Influence Of Ultraviolet Light Research Articles

On the necessity of new hydrophobic treatment after repointing of water repellent masonry

The impregnation of the exterior surface of a masonry wall with a water repellent is a common intervention in (historic) building renovation and maintenance. Such treatments, whilst degrading at the surface with time under influence of ultra violet light, remain effective below the surface several decades after their application. During renovation works of masonry previously treated with a water repellent, the question arises whether it is necessary to repeat the hydrophobic treatment of the entire masonry after repointing. Opposing opinions exist with this regard, but no research clearly supporting one or the other. This research investigates for the first time the effect of hydrophobic treatment when applied on previously treated and repointed masonry walls. Small masonry walls were subjected to rain periods in the laboratory and their water uptake and drying behaviour were studied. Moreover, this laboratory research was followed by 30 months of outdoor exposition of the masonry specimens. The following cases were considered: (1) wall treated with water repellent, (2) wall treated with water repellent, followed by repointing but without new water repellent treatment, (3) wall treated with water repellent, followed by repointing and retreatment. This was done for three different types of pointing mortar: ordinary Portland cement and natural hydraulic lime with standard sand, and natural hydraulic lime with sand with one grain size. The results show that, after prolonged rain periods, the water uptake by repointed but not retreated masonry is comparable to that of untreated, non-hydrophobic masonry, whereas drying is considerably slower. This leads to a high saturation degree in repointed but not retreated masonry, which, in turn, increases the risk of damage to the masonry by e.g. frost. Therefore, retreating repointed hydrophobic masonry should definitively be considered.

Influence of UV light on the corrosion behavior of AA6061-T6 in a CMA solution

The effect of ultraviolet (UV) light illumination on the corrosion behavior of AA6061-T6 in an alkaline snowmelt-agent solution (CMA solution) was investigated using electrochemical and spectroscopic techniques. The corrosion products and passive films formed under different exposure conditions were n-type semiconductors. Exposure for 1 and 2 weeks facilitated the corrosion process. Under UV light illumination, the extent of corrosion and size of corrosion pits were larger than those in the dark; this was attributed to the facilitation of the dissolution of AlFeSi intermetallics and formation of fewer oxides such as Al2O3 under UV light illumination. After exposure for 4 weeks, under UV light illumination, the formation of passive films was fewer defects, and more compact structures offered more protection to the aluminum substrates, resulting in slightly suppressed corrosion.

Influence of the urease inhibitor suspension (Atmowell®) on the fluorescent dye pyranine and its spray and drift behavior in wind tunnel measurements

Too many ammonia emissions are released into the environment from cattle farming. These damage the environment and have an impact on animal and human health. Ammonia Emissions could be reduce by urease inhibitors. Before using the urease inhibitor suspension Atmowell® in cattle farming a risk assessment is required. This includes exposure data on the animal and human in the barn. As there is no method for exposure measurements yet the approach of fluorometry was taken. The fluorescent dye pyranine shall replace Atmowell® in later studies as a tracer. Before Atmowell® can be replaced, the interaction between Atmowell® and pyranine—according to the fluorescence and storage stability under the influence of ultraviolet light, has to be observed and excluded. Also, the spray and drift behavior must be examined in the wind tunnel with three different nozzles. The results show that Atmowell® has no effect on neither the fluorescence nor the degradation rate of a pyranine-solution. Furthermore, it is shown that a pyranine + Atmowell® mixture does not differ in drift behavior from a pure pyranine-solution. Because of these findings, an Atmowell®-solution can be substituted by a pyranine-solution without any effects on the results of an exposure measurement being expected.

Theoretical Nanoarchitectonics of GaN Nanowires for Ultraviolet Irradiation-Dependent Electromechanical Properties.

In this paper, we propose a one-dimensional model that combines photoelectricity, piezoelectricity, and photothermal effects. The influence of ultraviolet light on the electromechanical coupling properties of GaN nanowires is investigated. It is shown that, since the ultraviolet photon energy is larger than the forbidden gap of GaN, the physical fields in a GaN nanowire are sensitive to ultraviolet. The light-induced polarization can change the magnitude and direction of a piezoelectric polarization field caused by a mechanical load. Moreover, a large number of photogenerated carriers under photoexcitation enhance the current density, whilst they shield the Schottky barrier and reduce rectifying characteristics. This provides a new theoretical nanoarchitectonics approach for the contactless performance regulation of nano-GaN devices such as photoelectric sensors and ultraviolet detectors, which can further release their great application potential.

Hydrothermal synthesis of mesoporous TiO2 nanoparticles for enhanced photocatalytic degradation of organic dye

In this work, mesoporous TiO2 nanoparticle photocatalyst has been prepared by hydrothermal method using titanium tetrachloride as precursor. The resulting photocatalysts have been characterized using X-ray diffraction (XRD), nitrogen adsorption-desorption analyses, RAMAN spectroscopy, Transmission Electron Microscopy (TEM) and UV-vis diffuse reflectance spectroscopy (UV-vis DRS). The results showed that the synthesized 2 OiT was anatase phase and mesoporous with specific surface 133.45 m2/g. The decomposition of methylene blue dye under the influence of ultraviolet light was used to test the photocatalytic performance of the produced TiO2 photocatalyst. The photocatalytic activity of the TiO2 photocatalyst for the breakdown of methylene blue dye was significantly higher than that of the commercial TiO2 P25 used as a reference. Moreover, the prepared photocatalyst was stable and reusable. The larger surface area of hydrothermally produced TiO2 was the reason for this enhanced photocatalytic activity. As a result, it is expected that this approach of photocatalytically active semiconducting nanocatalysts will be used in industry to eliminate undesired organics from the environment.

Effect of proton irradiation temperature on persistent photoconductivity in zinc oxide metal-semiconductor-metal ultraviolet photodetectors

The electrical and structural characteristics of 50-nm-thick zinc oxide (ZnO) metal-semiconductor-metal ultraviolet (UV) photodetectors subjected to proton irradiation at different temperatures are reported and compared. The devices were irradiated with 200 keV protons to a fluence of 1016 cm−2. Examination of the x-ray diffraction (XRD) rocking curves indicates a preferred (100) orientation prior to irradiation, with decrease in crystal quality afterward. Additionally, peak shifts in XRD and Raman spectra of the control sample relative to well-known theoretical positions are indicative of tensile strain in the as-deposited ZnO films. Shifts toward theoretical unstrained positions are observed in the irradiated films, which indicates partial relaxation. Raman spectra also indicate increase in oxygen vacancies (VO) and zinc interstitial defects (Zni) compared to the control sample. Additionally, transient photocurrent measurements performed on each sample at different temperatures showed up to 2× increase in photocurrent decay time constants for irradiated samples vs the control. This persistent photoconductive behavior is linked to the activation of electron and hole traps near the surface, and to the desorption and reabsorption of O2 molecules on the ZnO surface under the influence of UV light. Using an Arrhenius model, trap activation energies were extracted and, by comparing with known energies from the literature, the dominant defects contributing to persistent photoconductivity for each irradiation condition were identified. The persistence of differences in photocurrent transients between different samples months after irradiation indicates that the defects introduced by the suppression of thermally activated dynamic annealing processes have a long-term deleterious effect on device performance.

The Influence of Ultraviolet Light on Luminescence (700–1000 nm) of LiF and LiF:OH Crystals Irradiated in a Nuclear Reactor

The Influence of Ultraviolet Light on Luminescence (700–1000 nm) of LiF and LiF:OH Crystals Irradiated in a Nuclear Reactor

Influence of Ultraviolet Light and Ultrasound Irradiation on the Physicochemical, Sensory and Microbiological Characteristics of Pear Jam Enriched with Fibers

The ultraviolet light and ultrasound irradiation present a green approach to non-thermal conservation in food processing. This research aimed to investigate the effect of ultraviolet light and ultrasound irradiation on the fiber-enriched pear fruit jam's physicochemical properties, sensory profile, and microbiological characteristics. The moisture, ash, pH, titrable acidity, sugar content, energy value, heavy metals were determined in the samples. The sensory and microbiological characteristics were also evaluated in pear jams. It was found that the treatment of ultraviolet light and ultrasound irradiation caused minimal changes in pH, titrable acidity, dry matter, and sucrose content. The sensory characteristics (color, odor, and taste) also did not alter significantly during treatment with ultraviolet light and ultrasound irradiation. The values of other sensory characteristics as graininess, elasticity, and juiciness showed better acceptance for jam treated with ultrasound irradiation. The pear jam's lowest microbial growth level was observed after ultraviolet light and ultrasonic irradiations for 10 minutes in polypropylene packaging and 15 minutes in glass packaging, respectively. However, ultrasonic irradiation demonstrated a more effective overall bactericidal effect in polypropylene packaging, while ultraviolet light showed better results in a glass packaging pear jam.

Investigation of the temperature influence on the dual curing urethane-methacrylate resin Rigid Polyurethane 70 (RPU 70) in digital light synthesis (DLS)

The two part urethane-methacrylate resin RPU 70, used in DLS, seems to have superior material properties. These properties are achieved by a dual curing process of ultraviolet (UV) and thermal curing. The temperature influence on the processability of the mixed resin and the resulting mechanical properties are still unknown. It was possible to solidify the liquid RPU 70 resin into an elastomer at 60 °C for 15 h without the influence of UV light by solely harnessing the temperature sensitive crosslinking reaction between part A and part B. The ongoing thermal conversion of the liquid resin into an elastomer was analyzed with viscosity measurements, Fourier-transform infrared spectroscopy (FT−IR), differential scanning calorimetry (DSC) and Photo-DSC. The latter method proved to be effective in tracking the thermal conversion and to identify optimal exposure times for preheated resins. Furthermore, thermogravimetric analysis (TGA) showed a linear evaporation of reactive diluents in RPU 70 over time. In order to investigate the processability and to understand the effects of the thermal curing on mechanical properties, the resin was preheated to 30 °C, 40 °C, 50 °C and 60 °C for one hour before the dual curing DLS process. Even though, the viscosity of the resin was increased by preheating and additionally by the released reaction heat of the photopolymerization during DLS, the build job could be produced with the same part quality as the unheated resin. Tensile tests were conducted on dual cured specimen and the results showed that with a preheating of the resin for one hour at 50 °C, the tensile modulus of RPU 70 increased 19.56%, while tensile strength and elongation at break values remained in the standard deviation range of the comparison group. The preheating at 60 °C improved elongation at break and tensile modulus 47.61% and 5.54% respectively, while at the same time tensile strength dropped −5.02% compared to no preheating. Apart from the possibility to slightly modify the mechanical properties by preheating the resin before DLS, there are two temperature-dependent challenges for RPU 70 during the DLS process, namely evaporation and undesirable thermal curing. However, there are also new innovative ways to utilize the result of this study that RPU 70 resin can be thermally solidified into an elastomer: the creation of parts that have a hard shell and a soft core. The hard shell can be produced by using DLS, the soft core by pouring the liquid resin in the shell and thermally curing both. • Mechanical properties can be modified by preheating the resin before DLS. • Reactive diluents evaporate from the resin. • Liquid RPU 70 resin solidifies into an elastomer after 15 h at 60 °C. • Photo-DSC can be used to track the thermal conversion between part A and B.

The Influence of UV Light on Rheological Properties of Collagen Extracted from Silver Carp Skin.

Acid soluble collagen (ASC) was extracted from Silver Carp fish skin. Collagen was dissolved in acetic acid at varying concentrations and its rheological properties were studied. Steady shear flow properties of collagen solutions at concentrations of 5 and 10 mg/mL were characterized using rheometry at 20 °C. Collagen solutions were irradiated with UV light (wavelength 254 nm) for up to 2 h and rheological properties were measured. All the collagen solutions showed a shear-thinning flow behavior. A constant viscosity region was observed after 1 h of UV irradiation, which showed that collagen molecules were fully denatured. A short treatment with collagen solution by UV (ultraviolet) light led to an increase in viscosity; however, the denaturation temperature of UV-irradiated collagen decreased. Depending on the time of UV treatment, collagen extracted from Silver Carp fish skin may undergo physical crosslinking or photodegradation. Physically crosslinked collagen may find applications in functional food, cosmetic, biomedical, and pharmaceutical industries.

Investigations of Sensors for Detection of Hydrogen Peroxide Vapors under the Influence of UV Illumination

The sensitivity of gas sensors made of doped SnO2:Co metal oxide for the detection of hydrogen peroxide vapors in the environment was studied using current-voltage, frequency-capacitance, and transient characteristics. Their measurements were carried out at room temperature under the influence of ultraviolet light and without it. It is shown that the influence of ultraviolet rays on the active surface of the sensor increases the gas sensitivity of the sensor. Studies of transient characteristics have also shown that the resistance of the sensor when it is exposed to ultraviolet rays, already at room temperature, after the feeding-off of hydrogen peroxide vapors is almost completely restored.

The Acceleration of Pitting Corrosion of AISI 304 Stainless Steel by Ultraviolet Light Illumination in Acidic Chloride Solution

The influence of ultraviolet light (UV, λ = 254 nm) illumination on pitting of AISI 304 stainless steel was investigated using critical pitting chloride concentration (CPCC) measurement. In a H2SO4 solution with a gradually increased chloride ion concentration, the CPCC was measured for AISI 304 samples at 0.65 VSCE and 30 °C under different illumination conditions. Direct UV illumination significantly reduced the CPCC value from 0.286 ± 0.018 M (in the dark) to 0.087 ± 0.008 M. Both the passivation process in pure H2SO4 solution and pit growth in acidic chloride solution were affected by UV illumination. The passive film formed in 0.1 M H2SO4 solution with UV illumination (in which a smaller ratio of metal oxides to metal hydroxides was observed) had a lower corrosion resistance than that formed in the dark, indicating the decreased stability of passive film after UV illumination. In addition, UV illumination also accelerated the pit growth rate of 304 samples in acidic chloride solution. After the CPCC tests, lacy cover and rough edges were observed with pits formed in the dark, while no lacy cover was present for pits developed under UV illumination.

Atomic force microscopy measurements probing the mechanical properties of single collagen fibrils under the influence of UV light in situ

Collagen plays a decisive role as a functional substrate in tissue engineering. In particular, the rigidity of the collagen influences the behaviour of the attached cells. Thus, modification and controlled adjustment of collagen's characteristics are essential. To this end, controlled exposure to ultraviolet (UV) light is a promising process because it can be temporally and spatially well defined. In this study, we investigated the effect of UV exposure on surface supported single collagen fibrils in situ. This procedure allowed for a direct comparison between the untreated and modified states of type I collagen. Atomic force microscopy was used to map the mechanical properties. Exposure to UV light was used to influence the mechanical properties of the fibrils in varied liquid environments (deionized water and phosphate-buffered saline (PBS)). The results led to the assumption that combined UV/thermal treatment in deionized water continuously lowers the elastic modulus. In contrast, experiments performed in PBS-based solutions in combination with UV-B and UV-C light or thermal treatment up to 45 °C suggested an increase in the modulus within the first 30–40 min that subsequently decreased again. Thus, the wavelength, exposure, temperature, and chemical environment are relevant parameters that need to be controlled when modifying collagen using UV light.

Investigating the color of the blood stains on archaeological cloths: the case of the Shroud of Turin.

The unique reddish blood stains on the archaeological cloth known as the Shroud of Turin caught the attention of several scholars, who proposed different hypotheses to explain the unusual blood color. To date, just a few hypotheses have been tested experimentally, and the results are debatable. In this paper, we test the strength of two hypotheses (namely, the presence of carboxyhemoglobin and the long-term influence of ultraviolet light on high-bilirubin blood) by the spectral reflectance of the blood stained regions on the Shroud and by color analyses of ultraviolet irradiated high-bilirubin blood stains on linen. The relevance of these simple methods to the study of stained textiles is discussed.

Modelling the Release, Transport and Fate of Engineered Nanoparticles in the Aquatic Environment - A Review.

Engineered nanoparticles, that is, particles of up to 100 nm in at least one dimension, are used in many consumer products. Their release into the environment as a consequence of their production and use has raised concern about the possible consequences. While they are made of ordinary substances, their size gives them properties that are not manifest in larger particles. It is precisely these properties that make them useful. For instance titanium dioxide nanoparticles are used in transparent sunscreens, because they are large enough to scatter ultraviolet light but too small to scatter visible light.To investigate the occurrence of nanoparticles in the environment we require practical methods to detect their presence and to measure the concentrations as well as adequate modelling techniques. Modelling provides both a complement to the available detection and measurement methods and the means to understand and predict the release, transport and fate of nanoparticles. Many different modelling approaches have been developed, but it is not always clear for what questions regarding nanoparticles in the environment these approaches can be applied. No modelling technique can be used for every possible aspect of the release of nanoparticles into the environment. Hence it is important to understand which technique to apply in what situation. This article provides an overview of the techniques involved with their strengths and weaknesses. Two points need to be stressed here: the modelling of processes like dissolution and the surface activity of nanoparticles, possibly under influence of ultraviolet light, or chemical transformation has so far received relatively little attention. But also the uncertainties surrounding nanoparticles in general-the amount of nanoparticles used in consumer products, what constitutes the appropriate measure of concentration (mass or numbers) and what processes are relevant-should be explicitly considered as part of the modelling.

Euphrasia spp. as a natural stabilizer of hyaluronic acid – A step closer to physiological human tear fluids?

Natural tears contain water, sodium chloride and various other components like proteins, lipids, mucins, antioxidants and buffer substances. Tear substitutes which are used for therapy of the dry eye syndrome mostly lack natural tear components and ingredients with antioxidative potential. Thus, the aim of our study was to identify substances with protective function against ultraviolet (UV) light and ozone, which could be used in artificial tear substitutes. Viscosity measurements were perfomed using a 0.25% hyaluronic acid solution with a viscosity of 2.12 centi Stokes (cSt) [range 2.09 – 2.15], as well as extracts and substances with possible antioxidative effects after irradiation with ultraviolet light and ozone. UV light and ozone lead to a depolymerisation of hyaluronic acid associated with an decrease of viscosity to 1.76 cSt [range 1.56 – 1.87] and 1.46 cSt [range 1.41 – 1.63], respectively. Eleven substances with possible hyaluronic acid stabilizing effects were investigated. Eyebright (Euphrasia spp.) and mannitol could significantly protect hyaluronic acid from a degradation (p < 0.01). The viscosity was 2.05 cSt [range 2.04 – 2.05] and 2.07 cSt [range 2.05 – 2.08] through influence of UV light and ozone, respectively, with the protective components. Uric acid (1.76 cSt) and melatonine (1.75 cSt) were able to achieve a significant stabilizing effect of hyaluronic acid against ozone (p < 0.01), but not against UV light. Arginine, curcumin, fructose, urea, lysine, spermidine and taurine did not stabilize hyaluronic acid after UV and ozone stress.

Long-term exposure of bacterial and protozoan communities to TiO2 nanoparticles in an aerobic-sequencing batch reactor

Titanium dioxide (TiO2) nanopowders at different concentrations (0–50 mg L−1) were injected into an aerobic-sequencing batch reactor (SBR) to investigate the effects of long-term exposure to nanoparticles on bacterial and protozoan communities. The detection of nanoparticles in the bioflocs was analyzed by scanning electron microscopy, transmission electron microscopy, and energy-dispersive x-ray spectroscopy. The SBR wastewater experiments were conducted under the influence of ultraviolet light with photocatalytic TiO2. The intrusion of TiO2 nanoparticles was found both on the surface and inside of the bioflocs. The change of microbial population in terms of mixed liquor-suspended solids and the sludge volume index was monitored. The TiO2 nanoparticles tentatively exerted an adverse effect on the microbial population, causing the reduction of microorganisms (both bacteria and protozoa) in the SBR. The respiration inhibition rate of the bacteria was increased, and the viability of the microbial population was reduced at the high concentration (50 mg L−1) of TiO2. The decreasing number of protozoa in the presence of TiO2 nanoparticles during 20 days of treatment with 0.5 and 1.0 mg L−1 TiO2 is clearly demonstrated. The measured chemical oxygen demand (COD) in the effluent tends to increase with a long-term operation. The increase of COD in the system suggests a decrease in the efficiency of the wastewater treatment plant. However, the SBR can effectively remove the TiO2 nanoparticles (up to 50 mg L−1) from the effluent.

Evolution of bituminous mix behaviour submitted to UV rays in laboratory compared to field exposure

Laboratory methods to simulate the short and long term ageing occurring during the service life of pure and polymer modified bitumens in a pavement are standardized but none of them takes into account the influence of ultraviolet (UV) radiations. Recently, attentions have been paid to the laboratory ageing tests with UV radiation applied to the bituminous binders. Even if this effect of UV radiation on binder’s films have been largely demonstrated and studied, however there are few studies dealing with the photo-oxidation of binders in a bituminous mix in relation with voids, film thickness and permeability. So, the aim of our study was to investigate whether the influence of UV light on bitumen ageing might be assessed in the bituminous mixes using an experimental apparatus dedicated to the ageing of paint. The results show that the influence of UV radiation on the ageing of bituminous mixes containing an elastomer modified bitumen can not be totally ignored: compared with thermal aging, the UV impact can be distinguished and found to be dominant for the production of carbonyl functions, the disappearance of C=C double bond of SBS and the increase of binder’s hardening. So, this study has highlighted, on the one hand, that inside the bituminous mix, the UV radiations do increase the rate of oxidation and, on the other hand, that the evolution’s kinetics due to a pure thermal oxidation or a photo-oxidation processes are different: the evolution due to 44 months of on site ageing is better assessed by photo-oxidation process than by pure thermal oxidation. Consequently, the UV exposure may affect the bitumen’s properties of pavement upper layers more strongly than the PAV simulation in laboratory (without UV action) does.

Retinal Responses in Pacific Salmon (Oncorhynchus masou) Fry to Weak Magnetic Fields and Ultraviolet Light

Pacific Ocean salmon (Oncorhynchus masou) fry aged six months mounted specific, previously undescribed, responses to exposure of retinal photoreceptors to ultraviolet light (UVL) in different combinations with a constant magnetic field (MF) (80 G). After exposure to UVL for 2 h (experiment 1), the pigment index (PI) of the retinomotor response increased from 0.30 ± 0.10 to 1.31 ± 0.20. Rods were present in the pigment layer, while cones were only partially screened by pigment. Overall, the retina demonstrated the twilight (mesopic) reaction. After exposure to UVL for 2 h followed by exposure to an MF with a constant magnet for 2 h (experiment 2), PI increased to 2.08 ± 0.10 and mean myoid height and the mean diameter of double cones increased. The retina showed a photopic response. Experiment 3 (MF for 2 h, followed by UVL for 2 h) gave the smallest PI values, 1.28 ± 0.12. Mean myoid height decreased, while mean cone diameter did not change. The retinal response was scotopic (as in the dark). Our own results, along with published data, led to the conclusion that MF distorts the influence of UVL and leads to unusual retinal reactions. These results support our previously described variant of the light-dependent magnetoreception model for vertebrates.

Ultraviolet resistance of azo-containing poly(1,3,4-oxadiazole) fibres

To improve the ultraviolet (UV) resistance of poly(1,3,4-oxadiazole) (POD) fibres, 4,4′-azodibenzoic acid (ADA) was introduced into the POD fibres through copolymerization and blending respectively. The influence of UV light on the intrinsic viscosity and mechanical properties of POD fibres with and without azo groups was investigated in detail. The results revealed that the tensile strength retention of the POD fibres containing ADA was much higher than that of the POD fibres without the azo groups (p-POD) after accelerated irradiation using an iodine-gallium lamp. It was also found that POD with ADA in the molecular chain (c-POD) by copolymerization showed better UV stability than that of the POD blended with the same amount of ADA (b-POD). The UV spectrum was used to explore the UV resistance mechanisms of the series of the POD containing azo groups and it was demonstrated that the mechanisms of b-POD and c-POD were different.