Microwave Assisted Short-Time Alkaline Extraction of Birch Xylan

Efficacy of microwave energy for the extraction of xylan from birch wood as an alternative to conventional method of extraction was investigated. Effect of irradiation time and microwave power input on the solubilization of wood and yield of extracted xylan was studied. The maximum yield of xylan obtained at the higher power level was significantly lesser compared to the lower power level indicating the molecular degradation of the polymer. The highest yield of xylan (60 % of the original xylan) was obtained at the lowest power level studied, 110 W, for an irradiation time of 10 min. Comparison with conventional extraction showed that 10 min of microwave extraction provided a similar wood dissolution to that at 90 °C for 1.5 h, but with a higher yield of xylan. Characterization of the precipitated xylan indicated that the extracted xylan contained 68–88 % of xylose with the major chemical structure consisting of a linear backbone of (1-4) β-d-xylopyransoyl residues. Molecular mass of the extracted xylan indicated that the xylan extracted using microwave contained 60–70 % of high molecular weight fraction, and about 30–40 % of low molecular weight fraction, whereas xylan extracted using conventional method showed a reverse trend. Molecular mass of non-aggregated xylan was reported to be 6,000 Da (in terms of dextran equivalents). Crystallinity of wood fibers increased irrespective of the method of extraction indicating no degradation of the strength of the fibers occurred during the extraction.     

Fungal-modification of Natural Fibers: A Novel Method of Treating Natural Fibers for Composite Reinforcement

Growing interest in green products has provided fresh impetus to the research in the field of renewable materials. Plant fibers are not only renewable but also light in weight and low in cost. Polymer composites manufactured using them find applications in diverse fields such as automobiles, housing, and furniture. However, their hydrophilic nature and inadequate adhesion with matrix limits their use in high performance applications. In this study, a novel method for improving adhesion characteristics of natural fibers has been developed. This method is carried out by treating hemp fibers with a fungus: Ophiostoma ulmi, obtained from elm tree infected with Dutch elm disease. Treated fibers showed improved acid–base characteristics and resistance to moisture. Improved acid–base interactions between fiber and resin are expected to improve the interfacial adhesion, whereas improved moisture resistance would benefit the durability of the composites. Finally, composites were prepared using untreated/treated fibers and unsaturated polyester resin. Composites with treated fibers showed slightly better mechanical properties, which is most probably due to improved interfacial adhesion.     

Multivariate Bayesian analysis of atmosphere–ocean general circulation models

Numerical experiments based on atmosphere–ocean general circulation models (AOGCMs) are one of the primary tools in deriving projections for future climate change. Although each AOGCM has the same underlying partial differential equations modeling large scale effects, they have different small scale parameterizations and different discretizations to solve the equations, resulting in different climate projections. This motivates climate projections synthesized from results of several AOGCMs’ output. We combine present day observations, present day and future climate projections in a single highdimensional hierarchical Bayes model. The challenging aspect is the modeling of the spatial processes on the sphere, the number of parameters and the amount of data involved. We pursue a Bayesian hierarchical model that separates the spatial response into a large scale climate change signal and an isotropic process representing small scale variability among AOGCMs. Samples from the posterior distributions are obtained with computer-intensive MCMC simulations. The novelty of our approach is that we use gridded, high resolution data covering the entire sphere within a spatial hierarchical framework. The primary data source is provided by the Coupled Model Intercomparison Project (CMIP) and consists of 9 AOGCMs on a 2.8 by 2.8 degree grid under several different emission scenarios. In this article we consider mean seasonal surface temperature and precipitation as climate variables. Extensions to our model are also discussed.     

Quantification of Polycyclic Aromatic Hydrocarbons in Tea and Coffee Samples of Mumbai City (India) by High Performance Liquid Chromatography

This paper describes a method for quantification of sixteen polycyclic aromatic hydrocarbons (PAHs) in tea and coffee samples of Mumbai City with the help of reversed phase high performance liquid chromatography with UV-VIS detector. This method is based on liquid–liquid extraction followed by clean up with C-18 cartridge. Concentration of total PAHs in different brands of tea and coffee samples varied from 18.79 to 31.37 μg/L and from 16.47 to 18.24 μg/L, respectively. Mean concentration of total PAHs was 27.56 μg/L in tea and 17.20 μg/L in coffee. Recoveries at different concentration levels were higher than 68% in samples of tea and coffee. Detection limit was found to be low (0.0006 ng) for anthracene and highest (0.174 ng) for naphthalene with relative standard deviation between 0.4%–7%.     

Injection Molded Wheat Straw and Corn Stem Filled Polypropylene Composites

Environmentally friendly composite materials can be prepared using wood fibers and/or various types of agro-derived fibers as reinforcements. In this study, agro-residues such as wheat straw and corn stem filled polypropylene were prepared and their suitability was investigated as a reinforcing filler in thermoplastics and as an alternative to the wood flour filled plastics. Effect of compounding techniques, compatibilizer and fungal treatment of agro-residues on the mechanical properties of the composites were evaluated. It was found that high shear compounding of wheat straw fibers exhibited similar properties to that produced by the milled wheat straw. This may be due to the extensive fiber breakage occurred during the high shear compounding that results in a similar aspect ratio to that of milled straw. Compatibilizer is needed for improving the strength properties of the agro-residue filled PP composites. Fungal treatment of milled wheat straw did not show much improvement in the strength properties of the composites. Comparison of mechanical properties of the agro-residue filled PP with that of the wood flour and the old newsprint filled PP showed the suitability of the agro-residues as alternative filler for thermoplastics.     

Bio-Treatment of Natural Fibers in Isolation of Cellulose Nanofibres: Impact of Pre-Refining of Fibers on Bio-Treatment Efficiency and Nanofiber Yield

Biodegradability, renewability and high specific strength properties of cellulose nanofibres and microfibrils have made them very attractive in nano-biocomposite science. Treatment of natural fibers with suitable enzymes or fungus has been found to substantially alleviate the high energy requirement associated with the isolation of cellulose nanofibers via high shear refining and subsequent cryocrushing. This article briefly describes a novel enzymatic fiber pretreatment developed to facilitate the isolation of cellulose nanofibres and explores the effect of pre-refining of fibers on the effectiveness of bio-treatment. Soft wood Kraft pulp was pre-sheared to different degree and treated with a genetically modified fungus isolated from fungus infected Dutch elm tree. Cellulose nanofibres were isolated from these treated fibers by high shear refining. The percentage yield of nanofibres from pre-refined fibers in the less than 50 nm range showed a substantial increase and at the same time the number of revolutions required during the high shear refining to attain a comparable level of nanofibres isolation decreased. This observation may be attributed to the better fiber internal accessibility of the enzymes due to loosening up of the fibers and increased number of fiber ends as a result of pre-refining.     

In Vitro Cytotoxicity of Amylose-Based Bioplastic for Packaging Applications

Amylose containing polysaccharides are one of the most abundant and inexpensive naturally occurring biopolymers. Therefore, they are one of the most promising candidates to produce substitute plastics, especially in packaging applications. To determine the suitability for packaging applications, cytotoxicity of a modified amylose based bioplastic was investigated using NIH 3T3 Fibroblast cells from observation of cell morphology and MTS assay. Chemical durability of the amylose based bioplastic film was also studied by ion release and pH measurement after immersing the film into water. In vitro cytotoxicity (Cell morphology study and MTS assay) showed that the amylose based bioplastic film has in vitro biocompatibility and can be used for packaging applications. The ion release and pH measurement also supported the results.     

Mechanical,Morphological and Dynamic Mechanical Analysis of Pineapple Leaf/Washingtonia Trunk Fibres Based Biophenolic Hybrid Composites

In this article, flexural, impact and dynamic mechanical properties of the Pineapple leaf fibres (PALF) and Washingtonia trunk fibres (GW) based bio-phenolic hybrid composites were examined. The pure and hybrid composites were fabricated using the hand lay-up technique with an overall fibre weight ratio of 50% in which GW and PALF were maintained in the fibre weight ratios of 50:50, 30:70, and 70:30 denoted as 1G1P, 3G7P, and 7G3P, respectively. Hybrid composites displayed better flexural strength, flexural modulus and impact strength than the GW composites and better viscoelastic properties than the PALF composites. Results revealed that 1G1P hybrid composites exhibited 25% and 12% improvements in flexural strength and modulus compared to the GW composites. 3P7K composites showed a twofold increase in impact strength than GW composites. The storage modulus of the pure and hybrid composites declined rapidly beyond the glass transition temperature. Furthermore, it was observed that the values of storage modulus for all the composites at 150 °C were similar regardless of the composite configuration. The Peak of loss modulus was found to increase in the following order: GW?>?7G3P?>?3G7P?>?1G1P?>?PALF. Furthermore, the temperature at the peak tan delta was improved, and a reduction in the tan delta peak was observed for hybrid composites compared to the pure composites. Finally, the PALF and GW hybrid combinations can be suitable for use in various applications such as textiles, machinery part production industries, medicine, automobiles, etc.

     

Visible light photocatalysts from low-grade iron ore: the environmentally benign production of magnetite/carbon (Fe3O4/C) nanocomposites

Environmental Science and Pollution Research - Magnetite (Fe3O4) nanoparticles coated with dextrose and gluconic acid possessing both super-paramagnetism and excellent optical properties have been...     

Dynamic Mechanical Behavior and Thermal Characterization of Biofilms Based on Starch Modified by Fungi Isolates

Starches modified by Ophiostoma spp. have been investigated to develop bio-materials with enhanced mechanical and physical properties for thermoplastic applications. In this study, glass transition temperature (T_g) of modified starches was investigated in both dynamic mechanical analyzer (DMA) and differential scanning calorimeter (DSC) to detect molecular changes in the starch’s structure. Overall, two thermal transitions were observed in modified starches, as opposed to one in their native counterparts. Scanning electron microscopy of granular modified starch indicated visible damages and internal structural perturbations in addition to occlusion of granular pores by extraneous materials owing to possible enzymatic degradation and production of secondary metabolites. Modified starches registered two-fold improvement in storage modulus as compared to that of native starches. From the study of second derivative of the mass loss against temperature, two thermal transitions were also identified in modified starches. X-ray diffraction analyses showed that crystalline regions of the starch granules remained intact after the modification. It is proposed that the second phase transition potentially corresponds to modified amylose fractions and/or exopolysaccharides produced by the fungi.