3,083 research outputs found
Portable self-powered device detects internal flaws in tubular structures
Portable probe and eddy-current-sensitive circuitry detects internal flaws or hard spot impurities in an electrically conductive tubular channel by recording the conductivity change at the defect point
Transistor circuit increases range of logarithmic current amplifier
Circuit increases the range of a logarithmic current amplifier by combining a commercially available amplifier with a silicon epitaxial transistor. A temperature compensating network is provided for the transistor
Testing for lack of fit in blocked and split-plot response surface designs
Textbooks on response surface methodology emphasize the importance of lack-of-fit tests when fitting response surface models, and stress that, to be able to test for lack of fit, designed experiments should have replication and allow for pure-error estimation. In this paper, we show how to obtain pure-error estimates and how to carry out a lack-of-fit test when the experiment is not completely randomized, but a blocked experiment, a split-plot experiment, or any other multi-stratum experiment. Our approach to calculating pure-error estimates is based on residual maximum likelihood (REML) estimation of the variance components in a full treatment model. It generalizes the one suggested by Vining et al. (2005) in the sense that it works for a broader set of designs and for replicates other than center point replicates. Our lack-of-fit test also generalizes the test proposed by Khuri (1992) for data from blocked experiments because it exploits replicates other than center point replicates and works for split-plot and other multi-stratum designs as well. We provide analytical expressions for the test statistic and the corresponding degrees of freedom, and demonstrate how to perform the lack-of-fit test in the SAS procedure MIXED. We re-analyze several published data sets and discover a few instances in which the usual response surface model exhibits significant lack of fit
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Xenon isotopes in nanodiamonds and other presolar grains
pdf freely available cb 18/07/0
The fluorine-NHC gauche effect: a structural and computational study
Herein, we report the synthesis and X-ray structural analysis of a collection of fluorinated metal
N-heterocyclic carbenes (Ag, Au, Pd, Rh, Ir) and their precursor salts. The common structural
feature of these species is a flanking fluoroethyl group which is either freely rotating or
embedded within a bicyclic framework. Solid state analysis confirmed a gauche conformational
preference in all cases with the fluorine adopting a syn clinal arrangement (ϕ[NCCF] ~ 60°) with
respect to the triazolium nitrogen at the vicinal position of the NHC. A density functional theory
analysis was employed to quantify these effects and evaluate the influence of electronic
modulation of the carbenic carbon [(C=N+); neutral carbene (C:); metal-bound carbene (C=M)],
on the relative gauche / anti preference, thus highlighting the potential of this conformational
phenomenon as a useful molecular design strategy for controlling the topology of organometallic
complexes
Synthesis and First Hyperpolarizabilities of Acceptor-substituted β-apo-8’-Carotenal Derived Compounds
The synthesis and second-order nonlinear optical properties of acceptor-substituted biologically derived β-apo-8′-carotenal compounds are reported; electric field-induced second harmonic generation (EFISH) measurements give values of β(0) which are 2–6 times greater than for 4-N,N-dimethylamino-4′-nitrostilbene (DANS)
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I-Xe analysis of a magnetic separate from Lodranite GRA95209
I-Xe dating of a magnetic mineral separate from lodranite GRA95209 suggests that peak temperatures (and therefore melt migration) occurred early, at least a few million years before closure of the I-Xe system in phosphates from Acapulco
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Did organic compounds in the Tagish Lake meteorite form via catalytic processes in the solar nebula and within parent bodies?
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Identification of Trace Organic Components in the CR Chondrites by 4D TOFMS
This paper reports preliminary results of a 4D TOFMS study of CR chondrite organic material, highlighting the low-level organic species that may further reveal the complexity of parent body modification of interstellar precursors
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