Wire tomography in the H-1NF heliac for investigation of fine structure of magnetic islands

Electron beam wire tomography in the H-1NF heliac enables high resolution mapping of vacuum flux surfaces with minimal disruption of the plasma operations schedule. Recent experimental results have proven this technique to be a highly accurate and high resolution method for mapping vacuum magnetic islands. Islands of width as small as delta approximately 8 mm have been measured, providing estimates of the internal rotational transform of the island. Point-to-point comparison of the mapping results with computer tracing, in conjunction with an image warping technique, enables systematic exploration of magnetic islands and surfaces of interest. Recent development of a fast mapping technique significantly reduced the mapping time and made this technique suitable for mapping at higher magnetic fields. This article presents recent experimental results and associated techniques.with support from the Australian Research Council Grant No. DP0344361

Measurements of electron density and temperature in the H-1 heliac plasma by helium line intensity ratios

Electron density and temperature distributions in the H-1 heliac plasma are measured using the helium line intensity ratio technique based on a collisional-radiative model. An inversion approach with minimum Fisher regularization is developed to reconstruct the ratios of the local emission radiances from detected line-integrated intensities. The electron density and temperature inferred from the He I 667.8/728.1 and He I 728.1/706.5 nm line ratios are in good agreement with those from other diagnostic techniques in the inner region of the plasma. The electron density and temperature values appear to be a little high in the outer region of the plasma. Some possible causes of the discrepancy in the outer region are discussed

Core magnetic islands and plasma confinement in the H-1NF heliac

Plasma confinement in the vicinity of vacuum magnetic islands near the magnetic axis in the H-1NF heliac [S. M. Hamberger et al., Fusion Technol.17, 123 (1990)] has been experimentally studied in a low temperature argon plasma. Experimental results indicate that, under favorable conditions, these low order (m=2)islands near the core of the plasma serve as “pockets” of higher electron density. This results in significant profile modifications including enhancement of the core radial electric field to a large positive value, possibly through an electron-root ambipolar condition. The characteristics of islands are found to be dependent on the plasma collisionality and island width.This research was supported in part by the Australian Research Council Grant No. DP0344361 and the U.S. Department of Energy under Contract No. DE-AC05- 00OR22725 with UT-Battelle, LLC

Tomographic interferometry of a filtered high-current vacuum arc plasma

Tomography of a plasma enables the distribution of electron density to be visualized. We report on the design of two tomographic interferometer systems used to measureplasma electron density distributions in a high-current pulsed cathodic vacuum arc. The method is shown to be capable of microsecond time resolution. The spatial resolution of the quasioptical interferometer operating at 2 mm wavelength is 20 mm and the spatial resolution of the waveguide-based interferometer operating at 8 mm wavelength is 50 mm. In both cases the resolution achieved depends on the launching and receiving geometries. We developed criteria for assessing the tomogram for artifacts arising from limited sampling. First results of the spatial and temporal history of plasma in a high-current vacuum arc guided by a curved magnetic filter are presented and indicate poloidal field fluctuations reminiscent of magnetohydrodynamic instabilities in pinches. The applicability of the tomographic interferometry method to optimize plasma transport through the filter is also demonstrated.This work was in part supported by the Australian Research Council

Non-Darcian Behavior of Pyrolysis Gas in a Thermal Protection System

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/83565/1/AIAA-44103-182.pd

Does Geography Matter to Bondholders?

We find that the location of corporate headquarters significantly affects the firm’s bondholders. Similar to Loughran and Schultz (2006) and others, who show that investors are better able to obtain information on nearby companies, we look at firms located in large metropolitan cities, small cities, and rural areas and find that firms located in remote rural areas exhibit significantly higher costs of debt capital (of up to 65 basis points) in comparison to their urban counterparts. Unlike other studies that focus on the role of information asymmetries in the local bias of investors and decision makers, we are able to show that firms in remote areas experience greater costs of debt capital primarily because of a greater difficulty of monitoring their activities. We find that the adverse impact of bad corporate governance on bondholders is magnified in geographically remote firms, primarily because geographic distance reduces the effectiveness of external monitoring. Consistent with that, we show that in the private placement market, where firms are closely monitored by institutional investors, location plays no role in explaining the cross-sectional variation in the cost of debt capital across companies. We also find that the passage of the 2002 Sarbanes-Oxley Act, which brought about regulatory improvements in monitoring and governance, significantly reduced the agency costs of debt in rural firms. Taken together, our results indicate that the firm’s information environment interacts with the impact of corporate governance, particularly affecting the effectiveness of external monitoring in alleviating agency problems between insiders and debt holders

Bostonia. Volume 9

Founded in 1900, Bostonia magazine is Boston University's main alumni publication, which covers alumni and student life, as well as university activities, events, and programs

A nontoxic polypeptide oligomer with a fungicide potency under agricultural conditions which is equal or greater than that of their chemical counterparts

Research ArticleThere are literally hundreds of polypeptides described in the literature which exhibit fungicide activity. Tens of them have had attempted protection by patent applications but none, as far as we are aware, have found application under real agricultural conditions. The reasons behind may be multiple where the sensitivity to the Sun UV radiation can come in first place. Here we describe a multifunctional glyco-oligomer with 210 kDa which is mainly composed by a 20 kDa polypeptide termed Blad that has been previously shown to be a stable intermediary product of β-conglutin catabolism. This oligomer accumulates exclusively in the cotyledons of Lupinus species, between days 4 and 12 after the onset of germination. Blad-oligomer reveals a plethora of biochemical properties, like lectin and catalytic activities, which are not unusual per si, but are remarkable when found to coexist in the same protein molecule. With this vast range of chemical characteristics, antifungal activity arises almost as a natural consequence. The biological significance and potential technological applications of Blad-oligomer as a plant fungicide to agriculture, its uniqueness stems from being of polypeptidic in nature, and with efficacies which are either equal or greater than the top fungicides currently in the market are addressedinfo:eu-repo/semantics/publishedVersio