Showing papers on "Chemical binding published in 1969"

Molecular Charge Distributions and Chemical Binding. IV. The Second‐Row Diatomic Hydrides AH

Abstract: An interpretation of the binding in the second‐row diatomic hydrides NaH, MgH, AlH, SiH, PH, SH, and HCl is presented based on the molecular charge distributions and the forces exerted on the nuclei. The total density distributions are discussed in relation to “molecular” size and the arbitrary partitioning of the total charge between different spatial regions. Density difference maps are employed to compare the Hartree–Fock molecular charge distribution with the appropriate Hartree–Fock separated‐atom charge densities and also the corresponding Hartree–Fock united‐atom charge density. In addition, for SiH, PH, SH, and HCl, two‐center Hartree–Fock molecular charge distributions are compared with extensive one‐center charge distributions. The molecular orbital charge densities are classified as binding, nonbinding, or antibinding on the basis of their partial contributions to the force acting on each nucleus. The orbital forces provide a quantitative assessment of the relative binding abilities of the orbi...

Measurement of Neutron Slowing Down Time in Light Water, Ice, Paraffin and Santowax

Abstract: Measurements of the neutron slowing down times in light water, ice, paraffin and santowax have been made by pulsed neutron technique. Bursts of D-T neutrons of 0.1μsee width were generated in moderator cubes of 40×40×40 cm3. The slowing down neutrons were detected by bare as well as energy-selective filter-covered BF3 counters, and analyzed with a 256-channel time analyzer. Slowing down times in the moderator were determined by interpreting the increment of the difference of events between the two counters as attributable to the fraction of the neutrons slowing down at the time of measurement below the cut-off energy of the filter. The measured slowing down times below 0.63 and 0.43 eV agreed well with theoretical values on the 0°K free gas model. On the other hand, the measured values below 0.20 eV were found to be appreciably greater than the theoretical, which would appear to indicate that he effect of thermal agitation and chemical binding come into play at this range of energy.

Disturbance of Energy Transfer as a Factor Promoting Changes in the Biologic Behavior of Tumor Cells

Abstract: Summary The chemical binding point of Janus green B, a selective stain of mitochondria, has been studied on rat liver mitochondria. More than 90 percent of the dye was bound by a specific lipoprotein fraction, the so-called coenzyme Q-lipoprotein. The biologic effect of the incubation at 38°C of a mixture composed of Janus green B and ascitic fluid depends on the concentration of oxygen in the gaseous portion of the incubation system. After incubation in pure 0 2 atmosphere, the ascites tumor fails to develop in healthy animals and their survival time is prolonged over 200 days. It was demonstrated in earlier experiments that in such cases the infected animals develop leukemia or hepatic malignancy after a latency period of some length. The viability of Janus green B-treated tumor cells was unaffected when the incubation was performed in air atmosphere. No biologic changes, such as those observed at 38°C, occurred when Amytal ascites tumor cells were incubated with Janus green B at 2°C in pure oxygen atmosphere. However, exposure to visible light of this system interfered with the growth of the tumors; the rate of tumor formation seemed to be inversely related and the survival time proportional to the period of illumination. This effect was canceled by placing a solution of Janus green B in the path of the light as a filter. As an interpretation of these phenomena, it is suggested that the transfer of energy produced during the biologic oxidation is disturbed. The mechanism of oxygen effect is discussed in detail since it plays a fundamental role in the development of pathologic energy transfer.

Megaoersted Fields and Their Relation to the Physics of High Energy Density

Abstract: The interaction of very high magnetic fields with metallic conductors is a very interesting but complicated physical process which has only received certain attention in recent years. Here we are interested in this problem mainly because of its energetical aspects, i.e., for its relation to a relatively new research field which we define as the “Physics of High Energy Density.” By “high energy density” we mean densities in excess of some 10 kJ/cm3, i.e., larger than the chemical binding energies of most solids.