Fermi-surface anisotropy in potassium and the effect of hydrostatic pressure

The anisotropy of the Fermi surface (FS) of potassium has been determined with improved precision. The anisotropy and absolute value of the pressure coefficient for the potassium FS in the 25-bar pressure range have also been measured. The pressure coefficient anisotropy is some eight times greater than, and of similar form to, the FS anisotropy. The mean value of the (area) pressure coefficient is 1.720±0.008×10^-2/kbar, which is some 5% lower than that predicted from the bulk modulus. No obvious reason has been found for the discrepancy between our result and that obtained from high-pressure measurements.     

Vertical fracture dislocation of the tarsal navicular

An isolated vertical fracture dislocation of the left tarsal navicular with some comminution was successfully treated with open reduction and internal fixation with a screw. The surgical treatment is described, and early mobilization strongly recommended.     

Intrauterine growth retardation associated with hypoxia due to bronchiectasis

Two pregnancies in a young patient who had undergone lobectomy for bronchiectasis are described. Both were complicated by intrauterine growth retardation. The only abnormality detected was maternal hypoxaemia, and this was assumed to be causal.     

The monolayer thickness dependence of quantized double-layer capacitances of monolayer-protected gold clusters

This report describes how the electrochemical double-layer capacitances of nanometer-sized alkanethiolate monolayer-protected Au clusters (MPCs) dissolved in electrolyte solution depend on the alkanethiolate chain length (C4 to C16). The double-layer capacitances of individual MPCs (C(CLU)) are sufficiently small (sub-attoFarad, aF) that their metal core potentials change by >0.1 V increments for single electron transfers at the electrode/solution interface. Thus, the current peaks observed are termed "quantized double layer charging peaks", and their spacing on the potential axis varies with C(CLU). Differential pulse voltammetric measurements of C(CLU) in solutions of core-size-fractionated (i.e., monodisperse) MPCs are compared to a simple theoretical model, which considers the capacitance as governed by the thickness of a dielectric material (the monolayer, whose chain length is varied) between concentric spheres of conductors (the Au core and the electrolyte solution). The experimental results fit the simple model remarkably well. The prominent differential pulse voltammetric charging peaks additionally establish this method, along with high-resolution transmission electron microscopy and laser ionization-desorption mass spectrometry, as a tool for evaluating the degree of monodispersity of MPC preparations. We additionally report on a new tactic for the preparation of monodisperse MPCs with hexanethiolate monolayers.     

PICquant: a quantitative platform to measure differential peptide abundance using dual-isotopic labeling with 12C6- and 13C6-phenyl isocyanate

We have developed a complete system for the isotopic labeling, fractionation, and automated quantification of differentially expressed peptides that significantly facilitates candidate biomarker discovery. We describe a new stable mass tagging reagent pair, (12)C(6)- and (13)C(6)-phenyl isocyanate (PIC), that offers significant advantages over currently available tags. Peptides are labeled predominantly at their amino termini and exhibit elution profiles that are independent of label isotope. Importantly, PIC-labeled peptides have unique neutral-mass losses upon CID fragmentation that enable charge state and label isotope identification and, thereby, decouple the sequence identification from the quantification of candidate biomarkers. To exploit these properties, we have coupled peptide fractionation protocols with a Thermo LTQ-XL LC-MS(2) data acquisition strategy and a suite of automated spectrum analysis software that identifies quantitative differences between labeled samples. This approach, dubbed the PICquant platform, is independent of protein sequence identification and excludes unlabeled peptides that otherwise confound biomarker discovery. Application of the PICquant platform to a set of complex clinical samples showed that the system allows rapid identification of peptides that are differentially expressed between control and patient groups.