10,160 research outputs found
The small behavior of the gluon structure function from total cross sections
Within a QCD-based eikonal model with a dynamical infrared gluon mass scale
we discuss how the small behavior of the gluon distribution function at
moderate is directly related to the rise of total hadronic cross
sections. In this model the rise of total cross sections is driven by
gluon-gluon semihard scattering processes, where the behavior of the small
gluon distribution function exhibits the power law . Assuming that the scale is proportional to the
dynamical gluon mass one, we show that the values of obtained in this
model are compatible with an earlier result based on a specific nonperturbative
Pomeron model. We discuss the implications of this picture for the behavior of
input valence-like gluon distributions at low resolution scales.Comment: 19 pages, 3 figures; revised version; to appear in Int. J. Mod. Phys.
Elastic scattering and the proton form factor
We compute the differential and the total cross sections for scattering
using the QCD pomeron model proposed by Landshoff and Nachtmann. This model is
quite dependent on the experimental electromagnetic form factor, and it is not
totally clear why this form factor gives good results even at moderate
transferred momentum. We exchange the eletromagnetic form factor by the
asymptotic QCD proton form factor determined by Brodsky and Lepage (BL) plus a
prescription for its low energy behavior dictated by the existence of a
dynamically generated gluon mass. We fit the data with this QCD inspired form
factor and a value for the dynamical gluon mass consistent with the ones
determined in the literature. Our results also provide a new determination of
the proton wave function at the origin, which appears in the BL form factor.Comment: 10 pages, 2 figures. Submitted to Physics Letters B. Submitted to
Phys. Lett.
Evaluation of Ca-Based Sorbents for Gaseous HCl Emissions Adsorption
The problem of acid gas exhaust emissions treatment has not been fully resolved at present. Dry adsorption of acid gases with alkaline sorbents is currently being investigated, to improve solid sorbents. In this study, 5 types of hydrated lime were characterised and tested. The sorption capacities were measured by means of a system consisting of a feed line (HCl/N2), a thermostatic reactor and a water absorber. The physical characteristics of sorbent samples were also compared. Analyses conducted with scanning electronic microscopy revealed that sample C1 showed uniform particle distribution. Samples C2 and C3 showed the co-presence of fine and coarse particles. Sample C4 showed very fine particles with agglomeration phenomena. In sample C5, fibrous elements were found. Energy dispersive spectrometry (EDS) analyses showed a similar composition of the samples, with the exception of the presence of Mg in some of them. After 30 min of testing, the following differences in sorption capacities with respect to C1 (3.59 mg gâ1) were found: C2, â20%; C3, â13%; C4, â17%; C5, â3%. Higher sorption capacities were associated with more uniform particle size distributions. Conversely, agglomeration of fine particles may have adversely affected the performance of sorbents
Survival analysis of piglet pre-weaning mortality
Survival analysis methodology was applied in order to analyse sources of variation of preweaning survival time and to estimate variance components using data from a crossbred piglets population. A frailty sire model was used with the litter effect treated as an additional random source of variation. All the variables considered had a significant effect on survivability: sex, cross-fostering, parity of the nurse-sow and litter size. The variance estimates of sire and litter were closed to 0.08 and 2 respectively and the heritability of pre-weaning survival was 0.03
O Uso do Sispinus/Carboplan como ferramenta de suporte para a estimativa do carbono em atividades de projetos florestais.
Para participar do mercado de carbono, atravĂ©s do Mecanismo de Desenvolvimento Limpo (MDL), Ă© necessĂĄrio elaborar um Documento de Concepção de Projeto (DCP) e utilizar uma metodologia de Linha de Base e Monitoramento (LB/M), que identificam o projeto Aflorestamento/ Reflorestamento (A/R) do MDL e permitem estimar as ReduçÔes Certificadas de EmissĂ”es (RCEâs) da atividade. Ferramentas de software utilizadas para modelagem de crescimento e produção florestal podem ser empregadas para agilizar e aumentar a precisĂŁo do cĂĄlculo das RCEs por atividade de projeto A/R do MDL. Em um cenĂĄrio de reflorestamento de 477 ha de Pinus sp. o software Sispinus/Carboplan foi empregado para estimar as RCEs em um perĂodo de 30 anos de crĂ©dito, estimando um total de 28.840 tCO2eq. O Sispinus/Carboplan mostrou-se efetivo na modelagem de carbono de biomassa aĂ©rea e subterrĂąnea da espĂ©cie em projeto de reflorestamento.bitstream/CNPF-2009-09/44479/1/BPD39_CD.pd
TLEP: A High-Performance Circular e+e- Collider to Study the Higgs Boson
The recent discovery of a light Higgs boson has opened up considerable
interest in circular e+e- Higgs factories around the world. We report on the
progress of the TLEP concept since last year. TLEP is an e+e- circular collider
capable of very high luminosities in a wide centre-of-mass (ECM) spectrum from
90 to 350 GeV. TLEP could be housed in a new 80 to 100 km tunnel in the Geneva
region. The design can be adapted to different ring circumference (e.g. LEP3 in
the 27 km LHC tunnel). TLEP is an ideal complementary machine to the LHC thanks
to high luminosity, exquisite determination of ECM and the possibility of four
interaction points, both for precision measurements of the Higgs boson
properties and for precision tests of the closure of the Standard Model from
the Z pole to the top threshold.Comment: Contribution to IPAC13, 12-17 May 2013, Shanghai, Chin
Development of microwave superconducting microresonators for neutrino mass measurement in the HOLMES framework
The European Research Council has recently funded HOLMES, a project with the
aim of performing a calorimetric measurement of the electron neutrino mass
measuring the energy released in the electron capture decay of 163Ho. The
baseline for HOLMES are microcalorimeters coupled to Transition Edge Sensors
(TESs) read out with rf-SQUIDs, for microwave multiplexing purposes. A
promising alternative solution is based on superconducting microwave
resonators, that have undergone rapid development in the last decade. These
detectors, called Microwave Kinetic Inductance Detectors (MKIDs), are
inherently multiplexed in the frequency domain and suitable for even
larger-scale pixel arrays, with theoretical high energy resolution and fast
response. The aim of our activity is to develop arrays of microresonator
detectors for X-ray spectroscopy and suitable for the calorimetric measurement
of the energy spectra of 163Ho. Superconductive multilayer films composed by a
sequence of pure Titanium and stoichiometric TiN layers show many ideal
properties for MKIDs, such as low loss, large sheet resistance, large kinetic
inductance, and tunable critical temperature . We developed Ti/TiN
multilayer microresonators with within the range from 70 mK to 4.5 K and
with good uniformity. In this contribution we present the design solutions
adopted, the fabrication processes and the characterization results
Produção, carbono e rentabilidade econÎmica de Pinus elliottii e Eucalyptus grandis em sistemas silvipastoris no Sul do Brasil.
O presente trabalho teve por objetivos estimar a produção de madeira, o estoque de carbono e a rentabilidade econĂŽmica, incluindo a venda de crĂ©ditos de carbono de plantaçÔes de Eucalyptus grandis e Pinus elliottii em consĂłrcio com pastagens. Foram utilizados dois experimentos com cada espĂ©cie, todos instalados em Alegrete, RS, em ĂĄreas de pastagem natural. Os experimentos possuĂam trĂȘs tratamentos, dois deles constituĂdos por sistemas silvipastoris implantados em fileiras triplas de ĂĄrvores, com ambas as espĂ©cies no espaçamento de 3,0 m x 1,5 m, sendo o primeiro com um corredor de 14 m, entre as fileiras triplas, destinado ao pastejo dos animais, e o outro com um corredor de 34 m. O terceiro tratamento possuĂa o cultivo isolado das duas espĂ©cies florestais, com espaçamento de 3,0 m x 3,0 m. Foram simulados desbastes e corte final aos 21 anos de idade para todos os tratamentos. As ĂĄrvores propiciaram retorno econĂŽmico em todos os sistemas testados, com rentabilidade a partir do desbaste aos 7 anos de idade. A venda de crĂ©ditos de carbono torna o componente florestal ainda mais atrativo devido, principalmente, Ă receita auferida desde o inĂcio do projeto
Origin of pyroxenites in the oceanic mantle and their implications on the reactive percolation of depleted melts
Pyroxenites are diffuse in fertile mantle peridotites and considered an important component in the mantle source of oceanic basalts. They are rarely documented in abyssal and ophiolitic peridotites representing residual mantle after melt generation, and few studies defining their origin are to date available. We present a field-based microstructural and geochemical investigation of the pyroxenite layers associated with depleted peridotites from the Mt. Maggiore ophiolitic body (Corsica, France). Field and petrographic evidence indicate that pyroxenite formation preceded the melt\u2013rock interaction history that affected this mantle sector during Jurassic exhumation, namely (1) spinel-facies reactive porous flow leading to partial dissolution of the pyroxenites, and (2) plagioclase-facies melt impregnation leading to [plagioclase + orthopyroxene] interstitial crystallization. Pyroxenes show major element compositions similar to abyssal pyroxenites from slow-spreading ridges, indicative of magmatic segregation at pressures higher than 7 kbar. Both the parental melts of pyroxenites and the melts involved in the subsequent percolation were characterized by Na2O-poor, LREE-depleted compositions, consistent with unaggregated melt increments. This implies that they represent the continuous evolution of similarly depleted melts leading to different processes (pyroxenite segregation and later melt\u2013rock interaction) during their upward migration. To support the genetic relation and the continuity between the formation of pyroxenites and the subsequent melt\u2013rock interaction history, we modeled all the documented processes in sequence, i.e.: (1) formation of single-melt increments after 6% mantle decompressional fractional melting; (2) high-pressure segregation of pyroxenites; (3) spinel-facies reactive porous flow, (4) plagioclase-facies melt impregnation. The early fractionation of pyroxenites leads to a decrease in pyroxene saturation that is necessary for the subsequent reactive porous flow process, without any significant change in the melt REE composition
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