On optimum perforation layout in low-rise steel plate shear walls.

The design and performance of Steel Plate Shear Walls (SPSW) strongly depends on infill panels. Any unnecessary increase in the thickness of infill panels, which is a common occurrence in low-rise buildings, results in extremely large boundary elements and a noneconomic design. Among the several remedies that have been proposed and discussed by researchers, infill panel perforation has become more popular in SPSW design and construction. As a designer, one should primarily choose a desirable perforation layout, then adopt an approximate stiffness reduction formula and try to replace the infeasible design infill panel with a perforated one which possesses a minimum practical thickness and provides a similar lateral stiffness and strength. In this paper for a 4-story SPSW, primarily designed with practically infeasible thin infill panels, the optimum perforation diameters corresponding to diverse diagonal and rectangular perforation layouts are explored and the results have been compared to those provided by the available stiffness reduction formulas. The optimization outcomes reveal that the uniformly spaced rectangular perforation layouts are more efficient in the sense of SPSW stiffness reduction. Also, the efficiency of stiffness reduction formulas for rectangular perforation layouts have been assessed and the reliable methods introduced. Finally, on the basis of the resulted optimum sets, some formula improvements and design recommendations are concluded which would be useful and beneficial for practicing engineers

High frequency of multidrug-resistant Staphylococcus aureus with SCCmec type III and Spa types t037 and t631 isolated from burn patients in southwest of Iran

Methicilin resistance Staphylococcus aureus (MRSA) infections are the major challenges in hospitals, especially in the burn units. The use of molecular typing methods is essential for tracking the spread of S. aureus infection and epidemiological investigations. The aim of this study was to find the profile of the spa types and also the prevalence of each SCCmec type of S. aureus strains in a central burn hospital in southwest of Iran. A total of 81 non-duplicate S. aureus were isolated from burn patients between April 2011 and February 2012. The susceptibility of the isolates against 13 different antibiotics was tested by disk agar diffusion (DAD) method. MRSA strains were identified by amplification of mecA gene. Multiplex-polymerase chain reaction (PCR) technique was used to determine the SCCmec types of MRSA strains and all the S. aureus isolates were typed by spa typing method. Detection of mecA gene showed that 70 (86.4) of the isolates were MRSA. The highest rate of resistance was observed for penicillin (97.5) and erythromycin (77.8). None of the isolates were resistant to vancomycin. Sixty-seven of the 70 MRSA isolates harbored only SCCmec type III and three untypeable isolates. Five different spa types were detected. The most common spa types were t037 (42.5) and t631 (34.5) and were only found in MRSA isolates. Only SCCmec type III was found in burn patients which emphasizes the HA-MRSA origin of these strains. Only five different spa types identified in this study are in accordance with one SCCmec type which indicates that a limited number of bacterial colons are circulated in the burn unit in this hospital. © 2016 APMIS Published by John Wiley & Sons Ltd

The American Journal of Physiology- Regulatory, Integrative and Comparative Physiology publishes original investigations that

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