Neutrino masses and mixing parameters in a left-right model with mirror fermions

In this work we consider a left-right model containing mirror fermions with gauge group SU(3)$_{C} \otimes SU(2)_{L} \otimes SU(2)_{R} \otimes U(1)_{Y^\prime}$. The model has several free parameters which here we have calculated by using the recent values for the squared-neutrino mass differences. Lower bound for the mirror vacuum expectation value helped us to obtain crude estimations for some of these parameters. Also we estimate the order of magnitude of the masses of the standard and mirror neutrinos.Comment: 13 pages, version submitted to European Physical Journal

New Higgs signals induced by mirror fermion mixing effects

We study the conditions under which flavor violation arises in scalar-fermion interactions, as a result of the mixing phenomena between the standard model and exotic fermions. Phenomenological consequences are discussed within the specific context of a left-right model where these additional fermions have mirror properties under the new SU(2)_R gauge group. Bounds on the parameters of the model are obtained from LFV processes; these results are then used to study the LFV Higgs decays (H --> tau l_j, l_j = e, mu), which reach branching ratios that could be detected at future colliders.Comment: 12 pages, 2 figures, ReVTex4, graphicx, to be published in Phys. Rev.

Lepton mass generation and family number violation mechanism in the SU(6)⊗U(1)SU(6)\otimes U(1) model

Lepton family number violation processes arise in the $SU(6)_L \otimes U(1)_Y$ model due to the presence of an extra neutral gauge boson, Z$'$, with family changing couplings, and due to the fact that this model demands the existence of heavy exotic leptons. The mixing of the standard Z with Z$'$ and the mixing of ordinary leptons with exotic ones induce together family changing couplings on the Z and therefore nonvanishing rates for lepton family number violation processes, such as $Z \to e \bar{\mu}$, $\mu \to ee\bar{e}$ and $\mu \to e\gamma$. Additional contributions to the processes $\mu \to e \gamma$ and $\mu \to ee \bar{e}$ are induced from the mass generation mechanism. This last type of contributions may compete with the above one, depending on the masses of the scalars which participate in the diagrams which generate radiatively the masses of the charged leptons. Using the experimental data we compute some bounds for the mixings parameters and for the masses of the scalars.Comment: 12 pages, Latex, 7 figures. Accepted for publication in Int. Journ. of Mod. Phys.

Estadísticas e Indicadores de la Universidad Nacional de Colombia 2002

Presentación Capitulo 1. Temas de debate: Bases para una política académica de la Universidad Nacional de Colombia Capitulo 2. Construcción de visibilidad: cifras y análisis Capitulo 2.1A. Filosofía, organización y resultados del programa Universidad Virtual de la Universidad Nacional de Colombia Capitulo 2.1B. Filosofía, organización y resultados del programa Universidad Virtual de la Universidad Nacional de Colombia Capitulo 2.1C. Filosofía, organización y resultados del programa Universidad Virtual de la Universidad Nacional de Colombia Capitulo 2.2A. La evaluación de la extensión universitaria y la construcción de pertinencia social de la universidad Capitulo 2.2B. La evaluación de la extensión universitaria y la construcción de pertinencia social de la universidad Capitulo 3. Contextos Capitulo 3.1A. Internacionalizar la Universidad Nacional de Colombia Capitulo 3.2A. Equidad en el acceso a la Universidad Nacional de Colombia: programas de admisión especial Capitulo 3.2B. Equidad en el acceso a la Universidad Nacional de Colombia: programas de admisión especial Capitulo 4.A. Indicadores de Gestión: los indicadores de la línea objetivo Capitulo 4.B. Indicadores de Gestión: los indicadores de la línea objetivo Capitulo 4.C. Indicadores de Gestión: los indicadores de la línea objetivo Capitulo 4.D. Indicadores de Gestión: los indicadores de la línea objetivo Capitulo 5. Información estadística Capitulo 5.A. Indicadores básicos Capitulo 5.B. Estadísticas de Inscritos y admitidos Capitulo 5.C. Estadísticas de estudiantes matriculados Capitulo 5.D. Estadísticas de estudiantes graduados Capitulo 5.E. Estadísticas de programas curriculares Capitulo 5.F. Estadísticas de talento human

Surface indicators are correlated with soil multifunctionality in global drylands

Multiple ecosystem functions need to be considered simultaneously to manage and protect the several ecosystem services that are essential to people and their environments. Despite this, cost effective, tangible, relatively simple and globally relevant methodologies to monitor in situ soil multifunctionality, that is, the provision of multiple ecosystem functions by soils, have not been tested at the global scale. We combined correlation analysis and structural equation modelling to explore whether we could find easily measured, field-based indicators of soil multifunctionality (measured using functions linked to the cycling and storage of soil carbon, nitrogen and phosphorus). To do this, we gathered soil data from 120 dryland ecosystems from five continents. Two soil surface attributes measured in situ (litter incorporation and surface aggregate stability) were the most strongly associated with soil multifunctionality, even after accounting for geographic location and other drivers such as climate, woody cover, soil pH and soil electric conductivity. The positive relationships between surface stability and litter incorporation on soil multifunctionality were greater beneath the canopy of perennial vegetation than in adjacent, open areas devoid of vascular plants. The positive associations between surface aggregate stability and soil functions increased with increasing mean annual temperature. Synthesis and applications. Our findings demonstrate that a reduced suite of easily measured in situ soil surface attributes can be used as potential indicators of soil multifunctionality in drylands world-wide. These attributes, which relate to plant litter (origin, incorporation, cover), and surface stability, are relatively cheap and easy to assess with minimal training, allowing operators to sample many sites across widely varying climatic areas and soil types. The correlations of these variables are comparable to the influence of climate or soil, and would allow cost-effective monitoring of soil multifunctionality under changing land-use and environmental conditions. This would provide important information for evaluating the ecological impacts of land degradation, desertification and climate change in drylands world-wide.Fil: Eldridge, David J.. University of New South Wales; AustraliaFil: Delgado Baquerizo, Manuel. Universidad Rey Juan Carlos; EspañaFil: Quero, José L.. Universidad de Córdoba; EspañaFil: Ochoa, Victoria. Universidad Rey Juan Carlos; España. Universidad de Alicante; EspañaFil: Gozalo, Beatriz. Universidad Rey Juan Carlos; España. Universidad de Alicante; EspañaFil: García Palacios, Pablo. Universidad Rey Juan Carlos; EspañaFil: Escolar, Cristina. Universidad Rey Juan Carlos; EspañaFil: García Gómez, Miguel. Universidad Politécnica de Madrid; EspañaFil: Prina, Aníbal. Universidad Nacional de La Pampa; ArgentinaFil: Bowker, Mathew A.. Northern Arizona University; Estados UnidosFil: Bran, Donaldo Eduardo. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Patagonia Norte. Estación Experimental Agropecuaria San Carlos de Bariloche; ArgentinaFil: Castro, Ignacio. Universidad Experimental Simón Rodríguez; VenezuelaFil: Cea, Alex. Universidad de La Serena; ChileFil: Derak, Mchich. No especifíca;Fil: Espinosa, Carlos I.. Universidad Técnica Particular de Loja; EcuadorFil: Florentino, Adriana. Universidad Central de Venezuela; VenezuelaFil: Gaitán, Juan José. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación de Recursos Naturales. Instituto de Suelos; Argentina. Universidad Nacional de Luján. Departamento de Tecnología; ArgentinaFil: Gatica, Mario Gabriel. Universidad Nacional de San Juan. Facultad de Ciencias Exactas Físicas y Naturales. Departamento de Biología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Centro de Investigaciones de la Geosfera y Biosfera. Universidad Nacional de San Juan. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones de la Geosfera y Biosfera; ArgentinaFil: Gómez González, Susana. Universidad de Cádiz; EspañaFil: Ghiloufi, Wahida. Université de Sfax; TúnezFil: Gutierrez, Julio R.. Universidad de La Serena; ChileFil: Guzman, Elizabeth. Universidad Técnica Particular de Loja; EcuadorFil: Hernández, Rosa M.. Universidad Experimental Simón Rodríguez; VenezuelaFil: Hughes, Frederic M.. Universidade Estadual de Feira de Santana; BrasilFil: Muiño, Walter. Universidad Nacional de La Pampa; ArgentinaFil: Monerris, Jorge. No especifíca;Fil: Ospina, Abelardo. Universidad Central de Venezuela; VenezuelaFil: Ramírez, David A.. International Potato Centre; PerúFil: Ribas Fernandez, Yanina Antonia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Centro de Investigaciones de la Geosfera y Biosfera. Universidad Nacional de San Juan. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones de la Geosfera y Biosfera; ArgentinaFil: Romão, Roberto L.. Universidade Estadual de Feira de Santana; BrasilFil: Torres Díaz, Cristian. Universidad del Bio Bio; ChileFil: Koen, Terrance B.. No especifíca;Fil: Maestre, Fernando T.. Universidad Rey Juan Carlos; España. Universidad de Alicante; Españ

Soil fungal abundance and plant functional traits drive fertile island formation in global drylands

International audience1.Dryland vegetation is characterised by discrete plant patches that accumulate and capture soil resources under their canopies. These “fertile islands” are major drivers of dryland ecosystem structure and functioning, yet we lack an integrated understanding of the factors controlling their magnitude and variability at the global scale.2.We conducted a standardized field survey across two hundred and thirty-six drylands from five continents. At each site, we measured the composition, diversity and cover of perennial plants. Fertile island effects were estimated at each site by comparing composite soil samples obtained under the canopy of the dominant plants and in open areas devoid of perennial vegetation. For each sample, we measured fifteen soil variables (functions) associated with carbon, nitrogen and phosphorus cycling and used the Relative Interaction Index to quantify the magnitude of the fertile island effect for each function. In eighty sites, we also measured fungal and bacterial abundance (quantitative PCR) and diversity (Illumina MiSeq).3.The most fertile islands, i.e. those where a higher number of functions were simultaneously enhanced, were found at lower-elevation sites with greater soil pH values and sand content under semiarid climates, particularly at locations where the presence of tall woody species with a low specific leaf area increased fungal abundance beneath plant canopies, the main direct biotic controller of the fertile island effect in the drylands studied. Positive effects of fungal abundance were particularly associated with greater nutrient contents and microbial activity (soil extracellular enzymes) under plant canopies.4.Synthesis. Our results show that the formation of fertile islands in global drylands largely depends on: (i) local climatic, topographic and edaphic characteristics, (ii) the structure and traits of local plant communities and (iii) soil microbial communities. Our study also has broad implications for the management and restoration of dryland ecosystems worldwide, where woody plants are commonly used as nurse plants to enhance the establishment and survival of beneficiary species. Finally, our results suggest that forecasted increases in aridity may enhance the formation of fertile islands in drylands worldwide

Decoupling of soil nutrient cycles as a function of aridity in global drylands

18 páginas.- 10 figuras.- 72 referencias.- Online Content Any additional Methods, Extended Data display items and Source Data are available in the online version of the paper; references unique to these sections appear only in the online paper..- Puede conseguir el texto completo en el Portal de la producción científica de la Universidad Complutense de Madrid https://produccioncientifica.ucm.es/documentos/5ec78dc52999520a1d557660 .- o en lel respositorio institucional CONICET digital https://ri.conicet.gov.ar/bitstream/handle/11336/29204/CONICET_Digital_Nro.ead4e2ed-0da6-4041-814b-259e8f27bbf6_D.pdf?sequence=5&isAllowed=yThe biogeochemical cycles of carbon (C), nitrogen (N) and phosphorus (P) are interlinked by primary production, respiration and decomposition in terrestrial ecosystems1. It has been suggested that the C, N and P cycles could become uncoupled under rapid climate change because of the different degrees of control exerted on the supply of these elements by biological and geochemical processes1,2,3,4,5. Climatic controls on biogeochemical cycles are particularly relevant in arid, semi-arid and dry sub-humid ecosystems (drylands) because their biological activity is mainly driven by water availability6,7,8. The increase in aridity predicted for the twenty-first century in many drylands worldwide9,10,11 may therefore threaten the balance between these cycles, differentially affecting the availability of essential nutrients12,13,14. Here we evaluate how aridity affects the balance between C, N and P in soils collected from 224 dryland sites from all continents except Antarctica. We find a negative effect of aridity on the concentration of soil organic C and total N, but a positive effect on the concentration of inorganic P. Aridity is negatively related to plant cover, which may favour the dominance of physical processes such as rock weathering, a major source of P to ecosystems, over biological processes that provide more C and N, such as litter decomposition12,13,14. Our findings suggest that any predicted increase in aridity with climate change will probably reduce the concentrations of N and C in global drylands, but increase that of P. These changes would uncouple the C, N and P cycles in drylands and could negatively affect the provision of key services provided by these ecosystems.This research is supported by the European Research Council (ERC) under the European Community's Seventh Framework Programme (FP7/2007-2013)/ERC Grant agreement no. 242658 (BIOCOM), and by the Ministry of Science and Innovation of the Spanish Government, grant no. CGL2010-21381. CYTED funded networking activities (EPES, Acción 407AC0323). M.D.-B. was supported by a PhD fellowship from the Pablo de Olavide University.Peer reviewe

Unforeseen plant phenotypic diversity in a dry and grazed world

23 páginas..- 4 figuras y 7 figuras.- 50 referencias y 90 referenciasEarth harbours an extraordinary plant phenotypic diversity1 that is at risk from ongoing global changes2,3. However, it remains unknown how increasing aridity and livestock grazing pressure—two major drivers of global change4,5,6—shape the trait covariation that underlies plant phenotypic diversity1,7. Here we assessed how covariation among 20 chemical and morphological traits responds to aridity and grazing pressure within global drylands. Our analysis involved 133,769 trait measurements spanning 1,347 observations of 301 perennial plant species surveyed across 326 plots from 6 continents. Crossing an aridity threshold of approximately 0.7 (close to the transition between semi-arid and arid zones) led to an unexpected 88% increase in trait diversity. This threshold appeared in the presence of grazers, and moved toward lower aridity levels with increasing grazing pressure. Moreover, 57% of observed trait diversity occurred only in the most arid and grazed drylands, highlighting the phenotypic uniqueness of these extreme environments. Our work indicates that drylands act as a global reservoir of plant phenotypic diversity and challenge the pervasive view that harsh environmental conditions reduce plant trait diversity8,9,10. They also highlight that many alternative strategies may enable plants to cope with increases in environmental stress induced by climate change and land-use intensification.This research was funded by the European Research Council (ERC Grant agreement 647038 1004 [BIODESERT]) and Generalitat Valenciana (CIDEGENT/2018/041). N.G. was supported by CAP 20–25 (16-IDEX-0001) and the AgreenSkills+ fellowship programme which has received funding from the European Union’s Seventh Framework Programme under grant agreement FP7-609398 (AgreenSkills+ contract). F.T.M. acknowledges support from the King Abdullah University of Science and Technology (KAUST), the KAUST Climate and Livability Initiative, the University of Alicante (UADIF22-74 and VIGROB22-350), the Spanish Ministry of Science and Innovation (PID2020-116578RB-I00), and the Synthesis Center (sDiv) of the German Centre for Integrative Biodiversity Research Halle–Jena–Leipzig (iDiv). Y.L.B.-P. was supported by a Marie Sklodowska-Curie Actions Individual Fellowship (MSCA-1018 IF) within the European Program Horizon 2020 (DRYFUN Project 656035). H.S. is supported by a María Zambrano fellowship funded by the Ministry of Universities and European Union-Next Generation plan. L.W. acknowledges support from the US National Science Foundation (EAR 1554894). G.M.W. acknowledges support from the Australian Research Council (DP210102593) and TERN. M.B is supported by a Ramón y Cajal grant from Spanish Ministry of Science (RYC2021-031797-I). L.v.d.B. and K.T. were supported by the German Research Foundation (DFG) Priority Program SPP-1803 (TI388/14-1). A.F. acknowledges the financial support from ANID PIA/BASAL FB210006 and Millenium Science Initiative Program NCN2021-050. A.J. was supported by the Bavarian Research Alliance for travel and field work (BayIntAn UBT 2017 61). A.L. and L.K. acknowledge support from the German Research Foundation, DFG (grant CRC TRR228) and German Federal Government for Science and Education, BMBF (grants 01LL1802C and 01LC1821A). B.B. and S.U. were supported by the Taylor Family-Asia Foundation Endowed Chair in Ecology and Conservation Biology. P.J.R. and A.J.M. acknowledge support from Fondo Europeo de Desarrollo Regional through the FEDER Andalucía operative programme, FEDER-UJA 1261180 project. E.M.-J. and C.P. acknowledge support from the Spanish Ministry of Science and Innovation (PID2020-116578RB-I00). D.J.E. was supported by the Hermon Slade Foundation. J.D. and A.Rodríguez acknowledge support from the FCT (2020.03670.CEECIND and SFRH/BDP/108913/2015, respectively), as well as from the MCTES, FSE, UE and the CFE (UIDB/04004/2021) research unit financed by FCT/MCTES through national funds (PIDDAC). S.C.R. acknowledges support from the US Department of Energy (DE-SC-0008168), US Department of Defense (RC18-1322), and the US Geological Survey Ecosystems Mission Area. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the US government. E.H.-S. acknowledges support from Mexican National Science and Technology Council (CONACYT PN 5036 and 319059). A.N. and C. Branquinho. acknowledge the support from FCT—Fundação para a Ciência e a Tecnologia (CEECIND/02453/2018/CP1534/CT0001, PTDC/ASP-SIL/7743/ 2020, UIDB/00329/2020), from AdaptForGrazing project (PRR-C05-i03-I-000035) and from LTsER Montado platform (LTER_EU_PT_001). Field work of G.P. and J.M.Z. was supported by UNRN (PI 40-C-873).Peer reviewe