The reaction D(p, γ )He³ was studied at incident proton energies of less than 50 kev. The method was to bombard heavy ice targets with the proton beam from the 50 kv accelerator. This machine develops an intense beam of 60 to 80 microamps which is necessary to produce a substantial yield despite the low reaction cross section. The angular distribution of the γ-rays was found to follow a (sin²θ +B) pattern as expected from earlier work carried out at higher energies. In the neighborhood of 35 kev the value of B was found, by measurements of the yield at 90° and at 0° to the incident beam direction, to be .283± .110. The total cross section was found to take on the following values: [In column] E(kev), 29.1, 37.5 44.0 ; [In column] σ(cm² ) x 10⁻³², 4.87 ± 1.05, 11.2 ± 2.8, 12.0 ± 4.0 / Science, Faculty of / Physics and Astronomy, Department of / Graduate

Interaction losses in sodium iodide crystals have been directly measured for protons in the range of energies from 139 to 444 MeV and for deuterons of 277 MeV. Calculations of the expected loss were made for protons over the range 151-500 MeV using the best currently available reaction cross section data. Our experimental values are typically about 21% lower than the calculated values. The interaction loss for 277 MeV deuteron in Nal is about 8% lower than the calculated value obtained using the deuteron cross section value of Measday and Schneider. Using their calculated value of 100 MeV deuteron interaction loss as a reference point, we calculated the loss for 277 MeV deuterons and from a fit to our data we obtained the cross section for deuterons at an average energy of 188.4 MeV to be 2590 ± 180 mb, which is about 20% lower than the cross section obtained from the empirical relation that σ(d-A) is 2σ(p-A) at half the energy. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

Measurements of the angular distribution and total reaction rate in neutron-proton scattering are described. The emphasis of this work has been to obtain an accurate normalization of the distribution, which is difficult to achieve with neutral beams. Nearly monoenergetic neutrons from the d(p,n)pp reaction were scattered from a liquid hydrogen target. The neutron beam energy was determined from the time of flight with respect to the radio frequency signal of the TRIUMF cyclotron. The differential cross section was measured at 319 and 493 MeV from 10 to 180 degrees in the centre of mass (CM.). Calibrated neutron beam monitors upstream of the scattering target provided an absolute normalization over the whole angular range. Between 10 and 100 degrees CM. a neutron detector consisting of a charged particle veto, a carbon convertor and two trigger scintillators sandwiching 7 multiwire proportional chambers was used to select elastic neutrons by time of flight techniques. The neutron angular distribution was measured with an average precision of 5% and an uncertainty on the normalization of 1.3%. An associated particle experiment (neutrons and recoil protons detected in coincidence) determined the efficiency of the neutron detector and the monitors were calibrated by measuring the incident neutron flux with the neutron detector in the beam, i.e. at zero degrees. The recoil protons were detected in the angular range between 60 and 180 degrees CM. with a precision of 1% to 2% and an error on the normalization of 2.8% at 319 MeV and 3.7% at 493 MeV. Elastic events were selected by time of flight and by either a measurement of magnetic rigidity (momentum) or total energy. The absolute normalization of the two experimental techniques is verified by the overlap of the two measurements and by comparing the integrated differential cross section with the measured total cross section. The neutron-proton total cross section was measured at six energies between 200 and 500 MeV by a transmission type experiment to a precision of 1% to 3%. The systematic corrections were small, of the order of 1%, and the statistical errors were increased to include monitor and beam instabilities. The measurements show a smooth quadratic energy dependence. The data was included in a phase shift analysis and a dispersion relation analysis along with the previous world data. Agreement between the real part of the forward scattering amplitude predicted by the phase shift analysis and by the dispersion relation analysis is improved. The errors on the 1=0 (isoscalar) phase shifts are decreased and to a lesser extent on the 1=1 phase shifts. There is a marked improvement in the smooth variation with energy of the 1=0 phase shifts and a better agreement of the higher partial waves with the theoretical predictions of the Paris potential. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

The purpose of the work reported here was to determine the feasibility of applying the nuclear induction technique of Bloch to the direct observation of nuclear magnetic resonance in the very weak magnetic field of the earth.

The log K, ΔH° and ΔS° values for the interaction of several metal ions with the two isomers of the cyclic polyether, 2,5,8,15,-18,21 hexaoxatricyclo[20.4.0.0^9,14]hexacosane are reported. The stability order found for alkali metal ion interaction with either isomer is identical to the order of ion permeability through reconstituted biological membranes for structurally related antibiotics. The size of the metal ion is critical in determining the extent of interaction. A calorimetric titration study of proton ionization from several monosaccharides and derivatives, pyrimidine bases and their nucleosides, adenosine and its derivatives, and cycloheptaamylose is described. The heats of reaction obtained in this study show the acidity of adenosine to be associated with the ribose portion of the molecule and that the presence of both the 2' and 3'-hydroxyl groups results in a marked acidity increase compared to similar compounds lacking vicinal OH groups. The acidity in the sugars is associated with the 1 position.

This dissertation represents an attempt to understand the mechanism of the action of pesticides derived from chlorinated phenols (pentachlorophenol, pentachlorobenzenethiol, and 2,4,5-trichlorophenol) in lipid membranes; specifically, the kinetics of pesticide induced hydrogen ion transfer in lecithin-cholesterol membranes and its relationship to uncoupling activity in energy transducing membranes. Information on pesticide induced charge transport in membranes was obtained from the measurements of steady state and transient membrane conductance and membrane potentials as a function of the composition of the aqueous phase surrounding the membrane and of membrane composition. In addition, a systematic theoretical study of a series of membrane transport models was performed in order to elucidate the various aspects of membrane transport kinetics and to make predictions relevant to the interpretation of experimental results. Based on the theoretical results, two kinetic schemes of membrane transport were proposed to explain the experimental results; one for pentachlorophenol and 2,4,5-trichlorophenol, and another for pentachlorobenzenthiol. The schemes differ in the proposed mechanism of charge transfer across membrane water interface. Some conclusions regarding the rate limiting step in the charge transport process are drawn. Measurements of membrane surface potentials based on the microelectrophoretic method reveal that the density of ionized pentachlorophenol at the membrane surface can be predicted from the Langmuir adsorption model, provided that electrostatic repulsion between pentachlorophenol ions adsorbed at the membrane and free ions in the aqueous phase is taken into account. The fact that the adsorption of positively charged tetraphenylarsonium ions and negatively charged salicylate ions modify the membrane charge transport induced by 2,4,5-trichlorophenol, can be explained by electrostatic arguments. The 2,4,5-trichlorophenol, can be explained by electrostatic arguments. The ability of pentachlorobenzenethiol and of chlorinated phenols to induce proton transport in membranes is regarded as the origin for both the membrane electrical conductivity and their toxic action in energy transducing membranes. We have found similarities between the pH dependence of pentachlorobenzenethiol induced membrane conductance and the pH dependence of the pentachlorobenzenethiol uncoupling activity found in mitochondria, as reported in the literature. We have also found that the level of pentachlorophenol concentration at which the membrane conductance increases above the background level corresponds to the onset of reduction of carbon uptake by algae.

No description available.

Proton sources driven by high-power lasers are a promising addition to the portfolio of conventional proton accelerators. Regarding particle cancer therapy, where tumours are irradiated with protons or ions, the novel accelerator technology can be particularly beneficial for translational research - the research branch in which results of basic research are transferred to new approaches for the prevention, diagnosis and treatment of cancer. The overarching aim in the thesis at hand was a translational pilot study to irradiate tumours on mice’s ears with laser-accelerated protons while achieving the quality level of conventional proton accelerators. This is the only way to compare the radiobiological data of the novel accelerator technology with those of the established ones. To enable such experiments a predetermined dose distribution according to the radiobiological model’s requirements must be delivered to a sample volume. Ergo, the laser-driven protons have to be transported and shaped after their initial acceleration. Intense laser-driven proton pulses, inherently broadband and highly divergent, pose a challenge to established beamline concepts on the path to application-adapted irradiation field formation, particularly for 3D. This work demonstrates the successful implementation of a highly efficient and tuneable pulsed dual solenoid setup to generate a homogeneous (laterally and in depth) volumetric dose distribution using only a single dose pulse from the broad laser-driven proton spectrum. The experiments using the ALBUS-2S beamline were conducted at the titanium:sapphire high-power laser Draco PW at the Helmholtz-Zentrum Dresden–Rossendorf. The beamline and its model were characterised and verified via independent methods, leading to first experimental studies providing volumetrically homogeneous dose distributions to detector targets as well as tumour and normal tissue in proof-of-concept studies. To perform the mouse pilot study, a new solenoid with cooling capacities was designed, characterised and implemented in the course of this thesis. The combination of the new solenoid and an overall performance improvement of the laser-proton accelerator, enabled the successful conduction of the mouse model study. The results show that laser-accelerated protons induce a comparable tumour growth delay as protons from conventional accelerators. This outcome and the demonstration of the flawless interaction between laser-proton accelerator, beam transport, dosimetry and biology qualify the laser-based accelerator technology for complex studies in translational cancer research. Looking into the future, their unique extremely high intensity renders them of particular interest for the investigation into the ultra-high dose rate regime. There, the so-called FLASH effect shows fewer side effects in normal tissue while maintaining the same effect in the tumour when the target dose is administered in milliseconds rather than minutes, as currently common. The ALBUS-2S setup at Draco PW already provides all necessary conditions to realise irradiation times of around ten nanoseconds in preclinical studies. This significantly expands the parameter space for investigating the FLASH effect and is presented as a proof-of-concept in this thesis.

A new method for molecular calculations was applied to the hydrogen molecule ion. Energies were calculated at different internuclear separations and simple energy differences were found. The method used was an approximate one which included two basic approximations: the use of Gaussian wave functions and the one-center method. The one-center method gives a good approximation for the electronic energies but does not give near-atomic electron densities. The title "Floating Potential Curves" comes from the fact that the Gaussian wave functions give good potential curves over a restricted region, but these curves are not oriented correctly with respect to the minimum energy. This is an indication that calculated energy differences would be more accurate than calculated energies. This was seen to be true in a prior calculation.

No description available.