N. K. Aras

Determination of minor and trace elements in Turkish diet by duplicate portion technique

The minor and trace element content of diet samples from two different social population groups were determined. Samples were prepared by duplicate portion technique by colecting everything 16 subjects ate and drank during a 3-day period. Samples were homogenized, freeze-dried and elemental concentrations of Br, Co, Cr, Cs, Fe, K, Na, Rb, Sc, Se and Zn were determined by instrumental neutron activation analysis. Elemental concentrations and daily dietary intake of the elements were compared with the diets of other nations.

Trace elements in human bone determined by neutron activation analysis

There is an evidence that some of the essential trace elements are crucial determinants of bone health. Excess or deficiency of these elements has a role in the development of bone diseases, therefore research on trace elements in bone is very important. Iliac crest bone biopsies were optioned from twelve persons undergoing orthopedic surgery due to any reason than osteoporosis. Cortical and trabecular parts were separated, and blood and fats were removed. Up to 30 minor and trace elements were determined in these samples by instrumental neutron activation analysis and other techniques and their relations were discussed.

Trace elements in the atmosphere determined by nuclear activation analysis and their interpretation

Concentrations of 30 elements in the atmospheric particulate material were determined by three defferent nuclear activation techniques, namely; photon, thermal neutron and 14 MeV neutron activation analysis. Trace element concentrations observed were interpreted in terms of Enrichment Factor, EF, of each element with respect to crustal abundance and coal in order to find any possible correlation between the existance of highly enriched elements in the atmosphere and pollution source materials. It was also found that enrichment factors of elements are inversly proportional with the size of particulate material.

Trace element composition of atmospheric aerosols in Ankara, Turkey, determined by instrumental neutron activation analysis

Twenty six trace elements were determined by INAA in the aerosol samples collected at two stations in Ankara, Turkey. Industrially derived elements, Se, As, Sb, Zn and Au did not show seasonal dependence and they were not substantially enriched. Elements originating from coal combustion are highly enriched and have higher concentrations in the winter. Correlation factors indicate that motor vehicles, coal and oil combustion are the main sources of aerosols over the city.

Composition and origin of trace elements in fog water studied by INAA

Multielement study of fog water at the Uludag mountain, Northwestern Turkey, is presented. Fourteen elements (Al, As, Br, Cl, Cs, Fe, I, K, Mn, Na, Sc, Sb, V, Zn) are determined by INAA. Sulfate is determined by ion chromatography. Sulfate showed good correlation with non-crustal Mn. Marine particles dominated fog water composition among four major sources. Low to moderate variations of trace element concentration were observed by using three different fog collectors.

INFLUENCE OF EVEN NUCLEON NUMBERS AND CLOSED SHELLS ON MASS AND CHARGE DISTRIBUTION IN LOW ENERGY FISSION

Extensive experimental and evaluated yield data are now available for the fragments in low energy nuclear fission. Using these data we re-examined the influence of even nuclear numbers and closed shells on the mass and charge distribution in low energy fission. We used WAHLs Zp model and Ap model. We also examined the effects ofZ=50,N=82 and possiblyN=88 shells. A new method was developed based on two Gaussian curves for the even and odd products. TheEOZ andEON values calculated are based on these different methods and are seen to be consistent with each other in spite of the somewhat different definitions of the even-odd effect. The even-odd effect decreases with an increasing fissility parameter. TheEON values are substantially lower than the correspondingEOZ values, probably due to the effect of washing out the neutron pairing effect by prompt neutron emission. The magnitude of the even-odd effect varies with different mass regions. TheEOZ andEON values decrease as they go from asymmetric to symmetric regions in mass distributions.

Fine structure of mass and charge distribution in low energy fission

Studies of finer details in mass and charge distribution fission leads to a better understanding of the fission process. Experimental determination of independent and cumulative yields using radiochemical techniques as well as mass spectrometers and fission product recoil separators form the basis of such studies. It has been established that closed shells as well as an even number of nucleons influence both mass and charge distributions. The magnitudes of these effects may be estimated from existing experimental yield data and various fission models. Using our measurements of several fission yields and those existing in the literature we have calculated even-odd proton and neutron effects for various low energy fissioning systems. Where enough data existed, direct calculations were made, whereas for other cases the Zp-model of WAHL has been used. It is found that the even-odd proton effect is well established and pronounced in thermal neutron fission of235U and233U. Lesser effects were found for reactor neutron induced fission of232Th, thermal neutron fission of239Pu and spontaneous fission of245Cm and249Cf. No effect seems to exist in the thermal neutron fission of241Pu and the spontaneous fission of252Cf. The even-odd neutron effect is found to be much lower than the corresponding proton effect in235U and233U fissions and is nonexistent in the rest of the fissioning systems.

Determination of pre-scission kinetic energy in low energy fission using isotonic charge distribution model

The parameters of Isotonic Charge Distribution Model have been calculated for several isotones of three low energy fissioning systems. The global charge even-odd effects are determined as 0.27±0.04 for thermal neutron induced fission of233U(U233T), 0.27±0.05 for U235T and 0.13±0.05 for PU239T. The pre-scission kinetic energies for U235T and PU239T are estimated and found to be ∼16 MeV.