Charged gravastars in modified Gauss–Bonnet gravity

This work probes the influence of charge field on the unique stellar structure, regarded as gravastar, under the corrections of [Formula: see text] theory, i.e. [Formula: see text] theory, where [Formula: see text] is named as Gauss–Bonnet invariant. The gravastar has also been recognized as an alternate candidate of black hole structure and is illustrated by three distinct regions termed as (1) the exterior (2) the intermediate thin shell (3) the interior domain. We discussed the mathematical solutions for each of three regions separately with the assistance of different equation-of-states (EoS). The exterior charged vacuum domain is expressed by the Reissner–Nordström solution. The central region is illustrated by the EoS, i.e. a positive pressure of ultra-relativistic matter is equal to the energy density. Whereas, the interior domain reflects that the negative pressure is equal to energy density and manifests a non-attractive force over the central spherical shell. We deduce that in the context of [Formula: see text] theory, the nonsingular charged model with distinct physical features, such as energy, length, entropy, is physically viable and consistent.

Effect of Trimethyl Chitosan with Different Degrees of Quaternization on the Properties of Tablets Prepared using Charged Model Drugs

Trimethyl chitosan (TMC) has demonstrated effectiveness as an absorption enhancer for hydrophilic and high molecular weight (MW) drugs across the intestinal epithelium. However, the effects of degrees of quaternization (DQ) of TMC on the absorption of negatively and positively charged drugs have not been investigated. This investigation aimed to determine the properties of the tablets formulated using TMC with different DQ. In this study, TMC with DQ of 20 % (TMC-20), 40 % (TMC-40) and 60 % (TMC-60) were synthesized and subsequently characterized. Cetirizine dihydrochloride (CHC) and hyoscine butylbromide (HBB) were used as negatively and positively charged model drugs. Eight tablet formulations were prepared using the wet granulation method. The formulated tablets were evaluated regarding their properties in terms of thickness and hardness, weight variation, disintegration time, and dissolution profile. These tablets were evaluated according to the standards set by the United States Pharmacopeia (USP41) guidelines. The results showed that TMC with all DQ have the MW and an intrinsic viscosity less than starting chitosan. The MW and an intrinsic viscosity of the synthesized TMC decreased with increasing DQ. In order to evaluate the effect of TMC with various DQ on the properties of the formulated tablets, all tablet formulations prepared had good characteristics and were found to be within the acceptable range based on the requirements of USP. In conclusion, TMC had a minor retarding effect on the dissolution profiles of CHC from the formulated tablets. Still, TMC was able to significantly delay the release of HBB from the formulated tablets (p > 0.05). When TMC with various DQ were compared, TMC-60 showed higher drug release than TMC-20 and TMC-40. In our study, we observed a possible interaction between the model drugs and TMC. This warrants the need for further studies. HIGHLIGHTS Degree of quaternization represents the charge density of trimethyl chitosan (TMC) Degradation of the polymer backbone occurred in the synthesis reaction step TMC affects dissolution profiles of a negative charged drug Ionic interaction and viscous gel layer of TMC affects the model drug release

An isotropic analytical model for charged stars

In this investigation report, we present a perfect charged fluid solution for a static and spherically symmetric spacetime; for its construction, we suppose a metric potential, [Formula: see text], and a specific form of the electric field’s intensity, [Formula: see text], in such a manner that the resulting stellar model is physically acceptable and stable. The model presented depends on two parameters [Formula: see text] related to the compactness and the magnitude of the electric field and these same parameters will generate different possibilities for the behavior of the speed of sound. For the particular case in which [Formula: see text], we obtain once more a chargeless model constructed previously, the compactness for the charged model case is greater than in the chargeless case. As an effect of the charge, the model admits two regions for the parameter [Formula: see text], in one of these the speed of sound is a monotonic decreasing function and in the other it is a monotonic increasing function. By means of a numerical analysis, it is shown that the orders of magnitude associated to the pressure and density are characteristic of the compact stars. In particular for [Formula: see text], the range of [Formula: see text], which implies that the radius of an object with mass [Formula: see text] is found between 6554.620 m and 7672.702 m with a maximum central density of [Formula: see text].

Direct translocation of a negatively charged nanoparticle across a negatively charged model cell membrane

Nanoparticles have attracted much attention as a carrier for drug, gene, and macromolecule delivery in next-generation biomedical and therapeutic technologies. In delivery applications, nanoparticles tend to have negative charge due...

Compact stars described by a charged model

A charged stellar model is presented by constructing a solution to the Einstein–Maxwell equations system in a spherically symmetrical static time-space. The rate of compactness for the model depends on two parameters [Formula: see text], one of them [Formula: see text] associated to the charge, which allows a value of compactness [Formula: see text] higher than the neutral case. The density and pressure are regular functions, positive and monotonically decreasing and the function of charge is positive regular and monotonically increasing, its shown that the model satisfies the condition of causality, the geometry is regular and as such the model is physically acceptable. Although the model can be applicable for a variety of stars, considering a star with mass [Formula: see text] for [Formula: see text] the range of compactness is [Formula: see text] and radius [Formula: see text], in this case the range of values for the central density is [Formula: see text] greater than the value of the nuclear density and consistent with that expected for stars with this compactness rate.