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We present new results on the microscopic nature of the ferroelectricity mechanisms in Ca3Mn2O7. and Ca3Ti2O7 . To the first approximation, we confirm the hybrid improper ferroelectric mechanism recently proposed by Benedek and Fennie for these Ruddlesden-Popper compounds. However, in Ca3Mn2O7 we find that there is a complex competition between lattice modes of different symmetry which leads to a phase coexistence over a large temperature range and the "symmetry trapping" of a soft mode. This trapping of the soft mode leads to a large uniaxial negative thermal expansion (NTE) reaching a maximum between 250 and 350 K (3.6 × 10- 6 K-1) representing the only sizable NTE reported for these and related perovskite materials to date. Our results suggest a systematic strategy for designing and searching for ceramics with large NTE coefficients. [ABSTRACT FROM AUTHOR]

A group of sunflower lines that exhibit a range of leaf Na + concentrations under high salinity was used to explore whether the responses to the osmotic and ionic components of salinity can be distinguished in leaf expansion kinetics analysis. It was expected that at the initial stages of the salt treatment, leaf expansion kinetics changes would be dominated by responses to the osmotic component of salinity, and that later on, ion inclusion would impose further kinetics changes. It was also expected that differential leaf Na + accumulation would be reflected in specific changes in cell division and expansion rates. Plants of four sunflower lines were gradually treated with a relatively high (130 m m NaCl) salt treatment. Leaf expansion kinetics curves were compared in leaves that were formed before, during and after the initiation of the salt treatment. Leaf areas were smaller in salt-treated plants, but the analysis of growth curves did not reveal differences that could be attributed to differential Na+ accumulation, since similar changes in leaf expansion kinetics were observed in lines with different magnitudes of salt accumulation. Nevertheless, in a high leaf Na+-including line, cell divisions were affected earlier, resulting in leaves with proportionally fewer cells than in a Na+-excluding line. A distinct change in leaf epidermal pavement shape caused by salinity is reported for the first time. Mature pavement cells in leaves of control plants exhibited typical lobed, jigsaw-puzzle shape, whereas in treated plants, they tended to retain closer-to-circular shapes and a lower number of lobes. [ABSTRACT FROM AUTHOR]

Five experimental bloomery iron ore smelts were carried out in a reconstruction of an early medieval furnace of the Boécourt type (Switzerland). A part of the bloom from the most successful experiment was forged to a billet. Starting materials and products were weighed, described and chemically characterized (ICP-MS, LA-ICP-MS and WD-XRF). The calculation of the yield and mass balance based on the chemical analyses from the ore (optimum) and from the ore, furnace lining, slag and ash (applied) allow the determination and quantification of the materials involved in the process. This permits the interpretation of the quality of the experiments. The chemical characterization of metal produced from hematite ore from the Gonzen Mountains in Switzerland gives archaeologists the possibility to compare the metal of iron artefacts to metal from this mine. Finally a good agreement between experiments and archaeological reality can be shown. [ABSTRACT FROM AUTHOR]

A periodic survey of methicillin-resistant Staphylococcus aureus (MRSA) in Zurich in 2004 and 2006 revealed a consistently low prevalence of MRSA. SCC mec and ccr typing showed fluctuations in the proportions of SCC mec types and in the carriage of mobile virulence determinants. Together with the presence of variant SCC mecs these findings suggest a high clonal diversity and level of SCC mec recombination. The prevalence of a local “drug clone", associated with low-level methicillin resistance and rapid growth, significantly decreased. This clone had spread among intraveneous drug users, steadily increasing from 1994 to 2001 and was dominant in 2001. Apparently, changes in the management of the Zurich drug scene have restricted the spread of this clone. [ABSTRACT FROM AUTHOR]

This study tested the hypothesis that purebred Boran ( Bos indicus) cows and crossbreds of Boran and Holstein respond differently to long-term changes of feeding level in nutrient partitioning to milk and body fat stores. A total of 27 cows of these two genotypes were subjected either to a low or a high feeding level from their first oestrus as heifers until birth of their third calf. Half of the cows of each genotype were then switched to the other feeding level during the third reproduction cycle. If at all, Boran cows responded to a change in the feeding level almost exclusively by a corresponding change in body weight but not milk yield. Crossbred cows kept continuously on the low feeding level had a lower milk yield than those continuously fed the high level, but lost similar amounts of body weight. In crossbred cows, changing the feeding level from high to low was accompanied by a mobilization of body reserves, whereas a change from low to high level resulted mostly in an increase in milk yield. Certain other genotype differences in metabolic response were obvious from differences in body composition and from the metabolic profile either reflected in blood (particularly insulin-like growth factor I) or in adipose tissue (lipoprotein lipase). Reproductive performance differed between genotypes, with shorter lactations associated with earlier occurrences of the first oestrus in the Boran cows. Generally, feeding history appeared to have at least as much influence on energy partitioning as the actual feeding level. In conclusion, purebred Boran cows seem to react to long-term food fluctuations mainly by mobilizing and restoring body fat reserves, whereas cows crossbred with Holstein tend to spend extra energy preferentially for milk production. [ABSTRACT FROM AUTHOR]

Synchrotron-based micro-X-ray fluorescence (micro-XRF) and micro-X-ray absorption spectroscopy (micro-XAS) were used in the present study to obtain spatially resolved micro-scale information on elemental composition, trace element distribution, chemical speciation and oxidation state and/or mineral phase distribution within historical iron artefacts dating from the Iron Age to early Medieval Times. Large area two-dimensional trace element distribution maps and oxidation state maps with micrometer spatial resolution were required to answer open archaeological questions in the context of ancient metal processing. The first set of examples was focusing on historical weapons and included two ancient iron sword blades. The micro-XRF maps revealed a distinct, highly correlated distribution pattern of trace elements such as As, Ni, Cu and Zn. Accordingly, the number of used raw materials could be determined unambiguously and key information concerning the used ancient smithing technique were gained. Further, the ability to record—in a fast manner—large area maps with high spatial resolution (‘elemental screening’) led to the discovery of a hitherto unknown enhanced occurrence of selected trace elements (Cu, Zn, and Au) at the blade surface. Complementary investigations by high resolution scanning electron microscopy were able to localize these trace metals within a carbon-rich matrix may be pointing towards an artifact induced during preservation. A second set of investigated artefacts is dealing with smithing waste products and related historical processing techniques and conditions. Synchrotron-based micro-XRF and micro-XAS were used to determine the structural composition as well as the spatial variation of the predominant Fe oxidation state and corresponding crystallographic phases. The study revealed the presence of distinct domains of Fe0, FeIIO (wustite), and α-FeIIIOOH (goethite), separated by sharp domain boundaries. These findings help to gain new insights concerning the nature and origin of used raw materials as well as regarding employed processing techniques during historic iron fabrication and weapon manufacturing.The study demonstrates the potential of oxidation state and mineral phase mapping based on energy selective micro-XRF maps and spectroscopic phase identification. Such a spatially resolved recording of the chemical speciation is based on X-ray absorption spectroscopy. This analytical technique is exclusive to synchrotron light sources. However, the steadily increasing number of available synchrotron-based X-ray microprobes allows nowadays for more routine utilization of such micro-XAS techniques. [Copyright &y& Elsevier]

Presents information on a study which examined the metabolic effects of adding lysine and methionine to a ration of calculated deficiency in amino acids in Brown Swiss cows. Material and methods; Results and discussion; Conclusions.

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This paper describes mass spectrometric studies of the peracetylated derivatives of synthetic and natural 6,6′-diesters of trehalose containing acyl radicals varying from C22 to C90. The peracetylated synthetic 6,6′-dieicosanoyl trehalose (I) gave a molecular ion at m/e 1238. The synthetic 2,3,4,2′,3′,4′-hexaacetyl-6,6′-di(α-eicosanyl-β-acetoxy tetracosanoyl)-trehalose (IIb) showed no molecular ion but a peak (M-60) at m/e 1910 (Fig. l). The cleavage of the glycosidic bond leads to typical oxonium ions which are at m/e 611 (A) for (I) and at m/e 977 (B2) for (IIb). The three natural trehalose 6,6′-diesters examined are the ‘cord factors’ of a human virulent strain of Mycobacterium tuberculosis (strain Prévois), of a bovine attenuated strain (BCG) and of Mycobacterium butyricum. The mycolic acids isolated after saponification of these compounds have also been studied by mass spectrometry. Formulae III, IV, V and VI are proposed for their methyl esters. The molecular weights of the paracetylated ‘cord factors’ are above 3000; no molecular ion could be detected. The oxonium ions, however, give significant peaks which are useful for structural determination. Oxonium ions for the glycolipid of the human virulent strain Prévois are found at m/e 1360–1528 (Fig.2). The peracetylated glycolipid of BCG contains two different series of homologous mycolic acids (acyl ions at m/e 1144–1284 and 1072–1184) and gives oxonium ions at m/e 1432–1572 for one series and at m/e 1360–1472 for the second one. The ‘cord factor’ of M. butyricum gives homologous oxonium ions from m/e 1361 to 1445 corresponding to acyl ions from m/e 1073 to 1157. [ABSTRACT FROM AUTHOR]

"Cord factors" are diesters of α,α-trehalose produced by Mycobacteriae and Corynebacteriae. Saponification of the "cord factor" of Corynebacterium diphtheriae gives an equimolecular mixture of homologues of the saturated corynomycolic and of the unsaturated corynomycolenic acids (I and II, R = H). Mass spectrometry of their methyl esters confirms their structures (see Fig. 1, R = CH3. The peracetylated cord factor (IV, a, b, c) gave very weak molecular ions at m/e 1630, 1632 and 1634 showing apparently that it is a mixture of the diesters having respectively two saturated, one saturated and one unsaturated, and two unsaturated acyl radicals. Strong peaks at m/e 809 and 807 are attributed to the oxonium ions (V and V b). These results as well as chemical degradations show that the "cord factor" or C. diphtheriae is a mixture of glycolipids (III a, b,c). [ABSTRACT FROM AUTHOR]

The magnetic ground state of Sr3ARuO6, with A = (Li, Na), is studied using neutron diffraction, resonant x-ray scattering, and laboratory characterization measurements of high-quality crystals. Combining these results allows us to observe the onset of long-range magnetic order and distinguish the symmetrically allowed magnetic models, identifying in-plane antiferromagnetic moments and a small ferromagnetic component along the c axis. While the existence of magnetic domains masks the particular in-plane direction of the moments, it has been possible to elucidate the ground state using symmetry considerations. We find that due to the lack of local anisotropy, antisymmetric exchange interactions control the magnetic order, first through structural distortions that couple to in-plane antiferromagnetic moments and second through a high-order magnetoelastic coupling that lifts the degeneracy of the in-plane moments. The symmetry considerations used to rationalize the magnetic ground state are very general and will apply to many systems in this family, such as Ca3ARuO6, with A = (Li, Na), and Ca3LiOsO6 whose magnetic ground states are still not completely understood. [ABSTRACT FROM AUTHOR]

By using a symmetry motivated basis to evaluate local distortions against pair distribution function data, we show without prior bias, that the off-center Ti displacements in the archetypal ferroelectric BaTiO3 are zone centered and rhombohedral-like across its known ferroelectric and paraelectric phases. We construct a simple Monte Carlo model that captures our main experimental findings and demonstrate how the rich crystallographic phase diagram of BaTiO3 emerges from correlations of local symmetry-breaking distortions alone. Our results strongly support the order-disorder picture for these phase transitions, but can also be reconciled with the soft-mode theory of BaTiO3 that is supported by some spectroscopic techniques. [ABSTRACT FROM AUTHOR]

Introduction: Methicillin resistance in Staphylococcus aureus can be influenced by factors outside the resistance island SCCmec (staphylococcal cassette chromosome mec), which encodes the resistance determinant penicillin binding protein 2a (PBP2a). PBPs are involved in the last steps of peptidoglycan synthesis, an essential component of bacterial cell wall. PBP2a is active in the presence of concentrations of beta-lactams blocking the endogenous PBPs and abolishing cell wall biogenesis in methicillin-sensitive S. aureus. The level of methicillin resistance, fitness, and virulence can be modulated by factors involved directly or indirectly in cell wall synthesis. As part of the ANTIRESDEV project, we identified several new factors affecting these properties. Methods: Transposon-mutant library screening, transcriptome analysis, whole genome sequencing, and virulence assessment using animal models were performed. Results: (1) The new regulator XdrA, influencing methicillin resistance levels and homogeneity, as well as growth rate, was shown by transcriptomic analysis to also affect gene expression, including transcription of one of the most prominent immunomodulatory S. aureus proteins, SpA. (2) The two-component system VraSR, involved in stress response to cell wall active antibiotics and influencing resistance towards these antibiotics, was further characterized. A new player, YvqF, was identified to physically interact with VraS and to influence resistance. (3) Studies on the LytR-CpsA-Psr proteins of S. aureus showed the importance of these factors for resistance, fitness, and virulence. Furthermore, experiments supported a role of these proteins in the synthesis of wall teichoic acids, cell envelope constituents influencing cation homeostasis, cell separation, and colonization of the human host. (4) Analysis of a transposon-mutant library identified 17 new genes modulating beta-lactam resistance, and in some cases also affecting growth rate, cell envelope stability, response to cell wall stress, and virulence factor expression. (5) Comparison by whole genome sequencing of a faster-growing, but less methicillin-resistant variant compared to its parent, revealed a single nucleotide polymorphism in the diadenylate cyclase gene dacA. DacA synthesizes the second messenger cyclic diadenosine monophosphate that has been proposed to be involved in cell envelope homeostasis. Re-introduction of the mutation into the highly resistant but slower growing parent strain reduced resistance and increased the growth rate, suggesting a direct connection between the dacA mutation and the phenotypic differences of these strains. Discussion: Numerous new factors influencing the resistance, virulence, and vital properties of S. aureus were identified, pointing to physiological processes previously unknown to be important for resistance. Unraveling how exactly all these factors can modulate such diverse properties and tasks such as sensitivity towards antibiotics, maintenance of fitness, or expression of virulence, requires further work. Importantly, these genes have the potential to reduce the biological cost caused by antibiotic resistances and to allow resistant strains to maintain considerable fitness and virulence, making them interesting targets for the development of much required new antimicrobial substances. [ABSTRACT FROM AUTHOR]

The non-steroidal, bis-acylhydrazine agonists of the insect molting hormone, 20-hydroxyecdysone, were first discovered over ten years ago. An extensive structure-activity optimization program yielded one commercial insecticide, tebufenozide (RH-5992) and two additional candidate insecticides (methoxyfenozide and halofenozide) which are in development. Tebufenozide is highly selective for lepidopteran pest control and is thus useful for IPM and resistance management programs. Methoxyfenozide (RH-2485) is also lepidopteran-selective but significantly more potent than tebufenozide and offers control of a wider rangeof lepidopteran pests. Halofenozide (RH-0345) is generally less potent and selective than tebufenozide or methoxyfenozide. However, its physical and biological properties make it well suited for control of beetle grubs and caterpillars in the soil. Target pest selectivity, new and novel mode of action, ecotoxicological safety and safety to beneficial arthropods make these insecticides valuable tools for integrated pest and resistance management programs. (c) 1999 Society of Chemical Industry [ABSTRACT FROM AUTHOR]