Automobile Fuel Economy Standards: Impacts, Efficiency, and Alternatives

This paper discusses fuel economy regulations in the United States and other countries. We first describe how these programs affect fuel use and other dimensions of the vehicle fleet. We then review different methodologies for assessing the costs of fuel economy regulations and discuss the policy implications of the results. We also compare the welfare effects of fuel economy standards with those of fuel taxes and assess whether these two policies complement each other. Finally, we review arguments in favor of a “feebate” system, which imposes fees on inefficient vehicles and provides rebates for efficient vehicles.fuel economy regulations, costs, welfare effects, climate change, feebates

Mutation analysis using the restriction site mutation (RSM) assay

The restriction site mutation RSM assay see Steingrimsdottir et al. H. Steingrimsdottir, D. Beare, J. Cole, J.F.M. Leal, Ž. Ž w T. Kostic, J. Lopez-Barea, G. Dorado, A.R. Lehmann, Development of new molecular procedures for the detection of genetic alteration in man, Mutat. Res. 353 1996 pp. 109–121 for a review has been developed as a genotypic mutation Ž . x . detection system capable of identifying mutations occurring in restriction enzyme sites of genomic DNA. Here we will report the steps taken to overcome some of the initial problems of the assay, namely the lack of quantitative data and limited sensitivity, the aim being to achieve a methodology suitable for the study of low dose chemical exposures. Quantitative data was achieved in the RSM assay by the inclusion of an internal standard molecule in the PCR amplification stage, thus allowing the calculation of both spontaneous and induced mutation frequencies. The sensitivity of the assay was increased through the discovery that intron sequences of genomic DNA accumulated more mutations in vivo compared to the exons, presumably due to differential selective pressure within genes G.J.S. Jenkins, I.deG. Mitchell, J.M. Parry, Enhanced w restriction site mutation RSM analysis of 1,2-dimethylhydrazine-induced mutations, using endogenous Ž . p53 intron sequences, Mutagenesis 12 1997 pp. 117–123 . This increased sensitivity was examined by applying the RSM assay to Ž . x analyse the persistence of N-ethyl-N-nitrosourea ENU -induced mutations in mice testes. Germ line mutations were sought Ž . in testes DNA 3, 10 and 100 days after ENU treatment. Mutations were detected in exons and especially intron regions, the intron mutations were more persistent, still being detected 100 days post-chemical treatment. Assignment of these mutations as ENU induced was complicated in some cases where the spontaneous mutation level was high. This theme of mutation persistence was further investigated by studying the presence of 4-nitroquinoline-1-oxide 4-NQO -induced DNA mutations Ž . in vitro. This study also analysed the relationship between DNA adduct formation and DNA mutation induction by the concurrent RSM analysis and 32P post-labelling analysis of 4-NQO treated human fibroblasts. The results demonstrated that early DNA mutations detected 4 days post-treatment by the RSM assay were probably ex vivo mutations induced by Taq polymerase misincorporation of 4-NQO adducted DNA, due to the maximum levels of 4-NQO adducts being present at this time point. A later mutational peak, after the adduct level had declined, was assumed to be due to DNA sequence changes produced in the fibroblasts by the in vivo processing of DNA adducts

Oxidation, Embrittlement, and Growth of TREAT Zircaloy-3 Cladding

This chapter analyzes the effects of oxidation, embrittlement, and cladding growth on the Zircaloy-3 alloy used for 25 mil thick TREAT fuel assembly cladding. The fuel cladding is a protective shell which is used to prevent damage to the enclosed fuel. Therefore, its integrity is important to guarantee this protection. The above three factors which can affect the Zircaloy-3 cladding are considered in this chapter and investigated. Limits to operation are determined. The oxidation of Zircaloy-3 in air is of interest to air-cooled reactors and Zircaloy-2 and 4 for accidents in fuel storage pools. The temperature range of interest is from room temperature where the fuel is stored for long periods of time, through the temperature range encountered in normal operation (400 to 600°C) to the highest temperatures which are possible in extreme accident situations. This temperature range is considered in this chapter to be from room temperature to 1200°C

Automobile Fuel Economy Standards: Impacts, Efficiency, and Alternatives

This paper discusses fuel economy regulations in the United States and other countries. We first describe how these programs affect the automobile market, including their impacts on fuel use and other dimensions of the vehicle fleet. We then review different methodologies for assessing the costs of fuel economy regulations and discuss what the results of these methodologies imply for policy. Following that, we compare the welfare effects of fuel economy regulations to those of fuel taxes and assess whether or not these two policies can be complements. Finally, we review arguments for transitioning away from fuel economy regulations towards a “feebate” system.

Isolation of a Campylobacter lanienae-like Bacterium from Laboratory Chinchillas (Chinchilla laniger)

Routine necropsies of 27 asymptomatic juvenile chinchillas revealed a high prevalence of gastric ulcers with microscopic lymphoplasmacytic gastroenteritis and typhlocolitis. Polymerase chain reaction (PCR) analysis using Campylobacter genus-specific partial 16S rRNA primers revealed the presence of Campylobacter spp. DNA in the faeces of 12 of 27 animals (44.4%). Species-specific partial 16S rRNA PCR and sequencing confirmed that these animals were colonized with Campylobacter lanienae, a gram-negative, microaerophilic bacterium that was first identified on routine faecal screening of slaughterhouse employees and subsequently isolated from faeces of livestock. Campylobacter lanienae was isolated from the faeces of six PCR-positive animals and identified with species-specific PCR and full 16S rRNA sequencing. Phylogenetic analysis showed that these isolates clustered with C. lanienae strain NCTC 13004. PCR analysis of DNA extracted from gastrointestinal tissues revealed the presence of C. lanienae DNA in the caecum and colon of these chinchillas. Gastrointestinal lesions were scored and compared between C. lanienae-positive and C. lanienae-negative animals. There was no correlation between colonization status and lesion severity in the stomach, liver, duodenum, or colon. Possible routes of C. lanienae infection in chinchillas could include waterborne transmission and faecal–oral transmission from wild mice and rats or livestock. Based on these findings, the authors conclude that C. lanienae colonizes the lower bowel of chinchillas in the absence of clinical disease. This is the first report of C. lanienae in any rodent species. Campylobacter lanienae isolates from different mammalian species demonstrate heterogeneity by 16S rRNA sequence comparison. Analysis using rpoB suggests that isolates and clones currently identified as C. lanienae may represent multiple species or subspecies.Ruth L. Kirschstein National Research Service AwardNational Institutes of Health (U.S.) (Grant R01-OD011141)National Institutes of Health (U.S.) (Grant T32-OD007036)National Institutes of Health (U.S.) (Grant P30-ES02109

Helicobacter hepaticus Infection Promotes Hepatitis and Preneoplastic Foci in Farnesoid X Receptor (FXR) Deficient Mice

Farnesoid X receptor (FXR) is a nuclear receptor that regulates bile acid metabolism and transport. Mice lacking expression of FXR (FXR KO) have a high incidence of foci of cellular alterations (FCA) and liver tumors. Here, we report that Helicobacter hepaticus infection is necessary for the development of increased hepatitis scores and FCA in previously Helicobacter-free FXR KO mice. FXR KO and wild-type (WT) mice were sham-treated or orally inoculated with H. hepaticus. At 12 months post-infection, mice were euthanized and liver pathology, gene expression, and the cecal microbiome were analyzed. H. hepaticus induced significant increases hepatitis scores and FCA numbers in FXR KO mice (P<0.01 and P<0.05, respectively). H. hepaticus altered the beta diversity of cecal microbiome in both WT and FXR KO mice compared to uninfected mice (P<0.05). Significant upregulation of β-catenin, Rela, Slc10a1, Tlr2, Nos2, Vdr, and Cyp3a11 was observed in all FXR KO mice compared to controls (P<0.05). Importantly, H. hepaticus and FXR deficiency were necessary to significantly upregulate Cyp2b10 (P<0.01). FXR deficiency was also a potent modulator of the cecal microbiota, as observed by a strong decrease in alpha diversity. A significant decrease in Firmicutes, particularly members of the order Clostridiales, was observed in FXR KO mice (P<0.05 and FDR<5%, ANOVA). While FXR deficiency strongly affects expression of genes related to immunity and bile acid metabolism, as well as the composition of the microbiome; however, its deficiency was not able to produce significant histopathological changes in the absence of H. hepaticus infection.National Institutes of Health (U.S.) (NIH R01 OD011141)National Institutes of Health (U.S.) (NIH T32 OD010978)National Institutes of Health (U.S.) (NIH P30 ES002109)National Institutes of Health (U.S.) (P01 CA026731

Social stress-enhanced severity of Citrobacter rodentium-induced colitis is CCL2-dependent and attenuated by probiotic Lactobacillus reuteri

Psychological stressors are known to affect colonic diseases but the mechanisms by which this occurs, and whether probiotics can prevent stressor effects, are not understood. Because inflammatory monocytes that traffic into the colon can exacerbate colitis, we tested whether CCL2, a chemokine involved in monocyte recruitment, was necessary for stressor-induced exacerbation of infectious colitis. Mice were exposed to a social disruption stressor that entails repeated social defeat. During stressor exposure, mice were orally challenged with Citrobacter rodentium to induce a colonic inflammatory response. Exposure to the stressor during challenge resulted in significantly higher colonic pathogen levels, translocation to the spleen, increases in colonic macrophages, and increases in inflammatory cytokines and chemokines. The stressor-enhanced severity of C. rodentium-induced colitis was not evident in CCL2[superscript −/−] mice, indicating the effects of the stressor are CCL2-dependent. In addition, we tested whether probiotic intervention could attenuate stressor-enhanced infectious colitis by reducing monocyte/macrophage accumulation. Treating mice with probiotic Lactobacillus reuteri reduced CCL2 mRNA levels in the colon and attenuated stressor-enhanced infectious colitis. These data demonstrate that probiotic L. reuteri can prevent the exacerbating effects of stressor exposure on pathogen-induced colitis, and suggest that one mechanism by which this occurs is through downregulation of the chemokine CCL2.National Cancer Institute (U.S.) (Grants AT006552-01A1, P30-CA016058, and T32-DE014320

Gut Microbiome Phenotypes Driven by Host Genetics Affect Arsenic Metabolism

Large individual differences in susceptibility to arsenic-induced diseases are well-documented and frequently associated with different patterns of arsenic metabolism. In this context, the role of the gut microbiome in directly metabolizing arsenic and triggering systemic responses in diverse organs raises the possibility that gut microbiome phenotypes affect the spectrum of metabolized arsenic species. However, it remains unclear how host genetics and the gut microbiome interact to affect the biotransformation of arsenic. Using an integrated approach combining 16S rRNA gene sequencing and HPLC-ICP-MS arsenic speciation, we demonstrate that IL-10 gene knockout leads to a significant taxonomic change of the gut microbiome, which in turn substantially affects arsenic metabolism.National Institute of Environmental Health Sciences (P30 ES010126)National Institute of Environmental Health Sciences (NIEHS grant P30 ES002109)University of Georgia. College of Public Health (internal grant)University of Georgia (Faculty Research Grant (FRG)

Golden gaskets: variations on the Sierpi\'nski sieve

We consider the iterated function systems (IFSs) that consist of three general similitudes in the plane with centres at three non-collinear points, and with a common contraction factor \la\in(0,1). As is well known, for \la=1/2 the invariant set, \S_\la, is a fractal called the Sierpi\'nski sieve, and for \la<1/2 it is also a fractal. Our goal is to study \S_\la for this IFS for 1/2<\la<2/3, i.e., when there are "overlaps" in \S_\la as well as "holes". In this introductory paper we show that despite the overlaps (i.e., the Open Set Condition breaking down completely), the attractor can still be a totally self-similar fractal, although this happens only for a very special family of algebraic \la's (so-called "multinacci numbers"). We evaluate \dim_H(\S_\la) for these special values by showing that \S_\la is essentially the attractor for an infinite IFS which does satisfy the Open Set Condition. We also show that the set of points in the attractor with a unique ``address'' is self-similar, and compute its dimension. For ``non-multinacci'' values of \la we show that if \la is close to 2/3, then \S_\la has a nonempty interior and that if \la<1/\sqrt{3} then \S_\la$ has zero Lebesgue measure. Finally we discuss higher-dimensional analogues of the model in question.Comment: 27 pages, 10 figure