No description available.

No description available.

Thesis (Ph. D.)--University of Pennsylvania, 1919. / A digital reproduction is available from the Open Collections Program at Harvard University, Women and work collection.

Thesis (Ph. D.)--University of Pennsylvania, 1919.

No description available.

The classical (proper) graph colouring problem asks for a colouring of the vertices of a graph with the minimum number of colours such that no two vertices with the same colour are adjacent. Equivalently the colouring is required to be such that the graph induced by the vertices coloured the same colour has the maximum degree equal to zero. The graph parameter associated with the minimum possible number of colours of a graph is called chromatic number of that graph. One generalization of this classical problem is to relax the requirement that the maximum degree of the graph induced by the vertices coloured the same colour be zero, and instead allow it to be some integer d. For d = 0, we are back at the classical proper colouring. For other values of d we say that the colouring has defect d. Another generalization of the classical graph colouring, is list colouring and its associated parameters: choosability and choice number. The main result of this thesis is to show that every graph G of Euler genus μ is ⌈2 + √(3μ + 3)⌉–choosable with defect 1 (equivalently, with clustering 2). Thus allowing any defect, even 1, reduces the choice number of surface embeddable graphs below the chromatic number of the surface. For example, the chromatic number of the family of toroidal graphs is known to be 7. The bound above implies that toroidal graphs are 5-choosable with defect 1. This strengthens the result of Cowen, Goddard and Jesurum (1997) who showed that toroidal graphs are 5-colourable with defect 1. In a graph embedded in a surface, two faces that share an edge are called adjacent. We improve the above bound for graphs that have embeddings without adjacent triangles. In particular, we show that every non-planar graph G that can be embedded in a surface of Euler genus μ without adjacent triangles, is ⌈(5+ √(24μ + 1)) /3⌉–choosable with defect 1. This result generalizes the result of Xu and Zhang (2007) to all the surfaces. They proved that toroidal graphs that have embeddings on the torus without two adjacent triangles are 4-choosable with defect 1.

RNA recombination is a major factor driving viral evolution and contributing to new disease outbreaks. Therefore, understanding the mechanism of RNA recombination can help scientists to develop longer lasting antiviral strategies. Tombusviruses are one of the best model RNA viruses to study RNA virus recombination. My goals were to dissect the mechanism of tombusviral RNA recombination. To do so, in my thesis, I describe my results on the roles of (i) the viral replicase and the viral RNA templates; and (ii) the effect of host factors on tombusvirus recombination events. To study the mechanism of RNA recombination without the influence of selection pressure on the emerging recombinants, we developed an in vitro RNA recombination assay based on viral RNA templates and purified viral replicase preparations. Using this in vitro assay, we demonstrated that replicase driven template switching is the mechanism of recombination, whereas RNA ligation seems less likely to be a major mechanism. In addition, we also studied the role of RNA substrates, in more detail. Our results showed that viral replicase preferred to use functional RNA domains in the acceptor RNAs over random switching events. Host factors may also play important roles in RNA recombination. Using yeast as a model system for studying replication and recombination of a tombusvirus replicon, we identified 9 host genes affecting tombusvirus RNA recombination. Separate deletion of five of these genes enhanced generation of novel viral RNA recombinants. Further studies on one of these genes, XRN1, a 5-3 exoribonuclease, indicated that it might be involved in degradation of tombusvirus RNAs. Lack of Xrn1p resulted in accumulation of truncated (partially degraded) replicon RNAs, which became good templates for RNA recombination. To further study Xrn1p, we overexpressed Xrn4p of Arabidopsis thaliana, a functional analogue of the yeast Xrn1p, in Nicotiana benthamiana plants. After superinfecting the Xrn4p-overexpressing N. benthamiana with tombusvirus, truncated tombusvirus genomic and subgenomic RNA1 were observed. Some of the identified tombusvirus variants were infectious in protoplasts and could systemically infected N. benthamiana plants. Overall, this is the first report that a single host gene can affect rapid viral evolution and RNA recombination.

Given a real parameter-dependent matrix, we obtain an algorithm for computing the value of the parameter and corresponding eigenvalue for which two eigenvalues of the matrix coalesce to form a 2-dimensional Jordan block. Our algorithms are based on extended versions of the implicit determinant method of Spence and Poulton [55]. We consider when the eigenvalue is both real and complex, which results in solving systems of nonlinear equations by Newton’s or the Gauss-Newton method. Our algorithms rely on good initial guesses, but if these are available, we obtain quadratic convergence. Next, we describe two quadratically convergent algorithms for computing a nearby defective matrix which are cheaper than already known ones. The first approach extends the implicit determinant method in [55] to find parameter values for which a certain Hermitian matrix is singular subject to a constraint. This results in using Newton’s method to solve a real system of three nonlinear equations. The second approach involves simply writing down all the nonlinear equations and solving a real over-determined system using the Gauss-Newton method. We only consider the case where the nearest defective matrix is real. Finally, we consider the computation of an algebraically simple complex eigenpair of a nonsymmetric matrix where the eigenvector is normalised using the natural 2-norm, which produces only a single real normalising equation. We obtain an under-determined system of nonlinear equations which is solved by the Gauss-Newton method. We show how to obtain an equivalent square linear system of equations for the computation of the desired eigenpairs. This square system is exactly what would have been obtained if we had ignored the non uniqueness and nondifferentiability of the normalisation.

Darbe aiškinamasi, kokiais teisės aktais ir kokiais juose įtvirtintais kokybės kriterijais remiantis nustatoma ar konkreti vartojimo prekė (paslauga) atitinka kokybės reikalavimus arba atvirkščiai jų neatitinka. Nekokybiškumo samprata atkleidžiama tiek Lietuvos, tiek Europos Sąjungos lygmenyje; išryškinamos problemos, susijusios su ES teisėje numatyto prekės atitikties sutarčiai principo perkėlimu į nacionalines teisės sistemas. Antrojoje darbo dalyje tiriami konkretūs probleminiai klausimai vartotojams įrodinėjant prekės (paslaugos) nekokybiškumą, o būtent: pareigos pranešti apie kokybės trūkumus įtaka vartotojo teisių gynimui, komercinės/teisinės garantijos, šešių mėnesių nekokybiškumo prezumpcijos taikymo problemos ir perspektyvos. Trečiojoje darbo dalyje kiekvienas teisės gynimo būdas aptariamas atskirai, atliekant išsamią Lietuvos ir ES teisinio reguliavimo, teisės doktrinos ir teismų praktikos analizę; atskleidžiama konkretaus vartotojo teisių gynimo būdo problematika, pateikiami galimi sprendimo variantai. Atkreiptinas dėmesys, kad kiekvienoje darbo dalyje, remiantis dabartiniu teisiniu reguliavimu pirmiausia pateikiamos konkretaus nagrinėjamo klausimo teorinės nuostatos, vėliau jos susiejamos su teismų praktika, teisės doktrinoje išsakytomis pozicijomis, atliktų tyrimų duomenimis, ir galiausiai pereinama prie konkrečių praktinių problemų analizės, pateikiami galimi jų sprendimo variantai ir įvertinamos teisinio reguliavimo perspektyvos. Kadangi šiuo darbu reaguojama... [toliau žr. visą tekstą] / The object of the academic master work is to analyze the problems faced by the consumers in case of defective goods (services) and the court’s practice on this matter. The academic master work begins with the examination of the legislation and of the special quality criteria that are laid down for determining whether a particular consumer good (service) meets the quality requirements or vice versa, they do not. The conception of defectiveness is revealed in the two levels: Lithuanian and European Union; the problems associated with the transposition of the principle of conformity with the contract to the national law systems are pointed out. In the second part of academic master work the particular problematic issues that arises while consumers prove the defectiveness of goods (services) are examined, namely: the duty of the consumer to notify the trader of quality deficiencies and it’s impact on consumer rights; the legal and commercial guarantees, six-month presumption’s of non-conformity application problems and perspectives. In the third part of work each of the possible remedies in the case of defective goods (services) is separately considered; by the analysis of Lithuanian and EU’s comprehensive regulatory, case law and legal doctrine, the problems associated with each remedy is revealed and the possible solutions are given. The point worth mentioning is that in each part of the academic master work first of all the theoretical provisions are pointed out, after they... [to full text]

Un simple regard porté sur la vie quotidienne suffit pour prendre conscience autant de la diversité des contrats que de la multitude des choses dangereuses qui nous entoure. La diversité contractuelle qui apparaît clairement dans le Code Civil et plus largement dans le droit civil, s’est aussi développée dans le droit commercial et plus amplement dans le droit des affaires. Quant aux choses dangereuses, comme souvent évoquée par la doctrine, elles sont de plus en plus considérées comme étant omniprésentes dans la société contemporaine. Les choses dangereuses peuvent être l’objet de tous les contrats qui existent et il ne fait pas de doute que l’intervention de ces dernières dans les contrats produit des effets autant sur leur formation que sur leur exécution. La présente recherche a donc pour objectif de déterminer quels sont ces effets dès lors que les choses dangereuses sont introduites volontairement ou non dans les contrats privés. Avant d’analyser lesdits effets, il s’est avéré nécessaire de définir au préalable et façon juridique, la notion de “chose dangereuse”. Cette définition a facilité l’étude de l’influence qu’exercent les choses dangereuses sur les contrats. L’analyse de ladite influence a permis d’élaborer un ensemble de règles pouvant s’appliquer, nos pas de façon sectorielle, mais d’une manière globale à tous les contrats portant sur les choses dangereuses. La détermination de cet ensemble de règle a pour objectif d’ assurer une gestion globale et efficace du danger (ou du risque) des choses dans le contrat. / A simple outlook on daily life is enough for becoming aware of the diversity of the contracts as well as the multitude of dangerous things which surround us. The contractual diversity which appears in the Civil Code and more widely in civil law, is also developed in commercial law and more generally in business law. As for dangerous things, like often mentioned by the doctrine, they are increasingly considered to be ubiquitous in the contemporary society.Dangerous things can be part of all contracts as diverse they may be. But there is no doubt that the intervention of dangerous things in contracts does not let them free and it has inevitably effects as much on their training as on their execution. That is the reason why which explains the choice of this subject. We intend to find what are the effects produced by dangerous things when they are intentionally or unintentionally introduced into private contracts.Before analyzing those effects, it was necessary to define first, legally speaking, the concept of "dangerous thing". Indeed, this definition facilitates the study of the influence of dangerous things on the contracts which concern them. The analysis of that influence of dangerous things will help to develop a set of rules that could be applied to all contracts relating to dangerous things.The purpose of this analysis is to explore ways to ensure comprehensive management of risk in the contract, which can be easily transposed to all contracts relating to dangerous things.