The aminoacyl-tRNA synthetases are among the major protein components in the translation machinery. These essential proteins are responsible for charging their cognate tRNAs with the correct amino acid. Mammalian arginyl-tRNA synthetase (ArgRS), unlike all other eukaryotic aminoacyl-tRNA synthetases, is unique due to the coexistence of two structurally distinct forms of the same enzyme within the same cell: a complexed (or high molecular weight) form that is part of the multi-synthetase complex, and a free (or low molecular weight) form. Until now, not much information is known as to why the cell would synthesize and utilize two different forms of the same enzyme. Do the two forms of ArgRS perform similar or different biological functions? The main hypothesis that was originally proposed is that only the complexed form of ArgRS plays a crucial role in protein synthesis, while the free form of this enzyme participates in the ubiquitination pathway by tagging proteins with acidic NH2-termini (destined for degradation) with an arginine residue on their NH2-terminal end which will serve as a signal for ubiquitin-mediated destruction. Based on my studies, the data indicate that the high molecular weight form of ArgRS, which is present exclusively as an integral component of the multisynthetase complex, is essential for normal protein synthesis and growth of CHO cells even when low molecular weight, free ArgRS is present and Arg-tRNA continues to be synthesized at close to wild type levels. Based on these observations, we can conclude that Arg-tRNA generated by the synthetase complex is a more efficient precursor for protein synthesis than Arg-tRNA generated by free ArgRS, exactly as would be predicted by the channeling model for mammalian translation. No phenotype has been determined for cells expressing only the complexed form of ArgRS, and no direct interaction has been observed between ArgRS and arginyl-tRNA-protein transferase (ATE). Based on this information, we suggest that the function(s) of the free form of ArgRS is either not necessary or is performed by the complexed form when the free form is missing.

The aldolase-dehydrogenase complex catalyzes the last two steps in the microbial meta-cleavage pathway of various aromatic compounds including polychlorinated biphenyls (bph pathway) and cholesterol (hsa pathway). The aldolase, BphI, cleaves 4-hydroxy-2-oxoacids to produce pyruvate and an aldehyde. Linear aldehydes of up to six carbons long and branched isobutyraldehyde were directly channeled to the aldehyde dehydrogenase BphJ, via a molecular tunnel, with greater than 80% efficiency. The molecular tunnel is narrow in positions lined by Gly-322 and Gly-323 in the aldolase. BphI variants G322F, G322L and G323F were found to block aldehyde channeling. The replacement of Asn-170 in BphJ with alanine and aspartate did not substantially alter aldehyde channeling efficiencies, thus disproving a previous hypothesis that hydrogen bonding between the Asn-170 and the nicotinamide cofactor induces the opening of the exit of the tunnel. The H20A and Y290F BphI variants displayed significantly reduced aldehyde channeling efficiencies indicating that these residues control the entry and exit of substrates and products from the aldolase reaction. The BphI reaction was activated by NADH binding to BphJ in the wild-type enzyme and channel blocked variants. Activation of BphI by BphJ N170A, N170D and I171A was decreased by ≥ 3-fold in the presence of NADH and ≥ 4.5-fold when BphJ was undergoing turnover. These results demonstrate that the dehydrogenase coordinates catalytic activity of BphI through allostery rather than through faster aldehyde release from substrate channeling. HsaF, an ortholog of BphI from Mycobacterium tuberculosis could be expressed as a soluble dimer, however HsaF was inactive in the absence of HsaG, a BphJ ortholog. Acetaldehyde and propionaldehyde were channeled directly to HsaG with similar efficiencies as in the BphI-BphJ system. The HsaF-HsaG complex was crystallized and its structure solved to a resolution of 1.93 Å. Substitution of Ser-41 in HsaG with isoleucine or aspartate resulted in about 35-fold increase in Km for CoA but only 4-fold increase in Km for dephospho-CoA, confirming its importance in interacting with the 3’- ribose phosphate of CoA. A second gene annotated as 4-hydroxy-2-oxopentanoic acid aldolase (Rv3469c) from M. tuberculosis was expressed, purified and found to possess oxaloacetate decarboxylase and not aldolase activity.

Konstanz, Univ., Diplomarb., 1996.

Channeling has already been an observed phenomenon that often occurs during settling and sedimentation processes of finer materials. However, it has been regarded as a minor factor affecting settling process, e.g. settling velocity or consolidation rate. In this study, settling behaviors of talcs, kaolins and attapulgite were reviewed by experiments with small and large settling columns with special focus on channel formation during sedimentation. The large settling column is equipped with twenty eight measuring points, which are connected to pressure transducers for measuring pore pressure changes during settling. Throughout the study, channel formation was observed and related to the experimental conditions affecting it. The excess pore pressure changes were measured during the large column tests. Channels occurred under flocculation in zone settling and also in consolidation zones; pressure drop was observed near channels in some cases. It was apparent that channels work as a facilitator to dissipate the excess pore water pressure. It is summarized that not only initial concentration but also the material properties, such as specific gravity and shape of particles, can affect the channel formation. / Master of Science

In diesem Buch geht es um ein Phänomen, das als konstantes Element in der Geschichte des Christentums bezeichnet werden kann: Neuoffenbarungen. Denn der Kanonisierung der Bibel und dem kritischen Blick der kirchlichen Orthodoxie zum Trotz gab und gibt es immer wieder Menschen, die behaupten, dass sich ihnen Gottvater, Christus, der Heilige Geist oder andere Wesenheiten (Maria, Engel, Verstorbene) offenbart haben. Religionswissenschaftler haben das Thema bislang weitgehend ignoriert. Sie haben den Bereich des Christentums den Theologen überlassen und sich allenfalls mit frei flottierender Esoterik befasst. Theologen neigen ihrerseits dazu, Neuoffenbarungen apologetisch zu bekämpfen. Die vorliegende Untersuchung leistet daher einen wichtigen Beitrag zur religionswissenschaftlichen Erforschung des Themas. Im ersten Teil des Buches wird der Begriff „Neuoffenbarung“ aus verschiedenen religionswissenschaftlichen Perspektiven betrachtet. Zunächst wird untersucht, was die christliche Theologie unter „Offenbarung“ versteht. Danach werden die verschiedenen Termini analysiert, die für das Feld der außer- und nachbiblischen Offenbarungen kursieren (Neuoffenbarung, Privatoffenbarung, Channeling, Spiritismus, Prophetie u. v. m.). Anschließend werden jene Argumente referiert, die von Neuoffenbarungsanhängern bzw. kirchlichen Apologeten ins Feld geführt werden, um die Legitimität von Neuoffenbarungen zu behaupten bzw. zu bestreiten. Dass Neuoffenbarungen gar nicht so neu sind, zeigt ein religionshistorischer Überblick. Denn der Anspruch, besondere Offenbarungen empfangen zu haben, lässt sich in jeder Epoche des Christentums nachweisen. Nachdem einige Exponenten des prophetischen Charismas als ideengeschichtliche Vorläufer und Geistesverwandte der modernen Neuoffenbarungen vorgestellt wurden, werden diese schließlich selbst in den Fokus genommen. Das disparate Feld der Neuoffenbarungsträger des 19. und 20. Jahrhunderts wird anhand exemplarischer Gestalten in einer Typologie geordnet dargestellt. Um den Zitationszirkel zu durchbrechen, der sich offensichtlich im Diskurs etabliert hat, werden darin auch bislang weniger bekannte Neuoffenbarer vorgestellt. In einer Art Tiefenbohrung werden diese religionsphilosophischen, semantischen, historischen und systematischen Zugänge im zweiten Teil an der mexikanischen Neuoffenbarung „Das Buch des Wahren Lebens“ exemplifiziert. Die analysierende Darstellung beschränkt sich jedoch nicht auf ein isoliertes Objekt, sondern dies wird in einen komparatistischen Kontext gestellt: Zentrale Topoi des „Buches des Wahren Lebens“ (Christologie, Reinkarnationslehre, Kirchenkritik u. v. m.) werden zum einen in einer Synopse mit anderen Neuoffenbarungen dargestellt und zum anderen an der orthodoxen Theologie gespiegelt. Damit wird eine doppelte Differenz gezeigt: die Nähe/Ferne zu ähnlichen Phänomenen und die Nähe/Ferne zum kirchlichen Christentum. / This book deals with a phenonmen that counts as a constant feature in the history of Christianity: New Revelations. Despite the canonization of the Bible and despite the critical look of the Church, there are and always have been people who claim that they have received a revelation by God, Christ, the Holy Spirit or other beings (such as Mary, angels or spirits). Scientists of religion have largely ignored this topic up to now. They have relinquished Christianity to theologians and have at best dealed with free-floating esotericism, while theologians on their part tend to fight New Revelations apologetically. The present study, however, sets out to investigate New Revelations from a Religious Studies perspective and will therefore address this neglect. In the first part of the book, different perspectives common in Religious Studies are applied to the investigation of the notion “revelation“. After first having outlined Christian theology’s understanding of revelation, different terms are being analysed, which are in use for post-Biblical revelations (such as New Revelation, Private Revelation, Channeling, Spiritism, Prophecy and more). This is followed by the presentation of arguments against and in favour of the legitimacy of New Revelations as they are being urged by adherents of New Revelations on the one hand and Clerical apologetics on the other hand. A historical survey then demonstrates that New Revelations are in fact not new at all. The claim of people, who are supposed to have received a special revelation, can be found at all times in Christian history. After having presented some exponents of the prophetic charisma as spiritual soulmates and precedesors of the modern New Revelations, those texts themselves become the focus of attention. With the help of a typology, the disparate array of recipients of revelation in the 19th and 20th century is being outlined based on several exemplary figures. To break through a circle of quotation, which has apparently established in the discourse, the typology also contains some New Revelationists who are yet relatively unknown. Based on the Mexican New Revelation “The Book of the True Life“, the second part of the book exemplifies these religio-philosophical, semantic, historical and systematical approaches. This analysis, however, is not limited to an isolated object but it is put into a comparative context: central topics of “The Book of the True Life“ (Christology, Doctrine of Reincarnation, Church criticism and many more) are presented in a synopsis with other New Revelations, as well as mirrored at orthodox theology. With this, a twofold difference is being demonstrated: the closeness/distance to similar phenomena and the closeness/distance to clerical Christianity.

Thesis (PhD)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: We investigate a model system for particle diffusion in elastically coupled one-dimensional narrow channels. The elastic coupling of the channels is such that channels mutually affect the stochastic dynamics of particles. This kind of constrained and coupled stochastic diffusion may occur in supramolecular lattices where pore occupancy by guest particles may induce a reversible mechanical deformation of the lattice hence, affecting particle evolution in neighbouring pores. The model is explored first for out-of-equilibrium conditions, where we look mainly at the kinetic properties of the system, and thereafter under equilibrium conditions, where we try to understand the nature of dynamic correlation within the coupled channel system. For an out-of-equilibrium version of the model the focus is placed on the steady state behaviour of the two elastically coupled finite channels. The channels are kept in contact with particle reservoirs at the boundaries. Three current-density regimes of different distinct behaviour are identified using a simulation experiment. The sensitivity of the system mean occupancy profile and the steady state particle flux to small and large coupling parameter strength are explored. We find that, for small coupling strength, the system steady state profile and flux behaviour can be approximated by a simple mean field theory ignoring density-density correlations. We present the analytic description of the system using a cellular automaton formalism and then we generalize the theory for a multi-coupled channel system using a hopping particle dynamics approach. For small coupling parameter values, the analytic results are confirmed by the stochastic simulation. From the equilibrium perspective, we model the elastically coupled channel system as a system of infinite narrow channels having a uniform guest particle occupancy and we calculate density fluctuation correlation functions. The elastic coupling between channels is modelled as short range interacting potential and the particle evolution is modelled through Langevin dynamics. The dynamics are cast into the functional integral formalism expressed in terms of the collective particle number density, current density and the associated density response fields. The resulting generating functional takes these fields into consideration within the random phase approximation (RPA) up to second order. For a short range interaction potential, we uncover the behaviour of the system by looking at the influence of the inter-channel interaction strength on the dynamic density-density correlation functions. We conclude that the system long time limit effective friction coefficient is reduced with increase in the coupling parameter values while the strength of thermal forces for the effective system becomes renormalized. We also find out that the RPA breaks down under certain conditions, signalling a transition to a behaviour that is no longer characterised by a homogeneous density. The work presented here provides the beginnings for microscopic insights into the filling, filtering and storage processes for which certain types of microporous materials can be utilised. / AFRIKAANSE OPSOMMING: Ons ondersoek ’n modelstelsel vir die diffusie van deeltjies in elasties gekoppelde, eendimensionele nou kanale. Die elastiese koppeling is sodanig dat die stogastiese dinamika wedersyds be¨ınvloed word. Hierdie gekoppelde en aan dwangvoorwaardes onderhewig diffusie kan in supermolekulˆere roosters gebeur waar die besetting van holtes deur deeltjies ’n omkeerbare meganiese vervorming van die kristalrooster kan veroorsaak en sodoende die tydontwikkeling in ’n aangrensende porie be¨ınvloed. Die model word eers vir nie-ewewig toestande ondersoek, waar ons hoofsaaklik die kinetiese eienskappe van die stelsel beskou, en daarna word dit vir ewewig ondersoek, waar ons die aard van die dinamiese korrelasie binne die gekoppelde kanaalstelsel probeer verstaan. Vir die nie-ekwilibrium weergawe van die model word die fokus op die gedrag van twee gekoppelde en eindige kanale se bestendige toestand gerig. Die porie¨e bly aan hulle eindpunte in kontak met reservoirs van deeltjies. Daar word drie deeltjiestroom-digtheid gebiede ge¨ıdentifiseer met behulp van ’n simulasieeksperiment. Die sensitiewiteit van die stelsel se gemiddelde deeltjiebesettingsprofiel en die deeltjievloed in ’n bestendige toestand is ondersoek vir groot en klein koppelingsparameters. Vir klein koppelingsterkte vind ons dat die stelsel se bestendige toestand deeltjiebesettingspofiel en deeltjievloed deur ’n eenvoudige gemiddelde-veld teorie beskryf kan word, waar digtheid-degtheids korrelasies verontagsaam kan word. Ons bied die analitiese beskrywing aan vir die gekoppelde stelsel deur van ’n sellulˆere outomaat-formalisme gebruik te maak, en om dan die teorie te veralgemeen vir ’n stelsel bestaande uit vele aanmekaar gekoppelde porie¨e ,deur gebruik te maak van ’n formalisme waarin deeltjies tussen holtes hop. Die analtiese resultate word vir kleine waardes van die koppelingsparameter deur ’n rekenaarsimulasie bevestig. Vir die ekwilibrium gesigspunt modelleer ons die gekoppelde stelsel van kanale as oneindig nou, met ’n homogene verdeling van die deeeltjiebesetting en ons bereken digtheids-korrelasiefunksies. Die elastiese vebinding tussen porie¨e word deur ’n kortrykwydte potensiaal gemodelleer en die deeltjies se dinamika met behulp van Langevindinamika. Die dinamika word met behulp van die funksionaal integraalformalisme uitgedruk in terme van die deeltjiegetaldigtheid-, stroomdigtheid- en meegaande antwoordvelde. Die resulterende genererende funksionaal neem hierdie hoeveelhede tot tweede order binne die “random field approximation” (RPA). Vir ’n potensiaal met kort rykwydte, ondersoek ons die stelsel se gedrag deur die dinamiese digtheid-digtheidskorrelasie te ondersoek. Ons lei af dat die stelsel se langtyd effektiewe wrywingsko¨effisi¨ent afneem met die toename in die koppelingsparameter se waardes terwyl die sterkte van die termiese kragte vir die effektiewe stelsel renormeer word. Ons vind ook dat die RPA onder sekere omstandighede sy geldigheid verloor, wat ’n oorgang kan beteken wat nie meer deur ’n homogene digtheid beskryf kan word nie. Die werk wat hier aangebied word dui die eerste stappe aan vir hoe mikroskopiese insigte vir vul-, filter- en stoorprosesse vir sekere tipes mikroporeuse materiale gebruik kan word.

No description available.

This thesis studies two important carbon structures, graphene and carbon nanotubes, with the purpose of understanding how their three-dimensional electron density distribution affects the way fast ions interact with them. <br /><br /> A brief introduction to research in pure carbon structures is made. We then use different models to calculate the equilibrium electron density distribution in graphene and carbon nanotubes. <br /><br /> In the second part of the thesis we investigate fast ions moving parallel to a graphene sheet and experiencing forces due to the dynamic polarization of carbon valence electrons. Using the three-dimensional electron density distribution of graphene, we calculate the force directly opposing the ion's motion (stopping force), as well as the force which bends the ion's trajectory towards the sheet (image force). It is our purpose to compare these results with those based on a two-dimensional hydrodynamic model of graphene, which approximates the electron distribution of graphene by a charged fluid confined to the two-dimensional plane of the sheet. <br /><br /> The results obtained for interactions of ions with a single graphene sheet should be useful for a further analysis of ion channeling through carbon nanostructures.

SiC has become an attractive wide bandgap semiconductor due to its unique physical and electronic properties and is widely used in high temperature, high frequency, high power and radiation resistant applications. SiC has been used as an alternative to Si in harsh environments such as in the oil industry, nuclear power systems, aeronautical, and space applications. SiC is also known for its polytypism and among them 3C-SiC, 4H-SiC and 6H-SiC are the most common polytypes used for research purposes. Among these polytypes 4H-SiC is gaining importance due to its easy commercial availability with a large bandgap of 3.26 eV at room temperature. Controlled creation of defects in materials is an approach to modify the electronic properties in a way that new functionality may result. SiC is a promising candidate for defect-induced magnetism on which spintronic devices could be developed. The defects considered are of room temperature stable vacancy types, eliminating the need for magnetic impurities, which easily diffuse at room temperature. Impurity free vacancy type defects can be created by implanting the host atoms of silicon or carbon. The implantation fluence determines the defect density, which is a critical parameter for defect induced magnetism. Therefore, we have studied the influence of low fluence low energy silicon and carbon implantation on the creation of defects in n-type 4H-SiC. The characterization of the defects in these implanted samples was performed using the techniques, RBS-channeling and Raman spectroscopy. We have also utilized these characterization techniques to analyze defects created in much deeper layers of the SiC due to implantation of high energy nitrogen ions. The experimentally determined depths of the Si damage peaks due to low energy (60 keV) Si and C ions with low fluences (< 1015 cm-2) are consistent with the SRIM-2011 simulations. From RBS-C Si sub-lattice measurements for different fluences (1.1×1014 cm-2 to 3.2×1014 cm-2) of Si implantation in 4H-SiC, the Si vacancy density is estimated to range from 1.29×1022 cm-3 to 4.57×1022 cm-2, corresponding to average vacancy distances of 4.26 Å to 2.79 Å at the damage peak (50±5 nm). Similarly, for C implanted fluences (1.85×1014 cm-2 to 1×1015 cm-2), the Si vacancy density varies from 1.37×1022 cm-3 to 4.22×1022 cm-3 with the average vacancy distances from 4.17 Å to 2.87 Å at the damage peak (110±10 nm). From the Raman spectroscopy, the implantation-induced lattice disorders calculated along the c-axis (LO mode) and perpendicular to c-axis (TO mode) in 4H-SiC are found to be similar. Furthermore, the results obtained from SQUID measurements in C implanted n-type 4H-SiC sample with fluences ranging from 1×1012 to 1.7×1016 ions/cm2 have been discussed. The implanted samples showed diamagnetism similar to the unimplanted sample. To date, to our best of knowledge, no experimental work has been reported on investigating defect induced magnetism for self-ion implantation in n-type 4H-SiC. These first reports of experimental results can provide useful information in future studies for a better understanding of self-ion implantation in SiC-based DMS.

This thesis studies two important carbon structures, graphene and carbon nanotubes, with the purpose of understanding how their three-dimensional electron density distribution affects the way fast ions interact with them. <br /><br /> A brief introduction to research in pure carbon structures is made. We then use different models to calculate the equilibrium electron density distribution in graphene and carbon nanotubes. <br /><br /> In the second part of the thesis we investigate fast ions moving parallel to a graphene sheet and experiencing forces due to the dynamic polarization of carbon valence electrons. Using the three-dimensional electron density distribution of graphene, we calculate the force directly opposing the ion's motion (stopping force), as well as the force which bends the ion's trajectory towards the sheet (image force). It is our purpose to compare these results with those based on a two-dimensional hydrodynamic model of graphene, which approximates the electron distribution of graphene by a charged fluid confined to the two-dimensional plane of the sheet. <br /><br /> The results obtained for interactions of ions with a single graphene sheet should be useful for a further analysis of ion channeling through carbon nanostructures.