Focal volume confinement by submicrometer-sized fluidic channels

Microfluidic channels with two lateral dimensions smaller than 1 microm were fabricated in fused silica for high-sensitivity single-molecule detection and fluorescence correlation spectroscopy. The effective observation volumes created by these channels are approximately 100 times smaller than observation volumes using conventional confocal optics and thus enable single-fluorophore detection at higher concentrations. Increased signal-to-noise ratios are also attained because the molecules are restricted to diffuse through the central regions of the excitation volume. Depending on the channel geometries, the effective dimensionality of diffusion is reduced, which is taken into account by simple solutions to diffusion models with boundaries. Driven by electrokinetic forces, analytes could be flowed rapidly through the observation volume, drastically increasing the rate of detection events and reducing data acquisition times. The statistical accuracy of single-molecule characterization is improved because all molecules are counted and contribute to the analysis. Velocities as high as 0.1 m/s were reached, corresponding to average molecular residence times in the observation volume as short as 10 micros. Applications of these nanofabricated devices for high-throughput, single-molecule detection in drug screening and genomic analysis are discussed.     

Transformation Textures in As‐hot rolled TRIP Steels

The microstructures of TRIP steels finish‐rolled above and below the recrystallization‐stop temperature (T_nr) are compared. Here, the retained austenite grains are equiaxed or elongated, respectively, according to whether final rolling was carried out above or below the T_nr. The recrystallized austenite did not contain a sharp texture, the best defined component of which was the cube. The bainite that formed in this case was characterized by weak concentrations of the Goss and rotated Goss and a fairly strong concentration of the rotated cube. It also displayed the transformation products of a retained rolling fibre in the prior austenite. The deformed austenite contained the typical fcc rolling texture, where the copper is considerably more intense than the brass under these conditions. After transformation to bainite, the presence of a strong transformed copper component is evident, together with somewhat less intense contributions from the three transformed brass components. The data indicate that strong variant selection took place in the deformed austenite and that it was also present in the recrystallized material, but to a lesser extent. The latter displayed evidence of incomplete recrystallization in that the transformation texture included components obtained from both “recrystallized” and “deformed” austenite.     

Time-resolved NIR spectroscopy for quantitative analysis of intact pharmaceutical tablets

Near-infrared (NIR) spectroscopy is a useful technique for quantitative measurements of intact tablets, but it suffers from limitations due to the fact that changes in the physical properties of a sample strongly affect the recorded spectrum. In this work, time-resolved transmission NIR spectroscopy was utilized to conduct quantitative measurements of intact tablets. The technique enables separation of the absorption properties of the sample from the scattering properties and can therefore handle changes of the physical parameters of the samples in a better way than conventional NIR transmission spectroscopy. The experiments were conducted using a pulsed Ti:sapphire laser coupled into a nonlinear photonic crystal fiber as light source. The light transmitted through the sample was measured by a time-resolving streak camera. A comparison of the results from the time-resolved technique with the results from conventional transmission NIR spectroscopy was made using tablets containing different concentrations of iron oxide and manufactured with different thicknesses. A PLS model made with data from the time-resolved technique predicted samples 5 times better than a PLS model made data from the conventional NIR transmission technique. Furthermore, an improvement to predict samples with physical properties outside those included in the calibration set was demonstrated.     

The influence of training on the accuracy of roentgenographic cephalometric tracings (author's transl)

The accuracy in landmark identification and in the determination of angular and linear measurements used in cephalometric analysis on lateral head film were statistically evaluated comparing operators with different levels of competence. The observed magnitude of methodological error was depending on - prior experience of the investigator - individual radiographic anatomical knowledge - rigour of landmark definition and - accuracy of the tracing procedure. Considering these sources of error some of the variability in the present investigation might be avoided by systematic instructions. In order to decrease the variation in landmark location the reproducibility of some points must be further improved by redefining them in their verbal assessments. From an educational point of view the correlation between individual radiographic anatomical knowledge and the magnitude of error in cephalometric analysis should be considered with particular emphasis.     

Dependence of gas adsorption rates on carbon granule size and linear flow velocity

A study was made of the dependence of the adsorption rate constant of an activated carbon for dimethyl methylphosphonate vapor on carbon granule size and superficial linear velocity using the adsorption kinetics equation to calculate the rate constant from critical bed weight values. Over a 30-fold range of velocities and a 7-fold range of granule diameters it was found, in accord with adsorption kinetics theory, that although the adsorption capacity for the vapor was invariant, the time for vapor breakthrough of the bed varied because of the effects of linear flow velocity and carbon granule size on the adsorption rate constant. In general, the rate constant increased nonlinearly with increase in velocity and decrease in carbon granule size. The slowest adsorption kinetics existed for the largest granule size at the lowest linear flow velocity, becoming increasingly faster as the velocity was increased and/or the granule size was decreased. For the smallest granule size the rate constant reached a limiting value of 2600 sec^?1 becoming essentially independent of linear velocity due to a change in the rate controlling step.     

Assessing the performance of OMEGA with respect to retrieving bioactive conformations

OMEGA is a rule-based program which rapidly generates conformational ensembles of small molecules. We have varied the parameters which control the nature of the ensembles generated by OMEGA in a statistical fashion (D-optimal) with the aim of increasing the probability of generating bioactive conformations. Thirty-six drug-like ligands from different ligand-protein complexes determined by high-resolution (< or =2.0A) X-ray crystallography have been analyzed. Statistically significant models (Q(2)> or =0.75) confirm that one can increase the performance of OMEGA by modifying the parameters. Twenty-eight of the bioactive conformations were retrieved when using a low-energy cut-off (5 kcal/mol), a low RMSD value (0.6A) for duplicate removal, and a maximum of 1000 output conformations. All of those that were not retrieved had eight or more rotatable bonds. The duplicate removal parameter was found to have the largest impact on retrieval of bioactive conformations, and the maximum number of conformations also affected the results considerably. The input conformation was found to influence the results largely because certain bond angles can prevent the bioactive conformation from being generated as a low-energy conformation. Pre-optimizing the input structures with MMFF94s improved the results significantly. We also investigated the performance of OMEGA in connection with database searching. The shape-matching program Rapid Overlay of Chemical Structures (ROCS) was used as search tool. Two multi-conformational databases were built from the MDDR database plus the 36 compounds; one large (maximum 1000 conformations/mol) and one small (maximum 100 conformations/mol). Both databases provided satisfactory results in terms of retrieval. ROCS was able to rank 35 out of 36 X-ray structures among the top 500 hits from the large database.     

Users as a Hidden Resource for Creativity: Findings from an Experimental Study on User Involvement

The main objective of this article is to report the empirical findings from a study on user involvement in service innovation. In doing this, we seek to answer the question of how user involvement affects the originality of new service ideas. An experimental investigation was carried out which included 54 participants arranged into three groups of creative users, ordinary users and professional service developers. The empirical data revealed that the users produced more original ideas than the company’s professional service developers. It is thus suggested that business organizations attempt to innovate original products would benefit from involving their customers.     

A creep technique for monitoring MnS precipitation in Si steels

A newly developed creep method is described for investigating the kinetics of manganese sulfide precipitation in two Si steels at hot working temperatures. The method was also applied to a Ti steel, in which the precipitation kinetics were previously determined using a stress relaxation technique. Prior to loading, the specimens are solution-treated for half an hour and then immediately cooled to the test temperature. A constant stress is applied to the sample by means of a computerized MTS machine, and the strain is recorded continuously during testing. The resulting creep rate is sensitive to the occurrence of precipitation; thus, the slope of the true strain-log (time) curve decreases immediately after the initiation and increases on the completion of precipitation. The precipitation-time-temperature (PTT) diagrams determined in this way on the three tested steels are of classical C shape. Because higher dislocation densities and internal stress levels are maintained, the present technique is more effective for monitoring the precipitation events occurring in both austenitic and ferritic phases than the previously developed stress relaxation method. formerly with the Department of Metallurgical Engineering, McGill University.     

Modeling of the plastic anisotropy of textured sheet

An alternative is proposed to the classical crystallographic and continuum techniques for representation of polycrystal anisotropy. It involves the use of continuum yield criteria to reproduce the yielding behavior of a collection of disoriented grains displaying typical experimental spreads. It is shown that the anisotropic properties pertaining to single ideal orientations are readily assessed. Yield surfaces as well as strain rateR(θ) and yield stressσ(θ)/σ(0) ratios are calculated for polycrystalline materials displaying several texture components. The Taylor, Sachs, and Kochendörfer grain interaction models are used for this purpose, the last of which leads to the fastest computations because it permits the texture/plastic properties relationship to be described analytically. Such methods are particularly well suited to FEM and CAD-CAM calculations. The predictions obtained from the present analysis are compared to experimental observations reported in the literature.