Another class of balanced graph designs: balanced circuit designs

A block considered as a set of elements together with its adjacency matrix A is called a C-block if A is the adjacency matrix of a circuit. A balanced circuit design with parameters v, b, r, k, λ (briefly, BCD(v, k, λ)) is an arrangement of v elements into bC-blocks such that each C-block contains k elements, each element occurs in exactly rC-blocks and any two distinct elements are linked in exactly λ C-blocks.We investigate conditions for the existence of BCD and show, in particular, that if the block-size k ? 6 and the trivial necessary conditions are satisfied, then the corresponding BCD exists.     

Palladium, rhodium and platinum complexes of ortho-xylyl-linked bis-N-heterocyclic carbenes: Synthesis, structure and catalytic activity

New Pd(II), Pt(II) and Rh(I) N-heterocyclic carbene (NHC) complexes containing two NHC units linked by an ortho-xylyl group are described and structurally and spectroscopically characterised. The Pt(II) complexes represent the first examples of Pt-bis(NHC) complexes where the NHC units are linked by an ortho-xylyl group. Functionalisation of the bis(NHC) ligands with heptyl groups has been used as a means of enhancing the solubility of the complexes, in order to facilitate spectroscopic characterisation and catalytic studies. The catalytic activity of the palladium(II) complexes in Heck and Suzuki cross-coupling reactions has been examined to investigate any effects of the diverse structural changes, though these appear to be insignificant.     

Size-specific reactions of copper cluster ions with a methanol molecule

Chemisorption of a methanol molecule onto a size-selected copper cluster ion, Cu(n)+ (n = 2-10), and subsequent reactions were investigated in a gas-beam geometry at a collision energy less than 2 eV in an apparatus based on a tandem-type mass spectrometer. Mass spectra of the product ions show that the following two reactions occur after chemisorption: dominant formation of Cu(n-1)+(H)(OH) (H(OH) formation) in the size range of 4-5 and that of Cu(n)O+ (demethanation) in the size range of 6-8 in addition to only chemisorption in the size range larger than 9. Absolute cross sections for the chemisorption, the H(OH) formation, and the demethanation processes were measured as functions of cluster size and collision energy. Optimized structures of bare copper cluster ions, reaction intermediates, and products were calculated by use of a hybrid method (B3LYP) consisting of the molecular orbital and the density functional methods. The origin of the size-dependent reactivity was explained as the structural change of cluster, two-dimensional to three-dimensional structures.     

Temporal onset-order discrimination through the tactual sense: effects of frequency and site of stimulation

This research extends the study of temporal resolution of the tactual sensory system through measurements of temporal-onset order discrimination for continuous tonal signals addressing (a) the effects of frequency separation of the two stimuli whose onset orders are to be discriminated and (b) the effects of redundant coding of frequency and site of stimulation on performance. Sinusoidal signals were presented either at two separate digits (thumb and index finger of the left hand) or at a single site of stimulation (left index finger) using a multifinger tactual stimulation system. Measurements were obtained using a one-interval two-alternative forced choice procedure in which each interval consisted of the random-order presentation of two different stimuli with roving values of amplitude and duration. Thresholds were estimated from psychometric functions of d' as a function of stimulus-onset asynchrony (SOA). On average, temporal onset-order thresholds were larger for one-finger conditions (mean SOA of 74.8 ms) than for two-finger conditions (mean SOA of 48.5 ms) and decreased as frequency separation increased, particularly for single-site presentation. Redundant coding of frequency and site of stimulation resulted in higher resolution by a factor of 1.5 compared to frequency alone and by a factor of 1.2 compared to site alone.     

Structural and photophysical studies of phenanthrene adducts involving C6F5HgCl and [o-C6F4Hg]3

Both pentafluorophenylmercury chloride and trimeric perfluoro-ortho-phenylene mercury interact with phenanthrene to form phosphorescent adducts which exhibit extended binary stacks in the solid state.     

Removing coordinated metal ions from proteins: a fast and mild method in aqueous solution

Thermodynamic and kinetic studies of metal binding to proteins require the investigation of metal-free proteins, which are often difficult to obtain. We have developed a very fast and mild method to eliminate metal ions from proteins by column chromatography using a commercially available Ni-NTA-type stationary phase. This material, initially designed for protein purification purposes in biotechnology, acts as a strong cation chelator when Ni²⁺ ions are removed. We have tested this new method with Ca-ATPase, an integral membrane protein exhibiting a strong affinity for Ca²⁺. By eluting the protein over the Ni²⁺-free NTA gel, we could remove 95% of the total Ca²⁺ and obtain an essentially Ca²⁺-free protein. This method is efficient with only a small amount of NTA gel, and we suggest that it can be applied in general for removal of metal ions from proteins. Moreover, as this procedure can be carried out under mild conditions, the chosen protein kept its enzymatic activity.