Intrinsic Optical Signal (IOS) imaging is a widely accepted technique for imaging brain activity. We propose an integrated device consisting of interleaved arrays of gallium arsenide (GaAs) based semiconductor light s...
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We present the use of the polysaccharide chitosan for immobilizing biomolecules on microfabricated device surfaces. The main advantages of chitosan are its abundance of primary amine groups and its ability to be elect...
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Crystal-melt interfacial free energies (γ) are computed for hcp Mg by employing equilibrium molecular-dynamics (MD) simulations and the capillary-fluctuation method (CFM). This work makes use of a newly developed emb...
Crystal-melt interfacial free energies (γ) are computed for hcp Mg by employing equilibrium molecular-dynamics (MD) simulations and the capillary-fluctuation method (CFM). This work makes use of a newly developed embedded-atom-method (EAM) interatomic potential for Mg fit to crystal, liquid, and melting properties. We describe how the CFM, which has previously been applied to cubic systems only, can be generalized for studies of hcp metals by employing a parametrization for the orientation dependence of γ in terms of hexagonal harmonics. The method is applied in the calculation of the Turnbull coefficient (α) and crystalline anisotropies of γ. We obtain a value of α=0.48, with interfacial free energies for different high-symmetry orientations differing by approximately 1%. These results are compared to those obtained in previous MD-CFM studies for cubic EAM metals as well as experimental studies of solid-liquid interfaces in hcp alloys. In addition, the implications of our results for the prediction of dendrite growth directions in hcp metals are discussed.
Femtosecond pulsed laser damage of Silicon (100) with thermal oxide thin films was studied in order to further understand the optical and electrical properties of thin films and to evaluate their influence on the dama...
Femtosecond pulsed laser damage of Silicon (100) with thermal oxide thin films was studied in order to further understand the optical and electrical properties of thin films and to evaluate their influence on the damage of the substrate. The damage threshold as a function of film thickness (2 – 1200 nm) was measured. The damage morphology produced by single laser pulses was also investigated. Two primary morphologies were observed, one in which the oxide film is completely removed, and the other in which the film is delaminated and expanded above the surface producing a bubble feature.
Highly selective and repeatable delamination of thermal oxide films from Si(100) substrates has been performed using single and multiple femtosecond laser pulses forming bubbles or blisters. By overlapping the bubbles...
Highly selective and repeatable delamination of thermal oxide films from Si(100) substrates has been performed using single and multiple femtosecond laser pulses forming bubbles or blisters. By overlapping the bubbles laterally, tubes or capillaries can be formed with a range of volumes suitable for nanofluidics. By scanning the sample through the laser using an automated translation stage, patterns of tubes with arbitrary complexity can be formed, while the scan velocity can easily control the volume of the tubes. The production time for capillaries in this fashion is considerably less than with other lithographic techniques, while the proximity of the tubes to the underlying silicon substrate yields the possibility for integrated devices. The mechanism responsible for the delamination will be discussed and the optimal laser and sample translation conditions will be presented which provide the most uniform tubes. Atomic force microscopy and optical microscopy of capillaries with a range of volumes will be presented.
The total dose radiation response of nitrided and nonnitrided n-type 4H-SiC is reported for metal oxide semiconductor capacitors exposed to 10-keV X-rays under positive bias. The radiation response is affected strongl...
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One dimensional “sonic vacuum”‐type phononic crystals were assembled from chains of polytetrafluoroethylene (PTFE) beads and Parylene coated spheres with different diameters. It was demonstrated for the first time ...
One dimensional “sonic vacuum”‐type phononic crystals were assembled from chains of polytetrafluoroethylene (PTFE) beads and Parylene coated spheres with different diameters. It was demonstrated for the first time that these polymer‐based granular system, with exceptionally low elastic modulus of particles, support the propagation of strongly nonlinear solitary waves with a very low speed. They can be described using classical nonlinear Hertz law despite the viscoelastic nature of the polymers and the high strain rate deformation of the contact area. Trains of strongly nonlinear solitary waves excited by an impact were investigated experimentally and were found to be in reasonable agreement with numerical calculations. Tunability of the signal shape and velocity was achieved through a non‐contact magnetically induced precompression of the chains. This applied prestress allowed an increase of up to two times the solitary waves speed and significant delayed the signal splitting. Anomalous reflection at the interface of two “sonic vacua”‐type systems was reported.
Rice husk can be an interesting source of raw material for obtaining silica, due to its composition, availability and cost. The extraction process of silica from rice husk can be divided in two parts. First some compo...
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Rice husk can be an interesting source of raw material for obtaining silica, due to its composition, availability and cost. The extraction process of silica from rice husk can be divided in two parts. First some components of rice husk are removed by acid leaching, using HCl, H2SO4, or a mixture of them, followed by calcination for burning out carbon compounds. The residue obtained after calcination is composed of about 95% amorphous silica. In this work, silica was produced from rice husk following the steps previously described, using leaching solutions of 10% HCl, 10% H 2SO4 and a mixture of 10% HCl and 10% H2SO 4. Calcination of leached materials was carried out at 600 or 700°C for 3 h. The silica powder obtained presented a mean particle size of 18 μm, around 98% amorphous SiO2 with a specific surface area of about 300 m2/g.
We investigate the formation of ringlike deposits in drying drops of DNA. In analogy with the colloidal “coffee rings,” DNA is transported to the perimeter by the capillary flow. At the droplet edge, however, DNA fo...
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We investigate the formation of ringlike deposits in drying drops of DNA. In analogy with the colloidal “coffee rings,” DNA is transported to the perimeter by the capillary flow. At the droplet edge, however, DNA forms a lyotropic liquid crystal (LC) with concentric chain orientations to minimize the LC elastic energy. During the final stages of drying, the contact line retracts, and the radial stress causes undulations at the rim that propagate inward through the LC and form a periodic zigzag structure. We examine the phenomenon in terms of a simple model based on LC elasticity.
We develop a time resolved fluorescence microscopy system to image the dynamics of optoinjection produced by the delivery of a highly focused pulsed Nd:YAG (λ=532nm, 6ns) laser microbeam to the cell membrane of PtK2 ...
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