Effects of electron-transfer chemical modification on the electrical characteristics of graphene

Because of the large reactivity of single layer graphene to electron-transfer chemistries, 4-nitrobenzene diazonium tetrafluoroborate is employed to modify the electrical properties of graphene field-effect transistors. After modification, the transfer characteristics of chemically modified graphene show a reduction in the minimum conductivity, electron-hole mobility asymmetry, a decrease in the electron/hole mobility, and a positive shift of the charge neutrality point with broadening of the minimum conductivity region. These phenomena are attributed to a dediazoniation reaction and the adsorbates on the graphene surface.     

Preparation and characterization of super-hydrophobic and oleophobic surface

A novel method for preparing and characterizing super-hydrophobic and oleophobic surface is presented. Aluminum (Al) substrate was roughened by sandblasting and electrolytic etching to obtain micro- and nano-sized complex morphologies. Then, its substrate was covered by a chemically adsorbed monolayer (CAM) containing a fluorocarbon group. The surface of Al substrate roughened and covered with CAM was observed by scanning electron microscope and atomic force microscope. The roughnesses of the surface were ca. 100 μm and ca. 30–60 nm, respectively. The surface of the wettability was characterized by contact angle measurements and its surface indicated super-hydrophobicity and oleophobicity: the water contact angle (WCA) and oil contact angle (OCA) of hexadecane was 158.9° and 139.6°, respectively. The wettability was also characterized by solid surface energy. The solid surface energy of each solvent was obtained from the equation by Neumann et al. These values were extremely low, ranging from 0.31 to 1.29 mN/m. The total solid surface energy was obtained from the equation by Kaelble et al. The value was 0.3 mN/m. Their values indicated that the hydrophobicity and oleophobicity of our sample reached the highest level possible. In addition, our research demonstrates that it is easy to compare many different surfaces with super-hydrophobicity and oleophobicity using the solid surface energy.     

A simple dynamical scale‐coupling method for concurrent simulation of hybridized atomistic/coarse‐grained‐particle system

We propose a simple method for dynamical coupling of two sub‐systems with different characteristic scales described with different theoretical models, such as the fine‐scale sub‐system with the atomistic model (AM) such as the empirical inter‐atomic potential and the coarse‐scale sub‐system with the coarse‐grained particle (CGP) method, in a concurrent hybrid simulation scheme. Naive coupling of the different‐scale sub‐systems results in reflection of high wavenumber waves at the interface because of the differences in the phonon Brillouin‐zone and in the dispersion relation. To solve the problem, the present scale‐coupling method introduces (virtual) extra atoms and particles for the AM and the CGP sub‐systems, respectively, beyond the atom–particle interface, and uses the extra atoms and the particles to mutually transfer information of the waves between the two sub‐systems and to suppress the artificial reflection of the incident wave in the whole wavenumber range. As the algorithm in the present scale‐coupling method is local in time and space, it is applicable to hybrid systems with any interface shape at low computation and memory requirement. Accuracy of the present scale‐coupling method is compared with that of the existing methods for a simple model system. The hybrid AM‐CGP simulation of indentation of a graphene nano‐drum using the present scale‐coupling method is performed to demonstrate its accuracy and usefulness through its comparison with the fully atomistic results. Copyright © 2010 John Wiley & Sons, Ltd.     

NOX reduction over paper-structured fiber composites impregnated with Pt/Al2O3 catalyst for exhaust gas purification

Pt/Al₂O₃ catalyst powder was successfully incorporated in a microstructured paper-like matrix composed of a ceramic fiber network, by use of a simple papermaking technique. As-prepared composite, denoted paper-structured catalyst, was applied to the reduction of nitrogen oxide (NO _X ) in the presence of propene, for exhaust gas purification. The paper-structured catalyst demonstrated higher NO _X reduction efficiency and more rapid thermal responsiveness than a conventional Pt-loaded honeycomb catalyst, indicating that the paper-like structure with interconnected pore spaces contributes to effective transport of heat and reactants to the catalyst surfaces. Furthermore, the paper-structured catalyst with the appearance of flexible paperboard has a high degree of utility. The efficiency of utilization of Pt catalyst was improved by using hierarchically assembled paper-structured catalysts with preferential location of Pt catalyst in the upper part. The paper-structured catalyst composite with paper-like utility and porous microstructure is thought to be a promising catalytic material for efficient NO _X gas purification.     

Identification of molecular target of AMP-activated protein kinase activator by affinity purification and mass spectrometry

We show an efficient method to identify molecular targets of small molecular compounds by affinity purification and mass spectrometry. Binding proteins were isolated from target cell lysate using affinity columns, which immobilized the active and inactive compounds. All proteins bound to these affinity columns were eluted by digestion using trypsin and then were identified by mass spectrometry. The specific binding proteins to the active compound, a candidate for molecular targets, were determined by subtracting the identified proteins in an inactive compound-immobilized affinity column from that in an active compound-immobilized affinity column. This method was applied to identification of molecular targets of D942, a furancarboxylic acid derivative, which increases glucose uptake in L6 myocytes through AMP-activated protein kinase (AMPK) activation. To elucidate the mechanism of AMPK activation by D942, affinity columns that immobilized D942 and its inactive derivative, D768, were prepared, and the binding proteins were purified from L6 cell lysate. NAD(P)H dehydrogenase [quinone] 1 (complex I), which was shown as one of the specific binding proteins to D942 by subtracting the binding proteins to D768, was partially inhibited by D942, not D768. Because inhibition of complex I activity led to a decrease in the ATP/AMP ratio, and the change in the ATP/AMP ratio triggered AMPK activation, we identified complex I as a potential protein target of AMPK activation by D942. This result shows our approach can provide crucial information about the molecular targets of small molecular compounds, especially target proteins not yet identified.     

Working memory impairments in multiple sclerosis: Evidence from a dual-task paradigm.

The aim of this study was to investigate working memory in multiple sclerosis (MS) patients. To test the hypothesis that the central executive system (CES) of working memory is impaired, 36 MS patients were administered a dual-task paradigm in which a judgment of line orientation measure was performed concurrently with finger tapping, humming a melody, or reciting the alphabet. MS patients exhibited a significantly greater decrement in performance than controls during the more demanding dual-task conditions (concurrent humming or alphabet recitation) as compared with the single-task condition. Dual-task performance in MS patients correlated with performance on the Paced Auditory Serial Addition Test but not with other cognitive or clinical measures. The authors conclude that MS patients have a working memory deficit reflecting an impaired central executive system. Moreover, impairments in speed of information processing in MS patients are associated with this CES deficit. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Verb confrontation naming and word-picture matching in Alzheimer's disease.

Patients with Alzheimer's disease (AD) were asked to name pictures and perform a multiple-choice word–picture matching task with verbs and nouns. AD patients were significantly more impaired with verbs than nouns for both naming and word–picture matching, and their patterns of semantic naming errors differed for verbs and nouns. One subgroup of AD patients was compromised on both naming and word–picture matching consistent with a semantic memory deficit. Naming was worse for verbs than for nouns in these patients, and they produced significantlv fewer hierarchically related semantic substitutions for verbs than for nouns. Other AD patients without semantic memory difficulty did not demonstrate these form class-sensitive patterns. The investigators hypothesize that form class-specific effects in AD patients' naming are due in part to differences in processing verbs and nouns in semantic memory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)