4,782 research outputs found
The modulated spin liquid: a new paradigm for URuSi
We argue that near a Kondo breakdown critical point, a spin liquid with
spatial modulations can form. Unlike its uniform counterpart, we find that this
occurs via a second order phase transition. The amount of entropy quenched when
ordering is of the same magnitude as for an antiferromagnet. Moreover, the two
states are competitive, and at low temperatures are separated by a first order
phase transition. The modulated spin liquid we find breaks symmetry, as
recently seen in the hidden order phase of URuSi. Based on this, we
suggest that the modulated spin liquid is a viable candidate for this unique
phase of matter.Comment: 4 pages, 2 figure
Interplay of tidal evolution and stellar wind braking in the rotation of stars hosting massive close-in planets
This paper deals with the application of the creep tide theory (Ferraz-Mello,
Cel. Mech. Dyn. Astron. vol. 116, 109, 2013) to the study of the rotation of
stars hosting massive close-in planets. The stars have nearly the same tidal
relaxation factors as gaseous planets and the evolution of their rotation is
similar to that of close-in hot Jupiters: they tidally evolve towards a
stationary solution. However, stellar rotation may also be affected by stellar
wind braking. Thus, while the rotation of a quiet host star evolves towards a
stationary attractor with a frequency () times the orbital mean-motion
of the companion, the continuous loss of angular momentum in an active star
displaces the stationary solution towards slower values: Active host stars with
big close-in companions tend to have rotational periods larger than the orbital
periods of their companions. The study of some hypothetical examples shows that
because of tidal evolution, the rules of gyrochronology cannot be used to
estimate the age of one system with a large close-in companion, no matter if
the star is quiet or active, if the current semi-major axis of the companion is
smaller than 0.03--0.04 AU. Details on the evolution of the systems: CoRoT
LRc06E21637, CoRoT-27, Kepler-75, CoRoT-2, CoRoT-18, CoRoT-14 and on
hypothetical systems with planets of mass 1--4 M_Jup in orbit around a star
similar to the Sun are given.Comment: 22 pages, 8 figures; Publication in Ap
Capybara (Hydrochoerus hydrochaeris) distribution in agroecosystems: a cross-scale habitat analysis.
Use of remote sensing to assess ecosystem integrity of the Brazilian Amazon rainforest: a Bayesian approach.
Biodiversity supports many ecosystem services that are very important for climate change mitigation and adaptation. There is a functional link between the tropical forest ecosystem biodiversity and their capacity for carbon uptake and storage as well as regulation of evapotranspiration flux. Nevertheless, land use changes and agriculture expansion reduce the ecosystems integrity modifying the functions related directly to the ecosystem services. The relationship between biodiversity loss and the impacts on ecosystem services of tropical forests, in face of the ongoing global climate change needs to be better quantified. In this work, we considered the concept of Ecosystem Integrity (EI), which represents the connection of biodiversity with the ability of ecosystems to sustain the processes of self-organization. Bayesian Networks (BBN-Bayesian Belief Network) can provide metrics for the generation of Ecosystem Integrity Index, from the training of probabilistic relationships of evidence obtained through Remote Sensing data. The objective of this work is to present the methodological approach and the results of EI mapping, elaborated at the regional scale for different patterns of phyto-ecologic landscape of the Brazilian Amazon. The modelling was based on learning from the parameters (data-driven model) through the use of the Expectation Maximization algorithm. For the validation of this probabilistic model, an evaluation was carried out in controlled areas with field observation by experts. Results showed that it is possible to generate an Ecosystem Integrity Index at regional scale using a probabilistic model based on Bayesian Belief Networks (BBN), and totally free web-available satellite products
Software para automação de Língua Eletrônica em análise de líquidos.
Pressionada pela crescente competitividade no mercado globalizado, a indústria alimentícia necessita aperfeiçoar continuamente os seus produtos visando produtividade e qualidade. Neste contexto, é forte a demanda pelo desenvolvimento de sensores capazes de monitorar qualidade e sabor durante os processos de produção, de forma automática e confiável. A Embrapa Instrumentação Agropecuária desenvolveu sensores gustativos (Riul Jr. et al., 2003) capazes de distinguir diferentes marcas de café, vinho, água mineral, suco de fruta, chá, leite e outras bebidas. Através destes sensores, os sabores podem ser detectados com sensibilidade maior do que a do paladar humano. O potencial de aplicação desta tecnologia se estende a diversos setores assim como a estudos ambientais, como o da contaminação dos corpos d'água. Atualmente, destaca-se o grande interesse que os setores cafeeiro e vinícola têm demonstrado em utilizar a língua eletrônica tanto no processo de produção quanto durante o armazenamento. Testes preliminares demonstraram o enorme potencial desta técnica. Deseja-se que a análise destas bebidas seja feita automaticamente, durante o processamento com equipamentos dedicados às aplicações específicas e de custo acessível. Com estes objetivos, está em andamento na Embrapa Instrumentação Agropecuária o projeto: "Desenvolvimento de sensores poliméricos para aplicações na agroindústria e meio ambiente", financiado pela FAPESP (proc. 01.13745-1).bitstream/CNPDIA/8723/1/CT54_2003.pd
Field-theoretical renormalization group for a flat two-dimensional Fermi surface
We implement an explicit two-loop calculation of the coupling functions and
the self-energy of interacting fermions with a two-dimensional flat Fermi
surface in the framework of the field theoretical renormalization group (RG)
approach. Throughout the calculation both the Fermi surface and the Fermi
velocity are assumed to be fixed and unaffected by interactions. We show that
in two dimensions, in a weak coupling regime, there is no significant change in
the RG flow compared to the well-known one-loop results available in the
literature. However, if we extrapolate the flow to a moderate coupling regime
there are interesting new features associated with an anisotropic suppression
of the quasiparticle weight Z along the Fermi surface, and the vanishing of the
renormalized coupling functions for several choices of the external momenta.Comment: 16 pages and 22 figure
Spatial variability of litter temperature, relative air humidity and skin temperature of chicks in a commercial broiler house
ArticleThe thermal environment inside a broiler house has a great influence on animal welfare
and productivity during the production phase. Among the importance of the chicken litter is the
function of absorbing moisture, provide thermal insulation and provide a soft surface for broilers.
The skin temperature is an important physiological parameter to quantify the thermal comfort of
animals, its variations may occur as a function of thermal variables. So, the aim of this work was
to analyse the magnitude and spatial variability of chicken litter temperature and relative humidity
of the air and to correlate them with the spatial distribution of chicks’ skin surface temperature
throughout the broiler house during the 7th, 14th and 21st days of the chicks’ life, using
geostatistical techniques. The experiment was performed in a commercial broiler house located
in the western mesoregion of Minas Gerais, Brazil, where 28,000 male Cobb chicks were housed.
The heating system consisted of an industrial indirect-fired biomass furnace. The heated air was
inflated by an AC motor, 2,206 W of power, 1,725 RPM. Geostatistical techniques were used
through semivariogram analysis and isochore maps were generated through data interpolation by
kriging. The semivariogram was fitted by the restricted maximum likelihood method. The used
mathematical model was the spherical one. After fitting the semivariograms, the data were
interpolated by ordinary kriging. The semivariograms along with the isochore maps allowed
identifying the non-uniformity of spatial distribution of the broiler litter temperature throughout
the broiler house for 3 days of chicks’ life. It was observed that skin surface presented a positive
correlation with the litter temperature and a negative correlation with the air humidity. The
semivariograms along with the isochore maps allowed identifying the non-uniformity of spatial
distribution of the litter temperature, air humidity and skin temperature of chicks throughout the
broiler aviary for the three days. In addition, the use of geostatistics and distribution maps made
possible to identify different environmental conditions in regions inside the broiler house that
may harm the development of chicks
Bioreduction of substituted a-tetralones promoted by Daucus carota root
The bioreduction of a series of substituted a-tetralones, carried out using Daucus carota root (carrot), afforded the corresponding homochiral a-tetralols in variable conversions (9 to 90%) and excellent enantiomeric excesses. Two of the assayed a-tetralones were resistant to the bioreduction conditions. The absolute configurations of four a-tetralols were assigned as being (S), by comparison to the (S)-enantiomers obtained by kinetic resolution promoted by CALB-catalysed acetylation. Additionally, the new 5-methoxy-6-methyl-1-tetralone was synthesized in seven steps from 3-methylsalicylic acid.FAPESPCoordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES)CNP
Interaction of genotype, environment and processing in the chemical composition expression and sensorial quality of Arabica coffee.
The present study was carried out to analyze chemical descriptors present in the raw coffee bean and to establish an association of these descriptors with the sensorial quality of the coffee beverage, based on expressions resulting from the interactions of coffee genotype, environment, and processing. The chemical descriptors caffeine, trigonelline, sucrose, and isomers of chlorogenic acid (3-CQA, 4-CQA, and 5-CQA), were analyzed through the use of high performance liquid chromatography (HPLC). Trained and qualified cuppers, certified as judges of specialty coffees, carried out the sensorial analysis using the methodology proposed by the Specialty Coffee Association of America (SCAA). Based on the cultivation environment, altitude and the genotype, it was possible to associate the chemical composition of the raw coffee bean with the coffee beverage sensorial quality. Yellow Bourbon cultivated above 1,200 m of altitude present higher contents of trigonelline and 3-CQA in the raw beans as well as high sensorial quality in the beverage
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