摘要:

According to the chemical composition of water, a vertical hydrochemical stratification has been observed, sodium bicarbonate water is predominant in deep Nubian aquifer, while calcium bicarbonates occur in the marginal and shallower zones of this aquifer. In comparison with more arid regions of North Africa no chloride types has been found within it. Stable isotope data clarifies the interaction between the different water bodies. The Nubia water is the most depleted on its stable heavy isotopes content while surface water is very enriched due to evaporation. The results give very important information about the sources of recharge of the groundwater in the area. The groundwater is mainly meteoric water from two sources of recharge first is paleo-water of paleo-climatic and second is recent water of local precipitation.

ISSN:0021-1915    

DOI:10.1080/10256019008624208

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Data on the tritium abundance in precipitation, the Sava, the Danube and water bearing layers at the Sava alluvium in Belgrade region during 1976–88 are presented. Tritium content in precipitation mostly fluctuates from 1.1 to 18.3 Bq/l. Similar values between 0.4 and 16.8 Bq/l were obtained in the Sava and in the lower layer (17–30m), while in the upper layer they were different depending on the location and hydrogeological characteristics of the aquifer on the right and left bank of the Sava, ranging between 0.0 and 12.9 Bq/l. In the Danube, the content was about 20% greater than in the Sava with occasionally extraordinary high amounts up to 63 Bq/l. In the Danube, the content was about 20% greater than in the Sava with occasionally extraordinary high amounts up to 63 Bq/l. Measuring tritium, temperature and level of ruer and grounduaters (Ranney-wells, shallow and deep piezometers from 8 to 30 m) a hydrological relation river aquifer of different intensity was found; very strong between the Sava and Ranney-well and weaker with the upper layer. Variations in temperature, levels and tritium concentrations in the piezometers and especially in the Ranney-wells follow those in the Sava with a time lag of a few or about ten days.

ISSN:0021-1915    

DOI:10.1080/10256019008624209

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

ISSN:0021-1915    

DOI:10.1080/10256019008624210

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

It is demonstrated that the slope m. and the intersect q of the regression line δD = m δ18O + q describing the correlation between δD and δ18O in precipitation water of typical global climatic zones are in the normal range of m = 7 ÷ 9 and q = 8 ÷ 12 with one pronounced exception. Meteoric water in northern polar and arctic zone is distinguished by normal m value (m = 7.68) and an extremely low q value (q = 4.50). This anomaly is probably due to the fact that the arctic ice cover prevents the formation of that particular surface layer the evaporation of which produces the common source of meteoric water with δD = −22‰ and δ18O = –;4‰.

ISSN:0021-1915    

DOI:10.1080/10256019008624211

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Am 13. August 1988 gegen 15 Uhr durchschlung ein offenbar mehrere kg schwerer Eisklumpen das Dach eines Wohnhauses in Weistropp bei Dresden. Die δD- und δ18O-Werte des Wassers (δD = –85,6‰, δ18O = –12,4‰) entsprechen (bei Berücksichtigung des Höhen-Effekts) denen des Niederschlags in der Region. Der δ13C-Wert des im Eis enthaltenen CO2(δ13C = –17,6‰) spricht für atmosphärisches CO2hochindustrialisierter Gebiete. Die Gehalte an gelösten Salzen geleichen den Gehalten des Regenwassers in solchen Regionen. Die gelösten Gase N2und O2entsprechen einer Sättigung mit Luft bei einem Druck von etwa 10 kPa. Aus diesen Daten läβt sich ableiten, daβ der Eiskörper wahrscheinlich durch Kondensation, und zwar überwiegend durch Desublimation, von Luftfeuchte des Raums um Dresden entstanden ist.

ISSN:0021-1915    

DOI:10.1080/10256019008624212

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The selective permeation of a H2+ HD + D2gas mixture through a poly (ethylene terephthalate), PET, membrane was studied at T = 20 °C. In was found that the permeation of the HD through the PET membrane leads to a smaller overall hydrogen-deuterium separation factor than that determined in the permeation experiments with pure H2and D2. On the other hand, a process of isotopic exchange between deuterium atoms from the penetrant gas stream and hydrogen atoms from the polymer membrane is assumed and discussed in order to explain temporal variations of the H2, HD and D2concentrations of the permeant gas stream.

ISSN:0021-1915    

DOI:10.1080/10256019008624213

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The stability constants K2of [AtX2−] with X−= Cl−, Br−and I−in ethanol and methanol as well as their ion mobilities at a temperature T being 298 K and an ionic strength being about 0.05 were determined by horizontal zone electromigration in homogenous electrolyte solution. The results are compared with existing data for aqueous electrolyte systems.

ISSN:0021-1915    

DOI:10.1080/10256019008624215

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The Monte Carlo method is selected to study the spatial distributions of the displaced atoms and to calculate the energy deposition profile in the irradiated matter. Furthermore, precise values of the range of the ions in the medium and its dependence on ion's energy are obtained. These ion range calculations are important in the doping process of semiconductors in which impurity atoms should penetrate to a prescribed depth. Three materials Fe, Ni and Cu are chosen as target materials. Atoms of the same kind as the target material and helium ions are chosen as projectiles. The parameters that affect the studied functions are systematically studied.

ISSN:0021-1915    

DOI:10.1080/10256019008624216

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

A Monte Carlo computer program was developed to precisely calculate the yield and the characteristics of the secondary gamma-radiations produced in an irradiated iron medium by fast neutrons of different initial energies (14.1 and 7.0 MeV) in an arrangement of a normally incident point parallel beam of neutrons to enable the analytical treatment of the gamma-radiation production in the complicated practical irradiation environments. A parametric study of the calculations of the flux-energy and angular distributions of the gamma-radiations in the medium was carried out, considering the neutron's initial energy and the thickness of the medium as the two important parameters.

ISSN:0021-1915    

DOI:10.1080/10256019008624218

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Dose response curves for lymphocyte chromosome aberration frequencies using X- and gamma radiations became an important and reliable indicators as biological dosimeters especially in radiation accidents and professional over exposures. Nowadays electron beams therapy are frequently used for their advantages in cases of tumours under or near to the body surface. Dose-response curves for these electron beams are rarely published. Human peripheral blood lymphocytes were in vitro irradiated with various low and high doses (0.1 Gy to 4.9 Gy) of 18 MeV electron beam to utilize such a dose-response curve using chromosome aberration frequencies as a biological marker. Then we compared this biological curve with physically obtained curves normally used in planning for radiotherapy treatment. It is interesting to find a significant difference between both of them. The biological curve is generally higher in value and that the aberrations induced by 93% of a dose is significantly higher and deeper in site than those aberrations induced by the 100% dose calculated physically. If the above observation is confirmed by detailed studies, it would be of importance to the radiotherapist to plan for isodose curves according to biological determinations.

ISSN:0021-1915    

DOI:10.1080/10256019008624219

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor