Hydroprocesssing of light gas oil — rape oil mixtures

Two series of experiments of hydroprocessing of light gas oil - rape oil mixtures were carried out. The reactor feed was composed of raw material: first series — 10 wt.% rape oil and 90 wt.% of diesel oil; second series — 20 wt.% rape oil and 80 wt.% of diesel oil.     

Sequential enzymatic quantification of two sugars in a single microchannel

This paper presents the implementation of a multiple analyte enzyme assay, based on the sequential injection of the different enzyme solutions, in an electrokinetic driven microfluidic chip. The assay methodology for the simultaneous quantification of d-glucose and d-fructose was reported in previous publications but here the real integration of both enzyme assays was achieved. When assays were executed separately, good reproducibility was observed with average CV values of 5.2% and 4.5% for the d-glucose and d-fructose assay, respectively. Next, the assays for the quantification of d-glucose and d-fructose were integrated simultaneously on chip, where each assay was executed consecutively in the same microreactor by applying a specific sequence of potentials at the reservoirs. This article proves the integration of a sequential based quantification approach in continuous microfluidic chips with electrokinetic actuation.     

Variance reduction for fixed-source Monte Carlo calculations in multiplying systems by improving chain-length statistics

For a fixed-source calculation in a multiplying system, the variance in the neutron-chain length can create an unstable calculation and a neutron flux with high variance. In this paper an analytical frame is derived to calculate a priori the variance of the neutron flux in a simple model of a fixed-source calculation. This method is then used to find better variance reduction techniques not only for this simplified problem, but also for general cases.     

Motivational profiles from a self-determination perspective: The quality of motivation matters.

The present research complements extant variable-centered research that focused on the dimensions of autonomous and controlled motivation through adoption of a person-centered approach for identifying motivational profiles. Both in high school students (Study 1) and college students (Study 2), a cluster analysis revealed 4 motivational profiles: a good quality motivation group (i.e., high autonomous, low controlled); a poor quality motivation group (i.e., low autonomous, high controlled); a low quantity motivation group (i.e., low autonomous, low controlled); and a high quantity motivation group (i.e., high autonomous, high controlled). To compare the 4 groups, the authors derived predictions from qualitative and quantitative perspectives on motivation. Findings generally favored the qualitative perspective; compared with the other groups, the good quality motivation group displayed the most optimal learning pattern and scored highest on perceived need-supportive teaching. Theoretical and practical implications of the findings are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Levels of polybrominated diphenyl ether (PBDE) flame retardants in animals representing different trophic levels of the North Sea food Web

The levels of individual PBDE congeners were investigated in the invertebrate species whelk (Buccinum undatum), seastar (Asterias rubens), and hermit crab (Pagurus bernhardus), the gadoid fish species whiting (Merlangius merlangus) and cod (Gadus morhua), and the marine mammal species harbor seal (Phoca vitulina) and harbor porpoise (Phocoena phocoena). These species are all important representatives of different trophic levels of the North Sea food web. All six major PBDE congeners detected (BDEs 28, 47, 99, 100, 153, and 154) are most prevalent in the commercial Penta-BDE formulation. There is no evidence for the occurrence of the Octa-BDE formulation in the North Sea food web, since its dominant congener, BDE183, was never detected. BDE209, the main congener (> 97%) in the Deca-BDE formulation, was detected only in a minority of the samples and always in concentrations around the limit of detection. Since BDE209 is often the major BDE congener in sediments from the area, the main reason for its low concentrations in biota from the North Sea seems to be a relatively low bioaccumulation potential. This can either be due to a low uptake rate of the very large molecule or a relatively rapid excretion after biotransformation. Since all invertebrates investigated are sentinel species, they are highly representative for the area of capture. The highest lipid-normalized concentrations of PBDEs in the invertebrates occurred near the mouth of the river Tees at the East coast of the UK. The geographical distribution of the PBDEs can be explained by the residual currents in the area. The direction of these currents differs between the summer and the winter season as a result of the presence or absence of vertical summer stratification of the deeper waters north of the Dogger Bank. Summer stratification results in the development of a density-driven bottom water current formed after the onset of vertical stratification of the water column in May leaving the UK coast near Flamborough Head toward the Dogger Bank. In winter, the residual currents run in a more southerly direction and follow the UK coastline. The distribution pattern of the PCBs and p,p'-DDE in the invertebrates was entirely different from that of the PBDEs, which could be expected, since the use of these organochlorines in western Europe peaked in the 1960s and 1970s but has been forbidden more than two decades ago, whereas the production and use of the penta-BDE formulation is of a more recent origin. The higher trophic levels of the North Sea food web were represented by the predatory gadoid fish species whiting and cod and the marine mammal species harbor seal and harbor porpoise. The lipid-normalized levels of the six major PBDE congeners in fish were similar to the levels in the invertebrates, but a biomagnification step in concentrations of generally more than an order of magnitude occurred from gadoid fish to marine mammals. Based on the limited number of samples, no differences could be observed between harbor seal and harbor porpoise. In summary, the results in three species of sentinel invertebrates from a network of stations covering a major part of the North Sea basin showed that the estuary of the river Tees at the UK East coast is a major source for tri- to hexa-PBDEs. Throughout the food-chain, the most marked increase in (lipid-normalized) levels of all six PBDE congeners occurred from predatory (gadoid) fish to marine mammals, agreeing with the transition from gill-breathing to lung-breathing animals. This has serious consequences for the route of elimination of POPs, since their elimination from the blood into the ambient seawater via the gill-membrane is no longer possible.     

A Difference Reference Voltage Buffer for ΔΣ-Converters

An open loop architecture for a reference voltage buffer in -converters is presented to achieve fast-settling, since the settling time of the references plays an important role in the global performance of sampled data converters. This design has been tested on a 2-1 -converter with an on-chip bandgap reference increasing the input related dynamic range up to 93.4 dB for a bandwidth of 99 kHz.     

Processing radio frequency ultrasound images: a robust method for local spectral features estimation by a spatially constrained parametric approach

Spectral estimation is a major component in studies aiming at characterizing biological tissues through the analysis of backscattered radio frequency (RF) ultrasonic signals and images. However, conventional spectral estimation techniques yield a well-known trade-off between spatial resolution and variance. The backscattered signals are stochastic by nature, so short-term local analysis results in a high variance of the estimates, which cannot efficiently be reduced through conventional spatial averaging. We address this issue by describing a spectral estimation technique that reduces the variance of the estimates (by smoothing the local estimates in spectrally homogeneous regions) while preserving spectral discontinuities (i.e., the smoothing is not performed across regions with different spectral contents). The proposed approach is set in a Bayesian framework and is based on local autoregressive (AR) estimation, constrained by smoothness priors. These smoothness priors are introduced through a Markov random field in which the associated potential functions are nonquadratic, allowing thereby to preserve discontinuity. The method is validated on simulated RF images and tested on echocardiographic images acquired in vivo. The results are compared to the estimates provided by the conventional Burg technique. These results clearly demonstrate the ability of the proposed approach to improve spectral estimation in terms of variance reduction and discontinuity detection.     

A Linear Image Reconstruction Framework Based on Sobolev Type Inner Products

Exploration of information content of features that are present in images has led to the development of several reconstruction algorithms. These algorithms aim for a reconstruction from the features that is visually close to the image from which the features are extracted. Degrees of freedom that are not fixed by the constraints are disambiguated with the help of a so-called prior (i.e. a user defined model). We propose a linear reconstruction framework that generalizes a previously proposed scheme. The algorithm greatly reduces the complexity of the reconstruction process compared to non-linear methods. As an example we propose a specific prior and apply it to the reconstruction from singular points. The reconstruction is visually more attractive and has a smaller 핃₂-error than the reconstructions obtained by previously proposed linear methods. Bart Jansen, Frans Kanters and Remco Duits are joint main authors of this article.     

Linear dynamic filtering with noisy input and output

State estimation problems for linear time-invariant systems with noisy inputs and outputs are considered. An efficient recursive algorithm for the smoothing problem is presented. The equivalence between the optimal filter and an appropriately modified Kalman filter is established. The optimal estimate of the input signal is derived from the optimal state estimate. The result shows that the noisy input/output filtering problem is not fundamentally different from the classical Kalman filtering problem.     

EMI resisting CMOS differential pair structure

An improved differential pair structure, which is highly immune to conducted electromagnetic interference (EMI), is described. This new structure has a very low input offset voltage, even when a large EMI is superimposed on the nominal input signal