A database of number fields

We describe an online database of number fields which accompanies this paper The database centers on complete lists of number fields with prescribed invariants. Our description here focuses on summarizing tables and connections to theoretical issues of current interest.Comment: 25 pages, 1 figur

Mineral Trioxide Aggregate Material Use in Endodontic Treatment: A Review of the Literature

Objective The purpose of this paper was to review the composition, properties, biocompatibility, and the clinical results involving the use of mineral trioxide aggregate (MTA) materials in endodontic treatment. Methods Electronic search of scientific papers from January 1990 to August 2006 was accomplished using PubMed and Scopus search engines (search terms: MTA, GMTA, WMTA, mineral AND trioxide AND aggregate). Results Selected exclusion criteria resulted in 156 citations from the scientific, peer-reviewed dental literature. MTA materials are derived from a Portland cement parent compound and have been demonstrated to be biocompatible endodontic repair materials, with its biocompatible nature strongly suggested by its ability to form hydroxyappatite when exposed to physiologic solutions. With some exceptions, MTA materials provide better microleakage protection than traditional endodontic repair materials using dye, fluid filtration, and bacterial penetration leakage models. In both animal and human studies, MTA materials have been shown to have excellent potential as pulp-capping and pulpotomy medicaments but studies with long-term follow-up are limited. Preliminary studies suggested a favorable MTA material use as apical and furcation restorative materials as well as medicaments for apexogenesis and apexification treatments; however, long-term clinical studies are needed in these areas. Conclusion MTA materials have been shown to have a biocompatible nature and have excellent potential in endodontic use. MTA materials are a refined Portland cement material and the substitution of Portland cement for MTA products is presently discouraged. Existing human studies involving MTA materials are very promising, however, insufficient randomized, double-blind clinical studies of sufficient duration exist involving MTA for all of its clinical indications. Further clinical studies are needed in these areas

Agreement in Principle: A Compromise for Activist Shareholders from the UK Stewardship Code

Equity ownership in the United States and Europe is now highly concentrated in the hands of institutional investors, which gives rise to new problems of agency and corporate governance. These large investment intermediaries, such as mutual funds, specialize in maximizing beneficial owner value based on short-term performance benchmarks but lack the expertise and incentive to actively engage corporate boards on business strategy and governance matters. Instead, institutional investors are rationally reticent, meaning that they are willing to respond to governance proposals but not to propose them. Activist shareholders may offer an endogenous solution to address latent activism in institutional intermediaries and, ultimately, spur the effective monitoring of corporate boards. Activist shareholders, such as hedge funds, often achieve their business strategy and governance objectives by obtaining toehold positions in a corporation and soliciting support from institutional investors for their governance proposals. However, this solution is in jeopardy. Recently proposed regulatory changes in the United States track adopted legislation in the United Kingdom and Europe, and pose a threat to domestic activist shareholder success. This Note argues that incorporation of the UK Stewardship Code\u27s Principle 5 into the U.S. regulatory scheme may help alleviate the potentially chilling effects of the proposed rule-making on shareholder activists

Object or context: an ecologist\u27s view of ecosystem management

There is a need to recognize a duality of object and context perspectives on ecosystems, and a need to synthesize the two in a way which clearly identifies the distinctions and links between them. This paper proposes a new terminology of spatially-fixed atoms, diffuse entities, and molecules to represent ecological entities; and it argues the need for identifying the processes linking them, Ecosystem management will require development of simple, mechanistic models of local ecosystem dynamics which incorporate basic successional dynamics, disturbance response, and management response. It will require development of statistical, predictive models of ecosystem distribution on the landscape. And it will require development of simple, spatial integration algorithms linked to a spatially explicit database in a GIS

Molecular basis for resistance of acanthamoeba tubulins to all major classes of antitubulin compounds

Tubulin is essential to eukaryotic cells and is targeted by several antineoplastics, herbicides, and antimicrobials. We demonstrate that Acanthamoeba spp. are resistant to five antimicrotubule compounds, unlike any other eukaryote studied so far. Resistance correlates with critical amino acid differences within the inhibitor binding sites of the tubulin heterodimers

Publishing philosophy Open Access without a Particle Collider

Open Access often appears to be a monolithic concept, covering all fields of research and publication. However, in practice its application is to a large extent determined by the needs and resources available to different academic communities. In this post, Bryan W. Roberts and David Teira discuss open access publishing in philosophy and how an emerging generation of open publications has developed to meet the needs of an academic discipline where funding for publication is scarce