The effect of substrate position on the microstructure and mechanical properties of SiC coatings on carbon/carbon composites

In this work, silicon carbide (SiC) coatings were produced on carbon/carbon composites using a chemical vapour deposition (CVD) method. During deposition, the temperature was fixed at 1200 °C and the coatings were produced by placing substrates at three different positions (340, 380 and 420 mm from the inlet) in the CVD reactor. The effect of substrate position on the microstructure and mechanical properties of the SiC coatings were experimentally investigated. The phase composition, surface morphology, defects and microstructure were studied using X-ray diffraction (XRD), scanning electron microscopy (SEM) and Raman Spectroscopy. The hardness and Young's modulus were measured using a nano-indentation method while fracture toughness was evaluated by micro-indentation. It was found that the deposition rate decreased linearly as substrate position moved far from the reactor inlet. In all coatings, only β-SiC phase was observed with a high density of stacking faults. It was found that the substrate position in the CVD reactor has a significant effect on the microstructure, grain size and crystallinity of the coating. At 340 and 420 mm substrate positions, a well-developed faceted microstructure with high crystallinity was observed while at 380 mm substrate position, the coating having lenticular-like fine grains with low crystallinity was obtained. The hardness values obtained from the top surface of the coatings are found to be higher than those from the cross-section, although the Young's modulus data (measured from the top surface and cross-section) were observed to be similar. At 380 mm substrate position, hardness, Young's modulus and fracture toughness were found to be the lowest compared to that of the coatings produced at 340 and 420 mm substrate positions. It is concluded that the SiC coatings with better mechanical properties can be produced by adjusting the substrate position in the CVD reactor.     

A new approach to modification of an agro-based raw material for Pb(II) adsorption

This paper describes a relatively new and effective modification with thiourea of an agro-based raw material, sorghum biomass for adsorption of Pb(II) ions. The modification was done under microwave irradiation. Changes in characteristics of modified material were determined by FT-IR and CHNS analysis. Effect of adsorbent dosage, contact time, solution pH and temperature on equilibrium process was extensively studied. Famous equilibrium models (Langmuir, Freundlich, Temkin, Dubinin-Radushkevich) in non-linear fashion were applied to evaluate the equilibrium data using different initial concentrations of Pb(II) ranging from 20 mg/L to 300mg/L. The adsorption process followed the pseudosecond-order kinetics. This paper also discusses the thermodynamic parameters (free energy, enthalpy and entropy) and reveals that the adsorption process is spontaneous. An appreciable increase in adsorption capacity of the modified adsorbent was observed, depicting the advantages of thiourea modification of sorghum biomass under microwave irradiation.     

Continuous and efficient removal of THMs from river water using MF membrane combined with high dose of PAC

A combination of microfiltration (MF) membrane with a high concentration (40 g/L of the reactor) of powdered activated carbon (PAC) efficiently and continuously removed trihalomethanes (THMs) and total organic carbon (TOC) from river water for a period of two months. Without PAC, the membrane reactor was able to remove less than 18% of THMs and less than 5% of TOC; with PAC, 65 to 95% of THMs and TOC were removed. Even though the THMs concentration in the influent was steadily increasing (reaching 50 μg/L), THMs concentration in the effluents from the reactors with PAC were consistently below 15 μg/L. While the MF membranes alone could not remove organics, PAC and microbial activity in the biofilm deposited on the PAC particles assured long term and continuous removal of THMs. No additional PAC was added into or removed from the reactors during the filtration period. Operational parameters such as the backwashing of the membrane, interval of the filtration cycle and biological pretreatment of the river water had a small effect on the extent of THMs removal, but they increased the filtration time prior to membrane cleaning and improved the overall performance of the reactors.     

Atomic force microscopy demonstration of cytoskeleton instability in mouse erythrocytes with dematin-headpiece and β-adducin deficiency

The pattern of disassembly of the cytoskeletal network of murine erythrocytes with deficiency of either dematin-headpiece or β-adducin or both proteins were investigated using atomic force microscopy. A heterogeneous complex structure with fine filament features and coarse features was observed in the cytoskeleton of wild type mouse erythrocytes, whereas a significant amount of rearrangement and aggregation occurred in the mutants, particularly in the cells carrying double gene mutations. These results are consistent with the cellular and biochemical phenotype of the mutant cell membranes as being more fragile due to weakened vertical connections with the plasma membrane.     

Morphological characterization of Hypnaceae (Bryopsida,Hypnales): Investigating four genera from Western Himalayas by using LM and SEM techniques

The Hypnaceae is one of the largest and diversified family among the pleurocarpous mosses which consists of nearly 60 genera and 1,000 species around the world. In Pakistan, it is represented by 15 species and 8 genera. The current research article provides the detail morphological investigation of four different species (genera) of the family Hypnaceae that is, Gollania clarescens, Hypnum revolutum, Homomallium andoi, and Taxiphyllum taxirameum in the Western Himalayas, Pakistan. The research article reports the first SEM study of the leaf surfaces of the studied taxa, along with comprehensive morphological characters of the four species. The main objective of the research project is to present the comparative light and scanning electron microscopic study to discuss the morphology in detail because previously the family is just reported in different bryophyte checklists of the Western Himalayas. Based on results, morphological characters, micromorphological observations, qualitative and quantitative attributes, taxonomic keys for the studied taxa, distribution, and habitat are described. Stereoscope was used to analyze different qualitative characters, and light microscope was used to observe and measure the laminal and alar cells of the leaf. The SEM study reveals many important surface features like cell shape and cell wall. The laminal cells were mostly linear and elongated with thin cell walls. The specimens used for the SEM were air dried, so the laminal cells were somewhat constricted and concaved. The current study project will help to make the contribution in the taxonomy and morphology of this family.     

Comparative foliar anatomical and pollen morphological studies of Acanthaceae using light microscope and scanning electron microscope for effective microteaching in community

In this study, foliar anatomy and pollen morphology of 10 species of Acanthaceae has been investigated using light and scanning electron microscopy. The study was aimed to highlight the role of microscopy in microteaching at community for proper characterization of plants using palyno‐anatomical characters including pollen type, exine sculpturing, shape of epidermal cells, pattern of anticlinal wall, type and size of stomata, and trichome. Most of the species have polygonal cell shapes but some species have irregular, tetragonal, and pentagonal shape of epidermal cells. The largest epidermal cell length on adaxial and abaxial surface were observed in Asystasia gangetica 66.95 and 87.40 μm whereas least was observed on adaxial surface in Justicia adhatoda 36.9 μm and on abaxial surface in Barleria cristata 35.65 μm. In anatomy, species have diacytic type of stomata, whereas stomata of paracytic type observed in two species, while in A. gangetica cyclocytic type of stomata are present. Quantitively on abaxial surface, largest stomata length 29.9 μm and width 24.30 μm was noted in B. cristata. While shortest stomata length was observed in Ruellia prostrata 25.95 μm whereas minimum width of stomata was examined in Barleria acanthoides 2.05 μm. The diversity of trichomes are present in all species except in Ruellia brittoniana. Acanthaceae can be characterized by exhibiting different pollen morphology having five types of pollen shapes, prolate, spheroidal, perprolate, subprolate, and oblate spheroidal. Exine peculiarities showing variations such as reticulate, granulate, coarsely reticulate, lophoreticulate, perforate tectate, and granulate surface were examined.     

Inheritance Pattern of Fiber Related Traits under Normal and Hypoxia Conditions in Cotton (Gossypium Hirsutum L.)

An 8 × 8 diallel crossing system was employed in F₁ generation of cotton to study the inheritance pattern of fiber related traits like micronaire, strength and maturity under normal and hypoxia conditions. Analysis of variance revealed significant variation (P < 0.01) for all the traits under both environments. The regression coefficient b deviated significantly from zero but not from unity for all studies traits allowed further analysis of the data. The additive component (D) was significant for all the traits and more than the values of dominance components H₁ and H₂ in case of fiber strength under both conditions and for fiber uniformity under normal conditions thus showing the preponderance of additive genetic effects. For micronaire non-additive effects were predominant under both environments. Estimates of narrow sense heritability for micronaire were 38.6% under normal and 49.5% for hypoxia, 79 and 80% for fiber strength and for fiber uniformity the estimates were 79% under normal conditions and 63% under hypoxia conditions. Predominance of additive genetic effects, high heritability along with partial dominance for fiber strength under both conditions and for fiber uniformity under normal conditions is indicative of early generation selection but for micronaire under both conditions selection may be practiced in later generations.