764 research outputs found
Systems Planning and Development in Finnish Newspapers
Newspapers are becoming a significant user of systems. This has changed the strategy, investment and personnel structure of Finnish newspaper production plants already during the 1970's National joint efforts and firm policies are reviewed. The reasons for this development are analyzed. At the same time as systems are implemented improvements have been obtained in work flow, productivity and economy. There are also problems as many newspapers cannot follow the accelerating technology transfer. In the most successful cases the firms change from passive buyers to active systems development and planning units which both create and transfer new technology. Newspaper systems are highly individual and require an essential software tailoring. On the other hand graphic mass communication -- such as newspaper -- gets new alternative and competing forms. Newspapers as many other institutions are interested in developing advertising and electronic media such as cable-TV, pay-TV, videotex and video recordings
Ab initio simulations of peptide-mineral interactions
We performed Car-Parrinello Molecular Dynamics (CPMD) simulations of two amino acids, aspartic acid (Asp) and phophoserine (pSer), on a calcium oxalate monohydrate (COM) surface as a model of the interactions of phosphoproteins with biominerals. In our earlier work using in vitro experiments and classical Molecular Dynamics (MD) simulations we have demonstrated the importance of phosphorylation of serine on the interactions of osteopontin (OPN) with COM. We used configurations from our previous classical MD simulations as a starting point for the ab initio simulations. In the case of Asp we found that the a-carboxyl and amine groups form temporary close contacts with the surface. For the dipeptide Asp-pSer the carboxyl groups form permanent close contacts with the surface and the distances of its other functional groups do not vary much. We show how the interaction of carboxyl groups with COM crystal is established and confirm the importance of phosphorylation in mediating the interactions between COM surfaces and OPN. Keywords: Molecular dynamics; Ab initio; Car-Parrinello; Osteopontin; Calcium oxalate monohydrate; Aspartic acid; Phosphoserin
The cognitive load of presupposition triggers: mandatory and optional repairs in presupposition failure
Key Role of Defects in Thermoelectric Performance of TiMSn (M = Ni, Pd, and Pt) Half-Heusler Alloys
Phase Diagram and Commensurate-Incommensurate Transitions in the Phase Field Crystal Model with an External Pinning Potential
We study the phase diagram and the commensurate-incommensurate transitions in
a phase field model of a two-dimensional crystal lattice in the presence of an
external pinning potential. The model allows for both elastic and plastic
deformations and provides a continuum description of lattice systems, such as
for adsorbed atomic layers or two-dimensional vortex lattices. Analytically, a
mode expansion analysis is used to determine the ground states and the
commensurate-incommensurate transitions in the model as a function of the
strength of the pinning potential and the lattice mismatch parameter. Numerical
minimization of the corresponding free energy shows good agreement with the
analytical predictions and provides details on the topological defects in the
transition region. We find that for small mismatch the transition is of
first-order, and it remains so for the largest values of mismatch studied here.
Our results are consistent with results of simulations for atomistic models of
adsorbed overlayers
Hydrophobicity within the three-dimensional Mercedes-Benz model: Potential of mean force
We use the three-dimensional Mercedes-Benz model for water and Monte Carlo simulations to study the structure and thermodynamics of the hydrophobic interaction. Radial distribution functions are used to classify different cases of the interaction, namely, contact configurations, solvent separated configurations, and desolvation configurations. The temperature dependence of these cases is shown to be in qualitative agreement with atomistic models of water. In particular, while the energy for the formation of contact configurations is favored by entropy, its strengthening with increasing temperature is accounted for by enthalpy. This is consistent with our simulated heat capacity. An important feature of the model is that it can be used to account for well-converged thermodynamics quantities, e.g., the heat capacity of transfer. Microscopic mechanisms for the temperature dependence of the hydrophobic interaction are discussed at the molecular level based on the conceptual simplicity of the model.Peer reviewe
Cutting Ice: Nanowire Regelation
Even below its normal melting temperature, ice melts when subjected to high pressure and refreezes once the pressure is lifted. A classic demonstration of this regelation phenomenon is the passing of a thin wire through a block of ice when sufficient force is exerted. Here we present a molecular-dynamics study of a nanowire cutting through ice to unravel the molecular level mechanisms responsible for regelation. In particular, we show that the transition from a stationary to a moving wire due to increased driving force changes from symmetric and continuous to asymmetric and discontinuous as a hydrophilic wire is replaced by a hydrophobic one. This is explained at the molecular level in terms of the wetting properties of the wire.Peer reviewe
Assessing the Nature of Lipid Raft Membranes
The paradigm of biological membranes has recently gone through a major update. Instead of being fluid and homogeneous, recent studies suggest that membranes are characterized by transient domains with varying fluidity. In particular, a number of experimental studies have revealed the existence of highly ordered lateral domains rich in sphingomyelin and cholesterol (CHOL). These domains, called functional lipid rafts, have been suggested to take part in a variety of dynamic cellular processes such as membrane trafficking, signal transduction, and regulation of the activity of membrane proteins. However, despite the proposed importance of these domains, their properties, and even the precise nature of the lipid phases, have remained open issues mainly because the associated short time and length scales have posed a major challenge to experiments. In this work, we employ extensive atom-scale simulations to elucidate the properties of ternary raft mixtures with CHOL, palmitoylsphingomyelin (PSM), and palmitoyloleoylphosphatidylcholine. We simulate two bilayers of 1,024 lipids for 100 ns in the liquid-ordered phase and one system of the same size in the liquid-disordered phase. The studies provide evidence that the presence of PSM and CHOL in raft-like membranes leads to strongly packed and rigid bilayers. We also find that the simulated raft bilayers are characterized by nanoscale lateral heterogeneity, though the slow lateral diffusion renders the interpretation of the observed lateral heterogeneity more difficult. The findings reveal aspects of the role of favored (specific) lipid–lipid interactions within rafts and clarify the prominent role of CHOL in altering the properties of the membrane locally in its neighborhood. Also, we show that the presence of PSM and CHOL in rafts leads to intriguing lateral pressure profiles that are distinctly different from corresponding profiles in nonraft-like membranes. The results propose that the functioning of certain classes of membrane proteins is regulated by changes in the lateral pressure profile, which can be altered by a change in lipid content
Phase diagram of pinned lattices in the phase field crystal model
We study the phase diagram and the commensurate-incommensurate phase transitions of a two-dimensional phase field crystal model for adsorbed layers. The model allows for both elastic and plastic deformations on atomic and diffusive time-scales, and provides a continuum description of lattice systems, such as adsorbed atomic layers or two-dimensional vortex lattices. Analytically, mode expansion analysis and numerical minimization of the free energy are used to determine the ground states as a function of the pinning potential and lattice mismatch parameter. The results show a rich phase diagram with several different types of commensurate and incommensurate phases.Peer reviewe
Nonlinear driven response of a phase-field crystal in a periodic pinning potential
We study numerically the phase diagram and the response under a driving force of the phase field crystal model for pinned lattice systems introduced recently for both one- and two-dimensional systems. The model describes the lattice system as a continuous density field in the presence of a periodic pinning potential, allowing for both elastic and plastic deformations of the lattice. We first present results for phase diagrams of the model in the absence of a driving force. The nonlinear response to a driving force on an initially pinned commensurate phase is then studied via overdamped dynamic equations of motion for different values of mismatch and pinning strengths. For large pinning strength the driven depinning transitions are continuous, and the sliding velocity varies with the force from the threshold with power-law exponents in agreement with analytical predictions. Transverse depinning transitions in the moving state are also found in two dimensions. Surprisingly, for sufficiently weak pinning potential we find a discontinuous depinning transition with hysteresis even in one dimension under overdamped dynamics. We also characterize structural changes of the system in some detail close to the depinning transition
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