Invariant Forms and Automorphisms of Locally Homogeneous Multisymplectic Manifolds

It is shown that the geometry of locally homogeneous multisymplectic manifolds (that is, smooth manifolds equipped with a closed nondegenerate form of degree > 1, which is locally homogeneous of degree k with respect to a local Euler field) is characterized by their automorphisms. Thus, locally homogeneous multisymplectic manifolds extend the family of classical geometries possessing a similar property: symplectic, volume and contact. The proof of the first result relies on the characterization of invariant differential forms with respect to the graded Lie algebra of infinitesimal automorphisms, and on the study of the local properties of Hamiltonian vector fields on locally multisymplectic manifolds. In particular it is proved that the group of multisymplectic diffeomorphisms acts (strongly locally) transitively on the manifold. It is also shown that the graded Lie algebra of infinitesimal automorphisms of a locally homogeneous multisymplectic manifold characterizes their multisymplectic diffeomorphisms.Comment: 25 p.; LaTeX file. The paper has been partially rewritten. Some terminology has been changed. The proof of some theorems and lemmas have been revised. The title and the abstract are slightly modified. An appendix is added. The bibliography is update

Involvement of the genicular branches in cystic adventitial disease of the popliteal artery as a possible marker of unfavourable early clinical outcome: a case report

<p>Abstract</p> <p>Introduction</p> <p>Cystic adventitial disease of the popliteal artery is a rare cause of non-atheromatous claudication. It usually requires surgery to improve the distance walked by patients.</p> <p>Case presentation</p> <p>We report the case of a 44-year-old Caucasian man with unilateral symptomatic popliteal cysts extending to his genicular branches and associated with multilevel stenosis of his anterior tibial artery. A surgical evacuation of the cysts successfully restored his arterial patency and led to an objective haemodynamic improvement but was associated with early recurrence of symptoms.</p> <p>Conclusion</p> <p>We suggest that the involvement of the genicular branches in cystic adventitial disease of the popliteal artery is a possible indicator of extensive adventitial degeneration and unfavourable clinical prognosis.</p

Performance of Indian Manufacturing in the Post Reform Period

Many emerging countries in recent decades have relied on a development strategy that focused primarily on promoting the manufacturing sector and the exports of manufactured goods. However, an acceleration of growth of output and employment in manufacturing has eluded India. This is despite the fact that the central focus of the reforms in the 1980s and 1990s was to unshackle the manufacturing sector. Instead it is the services sector which has grown rapidly, contributing about two-third of GDP growth in recent years. This paper discusses the reasons behind the modest performance of the manufacturing sector in India post reforms. It argues that there are many factors that have inhibited the growth of industrial sector in India. One major factor is the rigid and strict labor laws which have affected the industrial performance in a number of ways, by keeping the size of the establishments small, by not encouraging the production of labor intensive goods, by pushing activities to the unorganized sector, and by keeping the Indian industry uncompetitive. Besides the labor laws other factors that are responsible for the modest performance of the manufacturing sector include difficulty in the acquisition of land for industrial use, inadequate financing and infrastructure, and cumbersome business climate. The paper presents arguments and evidence which shows the importance of these factors

CO Adsorption on Supported Gold Nanoparticle Catalysts: Application of the Temkin Model

The adsorption of CO on the supported gold nanoparticle catalysts Au/TiO2, Au/Fe2O3, and Au/ZrO2 was examined using infrared transmission spectroscopy to quantify the isobaric CO coverage as a function of temperature. The Temkin adsorbate interaction model was then applied to account for the adsorption behavior. To test the general applicability of the Temkin model, this treatment was also applied to three data sets from the literature. This included another real-world catalyst and two model catalysts. All data sets were accurately represented by the Temkin adsorbate interaction model. The resulting thermodynamic metrics are consistent with previous determinations and reflect a particle size-dependence. In particular, the intrinsic adsorption enthalpy at zero CO coverage varies almost linearly with Au particle size, and this trend appears to be correlated with the abundance of low-coordinate Au sites (cf., CN = 6 and 7 for corners and edges, respectively). For very small particles with mostly CN = 6 corner sites, the enthalpy reflects strong binding (cf., −ΔH0 ≈ 78 kJ/mol), while for large particles with mostly CN = 7 edge sites, the enthalpy reflects weaker binding (cf., −ΔH0 ≈ 63 kJ/mol). The results also suggest that these sites are coupled. This study demonstrates that the Temkin adsorbate interaction model accurately represents adsorption data, yields meaningful metrics that are useful for characterizing nanoparticle catalysts, and should be applicable to other adsorption data sets

Avoiding Dangerous Missense: Thermophiles Display Especially Low Mutation Rates

Rates of spontaneous mutation have been estimated under optimal growth conditions for a variety of DNA-based microbes, including viruses, bacteria, and eukaryotes. When expressed as genomic mutation rates, most of the values were in the vicinity of 0.003–0.004 with a range of less than two-fold. Because the genome sizes varied by roughly 104-fold, the mutation rates per average base pair varied inversely by a similar factor. Even though the commonality of the observed genomic rates remains unexplained, it implies that mutation rates in unstressed microbes reach values that can be finely tuned by evolution. An insight originating in the 1920s and maturing in the 1960s proposed that the genomic mutation rate would reflect a balance between the deleterious effect of the average mutation and the cost of further reducing the mutation rate. If this view is correct, then increasing the deleterious impact of the average mutation should be countered by reducing the genomic mutation rate. It is a common observation that many neutral or nearly neutral mutations become strongly deleterious at higher temperatures, in which case they are called temperature-sensitive mutations. Recently, the kinds and rates of spontaneous mutations were described for two microbial thermophiles, a bacterium and an archaeon. Using an updated method to extrapolate from mutation-reporter genes to whole genomes reveals that the rate of base substitutions is substantially lower in these two thermophiles than in mesophiles. This result provides the first experimental support for the concept of an evolved balance between the total genomic impact of mutations and the cost of further reducing the basal mutation rate

Mismatch Repair–Independent Increase in Spontaneous Mutagenesis in Yeast Lacking Non-Essential Subunits of DNA Polymerase ε

Yeast DNA polymerase ε (Pol ε) is a highly accurate and processive enzyme that participates in nuclear DNA replication of the leading strand template. In addition to a large subunit (Pol2) harboring the polymerase and proofreading exonuclease active sites, Pol ε also has one essential subunit (Dpb2) and two smaller, non-essential subunits (Dpb3 and Dpb4) whose functions are not fully understood. To probe the functions of Dpb3 and Dpb4, here we investigate the consequences of their absence on the biochemical properties of Pol ε in vitro and on genome stability in vivo. The fidelity of DNA synthesis in vitro by purified Pol2/Dpb2, i.e. lacking Dpb3 and Dpb4, is comparable to the four-subunit Pol ε holoenzyme. Nonetheless, deletion of DPB3 and DPB4 elevates spontaneous frameshift and base substitution rates in vivo, to the same extent as the loss of Pol ε proofreading activity in a pol2-4 strain. In contrast to pol2-4, however, the dpb3Δdpb4Δ does not lead to a synergistic increase of mutation rates with defects in DNA mismatch repair. The increased mutation rate in dpb3Δdpb4Δ strains is partly dependent on REV3, as well as the proofreading capacity of Pol δ. Finally, biochemical studies demonstrate that the absence of Dpb3 and Dpb4 destabilizes the interaction between Pol ε and the template DNA during processive DNA synthesis and during processive 3′ to 5′exonucleolytic degradation of DNA. Collectively, these data suggest a model wherein Dpb3 and Dpb4 do not directly influence replication fidelity per se, but rather contribute to normal replication fork progression. In their absence, a defective replisome may more frequently leave gaps on the leading strand that are eventually filled by Pol ζ or Pol δ, in a post-replication process that generates errors not corrected by the DNA mismatch repair system

Replication and Recombination Factors Contributing to Recombination-Dependent Bypass of DNA Lesions by Template Switch

Damage tolerance mechanisms mediating damage-bypass and gap-filling are crucial for genome integrity. A major damage tolerance pathway involves recombination and is referred to as template switch. Template switch intermediates were visualized by 2D gel electrophoresis in the proximity of replication forks as X-shaped structures involving sister chromatid junctions. The homologous recombination factor Rad51 is required for the formation/stabilization of these intermediates, but its mode of action remains to be investigated. By using a combination of genetic and physical approaches, we show that the homologous recombination factors Rad55 and Rad57, but not Rad59, are required for the formation of template switch intermediates. The replication-proficient but recombination-defective rfa1-t11 mutant is normal in triggering a checkpoint response following DNA damage but is impaired in X-structure formation. The Exo1 nuclease also has stimulatory roles in this process. The checkpoint kinase, Rad53, is required for X-molecule formation and phosphorylates Rad55 robustly in response to DNA damage. Although Rad55 phosphorylation is thought to activate recombinational repair under conditions of genotoxic stress, we find that Rad55 phosphomutants do not affect the efficiency of X-molecule formation. We also examined the DNA polymerase implicated in the DNA synthesis step of template switch. Deficiencies in translesion synthesis polymerases do not affect X-molecule formation, whereas DNA polymerase δ, required also for bulk DNA synthesis, plays an important role. Our data indicate that a subset of homologous recombination factors, together with DNA polymerase δ, promote the formation of template switch intermediates that are then preferentially dissolved by the action of the Sgs1 helicase in association with the Top3 topoisomerase rather than resolved by Holliday Junction nucleases. Our results allow us to propose the choreography through which different players contribute to template switch in response to DNA damage and to distinguish this process from other recombination-mediated processes promoting DNA repair