scholarly journals Influence of Types and Doses of Fertilizer on the Physicochemical Characteristics of Water, Composition and Structure of Zooplankton Populations in Ponds

2019 ◽  
Vol 1 (4) ◽  
Author(s):  
Algrient Nana Towa
Keyword(s):  
Physicochemical Characteristics ◽  
Water Composition ◽  
Composition And Structure

Study of graphite-like materials obtained from coal-tar pitch

2020 ◽  
Vol 63 (7) ◽  
pp. 46-53
Author(s):  
Sergey A. Sozinov ◽  
◽  
Anna N. Popova ◽  
Larisa V. Sotnikova ◽  
Anastasiya S. Valnukova ◽  
...  
Keyword(s):  
Coal Tar ◽  
Functional Materials ◽  
Xrd Analysis ◽  
Physicochemical Characteristics ◽  
Coal Tar Pitch ◽  
Medium Temperature ◽  
Paramagnetic Resonance ◽  
Derivative Analysis ◽  
Composition And Structure ◽  
The Individual

In the research, the study of precursors of graphite-like materials obtained from medium-temperature coal tar pitch was carried out on the individual components of coal tar pitch by separating the multicomponent composition of the pitch into separate fractions. Such approach, to study the physicochemical characteristics of the individual components of coal tar pitch, contributes to both the determination of the contribution of individual pitch components to the process of its structuring during carbonization and the development of new environmentally friendly methods for the synthesis of functional materials for various applications. The β-fraction was precipitated with n-hexane from toluene extract of coal tar pitch. γ-fraction was isolated from n-hexane by solvent evaporation. α2-fraction was isolated from the residue, insoluble in toluene, by quinoline extraction. The composition and structure of the isolated individual fractions of coal tar pitch were studied by physicochemical methods of analysis. The shape and morphology were investigated by electron microscopy. To study the composition and structure, the methods of elemental analysis, infrared spectroscopy, electron-paramagnetic resonance, XRD-analysis, and thermoanalysis were used in combination with methods of derivative analysis, chromatography, and mass spectrometry. The authors of the work propose new approaches to the use of individual fractions of coal tar pitch in order to obtain new graphite-like materials on their basis.

Influence of the preparing conditions on the physicochemical characteristics of glasses for thick film hybrid microelectronics

1994 ◽  
Vol 9 (9) ◽  
pp. 2304-2313 ◽  
Author(s):  
M. Prudenziati ◽  
B. Morten ◽  
P. Savigni ◽  
G. Guizzetti
Keyword(s):  
Thick Film ◽  
Specular Reflection ◽  
Physicochemical Characteristics ◽  
Systematic Investigation ◽  
Glassy Matrix ◽  
Lead Glass ◽  
Preparation Methods ◽  
Composition And Structure ◽  
The Difference ◽  
High Lead

Seven batches of a high-lead glass were used for the preparation of RuO2-based thick film resistors. Investigation of their electrical properties showed a lack of reproducibility of results whose origin was related to changes of the physicochemical properties of the glassy matrix. A systematic investigation of the glass batches, both in form of frit powders and screen printed and fired layers, was carried out with several spectroscopies to detect changes in composition and structure. The spectroscopic methods included x-ray Energy Dispersive Fluorescence (EDS), Scanning Electron Microscopy (SEM), Atomic Absorption (AA), diffuse optical reflection of the powders and specular reflection of the layers, optical transmission, and other complementary methods. The dissolution of Al, due to interaction between the glasses and the alumina substrate, as well as the diffusivity and solubility of Ag due to interaction with the Ag-bearing terminations were measured. The results demonstrated that, apart from small compositional differences, the various batches were characterized by differences in residual stresses, redox reactions, and “microstructure.” The latter was responsible for very notable differences in the optical properties of the glasses, which in turn are closely related with the difference in atomic solubility and diffusivity. Optical spectroscopies have been found to be a suitable means for testing reproducible preparation methods of glass frits for thick-film hybrid microelectronics.

The factors determining the skin penetration and cellular uptake of nanocarriers: New hope for clinical development

2021 ◽  
Vol 27 ◽  
Author(s):  
Afsaneh Farjami ◽  
Sara Salatin ◽  
Samira Jafari ◽  
Mohammad Mahmoudian ◽  
Mitra Jelvehgari
Keyword(s):  
Drug Delivery ◽  
Skin Permeation ◽  
Direct Interaction ◽  
Skin Barrier ◽  
Skin Penetration ◽  
Physicochemical Characteristics ◽  
Skin Permeability ◽  
Topical Drug Delivery ◽  
Major Barrier ◽  
Composition And Structure

: The skin provides a protective barrier against toxic environments and also offers a valuable route for topical drug delivery. The stratum corneum (SC) is the outermost layer of the skin and serves as the major barrier to chemical transfer through the skin. The human skin barrier is particularly diffcult to overcome because of the complex composition and structure of the SC. Nanoparticulate carriers have gained widespread attention in topical drug delivery due to their tunable and versatile properties. The present review summarizes the main factors involved in the skin penetration of nanocarriers containing drug. Employment of nanotechnology in topical delivery has grown progressively during recent years; however, it is important to monitor the skin penetration of nanocarriers prior to their use due to avoid possible toxic effects. Nanocarriers can act as a means to increase the skin permeation of drugs by supporting a direct interaction with the SC and increasing the period of permanence on the skin. The skin penetration is influenced by the physicochemical characteristics of nanocarriers such as composition, size, shape, surface chemistry as well as skin features. Considering that the target of topical systems based on nanocarriers is the penetration of therapeutic agents in the skin layers, so a detailed understanding of the factors influencing skin permeability of nanocarriers is essential for safe and efficient therapeutic applications.

scholarly journals Current Aspects of Prevention of Coal Freezing by Means of Inorganic and Organic Reagents

2021 ◽  
Vol 100 ◽  
pp. 06003
Author(s):  
Ekaterina Shmeltser ◽  
Maryna Kormer ◽  
Vitalij Lyalyuk
Keyword(s):  
Alkaline Earth ◽  
Physicochemical Characteristics ◽  
Cold Season ◽  
Chemical Additives ◽  
Organic Reagents ◽  
Alkaline Metals ◽  
Structure Of Molecules ◽  
Coke Plants ◽  
Composition And Structure ◽  
Effective Use

In the cold season, irregular coal supplies to coke plants are aggravated by the need to heat the coal cars. Thawing of rail cars in garages (enclosures) is the least efficient and most expensive approach. Treatment of the coal concentrates with chemical additives reliably prevents freezing in winter during transit from suppliers to consumers. With a view to finding new reagents for preventing the freezing of coal in winter, the lime, the acetates and chlorides of alkaline-earth and alkaline metals are studied. Attention focuses on their physicochemical characteristics, methods of preparation and of introduction in coal concentrate, and their influence on freezing. The results of studies have shown that the use of organosilicon is more effective use of acetates and chlorides of metals. The high activity of organosilicon substances is explained by their elemental composition and structure of molecules.

Crystal Structure Analysis of Cu-Zr Alloys by Convergent Beam Diffraction

1981 ◽  
Vol 39 ◽  
pp. 354-355
Author(s):  
A. F. Marshall ◽  
J. W. Steeds ◽  
D. Bouchet ◽  
S. L. Shinde ◽  
R. G. Walmsley
Keyword(s):  
Crystal Structure ◽  
Point Group ◽  
Intermetallic Phase ◽  
Three Dimensional ◽  
Crystal Structure Analysis ◽  
Ion Milling ◽  
Composition And Structure ◽  
Unit Cells ◽  
Sputter Deposited ◽  
Convergent Beam

Convergent beam electron diffraction is a powerful technique for determining the crystal structure of a material in TEM. In this paper we have applied it to the study of the intermetallic phases in the Cu-rich end of the Cu-Zr system. These phases are highly ordered. Their composition and structure has been previously studied by microprobe and x-ray diffraction with sometimes conflicting results.The crystalline phases were obtained by annealing amorphous sputter-deposited Cu-Zr. Specimens were thinned for TEM by ion milling and observed in a Philips EM 400. Due to the large unit cells involved, a small convergence angle of diffraction was used; however, the three-dimensional lattice and symmetry information of convergent beam microdiffraction patterns is still present. The results are as follows:1) 21 at% Zr in Cu: annealed at 500°C for 5 hours. An intermetallic phase, Cu3.6Zr (21.7% Zr), space group P6/m has been proposed near this composition (2). The major phase of our annealed material was hexagonal with a point group determined as 6/m.

Off-axis electron holography applied to the study of interfaces

1992 ◽  
Vol 50 (1) ◽  
pp. 244-245
Author(s):  
J.K. Weiss ◽  
M. Gajdardziska-Josifovska ◽  
M. R. McCartney ◽  
David J. Smith
Keyword(s):  
Electric Fields ◽  
Resolution Enhancement ◽  
Interfacial Structure ◽  
Atomic Scale ◽  
Bulk Property ◽  
Electron Holography ◽  
Specimen Thickness ◽  
Composition And Structure ◽  
Chemical Segregation ◽  
Diffraction Effects

Interfacial structure is a controlling parameter in the behavior of many materials. Electron microscopy methods are widely used for characterizing such features as interface abruptness and chemical segregation at interfaces. The problem for high resolution microscopy is to establish optimum imaging conditions for extracting this information. We have found that off-axis electron holography can provide useful information for the study of interfaces that is not easily obtained by other techniques.Electron holography permits the recovery of both the amplitude and the phase of the image wave. Recent studies have applied the information obtained from electron holograms to characterizing magnetic and electric fields in materials and also to atomic-scale resolution enhancement. The phase of an electron wave passing through a specimen is shifted by an amount which is proportional to the product of the specimen thickness and the projected electrostatic potential (ignoring magnetic fields and diffraction effects). If atomic-scale variations are ignored, the potential in the specimen is described by the mean inner potential, a bulk property sensitive to both composition and structure. For the study of interfaces, the specimen thickness is assumed to be approximately constant across the interface, so that the phase of the image wave will give a picture of mean inner potential across the interface.

Applications of SEM/EDXA in cement clinker investigation

1990 ◽  
Vol 48 (4) ◽  
pp. 870-871
Author(s):  
Arezki Tagnit-Hamou ◽  
Shondeep L. Sarkar
Keyword(s):  
Mineralogical Composition ◽  
Physicochemical Characteristics ◽  
Cement Clinker ◽  
Accurate Information ◽  
Phase Identification ◽  
History Of ◽  
Bulk Chemical ◽  
Resolution Imaging ◽  
Proven Method ◽  
Instantaneous Chemical

All the desired properties of cement primarily depend on the physicochemical characteristics of clinker from which the cement is produced. The mineralogical composition of the clinker forms the most important parameter influencing these properties.Optical microscopy provides reasonably accurate information pertaining to the thermal history of the clinker, while XRDA still remains the proven method of phase identification, and bulk chemical composition of the clinker can be readily obtained from XRFA. Nevertheless, all these microanalytical techniques are somewhat limited in their applications, and SEM/EDXA combination fills this gap uniquely by virtue of its high resolution imaging capability and possibility of instantaneous chemical analysis of individual phases.Inhomogeneities and impurities in the raw meal, influence of kiln conditions such as sintering and cooling rate being directly related to the microstructure can be effectively determined by SEM/EDXA. In addition, several physical characteristics of cement, such as rhcology, grindability and hydraulicity also depend on the clinker microstructure.

Common modifications of selenocysteine in selenoproteins

2019 ◽  
Vol 64 (1) ◽  
pp. 45-53 ◽  
Author(s):  
Elias S.J. Arnér
Keyword(s):  
Amino Acids ◽  
Covalent Binding ◽  
Physicochemical Characteristics ◽  
Redox Active

Abstract Selenocysteine (Sec), the sulfur-to-selenium substituted variant of cysteine (Cys), is the defining entity of selenoproteins. These are naturally expressed in many diverse organisms and constitute a unique class of proteins. As a result of the physicochemical characteristics of selenium when compared with sulfur, Sec is typically more reactive than Cys while participating in similar reactions, and there are also some qualitative differences in the reactivities between the two amino acids. This minireview discusses the types of modifications of Sec in selenoproteins that have thus far been experimentally validated. These modifications include direct covalent binding through the Se atom of Sec to other chalcogen atoms (S, O and Se) as present in redox active molecular motifs, derivatization of Sec via the direct covalent binding to non-chalcogen elements (Ni, Mb, N, Au and C), and the loss of Se from Sec resulting in formation of dehydroalanine. To understand the nature of these Sec modifications is crucial for an understanding of selenoprotein reactivities in biological, physiological and pathophysiological contexts.

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