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Structure and Properties of Polyamide 11 Nanocomposites Filled with Fibrous Palygorskite Clay
No full textVarious amounts (up to 10 wt%) of palygorskite nanofibers functionalized by 3-aminopropyltriethoxysilane (APTES) coupling agent were used to reinforce polyamide 11 nanocomposites prepared by melt compounding. The covalent bonding of the silane on the palygorskite surface was confirmed by infrared spectroscopy and thermogravimetric analysis. X-ray diffraction revealed the retention of the α-form of polyamide crystals upon the addition of both natural and silane treated palygorskite nanorods. All the investigated nanocomposites showed an improvement of the thermal stability, especially when surface treated palygorskite nanofibers were considered. Tensile tests and dynamic mechanical thermal analyses on the prepared materials evidenced how the incorporation of palygorskite nanofibers significantly increased the elastic and the storage moduli of polyamide, and this enhancement was more evident when natural palygorskite nanorods were used
Biocatalytic Synthesis of Fluorescent Conjugated Polyserotonin
No full textPolyserotonin was enzymatically synthesized using Horseradish peroxidase (HRP) as the catalyst. This novel conjugated polymer exhibited good fluorescent properties with significantly higher Stokes shift than its monomer. The enzymatic polymerization eliminated the need for extensive purification of the product (typically necessary for the removal of residual metal catalyst) allowing the product to be naturally fluorescent as synthesized. The reaction was monitored using UV-Vis spectrophotometry and the polymers were characterized using Fluorescence, Fourier Transform Infrared Spectroscopy (FTIR) and Thermogravimetry. The possibility of using polyserotonin for the detection of nitro-aromatic compounds, including 2,4-dinitrotoluene (DNT) and trinitrotoluene (TNT), through fluorescence quenching at parts per million levels in solution has also been demonstrated
Electromagnetic Characterization of Recyclable Polymer Nanofibers Based on PSU/Carbonyl Iron
No full textThis study investigated and defined the optimal processing parameters for the electrospinning of polysulfone polymer solutions with N,N-dimethylacetamide. Variation of parameters such as solute concentration, electrical voltage, and working distance were correlated with the quality of the obtained nanofibers using morphological characterization via scanning electron microscopy (SEM). Carbonyl iron additive was dispersed in the polymer solutions, using ultrasonic tip, and the material processed via electrospinning with aforementioned parameters defined. Nanofibers with the property of interaction with electromagnetic waves were obtained. The dispersion of different concentrations of the additive and electromagnetic characterizations in the X-band of microwaves (8.2 and 12.4 GHz), using vector network analyzer (VNA) and rectangular waveguide, allowed the identification of the materials electromagnetic behaviors. Scattering parameters allowed the calculation of reflected and transmitted energy by the material
Extraction and Characterization of Aucoumea klaineana Pierre (Okoume) Extractives
No full textIn order to promote convenient strategies for the utilization of wood wastes from aucoumea klaineana pierre (okoume) timber industry, various chemical analysis were carried out on samples from different origins. Total extractives content of the bark, sapwood and heartwood of okoume were evaluated. thermogravimetric analyses were performed and the stiasny number was calculated. it was found that the bark was richer in fatty acid of high molecular weight while the sapwood was rich in fatty acid of low molecular weight. the condensed tannins content varied according to the origin and the part of the tree. these new findings should be useful for green okoume based tannin adhesives
Review on Connections for Original Bamboo Structures
No full textBamboo is a green construction material in line with sustainable development strategies. The use of raw bamboo in architecture has existed since ancient times. In the long development years of original bamboo buildings, many areas in the world gradually formed unique bamboo buildings, which have become an important local cultural feature. For building structures, joints are the key to ensure structural load transfer. Because of hollow and thin-walled material property of bamboo, the connection in raw bamboo buildings has always been a major difficulty and problem in the application of bamboo, which seriously hinders the development of original bamboo structures. In order to promote the use of raw bamboo, two traditional connection methods in raw bamboo structures are described in this paper firstly, with the advantages and disadvantages of the two methods pointed out. Also, research progress on four categories of raw bamboo building joints is described namely, bolt joints, steel member joints, filler reinforced joints and other types of joints. This work can provide a reference for future research and engineering applications
Hygrothermal/UV Aging Effect on Visual Aspect and Mechanical Properties of Non-Woven Natural-Fiber Composites
No full textThis work aims at studying the effect of hygrothermal and UV cyclic aging on the tensile properties and esthetic characteristics of non-woven composites. The composite materials were thermo-compressed from non-woven mats made up of PP and flax or kenaf fibers. This works included evaluating the change in color appearance and analyzing the variations in tensile properties and damage mechanisms, depending on the aging time. The presence of the UV protection film on the composite surface showed its effectiveness against aging. From visual observations and measurement of colorimetric parameters, it has been proved effective in the reduction of the bleaching and yellowing of the composites. As regards the tensile tests, the UV protection film enabled to stabilize the Young’s modulus after 1-week aging for Kenaf/PP and after 3-weeks for Flax/PP. After 4-weeks aging, it halved the number of acoustic emission events related to interfacial decohesion and fiber slippage/pull out for Flax/PP and Kenaf/PP composites
Soy Protein Isolate Film by Incorporating Mandelic Acid as Well as Through Fermentation Mediated by Bacillus Subtilis
No full textSoy protein isolate (SPI) biopolymeric films were prepared by adding different contents of mandelic acid (1 to 5% wrt SPI) to glycerol plasticized SPI by solution casting method. Also, SPI was fermented by Bacillus subtilis to get fermented SPI films by solution casting. Molecular mass determination of mandelic acid incorporated and fermented SPI films was carried out by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). Mandelic acid incorporated and fermented SPI films were characterized by Fourier-transform infrared spectroscopy (FT-IR), dynamic mechanical analysis (DMA), tensile strength, water uptake and optical transmittance studies. Results indicated that incorporation of mandelic acid in SPI resulted in high tensile strength (8.03 MPa) and high α-relaxation (Tα) as well as low water uptake. On the other hand, films cannot be prepared from fermented SPI with SPI contents of 8% and 12%. However, film from fermented SPI with 16% SPI content could be prepared but it exhibited low tensile strength (3.18 MPa) and low Tα as well as high water uptake. The resulting mandelic acid incorporated SPI films were also subjected to antimicrobial studies. At all the concentration of mandelic acid, we can easily observe the antimicrobial effect in mandelic acid incorporated SPI films unlike fermented SPI films. This work will be helpful in fabricating antimicrobial SPI film from renewable resources
Morphological Characterization of Brazil Nut Tree (Bertholletia excelsa) Fruit Pericarp
No full textThis article presents the overall morphological structure of the Brazil nut tree (Bertholletia excelsa) fruit pericarp, from macro to nano scale. The acquired knowledge would be used for the development of new applications, like using the materials as fillers for biocomposites, or as a hierarchical architecture model for biomimetics. This research was performed using stereo and light microscopy and conventional and force field emission scanning electron microscopy. The pericarp presents three layers: the exocarp, a dark gray, brittle and fragile outer layer; the mesocarp, a beige, dry, rigid, impermeable and fibrous intermediate layer; and the endocarp, an inner layer with similar characteristic as the exocarp, but formed next to the seeds. Morphologically, the exocarp and the endocarp presented minor regions of sclereids, fibers and vascular cell bundles, inside major regions of parenchyma cells. The mesocarp presents a structure of fiber cells regions alternating with sclereids and vascular cells regions, arranged in a composite like arrangement, with the fibers cells bundles acting as randomly oriented disperse phases in a sclereid cells matrix. This arrangement was associated with the mesocarp relative superior proprieties, indicating a great material for using as fillers for biocomposites or in biomimetics applications
The expressional level of tankyrase-1 gene and its regulation in colorectal cancer in a Saudi population
No full textTankyrase1 plays an essential role in cancer progression by regulating telomere length. The study aimed
to determine expression of TNKS1 and its regulation in colorectal cancer (CRC) in 20 samples from Saudi patients.
mRNA expression of TNKS1 in CRC and paired normal tissues was measured by qRT-PCR. Epigenetic modification
of TNKS1 promoter was determined by methylation-specific PCR while somatic mutation was analyzed by Sanger
sequencing in exon 10 of the gene. All cancerous and normal tissues expressed TNKS1, but level of expression in CRC
tissues was significantly associated with tumor stage though no other parameters; age, gender, and tumor location,
showed any correlation. Expression of TNKS1 was markedly higher in earlier (I, II) than later (III, IV) stages of CRC
development. Both cancerous and healthy tissues had unmethylated promoter. Sanger sequencing of exon 10 masked
any somatic mutation in the samples. Our findings suggest that up-regulation of TNKS1 was inversely correlated with
cancer progression in CRC, indicating that TNKS1 participates in the initiation of CRC by stabilizing telomere length in
the first phase of cancer progression. Mechanisms other than TNKS1 might play a role in malignant tumor progression
and telomere maintenance in the late stages of CRC
Generating Questions Based on Semi-Automated and End-to-End Neural Network
No full textWith the emergence of large-scale knowledge base, how to use triple information to generate natural questions is a key technology in question answering systems. The traditional way of generating questions require a lot of manual intervention and produce lots of noise. To solve these problems, we propose a joint model based on semi-automated model and End-to-End neural network to automatically generate questions. The semi-automated model can generate question templates and real questions combining the knowledge base and center graph. The End-to-End neural network directly sends the knowledge base and real questions to BiLSTM network. Meanwhile, the attention mechanism is utilized in the decoding layer, which makes the triples and generated questions more relevant. Finally, the experimental results on SimpleQuestions demonstrate the effectiveness of the proposed approach