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At least 685 records · Page 38Linked to original sources
PubMed2005

Effects of a mixture of tetracyclines to Lemna gibba and Myriophyllum sibiricum evaluated in aquatic microcosms.

The impact of a mixture of oxytetracycline, chlortetracycline, tetracycline and doxycycline on Myriophyllum sibiricum and Lemna gibba was investigated using fifteen 12,000-L microcosms (k=5, n=3). Significant concentration-response relationships were only found for M. sibiricum, where dry mass was 69, 47, 30, and 7% of controls at respective treatment concentrations of 0.080, 0.218, 0.668, and 2.289 micromol/L. Somatic endpoints were strongly and negatively correlated with percent light transmission, except plant length, which was positively correlated. Treated microcosms experienced a reduction in the percent of surface irradiance penetrating the water column as high as 99.8% at a depth of 70 cm, relative to controls. Position relative to the water column was likely responsible for the differential effects observed between floating (L. gibba) and submerged (M. sibiricum) species of macrophytes. A hazard quotient assessment of the lowest EC10 value indicated significant risk, exceeding the critical HQ value, but not the lowest EC25 value.

Anti-Infective Agents↗
PubMed2006

Adaptation of office workers to a new building - impaired well-being as part of the sick-building-syndrome.

AIM: The focus of our study was the assessment of the effects of spatial relocation on office staff. Our aim was to investigate whether psychosocial or personal factors are better predictors of the occurrence of impaired well-being. METHODS: Before relocation the administration of the university hospital of Ulm (Germany) was located in ten different buildings. Chemical and physical parameters of the indoor air were measured. The employees were surveyed with a questionnaire for their health status and psychosocial determinants. After moving to a new wide-spaced building, the same procedure was reapplied shortly afterwards and half a year later. Only respondents who had taken part in all three surveys are taken into account (n=84). The definition of impaired well-being as defined by the ProKlimA-study group was used as the criterion variable. RESULTS: The overall prevalence of impaired well-being rose from 24% to 36% after relocation. Contrarily, persons who were formerly accommodated in a wide spaced-building showed a reduced risk (OR(post1)=0.3). Affected persons had at all times a more negative response pattern. Chemical and physical parameters did not have any influence in this context. CONCLUSIONS: The adaptation to a new environment is influenced by the old "socialization" of the former buildings. Impaired well-being is not limited to bodily complaints, it rather has a systemic character in the form of a distinctive overall response pattern. For an adequate analysis of impaired well-being - and the sick-building-syndrome in consequence - the elucidation of individual and other potentially intervening factors is essential. Taking this into consideration, the search for norm values or a framework seems to be of limited value.

Air Pollutants, Occupational↗
PubMed2004

Use of ultrabright LEDs for the determination of static and time-resolved florescence information of liquid and solid crude oil samples.

Ultrabright light emitting diodes (LEDs) are an inexpensive alternative to laser diodes (LDs) and other short wavelength emitting light sources. They have a high stability, a long lifetime, and a very low power consumption. A large number of publications are already available for fluorescence applications using this type of LEDs. Most of them are describing fluorescence intensity measurements. Only some of them are dealing with time-resolved methods, like single photon timing. LED modulation fluorometry is a very recent application, which can also be used for environmental investigations, like the detection of polycyclic aromatic hydrocarbons (PAHs). This article demonstrates the possible application of ultrabright LEDs for the time-resolved fluorescence detection of crude oil contaminated samples.

Environmental Monitoring↗
PubMed2006

Surface modification of nanometer size TiO2 with salicylic acid for photocatalytic degradation of 4-nitrophenol.

The efficiency of photocatalytic reactions was limited by the wide band-gap of TiO(2) and the high degree of electron-hole recombination inherent in photocatalytic process, as well as by the limited adsorption capability of photocatalysts. In order to increase the overall efficiency, the surface of nanometer size TiO(2) was simply and fast modified by chemical adsorption in saturated solution of salicylic acid. A stable, light yellow surface complex was formed quickly, which has obvious absorption in the region from 320 to 420 nm. Through surface modification, the adsorption efficiency of 4-nitrophenol by TiO(2) was enhanced from 42 to 84%. The photocatalytic efficiency was tested on the degradation of 4-nitrophenol. The influences of catalyst and its dosage, pH value, and 4-nitrophenol concentration on the degradation were investigated. Under such photodegradation conditions as initial pH 4.0, 4-nitrophenol 5 mg l(-1), catalyst 100 mg, and irradiation time 160 min with 160 W high-pressure mercury lamp, the degradation efficiency of 4-nitrophenol by TiO(2) was increased from 39.5 to 79.3% after surface modification, and furthermore, the degradation efficiency could be enhanced to 91.1% if the concentration of 4-nitrophenol was not more than 1 mg l(-1). Compared with the pure TiO(2), surface modification led not only to improve the surface coverage of 4-nitrophenol, but also to increase the light utilization. Both of these factors were crucial for the photocatalytic activity of heterogeneous photocatalysis, especially for photodegradation of aromatic pollutants.

Adsorption↗
PubMed2005

Development of a growth inhibition test with the marine and brackish water red alga Ceramium tenuicorne.

The marine red macroalga Ceramium tenuicorne is cosmopolitan and naturally found in both brackish and marine waters. A growth inhibition test with this species can be carried out in salinities from 4 per thousand to 32 per thousand. The species is easily held in culture in the laboratory and the test can be performed in a completely defined medium. The robustness of the method is good with a CV of 14.6% of the controls. The EC calculations can be performed on linear regression on the length data. EC50 values of repetitive tests for zinc (20-33 microg Zn(2+)/l in 7 per thousand and 32-61 microg Zn(2+)/l in 20 per thousand) and copper (1.9-3.8 Cu(2+)/l in 7 per thousand and 7.9-13 Cu(2+)/l in 20 per thousand) show high sensitivity. This test is a good complement to any test battery with the purpose of estimating the hazard of substances to the brackish and marine environment.

Copper↗
PubMed2001

Capillary zone electrophoresis for the determination of light-absorbing anions in environmental samples.

A rapid and simple method for separation and determination of inorganic anions by capillary zone electrophoresis was described. The detection was carried out directly with a diode array detector. The experimental conditions, such as concentration of carrier electrolyte, capillary length, voltage, and temperature were optimized. In order to improve selectivity, different organic modifiers were also investigated. The baseline separation of 10 light-absorbing anions was accomplished within 3.5 min with a background electrolyte consisting of 50 mM sodium tetraborate containing 5% MeOH. Linear plots were obtained in the concentration range of 0.1-10 microg/ml. With sample stacking injection, the quantitation limits of the anions were found to be in the range of 0.02-0.1 microg/ml. The proposed method was successfully applied to the determination of inorganic anions in environmental samples and in effluents of a power plant.

Anions↗
PubMed2002

Decomposition of gas-phase trichloroethene by the UV/TiO2 process in the presence of ozone.

The decomposition of gas-phase trichloroethene (TCE) in air streams by direct photolysis, the UV/TiO2 and UV/O3 processes was studied. The experiments were carried out under various UV light intensities and wavelengths, ozone dosages, and initial concentrations of TCE to investigate and compare the removal efficiency of the pollutant. For UV/TiO2 process, the individual contribution to the decomposition of TCE by direct photolysis and hydroxyl radicals destruction was differentiated to discuss the quantum efficiency with 254 and 365 nm UV lamps. The removal of gaseous TCE was found to reduce by UV/TiO2 process in the presence of ozone possibly because of the ozone molecules could scavenge hydroxyl radicals produced from the excitation of TiO2 by UV radiation to inhibit the decomposition of TCE. A photoreactor design equation for the decomposition of gaseous TCE by the UV/TiO2 process in air streams was developed by combining the continuity equation of the pollutant and the surface catalysis reaction rate expression. By the proposed design scheme, the temporal distribution of TCE at various operation conditions by the UV/TiO2 process can be well modeled.

Air Pollutants↗
PubMed2002

Photocatalytic atrazine degradation by synthetic minerals, atmospheric aerosols, and soil particles.

In this work, the photocatalytic atrazine degradation by seven synthetic minerals and five environmental particle samples was examined to investigate a possible contribution of photocatalysis to the abiotic degradation of atrazine in the environment. Particle suspensions containing 500 ng/L atrazine were irradiated with a sun simulator, and the atrazine degradation was monitored by enzyme-linked immunosorbent assay (ELISA). Atrazine detection by ELISA proved to be an useful analytical tool because of low cross-reactivity of atrazine metabolites and high sensitivity with detection limits in the lower nanograms per liter range. The atrazine degradation followed first-order kinetics, and the obtained rate coefficients were compared with the rate of direct photolysis. Known photocatalysts, such as TiO2 and ZnO, showed the expected fast photocatalytic degradation (k = 27-327 x 10(-3) min(-1)) of atrazine. The degradation rates detected upon irradiation of titanium-, zinc-, or iron-containing minerals were orders of magnitudes lower (k = 0.15-0.70 x 10(-3) min(-1)) but still significantly faster than direct photolysis without particles (k = 0.10 x 10(-3) min(-1)). With environmental particle samples (soot, fly ash, sand, road dust, and volcanic ash), however, no significant photocatalytic activity was observed (k = 0.07-0.16 x 10(-3) min(-1)). The atrazine degradation rates were in the range of direct photolysis. Thus photocatalysis by aerosol or soil particles appears not to enhance abiotic atrazine degradation in the environment.

Aerosols↗
PubMed2003

Systemic genotoxic effects produced by light, and synergism with cigarette smoke in the respiratory tract of hairless mice.

No information is available on the interaction between cigarette smoke, the most important man-made carcinogen, and light, the most widespread natural carcinogen. In order to clarify this issue, SKH-1 hairless mice were exposed to environmental smoke and/or to the light emitted by sunlight-simulating halogen quartz bulbs. After 28 days, intermediate biomarkers were evaluated in skin, respiratory tract, bone marrow and peripheral blood. The results showed that, individually, the light produced extensive alterations not only in the skin but even at a systemic level, as shown by formation of bulky DNA adducts in both lung and bone marrow and induction of cytogenetic damage in bone marrow and peripheral blood erythrocytes. Smoke damaged the respiratory tract and produced significant alterations in the skin as well as an evident cytogenetic damage in both bone marrow and peripheral blood. Interestingly, as compared with exposure to smoke only, alternate daily cycles of exposure to both light and smoke significantly increased malondialdehyde concentrations and DNA adduct levels in lung and the frequency of micronuclei in pulmonary alveolar macrophages. The oral administration of sulindac, a non-steroidal anti-inflammatory drug, attenuated several biomarker alterations due to the combined exposure of mice to light and smoke. In conclusion, the light induces a systemic genotoxic damage, which is presumably due to the UV-mediated formation in the skin of long-lived derivatives, such as aldehydes. This damage may mechanistically be involved in light-related hematopoietic malignancies. In addition, the light displayed an insofar unsuspected synergism with smoke in the induction of DNA damage in the respiratory tract.

Animals↗
PubMed2004

Preliminary study on the photoproduction of hydroxyl radicals in aqueous solution with Aldrich humic acid, algae and Fe(III) under high-pressure mercury lamp irradiation.

Under a high-pressure mercury lamp (HPML) and using an exposure time of 4 h, the photoproduction of hydroxyl radicals (*OH) could be induced in an aqueous solution containing humic acid (HA). Hydroxyl radicals were determined by high-performance liquid chromatography using benzene as a probe. The results showed that *OH photoproduction increased from 1.80 to 2.74 microM by increasing the HA concentration from 10 to 40 mg L(-1) at an exposure time of 4 h (pH 6.5). Hydroxyl radical photoproduction in aqueous solutions of HA containing algae was greater than that in the aqueous solutions of HA without algae. The photoproduction of *OH in the HA solution with Fe(III) was greater than that of the solution without Fe(III) at pH ranging from 4.0 to 8.0. The photoproduction of *OH in HA solution with algae with or without Fe(III) under a 250 W HPML was greater than that under a 125 W HPML. The photoproduction of *OH in irradiated samples was influenced by the pH. The results showed that HPML exposure for 4 h in the 4-8 pH range led to the highest *OH photoproduction at pH 4.0.

Benzene↗
PubMedDate not supplied

Light-catalyzed chromium(VI) reduction by organic compounds and soil minerals.

Detoxification of Cr(VI) through reduction has been considered an effective method for reclaiming Cr-contaminated soil, sediment, and waste water. Organic matter is widely distributed in soil and aquatic systems; however, low Cr(VI) reduction rates inhibit the adoption of Cr reduction technologies by industry. Scientists have been aware of Cr(VI) reduction catalyzed by soil minerals; however, most of the studies focused on using semiconductors as catalysts with UV irradiation to accelerate the redox reactions. The objective of this study was to evaluate the rates of Cr(VI) reduction by fluorescence light in the presence of organic materials with or without specific soil minerals. Experimental results showed that dissolved organic compounds reduced Cr(VI) slowly under laboratory light; however, Cr(VI) reduction was greatly enhanced when growth chamber light was applied. Low photon flux (i.e., laboratory light) only enhanced Cr(VI) reduction by organics when Fe(III) was also present, because the Fe(II)-Fe(III) redox couple accelerated electron transfer and decreased electrostatic repulsion between reactants. Laboratory light was required to initiate Cr(VI) reduction catalyzed by TiO2; nonetheless, light-catalyzed Cr(VI) reduction by smectite and ferrihydrite could occur only when greater light energy was provided with a growth chamber light. Our results suggest a potential pathway for Cr(VI) reduction using naturally occurring organic compounds and colloids in acidic water systems or in surface soils when light is available.

Catalysis↗
PubMed2002

Resonance scattering spectral analysis of chlorides based on the formation of (AgCl)n(Ag)s nanoparticle.

A novel resonance scattering spectral method has been proposed for the determination of trace amounts of chlorides in the range of 2 x 10(-7)-8 x 10(-6) mol/l. It was based on the photochemical reaction system of AgNO3-NaCl-sodium oxalic to form the (AgCl)nucleus (n)(Ag)shell (s) nanoparticle. There is a strongest resonance scattering peak at 470 nm and a maximum absorption peak at 425 nm. The concentration of chlorides is proportional to the intensity of resonance scattering at 470 nm. The nonlinear resonance scattering peaks of the nanoparticle system have been also considered, according to the theory of the interaction between the surface electron of nanoparticle and the incidence photon.

Chlorides↗
PubMedDate not supplied

Urban birth and risk of schizophrenia: a worrying example of epidemiology where the data are stronger than the hypotheses.

There is robust and consistent evidence from epidemiological studies showing that urban birth is associated with an increased risk of developing schizophrenia. Evidence suggests that this exposure may be associated with a sizeable proportion of cases. To date the candidate exposures underlying the urban birth risk factor have included infectious agents, low prenatal vitamin D, toxins associated with pollution, and stress. However, in general, the hypotheses proposed to explain the urban birth risk factor have been unsatisfying. In light of the general trend towards increasing urbanization, it is feasible that the attributable fraction of schizophrenia associated with urban birth may increase. The psychiatric research community should have a sense of urgency in exploring the mechanisms linking urban birth and risk of schizophrenia.

Humans↗
PubMed1989

Detectability of emergency lights for underwater escape.

The time to detect each of three underwater lights by six subjects was measured in clear and turbid (attenuation coefficient = 4.2.m-1) water, at distances of 1.54 m and 3.1 m, from two viewing angles, straight ahead (0 degrees) or 65 degrees to one side, and under three levels of ambient illumination. The lights were viewed either through a window, to simulate the use of a face mask, or with the subjects immersed. All lights were detected rapidly (less than 1 s) when viewed through the window in clear water. In turbid conditions, none of the lights was seen at 3.1 m by any subject. At a 1.54 m viewing distance, reliable detection by immersed subjects was found only in the clear water under the two darker ambient illuminations. In turbid water, detection was unreliable. We conclude that the design of underwater escape lighting should not rely on visibility over distances greater than 1.5 m, and that an illuminated guide-bar might provide valuable assistance in directing escape from aircraft.

Accidents, Aviation↗