Screening phosphatidylcholine biomarkers in mouse liver extracts from a hypercholesterolemia study using ESI-MS and chemometrics

When fed a high-fat, high-cholesterol diet (HFD), homozygous LDL receptor knockout mice exhibit extremely high levels of plasma cholesterol that are expected to influence liver metabolism. One step in the investigation of potential hepatic alterations was the analysis of organic extracts of livers from these and control mice by electrospray mass spectrometry (ESI-MS). Chemometrics (bioinformatics) analysis shows that the sample spectra cluster into two groups: one from mice with plasma cholesterol levels in excess of 900 mg dL⁻¹ and one from animals with cholesterol levels of 60–250 mg dL⁻¹. The loadings plot of the first PC in the principal-components analysis (PCA) reveals the chemical basis for clustering, i.e., biomarkers present at different concentrations in the different groups. The exact masses of the key peaks in this loadings plot indicate these species are phosphatidylcholines (PtdChos). This assignment is confirmed by tandem MS. Partial least-squares (PLS) with variable selection shows that the spectra are well correlated with plasma total cholesterol, HDL cholesterol, and triglyceride (TG) levels.     

Anisotropic transport scattering times for pure and dilute aluminium alloys

The ideal transport scattering times for pure Al are calculated and found to be very anisotropic. The anisotropy is a sensitive function of temperature. It is due to the Fermi surface, the multi-plane-wave character of the electronic wavefunctions, the Umklapp processes, as well as the phonon spectrum. In addition, for a magnesium impurity in Al we have computed the residual transport scattering times as well as the quasiparticle lifetimes which we then compare. The scattering time anisotropy gives rise to deviations from Matthiessen's rule in dilute alloys.     

Perception of the missing fundamental in nonhuman primates

In preparation for neurophysiological experiments aimed at mechanisms of pitch perception, four rhesus monkeys were trained to press a button when the fundamental frequencies (missing or present) of two complex tones in a tone pair matched. Both tones were based on a five-component harmonic series. Zero to three of the lowest components could be missing in the first tone, while the second (comparison) tone contained all five harmonics. The range of fundamentals tested varied from 200 to 600 Hz. Three monkeys learned to match tones missing their fundamentals to comparison harmonic complexes with the same pitch, whereas the fourth monkey required the physical presence of the fundamental. Consideration of several cues available to the monkeys suggests that the animals could perceive the missing fundamental.     

Developing a Systems Approach to the Problems of Industry — Lessons Based on Experience at IIASA

This paper describes progress on a number of research projects initiated in the Management and Technology Area of the International Institute of Applied Systems Analysis in the period 1977/80. The projects were undertaken by an international, multi-disciplinary, team concerned with the study of management problems arising from technological change. The experience obtained is used to explore the need for, and feasibility of, undertaking such problem-oriented programme research at the national level. It is concluded that the need to conduct methodological research of this nature is great, though not always self-evident; that the financial and organisational problems would be severe, though not insuperable; and that it is time for practising operational researchers and applied systems analysts to flex their muscles to this end.     

Verification of CuInSe2 density of states features by reflection electron energy loss spectroscopy

Reflection electron energy loss measurements of CuInSe₂ single crystals are reported and when possible, the losses are compared with former results by Kazmerski and Jamjoum et al. Their identification of the transitions is confirmed and refined by spectrum simulations with total and partial densities of states from band structure calculations of Jaffe, Bendt, Zunger, and Bullett.New conduction-band maxima at energies not covered by the available calculations, are proposed and their consistency with the experimental loss energies is shown by another simulation with Lorentzian density peaks.     

Theory of the contribution of the electron-phonon interaction to the anisotropic electronic lifetime and transport properties of zine

Using pseudopotential theory for the phonons, electrons, and electron-phonon interaction of zine, we have calculated several electronic properties of this metal. Among these are the electron lifetime at three positions on the Fermi surface, the anisotropic electrical resistivity, the anisotropic thermal conductivity, and the ultrasonic attenuation, all due to the electron-phonon interaction, and all as a function of temperature. For the electrical resistivity, two solutions of the Boltzmann equation were obtained, one consisting of a single spherical harmonic, and the other made up of six spherical harmonics. The single spherical harmonic is not adequate at low temperatures.     

Electron interactions and transport between coupled quantum Hall edge states

We examine the effects of electron-electron interactions on transport between edge states in a multilayer integer quantum Hall system. The edge states of such a system, coupled by interlayer tunneling, form a two-dimensional, chiral metal at the sample surface. We calculate the temperature-dependent conductivity and the amplitude of conductance fluctuations in this chiral metal, treating Coulomb interactions and disorder exactly in the weak-tunneling limit. We find that the conductivity increases with increasing temperature, as observed in recent experiments, and we show that the correlation length characterizing conductance fluctuations varies inversely with temperature.