Mixing history

A toxic component of braken fern, perhaps either quercetin (105) or ptaquiloside, a glucoside (106), has a mixed history of carcinogenicity. It is sometimes impHcated in an increased incidence of bladder cancer in animals and esophageal cancer in humans. Multiple other dietary components seem to either promote or interfere with its action, and the significance of braken fern in human carcinogenesis remains unproven. 

There is a long and mixed history for the claims of discovery for ruthenium. In 1748 Antonio de UUoa (1716—1795), a Spanish scientist and explorer, reported finding a special metal in South America. It was silvery-gray and denser than gold, but it did not have the attractive luster of gold or silver. He did know that he had located a new element along with the platinum metal. 

Klochko K, Kaufman AJ, Yao W, Byrne RH, Tossell JA (2006) Experimental measurement of boron isotope fractionation in seawater. Earth Planet Sci Lett 248 276-285 Kloppmann Girard NSgrel P (2002) Exotic stable isotope composition of saline waters and brines from the crystalline basement. Chem Geol 184 49-70 Knauth LP (1988) Origin and mixing history of brines, Palo Duro Basin, Texas, USA, Applied Geochemistry 3 455 74... 

It is known that the spread of an inert tracer during its transit in the reactor can only yield information on macromixing (unless concentration fluctuations are measured as explained above). However, owing to its sensitivity to mixing history,... 

The primary research tools used in this program were C-E s Drop Tube Furnace System (DTFS), a bench scale entrained laminar flow furnace and the Controlled Mixing History Furnace (CMHF), a pilot scale entrained plug flow furnace. Both the DTFS and CMHF by virtue of their ability to resolve combustion time into distance along their respective furnace lengths were used to examine carbon burnout phenomena associated with the SRC and reference coals. In addition, the CMHF by virtue of its staged combustion capabilities was used extensively to evaluate N0X emissions and to establish conditions conducive to low N0X ... 

A number of standard and special bench scale tests along with the Drop Tube Furnace System (DTFS) and pilot scale Controlled Mixing History Furnace (CMHF) were employed in this program. 

In order to extrapolate the laboratory results to the field and to make semiquantitative predictions, an in-house computer model was used. Chemical reaction rate constants were derived by matching the data from the Controlled Mixing History Furnace to the model predictions. The devolatilization phase was not modeled since volatile matter release and subsequent combustion occurs very rapidly and would not significantly impact the accuracy of the mathematical model predictions. The "overall" solid conversion efficiency at a given residence time was obtained by adding both the simulated char combustion efficiency and the average pyrolysis efficiency (found in the primary stage of the CMHF). 

Knauth L. P. (1988) Origin and mixing history of brines, Palo Duro Basin Texas, USA. Appl. Geochem. 3, 455 -479. 

Standard mixing conditions were to melt blend the samples at 300 C for five minutes at a rotor speed of 40 RPM. The effect of mixing history on the structure of the LCP/LCP blends has not been investigated in the present work. Such a study has been reported by Mehta and Baird (i ).The samples were, then, given two minutes at 5 RPM followed by programming the rotor speed to 100 RPM in a two minute period. The speed is, then, instantaneously lowered back down to 5 RPM in two minutes. This is followed by two minutes at 5 RPM to determine whether the ramp test has affected the sample i n any way. 

Overall, the utility of 5HT-2 antagonists in the treatment of anxiety remains in question, given the mixed history of these compounds in animal and human studies. The fact that 5HT-2 agonists and antagonist have both been reported to show anxiolytic effects leaves the relative roles of the 5HT-2 subtypes in anxiety unclear. A fuller understanding of the contributions of the 2A, 2B, and 2C receptors to anx-... 

The lanthanides are notably insoluble under conditions existing at the surface of the earth and relatively immobile under most metamorphic conditions. They have extremely short residence times in sea water, less than the mixing time of the oceans, which is about 1000 years. Accordingly, this property is of use in tracing oceanic mixing history. 

Experiments on the pyrolysis of cellulose were carried out in a controlled mixing history reactor (CMHR), which is a plasma-operated drop-tube furnace capable of operating at temperatures up to 2500 K. A schematic diagram of the CMHR is shown in Figure 15.1. The graphite core reactor tube is 2 inches in diameter and 60 inches long. The central test section of the reactor has two 24-inch long... 

Figure 15.1. A schematic diagram of controlled mixing history reactor (CMHR).

Electrofusion technology for PE joint connections is essentially common to gas, water and industrial applications of MDPE and HOPE pipes and, because the coupler does not require direct pipe to pipe welding, the method can be used to join PE pipes with dissimilar melt flow characteristics. Where pipework of mixed history may occur this is a considerable advantage over butt welding. Similarly pipes of the same outer diameter but differing thickness, which cannot be securely butt welded, may be electrofused. Electrofusion couplers have also been made for PP and PB industrial and heating pipe systems. 

A polymer element that melts early will be exposed to a significant mixing history by the time it reaches the end of the melting zone. On the other hand, a polymer element that melts at the very end of the melting zone will have hardly any mixing history at the end of the melting zone. 

Rubber Chemistry and Technology 71, No.2, May/June 1998, p.310-22 NTTROSAMINE FORMATION IN RUBBER. I. INFLUENCE OF MIXING HISTORY... 

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