Ultraviolet Violet Research Articles

Development of an Environment and Climate Data Acquisition System (EC-DAQS) for Radio Propagation Studies

Most weather monitoring systems used for measuring meteorological parameters are imported. For many developing countries like Nigeria, importing measuring instruments is practically bedeviled with problems due to erratic exchange rates. This has hampered weather-related research especially in radio propagation studies where finite weather data are required. In the quest to develop a home-grown monitoring system, this paper presents an Environment and Climate data acquisition system (EC-DAQS). In the EC-DAQS, an Arduino Mega2560 microcontroller along with six environment and weather sensors were coded to measure, record and display atmospheric parameters. For digital signal processing and data logging, the sensors were interconnected to the microcontroller through an analogue-to-digital-converter (ADC). The measured data were displayed on a liquid crystal display (LCD) screen remotely connected to the controller. Temperature, Ultraviolet Violet (UV) rays, humidity and sound level were tested and calibrated with “off-the shelf” instruments. The mean bias error (MBE) and the root mean square error (RMSE) were used to validate the temperature readings from the EC-DAQS with readings from a standard infra-red thermometer. The low results of the MBE (0.16°C) and RMSE (0.51°C) – showed close proximity between the EC-DAQS and the standard infra-red digital thermometer measurements. Also, the equation obtained from modelling is a straight line of near unity slope (0.994) and a correlation of 99.98%. The EC-DAQS developed will be a useful meteorological instrument, and a suitable replacement for imported weather stations in terms of performance, cost and maintenance. It will also provide some invaluable data needed for radio-propagation research and applications.

Cryptochrome 1a localisation in light- and dark-adapted retinae of several migratory and non-migratory bird species: no signs of light-dependent activation

The magnetic compass of birds seems to be based on light-dependent radical-pair processes in the eyes. Cryptochromes are currently the only candidate proteins known in vertebrates that may serve as the primary radical-pair-based magnetoreceptor molecules. Previous immunohistochemical studies have suggested that cryptochrome 1a (Cry1a) is localised in the photoreceptor outer segments of the ultraviolet/violet (UV/V) cones, and it has been claimed that differences in Cry1a antibody staining intensities show that Cry1a is activated by light and that this should make Cry1a the most likely magnetoreceptive candidate molecule. Here, we present an independent study of Cry1a distribution within retinae of several bird species, ranging from non-migratory domestic chicken and rock pigeon to night-migratory passerines, using both the previously used antibody and two newly generated antibodies, one against the same epitope as the originally used antibody and one against a different epitope of Cry1a. We confirm the UV/V cone outer segment localisation of Cry1a in all the tested bird species. In some stainings, we found Cry1a immunoreactivity as a distinct punctate pattern throughout the whole length of the UV/V cone outer segments. These dots with a diameter of around 170 nm might suggest that many Cry1a molecules accumulate in distinct spots in the UV/V cone outer segments. However, we did not see any notable difference in Cry1a immunoreactivity between light- and dark-adapted retinae. We find no evidence whatsoever that a C-terminal antibody against Cry1a labels only a light-activated form of the Cry1a protein.

Optical band gap engineering of ZnO nanophosphors via Cu incorporation for ultraviolet–violet LED

The tunability of optical band gap and augmentation of luminescence intensity of Cu-doped ZnO nanophosphors for ultraviolet and violet light-emitting diodes grown by microwave-assisted aqueous solution technique were studied at room temperature for various doping concentrations. The UV–Vis spectral analysis demonstrated that band gap engineering of ZnO nanophosphors can be performed through incorporation of Cu ions into the ZnO matrix by controlling the dopant content. The photoluminescence investigations revealed that a strong UV emission centred around 346–348 nm and an intense violet band comprising of two peaks centred about 403 nm and 424 nm occur in the absence of any other band. A thorough study of the defect-related PL spectra elucidated that these violet peaks originated from energetically more probable deep-acceptor zinc vacancy and shallow-donor zinc interstitial defect transitions. The luminescence intensity of nanophosphors can be optimized through modification of intrinsic defect density by adjusting Cu concentration in the ZnO host. The results are significant for ZnO-based photoluminescence cutting-edge technology.

SiPM optical modules for the Schwarzschild-Couder Medium Size Telescopes proposed for the CTA observatory

Silicon Photomultipliers (SiPMs) are excellent devices to detect the faint and short Cherenkov light emitted in high energy atmospheric showers, and therefore suitable for use in imaging air Cherenkov Telescopes. The high density Near Ultraviolet Violet SiPMs (NUV-HD3) produced by Fondazione Bruno Kessler (FBK) in collaboration with INFN were used to equip optical modules for a possible upgrade of the Schwarzschild-Couder Telescope camera prototype, in the framework of the Cherenkov Telescope Array project. SiPMs are 6×6 mm2 devices based on 40×40 μm2 microcells optimized for photo-detection at the NUV wavelengths. More than 40 optical modules, each composed by a 4×4 array of SiPMs, were assembled. In this contribution we report on the development and on the assembly of the optical modules, their validation and integration in the camera.

Isolation and characterization of a new gamma and UV radiation resistant bacterium from soil samples of an iranian radioactive site and analysis of its pigment

Radiation resistance has been detected dispersedly among bacteria and some microorganisms growing in natural radioactive environments. Herein, we provide data of isolation and characterization of a new radiation resistant bacterium from a radioactive site in Mashhad, Iran. The soil samples were collected and serial dilution plating was performed in TGY agar. All distinct colonies were isolated and irradiated by gamma radiation. The radioresistant bacterium was characterized by its morphology, biochemistry properties and 16S rRNA gene sequencing. In addition, pigment of the isolate was analysed by spectroscopic properties and LC-MS system and its antioxidant activity was measured by DPPH activity. Among 20 pure colonies, a new gamma and ultraviolet violet radiation resistant bacterium was designated as F3 strain. The isolated bacterium was coccoid in shape, nonmotile, non-sporulating, aerobic and with yellow pigmentation. Phylogenetic analysis based on 16S rRNA gene sequencing revealed that the strain related most closely to Micrococcus lylae. The results of spectroscopic and LC-MS analysis of the pigment show that it was belonged to Astaxanthin. Moreover, the isolate was resistant to gamma radiation (15 kGy) and UV light (400 j m−2). The isolate is the first report on radioresistant bacteria belonged to the Micrococcus genus isolated from radioactive region. Due to its antioxidant activity, pigment production and radiation resistant properties, we supposed that this isolate could be a candidate in industrial and bioremediation applications.

Synthesis and characterization of LiNbO3 nanocrystals prepared by the aerosol assisted chemical vapor deposition method

This work reports the synthesis of LiNbO3 nanocrystals by an aerosol assisted chemical vapor deposition method, onto silicon (001) substrates. Some of the nanocrystals showed a hexagonal morphology and characteristic sizes ranging from a few tens to a few hundreds of nanometers. The nanocrystals with hexagonal structure were obtained at 773K using a carrier gas flow of 6L/min and a deposition time of 90min. Structural, morphological, photoluminescence and cathodoluminescence properties were studied by grazing incidence X-ray diffraction, scanning electron microscopy, high resolution transmission electron microscopy, fluorospectrometry, and cathodoluminescence, respectively. An extraordinary violet luminescence at 396nm with excitation in UV region (280nm) was observed in one of the samples. Cathodoluminescence (CL) imaging and spectroscopy studies of the nanocrystals exhibit stimulated emission of light in the near ultraviolet–violet–green spectral region. The emission peaks in CL spectra varied according to the nature of nanoparticles. A red-shift in the CL spectra with a decrease in the particle size was observed. Apparently the size of LiNbO3 typical nanocrystals investigated in this work has tuned the photoluminescence emission. This result encourages the use and integration of LiNbO3 nanocrystals into nanophotonics applications.

Improvement of the electroluminescence performance of ZnO nanorods/p-GaN light emitting diodes with a ZnO films interlayer

Heterostructure light-emitting diodes (LEDs) were fabricated by growing ZnO nanorods and undoped ZnO films on p-GaN templates. The heterojunction showed a diode-like I—V characteristic and emitted electroluminescence (EL) peaks at 383 nm, 402 nm, 438 nm, and 507 nm under forward bias. Since the electrons from ZnO nanorods and the holes from p-GaN could be injected into ZnO films with a relatively low carrier concentration and mobility, the radiative recombination was mainly confined in the ZnO film region. As a result, the ZnO nanorods/i-ZnO/p-GaN light emitting diode exhibits a stronger ultraviolet—violet emission peak.

Luminescent ZnS:Mn/thioglycerol and ZnS:Mn/ZnS core/shell nanocrystals: Synthesis and characterization

The synthesis and photoluminescent properties of Mn2+-doped ZnS nanocrystals coated with an organic shell of thioglycerol and an inorganic shell of ZnS are reported in this paper. The photoluminescence spectra of bare ZnS:Mn nanocrystals exhibited a dominant ultraviolet–violet emission peaked at the wavelength range of 395–450nm and an weak orange emission peaked at the wavelength range of 580–600nm. The ultraviolet–violet emission was attributed to the surface defect states. The orange emission was assigned to the 4T1–6A1 transition of Mn2+ ions. These two channels of radiative recombination compete with each other. The coating ZnS:Mn nanocrystals with the thioglycerol shells or the ZnS shells reduced the surface defects and led to the enhancement of the emission of Mn2+ ions. On the other hand, the overcoating ZnS:Mn nanocrystals by thioglycerol shell restricted the growth of the nanocrystals, while the overcoating ZnS:Mn nanocrystals by ZnS shells made the band edge of the ZnS:Mn/ZnS core/shell nanocrystals shift to the lower energy side (the red shift) compared with the bare ZnS:Mn nanocrystals as observed in both the absorption and the photoluminescence excitation spectra.

Application of TL-OSL from surface soil to retrospective dosimetry

Abstract Radiation-induced luminescence dosimetry was developed using combined thermoluminescence (TL) and optically stimulated luminescence (OSL) measurements from natural quartz in Japanese soil. TL emissions from the quartz grains were observed at ∼350–450 nm (ultraviolet–violet TL; UVTL) and 630 nm (red TL; RTL) using a TL spectrometer system. The UVTL glowcurve was measured for an irradiated sample, which exhibited five peaks: at 80, 110, 130, 200 and 270 °C. On the other hand, the UVTL glowcurve was also measured for an as-received sample, which showed no peaks in any range of heating temperature. In the irradiated UVTL glowcurves, the integrated UVTL intensity at each peak temperature was proportional to the irradiation dose except for the 80 °C peak. The TL-OSL protocol was used in a recovery test for determining the irradiation dose of a sample using thermal treatment for TL measurement instead of preheat treatment before OSL measurement. In the test, the doses measured by the UVTL peak at 200 °C agreed well with the given dose and the doses measured by OSL were 80% of the given dose at an interval of 120 h between dose delivery and dose measurement. From these results, we concluded that TL-OSL dosimetry is suitable for accident evaluation although further research is required to improve the protocol.

Avian Ultraviolet/Violet Cones Identified as Probable Magnetoreceptors

BackgroundThe Radical-Pair-Model postulates that the reception of magnetic compass directions in birds is based on spin-chemical reactions in specialized photopigments in the eye, with cryptochromes discussed as candidate molecules. But so far, the exact subcellular characterization of these molecules in the retina remained unknown.Methodology/Principal FindingsWe here describe the localization of cryptochrome 1a (Cry1a) in the retina of European robins, Erithacus rubecula, and domestic chickens, Gallus gallus, two species that have been shown to use the magnetic field for compass orientation. In both species, Cry1a is present exclusively in the ultraviolet/violet (UV/V) cones that are distributed across the entire retina. Electron microscopy shows Cry1a in ordered bands along the membrane discs of the outer segment, and cell fractionation reveals Cry1a in the membrane fraction, suggesting the possibility that Cry1a is anchored along membranes.Conclusions/SignificanceWe provide first structural evidence that Cry1a occurs within a sensory structure arranged in a way that fulfils essential requirements of the Radical-Pair-Model. Our findings, identifying the UV/V-cones as probable magnetoreceptors, support the assumption that Cry1a is indeed the receptor molecule mediating information on magnetic directions, and thus provide the Radical-Pair-Model with a profound histological background.

Colorimetric comparison of light-filtering intraocular lenses and human crystalline lenses at various ages

To perform colorimetric characterization of 2 blue light-filtering intraocular lens (IOL) models and an IOL that filters ultraviolet-violet (UV-v) light and compare the charactizations with those of a standard UV light-filtering IOL and the human crystalline lens at various ages. Department of Clinical Physiopathology, University of Florence, and National Institute of Applied Optics, CNR, Florence, Italy. Experimental study. Three IOLs of each model with different dioptric powers (16.0, 21.0, and 26.0 diopters) were analyzed. The colorimetric coordinates of the IOLs were calculated by measuring their transmission spectra using a microspectroscopy technique. Subsequently, a parameter (ΔE) that was proportional to the perceived color differences was defined. The results of the IOLs and of the human crystalline lens at different ages (4, 22, 41, 53, and 72 years; values taken from the literature) were compared. The colorimetric analysis was performed using Commission Internationale de l'Éclairage standards. The maximum ΔE value was with the standard UV light-filtering IOL at any crystalline lens age and was greatest with a 72-year-old human lens. The minimum ΔE value was obtained for both blue light-filtering IOLs with middle-aged human lenses. None of the analyzed IOLs had the same colorimetric performance of the human crystalline lens. The 2 blue light-filtering IOLs best reproduced yellowing of the human lens at 40 to 50 years of age. No author has a financial or proprietary interest in any material or method mentioned.

Developing an on-line derivatization of FAs by microwave irradiation coupled to HPLC separation with UV detection

The development of analytical methods for routine simultaneous identification and quantification of carboxylic fatty acids (CFAs) are required in different fields, such as, pharmaceutical cosmetics, food products and formulations of water–microemulsion–oil systems. Determination of CFAs has been developed mainly by gas chromatography (GC). As an alternative to GC, liquid chromatography (LC) has better sensitivity and selectivity. However, most CFAs show no useful absorption in ultraviolet–violet (UV–Vis) region, one of the more used detection technique in high-performance liquid chromatography (HPLC). In order to allow the use of UV–Vis detection, the use of pre-column derivatization has been reported to increase sensitivity and selectivity. Therefore, establishment of a simpler and faster on-line method with complete separation is needed for the screening of large numbers of samples. 2,4-Dinitrophenylhydrazine (2,4-DNPH.), benzoil chloride (BC), and phenylhydrazine (PH) were used for derivatization of different FAs by microwaves radiation (MW). After the on-line derivatization, products were separated and quantified by HPLC. Reactor coil was placed inside of microwaves oven at 450 W. Parameters as flow, amount of reagents, irradiation time, and chromatographic conditions were optimized. The continuous analysis using the MW–HPLC–UV system provided high sensitivity and reduced both the amount of reagent used and the analysis times. This proposed method can be used for the routine analysis of FAs contained in water–microemulsion–oil systems, to quantify the total acid fraction in each phase.

Combinatorial fabrication and studies of intense efficient ultraviolet–violet organic light-emitting device arrays

Arrays of ultraviolet–violet (indium tin oxide)/[copper phthalocyanine (CuPc)]/[4,4′-bis(9-carbazolyl)biphenyl (CBP)]/[2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4oxadiazole (Bu-PBD)]/CsF/Al organic light-emitting devices, fabricated combinatorially using a sliding shutter technique, are described. Comparison of the OLED electroluminescence and CBP photoluminescence spectra indicates that the emission originates from the bulk of that layer. In arrays of devices in which the thickness of the CuPc and Bu–PBD were varied, but that of CBP was fixed at 50 nm, the optimal radiance R was obtained at CuPc and Bu–PBD thicknesses of 15 and 18 nm, respectively. At 10 mA/cm2, R was 0.38 mW/cm2, i.e., the external quantum efficiency was 1.25%; R increased to ∼1.2 mW/cm2 at 100 mA/cm2.

The mechanism of muscle-fiber relaxation adenosine triphosphatase and relaxing activity of the sarcotubular system

A subcellular fraction from frog skeletal muscle, composed of fragments originating from the sarcotubular system, is shown to induce inhibition of the myofibrillar ATPase. No relaxing activity is found in the fractions composed of mitochondrial fragments. The relaxing activity of the Kielley and Meyerhof ATPase preparation could be attributed to the large number of sarcotubular vesicles present in the preparation. It is concluded that the sarcotubular system is the only site in the muscle cell where the relaxing factor is produced. The functional relation between ATPase and relaxing activities was studied by testing the effect of several physical and chemical agents on the rate of both activities. ATPase and relaxing activities were both found to be stimulated by addition of sodium ions and inhibited by the addition of Ca 2+, Atebrine, and after ultraviolet irradiation. Addition of FMN of FAD, in the presence of Atebrine or after irradiation with ultraviolet violet light, results in a complete restoration of ATPase and relaxing activities. Stimulation of the myofibrillar ATPase activity by ultraviolet irradiation is found in frog myofibrils suspension. In these preparations a contamination from residues of the sarcotubular system is demonstrated. Addition of 5 m M Amytal, which does not interfere either with the myofibrillar or the sarcotubular ATPase, results in a complete inhibition of the relaxing activity. From the above findings the hypothesis is developed that the sarcotubular system inhibits the interaction between myosin and actin by means of a phosphorylated high-energy intermediate synthesized through the operation of the sarcotubular ATPase. The evidence in favour of this hypothesis is discussed.