Decomposition of carthamin in aqueous solutions: influence of temperature, pH, light, buffer systems, external gas phases, metal ions, and certain chemicals

Summary External factors suspecting to influence the chemical nature of carthamin in aqueous media were assessed under experimentally designed model systems. The pigment was more readily decomposed to orange-yellow or yellow compounds at higher temperature. The stability of carthamin was evidently pH-dependent, with increased degradation occurring above and below the pH range in which the red pigmentation is most stable (pH 1.5–5.5). On exposure to visible and ultraviolet light, the red colour in aqueous solutions decreased with half-lives of approximately 1 and 40 min, respectively. Loss of carthamin red coloration also occurred without perceptible dependence on the buffer systems, external gas phases or certain chemicals. Metal ions at a level of 0.03–3.0 mmol concentration caused an increase in the degradation rate compared to that of the control with no metal cations. Fe²⁺ had the greatest effect, reducing the rate of degradation approximately 47-fold compared to the control. The reaction systems were surveyed spectrophotometrically to check carthamin composition patterns.

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Abbau von Carthamin in wäßrigen Lösungen: Einfluß von Temperatur, pH-Wert, Licht, Puffersystemen, äußerer Gasphase, Metallionen und einiger Chemikalien

Zusammenfassung Äußere Faktoren stehen im Verdacht, die chemische Natur des Carthamin zu beeinflussen; es wurde daher der Versuch unter Modellbedingungen im wäßrigen Milieu unternommen. Das Pigment wurde leicht bei höheren Temperaturen in orangegelbe und gelbe Verbindungen zersetzt. Die Stabilität von Carthamin war pH-abhängig, wobei die rote Färbung die stabilere ist (pH 1,5–5,5). Gegenüber dem sichtbaren und dem UV-Licht nahm die Farbstärke innerhalb 1–40 min rund um die Hälfte ab. Der Verlust der roten Farbe von Carthamin ist augenscheinlich bedingt durch das Puffersystem, die äußere Atmosphäre und einige Chemikalien. Metallionen in Konzentration von 0,03–3,0 mmol erniedrigen die Farbstärke, wobei Eisenionen den größten Effekt haben, nämlich daß die Abbaurate das 47fache der Kontrolle beträgt. Die Reaktionen wurden spektrometrisch überwacht, um die Carthaminzusammensetzung zu kontrollieren.

     

Effects of initial diaphragm shape on spontaneous ignition of high-pressure hydrogen in a two-dimensional duct

A two-dimensional (2-D) simulation of spontaneous ignition of high-pressure hydrogen in a length of duct is conducted to explore ignition mechanisms. The present study adopts a 2-D rectangular duct and focuses on effects of the initial diaphragm shape on spontaneous ignition. The Navier–Stokes equations with a detailed chemical kinetics mechanism are solved in a manner of direct numerical simulation. The detailed mechanisms of spontaneous ignitions are discussed for each initial diaphragm shape. For a straight diaphragm, ignition only occurs near the wall owing to the adiabatic wall condition, while three ignition events are identified for a greatly deformed diaphragm: ignition due to reflection of leading shock wave at the wall, hydrogen penetration into shock-heated air near the wall, and deep penetration of hydrogen into shock-heated air behind the leading shock wave.     

Negative thermal expansion materials: technological key for control of thermal expansion

Most materials expand upon heating. However, although rare, some materials contract upon heating. Such negative thermal expansion (NTE) materials have enormous industrial merit because they can control the thermal expansion of materials. Recent progress in materials research enables us to obtain materials exhibiting negative coefficients of linear thermal expansion over −30 ppm K⁻¹. Such giant NTE is opening a new phase of control of thermal expansion in composites. Specifically examining practical aspects, this review briefly summarizes materials and mechanisms of NTE as well as composites containing NTE materials, based mainly on activities of the last decade.     

A method to cope with the random errors of observed accident rates in regression analysis

The paper is concerned with linear multiregression analysis on accident rates related to road geometric design elements. Supposing that a data set of accident records and geometric design elements of a certain stretch of a road is given, there are two steps for regression analysis: first, division of the road into a number of segments; and second, application of regression analysis to the set of segments. The main interest of the present paper is the first step. Occurrence of a traffic accident in a road segment is a stochastic event and an observed accident rate in a segment contains a certain magnitude of random error that deteriorates the explanatory power and reliability of the regression analysis. Random errors are required to be appropriately controlled for an effective regression analysis. The first part of the paper discusses how to evaluate a random error contained in an accident rate of a road segment and shows that a random error depends on the number of accidents and vehicle-kilometerage of the segment. It is then shown that random errors of the segment should be as much as possible equal to each other and small enough compared with the accident rate variance based on the discussion of how the random errors affect the efficiency of regression analysis. Several alternative criteria on the random errors for dividing a road into segments are proposed and numerical examples of Tokyo-Kobe Expressway are presented to examine the appropriateness of the alternative criteria. One of them is finally recommended as the most practically useful criterion.     

Enteric vascular endothelial response to bacterial endotoxin

The response of enteric vasculature to endotoxin was examined at the ultrastructural level using a murine model of endotoxin-induced acute diarrhoea. Morphological changes indicative of endothelial damage were evident as early as 15 minutes following endotoxin challenge. These changes, characterized by widening of intercellular spaces, increased microvillous projections and the appearance of stress fibres, preceded the leucocytic response. Endothelial damage increased with time, being associated with progressive degenerative changes in the plasma membrane, cytoplasm and organelles, ultimately leading to desquamation. These latter changes were temporally associated with margination of neutrophils and platelet adhesion to the denuded subendothelium. The venules were the primary site of these changes while the capillaries were the least affected. The arterioles were markedly constricted with minimal endothelial damage. These changes suggest that the enteric vascular endothelium may be an important target organ, and the resultant endothelial injury may have implications in host responses to endotoxin.