Memory characteristics of a self-assembled monolayer of Pt nanoparticles as a charge trapping layer

A self-assembled monolayer of Pt nanoparticles (NPs) was studied as a charge trapping layer for non-volatile memory (NVM) applications. Pt NPs with a narrow size distribution (diameter ～4?nm) were synthesized via an alcohol reduction method. The monolayer of these Pt NPs was immobilized on a SiO(2) substrate using poly(4-vinylpyridine) (P4VP) as a surface modifier. A metal-oxide-semiconductor (MOS) type memory device with Pt NPs exhibits a relatively large memory window of 5.8?V under ± 7?V for program/erase voltage. These results indicate that the self-assembled Pt NPs can be utilized for NVM devices.     

Mechanical properties of functionalized carbon nanotubes

Carbon nanotubes (CNTs) used to reinforce polymer matrix composites are functionalized to form covalent bonds with the polymer in order to enhance the CNT/polymer interfaces. These bonds destroy the perfect atomic structures of a CNT and degrade its mechanical properties. We use atomistic simulations to study the effect of hydrogenization on the mechanical properties of single-wall carbon nanotubes. The elastic modulus of CNTs gradually decreases with the increasing functionalization (percentage of C-H bonds). However, both the strength and ductility drop sharply at a small percentage of functionalization, reflecting their sensitivity to C-H bonds. The cluster C-H bonds forming two rings leads to a significant reduction in the strength and ductility. The effect of carbonization has essentially the same effect as hydrogenization.     

Novel fabrication of an SnO(2) nanowire gas sensor with high sensitivity

We fabricated a nanowire-based gas sensor using a simple method of growing SnO(2) nanowires bridging the gap between two pre-patterned Au catalysts, in which the electrical contacts to the nanowires are self-assembled during the synthesis of the nanowires. The gas sensing capability of this network-structured gas sensor was demonstrated using a diluted NO(2). The sensitivity, as a function of temperature, was highest at 200?°C and was determined to be 18 and 180 when the NO(2) concentration was 0.5 and 5?ppm, respectively. Our sensor showed higher sensitivity compared to different types of sensors including SnO(2) powder-based thin films, SnO(2) coating on carbon nanotubes or single/multiple SnO(2) nanobelts. The enhanced sensitivity was attributed to the additional modulation of the sensor resistance due to the potential barrier at nanowire/nanowire junctions as well as the surface depletion region of each nanowire.     

Atomistic study of structures and elastic properties of single crystalline ZnO nanotubes

The structural stability and Young's modulus of single crystalline ZnO nanotubes are investigated using atomistic simulations. Unlike the case for conventional layered nanotubes, the energetic stability of single crystalline ZnO nanotubes is related to the wall thickness. The potential energy of ZnO nanotubes with fixed outer and inner diameters decreases with increasing wall thickness, while the nanotubes with the same wall thickness are independent of the outer and inner diameters. The transformation of single crystalline ZnO nanotubes with a double layer from wurtzite phase to graphitic phase suggests the possibility of wall-typed ZnO nanotubes. The size-dependent Young's modulus of ZnO nanotubes is also investigated. The wall thickness plays a significant role in the Young's modulus of single crystalline ZnO nanotubes, whereas the variation of outer and inner diameters slightly affects the Young's modulus of nanotubes with same wall thickness.     

Effects of bioactive ceramics on the pathogenesis of rat vascular smooth muscle cells treated with phorbol 12-myristate 13-acetate

Vascular smooth muscle cells (VSMCs) play a pivotal role in vascular injury through proliferation and migration. Pro-inflammatory cytokines and cyclooxygenase (COX)-2 and nitric oxide synthase (NOS) are highly associated with the pathogenesis of VSMCs. We investigated the effect of bioactive ceramics on the expression of inflammatory cytokines, COX-2, and inducible NOS (iNOS) induced by phorbol 12-myristate 13-acetate (PMA) in rat VSMCs. The ceramics inhibited mRNA expression of IL-1β, TNF-α, IL-6, COX-2, and iNOS. Prostaglandin release was also diminished by the ceramics. The bioactive ceramics effect on cytokines, COX-2, and iNOS expression was achieved by inhibition of NF-κB activity. Interestingly, the ceramics-induced up-regulation of expression of endothelial NOS resulted in an increase of nitric oxide production. Thus, bioactive ceramics may have dual effects on the pathogenesis of VSMCs by regulation of NF-κB activity and NO production.     

Ordered silicon vacancies in the framework structure of the zeolite catalyst SSZ-74

Physico-chemical characterization of the high-silica zeolite catalyst SSZ-74 (ref. 1) suggested that it, like the related materials TNU-9 (ref. 2) and IM-5 (ref. 3), has a multidimensional 10-ring channel system. Such pore systems are ideal for many petrochemical applications, and indeed SSZ-74 has been shown to be a good catalyst for a wide variety of reactions. The elucidation of its framework structure, however, proved to be difficult. Comparable problems were encountered with TNU-9 and IM-5, which were synthesized with related structure-directing agents. Their framework structures, which are the two most complex ones known, both have 24 Si atoms in the asymmetric unit, and were finally solved by combining high-resolution powder diffraction data with information derived from high-resolution electron microscopy images. Therefore, a similar approach, using the powder charge-flipping algorithm to combine the two types of data and molecular modelling to help to locate the structure-directing agent, was applied to SSZ-74. This procedure eventually revealed a most unusual 23-Si-atom framework structure (|(C(16)H(34)N(2))(4)&Si(92)(4)O(184)(OH)(8)]) with ordered Si vacancies.     

Adapting cognitive-behavioral therapy for Mexican American students with anxiety disorders: Recommendations for school psychologists.

Mexican American students are the fastest growing group in U.S. public schools. There is a growing body of research indicating that Mexican American families underutilize mental health services and are more likely to drop out of care prematurely when they do seek help. These findings may indicate that our health care system is not providing ethnic minorities with culturally competent care. Although cognitive?behavioral interventions are considered to be evidence-based treatments for child anxiety disorders, previous protocols have not taken cultural factors into account. This article discusses how to adapt cognitive?behavioral therapy (CBT) for Mexican American students with anxiety disorders. Working within the Psychotherapy Adaptation and Modification Framework (PAMF), this article offers adaptation principles that may guide school psychologists in implementing CBT strategies when working with Mexican American youth and their families. A case study is provided illustrating how cultural modifications of CBT can lead to positive outcomes for Mexican American students. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Isolation and identification of antimicrobial substances from Korean Lettuce (<Emphasis Type="Italic">Youngia sonchifolia</Emphasis> M.)

The aim of this study was to identify of antimicrobial substances from Korean Lettuce (Youngia sonchifolia M.). Water and ethanol extracts of Youngia sonchifolia M. exhibited antimicrobial activities against the microorganisms tested. Ethanol extract showed strong antimicrobial activities against most Gram positive and Gram negative microorganisms, whereas no lactic acid bacteria and yeasts were not affected. The antimicrobial compound G-6 was isolated from the ethyl acetate fraction obtained by silica gel column chromatography and HPLC and was confirmed as stable against heat treatment. Molecular weight of G-6 was calculated as 154 kDa based on information in the MS spectrum. G-6 was identified as 2-nonynoic acid (C₉H₁₄O₂) by UV, LC-EI/MS, and LC-CI/MS. In support of this, the chromatogram of G-6 was consistent with that of the 2-nonynoic acid standard. Antimicrobial activity of 2-nonynoic acid was identified in all samples, with a significant difference based on concentratio.