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排序方式: 共有625条查询结果,搜索用时 171 毫秒
1.
W. J. Altaf O. A. Akanle L. L. Admans D. Beasley C. Butler N. M. Spyrou 《Journal of Radioanalytical and Nuclear Chemistry》2004,259(3):493-498
The elemental composition of human hair obtained from different studies at Surrey University over a period of 25 years has
been recorded and forms part of a database, for biological and environmental samples, which is being developed. Instrumental
neutron activation analysis (INAA), using reactor neutrons, was the principal method employed and from which reported data
are presented.Elemental concentrations of Br, Ca, Ce, Cl, Co, Cr, Cs, F, Fe, Hf, K, Mg, Mn, Na, Rb, Sb, Sc, Se, V and Zn were obtained and
recorded in the database. Chronological variations in two sets of subjects separated by a period of time of 16 years are also
given. Variations in the concentration values of some elements related to the state of health and disease were reported for
hair samples collected from subjects suffering from manic depression, senile dementia and breast cancer. Concentration values
of some elements with relation to the nationality of subjects from Bulgaria, England, Kenya, Nigeria and Wales are presented
and compared. This study is part of on-going research in the analysis of biomedical and bioenvironmental materials. The database
is still in its infancy.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
2.
N. N. Papadopoulos N. M. Spyrou N. F. Tsagas G. E. Hatzakis 《Journal of Radioanalytical and Nuclear Chemistry》1995,192(1):55-64
A novel technique has been developed to increase the sensitivity, precision and accuracy of short-lived nuclide activation analysis and especially of delayed fission neutron counting, by improving the counting statistics. This has been achieved by approaching the irradiated sample to the detector during the counting period in order to compensate for the rapid radioactive decay by variation of the counting efficiency, permitting prolongation of the counting period with constant count rate. The sample holder movement with approximately exponentially decreasing velocity is implemented by a variable DC motor with a rotary to linear movement converter, which is being replaced by a more reliable stepping motor. 相似文献
3.
Aplada-Sarlis P Miliadis GE Liapis K Tsiropoulos NG 《Journal of AOAC International》2004,87(1):146-150
A gas chromatographic (GC) method was developed and statistically validated for the simultaneous determination of residues of pyrethroid, endosulfan, and organophosphorus insecticides and some of their metabolites on olive tree leaves. Pesticide residues were extracted by static extraction with acetone-dichloromethane. After evaporation of the extract to dryness and redissolution in acetone, the organophosphorus insecticides were determined by GC with nitrogen-phosphorus detection. Another portion of the extract, after solvent change to acetonitrile, was cleaned up on an Alumina-N cartridge and analyzed for insecticides sensitive to electron-capture detection (ECD), i.e., pyrethroids and endosulfan and its metabolite. Recoveries of the organophosphorus insecticides ranged from 80.7 to 93.3% with relative standard deviations (RSDs) of < or = 7.2%; recoveries of the ECD-sensitive insecticides ranged from 71.6 to 89.5% with RSDs of < or = 11.6%. The method was used to analyze 26 samples of olive tree leaves from organic olive groves all over Greece, and the results confirmed the viability of the method for routine analysis. Residues of fenthion and fenthion sulfoxide were found in one and 3 samples, respectively, and their identities were confirmed by GC with mass spectrometry. 相似文献
4.
M. A. Durosinmi J. O. Ojo A. F. Oluwole O. A. Akanle W. Arshed N. M. Spyrou 《Journal of Radioanalytical and Nuclear Chemistry》1993,168(1):233-242
Instrumental Neutron Activation Analysis (INAA) and Proton-Induced X-ray Emission (PIXE) analysis (employed as a complementary technique) have been used to determine the concentration of 11 elements in blood samples and its components erythrocytes and plasma obtained, from three groups of subjects in Nigeria viz: sickle cell anaemia (SCA) subjects, subjects with sickle cell trait and normal control subjects. The results suggest that SCA subjects have significantly higher concentrations of Na, Cl, Ca and Cu in their whole blood and erythrocytes and a higher concentration, of Cl and Cu in their plasma relative to the control subjects. Furthermore, a significantly lower concentration of K, Fe, Zn, Se, Br and Rb were found in the whole blood and erythrocytes of the SCA subjects as compared to the controls while the concentration of K and Fe in the plasma of the SCA subjects were however, found to be significantly higher than that of the control group. The study also shows that there was no significant differences between the concentration of these 11 elements in the group with sickle cell trait and the normal control group. 相似文献
5.
N. M. Spyrou 《Journal of Radioanalytical and Nuclear Chemistry》1987,110(2):641-653
Nuclear and atomic methods of analysis, which rely on the detection of prompt and delayed radiations, emitted as a result of interactions between radiation probe and target, for determining the elemental concentration in vivo and in vitro, are summarily reviewed, with reference to bone analysis; the demand for methods which provide information about elemental distribution is highlighted. The way neutrons can be used as probes to investigate the composition and structure of objects by employed the principles of computerised tomography are outlined and the novel modes of utilisation are briefly described: neutron transmission tomography, neutron induced prompt gammaray emission tomography and neutron induced delayed gamma-ray emission tomography. The latter method, alternatively termed neutron activation tomography, is then used to determine on-destructively the distribution of Na in selected planes of a human tibia, in vitro, by measuring the activity of24Na using a NaI(Tl) and a Ge(Li) detector in a tomographic scanner which incorporates a microcomputer for control, data acquisition and image reconstruction. The problems of attenuation and scattering are discussed as are the limitations for quantitative results of this useful new mode of tomography which provided information about composition and elemental distribution in a material. 相似文献
6.
Patrina Paraskevopoulou Eleftheria Petalidou Nikos Psaroudakis Pericles Stavropoulos Konstantinos Mertis 《Monatshefte für Chemie / Chemical Monthly》2005,136(12):2035-2039
Summary. Primary phenylmethanols are selectively and efficiently oxidized to the corresponding aldehydes by the system C6H5IO/(C6H5)4PBr/CH2Cl2, T = 298 K under aerobic conditions. The use of the relatively stable iodosobenzene, an iodine(III) compound, in place of the
usually employed and potentially explosive iodine(V) reagents, the easy work-up procedure, and the facile recycling of solvent
and oxidant provides a convenient and environmentally benign oxidation method. 相似文献
7.
Organic functionalization of carbon nanotubes 总被引:11,自引:0,他引:11
Georgakilas V Kordatos K Prato M Guldi DM Holzinger M Hirsch A 《Journal of the American Chemical Society》2002,124(5):760-761
A very general and versatile method for functionalizing different types of carbon nanotubes is described, using the 1,3-dipolar cycloaddition of azomethine ylides. Approximately one organic group per 100 carbon atoms of the nanotube is introduced, to yield remakably soluble bundles of nanotubes, as seen in transmission electron micrographs. The solubilization of the nanotubes generates a novel, interesting class of materials, which combines the properties of the nanotubes and the organic moiety, thus offering new opportunities for applications in materials science, including the preparation of nanocomposites. 相似文献
8.
The design and construction of an activation analysis system using an isotopic neutron source which allows the measurement
of prompt and delay gamma-rays, in conventional activation and cyclic activation modes, is briefly described with emphasis
laid on its flexibility, transportability and low cost. Photon spectra obtained from the irrdiation of large samples under
prompt, delay and cyclic conditions using both NaI(Tl) and Ge(Li) detectors are presented and described with respect to ‘in-vivo’
neutron activation analysis and the measurement of N, O, Na, P, Cl and Cd. It is pointed out that, despite the attractive
possiblity of measuring Se in liver, ‘in-vivo’, by cyclic activation analysis, the system may potentially prove a very useful
tool for industrial and other non-medical applications. 相似文献
9.
G. E. Nicolaou N. M. Spyrou Y. S. Khrbish 《Journal of Radioanalytical and Nuclear Chemistry》1987,114(1):195-202
When a beam of radiation is used as a probe in order to study the elemental composition of an object, the factors involved in obtaining maximum detection sensitivity include target homogeneity, beam uniformity and the solid angle subtended between target and detector. Here we have investigated, both theoretically and experimentally, the significance of these factors in an experimental facility for in-vitro prompt gamma-ray neutron activation analysis and an arrangement used in in-vivo activation analysis. The correction factor to the solid angle, to account for non-uniformity, and the optimisation of reaction rate and solid angle are considered. 相似文献
10.
The determination of elemental concentration in biological and environmental samples through the detection of short-lived nuclides has been of considerable interest in the last few years. In this context the relative advantages and disadvantages of cyclic activation analysis (CAA) with respect to single conventional one-shot irradiation and counting sequence (for one sample or replicate samples) and what has been termed pseudo-cyclic activation have been discussed with conflicting interpretations. It is the objective of this study to demonstrate through the irradiation of uranium standards by measurement of short-lived fission products how each mode of activation is best utilised. Application of CAA to the problem, in order to enhance signal-to-noise ratio, must also take into account an increasing dead-time with each cycle and therefore mass fractionation of a given sample and standard are investigated for replicate and pseudo-cyclic activation conditions. The variation of timing parameters in the cyclic mode, as well as irradation in a mixed reactor flux and epi-cadmium neutron flux, produces a set of equations from which half-life can be determined to confirm fission product identification in these complex gamma-ray spectra. 相似文献