Search

This paper is designed for heavy pulsars coming from the Neutron Star Interior Composition Explorer. The research model is describe by Einstein field equations for anisotropic fluid configuration with spherical symmetry. As per present perceptiveness, modified non-linear Van der Waals equation of state is used to relate physical variables. The continuity of inner and outer matter is obtained by comparing inner spacetime to outer Schwarzschild metric. The physical viability of this model is evaluated and further it is compared with observational data of pulsars PSR J0348+0432, PSR J0740+6620 and PSR J0030+0451. The model fulfils all physical and mathematical characteristics of the dense structure studies. It offers the factual proofs carried by evolution of celestial configurations. The working model presented here is physically viable and shows stable behaviour. [ABSTRACT FROM AUTHOR]

Copyright of Retos: Nuevas Perspectivas de Educación Física, Deporte y Recreación is the property of Federacion Espanola de Asociaciones de Docentes de Educacion Fisica and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Retos: Nuevas Perspectivas de Educación Física, Deporte y Recreación is the property of Federacion Espanola de Asociaciones de Docentes de Educacion Fisica and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Retos: Nuevas Perspectivas de Educación Física, Deporte y Recreación is the property of Federacion Espanola de Asociaciones de Docentes de Educacion Fisica and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The present work deals with a study of non-Newtonian Casson and Williamson nanofluids flow models with a linearly porous stretching sheet across convective conditions. The heat transfer phenomenon has been explored under the impacts of heat source, radiation and viscous dissipation. The higher-order chemical reaction and suction/injection are also taken into consideration. The system of nonlinear dimensionally governing PDEs are converted into dimensionless nonlinear ODEs with the use of appropriate similarity transformations. The transformed set of ODEs are numerically solved by using R–K Fehlberg approach based on shooting technique. The graphical representations for physical parameters are plotted using the in-built MATLAB solver bvp5c. Additionally, the numerical tabular values calculated for the skin friction coefficient, heat transfer rate and mass transfer rate. It is noticed that with elevated amounts of magnetic field, Brownian motion parameter, heat generation and thermal radiation, the temperature significantly increases. The velocity increases with increased thermal and mass Grashof numbers, and the reverse phenomenon exists with increasing magnetic field, porous medium and suction. The Williamson nanofluid velocity is less significant than the Casson nanofluid velocity. The concentration drops while enhancing the higher-order chemical reaction and Schmidt number. Moreover, the increment in the radiation and Biot number increases the Nusselt number. [ABSTRACT FROM AUTHOR]

Copyright of Retos: Nuevas Perspectivas de Educación Física, Deporte y Recreación is the property of Federacion Espanola de Asociaciones de Docentes de Educacion Fisica and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Palabra Clave is the property of Universidad de la Sabana and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this work, an exact solution of Einstein's field equations in isotropic coordinates for anisotropic matter distribution is obtained by considering a particular metric choice of metric potential g rr . To check the feasibility of the model, we have investigated all the physical characteristics of a realistic star. It is found that the model is potentially stable, and the adiabatic index is greater than 4 3 . The model has been analyzed for compact star 4U 1538-52. [ABSTRACT FROM AUTHOR]

In this work, we have investigated a new solution for charged anisotropic compact stellar system in the framework of an extended theory of symmetric teleparallel gravity known as f(Q, T) gravity with the non-metricity term Q and the trace T for energy–momentum tensor. We have constructed a complete set of the gravitational field equations for a non-linear function f (Q , T) = α Q + β (1 + Q 2) + λ T with α , β and λ are dimensionless constant parameters in case of static spherically symmetric space-time. To evaluate the expression of relevant unknown constants interior space-time has been matched with exterior Reissner–Nordstr o ¨ m metric. We have performed a graphical discussion in detail to test the behavior of physical parameters in the interior region of a stellar system like energy density, radial and tangential pressure, anisotropies of matter portion, electric field intensity etc. Also, to check the physical validity of our solutions, we have performed various tests viz., energy conditions, stability, mass–radius relation, surface redshift etc. The hydrostatic equilibrium position of our stellar system has been analysed through the TOV equation. Finally, we have determined that our stellar structure solutions satisfy all required physical conditions for viability and acceptability in the context of some pulsar like neutron stars. So our model can be used to characterise the neutron stars in f(Q, T) modified gravity. [ABSTRACT FROM AUTHOR]

This paper is devoted to obtaining and studying two interior exact solutions of Einstein's Field Equations (EFE) for spherical geometry in the context of gravitational decoupling (GD) through minimal geomentric deformation (MGD). We take the well-known Kohler–Chao–Tikekar cosmological solution as a seed in the framework of GD to first obtain an isotropic solution, which is decoupled again in order to obtain a second stellar anisotropic solution. Both resulting models turn out to be physically viable stellar models. Their stability is also being studied. [ABSTRACT FROM AUTHOR]

Copyright of Retos: Nuevas Perspectivas de Educación Física, Deporte y Recreación is the property of Federacion Espanola de Asociaciones de Docentes de Educacion Fisica and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this article, the Segre classification approach is used to obtain some new solutions for spherically symmetric static spacetime metric corresponding to Segre types [(1, 111)], [1, (111)], [(1, 1)(11)], or [1, 1(11)]. The eigenvalue degeneracy in these situations correlates to timelike and spacelike eigenvectors and their primary null direction, which identify the kind of matter distribution in space and aid in the consideration of novel solutions for the corresponding energy momentum tensor. The isotropic Segre type [(1, 111)] in modified theory provides the Schwarzschild de-Sitter/anti-de-Sitter solutions, whereas in types [1, (111)] and [1, 1(11)] depending upon matter distribution new obtained solutions adhere all the physical conditions and present the viable trends of energy and causality conditions. Moreover, the profiles of the adiabatic index, surface, and gravitational redshift are observed along with the hydrostatic equilibrium using the Tolman–Oppenheimer–Volkoff equation. Additionally, for these types the solution is compared with observational data, and numerical values are calculated for central and surface densities and central pressure of compact star candidates K S 1731 - 260 and P S R J 1614 - 2230 . Segre type [(1, 1)(11)] relates to a non-null electromagnetic field that corresponds to models with anisotropy in dark energy, which is demonstrated by graphical analysis. Dark energy does not behave as an ordinary matter resulting in the violation of strong energy condition and the causality condition. [ABSTRACT FROM AUTHOR]

The following differential quadratic polynomial differential system   d x d t = y − x ,   d y d t = 2 y − y γ − 1 2 − γ y − 5 γ − 4 γ − 1 x , when the parameter γ ∈ (1 , 2 ] models the structure equations of an isotropic star having a linear barotropic equation of state, being x = m (r) / r where m (r) ≥ 0 is the mass inside the sphere of radius r of the star, y = 4 π r 2 ρ where ρ is the density of the star, and t = ln (r / R) where R is the radius of the star. First, we classify all the topologically non-equivalent phase portraits in the Poincaré disc of these quadratic polynomial differential systems for all values of the parameter γ ∈ R ∖ { 1 } . Second, using the information of the different phase portraits obtained we classify the possible limit values of m (r) / r and 4 π r 2 ρ of an isotropic star when r decreases. [ABSTRACT FROM AUTHOR]

The aim of the present work is to apply the Caputo-fractional derivative to the heat transformation of unsteady incompressible magnetohydrodynamic (MHD) Casson nanofluid flow. Ethylene Glycol-Graphene oxide and Ethylene glycol-Multiwall Carbon nanotubes considered as nanofluids. The current study helps in understanding the fluid dynamics involved in water purification, energy conservation, solar energy, coolants, cancer therapies, and physiological fluid dynamics. By using appropriate non-dimensional variables, the leading PDE of the problem are non dimensionalized. The governing equations are solved by the combined integral transforms of Fourier sine and Laplace transform technique. For an extensive study of the problem, graphical illustrations and tables are developed by using the MATLAB software. The effects of the order of the Caputo derivative, thermal Grashof number, viscous dissipation, and Casson parameter oscillations on the fractional heat and momentum equations are inspected. The thermal and velocity profiles are increased for thermal Grashof number and Casson parameter. Symmetry phenomena are also observed in the case of cooling and heating plate for thermal Grashof number. Different shapes of nanoparticles are performed for ordinary fractional parameters which is increased for temperature as well as velocity. [ABSTRACT FROM AUTHOR]

We imagine spherically symmetric configurations made of both dark matter and dark energy in the halo of spiral galaxies. Adopting a polytropic equation of state for dark matter and the Extended Chaplygin gas equation of state for dark energy, we model the same object with three different dark matter–dark energy compositions. We compute the frequencies and the corresponding eigenfunctions of the ten lowest modes, integrating the equations for the radial perturbations by imposing the appropriate boundary conditions at the center and the surface of the object. Also, a comparison between the different models is made. [ABSTRACT FROM AUTHOR]

This study examines the flow properties of a ternary hybrid nanofluid composed of GO-MoS2-Al2O3 in a base mixture of C2H6O2-H2O (50%-50%) fluid as it moves through a porous longitudinal rectangular fin. The primary objective aimed to analyze the influence of nanoparticle concentration and its shape on the heat transfer rate of the system. Darcy's model was utilized to analyze the flow and thermal behaviour of the nanofluid within the fin, incorporating temperature-dependent natural convection and radiation effects. The governing thermal equilibrium equation is transitioned to non-dimensional form and numerically solved using the 3 stage Lobatto - IIIa numerical technique, incorporating suitable boundary conditions for convective and insulated tips. The simulation results illustrate the impact of various similarity parameters on the thermal behaviour of the fin and the heat transfer rate. Natural convection, radiation and wet porous parameter are the key similarity parameters that determine the heat transfer rate of our proposed model. In our investigation, the heat transfer rate of convective fin tip was enhanced by 14.61%, 25% and 6.5% compared to an insulated tip for Nc = Nr = m2 = 0:5: Changing the shapes of the nanoparticle from spherical to lamina, the temperature distribution on the fin enhanced by 23.26%. The findings have significant implications for the design and optimization of thermal management systems in industries. [ABSTRACT FROM AUTHOR]

Copyright of Revista Vínculos is the property of Revista Vinculos and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A new class of exact solutions depicting anisotropic compact objects is presented in the current work. This spherically symmetric matter distribution assumes a specific form of anisotropy to obtain the exact solution for the field equations. The obtained interior solutions are smoothly matched with the Schwarzschild exterior metric over the bounding surface of a compact star and together with the condition that the radial pressure vanishes at the boundary, the form of the model parameters are attained. One of the interesting features of the obtained solutions is the codependency of the metric potentials. We have considered the pulsar 4U1608-52 with its current estimated data (mass = 1. 57 - 0.29 + 0.30 M ⊙ and radius = 9.8 ± 1.8 km [Özel in Astrophys J 820(1):28, 2016]) to study the model graphically. Moreover, we have studied the physical features and some important stability conditions for the model. Tabular comparison with other known pulsars infers that the obtained model represents a compact star within a radius of 8–12 km. Finally, we have found the angular momentum that causes the dragging of inertial frames of the slowly rotating equilibrium compact objects. [ABSTRACT FROM AUTHOR]

We make use of the condition of vanishing complexity, based on the current definition proposed by Herrera (Phys Rev D 97:044010, 2018), to find exact interior solutions to the Einstein equations for describing compact stellar objects. In the framework of general relativity, the complexity factor is an outcome of the orthogonal splitting of the Riemann tensor from which structure scalars are obtained. By using the Vaidya–Tikekar (V–T) metric ansatz (J Astrophys Astron 3:325, 1982) for the spacetime of a static spherically symmetric matter distribution, we model superdense, relativistic stars. The interior spacetime is matched to the exterior Schwarzschild solution across the boundary of the star where the radial pressure vanishes. The physical viability of the model has been tested following the current data corresponding to the pulsar 4 U 1820 - 30 . The stability of the model fulfilled the given criteria, namely the Tolman–Oppenheimer–Volkoff equation, the adiabatic index and the causality conditions. [ABSTRACT FROM AUTHOR]

Copyright of Retos: Nuevas Perspectivas de Educación Física, Deporte y Recreación is the property of Federacion Espanola de Asociaciones de Docentes de Educacion Fisica and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this article, we present a new model for anisotropic compact stars confined to physical dark matter (DM) based on the Bose–Einstein DM density profile and a bag model type equation of state (EoS). The obtained solutions are physically well-behaved and represent the physical and stable matter configuration by satisfying the energy conditions, causality conditions, and essential conditions on the stability factor and adiabatic index. The solutions supporting the matter sphere are in an equilibrium state by satisfying the generalized TOV equation. We also find the surface redshift, compactness parameter at the surface, maximum mass, and interestingly, all these values are under the desired range that makes our solution more physically viable. Here, the radially symmetric profiles of energy density, radial and transverse pressures are demonstrated. [ABSTRACT FROM AUTHOR]

We investigate some properties of exotic spherical configurations made of dark matter and dark energy. For the former, we adopt a polytropic equation-of-state, while for the latter, we adopt the extended Chaplygin gas equation-of-state. Solving the Tolman–Oppenheimer–Volkoff equations, within the two-fluid formalism, we compute the factor of compactness, the mass-to-radius relationships, as well as the tidal Love numbers and dimensionless deformabilities. A comparison between single-fluid objects and two-fluid configurations is made as well. [ABSTRACT FROM AUTHOR]

Copyright of GeSec: Revista de Gestao e Secretariado is the property of Sindicato das Secretarias e Secretarios do Estado de Sao Paulo (SINSESP) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Because of their thermophysical and rheological properties, graphene oxide (GO) nanofluids show promising advances in heat transfer enhancement. In particular, in magnetohydrodynamic (MHD) studies, where the fluid flow is kept in check, heat transfer tends to diminish due to magnetic field strength. GO nanoparticles, with the highest thermal conductivity, significantly impacts heat transfer devices through conductive heat transfer enhancement. This paper computationally investigates the MHD flow of GO nanofluid over a linearly stretching cylinder. The nanofluid flow is modelled using Buongiorno model under the influence of viscous dissipation effects and the effects of nanoparticle characteristics such as thermophoresis and Brownian motion. The modelled equations are solved using spectral collocation method under isothermal and slip boundary conditions. An examination of the impacts of embedded parameters is presented in detail and it is shown that the conductive heat transfer and diffusive mass transfer are enhanced by dispersing GO nanoparticles in the base fluid. A quantitative analysis is made with the previously published results for special cases. As suggested, this study is significant in heat transfer applications which demand the use of magnetic fields. [ABSTRACT FROM AUTHOR]

Neutrophils can contribute to inflammatory disease propagation via innate mechanisms intended for inflammation resolution. For example, neutrophil extracellular traps (NETs) are necessary for trapping pathogens but can contribute to clot formation and blood flow restriction, that is, ischemia. Currently, no therapeutics in the clinic directly target NETs despite the known involvement of NETs contributing to mortality and increased disease severity. Vascular-deployed particle-based therapeutics are a novel and robust alternative to traditional small-molecule drugs by enhancing drug delivery to cells of interest. This work designs a high-throughput assay to investigate the immunomodulatory behavior and functionality of salicylic acid-based polymer-based particle therapeutics against NETosis in human neutrophils. Briefly, this work finds that polymeric composition plays a role, and particle size can also influence rates of NETosis. Salicylate-based polymeric (Poly-SA) particles are found to functionally inhibit NETosis depending on the particle size and concentration exposed to neutrophils. This work demonstrates the high throughput method can help fast-track particle-based therapeutic optimization and design, more efficiently preparing this innovative therapeutics for the clinic., (© 2024 The Author(s). Advanced Healthcare Materials published by Wiley‐VCH GmbH.)

In this work, we investigate astrophysical systems in a Newtonian regime using anisotropic matter. For this purpose, we considered that both radial and tangential pressures satisfy a generalized Chaplygin-type equation of state. Using this model, we found the Lane–Emden equation for this system and solved it numerically for several sets of parameters. Finally, we explored the mass supported by this physical system and compared it with the Chandrasekhar mass. [ABSTRACT FROM AUTHOR]

The collapsing dynamics of relativistic fluid are explored in f(R) gravity in detailed systematic manner for the non-static spherically symmetric spacetime satisfying the equation of the conformal Killing vector. With quasi-homologous condition and diminishing complexity factor condition, exact solutions for dissipative as well as for non-dissipative system are found and the astrophysical applications of these exact solutions are discussed. Furthermore, it is demonstrated that f (R) = R , which is the extensive restriction of f(R) gravity, prior solutions of the collapsing fluid in general relativity, can be retrieved. [ABSTRACT FROM AUTHOR]

The concept of dark energy can be used as a possible option to prevent the gravitational collapse of compact objects into singularities. It affects the universe on the largest scale, as it is responsible for our universe’s accelerated expansion. As a consequence, it seems possible that dark energy will interact with any compact astrophysical stellar object [Phys. Rev. D 103, 084042 (2021)]. In this work, our prime focus is to develop a simplified model of a charged strange star coupled to anisotropic dark energy in Tolman–Kuchowicz spacetime (Tolman in Phys Rev 55:364, 1939; Kuchowicz in Acta Phys Pol 33:541, 1968) within the context of general relativity. To develop our model, here we consider a particular strange star object, Her X-1 with observed values of mass = (0.85 ± 0.15) M ⊙ and radius = 8. 1 - 0.41 + 0.41 km. respectively. In this context, we initially started with the equation of state (EoS) to model the dark energy, in which the dark energy density is proportional to the isotropic perfect fluid matter-energy density. The unknown constants present in the metric have been calculated by using the Darmois–Israel condition. We perform an in-depth analysis of the stability and force equilibrium of our proposed stellar configuration as well as multiple physical attributes of the model such as metric function, pressure, density, mass–radius relation, and dark energy parameters by varying dark energy coupling parameter α . Thus after a thorough theoretical analysis, we found that our proposed model is free from any singularity and also satisfies all stability criteria to be a stable and physically realistic stellar model. [ABSTRACT FROM AUTHOR]

Sodium-alginate (SA) based nanofluids represent a new generation of fluids with improved performances in terms of heat transfer. This work examines the influence of the nanoparticle shape on a non-Newtonian viscoplastic Cu-nanofluid pertaining to this category. In particular, a stretching/shrinking sheet subjected to a transverse magnetic field is considered. The proposed Cu-nanofluid consists of four different nanoparticles having different shapes, namely bricks, cylinders, platelets, and blades dispersed in a mixture of sodium alginate with Prandtl number Pr = 6.45. Suitable similarity transformations are employed to reduce non-linear PDEs into a system of ODEs and these equations and related boundary conditions are solved numerically by means of a Runge-Kutta-Fehlberg (RKF) method. Moreover, analytical solutions are obtained through the application of a MAPLE built-in differential equation solver (Dsolve). The behavior of prominent parameters against velocity and temperature is analyzed. It is found that the temperature increases for all shapes of nanoparticles with the viscoplastic parameter and the Eckert number. [ABSTRACT FROM AUTHOR]

New exact solutions of Einstein's field equations for charged stellar models by assuming linear equation of state P r = A (ρ − ρ a) , where P r is the radial pressure and ρ a is the surface density. By assuming e λ = 1 + r 2 R 2 for metric potential. The physical acceptability conditions of the model are investigated, and the model is compatible with several compact star candidates like 4U 1820-30, PSR J1903+327, EXO 1785-248, LMC X-4, SMC X-4, Cen X-3. A noteworthy feature of the model is that it satisfies all the conditions needed for a physically acceptable model. [ABSTRACT FROM AUTHOR]

Copyright of Revista En-Contexto is the property of Tecnologico de Antioquia, Institucion Universitari and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Background: The meanings and experiences related to malaria in pregnancy (MiP) and its processes of social determination of health (PSDH) have not been reported in the world scientific literature. The objective was to understand the meanings and experiences of MiP, and to explain their PSDH in an endemic area from Colombia, 2022. Methods: Critical ethnography with 46 pregnant women and 31 healthcare workers. In-depth and semi-structured interviews, focus group discussions, participant and non-participant observations, and field diaries were applied. A phenomenological-hermeneutic analysis, saturation and triangulation was carried out. The methodological rigor criteria were reflexivity, credibility, auditability, and transferability. Results: At the singular level, participants indicated different problems in antenatal care and malaria control programmes, pregnant women were lacking knowledge about MiP, and malaria care was restricted to cases with high obstetric risk. Three additional levels that explain the PSDH of MiP were identified: (i) limitations of malaria control policies, and health-system, geographic, cultural and economic barriers by MiP diagnosis and treatment; (ii) problems of public health programmes and antenatal care; (iii) structural problems such as monetary poverty, scarcity of resources for public health and inefficiency in their use, lacking community commitment to preventive actions, and breach of institutional responsibilities of health promoter entity, municipalities and health services provider institutions. Conclusion: Initiatives for MiP control are concentrated at the singular level, PDSH identified in this research show the need to broaden the field of action, increase health resources, and improve public health programmes and antenatal care. It is also necessary to impact the reciprocal relationships of MiP with economic and cultural dimensions, although these aspects are increasingly diminished with the predominance and naturalization of neoliberal logic in health. [ABSTRACT FROM AUTHOR]

In this work, we construct a new stellar model in the regime of anisotropic fluid pressure using the concept of vanishing complexity for spherically symmetric fluid distributions (Herrera in Phys Rev D 97:044010, 2018) and a convenient ansatz in order to close the Einstein's field equations. The resulting model fulfills the fundamental physical acceptability stellar conditions for a specific set of compactness factor. The stability and its response against fluctuations in the matter sector is also investigated. [ABSTRACT FROM AUTHOR]

In this study, we investigate a new relativistic anisotropic Einstein field equations solution for compact stars under embedding class 1 conditions. In order to do this, we apply the Karmarkar condition and the embedding class one technique. By taking Buchdahl type metric potential g rr into consideration, the precise analytical solution has been investigated. We have studied physical characteristics of various compact star using this analytical solution. Central singularities are absent from the solution. We have explored thermodynamic observables inside the stellar models, such as radial and tangential pressures, matter density, anisotropic factor, energy conditions, TOV, red-shift, and the speed of sound, etc., after establishing this space-time geometry for the stellar models. From the graphical representation of various physical characteristics, it is demonstrated that our model meets all the specification for ultra-high density compact bodies. [ABSTRACT FROM AUTHOR]

We obtain the clean semi-analytical solutions with method of directly defining inverse mapping (MDDiM) to the system of nonlinear equations arising in the magnetohydrodynamic (MHD) convection motion of Molybdenum disulfide (MoS2) engine-oil intrinsic nanofluid in a circumnavigatethe structure is considered for analysis. Finding the solutions by using MDDiM is a novel idea and first time solving for the system of nonlinear partial differential equations. We have chosen inverse linear mapping for the five-term solution and it emphasizes by residual error and this gives the low error (10−2 to 10−17) and can easily derive deformation terms by spending very low CPU time. Based on the proposed method, the convergence rate, accuracy, and efficiency of the governing equations are demonstrated, and result outputs shown in tabular and graphically, which exhibit meaningful structures and advantages in science and engineering. [ABSTRACT FROM AUTHOR]

Within Einstein’s General Relativity we study exotic stars made of dark energy assuming an extended Chaplygin gas equation-of-state. Taking into account the presence of anisotropies, we employ the formalism based on the complexity factor to solve the structure equations numerically, obtaining thus interior solutions describing hydrostatic equilibrium. Making use of well-established criteria we demonstrate that the solutions are well behaved and realistic. A comparison with another, more conventional approach, is made as well. [ABSTRACT FROM AUTHOR]

After introducing the gravitational decoupling method and the hairy black hole recently derived from it, we investigate the formation of quantum hairy black holes by applying the horizon quantum mechanics formalism. It enables us to determine how external fields, characterized by hairy parameters, affect the probability of spherically symmetric black hole formation and the generalized uncertainty principle. [ABSTRACT FROM AUTHOR]

The impacts of Stefan blowing along with slip and Joule heating on hybrid nanofluid (HNF) flow past a shrinking cylinder are investigated in the presence of thermal radiation. Using the suitable transformations, the governing equations are converted into ODEs, and the MATLAB tool bvp4c is used to solve the resulting equations. As Stefan blowing increases, temperature and concentration profiles are accelerated but the velocity profile diminishes and also the heat transfer rate improves up to 25% as thermal radiation upsurges. The mass transfer rate diminishes as increasing Stefan blowing. The Sherwood number, the Nusselt number, and the skin friction coefficient are numerically tabulated and graphs are also plotted. The outcomes are conscientiously and thoroughly discussed. [ABSTRACT FROM AUTHOR]

We generate a new exact model for neutral anisotropic star using Einstein field equations. In this model, we consider a quadratic equation of state (QEoS) and a choice of gravitational potential which generalizes the choice formulated by Pant and Fuloria. We generate stellar masses consistent with previous findings which describe the astrophysical objects like PSR J1614-2230, Cen X-3, Vela X-1 and Exo 1785-248. New relativistic stellar masses and surface gravitational redshifts in acceptable ranges are also generated using our model. It is observed that the matter variables and gravitational potentials are well behaved. The model satisfies energy and stability conditions and all forces within the stellar object sum to zero. [ABSTRACT FROM AUTHOR]

We obtain a new nonsingular exact model for compact stellar objects by using the Einstein field equations. The model is consistent with stellar star with anisotropic quark matter in the absence of electric field. Our treatment considers spacetime geometry which is static and spherically symmetric. Ansatz of a rational form of one of the gravitational potentials is made to generate physically admissible results. The balance of gravitational, hydrostatic, and anisotropic forces within the stellar star is tested by analysing the Tolman-Oppenheimer-Volkoff (TOV) equation. Several stellar objects with masses and radii comparable with observations found in the past are generated. Our model obeys different stability tests and energy conditions. The profiles for the potentials, matter variables, stability, and energy conditions are well behaved. [ABSTRACT FROM AUTHOR]

It is well known that solar energy is the main source of thermal energy coming from the sun responsible for huge operations in engineering studies. It can be seen in the technology of photovoltaic cells, solar streetlights, solar energy plates, and solar water pumping. This study is for investigating solar radiation as well as a method to improve the performance of the solar water pump (SWP) with the use of solar radiation along with nanotechnology. The thermal transfer performance of the pump is checked for the case of many impacts including heat radiations and variable thermal conductivity. An Oldroyd‐B nanofluid with entropy production analysis has been scrutinized as a working coolant liquid in the system. Graphene oxide (GO) and Cu nanoparticles have been employed in engine oil (EO) as the base liquid. It is noticed that the heat transfer performance of SWP increases in the case of amplification in thermal radiation and temperature‐dependent thermal conductivity characteristics. In comparison to low thermal conductivity nanofluid, high thermal conductivity nanofluid provides the best capability for heat transmission. The thermal efficiency of the used (GO/EG) nanofluid has been enhanced by between 7.70% and 26.68% than (Cu/EO) nanofluid. [ABSTRACT FROM AUTHOR]

In this work, we use the gravitational decoupling framework through the extended minimal geometric deformation to construct and study a new interior isotropic extension of Einstein’s universe solution. The resulting model fulfills the fundamental physical acceptance conditions. As well, we study the energy exchange between the Einstein’s fluid distribution and an extra perfect fluid which supports the resulting isotropic stellar configuration. [ABSTRACT FROM AUTHOR]

In this work we will analyse the complexity factor, proposed by L. Herrera, for spherically symmetric static matter distributions satisfying a polytropic equation through the gravitational decoupling method. Specifically, we will use the 2-step GD, which is a particular case of the extended geometric deformation (EGD), to obtain analytic polytropic solutions of Einstein's equations. In order to give an example, we construct a model satisfying a polytropic equation of state using Tolman IV as a seed solution. [ABSTRACT FROM AUTHOR]

In this paper, an innovative work has been explored on mixed convective hybrid nanofluid flow in the presence of a moving cone with surface roughness. The primary aim of this analysis is to establish the significance of hybrid nanofluid characteristics influencing the wall gradients such as skin friction coefficient and the rate of heat transfer. The hybrid nanofluid comprises water as the base fluid with silver (Ag) nanoparticles and magnesium oxide (MgO) nanoparticles added to it. The flow and heat transfer characteristics governing equations are expressed in terms of nonlinear coupled partial differential equations. The solutions of these equations are attempted numerically by employing the Quasilinearization technique in combination with the implicit finite difference approximation. It is noted that the rate of energy transfer and surface friction are higher for hybrid nanofluid ( φ 1 = 0.025 , φ 2 = 0.025 ) than that for the pure MgO nanofluid ( φ 1 = 0 , φ 2 = 0.05 ) and pure Ag nanofluid ( φ 1 = 0.05 , φ 2 = 0 ), wherein the net volume fraction of 5% of nanoparticles is maintained. For hybrid nanofluid, the Nusselt number rises by 12% and 6% approximately in comparison with that for the pure Ag nanofluid and pure MgO nanofluid, respectively. This result can be attributed to the strong molecular interaction between the hybrid nanoparticles suspended in the water medium. In order to confirm the authentication of the accuracy of the results of the present analysis, the fluid friction and rate of energy transfer are compared with the previous research findings. It is revealed that the present results are in good agreement with those published outcomes. [ABSTRACT FROM AUTHOR]

In this paper, the numerical solution for heat transfer through a rotating heat pipe is studied and a sensitivity analysis is presented by using statistical experimental design technique. Graphene oxide-molybdenum disulfide (GO-MoS2) hybrid nanofluid is taken as working fluid inside the pipe. The impact of the heat pipe parameters (rotation speed, initial mass, temperature difference) on the heat transfer and liquid film thickness is investigated. The mathematical model coupling the fluid mass flow rate and liquid film evolution equations in evaporator, adiabatic, and condenser zones of the heat pipe is constructed. The mathematical model is solved by implementation of "Particle Swarm Optimization" along with the finite difference method. The outcomes demonstrate that hybrid nanoparticles help to improve the heat transfer through the heat pipe and reduce liquid film thickness. The heat transfer rises with increasing temperature difference and reducing inlet mass, and it reduces slightly with rising rotation speed. The difference in liquid film thickness between the evaporator and condenser zones increases with increasing temperature difference and decreasing rotation speed. The impact of increasing the volume fraction of GO on the liquid film thickness is higher than that in the case of the MoS2 nanoparticles. However, an increase of the heat transfer is noticed in case of increasing the volume fraction of GO relative to increasing MoS2 concentration. Statistical analysis of the computed numerical data and the identification of significant parameters for total heat transfer are found using the response surface method. At 95% level of significance, the GO concentration in the hybrid nanofluid, inlet mass of the hybrid nanofluid and the temperature difference inside the evaporator zone of the pipe are found to be significant linear parameters for increasing heat transfer. [ABSTRACT FROM AUTHOR]

Water has drawn a lot of interest as a manufacturing lubricant since it is affordable, eco-friendly, and effective. Due to their exceptional mechanical qualities, water solubility, and variety of application scenarios, graphene oxide (GO)-based materials have the potential to increase the lubricant performance of water. The idea of this research was to quantify the linear 3D radiative stagnation-point flow induced by nanofluid through a vertical plate with a buoyancy or a mixed convection effect. The opposing, as well as the assisting, flows were considered in the model. The leading partial differential equations (PDEs) were transformed into dimensionless similarity equations, which were then solved numerically via a bvp4c solver. The influences of various physical constraints on the fluid flow and thermal properties of the nanofluid were investigated and are discussed. Water-based graphene oxide nanoparticles were considered in this study. The numerical outcomes indicated that multiple solutions were obtained in the case of the opposing flow (λ < 0). The critical values increased as the nanoparticle volume fraction became stronger. Furthermore, as the nanoparticles increased in strength, the friction factor increased and the heat transfer quickened. The radiation factor escalated the heat transfer in both solutions. In addition, a temporal stability analysis was also undertaken to verify the results, and it was observed that the branch of the first outcome became physically reliable (stable) whilst the branch of the second outcome became unstable, as time passed. [ABSTRACT FROM AUTHOR]

The horizon structure and thermodynamics of hairy spherically symmetric black holes generated by the gravitational decoupling method are carefully investigated. The temperature and heat capacity of the black hole is determined, as well as how the hairy parameters affect the thermodynamics. This allows for an analysis of thermal stability and the possible existence of a remanent black hole. We also calculate the Hawking radiation corrected by the generalized uncertainty principle. We consider the emission of fermions and apply the tunneling method to the generalized Dirac equation. This shows that, despite the horizon location being the same as the Schwarzschild one for a suitable choice of parameters, the physical phenomena that occur near the horizon of both black holes are qualitatively different. [ABSTRACT FROM AUTHOR]

Copyright of Verba Iuris is the property of Universidad Libre Bogota, Centre de Investigaciones Socio Juridicas de la Facultad de Derecho and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)