Violating the string winding number maximally in Anti-de Sitter space

We study n-string scattering amplitudes in three-dimensional Anti-de Sitter space (AdS3). We focus our attention on the processes in which the winding number conservation is violated maximally; that is, those processes in which it is violated in n-2 units. A worldsheet conformal field theory calculation leads us to confirm a previous conjecture about the functional form of these observables.Comment: 15 pages. V2 references added and minor typo corrected. V3, V4 addendum on an alternative derivation of the main formula for short string

On the timelike Liouville three-point function

In a recent paper, D. Harlow, J. Maltz, and E. Witten showed that a particular proposal for the timelike Liouville three-point function, originally due to Al. Zamolodchikov and to I. Kostov and V. Petkova, can actually be computed by the original Liouville path integral evaluated on a new integration cycle. Here, we discuss a Coulomb gas computation of the timelike three-point function and show that an analytic extension of the Selberg type integral formulas involved reproduces the same expression, including the adequate normalization. A notable difference with the spacelike calculation is pointed out.Comment: 11 pages. v2 comments and references added. Appropriate credit is given to Ref. arXiv:hep-th/0512346, where the Coulomb gas computation of the c<1 theory has already been discusse

Population trends and priority conservation sites for Mexican Duck Anas diazi

Little is known about Mexican Duck Anas diazi biology and populations. We analyse long-term (1960–2000) trends of Mexican Duck numbers in Mexico and employ contemporary count data (1991–2000) from the U.S. Fish and Wildlife Service midwinter surveys to identify key sites for conservation using a complementarity approach. The overall Mexican Duck population showed a significant long-term increase of 2.5% per year, with large fluctuations throughout the study period. The Northern highlands population increased at an annual rate of 7.7%, while the Central highlands population showed no significant long-term trend. During the last decade, counts in both the Northern and Central highlands exhibited no significant change. At the site level, significant long-term increases occurred in four localities in the Northern highlands (Laguna Babícora +13.9% annually, Laguna Bustillos +25.9%, Laguna Mexicanos +20.4% and Laguna Santiaguillo +16.9%) and in three localities in the Central highlands (Languillo +15.3% annually, Presa Solís +8.9%, Zacapu +13.4%). Two sites in the Central highlands showed significant declines, in the long term (Lago de Chapala, -5.2% per year) and during the last decade (Lerma, -11.8% per year). The Northern highlands held 16% and the Central highlands 84% of the Mexican Duck population in the period 1960–2000; during the last decade, these figures were 31% and 69%, respectively. A set of priority sites for conservation of the Mexican Duck was identified, consisting of 15 sites holding more than 70% of the midwinter Mexican Duck counts in Mexico. Ten sites from the priority set also qualify for designation as wetlands of international importance under the Ramsar Convention on Wetlands, by holding [greater-than-or-equal] 1% of the estimated population. Four of the priority sites are in the Northern highlands and 11 in the Central highlands, of which eight are distributed along the Rio Lerma drainage. The most urgent actions that need to be undertaken are to estimate the current minimum population size in Mexico; to establish a programme for monitoring populations in the priority sites, especially those located within the highly degraded Rio Lerma drainage; and to determine the most feasible management actions for the species, concentrating efforts around the priority sites

Supertranslations and Superrotations at the Black Hole Horizon

We show that the asymptotic symmetries close to nonextremal black hole horizons are generated by an extension of supertranslations. This group is generated by a semidirect sum of Virasoro and Abelian currents. The charges associated with the asymptotic Killing symmetries satisfy the same algebra. When considering the special case of a stationary black hole, the zero mode charges correspond to the angular momentum and the entropy at the horizon.Comment: 6 pages, references added, published versio

When in Peril, Retrench: Testing the Portfolio Channel of Contagion

One plausible mechanism through which financial market shocks may propagate across countries is through the effect of past gains and losses on investors' risk aversion. The paper first presents a simple model examining how heterogeneous changes in investors' risk aversion affects portfolio decisions and stock prices. Second, the paper shows empirically that, when funds' returns are below average, they adjust their holdings toward the average (or benchmark) portfolio. In other words, they tend to sell the assets of countries in which they were "overweight", increasing their exposure to countries in which they were "underweight." Based on this insight, the paper discusses a matrix of financial interdependence reflecting the extent to which countries share overexposed funds. Comparing this measure to indices of trade or bank linkages indicates that our index can improve predictions about which countries are likely to be affected by contagion from crisis centers.

DNA compaction by the higher-order assembly of PRH/Hex homeodomain protein oligomers

Protein self-organization is essential for the establishment and maintenance of nuclear architecture and for the regulation of gene expression. We have shown previously that the Proline-Rich Homeodomain protein (PRH/Hex) self-assembles to form oligomeric complexes that bind to arrays of PRH binding sites with high affinity and specificity. We have also shown that many PRH target genes contain suitably spaced arrays of PRH sites that allow this protein to bind and regulate transcription. Here, we use analytical ultracentrifugation and electron microscopy to further characterize PRH oligomers. We use the same techniques to show that PRH oligomers bound to long DNA fragments self-associate to form highly ordered assemblies. Electron microscopy and linear dichroism reveal that PRH oligomers can form protein–DNA fibres and that PRH is able to compact DNA in the absence of other proteins. Finally, we show that DNA compaction is not sufficient for the repression of PRH target genes in cells. We conclude that DNA compaction is a consequence of the binding of large PRH oligomers to arrays of binding sites and that PRH is functionally and structurally related to the Lrp/AsnC family of proteins from bacteria and archaea, a group of proteins formerly thought to be without eukaryotic equivalents

DNA compaction by the higher-order assembly of PRH/Hex homeodomain protein oligomers

Protein self-organization is essential for the establishment and maintenance of nuclear architecture and for the regulation of gene expression. We have shown previously that the Proline-Rich Homeodomain protein (PRH/Hex) self-assembles to form oligomeric complexes that bind to arrays of PRH binding sites with high affinity and specificity. We have also shown that many PRH target genes contain suitably spaced arrays of PRH sites that allow this protein to bind and regulate transcription. Here, we use analytical ultracentrifugation and electron microscopy to further characterize PRH oligomers. We use the same techniques to show that PRH oligomers bound to long DNA fragments self-associate to form highly ordered assemblies. Electron microscopy and linear dichroism reveal that PRH oligomers can form protein–DNA fibres and that PRH is able to compact DNA in the absence of other proteins. Finally, we show that DNA compaction is not sufficient for the repression of PRH target genes in cells. We conclude that DNA compaction is a consequence of the binding of large PRH oligomers to arrays of binding sites and that PRH is functionally and structurally related to the Lrp/AsnC family of proteins from bacteria and archaea, a group of proteins formerly thought to be without eukaryotic equivalents