Slow dynamics due to entropic barriers in the one-dimensional `descent model'

We propose a novel one-dimensional simple model without disorder exhibiting slow dynamics and aging at the zero temperature limit. This slow dynamics is due to entropic barriers. We exactly solve the statics of the model. We derive an evolution equation for the slow modes of the dynamics which are responsible for the aging. This equation is equivalent to a random walker on the energetic landscape. This latter elementary model can be solved analytically up to some basic approximations and is eventually shown to present aging by itself, as well as a slow logarithmic relaxation of the energy: e(t) ~ 1/ln(t) at large t.Comment: 8 pages,4 figures, we add analytical development of the energy-energy correlation function showing aging, and figures 1 and

The statistical mechanics of combinatorial optimization problems with site disorder

We study the statistical mechanics of a class of problems whose phase space is the set of permutations of an ensemble of quenched random positions. Specific examples analyzed are the finite temperature traveling salesman problem on several different domains and various problems in one dimension such as the so called descent problem. We first motivate our method by analyzing these problems using the annealed approximation, then the limit of a large number of points we develop a formalism to carry out the quenched calculation. This formalism does not require the replica method and its predictions are found to agree with Monte Carlo simulations. In addition our method reproduces an exact mathematical result for the Maximum traveling salesman problem in two dimensions and suggests its generalization to higher dimensions. The general approach may provide an alternative method to study certain systems with quenched disorder.Comment: 21 pages RevTex, 8 figure

Distances on Lozenge Tilings

International audienceIn this paper, a structural property of the set of lozenge tilings of a 2n-gon is highlighted. We introduce a simple combinatorial value called Hamming-distance, which is a lower bound for the flipdistance (i.e. the number of necessary local transformations involving three lozenges) between two given tilings. It is here proven that, for n5, We show that there is some deficient pairs of tilings for which the flip connection needs more flips than the combinatorial lower bound indicates

Cryopreservation and thawing of hematopoietic stem cells CD34 induced apoptosis through caspases pathway activation

43rd Annual Meeting of the European-Society-for-Blood-and-Marrow-Transplantation (EBMT), Marseille, FRANCE, MAR 26-29, 2017International audienc

Pronase treatment improves flow cytometry crossmatching results

International audienceFlow cytometry crossmatching (FC-XM) is the most sensitive cell-based method for detecting donor-specific antibodies in clinical organ transplantation. Unfortunately, background FC-XM reactivity is elevated in assays with B lymphocytes-partly because of nonspecific immunoglobulin binding by Fc receptors and B-cell surface immunoglobulins. To reduce the background reactivity in a B-cell FC-XM assay, we treated lymphocytes with pronase (1 mg/mL for 30 minutes). This treatment drastically reduced the presence of kappa light chains and Fc receptors (CD32b), while the concomitant decrease in CD19, CD20 and major histocompatibility complex (MHC) I and II expression on B-cells was acceptable. Higher pronase concentrations (>2 mg/mL) started to significantly affect CD19, CD20, MHC-I and -II expression on B-cells. In subsequent prospective experiments (on 42 donor cells tested with 102 sera), we found that pronase treatment was associated with a relative increase of the sensitivity and specificity in our B-cell FC-XM assay

ASSOCIATION OF PO4 LOADED POROUS SILICON MICROPARTICLES WITH NACRE PROTEINS ENHANCES MINERALIZED BONE FORMATION IN VIVO

International audienceWe investigated bone regeneration in vitro and in vivo, using porous silicon (pSi) microparticles coupled with nacre proteins. We prepared a composite powder formed by pSi particles loaded with phosphate, and nacre proteins carrying calcium. For in vitro experiments, we used primary culture of human Dental Pulp Stem Cells. Results showed efficiency for both cell adhesion, cell differentiation and CaPO4 formation. But the most interesting results were that this composite was highly efficient to regenerate bone in vivo, even without any additional stem cells grafting

ASSOCIATION OF PO4 LOADED POROUS SILICON MICROPARTICLES WITH NACRE PROTEINS ENHANCES MINERALIZED BONE FORMATION IN VIVO

International audienceWe investigated bone regeneration in vitro and in vivo, using porous silicon (pSi) microparticles coupled with nacre proteins. We prepared a composite powder formed by pSi particles loaded with phosphate, and nacre proteins carrying calcium. For in vitro experiments, we used primary culture of human Dental Pulp Stem Cells. Results showed efficiency for both cell adhesion, cell differentiation and CaPO4 formation. But the most interesting results were that this composite was highly efficient to regenerate bone in vivo, even without any additional stem cells grafting