The detection of extragalactic 15^{15}N: Consequences for nitrogen nucleosynthesis and chemical evolution

Detections of extragalactic $^{15}$N are reported from observations of the rare hydrogen cyanide isotope HC$^{15}$N toward the Large Magellanic Cloud (LMC) and the core of the (post-) starburst galaxy NGC 4945. Accounting for optical depth effects, the LMC data from the massive star-forming region N113 infer a $^{14}N/^{15}$N ratio of 111 $\pm$ 17, about twice the $^{12}C/^{13}$C value. For the LMC star-forming region N159HW and for the central region of NGC 4945, $^{14}N/^{15}$N ratios are also $\approx$ 100. The $^{14}N/^{15}$N ratios are smaller than all interstellar nitrogen isotope ratios measured in the disk and center of the Milky Way, strongly supporting the idea that $^{15}$N is predominantly of `primary' nature, with massive stars being its dominant source. Although this appears to be in contradiction with standard stellar evolution and nucleosynthesis calculations, it supports recent findings of abundant $^{15}$N production due to rotationally induced mixing of protons into the helium-burning shells of massive stars.Comment: 15 pages including one postscript figure, accepted for publication by ApJ Letter, further comments: please contact Yi-nan Chi

Synthesis of Sorbitol Fatty Acid Ester through Esterification of Sorbitol and Azelaic Acid Catalysed by Germanium (IV) Oxide

Conventionally, polyurethane (PU) is produced using polyol polyester derived from non-renewable petroleum feedstock. In addition to the restricted resources of petroleum feedstock, inefficient disposal of the non-biodegradable petroleum-based PU waste through landfill and incineration has caused environmental problem. [1]. As an alternative for the current resource, bio-based polyol polyester such as sorbitol fatty acid ester is introduced. Commonly, homogeneous acid catalyst such as sulfuric acid is used in esterification process for the synthesis of polyol polyester [2, 3]. In this study, sorbitol (SL) and azelaic acid (AA) derived from renewable resources were used in the esterification reaction to produce bio-based polyol polyester. Germanium (IV) oxide, a heterogeneous acid catalyst was chosen to eliminate the use of homogeneous acid catalyst that renders corrosiveness, difficulty in the downstream separation and catalyst reuse [4, 5]. The effects of important operating parameters include reaction temperature (160˚C to 220˚C), molar ratio of SL/AA (1:1 to 4:1) and catalyst loading (1 to 4 vol%) were investigated. The reaction was carried out in a batch reactor and the products were analyzed for its acid value through titration and concentration sorbitol and its anhydrides through gas chromatography (GC)

Simultaneous multiple responses modelling, optimisation and correlation of Asian type peanuts (Arachis hypogaea L.) roasting using response surface methodology

The effect of hot-air roasting temperatures and time on colour (L*), moisture content (% d.b.), hardness (N), and fracturability (mm) attributes of two different type of peanuts (China and India origin) were investigated using response surface methodology (RSM). The central composite design (CCD) was used to investigate temperatures ranging from 130–170 °C (China) and 130–200 °C (India), while roasting time was from 20–80 min (China) and 15–50 min (India). The results revealed that temperature and time have significant effect on all the responses. Increase in roasting time and temperature caused a decrease in all the responses for both peanuts. A feasible experimental condition of peanut roasting obtained from the optimisation of simultaneous multiple attributes’ response for the China and India peanuts was 152 °C for 60 min and 158 °C for 45 min, respectively. The strongest linearrelationship was found between hardness and fracturability, while the weakest was between colour and fracturability for both peanuts

Orbital occupation and magnetic moments of tetrahedrally coordinated iron in CaBaFe4O7

CaBaFe4O7 is a mixed-valent transition metal oxide having both Fe2+ and Fe3+ ions in tetrahedral coordination. Here we characterize its magnetic properties by magnetization measurements and investigate its local electronic structure using soft x-ray absorption spectroscopy at the Fe L2,3 edges, in combination with multiplet cluster and spin-resolved band structure calculations. We found that the Fe2+ ion in the unusual tetrahedral coordination is Jahn-Teller active with the high-spin e^2 (up) t2^3 (up) e^1 (down) configuration having a x^2-y^2-like electron for the minority spin. We deduce that there is an appreciable orbital moment of about L_z=0.36 caused by multiplet interactions, thereby explaining the observed magnetic anisotropy. CaBaFe4O7, a member of the '114' oxide family, offers new opportunities to explore charge, orbital and spin physics in transition metal oxides