Shock Theory of a Bubbly Liquid in a Deformable Tube

Shock propagation through a bubbly liquid filled in a deformable cylindrical tube is considered. Quasi-one-dimensional bubbly flow equations that include fluid-structure interaction are formulated, and the steady shock relations are derived. Experiments are conducted in which a free-falling steel projectile impacts the top of an air/water mixture in a polycarbonate tube, and stress waves in the tube material are measured. The experimental data indicate that the linear theory cannot properly predict the propagation speeds of shock waves in mixture-filled tubes; the shock theory is found to more accurately estimate the measured wave speeds

Activation volumes in CoPtCr-SiO2 perpendicular recording media

CoPtCr-SiO2 perpendicular recording media with varying levels of SiO2 were examined by two different methods to determine the activation volume. The first is based on the sweep-rate dependence of the remanence coercivity using Sharrock's equation. The second is based on the measurement of the fluctuation field from time-dependence data, determined using a magneto-optical Kerr effect (MOKE) magnetometer. The values of V-act measured at the coercivity for both methods are almost the same, with the fluctuation field and activation volumes increasing with the SiO2 content. The difference between V-act and the grain volume measured directly from bright-field TEM images decreases as the SiO2 content increases due to the reduction of intergranular exchange coupling. The experimental results indicate that values of V-act obtained from single- and double-layered media are consistent. It was also found that the coercivity and normalized hysteresis loop slope at coercivity varied with SiO2 content, with the coercivity peaking at 8 at % SiO2 (nearly 26 vol% SiO2)

Shock propagation through a bubbly liquid in a deformable tube

Shock propagation through a bubbly liquid contained in a deformable tube is considered. Quasi-one-dimensional mixture-averaged flow equations that include fluid–structure interaction are formulated. The steady shock relations are derived and the nonlinear effect due to the gas-phase compressibility is examined. Experiments are conducted in which a free-falling steel projectile impacts the top of an air/water mixture in a polycarbonate tube, and stress waves in the tube material and pressure on the tube wall are measured. The experimental data indicate that the linear theory is incapable of properly predicting the propagation speeds of finite-amplitude waves in a mixture-filled tube; the shock theory is found to more accurately estimate the measured wave speeds

Electronic Structure of Charge- and Spin-controlled Sr_{1-(x+y)}La_{x+y}Ti_{1-x}Cr_{x}O_{3}

We present the electronic structure of Sr_{1-(x+y)}La_{x+y}Ti_{1-x}Cr_{x}O_{3} investigated by high-resolution photoemission spectroscopy. In the vicinity of Fermi level, it was found that the electronic structure were composed of a Cr 3d local state with the t_{2g}^{3} configuration and a Ti 3d itinerant state. The energy levels of these Cr and Ti 3d states are well interpreted by the difference of the charge-transfer energy of both ions. The spectral weight of the Cr 3d state is completely proportional to the spin concentration x irrespective of the carrier concentration y, indicating that the spin density can be controlled by x as desired. In contrast, the spectral weight of the Ti 3d state is not proportional to y, depending on the amount of Cr doping.Comment: 4 pages, 3 figures. Accepted for publication in Phys. Rev. Let

A debris-flow monitoring devices and methods bibliography

International audienceDebris-flow monitoring has two functions, warning and modeling. The warning function includes the following parameters: occurrence prediction and detection, proximity sensing, and discharge-estimation. The parameters obtained from debris-flow measurements can deduce a numerical model for creating a hazard map and designing various types of control structures to mitigate the hazards. Many devices and methods of monitoring are tabulated here for comparative study. Some of them are in operation. Advanced comparative studies lead to an improvement in debris-flow monitoring, an integrated system that can be applied to any torrent, and a breakthrough in future developments

Microbubble disruption by ultrasound and induced cavitation phenomena

Aiming at the enhancement of in vitro sonoporation effect to cells in drug delivery, cavitation phenomena ultrasonically generated in a cylindrical vessel, which is one of a 24 wellplate, were observed with long-term photography by using a digital video camera synchronized with a repeatable flash light with the duration of 1 ?s as well as by taking a number of snapshots. A suspension consisting of distilled water and microbubbles (Sonazoid ultrasound contrast agent containing C4F10 gas) was used as a test liquid in the present experiment. It was found that microbubbles were rapidly destroyed after the ultrasound irradiation and their survival numbers were reduced by half at the exposure time of 100 ms. A maximum number of cavitation bubbles, sometimes more than sixty cavitation bubbles detected in the observation volume, were generated at a certain exposure time less than one second. Cavitation bubbles were mainly observed near the second products consisting of the fragments of the shell material and the flowing gas out of the interior of individual microbubbles. By exploring the free surface oscillation of a Sonazoid suspension, we found out that the (1,1) mode with the frequency of about 5 Hz was prominent. This seems important because the flow induced by this surface oscillation as well as by the acoustic radiation pressure can provide a higher possibility to convey the second products everywhere in the liquid. Consequently cavitation bubbles can be generated at a relatively long time after the ultrasound irradiation even though the majority of microbubbles are destroyed during an earlier period. In fact plenty of cavitation bubbles were occasionally generated even at the ultrasound exposure time of five seconds.http://deepblue.lib.umich.edu/bitstream/2027.42/84289/1/CAV2009-final109.pd

Antigen processing by epidermal langerhans cells correlates with the level of biosynthesis of major histocompatibility complex class II molecules and expression of invariant chain

Two prior studies with a small number of T cell lines have shown that the presentation of native protein antigens by epidermal Langerhans cells (LC) is regulated. When freshly isolated, LC are efficient antigen-presenting cells (APC), but after a period of culture LC are inefficient or even inactive. The deficit in culture seems to be a selective loss in antigen processing, since cultured LC are otherwise rich in major histocompatibility complex (MHC) class II products and are active APC for alloantigens and mitogens, which do not require processing. We have extended the analysis by studying presentation to bulk populations of primed lymph node and a TT hybrid. Only freshly isolated LC can be pulsed with the protein antigens myoglobin and conalbumin, but once pulsed, antigen is retained in an immunogenic form for at least 2 d. The acquisition of antigen, presumably as MHC-peptide complexes, is inhibited if the fresh LC are exposed to foreign protein in the presence ofchloroquine or cycloheximide. The latter, in contrast, improves the efficacy ofantigen pulsing in anti-Ig-stimulated B blasts. In additional studies of mechanism, we noted that both fresh and cultured LC endocytose similar amounts of an antigen, rhodamineovalbumin, into perinuclear granules. However, freshly isolated LC synthesize high levels of class II MHC molecules and express higher amounts of the class II-associated invariant chain. Fresh LC are at least 5-10 times more active than many other cell types in the level of biosynthesis ofMHC class II products. These findings provide a physiologic model in which newly synthesized MHC class II molecules appear to be the principal vehicle for effective antigen processing by APC of the dendritic cell lineage. Another APC, the B lymphoblast, does not appear to require newly synthesized MHC class II molecules for presentation

Antigen processing by epidermal Langerhans cells correlates with the level of biosynthesis of MHC class II molecules and expression of invariant chain

Puré, E., Inaba, K., Crowley, M.T., Tardelli, L., Witmer-Pack, M.D., Ruberti, G., Fathman, G., and Steinman, R.M. Antigen processing by epidermal Langerhans cells correlates with the level of biosynthesis of MHC class II molecules and expression of invariant chain. J. Exp. Med. 172: 1459-1469, 1990https://digitalcommons.rockefeller.edu/historical-scientific-reports/1028/thumbnail.jp

Factors Affecting Repair Costs of Small Tractor Use in Riau Province, Indonesia

Factors affecting annual repair costs were analyzed and a reasonable function was proposed by including more explanatory variables than the previous models for small tractors. Data used in this study was based on a survey of 62 tractors from three selected regencies in Riau Province in 2003. As a result, tractor age, usage, horsepower and operator skill were statistically significant explanatory variables, whereas the ownership system and manufacturer weren’t. Using the proposed model, the annual repair costs were estimated to increase during the expected life of tractors. Changes in usage, horsepower, and operator skill increased more rapidly for annual and cumulative repair costs over the tractor lifespan. Of the significant variables, the effect is more pronounced for operator skill variable. The results suggest that priority should be given to operator training and selection