Morphology and Alignment Transition of Hexabenzocoronene (HBC) Mesogen Films by Bar Coating: Effect of Coating Speed.

Films of the discotic liquid crystalline hexabenzocoronene (HBC) derivative, HBC-1,3,5-Ph-C12, were prepared on the quartz substrate by the bar-coating method. Depending on the coating speed, regularly spaced stripes or continuous films were observed. In the former case, columns of the HBC derivatives align more along the stripes, which are perpendicular to the coating direction, whereas in the latter case, columns of the HBC derivatives in the film align more along the coating direction. These distinctive structures are confirmed via polarized optical microscopy (POM), polarized UV-vis spectroscopy, and grazing incidence small-angle X-ray scattering measurements.

Scanning Line Probe Microscopy: Beyond the Point Probe.

Scanning probe microscopy (SPM) techniques have become indispensable tools for studying nano- and microscale materials and processes but suffer from a trade-off between resolution and areal scan rate that limits their utility for a number of applications and sample types. Here, we present a novel approach to SPM imaging based on combining nonlocal scanning line probes with compressed sensing (CS) signal analysis methods. Using scanning electrochemical microscopy (SECM) as an exemplar SPM technique, we demonstrate this approach using continuous microband electrodes, or line probes, which are used to perform chemical imaging of electrocatalytic Pt discs deposited on an inert substrate. These results demonstrate the potential to achieve high areal SPM imaging rates using nonlocal scanning probes and CS image reconstruction.

A bio-inspired two-layer sensing structure of polypeptide and multiple-walled carbon nanotube to sense small molecular gases.

In this paper, we propose a bio-inspired, two-layer, multiple-walled carbon nanotube (MWCNT)-polypeptide composite sensing device. The MWCNT serves as a responsive and conductive layer, and the nonselective polypeptide (40 mer) coating the top of the MWCNT acts as a filter into which small molecular gases pass. Instead of using selective peptides to sense specific odorants, we propose using nonselective, peptide-based sensors to monitor various types of volatile organic compounds. In this study, depending on gas interaction and molecular sizes, the randomly selected polypeptide enabled the recognition of certain polar volatile chemical vapors, such as amines, and the improved discernment of low-concentration gases. The results of our investigation demonstrated that the polypeptide-coated sensors can detect ammonia at a level of several hundred ppm and barely responded to triethylamine.

A single-walled carbon nanotube network gas sensing device.

The goal of this research was to develop a chemical gas sensing device based on single-walled carbon nanotube (SWCNT) networks. The SWCNT networks are synthesized on Al(2)O(3)-deposted SiO(2)/Si substrates with 10 nm-thick Fe as the catalyst precursor layer using microwave plasma chemical vapor deposition (MPCVD). The development of interconnected SWCNT networks can be exploited to recognize the identities of different chemical gases by the strength of their particular surface adsorptive and desorptive responses to various types of chemical vapors. The physical responses on the surface of the SWCNT networks cause superficial changes in the electric charge that can be converted into electronic signals for identification. In this study, we tested NO(2) and NH(3) vapors at ppm levels at room temperature with our self-made gas sensing device, which was able to obtain responses to sensitivity changes with a concentration of 10 ppm for NO(2) and 24 ppm for NH(3).

On the Global Geometry of Sphere-Constrained Sparse Blind Deconvolution.

Blind deconvolution is the problem of recovering a convolutional kernel a0 and an activation signal x0 from their convolution [Formula: see text]. This problem is ill-posed without further constraints or priors. This paper studies the situation where the nonzero entries in the activation signal are sparsely and randomly populated. We normalize the convolution kernel to have unit Frobenius norm and cast the sparse blind deconvolution problem as a nonconvex optimization problem over the sphere. With this spherical constraint, every spurious local minimum turns out to be close to some signed shift truncation of the ground truth, under certain hypotheses. This benign property motivates an effective two stage algorithm that recovers the ground truth from the partial information offered by a suboptimal local minimum. This geometry-inspired algorithm recovers the ground truth for certain microscopy problems, also exhibits promising performance in the more challenging image deblurring problem. Our insights into the global geometry and the two stage algorithm extend to the convolutional dictionary learning problem, where a superposition of multiple convolution signals is observed.

Design and operation of a scanning electrochemical microscope for imaging with continuous line probes.

This article describes a home-built scanning electrochemical microscope capable of achieving high areal imaging rates through the use of continuous line probes (CLPs) and compressed sensing (CS) image reconstruction. The CLP is a nonlocal probe consisting of a band electrode, where the achievable spatial resolution is set by the thickness of the band and the achievable imaging rate is largely determined by its width. A combination of linear and rotational motors allows for CLP scanning at different angles over areas up to 25 cm2 to generate the raw signal necessary to reconstruct the desired electrochemical image using CS signal analysis algorithms. Herein, we provide detailed descriptions of CLP fabrication, microscope design, and the procedures used to carry out scanning electrochemical microscopy imaging with CLPs. In order to illustrate the basic operating procedures for the microscope, line scans and images measured in the substrate generation-probe-collection mode for flat samples containing platinum disk electrodes are presented. These exemplary measurements illustrate methods for calibrating the positioning system, positioning and cleaning the CLP, and verifying proper positioning/probe sensitivity along its length.

Trace determination of bisphenol A and phytoestrogens in infant formula powders by gas chromatography-mass spectrometry.

This investigation describes a reliable and sensitive method for simultaneously determining bisphenol A (BPA) and two major phytoestrogens, daidzein and genistein, in powdered milks and infant formulas by gas chromatography-mass spectrometric analysis after trimethylsilylation. To reduce the matrix interference associated with the constituents of the formulas, the dissolved formula solutions were firstly ultra-centrifuged and the analytes in the supernatant were then extracted using a C18 solid-phase extraction column. The accuracy and precision of the method were determined and the technique was successfully employed to measure trace concentrations of BPA, daidzein and genistein in powdered formulas. The results show that BPA, daidzein and genistein were detected in all the testing samples (n = 6) at concentrations from 45 to 113 ng/g (except one infant formula), 20 to 2050 ng/g and 21 to 6510 ng/g, respectively. The highest concentrations of daidzein and genistein (i.e., 2050 and 6510 ng/g) were detected in a soy-based powdered infant formula. The quantitation limits were 1.0 ng/g for BPA, and 10 ng/g for daidzein and genistein using 0.5 g powdered milk samples.

A fully integrated nose-on-a-chip for rapid diagnosis of ventilator-associated pneumonia.

Ventilator-associated pneumonia (VAP) still lacks a rapid diagnostic strategy. This study proposes installing a nose-on-a-chip at the proximal end of an expiratory circuit of a ventilator to monitor and to detect metabolite of pneumonia in the early stage. The nose-on-a-chip was designed and fabricated in a 90-nm 1P9M CMOS technology in order to downsize the gas detection system. The chip has eight on-chip sensors, an adaptive interface, a successive approximation analog-to-digital converter (SAR ADC), a learning kernel of continuous restricted Boltzmann machine (CRBM), and a RISC-core with low-voltage SRAM. The functionality of VAP identification was verified using clinical data. In total, 76 samples infected with pneumonia (19 Klebsiella, 25 Pseudomonas aeruginosa, 16 Staphylococcus aureus, and 16 Candida) and 41 uninfected samples were collected as the experimental group and the control group, respectively. The results revealed a very high VAP identification rate at 94.06% for identifying healthy and infected patients. A 100% accuracy to identify the microorganisms of Klebsiella, Pseudomonas aeruginosa, Staphylococcus aureus, and Candida from VAP infected patients was achieved. This chip only consumes 1.27 mW at a 0.5 V supply voltage. This work provides a promising solution for the long-term unresolved rapid VAP diagnostic problem.

Determination of estrogenic compounds in wastewater using liquid chromatography-tandem mass spectrometry with electrospray and atmospheric pressure photoionization following desalting extraction.

Two complementary LC-MS ionization methods, electrospray (ESI) and atmospheric pressure photoionization (APPI), have been optimized to determine three natural estrogenic compounds (estrone, 17beta-estradiol and estriol) and two synthetic estrogenic compounds (17alpha-ethynylestradiol and diethylstilbestrol) in the influent and effluent of wastewater treatment plants (WWTPs). The wastewater samples were first subjected to solid-phase extraction coupled with desalting extraction to remove matrix interference. The analytes were then detected using liquid chromatography-tandem mass spectrometry (LC-MS-MS) with ESI and dopant-assisted (DA) APPI to evaluate the ion suppression effect and to complement the detection and quantification of estrogenic compounds in complex wastewater samples. The average ion suppression factors for the extracts of the WWTP influent analyzed using ESI and APPI were 52+/-5% and 27+/-7%, respectively. The sensitivity and ionization efficiency of the LC-ESI-MS-MS system decreased dramatically when a complex matrix was present in the WWTP influent sample. Estrogenic compounds could be detected in the WWTP influent and effluent samples at concentrations below the parts-per-billion level. The lower detection limits obtained when using ESI and the higher matrix tolerance of the APPI method allowed the complete quantification of estrogenic compounds in very complex samples in a complementary manner.