Strong Ultraviolet Radiation Research Articles

Solar race car tests biobased hardener

This week, 40 teams will race solar-powered cars from Darwin to Adelaide, Australia, a distance of 3,000 km. Covestro will take advantage of the region’s harsh conditions—45 °C temperatures and strong ultraviolet radiation— to test the performance of its 70% biobased coating hardener. Made from pentamethylene diisocyanate, it’s part of a urethane coating system from PPG Industries. The coating will grace the Sonnenwagen race car, designed by students at Germany’s RWTH Aachen University and Aachen University of Applied Sciences.

Study of asphalt performance impact with ultraviolet aging

To solve the problem of strong ultraviolet radiation on the road asphalt aging, ultraviolet aging environment box analog wild aging condition to be used to experiment, Through dynamic shear rheometer respectively to study the effect of SBS modified asphalt and asphalt matrix high temperature, low temperature and fatigue performance with the aging time to change. The results show that SBS modified asphalt can produce serious aging under strong ultraviolet light, the Main aspects is fatigue performance and low temperature performance greatly reduced, high temperature performance is further improved, They have a closer relationship with aging time; At the same time, along with the test temperature, aging time on the influence of G*/sinδ, G*sinδ of amplitude decreases. That ultraviolet on SBS modified asphalt aging has temperature sensitivity. The research conclusion can choose the light aging resistance of airport pavement asphalt to provide good technical support.

No Ly α emitters detected around a QSO at z = 6.4: Suppressed by the QSO?

Abstract Understanding how quasars’ (QSOs’) ultraviolet (UV) radiation affects galaxy formation is vital to our understanding of the reionization era. Using a custom-made narrow-band filter, NB906, on Subaru/Suprime-Cam, we investigated the number density of Ly α emitters (LAEs) around a QSO at z = 6.4. To date, this is the highest redshift narrow-band observation, where LAEs around a luminous QSO are investigated. Due to the large field of view of Suprime-Cam, our survey area is ∼5400 cMpc2, much larger than previous studies at z = 5.7 (∼200 cMpc2). In this field, we previously found a factor of 7 overdensity of Lyman break galaxies. Based on this, we expected to detect ∼100 LAEs down to NB906 = 25 ABmag. However, our 6.4 h exposure found none. The obtained upper limit on the number density of LAEs is more than an order lower than the blank fields. Furthermore, this lower density of LAEs spans a large scale of 10 pMpc across. A simple argument suggests that a strong UV radiation from the QSO can suppress star formation in haloes with Mvir < 1010 M⊙ within a pMpc from the QSO, but the deficit at the edge of the field (5 pMpc) remains to be explained.

Genome-wide identification of genes probably relevant to the adaptation of schizothoracins (Teleostei: Cypriniformes) to the uplift of the Qinghai-Tibet Plateau

BackgroundMolecular adaptation to the severe environments present during the uplift of the Qinghai-Tibet Plateau has attracted the attention of researchers. The divergence of the three specialization groups of schizothoracins (Primitive, Specialized and Highly Specialized) may correspond to the three phases of plateau uplift. Based on the transcripts of representative species of the three specialized groups and an outgroup, genes in schizothoracins that may have played important roles during the adaptation to new environments were investigated.ResultsThe contigs of Gymnodiptychus dybowskii and Schizothorax pseudaksaiensis were compared with those of Gymnocypris przewalskii ganzihonensis and the outgroup Sinocyclocheilus angustiporus, and 5,894 ortholog groups with an alignment length longer than 90 nt after deleting gaps were retained. Evolutionary analyses indicated that the average evolutionary rate of the branch leading to the Specialized group was faster than that of the branch leading to the Highly Specialized group. Moreover, the numbers of gene categories in which more than half of the genes evolved faster than the average values of the genome were 117 and 15 along the branches leading to the Specialized and Highly Specialized groups, respectively. A total of 40, 36, and 55 genes were likely subject to positive selection along the branches leading to the Primitive, Specialized and Highly Specialized groups, respectively, and many of these genes are likely relevant to adaptation to the cold temperatures, low oxygen concentrations, and strong ultraviolet radiation that result from elevation.ConclusionsBy selecting representative species of the three groups of schizothoracins and applying next-generation sequencing technology, several candidate genes corresponding to adaptation to the three phases of plateau uplift were identified. Some of the genes identified in this report that were likely subject to positive selection are good candidates for subsequent evolutionary and functional analyses of adaptation to high altitude.

Molecular studies of Planetary Nebulae

AbstractCircumstellar envelopes (CEs) around evolved stars are an active site for the production of molecules. After evolving through the Asymptotic Giant Branch (AGB), proto-planetary nebula (PPN), to planetary nebula (PN) phases, CEs ultimately merge with the interstellar medium (ISM). The study of molecules in PNe, therefore, is essential to understanding the transition from stellar to interstellar materials. So far, over 20 molecular species have been discovered in PNe. The molecular composition of PNe is rather different from those of AGB and PPNe, suggesting that the molecules synthesized in PN progenitors have been heavily processed by strong ultraviolet radiation from the central star. Intriguingly, fullerenes and complex organic compounds having aromatic and aliphatic structures can be rapidly formed and largely survive during the PPN/PN evolution. The similar molecular compositions in PNe and diffuse clouds as well as the detection of C60+ in the ISM reinforce the view that the mass-loss from PNe can significantly enrich the ISM with molecular species, some of which may be responsible for the diffuse interstellar bands. In this contribution, I briefly summarize some recent observations of molecules in PNe, with emphasis on their implications on circumstellar chemistry.

Corrosion Resistant and UV Durable PVDF-Co-HFP /Al2O3 Superhydrophobic Nanocomposite Coating for Aluminum

The interest in superhydrophobic surfaces, which demonstrate high water-repellency, have recently increased dramatically because of their wide range of applications in many fields. The two major needed conditions to get a nanostructured superhydrophobic surfaces are the optimum surface roughness and low surface energy. In our present work, the fabrication process of a porous superhydrophobic coating on aluminum surfaces was achieved using a one-step electrospinning technique. The wettability properties of the prepared coating was inspected by measuring the water contact (WCA) and sliding angle (WCAH) before the addition of Al2O3 nanoparticles (150±2.9 and 6.25±1) while the measured WCA and WCAH after addition of nanoparticles was found to be 152±0.59 and 5±2.5, respectively. The wettability of the prepared coatings was inspected also after being irradiated with strong ultraviolet (UV) radiation of 1.5 W/m2 at a high temperature of 70 °C for 64 h. In fact no big difference was noticed after the UV test with respect to the wettability properties. The morphology of the superhydrophobic coating was studied using scanning electron microscope (SEM) coupled with energy dispersive X-ray (EDX). It shows the formation of a beaded fiber structure. Furthermore, Fourier transform infrared (FTIR) spectroscopy was used to check the nanocomposite coating before and after irradiation with UV. The surface roughness of the composite materials were measured using atomic force microscope (AFM). The corrosion behavior of the superhydrophobic nanocomposite coating was evaluated by the electrochemical impedance spectroscopy (EIS) and the potentiodynamic polarization in 3.5% NaCl. The results have shown that new nanocomposite coating exhibits a very high corrosion resistance.

Systematic evaluation of sample preparation method for simultaneous voltammetric determination of Zn, Cd, Pb, and Cu in macroalgae

In this paper, four mineralization procedures of macroalgae were evaluated. Two methods used a closed system microwave) and two an open system (strong acid and ultraviolet radiation). Zn, Cd, Pb, and Cu were determined by square-wave anodic stripping voltammetry (SWASV) and graphite furnace atomic absorption spectrometry (GF AAS) was used as comparative method. Determinations of total, inorganic, and organic carbon, as well as the study of matrix effect, were performed. It could be observed that, although mineralizations accomplished with open systems presented lower levels of total carbon and lower matrix effect, the determinations of compounds from standard reference material (SRM) did not show acceptable recoveries. However, the mineralization using microwave (closed system—methods A and B) showed recovery within the acceptable range to all compounds (78 to 115 %), and after statistical analysis, it can be concluded that the method A is more accurate than the method B; therefore, most suitable for macroalgae mineralization and simultaneous determination of Zn, Cd, Pb, and Cu by voltammetry.

Compression and ablation of the photo-irradiated molecular cloud the Orion Bar.

The Orion Bar is the archetypal edge-on molecular cloud surface illuminated by strong ultraviolet radiation from nearby massive stars. Owing to the close distance to Orion (about 1,350 light-year), the effects of stellar feedback on the parental cloud can be studied in detail. Visible-light observations of the Bar1 show that the transition between the hot ionised gas and the warm neutral atomic gas (the ionisation front) is spatially well separated from the transition from atomic to molecular gas (the dissociation front): about 15 arcseconds or 6,200 astronomical units. (One astronomical unit is the Earth-Sun distance.) Static equilibrium models2,3 used to interpret previous far-infrared and radio observations of the neutral gas in the Bar4,5,6 (typically at 10-20 arcsecond resolution) predict an inhomogeneous cloud structure consisting of dense clumps embedded in a lower density extended gas component. Here we report 1 arcsecond resolution millimetre-wave images that allow us to resolve the molecular cloud surface and constrain the gas density and temperature structures at small spatial scales. In contrast to stationary model predictions7,8,9, there is no appreciable offset between the peak of the H2 vibrational emission (delineating the H/H2 transition) and the edge of the observed CO and HCO+ emission. This implies that the H/H2 and C+/C/CO transition zones are very close. These observations reveal a fragmented ridge of high-density substructures, photo-ablative gas flows and instabilities at the molecular cloud surface. They suggest that the cloud edge has been compressed by a high-pressure wave that currently moves into the molecular cloud. The images demonstrate that dynamical and nonequilibrium effects are important. Thus, they should be included in any realistic description of irradiated interstellar matter.

Trolox-equivalent antioxidant capacity and composition of five alpine plant species growing at different elevations on the Qinghai–Tibetan Plateau

Background: Alpine plants on the Qinghai–Tibetan Plateau are exposed to an extremely harsh environment, namely severe cold, strong ultraviolet radiation, hypoxia and low CO2 partial pressure. These conditions are sources of oxidative stress, which increase in severity with increasing elevation.Aims: To examine whether antioxidant capacity and chemical composition of alpine plants change with increasing elevation.Methods: We measured the Trolox-equivalent antioxidant capacity (TEAC) and chemical composition of five alpine plant species at 3016, 3814 and 4621 m a.s.l.Results: With increasing elevation: (1) the TEAC increased and total phenols and tannins tended to increase in two forb and two shrub species but not in a sedge species; (2) concentrations of protein and fat increased in all five plant species; (3) polyunsaturated fatty acids (PUFA) increased and (4) mineral concentrations tended to decrease, but trends were inconsistent.Conclusions: We conclude that with increasing elevation, TEAC and total phenols and tannins increased which we interpreted as an adaptation to higher oxidative stress; and protein and fat contents increased to support high metabolic activity. The increase in PUFA and the trend for minerals to decrease with increasing elevation require further investigation.

Genetic Adaptation of Giant Lobelias (Lobelia aberdarica and Lobelia telekii) to Different Altitudes in East African Mountains.

The giant lobelias in East African mountains are good models for studying molecular mechanisms of adaptation to different altitudes. In this study, we generated RNA-seq data of a middle-altitude species Lobelia aberdarica and a high-altitude species L. telekii, followed by selective pressure estimation of their orthologous genes. Our aim was to explore the important genes potentially involved in adaptation to different altitudes. About 9.3 Gb of clean nucleotides, 167,929–170,534 unigenes with total lengths of 159,762,099–171,138,936 bp for each of the two species were generated. OrthoMCL method identified 3,049 1:1 orthologous genes (each species was represented by one ortholog). Estimations of non-synonymous to synonymous rate were performed using an approximate method and a maximum likelihood method in PAML. Eighty-five orthologous genes were under positive selection. At least 8 of these genes are possibly involved in DNA repair, response to DNA damage and temperature stimulus, and regulation of gene expression, which hints on how giant lobelias adapt to high altitudinal environment that characterized by cold, low oxygen, and strong ultraviolet radiation. The negatively selected genes are over-represented in Gene Ontology terms of hydrolase, macromolecular complex assembly among others. This study sheds light on understanding the molecular mechanism of adaptation to different altitudes, and provides genomic resources for further studies of giant lobelias.

Analysis on the Relationship Between Ultraviolet Radiation Characteristics and Asphalt Pavement Disease in Tibet Plateau

Through the analysis of the monitoring data of ultraviolet radiation in Tibet, and compared with the related areas, the distribution and intensity characteristics of ultraviolet radiation in Tibet plateau were obtained. Tibet Plateau radiation intensity equivalent to about three times more than the same latitude as the southern region, and also much higher than in eastern Tibet, the solar ultraviolet radiation is the strongest region in the world. The survey summarized the main characteristics of Tibetan asphalt pavement disease, analysed the strong ultraviolet irradiation, the relationship between Tibetan road disease and strong ultraviolet radiation, and obtained the general rule of the damage of asphalt pavement in Tibetan: ultraviolet radiation→asphalt pavement whitened→asphalt hardening→micro cracks appeared→crack expansion→cracking→water→asphalt peeling (loose), pit slot etc. The origin of this Law in the Tibetan strong ultraviolet radiation, High ultraviolet radiation causes aging of asphalt，losing its original performance, which led to destruction of roads in climate and traffic load, therefore, to strengthen the anti-aging properties of asphalt will be greatly improved Tibet District road usage.

Genomic characterization and phylogenetic analysis of Chinese sacbrood virus isolated from Loess Plateau, China.

The complete genomic RNA of the Chinese sacbrood virus (CSBV) strain, which infects the honeybees in the Loess plateau, was sequenced and analyzed. The CSBV-SX strain contains 8705 nucleotides, which includes a single large open reading frame (99-8681 nucleotides) encoding 2860 amino acids. A novel efficient identification method was used to investigate the samples infected by CSBV. The putative amino acid sequence alignment analysis showed that, except for some normal well characterized domains such as RNA helicase, RNA protease, and RNA-dependent RNA polymerase domains, a calicivirus coat protein domain was identified at amino acids 493-564. Phylogenetic analysis indicated that CSBV-SX was closely related to CSBV-BJ, and this result was supported by nucleotide multiple sequence alignment and protein multiple sequence alignment analysis results. These differences in the CSBV-SX strain may be related to virus adaptation to the xerothermic, low relative humidity, and strong ultraviolet radiation conditions in the Loess Plateau.

The genome of Bacillus aryabhattai T61 reveals its adaptation to Tibetan Plateau environment

Tibetan Plateau is called ‘the Roof of the World’. Organisms survive there have to adapt to the high altitude environment. By shotgun method, we sequenced the genome of Bacillus aryabhattai T61, which inhabits in the soil at the altitude of 4123 m in Shigatse, Tibetan. Further, we explored the genomic basis for its adaptations to the plateau environment. The results showed that B. aryabhattai T61 has evolved an array of ROS defense systems and sporulation system for adaptations to the stresses caused by the plateau strong ultraviolet radiation, extreme oxygen limitation and low temperature. Specifically, B. aryabhattai T61 encodes the ResE–ResD two-component to sense the oxygen limitation and regulates COX15 for aerobic and anaerobic respiration. The two-component system DesK–DesR, which regulates the gene Des initiating the biosynthesis of unsaturated fatty acids, along with 33 temperature-shock proteins contribute to low temperature adaptation. With the comparative analysis, we deduced the novel gene cbiY may be involved in cobalamin biosynthesis. We also found that B. aryabhattai T61 may have novel regulatory mechanisms for sporulation initiation. B. aryabhattai T61 is the first Tibetan strain with high quality genome sequenced. The genome provides a paradigm for understanding the adaptations to the plateau environment in Bacteria kingdom.

CAN STAR CLUSTER ENVIRONMENT AFFECT DUST INPUT FROM MASSIVE AGB STARS?

We examine the fraction of massive asymptotic giant branch (AGB) stars remaining bound in their parent star clusters and the effect of irradiation of these stars by intracluster ultraviolet (UV) field. We employ a set of N-body models of dynamical evolution of star clusters rotating in a galactic potential at the solar galactocentric radius. The cluster models are combined with stellar evolution formulae, a library of stellar spectra, and simple models for SiO photodissociation in circumstellar environment (CSE). The initial stellar masses of clusters are varied from $50\rm M_\odot$ to $10^{5}\rm M_\odot$. Results derived for individual clusters are combined using a mass distribution function for young star clusters. We find that about 30% of massive AGB stars initially born in clusters become members of the field population, while the rest evolves in star clusters. They are irradiated by strong intracluster UV radiation resulting in the decrease of the photodissociation radius of SiO molecules, in many stars down to the dust formation zone. In absence of dust shielding, the UV photons penetrate in the CSE deeper than $10R_*$ in 64% and deeper than $2 R_*$ in 42% of all massive AGB stars. If this suppresses following dust formation, the current injection rate of silicate dust from AGB stars in the local Galaxy decreases from $2.2 \times 10^{-4}\rm M_\odot\,kpc^{-2}\,Gyr^{-1}$ to $1.8 \times 10^{-4}\rm M_\odot\,kpc^{-2}\,Gyr^{-1}$ at most. A lower revised value of 40% for the expected fraction of presolar silicate grains from massive AGB stars is still high to explain the non-detection of these grains in meteorites.

Impact-driven planetary desiccation: The origin of the dry Venus

The fate of surface water on Venus is one of the most important outstanding problems in comparative planetology. Although Venus should have had a large amount of surface water (like the Earth) during its formation, the current water content on the Venusian surface is only 1 part in 100 000 of that of the mass of Earth's oceans. Here a new concept is proposed to explain water removal on a steam-covered proto Venus, referred to as “impact-driven planetary desiccation”. Since a steam atmosphere is photochemically unstable, water vapor dissociates into hydrogen and oxygen. Then, hydrogen escapes easily into space through hydrodynamic escape driven by strong extreme ultraviolet radiation from the young Sun. The focus is on the intense impact bombardment during the terminal stage of planetary accretion as generators of a significant amount of reducing agent. The fine-grained ejecta remove the residual oxygen, the counter part of escaped hydrogen, via the oxidation of iron-bearing rocks in a hot atmosphere. Thus, hypervelocity impacts cause net desiccation of the planetary surface. I constructed a stochastic cratering model using a Monte Carlo approach to investigate the cumulative mass of nonoxidized, ejected rocks due to the intense impact bombardment. The ejecta mass after each impact was calculated using the π-group scaling laws and a modified Maxwell's Z model. The effect of projectile penetration into the ground on the ejecta mass was also included. Next, an upper limit on the total amount of removed water was calculated using the stoichiometric limit of the oxidation of basaltic rocks, taking into account the effect of fast H2 escape. It is shown that a thick steam atmosphere with a mass equivalent to that of the terrestrial oceans would be removed. The cumulative mass of rocky ejecta released into the atmosphere reaches 1 wt% of the host planet, which is 10 000 times of the current mass of the Earth's atmosphere. These results strongly suggest that chemical reactions between such large amounts of ejecta and planetary atmospheres are among the key factors required to understand atmospheric mass and its composition, not only in the Solar System but also in extrasolar systems.

Gamma-ray bursts from dusty regions with little molecular gas

AbstractWe detected CO line and 1.2-mm continuum emission from the two GRB host galaxies (GRB 020819B and GRB 051022) by using the Atacama Large Millimeter/submillimeter Array (ALMA). This is the first case for detecting molecular gas emission in GRB hosts. The ratio of molecular gas to dust mass of the GRB 020819B site is significantly lower than those of the Milky Way and nearby star-forming galaxies, suggesting that the star-forming environment where the GRB occur is different from those in local galaxies. The possible reason is that much of the dense gas is dissipated by a strong interstellar ultraviolet radiation field.

Experiment Research on Concrete Block by Ultraviolet Irradiation in Tibet Plateau

According to the characteristics of high altitude and strong ultraviolet radiation in Tibet, this paper do ultraviolet irradiation experiment research to different strength grades of concrete blocks in a closed laboratory, it is found that ultraviolet rays has promoting effect to early strength growth of test block, but the growth became slow along with the time.

Above threshold ionization of Argon atoms by multicolor XUV radiation

We analyse theoretically the Argon photoelectron spectra produced by strong and extreme ultraviolet radiation of six colors: from the 11th to the 16th harmonics of ω0 (800nm). In particular we concentrate in the range of the spectra where absorption of two photons occurs. The combination of photons of different frequencies results in eleven peaks that are separated by ω0. We point out that their relative intensities are very sensitive to the laser pulse parameters and target description. We also compare the theoretical description with experimental results finding good qualitative agreement.

Is there a golden mean for sun exposure?

Is there a golden mean for sun exposure?

Importance of Functional Ingredients in Yak Milk-Derived Food on Health of Tibetan Nomads Living Under High-Altitude Stress: A Review

Tibetan nomads have lived since ancient times in the unique and harsh environment of the Qinghai-Tibetan Plateau with average altitudes over 4000 m. These people have been able to live and multiply healthily over numerous generations under the extreme stress of high-altitude environment, including cold, hypoxia, and strong ultraviolet radiation, and with a simple diet devoid of vegetables and fruits for most of the year. Their survival depends heavily on yak milk, and its products comprise the main portion of their daily diet. In this review, yak milk and its derived products are examined in detail and compared with milk from other ruminant species. Yak milk products seem to be particularly rich in functional and bioactive components, which may play a role in maintaining the health status of Tibetan nomads. This includes particular profiles of amino acids and fatty acids, and high levels of antioxidant vitamins, specific enzymes, and bacteria with probiotic activity (yoghurt is the main food). Based on that, it is proposed that the Tibetan nomads have developed a nutritional mechanism adapted to cope with the specific challenges posed by the environment of the world's highest plateau. Systematic studies are required to demonstrate this in a more mechanistic way.