Measurement of Electron-Optical Parameters for High-Resolution Electron Microscopy Image Interpretation

A method is presented to measure various electron-optical parameters needed for high-resolution electron microscopy image interpretation with high accuracy. The method is based on the measurement of a series of beam-tilt induced image displacements. The displacements are calculated via cross-correlation of the images, and subsequently fitted to a third-order polynomal in the beam tilt. From two series of images (using the x and y beam tilt coils), the spherical aberration constant of the microscope can be measured, as well as the current values of defocus, beam tilt and astigmatism. The spherical aberration constant of three Philips microscopes is measured with a precision better than 1 %, apart from calibration errors.The misalignment in the reference image (i.e. without induced beam tilt) can be measured with an absolute accuracy of 0.05 mrad, while the accuracy in the measured defocus value is 5 nm (at a magnification of 250,000). A computer is used to direct the experiments via remote control of the microscope and perform fast image processing to calculate the cross-correlations

Predicted band structures of III-V semiconductors in wurtzite phase

While non-nitride III-V semiconductors typically have a zincblende structure, they may also form wurtzite crystals under pressure or when grown as nanowhiskers. This makes electronic structure calculation difficult since the band structures of wurtzite III-V semiconductors are poorly characterized. We have calculated the electronic band structure for nine III-V semiconductors in the wurtzite phase using transferable empirical pseudopotentials including spin-orbit coupling. We find that all the materials have direct gaps. Our results differ significantly from earlier {\it ab initio} calculations, and where experimental results are available (InP, InAs and GaAs) our calculated band gaps are in good agreement. We tabulate energies, effective masses, and linear and cubic Dresselhaus zero-field spin-splitting coefficients for the zone-center states. The large zero-field spin-splitting coefficients we find may lead to new functionalities for designing devices that manipulate spin degrees of freedom

Attentional avoidance of high-fat food in unsuccessful dieters

Using the exogenous cueing task, this study examined whether restrained and disinhibited eaters differ in their orientation of attention towards and their difficulty to disengage from high versus low-fat food pictures in a relatively short (500 ms) and a long presentation format (1500 ms). Overall, participants in the 500 ms condition showed a tendency to direct attention away from high-fat food pictures compared to neutral pictures. No differential pattern was evident for the 1500 ms condition. Correlational analysis revealed that reduced engagement with high-fat food was particularly pronounced for disinhibited eaters. Although in the short term this seems an adaptive strategy, it may eventually become counterproductive, as it could hinder habituation and learning to cope with seductive characteristics of high-fat food. (C) 2010 Elsevier Ltd. All rights reserved

Does perceived support in employee development affect personnel turnover?

This article focuses on whether it is beneficial for firms to invest in the general skills of their workforce or whether these training investments merely encourage personnel turnover. Estimation results derived from a sample of 2833 dutch pharmacy assistants show that participation in general training does not induce employees' intention to quit, as predicted by human capital theory. We find that a firm's investments in general training significantly contribute to the perceived support in employee development (psed) among the workforce, as predicted by social exchange theory. Moreover, we show that psed is negatively related to employees' intention to quit the firm; however, this effect is to a large extent mediated by employee job satisfaction. Our findings support the importance of social exchange theory in explaining turnover behaviour as a consequence of personnel development practices

Assessment and enhancement of MERRA land surface hydrology estimates

The Modern-Era Retrospective Analysis for Research and Applications (MERRA) is a state-of-the-art reanalysis that provides, in addition to atmospheric fields, global estimates of soil moisture, latent heat flux, snow, and runoff for 1979 present. This study introduces a supplemental and improved set of land surface hydrological fields ("MERRA-Land") generated by rerunning a revised version of the land component of the MERRA system. Specifically, the MERRA-Land estimates benefit from corrections to the precipitation forcing with the Global Precipitation Climatology Project pentad product (version 2.1) and from revised parameter values in the rainfall interception model, changes that effectively correct for known limitations in the MERRA surface meteorological forcings. The skill (defined as the correlation coefficient of the anomaly time series) in land surface hydrological fields from MERRA and MERRA-Land is assessed here against observations and compared to the skill of the state-of-the-art ECMWF Re-Analysis-Interim (ERA-I). MERRA-Land and ERA-I root zone soil moisture skills (against in situ observations at 85 U.S. stations) are comparable and significantly greater than that of MERRA. Throughout the Northern Hemisphere, MERRA and MERRA-Land agree reasonably well with in situ snow depth measurements (from 583 stations) and with snow water equivalent from an independent analysis. Runoff skill (against naturalized stream flow observations from 18 U.S. basins) of MERRA and MERRA-Land is typically higher than that of ERA-I. With a few exceptions, the MERRA-Land data appear more accurate than the original MERRA estimates and are thus recommended for those interested in using MERRA output for land surface hydrological studies

Very complex internal standard response variation in LC-MS/MS bioanalysis: Root cause analysis and impact assessment

Internal standards (ISs) are essential for the development and use of reliable quantitative bioanalytical LC-MS/MS methods, because they correct for fluctuations in the analytical response that are caused by variations in experimental conditions. Sample-to-sample differences in the IS response are thus to be expected, but a large variability often is an indication of nonoptimal sample handling or analysis settings. This paper discusses a number of cases of very complex variation of IS responses that could be attributed to analytical problems such as injection errors and sample inhomogeneity, and matrix-related issues such as degradation and increased ionization efficiency. A decision tree is proposed to help find the underlying root cause for extreme IS variability

Optimal Stack Layout in a Sea Container Terminal with Automated Lifting Vehicles

Container terminal performance is largely determined by its design decisions, which include the number and type of quay cranes (QCs), stack cranes (SCs), transport vehicles, vehicle travel path, and stack layout. The terminal design process is complex because it is affected by factors such as topological constraints, stochastic interactions among the quayside, vehicle transport and stackside operations. Further, the orientation of the stack layout (parallel or perpendicular to the quayside) plays an important role in the throughput time performance of the terminals. Previous studies in this area typically use deterministic optimization or probabilistic travel time models to analyze the effect of stack layout on terminal throughput times, and ignore the stochastic interactions among the resou

Experimental investigation and modelling of consolidation and layering mechanisms in high-shear granulation

High-shear wet granulation is a particle size enlargement process widely used in industries such as the pharmaceutical, food and agricultural industries. Despite its predominance, knowledge on several of the key mechanisms of granulation is lacking, driving up the costs of the design of new processes, scale-up and control. For the rate mechanism of consolidation and layered growth, models can be found in literature, one of which has been validated for the case of growth in a static powder bed. However, these models remain to be experimentally validated for application in an actual granulator. This study is the first to develop a method to investigate consolidation and layered growth under such dynamic conditions, and presents a detailed investigation of the kinetics, as well as a model to describe them. Initially, a high-shear mixer with three-bladed impeller was used for the method development of the study of the kinetics of consolidation and layered growth. However, experiments quickly showed that a dedicated piece of equipment was needed in order to isolate consolidation and growth from the other granulation phenomena, breakage in particular. Therefore, a novel, consolidation-only granulator (COG) was designed. Using the COG, the growth kinetics of a variety of powder-binder systems was evaluated. The granule mass was found to increase linearly with the square root of time, until a critical-packing liquid volume fraction had been achieved. This behaviour corresponds with surface tension-driven growth models. However, breakage and attrition were found to be prevalent for long granulation times, making it impossible to determine both the critical-packing liquid volume fraction and the final granulation time. Additionally, an unexpected rapid increase in initial granule mass was observed. Remarkably, the overall granule porosity was found to be constant. Tomography revealed that the granules developed a core-shell structure, with the higher-density shell becoming increasingly thick during granulation and the core becoming less dense. A further study using a high-shear mixer with flat plate impeller was successfully performed to determine the critical-packing liquid volume fraction and final granulation time. Although the qualitative kinetic behaviour was found to match that predicted by the surface tension-driven growth model, the quantitative behaviour varied. Efforts to incorporate the observed core-shell structure into the existing model revealed that such an extension did not represent the observed behaviour. As such, no predictive expression was found for the critical-packing liquid volume fraction and final granulation time. However, these parameters can be obtained from experimental work. Finally, the initial rapid increase in granule was addressed, and it was deemed probable that this effect would not have a significant impact on in-situ nucleation in a granulator. Finally, the results from all the studies were combined to adjust the existing model and convert it into two different population balance models (PBMs). The first, a three-dimensional PBM, was simply proposed. The second, a one-dimensional PBM, was solved by discretisation and compared to the experimental results to evaluate its performance. It was found that the discretisation method showed some deviation from the experimental results, but that this error could be reduced by decreasing the bin width. This work has successfully identified the underlying kinetics of layered growth, elucidated the consolidation and growth behaviour of granules, and contributed to the modelling and design of granulation processes