Studies on bacterial gene transposition

(1) Two Escherichia coli K12 based transposition frequency assay systems have been designed and developed to allow the frequency of prokaryotic transposable element movements to be simply assayed. One of these systems involves the giant transposon bacteriophage Mu dl(ApRlac), that carries the P-galactosidase gene so that insertion adjacent to promotors can be quantified. The other system developed involves transposon 5 (Tn5), initially inserted in the host genome, that encodes kanamycin resistance which allows transposition to (and amplification in) plasmids to be quantified. (2) The most transposogenic compounds identified in the two transposition frequency assays are the alkyl-nitro-nitrosoguanidine alkylating agents. Most other alkylating agents exam­ined were either weakly transposogenic or non-transposogenic. (3) The alkyl-nitro-nitrosoguanidines appear to act by guanylate cyclase activation, via nitroxide radical release, and subsequent elevation of the cGMP concentration. The transposogen- icity of cGMP is confirmed by an apparant effect of permeable cGMP derivatives on Mu d\(ApRlac) and Tn5 transposition frequency. (4) A group of metals were examined for transposogenicity, and showed that transposogeni- city may be related to mutagenicity since mutagenic metals (Cd(II), Cr(VI) and Mn(II)) are tran­sposogenic and an anti-mutagenic metal (Co(II)) is anti-transposogenic. (5) The majority of transposogens identified in the two transposition frequency assays were mutagens, well documented in literature, and the putative non-transposogens were non- mutagenic. However, one group of compounds investigated were three non-mutagenic (Ames test negative) carcinogens. Diethylstilbesuol, DDT and o-toluidine each gave increases in Mu d\{ApRlac) transposition frequency which, although weak effects, might not have been expected from the other data, which suggested that mutagenicity and transposogenicity are inter-connecte

The Child Adoption Marketplace: Parental Preferences and Adoption Outcomes

In the United States child adoption costs vary considerably, ranging from no out-of-pocket expense to $50,000 or more. What are the causes for the variability in adoption expenses? We administered a survey to a sample of Michigan adoptive families to link adoptive parent characteristics, child characteristics, and adoption-related expenses and subsidies. We then estimate “hedonic” regressions in which adoption cost is a function of child characteristics. The analysis shows that most of the variation in adoption costs is explained by child characteristics. In particular, costs lower for older children, children of African descent, and special needs children. Findings inform policies regarding the transition of children from foster care to adoptive families.child welfare, adoption, subsidy

Improvement and evaluation of simulated global biogenic soil NO emissions in an AC-GCM

Biogenic NO emissions from soils (SNOx) play important direct and indirect roles in tropospheric chemistry. The most widely applied algorithm to calculate SNOx in global models was published 15 years ago by Yienger and Levy (1995), and was based on very few measurements. Since then, numerous new measurements have been published, which we used to build up a compilation of world wide field measurements covering the period from 1978 to 2010. Recently, several satellite-based top-down approaches, which recalculated the different sources of NOx (fossil fuel, biomass burning, soil and lightning), have shown an underestimation of SNOx by the algorithm of Yienger and Levy (1995). Nevertheless, to our knowledge no general improvements of this algorithm, besides suggested scalings of the total source magnitude, have yet been published. Here we present major improvements to the algorithm, which should help to optimize the representation of SNOx in atmospheric-chemistry global climate models, without modifying the underlying principals or mathematical equations. The changes include: (1) using a new landcover map, with twice the number of landcover classes, and using annually varying fertilizer application rates; (2) adopting a fraction of 1.0 % for the applied fertilizer lost as NO, based on our compilation of measurements; (3) using the volumetric soil moisture to distinguish between the wet and dry states; and (4) adjusting the emission factors to reproduce the measured emissions in our compilation (based on either their geometric or arithmetic mean values). These steps lead to increased global annual SNOx, and our total above canopy SNOx source of 8.6 Tg yr−1 (using the geometric mean) ends up being close to one of the satellite-based top-down approaches (8.9 Tg yr−1). The above canopy SNOx source using the arithmetic mean is 27.6 Tg yr−1, which is higher than all previous estimates, but compares better with a regional top-down study in eastern China. This suggests that both top-down and bottom-up approaches will be needed in future attempts to provide a better calculation of SNOx

The Summer Flounder, Scup, and Black Sea Bass Fishery of the Middle Atlantic Bight and Southern New England Waters

Summer flounder, Paralichthys dentatus, scup, Stenotomus chrysops, and black sea bass, Centropristis striata, cooccur within the Middle Atlantic Bight and off southern New England and are important components of commercial and recreational fisheries. The commercial otter trawl fishery for these species is primarily a winter fishery, whereas the recreational fishery takes place between late spring and autumn. The otter trawl fishery generally targets summer flounder, and less frequently scup, while black sea bass occurs as bycatch. Trips in which all three species were present yielded highest aggregate landings per unit of effort (LPUE) levels and occurred more often than trips landing only one or two species. More than 50% of the trips in the trawl fishery landed at least two of the three species. In contrast, greater than 75% of the recreational landings of each species occurred as a result of trips landing only one species. Differences in the fisheries resulted from the interactions of seasonal changes in species distributions and gear selectivity. (PDF file contains 18 pages.

A decision theoretic analysis of the unit root hypothesis using mixtures of elliptical models

This paper develops a formal decision theoretic approach to testing for a unit root in economic time series. The approach is empirically implemented by specifying a loss function based on predictive variances; models are chosen so as to minimize expected loss. In addition, the paper broadens the class of likelihood functions traditionally considered in the Bayesian unit root literature by: i) Allowing for departures from normality via the specification of a likelihood based on general elliptical densities; ii) allowing for structural breaks to occur; iii) allowing for moving average errors; and iv) using mixtures of various submodels to create a very flexible overall likelihood. Empirical results indicate that, while the posterior probability of trend-stationarity is quite high for most of the series considered, the unit root model is often selected in the decision theoretic analysis

MEASURING CHILDREN'S FOOD SECURITY IN U.S. HOUSEHOLDS, 1995-99

The capacity to accurately measure the food security status of children in household surveys is an essential tool for monitoring food insecurity and hunger at the most severe levels in U.S. households and for assessing programs designed to prevent or ameliorate these conditions. USDA has developed a children's food security scale to meet this measurement need. The scale is calculated from 8 questions in the 18-item food security survey module that ask specifically about food-related experiences and conditions of children. The scale measures the severity of food insecurity among children in surveyed households and identifies - in the most severe range of the scale - households in which children have been hungry at times because of a lack of household resources for food. The reliability of the children's food security scale is assessed, and the scale is compared with the household-level food security scale. Details are provided on how to calculate the children's food security scale from the questions in the standard food security survey module. The prevalence of hunger among children in U.S. households is estimated by applying the newly developed children's food security scale to data from the nationally representative Current Population Survey Food Security Supplements for the years 1995-99. Prevalence estimates are presented for all U.S. households and for subgroups defined by household structure, race and ethnicity, income, and rural/urban residence.Food Security and Poverty,

Identifying the task variables that predict object assembly difficulty.

We investigated the physical attributes of an object that influence the difficulty of its assembly. Identifying attributes that contribute to assembly difficulty will provide a method for predicting assembly complexity

The Baryonic Fraction in Groups of Galaxies from X-Ray Measurements

The recent {\sl ROSAT \/} X-ray detections of hot intergalactic gas in three groups of galaxies are reviewed and the resulting baryonic fraction in these groups is reevaluated. We show that the baryonic fraction obtained, assuming hydrostatic equilibrium, should depend, perhaps sensitively, on the radius out to which the X-rays are detected, and the temperature profile of the gas. We find that the NGC 2300 group has a baryonic fraction out to $25'$ of at least 20\%, thus over five times higher than in the original analysis of Mulchaey \etal\ (1993), and also much higher than one would obtain from big-bang nucleosynthesis, but similar to the other two groups as well as rich clusters. With this baryonic fraction, groups would be fair tracers of the distribution of baryons in the Universe if $\Omega h_{50}^2 = 0.3$. A baryonic fraction that increases with radius is consistent with the X-ray data from all three groups. However, a detailed analysis of the NGC 2300 group shows that the dependence of baryonic fraction on radius is not well constrained by the data, in part because of uncertainties in the estimated background.Comment: ApJ Lett 421 (Feb 1 1994), in press. 4 pages of uuencoded compressed Postscript (extract on UNIX with 'csh' after removing header: 1st line should be '#/bin/csh -f') with 3 figures. POP-DAEC-9306

Alternative efficiency measures for multiple-output production

This paper has two main purposes. Firstly, we develop various ways of defining efficiency in the case of multiple-output production. Our framework extends a previous model by allowing for nonseparability of inputs and outputs. We also specifically consider the case where some of the outputs are undesirable, such as pollutants. We investigate how these efficiency definitions relate to one another and to other approaches proposed in the literature. Secondly, we examine the behavior of these definitions in two examples of practically relevant size and complexity. One of these involves banking and the other agricultural data. Our main findings can be summarized as follows. For a given efficiency definition, efficiency rankings are found to be informative, despite the considerable uncertainty in the inference on efficiencies. It is, however, important for the researcher to select an efficiency concept appropriate to the particular issue under study, since different efficiency definitions can lead to quite different conclusions