Garvey-Rodney-Marley: a Pan-African bridge over Cuba

The race/colour question and its political implications in Cuba have been foregrounded recently. A cross-section of Cuban society has encouraged discourses on racial awareness and anti-racist epistemologies as direct or indirect, but positive, outcomes of the encounter with ideas of decolonisation promoted by Black movements and readings of Black Caribbean intellectuals. Through history and the multidisciplinary nature of cultural studies, this article explores regional intersections among Pan-Africanism, Caribbean social and intellectual thought, and some expressions of these ideas in Cuba. It focuses on identity, Black consciousness and the tangential impact of Pan-Africanism as a political ideology on Cuba in three different periods. The author argues that the ideas of Marcus Garvey, Walter Rodney and Bob Marley provide ideologically connecting points in the assessment of cross-cultural connections between Cuba and the Caribbean.

Theoretical, Experimental and Numerical Analyses for Painlevé Paradox of Two-Link Robotic Manipulator System

When multi-rigid-body come into contact with a rough surface in certain configurations, multiple solutions or no solution would occur in the theoretical derivation of the dynamic equation, which is termed Painlevé paradox. In this paper, two-link robotic manipulator system as a kind of Painlevé paradox model is studied from theory, experiment and simulation. The theoretical solution is obtained by the linear complementary problem (LCP) method, which offers guidance to the experiment. Then the feasibility of experiment is validated by numerical simulation. For experiment, two-link robotic manipulator set-up is built. The apparatuses verify the continuity of two-link system motion as a function of initial configuration. The two-link robotic manipulator model is also built in LS-DYNA. The experiment and simulation results show that Painlevé paradox is always accompanied with dynamic jam. Meanwhile, there is no clear boundary between dynamic jam region and non-dynamic jam region derived as the LCP solution indicates. Instead, it tends to be a gradual change process with certain transformation law. Sticking-bounce motion is found in the experiment and simulation. Several different motion characteristics are concluded corresponding to the initial angles of the two links. The summary of the variation of dynamic responses is given for further studying the mechanism of tangential impact of similar robotic manipulator system, especially for guiding how to avoid such universal but unexpected action existing in robotic manipulator system.

Linnaeus, smut disease and living contagion

This paper examines the rise and fall of Carl Linnaeus's ideas on living contagion, focusing on his work with plant smut diseases. Early in his career, Linnaeus named a plant altered by anther-smut disease as a separate species, but then, probably realizing it was a diseased specimen, demoted it to a variety. He later drew direct parallels between minute insects attacking plants and infectious diseases in humans, but did not yet draw an analogy to smut diseases. After Otto von Münchhausen had sent Linnaeus the first instalment of his book Der Hausvater (1764) , Linnaeus realized smuts were contagious. He carried out his own investigations that appeared to confirm Münchhausen's conclusion that smut spores germinated to produce living and mobile animalcules. This cemented Linnaeus's view that animalcules caused contagion in human diseases, a view which he expressed forcefully, urging further studies. However, his results were questioned and discounted by others, especially John Ellis. An analysis of correspondence between Linnaeus and other microscopists shows that it is likely Linnaeus did actually see “animalcules” emerging from cereal grains. He was unaware that smut-like symptoms in wheat could also be caused by seed-gall nematodes in the genus Anguina. Linnaeus himself came to doubt the connection between fungi and contagion, and did not pursue these studies further. The presumption that Linnaeus was fanciful in his observations of animalcules may partly explain why his views had only a tangential impact on the germ-theory of disease, and why his insights remain unappreciated to this day.

The Bounds on the Coefficients of Restitution for the Frictional Impact of Rigid Pendulum Against a Fixed Surface

Upper bounds on Newton’s, Poisson’s, and energetic coefficients of normal restitution for the frictional impact of rigid pendulum against a fixed surface are derived, demonstrating that the upper bound on Newton’s coefficient is smaller than 1, while the upper bound on Poisson’s coefficient is greater than 1. The upper bound on the energetic coefficient of restitution, which is a geometric mean of Newton’s and Poisson’s coefficients of normal restitution, is equal to 1. Lower bound on all three coefficients is equal to zero. The bounds on the tangential impact coefficient, defined by the ratio of the frictional and normal impulses, are also derived. Its lower bound is negative, while its upper bound is equal to the kinetic coefficient of friction. Simplified bounds in the case of a nearly vertical impact are also derived.

Experimental Investigation of the Painlevé Paradox in a Robotic System

This paper aims at experimentally investigating the dynamical behaviors when a system of rigid bodies undergoes so-called paradoxical situations. An experimental setup corresponding to the analytical model presented in our prior work Liu et al. [2007, “The Bouncing Motion Appearing in a Robotic System With Unilateral Constraint,” Nonlinear Dyn., 49(1–2), 217–232] is developed, in which a two-link robotic system comes into contact with a moving rail. The experimental results show that a tangential impact exists at the contact point and takes a peculiar property that well coincides with the maximum dissipation principle stated in the work of Moreau [1988, “Unilateral Contact and Dry Friction in Finite Freedom Dynamics,” Nonsmooth Mechanics and Applications, Springer-Verlag, Vienna, pp. 1–82] the relative tangential velocity of the contact point must immediately approach zero once a Painlevé paradox occurs. After the tangential impact, a bouncing motion may be excited and is influenced by the speed of the moving rail. We adopt the tangential impact rule presented by Liu et al. to determine the postimpact velocities of the system, and use an event-driven algorithm to perform numerical simulations. The qualitative comparisons between the numerical and experimental results are carried out and show good agreements. This study not only presents an experimental support for the shock assumption related to the problem of the Painlevé paradox, but can also find its applications in better understanding the instability phenomena appearing in robotic systems.

There's “Private” and Then There's “Private”: ERISA, Its Impact, and Options for Reform

For most of the first two decades after the enactment of the Employee Retirement Income Security Act of 1974 (ERISA), health policymakers did not seem to recognize the full impact that ERISA would have on regulation of health insurance and health care coverage. Perhaps the early court decisions in which the courts clarified that states could regulate insurance companies and the products they sold to ERISA plan sponsors gave them false comfort that because Congress appeared to recognize the role of the states in regulating insurance, ERISA might have only a tangential impact on health care reform efforts.

Two-Dimensional Rigid-Body Collisions With Friction

This paper presents an analysis of a two-dimensional rigid-body collision with dry friction. We use Routh’s graphical method to describe an impact process and to determine the frictional impulse. We classify the possible modes of impact, and derive analytical expressions for impulse, using both Poisson’s and Newton’s models of restitution. We also address a new class of impacts, tangential impact, with zero initial approach velocity. Some methods for rigid-body impact violate energy conservation principles, yielding solutions that increase system energy during an impact. To avoid such anomalies, we show that Poisson’s hypothesis should be used, rather than Newton’s law of restitution. In addition, correct identification of the contact mode of impact is essential.