The 1D Hubbard model within the Composite Operator Method

Although effective for two dimensional (2D) systems, some approximations may fail in describing the properties of one-dimensional (1D) models, which belong to a different universality class. In this paper, we analyze the adequacy of the Composite Operator Method (COM), which provides a good description of many features of 2D strongly correlated systems, in grasping the physics of 1D models. To this purpose, the 1D Hubbard model is studied within the framework of the COM by considering a two-pole approximation and a paramagnetic ground state. The local, thermodynamic and single-particle properties, the correlation functions and susceptibilities are calculated in the case of half filling and arbitrary filling. The results are compared with those obtained by the Bethe Ansatz (BA) as well as by other numerical and analytical techniques. The advantages and limitations of the method are analyzed in detail.Comment: 19 RevTeX pages, 41 embedded eps figure

Merger as a Formula to Establish European Cooperative Societies

Council Regulation (EC) No 1.435/2003, of 22 July 2003, concerning the European Co-operative Statute (ECS), constitutes the legal basis for the creation of european cooperatives, facilitating the development of their cross-border activities and contributing to their economic development. So, the aim of this regulation is to enable the creation of European cooperatives by physical persons or legal entities resident or established under the laws of different Member States, but it also makes possible the establishment of European cooperatives by merger or transformation of existing cooperatives from different Member States. The aim of this paper is to show the specific features of formation of crossborder cooperatives by merger, covered by the ECS, with special attention to those aspects that distance them from the internal formation by merger, within the Spanish legal framework. For the purpose of comparison, Spain will be considered as regards the regulations governing mergers, depending on whether the ECS or the Spanish Cooperative Law is taken into consideration.Statute for a European Cooperative Society, Spanish cooperative regulation, cooperative mergers, crossborder activity, Agribusiness,

Análisis de la ampliación de los recursos locales hortofrutícolas mediante la internacionalización: Potencial del sector cooperativo hortofrutícola

El presente trabajo analiza la posibilidad de ampliar los recursos locales de las cooperativas hortofrutícolas mediante la internacionalización de su actividad. Para ello se examinan las estrategias de internacionalización disponibles para estas entidades y se analiza el potencial del sector hortofrutícola, mediante el estudio de los datos básicos del sector comparando entidades asociativas con las no cooperativas. Dichos datos nos permiten evaluar su potencial exportador, resultando mucho mayor en las cooperativas hortofrutícolas. Sin embargo la internacionalización se manifiesta principalmente a través de la exportación mediante acuerdos comerciales, y en menor medida, mediante la constitución de sociedades mercantiles participadas por la cooperativa, por lo que no redunda en incrementos de la intercooperación a nivel internacional, mientras sí que existen a nivel nacional. Por tanto, las conclusiones alcanzadas destacan un elevado grado de internacionalización de las cooperativas hortofrutícolas frente al sector no cooperativo y con respecto a otros sectores agroalimentarios.Cooperativas hortofrutícolas, internacionalizacion, potencial exportador., Agribusiness, Agricultural and Food Policy, Community/Rural/Urban Development, Labor and Human Capital,

V, R, I and Halpha photometry of circumnuclear star forming regions in four galaxies with different levels of nuclear activity

V,R,I continuum bands and Halpha + [NII] photometry for circumnuclear star forming regions (CNSFR) is presented, for galaxies with different kinds of nuclear activity: NGC 7469 (Sy 1), NGC 1068 (Sy 2), NGC 7177 (LINER) and NGC 3310 (Starburst). Their Halpha luminosities (0.02 - 7x10**40 erg/s; uncorrected for internal extinction), are comparable to those observed in other galaxies. No systematic differences in the broad band colours are found for the CNSFR in the different galaxies, except for those in NGC 3310 which are considerably bluer, partially due to a younger stellar population. Using theoretical evolutionary synthesis models some colours can be reproduced by single populations (between 7 and 300 Myr) and extinction 0.5-1.5 mag). However, in many cases, the observed equivalent width of Halpha, require a younger population. NGC 1068, 7177 and 7469, are fitted by a two-burst population model at solar metallicity; the age difference between both populations is around 5-7 Myr and the younger burst involves 3 - 61% of the total mass of the cluster,consistent with the younger burst being originated by supernova activity from the previous one. NGC 3310, requires younger ionizing population ages and lower metallicity. An excess (R-I) observed/predicted, not consistent with a normal reddening law can be atributted to red supergiants present in the older population, and not properly accounted for by the models. The two-population scenario seems to show a trend of the evolutionary state of the CNSFR with the nuclear type of the parent galaxy that remains to be explored.Comment: Accepted for publication in MNRAS, 22pages, 11 figure

Valorization of Posidonia oceanica biomass: Role on germination of cucumber and tomato seeds

Biostimulants are organic compounds from plant sources such as botanical extracts and bioactive substances that promote plant growth, enhance photosynthesis and increase crop quality. The accumulation of detached Posidonia oceanica leaves on coasts of the Mediterranean Sea results in economic problems, due to the rejection of the tourists who frequent the beaches in the summer months. However, it is a plant with high content of secondary metabolites that can be used in sustainable agriculture. In this study we investigated the physicochemical characterization of Posidonia oceanica extracts with three different solutions and their application in tomato and cucumber seeds germination. The results showed that the aqueous extract of Posidonia oceanica had a high concentration of macro and micronutrients, as well as secondary metabolites with bioactive activity. The aqueous extract had a beneficial effect on both leaf and root growth on tomato seeds, specifically, an increase of 76% for the relative root growth and 73% for the germination index was obtained with respect to the control using the sample with the intermediate dilution (POe0.5). In addition, the extracts did not show toxicity to either germination or growth of the tomato plant. As for cucumber seed germination, the improvement was less significant and did result in a phytotoxic effect on both germination and plant growth. The most diluted extract had better results on seed germination. Therefore, the application of aqueous extracts of Posidonia oceanica were suitable to be appropriate for tomato germination and in turn contribute to eliminate the lots of Posidonia oceanica remains recovered in summer months in Mediterranean beaches.This study was funded by Ministerio de Economía y Competitividad Spain (CGL2016-79054-R)

Enhancing Salt Stress Tolerance in Tomato (Solanum lycopersicum L.) through Silicon Application in Roots

Soil salinization poses a significant threat to agricultural productivity, necessitating innovative agronomic strategies to mitigate its impact. This study focuses on improving salt stress resistance in tomato plants through the application of silicon (Si) in roots. A greenhouse experiment was carried out under normal conditions (control, and 1 and 4 mM Si) and under salinity stress (salt control, and 1 and 4 mM Si). Various parameters were analyzed in leaves and roots. Under normal conditions, tomato plants grown in non-saline conditions exhibited some toxicity when exposed to Na2SiO3. As for the experiments under salt stress conditions, Si mitigated oxidative damage, preserving root cell membrane integrity. The concentration of malondialdehyde was reduced by 69.5%, that of proline was reduced by 56.4% and there was a 57.6% decrease in catalase activity for tomato plants treated with 1 mM Si under salt stress. Furthermore, Fe uptake and distribution, under salt conditions, increased from 91 to 123 mg kg−1, the same concentration as that obtained for the normal control. In all cases, the lower dose produced better results under normal conditions than the 4 mM dose. In summary, this research provides a potential application of Si in non-fertigated crop systems through a radicular pathway

Characterization of soil mineralogy by FTIR: application to the analysis of mineralogical changes in soils affected by vegetation patches

Aims The objective of this paper was to develop a method based on infrared spectroscopy to compare mineral content in soils and apply it to evaluate soil mineralogical variations in pairs of inter-patch and patch soils in a semi-arid area. Methods Mixtures of several minerals were analyzed by infrared spectroscopy, the second derivative of the spectra was calculated and the spectra normalized respect to calcite or quartz signals (711 cm−1 or 800 cm−1 respectively). The intensities of representative signals of each mineral were related to their concentration in the mixtures. Pairs of patch and inter-patch soils from five different sites were analyzed by this method. Elemental analysis and total lime analysis were performed in some soil pairs. Results Soils were dominated by calcite and quartz, or by montmorillonite and kaolinite. Inter-patch soils were richer in calcite and poorer in quartz or clays than patch soils. Calcite losses in patch soils might be related to soil acidification by CO2 from respiration and/or organic matter. Elemental analysis showed high values of S, Cl, and K in patch soils with respect to inter-patch soils. Conclusions The proposed FTIR method was useful to compare soil mineralogy in specific areas. Fertile spots by accumulation of water, soluble salts and sediments may favor plant growth in semi-arid regions and these plants may increase the fertility of the spot. Changes in soil mineral composition could be used to monitor the biological activity of soil in arid and semi-arid zones.Research funded by the Spanish Ministry of Science and Innovation (projects UNCROACH, CGL2011–30581- C02–01 and GRACCIE Programa Consolider-Ingenio 2010, CSD2007–00067), Spanish Ministry of the Environment, Rural and Marine Areas (Project RECUVES; 077/RN08/04.1) and Generalitat Valenciana (Programa G. Forteza; FPA/2009/029)

Perception of the Effects of Working from Home on Isolation and Stress by Spanish Workers during COVID-19 Pandemic

This paper tests the explanatory capability of the individual, organizational, environmental and job factors regarding Spanish workers’ perception of isolation and stress owing to working from home (WFH). We used a survey of the Spanish agency Centro de Investigaciones Sociológicas on the Spanish population’s perceptions of several aspects of information technologies that was carried out in March 2021. Information overload, work overload and isolation are perceived to be the principal factors involved in WFH. Because WFH could be inhibit professional development, drawbacks in the infrastructure include overload and impediments to career development as the most relevant variables to explain the perception of isolation. Age and balance between family and work also have explanatory power, but less so for isolation and stress. While people with intermediate ages are less sensitive to isolation and stress, having a correct balance between work and personal life is a protective factor against these effects. From the results in this paper, we outline several questions that must be addressed by labour authorities via legal regulations and by firms and workers to adapt organizational and working culture to ensure the efficient implementation of WFH settings compatible with employees’ well-being

An essay about how much training the primary school teachers have about TIC use.

La sociedad actual se encuentra inmersa en una serie de cambios y como tal, esos cambios están afectando a la comunidad educativa. Para poder hacer frente a estos avances, la formación del profesorado se convierte en el elemento clave para facilitar la integración de las nuevas tecnologías al curriculum escolar.Esta investigación se centra en el proyecto “Escuela TIC 2.0”, de los centros educativos de Málaga. Se ha realizado un estudio de los efectos que la implantación de este proyecto tiene sobre la a metodología de enseñanza aprendizaje aplicado por el profesorado, como en la formación que éste debe tener para poder integrarlas en su metodología activa.Los datos obtenidos han constatado que sigue siendo una tarea pendiente la formación de determinado sector del profesorado que no se involucra con el nuevo concepto metodológico del proceso de enseñanza-aprendizaje en el que se han integrado TIC