Dynamics of the mapping class group action on the variety of PSL(2,C) characters

We study the action of the mapping class group Mod(S) on the boundary dQ of quasifuchsian space Q. Among other results, Mod(S) is shown to be topologically transitive on the subset C in dQ of manifolds without a conformally compact end. We also prove that any open subset of the character variety X(pi_1(S),SL(2,C)) intersecting dQ does not admit a nonconstant Mod(S)-invariant meromorphic function. This is related to a question of Goldman.Comment: This is the version published by Geometry & Topology on 11 July 200

What We Don\u27t Know Can Help Us: Eliciting Out-of-Discipline Knowledge for Work with Intractable Conflicts

In this article, the authors present the results of a study in which a diverse variety of experts in fields outside the traditional conflict domain were interviewed about their ideas regarding intractable conflicts. The purpose of this study was to gather frame-breaking insights and practical approaches that could shed new light on complex, persistent conflict that has been particularly resistant to resolution. The authors argue that outsiders to the field are more likely to provide fresh perspective and radical approaches to the conflict field’s most intransigent problems because they are not constrained by the field’s pre-existing normative frames. This article examines some of their findings—from ideas on how globalization has exacerbated intractable conflicts, to ways that Biblical metaphors can be used to promote reconciliation, to an analysis of how philosophical concepts such as morality and impartiality can be used to produce fair outcomes, to ideas on the creation of an independent, international regional facilitation corps. In addition to a summary of content findings, methodological recommendations for future similar studies are offered

Resilient Communities: Empowering Older Adults in Disasters and Daily Life

New York City's 1.4 million people age 60 and over consti-tute 17 percent of the city's total population. This number is projected to increase by 50 percent over the next 20 years. The vast majority of older adults live independently, requiring little to no assistance under routine conditions.Yet over the last 12 years, New York City has experienced multiple catastrophic events. The 2001 attack on the World Trade Center, the blackout of 2003, Hurricane Irene, and, most recently, Hurricane Sandy, posed significant chal-lenges to older adults. A common denominator of these incidents was the loss of power and the disruption of sys-tems and services upon which older adults rely, including but not limited to transportation, communication, health care, elevators, and social supports. As a result, tens of thousands of older adults were isolated in high-rise build-ings and private homes, in need of food, water, warming or cooling, medical attention, and medication.Efforts to increase individual preparedness among older people through the creation of "go-bags" and the stock-piling of supplies have been repeatedly undertaken but have not improved overall outcomes for older people following subsequent disasters in New York City. With extreme weather projected to increase, a new strategy is required to keep older adults, who are often among the city's most long-term, civically engaged residents, safe

A simplified immunoprecipitation method for quantitatively measuring antibody responses in clinical sera samples by using mammalian-produced Renilla luciferase-antigen fusion proteins

BACKGROUND: Assays detecting human antigen-specific antibodies are medically useful. However, the usefulness of existing simple immunoassay formats is limited by technical considerations such as sera antibodies to contaminants in insufficiently pure antigen, a problem likely exacerbated when antigen panels are screened to obtain clinically useful data. RESULTS: We developed a novel and simple immunoprecipitation technology for identifying clinical sera containing antigen-specific antibodies and for generating quantitative antibody response profiles. This method is based on fusing protein antigens to an enzyme reporter, Renilla luciferase (Ruc), and expressing these fusions in mammalian cells, where mammalian-specific post-translational modifications can be added. After mixing crude extracts, sera and protein A/G beads together and incubating, during which the Ruc-antigen fusion become immobilized on the A/G beads, antigen-specific antibody is quantitated by washing the beads and adding coelenterazine substrate and measuring light production. We have characterized this technology with sera from patients having three different types of cancers. We show that 20–85% of these sera contain significant titers of antibodies against at least one of five frequently mutated and/or overexpressed tumor-associated proteins. Five of six colon cancer sera tested gave responses that were statistically significantly greater than the average plus three standard deviations of 10 control sera. The results of competition experiments, preincubating positive sera with unmodified E. coli-produced antigens, varied dramatically. CONCLUSION: This technology has several advantages over current quantitative immunoassays including its relative simplicity, its avoidance of problems associated with E. coli-produced antigens and its use of antigens that can carry mammalian or disease-specific post-translational modifications. This assay should be generally useful for analyzing sera for antibodies recognizing any protein or its post-translational modifications

Weather on Other Worlds. II. Survey Results: Spots Are Ubiquitous on L and T Dwarfs

We present results from the "Weather on Other Worlds" Spitzer Exploration Science program to investigate photometric variability in L and T dwarfs, usually attributed to patchy clouds. We surveyed 44 L3-T8 dwarfs, spanning a range of $J-K_s$ colors and surface gravities. We find that 14/23 (61%; 95% confidence interval: 41%-78%) of our single L3-L9.5 dwarfs are variable with peak-to-peak amplitudes between 0.2% and 1.5%, and 5/16 (31%; 95% confidence interval: 14%-56%) of our single T0-T8 dwarfs are variable with amplitudes between 0.8% and 4.6%. After correcting for sensitivity, we find that 80% (95% confidence interval: 53%-100%) of L dwarfs vary by >0.2%, and 36% (95% confidence interval: 19%-52%) of T dwarfs vary by >0.4%. Given viewing geometry considerations, we conclude that photospheric heterogeneities causing >0.2% 3-5-micron flux variations are present on virtually all L dwarfs, and probably on most T dwarfs. A third of L dwarf variables show irregular light curves, indicating that L dwarfs may have multiple spots that evolve over a single rotation. Also, approximately a third of the periodicities are on time scales >10 h, suggesting that slowly-rotating brown dwarfs may be common. We observe an increase in the maximum amplitudes over the entire spectral type range, revealing a potential for greater temperature contrasts in T dwarfs than in L dwarfs. We find a tentative association (92% confidence) between low surface gravity and high-amplitude variability among L3-L5.5 dwarfs. Although we can not confirm whether lower gravity is also correlated with a higher incidence of variables, the result is promising for the characterization of directly imaged young extrasolar planets through variability.Comment: 42 pages, 11 figures, 2 tables, accepted by Ap

SPASM and Twitch Domains in S-Adenosylmethionine (SAM) Radical Enzymes

S-Adenosylmethionine (SAM, also known as AdoMet) radical enzymes use SAM and a [4Fe-4S] cluster to catalyze a diverse array of reactions. They adopt a partial triose-phosphate isomerase (TIM) barrel fold with N- and C-terminal extensions that tailor the structure of the enzyme to its specific function. One extension, termed a SPASM domain, binds two auxiliary [4Fe-4S] clusters and is present within peptide-modifying enzymes. The first structure of a SPASM-containing enzyme, anaerobic sulfatase-maturating enzyme (anSME), revealed unexpected similarities to two non-SPASM proteins, butirosin biosynthetic enzyme 2-deoxy-scyllo-inosamine dehydrogenase (BtrN) and molybdenum cofactor biosynthetic enzyme (MoaA). The latter two enzymes bind one auxiliary cluster and exhibit a partial SPASM motif, coined a Twitch domain. Here we review the structure and function of auxiliary cluster domains within the SAM radical enzyme superfamily.Massachusetts Institute of Technology. Office of the Dean for Graduate Education (Fellowship)National Science Foundation (U.S.) (Grant MCB-0543833

The roles of redox active cofactors in catalysis : structural studies of iron sulfur cluster and flavin dependent enzymes

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2013.Cataloged from PDF version of thesis.Includes bibliographical references.Cofactors are highly prevalent in biological systems and have evolved to take on many functions in enzyme catalysis. Two cofactors, flavin adenine dinucleotide (FAD) and [4Fe-4S] clusters, were originally determined to aid in electron transfer and redox chemistry. However, additional activities for these cofactors continue to be discovered. The study of FAD in the context of rebeccamycin and staurosporine biosynthesis has yielded another role for this cofactor in the enzyme StaC. A homolog of this enzyme, RebC, uses its FAD cofactor in the oxidation of 7-carboxy-K252c. StaC also uses 7-carboxy-K252 as a substrate, but its reaction does not result in a redox transformation. Biochemical and X-ray crystallographic methods were employed to determine that, indeed, the role of FAD in the StaC system is not to catalyze redox chemistry. Instead, FAD sterically drives an initial decarboxylation event. Subtle differences in the active sites of RebC and StaC promote this redox neutral decarboxylation, by activating water for a final protonation step. In another system, the characterization of the S-adenosyl-L-methionine (AdoMet) radical superfamily showed the versatility of these cofactors. In this superfamily, which includes over 40,000 unique sequences, [4Fe-4S] clusters are responsible for the initiation of radical chemistry. A recently described subclass of this superfamily, the dehydrogenases, require additional [4Fe-4S] cluster for activity. This requirement led to the hypothesis that these enzymes are catalyzing redox chemistry by directly ligating substrates to auxiliary (Aux) clusters. X-ray structures of 2-deoxy-scyllo-inosamine dehydrogenase (BtrN), required for the biosynthesis of 2-deoxystreptamine, and an anaerobic sulfatase maturating enzyme, anSMEcpe, which installs a required formylglycine posttranslational modification, refute this hypothesis. In these structures, substrate binding is distal from each enzymes' Aux clusters. However, the Aux cluster binding architecture shared between BtrN, anSMEcpe, and another AdoMet radical enzyme, MoaA, involved in molybdenum cofactor biosynthesis, suggests that the structural features will be a staple in the AdoMet radical superfamily, common to - 30% of the AdoMet radical reactions.by Peter John Goldman.Ph.D

A Gaia-PS1-SDSS (GPS1) Proper Motion Catalog Covering 3/4 of the Sky

We combine Gaia DR1, PS1, SDSS and 2MASS astrometry to measure proper motions for 350 million sources across three-fourths of the sky down to a magnitude of $m_r\sim20$\,. Using positions of galaxies from PS1, we build a common reference frame for the multi-epoch PS1, single-epoch SDSS and 2MASS data, and calibrate the data in small angular patches to this frame. As the Gaia DR1 excludes resolved galaxy images, we choose a different approach to calibrate its positions to this reference frame: we exploit the fact that the proper motions of stars in these patches are {\it linear}. By simultaneously fitting the positions of stars at different epochs of -- Gaia DR1, PS1, SDSS, and 2MASS -- we construct an extensive catalog of proper motions dubbed GPS1. GPS1 has a characteristic systematic error of less than 0.3 \masyr\, and a typical precision of $1.5-2.0$\masyr. The proper motions have been validated using galaxies, open clusters, distant giant stars and QSOs. In comparison with other published faint proper motion catalogs, GPS1's systematic error ($<0.3$ \masyr) should be nearly an order of magnitude better than that of PPMXL and UCAC4 ($>2.0$ \masyr). Similarly, its precision ($\sim 1.5$ \masyr) is a four-fold improvement relative to PPMXL and UCAC4 ($\sim 6.0$ \masyr). For QSOs, the precision of GPS1 is found to be worse ($\sim 2.0-3.0$\masyr), possibly due to their particular differential chromatic refraction (DCR). The GPS1 catalog will be released on-line and available via the VizieR Service and VO Service. (===GPS1 is available with VO TAP Query now, see http://www2.mpia-hd.mpg.de/~tian/GPS1/ for details=== )Comment: 17 pages, 19 figures, published on-line in ApJS (GPS1 is available with VO TAP Query now

Representations of the fundamental group of a surface in PU(p,q) and holomorphic triples

We count the connected components in the moduli space of PU(p,q)-representations of the fundamental group for a closed oriented surface. The components are labelled by pairs of integers which arise as topological invariants of the flat bundles associated to the representations. Our results show that for each allowed value of these invariants, which are bounded by a Milnor-Wood type inequality, there is a unique non-empty connected component. Interpreting the moduli space of representations as a moduli space of Higgs bundles, we take a Morse theoretic approach using a certain smooth proper function on the Higgs moduli space. A key step is the identification of the function's local minima as moduli spaces of holomorphic triples. We prove that these moduli spaces of triples are non-empty and irreducible.Comment: 6 pages, to appear in C. R. Acad. Sci. Paris Ser. I Mat