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.     

Direct deflection method for determining refractive-index profiles of polymer optical fiber preforms

We present a method for determining the refractive-index profile of polymer optical fiber preforms through a direct-deflection measurement. The method is simple to use, compact, and has good resolution. The profile is obtained from the deflection data by numerically integrating the differential-ray equation for a radial refractive-index gradient. Corrections for topographical deviations are also discussed. Results for both graded-index and step-index fibers are presented.     

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.     

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.     

On the friction and wear performance of boric acid lubricant combinations in extended duration operations

Lubrication is critical for minimizing wear in mechanical systems that operate for extended time periods. Developing lubricants that can be used in engineering systems without replenishment – particularly those that are environmentally friendly – is very important for increasing the functional lifetime of mechanical components. In the present investigation, extended duration pin-on-disk experiments were carried out to determine the relative performance of a wide range of lubricant combinations in a commercial brake valve assembly. In the experiments, the lubricants were initially applied to the disk surface but were not replenished over a sliding distance of more than 6000 m. The experimental results revealed that the environmentally friendly lubricant boric acid was highly ineffective for reducing the wear in the surfaces tested. When combined with a commercial transmission fluid, however, the boric acid mixture proved to be highly effective in terms of both friction and wear performance. Based on the success of the combined lubricant experiments, the boric acid was then mixed with canola oil to form a completely natural lubricant combination. Based on further pin-on-disk experiments, this lubricant combination yielded the best wear performance of all the lubricants tested. The importance of these results, as related to the use of the natural lubricant combination in other engineering systems such as sheet metal stamping, was subsequently ascertained and discussed.     

Verhalten austenitischer Manganstähle in Meerwasser

Auslagerungsversuche mit verschiedenen geschweißten und verspannten Proben aus den chromhaltigen austenitischen Manganstählen X 40 MnCrN 19 und X 12 MnCr 18 12 sowie dem chromfreien Stahl X 50 Mn 20 in Meerwasser der Nord- und Ostsee. Makroskopische und mikroskopische Beurteilung der Proben nach sechs Wochen, einem halben Jahr, einem Jahr und zwei Jahren hinsichtlich Beständigkeit gegen unterschiedliche Korrosionserscheinungen, besonders hinsichtlich transkristalliner Spannungsrißkorrosion.     

Die Thermokraft von Aluminiumnitrid bei Temperaturen zwischen 1350 und 1650 °C in Argon- und Stickstoffatmosphäre

Beschreibung der Versuchsapparatur zur Messung der Thermospannung der Kette Rh |_{T + Δ} AIN |_T Rh für Temperatur-differenzen bis zu ± 60 °C zwischen 1350 und 1650 °C. Ermittlung der Thermokraft und ihres homogenen Anteils. Berechnung der Überführungswärme der wandernden Ionen aus der homogenen Thermokraft. Erörterung zum Leitungsmechanismus im Aluminiumnitrid AlN.     

Atlas-based segmentation of pathological MR brain images using a model of lesion growth

We propose a method for brain atlas deformation in the presence of large space-occupying tumors, based on an a priori model of lesion growth that assumes radial expansion of the lesion from its starting point. Our approach involves three steps. First, an affine registration brings the atlas and the patient into global correspondence. Then, the seeding of a synthetic tumor into the brain atlas provides a template for the lesion. The last step is the deformation of the seeded atlas, combining a method derived from optical flow principles and a model of lesion growth. Results show that a good registration is performed and that the method can be applied to automatic segmentation of structures and substructures in brains with gross deformation, with important medical applications in neurosurgery, radiosurgery, and radiotherapy.