Generic Hypothesis Research Articles

The complex viewpoint for transverse impasse points of quasi-linear differential equations

The main purpose of this paper is to show that the singularities called impasse points of real implicit ordinary differential equations are generically branch points of the solution, using a complex viewpoint. This research starts from a result asserting that the real solution in most cases behaves like ±x−x0 at an impasse point (x0,y0). We extend the notion of regular impasse point defined in previous works, and consider instead transverse impasse point, where the underlying vector field is transverse to the singular locus, even in the case when this hypersurface is not a manifold locally.Here we make use of Puiseux expansions and we show that, under generic hypotheses, the solution is multivalued at such a point. We prove that the Puiseux exponent is related simply to the multiplicity of the impasse point in the singular locus: if M is the total multiplicity of the singularity (z0,y0), there is a unique solution at this point and it is M+1-valued.

Symmetries of the rolling model

In the present paper, we study the infinitesimal symmetries of the model of two Riemannian manifolds (M, g) and \(({\hat{M}},\hat{g})\) rolling without twisting or slipping. We show that, under certain genericity hypotheses, the natural bundle projection from the state space Q of the rolling model onto M is a principal bundle if and only if \({\hat{M}}\) has constant sectional curvature. Additionally, we prove that when M and \({\hat{M}}\) have different constant sectional curvatures and dimension \(n\ge 3\), the rolling distribution is never flat, contrary to the two dimensional situation of rolling two spheres of radii in the proportion \(1{:}3\), which is a well-known system satisfying E. Cartan’s flatness condition.

Does Immigration Undermine Public Support for Social Policy?

There has been great interest in the relationship between immigration and the welfare state in recent years, and particularly since Alesina and Glaeser’s (2004) influential work. Following literatures on solidarity and fractionalization, race in the U.S. welfare state, and anti-immigrant sentiments, many contend that immigration undermines public support for social policy. This study analyzes three measures of immigration and six welfare attitudes using 1996 and 2006 International Social Survey Program (ISSP) data for 17 affluent democracies. Based on multi-level and two-way fixed-effects models, our results mostly fail to support the generic hypothesis that immigration undermines public support for social policy. The percent foreign born, net migration, and the 10-year change in the percent foreign born all fail to have robust significant negative effects on welfare attitudes. There is evidence that the percent foreign born significantly undermines the welfare attitude that government “should provide a job for everyone who wants one.” However, there is more robust evidence that net migration and change in percent foreign born have positive effects on welfare attitudes. We conclude that the compensation and chauvinism hypotheses provide greater potential for future research, and we critically consider other ways immigration could undermine the welfare state. Ultimately, this study demonstrates that factors other than immigration are far more important for public support of social policy.

Inductive Solution of the Tangential Center Problem on Zero-Cycles

Given a polynomial $f\in\C[z]$ of degree $m$, let $z_1(t),...,z_m(t)$ denote all algebraic functions defined by $f(z_k(t))=t$. Given integers $n_1...,n_m$ such that $n_1+...+n_m=0$, the tangential center problem on zero-cycles asks to find all polynomials $g\in\C[z]$ such that $n_1g(z_1(t))+...+n_mg(z_m(t))\equiv 0$. The classical Center-Focus Problem, or rather its tangential version in important non-trivial planar systems lead to the above problem. The tangential center problem on zero-cycles was recently solved in a preprint by Gavrilov and Pakovich. Here we give an alternative solution based on induction on the number of composition factors of $f$ under a generic hypothesis on $f$. First we show the uniqueness of decompositions $f=f_1\circ...\circ f_d$, such that every $f_k$ is 2-transitive, monomial or a Chebyshev polynomial under the assumption that in the above composition there is no merging of critical values. Under this assumption, we give a complete (inductive) solution of the tangential center problem on zero-cycles. The inductive solution is obtained through three mechanisms: composition, primality and vanishing of the Newton-Girard component on projected cycles.

Bifurcations of heteroclinic loop accompanied by pitchfork bifurcation

In this paper, using the local coordinate moving frame approach, we investigate bifurcations of generic heteroclinic loop with a hyperbolic equilibrium and a nonhyperbolic equilibrium which undergoes a pitchfork bifurcation. Under some generic hypotheses, the existence of homoclinic loop, heteroclinic loop, periodic orbit and three or four heteroclinic orbits is obtained. In addition, the non-coexistence conditions for homoclinic loop and periodic orbit are also given. Note that the results achieved here can be extended to higher dimensional systems.

Bifurcation of a heterodimensional cycle with weak inclination flip

Local moving frame is constructed to analyze the bifurcation of aheterodimensional cycle with weak inclination flip in$\mathbb{R}^4$. Under some generic hypotheses, the existenceconditions for the heteroclinic orbit, $1$-homoclinic orbit,$1$-periodic orbit and two-fold or three-fold $1$-periodic orbit aregiven, respectively.

Revision of the Genus Prismatospora and Description of Prismatospora cloptoni n. sp. (Apicomplexa: Actinocephalidae: Acanthosporinae) from Naiads of the Green Darner, Anax junius (Odonata: Anisoptera: Aeshnidae), in East Texas, U.S.A

Abstract Prismatospora cloptoni n. sp. (Apicomplexa: Eugregarinida: Actinocephalidae: Acanthosporinae) is described from naiads of Anax junius (Odonata: Anisoptera: Aeshnidae) collected from the pond at the Sam Houston State University Center for Biological Field Studies, Walker County, Texas, U.S.A. This is the second species described in the genus, and it confirms the generic hypothesis of Prismatospora. The generic diagnosis is revised to reflect common characters of its constituent species.

Plücker formulae for singular space curves

AbstractIn [4] I extended the Plücker formulae to curves in Pn for any n, under fairly strong genericity hypotheses. In this paper we seek to weaken these hypotheses using the theory of excess intersections. The method applies to just one of the formulae (so the results are complete only for n=3), and for this we obtain a number which is a sum of local contributions, given by an explicit rule. We evaluate these contributions in the cases when they are determined by the terms of least order in the respective Taylor expansions, thus obtaining explicit formulae in numerous cases.

On the taxonomic status of the Brazilian mouse Calomys anoblepas Winge, 1887 (Mammalia, Rodentia, Cricetidae)

We studied the holotype and only known specimen of the rodent Calomys anoblepas Winge, 1887, an enigmatic and putatively extinct pentalophodont sigmodontine found in the limestone caves of Lagoa Santa, Minas Gerais, Brazil. Comparisons with other sigmodontines suggest that anoblepas can be allocated under the genus Juliomys González, 2000 and probably represents an extinct form within it. Cranial characters that support our generic hypothesis include the combination of an interlacrymal depression behind nasals, anterior portion of interfrontal suture with incomplete fusion, zygomatic plate nearly vertical with almost nonexistent upper free border, anterior border of the mesopterygoid fossa located at the level of third molar hypoflexus, and brachyodont molars with crested coronal topography. Juliomys includes three living species of sylvan and arboreal mice endemic of the Atlantic forests. This genus is absent in contemporaneous rodent assemblage from Lagoa Santa area, suggesting different environmental conditions during Pleistocene deposition times.

Generic event trees and probabilities for the release of different types of hazardous materials

To simplify quantitative risk analysis, the initiating events leading to loss of containment are normally described using generic hypotheses. For example, the following hypothesis is applied to the loss of containment from a storage tank: instantaneous release of the complete inventory, continuous release of the complete inventory in 10 min, and continuous release from a hole with a diameter of 10 mm. Once the initiating events have been specified, the corresponding event trees must be drawn to establish the sequences from each initiating event to the diverse final outcomes or accident scenarios, which will depend on the properties of the released material or on other specific factors. In this paper we propose, in a systematic way, a set of short generic event trees for the main loss of containment scenarios involving different types of hazardous materials. Even though most of them have been taken from the literature (BEVI Reference Manual), we have modified some of them, added the corresponding intermediate probabilities (immediate ignition, delayed ignition, flame front acceleration, etc.) obtained from a literature review and expert judgment, and associated the use of each event tree to the hazardous properties of the material (flammability, volatility and toxicity) and to its category according to EC labeling directives.

Two faces of active learning

An active learner has a collection of data points, each with a label that is initially hidden but can be obtained at some cost. Without spending too much, it wishes to find a classifier that will accurately map points to labels. There are two common intuitions about how this learning process should be organized: (i) by choosing query points that shrink the space of candidate classifiers as rapidly as possible; and (ii) by exploiting natural clusters in the (unlabeled) data set. Recent research has yielded learning algorithms for both paradigms that are efficient, work with generic hypothesis classes, and have rigorously characterized labeling requirements. Here we survey these advances by focusing on two representative algorithms and discussing their mathematical properties and empirical performance.

On scattering of small energy solutions of non-autonomous hamiltonian nonlinear Schrödinger equations

We revisit a result by Cuccagna, Kirr and Pelinovsky about the cubic nonlinear Schrödinger equation (NLS) with an attractive localized potential and a time-dependent factor in the nonlinearity. We show that, under generic hypotheses on the linearization at 0 of the equation, small energy solutions are asymptotically free. This is yet a new application of the hamiltonian structure, continuing a program initiated in a paper by Bambusi and Cuccagna.

A new genus and new species of fan worms (Polychaeta: Sabellidae) from Atlantic and Pacific Oceans—the formal treatment of taxon names as explanatory hypotheses

Members of Parasabella minuta Treadwell, 1941, subsequently moved to Perkinsiana, were collected during a survey of rocky intertidal polychaetes along the state of São Paulo, Brazil. Additional specimens, which are referred to two new species, were also found in similar habitats from the Bocas del Toro Archipelago, Caribbean Panama, and Oahu Island, Hawaii. A phylogenetic analysis of Sabellinae, including members of P. minuta and the two new species, provided justification for establishing a new generic hypothesis, Sabellomma gen. nov., for these individuals. Formal definitions are also provided for Sabellomma minuta gen. nov., comb. nov., S. collinae gen. nov., spec. nov., and S. harrisae gen. nov., spec. nov., along with descriptions of individuals to which these hypotheses apply. The generic name Aracia nom. nov., is provided to replace Kirkia Nogueira, López and Rossi, 2004, pre-occupied by a mollusk.

HETERODIMENSIONAL CYCLE BIFURCATION WITH ORBIT-FLIP

The local moving frame approach is employed to study the bifurcation of a degenerate heterodimensional cycle with orbit-flip in its nontransversal orbit. Under some generic hypotheses, we provide the conditions for the existence, uniqueness and noncoexistence of the homoclinic orbit, heteroclinic orbit and periodic orbit. And we also present the coexistence conditions for the homoclinic orbit and the periodic orbit. But it is impossible for the coexistence of the periodic orbit and the persistent heterodimensional cycle or the coexistence of the homoclinic loop and the persistent heterodimensional cycle. Moreover, the double and triple periodic orbit bifurcation surfaces are established as well. Based on the bifurcation analysis, the bifurcation surfaces and the existence regions are located. An example of application is also given to demonstrate our main results.

Theoretical approach for the calculation of a feasible point of the special non-convex set described by a polyhedron and a quadratic function

Let M be a set described as the intersection of a polyhedron and the set . In this work a method is proposed for detecting if , and in this case it will approach to a point . Roughly speaking, we define a parametric optimization problem P(t), adapted to the particular structure of M such that its solvability at t = 1 is equivalent to . Moreover x is a feasible point of P(1). The main part of the article is to prove that under generic hypothesis P(t) will be regular in the sense of Jongen–Jonker and Twilt and so the strategy of path following and jumps can be applied to P(t).

Is Antibiotic Prophylaxis in Surgery a Generally Effective Intervention?

While the main focus of a meta-analysis is often to assess the effectiveness of a particular intervention in managing or curing a specific condition, there exists a substantial amount of information within published systematic reviews that could be used to assess the validity of a generic hypothesis about the effectiveness of an intervention across a range of different but related conditions. To systematically search for and then collate the results of meta-analyses for the effectiveness of antibiotic prophylaxis in preventing postoperative wound infection across various types of surgery in order to assess generic hypotheses about the effectiveness of this intervention in surgery as a whole. With the relative risk of wound infection used as the measure of clinical effectiveness, the hypotheses to be assessed were first that antibiotic prophylaxis would be an effective intervention for preventing wound infection over a broad range of different surgical procedures, and second that there would be a substantial difference in the effectiveness of antibiotic prophylaxis between "clean" and "contaminated" surgical procedures. Medline and the Cochrane Database of Systematic Reviews. Eligible meta-analyses were meta-analyses published between 1990 and 2006 of randomized controlled trials that looked at the effectiveness of prophylactic antibiotics versus no antibiotic or placebo in preventing postoperative wound infections. Independent data extraction by multiple observers. The first hypothesis was strongly supported by the data as evidenced by the fact that the estimates of the relative risk of infection for the 23 types of surgery that were included in the study were all less than 1. However, there was no real evidence supporting the second hypothesis that the relative risk of wound infection would substantially vary over different levels of surgery cleanliness. : As well as antibiotic prophylaxis being a generally effective intervention for preventing postoperative wound infection, the level of this effectiveness would appear to be reasonably independent of what type of surgery is being considered. Therefore, the general prevailing attitude that antibiotic prophylaxis should be assumed to be ineffective unless its effectiveness has been experimentally proven beyond doubt for the specific type of surgery being considered, perhaps should be revised. In particular, perhaps a sensible philosophy would be to assume that antibiotic prophylaxis is effective in reducing the risk of wound infection for all types of surgery, even ones where no clinical trial data exists and make exceptions to this rule if, for certain types of surgery, it can be proved to the contrary.

Uso de bibliotecas digitais de periódicos: um estudo comparativo do uso do Portal de Periódicos da Capes entre áreas do conhecimento

A presente pesquisa relata o uso do Portal de Periódicos Capes por pesquisadores das áreas de Ciências Biológicas, Linguística, Letras e Artes e Ciências Humanas da UFMG. O estudo foi de caráter qualitativo e utilizou técnicas de entrevista e incidente crítico para investigar a razão dos comportamentos informacionais distintos de pesquisadores das três áreas, considerando, entre outros fatores, as diferenças na organização da literatura de cada área. Estiveram envolvidos os departamentos de Ciências Aplicadas à Educação, História e Psicologia (Ciências Humanas), Linguística, Fotografia, Teatro e Cinema e Artes Plásticas (Linguística, Letras e Artes), Parasitologia, Farmacologia e Microbiologia (Ciências Biológicas). Nessas unidades foram entrevistados 5 diretores e 18 pesquisadores. Investigaram-se as características do domínio de conhecimento, tais como o grau de dispersão, tamanho do domínio, tipo de fontes, tipo de conhecimento contido nas fontes, tipo específico de relevância do domínio. Outros fatores verificados foram aspectos do comportamento de busca, os motivos de uso e não uso, barreiras, recompensas e outros fatores que poderiam influenciar o uso do Portal. As análises mostram diferenças de comportamento dos docentes e dos fatores que interferem o uso e o não uso do Portal entre departamentos de uma mesma área e entre pesquisadores de um mesmo departamento. Os resultados da pesquisa qualitativa indicam que não se devem formular hipóteses genéricas para as grandes áreas do conhecimento e que os fatores de uso e não uso são específicos para cada disciplina.

Bifurcations in a Class of Polycycles Involving Two Saddle-Nodes on a Möbius Band

In this paper we study the bifurcations of a class of polycycles, called lips, occurring in generic three-parameter smooth families of vector fields on a Mobius band. The lips consists of a set of polycycles formed by two saddle-nodes, one attracting and the other repelling, connected by the hyperbolic separatrices of the saddle-nodes and by orbits interior to both nodal sectors. We determine, under certain genericity hypotheses, the maximum number of limits cycles that may bifurcate from a graphic belonging to the lips and we describe its bifurcation diagram.

Pseudo-Abelian integrals along Darboux cycles

We study polynomial perturbations of integrable, non-Hamiltonian system with first integral of Darboux-type with positive exponents. We assume that the unperturbed system admits a period annulus. The linear part of the Poincaré return map is given by pseudo-Abelian integrals. In this paper we investigate analytic properties of these integrals. We prove that iterated variations of these integrals vanish identically. Using this relation we prove that the number of zeros of these integrals is locally uniformly bounded under generic hypothesis. This is a generic analog of the Varchenko-Khovanskii theorem for pseudo-Abelian integrals. Finally, under some arithmetic properties of exponents, the pseudo-Abelian integrals are a sum over exponents aj of polynomials in log h with meromorphic functions of h 1 / a j as coefficients.

Revision of the Genus Nubenocephalus and Description of Nubenocephalus secundus n. sp. (Apicomplexa: Actinocephalidae) Parasitizing Adults of Argia sedula (Odonata: Zygoptera: Coenagrionidae) in the Primitive Texas Big Thicket, U.S.A.

Abstract Nubenocephalus secundus n. sp. (Apicomplexa: Eugregarinida) is described from adults of Argia sedula (Odonata: Zygoptera: Coenagrionidae) collected from Harmon Creek, Sam Houston State University Center for Biological Field Studies, Walker County, Texas, U.S.A. This is the second species described in the genus and confirms the generic hypothesis of Nubenocephalus. The generic diagnosis of Nubenocephalus is revised to reflect common characters of its constituent species and a previously described Asian gregarine, Nubenocephalus mutabilis n. comb. (=Ancyrophora mutabilis) is recognized as a member of the genus.