Interface Morphology Development Research Articles

Under-wrapped soluble proteins as signals triggering membrane morphology

This work identifies signals structurally encoded in soluble cytosolic proteins that induce an intricate or simple spanning of the inner membrane in a cellular compartment. Such signals are defined by the extent of intramolecular desolvation of backbone hydrogen bonds, a determinant factor in the interactivity of soluble proteins. The protein scaffolding of inner membranes varies widely but such differences do not explain a priori whether the membrane spanning will be simple or intricate. To address this problem, we show that a fluid phospholipid bilayer confining a water compartment for a soluble protein at 38 μM concentration is drawn to increase its interface area proportionally with the extent of intramolecular under-desolvation of the protein structure. We also predict and measure the optimal interface surface tension that enables such phenomenology. The in vitro kinetics of interface morphology development is autocatalytic, with an inhibitory mechanism switching on as the local concentration of protein molecules adsorbed on the bilayer reaches a threshold.

In situ observation of concentrational stratification and solid–liquid interface morphology during Ga–5% In alloy melt solidification

Segregation of indium during solidification of a Ga–5 wt% In alloy melt was investigated with in situ real-time X-ray density visualization under various solidification conditions. Indium stratification in the melt was observed at the very beginning of solidification. Substantial indium stratification developed even with convective flow in the melt. The solid–liquid interface morphology was found to be strongly dependent on the chemical stratification in the melt and the hydrodynamic state (convective or conductive). On the other hand, the interface morphology development was found to affect (decelerate or accelerate) the indium stratification by influencing the convection pattern in the melt.

Reaction and growth of Yb/Hg1−xCdxTe(110) interfaces

Detailed synchrotron radiation photoemission studies of Yb/Hg1−xCdxTe junctions as a function of Yb coverage were performed at room temperature. Photoemission from physisorbed xenon after cooling the sample to 35 K was also used to examine the local overlayer work function and the development of interface morphology. For Yb coverages less than 6 Å, the data provide evidence for the lateral growth of islands consisting of Yb-Te reaction products involving divalent Yb, and an associated Hg depletion within an 18-Å-thick near-surface layer. Upon island coalescence at an Yb coverage of 6 Å, the formation of a metallic Yb-rich layer at the surface is observed. This layer traps Hg atoms diffusing across the interface through the formation of an Yb-Hg alloy, and is responsible for the nonmonotonic behavior of the Hg interface concentration as a function of Yb coverage.

AN EXPERIMENTAL STUDY OF MORPHOLOGY DEVELOP-MENT OF SOLIDIFICATION INTERFACE

Time-dependent development of interface morphology from initial perturbation of a planar interface to a steady periodic array of cells or dendrites was directly observed during directional solidification brocess of a transparent model alloy, succinonitrile -1.1 wt% ethanol. The following results are obtained: 1) The measured wavelength of initial perturbation of planar interface instability is within the expected wavelength range by the MS theory, but not the same as the expected wavelength with the fastest amplitude developing speed. 2) During the initial stage of a planar interface instability, the developing speed of perturbation amplitude is indeed a linear function of the amplitude, but the measured value of the amplitude developing rate is much smaller than the theoretical value. 3) The features of morphology development of cells and dendrites are different from each other, and the main cause leading to the different developing behaviour is that the relative scale of the steady primary spacing and the initial perturbation wavelength is different in the two cases.

Interface morphology development during stress corrosion cracking—II. Via volume diffusion

The initial response functions of the Fourier wave components for an infinitesimal surface notch in a single crystal sample under Mode I or tensile loading has been evaluated with respect to volume diffusion mechanisms of morphological change. The results are qualitatively similar to those found in Part I for a surface diffusion mechanism. A comparison of response rates between the surface and the volume diffusion mechanism is provided.

Interface morphology development during stress corrosion cracking part II: Via volume diffusion: P. Vasudev ∗, R. J. Asaro ∗∗ & W. A. Tiller [formula omitted]∗Department of Materials Science Stanford University Stanford, California ∗∗Ford Motor Company Scientific Research, Metallurgy Dearborn, Michigan [formula omitted]Department of Materials Science Stanford University Stanford, California

Interface morphology development during stress corrosion cracking part II: Via volume diffusion: P. Vasudev ∗, R. J. Asaro ∗∗ & W. A. Tiller [formula omitted]∗Department of Materials Science Stanford University Stanford, California ∗∗Ford Motor Company Scientific Research, Metallurgy Dearborn, Michigan [formula omitted]Department of Materials Science Stanford University Stanford, California

Interface morphology development during stress corrosion cracking: Part I. Via surface diffusion

The initiation of a crack in a specimen under tensile or compressive stresses is treated from the point of view of perturbation analysis. A surface distortion is Fourier analyzed into a series of waves and the amplitude response of a single component of varying frequency is theoretically investigated. The response of the individual components yields a Griffith-type criterion for wave amplitude growth. The model is applied to alloy systems undergoing stress corrosion cracking via surface diffusion.