Short Ultraviolet Wavelengths Research Articles

Retrieval of upper stratospheric ozone profiles from SCIAMACHY Hartley-Huggins limb scatter spectra using WMART

ABSTRACT The hyperspectral SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY) instrument, launched by Envisat in March 2002, measures atmospheric scattered radiance within the ultraviolet (UV) to near infrared range and has three geometric observation modes: nadir, occultation, and limb. This study describes a retrieval scheme to obtain middle and upper stratospheric ozone profiles from SCIAMACHY limb-scattered solar radiance. Owing to the low ozone concentration at high altitudes and rapid changes in ozone absorption cross-sections in the Hartley – Huggins band, a fundamental objective of this study was to establish a simple and effective retrieval scheme to derive reliable ozone profiles at high altitudes from UV spectral bands. In this study, short UV wavelengths of 302, 312, and 322 nm and a long wavelength of 331 nm were used for wavelength pairing to simplify the retrieval algorithm. Moreover, we employed the weighted multiplicative algebraic reconstruction technique (WMART), which is straightforward to understand, and easy to implement, combined with a radiative transfer model (i.e. SCIATRAN), and produced stable results. The retrieval error estimates for the upper stratosphere were provided, and the total retrieval error of the ozone profile was usually < 18% in the altitude range of 30–53 km. The results were compared with the SCIAMACHY v3.5 product and validated against profiles derived from Optical Spectrometer and InfraRed Imaging System (OSIRIS) v7.1, and Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) v4.0 for 30–53 km altitude. The retrieved ozone profiles agreed with data from SCIAMACHY v3.5 within − 10%–5%, except at an altitude of 45 km, where the bias became larger (approximately −15%). The comparison of retrieved profiles with OSIRIS v7.1 showed differences within ± 10% for 30–53 km altitude. The errors were mostly less than − 5% below 43 km compared with ACE-FTS v4.0, but there was a large negative deviation in the upper stratosphere.

Germicidal Efficiency of 272 nm LED in Relation to the Hospital Strain of Klebsiella Pneumoniae

Relevance. Currently, the use of ultraviolet (UV) radiation for the disinfection of objects and the treatment for infectious diseases is considered as a promising alternative to chemical biocides and antibiotics. Shortwave — UV-C and UV-B -light emitting diodes (LED) are a relatively new type of UV radiation sources and potentially able to meet the requirements of current medical technologies. However, their possibilities for the treatment of wounds and infectious diseases have not been practically researched to date, which determines the relevance of experiments aimed at studying the biocidal and therapeutic properties of shortwavelength UV LEDs.Purpose. OF STUDY To evaluate the bactericidal efficacy of 272 nm LED radiation against hospital strains of Klebsiella pneumoniae bacteria characterized by multidrug resistance.Materials and Methods. The studies were carried out with an experimental sample of the LED apparatus for UV irradiation. In the irradiator of the device, 5 LEDs are installed with a maximum radiation at a wavelength of 272 nm and a total electrical power of 10 watts. The UV radiation dose achieved in one irradiation session (12 seconds) at a distance of 10 cm from the irradiator was 8 mJ/cm2 . In the experiments, a hospital strain of the bacterium Klebsiella pneumoniae, isolated from the patient’s blood, was used. The strain was characterized by multidrug resistance. A daily culture suspension of K. pneumoniae with a concentration of 108 CFU/ml in a volume of 100 µl was transferred into a Petri dish with a diameter of 9 cm with meat-peptone agar and evenly distributed over a surface with a diameter of 8 cm. Petri dishes were irradiated from a distance of 10 cm from the irradiator. The change in the dose of UV irradiation from 4 to 80 mJ/cm2 was carried out by varying the exposure time. Studies were carried out in 4 repetitions at each dose. After irradiation, the experimental and control (without irradiation) Petri dishes were placed in a thermostat at 37ºC for 24 hours, then the grown colonies were counted. A total of 60 experiments were carried out.Results. As a result of the research, it was shown that the LED device based on five 272 nm diodes provides deep and prompt disinfection of the surface from hospital strains of K. pneumoniae bacteria characterized by multidrug resistance. A dose of UV radiation of 8 mJ/cm2 reduces surface contamination with K. pneumoniae bacteria by more than a million times (decontamination efficiency over 99.9999%). At doses less than 10 mJ/cm2 , the efficiency of the 272 nm LED device in terms of inactivation of K. pneumoniae bacteria is 3–4 times higher than the bactericidal efficiency of mercury lamps.Conclusion.The prospects of using UV devices based on LEDs with a maximum radiation at a wavelength of 272 nm in systems for the operational disinfection of massively contaminated surfaces, potentially including wound surfaces, have been shown.

Ultraviolet Exposure Improves SERS Activity of Graphene-Coated Ag/ZrO2 Substrates

This study reveals a significant improvement in surface-enhanced Raman scattering (SERS) activity of Ag/ZrO2 substrates covered with a few-layer graphene preliminary exposed to ultraviolet (UV) light. The SERS-active substrates are formed by the “silver mirror” deposition of Ag nanoparticles on annealed zirconia blocks. The film composed of ~3 graphene layers is grown on copper foil by a chemical vapor deposition and then wet-transferred to the SERS-active substrates. The graphene-free Ag/ZrO2 samples are found to provide an enhancement of the Raman scattering from rhodamine 6G (R6G) at a micromolar concentration, which is associated with combined effects from the surface plasmon resonance in the Ag nanoparticles and a charge transfer facilitated by zirconium dioxide. It is revealed that the SERS signal from the analyte molecules can be suppressed by a UV exposure of the Ag/ZrO2 samples due to photocatalytic activity of the wide band gap semiconductor. However, if the samples are covered with a few-layer graphene (Gr/Ag/ZrO2) it prevents the dye molecule decomposition upon the UV treatment and improves SERS activity of the substrates. The 365 nm treatment leads to a 40% increase in the 10–6 M R6G SERS spectrum intensity, while the 254 nm irradiation causes it to rise by 47%, which is explained by different responses from the surface and bulk zirconia crystals to the short and long UV wavelengths. This enhancement is attributed to the distinct responses of surface and in-depth zirconia crystals to varied UV wavelengths and underscores the pivotal role of graphene as a protective and enhancing layer.

Long persistent luminescence and photostimulated luminescence in Y3GaO6:Pr3+ phosphor

Long persistent luminescence (LPL) phosphors have a wide range of potential applications, including multi-color anticounterfeiting and long-term continuous detection of short-wavelength ultra-violet (UV) radiation. However, developing a stable carrier container that can provide ultra-long carrier storage for activators and visible multi-color LPL is a challenging task. In this work, we presented a series of Pr3+-doped Y3GaO6 (YGO) LPL phosphors that take full advantage of the synergistic relationship between the host lattice, emitters, and carrier traps. The host provides a suitable lattice site for rare-earth Pr3+ and offers a broad band gap of 5.69 eV to hold traps with depths ranging from 1.01 to 2.17 eV. We observed LPL that was visible to the naked eye for 6 h after excitation, and strong thermoluminescence (TL) spectra could be detected after the phosphor was placed in darkness for 20 days at room temperature. Additionally, we observed photostimulated luminescence under 980 nm and 808 nm laser irradiation with a power density of 5 W cm-2, indicating that low-energy excitation not only leads to LPL but also accelerates the elimination of previously stored carriers. After investigating the crystal structure and possible defects generated in the materials, we proposed a mechanism for LPL. Our findings demonstrate the potential of Pr3+-doped YGO LPL phosphors for a range of applications, such as multi-color anticounterfeiting and long-term continuous detection of short-wavelength UV radiation.

KHC2O4·B(OH)3: A nonlinear optical crystal with large birefringence in the short‐wavelength ultraviolet region

AbstractExploring nonlinear optical crystals with large birefringence in the short‐wavelength ultraviolet (SWUV) regions (≤300 nm) is a valuable pursuit. Herein, KHC2O4·B(OH)3, which is composed of infinite [HC2O4]− and [B(OH)3] chains, was successfully grown via the slow evaporation method. The [HC2O4]− and [B(OH)3] chains endow KHC2O4·B(OH)3 with the largest birefringence (0.164@1064 nm) of all B(OH)3‐containing compounds that have been reported in the SWUV regions. Moreover, it possesses a moderate second‐harmonic generation response (0.3 × KH2PO4) and a short UV cutoff edge of 254 nm. The electron localization function diagram indicates the large birefringence originates from the HC2O4 and B(OH)3 groups. This work provides a new method to investigate crystals with large birefringence in the B(OH)3‐based oxalate system.

Observation of the electronic band system 23Σg--a3Πu of C2 in the vacuum ultraviolet region.

A systematic spectroscopic study of the dicarbon molecule C2 has important applications in various research fields, such as astrochemistry and combustion. In the short vacuum ultraviolet (VUV) wavelength region, recent theoretical calculations have predicted many absorption band systems of C2, but only few of them have been verified experimentally yet. In this work, we employed a tunable VUV laser radiation source based on the two-photon resonance-enhanced four-wave mixing method and a time-of-flight mass spectrometer to investigate the absorption bands of C2 in the VUV range of 64 000-66 000cm-1. The electronic transition 23Σg-(v')-a3Πu(v″) of C2 has been observed and identified experimentally for the first time. The term value Te for the 23Σg- state is determined to be 66 389.9 ± 0.5cm-1 above the ground state X1Σg+, and the vibrational and rotational constants are also determined. The experimentally measured spectroscopic parameters in this study are in excellent agreement with the theoretical results based on high-level abinitio calculations.

Absorption enhancement of black carbon particles in a Mediterranean city and countryside: effect of particulate matter chemistry, ageing and trend analysis

Abstract. Black carbon (BC) is recognized as the most important warming agent among atmospheric aerosol particles. The absorption efficiency of pure BC is rather well-known, nevertheless the mixing of BC with other aerosol particles can enhance the BC light absorption efficiency, thus directly affecting Earth's radiative balance. The effects on climate of the BC absorption enhancement due to the mixing with these aerosols are not yet well constrained because these effects depend on the availability of material for mixing with BC, thus creating regional variations. Here we present the mass absorption cross-section (MAC) and absorption enhancement of BC particles (Eabs), at different wavelengths (from 370 to 880 nm for online measurements and at 637 nm for offline measurements) measured at two sites in the western Mediterranean, namely Barcelona (BCN; urban background) and Montseny (MSY; regional background). The Eabs values ranged between 1.24 and 1.51 at the urban station, depending on the season and wavelength used as well as on the pure BC MAC used as a reference. The largest contribution to Eabs was due to the internal mixing of BC particles with other aerosol compounds, on average between a 91 % and a 100 % at 370 and 880 nm, respectively. Additionally, 14.5 % and 4.6 % of the total enhancement at the short ultraviolet (UV) wavelength (370 nm) was due to externally mixed brown carbon (BrC) particles during the cold and the warm period, respectively. On average, at the MSY station, a higher Eabs value was observed (1.83 at 637 nm) compared to BCN (1.37 at 637 nm), which was associated with the higher fraction of organic aerosols (OA) available for BC coating at the regional station, as denoted by the higher organic carbon to elemental carbon (OC:EC) ratio observed at MSY compared to BCN. At both BCN and MSY, Eabs showed an exponential increase with the amount of non-refractory (NR) material available for coating (RNR-PM). The Eabs at 637 nm at the MSY regional station reached values up to 3 during episodes with high RNR-PM, whereas in BCN, Eabs kept values lower than 2 due to the lower relative amount of coating materials measured at BCN compared to MSY. The main sources of OA influencing Eabs throughout the year were hydrocarbon OA (HOA) and cooking-related OA (COA), i.e. primary OA (POA) from traffic and cooking emissions, respectively, at both 370 and 880 nm. At the short UV wavelength (370 nm), a strong contribution to Eabs from biomass burning OA (BBOA) and less oxidized oxygenated OA (LO-OOA) sources was observed in the colder period. Moreover, we found an increase of Eabs with the ageing state of the particles, especially during the colder period. This increase of Eabs with particle ageing was associated with a larger relative amount of secondary OA (SOA) compared to POA. The availability of a long dataset at both stations from offline measurements enabled a decade-long trend analysis of Eabs at 637 nm, that showed statistically significant (s.s.) positive trends of Eabs during the warmer months at the MSY station. This s.s. positive trend in MSY mirrored the observed increase of the OC:EC ratio over time. Moreover, in BCN during the COVID-19 lockdown period in spring 2020 we observed a sharp increase of Eabs due to the observed sharp increase of the OC:EC ratio. Our results show similar values of Eabs to those found in the literature for similar background stations.

Mayflies see the world in a different light

Everyone gains new perspectives as they grow up, but insects that go through metamorphosis see with a completely different set of eyes as adults. Mayflies spend most of their lives under water as larvae before emerging as adults for one final day of speed dating in a last-ditch effort to produce the next generation. In order to compare how mayflies navigate the two different visual landscapes in which they live, Ádám Egri with Ádám Mészáros and György Kriska at the Eötvös Loránd Research Network Centre for Ecological Research, Hungary, measured how mayflies’ eyes respond to different wavelengths of light and compared what they found to the light levels where the insects tend to congregate.Adult mayflies don't have much time to travel so they spend most of their airborne life mingling around the local neighborhood. By reviewing footage from webcam videos, the researchers determined that Ephoronvirgo mayflies typically swarm in the evening when the sun elevation is low, about –15 to –7 deg below the horizon. They then measured the visual environment when the sun is at different elevations with a spectrophotometer, which measures the strength of light across a range of wavelengths. It turned out that light levels when the adults congregate at dusk are low and the majority of the light is made up of short wavelength colours, closer to ultraviolet. In contrast, the water where the larvae grow up is murky, so longer wavelengths like visible green light are better able to permeate the darkness. These differences suggest that the insects’ eyes may be adapted to distinct environments throughout their life cycle.In order to measure what the insects can see, the team collected larval and adult wild mayflies to test their vision in the lab. Light is sensed when photons are absorbed by specialized cells in the eye that communicate with the brain via electrical signals. The researchers measured these electrical signals with a fine electrode probe while shining lights of different wavelengths onto the insects’ eyes. The adult mayfly's eyes were less sensitive to light that is visible to humans and instead picked up on short ultraviolet wavelengths that are invisible to us. Given that the adults emerge in the evening and die the following day, the reduced sensitivity to visual light suits the insects. However, the larvae living in muddy riverbeds sense light and darkness through simple eyes called ocelli, which absorb photons and send electrical signals to the brain, but can't resolve shapes. The researchers found that larval eyes were also sensitive to UV light, but they were most sensitive to light with longer wavelengths closer to green, which is fitting given the murky world they grow up in.Many insects can see ultraviolet, but these experiments shed light on the green sensitivity of larval ocelli. Although they can't see as well as other animals, the simple eyes of larval mayflies are well matched for the muddy riverbed conditions where they spend most of their lives. As adults, mayflies emerge and face their first and last evening of life above water with a fresh set of eyes that help them find a mate in the dark.

Embedded UV Sensors in CMOS SOI Technology.

We report on ultraviolet (UV) sensors employing high voltage PIN lateral photodiode strings integrated into the production RF SOI (silicon on isolator) CMOS platform. The sensors were optimized for applications that require measurements of short wavelength ultraviolet (UVC) radiation under strong visible and near-infrared lights, such as UV used for sterilization purposes, e.g., COVID-19 disinfection. Responsivity above 0.1 A/W in the UVC range was achieved, and improved blindness to visible and infrared (IR) light demonstrated by implementing back-end dielectric layers transparent to the UV, in combination with differential sensing circuits with polysilicon UV filters. Degradation of the developed sensors under short wavelength UV was investigated and design and operation regimes allowing decreased degradation were discussed. Compared with other embedded solutions, the current design is implemented in a mass-production CMOS SOI technology, without additional masks, and has high sensitivity in UVC.

Surface Coating- and Light-Controlled Oxygen Doping of Carbon Nanotubes

Tuning the optical properties of single-wall carbon nanotubes (SWCNTs) via oxygen doping has been a simple and effective approach to create fluorescent quantum emitters. We performed oxygen doping of SWCNTs in water utilizing chirality-pure (6,5) enantiomers with different surface coatings of DNA and surfactants by ultraviolet (UV) light irradiation. We found the reaction to be primarily dependent on the wavelength of UV light and the specific coating material on the nanotube surface. Particularly, DNA coatings react more readily with the reactive oxygen species that is photochemically produced under short-wavelength UV light than SWCNTs, preventing oxygen doping of nanotubes from occurring. The surface coverage of SWCNTs created by coating materials plays a weaker role in controlling the reaction efficiency of oxygen doping. This is demonstrated clearly by the lack of oxygen doping for two (6,5) enantiomers wrapped by DNA with drastically different surface coverages. These findings reveal important mechanisms of oxygen doping of SWCNTs, providing methods of controlling optical properties of nanotubes for developing unique applications.

Functional Characterization of Pseudoidium neolycopersici Photolyase Reveals Mechanisms Behind the Efficacy of Nighttime UV on Powdery Mildew Suppression.

Powdery mildews can be controlled by brief exposure to ultraviolet (UV) radiation with devastating effect on their developmental stages including conidia germination. The treatment effect can be impaired by subsequent exposure to UV-A/blue light. UV-A/blue light-activated photolyase may be responsible for this and therefore we tested the function of three cryptochrome/photolyase family (CPF)-like genes (OINE01015670_T110144, OINE01000912_T103440, and OINE01005061_T102555) identified in the obligate biotrophic fungus Pseudoidium neolycopersici, the cause of tomato powdery mildew. A photolyase-deficient mutant of Escherichia coli transformed with coding sequence of OINE01000912_T103440 and exposed to brief (UV)-C treatment (peak emission at 254 nm) showed photoreactivation and cell survival when exposed to subsequent blue light, indicating complementation of photolyase activity. In contrast, the same photolyase-deficient E. coli transformed with the coding sequences of other two CPF-like genes did not survive this treatment, even though their expression were confirmed at protein level. This confirmed that OINE01000912_T103440 is a gene encoding photolyase, here named PnPHR1, with functionality similar to the native photolyase in E. coli, and classified as a class I cyclobutane pyrimidine dimer (CPD) photolyase. Modeling of the 634-amino acid sequence of PnPHR1 suggested that it is capable of binding flavin adenine dinucleotide (FAD) and methenyltetrahydrofolate (MTHF). However, spectroscopic data of the protein produced in an E. coli expression system could only reveal the presence of a reduced form of FAD, i.e., FADH– as an intrinsic chromophore. Within the tested wavelength range of 365–525 nm, the survival of photolyase-deficient mutant E. coli transformed with PnPHR1 showed a broad action spectrum from 365 to 454 nm. This was very similar to the previously characterized action spectrum for survival of P. neolycopersici conidia that had been treated with UV-C. Quantitative RT-PCR revealed that the expression of PnPHR1 in P. neolycopersici conidia was induced by UV-C, and peak expression occurred 4 h after brief UV-C treatment. The expression of PnPHR1 was repressed when incubated in red light after the UV-C treatment, but not when incubated in UV-A/blue light. The results may explain why the disease-reducing effect of short wavelength UV is impaired by exposure to UV-A and blue light.

Different water environment coupled with ultraviolet radiation on ageing of asphalt binder

Asphalt pavement is inevitably exposed to sunlight and different water environment during the service life, and the environment changes have caused the asphalt to be aged under the more complex environment such as more severe ultraviolet (UV) radiations, acid rain, or deicing salt conditions, however, the ageing mechanism and impact of coupled water and UV radiation is still not clear. In order to evaluate the coupling impact of different water environment (salt, acid) and UV radiation on the rheological properties and microstructure of asphalt material, short-term aged Rolling Thin Film Oven (RTFO) samples were further aged in UV and various water environment to simulate the UV and acid rain or salt condition, the Dynamic Shear Rheological (DSR) test, Bending Beam Rheological (BBR) test, SARA (saturates, aromatics, resin, and asphaltene) four-component analysis test and Fourier Transform Infrared Spectrometer (FTIR) tests were carried out. The results show that the coupling of different water environments and UV radiation accelerated the ageing of asphalt, which leads to the decrease of saturated, aromatic and resin content, the increase of asphaltene, and the enhancement of absorption peaks of carbonyl and sulfoxide groups. The result also found that shorter wavelength UV radiation has a severer effect on asphalt ageing under the same UV radiation level. Highlights UV and different water environment on asphalt ageing were investigated. UV and water ageing reduced the low temperature cracking resistance. UV and water ageing reduced the light component of asphalt and increased the heavy component of asphaltene. Shorter wavelength of UV have a server impact on asphalt ageing.

A new ultraviolet transparent hydra-cyanurate K2(C3N3O3H) with strong optical anisotropy from delocalized π-bonds.

A new metal hydra-cyanurate, K2(C3N3O3H), was synthesized by a slow evaporation method in aqueous solution. It possesses a short ultraviolet cutoff wavelength at 240 nm. First-principles calculations reveal that its birefringence (∼0.35@800nm) is two times larger than that of commercial calcite crystals. Therefore, K2(C3N3O3H) and metal cyanurates, are very promising ultraviolet birefringent materials in future optical devices.

Patterns of spectral, spatial, and long‐term variability in light attenuation in an optically complex sub‐estuary

AbstractThe attenuation of solar radiation controls many processes and characteristics of aquatic ecosystems and is a sentinel of larger‐scale environmental change. While light attenuation is often characterized with a single broadband diffuse attenuation coefficient of photosynthetically active radiation (K d PAR), attenuation can exhibit substantial variability across the solar spectrum and through time and space. Understanding this variability and its proximate causes may provide information to characterize large‐scale environmental change. We implemented a semi‐analytical K d model in four segments of the Rhode River sub‐estuary of the Chesapeake Bay to examine spectral, spatial, and temporal variability in K d across the ultraviolet (UV) to PAR wavelengths (290–710 nm) over the period 1986–2014. We used this model to identify wavelengths most sensitive to long‐term change, the seasonal phenology of long‐term change, and the optical constituents driving changes. The model included contributions by phytoplankton, non‐algal particulates, chromophoric dissolved organic matter (CDOM), and water. Over the period of record, K d increased (water transparency decreased) in both UV and PAR wavelengths, with the largest increases at the most upstream site, during summer months, and at short UV wavelengths. These increases were due primarily to an increase in non‐algal particulates, and particularly since year 2005, however there was substantial seasonality in K d. The model reveals how different changes in water quality have a differential effect on UV and PAR attenuation, and enables insight into what types of long‐term change in transparency have occurred over the long period of human impacts in the Chesapeake Bay watershed.

Effect of Oxidation Process on Complex Refractive Index of Secondary Organic Aerosol Generated from Isoprene.

Oxidation of isoprene by hydroxyl radical (OH), ozone (O3), or nitrate radical (NO3) leads to the formation of secondary organic aerosol (SOA) in the atmosphere. This SOA contributes to the radiation balance by scattering and absorbing solar radiation. In this study, the effect of oxidation processes on the wavelength-dependent complex refractive index (RI) of SOA generated from isoprene was examined. Oxidation conditions did not have a large effect on magnitude and wavelength dependence of the real part of the RI. In the case of SOA generated in the presence of sulfur dioxide (SO2), significant light absorption at short visible and ultraviolet wavelengths with the imaginary part of the RI, up to 0.011 at 375 nm, was observed during oxidation with OH. However, smaller and negligible values were observed during oxidation with O3 and NO3, respectively. Moreover, in the absence of SO2, light absorption was not observed regardless of the oxidation process. There was an empirical correlation between the imaginary part of the RI and the average degree of unsaturation of organic molecules. The results obtained herein demonstrate that oxidation processes should be considered for estimating the radiative effect of isoprene-derived SOA.

Surprising Separation of Cannabinoid Physical Dependence and Withdrawal in an Invertebrate Model

Planarians have mammalian-like neurotransmitter systems and have been established as a novel in vivo model for neuropharmacology. In previous research, planarians that have been exposed to the cannabinoid receptor (CB-R) agonist WIN 55,212-2 for 1 h displayed abstinence-induced withdrawal when tested in drug-free, but not in drug-containing, water. The goals of the present study were to extend previous work and to further establish a cannabinoid behavioral model with planarians. The results showed 1) four different CB-R antagonists (AM251, AM281, SLV319 and SR144528) dose-relatedly blocked development of physical dependence induced by two different CB-R agonists (WIN 55,212-2 and JWH251); 2) none of the same four antagonists (AM251, AM281, SLV319 or SR144528) precipitated withdrawal; 3) short wavelength (254 nm), but not long wavelength (366 nm), ultraviolet (UV) light attenuated abstinence-induced withdrawal from WIN 55,212-2, while short wavelength UV light induced moderate withdrawal behavior. The results confirm the use of a planarian model as a simple yet robust way to study development of physical dependence to cannabinoid agonists. The effect of UV irradiation adds to the evidence that the results are receptor-related. The results also give rise to the surprising suggestion, within the limitations of the methodology, that development of cannabinoid physical dependence and antagonist-induced precipitated withdrawal might be separable phenomena in planarians.

UNLAMINATED GAFCHROMIC EBT3 FILM FOR ULTRAVIOLET RADIATION MONITORING.

Measurement of ultraviolet (UV) radiation is important for human health, especially with the expanded usage of short wavelength UV for sterilization purposes. This work examines unlaminated Gafchromic EBT3 film for UV radiation monitoring. The authors exposed the film to select wavelengths in the UV spectrum, ranging from 207 to 328 nm, and measured the change in optical density. The response of the film is wavelength dependent, and of the wavelengths tested, the film was most sensitive to 254 nm light, with measurable values as low as 10 µJ/cm2. The film shows a dose-dependent response that extends over more than four orders of magnitude. The response of the film to short wavelength UV is comparable to the daily safe exposure limits for humans, thus making it valuable as a tool for passive UV radiation monitoring.

Ultraviolet 320 nm laser excitation for flow cytometry.

Although multiple lasers and high-dimensional analysis capability are now standard on advanced flow cytometers, ultraviolet (UV) lasers (usually 325-365 nm) remain an uncommon excitation source for cytometry. This is primarily due to their cost, and the small number of applications that require this wavelength. The development of the Brilliant Ultraviolet (BUV fluorochromes, however, has increased the importance of this formerly niche excitation wavelength. Historically, UV excitation was usually provided by water-cooled argon- and krypton-ion lasers. Modern flow cytometers primary rely on diode pumped solid state lasers emitting at 355 nm. While useful for all UV-excited applications, DPSS UV lasers are still large by modern solid state laser standards, and remain very expensive. Smaller and cheaper near UV laser diodes (NUVLDs) emitting at 375 nm make adequate substitutes for 355 nm sources in many situations, but do not work as well with very short wavelength probes like the fluorescent calcium chelator indo-1. In this study, we evaluate a newly available UV 320 nm laser for flow cytometry. While shorter in wavelength that conventional UV lasers, 320 is close to the 325 nm helium-cadmium wavelength used in the past on early benchtop cytometers. A UV 320 nm laser was found to excite almost all Brilliant Ultraviolet dyes to nearly the same level as 355 nm sources. Both 320 nm and 355 nm sources worked equally well for Hoechst and DyeCycle Violet side population analysis of stem cells in mouse hematopoetic tissue. The shorter wavelength UV source also showed excellent excitation of indo-1, a probe that is not compatible with NUVLD 375 nm sources. In summary, a 320 nm laser module made a suitable substitute for conventional 355 nm sources. This laser technology is available in a smaller form factor than current 355 nm units, making it useful for small cytometers with space constraints. © 2017 International Society for Advancement of Cytometry.

Effect of UV-LED wavelengths on direct photolytic and TiO2 photocatalytic degradation of emerging contaminants in water

Ultraviolet (UV) irradiation is known to be effective for chemical oxidation and disinfection of water and wastewater. Recently, light emitting diode (LED) has been recognized as a cost-effective, environmentally friendly, and sustainable source of UV to replace conventional mercury lamps, so-called UV-LED. Less is known about the effectiveness of UV-LEDs, i.e., UVA, UVB, and UVC in comparison, for the decomposition of recalcitrant organic chemicals. In this study, direct photolytic decomposition and TiO2 photocatalytic decomposition of model pharmaceuticals, including acetaminophen (ACT), diclofenac (DCF), ibuprofen (IBP), and sulfamethoxazole (SMX), was tested, and the effects of different UV-LED wavelengths on their decomposition were investigated. UV wavelength was found to be a more important parameter for the decomposition than light intensity. Shorter wavelength UV in order of UVC>UVB>UVA was more effective for the decomposition of the pharmaceuticals. Photocatalytic decomposition was much more significant than photolytic decomposition. Decomposition kinetics of the pharmaceuticals followed SMX>DCF>IBP>ACT, reflecting their molecular structures. Results on the mineralization of the pharmaceuticals also supported the observed trends for their disappearance. The investigation was resumed with microcystin-LR (MC-LR), a known lethal biological toxin often found in water resource, and the similar result to the pharmaceuticals was also observed for MC-LR. This study and the consequent results would facilitate applications of UV-LEDs for the treatment of water contaminated with recalcitrant toxic chemicals.

Ultraviolet optical properties of aluminum fluoride thin films deposited by atomic layer deposition

Aluminum fluoride (AlF3) is a low refractive index material with promising optical applications for ultraviolet (UV) wavelengths. An atomic layer deposition process using trimethylaluminum and anhydrous hydrogen fluoride has been developed for the deposition of AlF3 at substrate temperatures between 100 and 200 °C. This low temperature process has resulted in thin films with UV-optical properties that have been characterized by ellipsometric and reflection/transmission measurements at wavelengths down to 200 nm. The optical loss for 93 nm thick films deposited at 100 °C was measured to be less than 0.2% from visible wavelengths down to 200 nm, and additional microstructural characterization demonstrates that the films are amorphous with moderate tensile stress of 42–105 MPa as deposited on silicon substrates. X-ray photoelectron spectroscopy analysis shows no signature of residual aluminum oxide components making these films good candidates for a variety of applications at even shorter UV wavelengths.