Current Universe Research Articles

A low-voltage, high-performing CMOS transistor based on multiple- output operation transconductance amplifier for current mode KHN Universal filter applications

This study proposes a current-mode KHN universal filter design that can perform three standard functions simultaneously: low-pass, high-pass, and band-pass. The circuit is built around a multiple-output operation transconductance amplifier (MO-OTA), which allows for electronically adjustable pole frequency and quality factor by modifying input bias currents (IB). The circuit layout is straightforward, with two MO-OTAs and two grounded capacitors, eliminating the need for external resistors and depending entirely on grounded components. Because of its simplicity, the circuit is suited for use in a tiny, efficient design. The proposed circuit's operation was validated using LT-Spice simulations, and the results were in line with theoretical expectations. The circuit used around 298μW of power at ±0.2V power supply voltages. These results demonstrate the circuit's potential for low-power applications, which are crucial in many modern electronic devices. The suggested current-mode KHN universal filter offers a viable option for combining various filter functions in a single circuit with customizable parameters. Its simplicity, efficiency, and performance qualities make it a feasible choice for incorporation into a variety of electronic systems, allowing for more filter design freedom.

Properties of Central Regions of the Dark Matter Halos in the Model with a Bump in the Power Spectrum of Density Perturbations

A surprisingly large number of galaxies with masses of ~109–1010\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${{M}_{ \\odot }}$$\\end{document} at redshifts of \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$z \\geqslant 9$$\\end{document} are discovered with the James Webb Space Telescope. A possible explanation for the increase in the mass function can be the presence of a local maximum (bump) in the power spectrum of density perturbations on the corresponding scale. In this paper, it is shown that simultaneously with the growth of the mass function, galaxies from the bump region must have a higher density (compactness) compared to cosmological models without a bump. These more compact galaxies have been partially included in larger galaxies and have been subjected to tidal gravitational disruption. They have been less destructed than “ordinary” galaxies of the same mass, and some of them could survive to z = 0 and persist on the periphery of some galaxies. The formation and evolution of compact halos in a cube with a volume of (47 Mpc)3 with (1024)3 dark matter particles in the redshift range from 120 to 0 have been numerically simulated and observational implications of the presence of such galaxies in the current Universe have been discussed.

Cosmic clues: DESI, dark energy, and the cosmological constant problem

Several attempts to solve the cosmological constant problem, which concerns the value of the cosmological constant being extremely smaller than the Standard Model mass scales, have introduced a scalar field with a very flat potential that can be approximated as linear around any given position. The scalar field scans the cosmological constant in such a way that the current small value is explained. Recently, Dark Energy Spectroscopic Instrument (DESI) reported the results of the first year. Combining the data with CMB, Pantheon, Union3, and/or DES-SN5YR, there is a preference or anomaly, indicating that the dark energy in the current Universe slightly deviates from that in the ΛCDM model and varies over time. In this paper, I show that the simple linear potential of a scalar field that may explain the small cosmological constant, can explain the DESI anomaly. The conclusions do not change by including or not including a thermal friction effect. In particular, the model proposed by the present author in [1], which relaxes the cosmological constant by the condition that inflation ends, predicts a time-dependence of the dark energy close to the one favored by the data.

Cosmology of Barrow holographic QCD ghost dark energy and a look into the thermodynamics

The present study endeavours to study the cosmology of QCD ghost dark energy based on Barrow holographic fluid, a particular example of Nojiri-Odintsov holographic dark energy (2006, General Relativity and Gravitation, 38, 1285–1304); (2017, The European Physical Journal C, 77, 1–8). The Hubble parameter is reconstructed and according the equation of state parameter is reconstructed for the Barrow holographic QCD ghost dark energy. It is observed that the effective equation of state parameter has a transition from quintessence to phantom and for the current universe the equation of state parameter is very close to −1. The deceleration parameter is computed based on the reconstructed Hubble parameter and it is observed that the model can have a transition from decelerated to accelerated universe. The statefinder trajectories are plotted and an interpolation between dust and ΛCDM phases is observed. Finally, the thermodynamics is studied considering apparent horizon as the enveloping horizon of the Universe.

Review on Minimally Extended Varying Speed of Light Model

It is known that dimensional constants, such as ℏ, c, G, e, and k, are merely human constructs whose values and units vary depending on the chosen system of measurement. Therefore, the time variations in dimensional constants lack operational significance due to their dependence on these dimensional constants. They are well structured and represent a valid discussion. However, this fact only becomes a meaningful debate within the context of a static or present Universe. As theoretically and observationally well established, the current Universe is undergoing accelerated expansion, wherein dimensional quantities, like the wavelength of light, also experience redshift phenomena elongating over cosmic time. In other words, in an expanding Universe, dimensional quantities of physical parameters vary with cosmic time. From this perspective, there exists the possibility that dimensional constants, such as the speed of light, could vary with the expansion of the Universe. In this review paper, we contemplate under what circumstances the speed of light may change or remain constant over cosmic time and discuss the potential for distinguishing these cases observationally.

Holographic dark energy in non-conserved gravity theory

Recently, reconsidering the Rastall idea Tμ;νν=a,μ through relativistic thermodynamics gives a new form for the scalar field a which led us to construct modern modified theory of gravity debugged ‘non-conserved gravity theory’ Fazlollahi 2023 Euro. Phys. J. C 83 923. This theory unlike other modified theories of gravity cannot directly explain the current acceleration expansion in the absence of the cosmological constant and or existence of other forms of dark energy. Hence, in this study we have reinvestigated holographic dark energy ρX∼H2 in the non-conserved theory of gravity. In this context, the density and pressure of dark energy depend on the non-conserved term and density of the dust matter field. As shown, due to non-conservation effects on large-scale structures, unlike the original holographic model, our model onsets an acceleration epoch for the current Universe satisfies observations. Moreover, the interaction and viscous scenarios are studied for this model.

Symmetry-based study and dynamics of casual bulk viscous matter-dominated universe

The dynamics of cosmological expansion is studied for a spatially flat matter-dominated universe filled with barotropic casual bulk viscous fluid. The evolution equation for the Hubble parameter is derived using Friedmann equations and conservation law for the viscous fluid, in which the viscous pressure is modeled by truncated version of the full Israel-Stewart theory of bulk viscosity. We use a Lie symmetry-based approach to study the evolution of the expansion rate of the Universe. The model equation possesses eight-parameter Lie symmetry generators and gives two different analytic group invariant solutions for the Hubble parameter. Expressions for various important cosmological parameters are obtained and values are estimated analytically for the explanation of the evolution dynamics of the Universe. The interesting features of the obtained symmetry-based solutions are that, one satisfies the present acceleration of the Universe, while the other could not support present accelerating phase, rather represents a universe dominated by non-viscous stiff fluid. We make useful checks on the observational constraints on the model parameters from the latest released observational data. The accelerating phase of the current universe is investigated using observational bounds and compared the model under investigation with the Λ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\Lambda $$\\end{document}CDM model. The evolutionary cosmic phases obtained from the analysis of the Lie symmetry-based solutions correspond to the association with the critical points in the equivalent phase space. These interesting features are investigated and analyzed using dynamical systems approach.

New Z copy- current differencing transconductance amplifier active filter using FinFET transistor based current Mode Universal Filter

This research paper presents the design of an active current mode device named Z-copy- Current Differencing Transconductance Amplifier (ZC-CDTA) in conjunction with FinFET (Fin Field-Effect Transistor) transistors. An input bias current can be used to adjust its parasitic resistances at its two current input ports. It is ideal for use in current-mode signal processing, which is steadily more common than voltage-style signal processing, because it operates in current mode on all terminals. The suggested component was implemented using Finfet technology, and its performances were assessed using simulations using cadence tools and linear technology SPICE. They demonstrate the new active element's usage, with a maximum bandwidth of 300MHz. The highest power consumption is 1.01 mW, and the supply voltages can be as low as ±0.1 V. The low-power consumption and wide current range tuning of the suggested Zc-CDTA are achieved.

Abstract 14823: Assessment of the Appropriateness and Prognostic Significance of the Current Universal Diagnostic Definition for Acute Kidney Injury in Patients After Cardiac Surgery and Exploration of Tailored Criteria

Background: Cardiac surgery-associated AKI (CSA-AKI) is prevalent and its diagnosis currently adheres to the Kidney Disease: Improving Global Outcomes (KDIGO) guidelines, commonly used criteria developed for general populations. Limited evidence exists on their appropriateness and prognostic value for CSA-AKI, which exhibits unique mechanisms and clinical courses. Aims: We aimed to assess the prognostic value of the KDIGO diagnostic criteria for CSA-AKI and explore potentially more prognostically relevant criteria for cardiac surgery. Methods: Patients undergoing coronary artery bypass grafting surgery at a single institution were included and categorized into four groups: no AKI, AKI stage-1, AKI stage-2, and AKI stage-3, based on KDIGO guidelines. Patients of AKI-1 were further divided based on specific criteria met: absolute criteria (0.3mg/dL serum creatinine (SCr) increase over 48-hour intervals), ratio criteria (1.5-1.9 times baseline SCr), and dual criteria (meeting both criteria) AKI-1. The primary outcome was 30-day all-cause mortality. Results: Among 20626 patients, the overall incidence of CSA-AKI was 47.4%, with rates of 44.2% for AKI-1, 2.2% for AKI-2, and 0.9% for AKI-3. The overall 30-day mortality was 0.6%. Among AKI-1, 72.4%, 3.2%, and 24.2% met the absolute criteria, ratio criteria, and dual criteria, respectively. After multivariate adjustment, AKI-2 and AKI-3 were significantly associated with increased 30-day mortality. However, neither AKI-1 nor its subcategories showed prognostic significance. Subsequent restricted cubic spline analysis identified more prognostically relevant cut-off values for AKI-1 criteria as >0.7 mg/dL SCr increase over 48-hour intervals and >1.3 times baseline SCr, respectively. Conclusions: The current universal KDIGO diagnostic criteria may not be suitable for CSA-AKI, especially regarding cut-off values for AKI stage-1, highlighting the necessity of tailored criteria for cardiac surgery.

Impact of m-projective curvature tensor in f (, G)-gravity and f (,  m )-gravity

This article deals with the characterization of a spacetime and modified gravity, such as -gravity and -gravity endowed with the m-projective curvature tensor. At first, we show that a m-projectively flat perfect fluid spacetime satisfying Einstein’s field equations represents a dark energy era. Also, we prove that such a spacetime obeying the strong energy condition is locally isometric to Minkowski spacetime. Moreover, it is established that a m-projectively flat perfect fluid spacetime is either a de-Sitter spacetime or a Minkowski spacetime. In addition, we show that a perfect fluid spacetime admitting harmonic m-projective curvature tensor is a Robertson-Walker spacetime. Next, we study m-projectively flat perfect fluid spacetime as a solution of -gravity and -gravity theories and explain their physical meaning. Several energy conditions in terms of Ricci scalar are investigated with the models and . For these models, the weak, null and dominant energy conditions are satisfied, while the strong energy condition is violated, which is good agreement with the recent observational studies and this reveals that the current Universe is in accelerating phase.

Nothing into Something and Vice Versa: A Cosmological Scenario

In the almost empty universe (with almost no matter in it), stochastic gravitational waves (SGW) of finite amplitude produce a de Sitter regime as a solution, which is invariant with respect to the Wick rotation. Asymptotically, super horizon SGWs do not “feel” difference between Lorentzian and Euclidean spacetime and belong simultaneously to both of them. The universe is finishing its evolution in Euclidean spacetime, i.e., it disappears into nothing. Quantum fluctuations of the gravitational field (gravitons) produce a de Sitter regime again in Euclidean spacetime where the current universe finished its existence, and due to the invariance of the de Sitter regime with respect to Wick rotation, the next universe starts its life with de Sitter inflation in Lorentzian spacetime. Such a scenario assumes that a permanent process of birth, death and rebirth of an infinite sequence of universes takes place on an infinite time axis.

Cosmographic studies of q = α − β H parametrization in f(T) framework

In this paper, we further investigate the cosmological tests of the deceleration parameter [Formula: see text] with [Formula: see text], where [Formula: see text] and [Formula: see text] are free parameters in [Formula: see text] framework by using 31 measurements from CC datasets, 1048 measurements of type Ia Supernovae (SNeIa) and 17 uncorrelated BAO measurements using Markov Chain Monte Carlo (MCMC). We obtained the best fit value of our model parameter and obtain the cosmological parameters of our model and analysis cosmographic studies of model. The statistical analysis revealed that our model is supported by the current Universe.

Effect of [formula omitted]-curvature tensor in spacetimes and [formula omitted]-gravity

First, we prove that a Lorentzian manifold is of constant curvature if and only if W2-curvature tensor vanishes. We investigate W2-flat perfect fluid spacetime as a solution of fG-gravity theory and we obtain a relation among deceleration, jerk, and snap parameters in a W2-flat spacetime using Friedmann–Robertson–Walker metric. Several energy conditions in terms of Ricci scalar are investigated with the models fG=a1Gn+b1a2Gn+b2 and fG=log(αGn+βe−Gα). For these models, the weak, null and dominant energy conditions are satisfied, while the strong energy condition is violated, which is good agreement with the recent observational studies and this reveals that the current Universe is in accelerating phase.

Cosmological constraints on dark energy in [formula omitted] gravity: A parametrized perspective

In this paper, we focus on the parametrization of the effective equation of state (EoS) parameter within the framework of f(Q) symmetric teleparallel gravity. Here, the gravitational action is represented by an arbitrary function of the non-metricity scalar Q. By utilizing a specific parametrization of the effective EoS parameter and a power-law model of f(Q) theory, namely f(Q)=βQm+1 (where β and m are arbitrary constants), we derive the cosmological solution of the Hubble parameter H(z). To constrain model parameters, we employ recent observational data, including the Observational Hubble parameter Data (OHD), Baryon Acoustic Oscillations data (BAO), and Type Ia supernovae data (SNe Ia). The current constrained value of the deceleration parameter is found to be q0=−0.50−0.01+0.01, indicating that the current Universe is accelerating. Furthermore, we examine the evolution of the density, EoS, and Om(z) diagnostic parameters to deduce the accelerating nature of the Universe. Finally, we perform a stability analysis with linear perturbations to confirm the model’s stability.

A single-domain green fluorescent protein catenane

Natural proteins exhibit rich structural diversity based on the folds of an invariably linear chain. Macromolecular catenanes that cooperatively fold into a single domain do not belong to the current protein universe, and their design and synthesis open new territories in chemistry. Here, we report the design, synthesis, and properties of a single-domain green fluorescent protein catenane via rewiring the connectivity of GFP’s secondary motifs. The synthesis could be achieved in two steps via a pseudorotaxane intermediate or directly via expression in cellulo. Various proteins-of-interest may be inserted at the loop regions to give fusion protein catenanes where the two subunits exhibit enhanced thermal resilience, thermal stability, and mechanical stability due to strong conformational coupling. The strategy can be applied to other proteins with similar fold, giving rise to a family of single-domain fluorescent proteins. The results imply that there may be multiple protein topological variants with desirable functional traits beyond their corresponding linear protein counterparts, which are now made accessible and fully open for exploration.

Evolutionary phases of the accelerating universe in modified gravity and its solar system test

Einstein’s gravity is modified to explain an accelerating universe’s present and past scenarios by numerically exploring different cosmological parameters. A new f ( R) gravity model constrained with coupling constants is introduced in the Einstein–Hilbert action to explain current issues and open up new possibilities in gravity physics by fitting the model with newly collected data from observations. It is proposed that the current universe is undergoing an accelerating expansion that behaves as Chaplygin Gas-type dark energy. The values of the coupling constants involved in f ( R) gravity are chosen so that the current value of the effective equation of state (ωeff0) is shown within the observational approximation, that is, between −0.8 and −1.0. Cosmological parameters such as deceleration, cosmic jerk, and snap are consistent with the fundamental observational constraint, and their relevance in terms of coupling constant is also emphasized. The viability of the model as well as the existence and origin of scalaron mass are also investigated.

Gravitation, cosmology and dark matter

In this work, we present the fundamentals of the general theory of relativity, the standard cosmology and a description of current and interesting research topics about our current Universe, in addition the emergence of the dark matter problem has been raised, trying to outline possible dark matter candidates. This assumption seems realistic, however the analysis, from the point of view of standard cosmology, which is also studied in this work, turns out to be more complex than if dark matter were considered with a single species of elementary particle.

A RESPONSABILIDADE CIVIL POR ABANDONO AFETIVO

The work in question will deal with civil liability for affective abandonment with a focus on the maternal/paternal-child relationship, given that it is a topic of great relevance for the current legal universe because it is increasingly recurrent for children to be sought by the Judiciary in order to to claim indemnities for moral damages against the father/mother. In order to better present and demonstrate the issues discussed here, the doctrine and jurisprudence of the Superior Court of Justice and some Brazilian regional courts were used. At first, we sought to analyze how the evolution of the Brazilian family occurred, based on the Federal Constitution of 1988, the Civil Code of 1916 and the Civil Code of 2002. Afterwards, civil liability was addressed, demonstrating its elements and how they present themselves in affective abandonment. For this purpose, jurisprudence and real cases wereused. Finally, the issue dealt with here was addressed, with emphasis on family power and affective abandonment. Positions in favor and against the issue of repairing moral damages in these cases were also presented.

Near-extremal charged black holes: greybody factors and evolution

As a charged black hole reaches its extremal state via Hawking radiation, quantum effects become important for its thermodynamic properties when its temperature is below a mass gap scale. Using AdS2/CFT1 correspondence and solutions for the corresponding Schwarzian action, we calculate the black hole greybody factors including the quantum effects. In the low temperature limit, the greybody factors scale as T2s+3/2 with s the radiated field spin. Hence, the Hawking radiation of a near-extremal charged black hole (NEBH) is dominated by emitting scalar particles including the Higgs boson. Time evolution of an NEBH is also calculated and shows a stochastic feature. For an NEBH lighter than around 108 times the Planck mass, its temperature at the current universe is below the mass gap scale and is universally tens of GeV, which is important if one searches for primordial (hidden) charged black holes.

The interaction of extended Bose–Einstein condensate dark matter with viscous f(T,B) gravity

In this paper, we study the viscous $f(T, B)$ gravity model as a source of dark energy, and the Extended Bose-Einstein Condensate (EBEC) as a source of dark matter, in a flat-FRW metric. In the presence of bulk viscosity, we obtain Friedmann equations and write two continuity equations of dark energy and dark matter by interacting them. Using the generalized Gross-Pitaeveskii equation, we earn Equation of State (EoS) of dark matter by EBEC regime as $p_m = \alpha \rho_{m} + \beta \rho_{m}^2$ in which the both of terms are respectively introduced as normal dark matter and dark matter halo. The innovation of the work is that we can simultaneously describe the nature of the dark parts of the universe with the viscous $f(T, B)$ gravity and the EBEC regime, which leads to a deep understanding of the different epochs of the universe from early to late times. In what follows, the energy density and the pressure of dark energy are reconstructed in terms of the redshift parameter, and then we fit the obtained results with 53 supernova data from the Hubble data constraints. Next, we plot the cosmological parameters in terms of the redshift parameter and conclude that the current universe is in an accelerated phase. Finally, we analyze the stability and instability of the current model with the sound speed parameter as well as we draw the density parameter values for dark energy in terms of the redshift parameter.