Gas-phase reaction of 1,2-dichloroethane with hydrogen in a tubular flow reactor

We have studied the reaction of 1,2-dichloroethane with H2 in three tubular flow reactors of different diameters at atmospheric pressure in the temperature range of 550° C to 1000°C. The kinetic parameters and product distribution were experimentally determined for each size reactor. The wall and bulk reaction rate constants were decoupled via analysis of three different surface to volume reaction data. The experimental reactor was an isothermal tubular flow reactor that operated within the domain of plug flow region. The reaction was found to follow first-order kinetics with respect to 1,2-dichloroethane when in the presence of excess hydrogen. The resulting rate constants were then used to determine the Arrhenius\u27 plot. Activation energy and frequency factor were determined and put in the form of a reaction rate constant equation. These equations are as follows: for d = 0.4 cm.ID k = 4.4 x 107 Exp(-32,000/RT) (1/sec) for d = 1.05 cm.ID k = 4.6 x 107 Exp(-33,000/RT) (1/sec) for d = 1.6 cm.ID k = 5.0 x 107 Exp(-33,000/RT) (1/sec) For the case of a reactor with internal diameter of 1.05 cm, the GC analysis showed an appreciable conversion of 1,2-dichloroethane above 550°C. The conversion was found to be proportional to both temperature and residence time. Chlorinated by-products, which all had lesser number of chlorine atoms than the reagent, were observed to increase with temperature from 550°C to 675°C. The major chlorinated products observed were vinyl chloride and chloroethane. Trace amounts of 1,1-dichloroethane and methyl chloride were found by GC/MS analysis. When the temperature reached 700°C, the only chlorinated by-products observed was vinyl chloride. Complete destruction of 1,2-dichloroethane was observed above 850°C for residence time of 1 sec. Benzene was also observed above 800°C in very small amounts. The major products of 1,2-dichloroethane and H2 reaction were methane, ethane, ethylene, acetylene, vinyl chloride, chloroethane and HCl. The hydrocarbons production increased with temperature. Applying the Arrhenius\u27 equation to the values of kb and kw obtained from the equation derived by Kaufman (1), for each temperature range examined, yielded the following rate constants expressions for wall and bulk reaction: kb = 4.8 x 107 Exp(-34,000/RT) (1/sec) kw = 2.0 x 106 Exp(-31,000/RT) (cm./sec

Xanthones from Calophyllum inophyllum

Repeated separation and purification of fractions from the crude chloroform extract of Calophyllum inophyllum via column chromatography afforded five known xanthone caloxanthones A, B, C, macluraxanthone and pyranojacareubin. Structural elucidations and determination of the isolated compounds were supported by spectral analyses obtained by subjecting the compounds to various spectroscopic techniques. The chloroform extract, when tested against RAW264.7 cells for anti-inflammatory potentials, exhibited the most promising activity with an IC50 value of 14.81±0.04 µg/mL compared to moderate activities shown by the ethyl acetate and n-hexane extracts. Antimicrobial tests showed that the n-hexane and chloroform extracts acted moderately against Staphylococcus epidermidis S273 and Bacillus subtilis B145

Molecular characterisation of Eimeria tenella porin, a potential anticoccidial drug target

Eimeria tenella is an apicomplexan parasite that causes the economically important disease coccidiosis in chickens. An estimated loss over $3 billion USD per annum has been reported. Control of coccidiosis relies on chemotherapy and vaccination but drug resistance is common and live vaccines are relatively expensive. Therefore, there is an urgent need to develop new drugs to control Eimeria infections. Recent studies have shown that the pore forming structures of porin play important roles in many eukaryotic organisms. In this study, we have generated and characterised a putative porin cDNA sequence from E. tenella that we have named Etporin. Sequence alignments showed that Etporin is 47 % similar to the putative porin sequence of Toxoplasma gondii, while a search against the Conserved Domain Database (CDD) shows that Etporin contains the Porin3 superfamily domain. Multiple sequence alignment with porin sequences from various eukaryotic organisms showed that the conserved VKXKX and GLK/STK motifs are present in Etporin. Analysis of the predicted Etporin 3D structure showed a classic beta barrel structure consisting of 19 beta-strands. Taken together, these results suggested Etporin has the potential to be developed into an anticoccidial drug target

Characterization of phenazine and phenazine-1-carboxylic acid isolated from Pseudomonas aeruginosa UPMP3 and their antifungal activities against Ganoderma boninense

The structural characterization of two phenazines, produced simultaneously through biosynthesis by Pseudomonas aeruginosa UPMP3 were studied. The phenazine antibiotics play an important role in antimicrobial activities and potentially could be used in biopesticide formulation to control basal stem rot of oil palm. The antibiotics were identified through high-performance liquid chromatography (HPLC) and confirmed using Fourier Transform Infrared (FTIR) spectroscopy. The specific representations in the FTIR spectra of the purified compounds such as absorption peaks at 1353.68 (aromatic nitro compound), 1118.84 and 729.43 cm-1 (aromatic ring) were indications of phenazine (PHZ) whereas, absorption peaks at 1717.92 (carboxylic acid), 861.78 and 738.54 cm-1 (aromatic ring) were indicatives of phenazine-1-carboxylic acid (PCA). The structures of the compounds were further confirmed by 1H NMR/13C NMR spectroscopy as PHZ (C12H8N2) and PCA (C13H8N2O2). Ganoderma boninense was sensitive to purified phenazine antibiotics especially phenazine and a concentration of 1000 ppm completely inhibited the mycelial growth. As far as we know, this is the first study where purified phenazine antibiotics isolated from P. aeruginosa UPMP3 were structurally characterised and tested to have positive antagonism against G. boninense

Deep UV transparent conductive oxide thin films realized through degenerately doped wide-bandgap gallium oxide

Deep UV transparent thin films have recently attracted considerable attention owing to their potential in UV and organic-based optoelectronics. Here, we report the achievement of a deep UV transparent and highly conductive thin film based on Si-doped Ga_{2}O_{3} (SGO) with high conductivity of 2500 S/cm. The SGO thin films exhibit high transparency over a wide spectrum ranging from visible light to deep UV wavelength and, meanwhile, have a very low work-function of approximately 3.2 eV. A combination of photoemission spectroscopy and theoretical studies reveals that the delocalized conduction band derived from Ga 4s orbitals is responsible for the Ga_{2}O_{3} films’ high conductivity. Furthermore, Si is shown to act as an efficient shallow donor, yielding high mobility up to approximately 60 cm^{2}/Vs. The superior optoelectronic properties of SGO films make it a promising material for use as electrodes in high-power electronics and deep UV and organic-based optoelectronic devices

Isolation and structural modifications of ananixanthone from Calophyllum teysmannii and their cytotoxic activities

Two naturally occurring xanthones, ananixanthone (1) and β-mangostin (2), were isolated using column chromatographic method from the nhexane and methanol extracts of Calophyllum teysmannii, respectively. The major constituent, ananixanthone (1), was subjected to structural modifications via acetylation, methylation and benzylation yielding four new xanthone derivatives, ananixanthone monoacetate (3), ananixanthone diacetate (4), 5-methoxyananixanthone (5) and 5-Obenzylananixanthone (6). Compound 1 together with its four new derivatives were subjected to MTT assay against three cancer cell lines; SNU-1, K562 and LS174T. The results indicated that the parent compound has greater cytotoxicity capabilities against SNU-1 and K562 cell lines with IC50 values of 8.97 ± 0.11 and 2.96 ± 0.06 μg/mL, respectively. Compound 5 on the other hand exhibited better cytotoxicity against LS174T cell line with an IC50 value of 5.76 ± 1.07 μg/mL

Writing in London. Home and Languaging in the Work of London Poets of Chinese Descent

This essay discusses literary works produced in London by poets of Chinese descent who are foreign-born or London native. Some of these works are written in English, and some in Chinese. The aim is to discuss poetry that has emphatically or reluctantly embraced the identity narrative, talking of home and belonging in substantially different ways from each other, according to each poet’s individual relationship with movement, migration, and stability. Therefore, through the use of the phrase ‘London poets of Chinese descent’, I do not aim at tracing a shared sense of identity, but instead I am interested in using London as a method for an oblique reading that recognises the variety of angles and approaches in these poets’ individual experience, history and circumstances that can range from occasional travel to political exile

Changes of water clarity in large lakes and reservoirs across China observed from long-term MODIS

Water clarity is a well-established first-order indicator of water quality and has been used globally by water regulators in their monitoring and management programs. Assessments of water clarity in lakes over large temporal and spatial scales, however, are rare, limiting our understanding of its variability and the driven forces. In this study, we developed and validated a robust Secchi disk depth (ZSD) algorithm for lakes across China based on two water color parameters, namely Forel-Ule Index (FUI) and hue angle α, retrieved from MODIS data. The MODIS ZSD model shows good results when compared with in-situ measurements from 17 lakes, with a 27.4% mean relative difference (MRD) in the validation dataset. Compared with other empirical ZSD models, our FUI and α-based model demonstrates improved performance and adaptability over a wide range of water clarity and trophic states. This algorithm was subsequently applied to MODIS measurements to provide a comprehensive assessment of water clarity in large lakes (N = 153) across China for the first time. The mean summer ZSD of the studied lakes between 2000 and 2017 demonstrated marked spatial and temporal variations. Spatially, the ZSD of large lakes presented a distinct spatial pattern of “high west and low east” over China. This spatial pattern was found to be associated with the significant differences in lake depth and altitude between west and east China while China's population, GDP, temperature, and precipitation distribution have also contributed to a certain extent. Temporally, the ZSD of most lakes increased during this period, with an overall mean rate of 3.3 cm/yr for all lakes. Here, 38.6% (N = 59) of the lakes experienced a significant increase in their ZSD value during the past 18 years while only 8.5% (N = 13) showed a significant decreasing trend. Significant increases in lake ZSD were observed in west China, which were found to correlate with the increase of air temperature and lake surface area. This is possibly a response of the lakes in west China to climate change. In the lake systems of east China, which are predominately used as a drinking water source, the increase in lake ZSD was found to be strongly correlated with changes in local GDP (gross domestic production), NDVI (normalized difference vegetation index) and lake surface area, suggesting a combined effect of the implemented management practices and climatic variability. The results of this study provide important information for water quality conservation and management in China, and also highlight the value of satellite remote sensing in monitoring water quality over lakes at a large scale and long-term

Characterization of two immunomodulating homogalacturonan pectins from green tea

Two natural homogalacturonan (HG) pectins (MW ca. 20 kDa) were isolated from green tea based on their immunomodulatory activity. The crude tea polysaccharides (TPS1 and TPS2) were obtained from green tea leaves by hot water extraction and followed by 40% and 70% ethanol precipitation, respectively. Two homogenous water soluble polysaccharides (TPS1-2a and TPS1-2b) were obtained from TPS1 after purification with gel permeation, which gave a higher phagocytic effect than TPS2. A combination of composition, methylation and configuration analyses, as well as NMR (nuclear magnetic resonance) spectroscopy revealed that TPS1-2a and TPS1-2b were homogalacturonan (HG) pectins consisting of a backbone of 1,4-linked α-d-galacturonic acid (GalA) residues with 28.4% and 26.1% of carboxyl groups as methyl ester, respectively. The immunological assay results demonstrated that TPS1-2, which consisted mainly of HG pectins, showed phagocytosis-enhancing activity in HL-60 cells