Equivariant Intersection Cohomology of Toric Varieties

We investigate the equivariant intersection cohomology of a toric variety. Considering the defining fan of the variety as a finite topological space with the subfans being the open sets (that corresponds to the "toric" topology given by the invariant open subsets), equivariant intersection cohomology provides a sheaf (of graded modules over a sheaf of graded rings) on that "fan space". We prove that this sheaf is a "minimal extension sheaf", i.e., that it satisfies three relatively simple axioms which are known to characterize such a sheaf up to isomorphism. In the verification of the second of these axioms, a key role is played by "equivariantly formal" toric varieties, where equivariant and "usual" (non-equivariant) intersection cohomology determine each other by Kunneth type formulae. Minimal extension sheaves can be constructed in a purely formal way and thus also exist for non-rational fans. As a consequence, we can extend the notion of an equivariantly formal fan even to this general setup. In this way, it will be possible to introduce "virtual" intersection cohomology for equivariantly formal non-rational fans.Comment: 31 pages, AMS-Latex (all "private" macros included), to be published in "Algebraic Geometry - Hirzebruch 70" (Proceedings of the conference at the Banach Centre, Warszawa, May 1998), Contemporary Mathematics, AM

Most Say Tensions Between Trump Administration and News Media Hinder Access to Political News

According to a new Pew Research Center survey, 94% of Americans say they have heard about the current state of the relationship between the Trump administration and the news media. And what they've seen does not reassure them: Large majorities feel the relationship is unhealthy and that the ongoing tensions are impeding Americans' access to important political news. Moreover, both of these concerns are widely shared across nearly all demographic groups, including large majorities of both Democrats and Republicans

On codimension two flats in Fermat-type arrangements

In the present note we study certain arrangements of codimension $2$ flats in projective spaces, we call them "Fermat arrangements". We describe algebraic properties of their defining ideals. In particular, we show that they provide counterexamples to an expected containment relation between ordinary and symbolic powers of homogeneous ideals.Comment: 9 page

The Modern News Consumer: News Attitudes and Practices in the Digital Era

Wave after wave of digital innovation has introduced a new set of influences on the public's news habits. Social media, messaging apps, texts and email provide a constant stream of news from people we're close to as well as total strangers. News stories can now come piecemeal, as links or shares, putting less emphasis on the publisher. And, hyper levels of immediacy and mobility can create an expectation that the news will come to us whether we look for it or not. How have these influences shaped Americans' appetite for and attitudes toward the news? What, in other words, are the defining traits of the modern news consumer?A new, two-part survey by Pew Research Center, conducted in early 2016 in association with the John S. and James L. Knight Foundation, reveals a public that is cautious as it moves into this more complex news environment and discerning in its evaluation of available news sources.To be sure, news remains an important part of public life. More than seven-in-ten U.S. adults follow national and local news somewhat or very closely – 65% follow international news with the same regularity. Fully 81% of Americans get at least some of this news through websites, apps or social networking sites. And, this digital news intake is increasingly mobile. Among those who get news both on desktop computers and mobile devices, more than half prefer mobile.In this digital news environment, the role of friends and family is amplified, but Americans still reveal strong ties to news organizations. The data also reinforce how, despite the dramatic changes witnessed over the last decade, the digital news era is still very much in its adolescence.These findings come from a two-part study which asked U.S. adults a wide range of questions about their news habits and attitudes, and then over the course of a subsequent week asked them in real time about news they had gotten in the last two hours. The first survey was conducted Jan. 12-Feb. 8, 2016, among 4,654 U.S. adults ages 18 and older who are members of Pew Research Center's American Trends Panel. The second survey consisted of 14 short, online surveys that were administered two per day from Feb. 24-March 1, 2016. Survey invitations were sent at different times each day, and responses were accepted for two hours after the invitations were sent. Panelists who completed the January wave on the web and reported that they get news online were asked to participate in the experiential study; 2,078 panelists participated and completed at least 10 of the 14 surveys

DYW domain structures imply an unusual regulation principle in plant organellar RNA editing catalysis

RNA上の遺伝情報を書き換える酵素であるDYWドメインの構造を解明 --植物オルガネラRNA編集のユニークな活性制御--. 京都大学プレスリリース. 2021-06-23.RNA editosomes selectively deaminate cytidines to uridines in plant organellar transcripts—mostly to restore protein functionality and consequently facilitate mitochondrial and chloroplast function. The RNA editosomal pentatricopeptide repeat proteins serve target RNA recognition, whereas the intensively studied DYW domain elicits catalysis. Here we present structures and functional data of a DYW domain in an inactive ground state and activated. DYW domains harbour a cytidine deaminase fold and a C-terminal DYW motif, with catalytic and structural zinc atoms, respectively. A conserved gating domain within the deaminase fold regulates the active site sterically and mechanistically in a process that we termed gated zinc shutter. Based on the structures, an autoinhibited ground state and its activation are cross-validated by RNA editing assays and differential scanning fluorimetry. We anticipate that, in vivo, the framework of an active plant RNA editosome triggers the release of DYW autoinhibition to ensure a controlled and coordinated cytidine deamination playing a key role in mitochondrial and chloroplast homeostasis

Distinguishing Between Factual and Opinion Statements in the News

In today's fast-paced and complex information environment, news consumers must make rapid-fire judgments about how to internalize news-related statements – statements that often come in snippets and through pathways that provide little context. A new Pew Research Center survey of 5,035 U.S. adults examines a basic step in that process: whether members of the public can recognize news as factual – something that's capable of being proved or disproved by objective evidence – or as an opinion that reflects the beliefs and values of whoever expressed it