Short Ultraviolet Wavelengths Research Articles

Ba(dl-C4H4O5) — An alkaline earth metal-dicarboxylate hybrid crystal with the synergy of multi-bonds

The organic–inorganic hybrid crystal, Ba(dl-C4H4O5), has been firstly prepared by hydrothermal method. It crystallizes in monoclinic crystal system with a centrosymmetric space group of P21/c with a=8.150(2) Å, b=10.447(3) Å, c=6.938(2) Å, β=95.599(3)° and Z=4. In this compound, the coexistence of organic ligand and the alkaline earth metal cation leads to the diversity of chemical bonds. The synergy of Ba–O ionic bonds and hydrogen bonds strengthens the crystal structure. Characterization of this earth metal-dicarboxylate hybrid crystal is described by using powder X-ray diffraction, infrared spectroscopy, UV–vis–NIR diffuse reflectance spectrum and the TG curve. In addition, Ba(dl-C4H4O5) possesses a short ultraviolet cutoff wavelength lower than 230nm determined by the electronic transition of C–O group, which signifies the potential use in UV region applications. And the electronic structure and optical properties are studied by first principle calculation method, which obtains a birefringence value of 0.04.

White-light vs. short-wavelength ultraviolet illumination of fingerprints developed with columnar thin films of Alq3

The deposition of a columnar thin film (CTF) of Alq3 on partial-bloody fingerprints has recently been shown to yield better development than many traditional development techniques. The Alq3-CTF-developed fingerprint is illuminated by short-wavelength ultraviolet (UV) light, to take advantage of the luminescence of Alq3. Experiments were undertaken to test the hypothesis that white-light illumination of Alq3-CTF-developed fingerprints is inferior to UV illumination. Objective and subjective grading of photographs of 18 Alq3-CTF-developed fingerprints on brass strongly indicate that white-light illumination is likely to be suitable for comparison; if that fails to yield a strong conclusion, then a photograph taken with short-wavelength UV illumination should be examined by a human. This procedure would reduce not only UV-induced health hazards in the laboratory but also the chance of denaturing potentially useful DNA information contained in the fingerprint.

Electrical Breakdown Properties and Space Charge Formation in High Temperature Region in Ultraviolet Ray Irradiated PVC

SUMMARYPolyvinyl chloride (PVC) is the most popular insulating material for electric wiring instruments. However, an exothermic reaction above 150 °C may cause deterioration of the insulating properties of PVC. Therefore, it is important to clarify the heat degradation in PVC, not only to investigate the ignition of electrical wiring products but also to use electrical products safely. It is known that ultraviolet (UV) irradiation causes chemical deterioration of PVC and an increase in its conductivity. Generally, it has been thought that the electrical breakdown properties, electrical conduction, and insulating performance are affected by space charge accumulation in an insulating material. A high temperature pulsed electroacoustic (PEA) system usable up to 250 °C has been developed, and the PEA system can measure the space charge distribution and conduction current in the high temperature range simultaneously. In this investigation, the space charge distribution and conduction current were measured up to electrical breakdown in a non‐UV irradiated sample (normal PVC) and in 353 nm and 253 nm UV‐irradiated PVC samples in the range from room temperature to 200 °C in a DC electric field. In the short wavelength UV irradiated PVC sample (253 nm, 300 h), a deterioration of breakdown strength at 90 °C to 150 °C and negative packet‐like charges were observed at 60 °C and 100 °C, a positive charge accumulated in front of both the anode and cathode above 90 °C, and a higher electric field near the cathode side because the positive charge of the cathode side was greater.

Occurrence and induction of a ultraviolet‐absorbing substance in the cyanobacterium Fischerella muscicola TISTR8215

SummaryThe filamentous cyanobacterium Fischerella muscicola TISTR8215 was tested for the presence of ultraviolet (UV)‐absorbing mycosporine‐like amino acids (MAAs) and their induction by UV radiation. Reverse‐phase high performance liquid chromatographic coupled with photodiode‐array detection studies revealed the presence of a MAA having an absorption maximum at 332 nm and a retention time of around 16.1 min. Based on absorption maximum, the compound was designated as M‐332. This is the first report for the occurrence of a MAA and its inducibility as influenced by UV radiation in Fischerella strains studied so far. Photosynthetically active radiation (PAR) had no significant impact on MAA induction. PAR + UV‐A radiation significantly induced the synthesis of M‐332; however, PAR + UV‐A + UV‐B radiation conferred highest impact on MAA synthesis. The cultures exposed to alternate light and dark conditions showed the induction of M‐332 synthesis mostly during the light period in contrast to the decreased levels of M‐322 during the dark period suggesting a circadian induction of its synthesis. Overall results indicate that F. muscicola may protect itself from deleterious short wavelength UV radiation by synthesizing the photoprotective compounds particularly during summer time in its natural brightly‐lit habitats.

Instability Induced by Ultraviolet Light in ZnO Thin-Film Transistors

We investigate the electrical properties of ZnO thin-film transistors (TFTs) under the ultraviolet (UV) light illumination to clarify the device reliability. The ON/OFF current ratio of ZnO TFTs shows an evident reduction due to the creation of UV photo-induced current. This behavior degradation becomes severe for devices exposed to a short-wavelength UV light. The persistent photoconductivity is observed in ZnO TFTs under the UV illumination with a much slower decay for the ON-state than the OFF-state, which is attributed to the reduced recombination under a positive gate bias. The UV light instabilities of ZnO TFTs can be explained on the basis of UV photoexcited oxygen vacancies. A feasible mechanism model is proposed in this paper. These observations and analytical model not only provide useful physical insight into the device behaviors, but also offer basic design guideline for oxide TFTs.

CDBA-liposome as an effective sunscreen with longer UV protection and longer shelf life

Harmful effects caused by the absorption of ultraviolet (UV) light can be reduced by using sunscreens. The long-wavelength UV (UVA) and short-wavelength UV (UVB) protective effects of an azobenzene compound, 4-cholesterocarbonyl-4′-(N,N′-diethylaminobutyloxy) azobenzene (CDBA) liposomal formulation, especially its repeated photo-isomerization were evaluated in the presence of substrates such as propylene glycol and glycerol. It was indicated that periodic UV and visible light irradiation did not affect the photo-isomerization and the structure of CDBA-liposome. The stability and photo-isomerization of CDBA-liposomes were not affected by coexistence of 5% propylene glycol and 5% glycerol. CDBA-liposomes could still perform photo-controlled release of encapsulated active component when mixed with propylene glycol. Moreover, the CDBA-liposome mixed with the cream substrate showed protective function for both UVA and UVB in vitro. The in vivo tests using nude mouse confirmed that the CDBA-liposome could provide a good UV protective efficacy with longer shelf life. Therefore, CDBA-liposomes have the potential using as a new type of commercial sunscreen.

Balancing the Risk of Eye Irritation from UV‐C with Infection from Bioaerosols

The very aspect (phototoxicity) that makes short-wavelength ultraviolet (UV) radiation an effective germicidal agent also is responsible for the unwanted side effects of erythema (reddening of the skin) and photokeratitis ("welder's flash" or "snow-blindness"). Overexposure to this short-wavelength UV radiation can produce these unwanted side effects from a very mild irritation of the skin and eyes to a rather painful case of photokeratitis. These effects are fortunately transient, as only superficial cells of the eye-the corneal epithelium-and the most superficial layer of the skin-the superficial epidermis-are significantly affected. Normal turnover of these cells soon erase the signs and symptoms of these effects. Radiant energy in the UV-C band has very shallow penetration depths which account for the very superficial nature of any injury to the skin and eyes from excessive exposure, minimum risk of delayed effects and at the same time the strong absorption by bioaerosols. Guidelines for human exposure to UV-C must be applied intelligently so as not to limit germicidal efficacy in upper-room ultraviolet germicidal irradiation.

The Evolution of Complexity in the Visual Systems of Stomatopods: Insights from Transcriptomics

Stomatopod crustaceans have complex visual systems containing up to 16 different spectral classes of photoreceptors, more than described for any other animal. A previous molecular study of this visual system focusing on the expression of opsin genes found many more transcripts than predicted on the basis of physiology, but was unable to fully document the expressed opsin genes responsible for this diversity. Furthermore, questions remain about how other components of phototransduction cascades are involved. This study continues prior investigations by examining the molecular function of stomatopods' visual systems using new whole eye 454 transcriptome datasets from two species, Hemisquilla californiensis and Pseudosquilla ciliata. These two species represent taxonomic diversity within the order Stomatopoda, as well as variations in the anatomy and physiology of the visual system. Using an evolutionary placement algorithm to annotate the transcriptome, we identified the presence of nine components of the stomatopods' G-protein-coupled receptor (GPCR) phototransduction cascade, including two visual arrestins, subunits of the heterotrimeric G-protein, phospholipase C, transient receptor potential channels, and opsin transcripts. The set of expressed transduction genes suggests that stomatopods utilize a Gq-mediated GPCR-signaling cascade. The most notable difference in expression between the phototransduction cascades of the two species was the number of opsin contigs recovered, with 18 contigs found in retinas of H. californiensis, and 49 contigs in those of P. ciliata. Based on phylogenetic placement and fragment overlap, these contigs were estimated to represent 14 and 33 expressed transcripts, respectively. These data expand the known opsin diversity in stomatopods to clades of arthropod opsins that are sensitive to short wavelengths and ultraviolet wavelengths and confirm the results of previous studies recovering more opsin transcripts than spectrally distinct types of photoreceptors. Many of the recovered transcripts were phylogenetically placed in an evolutionary clade of crustacean opsin sequences that is rapidly expanding as the visual systems from more species are investigated. We discuss these results in relation to the emerging pattern, particularly in crustacean visual systems, of the expression of multiple opsin transcripts in photoreceptors of the same spectral class, and even in single photoreceptor cells.

Laser-induced breakdown spectroscopy of Zr in short ultraviolet wavelength range

Emission and absorption spectra of a laser-induced zirconium plasma are studied at early times after plasma formation in the short UV spectral range from 190 to 240nm. Many lines from highly ionized Zr ions, such as Zr IV at 216.4 and 228.7nm and Zr III at 194.1, 194.7, 193.1, 196.3, 196.6, 197.5, 199.0, 200.3, 200.8, 202.8, 203.6, 205.7, 206.1, 207.1, 208.6, 210.2, 211.4, 217.6, and 219.1nm have been found in the plasma under ambient and vacuum conditions. These lines could be detected in both single-pulse and double-pulse ablation modes. Several of the detected lines, namely those observed at 195.0, 198.2, 199.7, 229.4, 231.6, 232.4 and 233.0nm, could not be attributed to Zr after inspecting known spectral data bases. From the temporal persistence behavior of these lines, it is concluded that they most likely belong to Zr I and Zr II emission lines that have not previously been reported.

Detecting RNA–Protein Interactions by Photocross-Linking Using RNA Molecules Containing Uridine Analogs

Various cross-linking techniques form covalent attachments between proteins and RNAs. Straight ultraviolet (UV) cross-linking using short-wavelength UV light is inherently very inefficient. Therefore, it is often desirable to increase the efficiency of cross-linking. The uridine analogs 4-thiouridine and halogenated uridine (5-bromouridine or 5-iodouridine) are much more photoreactive than uridine. Accordingly, RNAs substituted with these bases are quite effective for cross-linking applications. This protocol describes the detection of RNA-protein interactions by photocross-linking using RNA molecules containing 4-thiouridine, but identical procedures apply to using 5-bromouridine or 5-iodouridine. Fully substituted RNAs are useful in determining whether any proteins interact with the RNA of interest. However, it may be preferable to use site-specifically substituted RNA if one has foreknowledge of critical regions in the RNA of interest. For any cross-linking application using substituted RNA, it is essential to remember that the uridine analogs are activated at a wavelength >304 nm (312 nm) than is used for short-wavelength (254 nm) cross-linking.

Spectral irradiance dependence of sunlight effects on plankton dimethylsulfide production

We investigated the short‐term effects of variable solar irradiance and spectrum on the gross biological production of dimethylsulfide (DMS), a trace gas with potential climatic effects, in eight experiments performed at different times of the year in a northwest Mediterranean coastal site. Experimentally determined net community DMS production, DMS photolysis, and dark microbial DMS consumption rates were used to calculate gross community DMS production by budgeting. In addition, the composition of the bacterioplankton and phytoplankton communities in the initial samples, and the photoinhibition of bulk bacterial heterotrophic activity and phytoplankton photosynthetic efficiency were monitored. Our results show that: (1) gross DMS production is irradiance dependent, with a maximum short‐term stimulation factor of 2‐ to 6‐fold compared to dark incubations; (2) its spectral shape is variable but generally similar to that of phytoplankton photoinhibition or photodamage, with more effective stimulation at shorter ultraviolet wavelengths; and (3) stronger stimulation occurs when samples are overexposed with respect to their prior exposure. Remarkably, the photoresponse of gross DMS production was in most cases strong enough to (at least) compensate the photochemical DMS loss at the water subsurface. Such response would prevent DMS depletion in stratified and highly irradiated waters. Since the initial microbial communities were representative of meso‐ to oligotrophic conditions, our observations should apply to a wide variety of oceanic regimes.

Measurement of solar UV radiation in Antarctica with collagen sheets

Collagen sheets were used in a unique evaluation method to examine skin damage caused by ultraviolet (UV) light of short wavelength during a season of the Antarctic ozone hole. The collagen sheets were exposed outdoors for 25 and 50 d, in the spring when the ozone hole was formed and in the ozone-hole-free autumn. Extracts from the exposed collagen sheets were analyzed for total protein and terminal amino acid concentrations as an index of collagen fragmentation. The results show that the amount of extractable collagen and terminal amino acid concentration in the spring exposure were approximately double and five times higher, respectively, when compared with those in the autumn exposure. During the ozone hole occurrence, the terminal amino acid concentration of the extracted collagen was about five times higher when exposure lasted 50 d from mid-September to the end of October compared to when exposure lasted 25 d from mid-September to early October. This result could be attributed to a limited amount of short-wavelength UV radiation reaching the ground surface as a result of the low height of the sun in September, when the ozone hole occurred. In fact, UV radiation measurements taken at Syowa Station indicate that short-wavelength UV radiation in the range 290-295 nm was not detected until approximately 1-2 months after the beginning of the ozone hole occurrence.

Silicon Carbide Ultraviolet Photodetector Modeling, Design and Experiments

We report measurements and modeling of silicon carbide (SiC) based ultraviolet photodetectors for the detection of light in the mid-to-short ultraviolet range where SiC’s absorption coefficients are high and the corresponding penetration depths are low. These large absorption coefficients result in increased susceptibility of photo-generated electron and holes to surface recombination and therefore give rise to lower quantum efficiencies. To increase responsivity and extend the detection capability of these photodetectors to short ultraviolet wavelengths (or UVC), we measure an existing silicon carbide avalanche photodiode (APD) designed and fabricated for 280 nm operation by General Electric Global Research Center, and then develop models and techniques to increase their operation range to lower UV wavelengths. The measurements aid the development and calibration of a silicon carbide modeling and design suite that is currently being used to assist the design of a new silicon carbide APD for UVC detection. Here the design considerations require low operating voltages, low noise, low dark count rate and high responsivity. We plan to satisfy design criteria by engineering thickness and doping of stacked layers as well as by designing an APD surface that gives rise to minimal recombination of electrons and holes generated by the incident light.

The dynamics of absorption coefficients of CDOM and particles in the St. Lawrence estuarine system: Biogeochemical and physical implications

Absorption spectra of chromophoric dissolved organic matter (CDOM) and particles were obtained in May 2007 in the St. Lawrence estuary (SLE, Canada), the northwestern Gulf of St. Lawrence (NWG), and the Saguenay Fjord (CDOM only), the main tributary of the SLE. CDOM absorption generally decreased downstream and with depth and showed an inverse relationship to tidal cycles. Phytoplankton absorption in surface water of the SLE increased seaward while non-algal particle absorption trended oppositely; both variables declined with depth. Surface water CDOM absorption surpassed particle absorption in the SLE while phytoplankton absorption dominated in the NWG. Elevated non-algal and CDOM absorption were found in the turbidity maximum zone near the head of the SLE. Enriched CDOM absorption also occurred in the bottom water of the lower SLE and NWG. The spectral slope ratio of CDOM absorption, defined as the ratio of the spectral slope between 275 and 295 nm to that between 350 and 400 nm, was confirmed to be an indicator of the source and molecular weight of CDOM. This surrogate functionality, however, failed for absorption spectra exhibiting shoulders in short ultraviolet wavelengths observed in deep waters of the SLE and NWG. CDOM absorption mainly displayed conservative mixing behavior in both the SLE and the Saguenay Fjord. CDOM was employed to trace the source identity of the Fjord's deepwater. It was found that the marine end member of the Fjord's deepwater possessed a salinity of 32.92 and a temperature of ca. 1 °C and originated from the intermediate cold layer of the lower SLE. The marine end member contributed 94% of the deepwater by volume while freshwater mainly flown from the Saguenay River supplied the remaining 6%. Implications of our results for remote sensing-based assessments of primary productivity, surface water circulation, and water column photochemistry in the SLE are also discussed.

Sensitivity of multi-angle photo-polarimetry to vertical layering and mixing of absorbing aerosols: Quantifying measurement uncertainties

The impact of tropospheric aerosols on climate can vary greatly based upon relatively small variations in aerosol properties, such as composition, shape and size distributions, as well as vertical layering. Polarimetric measurements have been advocated in recent years as an additional tool to better understand and retrieve the aerosol properties needed for improved predictions of aerosol radiative forcing on climate. The goal of this study is to introduce a formal approach to assessing the sensitivity of both intensity and polarization signals to absorbing aerosol layering, explicitly accounting for instrument measurement uncertainties. If ignored, sensitivity to aerosol height can introduce biases in aerosol property retrievals at short (ultraviolet or blue) wavelengths; if properly exploited, it may enable the extraction of some basic information on aerosol profiles. Employing a vector successive-orders-of-scattering (SOS) radiative transfer code, we conducted modeling experiments to determine how the measured Stokes vector elements are affected at 446 nm (blue band) by the vertical distribution, mixing and layering of smoke and dust aerosols under the assumption of a simple Lambertian surface and predefined aerosol microphysical properties. We find that smoke and dust vertical layering, if ignored, can introduce biases in radiometric and polarimetric aerosol property retrievals for aerosol optical depth ( AOD) above 0.3 (polarimetric) and AOD above 0.5 (radiometric), and should, therefore, be accounted for in retrievals at high aerosol loadings.

The current status of ultraviolet laser diodes

AbstractWe report on nitride laser diode lasing at short ultraviolet wavelengths. We first present room temperature operations of GaN/AlGaN multiple‐quantum‐well (MQW) laser diodes under pulsed current mode. Then we report on the results of thorough investigation of the device characteristics. The optical and temperature characteristics as well as the carrier recombination of the devices have been investigated. We lastly present the first demonstration of indium‐free nitride laser diode. The laser operation of the AlGaN MQW laser diodes open the door to laser operation at shorter ultraviolet wavelengths.

Evaluation of sol–gel derived Eu 2+ activated SrMgAl 2SiO 7 as a novel nanostructure luminescent pigment

A novel nanostructure pigment of Eu 2+ doped SrMgAl 2SiO 7 was prepared via the sol–gel route. The phase composition and condition of crystallites during heating were characterized by X-ray diffraction (XRD) analysis. Investigation of optical properties by spectrophotometer illustrated that under short ultraviolet excitation wavelength, the main emission peak occurred at about 415–420 nm. Also, relatively pure purplish blue color was observed that can be ascribed to the 4f 65d 1( 2D) →4f 7( 8S 7/2) transition of Eu 2+. The effect of calcination temperature on the luminescence properties of the phosphors was evaluated and, also in this case, scanning electron microscope (SEM) was employed. From colorimetry results, color coordinations of phosphor shift towards the deep blue region as calcination temperature increases. Finally, grain size of products at optimum calcination temperature was estimated to be about 20–30 nm using Scherrer’s equation, which was consistent with transmission electron microscopy (TEM) observations.

Influence of the absorption behavior of sunscreens in the short-wavelength UV range (UVB) and the long-wavelength UV range (UVA) on the relation of the UVB absorption to sun protection factor

The absorption of filter substances in sunscreens, reducing the incident ultraviolet (UV) radiation, is the basis for the protecting ability of such formulations. The erythema-correlated sun protection factor (SPF), depending mainly on the intensity of the UVB radiation, is the common value to quantify the efficacy of the formulations avoiding sunburn. An ex vivo method combining tape stripping and optical spectroscopy is applied to measure the absorption of sunscreens in the entire UV spectral range. The obtained relations between the short-wavelength UV (UVB) absorption and the SPF confirm a clear influence of the long-wavelength UV (UVA) absorption on the SPF values. The data reflect the historical development of the relation of the concentration of UVB and UVA filters in sunscreens and points to the influence of additional ingredients, e.g., antioxidants and cell-protecting agents on the efficacy of the products.

Degradation of Electrospun Nanofiber Scaffold by Short Wave Length Ultraviolet Radiation Treatment and Its Potential Applications in Tissue Engineering

Development in the field of tissue engineering has brought much attention in the fabrication and preparation of scaffold with biodegradable synthetic polymer nanofibers. Electrospun biodegradable polymeric nanofibers are increasingly being used to fabricate scaffolds for tissue engineering applications as they provide high surface area-to-volume ratio and possess high porosity. One common way to sterilize polymeric nanofiber scaffolds is 254-nm ultraviolet (UV) irradiation. In this study, we aim to evaluate the effects of UV radiation on the degradation in polymeric nanofibers, and then capitalize on UV-induced degradation and UV photolithography in polymeric nanofiber scaffolds for tissue engineering applications. Poly(D,L-lactic-co-glycolic) acid (PLGA, 75:25) and poly(L-lactide-co-epsilon-caprolactone) [P(LLA-CL), 70:30] nanofibrous meshes were produced by electrospinning. The nanofibers were irradiated by commercial germicide UV (lambda=254 nm) lamp for different intervals. We found that UV sterilization induced significant degradation of nanofiber. At 1 h UV irradiation, the average molecular weight of PLGA and P(LLA-CL) nanofibers were reduced by 46% and 35%, respectively, with corresponding reduction in the tensile strength of 26% for PLGA and 28% for P(LLA-CL). Hence, precautions may have to be taken into consideration when sterilizing polymeric nanofibers by UV treatment. UV-induced degradation on nanofibers was applied to fabrication of a three-dimensional (3D) tissue engineering scaffold by UV photolithography. Masked exposure to UV could generate patterned holes (d=100 microm) on the nanofibrous mesh. Cell culture study showed that smooth muscle cells were able to migrate into the holes. This method can be used to fabricate a 3D nanofibrous scaffold with micropores.

Reaching the end of the FUSE

The Far Ultraviolet Spectroscopic Explorer (FUSE) space telescope will be turned off on 18 October, after its pointing system failed. The NASA mission, which has been managed by a team of researchers with the Johns Hopkins University, in Maryland, produced spectrographs at short ultraviolet light wavelengths below the range in which the Hubble Space Telescope operates.By analyzing FUSE data, astronomers were able to measure temperatures, densities, and chemical compositions of many objects. The 8‐year mission, extended from its original 3 years, resulted in numerous discoveries, including a glimpse into molecular hydrogen in Mars's atmosphere and a first‐ever observation of molecular nitrogen outside our solar system. While FUSE'S scientific data will remain available to astronomers for years, the science team will close out the mission in less than a year. After 30 years or so, FUSE'S orbit is expected to decay and the satellite will burn up in the atmosphere.