1,915 research outputs found
Laser ablation sample transfer for mass spectrometry
In this research, a new ambient sampling technique for mass spectrometry was developed that uses an infrared laser to ablate materials under ambient conditions that are captured in a solvent or on a surface. An infrared optical parametric oscillator (OPO) laser system at 3 μm wavelength was focused onto samples for ablation at atmospheric pressure. The ablated materials were transferred to a solvent or surface. For off-line electrospray ionization (ESI) and matrix-assisted laser desorption/ionization (MALDI) analysis, the ablated material was captured in a static solvent droplet that was deposited on a MALDI target or flow-injected into a nanoelectrospray source. The direct analysis of biological fluids for off-line MALDI and electrospray was demonstrated with untreated blood, milk, and egg. For one-line ESI, the ablated material was captured in an exposed flowing solvent stream that carried the ablated material to the ESI source. For on-line liquid chromatography ESI (LC-ESI) and on-line capillary electrophoresis ESI (CE-ESI), the ablated material was captured in the flowing solvent and injected into a LC column or a capillary with pressure driven or electrokinetic flows, respectively. The performance of the system was assessed using peptide and protein mixtures ablated from the target and analyzed with LC or CE separation. For MALDI imaging with IR laser ablation sampling, a thin tissue section placed on a microscope slide was scanned in two dimensions under a focused IR laser beam to transfer material to the target slide via ablation. After the material was transferred to the target slide, it was analyzed using MALDI imaging. Images were obtained from peptide standards for initial optimization of the system and from mouse brain tissue sections
Simultaneous detection of the nonlinear restoring and excitation of a forced nonlinear oscillation: an integral approach
We address in this article, how to calculate the restoring characteristic and the excitation of a nonlinear forced oscillating system. Under the assumption that the forced nonlinear oscillator has a periodic solution with period, we constructed a system of linear equations by introducing time-dependent multipliers. The periodicity assumption helps simplify the system of linear equations. The stability and uniqueness are also presented for the inverse problem. Numerical testing is conducted to show the effectiveness of our presented methodology.Peer ReviewedPostprint (author's final draft
Emergence of new topological gapless phases in the modified square-lattice Kitaev model
We investigate emergent topological gapless phases in the square-lattice
Kitaev model with additional hopping terms. In the presence of nearest-neighbor
hopping only, the model is known to exhibit gapless phases with two topological
gapless points. When the strength of the newly added next-nearest-neighbor
hopping is smaller than a certain value, qualitatively the same phase diagram
persists. We find that further increase of the extra hopping results in a new
topological phase with four gapless points. We construct a phase diagram to
clarify the regions of emergent topological gapless phases as well as
topologically trivial ones in the space of the chemical potential and the
next-nearest-neighbor hopping strength. We examine the evolution of the gapless
phases in the energy dispersions of the bulk as the chemical potential varies.
The topological properties of the gapless phases are characterized by the
winding numbers of the present gapless points. We also consider the ribbon
geometry to examine the corresponding topological edge states. It is revealed
that Majorana-fermion edge modes exist as flat bands in topological gapless
phases. We also perform the analytical calculation as to Majorana-fermion
zero-energy modes and discuss its implications on the numerical results
Nanoparticle Engineering for Chemical-Mechanical Planarization
Increasing reliance on electronic devices demands products with high performance and efficiency. Such devices can be realized through the advent of nanoparticle technology. This book explains the physicochemical properties of nanoparticles according to each step in the chemical mechanical planarization (CMP) process, including dielectric CMP, shallow trend isolation CMP, metal CMP, poly isolation CMP, and noble metal CMP. The authors provide a detailed guide to nanoparticle engineering of novel CMP slurry for next-generation nanoscale devices below the 60nm design rule. This comprehensive text also presents design techniques using polymeric additives to improve CMP performance
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