Note on the mean error and standard deviation in the output of a least square quadratic filter - case 20061-1

Equations for mean error and standard deviation in output of least squares quadratic filter - rada

Information systems requirements for the microgravity science and applications program

NASA's Microgravity Science and Applications (MSAD) Program is presented. Additionally, the types of information produced within the program and the anticipated growth in information system requirements as the program transitions to Space Station Freedom utilization are discussed. Plans for payload operations support in the Freedom era are addressed, as well as current activities to define research community requirements for data and sample archives

Monte Carlo Simulation of Long Chain Polymer Melts: Crossover from Rouse to Reptation Dynamics

We present data of Monte Carlo simulations for monodisperse linear polymer chains in dense melts with degrees of polymerization between N=16 and N=512. The aim of this study is to investigate the crossover from Rouse-like dynamics for short chains to reptation-like dynamics for long chains. To address this problem we calculate a variety of different quantities: standard mean-square displacements of inner monomers and of the chain's center of mass, the recently proposed cubic invariant, persistence of bond-vector orientation with time, and the auto-correlation functions of the bond vector, the end-to-end vector and the Rouse modes. This analysis reveals that the crossover from non- to entangled dynamics is very protracted. Only the largest chain length N=512, which is about 13 times larger than the entanglement length, shows evidence for reptation.Comment: 38 pages of REVTeX, 14 PostScript figure

On the Dynamics and Disentanglement in Thin and Two-Dimensional Polymer Films

We present results from molecular dynamics simulations of strictly two-dimensional (2D) polymer melts and thin polymer films in a slit geometry of thickness of the order of the radius of gyration. We find that the dynamics of the 2D melt is qualitatively different from that of the films. The 2D monomer mean-square displacement shows a $t^{8/15}$ power law at intermediate times instead of the $t^{1/2}$ law expected from Rouse theory for nonentangled chains. In films of finite thickness, chain entanglements may occur. The impact of confinement on the entanglement length $N_\mathrm{e}$ has been analyzed by a primitive path analysis. The analysis reveals that $N_\mathrm{e}$ increases strongly with decreasing film thickness.Comment: 6 pages, 3 figures, proceedings 3rd International Workshop on Dynamics in Confinement (CONFIT 2006

N-glycosylation of intrinsic and engineered N-X-S/T motifs by <em>Pichia pastoris</em> can be exploited to ligate the mannose receptor but reveals no gain in immunogenicity per se

Vaccination has the power to eradicate viral diseases and is a promising approach to cure cancer. However, modern vaccination strategies repeatedly fail in inducing a robust cytotoxic CD8+ T cell response, which is needed to eradicate virus-infected or malignantly transformed cells. One way to improve this induction is the targeting of C-type lectin receptors on dendritic cells that lead to the presentation of antigens on MHC class I molecules to CD8+ T cells in a process termed cross-presentation. In addition, certain C-type lectin receptors have the capacity to induce DC maturation, which provides the second crucial signal to induce cytotoxic T cell activation. Yeasts such as Pichia pastoris produce N-glycans that are able to ligate such C-type lectin receptors and are thus generally considered to be immunostimulatory. N-glycosylation by P. pastoris might hence be exploited in vaccine strategies to promote both MHC I-restricted antigen presentation and DC maturation. However, the benefit of such a vaccination approach remains elusive since the particular effect of P. pastoris-derived N-glycans on a cellular and humoral response in vivo has not been investigated so far. Here we tested whether it is possible to introduce N-glycans on proteins that are not glycosylated in their native state by recombinant expression in P. pastoris in order to target C-type lectin receptors and increase antigen cross-presentation. For this purpose we expressed β-galactosidase (β-gal), a cytosolic Escherichia coli protein bearing several potential glycosylation sites, and a GFP-derivative with an engineered glycosylation site (NST-GFP) in P. pastoris. We show that both intrinsic and artificially designed N-glycosylation motifs are readily glycosylated after secretion by P. pastoris. We demonstrate that the attached N-glycans ligate the calcium-dependet carbohydrate recognition domains of the mannose receptor (MR), a C-type lectin receptor that mediates cross-presentation of the model antigen ovalbumin (OVA). Antigens internalized by bone marrow-derived dendritic cells (BM-DCs) were consistently routed to OVA-positive compartments related to cross-presentation. However, subsequent in vitro analysis revealed that P. pastoris-derived N-glycans had no immunostimulatory capacity on BM-DCs per se. To elucidate the impact of such enforced N-glycosylation in vivo we subcutaneously immunized mice with N-glycosylated or enzymatically deglycosylated β-gal or NST-GFP. Surprisingly, the effect of N-glycosylation on in vivo cross-presentation proved to be dependent on the nature of the antigen. The presence of N-glycans increased the in vivo cytotoxicity against β-gal, whereas a decrease was observed against NST-GFP fused to an immunodominant OVA-epitope. Importain vivo ntly, for both antigens tested we observed a reduction of the humoral immune response in the presence of N-glycans as indicated by decreased serum IgG in comparison to the group immunized with deglycosylated proteins. Our data demonstrate that P. pastoris can be used to tag non-glycoproteins with N-glycans that target the MR. However, a beneficial effect of such N-glycans on in vivo cross-presentation was dependent on the antigen, and the presence of N-glycans consistently decreased a humoral response. These findings have important implications on recombinant vaccines using Pichia pastoris as an expression system

A finite excluded volume bond-fluctuation model: Static properties of dense polymer melts revisited

The classical bond-fluctuation model (BFM) is an efficient lattice Monte Carlo algorithm for coarse-grained polymer chains where each monomer occupies exclusively a certain number of lattice sites. In this paper we propose a generalization of the BFM where we relax this constraint and allow the overlap of monomers subject to a finite energy penalty \overlap. This is done to vary systematically the dimensionless compressibility $g$ of the solution in order to investigate the influence of density fluctuations in dense polymer melts on various s tatic properties at constant overall monomer density. The compressibility is obtained directly from the low-wavevector limit of the static structure fa ctor. We consider, e.g., the intrachain bond-bond correlation function, $P(s)$, of two bonds separated by $s$ monomers along the chain. It is shown that the excluded volume interactions are never fully screened for very long chains. If distances smaller than the thermal blob size are probed ($s \ll g$) the chains are swollen acc ording to the classical Fixman expansion where, e.g., $P(s) \sim g^{-1}s^{-1/2}$. More importantly, the polymers behave on larger distances ($s \gg g$) like swollen chains of incompressible blobs with P(s) \si m g^0s^{-3/2}.Comment: 46 pages, 12 figure

An Optimal Control Algorithm for Ramp Metering of Urban Freeways

An urban freeway is treated as a dynamic process. A state model for the freeway is obtained with sectional traffic densities as states and entrance flow rates as controls. A linear programming problem is solved to obtain the optimal freeway densities and entrance flow rates under steady-state conditions, and a state regulator is used to minimize the deviations in traffic densities from these optimal steady-state values