A one-dimensional Keller-Segel equation with a drift issued from the boundary

We investigate in this note the dynamics of a one-dimensional Keller-Segel type model on the half-line. On the contrary to the classical configuration, the chemical production term is located on the boundary. We prove, under suitable assumptions, the following dichotomy which is reminiscent of the two-dimensional Keller-Segel system. Solutions are global if the mass is below the critical mass, they blow-up in finite time above the critical mass, and they converge to some equilibrium at the critical mass. Entropy techniques are presented which aim at providing quantitative convergence results for the subcritical case. This note is completed with a brief introduction to a more realistic model (still one-dimensional).

Transport pathways in the malaria-infected erythrocyte: characterization and their use as potential targets for chemotherapy

The intraerythrocytic malarial parasite is involved in an extremely intensive anabolic activity while it resides in its metabolically quiescent host cell. The necessary fast uptake of nutrients and the discharge of waste product, are guaranteed by parasite-induced alterations of the constitutive transporters of the host cell and the production of new parallel pathways. The membrane of the host cell thus becomes permeable to phospholipids, purine bases and nucleosides, small non-electrolytes, anions and cations. When the new pathways are quantitatively unimportant, classical inhibitors of native transporters can be used to inhibit parasite growth. Several compounds were found to effectively inhibit the new pathways and consequently, parasite growth. The pathways have also been used to introduce cytotoxic agents. The parasitophorous membrane consists of channels which are highly permeable to small solutes and display no ion selectivity. Transport of some cations and anions across the parasite membrane is rapid and insensitive to classical inhibitors, and in some cases it is mediated by specific antiporters which respond to their respective inhibitors. Macromolecules have been shown to reach the parasitophorous space through a duct contiguous with the host cell membrane, and subsequently to be endocytosed at the parasite membrane. The simultaneous presence of the parasitophorous membrane channels and the duct, however, is incompatible with experimental evidences. No specific inhibitors were found as yet that would efficiently inhibit transport through the channels or the duct.

A functional equation related to the product in a quadratic number field

"Vegeu el resum a l'inici del document del fitxer adjunt."

Gaussian estimates for the density of the non-linear stochastic heat equation in any space dimension

In this paper, we establish lower and upper Gaussian bounds for the probability density of the mild solution to the stochastic heat equation with multiplicative noise and in any space dimension. The driving perturbation is a Gaussian noise which is white in time with some spatially homogeneous covariance. These estimates are obtained using tools of the Malliavin calculus. The most challenging part is the lower bound, which is obtained by adapting a general method developed by Kohatsu-Higa to the underlying spatially homogeneous Gaussian setting. Both lower and upper estimates have the same form: a Gaussian density with a variance which is equal to that of the mild solution of the corresponding linear equation with additive noise.

Refined asymptotics for the subcritical Keller-Segel system and related functional inequalities

We analyze the rate of convergence towards self-similarity for the subcritical Keller-Segel system in the radially symmetric two-dimensional case and in the corresponding one-dimensional case for logarithmic interaction. We measure convergence in Wasserstein distance. The rate of convergence towards self-similarity does not degenerate as we approach the critical case. As a byproduct, we obtain a proof of the logarithmic Hardy-Littlewood-Sobolev inequality in the one dimensional and radially symmetric two dimensional case based on optimal transport arguments. In addition we prove that the onedimensional equation is a contraction with respect to Fourier distance in the subcritical case.

Existence and uniqueness of viscosity solution for Hamilton-Jacobi equation with discontinuous coefficients dependent on time

The main result is a proof of the existence of a unique viscosity solution for Hamilton-Jacobi equation, where the hamiltonian is discontinuous with respect to variable, usually interpreted as the spatial one. Obtained generalized solution is continuous, but not necessarily differentiable.

Glutamate Transport Decreases Mitochondrial pH and Modulates Oxidative Metabolism in Astrocytes.

During synaptic activity, the clearance of neuronally released glutamate leads to an intracellular sodium concentration increase in astrocytes that is associated with significant metabolic cost. The proximity of mitochondria at glutamate uptake sites in astrocytes raises the question of the ability of mitochondria to respond to these energy demands. We used dynamic fluorescence imaging to investigate the impact of glutamatergic transmission on mitochondria in intact astrocytes. Neuronal release of glutamate induced an intracellular acidification in astrocytes, via glutamate transporters, that spread over the mitochondrial matrix. The glutamate-induced mitochondrial matrix acidification exceeded cytosolic acidification and abrogated cytosol-to-mitochondrial matrix pH gradient. By decoupling glutamate uptake from cellular acidification, we found that glutamate induced a pH-mediated decrease in mitochondrial metabolism that surpasses the Ca(2+)-mediated stimulatory effects. These findings suggest a model in which excitatory neurotransmission dynamically regulates astrocyte energy metabolism by limiting the contribution of mitochondria to the metabolic response, thereby increasing the local oxygen availability and preventing excessive mitochondrial reactive oxygen species production.

Health and Transport, Sources of Information

The Institute of Public Health in Ireland (IPH) has produced a series of reviews which look at the health impacts of identified subject areas. Four reviews have been produced in the areas of employment, transport, the built environment and education. All reviews may be found at http://www.publichealth.ie/ireland/hiaresources. This resource supplements the ‘Health Impacts of Transport’ report. It highlights a number of organisations whose work considers issues relevant to the relationship between health and transport.

IPH response to the National Transport Authority on the Greater Dublin Area Draft Transport Strategy 2011-2030

The remit of the Institute of Public Health in Ireland (IPH) is to promote cooperation for public health between Northern Ireland and the Republic of Ireland in the areas of research and information, capacity building and policy advice. Our approach is to support Departments of Health and their agencies in both jurisdictions, and maximise the benefits of all-island cooperation to achieve practical benefits for people in Northern Ireland and the Republic of Ireland.IPH has a keen interest in the interactions between transport and health. IPH has produced two papers in the recent past on this topic, the most recent being Active travel – healthy lives published in January 2011 which built on the 2005 publication Health impacts of transport. The IPH welcomes the draft transport strategy in terms of addressing each of the key messages outlined in the Active travel – healthy lives paper.IPH is interested in this area not only in terms of increasing ‘active travel’ for healthier lives, but also in terms of the environmental and social impacts of inequitable access to forms of private and public transport.

IPH response to Department for Regional Development public transport reform consultation

This is the IPH response to the Department for Regional Development's public transport reform consultation.

IPH responds to Northern Ireland Assembly Inquiry into Sustainable Transport

The Institute of Public Health in Ireland (IPH) aims to improve health on the island of Ireland by working to combat health inequalities and influence public policies in favour of health.  The Institute promotes cooperation between Northern Ireland and the Republic of Ireland in public health research, training and policy advice. IPH commends the Regional Development Committee on selecting sustainable transport as its subject for inquiry and welcomes the inquiry’s focus on identifying a move to more sustainable transport in Northern Ireland. IPH thanks the Committee for the opportunity to contribute views and experience

Draft Regional Transport Services Strategy - March 2005 (PDF 232 KB)

A Consultation Paper

Regional Transport Services Strategy (PDF 232 KB)

Regional Transport Services Strategy