Prolonged Ultraviolet Exposure Research Articles

Effects of UV degradation on building materials with emphasis on microplastic generation potential

This study investigates the effects of ultraviolet (UV) exposure on indoor building materials, focusing on color change, surface degradation, and chemical composition alterations. UV-exposed materials, quantitatively assessed using RGB and HSL color models, demonstrated progressive yellowing. Atomic force microscopy (AFM) measurements revealed significant surface deterioration in specific materials, indicating compromised protective coatings due to UV exposure.Chemical analyses via FT-IR and X-ray photoelectron spectroscopy confirmed increased oxygen content in these materials, suggesting oxidative processes affecting plastic components. Assessment of microplastic generation potential based on surface roughness data identified higher production rates in certain materials, raising concerns about the environmental implications of prolonged UV exposure indoors. Moreover, evaluating human health risks associated with indoor microplastic exposure highlighted elevated hazard indices for wallpapers and sheets, emphasizing potential risks from ingestion, inhalation, and dermal contact with microplastics. These findings underscore the necessity for enhanced approaches in architectural material design and regulation to mitigate these risks effectively.

UV-Induced DNA Repair Mechanisms and Their Effects on Mutagenesis and Culturability in Escherichia coli.

Mutagenic processes drive evolutionary progress, with ultraviolet (UV) radiation significantly affecting evolution. Despite extensive research on SOS response-mediated mutagenesis, UV-induced repair mechanisms remain complex, and their effects on cell survival and mutagenesis are not fully understood. We previously observed a near-perfect correlation between RecA-mediated SOS response and mutation levels in Escherichia coli following UV treatment. However, prolonged UV exposure caused transient non-culturability and impaired SOS-mediated mutagenesis. Using fluorescent reporters, flow cytometry, promoter-reporter assays, single-gene deletions, knockouts, and clonogenic assays, we found that excessive UV exposure disrupts cellular translation, reducing SOS gene expression, albeit with minimal impact on membrane permeability or reactive oxygen species levels. While our findings underline the abundance of repair mechanisms in E. coli cells, enabling them to compensate when specific genes are disrupted, they also highlighted the differential impacts of gene deletions on mutagenesis versus culturability, leading to three major outcomes: (i) Disruption of proteins involved in DNA polymerase for translesion synthesis (UmuC and UmuD) or Holliday junction resolution (RuvC) results in significantly decreased mutagenesis levels while maintaining a transient non-culturability pattern after UV exposure. (ii) Disruption of proteins involved in homologous recombination (RecA and RecB) and nucleotide excision repair (UvrA) leads to both significantly reduced mutagenesis and a more severe transient non-culturability pattern after UV exposure, making these cells more sensitive to UV. (iii) Disruption of DNA Helicase II (UvrD), which functions in mismatch repair, does not affect mutagenesis levels from UV radiation but results in a very pronounced transient non-culturability pattern following UV exposure. Overall, our results further advance our understanding of bacterial adaptation mechanisms and the role of DNA repair pathways in shaping mutagenesis.

Evaluation of astaxanthin stability under varying temperatures and ultraviolet irradiation durations based on Raman spectroscopy

As a potent naturally carotenoid, Astaxanthin (AST) is commonly used as a natural coloring agent and antioxidant in food products, and it's stability is of great interest. The stability of AST solution stored in glass bottle under different temperatures and ultraviolet (UV) irradiation durations was analyzed in situ using confocal Raman spectroscopy, and the acceptable depth of focus was optimized. Raman spectra of AST geometrical isomers were determined by density functional theory (DFT) simulation, and characteristic peaks were selected for studying AST degradation and isomerization. Raman spectra and peak-fitting spectra based on gaussian multi-peak fitting analysis combined with Pearson's correlation analysis were conducted to study the effect of temperatures and UV irradiation on AST degradation and isomerization. The peak intensity ratio of I1518/I880 had been selected as the optimal Raman spectral variable for AST degradation based on Pearson's correlation analysis. Finally, degradation kinetic curves and degradation rate prediction equation were established. The results indicated that the isomerization of 9,13-di-cis isomer occurred at a UV irradiation of 288 h. Moreover, high temperatures above 60 °C and prolonged UV exposure exceeds 48 h can cause significant degradation of AST, with a degradation rate above 20 %. This study provided an in-situ, nondestructive potential method for the calculation of AST degradation under different temperatures and UV irradiation durations, which contribute guiding insights into the development and utilization of AST in food industry.

Evaluating the Dermatological Benefits of Snowberry (Symphoricarpos albus): A Comparative Analysis of Extracts and Fermented Products from Different Plant Parts.

Skin ageing is influenced by both intrinsic and extrinsic factors, with excessive ultraviolet (UV) exposure being a significant contributor. Such exposure can lead to moisture loss, sagging, increased wrinkling, and decreased skin elasticity. Prolonged UV exposure negatively impacts the extracellular matrix by reducing collagen, hyaluronic acid, and aquaporin 3 (AQP-3) levels. Fermentation, which involves microorganisms, can produce and transform beneficial substances for human health. Natural product fermentation using lactic acid bacteria have demonstrated antioxidant, anti-inflammatory, antibacterial, whitening, and anti-wrinkle properties. Snowberry, traditionally used as an antiemetic, purgative, and anti-inflammatory agent, is now also used as an immune stimulant and for treating digestive disorders and colds. However, research on the skin benefits of Fermented Snowberry Extracts remains limited. Thus, we aimed to evaluate the skin benefits of snowberry by investigating its moisturising and anti-wrinkle effects, comparing extracts from different parts of the snowberry plant with those subjected to fermentation using Lactobacillus plantarum. Chlorophyll-free extracts were prepared from various parts of the snowberry plant, and ferments were created using Lactobacillus plantarum. The extracts and ferments were analysed using high-performance liquid chromatography (HPLC) to determine and compare their chemical compositions. Moisturising and anti-ageing tests were conducted to assess the efficacy of the extracts and ferments on the skin. The gallic acid content remained unchanged across all parts of the snowberry before and after fermentation. However, Fermented Snowberry Leaf Extracts exhibited a slight decrease in chlorogenic acid content but a significant increase in ferulic acid content. The Fermented Snowberry Fruit Extract demonstrated increased chlorogenic acid and a notable rise in ferulic acid compared to its non-fermented counterpart. Skin efficacy tests revealed that Fermented Snowberry Leaf and Fruit Extracts enhanced the expression of AQP-3, HAS-3, and COL1A1. These extracts exhibited distinct phenolic component profiles, indicating potential skin benefits such as improved moisture retention and protection against ageing. These findings suggest that Fermented Snowberry Extracts could be developed into effective skincare products, providing a natural alternative for enhancing skin hydration and reducing signs of ageing.

Ultraviolet-Protective Clothing and Sunscreen: Sun-Protection for Healthy Skin

Introduction Prolonged exposure to ultraviolet (UV) radiation from the sun poses numerous risks to the skin, ranging from premature aging to serious health conditions such as skin cancer. UV radiation can penetrate the skin's surface, causing damage to its cells and DNA, which can lead to the formation of wrinkles, sunspots, and other signs of aging. Therefore, consistent and effective sun protection is essential for maintaining the health and vitality of the skin, as well as reducing the risk of sun-related skin damage and diseases. Aim of the study The objective of the study is to conduct a thorough investigation into different aspects of photoprotection and its effects on the skin. This entails assessing the effectiveness and safety of sunscreens, as well as evaluating the impact of sun-protection clothing on skin health. Materials and methods The purpose of this review is to assess the current literature of the effectiveness of the various sun protection measures. The literature was reviewed in the Pubmed, Google Scholar data base. Results Prolonged UV exposure incites photoaging, carcinogenesis, and immunosuppression, amplifying the risk of skin malignancies. Sun-protective clothing, with adequate UPF ratings, emerges as a pivotal element in mitigating UV-induced skin damage, notably reducing the development of pigmented moles and melanoma. Furthermore, effective sunscreen usage, coupled with broad-spectrum protection, is essential in averting UV-induced skin damage and curbing the incidence of skin cancer. These findings emphasize the imperative of comprehensive photoprotection strategies, integrating sunscreen application, sun-protective clothing, and individual risk assessment, to safeguard against solar-induced skin damage and mitigate the prevalence of skin cancer.

Correlation and stage change of key groups and thermal effects of spontaneous coal combustion due to long-term ultraviolet illumination

This study aimed to unveil the correlation between the changes in active groups and thermal effects during the spontaneous coal combustion under prolonged ultraviolet (UV) irradiation. In situ Fourier transform–infrared spectroscopy (FTIR) and microcalorimetry (C80) experiments were conducted. Thermodynamic analysis, Pearson's correlation analysis, and Grey Relational Analysis (GRA) were employed to analyze the raw coal (R0) and the coal after UV irradiation for 3, 6, 9, and 12 months (R3, R6, R9, and R12). The results indicated that UV irradiation promotes the generation of Ar-CH, –CC-, CO, and –OH, while causing the consumption of –CH3. This promoting effect gradually increases within the first 6 months and then diminishes after 6 months. A thermodynamic analysis revealed a consistent trend in the apparent activation energy during Stages I and II, where R0<R12<R3<R9<R6. This result suggests that UV exposure promotes coal–oxygen reactions. In the correlation analysis, it was observed that the key active groups for R0 and UV-irradiated coal are not consistent across different stages, with –OH and –CO identified as the key active groups in Stages I and II of UV-irradiated coal, respectively. The correlation between –OH and –CO exhibits a distinct stage-wise variation with prolonged UV exposure.

Electronic relaxation mechanism of 9-methyl-2,6-diaminopurine and 2,6-diaminopurine-2'-deoxyribose in solution.

Prolonged ultraviolet exposure results in the formation of cyclobutane pyrimidine dimers (CPDs) in RNA. Consequently, prebiotic photolesion repair mechanisms should have played an important role in the maintenance of the structural integrity of primitive nucleic acids. 2,6-Diaminopurine is a prebiotic nucleobase that repairs CPDs with high efficiency when incorporated into polymers. We investigate the electronic deactivation pathways of 2,6-diaminopurine-2'-deoxyribose and 9-methyl-2,6-diaminopurine in acetonitrile and aqueous solution to shed light on the photophysical and excited state properties of the 2,6-diaminopurine chromophore. Evidence is presented that both are photostable compounds exhibiting similar deactivation mechanisms upon the population of the S1 (ππ* La ) state at 290 nm. The mechanism involves deactivation through the C2- and C6-reaction coordinates and >99% of the excited state population decays through nonradiative pathways involving two conical intersections with the ground state. The radiative and nonradiative lifetimes are longer in aqueous solution compared to acetonitrile. While τ1 is similar in both derivatives, τ2 is ca. 1.5-fold longer in 2,6-diaminopurine-2'-deoxyribose due to a more efficient trapping in the S1 (ππ* La ) minimum. Therefore, 2,6-diaminopurine could have accumulated in significant quantities during prebiotic times to be incorporated into non-canonical RNA and play a significant role in its photoprotection.

Flexible humidity sensor for smart agricultural applications

In order to meet the increasing food demand, sensors that measure the ambient temperature and humidity in greenhouses are needed for more efficient vegetable and fruit production. For this purpose, two different flexible and resistant textile-based humidity sensors that can measure the humidity at higher levels (80%, 90%, and 100% relative humidity (RH)) were designed and printed directly on the four different greenhouse fabrics using silver and carbon conductive inks. Depending on the humidity value in the environment, the sensor performance was tested based on sensor electrical resistance measurements with respect to repeated bending/cyclic tests, rubbing, ultraviolet (UV) exposure/ weatherability (against UV and raining) tests in order to simulate greenhouse conditions for smart agriculture. Despite applying 1024 bending cycles, up to 20 rubbing cycles, and 10 times UV and rain exposure to the humidity sensors at high RH, no significant change was detected in the resistance values of the humidity sensors. Moreover, some important features of the sensors such as hysteresis, repeatability, response time have been also examined. According to hysteresis test results, humidity sensors show acceptable dynamic response and response time of the sensors are 15.8, 17.3, 24.8, and 25 s at 100% RH for G2S, W1S, B2C, and W1C, respectively. Statistical analyses showed that the sensor designs and type of conductive inks had significant effects on the performance of the humidity sensors and the best sensor performance was obtained with the polypropylene coated fabric using design II and silver based conductive ink. The fabricated textile based flexible humidity sensors detect the change in RH levels from 80% RH to 100% RH and achieve good durability, and repeatability even after prolonged UV exposure and raining. Thus, the developed textile-based flexible humidity sensor might be useful for future smart agricultural applications.

Halide-exchanged perovskite photodetectors for wearable visible-blind ultraviolet monitoring

Wearable sensing technologies are essential for personalized healthcare via continuously monitoring the surrounding information. Ultraviolet (UV) light, an important component of solar radiation, is recognized as the main inducement of skin cancers. So far, the use of rigid and costly technologies to fabricate UV sensors still hinders their implementation in wearable and portable electronics. Here we present a wearable UV wristband based on a self-powered flexible perovskite photodetector for real-time UV monitoring. Utilizing a solution-assisted halide exchange strategy, device based on CH3NH3PbCl3 film exhibits excellent UV detection performance (high responsivity of 359.03 mA/W, fast rise/fall time of 3.91/4.55 ms), outstanding mechanical robustness (remaining over 80% of initial performance after 2500 bending cycles), as well as desirable operational stability (unchanged photoresponse under 500 h of continuous UV light soaking). Integrated with commercially available soft circuits, this fully flexible sensor system enables round-the-clock probing for UV radiation indoor and outdoor in conjunction with necessary environmental information, which can be displayed and recorded on a smartphone, to prevent prolonged UV exposure. The wearable platform not only paves the way for seamlessly integrated photodetectors, but also enables a wide range of personalized environmental and health monitoring applications.

Deterioration mechanism on flame retardancy of aliphatic waterborne polyurethane-based hybrid coatings under ultraviolet radiation: Experiment and pyrolysis kinetics

Organic-inorganic hybrid intumescent flame retardant coating (IFRC) has been manifested as a promising solution to prevent fire spread of the plywood for indoor decoration. The aliphatic waterborne polyurethane (AWP)-based IFRC is prepared using the silicon-based aerogel, β-cyclodextrin, and nano-ZnO as the functional filler, and its ultraviolet-aging deterioration mechanism on flame retardancy is investigated through microstructure characterizations and pyrolysis kinetic calculation. The results show that the flame-retarding and smoke-suppressing properties of the IFRC gradually deteriorate with the prolonged ultraviolet exposure from 6 to 60 cycles, evidenced by the reduced flame retardancy index of 0.19 (drops from 1.00), the rising fire growth index from 0.87 to 1.45 kW m −2 s −1 , the increased average effective heat of combustion from 3.45 to 5.65 MJ·kg −1 , and the rising total smoke production from 91 to 153 m 2 . Because the ultraviolet radiation favors the chain scission of AWP and cleavage of –HN-CO-, crystallization of Zn 3 (PO 4 ) 2 , ZnP 4 O 11 , and SiP 2 O 7 for the IFRC during burning, leading to the reduced E α of 330–150 ℃ (decreases by 20%) approximately, presenting a reduced water contact angle and a fluffy char. It preliminary seeks the ultraviolet-aging flame-retarding mechanism with quantitative techniques and explores the condensed flame-retarding mechanism further. • Ultraviolet-aging deterioration mechanism of hybrid IFRCs is quantitatively investigated. • The ultraviolet radiation favors the crystallization of Zn 3 (PO 4 ) 2 , ZnP 4 O 11 , and SiP 2 O 7 . • The ultraviolet radiation contributes to the E α of 330–150 ℃ decreased by 20% approximately.

Characterizing the Effects of Synergistic Thermal and Photo-Cross-Linking during Biofabrication on the Structural and Functional Properties of Gelatin Methacryloyl (GelMA) Hydrogels.

Gelatin methacryloyl (GelMA) hydrogels have emerged as promising and versatile biomaterial matrices with applications spanning drug delivery, disease modeling, and tissue engineering and regenerative medicine. GelMA exhibits reversible thermal cross-linking at temperatures below 37 °C due to the entanglement of constitutive polymeric chains, and subsequent ultraviolet (UV) photo-cross-linking can covalently bind neighboring chains to create irreversibly cross-linked hydrogels. However, how these cross-linking modalities interact and can be modulated during biofabrication to control the structural and functional characteristics of this versatile biomaterial is not well explored yet. Accordingly, this work characterizes the effects of synergistic thermal and photo-cross-linking as a function of GelMA solution temperature and UV photo-cross-linking duration during biofabrication on the hydrogels' stiffness, microstructure, proteolytic degradation, and responses of NIH 3T3 and human adipose-derived stem cells (hASC). Smaller pore size, lower degradation rate, and increased stiffness are reported in hydrogels processed at lower temperature or prolonged UV exposure. In hydrogels with low stiffness, the cells were found to shear the matrix and cluster into microspheroids, while poor cell attachment was noted in high stiffness hydrogels. In hydrogels with moderate stiffness, ones processed at lower temperature demonstrated better shape fidelity and cell proliferation over time. Analysis of gene expression of hASC encapsulated within the hydrogels showed that, while the GelMA matrix assisted in maintenance of stem cell phenotype (CD44), a higher matrix stiffness resulted in higher pro-inflammatory marker (ICAM1) and markers for cell-matrix interaction (ITGA1 and ITGA10). Analysis of constructs with ultrasonically patterned hASC showed that hydrogels processed at higher temperature possessed lower structural fidelity but resulted in more cell elongation and greater anisotropy over time. These findings demonstrate the significant impact of GelMA material formulation and processing conditions on the structural and functional properties of the hydrogels. The understanding of these material-process-structure-function interactions is critical toward optimizing the functional properties of GelMA hydrogels for different targeted applications.

Predicting Early EVA Degradation in Photovoltaic Modules From Short Circuit Current Measurements

One of the common failures in photovoltaic modules is the degradation of the ethylene-vinyl acetate (EVA) encapsulant due to prolonged ultraviolet exposure and other environmental stress factors, such as temperature and humidity. Experimental studies have shown that significant reduction in the optical transmission due to EVA degradation leads to loss in the available power by more than 50%. In this article, a novel approach to predict the early degradation of EVA encapsulant is proposed by correlating EVA degradation with short-circuit current (I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">SC</sub> ). An electrical circuit simulator, simulation program with integrated circuit emphasis (SPICE), is used to evaluate the short-circuit current obtained under varying optical transmission caused by EVA discoloration. The simulation follows three steps: simulation of the transmitted solar spectrum; simulation of the spectral short-circuit current density; and simulation of the current-voltage (I-V) curve to obtain short-circuit current (I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">SC</sub> ), maximum power output (P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</sub> ), open-circuit voltage (V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">OC</sub> ) and fill factor. Results show that the reduction in short-circuit current due to EVA degradation differs from the reductions expected due to a spectrally-uniform reduction of intensity of the solar irradiance. Both types of variation are linear, however, the slope due to EVA degradation is larger than the slope obtained for normal intensity variations in the solar irradiance. This model, when applied in conjunction with solar irradiance measurements, can predict early onset of EVA encapsulant failure, thereby enabling preventative measures to be taken.

Dynamic Mechanical Analysis of Bio-Based and Synthetic Petroleum Based Polymer Foams with Powder Type Organic Filler at Prolonged Ultra-Violet Exposure

Wood powder filler applied to the bio-based and epoxy polymer foams has the potential to reinforce the polymer foam structure. The 'Meranti' wood filler type was used as the filler in this analysis. In order to observe the pore size of each sample when exposed to different hours of UV exposure using optical microscopy (OM), this study was made.This analysis was conducted to compare the mechanical properties of each sample with different filler ratios of 0 wt%, 5 wt%, 10 wt%, 15wt% and 20 wt% at different UV exposure hours, which is 0 hour to 6000 hours with a 2000 hour rapid increase. Using the DMA Q800 TA unit, the mechanical properties were studied. In order to obtain the product of their mechanical properties, samples having a scale of 40 x 10 x 5 mm were clamped into the machine. The results will show the value of tan δ, loss modulus and storage modulus from the DMA test.The tan δ value shows that the high tanδvalue will be produced by the higher ratio filler. In contrast to bio-based polymer foams, epoxy polymer foams with powder fillers have the highest tan δ value. It shows that the higher filler ratio can be reported with the lower tan δ value. As the filler ratio filler in the polymer foams increased, the consequence of storage and loss modulus was found to increase. The greater the modulus of loss and the modulus of storage, the lower the temperature. As energy is lost as heat during UV irradiation exposure, bio-based polymer foams with a high powder filler ratio can dissipate more energy.

Exploring the Photochemistry of an Ethyl Sinapate Dimer: An Attempt Toward a Better Ultraviolet Filter.

The photochemistry and photostability of a potential ultraviolet (UV) radiation filter, dehydrodiethylsinapate, with a broad absorption in the UVA region, is explored utilizing a combination of femtosecond time-resolved spectroscopy and steady-state irradiation studies. The time-resolved measurements show that this UV filter candidate undergoes excited state relaxation after UV absorption on a timescale of ~10 picoseconds, suggesting efficient relaxation. However, steady-state irradiation measurements show degradation under prolonged UV exposure. From a photochemical standpoint, this highlights the importance of considering both the ultrafast and “ultraslow” timescales when designing new potential UV filters.

Polybenzimidazole-Benzophenone Composite Nanofiber Window Air Filter with Superb UV Resistance and High Chemical and Thermal Durability.

There is a growing interest in window air filters to protect indoor air quality from ultrafine particulate matter (PM) in outdoor air. The filters for this purpose must achieve high filtering efficiency without compromising the original functions of the window, such as high air permeability and visibility. Several filters meeting these requirements have been developed and demonstrate a high PM2.5 filtering efficiency. However, these filters are installed outside the window or on the window screen guard, thereby requiring high levels of ultraviolet (UV), chemical, and thermal resistance. These requirements have been overlooked so far. In this study, we examine the fabrication and performance of a polybenzimidazole-benzophenone (PBI-BP) composite nanofiber air filter that demonstrates superb UV resistance and chemical and thermal durability. Because of the UV absorbance of the BP in the nanofibers, the filter membrane is robust even under prolonged UV exposure, which is essential for filters for this purpose. The filter membrane is not damaged even after treatment in strong acids or annealing at high temperature up to 400 °C. Thus, the PBI-BP composite filter is suitable for practical application in window air filters and can be adapted to develop filters used under other harsh environments.

Ultra-violet health monitoring of smart composite laminate using embedded fiber Bragg grating sensors

A novel approach is developed to evaluate the property retention on prolonged ultra-violet exposure and hence, health monitoring of glass fiber reinforced polymer composite laminate. This is achieved in a non-destructive manner by mapping the strength retention with the established strain. Embedded fiber Bragg grating sensor and strain gauges are employed to monitor the strain evolution within the laminate. Tensile and flexural tests are conducted at regular intervals to estimate the mechanical strength retention with varying duration of ultra-violet exposure. Through this analysis, it is observed that the property degradation mechanism follows the first-order reaction kinetics. The degradation of matrix material along with the stress relaxation over time develops the stress–strain fields near the interfaces of matrix and fiber. Moreover, the established strain is interpreted by formulating the model that considers the unifying influence of stress relaxation and chemical degradation. This model has closely (R2 = 0.9810 and 0.9790) predicted the experimental data of strain than the existing ones (R2 = 0.9142 and 0.9119). Besides, property retention is mapped with the predicted strain. More importantly, FESEM and FTIR confirm the fact that ultra-violet radiation degrades the matrix material, and thus the mechanical property gets significantly deteriorated. This suggests that the strain measurement is an effective, non-destructive and health monitoring technique to assess the property degradation of the manufactured glass fiber reinforced polymer composites.

Limitations of a polymer-based hole transporting layer for application in planar inverted perovskite solar cells.

Planar inverted lead halide photovoltaics demonstrate remarkable photoconversion properties when employing poly(triarylamine) (PTAA) as a hole transporting layer. Herein, we elucidate the effect of ambient ultraviolet (UV) degradation on the structural and operational stability of the PTAA hole transporter through a series of rigorous optoelectrical characterization protocols. Due attention was given to the interplay between the polymer and perovskite absorber, both within the framework of a bilayer structure and fully assembled solar cells. The obtained results imply that UV degradation exerts a major influence on the structural integrity of PTAA, rather than on the interface with the perovskite light harvester. Moreover, UV exposure induced more adverse effects on tested samples than environmental humidity and oxygen, contributing more to the overall reduction of charge extraction properties of PTAA, as well as increased defect population upon prolonged UV exposure.

Development and Characterization on sound acoustic at photo-induced polymer foam composited at prolonged ultra-violet exposure

In this paper, polymer foam composites (FC) have been developed based on polyol mixed flexible crosslinker and fibre filler of Meranti Merah. 10 mm, 20 mm and 30 mm thickness of foam polymer and its composites have been use in this study. The percentage loading of wood fibre of 5%, 10%, 15% and 20% added with polymer foam is namely as polymer foam (PP) and its composites of PP5, PP10, PP15 and PP20. The sound absorption coefficient (α) and pore structure of the foam samples have been measure by using Impedance Tube test and Scanning Electron Microscopy (SEM). UV Weatherometer is used to examine the durability and weatherproof of its composite. The results show that the highest thickness of the highest percentage fiber filler (Pp2030) gives higher sound absorption coefficient (α). 0.9922 and 0.99889 which contributed from low and high frequency absorption level respectively. The smallest pores size structure was observed with highest filler loading of PP20. The higher the thickness and the higher the percentage loading of wood filler gives smaller pore structure, consequently, increased the sound absorption coefficient level. Meanwhile, the stability of polymer foam composites is high due to unchanged pore structures morphology with prolonged ultra violet exposure.

Vitamin D levels in actinic keratosis: a preliminary study

Background:Recent studies that investigated the effect of vitamin D on skin cancer risk have exhibited inconsistent results. Objective:The aim of the study was to evaluate vitamin D status in patients with actinic keratosis. Methods:A cross-sectional study was conducted on 31 patients with actinic keratosis and 29 healthy controls. Serum vitamin D levels in the study group were determined by liquid chromatography/tandem mass spectrometry. Results:Serum 25(OH)D levels in patients with actinic keratosis were significantly higher than those of the healthy controls (P=0.04). Prevalence of 25(OH)D deficiency was significantly higher in the healthy controls (75.9%) compared to the patients with actinic keratosis (54.8%), but the difference was not statistically significant (P= 0.09). Study limitations:The cross-sectional design of the study, data on smoking based on patient self-report, and subjects’ different dietary habits, which can influence 25(OH)D levels, are the study’s limitations. Conclusion:Serum vitamin D level can be used as a marker for ultraviolet B radiation from sun exposure; therefore, it can be used in individuals at risk of actinic keratosis. Oral intake of vitamin D through diet or supplements is proposed instead of prolonged ultraviolet exposure to maintain adequate vitamin D serum levels. Further research is needed to elucidate the role of vitamin D in skin carcinogenesis

Effect of UV irradiation on solution processed low voltage flexible organic field-effect transistors

Effect of ultra-violet (UV) irradiation (λpeak = 365 nm) on the electrical characteristics of solution processed flexible TIPS-pentacene organic field-effect transistors (OFETs) has been investigated. Pristine TIPS-pentacene OFETs demonstrated average field-effect mobility of 0.1 cm2 V−1 s−1, with near zero threshold voltage and current on-off ratio of ∼104. On UV irradiation, OFETs displayed a joint photoconductive and photovoltaic effect due to photo-generated excitons. The maximum current modulation and photo-responsivity obtained from these OFETs were ∼500 and ∼43 mA/W respectively at an intensity of 1.8 mW/cm2 while operating at a low voltage of −5 V. On increasing the irradiation time, a positive shift in the threshold voltage was observed. At larger values of irradiation time, a roll-off in maximum drain current and mobility values were observed, which was attributed to slight deterioration in crystallinity due to prolonged UV exposure, as confirmed from X-ray diffraction studies. Similar trend was observed for mobility and threshold voltage values, when gate bias during UV irradiation was increased. In addition, transistors exhibited a repeatable dynamic response to periodic pulses of UV irradiation.