The kinetics of the annealing of point defects, either by migration to sinks or by recombination, is complicated by the occurrence of a variety of simultaneous reactions. An extensive theoretical study of annealing processes is in progress at Brookhaven based on the isolation and combination of simple kinetic steps. When analytic solutions could not be found, computer solutions have been used to obtain useful approximations and to determine their regions of validity. Two migration reaction schemes have been studied; the simultaneous annealing of single and divacancies, and the annealing of single vacancies with impurity trapping. These recombination reactions and interstitial migration to sinks, di-interstitial formation, and interstitial trapping at impurities.

An automatic delayed reactivity feedback based on exit coolant temperature is shown to lead to an increase in linear stability against xenon oscillations when the delay time is within a few percent of the free period of oscillation. Numerical calculations show that the stabilizing effect extends into the nonlinear range as well. It is shown that dead band control is spatially destabilizing if the dead band width is too small. A width of ± 5% is, however, found sufficient to avoid this form of instability for large changes in power demand.

The severe local damage caused by neutron irradiation of an alloy can create extra sites for the nucleation of phase changes. This effect of enhanced nucleation has been studied in the iron--carbon system. Measurements were made by electrical resistivity, internal friction, and electron microscopy. Two effects were found. When the alloy is irradiated at ambient temperature (~60 deg C) the number of precipitation particles formed and, hence, the rate of precipitation of carbon, is ten times the number in the unirradiated alloy. Further irradiation does not increase the number of precipitate particles. When the alloy is irradiated at low temperature (~ -100 deg C) the disappearance of carbon from solution is one thousand times faster than the thermal rate. It is deduced that the carbon is temporarily trapped by vacancies and later released to precipitate at a temperature higher than the precipitation temperature in the unirradiated alloy.

A discussion concerning the mechanism of extrusion and intrusion formation is presented. A model involving dislocation motions is proposed by which experimental results are explained. In this first stage of fatigue defect formation, it appears that O₂ is not involved. While in the second stage, in which microcracks are formed oxidation is probably important. The effects of oxidation in the third stage, in which cracks of macroscopic size propagate steadily through the area and lead finally to fatigue failure, are most significant. A discussion of each phase is included.

This note describes some results of the study of single pion production in π⁻-p interactions at 4.65 Bev/c, using the BNL 20" Hydrogen Bubble Chamber. It is well known that the observability of some of the particle resonances (e.g. 33 Isobar and η) varies markedly with the energy of the incident particle. The ρ meson has been observed in π⁻-p interactions at 1.25 Bev/c and 1.9 Bev/c incident pion energies. Evidence will be shown that this resonance persists with the much higher incident pion energy used in the present experiment.

Extracorporeal irradiation of the blood was prolonged for as long as 38 hours. Red cells are injured by the radiation dose. Hemolysis may commence after 28 hours presumably due to the irradiation. Utilizing extracorporeal irradiation of the blood combined with thoracic duct cannulation, one can measure minima for net lymphocyte input into the peripheral blood from all sources other than the thoracic duct. An unusual and new pathologic picture of lymph nodes and spleen has been produced by extracorporeal irradiation of the blood. Heparin mobilization of a large pool of lymphocytes into the blood directly and via the thoracic duct must be considered in all studies utilizing heparin as an anticoagulant. The lymphocytosis produced by this mobilization is suppressed by concurrent extracorporeal irradiation. The apparent quantitative destruction of the lymphocytes by extracorporeal irradiation of the blood may permit studies of lymphocytic function hitherto not possible by direct experimentation

Even though bi-lateral or more complicated exposure procedures are of considerable importance in "total-body" exposure of large animals or man, these measures may not result in even approximately the same dose to different tissues. Because of body contour, depth-dose patterns determined in a rice-and-wax phantom contoured to the shape of a dog were appreciably different from the calculated values based on published standard depth-dose tables (400 cm² portal: other factors being approximately equal). In addition to differences due to contour, the tissue traversed by the beam makes considerable difference. Depth-dose patterns in a cadaver dog, compared with the contoured rice-phantom, differed by as much as plus or minus 30%.

Results are included of a study of the formation of methylene-C complexes in neutron-irradiated propane in the gas, liquid, and solid phases. It is considered that the results support the view that discrete species, such as carbon atoms, methyne, and methylene, react at thermal or near thermal energies in the gas phase accounting for a major fraction of the products. Products which contain Carbon-11 produced in the neutron reactions with propane are tabulated.

The contribution to electrical resistivity of impurity atoms adjacent to vacancies in metals is calculated. The calculation is based on the Born approximation, which allows separations of the effects of the individual imperfections from interference effects. Lattice relaxation is neglected. The resistivity due to Ag or Zn impurities adjacent to a vacancy in Au is related to the resistivity of the separate imperfections as ∫Ag + vac = ∫ Ag + ∫ vac - 0.11 (∫Ag * ∫vac)^(1/2) ; ∫Zn + vac = ∫Zn + ∫vac + 0.10 (∫Zn * ∫vac)^(1/2). Effects of anisotropy of the scattering are found to be almost completely removed if the vacancy-impurity pairs are randomly oriented along several directions.

Using requirements of analyticity and the unitarity of the S-matrix we obtain the dependence of a transition amplitude on the invariant mass of two particles strongly coupled to other two particle channels. As an example, we consider the production of a Σπ state near the Y*₀ resonance assuming it is coupled to a KN state in an s 1/2 state.

Behavior and functions of small lymphocytes during immune processes leading to production of demonstrable circulating antibodies are still unknown in many respects. This report will describe some observations made on autoradiographically detectable incorporation of tritiated thymidine, tritiated cytidine, tritiated histidine, and tritiated DL-leucine into small lymphocytes of regional lymph nodes after secondary simulation with tetanus toxoid in mice. These tritiated compounds have been used in the past to study in vivo DNA, RNA, and protein metabolism of mouse lymphocytic tissue. Previous studies have not dealt with the uptake of these precursors by small lymphocytes as a function of time during secondary antibody responses.

A brief review of the statistical properties of spectra is presented. The purpose of this paper is to present a rapid survey of the statistical properties of spectra using both atomic spectral data and nuclear spectral data. In many cases, only one kind of relevant data exists, for example, very little is known about atomic particle transition probability data so that for that sort of data, we must confine our attention to nuclear data. When there are both atomic and nuclear data available, we have tried to select that data which is usually not treated according to the general approach of this paper. Throughout our discussion, then, we will be mainly emphasizing analogies and the manner of handling different sorts of data according to the spirit of this paper.

Information on the metabolism of fission products in man has been obtained largely from studies carried out with parenterally-administered soluble salts of radioisotopes administered in medical treatment or in tracer studies. The recent development of the whole-body gamma spectrometer with its highly sensitive detection system has been of considerable value in extending these studies by providing data on very low levels of isotopes in man over long periods of time.

An air cored pulse deflection coil has been constructed for the Brookhaven AGS. The system produces a deflecting pulse with a peak radial deflection of 2.5 cms and duration of 70 microseconds. Beam spill duration of 15 to 50 microseconds from the target is readily achieved. One deflector has given satisfactory service for over a year and a second unit has been installed this summer.

In order to perform the various experiments with a bubble chamber, a high intensity flash tube is used. This report briefly describes the power supplies designed and constructed to power these lamps.