STepwise Magnetic Behavior of the Liquid Crystal Iron(Iii) Complex

EPR and Mossbauer spectroscopy is used to study a new liquid crystal complex of iron(III) with a Schiff base: 4,4'S-dodecyloxybenzoyloxybenzoyl-4- oxysalicylidene-2-aminopyridine with a PF6'{ counterion. It is shown that Fe(III) ions exist only in the high-spin (HS, S = 5/2) state. It is found that under the influence of temperature the system demonstrates the stepwise behavior of the product of the integrated intensity of EPR lines (I ) and temperature (proportional to "where" is the magnetic susceptibility) with an inflection point at "80 K. Above 80 K a new EPR spectrum is detected due to the excited S = 2 state and the formation of dimeric molecules (through oxygen bridges) with a strong intramolecular antiferromagnetic exchange interaction J1 = 162.1 cm-V1. Below 80 K iron(III) complexes are organized in 1D chains where the exchange value J2 = 2.1 cm-V1. At 80 K there is a structural phase transition in the system: the transition from a 1D chain organization of HS Fe(III) centers to dimeric molecules. Based on quantum chemical calculations a model of the binuclear iron(III) complex is proposed. Copyright © 2013 by N. E. Domracheva, V. E. Vorob'eva, A. V. Pyataev, R. A. Manapov, E. M. Zueva, M. S. Gruzdev, U. V. Chervonova

The laurentian record of neoproterozoic glaciation, tectonism, and eukaryotic evolution in Death Vally, California

Neoproterozoic strata in Death Valley, California contain eukaryotic microfossils and glacial deposits that have been used to assess the severity of putative Snowball Earth events and the biological response to extreme environmental change. These successions also contain evidence for syn-sedimentary faulting that has been related to the rifting of Rodinia, and in turn the tectonic context of the onset of Snowball Earth. These interpretations hinge on local geological relationships and both regional and global stratigraphic correlations. Here we present new geological mapping, measured stratigraphic sections, carbon and strontium isotope chemostratigraphy, and micropaleontology from the Neoproterozoic glacial deposits and bounding strata in Death Valley. These new data enable us to refine regional correlations both across Death Valley and throughout Laurentia, and construct a new age model for glaciogenic strata and microfossil assemblages. Particularly, our remapping of the Kingston Peak Formation in the Saddle Peak Hills and near the type locality shows for the first time that glacial deposits of both the Marinoan and Sturtian glaciations can be distinguished in southeastern Death Valley, and that beds containing vase-shaped microfossils are slump blocks derived from the underlying strata. These slump blocks are associated with multiple overlapping unconformities that developed during syn-sedimentary faulting, which is a common feature of Cyrogenian strata along the margin of Laurentia from California to Alaska. With these data, we conclude that all of the microfossils that have been described to date in Neoproterozoic strata of Death Valley predate the glaciations and do not bear on the severity, extent or duration of Neoproterozoic Snowball Earth events

Оценка влияния разложения твердого раствора алюминия на геометрическое строение изобарной фазовой диаграммы Al-Sn-Zn

Three-dimensional (3D) computer model of the Al-Sn-Zn isobaric phase diagram is presented. It is shown that the T-x-y diagram consists of 64 surfaces and 25 phase regions. Features of Al-Zn binary system phase diagram related to decomposition of aluminum solid solution and its influence on geometric structure of liquidus and solidus surfaces in the ternary system, formed by this binary system and tin, are considered. Critical analysis of the published data was carried out and errors in visualization of those fragments of the Al-Zn T-x diagram, in which phase regions are formed with the participation of new aluminum solid solutions, appeared after the decomposition of the initial solid solution, are discussed. To design this 3D model, literary data were used, and the assessment of its quality is based on isopleths and isothermal sections from the same primary sources.Представлена трехмерная (3D) компьютерная модель изобарной фазовой диаграммы Al-Sn-Zn. Показано, что T-x-y диаграмма состоит из 64 поверхностей и 25 фазовых областей. Рассмотрены особенности фазовой диаграммы двойной системы Al-Zn, связанные с распадом твердого раствора алюминия, и их влияние на геометрическое строение поверхностей ликвидуса и солидуса в тройной системе, формируемой этой системой при добавлении олова. Проведен критический анализ опубликованных данных и обсуждаются ошибки в визуализации тех фрагментов T-x диаграммы Al-Zn, в которых затрагиваются фазовые области, формируемые с участием новых твердых растворов алюминия, появившихся после распада исходного твердого раствора. Для построения 3D модели использовали литературные данные, а в основу оценки ее качества положены изо- и политермические разрезы из тех же первоисточников

3D компьютерная модель T-x-y диаграммы Ag-Cu-Ni: верификация разрезов в атласе фазовых диаграмм для бессвинцовых припоев

Spatial (three-dimensional - 3D) computer model of the T-x-y diagram of the Ag - Cu - Ni system, which is promising for the development of environmentally friendly solders, is presented. The model is constructed on the basis of published data on the binary systems forming this ternary system, the concentration projection of the liquidus surfaces, and four isothermal sections. It is shown that the phase diagram (PD) consists of 14 surfaces and 9 phase regions. The adequacy of the model is confirmed by comparing the isothermal sections and the liquidus projection.Представлена пространственная (трехмерная - 3D) компьютерная модель T-x-y диаграммы системы Ag-Cu-Ni, перспективной для разработки экологически безопасных припоев. Модель построена на основе опубликованных данных по формирующим эту тройную систему бинарным системам, концентрационной проекции поверхностей ликвидуса и четырем изотермическим разрезам. Показано, что фазовая диаграмма состоит из 14 поверхностей и 9 фазовых областей. Адекватность модели подтверждается сравнением изотермических разрезов и проекции ликвидуса

Elucidation of a novel Vibrio cholerae lipid A secondary hydroxy-acyltransferase and its role in innate immune recognition

Similar to most Gram-negative bacteria, the outer leaflet of the outer membrane of Vibrio cholerae is comprised of lipopolysaccharide. Previous reports have proposed that V. cholerae serogroups O1 and O139 synthesize structurally different lipid A domains, which anchor lipopolysaccharide within the outer membrane. In the current study, intact lipid A species of V. cholerae O1 and O139 were analysed by mass spectrometry. We demonstrate that V. cholerae serogroups associated with human disease synthesize a similar asymmetrical hexa-acylated lipid A species, bearing a myristate (C14:0) and 3-hydroxylaurate (3-OH C12:0) at the 2′- and 3′-positions respectively. A previous report from our laboratory characterized the V. cholerae LpxL homologue Vc0213, which transfers a C14:0 to the 2′-position of the glucosamine disaccharide. Our current findings identify V. cholerae Vc0212 as a novel lipid A secondary hydroxy-acyltransferase, termed LpxN, responsible for transferring the 3-hydroxylaurate (3-OH C12:0) to the V. cholerae lipid A domain. Importantly, the presence of a 3-hydroxyl group on the 3′-linked secondary acyl chain was found to promote antimicrobial peptide resistance in V. cholerae; however, this functional group was not required for activation of the innate immune response

Development of the Immuno-Enzyme Test-System for the Detection of <i>Legionella pheumophila</i>, Serogroup I

Developed is the highly sensitive and specific immuno-enzyme test-system, which is perspective for the detection of L. pneumophilia, serogroup 1. Isolated are the three hybrid cell lines that secrete monoclonal antibodies to specific epitopes of L. pneumophilia, serogroup 1 lipopolysaccharide antigen. Hyper immune rabbit sera, characterized by highly specific activity and specificity, are obtained using lipopolysaccharide antigen

A Raman spectroscopic study of arsenite and thioarsenite species in aqueous solution at 25°C

The Raman spectra of thioarsenite and arsenite species in aqueous solution were obtained at room temperature. Solutions at constant ΣAs + ΣS of 0.1 and 0.5 mol kg(-1 )were prepared with various ΣS/ΣAs ratios (0.1–9.0) and pH values (~7–13.2). Our data suggest that the speciation of As under the conditions investigated is more complicated than previously thought. The Raman measurements offer evidence for at least six separate S-bearing As species whose principal bands are centered near 365, 385, 390, 400, 415 and 420 cm(-1). The data suggest that at least two different species may give rise to bands at 385 cm(-1), bringing the probable minimum number of species to seven. Several additional species are possible but could not be resolved definitively. In general, the relative proportions of these species are dependent on total As concentration, ΣS/ΣAs ratio and pH. At very low ΣS/ΣAs ratios we also observe Raman bands attributable to the dissociation products of H(3)AsO(3)(aq). Although we were unable to assign precise stoichiometries for the various thioarsenite species, we were able to map out general pH and ΣS/ΣAs conditions under which the various thioarsenite and arsenite species are predominant. This study provides a basis for more detailed Raman spectroscopic and other types of investigations of the nature of thioarsenite species

Controls on the evolution of Ediacaran metazoan ecosystems: A redox perspective

A growing number of detailed geochemical studies of Ediacaran (635–541 Ma) marine successions have provided snapshots into the redox environments that played host to the earliest known metazoans. Whilst previous compilations have focused on the global evolution of Ediacaran water column redox chemistry, the inherent heterogeneity evident in palaeogeographically distinct environments demands a more dissected approach to better understand the nature, interactions and evolution of extrinsic controls on the development of early macrobenthic ecosystems. Here, we review available data of local-scale redox conditions within a palaeogeographic and sequence stratigraphic framework, to explore the mechanisms controlling water column redox conditions and their potential impact on the record of metazoans. The openly connected Laurentian margin, North America (632–540 Ma) and Nama basin, Namibia (550–538 Ma), and the variably restricted Yangtze Block, South China (635–520 Ma), show continued redox instability after the first fossil evidence for metazoans. This may support opportunistic benthic colonisation during periods of transient oxygenation amidst episodic upwelling of anoxic waters beneath a very shallow, fluctuating chemocline. The first skeletal metazoans appeared under conditions of continued redox stratification, such as those which characterise the Dengying Formation of the Yangtze Block and the Kuibis Subgroup of the Nama basin. Current data, however, suggests that successful metazoan reef-building demanded more persistent oxia. We propose that cratonic positioning and migration throughout the Ediacaran Period, in combination with gradually increasing dissolved oxygen loading, may have provided a first-order control on redox evolution through regulating circulation mechanisms in the Mirovian Ocean. Some unrestricted lower slope environments from mid-high latitudes benefited from sustained oxygenation via downwelling, whilst transit of isolated cratons towards more equatorial positions stifled pervasive ventilation either through ineffective surface ocean mixing, Ekman-induced upwelling, elevated surface ocean productivity or a combination of these processes