Uniqueness of the compactly supported weak solutions of the relativistic Vlasov-Darwin system

We use optimal transportation techniques to show uniqueness of the compactly supported weak solutions of the relativistic Vlasov-Darwin system. Our proof extends the method used by Loeper in J. Math. Pures Appl. 86, 68-79 (2006) to obtain uniqueness results for the Vlasov-Poisson system.Comment: AMS-LaTeX, 21 page

Cytosolic Sequestration of Prep1 Influences Early Stages of T Cell Development

Objective: Prep1 and Pbx2 are the main homeodomain DNA-binding proteins of the TALE (three amino acid loop extension) family expressed in the thymus. We previously reported reduced Pbx2 expression and defective thymocyte maturation in Prep1 hypomorphic mice. To further investigate the role of this homeodomain DNA-binding protein in T cell development, we generated transgenic mice expressing the N-terminal fragment of Pbx1 (Pbx1NT) under the control of the Lck proximal promoter. Principal Findings: Pbx1NT causes Prep1 cytosolic sequestration, abolishes Prep1-dependent DNA-binding activity and results in reduced Pbx2 expression in developing thymocytes. Transgenic thymi reveal increased numbers of CD4 2 CD8 2 CD44 2 (DN3 and DN4) thymocytes, due to a higher frequency of DN2 and DN4 Pbx1NT thymocytes in the S phase. Transgenic thymocytes however do not accumulate at later stages, as revealed by a normal representation of CD4/CD8 double positive and single positive thymocytes, due to a higher rate of apoptotic cell death of DN4 Pbx1NT thymocytes. Conclusion: The results obtained by genetic (Prep1 hypomorphic) and functional (Pbx1NT transgenic) inactivation of Prep

Site-directed mutagenesis reveals a unique requirement for tyrosine residues in IL-7Rα and TSLPR cytoplasmic domains in TSLP-dependent cell proliferation

<p>Abstract</p> <p>Background</p> <p>Thymic stromal lymphopoietin (TSLP) is an interleukin-7 (IL-7) like cytokine, which plays an important role in the regulation of immune responses to allergens. TSLP binds to a heterodimeric receptor complex composed of the IL-7 receptor α chain (IL-7Rα) and the TSLP receptor (TSLPR, also known as CRLF2). It has previously been suggested that the lone tyrosine residue in the mouse TSLPR cytoplasmic domain is required for cell proliferation using chimeric receptor systems. Also the role of tyrosine residues in the IL-7Rα cytoplasmic domain in TSLP signaling has not yet been investigated. We undertook a systematic analysis to test the role of tyrosine residues of both the IL-7Rα and the TSLPR in inducing cell proliferation in a growth factor dependent cell line, Ba/F3.</p> <p>Results</p> <p>A multiple sequence alignment of the IL-7Rα and TSLPR cytoplasmic domains revealed conservation of most, but not all, cytoplasmic tyrosine residues across several species. Our site-directed mutagenesis experiments revealed that the single tyrosine residue in human TSLPR was not required for TSLP-dependent cell proliferation. It has previously been reported that Y449 of human IL-7Rα is required for IL-7 dependent proliferation. Interestingly, in contrast to IL-7 signaling, none of tyrosine residues in the human IL-7Rα cytoplasmic domain were required for TSLP-dependent cell proliferation in the presence of a wild type TSLPR. However, the mutation of all cytoplasmic four tyrosine residues of human IL-7Rα and human TSLPR to phenylalanine residues abolished the proliferative ability of the TSLP receptor complex in response to TSLP.</p> <p>Conclusion</p> <p>These results suggest that TSLP requires at least one cytoplasmic tyrosine residue to transmit proliferative signals. Unlike other members of IL-2 cytokine family, tyrosine residues in IL-7Rα and TSLPR cytoplasmic domains play a redundant role in TSLP-mediated cell growth.</p

HIV infection of thymocytes inhibits IL-7 activity without altering CD127 expression

Abstract Background Thymic function is altered in HIV infection and characterized by dysregulation of the thymic epithelial network, reduced thymic output and ultimately an impaired naïve T-cell pool. The IL-7/IL-7 receptor (IL-7R) signalling pathway is critical for the maturation and differentiation of thymocytes. HIV infection is associated with a decrease in IL-7Rα (CD127) expression and impaired CD127 signalling in circulating CD8+ T-cells; however, little is known about the effect of HIV on CD127 expression and IL-7 activity in the thymus. Therefore, the effect of in vitro HIV infection on CD127 expression and IL-7-mediated function in thymocytes was investigated. Findings In vitro HIV infection of thymocytes did not affect CD127 expression on either total thymocytes or on single positive CD4 or single positive CD8 subsets. However, HIV infection resulted in a decrease in the level of IL-7-induced STAT-5 phosphorylation and Bcl-2 expression in unfractionated thymocytes. Conclusion These findings indicate that HIV infection alters IL-7 responsiveness of thymocytes by a mechanism other than CD127 downregulation and potentially explain the disruption in thymopoiesis observed in HIV infection

The Einstein-Vlasov System/Kinetic Theory

The main purpose of this article is to provide a guide to theorems on global properties of solutions to the Einstein--Vlasov system. This system couples Einstein's equations to a kinetic matter model. Kinetic theory has been an important field of research during several decades in which the main focus has been on non-relativistic and special relativistic physics, i.e., to model the dynamics of neutral gases, plasmas, and Newtonian self-gravitating systems. In 1990, Rendall and Rein initiated a mathematical study of the Einstein--Vlasov system. Since then many theorems on global properties of solutions to this system have been established.Comment: Published version http://www.livingreviews.org/lrr-2011-

Motions of a 1:100 scale model of a floating gravity-based structure during shallow water towing tank tow-out experiments

In October 1992, the Institute for Marine Dynamics (IMD) conducted a series of experiments with a 1:100 scale model of a Gravity-Based Structure (GBS). The experiments were performed in the Wave/Tow Tank at the Memorial University of Newfoundland (MUN). The primary purpose of the experiments was to demonstrate that the IMD has the capability to perform tow tests with waves and wind-induced moment, with measurements of model motions in six degrees of freedom, and bottom clearance in shallow water conditions. It was not intended that this be an exhaustive set of experiments which covers all combinations of drafts, tow and wind speeds, water depths, wave heights and periods, and towline geometries that might be specified in a commercial Request for Proposal. This report gives details of the model, the apparatus, and the instrumentation system. This report also defines the scope of the experiments and describes the experimental procedures, and finally outlines future experiments which would continue the study. This report presents the data in coherent form, and provides preliminary analysis of the data. This report makes suggestions for further analysis of the data and future experiments.Peer reviewed: NoNRC publication: Ye

Preliminary CFD Study of Model Induced Circulation in the IMD Clearwater Towing Tank

It was observed when testing large models of sailing yachts in the NRC/IMD towing tank that lasting flow patterns were being produced in the tank, which could affect force measurements. Some assessments of the phenomena were made, but the nature of the flow was not well understood. Attempts to minimize the circulation effects on model testing were primarily made by trial and error. This report presents results from a preliminary CFD study (2D) of the dynamics of this induced flow.NRC publication: Ye

Preliminary CFD Study of Model Induced Circulation in the IMD Clearwater Towing Tank

It was observed when testing large models of sailing yachts in the NRC/IMD towing tank that lasting flow patterns were being produced in the tank, which could affect force measurements. Some assessments of the phenomena were made, but the nature of the flow was not well understood. Attempts to minimize the circulation effects on model testing were primarily made by trial and error. This report presents results from a preliminary CFD study (2D) of the dynamics of this induced flow.NRC publication: Ye

Analysis of rudder span effects on IMS hydrodynamic induced drag

The physical draft of keels has long been known to be critical for the upwind performance of sailboats and has long been an element of handicap rules. The IMS rule uses a relatively sophisticated algorithm for assessing keel draft yet, as is the case with other rules, has never included any influence of rudder span. However, there is considerable empirical evidence that rudders can make a significant contribution to performance by increasing the total effective draft. Tank test research was conducted to explore rudder span and quantify performance differences. The results have been incorporated into the IMS 2002 rule in a way that is intended to give some rating relief to boats with shallow rudders yet to not drive optimised design in that direction.Peer reviewed: YesNRC publication: Ye