Anatomy and Morphometry of Myocardial Capillaries Studied with Vascular Corrosion Casting and Scanning Electron Microscopy: A Method for Rat Heart

The present paper describes a procedure for preparing vascular corrosion casts of rat myocardial microvasculature. Essential components of the procedure include: partial self clearing of the heart in vitro; cardiac arrest by infusion of KCl; retrograde aortic root infusion of Mercox-Sevriton casting resin; KOH digestion of ventricular tissue; and desiccation and mounting of casts for scanning electron microscopy. About 50% of rats yielded complete casts. Vasculature closely paralleled muscle fiber orientation. Capillary beds characteristically exhibited branching, many intercapillary cross bridges, and occasional coil-ing. Average capillary cast diameter (5.6 μm) and intercapillary distance (15 μm) are comparable to results from in vivo studies. From preliminary calculations, vascular volume represents about 10% of the ventricular walls. These data indicate that vascular corrosion casts may be useful in the analysis of pathologic states and in determining the role of potential therapeutic interventions

Application of diffusion barriers to the refractory fibers of tungsten, columbium, carbon and aluminum oxide

A radio frequency powered ion-plating system was used to plate protective layers of refractory oxides and carbide onto high strength fiber substrates. Subsequent overplating of these combinations with nickel and titanium was made to determine the effectiveness of such barrier layers in preventing diffusion of the overcoat metal into the fibers with consequent loss of fiber strength. Four substrates, five coatings, and two metal matrix materials were employed for a total of forty material combinations. The substrates were tungsten, niobium, NASA-Hough carbon, and Tyco sapphire. The diffusion-barrier coatings were aluminum oxide, yttrium oxide, titanium carbide, tungsten carbide with 14% cobalt addition, and zirconium carbide. The metal matrix materials were IN 600 nickel and Ti 6/4 titanium. Adhesion of the coatings to all substrates was good except for the NASA-Hough carbon, where flaking off of the oxide coatings in particular was observed

DETERMINANTS OF BORROWER DROPOUT IN MICROFINANCE: AN EMPIRICAL INVESTIGATION IN MALI

Repeat borrowing is critical for the long-term financial viability of microfinance institutions (MFIs), which provide financial services to low-income households in developing countries. Repeat borrowers reduce MFI administrative costs, lower risks, and increase institutional productivity. In this paper we study the determinants of borrower dropout of an MFI operating in an urban center in Mali. Specifically, we quantify the explicit and implicit costs that a borrower must incur in obtaining loans from an MFI.Financial Economics,

Statistical Uncertainties in Temperature Diagnostics for Hot Coronal Plasma Using the ASCA SIS

Statistical uncertainties in determining the temperatures of hot (0.5 keV to 10 keV) coronal plasmas are investigated. The statistical precision of various spectral temperature diagnostics is established by analyzing synthetic ASCA Solid-state Imaging Spectrometer (SIS) CCD spectra. The diagnostics considered are the ratio of hydrogen-like to helium-like line complexes of $Z\ge14$ elements, line-free portions of the continuum, and the entire spectrum. While fits to the entire spectrum yield the highest statistical precision, it is argued that fits to the line-free continuum are less susceptible to atomic data uncertainties but lead to a modest increase in statistical uncertainty over full spectral fits. Temperatures deduced from line ratios can have similar accuracy but only over a narrow range of temperatures. Convenient estimates of statistical accuracies for the various temperature diagnostics are provided which may be used in planning ASCA SIS observations.Comment: postscript file of 8 pages+3 figures; 4 files tarred, compressed and uuencoded. To appear in the Astrophysical Journal Letters; contents copyright 1994 American Astronomical Societ

Anatomy of a Community-Level Fiscal Impact Model: FIT-4-NH.

Abstract: This paper describes the development of a fiscal impact tool for New Hampshire communities (HT -4-NH). FIT -4-NH belongs to a family of computergenerated fiscal impact assessment models designed to estimate the impacts to local government revenues and expenditures that result from economic changes. In the past, work in this area has centered on the completion of countylevel models for the midwestern states. FIT-4-NH is unique in that it was designed for rural community-level use in the northern New England region of the country

The Best of Times, the Worst of Times: Understanding Pro-cyclical Mortality

A growing literature documents cyclical movements in mortality and health. We examine this pattern more closely and attempt to identify the mechanisms behind it. Specifically, we distinguish between mechanisms that rely on fluctuations in own employment or time use and those involving factors that are external to the individual. Our investigation suggests that changes in individuals’ own behavior contribute very little to pro-cyclical mortality. Looking across broad age and gender groups, we find that own-group employment rates are not systematically related to own-group mortality. In addition, we find that most of the additional deaths that occur during times of economic growth are among the elderly, particularly elderly women, who have limited labor force attachment. Focusing on mortality among the elderly, we show that cyclicality is especially strong for deaths occurring in nursing homes, and is stronger in states where a higher fraction of the elderly reside in nursing homes. We also demonstrate that staffing in skilled nursing facilities moves counter-cyclically. Taken together, these findings suggest that cyclical fluctuations in the mortality rate may be largely driven by fluctuations in the quality of health care.

Decoding the Encoding of Functional Brain Networks: an fMRI Classification Comparison of Non-negative Matrix Factorization (NMF), Independent Component Analysis (ICA), and Sparse Coding Algorithms

Brain networks in fMRI are typically identified using spatial independent component analysis (ICA), yet mathematical constraints such as sparse coding and positivity both provide alternate biologically-plausible frameworks for generating brain networks. Non-negative Matrix Factorization (NMF) would suppress negative BOLD signal by enforcing positivity. Spatial sparse coding algorithms ($L1$ Regularized Learning and K-SVD) would impose local specialization and a discouragement of multitasking, where the total observed activity in a single voxel originates from a restricted number of possible brain networks. The assumptions of independence, positivity, and sparsity to encode task-related brain networks are compared; the resulting brain networks for different constraints are used as basis functions to encode the observed functional activity at a given time point. These encodings are decoded using machine learning to compare both the algorithms and their assumptions, using the time series weights to predict whether a subject is viewing a video, listening to an audio cue, or at rest, in 304 fMRI scans from 51 subjects. For classifying cognitive activity, the sparse coding algorithm of $L1$ Regularized Learning consistently outperformed 4 variations of ICA across different numbers of networks and noise levels (p$<$0.001). The NMF algorithms, which suppressed negative BOLD signal, had the poorest accuracy. Within each algorithm, encodings using sparser spatial networks (containing more zero-valued voxels) had higher classification accuracy (p$<$0.001). The success of sparse coding algorithms may suggest that algorithms which enforce sparse coding, discourage multitasking, and promote local specialization may capture better the underlying source processes than those which allow inexhaustible local processes such as ICA

Local u'g'r'i'z' Standard Stars in the Chandra Deep Field-South

Because several observing programs are underway in various spectral regimes to explore the Chandra Deep Field South (CDF-S), the value of local photometric standards is obvious. As part of an NOAO Surveys Program to establish u'g'r'i'z' standard stars in the southern hemisphere, we have observed the central region of the CDF-S to create local standards for use by other investigators using these filters. As a courtesy, we present the CDF-S standards to the public now, although the main program will not finish until mid-2005.Comment: Accepted by AJ (scheduled for October 2003 issue). 26 pages, 5 tables, 5 figures. High resolution version of Figure 7 available at http://home.fnal.gov/~dtucker/Southern_ugriz/index.htm