Element distributions in metallic fractions of an Antarctic ordinary chondrite ALH-77231(L6)

A chemical dissolution method based on different leaching rates of kamacite, taenite and tetrataenite in concentrated HF was developed for isolating metal phases from non-magnetic minerals (mainly silicates) in chondritic meteorites, and for separating taenite from kamacite. This method was applied to an Antarctic chondrite, ALH-77231 (L6), to study the elemental distributions between metal and non-magnetic phases and between taenite and kamacite. The separated phases as well as the bulk metal were studied by Mossbauer spectrometry and by INAA. Mossbauer spectra of ^Fe show that our procedure is efficient in removing silicates from metal and separating taenite from kamacite. The existence of tetrataenite and the absence of disordered taenite in ALH-77231 metals imply that the parent body of ALH-77231 has not experienced severe shock events that redistribute elements among different phases. Thus, element distributions among different phases reflect, in general, the metamorphic history of ALH-77231. INAA results show that siderophile elements are differently distributed between taenite and kamacite. Most siderophiles have very strong to moderate affinities to taenite, while Co is enriched in kamacite. Refractory siderophile elements seem to behave as an individual group. Distribution of Ir between the metal and the non-magnetic fractions implies that a portion of Ir is present in the silicate fraction. This portion of Ir cannot be attributed to the contamination of FeNi metal in the silicates. While the Os/Ir rations in the metals of ALH-77231 are in agreement with the CI value, the Re/Ir rations are significantly higher than the CI value, indicating that Re is fractionated from Ir and Os, between the metal and the non-magnetic fractions. This may be attributable to either the later redistribution of Re between metal and non-magnetic fractions or differences in the condensation phases for Re, and for Ir and Os

Improvement of pulmonary surfactant activity by introducing D-amino acids into highly hydrophobic amphiphilic α-peptide Hel 13-5

AbstractThe high costs of artificial pulmonary surfactants, ranging in hundreds per kilogram of body weight, used for treating the respiratory distress syndrome (RDS) premature babies have limited their applications. We have extensively studied soy lecithins and higher alcohols as lipid alternatives to expensive phospholipids such as DPPC and PG. As a substitute for the proteins, we have synthesized the peptide Hel 13-5D3 by introducing D-amino acids into a highly lipid-soluble, basic amphiphilic peptide, Hel 13-5, composed of 18 amino acid residues. Analysis of the surfactant activities of lipid-amphiphilic artificial peptide mixtures using lung-irrigated rat models revealed that a mixture (Murosurf SLPD3) of dehydrogenated soy lecithin, fractionated soy lecithin, palmitic acid (PA), and peptide Hel 13-5D3 (40:40:17.5:2.5, by weight) superior pulmonary surfactant activity than a commercially available pulmonary surfactant (beractant, Surfacten®). Experiments using ovalbumin-sensitized model animals revealed that the lipid-amphiphilic artificial peptide mixtures provided significant control over an increase in the pulmonary resistance induced by premature allergy reaction and reduced the number of acidocytes and neutrophils in lung-irrigated solution. The newly developed low-cost pulmonary surfactant system may be used for treatment of a wide variety of respiratory diseases

Discovery of the element with atomic number 112 (IUPAC Technical Report)

The IUPAC/IUPAP Joint Working Party (JWP) on the priority of claims to the discovery of new elements has reviewed the relevant literature pertaining to several claims. In accordance with the criteria for the discovery of elements previously established by the 1992 IUPAC/IUPAP Transfermium Working Group (TWG), and reiterated by the 1999 and 2003 IUPAC/IUPAP JWPs, it was determined that the 1996 and 2002 claims by the Hofmann et al. research collaborations for the discovery of the element with atomic number 112 at Gesellschaft für Schwerionenforschung (GSI) share in the fulfillment of those criteria. A synopsis of Z = 112 experiments and related efforts is presented. A subsequent report will address identification of higher-Z elements including those of odd atomic numbe

Diastereoselective Desymmetrization of Symmetric Dienes and its Synthetic Application

The desymmetrization of symmetric compounds is a useful approach to obtain chiral building blocks. Readily available precursors with a prochiral unit could be converted into complex molecules with multiple stereogenic centers in a single step. In this review, recent advances in the desymmetrization of symmetric dienes in the diastereotopic group differentiating reaction and its synthetic application are presented