A Novel Electrochemical Method for Enhancing the Conductivity of Polyaniline Solid Matrices in Pre-Formed Films

A fast, simple and environmentally friendly new electrochemical method capable of enhancing the conductivity of a preformed polyaniline film has been found. Utilizing this method of electrochemical forcing pre-treatment at a certain effective voltage, a polyaniline solid matrix can be made more conductive. For example, the conductivity of a preformed polyaniline film (as thick as 10 μm) can be easily enhanced by about an order of magnitude within a pretreatment time of only ca. 5 min. The UV-Vis-NIR and ESR spectroscopic evidences indicated that the charge carriers in the polyaniline matrix are more delocalized after such electrochemical pretreatments. The results of CV studies indicated that the resultant polyaniline film has higher charge transport efficiency and a greater redox rate. Such phenomenon may be linked with a possible backbone conformational change, as induced by this novel electrochemical pretreatment, within the solid matrix ofpolyaniline film.     

Observation of trielectronic recombination in Be-like Cl ions

Recombination involving the core excitation of two electrons, which may be termed trielectronic recombination, has been experimentally identified for the first time. Using Cl13+ ions circulating in the TSR heavy-ion storage ring, we have observed surprisingly strong low-energy trielectronic recombination resonances, comparable to the dielectronic process. At higher electron-ion collision energies, trielectronic recombination is suppressed due to the autoionization of the triply excited intermediate state into excited final states. The formation of the intermediate state depends sensitively on configuration mixing, making trielectronic recombination a challenge to atomic-structure calculations.     

Site-selective DNA photocleavage involving unusual photoinitiated tautomerization of chiral tridentate vanadyl(V) complexes derived from N-salicylidene alpha-amino acids

The titled vanadyl(V) complexes serve as efficient reagents for cleaving supercoiled plasmid DNA by photoinitiation. Complex 3d, derived from 2-hydroxy-1-naphthaldehyde and l-phenylalanine, exhibits a unique wedge feature, inducing a site-selective photocleavage at the C22-T23 of the bulge backbone for a HIV-27 DNA system at 0.1-5 muM. Transient absorption experiments for 3d indicate the involvement of LMCT with concomitant tautomerization, leading to an o-quinone-methide V-bound hydroxyl species responsible for the cleavage profiles. [structure: see text]     

Estimation of microscopic rubbing alignment parameters

Abstract

We report an examination of the cloth-rubbing process, widely used to effect liquid crystal alignment, from a simplified microscopic perspective. We define strength of rubbing by the average applied force per rubbing fibre (approximately 11-22μN under our conditions, assuming all fibres passing the surface make contact), and extent of rubbing by the fraction of total surface area contacted during the process. Fibre-surface microscopic contact widths estimated from atomic force microscopy images of rubbed alignment polymer surfaces were in the range 10-500 nm. Taking 100 nm as an average value, we show that the entire alignment surface may be contacted several times during a typical rubbing process. Fibre-surface contact shear stresses can approach the GPa range, several orders of magnitude greater than the macroscopic rubbing pressure.     

Microstructural and microspectral characterization of a vertically aligned liquid crystal display panel

The microstructural and microspectral characteristics of a vertically aligned liquid crystal display (VA-LCD) panel were obtained noninvasively for the first time. With 1?μm axial and 2?μm transversal resolutions, the cell gap profile beneath the patterned thin-film transistor of the VA-LCD panel can clearly be resolved. The thicknesses of the multiple thin-film layers and the embedded defects can also be unveiled. As far as spectral response is concerned, the light transmittance at the layer boundaries can be estimated from the measured reflectance, which is crucial information for the design of a highly transmissive panel. The color shift of the VA-LCD panel due to fabrication error was evaluated.     

A Chemical Probe for the ATAD2 Bromodomain

ATAD2 is a cancer‐associated protein whose bromodomain has been described as among the least druggable of that target class. Starting from a potent lead, permeability and selectivity were improved through a dual approach: 1) using CF₂ as a sulfone bio‐isostere to exploit the unique properties of fluorine, and 2) using 1,3‐interactions to control the conformation of a piperidine ring. This resulted in the first reported low‐nanomolar, selective and cell permeable chemical probe for ATAD2.     

Single channel layer, single sheath-flow inlet microfluidic flow cytometer with three-dimensional hydrodynamic focusing

Flow cytometry is a technique capable of optically characterizing biological particles in a high-throughput manner. In flow cytometry, three dimensional (3D) hydrodynamic focusing is critical for accurate and consistent measurements. Due to the advantages of microfluidic techniques, a number of microfluidic flow cytometers with 3D hydrodynamic focusing have been developed in recent decades. However, the existing devices consist of multiple layers of microfluidic channels and tedious fluidic interconnections. As a result, these devices often require complicated fabrication and professional operation. Consequently, the development of a robust and reliable microfluidic flow cytometer for practical biological applications is desired. This paper develops a microfluidic device with a single channel layer and single sheath-flow inlet capable of achieving 3D hydrodynamic focusing for flow cytometry. The sheath-flow stream is introduced perpendicular to the microfluidic channel to encircle the sample flow. In this paper, the flow fields are simulated using a computational fluidic dynamic (CFD) software, and the results show that the 3D hydrodynamic focusing can be successfully formed in the designed microfluidic device under proper flow conditions. The developed device is further characterized experimentally. First, confocal microscopy is exploited to investigate the flow fields. The resultant Z-stack confocal images show the cross-sectional view of 3D hydrodynamic with flow conditions that agree with the simulated ones. Furthermore, the flow cytometric detections of fluorescence beads are performed using the developed device with various flow rate combinations. The measurement results demonstrate that the device can achieve great detection performances, which are comparable to the conventional flow cytometer. In addition, the enumeration of fluorescence-labelled cells is also performed to show its practicality for biological applications. Consequently, the microfluidic flow cytometer developed in this paper provides a practical platform that can be used for routine analysis in biological laboratories. Additionally, the 3D hydrodynamic focusing channel design can also be applied to various applications that can advance the lab on a chip research.     

Catalyst-free, low-temperature growth of high-surface area carbon nanoflakes on carbon cloth

We have used a microwave plasma-enhanced chemical vapor deposition system to synthesize two-dimensional (2D) and three-dimensional (3D) structures of carbon nanoflakes (CNFs). This catalyst-free, low-temperature synthesis involved introducing CO₂ and CH₄ as reactants at a specified ratio of 2:3. We obtained uniform 2D arrays of CNFs at lower microwave powers (200 or 300 W) and substrate temperatures (up to 420 °C); their thickness was close to 1 μm. At a microwave power of 400 W, we obtained a 3D architecture comprising the smallest nanoflakes reported to date. The specific surface area of the 3D structure was double that of the corresponding 2D arrays. We suspect that such structured carbon materials might have great potential for energy storage applications.     

Estimation of microscopic rubbing alignment parameters

We report an examination of the cloth-rubbing process, widely used to effect liquid crystal alignment, from a simplified microscopic perspective. We define strength of rubbing by the average applied force per rubbing fibre (approximately 11-22μN under our conditions, assuming all fibres passing the surface make contact), and extent of rubbing by the fraction of total surface area contacted during the process. Fibre-surface microscopic contact widths estimated from atomic force microscopy images of rubbed alignment polymer surfaces were in the range 10-500 nm. Taking 100 nm as an average value, we show that the entire alignment surface may be contacted several times during a typical rubbing process. Fibre-surface contact shear stresses can approach the GPa range, several orders of magnitude greater than the macroscopic rubbing pressure.