Moments and cumulants of the multivariate normal distribution

Expressions in vector notation are given for the central moments, the non–central moments and the cumulants of arbitrary order of the multivariate normal distribution     

Market Price Calculations in Restructured Electricity Markets

In the traditional organisation of the power market, the generation Unit Commitment and Dispatch problem was solved as a cost minimisation problem. After deregulation of the electricity sector, the problem must be solved as a profit maximising problem. It is necessary to find feasible market prices. This is difficult, because simple marginal cost based prices not always cover startup and operation-independent costs, with the result that the generator would choose not to run with such prices. In this paper a market structure is proposed with a central market operator computing the market equilibrium for both energy and reserves, based on generator offers and consumer bids. It is shown that it is possible to find feasible market prices. Using a simple test system, it is shown that demand elasticity can have a profound impact on prices and generator revenues and profits during peaking hours.     

Electron paramagnetic resonance and density-functional theory studies of Cu(II)-bis(oxamato) complexes

In this work we present the investigation of the influence of electronic and structural variations induced by varying the N,N'-bridge on the magnetic properties of Cu(II)- bis(oxamato) complexes. For this study the complexes [Cu(opba)] (2-) ( 1, opba = o-phenylene- bis(oxamato)), [Cu(nabo)] (2-) ( 2, nabo = 2,3-naphthalene- bis(oxamato)), [Cu(acbo)] (2-) ( 3, acbo = 2,3-anthrachinone- bis(oxamato)), [Cu(pba)] (2-) ( 4, pba = propylene- bis(oxamato)), [Cu(obbo)] (2-) ( 5, obbo = o-benzyl- bis(oxamato)), and [Cu(npbo)] (2-) ( 6, npbo = 1,8-naphthalene- bis(oxamato)), and the respective structurally isomorphic Ni(II) complexes ( 8- 13) have been prepared as ( (n)Bu 4N) (+) salts. The new complex ( (n)Bu 4N) 2[Cu(R-bnbo)].2H 2O ( 7, R-bnbo = (R)-1,1'-binaphthalene-2,2'- bis(oxamato)) was synthesized and is the first chiral complex in the series of Cu(II)-bis(oxamato) complexes. The molecular structure of 7 has been determined by single crystal X-ray analysis. The Cu(II) ions of the complexes 1- 7 are eta (4)(kappa (2) N, kappa (2) O) coordinated with a more or less distorted square planar geometry for 1- 6 and a distorted tetrahedral geometry for 7. Using pulsed Electron Nuclear Double Resonance on complex 6, detailed information about the relative orientation of the hyperfine ( A) and nuclear quadrupole tensors ( Q) of the coordinating nitrogens with respect to the g tensor were obtained. Electron Paramagnetic Resonance studies in the X, Q, and W-band at variable temperatures were carried out to extract g and A values of N ligands and Cu ion for 1- 7. The hyperfine values were interpreted in terms of spin population on the corresponding atoms. The obtained trends of the spin population for the monomeric building blocks were shown to correlate to the trends obtained in the dependence of the exchange interaction of the corresponding trinuclear complexes on their geometry.     

Size and morphology of assemblies formed by DNA and lysozyme in dilute aqueous mixtures

Assemblies formed by a well-defined quality of DNA (4331 bp T7 DNA) and the small net-cationic protein lysozyme in dilute aqueous solutions have been characterized using cryo-transmission electron microscopy (cryo-TEM) and dynamic light scattering (DLS) as the main techniques. In a wide range of different DNA to lysozyme ratios in solutions of low ionic strength, dispersions of aggregates with the same general morphology and a practically constant hydrodynamic size are formed. The basic structure formed in the dispersions is that of rather flexible worm-like assemblies with a diameter of 10-20 nm, which are suggested to be made up by bundles of on the order of 10 DNA chains with an intervening matrix of lysozyme. With increased ionic strength, the worm-like appearance of the assemblies is lost and they adopt a less well-defined shape. The results suggest that the formation of the DNA-lysozyme aggregates is strongly influenced by cooperative assembly of the components and that, in addition to the electrostatic attraction between DNA and lysozyme, attractive interactions between the protein units are important in governing the behavior of the system.     

Influence of the formation of an oxidized layer on the dynamic-mechanical properties of natural rubber

Natural rubber cylinders vulcanized with two different systems, TMTD and S/CBS, were aged for more than 2000 h in an air oven at 100 °C. During the ageing an oxidized layer formed on the surfaces of the specimens. To study the differences between the interior of the materials and their surfaces, and to find out how the interior of the materials was affected by the ageing, measurements were performed both on whole specimens and on specimens from which the surface layer had been removed. Dynamic mechanical (complex) modulus and loss-angle were recorded intermittently. The surface layer was hard and brittle because of thermo-oxidative crosslinking and probably had a low permeability to oxygen. The modulus of the interior material decreased slightly during the ageing. After ageing, the specimens cracked easily during deformation. The difference between surface and interior was greater, and the formation of the surface layer started earlier, when the material was vulcanized with S/CBS.     

Synthesis, Structure and Properties of Na2Zn(OEt)4(HOEt)5

The synthesis, structure and properties of Na₂Zn(OEt)₄(HOEt)₅, having the right Na:Zn ratio for sol–gel synthesis of the highly Na-ion conducting ceramic Na_1.8Zn_0.9Si_1.1O₄, is described. It was synthesised in high yield by a metathesis reaction of ZnCl₂ and 4NaOEt in ethanol or ethanol/toluene solvent. The structure was determined by single-crystal X-ray methods and consists of two symmetry related polymeric strands with the metal sequence ...–Zn–Na–Na–Zn–.... Extensive hydrogen bonding is present within each chain. Further characterization was made with IR- and Raman-spectroscopy and thermo-calorimetry, showing that the compound is stable to 65°C.     

Self-assembled heterogeneous argon/neon core-shell clusters studied by photoelectron spectroscopy

Clusters formed by a coexpansion process of argon and neon have been studied using synchrotron radiation. Electrons from interatomic Coulombic decay as well as ultraviolet and x-ray photoelectron spectroscopy were used to determine the heterogeneous nature of the clusters and the cluster structure. Binary clusters of argon and neon produced by coexpansion are shown to exhibit a core-shell structure placing argon in the core and neon in the outer shells. Furthermore, the authors show that 2 ML of neon on the argon core is sufficient for neon valence band formation resembling the neon solid. For 1 ML of neon the authors observe a bandwidth narrowing to about half of the bulk value.