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This study presents the investigation of the influence of heat treatment on microstructure, hardness and tensile properties of high-speed selective laser melted Ti6Al4V components. Heat treatment was performed to obtain an improved microstructure with enhanced hardness and tensile properties. It was found that the acicular martensitic α′ structure on the as-built sample lead to high hardness, yield strength and ultimate tensile strengths of 389±10 HV0.3, 949 ± 10 MPa and 1045 ± 3 MPa, respectively,with a low ductility of 5%. Heat treatment transformed the martensitic α′ structure into lamella α + β phases, with heat treatment at 1000 °C resultingin the most improved hardness and ductility from 389 ± 10 HV0.3 and 5% to 325 ± 20 HV0.3 and 13%, and a decrease in yield and ultimate tensile strength from 949 ± 10 MPa and 1045 ± 13MPa to 835 ± 11 MPa and 911 ± 5 MPa, respectively.

The following article looks at using scanning electron microscopy- electron back scatter diffraction techniques to study recrystallisation structures produced through hot rolling of 436 ferritic stainless steel. Characterisation of recrystallisation textures was undertaken through analysis of misorientation angle distribution diagrams, orientation distribution function maps, inverse pole figures and Taylor factor maps. These techniques were applied in a case study where typical industrial hot rolling conditions were simulated through uniaxial compression tests in a Bähr Dilatometer 850D, whereby the effect of strain rate and interpass time on recrystallisation structures was investigated.

This paper presents the numerical and experimental results of the mechanical and microstructural properties of liquefied petroleum gas cylinders from local sources. The tensile strength, burst and fracture toughness of the materials were also investigated. The results show that the carbon content for all samples averaged ~0.22 wt% and manganese ~0.76 wt% and the microstructure was largely pearlitic. The tensile strength showed that LPG-C3 recorded high tensile strength of ~ 611 MPa and hardness of ~ 200 HV while LPG-C5 recorded low tensile strength of ~ 450 MPa. The finite element analysis (FEA) showed fracture toughness of ~5 × 105 MPa.mm0.5 for LPG-C2 and the energy release rate of ~2 × 106J/m² for LPG-C5. All samples exhibited high resilience to crack propagation which showed ductile fracture after tensile test. The implications of the results are discussed to elaborate on the influence of carefully controlling the alloying elements of LPG cylinder materials on their mechanical and microstructures during fabrication. [ABSTRACT FROM AUTHOR]

Author(s): Kofi Annan In 2000, the United Nations hosted the largest gathering of political leaders ever held. At that meeting, all 189 UN member states, plus leading development institutions, committed [...]

Abstract Background Microorganisms have provided a wealth of metabolites with interesting activities such as antimicrobial, antiviral and anticancer. In this study, a total of 119 aquatic microbial isolates from 30 samples (taken from water bodies in Ghana) were screened by the agar-well diffusion method for ability to produce antibacterial-metabolites. Results Antibacterial activity was exhibited by 27 of the isolates (14 bacteria, 9 actinomycetes and 4 fungi) against at least one of the indicator microorganisms: Enterococcus faecalis (ATCC 29212), Bacillus thuringiensis (ATCC 13838), Pseudomonas aeruginosa (ATCC 27853), Staphylococcus aureus (ATCC 25923), Proteus vulgaris (NCTC 4635) and Bacillus Subtilis (NCTC 10073). A sea isolate MAI2 (identified as a strain of Pseudomonas aeruginosa) exhibited the highest antibacterial activity (lowest zone of inhibition = 22 mm). The metabolites of MAI2 extracted with chloroform were stable to heat and gave minimum inhibitory concentrations ranging between 250 and 2000 μg/ml. Bioautography of the extract revealed seven active components. Conclusion This study has therefore uncovered the potential of water bodies in the West African sub-region as reservoirs of potent bioactive metabolite producing microorganisms.

Globalization in the 21st Century What is globalization? More than ever before, groups and individuals are interacting directly across borders without involving the state. This happens partly due to new [...]

Background: Discovery of novel gametocytocidal molecules is a major pharmacological strategy in the elimination and eradication of malaria. The high patronage of the aqueous root extract of the popular West African anti-malarial plant Cryptolepis sanguinolenta (Periplocaceae) in traditional and hospital settings in Ghana has directed this study investigating the gametocytocidal activity of the plant and its major alkaloid, cryptolepine. This study also investigates the anti-malarial interaction of cryptolepine with standard anti-malarials, as the search for new anti-malarial combinations continues. Methods: The resazurin-based assay was employed in evaluating the gametocytocidal properties of C. sanguinolenta and cryptolepine against the late stage (IV/V) gametocytes of Plasmodium falciparum (NF54). A fixed ratio method based on the SYBR Green I fluorescence-based assay was used to build isobolograms from a combination of cryptolepine with four standard anti-malarial drugs in vitro using the chloroquine sensitive strain 3D7. Results: Cryptolepis sanguinolenta (IC50 = 49.65 nM) and its major alkaloid, cryptolepine (IC50 = 1965 nM), showed high inhibitory activity against the late stage gametocytes of P. falciparum (NF54). In the interaction assays in asexual stage, cryptolepine showed an additive effect with both lumefantrine and chloroquine with mean SFIC50s of 1.017 ± 0.06 and 1.465 ± 0.17, respectively. Cryptolepine combination with amodiaquine at therapeutically relevant concentration ratios showed a synergistic effect (mean SFIC50 = 0.287 ± 0.10) whereas an antagonistic activity (mean SFIC50 = 4.182 ± 0.99) was seen with mefloquine. Conclusions: The findings of this study shed light on the high gametocytocidal properties of C. sanguinolenta and cryptolepine attributing their potent anti-malarial activity mainly to their effect on both the sexual and asexual stages of the parasite. Amodiaquine is a potential drug partner for cryptolepine in the development of novel fixed dose combinations. [ABSTRACT FROM AUTHOR]

Background: The edible and medicinal leguminous plant Cassia tora L. (Fabaceae) is known to possess insecticidal properties against a wide range of plant-feeding insects. However, the bioactivity of extracts of this plant and their constituents against vectors of medical importance has been largely unexplored. We investigated the mosquito larvicidal activity of the seed extract and its major anthraquinones against larvae of the African malaria vector Anopheles gambiae (s.s.). Methods: Third-fourth instar larval mortality was observed after 24, 48, 72 and 96 h of exposure to varying doses of the extracts, and two anthraquinones isolates identified using liquid chromatography- quadrupole time of flight mass spectrometry (LC-QtoF-MS). The mosquito larval mortality was evaluated relative to the natural insecticide azadirachtin. Results: Fractionation of the crude extract decreased mosquito larvicidal activity, however, larvicidal activity increased with increasing dose of the treatment and exposure time. The known anthraquinones aurantio-obtusin and obtusin were identified as key larvicidal compounds. Aurantio-obtusin and obtusin, exhibited similar toxicity to larvae of A. gambiae (s.s.) with LD50 values of 10 and 10.2 ppm, respectively. However, the two anthraquinones were four- and ~ six-fold less potent than that of the crude seed extract and azadirachtin, which had comparable LD50 values of 2.5 and 1.7 ppm, respectively. Conclusion: Both aurantio-obtusin and obtusin showed mosquito larvicidal activity which were comparable to their respective fractions although they were less potent relative to the crude extract and azadirachtin. Further studies need to be conducted on C. tora for its exploitation as a potential eco-friendly tool in mosquito larval source reduction. [ABSTRACT FROM AUTHOR]