Curvature singularity of the distributional BTZ black hole geometry

For the non-rotating BTZ black hole, the distributional curvature tensor field is found. It is shown to have singular parts proportional to a $\delta$-distribution with support at the origin. This singularity is related, through Einstein field equations, to a point source. Coordinate invariance and independence on the choice of differentiable structure of the results are addressed.Comment: Latex, 7 page

Condensed-phase signaling can expand kinase specificity and respond to macromolecular crowding

Phase separation can concentrate biomolecules and accelerate reactions. However, the mechanisms and principles connecting this mesoscale organization to signaling dynamics are difficult to dissect because of the pleiotropic effects associated with disrupting endogenous condensates. To address this limitation, we engineered new phosphorylation reactions within synthetic condensates. We generally found increased activity and broadened kinase specificity. Phosphorylation dynamics within condensates were rapid and could drive cell-cycle-dependent localization changes. High client concentration within condensates was important but not the main factor for efficient phosphorylation. Rather, the availability of many excess client-binding sites together with a flexible scaffold was crucial. Phosphorylation within condensates was also modulated by changes in macromolecular crowding. Finally, the phosphorylation of the Alzheimer’s-disease-associated protein Tau by cyclin-dependent kinase 2 was accelerated within condensates. Thus, condensates enable new signaling connections and can create sensors that respond to the biophysical properties of the cytoplasm

Closed-Form Expressions for the Radiation Properties of Nanoloops in the Terahertz, Infrared and Optical Regimes

This work was supported in part by the Spanish Ministry of Education through the Commission Fulbright Program “Salvador de Madariaga” under Grant PR X14/00320, in part by the Spanish and Andalusian Research Programs under Grant TEC2013-48414-C3-01 and Grant P12-TIC-1442, and in part by the Center for Nanoscale Science, NSF Materials Research Science a nd Engineering Center, under Award DMR-1420620Since the pioneering work of Heinrich Hertz, perfect-electric conductor (PEC) loop antennas for RF appli- cations have been studied extensively. Meanwhile, nanoloops are promising in the optical regime for their applications in a wide range of emerging technologies. Unfortunately, analytical expressions for the radiation properties of conducting loops have not been extended to the optical regime. This paper presents closed-form expressions for the electric fields, total radiated power, directivity, and gain for thin-wire nanoloops operating in the terahertz, infrared and optical regimes. This is accomplished by extending the formulation for PEC loops to include the effects of dispersion and loss. The expressions derived for a gold nanoloop are implemented and the results agree well with full-wave computational simulations, but with a speed increase of more than 300 × . This allows the scientist or engineer to quickly prototype designs and gain a deeper understanding of the underlying physics. Moreover, through rapid numerical experimentation, these closed-form expressions made possible the discovery that broadband superdirectivity occurs naturally for nanoloops of a specific size and material composition. This is an unexpected and potentially transformative result that does not occur for PEC loops. Additionally, the Appendices give useful guidelines on how to efficiently compute the required integrals.Spanish Ministry of Education through the Commission Fulbright Program “Salvador de Madariaga” under Grant PR X14/00320Spanish and Andalusian Research Programs under Grant TEC2013-48414-C3-01 and Grant P12-TIC-1442Center for Nanoscale Science, NSF Materials Research Science a nd Engineering Center, under Award DMR-142062

Infecção intestinal causada por Neoechinorhynchus buttnerae (Acanthocephala: Neochinorhynchidae) em híbridos de tambatingas cultivados na Amazônia Oriental.

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Sustainable Agriculture for Alaska and the Circumpolar North: Part I. Development and Status of Northern Agriculture and Food Security

Alaska is food insecure, importing the vast majority of its agricultural products and commodities and maintaining a minimal year-round food supply. Much of the circumpolar North, with some notable exceptions, is also food insecure and similarly reliant on foods imported from outside regions. The stark differences in food policies, food security, and overall production that exist between individual countries and regions of the circumpolar North are likely due to variability in their physical and social environments, their varying agrarian histories (e.g., Old World vs. New World), and their different first-hand experiences with food insecurity, often during wartime. Alaska’s agricultural history is unique, having progressed through periods of exploration and expansion and having experienced both success and failure. Agriculture exists today in Alaska as an underdeveloped natural resource – based industry that has been shaped by historical events and developmental processes and continually influenced by a host of environmental and socioeconomic factors. Continued interaction between stakeholders, agencies, and others will help the industry to progress to the point of meeting increasing food demands and improving food security.L’Alaska est aux prises avec l’insécurité alimentaire en ce sens que l’État importe la grande majorité de ses produits et marchandises agricoles et qu’il maintient un approvisionnement alimentaire minime à l’année. Malgré quelques exceptions remarquables, une grande partie du Nord circumpolaire souffre d’insécurité alimentaire et dépend de produits alimen­taires importés d’autres régions. Les importantes différences qui existent en matière de politiques alimentaires, d’insécurité alimentaire et de production générale entre les pays et les régions du Nord circumpolaire sont vraisemblablement attribuables aux divers environnements physiques et sociaux, à leur histoire agraire variée (celle de l’Ancien Monde par opposition à celle du Nouveau Monde) et à leurs différentes expériences directes en matière d’insécurité alimentaire, plus particulièrement en temps de guerre. L’histoire agricole de l’Alaska est unique, ayant passé par des périodes d’exploration et d’expansion, et connu tant des réussites que des échecs. De nos jours, l’agriculture en Alaska est une industrie sous-développée de ressources naturelles qui a été façonnée par des événements historiques et des processus développementaux, continuellement influencée par une panoplie de facteurs environnementaux et socioéconomiques. Les efforts collectifs déployés par les parties prenantes, les organismes et d’autres parties aideront cette industrie à progresser au point de pouvoir répondre à la demande croissante de nourriture et d’améliorer la sécurité alimentaire

Natural based products for cleaning copper and copper alloys artefacts

Copper alloys objects can deteriorate their conservation state through irreversible corrosion. Since in the cultural heritage field every artefact is unique and any loss irreplaceable, solutions for conservation are needed. Hence, there is the necessity to stop the corrosion process with a suitable cleaning and conservation process to avoid further degradation processes without changing its morphological aspect. Chelating solutions are commonly used in chemical cleaning, mainly sodium salts of ethylenediaminetetraacetic acid (EDTA). However, it is resistant to water purification procedures and is not biodegradable. The goal of this study was to see if applying an ecologically friendly chelating agent as an alternative to EDTA cleaning procedures for cultural heritage was suitable. In this study were chosen six natural-based chelators that could be a new green non-toxic alternative to EDTA in corrosion-inhibiting properties. They were tested for cleaning copper artefacts exposed to atmospheric environment in polluted areas. The study considered four amino acids, a glucoheptonate (CSA) and an industrial green chelator (GLDA). The effectiveness was tested on corrosion copper compounds and on laboratory corroded copper sheets. Finally, the cleaning efficacy was tested on four Roman coins and a modern copper painting. To define the cleaning efficacy, surface analytical investigations have been carried out by means ICP-OES, UV-VIS, µ-Raman, spectro-colorimetry, XRD and FTIR. Among the amino acids, alanine was the most effective, showing an unaltered noble patina and a good effective copper recovery from corrosion patinas