Die betrokkenheid van die Nederduitsch Hervormde Kerk by Bybelkunde aan die Universiteit van Pretoria

The involvement of the Nederduitsch Hervormde Kerk van Afrika in Biblical Studies at the University of PretoriaThe two sections of the Faculty of Theology (Nederduitsch Hervormde Kerk and Nederduitse Gereformeerde Kerk) have equal responsibilities regardingBiblical Studies at the University of Pretoria. In this historical survey, however, attention is focused on the part of the Nederduitsch Hervormde Kerk. The Departmentof Biblical Studies has a proud record, and interesting possibilities for the future are mentioned. The Department functions (unofficially) as a third and ‘ecumenical’ section of the Faculty of Theology, its students coming from a variety of churches and beliefs, and its lecturers belonging to different churches

Dynamical Phase Transitions In Driven Integrate-And-Fire Neurons

We explore the dynamics of an integrate-and-fire neuron with an oscillatory stimulus. The frustration due to the competition between the neuron's natural firing period and that of the oscillatory rhythm, leads to a rich structure of asymptotic phase locking patterns and ordering dynamics. The phase transitions between these states can be classified as either tangent or discontinuous bifurcations, each with its own characteristic scaling laws. The discontinuous bifurcations exhibit a new kind of phase transition that may be viewed as intermediate between continuous and first order, while tangent bifurcations behave like continuous transitions with a diverging coherence scale.Comment: 4 pages, 5 figure

One-Particle Excitation of the Two-Dimensional Hubbard Model

The real part of the self-energy of interacting two-dimensional electrons has been calculated in the t-matrix approximation. It is shown that the forward scattering results in an anomalous term leading to the vanishing renormalization factor of the one-particle Green function, which is a non-perturbative effect of the interaction U. The present result is a microscopic demonstration of the claim by Anderson based on the conventional many-body theory. The effect of the damping of the interacting electrons, which has been ignored in reaching above conclusion, has been briefly discussed.Comment: 7 pages, LaTeX, 1 figure, uses jpsj.sty, to be published in J. Phys. Soc. Jpn. 66 No. 3 (1997

Numerical Evidence of Luttinger and Fermi Liquid Behaviour in the 2D Hubbard Model

The two dimensional Hubbard model with a single spin-up electron interacting with a finite density of spin-down electrons is studied using the quantum Monte Carlotechnique, a new conjugate gradient method for the evaluation of the Edwards wavefunction ansatz, and the standard second order perturbation theory. We performed simulations up to 242 sites at $U/t=4$ reaching the zero temperature properties with no ``fermion sign problem'' and found a surprisingly good accuracy of the Edwards wavefunction ansatz at low density or low doping. The conjugate gradient method was then applied to system up to 1922 sites and infinite $U$ for the Edwards state. Fermi liquid theory seems to remain stable in 2D for all cases studied with the exception of the half filling case where a ``Luttinger like behavior'' survives in the Hubbard model , yielding a vanishing quasiparticle weight in the thermodynamic limit.Comment: 10 pages + 4 pictures, RevTex, SISSA 121/93/CM/M

Metabolic changes in the lungs after ischaemia

CITATION: Engelbrecht, F. M., Edwards, I. J. & De Beer, D. P. 1980. Metabolic changes in the lungs after ischaemia. South African Medical Journal, 58:409-413.The original publication is available at http://www.samj.org.zaThe effects of variable periods of ischaemia on the isolated lungs of rats and rabbits, stored for up to 6 hours at 4°C, 21°C and 37°C under standardized conditions, were investigated in vitro in terms of oxygen consumption, the rate of 1-14C-leucine incorporation into soluble proteins, and 1-14C-palmitate incorporation into total phospholipids and lipid fractions. The endogenous oxygen uptake of rat lung slices in an air phase, from tissues stored at 4°C and 21°C under ischaemic conditions for 6 hours and at 37°C for 4 hours, was significantly different from the control values. The oxygen uptake of lungs from animals anaesthetized with pentobarbitone prior to exsanguination and stored for only 2 hours at 37°C differed significantly from control values. Judged by the rate of incorporation of radiolabelled leucine into soluble proteins and that of palmitate into total lipids and phospholipids of lungs after storage for increasing periods at 4°C and 37°C, significant differences were already found after 1 1/2 hours. From this observation it would appear that these parameters are very sensitive indicators for assessing irreversible lung damage due to ischaemia.Publisher’s versio

Quasi-Particles in Two-Dimensional Hubbard Model: Splitting of Spectral Weight

It is shown that the energy $(\varepsilon)$ and momentum $(k)$ dependences of the electron self-energy function $\Sigma (k, \varepsilon + i0) \equiv \Sigma^{R}(k, \varepsilon)$ are, ${\rm Im} \Sigma^{R} (k, \varepsilon) = -a\varepsilon^{2}|\varepsilon - \xi_{k}|^{- \gamma (k)}$ where $a$ is some constant, $\xi_{k} = \varepsilon(k)-\mu, \varepsilon(k)$ being the band energy, and the critical exponent $\gamma(k)$, which depends on the curvature of the Fermi surface at $k$, satisfies, $0 \leq \gamma(k) \leq 1$. This leads to a new type of electron liquid, which is the Fermi liquid in the limit of $\varepsilon, \xi_{k} \rightarrow 0$ but for $\xi_{k} \neq 0$ has a split one-particle spectra as in the Tomonaga-Luttinger liquid.Comment: 8 pages (LaTeX) 4 figures available upon request will be sent by air mail. KomabaCM-preprint-O

An Efficient Algorithm for Optimizing Adaptive Quantum Metrology Processes

Quantum-enhanced metrology infers an unknown quantity with accuracy beyond the standard quantum limit (SQL). Feedback-based metrological techniques are promising for beating the SQL but devising the feedback procedures is difficult and inefficient. Here we introduce an efficient self-learning swarm-intelligence algorithm for devising feedback-based quantum metrological procedures. Our algorithm can be trained with simulated or real-world trials and accommodates experimental imperfections, losses, and decoherence

Theory of the temperature and doping dependence of the Hall effect in a model with x-ray edge singularities in d=oo

We explain the anomalous features in the Hall data observed experimentally in the normal state of the high-Tc superconductors. We show that a consistent treatment of the local spin fluctuations in a model with x-ray edge singularities in d=oo reproduces the temperature and the doping dependence of the Hall constant as well as the Hall angle in the normal state. The model has also been invoked to justify the marginal-Fermi-liquid behavior, and provides a consistent explanation of the Hall anomalies for a non-Fermi liquid in d=oo.Comment: 5 pages, 4 figures, To appear in Phys. Rev. B, title correcte

Labeling and purification studies on cancer targeting DOTA-TATE labeled with radiolanthanides

Abstract only availableMolecular imaging and targeted radiotherapy are emerging fields for cancer treatment. DOTA-Tyr (3)-Thr(9)-octreotate (DOTA-TATE) is used for peptide receptor-mediated radionuclide therapy (PRMRT) in neuroendocrine tumours. These biomolecules can be radiolabeled with an appropriated radioisotope to produce radiopharmaceuticals for diagnostic and therapeutic applications. The DOTA-TATE molecule is comprised of a bifunctional chelate (DOTA) that is capable of stably binding a radiolanthanide as well as being covalently attached to a targeting biomolecule (e.g.,octreotate). Among the radiolanthanides, Ho-166, Tb-161 and Lu-177, that were used to label the peptide, Lu-177 was used to obtain optimum conditions. Direct neutron capture on Lu-176 produces Lu-177. The indirect production of Lu-177 proceeds by neutron capture on Yb-176 producing Yb-177, which beta decays to Lu-177. Chromatographic separation yields high specific activity Lu-177 that minimizes the presence of cold Lu-176. Lanthanides have similar chemical properties that allow further studies to apply similar conditions as those developed for Lu-177. In addition, longevity of half-life of Lu-177 enables longer periods of dose delivery to targeted tumors. This research focused on identifying appropriate buffer solutions and volumes that could neutralize the acidic radioisotope to appropriate pH levels to label the peptide in high yield. The sample was purified from the unlabeled peptide by using HPLC separations methods and adding stabilizing agents (ascorbic and gentisic acid) to prevent radiolysis of the radiolabeled peptide. The results for the labeled peptide with various radioisotopes shows that 0.4 M NH4OAc, 0.4 M NaOAc, and 0.01 M HEPES buffer solution in 500 µL yields 99% labeling at pH ranging from 6.0 to 7.5. The labeled ligand at equimolar ratio with the metal yields 3 mCi/µg of the ligand, whereas as high specific activity sample can label up to 6.68 mCi/µg of the ligand. Carrier free Lu-177-DOTA-TATE was labeled using 0.01 M HEPES buffer at pH 6.0 and remains stable after using ascorbic acid; gentisic acid shows interference on HPLC which may cause some purification problems. (Ho- holmium, Tb- terbium Lu- lutetium)U.S. Dept. of Energy Innovations in Nuclear Infrastructure and Education Summer MURR Undergraduate Research Scholarshi