Influence of short dispersed and short integral glass fibres on the mechanical behaviour of textile-reinforced concrete

This article addresses the influence of the addition of short dispersed and short integral fibres made of alkali-resistant (AR) glass on the fracture behaviour of textile-reinforced concrete (TRC) subject to tensile loading. A series of uniaxial, deformation-controlled tension tests was performed to study the strength, deformation, and fracture behaviour of thin, narrow plates made of TRC, both with and without the addition of short fibres. Additionally, uniaxial tension tests on specimens reinforced with only short fibres were performed to figure out the difference in behaviour in the absence of textile reinforcement. Furthermore, multifilament-yarn and single-fibre pullout tests were carried out to gain a better understanding of bonding properties and crack-bridging behaviour. While pronounced enhancement of first-crack stress was achieved due to the addition of short dispersed fibres (the value increased by a factor of 2), a significant improvement in tensile strength was recorded for TRC specimens with the addition of integral glass fibres; the value increased by approximately 30 %. Moreover, TRC specimens reinforced with short dispersed glass fibres showed formation of more and finer cracks in comparison to the specimens with integral fibres. It was also found that short integral fibres can improve the bond between multifilament-yarns and the surrounding matrix by means of “special” cross-links. In TRC with short dispersed fibres this phenomenon was less pronounced. The investigations were accompanied by microscopical investigations which provided additional basis for an in-depth discussion of the decisive working mechanisms of hybrid reinforcement.     

Magnetization reversal in YIG/GGG(111) nanoheterostructures grown by laser molecular beam epitaxy

Abstract

Thin (4–20 nm) yttrium iron garnet (Y₃Fe₅O₁₂, YIG) layers have been grown on gadolinium gallium garnet (Gd₃Ga₅O₁₂, GGG) 111-oriented substrates by laser molecular beam epitaxy in 700–1000 °C growth temperature range. The layers were found to have atomically flat step-and-terrace surface morphology with step height of 1.8 Å characteristic for YIG(111) surface. As the growth temperature is increased from 700 to 1000 °C the terraces become wider and the growth gradually changes from layer by layer to step-flow regime. Crystal structure studied by electron and X-ray diffraction showed that YIG lattice is co-oriented and laterally pseudomorphic to GGG with small rhombohedral distortion present perpendicular to the surface. Measurements of magnetic moment, magneto-optical polar and longitudinal Kerr effect (MOKE), and X-ray magnetic circular dichroism (XMCD) were used for study of magnetization reversal for different orientations of magnetic field. These methods and ferromagnetic resonance studies have shown that in zero magnetic field magnetization lies in the film plane due to both shape and induced anisotropies. Vectorial MOKE studies have revealed the presence of an in-plane easy magnetization axis. In-plane magnetization reversal was shown to occur through combination of reversible rotation and abrupt irreversible magnetization jump, the latter caused by domain wall nucleation and propagation. The field at which the flip takes place depends on the angle between the applied magnetic field and the easy magnetization axis and can be described by the modified Stoner–Wohlfarth model taking into account magnetic field dependence of the domain wall energy. Magnetization curves of individual tetrahedral and octahedral magnetic Fe³⁺ sublattices were studied by XMCD.     

EELS microanalysis of polycrystalline silicon thin films for solar cells grown at low temperatures

The aim of this work is the quantitative chemical analysis of polycrystalline silicon thin films grown on glass substrates at temperatures <600°C by means of transmission electron microscopy (TEM) and electron energy-loss spectrometry (EELS). Specimens produced with two different methods were investigated. We found significant differences in grain size and morphology, as well as in the distribution of oxygen. A surprisingly high amount of Ba diffusion from the subtrate was detected.     

Chlorinated phenols in human milk

The paper deals with the contamination of human milk with chlorinated phenols. The average and median concentrations of the chlorophenols investigated ranged from 0.75 to 9.74 g.kg^–1 and from being not detectable to 5.62 g.kg^–1, respectively, for the different compounds. The highest average and median levels were found for pentachlorophenol and 2,4,5-trichlorophenol. The concentrations determined were below the permissible levels.     

The effect of water temperature on the adsorption equilibrium of dissolved organic matter and atrazine on granular activated carbon

The influence of water temperature on the adsorption of natural dissolved organic matter (DOM) on activated carbon has not been investigated intensively yet. In this study, batch experiments with granular activated carbon (GAC) have been carried out at three temperatures (5 degrees C, 20 degrees C, 35 degrees C) using a humic acid model water and different types of surface water (lake, river, canal). Furthermore, the adsorption of an anthropogenic contaminant, atrazine, was quantified in the absence and presence of DOM. The results indicate a significant influence of water temperature on the adsorption equilibrium of DOM and atrazine. Contrary to expectations, DOM and atrazine adsorption in surface water tends to be increased with increasing water temperature, whereas the extent of this effect is dependent on the type and concentration of DOM. Furthermore, the temperature effect on atrazine adsorption is controlled by competition of DOM and atrazine on adsorption sites. Some assumptions are proposed and discussed for explaining the temperature effects observed in the batch studies.     

Intrinsic instability of flame–acoustic coupling

This paper shows that a flame can be an intrinsically unstable acoustic element. The finding is clarified in the framework of an acoustic network model, where the flame is described by an acoustic scattering matrix. The instability of the flame acoustic coupling is shown to become dominating in the limit of no acoustic reflections. This is in contrast to classical standing-wave thermoacoustic modes, which originate from the positive feedback loop between system acoustics and the flame. These findings imply that the effectiveness of passive thermoacoustic damping devices is limited by the intrinsic stability properties of the flame.     

Applying Petri Nets to Modeling of Many-Core Processor Self-Testing when Tests are Performed Randomly

Today’s many-core processors are manufactured in inherently unreliable technologies. Massively defective technologies used for production of many-core processors are the direct consequence of the feature size shrinkage in today’s CMOS (complementary metal-oxide-semiconductor) technology. Due to these reliability problems, fault-tolerance of many-core processors becomes one of the major challenges. To reduce the probability of failures of many-core processors various fault tolerance techniques can be applied. The most preferable and promising techniques are the ones that can be easily implemented and have minimal cost while providing high level of processor fault tolerance. One of the promising techniques for detection of faulty cores, and consequently, for performing the first step in providing many-core processor fault tolerance is mutual testing among processor cores. Mutual testing can be performed either in a random manner or according to a deterministic scheduling policy. In the paper we deal with random execution of mutual tests. Effectiveness of such testing can be evaluated through its modeling. In the paper, we have shown how Stochastic Petri Nets can be used for this purpose and have obtained some results that can be useful for developing and implementation of testing procedure in many-core processors.     

Zur Querkraftbemessung von Stahlbetonträgern

Shear Design of Structural Concrete Girders Today, shear design is carried out using uniform models; the basis for this was laid 100 years ago and since the 1960's theoretically substantiated by the work in the field of the theory of plasticity. In recent investigations the models were extended with respect to compatibility of deformations as well as to the determination of the effective concrete compressive strength. This contribution gives an overview on these developments and demonstrates how the models can be used in design and detailing.     

Helium Conditioning Increases Cardiac Fibroblast Migration Which Effect Is Not Propagated via Soluble Factors or Extracellular Vesicles

Helium inhalation induces cardioprotection against ischemia/reperfusion injury, the cellular mechanism of which remains not fully elucidated. Extracellular vesicles (EVs) are cell-derived, nano-sized membrane vesicles which play a role in cardioprotective mechanisms, but their function in helium conditioning (HeC) has not been studied so far. We hypothesized that HeC induces fibroblast-mediated cardioprotection via EVs. We isolated neonatal rat cardiac fibroblasts (NRCFs) and exposed them to glucose deprivation and HeC rendered by four cycles of 95% helium + 5% CO₂ for 1 h, followed by 1 h under normoxic condition. After 40 h of HeC, NRCF activation was analyzed with a Western blot (WB) and migration assay. From the cell supernatant, medium extracellular vesicles (mEVs) were isolated with differential centrifugation and analyzed with WB and nanoparticle tracking analysis. The supernatant from HeC-treated NRCFs was transferred to naïve NRCFs or immortalized human umbilical vein endothelial cells (HUVEC-TERT2), and a migration and angiogenesis assay was performed. We found that HeC accelerated the migration of NRCFs and did not increase the expression of fibroblast activation markers. HeC tended to decrease mEV secretion of NRCFs, but the supernatant of HeC or the control NRCFs did not accelerate the migration of naïve NRCFs or affect the angiogenic potential of HUVEC-TERT2. In conclusion, HeC may contribute to cardioprotection by increasing fibroblast migration but not by releasing protective mEVs or soluble factors from cardiac fibroblasts.     

Synergistic effect of metal components of the low-loaded Pt-Ni-Cr/C catalyst in the bicyclohexyl dehydrogenation reaction

The problem of hydrogen storage in liquid organic hydrogen carriers is not only the choice of an appropriate organic substrate, but the development of a selective and active catalyst containing as low as possible noble metals. A synergistic effect of increasing conversion and selectivity in bicyclohexyl dehydrogenation to biphenyl on trimetallic Pt-Ni-Cr/C catalysts with an extremely low Pt loading (0.1 wt %), compared with bimetallic Ni-Cr/C and Pt/Ni/C systems, due to the supporting of platinum on nickel-chromium nanoparticles was established for the first time. The TOF values (mmol (H₂)/g_Pt min) for hydrogen evolution under conditions of the reaction of bicyclohexyl dehydrogenation (320 °C, 0.1 MPa) on Pt supported onto a Ni-Cr/С composite exceed by two orders of magnitude the values found for the two-component catalysts. The maximum amount of the evolved hydrogen correlates to the selectivity of the complete dehydrogenation of bicyclohexyl into biphenyl on the Pt-Ni-Cr/C catalyst. The formation of a Ni-Cr solid substitution solution in a Ni-Cr composite deposited on a carbon carrier is shown by magnetometry, XRD, and TEM methods.