A study of resonance tongues near a Chenciner bifurcation using MatcontM

MatcontM is a matlab toolbox for numerical analysis of bifurcations of fixed points and periodic orbits of maps. It computes codim 1 bifurcation curves and supports the computation of normal coefficients including branch switching from codim 2 points to secondary curves. Recently, the initialization and computation of connecting orbits was improved. Moreover, a graphical user interface was added enabling interactive control of all these computations. To further support these computations it allows to compute orbits of the map and its iterates and to represent them in 2D, 3D and numeric windows. We demonstrate the use of the toolbox in a study of Arnol'd tongues near a degenerate Neimark-Sacker (Chenciner) bifurcation. Here we illustrate the recent theory of [Baesens&Mackay,2007] how resonance tongues interact with a quasi-periodic saddle-node bifurcation of invariant curves in maps. Using normal form coefficients we find evidence for one of their cases, but not the other. Actually, we find another unfolding, i.e. a third possibility. We also find a structure that resembles a quasi-periodic cusp bifurcation of invariant curves

Early Stages of Homopolymer Collapse

Interest in the protein folding problem has motivated a wide range of theoretical and experimental studies of the kinetics of the collapse of flexible homopolymers. In this Paper a phenomenological model is proposed for the kinetics of the early stages of homopolymer collapse following a quench from temperatures above to below the theta temperature. In the first stage, nascent droplets of the dense phase are formed, with little effect on the configurations of the bridges that join them. The droplets then grow by accreting monomers from the bridges, thus causing the bridges to stretch. During these two stages the overall dimensions of the chain decrease only weakly. Further growth of the droplets is accomplished by the shortening of the bridges, which causes the shrinking of the overall dimensions of the chain. The characteristic times of the three stages respectively scale as the zeroth, 1/5 and 6/5 power of the the degree of polymerization of the chain.Comment: 11 pages, 3 figure

Interplay between Normal Forms and Center Manifold Reduction for Homoclinic Predictors near Bogdanov-Takens Bifurcation

This paper provides for the first time correct third-order homoclinic predictors in n-dimensional ODEs near a generic Bogdanov-Takens bifurcation point, which can be used to start the numerical continuation of the appearing homoclinic orbits. To achieve this, higher-order time approximations to the nonlinear time transformation in the Lindstedt-Poincar\'e method are essential. Moreover, a correct transform between approximations to solutions in the normal form and approximations to solutions on the parameter-dependent center manifold is derived rigorously. A detailed comparison is done between applying different normal forms (smooth and orbital), different phase conditions, and different perturbation methods (regular and Lindstedt-Poincar\'e) to approximate the homoclinic solution near Bogdanov-Takens points. Examples demonstrating the correctness of the predictors are given. The new homoclinic predictors are implemented in the open-source MATLAB/GNU Octave continuation package MatCont

Bifurcation Analysis of Bogdanov-Takens Bifurcations in Delay Differential Equations

In this paper, we will perform the parameter-dependent center manifold reduction near the generic and transcritical codimension two Bogdanov-Takens bifurcation in classical delay differential equations. Using an approximation to the homoclinic solutions derived with a generalized Lindstedt-Poincar\'e method, we develop a method to initialize the continuation of the homoclinic bifurcation curves emanating from these points. The normal form transformation is derived in the functional analytic perturbation framework for dual semigroups (sun-star calculus) using a normalization technique based on the Fredholm alternative. The obtained expressions give explicit formulas, which have been implemented in the freely available bifurcation software package DDE-BifTool

Instanton propagator and instanton induced processes in scalar model

The propagator in the instanton background in the $(- \lambda \phi^{4})$ scalar model in four dimensions is studied.Leading and sub-leading terms of its asymptotics for large momenta and its on-shell double residue are calculated analytically. These results are applied to the analysis of the initial-state and initial-final-state corrections and the calculation of the next-to-leading (propagator) correction to the exponent of the cross section of instanton induced multiparticle scattering processes.Comment: 44 pages, 7 postscript figures, LaTe

Switching to nonhyperbolic cycles from codim 2 bifurcations of equilibria in ODEs

The paper provides full algorithmic details on switching to the continuation of all possible codim 1 cycle bifurcations from generic codim 2 equilibrium bifurcation points in n-dimensional ODEs. We discuss the implementation and the performance of the algorithm in several examples, including an extended Lorenz-84 model and a laser system.Comment: 17 pages, 7 figures, submitted to Physica

A imigração e a língua de acolhimento em Portugal: questões de identidade e integração

A imigração, a diversidade e a multiculturalidade estão cada vez mais presentes nas sociedades modernas e a gestão desta realidade representa um enorme desafio, tanto para as sociedades de acolhimento como para os próprios imigrantes. Esse desafio implica um processo de adaptação e integração que apenas pode funcionar havendo vontade e esforço de ambas as partes envolvidas. O país (sociedade) de acolhimento deve trabalhar no sentido de promover um ambiente onde nativos e imigrantes possam conviver pacificamente garantindo a todos o respeito por direitos e deveres, bem como pelas suas identidades. Quanto aos imigrantes, têm que se adaptar a uma nova vida e uma nova realidade longe dos seus países de origem, devendo também eles respeitar o meio em que se encontram e do qual passam a fazer parte, ao mesmo tempo que tentam preservar as suas identidades e os laços com o seu país de origem. É um processo que envolve muitas mudanças, particularmente para os imigrantes. O país, a sociedade, os costumes, a cultura, o clima, as crenças, a língua, etc, fazem parte de um conjunto de novas experiências e novas aprendizagens para o imigrante. Essas novas experiências trazidas pela imigração têm a potencialidade de gerar mudança identitária. Através de um estudo que pretendeu dar voz aos próprios imigrantes, procurei neste trabalho perceber se há realmente mudanças ao nível da identidade provocadas pelo processo de imigração e de que modo atuam alguns elementos nessa mudança e no processo de integração, nomeadamente a língua – língua materna e língua de acolhimento.Abstract: Immigration, diversity and multiculturalism are every day more present in the modern society and dealing with this reality represents a big challenge for both, host society and the immigrants. It requires a process of adaptation and integration that can only work if both parts are involved and willing to make things work. The host society must promote an environment where natives and immigrants can live together peacefully and also guarantee that all legal rights and obligations are respected as well as people’s identities. When it comes to the immigrants, they have to adapt to a new culture and environment, making sure they respect the society which they are now part of, and also try to preserve their identities and the bound with their own country and people. It's a process that involves many changes, more so to the immigrants. The nation, society, habits, culture, weather, beliefs, language, etc., are all new experiences to them. These integration and experiences could have the potential to generate identity changes. Through a study that wanted to listen to the immigrants opinions and experiences, I’ve tried to understand if there are actually changes in immigrants identities as a result of the migration process and how do some elements take place in that change, particularly the language - language from the host society and language from the origin country

Partonic flow and ϕ\phi-meson production in Au+Au collisions at sNN\sqrt{s_{NN}} = 200 GeV

We present first measurements of the $\phi$-meson elliptic flow ($v_{2}(p_{T})$) and high statistics $p_{T}$ distributions for different centralities from $\sqrt{s_{NN}}$ = 200 GeV Au+Au collisions at RHIC. In minimum bias collisions the $v_{2}$ of the $\phi$ meson is consistent with the trend observed for mesons. The ratio of the yields of the $\Omega$ to those of the $\phi$ as a function of transverse momentum is consistent with a model based on the recombination of thermal $s$ quarks up to $p_{T}\sim 4$ GeV/$c$, but disagrees at higher momenta. The nuclear modification factor ($R_{CP}$) of $\phi$ follows the trend observed in the $K^{0}_{S}$ mesons rather than in $\Lambda$ baryons, supporting baryon-meson scaling. Since $\phi$-mesons are made via coalescence of seemingly thermalized $s$ quarks in central Au+Au collisions, the observations imply hot and dense matter with partonic collectivity has been formed at RHIC.Comment: 6 pages, 4 figures, submit to PR

Measurement of open charm production in dd+Au collisions at sNN\sqrt{s_{NN}}=200 GeV

We present the first comprehensive measurement of $D^{0}, D^{+}, D^{*+}$ and their charge conjugate states at mid-rapidity in $d$+Au collisions at $\sqrt{s_{_{NN}}}$=200 GeV using the STAR TPC. The directly measured open charm multiplicity distribution covers a broad transverse momentum region of 0$<p_{T}<11$ GeV/$c$. The measured $dN/dy$ at mid-rapidity for $D^{0}$ is $0.0265\pm 0.0036 (stat.) \pm 0.0071 (syst.)$ and the measured $D^{*+}/D^{0}$ and $D^{+}/D^{0}$ ratios are approximately equal with a magnitude of $0.40\pm 0.09(stat.) \pm 0.13(syst.)$. The total $c\bar{c}$ cross section per nucleon-nucleon collision extracted from this study is $1.18 \pm 0.21(stat.) \pm 0.39(syst.)$mb. The direct measurement of open charm production is consistent with STAR single electron data. This cross section is higher than expectations from PYTHIA and other pQCD calculations. The measured $p_{T}$ distribution is harder than the pQCD prediction using the Peterson fragmentation function.Comment: Quark Matter 2004 Proceeding

Влияние трансплантации островковых клеток поджелудочной железы плодов кролика на течение индуцированного сахарного диабета у лабораторных животных

This article is about the trial of transplantation of fetal cells of pancreas to laboratory mice with streptosotozin diabetes. Cells were infused into liver in the dose of 105 cells/0,5 ml. Mices that received rabbit β-cells had normal level blood glucose within 2 months after xenotransplantation.В данной работе показан опыт по трансплантации островковых клеток поджелудочной железы плодов кролика лабораторным мышам со стрептозотоцин-индуцированным сахарным диабетом. Клетки были трансплантированы в печень в дозе 105 кл./0,5 мл. В течение 2 месяцев после ксенотрансплантации у мышей отмечалась стойкая нормогликемия