On Love-type waves in a finitely deformed magnetoelastic layered half-space

In this paper, the propagation of Love-type waves in a homogeneously and finitely deformed layered half-space of an incompressible non-conducting magnetoelastic material in the presence of an initial uniform magnetic field is analyzed. The equations and boundary conditions governing linearized incremental motions superimposed on an underlying deformation and magnetic field for a magnetoelastic material are summarized and then specialized to a form appropriate for the study of Love-type waves in a layered half-space. The wave propagation problem is then analyzed for different directions of the initial magnetic field for two different magnetoelastic energy functions, which are generalizations of the standard neo-Hookean and Mooney–Rivlin elasticity models. The resulting wave speed characteristics in general depend significantly on the initial magnetic field as well as on the initial finite deformation, and the results are illustrated graphically for different combinations of these parameters. In the absence of a layer, shear horizontal surface waves do not exist in a purely elastic material, but the presence of a magnetic field normal to the sagittal plane makes such waves possible, these being analogous to Bleustein–Gulyaev waves in piezoelectric materials. Such waves are discussed briefly at the end of the paper

CURRENT DEVELOPMENT OF HELICOBACTER PYLORI ERADICATION PROTOCOLS

H. pylori is one of the most common commensal microorganisms in the human body, colonizing up to 60% of the inhabitants of all continents. Some strains of H. pylori have acquired virulent properties and their presence can significantly complicate the course of atrophic gastritis of type B, gastric ulcer and duodenal ulcer, as well as malignant diseases of the stomach. In such situations, eradication therapy seems to be pathogenetically justified. International recommendations for standard first-line triple eradication therapy, including a proton pump inhibitor (PPI), amoxicillin and clarithromycin in a course of 7–10 days, were proposed in 1996. Until the beginning of the XXI century, it was actively and with high efficiency (up to 90%) used everywhere, but later reports began to appear about a catastrophic decrease in results (up to 60%). Then it turned out that the effectiveness of the three-component (triple) therapy directly correlates with the resistance to clarithromycin, which has increased significantly in recent decades, and so necessitated the creation of new H. pylori elimination schemes. The results of various schemes for H. pylori eradication were analyzed, including variants of modified triple therapy associated with the inclusion of new drugs or an increase in the duration of eradication. In particular, it was proposed to replace amoxicillin with metronidazole. However, further studies have shown that the combination of clarithromycin with amoxicillin seems to be preferable, which is due to the high level of H. pylori resistance to metronidazole in many countries. Attempts to use probiotics in parallel, in particular cultures of various Lactobacillus species, were analyzed, which increases the level of eradication during standard triple therapy from 61.5 to 81.6%, and also significantly reduces the severity of side effects. It has been shown that a promising way to increase the effectiveness of 7-day first-line therapy schemes with clarithromycin is the use of modern effective PPIs (for example, esomeprazole or rabeprazole). The scheme of modified sequential therapy with the replacement of clarithromycin with tetracycline or levofloxacin, which has shown high efficiency, is considered. A variant of standard triple therapy modified into quadrotherapy with the addition of metronidazole or tinidazole was analyzed. It has been shown that the sequential therapy scheme is ineffective for eradication of multidrug-resistant strains. Ideally, the treatment of bacterial infections should be based on endoscopic sampling of gastric mucosa biopsies, followed by microbiological determination of the sensitivity of the isolated isolates to antibacterial drugs in vitro

A thin film triode type carbon nanotube field emission cathode

The field electron emission of carbon nanotubes has been heavily studied over the past two decades for various applications, such as in display technologies, microwave amplifiers, and spacecraft propulsion. However, a commercializable lightweight and internally gated electron source has yet to be realized. This work presents the fabrication and testing of a novel internally gated carbon nanotube field electron emitter. Several specific methods are used to prevent electrical shorting of the gate layer, a common failure for internally gated devices. A unique design is explored where the etch pits extend into the Si substrate and isotropic etching is used to create a lateral buffer zone between the gate and carbon nanotubes. Carbon nanotubes are self-aligned to and within 10 microns from the gate, which creates large electric fields at low potential inputs. Initial tests confirm high field emission performance with an anode current density (based on total area of the device) of 293 μA cm-2 and a gate current density of 1.68 mA cm-2 at 250 V