超共轭有机苯甲脒类紫外线吸收剂

本文在总结了不同种类的紫外线吸收剂的基础上,重点介绍了苯甲脒类紫外线吸收剂。基于苯甲脒类紫外线吸收剂具有非常好的抗紫外线的效果,同时与高分子化合物有很好的相容性、并且沸点较高、热稳定性很好,所以能很好的适用于如塑料成型等高温实验中。特别是苯甲脒类紫外线吸收剂还可应用在聚氨酯PU上,使其抗紫外线效果明显优于使用其他的紫外线吸收剂。     

Repression of photoreactivation and dark repair of coliform bacteria by TiO2-modified UV-C disinfection

Photoreactivation and dark repair of damaged DNA can occur after some bacteria are disinfected with UV-C irradiation and thus reduce the disinfection efficiency. We have discovered that the provision of 1 mg/L titanium dioxide (TiO₂) in suspension during UV-C irradiation at normal disinfection doses repressed the photoreactivation and dark repair. The repressive effect was also observed when a TiO₂-coated plate was used during UV-C exposure but removed thereafter, indicating the repressive effect does not require the presence of TiO₂ in the post-UV event. The repressive effect was consistently observed with changes of bacteria species, temperature, salinities, UV sources, doses and intensities, and with/without nutrients. The repressive effect is likely associated with the additional radical attack during UV-TiO₂ irradiation and/or formation of a small amount of stable residual oxidants (primarily hydrogen peroxide). The TiO₂-modified UV-C disinfection represents an innovative means to disinfect water. It is particularly useful in situations where additions of residual chlorine or chloramines are not allowed or not possible. Nevertheless, the TiO₂ shall be properly included, by either using the optimum dose in suspension or immobilizing it onto a surface, since too little TiO₂ cannot provide the repression while too much TiO₂ in suspension gives a detrimental effect on the UV-C disinfection.     

Reconsidering the quantitative analysis of organic carbon concentrations in size exclusion chromatography

The evaluation of the molecular size distribution of natural organic matter (NOM) in aquatic environments via size exclusion chromatography (SEC) is important for the understanding of environmental processes such as nutrient cycling and pollutant transport as well as of technical water treatment processes. The use of organic carbon (OC) detectors has become popular in recent studies due to improved availability and quantification possibilities, which supposedly are superior to those of ultraviolet (UV) detectors. A set of 12 NOM samples was used to demonstrate the limitations of online OC detection (OCD) when analyzing complex aquatic organic matter. A novel evaluation approach for SEC data is introduced by combining the information from UV absorbance (UVA) and OCD chromatograms as well as offline total OC (t-OC) and dissolved OC-specific UVA (SUVA) measurements. It could be shown that about 70% of certain OC components were not detected with the OCD system used in this study. For the investigated samples, these types of carbon accounted for up to 72% of the t-OC, i.e. for such NOM samples quantification by OCD is not possible or at least highly questionable. The addition of an oxidant improved the overall oxidation efficiency only slightly. Most likely NOM that predominantly consists of polysaccharides and features a nominal molecular weight of 150 kg/mol or more was responsible for low OCD yields. For future applications, a further improvement of the OCD system would be worthwhile so that quantitative analytical data on the molecular size distribution of NOM and its structural characteristics such as the SUVA distribution can be obtained.     

The Ultraviolet Irradiation Modification of PTFE on the Compatible Properties of Clay/EPDM Composite

Clay and ultraviolet irradiation treated PTFE filled clay/EPDM/PTFE composites were prepared. Results show that the tensile strength increase with the irradiation time, and the tribological properties of the ultraviolet irradiation treated PTFE filled clay/EPDM/PTFE composites are superior to those of clay/EPDM/PTFE composites in terms of the crosslink between the reinforcing particle and matrix. This may be due to the nanoscale effects, and the strong interaction force existed between the matrix and the clay interface.     

Photodegradation of the antibiotics nitroimidazoles in aqueous solution by ultraviolet radiation

The objective of this study was to analyze the efficacy of ultraviolet (UV) radiation in the direct photodegradation of nitroimidazoles. For this purpose, i) a kinetic study was performed, determining the quantum yield of the process; and ii) the influence of the different operational variables was analyzed (initial concentration of antibiotic, pH, presence of natural organic matter compounds, and chemical composition of water), and the time course of total organic carbon (TOC) concentration and toxicity during nitroimidazole photodegradation was studied. The very low quantum yields obtained for the four nitroimidazoles are responsible for the low efficacy of the quantum process during direct photon absorption in nitroimidazole phototransformation. The R₂₅₄ values obtained show that the dose habitually used for water disinfection is not sufficient to remove this type of pharmaceutical; therefore, higher doses of UV irradiation or longer exposure times are required for their removal. The time course of TOC and toxicity during direct photodegradation (in both ultrapure and real water) shows that oxidation by-products are not oxidized to CO₂ to the desired extent, generating oxidation by-products that are more toxic than the initial product. The concentration of nitroimidazoles has a major effect on their photodegradation rate. The study of the influence of pH on the values of parameters ? (molar absorption coefficient) and k′_E (photodegradation rate constant) showed no general trend in the behavior of nitroimidazoles as a function of the solution pH. The components of natural organic matter, gallic acid (GAL), tannic acid (TAN) and humic acid (HUM), may act as promoters and/or inhibitors of OH· radicals via photoproduction of H₂O₂. The effect of GAL on the metronidazole (MNZ) degradation rate markedly differed from that of TAN or HUM, with a higher rate at low GAL concentrations. Differences in MNZ degradation rate among waters with different chemical composition are not very marked, although the rate is slightly lower in wastewaters, mainly due to the UV radiation filter effect of this type of water.     

A novel approach to documenting artifacts at the Gold Museum in Bogota

We present our work on novel digitizing techniques to create virtual exhibitions in the context of the Gold Museum in Bogotá, Colombia, a world renown space for precious pre-Colombian gold artifacts. In order to solve issues related to high specular reflection in gold artifacts, we developed a multi-spectral approach that solves some of the shortfalls of many commercial scanners. We also integrated commercial haptic devices into a new virtual installation that allows visitors to touch, hear, and see virtual approximations of the real objects. As an evaluation methodology, we compare the results of a scanner with normal light with our approach, and we also present results from user studies on our virtual installation.     

Photoreduction of Reactive Brilliant Red X-3B by Ultraviolet Irradiation/Potassium Borohydride/Sodium Bisulfite

Photoreduction of Reactive Brilliant Red X-3B in aqueous solution by ultraviolet irradiation/potassium borohydride/sodium bisulfite (UV/KBH4/NaHSO3) was investigated. The effects of operational parameters including KBH4 dosage, NaHSO3 dosage, pH value, and temperature were studied. The reaction mechanism was also discussed. The preliminary results showed that UV and KBH4/NaHSO3 had a significant synergy for the decolorization. At the conditions of 6-mg KBH4, 250-mg NaHSO3, pH 6.0, and room temperature, highest color removal percentage was achieved. From the mechanism discussion, we could conjecture that the mechanism of photoreduction was mainly caused by the production of sulfur dioxide anion radicals, and UV irradiation played a vital role during the process.     

Method to evaluate UV dose of upper-room UVGI system using the concept of ventilation efficiency

Several countermeasures against the prevalence of infectious diseases have recently been issued, and one of them, the ultraviolet germicidal irradiation (UVGI) system, has been carefully considered for building environments especially. Besides experimental methods to evaluate the germicidal performance of upper air UVGI systems, this research introduces two numerical methods using the concept of ventilation performance, and illustrates the methods with a ward model. The first calculates the average residence time of air using the concept of local purging flow rate (L-PFR) which is multiplied by the average UV intensity of the upper area to obtain a UV dose. The other calculates the UV dose with the distributional UV intensity and deals with UV intensities as contaminant sources. The results of the illustrative cases with a ward model show that the method using the L-PFR concept could not clearly identify the difference in UV doses for each case with different exhaust opening setups, although the other could. The results from the method using the distributional UV intensity indicated the layout of ventilation openings and upper-room UVGI systems are important to optimize the germicidal performance.     

SIMULATION OF BROAD-BAND AND SPECTRAL SOLAR ULTRAVIOLET RADIATION

Daily broad-band and spectral measurements of solar ultraviolet radiation reaching the ground at Athens, Greece (38^°N, 24^°E) during 1989-1993 in conjunction with daily total ozone measurements deduced from satellite and ground-based instrumentation were used to investigate their association. Furthermore, employing a new parametric model, the spectral and broad-band solar ultraviolet radiation for die period 1979-1993 were calculated considering the total ozone values, derived from both the satellite Nimbus-7, and the ground-based Dobson spectrophotometer.     

UV Radiation and the Skin

UV radiation (UV) is classified as a “complete carcinogen” because it is both a mutagen and a non-specific damaging agent and has properties of both a tumor initiator and a tumor promoter. In environmental abundance, UV is the most important modifiable risk factor for skin cancer and many other environmentally-influenced skin disorders. However, UV also benefits human health by mediating natural synthesis of vitamin D and endorphins in the skin, therefore UV has complex and mixed effects on human health. Nonetheless, excessive exposure to UV carries profound health risks, including atrophy, pigmentary changes, wrinkling and malignancy. UV is epidemiologically and molecularly linked to the three most common types of skin cancer, basal cell carcinoma, squamous cell carcinoma and malignant melanoma, which together affect more than a million Americans annually. Genetic factors also influence risk of UV-mediated skin disease. Polymorphisms of the melanocortin 1 receptor (MC1R) gene, in particular, correlate with fairness of skin, UV sensitivity, and enhanced cancer risk. We are interested in developing UV-protective approaches based on a detailed understanding of molecular events that occur after UV exposure, focusing particularly on epidermal melanization and the role of the MC1R in genome maintenance.