Household Expenditures, Wages, Rents

We provide new evidence from the 1980, 1990, and 2000 Decennial Census of Housing that the expenditure share on housing is constant over time and across U.S. metropolitan areas (MSA). Consistent with this observation, we consider a basic model in which identical households with Cobb-Douglas preferences for housing and numeraire consumption choose an MSA in which to live and MSAs differ with respect to income earned by residents. We compute constant-quality wages and rental prices for a sample of 50 U.S. MSAs. Given estimated wages, the calibrated model predicts that rental prices should be more dispersed than observed. That is, the model suggests that rental prices are too low in many high-wage MSAs in the year 2000.household expenditures, housing prices, Cobb-Douglas utility

Comparing recovering efficiency of immunomagnetic separation and centrifugation of mycobacteria in metalworking fluids

The accurate detection and enumeration of Mycobacterium immunogenum in metalworking fluids (MWFs) is imperative from an occupational health and industrial fluids management perspective. We report here a comparison of immunomagnetic separation (IMS) coupled to flow-cytometric enumeration, with traditional centrifugation techniques for mycobacteria in a semisynthetic MWF. This immunolabeling involves the coating of laboratory-synthesized nanometer-scale magnetic particles with protein A, to conjugate a primary antibody (Ab), specific to Mycobacterium spp. By using magnetic separation and flow-cytometric quantification, this approach enabled much higher recovery efficiency and fluorescent light intensities in comparison to the widely applied centrifugation technique. This IMS technique increased the cell recovery efficiency by one order of magnitude, and improved the fluorescence intensity of the secondary Ab conjugate by 2-fold, as compared with traditional techniques. By employing nanometer-scale magnetic particles, IMS was found to be compatible with flow cytometry (FCM), thereby increasing cell detection and enumeration speed by up to two orders of magnitude over microscopic techniques. Moreover, the use of primary Ab conjugated magnetic nanoparticles showed better correlation between epifluorescent microscopy counts and FCM analysis than that achieved using traditional centrifugation techniques. The results strongly support the applicability of the flow-cytometric IMS for microbial detection in complex matrices.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47949/1/10295_2005_Article_238.pd

Identification of the surface-exposed lipids on the cell envelopes of Mycobacterium tuberculosis and other mycobacterial species.

The surface-exposed lipids of Mycobacterium tuberculosis, Mycobacterium avium, Mycobacterium kansasii, Mycobacterium gastri, Mycobacterium smegmatis, and Mycobacterium aurum were isolated by gentle mechanical treatment of cells with glass beads. Analysis of the exposed lipids demonstrated a selective location of classes of ubiquitous lipids on the surfaces of mycobacteria. While phosphatidylethanolamine and phosphatidylinositol mannosides were exposed in all the species examined, dimycoloyl trehalose ("cord factor") was identified in the surface components of M. aurum only. Furthermore, monomycoloyl trehaloses and triacylglycerides were identified in the surface-exposed lipids of M. avium and M. smegmatis but not in those of the other mycobacterial species examined. The species- and type-species specific lipids were present on the mycobacterial cell surface: phenolic glycolipids, dimycocerosates of phthiocerols, and lipooligosaccharides were identified in the surface-exposed materials of M. tuberculosis (Canetti), M. kansasii, and M. gastri, whereas glycopeptidolipids were identified in the outermost lipid constituents of M. avium and M. smegmatis. This difference in the surface exposure of lipids of various mycobacterial species may reflect differences in their cell envelope organizations. Brief treatments of M. tuberculosis with Tween 80 prior to the use of glass beads led to erosion of regions of the capsule to expose gradually both cord factor and other lipids on the cell surface of the tubercle bacillus, demonstrating that the latter lipids are buried more deeply in the cell envelope and leading to the proposal of a scheme for the location of the capsular lipids of the tubercle bacillus

Household Expenditures, Wages, Rents

New evidence from the 1980, 1990, and 2000 Decennial Census of Housing indicates that expenditure shares on housing are constant over time and across U.S. metropolitan statistical areas (MSA). Consistent with this observation, we consider a model in which identical households with Cobb-Douglas preferences for housing and non-housing consumption choose a location and locations differ with respect to income earned by their residents. The model predicts that the relative price of housing of any two MSAs disproportionately reflects differences in incomes of those MSAs and is independent of housing supply in each MSA. According to the predictions of our calibrated model, the dispersion of rental prices across low- and high- wage MSAs should be larger than we observe: High-wage MSAs like San Francisco are puzzlingly inexpensive relative to low-wage MSAs like Pittsburgh. (Copyright: Elsevier)Housing expenditures; Expenditure shares; Cobb-Douglas preferences; Multi-city models