The relation of radiosensitivity to nuclear and chromosomal volumes and DNA contents has been studied in whole-body-irradiated adult amphibians. Data are presented on liver cell nuclear ...parameters-volume and DNA contents, per nucleus and per chromosome (NV, ICV; DNA/N, DNA/ch)-on correlation of LD50 with nuclear parameters, and on mean survival times for a number of species. In a few species, some individuals have detectable polyploid subpopulations in their liver cells. Nuclear and chromosomal volumes (NV and ICV) are linearly related to DNA contents. On the average, for 25 amphibian species an increase of $1.0\ \mu {\rm m}^{3}$ in nuclear DNA content causes an increase of $17\ \mu {\rm m}^{3}$ in NV, and residual NV is $72\ \mu {\rm m}^{3}$ when DNA content goes to zero. It is clear that a large fraction (about 80%) of amphibian NV and ICV is nonchromosomal, i.e., is nuclear "sap." This difference between actual genome size and its estimate as measured by NV may account for some of the difference in radiosensitivity, at the same measured NV or ICV, between amphibians and other higher organisms. Whole-body-irradiated amphibians are very slow to die, requiring 70 to >150 days to complete radiation-induced deaths, with mean survival times (MST) at the LD50 of 31-190 days. MST increases with increasing nuclear parameter size, but variability is high. Three modes of death (a three-component MST vs dose curve) are apparent. At the minimal LD50, animals die of a hematopoietic death; the mechanism for death at greater doses is not apparent, but is not intestinal damage. LD50 decreases with increasing nuclear parameter size, but less rapidly than linearly, with a slope of -0.58 for the eight species analyzed (13-fold range of NV). Sensitivity-volume data are available for only two other groups of whole-body-irradiated organisms. At the same ICV, amphibians are about seven times as radiosensitive as herbaceous plants, about three times as sensitive as woody plants. Compared to the four radiosensitivity groups (radiotaxa) found previously among single-cell systems from higher organisms, the correlation of D0 against ICV for these whole-body-irradiated amphibians falls very close to the $D_{0}-{\rm ICV}$ correlation line for the single-cell group which contained amphibians.
The liquid densities of cerium, lanthanum, praseodymium samarium, and yttrium trifluorides are presented at temperatures from the melting point to 2600 deg K. From the density values obtained the ...molar volumes and cubical thermal coefficients of expansion are calculated. The densities at the melting and boiling points are: cerium trifluoride, 4.631 g/cc(l733 deg K) and 3.8l9 g/ cc(2600 deg K); lanthanum trifluoride, 4.634 g/cc(1700 deg K) and 4.020 g/cc (2600 deg K); praseodymium trifluoride, 4.862 g/cc(1643 deg K) and 4.192 g/ cc(2600 deg K); samarium trifluoride, 4.879 g/cc (1670 deg K) and 4.362 g/cc(2600 deg K); and yttrium trifluoride, 3.808 g/cc(1660 deg K) and 3.376 g/cc(2500 deg K). (N.W.R.)
Density of Liquid Uranium Grosse, A. V.; Cahill, J. A.; Kirshenbaum, A. D.
Journal of the American Chemical Society,
11/1961, Letnik:
83, Številka:
22
Journal Article
Recenzirano
The density of pure liquid U was determined by the Archimedean method, from its melting point (l406 deg K) to about 1900 deg K. The equation of the density of liquid uranium, determined by the method ...of least squares, is Dliq in g/cm3 == It was concluded that liquid density is a straight line function of temperature far beyond the metal's normal boiling point, because the saturated vapor density of metal, which according to the law of rectilinear diameter causes deviation from linearity, assumes significant values only substantially above the normal boiling point. From the data tabulated, liquid densities of pure U235, U233, and U238 can be calculated. (P.C.H.)
The frequency of anaphase abnormalities (usually presented as bridges, bridges plus fragments, or percentage of normal anaphases) is widely used as a criterion of radiation damage in many materials. ...Here, the frequency of these three abnormal anaphase categories has been studied in a material frequently used for this purpose, regenerating mouse liver, following fast neutron irradiation (50 to 800 rads). A previous study with the plants Tradescantia and barley had shown that detected anaphase bridges increased with dose more or less linearly at first, to a maximum, and then actually declined at higher doses. Two different bridge-loss processes between metaphase and anaphase were shown to account quantitatively for this dose response. The results and conclusions were felt to be applicable to anaphase data in general, from any material. The same response was found here in the mouse liver. The frequency of anaphase bridges per cell increased with dose to a maximum, then declined at larger doses. The percentage of normal (aberration-free) anaphases reflected this increasing-with-dose loss of bridges by showing an actual increase in normalcy at larger doses, after an initial decline to a minimum of normalcy. In addition, for the mouse liver cells, it is shown that only 40% or less of the fragments actually present at anaphase are detected. In the practical sense, the widely used criterion of abnormal anaphases is an inefficient but reasonable measurement of damage in the range of low dose and low level of effect; that is, the amount of effect is about proportional to the dose. For mouse livers, it is estimated herein that the observation of abnormal anaphases detects only about 40 to 50% or less (about 40% of fragments, 50% of bridges) of the aberrations actually present, up to a dose of about 200 rads of fast neutrons. At higher doses, as the exponential-with-dose disappearance of bridges becomes appreciable, abnormal anaphases become grossly incorrect, actually decreasing with dose.
