Materials Literature
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Collagen fibers form the structural units of connective tissue throughout the body, transmitting force, maintaining shape, and providing a scaffold for cells. Our laboratory has studied collagen self-assembly since the 1970s. In this study, collagen fibers were self-assembled from molecular collagen solutions and then…
We present a detailed molecular-dynamics study of the melting, freezing, and coalescence of gold nanoclusters within the framework of the embedded-atom method. Concerning melting, we find the process to first affect the surface (``premelting''), then to proceed inwards. The curve for the melting temperature vs cluster…
Abstract During the last thirty years the research field of surface science with its various disciplines has progressively played a more and more important role in the field of catalysis. The main focus of attention for a long time was research on metal surfaces, on which, in time, the whole spectrum of developed surf…
Nonionic polyethylene oxide surfactants are versatile structure-directing agents for the assembly of mesoporous molecular sieves, but their greatest benefit may lie in their ability to control the pore size of the mesostructure by the assembly temperature (see dependence of pore diameter R on temperature shown on the…
The analysis of the infrared and ligand field spectra of COM 2 O 4 spinels reveals that the ionicity of these compounds varies in the following order aluminate > gallate > ferrite and chromite > rhodite and cobaltite. A linear relation has been established between the Δ(LO‐TO) 1 splitting, Racah parameter and…
A systematic investigation of the ground-state geometries and stabilities of clusters made by employing ab initio density-based molecular dynamics is reported. Although in the solid-state form, the 50:50 alloy takes on a B32-ordered structure, no evidence for such ordering has been seen for small clusters. Instead the…
Porous silicon treated by amine immersion and then rapid thermal oxidation results in a photoluminescence peak shift from ∼650 nm (red light) to a stable and intense ∼520 nm blue-green light. The amine immersion may catalyze a process during rapid thermal oxidation that both reduces the sizes of Si cores and more effe…
Optical amplification at 1.083 μm with neodymium-doped chalcogenide fiber is observed. The thermal and spectroscopic properties of a new chalcogenide glass system are measured in view of its potential use as a rare-earth host. A maximum internal gain of 6.8 dB is achieved for a pump power of 180 mW.
We have simulated by ab initio constant pressure molecular dynamics the solid-state polymerization of acetylene recently observed experimentally in the pressure range 3.5--14 GPa. We have found a massive polymerization only at much higher pressure (25 GPa). However, we have also found that a triplet exciton self-trapp…
We show that the crossover from exponential to nonexponential behavior displayed in the short-time range by the local segmental relaxation in polymers leads to the existence of a temperature ${T}^{*}$ at which the dynamics changes from independent to cooperative. ${T}^{*}$ depends on the C-C rotational barrier in the…
A flat, freely suspended film of smectic-A liquid crystal supports a pressure difference, \ensuremath{\Delta}p, across its two free surfaces. The size of its meniscus is about 10 \ensuremath{\mu}m, 2 orders of magnitude smaller than the capillary length, and its profile is predicted to be circular, in accordance with…
Photoluminescence (PL), electron spin resonance (ESR), and high resolution transmission electron microscopy (HRTEM) were used to investigate the luminescence mechanism in Si nanocrystals. Si ions were implanted in SiO2 films at 190 keV to a dose of 3×1017/cm2.An intense photoluminescence (PL) band at 755 nm (1.65 eV)…
Grain boundary misorientations were determined by electron backscattering diffraction for tantalum-encapsulated, copper interconnects which contained thermal-stress-induced voids. The misorientation angles at voided and unvoided line segments were analyzed for two differently heat treated sample types, which were not…
We propose to study the conditions for implementation of complex amplitude modulation on standard liquid-crystal spatial light modulators when illuminated by polarized light. The spatial light modulators are used in a conventional configuration, i.e., the voltage is applied parallel to the wave-front propagation direc…
Dissipative particle dynamics (DPD) is a relatively new technique which has proved successful in the simulation of complex fluids. We caution that for the equilibrium achieved by the DPD simulation of a simple fluid the temperature depends strongly on the time step. An analytic expression for the dependence is obtaine…
It is shown that the exchange-correlation functional of spin-density functional theory is identical, on a certain set of densities, with the exchange-correlation functional of current-density functional theory. This rigorous connection is used to construct new approximations of the exchange-correlation functionals. Th…
A general mathematical model which describes the motion of an interface between immiscible viscous fluids along a smooth homogeneous solid surface is examined in the case of small capillary and Reynolds numbers. The model stems from a conclusion that the Young equation, σ 1 cos θ = σ 2 − σ 3 , which expresses the bala…
A theory of the long-wavelength low-energy electronic structure of graphite-derived nanotubules is presented. The propagating $\ensuremath{\pi}$ electrons are described by wrapping a massless two dimensional Dirac Hamiltonian onto a curved surface. The effects of the tubule size, shape, and symmetry are included throu…
We attribute similarities in the rheology of many soft materials (foams, emulsions, slurries, etc.) to the shared features of structural disorder and metastability. A generic model for the mesoscopic dynamics of ``soft glassy matter'' is introduced, with interactions represented by a mean-field noise temperature $x$.…
Abstract Stress corrosion cracking (SCC) and hydrogen embrittlement (HE) susceptibility of three different steels were determined using the methodology of the slow strain rate (SSR) testing as currently discussed within ASTM G129 and more specifically in the proposed NACE T-1F-9e test method. The materials included 13…