Intensity Of UV Radiation Research Articles

Theoretical Transmission Spectra of Exoplanet Atmospheres with Hydrocarbon Haze: Effect of Creation, Growth, and Settling of Haze Particles. I. Model Description and First Results

Abstract Recently, properties of exoplanet atmospheres have been constrained via multi-wavelength transit observation, which measures an apparent decrease in stellar brightness during planetary transit in front of its host star (called transit depth). Sets of transit depths so far measured at different wavelengths (called transmission spectra) are somewhat diverse: some show steep spectral slope features in the visible, some contain featureless spectra in the near-infrared, some show distinct features from radiative absorption by gaseous species. These facts imply the existence of haze in the atmospheres, especially of warm, relatively low-density super-Earths and mini-Neptunes. Previous studies that addressed theoretical modeling of transmission spectra of hydrogen-dominated atmospheres with haze made some assumptions about the distribution and size of haze particles. In this study, we model the atmospheric chemistry, and derive the spatial and size distributions of haze particles by directly simulating the creation, growth, and settling of hydrocarbon haze particles. We then develop transmission spectrum models of UV-irradiated, solar-abundance atmospheres of close-in warm (∼500 K) exoplanets. We find that the haze is distributed in the atmosphere much more broadly than previously assumed, and consists of particles of various sizes. We also demonstrate that the observed diversity of transmission spectra can be explained by the difference in the production rate of haze monomers, which is related to the UV irradiation intensity from host stars.

Synthesis and spectroscopic characterization of gold nanoparticles via plasma-liquid interaction technique

Fabrication of non-functionalized gold nanoparticles is interesting owing to their potential applications in sensing and biomedicine. We report on the synthesis of surfactant-free gold nanoparticles (AuNPs) by Plasma-Liquid Interaction (PLI) technique, using micro-atmospheric pressure D.C. plasma. The effects of discharge parameters, such as discharge current, precursor concentration and gas flow rates on the structure and morphology of AuNPs have been investigated. Optical Emission Spectroscopy (OES) was employed to estimate the UV radiation intensity and OH radical density. Scanning electron microscopy (SEM) and ultraviolet-visible (UV-Vis) optical spectroscopy were employed to study the morphology and structure of AuNPs. The normalized intensities of UV radiation and OH radical density found to increase with increase in discharge current. We observed that the particle size can be tuned by controlling any of the following parameters: intensity of the UV radiation, OH radical density, and concentration of the Au precursor. Interestingly, we found that addition of 1% Ar in the feedstock gas results in formation of relatively uniform size distribution of nanoparticles. The surfactant-free AuNPs, due to their bare-surface, exhibit excellent surface-enhanced Raman scattering (SERS) properties. The SERS study of Rhodamine 6G using AuNPs as substrates, shows significant Raman enhancement and fluorescence quenching, which makes our technique a potentially powerful route to detection of trace amounts of dangerous explosives and other materials.

Impacts of UV Radiation on the Polymorphic Transformation of β Glycine to α Glycine

AbstractThe influence of UV radiation on the phase transformation of β glycine to α glycine was investigated at 25 °C in the absence and the presence of varying intensities of UV radiation. The transformation of the polymorph was monitored by continuously measuring the ultrasonic velocity in the crystallizer, and the crystals obtained were analyzed using XRD to determine the polymorphic form. In addition, the crystals were characterized by SEM, a particle sizer and ATR–FTIR. The results indicated that the UV radiation and its intensity have significant effects on the both the average particle size and the morphology of glycine crystals. To further understand the role of UV radiation and its intensity on glycine phase transformation, these experiments were also performed in the presence of propane‐1,2,3‐tricarboxylic acid. It was found that the presence of the additive in the crystallization media caused the transition time to be extended; however, the presence of both the additive and UV radiation lessened the phase transformation time significantly, depending on the increase in UV radiation intensity. In addition, TGA–MS results revealed that the amount of evolved gases in the presence of UV radiation was reduced, and that the UV radiation caused changes in the glycine.

Effects of ultraviolet radiation on photosynthetic performance and N<sub>2</sub> fixation in <i>Trichodesmium erythraeum</i> IMS 101

Abstract. Biological effects of ultraviolet radiation (UVR; 280–400 nm) on marine primary producers are of general concern, as oceanic carbon fixers that contribute to the marine biological CO2 pump are being exposed to increasing UV irradiance due to global change and ozone depletion. We investigated the effects of UV-B (280–320 nm) and UV-A (320–400 nm) on the biogeochemically critical filamentous marine N2-fixing cyanobacterium Trichodesmium (strain IMS101) using a solar simulator as well as under natural solar radiation. Short exposure to UV-B, UV-A, or integrated total UVR significantly reduced the effective quantum yield of photosystem II (PSII) and photosynthetic carbon and N2 fixation rates. Cells acclimated to low light were more sensitive to UV exposure compared to high-light-grown ones, which had more UV-absorbing compounds, most likely mycosporine-like amino acids (MAAs). After acclimation under natural sunlight, the specific growth rate was lower (by up to 44 %), MAA content was higher, and average trichome length was shorter (by up to 22 %) in the full spectrum of solar radiation with UVR, than under a photosynthetically active radiation (PAR) alone treatment (400–700 nm). These results suggest that prior shipboard experiments in UV-opaque containers may have substantially overestimated in situ nitrogen fixation rates by Trichodesmium, and that natural and anthropogenic elevation of UV radiation intensity could significantly inhibit this vital source of new nitrogen to the current and future oligotrophic oceans.

Electrochemical UV Sensor Using Carbon Quantum Dot/Graphene Semiconductor

Our group has developed an electrochemical UV sensor utilizing carbon quantum dots as the photoactive material functionalizing a graphene semiconductor layer. When used as a photoactive electrode in contact with a solid polymer electrolyte in a photoelectrochemical cell, illumination under UV radiation at 365 nm induces a photocurrent with a corresponding change in device voltage. The time-dependent change in voltage is a function of UV radiation intensity. Varying the UV LED power density from 26.6 mW/cm2 (approximately 100% intensity) to 5.1 mW/cm2 (approximately 20% intensity) results in time-dependent potential changes (dU/dt) ranging from approximately 4.0 mV/s to 0.5 mV/s. The dU/dt vs. LED power density trend is nearly linear (r2 = 0.97). Similarly, when a constant bias potential is applied to the cell, a sustained photocurrent is observed under UV illumination, with the magnitude of the photocurrent a linear function of the LED power density. In that case, the coefficient of determination r2 = 0.98. These results indicate that a graphene semiconductor, when functionalized with a photoactive material like carbon quantum dots, has application as a UV sensor with the ability to quantify the intensity of UV radiation.

Synthesis and characterization of Ag doped ZnS quantum dots for enhanced photocatalysis of Strychnine as a poison: Charge transfer behavior study by electrochemical impedance and time-resolved photoluminescence spectroscopy

In this study, the photocatalytic degradation of Strychnine was investigated by ZnS quantum dots and doped with silver in UV systems. ZnS and Ag-ZnS quantum dots were synthesized by chemical method and characterized by powder X-ray diffraction, transmission electron microscopy, UV–vis spectra and photoluminescence. The charge transfer process on the semicon-ductor/electrolyte interface was investigated via electrochemical impedance spectroscopy (EIS) and time-resolved photoluminescence. The average diameters of ZnS and Ag doped ZnS QDs were 3.0–5.0nm and 3.0–5.3nm, respectively. The band gap of ZnS and Ag-ZnS QDs was computed as 3.47 and 3.1eV, respectively. The surface area values of ZnS and Ag-ZnS QDs have been found as 78.25 and 89.54m2/g, respectively. The influences of key operating parameters such as initial pH, catalyst dosage, UV radiation intensity, reaction time as well as the effect of initial Strychnine concentration on mineralization extents were studied. The results of the study showed that the maximum removal efficiency of Strychnine had been achieved by un-doped and Ag-doped ZnS QDs at radiation intensity of 100W/m2, at time of 60min, pH of 3 and initial Strychnine concentration of 20mg/ml. Also the observations clearly showed that the photocatalysis process with Ag doped ZnS QDs are more effective than un-doped ZnS QDs.

Integration of a Genetically Encoded Calcium Molecular Sensor into Photopolymerizable Hydrogels for Micro-Optrode-Based Sensing.

Genetically encoded molecular-protein sensors (GEMS) are engineered to sense and quantify a wide range of biological substances and events in cells, in vitro and even in vivo with high spatial and temporal resolution. Here, we aim to stably incorporate these proteins into a photopatternable matrix, while preserving their functionality, to extend the application of these proteins as spatially addressable optical biosensors. For this reason, we examined the fabrication of 3D hydrogel microtips doped with a genetically encoded fluorescent biosensor, GCaMP3, at the end of an optical fiber. Stable incorporation parameters of GCaMP3 into a photo-cross-linkable monomer matrix were investigated through a series of characterization and optimization experiments. Different precursor-solution formulations and irradiation parameters of in situ photopolymerization were tested to determine the factors affecting protein stability and sensor reproducibility during photoencapsulation. The microstructure and performance of hydrogel microtips were controlled by varying UV irradiation intensity as well as the molecular weight and concentration of the photocurable monomer, PEGDA (polyethylene glycol diacrylate), in precursor solution. Protein-doped hydrogel micro-optrodes (microtip sensors) were fabricated successfully and reproducibly at the distal end of optical fiber. Under optimized conditions, the bioactivity of GCaMP3 within a hydrogel matrix of micro-optrodes remained similar to that of the protein-free matrix in buffer. The limit of detection of protein optrodes for free calcium was also determined to be 4.3 nM. The hydrogel formulation and fabrication process demonstrated here using microtip optrodes can be easily adapted to other conformation-dependent protein biosensors and can be used in sensing applications.

Dermatologic neoplasms: a perspective from Makurdi, North Central Nigeria

<p class="abstract"><strong>Background:</strong> Skin cancers are the commonest malignancies in Caucasians but are relatively less common in dark skinned persons. They are strongly linked to ultraviolet exposure, skin melanin content, and immune status.</p><p class="abstract"><strong>Methods:</strong> This study reviewed all histologically diagnosed skin neoplasms at the Federal Medical Centre, Makurdi from January 2012 to December 2016.<strong></strong></p><p class="abstract"><strong>Results:</strong> A total of 84 neoplasms were seen, with 42 (50%) being malignant. Of the malignant lesions, Squamous cell carcinomas were the most frequent (45.2%), followed by melanomas (23.8%). The lower limb was the most frequent site of both benign and malignant neoplasms, while a male to female ratio of 0.88:1 was observed.</p><p><strong>Conclusions:</strong> A relatively high UV radiation intensity, combined with a predominance of outdoor agricultural based activities, alongside chronic ulcerative/inflammatory lesions and a high HIV burden all indicate a need for widespread enlightenment and screening campaigns to prevent occurrence of skin cancers and aid early diagnosis.</p>

Controlling sunbathing safety during the summer holidays - The solar UV campaign at Baltic Sea coast in 2015

Information regarding the intensity of surface UV radiation, provided for the public, is frequently given in terms of a daily maximum UV Index (UVI), based on a prognostic model. The quality of the UV forecast depends on the accuracy of column amount of ozone and cloudiness prediction. Daily variability of UVI is needed to determine the risk of the UV overexposure during outdoor activities. Various methods of estimating the temporary UVI and the maximum duration of UV exposures (received a dose equal to minimal erythemal dose – MED), at the site of sunbathing, were compared. The UV indices were obtained during a field experiment at the Baltic Sea coast in the period from 13th to 24th July 2015. The following UVI calculation models were considered: UVI measurements by simple hand-held biometers (Silver Crest, Oregon Scientific, or more advanced Solarmeter 6.5), our smartphone models based on cloud cover observations at the site and the cloudless-sky UVI forecast (available for any site for all smartphone users) or measured UVI, and the 24h weather predictions by the ensemble set of 10 models (with various cloud parameterizations). The direct UV measurements, even by a simple biometer, provided useful UVI estimates. The smartphone applications yielded a good agreement with the UV measurements. The weather prediction models for cloudless-sky conditions could provide valuable information if almost cloudless-sky conditions (cloudless-sky or slightly scattered clouds) were observed at the sunbathing site.

Fabrication of High Sensitive UV Photodetector Based on n-ZnO Nanowire/n-Porous-Si Heterojunction

In this paper, we have reported the high sensitive UV detector using ZnO nanowires prepared on porous silicon (PS). The aligned naturally doped n-type zinc oxide (ZnO) nanowires were grown on both PS and n-Si(100) substrates to produce isotype heterojunctions using hydrothermal method. The length of the nanowires ranges 3–4[Formula: see text][Formula: see text]m and the diameter 150–200[Formula: see text]nm. Grown ZnO nanowires on PS substrate has lower reflectivity value compared with Si substrate. The electrical behavior of such devices has been examined at different intensities of UV radiation. The current–voltage curve of the isotype heterojunction shows rectifying behavior in a dark environment. Under UV light, the current was increased by using PS instead of n-Si under reverse bias. The I–V characteristics of the device show a significant rise in the current for low intensity of UV radiation evidencing the high sensitivity of the reported structure. The sensitivity for such devices is obtained, [Formula: see text] and [Formula: see text] at UV radiation of 1.5[Formula: see text]mW/cm2 intensity at bias voltage of −0.75 V for three proposed structures. The samples have been analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM) to investigate their structures and geometries.

Genotype‐by‐environment effect on bioactive compounds in strawberry (Fragaria x ananassa Duch.)

The assessment of the relative contribution of genotype, environment and the genotype-by-environmental (G × E) interaction to the performance of varieties is necessary when determining adaptation capacity. The influence of temperature, ultraviolet (UV)-irradiation and sunshine duration on the quality and the composition of fruits was investigated in nine strawberry cultivars grown at three different altitudes. The UV-radiation intensity affected both pH and sugar content, which were higher for most of the varieties at low altitudes, whereas total titratable acidity was less. Fruits from plants grown at low elevation generally had a higher benzoic acid derivative content. A significant correlation was found between phenylpropanoid content and UV-radiation and sunshine duration. The flavone class appeared to be affected most by the variety effect, in contrast to flavonols and ellagitannins, which were highly affected by the environment. The accumulation of a number of secondary metabolites in strawberry fruits grown in an unusual environmental condition highlighted the acclimation effects in terms of the response of plants to abiotic stress. Finally, the genetic factor only appears to be more influential for the varieties 'Sveva' and 'Marmolada' with respect to all of the parameters considered. A 'plant environmental metabolomics' approach has been used successfully to assess the phenotypic plasticity of varieties that showed different magnitudes with respect to the relationship between environmental conditions and the accumulation of healthy compounds. © 2017 Society of Chemical Industry.

Phototriggered Ring-Opening Polymerization of a Photocaged l-Lysine N-Carboxyanhydride to Synthesize Hyperbranched and Linear Polypeptides.

Increasing efforts are being made on controlled photopolymerization methodologies; however, the previous polymerization systems need additional photoactive initiators or catalysts. The controlled synthesis of the hyperbranched polypeptide is still challenging, and developing a photopolymerization method to prepare a hyperbranched polypeptide is urgent for constructing biodegradable polymers and biomaterials. Without addition of any initiator/catalyst, we combine the inimer (initiator + monomer) ring-opening polymerization (ROP) and photocaged chemistry to prepare hyperbranched and linear polypeptides. The photocaged Nε-(o-nitrobenzyloxycarbonyl)-l-lysine-N-carboxyanhydride possesses intrinsic photosensitivity and will be transformed into an activated AB* inimer-type α-amino acid N-carboxyanhydride (NCA) containing a primary ε-amine, which further triggers ROP to produce linear and/or hyperbranched polypeptides in one pot and at room temperature. The microstructure and topology of the resulting polypeptide were clarified by means of mass spectroscopy and various NMR techniques including 1H NMR, 1H, 1H-COSY, and quantitative 13C NMR. By tuning the UV irradiation time or intensity, this methodology can produce a linear polypeptide with a high Mw,GPC of 109 kDa and/or (hyper)branched counterparts with tunable Mw,GPC's of 1.4-73.5 kDa and degree of branching of 0.09-0.60.

Removal of organic materials and hexavalent chromium from landfill leachate using a combination of electrochemical and photocatalytic processes

Leachate is one of the major problems of municipal waste landfills. Landfills produce a dark black colored liquid with high levels of chemical oxygen demand (COD) and heavy metals and low biochemical oxygen demand (BOD)/COD ratio. The objectives of this study were to evaluate the effectiveness of an electrochemical process using graphite and platinum electrodes and photocatalytic properties of titanium dioxide nanoparticles stabilized on bentonite at different reaction times for removal of chromium and organic materials from leachate. Equipment used in the electrochemical reactor included an anode electrode plate, a commercial platinum electrode and a graphite cathode. We also evaluated the impact of electrical current density (1-4 A/m(2)), reaction time (1-8 h), concentration of catalyst (1-4 g/L) and UV radiation intensity (3-8 UV lamps). The results showed that the removal efficiency increased with increasing reaction time, current density, intensity of UV radiation and dose of catalyst. Moreover, biodegradability (BOD/COD ratio) was improved. Based on the results, this electrochemical pretreatment process can remove organics materials, heavy metals, reduce organic load and increase wastewater biodegradability. Thus, it can be used as an efficient option for treating sewage and preventing environment pollution. Keywords Author Keywords:Leachate; Organic matter; Chromium; Electrochemical; Photocatalytic processes KeyWords Plus:WASTE-WATER; ALUMINUM ELECTRODES; ELECTROCOAGULATION; OXIDATION; IRRADIATION; WASTEWATERS; DEGRADATION; REACTOR; CR(VI); IRON

THE DYNAMICS OF ENDEGENOUS HORMONES ACTIVITY IN PLANT LEAVES DEPENDING ON THE ALTITUDE OF THEIR GROWING

The hormonal response of cultivated and wild plants to high intensity of UV-radiation and other stress factors of the highlands was studied. The activity of auxins and growth inhibitors substances in wheat (Triticum aеstivum L), barley (Hordium vulgare L), horse bean (Vicia faba L), and eurotia (Ceratoides papposa) leaves, that grew in a field condition were analyzed at different stages of development, using thin-layer chromatography and bioassay. The leaves of cultivated plants (2320 and 2700 m above the sea level) and wild plants (2320 and 4000 m above the sea level) were collected at two elevations in Pamir highland (Tajikistan). The level of auxin activity at the beginning of ontogenesis in plant leaves that grew at both elevations was relatively higher in comparison with the activity of growth inhibitors. However, at the end of the vegetation period an increase in growth inhibitor activity was observed in plant leaves at both elevations. Increasing of the total auxin activity in plants was observed at low altitude compared to higher. Conversely, the activity of growth inhibitors substances increased in plants that grow at higher elevations.

Characteristic shrinkage evaluation of photocurable materials

Photocurable materials have many advantages such as rapid curing, low energy consumption and a broad variety of favorable characteristics; as a result, their application areas are currently expanding. In order to fully utilize the properties of these materials, the related “shrinkage” problem (corresponding to the specific volume reduction due to the reaction between monomer species) must be resolved first. In this study, we investigated the dependence of the linear shrinkage of a monomer in the axial direction on various internal and external factors. In addition, a complementary relationship describing the photocuring behavior of a polymer was studied by photo-differential scanning calorimetry (photo-DSC). The observed shrinkage characteristics depend on the monomer size and structure, UV radiation intensity and photoinitiator concentration. In contrast to the photo-DSC results, the monomer shrinkage parameters are related to the bulk properties of a material. Hence, the dependence of the material depth profile on external factors was evaluated.

Seasonal changes in the concentrations of airborne bacteria emitted from a large wastewater treatment plant

Various factors influence the concentrations of bacteria and fungi found in the air surrounding wastewater treatment plants. These include the relative humidity, temperature, intensity of UV and visible radiation, and wind speed. Typically, higher emissions of bioaerosols are observed in the summer months due to the smaller amount of rainfall. The purpose of this study was to undertake a microbiological analysis of wastewater samples from a wastewater treatment plant (with samples taken before and after treatment) together with an analysis of bioaerosol samples taken in and around the plant. The study was undertaken in different seasons and samples were collected during a variety wastewater and sludge treatment operations. The most intense airborne emissions were found in the summer when, in most cases, all groups of bacteria (mesophilic bacteria, total coliforms, faecal coliforms and mannitol-positive staphylococci) were isolated from the air samples. The highest concentrations of airborne bacteria were observed at a grit chamber and a sludge storage site. The same seasonal trend was found in wastewater – bacteria numbers were significantly higher in the summer; mannitol-positive staphylococci were only present in treated wastewater in the summer.

Flower-like ZnO hollow microspheres on ceramic mesh substrate for photocatalytic reduction of Cr(VI) in tannery wastewater

Flower-like ZnO hollow microspheres were synthesized on flexible ceramic mesh substrate using a simple and economical hydrothermal technique and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The photocatalytic reduction of Cr(VI) in leather tannery wastewater by flower-like ZnO hollow microspheres was evaluated under ultraviolet light irradiation for the first time. The addition of different organics and pH value of the reaction solution played important roles in the photocatalytic reduction of Cr(VI). In addition, UV radiation intensity and catalyst content were critical parameters in the photocatalytic reduction process and their effects were also investigated. Under the optimal conditions, ZnO hollow microspheres exhibited excellent removal efficiency of Cr(VI) (~86%) and good photocatalytic stability. Moreover, more than 24% biochemical oxygen demand (BOD5), 32% chemical oxygen demand (COD) and 30% total organic carbon (TOC) of tannery wastewater were reduced significantly after only 180min of exposure to the UV lamp. It shows much promise to be an attractive photocatalyst for photocatalytic application.

A novel cell culture model as a tool for forensic biology experiments and validations

To improve and advance DNA forensic casework investigation outcomes, extensive field and laboratory experiments are carried out in a broad range of relevant branches, such as touch and trace DNA, secondary DNA transfer and contamination confinement. Moreover, the development of new forensic tools, for example new sampling appliances, by commercial companies requires ongoing validation and assessment by forensic scientists. A frequent challenge in these kinds of experiments and validations is the lack of a stable, reproducible and flexible biological reference material. As a possible solution, we present here a cell culture model based on skin-derived human dermal fibroblasts. Cultured cells were harvested, quantified and dried on glass slides. These slides were used in adhesive tape-lifting experiments and tests of DNA crossover confinement by UV irradiation. The use of this model enabled a simple and concise comparison between four adhesive tapes, as well as a straightforward demonstration of the effect of UV irradiation intensities on DNA quantity and degradation. In conclusion, we believe this model has great potential to serve as an efficient research tool in forensic biology.

Formation of the center of ignition in a CH3Cl–Cl2 mixture under the action of UV light

The dependence of temperature on time is investigated using a microthermocouple at different distances from a UV light source in a mixture of chlorine and chloromethane. These relationships give an idea of the size and location of a center of photoignition. It is found that if the size of the reaction vessel in the direction of the luminous flux is much greater than the dimensions of the ignition center, the thermal expansion of a reacting gas mixture has a huge impact on such photoignition parameters as the critical concentration limits and the critical intensity of UV radiation. It is found that by increasing the length of the vessel, some chlorinated combustible mixtures lose the ability to ignite when exposed to UV light.

Solar Photoelectro-Fenton Degradation of Acid Orange 7 Azo Dye in a Solar Flow Plant: Optimization by Response Surface Methodology

The experimental variables to optimize the solar photoelectro-Fenton (SPEF) degradation of 10 L of Acid Orange 7 (AO7) azo dye in 0.05 M Na2SO4 of pH 3.0 have been determined from a central composite rotatable design and response surface methodology. Trials were performed with a solar flow plant with a Pt/air-diffusion reactor generating H2O2 and a solar compound parabolic collector photoreactor under an UV irradiation intensity of about 31 W m−2. Optimum variables of 4.0 A, 0.75 mM Fe2+, and 150 mg L−1 total organic carbon (TOC) of the azo dye were found for 90 % color and 70 % TOC removals. Under optimized conditions, total decolorization was achieved in 300 min, but AO7 decay obeyed a pseudo-first-order kinetics to disappear in 80 min, pointing to the generation of recalcitrant colored aromatic products. After 360 min of electrolysis, TOC was reduced by 96 %, with 64 % mineralization current efficiency and 133 kWh kg−1 TOC energy consumption. The final solution contained carboxylic acids like tartronic, oxalic, oxamic, and in larger proportion, formic. An almost total mineralization was achieved by SPEF due to the persistence of Fe(III)-formate complexes to be photolyzed by sunlight. The initial N of the azo dye was mainly released as NH4 +.