Study of advanced fuel system concepts for commercial aircraft and engines

The impact on a commercial transport aircraft of using fuels which have relaxed property limits relative to current commercial jet fuel was assessed. The methodology of the study is outlined, fuel properties are discussed, and the effect of the relaxation of fuel properties analyzed. Advanced fuel system component designs that permit the satisfactory use of fuel with the candidate relaxed properties in the subject aircraft are described. The two fuel properties considered in detail are freezing point and thermal stability. Three candidate fuel system concepts were selected and evaluated in terms of performance, cost, weight, safety, and maintainability. A fuel system that incorporates insulation and electrical heating elements on fuel tank lower surfaces was found to be most cost effective for the long term

Explorations in the Deictic Field

This paper focuses on the ways in which speakers make reference to themselves, to one another, and to objects in the everyday settings of talk. Drawing on research in linguistic anthropology, sociology, and linguistics, it proposes an approach to language based on the concepts of communicative practice, deictic field, and socially constituted objects of reference. Found in all human languages, deictics are expressions like English "this," "that," "here," and "there" whose meanings depend strictly on the occasions of their use. This paper critically examines current approaches to deixis, proposes an alternative framework based on the sociological concept of field, and applies this framework to deictic practice in Yucatec Maya. Drawing on the work of Buhler, Goffman, and Bourdieu, it adapts the field concept to the semiotic structure of deixis. The result is an analysis of deictic practice as an emergent construal of socially embedded deictic fields involving practical equivalences, counterpart relations among objects, and rules of thumb

The plurality of temporal reckoning among the Maya

This paper presents an overview of time reckoning in several domains of Maya language and culture, as observed in the Sierra region of Yucatan in the last decades of the twentieth century. It demonstrates that multiple systems of temporal reckoning and orientation co-operate in the traditional domains of daily practice, and it attempts to formulate principles by which different systems are combined in actional frameworks It is argued that most cyclicity in contemporary Yucatec Maya is derivative of natural or social processes and that in rituals it results from the translation of spatial arrays into temporal sequences. The paper tracks the varieties of cyclic and spiral time measurement in several domains, where different units and levels of temporal measurement and different rhythms are observed: 1) the field of co-presence in which utterances are performed, including deictic time; 2) the diurnal cycle and its actional correlates; 3) the agricultural cycles, the forest life cycle and the labor they imply; 4) domestic space whose time involves in addition the age and generational relations among co-residents; 5) ritual time in Yucatec shamanic practice, which is given special attention. Ritual practices display the most dramatic cyclicity, compounded by sedimentation, deictic time, historical time and cosmological space. Their chronometric dimensions are so elaborate that rituals can be considered a time machine. Viewed from practice, there is no single modality of Maya time, but a diachronic synchronization of multiple temporal streams which produces time as the variable product of tzol reproduction and meyah ‘work.’Este artículo presenta una vista de conjunto de las formas de comput del tiempo en varios dominios de la cultura y de la lengua maya, tal como fueron observadas en la región de la sierra de Yucatán en los últimos decenios del siglo xx. Se demuestra que una multiplicidad de sistemas de cálculo y orientación temporales cooperan en los ámbitos tradicionales de las prácticas cotidianas, y se intenta formular ciertos principios que rigen la combinación de los diferentes sistemas dentro de los marcos de la acción. Se arguye que la mayor parte de las configuraciones cíclicas de los mayas yucatecos contemporáneos puede derivarse de procesos naturales o sociales y que, en el ritual, resulta de la traducción de disposiciones espaciales en secuencias temporales. El autor rastrea la variedad de mediciones del tiempo en varios dominios, para los cuales se observa una diversidad tanto de unidades y niveles de medida temporal como de ritmos: 1) el campo de co-presencia en el cual ocurren las enunciaciones, incluyendo el tiempo deíctico; 2) el ciclo diurno y sus correlatos accionales ; 3) los ciclos agrícolas y silvestres, y las labores que implican ; 4) el espacio doméstico que supone además la edad y las relaciones intergeneracionales entre coresidentes. 5) el tiempo ritual en las prácticas chamanicas yucatecas, al cual se presta mayor atención. Éstas prácticas manifiestan la forma de ciclicidad más dramática, compuesta por sedimentación, tiempo deíctico, tiempo cíclico y espacio cosmológico. Sus dimensiones cronométricas son tan elaboradas que los rituales pueden ser considerados como máquinas del tiempo. Del punto de vista de las prácticas, no existe una modalidad del tiempo maya única, sino una sincronización diacrónica de corrientes temporales múltiples que hacen del tiempo un producto variable del ordenamiento ‘tzol’ y del trabajo ‘meyah’.Cet article présente une vue d’ensemble des formes de comput du temps dans plusieurs domaines de la culture et de la langue maya, telle qu’observée dans la région centrale du Yucatán durant les dernières décennies du xxe siècle. Il s’attache à démontrer qu’une multiplicité de systèmes de calcul et d’orientation temporels sont conjointement à l’œuvre dans les domaines traditionnels des pratiques quotidiennes. Il tente de formuler certains des principes qui régissent la combinaison des différents systèmes au sein de cadres actionnels. L’auteur argumente que la plupart des configurations cycliques des Mayas yucatèques contemporains sont dérivées de processus naturels ou sociaux et que, dans le rituel, elles résultent de la traduction de dispositions spatiales dans des séquences temporelles. Il recherche la variété des mesures du temps dans plusieurs domaines, où on observe une diversité tant d’unités et niveaux de mesure temporelle que de rythmes : 1) le champ de co-présence au sein duquel prennent place les énonciations, incluant le temps déictique ; 2) le cycle diurne et ses corrélats actionnels ; 3) les cycles agricoles et sylvestres et les tâches qu’ils impliquent ; 4) l’espace domestique pour lequel s’ajoutent l’âge et les relations intergénérationnelles entre co-résidents ; 5) le temps rituel dans les pratiques chamaniques yucatèques, auquel il est porté une particulière attention. Ces pratiques manifestent la forme de cyclicité la plus dramatique, composée par sédimentation de temps déictique, temps historique et espace cosmologique. Leurs dimensions chronométriques sont si élaborées que les rituels peuvent être considérés comme des machines à voyager dans le temps. Du point de vue des pratiques, il n’y a pas une simple modalité du temps maya, mais plutôt une synchronisation diachronique de courants temporels multiples qui fait du temps une variable soumise à l’ordonnancement ‘tzol’ et au travail ‘meyah’

Présent passé, passé présent : les enjeux de l’histoire régressive

L’anthropologie s’est longtemps interrogé sur le rapport entre la société comme système actuel d’une part, et l’histoire plus ou moins longue dont elle est issue, de l’autre. Sont impliqués les disciplines de l’archive et du terrain, la diachronie de l’histoire et la synchronie dynamique du présent, le passage du passé au présent, et son inverse, la contingence et la necessité, la valeur des pratiques culturelles du présent comme archive vivante du passé, et la réproduction des « visions » culturelles. Toutes ces problématiques sont en jeu dans le projet de l’histoire regressive selon Nathan Wachtel. qui a ouvert tout un horizon de recherches Americanistes. Ces recherches comprennent « la nouvelle philologie » de Lockhart et de ses élèves, les recherches de VR Bricker, M. Edmonson, NM Farriss, G. Jones, d’Aurore Monod Becquelin et de moi-même en zone Maya, et une litterature importante qui réanalyse le monde colonial dans des termes qui auraient été impensables pour les chercheurs de générations antérieurs. Une esquisse des grands débats contemporains dans la zone maya présente la possibilité de mieux cerner le génératif cette approche de la societé dans l’histoire

Cytotoxicity and Dentin Permeability of Carbamide Peroxide and Hydrogen Peroxide Vital Bleaching Materials, in vitro

There has been recent concern about the inadvertent exposure of dentin with patent tubules as well as gingiva to bleaching systems containing 10-15% carbamide peroxide or 2-10% hydrogen peroxide for more than a few minutes. The aims of the present study were: (1) to determine the cytotoxicity of dilutions of hydrogen peroxide in cell culture; (2) to measure hydrogen peroxide diffusion from bleaching agents through dentin in vitro; and (3) to determine the risk of hydrogen peroxide-induced cytotoxicity from exposure of dentin to these vital bleaching agents. The 50% inhibitory dose (ID50) of hydrogen peroxide to succinyl dehydrogenase activity in cultured cells was found to be 0.58 mmol/L after 1 h. All bleaching materials demonstrated diffusion of hydrogen peroxide through dentin in an "in vitro pulp chamber" device. The one- and six-hour diffusates of all bleaching agents through 0.5-mm dentin exceeded the ID50 in monolayer cultures. Inhibition of succinyl dehydrogenase activity corresponded to the amount of hydrogen peroxide that can rapidly diffuse through dentin in vitro and reach concentrations which are toxic to cultured cells in less than 1 h.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66707/2/10.1177_00220345930720051501.pd

Interactive Online Tool for Educating the Public About Landscape Conservation

Landscape-scale conservation planning performed in a systematic and transparent manner is becoming more common as it is increasingly evident that ecological processes are being affected at large spatial scales. The Appalachian Landscape Conservation Cooperative undertook a 15-state landscape conservation planning project, resulting in a landscape conservation design called NatureScape. To facilitate NatureScape\u27s implementation by groups and individuals participating in on-the-ground landscape conservation, we developed an online decision support tool. This tool has the potential to assist Extension services in delivering research-based information to varied stakeholders as they make land use decisions

Common Cerambycid Pheromone components as attractants for Longhorn Beetles (Cerambycidae) breeding in ephemeral oak substrates in Northern Europe

Longhorn beetles are ecologically important insects in forest ecosystems as decomposers of woody substrates, microhabitat engineers, and as components of forest food webs. These species can be greatly affected both positively and negatively by modern forestry management practices, and should be monitored accordingly. Through headspace sampling, coupled gas chromatography-electroantennography, gas chromatography-mass spectrometry, and field bioassays, we identified two compounds, 2-methyl-1-butanol and 3-hydroxy-2-hexanone, that constitute aggregation-sex pheromone attractants of three cerambycid species which breed primarily in different types of fresh, recently dead oak wood in Northern Europe: Pyrrhidium sanguineum (L.), Phymatodes alni ssp. alni (L.), and Phymatodes testaceus (L.) (Cerambycinae: Callidiini). Analyses of headspace volatiles collected from live insects indicated that the male-produced aggregation-sex pheromone of P. sanguineum is a 1–15:100 blend of (R)-2-methyl-1-butanol and (R)-3-hydroxy-2-hexanone, whereas the corresponding ratios for P. alni were 70–110:100. In field bioassays, adult P. sanguineum and P. alni were significantly attracted to multiple blends with varying ratios of the two compounds. When tested individually, the compounds were minimally attractive. In contrast, adult P. testaceus exhibited nonspecific attraction to both of the individual compounds and to different blends, despite the hydroxyketone not being part of its pheromone, which consists of (R)-2-methyl-1-butanol alone. Overall, our results suggest that a blend of 50:100 of racemic 2-methyl-1-butanol and 3-hydroxy-2-hexanone is appropriate for parallel, cost-efficient pheromone-based monitoring of all three species. In particular, these species could serve as useful indicators of how modern forestry practices affect a whole guild of saproxylic insects that require ephemeral deadwood substrates for successful breeding