scholarly journals A Diffusion Mechanism for Liesegang Rings. I. Spacing Law

1961 ◽  
Vol 34 (3) ◽  
pp. 437-440 ◽  
Author(s):  
Prem Behari Mathur
Keyword(s):  
Diffusion Mechanism ◽  
Liesegang Rings

Direct observations of radiation-enhanced transformations in glass

1983 ◽  
Vol 41 ◽  
pp. 354-355
Author(s):  
J. F. DeNatale ◽  
D. G. Howitt
Keyword(s):  
Glass Matrix ◽  
Diffusion Mechanism ◽  
Bubble Formation ◽  
Silicate Glasses ◽  
Phase Decomposition ◽  
Direct Observations ◽  
Thin Foils ◽  
Oxygen Bubble ◽  
Electron Energy Loss ◽  
Kinetics Of

The electron irradiation of silicate glasses containing metal cations produces various types of phase separation and decomposition which includes oxygen bubble formation at intermediate temperatures figure I. The kinetics of bubble formation are too rapid to be accounted for by oxygen diffusion but the behavior is consistent with a cation diffusion mechanism if the amount of oxygen in the bubble is not significantly different from that in the same volume of silicate glass. The formation of oxygen bubbles is often accompanied by precipitation of crystalline phases and/or amorphous phase decomposition in the regions between the bubbles and the detection of differences in oxygen concentration between the bubble and matrix by electron energy loss spectroscopy cannot be discerned (figure 2) even when the bubble occupies the majority of the foil depth.The oxygen bubbles are stable, even in the thin foils, months after irradiation and if van der Waals behavior of the interior gas is assumed an oxygen pressure of about 4000 atmospheres must be sustained for a 100 bubble if the surface tension with the glass matrix is to balance against it at intermediate temperatures.

Ordered Intermetallic Nanoparticles with High Catalytic Activity Prepared by an Electrochemically Induced Phase Transformation

2019 ◽  
Author(s):  
Du Sun ◽  
yunfei wang ◽  
Kenneth Livi ◽  
chuhong wang ◽  
ruichun luo ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Diffusion Mechanism ◽  
Reduction Reaction ◽  
Atomic Scale ◽  
High Catalytic Activity ◽  
Ambient Conditions ◽  
Magnetic Devices ◽  
Disordered Alloys ◽  
Ordered Intermetallic ◽  
Intermetallic Nanoparticles

<div> <p>The synthesis of alloys with long range atomic scale ordering (ordered intermetallics) is an emerging field of nanochemistry. Ordered intermetallic nanoparticles are useful for a wide variety of applications such as catalysis, superconductors, and magnetic devices. However, the preparation of nanostructured ordered intermetallics is challenging in comparison to disordered alloys, hindering progress in materials development. We report a process for converting colloidally synthesized ordered intermetallic PdBi<sub>2</sub> to ordered intermetallic Pd<sub>3</sub>Bi nanoparticles under ambient conditions by an electrochemically induced phase transition. The low melting point of PdBi<sub>2</sub> corresponds to low vacancy formation energies which enables the facile removal of the Bi from the surface, while simultaneously enabling interdiffusion of the constituent atoms via a vacancy diffusion mechanism under ambient conditions. The resulting phase-converted ordered intermetallic Pd<sub>3</sub>Bi exhibits 11x and 3.5x higher mass activty and high methanol tolerance for the oxygen reduction reaction compared to Pt/C and Pd/C, respectively,which is the highest reported for a Pd-based catalyst, to the best of our knowledge. These results establish a key development in the synthesis of noble metal rich ordered intermetallic phases with high catalytic activity, and sets forth guidelines for the design of ordered intermetallic compounds under ambient conditions.</p> </div>

THE INTERFACIAL THERMAL STABILITY AND ELEMENT DIFFUSION MECHANISM OF SiCf/TC17 COMPOSITE

2012 ◽  
Vol 48 (11) ◽  
pp. 1306 ◽  
Author(s):  
Xu ZHANG ◽  
Yumin WANG ◽  
Jiafeng LEI ◽  
Rui YANG
Keyword(s):  
Thermal Stability ◽  
Diffusion Mechanism ◽  
Element Diffusion

Development and Evaluation of Controlled Release Mucoadhesive Tablets of Captopril

1970 ◽  
Vol 9 (3) ◽  
pp. 3318-3329
Author(s):  
Kranthi Kumar Kotta ◽  
L. Srinivas
Keyword(s):  
Controlled Release ◽  
Drug Release ◽  
Xanthan Gum ◽  
Diffusion Mechanism ◽  
Matrix Tablets ◽  
Fickian Diffusion ◽  
Content Uniformity ◽  
In Vitro Drug Release ◽  
Mucoadhesive Tablets

The present investigation focuses on the development of mucoadhesive tablets of captopril which are designed to prolong the gastric residence time after oral administration. Matrix tablets of captopril were formulated using four mucoadhesive polymers namely guar gum, xanthan gum, HPMC K4M and HPMC K15M and studied for parameters such as weight variation, thickness, hardness, content uniformity, swelling index, mucoadhesive force and in vitro drug release. Tablets formulated Xanthan gum or HPMC K4M with HPMC K15M provide slow release of captopril over period of 12 hr and were found suitable for maintenance portion of oral controlled release tablets. The cumulative % of drug release of formulation F9 and F10 were 90 and 92, respectively. In vitro release from these tablets was diffusion controlled and followed zero order kinetics. The ‘n’ values obtained from the pappas-karsemeyer equation suggested that all the formulation showed drug release by non-fickian diffusion mechanism. Tablets formulated Xanthan gum or HPMC K4M with HPMC K15M (1:1) were established to be the optimum formulation with optimum bioadhesive force, swelling index & desired invitro drug release. This product was further subjected to stability study, the results of which indicated no significant change with respect to Adhesive strength and in vitro drug release study.

scholarly journals Influence of Chemical Osmosis on Solute Transport and Fluid Velocity in Clay Soils

2020 ◽  
Vol 18 (1) ◽  
pp. 232-238
Author(s):  
Zhihong Zhang ◽  
Gailei Tian ◽  
Lin Han
Keyword(s):  
Solute Transport ◽  
Transport Model ◽  
Fluid Velocity ◽  
Diffusion Mechanism ◽  
Clay Material ◽  
Chemical Osmosis ◽  
Advection Diffusion Equation ◽  
Test Study ◽  
Proposed Model ◽  
Membrane Effect

AbstractSolute transport through the clay liner is a significant process in many waste landfills or unmanaged landfills. At present, researchers mainly focus on the test study about semi-membrane property of clay material, however, the influence of chemical osmosis caused by membrane effect on solute transport and fluid velocity is insufficient. In this investigation, based on the classical advection-diffusion equation, a one-dimensional solute transport model for low-permeable clay material has been proposed, in which the coupled fluid velocity related with hydraulic gradient and concentration gradient is introduced, and the semi-membrane effect is embodied in the diffusion mechanism. The influence of chemical osmosis on fluid velocity and solute transport has been analyzed using COMSOL Multiphysics software. The simulated results show that chemical osmosis has a significant retarded action on fluid velocity and pollutant transport. The proposed model can effectively reveal the change in process of coupled fluid velocity under dual gradient and solute transport, which can provide a theoretical guidance for similar fluid movement in engineering.

scholarly journals Learning at Home and Abroad: How Competition Conditions the Diffusion of Party Strategies

2021 ◽  
pp. 1-20
Author(s):  
Sebastian Juhl ◽  
Laron K. Williams
Keyword(s):  
Diffusion Mechanism ◽  
Spillover Effects ◽  
Party Manifestos ◽  
Party Strategies ◽  
Electoral Campaign ◽  
Electoral Strategies ◽  
Learning At Home ◽  
Independent Decision ◽  
Issue Competition ◽  
Issue Emphasis

How do parties decide when to campaign on valence issues given high degrees of uncertainty? Although past studies have provided evidence of transnational emulation of parties' position-taking strategies, these findings do not directly apply to saliency strategies. Moreover, the exact diffusion mechanism remains largely elusive. Based on the issue saliency literature, this study develops novel theoretical propositions and argues that conscious learning enables parties to infer the relative utility of emphasizing consensual issues during an electoral campaign. The proposed theory gives rise to different expectations at the domestic and transnational levels because of the distinct logic of issue competition. By analyzing environmental issue emphasis in party manifestos, the authors find direct transnational dependencies and indirect spillover effects among the parties' saliency strategies. They identify conscious learning, rather than mere imitation or independent decision making, as the diffusion mechanism at work. Yet, in line with saliency-based theories, electoral competition mutes the diffusion of electoral strategies domestically.

scholarly journals The diffusion mechanism of the application of intelligent manufacturing in SMEs model based on cellular automata

Open Physics ◽  
2021 ◽  
Vol 19 (1) ◽  
pp. 170-178
Author(s):  
Lei Wang ◽  
Sijia Yang ◽  
Wenqi Fan ◽  
Fangqing Tang
Keyword(s):  
Cellular Automata ◽  
Information Exchange ◽  
Market Competition ◽  
Diffusion Mechanism ◽  
Real Data ◽  
Intelligent Manufacturing ◽  
Industrial Clusters ◽  
Manufacturing Technology ◽  
Government Support ◽  
Support Policy

Abstract Based on the characteristics of intelligent manufacturing and the theory of technology diffusion, this paper constructs a cellular automata model with government support policy, information exchange, technology maturity, diffusion intermediary, and market competition as the influencing factors and analyzes the influence mechanism of the first three main factors on the diffusion of intelligent manufacturing technology in industrial clusters using MATLAB. This paper also makes an empirical analysis of the diffusion of intelligent manufacturing technology in the bearing industry cluster in Xinchang County and finds that the results are basically consistent by comparing the simulation data with the fit degree of the real data. In this paper, the diffusion intermediary and government support policy have the greatest influence on the application of intelligent manufacturing in small- and medium-sized enterprises, and the model proposed in this paper is effective.

Elemental iron: reduction of pertechnetate in the presence of silica and periodicity of precipitated nano-structures

2021 ◽  
Author(s):  
Daria Boglaienko ◽  
Odeta Qafoku ◽  
Ravi K. Kukkadapu ◽  
Libor Kovarik ◽  
Yelena P. Katsenovich ◽  
...  
Keyword(s):  
Iron Reduction ◽  
Layered Structures ◽  
Elemental Iron ◽  
Liesegang Rings ◽  
Dissolved Iron ◽  
Nano Structures

Enhanced TcO4− reduction by metallic Fe0 in the presence of particulate and structural Si. Rhythmical precipitation of dissolved iron leads to formation of layered structures related to geological phenomena such as orbicular rocks and Liesegang rings.

scholarly journals The Diffusion Mechanism of Megaproject Citizenship Behavior: The Role of Institutional Isomorphism

2021 ◽  
Vol 13 (15) ◽  
pp. 8123
Author(s):  
Delei Yang ◽  
Jun Zhu ◽  
Qingbin Cui ◽  
Qinghua He ◽  
Xian Zheng
Keyword(s):  
Structural Equation ◽  
Diffusion Mechanism ◽  
Vital Role ◽  
Citizenship Behavior ◽  
Equation Modeling ◽  
Positive Effects ◽  
Diffusion Limited ◽  
The Relationship ◽  
Mimetic Isomorphism

Megaproject citizenship behavior (MCB) has been confirmed to a play vital role on megaproject performance. Although current research has argued that institution elements have had an impact on MCB diffusion, limited studies have empirically investigated the distinct effectiveness of various institution elements on driving MCB’s widespread diffusion in construction megaprojects. Based on institution theory, this study proposes a theoretical model comprising institutional elements (i.e., normative and mimetic isomorphism), owner’s support, relationship-based trust, and their effect or impact on MCB’s diffusion. Based on 171 industrial questionnaires collected from managers of contractors and designers in megaprojects. Partial least squares structural equation modeling (PLS-SEM) was used to validate the established model. The results indicated that both normative and mimetic isomorphism have positive effects on facilitating MCB diffusion, and owner’s support has shown partial mediation in promoting MCB diffusion through normative isomorphism, as well as full mediation in the promoting of MCB diffusion through mimetic isomorphism. Meanwhile, relationship-based trust exerts a positive moderating effect on the relationship between mimetic isomorphism and MCB. This study extends current literature on driving MCB diffusion from the perspective of institutional theory, contributing by providing four implications for megaprojects managers to “buy in” more extensive MCB.

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