Stability enhancement of polypyrrole thin film ammonia sensor by camphor sulfonic acid dopant

Journal of Materials Science: Materials in Electronics - The main weakness of polymer gas sensors is its stability. Here, we report stability enhancement of a 100 nm polypyrrole (PPy) thin...     

Environmental Impacts of Dams Constructed in Iran

Construction of dams is essential for an arid country like Iran so water can be stored to assure the availability of a reliable supply to satisfy domestic, industrial and agricultural requirements, control floods and generate hydroelectricity. Dams are thus essential for the country's socio-economic development. While dams have contributed to very significant benefits, their construction has also resulted in many negative environmental impacts. Only these negatives impacts are analysed in this paper. Assessments and understanding of these negative impacts will contribute to more efficient water management practices in the future.     

Cervical and breast cancer screening rates in Sioux Indian women

We cloned a novel human beta-defensin gene and determined its full-length cDNA sequence. The entire gene spanned more than 7 kb and included a large 6962-bp intron. The 362-bp cDNA encoded a prepropeptide that corresponded precisely to the recently identified human beta-defensin HBD-1, an antimicrobial peptide implicated in the resistance of epithelial surfaces to microbial colonization. By two-color fluorescence in situ hybridization on both metaphase chromosome and released chromatin fiber, HBD-1 gene (DEFB1 in HUGO/GDB nomenclature) mapped to chromosomal region 8p23.1-p23.2 in close proximity (within 100-150 kb) to the gene for the human neutrophil alpha-defensin HNP-1 (DEFA1). Thus, despite a complete lack of DNA sequence similarity and despite differences in their disulfide-pairing pattern, the alpha- and beta-families appear to have evolved from a common premammalian defensin gene.     

Study the Synthesis,Characterization and Immersion of Dense and Porous Bovine Hydroxyapatite Structures in Hank’s Balanced Salt Solution

The bone-bonding potential of biomaterials is evaluated in vitro through examining the surface apatite formation in Hank’s media to enhance biocompatibility, which is also applicable to facilitate in vivo osseointegration of implantable devices. Hence, bovine hydroxyapatite (BHA) bioceramic structures have been used in various biomedical applications such as orthopedic implants. In this article, the microstructure, in vitro bioactivity, and nanomechanical properties of the synthesized dense and porous BHA are investigated via scanning electron microscopy, x-ray diffraction, energy-dispersive x-ray spectroscopy, Fourier transform infrared spectroscopy, and nanoindentation analysis. From the obtained results, porous BHA mostly possesses adequate requirements for substitution as implants in the human body.     

Effects of Al-Ni powder addition on dissimilar friction stir welding between AA7075-T6 and 304 L

Friction stir welding between AA7075-T6 aluminum alloy and 304 L stainless steel sheet metal was performed with the addition of Al−Ni powder between the joining interfaces to increase the joining performance. The welding tool was rotated at 200 min⁻¹ to 800 min⁻¹ with the constant traverse speed of 25 mm/min. The resulting joint interfaces were analyzed using a field emission-scanning electron microscope and energy-dispersive x-ray spectroscopy analysis. The tensile strength was greater for the Al−Ni powder added specimens at the lower tool rotational speeds. The tensile strength of 360 MPa was obtained for the ‘with-powder’ specimen as compared to 220 MPa for the ‘without-powder’ specimen at the 200 min⁻¹ tool speed. Electron microscope images of the stir zone showed a significant mixing of the Al−Ni powder with the base materials, increased contact at the interface, which resulted in increased joining strength at the lower tool rotational speeds. However, based on the images, intermetallic compound that may contribute to the joining strength in the vicinity of the interfacial region was not detected.     

Smart lubrication via pump response interval (PRI) variation in the machining process

The development of new lubrication methods in CNC machine carriages is a current requirement in the machining industry. Previously, lubrication systems of CNC machines were only improved via injection automation approaches. This paper focuses on the lubrication mode on the linear guideways of CNC machines. Additionally, the research investigates the effects of oil injection time and the amount of the required lubricant for accurate and precise machining. This study was also concerned with variations in environmental temperature and carriage movement conditions. Oil injection amount was determined by pump response interval (PRI), which was varied for optimization. Smart optimum quantity lubrication (SOQL) was applied to overcome unexpected changes in practical parameters during machining. The optimum oil consumption of SOQL was achieved when PRI was 15 s, resulting in a reduction of oil consumption of up to 25 %. The SOQL technique is an emerging method in lubrication technology and plays an important role in alleviating the current issues that CNC lubrication systems are faced with.     

Structural failure assessment of buried steel water pipes subject to corrosive environment

It is essential to predict the lifetime of buried pipelines since they are not easily accessible for inspection. In this study a time-dependent, non-linear state model has been introduced for the structural analysis of corrosion affected steel water pipes, stressed by external forces. Using limit state concept, the simultaneous effect of externally applied loading and material corrosion are considered through failure modes. A non-linear corrosion model is used to simulate the loss of pipe wall thickness during the operation period. In order to take the uncertainty associated with the design and environmental variables into account, a Monte Carlo simulation technique has been adopted using MATLAB. A parametric sensitivity analysis is also carried out to measure the effectiveness of each parameter on the probability of pipe failure. Results obtained for a steel water pipeline in Eastern Sydney are presented and discussed.     

Physico-chemical and antimicrobial properties of Ag/Ta2O5 nanocomposite coatings

Surface modification of surgical instruments is carried out in order to improve the antibacterial performance against the surgical site infections. Healthcare acquired infections (HAI) and Nosocomial infections are one of the leading causes of complications/deaths after surgery. There is an increasing trend of antibiotic resistance in bacteria such as, vancomycin-resistant Enterococcus (VRE), carbapenem-resistant Enterobacteriaceae (CRE), multi-drug-resistant Mycobacterium tuberculosis (MDR-TB), methicillin-resistant Staphylococcus aureus (MRSA), and Neisseria gonorrhoeae. Thus, surfaces that counteract the adherence and growth of bacteria are employed to avoid the infections. In present study, stainless steel 316 L (SS 316 L) was coated with Silver/Tantalum oxide (Ag/Ta₂O₅) nanocomposite using reactive magnetron sputtering. The as-sputtered Ag/Ta₂O₅ nanocomposite (a-Ag/Ta₂O₅) film was crystallized via thermal treatment at 400 °C. Due to the annealing, the AgNPs migrated to the surface through the columnar paths of the a-Ag/Ta₂O₅. Thus, the crystallized layer (c-Ag/Ta₂O₅) exhibited 302% improvement in adhesion strength and enhanced hydrophopibicity. The c-Ag/Ta₂O₅ also demonstrated excellent antibacterial performance against Staphylococcus aureus (NCTC 6571) (gram-positive bacteria) and Escherichia coli (ATCC 15597) (gram-negative bacteria) according to the inhibition zone measurements. These results suggest that c-Ag/Ta₂O₅ deposition on SS 316 L substrate has a high potential to serve as an adherent, antibacterial layer on the surgical tools, in order to resist surgical site infections.