Label-free visualization of carbapenemase activity in living bacteria

Evaluating enzyme activity intracellularly on natural substrates is a significant experimental challenge in biomedical research. We report a label‐free method for real‐time monitoring of the catalytic behavior of class A, B, and D carbapenemases in live bacteria based on measurement of heat changes. By this means, novel biphasic kinetics for class D OXA‐48 with imipenem as substrate is revealed, providing a new approach to detect OXA‐48‐like producers. This in‐cell calorimetry approach offers major advantages in the rapid screening (10 min) of carbapenemase‐producing Enterobacteriaceae from 142 clinical bacterial isolates, with superior sensitivity (97 %) and excellent specificity (100 %) compared to conventional methods. As a general, label‐free method for the study of living cells, this protocol has potential for application to a wider range and variety of cellular components and physiological processes

High temperature deformation behavior of permanent casting AZ91 alloy with and without Sb addition

The elevated temperature deformation behavior of permanent cast magnesium alloy AZ91 with and without Sb addition has been investigated using slow strain rate (5.0 × 10 −4 s −1 ) elevated temperature tensile and constant load creep testing at 150 • C and 50 MPa. The alloy with 0.4 wt% Sb showed a higher elevated temperature tensile strength and creep resistance due to the formation of thermal stable Mg 3 Sb 2 precipitates and a smaller microstructure as well as the suppressing of the discontinuous precipitation. Plastic deformation of AZ91 based alloys is determined by motion of dislocation in basal plane and non-basal slip systems. The dislocation motion in a slip system is influenced by temperature, precipitates and other lattice defects. Dislocations jog, grain boundaries and/or precipitates are considered as obstacles for moving dislocations. The (0112) deformation twinning were founded in the creep process by TEM. Cross slip of dislocations was taken into account as the main softening mechanism for permanent cast AZ91 alloy during elevated temperature deformation process. C 2002 Kluwer Academic Publisher

Precipitation of secondary phase in Mg-Zn-Gd alloy after room-temperature deformation and annealing

Mg-Zn-RE alloys reinforced with quasicrystals have been investigated extensively because they show excellent balance in mechanical properties. Here, we perform deformation and annealing for Mg-1.50Zn-0.25Gd (at.%) alloy at various temperatures, aimed to gain nanoscale precipitates. We find that after the room-temperature compression, the non-basal dislocation, stacking fault and twining are identified in the as-deformed samples, offering clear evidence that these deformation mechanisms can accommodate room-temperature deformation. We also perform systematic transmission electron microscopy observations of the precipitates in both the as-deformed and as-annealed samples. The results identify the formation of a large amount of secondary-phase precipitates, I-phase and MgZn2, when annealed at 200 °C, and precipitation of a small amount of W-phase when annealed at 400 °C. Keywords: Mg alloys, Quasicrystal, Deformation, Annealing, Precipitatio

Fabrication of ultra-high strength magnesium alloys over 540 MPa with low alloying concentration by double continuously extrusion

We prepare a new type of patented biodegradable biomedical Mg–Nd–Zn–Zr (JDBM) alloy system and impose double continuously extrusion (DCE) processing. The lowest processing temperature is 250 °C for JDBM-2.1Nd and 310 °C for JDBM-2.8Nd, which increases with the Nd concentration. The highest yield strength of 541 MPa is achieved in JDBM-2.1 Nd samples when extruded at 250 °C and the elongation is about 3.7%. Moreover, the alloy with a lower alloying element content can reach a higher yield strength while that with a higher alloying element content can reach a larger elongation after DCE processing. However, when extruded under the same conditions, the alloy with a higher alloying contents exhibits better tensile properties. Keywords: Magnesium alloys, Microstructure, Mechanical properties, Double continuously extrusio