Experimental sensitivity analysis applied to sample preparation uncertainties: are ruggedness tests enough for measurement uncertainty estimates?

It has been suggested that typical ruggedness tests might lead directly to uncertainty estimates. This assertion is tested using simple experimental studies of uncertainties associated with sample grinding and oven-drying operations. The results are used to predict the outcome of typical ruggedness tests on the same systems. It is concluded that uncertainty estimation from ruggedness tests is appropriate only where a strong effect can be observed. Since current practice in ruggedness testing is predisposed to confirming insignificance, typical ruggedness tests are not likely to lead to reliable uncertainty estimates; instead, lack of statistical significance in ruggedness tests is better interpreted as reason to leave an effect out of the uncertainty budget. Only where the ruggedness study is modified in order to achieve statistically significant change is it useful for uncertainty estimation. Received: 27 November 2000 Accepted: 13 February 2001     

Large Pore Mesoporous MCM-41 Templated from Cetyltriethylammonium Bromide

Following hydrothermal synthesis process, MCM-41 was synthesized by using cetyltfiethylammonium bromide as templating agent. The experimental results showed that MCM-41 with pore diameter in the range of 4-7 nm can be obtained by adjusting nSurf./nSi. It was proved that cetyltriethylammonium bromide is an effective templating agent for increasing pore diameter of molecular sieve MCM-41.     

Comparison of 3-Dimensional ℤ-Graded and ℤ2-Graded L ∞ Algebras

This article explores L _∞ structures on 3-dimensional vector spaces with both ?- and ?₂-gradings. Since ?-graded L _∞ algebras are special cases of ?₂-graded algebras in the induced ?₂-grading, there are generally fewer ?-graded L _∞ structures on a given space. However, degree zero automorphisms (rather than even automorphisms) determine equivalence in a ?-graded space. We therefore find nontrivial examples in which the map from the ?-graded moduli space to the ?₂-graded moduli space is bijective, injective but not surjective, or surjective but not injective. Additionally, we study how the codifferentials in the moduli spaces deform into other nonequivalent codifferentials.     

Near-resonant Rayleigh scattering and atomic flame flourescence spectroscopy

Near-resonant Rayleigh scattering and collision-induced resonance fluorescence of sodium have been observed in a combustion environment at atmospheric pressure. Sodium atoms in the equilibrium region of a flat-flame burner were excited by a pulsed-dye laser. The behavior of the two signals as the laser was detuned from the resonance line was studied and was found to agree with theoretical predictions. The results have important implications for atomic flame-fluorescence spectroscopy in that trapping is avoided at large atom number densities.     

Laser-based characterization of a flame-assisted plasma

A well-characterized flame-assisted plasma was developed to understand the role of flow nonuniformities and plasma/wall interactions in plasma devices for use in validation of laser-based Doppler shift spectroscopic methods. A hydrogen/oxygen capillary diffusion flame burner was used as a plasma source, with barium seeded into the reactants to provide a source of ions and electrons. For analysis the plasma was assumed to be a stationary, partially ionized, collision dominated, thermal plasma consisting of barium ions, electrons, and neutrals between two parallel-plate electrodes. The plasma was examined in terms of the continuum equations for ions and electrons, together with Poisson's equation to predict spatial profiles of electron and positive ion density and potential as functions of applied potential. First an analytic solution based on constant plasma properties and negligible difusion was introduced. The model was then extended by including effects of diffusion and variable plasma properties. Experimentally, current/voltage characteristics of the plasma were measured conventionally, relative ion concentration and temperature were measured with laser-induced fluorescence, and local potential distribution was measured using an electrostatic probe. The diffusionless theory predicted well the bulk behavior of the plasma, but not the correct spatial distributions of ion concentration and potential. The extended model produced a more satisfactory fit to the data. At conditions of 1.4 equivalence ratio, 70 torn pressure, 300 ppm seed concentration, and 100–400 V applied potentials, electric fields of the order of 10², 10³ V/cm were observed near the powered electrode, and of few tens of V/cm in the hulk of tire plasma. The field strength in the sheath ensures the operation of the Doppler shift diagnostics, once the recommendations tor LIF signal detectability are fulfilled.     

The homestake scintillation detectors: A status report

Summary We describe the 140 ton, 1200 m²sr Large-Area Scintillation Detector located underground at a depth of 4850 ft and the 0.8 km² surface air shower array at the Homestake Mine. Half of the underground detector is currently operating. We discuss its performance and describe the monopole sensitivity of the LASD and the ability of the surface-underground telescope to detect cosmic point sources.

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Riassunto Si descrive il rivelatore a scintillazione di 140 tonnellate a grande area situato sottoterra ad una profondità di 4850 piedi e l'apparecchiatura di superficie di 0.8 km² per rivelare i raggi cosmici a Homestake Mine. Metà del rivelatore sotterraneo è attualmente in funzione. Si discute il suo funzionamento e si descrive la sensibilità del monopolo del LASD e la capacità del telescopio di superficie-sottosuolo di rilevare sorgenti cosmiche puntiformi.

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Резюме Мы описываем 140-тонный 1200 м² сцинтилляционный детектор большой площади, расположенный под землей на глубине 4850 футов и антенную решетку площадью 0.8 км² для атмосферных ливней в шахте Хоумстейк. Половина подземного детектора в настоящее время уже действует. Мы обсуждаем конструкцию и описываем чувствительность к монополям сцинтилляционного детектора большой площади и возможность подземного телескопа—детектировать точечные космические источники.