Sparse geometric graphs with small dilation

Given a set S of n points in , and an integer k such that 0k<n, we show that a geometric graph with vertex set S, at most n−1+k edges, maximum degree five, and dilation O(n/(k+1)) can be computed in time O(nlogn). For any k, we also construct planar n-point sets for which any geometric graph with n−1+k edges has dilation Ω(n/(k+1)); a slightly weaker statement holds if the points of S are required to be in convex position.     

g-Factor for the K=6, Jπ=6+ isomer in178Hf

Hyperfine Interactions -     

Laser photolysis of 2-phenylheptamethyltrisilane

Two transient absorptions have been detected in the 266 nm laser photolysis of 2-phenylheptamethyltrisilane in cyclohexane solution at room temperature, and their time evolution was recorded in the presence and absence of air and added trapping agents. The shorter-lived 440 nm transient (t1/2 < 20μs) is tentatively assigned to the silylene :SiMePh and the more persistent 380 nm transient to the disilene MePhSiSiMePh. The reactivity of this silylene is much lower than had been expected.     

Liquid chromatographic determination of flumetsulam in soybeans

A liquid chromatography (LC) method with UV detection is reported for the determination of the sulfonamide herbicide flumetsulam in soybeans. The ground soybean sample was partitioned between methanol and hexane. The hexane removed the lipids, and the methanol layer containing the analyte was further partitioned between dichloromethane and aqueous phosphate buffer at pH 7.0. The aqueous layer, containing the analyte, was acidified to pH 2.2 and partitioned with fresh dichloromethane. The dichloromethane layer containing the analyte was evaporated, and the residue was dissolved in the LC mobile phase for analysis. A polar embedded C18 column was used with a mobile phase of pH 2.2 aqueous phosphate buffer-acetonitrile (68 + 32), run isocratically with detection at 225 nm. The average recovery was 82% with a relative standard deviation (RSD) of 10%. A coefficient of determination of R2 = 0.9992 was achieved for the analyte calibration curve, from 0.005 to 1 microg/mL. The limit of detection, determined from 3 times the standard deviation of 7 replicate extractions of the lowest fortification level (0.01 microg/g), was 0.005 microg/g with an RSD of 22%. LC/electrospray ionization/mass spectrometry in the positive-ion mode was used for identity confirmation of flumetsulam in the fortified soybean extract. The ions at m/z 326, 348, and 129 were observed.     

Die Kennzeichnung technischer Kolloidgraphite

Zusammenfassung Es werden mehrere Prüfverfahren beschrieben, die zur Kennzeichnung technischer Kolloidgraphite verwendet werden k?nnen. Durch Flockung und Elektrophorese k?nnen Aquadag und Hydrokollag qualitativ unterschieden werden. Durch Chromatographie werden Best?ndigkeit und Netzf?higkeit beurteilt. Schlie?lich, bieten die Viskosit?tsmessungen die M?glichkeit, die Flie?eigenschaften qualitativ zu erfassen.     

Activity coefficients for HCl+NiCl2+H2O at 298.15°K and effects of higher-order electrostatic terms

Activity coefficients for CHl in the system HCl+NiCl ₂ +H ₂ O at 298.15°K at constant total ionic strengths of 0.1, 0.5, 1.0, 2.0, and 3.0 moles-kg ^–1 have been determined by an emf method. A comparison was made between Scatchard's and Pitzer's interpretations of mixed-electrolyte solutions for this system and six related systems. Preference can be given to Pitzer's method provided cognizance is taken of the effects of higher-order electrostatic terms beyond the Debye-Hückel approximation on the thermodynamic properties of asymmetrical mixtures.