The interaction of fast neutrons with shielding and fusion blanket materials

In the present work the neutron emission spectra from a graphite cube, and from natural uranium, lithium fluoride, graphite, lead and steel slabs bombarded with 14.1 MeV neutrons were measured to test nuclear data and calculational methods for D - T fusion reactor neutronics. The neutron spectra measured were performed by an organic scintillator using a pulse shape discrimination technique based on a charge comparison method to reject the gamma rays counts. A computer programme was used to analyse the experimental data by the differentiation unfolding method. The 14.1 MeV neutron source was obtained from T(d,n)4He reaction by the bombardment of T - Ti target with a deuteron beam of energy 130 KeV. The total neutron yield was monitored by the associated particle method using a silicon surface barrier detector. The numerical calculations were performed using the one-dimensional discrete-ordinate neutron transport code ANISN with the ZZ-FEWG 1/ 31-1F cross section library. A computer programme based on Gaussian smoothing function was used to smooth the calculated data and to match the experimental data. There was general agreement between measured and calculated spectra for the range of materials studied. The ANISN calculations carried out with P3 - S8 calculations together with representation of the slab assemblies by a hollow sphere with no reflection at the internal boundary were adequate to model the experimental data and hence it appears that the cross section set is satisfactory and for the materials tested needs no modification in the range 14.1 MeV to 2 MeV. Also it would be possible to carry out a study on fusion reactor blankets, using cylindrical geometry and including a series of concentric cylindrical shells to represent the torus wall, possible neutron converter and breeder regions, and reflector and shielding regions.

N–Dimensional Orthogonal Tile Sizing Problem

AMS subject classification: 68Q22, 90C90

Double complexes and vanishing of Novikov cohomology

2010 Mathematics Subject Classification: Primary 18G35; Secondary 55U15.

Fibrations and contact structures

We prove that a closed 3-dimensional manifold is a torus bundle over the circle if and only if it carries a closed nonsingular 1-form which is linearly deformable into contact forms.

Some examples of special Lagrangian tori

A short paper giving some examples of smooth hypersurfaces M of degree n+1 in complex projective n-space that are defined by real polynomial equations and whose real slice contains a component diffeomorphic to an n-1 torus, which is then special Lagrangian with respect to the Calabi-Yau metric on M.

A solution to the three disjoint path problem on honeycomb tori

In a previous paper we solved an open problem named as the three disjoint path problem on honeycomb meshes. In this paper we extend the technique used to solve the related problem on honeycomb tori. The result gives the minimum possible length of the longest of any three disjoint paths between two given nodes in a torus. The problem has practical benefits in the fault tolerant aspects of interconnection topologies.

The silent statue theme: complex imitation and Neo-Latin poetry

This paper analyses how the topic of the silent statue is dealt with in Neo-Latin literature. The subject matter comes from the epigrams about Pythagoras of the Palatine Anthology. There are numerous Neo-Latin imitations of this topic that are complex as various sources are used at the same time. The authors focus on an active reading of the epigrams of their predecessors, applying the traditional motive to new subjects and adapting it to the religious theme.

Tração de caninos superiores inclusos

Hoje em dia o médico dentista depara-se frequentemente com situações de inclusão canina. Sendo o canino um dente fundamental para o desenvolvimento harmonioso da estética dentária, facial e da função mastigatória, torna-se importante estudar abordagens que solucionem esta condição. Várias abordagens multidisciplinares têm sido desenvolvidas com recurso à Ortodontia, Cirurgia, Periodontia e Dentisteria. O objetivo desta revisão bibliográfica é o estudo e comparação de duas técnicas cirúrgicas de exposição de caninos inclusos maxilares: técnica aberta e técnica fechada. A técnica aberta consiste na exposição do canino, isolamento da área cirúrgica recorrendo a um cimento periodontal e posterior instalação de um acessório com vista à tração ortodôntica. Na técnica fechada a exposição cirúrgica e a instalação do acessório de tração são executados na mesma consulta, procedendo-se de seguida ao fecho e sutura do retalho. A escolha da técnica tem por base critérios como a localização vestíbulo-palatina, a quantidade de gengiva aderida presente na área de inclusão, posição mésio-distal e vertical da coroa do canino. Existe controvérsia entre os autores no que toca à escolha da técnica cirúrgica a utilizar. Nesse sentido são expostas as vantagens, desvantagens, indicações e protocolos de cada técnica, de modo a obter um melhor entendimento do tema. Existem também diversas opções em relação à escolha do dispositivo de tração ortodôntica a utilizar. Na década de 60 começou por se utilizar a técnica do laço de fio de aço, no entanto a manifestação de problemas periodontais decorrentes da sua utilização, bem como a evolução dos sistemas adesivos levaram ao desenvolvimento de acessórios de colagem direta e o uso de correntes metálicas.

Prótese obturadora palatina

Nos pacientes com defeitos ósseos palatinos congénitos ou adquiridos, quando a possibilidade de reconstrução cirúrgica não existe, poderá ter de se utilizar uma prótese obturadora palatina, com vista ao restabelecimento das funções do sistema estomatognático, tais como, a fonética, deglutição e mastigação. Contudo, esta necessidade não é só funcional mas também estética e psicológica, com vista a melhorar a qualidade de vida dos pacientes. As próteses obturadoras palatinas têm vindo a desenvolver há alguns séculos, com o aprimoramento das técnicas de confecção e materiais dentários que auxiliam na elaboração, cada vez mais eficientes, principalmente no que se refere a sua adaptação. Neste trabalho realizou-se uma revisão narrativa da literatura sobre próteses obturas palatinas utilizando as palavras-chave: maxillary birth bony defects; maxillary acquired bony defects; obturator prosthesis; prosthetic rehabilitation in maxillary defects; inflatable hollow obturator; prosthodontic rehabilitation of maxillary defects. Os objectivos deste trabalho foi o de conhecer os diferentes tipos de próteses obturadoras palatinas utilizadas na reabilitação de pacientes com defeitos ósseos palatinos, bem como, as suas indicações, contra-indicações, os cuidados de utilização e o protocolo clínico e laboratorial de confecção. As próteses obturadoras palatinas são assim uma solução possível na reabilitação funcional de um número grande de pacientes com defeitos ósseos palatinos, no entanto, o seu sucesso está dependente do correcto planeamento e da execução clínica e laboratorial cuidadosa.

ANOSOV MAPS, POLYCYCLIC GROUPS AND HOMOLOGY

Many manifolds that do not admit Anosov diffeomorphisms are constructed. For example: the Cartesian product of the Klein bottle and a torus.

Alternating surgeries

This thesis is concerned with the question of when the double branched cover of an alternating knot can arise by Dehn surgery on a knot in S^3. We approach this problem using a surgery obstruction, first developed by Greene, which combines Donaldson's Diagonalization Theorem with the $d$-invariants of Ozsvath and Szabo's Heegaard Floer homology. This obstruction shows that if the double branched cover of an alternating knot or link L arises by surgery on S^3, then for any alternating diagram the lattice associated to the Goeritz matrix takes the form of a changemaker lattice. By analyzing the structure of changemaker lattices, we show that the double branched cover of L arises by non-integer surgery on S^3 if and only if L has an alternating diagram which can be obtained by rational tangle replacement on an almost-alternating diagram of the unknot. When one considers half-integer surgery the resulting tangle replacement is simply a crossing change. This allows us to show that an alternating knot has unknotting number one if and only if it has an unknotting crossing in every alternating diagram. These techniques also produce several other interesting results: they have applications to characterizing slopes of torus knots; they produce a new proof for a theorem of Tsukamoto on the structure of almost-alternating diagrams of the unknot; and they provide several bounds on surgeries producing the double branched covers of alternating knots which are direct generalizations of results previously known for lens space surgeries. Here, a rational number p/q is said to be characterizing slope for K in S^3 if the oriented homeomorphism type of the manifold obtained by p/q-surgery on K determines K uniquely. The thesis begins with an exposition of the changemaker surgery obstruction, giving an amalgamation of results due to Gibbons, Greene and the author. It then gives background material on alternating knots and changemaker lattices. The latter part of the thesis is then taken up with the applications of this theory.

Problems in number theory and hyperbolic geometry

In the first part of this thesis we generalize a theorem of Kiming and Olsson concerning the existence of Ramanujan-type congruences for a class of eta quotients. Specifically, we consider a class of generating functions analogous to the generating function of the partition function and establish a bound on the primes ℓ for which their coefficients c(n) obey congruences of the form c(ℓn + a) ≡ 0 (mod ℓ). We use this last result to answer a question of H.C. Chan. In the second part of this thesis [S2] we explore a natural analog of D. Calegari’s result that there are no hyperbolic once-punctured torus bundles over S^1 with trace field having a real place. We prove a contrasting theorem showing the existence of several infinite families of pairs (−χ, p) such that there exist hyperbolic surface bundles over S^1 with trace field of having a real place and with fiber having p punctures and Euler characteristic χ. This supports our conjecture that with finitely many known exceptions there exist such examples for each pair ( −χ, p).

On Besov spaces modelled on Zygmund spaces

Working on the d-torus, we show that Besov spaces Bps(Lp(logL)a) modelled on Zygmund spaces can be described in terms of classical Besov spaces. Several other properties of spaces Bps(Lp(logL)a) are also established. In particular, in the critical case s=d/p, we characterize the embedding of Bpd/p(Lp(logL)a) into the space of continuous functions.

On continuous families of geometric Seifert conemanifold structures

In this paper, dedicated to Prof. Lou Kauffman, we determine the Thurston’s geometry possesed by any Seifert fibered conemanifold structure in a Seifert manifold with orbit space (Formula presented.) and no more than three exceptional fibers, whose singular set, composed by fibers, has at most three components which can include exceptional or general fibers (the total number of exceptional and singular fibers is less than or equal to three). We also give the method to obtain the holonomy of that structure. We apply these results to three families of Seifert manifolds, namely, spherical, Nil manifolds and manifolds obtained by Dehn surgery on a torus knot (Formula presented.). As a consequence we generalize to all torus knots the results obtained in [Geometric conemanifolds structures on (Formula presented.), the result of (Formula presented.) surgery in the left-handed trefoil knot (Formula presented.), J. Knot Theory Ramifications 24(12) (2015), Article ID: 1550057, 38pp., doi: 10.1142/S0218216515500571] for the case of the left handle trefoil knot. We associate a plot to each torus knot for the different geometries, in the spirit of Thurston.