Range Of Mass Ratios Research Articles

CHARACTERIZATION OF NANOPARTICLES PRODUCED BY CHLOROFORM FRACTION OF KAEMPFERIA ROTUNDA RHIZOME LOADED WITH ALGINIC ACID AND CHITOSAN AND ITS BIOLOGICAL ACTIVITY TEST

Objective: The main objectives of this research are to characterize of nanoparticles produced by chloroform fraction of K. rotunda loaded with alginic acid and combination alginic acid-chitosan, and its biological activity test. Methods: Chloroform fraction of K. rotunda was loaded on alginic acid and combination of alginic acid-chitosan nanoparticles by ionic gelation method in various compositions. Characterizations of the products were investigated in particle size, zeta potential, and morphology by Scanning Electron Microscopy (SEM). The biological activity of the products as an antioxidant was tested by the DPPH (2,2-diphenyl-1-picrylhydrazyl) method. The cytotoxic effect was analysed using MTT [3-(4,5 dimethyltiazol-2-yl)-2,5-diphenyltetrazoilium bromide] assay.Result:The nanoparticles alginic acid can be synthesized at the optimal mass ratio range of alginic acid : CaCl2 of 10 :1 (% w/v),the percentage nanoparticle products was100%, the size range of the nanoparticles were 87 to 584 nm, with a zeta potential of -39.0 mV, and the morphology shows a spherical shape and smooth surface. Furthermore, nanoparticles result from the combination of alginic acid-chitosan at the optimal mass ratio range of alginic acid : chitosan of 10 :1 (% w/v) and added calsium ion at 0.015% w/v, the percentage nanoparticle products was100%, the size range of the nanoparticle were 87 to 877 nm, with a zeta potential of -27.1 mV, and the morphology shows a form of rectangular beam.Conclusion: The nanoparticle products of chloroform fraction of K. rotunda loaded alginic acid and combination alginic acid-chitosan were successfully obtained by ionic gelation method. The nanoparticle products show lower activity in antioxidant and cytotoxic effect against human breast cancer T47D cell lines than the starting material chloroform fraction of K. rotunda.Keywords: Alginic acid, Chitosan, Nanoparticles, Kaempferia rotunda, Antioxidant, Cytotoxic effect, Human breast cancer T47D cell lines.

Synthesis of cellulose/silica gel polymer hybrids via in-situ hydrolysis method

Homogeneous cellulose/silica gel polymer hybrids were prepared by hydrolysis of acetyl cellulose (AcCL) in a sol–gel reaction mixture of alkoxysilane such as tetramethoxysilane (TMOS). To a mixture of AcCL and TMOS in a mixed solvent of THF and methanol (v/v, 7/3), an HCl aqueous solution was added to initiate hydrolysis and condensation of the alkoxysilane. The resulting mixture was constantly stirred for 5 h and heated at 60 °C for two weeks to allow evaporation of the solvents. Consequently, corresponding transparent and homogeneous polymer hybrids could be obtained in a range of mass ratios (AcCL/TMOS = 1/5–1/2). In the FT-IR spectra, the absorption peaks corresponding to the acetyl group decreased as the amount of 0.1 M aqueous HCl solution increased, which indicates hydrolysis of acetyl groups of AcCL, whereas the intensity of the Si–O-Si stretching vibration peak increased. The thermal properties of the obtained polymer hybrids were evaluated by TG/DTA and DSC measurements.

Steady-state protein focusing in carrier ampholyte-based isoelectric focusing: Part II-validation and case studies.

In this study, we systematically investigate the validity and applicability of an analytical model developed for carrier ampholyte-based isoelectric focusing (IEF). Three different IEF cases are considered in order to evaluate the efficacy of the approximate analytical results by comparison with high-resolution computer simulations. In the first case, three proteins are separated in a narrow pH range (6-9) by using 50 carrier ampholytes. In the second and third cases, the separation of proteins is studied in broad pH range (3-10) IEF by using 100 carrier ampholytes. Results obtained from the approximate analytical models are in very good agreement with the numerical results for IEF separation of cardiac troponin I, albumin, and hemoglobin in both narrow and broad pH ranges. The sensitivity of the analytical model is also tested for different initial mass ratios of proteins to ampholytes. No appreciable differences are observed between the approximate analytical and numerical results within the mass ratio range studied. The effect of a nominal electric field and/or a nominal pH gradient on protein focusing is also examined to demonstrate the effectiveness of the analytical model. Our results indicate that the use of both nominal electric field and pH gradient will result in erroneous peak concentrations for proteins. Finally, we describe the limitations of the approximate analytical solutions.

A new partitioned staggered scheme for flexible multibody interactions with strong inertial effects

In generic flexible multibody interaction problems, the differences in the mass, damping and stiffness of the bodies can be very large. Of particular interest is a small change in the higher mass structure which triggers relatively large inertial effects on the lower mass structure. In this work, a new partitioned staggered time integration scheme is developed and its applicability is extended to the problems involving low mass ratios in coupled multibody problems. The equation of motion of body with larger inertia is integrated by implicit Newmark method, whereas the smaller inertia is solved using a robust self-starting explicit integration procedure. The coupled formulation includes explicit correction terms that adjusts the amount of interfacial velocity, which plays a key role in the stability and accuracy of the simulations. A wide range of mass (10−6–10−1), damping and stiffness (10−3–103) ratios are chosen to assess the stability and accuracy characteristics of the proposed scheme. The closed-form expressions for the coupling parameter have been constructed for both matching and non-matching time stepping through the Godunov–Ryabenkii normal mode analysis. The stability of the proposed method is observed as a function of the relative properties and temporal discretisation of the coupled system. The time step of the heavier body significantly influences the stability more than the lighter body. To maintain the staggering error minimal, an optimal range of the coupling parameter is identified. The error computed with uniform variation in the time step revealed that the present method is more accurate than the existing methods. The partitioned method is an energy preserving integration method for the dynamic analysis of multibody systems. As a potential application of this scheme, flexible multibody problems in the field of offshore engineering, viz., wave energy converter and floater–mooring systems are presented and validated with experimental measurements.

Exact solution for the vibrations of an arbitrary plane curved pipe conveying fluid

In this paper, the response of an arbitrary plane curved pipe subjected to fluid flow is investigated analytically. The pipe cross‐section is restricted to have a certain symmetry so that the pipe stays in its plane while under the effects of the fluid motion. Influence of fluid motion is considered in three terms. One is the inertial force due to the fluid mass which is assumed to be distributed uniformly along the length of the pipe. The inertial force naturally varies since the pipe has a variable curvature. The second one is due to the weight of the fluid and the last one is the friction force between the fluid and the pipe. These forces also vary along the length of the pipe. The general equations are given for any plane curved pipe and solved for a specific example using the method of power series. The equations are non‐dimensionalised and the dynamic response of the pipe is plotted for a range of mass ratios between the fluid and the pipe material.

Modal analysis of gravitational instabilities in nearly Keplerian, counter-rotating collisionless discs

We present a modal analysis of instabilities of counter-rotating, self-gravitating collisionless stellar discs, using the recently introduced modified WKB formulation of spiral density waves for collisionless systems (Gulati \& Saini). The discs are assumed to be axisymmetric and in coplanar orbits around a massive object at the common center of the discs. The mass in both discs is assumed to be much smaller than the mass of the central object. For each disc, the disc particles are assumed to be in near circular orbits. The two discs are coupled to each other gravitationally. The perturbed dynamics of the discs evolves on the order of the precession time scale of the discs, which is much longer than the Keplerian time scale. We present results for the azimuthal wave number $m=1$ and $m=2$, for the full range of disc mass ratio between the prograde and retrograde discs. The eigenspectra are in general complex, therefore all eigenmodes are unstable. Eigenfunctions are radially more compact for $m = 1$ as compared to $m = 2$. Pattern speed of eigenmodes is always prograde with respect to the more massive disc. The growth rate of unstable modes increases with increasing mass fraction in the retrograde disc, and decreases with $m$; therefore $m=1$ instability is likely to play the dominant role in the dynamics of such systems.

Effects of inclined star-disk encounter on protoplanetary disk size

Most, if not all, young stars are initially surrounded by protoplanetary disks. Owing to the preferential formation of stars in stellar clusters, the protoplanetary disks around these stars may potentially be affected by the cluster environment. Various works have investigated the influence of stellar fly-bys on disks, although many of them consider only the effects due to parabolic, coplanar encounters often for equal-mass stars, which is only a very special case. We perform numerical simulations to study the fate of protoplanetary disks after the impact of parabolic star-disk encounter for the less investigated case of inclined up to coplanar, retrograde encounters, which is a much more common case. Here, we concentrate on the disk size after such encounters because this limits the size of the potentially forming planetary systems. In addition, with the possibilities that ALMA offers, now a direct comparison to observations is possible. Covering a wide range of periastron distances and mass ratios between the mass of the perturber and central star, we find that despite the prograde, coplanar encounters having the strongest effect on the disk size, inclined and even the least destructive retrograde encounters mostly also have a considerable effect, especially for close periastron passages. Interestingly, we find a nearly linear dependence of the disk size on the orbital inclination for the prograde encounters, but not for the retrograde case. We also determine the final orbital parameters of the particles in the disk such as eccentricities, inclinations, and semi-major axes. Using this information the presented study can be used to describe the fate of disks and also that of planetary systems after inclined encounters.

Thickening behavior and synergistic mechanism of mixed system of two hydrophobically associating polymers

ABSTRACTThe thickening behavior and synergistic mechanism of the mixed system of the hydrophobically associating polymer (HAP-S) (acrylamide/acrylate-EOm-POn/sodium acrylate terpolymer) with small molecular weight and the acrylamide/N-isooctyl acrylamide/sodium acrylate terpolymer (HAP-L) with large molecular weight were investigated via the rheology, inclusion action of β-cyclodextrin (β-CD), cohesive energy, dynamic light scattering (DLS), and scanning electron microscope (SEM). The apparent viscosity of the mixed-system solution was higher than that of the HAP solution alone in a wide range of mass ratios and concentrations of the two polymers, ascribing to the enhancement of associated viscosity and strength of the network structure by forming mixed aggregates and bridging among them. Furthermore, the hydrodynamic radius of the mixed-system aggregates increased due to the improved network structure and the electrostatic repulsion effect among the different kinds of HAP molecules. Under the synthetical influence of the above-mentioned factors, the mixed system displayed better temperature resistance and salt tolerance as compared to the HAP solution alone.

Validation of the Gurney Model in Planar Geometry for a Conventional Explosive

AbstractThe analytical model developed by Gurney is a seminal tool for analyzing the acceleration of metal flyers driven by detonating high explosives. Despite the continued relevance of this model, relatively few experimental validations over a wide range of flyer‐to‐charge mass ratios exist in the open literature. The current study presents experimental results for planar aluminum flyers propelled by a conventional explosive over a range of mass ratios varying from 4.65 to 0.03. Flyer velocity was measured via Heterodyne Laser Velocimetry (PDV), permitting a continuous measurement of the acceleration process. Measured flyer velocities are compared to terminal velocity estimations from the Gurney model. Experimental terminal velocities are compared to the open face and asymmetric sandwich Gurney models. Excellent agreement is observed for terminal velocity predictions considering the gasdynamic simplifications inherent in the model formulation.

ASAS J083241+2332.4: A NEW EXTREME LOW MASS RATIO OVERCONTACT BINARY SYSTEM

ABSTRACT We present the R- and V-band CCD photometry and Hα line studies of an overcontact binary ASAS J083241+2332.4. The light curves exhibit totality along with a trace of the O’Connell effect. The photometric solution indicates that this system falls into the category of extreme low-mass ratio overcontact binaries with a mass ratio, q ∼ 0.06. Although a trace of the O’ Connell effect is observed, constancy of the Hα line along various phases suggest that a relatively higher magnetic activity is needed for it to show a prominent fill-in effect. The study of O–C variations reveals that the period of the binary shows a secular increase at the rate of dP/dt ∼ 0.0765 s years−1, which is superimposed by a low, but significant, sinusoidal modulation with a period of ∼8.25 years. Assuming that the sinusoidal variation is due to the presence of a third body, orbital elements have been derived. There exist three other similar systems, SX Crv, V857 Her, and E53, which have extremely low mass ratios and we conclude that ASAS J083241+2332.4 resembles SX Crv in many respects. Theoretical studies indicate that at a critical mass ratio range, q critical = 0.07–0.09, overcontact binaries should merge and form a fast rotating star, but it has been suggested that q critical can continue to fall up to 0.05 depending on the primary's mass and structure. Moreover, the obtained fill-out factors (50%–70%) indicate that mass loss is considerable and hydrodynamical simulations advocate that mass loss from L 2 is mandatory for a successful merging process. Comprehensively, the results indicate that ASAS J083241+2332.4 is at a stage of merger. The pivotal role played by the subtle nature of the derived mass ratio in forming a rapidly rotating star has been discussed.

Uniform Damping Ratio For Non-Classically Damped Hybrid Steel Concrete Structures

Steel–concrete hybrid systems are used in buildings, in which a steel structure has been placed on a concrete structure to make a lighter structure and have a faster construction. Dynamic analysis of hybrid structures is usually a complex procedure due to various dynamic characteristics of each part, i.e., stiffness, mass and especially damping. Dynamic response of hybrid structures has some complications. One of the reasons is the different stiffness of the two parts of structure and another reason is non-uniform distribution of materials and their different features such as damping in main modes of vibration. The available software is not able to calculate damping matrices and analyze these structures because the damping matrix of these irregular structures is non-classical. Also an equivalent damping should be devoted to the whole structure and using the available software. In the hybrid structures, one or more transitional storeys are used for better transition of lateral and gravity forces. In this study, an equation has been proposed to determine the equivalent uniform damping ratio for hybrid steel–concrete buildings with transitional storey(s). In the proposed method, the hybrid structure containing concrete, steel and transitional storeys appropriately substituted with 3-DOF structure. A wide range of eigenfrequency and mass ratios is examined for each ratio pair, and given the characteristics of the primary system, the complete 3-DOF structure can be formed. Equivalent uniform damping ratio is derived by means of a semi-empirical error minimization procedure. The multiple nonlinear regressions are used for determination of equations of modal damping ratios of hybrid buildings.

Obtaining Ceramic Based on Si3N4 and TiN by Spark Plasma Sintering

The dependences of the microstructure and physical-mechanical properties of Si3N4–TiN-based ceramic in a wide range of mass ratios of the components are examined. The sintering process and the accompanying physical and chemical processes, viz. the dependence of the hardness and density of the material on the ratios of the conducting phase of titanium nitride and the dielectric phase of silicon nitride with values above and below the percolation threshold, are examined. A ceramic based on pure titanium nitride with high physical-mechanical characteristics (H = 21.5 GPa) is obtained.

Lightweight and Anisotropic Porous MWCNT/WPU Composites for Ultrahigh Performance Electromagnetic Interference Shielding

Lightweight, flexible and anisotropic porous multiwalled carbon nanotube (MWCNT)/water‐borne polyurethane (WPU) composites are assembled by a facile freeze‐drying method. The composites contain extremely wide range of MWCNT mass ratios and show giant electromagnetic interference (EMI) shielding effectiveness (SE) which exceeds 50 or 20 dB in the X‐band while the density is merely 126 or 20 mg cm−3, respectively. The relevant specific SE is up to 1148 dB cm3 g−1, greater than those of other shielding materials ever reported. The ultrahigh EMI shielding performance is attributed to the conductivity of the cell walls caused by MWCNT content, the anisotropic porous structures, and the polarization between MWCNT and WPU matrix. In addition to the enhanced electrical properties, the composites also indicate enhanced mechanical properties compared with porous WPU and CNT architectures.

Interacting binaries W Serpentids and double periodic variables

W Serpentids and Double Periodic Variables (DPVs) are candidates for close interacting binaries in a non-conservative evolutionary stage; while W Serpentids are defined by high-excitation ultraviolet emission lines present during most orbital phases, and by usually showing variable orbital periods, DPVs are characterized by a long photometric cycle lasting roughly 33 times the (practically constant) orbital period. We report the discovery of 7 new Galactic DPVs, increasing the number of known DPVs in our Galaxy by 50%. We find that DPVs are tangential-impact systems, i.e. their primaries have radii barely larger than the critical Lubow-Shu radius. These systems are expected to show transient discs, but we find that they host stable discs with radii smaller than the tidal radius. Among tangential-impact systems including DPVs and semi-detached Algols, only DPVs have primaries with masses between 7 and 10 $M_{\odot}$. We find that DPVs are in a Case-B mass transfer stage with donor masses between 1 and 2 M$_{\odot}$ and with primaries resembling Be stars. W Serpentids are impact and non-impact systems, their discs extend until the last non-intersecting orbit and show a larger range of stellar mass and mass ratio than DPVs. Infrared photometry reveals significant color excesses in many DPVs and W Serpentids, usually larger for the latter ones, suggesting variable amounts of circumstellar matter.

Precessional Instability in Binary Black Holes with Aligned Spins.

Binary black holes on quasicircular orbits with spins aligned with their orbital angular momentum have been test beds for analytic and numerical relativity for decades, not least because symmetry ensures that such configurations are equilibrium solutions to the spin-precession equations. In this work, we show that these solutions can be unstable when the spin of the higher-mass black hole is aligned with the orbital angular momentum and the spin of the lower-mass black hole is antialigned. Spins in these configurations are unstable to precession to large misalignment when the binary separation r is between the values r(ud±)=(√(χ(1))±√(qχ(2)))(4)(1-q)(-2)M, where M is the total mass, q≡m(2)/m(1) is the mass ratio, and χ(1) (χ(2)) is the dimensionless spin of the more (less) massive black hole. This instability exists for a wide range of spin magnitudes and mass ratios and can occur in the strong-field regime near the merger. We describe the origin and nature of the instability using recently developed analytical techniques to characterize fully generic spin precession. This instability provides a channel to circumvent astrophysical spin alignment at large binary separations, allowing significant spin precession prior to merger affecting both gravitational-wave and electromagnetic signatures of stellar-mass and supermassive binary black holes.

Ceramics based on titanium nitride and silicon nitride sintered by SPS-method

The dependences of the microstructure and physical and mechanical properties of ceramic mixtures Si3N4/TiN in the full range of mass ratios of the components. Was also investigated directly, and the process of sintering occurring during a physical or chemical processes, in particular, has been obtained and the hardness of the material density on the ratio of the conductive titanium nitride phase and a silicon nitride insulating phase with values above and below the percolation threshold. Also obtained was pure ceramics based on titanium nitride with high physical-mechanical characteristics (H = 21.5 GPa).

Binary accretion rates: dependence on temperature and mass ratio

We perform a series of 2D smoothed particle hydrodynamics (SPH) simulations of gas accretion onto binaries via a circumbinary disc, for a range of gas temperatures and binary mass ratios ($q$). We show that increasing the gas temperature increases the accretion rate onto the primary for all values of the binary mass ratio: for example, for $q=0.1$ and a fixed binary separation, an increase of normalised sound speed by a factor of $5$ (from our "cold" to "hot" simulations) changes the fraction of the accreted gas that flows on to the primary from $ 10\%$ to $\sim40\%$. We present a simple parametrisation for the average accretion rate of each binary component accurate to within a few percent and argue that this parametrisation (rather than those in the literature based on warmer simulations) is relevant to supermassive black hole accretion and all but the widest stellar binaries. We present trajectories for the growth of $q$ during circumbinary disc accretion and argue that the period distribution of stellar "twin" binaries is strong evidence for the importance of circumbinary accretion. We also show that our parametrisation of binary accretion increases the minimum mass ratio needed for spin alignment of supermassive black holes to $q \sim 0.4$, with potentially important implications for the magnitude of velocity kicks acquired during black hole mergers.

Development and analysis of gas barrier properties of microfibrillar polymer–polymer composites

Polyethylene terephthalate microfibril-reinforced composites with linear low-density polyethylene (LLDPE) matrix were manufactured by four industrial processing methods: compression moulding, slit-die extrusion with calendering, extrusion blow moulding and injection moulding. The microfibrils were generated in situ by blending the two polymers together and thermomechanically processing the blend. Thin sheets were manufactured in all the processes, except injection moulding, which was employed for making containers. The oxygen permeability of the films was determined using a commercial machine. The greatest improvement in oxygen barrier property (compared to neat LLDPE films), was found in the compression-moulded microfibrillar composite (MFC) films. Two existing theoretical models were modified to reasonably forecast the oxygen permeability of compression-moulded MFC films. The parallel filler model provides a very good fit to the experimental data for the full mass ratio range. The Lewis and Nielsen model was also trialled for various polymer combinations, producing reasonable results with minor modifications.

A relativistic PIC model of nonlinear laser absorption in a finite-size plasma with arbitrary mass and density ratios

AbstractIn this paper, we have studied the nonlinear laser absorption in a finite-size plasma, using a fully kinetic relativistic 1½-dimensional particle-in-cell simulation code, and shown that the rate in which laser absorption increases depends on the mass ratio (δ = m+/m−) and the equilibrium density ratio (α = n0+/n0− = z−/z+), respectively. This can be attributed to the essential effects of these parameters on the nonlinear phenomena related to the laser absorption such as phase-mixing and laser-scattering process. We have indicated that the reduction of the defined mass and density ratios increases the absorption rate in the finite-size plasma as long as the laser scattering from the plasma is not considerable. Moreover, the study of kinetic phase-space distributions indicates in a specific range of mass and density ratios a large amount of laser energy leads to arise a population of charged particles having directed kinetic energy along the laser direction. These simulation results are expected to be relevant to the experiments on the intense laser–plasma interactions with applications to the particle acceleration and fast ignition concept as well as to the astrophysical environments.

STABILITY AND COALESCENCE OF MASSIVE TWIN BINARIES

Massive stars are usually found in binaries, and binaries with periods less than 10 days may have a preference for near equal component masses. In this paper we investigate the evolution of these binaries all the way to contact and the possibility that these systems can be progenitors of double neutron star binaries. The small orbital separations of observed double neutron star binaries suggest that the progenitor systems underwent a common envelope phase at least once during their evolution. Bethe & Brown (1998) proposed that massive binary twins will undergo a common envelope evolution while both components are ascending the red giant branch or asymptotic giant branch simultaneously, also known as double-core evolution. Using models generated from the stellar evolution code Evolve Zero Age Main Sequence, we determine the range of mass ratios resulting in both components simultaneously ascending the RGB or AGB as a function of the difference in birth times, t. We find that, even for a generous t=5 Myr, the minimum mass ratio qmin=0.933 for an 8 Solar Mass primary and increases for larger primaries. We use a hydrodynamics code, StarSmasher, to study specifically the evolution of q=1 common envelope systems as a function of initial component mass, age, and orbital separation. We find the dynamical stability limit, the largest orbital separation where the binary becomes dynamically unstable, as a function of the component mass and age. Finally, we calculate the efficiency of ejecting matter during the inspiral phase to extrapolate the properties of the remnant binary from our numerical results, assuming the common envelope is completely ejected. We find that for the nominal core masses, there is a minimum orbital separation for a given component mass such that the helium cores survive common envelope evolution in a tightly bound binary and are viable progenitors for double neutron stars.