Racemization of Valine by Impact-Induced Heating.

Homochirality plays an important role in all living organisms but its origin remains unclear. It also remains unclear whether such chiral molecules survived terrestrial heavy impact events. Impacts of extraterrestrial objects on early oceans were frequent and could have affected the chirality of oceanic amino acids when such amino acids accumulated during impacts. This study investigated the effects of shock-induced heating on enantiomeric change of valine with minerals such as olivine ([Mg0.9, Fe0.1]2SiO4), hematite (Fe2O3), and calcite (CaCO3). With a shock wave generated by an impact at ~0.8 km/s, both D- and L-enriched valine were significantly decomposed and partially racemized under all experimental conditions. Different minerals had different shock impedances; therefore, they provided different P-T conditions for identical impacts. Furthermore, the high pH of calcite promoted the racemization of valine. The results indicate that in natural hypervelocity impacts, amino acids in shocked oceanic water would have decomposed completely, since impact velocity and the duration of shock compression and heating are typically greater in hypervelocity impact events than those in experiments. Even with the shock wave by the impact of small and decelerated projectiles in which amino acids survive, the shock heating may generate sufficient heat for significant racemization in shocked oceanic water. However, the duration of shock induced heating by small projectiles is limited and the population of such decelerated projectiles would be limited. Therefore, even though impacts of asteroids and meteorites were frequent on the prebiotic Earth, impact events would not have significantly changed the ee of proteinogenic amino acids accumulated in the entire ocean.

Wide Carbon Nanopores as Efficient Sites for the Separation of SF6 from N2.

SF6 and SF6-N2 mixed gases are used widely as insulators, but such gases have high greenhouse gas potential. The separation of SF6 from SF6-N2 mixed gases is an inevitable result of their use. Single-walled carbon nanohorns (CNHs) were used here for a fundamental study of the separation of SF6 and N2. The diameters of the interstitial and internal nanopores of the CNHs were 0.7 and 2.9 nm, respectively. The high selectivity of SF6 over N2 was observed only in the low-pressure regime in the interstitial 0.7 nm nanopores; the selectively was significantly decreased at higher pressures. In contrast, the high selectivity was maintained over the entire pressure range in the internal 2.9-nm nanopores. These results showed that the wide carbon nanopores were efficient for the separation of SF6 from the mixed gas.

Use of gadolinium contrast adrenal venography for the assessment of primary aldosteronism in a patient with iodine allergy.

Primary aldosteronism is a relatively common cause of secondary hypertension. It is often important to diagnose this disease accurately, since appropriate surgical therapy may result in cure of the disease. Assessment of the laterality of adrenal hyperfunction is possible using adrenal venous sampling of steroid hormones, but this procedure may not be feasible in patients with allergy to iodinated radiocontrast agents. In this paper, we report a patient with primary aldosteronism who was found to have bilateral adrenal tumors on CT. Because preoperative localization of the hyperfunctioning tumor was important, adrenal venous sampling and venography was performed by a highly-experienced radiologist using the MRI contrast agent gadolinium. After reviewing the data, the patient received a right adrenalectomy. This case report demonstrates that it was possible to perform adrenal venography using gadolinium in this patient, however the safety and efficacy should be re-assessed in individual cases.