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Public Health Risks: Antibiotic Resistance - Review -
Barton, Mary D,Hart, Wendy S Asian Australasian Association of Animal Productio 2001 Animal Bioscience Vol.14 No.3
Antibiotic resistance in human pathogens is a major public health issue. Some of the resistance problem can be attributed to the transfer of resistant bacteria from animals to people and the transfer of resistance genes from animal pathogens and commensal bacteria to human pathogens. Control measures include improvements in food hygiene to reduce the spread of zoonotic bacteria to people via the food chain. However, to specifically address the issue, the medical profession must control misuse and overuse of antibiotics in hospitals and community practice. In addition, the livestock industries and their advisors must reduce and refine the use of antibiotics in animal production and replace antibiotics with alternative disease control measures as much as possible.
Barton Mensah Arkhurst,박진주,이창훈,김정한 대한금속·재료학회 2017 대한금속·재료학회지 Vol.55 No.8
This study investigated the feasibility of using HfO2 as a dispersoid in the additive manufacturing process, compared to Y2O3. The effect of pre-annealing treatment was investigated too. Scanning electron microscopy (SEM) analyses revealed unusually coarse deposition layers for both the HfO2 and Y2O3 dispersed oxide dispersion strengthed (ODS) steels, in both the as-milled and the pre-annealed conditions. The deposited layer of the HfO2 dispersed ODS steel had relatively coarser grains than the deposited layer of the Y2O3 dispersed ODS steel in both the as-milled and the pre-annealed conditions. Moreover, the SEM results also revealed the presence of nanometer sized particles in all the deposition layers of both Y2O3 and HfO2 dispersed ODS steels, and their number densities were far lower than those in conventional bulk ODS steels. However, transmission electron microscopy analyses revealed that the dispersion and retention of nanoparticles within the melt were not achieved, even with HfO2 as a dispersoid, in contrast to the results from the SEM analyses. Furthermore, the deposition layers of both the as-milled Y2O3 and HfO2 ODS steels also exhibited an unusual nano-grained structure. The microhardnesses of the HfO2 and the Y2O3 dispersed ODS steels in both the as-milled and the pre-annealed conditions were higher than the substrate. Furthermore, the Y2O3 dispersed ODS steel had a higher microhardness than the HfO2 dispersed ODS steel in both the as-milled and the pre-annealed conditions.
Barton Mensah Arkhurst,Jin-ju Park,Chang-hoon Lee,Jeoung Han Kim 대한금속재료학회(구 대한금속학회) 2017 대한금속·재료학회지 Vol.55 No.8
This study investigated the feasibility of using HfO<sub>2</sub> as a dispersoid in the additive manufacturing process, compared to Y<sub>2</sub>O<sub>3</sub>. The effect of pre-annealing treatment was investigated too. Scanning electron microscopy (SEM) analyses revealed unusually coarse deposition layers for both the HfO<sub>2</sub> and Y<sub>2</sub>O<sub>3</sub> dispersed oxide dispersion strengthed (ODS) steels, in both the as-milled and the pre-annealed conditions. The deposited layer of the HfO<sub>2</sub> dispersed ODS steel had relatively coarser grains than the deposited layer of the Y<sub>2</sub>O<sub>3</sub> dispersed ODS steel in both the as-milled and the pre-annealed conditions. Moreover, the SEM results also revealed the presence of nanometer sized particles in all the deposition layers of both Y<sub>2</sub>O<sub>3</sub> and HfO<sub>2</sub> dispersed ODS steels, and their number densities were far lower than those in conventional bulk ODS steels. However, transmission electron microscopy analyses revealed that the dispersion and retention of nanoparticles within the melt were not achieved, even with HfO<sub>2</sub> as a dispersoid, in contrast to the results from the SEM analyses. Furthermore, the deposition layers of both the as-milled Y<sub>2</sub>O<sub>3</sub> and HfO<sub>2</sub> ODS steels also exhibited an unusual nano-grained structure. The microhardnesses of the HfO<sub>2</sub> and the Y<sub>2</sub>O<sub>3</sub> dispersed ODS steels in both the as-milled and the pre-annealed conditions were higher than the substrate. Furthermore, the Y<sub>2</sub>O<sub>3</sub> dispersed ODS steel had a higher microhardness than the HfO<sub>2</sub> dispersed ODS steel in both the as-milled and the pre-annealed conditions. (Received February 8, 2017; Accepted March 27, 2017)
Arkhurst, Barton Mensah,Kim, Jeoung Han,Lee, Mok-Young Elsevier 2019 APPLIED SURFACE SCIENCE - Vol.477 No.-
<P><B>Abstract</B></P> <P>In this study, a new material joining process called hot metal pressing (HMP) was developed. The feasibility, nature and mechanisms of this process were investigated for joining carbon fiber reinforced plastic (CFRP) and an AZ31 Mg alloy. Two sets of joint specimens were prepared, one set with as-received Mg sheets, and the other with Mg alloy sheets that had been annealed for different duration times. It was observed that an oxide layer, introduced on the surface of the Mg alloy by the annealing, had a significant influence on the bonding strength of the joints. Tensile shear test results showed that a high strength joint of approximately 5.1kN could be achieved. Bubble formation and the decomposition of the CFRP near the joint interface was observed on the joints with the as-received Mg alloy sheets, but was not observed on the joints that had oxide layers on the Mg alloy sheets after annealing. Moreover, the oxide layer grew into the CFRP near the joint interface for joints with the annealed Mg alloy sheets, indicating the possibility of mechanical anchoring effects which greatly enhanced the joining strength.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Joining of a CFRP to an AZ31 Mg alloy was successfully achieved. </LI> <LI> Higher joint strengths were achieved by formation of an oxide layer on the surface of the AZ31 Mg alloy. </LI> <LI> Decomposition of the CFRP and significant bubble formation was prohibited by the formation of oxide layer. </LI> <LI> Oxide layer was observed to grow into the CFRP near the joint interfaces. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Arkhurst, Barton Mensah,Lee, Mokyoung,Kim, Jeoung Han Elsevier 2018 COMPOSITE STRUCTURES -BARKING THEN OXFORD- Vol.201 No.-
<P><B>Abstract</B></P> <P>This study investigated the effect of two types of carbon fiber reinforced plastics (CFRPs) with different matrices, on the strength of a metal alloy–plastic composite joint made by the hot metal pressing (HMP) technique. One set of experiments was carried out with a PAN-type CFRP with a thermoplastic polyurethane (TPU) matrix, and the other with a PAN-type CFRP with a polyamide 6 (PA6) matrix. Both matrices were joined with either as-received or annealed AZ31 Mg-alloy sheets processed at different annealing durations to produce oxide layers on the alloy sheets. Due to the complete suppression of CFRP-resin decomposition at its joint interface, the CFRP with a PA6 matrix exhibited superior joint strength as compared to the TPU-matrix CFRP, which showed partial suppression of the CFRP-resin decomposition and bubble formation, with complete suppression characterized by microcracking at its joint interface. A reaction between C and MgO was observed at the joint interface for the TPU-CFRP but not for the PA6-CFRP. The melting/decomposition temperature of the matrix materials and the influence of the oxide layer on the conduction of heat between the materials were the key determinants of the AZ Mg alloy-CFRP joint strength.</P>