material considerations, semiconductor structural designs, thermal management techniques and suitable cavity configurations. This summary is completed by a presentation of new developments in the field, with a particular focus on the trends towards miniaturization.

Ignition on the National Ignition Facility: a path towards inertial fusion energy

Abstract: The National Ignition Facility (NIF), the world's largest and most powerful laser system for inertial confinement fusion (ICF) and experiments studying high-energy-density (HED) science, is nearing completion at Lawrence Livermore National Laboratory (LLNL). NIF, a 192-beam Nd-glass laser facility, will produce 1.8 MJ, 500 TW of light at the third-harmonic, ultraviolet light of 351 nm. The NIF project is scheduled for completion in March 2009. Currently, all 192 beams have been operationally qualified and have produced over 4.0 MJ of light at the fundamental wavelength of 1053 nm, making NIF the world's first megajoule laser. The principal goal of NIF is to achieve ignition of a deuterium–tritium (DT) fuel capsule and provide access to HED physics regimes needed for experiments related to national security, fusion energy and for broader scientific applications.The plan is to begin 96-beam symmetric indirect-drive ICF experiments early in FY2009. These first experiments represent the next phase of the National Ignition Campaign (NIC). This national effort to achieve fusion ignition is coordinated through a detailed plan that includes the science, technology and equipment such as diagnostics, cryogenic target manipulator and user optics required for ignition experiments. Participants in this effort include LLNL, General Atomics, Los Alamos National Laboratory, Sandia National Laboratory and the University of Rochester Laboratory for Energetics (LLE). The primary goal for NIC is to have all of the equipment operational and integrated into the facility soon after project completion and to conduct a credible ignition campaign in 2010. When the NIF is complete, the long-sought goal of achieving self-sustaining nuclear fusion and energy gain in the laboratory will be much closer to realization.Successful demonstration of ignition and net energy gain on NIF will be a major step towards demonstrating the feasibility of inertial fusion energy (IFE) and will likely focus the world's attention on the possibility of an ICF energy option. NIF experiments to demonstrate ignition and gain will use central-hot-spot (CHS) ignition, where a spherical fuel capsule is simultaneously compressed and ignited. The scientific basis for CHS has been intensively developed (Lindl 1998 Inertial Confinement Fusion: the Quest for Ignition and Energy Gain Using Indirect Drive (New York: American Institute of Physics)) and has a high probability of success. Achieving ignition with CHS will open the door for other advanced concepts, such as the use of high-yield pulses of visible wavelength rather than ultraviolet and fast ignition concepts (Tabak et al 1994 Phys. Plasmas 1 1626–34, Tabak et al 2005 Phys. Plasmas 12 057305). Moreover, NIF will have important scientific applications in such diverse fields as astrophysics, nuclear physics and materials science.This paper summarizes the design, performance and status of NIF, experimental plans for NIC, and will present laser inertial confinement fusion–fission energy (LIFE) as a path to achieve carbon-free sustainable energy.

Multilayer film for encapsulating oxygen and/or moisture sensitive electronic devices

Abstract: The present invention refers to a multilayer barrier film capable of encapsulating a moisture and/or oxygen sensitive electronic or optoelectronic device, the barrier film comprises at least one nanostructured layer comprising reactive nanoparticles capable of interacting with moisture and/or oxygen, the reactive nanoparticles being distributed within a polymeric binder, and at least one ultraviolet light neutralizing layer comprising a material capable of absorbing ultraviolet light, thereby limiting the transmission of ultraviolet light through the barrier film.

Role of defects in the anomalous photoconductivity in ZnO nanowires

Abstract: The anomalous photocurrent decay in aqueous solution grown ZnO nanowires (NWs) under steady ultraviolet light illumination have been investigated. The photocurrent growth-decay measurements using the above-band and subband gap light excitation energies in the as-grown and annealed NWs show that while a VZn-related defect complex is formed by the surface adsorbed H2O molecules, a faster carrier trapping by the surface adsorbed O2 molecules and a slower carrier recombination at the defect, Zni cause the photocurrent decay under steady illumination supported by the results of the photocurrent spectra and photoluminescence measurements. The predicted mechanism has been explained through a model.

Association of Low Vitamin D Levels With the Frailty Syndrome in Men and Women

Abstract: FRAILTY has been described as “a biologic syndrome of decreased reserve and resistance to stressors, resulting from cumulative declines across multiple physiologic systems and causing vulnerability to adverse outcomes” (1) The syndrome is associated with incident falls, functional limitation, disability, and mortality (1,2); thus, preventing frailty may help slow progression of the disablement process in older persons Low 25-hydroxyvitamin D [25(OH)D] levels are common in older adults (3,4) and have been linked to falls (5,6), fractures (5), pain (3,5,7), sarcopenia (4), poor physical function (8,9), disability (3), and frailty (10) Further, vitamin D supplementation has been shown to improve physical function (11,12) The importance of vitamin D in maintaining calcium homeostasis is well known Cholecalciferol is synthesized in the skin in response to ultraviolet light or is ingested through food (eg, fatty fish, eggs, fortified dairy products) and hydroxylated into 25(OH)D in the liver Older persons often have low 25(OH)D levels owing to age-related decreased efficiency of hydroxylation and reduced sunlight exposure (3,13) When 25(OH)D levels are low, active metabolite 1,25-dihydroxyvitamin D [1,25-(OH)2D] and calcium absorption decrease The reduced serum calcium causes parathyroid hormone (PTH) levels to rise to stimulate 1,25-(OH)2D production, resulting in increased bone turnover and hip fracture risk (3,13) Emerging research suggests that vitamin D affects muscle strength and function (4,8), both directly and indirectly through PTH regulation and inflammation (3,4,9,14,15) Many sequelae of low 25(OH)D (3,4,8–10) are considered dimensions of the frailty syndrome (1,2); thus, low 25(OH)D may be a reversible cause of frailty Also, low vitamin D may affect men and women differently Age-related levels of 25(OH)D decline earlier and faster in women than in men (16), which may explain the greater prevalence of frailty in women versus men Whether the pathway to frailty differs by sex is unknown In this study, we examined sex-specific associations between low 25(OH)D and prevalent frailty in community-dwelling men and women aged 65 years and older We also explored PTH as a potential mediator in the pathway between low 25(OH)D and frailty

Method for removal of carbon from an organosilicate material

Abstract: Described herein is a method for removing at least a portion of the carbon-containing species within an organosilicate (OSG) film by treating the OSG film with a chemical, such as but not limited to an oxidizer, exposing the OSG film to an energy source comprising ultraviolet light, or treating the OSG film with a chemical and exposing the OSG film to an energy source.