Hydrophilic modification of neural microelectrode arrays based on multi-walled carbon nanotubes

To decrease the impedance of microelectrode arrays, for neuroscience applications we have fabricated and tested MEA based on multi-walled carbon nanotubes. With decreasing physical size of a microelectrode, its impedance increases and charge-transfer capability decreases. To decrease the impedance, the effective surface area of the electrode must generally be increased. We explored the effect of plasma treatment on the surface wettability of MWCNT. With a steam-plasma treatment the surface of MWCNT becomes converted from superhydrophobic to superhydrophilic; this hydrophilic property is attributed to?-OH bonding on the surface of MWCNT. We reported the synthesis at 400?°C of MWCNT on nickel-titanium multilayered metal catalysts by thermal chemical vapor deposition. Applying plasma with a power less than 25?W for 10?s improved the electrochemical and biological properties, and circumvented the limitation of the surface reverting to a hydrophobic condition; a hydrophilic state is maintained for at least one month. The MEA was used to record neural signals of a lateral giant cell from an American crayfish. The response amplitude of the action potential was about 275?μV with 1?ms period; the recorded data had a ratio of signal to noise up to 40.12?dB. The improved performance of the electrode makes feasible the separation of neural signals and the recognition of their distinct shapes. With further development the rapid treatment will be useful for long-term recording applications.     

Effective Control Charts for Monitoring Multivariate Process Dispersion

When monitoring process dispersion, it is common to pay more attention to dispersion increases than to decreases for practical reasons. Nonetheless, it is also important to detect dispersion decreases for two reasons: (i) it deserves further investigations as to why the process has improved; and (ii) if the process has changed, the settings of the control chart would need to be adjusted for effective future monitoring. In this paper, we first propose an effective control chart for detecting multivariate dispersion decreases in phase II process monitoring, which is constructed using the same approach as that of the one‐sided likelihood‐ratio‐test‐based multivariate chart proposed recently in the literature for detecting dispersion increases. We then discuss a combined charting scheme by combining these two one‐sided charts for detecting either dispersion increases or decreases. Comparative simulation studies show that the proposed combined control charting scheme outperforms several existing two‐sided control charts in terms of the average run length when the process dispersion indeed increases or decreases. Two real‐life examples are presented to demonstrate the applicability of the proposed charts. Copyright © 2011 John Wiley & Sons, Ltd.     

An improved sum-of-disjoint-products technique for the symbolic network reliability analysis with known minimal paths

Evaluating the network reliability is an important topic in the planning, designing, and control of systems. The sum-of-disjoint products technique (SDP) is a major fundamental tool for evaluating stochastic network reliability. In this study, a new SDP based on some intuitive properties that characterize the structure of minimal paths (MPs), and the relationships between MPs and subpaths are developed to improved SDP. The proposed SDP is easier to understand and implement, and better than the existing best- known SDP based algorithms under some special situation. The correctness of the proposed algorithm will be analyzed and proven. One bench example is illustrated to show how the network reliability with known MPs is determined using the proposed SDP.     

Formation of various metal nanostructures with thermal annealing to control the effective coupling energy between a surface plasmon and an InGaN/GaN quantum well

We demonstrate the variations of the photoluminescence (PL) spectral peak position and intensity through the surface plasmon (SP) coupling with an InGaN/GaN quantum well (QW) by forming Ag nanostructures of different scale sizes on the QW structure with thermal annealing. By transferring an Ag thin film into a nanoisland structure, we can not only enhance the PL intensity, but also adjust the SP dispersion relation and hence red-shift the effective QW emission wavelength. Such an emission spectrum control can be realized by initially coating Ag films of different thicknesses. Although the screening process of the quantum-confined Stark effect, which can result in PL spectrum blue-shift and intensity enhancement, also contributes to the variations of the emission behaviour, it is found that the SP-QW coupling process dominates in the observed phenomena.     

Synthesis and electroluminescent property of tris{2-(naphtha [3,4]imidazol-2-yl) pyridinato} Aluminum

An emission material, tris{2-(naphtha [3,4]imidazol-2-yl) pyridinato} Aluminum (AlNIP) used for organic light emitting devices, has been synthesized. The decomposition temperature was observed at 510 °C and no melting transition (T_m) of AlNIP was observed up to 400 °C. The emission spectrum of organic emitting device using AlNIP as emitted layer exhibits a broad maximum at 536 nm. The color of the emitted light is in the orange region in the CIE coordinate of x = 0.41 y = 0.53.     

3-D ultrasound imaging using a forward-looking CMUT ring array for intravascular/intracardiac applications

Forward-viewing ring arrays can enable new applications in intravascular and intracardiac ultrasound. This work presents compelling, full-synthetic, phased-array volumetric images from a forward-viewing capacitive micromachined ultrasonic transducer (CMUT) ring array wire bonded to a custom integrated circuit front end. The CMUT ring array has a diameter of 2 mm and 64 elements each 100 microm x 100 microm in size. In conventional mode, echo signals received from a plane reflector at 5 mm had 70% fractional bandwidth around a center frequency of 8.3 MHz. In collapse mode, 69% fractional bandwidth is measured around 19 MHz. Measured signal-to-noise ratio (SNR) of the echo averaged 16 times was 29 dB for conventional operation and 35 dB for collapse mode. B-scans were generated of a target consisting of steel wires 0.3 mm in diameter to determine resolution performance. The 6 dB axial and lateral resolutions for the B-scan of the wire target are 189 microm and 0.112 radians for 8 MHz, and 78 microm and 0.051 radians for 19 MHz. A reduced firing set suitable for real-time, intravascular applications was generated and shown to produce acceptable images. Rendered three-dimensional (3-D) images of a Palmaz-Schatz stent also are shown, demonstrating that the imaging quality is sufficient for practical applications.     

Monitoring explosive crystallization phenomenon of amorphous silicon thin films during short pulse duration XeF excimer laser annealing using real-time optical diagnostic measurements

Melting and crystallization scenario of amorphous silicon (a-Si) thin films have been investigated using in situ time-resolved optical reflection and transmission measurements. The explosive crystallization phenomenon is observed using a single-mode continuous wave He-Ne probe laser for thickness of 50 nm and 90 nm a-Si thin films upon 25 ns pulse duration of XeF excimer laser irradiation, respectively. The explosive crystallization phenomenon is easier to observe in the large thickness of a-Si thin films, a sample with pure a-Si microstructure and under longer pulse duration of excimer laser irradiation by time-resolved optical reflection and transmission measurements.     

Application of the low dielectric methyl-silsesquiazane (MSZ) as a passivation layer on TFT-LCD

In this study a low-k material, methyl-silsesquiazane (MSZ) has been investigated as a passivation dielectric layer for thin-film transistor (TFT) arrays. Compared with the conventional nitride film (k ∼ 7), the MSZ passivation layer exhibits a low residual stress and low dielectric constant (k ∼ 2.6) which lowers the RC delay in a device. The high transmittance and good planarization characteristics of a low-k MSZ film enhance the brightness and aperture ratio of thin-film transistors liquid crystal displays (TFT-LCDs).     

Comparison of the abilities of ambient and manufactured nanoparticles to induce cellular toxicity according to an oxidative stress paradigm

Nanomaterial properties differ from those bulk materials of the same composition, allowing them to execute novel activities. A possible downside of these capabilities is harmful interactions with biological systems, with the potential to generate toxicity. An approach to assess the safety of nanomaterials is urgently required. We compared the cellular effects of ambient ultrafine particles with manufactured titanium dioxide (TiO2), carbon black, fullerol, and polystyrene (PS) nanoparticles (NPs). The study was conducted in a phagocytic cell line (RAW 264.7) that is representative of a lung target for NPs. Physicochemical characterization of the NPs showed a dramatic change in their state of aggregation, dispersibility, and charge during transfer from a buffered aqueous solution to cell culture medium. Particles differed with respect to cellular uptake, subcellular localization, and ability to catalyze the production of reactive oxygen species (ROS) under biotic and abiotic conditions. Spontaneous ROS production was compared by using an ROS quencher (furfuryl alcohol) as well as an NADPH peroxidase bioelectrode platform. Among the particles tested, ambient ultrafine particles (UFPs) and cationic PS nanospheres were capable of inducing cellular ROS production, GSH depletion, and toxic oxidative stress. This toxicity involves mitochondrial injury through increased calcium uptake and structural organellar damage. Although active under abiotic conditions, TiO2 and fullerol did not induce toxic oxidative stress. While increased TNF-alpha production could be seen to accompany UFP-induced oxidant injury, cationic PS nanospheres induced mitochondrial damage and cell death without inflammation. In summary, we demonstrate that ROS generation and oxidative stress are a valid test paradigm to compare NP toxicity. Although not all materials have electronic configurations or surface properties to allow spontaneous ROS generation, particle interactions with cellular components are capable of generating oxidative stress.     

Highly Efficient 2D/3D Hybrid Perovskite Solar Cells via Low‐Pressure Vapor‐Assisted Solution Process

The fabrication of multidimensional organometallic halide perovskite via a low‐pressure vapor‐assisted solution process is demonstrated for the first time. Phenyl ethyl‐ammonium iodide (PEAI)‐doped lead iodide (PbI₂) is first spin‐coated onto the substrate and subsequently reacts with methyl‐ammonium iodide (MAI) vapor in a low‐pressure heating oven. The doping ratio of PEAI in MAI‐vapor‐treated perovskite has significant impact on the crystalline structure, surface morphology, grain size, UV–vis absorption and photoluminescence spectra, and the resultant device performance. Multiple photoluminescence spectra are observed in the perovskite film starting with high PEAI/PbI₂ ratio, which suggests the coexistence of low‐dimensional perovskite (PEA₂MA_n?1Pb_nI_3n+1) with various values of n after vapor reaction. The dimensionality of the as‐fabricated perovskite film reveals an evolution from 2D, hybrid 2D/3D to 3D structure when the doping level of PEAI/PbI₂ ratio varies from 2 to 0. Scanning electron microscopy images and Kelvin probe force microscopy mapping show that the PEAI‐containing perovskite grain is presumably formed around the MAPbI₃ perovskite grain to benefit MAPbI₃ grain growth. The device employing perovskite with PEAI/PbI₂ = 0.05 achieves a champion power conversion efficiency of 19.10% with an open‐circuit voltage of 1.08 V, a current density of 21.91 mA cm^?2, and a remarkable fill factor of 80.36%.