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1.
High-volume air samplers were used to collect aerosol samples on Whatman 41 air filters at the Canadian air sampling stations
Burnt Island, Egbert, and Point Petre. Once collected, the samples were analyzed for trace elements by neutron activation
analysis. Air concentrations of over 30 trace elements were determined. A special focus was made to utilize Compton suppression
gamma-ray spectroscopy and epithermal irradiations to enhance the detection limits of neutron activation analysis. These techniques
allowed for the determination of trace elements at very low levels. Results of the study of the tracemetal dry deposition
into Lakes Huron and Ontario indicated that the majority of the total deposition resulted from crustal materials. However,
dry deposition is also a significant pathway for many toxic anthropogenic trace metals into the Great Lakes. 相似文献
2.
The biological effectiveness of neutrons from the neutron therapy facility MEDAPP (mean neutron energy 1.9 MeV) at the new
research reactor FRM II at Garching, Germany, has been analyzed, at different depths in a polyethylene phantom. Whole blood
samples were exposed to the MEDAPP beam in special irradiation chambers to total doses of 0.14–3.52 Gy at 2-cm depth, and
0.18–3.04 Gy at 6-cm depth of the phantom. The neutron and γ-ray absorbed dose rates were measured to be 0.55 Gy min−1 and 0.27 Gy min−1 at 2-cm depth, while they were 0.28 and 0.25 Gy min−1 at 6-cm depth. Although the irradiation conditions at the MEDAPP beam and the RENT beam of the former FRM I research reactor
were not identical, neutrons from both facilities gave a similar linear-quadratic dose–response relationship for dicentric
chromosomes at a depth of 2 cm. Different dose–response curves for dicentrics were obtained for the MEDAPP beam at 2 and 6 cm
depth, suggesting a significantly lower biological effectiveness of the radiation with increasing depth. No obvious differences
in the dose–response curves for dicentric chromosomes estimated under interactive or additive prediction between neutrons
or γ-rays and the experimentally obtained dose–response curves could be determined. Relative to 60Co γ-rays, the values for the relative biological effectiveness at the MEDAPP beam decrease from 5.9 at 0.14 Gy to 1.6 at
3.52 Gy at 2-cm depth, and from 4.1 at 0.18 Gy to 1.5 at 3.04 Gy at 6-cm depth. Using the best possible conditions of consistency,
i.e., using blood samples from the same donor and the same measurement techniques for about two decades, avoiding the inter-individual
variations in sensitivity or the differences in methodology usually associated with inter-laboratory comparisons, a linear-quadratic
dose–response relationship for the mixed neutron and γ-ray MEDAPP field as well as for its fission neutron part was obtained.
Therefore, the debate on whether the fission-neutron induced yield of dicentric chromosomes increases linearly with dose remains
open. 相似文献
3.
Cyclic and pseudocyclic instrumental neutron activation analysis (INAA) has been used to determine the Se content of 40 Libyan
food items. The selected samples include different varieties of local and imported foods such as wheat and barley products
(bran and flours), rice, bread, almond, peanuts, vegetables as bean and peas, tea, coffee, sugar, and commonly used spices
such as red and black paper, curry, cumin, mixture of spices, thyme, coriander, and fenugreek. Both conventional and anticoincidence
γ-ray spectrometry techniques have been employed. Pseudocyclic INAA in conjunction with anticoincidence counting has been
found to provide the most reliable results. The precision of the method has been significantly improved by recycling the samples
up to three times. The accuracy has been evaluated by analyzing a number of certified reference materials of varied Se levels.
The detection limit has been found to vary between 26 and 90 ppb Se depending on the sample composition. The range of daily
dietary intake has been calculated as 13–44 μg of Se per day. 相似文献
4.
M. Kunioka 《Applied microbiology and biotechnology》1997,47(5):469-475
The biosynthesis and chemical reactions of poly(amino acid)s produced by microorganisms are reviewed. A large amount of γ-poly(glutamic
acid) (PGA) has been produced by Bacillus strains. ε-Polylysine (PL) has been produced by Streptomyces albulus. As a modification of PGA and PL, pH-sensitive hydrogels have been prepared by means of γ irradiation or the addition of
a crosslinking agent to an aqueous solution of PGA and PL.
Received: 4 September 1996 / Received revision: 27 January 1997 / Accepted: 28 January 1997 相似文献
5.
Epithermal instrumental neutron activation analysis (EINAA) has been used to determine the iodine content of many individual
food materials that constitute the typical Libyan diet. The selected samples include different varieties of local and imported
foods such as wheat and barley products, rice, bread, legumes such as chick peas and lentil, table salt, and commonly used
spices, including thyme and fenugreek. Both conventional and anticoincidence γ-ray spectrometry techniques have been employed.
Epithermal INAA in conjunction with anticoincidence counting has been found to provide the most reliable results. For quality
control purposes, a number of NIST biological reference materials were analyzed. The range of daily dietary intake has been
calculated as 100–180 μg of iodine per day, which is within the recommended range. Bread was identified as a significant source
of iodine in the Libyan diet, as it contributed 99 μg/d. 相似文献
6.
While it is recognized that neutrons contributed to the excess cancer incidence and mortality among the atomic bomb survivors
in Hiroshima, there is no possibility to deduce the magnitude of this contribution from the data. This remains true even if
the neutron doses in the dosimetry system DS86 are corrected upwards in line with recent neutron activation measurements.
In spite of this fact, important information can be obtained in the form of an inverse relation of the risk coefficients for
γ-rays and neutrons. Such an interrelation must apply because the observed excess incidence or mortality is made up of a γ-ray and a neutron component; increased attribution to neutrons decreases the attribution to photons. Computations with the
uncorrected and the corrected DS86 are performed for the mortality and the incidence of solid tumors combined. They refer
to doses up to 2 Gy and employ the constant relative risk model and a linear-quadratic dose dependence with variable ratio
– the neutron relative biological effectiveness (RBE) at low doses – of the linear component for neutrons and γ-rays. In line with past analyses, no quadratic component is obtained with the uncorrected DS86, but it is seen, even in these
calculations, that the assumption of increased neutron RBEs does not translate into proportional increases of the risk coefficients
of neutrons, because it leads to substantially reduced risk estimates for γ-rays. Calculations with the corrected dosimetry bring out this reciprocity even more clearly. High values of the neutron
RBE reduce – in line with recent suggestions by Rossi and Zaider – the risk estimates for γ-rays substantially. Even a purely quadratic dose relation for γ-rays is consistent with the data; it requires no major increase of the nominal risk coefficients for neutrons over the currently
assumed values. The cancer data from Hiroshima can still provide `prudent' risk estimates for photons, but with the corrected
DS86, they do not prove that there is a linear component in the dose dependence for photons.
Received: 20 January 1997 / Accepted in revised form: 14 March 1997 相似文献
7.
A newly devised, very accurate (“definitive”) method for the determination of trace amounts of cobalt in biological materials
was validated by the analysis of several certified reference materials. The method is based on a combination of neutron activation
and selective and quantitative postirradiation isolation of radiocobalt from practically all other radionuclides by ion-exchange
and extraction chromatography followed by γ-ray spectrometric measurement. The significance of criteria that should be fulfilled
in order to accept a given result as obtained by the “definitive method” is emphasized. In view of the demonstrated very good
accuracy of the method, it is suggested that our values for cobalt content in those reference materials in which it was originally
not certified (SRM 1570 spinach, SRM 1571 orchard leaves, SRM 1577 bovine liver, and Czechoslovak bovine liver 12-02-01) might
be used as provisional certified values. 相似文献
8.
This article deals with the radioanalytical work performed at Pelindaba, Atomic Energy Corporation of South Africa. It reports
on the activities of a commercial laboratory, employing analytical techniques, such as total α/β counting, α spectrometry,
liquid scintillation counting, γ spectrometry, and neutron activation analysis. Techniques discussed in more detail include
semicyclic activation analysis for the determination of fluorine in vitamin mixes, as well as the determination of uranium
and radium in urine samples for personnel monitoring. 相似文献
9.
A. M. M. Attia W. M. Aboulthana G. M. Hassan E. Aboelezz 《Radiation and environmental biophysics》2020,59(1):131-144
Biological dosimetry based on sulfhemoglobin (SHb), methemoglobin (MetHb), and carboxyhemoglobin (HbCO) levels was evaluated. SHb, MetHb and HbCO levels were estimated in erythrocytes of mice irradiated by γ rays from a 60Co source using the method of multi-component spectrophotometric analysis developed recently. In this method, absorption measurements of diluted aqueous Hb-solution were made at λ = 500, 569, 577 and 620 nm, and using the mathematical formulas based on multi-component spectrophotometric analysis and the mathematical Gaussian elimination method for matrix calculation, the concentrations of various Hb-derivatives and total Hb in mice blood were estimated. The dose range of γ rays was from 0.5 to 8 Gy and the dose rate was 0.5 Gy min−1. Among all Hb-derivatives, MetHb, SHb and HbCO demonstrated an unambiguous dose-dependent response. For SHb and MetHb, the detection limits were about 0.5 Gy and 1 Gy, respectively. After irradiation, high levels of MetHb, SHb and HbCO persisted for at least 10 days, and the maximal increase of MetHb, SHb and HbCO occurred up to 24 h following γ irradiation. The use of this “MetHb + SHb + HbCO”-derivatives-based absorbed dose relationship showed a high accuracy. It is concluded that simultaneous determination of MetHb, SHb and HbCO, by multi-component spectrophotometry provides a quick, simple, sensitive, accurate, stable and inexpensive biological indicator for the early assessment of the absorbed dose in mice. 相似文献
10.
Neutron-induced γ-ray emission tomography for quantitative determination of the concentration and distribution of elements
in a selected plane through a biological specimen is briefly explained and applied by way of illustration to the analysis
of gallstones. A system capable of carrying out studies of the binding site of75Se in different matrices using time differential perturbed angular correlation spectroscopy is also briefly described. Developments
in the detector technology of positron emission tomography have allowed small-diameter imaging devices to be built for in
vivo preclinical evaluation of new tracers in small animals and are discussed in the context of a proposed experiment combining
the techniques mentioned above. 相似文献
11.
E. S. Ahmed A. A. El-Essaway M. E. Abou El-Hawa S. M. Ezzat M. Batta Metwaly 《Folia microbiologica》1997,42(5):468-472
γ-Ray irradiation of pre-sowing seeds of tomato did not trigger the formation of the phytoalexin “rishitin” in either leaves
or fruits of tomato plants through different growth seasons. Application of copper sulfate initiated rishitin formation in
both leaves and fruits. Increasing of γ-ray dose was accompanied by decreasing rishitin accumulation in the presence of copper
sulfate. Rishitin of tomato leaves was found to be reduced significantly, concomitant with increasing the disease incidence
for late and early blight, andFusarium wilt disease, after applying γ-irradiation, in the case of biotic initiatorsPhytophthora infestans, Alternaria solani orFusarium oxysporum alone or together with the abiotic inducer copper sulfate. Shelf-extending γ-ray doses of 1.0, 1.5 and 2.0 kGy decreased
rishitin amounts in tomato fruits treated with copper sulfate alone or infected withPhytophthora infestans. Also, the amount of formed rishitin was reduced by extending the storage period. 相似文献
12.
Michela Zottini Giuseppe Mandolino Paolo Ranalli 《Plant Cell, Tissue and Organ Culture》1997,47(2):189-194
The viability and thein vitro germination capability of hemp pollen (cv. Carmagnola) were studied. Viability tests were based on the microscopic observation
of the fluorescence of loaded fluorescein diacetate (FDA), while, for germinability tests, five different media were tested.
The effects of irradiation with γ-rays on pollen viability and germination and on seed set were also studied, at three different
irradiation doses (20, 60 and 100krad). The results show that in one of the media tested, about 85–90% of the pollen grains are viable and able to germinate in
control samples, and that while viability measured by FDA test is not affected by increased γ-ray doses, the pollenin vitro germinability drops to about one-half of the controls at the maximum γ-ray dose employed, 100krad. Seed set of hemp plants pollinated with the irradiated pollen dropped to less than 1% of that of plants pollinated by untreated
pollen for the higher dose used. The different media suitable forin vitro germination of hemp pollen, and the observed lack of correspondence between viability and germination capacity tests are
discussed. 相似文献
13.
Stone S. F. Bernasconi G. Haselberger N. Makarewicz M. Ogris R. Wobrauschek P. Zesler R. 《Biological trace element research》1994,(1):299-307
Microbeam X-ray spectrometry, energy-dispersive X-ray fluorescence analysis, and neutron activation analysis were evaluated
for the detection of selenium contained in the selenoprotein glutathione peroxidase. The glutathione peroxidase had been previously
separated using polyacrylamide gel electrophoresis. The use of Bragg-reflected polarized X-ray beams was employed in the X-ray
fluorescence measurements to minimize the problem of scatter owing to the gel matrix. Current detection limits of selenium
in a gel matrix are 2.1 ng in the bench-top microbeam X-ray system and 30–60 ng using XRF with polarized beams. Neutron activation
analysis was used for qualitycontrol measurements, with a detection limit here of <0.08 ng. The work has in principle established
the feasibility of such an approach. 相似文献
14.
Sasaki MS Endo S Ejima Y Saito I Okamura K Oka Y Hoshi M 《Radiation and environmental biophysics》2006,45(2):79-91
The effective dose of combined spectrum energy neutrons and high energy spectrum γ-rays in A-bomb survivors in Hiroshima and Nagasaki has long been a matter of discussion. The reason is largely due to the paucity of biological data for high energy photons, particularly for those with an energy of tens of MeV. To circumvent this problem, a mathematical formalism was developed for the photon energy dependency of chromosomal effectiveness by reviewing a large number of data sets published in the literature on dicentric chromosome formation in human lymphocytes. The chromosomal effectiveness was expressed by a simple multiparametric function of photon energy, which made it possible to estimate the effective dose of spectrum energy photons and differential evaluation in the field of mixed neutron and γ-ray exposure with an internal reference radiation. The effective dose of reactor-produced spectrum energy neutrons was insensitive to the fine structure of the energy distribution and was accessible by a generalized formula applicable to the A-bomb neutrons. Energy spectra of all sources of A-bomb γ-rays at different tissue depths were simulated by a Monte Carlo calculation applied on an ICRU sphere. Using kerma-weighted chromosomal effectiveness of A-bomb spectrum energy photons, the effective dose of A-bomb neutrons was determined, where the relative biological effectiveness (RBE) of neutrons was expressed by a dose-dependent variable RBE, RBE(γ, D
n), against A-bomb γ-rays as an internal reference radiation. When the newly estimated variable RBE(γ, D
n) was applied to the chromosome data of A-bomb survivors in Hiroshima and Nagasaki, the city difference was completely eliminated. The revised effective dose was about 35% larger in Hiroshima, 19% larger in Nagasaki and 26% larger for the combined cohort compared with that based on a constant RBE of 10. Since the differences are significantly large, the proposed effective dose might have an impact on the magnitude of the risk estimates deduced from the A-bomb survivor cohort. 相似文献
15.
Arnaud Morel Nadine Fernandez A. de La Coste Hédi Haddada Mireille Viguier Barbara S. Polla Bénédicte Antoine A. Kahn 《Cancer immunology, immunotherapy : CII》1998,46(5):277-282
The use of gene-modified tumor cells as a strategy for active immunotherapy is currently undergoing intensive fundamental
and clinical research. Most clinical trials use γ-ray-irradiated tumor cells as vaccine, although little is known about the
effects of irradiation on the immunogenicity of tumor cells. In particular, no data have been reported so far concerning the
effects of γ-ray irradiation on the expression of B7 molecules in tumor cells. In this paper, we show a neoexpression of the
B7.1 molecule after γ-ray irradiation in tumor cell lines from different tissues, while the B7.2 molecule remains unexpressed
in all the cell lines tested. Furthermore, the induction of B7.1 molecule membrane expression after irradiation is shown to
result from the neoexpression of B7.1 mRNA, and to be reproduced with H2O2 oxidative stress. These data could explain the enhanced immunogenicity of many tumor cells after irradiation, and could lead
to new immunotherapy protocols.
Received: 27 November 1997 / Accepted: 26 February 1998 相似文献
16.
K. O. Muranov N. B. Poliansky V. C. Kurova A. M. Riabokon N. L. Sheremet A. A. Fedorov K. I. Bannik A. N. Abrosimova M. A. Ostrovsky 《Biophysics》2010,55(5):870-877
Four randomized groups of male mice Fl (C57Black/CBA) were investigated: (a) UV-irraidated (UV-A, 15 min daily over 10 months,
51 ± 7 W/m2); (b) γ-ray irradiated (2 Gy), single; (c) influence of combination of UV- and γ-ray treatment; (d) aging. The lens opacities
were measured at the seventh and tenth month. An expert method based on a six-point scale was used for cataract measurement.
At the seventh month, the median of lens opacities were Aging group = 0; UV-irradiated group = 2.5; γ-irradiated group = 4.75;
γ- and UV-irradiated group = 6.0. The difference between all groups was significant (p < 0.004, Kruskall-Wallis ANOVA test). The Conover post hock test has shown a significant difference for all comparison pairs
(p < 0.002) with the exception of the γ- and UV-irradiated group. At the tenth month, the lens opacities strongly increased:
Aging group = 2.5; UV-irradiated group = 5.0; γ-irradiated group = 6.5; γ- and UV-irradiated group = 7.5 (median). The difference
between groups was significant (p < 0.0001, Kruskall-Willis ANOVA test). The Conover post hock test has shown a significant difference for all comparison pairs
(p < 0.003) with the exception of the UV-irradiated group and γ-irradiated group. No formation of specific lens opacities for
any group was found. Morphology and protein composition were investigated at the tenth month. The results of a study of morphological
changes show destructive and degenerative impairments of the capsule, epithelium cages, and lens fibers. However, no specific
changes related to certain particular actions have been found. In addition, there were no specific changes in the protein
composition of either water-soluble and water-insoluble fractions estimated by the differential gel electrophoresis technique.
The data mean that aging, UV treatment, and γ-radiation causes similar lens changes. It was supposed that UV treatment and/or
γ-radiation act as an aging factor on the lens. 相似文献
17.
γ-Glutamyl compounds and their enzymatic production using bacterial γ-glutamyltranspeptidase 总被引:1,自引:0,他引:1
Summary. Some amino acids and peptides, which have low solubility in water, become much more soluble following γ-glutamylation. Compounds
become more stable in the blood stream with γ-glutamylation. Several γ-glutamyl compounds are known to have favorable physiological
effects on mammals. γ-Glutamylation can improve taste and can stabilize glutamine in aqueous solution. Because of such favorable
features, γ-glutamyl compounds are very attractive. However, only a small number of γ-glutamyl amino acids have been studied
although many other γ-glutamyl compounds may have characteristics that will benefit humans. This is mainly because γ-glutamyl
compounds have not been readily available. An efficient and simple method of producing various γ-glutamyl compounds, especially
γ-glutamyl amino acids, using bacterial γ-glutamyltranspeptidase has been developed. With this method, modifications of reactive
groups of the substrate and energy source such as ATP are not required, and a wide-range of γ-glutamyl compounds can be synthesized.
Moreover, bacterial γ-glutamyltranspeptidase, a catalyst for this method, is readily available from the strain over-producing
this enzyme. The superiority of producing γ-glutamyl compounds with bacterial γ-glutamyltranspeptidase over other methods
of production is discussed. 相似文献
18.
M. D. Fedorova I. P. Andreeva E. S. Vilegzhanina A. A. Komarov M. Yu. Rubtsova J. V. Samsonova A. M. Egorov 《Applied Biochemistry and Microbiology》2010,46(8):795-801
A test-system based on enzyme-linked immunosorbent assay (ELISA) for the quantitative detection of chloramphenicol (CAP) in
foodstuff has been developed. The detection limit of the method was 0.05 μg/l. The procedures for milk samples preparation
of various fat content and chicken muscles were optimized. Before the analysis milk was diluted 5-fold with a buffer. The
detection limit for milk was 0.3 μg/l; recoveries varied from 74 to 118%. Two protocols for chicken muscles preparation were
elaborated; extraction with buffer (the express method) and extraction with acetonitrile. The detection limits of CAP in chicken
muscles were 0.5 and 0.3 μg/kg, respectively; recovery values were 71–107% and 95–115%, respectively. The results of residual
amounts of CAP detection in foodstuff by ELISA and HPLC-MS were in good correlation. 相似文献
19.
Antimony was preconcentrated from natural waters on thionalide-loaded acrylic polymer (Bio-Beads SM-7) from 0.5 m HCl solution.
Prior to the preconcentration, Sb(V) was reduced to Sb(III) with potassium iodide. The antimony retained on the resin was
determined by neutron activation and γ-spectrometric measurement of122Sb (564 keV). The lower limit of detection was 0.023 μg/L for a 100-mL sample. 相似文献
20.
In this paper, we proposed a new method for the determination of either human serum albumin (HSA) or 5-Aminosalicylic acid
(5-ASA) by synchronous fluorescence spectra and examined the interaction between them using the molecular modeling method
under simulative physiological conditions. The optimum conditions of synchronous fluorometric determination of HSA were investigated
and the method was successfully applied to the determination of 5-ASA added to serum, urine, and saliva samples. The linear
range of the determination of HSA and 5-ASA were 1.60 – 414 μg mL−1 and 0.76 –22.95 μg mL−1, the detection limits were 0.552 μg mL−1 and 0.38 μg mL−1, respectively. In addition, the effect of various common ions on the determination of HSA with 5-ASA was also discussed at
room temperature.
Figure The salicylic acid moiety is located within the binding pocket. The ring of 5-ASA was inserted in the hydrophobic cavity of
site I, and it is important to note that the residue ARG-218 and the trptophan residue of HSA (Trp214) are in close proximity
to the ring of 5-ASA suggesting the existence of hydrophobic interaction between them. 相似文献