Zur Reduktion von Schwefeldioxid-Restmengen in Getreidestärken

On the Reduction of Residual Amounts of Sulfur Dioxide in Cereal Starches. New economically applicable methods for considerable elimination of sulfur dioxide from starch products are described. Extraction experiments show that a part of the sulfur dioxide is chemically bounded. The SO₂-content of corn starches can be decreased below 20 ppm by application of less than the stoichiometrically calculated amount of sodium hydroxide or hydrogen peroxide in aqueous solution. Because of the more favourable process conditions the hydrogen peroxide-method is preferred to the others.     

Studies on the Autoxidation of Phenylacetylene

Phenylacetylene is oxidized slowly by molecular oxygen at 110°C. The main oxidation products are benzoic acid, benzoic anhydride, and benzaldehyde. Besides the oxidation, thermal dimerization, oligomerization, and polymerization processes also take place. As individual products 1,4-diphenylbut-1-yn-3-ene and 1,3,5-triphenylbenzene were identified. About 80% of the phenylacetylene consumed are converted into products of low volatility which could not be detected by gas chromatography. The autoxidation of acetylenic hydrocarbones [1] preferably yields products of the attack at C H bonds in α-position to the CC triple bond. An attack at the CC riple bond was a first proved in the case of phenylacetylene, which besides polymeric products yielded benzaldehyde, acetophenone, and organic acids [2]. Later, in the causes of the isomeric octynes [3] and of various 1-Phenylalk-1-ynes [4] an attack at the CC triple bond was also proved. As the primary products of the oxidative attack at the CC triple bond short-lived oxirenes or their valence isomers, the corresponding ketocarbenes are to be expected. Indeed, their rearrangement products were found in the oxidation mixtures of both the isomeric ocytnes [3] and the 1-phenylalk-1-ynes [4]. Other products of the oxidative attack at the CC triple bond are lower carboxylic acids, formally produced by oxidative cleavage of the CC triple bond [3, 4].     

Residual stress measurements in irradiated solution-annealed type 304 stainless steel tubing

Immersion density and residual stress measurements were made on solution-annealed type 304 stainless steel capsule tubing irradiated up to fluence levels of 9 × 10²² n/cm² (E > 0.1 MeV). The measured residual stress is dependent on the competition between differential swelling which builds up differential stresses, and irradiation creep which relaxes these stresses. The measurements were analyzed using a bilinear swelling equation formulated with swelling data from the same heat of material. The temperatures and fluence levels of the swelling and slit tube data were each calculated with the same computer code. At high fluence, when swelling was in the steady-state region, the effective irradiation creep rate increased by a factor of about three. Further analysis was made assuming that stress-enhanced swelling and swelling-enhanced irradiation creep were the enhanced relaxation mechanisms.     

Role of the Blood-Brain Barrier in the Formation of Brain Metastases

The majority of brain metastases originate from lung cancer, breast cancer and malignant melanoma. In order to reach the brain, parenchyma metastatic cells have to transmigrate through the endothelial cell layer of brain capillaries, which forms the morphological basis of the blood-brain barrier (BBB). The BBB has a dual role in brain metastasis formation: it forms a tight barrier protecting the central nervous system from entering cancer cells, but it is also actively involved in protecting metastatic cells during extravasation and proliferation in the brain. The mechanisms of interaction of cancer cells and cerebral endothelial cells are largely uncharacterized. Here, we provide a comprehensive review on our current knowledge about the role of junctional and adhesion molecules, soluble factors, proteolytic enzymes and signaling pathways mediating the attachment of tumor cells to brain endothelial cells and the transendothelial migration of metastatic cells. Since brain metastases represent a great therapeutic challenge, it is indispensable to understand the mechanisms of the interaction of tumor cells with the BBB in order to find targets of prevention of brain metastasis formation.     

Photorheology of Fast UV‐Curing Multifunctional Acrylates

Summary: The fast photopolymerization of different multifunctional acrylates was analyzed by means of photorheology. The materials studied included a penta/hexaacrylate monomer and two different acrylated hyperbranched polymers. The sensitivity of the commercial rheometer was improved several‐fold, by a combination of an adaptive filter algorithm and improved data treatment, using powerful oversampling acquisition hardware. The novel set‐up was capable of monitoring up to a five orders of magnitude increase in shear modulus within short experiment timescales (about 10 s). The improvement in sensitivity and acquisition rate enabled the induction time, gelation, and vitrification of the multifunctional acrylates to be determined. In addition, the influence of UV intensity on stiffness build‐up within these materials was studied. In the case of the penta/hexaacrylate system, gelation and vitrification were detected as distinct events, in contrast to the second‐generation hyperbranched polyester, for which vitrification could not be identified. These findings are related to the difference in the glass transition temperature of the cured networks.

Absolute value of the complex shear modulus as a function of time for different acrylate monomers during UV curing.     

Fourier‐Transform Rheology of Unvulcanized,Carbon Black Filled Styrene Butadiene Rubber

Rubber materials filled with reinforcing fillers display nonlinear rheological behavior at small strain amplitudes below γ₀ < 0.1. Nevertheless, rheological data are analyzed mostly in terms of linear parameters, such as shear moduli (G′, G″), which loose their physical meaning in the nonlinear regime. In this work styrene butadiene rubber filled with carbon black (CB) under large amplitude oscillatory shear (LAOS) is analyzed in terms of the nonlinear parameter I_3/1. Three different CB grades are used and the filler load is varied between 0 and 70 phr. It is found that I_3/1(φ) is most sensitive to changes of the total accessible filler surface area at low strain amplitudes (γ₀ = 0.32). The addition of up to 70 phr CB leads to an increase of I_3/1(φ) by a factor of more than ten. The influence of the measurement temperature on I_3/1 is pronounced for CB levels above the percolation threshold.