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1.
Abstract: Robertson-Berger sunburn meter data recorded from August 1992 to May 1993 (Innsbruck, 577 m above sea level, Austria) were compared with measurements taken in previous years. In February and March 1993 instantaneous values on clear days were found to be higher by up to 37% than those registered in previous years (1986–1988). However, in winter/spring 1993 daily totals for all days, averaged over 7 days, were within the range of standard deviation of the previous years (1981–1988). Therefore the cumulative UV-B exposure of the ecosystem is within the general range of variability even under the record low ozone values in winter/spring 1993, while single peak doses were enhanced significantly.  相似文献   

2.
INCREASED UV EXPOSURE IN FINLAND IN 1993   总被引:1,自引:0,他引:1  
Abstract—
Exceptionally low total ozone, up to 40% below the normal level, was measured over Northern Europe during winter and spring in 1992 and 1993. In 1993 the depletion persisted up to the end of May, resulting in a significant increase of biologically effective UV radiation. The increases were significantly smaller in 1992 and 1994 than in 1993. The UV exposure of the Finnish population was evaluated through measurements and theoretical calculations. The increase in measured erythemal (International Lighting Commission) UV falling onto horizontal surfaces on clear days was determined relative to model calculations for an average ozone amount. The increase was on average 10% from April to May 1993, and the maximal measured increase was 34%. Theoretical calculations for both erythemal and carcinogenic (Skin Cancer Utrecht-Philadelphia) UV indicated that in 1993 the theoretical annual increase to a vertical (cylinder) surface ranged from 8 to 13% in Finland. The reflection of UV from snow considerably increases facial UV doses in Northern Finland.  相似文献   

3.
We carried out experiments to evaluate seasonal changes in the impacts of UV radiation (UVR, 280–400 nm) on photosynthetic carbon fixation of phytoplankton assemblages. Surface water samples were obtained in the coastal area of the South China Sea, where chlorophyll a ranged 0.72–3.82 μg L−1. Assimilation numbers (photosynthetic carbon fixation rate per chl a) were significantly higher during summer 2005 than those in spring and winter 2004. The mean values obtained under photosynthetically active radiation (PAR) were 2.83 (spring 2004), 4.35 (winter 2004) and 7.29 μg C (μg chl a)−1 h−1 (summer 2005), respectively. The assimilation numbers under PAR + UVR were 1.58, 2.71 and 5.28 μg C (μg chl a)−1 h−1, for spring, winter and summer, respectively. UVR induced less inhibition of photosynthesis during summer 2005 than during the other seasons, in spite of the higher UVR during summer. The seasonal differences in the productivity and photosynthetic response to UV were mainly due to changes in water temperature, while irradiance and vertical mixing explained >80% of the observed variability. Our data suggest that previous studies in the SCS using UV-opaque vessels might have overestimated the phytoplankton production by about 80% in spring, 61% in winter and 38% in summer.  相似文献   

4.
Atmospheric tritium concentrations of tritiated water vapor (HTO), tritiated hydrogen (HT) and tritiated hydrocarbons (primarily tritiated methane, CH3T) have been measured in Fukuoka prefecture, Japan from 1984 to the present to establish a general database on the behavior of atmospheric tritium. HTO concentrations expressed in Bq/l-H2O vary within a range of 1.19 to 2.45, giving an overall average value of 1.86±0.077. HTO concentrations expressed in-mBq/m3-air vary within a range of 7.8 to 46.1 and have a strong correlation with the atmospheric humidity, being high in the summer and low in winter. In the case of HT and CH3T, no seasonal variations were observed with average monthly values of 23.1 to 61.0 mBq/m3-air and 8.3 to 23.9 mBq/m3-air, respectively. The present HTO concentrations are already close to the tritium level before nuclear testings. However, the present HT and CH3T concentrations are still higher by a factor of about 140 and 30, respectively, than those before the testings. Specific activities are estimated to be 14.6–16.7 TU for HTO, 5.5·105–1.0·106 TU for HT and 3.2·104–4·104 TU for CH3T. The apparent difference in the specific activities suggests a very slow transformation of these species in the atmosphere or a continuous supply of HT and CH3T with high specific activity. Residence time for atmospheric HT was found to be 6.5 years over the period 1988–92 and 10 years for 1988–95. These times are longer than 4.8 years given by Mason and Östlund in the 1970s, and thus indicate a supply to the atmosphere of HT from various tritium sources.  相似文献   

5.
Martyn S. Ray 《Adsorption》1996,2(2):157-178
This paper provides a review of the 1994 journal literature and complete bibliography concerned with adsorptive separations. The references are taken from the 45 most important chemical engineering journals. This paper provides an update to the literature as provided in previous bibliographic papers (Ray 1990; 1991; 1995). References for membranes and membrane-type separations (for 1992–1993) were the subject of a separate bibliographic paper (Ray 1994), due to the number of papers now published on this topic each year. A review and bibliography paper covering 1994 for membranes has been submitted for publication. Bibliographic papers covering traditional unit operations (Ray 1992; 1993; 1994; 1994) and supercritical extraction (Ray 1994) have been published. A bibliography of the chemical engineering journal literature from 1967–1988 has been published by the author (Ray 1990), and can provide access to a wider range of topics. A complete bibliographic listing of the chemical engineering journal literature from 1989 to 1994 (with subsequent six-monthly updates) is available on a CD-ROM database (Published by Royal Melbourne Institute of Technology) and full details can be obtained from the author.  相似文献   

6.
A multiwalled carbon nanotubes/poly(bromocresol green) modfied glassy carbon electrode (MWNTs-PBG/GCE) was used to investigate the electrochemical behavior of reduced glutathione(GSH). GSH showed an irreversible oxidation process on MWNTs-PBG/GCE with an oxidation peak at 0.77 V(vs. SCE) in a phosphate buffer solution(pH=4.0). The kinetic parameters of the electrochemical behavior of GSH on MWNTs-PBG/GCE were calculated. Under the optimal conditions and with the help of amperometric method, a linear relationship was obtained between the oxidation peak current and GSH concentration in the range from 2×10–7 mol/L to 5×10–6 mol/L with the detection limit as 1×10–8 mol/L(signal-to-noise ratio of 3). The current reached the steady-state current within about 5 s. The modified electrode surface had very good reproducibility and stability.  相似文献   

7.
The deposition flux of 7Be was measured in the range from 0.4 to 5.2 Bq m?2 d?1, with a mean value of 2.6 Bq m?2 d?1, during the period of May 31, 2009?CMay 31, 2010 in the Three Gorges Reservoir region, China. The low annual deposition flux of 7Be was probably due to the adsorption of 7Be within high altitude clouds and the Qinling-Daba Mountain??s barrier and blocking effects on the cold air during winter months. There was a seasonal trend for 7Be deposition, showing a spring maximum and winter minimum, which may be attributed to the seasonal folding of tropopause in spring and little rainfall amount in winter. A strong positive correlation (R 2 = 0.67) between 7Be deposition flux and rainfall was observed. The depth distribution of 7Be in undisturbed purple soil profiles suggested that the nuclide was mainly distributed within the top 20.0 kg m?2 (~1.5 cm) of soil in depth and the maximum concentration occurred at a depth of 3.0 kg m?2 (~0.2 cm), then the concentration declined quickly and exponentially with depth. The seasonal inventories of 7Be in soils were consistent with the values calculated from the atmospheric fluxes, which shows a great potential for using 7Be as a tracer to assess soil redistribution in purple soil areas of China.  相似文献   

8.
Two new mutants of Neurospora craasa , designated hth-1 and hth-2 , have been isolated which allow clear expression of the circadian conidiation rhythm at high temperature (36°C). Both strains showed single-gene segregation and produced similar phenotypes but mapped to different genetic loci. These mutants allowed an analysis of the effect of temperature on (1) light-induced phase-shifting of the circadian rhythm, (2) period length of rhythm, and (3) growth rate. The amplitude of the phase response curve to light was drastically reduced as the temperature was increased from 25°C to 34°C. Phase advances were decreased more than phase delays. As previously reported (Sargent et al. , 1966), the period length of the rhythm is temperature-compensated below 30°C ( Q 10˜ 1) but not well-compensated above 30°C ( Q 10 1.3–1.7). The decrease in amplitude of the light phase response curve occurred in both temperature ranges. Furthermore, the Q 10 value was lowered by addition of yeast extract in the high temperature range but not in the low range. Q 10 values for growth rate also differed in these strains both in the low temperature range (25–30°C) and the high temperature range (30–34°C).  相似文献   

9.
Various Be-containing micro-particle suspensions were equilibrated with simulated lung fluid (SLF) to examine their dissolution behavior as well as the potential generation of nanoparticles. The motivation for this study was to explore the relationship between dissolution/particle generation behaviors of Be-containing materials relevant to Be-ore processing, and their epidemiologically indicated inhalation toxicities. Limited data suggest that BeO is associated with higher rates of beryllium sensitization (BS) and chronic beryllium disease (CBD) relative to the other five relevant materials studied: bertrandite-containing ore, beryl-containing ore, frit (a processing intermediate), Be(OH)2 (a processing intermediate), and silica (control). These materials were equilibrated with SLF at two pH values (4.5 and 7.2) to reflect inter- and intra-cellular environments in lung tissue. Concentrations of Be, Al, and Si in SLF increased linearly during the first 20 days of equilibration, and then rose slowly, or in some cases reached a maximum, and subsequently decreased. Relative to the other materials, BeO produced relatively low Be concentration in solution at pH 7.2; and relatively high Be concentration in solution at pH 4.5 during the first 20 days of equilibration. For both pH values, however, the Be concentration in SLF normalized to Be content of the material was lowest for BeO, demonstrating that BeO was distinct among the four other Be-containing materials in terms of its persistence as a source of Be to the SLF solution. Following 149 days of equilibration, the SLF solutions were fractionated using flow-field flow fractionation (FlFFF) with detection via ICP-MS. For all materials, nanoparticles (which were formed during equilibration) were dominantly distributed in the 10–100 nm size range. Notably, BeO produced the least nanoparticle-associated Be mass (other than silica) at both pH values. Furthermore, BeO produced the highest Be concentrations in the size range corresponding to < 3 kDa (determined via centrifugal ultrafiltration), indicating that in addition to persistence, the BeO produced the highest concentrations of truly dissolved (potentially ionic) Be relative to the other materials. Mass balance analysis showed reasonable sample recoveries during FFF fractionation (50–100%), whereas recoveries during ICP-MS (relative to acidified standards) were much lower (5–10%), likely due to inefficiencies in nebulizing and ionizing the nanoparticles.  相似文献   

10.
Abstract This study evaluated the effectiveness of dual-wavelength ratio fluorescence imaging using a pH-dependent indicator (5,6–carboxyfluorescein, 5,6–CF) for in vivo pH mapping of tissue. A prototype version of a highly sensitive fluorescence imaging device consisting of a modified xenon lamp, an image-intensified camera and a digital imageprocessing system has been developed. 5,6–Carboxyfluorescein was used because its fluorescence emission increases as a function of pH in the physiological (6.0–7.4) pH range. The ratio of fluorescence intensities obtained with the imaging system has been calibrated using aqueous 5,6–CF standards at various pH values. Because the pH of interstitial fluid of malignant tumors tends to be lower than that of normal tissue and can be depressed by glucose administration, experiments were performed on 10 CDF mice bearing lymphoid leukemia P388 grafted subcutaneously. The range of linearity of the calibration curve was obtained between 5.3 and 6.7 with a measured pK, value of 5.93. Consequently the maximum sensitivity was observed in this range. The calculated pH from ratio images was 6.21 ± 0.12 in tumorous tissue. This value was equivalent to those obtained at the same time using microelectrodes (6.2 ± 0.3).
These experiments showed that a dose of 5 mg/kg 5,6–CF and an excitation power density of 2.5 mW/cm2 are sufficient to give a fluorescent pH image of tumors. The limitation of 5,6–CF for the in vivo mapping of tissue results from its low pKa and consequent range of sensitivity. The advantages of this imaging technique compared to microelectrodes are that it (1) is noninvasive, (2) displays a two-dimensional pH image with high resolution (profile distribution of pH in tissue) and (3) can be used to monitor pH over a few hours.  相似文献   

11.
Abstract The fluorescence quenching of indole, tryptophan, tryptamine and indole-3-acetic by aliphatic amino acids was studied. The bimolecular rate constant ( k q) for the deactivation of the excited state was determined. The k q values were in the range 0.6 × 108–1.6 × 109 M –1 S–1 and they increased in the order tryptophan < tryptamine < indole ≈ indole-3-acetic acid. When the rate constant was corrected for diffusion al effects a good linear correlation was found between the log ( k 'q) and the ionization equilibrium constant of the carboxylic group of the amino acid (p k a1). This was interpreted as arising from a charge transfer mechanism in which the indole moiety acts as an electron donor and the carbonyl group of the amino acid as the acceptor.
The activation parameter for the quenching processes were also determined. The ΔH values were in the range —4.0 to +4.0 kcal/mol and the ΔH in the range –7 to –37 e.u. For the systems with lower values of k q negative values for ΔH were observed. A good enthalpy-entropy compensation was found with an isokinetic temperature of 229 K. These results suggest that a common mechanism is operating for all the systems and that it involves the formation of an excited state complex between the indolic compound and the amino acid.  相似文献   

12.
This study of the origin and fate of dimethyl sulphide (DMS) in a particular and complex lagoon ecosystem such as that of the Venice lagoon focuses on the temporal evolutions of DMS concentrations in surface water together with those of dimethylsulphoniopropionate (DMSP), carbon disulphide (CS2), nutrients (nitrate, nitrite, ammonium, phosphate, silicate), sulphate, chlorophyll a, chlorinity, water temperature and phytoplankton (composition and density). Measurements were made from 3 March 1997 to 23 July 1998 at three stations in the central part of the Venice lagoon. The temporal trends of DMS concentration showed an absolute maximum concentration in winter (65 nmol S/l, 19/2/1998, Stn. 1; 119 nmol S/l, 19/2/1998, Stn. 2; 29 nmol S/l, 17/2/1998, Stn. 3) and two relative maxima in the spring-summer period. The spring-summer secondary maxima of DMS concentration were related to the maxima of DMSP and chlorophyll a concentrations and consequently to phytoplanktonic abundance while the winter DMS maximum showed no relation to DMSP or to chlorophyll a suggesting that the production and the fate of DMS could be different for the two periods. According to previous studies the CS2 concentration increased in the spring, achieved its maximum in summer, decreased in autumn and fell to its minimum in winter.  相似文献   

13.
SOLAR UVB-ALBEDO OF VARIOUS SURFACES   总被引:4,自引:0,他引:4  
Abstract— Measurements of the albedo of various surfaces in open grounds show significant differences for solar UVB radiation and total solar radiation (0.3–3μm). Above grassland, that albedo for solar UVB radiation is significantly smaller than that for total solar radiation (UVB: 1.3%, total: 20.7%); contrary to that, the albedo for UVB radiation is significantly higher above new dry snow (UVB: 94.4%, total: 87.0%). Consequences resulting therefrom are being quantitatively discussed with respect to the solar radiant exposure of individuals standing outdoors. Keratitis Solaris, for example, hardly occurs in snow-free terrain, even at high solar irradiance in summer; it occurs, however, in snow-covered terrain, in spite of low solar irradiance in winter and spring.  相似文献   

14.
The concentrations of polycyclic aromatic hydrocarbons (PAHs) in particulate matter (PM) with a diameter <10 µm (PM10, 50% cut off) were investigated in the Kathmandu Valley, Nepal, during 2003. In order to understand the dynamics of atmospheric PAHs in winter, the PAH concentrations in total PM and in the gaseous phase were investigated in the valley in December 2005. Total of 45 PAH compounds (∑45PAHs) were analysed by high-resolution gas chromatography/high-resolution mass spectrometry (HRGC/HRMS). In 2003, the ∑45PAH concentrations in PM10 ranged between 4.3 and 89 ng m?3 (annual average; 27 ± 24 ng m?3). The average concentrations of ∑45PAHs in December 2005 were 210 ± 33 ng m?3 in total PM and 430 ± 90 ng m?3 in the gaseous phase. The ∑45PAH concentration in PM accounted for more than 30% of the sum of their particulate and gaseous forms. Phenanthrene (Ph) was the most predominant compound in the gaseous phase, whereas four- to seven-ring PAHs were predominant in total PM. The highest values of ∑45PAHs occurred in the winter and spring. Estimates of emission sources based on diagnostic molecular ratios showed that atmospheric PAHs in the Kathmandu Valley mainly originated from the exhaust gas of diesel engine. In the winter and spring, PAH pollution would be accelerated by the operations of brick kilns and the frequent formation of an atmospherically stable layer in the valley.  相似文献   

15.
To characterize the relationship between occupational sun exposure and seasonal variations in serum 25-OH-D3, four consecutive measurements of 25-OH-D3, one per season, were taken in 122 outdoor and 104 indoor Israeli workers. Continuous UVB measurements, taken in Beer Sheva, Israel, provided the average daily standard erythema dose (SED) of ambient solar UVB. The average daily exposure of the outdoor and indoor workers to solar UVB was 4.4 ± 1.6 h (4.0–37.6 SED) and 0.9 ± 0.5 h (0.6–8.2 SED), respectively. At each season mean 25-OH-D3 were significantly higher among outdoor workers than among indoor workers. Mean 25-OH-D3 increased significantly from spring to autumn in both gender and occupational groups. Adjusting for confounders, high (>median) 25-OH-D3 among males was significantly associated with occupational sun exposure in the autumn (odds ratio [OR] 4.31; 95% confidence interval [CI] 1.4–13.3), and among females in the spring (OR 3.35; 95% CI 1.53–7.32). Among this working population optimal vitamin D status (≥30 ng mL−1) was approached only in summer by males working either outdoor or indoor. In the rest of the year 25-OH-D3 ranged between ≥20.0 and 29.0 ng mL−1. Monitoring 25-OH-D3 may disclose undesirable vitamin D status following reduced sun exposure for skin cancer prevention among outdoor workers.  相似文献   

16.
Abstract— Daily exposures to relatively small suberythemogenic fluences of UVA (50–200 kj/m2) for 8 days resulted in cumulative morphological skin alterations indicative of early tissue injury. Histologically, irradiated skin revealed epidermal hyperplasia, inflammation and deposition of lysozyme along the dermal elastic fiber network. Sunburn cells were also present within the epidermis. These changes were quantified by image analysis and were found to be related to the cumulative UVA fluence. A long UVA waveband (UVAI, 340–400 nm) was as effective as a broad UVA band (320–400 nm), suggesting that these changes are induced by longer UVA wavelengths.  相似文献   

17.
Abstract —The pulsed ruby laser (347 nm) flash photolysis technique has been used to measure the triplet-triplet absorption spectra and triplet lifetimes of trans -retinal, N-frans -retinylidene- n -butylamine (NRBA), and protonated NRBA (NRBAH+) at room temperature. In methylcyclohexane solution, the triplet lifetimes are in the range 10–20 μs and decrease in the order NRBAH+ > NRBA > trans -retinal. Intersy stem-crossing efficiencies (φISC) were determined by a comparison technique using anthracene and 1,2-benzanthracene as reference compounds. For trans -retinal, φISC is 0–50 pM 0–05 in methylcyclohexane and 0–08 in methanol, which confirms that earlier values of 0–11 and 0–017 in these solvents are in error. For NRBA and NRBAH+ in methylcyclohexane, ΦISC values are 0008 and < 0–001, respectively. Evidence is presented for a significant solvent effect in the isomerization of retinal via the triplet state, and that cis φ trans isomerization occurs from the triplet state of NRBAH+. The relation between the intersystem-crossing properties of model compounds and the photochemistry of rhodopsin is discussed.  相似文献   

18.
Abstract— Phytochrome photoequilibria have been measured in dark-grown Phaseolus uulgaris L . and Cucurbita pepo I . hypocotyl hooks which had been exposed to various natural and artificial radiation sources. Mean phytochrome photoequilibria ( φ ) varied from 0.20 within a wheat canopy to 0.54 above, although lower values were occasionally observed in densely shaded areas. Greater variation in phyto chrome photoequilibria and lower levels of Pfr were recorded within a sugar beet canopy. The range of photoequilibria was φ= 0.04 in dense shade to φ= 0.54 above the canopy. Photoequilibrium was achieved within 5 s in mid-day sunlight and approximately 30 s in dense canopy shade.
A close correlation was found between φ and the ratio of the quantum flux in the red and far-red wavelength bands (ζ) in broad spectrum (400–800 nm) radiation. This relationship allows direct prediction of φ from a knowledge of ζ. Phytochrome showed greatest sensitivity to spectral changes in the range ζ= zero to ζ= 1.0, which is the range found in the natural environment.
The observations provide support for the hypothesis that phytochrome is involved in the detection of shading by plants.  相似文献   

19.
Selenomethionine contents of NIST wheat reference materials   总被引:1,自引:0,他引:1  
Values of the total selenium and selenomethionine (Semet) content of four wheat-based reference materials have been obtained by gas chromatography-stable isotope dilution mass spectrometry methods. The total Se method is an established one, and the results obtained with it are consistent with previously-assigned values. The Semet method (previously reported by our laboratory) is based on reaction with CNBr. Our data indicate that the four wheat samples (wheat gluten, durum wheat, hard red spring wheat, and soft winter wheat), though having a 30-fold range in total Se content, all have about 45% of their total Se values in the form of selenomethionine. Investigation of the CNBr-based method suggests that additional experiments are needed to verify that all selenomethionine in the wheat samples is accounted for, but also indicates that the values obtained are within 15% of the true values. As the form in which Se occurs in foods and dietary supplements is important from a nutritional perspective, adding information about Se speciation to total Se values in appropriate reference materials makes these materials more valuable in relevant analytical work.  相似文献   

20.
A novel analytical protocol based on interfacing on-line matrix solid-phase dispersion (MSPD) with high-performance liquid chromatography–tandem mass spectrometry (HPLC–MS/MS) was developed for extraction and determination of 13 sulfonamide residues in grass carp tissues. The target analytes were separated on a fused-core C18-silica column with a period of 7 min and quantified by a triple–quadrupole linear ion-trap mass spectrometer in positive ion multiple-reaction monitoring (MRM) mode. The proposed method was optimized and validated according to Commission Decision 2002/657/EC. The matrix-matched calibration curves were performed at six concentration levels and good linear relationship (R2 = 0.993–0.998) was observed within the range of 0.1–100 ng mL−1. The mean values of relative standard deviation of intra- and inter-day ranging from 1.8% to 7.8% and from 2.8% to 10.3% were obtained, respectively. Moreover, satisfied recoveries (69.0–96.3%) of all studied sulfonamides were demonstrated in different spiked levels, with RSDs ≤ 13.2%. The proposed method has been applied successfully to the analysis of sulfonamides in several grass carp samples, and the results indicated that this novel instrumental coupling was fast, sensitive, reliable and environmental friendly with good prospects.  相似文献   

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