Particle Creation by a Moving Boundary with Robin Boundary Condition

We consider a massless scalar field in 1+1 dimensions satisfying a Robin boundary condition (BC) at a non-relativistic moving boundary. We derive a Bogoliubov transformation between input and output bosonic field operators, which allows us to calculate the spectral distribution of created particles. The cases of Dirichlet and Neumann BC may be obtained from our result as limiting cases. These two limits yield the same spectrum, which turns out to be an upper bound for the spectra derived for Robin BC. We show that the particle emission effect can be considerably reduced (with respect to the Dirichlet/Neumann case) by selecting a particular value for the oscillation frequency of the boundary position

Future dynamics in f(R) theories

The $f(R)$ gravity theories provide an alternative way to explain the current cosmic acceleration without invoking dark energy matter component. However, the freedom in the choice of the functional forms of $f(R)$ gives rise to the problem of how to constrain and break the degeneracy among these gravity theories on theoretical and/or observational grounds. In this paper to proceed further with the investigation on the potentialities, difficulties and limitations of $f(R)$ gravity, we examine the question as to whether the future dynamics can be used to break the degeneracy between $f(R)$ gravity theories by investigating the future dynamics of spatially homogeneous and isotropic dust flat models in two $f(R)$ gravity theories, namely the well known $f(R) = R + \alpha R^{n}$ gravity and another by A. Aviles et al., whose motivation comes from the cosmographic approach to $f(R)$ gravity. To this end we perform a detailed numerical study of the future dynamic of these flat model in these theories taking into account the recent constraints on the cosmological parameters made by the Planck team. We show that besides being powerful for discriminating between $f(R)$ gravity theories, the future dynamics technique can also be used to determine the fate of the Universe in the framework of these $f(R)$ gravity theories. Moreover, there emerges from our numerical analysis that if we do not invoke a dark energy component with equation-of-state parameter $\omega < -1$ one still has dust flat FLRW solution with a big rip, if gravity deviates from general relativity via $f(R) = R + \alpha R^n$. We also show that FLRW dust solutions with $f''<0$ do not necessarily lead to singularity.Comment: 12 pages, 8 figures. V2: Generality and implications of the results are emphasized, connection with the recent literature improved, typos corrected, references adde

Dermatology case

ABSTRACT Glomuvenous malformations, also known as glomangiomas, are tumor-like malformations or hamartomas of the glomus body. They can be sporadic or inherited as an autosomal dominant disease. Glomuvenous malformations tend to resemble hemangiomas. Clinical distinction between these entities is important due to their different therapeutic approaches. Surgical excision is the treatment of choice for isolated, painful glomuvenous malformations. We describe a case of a 7-year-old girl with multiple glomuvenous malformations

Quantum radiation in a plane cavity with moving mirrors

We consider the electromagnetic vacuum field inside a perfect plane cavity with moving mirrors, in the nonrelativistic approximation. We show that low frequency photons are generated in pairs that satisfy simple properties associated to the plane geometry. We calculate the photon generation rates for each polarization as functions of the mechanical frequency by two independent methods: on one hand from the analysis of the boundary conditions for moving mirrors and with the aid of Green functions; and on the other hand by an effective Hamiltonian approach. The angular and frequency spectra are discrete, and emission rates for each allowed angular direction are obtained. We discuss the dependence of the generation rates on the cavity length and show that the effect is enhanced for short cavity lengths. We also compute the dissipative force on the moving mirrors and show that it is related to the total radiated energy as predicted by energy conservation.Comment: 17 pages, 1 figure, published in Physical Review

Yield stability of soybean lines using addtive main effects and multiplicative interaction analysis - AMMI.

The grain yield of 27 soybean lines was evaluated at three locations (Anhembi, Areão and Esalq) in Piracicaba, State of São Paulo, Brazil, during four crop years to study the effect of environment (E) on the adaptability and stability of the lines (G) using additive main effects and multiplicative interaction analysis (AMMI). Effects of the G, E, and GE interaction were found to be significant and accounted for 51, 12, and 36% of the variation, respectively. The first and only significant interaction principal component axis (IPCA1) accounted for 26% of the sum of squares due to original GE interaction. This concentrated the largest proportion of the pattern of GE interaction. Environments associated with Anhembi and Esalq proved more favorable, while Areão contributed negatively to the grain yield. However, Anhembi and Areão were more predictable for the crop years. USP 93-5082 and USP 93-5243 lines combined high adaptability and stability

Magnitude da interação genótipos X ambientes para o caráter teor de óleo em linhagens de soja.

RESUMO: Com o objetivo de se estimar a interação genótipos x ambientes sobre o teor de óleo, avaliaram-se 28 linhagens de soja em três locais do município de Piracicaba (Anhembi, Areão e ESALQ), SP, com altitude de 540 m, 22 o 45' de latitude sul e 47 o 38' de longitude oeste, nos anos agrícolas de 1996/97, 1997/98, 1998/99 e 1999/00, totalizando 12 ambientes. O delineamento experimental utilizado foi o de blocos completos casualisados com duas repetições, estratificadas em conjuntos experimentais com quatro testemunhas comuns. A parcela experimental correspondeu a quatro fileiras de 5,0 x 0,5 m, avaliando-se os 4 m centrais das duas fileiras intermediárias de cada parcela. Pelos resultados obtidos pode-se evidenciar significância para os efeitos de genótipos, ambientes e interação genótipos x ambientes. A interação locais x anos contribuiu mais que os efeitos isolados de locais e anos para a variação ambiental, enquanto a interação genótipos x anos foi responsável pela maior parte da interação genótipos x ambientes. Destacaram-se as linhagens USPs 93-1188, 93-1024, 93-1042, 93-1043, 93-1044, 93-1012, 94-1195 e 94-1203, com teores de óleo acima de 22%. Na seleção de linhagens para estabilidade e adaptabilidade do teor de óleo no município de Piracicaba, SP, deve-se considerar os testes realizados em mais de um ano, com o propósito de amenizar os efeitos da interação genótipos x ambientes e obter maior garantia na recomendação de cultivares. Termos para indexação: comportamento genotípico, Glycine max, resposta ambiental, variação fenotípica. ABSTRACT: With the objective of estimating the magnitude of the genotype x environment interaction on the oil content, twenty eight soybean lines were evaluated in three location (Anhembi, Areão and Esalq) of Piracicaba, state of São Paulo, Brazil, at 540 m of altitude, 22 o 45' South latitude, and 47 o 38' West longitude, during the agricultural years of 1996/ 97, 1997/98, 1998/99 and 1999/00, totalizing 12 environments. A randomized complete block experiment was designed, with two replications stratified in experimental sets with four common checks. The experimental plot corresponded to four rows 5,0 x 0,5 m, where the four central meters of the two intermediate rows were evaluated. The results evidenced that significative effects were detected for genotypes, environments and genotype x environment interaction. The locations x years interaction contributed more than the effects isolated of locations and years for the environmental variation, while the genotypes x years was responsible for most of the genotype x environment interaction. USP 93-1188, 93-1024, 93-1042, 93-1043, 93-1044, 93-1012, 94-1195 and 94-1203 presented superiority, with oil percentage above 22%. In the selection of lines for stability and adaptability of the oil content in Piracicaba, SP, trials conducted in more than one year should be considered, with the purpose to decrease the effects of the genotype x environment interaction and obtain larger reliability in the recommendation of cultivars. Index terms: genotypic behavior, Glycine max, environmental response, phenotypic variation

Study od a Slice at +9 to +15 degrees of Declination: I. The Neutral Hydrogen Content of Galaxies in Loose Groups

We examine the H1 content of spiral galaxies in groups by using a catalog of loose groups of galaxies identified in a magnitude limited sample m < 15.7 spanning the range 8 h to 18 h in right ascension and +9 to +15 in declination. The redshift completeness of the galaxy sample is ~95%. No significant effect of H1 depletion is found, although there may be a hint that the earliest type spirals are slightly deficient.Comment: 10 pages, Latex, 3 tables, 5 figures, to appear in the Astronomical Journa

Theory of Optical Tweezers

We derive a partial-wave (Mie) expansion of the axial force exerted on a transparent sphere by a laser beam focused through a high numerical aperture objective. The results hold throughout the range of interest for practical applications. The ray optics limit is shown to follow from the Mie expansion by size averaging. Numerical plots show large deviations from ray optics near the focal region and oscillatory behavior (explained in terms of a simple interferometer picture) of the force as a function of the size parameter. Available experimental data favor the present model over previous ones.Comment: 4 pages, 3 figure