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  • Author or Editor: S. Krishnan x
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Abstract  

The present status of forensic activation analysis (FAA) is critically discussed. The areas in forensic science in which it has contributed a new capability and those in which it has not, are both pointed out. The limitations and advantages in using FAA under different circumstances are noted. The value of FAA of hair, metal fragments, glass, soil, paint, fibre, heavy metal poisons and gunshot residue in comparison with conventional forensic techniques, is discussed.

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Abstract  

In-vivo neutron activation analysis (IVNAA) has been used in this laboratory, approximately for the past twenty years, to determine the bone status of humans. For this purpose, the total body calcium (TBCa) is assayed and that is indicative of the bone mineral concentration of the individual. We have effectively used this method to diagnose, understand and monitor the treatment of osteoporosis among elderly women, particularly in post-menopausal women. This paper summarizes the technique and our experience in dealing with osteoporosis.

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Abstract  

This paper describes the design of the system and the uses of in-vivo neutron activation analysis (IVNAA) for the determination of total body calcium (TBCa) and total body nitrogen (TBN) in humans. TBCa and TBN assay are useful in a variety of clinical situations dealing with the diagnosis and management of patients with osteopenia, nutritional deficiency, renal dysfunction, transplantation, cancer, thyroid dysfunction and many others. The system can be put together with readily available nuclear components and within a reasonable cost. This paper examines the present status of IVNAA for medical applications in a hospital setting.

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Abstract  

In-vivo neutron activation analysis (IVNAA) is now routinely used for the diagnosis and therapeutic monitoring of many diseases e.g. those of the skeletal system and those involving nutrition. Total body calcium (TBCa) and total body nitrogen(TBN) measurement are two such procedures. IVNAA facilities are designed for patient comfort and ease of operation in a hospital setting. They use portable isotopic neutron sources and conventional electronics. They are effective, non-invasive and, often, revenue generating in health care settings. They are now becoming common in health care facilities.

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Abstract  

Calcium may be measured in vivo by neutron activation analysis /IVNAA/, observing the 3.1 MeV -ray from the decay of49Ca. Normally the detection of this -ray is done in a heavily shielded whole body counter. It is shown that the use of shielding is unnecessary. As a result, the cost of building an IVNAA facility for Ca is very much reduced.

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Abstract  

The measurement of total body calcium is an important tool in the diagnosis and treatment of many diseases associated with bone. This measurement is done by IVNAA or DEXA. A knowledge of normal bone mineral mass for a given person, is necessary to determine whether or not a measured quantity is normal or low. The factors that determine bone mineral mass in a person are not clearly known. IVNAA indicates that bone mineral mass is a function of height but not the age whereas the reverse is indicated by DEXA. In this work, we have measured the bone mineral mass of over 200 normal volunteers by IVNAA and DEXA and have developed a methametical model for DEXA (for lumbar spine and femoral neck) as a function of height, age, weight and years after menopause. In determining the bone mineral mass, height is the predominant factor under 20 years of age and age appers to be the dominant factor for over 20 years. The equation derived is useful in calculating the normal bone mineral mass in a patient against which the measured value can be compared.

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Abstract  

The presence of toxic heavy elements such as arsenic, cadmium and mercury in industrial wastewater and waterways is a serious pollution problem. The treatment of such contaminated water by conventional techniques, which often includes an ion-exchange or similar step, is expensive. This paper examines the use of natural materials such as hair, and certain plants, which are inexpensive, for the absorption and hence the clean up of heavy elements from polluted water. Our results show that these natural materials concentrate the heavy elements, in certain cases, to the extent of up to 500 fold or even better. The contact time required is of the order of several hours. The capacities of absorption vary from about 1 g/kg to about 5 g/kg for mercury, and are lower for arsenic and cadmium. The results show that with hair, nearly 10,000 liters of mercury contaminated water, a typical daily output from a 100 ton chlor-alkali plant, can be treated with about 1/2 kg of hair valued at about 25 cents. This makes the process extremely cost-effective compared to the conventional processes now in use.

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Abstract  

Nitrogen in the human body is measured in vivo using prompt neutron capture gamma-rays. The quantity of nitrogen can then be used as measured of protein. Data are presented on three groups of subjects; volunteers of different ages, those with liver ailments, and those on peritoneal dialysis. The data show that the nitrogen measurements given information (in accord with clinical findings) which is not given by indirect methods of estimating lean body mass.

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Abstract  

Neutron activation analysis provides a useful clinical test to assess bone mass status in vivo. The neutron flux is obtained from Pu/Be sources and49Ca activity is measured by NaI detectors. For diagnostic value, the49Ca measurement is related to the mean value for normal subjects of the same body size. This normalized index, our CaBI, is used extensively to diagnose the bone loss associated with osteoporosis and to asses changes in bone mass with progression of disease and in response to treatments. Our facility operates at maximum capacity (35 tests/wk.). The hospital location and the dependability and ease of operation (provided by neutron sources) have facilitated extensive clinical use.

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Abstract  

Human hair has been proved to be a better dosimeter than even blood for tracing most of the heavy metal toxins when they penetrate the biosphere. The high precision of the neutron activation analysis (NAA) enabled researchers to elegantly differentiate between endogenous and exogenous contamination and to thoroughly study poisonings caused by these physiologically-unimportant elements. An extensive amount of bench-scale work has been accomplished in these laboratories to show the capacity of INAA to detect the presence of 10 nuclides (or more) with a precision of about 5%. The principal objective of the present study was to employ this assaying power and the tendency of scalp hair to uptake metals from aqueous solutions, to design an adsorption system which can easily be used by the waste-management people who are searching for a cost-effective technique to monitor and remove these pollutants from relatively large volumes of industrial effluents.

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