Computer-controlled vibration testing

System features quickly achieved steady state, increased accuracy of spectrum definition, and true Gaussian amplitude distribution of resulting signals. Controlled shock-tests might also be tried with this system

Hopf Bifurcations in a Watt Governor With a Spring

This paper pursues the study carried out by the authors in "Stability and Hopf bifurcation in a hexagonal governor system", focusing on the codimension one Hopf bifurcations in the hexagonal Watt governor differential system. Here are studied the codimension two, three and four Hopf bifurcations and the pertinent Lyapunov stability coefficients and bifurcation diagrams, ilustrating the number, types and positions of bifurcating small amplitude periodic orbits, are determined. As a consequence it is found an open region in the parameter space where two attracting periodic orbits coexist with an attracting equilibrium point.Comment: 30 pages and 7 figure

Latin America's Increased Role in UN Peace Operations: Current Trends and a Note of Caution

Chapter 7Latin America is an active participant in United Nations (UN) peacekeeping operations (PKO). Blue helmets from South and Central America are currently deployed in various UN-sponsored missions around the world. T his picture contrasts markedly from past decades, when military institutions were widely known for intervening in domestic affairs via coups, rather than for promoting human rights and democracy abroad. Historically, the region has been a recipient, not an exporter, of foreign troops. Throughout the 1990s, peacekeeping (PK) soldiers were deployed to pacify Central America and the Andes; to date, Central American and Andean blue helmets are pacifying regions within and beyond the Western Hemisphere. Hence, Latin America has now become an exporter of peace, not because instability and violence ha\'e diminished at home, but because governments across the region have gradually increased their troop commitment to UN peace efforts. At a time when military budgets in North America and Europe are in decline, Latin America's commitment to international security appears to be rising. This could signify a new era for regional security affairs, with Latin American states increasingly engaged in world politics and the armed forces exposed to globalizing trends

Migration, Race and Identity: Arab Migration and its Impact on Cuban Society through History and the Visual Arts

Diversas investigaciones sobre la historia de Cuba se han enfocado a las experiencias de los afrocubanos (provenientes de los esclavos de África) que llegaron al país dentro del comercio de esclavos par aver cómo impactaron a la sociedad cubana. Pero hay poca investigación sobre la historia de la inmigración árabe a Cuba ocurrida entre la década de 1860 y la de 1940. En ella se centra este estudio. Usando documentos históricos y de artes visuales de los artistas cubano-árabes, trato de mostrar el impacto en la sociedad económica, política y cultural de la sociedad cubana. Es un intento de examinar los efectos de esta migración en las relaciones de raza, en la asmiliación y en la formación de raza e identidad dentro de Cuba

On a class of complete polynomial vector fields in the plane

AbstractThe class bn of polynomial vector fields of degree n which define global flows in R2 is characterized, provided the zeros of the vector fields at infinity are simple. Some analytical properties of bn are also established

Probing the electron-phonon coupling in ozone-doped graphene by Raman spectroscopy

We have investigated the effects of ozone treatment on graphene by Raman scattering. Sequential ozone short-exposure cycles resulted in increasing the $p$ doping levels as inferred from the blue shift of the 2$D$ and $G$ peak frequencies, without introducing significant disorder. The two-phonon 2$D$ and 2$D'$ Raman peak intensities show a significant decrease, while, on the contrary, the one-phonon G Raman peak intensity remains constant for the whole exposure process. The former reflects the dynamics of the photoexcited electrons (holes) and, specifically, the increase of the electron-electron scattering rate with doping. From the ratio of 2$D$ to 2$D$ intensities, which remains constant with doping, we could extract the ratio of electron-phonon coupling parameters. This ratio is found independent on the number of layers up to ten layers. Moreover, the rate of decrease of 2$D$ and 2$D'$ intensities with doping was found to slowdown inversely proportional to the number of graphene layers, revealing the increase of the electron-electron collision probability

Canard Cycles and Poincar\'e Index of Non-Smooth Vector Fields on the Plane

This paper is concerned with closed orbits of non-smooth vector fields on the plane. For a subclass of non-smooth vector fields we provide necessary and sufficient conditions for the existence of canard kind solutions. By means of a regularization we prove that the canard cycles are singular orbits of singular perturbation problems which are limit periodic sets of a sequence of limit cycles. Moreover, we generalize the Poincar\'e Index for non-smooth vector fields.Comment: 20 pages, 25 figure

Structural Stability of Asymptotic Lines on Surfaces Immersed in R3

AbstractIn this paper are studied immersions of surfaces into to R3 whose nets of asymptotic lines are topologically undisturbed under small perturbations of the immersion. These immersions are called structurally asymptotic stable. Sufficient conditions to belong to this class are established here. These conditions focus on the stable patterns around parabolic points, parabolic separatrix connections, periodic asymptotic lines (including those that intercept the parabolic lines) as well the exclusion of recurrent asymptotic lines. The class of immersions that are structurally stable in this sense is open in the C5-topology

“Galectin-1 Induces Central and Peripheral Cell Death: Implications in T-Cell Physiopathology”

The immune system has a remarkable capacity to maintain a state of equilibrium even as it responds to a diverse array of foreign proteins and despite its contact exposure to self-antigens. Apoptosis is one of the mechanisms aimed at preserving the homeostasis after the completion of an immune response, thus returning the immune system to a basal state and warranting the elimination of autoagressive cells in both central and peripheral lymphoid organs. Targeted deletions in critical genes involved in the apoptotic death machinery together with natural spontaneous mutations have clearly shown the importance of apoptosis in the regulation of the immune response. This complex scenario of stimulatory and inhibitory genes has been enriched with the finding that galectin-1, a 14.5 kDa β-galactoside-binding protein, is able to induce apoptosis of immature cortical thymocytes and mature T cells by cross-linking cell surface glycoconjugates. Galectin-1 is present not only in central and peripheral lymphoid organs, but also at sites of immune privilege. In the present article we will discuss the implications of galectin-1-induced apoptosis in T-cell physiopathology in an attempt to validate its therapeutic potential in autoimmune and inflammatory diseases