Conformation and configuration of tertiary amines via GIAO-derived (13)C NMR chemical shifts and a multiple independent variable regression analysis.

The (13)C chemical shifts of six tertiary amines of unambiguous conformational structure are compared to predicted (13)C NMR chemical shifts obtained via empirically scaled GIAO shieldings for geometries from MM3 molecular mechanics calculations. An average deviation, absolute value of Deltadelta(av), of 0.8 ppm and a maximum deviation, absolute value of Deltadelta(max), of 2.8 ppm between predicted and experimental (13)C shifts of the six tertiary amines of unambiguous structure are found. In several cases of tertiary amines subject to rapid exchange, where experimental (13)C shifts at room temperature are weighted averages of multiple conformers, a comparison of calculated (13)C shifts of all reasonable MM3 predicted conformers with experimental (13)C shifts via a multiple independent variable regression analysis provides an efficient method of determining the major and minor conformers. The examples presented are 2-methyl-2-azabicyclo[2.2.1]heptane and 1,6-diazabicyclo[4.3.1]decane, which each have two expected contributing structures, and 2-(diethylamino)propane and 1,8-diazabicyclo[6.3.1]dodecane, where ten and seven low-energy conformers, respectively, are predicted by MM3 calculations.     

Enhancing comprehension of web information for users with special linguistic needs

In this essay we review the special linguistic needs of language-disordered users who are potential users of the world wide web hypertext system. For the web to be a true information highway, there must be facilities to enhance the comprehension of those users who have special requirements, and who will benefit enormously from appropriately aided access to the web. We provide some guidelines for the development of such facilities.     

Sequencing a Set of Alternatives Under Time Constraints

We consider a problem of sequencing a set of alternatives (i.e. manufacturing methods, job applicants or target journals) available for selection to complete a project. Associated with each alternative are the probability of successful completion, the completion time, and the reward obtained upon successfully completing the alternative. The optimal sequencing strategy that maximizes the expected present value of total rewards, is derived based on a simple ordering parameter. We further consider an extension in which one of the alternatives will not be available for selection if not selected by a certain time, and another extension in which the selection process is allowed only for a limited period of time. We propose solution strategies to the selection and sequencing problem under time constraints.     

Solid-state structures of ureidoimidazoles

This work outlines the synthesis and solid-state structures of a series of ureidoimidazole derivatives. The ureidoimidazoles all adopt a common tautomeric configuration and possess remarkably consistent features of supramolecular organisation that are affected by both steric factors and proximal hydrogen-bonding functionality.     

Minimum cost allocation of quality improvement targets under supplier process disruption

This paper presents a system cost model to assist a manufacturer in assessing the minimum cost allocations of quality improvement targets to suppliers. The model accounts for the effects of autonomous learning and induced learning on quality improvement, via variance reductions of supplier processes. The model further accounts for the effects of planned and unplanned disruptions in supplier production processes, where such gaps in production decreases the amount of autonomous learning while providing an opportunity for induced learning, thereby counteracting the effect of disruptions on process improvement. An optimization model is developed that obtains the quality improvement allocations that minimize system expected cost to both suppliers and manufacturer. The proposed models also account for both the uncertainty in the realized induced learning rate as well as uncertainty in the realized level of process disruptions. An example is used to demonstrate an implementation of the proposed models and to assess the sensitivity of the optimal target allocations to several model parameters.     

Product and process yield estimation with Gaussian quadrature (GQ) reduction: Improvements over the GQ full factorial approach

Manufacturing or multivariate yield, the fraction of unscreened products which conforms to all product specification limits, is an important and commonly used metric for assessing and improving the quality of a production process. Current procedures for multivariate yield evaluation, such as Monte Carlo simulation, require substantial computing effort, making the iterative adjustment of design parameters often impractical. This paper introduces a new approach to multivariate yield evaluation based on a numerical integration procedure called Gaussian quadrature reduction (GQR). The advantage of this approach is a large reduction in the computational burden associated with multivariate yield evaluation with virtually no loss in accuracy of the estimates. The proposed procedure can be generalized to evaluate many other multivariate criteria such as expected costs and the desirability index. The method is demonstrated for three yield evaluation test problems, and comparisons to Monte Carlo-based evaluations are presented.     

Application of INAA in the Characterisation and Quantification of Dy-Labeled Ceramic Spheres and Their Use as Inert Tracers in Soil Studies

An inert, activable tracer method, using sized ceramic spheres custom labeled with 15% Dy₂O₃ during manufacture, has been developed to study soil aggregation. Instrumental neutron activation analysis (INAA) with a Slowpoke reactor, using ^165mDy (T _1/2 = 1.26 min), provides an extremely rapid means with which to characterise the Dy-content of the various size fractions of labeled spheres from different production runs. In contrast, the Dy-content (and hence number of spheres) of 5—g soil/sphere mixtures is determined using the longer-lived ¹⁶⁵Dy (T _1/2 = 2.33 hrs) following a 30-minute decay period during which the otherwise interfering ²⁸Al (T _1/2 = 2.24 min) preferentially decays. The method is expected to find many applications.     

Fluorescence spectral imaging of dihydroxyacetone on skin in vivo

Dihydroxyacetone (DHA) has been proposed as a potential alternative to dansyl chloride for use as a fluorescence marker on skin to assess stratum corneum turnover time in vivo. However, the fluorescence from DHA on skin has not been adequately studied. To address this void, a noninvasive, noncontact spectral imaging system is used to characterize the fluorescence spectrum of DHA on skin in vivo and to determine the optimal wavelengths over which to collect the DHA signal that minimizes the contributions from skin autofluorescence. The DHA-skin fluorescence signal dominates the 580-680 nm region of the visible spectrum when excited with ultraviolet radiation in the 320-400 nm wavelength region (UVA). An explanation of the time-dependent spectral features is proposed in terms of DHA polymerization and binding to skin.     

First dark matter results from the XENON100 experiment

The XENON100 experiment, in operation at the Laboratori Nazionali del Gran Sasso in Italy, is designed to search for dark matter weakly interacting massive particles (WIMPs) scattering off 62 kg of liquid xenon in an ultralow background dual-phase time projection chamber. In this Letter, we present first dark matter results from the analysis of 11.17 live days of nonblind data, acquired in October and November 2009. In the selected fiducial target of 40 kg, and within the predefined signal region, we observe no events and hence exclude spin-independent WIMP-nucleon elastic scattering cross sections above 3.4 × 10??? cm2 for 55 GeV/c2 WIMPs at 90% confidence level. Below 20 GeV/c2, this result constrains the interpretation of the CoGeNT and DAMA signals as being due to spin-independent, elastic, light mass WIMP interactions.     

Shape-selective fluorescent sensing ensemble using a tweezer-type metalloreceptor

[reaction: see text] A fluorescent sensing ensemble for pyridine-derived compounds is described. The receptor portion of the ensemble is prepared from a bisimidazole pyridine which coordinates copper to form a well-defined cavity. Small heteroaromatic guests such as adenine bind strongly in the cavity. The fluorescent response is provided by a dye which is coordinated to the receptor and quenched by the metal ion. The dye is released upon guest binding providing up to 25-fold fluorescence increases.