Large Negative Values Research Articles

Design and analysis of a thick Miura-ori folded structure with large negative Poisson’s ratio

In this article, effective properties of Miura-ori patterned sheets are studied. The thickness of the facets is allowed to have considerably large values; hence, the structural response of the system cannot be determined by considering only the kinematics of the folding. In particular, large negative values of the Poisson’s ratio have been observed for particular sets of parameters. Numerical outcomes, for periodic and finite systems, have been validated by an experimental campaign, where several specimens with different geometries and materials have been tested. The elastic fields of the specimens have been measured with the digital image correlation method.

Enthalpy-related parameters of interaction of sucrose, lactose and their monosaccharide constituents with the mebicar (N-tetramethylglycoluril) drug in an aqueous medium at 298.15 K

The molar enthalpies of dissolution of N-tetramethylglycoluril, a known psychotropically active pharmaceutical mebicar (Meb) (solute x), in aqueous solutions of d-monosaccharide glucose (Glu), fructose (Fru) and galactose (Gal) as well as disaccharide sucrose (Suc) and α-lactose (Lac) (cosolute y), were measured by the precision calorimetry method at T = 298.15 K and ambient pressure. Unlike the heat absorption in aqueous monosaccharides or Lac, the endothermicity of Meb dissolution in {water (W) + Suc} decreases as the sugar content becomes higher. The enthalpy-heterotactic coefficients for pair interactions between the solute and cosolute molecules, hxy, were determined using the McMillan-Mayer theory formalism. Similar to the homotactic parameters hyy, the hxy values (in J·kg·mol−2) were found to be positive, increasing in the series Suc (86) ≪ Lac (329) < Fru (456) < Glu (545) < Gal (663), despite the existing unusually large (in magnitude) negative hxx value, which is about −2000 J·kg·mol−2. Overall, the number of hydroxy groups and their axial(a)/equatorial(e) positions as well as the peculiarities of a glycoside bond and intramolecular H-bonding in cosolute saccharide molecules cause a stereospecificity of Meb hydration manifested in pair-interaction enthalpic coefficients hxy. So, the inequality hxy > hyy was found to be characteristic of monosaccharide containing aqueous Meb solutions (down to hyy ≈ 0.2hxy for Gal), and hxy < hyy – to be related to disaccharide containing aqueous Meb solutions. Thus, if hxy for (W + Lac + Meb) is ca. 0.65hyy, then it is only about 0.15hyy in the case of (W + Suc + Meb).

Large tunable thermal expansion in ferroelastic alloys by stress

Metallic materials inherently possess small coefficients of thermal expansion (CTE). Engineering the CTEs of metals to achieve large values is demanded in many applications but has proved challenging. Here, we propose a strategy to obtain large CTEs in ferroelastically-transformable alloys through uniaxial stress control by utilizing the alloys' inherenty strong temperature dependence of Young's modulus (dE/dT). In nanostructured NiTi alloy with large elastic limit and large dE/dT, we tune the CTE from a large negative value of -53.2×10 −6 K −1 to a large positive value of +40.4×10 −6 K −1 by applying 1 GPa tensile stress. Such stress effect on CTE is 40 times those of non-ferroelastic metals and the created tunable CTE span is one order of magnitude larger than the typical span (10×10 −6 K −1 ) obtained via the existing chemical modification and hydrostatic pressure control. Through in-situ neutron diffraction experiment and theoretical calculation based on Reuss approximation, we show that the observed large thermal expansion under stress mainly comes from the elastic strain change with temperature due to the large dE/dT of the NiTi and can be generally achieved in ferroelastic alloys. In contrast to the stress-insensitive thermal expansion of most metals, the unique stress-sensitive thermal expansion of ferroelastic alloys may enable new solutions to problems arising from thermal expansion problems.

Timelike orbits around accelerating black holes

We study the geodesics of massive particles around an accelerating Schwarzschild black hole. We show that the radius of the innermost stable circular orbit and the angular momentum of a particle at this orbit decrease by increasing the acceleration. Apart from quantitative influence, the acceleration qualitatively changes the physics. We show that in accelerating black hole spacetime there exists an outermost stable circular orbit in flat, de Sitter, and anti--de Sitter backgrounds. Investigations of radial geodesics show that the acceleration acts like a repulsive force in the sense that test particles around accelerating black holes can move radially outward, unless there exists a large negative value of cosmological constant in the background to compensate the repulsive force. We also investigate the precession of perihelion of orbits around accelerating black holes. The precession would be larger compared to the nonaccelerating case. It is also shown that the precession in anti--de Sitter background could be opposite to the particle motion.

S-Shaped Fused Azacorannulene Dimer: Structural and Redox Properties

S-Shaped Fused Azacorannulene Dimer: Structural and Redox Properties

Diffusion of heat and mass in flow of viscous fluid over a moving porous and rotating disk

In this paper, we have studied the transport of heat and mass in viscous fluid flow over a disk, rotating with variable angular velocity, whereas, both the nonuniform injection and suction velocities can take place through its porous surface. Moreover, the disk is stretched (shrunk) with variable velocity in its own plane. Besides that the temperature and concentration functions, defined at the surface of disk, are assumed nonuniform and nonlinear, whereas, their nonlinear nature can be expressed in the form of algebraic and non-algebraic functions, however, the uniform and linearly variable temperature and concentration functions at the surface of the disk are easily obtained by fixing the exponents of these functions either zero or one. Diffusion of these two quantities in flows over such disk are the fundamental objective of current investigations. Six PDE’s control the fluid motion along with the diffusion of heat and mass in flow over the rotating disk of such special characteristics. The system of PDE’s is transformed into a set of ODE’s, which is solved numerically with the help of bvp4c package of MATLAB. The present simulation and its solution are exactly matched with the solution of classical problems of rotating disk flows with the additional characteristic of diffusion of heat and mass in flows. Therefore, we have seen the individual and combined effects of all physical parameters on field variables under consideration. The higher order governing equations are nonlinear PDE’s, which are converted into the system of ODE’s in view of proper similarity transformations. Moreover, the tangential and radial shears, shaft torque, rates of the diffusion are evaluated at the surface of the disk, whereas, they are graphed against different parameters and interesting results have been presented. It is found that the nonlinear nature of surface temperature and concentration reduced the thermal and concentration boundary layers, however, the large negative values of power index parameters give rise to an overshoot in temperature and concentration profiles.

Radiative impacts of the Australian bushfires 2019–2020 – Part 1: Large-scale radiative forcing

Abstract. As a consequence of extreme heat and drought, record-breaking wildfires developed and ravaged south-eastern Australia during the fire season 2019–2020. The fire strength reached its paroxysmal phase at the turn of the year 2019–2020. During this phase, pyrocumulonimbus clouds (pyroCb) developed and injected biomass burning aerosols and gases into the upper troposphere and lower stratosphere (UTLS). The UTLS aerosol layer was massively perturbed by these fires, with aerosol extinction increased by a factor of 3 in the visible spectral range in the Southern Hemisphere, with respect to a background atmosphere, and stratospheric aerosol optical depth reaching values as large as 0.015 in February 2020. Using the best available description of this event by observations, we estimate the radiative forcing (RF) of such perturbations of the Southern Hemispheric aerosol layer. We use offline radiative transfer modelling driven by observed information of the aerosol extinction perturbation and its spectral variability obtained from limb satellite measurements. Based on hypotheses on the absorptivity and the angular scattering properties of the aerosol layer, the regional (at three latitude bands in the Southern Hemisphere) clear-sky TOA (top-of-atmosphere) RF is found varying from small positive values to relatively large negative values (up to −2.0 W m−2), and the regional clear-sky surface RF is found to be consistently negative and reaching large values (up to −4.5 W m−2). We argue that clear-sky positive values are unlikely for this event, if the ageing/mixing of the biomass burning plume is mirrored by the evolution of its optical properties. Our best estimate for the area-weighted global-equivalent clear-sky RF is -0.35±0.21 (TOA RF) and -0.94±0.26 W m−2 (surface RF), thus the strongest documented for a fire event and of comparable magnitude with the strongest volcanic eruptions of the post-Pinatubo era. The surplus of RF at the surface, with respect to TOA, is due to absorption within the plume that has contributed to the generation of ascending smoke vortices in the stratosphere. Highly reflective underlying surfaces, like clouds, can nevertheless swap negative to positive TOA RF, with global average RF as high as +1.0 W m−2 assuming highly absorbing particles.

Thermal Vibrational Convection in a Rotating Plane Layer

The influence of rotation on the thermal vibrational convection of liquid in a horizontal plane layer is studied experimentally. The convection in the layer is excited by the vibrations of circular polarization in the horizontal plane. The research is carried out in a liquid layer heated from above, under conditions of a strong stabilizing effect of gravity. In this case, the vibrational convection is excited at a relatively high intensity of vibrations and manifests itself in the development of short-wavelength convective structures in the form of beads. It is found that the rotation has a stabilizing effect and increase the vibrational convection excitation threshold. A map of convective stability is plotted on the plane of dimensionless parameters: vibrational parameter, and dimensionless velocity of rotation, for different values of the gravitational Rayleigh number. The results are compared with the classic case of gravitational convection in a rotating layer. It is shown that, similarly to the case of gravitational convection, rotation has a stabilizing effect on vibroconvective stability; the threshold value of the vibration parameter increases with the dimensionless velocity. It is found that at large negative values of the gravitational Rayleigh number, when cellular convective structures of vibroconvective nature are characterized by large wave numbers, in the studied area of the dimensionless frequency, rotation has little effect on the wave number of spatial convective structures, but changes their shape. (Clinical trials: no any clinical trials were performed).

Electrostatic polyelectrolyte complexes: thermodynamic assembly properties

Polysaccharides are common ingredients in medical, technological and industrial products. In many formulations, the oppositely charged polysaccharides (two major biopolymers) are used simultaneously. Understanding their interactions can help control physical properties and stability of formulating. The excess conductivity, σE, and excess energy of activation (ΔΕσ)Ε of electrical conductivity have been investigated by using electrical conductivities measurements for solution of Sodium carboxymethylcellulose (CMC) + solution of chitosan (CH) mixtures over the entire range of volumes fractions X1 of CMC for three different temperatures. This system exhibited a very large negative value of σE and very large positive values (ΔΕσ)Ε due to increased hydrogen bonding interactions and correlation length between unlike molecules in the two critical regions, and very large differences between the pure components. The activations parameters ΔΗσ and ΔSσ have been also calculated, and show that the two critical regions have an important effect on the electrical conductivity properties. In this study, (ΔHσ)ϕ1, (ΔHσ)c ϕ1, (ΔHσ)ϕ2, (ΔHσ)c ϕ2, Xϕ1, Xϕ1, XC ϕ1 and XC ϕ2 were identified.

Dynamics of Nonpolar Solutions to the Discrete Painlevé I Equation

This manuscript develops a novel understanding of non-polar solutions of the discrete Painlev\'e I equation (dP1). As the non-autonomous counterpart of an analytically completely integrable difference equation, this system is endowed with a rich dynamical structure. In addition, its non-polar solutions, which grow without bounds as the iteration index $n$ increases, are of particular relevance to other areas of mathematics. We combine theory and asymptotics with high-precision numerical simulations to arrive at the following picture: when extended to include backward iterates, known non-polar solutions of dP1 form a family of heteroclinic connections between two fixed points at infinity. One of these solutions, the Freud orbit of orthogonal polynomial theory, is a singular limit of the other solutions in the family. Near their asymptotic limits, all solutions converge to the Freud orbit, which follows invariant curves of dP1, when written as a 3-D autonomous system, and reaches the point at positive infinity along a center manifold. This description leads to two important results. First, the Freud orbit tracks sequences of period-1 and 2 points of the autonomous counterpart of dP1 for large positive and negative values of $n$, respectively. Second, we identify an elegant method to obtain an asymptotic expansion of the iterates on the Freud orbit for large positive values of $n$. The structure of invariant manifolds emerging from this picture contributes to a deeper understanding of the global analysis of an interesting class of discrete dynamical systems.

Analysis and design of laminated composite beams based on a refined higher-order theory

In this work, a new analysis and design methodology of laminated composite beams is presented. The problem is formulated for both symmetric and antisymmetric ply-stacking configurations, based on a refined higher-order shear deformation theory. The solution is obtained using the Analog Equation Method (AEM) while the design process is based on the Differential Evolution (DE) metaheuristic optimization algorithm, using both displacement and strength-related objective functions. Numerical examples are presented, demonstrating the applicability and effectiveness of the proposed analysis and design methodology. The results indicate that to minimize the deflection of an orthotropic laminated beam the principal material orientation must coincide with the longitudinal axis of the beam. Moreover, for the strength optimization problem, the Tsai-Wu failure criterion proved to be numerically unstable, returning very large negative values for seemingly indifferent configurations. Conversely, Hashin’s criterion manifests robustness during the optimization process ensuring efficacious design.

A comprehensive study of large negative dispersion and highly nonlinear perforated core PCF: theoretical insight

A photonic crystal fiber (PCF) containing circularly organized square-shaped air holes in the cladding region is investigated. The fiber core is perforated with four circular air-filled holes to instate high nonlinearity and large negative dispersion. The numerical analysis is done with a finite element method based COMSOL Multiphysics tool to investigate different optical properties of the propounded PCF. The simulation outcome verifies a high nonlinear coefficient value of 85 W−1 Km−1 at telecommunication window 1.55 μm which is, the highest ever achieved value on comparing with the other existing literature without using any nonlinear materials or liquids to the best of the authors’ knowledge. In parallel, the large negative value of dispersion −597 ps nm−1 km−1 is achieved for S/Λ equals 0.70 at the same communication window. However, the highest achieved nonlinearity and negative dispersion are 300 W−1 Km−1 and −1689 ps/nm/km. Moreover, birefringence, numerical aperture, and propagation loss are also measured as 2.40 × 10−3, 0.59, and 4.12 × 10−11 dB m−1 respectively along with an extremely high core power fraction of 99.98%. Hence, the propounded PCF is suitable for residual dispersion compensation, supercontinuum generation, and high bitrate transmission.

Analysis of radial expansion, eversion, and cavitation of soft functionally graded material spheres

We study radial expansion, cavitation, and eversion of spherical shells made of incompressible, isotropic, and functionally graded (i.e. inhomogeneous) soft (or rubber-like) materials that are increasingly being used in prosthetics, seals, tires, flexible electronics, soft robots, and many other applications. We consider all geometric and material nonlinearities and assume the sphere material to be Mooney–Rivlin material whose two parameters, C1(R) and C2(R), are smooth functions of the radial coordinate, R, in the stress-free undeformed configuration. The shell’s inversion illustrates non-uniqueness of solutions in finite elasticity since sphere’s bounding surfaces are traction free in the reference and the deformed configurations but stresses/strains in the interior are different. Assuming that a shell under a dead tensile pressure on the outer surface cavitates when the radial stretch at the inner surface equals four, we delineate effects of functions C1(R) and C2(R) on the cavitation pressure. It is found that for power-law variations with indices m and n, respectively, for C1(R) and C2(R) the cavitation pressure can be controlled by suitably choosing m and n. Large positive and negative values of m and n are deleterious for a sphere loaded only by a pressure on the inner surface since they produce high hoop stresses within the sphere. Other results given in the paper will enable one to tailor functions C1(R) and C2(R) to either mitigate cavitation or initiate it at a desired pressure or have prescribed through-the-thickness variations of stresses to optimize sphere’s performance.

The excess specific conductivity and energy of activation for Sodium carboxymethylcellulose (CMC) and chitosan (CH) aqueous solutions complex

ABSTRACT Polysaccharides are common ingredients in medical, technological, and industrial products. In many formulations, the oppositely charged polysaccharides (two major biopolymers) are used simultaneously. Understanding their interactions can help control the physical properties and stability of formulating. The excess specific conductivity, (σ E)sp and excess specific energy of activation (ΔEσ)E)sp of electrical conductivity have been investigated by using electrical conductivities measurements for solution of Sodium carboxymethylcellulose (CMC) + solution of chitosan (CH) mixtures over the entire range of volumes fractions X1 of CMC for three different temperatures. This system exhibited a very large negative value of (σ E)sp and very large negative values (ΔEσ)E)sp due to increased hydrogen bonding interactions and correlation length between unlike molecules in the two critical regions, and very large differences between the pure components. The Redlich-Kister function f1 and f2 of the excess of specific conductivities and excess specific energy, respectively, have been also calculated, and show that the two critical regions have an important effect on the electrical conductivity properties. In this study, f1 c ϕ 1 , f 1 c ϕ 2, f1ϕ 1,f1ϕ 2 , Xϕ1, Xϕ1, XC ϕ1, and XC ϕ2 were identified

Characterization of structure and chemical bond in high-Q microwave dielectric ceramics LiM2GaTi2O8 (M = Mg, Zn)

LiM2GaTi2O8 (M = Mg, Zn) ceramics with the Fd-3m space group were synthesized using the solid-state method. In comparison with Mg2+ that fully occupied the tetrahedral (A) site in LiMg2GaTi2O8, LiZn2GaTi2O8 was jointly occupied by Zn2+ and Li+ at the A site. Excellent microwave dielectric properties of Q×f = 133,400 ± 500 GHz, 101,800 ± 500 GHz, εr = 17.1 ± 0.2, 15.8 ± 0.2, and τf = −60.1 ± 3.0 ppm/°C, − 42.2 ± 3.0 ppm/°C for LiZn2GaTi2O8 and LiMg2GaTi2O8 were obtained, respectively. The large deviations (30.3% for LiMg2GaTi2O8 and 19.6% for LiZn2GaTi2O8) between the corrected εcorr and theoretical εth were observed, which might be attributed to the underestimated Shannon’s ionic polarizability of Ti4+ in Ti-containing spinels. Their intrinsic microwave dielectric properties were discussed based on bond valence, lattice energy (U), and B-site bond energy (E). Besides, their large negative τf values were compensated to near-zero by CaTiO3.

Temperature stable Li5.5Nb1.5O6F-based microwave dielectric ceramics for LTCC applications

Herein, low-fired (1−x)Li5.5Nb1.5O6F–xBa3(VO4)2 (x = 0, 0.15, 0.2, 0.25 and 0.3) composite ceramics were fabricated using a standard solid-state reaction method. The X-ray diffraction and Rietveld refinement results demonstrated that the Li5.5Nb1.5O6F ceramics crystallised in a cubic rock-salt structure. Based on the refined crystal parameters, the calculated εr was highly close to the measured value. The variation in Q × f values was mainly controlled by the density and packing fraction. The single-phase Li5.5Nb1.5O6F ceramic sintered at 875 °C displayed satisfactory dielectric properties: εr = 17.05, Q × f = 77,500 GHz and τf = −44.1 ppm/°C. Considering of the relatively large negative τf value of the Li5.5Nb1.5O6F ceramic, different mole ratios of Ba3(VO4)2 were added to enhance its temperature stability. The τf value increased continuously as the Ba3(VO4)2 amount increased. When x = 0.25, the optimal microwave dielectric properties were achieved for the composite ceramics at 875 °C, with εr = 16.68, Q × f = 55,800 GHz and τf = −1.7 ppm/°C at a frequency of 7.68 GHz. Such samples were compatible with the Ag electrodes and would be a promising candidate for low-temperature cofired ceramics applications.

7 February Chamoli (Uttarakhand, India) Rock-Ice Avalanche Disaster: Model-Simulated Prevailing Meteorological Conditions

The present study aims to analyze the high-resolution model-simulated meteorological conditions during the Chamoli rock-ice avalanche event, which occurred on 7 February 2021 in the Chamoli district of Uttarakhand, India (30.37° N, 79.73° E). The Weather Research and Forecasting (WRF) model is used to simulate the spatiotemporal distribution of meteorological variables pre- and post-event. The numerical simulations are carried out over two fine resolution nested model domains covering the Uttarakhand region over a period of 2 weeks (2 February to 13 February 2021). The model-simulated meteorological variables, e.g., air temperature, surface temperature, turbulent heat flux, radiative fluxes, heat and momentum transfer coefficients, specific humidity and upper wind patterns, were found to show significant departures from their usual patterns starting from 72 h until a few hours before the rock-ice avalanche event. The average 2 m air and surface temperatures near the avalanche site during the 48 h before the event were found to be much lower than the average temperatures post-event. In-situ observations and the ERA5-Land dataset also confirm these findings. The total turbulent heat flux mostly remained downward (negative) in the 72 h before the event and was found to have an exceptionally large negative value a few hours before the rock-ice avalanche event. The model-simulated rainfall and Global Precipitation Measurement (GPM, IMERG)-derived rainfall suggest that the part of the Himalayan region falling in the simulation domain received a significant amount of rainfall on 4 February, around 48 h prior to the event, while the rest of the days pre- and post-event were mostly dry. The results presented here might be helpful in further studies to identify the possible trigger factors of this event.

Partial atomic volumes of early transition metals in A10 metal-based solid solutions

Abstract Unit-cell parameters were measured for the A10 metal-based (= Ni, Pd, Pt) solid solutions (Pearson symbol cF4, space group Fm 3 ¯ ${\bar 3}$ m, Cu type) with the A5 transition metals (V, Nb, Ta) in the whole range of homogeneity. Composition dependence both of the average atomic volume and the enthalpy of formation were investigated for the A10 metal-based solid solutions with the A5 and A6 transition metals; the partial atomic volume and the partial molar enthalpy of formation of the A5 and A6 transition were determined for the A10-rich terminal phases. Among the systems investigated, only the solid solutions Pd(Cr) and Pt(Cr) show partial atomic volume of chromium larger than the chromium atomic volume. In the nickel-based solid solution, the partial atomic volume of chromium is equal to the chromium atomic volume. The partial molar enthalpy of formation for the A5 transition metals – in the nickel, palladium and platinum-rich alloys – shows larger negative values than values evaluated for the A6 transition metals. An enlarged investigation of the data available in literature shows that both the relative volume change, resulting from the dissolving process of the early transition metals in the A10 metal-based alloys, and the negative values of the partial molar enthalpy of formation increase with decreasing number of the 3d and 4d electrons of the early transition elements. For the 5d quasihomologous transition metals, this observation is valid for the A4 . . . A6 elements as well.

Coexistence of spontaneous dimerization and magnetic order in a transverse-field Ising ladder with four-spin interactions

The spin-1/2 transverse field two-leg Ising ladder with nearest-neighbor exchange and plaquette four-spin interaction ${J}_{4}$ is studied analytically and numerically with the density matrix renormalization group approach. The quantum phase diagram in the transverse field $B$ versus ${J}_{4}$ plane has been obtained. There are three different phases: a paramagnetic (PM) phase for high values of the transverse field and, for low values of $B$, a ferromagnetic (FM) ordered phase for small ${J}_{4}$, and a dimerized-rung (DR) phase for large negative values of ${J}_{4}$. All phases are separated by quantum phase transition lines meeting at a multicritical point. The critical lines have been obtained by exploring the entanglement entropy. The results show that along the critical lines the central charge is $c=1/2$, while at the multicritical point one has $c=1$. The scaling dimension of the energy operator is ${X}_{\ensuremath{\epsilon}}=1$, in agreement with the universality class of the critical behavior of the quantum Ising chain. An effective field theory for the multicritical point is also discussed. The FM and the DR order parameters have also been computed and we found a region where the FM and the DR phases coexist.

Big Rip Scenario in Brans-Dicke Theory

In this work, we present a Big Rip scenario within the framework of the generalized Brans-Dicke (GBD) theory. In the GBD theory, we consider an evolving BD parameter along with a self-interacting potential. An anisotropic background is considered to have a more general view of the cosmic expansion. The GBD theory with a cosmological constant is presented as an effective cosmic fluid within general relativity which favours a phantom field dominated phase. The model parameters are constrained so that the model provides reasonable estimates of the Hubble parameter and other recent observational aspects at the present epoch. The dynamical aspects of the BD parameter and the BD scalar field have been analysed. It is found that the present model witnesses a finite time doomsday at a time of tBR≃16.14Gyr, and for this scenario, the model requires a large negative value of the Brans-Dicke parameter.