Quark Delocalization, Color Screening, and Nuclear Intermediate Range Attraction

We consider the effect of including quark delocalization and color screening, in the nonrelativistic quark cluster model, on baryon-baryon potentials and phase shifts. We find that the inclusion of these additional effects allows a good qualitative description of both.Comment: 10 pages, LaTeX, 4 figures in PostScript after text, LA-UR-91-215

Comparative bactericidal activities of daptomycin, glycopeptides, linezolid and tigecycline against blood isolates of Gram-positive bacteria in Taiwan

ABSTRACTIn-vitro MICs and minimum bactericidal concentrations (MBCs) of daptomycin, linezolid, tigecycline, vancomycin and teicoplanin against Gram-positive bacteria were determined using the broth microdilution method for ten blood isolates each of methicillin-susceptible Staphylococcus aureus (MSSA), methicillin-resistant S. aureus (MRSA), including two vancomycin-intermediate S. aureus (VISA), vancomycin-resistant Enterococcus faecium and Enterococcus faecalis. One strain of VISA was tested in a time-kill synergism assay of daptomycin combined with oxacillin, imipenem, rifampicin and isepamicin. Daptomycin showed excellent in-vitro bactericidal activity against all the isolates tested, with no tolerance or synergism effects when combined with other agents, except with rifampicin against VISA. Vancomycin had better bactericidal activity against MRSA and MSSA than did teicoplanin. Linezolid had the poorest bactericidal activity against the isolates tested, with 100% tolerance by the MSSA and VRE isolates, and 80% tolerance by the MRSA isolates. Tolerance towards tigecycline was exhibited by 40% of the MRSA isolates, 100% of the MSSA and vancomycin-resistant E. faecalis isolates, and 90% of the vancomycin-resistant E. faecium isolates

Local infiltration analgesia versus femoral nerve block in total knee arthroplasty: A meta-analysis

AbstractIntroductionLocal infiltration analgesia (LIA) and femoral nerve block (FNB) are both used for the pain management after total knee arthroplasty (TKA). Controversy still remains regarding the optimal technique for pain relief in patients undergoing TKA. The purpose of this meta-analysis was to compare the analgesia achieved with LIA and the one from FNB following TKA.HypothesisLIA achieves better pain control than FNB in patients with TKA.MethodsDatabases, including Pubmed, EMBASE, the Cochrane Library and Web of Science were comprehensively searched to identify studies comparing LIA with FNB for patients with TKA. Two reviewers independently selected trials, extracted data, and assessed the methodological qualities of included studies. Data were analyzed by RevMan 5.2.ResultsNine RCTs involving 782 patients were included. LIA achieved more rapid pain relief (VAS) at 6h postoperatively [SMD6h=−0.92, 95% CI (−1.38, −0.47)] than FNB. There were no significant differences at 24h and 48h [SMD24h=−0.03, 95% CI (−0.46, 0.40); SMD48h=0.28, 95% CI (−0.35, 0.91)], VAS with activity at 24h and 48h [SMD6h=−0.54, 95% CI (−1.62, 0.54); SMD24h=−0.22, 95% CI (−1.41, 0.96); SMD48h=−0.08, 95% CI (−0.52, 0.69)], opioid consumption at 24h and 48h [SMD24h=−0.24, 95% CI (−0.82, 0.34); SMD48h=0.15, 95% CI (0.25, 0.54)] and length of hospital stay [MD=−0.52, 95% CI (−1.13, 0.09)].DiscussionLIA may be the better choice in the pain management of TKA for it could achieve fast pain relief and is easier to perform than FNB for patients with TKA.Level of evidenceLevel II, meta-analysis and systematic review

Flexural behaviour of hybrid FRP-concrete-steel double skin tubular members

This paper presents the results of an experimental study on the flexural behavior of a new type of hybrid FRP-concrete-steel member as well as results from a corresponding theoretical model based on the plane section assumption and the fiber element approach. This new type of hybrid member is in the form of a double-skin tube, composed of a steel inner tube and an FRP outer tube with a concrete infill between the two tubes, and may be employed as columns or beams. The parameters examined in this study include the section configuration, the concrete strength, and the thicknesses of the steel tube and the FRP tube, respectively. The results presented in this paper show that these hybrid beams have a very ductile response because the compressive concrete is confined by the FRP tube and the steel tube provides ductile longitudinal reinforcement. The beams\u27 flexural response, including the flexural stiffness, ultimate load, and cracking, can be substantially improved by shifting the inner steel tube toward the tension zone or by providing FRP bars as additional longitudinal reinforcement. The predictions from the theoretical model are in reasonably close agreement with the test results. Differences between the test and predicted results arise from factors not considered in the theoretical model, including the existence of a strain gradient in the confined concrete, concentrations of cracks and the slips between the concrete and the two tubes; these are issues to be accounted for in the development of a more accurate model in the future

Tests on RC Beams Strengthened at the Span with Externally Bonded Polymers Reinforced with Carbon or Steel Fibers

The main objective of the experimental work reported herein is the comparative evaluation of steel-reinforced polymers (SRPs) and carbon-reinforced polymers (CFRPs) used as externally-bonded reinforcement in strengthening of reinforced-concrete (RC) members. Tensile stress strain as well as bond constitutive laws for these materials were first derived from 16 tests and are summarized here. Results are then reported from four-point bending tests of five full-scale RC beams strengthened at their span using SRP and CFRP strips. The bond tests have shown that by providing a bond length greater than the effective one, neither the bond strength nor the deformation capacity are increased, whereas by increasing the width of the strip the bond strength is increased. From the bending tests of beams it was found that the use of both SRP and CFRP strips resulted in a significant increase in strength (up to 92%) with respect to the strength of the initial specimen. The experimentally measured strengths were estimated analytically using both the experimental measurements of the specimen deformations and the pertinent provisions of standards from the American Concrete Institute and the European Committee for Standardization

Flexural Rigidity Evaluation of Seismic Performance of Hollow-Core Composite Bridge Columns

This paper investigates experimentally the seismic behavior of two hollow-core fiber-reinforced polymer-concrete-steel HC-FCS columns under cyclic loading as a cantilever. The typical precast HC-FCS member consists of a concrete wall sandwiched between an outer fiber-reinforced polymer (FRP) tube and an inner steel tube. The FRP tube provides continuous confinement for the concrete wall along the height of the column. Five large-scale HC-FCS columns were investigated during this study to estimate the effective flexural (which is an important factor to define the buckling capacity and deflection of such columns) and the effective structural stiffness of the composite columns. These columns have the same geometric properties; the only difference was in the thickness of the inner circular steel tubes and the steel tube embedded length into the footing. A three-dimensional numerical model has been developed using LS_DYNA software for modeling this large scale HC-FCS columns. The nonlinear FE models were designed and validated against experimental results gathered from HC-FCS columns tested under cyclic lateral loading and used to evaluate the effective stiffness’s results. The estimated effective stiffness results that obtained from the experimental work were compared with the FE results. This study revealed that the effective flexural and the effective structural stiffness for the HC-FCS columns need more investigation to be addressed in the standard codes. Since the embedded hollow core steel tube socket connections cannot reach the fully fixed end condition to act as a cantilever member subjected to a lateral load with a fully fixed end condition. Moreover, the effective stiffness results were found to be highly sensitive to the steel tube embedded length and slightly to the unconfined concrete strength

Effects of hydroxyapatite and PDGF concentrations on osteoblast growth in a nanohydroxyapatite-polylactic acid composite for guided tissue regeneration

The technique of guided tissue regeneration (GTR) has evolved over recent years in an attempt to achieve periodontal tissue regeneration by the use of a barrier membrane. However, there are significant limitations in the currently available membranes and overall outcomes may be limited. A degradable composite material was investigated as a potential GTR membrane material. Polylactic acid (PLA) and nanohydroxyapatite (nHA) composite was analysed, its bioactive potential and suitability as a carrier system for growth factors were assessed. The effect of nHA concentrations and the addition of platelet derived growth factor (PDGF) on osteoblast proliferation and differentiation was investigated. The bioactivity was dependent on the nHA concentration in the films, with more apatite deposited on films containing higher nHA content. Osteoblasts proliferated well on samples containing low nHA content and differentiated on films with higher nHA content. The composite films were able to deliver PDGF and cell proliferation increased on samples that were pre absorbed with the growth factor. nHA–PLA composite films are able to deliver active PDGF. In addition the bioactivity and cell differentiation was higher on films containing more nHA. The use of a nHA–PLA composite material containing a high concentration of nHA may be a useful material for GTR membrane as it will not only act as a barrier, but may also be able to enhance bone regeneration by delivery of biologically active molecules