Plant-level Productivity and Imputation of Missing Data in U.S. Census Manufacturing Data

Within-industry differences in measured plant-level productivity are large. A large literature has been devoted to explaining the causes and consequences of these differences. In the U.S. Census Bureau's manufacturing data, the Bureau imputes for missing values using methods known to result in underestimation of variability and potential bias in multivariate inferences. We present an alternative strategy for handling the missing data based on multiple imputation via sequences of classification and regression trees. We use our imputations and the Bureau's imputations to estimate within-industry productivity dispersions. The results suggest that there is more within-industry productivity dispersion than previous research has indicated. We also estimate relationships between productivity and market structure and between output prices, capital, and the probability of plant exit (controlling for productivity) based on the improved imputations. For some estimands, we find substantially different results than those based on the Census Bureau's imputations.

Stiffness matrices of carbon nanotube structures

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2005.Includes bibliographical references (leaf 28).An analytical modeling study was done to determine the stiffness matrices of the lattice structure of graphene, the planar building block of carbon nanotubes. Through continuum linear elastic analysis and a displacement-based finite element method, the global in-plane stiffness matrix for an arbitrary carbon atom of the lattice was found. The matrix provides the atomic level forces induced on members of the lattice structures due to local atomic displacements.by Kirk J. Samaroo.S.B

Adaptive model-based control systems and methods for controlling a gas turbine

Adaptive model-based control systems and methods are described so that performance and/or operability of a gas turbine in an aircraft engine, power plant, marine propulsion, or industrial application can be optimized under normal, deteriorated, faulted, failed and/or damaged operation. First, a model of each relevant system or component is created, and the model is adapted to the engine. Then, if/when deterioration, a fault, a failure or some kind of damage to an engine component or system is detected, that information is input to the model-based control as changes to the model, constraints, objective function, or other control parameters. With all the information about the engine condition, and state and directives on the control goals in terms of an objective function and constraints, the control then solves an optimization so the optimal control action can be determined and taken. This model and control may be updated in real-time to account for engine-to-engine variation, deterioration, damage, faults and/or failures using optimal corrective control action command(s)

On the mass segregation of stars and brown dwarfs in Taurus

We use the new minimum spanning tree (MST) method to look for mass segregation in the Taurus association. The method computes the ratio of MST lengths of any chosen subset of objects, including the most massive stars and brown dwarfs, to the MST lengths of random sets of stars and brown dwarfs in the cluster. This mass segregation ratio (Lambda_MSR) enables a quantitative measure of the spatial distribution of high-mass and low-mass stars, and brown dwarfs to be made in Taurus. We find that the most massive stars in Taurus are inversely mass segregated, with Lambda_MSR = 0.70 +/- 0.10 (Lambda_MSR = 1 corresponds to no mass segregation), which differs from the strong mass segregation signatures found in more dense and massive clusters such as Orion. The brown dwarfs in Taurus are not mass segregated, although we find evidence that some low-mass stars are, with an Lambda_MSR = 1.25 +/- 0.15. Finally, we compare our results to previous measures of the spatial distribution of stars and brown dwarfs in Taurus, and briefly discuss their implications.Comment: 10 pages, 8 figures, accepted for publication in MNRA

Characterization of extrasolar terrestrial planets from diurnal photometric variability

The detection of massive planets orbiting nearby stars has become almost routine, but current techniques are as yet unable to detect terrestrial planets with masses comparable to the Earth's. Future space-based observatories to detect Earth-like planets are being planned. Terrestrial planets orbiting in the habitable zones of stars-where planetary surface conditions are compatible with the presence of liquid water-are of enormous interest because they might have global environments similar to Earth's and even harbor life. The light scattered by such a planet will vary in intensity and colour as the planet rotates; the resulting light curve will contain information about the planet's properties. Here we report a model that predicts features that should be discernible in light curves obtained by low-precision photometry. For extrasolar planets similar to Earth we expect daily flux variations up to hundreds of percent, depending sensitively on ice and cloud cover. Qualitative changes in surface or climate generate significant changes in the predicted light curves. This work suggests that the meteorological variability and the rotation period of an Earth-like planet could be derived from photometric observations. Other properties such as the composition of the surface (e.g., ocean versus land fraction), climate indicators (for example ice and cloud cover), and perhaps even signatures of Earth-like plant life could be constrained or possibly, with further study, even uniquely determined.Comment: Published in Nature. 9 pages including 3 figure

Occasional Publications of the Bounds Law Library, Number Five: Commonplace Books of Law: A Selection of Law-Related Notebooks

Occasional Publications of the Bounds Law Library, Number Five contains the transcriptions of five notebooks, one ledger, and one diary as well as critical introductions to each piece and an essay on notebooks in legal culture. Primary sources include: a seventeenth century notebook authored by multiple anonymous persons likely to have been students in the Inns of Courts, Alexander Dorcas\u27 ledger used from 1785 to 1817, George Josiah Sturges Walker\u27s 1826 Litchfield Law School notebook, Thomas K. Jackson\u27s 1871 diary, James Thomas Kirk\u27s notebook used from 1891 to 1916, Jerome T. Fuller\u27s notebook used from 1925 to 1935, and Hugo L. Black\u27s notebook used from 1938 to 1940.https://scholarship.law.ua.edu/occasional_publications/1004/thumbnail.jp

The Biology of Chronic Graft-versus-Host Disease: A Task Force Report from the National Institutes of Health Consensus Development Project on Criteria for Clinical Trials in Chronic Graft-versus-Host Disease

Chronic graft-versus-host disease (GVHD) is the leading cause of late, nonrelapse mortality and disability in allogeneic hematopoietic cell transplantation recipients and a major obstacle to improving outcomes. The biology of chronic GVHD remains enigmatic, but understanding the underpinnings of the immunologic mechanisms responsible for the initiation and progression of disease is fundamental to developing effective prevention and treatment strategies. The goals of this task force review are as follows: • Summarize the current state of the science regarding pathogenic mechanisms of chronic GVHD and critical knowledge gaps. • Develop working hypotheses/overriding concepts for chronic GVHD development. • Define the usefulness of current preclinical models to test working hypotheses and ultimately discover and develop new therapeutic strategies. • Identify shortcomings of preclinical models, and define criteria for the creation of additional models to address these limitations. This document is intended as a review of our understanding of chronic GVHD biology and therapies resulting from preclinical studies, and as a platform for developing innovative clinical strategies to prevent and treat chronic GVHD

Laughing when you shouldn't Being "good" among the Batek of Peninsular Malaysia

Batek people describe their many laughter taboos with utmost seriousness, and in ethical terms of good and bad. Despite this, people often get it wrong—sometimes laughing all the more when the taboos forbid it. Because laughter can be ambiguous and impossible to control, being wrong can be accepted without the need for discussion or reflection. People thus act autonomously while holding deeply shared ethical orientations. Here, ethics can be both culturally predefined and shaped by individuals, as when it comes to laughter people draw on individual and shared concerns in an ad hoc, flexible manner. Laughter's tangled contradictions thus demonstrate that people's understandings of being “good” are mutually implicated with their understandings of what it means to be a person in relation to others