Forecasting with cue information: A comparison of multiple regression with alternative forecasting approaches

Multiple linear regression (MLR) is a popular method for producing forecasts when data on relevant independent variables (or cues) is available. The accuracy of the technique in forecasting the impact on Greek TV audience shares of programmes showing sport events is compared with forecasts produced by: (1) a simple bivariate regression model, (2) three different types of artificial neural network, (3) three forms of nearest neighbour analysis and (4) human judgment. MLR was found to perform relatively poorly. The application of Theil’s bias decomposition and a Brunswik lens decomposition suggested that this was because of its inability to handle complex non-linearities in the relationship between the dependent variable and the cues and its tendency to overfit the in-sample data. Much higher accuracy was obtained from forecasts based on a simple bivariate regression model, a simple nearest neighbour procedure and from two of the types of artificial neural network.     

Capillary electrophoresis of the scrapie prion protein from sheep brain

Scrapie in sheep and goats causes a progressive, degenerative disease of the central nervous system and is the prototype of other transmissible spongiform encephalopathies (TSE) found in humans and in animals. In samples of TSE-affected brains, unique rod-shaped structures are found and are infectious. These rods are composed of a protease-resistant, post-translationally modified cellular protein (PrP^sc) that has a molecular mass of ca. 27 000 on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Laboratory tests used for the diagnosis of scrapie detect PrP^sc. The overall concentration of PrP^sc in tissues is low. The present methods to diagnose scrapie are lengthy, require relatively large quantities of starting material to detect PrP^sc and lack sensitivity. We explored the use of free zone capillary electrophoresis and immunocomplex formation to detect PrP^sc in the brain tissue of infected sheep. Brain tissue from both infected (as confirmed by histological and biological tests) and from normal animals was used to prepare the PrP^sc. After treatment with proteinase K and non-ionic detergents, PrP^sc was solubilized and reacted with a rabbit antiserum specific for a peptide of the prion protein. Immunocomplex formation was observed for the samples from scrapie-infected brain but not for samples from normal brain. When a fluorescein-labeled goat anti-rabbit immunoglobulin was used as a second antibody, the detection of immunocomplex formation was enhanced both by the immunological technique and by using laser-induced fluorescence for detection. This same rabbit antiserum was used on immunoblot analysis. Three bands were observed for material from an infected sheep but none in preparations from brain material from normal sheep. Capillary electrophoresis can be used to show immunocomplex formation when PrP^sc is present in sheep brain.     

Vortex pinning in polycrystalline Eu1.5Ce0.5Sr2Cu2NbO10 from rotational magnetic measurements

Rotational magnetization-vector measurements were carried out on a superconducting polycrystalline disk of EuCSCNO. The results at 4.2 K and low fields resemble recent results for YBa₂Cu₃O_7−δ (YBCO) and Ba_0.57K_0.43BiO₃ (BKBO) in revealing a broad distribution in the strength of the vortex pinning torques. This resemblance extends to higher fields, where it was found that the average pinning torque per vortex (τ_p), which is directly related to the critical current density, decreases steadily with increasing field in a manner consistent with vortex bundling. Quantitatively, however, the values of τ_p for EuCSCNO are smaller by an order of magnitude than those for YBCO but are only moderately smaller than those for BKBO. This comparison supports the notion that the vortex pinning may derive in part from deviations from oxygen stoichiometry, which are normally present in YBCO but are essentially absent in EuCSCNO and BKBO. Moreover, as in YBCO and BKBO, the τ_p in EuCSCNO at fixed field is found to diminish rapidly as the temperature rises towards T_c.     

A possible replacement of single crystal by melt-textured material in the study of YBa2Cu3O7−y

Improved superconducting properties were observed in melt-textured YBa₂Cu₃O_7-y ceramic material. The inductive current density has a small field dependence up to 5.5 T over a wide temperature range. The field and temperature dependences of the magnetic properties are similar to the behavior found in single crystals. Values of the intragrain critical current density in melt-texture samples have the same order of magnitude as in single crystals. The reduced porosity and improved grain alignment help to probe intrinsic physical properties that depend on crystallographic orientation. Thus experiments similar to those involving single crystals are possible. The modified Bean critical state model applied to single crystals can also be used in these melt-textured samples. Thus, it is possible to use melt-textured samples in some basic research which originally required the use of single crystals.     

SYNTHESIS AND SPECTROSCOPIC DIFFERENTIATION OF 2- AND 4-ALKOXYTHIOTETRONIC ACIDS

O-Alkylation of thiotetronic acids gives a mixture of 2- and 4-position enol ether products. Comparison of the physical data revealed that UV spectroscopy was the most reliable method of distinguishing between these related ethers. We have determined that 4-position ethers have a distinct absorption between 235-240 nm, while 2-position ethers have two absorbance peaks, one between 205-220 nm and the other between 305-310 nm. This report describes the synthesis and unambiguous characterization of 2- and 4-methoxy-3,5-dimethylthiotetronic acids. The UV absorption properties of several other pairs of thiotetronic acid ethers confirm that these differences are general features that provide a simple method for distinguishing between 2- and 4-substituted isomers.     

Liquid Extraction Surface Analysis (LESA) Electron-Induced Dissociation and Collision-Induced Dissociation Mass Spectrometry of Small Molecule Drug Compounds

Here, we present liquid extraction surface analysis (LESA) coupled with electron-induced dissociation (EID) mass spectrometry in a Fourier-transform ion cyclotron resonance mass spectrometer for the analysis of small organic pharmaceutical compounds directly from dosed tissue. First, the direct infusion electrospray ionisation EID and collision-induced dissociation (CID) behaviour of erlotinib, moxifloxacin, clozapine and olanzapine standards were compared. EID mass spectra were also compared with experimental or reference electron impact ionisation mass spectra. The results show that (with the exception of erlotinib) EID and CID result in complementary fragment ions. Subsequently, we performed LESA EID MS/MS and LESA CID MS/MS on singly charged ions of moxifloxacin and erlotinib extracted from a thin tissue section of rat kidney from a cassette-dosed animal. Both techniques provided structural information, with the majority of peaks observed for the drug standards also observed for the tissue-extracted species. Overall, these results demonstrate the feasibility of LESA EID MS/MS of drug compounds from dosed tissue and extend the number of molecular structures for which EID behaviour has been determined.

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