New inequalities involving the geometric-arithmetic index

Let G = (V, E) be a simple connected graph and di be the degree of its ith vertex. In a recent paper [J. Math. Chem. 46 (2009) 1369-1376] the first geometricarithmetic index of a graph G was defined as GA1 = X uv∈E 2 √ dudv du + dv . This graph invariant is useful for chemical proposes. The main use of GA1 is for designing so-called quantitative structure-activity relations and quantitative structureproperty relations. In this paper we obtain new inequalities involving the geometricarithmetic index GA1 and characterize the graphs which make the inequalities tight. In particular, we improve some known results, generalize other, and we relate GA1 to other well-known topological indices.We are grateful to the constructive comments from anonymous referee on our pape. The first and third authors are supported by the "Ministerio de Economía y Competititvidad" (MTM2013-46374-P and MTM2015-69323-REDT), Spain, and by the CONACYT (FOMIX-CONACyT-UAGro 249818), Mexico

The energy spectrum of cosmic rays beyond the turn-down around 10^17 eV as measured with the surface detector of the Pierre Auger Observatory

We present a measurement of the cosmic-ray spectrum above 100 PeV using the part of the surface detector of the Pierre Auger Observatory that has a spacing of 750 m. An inflection of the spectrum is observed, confirming the presence of the so-called second-knee feature. The spectrum is then combined with that of the 1500 m array to produce a single measurement of the flux, linking this spectral feature with the three additional breaks at the highest energies. The combined spectrum, with an energy scale set calorimetrically via fluorescence telescopes and using a single detector type, results in the most statistically and systematically precise measurement of spectral breaks yet obtained. These measurements are critical for furthering our understanding of the highest energy cosmic rays

Boundary powerful k-alliances in graphs

A global boundary defensive k-alliance in a graph G = (V, E) is a dominating set S of vertices of G with the property that every vertex in 5 has fc more neighbors in 5 than it has outside of S. A global boundary offensive fc-alliance in a graph G is a set S of vertices of G with the property that every vertex in V - S has fc more neighbors in S than it has outside of S. We define a global boundary powerful fc-alliance as a set 5 of vertices of G, which is both global boundary defensive kalliance and global boundary offensive (k + 2)-alliance. In this paper we study mathematical properties of boundary powerful k-alliances. In particular, we obtain several bounds (closed formulas for the case of regular graphs) on the cardinality of every global boundary powerful k-alliance. In addition, we consider the case in which the vertex set of a graph G can be partitioned' into two boundary powerful fcalliances, showing that, in such a case, k = - 1 and, if G is amp;d-regular, its algebraic connectivity is equal to amp;d +1

Prolegomeni a un\u2019edizione della C\ue1rcel de amor di Diego de San Pedro

There is evidence that in ancient cultures in Mexico copal was probably used for gluing precious stones in teeth cavities and for dental restorations as well. We have investigated potential applications of this material in modern dentistry. In this work we report the presence of preferred orientation of the apatite crystallites in the visible tooth surface and a possible monoclinic symmetry of a crystalline phase in copal from X-ray powder diffraction analysis. Scanning Electron Microscopy shows adhesion of copal to dental tissue by penetrating the dentin tubules in the tooth tissue. Then, copal can be considered seriously as an adhesive to use in dentistry today. © by Oldenbourg Wissenschaftsverlag

Microdureza de la Superlación Nickelvac (n-90) Manufacturada por Pulvimetalúrgica

A través de la técnica de metalurgia de polvos se fabricó la aleación denominada comercialmente como nickelvac (N-90), que se trata de una superaleación hecha principalmente a base de níquel. La aleación fabricada fue sometida primeramente a un proceso de homogenizado a dos temperaturas distintas (1000 y 1065°C durante 2 h) y posteriormente fue envejecida a 350°C durante diferentes tiempos (0.5, 1, 2 y 3 h). De las mediciones de microdureza realizadas en las diferentes muestras, se obtuvo que mayores tiempos de envejecido reflejan mayores valores de dureza. De las observaciones de la microestructura con ayuda de microscopía electrónica de barrido, se pudo determinar la formación de precipitados del tipo NixTiy, siendo estos los causantes de los incrementos en la dureza de la aleación, estos precipitados tienen su origen durante el envejecido de la aleación

Sexually active bucks are able to stimulate three successive groups of females per day with a 4-hour period of contact

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Biodiversity and climate determine the functioning of Neotropical forests

Tropical forests account for a quarter of the global carbon storage and a third of the terrestrial productivity. Few studies have teased apart the relative importance of environmental factors and forest attributes for ecosystem functioning, especially for the tropics. This study aims to relate aboveground biomass (AGB), biomass dynamics (i.e., net biomass productivity and its underlying demographic drivers: biomass recruitment, growth and mortality) to forest attributes (tree diversity, community-mean traits, and stand basal area) and environmental conditions (water availability, soil fertility and disturbance). We used data from 26 sites, 201 one-ha plots and >92,000 trees distributed across the Neotropics. We quantified for each site water availability and soil total exchangeable bases and for each plot three key community-weighted mean functional traits that are important for biomass stocks and productivity. We used structural equation models to test the hypothesis that all drivers have independent, positive effects on biomass stocks and dynamics. Of the relationships analysed, vegetation attributes were more frequently significantly associated with biomass stocks and dynamics than environmental conditions (in 67% versus 33% of the relationships). High climatic water availability increased biomass growth and stocks, light disturbance increased biomass growth, and soil bases had no effect. Rarefied tree species richness had consistent positive relationships with biomass stocks and dynamics, probably because of niche complementarity, but was not related to net biomass productivity. Community-mean traits were good predictors of biomass stocks and dynamics. Water availability has a strong positive effect on biomass stocks and growth, and a future predicted increase in (atmospheric) drought might, therefore, potentially reduce carbon storage. Forest attributes – including species diversity and community-weighted mean traits – have independent and important relationships with AGB stocks, dynamics, and ecosystem functioning, not only in relatively simple temperate systems, but also in structurally complex hyper-diverse tropical forests

The FRAM robotic telescope for atmospheric monitoring at the Pierre Auger Observatory

FRAM (F/Photometric Robotic Atmospheric Monitor) is a robotic telescope operated at the Pierre Auger Observatory in Argentina for the purposes of atmospheric monitoring using stellar photometry. As a passive system which does not produce any light that could interfere with the observations of the fluorescence telescopes of the observatory, it complements the active monitoring systems that use lasers. We discuss the applications of stellar photometry for atmospheric monitoring at optical observatories in general and the particular modes of operation employed by the Auger FRAM. We describe in detail the technical aspects of FRAM, the hardware and software requirements for a successful operation of a robotic telescope for such a purpose and their implementation within the FRAM system