ABSTRACT
Landslide deposits often exhibit surface features, such as transverse ridges and X-shaped conjugate troughs, whose physical formation origins are not well understood. To study the deposit morphology, laboratory studies typically focus on the simplest landslide geometry: an inclined plane accelerating the sliding mass immediately followed by its deceleration on a horizontal plane. However, existing experiments have been conducted only for a limited range of the slope angle θ. Here, we study the effect of θ on the kinematics and deposit morphology of laboratory landslides along a low-friction base, measured using an advanced 3D scanner. At low θ (30°-35°), we find transverse ridges formed by overthrusting on the landslide deposits. At moderate θ (40°-55°), conjugate troughs form. A Mohr-Coulomb failure model predicts the angle enclosed by the X-shaped troughs as 90° - φ, with φ the internal friction angle, in agreement with our experiments and a natural landslide. This supports the speculation that conjugate troughs form due to failure associated with a triaxial shear stress. At high θ (60°-85°), a double-upheaval morphology forms because the rear of the sliding mass impacts the front during the transition from the slope to the horizontal plane. The overall surface area of the landslides increases during their downslope motion and then decreases during their runout.
ABSTRACT
OBJECTIVES: This study introduces the structural design, working principles, performance testing and treatment effects of a newly developed ultrasonic irradiation delivery and treatment catheter system that integrates interventional catheterization technology. BACKGROUND: Systemic administration method needs a high dose of gene and induces side effect of non-target organ delivery. Direct intramyocardial injection of a low-dose angiogenic gene followed by insonation treatment can enhance gene expression. So, a novel transendocardial gene delivery and intracardiac ultrasound irradiation strategy was tested. METHODS: The medical interventional ultrasonic therapeutic apparatus is comprised of an ultrasonic irradiation catheter and a host. The ultrasonic irradiation catheter, which is equipped with an advance-and-retreat convenient miniature syringe needle and a miniature piezoelectric transducer on the tip, was used. Twelve dogs were divided into three groups: (1) EGFP and US (EGFP + US), (2) EGFP alone and (3) control group. In the EGFP + US group, EGFP plasmid DNA (500 µg) was injected and followed by intracardiac insonation. In the EGFP alone group, EGFP plasmid DNA (500 µg) was injected without insonation. In the control group, saline was injected. RESULTS: The catheter can enter the heart through percutaneous intervention to realize intramyocardial injection, directly irradiate cardiac muscular tissues at close range and correctly control the ultrasonic irradiation energy delivered to cardiac muscular tissues. Compared with the EGFP gene group, an average sixfold enhancement in gene expression was achieved in the EGFP EGFP + US group (p < 0.05). CONCLUSIONS: The experimental results confirmed that the treatment catheter was safe and reliable, which can realize transendocardial intramyocardial gene injection in the left ventricular chamber, and the ultrasonic parameter can increase gene expression after intracardiac ultrasonic irradiation. The intracardiac ultrasound irradiation treatment catheter may be a useful delivery and therapy tool in the future.
