scholarly journals Evidence of Structural Inhomogeneities in Hard-Soft Dimeric Particles without Attractive Interactions

Materials ◽  
2019 ◽  
Vol 13 (1) ◽  
pp. 84 ◽  
Author(s):  
Gianmarco Munaò ◽  
Franz Saija
Keyword(s):  
Hard Spheres ◽  
Hard Core ◽  
Fluid Phase ◽  
Colloidal Dispersion ◽  
Systematic Investigation ◽  
Distribution Functions ◽  
Structure Factors ◽  
Soft Spheres ◽  
Wide Range ◽  
Structural Inhomogeneities

We perform Monte Carlo simulations of a simple hard-soft dimeric model constituted by two tangent spheres experiencing different interactions. Specifically, two hard spheres belonging to different dimers interact via a bare hard-core repulsion, whereas two soft spheres experience a softly repulsive Hertzian interaction. The cross correlations are soft as well. By exploring a wide range of temperatures and densities we investigate the capability of this model to document the existence of structural inhomogeneities indicating the possible onset of aggregates, even if no attraction is set. The fluid phase behavior is studied by analyzing structural and thermodynamical properties of the observed structures, in particular by computing radial distribution functions, structure factors and cluster size distributions. The numerical results are supported by integral equation theories of molecular liquids which allow for a finer and faster spanning of the temperature-density diagram. Our results may serve as a framework for a more systematic investigation of self-assembled structures of functionalized hard-soft dimers able to aggregate in a variety of structures widely oberved in colloidal dispersion.

scholarly journals Bulk fluid phase behaviour of colloidal platelet–sphere and platelet–polymer mixtures

2013 ◽  
Vol 371 (1988) ◽  
pp. 20120259 ◽  
Author(s):  
Daniel de las Heras ◽  
Matthias Schmidt
Keyword(s):  
Phase Diagrams ◽  
Nematic Phase ◽  
Density Functional ◽  
Hard Spheres ◽  
Hard Core ◽  
Fluid Phase ◽  
Phase Behaviour ◽  
Size Ratio ◽  
Polymer Mixtures ◽  
Bulk Fluid

Using a geometry-based fundamental measure density functional theory, we calculate bulk fluid phase diagrams of colloidal mixtures of vanishingly thin hard circular platelets and hard spheres. We find isotropic–nematic phase separation, with strong broadening of the biphasic region, upon increasing the pressure. In mixtures with large size ratio of platelet and sphere diameters, there is also demixing between two nematic phases with differing platelet concentrations. We formulate a fundamental measure density functional for mixtures of colloidal platelets and freely overlapping spheres, which represent ideal polymers, and use it to obtain phase diagrams. We find that, for low platelet–polymer size ratio, in addition to isotropic–nematic and nematic–nematic phase coexistence, platelet–polymer mixtures also display isotropic–isotropic demixing. By contrast, we do not find isotropic–isotropic demixing in hard-core platelet–sphere mixtures for the size ratios considered.

Generalized van der Waals theory. IX. Excess properties of simple fluid mixtures

1982 ◽  
Vol 35 (2) ◽  
pp. 247 ◽  
Author(s):  
S Nordholm ◽  
PR Harrowell ◽  
K Cheung
Keyword(s):  
Hard Spheres ◽  
Van Der Waals ◽  
Pair Potential ◽  
Distribution Functions ◽  
Single Component ◽  
Excess Properties ◽  
Fluid Mixtures ◽  
Simple Fluid ◽  
Wide Range ◽  
Van Der Waals Theory

The generalized van der Waals theory, recently developed and applied to a wide range of problems involving simple single component fluids, is here extended to uniform simple fluid mixtures. Binary mixtures of hard spheres or particles interacting by Lennard-Jones pair potentials are considered, the Lorentz-Berthelot rules being used to generate the between-species pair-potential. The basic theory is very simple, combining features of cell and mean field theories. Yet it differs considerably from the presently favoured theories of mixtures. The new GvdW theory is implemented at four levels of sophistication but the calculations remain very simple by present standards even for the most accurate form of the theory wherein the effective hard-sphere diameters are determined variationally. The results obtained for the equation of state and thermodynamic excess properties indicate that the very favourable accuracy relative to the simplicity of the theory observed for single component fluids is retained for mixtures. In the case of excess properties calculations for a wide range of equimolar mixtures suggest that the GvdW accuracy is substantially better than that obtained by random mixture or average potential theories but not as good as that obtained by the best theories based on the estimation of the radial distribution functions of the fluid.

Optical Properties of HVEM Accelerators

1975 ◽  
Vol 33 ◽  
pp. 180-181
Author(s):  
A. Strojnik ◽  
J.W. Scholl ◽  
V. Bevc
Keyword(s):  
Optical Properties ◽  
Electron Accelerator ◽  
Systematic Investigation ◽  
Electron Source ◽  
High Brightness ◽  
The Past ◽  
Wide Range ◽  
Optical Behavior

The electron accelerator, as inserted between the electron source (injector) and the imaging column of the HVEM, is usually a strong lens and should be optimized in order to ensure high brightness over a wide range of accelerating voltages and illuminating conditions. This is especially true in the case of the STEM where the brightness directly determines the highest resolution attainable. In the past, the optical behavior of accelerators was usually determined for a particular configuration. During the development of the accelerator for the Arizona 1 MEV STEM, systematic investigation was made of the major optical properties for a variety of electrode configurations, number of stages N, accelerating voltages, 1 and 10 MEV, and a range of injection voltages ϕ0 = 1, 3, 10, 30, 100, 300 kV).

Computer processing of high-resolution images of periodic specimens

1986 ◽  
Vol 44 ◽  
pp. 2-5
Author(s):  
W. Chiu ◽  
M.F. Schmid ◽  
T.-W. Jeng
Keyword(s):  
High Resolution ◽  
Fourier Transforms ◽  
Complex Structure ◽  
Distribution Functions ◽  
Multiple Image ◽  
Cryo Electron Microscopy ◽  
Structure Factors ◽  
Unit Cells ◽  
High Resolution Images ◽  
Phase Probability Distribution

Cryo-electron microscopy has been developed to the point where one can image thin protein crystals to 3.5 Å resolution. In our study of the crotoxin complex crystal, we can confirm this structural resolution from optical diffractograms of the low dose images. To retrieve high resolution phases from images, we have to include as many unit cells as possible in order to detect the weak signals in the Fourier transforms of the image. Hayward and Stroud proposed to superimpose multiple image areas by combining phase probability distribution functions for each reflection. The reliability of their phase determination was evaluated in terms of a crystallographic “figure of merit”. Grant and co-workers used a different procedure to enhance the signals from multiple image areas by vector summation of the complex structure factors in reciprocal space.

Sanctions with Chinese Characteristics

2020 ◽  
Author(s):  
Angela Poh
Keyword(s):  
Systematic Investigation ◽  
United Nations Security Council ◽  
Media Discourse ◽  
Middle Ground ◽  
Xi Jinping ◽  
Policy Makers ◽  
Chinese Characteristics ◽  
Wide Range ◽  
Complete Alignment ◽  
Depth Interviews

The view that China has become increasingly assertive under President Xi Jinping is now a common trope in academic and media discourse. However, until the end of Xi Jinping’s first term in March 2018, China had been relatively restrained in its use of coercive economic measures. This is puzzling given the conventional belief among scholars and practitioners that sanctions are a middle ground between diplomatic and military/paramilitary action. Using a wide range of methods and data — including in-depth interviews with 76 current and former politicians, policy-makers, diplomats, and commercial actors across 12 countries and 16 cities — Sanctions with Chinese Characteristics: Rhetoric and Restraint in China’s Diplomacy examines the ways in which China had employed economic sanctions to further its political objectives, and the factors explaining China’s behaviour. This book provides a systematic investigation into the ways in which Chinese decisionmakers approached sanctions both at the United Nations Security Council and unilaterally, and shows how China’s longstanding sanctions rhetoric has had a constraining effect on its behaviour, resulting in its inability to employ sanctions in complete alignment with its immediate interests.

scholarly journals Monte Carlo Calculations of the Radial Distribution Functions for a Proton?Electron Plasma

1965 ◽  
Vol 18 (2) ◽  
pp. 119 ◽  
Author(s):  
AA Barker
Keyword(s):  
Monte Carlo ◽  
Crystal Lattice ◽  
Radial Distribution ◽  
Lattice Theory ◽  
Electron Plasma ◽  
Distribution Functions ◽  
Radial Distribution Functions ◽  
Monte Carlo Calculations ◽  
Wide Range ◽  
General Method

A general method is presented for computation of radial distribution functions for plasmas over a wide range of temperatures and densities. The method uses the Monte Carlo technique applied by Wood and Parker, and extends this to long-range forces using results borrowed from crystal lattice theory. The approach is then used to calculate the radial distribution functions for a proton-electron plasma of density 1018 electrons/cm3 at a temperature of 104 OK. The results show the usefulness of the method if sufficient computing facilities are available.

scholarly journals Recognition and inhibition of SARS-CoV-2 by humoral innate immunity pattern recognition molecules

2021 ◽  
Author(s):  
Matteo Stravalaci ◽  
Isabel Pagani ◽  
Elvezia Maria Paraboschi ◽  
Mattia Pedotti ◽  
Andrea Doni ◽  
...  
Keyword(s):  
Pattern Recognition ◽  
Innate Immunity ◽  
Disease Severity ◽  
Fluid Phase ◽  
Systematic Investigation ◽  
In Vitro Models ◽  
Lectin Pathway ◽  
Mannose Binding ◽  
Binding Lectin

The humoral arm of innate immunity includes diverse molecules with antibody-like functions, some of which serve as disease severity biomarkers in COVID-19. The present study was designed to conduct a systematic investigation of the interaction of humoral fluid phase pattern recognition molecules (PRM) with SARS-CoV-2. Out of 10 PRM tested, the long pentraxin PTX3 and Mannose Binding Lectin (MBL) bound the viral Nucleoprotein and Spike, respectively. MBL bound trimeric Spike, including that of variants of concern, in a glycan-dependent way and inhibited SARS-CoV-2 in three in vitro models. Moreover, upon binding to Spike, MBL activated the lectin pathway of complement activation. Genetic polymorphisms at the MBL locus were associated with disease severity. These results suggest that selected humoral fluid phase PRM can play an important role in resistance to, and pathogenesis of, COVID-19, a finding with translational implications.

scholarly journals Generating dense packings of hard spheres by soft interaction design

2018 ◽  
Vol 4 (6) ◽  
Author(s):  
Thibaud Maimbourg ◽  
Mauro Sellitto ◽  
Guilhem Semerjian ◽  
Francesco Zamponi
Keyword(s):  
Interaction Design ◽  
Optimization Problem ◽  
Hard Spheres ◽  
Hard Core ◽  
Packing Fraction ◽  
Exact Formulation ◽  
Simple Liquids ◽  
Soft Interaction ◽  
Dense Packings ◽  
Number Of Particles

Packing spheres efficiently in large dimension dd is a particularly difficult optimization problem. In this paper we add an isotropic interaction potential to the pure hard-core repulsion, and show that one can tune it in order to maximize a lower bound on the packing density. Our results suggest that exponentially many (in the number of particles) distinct disordered sphere packings can be efficiently constructed by this method, up to a packing fraction close to 7 \, d \, 2^{-d}7d2−d. The latter is determined by solving the inverse problem of maximizing the dynamical glass transition over the space of the interaction potentials. Our method crucially exploits a recent exact formulation of the thermodynamics and the dynamics of simple liquids in infinite dimension.

scholarly journals Charge Compensation in Europium-Doped Hafnia Nanoparticles: Solvothermal Synthesis and Colloidal Dispersion

Crystals ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 1042
Author(s):  
Xavier H. Guichard ◽  
Francesco Bernasconi ◽  
Alessandro Lauria
Keyword(s):  
Low Temperature ◽  
Hafnium Oxide ◽  
Aqueous Media ◽  
Charge Compensation ◽  
Colloidal Dispersion ◽  
X Ray Diffraction ◽  
X Ray ◽  
Wide Range ◽  
Direct Formation ◽  
Enhanced Luminescence

Effective charge compensation of europium in hafnium oxide nanoparticles was achieved at low temperature, allowing high doping incorporation (up to 6 at.%) and enhanced luminescence. The efficiency of the incorporation and charge compensation was confirmed by scanning electron microscope energy dispersive X-ray spectroscopy and powder X-ray diffraction measurements. Despite the known polymorphism of hafnium oxide, when doped to a concentration above 3 at.%, only the pure monoclinic phase was observed up to 6 at.% of europium. Furthermore, the low-temperature solvothermal route allowed the direct formation of stable dispersions of the synthesized material over a wide range of concentrations in aqueous media. The dispersions were studied by diffuse light scattering (DLS) to evaluate their quality and by photoluminescence to investigate the incorporation of the dopants into the lattice.

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