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Low Thermal Conductivity of RE-Doped SrO(SrTiO3)1 Ruddlesden Popper Phase Bulk Materials Prepared by Molten Salt Method
No full textThe SrO(SrTiO3)1 (Sr2TiO4) Ruddlesden Popper (RP) phase is a natural superlattice comprising of alternately stacking perovskite-type SrTiO3 layers and rock salt SrO layers along the crystallographic c direction. This paper discusses the properties of the Sr2TiO4 and (La, Sm)-doped Sr2TiO4 RP phase synthesized via molten salt method, within the context of thermoelectric applications. A good thermoelectric material requires high electrical conductivity, high Seebeck coefficient and low thermal conductivity. All three conditions have the potential to be fulfilled by the Sr2TiO4 RP phase, in particular, the superlattice structure allows a higher degree of phonon scattering hence resulting in lowered thermal conductivity. In this work, the Sr2TiO4 RP phase is doped with Sm and La respectively, which allows injection of charge carriers, modification of its electronic structure for improvement of the Seebeck coefficient, and most significantly, reduction of thermal conductivity. The particles with submicron size allows excessive phonon scattering along the boundaries, thus reduces the thermal conductivity by fourfold. In particular, the Sm-doped sample exhibited even lower lattice thermal conductivity, which is believed to be due to the mismatch in the ionic radius of Sr and Sm. This finding is useful as a strategy to reduce thermal conductivity of Sr2TiO4 RP phase materials as thermoelectric candidates, by employing dopants of differing ionic radius
Mild cell disruption methods for bio-functional proteins recovery from microalgae—Recent developments and future perspectives
No full textBio-functional proteins from microalgae have numerous biological properties with health-promoting effects. However, efficient harnessing of bio-functional proteins from microalgae is still in its infancy. One of the major obstacles that hinder the mass production of bio-functional proteins is the presence of resistant cell wall that diminishes the liberation of cell contents. As the bio-functional proteins are very sensitive to denaturation, selecting a mild disruption method to rupture the cell wall, while preserving their bioactivity and functionality, is of vital importance in downstream processing. To ensure the future development of efficient mild disruption methods for maximum recovery of bio-functional proteins from microalgae, this review provides useful information on various mild disruption approaches, current status, potential technologies that are still under development, as well as their advantages and constraints. In particular, those potential technologies that require further attention in the future (namely, explosive decompression, microfluidization, pulsed arc technology and cationic polymer coated membranes) are also discussed in this review
Effect of Titanium Dioxide on Adhesion and Conductivity Behavior of Polyaniline/Alkyd Composite for Solar Cell Application
No full textThis study attempts to improve the adhesion and conductivity of polyaniline (PAni) by incorporating an alkyd and titanium dioxide (TiO 2 ), respectively. PAni with different TiO 2 content (10, 20, and 40%) are synthesized through chemical oxidation method by using aniline (Ani) monomer, dioctyl sodium sulfosuccinate (AOT) dopant, and ammonium persulphate (APS) oxidant at 0 °C for 24 h. In order to improve the adhesion of PAni-TiO 2 on fluoride doped-tin oxide (FTO) glass prior to its application as counter electrode (CE) in Dye-Sensitized Solar Cell (DSSC), a palm oil-based alkyd is added into PAni-TiO 2 composite. Chemical structures of PAni-TiO 2 /Alkyd are confirmed by Fourier transform infrared spectrophotometer (FTIR) and ultraviolet-visible (UV-Vis) spectrophotometry analyses. Conductivity measurement is determined by using four point probe method and adhesion test is performed following ASTM D3599. Results showed that conductivity of PAni had significantly improved from 3.53 × 10 −3 (without TiO 2 ) to 8.16 × 10 −3 –6.59 × 10 −2 S cm −1 (with TiO 2 ). However, the conductivity of all PAni-TiO 2 /Alkyd samples on FTO glass showed high conductivity (6.11–6.32 × 10 2 S cm −1 ) and better adhesion behavior on FTO glass except for the sample with 40% of TiO 2 . The plausible mechanisms between PAni-TiO 2 /Alkyd and FTO glass are proposed in this study based on the FTIR and UV-Vis analyses
Midterm results of conversion from failed bipolar hemiarthroplasty to total hip arthroplasty
No full textBackground: Conversion from failed bipolar hemiarthroplasty (HA) to total hip arthroplasty (THA) presents a great challenge to orthopedic surgeons for bipolar head removal and cup placement with or without change of femoral stem. Conversion THA after failed bipolar arthroplasty is known to offer both symptomatic and functional improvement. This study evaluates the midterm functional outcome and complications, especially dislocation associated with femoral head diameter, after conversion THA. Materials and Methods: Forty eight hips with the conversion of bipolar HA to THA were followed up for an average 6.2 years (range 2.0-11.5 years). Twenty one hips had conversion surgery to THA using metal-on-metal articulation (28 or 32 mm head). Nine hips used ceramic-on-ceramic (28-40 mm) and eighteen hips used large head metal-on-metal bearing (>40 mm). Outcome was evaluated using Harris Hip Score (HHS) and Western Ontario McMaster Universities Osteoarthritis Index (WOMAC) score. The radiographs were analyzed for evidence of osteolysis and/or loosening. The complications were evaluated, especially dislocation with different femoral head diameter. Results: Average HHS significantly improved from 42 preoperatively to 86 postoperatively and the average WOMAC score also significantly improved from 47 to 22 postoperatively. Radiological evaluation showed all the femoral components were stable. There was one acetabular component loosening, which required revision 9 years after conversion to THA. One dislocation and one recurrent dislocation were recorded in isolated acetabular revision hip; whereas one dislocation, one recurrent dislocation, and one trochanteric nonunion occurred in the hips with revision of both components. All dislocations occurred in hips with a femoral head size of 28 mm (P = 0.052). The cup and femoral head interval length was the most significant factor contributing to dislocation (P = 0.013). Conclusions: Conversion THA after failed bipolar HA offers a reliable pain relief and functional improvement. To prevent dislocation, it is highly recommended to use a larger diameter femoral head, especially where the cup size is big
Improved electron density through hetero-junction binary sensitized TiO 2 / CdTe / D719 system as photoanode for dye sensitized solar cell
No full textThe combined effect of dual sensitization and hetero-junction symmetry has been investigated on the performance of TiO2 based dye sensitized solar cell. CdTe nanoparticles have been introduced in TiO2 matrix to function as sensitizer as well as act as hetero-junction between D719 dye and TiO2 nanoarchitecture. Four concentrations of CdTe i.e. 0.5 wt%, 2 wt%, 5 wt% and 8 wt% have been investigated. Morphological and compositional studies have been conducted using scanning electron microscope (SEM) and X-ray diffraction (XRD) respectively. Light absorption characteristics have been investigated by employing Uv–vis spectroscopy and the overall performance has been studied using solar simulator and electrochemical impedance spectroscopy (EIS). Performance has been found to be increased with the addition of CdTe due to high electron density and reduction in recombination reactions. An increase of 41.73% in incident photo conversion efficiency (IPCE) and 75.57% in short circuit current density (Jsc) have been recorded for the specimens containing 5 wt% CdTe compared to bare TiO2 based DSSCs. Further addition of CdTe leads to reduction in overall performance of DSSCs
Parametric optimization of polycaprolactone synthesis catalysed by Candida antarctica lipase B using response surface methodology
No full textA statistical approach with D-optimal design was used to optimize the process parameters for polycaprolactone (PCL) synthesis. The variables selected were temperature (50°C-110°C), time (1-7 h), mixing speed (50-500 rpm) and monomer/solvent ratio (1:1-1:6). Molecular weight was chosen as response and was determined using matrix-assisted laser desorption/ionization time of flight (MALDI TOF). Using the D-optimal method in design of experiments, the interactions between parameters and responses were analysed and validated. The results show a good agreement with a minimum error between the actual and predicted values
Variation of polypharmacy in older primary care attenders occurs at prescriber level
No full textBackground: Polypharmacy is particularly important in older persons as they are more likely to experience adverse events compared to the rest of the population. Despite the relevance, there is a lack of studies on the possible association of patient, prescriber and practice characteristics with polypharmacy. Thus, the aim of this study was to determine the rate of polypharmacy among older persons attending public and private primary care clinics, and its association with patient, prescriber and practice characteristics. Methods: We used data from The National Medical Care Survey (NMCS), a national cross-sectional survey of patients' visits to primary care clinics in Malaysia. A weighted total of 22,832 encounters of patients aged ≥65 years were analysed. Polypharmacy was defined as concomitant use of five medications and above. Multilevel logistic regression was performed to examine the association of polypharmacy with patient, prescriber and practice characteristics. Results: A total of 20.3% of the older primary care attenders experienced polypharmacy (26.7%% in public and 11.0% in private practice). The adjusted odds ratio (OR) of polypharmacy were 6.37 times greater in public practices. Polypharmacy was associated with patients of female gender (OR 1.49), primary education level (OR 1.61) and multimorbidity (OR 14.21). The variation in rate of polypharmacy was mainly found at prescriber level. Conclusion: Polypharmacy is common among older persons visiting primary care practices. Given the possible adverse outcomes, interventions to reduce the burden of polypharmacy are best to be directed at individual prescribers
Embedded AlN/GaN multi-layer for enhanced crystal quality and surface morphology of semi-polar (11-22) GaN on m-plane sapphire
No full textWe demonstrate high quality semi-polar (11-22) gallium nitride thin film grown on m-plane sapphire substrate with the insertion of AlN/GaN multi-layer via MOCVD. The influence of three different number of multi-layers AlN/GaN pairs on the crystal quality and surface morphology of semi-polar (11-22) gallium nitride thin film is investigated. The surface morphology analysis strongly suggests that increasing the number of AlN/GaN pairs from 20 to 60 suppresses the arrowhead-like and undulated features. The increase of AlN/GaN pairs also enhanced the surface quality, with the root mean square roughness improving from 16.24 nm to 6.08 nm. The abruptness of the interface between the AlN/GaN pairs was seen to improve significantly upon reaching the 40th pair where a continuous thin layer was clearly observed for each pair. The crystal quality was also observed to be enhanced at higher number of AlN/GaN pairs, where the on- and off-axis X-ray rocking curve showed significant reduction in the full width at half maximum of at least ~10% and 20%. Finally, x-ray reciprocal space mapping analysis further confirms the enhancement of the crystal quality as the diffuse scattering streak was suppressed, which may indicate a significant reduction of the defect density
Hybrid renewable energy supply for rural healthcare facilities: An approach to quality healthcare delivery
No full textThe lack of modern electricity supply has been a major impediment to proper functioning of the healthcare centers in the rural areas, contributing to high maternal and child mortality rates in a country. Therefore, this study focuses on how to address the identified problem so that the healthcare centers or clinics in the remote areas can provide timely delivery of medical services for the concerned people. This paper, then, presents the analysis of stand-alone hybrid renewable energy systems for basic healthcare services in the rural areas, where there is no grid energy supply or the supply from the existing grid is erratic and unreliable. One major factor that informs the selection of the hybrid energy system in this study is that it promises high reliability compared to a single energy system. The research presents a statistical analysis of the potential of wind and solar energies for a selected rural locations in Nigeria based on the available long-term hourly and daily meteorological data. It employs an optimal technical and economic design and sizing of hybrid electrical power systems’ components such as the wind, PV, battery and inverter systems, using the hybrid optimisation software (HOMER). Results show that Sokoto and Jos sites exist in the high wind potential regions, while the remaining sites are only suitable for small wind applications. Values obtained for global radiation show that all the sites enjoy considerable solar energy potential suitable for varying degree of solar energy applications. PV/wind/diesel/battery hybrid system configuration is considered optimum for rural health center at Iseyin, Sokoto, Maiduguri, Jos and Enugu, while hybrid systems involving PV/diesel/battery is considered ideal for Port-Harcourt, due to the quality of renewable energy potential. Hence, it was concluded that, the abundance of wind and solar resources in the country create an ideal environment for inclusion of renewable energy systems in the design and implementation of standalone power supply systems to improve rural healthcare delivery
Photocatalytic degradation of methylene blue with silver doped ZnO nanoparticles grown on microscopic sand particles (Degradasi metilena biru menggunakan nanopartikel ZnO sebagai fotomangkin yang didopkan dengan perak tumbuh di atas pasir bersaiz mikro)
No full textPure and Ag doped ZnO nanoparticles were synthesized on microscopic sand particles by sol-gel method. Silver nitrate was used as the doping precursor, Ag doping levels of 1.3 to 7.7 of Ag/Zn ratios were obtained based on energy dispersive X-ray spectroscopy analysis. X-ray diffraction results show that a ZnO (101) peak of Ag doped samples are shifted towards lower degree which around 0.17o compared to pure ZnO NPs, indicating the existence of doping in the Ag doped samples. The pure and Ag doped ZnO samples were used as photocatalysts in the degradation of methylene blue under UV irradiation. Photodegradation efficiency based on the pseudo-first kinetics model gave measured values of the photodegradation rate, k of 8.9, 11.8, 12.7, 14.8 and 17.4 x 10-3 min-1 for pure, 1.3, 1.6, 1.7 and 2.4 of Ag/Zn ratios, respectively. At higher doping levels of 3.3 and 7.7 of Ag/Zn ratios, the k values receded to 12.7 and 12.0 x 10-3 min-1, respectively. The increasing trend on k values can be due to the doping defect levels which trapped the recombining electrons, thus lengthening the lifetime of the electron hole pairs