Documents mathematical analysis 20 results

"Recently, White (2007) analysed the international inequalities in ecological footprints per capita (EF hereafter) based on a two-factor decomposition of an index from the Atkinson family (Atkinson, 1970). Specifically, this paper evaluated the separate role of environment intensity (EF/GDP) and average income as explanatory factors for these global inequalities. However, in addition to other comments on their appeal, this decomposition suffers from the serious limitation of the omission of the role exerted by probable factorial correlation (York et al., 2005). This paper proposes, by way of an alternative, a decomposition of a conceptually similar index like Theil's (1967) which, in effect, permits clear decomposition in terms of the role of both factors plus an inter-factor correlation, in line with Duro and Padilla (2006). This decomposition might, in turn, be extended to group inequality components (Shorrocks, 1980), an analysis that cannot be conducted in the case of the Atkinson indices. The proposed methodology is implemented empirically with the aim of analysing the international inequalities in EF per capita for the 1980–2007 period and, amongst other results, we find that, indeed, the interactive component explains, to a significant extent, the apparent pattern of stability observed in overall international inequalities."

Background Recall bias remains a concern in case-control studies, although few investigations have found evidence of differential recall. This study examined whether differences in occupational exposure reporting occur in volunteered vs. prompted questionnaire responses. Methods In a large, population-based, case-control study of a childhood cancer, neuroblastoma, we calculated odds ratios for broad occupational exposure groups on the assumption that in the absence of recall bias, risk estimates for such broad groupings should be close to the null value. Results Prompted exposures and work activities showed little evidence of differential recall by parents of cases and controls (all OR < 1.2), but case parents were more likely to volunteer information about other exposures or activities (ORs: 1.35-1.71). Case mothers were also more likely than control mothers to report activities involving indirect exposure (OR = 1.41). Conclusions These findings suggest that prompted exposure questions are less likely to be subject to recall bias than open-ended questions.

"The NIOSH Analytical Method 7400 for airborne fibers specifies the use of electrically conductive cowls for air sampling. Data collected from a number of laboratories indicate that a significant fraction of collected dust may be deposited on the inside of electrically conductive cowls during air sampling for man-made mineral fibers. The purpose of this article is to present a cowl rinsing procedure for airborne fiber sampling. This method is the consensus of an ad hoc group formed to evaluate existing cowl rinsing procedures. A number of issues related to cowl rinsing are also addressed."

"National Institute for Occupational Safety and Health Method 7400 is commonly used to evaluate airborne exposures to man-made mineral fibers (MMMFs). Although recent evidence suggests that current methods for collecting air samples may be biased due to fiber deposition on the inside of the sampling-cassette extension cowl, few data are available on the mechanism of deposition, the number of fibers deposited on the cowl, or potential bias in size selection associated with this deposition. The length and diameter distributions of fiber populations collected on the air-sample filters were compared to those deposited on the inside of the electrically conductive extension cowl. The samples were collected during insulation of residential buildings with pneumatically conveyed loose-fill insulation. Two different filters recommended for sample collection in the World Health Organization Reference Method for MMMFs were used. It was determined that a significantly different fiber-size distribution is derived from analysis of fibers collected on the air-sample filter versus fibers deposited on the extension cowl. In general, fibers deposited on the inside of the extension cowl were longer and thicker than fibers from the air-sample collection filter."

"The void-counting technique for evaluation of the concentration of airborne respirable fibrous dust by phase contrast optical microscopy is assessed with respect to accuracy, reproducibihty, ease and saving of counting time compared with the conventional method of fibre counting. The method is found to have several advantages over the latter. These are outlined. Based on our own data and those of 10 other Swedish laboratories, it is concluded that more reliable and accurate estimates are obtained in the routine evaluation of airborne fibrous dust concentrations by using the void-counting method, provided the sampling is conducted properly"