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1.
Thorotrast was widely used in the past as an X-ray contrast medium, containing a colloidal solution of thorium dioxide ( 232ThO 2). After injection, thorium accumulates and is mainly retained in the liver. Thus once Thorotrast is administered, patients might be chronically exposed to -radiations. Recently, significant development of cirrhosis and cancer of the liver has often been noted among Thorotrast patients. Additionally the incidence of lung and breast disease has significantly increased. Thus, the assessment of internal radiation dose from deposits of Thorotrast is very important. In this report, the thorium content in various organs was determined by means of neutron activation analysis. All the samples were taken from organs of Thorotrast patients subsequent to death. The ashed samples were irradiated in a reactor. After cooling, the content of thorium was determined by measurement of gamma rays resulting from the decay of protactinium-233. For comparison, measurements by other analytical methods such as inductively coupled plasma mass spectrometry, colorimetric analysis using ArsenazoIII and radiation measurement of -rays from actinium-228, were carried out. 相似文献
3.
There is currently great interest in iodine as a micro nutrient. Both high and low intakes have been associated with thyroid cancer incidence. Development of dietary iodine monitors is needed to supplement the use of dietary recall methods which have not been well validated for iodine. In this study, 30 pooled urine samples, from ethnic groups on various islands in the South Pacific, were analyzed for iodine using epithermal instrumental neutron activation analysis (EINAA).University of Mo Chemistry Department, Columbia, MO 65211 相似文献
4.
Desorption tests, using a sequential extraction method, were used to characterize and quantify thorium and uranium sorption to contaminated wetland sediments collected from the Department of Energy's Savannah River Site located in South Carolina. In situ distribution coefficients, or K
d values ( K
d = C
solid/ C
liquid), were determined. Sequential extraction data were used to assign solid-phase radionuclide concentrations ( C
solid) that, by definition, should represent only the reversibly sorbed fraction. A series of selective and sequential extractions was used to determine desorption K
d values. Thorium K
d values ranged from 115 to 2255 ml/g. Uranium K
d values ranged from 170 to 6493 ml/g. Compared to sorption K
d values, these desorption K
d values were appreciably greater because they captured the aging process of the radionuclides with the sediment, making the radionuclide more refractory. Compared to nonsite-specific data, these in situ K
d values improved accuracy, were more defensible, and removed unnecessary conservatism for subsequent transport and risk calculations. Additional tests were conducted to provide geochemical information relevant for selecting appropriate remediation technologies for the contaminated site. Thorium and uranium were associated with labile fractions and were not concentrated with the smaller sediment particles. These findings suggest that phytoremediation or heap leaching, and not soil washing, are viable remediation approaches for this site. 相似文献
5.
We investigated glucose and amino acid metabolism in tumors and other organs using whole body autoradiography with a short-lived positron emitter and a long-lived beta emitter. The radioactive compounds used were 2-deoxy-2-[18F]-fluoro-D-glucose (18F-FDG) with a half life of 109.8 min and L-[methyl-14C]-methionine (14C-MET) with a half life of 5,730 years. A Donryu rat weighing about 150 g was subcutaneously inoculated at the back with experimental tumors of AH109A and AH272. 74 MBq (2 mCi) of 18F-FDG and 740 kBq (20 microCi) of 14C-MET was administered and after 30 min, the rat was sacrificed. Whole body frozen sections were obtained using autocryotome. For the 18F-FDG autoradiogram, the frozen sections were exposed to an X-ray film for 6 h. After seven days, these frozen sections were again exposed to 14C-MET for a week. Cross-contamination was minimized by adjusting the exposure time, the interval of exposures and the administered dose. The accumulation of the tracers was represented as the optical density ratio of the tissue of interest to the muscle. The tumor ratios were 12.5 for 18F-FDG and 8.6 for 14C-MET showing the highest accumulation in the whole body autoradiogram. In contrast the inflammatory tissue ratios were 1.27 for 18F-FDG and 0.77 for 14C-MET showing very low amino acid metabolism. With the present double tracer whole body autoradiogram, 18F-FDG accumulation was seen in the brain and the heart but not to the liver as against 14C-MET accumulation which was seen to the liver but not to the brain and the heart. 相似文献
6.
A new dosimeter material has been developed which consists of a radiation sensitive layer on a reflective base, and utilises a portable microdensitometer for response measurement. The instrument, modified from a readily available hand-held unit, is a standard in the printing industry. The system was designed with the demands of ‘in plant’ use in mind, and is equally suitable for either gamma or electron beam irradiation. The dosimeter material develops an easily visible colour change, which is quantitative, highly reproducible and stable over the dose range of approximately 5–45 kGy. The results presented demonstrate the calibration and characteristics of the dosimetry system, and explore some of its potential. 相似文献
8.
A portable tandem mass spectrometer, capable of performing atmospheric pressure chemical ionization (APCI) using a direct atmospheric inlet, is applied to the real-time monitoring of toxic compounds in air. Analytes of interest include dimethyl methylphosphonate, arsine, benzene, toluene, pyridine and vinyl acetate. The detection, identification and quantification of organic and inorganic compounds in air is demonstrated using short analysis times (<5 seconds) with detection limits in the low ppb (v/v) levels and linear dynamic ranges of several orders of magnitude. Highly specific detection and identification is achieved, even when the analyte is a trace component in a complex mixture including such interferents as fuels, lubricants, and cleaners. The effects of environmental conditions, including temperature and humidity, are delineated. Receiver operating characteristic (ROC) curves are presented to show the trade-off between false positive and false negative detection rates. Tandem mass spectrometry based both on collision-induced dissociation and on selective atmospheric pressure ion/molecule reactions is also used to increase selectivity and sensitivity. 相似文献
10.
Summary Conductometric titrations of thorium chloride against oxalic acid, ammonium oxalate and silver nitrate have been carried out at high dilutions (0.001, 0.0005 and 0.00033 M) of the chloride. Oxalic acid is found to be a suitable titrant for rapid estimation of thorium, the minimum error being +0.5%. The other titrants do not give good results. The titrations with ammonium oxalate indicate the step-wise ionisation of ThCl 4 into ThCl 2
2+, ThCl 3+ and Th 4+. For mixtures of thorium chloride and cerous chloride, only the equivalence point corresponding to complete precipitation of both thorium and cerium is indicated.The authors express their sincere thanks to Prof. S. S. Joshi for his keen interest in this work and to Dr. G. S. Deshmukh for his advice and help in so many ways during the progress of these studies. 相似文献
12.
The extraction behavior of thorium from Baotou iron ore with primary amine N1923 levextrel resins by a micro-column was investigated under the decompression technology. Thorium was adsorbed on the micro-column conditioned by 3 mol L−1 HCl solution before use. The washing liquor of 0.5 mol L−1 H2SO4–0.1 mol L−1 H3PO4 solution was used to wash impurity elements and the solution of 3 mol L−1 HCl was used as the eluent for thorium. The method was applied to analyze thorium in the Baotou iron ore sample. The relative standard deviations of thorium in R-715 standard sample, Baotou main ore standard sample and Baotou west ore were of 0.49%, 1.63%, 1.16%, respectively. The accuracy of the method was satisfactory.
相似文献
13.
We report a portable lensless on-chip microscope that can achieve <1 μm resolution over a wide field-of-view of ~ 24 mm(2) without the use of any mechanical scanning. This compact on-chip microscope weighs ~ 95 g and is based on partially coherent digital in-line holography. Multiple fiber-optic waveguides are butt-coupled to light emitting diodes, which are controlled by a low-cost micro-controller to sequentially illuminate the sample. The resulting lensfree holograms are then captured by a digital sensor-array and are rapidly processed using a pixel super-resolution algorithm to generate much higher resolution holographic images (both phase and amplitude) of the objects. This wide-field and high-resolution on-chip microscope, being compact and light-weight, would be important for global health problems such as diagnosis of infectious diseases in remote locations. Toward this end, we validate the performance of this field-portable microscope by imaging human malaria parasites (Plasmodium falciparum) in thin blood smears. Our results constitute the first-time that a lensfree on-chip microscope has successfully imaged malaria parasites. 相似文献
14.
Summary A rapid titrimetric method for the estimation of thorium in the range from 5 to 88 mg. in a 50 ml. of final volume has been developed which involves the adjustment of P h at 3.0, addition of 2 ml. of 0.02% SPADNS indicator, dilution to volume and titration with standard NaF until the colour obtained matches a blank containing the buffered solution of the indicator alone. The method has been standardised against known amounts of thorium and a calibration curve relating the titre of the fluoride solution to thorium content has been prepared. Interferences of various cations and anions have also been studied. From the results, the quantitative nature of zirconium interference has been confirmed. The method for the determination of thorium is very rapid and the colour change being sharp from blue-violet to scarlet-red, the detection of endpoint is not at all difficult.The author wishes to thank Dr. A. K. Ghosal, Principal, Darjeeling Government College, for providing Laboratory facilities and Prof. P. Ray and Dr. A. K. Mukherjee of the Indian Association for the Cultivation of Science, Calcutta for their encouragement in the research work. 相似文献
15.
The visualization of hazardous gaseous emissions at volcanoes using in-situ mass spectrometry (MS) is a key step towards a
better comprehension of the geophysical phenomena surrounding eruptive activity. In-situ data consisting of helium, carbon
dioxide, sulfur dioxide, and other gas species, were acquired with a quadrupole based MS system. Global position systems (GPS)
and MS data were plotted on ground imagery, topography, and remote sensing data collected by a host of instruments during
the second Costa Rica Airborne Research and Technology Applications (CARTA) mission. This combination of gas and imaging data
allowed three-dimensional (3D) visualization of the volcanic plume and the mapping of gas concentration at several volcanic
structures and urban areas. This combined set of data has demonstrated a better tool to assess hazardous conditions by visualizing
and modeling of possible scenarios of volcanic activity. The MS system is used for in-situ measurement of 3D gas concentrations
at different volcanic locations with three different transportation platforms: aircraft, auto, and hand-carried. The demonstration
for urban contamination mapping is also presented as another possible use for the MS system. 相似文献
16.
The ability of zeolites to remove thorium-232 from naturally radioactive thorium nitrate solutions was studied by ion exchange, adsorption and surface phenomena. The best zeolites were a clinoptilolite from Mudhills, California, USA and a mordenite rich tuff from Eastgate, Nevada, USA. As the concentration of thorium in solution was increased the mechanism of thorium removal switches from that of partial ion-exchange to a surface precipitation. This was confirmed by electron probe microanalysis (EPMA) in conjunction with XRD and Energy Dispersive X-ray analysis (EDX). A Langmuir-type of adsorption occurred with the thorium-232 daughter isotopes at the same time as partial exchange/precipitation of the thorium parent which is in regular equilibrium with its natural daughters. Some experiments with 234Th were carried out to confirm this hypothesis as well as column experiments to confirm the usefulness of the Th removal. 相似文献
17.
In this study we investigate the basic features of thorium adsorption from aqueous systems by silk fibroin. Our previous study
showed that this biopolymer has high efficiency for U(VI) adsorption. It is well-known that thorium, which is a tetravalent
metal, is a more reactive element than uranium. Thorium(IV) adsorption proves to be very rapid and dependent on pH, temperature,
retention time, concentration of ion, amount of fibroin, volume of solution and volume-to-mass ratio. 相似文献
18.
Summary The existing volumetric methods for the determination of thorium are indirect and unsatisfactory. A direct titrimetric method for the estimation of thorium has been developed which involves the adjustment of ph, addition of 1 ml. of 0.02% SPADNS indicator, dilution to volume and titration with versene. It is based on the fact that thorium forms a coloured complex with SPADNS and after the bulk of thorium has reacted with versene, the highly coloured thorium- indicator complex is destroyed, marking the end point. Quantity of thorium as small as 5 mg. can be titrated accurately when present in a volume of 50 ml. Determination of thorium can also be made in presence of large amount of iron by adding ascorbic acid prior to the titration. Interferences of various ions have also been studied. The method proposed for thorium is selective and should be of considerable use in many cases.The author's thanks are due to Dr. A. K. Ghosal, Principal Darjeeling Government College, for providing all laboratory facilities and Dr. A. K. Mukherjee, Indian Association for the Cultivation of Science, Calcutta for his kind help in the work. 相似文献
19.
A liquid chromatography-tandem mass spectrometry method was developed and validated for the simultaneous quantification of vincristine and tariquidar in 10 μL of mouse whole blood using volumetric absorptive microsampling devices. Samples were extracted from the devices and quantified against calibrators prepared in a human blood plasma matrix. Separation of vincristine and tariquidar was achieved using a Shimpack XR ODS III C18 stationary phase and H 2O and methanol mobile phase solvents containing 0.1% formic acid, running a gradient elution at a flow rate of 0.2 mL/min over 6.0 min. The method was linear up to 1200 ng/mL ( R2 > 0.99 for both analytes), with calibrator accuracy within ± 15% of the nominal concentrations and analyte coefficient of variance <15% for both vincristine and tariquidar. Pharmacokinetic assessment of both analytes was successfully applied in mice as both single-agent therapy and combination therapy over a 24-h period, and a 2.3-fold increase in vincristine drug exposure was observed in combination with tariquidar. This study validates the use of this approach for longitudinal analysis of drug exposure in animal studies. 相似文献
20.
A method for the continuous on-stream determination of trace concentrations of uranium and thorium in flowing streams is developed.
The 14 MeV neutron generator was used for irradiation and the delayed neutron counting technique was employed in counting
the induced neutron activity. The dependence of the minimum detectable concentration on the irradiation, decay and counting
times, liquid flow-rate and the background was studied. At optimal conditions, uranium and thorium concentrations were determined
down to 20 and 100 ppm, respectively. The interference of the neutron emitting nuclide 17m
O was reduced to an insignificant level by optimizing the decay time. 相似文献
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