Über den Einfluß von Licht auf den oxydativen Verderb von Speiseölen III: Abhängigkeit der Oxydationsgeschwindigkeit vom Sauerstoffpartialdruck und der Lichtintensität

Effect of Light on the Oxidative Deterioration of Edible Oils III: Effect of Partial Pressure of Oxygen and Intensity of Light on the Rate of Oxidation An apparatus is described for the measurement of oxygen consumption during oxidation of edible oils. Oxidation can be followed in this apparatus under the action of light of any desired intensity and spectral composition, and at various O₂-pressures. Sunflower, peanut and soybean oils were chosen as substrates. The characteristic curves representing oxygen uptake versus time during photo-oxidation showed an unique behaviour of soybean oil; its photo-oxidation proceeded in two phases. With decreasing pressures, a noticeable decrease in the rate of oxidation of the aforesaid oils is observed only at pressures as low as 10-20 mm Hg; up to this region the effect of oxygen pressure is insignificant. The effect of light intensity on the rate of oxidation shows for soybean oil a linear function in the first phase, and a square root function for sunflower oil, and peanut oil and for soybean oil in the second phase.     

Über den Einfluß von Licht verschiedener Intensität und Wellenlängenbereiche Auf den oxydativen Verderb von Speiseölen I

Influence of light of Varying Intensity and Wavelengths on the Oxydative Deterioration of Edible Oils I The basic requirements for the experiments on light exposure are reported in this paper. This involves the use of an apparatus which holds the oil under a constant oxygen pressure and is able to measure very sensitively the amount of consumed oxygen. Furthermore, the equipment required, measuring methods and the basis for calculation are given for an exactly defined exposure.     

Über den Einfluß von Licht auf den oxydativen Verderb von Speiseölen IV: Abhängigkeit der Oxydationsgeschwindigkeit von der Wellenlänge des eingestrahlten Lichts

Influence of Light on Oxidative Deterioration of Edible Oils IV: Dependence of Rate of Oxidation on Wave-Length of Incident Light A distinct decrease in the rate of oxidation with increasing wave-length is observed for soybean, sunflower and peanut oils when these oils are irradiated with various coloured lights having the same quantum-density. While studying the causes of this behaviour, pure absorption curves for the aforesaid oils were determined. Light of short wave was completely absorbed, whereas long-wave light was barely absorbed to any measurable extent. A considerable increase in quantum yield during oxidation occurs with increasing wave-length. Inspite of this, the oxidation of oils is catalysed most strongly by short-wave light, because the influence of pure absorption exceeds the increase in quantum yield. Pure absorption is therefore considered as the decisive factor with regard to the dependence of photooxidation on wave-length. Finally, the rate of oxidation, as determined in darkness, was found to increase with decreasing wave-length of light used for pre-oxidation of the oil.     

1,2,3-Triazabutadiene. XI. Untersuchungen zur iod-sensibilisierten Fotoisomerisierung von 1-Aryl-3-(3-methyl-benzthiazolin-2-yliden) triazenen

1,2,3-Triazabutadienes. XI. Investigation of the Iodine-induced Photoisomerization of 1-Aryl-3-(3-methyl-benzthiazolin-2-yliden) triazenes cis-1-Aryl-3-(3-methyl-benzthiazolin-2-yliden)triazenes isomerize induced photo-chemically by iodine to the trans-isomer. The wavelength of the used irradiation light was 546 nm so that only I₂ absorb. The dependence of the quantum yields on the concentration of the cis-isomer and on the intensity of the irradiation light was investigated. The influence of the light intensity on the quantum yields shows, that the primary step is the dissoziation of I₂-molecules to I·- radicals, which induce the isomerization.     

Photoabbau von PVC-folien. I. Einfluß von bestrahlungsstärke und temperature

Films from mass-PVC have been irradiated by a high pressure mercury lamp under nitrogen. The influence of variable light intensity and temperature of the sample on the dehydrochlorination reaction and changes in the absorption spectrum of the polymer were investigated.     

Der Einfluß des Photoinitiators auf die radikalische Härtung von Siliconacrylaten, 9

The photo-induced, free-radical network formation of silicone acrylates has been investigated in the presence of several photoinitiators containing benzoyl groups. The crosslinking process can be described by means of a free-radical chain process. From calorimetrical measurements it is inferred that oxygen inhibits and terminates the chain propagation process. Both the reaction rate and the inhibition time of the crosslinking are proportional to the air pressure, to the intensity of the incident light, and to the quantum yield of the initiator photolysis. The reaction starts when all oxygen is consumed in the silicone layer. Using Fick's 1st diffusion law it can be show that only oxygen, which diffused into the system, determines the final conversion. Contrary, O₂ influences the reaction rate, the inhibition time, and the final conversion. The network density does not depend on the oxygen concentration. The negative influence of oxygen on the reaction rate, on the inhibition time, and on the final conversion can be reduced by means of a high rate of the start reaction which depends on the incident light intensity, light absorption, and the quantum yield of the initiator photolysis. By means of two kinetical methods it is possible to show that any initiator used exhibits a different initiating efficienty; their relative order has been estimated.     

Beeinflussung der Waschintensität (WI) in Abhängigkeit von Chemie und Mechanik

Influence of Chemical and Mechanical Factors on the Intensity of Washing Mutual effects of the two significant chemical and mechanical factors that influence the removal of dirt could be studied by treating the fabric in specific manner using a roller-type washing machine, which was developed in author's institute, and a device for measuring the working force. The tests revealed distinctly that intensity of washing is preferably promoted under the action of a solution of washing agent when fibres within the thread are displaced as widely as possible. When the aforesaid conditions are fulfilled, dirt substances from fabrics are suitably dispersed and suspended, which result in optimum washing action.     

Scherfließen und Wandgleiten von Massen für den Pulverspritzguss

This contribution presents coupling of laws for shear flow and wall slipping by the shear stress at the slipping interface. It includes the special case of Coulombian friction postulated by Uhland as well as the assumption of a constant sliding velocity along the flow channel according to Mooney. As an example, Ostwald and de Waele's law of shear thinning flow is combined with a shear stress of sliding depending on internal pressure by a power law. Examined feedstocks for metal injection molding showed a rheological behavior according to the model presented.     

Der Einfluß von Hautreinigungs- und Textilwaschmitteln auf den Hautlipoidmantel. Bestimmungen mit einer neuen Methode

Influence of Skin Cleansing Agents and Textile Washing Agents on the Surface Lipids of Skin. Determinations Using a New Method The hitherto known methods do not permit the repeated sampling of lipids. A combined absorption and diffusion method was therefore evolved. The lipid removal is most pronounced with textile washing agents and generally lesser (but not in all cases) with skin cleansing agents. The skin surface lipid is hardly affected adversely by bathing with bran. Following a bathing with oil, the lipid content exceeds the initial value. The regeneration of lipids is dependent on the intensity of the preceding lipid removal, requiring longer periods in the case of textile washing agents. The amount of lipid that can be removed immediately after bathing is mostly larger than before. This important fact was overseen uptil now. Soaking of the epidermis layers and emulsifier action must account for this phenomenon.     

1,2,3-Triazabutadiene. VII. Untersuchungen zum Mechanismus der fotochemischen cis-trans-Isomerisierung von 1-Aryl-3[3-methyl-benzthiazolinyliden-(2)]-triazenen

1,2,3-Triazabutadienes. VII. Investigation of the Mechanism of the Photochemical cis-trans-Isomerization of 1-Aryl-3-[3-methyl-benzthiazolinyliden-(2)]-triazenes The direct photoisomerizations of substituted triazabutadienes are investigated. The quantum yields do not considerably depend on substituents in the phenyl-group of triazabutadienes, on the wavelength of irradiation light and on the solvent. The quantum yields of the cis→trans-transformation are always higher than the quantum yields of the back reaction. The sums of quantum yields approximate 1. At low temperatures the quantum yields of photoisomerization become smaller in a significant way. With flash photolysis it is not possible to prove triplet state of triazabutadienes. Triplet quenchers have no influence on photoisomerization. The mechanism of the photochemical cis-trans-isomerization of triazabutadienes is discussed.     

Veränderungen im Fettsäuremuster von Leinsaat durch Standortfaktoren,spezifische Klimakonstellationen und mutagene Behandlung

Changes in the Fatty Acid Pattern of Linseed by Regional Factors, Specific Climatic Constellations and Mutagenic Treatment Studies on 9 varieties of linseed from a worldwide experiment at 14 locations showed distinct regional differences in the content of oleic and linolenic acid, while the content of saturated fatty acids and linoleic acid was almost constant. Since it was not evident as to which of the factors were especially effective, the effect of climatic factors, photo period, humidity of air, and temperature were studied in a phytotrone experiment using the same varieties. The intensity of the well known effect of temperature, i. e. low content of linolenic acid at higher temperatures and vice versa, was found to be dependent on the constellation of the ether two climatic factors. Greatly varying species specific responses to climatic parameters indicate strong interaction between variety and location as well as variety and weather. A mutagenic treatment by irradiation of the seeds and plants in EMS-solution yielded in the M₂ generation considerable alteration in the fatty acid pattern, especially a decrease in the linolenic acid content. Examination of the M₃ generation showed, however, that these effects were mainly due to modification. Only in two cases, mutants with lower content of linolenic acid were found after treatment with EMS.     

Phosphor-Free Apple-White LEDs with Embedded Indium-Rich Nanostructures Grown on Strain Relaxed Nano-epitaxy GaN

Phosphor-free apple-white light emitting diodes have been fabricated using a dual stacked InGaN/GaN multiple quantum wells comprising of a lower set of long wavelength emitting indium-rich nanostructures incorporated in multiple quantum wells with an upper set of cyan-green emitting multiple quantum wells. The light-emitting diodes were grown on nano-epitaxially lateral overgrown GaN template formed by regrowth of GaN over SiO₂ film patterned with an anodic aluminum oxide mask with holes of 125 nm diameter and a period of 250 nm. The growth of InGaN/GaN multiple quantum wells on these stress relaxed low defect density templates improves the internal quantum efficiency by 15% for the cyan-green multiple quantum wells. Higher emission intensity with redshift in the PL peak emission wavelength is obtained for the indium-rich nanostructures incorporated in multiple quantum wells. The quantum wells grown on the nano-epitaxially lateral overgrown GaN has a weaker piezoelectric field and hence shows a minimal peak shift with application of higher injection current. An enhancement of external quantum efficiency is achieved for the apple-white light emitting diodes grown on the nano-epitaxially lateral overgrown GaN template based on the light -output power measurement. The improvement in light extraction efficiency, η_extraction, was found to be 34% for the cyan-green emission peak and 15% from the broad long wavelength emission with optimized lattice period.     

Neue Befunde zum natürlichen und künstlichen Lichtschutz der Haut

New Observations on the Natural and Artificial Light Protection of Skin The hitherto known properties and mechanism of action of artificial light protection agents on human skin have been compared with author's own investigations pertaining to the base on which the preparations are formulated, significance of the UV B-absorption and the interrelationships between erythema and pigment reaction. Following results could be established: 1. Solutions of light filters in volatile solvents can act strongly light protecting; 2. the light protecting action is not only dependent on the protective film formed on the skin; 3. substances without appreciable UV B-absorption (purines and pyrimidines) have light protecting action; 4. intensity of browning of the skin is dependent on the preceding erythema reaction.     

Änderung der Lichtabsorption von 4′-Diethylamino-α-cyanostilben-4-diazoniumionen durch Komplexbildung mit Ethylenglycolderivaten,Kronenethern und Valinomycin

Colour Change of 4-Diethylamino-α-cyano-stilbene-4-diazonium Ions by Complex Formation with Ethylenglycol Derivatives, Crownethers and Valinomycine The formation and light absorption of complexes consisting of coloured stilbene-4-diazonium ions and different ethylenglycoles, crownethers and valinomycine were investigated. On complex formation the longest wavelength absorption band of the diazonium compounds shifts hypsochromically. This hypsochromism is solvent dependent. The difference between the absorption maximum of a free and complexed diazonium ion increases with increasing polarity and decreasing n-donicity of the solvents. Other complex forming cations are able to replace the diazonium ions in the complexes, whereby the colours of the original diazonium ions are regenerated. These colour changes can be used to indicate the ability of n-donor compounds to act as an ionophore.     

Einfluß von Licht und Tocopherolgehalt auf die Oxidationsstabilität von Fettsäuremethylestern

Influence of light and contents of tocopherols on the oxidative stability of fatty acid methyl esters The oxidative stability of different plant oil based fatty acid methyl esters can be estimated by determining the induction period with the active oxygen method. Measuring the volatile and oil soluble acids for a long period preceding the induction period shows that the values are approaching a certain limit. Even if the esters do not differ dramatically in the composition of fatty acids it is a fact that the different production processes influence the amount of tocopherols significantly. The exclusion of light is more crucial than the exclusion of air when storing plant oil based fatty acid esters.     

Über den Einfluß von Licht auf den oxydativen Verderb von Speiseölen V: Reaktionskinetik

Influence of Light on the Oxidative Deterioration of Edible Oils V: Kinetics of Reaction A time law for the photochemical oxidation without the decomposition of hydroperoxides has been derived from the radical chain mechanism in the oxidation of edible oils. Quantum yield of the photochemical start reaction and of the chain length can be calculated from the experimental results for soybean oil in the first phase. Using these kinetic values as well as from the quantum yield of the brutto reaction it is proven that the first phase in the autoxidation of soybean oil does not proceed by autocatalysis. Autocatalytic oxidations, e. g. soybean oil in the second phase, sunflower oil, and peanut oil, are discussed on the basis of investigations on the oxidation rate as a function of absorbed quantum current. It is found that owing to the presence of antioxidants, the degree of unsaturation of oils alone is not responsible for the readiness with which the oil is oxidized.     

Untersuchungen über den Gelierungsvorgang in Lösungen von stereoregulären Polymethylmethacrylaten

Gel formation in moderately concentrated solutions of mixtures of iso- and syndiotactic PMMA was studied using volumetric and dynamic mechanical techniques. The volume-temperature-curve and the gelation isotherms have the shape typical for partially crystalline systems. The analysis of the viscoelastic behaviour shows that the gel crosslinked by physical bonds is very similar to chemically crosslinked swollen systems in an according temperature range. Dynamic storage and loss moduli increase with decreasing temperature even after waiting for constant values of G' and G″ at higher temperatures. This is due to some further crosslinking after the initial network formation. Experimental results let us suppose that additional polymer molecules being dissolved at this time cause the subsequent crosslinking. The structure and, consequently, the mechanical properties are mainly dependent on the condition of gel formation. This is related to a nucleation mechanism.     

Zum abbau von polymerlösungen durch kapillarscherung. Einfluß der kapillarlänge und strömungsform auf den abbau

The dependence of shear degradation of polymer solutions on capillary length at constant shear stress is investigated with solutions of poly(isobutylene) (M_vis=6,1 · 10⁶) in toluene. We examined concentrations of 0.1, 0.25, 1 and 4% and found the degradation to increase with capillary length. In 0,1% solution we found a decreased efficiency of degradation, due to a change in the structure of solution. Flow instabilities, which appear above a critical shear rate D in polymer solutions and pretend a loss in viscosity, are not caused by shear degradation. This result supports our interpretation of unstable flow of polymer solutions as slip flow (spurt).     

Das Verhalten von Detergentien in Küstengewässern

Behaviour of Detergents in Coastal Water The action of tetrapropylene-benzene sulfonate on various organisms of brackish water having different salt contents was studied in laboratory experiments. At a constant amount of detergent, the detrimental action increases with increasing salt content. This is due to the reduction in surface tension caused by the detergent. In further experiments, the degradation of soft detergents (n-alkyl benzene sulfonate) in seawater was studied. After a certain period of adaptation, soft detergents are degraded in seawater in the same manner as in sweet water. In the estuaries of big German rivers, in general 0.1 mg/l surfactant was measured; only in the immediate neighbourhood of waste-water inlets higher levels (0.3 mg/l) can occur.