v.8 n.8 November

Law of Conservation of Energy of Gravitational Fields and the Gravitational Field Equation

Valery Borisovich Morozov

Parana J. Sci. Educ., v.8, n.8, (1-6), November 1, 2022.

DOI: 10.5281/zenodo.7268383

Abstract

A gravitational field equation has been found that is completely in keeping with all of the postulates of Einstein's Theory of Relativity and the Law of Conservation of Momentum and Energy. This is achieved by introducing the gravitational field into the energy-momentum tensor equation. In the region of the small fields possessed by smaller fields, the equation differs slightly from the Einstein equation and it is important to note that the solutions of the new equation do not contain singularities. The local law of conservation of energy-momentum of a system substance-gravitational field follows directly from the new equation. A numerical solution of the equation for a point source of the gravitational field was obtained.

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Theoretical evaluation of the interaction of biguanides with Vitamin B12 transporter BtuCD

Lauro Figueroa Valverde, María López-Ramos, Marcela Rosas Nexticapa, María Magdalena Álvarez Ramírez, Virginia Mateu Armand, Karen Priego-Delgado, and Estrella Pinkney-Rivas

Parana J. Sci. Educ., v.8, n.8, (7-13), November 1, 2022.

DOI: tiny.cc/PJSE24476153v8i8p007-013

Abstract

A theoretical study was to carry out to evaluate the interaction of biaguanides (metformin, buformin and phenformin) with Vitamin B12 transporter BtuCD using 4r9u protein as tool theoretical in Docking Server software. The results showed different type of aminoacid residues involved in the interaction of biaguanides with 4r9u protein surface. Other data display that inhibition constant (Ki) was lower for metformine (4.01) compared with buformine (5.91) and phenformine (7.57). This phenomenon may depend of functional groups involved in the chemical structure of each biguanide, which can be translated as changes in absorption of metformine, buformine, and phenformine.

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Black hole or Gravastar? The GW190521 case

Ioannis Antoniou

Parana J. Sci. Educ., v.8, n.8, (14-18), November 1, 2022.

DOI: tiny.cc/PJSE24476153v8i8p014-018

Abstract

The existence of cosmological compact objects with very strong gravity is a prediction of the theory of General Relativity and an exact solution of the Einstein equations. The most known of these objects are called black holes and recently observed for the first time. However, the theory of black hole formation has some disadvantages. In order to avoid these, has been proposed the existence of gravastars (gravitation vacuum stars), an alternative stellar model which seems to solve the problems of the black hole theory. This work compares black holes and gravastars using a wide range of the literature and emphasize the properties of gravastars, which are consistent with the current cosmological observations. Gravastars has been proposed as the solution of the ”pair-instability” effect and a possible explanation for the observed masses of the compact objects, before the collapse, from the gravitational signal GW190521, since in the formation of a gravastar there aren’t mass restrictions.

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Impact of toxic heavy metals on the Condition Index of Cirrhinus mrigala

Abhijit Mitra, Sana Ahmed, Subra Bikash Bhattacharyya, Sitangshu Roy, Prosenjit Pramanick, Nabonita Pal, Ricardo Gobato, and Sufia Zaman

Parana J. Sci. Educ., v.8, n.8, (19-29), November 1, 2022.

DOI: tiny.cc/PJSE24476153v8i8p019-029

Abstract

The paper presents evidence that dissolved toxic heavy metals like cadmium, lead, and chromium pose significant adverse impact on the overall average Condition Index (CI) of Cirrhinus mrigala, a commercially important freshwater finfish consumed in India. This index serves as a better proxy to ambient environmental health of the species compared to the existing Fulton’s condition equation. Observations of fish culture related hydrological parameters such as surface water temperature, surface water pH, Dissolved Oxygen (DO), dissolved nitrate, dissolved phosphate, and dissolved silicate during the culture period of 5 months exhibit significant positive relationships with the overall average CI (exception is silicate), which indicate the growth of the fish species as functions of these variables.

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Flat Rotation Curves of Spiral Galaxies

Stefan Bernhard Rüster

Parana J. Sci. Educ., v.8, n.8, (30-42), November 1, 2022.

DOI: tiny.cc/PJSE24476153v8i8p030-042

Abstract

In this article, a simple but quite accurate model conforming to observations and solving the modified Poisson equation is utilized in order to compute the rotation curves as well as the radial acceleration relations of spiral galaxies being composed of several components: the central region of the bulge, the bulge, the disk, and dark matter. With this model, flat rotation curves of spiral galaxies are obtained, because the modified Poisson equation approximately meets the requirement of conservation of total energy in Newton’s theory of gravity, wherefore the model contains the exact circular speeds of test particles which are caused by the dark matter component of the respective considered spiral galaxies. The computed rotation curves are fitted to the observed speeds in spiral galaxies taken from SPARC. It turns out, that the simple model in this article is able to explain the observed flat rotation curves as well as the increasing rotation curves at large distances from the center of spiral galaxies with a very good accuracy.

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