Common bearing material has highest fatigue life at moderate temperature

AISI 52100, a high carbon chromium steel, has the longest fatigue life of eight bearing materials tested. Fatigue lives of the other materials ranged from 7 to 78 percent of the fatigue life of AISI 52100 at a temperature of 340 K (150 F)

Flexural fatigue of hollow rolling elements

Hollow cylindrical bars were tested in the rolling-contact fatigue tester to determine the effects of material and outside diameter to inside diameter (OD/ID) ratios of 2.0, 1.6, 1.4, and 1.2 on fatigue failure mode and subsequent failure propagation. The range of applied loads with these OD/ID ratios resulted in maximum tangential tensile stresses ranging from 165 to 655 megapascals (24,000 to 95,000 psi) at the bore surface. Flexural failures of the hollow test bars occurred when this bore stress was 490 megapascals (71,000 psi) or greater with AISI 52100 hollow bars and 338 megapascals (49,000 psi) or greater with AISI M-50 hollow bars. Good correlation was obtained in relating the failures of these hollow bars with flexural failures of drilled balls from previously published full scale bearing tests

Diffusion in simple fluids

Computed self diffusion coefficients for the Lennard-Jones and hard sphere fluids are related by Dej = DNs(aB) exp (--e/2kB T) where σB=σLJ(2/[1+ii(1+2kBT/ε)])1/6, the effective hard sphere diameter, is the (average) distance of closest approach in collisions between molecules which interact with the positive part of the LJ potential, and the Arrhenius term reflects the influence of the negative part. σLJ and ε are the size and well depth parameters. Measured diffusion coefficients of the halomethane liquids are reproduced by the equation over wide ranges of temperature and density and do not reveal any influence of the inelastic effects associated with molecular anisotropy

Integration of Peripheral and Glandular Regulation of Triiodothyronine Production by Thyrotropin in Untreated and Thyroxine-Treated Subjects

Objective: We evaluated the roles of central and peripheral T3 regulation. Design and Methods: In a prospective study involving 1796 patients the equilibria between FT3 and TSH were compared in untreated and L-T4-treated patients with varying functional states, residual thyroid secretory capacities and magnitudes of TSH stimulation. Results: T3 concentrations were stable over wide variations in TSH levels (from 0.2 to 7 mU/l) and endogenous T4 production in untreated patients, but unbalanced in L-T4-treated athyreotic patients where T3 correlated with exogenous T4 supply. T3 stability was related to TSH-stimulated deiodinase activity by clinical observation, as predicted by theoretical modelling. Deiodinase activity in treated patients was reduced due to both diminished responsiveness to TSH and lack of thyroidal capacity. Deiodinase activity was increased in high thyroid volume, compared to lower volumes in euthyroid patients (< 5 ml, p<0.001). While deiodinase differed between euthyroid and subclinically hypothyroid patients in high volume, 26.7 nmol/s (23.6, 29.2), n=214 vs 28.9 nmol/s (26.7, 31.5), n=20, p=0.02, it was equivalent between the two functional groups in low volume, 23.3 nmol/s (21.3, 26.1), n=117 vs 24.6 nmol/s (22.2, 27.5), n=38, p=0.22. Conclusions: The findings suggest that the thyroid gland and peripheral tissues are integrated in the physiological process of T3 homeostasis in humans via a feed-forward TSH motif, which coordinates peripheral and central regulatory mechanisms. Regulatory and capacity deficiencies collectively impair T3 homeostasis in L-T4-treated patients

Local orientations of fluctuating fluid interfaces

Thermal fluctuations cause the local normal vectors of fluid interfaces to deviate from the vertical direction defined by the flat mean interface position. This leads to a nonzero mean value of the corresponding polar tilt angle which renders a characterization of the thermal state of an interface. Based on the concept of an effective interface Hamiltonian we determine the variances of the local interface position and of its lateral derivatives. This leads to the probability distribution functions for the metric of the interface and for the tilt angle which allows us to calculate its mean value and its mean square deviation. We compare the temperature dependences of these quantities as predicted by the simple capillary wave model, by an improved phenomenological model, and by the microscopic effective interface Hamiltonian derived from density functional theory. The mean tilt angle discriminates clearly between these theoretical approaches and emphasizes the importance of the variation of the surface tension at small wave lengths. Also the tilt angle two-point correlation function is determined which renders an additional structural characterization of interfacial fluctuations. Various experimental accesses to measure the local orientational fluctuations are discussed.Comment: 29 pages, 12 figure

Precision measurement of the branching ratio in the 6P3/2 decay of BaII with a single trapped ion

We present a measurement of the branching ratios from the 6P3/2 state of BaII into all dipoleallowed decay channels (6S1/2, 5D3/2 and 5D5/2). Measurements were performed on single 138Ba+ ions in a linear Paul trap with a frequency-doubled mode-locked Ti:Sapphire laser resonant with the 6S1/2->6P3/2 transition at 455 nm by detection of electron shelving into the dark 5D5/2 state. By driving a pi Rabi rotation with a single femtosecond pulse, a absolute measurement of the branching ratio to 5D5/2 state was performed. Combined with a measurement of the relative decay rates into 5D3/2 and 5D5/2 states performed with long trains of highly attenuated 455 nm pulses, it allowed the extraction of the absolute ratios of the other two decays. Relative strengths normalized to unity are found to be 0.756+/-0.046, 0.0290+/-0.0015 and 0.215+/-0.0064 for 6S1/2, 5D3/2 and 5D5/2 respectively. This approximately constitutes a threefold improvement over the best previous measurements and is a sufficient level of precision to compare to calculated values for dipole matrix elements.Comment: 6 pages, 5 figures, 1 tabl

Microscopic theory of solvent mediated long range forces: influence of wetting

We show that a general density functional approach for calculating the force between two big particles immersed in a solvent of smaller ones can describe systems that exhibit fluid-fluid phase separation: the theory captures effects of strong adsorption (wetting) and of critical fluctuations in the solvent. We illustrate the approach for the Gaussian core model, a simple model of a polymer mixture in solution and find extremely attractive, long ranged solvent mediated potentials between the big particles for state points lying close to the binodal, on the side where the solvent is poor in the species which is favoured by the big particles.Comment: 7 pages, 3 figures, submitted to Europhysics Letter

Solvent mediated interactions between model colloids and interfaces: A microscopic approach

We determine the solvent mediated contribution to the effective potentials for model colloidal or nano- particles dispersed in a binary solvent that exhibits fluid-fluid phase separation. Using a simple density functional theory we calculate the density profiles of both solvent species in the presence of the `colloids', which are treated as external potentials, and determine the solvent mediated (SM) potentials. Specifically, we calculate SM potentials between (i) two colloids, (ii) a colloid and a planar fluid-fluid interface, and (iii) a colloid and a planar wall with an adsorbed wetting film. We consider three different types of colloidal particles: colloid A which prefers the bulk solvent phase rich in species 2, colloid C which prefers the solvent phase rich in species 1, and `neutral' colloid B which has no strong preference for either phase, i.e. the free energies to insert the colloid into either of the coexisting bulk phases are almost equal. When a colloid which has a preference for one of the two solvent phases is inserted into the disfavored phase at statepoints close to coexistence a thick adsorbed `wetting' film of the preferred phase may form around the colloids. The presence of the adsorbed film has a profound influence on the form of the SM potentials.Comment: 17 Pages, 13 Figures. Accepted for publication in Journal of Chemical Physic