Stability of molecular aggregates of hydrocarbons with all-trans chains and translation of the molecules

1985 ◽  
Vol 50 (7) ◽  
pp. 1553-1564 ◽  
Author(s):  
Ján Gajdoš ◽  
Tomáš Bleha
Keyword(s):  
Potential Energy ◽  
Interaction Potential ◽  
Conformational Transition ◽  
Molecular Aggregates ◽  
Hydrocarbon Chains ◽  
Central Molecule ◽  
The Matrix ◽  
Rotational Phase

Potential energy has been calculated for molecular aggregates formed of all-trans extended hexanes with various arrangements of the central molecule surrounded by the first coordination sphere. Differences in stabilities of the aggregates are connected with biaxial character of asymmetry of the interaction energy of extended paraffins. When investigating the multiparameter interaction potential of the partially ordered systems of hydrocarbon chains, the first step consisted in determination of the energy barriers to longitudinal shifts of the central molecules at various distances of the surrounding molecules. Destabilization of the aggregates with displaced molecules is due to both the mismatch of the central molecule to the matrix and effective shortening of that part of the central molecule which is "immersed" in the aggregate. The energetics of the model aggregates is made use of in elucidating the role of translation of paraffins and cognate molecules in rotational phase, in mesophases, and at a forced shortening of the chains connected with conformational transition.

In situobservation of morphological changes of γ′ precipitates in a pre-deformed single-crystal Ni-base superalloy

2011 ◽  
Vol 44 (5) ◽  
pp. 935-944 ◽  
Author(s):  
Pavel Strunz ◽  
Gerhard Schumacher ◽  
Hellmuth Klingelhöffer ◽  
Albrecht Wiedenmann ◽  
Jan Šaroun ◽  
...  
Keyword(s):  
External Load ◽  
Morphological Changes ◽  
The Past ◽  
Subsequent Heating ◽  
Detailed Evaluation ◽  
The Matrix ◽  
Base Superalloy

Exposure of a superalloy to an external load results in anisotropic coarsening of the γ′ precipitates, so-called rafting. It was reported in the past that γ′ rafting can also occur as a result of purely thermal treatment, without the simultaneous presence of an external load, if the specimen has been pre-deformed at relatively low temperature. The evolution of γ′ morphology in pre-deformed specimens of SCA425 Ni-base superalloy was examined in the present study. Unlike in the previous experiments, the compressive stress was used for pre-straining.In situsmall-angle neutron scattering (SANS) was employed, which enabled the determination of the morphology directly at high temperature. Both for strong and for weak pre-straining, rounding of the originally cuboidal precipitates towards an ellipsoidal shape on heating was observed. Weak pre-straining (0.1, 0.5%) does not cause rafting on subsequent heating. On the other hand, the detailed evaluation of SANS data provides some indication of rafting during the subsequent heating after severe compressive pre-straining (2%). The experiment indicates the role of dislocation rearrangement at the matrix/precipitate interface during pre-straining.

Filament Fragmentation Phenomena

1989 ◽  
Vol 170 ◽  
Author(s):  
Juan C. Figueroa ◽  
Linda S. Schadler ◽  
Campbell Laird
Keyword(s):  
Strain Energy ◽  
Stress Transfer ◽  
Fiber Surface ◽  
Yield Information ◽  
The Matrix ◽  
Two Parameters ◽  
The Relationship

AbstractThe effect of fiber surface treatments on the relationship between the tensile strength of a filament and the shear strength of its interphase is one of the central issues facing composite materials technologists today. We demonstrate here that analysis of fragmentation phenomena in monofilament composites can simultaneously yield information about these two parameters. Characterization of shear stress transfer zones in non-critical fragments has led us to the determination of interphase strength.A phenomenological treatment that highlights the role of the matrix in the fragmentation process is presented here. This analysis considers issues such as the strain energy exchange between a failing fiber and the matrix, as well as interphase relaxation due to the viscoelastic nature of the matrix. Our observations of the fragmentation phenomena in AU4/polycarbonate monofilament composites indicate that the fiber/matrix interaction in this system is governed by micromechanical locking.

Rheological Determination of Interaction Potential Energy for Aqueous Clay Suspensions

Langmuir ◽  
2003 ◽  
Vol 19 (19) ◽  
pp. 8109-8114 ◽  
Author(s):  
Christophe Baravian ◽  
Delphine Vantelon ◽  
Fabien Thomas
Keyword(s):  
Potential Energy ◽  
Interaction Potential ◽  
Interaction Potential Energy ◽  
Clay Suspensions

scholarly journals Prediction of the Elastic Tensor of 3D Composites by an Analytical Model

1999 ◽  
Vol 8 (5) ◽  
pp. 096369359900800
Author(s):  
C. Tallaron ◽  
S. Barre
Keyword(s):  
Volume Fraction ◽  
Unidirectional Composite ◽  
Second Step ◽  
Relative Role ◽  
Elastic Tensor ◽  
The Matrix ◽  
Three Bundles ◽  
Transversally Isotropic

The aim of this study is the determination of the overall elastic tensor of two 3D composites. These materials have a multiscale architecture. The representative volume element of the composite architecture (symbolised by a unit-cell) is composed of three bundles in three orthogonal directions and two matrix pockets. Each bundle is a unidirectional composite formed by a juxtaposition of long fibres surrounded by the matrix. Due to their symmetry, the bundles are considered transversally isotropic according to the fibres axis, whereas the pockets are macroscopically isotropic. The analytical computation is produced in two steps. The first step consists of determining the elastic tensor of the bundles. The second step is the calculation of the elastic tensor of the whole composite. The most part of the used equations comes from bibliography, excepted the determination of shear coefficients of the composite. The last part of this study devoted to the influence of material parameters presents the relative role of the fibres, the matrix and their volume fraction.

scholarly journals A Green Approach to the Production of Hybrid Diindolylmethane-Phenylboronic Acids via a 3MCR: Promising Antineoplasic Molecules

2013 ◽  
Vol 2013 ◽  
pp. 1-9 ◽  
Author(s):  
Mónica Zarco Juarez ◽  
Joel Omar Martínez ◽  
Olivia Noguez Cordova ◽  
María Inés Nicolás Vazquez ◽  
Teresa Ramírez-Apan ◽  
...  
Keyword(s):  
Time Frame ◽  
Green Approach ◽  
Central Nerve System ◽  
The Matrix ◽  
Target Molecules ◽  
Phenylboronic Acids ◽  
Short Time ◽  
Nerve System

The current role of the “Green Chemistry Protocol” in multicomponent reactions is first highlighted. Then, the green approach to the production of three novel hybrid diindolylmethanes-phenylboronic acids via a 3MCR is discussed, which features the following: solventless conditions, the use of microwave irradiation to activate the reactions, the absence of catalyst, and an efficient atom economy. The products were achieved with moderate yields (41–61%) within a short time frame (5 min) and appropriately characterized by elemental analysis and spectroscopic methods (NMR:1H,13C,11B; MS: EI, CI, FAB+, HRMS). During the FAB+MS determinations, various artifacts that are associated with the boron atom via an interaction with thioglycerol from the matrix were noted in the corresponding FAB+mass spectra; in addition, the accurate mass determination of these adducts unequivocally confirmed the presence of the target molecules. Moreover, the activity of these target molecules was evaluated in the presence of six cancer cell lines (U251 = glia of the central nerve system, PC-3 = prostate, K562 = leukemia, HCT-15 = colon, MCF-7 = breast, and SKLU-1 = lung), which resulted in themeta-regioisomer being the most active. Finally, the products were also analyzed using computational chemistry in order to determine their most stable geometries and reactivities by computing the respective molecular electrostatic potentials.

scholarly journals Фазы в октамере воды: молекулярный подход

2017 ◽  
Vol 12 (2) ◽  
pp. 487-495 ◽  
Author(s):  
Е.Д. Белега ◽  
E.D. Belega
Keyword(s):  
Phase Transition ◽  
Molecular Dynamics ◽  
Potential Energy ◽  
Interaction Potential ◽  
Point Of View ◽  
Molecular Dynamics Method ◽  
Dynamical Characteristics ◽  
Different Types ◽  
Dynamics Method

Results of modeling of phases and phase transition in the water octamer with TIP4P interaction potential from molecular point of view are presented. In the study the molecular dynamics method was applied. The advantage of using the dynamical characteristics of individual molecules in the cluster is shown, particularly, the distribution of the potential energy, to identify the phase of the cluster. The criteria for solid like and liquid like phases in the octamer are suggested and the connection isomer’s structures with dynamics are discussed. The role of different types of H-bonds (DDA- and DAA-type) in dynamical characteristics of the cluster is clarified.

Role of Pyrolysis Conditions on Fracture Behaviour of Fibre Reinforced Composites

2011 ◽  
Vol 465 ◽  
pp. 455-458 ◽  
Author(s):  
Zdeněk Chlup ◽  
Martin Černý ◽  
Adam Strachota ◽  
Ivo Dlouhý
Keyword(s):  
Pyrolysis Temperature ◽  
Fracture Behaviour ◽  
Reinforced Composites ◽  
Instrumented Indentation ◽  
Microstructural Changes ◽  
Air Atmosphere ◽  
The Matrix ◽  
Fibre Reinforced Composites

Fracture response of matrix prepared by pyrolysis of polysiloxane resin used for composite reinforced by long fibres was the main goal of this contribution. A set of composites with matrix prepared by partial pyrolysis of polysiloxane resin was studied. An effect of pyrolysis temperature on the composite behaviour and fracture resistance was monitored. An optimal procedure of pyrolysis was established. Heat treatment at 1550°C in air atmosphere was conducted on fully pyrolysed matrix to explore its high temperature potential. Determination of reliable parameters characterising microstructural changes in the matrix by instrumented indentation technique was used. Both optical and scanning electron microscopy was employed in microstructural observations and fracture mechanism qualification. Observation of indents and associated cracking caused by microstructural changes as well as 3D surface reconstruction using confocal microscopy was employed.

Lateral resolution of the electron microbeam analysis

1978 ◽  
Vol 36 (1) ◽  
pp. 542-543
Author(s):  
H.J. Dudek
Keyword(s):  
Quantitative Analysis ◽  
Depth Resolution ◽  
Lateral Resolution ◽  
Cylindrical Particle ◽  
Correction Procedure ◽  
X Ray ◽  
Element Concentrations ◽  
Microbeam Analysis ◽  
The Matrix

The chemical inhomogenities in modern materials such as fibers, phases and inclusions, often have diameters in the region of one micrometer. Using electron microbeam analysis for the determination of the element concentrations one has to know the smallest possible diameter of such regions for a given accuracy of the quantitative analysis.In th is paper the correction procedure for the quantitative electron microbeam analysis is extended to a spacial problem to determine the smallest possible measurements of a cylindrical particle P of high D (depth resolution) and diameter L (lateral resolution) embeded in a matrix M and which has to be analysed quantitative with the accuracy q. The mathematical accounts lead to the following form of the characteristic x-ray intens ity of the element i of a particle P embeded in the matrix M in relation to the intensity of a standard S

Determination of the phase structure of polymerblends by electron microscopy

1978 ◽  
Vol 36 (1) ◽  
pp. 492-493
Author(s):  
Dr. G. Kaemof
Keyword(s):  
Screw Extruder ◽  
Electron Microscopic ◽  
Thin Sections ◽  
Single Screw Extruder ◽  
Transmission Electron ◽  
The Matrix ◽  
Twin Screw ◽  
Special Case ◽  
Microscopic Investigations

A mixture of polycarbonate (PC) and styrene-acrylonitrile-copolymer (SAN) represents a very good example for the efficiency of electron microscopic investigations concerning the determination of optimum production procedures for high grade product properties.The following parameters have been varied:components of charge (PC : SAN 50 : 50, 60 : 40, 70 : 30), kind of compounding machine (single screw extruder, twin screw extruder, discontinuous kneader), mass-temperature (lowest and highest possible temperature).The transmission electron microscopic investigations (TEM) were carried out on ultra thin sections, the PC-phase of which was selectively etched by triethylamine.The phase transition (matrix to disperse phase) does not occur - as might be expected - at a PC to SAN ratio of 50 : 50, but at a ratio of 65 : 35. Our results show that the matrix is preferably formed by the components with the lower melting viscosity (in this special case SAN), even at concentrations of less than 50 %.

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