Ultraviolet Exposure Research Articles

The association between hydrochlorothiazide use and non-melanoma skin cancer in kidney transplant recipients.

hydrochlorothiazide (HCTZ) diuretics were correlated with an increased risk of non-melanoma skin cancer (NMSC) and melanoma in the general population. Information is a scarce regarding this effect in kidney transplant recipients who are at increased risk of skin malignancies under immunosuppression. Single-center retrospective analysis of adult kidney transplant recipients between 1 January 2010 and 31 December 2015. The primary outcome of the study was the first diagnosis of skin cancer that was removed and pathologically analyzed. Exposure to thiazides was defined as HCTZ use daily for at least one year at a dose of 12.5mg. Among 520 kidney transplant recipients, 50 (9.4%) were treated with HCTZ. During a median follow-up of 9.8years, 67patients underwent surgical removal and pathological analysis of at least one skin cancer. Exposure to HCTZ during the 3 years following transplantation was associated with an increased risk of skin cancer (P=0.004). In a multivariate model, there was a significant association between HCTZ exposure and NMSC (HR 2.54, 95%CI 1.26-5.15, P=0.007). There was a higher rate of basal cell carcinoma with HCTZ exposure, according to both univariate and multivariate analyses (HR 2.61, 95%CI 1.06-6.43, P=0.037) and (HR 3.03, 95%CI 1.22-7.55, P=0.017, respectively). However, no significant association was observed between HCTZ exposure and squamous cell carcinoma. These findings suggest a benefit of increased frequency of dermatologist inspection in kidney transplant recipients receiving HCTZ especially in increased ultraviolet exposure area.

Preparation and patterning of HfO2 film via sol–gel method and resistive switching effect of Pt/HfO2/LaNiO3

Sol–gel method is a low-cost material preparation method; however, it is difficult to obtain a stable sol containing easily hydrolyzable metal ions via this method. In this study, a stable hafnium(IV) oxide (HfO2) sol was prepared by adding benzoyl acetone (BzAcH) modifier. Infrared absorption spectroscopy results showed that the BzAcH additive chelated with the Hf4+ ions in the sol, thus improving the hydrolysis resistance of the HfO2 sol, which in turn improved its stability. It was also found that the BzAcH-modified HfO2 gel film exhibited ultraviolet (UV) photosensitivity. After UV exposure, the film did not dissolve easily in organic solvents. Based on these properties, the micro processing of the HfO2 film was preliminarily explored, and HfO2 microstructures were successfully obtained. Additionally, the relative permittivity (εr) of HfO2 exhibited minimum (∼10.9) and maximum (∼20.6) values at heat-treatment (HT) temperatures of 350 and 450 °C, respectively. With the continuous increase in the HT temperature, εr first decreased and then increased slightly. Moreover, the current–voltage curves showed that the Pt/HfO2/LaNiO3 (LNO) structure exhibited a pronounced bipolar resistive switching (RS) effect, which was attributed to the fact that LNO could be used as an electrode and an oxygen vacancy (OV2+) storage layer for RS materials. Notably, the oxygen ions in HfO2 with a low degree of crystallinity are more likely to migrate within its body (which makes it easier to form OV2+s), therefore, the “Set” voltage of low-crystallinity HfO2 films is lower than that of high-crystallinity HfO2 films. The RS mechanism can be explained by the OV2+ conductive filament model. These results are of great practical significance for the low-cost preparation of HfO2 and the application of LNO as an oxide electrode.

Human Papillomavirus-Associated Giant Clear Cell Acanthoma and Squamous Cell Carcinoma: A Rare Case Report and Literature Review.

Clear cell acanthoma (CCA) and squamous cell carcinoma (SCC) represent distinct entities within dermatological oncology, each posing unique diagnostic and therapeutic challenges. CCA is a rare, benign epidermal growth, often not associated with human papillomavirus (HPV) infection, whereas SCC, a more aggressive form of skin cancer, has been linked to both ultraviolet (UV) exposure and HPV. Understanding the co-occurrence of these conditions in a single patient can enhance diagnostic accuracy and therapeutic outcomes. We report a 64-year-old male who underwent an operation for a verruciform lesion in the right groin, which was diagnosed as HPV-positive CCA alongside keratinised SCC. A literature search across January 2024 revealed limited evidence directly linking HPV to CCA, suggesting a need for further investigation. The speculative association between HPV and CCA warrants deeper exploration, especially considering the potential for HPV to contribute to lesion development through indirect mechanisms. The coexistence of CCA and SCC in an elderly patient presents a unique clinical scenario. This emphasises the need for vigilant diagnosis and tailored treatment strategies, highlighting the gap in understanding the pathogenesis of CCA, particularly its potential association with HPV. Further research is crucial for elucidating the complex interactions governing these conditions and for developing targeted interventions.

Uniform and local degradation of epoxy-based powder coatings: Salt transport and accelerated exposure analysis

The barrier performance of epoxy-based powder coatings for pipelines was evaluated through salt transport measurements through free-standing coating films and via cyclic testing of coated steel panels. The permeability of salt through the free-standing coating films was measured using reverse osmosis techniques under hydraulic pressures relevant to industrial use. These tests showed that fusion bonded epoxy (FBE) and high-performance powder coating (HPPC) have low salt permeability. Accelerated exposure tests were then conducted on the coated steel panels, subjecting them to humidified environments, ultraviolet (UV) light, and salt/fog conditions, all in accordance with ASTM D5894. Some of the exposure conditions (e.g., intensity of UV light and humidity) were modified to examine the impact of each parameter on the relative performance of these coating systems. The reversibility of the coating properties was characterized by a thermal cycling protocol and adhesion performance analysis. Alternative exposure to dry- and wet-cycles (at 60 °C and 50 °C, respectively), salt/fog conditions and UV light results in irreversible damage to the coatings as early as two weeks. However, coated panels exposed to a lower UV intensity (one tenth of the value defined by the standard) showed minimal degradation of FBE, meaning that the most critical parameter was the UV radiation exposure. For one 336-h ageing sequence under UV exposure, the HPPC exhibited superior performance compared to FBE. More importantly, our extended exposure sequences showed that while the FBE coating structure undergoes a slow ablation process, indicating significant surface damage, it still retains its effectiveness as a barrier. However, the osmotic pressures around coated pipes and the pre-existing, unavoidable, porosity throughout the coating thickness can facilitate local through-thickness pinholes, which could potentially serve as areas susceptible to cathodic disbondment.

Synergistic effects of ultraviolet radiation and corrosion on Zr alloys

Ultraviolet (UV) radiation and corrosion can be coupled in non-trivial ways and such coupling is of critical importance for the performance of materials in extreme environments. However, the confluence of these phenomena and their collective impact remains underexplored. This study bridges this knowledge gap by presenting a thorough investigation of Zr alloys exposed to corrosive high-temperature water under in-situ UV irradiation. We found that initial UV exposure significantly accelerates corrosion and induces distinct changes in the microstructure of ZrO2 oxides. Over time, we observed the formation of Fe3O4 particles on the ZrO2 surface due to photo-dissolution of zirconia and photo-deposition of iron oxide magnetite. The emergence of Fe3O4 particles could enhance the corrosion resistance of the Zr alloy substrate. Furthermore, our results indicate that UV irradiation modulates the density and distribution of nanopores within the oxide layer by influencing oxygen speciation and the dynamics of oxide growth. These insights advance our understanding of the complex interplay between UV irradiation and high-temperature water corrosion.

The hydrophilicity mechanism of anatase and rutile (110) TiO2 films based on donor-acceptor complexes

When the surface of TiO2 is exposed to ultraviolet (UV) light, its hydrophilicity increases initially and then contact angle relaxation progresses over time. We investigated the source mechanism and working principles of long-lasting hydrophilicity in an ambient environment. Previously, we reported that the amount of donor-acceptor complexes (DACs) generated by polarizable OH groups with strong charge polarity is critical for maintaining long-lasting hydrophilicity (>90 days) on an anatase surface. In less reactive TiO2 films with low surface energy, a fast relaxation occurs due to the loss of polarizable OH groups. In this research, quantitative four-peak X-ray photoelectron spectroscopy analysis with TiO2 O 1 s spectra surface analysis was used to determine the relative amount of DACs and the binding energy shifting of water adsorbates on single crystal rutile (110) and polycrystalline anatase after UV exposure or plasma treatment. Films treated with oxygen or argon plasma and/or UV were analyzed and compared to suggested mechanisms that can occur on the surface of the TiO2 phase. All treated rutile (110) films except those treated with an Ar plasma exhibited rapid contact angle relaxation during the first 3 days, and the angle increased gradually to >50° over 14 days. In contrast, all anatase films retained long-lasting hydrophilicity, demonstrating a <∼10° contact angle over 56 days. At the first measurement, the binding energies were shifted for rutile (110) treated with O2 plasma and O2 plasma+UV films, demonstrating Ti–OH and DAC values of +0.15 eV each. However, the Ti–OH and DACs of all anatase films were located in the negative binding energy position, indicating that the DACs of rutile (110) were unstable due to a relatively weak bonding. In addition, the IOH/Ibulk intensity ratio of Ti–OH for rutile (110) treated with an O2 plasma increased significantly from 20 % to 37 %. However, the intensity ratio for O2 plasma+UV increased only from 20 % to 23.8 %. This result in combination with the binding energy shifting tendency indicates that relaxed OH groups increased rapidly without UV treatment. When rutile (110) was irradiated with UV, the effect of photoinduced electron-hole pairs shown with Ti 2p spectra was much shorter than that of anatase. Differences in relaxation occurred in both phases due to the charge polarity effect between rutile (110) and anatase, the unstable DACs related to weak OH groups, and the difference in surface characteristics. Using single crystal rutile (110) with a well-defined surface, these experiments validated further the DAC mechanism and theory presented by our group. Specifically, we confirmed that both the amount of DACs and the binding energy position shifting are important for long-term hydrophilicity.

Students’ Knowledge, Attitude, and Practices Regarding Solar Ultraviolet Exposure in Karachi, Pakistan

BACKGROUND: Ultraviolet Radiation (UVR) from the sun is a significant environmental component that impacts on human health. Excessive UVR exposure has immediate impacts like burning and tanning, as well as long-term consequences including skin damage, photo-aging, skin malignancies. The objective for this study is to determine the student’s knowledge, attitude and practice regarding solar ultraviolet exposure in Karachi, Pakistan. METHODS: A cross-sectional study was done in Public Sector University; total 361 students were recruited through stratified cluster sampling from different colleges of university. Data collection was done by validated structured questionnaire. Logistic regression was used to determine the association of outcome variables with risk factors and p-value of &lt;0.05 as a threshold of statistical analysis. RESULTS: Most of the students were appropriate knowledge (71%), positive attitude (51%) and safe practice (54%) regarding ultraviolet solar exposure. Almost half (69%) of participants were used sun protective agents. After adjustment of covariate, female gender (OR 2.20 (95% CI 1.29-4.07) (p-value 0.004), significantly associated with in-appropriate knowledge, third year students (OR 2.93 (95% CI 1.01-8.95) p-value 0.048) were significantly associated with negative attitude. Age group 18-21 years (OR 1.75(95% CI 1.43-5.31) p-value 0.003) were significantly associated with un-safe practice regarding solar ultraviolet exposure harmful effects. CONCLUSION: This study found that knowledge level was appropriate but attitude and practice level need to improve for prevention of harmful effects of solar ultra violet ray exposure. The study encourages students to be more aware of sun protection behavior in order to avoid the long-term effects of sun exposure.

Shedding light on the problem: Influence of the radiator power, source-sample distance, and exposure time on the performance of UV-C lamps in laboratory and real-world conditions.

Effective surface disinfection is crucial for preventing the spread of pathogens in hospitals. Standard UltraViolet-C (UV-C) lamps have been widely used for this purpose, but their disinfection efficiency under real-world conditions is not well understood. To fill this gap, the influence of the power of the ultraviolet radiator, source-sample distance, and exposure time on the performance of UV-C lamps against Escherichia coli and Staphylococcus epidermidis were experimentally determined in the laboratory and hospital. The obtained results showed that the UV irradiance and, thus, the UV-C disinfection efficiency decreased significantly at distances greater than 100 cm from the UV-C lamp. Moreover, increasing the total power of the radiators does not improve the performance of UV-C lamps under real conditions. The UV-C disinfection efficiency greater than 90% was achieved only under laboratory conditions at a close distance from the UV-C lamp, i.e., 10 cm. These findings provide novel insights into the limitations of UV-C lamps in real-world conditions and highlight the need for more effective disinfection strategies in hospitals.

Type I Diabetes Mellitus Suppresses Experimental Skin Carcinogenesis.

This study explores the previously uncharted territory of the effects of ultraviolet (UV) radiation on diabetic skin, compared to its well-documented impact on normal skin, particularly focusing on carcinogenesis and aging. Employing hairless SKH-hr2, Type 1 and 2 diabetic, and nondiabetic male mice, the research subjected these to UV radiation thrice weekly for eight months. The investigation included comprehensive assessments of photoaging and photocarcinogenesis in diabetic versus normal skin, measuring factors such as hydration, trans-epidermal water loss, elasticity, skin thickness, melanin, sebum content, stratum corneum exfoliation and body weight, alongside photo documentation. Additionally, oxidative stress and the presence of hydrophilic antioxidants (uric acid and glutathione) in the stratum corneum were evaluated. Histopathological examination post-sacrifice provided insights into the morphological changes. Findings reveal that under UV exposure, Type 1 diabetic skin showed heightened dehydration, thinning, and signs of accelerated aging. Remarkably, Type 1 diabetic mice did not develop squamous cell carcinoma or pigmented nevi, contrary to normal and Type 2 diabetic skin. This unexpected resistance to UV-induced skin cancers in Type 1 diabetic skin prompts a crucial need for further research to uncover the underlying mechanisms providing this resistance.

Improving the stability and transdermal permeability of phycocyanin loaded cubosomes

Instability and low transdermal permeability of protein antioxidants are major obstacles to resist oxidative stress in transdermal drug delivery system. To overcome these shortcomings, cubosomes were developed as an advanced transdermal delivery system to improve stability and transdermal absorption of the model antioxidant phycocyanin in this study. Glyceryl monooleate and poloxamer 407 (P407) were used to prepare cubosomes as carrier matrix and stabilizer, respectively. Phycocyanin loaded cubosomes (PC-cubosomes) were prepared by the emulsification and homogenization method. A 33 full factorial design was used to optimize the cubosome formulations. The final optimal PC-cubosomes possessed an average particle size of 183.2 ± 0.5 nm and a negative surface charge as well as achieved a high encapsulation efficiency of 87.2% ± 2.7%. PC-cubosomes appeared as nano-sized and well-shaped spheres with highly ordered cubical structures. The residual amount of phycocyanin in PC-cubosomes was 3-fold higher than that in the free drug solution after 10 days ultraviolet radiation exposure. In vitro release kinetics of phycocyanin from PC-cubosomes fitted to the Higuchi kinetic model, indicating that phycocyanin released from cubosomes mainly attributed to drug diffusion and dissolution. PC-cubosomes also exhibited higher permeability (39.79 μg⋅cm−2⋅hour−1) across the rat skin than phycocyanin solution (16.33 μg⋅cm−2⋅hour−1). Furthermore, PC-cubosomes were easily taken up by keratinocytes, thereby achieving a prolonged anti-oxidative stress effect. These results therefore suggested that cubosomes could be a promising transdermal delivery system to improve the stability and transdermal permeability of phycocyanin.

Interferon alpha promotes caspase-8 dependent ultraviolet light-mediated keratinocyte apoptosis via interferon regulatory factor 1.

Ultraviolet (UV) light is a known trigger of both cutaneous and systemic disease manifestations in lupus patients. Lupus skin has elevated expression of type I interferons (IFNs) that promote increased keratinocyte (KC) death after UV exposure. The mechanisms by which KC cell death is increased by type I IFNs are unknown. Here, we examine the specific cell death pathways that are activated in KCs by type I IFN priming and UVB exposure using a variety of pharmacological and genetic approaches. Mice that overexpress Ifnk in the epidermis were exposed to UVB light and cell death was measured. RNA-sequencing from IFN-treated KCs was analyzed to identify candidate genes for further analysis that could drive enhanced cell death responses after UVB exposure. We identify enhanced activation of caspase-8 dependent apoptosis, but not other cell death pathways, in type I IFN and UVB-exposed KCs. In vivo, overexpression of epidermal Ifnk resulted in increased apoptosis in murine skin after UVB treatment. This increase in KC apoptosis was not dependent on known death ligands but rather dependent on type I IFN-upregulation of interferon regulatory factor 1 (IRF1). These data suggest that enhanced sensitivity to UV light exhibited by lupus patients results from type I IFN priming of KCs that drives IRF1 expression resulting in caspase-8 activation and increased apoptosis after minimal exposures to UVB.

Multi-System-Level Analysis Reveals Differential Expression of Stress Response-Associated Genes in Inflammatory Solar Lentigo.

Although the pathogenesis of solar lentigo (SL) involves chronic ultraviolet (UV) exposure, cellular senescence, and upregulated melanogenesis, underlying molecular-level mechanisms associated with SL remain unclear. The aim of this study was to investigate the gene regulatory mechanisms intimately linked to inflammation in SL. Skin samples from patients with SL with or without histological inflammatory features were obtained. RNA-seq data from the samples were analyzed via multiple analysis approaches, including exploration of core inflammatory gene alterations, identifying functional pathways at both transcription and protein levels, comparison of inflammatory module (gene clusters) activation levels, and analyzing correlations between modules. These analyses disclosed specific core genes implicated in oxidative stress, especially the upregulation of nuclear factor kappa B in the inflammatory SLs, while genes associated with protective mechanisms, such as SLC6A9, were highly expressed in the non-inflammatory SLs. For inflammatory modules, Extracellular Immunity and Mitochondrial Innate Immunity were exclusively upregulated in the inflammatory SL. Analysis of protein-protein interactions revealed the significance of CXCR3 upregulation in the pathogenesis of inflammatory SL. In conclusion, the upregulation of stress response-associated genes and inflammatory pathways in response to UV-induced oxidative stress implies their involvement in the pathogenesis of inflammatory SL.

Sol-Gel technique, characterization and photocatalytic degradation activity of Manganese doped ZnO nanoparticles

Photocatalysis using semiconductor metal oxide stands out as a highly effective and efficient method for eliminating organic pollutants from wastewater. This study aims to assess the photocatalytic capabilities of Mn doped ZnO nanocomposites in degrading methylene blue (MB) dye under ultra-violet light exposure. This study details the synthesis of ZnO photocatalysts through a straightforward one-step sol-gel method, incorporating varying levels of Mn-doping (0%, 2% &amp; 4%). The structural and optical attributes were examined using techniques such as powder X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS) and UV-Vis diffuse reflectance spectra. X-ray diffraction analyses verified the presence of a hexagonal wurtzite crystal structure in all synthesized samples, exhibiting a high degree of crystallinity. In addition, an investigation into the impact of Mn impurities on the photocatalytic performance of ZnO catalysts was conducted in the context of methylene blue (MB) degradation. The experimental findings revealed that the Mn doped ZnO nanoparticles produced exhibited significantly superior photocatalytic performance compared to pure ZnO when used in breaking down methylene blue under UV-light exposure. This study proposes that these Mn doped ZnO could serve as a highly effective photocatalyst for treating water contaminated with certain chemically persistent synthetic organic dyes. The improved photocatalytic capabilities of ZnO nanostructures doped with Mn were ascribed to the synergistic impact of increased surface area in ZnO nanosphere and enhanced efficiency in charge separation resulting from optimized Mn doping. A potential explanation for the heightened photocatalytic performance of Mn-doped ZnO nanostructures is proposed tentatively.

Exploring the biomedical potential of chitosan‐ceria nanocomposites: synthesis and characterizations

The objective of this study was to synthesize and evaluate the biological effectiveness of cerium oxide (CeO2) against various bacterial and fungal strains. The chitosan‐CeO2 nanocomposite was comprehensively characterized. The Fourier transform infrared (FTIR) spectra displayed a combination of bands that provided evidence for the existence of a composite complex between the chitosan (CS) structure and the Ce–O bands originating from CeO2 nanoparticles. SEM measurements showed uniform dispersion across the whole CS surface, and the morphological changes were clearly observed as the CeO2 nanoparticle content was increased. In contrast, CS‐CeO2 demonstrates enhanced antibacterial efficacy against both Gram‐positive and Gram‐negative pathogens. The MTT method was utilized to assess the cytotoxicity of the examined CS‐CeO2, with the aim of evaluating the cell viability of various cancer cell lines under varying ultraviolet (UV) exposures. The enhanced penetration of CS and CeO2 nanocomposites into cancer cells during their anticancer activity, even in the absence of UV light, led to an increased rate of cell death. The administration of greater dosages of CS and its CeO2 nanocomposites led to an increased generation of reactive oxygen species (ROS), which was observed to be associated with an enhancement in the efficacy of anticancer activity. The impact was additionally amplified through exposure to UV radiation. The nanocomposite thin films demonstrated much higher antioxidant activity against the DPPH radical as compared to ordinary vitamin C. The aforementioned observation was derived from an evaluation of the antioxidant properties of the subject utilizing the DPPH free radical scavenging technique.

Is beauty worth the risk? Self-confidence is the key motivating factor driving tanning bed use among undergraduate students at South Dakota universities.

Exposure to ultraviolet radiation is a leading risk factor for developing all types of skin cancer. In the United States, an estimated 7.8 million young adults engage in indoor tanning. Here, it is hypothesized that certain populations of students at undergraduate universities, namely sorority members, have a greater frequency of tanning bed usage than other groups of students and that regardless of sorority status, the most important motivating factor will be the intent to enhance one's appearance. Undergraduate students at 2 state-funded universities were recruited for participation in this institutional review board-exempt survey via distribution to e-mail addresses and social media accounts affiliated with student organizations/clubs. Among all respondents, the most common motivating factors for tanning bed use were the perception of improved self-appearance and boosted self-confidence. Female sorority members were more likely to use tanning beds and also more likely to report being motivated by enhanced appearance and self-confidence, than their female counterparts who were not sorority members. The sample size (n = 321) and population of this study allows data to only be generalizable to surrounding states with similar demographics. The findings of this study are subject to recall bias as the data is self-reported. Tanning bed use remains a popular practice among young people. Understanding motivations for tanning bed use among populations at increased risk of partaking in this behavior allows for educating these groups on the risks associated with ultraviolet radiation exposure. It is crucial that providers continue to promote skin health and take steps to dissuade detrimental practices and possible habit-forming behaviors at the individual and state levels.

Optimization of Skin Cancer Detection to Improve Accuracy with the Application of Efficient Convolutional Neural Network and EfficientNetB2 Models

Skin cancer, related to ultraviolet light exposure, can be caused by genetic mutations in skin cells. Risk factors include family history, fair skin, moles, weak immunity and solar keratosis. Diagnosis involves skin examination and biopsy. Previous studies using Convolutional Neural Network (CNN) successfully classified skin cancer with an accuracy of up to 99%. The process of developing an image classification model involves structured steps. The dataset is divided into training, validation, testing. Data augmentation is performed with ImageDataGenerator to enrich the dataset. CNN model (EfficientNetB2) was customized, trained for 50 epochs. Evaluation of testing data model, metrics such as loss, accuracy, precision, recall, and F1-score. Visualization of Classification Reports, Confusion Matrix. The entire process ensured in-depth analysis of the model's performance and focused attention on prediction. The study used Kaggle's secondary data "HAM10000 Preprocessed Data" with 11644 data and three attributes, showing variations before normalization. The CNN model peaked at the 8th epoch with 86% accuracy, but there is a risk of overfitting. Evaluation using Classification Report and Confusion Matrix provides details of model performance on each skin cancer class, supporting diagnosis and treatment.This article highlights the positive impact of using the EfficientNetB2 Model on skin cancer detection through an efficient Convolutional Neural Network (CNN). The model is optimal in size and structure, resulting in superior feature representation. Evaluations including Classification Report and Confusion Matrix demonstrate the model's superiority in classifying skin cancer types, particularly in the ''akiec'' and ''bcc'' classes, with high accuracy, significantly improving detection performance.

Dragline silk fibers from golden orb‐web spider Trichonephila clavata ensure structural and mechanical robustness against ultraviolet radiation

AbstractA diurnal spider, Trichonephila clavata (T. clavata), is often called a golden orb‐weaver because its dragline or lifeline silk fibers exhibit a golden color. However, little is known about the biological roles of the golden pigment. Meanwhile, Araneus ventricosus, which is a nocturnal spider, spins colorless silk fibers. Here, we investigated the effect of ultraviolet (UV) irradiation on physical properties of silk fibers obtained from these diurnal and nocturnal spiders. After UV exposure, the dragline silk of the nocturnal spiders appeared abraded and became insoluble due to gelation, whereas the diurnal spider silk remained intact. A dynamic mechanical thermal analysis under different humidity conditions revealed that the storage modulus of the silk from the nocturnal spider dropped markedly at low humidity levels after UV irradiation. This indicated that the molecular weight of this silk degraded under UV exposure and that the number of terminal amino and carboxyl groups increased due to the breakage of the main protein chains. In contrast, the structural and mechanical properties of the diurnal spider silk were maintained regardless of the UV irradiation. Therefore, the golden pigments in the dragline silk of T. clavata most likely played a role in protecting the silk from UV damage.

Effect of Bisoctrizole on Ultraviolet (UV) Absorption Properties of Silicone and Effect on Surface Roughness - An In Vitro Study.

Premature degradation is the problem of maxillofacial silicones, significantly affected by ultraviolet exposure, contributing to silicones photodegradation. Degradation necessitates frequent replacement of prostheses that increase the total cost of rehabilitation. This study evaluated the effect of bisoctrizole on the ultraviolet absorption properties of silicone material and the stability of this absorption over time. Also, the bisoctrizole effect on the surface roughness of silicone was evaluated. There were 60 prepared specimens of room temperature-vulcanising maxillofacial silicone equally divided into two groups according to the conducted tests: ultraviolet absorption test and the surface roughness test. Each group was further subdivided into groups of 10 specimens based on the weight concentration of the ultraviolet (UV) absorber added: 0%, 1% and 2%. The UV absorbance of coloured specimens was measured before and after artificial weathering for 100 and 200 hours. Repeated-measures analysis of variance (ANOVA) was applied for UV absorption results, and one-way ANOVA was applied for the roughness test results to test the changing significances. Bisoctrizole incorporation led to a highly significant improvement in ultraviolet absorption in all groups, maintaining a high level even after subjecting the specimens to artificial weathering. Furthermore, the addition resulted in a significant increase in surface roughness as the concentration of bisoctrizole increased. Despite the surface roughness changes, bisoctrizole demonstrated efficacy as a UV absorber for maxillofacial silicone, making it valuable for applications such as maxillofacial prosthetics that require UV protection.

Mechanical and Thermal Properties of Aged Helmet Outer Shells Made of Acrylonitrile-Butadiene-Styrene

Acrylonitrile-butadiene-styrene (ABS) material is widely used as a protective rigid shell and impact absorber in bike helmets, providing vital protection against head injuries under specific working conditions. However, ABS aging in helmets could affect the safety factor of helmets and shorten the service life. Exploring the transformation during aging process for real assembled helmets made of ABS out shells is crucial for the investigation and fabrication of high performance helmets. Herein, the effect of long-term aging on the physical properties of practical helmets made of ABS outer shells has been discussed systematically. Four different types of helmets were subjected to different aging conditions, i.e., outdoor environment, ultraviolet exposure, hot air, and humid-heat conditions. The impact property and stiffness tests were carried out as a function of aging time and aging conditions. The measured helmets were capable of meeting engineering tolerances when aged under outdoor, ultraviolet, and hot air conditions, and could deliver competitive mechanical performance to their pristine helmets. Yet, after aging under humid-heat for 800 h, the helmets showed an obvious decrease in impact strength, gloss, and stiffness. The influence of different aging conditions was further investigated by thermal and spectral characterizations. The study might provide some valuable advice for helmet performance evaluation.

High-speed performance self-powered short wave ultraviolet radiation detectors based on κ(ε)-Ga2O3

High-speed solar-blind short wavelength ultraviolet radiation detectors based on κ(ε)-Ga2O3 layers with Pt contacts were demonstrated and their properties were studied in detail. The κ(ε)-Ga2O3 layers were deposited by the halide vapor phase epitaxy on patterned GaN templates with sapphire substrates. The spectral dependencies of the photoelectric properties of structures were analyzed in the wavelength interval 200–370 nm. The maximum photo to dark current ratio, responsivity, detectivity and external quantum efficiency of structures were determined as: 180.86 arb. un., 3.57 A/W, 1.78 × 1012 Hz0.5∙cm∙W−1 and 2193.6%, respectively, at a wavelength of 200 nm and an applied voltage of 1 V. The enhancement of the photoresponse was caused by the decrease in the Schottky barrier at the Pt/κ(ε)−Ga2O3 interface under ultraviolet exposure. The detectors demonstrated could functionalize in self-powered mode due to built-in electric field at the Pt/κ(ε)-Ga2O3 interface. The responsivity and external quantum efficiency of the structures at a wavelength of 254 nm and zero applied voltage were 0.9 mA/W and 0.46%, respectively. The rise and decay times in self-powered mode did not exceed 100 ms.