Stone Column Ground Improvement Against Liquefaction for the Preveza-Aktio Immersed Tunnel

The construction of the road fixed-link crossing between Preveza and Aktio on the north-western coast of Greece has recently been completed. The project consists of an immersed single-tube tunnel under the strait and two cut-and-cover tunnels at the ends of the immersed part. The immersed section is constructed of eight precast rectangular concrete elements placed on the sea bottom at a depth of 25 m. The site is characterized by high seismicity. Foundation soil consists of Holocene marine sediments comprising irregular layers of sands, silts and clays that extend to great depth in the central part of the strait. Along the entire tunnel alignment the silty sands and sandy silts of the top layers are classified as potentially liquefiable due to their low density. Soil improvement in the form of stone columns has been carried out below the tunnel foundation for reducing risk from liquefaction. The soil conditions and the seismic input parameters are presented and an overview of the extensive dynamic laboratory testing program conducted is given. The seismic site response analyses performed for determining the depth of ground improvement are summarized. The design of the stone columns as well as a practical method for estimating the stiffness of the composite soil are described

A discrete element model for cohesive soil

Soil can roughly be classified into cohesionless, cohesive, and cemented soil. In this contribution, a discrete element model for the simulation of cohesive soil is presented. It is based on a model for cohesionless material with spherical particles, normal repulsive and frictional contacts, as well as rolling resistance with an elastic limit to compensate the excessive particle rolling. The cohesive behavior is modeled by an additional attractive normal force between particles. The model is not derived from the microscopic origin of cohesion, such as liquid bridges or electrostatic forces. Instead, it is set up in analogy to the macroscopic shear failure characteristics of cohesive soil. It is observed in video inspections of a bulldozer blade operating in cohesive soil that after the cutting takes place the soil recovers more of its initial cohesion in areas of high compression. In areas away from the blade, the material behaves more like cohesionless soil, forming an angle of response. This behavior is reproduced by introducing a memory effect in the simulation. By that, the amount of cohesion is limited by the pressure that the contacting particles have experienced during the simulation. The discrete element model is shown to be scale invariant in the quasi-static regime, i.e. if all length scales of the model are scaled by a constant factor, the results remain unaffected by the scaling. The model is applied to a bulldozer blade pushing cohesive soil. The contact parameters are calibrated by simulated triaxial compression tests. A comparison between simulation and measurement shows good qualitative agreement

A discrete element model for cohesive soil

Soil can roughly be classified into cohesionless, cohesive, and cemented soil. In this contribution, a discrete element model for the simulation of cohesive soil is presented. It is based on a model for cohesionless material with spherical particles, normal repulsive and frictional contacts, as well as rolling resistance with an elastic limit to compensate the excessive particle rolling. The cohesive behavior is modeled by an additional attractive normal force between particles. The model is not derived from the microscopic origin of cohesion, such as liquid bridges or electrostatic forces. Instead, it is set up in analogy to the macroscopic shear failure characteristics of cohesive soil. It is observed in video inspections of a bulldozer blade operating in cohesive soil that after the cutting takes place the soil recovers more of its initial cohesion in areas of high compression. In areas away from the blade, the material behaves more like cohesionless soil, forming an angle of response. This behavior is reproduced by introducing a memory effect in the simulation. By that, the amount of cohesion is limited by the pressure that the contacting particles have experienced during the simulation. The discrete element model is shown to be scale invariant in the quasi-static regime, i.e. if all length scales of the model are scaled by a constant factor, the results remain unaffected by the scaling. The model is applied to a bulldozer blade pushing cohesive soil. The contact parameters are calibrated by simulated triaxial compression tests. A comparison between simulation and measurement shows good qualitative agreement

Light intensity affects RNA silencing of a transgene in Nicotiana benthamiana plants

Abstract Background Expression of exogenous sequences in plants is often suppressed through one of the earliest described RNA silencing pathways, sense post-transcriptional gene silencing (S-PTGS). This type of suppression has made significant contributions to our knowledge of the biology of RNA silencing pathways and has important consequences in plant transgenesis applications. Although significant progress has been made in recent years, factors affecting the stability of transgene expression are still not well understood. It has been shown before that the efficiency of RNA silencing in plants is influenced by various environmental factors. Results Here we report that a major environmental factor, light intensity, significantly affects the induction and systemic spread of S-PTGS. Moreover, we show that photoadaptation to high or low light intensity conditions differentially affects mRNA levels of major components of the RNA silencing machinery. Conclusions Light intensity is one of the previously unknown factors that affect transgene stability at the post-transcriptional level. Our findings demonstrate an example of how environmental conditions could affect RNA silencing.</p

Parameter identification for soil simulation based on the discrete element method and application to small scale shallow penetration tests

The Discrete Element Method (DEM) is well-established and widely used in soil-tool interaction related applications. As for all simulation tools, a proper calibration of the model parameters is crucial. In this contribution, we present the parametrization procedure of the DEM software GRAnular Physics Engine (GRAPE), developed and implemented at Fraunhofer ITWM, and attempt to use two parametrized soil samples for the simulation of small scale shallow penetration tests. The results are compared to laboratory measurements

Triaxial compression and direct shear tests in the parametrization of soil modeled via the Discrete Element Method

Investigation in the parametrization of soil modeled with DEM based on measurements in triaxial compression and direct shear tests

Association between sodium-glucose cotransporter-2 inhibitors and incident atrial fibrillation/atrial flutter in heart failure patients with reduced ejection fraction: a meta-analysis of randomized controlled trials

Atrial fibrillation (AF) and atrial flutter (AFL) are associated with adverse outcomes in patients with heart failure and reduced ejection fraction (HFrEF). We investigated the effects of sodium-glucose cotransporter-2 inhibitors (SGLT2i) on the incidence of AF and/or AFL in HFrEF patients. PubMed and linicalTrials.gov were systematically searched until March 2022 for randomized controlled trials (RCTs) that enrolled patients with HFrEF. A total of six RCTs with 9467 patients were included (N=4731 in the SGLT2i arms; N=4736 in the placebo arms). Compared to placebo, SGLT2i treatment was associated with a significant reduction in the risk of AF [relative risk (RR) 0.62, 95% confidence interval CI 0.44–0.86; P=0.005] and AF/AFL (RR 0.64, 95% CI 0.47–0.87; P=0.004). Subgroup analysis showed that empagliflozin use resulted in a significant reduction in the risk of AF (RR 0.55, 95% CI 0.34–0.89; P=0.01) and AF/AFL (RR 0.50, 95% CI 0.32–0.77; P=0.002). By contrast, dapagliflozin use was not associated with a significant reduction in the risk of AF (RR 0.69, 95% CI 0.43–1.11; P=0.12) or AF/AFL (RR 0.82, 95% CI 0.53–1.27; P=0.38). Additionally, a “shorter” duration (<1.5 years) of treatment with SGLT2i remained associated with a reduction in the risk of AF (<1.5 years; RR 0.58, 95% CI 0.36–0.91; P=0.02) and AF/AFL (<1.5 years; RR 0.52, 95% CI 0.34–0.80; P=0.003). In conclusion, SGLT2i therapy was associated with a signifcant reduction in the risk of AF and AF/AFL in patients with HFrEF. These results reinforce the value of using SGLT2i in this setting

Constraints on the shallow elastic and anelastic structure of Mars from InSight seismic data

Mars’s seismic activity and noise have been monitored since January 2019 by the seismometer of the InSight (Interior Exploration using Seismic Investigations, Geodesy and Heat Transport) lander. At night, Mars is extremely quiet; seismic noise is about 500 times lower than Earth’s microseismic noise at periods between 4 s and 30 s. The recorded seismic noise increases during the day due to ground deformations induced by convective atmospheric vortices and ground-transferred wind-generated lander noise. Here we constrain properties of the crust beneath InSight, using signals from atmospheric vortices and from the hammering of InSight’s Heat Flow and Physical Properties (HP3) instrument, as well as the three largest Marsquakes detected as of September 2019. From receiver function analysis, we infer that the uppermost 8–11 km of the crust is highly altered and/ or fractured. We measure the crustal diffusivity and intrinsic attenuation using multiscattering analysis and find that seismic attenuation is about three times larger than on the Moon, which suggests that the crust contains small amounts of volatiles