Field-based ion generation from microscale emitters on natural and artificial objects for atmospheric pressure mass spectrometry

Field-based ion generation is described for ambient mass spectrometry. The technique allows the analysis of endogenously expressed chemicals and exogenously applied compounds directly from the cuticle of live insects in real time. Cuticular hairs serve as electric field-enhancing structures and play a key role in ion generation. Artificial emitters such as graphite whiskers or sharp metal tips replicate this effect.     

A Comparison of Density‐Functional Theory and Hartree?Fock Modeling of Organolithium Equilibria

Experimental values for a number of organolithium equilibria in THF solution expressed as pK values are compared with computational results at several theory levels. Solvation effects are considered only by coordination of lithium with two THF molecules. Best results are obtained with the hybrid density‐functional method mPW1PW91, which gives satisfactory results over a range of almost 40 pK units, but explicit thermal corrections to 25° are required.     

Current conduction mechanisms of RF-Magnetron sputtered Y2O3 gate oxide on gallium nitride

Current conduction mechanisms through as-deposited and post-deposition annealed (200–800 °C) RF-magnetron sputtered Y₂O₃ gate oxides on n-type GaN have been systematically investigated with current–voltage measurements at temperature in the range of 25–175 °C. The possible current conduction mechanisms that govern the leakage current of Y₂O₃/GaN metal-oxide-semiconductor test structure are space-charge-limited conduction, Schottky emission, Poole–Frenkel emission, and Fowler-Nordheim tunneling. The dominance of these conduction mechanisms is depending on applied electric field and measurement temperatures.     

Second harmonic generation polarization microscopy with tightly focused linearly and radially polarized beams

Second harmonic generation microscopy was conducted on rat-tail tendons with linearly and radially polarized beams. Transverse and axial field components were generated in the focal region through tight focusing of linearly and radially polarized. It was found that the generated SHG signals could not be qualitatively explained with a scalar approximation to the electric field at the focus. Only by accounting for the interactions of the axial and transverse components of the electric field interacting through the nonlinear susceptibility χ⁽²⁾ tensor could the SHG images be explained. For the case of collagen we find that the SHG signal varies as a function of the analyzer angle with a cos² or sin² dependency for linearly polarized beams. For tightly focused radially polarized beams we find that the output SHG is radially polarized after collimation and is independent of the analyzer angle.     

Synthesis of silica supported titania nanocomposite in controllable phase content and morphology

The silica supported titania nanocomposite thin films with controllable particle size and phase content were successfully prepared by a convenient post annealing approach involving in solid-solid interfacial reaction. The effects of growth conditions, such as the annealing temperature and silicon concentration on the particle size and phase content, were systematically studied by using Atomic force microscopy (AFM), Raman spectroscopy, X-ray diffraction (XRD), and X-ray spectroscopy (XPS). The results indicate that the silicon concentration is a dominant factor in the morphology, crystallization and phase transformation of these nanocomposites. A mechanism for the high temperature phase transformation is also proposed based on the migration of the oxygen vacancies.     

Tight focusing of radially polarized Gaussian and Bessel-Gauss beams

We examine the effects of tightly focusing a radially polarized beam with uniform, Gaussian, or Bessel-Gauss pupil functions. The resulting FWHM is smallest for the case of a uniform amplitude profile, while the Bessel-Gauss beam results in the largest FWHM. The uniform amplitude profile also results in an axial field component that increases fastest with increasing NA. The ratio of the axial component to the transverse component is also the greatest for the uniform pupil function. On the other hand, the Bessel-Gauss beam benefits the most from the use of an annulus.