1,351 research outputs found
Comment on "Electromagnetic dissociation of ^8B and the astrophysical S-factor for ^7Be(p,gamma)^8B"
Recently, Davids and Typel recommended a "low" value of S_{17}(0) based on
fits to published direct and Coulomb dissociation data, in which they excluded
the precise result of Junghans et al. We show that their statistical analysis
is incorrect, due to a substantial underestimate of the experimental
uncertainties, and leads to conclusions that are not supported by a proper
analysis.Comment: submitted to Phys. Rev.
Classical-path integral adaptive resolution in molecular simulation: towards a smooth quantum-classical coupling
Simulations that couple different classical molecular models in an adaptive
way by changing the number of degrees of freedom on the fly, are available
within reasonably consistent theoretical frameworks. The same does not occur
when it comes to classical-quantum adaptivity. The main reason for this is the
difficulty in describing a continuous transition between the two different kind
of physical principles: probabilistic for the quantum and deterministic for the
classical. Here we report the basic principles of an algorithm that allows for
a continuous and smooth transition by employing the path integral description
of atoms.Comment: 8 pages 4 figure
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Large field ranges from aligned and misaligned winding
We search for effective axions with super-Planckian decay constants in type
IIB string models. We argue that such axions can be realised as long winding
trajectories in complex-structure moduli space by an appropriate flux choice.
Our main findings are: The simplest models with aligned winding in a 2-axion
field space fail due to a general no-go theorem. However, equally simple models
with misaligned winding, where the effective axion is not close to any of the
fundamental axions, appear to work to the best of our present understanding.
These models have large decay constants but no large monotonic regions in the
potential, making them unsuitable for large-field inflation. We also show that
our no-go theorem can be avoided by aligning three or more axions. We argue
that, contrary to misaligned models, such models can have both large decay
constants and large monotonic regions in the potential. Our results may be used
to argue against the refined Swampland Distance Conjecture and strong forms of
the axionic Weak Gravity Conjecture. It becomes apparent, however, that
realising inflation is by far harder than just producing a light field with
large periodicity
IBI: Targeting cumulative coordination within an iterative protocol to derive coarse-grained models of (multi-component) complex fluids
We present a coarse-graining strategy that we test for aqueous mixtures. The
method uses pair-wise cumulative coordination as a target function within an
iterative Boltzmann inversion (IBI) like protocol. We name this method
coordination iterative Boltzmann inversion (IBI). While the
underlying coarse-grained model is still structure based and, thus, preserves
pair-wise solution structure, our method also reproduces solvation
thermodynamics of binary and/or ternary mixtures. Additionally, we observe much
faster convergence within IBI compared to IBI. To validate the
robustness, we apply IBI to study test cases of solvation
thermodynamics of aqueous urea and a triglycine solvation in aqueous urea
Temperatura e tempo de embebição na germinação de sementes de abacaxizeiro.
O abacaxizeiro (Ananas comosus var. comosus) é a terceira fruteira tropical mais plantada no Brasil e ocupa em torno de 67.000 ha. Nos plantios comerciais de abacaxi são utilizadas mudas obtidas por propagação assexuada, como filhote, filhote-rebentão e rebentão. As sementes são raras nos frutos em decorrência da reduzida fertilidade conjugada com a forte auto-incompatibilidade e o cultivo monoclonal em plantios comerciais (Coppens d'Eeckenbrugge et al., 2003). O melhoramento genético do abacaxizeiro é conduzido em diferentes instituições de pesquisa no mundo, com objetivo de desenvolver variedades mais produtivas e de melhor qualidade no fruto. No Brasil, além dessas caracterÃsticas, os programas de melhoramento genético de abacaxi buscam variedades resistentes à fusariose (Fusarium subglutinans), principal doença da cultura, além de outras caracterÃsticas desejáveis como ausência de espinhos nas folhas, pedúnculo curto e fruto com peso entre 1,5 kg e 2,5 kg (Cabral, 2000).pdf 213
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A neutral low-coordinate heterocyclic bismuth-tin species
The reaction of distannadiazane bearing bulky RAr*-groups (RAr* = C6H2{C(H)Ph2}2R-2,6,4; R = iPr, tBu) with ECl3 (E = Sb, Bi) was studied resulting in the isolation of previously unknown N,N-bis(dichloropnictino)amines (3) and a novel heterocyclic carbenoid bismuth species (4) bearing a Bi(III) and a Sn(IV) center. The structure and bonding was investigated by means of X-ray structure elucidations and DFT calculations
Sc3CH@C80: selective 13C enrichment of the central carbon atom
Sc3CH@C80 is synthesized and characterized by 1H, 13C, and 45Sc NMR. A large negative chemical shift of the proton, -11.73 ppm in the Ih and -8.79 ppm in the D5h C80 cage isomers, is found. 13C satellites in the 1H NMR spectrum enabled indirect determination of the 13C chemical shift for the central carbon at 173 ± 1 ppm. Intensity of the satellites allowed determination of the 13C content for the central carbon atom. This unique possibility is applied to analyze the cluster/cage 13C distribution in mechanistic studies employing either 13CH4 or 13C powder to enrich Sc3CH@C80 with 13C
Variedades de abacaxi resistentes à fusariose.
O abacaxizeiro, conhecido botanicamente como Ananas comosus var. comosus (syns. Ananas comosus, Ananas sativus, Ananassa sativa, Brame/ia ananas, Brame/ia comosa L.), pertence à famÃlia Brame/iaceae a qual agrupa cerca de 2.000 espécies, a grande maioria delas epÃfitas e muitas com alto valor ornamental. Considera-se que a base do processo de seleção de A. comosus var. comosus foi o maior tamanho do fruto (frutilhos maiores e em maior número), a qualidade (baixa acidez) e poucas sementes.PDF. 52
Herança da resistência à fusariose em progênies de abacaxizeiro obtidas de cruzamentos entre hÃbridos resistentes.
O abacaxi é a terceira fruteira tropical mais plantada no paÃs e ocupa em torno de 67.000 ha. O Brasil é o centro de origem desta fruteira, mas nos plantios comerciais brasileiros observa-se o predomÃnio de apenas duas cultivares: a cv. Pérola, com 80% da produção nacional e a cv. Smooth Cayenne, com os demais 20%. A fusariose, causada pelo fungo Fusarium subglutinans f. sp. ananas, é a doença mais importante da cultura no Brasil. As cvs. Pérola e Smooth Cayenne são suscetÃveis à fusariose. O método mais recomendado para controle da fusariose é a utilização de material propagativo sadio e cultivares resistentes. O melhoramento genético do abacaxi conduzido nas instituições de pesquisa no mundo tem como objetivos desenvolver cultivares mais produtivas e de melhor qualidade de fruto. No Brasil, os programas de melhoramento genético de abacaxi buscam também cultivares resistentes à fusariose. Trabalhos anteriores avaliaram a segregação da resistência em mudas obtidas de semente, ou seja, sem repetições. Maior confiabilidade nos resultados é obtida com uso de repetições dos genótipo avaliados. Esse trabalho teve como objetivo estudar a herança da resistência à fusariose do abacaxizeiro em progênies oriundas de dois cruzamentos com fontes distintas de resistência.PDF. 038
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