On lineγ-Ray emission following 30 MeV/A12C induced reactions on some medium-heavy targets

Preliminary results on residual nuclei production in 30 MeV/A¹²C interaction with medium heavy targets are presented. Gamma-ray spectroscopic techniques were used. Evidence for charge and angular momentum transfer is found.

     

Fast generation of molecular surfaces from 3D data fields with an enhanced “marching cube” algorithm

An improved version of the “marching cubes” algorithm [W. Lorensen and H. Cline, Comp. Graph. 21 , (1987)] for the generation of isosurfaces from 3D data fields is presented and applied to molecular surfaces. The new algorithm avoids inconsistent pattern definitions of the original one, which lead to artificial gaps. The advantage of a logarithmic interpolation procedure, in particular for data fields typically occurring in molecular science, is demonstrated. An example is the generation of molecular surfaces based upon electron density data. © 1993 John Wiley & Sons, Inc.     

Methotrexate analogs. 7. Synthesis of two higher homologs and a positional isomer of methotrexate diethyl ester as potential antitumor agents

Analogs of methotrexate diethyl ester ( 1 ) were prepared, in which the distances separating the ester functions from each other and from the carboxamide function of the p-aminobenzoate moiety were varied via the use of methylene groups as “spacers”. The diethyl esters 3 and 4 , with D,L-α-aminoadipate and D,L-α-aminopimelate side chains in place of L-glutamate, displayed approximately the same order of activity as compound 1 against bacterial and mammalian cells in culture, and were inhibitors of the enzyme dihydrofolate reductase. When given intraperitoneally to L1210 1eukemic mice at a dose of 120 mg./kg. q3d 1,4,7, compound 4 produced a 67% increase in survival and no evidence of toxicity, whereas methotrexate diethyl ester ( 1 ) gave a 44% increase in survival at a dose of 45 mg./kg. q3d 1,4,7 but was toxic at higher doses. The positional isomer 2 was inactive.     

Zerfallsschema und β-Spektrum des MsTh1 (Ra228)

Theβ-spectrum of MsTh1 (Ra²²⁸) has been measured in a proportional counter in 2π — and in 4π-geometry. Comparison of these measurements shows that there are no conversion electrons. Theβ-decay of MsTh 1 therefore leads in all cases to the ground level of MsTh2. The Kurie plot is straight from 15 keV up to the upper energy limit ofE ₀=55±3 keV (logft=5·6). The result has been checked by a search for photons emitted by the MsTh1. Noγ-rays and no X-rays have been found. The measurements had to be made with a relatively large amount of natural Ra²²⁶ in the sources. — The results do not agree with those ofLecoin, Perey, Teillac andRiou, who proposed a complex decay sheme for MsTh1.     

Superconducting tunnel junctions as quantitative detector of intense thermal phonon radiation

Thermal phonons are emitted from a pulse-heated constantan film into an a-cut sapphire (kept at 1.2 K) and are detected quantitatively by recording the current-voltage characteristic of the tunnel junction during the relatively strong phonon irradiation. These measurements are made with the maximum of the Planck distribution of the emitted phonons varied in the frequency range from 0.3 to 1.5 THz. These momentary diode characteristics coincide within experimental error withd c-characteristics at higher substrate temperatures. Assuming thermal equilibrium between electrons and phonons in the tin film and assuming the validity of the acoustic-mismatch model, a comparison can be made between observed phonon power and theoretically expected phonon power. Good agreement is achieved if the influence of the acoustic cut-off frequencies of the tin detector material is taken into account.Supported by Deutsche Forschungsgemeinschaft     

Novel electrophoresis mechanism based on synchronous alternating drag perturbation

We present a novel means of transporting molecules in solution by applying a zero-time-average alternating motive force to the molecules, and perturbing the molecular drag coefficient synchronously with the applied force, thus causing a net drift in a direction determined by the phase of the alternating drag perturbation relative to the alternating force. We apply an electrophoretic form of the method to transport and concentrate DNA in a gel, such that all molecules migrate on average away from the nearest electrode and toward a central region. Since an electrode does not occupy this central region, this method presents the possibility of transporting and focusing DNA and other charged molecules in regions free from electrodes and the associated electrochemistry.