University of Arizona

About: University of Arizona is a education organization based out in Tucson, Arizona, United States. It is known for research contribution in the topics: Population & Galaxy. The organization has 63805 authors who have published 155998 publications receiving 6854915 citations. The organization is also known as: UA & U of A.

An extended upper atmosphere around the extrasolar planet HD209458b

Abstract: The planet in the system HD209458 is the first one for which repeated transits across the stellar disk have been observed1,2. Together with radial velocity measurements3, this has led to a determination of the planet's radius and mass, confirming it to be a gas giant. But despite numerous searches for an atmospheric signature4,5,6, only the dense lower atmosphere of HD209458b has been observed, through the detection of neutral sodium absorption7. Here we report the detection of atomic hydrogen absorption in the stellar Lyman α line during three transits of HD209458b. An absorption of 15 ± 4% (1σ) is observed. Comparison with models shows that this absorption should take place beyond the Roche limit and therefore can be understood in terms of escaping hydrogen atoms.

Abrupt climate change

Abstract: Large, abrupt, and widespread climate changes with major impacts have occurred repeatedly in the past, when the Earth system was forced across thresholds. Although abrupt climate changes can occur for many reasons, it is conceivable that human forcing of climate change is increasing the probability of large, abrupt events. Were such an event to recur, the economic and ecological impacts could be large and potentially serious. Unpredictability exhibited near climate thresholds in simple models shows that some uncertainty will always be associated with projections. In light of these uncertainties, policy-makers should consider expanding research into abrupt climate change, improving monitoring systems, and taking actions designed to enhance the adaptability and resilience of ecosystems and economies.

Estimate of the Mutation Rate per Nucleotide in Humans

Abstract: Many previous estimates of the mutation rate in humans have relied on screens of visible mutants. We investigated the rate and pattern of mutations at the nucleotide level by comparing pseudogenes in humans and chimpanzees to (i) provide an estimate of the average mutation rate per nucleotide, (ii) assess heterogeneity of mutation rate at different sites and for different types of mutations, (iii) test the hypothesis that the X chromosome has a lower mutation rate than autosomes, and (iv) estimate the deleterious mutation rate. Eighteen processed pseudogenes were sequenced, including 12 on autosomes and 6 on the X chromosome. The average mutation rate was estimated to be approximately 2.5 x 10(-8) mutations per nucleotide site or 175 mutations per diploid genome per generation. Rates of mutation for both transitions and transversions at CpG dinucleotides are one order of magnitude higher than mutation rates at other sites. Single nucleotide substitutions are 10 times more frequent than length mutations. Comparison of rates of evolution for X-linked and autosomal pseudogenes suggests that the male mutation rate is 4 times the female mutation rate, but provides no evidence for a reduction in mutation rate that is specific to the X chromosome. Using conservative calculations of the proportion of the genome subject to purifying selection, we estimate that the genomic deleterious mutation rate (U) is at least 3. This high rate is difficult to reconcile with multiplicative fitness effects of individual mutations and suggests that synergistic epistasis among harmful mutations may be common.

Universal scaling laws in fully developed turbulence.

Abstract: The inertial-range scaling laws of fully developed turbulence are described in terms of scalings of a sequence of moment ratios of the energy dissipation field ${\mathrm{\ensuremath{\epsilon}}}_{\mathit{l}}$ coarse-grained at inertial-range scale l. These moment ratios ${\mathrm{\ensuremath{\epsilon}}}_{\mathit{l}}^{(\mathit{p})}$=〈${\mathrm{\ensuremath{\epsilon}}}_{\mathit{l}}^{\mathit{p}+1}$〉/〈${\mathrm{\ensuremath{\epsilon}}}_{\mathit{l}}^{\mathit{p}}$〉(p=0, 1, 2,...,) form a hierarchy of structures. The most singular structures ${\mathrm{\ensuremath{\epsilon}}}_{\mathit{l}}^{(\mathrm{\ensuremath{\infty}})}$ are assumed to be filaments, and it is argued that ${\mathrm{\ensuremath{\epsilon}}}_{\mathit{l}}^{(\mathrm{\ensuremath{\infty}})}$\ensuremath{\sim}${\mathit{l}}^{\mathrm{\ensuremath{-}}2/3}$. Furthermore, a universal relation between scalings of successive structures is postulated, which leads to a prediction of the entire set of the scaling exponents: 〈${\mathrm{\ensuremath{\epsilon}}}_{\mathit{l}}^{\mathit{p}}$〉\ensuremath{\sim}${\mathit{l}}_{\mathit{p}}^{\mathrm{\ensuremath{\tau}}}$, ${\mathrm{\ensuremath{\tau}}}_{\mathit{p}}$=-2/3p+2[1-( 2) / 3 ${)}^{\mathit{p}}$] and 〈\ensuremath{\delta}${\mathit{v}}_{\mathit{l}}^{\mathit{p}}$〉\ensuremath{\sim}${\mathit{l}}_{\mathit{p}}^{\mathrm{\ensuremath{\zeta}}}$, ${\mathrm{\ensuremath{\zeta}}}_{\mathit{p}}$=p/9+2[1-(2/3${)}^{\mathit{p}/3}$].

Evidence for terror management theory: I. The effects of mortality salience on reactions to those who violate or uphold cultural values.

Abstract: On the basis of terror management theory, it was hypothesized that when mortality is made salient, Ss would respond especially positively toward those who uphold cultural values and especially negatively toward those who violate cultural values. In Experiment 1, judges recommended especially harsh bonds for a prostitute when mortality was made salient. Experiment 2 replicated this finding with student Ss and demonstrated that it occurs only among Ss with relatively negative attitudes toward prostitution. Experiment 3 demonstrated that mortality salience also leads to larger reward recommendations for a hero who upheld cultural values. Experiments 4 and 5 showed that the mortality salience effect does not result from heightened self-awareness or physiological arousal. Experiment 6 replicated the punishment effect with a different mortality salience manipulation. Implications for the role of fear of death in social behavior are discussed.