Multiwalled carbon nanotubes synthesis with high yield utilizing Pt/Al-MCM-41 via catalytic chemical vapour deposition technique

Multiwalled carbon nanotubes (MWNTs) were synthesized over Pt impregnated Al-MCM-41 catalyst by decomposition of acetylene and characterized by XRD and nitrogen sorption isotherm to study the mesophase nature of the material. The optimum temperature and flow rate of the carbon source for CNTs synthesis are 800 °C and 60 mL/min, respectively, within a short reaction period, typically 10 min. Moreover, longer reaction time (i.e. 30 min) favours the formation of more amorphous carbon. When the reaction time is reduced to less than 10 min, formation of amorphous carbon is greatly suppressed by the high yield of MWNTs (85%). The products obtained from the decomposition of acetylene over these catalysts were characterized by TGA, SEM, TEM and Raman spectroscopy. The TEM analysis reveals that CNTs are free from amorphous carbon, whereas Raman spectrum shows two prominent peaks at 1,327 and 1,594 cm⁻¹ as the tangential modes of CNTs. As a conclusion, Pt/Al-MCM-41 is an effective template for MWNTs synthesis using acetylene as a carbon source.     

Visual inspection of the uterine cervix after the application of acetic acid in the detection of cervical carcinoma and its precursors

BACKGROUND: Organized cervical cytology screening programs are not feasible in many developing countries where cervical carcinoma is an important cause of mortality among adult women. This study compared visual inspection of the cervix after application of 3-4% acetic acid (VIA, or cervicoscopy) with cytology as methods for the detection of cervical carcinoma and its precursors. METHODS: Three thousand women were examined by both VIA and cytology. Those positive on one or both of the screening tests (n = 423) or those who had clinically suspicious lesions even if the tests were negative (n = 215) were invited for colposcopy. Directed biopsies were obtained from 277 of 573 women at colposcopy. Those with moderate dysplasia or worse lesions diagnosed by histology were considered true-positives. Those with no lesions or with reactive or reparative changes at colposcopy and those for whom histology revealed no pathology, reactive or reparative changes, atypia, or mild dysplasia were considered false-positives. The detection rate of true-positive cases and the approximate specificity of the two tests were compared. RESULTS: VIA was positive in 298 women (9.8%), and cytology was positive (for atypia or worse lesions) in 307 women (10.2%). Of the 51 true-positive cases (20 cases of moderate dysplasia, 7 of severe dysplasia, 12 of carcinoma in situ, and 12 of invasive carcinoma), VIA detected 46 (90.1%) and cytology 44 (86.2%), yielding a sensitivity ratio of 1.05. VIA detected five lesions missed by cytology, and cytology detected three missed by VIA; both missed two lesions. The approximate specificities were 92.2% for VIA and 91.3% for cytology. The positive predictive value of VIA was 17.0%, and that of cytology was 17.2%. CONCLUSIONS: These results indicate that VIA and cytology had very similar performance in detecting moderate dysplasia or more severe lesions in this study. VIA merits further evaluation as a primary screening test in low-resource settings.     

Biomechanisms of nanoparticles (toxicants, antioxidants and therapeutics): electron transfer and reactive oxygen species

In recent years, nanoparticles have received increasing attention in research and technology, including a variety of practical applications. The bioactivity appears to be related to the small particle size, in addition to inherent chemical activity as electron transfer (ET) agents, generators of reactive oxygen species (ROS) with subsequent oxidative stress (OS) and as antioxidants (AOs). The mechanism of toxicity, therapeutic action and AO property is addressed based on the ET-ROS-OS approach. There are several main classes of ET functionalities, namely, quinones (or phenolic precursors), metal compounds, aromatic nitro compounds (or reduction products) and imine or iminium species. Most of the nanospecies fall within the metal category. Cell signaling is also discussed. This review is apparently the first to address the various bioactivities based on the ET-ROS-OS-AO framework.     

Chemiresistor Sensors Based on Conducting Polymers for Hypergolic Propellants and Acidic Vapors of Rocket Exhaust Plumes – A Review

This review covers the main applications of conducting polymers in chemiresistor sensors for sensing hazardous hypergolic liquid propellant vapors and toxic exhaust plume acidic vapors of solid rocket motors at explosive (percent), toxic and threshold limit value concentration levels. The First part is focused on vapors of NO₂ and mixed oxides of nitrogen (MON‐3). The Second part is focused on vapors of hydrazines such as hydrazine, monomethylhydrazine (MMH) and unsymmetrical dimethylhydrazine (UDMH). Chemiresistor sensors for toxic HCl vapors of exhaust plume of rockets and missiles are reviewed in the third part. Salient features of the sensors such as conducting mechanisms during sensing, thickness of sensing layer, factors that influence conductivity, response time, recovery time, detectable range, and minimum detectable limit are discussed in this review. Advantages and disadvantages of conducting polymer coated fabrics as novel chemiresistor sensors over inorganic substrates are also discussed.     

Thermal Degradation Studies of Polythiophenes Containing Hetero Aromatic Side Chains

Thiophene monomer structures containing different hetero aromatic rings (containing five-member/six-member, varying electronegativity, functional groups) were designed and synthesized. The influence of structural components of the side chain on the thermal stability of the polymers of the above monomers was analyzed using thermogravimetric analysis. The results show that thiophene-containing hetero aromatic side chains linked through six-member ring show high thermal stability.     

A 100-MHz macropipelined VAX microprocessor

A macropipelined CISC microprocessor was implemented in a 0.75-μm CMOS 3.3-V technology. The 1.3-million-transistor custom chip measures 1.62×1.46 cm² and dissipates 16.3 W. The 100-MHz parts were benchmarked at 50 SPEC marks. The on-chip clocking system and several high-performance logic and circuit techniques are described. Macroinstruction handling, micropipeline management, and control store structures highlight the design architecture. The hierarchical array organization and fast tag comparison technique of the primary cache are discussed. Power estimation procedures are outlined, and the results are compared to measurements. Physical design and verification methods, and CAD tools are also described. After extensive functional verification efforts are described, chip and system test results are presented     

Mechanical properties of grafted casein films

Casein was grafted with mixtures of acrylonitrile (AN) and n-butyl methacrylate (n-BMA). The mole ratios of AN: n-BMA were 0.9:0.1 and 0.8:0.2. The mechanical properties of the grafted casein films were studied under uniaxial and biaxial stress conditions. A reduction in longitudinal stress and elongation at break was observed with the simultaneous application of lateral stress. Scanning electron micrographs of the stretched films (uniaxial and biaxial stress) are also presented.     

Fuzzy-Based Cluster Head Amendment (FCHA) Approach to Prolong the Lifetime of Sensor Networks

Wireless Personal Communications - Wireless sensor networks (WSN) consist of large number of sensor nodes that work collaboratively. Sensors segregate groups with similar traits and get arranged in...