The aim of this study was to determine the spectrum of antimicrobial activity of 11 samples of stingless bee honey compared to medicinal, table and artificial honeys. Activity was assessed by agar ...diffusion, agar dilution, broth microdilution and time-kill viability assays. By agar dilution, minimum inhibitory concentration (MIC) ranges were 4% to >10% (w/v) for Gram-positive bacteria, 6% to >16% (w/v) for Gram-negative bacteria and 6% to >10% (w/v) for Candida spp. By broth microdilution, all organisms with the exception of Candida albicans and Candida glabrata were inhibited at less-than or equal to32% (w/v). Geometric MIC (w/v) means for stingless bee honeys ranged from 7·1% to 16·0% and were 11·7% for medicinal honey and 26·5% for table honey. Treatment of organisms with 20% (w/v) stingless bee honey for 60 min resulted in decreases of 1-3 log for Staphylococcus aureus, >3 log for Pseudomonas aeruginosa and <1 log for C. albicans. Similar treatment with each control honey resulted in decreases of <1 log for all organisms. Stingless bee honey has broad-spectrum antibacterial activity although activity against Candida was limited. Stingless bee honey samples varied in activity and the basis for this remains to be determined. Stingless bee honey had similar activity to medicinal honey and may therefore have a role as a medicinal agent.
We investigated the effect of international collaboration (in the form of international co-authorship) on the impact of publications of young universities (<50 years old), and compared to that of ...renowned old universities (>100 years old). The following impact indicators are used in this study, they are: (1) the 5-year citations per paper (CPP) data, (2) the international co-authorship rate, (3) the CPP differential between publications with and without international co-authorships, and (4) the difference between the percentage of international co-authored publications falling in the global top 10 % highly cited publications and the percentage of overall publications falling in the global top 10 % highly cited publications (Δ%
Top10%
). The increment of 5-year (2010–2014) field weighted citation impact (FWCI) of internationally co-authored papers over the 5-year overall FWCI of the institutions in SciVal
®
is used as another indicator to eliminate the effect of discipline difference in citation rate. The results show that, for most top institutions, the difference between the citations per paper (CPP) for their publications with and without international co-authorship is positive, with increase of up to 5.0 citations per paper over the period 1996–2003. Yet, for some Asian institutions, by attracting a lot of researchers with international background and making these collaborating “external” authors as internal researchers, these institutions have created a special kind of international collaboration that are not expressed in co-authorship, and the CPP gaps between publications with and without international co-authorship are relatively small (around 0–1 citations per paper increment) for these institutions. The top old institutions have higher CPP than young institutions, and higher annual research expenditures; while young universities have a higher relative CPP increment for the current 5-year period over the previous 5-year period. The Δ%
Top10%
for international co-authored publications is generally higher than that for all journal publications of the same institution. With the increase of international co-authorship ratio, the mean geographical collaboration distance (MGCD, an indication of increased international co-authorship) of one institution based on the Leiden Ranking data also increases, and young institutions have relatively higher CPP increment over MGCD increment. International co-authorship has a positive contribution to the FWCI of the institution, yet there are untapped potential to enhance the collaboration among young institutions.
Abstract The use of synthetic hydroxyapatite as bone substitute calls for the knowledge of the influence on adjacent cells. The aim of this study was to investigate the proteins with differential ...protein expression levels in the proteome of human osteoblast cell line incubated separately with various nano sized hydroxyapatite powders with different shapes and chemical compositions using iTRAQ-coupled 2D LC-MS/MS approach. In the present study, we investigated several intracellular signaling molecules involved in calcium regulation to analyze how osteoblast cells respond to dissimilar HA nanoparticles. It was found there was a significant decrease in cell population after adding the HA nanoparticles to the osteoblasts. Our results combining proteomics analysis and RT-PCR validation on targeted genes involved in calcium regulation confirmed the differences in the cellular response to dissimilar HA nanoparticles.
ZnO:Co nanoclusters were synthesized by nanocluster-beam deposition with averaged particle size of 5
nm and porous structure, which were for the first time adopted to construct a novel amperometric ...glucose biosensor. Glucose oxidase was immobilized into the ZnO:Co nanocluster-assembled thin film through Nafion-assisted cross-linking technique. Due to the high specific active sites and high electrocatalytic activity of the ZnO:Co nanoclusters, the constructed glucose biosensor showed a high sensitivity of 13.3
μA/mA
cm
2. The low detection limit was estimated to be 20
μM (S/N
=
3) and the apparent Michaelis–Menten constant was found to be 21
mM, indicating the high affinity of the enzyme on ZnO:Co nanoclusters to glucose. The results show that the ZnO:Co nanocluster-assembled thin films with nanoporous structure and nanocrystallites have potential applications as platforms to immobilize enzyme in biosensors.
This paper presents a complete polarization model of a solid oxide fuel cell (SOFC) that eliminates the ambiguity of the suitability of such model when used under different design and operating ...conditions. The Butler–Volmer equation is used in the model to describe the activation overpotential instead of using simplified expressions such as the Tafel equation and the linear current–potential equation. In the concentration overpotential, both ordinary and Knudsen diffusions are considered to cater for different porous electrode designs. Sensitivity tests are then conducted to show the effect of the thickness of the respective fuel cell components on the drop in cell voltage. Results show that the performance of an anode-supported fuel cell is superior to that using cathode as the support under elevated operating pressure in the cathode compartment. The former can achieve an improved operating range of current density under normal atmospheric conditions.
An anode-supported solid oxide fuel cell (SOFC), consisting of a dense 10
μm Gd
0.1Ce
0.9O
1.95 (GDC) electrolyte, a porous Ba
0.5Sr
0.5Co
0.8Fe
0.2O
3−
δ
(BSCF) cathode and a porous Ni–GDC cermet ...anode, is successfully assembled and electrochemically characterized. With humidified (3% water vapour) hydrogen as the fuel and air as the oxidant, the cell exhibits open-circuit voltages of 0.903 and 0.984
V when operating at 600 and 500
°C, respectively. The cell produces peak power densities of 1329, 863, 454, 208 and 83
mW
cm
−2 at 600, 550, 500, 450 and 400
°C, respectively. These results are impressive and demonstrate the potential of BSCF for use as the cathode material in new-generation SOFCs with GDC as the electrolyte. In addition, the sustained performance at temperatures below 600
°C warrants commercial exploitation of this SOFC in stationary and mobile applications.
Hydroxyapatite (HA) is synthesized by a wet chemical route using calcium hydroxide and ortho-phosphoric acid at various temperatures (40, 80, and 100 °C). X-ray diffraction of the precipitate ...particles revealed HA as the predominant phase (>99%) with a small amount of β-tricalcium phosphate. Fourier transform infrared spectroscopy indicated the presence of carbonate substitution, which decreased with increasing temperature. Transmission electron microscopy observations revealed needle-shaped particles with a high aspect ratio at 40 °C, which changed to spheroidal when the precipitation temperature was increased to 100 °C. The changes in the morphology with temperature were analyzed taking into account the driving force for the HA precipitation and the supersaturation level of Ca2+ and PO4 3- ions with respect to HA. The analysis indicated that the supersaturation level of the reactants, especially the concentration of Ca2+ ions, played a predominant role on the precipitate morphology for this classical acid−base reaction.
The antibacterial behavior of HA-Ag (silver-doped hydroxyapatite) nanopowder and their composite coatings were investigated against
Escherichia coli
(DH5α). HA-Ag nanopowder and PEEK ...(poly-ether-ether-ketone)-based HA-Ag composite powders were synthesized using in-house powder processing techniques. Bacteria culture assay of HA-Ag nanopowder and their composite powders displayed excellent bacteriostatic activity against
E. coli
. The antibacterial activity increased with increasing concentration of HA-Ag nanoparticle in these composite powders. These nanocomposite powders were subsequently used as feedstock to generate antibacterial coatings via cold spray technology. The ratios of HA-Ag to PEEK in their composite powders were 80:20, 60:40, 40:60, and 20:80 (wt.%). Microstructural characterization and phase analysis of feedstock powders and as-deposited coatings were carried out using FESEM/EDX and XRD. Antibacterial nanocomposite HA-Ag/PEEK coatings were successfully deposited using cold spraying parameters of 11-12 bars at preheated air temperature between 150 and 160 °C. These as-sprayed coatings of HA-Ag/PEEK composite powders comprising varying HA-Ag and PEEK ratios retained their inherent antibacterial property as verified from bacterial assay. The results indicated that the antibacterial activity increased with increasing HA-Ag nanopowder concentration in the composite powder feedstock and cold-sprayed coating.
Thermal barrier coating (TBC) systems reduce the temperature of the metallic substrate of aerospace engines, resulting in improved component durability, better fuel economy and performance. ...Scientific research and innovation on TBC systems evolves rapidly and diversely over the years. Hence, an understanding of the research and innovation pathways on TBC systems is extremely important for the future development of aerospace engines. This study examines research publications and patents on TBC during 1980–2019. While USA led the TBC publication output from 1980 to 2010, China takes the lead after 2011 and India too is emerging noticeably on TBC research. The citation impact of publications reveal key topic shifts. Distinct peaks identified for (1) materials sciences during 1998–2003; (2) energy during 2001–2007, and (3) chemical engineering during 2009–2018. The visual mappings of author keywords of the publications reveal the progress of TBC technology. Results show shifts in deposition techniques for TBC coating preparation, and thermal management in the engines. The journal papers cited by patents have low correlation to the highly cited papers. This paper introduced an innovation relevance indicator to gauge the relevance of an institution’s scientific research to technological innovation. This novel indicator reveals the industry relevant work among the active institutions and companies with patents in TBC technologies. Universities with significant number TBC patents fall into two broad categories, (1) those who have high (> 70%) collaborations on patents filed, and (2) those that filed patents without existing external collaborations.
ZrO
2-hydroxyapatite composites spark plasma sintered (SPS) at 1075
±
25°C involve inter and intra particle porosities. The porosity level in the compacts (<3–42%) varied with sintering pressure ...(4.5–17.3 MPa), and apparently contributed to the increase in indentation fracture toughness. Rietveld phase analysis revealed that the powders and SPS compacts composed of HA, tricalcium phosphate (TCP), zirconia (t- and c-ZrO
2) and CaZrO
3. The indentation toughness increased in tandem with porosity to about 20
vol% after which little or no cracking was observed in the compacts (even at loads up to 1 kgF). Possible reasons for this exceptional toughness are discussed. A 2-D model is proposed to describe the increase in toughness, which agrees with the experimental results. Thus, SPS compacts of nanoZrO
2-HA composite powders could be considered for load-bearing orthopaedic implants because of its unique fracture toughness and high porosity.
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