High-performance liquid chromatography assays for desmethoxyyangonin, methysticin, kavain and their microsomal metabolites

Three novel, simple and reproducible high-performance liquid chromatography quantitative assays with UV detection were developed and validated for three major kavalactones--desmethoxyyangonin, methysticin and kavain--in rat liver microsomes using diazepam as an internal standard; liquid-liquid extraction was used for sample preparation and analysis was performed on a Shimadzu 10A high-performance liquid chromatography system. The analysis was carried out in reversed-phase mode with a Luna C(18) column (150 x 2.00 mm, 3 microm) at 40 degrees C. The limit of quantitation was 0.1 microg/mL using 0.25 mL of microsomal solution. The assays were linear over the range 0.1-10 microg/mL for desmethoxyyangonin, methysticin and kavain. Quality control samples exhibited good accuracy and precision with relative standard deviations lower than 15% and recoveries between 85 and 105%. The assays exhibited satisfactory performance with high sensitivity for quantifying desmethoxyyangonin, methysticin and kavain in rat liver microsomes and were successfully used to determine the three kavalactones and their microsomal metabolites.     

Copper(II) malonate coordination frameworks with amino-1,2,4-triazole: Crystal structures and magnetic properties of [Cu2(mal)2(datz)2(H2O)]·5H2O and [Cu2(mal)2(atz)2(H2O)]·3H2O

Two new malonato-bridged copper(II) complexes of the composition [Cu₂(mal)₂(datz)₂(H₂O)]·5H₂O (1) and [Cu₂(mal)₂(atz)₂(H₂O)]·3H₂O (2) (mal = malonate, atz = 4-amino-1,2,4-triazole, datz = 3,5-diamino-1,2,4-triazole) are prepared and characterized by X-ray crystal structure determination and magnetic studies. The environment of each copper atom in 1 and 2 has distorted square pyramidal and octahedral geometries. The intrachain copper-copper separation is 6.305 Å and 3.640 Å across the carboxylates and trizolates bridges respectively for complexes 1 and 2. The magnetic properties of 1 and 2 are investigated in the temperature range 2–300 K. The overall antiferromagnetic behavior is observed in both cases.     

Rational period functions and cycle integrals

In this paper we give some applications of weakly holomorphic forms and their cycle integrals to rational period functions for the modular group. In particular, we give a simple construction of the associated modular integrals that works for all weights.     

The surface geometry of GaAs(110): A response

A brief survey of the various surface structure analyses for GaAs(110) is presented. The interplay between studies based on low-energy-electron diffraction (LEED), ion channeling, ion scattering, photoemission and isochromat spectroscopy leads to a structure in which a relaxation within the top layer (characterized by a perpendicular displacement of the As and Ga species by $\text{Δ}{}_{\mathrm{1,\; \perp }}\text{= 0.69±0.05}\text{A}\text{?}$ with the As species relaxing outward by $\text{0.21±0.05}\text{A}\text{?}$ and the Ga species inward by $\text{0.48±0.05}\text{A}\text{?}$) is accompanied by a uniform relaxation of the top layer by $\text{0.05±0.1}\text{A}\text{?}$ toward the substrate and a perpendicular displacement in the second layer in the opposite sense by $\text{0.06±0.1}\text{A}\text{?}$. The displacements of the top-layer Ga and As species parallel to the surface remain controversial. LEED and medium-energy ion-scattering analysis favor bond-length-conserving rotated top-layer structures (i.e., large $\text{(Δd}{}_{\mathrm{|}}\text{～ 0.3}\text{A}\text{?}\text{)}$ displacements parallel to the surface) whereas high-energy ion-channeling and isochromat spectroscopy experiments favor small displacements $\text{(Δd}{}_{\mathrm{|}}\text{? 0.1}\text{A}\text{?}\text{)}$ parallel to the surface.     

Extreme Values of Artin L-Functions and Class Numbers

Assuming the generalized Riemann hypothesis (GRH) and Artin conjecture for Artin L-functions, we prove that there exists a totally real number field of any fixed degree (>1) with an arbitrarily large discriminant whose normal closure has the full symmetric group as Galois group and whose class number is essentially as large as possible. One ingredient is an unconditional construction of totally real fields with small regulators. Another is the existence of Artin L-functions with large special values. Assuming the GRH and Artin conjecture it is shown that there exist an Artin L-functions with arbitrarily large conductor whose value at s=1 is extremal and whose associated Galois representation has a fixed image, which is an arbitrary nontrivial finite irreducible subgroup of GL(n, ) with property Gal _T .     

Some anomalous rheological responses of thermotropic liquid crystals

Summary The rheological properties of smectic, nematic and cholesteric thermotropic liquid crystals have been investigated with the Rheometrics Mechanical Spectrometer. Steady flow, relaxation after cessation of steady flow, sinusoidal deformation and step strain modes have been employed. Highly non-linear responses for the smectic systems have been observed which can possibly lead to new areas of applications some of which are briefly discussed.

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Zusammenfassung Die rheologischen Eigenschaften von smektischen, nematischen und cholesterischen thermotropen flüssigen Kristallen wurden mit dem Mechanischen Spektrometer der Fa. Rheometrics untersucht, wobei die Betriebsweisen der stationären Strömung, der Relaxation nach Anhalten der stationären Strömung, der sinusförmigen Deformation und der stufenweisen Dehnung angewendet wurden. Bei den smektischen Systemen wird ein hochgradig nicht-lineares Verhalten beobachtet, das möglicherweise auf neue Anwendungsbereiche hinweist. Einige derselben werden kurz diskutiert.

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With 8 figures and 2 tables