Sound Velocity of Kaolin in the Temperature Range from 20 °C to 1100 °C

The sound velocity of Sedlec kaolin during heating from 20 °C to 1100 °C was investigated by modulated force thermomechanical analysis (mf-TMA). In the interval from 20 °C to 250 °C, the sound velocity increases which can be explained by liberation of the water molecules from pores and micropores. Dehydroxylation (450 °C to 650 °C) presents itself with a decrease of the sound velocity. After dehydroxylation, a two-step increase of the sound velocity was observed. The first step of the increase of the sound velocity is due to solid-state sintering at low temperatures. The second step starts at 950 °C as a consequence of the collapse of the metakaolinite structure. After the maximum, a steep increase of the sound velocity follows as a result of solid-state sintering.     

Phenology of the landscape: the role of organic agriculture

It is becoming increasingly clear that the agricultural sector will have to find an additional raison d'être beyond the production of food alone. One of the new services that agriculture can provide is contributing to the environmental quality of rural areas. In this respect a great burden of expectation is placed on organic farming. Here we examine how organic farming can contribute to the quality of specific regional landscapes. We do this with the help of a new instrument, the phenology of the landscape, which measures the contributions made by organic and conventional farming to the succession of colours and shapes during the seasons. This seasonal development plays an important role in people's appreciation of the landscape. The study shows that seasonal development is more recognizable on organic farms than on conventional farms, and that seasonal development is a scientifically‐usable criterion for evaluating the environmental quality of farms.     

Energy efficient control of a BTX dividing-wall column

Dividing-wall column (DWC) is considered nowadays the new champion in distillation, as it can bring substantial reduction in the capital invested as well as savings in the operating costs. This work presents the simulation results of energy efficient control and dynamics of a dividing-wall column (DWC). In order to allow a fair comparison of the results with previously published references, the case-study considered here is the industrially relevant ternary separation of the mixture benzene-toluene-xylene (BTX) in a DWC. Rigorous simulations were carried out in Aspen Plus and Aspen Dynamics. Several conventional control structures based on PID control loops (DB/LSV, DV/LSB, LB/DSV, LV/DSB) were used as a control basis. These control structures were enhanced by adding an extra loop controlling the heavy component composition in the top of the prefractionator, by using the liquid split as an additional manipulated variable, thus implicitly achieving minimization of energy requirements. The results of the dynamic simulations show relatively short settling times and low overshooting especially for the DB/LSV and LB/DSV control structures. Moreover, the energy efficient control proposed in this work allows the operation of DWC with minimum energy requirements or maximum purity of products.     

Modification of the formulas for third-order aberration coefficients

New parameters for calculation of third-order aberration coefficients (Seidel aberration coefficients) are introduced. The formulas for Seidel aberration coefficients are linear in these new variables. With these new variables it is possible to calculate the shape and the refractive index of the glass of the individual lenses of the optical system, which was not possible before.     

Optical properties and quantum efficiency of thin-film alkali halides in the far ultraviolet

The optical constants of thin films of CsI, KI, and KBr and the quantum efficiency (QE) of planar photocathodes made with these alkali halides in the 53.6-174.4-nm spectral range are presented. The optical constants were obtained from measurements of the reflectance as a function of incidence angle. The effect of film heating and exposure to UV irradiation on the optical properties and on the QE of the three alkali halides was investigated. KBr was found to be the most stable material for both heating and UV irradiation. KI appeared to be close to temperature stable, whereas UV exposure affected its optical constants. CsI optical constants changed after 420 K heating and after UV exposure. The changes in the optical constants were related to the QE changes, and a certain correlation between both variations was determined. However, it was also demonstrated that the QE changes cannot be explained solely by the changes in optical constants.     

Identification of cross-linked peptides for protein interaction studies using mass spectrometry and 18O labeling

A new method is presented to screen proteolytic mass maps of cross-linked protein complexes for the presence of cross-linked peptides and for the verification of proposed structures. On the basis of the incorporation of 18O from isotopically enriched water into the C-termini of proteolytic peptides, cross-linked peptides are readily distinguished in mass spectra by a characteristic 8 amu shift. This is due to the incorporation of two 18O atoms in each C-terminus, so that normal and surface-labeled peptides shift 4 amu and cross-linked peptides containing two C-termini will shift 8 amu compared with their unlabeled counterparts. The method is fast, sensitive, and reliable and can be combined with any available cross-linking reagent and a wide range of proteolytic agents. As proof of principle, we successfully applied the method to a complex of two DNA repair proteins (Rad18-Rad6) and identified the interaction domain.     

Neuronal morphology data bases: morphological noise and assesment of data quality

For technical, instrumental and operator-related reasons, three-dimensional reconstructions of neurons obtained from intracellularly stained neuronal pieces scattered in serial sections are blurred by some morphological noise. This noise may strongly invalidate conclusions drawn from models built using the three-dimensional reconstructions and it must be taken into account when retrieving digitized neurons from available databases. We analyse the main generating sources of the noise and its consequences for the 'quality' of the data. We provide tools for detecting and evaluating the noise in any database providing sufficient information is given in the database. We propose a unified format for submitting data and a new neuron viewer/editor to analyse the digitized neurons with our tools.     

High-resolution capillary zone and gel electrophoresis of structurally similar amphipathic glutathione conjugates based on interaction with beta-cyclodextrins

The tripeptide glutathione is a prominent intracellular constituent that provides protection against genotoxic and carcinogenic electrophiles and is also a component of several biological signal substances. Glutathione conjugates, free glutathione, and glutathione disulfide contain charged amino acid residues, which contribute to solubility in aqueous media. However, the amphipathic nature of glutathione conjugates and the small differences that may distinguish the S substituents, pose analytical problems in their resolution. The present study demonstrates how homologous S-alkyl and S-benzyl conjugates of high structural similarity can be efficiently resolved by capillary electrophoresis. Inclusion of beta-cyclodextrins in the buffer or in a polyacrylamide gel affords baseline separation of the analytes. The separation methods described are applicable to enzyme assays in vitro and to the identification and quantification of glutathione conjugates of importance in toxicology and physiology. The contribution of beta-cyclodextrin to the separation is primarily based on interactions between its hydrophobic cavity and the S-alkyl and S-benzyl groups of the analytes.     

A multilevel relaxation algorithm for simultaneous localization and mapping

This paper addresses the problem of simultaneous localization and mapping (SLAM) by a mobile robot. An incremental SLAM algorithm is introduced that is derived from multigrid methods used for solving partial differential equations. The approach improves on the performance of previous relaxation methods for robot mapping, because it optimizes the map at multiple levels of resolution. The resulting algorithm has an update time that is linear in the number of estimated features for typical indoor environments, even when closing very large loops, and offers advantages in handling nonlinearities compared with other SLAM algorithms. Experimental comparisons with alternative algorithms using two well-known data sets and mapping results on a real robot are also presented.     

Systematic Evaluation of One-Dimensional Unsteady Friction Models in Simple Pipelines

In this paper, basic unsteady flow types and transient event types are categorized, and then unsteady friction models are tested for each type of transient event. One important feature of any unsteady friction model is its ability to correctly model frictional dissipation in unsteady flow conditions under a wide a range of possible transient event types. This is of importance to the simulation of transients in pipe networks or pipelines with various devices in which a complex series of unsteady flow types are common. Two common one-dimensional unsteady friction models are considered, namely, the constant coefficient instantaneous acceleration-based model and the convolution-based model. The modified instantaneous acceleration-based model, although an improvement, is shown to fail for certain transient event types. Additionally, numerical errors arising from the approximate implementation of the instantaneous acceleration-based model are determined, suggesting some previous good fits with experimental data are due to numerical error rather than the unsteady friction model. The convolution-based model is successful for all transient event types. Both approaches are tested against experimental data from a laboratory pipeline.