The 35S U5 snRNP is generated from the activated spliceosome during In vitro splicing

Primary gene transcripts of eukaryotes contain introns, which are removed during processing by splicing machinery. Biochemical studies In vitro have identified a specific pathway in which introns are recognised and spliced out. This occurs by progressive formation of spliceosomal complexes designated as E, A, B, and C. The composition and structure of these spliceosomal conformations have been characterised in many detail. In contrast, transitions between the complexes and the intermediates of these reactions are currently less clear. We have previously isolated a novel 35S U5 snRNP from HeLa nuclear extracts. The protein composition of this particle differed from the canonical 20S U5 snRNPs but was remarkably similar to the activated B* spliceosomes. Based on this observation we have proposed a hypothesis that 35S U5 snRNPs represent a dissociation product of the spliceosome after both transesterification reactions are completed. Here we provide experimental evidence that 35S U5 snRNPs are generated from the activated B* spliceosomes during In vitro splicing

Fingerprints of Spin-Orbital Physics in Crystalline O2_2

The alkali hyperoxide KO$_2$ is a molecular analog of strongly-correlated systems, comprising of orbitally degenerate magnetic O$_2^-$ ions. Using first-principles electronic structure calculations, we set up an effective spin-orbital model for the low-energy \textit{molecular} orbitals and argue that many anomalous properties of KO$_2$ replicate the status of its orbital system in various temperature regimes.Comment: 4 pages, 2 figures, 1 tabl

Observation of Magnetic Edge State and Dangling Bond State on Nanographene in Activated Carbon Fibers

The electronic structure of nanographene in pristine and fluorinated activated carbon fibers (ACFs) have been investigated with near-edge x-ray absorption fine structure (NEXAFS) and compared with magnetic properties we reported on previously. In pristine ACFs in which magnetic properties are governed by non-bonding edge states of the \pi-electron, a pre-peak assigned to the edge state was observed below the conduction electron {\pi}* peak close to the Fermi level in NEXAFS. Via the fluorination of the ACFs, an extra peak, which was assigned to the \sigma-dangling bond state, was observed between the pre-peak of the edge state and the {\pi}* peak in the NEXAFS profile. The intensities of the extra peak correlate closely with the spin concentration created upon fluorination. The combination of the NEXAFS and magnetic measurement results confirms the coexistence of the magnetic edge states of \pi-electrons and dangling bond states of \sigma-electrons on fluorinated nanographene sheets.Comment: 4 figures, to appear in Phys. Rev.

Associations of Dwarf Galaxies

Hubble Space Telescope Advanced Cameras for Surveys has been used to determine accurate distances for 20 galaxies from measurements of the luminosity of the brightest red giant branch stars. Five associations of dwarf galaxies that had originally been identified based on strong correlations on the plane of the sky and in velocity are shown to be equally well correlated in distance. Two more associations with similar properties have been discovered. Another association is identified that is suggested to be unbound through tidal disruption. The associations have the spatial and kinematic properties expected of bound structures with 1 - 10 x 10^11 solar mass. However, these entities have little light with the consequence that mass-to-light ratios are in the range 100 - 1000 in solar units. Within a well surveyed volume extending to 3 Mpc, all but one known galaxy lies within one of the groups or associations that have been identified.Comment: 50 pages, 2 tables, 15 encapsulated figures, 1 (3 part) jpg figure. Submitted to Astronomical Journa

Late Permian palynomorph assemblages from Ufimian and Kazanian type sequences in Russia, and comparison with Roadian and Wordian assemblages from the Canadian Arctic

Tentative biostratigraphic correlations, based on marine faunas, have been made by various workers between Ufimian and Kazanian sequences in their type areas in the Volga-Urals region of Russia and Roadian and Wordian sequences in their type area in Texas, United States. Unfortunately, palynological correlation between the Russian and United States sequences is not possible, due to lack of data from the latter. However, detailed palynological data are available from rocks of Roadian and Wordian age in the Canadian Arctic Archipelago, and therefore indirect correlations are possible. Palynomorph assemblages from the Canadian Arctic and other circumpolar areas, such as the southern Barents Sea and Greenland, are different from those of the Ufimian and Kazanian Russian sequences in their type areas. This is likely to be the result of variations in the parent flora in response to significant paleoclimatic differences. For example, the climate of the Volga-Urals region in Late Permian times was probably hot and arid, whereas that of the Canadian Arctic, Barents Sea, and Greenland was cooler and probably more humid

High-temperature ferromagnetism of spsp electrons in narrow impurity bands: Application to CaB6_6

Ferromagnetism with high Curie temperature $T_c$, well above room temperature, and very small saturation moment has been reported in various carbon and boron systems. It is argued that the magnetization must be very inhomogeneous with only a small fraction of the sample ferromagnetically ordered. It is shown that a possible source of high $T_c$ within the ferromagnetic regions is itinerant electrons occupying a narrow impurity band. Correlation effects do not reduce the effective interaction which enters the Stoner criterion in the same way as in a bulk band. It is also shown how, in the impurity band case, spin wave excitations may not be effective in lowering $T_c$ below its value given by Stoner theory. These ideas are applied to CaB$_6$ and a thorough review of the experimental situation in this material is given. It is suggested that the intrinsic magnetism of the B$_2$ and O$_2$ dimers might be exploited in suitable structures containing these elements.Comment: 26 pages, 2 figure

Interaction Between Superconducting and Ferromagnetic Order Parameters in Graphite-Sulfur Composites

The superconductivity of graphite-sulfur composites is highly anisotropic and associated with the graphite planes. The superconducting state coexists with the ferromagnetism of pure graphite, and a continuous crossover from superconducting to ferromagnetic-like behavior could be achieved by increasing the magnetic field or the temperature. The angular dependence of the magnetic moment m(alpha) provides evidence for an interaction between the ferromagnetic and the superconducting order parameters.Comment: 11 pages, 4 figures, to be published in Phys. Rev.

Understanding Human and Ecosystem Dynamics in the Kola Arctic : A Participatory Integrated Study

The Lake Imandra watershed is located in one of the most developed regions in the Arctic - the Kola Peninsula of Russia. Approximately 300 000 people live on the roughly 27 000 km² watershed, making it one of the most densely populated areas of the Arctic. Most of the people are involved in large-scale mineral extraction and processing and the infrastructure needed to support this industry. This paper reports the results of a pilot project staged for the Lake Imandra watershed that has put human dynamics within the framework of ecosystem change to integrate available information and formulate conceptual models of likely future scenarios. The observation period is one of both rapid economic growth and human expansion, with an overall economic decline in the past decade. We are applying the Participatory Integrated Assessment (PIA) approach to integrate information, identify information gaps, generate likely future scenarios, and link scientific findings to the decision-making process. We found an increasingly vulnerable human population in varying states of awareness about their local environment and fully cognizant of their economic troubles, with many determined to attempt maintenance of relatively high population densities in the near future even as many residents of northern Russia migrate south. A series of workshops have involved the citizens and local decision makers in an attempt to tap their knowledge of the region and to increase their awareness about the linkages between the socioeconomic and ecological components.Le bassin hydrographique du lac Imandra est situé dans l'une des régions les plus développées de l'Arctique, soit la presqu'île de Kola, en Russie. Près de 300 000 personnes vivent dans la zone du bassin qui couvre environ 27 000 km², ce qui en fait l'une des régions les plus peuplées de l'Arctique. La plupart des habitants travaillent dans l'extraction et le traitement miniers à grande échelle ainsi que dans l'infrastructure qui soutient cette industrie. Le présent article rapporte les résultats d'un projet pilote mis sur pied pour le bassin du lac Imandra, projet qui a placé la dynamique humaine dans le cadre du changement des écosystèmes, afin d'intégrer l'information disponible et de formuler des modèles conceptuels de scénarios probables dans l'avenir. La période d'observation en est une à la fois de croissance économique et d'expansion démographique rapides, suivie d'un déclin général au cours de la dernière décennie. On a recours à la méthode d'évaluation participative intégrée (EPI) pour intégrer l'information, y dégager des lacunes, générer des scénarios probables dans l'avenir et établir un lien entre résultats de la recherche et processus décisionnel. On a trouvé qu'il y avait une population humaine de plus en plus vulnérable qui était sensibilisée à divers degrés aux problèmes locaux de l'environnement et pleinement consciente des difficultés économiques, population dont une bonne part était fermement décidée à tenter de maintenir à brève échéance des densités de population relativement élevées, alors même que les résidents du nord de la Russie migrent en grand nombre vers le Sud. On a tenu une série d'ateliers avec citoyens et décideurs locaux pour chercher à capter leurs connaissances de la région et à accroître leur sensibilisation aux liens existant entre les composantes socio-économiques et écologiques

Localized States at Zigzag Edges of Multilayer Graphene and Graphite Steps

We report the existence of zero energy surface states localized at zigzag edges of $N$-layer graphene. Working within the tight-binding approximation, and using the simplest nearest-neighbor model, we derive the analytic solution for the wavefunctions of these peculiar surface states. It is shown that zero energy edge states in multilayer graphene can be divided into three families: (i) states living only on a single plane, equivalent to surface states in monolayer graphene; (ii) states with finite amplitude over the two last, or the two first layers of the stack, equivalent to surface states in bilayer graphene; (iii) states with finite amplitude over three consecutive layers. Multilayer graphene edge states are shown to be robust to the inclusion of the next nearest-neighbor interlayer hopping. We generalize the edge state solution to the case of graphite steps with zigzag edges, and show that edge states measured through scanning tunneling microscopy and spectroscopy of graphite steps belong to family (i) or (ii) mentioned above, depending on the way the top layer is cut.Comment: 6 pages, 4 figure

Comparative genomics of Thermus thermophilus and Deinococcus radiodurans: divergent routes of adaptation to thermophily and radiation resistance

BACKGROUND: Thermus thermophilus and Deinococcus radiodurans belong to a distinct bacterial clade but have remarkably different phenotypes. T. thermophilus is a thermophile, which is relatively sensitive to ionizing radiation and desiccation, whereas D. radiodurans is a mesophile, which is highly radiation- and desiccation-resistant. Here we present an in-depth comparison of the genomes of these two related but differently adapted bacteria. RESULTS: By reconstructing the evolution of Thermus and Deinococcus after the divergence from their common ancestor, we demonstrate a high level of post-divergence gene flux in both lineages. Various aspects of the adaptation to high temperature in Thermus can be attributed to horizontal gene transfer from archaea and thermophilic bacteria; many of the horizontally transferred genes are located on the single megaplasmid of Thermus. In addition, the Thermus lineage has lost a set of genes that are still present in Deinococcus and many other mesophilic bacteria but are not common among thermophiles. By contrast, Deinococcus seems to have acquired numerous genes related to stress response systems from various bacteria. A comparison of the distribution of orthologous genes among the four partitions of the Deinococcus genome and the two partitions of the Thermus genome reveals homology between the Thermus megaplasmid (pTT27) and Deinococcus megaplasmid (DR177). CONCLUSION: After the radiation from their common ancestor, the Thermus and Deinococcus lineages have taken divergent paths toward their distinct lifestyles. In addition to extensive gene loss, Thermus seems to have acquired numerous genes from thermophiles, which likely was the decisive contribution to its thermophilic adaptation. By contrast, Deinococcus lost few genes but seems to have acquired many bacterial genes that apparently enhanced its ability to survive different kinds of environmental stresses. Notwithstanding the accumulation of horizontally transferred genes, we also show that the single megaplasmid of Thermus and the DR177 megaplasmid of Deinococcus are homologous and probably were inherited from the common ancestor of these bacteria