Developing the aggregate empirical side of computational social choice

The aggregate empirical side of computational social choice has received relatively little attention. This paper provides a progress report on our on-going research project on statistical characterizations of the outcomes of vote-casting processes. We describe a statistical model that is capable of generating voting situations for three-candidate elections that have a distribution very similar to that of observed voting situations. We show that our simulated voting situations can provide interesting insights into the question of which voting rule is most likely to identify the best candidate.     

Synthesis and characterization of electrochemically active graphite–silicon–tin composite anodes for Li-ion applications

Electrochemically active Si_0.66Sn_0.34 (SiSn) composite alloys dispersed in a carbon (graphite) matrix were synthesized using both wet and dry high-energy mechanical milling (HEMM). The resultant composites are comprised of amorphous carbon (in the case of dry HEMM) or crystalline carbon (in the case of wet HEMM), and crystalline silicon and tin (for both cases) as verified by X-ray diffraction (XRD). The XRD results also indicate the presence of iron–tin intermetallic (FeSn₂) arising as a contaminant during dry HEMM. The composite composition of 85C–15[Si_0.66Sn_0.34] (mol%) resulted in reversible discharge capacities as high as 800 mAh g⁻¹ with a reasonable capacity retention (1.36% loss/cycle). Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) analyses were further conducted to examine the surface of the electrode and to determine the presence/absence of organic species resulting from reactions between the electrode, lithium ions and electrolyte, respectively.     

Single-shot t1-and t2-weighted magnetic resonance imaging of the heart with black blood: preliminary experience

Purpose: To implement and evaluate two robust methods for T1-and T2-weighted snapshot imaging of the heart with data acquisition within a single heart beat and suppression of blood signal. Methods: Both Tl-and T2-weighted diastolic images of the heart can be obtained with half Fourier single-shot turbo spin echo (HASTE) and turbo fast low-angle shot (turboFLASH) sequences, respectively, in less than 350 ms. Signal from flowing blood in the ventricles and large vessels can be suppressed by a preceding inversion recovery preparing pulse pair (PRESTO). Fifteen volunteers and five patients have been evaluated quantitatively for signal-to-noise ratio (SNR) contrast-to-noise ratio (CNR) and flow void and qualitatively for image quality, artifacts, and black-blood effect. Results: Both PRESTO-HASTE and PRESTO-turboFLASH achieved consistently good image quality and blood signal suppression. In contrast to gradient-echo (GRE) echo-planar imaging techniques, (EPI) HASTE and turboFLASH are much less sensitive to local susceptibility differences in the thorax, resulting in a more robust imaging technique without the need for time-consuming system tuning. Compared to standard spin-echo sequences with cardiac triggering, HASTE and turboFLASH have significantly shorter image acquisition times and are not vulnerable to respiratory motion artifacts. Conclusion: PRESTO-HASTE and PRESTO-turboFLASH constitute suitable methods for fast and high-quality cardiac magnetic resonance imaging (MRI).     

Der Einsatz eines geschlossenen Wikis als neuer Bestandteil der Hochschullehre – Ein Erfahrungsbericht

Ohne Zusammenfassung Zuschriften zum Studierendenforum bitte an: Universit?t Bayreuth, Lehrstuhl BWL VII (Wirtschaftsinformatik), Prof. Dr. Torsten Eymann, Redaktion Studierendenforum, z. Hd. Dipl.-Wirtschaftsinformatiker Stefan K?nig, Universit?tsstra?e 30, 95447 Bayreuth, stefan.koenig@uni-bayreuth.de     

Elektrophoretische Differenzierung hitzedenaturierter und eisgelagerter Fischproteine

Zusammenfassung Eine Natrium-dodecylsulfat(SDS)-Lösung mit Mercapto-ethanol in Tris-Borat-Puffer pH 8.9 löst bei Raumtemperatur alle Fischproteine, auch die von gekochten Proben. Die Trennung durch Polyacrylamidgel(PAG)-Elektrophorese in Gegenwart von SDS ergibt trotz verschiedener Vorbehandlung artencharakteristische Pherogramme, vor allem im Bereich der sarkoplasmatischen Proteine. Die PAG-Focussierung der SDS-extrahierten Proteine gelingt nach Fällung von überschüssigem SDS und Trennung in PAG unter Zugabe von Harnstoff und Tetramethylharnstoff im pH-Bereich von 2–11. Dabei wird das artenspezifische Muster überlagert von einer Veränderung, die z. T. die fortschreitende Autolyse etc. während der Lagerung widerspiegelt.

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Evaluation of fish proteins by electrophoretic methods after boiling and after storage on ice

Summary All proteins from fish including boiled samples can be dissolved at room temperature in Tris-borate-buffer pH 8.9 containing 2% Sodiumdodecylsulfate (SDS) and 1% mercapto-ethanol. The separation is carried out in polyacrylamidegels (PAG) by SDS-electrophoresis, showing a species-specific pattern even for the heated samples. Focussing in PAG after removing SDS by precipitation and separation in the presence of urea and tetramethyl-urea between pH 2 and 11 showed species-specificity and a shift of protein bands which partially mirrored the increasing autolysis and degradation of the samples during storage.

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Verwendete Abkürzungen PAA Polyacrylamid - PAGE Polyacrylamidgelelektrophorese - PAGIF Polyacrylamidgelisoelektrische Focussierung - SDS Natrium(Sodium)-dodecylsulfat - ME 2-Mercapto-ethanol - Tris Tris-(hydroxymethyl)aminomethan - kD Kilo-Dalton (Einheit für scheinbares Molekular-Gewicht)     

Grenzflächenenergien von Teflon und verschiedenen Flüssigkeiten in einer verdichteten Stickstoffatmosphäre

Measurements of interfacial tensions (±1–2%) for water, formamide, ethanediole and toluene in dense nitrogen up to 23?MPa and T=295.7?K were made with the pendant drop method. Additionally contact angles of these liquids were measured as advancing contact angles on Teflon. Contact angles (ca.?±?3°.) were evaluated by hand and software. Interfacial Free Energy in the system Teflon/N₂, which was calculated by the interaction parameter Φ, is σ _Teflon/N2=19.4–25.2?mN?m^?1 for 0.1?MPa and σ _Teflon/N2=8.2–9.3?mN?m^?1 for 20?MPa. The Interfacial Free Energy in the system Teflon/N₂ was determined through linear regression or solving the system of equations (Section 5). Using the contact angle and interfacial tension measurements a mean value for σ _Teflon/N2=22.3?mN?m^?1 at 0.1?MPa and 9.2?mN?m^?1 at 20?MPa (without Acid-Base procedure) and a pressure independent σ _{Teflon/liquid} results. For the different methods for calculating the Interfacial Free Energy of a solid, suggestions were made with which the contact angle on Teflon can be estimated at the given pressure, if the interfacial tension of the liquid is known. In chapter 5, the contact angles of 48 substances on Teflon at 0.1?MPa were taken from literature [8, 17] and compared to estimations made by the methods of Zisman and Fowkes. For C₁₀ and higher n-alkanes, the results predicted by the method of Zisman are satisfactory. The estimations are less than 10°, compared to the literature values, whereas the calculated values with the method of Fowkes aren't satisfactory. For 38 non- n-alkanes the contact angle estimation with the method of Fowkes is significantly better than the estimations with the method of Zisman. The average deviation relative to the literature values are 4.9° and 6.9°.