Periodic orbits of the planar collision restricted 3-body problem

Using the continuation method we prove that the circular and the elliptic symmetric periodic orbits of the planar rotating Kepler problem can be continued into periodic orbits of the planar collision restricted 3–body problem. Additionally, we also continue to this restricted problem the so called “comets orbits”.

Polynomial-time complexity for instances of the endomorphism problem in free groups

We say the endomorphism problem is solvable for an element W in a free group F if it can be decided effectively whether, given U in F, there is an endomorphism Φ of F sending W to U. This work analyzes an approach due to C. Edmunds and improved by C. Sims. Here we prove that the approach provides an efficient algorithm for solving the endomorphism problem when W is a two- generator word. We show that when W is a two-generator word this algorithm solves the problem in time polynomial in the length of U. This result gives a polynomial-time algorithm for solving, in free groups, two-variable equations in which all the variables occur on one side of the equality and all the constants on the other side.

Bribe-proof rules in the division problem

The division problem consists of allocating an amount of a perfectly divisible good among a group of n agents with single-peaked preferences. A rule maps preference profiles into n shares of the amount to be allocated. A rule is bribe-proof if no group of agents can compensate another agent to misrepresent his preference and, after an appropriate redistribution of their shares, each obtain a strictly preferred share. We characterize all bribe-proof rules as the class of efficient, strategy-proof, and weak replacement monotonic rules. In addition, we identify the functional form of all bribe-proof and tops-only rules.

Stable condorcet rules

We consider the following allocation problem: A fixed number of public facilities must be located on a line. Society is composed of $N$ agents, who must be allocated to one and only one of these facilities. Agents have single peaked preferences over the possible location of the facilities they are assigned to, and do not care about the location of the rest of facilities. There is no congestion. In this context, we observe that if a public decision is a Condorcet winner, then it satisfies nice properties of internal and external stability. Though in many contexts and for some preference profiles there may be no Condorcet winners, we study the extent to which stability can be made compatible with the requirement of choosing Condorcet winners whenever they exist.

A maximal domain of preferences for tops-only rules in the division problem

The division problem consists of allocating an amount M of a perfectly divisible good among a group of n agents. Sprumont (1991) showed that if agents have single-peaked preferences over their shares, the uniform rule is the unique strategy-proof, efficient, and anonymous rule. Ching and Serizawa (1998) extended this result by showing that the set of single-plateaued preferences is the largest domain, for all possible values of M, admitting a rule (the extended uniform rule) satisfying strategy-proofness, efficiency and symmetry. We identify, for each M and n, a maximal domain of preferences under which the extended uniform rule also satisfies the properties of strategy-proofness, efficiency, continuity, and "tops-onlyness". These domains (called weakly single-plateaued) are strictly larger than the set of single-plateaued preferences. However, their intersection, when M varies from zero to infinity, coincides with the set of single-plateaued preferences.

Morfologia do Mycobacterium leprae hominis e do M. leprae muris: estudo baseado na microscopia electrônica e de contraste de fases

Hansen's Bacillus: By electron microscopy this bacillus shows membrane and halo, this being more visible when sorrounding the globi or bundles of bacilli; shows, also, free granules of various sizes which were before considered as dust of the dyes; shows external granules bound with the membrane and some times branching. By phases contrast microscopy examining leproma suspensions and subcataneous lymph at 400 x we saw many free granules with intense rotatory movement; granulated bacilli with screw, skip or stroke motion, producing slow progressive motion. All such elementes are surrounded by a halo, corresponding to the classical gloea. By a patient and delayed examination we were able to see that the internal granules are motile and help the progression of the bacilli, giving the impression that the cytoplasm is liquid. By a lasting observation we could see the larger granules form prolapse, like a pseudopode and abandon the bacilli and going in very rapid rotatory movement. There are branched bacilli; there are pedunculated fred granules like comets. The addition of a drop of formol at the preparation stops all movements. Stefansky's Bacillus: Repeated examination by RCA electron microscope, type EMU-25 of fresh suspensions of rat lepromas, led us to confirm the close relationship between human and murine leprosy agents. We examined also material from carabo (Lepra bubalorum) from Java, but due to fixation, the material was unsuitable for comparative studies. The Stefansky's bacilli showed also emmbranes and halos, internal or external granules (smaller than those of Hansen's bacillus). The bacilli shaded by chromium look thicker and shorter than those of Hansen. Due to electron bombardment both, Hansen's and Stefansky's baccilli suffer considerable alterations in their structure, showing black barrs of chromatin condensation at their extremities as also in their centers. By phase microscopy the Stefansky's bacilli showed elements with 1, 2 (bipolar), 3 or more internal small granules, developing identical movements as those of Hansen. The globi seem to be non-motile but the free bacilli appearing around the globi show intense movement. At 1000 x the examination is less satisfactory than at 400 x. The addition of formol solution in the preparation suppresses all movements, even the brownian, but the material becomes more suitable for the study of static morphology of the bacilli. CONCLUSION - The electron and phases contrast microscopy of leprous material from different types and phases of the disease may explain some of the unknown aspects of the biology and morphology of the bacilli.

Limitations and biases of conventional analysis of climate change. Towards an analysis coherent with sustainable development

This paper shows the numerous problems of conventional economic analysis in the evaluation of climate change mitigation policies. The article points out the many limitations, omissions, and the arbitrariness that have characterized most evaluation models applied up until now. These shortcomings, in an almost overwhelming way, have biased the result towards the recommendation of a lower aggressiveness of emission mitigation policies. Consequently, this paper questions whether these results provide an appropriate answer to the problem. Finally, various points that an analysis coherent with sustainable development should take into account are presented.

Normal forms for rational difference equations with applications to the global periodicity problem

We propose a classification and derive the associated normal forms for rational difference equations with complex coefficients. As an application, we study the global periodicity problem for second order rational difference equations with complex coefficients. We find new necessary conditions as well as some new examples of globally periodic equations.

Terceira contribuicäo ao conhecimento do gênero Archytas Jaennicke, 1867: (Diptera, Tachinidae)

Twelve species of the genus Archytas Jennicke, 1867, eight of which described as new are studied and figured in detail. Definitions of the species are based mainly on characters of male genitalia. The male genital characters are the most significant for separation of the species and most demonstrative of their affinities. By examining a long series of species of this genus we came to the conclusion that the presence of one pair of median marginal bristles on the third abdominal tergite seems to be characteristic of the genus. This caracter apparently so important, is not however considered fundamental. The most significant example is found in Archytas lenkoi sp. n. and Archytas vexor Curran, 1928. In A. lenkoi we can find one or two pairs or thay may, less frquently, be absent. In A. vexor these bristles are lacking. The shape of the male copulatory apparatus of Jurinia nitidiventris Curran, 1928 refered to by CURRAN in his "Revision of Archytas", is not characteristic of any species of the group and so, is not considered in this paper. To help in the identification, the species studied here are divided into groups. The analis group" includes: A. apicifer (Walker, 1894), A. californiae (Walker, 1856), A. nivalis Curran, 1928, a. giacomellii (Blanchard, 1941), A. basifulvus (Walker, 1849), A. incasanus Townsend, 1912 and A. cirphis Curran, 1927. The identification of members of these group is extremely difficult owing both to their similarity in colour pattern and to their variability. They all have black testaceous or dark brown abdomen, the last segment pale or brownish pollinose; second segment without bristles; third with a pair of strong marginals, fourth and fifth with two rows of discals on apical third. The final determination often rests upon the structure of the male copulatory apparatus. Fortunately in this group, many of the forcipes superiores and palpi genitalium are strikingly different from one another. The "zikani group" includes: A. zikani sp. n., A seabrai sp. n., A. duckei sp. n. and A. vernalis Curran, 1928. This group may be characterized as follows: forcipes interiores absent; forcipes superiores strongly chitinized an dilated at anex. Within this group, the forcipes of. A. seabrai sp. n. do not present an aberrant form. The "dissimilis group" will be studied in forthcoming papers. The limits of the genus Archyta Jaen. are not as yet sharply difined, the evaluation of the significance of each character used in the definition remaining as most difficult problem. The distinction between Archytas and other related genera is very difficult, chiefly because it is based on variable characters. In this paper we place the genera Parafabricia Towsend, 1931, Itachytas Blanchard, 1940, Archynemochaeta Blanchard, 1941, Proarchytoides Blanchard, 1941 and Archytodejeania Blanchard, 1941 in the synonymy of Archytas Jaen. The detailed examination of the characters used in their definition, proved them to be fundamentally proposed on basis of chaetotasy, these characters alone being precarious, because of the considerabel intraspecifical variation. The type of the new species are in the Oswaldo Cruz Institute collection. Rio de Janeiro, Brazil, and paratypes in the collections of the followings institutions: Departamento de Zoologia da Secretaria de Agricultura do Estado de São Paulo; Instituto de Ecologia e Experimemtação Agrícolas; Departamento de Defesa Sanitária Vegetal; Campos Seabra collection; and Barbiellini collection.

Fabricació de Lents Zonals de Fresnel per aplicació als raigs X tous

Estudi elaborat a partir d’una estada al Paul Scherrer Institut del Maig a l’Octubre del 2006 amb l’ajuda i supervisió dels Dr. Konstantins Jefimovs i Dr. Christian David. Focalitzar raigs X tous és una necessitat essencial per al microanàlisis, la microscopia, i fer imatges en moltes Instal·lacions de Radiació Sincrotró. Les Lents Zonals de Fresnel (FZP, de la denominació anglesa “Fresnel Zone Plates”) han demostrat donar uns punts focals amb una resolució espacial destacada i una baixa il·luminació de fons. Tanmateix, la fabricació de FZP és complexa i no totalment reproduïble. A més a més, el temps de vida de les FZP és força curt, ja que estant situades sobre membranes de nitrur de silici molt fines i altament absorbents. Per tant, hem fet esforços per implementar FZP de silici, que s’espera que siguin més resistents. L’element està fet d’una oblia de cristall de silici poc absorbent, i no presenta cap interfase entre materials. Així doncs, aquestes lents són especialment adequades per a aguantar les extremes càrregues de radiació de les fonts de raigs X més brillants. Particularment, això és molt important per a les aplicacions a les pròximes generacions de fonts de raigs X, com els Làsers d’Electrons Lliures (FEL, de la denominació anglesa “Free Electron Laser”). El silici també garanteix que no hi hagi cap banda d’absorció en el rang d’energies de la finestra de l’aigua (200-520 eV), fent aquestes lents ideals per a fer imatges de mostres biològiques. En aquest informe, hi ha una descripció detallada de tots els passos involucrats en la fabricació de les Lents Zonals de Fresnel de silici. En resum, les estructures de FZP es modelen sobre una resina utilitzant litografia per feix d’electrons i llavors el patró es transmet al silici mitjançant un gravat d’ions reactius (RIE, de la denominació anglesa ‘Reactive Ion Etching’) utilitzant una fina (20 nm) màscara de Crintermitja. Les membranes de silici es poden aprimar després de la fabricació de les estructures per a garantir una transmissió suficient fins i tot a baixes energies. Aquest informe també inclou l’anàlisi i la discussió d’alguns experiments preliminars per avaluar el rendiment de les Si FZPs fets a la línia de llum PolLux del Swiss Ligth Source amb l’ajuda dels Dr. Jörg Raabe i Dr. George Tzvetkov.

Metodologia a seguir per la reconstrucció d’imatges mèdiques i la seva transformació en geometries mallades per a l’ús computacional

Estudi elaborat a partir d’una estada a l'Imperial College of London, Gran Bretanya, entre setembre i desembre 2006. Disposar d'una geometria bona i ben definida és essencial per a poder resoldre eficientment molts dels models computacionals i poder obtenir uns resultats comparables a la realitat del problema. La reconstrucció d'imatges mèdiques permet transformar les imatges obtingudes amb tècniques de captació a geometries en formats de dades numèriques . En aquest text s'explica de forma qualitativa les diverses etapes que formen el procés de reconstrucció d'imatges mèdiques fins a finalment obtenir una malla triangular per a poder‐la processar en els algoritmes de càlcul. Aquest procés s'inicia a l'escàner MRI de The Royal Brompton Hospital de Londres del que s'obtenen imatges per a després poder‐les processar amb les eines CONGEN10 i SURFGEN per a un entorn MATLAB. Aquestes eines les han desenvolupat investigadors del Bioflow group del departament d'enginyeria aeronàutica del Imperial College of London i en l'ultim apartat del text es comenta un exemple d'una artèria que entra com a imatge mèdica i surt com a malla triangular processable amb qualsevol programari o algoritme que treballi amb malles.

The viral nature of Toddia França, 1912

Toddia França, 1912 under the light microscope occurs as inclusion corpuscles in the cytoplasm of erythrocytes of cold-blooded vertebrates sometimes accompanied by crystalloid bodies. Its position among the protozoans or the viruses has been discussed by some authors, but remained unclear. To elucidate this problem we studied Toddia from a Brazilian frog (Leptodactylus ocellatus) by electron microscopy. In the cytoplasm of the infected cells we found no protozoan, but rather virus-like particles often hexagonal in outline, averaging 195 nm excluding their two involving membranes, and presenting a central area of variable electron density. Particles at different stages of development were generally found around or on area lighter density than the cytoplasm. which resembled a virus synthesis site. At high magnification, the nuclear or cytoplasmic crystals allied to Toddia resembled the crystalline lattice of the inclusion bodies associated with the polyhedrosis viruses and poxviruses from insects, of the capsules of granulosis viruses and of other protein crystals in ultrathin sections. Cytochemical tests in Toddia corpuscles displayed exclusively the presence of deoxyribonucleic acid. These findings indicate that Toddia is not a protozoan and demonstrate that it is in all probability a viral inclusion corpuscle. Taking into account the nucleic acid type found in its structure (DNA) and the hexagonal shape usually shown in ultrathin sections by its component particles, which have a cytoplasmic site of synthesis and assembly, we tentatively relate Toddia with the so-called "Icosahedral Cytoplasmic Deoxyriboviruses". We believe that the present paper gives the first report of virus-like particles in L. ocellatus.