On the system cerium-platinum-silicon

Phase relations in the ternary system Ce-Pt-Si have been established for the isothermal section at 800 °C based on X-ray powder diffraction, metallography, scanning electron microscopy (SEM) and electron probe microanalysis (EPMA) techniques on about 120 alloys, which were prepared by various methods employing arc-melting under argon or powder reaction sintering. Nineteen ternary compounds were observed. Atom order in the crystal structures of τ₁₈-Ce₅(Pt,Si)₄ (Pnma; a=0.77223(3) nm, b=1.53279(8) nm c=0.80054(5) nm), τ₃-Ce₂Pt₇Si₄ (Pnma; a=1.96335(8) nm, b=0.40361(4) nm, c=1.12240(6) nm) and τ₁₀-CePtSi₂ (Cmcm; a=0.42943(2) nm, b=1.67357(5) nm, c=0.42372(2) nm) was determined by direct methods from X-ray single-crystal CCD data and found to be isotypic with the Sm₅Ge₄-type, the Ce₂Pt₇Ge₄-type and the CeNiSi₂-type, respectively. Rietveld refinements established the atom arrangement in the structures of Pt₃Si (Pt₃Ge-type, C2/m, a=0.7724(2) nm, b=0.7767(2) nm, c=0.5390(2) nm, β=133.86(2)°), τ₁₆-Ce₃Pt₅Si (Ce₃Pd₅Si-type, Imma, a=0.74025(8) nm, b=1.2951(2) nm, c=0.7508(1) nm) and τ₁₇-Ce₃PtSi₃ (Ba₃Al₂Ge₂-type, Immm, a=0.41065(5) nm, b=0.43221(5) nm, c=1.8375(3) nm). Phase equilibria in Ce-Pt-Si are characterised by the absence of cerium solubility in platinum silicides. Cerium silicides and cerium platinides, however, dissolve significant amounts of the third component, whereby random substitution of the almost equally sized atom species platinum and silicon is reflected in extended homogeneous regions at constant Ce content such as for τ₁₃-Ce(Pt_xSi_1−x)₂, τ₆-Ce₂Pt_3+xSi_5−x or τ₇-CePt_2−xSi_2+x.     

Predicting time-to-churn of prepaid mobile telephone customers using social network analysis

Mobile phone carriers in a saturated market must focus on customer retention to maintain profitability. This study investigates the incorporation of social network information into churn prediction models to improve accuracy, timeliness, and profitability. Traditional models are built using customer attributes, however these data are often incomplete for prepaid customers. Alternatively, call record graphs that are current and complete for all customers can be analysed. A procedure was developed to build the call graph and extract relevant features from it to be used in classification models. The scalability and applicability of this technique are demonstrated on a telecommunications data set containing 1.4 million customers and over 30 million calls each month. The models are evaluated based on ROC plots, lift curves, and expected profitability. The results show how using network features can improve performance over local features while retaining high interpretability and usability.     

Single‐Walled Carbon Nanotubes as Scaffolds to Concentrate DNA for the Study of DNA–Protein Interactions

Genomic DNA in bacteria exists in a condensed state, which exhibits different biochemical and biophysical properties from a dilute solution. DNA was concentrated on streptavidin‐covered single‐walled carbon nanotubes (Strep ? SWNTs) through biotin–streptavidin interactions. We reasoned that confining DNA within a defined space through mechanical constraints, rather than by manipulating buffer conditions, would more closely resemble physiological conditions. By ensuring a high streptavidin loading on SWNTs of about 1 streptavidin tetramer per 4 nm of SWNT, we were able to achieve dense DNA binding. DNA is bound to Strep ? SWNTs at a tunable density and up to as high as 0.5 mg mL^?1 in solution and 29 mg mL^?1 on a 2D surface. This platform allows us to observe the aggregation behavior of DNA at high concentrations and the counteracting effects of HU protein (a histone‐like protein from Escherichia coli strain U93) on the DNA aggregates. This provides an in vitro model for studying DNA–DNA and DNA–protein interactions at a high DNA concentration.     

Biomarker discovery in breast cancer serum using 2-D differential gel electrophoresis/ MALDI-TOF/TOF and data validation by routine clinical assays

In the present study, we used 2-D differential gel electrophoresis (2-D DIGE) and MS to screen biomarker candidates in serum samples obtained from 39 patients with breast cancer and 35 controls. First, we pooled the serum samples matched with age and menopausal status. Then, we depleted the two most abundant proteins albumin and IgG by immunoaffinity chromatography under partly denaturing conditions in order to enrich low-abundance proteins and proteins with low molecular weight. Concentrated and desalted samples were labeled with three different CyDyes including one internal standard, pooled from all the samples, and separated with 2-D DIGE in triplicate experiments. Biological variations of the protein expression level were analyzed with DeCyder software and evaluated for reproducibility and statistical significance. The profile of differentially expressed protein spots between patients and controls revealed proapolipoprotein A-I, transferrin, and hemoglobin as up-regulated and three spots, apolipoprotein A-I, apolipoprotein C-III, and haptoglobin alpha2 as down-regulated in patients. Finally, routine clinical immunochemical reactions were used to validate selected candidate biomarkers by quantitative determination of specific proteins in all individual serum samples. The serum level of transferrin correlated well with the 2-D-DIGE results. However, the serum levels of apolipoprotein A-I and haptoglobin could not be detected with the clinical routine diagnostic tests. This demonstrated an advantage 2-D DIGE still has over other techniques. 2-D DIGE can distinguish between isoforms of proteins, where the overall immunochemical quantification does fail due to a lack of isoform-special antibodies.     

Gas chromatographic-mass spectrometric analysis of N-acetylated amino acids: the first case of aminoacylase I deficiency

During the metabolic work-up of a patient presenting with neonatal convulsions, we consistently observed the presence of unusual peaks in the gas chromatographic-mass spectrometric analysis of urinary organic acids. The gas chromatographic-mass spectrometric characteristics of the unusual peaks suggested that they corresponded to derivatives of N-acetylated amino acids. The tentative identification was confirmed by the identity of retention times and mass spectra of the trimethylsilyl derivatives of the authentic compounds. We describe our observations that led to the identification of the various N-acetylated amino acids in this first patient with a confirmed deficiency of aminoacylase I, an enzyme involved in the cytosolic degradation of N-terminally modified proteins. The potential and limitations of urinary organic acid analysis for the detection of N-acetylated amino acids was further studied using pure compounds. In addition, we provide mass spectral data for 37 trimethylsilyl derivatives from 17 N-acetylated amino acids, most of which have not been reported previously. Our data provide valuable information that will help the clinical laboratorians who are responsible for organic acid analysis to recognize this new condition and could aid its detection in other patients.     

Structural implications of ring shape, dimension, and metal atom insertion in nanosized cyclic oligothiophenes: joint Raman and density functional theory study

This paper reports on a combined spectroscopic and density functional theory study on a series of cyclo(diacetylenes-oligothiophenes) with different shapes and dimensions. The case of a macrocycle fragmented by the insertion of Pt metallic atoms is illustrated as well. The analysis covers the neutral and oxidized samples. A full assignment of the spectra has been proposed, supported by BP86/cc-pVDZ theoretical calculations. Ring shape and molecular dimension have been related with the C[Double Bond]CC-C structural parameters and Raman wave numbers. Platinum atom insertion within the acetylene spacer seems to soften ring strain owing to the rupture of the strained circular shape. Oxidation causes an overall downshift of the Raman wave numbers likely due to the skeletal relaxation of CC conjugated path, while the ring shape of each macrocycle is conserved upon oxidation.     

Chemiker im Gespräch: Erinnerungen an Heinrich Wieland

Am 4. Juni 1877 wurde Heinrich Wieland geboren – nach allen Kriterien einer der bedeutendsten deutschen Chemiker. Darstellungen seines Lebens und Werkes sind nach seinem Tod (5. August 1957) in großer Zahl geschrieben worden, und in diesen Tagen werden noch einmal zahlreiche Gedenkaufsätze veröffentlicht. Die Redaktion dieser Zeitschrift wollte die Reihe dieser Aufsätze nicht verlängern, sondern versuchte im Gespräch mit zwei ehemaligen Schülerinnen Wielands, die allerdings beide der Chemie etwas abtrünnig geworden sind, einem wenig bekannten Zug in der Biographie Heinrich Wielands nachzuspüren: seiner ungewöhnlichen Haltung im „Dritten Reich”︁. Hildegard Hamm-Brücher, geboren 1921, ist als Bildungspolitikerin sicher bekannter, als als Chemikerin, obwohl Wieland ihr, als sie schon tief in der Politik steckte, einmal sagte, als sie im Bayerischen Landtag die ersten Millionen zum Wiederaufbau des „Staatslabors”︁ erkämpft hatte: „Fräulein Brücher, eines muß ich Ihnen sagen, in der Chemie hätten Sie sich größeren Ruhm geholt als in der Politik.”︁ Nach ihrer Promotion am chemischen Institut der Universität München arbeitete Frau Hamm-Brücher als wissenschaftliche Redakteurin bei der „Neuen Zeitung”︁ in München, um sich und ihre Geschwister zu ernähren. Über die FDP kam sie 1948 in den Münchener Stadtrat und wenig später in den Bayerischen Landtag. 1967 wechselte sie von der Legislative in die Exekutive, wurde Staatssekretärin im hessischen Kultusministerium und 1969 Staatssekretärin im Bundesministerium für Bildung und Wissenschaft. Zur Zeit ist sie in Bonn Staatsminister im Auswärtigen Amt und dort vor allem für auswärtige Kulturpolitik zuständig. Gerda Freise, geboren 1919, studierte Chemie in Bonn und München und promovierte bei Heinrich Wieland unter der Betreuung von Rudolf Hüttel. Nach dem Krieg arbeitete sie erst bei Burkhard Helferich in Bonn und anschließend bei Karl Friedrich Bonhoeffer am Max-Planck-Institut für physikalische Chemie in Göttingen. Mit vierzig Jahren entschloß sie sich zu einem Neubeginn und begann ein Studium als Volksschullehrerin. Nach einigen Jahren Praxis and der Schule wurde sie Dozentin an der Pädagogischen Hochschule Heidelberg und dort vor allem als Verfechterin des „integrierten naturwissenschaftlichen Unterrichts”︁ bekannt. Heute ist sie H4-Professor für „Erzie-hungswissenschaft unter besonderer Berücksichtigung der Didaktik der Chemie”︁ im Fachbereich Erziehungswissenschaft der Universität Hamburg.