3α‐Hydroxytirucalla‐7,24‐dien‐21‐oic acid: a triterpene from Protium crenatum Sandwith

The crystal structure of the title compound, C₃₀H₄₈O₃, a triterpene extracted from the resin of Protium crenatum Sandwith, is reported. The aliphatic acidic side chain is attached to the tirucallene four‐ring system on its α‐face and is extended by 7.248 (5) Å in the `left‐hand' orientation.     

Self-Assembled Nanotubes in Organic Solvents

Self-assembled nanotubes are formed spontaneously in alkane solvents by a simple diamide compound: the 3,5-Bis-(5-hexylcarbamoyl-pentyloxy)-benzoic acid decyl ester (BHPB-10). The tubular shape was proved by freeze fracture TEM and by SANS techniques. The tubes have a mean radius of 121 Å and a length of the order of a micron. BHPB-14, a homologue of this compound, bearing a longer ester chain (C14 instead of C10), self-assemble into flat ribbons under the same conditions. FTIR and UV spectroscopy showed that H-bonds between amide groups and π-π interaction between aromatic groups are involved in both kinds of aggregates and in the solid state as well. The nanotubes feature specific interactions between the ester carbonyls. Hence we show that ester, by its length and by the interactions between carbonyls determines the formation of nanotubes.     

A penalized nonparametric method for nonlinear constrained optimization based on noisy data

The objective of this study is to find a smooth function joining two points A and B with minimum length constrained to avoid fixed subsets. A penalized nonparametric method of finding the best path is proposed. The method is generalized to the situation where stochastic measurement errors are present. In this case, the proposed estimator is consistent, in the sense that as the number of observations increases the stochastic trajectory converges to the deterministic one. Two applications are immediate, searching the optimal path for an autonomous vehicle while avoiding all fixed obstacles between two points and flight planning to avoid threat or turbulence zones.     

Reflections on the journey: six short stories

The low-temperature heat capacities of nickel titanate (NiTiO₃), cobalt titanate (CoTiO₃), and cobalt carbonate (CoCO₃) were measured between 2 and 300 K, and thermochemical functions were derived from the results. Our new data show previously unknown low-temperature lambda-shaped heat capacity anomalies peaking at 37 K for CoTiO₃ and 26 K for NiTiO₃. From our data we calculate standard molar entropies (298.15 K) for NiTiO₃ of 90.9 ± 0.7 J mol^-1 K^-1 and for CoTiO₃ of 94.4 ± 0.8 J mol^-1 K^-1. For CoCO₃, we find only a small broad heat capacity anomaly, peaking at about 31 K. From our data, we suggest a new standard entropy (298.15 K) for CoCO₃ of 88.9 ± 0.7 J mol^-1 K^-1.     

Australian Synchrotron 2010 User Meeting

The 2010 Australian Synchrotron User Meeting attracted around 230 synchrotron experts, users and potential users, and other interested observers, mainly from around Australia and New Zealand, to Melbourne, Australia, in late November. Held within easy walking distance of Carlton's many cosmopolitan cafes and shops, the User Meeting provided numerous opportunities for participants to discuss their research, learn from each others' experiences, and plan future collaborations.     

On second and eighth order mock theta functions

The Ramanujan Journal - Mock theta functions have been deeply studied in the literature. Historically, there are many forms of representations for mock theta functions: Eulerian forms, Hecke-type...     

Thermal decomposition behavior of potassium and sodium jarosite synthesized in the presence of methylamine and alanine

Biomolecules, methylamine and alanine, found associated with natural jarosite samples peaked the interest of astrobiologists and planetary geologists. How the biomolecules are associated with jarosite remains unclear although the mechanism could be important for detecting biosignatures in the rock record on Earth and other planets. A series of thermal gravimetric experiments using synthetic K-jarosite and Na-jarosite were conducted to determine if thermal analysis could differentiate physical mixtures of alanine and methylamine with jarosite from samples where the methylamine or alanine was incorporated into the synthesis procedure. Physical mixtures and synthetic experiments with methylamine and alanine could be differentiated from one another and from the standards by thermal analysis for both the K-jarosite and Na-jarosite end-member suites. Changes included shifts in on-set temperatures, total temperature changes from on-set to final, and the presence of indicator peaks for methylamine and alanine in the physical mixture experiments.