La hojarasca y su descomposición en bosques de castaño de monte alto en el Norte de Portugal

This research aimed to: estimate the inputs of litterfall; model the decomposition process and assess the rates of litter decay and turnover; study the litter decomposition process and dynamics of nutrients in old chestnut high forests. This study aimed to fill a gap in the knowledge of chestnut decomposition process as this type of ecosystems have never been modeled and studied from this point of view in Portugal. The study sites are located in the mountains of Marão, Padrela and Bornes in a west-to-east transect, across northern Portugal, from a more-Atlantic-to-lessmaritime influence. This research was developed on old chestnut high forests for quality timber production submitted to a silviculture management close-to-nature. We collected litterfall using littertraps and studied decomposition of leaf and bur litter by the nylon net bag technique. Simple and double exponential models were used to describe the decomposition of chestnut litterfall incubated in situ during 559 days. The results of the decomposition are discussed in relation to the initial litter quality (C, N, P, K, Ca, Mg) and the decomposition rates. Annually, the mature chestnut high-forest stands (density 360-1,260 tree ha–1, age 55-73 years old) restore 4.9 Mg DM ha–1 of litter and 2.6 Mg ha–1 yr–1 of carbon to the soil. The two-component litter decay model proved to be more biologically realistic, providing a decay rate for the fast initial stage (46-58 yr–1for the leaves and 38-42 yr–1for the burs) and a decay rate related to the recalcitrant pool (0.45-0.60 yr–1for the leaves and 0.22-0.36 yr–1for the burs). This study pointed to some decay patterns and release of bioelements by the litterfall which can be useful for calibrating existing models and indicators of sustainability to improve both silvicultural and environmental approaches for the management of chestnut forests.Esta investigación tuvo como objetivo calcular los aportes de hojarasca; modelar el proceso de descomposición y evaluar las tasas de descomposición de la hojarasca y el turnover; estudiar el proceso de descomposición de la hojarasca y la dinámica de nutrientes en bosques de castaños de monte alto. Asimismo, se quiso llenar un vacío en el conocimiento del proceso de descomposición del castaño ya que este tipo de ecosistemas no han sido modelados y estudiados desde este punto de vista en Portugal. El estudio se realizó en las montañas de Marão, Padrela y Bornes situados en un transepto que va de oeste a este, en el norte de Portugal, de mayor a menor influencia Atlántica. La investigación se desarrolló en bosques de castaños antiguos dedicados a la producción de madera de calidad sometida a una gestión silvícola cercana a la naturaleza. Se emplearon colectores de hojarasca y se estudió la descomposición de hojarasca y erizos mediante el empleo de bolsas de red de nylon. Para describir la descomposición de hojarasca del castaño mediante la incubación in situ durante 559 días se utilizaron modelos exponenciales simple y doble. Los resultados de la descomposición se discuten en relación a la calidad de la hojarasca inicial (C, N, P, K, Ca, Mg) y las tasas de descomposición. Anualmente, las masas de castaño (densidad 360-1.260 árboles ha–1, edad 55-73 años) producen 4,9 Mg DM ha–1 de hojarasca al suelo y 2,6 Mg ha–1 año–1 de carbono. El modelo exponencial doble de descomposición de hojarasca demostró ser biológicamente más realista, con una tasa de descomposición para la fracción lábil (46-58 años–1 para las hojas y 38-42 años–1 para los erizos) y una tasa de descomposición para la fracción recalcitrante (0,45-0,60 años–1 para las hojas y 0,22-0,36 años–1 para los erizos). Los resultados obtenidos mostraron la existencia de patrones de descomposición y liberación de los bioelementos de la hojarasca que pueden ser útiles para la calibración de los modelos existentes y indicadores de sostenibilidad que permitan mejorar los enfoques silvícolas y medioambientales de cara a una gestión sostenible de los bosques de castaño

Heavy fermion d-wave superconductivity: a X-boson approach

From an extension of the periodic Anderson model (PAM) in the $U=\infty$ limit taking into account the effect of a nearest neighbor attractive interaction between $f$-electrons, we compare the obtained superconducting phase diagram of a two dimensional d-wave superconductor with the results obtained for an isotropic s-wave superconductor employing the X-boson method.Comment: Submitted to the Proceeding of the ICM 2003-Rome. Requires elsart3.cl

Laboratório de Solos e Fertilidade.

Laboratório de Solos e Fertilidade.info:eu-repo/semantics/publishedVersio

A Experiência De Trabalho E Dos Riscos Entre Os Trabalhadores-migrantes Nordestinos Nos Canaviais Paulistas

Every year thousands of workers from the Brazilian Northeastern states move to the sugarcane plantations in the state of São Paulo to work in sugarcane mills. Most of them are young with little schooling and come from peasant families. Among other things, researchers call attention to the risks to which these workers are submitted, related to transportation conditions, housing and work environment. The organization of work is always focused on increasing the surplus value, which has resulted in the deterioration of the labor force, expressed by several diseases and countless deaths of migrant workers. In the scope of this article, it is our intention to define “risk” concept and relate it to the processes of subjectivities and to understand the meanings that migrant workers attribute to the risks to which they are exposed during the trip and also in workplaces (sugarcane plantations). Regarding methodology, we used a qualitative approach. Data were collected through semi-structured interviews conducted with a sample of 12 migrant workers from the city of Santa Cruz da Baixa Verde (Pernambuco), in the Pajeú microregion, and also of cities located in the microregion of Serra do Teixeira (Paraíba), especially the surrounding areas of Princesa Isabel (state of Paraíba). The data allow us to assert the existence of an intrinsic relationship between the risks they run and the affirmation of the gender identity of the subjects investigated. © 2016, UNIV SAOPAULO. All rights reserved.2541122113

Scaling and Interference in the Dissociation of Halo Nuclei

The dissociation of halo nuclei through their collision with light and heavy targets is considered within the Continuum Discretized Coupled Channels theory. We study the one-proton halo nucleus $^8$B and the one-neutron halo nucleus $^{11}$Be, as well as the more normal $^7$Be. The procedure previously employed to extract the Coulomb dissociation cross section by subtracting the nuclear one is critically assessed, and the scaling law usually assumed for the target mass dependence of the nuclear breakup cross section is also tested. It is found that the nuclear breakup cross section for these very loosely bound nuclei does indeed behave as $a+bA^{1/3}$. However, it does not have the geometrically inspired form of a circular ring which seems to be the case for normal nuclei such as $^{7}$Be. We find further that we cannot ignore Coulomb-nuclear interference effects, which may be constructive or destructive in nature, and so the errors in previously extracted B(E1) using the subtraction procedure are almost certainly underestimated.Comment: version submitted to PRL + minor text change

MICROMORFOLOGIA DE SOLOS APLICADA AO ESTUDO DA DIFERENCIAÇÃO DE CAMBISSOLOS EM UMA VERTENTE DO PLANALTO DO ESPINHAÇO MERIDIONAL/MG

Este trabalho caracteriza dois Cambissolos de uma vertente no Espinhaço Meridional/MG a partir de análises texturais e de seções delgadas. Diferenças significativas foram observadas, como cor, espessura do horizonte Bi e presença de mosqueados na média vertente. Diante das diferenças, este perfil foi considerado um Cambissolo em vias de transformação para Latossolo, fato evidenciado pelos indícios de microagregação

Effect of palladium on gold in core-shell catalyst for electrooxidation of ethanol in alkaline medium

In this paper the effect of small amounts of palladium deposited on gold nanoparticles supported on Vulcan XC-72 carbon (core-shell structure denoted Au@Pd/C) is studied. Different nominal atomic compositional ratios of Au@Pdx maintaining fixed gold nuclei and varying the amount of palladium (x = 0.10; 0.80 and 1.60) were synthesized via seed growth method for the ethanol oxidation reaction in alkaline medium. UV–Vis spectrometric, X-ray powder diffraction, X-ray energy dispersive spectroscopy, transmission electron microscopy and electrochemical measurements were performed for the characterization of these catalysts. Electrocatalytic activity toward ethanol oxidation on Au@Pd/C catalysts were investigated by cyclic voltammetry and chronoamperometry showed that [email protected]/C electrocatalyst has the highest current density and low onset potential for ethanol oxidation reaction in alkaline medium. In-situ Fourier transform infrared spectroscopy measurements demonstrated that acetate is the main product of ethanol oxidation and CO2 can be slightest observed, the latter could be visualized in greater quantity on catalyst [email protected]/C catalyst

Effect of continuum couplings in fusion of halo 11^{11}Be on 208^{208}Pb around the Coulomb barrier

The effect of continuum couplings in the fusion of the halo nucleus $^{11}$Be on $^{208}$Pb around the Coulomb barrier is studied using a three-body model within a coupled discretised continuum channels (CDCC) formalism. We investigate in particular the role of continuum-continuum couplings. These are found to hinder total, complete and incomplete fusion processes. Couplings to the projectile $1p_{1/2}$ bound excited state redistribute the complete and incomplete fusion cross sections, but the total fusion cross section remains nearly constant. Results show that continuum-continuum couplings enhance the irreversibility of breakup and reduce the flux that penetrates the Coulomb barrier. Converged total fusion cross sections agree with the experimental ones for energies around the Coulomb barrier, but underestimate those for energies well above the Coulomb barrier.Comment: 15 pages, 7 figures, accepted in Phys. Rev.

Anomalous anapole moment of an exotic nucleus

Using the information on the nuclear structure of exotic neutron-rich halo nucleus $^{11}$Be, we evaluate the parity violating anapole moment in its ground state. The resulting value $\kappa(^{11}$Be)$=0.17$ is fifteen times bigger than the typical value of the anapole moment of a normal nucleus of the same mass, and in fact exceeds by few times anapole moments of any known neutron-odd nuclei (e.g., kappa(^{11}Be) > 2|\kappa(^{207}Pb)|. It is also few times bigger than the neutral current contribution to the lepton-nucleus interaction.Comment: 12 pages, 2 figure

Modeling tourists' personality in recommender systems: how does personality influence preferences for tourist attractions?

Personalization is increasingly being perceived as an important factor for the effectiveness of Recommender Systems (RS). This is especially true in the tourism domain, where travelling comprises emotionally charged experiences, and therefore, the more about the tourist is known, better recommendations can be made. The inclusion of psychological aspects to generate recommendations, such as personality, is a growing trend in RS and they are being studied to provide more personalized approaches. However, although many studies on the psychology of tourism exist, studies on the prediction of tourist preferences based on their personality are limited. Therefore, we undertook a large-scale study in order to determine how the Big Five personality dimensions influence tourists' preferences for tourist attractions, gathering data from an online questionnaire, sent to Portuguese individuals from the academic sector and their respective relatives/friends (n=508). Using Exploratory and Confirmatory Factor Analysis, we extracted 11 main categories of tourist attractions and analyzed which personality dimensions were predictors (or not) of preferences for those tourist attractions. As a result, we propose the first model that relates the five personality dimensions with preferences for tourist attractions, which intends to offer a base for researchers of RS for tourism to automatically model tourist preferences based on their personality.GrouPlanner Project under the European Regional Development Fund POCI-01-0145-FEDER29178 and by National Funds through the FCT – Fundação para a Ciência e a Tecnologia (Portuguese Foundation for Science and Technology) within the Projects UIDB/00319/2020 and UIDB/00760/202