Fine Grained Access Control for Computational Services

Grid environment concerns the sharing of a large set of resources among entities that belong to Virtual Organizations. To this aim, the environment instantiates interactions among entities that belong to distinct administrative domains, that are potentially unknown, and among which no trust relationships exist a priori. For instance, a grid user that provides a computational service, executes unknown applications on its local computational resources on behalf on unknown grid users. In this context, the environment must provide an adequate support to guarantee security in these interactions. To improve the security of the grid environment, this paper proposes to adopt a continuous usage control model to monitor accesses to grid computational services, i.e. to monitor the behaviour of the applications executed on these services on behalf of grid users. This approach requires the definition of a security policy that describes the admitted application behaviour, and the integration in the grid security infrastructure of a component that monitors the application behaviour and that enforces this security policy. This paper also presents the architecture of the prototype of computational service monitor we have developed, along with some performance figures and its integration into the Globus framework

The chain structure of [Ni(C4H2O4)(C12H8N2)(H2O)]n with different types of fumarate bridging

Using modified solvothermal conditions (longer cooling time), beside previously characterized dark-green crystals of [Ni(C4H2O4)(C12H8N2)] (main product), a few light-green crystals of the polymeric title compound, catena-poly[[aqua­(1,10-phenanthroline-κ2 N,N′)nickel(II)]-μ-fumarato-κ2 O:O′-[aqua­(1,10-phenanthroline-κ2 N,N′)nickel(II)]-μ-fumarato-κ4 O,O′:O′′,O′′′], [Ni(C4H2O4)(C12H8N2)(H2O)]n were isolated. Its crystal structure is made up from zigzag chains, propagating in [001], in which the Ni2+ ions are linked alternatively by μ2-fumarato and bis-chelating fumarato bridging ligands. The Ni2+ ion is coordinated in a deformed octa­hedral geometry by one chelating 1,10-phenanthroline ligand, one aqua ligand in a cis position with regard to both N-donor atoms and by two different fumarato ligands, each residing with its central C=C bond on an inversion centre, occupying the remaining coordination sites in a fac fashion. The chains thus formed are linked by O—H⋯O hydrogen bonds and π–π inter­actions between the aromatic rings of the phenanthroline ligands with a shortest ring centroid separation of 3.4787 (10) Å

A Plant Germline-Specific Integrator of Sperm Specification and Cell Cycle Progression

The unique double fertilisation mechanism in flowering plants depends upon a pair of functional sperm cells. During male gametogenesis, each haploid microspore undergoes an asymmetric division to produce a large, non-germline vegetative cell and a single germ cell that divides once to produce the sperm cell pair. Despite the importance of sperm cells in plant reproduction, relatively little is known about the molecular mechanisms controlling germ cell proliferation and specification. Here, we investigate the role of the Arabidopsis male germline-specific Myb protein DUO POLLEN1, DUO1, as a positive regulator of male germline development. We show that DUO1 is required for correct male germ cell differentiation including the expression of key genes required for fertilisation. DUO1 is also necessary for male germ cell division, and we show that DUO1 is required for the germline expression of the G2/M regulator AtCycB1;1 and that AtCycB1:1 can partially rescue defective germ cell division in duo1. We further show that the male germline-restricted expression of DUO1 depends upon positive promoter elements and not upon a proposed repressor binding site. Thus, DUO1 is a key regulator in the production of functional sperm cells in flowering plants that has a novel integrative role linking gametic cell specification and cell cycle progression

catena-Poly[[[diaqua­(di-2-pyridylamine-κ2 N,N′)nickel(II)]-μ-fumarato-κ2 O 1:O 4] tetra­hydrate]

In the crystal structure of the title compound, {[Ni(C4H2O4)(C10H9N3)(H2O)2]·4H2O}n, zigzag chains are built up from cis-[Ni(dpya)(H2O)2]2+ cations (dpya is di-2-pyridylamine) linked by bis-monodentate coordinated bridging fumarate ligands. The NiII atom is coordinated by one chelating dpya ligand, two aqua ligands in trans positions and two monodentate fumarate ligands in cis positions in the form of a deformed octa­hedron. The water mol­ecules, O atoms of the fumarate carboxyl­ate groups and the amine group of the dpya ligand are involved in an extended network of intra- and inter­molecular O—H⋯O hydrogen bonds. Moreover, π–π inter­actions between the pyridine rings of the dpya ligand contribute to the stability of the structure. Two of the five uncoordinated water molecules are half-occupied