Chiral high-performance liquid chromatography of N-octyl bicycloheptene dicarboximide and confirmatory studies using liquid chromatography-tandem mass spectrometry and two-dimensional nuclear magnetic resonance spectroscopy

N-Octyl bicycloheptene dicarboximide (MGK 264) has exo and endo diastereomers. Each structure has a chiral center at the nitrogen side chain. Enantioselective separation of MGK 264 was achieved by normal-phase high-performance liquid chromatography (HPLC) using cellulose-based Chiralcel OD column with diode-array and optical rotation detectors. Peaks were isolated with the purpose of identifying their stereochemical structures. Molecular mass of the HPLC peaks and their structural information was determined by liquid chromatography-electrospray tandem mass spectrometry (LC-ES-MS-MS). A two-dimensional nuclear magnetic resonance (NMR) spectroscopic technique was used to establish the structural features. Correlation of the data obtained from chiral separation and NMR facilitated in unambiguous assignment of the HPLC peaks.     

焙烧硼钠钙石在高固液比氯化铵溶液中的溶解动力学

Boron is available in the form of metal borates, especially of sodium and calcium, in nature[1]. The production of boron compounds has substantially increased recently due to increasing uses of these compounds in nuclear technology, in rocket engines as f…     

Lattice dynamics of InAs under hydrostatic pressures

The lattice dynamics of InAs under variable hydrostatic pressures is investigated on the basis of an ‘11-parameter’ rigid-ion model (RIM). The calculated phonon dispersion curves are in satisfactory agreement with the neutron scattering data (available for the TA modes only) measured at room temperature and atmospheric pressure. The one- and two-phonon densities of states functions and mode Gruneisen parameters have been computed at two arbitrary hydrostatic pressures. The effect of high pressure on the phonon dispersion curves is shown to lead to a typical ‘softening’ in the transverse acoustic modes and eventually to a phase trnasformation of the compound.     

CLL = (L,L; 0, 0) measurements and a structure due to a P partial wave in the pp system

Measurements of C_LL of pp elastic scattering near θ_c.m. = 90° at thirteen energies between 300 and 800 MeV are reported. These, together with previous values of C_NN, are used to extract values of two quantities, $\text{?}{}_{\mathrm{<mtext>s</mtext>}}$ and $\text{?}{}_{\mathrm{<mtext>t</mtext>}}$, which contain only spin-singlet and only coupled spin-triplet partial waves, respectively. The $\text{?}{}_{\mathrm{<mtext>s</mtext>}}$ curve, which is not dependent on C_LL, exhibits the behavior expected for the previously conjectured ¹D₂ resonance. The $\text{?}{}_{\mathrm{<mtext>t</mtext>}}$ curve also exhibits a resonance-like behavior, which could be due either to the ³P₀ or the ³P₂ partial wave.