Tumbling Parameter Research Articles

Effect of Tumbling Conditions on the Tendinous and Tenderness Index of Chicken Leg Meat

This article presents the results of the effect of chicken leg meat tumbling parameters on its texture, as assessed by the tendinous-tenderness index KZ-S, where the value of KZ-S = 1 index means maximum tendinous—no tenderness and the value of KZ-S = 0 means no tendinous—maximum tenderness. The tumbling of the meat was performed in an agitator-tilt tumbler. The variable factors of the tumbling process were temperature (T), time (τ), rotational speed (ω) and angle of the tumbler drum inclination (α). The meat texture was tested using the universal testing machine TMS-Pro with a Warner–Bratzler knife. The results of the study were described using second-degree polynomial correlation functions with couplings and presented in the form of diagrams. The effect of the favorable reduction of the tendinous in favor of the tenderness of meat is most significantly influenced by the angle of the inclination of the drum of the tumbler and the time of massage. The optimal results for the tendinous-tenderness index KZ-S were obtained for the angle of the inclination of the drum of the tumbler α = 45° and tumbling duration τ = 50 min. For such tumbling parameters, the index KZ-S = 0.25 (reduced meat tendons). It is unfavorable, whereas massage tumbling at T = 0 °C, compared to higher and lower temperatures of massaging. The effect of the agitator speed ω depends on the time and temperature. The research results showed that the most favorable effects of the tendinous loss in favor of the tenderness, determined by the tendinous-tenderness index KZ-S, are obtained by the tumbling condition with high a high angle of inclination of the tank (α > 45°), a low value of the rotational speed (ω < 12 [1/min]), a longer time (τ > 50 min) and a temperature different from 0 °C.

Spontaneous helical flows in active nematics lying on a cylindrical surface.

Within the framework of the two-dimensional Ericksen-Leslie model, we explore the effect of geometric confinement on the spontaneous flow of active nematic gels. The nematic particles are assumed to flow on a cylindrical surface, while a degenerate tangential anchoring is enforced. Using the linear approximation of the motion equations, we show that there is a close interplay among extrinsic curvature, flow, director alignment, and activity. We find that the extrinsic curvature promotes the director alignment parallel to the cylindrical axis and is responsible for raising the critical threshold with respect to the flat case. Our analysis reveals a very rich scenario where the key quantities are the activity coefficient, the tumbling parameter, and the anisotropic viscosity ratio. Thus, solutions can exhibit a double periodicity in both the azimuthal and axial variables. As a consequence, the velocity field can make a finite angle with the cylinder axis and the active flow winds on the surface with a helical pattern, while the director oscillates around the cylinder generators. Our results can be validated on thin layers of nematic gels placed between two concentric cylinders and suggest which material properties are most suited for the design of active microfluidic devices.

Effect of Mechanical Tumbling Parameters on Surface Roughness and Edge Radius of Medical Grade Cobalt Chromium Alloy

Smoothly polished prosthesis surface is a crucial requirement in medical application and important feature that determine the proper response to corrosion and biocompatibility in the human body. Tumbling is one of the pre-polishing processes that can be conducted in order to improve the surface roughness of the machined prosthesis. However, the using of ceramic media for the tumbling process in medical application is not widely reported. This study was conducted to investigate the effect of mechanical tumbling parameters on the surface roughness of medical grade CoCr alloy by using alumina (Al2O3) based ceramic media. The experiment was performed with a different level of rotational speed (35, 55, and 75 rpm) and soaking time (4, 6 and 8 hours) of the tumbling process. The surface roughness of specimens before and after the process was measured using Mitutoyo Formtracer CS-5000 and the edge radius was measured using Olympus SZX9 microscope integrated with I-solution Lite software. It was figured that 6 hours tumbling time at 55 rpm showed the most significant reduction (32 %) in surface roughness (Ra) of the CoCr alloy specimen, while 8 hours tumbling time at 75 rpm showed the highest effect on the edge radius of the specimen at 63 % increment.

Oscillatory motion of sheared nanorods beyond the nematic phase

We study the role of the control parameter triggering nematic order (temperature or concentration) on the dynamical behavior of a system of nanorods under shear. Our study is based on a set of mesoscopic equations of motion for the components of the tensorial orientational order parameter. We investigate these equations via a systematic bifurcation analysis based on a numerical continuation technique, focusing on spatially homogeneous states. Exploring a wide range of parameters we find, unexpectedly, that states with oscillatory motion can exist even under conditions where the equilibrium system is isotropic. These oscillatory states are characterized by a wagging motion of the paranematic director, and they occur if the tumbling parameter is sufficiently small. We also present full nonequilibrium phase diagrams in the plane spanned by the concentration and the shear rate.

Some Aspects of the Rheo-Nmr Behavior of the Lyotropic Liquid Crystal Poly(γ-BENZYL-L-GLUTAMATE) in m-Cresol

We report the use of 2H NMR spectroscopy to study the director orientation in two nematic solutions of poly(γ-benzyl-L-glutamate) (PBLG) in m-cresol during simple shear flow and after its sudden cessation. In the range of applied shear rates$(\\dot{\\gamma} = 5 \\ldots 150 \\, \\hbox{s}^{\\!-\\!1})$, a steady-state NMR line shape is reached after a deformation of a few hundred units. Two different line shapes occur that can be related to distinct shear responses in mechanical rheology: the tumbling/wagging and the flow-aligning regimes. The relaxation after cessation of the shear is similar for both cases and essentially follows the “inhomogeneous reorientation” regime known from sudden-rotation NMR experiments. A fit of the relaxation curves indicates that the tumbling parameter λ is (slightly) less than one, as expected for a tumbling system.

Shear alignment behavior of nematic solutions induced by ultralong side-group liquid crystal polymers.

Addition of a low concentration of a very long (430 kg/mol) side group liquid crystal polymer is shown to produce dramatic changes in the flow characteristics of a calamitic nematic liquid crystal. This polymer causes a typical flow-aligning nematic liquid crystal to align near the velocity gradient direction rather than near the velocity direction, corresponding to having a tumbling parameter lambda<-1, for concentrations greater than 7.5% polymer. Such flow-aligning behavior has not been reported previously in a calamitic nematic. The large molecular weight of the present polymer relative to those examined in the prior literature is responsible for these new phenomena.

Full-tensor alignment criteria for sheared nematic polymers

The shear problem for nematic polymers consists in characterizing all stable stationary orientational distributions, steady and unsteady, versus shear rate and material parameters. Continuum theory [cf. Leslie (1968), Ericksen (1960)] provides formulas for the shear response of liquid crystals in terms of a single viscosity ratio, the Leslie tumbling parameter λL. Kuzuu and Doi (1983, 1984) developed a weak-flow asymptotic analysis of kinetic theory, which gives a molecular basis for all continuum theory parameters. In this paper, we develop a mesoscopic extension of the Kuzuu–Doi method, applicable to any tensor model. Our method yields orientational and rheological features of nematic polymers in weak shear with explicit formulas, parametrized by the parameters of the second-moment tensor model. This provides an explicit mesoscopic theory solution to the problem posed by Marrucci and Greco (1993) of how orientational degeneracy of quiescent nematic equilibria breaks in weak shear, leaving a finite set of steady stationary states, whose number, type (in-plane, out-of-plane), stability, phase transitions, and rheological properties scale with parameters of the model. An intriguing feature to resolve is the multiple transitions associated with distinct steady distributions (logrolling, in-plane flow alignment, out-of-plane alignment), each with its analog of the Leslie criterion |λL|=1. We illustrate our method and its physical predictions by solving the weak shear problem for the Doi quadratic closure model, whose material parameters are nematic concentration and molecular aspect ratio. The predictions are confirmed with numerical simulations of the model, and compared with experimental data in weak shear from the review article of Burghardt (1998). We further predict scaling properties due to changes in concentration and aspect ratio that are less readily available from experiments.The shear problem for nematic polymers consists in characterizing all stable stationary orientational distributions, steady and unsteady, versus shear rate and material parameters. Continuum theory [cf. Leslie (1968), Ericksen (1960)] provides formulas for the shear response of liquid crystals in terms of a single viscosity ratio, the Leslie tumbling parameter λL. Kuzuu and Doi (1983, 1984) developed a weak-flow asymptotic analysis of kinetic theory, which gives a molecular basis for all continuum theory parameters. In this paper, we develop a mesoscopic extension of the Kuzuu–Doi method, applicable to any tensor model. Our method yields orientational and rheological features of nematic polymers in weak shear with explicit formulas, parametrized by the parameters of the second-moment tensor model. This provides an explicit mesoscopic theory solution to the problem posed by Marrucci and Greco (1993) of how orientational degeneracy of quiescent nematic equilibria breaks in weak shear, leaving a finite set o...

Factors determining the reliable description of global tumbling parameters in solution NMR.

An accurate description of global tumbling of a protein is essential for correct analysis and interpretation of internal dynamics and thermodynamics. The accurate fitting of global tumbling parameters is affected by the number of experimental relaxation data points available for analysis, the distribution of data points over the domain of the function describing the tumbling, the measurement error associated with the data, the error associated with use of an approximate functional form, and errors in the protein structure. We present an analysis of the influence of these factors on the error in global tumbling parameters and the corresponding error in the calculated T(1)/T(2) values. We find that reduction of experimental and approximation error can compensate for a less-than-ideal quantity or distribution of data points, and that accurate parameters can be obtained for proteins with highly anisotropic distributions of bond vectors, as illustrated using the helical bundle protein G-CSF. This indicates that proteins with anisotropic distributions, such as the helical bundle class of proteins, should not summarily be excluded when selecting proteins for dynamic and thermodynamic analyses of (15)N backbone relaxation measurements.

Shear Aligning Properties of a Main-Chain Thermotropic Liquid Crystalline Polymer

We report the first direct, quantitative measurements of the shear aligning properties of a main-chain thermotropic liquid crystalline polymer (LCP). We find that a model thermotrope with alternating mesogen and spacer structure is of the shear aligning type throughout its nematic range. The director rotates uniformly in the shear flow toward the Leslie alignment angle as probed by in situ flow conoscopy. The Leslie alignment angle becomes progressively closer to the flow direction as temperature decreases, corresponding to a decrease of the tumbling parameter λ with increasing order parameter S. Our measurements of λ(S) enable direct comparison with predictions from molecular models, which predict that shear alignment prevails in the limit of flexible nematic chains. This is in direct contrast to rodlike lyotropic LCPs for which director tumbling is the rule.

An improved method for distinguishing between anisotropic tumbling and chemical exchange in analysis of 15N relaxation parameters.

Although an accurate description of global tumbling of a protein is essential for correct analysis of internal motions. proper distinction between the effects of anisotropic rotational diffusion and conformational exchange has remained a challenge. We present a novel two-part filtering procedure designed specifically to distinguish between the effects of anisotropy and conformational exchange. The efficacy of this method is assessed using synthetic data sets. The method is then applied to two proteins of dramatically different size and shape, OspA and SH3. The large size and extreme anisotropy of OspA provide a challenging case, where conformational exchange is a small perturbation of the effects of anisotropy on transverse relaxation rates. Conversely, in the chicken c-Src SH3 domain, with its small size and nearly spherical shape, anisotropy is a small perturbation of the effects of conformational exchange on transverse relaxation rates. Accurate extraction of the global tumbling parameters for each protein allows optimal characterization of conformational exchange processes, as well as ps-ns time scale motions.

Twist viscosity of mixtures of low molar mass nematics

Measurements of the twist viscosity, γ1(DLS) and twist elastic coefficient, K22(DLS) by electric-field-dependent dynamic light scattering (EFDLS) are reported for low molar mass nematics (LMMNs) 4′-heptyl-4-cyanobiphenyl (7CB) and 4′-octyl-4-cyanobiphenyl (8CB), and their binary mixtures at several temperatures in the nematic state. The results are compared with values (γ1(Rheol)=α3–α2) computed from rheological measurements of the Leslie viscosities α2 and α3. For the binary mixtures, at each temperature, the measured twist viscosity γ1(DLS) and corresponding twist elastic constant K22(DLS) show approximately a linear additive dependence on concentration. The calculated twist viscosity, γ1(Rheol), agrees with γ1(DLS) for the pure components, but is significantly smaller for the binary mixtures. Our observations appear to be consistent with a recent report of a discrepancy between values of the tumbling parameter λ, determined using a small-strain oscillatory optical technique, vs those measured by a rheological method. These results suggest that, in the rheological measurements at large strains, the rate of director rotation for mixtures may be affected by a flow-induced change in structure, e.g., shear-induced biaxiality.

A Bayesian statistical method for the detection and quantification of rotational diffusion anisotropy from NMR relaxation data.

It has recently become more widely appreciated that the presence of rotational diffusional anisotropy in proteins and other macromolecules can have a significant affect on the interpretation of NMR relaxation data in terms of molecular motion. In this paper, we show how commonly used NMR relaxation data (R(1), R(2), and NOE) obtained at two spectrometer frequencies can be analyzed using a Bayesian statistical approach to reliably detect and quantify the degree of rotational diffusion anisotropy. Our approach differs from previous methods in that it does not make assumptions concerning the internal motions experienced by the residues which are used to quantify the diffusion anisotropy, but rather averages the results over all internal motions consistent with the data. We demonstrate our method using synthetic data corresponding to isotropic, axially symmetric anisotropic, and fully asymmetric anisotropic rotational diffusion, as well as experimental NMR data. We compare the Bayesian statistical approach with a widely used method for extracting tumbling parameters using both synthetic and experimental data. While it can be difficult to separate the effects of chemical exchange from rotational anisotropy using this "standard" method, these effects are readily separated using Bayesian statistics. In addition, we find that the Bayesian statistical approach requires considerably less CPU time than an equivalent standard analysis.

Flow-aligning and tumbling in small-molecule liquid crystals: pure components and mixtures

The results of an experimental study to measure the tumbling parameter, λ, for various small-molecule liquid crystals and their mixtures are presented. The methods used include textural observations (twist walls), a direct method, a rheological method, and the oscillatory method developed by Mather, Pearson, and Burghardt in 1995. The single-component results are compared with a molecular theory derived in 1995 by Archer and Larson as well as Kroger and Sellers, which predicts the temperature dependence of λ, while the results from the binary mixtures are compared to a continuum theory derived by Rey in 1996, giving the concentration dependence of λ. The results from the four experimental methods agree with each other for single-component liquid crystals, but not for mixtures. This suggests a failure of the single director Leslie-Ericksen theory to describe the rheology of liquid crystal mixtures.

Spatial development of director orientation of tumbling nematic liquid crystals in pressure-driven channel flow

The Leslie-Ericksen equations in the tumbling regime were solved for developing flow between parallel plates to study the two-dimensional spatial development of director orientation. Calculations were carried out using the physical properties of 8CB. Texture development is governed by the number of director rotations required to reach the equilibrium distribution for fully-developed flow, with complex textures developing at large values of both the tumbling parameter ( e) and the Ericksen number (Er). The entry length for structure for a given value of e is a non-monotonic function of Er, and entry lengths of >40 can occur for the parameter range studied here when Er is near a value corresponding to a discontinuous jump in the number of rotations required to reach equilibrium.

Molecular theory for the Leslie viscosities of nematics

Abstract Simple analytic expressions for all six Leslie viscosities for nematics are obtained from the molecular theory for rigid prolate molecules. The theory relates the viscosities to the second and fourth moments, P 2 and P 4, of the molecular distribution function, the aspect ratio a of the molecules, and an isotropic viscosity that accounts for the effects of orientation-independent momentum transport. The theory is obtained by using expressions derived from a molecular theory by Kuzuu and Doi, as well as an approximate formula for the ‘tumbling parameter’ λ in terms of P 2 and P 4; this approximate formula agrees well with data for many small-molecule nematics. Using the Maier-Saupe potential to compute P 2 and P 4, we find that the temperature dependencies of all six Leslie viscosities are in surprisingly good agreement with measurements of these viscosities for MBBA.