Compact Spheres Research Articles

Complexity characterization in modeling anisotropic compact stellar structures

In this study, we present an exact solution to the Einstein field equations, featuring a static, spherically symmetric, anisotropic compact stellar fluid sphere with non-zero complexity. The model is constructed using a specific metric potential for the gtt\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$g_{tt}$$\\end{document} component, along with a defined complexity profile. The model parameters are fixed by ensuring the continuity of the interior and exterior metrics across the surface of the star and by setting the radial pressure to zero across the boundary. The stability of the model has been analyzed by verification of different standard conditions. Validation of our model is supported by recent observational data from well-known pulsars.

Aspects of charged decoupled solutions in ℛ+ϖℛ2 gravity

This study deals with the physical aspects of the gravitationally decoupled solutions under [Formula: see text] gravity scenario. In doing so, charged anisotropic matter composition is assumed as the parent (seed) source for the static spherically symmetric configuration. Commencing with the Kuchowicz ansatz for the charged static parent matter formation, we establish the Karmarkar condition to thoroughly address the deformed functions and the gravitational aspects of the compact spheres. Besides these, null-complexity and isotropized conditions will enforce to grasp the system’s stability by the inclusion of charge and [Formula: see text] factors through graphical trends.

Design of GRETA Cooling Systems

The Gamma-Ray Energy Tracking Array (GRETA) is a full 4π gamma-ray tracking detector capable of reconstructing the energy and three-dimensional position of gamma-ray interactions within a compact sphere of high-purity germanium crystals. The GRETA Detector Array Sphere will have the capacity to accommodate a total of 30 Germanium Quad Detector Modules (QDM). The 30 QDMs are to be cooled and maintained below 100 K using liquid nitrogen (LN) at all times while the array is in normal operation, and will require regular filling of a LN Dewar on each module. The Dewar is designed to allow the Quad Module to be operated in any orientation with a LN holding time of no less than 12 hours when the detector module is fully powered. An automated LN cooling and refilling system is required to supply LN to the 30 QDMs and ensure them maintained below 100 K. Each of the GRETA QDMs houses a total of 148 pre-amplifier units within the module, and with the high power consumption of each pre-amplifier, active cooling of the pre-amplifier compartment is required. Additionally, each Quad Module will have 4 digitizer modules attached to it, which generate heat and require cooling as well. A closed-loop liquid (Glycol) cooling system will provide the required temperature stability and dissipate power generated heat for electronics. This paper presents design of the GRETA LN cooling system for detectors and the closed-loop liquid cooling system for electronics including technical requirements, design schemes, key components, operation modes, and so on.

The impact of ultrasonic-assisted extraction on the in vitro hypoglycemic activity of peach gum polysaccharide in relation to its conformational conversion.

Peach gum (PG) is an exudate of the peach tree (Prunus persica of the Rosaceae family), which consists primarily of polysaccharides with a large molecular weight and branching structure. Consequently, PG can only swell in water and does not dissolve easily, which severely limits its application. Current conventional extraction methods for PG polysaccharide (PGPS) are time consuming and inefficient. This study investigated the impact of ultrasonic-assisted extraction (UAE) on PGPS structure and conformation, and their relationship to hypoglycemic activity in vitro. In comparison with conventional aqueous extraction, UAE enhanced PGPS yielded from 28.07-32.83% to 80.37-84.90% (w/w) in 2 h. It drastically decreased the molecular size and conformational parameters of PGPS, including weight-average molecular weight (Mw), number-average molecular weight (Mn), z-average radius of gyration (Rg), hydrodynamic radius (Rh) and instrinsic viscosity ([η]) values. Peach gum polysaccharide conformation converted extended molecules to flexible random coil chains or compact spheres with no obvious primary structure alteration. Furthermore, UAE altered the flow behavior of PGPS solution from that of a non-Newtonian fluid to that of a Newtonian fluid. As a result, PGPS treated with UAE displayed weaker inhibitory activity than untreated PGPS, mostly because UAE weakens the binding strength of PGPS to α-glucosidase. However, this negative effect of UAE on PGPS activity was compensated by the increased solubility of polysaccharide. This enabled PGPS to achieve a wider range of doses. Ultrasonic-assisted extraction is capable of degrading PGPS efficiently while preserving its primary structure, resulting in a Newtonian fluid solution. The degraded PGPS conformations displayed a consistent correlation with their inhibitory effect on α-glucosidase activity. © 2024 Society of Chemical Industry.

Understanding the two-stage degradation process of peach gum polysaccharide within ultrasonic field

This study investigated the dynamic degradation process of peach gum polysaccharide (PGPS) within ultrasonic field. The results show that the molecular weight, intrinsic viscosity, and polydispersity of PGPS were rapidly reduced within the initial 30 min and then gradually decreased. The solubility of PGPS was drastically improved from 3.0% to 40.0–42.0% (w/w) after 120 min. The conformation of PGPS changed from an extended chain to a flexible random coil within initial time of ultrasound, and gradually tended to be compact spheres. The apparent viscosity of PGPS significantly decreased after 30 min, and PGPS solution exhibited a near-Newtonian fluid behavior. It is possible that these above changes are a result of random cleavage of the decrosslinking and the backbone of PGPS, resulting in the preservation of its primary structure. The results will provide a fundamental basis for orientation design and process control of ultrasonic degradation of PGPS.

A generalized static spherically symmetric anisotropic compact stellar model

We report here a new exact solution of the Einstein field equations that describes a static spherically symmetric, anisotropic compact stellar fluid sphere. A generalized metric form corresponding to the grr\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$g_{rr}$$\\end{document} component and a specific anisotropic profile generates the model. The new class of generalized solutions reduces to Finch-Skea, Vaidya Tikekar and Schwarzschild interior solutions for specific cho-ices of the model parameters. The model parameters have been determined from the continuity of the interior and exterior metrics at the surface of the star and setting the radial pressure at the boundary to zero. Recent observed measurements from some pulsars as sources have been utilized to validate our model.

Singularity‐Free Charged Compact Star Model Under F(Q)$F(Q)$‐Gravity Regime

AbstractIn this paper, the possibility of existing a novel class of compact charged spheres based on a charged perfect fluid within the realm of gravity theory is explored. The authors started by proposing physically meaningful explicit formulas for the potential, denoted , and the electric field to find a close‐form solution. More precisely, the change of the dependent variable approach by exploiting the transformation is applied. Successively, the field equations analytically are solved and generate the most general solution, which leads us to examine various significant aspects of the stellar system. These aspects comprise the regularity of gravitational potentials, energy density and pressure, electric charge, the mass‐radius relationship, subluminal sound velocities in the radial direction, and the adiabatic index for charged compact stars. For a more in‐depth system study, mass measurements using contour diagrams are carried out. This mainly involves varying the variable parameters and to distinguish their effect on the mass distribution within the stellar structure. What is more, the electric charge controls the stability of the stellar system is shown, which yields that a stable system can possess a maximum charge of order . The results strongly argue that charged stars could conceivably exist in nature and that such a deviation from traditional theories may be seen in future astrophysical observations.

On Compact Packings of Euclidean Space with Spheres of Finitely Many Sizes

AbstractFor $$d\in {\mathbb {N}}$$ d ∈ N , a compact sphere packing of Euclidean space $${\mathbb {R}}^{d}$$ R d is a set of spheres in $${\mathbb {R}}^{d}$$ R d with disjoint interiors so that the contact hypergraph of the packing is the vertex scheme of a homogeneous simplicial d-complex that covers all of $${\mathbb {R}}^{d}$$ R d . We are motivated by the question: For $$d,n\in {\mathbb {N}}$$ d , n ∈ N with $$d,n\ge 2$$ d , n ≥ 2 , how many configurations of numbers $$0<r_{0}<r_{1}<\cdots <r_{n-1}=1$$ 0 < r 0 < r 1 < ⋯ < r n - 1 = 1 can occur as the radii of spheres in a compact sphere packing of $${\mathbb {R}}^{d}$$ R d wherein there occur exactly n sizes of sphere? We introduce what we call ‘heteroperturbative sets’ of labeled triangulations of unit spheres and we discuss the existence of non-trivial examples of heteroperturbative sets. For a fixed heteroperturbative set, we discuss how a compact sphere packing may be associated to the heteroperturbative set or not. We proceed to show, for $$d,n\in {\mathbb {N}}$$ d , n ∈ N with $$d,n\ge 2$$ d , n ≥ 2 and for a fixed heteroperturbative set, that the collection of all configurations of n distinct positive numbers that can occur as the radii of spheres in a compact packing is finite, when taken over all compact sphere packings of $${\mathbb {R}}^{d}$$ R d which have exactly n sizes of sphere and which are associated to the fixed heteroperturbative set.

Compact wirelessly-powered photocatalyst-coated spheres: Concept development and application for oxidative wastewater treatment and membrane fouling control

Wirelessly powered photocatalyst-coated spheres (WPS) were successfully developed and wirelessly powered from outside the reactor using resonant inductive coupling. Diverse applications of WPS were demonstrated for the visible light-assisted photocatalytic degradation of methylene blue (textile dye), diclofenac, and triclosan (pharmaceutical compounds) and fouling control of ceramic membranes. These catalyst-coated WPS successfully generated O2− as the main reactive oxygen species (ROS). As demonstrated, these WPS are low-cost, easy to fabricate, have excellent visible light sources, and can be used as the photocatalyst carrier. The acrylic shell of WPS is transparent to light with wavelengths from 300 to 800 nm. Increasing the number of WPS can increase the light intensity proportionally, and 8 WPS can be powered by one power coil outside the reactor. A higher quantity of WPS per reaction volume can be used to improve the reactivity, bringing the use of WPS reactors closer to industrial applications. This is the first report on the use of WPS in the ceramic membrane reactor for fouling control, a 50 % delay compared to control, and highlights the versatility of this system. This work would open up new exploration avenues for membrane fouling control using WPS-based heterogeneous photocatalysis.

Functionalization of surfactant templated magnetite by chitosan and PEGylated/Chitosan – In vitro studies on drug loading, release and anti-proliferative activity

Magnetite iron oxide nanoparticles (MNPs) were synthesized using micro emulsion assisted co-precipitation method. The surface functionalization of MNPs was done with chitosan and PEGylated/chitosan and three samples of each were prepared. These materials were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron (SEM), and transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM). The Methotrexate (MTX) drug was then loaded on each functionalized MNPs as MCT-1–3 (chitosan; 0.1,0.5, and 1%) and MPCT-1–3 (PEGylated/chitosan (1% each with volume ratio 1:1, 3:1, and 1:3). Each composition showed maximum encapsulation efficiency (>95%). The pH dependent drug release studies were done under acidic (pH 5.0) and physiological (pH 7.4) conditions. These studies revealed consistent drug release and no burst release was observed from both functionalized MNPs. A comparatively delayed release from MPCTs than MCTs could be attributed to the formation of more compact sphere due to cross-linking of chitosan with PEG. The drug release was found greater at pH 5.0 for all functionalized MNPs. However, among all functionalized MNPs, maximum drug release was found to be 78.88% by MPCT-1 in acidic medium (pH 5.0). Cyclic voltametric (CV) analysis at slow scan rate (10 mV/s) further indicated controlled drug release and complimented the UV-findings. The MCF-7 (human breast cancer) cell line studies, however, indicated anticancer potential only for MPCT-1–3 with IC50 values ranging from 1.4 to 1.7 μM. Overall results pointed that methotrexate loaded PEGylated/chitosan coated magnetic nanoparticles MPCT-1 is the more compassionate material to be used as vehicle for controlled drug delivery.

Impact of generic complexity factor on gravitationally decoupled solutions

In this work, we address the analysis of gravitationally decoupled sources within the context of f(R) gravity. By doing so, complete geometric deformation (CGD) strategy is deployed which makes it easier to comfortably identify the exact solutions of anisotropic spherical complex system by executing the Kuchowicz-ansatz for the metric potential of the seed (parent) solution. The generalized notion of complexity is then applied to Class-one spacetime for bounded spheres at large curvature domains. This CGD strategy, along with the extent to which null effective anisotropy and null complexity result in an isotropic structure, is then used to deduce the deformed functions. To understand the full gravitational features of non-dynamic compact spheres and the implications of the f(R) matter profile, the Karmarkar constraint is followed. Two distinct aspects of the related relativistic consequences are thus provided, and their physical credibility is subsequently discussed. Additionally, role of the decoupling parameter in governing the energy transition across the usual and effective matter profile is exhibited. We also indicate how the presence of R+βR2 modifications in pressure anisotropy and density inhomogeneity within the enclosed spheres have a profound impact on determining its stability.

Comprehensive analysis of relativistic embedded class-I exponential compact spheres in f(R, ϕ) gravity via Karmarkar condition

In this article, we use the prominent Karmarkar condition to investigate some novel features of astronomical objects in the f(R, ϕ) gravity; R and ϕ represent the Ricci curvature and the scalar field, respectively. It is worth noting that we classify the exclusive set of modified field equations using the exponential type model of the f(R, ϕ) theory of gravity f(R, ϕ) = ϕ(R + α(e β R − 1)). We show the embedded class-I approach via a static, spherically symmetric spacetime with an anisotropic distribution. To accomplish our objective, we use a particular interpretation of metric potential (g rr ) that has already been given in the literature and then presume the Karmarkar condition to derive the second metric potential. We employ distinct compact stars to determine the values of unknown parameters emerging in metric potentials. To ensure the viability and consistency of our exponential model, we execute distinct physical evolutions, i.e. the graphical structure of energy density and pressure evolution, mass function, adiabatic index, stability, equilibrium, and energy conditions. Our investigation reveals that the observed anisotropic findings are physically appropriate and have the highest level of precision.

Compact relativistic sphere with charged anisotropic matter in f(R,G) gravity

The main purpose of this research is to examine a number of interior configurations of stable anisotropic objects formed in the shape of spherical charged stars within the gravity region described by [Formula: see text], where [Formula: see text] represents the Gauss–Bonnet invariant and [Formula: see text] defines the Ricci Scalar in this scenario. The formation of these charged stars is investigated using the solutions found by Karori and Barua, among several feasible models within the theory of [Formula: see text] gravity. The study explores the behavior of these realistically charged compact stars, analyzing various physical components through the use of graphs. Furthermore, the feasibility of our model is assessed by evaluating it against different energy conditions. Additionally, topics such as density modification, stress evolution, various forces, star stability, anisotropy measurement, state parameter equations, and charge distribution are discussed.

Role of decoupling measure on the complexity factor and isotropization of the charged anisotropic spheres

An electromagnetic field is a consequential aspect of the space carried by moving electric charges. The contemporaneous interaction of Einstein–Maxwell field could be provoked by the dispersing electro-magnetic waves owing to the warping of the spacetime. Within the complete geometric deformation scenario, current work is devoted to exploring the substantial impact of an electromagnetic field on the anisotropic spherically symmetric structures that are taken to be the seed source, and then augment to the additional source. In this case, the gravitational decoupling strategy and embedding Class-I constraint will be used as two techniques to address the issue. We compute the Einstein–Maxwell field equations for the desired configuration. The transformed metric potentials corresponding to the temporal and radial components are then applied to formulate the two distinct sets of field equations. Through the Kuchowicz-ansatz for the seed metric potential, we enforce the Karmarkar constraint to grasp the entire gravitational aspect of a static compact sphere together with the effects of charged anisotropic pressure. The uniqueness of our study is that we used isotropization and disappearing complexity requirements to derive the deformation function within the bounds of a charged scenario. Thereby, two solutions to the associated relativistic equations are then presented for physical validity. We address the fact that the existence of charged pressure anisotropy in the bounded sphere has a consequential influence on governing its stability. Furthermore, it is identified that the decoupling-constant magnitude controls the energy flow within both the generically charged fluid and the fluid matter composition.

Machine learning-based modulation of Ca2+-binding affinity in EF-hand proteins and comparative structural insights into site-specific cooperative binding

Ca2+-binding proteins are present in almost all living organisms and different types display different levels of binding affinities for the cation. Here, we report two new scoring schemes enabling the user to estimate and manipulate the calcium binding affinities in EF hand containing proteins. To validate this, we designed a unique EF-hand loop capable of binding calcium with high affinity by altering five residues. The N-terminal domain of Entamoeba histolytica calcium-binding protein1 (NtEhCaBP1) is used for site-directed mutagenesis to incorporate the designed loop sequence into the second EF-hand motif of this protein, referred as Nt-EhCaBP1-EF2 mutant. The binding isotherms calculated using ITC calorimetry showed that Nt-EhCaBP1-EF2 mutant site binds Ca2+ with higher affinity than Wt-Nt-EhCaBP1, by ∼600 times. The crystal structure of the mutant displayed more compact Ca2+-coordination spheres in both of its EF loops than the structure of the wildtype protein. The compact coordination sphere of EF-2 causes the bend in the helix-3, which leads to the formation of unexpected hexamer of NtEhCaBP1-EF2 mutant structure. Further dynamic correlation analysis revealed that the mutation in the second EF loop changed the entire residue network of the monomer, resulting in stronger coordination of Ca2+ even in another EF-hand loop.

Analytic one-dimensional maps and two-dimensional ordinary differential equations can robustly simulate Turing machines

In this paper, we analyze the problem of finding the minimum dimension n such that an analytic map/ordinary differential equation over R n can simulate a Turing machine in a way that is robust to perturbations. We show that one-dimensional analytic maps are sufficient to robustly simulate Turing machines; but the minimum dimension for the analytic ordinary differential equations to robustly simulate Turing machines is two, under some reasonable assumptions. We also show that any Turing machine can be simulated by a two-dimensional C ∞ ordinary differential equation on the compact sphere S 2 .

Neural Network-Based Airflow Vector Sensor Using Multiple MEMS Differential Pressure Sensors

As airflow information is significant in various fields, several airflow measurement devices have been developed. Differential pressure (DP)-type sensors, including pitot tubes, are extensively used because they can directly measure dynamic pressure due to airflow. However, this method has a disadvantage in that it is difficult to measure some wind directions because of the non-monotonic pressure distribution around the device. This study proposes a compact sphere airflow vector sensor using a neural network model that compensates for nonmonotonicity. It consists of three built-in microelectromechanical system (MEMS)-based DP sensor elements that simultaneously measure the DPs around the spherical sensor housing. The measured DPs are converted into 2D wind speed and direction using a neural network. The network model was trained using the simulated output of each sensor, and it was confirmed that the proposed design guideline contributed to achieving high accuracy. An airflow sensor was fabricated on the basis of the designed model. A network model was trained using the sensor responses in a wind tunnel experiment. The wind speed and direction accuracies obtained by the neural network model for 2–10 m/s and 0°–359° were 0.24 m/s and 3.62°, respectively. Finally, we demonstrated a drone flight test by attaching the calibrated sensor to a toy drone. This study is expected to contribute to realizing highly accurate low airflow measurement devices.

Nano Porous Zinc Synthesis on Soft Polyurethane Foam Using Conductive Ink and Electroplating Method

High specific surface is a significant characteristic in zinc coatings that can be highly applicable in batteries and catalysts. Conventional methods to create foams are not cost-efficient, nor could they make a high specific surface. Electroplating has been developed that can produce a very high specific surface foam. On the other hand, conductive ink can create an affordable conductive surface with a high specific surface, so the study on using conductive ink, which has a cost-efficient nature, was necessary to create a conductive surface. This work has investigated the effect of crucial parameters, such as graphite size, coating time and bath composition, on the current efficiency and SEM microstructure. As a result, a 3 µm graphite size was found to be appropriate. Coated zinc escalates linearly with current efficiency for up to 5 h, and then it decreases. Although the zinc concentration increases up to 0.12 mol/L in the electrolyte, making a slight increase in loading, the current efficiency was almost unchanged. However, if it increases more, the loading and current efficiency significantly rise so that the loading grows up to 16 times and the current density increases up to 86%. Additionally, the morphology changes from dendritic to compact plates, sphere and semi-sphere, subsequently.

Nanothermometer with Temperature Induced Reversible Emission for Evaluation of Intracellular Thermal Dynamics.

Temperature dynamics reflect the physiological state of cells, and accurate measurement of intracellular temperature helps to understand the biological processes. Herein, we report a novel nanothermometer by conjugating a fluorescent probe 3-ethyl-2-[4-(1,2,2-triphenylvinyl)styryl]benzothiazol-3-ium iodide (TPEBT) with a thermoresponsive polymer poly(N-isopropylacrylamide-co-tetrabutylphosphonium styrenesulfonate) [P(NIPAM-co-TPSS)]. The derived nanoprobe TPEBT-P(NIPAM-co-TPSS) self-assembles into micelles with TPEBT as hydrophobic core and PNIPAM as hydrophilic shell. It exhibits aggregation-induced emission (AIE) at λex/λem = 420/640 nm in aqueous medium with a quantum yield of ΦF 11.9%. The rise in temperature transforms PNIPAM chains from linear to compact spheres to serve as the core of micelles, and meanwhile converts TPEBT from the state of aggregation to dispersion and redistributes in the micellar shell. Temperature-driven phase transition of P(NIPAM-co-TPSS) mediates the reversible aggregation and disaggregation of TPEBT and endows the nanothermometer with temperature-dependent AIE features and favorable sensitivity for temperature sensing in 32-40 °C. TPEBT-P(NIPAM-co-TPSS) is taken up by HeLa cells to distribute mainly in lysosomes. It enables quantitative visualization of in situ thermal dynamics in response to stimuli from carbonyl cyanide 4-(trifluoromethoxy)phenylhydrazone, oligomycin, genipin, and lipopolysaccharide. The real-time monitoring of photothermal-induced intracellular temperature variation is further conducted.

Self-Assembly of Amphiphilic Cubes in Suspension.

We study the self-assembly of amphiphilic cubic colloids using molecular dynamics as well as rejection-free kinetic Monte Carlo simulations. We vary both the number and location of the solvophobic faces (patches) on the cubes at several colloid volume fractions and determine the resulting size and shape distributions of the self-assembled aggregates. When the binding energy is comparable to the thermal energy of the system, aggregates typically consist of only few spontaneously associating/dissociating colloids. Increasing the binding energy (or lowering the temperature) leads to the emergence of highly stable aggregates, e.g., small dimers in pure suspensions of one-patch cubes or large (system-spanning) aggregates in suspensions of multipatch colloids. In mixtures of one- and multipatch cubes, the average aggregation number increases with increasing number of solvophobic faces on the multipatch cubes as well with increasing fraction of multipatch cubes. The resulting aggregate shapes range from elongated rods over fractal objects to compact spheres, depending on the number and arrangement of solvophobic patches on the cubic colloids. Our findings establish the complex self-assembly pathways for a class of building blocks that combine both interaction and shape anisotropy, with the potential of forming hierarchically ordered superstructures.