scholarly journals A model study on controlling dealloying corrosion attack by lateral modification of surfactant inhibitors

2021 ◽  
Vol 5 (1) ◽  
Author(s):  
Shova Neupane ◽  
Nicolás A. Rivas ◽  
Patricia Losada-Pérez ◽  
Jan D’Haen ◽  
Heshmat Noei ◽  
...  
Keyword(s):  
Surface Science ◽  
Intermolecular Forces ◽  
Molecular Assembly ◽  
Corrosion Attack ◽  
Contact Printing ◽  
Model Study ◽  
Step Density ◽  
The Stability ◽  
Molecular Layers ◽  
Organic Corrosion Inhibitors

AbstractDetrimental corrosion is an ever-concerning challenge for metals and alloys. One possible remedy is to apply organic corrosion inhibitors. Despite progress in molecular assembly and inhibitor research, better mechanistic insight on the molecular level is needed. Here we report on the behavior of well-defined artificial molecular interfaces created by micro-contact printing of thiol-inhibitor molecules and subsequent backfilling. The obtained heterogeneity and defects trigger localized dealloying-corrosion of well-defined Cu3Au surfaces. The stability of applied inhibitor molecules depends on alloy surface morphology and on intermolecular forces of the molecular layers. On extended terraces, dealloying preferentially starts at the boundary between areas composed of the two different chain-length inhibitor molecules. Inside of the areas hardly any nucleation of initial pits is visible. Step density strongly influences the morphology of the dealloying attack, while film heterogeneity avoids cracking and controls molecular-scale corrosion attack. The presented surface-science approach, moreover, will ultimately allow to verify the acting mechanisms of inhibitor-cocktails to develop recipes to stabilize metallic alloy surfaces.

Effect of Intermolecular Forces on the Static and Dynamic Performance of Air Bearing Sliders: Part II—Dependence of the Stability on Hamaker Constant, Suspension Preload and Pitch Angle

2005 ◽  
Vol 128 (1) ◽  
pp. 203-208 ◽  
Author(s):  
Vineet Gupta ◽  
David B. Bogy
Keyword(s):  
Pitch Angle ◽  
Dynamic Performance ◽  
Hard Disk Drives ◽  
Intermolecular Forces ◽  
Flying Height ◽  
Total Force ◽  
Air Bearing ◽  
Force Increase ◽  
The Stability ◽  
Fly Height

Intermolecular and surface forces contribute significantly to the total forces acting on air bearing sliders for flying heights below 5 nm. Their contributions to the total force increase sharply with the reduction in flying height, and hence their existence can no longer be ignored in air bearing simulation for hard disk drives. Various experimentally observed dynamic instabilities can be explained by the inclusion of these forces in the model for low flying sliders. In this paper parametric studies are presented using a 3-DOF model to better understand the effect of the Hamaker constants, suspension pre load and pitch angle on the dynamic stability/instability of the sliders. A stiffness matrix is used to characterize the stability in the vertical, pitch, and roll directions. The fly height diagrams are used to examine the multiple equilibriums that exist for low flying heights. It has been found that the system instability increases as the magnitude of the van der Waals force increases. It has also been found that higher suspension pre load and higher pitch angles tend to stabilize the system.

Stability of Pt near surface alloys under electrochemical conditions: a model study

2014 ◽  
Vol 16 (31) ◽  
pp. 16615-16622 ◽  
Author(s):  
Xiaoming Zhang ◽  
Shansheng Yu ◽  
Weitao Zheng ◽  
Ping Liu
Keyword(s):  
Fuel Cell ◽  
Automotive Applications ◽  
Surface Alloys ◽  
Near Surface ◽  
Model Study ◽  
The Stability

The stability is one of the key requirements for commercializing the fuel cell electrocatalysts in automotive applications.

scholarly journals Stability of SG1 nitroxide towards unprotected sugar and lithium salts: a preamble to cellulose modification by nitroxide-mediated graft polymerization

2013 ◽  
Vol 9 ◽  
pp. 1589-1600 ◽  
Author(s):  
Guillaume Moreira ◽  
Laurence Charles ◽  
Mohamed Major ◽  
Florence Vacandio ◽  
Yohann Guillaneuf ◽  
...  
Keyword(s):  
Graft Polymerization ◽  
Polymer Chains ◽  
Lithium Salts ◽  
Organic Media ◽  
Cellulose Derivatives ◽  
Cellulose Modification ◽  
Model Study ◽  
The Stability ◽  
Grafting From ◽  
Intramolecular Hydrogen

The range of applications of cellulose, a glucose-based polysaccharide, is limited by its inherently poor mechanical properties. The grafting of synthetic polymer chains by, for example, a “grafting from” process may provide the means to broaden the range of applications. The nitroxide-mediated polymerization (NMP) method is a technique of choice to control the length, the composition and the architecture of the grafted copolymers. Nevertheless, cellulose is difficult to solubilize in organic media because of inter- and intramolecular hydrogen bonds. One possibility to circumvent this limitation is to solubilize cellulose in N,N-dimethylformamide (DMF) or N,N-dimethylacetamide (DMA) with 5 to 10 wt % of lithium salts (LiCl or LiBr), and carry out grafted polymerization in this medium. The stability of nitroxides such as SG1 has not been studied under these conditions yet, even though these parameters are of crucial importance to perform the graft modification of polysaccharide by NMP. The aim of this work is to offer a model study of the stability of the SG1 nitroxide in organic media in the presence of unprotected glucose or cellobiose (used as a model of cellulose) and in the presence of lithium salts (LiBr or LiCl) in DMF or DMA. Contrary to TEMPO, SG1 proved to be stable in the presence of unprotected sugar, even with an excess of 100 molar equivalents of glucose. On the other hand, lithium salts in DMF or DMA clearly degrade SG1 nitroxide as proven by electron-spin resonance measurements. The instability of SG1 in these lithium-containing solvents may be explained by the acidification of the medium by the hydrolysis of DMA in the presence of LiCl. This, in turn, enables the disproportionation of the SG1 nitroxide into an unstable hydroxylamine and an oxoammonium ion. Once the conditions to perform an SG1-based nitroxide-mediated graft polymerization from cellobiose have been established, the next stage of this work will be the modification of cellulose and cellulose derivatives by NMP.

A Model Study of Instabilities Present in the Mean-Field Description and in Linearized Correlation Schemes

1989 ◽  
Vol 44 (2) ◽  
pp. 117-124
Author(s):  
Michael C. Böhm ◽  
Gerd Bubeck ◽  
Andrzej M. Oles
Keyword(s):  
Theoretical Calculations ◽  
Mean Field ◽  
Numerical Data ◽  
Local Approach ◽  
Stability Range ◽  
Hartree Fock ◽  
Model Study ◽  
Correlation Models ◽  
The Stability ◽  
Hf Wave

Abstract In this work we discuss the cooperative occurrence of instabilities in the Hartree-Fock (HF) approximation and linearized correlation models. Both breakdown phenomena can be analyzed via eigenvalues of characteristic matrices. The well known HF instabilities follow from a quasidegeneracy between the symmetry-adapted mean-field state and singly excited configurations. Quasi-degeneracies between the HF wave function and doubly excited configurations restrict the applicability of linearized correlation models. In the theoretical calculations the method of the local approach (LA) has been employed to derive the correlated ground state. For a system of the general topology XH2 (X = C, Si, etc.) the bond orbital approximation (BOA) has been used to derive analytic formulae indicating the stability range of linearized correlation schemes. Numerical calculations on the basis of a simple model-Hamiltonian are given for the π systems C2H4 and C2H2, respectively, which have been studied as a function of the CC bondlength. The comparison of the respective numerical data indicates that both breakdown phenomena are enhanced via coupling terms between strongly correlated bonds.

scholarly journals Vault Poly(ADP-Ribose) Polymerase Is Associated with Mammalian Telomerase and Is Dispensable for Telomerase Function and Vault Structure In Vivo

2004 ◽  
Vol 24 (12) ◽  
pp. 5314-5323 ◽  
Author(s):  
Yie Liu ◽  
Bryan E. Snow ◽  
Valerie A. Kickhoefer ◽  
Natalie Erdmann ◽  
Wen Zhou ◽  
...  
Keyword(s):  
Telomere Length ◽  
Telomerase Activity ◽  
Molecular Assembly ◽  
Cellular Functions ◽  
Telomere Function ◽  
Minor Protein ◽  
The Stability ◽  
A Minor

ABSTRACT Vault poly(ADP-ribose) polymerase (VPARP) was originally identified as a minor protein component of the vault ribonucleoprotein particle, which may be involved in molecular assembly or subcellular transport. In addition to the association of VPARP with the cytoplasmic vault particle, subpopulations of VPARP localize to the nucleus and the mitotic spindle, indicating that VPARP may have other cellular functions. We found that VPARP was associated with telomerase activity and interacted with exogenously expressed telomerase-associated protein 1 (TEP1) in human cells. To study the possible role of VPARP in telomerase and vault complexes in vivo, mVparp-deficient mice were generated. Mice deficient in mVparp were viable and fertile for up to five generations, with no apparent changes in telomerase activity or telomere length. Vaults purified from mVparp-deficient mouse liver appeared intact, and no defect in association with other vault components was observed. Mice deficient in mTep1, whose disruption alone does not affect telomere function but does affect the stability of vault RNA, showed no additional telomerase or telomere-related phenotypes when the mTep1 deficiency was combined with an mVparp deficiency. These data suggest that murine mTep1 and mVparp, alone or in combination, are dispensable for normal development, telomerase catalysis, telomere length maintenance, and vault structure in vivo.

Underground Barrier Protection against the Spread of Vibration - A Model Study

2014 ◽  
Vol 1020 ◽  
pp. 451-456
Author(s):  
Tomáš Petřík ◽  
Eva Hrubesova ◽  
Miroslav Pinka ◽  
Alice Hastíková
Keyword(s):  
Finite Element Method ◽  
Urban Areas ◽  
Seismic Waves ◽  
Static Load ◽  
Geological Environment ◽  
The Finite Element Method ◽  
Ground Vibrations ◽  
Industrial Activity ◽  
Model Study ◽  
The Stability

The designs of the buildings are in addition to the static load exposed to ground vibrations spreading from the surrounding geological environment. Ground vibrations, which are produced by anthropogenic phenomena, are not usually the crucial load for the stability of the building. But this load have an adversely affect the walls of buildings or sensitive equipment in these buildings. This article will be deal with model study of underground barriers utilized as a protection against the spread of ground vibrations in geological environment. These underground barriers maybe used in the vicinity of roads or railway lines or in urban areas around the halls with heavy industrial activity. Material of underground barriers will be designed from material with different parameters, so that it could be assessed the best variant in terms of absorption of seismic waves. The different variations of the thickness of underground barriers and different distances from the source of vibration will be designed in the analysis. The analysis will be performed in mathematical models that will be created in the software’s based on the finite element method.

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