Taal en kerkeenheid: Calvyn se 1545-Kategismus in Latyn

Language and church unity: Calvin’s 1545 Catechism in Latin In 1545 Calvin wrote a catechism. He defended the fact that he had done it in Latin, saying: “I judge it useful that there should be public testimonies, whereby churches which, though widely separated by space, agree in the doctrine of Christ, may mutually recognize each other.” Although he was constantly being accused by the Roman Catholic Church of being a schismatic, Calvin’s ecumenical intentions were above re-proach. At every opportunity he stressed the sinfulness of schism from a church that bears the marks of the true church. By the time of the Reformation Latin wasn’t regarded any more as a “holy” language, but as a role model for other languages. Although the reformers increasingly propagated the use of the vernacular in religious service, they still maintained cor-respondence with each other in Latin and wrote many of their treatises in this language. The art of printing presented the same phenomenon: both vernacular and Latin (especially academic works), were produced and distributed. Calvin’s “Catechism” of 1545, written in Latin, was soon translated into many languages, even into Greek and Hebrew. Thereby Calvin reached his goal of promoting unity of faith between the different reformation churches. The fact that the catechism was written in Latin gave it a special status as church-historical document: a symbol of Calvin’s hope for church unity

Free-induction decay and envelope modulations in a narrowed nuclear spin bath

We evaluate free-induction decay for the transverse components of a localized electron spin coupled to a bath of nuclear spins via the Fermi contact hyperfine interaction. Our perturbative treatment is valid for special (narrowed) bath initial conditions and when the Zeeman energy of the electron $b$ exceeds the total hyperfine coupling constant $A$: $b>A$. Using one unified and systematic method, we recover previous results reported at short and long times using different techniques. We find a new and unexpected modulation of the free-induction-decay envelope, which is present even for a purely isotropic hyperfine interaction without spin echoes and for a single nuclear species. We give sub-leading corrections to the decoherence rate, and show that, in general, the decoherence rate has a non-monotonic dependence on electron Zeeman splitting, leading to a pronounced maximum. These results illustrate the limitations of methods that make use of leading-order effective Hamiltonians and re-exponentiation of short-time expansions for a strongly-interacting system with non-Markovian (history-dependent) dynamics.Comment: 13 pages, 9 figure

Memory-Controlled Diffusion

Memory effects require for their incorporation into random-walk models an extension of the conventional equations. The linear Fokker-Planck equation for the probability density $p(\vec r, t)$ is generalized to include non-linear and non-local spatial-temporal memory effects. The realization of the memory kernels are restricted due the conservation of the basic quantity $p$. A general criteria is given for the existence of stationary solutions. In case the memory kernel depends on $p$ polynomially the transport is prevented. Owing to the delay effects a finite amount of particles remains localized and the further transport is terminated. For diffusion with non-linear memory effects we find an exact solution in the long-time limit. Although the mean square displacement shows diffusive behavior, higher order cumulants exhibits differences to diffusion and they depend on the memory strength

Grasses in shade

"Trees and shade create a naturally pleasing environment in the landscape, however it is very difficult to grow grass under trees. Shady areas often have less light, tree root competition for nutrients and water, phytotoxic responses from alleopathic tree compounds, compacted soil from heavy use, and excessive organic matter from leaf litter. It's no wonder that growing grass is quite a challenge. Sweet gum, maple and unpruned pin oak are extremely difficult to grow grass under, while locust and poplar plantings are easily grassed."--First page.David D. Minner and Barbara J. Fick (Department of Horticulture, College of Agriculture)New 5/90/7

Hyperfine interaction in a quantum dot: Non-Markovian electron spin dynamics

We have performed a systematic calculation for the non-Markovian dynamics of a localized electron spin interacting with an environment of nuclear spins via the Fermi contact hyperfine interaction. This work applies to an electron in the s -type orbital ground state of a quantum dot or bound to a donor impurity, and is valid for arbitrary polarization p of the nuclear spin system, and arbitrary nuclear spin I in high magnetic fields. In the limit of p=1 and I=1/2, the Born approximation of our perturbative theory recovers the exact electron spin dynamics. We have found the form of the generalized master equation (GME) for the longitudinal and transverse components of the electron spin to all orders in the electron spin--nuclear spin flip-flop terms. Our perturbative expansion is regular, unlike standard time-dependent perturbation theory, and can be carried-out to higher orders. We show this explicitly with a fourth-order calculation of the longitudinal spin dynamics. In zero magnetic field, the fraction of the electron spin that decays is bounded by the smallness parameter \delta=1/p^{2}N, where N is the number of nuclear spins within the extent of the electron wave function. However, the form of the decay can only be determined in a high magnetic field, much larger than the maximum Overhauser field. In general the electron spin shows rich dynamics, described by a sum of contributions with non-exponential decay, exponential decay, and undamped oscillations. There is an abrupt crossover in the electron spin asymptotics at a critical dimensionality and shape of the electron envelope wave function. We propose a scheme that could be used to measure the non-Markovian dynamics using a standard spin-echo technique, even when the fraction that undergoes non-Markovian dynamics is small.Comment: 22 pages, 8 figure

Lepton-mediated electroweak baryogenesis

We investigate the impact of the tau and bottom Yukawa couplings on the transport dynamics for electroweak baryogenesis in supersymmetric extensions of the Standard Model. Although it has generally been assumed in the literature that all Yukawa interactions except those involving the top quark are negligible, we find that the tau and bottom Yukawa interaction rates are too fast to be neglected. We identify an illustrative "lepton-mediated electroweak baryogenesis" scenario in which the baryon asymmetry is induced mainly through the presence of a left-handed leptonic charge. We derive analytic formulae for the computation of the baryon asymmetry that, in light of these effects, are qualitatively different from those in the established literature. In this scenario, for fixed CP-violating phases, the baryon asymmetry has opposite sign compared to that calculated using established formulae.Comment: 26 pages, 5 figure

Asymmetric Quantum Shot Noise in Quantum Dots

We analyze the frequency-dependent noise of a current through a quantum dot which is coupled to Fermi leads and which is in the Coulomb blockade regime. We show that the asymmetric shot noise as function of frequency shows steps and becomes super-Poissonian. This provides experimental access to the quantum fluctuations of the current. We present an exact calculation for a single dot level and a perturbative evaluation of the noise in Born approximation (sequential tunneling regime but without Markov approximation) for the general case of many levels with charging interaction.Comment: 5 pages, 2 figure

Microscopic Theory for the Markovian Decay of Magnetization Fluctuations in Nanomagnets

We present a microscopic theory for the phonon-driven decay of the magnetization fluctuations in a wide class of nanomagnets where the dominant energy is set by isotropic exchange and/or uniaxial anisotropy. Based on the Zwanzig-Mori projection formalism, the theory reveals that the magnetization fluctuations are governed by a single decay rate $\omega_c$, which we further identify with the zero-frequency portion of the associated self-energy. This dynamical decoupling from the remaining slow degrees of freedom is attributed to a conservation law and the discreteness of the energy spectrum, and explains the omnipresent mono-exponential decay of the magnetization over several decades in time, as observed experimentally. A physically transparent analytical expression for $\omega_c$ is derived which highlights the three specific mechanisms of the slowing down effect which are known so far in nanomagnets.Comment: 7 page

Evaluation of the constant current angle controlled reluctance synchronous machine drive

Thesis (MScEng)--University of Stellenbosch, 2002.ENGLISH ABSTRACT: This thesis describes. the design and evaluation of a constant current angle controller for a variable speed reluctance synchronous machine (RSM) drive, as an energy efficient high performance drive. An accurate model of the RSM, with the use of finite element analysis, is derived and implemented in simulation software. The current- and speed controllers are designed and evaluated using a complete simulation model of the whole drive. The controller is implemented on a TMS320F240 DSPbased digital controller, which was developed. The dynamic performance of the constant-current-angle control is compared with that of the conventional constant-daxis- current control method. The results obtained from the RSM drive confirm the simulation results. In the comparison of the two control methods it is shown that the constant-current-angle controlled RSM drive is an energy-efficient drive with good dynamic performance.AFRIKAANSE OPSOMMING: Hierdie tesis beskryf die ontwerp en evaluering van 'n konstante stroomhoek beheerder vir 'n reluktansie sinchroon masjien (RSM) aandryfstelsel vir optimum effektiwiteit en dinamika. 'n Akkurate model van die RSM, met behulp van eindige element analise, is opgestel en geimplimenteer in 'n simulasie pakket. Die stroom- en spoedbeheerders is ontwerp en geëvalueer deur middel van 'n simulasiemodel vat die volledige aandryfstelsel. Die beheerder is geimplimenteer deur gebruik te maak van 'n TMS320F240 DSP-gebaseerde digitale beheerder, wat ontwikkel is. Die konstantestroornhoek beheer is vergelyk met die konvensionele konstante-d-as-stroom beheer metode. Die resultate van die praktiese stelsel korreleer baie goed met die resultate van die simulasie. Deur die vergelyking van die twee metodes is dit bevind dat die konstante-stroomhoek beheerde RSM aandryfstelsel 'n energie effektiewe aandryfstelsel met baie goeie dinamiese vermoë is

Spatial Resolution with Time-and-Polarization-Resolved Acoustic Microscopy

Spatial resolution is an important factor in ultrasonic materials characterization. Scanning acoustic microscopy [1–2] has proved to be a useful tool for materials evaluation with micrometer-scale spatial resolution. Point-focus-beam (PFB) acoustic microscopy has high spatial resolution and is often used to produce images as well as to probe material inhomogeneity. However, a disadvantage of the PFB technique lies in its insensitivity to material anisotropy. In contrast, line-focus-beam (LFB) acoustic microscopy can provide a directional ultrasonic velocity measurement and is employed for characterization of anisotropic materials [3–5]. But the LFB technique, with its unidirectional spatial resolution, is generally incapable of producing images, and is therefore disadvantageous for probing inhomogeneous materials. In response to this need, a variety of lens designs [6–9] in acoustic microscopy have been proposed for measuring materials, which are both inhomogeneous and anisotropic