Studies of the effects of O-methylation on the pyrolysis behaviour of four coals

O-methylation of coal was found to exhibit a noticeable effect on the pyrolysis behaviour of the original coal. Significant increases in tar yields and a low-temperature fraction, 150–300 °C, were found for the low-rank O-methylated coals. It is proposed that methylation prevents formation of new ether cross linkages through water elimination reactions of hydroxyl functional groups thus allowing for the release of a low-temperature fraction as well as a higher temperature tar. KBr studies of CD₃ labelled O-methylated coals using CD₃I as the methylating agent have resulted in the identification of three distinct i.r. absorptions in the C-D stretching region which have been assigned to methylated phenolic, methylated carboxylic and methylated aliphatic hydroxyl groups. Pyrolysis studies of the O-methylated coals have resulted in better insight into the decomposition mechanisms of different methylated hydroxyl functional groups. Methanol or formaldehyde are seen to be the principle products from the pyrolysis of methylated carboxylic and aliphatic hydroxyls. Decomposition of methylated phenolic groups occurs at a slightly higher temperature and produces principally methane and carbon monoxide.     

Advanced system‐level simulation paradigm for ultra‐wideband systems using SCERNE platform

In this article, a progressive system‐level simulation framework is developed based on Simulation de Chaînes d'Emission/Réception Nouvelle gEnération (SCERNE) platform to simulate an ultra‐wideband (UWB) impulse radar transmitter and accurately predict its performance. With the purpose of demonstrating the usefulness of the SCERNE ability in system‐level modeling, we present and simulate a simplified structure of UWB impulse radar transmitter. First, after simulation each component in different circuit‐level tools such as ADS, CST, and HFSS, each part has been modeled by using different modeling methods to transfer their data into MATLAB environment. Then, we duplicate the transmitter structure in SCERNE toolbox to validate the results. The advantage conferred by the proposed SCERNE toolbox is that fast and accurate bilateral modeling method is available at multi‐medium structures in contrast with conventional unilateral modeling, and so a lower memory and higher accuracy of the behavioral model is achieved. It can also be beneficial when the user is looking for system‐level, as the increased components amounts can help as a surrogate model. The system model can be easily extended to other UWB radar systems by simply changing the input pulse shape, UWB channel environment, transceiver topology, etc. Various effects such as signal quality, and pulse shape that can easily investigate and re‐optimize for high performance are using the developed model. To validate the practicality of the proposed paradigm, the simulations and predictions through model results are being outlined.     

Biosynthesis of ~(13)C-Labeled Amino Acids and Sugars by Spirulina (Arthrospira) Maxima in a Parallelepiped Photobioreactor

This paper presents the investigation on biosynthesis of high-value-added amino acids and sugars labeled uniformly with stable isotope 13C by microalga Spirulina (Arthrospira) maxima in a parallelepiped photobioreactor. The kinetic data of both batch and continuous cultures with characterization of the amino acids and sugars are shown. The continuous culture without nutrients deficiency is for biosynthesis of amino acids, with tyrosine as one of the principal constituents, and the batch culture with deficiency in nitrogen is for biosynthesis of labeled glucose that is up to 64% versus dry mass of cells.     

Odako growth of dense arrays of single-walled carbon nanotubes attached to carbon surfaces

A novel process is demonstrated whereby dense arrays of single-walled carbon nanotubes (SWNT) are grown directly at the interface of a carbon material or carbon fiber. This growth process combines the concepts of SWNT tip growth and alumina-supported SWNT base growth to yield what we refer to as “odako” growth. In odako growth, an alumina flake detaches from the carbon surface and supports catalytic growth of dense SWNT arrays at the tip, leaving a direct interface between the carbon surface and the dense SWNT arrays. In addition to being a new and novel form of SWNT array growth, this technique provides a route toward future development of many important applications for dense aligned SWNT arrays. Electronic Supplementary Material  Supplementary material is available for this article at and is accessible for authorized users. This article is published with open access at Springerlink.com     

Cutting single-walled carbon nanotubes

A two-step process is utilized for cutting single-walled carbon nanotubes (SWNTs). The first step requires the breakage of carbon-carbon bonds in the lattice while the second step is aimed at etching at these damage sites to create short, cut nanotubes. To achieve monodisperse lengths from any cutting strategy requires control of both steps. Room-temperature piranha and ammonium persulfate solutions have shown the ability to exploit the damage sites and etch SWNTs in a controlled manner. Despite the aggressive nature of these oxidizing solutions, the etch rate for SWNTs is relatively slow and almost no new sidewall damage is introduced. Carbon-carbon bond breakage can be introduced through fluorination to ～C(2)F, and subsequent etching using piranha solutions has been shown to be very effective in cutting nanotubes. The final average length of the nanotubes is approximately?100?nm with carbon yields as high as 70-80%.     

Controlled multistep purification of single-walled carbon nanotubes

A controlled and scalable multistep purification method has been developed to remove iron impurity and nonnanotube carbon materials from raw single-walled carbon nanotubes (SWNTs) produced in the HiPco (high-pressure CO) process. In this study, iron nanoparticles, coated by carbon, are exposed and oxidized by multiple step oxidation at increasing temperatures. To avoid catalytic oxidation by iron oxide of carbon nanotubes, the exposed and oxidized iron oxide is deactivated by reaction with C(2)H(2)F(4) or SF(6). The iron fluorides are removed by a Soxhlet extraction with a 6 M HCl solution. The purity and quality of each sample were determined by thermogravimetric analysis (TGA), Raman spectrometry, ultraviolet-visible-near-IR (UV-vis-near-IR) spectrometry, fluorescence spectrometry, and transmission electron microscope (TEM) spectroscopy. The purity and yield of SWNTs are improved due to reduced catalytic activity of the iron oxide. Greater iron oxide removal also resulted from oxidation at higher temperatures.     

Survival tests with Chironomus riparius exposed to spiked sediments can profit from DEBtox model

DEBtox model is a biologically based model used to analyse aquatic toxicity data (The analysis of aquatic toxicity data, VU University Press, Amsterdam, The Netherlands, 1996, 149pp.). To date, it has not been used to analyse sediment survival tests, mainly because this would require daily counting of survivors, which is difficult for benthic organisms. In the present study, we adapted survival toxicity tests with the midge Chironomus riparius to permit survival data analysis with DEBtox. To validate the adaptation proposed, we exposed organisms to two chemicals, copper and methiocarb. We exposed larvae of second, third and fourth instar to different concentrations of the tested compounds and two different diets to assess the influence of diet and instar on DEBtox parameter estimates. Daily counting of organisms did not affect survival and did not lead to much more effort when compared to usual tests. Moreover, the analysis profited much from use of the DEBtox model. It was possible, with only survival data to estimate and validate the kinetics of the compounds, to predict survival during the recovery of exposed organisms and to assess the influence of food availability on toxicity. Food availability did not influence methiocarb toxicity, but copper was more toxic to food-limited organisms when a threshold concentration was exceeded. Comparison of parameters estimate also helped in understanding the differences in toxicity responses between instars. For the two compounds we studied, the difference was entirely explained by differences in threshold values.     

The impact of bronchial colonization in the quality of life of patients with chronic, stable bronchitis

BACKGROUND: The aim of this study was to determine the impact of respiratory function and bacterial colonization of the lower airway on the quality of life of patients with chronic, stable bronchitis (CB). MATERIALS AND METHODS: A series of 41 patients with stable CB was studied (age: 63.8; standard deviation (SD) 9.1 years; FVC% 91.0 (18.9); FEV1% 74.6 (23.7); FEV1/FEC 62.8 (11.2) with normal thoracic radiography. Patients with previous diagnosis of bronchiectasia, bronchial asthma and/or positive bronchodilatory tests (> 15%) were not included in the study. Bacterial growth in a sputum sample of grade 4-5 of the Murray-Washington scale was considered diagnostic of bronchial colonization. Measurement of the quality of life was performed with the Nottingham Health Profile (NHP) and the St. George Respiratory Questionnaire (SGRQ). RESULTS: The patients presented a moderate alteration in their quality of life with scores over 25 in most of the dimensions of the NHP and the SGRQ. In 9 out of 41 cases (22%), the sputum cultures demonstrated bronchial colonization with the most frequently isolated bacterias being Haemophilus influenzae and Moraxella catarrhalis. Multivariate analysis performed with the quality of life as the dependent variable showed an association between FEV1/FEC1 and the SGRQ score (R2 = 0.18), and energy (R2 = 0.09) and physical mobility (R2 = 0.05) of NHP. CONCLUSIONS: Bronchial obstruction is the main determinant in the quality of life in patients with stable CB. Colonization of the lower airway is observed in 22% of the patients and also influences the quality of life of the patients but to a much lesser extent.