Structural and spectroscopic studies with dithizone and its derivatives

Bibliography: p. 262-274.An X-ray crystal structure detennination of 3-nitro-l,5-di(2,6-dimethylphenyl) fonnazan, ArN:N•C(N02):N•NHAr (Ar= 2,6-dimethylphenyl), has shown that the N-N-C-N-N chain is stabilized by an unusual hydrogen bond in the closed-ring syn,s-cis configuration relative to the formal double C=N and single C-N bonds. The bond lengths reveal complete n-electron delocalization along the chain which results in a mesomeric structure; the possibility of such a mesomeric structure existing in solution rather than a rapid tautomeric equilibrium between two limiting forms of the resonance hybrid has been considered in the light of i.r. and n.m.r. spectroscopic measurements. The temporal changes in the visible absorption spectrum of S-methyldithizone, PhN:N•C(SCH3):N•NHPh, have been shown to arise from syn-anti isomerization about the fonnal C=N double bond and rotation about the C-N single bond by considering the evidence provided by i. r. and n.m.r. spectroscopic studies combined with the X-ray crystal structure of the di(o-tolyl) homologue. The parent compound dithizone, PhN:N•C(SH):N•NHPh, previously thought to exist as an equilibritim of thiol and thione forms in solution has now been shown to consist of a single species in solution mainly by consideration of its n.m.r. spectroscopic properties. Organomercury(II) complexes of dithizone have been shown to be photochromic in solution; X-ray crystal structure detenninations of phenyland methylmercury(II) dithizonate, besides revealing rare three-coordination of mercury, have been combined with spectroscopic measurements on the normal and activated fonns to reveal the structure of the labile photo-isomers

Development and Application of Two New Brushless Reluctance Motor Drives

The switched reluctance (SR) motor is a new form of brushless DC motor without permanent magnets, capable of low cost manufacture and a wide speed range. Because of its simplicity, ruggedness and wide speed range, it is a candidate for a broad range of applications from domestic appliances to aerospace and automotive actuators. In this thesis, two original aspects of the SR motor drive are explored. First, the application of the SR motor to a domestic food processor is explored by designing, building and testing two prototype drives. This project provided experience on the entire system design. In particular, it permitted an evaluation of the SR drive at high speed with respect to its efficiency, thermal characteristics, power density and noise level in comparison with a conventional AC series commutator motor with triac control. The second aspect of this thesis is an original investigation into the use of flux screens to improve the specific torque (torque per unit volume) of 'the switched reluctance motor. The torque of the SR motor is determined by the variation of self-inductance of the phase windings as the rotor rotates. Under dynamic operating conditions this variation can, in principle, be increased by dynamically decreasing the minimum selfinductance through the use of eddy current screens. Several configurations of screens are postulated, analyzed by finite-element techniques and tested in an experimental motor. Although the experimental results are inconclusive, this investigation introduces some interesting possibilities for future motors. The work described in this thesis was entirely sponsored by industry, and particular acknowledgement is made to Kenwood Ltd. (food processor project); Lucas (disk motor project); and the SPEED consortium (flux screen project)

The Scottish Political Economy Tradition and Modern Economics

The purpose of this article is to re-examine the notion of a Scottish tradition in political economy in the light of recent developments in the methodology of economics. Consideration is given to the concept of tradition itself, which puts the focus on approach to theorising and the relationship between theory and reality rather than theoretical content. It is argued that the Scottish approach provided the foundations for much of modern political economy. Further, modern discussion of constructivism and critical realism can both be seen to have precedents in the Scottish tradition. Indeed the Scottish political economy tradition provides an exemplar of a constructive blending of the two strands

Rae and the Tradition of Scottish Political Economy

The purpose of the chapter is to investigate how far Rae is representative of the Scottish Political Economy Tradition, where tradition is understood in terms of continuity in a shared approach, allowing for theoretical differences. While Rae conforms to most features identified with the Scottish tradition, his opposition to Smith’s methodology suggests a divergence of approach which would put him outside the tradition. It is argued here that this divergence applies only to Rae’s professed methodology, not to his practice

Traditions in thought: The case of Scottish political economy

A number of commentators have recently identified a 'uniquely Scottish mode of thought in economics', or a particular 'Scottish political economy tradition'. In this paper the concept of tradition, defined as those features common to practitioners over a relatively long period, is investigated in relation to 'school', 'paradigm' and 'research programme'. An application of the concept to the Scottish Enlightenment period suggests that its use is in line with the philosophical approach of Adam Smith, and shows that the concept allows account to be taken of external institutional/historical influences in interpreting the history of economics

Young Latinos Use of Mobile Phones: A Cross-Cultural Study

Article discussing a cross-cultural study designed to analyze how young people, operationalized in this study as people of Latino descent between the ages of 18-25, are using their mobile phone for various applications and what particular gratifications they derive from using the phone

Anticipating causes and consequences

Two visual world eye-tracking experiments investigated anticipatory looks to implicit causes and implicit consequences in two clause sentences with mental state verbs (Stimulus-Experiencer and Experiencer-Stimulus) in the first main clause, and an explicit cause or consequence in the second. The first experiment showed that, just as when all continuations are causes, people look early at the implicit cause, when all continuations are consequences they look early at the implicit consequence, for the same verbs. When causes and consequences are intermixed, people direct their looks at the cause or consequence on a trial-by-trial basis depending on the connective (“because” or “and so”). Numerically, causes were favored overall, even when all the endings were consequences, but the effect was only significant at the end of the sentences in Experiment 2. The results are discussed in terms of rapid deployment of causal and consequential information implicit in mental state verbs, and in relation to conflicting accounts of why causes or consequences might generally be favored

Southern California Seismic Network Update

The authoritative region of the Southern California Seismic Network (SCSN) extends across southern California, from the U.S./Mexico international border to Coalinga and Owens Valley in central California (Figure 1). This area contains almost 20 million inhabitants, including two of the ten largest cities in the United States (Los Angeles and San Diego) and the two largest harbors (Los Angeles and Long Beach) in the nation. SCSN also reports on earthquakes in Baja California, which could potentially cause damage in the U.S. More than fifty earthquakes (not including aftershocks) are felt each year, and an average of 1.5 events per year are potentially damaging (magnitude greater than 5.0). Immediately after a moderate or large earthquake, SCSN provides information about the size, location, and distribution of ground shaking. Emergency managers use this information to coordinate rescue operations, guide inspectors in the search for damage, and satisfy the public's need for information. The historical record of earthquake occurrences in California is important to insurers, geotechnical engineers, and city planners

Mapping the topography of a protein energy landscape

Protein energy landscapes are highly complex, yet the vast majority of states within them tend to be invisible to experimentalists. Here, using site-directed mutagenesis and exploiting the simplicity of tandem-repeat protein structures, we delineate a network of these states and the routes between them. We show that our target, gankyrin, a 226-residue 7-ankyrin-repeat protein, can access two alternative (un)folding pathways. We resolve intermediates as well as transition states, constituting a comprehensive series of snapshots that map early and late stages of the two pathways and show both to be polarized such that the repeat array progressively unravels from one end of the molecule or the other. Strikingly, we find that the protein folds via one pathway but unfolds via a different one. The origins of this behavior can be rationalized using the numerical results of a simple statistical mechanics model that allows us to visualize the equilibrium behavior as well as single-molecule folding/unfolding trajectories, thereby filling in the gaps that are not accessible to direct experimental observation. Our study highlights the complexity of repeat-protein folding arising from their symmetrical structures; at the same time, however, this structural simplicity enables us to dissect the complexity and thereby map the precise topography of the energy landscape in full breadth and remarkable detail. That we can recapitulate the key features of the folding mechanism by computational analysis of the native structure alone will help toward the ultimate goal of designed amino-acid sequences with made-to-measure folding mechanisms—the Holy Grail of protein folding