The biological evaluation of the thermal neutron capture reaction of boron-10, B10 (n,α)Li7 + 2.786 MeV, has previously been studied, using different particles from the boron-10 thermal neutron capture reaction compared with 250 kvp x-rays has been reported as 1.05 for spleen-thymic weight reduction (1), as 1.5 to 2.0 for skin lesions in pigs (2), and 1.87 for skin lesions of the rabbit's ear (3). The significance of such a calculation is felt to be unreliable for the boron-10 reaction in animals because of the vagaries of dose determination resulting from irregular boron distribution, and by the presence of an adventitious irradiation from fast neutrons and capture gammas that is inadequately determined at present. Our present experiment attempts to circumvent the difficulties attendent to studies of the boron-10 reaction in animals by comparing the effect of this reaction on the proliferative capacity of HeLa cells with those produced with 250 kvp x-ray.

In these lectures we will discuss some examples of information about magnetic properties of solids which can be obtained by neutron scattering. We consider a scattering process in which a neutron with wave vector k and spin σ is incident upon a solid in state q>. (Here q stands for all of the quantum numbers which describe the state of the solid, such as spin and orbital electronic states, phonon numbers, etc.) After interacting with the solid, the neutron goes off with wave-vector k' and spin σ', leaving the solid in state q'>. In performing an experiment of this sort one does not usually observe the initial and final spin states of the neutron or the initial and final states of the solid. We must then sum over all possible final states and average over all initial states.

The present core of the Brookhaven Graphite Reactor consists of some 4900 highly enriched uranium fuel loaded in 615 horizontal fuel channels passing through a 25 foot cube of graphite moderator and reflector. The core is divided into two halves (north and south) by an 8 cm. wide vertical gap in the center of the graphite. The cooling air enters the reactor through inlet filters, at the rate of 270,000 CFM, passes into the central gap and flows bi-directionally through the north and south halves of the core. It then enters the collecting plenums and flows into the north and south ducts. The air is first monitored by the north and south exit air monitors located within the pile building. These are moving filter tape monitors with beta scintillation detectors. They are essentially operational monitors and are maintained by reactor operations. They are essentially operational monitors and are maintained by a reactor operations. The air then passes through the exit air filters, heat exchanger, venturi and on to the fan house where the north and south ducts join. After the fan house the air is monitored by Argon-41 by a Kanne ion chamber syste.

Boron-10 has a high thermal neutron capture cross section (3880 barns). Following neutron capture, the subsequent nuclear disintegration produces an alpha particle and a lithium-7 nucleus with the release of an average of 2.34 MeV for the particle irradiation, and in 93% of the reactions there is also the emission of an 0.48 MeV gamma ray: [equation not transcribed]. The kinetic energy is divided between the lithium-7 nucleus and the alpha particle giving the equal and opposite momentums with a range in tissue of about 8-14μ or approximately 1 cell diameter (1). This fact and the reported favorable partition of boron between tumor and the normal brain suggested a possible therapeutic usefulness which has been investigated clinically. The object of our study is to document the biological effects of the B10 (n,α) Li7 reaction on the brain of dogs injected with boron-10 30 minutes prior to irradiation with thermal neutrons. For this, we felt it desirable to estimate a dose for the boron-10 reaction which if exceeded, produces destruction of normal tissue. This dose could then be a reference dose to be utilized as a maximal limit for the irradiation of normal tissue. We have assured that the largest fluence …

If one injects into an animal H3-thymidine, 50% of it is incorporated into deoxyribonucleic acid (DNA), within approximately 30 to 45 minutes, while the rest is catabolized. A storage of H3-thymidine for later incorporation into DNA does not occur, on the basis of available evidence. Once incorporated, the label remains bound to DNA until cell death and no unequivocal evidence has as yet been presented to indicate metabolic renewal or intracellular turnover of the DNA molecule. The loss of labeled DNA from the bone marrow is therefore directly influenced by the rate of proliferation of the various cell types with release of mature cells into the peripheral blood.

Investigations on the relative biological effectiveness (RBE) of densely ionizing radiations (with high LET, rate of linear energy transfer) are of importance in both fundamental and applied radiobiology. In the latter, they serve as a basis in setting permissible exposure levels for types of radiation about which little long range experience is available. Some of the best RBE studies have been done on chromosomal aberrations. The difficulty is determining RBE on the basis of chromosomal exchanges or 2-break aberrations is that the dose-response curves differ for radiations of different LET and dose rate. The dose-squared term tends to predominate with radiations of low LET (such as γ rays and most X rays) and high doses or dose rates; the linear term dominates with high LET tracks in general and at low doses or dose rates. The shape of the curves is thought to reflect the existence of two classes of mechanisms by which chromosome exchanges are produced; exchanges caused by the passage of a single ionizing particle account for the linear component of the dose-response curve, exchanges due to the interaction of effects of two independent ionizing particles are responsible for the dose-squared component. This model has been amply confirmed …

In brief, these facilities consist of a 250 KvP X-ray generator; two areas of a research reactor, one a well thermalized unit of moderate capacity and a larger area with a mixed thermal and fast neutron distribution, all of which are used for brief, acute exposure. A 10 acre field, currently with almost 4000 curies of cobalt 60, serves to irradiate entire plants for either short or long periods of time. Recently, the flux density of the thermal column was increased by a factor of 5 over the original density. This was accomplished by lowering the thermal column 12 inches deeper into the reactor shield. Fast neutrons at this higher flux density are also available to the cooperator. An additional facility available to the program is the array of kilocurie gamma sources in the Nuclear Engineering Department of Brookhaven National Laboratory.