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About 5,925 papers for “Dispersity”

Substance Dispersity

National Cancer Institute · Definitions · 2020

Ope n Pe e r Re v ie w on Qe ios

Cited by 0Open access

particle-diameter dispersity

2025

Citation: 'particle-diameter dispersity' in the IUPAC Compendium of Chemical Terminology, 5th ed.; International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. 10.1351/goldbook.14296 • License: The IUPAC Gold Book is licensed under Creative Commons Attribution-ShareAlike CC BY-SA 4.0 International for individual terms. Requests for commercial usage of the compendium should be directed to IUPAC.

Cited by 0Open access

TITANIUM PIGMENT DIOXIDE DISPERSITY

N.N. FOMINA, А. Р. Исмагилов, V.G. FOMIN · Building and reconstruction · 2020

The criterion for assessing the quality of the pigment may be a detailed characteristic of its dispersion. The dispersion parameters of two grades of pigment titanium dioxide were studied: from an expensive and affordable price range. The method of laser diffraction was used. It has been established that most of the mass (volume) of particles of the studied pigments has sizes outside the effective range from the point of view of scattering power. Pigments have a close number of particles with sizes in the effective range (in the range of 0.19-0.25 microns). The most probable particle size of the cheaper pigment corresponds to the region of the optimum particle size, while that of the expensive pigment is below the optimal values. In both investigated brands of pigment there are nanoparticles with sizes less than 115 nm. Their volumetric (or mass) content is not less than 1.5%; or at least 7% of the total specific surface area of all pigment particles. Studies are needed on the dependences of the durability of pigmented coatings on the presence and content of nanosized particles.

Cited by 2

Dispersity-Based Test Case Prioritization

Liu, Chen · Figshare · 2021

With real-world projects, existing test case prioritization (TCP) techniques have limitations when applied to them, because these techniques require certain information to be made available before they can be applied. For example, the family of input-based TCP techniques are based on test case values or test script strings; other techniques use test coverage, test history, program structure, or requirements information. Existing techniques also cannot guarantee to always be more effective than random prioritization (RP) that does not have any precondition. As a result, RP remains the most applicable and most fundamental TCP technique. In this thesis, we propose a new TCP technique, and mainly aim at studying the Effectiveness, Actual execution time for failure detection, Efficiency and Applicability of the new approach.

Cited by 0Open access

Ultralow Dispersity Poly(vinyl alcohol) Reveals Significant Dispersity Effects on Ice Recrystallization Inhibition Activity

Nicholas S. Vail, Christopher D. Stubbs, Caroline I. Biggs et al. · ACS Macro Letters · 2017

Polymer mimics of antifreeze proteins are emerging as an exciting class of macromolecular cryoprotectants for the storage of donor cells and tissue. Poly(vinyl alcohol), PVA, is the most potent polymeric ice growth inhibitor known, but its mode of action and the impact of valency (DP) are not fully understood. Herein, tandem RAFT polymerization and column chromatography are used to isolate oligomers with dispersities <1.01 to enable the effect of molecular weight distribution, as well as length, to be probed. It is found that polymers with equal number average molecular weight, but lower dispersity, have significantly less activity, which can lead to false positives when identifying structure-property relationships. The minimum chain length for PVA's unique activity, compared to other non-active poly-ols was identified. These results will guide the design of more active inhibitors, better cryopreservatives and a deeper understanding of synthetic and biological antifreeze macromolecules.

Cited by 31Open access

Controlling primary chain dispersity in network polymers: elucidating the effect of dispersity on degradation

Takanori Shimizu, Richard Whitfield, Glen R. Jones et al. · Chemical Science · 2023

Although dispersity has been demonstrated to be instrumental in determining many polymer properties, current synthetic strategies predominantly focus on tailoring the dispersity of linear polymers. In contrast, controlling the primary chain dispersity in network polymers is much more challenging, in part due to the complex nature of the reactions, which has limited the exploration of properties and applications. Here, a one-step method to prepare networks with precisely tuned primary chain dispersity is presented. By using an acid-switchable chain transfer agent and a degradable crosslinker in PET-RAFT polymerization, the <i>in situ</i> crosslinking of the propagating polymer chains was achieved in a quantitative manner. The incorporation of a degradable crosslinker, not only enables the accurate quantification of the various primary chain dispersities, post-synthesis, but also allows the investigation and comparison of their respective degradation profiles. Notably, the highest dispersity networks resulted in a 40% increase in degradation time when compared to their lower dispersity analogues, demonstrating that primary chain dispersity has a substantial impact on the network degradation rate. Our experimental findings were further supported by simulations, which emphasized the importance of higher molecular weight polymer chains, found within the high dispersity materials, in extending the lifetime of the network. This methodology presents a new and promising avenue to precisely tune primary chain dispersity within networks and demonstrates that polymer dispersity is an important parameter to consider when designing degradable materials.

Cited by 20Open access

DISPERSITY OF CATALYST AND CATALYTIC ACTIVITY

Kiyoshi YOSHIKAWA · Bulletin of the Chemical Society of Japan · 1932

Abstract 1. In the study of the hydrogenation of acetylene in presence of nickel and palladium catalysts distributed on kieselguhr, it was observed that markedly selective action of catalysts was produced by the variation of the dispersity of the catalytic agents on kieselguhr. The phenomenon which was met with, suggests a possible mechanism of one case of promoter and carrier actions and on the other hand, a method of hydrogenation of acetylene to ethylene. 2. With regard to the simple hydrogenation process, in presence of a metallic catalyst, inert irreducible oxides being employed as the promoter and as the carrier, stimulation and restriction of the catalytic activity can be explained on the basis of the assumed co-activation of active centres on the catalytic surface by the heat of reaction. 3. Acetylene was readily hydrogenated to ethylene by the employment of the palladium-kieselguhr catalysts of proper dispersity. With equal volumes of acetylene and hydrogen, the product containing more than 90 per cent, ethylene, was obtained.

Cited by 5Open access

Flow control for ABR dispersity multicasting

Wei-Kuo Liao, Abdol‐Hossein Esfahanian, Lei Ni · 2002

Dispersity multicasting is an extension of dispersity routing for multicast communication. In dispersity multicasting, m arc-disjoint subtrees are used for source-destination message delivery. If the bottleneck flow control is applied to each of the m arc-disjoint subtrees, there might still exist extra bandwidth for the multicast communication. To exploit the extra bandwidth, we introduce the concept of virtual connections. We design a flow control algorithm for the available-bit-rate dispersity multicasting with two arc-disjoint subtrees and one virtual connection. Issues in applying the algorithm to ATM networks are discussed. Simulation studies show that, in general, our algorithm enhances the throughput of dispersity multicasting.

Cited by 0

Size-dispersity effects in two-dimensional melting

Hiroshi Watanabe, Satoshi Yukawa, Nobuyasu Ito · Physical Review E · 2005

In order to investigate the effect of size dispersity on two-dimensional melting transitions, hard-disk systems with equimolar bidispersity are studied by means of particle dynamics simulations. From the nonequilibrium relaxation behaviors of bond-orientational order parameters, we find that (i) there is a critical dispersity at which the melting transition of the hexagonal solid vanishes and (ii) the quadratic structure is metastable in a certain region of the dispersity-density parameter space. These results suggest that the dispersity not only destroys order but produces new structures under certain specific conditions.

Cited by 12

Average Particle Diameters and Particle-Diameter Dispersity

Stanisław Słomkowski, José Alemán, Robert G. Gilbert et al. · IUPAC Standards Online · 2016

A large group of industrially important polymerization processes is carried out in dispersed systems. These processes differ with respect to their physical nature, mechanism of particle formation, particle morphology, size, charge, types of interparticle interactions, and many other aspects. Polymer dispersions, and polymers derived from polymerization in dispersed systems, are used in diverse areas such as paints, adhesives, microelectronics, medicine, cosmetics, biotechnology, and others. Frequently, the same names are used for different processes and products or different names are used for the same processes and products. The document contains a list of recommended terms and definitions necessary for the unambiguous description of processes, products, parameters, and characteristic features relevant to polymers in dispersed systems.

Cited by 0Open access

What Controls Au Nanoparticle Dispersity during Growth?

Giannis Mpourmpakis (1452985), Stavros Caratzoulas (1355817), Dionisios G. Vlachos (261715) · Figshare · 2016

Nanoparticles are critical in diverse nanotechnological areas. Their physical and chemical properties are essentially determined by their size, shape, and dispersity, but the underlying mechanisms that determine these are generally poorly understood. Herein, we focus on the electronic structure and solvation properties of the Au−thiolate capping agents (Au&lt;sub&gt;&lt;i&gt;n&lt;/i&gt;&lt;/sub&gt;MBA&lt;sub&gt;&lt;i&gt;n&lt;/i&gt;&lt;/sub&gt;) used in the synthesis of gold nanoparticles and whose accepted function is to stump growth. By DFT calculations we show that they exhibit “magic” number, electronic configuration, and stability for &lt;i&gt;n&lt;/i&gt; = 4 and 8. By Molecular Dynamics simulations, we learn that in water−methanol solution the dominant species is the Au&lt;sub&gt;4&lt;/sub&gt;MBA&lt;sub&gt;4&lt;/sub&gt; complex, in a conformation stabilized by hydrogen bonds. We argue that the solvent has a multifunctional role: the water acts via hydrogen bonding as a “molecular locker” stabilizing particular conformers, while the methanol prevents polymeric growth of the Au&lt;sub&gt;&lt;i&gt;n&lt;/i&gt;&lt;/sub&gt;MBA&lt;sub&gt;&lt;i&gt;n&lt;/i&gt;&lt;/sub&gt; complexes. A plausible growth mechanism conducive to the formation of monodisperse gold nanoparticles is proposed.

Cited by 0Open access

Dispersity in polymer science (IUPAC Recommendation 2009)

R. F. T. Stepto · Polymer International · 2009

Abstract This recommendation defines just three terms, viz., 1. molar‐mass dispersity, relative‐molecular‐mass dispersity, or molecular‐weight dispersity, 2. degree‐of‐polymerization dispersity, and 3. dispersity. “Dispersity” is a new word, coined to replace the misleading, but widely used term “polydispersity index” for M̄ w / M̄ n and X̄ w / X̄ n . The document, although brief, also has a broader significance in that it seeks to put the terminology describing dispersions of distributions of properties of polymeric (and non‐polymeric) materials on an unambiguous and justifiable footing. Copyright © 2009 Society of Chemical Industry

Cited by 33