The Stability of Bredigite and Other Ca-Mg Silicates

The phase Ca₇Mg(SiO₄)₄, bredigite, is chemically and structurally distinct from α-Ca₂SiO₄. Experiments on its lower stability limit represent a synthesis limit which is not likely to be an equilibrium boundary. Equilibrium experiments place its upper stability limit at 1372°C and 98 kPa by the reaction

The experimental data also require a second reaction

at the same pressure and temperature and imply that two other reactions relating these phases are located near 1372°C and 98 kPa. Location of these four reactions around an invariant point in P-T space shows that bredigite is on the low-pressure side of the reactions.     

AI and the mechanistic forces of darkness

In this paper we have studied the empirical relation between the hardness of the temporal 3-consistency problem with respect to its inherent problem structure. This is a sub-problem of the temporal constraint satisfaction problem (TCSP). The problem structure has been identified with some quantifiable parameters of the constraint graph. Our work is in line with the recent experimental studies of NPcomplete problems, except that in our case a richer repertoire of independent variables make a straight forward study impossible. Hence we have resorted to a deeper statistical analysis in order to develop a regression model as the sought after quantitative empirical relationship between the problem structure and the timecomplexity. Our model shows robustness against repeated experimentation and, a strong predictive power on independent verification. We also hope that this paper will contribute towards the development of a more rigorous experimental methodology in artificial intelligence than what is being practiced now.     

Initial observations on using SAR to monitor wildfire scars in boreal forests

Abstract

Initial observations on the effects of wildfires in black spruce forests on radar backscatter are presented. Airborne and spaceborne SAR imagery are utilized to illustrate two distinct fire signatures. A theory is presented to explain these differences.     

Aggregate Characteristics in Coagulation and Flocculation

Physical characteristics of mineral aggregates (such as density, size, shape, structure and strength) formed by either electrolytic coagulation or polymeric flocculation, need to be critically controlled by optimum conditioning in mineral processing. The present paper discusses the various experimental techniques used to determine these properties. In addition, physical and chemical factors that determine the rates of floe growth and which subsequently influence the floe morphology are summarised. This review also elucidates the hydrodynamic aspects of creeping flow and summarises the various settling velocity equations pertaining to the calcuation of floe density.     

WHAT IT MEANS TO BE "SITUATED"

Situated action is a new approach to artificial intelligence that has thus far functioned without any explicit underlying theoretical foundation. As a result, many researchers in artificial intelligence have misunderstood the goals and claims of situated action. In order to rectify this situation, we provide an explicit formulation of the theoretical foundations of situated action.     

A review of: “ANTICIPATORY SYSTEMS”, by Robert Rosen,Pergamon Press,Oxford, 1985, X + 436pp.

In rough set theory there exists a pair of approximation operators, the upper and lower approximations, whereas in Dempster-Shafer theory of evidence there exists a dual pair of uncertainty measures, the plausibility and belief functions. It seems that there is some kind of natural connection between the two theories. The purpose of this paper is to establish the relationship between rough set theory and Dempster-Shafer theory of evidence. Various generalizations of the Dempster-Shafer belief structure and their induced uncertainty measures, the plausibility and belief functions, are first reviewed and examined. Generalizations of Pawlak approximation space and their induced approximation operators, the upper and lower approximations, are then summarized. Concepts of random rough sets, which include the mechanisms of numeric and non-numeric aspects of uncertain knowledge, are then proposed. Notions of the Dempster-Shafer theory of evidence within the framework of rough set theory are subsequently formed and interpreted. It is demonstrated that various belief structures are associated with various rough approximation spaces such that different dual pairs of upper and lower approximation operators induced by the rough approximation spaces may be used to interpret the corresponding dual pairs of plausibility and belief functions induced by the belief structures.     

The Aqueous and Surface Chemistry of Activation in the Flotation of Sulphide Minerals—A Review. Part II: A Surface Precipitation Model

The activation of sulphide minerals by heavy metal ions at medium to alkaline pH solutions is reviewed. The pH-dependent characteristics of adsorption are identically indicated by adsorption isotherms, surface potential and flotation responses. The mechanisms involved are explored. It is found that the initial adsorption process is controlled essentially by surface precipitation of the activator hydroxide. The real activation of flotation is obtained during the second stage—the surface conversion step. The industrial practice of activation and flotation with a highly alkaline solution highlights the proposed model and mechanisms. The mechanism underlying the intermediate pH depression of flotation of the activated mineral is discussed.     

The Chemistry of Cyanide-Metal Complexes in Relation to Hydrometallurgical Processes of Precious Metals

Abstract

Thermodynamic stability diagrams have been constructed for the cyanide-metal-sulphide/telluride/selenide systems. These were used to study the solution chemistry of the various metal-cyanide complexes in connection with cyanide leaching of gold and silver from complex sulphide, arsenosulphide, telluride and selenide ores. The results show that the formation of the metal-cyanide complexes and their stability relative to the metal oxides and sulphides depend critically on the total concentration of the cyanide and metal ions. At lower concentration ratios of Tc(CN)/Tc(Me), Ag, Cu, Ni and Zn all form insoluble metal cyanide precipitates. At higher concentration ratios, the precipitates are dissolved to form soluble cyano-metal complexes. The formation of gold and silver sulphides does not affect the stability region of aurocyanide and silver-cyanide complexes. Gold and silver telluride and selenide are stable in the presence of cyanide. These results suggest that direct leaching of gold and silver tellurides and selenides with cyanide is probably ineffective. The metal sulphides are classified into two groups according to their stability relative to the cyano-metal complexes. The application of these results to the cyanide leaching of gold and silver is discussed.     

Oxymyoglobin Oxidation as Affected by Oxidation Products of Phosphatidylcholine Liposomes

Supernatants (105,000 ×g) of oxidized phosphatidylcholine (PC) liposomes contained higher levels of thiobarbituric acid-reactive substances, and caused greater metmyoglobin formation when combined with oxymyoglobin than those of controls (C) or PC plus tocopherol (PCT) (P<0.05). Products of PC liposome oxidation crossed dialysis membranes (mol wt cut-off = 500 Dalton) and accelerated the oxidation of oxymyoglobin more than C or PCT (P<0.05). The addition of known oxidation products of oleic acid and linoleic acid, fatty acids typical of PC, accelerated oxymyoglobin oxidation relative to controls (P<0.05). Results demonstrated that oxidation products of PC were prooxidative towards oxymyoglobin.     

邻苯二甲酸二异壬酯增塑剂在提高挤出效益方面的应用

重点探讨了邻苯二甲酸二异壬酯（DINP-S）在提高挤出效益方面的优越性，在典型的挤出加工条件下，DINP-S比DOP更能降低混合料的熔融粘度，这有助于降低口模压力，减少机械磨损或提高挤出生产率（高达21%），这种生产率的提高可在无须更改产品配方和生产工艺，无须额外固定投资，无须额外能耗，且保持产品品质的情况下实现。