2,564 research outputs found

    Occurrence and mineral chemistry of high pressure phases, Portrillo basalt, southcentral New Mexico

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    Inclusions of clinopyroxenite, kaersutiteclinopyroxenite, kaersutite-rich inclusions, wehrlite and olivine-clinopyroxenite together with megacrysts of feldspar, kaersutite and spinel are found loose on the flanks of cinder cones, as inclusions within lava flows and within the cores of volcanic bombs in the Quaternary alkali-olivine basalt of the West Potrillo Mountains, southcentral New Mexico. Based on petrological and geochemical evidence the megacysts are interpreted to be phenocrysts which formed at great depth rather that xenocrysts of larger crystal aggregates. These large crystals are believed to have formed as stable phases at high temperature and pressure and have partially reacted with the basalt to produce subhedral to anhedral crystal boundaries. It can be demonstrated that the mafic and ultramafic crystal aggregates were derived from an alkali-basalt source rock generated in the mantle. The inclusions are believed to represent a cumulus body or bodies injected within the lower crust or upper mantle

    An Enhanced Spectroscopic Census of the Orion Nebula Cluster

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    We report new spectral types or spectral classification constraints for over 600 stars in the Orion Nebula Cluster (ONC) based on medium resolution R~ 1500-2000 red optical spectra acquired using the Palomar 200" and Kitt Peak 3.5m telescopes. Spectral types were initially estimated for F, G, and early K stars from atomic line indices while for late K and M stars, constituting the majority of our sample, indices involving TiO and VO bands were used. To ensure proper classification, particularly for reddened, veiled, or nebula-contaminated stars, all spectra were then visually examined for type verification or refinement. We provide an updated spectral type table that supersedes Hillenbrand (1997), increasing the percentage of optically visible ONC stars with spectral type information from 68% to 90%. However, for many objects, repeated observations have failed to yield spectral types primarily due to the challenges of adequate sky subtraction against a bright and spatially variable nebular background. The scatter between our new and our previously determined spectral types is approximately 2 spectral sub-classes. We also compare our grating spectroscopy results with classification based on narrow-band TiO filter photometry from Da Rio et al. (2012, finding similar scatter. While the challenges of working in the ONC may explain much of the spread, we highlight several stars showing significant and unexplained bona fide spectral variations in observations taken several years apart; these and similar cases could be due to a combination of accretion and extinction changes. Finally, nearly 20% of ONC stars exhibit obvious Ca II triplet emission indicative of strong accretion.Comment: Accepted to the Astronomical Journal; 37 pages, including 11 Figures and 3 Tables (one long table not reproduced here but available upon request or from the journal

    Microscopic calculations of collective flow probing the short-range nature of the nuclear force

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    Collisions between two nuclei have been modeled by numerical solution of classical approximations to the equations of motion of the constituent nucleons. For the reaction Nb(400 MeV/u)+Nb, a correlated sidewards emission of nucleons is observed. This is attributed to the repulsive short-range component of the nucleon-nucleon potential. A strong dependence of the flow angle on the impact parameter is observed, in accord with recent experimental results

    Evaluation of SLAR and thematic mapper MSS data for forest cover mapping using computer-aided analysis techniques

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    A set of training statistics for the 30 meter resolution simulated thematic mapper MSS data was generated based on land use/land cover classes. In addition to this supervised data set, a nonsupervised multicluster block of training statistics is being defined in order to compare the classification results and evaluate the effect of the different training selection methods on classification performance. Two test data sets, defined using a stratified sampling procedure incorporating a grid system with dimensions of 50 lines by 50 columns, and another set based on an analyst supervised set of test fields were used to evaluate the classifications of the TMS data. The supervised training data set generated training statistics, and a per point Gaussian maximum likelihood classification of the 1979 TMS data was obtained. The August 1980 MSS data was radiometrically adjusted. The SAR data was redigitized and the SAR imagery was qualitatively analyzed

    Production Costing Simulation in Thermal Power Systems Using the Mixture of Conditional Load Distribution Functions

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    In the 1980's the cumulant method became popular in reliability type algorithms for production cost evaluation, particularly in the evaluation of loss-of-load probability (LOLP), energy not served (ENS) and expected energy generation (EEG) of a set of generating units belonging to an electric power system. We developed a probabilistic model which is able to handle the uncertainty of both generating units and peak load forecast. In order to model the load including peak load forecast uncertainty we use conditional probability distributions. We show that the cumulant method is still applicable, as we can compute all the moments of the load duration curve (load distribution) without discretizing the density function of peak load forecast

    Up In The Air: How Airlines Can Improve Performance by Engaging Their Employees

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    [Excerpt] In the chapters that follow, we explore the competitive strategies and employment-relations strategies found in the United States (chapter 2) and in a range of other countries (chapter 3), before and after deregulation. In chapter 4 we analyze recent trends in quality, productivity, and costs, as well as employee outcomes. In chapter 5 we look more closely at selected new-entrant airlines and find a wide range of competitive and employment-relations strategies being used in this segment of the industry. In chapter 6, we examine several legacy airlines and identify the distinct strategies they have adopted to respond to competitive pressures from new-entrant airlines. These chapters each focus on selected U.S. airlines and those based in some other countries. In chapter 7, we summarize the strategies of new-entrant and legacy airlines, and offer lessons about how airlines can and do change their strategies over time in their efforts to compete more effectively. We offer recommendations, using our historical and comparative analyses to discuss whether a path forward can be identified that can provide a better balance in stakeholder outcomes. We end on a positive note, arguing that if the parties learn from their experiences and from each other, in the United States and other countries, there is a path that deals with the pressures building up in the airline industry, offering hope for a better balance between investor, employee, customer, and societal interests. Key questions are whether and from where the leadership will come to get the industry moving down this path or whether the main parties might not take such action before there is a perfect storm

    Evaluation of SLAR and thematic mapper MSS data for forest cover mapping using computer-aided analysis techniques

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    Separate holograms of horizontally (HH) and vertically (HV) polarized responses obtained by the APQ-102 side-looking radar were processed through an optical correlator and the resulting image was recorded on positive film from which black and white negative and positive prints were made. Visual comparison of the HH and HV images reveals a distinct dark band in the imagery which covers about 30% of the radar strip. Preliminary evaluaton of the flight line 1 date indicates that various features on the HH and HV images seem to have different response levels. The amount of sidelap due to the look angle between flight lines 1 and 2 is negligible. NASA mission #425 to obtain flightlines of NS-001 MSS data and supporting aerial photography was successfully flown. Flight line 3 data are of very good quality and virtually cloud-free. Results of data analysis for selection of test fields and for evaluation of waveband combination and spatial resolution are presented

    The Death of Tax Court Exceptionalism

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    This Article turns to another area where tax exceptionalism persists: the status of the United States Tax Court in the modern administrative state.4 The Tax Court plays an important role in the life of the federal judiciary. It functions as a tax specialist and hears over ninety-five percent of federal tax-related litigation." The overall volume of its work is impressive. As of 1995, for instance, the court had heard ap- proximately 360,000 cases with total tax liabilities reaching about 34billion.6Andthenumberofcasesfiled,closed,andstillpendinghasgenerallyriseneachyear.From2000to2010,theTaxCourtclosednearly260,000caseswhilenearly265,000caseswerefiledduringthesameperiod.7Regardlessofthislargenumberofcases,theTaxCourtstillhadover250,000casespending.8Ofthecasesclosed,thecourtreleasedwrittenopinionsforover8,400ofthem.19Thedollaramountisalsostaggering.In2006,theTaxCourtclosedcaseswithanaggre−gatetaxliabilityofnearly34 billion.6 And the number of cases filed, closed, and still pending has generally risen each year. From 2000 to 2010, the Tax Court closed nearly 260,000 cases while nearly 265,000 cases were filed during the same period.7 Regardless of this large number of cases, the Tax Court still had over 250,000 cases pending.8 Of the cases closed, the court released written opinions for over 8,400 of them.19 The dollar amount is also staggering. In 2006, the Tax Court closed cases with an aggre- gate tax liability of nearly 7.4 billion.20 From fiscal year 2008 to 2012, the Tax Court closed cases with an aggregate amount exceeding $33 billion.
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