Periodic Complexes and Group Actions

In this paper we show that the cohomology of a connected CW complex is periodic if and only if it is the base space of an orientable spherical fibration with total space that is homotopically finite dimensional. As applications we characterize those discrete groups that act freely and properly on a cartesian product of euclidean space and a sphere; we construct non-standard free actions of rank two simple groups on finite complexes Y homotopy equivalent to a product of two spheres and we prove that a finite p-group P acts freely on such a complex if and only if it does not contain a subgroup isomorphic to Z/p X Z/p X Z/p.Comment: Revised versio

Control of Arabidopsis apical-basal embryo polarity by antagonistic transcription factors.

Plants, similarly to animals, form polarized axes during embryogenesis on which cell differentiation and organ patterning programs are orchestrated. During Arabidopsis embryogenesis, establishment of the shoot and root stem cell populations occurs at opposite ends of an apical-basal axis. Recent work has identified the PLETHORA (PLT) genes as master regulators of basal/root fate, whereas the master regulators of apical/shoot fate have remained elusive. Here we show that the PLT1 and PLT2 genes are direct targets of the transcriptional co-repressor TOPLESS (TPL) and that PLT1/2 are necessary for the homeotic conversion of shoots to roots in tpl-1 mutants. Using tpl-1 as a genetic tool, we identify the CLASS III HOMEODOMAIN-LEUCINE ZIPPER (HD-ZIP III) transcription factors as master regulators of embryonic apical fate, and show they are sufficient to drive the conversion of the embryonic root pole into a second shoot pole. Furthermore, genetic and misexpression studies show an antagonistic relationship between the PLT and HD-ZIP III genes in specifying the root and shoot poles

Symmetric spectra

The long hunt for a symmetric monoidal category of spectra finally ended in success with the simultaneous discovery of the third author's discovery of symmetric spectra and the Elmendorf-Kriz-Mandell-May category of S-modules. In this paper we define and study the model category of symmetric spectra, based on simplicial sets and topological spaces. We prove that the category of symmetric spectra is closed symmetric monoidal and that the symmetric monoidal structure is compatible with the model structure. We prove that the model category of symmetric spectra is Quillen equivalent to Bousfield and Friedlander's category of spectra. We show that the monoidal axiom holds, so that we get model categories of ring spectra and modules over a given ring spectrum.Comment: 77 pages. This version corrects some errors in the section on topological symmetric spectr

Constituent pressure may be more effective than lobbying in determining whether a bill passes or fails.

What has a greater effect on legislative outcomes, campaign donations and lobbying efforts (the inside game) or constituent activism (the outside game)? In new research, Jeff Smith – who once served in the Missouri Senate, representing 175,000 St. Louisans – analyzes the impact of each method. He finds that contributions had no statistically significant impact on policy outcomes; other than nourishing a class of political fixers, corporate political spending accomplished little. However, constituent contacts seem to have had a substantial impact

David Orentlicher, Two Presidents Are Better Than One: The Case for a Bipartisan Executive Branch

In recent years, American politics has fallen into what amounts to an ongoing, low-grade constitutional crisis. This condition still goes by time-honored names like “gridlock,” “polarization” and “brinksmanship,” but as it has grown more serious, other terms have come into vogue: “radicalization,” “dysfunction,” “constitutional hardball,” “total obstruction,” “hostage-taking,” a “toxic” or “scorched-earth” politics, the “death of comity,” the destruction of “political norms,” the “weaponizing..

Cornelis A. van Minnen and Manfred Berg, eds. The U.S. South and Europe: Transatlantic Relations in the Nineteenth and Twentieth Centuries. New Directions in Southern History

Originating at a 2011 conference at the Roosevelt Study Center in the Netherlands, the fourteen essays in this collection are an informative hybrid of region-specific American Studies and the currently fashionable “Atlanticist” or hemispheric / transnational approaches. The periods covered range from the era of Tocqueville and other European observers of antebellum America to the age of civil rights and decolonization in the late twentieth century. By and large, the essays deal with the expe..

Lived Religion: An Examination of Pass the Salt Luncheons.

This study used a case study approach to examine how religious culture, such as theologies and doctrines, is lived or practiced by Pass the Salt luncheon participants. Pass the Salt participants are taught the teachings of Harvest Evangelism, an interdenominational Para-church organization; these teachings are evidenced through their cultural toolkit. It was expected that the luncheon participants would practice Harvest Evangelism\u27s religious culture in the workplace. Participant observation and personal interviews were conducted to examine participants\u27 application of the cultural toolkit to their everyday lives, specifically in the workplace. Findings indicated that the leader of the Pass the Salt luncheon was more likely to practice or live the religious doctrines provided by Harvest Evangelism, while others lived religion in a different way

Scintillation detectors constructed with an optimized 2x2 silicon photomultiplier array

Silicon photomultipliers (SiPMs) are a good alternative to photomultiplier tubes (PMTs) because their gain and quantum efficiency are comparable to PMTs. However, the largest single-chip SiPM is still less than 1~cm$^2$. In order to use SiPMs with scintillators that have reasonable sensitivity, it is necessary to use multiple SiPMs. In this work, scintillation detectors are constructed and tested with a custom 2x2 SiPM array. The layout of the SiPMs and the geometry of the scintillator were determined by performing Geant4 simulations. Cubic NaI, CsI, and CLYC with 18~mm sides have been tested. The output of the scintillation detectors are stabilized over the temperature range between --20 and 50~$^{\circ}$C by matching the gain of the SiPMs in the array. The energy resolution for these detectors has been measured as a function of temperature. Furthermore, neutron detection for the CLYC detector was studied in the same temperature range. Using pulse-shape discrimination, neutrons can be cleanly identified without contribution from $\gamma$-photons. As a result, these detectors are suitable for deploying in spectroscopic personal radiation detectors (SPRD).Comment: IEEE Nuclear Science Symposium Conference Record (2016