Probabilistic Analysis of Circular Tunnels in Homogeneous Soil Using Response Surface Methodology

A probabilistic analysis of a shallow circular tunnel driven by a pressurized shield in a frictional and/or cohesive soil is presented. Both the ultimate limit state (ULS) and serviceability limit state (SLS) are considered in the analysis. Two deterministic models based on numerical simulations are used. The first one computes the tunnel collapse pressure and the second one calculates the maximal settlement due to the applied face pressure. The response surface methodology is utilized for the assessment of the Hasofer-Lind reliability index for both limit states. Only the soil shear strength parameters are considered as random variables while studying the ULS. However, for the SLS, both the shear strength parameters and Young’s modulus of the soil are considered as random variables. For ULS, the assumption of uncorrelated variables was found conservative in comparison to the one of negatively correlated parameters. For both ULS and SLS, the assumption of nonnormal distribution for the random variables has almost no effect on the reliability index for the practical range of values of the applied pressure. Finally, it was found that the system reliability depends on both limit states. Notice however that the contribution of ULS to the system reliability was not significant. Thus, SLS can be used alone for the assessment of the tunnel reliability.     

Influence of the Martensitic Transformation on the Microscale Plastic Strain Heterogeneities in a Duplex Stainless Steel

The influence of the martensitic transformation on microscale plastic strain heterogeneity of a duplex stainless steel has been investigated. Microscale strain heterogeneities were measured by digital image correlation during an in situ tensile test within the SEM. The martensitic transformation was monitored in situ during tensile testing by high-energy synchrotron X-ray diffraction. A clear correlation is shown between the plasticity-induced transformation of austenite to martensite and the development of plastic strain heterogeneities at the phase level.     

Structural Characterization,Technological Functionality,and Physiological Aspects of Fungal β-D-glucans: A Review

β-D-glucans are a (1→3)-linked glucose polymer with (1→6)-linked side chains and a major component of fungal cell walls. They exhibit structural integrity to the fungal cell wall. In addition, β-glucans are widely used as food adjuvant in food and pharmaceutical industries because of their physico-chemical properties. Several studies have focused on different isolation processes of (1→3) (1→6)-β-glucan that could affect the physico-chemical and functional properties of β-glucan such as chemical composition, solubility, viscosity, hydration properties, and oil binding capacity. Immunological activity is one of the most important properties of β-glucans. Thus, they are effective in inhibiting growth of cancer cells and metastasis and preventing bacterial infection. In humans, β-glucans reduce blood cholesterol, improve glucose absorption by body cells, and so help wound healing. This review described the prebiotic potentiality of fungal β-D-glucans with the objective to detail the methodologies applied for their extraction, their structure and techno-functional properties, and finally their biological effects.     

Fast scanning calorimetry clarifies the understanding of the complex melting and crystallization behavior of polyesteramide multi‐block copolymers

Fast scanning calorimetry has been applied in order to understand the phase transitions in thermoplastic elastomers (TPEs) based on well‐defined multi‐block copolymers made of ‘soft’ polytetrahydrofuran and ‘hard’ terephthalate ester diamides. The intrinsically complex chemical structure of TPEs leads to complex phase transitions. By changing their thermal history over a wide range of temperature (from ?100 °C to 200 °C) and cooling rates (from 10 to 4000 °C s^?1), we clarify the origins of the various phases present in these materials. In particular, we study the different possibilities for the hard segments to associate depending on their mobility during the quenching phase, forming either strong and stable structures or weaker and metastable ones. Besides, we demonstrate that a minimal cooling rate of 800 °C s^?1 is necessary to keep these TPEs (made of short and monodisperse hard segments) amorphous leading to a subsequent cold crystallization when heating back, at around 30 °C. Finally, we validate our interpretations by varying the copolymer composition (from 10 wt% to 20 wt% hard segments), revealing the thermal invariance of poorly organized domains. Based on these data, we also discuss the importance of chain diffusion in the crystallization process. Applying fast scanning calorimetry allows us to link fundamental understanding to industrial application. © 2018 Society of Chemical Industry     

A macro- and micromechanics investigation of hot cracking in duplex steels

The relationship between microstructure and high temperature ductile tearing in duplex stainless steels has been investigated. Several grades were considered corresponding to different chemical compositions, different volume fractions and morphologies of the ferrite and austenite phases and different oxide inclusion contents. The high temperature cracking resistance has been quantified using both the essential work of fracture (EWF) and the fracture strain. The EWF discriminates the different grades of duplex steels and the different microstructures in terms of hot tearing resistance better than does the fracture strain. Metallographic characterization reveals that damage preferentially nucleates near inclusions at the austenite/ferrite boundary. Voids grow inside the ferrite until they coalesce. Damage develops more rapidly when increasing either the mismatch of rheology between the phases, which was evaluated by micro-scale strain measurements, or the inclusion content. The cracking resistance is related to the plastic work performed in the fracture process zone whereas the fracture strain depends on the damage kinetics. Both processes involve length scales related to the morphology and to the microstructure dimensions. Guidelines for improving the hot cracking resistance of duplex steels are formulated.     

Tandem Catalysis: Access to Ketones from Aldehydes and Arylboronic Acids via Rhodium‐Catalyzed Addition/Oxidation

Direct cross‐coupling reactions of aromatic aldehydes with arylboronic acids afforded ketones in high yields and under mild conditions in the presence of a rhodium catalyst, acetone and a base. This new reaction, involving a formal aldehyde C H bond activation, is believed to proceed via a tandem process involving addition of the organometallic species to the aldehyde followed by oxidation by β‐hydride transfer.     

Microfluidic tools for cell biological research

Microfluidic technology is creating powerful tools for cell biologists to control the complete cellular microenvironment, leading to new questions and new discoveries. We review here the basic concepts and methodologies in designing microfluidic devices, and their diverse cell biological applications.