Evidence of DNA transfer through F-pilus channels during Escherichia coli conjugation

The mechanism of DNA transfer from Escherichia coli ( E. coli) Hfr donor strain AT2453 to recipient strain AB1157 during the conjugation process has been investigated by liquid atomic force microscopy (AFM). With the success of immobilizing both E. coli strains on gelatin-treated glass under aqueous solution, the F-pilus between an E. coli mating pair could be clearly imaged and dissected by an AFM probe. Another AFM probe functionalized with an anti-single-stranded DNA (ssDNA) antibody was then applied to detect transferring ssDNA. According to the AFM force spectrum, the transferring ssDNA could be detected only in the dissected area with a binding force of 109 +/- 5 pN measured. Our results provide direct evidence indicating that the DNA was transferred through the F-pilus channel between an E. coli mating pair during their conjugation.     

Development of Prototype Wireless Transmission Measurement for Glucose in Subcutaneous and Brain Striatum

Monitoring of glucose in subcutaneous and brain striatum have been extensively studied in the past. While biocompatibility was one of the limitations, others included the messy measuring equipments preclude monitoring in a complex environment. This study tried to establish an amperometric measurement of glucose in pre‐ and post‐insulin‐administration on diabetic and hyperglycemia rats via wireless. The results have indicated that the wireless sensing kit used was capable of monitoring glucose in both subcutaneous and brain. The physiological data have also shown a new insight on the fabrication of implantable glucose sensors.     

Multiscale approach to explore the potential energy surface of water clusters (H2O)nn <or= 8

We propose a multiscale method to explore the energy landscape of water clusters. An asynchronous genetic algorithm is employed to explore the potential energy surface (PES) of OSS2 and TTM2.1-F models. Local minimum structures are collected on the fly, and the ultrafast shape recognition algorithm was used to remove duplicate structures. These structures are then refined at the B3LYP/6-31+G* level. The number of distinct local minima we found (21, 76, 369, 1443, and 3563 isomers for n = 4-8, respectively) reflects the complexity of the PES of water clusters.     

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.     

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.     

De novo sequencing of novel neuropeptides directly from Ascaris suum tissue using matrix-assisted laser desorption/ionization time-of-flight/time-of-flight

Direct analysis of tissue by matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) allows for the rapid profiling of biological molecules with minimal loss of sample or degradation and reduced likelihood of chemical modification. However, there are still considerable challenges to overcome due to the complexity of tissue and the low quantity of endogenous peptide in a single cell. These problems are exacerbated in the nematode Ascaris suum because of the small size of individual neurons and the paucity of peptide per cell. In an effort to address these difficulties, the recently developed matrix-assisted laser desorption/ionization time-of-flight/time-of-flight (MALDI-TOF/TOF) technology was used in combination with an on-target derivatization in order to sequence novel neuropeptides directly from Ascaris nervous tissue. Direct MALDI-TOF/TOF analysis of Ascaris tissue provided the complete amino acid sequences for a previously characterized neuropeptide as well as for three novel peptides with homologues found in other nematodes. These results demonstrate a method for the rapid characterization of sub-femtomolar amounts of peptide directly from tissue using MALDI-TOF/TOF.     

Analysis of charge conduction mechanisms in nitrided SiO2 Film on 4H SiC

Seven different thicknesses (2-20 nm) of nitrided SiO₂ on n-type 4H-SiC have been employed to investigate the charge conduction mechanism through these oxides. Several potential mechanisms have been identified. The mechanisms are depending on electric field and oxide thickness. A relationship plot among these three parameters has been established.     

Performance parameters for focusing of radial polarization

Performance parameters are presented for high-aperture radially polarized focusing systems. These can be used for comparing the focusing performance of different optical systems, including the effect of pupil filters.