scholarly journals Electronic spectra of polyatomic molecules I–Saturated aldehydes

1935 ◽  
Vol 149 (868) ◽  
pp. 434-446 ◽  
Keyword(s):  
Electronic Structures ◽  
Hydrogen Molecule ◽  
Electron Pair ◽  
Polyatomic Molecules ◽  
The Other ◽  
Orbital Method ◽  
Atom Pair ◽  
Advantages And Disadvantages ◽  
Lennard Jones ◽  
Pair Method

Of the two methods which are now available to describe the electronic structures of polyatomic molecules, only the more recent—the orbital method—can at present be applied to the excited levels of molecules, and so any interpretation of the spectra of polyatomic molecules must be done in its terms. This method, which was suggested by Lennard-Jones for diatomic molecules and applied to polyatomic molecules by Hund, Mulliken, and Lennard-Jones, starts on the assumption of the symmetry of the nuclear framework; the electrons are then added one by one to orbitals characteristic of the molecule as a whole and not of any particular atom-pair. In this last feature, the method differs from the earlier one developed by Pauling and Slater on the lines of the Heitler-London treatment of the hydrogen molecule, where the electron-pair bond between two atoms is generally assumed. For some purposes the electron-pair method has advantages over the orbital method (an example of the use of the electron-pair method where the other would be inapplicable is given by fennel's recent work on benzene); the advantages and disadvantages of each have been discussed in various papers, and it is probable that they will both be necessary complement of each other for some time in the elucidation of any particular problem.

scholarly journals The electronic structure of some polyenes and aromatic molecules III—Bonds of fractional order by the pair method

1937 ◽  
Vol 158 (894) ◽  
pp. 306-324 ◽  
Keyword(s):  
Electronic Structure ◽  
Fractional Order ◽  
Preceding Paper ◽  
Orbital Method ◽  
Aromatic Molecules ◽  
Lennard Jones ◽  
Pair Method

Lennard-Jones and Turkevich in the preceding paper have investigated by the orbital method the nature of the binding in various aromatic molecules due to the mobile electrons. The purpose of the present paper is to make somewhat similar calculations by the pair method. The author has had the benefit of several discussions with Professor Lennard-Jones, and he is glad to take this opportunity of acknowledging them.

Electronic Structures and Nonlinear Optical Properties for Cross-Conjugated Polyene

1989 ◽  
Vol 173 ◽  
Author(s):  
Yuhei Mori ◽  
Yoshimichi Okano
Keyword(s):  
Excited States ◽  
Electronic Structures ◽  
Nonlinear Optical ◽  
The Other ◽  
Orbital Method ◽  
Molecular Orbital Method ◽  
Third Order ◽  
Conjugated Molecules ◽  
Semi Empirical ◽  
Order Susceptibility

ABSTRACTFor several cross-conjugated molecules, molecular excited states and third-order nonlinear susceptibilities γ are calculated by semi-empirical molecular orbital method. The calculated γ are compared with each other and the reason for the differences are discussed in terms of the orbital shapes which contribute mainly to γ. The reason that long polyene chains have large γ, is ascribed to the large transition moment which is explained by the signs of the LCAO coefficients. On the other hand, it is found that the cross-conjugated molecules in which two similar-length chain cross at the center is not good for large third-order susceptibility.

Hybrid polymer composite materials. Part 2. Preparation technology

2020 ◽  
pp. 8-13
Keyword(s):  
Composite Materials ◽  
Impact Toughness ◽  
Polymer Composites ◽  
The Other ◽  
Polymer Materials ◽  
Hybrid Polymer ◽  
Preparation Technology ◽  
Advantages And Disadvantages ◽  
Hybrid Polymer Composite ◽  
The One

The main methods (pressing and winding) of the processing of hybrid polymer composites to obtain items were examined. Advantages and disadvantages of the methods were noted. Good combinations of different-module fibers (carbon, glass, boron, organic) in hybrid polymer materials are described, which allow one to prepare materials with high compression strength on the one hand, and to increase fracture energy of samples and impact toughness on the other hand.

scholarly journals COVID-19 Shutdown: A Qualitative Study on Pearls and Pitfalls

Proceedings ◽  
2021 ◽  
Vol 74 (1) ◽  
pp. 4
Author(s):  
Naciye Güliz Uğur
Keyword(s):  
Qualitative Study ◽  
Human Health ◽  
Social Distance ◽  
The Other ◽  
Adoption Of Technology ◽  
Family Ties ◽  
Advantages And Disadvantages ◽  
Modern Period ◽  
Long Term Impact

The extraordinary and tragic conditions that humanity has not experienced before in the modern period have become ordinary, namely, a “new normal” with the presence of the COVID-19 pandemic. COVID-19 has had frightening consequences for human health and has caused one million deaths as of September 2020. On the other hand, it has set a new standard of good habits, approaches, and benefits. Due to its global and long-term impact, this unique virus has laid the groundwork for unprecedented helping and sharing behaviors between people and countries. In this study, findings are compiled from the open-ended responses of 626 individuals, all of whom live in Turkey. Within the study’s scope, individuals were asked about the unique advantages and disadvantages of the restrictions imposed under COVID-19. While the categories of economy, social distance, and health came to the fore among the harms, the strengthening of family ties, adoption of technology, and the spread of solidarity culture were mentioned among the advantages.

scholarly journals Metal-Rich Metallaboranes: Synthesis, Structures and Bonding of Bi- and Trimetallic Open-Faced Cobaltaboranes

Inorganics ◽  
2021 ◽  
Vol 9 (4) ◽  
pp. 28
Author(s):  
Kriti Pathak ◽  
Chandan Nandi ◽  
Jean-François Halet ◽  
Sundargopal Ghosh
Keyword(s):  
Electronic Structures ◽  
Density Functional ◽  
Room Temperature ◽  
Electron Pair ◽  
X Ray Diffraction ◽  
Functional Theory ◽  
X Ray ◽  
Cluster 2 ◽  
Cobalt Center

Synthesis, isolation, and structural characterization of unique metal rich diamagnetic cobaltaborane clusters are reported. They were obtained from reactions of monoborane as well as modified borohydride reagents with cobalt sources. For example, the reaction of [Cp*CoCl]2 with [LiBH4·THF] and subsequent photolysis with excess [BH3·THF] (THF = tetrahydrofuran) at room temperature afforded the 11-vertex tricobaltaborane nido-[(Cp*Co)3B8H10] (1, Cp* = η5-C5Me5). The reaction of Li[BH2S3] with the dicobaltaoctaborane(12) [(Cp*Co)2B6H10] yielded the 10-vertex nido-2,4-[(Cp*Co)2B8H12] cluster (2), extending the library of dicobaltadecaborane(14) analogues. Although cluster 1 adopts a classical 11-vertex-nido-geometry with one cobalt center and four boron atoms forming the open pentagonal face, it disobeys the Polyhedral Skeletal Electron Pair Theory (PSEPT). Compound 2 adopts a perfectly symmetrical 10-vertex-nido framework with a plane of symmetry bisecting the basal boron plane resulting in two {CoB3} units bridged at the base by two boron atoms and possesses the expected electron count. Both compounds were characterized in solution by multinuclear NMR and IR spectroscopies and by mass spectrometry. Single-crystal X-ray diffraction analyses confirmed the structures of the compounds. Additionally, density functional theory (DFT) calculations were performed in order to study and interpret the nature of bonding and electronic structures of these complexes.

Cycles in symbol production? A new model to explain concentration, diversity and innovation in the music industry

Popular Music ◽  
1995 ◽  
Vol 14 (1) ◽  
pp. 55-93 ◽  
Author(s):  
Michael Christianen
Keyword(s):  
Negative Correlation ◽  
Music Industry ◽  
The Other ◽  
Recording Industry ◽  
Cultural Goods ◽  
New Model ◽  
Advantages And Disadvantages ◽  
Factors Influencing ◽  
Using Data ◽  
The One

With the publication of the article ‘Cycles in symbol production’ (Peterson and Berger 1975) a discussion started concerning the advantages and disadvantages of the production of cultural goods under market conditions. The analysis by Peterson and Berger showed a negative correlation between concentration in the recording industry, on the one hand, and the diversity and innovativeness of the music, on the other. Repetition of the analysis using data from the 1980s (Burnett 1990; Lopes 1992) has shown that for this period Peterson and Berger's hypotheses should be rejected. Is there a connection between concentration and diversity and innovation? Are there cycles in symbol production? There seems to be no conclusive answer. In this article, I will attempt to clear up this matter. First, I will repeat the analysis of the relation between concentration and diversity/innovation, using the same model as Peterson and Berger, but with different definitions for the variables concentration, diversity and innovation. Then I will suggest a new model, which can be helpful in uncovering other factors influencing diversity and innovation in the music industry. I will come to that later. Let me first give the reader a brief overview of previous research.

Sewage Clarification with Magnetite Particles

1991 ◽  
Vol 23 (7-9) ◽  
pp. 1703-1712 ◽  
Author(s):  
N. A. Booker ◽  
D. Keir ◽  
A. J. Priestley ◽  
C. B. Ritchie ◽  
D. L. Sudarmana ◽  
...  
Keyword(s):  
Sewage Treatment ◽  
The Other ◽  
New Approach ◽  
Chemical Coagulation ◽  
Advantages And Disadvantages ◽  
Magnetite Particles

A new approach to sewage treatment which involves rapid clarification of raw sewage with fine magnetite particles is described. The process, which is essentially a greatly accelerated chemical coagulation, provides a quick separation of the sewage into two liquid streams, one clarified, the other highly concentrated. Development of the process up to and including operation of a fully continuous pilot is outlined and potential advantages and disadvantages identified.

The variational alternant molecular orbital method for 3-D and 2-D hydrogen molecule

1986 ◽  
Vol 30 (5) ◽  
pp. 685-694 ◽  
Author(s):  
E. A. de Andrada E Silva ◽  
I. C. da Cunha Lima ◽  
A. Ferreira da Silva
Keyword(s):  
Molecular Orbital ◽  
Hydrogen Molecule ◽  
Orbital Method ◽  
Molecular Orbital Method

scholarly journals DEVELOPMENT OF THE MODEL OF STUDENTS’ INDEPENDENT WORK UNDER CONDITIONS OF DISTANCE LEARNING

2021 ◽  
pp. 273-289
Author(s):  
Olena Osadcha
Keyword(s):  
Distance Learning ◽  
Information Technologies ◽  
The Other ◽  
Advantages And Disadvantages ◽  
Other Hand ◽  
The One ◽  
Independent Work ◽  
Further Development

The article deals with the development of the model of students’ independent work under conditions of distance learning. The importance of the research into this problem is determined, on the one hand, by the growing possibilities of using various information technologies and, on the other hand by the necessity to adapt to the conditions of today’s world where independent work of students is becoming increasingly important. The advantages and disadvantages of distance learning have been explored. The author studied the role of independent work in the formation of the professional competences of students. The issue of modeling in the area of education has been tackled. The approaches to the development of the model of independent work have been identified and analyzed. The components of the model, such as the goal, the tasks, the content, the methods, the means and evaluation of results have been determined and characterized. The prospects of further development of this research are related to the exploration of models of independent work of students majoring in different areas.

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