The generalized advancing conformal contact problem with friction,pin loads and remote loading – Case of rigid pin

The advancing, frictional contact problem for a rigid pin indenting an infinite plate with a circular hole is considered. The formulation is general, and considers remotely applied plate-stresses in addition to pin loads. Using the theory of generalized functions, it is found that the governing equation in full sliding is a singular integro-differential equation (SIDE). Partial-slip behavior is governed by an implicit, coupled singular integral equation (SIE) pair. Numerical solutions are presented for both types of problems. It is found that the contact tractions in monotonic loading become independent of the coefficient of friction above a certain threshold value. Finally, problems involving typical ‘fretting-type’ pin loads with and without remote-stresses are also investigated, revealing remarkable effects of the degree of conformality and load path on the steady-state traction distributions.     

Interplay between symmetry breaking and quasiperiodicity in spin chains

Summary An isotropicXY spin chain is studied in the presence of symmetry-breaking perturbations and a periodic modulation with wave vector incommensurate with the periodicity of the chain. The ground states of the system are obtained in terms of a two-dimensional area-preserving map defined on a cylinder of finite extent. The spin distributions are found to exhibit KAM and Cantorus phases with the onset of transition being the critical phase. The relationship between these three phases and the magnetic properties of the model is also studied. The presence of two competing easy axes for spin alignment results in incommensurate reentrant phase diagram with fractal boundary.     

The Mössbauer effect of ferroelectric transitions

The observed anomalous behavior of the Mössbauer fraction during the ferroelectric transition in PbTiO₃ is explained using a model consistent with Cochran's analysis of ferroelectricity. Our calculations show no anomalous behavior in the second order Doppler shift.     

Uric acid determination using an aldehyde dehydrogenase and a uricase-aldehyde dehydrogenase nylon-tube reactor

Summary The preparation of a coimmobilized uricase-aldehyde dehydrogenase nylon-tube reactor is described and the reactor is characterized. Routine estimation of uric acid by use of a continuous-flow system can be performed with either an aldehyde dehydrogenase nylon-tube reactor aided by catalase and uricase in solution or a uricase-aldehyde dehydrogenase coupled-enzyme reactor, with only catalase in solution. The methods have been rigorously tested by inter-method comparison, precision analysis, recovery, interferences, and cofactor requirement. More than 5000 tests can be carried out with one coupled-enzyme reactor, which reduces the cost of enzymes in analysis to a negligible amount.Part of this paper was presented as poster at the Tagung für Biochemische Analytik, Munich 1980. [Abstract in this Journal 301, 161 (1980)]     

Parameter scaling in the decoherent quantum-classical transition for chaotic systems

The quantum to classical transition for a system depends on many parameters, including a scale length for its action, variant Planck's over 2 pi, a measure of its coupling to the environment, D, and, for chaotic systems, the classical Lyapunov exponent, lambda. We propose measuring the proximity of quantum and classical evolutions as a multivariate function of (Planck's over 2 pi,lambda,D) and searching for transformations that collapse this hypersurface into a function of a composite parameter zeta= Planck's over 2 pi alpha)lambda beta D gamma. We report results for the quantum Cat Map and Duffing oscillator, showing accurate scaling behavior over a wide parameter range, indicating that this may be used to construct universality classes for this transition.     

Systematics of final state screening in 5d metals

The experimental systematics of the Auger parameter, ε, in the 3d metal series have been well described in terms of a quasi-atomic model of screening. Whether these results are transferrable from a narrow to a wide d-band series has been moot. We present, for the first time, measurements of ε in the 5d series, manifesting systematics similar to those in the 3d series. Model calculations support the validity of the qam.     

Linear,hydrodynamic flow in a rotating saturated porous medium

Linear, steady, axisymmetric flow of a homogeneous fluid in a rigid, bounded, rotating, saturated porous medium is analyzed. The fluid motions are driven by differential rotation of horizontal boundaries. The dynamics of the interior region and vertical boundary layers are investigated as functions of the Ekman number E(=v/ΩL ²) and rotational Darcy 3 numberN(=kΩ/v) which measures the ratio between the Coriolis force and the Darcy frictional term. IfN≫E ^−1/2, the permeability is sufficiently high and the flow dynamics are the same as those of the conventional free flow problem with Stewartson'sE ^1/3 andE ^1/4 double layer structure. For values ofN≤E ^−1/2 the effect of porous medium is felt by the flow; the Taylor-Proudman constraint is no longer valid. ForN≪E ^−1/3 the porous medium strongly affects the flow; viscous side wall layer is absent to the lowest order and the fluid pumped by the Ekman layer, returns through a region of thicknessO(N ⁻¹). The intermediate rangeE ^−1/3≪N≪E ^−1/2 is characterized by double side wall layer structure: (1)E ^1/3 layer to return the mass flux and (ii) (NE)^1/2 layer to adjust the interior azimuthal velocity to that of the side wall. Spin-up problem is also discussed and it is shown that the steady state is reached quickly in a time scaleO(N).     

Solvent extraction studies of indium-mixed chelates withβ-diketones in benzene media

Mixed chelate formation of indium with severalβ-diketones has been studied from benzene media. The extraction of indium by BFA and FFA has been carried out as a function of pH and concentration of the ligand to ascertain the nature of the complexes. The extraction of indium by a mixture ofβ-diketones,viz., BFA-BA, BFA-DBM, FFA-BA, FFA-DBM, FFA-BFA and DBM-BA has also been studied as a function of the solution parameters. The nature of the mixed complexes formed as well as their equilibrium constants, statistical and stabilisation constants have been evaluated.     

A novel kinetic and mechanistic study of the oxidation of pinacol by acid bromate—homogeneous catalysis of maganous ions

A detailed kinetic study of the Mn(II)-catalyzed and -uncatalyzed oxidation of pinacol by bromate has been carried out in aqueous acetic acid media containing Hg(II) ions. The uncatalyzed reaction exhibits 1.5 order that is, 0.5 order in [pinacol] and 1.0 in [bromate]. A decrease in k₁ by increasing [bromate] has been accounted for due to the formation of Br₂O₅, which is inactive toward reduction. Mn(II)-catalyzed oxidation follows first order in [oxidant], 0.5 order in [manganous ion], and variable order with respect to [pinacol]. At lower [pinacol] (0.005–0.025M) the order is 0.5, but at higher concentration (0.03–0.15M) it becomes negative (?1.0). These observations can be accounted for qualitatively by the formation of 1:1 and 1:2 Mn(II)–pinacol complexes of which only 1:1 is active toward bromate oxidation. At higher [pinacol] the ratio of 1:2 and 1:1 complexes reached 98.2. All reactions were accelerated with acidity, and the rate constant follows the h₀ function. Participation of H₂O in the rate-limiting step and a free-radical mechanism were proposed for the manganous-ion-catalyzed reaction, whereas for the uncatalyzed reaction this was not true. The effects of NaClO₄, Na₄P₂O₇, and the dielectric constant of the media are also in accordance with the proposed mechanism.