New parametrization method for dissipative particle dynamics

We introduce an improved method of parameterizing the Groot-Warren version of Dissipative Particle Dynamics (DPD) by exploiting a correspondence between DPD and Scatchard-Hildebrand regular solution theory. The new parameterization scheme widens the realm of applicability of DPD by first removing the restriction of equal repulsive interactions between like beads, and second, by relating all conservative interactions between beads directly to cohesive energy densities. We establish the correspondence by deriving an expression for the Helmoltz free energy of mixing obtaining a heat of mixing which is exactly the same form as that for a regular mixture (quadratic in the volume fraction) and an entropy of mixing which reduces to the ideal entropy of mixing for equal molar volumes. We equate the conservative interaction parameters in the DPD force law to the cohesive energy densities of the pure fluids providing an alternative method of calculating the self-interaction parameters as well as a route to the cross-interaction parameter. We validate the new parameterization by modelling the binary system: SnI4/SiCl4, which displays liquid-liquid coexistence below an upper critical solution temperature around 140°C. A series of DPD simulations were conducted at a set of temperatures ranging from 0°C to above the experimental upper critical solution temperature using conservative parameters based on extrapolated experimental data. These simulations can be regarded as being equivalent to a quench from a high temperature to a lower one at constant volume. Our simulations recover the expected phase behaviour ranging from solid-liquid coexistence to liquid-liquid co-existence and eventually leading to a homogeneous single phase system. The results yield a binodal curve in close agreement with one predicted using regular solution theory, but, significantly, in closer agreement with actual solubility measurements

Poly(A)-binding proteins are required for diverse biological processes in metazoans

PABPs [poly(A)-binding proteins] bind to the poly(A) tail of eukaryotic mRNAs and are conserved in species ranging from yeast to human. The prototypical cytoplasmic member, PABP1, is a multifunctional RNA-binding protein with roles in global and mRNA-specific translation and stability, consistent with a function as a central regulator of mRNA fate in the cytoplasm. More limited insight into the molecular functions of other family members is available. However, the consequences of disrupting PABP function in whole organisms is less clear, particularly in vertebrates, and even more so in mammals. In the present review, we discuss current and emerging knowledge with respect to the functions of PABP family members in whole animal studies which, although incomplete, already underlines their biological importance and highlights the need for further intensive research in this area

Evidence for limited activation of distinct CD4⁺ T cell subsets in response to the Plasmodium falciparum circumsporozoite protein in Papua New Guinea

Both CD4⁺ and CD8⁺ T cells, as well as antibody, are known to be important in sporozoite immunity. Data from animal studies suggest that cytokines, in particular γ-interferon and interleukin-6, are involved. The interplay of these various factors and their importance in vaccine development has, however, not yet been elucidated. In this study, we have studied cellular and humoral responses of individuals naturally exposed to malaria in a highly endemic region of Papua New Guinea to the circumsporozoite protein of Plasmodium falciparum, a prime vaccine candidate antigen. A paucity of any CD4⁺ lymphoproliferative response to this protein by Papua New Guineans was notable which parallels our recent observation of a paucity of CD8⁺ T cell response and contrasts markedly with the responses of other endemic populations. There was nevertheless a significant antibody response to the central conserved B cell epitope, (NANP)ₙ, as well as to other critical epitopes. An inverse relationship between γ-interferon production and interleukin-6 production and a positive correlation between γ-interferon production and CS peptide-specific lymphoproliferation was observed. High levels of peptide-specific IL-6 production were associated with high levels of peptide-specific serum antibodies. Our data provide evidence for the limited activation of distinct CD4⁺ T cell subsets and for the existence of functionally distinct subpopulations of human CD4⁺ T cells with respect to cytokines known to be important in sporozoite immunity

Annual Report of the Municipal Officers of the Town of Turner Maine For the Year Ending Feb. 15 1920

\u3cp\u3eThis chapter addresses the problem of estimating the parameters of a Bayesian network from incomplete data. This is a hard problem, which for computational reasons cannot be effectively tackled by a full Bayesian approach. The work around is to search for the estimate with maximum posterior probability. This is usually done by selecting the highest posterior probability estimate among those found by multiple runs of Expectation-Maximization with distinct starting points. However, many local maxima characterize the posterior probability function, and several of them have similar high probability. We argue that high probability is necessary but not sufficient in order to obtain good estimates.We present an approach based on maximum entropy to address this problem and describe a simple and effective way to implement it. Experiments show that our approach produces significantly better estimates than the most commonly used method.\u3c/p\u3