Tensile Behavior of High-Strength,Strain-Hardening Cement-Based Composites (HS-SHCC) Reinforced with Continuous Textile Made of Ultra-High-Molecular-Weight Polyethylene

The paper at hand presents an investigation of the tensile behavior of high-strength, strain-hardening cement-based composites (HS-SHCC), reinforced with a single layer of continuous, two-dimensional textile made of ultra-high molecular weight polyethylene (UHMWPE). Uniaxial tension tests were performed on the bare UHMWPE textiles, on plain HS-SHCC, and on the hybrid fiber-reinforced composites. The bond properties between the textile yarns and the surrounding composite were investigated in single-yarn pullout experiments. In order to assess the influence of bond strength between the yarn and HS-SHCC on the tensile behavior of the composites with hybrid fiber reinforcement, the textile samples were analyzed both with, and without, an additional coating of epoxy resin and sand. Compared to the composites reinforced with carbon yarns in previous studies by the authors, the high elongation capacity of the UHMWPE textile established the higher strain capacity of the hybrid fiber-reinforced composites, and showed superior energy absorption capacity up to failure. The UHMWPE textile limited the average crack width in comparison with that of plain HS-SHCC, but led to slightly larger crack widths when compared to equivalent composites reinforced with carbon textile, the reason for which was traced back to the lower Young’s modulus and the higher elongation capacity of the polymer textile.     

Radiofrequency by open surgical approach in the treatment of hepatic tumours: early experience with 14 cases

The aim of the study was the evaluation of radiofrequency in the treatment of hepatic tumours during laparotomy performed for hepatic tumours. The initial experience with 14 patients operated for hepatic tumours (5 primary and 9 metastatic) is presented. The paper also presents the technique concerning the intensity and duration of the power applied, the association with the surgical resection, the immediate postoperative evolution and the dynamics of the hepatic enzymes as well as the postoperative results of ultrasound and CT examinations performed within the first 6 weeks. The indications of RF during laparotomy and the place of RF ablation in the treatment of liver tumours in comparison with other ablation techniques are discussed     

Comparison of 400 mcg buccal and 400 mcg sublingual misoprostol after mifepristone medical abortion through 63 days' LMP: a randomized controlled trial

BackgroundBuccal misoprostol 800 mcg and sublingual misoprostol 400 mcg demonstrate high efficacy and few adverse effects when used with 200 mg mifepristone for medical abortion through 63 days since the last menstrual period (LMP). Little is known about a 400-mcg buccal dose. This study compares two in-the-mouth routes of misoprostol using the same dose.Study DesignEligible and consenting women (n=550) were randomized to 400 mcg of misoprostol buccally or sublingually 24 h after ingestion of 200 mg of mifepristone. Abortion status was assessed 2 weeks later.ResultsComplete abortion occurred in 97.1% of the buccal group and 97.4% of the sublingual group (p=.97, RR: 1.00, 95% CI=0.97–1.03). Adverse effects were similar in both groups. Over 90% of women in both arms expressed high satisfaction with the method.ConclusionsBoth 400 mcg buccal misoprostol and 400 mcg sublingual misoprostol after mifepristone appear to be good options for medical abortion through 63 days' LMP.     

Probabilistic Finite Element Modeling of Textile Reinforced SHCC Subjected to Uniaxial Tension

The paper presents a finite element investigation of the effect of material composition and the constituents’ interaction on the tensile behavior of strain-hardening cement-based composites (SHCC) both with and without textile reinforcement. The input material parameters for the SHCC and continuous reinforcement models, as well for their bond, were adopted from reference experimental investigations. The textile reinforcement was discretized by truss elements in the loaded direction only, with the constitutive relationships simulating a carbon and a polymer textile, respectively. For realistic simulation of macroscopic tensile response and multiple cracking patterns in hybrid fiber-reinforced composites subjected to tension, a multi-scale and probabilistic approach was adopted. SHCC was simulated using the smeared crack model, and the input constitutive law reflected the single-crack opening behavior. The probabilistic definition and spatial fluctuation of matrix strength and tensile strength of the SHCC enabled realistic multiple cracking and fracture localization within the loaded model specimens. Two-dimensional (2D) simulations enabled a detailed material assessment with reasonable computational effort and showed adequate accuracy in predicting the experimental findings in terms of macroscopic stress–strain properties, extent of multiple cracking, and average crack width. Besides material optimization, the model is suitable for assessing the strengthening performance of hybrid fiber-reinforced composites on structural elements.     

Dynamic Single-Fiber Pull-Out of Polypropylene Fibers Produced with Different Mechanical and Surface Properties for Concrete Reinforcement

In strain-hardening cement-based composites (SHCC), polypropylene (PP) fibers are often used to provide ductility through micro crack-bridging, in particular when subjected to high loading rates. For the purposeful material design of SHCC, fundamental research is required to understand the failure mechanisms depending on the mechanical properties of the fibers and the fiber–matrix interaction. Hence, PP fibers with diameters between 10 and 30 µm, differing tensile strength levels and Young’s moduli, but also circular and trilobal cross-sections were produced using melt-spinning equipment. The structural changes induced by the drawing parameters during the spinning process and surface modification by sizing were assessed in single-fiber tensile experiments and differential scanning calorimetry (DSC) of the fiber material. Scanning electron microscopy (SEM), atomic force microscopy (AFM) and contact angle measurements were applied to determine the topographical and wetting properties of the fiber surface. The fiber–matrix interaction under quasi-static and dynamic loading was studied in single-fiber pull-out experiments (SFPO). The main findings of microscale characterization showed that increased fiber tensile strength in combination with enhanced mechanical interlocking caused by high surface roughness led to improved energy absorption under dynamic loading. Further enhancement could be observed in the change from a circular to a trilobal fiber cross-section.