3,317 research outputs found

    New Trees For The North Central States

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    OUR present forest trees are good. They are not perfect, though. They developed as the result of natural selection to fit various ecological niches in pre-white man forests. Our forest sites have changed and wild type trees are no longer in perfect equilibrium with their environment. Also, natural selection favored types which survived and reproduced best, not the types which would produce the best sawlogs or the best pulpwood

    Minimizing Secular J\u3csub\u3e2\u3c/sub\u3e Perturbation Effects on Satellite Formations

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    The purpose of this thesis is to examine the secular effects of the J2 oblateness perturbation on close proximity satellites. The main objective is to analyze the deputy’s position and velocity with respect to the chief and adjust the initial conditions of the deputy in an attempt to minimize the secular effects of J2 perturbations. Previous work has provided a method of obtaining a closed form solution for J2 invariance with co-planar orbits. Therefore, this work will primarily consider deputy orbits that experience motion outside of the chief’s orbital plane. Upon determining the required initial conditions, the invariance will be verified through numerical integration. The method will be considered successful when it is able to reduce secular effects to near numerical tolerances

    Advancements of In-Flight Mass Moment of Inertia and Structural Deflection Algorithms for Satellite Attitude Simulators

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    Experimental satellite attitude simulators have been used to test and analyze control algorithms; driving down risk before implementation on operational satellites. Ideally, the dynamic response of a terrestrial-based experimental satellite attitude simulator matches that of an on-orbit satellite. Unfortunately, gravitational disturbance torques and poorly characterized moments of inertia introduce uncertainty into the system dynamics leading to questionable experimental results. This research consists of three distinct, but related contributions to the field of developing robust satellite attitude simulators. First, existing approaches to estimate mass moments and products of inertia are evaluated followed by a proposition and evaluation of a new approach that increases both the accuracy and precision of these estimates using typical on-board satellite sensors. Next, to better simulate the micro-torque environment of space, a new approach to mass balancing satellite attitude simulator is presented, experimentally evaluated, and verified. Finally, we experimentally analyzed a control moment gyroscope singularity avoidance steering law

    Genetic Variation in Resistance of Scotch Pine to Zimmerman Pine Moth

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    (excerpt) Scotch pine (Pinus sylvestris L.), a forest tree introduced from Eurasia, is commonly planted for Christmas tree and timber use in northeastern United States. In this country it has numerous insect enemies. Among the most important are European pine shoot moth, Rhyacionia buoliana (Schiffermiieller); pine root collar weevil, Hylobius radicis Buchanan;,European pine sawfly, Neodiprion sertifer (Geoffroy); and eastern white-pine shoot borer, Eucosma gloriola Heinrich. Previous studies (Wright et al., 1967; Wright and Wilson, 1972; Steiner, 1974) have revealed large genetic differences in resistance to some of these pests. Another destructive pest is the Zimmerman pine moth, Dioryctria zimmermani (Grote). In 1968 this insect, native to the United States, was found attacking trees in a Scotch pine provenance test in southwestern Michigan. The attack rate was heavy and by 1973 it was obvious that some rams or varieties were attacked more heavily than others. This is a report on those differences

    Efficient many-body non-Markovian dynamics of organic polaritons

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    Funding: P.F.-W. acknowledges support from EPSRC (EP/T518062/1). B.W.L. and J.K. acknowledge support from EPSRC (EP/T014032/1).We show how to simulate a model of many molecules with both strong coupling to many vibrational modes and collective coupling to a single photon mode. We do this by combining process tensor matrix product operator methods with a mean-field approximation which reduces the dimension of the problem. We analyze the steady-state of the model under incoherent pumping to determine the dependence of the polariton lasing threshold on cavity detuning, light-matter coupling strength, and environmental temperature. Moreover, by measuring two-time correlations, we study quadratic fluctuations about the mean-field to calculate the photoluminescence spectrum. Our method enables one to simulate many-body systems with strong coupling to multiple environments, and to extract both static and dynamical properties.Publisher PDFPeer reviewe

    Estimating hypothetical estimands with causal inference and missing data estimators in a diabetes trial

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    The recently published ICH E9 addendum on estimands in clinical trials provides a framework for precisely defining the treatment effect that is to be estimated, but says little about estimation methods. Here we report analyses of a clinical trial in type 2 diabetes, targeting the effects of randomised treatment, handling rescue treatment and discontinuation of randomised treatment using the so-called hypothetical strategy. We show how this can be estimated using mixed models for repeated measures, multiple imputation, inverse probability of treatment weighting, G-formula and G-estimation. We describe their assumptions and practical details of their implementation using packages in R. We report the results of these analyses, broadly finding similar estimates and standard errors across the estimators. We discuss various considerations relevant when choosing an estimation approach, including computational time, how to handle missing data, whether to include post intercurrent event data in the analysis, whether and how to adjust for additional time-varying confounders, and whether and how to model different types of ICE separately

    Effect of collecting duct histology on renal cell cancer outcome.

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    PURPOSE: Collecting duct renal cell carcinoma is a rare entity. Recent surgical series of the condition showed conflicting results. We used an American population based data set to compare the survival experience of patients with collecting duct vs clear cell renal cell carcinoma. MATERIALS AND METHODS: Cases of collecting duct and clear cell renal cell carcinoma were identified in the Surveillance, Epidemiology and End Results program (2001 to 2005). Demographic and pathological characteristics at diagnosis were compared. Differences in disease specific survival were compared with univariate and multivariate Cox regression analysis. RESULTS: A total of 160 collecting duct renal cell carcinoma cases were present in the database from 2001 to 2005. In that time 33,252 clear cell renal cell carcinoma cases were diagnosed. Collecting duct renal cell carcinoma was more common in black than in white patients (23% vs 9%, p <0.001). Collecting duct renal cell carcinoma was more commonly T3+ than T2/T1 (33% vs 18%, p <0.001) and metastatic than regional/local (28% vs 17%, p = 0.001). Nephrectomy rates were similar (84% and 78%, p = 0.06). The 3-year disease specific survival rate was 58% and 79% for collecting duct and clear cell renal cell carcinoma, respectively. On multivariate analysis there was an increased mortality risk in patients with collecting duct vs clear cell renal cell carcinoma (HR 2.42, 95% CI 1.72-3.39, p = 0.001). CONCLUSIONS: Compared to patients with clear cell renal cell carcinoma those with collecting duct renal cell carcinoma have higher stage and are more often black. Even after adjusting for demographic, surgical and pathological factors disease specific survival is significantly worse in patients with collecting duct rather than clear cell renal cell carcinoma. Further research into the biology of this rare tumor is required to explain these results

    Preliminary study of the diversion of 283 m3 s-1 (10,000 cfs) from Lake Superior to the Missouri River basin

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    Trans-basin diversion is an established practice in this country. The High Plains Study authorized by the U.S. Congress in 1976 examined large-scale intra-basin diversion to replenish the depleted groundwater resources of the Ogallala aquifer. A portion of this intra-basin diversion could come from the Missouri River basin. This study presents the preliminary engineering associated with a large-scale diversion of Lake Superior water out of the Great Lakes and into the Missouri River basin in order to replace intra-basin water diverted for recharge of the Ogallala aquifer. The magnitude of the diversion is 283 m3 s-1 (10,000 cfs). The first cost of the conveyance structure is estimated at US 19.6billion.Thetotallengthisestimatedat984kmandthetotalstaticliftincludingfrictionlosses,statichead,andpumpingplantlossesis1130m.ItisestimatedthateighteenpumpingplantswillberequiredtoliftthewaterfromLakeSuperiorandtransportittotheMissouriBasin.Thisstudyestimatedanenergyrequirementtomovethiswaterequivalenttotheannualenergyproductionfromseven1000−MWplants.Initialcostsofthesepowerplantsisestimatedat19.6 billion. The total length is estimated at 984 km and the total static lift including friction losses, static head, and pumping plant losses is 1130 m. It is estimated that eighteen pumping plants will be required to lift the water from Lake Superior and transport it to the Missouri Basin. This study estimated an energy requirement to move this water equivalent to the annual energy production from seven 1000-MW plants. Initial costs of these power plants is estimated at 7 billion.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/24926/1/0000353.pd

    Aftershocks in Slowly Compressed Bulk Metallic Glasses: Experiments and Theory

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    We observe two distinct interevent time patterns in the slip avalanches of compressed bulk metallic glasses (BMGs). Small slip avalanches cluster together in time, but large slip avalanches recur roughly periodically. We compare the timing patterns of BMG slip avalanches with timing patterns of earthquakes and with the predictions of a mean-field model. The time clustering of small avalanches is similar to the known time clustering of earthquake foreshocks and aftershocks
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