A joint time-dependent density-functional theory for excited states of electronic systems in solution

We present a novel joint time-dependent density-functional theory for the description of solute-solvent systems in time-dependent external potentials. Starting with the exact quantum-mechanical action functional for both electrons and nuclei, we systematically eliminate solvent degrees of freedom and thus arrive at coarse-grained action functionals which retain the highly accurate \emph{ab initio} description for the solute and are, in principle, exact. This procedure allows us to examine approximations underlying popular embedding theories for excited states. Finally, we introduce a novel approximate action functional for the solute-water system and compute the solvato-chromic shift of the lowest singlet excited state of formaldehyde in aqueous solution, which is in good agreement with experimental findings.Comment: 11 page

Metallothionein in the pond perch Diplectrum radiale (Teleostei) as a biomarker of pollution in Guanabara Bay estuary, Brazil

Guanabara Bay is a semi-closed tropical bay located in the center of metropolitan Rio de Janeiro. The ecological integrity of this system has a spatial gradient, with better environmental conditions near the mouth than in the inner bay. The objectives of this study were to monitor the exposure of the pond perch Diplectrum radiale (Perciformes; Serranidae) to metal pollution, using metallothionein as a specific biomarker, and to detect spatial differences in metal contamination in this large water body. The effects of biological factors (allometric condition factor, size, weight, and reproductive stage) and spatial variations on MT levels were also investigated among sampling sites. The results revealed intraspecific sources of variation influencing MT expression. Therefore, it was not possible to use MT as a sensitive biomarker to distinguish heavy metal pollution among sites within this bay. The spatial heterogeneity of metal bioavailability and the probable mobility of individual fish contributed to those findings. However, the pond perch can still be considered a good target organism to evaluate the effects of metal contamination through comparison with other estuarine ecosystems on the Brazilian coast. Key words: estuary, Guanabara Bay, metallothionein, teleos

Análise da capacidade combinatória entre linhagens de girassol.

A capacidade geral (CGC) e a capacidade específica de combinação (CEC), entre duas linhagens macho-estéreis (mãe) e um grupo de sete linhagens S4 restauradoras de fertilidade (pai), foram estimadas para estudar o potencial desses materiais em programas de melhoramento de girassol (Helianthus annuus L.). O método IV de Griffing, adaptado para cruzamentos dialélicos parciais, foi usado na análise das combinações híbridas. Considerando a CGC para rendimento de aquênios e teor de óleo, os progenitores com maior potencial para o melhoramento foram CMS HA 302 (originária de uma população norte-americana) para ser usada como mãe, e as linhagens 89V2345)3382 e 89V2345)3311 (derivadas da população V2000, obtida por seleção sobre a população Issanka, originária da França) como pais nos cruzamentos. Para o rendimento de aquênios, os efeitos gênicos não aditivos foram importantes na determinação das diferenças entre progenitores. Considerando-se os efeitos gênicos aditivos e não-aditivos conjuntamente, as melhores combinações são CMS HA 302 x 89V2396)5333 para rendimento de aquênios e CMS HA 30379NW22 x 89V2345)3382 para teor de óleo e rendimento de óleo

Mapeamento de QTLs de características sob influência da ferrugem asiática da soja.

A ferrugem asiática da soja, causada pelo fungo Phakopsora pachyrhizi (Syd. & P.Syd.), é um dos principais fatores bióticos causadores de prejuízos de redução do potencial sobre a cultura da soja, podendo causar redução de produtividade superiores a 75%. Hoje, sabe-se que uma das formas mais eficazes de controle da doença é através da resistência genética. Devido à baixa durabilidade de genes de resistência vertical, estudos para o desenvolvimento de linhagens com genes de resistência horizontal são de extrema importância. Assim, objetivou-se nesse trabalho identificar QTLs em soja para características agronômicas sob influência da ferrugem asiática. Métodos: 83 marcadores de microssatélites e 2 marcadores morfológicos foram utilizados para a construção de um mapa genético em uma população de linhagens endogâmicas recombinantes (RILs) Ao mesmo tempo, foram feitas avaliações fenotípicas para várias características correlacionadas a doença nas RILs sob ação do patógeno em campo experimental da Embrapa Soja e em fitotron no Japão, a fim de buscar QTLs relacionados à resistência horizontal ao patógeno, e também para verificar a existência de linhagens com maior nível de resistência à doença. Resultados: Uma cobertura parcial de 1.023,5 cM do genoma da soja foi obtida em 19 grupos de ligação. Foram detectados 17 QTLs que possam estar contribuindo para a resistência horizontal à doença, sendo a maior parte deles localizados no grupo C2 e L. Grande parte dos QTLs observados possui efeito pleiotrópico para mais de uma característica analisada, fato constatado através de análises de correlação entre as características estudadas. Foram selecionadas 16 linhagens que apresentaram as melhores características sob ação da ferrugem asiática da soja. Para algumas características, verificou-se a existência de segregação transgressiva, já que neste caso os genes estavam dispersos entre os parentais. Conclusão: Os dados gerados poderão contribuir para o programa de melhoramento contra a doença, O mapa gerado também pode servir para detecção de outros QTLs relacionados a outras características de grande interesse agronômico, já que ambas as cultivares que foram cruzadas possuem resistência a várias outras doenças

Biexciton oscillator strength

Our goal is to provide a physical understanding of the elementary coupling between photon and biexciton and to derive the physical characteristics of the biexciton oscillator strength, following the procedure we used for trion. Instead of the more standard two-photon absorption, this work concentrates on molecular biexciton created by photon absorption in an exciton gas. We first determine the appropriate set of coordinates in real and momentum spaces to describe one biexciton as two interacting excitons. We then turn to second quantization and introduce the "Fourier transform in the exciton sense" of the biexciton wave function which is the relevant quantity for oscillator strength. We find that, like for trion, the oscillator strength for the formation of one biexciton out of one photon plus a \emph{single} exciton is extremely small: it is one biexciton volume divided by one sample volume smaller than the exciton oscillator strength. However, due to their quantum nature, trion and biexciton have absorption lines which behave quite differently. Electrons and trions are fermionic particles impossible to pile up all at the same energy. This would make the weak trion line spread with electron density, the peak structure only coming from singular many-body effects. By contrast, the bosonic nature of exciton and biexciton makes the biexciton peak mainly rise with exciton density, this rise being simply linear if we forget many-body effects between the photocreated exciton and the excitons present in the sample

Phase diagram for a Cubic Consistent-Q Interacting Boson Model Hamiltonian: signs of triaxiality

An extension of the Consistent-Q formalism for the Interacting Boson Model that includes the cubic QxQxQ term is proposed. The potential energy surface for the cubic quadrupole interaction is explicitly calculated within the coherent state formalism using the complete chi-dependent expression for the quadrupole operator. The Q-cubic term is found to depend on the asymmetry deformation parameter gamma as a linear combination of cos(3gamma) and cos^2(3\gamma) terms, thereby allowing for triaxiality. The phase diagram of the model in the large N limit is explored, it is described the order of the phase transition surfaces that define the phase diagram, and moreover, the possible nuclear equilibrium shapes are established. It is found that, contrary to expectations, there is only a very tiny region of triaxiality in the model, and that the transition from prolate to oblate shapes is so fast that, in most cases, the onset of triaxiality might go unnoticed.Comment: 18 pages, 19 figure

Analytic and geometric properties of photoinduced effects in noncentrosymmetric crystals: photovoltaic current and optical rectification

An original dispersion relation between the stationary coherent nonlinear optical responses by current and polarisation is obtained. The dispersion relation provides a new complimentary tool that can be employed to study light-induced charge transport models and facilitate experimental data analysis. It is shown that the origin of the coherent current and the dc-polarisation induced in a noncentrosymmetric crystal under illumination is related to the theory of the Berry phase and can be represented in terms of the renormalised geometric potentials. This renormalisation originates from the extra phase difference acquired by a carrier in the light field on the quantum transition between the electronic bands. The gauge invariance of the corresponding expressions for the current and the polarisation is demonstrated.Comment: 7 page

Remarcs on the shape transition from spherical to deformed gamma unstable nuclei

Energies and transition probabilities for low lying states in $^{134}$Ba and ^{104Ru were calculated within a hybrid model.The ground and the first $2^+$ states are described alternatively as a harmonic and anharmonic vibrator states while the remaining states as states with E(5) symmetry. One concludes that a gradual setting of the 'critical' potential yields a better agreement with the experimental data. Very good agreement with the data is obtained for $^{104}$Ru. Comparing the present results with those of E(5) symmetry, it is conspicuous that the present formalism add corrections to the E(5) formalism by bringing the predictions closer to the experimental data. Analytical relationship between the states with U(5) symmetry and those given by the E(5) description is established.Comment: 21 pages, 3 figures, submitted for publicatio

Ab Initio Study of Screw Dislocations in Mo and Ta: A new picture of plasticity in bcc transition metals

We report the first ab initio density-functional study of screw dislocations cores in the bcc transition metals Mo and Ta. Our results suggest a new picture of bcc plasticity with symmetric and compact dislocation cores, contrary to the presently accepted picture based on continuum and interatomic potentials. Core energy scales in this new picture are in much better agreement with the Peierls energy barriers to dislocation motion suggested by experiments.Comment: 3 figures, 3 table

On the rotational dynamics of the Rattleback

The Rattleback is a very popular science toy shown to students all over the world to demonstrate the non-triviality of rotational motion. When spun on a horizontal table, this boat-shaped object behaves in a peculiar way. Although the object appears symmetric, the dynamics of its motion seem very asymmetric. When spun in the preferred direction, it spins smoothly, whereas in the other direction it starts to oscillate wildly. The oscillation soon dies out and the rattleback starts to spin in the preferred way. We will construct and go through an analytical model capable of explaining this behaviour in a simple and intelligible way. Although we aim at a semi-pedagogical treatise, we will study the details only when they are necessary to understand the calculation. After presenting the calculations we will discuss the physical validity of our assumptions and take a look at more sophisticated models requiring numerical analysis. We will then improve our model by assuming a simple friction force.Comment: 17 pages and 2 figures, typos corrected, some minor additions and rewording