Efficacy of novel organotin(IV) complexes on non-durable tropical wood against decay fungi

Interest in organotin(IV) compounds is increasing due to their interesting structural features and possession of biological activities. The objective of this study was to determine the efficacy of novel organotin(IV) complexes against Trametes versicolor and Gloeophyllum trabeum decay fungi. Soil block decay test was performed using T. versicolor and G. trabeum for 16 weeks. Ten 19 × 19 × 19 mm³ sized wood cubes of Alstonia scholaris, Macaranga triloba and Hevea brasiliensis were treated with three levels of concentration (0.1, 0.5 and 1 %) of monomethyltin(IV) (MMT) and monophenyltin(IV) (MPT) of monosubstituted organotin(IV) and dimethyltin(IV) (DMT), diphenyltin(IV) (DPT) and dibutyltin(IV) (DBT) of disubstituted organotin(IV) complexes with 2-acetylpyridine-N(4)-cyclohexyl thiosemicarbazone (APCT) ligand and their respective retention uptake was determined. The best protection against decay fungi was provided by dibutyltin(IV) complex followed by diphenyltin(IV), dimethyltin(IV), monophenyltin(IV) and monomethyltin(IV) complexes with mean weight loss ranging from 4 to 5, 5 to 7, 8 to 9, 10 to 11 and 14 to 19 percent, respectively while the weight loss of the untreated wood cubes varied from 51 to 65 %. Wood densities decreased with increased weight loss. Density reduction of monosubstituted organotin(IV) treated wood cubes was higher than disubstituted organotin(IV) treated wood cubes. Soil block test showed that selected organotin(IV) complexes are effective and among all of them dibutyltin(APCT) complex gave the best protection against the tested T. versicolor and G. trabeum decay fungi.     

Outage capacity and outage rate performance of MIMO free-space optical system over strong turbulence channel

Abstract

In this paper, we investigate outage capacity, outage probability, and outage rate performance of multiple-input multiple-output (MIMO) free-space optical system operating over strong turbulence channels. The MIMO optical system employs intensity modulation direct detection with on-off signaling, and equal gain combining technique at the receiver. We derived novel closed-form expressions for three system metrics, namely, outage capacity, outage probability, and outage rate. Expressions derived here are based on the generalized Gamma–Gamma channel model, which is based on scintillation theory that assumes that the irradiance of the received optical wave is modeled as the product of small-scale and large-scale turbulence eddies. The results are evaluated for different values of received signal-to-noise ratios, strong turbulence conditions, and several values of transmit/receive diversity.     

Examining student rating of teaching effectiveness using FACETS

Students' evaluations of teaching staff can be considered high-stakes, as they are often used to determine promotion, reappointment, and merit pay to academics. Using Facets, the reliability and validity of one student rating questionnaire is analyzed. A total of 13,940 respondents of the Human Science Division of International Islamic University Malaysia were involved in the study. The analysis shows that the student rating questionnaire used was valid and reliable, and it allows identification of staff for the institution's prestigious teaching excellence awards, and those needing in-service training. It was found that there was no significant difference in terms of rank, age and gender of the staff. The study also shows that the majority of staff have problems keeping the class interested and getting students to participate in class activities. Faculty also hardly discussed common errors in assignments and tests.     

Sedimentological and petrophysical characteristics of Raha Formation at Wadi Tubia,Northern Gulf of Aqaba,Sinai, Egypt

The main aim of this study is to shed some light on the microfacies association, geochemistry and petrophysical properties of the rock types: dolomite, sandstone, shale and limestone forming the Raha Formation.The microfacies association includes: ferroan dolomite, sublithic arenite, ferruginous sublithic arenite, dolomitic lithic arenite, sandy bioclastic wackstone, bioclastic packstone, calcareous ferruginous lithic arenite and fossiliferous bioclastic grainstone.The depositional environments of these sediments are interpreted as restricted, shelf lagoon and open circulation.The dominant diagenetic processes presented in the studied samples are cementation, compaction, replacement, dissolution and dolomitization in sandstone rocks, while neomorphism, micritization, cementation, dolomitization, compaction and dissolution are present in carbonate facies. Geochemically, the ferruginous sublithic arenite microfacies are characterized by phosphate bands and high chemical weathering. Calcareous ferruginous lithic arenite microfacies are characterized by high concentration of iron oxides and fossiliferous bioclastic grainstone is characterized by high concentration of barium, as indicated from the chemical index of alteration (CIA).Statistical analysis of the measured petrophysical data shows that, the dolomitic lithic arenite and fossiliferous bioclastic grainstone microfacies have a good storage capacity in the Raha Formation of Wadi Tubia, Northern Gulf of Aqaba, Sinai, Egypt.     

Novel grafted nafion membranes for proton‐exchange membrane fuel cell applications

Novel poly(glycidyl methacrylate)‐grafted Nafion–phosphoric acid membranes for direct‐oxidation methanol fuel cells were prepared with a potassium persulfate chemical initiation system for the first time. The introduced epoxy groups were converted to amine groups through a reaction with ethylenediamine, which consequently doped with phosphoric acid ( PO₃H) groups. The latter significantly contributed to enhancing the ion‐exchange capacity, mechanical properties, and thermal stability. Factors affecting the modification steps were studied. Changes in the chemical and morphological structure were verified through Fourier transform infrared spectroscopy, TGA, and scanning electron microscopy characterization. Various grafting percentages (GP%'s) up to 32.31% were obtained. As a result, the thickness of the grafted membranes increased. Furthermore, the methanol permeability of the modified membranes was reduced with increasing grafted polymer content compared with that of the Nafion membrane. An 83.64% reduction in the methanol permeability was obtained with a polymer grafted content of 18.27%. Finally, the efficiency factor for all of the modified Nafion membranes was enhanced compared with that of Nafion. A fourfold improvement was obtained with membranes with a GP% of 18.27% as a maximum value. Such promising results nominate the used technique as a one for the improvement of Nafion membrane efficiency. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Effects of ten year application of empty fruit bunches in an oil palm plantation on soil chemical properties

The oil palm empty fruit bunches (EFB), a major waste product of the palm oil mills, were earlier incinerated at the mills and had contributed to air quality problems in Malaysia. This lead to the introduction of the Malaysian Environmental Air Quality Regulation in 1978 which prompted mills to look for alternative management methods in disposal of the EFB. A convenient method is applying the EFB to the oil palm field near the mill for nutrient cycling. A study was conducted to investigate the effects of 10 years of EFB yearly application in an oil palm plantation, as a source of nutrients, on the chemical properties of a well-drained, highly weathered acidic soil, classified as Typic Kandiudult. The experimental plots receiving 3 treatments, i.e. chemical fertilization, without EFB application (CHEM)), application of 150 kg EFB palm⁻¹ year⁻¹ (EFB150) and application of 300 kg EFB palm⁻¹ year⁻¹ (EFB300) with four replications, from 1983 to 1992. The EFB was applied in heaps in the middle of every 4 palms. The cumulative addition of EFB had increased the soil pH by two units with application of EFB300 and a one unit increase with EFB150 in the 0–60 cm soil layer, compared to CHEM. The application of EFB even at the lower rate decreased significantly exchangeable Al contents and the cation exchange capacity increased up to 60 cm soil depth. Overall increases in exchangeable bases were also observed in soils treated with EFB. The increase was more evident in EFB300 compared to EFB150. Organic C in the topsoil increased from 1.49 to 2.50% and 2.73% in EFB150 and EFB300, respectively. There was also an increase in total nitrogen with EFB application but only in the topsoil. An overall analysis of the yield response in the 10 year-period shows that EFB300 resulted in higher fresh fruit bunch (FFB) yield than EFB150 and CHEM while the yield of EFB150 was not significantly different from CHEM. This study showed that it is beneficial to dispose the EFB by applying them in the oil palm fields around the mills.     

The antioxidant activity of new coumarin derivatives

The antioxidant activity of two synthesized coumarins namely, N-(4,7-dioxo-2- phenyl-1,3-oxazepin-3(2H,4H,7H)-yl)-2-(2-oxo-2H-chromen-4-yloxy)acetamide 5 and N-(4-oxo-2-phenylthiazolidin-3-yl)-2-(2-oxo-2H-chromen-4-yloxy)acetamide 6 were studied with the DPPH, hydrogen peroxide and nitric oxide radical methods and compared with the known antioxidant ascorbic acid. Compounds 5 and 6 were synthesized in a good yield from the addition reaction of maleic anhydride or mercaptoacetic acid to compound 4, namely N'-benzylidene-2-(2-oxo-2H-chromen-4-yloxy)acetohydrazide. Compound 4 was synthesized by the condensation of compound 3, namely 2-(2-oxo-2H-chromen-4-yloxy) acetohydrazide, with benzaldehyde. Compound 3, however, was synthesized from the addition of hydrazine to compound 2, namely ethyl 2-(2-oxo-2H-chromen-4-yloxy)acetate, which was synthesized from the reaction of ethyl bromoacetate with 4-hydroxycoumarin 1. Structures for the synthesized coumarins 2-6 are proposed on the basis of spectroscopic evidence.     

Development of antifouling properties and performance of nanofiltration membranes modified by interfacial polymerisation

Two types of bisphenol monomers, Bisphenol A (BPA) and Tetramethyl Bisphenol A (TMBPA), with different concentrations of bisphenol aqueous solution (0.5% to 2.%w/v) and various interfacial polymerisation times (10 s, 30 s and 60 s) in the fixed 0.15%w/v organic solution of trimesoyl chloride (TMC)-hexane were studied. Irreversible fouling of both unmodified polyethersulfone NFPES10 and modified polyester thin-film composite polyethersulfone membranes were studied using humic acid model solutions at two different pH values, pH 7 and pH 3. It was observed that polyester thin-film composite membranes prepared by BPA exhibited fewer tendencies for irreversible fouling by humic acid molecules at neutral environment compared to unmodified NFPES10 and TMBPA-polyester series. This is most probably due to high electrostatic repulsion force between negatively charged of BPA-polyester layer and highly negative charged of humic acid at pH7. However, some modified membranes with rougher surfaces were severely fouled by humic acid molecules at acidic environment, pH 3. Under this acidic environment, carboxylic acid groups of humic acid lost their charge and the macromolecules of humic acid have smaller macromolecular configuration due to the increased hydrophobicity and reduced inter-chain electrostatic repulsion. Thus the molecules of humic acid may be preferentially accumulated at the valleys of the rougher membrane surface blocking them and resulting in a more severe fouling. In addition, the modification also affected membrane pore size and pore size distribution as shown by AFM images. It was also observed that the smaller pore size generated after modification does not have significant effect on humic acid removal due to the larger size of humic acid molecules. All the modified membranes posses smaller pore size than the unmodified NFPES10 (1.47 nm) in the range of 0.8–1.34 nm.     

Porous epoxy microparticles prepared by an advanced aqueous method

This paper reports the synthesis of emulsions of epoxy compounds with various ratios of epoxy, polyamide and calcium carbonate by homogenization in water at room temperature. The emulsion is cured at 80 °C, and during curing the small epoxy droplets in the emulsion coalesce. The cured coalesced epoxy droplets contain holes formed due to water trapped inside them and also due to the difference in curing rates between epoxy molecules on the outside versus inside of the coalesced droplets. The porous epoxy particles are obtained when the cured coalesced epoxy droplets are treated with hydrochloric acid to remove the calcium carbonate. The size of the porous epoxy particles and the number of holes formed depends on the curing rate of the epoxy compound.     

Preparation,characterization, and electrical properties of ZSM‐5/PEG composite particles

ZSM‐5/PEG composites were synthesized by a simple solution method with polyethylene glycol (PEG) and H‐ZSM‐5 zeolite (Si/Al = 11.4). The obtained composites were characterized using X‐ray powder diffraction and Fourier transform infrared spectroscopy. The obtained results indicated that the ZSM‐5 was physically combined with PEG. The thermal properties and thermal stability were investigated by thermogravimetric and differential thermal analyses. In situ electrical conductivity was used to follow‐up the changes in the electrical conductance during the heating of the ZSM‐5/PEG composite. It was found that ZSM‐5 is able to effectively enhance the electrical conductivity of PEG. The results showed that the obtained weight loss during the composite decomposition to charcoal is accompanied by a decrease in the electrical conductivity. Moreover, the removal of the formed charcoal is associated with an electrical conductivity increase. Calcining the ZSM‐5/PEG composite having a content of 30% results in many effects on the structural, textural, and electrical properties of the obtained products. POLYM. COMPOS., 35:1160–1168, 2014. © 2013 Society of Plastics Engineers