An analytical solution for the elastoplastic response of a continuous fiber composite under uniaxial loading

A continuous fiber composite is modelled by a two-element composite cylinder in order to predict the elastoplastic response of the composite under a monotonically increasing tensile loading parallel to fibers. The fibers and matrix are assumed to be elastic-perfectly plastic materials obeying Hill's and Tresca's yield criteria, respectively. Here, the composite behavior when the fibers yield prior to the matrix is investigated

Cryogenic-coolant He-4-superconductor interaction

The thermodynamic and thermal interaction between a type 2 composite alloy and cryo-coolant He4 was studied with emphasis on post quench phenomena of formvar coated conductors. The latter were investigated using a heater simulation technique. Overall heat transfer coefficients were evaluated for the quench onset point. Heat flux densities were determined for phenomena of thermal switching between a peak and a recovery value. The study covered near saturated liquid, pressurized He4, both above and below the lambda transition, and above and below the thermodynamic critical pressure. In addition, friction coefficients for relative motion between formvar insulated conductors were determined

Symmetry-Breaking Motility

Locomotion of bacteria by actin polymerization, and in vitro motion of spherical beads coated with a protein catalyzing polymerization, are examples of active motility. Starting from a simple model of forces locally normal to the surface of a bead, we construct a phenomenological equation for its motion. The singularities at a continuous transition between moving and stationary beads are shown to be related to the symmetries of its shape. Universal features of the phase behavior are calculated analytically and confirmed by simulations. Fluctuations in velocity are shown to be generically non-Maxwellian and correlated to the shape of the bead.Comment: 4 pages, 2 figures, REVTeX; formatting of references correcte

Faddeev-Jackiw Analysis of Topological Mass Generating Action

We analyze the gauge symmetry of a topological mass generating action in four dimensions which contains both a vector and a second rank antisymmetric tensor fields. In the Abelian case, this system induces an effective mass for the vector gauge field via a topological coupling $B \wedge F$ in the presence of a kinetic term for the antisymmetric tensor field $B$, while maintaining a gauge symmetry. On the other hand, for the non-Abelian case the $B$ field does not have a gauge symmetry unless an auxiliary vector field is introduced to the system. We analyze this change of symmetry in the Faddeev-Jackiw formalism, and show how the auxiliary vector field enhances the symmetry. At the same time this enhanced gauge symmetry becomes reducible. We also show this phenomenon in this analysis.Comment: 20 pages, REVTe

Aging to Equilibrium Dynamics of SiO2

Molecular dynamics computer simulations are used to study the aging dynamics of SiO2 (modeled by the BKS model). Starting from fully equilibrated configurations at high temperatures T_i =5000K/3760K the system is quenched to lower temperatures T_f=2500K, 2750K, 3000K, 3250K and observed after a waiting time t_w. Since the simulation runs are long enough to reach equilibrium at T_f, we are able to study the transition from out-of-equilibrium to equilibrium dynamics. We present results for the partial structure factors, for the generalized incoherent intermediate scattering function C_q(t_w, t_w+t), and for the mean square displacement msd(t_w,t_w+t). We conclude that there are three different t_w regions: (I) At very short waiting times, C_q(t_w, t_w+t) decays very fast without forming a plateau. Similarly msd(t_w,t_w+t) increases without forming a plateau. (II) With increasing t_w a plateau develops in C_q(t_w, t_w+t) and msd(t_w,t_w+t). For intermediate waiting times the plateau height is independent of t_w and T_i. Time superposition applies, i.e. C_q=C_q(t/t_r) where t_r=t_r(t_w) is a waiting time dependent decay time. Furthermore C_q=C(q,t_w,t_w+t) scales as C_q=C(q,z(t_w,t) where z is a function of t_w and t only, i.e. independent of q. (III) At large t_w the system reaches equilibrium, i.e. C_q(t_w,t_w+t) and msd(t_w,t_w+t) are independent of t_w and T_i. For C_q(t_w,t_w+t) we find that the time superposition of intermediate waiting times (II) includes the equilibrium curve (III).Comment: 9 pages, 11 figures, submission to PR

\u3ci\u3eHaemophilus influenzae\u3c/i\u3e Type b Polysaccharide Vaccine: An Efficacy Study

The Haemophilus influenzae type b polysaccharide vaccine was licensed for use in the United States in April 1985. Postlicensure case-control efficacy studies have yielded markedly different estimates of efficacy, leading to contradictory recommendations to practicing physicians. To obtain additional information about the efficacy of the vaccine, we studied cases of invasive Haemophilus influenzae type b disease ascertained through active surveillance in areas with a total population of 34 million. We enrolled children 24 to 59 months of age who did not attend day-care centers. (Data from our day-care study have been published elsewhere.) For each case child, as many as three 24- to 59-month-old control children were chosen from a roster of acquaintances supplied by the child\u27s parent. Conditional logistic regression was used, and vaccine efficacy was estimated to be 62% (95% confidence interval = 0%, 85%), which did not change significantly after adjusting for age and parental smoking, variables that were significantly different for case and control children. Results of this study support our previous finding of a positive protective efficacy, albeit lower than the efficacy of 90% found in children 18 to 71 months of age in the Finnish prelicensure trial

Relationship Between Static Mobility of the First Ray and First Ray, Midfoot, and Hindfoot Motion During Gait

The relationship between a static measure of dorsal first ray mobility and dynamic motion of the first ray, midfoot, and hindfoot during the stance phase of walking was investigated in healthy, asymptomatic subjects who represented the spectrum of static flexibility. Static first ray mobility of 15 subjects was measured by a load cell device and ranged from stiff (3.1 mm) to lax (8.0 mm). Using three-dimensional motion analysis, mean first ray dorsiflexion/eversion and mid-/hindfoot eversion peak motion, time-to-peak, and eversion excursion were evaluated. Subjects with greater static dorsal mobility of the first ray demonstrated significantly greater time-topeak hindfoot eversion and eversion excursion (p \u3c .01), and midfoot peak eversion and eversion excursion (p \u3c .01). No significant association was found between static first ray mobility and first ray motion during gait. This research provides evidence that the dynamic response of the foot may modulate the consequences of first ray mobility and that compensory strategies are most effective when static measures of dorsal mobility are most extreme