Stress Effect on Ultrasonic Wave Propagation Through the Solid-Solid and Liquid-Solid Plane Interface

Ultrasonic wave propagation in prestressed materials has been studied extensively in the last 40 years. Most of this work was concentrated on the effect of stress on the velocities of different types of ultrasonic waves in homogeneous materials. Actually stresses affect not only wave velocities but also the boundary conditions at the interface. Many practical applications of ultrasonic stress characterization involve wave propagation through the interface between fluid and solid or two solids. In immersion measurements one needs to consider the effect of stress on wave propagation from fluid to solid. This leads to change in propagation direction and energy redistribution. Also additional modes could be excited leading to stress-induced birefringence. These are all important phenomena which require rigorous quantitative description since the stress effect in general is very small. Another important problem is ultrasonic characterization of residual stresses in composite materials [1]. It involves wave propagation through an interface between layers with different properties and stress levels

Legionella pneumophila Secretes a Mitochondrial Carrier Protein during Infection

The Mitochondrial Carrier Family (MCF) is a signature group of integral membrane proteins that transport metabolites across the mitochondrial inner membrane in eukaryotes. MCF proteins are characterized by six transmembrane segments that assemble to form a highly-selective channel for metabolite transport. We discovered a novel MCF member, termed Legionella nucleotide carrier Protein (LncP), encoded in the genome of Legionella pneumophila, the causative agent of Legionnaire's disease. LncP was secreted via the bacterial Dot/Icm type IV secretion system into macrophages and assembled in the mitochondrial inner membrane. In a yeast cellular system, LncP induced a dominant-negative phenotype that was rescued by deleting an endogenous ATP carrier. Substrate transport studies on purified LncP reconstituted in liposomes revealed that it catalyzes unidirectional transport and exchange of ATP transport across membranes, thereby supporting a role for LncP as an ATP transporter. A hidden Markov model revealed further MCF proteins in the intracellular pathogens, Legionella longbeachae and Neorickettsia sennetsu, thereby challenging the notion that MCF proteins exist exclusively in eukaryotic organisms

Reimagining America

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Phase Correction for Ultrasonic Bulk Wave Measurements of Elastic Constants in Anisotropic Materials

When an ultrasonic wave is incident on a water/solid interface generally three waves are excited in the solid: one longitudinal and two shear. The complex amplitudes of the transmitted waves depend on the material properties and the angle of incidence. At incident angles higher than the first critical angle an evanescent longitudinal wave is excited near the surface. To satisfy the boundary conditions the imaginary parts of the shear wave amplitudes become non-zero. This implies that the shear waves experience a phase shift at the water/solid interface at incident angles higher than the first critical

Is fatigue a real threat leading to NiTi instrument breakage?

Structural parts made from metal matrix composites are expected to sustain high levels of mechanical and thermal loadings. In most cases these loadings have a cyclic nature. They lead to the development of fatigue damage. It is important to have nondestructive testing tools which would allow one to detect and quantify the damage in these materials at early stages of its development and predict the remaining fatigue life

Surface dyslexia in Chinese

We report the oral reading performance of a Chinese anomic patient LJG, whose reduced confrontation naming was accompanied by impaired written word and spoken word comprehension. LJG's oral reading is significantly better than his comprehension of the same lexical items from written word and from spoken word input, although his oral reading is not flawless. We examined the effects of character regularity, frequency and concreteness on LJG's oral reading of single-character monosyllabic Chinese words. LJG displayed impairment when reading aloud irregular Chinese characters that have an unpredictable correspondence between their components and the pronunciation of the character as a whole. This deficit was particularly severe for irregular, low-frequency, abstract items. In addition, LJG produced a number of oral reading errors in which characters were assigned pronunciations appropriate to a character component rather than the character itself. We characterize LJG's oral reading as surface dyslexia. We argue that the oral reading of irregular Chinese characters is more prone to error than oral reading of regular Chinese characters following brain damage because of response competition at the level of phonological output.link_to_subscribed_fulltex