Duration Of UV Exposure Research Articles

Study on the Influence of UV Light on Selective Antibacterial Activity of Silver Nanoparticle Synthesized Utilizing Protein/Polypeptide-Rich Aqueous Extract from The Common Walkingstick, Diapheromera femorata.

Common walkingstick (Diapheromera femorata) aqueous extract (CWSAE) can induce the synthesis of useful bionanomaterials. CWSAE is rich in water-soluble organic compounds such as proteins and polypeptides that function as reducing/stabilizing agents for nanoparticle formation from Ag+ ion precursors. The synthesized AgNPs exhibited a moderately uniform size, with the majority falling within the range of 20-80 nm. These AgNPs were UV-treated and tested as antibacterial agents to inhibit the growth of four pathogenic bacteria (Burkholderia cenocepacia K-56, Klebsiella pneumoniae ST258, Pseudomonas aeruginosa PAO1, and Staphylococcus aureus USA300), as well as one common bacterium (Escherichia coli BW25113). The disk diffusion test demonstrated that the UV-treated AgNPs significantly and selectively inhibited the growth of Staphylococcus aureus USA300 and P. aeruginosa, while showing a small effect on the other two species. This suggests the potential application of green-chemically synthesized AgNPs as selective antibacterial agents. Furthermore, we studied the effects of short-term (1-2 min) and long-term (5-30 min) UV treatment on the selective cytotoxicity of the AgNPs and found that the cytotoxicity of the AgNPs could depend on the duration of UV exposure against certain bacteria.

Phenol red dye removal from wastewater using TiO2-FSM-16 and Ni-FSM-16 photocatalysts

In this study, the performance of Ni-FSM-16 and TiO2-FSM-16 photocatalysts in phenol red removal was explored. The XRD, FE-SEM, and BET tests were used to characterize the catalysts. All experiments were performed at ambient temperature and under UV (20 W). The parameters including dye concentration (20–80 mg/L), photocatalyst concentration (0–8 g/L), UV exposure duration, and contact time (0–160 min) were optimized using RSM software. BET values of Ni-FSM-16 and TiO2-FSM-16 were 718.63 m2/g and 844.93 m2/g, respectively. TiO2-FSM-16 showed better performance in dye removal than Ni-FSM-16. At pH 3, the maximum dye removal by TiO2-FSM-16/UV and Ni-FSM-16/UV was obtained 87% and 64%, respectively. The positive hole species had the main role in photocatalytic phenol red removal. The reusability study was done for up to 7 cycles, but the catalysts can be reused effectively for up to 3 cycles. The synergistic factor for the TiO2-FSM-16 and TiO2-FSM-16/UV processes were calculated to be 1.55 and 2.12, respectively. The dye removal efficiency by TiO2-carbon and Ni-carbon was slightly lower than those obtained by the FSM-16 ones. The TiO2-FSM-16 and Ni-FSM-16 catalysts had a suitable surface and acceptable efficiency in phenol red removal.

Physicochemical Properties of UV-Irradiated, Biaxially Oriented PLA Tubular Scaffolds

PLA and its blends are the most extensively used materials for various biomedical applications such as scaffolds, implants, and other medical devices. The most extensively used method for tubular scaffold fabrication is by using the extrusion process. However, PLA scaffolds show limitations such as low mechanical strength as compared to metallic scaffolds and inferior bioactivities, limiting their clinical application. Thus, in order to improve the mechanical properties of tubular scaffolds, they were biaxially expanded, wherein the bioactivity can be improved by surface modifications using UV treatment. However, detailed studies are needed to study the effect of UV irradiation on the surface properties of biaxially expanded scaffolds. In this work, tubular scaffolds were fabricated using a novel single-step biaxial expansion process, and the surface properties of the tubular scaffolds after different durations of UV irradiation were evaluated. The results show that changes in the surface wettability of scaffolds were observed after 2 min of UV exposure, and wettability increased with the increased duration of UV exposure. FTIR and XPS results were in conjunction and showed the formation of oxygen-rich functional groups with the increased UV irradiation of the surface. AFM showed increased surface roughness with the increase in UV duration. However, it was observed that scaffold crystallinity first increased and then decreased with the UV exposure. This study provides a new and detailed insight into the surface modification of the PLA scaffolds using UV exposure.

Colorectal cancer and occupational exposure to solar ultraviolet B radiation in Denmark

ObjectivesSolar ultraviolet B radiation (UV) may reduce the risk of cancer, including colorectal cancer (CRC), although the evidence is inconclusive. To contribute with evidence, the present largescale register-based nested case-control study aimed to investigate the association between occupational UV exposure and CRC in Denmark. MethodsThe Danish Cancer Registry was used to identify a total of 12,268 men and women diagnosed with primary CRC before age 70. Five controls matched on year of birth and sex, alive and free of CRC at the time of diagnosis of the index case were randomly selected from The Danish Civil Registration System. Occupational UV exposure was assessed by obtainment of full employment history from the Danish Supplementary Pension Fund Register, which was linked to a job exposure matrix. Conditional logistic regression was used to estimate odds ratios (ORs) with corresponding 95% confidence intervals. ResultsWe observed an inverse association between longer duration of UV exposure and CRC in women (≥20 years: OR = 0.84, 95% CI: 0.69–1.03), while no noteworthy associations were observed in men. When focusing on colon cancer only, longer duration of UV exposure (>20 years: OR = 0.92, 95% CI: 0.83–1.01) and higher cumulative UV exposure (highest exposure category: OR = 0.90, 95% CI: 0.83–0.99) were indicated to lower the risk in the study population including both men and women, although the risk reduction appeared to be more evident for women. No consistent risk patterns were observed for rectal cancer. ConclusionsThe present study suggests a modest protective effect from long-term occupational UV exposure on the risk of colon cancer. The effect may be greater in women and these findings need further attention in future large-scale studies.

Chelation and AOP Approach on Mn-Metal and COD Reduction of Liquid Laboratory Waste

Heavy metal waste and organic material used in flushing laboratory glassware can accumulate and potentially damage the environment. Thus, it needs to be processed before being disposed of to avoid any damage to the aquatic ecosystem. This research aimed to determine the pH wastewater sample and APDC concentration as chelating agents that would be the best for chelation treatment and determine the H2O2 concentration and UV exposure duration to identify the best treatment for the advanced oxidation process. This research was expected to find an alternative in wastewater treatment and provide an overview of the interaction of chelation treatment with organic pollutants as the basis for AOP-treatment management. Laboratory wastewater quality has improved through the extraction treatment of chelate from the pH 4 experiment, ammonium pyrrolidine dithiocarbamate (APDC) concentration at 7.5% with the manganese metal value decreased by 53%, an advanced oxidation process (AOP) treatment of H2O2 concentration at a 5.10-5%, and 31-hour UV exposure, resulting in chemical oxygen demand (COD) decreased by 98.98%. Waste containing both materials was reduced by combining the extraction of chelate formation and AOP, which was detected from the presence of manganese metal and the COD. This treatment can be an appropriate and easy way to degrade laboratory waste in a mini wastewater treatment process. This research succeeded in finding several novelties: first, a suitable pH value to reactivate Mn metal for chelation with APDC; second, the concentration of APDC determined to optimize the Mn metal chelate; third, the concentration of H2O2 to increase the effectiveness of organic matter reduction; fourth, the duration of UV irradiation is effective and efficient as a photocatalyst to reduce organic matter.

Investigation of UV light treatment (254 nm) on the reduction of aflatoxin M1 in skim milk and degradation products after treatment

This study investigates the reduction of aflatoxin M1 (AFM1) in skim milk by using ultraviolet light at 254 nm and the effects of influencing factors on the efficacy including treatment time (min), depth of samples (mm), contamination level (μg L−1), stirring, temperature, and fat content in milk. The colour and pH of milk samples were measured to evaluate the influence of the treatment on these values. It was found that short-wave ultraviolet radiation (UVC) reduced up to 50% of AFM1 in milk after 20 min of treatment regardless of the initial AFM1 contamination level. Treatment time, depth of samples, and stirring were all found to significantly (P < 0.05) enhance the reduction of AFM1. The milk colour was affected but there was no influence on the pH of milk samples at any duration of UV exposure. It is concluded that UVC light treatment has the potential to reduce AFM1 in milk.

Micromechanical behavior of ultraviolet-exposed polyurea

The present study focuses on the microstructural characterization of polyurea after extended UV exposure using a mechanics-based, atomic force microscope (AFM) investigation. Extended exposure to UV radiation resulted in photo-degradation with subsequent photo-oxidation reactions causing an increase in the surface roughness associated with crack nucleation. The crack opening and length were found to increase considerably with the rise in UV exposure duration. The crack growth was modeled using linear elastic fracture mechanics (LEFM) since the mechanical properties of the surface degraded layer were found to be within the limits of applicability of the theory. Force-distance measurements performed on the surface of the samples revealed a significant increase in the local modulus after 4.5 weeks of exposure. The local modulus was found to reach a steady limit after 7.5 weeks of UV radiation. The adhesive tip-sample forces resolved from the AFM force-displacement measurements indicated a drastic decrease after 3 weeks of exposure due to embrittlement of photo-oxidized exposed surface.Radiation effect; Microstructure; Polymers; LEFM

UV-induced anthocyanin in the host plant Sedum lanceolatum has little effect on feeding by larval Parnassius smintheus

Climate change has resulted in shorter periods of snow cover in alpine meadows, increasing the duration of UV exposure. We established the relationship between increased exposure to UV light and anthocyanin pigment levels in host plant Sedum lanceolatum and tested whether increased exposure changed the feeding behavior of its herbivore Parnassius smintheus. Anthocyanin concentrations were significantly greater in plants exposed to UV. Under field conditions, we found a preference of P. smintheus caterpillars for plants with slightly above average levels of anthocyanin; however, no-choice feeding experiments in which larvae ranging from 1 to 3 days old were placed on UV-rich and UV-low plants showed no difference in feeding. These results indicate that the reduction of snow cover in alpine meadows will change the pigment profile of plants, but these changes may have little effect on herbivory.

Application of Luminescent Netting in Traps to Improve the Catchability of the Snow Crab Chionoecetes opilio

AbstractIn this study, we investigated luminescent netting as a means to improve the catch rates of snow crabs Chionoecetes opilio. A laboratory experiment was conducted to investigate the intensity and duration of luminescence using time‐lapse photography. We exposed experimental traps to five different treatments of UV light to excite the luminescent fibers in the netting. Our results showed that luminescent netting can be effectively activated to emit light, and that the resulting intensity and duration of luminescence emitted over time depends on the initial duration of UV exposure and the source of light. A fishing experiment was subsequently conducted in eastern Canada to compare the catch rate of traditional and luminescent traps, and to determine how soak time affected catch rate. Results indicate that the effect of luminescent traps on the CPUE (measured as number of crab per trap) depended on the soak time. The CPUE was significantly higher (a 55% increase) in luminescent traps that underwent relatively short soak times (~1 d), but when soak times were longer (~8 d), the CPUE was not significantly different.

Use of GelMA for 3D printing of cardiac myocytes and fibroblasts.

To 3D print heart tissue, one must understand how the main two types of cardiac cells are affected by the printing process. Effects of gelatin methacryloyl (GelMA) concentration, extruder pressure and duration of UV exposure on survival of cardiac myocytes and fibroblasts were examined using lactate dehydrogenase and LIVE/DEAD assays, bioluminescence imaging and morphological assessment. Cell survival within 3D printed cardiomyocyte-laden GelMA constructs was more sensitive to extruder pressure and GelMA concentrations than within 3D fibroblast-laden GelMA constructs. Cells within both types of constructs were adversely impacted by the UV curing step. Use of mixed cell populations and enrichment of bioink formulation with fibronectin led to an improvement of cardiomyocyte survival and spreading.

Estimating degree of degradation of spilled oils based on relative abundance of aromatic compounds observed by paper spray ionization mass spectrometry

Paper spray ionization mass spectrometry (PSI-MS) was applied for the first time to study temporal change of photo-oxidized and weathered oils subjected to degradation. PSI is chosen in this study because it is an optimal ionization technique for the analysis of degraded oils with limited sample quantity and prone to salt and particulate contamination. With PSI-MS, quantitative analysis of oils can be successfully performed with as little as 2 μg of oil sample. In addition, oil solutions containing up to 0.05% sodium chloride were successfully analyzed with PSI-MS. In the PSI-MS spectra of photo-degraded oils, the relative abundance of compounds having double equivalence value (DBE) ≥ 5 increased but those with DBE < 5 decreased in number. The summed abundance ratio of compounds having DBE < 5 and DBE ≥ 5 showed a negative exponential correlation with the duration of UV exposure in laboratory experiments. The same trend was observed from spilled oils obtained from the environment. Therefore, this ratio serves as an effective means to estimate the degree of weathering in spilled oils.

Photocatalytic discoloration of denim using advanced oxidation process with H2O2/UV

Nowadays, various physical and chemical methods have been presented by researchers around the World for discoloration of denim fabrics. Although they have their own advantages and disadvantages, some of them have been used in garment industry for many years. In the present study, indigo dyed denim was discolored with one of the most popular advanced oxidation procedures (AOP) using combination of H2O2/UV. We observed a very effective discoloration (ΔE* = 17.44 after 150 min UV exposure). UV–vis spectra showed the disappearance of absorption peaks of indigo due to decomposition of chromophores and aromatic rings. Based on the FTIR spectra from discolored denim, we concluded that photolysis reactions occurred on denim following by generation of OH and OOH radicals. Cotton fibers in discolored denim samples showed disorientation, wrinkling and defibrillation depending on UV exposure duration. Hence, H2O2/UV process could be recommended to as a simple and effective method for denim discoloration.

Corrections to "Combined Effects of UV Exposure Duration and Mechanical Abrasion on Microplastic Fragmentation by Polymer Type".

Corrections to "Combined Effects of UV Exposure Duration and Mechanical Abrasion on Microplastic Fragmentation by Polymer Type".

Human health risk evaluation of a microwave-driven atmospheric plasma jet as medical device

PurposeThe aim of this study was the characterisation of a microwave-driven atmospheric plasma jet (APJ) dedicated for medical applications. The scientific focus includes harmless sterilization of surfaces and therapeutic treatments in dentistry. MethodesThe plasma was investigated with respect to potential health risks for human beings, which could occur especially by the gas temperature, heat flow, patient leakage current, UV emission and ozone emission from the plasma jet, according to DIN SPEC 91315:2014-06 (General requirements for plasma sources in medicine) [1]. ResultsThe results of the experiments indicate a high potential of the plasma jet to be used as a medical device exhibiting low gas temperatures up to 34 °C. The calculated leakage currents are mostly below the 10 μA threshold. The limiting UV exposure duration for the APJ with a calculated maximum effective irradiance of 2.6 μW/cm2 is around 19 min, based on the exposure limits of the international commission on non-ionizing radiation protection guidelines (ICNIRP) [2]. A significant ozone concentration was observed mainly in the axial effluent gas flow. Ozone concentration strongly decreases with increasing distance from the plasma source exit nozzle. ConclusionThe investigated APJ exhibits physical properties that might not constitute health risks to humans, e.g. during treatment in dentistry. Thus, the APJ shows a high potential for application as a device in dental therapy.

Thermoluminescence and photoluminescence study of KY3F10:Ho3+ commercial phosphor powder

Thermoluminescence (TL) and photoluminescence (PL) properties of KY3F10:Ho3+ phosphor powder is reported. The TL measurements were carried out for different heating rates and for various durations of UV exposure. The TL intensity increases with the duration of UV exposure up to 20 min and then decreases. A decrease of the glow peak height was observed for the glow curves with an increasing heating rate. The area under the TL-time plot is calculated for each heating rate at a constant UV dose and it is found to be constant and independent of the heating rate. It is found that the observed decrement in intensity of each glow curve following an increment in the heating rate is not attributed to the thermal quenching effect. Important TL kinetic parameters namely, the activation energy (E) and the frequency factor (s) were calculated using a variable heating rate (VHR) method. The glow peaks obey first order kinetics. PL emission spectra were also investigated at four main excitation wavelengths; namely, 362, 416, 454 and 486 nm. Green emission at 540 nm and faint red emission at 750 nm were observed for all the excitations. The green emission at 540 nm is ascribed to the 5F4–5I8 and 5S2–5I8 transitions and the faint red emission at 750 nm is due to the 5F4–5I7 and 5S2–5I7 transitions. In addition to the sharp green emission at 540 nm, a broad emission centered at 600 nm was observed for excitation wavelength of 362 nm.

Mechanical Characterization of a Dynamic and Tunable Methacrylated Hyaluronic Acid Hydrogel.

Hyaluronic acid (HA) is a commonly used natural polymer for cell scaffolding. Modification by methacrylate allows it to be polymerized by free radicals via addition of an initiator, e.g., light-sensitive Irgacure, to form a methacrylated hyaluronic acid (MeHA) hydrogel. Light-activated crosslinking can be used to control the degree of polymerization, and sequential polymerization steps allow cells plated onto or in the hydrogel to initially feel a soft and then a stiff matrix. Here, the elastic modulus of MeHA hydrogels was systematically analyzed by atomic force microscopy (AFM) for a number of variables including duration of UV exposure, monomer concentration, and methacrylate functionalization. To determine how cells would respond to a specific two-step polymerization, NIH 3T3 fibroblasts were cultured on the stiffening MeHA hydrogels and found to reorganize their cytoskeleton and spread area upon hydrogel stiffening, consistent with cells originally cultured on substrates of the final elastic modulus.

The effect of ultraviolet radiation on ultrasonic properties of polyurea

Polyurea is used in military and civilian applications where exposure to the sun is commonly of long duration, which can deteriorate its mechanical performance to suboptimal levels. This study reports on the ultrasonic properties of polyurea as a function of ultraviolet radiation exposure duration and temperature. Six sets of samples were continuously exposed to ultraviolet radiation for different durations up to 15 weeks. Control samples were also tested that did not receive UV exposure. The ultrasonic properties were measured using high-frequency contact ultrasound transducers in pitch-catch configuration. All exposed samples exhibited significant color changes from transparent yellow to opaque light brown. Changes of color were observed as early as 3 weeks of UV exposure. Nonetheless, crazing was only observed in samples of 6, 9, 12, and 15 weeks of continuous exposure. The size of the surface cracks increased as the duration of exposure continued. The effect of extended UV radiation on the acoustic properties was noted to be minimal, where elastic and shear moduli decreased monotonically after an initial increase during the first 3 weeks of exposure. The attenuation properties were measured at 23 °C and 40 °C. The p-wave attenuation did not show any notable change, while the s-wave attenuation monotonically decreased as the temperature and UV exposure duration increased.

Programmable gradational micropatterning of functional materials using maskless lithography controlling absorption.

The demand for patterning functional materials precisely on surfaces of stimuli-responsive devices has increased in many research fields. In situ polymerization technology is one of the most convenient ways to place the functional materials on a desired location with micron-scale accuracy. To fabricate stimuli-responsive surfaces, controlling concentration of the functional material is much as important as micropatterning them. However, patterning and controlling concentration of the functional materials simultaneously requires an additional process, such as preparing multiple co-flow microfluidic structures and numbers of solutions with various concentrations. Despite applying these processes, fabricating heterogeneous patterns in large scale (millimeter scale) is still impossible. In this study, we propose an advanced in situ polymerization technique to pattern the surface in micron scale in a concentration-controlled manner. Because the concentration of the functional materials is manipulated by self-assembly on the surface, a complex pattern could be easily fabricated without any additional procedure. The complex pattern is pre-designed with absorption amount of the functional material, which is pre-determined by the duration of UV exposure. We show that the resolution reaches up to 2.5 μm and demonstrate mm-scale objects, maintaining the same resolution. We also fabricated Multi-bit barcoded micro particles verify the flexibility of our system.

Selective pattern of cancer cell accumulation and growth using UV modulating printing of hydrogels.

Fabrication of extracellular microenvironment for cancer cell growth in vitro is an indispensable technique to precisely control the cell spatial arrangement and proliferation for cell-behavior research. Current micropatterning methods usually require relatively complicated operations, which makes it difficult to investigate the effects of different cell growth patterns. This manuscript proposes a DMD-based projection technique to quickly pattern a poly(ethylene) glycol diacrylate (PEGDA)-based hydrogel on a common glass substrate. Using this method, we can effectively control the growth patterns of cells. Compared with these traditional methods which employ digital dynamic mask, polymerization of PEGDA solution can be used to create arbitrary shaped microstructures with high efficiency, flexibility and repeatability. The duration of UV exposure is less than 10s through controlling the projected illumination pattern. The ability of patterned PEGDA-coated film to hinder cell adhesion makes it possible to control area over which cells attach. In our experiments, we take advantage of the blank area to pattern cells, which allows cells to grow in various pre-designed shapes and sizes. And the patterning cells have a high viability after culturing for several days. Interestingly, we found that the restricted space could stiffen and strengthen the cells. These results indicate that cells and extracellular microenvironment can influence each other.

Material Safety and Integrity of Water-Filled Low-Density Polyethylene Bags in an Accelerated Weathering Investigation for Applications in Solar Water Disinfection (SODIS)

In this work, the potential use of LDPE bags as containers in the SODIS application by simulated in an accelerated weathering tester (QUV), with respect to material safety and durability, was investigated. For the material integrity, a decrease in the elongation at break from 818% (at the beginning) to 21% (after 6 weeks of UV exposure) corresponded to the long UV exposure. A significant degree of mechanical degradation was evident during 2 to 4 weeks of UV exposure. The UV-Vis results showed that the UV transmittance of the bags, mostly in the UV-B region, decreased with longer duration of UV exposure. The FT-IR results showed a slight increase in carbonyl group, particularly observable in the bags exposed under UV for 3 weeks or longer. For the material safety, the amount of plastic additives that were leached into water was negligibily small and much lower than the limit of the safety standard. The results and analyses from this work provide insights into the feasibility of LDPE as an alternative material for SODIS containers and potentially be useful for future designs of SODIS containers to improve the disinfection and durability performances.