A Neutral and Aromatic Boron-Rich Inorganic Benzene

A neutral 1,4-diaza-2,3,5,6-tetraborinine derivative ( 3 ) featuring a 6π ring system has been synthesized and structurally characterized. The prospective aromatic nature of 3 was assessed by single-crystal X-ray analysis, NMR, and UV/Vis absorption spectroscopy as well as computational studies. Furthermore, preliminary reactivity investigations showed that 3 does not only react with diphenyl acetylene but also readily captures CO₂ in a [4+2] cycloaddition under ambient conditions.     

A Rapid Sample Preparation Procedure Using MonoSpin CBA and Amide Columns for Tetrodotoxin Detection in Serum and Urine Using LC–MS/MS Analysis

Clinical diagnosis of tetrodotoxin (TTX) poisoning can be difficult because of the lack of characteristic morphological findings and a screening test, such as an immunoassay. Here, we present a fully validated method for the analysis of TTX in serum and urine. In this method, serum and urine samples were extracted using MonoSpin CBA or amide columns, followed by LC–MS/MS analysis. The TTX was eluted from the column by 0.1 mL of 10 % acetic acid solution, and was directly injected into LC–MS/MS. An Agilent 1200 HPLC system equipped with a HILIC separation column (Zorbax HILIC Plus 2.1 × 100 mm, 3.5 μm) was used for isocratic elution, with a mobile phase of 10 mM ammonium formate with formic acid (95:5, v/v), along with 5 mM trifluoroacetic acid and 2 % acetonitrile. TTX was detected with an Agilent 6410 mass spectrometer utilizing positive electrospray ionization and multiple reaction monitoring. Limits of quantification for serum and urine were established to be 1 and 0.5 ng mL^?1, respectively. Limits of detection for serum and urine were 0.5 and 0.25 ng mL^?1, respectively. Intra-day and inter-day precision varied from 1.5 to 8.5 %. The recovery was >86.5 % for both matrices. In this method, the sample preparation process prior to injection into the LC–MS/MS takes approximately 10–15 min, which reduces the extraction time to one-tenth of that of previous methods. The application of this method was further verified by analysis of biological materials from a patient suffering from puffer fish poisoning.     

Molecular gas dynamics approaches to interfacial phenomena accompanied with condensation

This paper deals with the condensation coefficient of methanol, which is evaluated from a condensation rate at the vapor–liquid interface. Film condensation is induced on the endwall of a vapor-filled shock tube, when a shock wave is reflected at the endwall and the vapor becomes supersaturated there. The liquid film grows with the lapse of time. The evolution in time of the liquid film thickness is measured by an optical interferometer with a high accuracy, and thereby the net condensation mass flux at the interface is obtained. The mass flux is incorporated into the kinetic boundary condition (KBC) at the interface for the Gaussian–BGK Boltzmann equation. Such a treatment of the boundary condition makes it possible to formally eliminate the evaporation and condensation coefficients in KBC and to obtain the unique numerical solution of the vapor–liquid system. In this way, the instantaneous condensation coefficient is accurately evaluated from the conformity with experiment and numerical solution. It is found that the values of condensation coefficient are, near vapor–liquid equilibrium states, close to those evaluated by molecular dynamics simulations.     

Diagonal Transformations of Graphs and Dehn Twists of Surfaces

In this paper we shall show that any two bipartite quadrangulations of a closed surface can be transformed into each other by diagonal slides and diagonal rotations, up to isotopy, if they have the same and sufficiently large number of vertices. Also, we show the same fact for triangulations of a closed surface.     

The transition density of shape oscillations

The transition density of the lowest 3^? state of ²⁰⁸Pb is examined by using the particle-vibration coupling model. The polarization effect as a function of the radial variable is discussed.     

Longest cycles in 3-connected graphs contain three contractible edges

We show that if G is a 3-connected graph of order at least seven, then every longest path between distinct vertices in G contains at least two contractible edges. An immediate corollary is that longest cycles in such graphs contain at least three contractible edges.     

High-speed liquid chromatograhic separation of glycerides, fatty acids and sterols.

The high-speed liquid chromatographic separation and detection of triglycerides, diglycerides, fatty acid and sterols was carried out to permit the analyses of total lipids from soybeans and soybean food. The study was conducted with a Varian Aerograph LC 1200 liquid chromatograph equipped with a hydrogen flame ionization detector. Linear-gradient, solvent-flow programming was used. Separation of the total lipids by the gradient was achieved in 30 minutes and the column prepared for the next analysis by washing with solvents. The detector response curves for authentic compounds were linear and equivalent to within 2.3% error, based on the response to 1-monopalmitin. The minimum detectable amounts of the authentic substances were between 0.1 and 1.4mug. When a three-stranded wire was used instead of single filament wire, the sensitivity was increased by 37%.     

The vibrational dynamics of carbon monoxide in a confined space-CO in zeolites

Based on theoretical calculations, and a survey of infrared spectra of CO adsorbed on different cation exchanged zeolites, a model is proposed to explain the influence of the zeolite framework on the vibrational behaviour of CO confined into small void spaces (zeolite channels and cavities). The concepts developed should help to understand a number of details relevant to both, precise interpretation of IR spectra and a better understanding of the vibrational dynamics of small molecules in a confined space.