Synthesis and antibacterial activity of novel neamine derivatives: preponderant role of the substituent position on the neamine core

A series of neamine derivatives were prepared from the cyclic carbonate and sulfate of 1,3,2',6'-tetraazido-3',4',-di-O-acetylneamine. Ring opening reactions with diversely substituted amines result in the formation of the corresponding carbamates or sulfonic acids with good overall yields. The antibacterial activities of the synthesized products against E. coli (DH5α) and S. aureus (RN4220) were evaluated. With isolated single regioisomers, the preponderant effect of the 5-positions of the carbamate substituent on the neamine core was demonstrated.     

Age-related decline in cognitive control: the role of fluid intelligence and processing speed

Background

Research on cognitive control suggests an age-related decline in proactive control abilities whereas reactive control seems to remain intact. However, the reason of the differential age effect on cognitive control efficiency is still unclear. This study investigated the potential influence of fluid intelligence and processing speed on the selective age-related decline in proactive control. Eighty young and 80 healthy older adults were included in this study. The participants were submitted to a working memory recognition paradigm, assessing proactive and reactive cognitive control by manipulating the interference level across items.

Results

Repeated measures ANOVAs and hierarchical linear regressions indicated that the ability to appropriately use cognitive control processes during aging seems to be at least partially affected by the amount of available cognitive resources (assessed by fluid intelligence and processing speed abilities).

Conclusions

This study highlights the potential role of cognitive resources on the selective age-related decline in proactive control, suggesting the importance of a more exhaustive approach considering the confounding variables during cognitive control assessment.     

Volcanic glass under fire – a comparison of three complementary analytical methods

The two obsidian sources from the island of Melos (Greece), Agia Nychia and Demenegakion, are chemically characterized by three complementary analytical techniques. Ion beam analysis (IBA) comprising particle induced X‐ray emission and particle induced gamma‐ray emission, neutron activation analysis (NAA) and laser ablation inductively coupled plasma mass spectrometry (LA‐ICP‐MS) is applied to the same set of geological obsidian samples. The combination of methods allows a more complete characterization of obsidian sources and reveals a highly specific chemical composition, the so‐called chemical fingerprint. This multi‐methodical approach checks also the self‐consistency of the analytical results and shows not only the most reliable and characteristic key elements Co and Sc but also Fe, Ca and Ti of Melos obsidian deposits. NAA contributes the largest number of reliable elements to the most unambiguous chemical fingerprint comprising in total of 41 elements. Therefore, NAA is the most suitable analytical method for a clear identification of Melos obsidian deposits. Moreover, the accuracy of methods is demonstrated by the excellent correspondences (calculated correlation coefficient R² = 1.00 for IBA and NAA, R² = 0.99 for LA‐ICP‐MS) between determined analytical results obained by IBA, NAA and LA‐ICP‐MS and certified values of the reference glass BAM‐S005B. Copyright © 2013 John Wiley & Sons, Ltd.     

Elliptic curve configurations on Fano surfaces

The elliptic curves on a surface of general type constitute an obstruction for the cotangent sheaf to be ample. In this paper, we give the classification of the configurations of the elliptic curves on the Fano surface of a smooth cubic threefold. That means that we give the number of such curves, their intersections and a plane model. This classification is linked to the classification of the automorphism groups of theses surfaces.     

First synthesis of 10 alpha-(trifluoromethyl)deoxoartemisinin

[reaction: see text] A novel, nonacetal (trifluoromethyl)deoxoartemisinin was prepared with good stereoselectivity. This compound was obtained by debromination of the 10 alpha-CF3-10-bromodeoxoartemisinin in the presence of tributyltin hydride at reflux in toluene without alteration of the endoperoxide bridge. It presented a reasonable antimalarial activity.     

Self-organizing properties of natural and related synthetic glycolipids

In this article we report on the syntheses, self-organizing properties, and structures of a variety of cerebrosides and related synthetic glycolipids. The thermotropic and lyotropic liquid crystalline properties of the materials were evaluated in detail. All of the families of materials studied exhibited columnar mesophases. In the dry state the aliphatic chains were found to be located on the exterior of the columns, whereas in the wet state the reverse was the case with the polar headgroups on the exterior. Thus, the aliphatic chains act almost like hydrocarbon solvents in the dry state.     

Using effective group potential methodology for predicting organometallic complex properties

Using the Effective Group Potentials (EGP) method, optimal geometries, harmonic vibrational frequencies, and relative energies of different sets of metal complexes are calculated. All of the systems under consideration contain the cyclopentadienyl (Cp) ligand. They are as follows: (i). Group V metal Atom complexes showing one Cp ligand, (ii). a tetrameric Al-Cp compound with four Cp ligands, (iii). homometallic lutetium hydrides containing six cyclopentadienyl rings. Various electron correlation treatments have been carried out. All of the results compare very satisfactorily with available experimental data and with all-electron ab initio calculations performed for this work or published in the literature. Furthermore, the performance of the EGP method was tested on a rather large complex for which experimental evidence exists, but no all-electron calculation has been reported so far.     

Can dynamical mechanical measurements predict brittle fracture behaviour?

The uptake of water by low moisture cereal products can have detrimental effects on their texture, and cause loss of quality. Following the interest in developing techniques suitable for determining texture properties, there has also been a move towards identifying the origins of the observed changes. Although the origins of the hydration effects are not fully understood, dynamic rheology is believed to be a suitable technique for characterising mechanical properties, and for identifying the origins of the features observed after moisture pick-up. In a previous paper, the sensory crispness of white bread and of extruded flat bread were correlated with tan, through the increase in tan resulting from the increased hydration associated with loss of crispness. The present work shows that such a correlation does not exist with extruded starch-sugar samples. This means that tan data cannot be used to predict fracture properties like those covered by crispness. The information revealed by the results did, however, address various questions about the significance of tan. Indeed, the increase in tan with increasing hydration was shown to be particularly acute when the starch was mixed with sugar (sucrose or fructose). In order to interpret these results several hypotheses have been suggested, including increased heterogeneity of the systems, and sensitivity of tan to solute mobility or to localised motions of the matrix.