scholarly journals Physical and chemical reactivity of mechanically primed glass surfaces of CSP reflectors

2020 ◽  
Author(s):  
Sofia Boukheir ◽  
Abdelouahed Chbihi ◽  
Amal Matal ◽  
Sara Lakhouil ◽  
Sanae Naamane ◽  
...  
Keyword(s):  
Chemical Reactivity ◽  
Glass Surfaces ◽  
Physical And Chemical

scholarly journals Topological invariants for the line graphs of some classes of graphs

2019 ◽  
Vol 17 (1) ◽  
pp. 1483-1490
Author(s):  
Xiaoqing Zhou ◽  
Mustafa Habib ◽  
Tariq Javeed Zia ◽  
Asim Naseem ◽  
Anila Hanif ◽  
...  
Keyword(s):  
Communication Theory ◽  
Chemical Reactivity ◽  
Line Graph ◽  
Chemical Properties ◽  
Topological Invariants ◽  
Line Graphs ◽  
Physical And Chemical Properties ◽  
Physical And Chemical ◽  
Ladder Graphs ◽  
And Chemical Properties

AbstractGraph theory plays important roles in the fields of electronic and electrical engineering. For example, it is critical in signal processing, networking, communication theory, and many other important topics. A topological index (TI) is a real number attached to graph networks and correlates the chemical networks with physical and chemical properties, as well as with chemical reactivity. In this paper, our aim is to compute degree-dependent TIs for the line graph of the Wheel and Ladder graphs. To perform these computations, we first computed M-polynomials and then from the M-polynomials we recovered nine degree-dependent TIs for the line graph of the Wheel and Ladder graphs.

Alkali emission accompanying fracture of sodium silicate glasses

1991 ◽  
Vol 6 (6) ◽  
pp. 1358-1368 ◽  
Author(s):  
S.C. Langford ◽  
L.C. Jensen ◽  
J.T. Dickinson ◽  
L.R. Pederson
Keyword(s):  
Complex Surface ◽  
Soda Lime ◽  
Charge Carriers ◽  
Soda Lime Glass ◽  
Surface Ionization ◽  
Fracture Event ◽  
Defect Sites ◽  
Glass Surfaces ◽  
Physical And Chemical ◽  
Kinetics Of

Measurements of atomic Na emission accompanying the fracture of sodium trisilicate glass and a soda lime glass in vacuum were made by quadrupole mass spectroscopy and surface ionization techniques. Peak Na° emission intensities occur some 3–6 ms after the fracture event and decay over tens of milliseconds. This behavior is attributed to the diffusion of Na+ ions into a layer of damaged material at the surface where the ions are subsequently neutralized and thermally emitted as Na°. Charge carriers generated during fracture and subsequently trapped at defect sites apparently play important roles in charge compensating Na+ diffusion and in neutralizing Na+. During the first 300 ms following fracture, we also observe intense, short lived (400 μs) bursts in Na° emission which may be associated with catastrophic relaxation of residual stresses. The kinetics of Na emission suggest that the relaxation of newly formed glass surfaces involves rather complex surface physical and chemical processes.

scholarly journals Marginal Leakage Around Fixed Dental Prosthesis - A review

2020 ◽  
Vol 11 (SPL3) ◽  
pp. 319-323
Author(s):  
Ritya Mary Jibu ◽  
Keerthi Sasanka ◽  
Geetha V R
Keyword(s):  
Clinical Skills ◽  
Chemical Reactivity ◽  
Ionic Charge ◽  
Fixed Dental Prosthesis ◽  
Carious Lesions ◽  
Restorative Materials ◽  
Chemical Character ◽  
Fluid Transfer ◽  
Restoration Failure ◽  
Physical And Chemical

Marginal leakage is the intrusion into the space between all the restorative materials and cavity walls of fluids, bacteria, and ions. It can cause irritation of the pulp, change of color in the tooth and secondary caries, and may also result in restoration failure. The freshly placed prosthetic margins invariably leak. As time goes by there is a rise in marginal leakage associated with the manufacture of corrosion products and the expansion of other materials into the space between the tooth and the prosthesis. Dental researchers have been interested in the efficacy of the restorative materials to seal cavity margins against the entry of salivary constituents for some time. Some studies have shown that normal dentin would allow the penetration of dyes into human teeth's tubules. An analysis of later micro-leakage studies reveals that the structure of the dentin is permeable to the diffusion of fluids by natural and acquired defects. Because the enamel surface contains natural cracks and that allow the fluid to penetrate, the enamel can also have areas of hypo calcification, , chemical breakdown, abrasion, and carious lesions that increase penetration. However, enables the transportation of fluids by processes. Cutting dentin with dental pressure increases the exposed surface area and thus increases the amount of tubules available for fluid transfer into the pulp chamber. While ionic charge and chemical reactivity of diffusing fluids lead to marginal leakage, the physical and chemical character of restorative materials, and the operator's clinical skills are equally essential.

Glass Surface Refining by Deposition of Nano-Particles

2013 ◽  
Vol 592-593 ◽  
pp. 329-332
Author(s):  
Marcin Drajewicz ◽  
Paweł Rokicki
Keyword(s):  
Glass Surface ◽  
Chemical Properties ◽  
Soda Lime ◽  
Nano Particles ◽  
X Ray ◽  
Spectrometry Analysis ◽  
Soda Lime Silica Glass ◽  
Glass Surfaces ◽  
Physical And Chemical ◽  
And Chemical Properties

In the paper a new surface refining technology which uses nano-particles to improve the soda – lime – silica glass surfaces is presented. The SEM-EDS (Energy Dispersive X-ray Spectrometry) analysis was carried out to determine modification of the glass surface. A very thin modification layer was observed on the glass surface. The surface modification leads to an improvement of physical and chemical properties of the investigated glass.

scholarly journals Relationship between snow microstructure and physical and chemical processes

2012 ◽  
Vol 12 (11) ◽  
pp. 30409-30541 ◽  
Author(s):  
T. Bartels-Rausch ◽  
H.-W. Jacobi ◽  
T. F. Kahan ◽  
J. L. Thomas ◽  
E. S. Thomson ◽  
...  
Keyword(s):  
Chemical Reactivity ◽  
Experimental Studies ◽  
Chemical Processes ◽  
Field Observations ◽  
Physical Processes ◽  
Micro Scale ◽  
Surface Disorder ◽  
Snow Microstructure ◽  
Physical And Chemical

Abstract. Ice and snow in the environment are important because they not only act as a host to rich chemistry but also provide a matrix for physical exchanges of contaminants within the ecosystem. This review discusses how the structure of snow influences both chemical reactivity and physical processes, which thereby makes snow a unique medium for study. The focus is placed on impacts of the presence of liquid and surface disorder using many experimental studies, simulations, and field observations from the molecular to the micro-scale.

scholarly journals Прозрачные фотокаталитические ZnO-SnO-=SUB=-2-=/SUB=- нанопокрытия, полученные полимерно-солевым методом

2019 ◽  
Vol 126 (4) ◽  
pp. 515
Author(s):  
С.К. Евстропьев ◽  
Л.Л. Лесных ◽  
Н.В. Никоноров ◽  
А.В. Караваева ◽  
Е.В. Колобкова ◽  
...  
Keyword(s):  
Substrate Surface ◽  
Chemical Processes ◽  
Structure And Properties ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Thin Oxide Films ◽  
Glass Surfaces ◽  
Physical And Chemical ◽  
Scanning Electron

AbstractThe structure and properties of transparent ZnO–SnO_2 photocatalytic coatings formed on glass surfaces by the polymer–salt method are studied. The physical and chemical processes occurring during formation of the coatings are studied by differential scanning calorimetry and X-ray diffraction analysis. The structure and optical properties of the obtained thin oxide films are studied by optical spectroscopy, photoluminescence, and scanning electron microscopy. It is shown that the polymer–salt method allows formation of homogeneous and transparent ZnO–SnO_2 coatings consisting of oxide nanoparticles completely covering the glass substrate surface. It is found that the formed transparent ZnO–SnO_2 coatings have high photocatalytic properties and can generate singlet oxygen under action of UV radiation.

scholarly journals Quasi-Continuously Tuning the Size of Graphene Quantum Dots via an Edge-Etching Mechanism

MRS Advances ◽  
2016 ◽  
Vol 1 (20) ◽  
pp. 1459-1467 ◽  
Author(s):  
Shujun Wang ◽  
Ivan S. Cole ◽  
Dongyuan Zhao ◽  
Qin Li
Keyword(s):  
Quantum Dots ◽  
Chemical Reactivity ◽  
Quantum Confinement Effect ◽  
Graphene Quantum Dots ◽  
Chemical Properties ◽  
Practical Applications ◽  
Etching Mechanism ◽  
Great Possibility ◽  
Scientific Attention ◽  
Physical And Chemical

ABSTRACTGraphene quantum dots (GQDs), a nano version of graphene whose interesting properties that distinguish them from bulk graphene, have recently received significant scientific attention. The quantum confinement effect referring to the size-dependence of physical and chemical properties opens great possibility in the practical applications of this material. However, tuning the size of graphene quantum dots is still difficult to achieve. Here, an edge-etching mechanism which is able to tune the size of GQDs in a quasi-continuous manner is discovered. Different from the ‘unzipping’ mechanism which has been adopted to cut bulk graphitic materials into small fragments and normally cut through the basal plane along the ‘zig-zag’ direction where epoxy groups reside, the mechanism discovered in this research could gradually remove the peripheral carbon atoms of nano-scaled graphene (i.e. GQDs) due to the higher chemical reactivity of the edge carbon atoms than that of inner carbon atoms thereby tuning the size of GQDs in a quasi-continuous fashion. It enables the facile manipulate of the size and properties of GQDs through controlling merely the reaction duration. It is also believed the as discovered mechanism could be generalized for synthesizing various sizes of GQDs from other graphitic precursors (e.g. carbon fibres, carbon nanotubes, etc).

scholarly journals The electronic structure of conjugated systems I. General theory

1947 ◽  
Vol 191 (1024) ◽  
pp. 39-60 ◽  
Keyword(s):  
General Theory ◽  
Structural Changes ◽  
Chemical Reactivity ◽  
Chemical Properties ◽  
Bond Orders ◽  
Electron Densities ◽  
Conjugated Systems ◽  
Interaction Terms ◽  
Energy Integrals ◽  
Physical And Chemical

This paper develops the general theory of conjugated systems by the method of molecular orbitals. The electron densities and bond orders appear as first-order derivatives of the energy of the mobile electrons with respect to the energy integrals in the secular equations; and various other relations are established which confirm the appropriateness of the definitions. A set of new quantities are introduced and discussed for the first time, namely, the mutual polarizability of two atoms or two bonds or an atom and a bond, and it is shown that they are important in determining the effect of structural changes on chemical reactivity, and also in calculating force constants and interaction terms for the vibration of bonds. Formulae are derived for the calculation of the total energy, electron densities, bond orders and mutual polarizabilities, and the relation of these quantities to other physical and chemical properties is briefly discussed.

scholarly journals The Effect of Shredding and Particle Size in Physical and Chemical Processing of Printed Circuit Boards Waste

2012 ◽  
Vol 730-732 ◽  
pp. 653-658
Author(s):  
Paula C. Oliveira ◽  
Filipa Charters Taborda ◽  
Carlos A. Nogueira ◽  
Fernanda Margarido
Keyword(s):  
Particle Size ◽  
Printed Circuit Boards ◽  
Chemical Reactivity ◽  
Reaction Rates ◽  
Chemical Processing ◽  
Particle Sizes ◽  
Circuit Boards ◽  
Adequate Treatment ◽  
Printed Circuit ◽  
Physical And Chemical

Circuit boards present in most electric and electronic devices are very important components, which should be removed during sorting and dismantling operations in order to allow further adequate treatment for recovering valuable metals such as copper, nickel, zinc, lead, tin and rare elements. This recovery can be made by physical and chemical processes being size reduction by shredding the first step. In this paper, the effect of particle size in physical and chemical processing of printed circuit boards is presented and discussed. Shredding using cutting-based equipment allowed the comminution of boards and the liberation of particles composed by different materials (mainly metals and resin). Particle sizes less than 1 mm seems to be appropriate to attain high liberation of materials, which is crucial for the physical separation using gravity or electrostatic processes. Concerning chemical treatment, hydrometallurgical processing involves a leaching operation which can be also influenced by particle size of shredded boards. Samples with different granulometries were leached with 1 M HNO3 solutions, being leaching yields evaluated. It was concluded that particle size can be an important factor for the solubilization of some metals, but the effect is not similar for all elements. When average diameters change from 2.0 to 0.20 mm, nickel, aluminium and tin reactivity were not significantly affected, being this effect important for copper. Zinc behavior was very dependent from extreme particle sizes but was less affected in intermediate granulometries. Lead leaching showed also a peculiar behavior, exhibiting high and almost constant yields (80-90%) for particle size of solids up to 1.2 mm, and decreasing suddenly for higher granulometries. The effect of time on chemical reactivity for samples with different granulometries demonstrated that particle size affects reaction rates but eventually similar efficiencies can be obtained for long time periods. Therefore the relationship between results from shredding operation and chemical leaching step needs to be optimized, considering the balance between factors like consumption of energy during grinding operation and residence time in leaching.

scholarly journals Characterization of Environmental Nano- and Macrocolloid Particles Extracted from Selected Soils and Biosolids

2014 ◽  
Vol 2014 ◽  
pp. 1-13
Author(s):  
J. L. Ghezzi ◽  
A. D. Karathanasis ◽  
C. J. Matocha ◽  
J. Unrine ◽  
Y. L. Thompson
Keyword(s):  
Chemical Reactivity ◽  
Pollution Prevention ◽  
Mineralogical Composition ◽  
Surface Reactivity ◽  
Hydrodynamic Diameter ◽  
Soil Systems ◽  
Scanning Transmission ◽  
Size And Morphology ◽  
Physical And Chemical

Environmental nanoparticles found in soil systems and biosolids may pose a considerable risk to groundwater quality as contaminant carriers. Little effort has been invested in the characterization of natural nanocolloids compared to corresponding macrocolloids. This study involved physicochemical, mineralogical, and morphological characterizations of nanocolloids and macrocolloids fractionated from three Kentucky soils and one biosolid. Particle size and morphology were investigated using scanning/transmission electron microscopy and dynamic light scattering. Mineralogical composition was determined by X-ray diffraction and thermogravimetric and Fourier-transform infrared spectroscopy analyses. Zeta potentials and cation exchange capacities assessed surface charge and chemical reactivity. The estimated average hydrodynamic diameter of nanoparticles was nearly twice the ideal 100 nm range, apparently due to irregular particle shapes and partial aggregation. Nanoparticles were also found attached to surfaces of macrocolloids, forming macro-nano aggregates and obscuring some of their physical and chemical characteristics. However, nanocolloids exhibited greater surface reactivity, likely due to their smaller size, poor crystallinity, and morphological shape distortions. In spite of some behavior modification due to nanoaggregation phenomena, nanocolloids appeared to be much more potent vectors of contaminant transport in subsurface environments than their macrosize fractions. Nevertheless, their heterogeneous nature brings to light important considerations in addressing pollution prevention and remediation challenges.

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