Initialization of the Shooting Method via the Hamilton-Jacobi-Bellman Approach

The aim of this paper is to investigate from the numerical point of view the possibility of coupling the Hamilton-Jacobi-Bellman (HJB) equation and Pontryagin's Minimum Principle (PMP) to solve some control problems. A rough approximation of the value function computed by the HJB method is used to obtain an initial guess for the PMP method. The advantage of our approach over other initialization techniques (such as continuation or direct methods) is to provide an initial guess close to the global minimum. Numerical tests involving multiple minima, discontinuous control, singular arcs and state constraints are considered. The CPU time for the proposed method is less than four minutes up to dimension four, without code parallelization

Rotating proto-neutron stars: spin evolution, maximum mass and I-Love-Q relations

Shortly after its birth in a gravitational collapse, a proto-neutron star enters in a phase of quasi-stationary evolution characterized by large gradients of the thermodynamical variables and intense neutrino emission. In few tens of seconds the gradients smooth out while the star contracts and cools down, until it becomes a neutron star. In this paper we study this phase of the proto-neutron star life including rotation, and employing finite temperature equations of state. We model the evolution of the rotation rate, and determine the relevant quantities characterizing the star. Our results show that an isolated neutron star cannot reach, at the end of the evolution, the maximum values of mass and rotation rate allowed by the zero-temperature equation of state. Moreover, a mature neutron star evolved in isolation cannot rotate too rapidly, even if it is born from a proto-neutron star rotating at the mass-shedding limit. We also show that the I-Love-Q relations are violated in the first second of life, but they are satisfied as soon as the entropy gradients smooth out.Comment: 15 pages, 9 figures, 7 tables; minor changes, and extended discussion on the I-Love-Q relation

The endoplasmic reticulum: a sensor of cellular stress that modulates immune responses.

Many inflammatory and infectious diseases are characterized by the activation of signaling pathways steaming from the endoplasmic reticulum (ER). These pathways, primarily associated with loss of ER homeostasis, are emerging as key regulators of inflammation and infection. Recent advances shed light on the mechanisms linking ER-stress and immune responses

Inflammation initiated by stressed organelles.

Key cellular functions including those related to energy metabolism, organization of the genetic information or production of membrane-bound and secreted proteins are compartmentalized within organelles. Various stresses such as differentiation programs, viral and bacterial infections, perturbations in protein production, mechanical constraints, changes in the environment and nutriment accessibility can impact cellular homeostasis and organelle integrity. Perturbations of these cellular compartments trigger repair and adaptation programs aimed at restoring homeostasis. These events are often associated with low-grade inflammation also termed parainflammation. While the nature and mechanisms of danger signals released by irremediably damaged cells are well understood, how transiently stressed cells trigger inflammation is still poorly understood. Emerging studies highlighted new mechanisms by which stress pathways promote inflammation. Cytosolic innate immune pathways are engaged by signals stemming from perturbed organelles such as the mitochondria, the endoplasmic reticulum (ER) or the nuclear envelope (NE). These observations indicate that these pathways function as guardians of cellular homeostasis and may contribute to disease in pathologies characterized by perturbations of cellular homoeostasis. Mitochondria-stress, ER-stress or NE-stress are emerging as proinflammatory signals that contribute to human conditions and diseases

Curators Serving the Public Good

his article investigates a principle inscribed at the top of most codes of ethics for curators: they should always “serve the public good.” No self-respecting curator would ever admit to serve “the private good,” that is, the good of the few, whether that of an elite in power or of a circle of friends or allies. The principle of “serving the public good” is inalienable and unquestionable even in situations where it is most open to doubt. However, what exactly is the meaning of this seemingly “true” and on all accounts “universal” principle: “to serve the public good”? To address this question, I look at this principle for the way it is perceived as being both majestic in its impressive widespread acceptance and cloaked in ridicule for being so often disregarded. I will argue—with an example taken from the history of curating—that it is not the meaning attached to the principle that counts, but the respect that it enjoins. I conclude by drawing a few remarks on how the value of the “good” remains, after the principle has been cast aside and the priority of respect is acknowledged, a ghost on the horizon of all curators’ work

Afterword: Respect for Derrida in/and Africa

The Afterword focuses on one of the most striking features of the essays included in this new anthology: the respect for both Derrida and Africa. It asks: how is one to make sense of the respect that permeates the work of these scholars? In order to address this topic, the Afterword focuses not only on the way Derrida himself addresses the topic of respect, it also aims at uncovering the way the essays themselves impart this respect. The overall point of such a short coda is not to provide an exhaustive analysis of respect or expose how respectful these scholars are, but to reveal the ethical imperative that always takes place and perhaps should always take place when either (or both) topic(s) (Derrida and/or Africa) is put forward for discussion

Marx 1845 or the Fateful Rejection of Anschauung

One of Marx’s most damning condemnation is that of Feuerbach’s intuitive-contemplative materialism in his Theses of 1845. This condemnation famously leads him to an understanding of human activity as purely objective (gegenständliche) and of “revolution” as praxis, that is, as a “practical-critical” activity exclusively based on reason and reason alone. The question that is rarely asked about this condemnation is this: what is lost in this abandonment of the intuitive on the way to historical materialism? The aim behind this question is purely speculative. It does not intend to provide yet again a historical reading of this famous turning point in Marx’s move away from Feuerbach. It simply intends to see whether something could be gained from revisiting Feuerbach’s understanding of the intuitive and/or contemplative and whether this could allow us to move beyond the 21st Century deadlock of Marx’s “rational praxis.” This essay offers a new reading of Marx’s Theses, explores key aspects of Feuerbach’s understanding of intuition/contemplation, and critically appraises the key readers of this major turning point in history, especially those in the French Marxist tradition such as Bloch, Henry, Althusser, Macherey, and of course, Balibar. The essay is published in the well-known US journal CR: The New Centennial Review. The essay’s originality consists not only in reappraising Marx's early materialism, but also, more broadly, in questioning the trend in today's materialisms to dismiss all forms of intuitive-contemplative approaches to matter and reality. As such, the essay has the capacity to alter the way realisms and materialisms are formulated today