Regioselective Synthesis, NMR, and Crystallographic Analysis of N1-Substituted Pyrazoles.

A systematic study of the N-substitution reactions of 3-substituted pyrazoles under basic conditions has been undertaken. Regioselective N1-alkylation, -arylation, and -heteroarylation of 3-substituted pyrazoles have been achieved using K2CO3-DMSO. The regioselectivity is justified by the DFT calculations at the B3LYP/6-31G**(d) level. A consistent steric effect on chemical shift has been observed for N-alkyl pyrazole analogues. Twenty-five X-ray crystallographic structures have been obtained to confirm the regiochemistry of the major products.

Developing Duplex Ultrasound Criteria for Diagnosis of Arteriovenous Fistula Stenosis.

BACKGROUND: The purpose of this study was to determine the best color-flow duplex ultrasound (US) criteria for the detection of significant stenoses in arteriovenous fistulas (AVFs) by comparing US with the angiographic gold standard. METHODS: Included in this retrospective study were all patients who had both US scans and angiograms of their AVFs performed from December 2008 to July 2015. Comparisons were made between the preoperative US peak systolic velocity (PSV) measurements and the angiographic images looking at the percent diameter reduction in the stenosis. The PSV ratio between the area of stenosis and the normal segment on the inflow side of the stenosis (systolic velocity ratio [SVR]) was also compared with the angiograms. Sensitivity and positive predictive values (PPV) with 95% confidence intervals were calculated. RESULTS: This study included 780 cases of stenotic accesses (47 brachiobasilic, 361 brachiocephalic, and 372 radiocephalic). PSVs of ≥500 cm/s predicted a 50% or greater stenosis with a sensitivity of 89% (95% confidence interval 87-91) and PPV of 99% (99-100). At lower PSVs, sensitivity and PPV remained high; however, there were an increased number of false positive cases compared with those at 500 cm/sec or greater. The SVR was unreliable in predicting the degree of stenosis in AVF. CONCLUSION: PSVs of ≥500 cm/sec are generally reliable in predicting stenosis of 50% or greater in AVFs.

Radiation-induced formation of chlorine oxides and their potential role in the origin of Martian perchlorates.

Carbon dioxide (CO2) rich chlorine-bearing ices were exposed to energetic electrons in laboratory simulation experiments to investigate the formation of chlorine oxides (ClxOy) in the condensed phase on Mars. The radiolysis-induced synthesis of chlorine oxides (ClxOy) was complementarily monitored online and in situ via infrared spectroscopy (IR) and quadrupole mass spectrometry (QMS). Three discrete chlorine oxides were identified: chorine dioxide (OClO), dichlorine monoxide (ClOCl), and chloryl chloride (ClClO2). Higher irradiation doses support the facile production of ClO3- and ClO2-bearing high-order chlorine oxides. We attribute manifolds of chlorine oxides, as invoked herein, to the potential origin of perchlorates as found on Mars.