Nonlinear stability of spatially-periodic traveling-wave solutions of systems of reaction diffusion equations

Using spatial domain techniques developed by the authors and Myunghyun Oh in the context of parabolic conservation laws, we establish under a natural set of spectral stability conditions nonlinear asymptotic stability with decay at Gaussian rate of spatially periodic traveling-waves of systems of reaction diffusion equations. In the case that wave-speed is identically zero for all periodic solutions, we recover and slightly sharpen a well-known result of Schneider obtained by renormalization/Bloch transform techniques; by the same arguments, we are able to treat the open case of nonzero wave-speeds to which Schneider's renormalization techniques do not appear to appl

Preaching as interaction between church and culture: with specific reference to the Korean church

The Korean church, famous for her rapid growth, has begun to notice a downward trend in her growth rate since the mid-eighties. Although many reputable investigations have recently been carried out with regard to this downward slide, these investigations have overlooked the full meaning of preaching in the interaction between church and culture. In view of this, this study sets the following four aims: (1) to investigate the reasons behind church decline in terms of preaching in the interaction between church and culture in Korea; (2) to interpret preaching in the interaction between church and culture biblically, historically and theologically in order to understand the normative Christian perceptions and practices of preaching; (3) to attempt an integration between the descriptive and the normative; and (4) to propose developmental strategies for the Korean church. To achieve these purposes, two kinds of methods are employed in this study: (a) an analysis of preaching in the interaction between church and culture both in Korea and in the normative Christian sources, with the model advocated by D Browning (1991); and (b) qualitative interviewing as an empirical interpretation with a model based on the findings of Rubin&Rubin (1995). Five claims emerge from this study: (1) How do we reset the context of preaching? (2) How do we revise the present preaching theory of the Korean church? (3) How do we define and defend conversion preaching that is seemingly exclusive in contemporary pluralistic Korean society? (4) How do we rethink and re-establish the ecclesiology of the Korean church? (5) How do we formulate the Christian culture against or in the rage of worldly thoughts and cultures in Korea? This thesis concludes by proposing preaching as interaction and the preacher as an inter-actor between church and culture. Practical strategies are developed to answer the claims.Thesis (PhD (Practical Theology))--University of Pretoria, 2005.Practical Theologyunrestricte

Electronic Commerce in the Retail Brokerage Industry: Trading Costs of Internet Versus Full Service Firms

Electronic brokerages on the Internet represent one of the most successful examples of electronic commerce, having captured over 20% of retail stock trades. According to economic theory, prices of commodities like securities should converge to one price in a market with the transparency of the Internet. A review of published commissions for online brokers shows that this "law of one price" does not appear to hold for the commissions charged by retail brokers. In this paper we explore one possible explanation for these differences in commissions. Specifically, we test whether the total cost of trading, including commissions and savings based on the quality of execution, obeys the law of one price. In a carefully designed experiment, we simultaneously purchased or sold 100 share lots of stock using a voice-broker, an expensive online broker and an inexpensive online broker in each trial. We found relatively few price improvements, which are a measure of execution quality. The difference among brokers in obtaining price improvements was not statistically significant. The brokers do exhibit statistically significant differences in total trading costs; at a volume of 100 shares commission costs dominate execution quality. We explore the implications of the findings for larger lot sizes, choosing a broker, and electronic commerce in the brokerage industry.Information Systems Working Papers Serie

Nonlinear modulational stability of periodic traveling-wave solutions of the generalized Kuramoto-Sivashinsky equation

In this paper we consider the spectral and nonlinear stability of periodic traveling wave solutions of a generalized Kuramoto-Sivashinsky equation. In particular, we resolve the long-standing question of nonlinear modulational stability by demonstrating that spectrally stable waves are nonlinearly stable when subject to small localized (integrable) perturbations. Our analysis is based upon detailed estimates of the linearized solution operator, which are complicated by the fact that the (necessarily essential) spectrum of the associated linearization intersects the imaginary axis at the origin. We carry out a numerical Evans function study of the spectral problem and find bands of spectrally stable periodic traveling waves, in close agreement with previous numerical studies of Frisch-She-Thual, Bar-Nepomnyashchy, Chang-Demekhin-Kopelevich, and others carried out by other techniques. We also compare predictions of the associated Whitham modulation equations, which formally describe the dynamics of weak large scale perturbations of a periodic wave train, with numerical time evolution studies, demonstrating their effectiveness at a practical level. For the reader's convenience, we include in an appendix the corresponding treatment of the Swift-Hohenberg equation, a nonconservative counterpart of the generalized Kuramoto-Sivashinsky equation for which the nonlinear stability analysis is considerably simpler, together with numerical Evans function analyses extending spectral stability analyses of Mielke and Schneider.Comment: 78 pages, 11 figure

Differential Expression and Function of Nicotinic Acetylcholine Receptors in Subdivisions of Medial Habenula

Neuronal nAChRs in the medial habenula (MHb) to the interpeduncular nucleus (IPN) pathway are key mediators of nicotine's aversive properties. In this paper, we report new details regarding nAChR anatomical localization and function in MHb and IPN. A new group of knock-in mice were created that each expresses a single nAChR subunit fused to GFP, allowing high-resolution mapping. We find that α3 and β4 nAChR subunit levels are strong throughout the ventral MHb (MHbV). In contrast, α6, β2, β3, and α4 subunits are selectively found in some, but not all, areas of MHbV. All subunits were found in both ChAT-positive and ChAT-negative cells in MHbV. Next, we examined functional properties of neurons in the lateral and central part of MHbV (MHbVL and MHbVC) using brain slice patch-clamp recordings. MHbVL neurons were more excitable than MHbVC neurons, and they also responded more strongly to puffs of nicotine. In addition, we studied firing responses of MHbVL and MHbVC neurons in response to bath-applied nicotine. Cells in MHbVL, but not those in MHbVC, increased their firing substantially in response to 1 μm nicotine. Additionally, MHbVL neurons from mice that underwent withdrawal from chronic nicotine were less responsive to nicotine application compared with mice withdrawn from chronic saline. Last, we characterized rostral and dorsomedial IPN neurons that receive input from MHbVL axons. Together, our data provide new details regarding neurophysiology and nAChR localization and function in cells within the MHbV

Esclerose múltipla e tratamentos

Multiple sclerosis is an autoimmune condition that affects the brain, as well as its optic nerves and spinal cord. When the myelin sheath is in its normal, healthy state, nerve signals are sent and received quickly. However, when the individual has Multiple Sclerosis, the body's immune system treats myelin as a threat, and hinders the sending of commands from the brain to the rest of the body, called demyelinating. The aim of the present study was to understand the formation of multiple sclerosis, its damage to the myelin sheath and possible treatments for the disease. This study is a literature review, carried out through the following databases: SciELO, PubMed and Science Direct. Treatments for multiplying sclerosis are based on steroids, physical activity, anti-inflammatory foods and foods rich in unsaturated fats. The element lithium has been studied and showing beneficial effects, being an effective treatment for this pathologyA esclerose múltipla é uma patologia autoimune que atinge o cérebro, bem como seus nervos ópticos e a medula espinhal. Quando a bainha de mielina está em seu estado normal e saudável, os sinais nervosos são enviados e recebidos rapidamente. Porem quando o indivíduo possuí a Esclerose Múltipla, o sistema imunológico do seu corpo trata a mielina como uma ameaça, atrapalhando o envio dos comandos do cérebro até o restante do corpo, denominado como desmielinização. O objetivo do presente estudo foi compreender a formação da esclerose múltipla, seus danos a bainha de mielina e os possíveis tratamentos da doença. O presente estudo é uma revisão de literatura, realizada por meio das bases de dados: SciELO, PubMed e Science Direct. Os tratamentos para a esclerose múltipla são a base de corticoides, atividade física, alimentos anti-inflamatórios e ricos em gorduras insaturadas. O elemento lítio vem sendo estudado e demonstrando efeitos benéficos, sendo um tratamento eficaz para esta patologia