1,963 research outputs found
Samuel McLean CdV (from House Representatives, 38th Congress Album)
No full textThe photograph features a portrait of Samuel McLean (United States Delegate from the Montana Territory). On its verso, it has a Mathew Brady backmark. The CdV is included in an album containing CdVs of Lincoln\u27s cabinet members as well as senators and representatives from the 38th Congress.https://scholarsjunction.msstate.edu/fvw-cdv/1214/thumbnail.jp
An algorithm for U-Pb isotope dilution data reduction and uncertainty propagation
No full textHigh-precision U-Pb geochronology by isotope dilution-thermal ionization mass spectrometry is integral to a variety of Earth science disciplines, but its ultimate resolving power is quantified by the uncertainties of calculated U-Pb dates. As analytical techniques have advanced, formerly small sources of uncertainty are increasingly important, and thus previous simplifications for data reduction and uncertainty propagation are no longer valid. Although notable previous efforts have treated propagation of correlated uncertainties for the U-Pb system, the equations, uncertainties, and correlations have been limited in number and subject to simplification during propagation through intermediary calculations. We derive and present a transparent U-Pb data reduction algorithm that transforms raw isotopic data and measured or assumed laboratory parameters into the isotopic ratios and dates geochronologists interpret without making assumptions about the relative size of sample components. To propagate uncertainties and their correlations, we describe, in detail, a linear algebraic algorithm that incorporates all input uncertainties and correlations without limiting or simplifying covariance terms to propagate them though intermediate calculations. Finally, a weighted mean algorithm is presented that utilizes matrix elements from the uncertainty propagation algorithm to propagate random and systematic uncertainties for data comparison between other U-Pb labs and other geochronometers. The linear uncertainty propagation algorithms are verified with Monte Carlo simulations of several typical analyses. We propose that our algorithms be considered by the community for implementation to improve the collaborative science envisioned by the EARTHTIME initiative.National Science Foundation (U.S.) (Grants EAR‐0746205)National Science Foundation (U.S.) (Grants EAR‐0930166
Engineering cyber infrastructure for U-Pb geochronology: Tripoli and U-Pb_Redux
No full textIn the past decade, major advancements in precision and accuracy of U-Pb geochronology, which stem from improved sample pretreatment and refined measurement techniques, have revealed previously unresolvable discrepancies among analyses from different laboratories. One solution to evaluating and resolving many of these discrepancies is the adoption of a common software platform that standardizes data-processing protocols, enabling robust interlaboratory comparisons. We present the results of a collaboration to develop cyber infrastructure for high-precision U-Pb geochronology based on analyzing accessory minerals by isotope dilution-thermal ionization mass spectrometry. This cyber infrastructure implements an architecture specifying the workflows of data acquisition, statistical filtering, analysis and interpretation, publication, community-based archiving, and the compilation and comparison of data from different laboratories. The backbone of the cyber infrastructure consists of two open-source software programs: Tripoli and U-Pb_Redux. Tripoli interfaces with commercially available mass spectrometers using standardized protocols, statistical filtering, and interactive visualizations to aid the analyst in preparing raw data for analysis in U-Pb_Redux. U-Pb_Redux implements the architecture by orchestrating the analyst's workflow with interactive visualizations and provides data reduction and uncertainty propagation that support data interpretations. Finally, U-Pb_Redux enables production of publication-ready graphics and data tables, the archiving of results, and the comparative compilation of archived results to support cooperative science
Protracted timescales of lower crustal growth at the fast-spreading East Pacific Rise
No full textAuthor Posting. © The Author(s), 2011. This is the author's version of the work. It is posted here by permission of Nature Publishing Group for personal use, not for redistribution. The definitive version was published in Nature Geoscience 5 (2012): 275-278, doi:10.1038/ngeo1378.Formation of the oceanic crust at mid-ocean ridges is a fundamental component of
plate tectonics. A majority of the crust at many ridges is composed of plutonic rocks
that form by crystallization of mantle-derived magmas within the crust. Recent
application of U/Pb dating to samples from in-situ oceanic crust has begun to
provide exciting new insight into the timing, duration and distribution of
magmatism during formation of the plutonic crust1-4. Previous studies have focused
on samples from slow-spreading ridges, however, the time scales and processes of
crustal growth are expected to vary with plate spreading rate. Here we present the
first high-precision dates from plutonic crust formed at the fast-spreading East
Pacific Rise (EPR). Individual zircon minerals yielded dates from 1.420–1.271
million years ago, with uncertainties of ± 0.006–0.081 million years. Within
individual samples, zircons record a range of dates of up to ~0.124 million years,
consistent with protracted crystallization or assimilation of older zircons from
adjacent rocks. The variability in dates is comparable to data from the Vema
lithospheric section on the Mid-Atlantic Ridge (MAR)3, suggesting that time scales
of magmatic processes in the lower crust may be similar at slow- and fast-spreading
ridges.This research was partially funded by NSF grant OCE-0727914 (SAB), a Cardiff
University International Collaboration Award (CJL) and NERC grant NE/C509023/1
(CJM).2012-07-2
Brochure: Anonymous, "The Commons of Mclean," Undated
No full textTextual: booklet, original; 11” x 4.75” (27.9 cm x 12.1 cm)Brochure by an anonymous author entitled "The Commons of Mclean" that is undated. This brochure is for The Commons development in Mclean, Virginia. The Commons was a development that consisted of garden apartments, townhouses, and recreational facilities. The brochure contains floor plans for three different townhouse designs as well as a map showing the location of the development. The brochure also has a map that shows the final layout of the Commons. Gates, Hudson and Associates currently manage the Commons. Planned Community Archives Collection, rm07.0
In Quest of Tolstoy
No full textLev Tolstoy has held the attention of mankind for well over a century. A supremely talented artist, whose novels and short stories continue to entrance readers all over the world, he was at the same time a fearless moral philosopher who explored and challenged the fundamental bases of human society—political, economic, legal, and cultural. Hugh McLean, Professor Emeritus of Russian literature at the University of California, Berkeley, has been studying and writing about Tolstoy for many years. In these essays he investigates some of the numerous puzzles and paradoxes in the Tolstoyan heritage, engaging both with Tolstoy the artist, author of those incomparable novels, and Tolstoy the thinker, who, from his impregnable outpost at Yasnaya Polyana, questioned the received ideas and beliefs of the whole civilized world. In two concluding essays, "Tolstoy beyond Tolstoy," McLean deals with the impact of Tolstoy on such diverse figures as Ernest Hemingway and Isaiah Berlin
192 - Ian Cook McLean
No full textCurrently, most in vitro experimental models of the intestine rely upon cell lines, and consequently, lack the diverse representation of cells present in vivo. Slices of intestine, removed from living organisms, offer a better representation of in vivo physiology. However, current techniques for maintaining intestinal tissue in vitro are not capable of recapitulating the in vivo environment.
This project utilizes 3D printing and microfluidic principles to design a device that delivers differential flows of media across the two surfaces of intestinal tissue. The device will enable the investigation of complex biological questions that previous models have been unable to address
Adjusted instruments for evaluating the efficiency of implementing knowledge management systems
No full textThe present paper aims to present the results of a scientific research based on application of DeLone and McLean model, for evaluating the efficiency of implementing a knowledge management system into a Romanian university. The model was made operational according to the suggestions of the author and was adjusted to the realities of the higher education institutions.knowledge management, efficiency, DeLone and McLean model
A Continuous Biochemical Reactor Study Using Mixed Microbial Cultures
No full textTitle: A Continuous Biochemical Reactor Study Using Mixed Microbial Cultures, Author: Howard A. McLean, Location: ThodeA completely-mixed biochemical reactor was used to study a mixed microbial culture using soluble organic carbon in the form of glucose as a growth limiting nutrient. The effect of various flow rates and feed concentrations was determined by evaluating the corresponding variations in unit organism growth rate, yield and effluent carbon concentration. The effluent carbon concentration was independent of flow rate and feed concentrations for the range studied. The unit growth rate was similarly independent of the feed concentration but varied directly as the flow rate. No trend indicated that yield varied with either flow rate or
feed concentration. Large variations in yield often occurred at any one condition due to changes in the mixed microbial population. However, the reason for this microbial variation was not determined.ThesisMaster of Engineering (ME
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