Synthesis of boron-doped double-walled carbon nanotubes by the catalytic decomposition of tetrahydrofuran and triisopropyl borate

Boron-doped double-walled carbon nanotubes (DWCNTs) were produced by the catalytic decomposition of tetrahydrofuran and triisopropyl borate over a Fe–Mo/MgO catalyst at 900 °C. The synthesized B-doped DWCNTs had average outer and inner diameters in the range of 1.6–2.4 nm and 0.8–1.6 nm within the bundle, respectively. They had a larger interlayer spacing in the range of 0.36–0.39 nm, than did undoped DWCNTs. The B-C bonding evident from the B 1s signals in the X-ray photoelectron spectroscopy results indicated that highly coordinated boron atoms replaced the carbon atoms within the graphene sheet. As the triisopropyl borate concentration was increased from 0 to 2.5 M, the substituted boron concentration increased from 0.8 to 3.1 at.%. The results demonstrate that the substituted boron concentration in the hexagonal carbon lattices can be easily controlled by regulating the triisopropyl borate concentration.     

Defect cluster recognition system for fabricated semiconductor wafers

The International Technology Roadmap for Semiconductors (ITRS) identifies production test data as an essential element in improving design and technology in the manufacturing process feedback loop. One of the observations made from the high-volume production test data is that dies that fail due to a systematic failure have a tendency to form certain unique patterns that manifest as defect clusters at the wafer level. Identifying and categorising such clusters is a crucial step towards manufacturing yield improvement and implementation of real-time statistical process control. Addressing the semiconductor industry’s needs, this research proposes an automatic defect cluster recognition system for semiconductor wafers that achieves up to 95% accuracy (depending on the product type).     

Thermal and mechanical behavior of copper molds during thin-slab casting (I): Plant trial and mathematical modeling

Three-dimensional (3-D) finite-element thermal-stress models have been developed to predict temperature, distortion, and residual stress in the mold of continuous casters of thin steel slabs, comparing both funnel-shaped and parallel molds. The mold shape and high casting speed leads to higher mold temperatures and shorter mold life than in conventional slab casters. This study investigates heat flux and the effects of mold shape on distortion and cracking of the thin-slab mold. In Part I of this two-part article, mold wall temperatures measured in the plant were analyzed to determine the corresponding heat-flux profiles in thin-slab molds. This data was then used in an elastic-visco-plastic analysis to investigate the deformation of the molds in service for the two different mold shapes. The model predictions of temperature and distortion during operation match plant observations. During operation, the hot-face temperature reaches 580 °C and heat flux varies from 7 to 4.5 MW/m² when casting at 3.6 m/min. The copper plates bend toward the steel, with a maximum outward distortion of about 0.3 mm. This occurs just above the center of the wide faces and is smaller than the distortion of a conventional slab mold.     

Design of single peptides for self-assembled conduction channels

Self-assembly of peptides provides the possibility of achieving relatively long range order on surfaces. These ordered peptides can also form channels that can be used as conduction channels. In the past, studies were focused on electron conduction through the secondary structure and amine bond of peptides and these restrict conduction of electrons over a short range (a few nanometers). In this work, we demonstrate the realization of electron conduction over a longer range of a few hundred nanometers via π-π stacking of the phenyl groups in the tyrosine residue of a single peptide. The peptide used in this work was designed with a phenyl ring for π-π stacking at one end and a carboxylic group at the other end for binding to aminopropyltriethoxysilane (APTES) treated silicon wafer. The distance between the peptides is controlled by a disulfide bond formed between neighboring cysteine residue and also by the amine groups of aminopropyltriethoxysilane. We demonstrate that the self-assembled peptide is conducting in the dry state over hundreds of nanometers, realizing the possibility of using peptide as a molecular wire.     

Retrospective study of empyema cases in National Pediatric Hospital, Cambodia

Majority of empyema cases admitted into the National Pediatric Hospital (NPH), Cambodia were of bacterial origin (EB: 95%), the rest were caused by tuberculosis bacilli (ETB: 5%). The morbidity of overall empyema, empyema of bacterial origin and empyema of TB origin between boys and girls was the same, even though boys were more likely to be exposed than girls. The mean age of patients with ETB was significantly greater than those of EB, 84.7 +/- 46 months versus 52.5 +/- 37 months. Since NPH is located in Phnom Penh, most of our cases were from Kandal, Phnom Penh, and provinces nearby. On average all of the patients stayed in the hospital for 23.26 +/- 14.9 days (rank 1-91 days), and the mean duration of hospitalization of the ETB patients was significantly longer than that of EB patients, 32 +/- 19 days versus 22 +/- 14 days respectirely. The yearly incidence of empyema cases in 1990-1993 had the trend of slightly increased frequency during March to May. The overall EB case fatality rate was 3%, contributed to by delayed referral of cases.     

Selective inactivation of glyceraldehyde-3-phosphate dehydrogenase by vinyl sulfones

Incubation of glyceraldehyde-3-phosphate dehydrogenase with vinyl sulfones resulted in a pseudo first-order loss of enzyme activity. The selective inactivation of the enzyme by vinyl sulfones is suggested from the structural requirement analysis and the enzyme susceptibility test. The enzyme inactivation was strongly reduced in the presence of NAD or glyceraldehyde-3-phosphate, and the prior treatment of the enzyme with 5,5'-dithio-bis-(2-nitrobenzoic acid) prevented the enzyme from the inactivation by vinyl sulfones (> or = 90%). Moreover, the early rapid phase of inactivation was much more responsive to L-cysteine reactivation, compared with the slower phase. Based on these results, it is proposed that vinyl sulfones inactivate the enzyme by inducing the oxidation of cysteine residue and/or covalent binding to cysteine residue in active site.     

Temperature-compensated film bulk acoustic resonator above 2 GHz

Two different types of temperature-compensated film bulk acoustic resonators (FBARs) are designed, fabricated, and tested. One is formed by integrating FBAR with a surface-micromachined air-gap capacitor, which passively reduces the FBAR's temperature coefficient of frequency (TCF) by about 40 ppm//spl deg/C at 2.8 GHz. With this approach, zero TCF would easily have been achieved if the FBARs were built on AlN rather than ZnO. The other type of temperature compensated FBAR is built on a surface-micromachined SiO/sub 2/ cantilever that is released by XeF/sub 2/ vapor etching of silicon. The Al-ZnO-Al-SiO/sub 2/ FBAR is measured to have a TCF of -0.45 ppm//spl deg/C (between 85/spl deg/C and 110/spl deg/C) at 4.4 GHz.     

Regional cooperation and benefit sharing for sustainable water resources management in the Lower Mekong Basin

Benefit sharing is a concept associated with regional cooperation for sustainable water resources management. To this end, the present study analyses how implementation of this concept may contribute to economic growth and the promotion of sustainable livelihoods in the Lower Mekong Basin (LMB). It focuses on the balance between economic and human development, national interests, and the procedures used to manage water resources in the basin. It was found that: (a) Benefits obtained from the Mekong River are not equally shared between riparian countries because of inadequate regional cooperation, with economic and social development in the LMB being uneven, with Thailand and Vietnam achieving better human development, poverty reduction and food security outcomes than Laos and Cambodia; (b) Lack of shared national interests, or a common development agenda, has resulted in unsustainable water resource management outcomes; and (c) Procedures for water resources management agreed by the four LMB countries are well‐aligned with the conceptual framework for benefit sharing defined by Sadoff and Grey (2002, Water Policy, 4, 389), although while these procedures have the potential to facilitate a more cooperative agenda for equitable sharing of social, economic and environmental benefits from the water resources of the Mekong River, implementation of the 1995 Mekong Agreement currently remains controversial. The five procedures for water resource management developed by the Mekong River Commission have not resulted in satisfactory outcomes, due in part to the institution lacking regulatory authority.     

Characterization of micellar film morphologies of semifluorinated block copolymers by AFM

The micellar morphologies of well-defined amphiphilic block copolymers composed of 1H,1H-dihydroperfluorooctyl methacrylate (FOMA) and ethylene oxide (EO) blocks with different chain lengths were effectively investigated by using tapping mode-atomic force microscopy (TM-AFM). By spin-casting chloroform solutions, well-ordered spherical micellar films could be obtained for poly(FOMA(10k)-b-EO(10k)) and poly(FOMA(20k)-b-EO(20k)) copolymers. The atomic force microscopy (AFM) height and phase image analysis indicated that dark regions of the micelles corresponded to PEO blocks and the light regions were for PFOMA blocks. The spherical micelles with PEO corona and PFOMA core were also identified by transmission electron microscopy (TEM) and X-ray photoelectron spectrometer (XPS) analysis. The core diameters of the block-copolymer aggregates were 20nm for poly(FOMA(10k)-b-EO(10k)) and 30nm for poly(FOMA(20k)-b-EO(20k)) by TM-AFM, whereas slightly lower values of 17 and 26nm were obtained from TEM. A detailed study on the inverted morphological change observed in the micelles films after annealing above glass transition temperature (T(g)) was also presented.     

The studies of physical properties of dimeric fatty acid-modified thiodiphenyl epoxy resins

A thermally stable thiodiphenyl epoxy resin was modified with a dimeric fatty acid at an epoxy resin:fatty acid molar ratio of 4:1. The thermal and mechanical properties of the modified epoxy resin were studied by preparing an epoxy composition with an amine curing agent and a catalyst, followed by curing at 170 °C to produce a neat plastic epoxy resin. The tensile and impact strengths of the resin indicated improved flexibility and toughness compared to other epoxy resins. Enhanced toughness was confirmed by the increased lap shear strength in single lap joints prepared with steel substrates attached by the resin.