Influence of Fiber Addition on the Properties of High-Performance Concrete

High performance fiber-reinforced concrete (HPFRC) has been frequently investigated in recent years. Plenty of studies have focused on different materials and types of fibers in combination with the concrete matrix. Experimental tests show that fiber dosage improves the energy absorption capacity of concrete and enhances the robustness of concrete elements. Fiber reinforced concrete has also been illustrated to be a material for developing infrastructure sustainability in RC elements like façade plates, columns, beams, or walls. Due to increasing costs of the produced fiber reinforced concrete and to ensure the serviceability limit state of construction elements, there is a demand to analyze the necessary fiber dosage in the concrete composition. It is expected that the surface and length of used fiber in combination with their dosage influence the structure of fresh and hardened concrete. This work presents an investigation of the mechanical parameters of HPFRC with different polymer fiber dosage. Tests were carried out on a mixture with polypropylene and polyvinyl alcohol fiber with dosages of 15, 25, and 35 kg/m³ as well as with control concrete without fiber. Differences were observed in the compressive strength and in the modulus of elasticity as well as in the flexural and splitting tensile strength. The flexural tensile strength test was conducted on two different element shapes: square panel and beam samples. These mechanical properties could lead to recommendations for designers of façade elements made of HPFRC.

Myocardial Perfusion Scans and Mortality in Asymptomatic Patients Awaiting Renal Transplantation

Cardiac risk assessment for asymptomatic patients awaiting renal transplantation is controversial. Patients awaiting renal transplantation in Southern Saskatchewan from 2005 to 2015 were retrospectively reviewed. Patients underwent cardiac risk stratification with stress myocardial perfusion scan. Baseline clinical characteristics, nuclear scan results, all-cause mortality, and cardiovascular events were analyzed. Abnormal scans were defined as studies with reversible defects, wall motion abnormalities, lung uptake, or transient ischemic dilation. Descriptive statistics and survival analysis were calculated. Charts from 285 consecutive patients with 608 nuclear scans were analyzed. Mean age was 55.2 ± 11.7 years and 34.7% were female. Forty-three (15.1%) patients were transplanted and 99 (40.9%) patients died while awaiting renal transplantation. One hundred fifty-three patients (63.2%) had at least one abnormal scan. The mean follow-up period was 5.47 ± 3.11 years. An abnormal scan was not associated with decreased survival and/or coronary events (hazard ratio: 0.94, P = .77; 95% confidence intervals: 0.62 to 1.43). Patients awaiting renal transplantation in Saskatchewan with abnormal myocardial perfusion scans were not at greater risk of death or coronary events.

Lipopolysaccharide binding protein, interleukin-6 and C-reactive protein in acute gastrointestinal infections: value as biomarkers to reduce unnecessary antibiotic therapy

AIM

Several new biomarkers, such as lipopolysaccharide binding protein (LBP) and interleukin-6 (IL-6), have the potential to determine the severity and outcome of infectious diseases. LBP and IL-6 serum levels have not been reported in patients with gastrointestinal infections. The aim of this study was to compare established markers of infection with new markers, such as LBP and IL-6, in patients with acute gastrointestinal infections

METHOD

LBP, C-reactive protein (CRP), white blood cell count (WBC) and IL-6 serum levels were determined in patients with acute viral or bacterial (positive stool cultures) gastroenteritis. The final diagnosis and empiric antibiotic use were recorded. In total, medical data on 88 patients with acute gastroenteritis (22 bacterial, 66 viral or nonspecific) were analyzed.

RESULTS

LBP and CRP levels were significantly increased in patients with acute bacterial gastroenteritis [28.5 ± 16.5 vs. 15.2 ± 11.5 μg/mL (p < 0.05) and 10.4 ± 9.6 vs. 3.8 ± 5.5 mg/dL (p < 0.001), respectively]. LBP at a cut-off value of 14.6 μg/mL and CRP at a cut-off value of 1.7 mg/dL distinguished between bacterial and non-bacterial gastrointestinal infection (receiver operator characteristic analysis). Empiric antibiotic therapy was initiated in 82% of patients with bacterial gastroenteritis and in 27% of patients with viral gastroenteritis.

CONCLUSION

The use of the cut-off values for LBP and CRP determined here would have avoided unnecessary antibiotic therapy in 14 and 11%, of patients respectively. CRP and LBP appear to be superior to IL-6 and WBC as diagnostic markers of bacterial gastrointestinal infection. Cut-off values may be a useful tool to support clinical decision-making on whether or not to initiate empiric antibiotic therapy.