High-purity synthesis of scrolled mats of multi-walled carbon nanotubes using temperature modulation

Felt-like mats (6-7 μm thick) of multiwalled carbon nanotubes wrapped into scrolls have been synthesized by chemical vapor deposition from a toluene-ferrocene mixture using a temperature ramp from 680 °C to 550 °C in hydrogen-argon atmosphere. Thermogravimetric analysis reveals a very low catalyst content of ca. 1.25 wt% in the as-synthesized sample while, X-ray photo electron and Raman spectroscopies suggest the results matching with that of multiwalled carbon nanotubes. Considering, different time scales of various reactions and the diffusion of different reactants and products a tentative base growth mechanism has been proposed as per the available characterization data in conjunction with possible scrolling effects. Thermal expansion effects could explain a tentative mechanism for rolling action of sheets. Interestingly, electrical conductivity measurements as a function of temperature suggest a semiconducting behavior, despite being governed by different electron transport mechanisms with activation energies of 0.33 and 1.03 meV corresponding to two temperature ranges respectively. Cyclic voltammetry and electrochemical impedance analysis show a reversible redox behavior due to very low catalyst content and an irreversible etching of the Fe catalyst after acid treatment.     

Waveform classification and information extraction from LIDAR databy neural networks

Two different neural network schemes for the classification of light detection and ranging (LIDAR) waveforms for the LARSEN 500 airborne system and for extraction of ocean information are proposed. The first method employs a single layer of linear neurons for classification of waveforms into various clusters. Both unsupervised and supervised learning algorithms have been employed to demonstrate the spatial distribution of milt in near-shore waters. In the second method, a new multistage multilayer feedforward architecture is used for the classification of the waveforms and for the extraction of various types of ocean information. The stage I networks work in a parallel fashion and map the input waveforms to a set of characteristics. The networks in stage II use these characteristics to assign a signature number to the waveform or extract other information. Both the schemes are used with real-world data collected by the LARSEN 500 system. The paper concludes with experimental results and comparisons     

Behavior of Oxide Scale on 9Cr–1Mo Steel Under Varying External Stresses

The effects of different external stresses on the oxidation behavior of9Cr–1Mo steel were investigated. Tensile specimens were subjected tostresses of 11, 20, 28, and 40 MPa and the oxidation behavior was studiedat a temperature of 973 K. The elongation of the specimen was determined byan extensometer. An acoustic-emission unit was employed to monitor theintegrity of the oxide scale. The oxide scale was found to undergo bucklingbefore spalling, in the case of unstressed specimens, and in the case ofthose specimens subjected to a stress up to 28 MPa. The specimen with 40 MPastress showed the development of cracks. The application of external stressup to 28 MPa (average strain rate for 28 MPa stress was1.2 x 10^-7 s^-1) had a beneficial effect with respectto the adherence of the oxide scale. The specimen with 40 MPa of stress(average strain rate of 5.2 x 10^-77 s^-1) showedsubstantial weight gain on oxidizing up to 140 hr. The unstressed specimenrevealed enhanced spallation when compared with the stressedones. Investigation by SEM revealed the spalling of the oxide scale when theduration of oxidation was higher than 70 hr at all stress levels employed inthe present investigation. Formation of cracks at 40 MPa exposed fresh areasto oxygen and caused accelerated oxidation. Analysis by energy-dispersiveX-ray spectrometry (EDS) revealed the segregation of chromium at the oxideridges. The segregation of silicon was also significant for the specimensubjected to a stress of 40 MPa. Analysis by XRD clearly revealed thepresence of oxides of chromium and iron (Cr₂O₃ andFe₂O₃) and spinel-type oxide (FeCr₂O₄).     

Synthetic and Biological Studies of Sesquiterpene Polygodial: Activity of 9‐Epipolygodial against Drug‐Resistant Cancer Cells

Polygodial, a terpenoid dialdehyde isolated from Polygonum hydropiper L., is a known agonist of the transient receptor potential vanilloid 1 (TRPV1). In this investigation a series of polygodial analogues were prepared and investigated for TRPV1‐agonist and anticancer activities. These experiments led to the identification of 9‐epipolygodial, which has antiproliferative potency significantly exceeding that of polygodial. 9‐Epipolygodial was found to maintain potency against apoptosis‐resistant cancer cells as well as those displaying the multidrug‐resistant (MDR) phenotype. In addition, the chemical feasibility for the previously proposed mechanism of action of polygodial, involving the formation of a Paal–Knorr pyrrole with a lysine residue on the target protein, was demonstrated by the synthesis of a stable polygodial pyrrole derivative. These studies reveal rich chemical and biological properties associated with polygodial and its direct derivatives. These compounds should inspire further work in this area aimed at the development of new pharmacological agents, or the exploration of novel mechanisms of covalent modification of biological molecules with natural products.     

Liquid flow in polyurethane foams for filtration applications: a study on their characterization and permeability estimation

Journal of Porous Materials - Open-cell polyurethane foams have been investigated for various filtration applications to treat industrial byproducts and waste water. Flow-related morphological...     

Genotype diversity of Escherichia coli isolates in natural waters determined by PFGE and ERIC-PCR

Most library-dependent bacterial source tracking studies using Escherichia coli (E. coli) have focused on strain diversity of isolates obtained from known human and animal faecal sources for library development. In contrast, this study evaluated the genotype variation of E. coli isolated from natural surface water using pulsed field gel electrophoresis (PFGE) and enterobacterial repetitive intergenic consensus sequence polymerase chain reaction (ERIC-PCR) to better understand these naturally occurring populations. A total of 650 water samples were collected over a nine month period from eleven sampling stations from Lake Waco and Belton Lake in Central Texas. Of the 650 water samples collected, 412 were positive for E. coli, yielding a total of 631 E. coli isolates (1-12 isolates collected per sample). PFGE and ERIC-PCR patterns were successfully generated for 555 isolates and were compared using the curve-based Pearson's product-moment correlation coefficient. The 555 E. coli isolates represented 461 PFGE genotypes, with 84% (386/461) of the genotypes being represented by individual isolates. The remaining 75 genotypes were represented by 2-5 isolates each. Using ERIC-PCR, the 555 E. coli isolates represented 175 genotypes, with 63% (109/175) of the genotypes being represented by individual isolates. In contrast to the PFGE results, two ERIC-PCR genotypes represented 37% of the E. coli isolates, (83 and 124 isolates, respectively), and were found throughout the watersheds both spatially and temporally. Based on the PFGE genotype diversity of water isolates, there is little evidence that a small number of environmentally-adapted E. coli represent dominant populations in the studied waterbodies. However, with the lower discriminatory power technique ERIC-PCR, an opposing conclusion might have been drawn. These results emphasize the importance of considering the resolving power of the source tracking technique being used when assessing strain diversity and geographical stability.