Two-component Body Research Articles

Void growth in swelled porous polymeric gels

A finite-strain theory for the study of the overall behavior of polymeric gels containing microvoids is presented. The swollen porous polymeric gel is modeled as a two-component body composed of two incompressible materials, namely, an elastic porous polymer imbibed with a solvent. The chemical equilibrium is assumed to be preponderate at the interface between the porous polymer and its environment where the chemical potential of the solvent is fixed. The initially dry porous polymer undergoes large deformations induced by absorption of a solvent from the environment and mechanical loading. In this paper an attempt is made toward obtaining an estimation of the macroscopic responses of the swollen porous polymer to prescribed proportional loadings. To this end, a two-level representation of the material at hand for which the Representative Volume Element (RVE) imbibed with a solvent is a simple axisymmetric cylinder composed of a homogeneous matrix surrounding a spherical void, is considered. The numerical study addresses the situation where the RVE is subjected to prescribed axial and lateral overall stresses under conditions of constant overall stress triaxiality. For fixed values of the Flory-Huggins parameter and nominal concentration of the solvent, the overall stress-strain behavior of the RVE model, the influence of the initial porosity, and the prescribed stress triaxiality ratio have been obtained.

O kilku możliwych śladach duale tantum w językach indoeuropejskich

On Some Possible Traces of Duale Tantum in Indo-European LanguagesThe paper is devoted to three selected Indo-European nouns that can be considered as dualia tantum. On the basis of lexical data preserved in historical Indo-European languages, I have reconstructed three probable archetypes:(1) IE. *ḱelī- (< PIE. *ḱel-ih1) f. duale tantum ‘two-component body of a human or animal’ is precisely attested in Avestan sairi f. du. tant. ‘two solid components of the human and animal body, i.e. the skin together with meat and bones; body, dead body, corpse’. The primitive dual form seems to appear in Old Indic (Vedic) śárīram n. ‘body, body frame, solid parts of the body, pl. bones’, also ‘a dead body’ (a derivative noun created by means of the suffix -ra- < IE. *-lo-), cf. also Pali sarīra- n. ‘body’, Prakrit sarira- n. ‘id.’; West Pahari sarīr, Old Gujarati saïra, sayara n. ‘body’.(2) IE. *agu̯ sī- f. sg. ‘axe’ (< PIE. *h2egu̯ s-ih1 f. du. tant. ‘double axe, two-edged battle-axe’) can be seen not only in the Germanic languages (e.g. Gothic aqisi f. ‘axe’, Old High German acchus ‘id.’, English axe ‘id.’), but also in some Greek-Latin derivatives (see Greek ἀξῑ́νη f. ‘double axe, twoedged battle-axe’, Modern Greek αξίνα f. ‘hoe, mattock, pickaxe’, Latin ascia f. ‘axe, trowel’). The original meaning ‘double axe, two-edged item’ is firmly confirmed by the Greek data.(3) IE. *oldhī- f. sg. ‘a kind of boat’ (< PIE. *h3eldh-ih1 f. du. tant. ‘a primitive boat built from two troughs’ ← *h3eldh- f. ‘trough’) is reflected in Tocharian AB olyi ‘boat’, Lithuanian eldijà f. ‘a canoe, a boat hollowed out from one trunk’, dial. aldijà f. ‘id.’, Old Church Slavic ladija f. ‘πλοῖον, σκάφη / navis, navicula’, also alъdija ‘id.’, Old Czech lodí f. ‘ship, boat’, Polish łódź f. ‘boat’ and so on. The basic noun *h3eldh- ‘trough’ is securely attested in the Germanic languages, cf. Norwegian alde f. ‘wooden trough’, Danish olde ‘id.’ (< Proto-Germanic *aldōn- f.).

Independent and Combined Effects of Sex and Biological Maturation on Motor Coordination and Performance in Prepubertal Children.

Sex differences and maturation-associated variation in fitness and motor coordination were examined in children aged 8-9 years (n = 128, 67 girls). Assessments included stature and body mass, two-component body composition, percentage of predicted adult stature (as an index of biological maturation), and motor performance and coordination (Körperkoordinationstest für Kinder). Compared to girls, boys were less advanced in maturation status, possessed larger fat mass, demonstrated superior performances in six tests of fitness, and obtained one superior score on the Körperkoordinationstest für Kinder. After controlling for somatic maturation, sex differences persisted in the two multivariate domains: motor performance and motor coordination.

Two types of interface defects

The solution of a plane problem in the theory of elasticity for a two-component body with an interface, a finite part of which is either weakly distorted or is a weakly curved crack is constructed using the perturbation method. In the first case, it is assumed that the discontinuities in the forces and displacements at the interface are known, and, in the second case, the non-equilibrium nature of the load in the crack is taken into account. General quadrature formulae are derived for the complex potentials, which enable any approximation to be obtained in terms of elementary functions in many important practical cases. An algorithm is indicated for calculating each approximation. Families of defects are studied, the form of which is determined by power functions. The effect of the amplitude of the distortion and the shape of the interface crack on the Cherepanov–Rice integral as well as the shape of the distorted part of the interface on the stress concentration is investigated in the first approximation. An analysis of the applicability of the oscillating solution for a distorted interface crack is carried out. The results of the calculations are shown in the form of graphical relations.

Reliability and Detecting Change Following Short-Term Creatine Supplementation: Comparison of Two-Component Body Composition Methods

The purpose of the present study was twofold: firstly, to assess the reliability of various body composition methods, and secondly, to determine the ability of the methods to estimate changes in fat-free mass (FFM) following creatine (Cr) supplementation. Fifty-five healthy male athletes (weight 78.3 +/- 10.3 kg, age 21 +/- 1 years) gave informed consent to participate in this study. Subjects' FFM was estimated by hydrostatic weighing (HW), air-displacement plethysmography (ADP), bioelectrical impedance analysis (BIA), near-infrared spectroscopy (NIR), and anthropometric measurements (ANTHRO). Measurements were taken on 2 occasions separated by 7 days to assess the reliability of the methods. Following this, 30 subjects returned to the laboratory for an additional test day following 7 days of Cr supplementation (20 g.d(-1) Cr + 140 g.d(-1) dextrose) to assess each method's ability to detect acute changes in FFM. In terms of reliability, we found excellent test-retest correlations for all 5 methods, ranging from 0.983 to 0.998 (p < 0.001). The mean biases for the 5 methods were close to 0 (range -0.1 to 0.3 kg) and their 95% limits of agreement (LOAs) were within acceptable limits (HW = -1.1 to 1.7 kg; ADP = -1.1 to 1.2 kg; BIA = -1.0 to 1.0 kg; NIR = -1.4 to 1.4 kg); however, the 95% LOAs were slightly wider for ANTHRO (-2.4 to 2.6 kg). Following Cr supplementation there was a significant increase in body mass (from 77.9 +/- 10.1 kg to 78.9 +/- 10.3 kg, p = 0.000). In addition, all 5 body composition techniques detected the change in FFM to a similar degree (mean change: HW = 0.9 +/- 0.6 kg; ADP = 0.9 +/- 0.6 kg; BIA = 0.9 +/- 0.6 kg; NIR = 0.8 +/- 0.5 kg; ANTHRO = 1.0 +/- 0.7 kg; intraclass correlation coefficient = 0.962). We conclude that between-day differences in FFM estimation were within acceptable limits, with the possible exception of ANTHRO. In addition, all 5 methods provided similar measures of FFM change during acute Cr supplementation.

Complex Optimal Control of a Thermally Stressed State of a Two-Component Body

New problems of optimal control for a thermally stressed state of a two-component solid body are considered in the paper. The body contains a thin and a weakly thermally penetrating inclusion. The existence of unique optimal controls is proved for every described case with quadratic cost functionals.

Hydration of the fat-free body mass in children and adults: implications for body composition assessment.

Previous studies have shown that children have a higher aqueous fraction of the fat-free body mass (FFM) than young adults. In older adults, methodological differences among studies limit evaluation of potential age-related differences in the water content of the FFM (W/FFM). Therefore, we determined W/FFM in 28 healthy white prepubescent children (age = 5-10 yr), 31 young adults (age = 22-39 yr), and 62 older adults (age = 65-84 yr), using 2H2O dilution to estimate total body water and a multicomponent approach based on body density, total body water, and regional bone mineral density to estimate FFM. To quantify the extent to which variation in W/FFM affects percent fat estimation error, differences in percent fat between our multicomponent approach and the Siri two-component model were related to W/FFM. Prepubescent children (72.7 +/- 1.6%) and older adults (72.5 +/- 1.4%) were found to have significantly higher (P < 0.01) mean W/FFM than young adults (70.8 +/- 1.2%). Differences in percent fat between the multicomponent and two-component models ranged from -10 to 6% fat and were significantly associated with W/FFM (r = -0.62, P < 0.0001). We conclude that prepubescent children and older adults, on average, have a higher W/FFM than young adults, and that, in adults, individual differences in W/FFM account for a substantial portion of the percent fat estimation errors associated with the use of two-component body composition models.

Elastoplastic model with damage for strain softening geomaterials

The paper examines certain important aspects of a rate independent model that accounts for distributed damage due to microcrack growth. Material behavior is considered as a mixture of two elastic-plastic interacting components, one termed topical (undamaged), and the other termed damaged. Energy considerations show the equivalence of the two-component body to an elastic-plastic body containing cracks; the equivalence is considered in the Griffith sense. The mechanisms of failure are considered and discussed with respect to multiaxial stress paths. An explanation of failure, at the microlevel, is given. A series of laboratory tests on a concrete are used to illustrate the development of failure.

Residual-stress determination of concentric layers of cylindrically orthotropic materials

Equations have been obtained for determining residual stresses in the wall of a hollow, axially symmetric body consisting of concentric layers of elastically dissimilar materials, all having cylindrical elastic orthotropy. These equations permit residual normal stresses in the radial, circumferential, and axial directions and residual shear stresses on planes normal to the axis of the body to be calculated from measurements of the strains developed on the inner or outer cylindrical surface of the body as thin layers of stressed material are serially removed from the outer or inner surfaces, respectively. The equations are applied to a parametric study of stresses in an elastically isotropic, two-component body to determine the nature of the differences in stresses between the composite body and a homogeneous body as a function of the difference in elastic constants.

Forced precession of neutron stars

The dynamics of a neutron star subject to an external torque is investigated. The neutron star is treated as a two-component body, one component being the solid crust together with the interior plasma coupled to it by a magnetic field, the other component being the interior neutron superfluid. The latter is treated with classical hydrodynamics.