The Kinetics and Mechanism of the Thermal Dehydrochlorination of Poly(vinyl Chloride)

Poly(vinyl chloride) degrades thermally by an acceleratory reaction in which the rate of hydrogen chloride evolution is slow at the beginning, increases with time (passing through a maximum), and then decreases. A kinetic model based on the zipper mechanism shows excellent agreement with observed data from the initial to the final stages of each dehydrochlorination. Hydrogen chloride is shown to be essential for the initiation of zip chains and may or may not be essential for the zip reaction. When hydrogen chloride is removed in a stream of inert gas, as it is in some tests purported to study the kinetics of degradation, the initiation of zip chains is significantly inhibited. The zip reaction, once it has been initiated, is not inhibited or stopped even by long exposure to atmospheric conditions.     

Selection of single,mode-locked CO2 laser pulses by semiconductor reflection switching

Reflection switching of high power, 10 μm radiation by optically induced carriers in a semiconductor has been achieved by irradiating germanium with 3 ns pulses of 1.06 μm radiation. This has permitted the selection of single mode-locked pulses of 10 μm radiation with energies in the 1–2 joule range.     

GC-FTIR and GC-MS in odour analysis of essential oils

The analysis of odour components in East Indian Sandalwood Oil (Santalum album L.) and in Patchouli Oil (Pogostemon cablin Benth.) based on GC-, GC-FTIR- and GC-MS-data resulted in the identification of-santalene,-santalal,-santalal, epi--santalal,-santalol,-santalol, (E)--santalol,-bergamotol and spirosantalol in Sandalwood Oil and of (–)-patchoulol,-guaiene,-patchoulene, seychellene,-bulnesene, norpatchoulenol and pogostol in Patchouli Oil as the most intense aroma compounds of these oils.     

Hydroxypropyl guar-borate interactions with tear film mucin and lysozyme

The interactions of hydroxypropyl guar (HPG) with boric acid, lysozyme, and mucin were characterized by rheology, light scattering, electrophoresis, and isothermal titration calorimetry to help understand how HPG interacts with tear film components. Borate binds to guar under pH, temperature, and ionic strength conditions representative of those found in the eye. The HPG-borate complexes behave as anionic polyelectrolytes and thus interact with cationic lysozyme, a major tear film protein, whereas HPG-borate does not appear to bind to mucin, an anionic glycoprotein. The interactions of HPG, borate, lysozyme, and mucin can be explained by two physical interactions: (1) pH-dependent binding of borate to carbohydrates and (2) the electrostatic attraction of oppositely charged macromolecules.     

Checkerboard maps

When a map has one positive Lyapunov exponent, its attractors often look like multidimensional, Cantorial plates of spaghetti. What saves the situation is that there is a deterministic jumping from strand to strand. We propose to approximate such attractors as finite sets of K suitably prescribed curves, each parametrized by an interval. The action of the map on each attractor is then approximated by a map that takes a set of curves into itself, and we graph it on a KxK checkerboard as a discontinuous one-dimensional map that captures the quantitative dynamics of the original system when K is sufficiently large. (c) 1995 American Institute of Physics.