Wollaston prism with large split angle

The image formation through a Wollaston prism with large split angle is studied. Formulas for the split angle, approximate calculations of aberrations, and ray tracings are used. The most important aberrations found are astigmatism and anamorphic distortion. Tilting the Wollaston with respect to the incident beam may reduce these aberrations, and if the orientation of the optical axis in the first element is varied it is possible to cancel one of the two aberrations for both images simultaneously, while the other one is substantially reduced. With an adequate adjustment of all the construction parameters the images become sharp enough to allow the use of large split angles (approximately 15 degrees).     

Interleukin 6 and Aneurysmal Subarachnoid Hemorrhage. A Narrative Review

Interleukin 6 (IL-6) is a prominent proinflammatory cytokine. Neuroinflammation in general, and IL-6 signaling in particular, appear to play a major role in the pathobiology and pathophysiology of aneurysm formation and aneurysmal subarachnoid hemorrhage (SAH). Most importantly, elevated IL-6 CSF (rather than serum) levels appear to correlate with delayed cerebral ischemia (DCI, “vasospasm”) and secondary (“vasospastic”) infarctions. IL-6 CSF levels may also reflect other forms of injury to the brain following SAH, i.e., early brain damage and septic complications of SAH and aneurysm treatment. This would explain why many researchers have found an association between IL-6 levels and patient outcomes. These findings clearly suggest CSF IL-6 as a candidate biomarker in SAH patients. However, at this point, discrepant findings in variable study settings, as well as timing and other issues, e.g., defining proper clinical endpoints (i.e., secondary clinical deterioration vs. angiographic vasospasm vs. secondary vasospastic infarct) do not allow for its routine use. It is also tempting to speculate about potential therapeutic measures targeting elevated IL-6 CSF levels and neuroinflammation in SAH patients. Corticosteroids and anti-platelet drugs are indeed used in many SAH cases (not necessarily with the intention to interfere with detrimental inflammatory signaling), however, no convincing benefit has been demonstrated yet. The lack of a robust clinical perspective against the background of a relatively large body of data linking IL-6 and neuroinflammation with the pathophysiology of SAH is somewhat disappointing. One underlying reason might be that most relevant studies only report correlative data. The specific molecular pathways behind elevated IL-6 levels in SAH patients and their various interactions still remain to be delineated. We are optimistic that future research in this field will result in a better understanding of the role of neuroinflammation in the pathophysiology of SAH, which in turn, will translate into the identification of suitable biomarkers and even potential therapeutic targets.     

Copolymerization in UF/pMDI adhesives networks

Kinetic evidence in thermomechanical analysis experiments and carbon‐13 nuclear magnetic resonance spectroscopy (¹³C NMR) evidence indicates that the strength of a joint bonded with UF (urea–formaldehyde)/polymeric 4,4'‐diphenylmethane diisocyanate (pMDI) glue mixes is improved by coreaction of the methylol groups of UF resins with pMDI to form a certain number of methylene cross‐links. The formation of these methylene cross‐links is predominant, rather than formation of urethane bridges which still appear to form but which are in great minority. This reaction occurs in presence of water and under the predominantly acid hardening conditions, which is characteristic of aminoplastic resins (thus, in presence of a hardener). Coreaction occurs to a much lesser extent under alkaline conditions (hence, without UF resins hardeners). The predominant reaction is then different in UF/pMDI adhesive systems than that observed in phenol‐formaldehyde (PF)/pMDI adhesive systems. The same reaction observed for UF/pMDI system at higher temperatures has also been observed in PF/pMDI systems, but only at lower temperatures. The water introduced in the UF/pMDI mix by addition of the UF resin solution has been shown not to react with pMDI to an extent such as to contribute much, if at all, to the increase in strength of the hardened adhesive. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3681–3688, 2002     

The effect of carbon black filling and cross-linking in stretched SBR networks: a 2H-NMR study

Summary The line splitting v in ²H-NMR spectra of deuterated benzene in stretched crosslinked SBR depended linearly on the classical stretch term ² – 1/ for samples with and without carbon black filling. The ratio LS = v/(² – 1/) was measured in dependence on the solvent fraction . The extrapolated value L of this ratio at =0 gave a linear dependence on the inverse molecular mass 1/M_c of inter-crosslink chains. This was expected according to a simple model of chain dynamics and offers a further NMR-method for M_c-determination even in filled networks. However, the slope of the L(1/M_c)-line increases with an addition of carbon black which indicates a higher molecular order. Three reasons for this could be discussed. However, one of them is preferable.     

LIGA micro-openings for coherence characterization of X-rays

Infinitely thin opaque screens serving for diaphragms as defined in the visible-light optics are not feasible for operation with X-ray beams due to their high penetrability. Micro-openings of predicted sidewall shape in a gold layer up to 140 μm thick which would provide low transparency, are proposed. The proposed micro-openings were made using the LIGA technique and tested successfully at photon energies of up to 25 keV. The micro-openings can be used as targets for coherence X-ray pattern or, if long interference tails are avoided by means of the advanced sidewall shape, as X-ray beam collimators.     

DIN-Norm-orientierte Standard-Spezifikationen für Rührwerke

DIN Standard-Oriented Specifications for Stirring Systems. Stirring as a unit operation is characterised by universal application possibilities for material and energy transmission in process industries. DIN standards provide an overview of the wide variety of equipment in technical use and define the conditions for low-cost, exchangeable standard stirring systems. In many cases important process parameters are fixed only for a limited time. Possible operation time should be long, therefore performance reserves are justified; they will be useful for later tasks as well as for improving safety of existing processes. Engineering of such stirring systems requires definition of standard stirring tasks. This article deals with economic aspects, defines standard stirring tasks as well as design conditions and shows the principal engineering data of standard stirring systems for stainless steel vessels up to 20 m³ by means of pictures, tables and nomograms. In conclusion, adequate processing of construction materials as well as surface finishing and practical work with standard specifications for stirring systems are discussed.     

Effects of estrogen-induced hyperlipidemia on the erythrocyte membrane in chicks

The effects of estrogen-induced hyperlipidemia on plasma lipid peroxidation, fatty acid composition and osmotic fragility of erythrocytes in chickens were studied. Young male chickens implanted with estrogen for three wk developed a marked hyperlipidemia. Plasma levels of triglyceride, cholesterol and phospholipid were elevated 68-, four- and 24-fold, respectively, over controls. There was also a two-fold increase in plasma lipid peroxidation measured by the thiobarbituric acid test. Vitamin E supplement (1,000 IU/kg diet) reduced the plasma lipid peroxidation to the control level, but had no effect on the plasma lipid content. Estrogen-induced hyperlipidemia resulted in changes in the fatty acid composition of membrane lipids of erythrocytes. The major changes were an increase in oleic acid from 10.0% to 14.2% and a decrease in linoleic acid from 31.3% to 26.0%. The erytrocytes with an altered membrane fatty acid composition were found to have an increased osmotic fragility. It was apparent that there was a direct correlation between the oleic acid content and the osmotic fragility of erythrocytes.     

A mathematical model of fluidized bed biomass gasification

A mathematical model of biomass gasification in a fluidized bed has been developed. It considers axial variations of concentrations and temperature in the bubble and emulsion phases. The mass balance involves instantaneous oxidation and equilibrium devolatilization of the biomass, kinetics of solid-gas gasification reactions as well as of gaseous phase reactions and interphase mass transfer and gas convection. The energy balance is solved locally for each vertical volume element, and globally on the reactor by iteration on the temperature at the bottom of the bed. Three parameters have been adjusted based on the experimental results: the heat transfer coefficient at the wall, the weighting of the kinetics of the water-gas shift reaction and the fraction of biomass carbon remaining as char after devolatilization. The model is used to simulate a pilot scale (50 kg/h) biomass gasifier, and its predictions compared to experimental measurements. The temperature and gaseous concentrations are estimated with good accuracy for the experiments using a wood feedstock, except for the concentration of hydrogen which is overestimated.     

Constructing and applying higher order textons: Estimating breast cancer risk

Texture analysis based on textons is extended by introducing a method for computing textons of arbitrary order. First-, second- and third-order textons are applied to classify screening mammograms as to indicate a low or high risk of breast cancer. First-order textons are found to provide better estimates of breast cancer risk than other orders on their own but the combination of first- and second-order textons outperforms first-order textons alone and other combinations of two orders. Combining all three orders of textons does not improve classification. This example indicates that including higher-order textons has the potential to improve classification performance.