Rapid Sliding Indentation with Friction of a Pre-Stressed Thermoelastic Material

A rigid indentor travels with a constant speed over the surface of an isotropic thermoelastic half-space. Friction exists between the indentor and half-space, and the latter is initially in equilibrium at a uniform temperature under a uniform normal pre-stress. This pre-stress, below but near yield, is assumed to produce deformations that dominate the additional deformations due to indentation. Thus, the process is treated as one of small deformations superposed upon (relatively) large. The governing equations for the superposed deformation are those of nonisotropic coupled thermoelasticity. A steady-state two-dimensional study uses robust asymptotic analytical solutions to reduce the associated mixed boundary value problem to a classical singular integral equation which can be solved analytically. The solutions show that the pre-stress-induced de facto nonisotropy alters the values of the rotational and dilatational wave and Rayleigh speeds in the half-space and, in the case of a compressive pre-stress, generates a second, lower, critical speed. In addition, pre-stress generates noncritical sliding speeds at which the friction-dependent integral equation eigenvalue changes sign. For purposes of illustration, expressions for the half-space surface temperature change and its average over the contact zone, the equations necessary to determine contact zone size and location, the resultant moment on the indentor, and the maximum compressive stress on the contact zone are presented for a parabolic indentor. This revised version was published online in August 2006 with corrections to the Cover Date.     

The dynamic stress intensity factor for a crack due to arbitrary rectilinear screw dislocation motion

The dynamic stress intensity factor for a stationary semi-infinite crack in an elastic plane due to the rectilinear motion of a screw dislocation is obtained analytically. The intensity factor is studied for its dependence on the (initial) dislocation position, orientation and speed. The speed is subsonic and possibly non-uniform. The position and orientation are arbitrary, so that crack-dislocation intersection is considered. It is assumed that a dislocation traveling toward the crack surface arrests upon arrival. It is found that, in general, dislocation motion initiation and arrest cause discontinuities in the intensity factor. In the latter instance, the factor takes on a constant value and, in the case of arrest on the crack surface, this value depends only on the initial dislocation position.     

Structure and optical properties of several organic-inorganic hybrids containing corner-sharing chains of bismuth iodide octahedra

Two organic-inorganic bismuth iodides of the form (H3N-R-NH3)BiI5 are reported, each containing long and relatively flexible organic groups, R. The norganic framework in each case consists of distorted BiI6 octahedra sharing cis vertexes to form zigzag chains. Crystals of (H3NC18H24S2NH3)BiI5 were grown from a slowly cooled ethylene glycol/2-butanol solution containing bismuth(III) iodide and AETH.2HI, where AETH = 1,6-bis[5'-(2' '-aminoethyl)-2'-thienyl]hexane. The new compound, (H2AETH)BiI5, adopts an orthorhombic (Aba2) cell with the lattice parameters a = 20.427(3) A, b = 35.078(5) A, c = 8.559(1) A, and Z = 8. The structure consists of corrugated layers of BiI5(2-) chains, with Bi-I bond lengths ranging from 2.942(3) to 3.233(3) A, separated by layers of the organic (H2AETH)(2+) cations. Crystals of the analogous (H3NC12H24NH3)BiI5 compound were also prepared from a concentrated aqueous hydriodic acid solution containing bismuth(III) iodide and the 1,12-dodecanediamine (DDDA) salt, DDDA.2HI. (H2DDDA)BiI5 crystallizes in an orthorhombic (Ibam) cell with a = 17.226(2) A, b = 34.277(4) A, c = 8.654(1) A, and Z = 8. The Bi-I bonds range in length from 2.929(1) to 3.271(1) A. While the inorganic chain structure is nearly identical for the two title compounds, as well as for the previously reported (H3NC6H12NH3)BiI5 [i.e., (H2DAH)BiI5] structure, the packing of the chains is strongly influenced by the choice of organic cation. Optical absorption spectra for thermally ablated thin films of the three organic-inorganic hybrids containing BiI5(2-) chains are reported as a function of temperature (25-290 K). The dominant long-wavelength feature in each case is attributed to an exciton band, which is apparent at room temperature and, despite the similar inorganic chain structure, varies in position from 491 to 541 nm (at 25 K).     

Instrumentation and Measurement Issues for Nanometer Particles: Workshop Summary

Journal of Nanoparticle Research -     

Probing Balitsky-Fadin-Kuraev-Lipatov dynamics in the dijet cross section at large rapidity intervals in pp collisions at sqrt[s]=1800 and 630 GeV

Inclusive dijet production at large pseudorapidity intervals (Deltaeta) between the two jets has been suggested as a regime for observing Balitsky-Fadin-Kuraev-Lipatov (BFKL) dynamics. We have measured the dijet cross section for large Deltaeta in pp collisions at sqrt[s]=1800 and 630 GeV using the D0 detector. The partonic cross section increases strongly with the size of Deltaeta. The observed growth is even stronger than expected on the basis of BFKL resummation in the leading logarithmic approximation. The growth of the partonic cross section can be accommodated with an effective BFKL intercept of alphaBFKL(20 GeV)=1.65+/-0.07.     

Analysis of the 33-133-133-1final state in photon-photon collisions

The reactione ⁺ e ^- e ⁺ e ^{- 00}e ⁺ e ^- 6 has been analysed using the full data sample taken with the Crystal Ball detector at the DORIS II storage ring at DESY. The ⁰⁰ invariant mass spectrum is dominated by the ', for which we determine the radiative width (') to be (4.5±0.3±0.5)keV. Near 1.9 GeV/c² we observe a second enhancement in the ⁰⁰ mass distribution. Assuming that these events are created by the production and subsequent decay of a wide resonanceX(1900), we have investigated the decay modes, the invariant mass distributions of the ⁰ and ⁰⁰ subsystems and the angular distributions of the final state mesons. We find that the data is best described byJ ^PC=2. For thisJ ^P assignment the resonance parameters are (X) BR(X)=(0.95±0.27±0.20) keV _tot (X)=(221±92±44)MeV, andM(X)=(1881±32±40) MeV/c².Deceased