Corrosion inhibition in magnesium-aluminium-based alloys induced by rapid solidification processing

The effect of rapid solidification on the corrosion behaviour in aerated 0.001 M NaCl solution of Mg-Al alloys containing 9.6 to 23.4wt% AI has been investigated in comparison with chill-cast material. Polarization studies show that rapid solidification decreases corrosion current by up to two orders of magnitude corresponding to a corrosion rate of 6 to 11 mil y^–1. Increasing the aluminium content in solid solution by rapid solidification gave rise to a steep increase in pitting potential between 10 and 23 wt% Al and resulted in development of an anodic plateau at 30Acm^–2 attributable to magnesium depletion for the alloy surface and formation of a protective film. Chemical analysis of the electrolyte as a function of dissolution time for the rapidly solidified material indicated that initially only magnesium dissolved and that this dissolution of magnesium ceased within 2 to 5 min. The results indicate the formation of an aluminium-enriched interdiffusion zone at the surface underlying a more stable surface oxide than for ingot-processed Mg-Al-based alloys.     

Single amino acid substitutions can further increase the stability of a thermophilic L-lactate dehydrogenase

Lactate dehydrogenases are of considerable interest as stereospecificcatalysts in the chemical preparation of enantiomerically pure-hydroxyacid synthons. For such applications in synthetic organicchemistry it would be desirable to have enzymes which tolerateelevated temperatures for prolonged reaction times, to increaseproductivity and to extend then applicability to poor substrates.Here, two examples are reported of significant thermostabilizations,induced by sitedirected mutagenesis, of an already thermostableprotein, the L-lactate dehydrogenase (EC 1.1.1.27 [EC] , 35 kDa permonomer subunit) from Bacillus stearothermophilus. Thermal inactivationof this enzyme is accompanied by irreversible unfolding of thenative protein structure. The replacement of Argl71 by Tyr stabilizesthe enzyme against thermal inactivation and unfolding. Thisstabilizing effect appears to be based on improved interactionsbetween the subunits in the core of the active dimeric or tetramericforms of the enzyme. The thermal stability of L-lactate dehydrogenasevariants with an active site Arg residue, either in the 171(wild-type) or in the 102 position, is further increased bysulfate ions. The two stabilizing effects are additive, as foundfor the Argl71Tyr/ Gln1O2Arg double mutant, for which the stabilityof the protein in 100 mM sulfate solution reaches that of L-lactatedehydrogenases from extreme thermophiles. All mutant proteinsretain significant catalytic activity, both in the presenceand absence of stnhilfoing salts, and are viable catalysts inpreparative scale reactions.     

Surface analytical study of the interaction between γ-amino propyl triethoxysilane and E-glass surface

Time-of-flight secondary ion mass spectrometry has been used to study the interaction of -amino propyl triethoxysilane with an E-glass surface. The fragmentation pattern has been interpreted by assigning a series of mass peaks to the structural unit of the poly(aminosiloxane). The composition of the coating is complicated by the presence of polydimethylsiloxane and its copolymers. The highest mass fragment was obtained from the coating exposed by extraction with warm water (697 AMU). The largest molecular fragments would appear to have degrees of polymerization of 6 with differing numbers of silanol groups. On re-extraction with hot water the fragment size decreased. It is postulated that the network chain length of the three-dimensional polymer decreased as the interface was approached. At the glass surface a chemically bound molecular layer could be identified. The full chemical nature of the deposit is complicated by the incorporation of aluminium from the substrate into the coating. It was also possible to confirm that a layer of warm-water soluble oligomers existed at the air interface.     

Investigation of the levels of N(τ)-Methylhistidine in a range of beef cuts and offals

Protein-bound N(τ)-methylhistidine (N-MeHis) has been suggested as an index for the estimation of muscle (meat) protein in meat and meat products. This paper examines the levels of N-MeHis in a range of six prime beef cuts together with beef flank, cheek, mechanically recovered meat (MRM) and offals. The study was undertaken by two separate laboratories using a previously reported HPLC procedure involving the conversion of N-MeHis to a fluorescent derivative. It is shown that, whilst similar N-MeHis levels are present in the prime cuts, there is considerable variation in those found in the other cuts and offals. The average N-MeHis level in six prime cuts observed at both laboratories is 122 μg/g fat-free connective tissue-free (FFCF) meat; however, flank exhibits apparently high N-MeHis levels, whilst cheek and MRM contain only approximately 70% of the level found in the prime cuts. The offals contain between 0 and 65% of the N-MeHis level found in prime cuts. The greater variability and the often lower value of the N-MeHis content of these legitimate meat materials preclude the establishment of a single realistic index for FFCF beef, and present fundamental problems for the assessment of the lean meat content of manufactured beef products by N-MeHis determination.     

Psychology, history, and the press: The case of William McDougall and The New York Times..

A number of reasons have been suggested for the rapid decline in influence and credibility experienced by William McDougall after his arrival in America. To obtain some evidence on this issue, all articles appearing in The New York Times between 1906 and 1940 in which McDougall was mentioned were coded for the nature of the image conveyed. Articles mentioning the two authors most similar to McDougall in terms of number of citations, Joseph Jastrow and Edward L. Thorndike, were also coded for the nature of the image conveyed. In contrast to the images of Jastrow and Thorndike, the image McDougall conveyed was significantly more negative. McDougall was more often satirized, and references to McDougall were significantly less likely to be simple reporting of something he had said or done. Results are discussed in terms of the role of the press in "deciding" controversies in which the scientific community has lost interest. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

An integrated size and roundness adaptive control system for the plunge grinding process

A time variant, roundness based adaptive size and roundness control system is presented for the plunge grinding process which avoids the need for a large data processing capacity and compares favourably in performance with the large and expensive control system previously developed and therefore improves the prospect of industrial use. The non-linear control functions and adaptive model are presented and analysed. The hardware of the integrated, low cost system and the software algorithms used to reduce the computational power requirements are discussed and the results of grinding experiments are presented.     

An Active Feedback System for Stabilizing Visual Images

In normal vision, eye movements cause the image to move on the retina. Special apparatus can stabilize the image on the retina so it cannot move, and vision fades away. Previous methods for stabilizing the image were either optical systems or complex computer-controlled feedback systems. A simpler feedback system is presented which detects eye motion and rotates a mirror through which the target is viewed, to exactly compensate for eye motion. Unlike previous optical systems, this new system has no lenses in either the viewing or the image-forming path to limit the spatial resolution.     

On the selection of a subgoal and the use of a priori information in learning control systems

Numerous methods have been proposed for the design of control systems which learn to function in unknown or partially known environments. Most learning schemes are radical departures from the techniques using continuous adjustment of parameters which grew out of early developments in model reference systems. Principal contributions to the area have been controller models and algorithms. In studying these models, the system is abstracted to such an extent that there is quite often a loss of contact with practical considerations. The objective of this paper is to present some results in the theory of learning control, but also to look again at some of the practical problems encountered in applying a learning controller to a problem.

This paper defines the subgoal as a subordinate to the primary goal of minimizing the performance index. It must evaluate each decision one control interval after it is instituted. The subgoal problem is to choose a subgoal which will direct the learning process to the optimal as prescribed by the given performance index. An analytical solution is presented and extended heuristically for the general case. This extended method makes use of the a priori information about the plant.

Two other problems are also discussed. A fixed grid is used to partition the state space into control situations, and a method of extending the grid is proposed and evaluated. The controller is initialized using the a priori information, too. A full scale simulation confirms that the proposed methods of choosing the subgoal, extending the fixed grid and initializing the controller are improvements over previous methods.     

Mössbauer studies of iron-bearing minerals in coal and coal ash

⁵⁷Fe Mössbauer spectroscopy has been used to characterize the iron-bearing minerals present in some British Columbia coals. The minerals observed in a range of samples include pyrite/marcasite, siderite, jarosite, rozenite or melanterite, and Fe²⁺ -bearing clay minerals such as illite. The presence of jarosite is confirmed through the magnetic hyperfine interaction observed at 4.2 K. The absence of magnetic ordering at 4.2 K for the ferrous sulphate component indicates the presence of rozenite, FeS0₄ · 4H₂0, or melanterite, FeS0₄ · 7H₂0, rather than szomolnokite, FeS0₄ · H₂0 or FeS0₄. The effects of ashing on two of the coals is also studied.     

INVESTIGATION OF THE USE OF LASER-DOPPLER VELOCIMETRY IN TWO-PHASE BUBBLY FLOWS

Understanding the dynamic phenomena of viability loss of shear sensitive cells and bubble breakage and coalescence within airlift reactors requires knowledge of local, liquid-phase hydrodynamics. The laser-Doppler velocimeter (LDV) is a non-invasive instrument which may be used to obtain this information. Experimental procedures and software were developed to detect and measure Doppler bursts in two-phase flow in a split-cylinder airlift reactor. Off-line analysis of the data indicated a detection rate approximately one order of magnitude greater than that observed using an available commercial frequency tracker. Approximately 400 to 500 observations are needed for the ensemble mean to characterize the local mean velocity to within ±5% for a superficial gas velocity of 10.4 cm/s, the highest superficial gas velocity used in these studies. The limitations, prospects, and signal-processing options for LDV in this application are also discussed