Hyperon coupling dependence of hadron matter properties in relativistic mean field model

The properties of hadronic matter at beta equilibrium in a wide range of densities are described by appropriate equations of state in the framework of the relativistic mean field model. Strange meson fields, namely the scalar meson field sigma*(975) and the vector meson field sigma*(1020), are included in the present work. We discuss and compare the results of the equation of state, nucleon effective mass, and strangeness fraction obtained by adopting the TM1, TMA, and GL parameter sets for nuclear sector and three different choices for the hyperon couplings. We find that the parameter set TM1 favours the onset of hyperons most, while at high densities the GL parameter set leads to the most hyperon-rich matter. For a certain parameter set (e.g. TM1), the most hyperon-rich matter is obtained for the hyperon potential model. The influence of the hyperon couplings on the effective mass of nucleon, is much weaker than that on the nucleon parameter set. The nonstrange mesons dominate essentially the global properties of dense hyperon matter. The hyperon potential model predicts the lowest value of the neutron star maximum mass of about 1.45 M-sun to be 0.4-0.5 M-sun lower than the prediction by using the other choices for hyperon couplings.

Measurement of the Bottom Quark Contribution to Nonphotonic Electron Production in p plus p Collisions at root s=200 GeV

The contribution of B meson decays to nonphotonic electrons, which are mainly produced by the semileptonic decays of heavy-flavor mesons, in p + p collisions at root s = 200 GeV has been measured using azimuthal correlations between nonphotonic electrons and hadrons. The extracted B decay contribution is approximately 50% at a transverse momentum of p(T) >= 5 GeV/c. These measurements constrain the nuclear modification factor for electrons from B and D meson decays. The result indicates that B meson production in heavy ion collisions is also suppressed at high p(T).

eta production off the proton in a Regge-plus-chiral quark approach

A chiral constituent quark model approach, embodying s- and u-channel exchanges, complemented with a Reggeized treatment for the t channel is presented. A model is obtained allowing data for pi(-)p ->eta n and gamma p ->eta p to be described satisfactorily. For the latter reaction, recently released data by the CLAS and CBELSA/TAPS Collaborations in the system total energy range 1.6 less than or similar to W less than or similar to 2.8 GeV are well reproduced by the inclusion of Reggeized trajectories instead of simple. and. poles. The contribution from "missing" resonances, with masses below 2 GeV, is found to be negligible in the considered processes.

Long-distant contribution and chi(c1) radiative decays to light vector meson

The discrepancy between the PQCD calculation and the CLEO data for chi (c1)->gamma V (V=rho (0), omega, phi) stimulates our interest in exploring other mechanisms of chi (c1) decay. In this work, we apply an important non-perturbative QCD effect, i.e., the hadronic loop mechanism, to study chi (c1)->gamma V radiative decay. Our numerical result shows that the theoretical results including the hadronic loop contribution and the PQCD calculation of chi (c1)->gamma V are consistent with the corresponding CLEO data of chi (c1)->gamma V. We expect further experimental measurement of chi (c1)->gamma V, which will be helpful to test the hadronic loop effect on chi (c1) decay.

The intermolecular coupling through space for stacked high spin molecules

Intermolecular ferromagnetic interactions in two stacking models for the dimer of high spin molecules are investigated by means of AM1-CI approach. It is shown that the stability of high spin ground state versus low spin state can be simply traced back to the number and the extent of atoms with reversed signs of pi-spin density in neighboring molecules coupled to each other in shortest distance.

SIMPLE-MODELS FOR STRESS-RELAXATION AND YIELD PHENOMENON OF PHENOLPHTHALEIN POLY(ETHER KETONE)

According to stress relaxation curves of phenolphthalein poly(ether ketone) (PEK-C) at different temperatures and the principle of time-temperature equivalence, the master curves of PEK-C at arbitrary reference temperatures are obtained. A coupling model (Kohlrausch-Williams-Watts) is applied to explain quantitatively the different temperature dependence of stress relaxation behavior and the relationship between stress relaxation and yield phenomenon is established through the coupling model.

Integration of micro- and macroscopic models for pedestrian evacuation simulation

Simulation of pedestrian evacuations of smart buildings in emergency is a powerful tool for building analysis, dynamic evacuation planning and real-time response to the evolving state of evacuations. Macroscopic pedestrian models are low-complexity models that are and well suited to algorithmic analysis and planning, but are quite abstract. Microscopic simulation models allow for a high level of simulation detail but can be computationally intensive. By combining micro- and macro- models we can use each to overcome the shortcomings of the other and enable new capability and applications for pedestrian evacuation simulation that would not be possible with either alone. We develop the EvacSim multi-agent pedestrian simulator and procedurally generate macroscopic flow graph models of building space, integrating micro- and macroscopic approaches to simulation of the same emergency space. By “coupling” flow graph parameters to microscopic simulation results, the graph model captures some of the higher detail and fidelity of the complex microscopic simulation model. The coupled flow graph is used for analysis and prediction of the movement of pedestrians in the microscopic simulation, and investigate the performance of dynamic evacuation planning in simulated emergencies using a variety of strategies for allocation of macroscopic evacuation routes to microscopic pedestrian agents. The predictive capability of the coupled flow graph is exploited for the decomposition of microscopic simulation space into multiple future states in a scalable manner. By simulating multiple future states of the emergency in short time frames, this enables sensing strategy based on simulation scenario pattern matching which we show to achieve fast scenario matching, enabling rich, real-time feedback in emergencies in buildings with meagre sensing capabilities.

Coupling of beta2-adrenoceptor to Gi proteins and its physiological relevance in murine cardiac myocytes.

-Transgenic mouse models have been developed to manipulate beta-adrenergic receptor (betaAR) signal transduction. Although several of these models have altered betaAR subtypes, the specific functional sequelae of betaAR stimulation in murine heart, particularly those of beta2-adrenergic receptor (beta2AR) stimulation, have not been characterized. In the present study, we investigated effects of beta2AR stimulation on contraction, [Ca2+]i transient, and L-type Ca2+ currents (ICa) in single ventricular myocytes isolated from transgenic mice overexpressing human beta2AR (TG4 mice) and wild-type (WT) littermates. Baseline contractility of TG4 heart cells was increased by 3-fold relative to WT controls as a result of the presence of spontaneous beta2AR activation. In contrast, beta2AR stimulation by zinterol or isoproterenol plus a selective beta1-adrenergic receptor (beta1AR) antagonist CGP 20712A failed to enhance the contractility in TG4 myocytes, and more surprisingly, beta2AR stimulation was also ineffective in increasing contractility in WT myocytes. Pertussis toxin (PTX) treatment fully rescued the ICa, [Ca2+]i, and contractile responses to beta2AR agonists in both WT and TG4 cells. The PTX-rescued murine cardiac beta2AR response is mediated by cAMP-dependent mechanisms, because it was totally blocked by the inhibitory cAMP analog Rp-cAMPS. These results suggest that PTX-sensitive G proteins are responsible for the unresponsiveness of mouse heart to agonist-induced beta2AR stimulation. This was further corroborated by an increased incorporation of the photoreactive GTP analog [gamma-32P]GTP azidoanilide into alpha subunits of Gi2 and Gi3 after beta2AR stimulation by zinterol or isoproterenol plus the beta1AR blocker CGP 20712A. This effect to activate Gi proteins was abolished by a selective beta2AR blocker ICI 118,551 or by PTX treatment. Thus, we conclude that (1) beta2ARs in murine cardiac myocytes couple to concurrent Gs and Gi signaling, resulting in null inotropic response, unless the Gi signaling is inhibited; (2) as a special case, the lack of cardiac contractile response to beta2AR agonists in TG4 mice is not due to a saturation of cell contractility or of the cAMP signaling cascade but rather to an activation of beta2AR-coupled Gi proteins; and (3) spontaneous beta2AR activation may differ from agonist-stimulated beta2AR signaling.

Adrenergic receptors. Models for regulation of signal transduction processes.

Adrenergic receptors are prototypic models for the study of the relations between structure and function of G protein-coupled receptors. Each receptor is encoded by a distinct gene. These receptors are integral membrane proteins with several striking structural features. They consist of a single subunit containing seven stretches of 20-28 hydrophobic amino acids that represent potential membrane-spanning alpha-helixes. Many of these receptors share considerable amino acid sequence homology, particularly in the transmembrane domains. All of these macromolecules share other similarities that include one or more potential sites of extracellular N-linked glycosylation near the amino terminus and several potential sites of regulatory phosphorylation that are located intracellularly. By using a variety of techniques, it has been demonstrated that various regions of the receptor molecules are critical for different receptor functions. The seven transmembrane regions of the receptors appear to form a ligand-binding pocket. Cysteine residues in the extracellular domains may stabilize the ligand-binding pocket by participating in disulfide bonds. The cytoplasmic domains contain regions capable of interacting with G proteins and various kinases and are therefore important in such processes as signal transduction, receptor-G protein coupling, receptor sequestration, and down-regulation. Finally, regions of these macromolecules may undergo posttranslational modifications important in the regulation of receptor function. Our understanding of these complex relations is constantly evolving and much work remains to be done. Greater understanding of the basic mechanisms involved in G protein-coupled, receptor-mediated signal transduction may provide leads into the nature of certain pathophysiological states.

ARFGAP1 plays a central role in coupling COPI cargo sorting with vesicle formation.

Examining how key components of coat protein I (COPI) transport participate in cargo sorting, we find that, instead of ADP ribosylation factor 1 (ARF1), its GTPase-activating protein (GAP) plays a direct role in promoting the binding of cargo proteins by coatomer (the core COPI complex). Activated ARF1 binds selectively to SNARE cargo proteins, with this binding likely to represent at least a mechanism by which activated ARF1 is stabilized on Golgi membrane to propagate its effector functions. We also find that the GAP catalytic activity plays a critical role in the formation of COPI vesicles from Golgi membrane, in contrast to the prevailing view that this activity antagonizes vesicle formation. Together, these findings indicate that GAP plays a central role in coupling cargo sorting and vesicle formation, with implications for simplifying models to describe how these two processes are coupled during COPI transport.

VCSEL to waveguide coupling for optical backplanes

Hybrid OECB (Opto-Electrical Circuit Boards) are expected to make a significant impact in the telecomm switches arena within the next five years, creating optical backplanes with high speed point-to-point optical interconnects. The critical aspect in the manufacture of the optical backplane is the successful coupling between VCSEL (Vertical Cavity Surface Emitting Laser) device and embedded waveguide in the OECB. Optical performance will be affected by CTE mismatch in the material properties, and manufacturing tolerances. This paper will discuss results from a multidisciplinary research project involving both experimentation and modelling. Key process parameters are being investigated using Design of Experiments and Finite Element Modelling. Simulations have been undertaken that predict the temperature in the VCSEL during normal operation, and the subsequent misalignment that this imposes. The results from the thermomechanical analysis are being used with optimisation software and the experimental DOE (Design of Experiments) to identify packaging parameters that minimise misalignment. These results are also imported into an optical model which solves optical energy and attenuation from the VCSEL aperture into, and then through, the waveguide. Results from the thermomechanical and optical models will be discussed as will the experimental results from the DOE.

Models for magnetohydrodynamics of aluminium electrolysis cells

The electric current and the associated magnetic field in aluminium electrolysis cells create effects limiting the cell productivity and possibly cause instabilities: surface waving, ‘anode effects’, erosion of pot lining, feed material sedimentation, etc. The instructive analysis is presented via a step by step inclusion of different physical coupling factors affecting the magnetic field, electric current, velocity and wave development in the electrolysis cells. The full time dependent model couples the nonlinear turbulent fluid dynamics and the extended electromagnetic field in the cell, and the whole bus bar circuit with the ferromagnetic effects. Animated examples for the high amperage cells are presented. The theory and numerical model of the electrolysis cell is extended to the cases of variable cell bottom of aluminium layer and the variable thickness of the electrolyte due to the anode non-uniform burn-out process and the presence of the anode channels. The problem of the channel importance is well known Moreau-Evans model) for the stationary interface and the velocity field, and was validated against measurements in commercial cells, particularly with the recently published ‘benchmark’ test for the MHD models of aluminium cells [1]. The presence of electrolyte channels requires also to reconsider the previous magnetohydrodynamic instability theories and the dynamic wave development models. The results indicate the importance of a ‘sloshing’ parametrically excited MHD wave development in the aluminium production cells.

Choosing the appropriate level of coupling in multi-physics modeling of metallurgical processes

A computational model for the interrelated phenomena in the process of vacuum arc remelting is analyzed and adjusted of optimal accuracy and computation time. The decision steps in this case study are offered as an example how the coupling in models of similar processes can be addressed. Results show dominance of the electromagnetic forces over buoyancy and inertia for the investigated process conditions.

A general framework for aquatic biogeochemical models

One of the most of challenging steps in the development of coupled hydrodynamic-biogeochemical models is the combination of multiple, often incompatible computer codes that describe individual physical, chemical, biological and geological processes. This “coupling” is time-consuming, error-prone, and demanding in terms of scientific and programming expertise. The open source, Fortran-based Framework for Aquatic Biogeochemical Models addresses these problems by providing a consistent set of programming interfaces through which hydrodynamic and biogeochemical models communicate. Models are coded once to connect to FABM, after which arbitrary combinations of hydrodynamic and biogeochemical models can be made. Thus, a biogeochemical model code works unmodified within models of a chemostat, a vertically structured water column, and a three-dimensional basin. Moreover, complex biogeochemistry can be distributed over many compact, self-contained modules, coupled at run-time. By enabling distributed development and user-controlled coupling of biogeochemical models, FABM enables optimal use of the expertise of scientists, programmers and end-users.

Automated mixed dimensional modelling from 2D and 3D CAD models

The motivation for this paper is to present procedures for automatically creating idealised finite element models from the 3D CAD solid geometry of a component. The procedures produce an accurate and efficient analysis model with little effort on the part of the user. The technique is applicable to thin walled components with local complex features and automatically creates analysis models where 3D elements representing the complex regions in the component are embedded in an efficient shell mesh representing the mid-faces of the thin sheet regions. As the resulting models contain elements of more than one dimension, they are referred to as mixed dimensional models. Although these models are computationally more expensive than some of the idealisation techniques currently employed in industry, they do allow the structural behaviour of the model to be analysed more accurately, which is essential if appropriate design decisions are to be made. Also, using these procedures, analysis models can be created automatically whereas the current idealisation techniques are mostly manual, have long preparation times, and are based on engineering judgement. In the paper the idealisation approach is first applied to 2D models that are used to approximate axisymmetric components for analysis. For these models 2D elements representing the complex regions are embedded in a 1D mesh representing the midline of the cross section of the thin sheet regions. Also discussed is the coupling, which is necessary to link the elements of different dimensionality together. Analysis results from a 3D mixed dimensional model created using the techniques in this paper are compared to those from a stiffened shell model and a 3D solid model to demonstrate the improved accuracy of the new approach. At the end of the paper a quantitative analysis of the reduction in computational cost due to shell meshing thin sheet regions demonstrates that the reduction in degrees of freedom is proportional to the square of the aspect ratio of the region, and for long slender solids, the reduction can be proportional to the aspect ratio of the region if appropriate meshing algorithms are used.