A lower bound in Nehari's theorem on the polydisc

By theorems of Ferguson and Lacey (d=2) and Lacey and Terwilleger (d>2), Nehari's theorem is known to hold on the polydisc D^d for d>1, i.e., if H_\psi is a bounded Hankel form on H^2(D^d) with analytic symbol \psi, then there is a function \phi in L^\infty(\T^d) such that \psi is the Riesz projection of \phi. A method proposed in Helson's last paper is used to show that the constant C_d in the estimate \|\phi\|_\infty\le C_d \|H_\psi\| grows at least exponentially with d; it follows that there is no analogue of Nehari's theorem on the infinite-dimensional polydisc

Von Bezold assimilation effect reverses in stereoscopic conditions

Lightness contrast and lightness assimilation are opposite phenomena: in contrast, grey targets appear darker when bordering bright surfaces (inducers) rather than dark ones; in assimilation, the opposite occurs. The question is: which visual process favours the occurrence of one phenomenon over the other? Researchers provided three answers to this question. The first asserts that both phenomena are caused by peripheral processes; the second attributes their occurrence to central processes; and the third claims that contrast involves central processes, whilst assimilation involves peripheral ones. To test these hypotheses, an experiment on an IT system equipped with goggles for stereo vision was run. Observers were asked to evaluate the lightness of a grey target, and two variables were systematically manipulated: (i) the apparent distance of the inducers; and (ii) brightness of the inducers. The retinal stimulation was kept constant throughout, so that the peripheral processes remained the same. The results show that the lightness of the target depends on both variables. As the retinal stimulation was kept constant, we conclude that central mechanisms are involved in both lightness contrast and lightness assimilation

Composition Operators and Endomorphisms

If $b$ is an inner function, then composition with $b$ induces an endomorphism, $\beta$, of $L^\infty(\mathbb{T})$ that leaves $H^\infty(\mathbb{T})$ invariant. We investigate the structure of the endomorphisms of $B(L^2(\mathbb{T}))$ and $B(H^2(\mathbb{T}))$ that implement $\beta$ through the representations of $L^\infty(\mathbb{T})$ and $H^\infty(\mathbb{T})$ in terms of multiplication operators on $L^2(\mathbb{T})$ and $H^2(\mathbb{T})$. Our analysis, which is based on work of R. Rochberg and J. McDonald, will wind its way through the theory of composition operators on spaces of analytic functions to recent work on Cuntz families of isometries and Hilbert $C^*$-modules

Rigidity and Non-recurrence along Sequences

Two properties of a dynamical system, rigidity and non-recurrence, are examined in detail. The ultimate aim is to characterize the sequences along which these properties do or do not occur for different classes of transformations. The main focus in this article is to characterize explicitly the structural properties of sequences which can be rigidity sequences or non-recurrent sequences for some weakly mixing dynamical system. For ergodic transformations generally and for weakly mixing transformations in particular there are both parallels and distinctions between the class of rigid sequences and the class of non-recurrent sequences. A variety of classes of sequences with various properties are considered showing the complicated and rich structure of rigid and non-recurrent sequences

Biologia y perspectiva de microorganismos endófitos asociados a plantas

The endophyte bacteria inhabit plant tissues mainly in intercellular spaces, rarely in intracellular spaces and inside vascular tissues without causing symptoms of disease in plants. Debates on the origin of the endophyte bacteria and the form of penetration, besides the colonization mechanisms, consider the hypothesis that they were originated from seeds, microflora rizosphere of“phylloplane” or material used for plant propagation. The penetration in the plant might take place by stomas, wounds, emergence areas in lateral roots, allowing these bacteria to produce hydrolytic enzymes able to degrade the vegetables cell wall. Recent molecular studies on the diversity of endophyte bacteria have revealed a high affluence of phylotypes promoting the plant growth, suppressing phytopathogens, helping to remove contaminants, dissolving phosphate and contributing to the biological nitrogen assimilation. The objective of this review is to show the evolution, ecology, diversity, function and physiological and molecular techniques for the isolation of endophyte bacteria associated with plant tissuesLas bacterias endófitas residen en tejidos de las plantas, principalmente espacios intercelulares, raramente en espacios intracelulares y dentro de tejidos vasculares sin causar síntomas de enfermedad en la planta. Las discusiones sobre el origen de las bacterias endófitas y la forma de penetración, además de los mecanismos de colonización, consideran la hipótesis de que se originaron desde semillas, de la rizosfera, de microflora de filoplano o de material utilizado para la propagación vegetativa. La penetración en la planta puede ocurrir por estomas, heridas, áreas de emergencia de raíces laterales, siendo que estas bacterias pueden producir enzimas hidrolíticas capaces de degradar la pared celular de los vegetales. Estudios moleculares reciente sobre diversidad de bacterias endófitas han revelado una alta riqueza de filotipos, que promueven el crecimiento de las planta, suprimen fitopatógenos, ayudan a remover contaminantes, solubilizan fosfato y contribuyen a la asimilación biológica de nitrógeno. El objetivo de esta revisión es dar a conocer la evolución, ecología, diversidad, funcionalidad y técnicas fisiológicas y moleculares para el aislamiento de bacterias endófitas asociadas a tejidos de plantas

Middle Aging in Women: Patterns of Personality Change from the 30s to the 50s

This three-sample study focused on changes in four key features of women's personalities (identity, generativity, confident power, and concern about aging) over the course of middle age. Based on women's retrospective and concurrent feelings about their lives in their 30s, 40s, and 50s, scales were developed and validated for the four themes. We found that identity certainty, generativity, confident power, and concern about aging all were experienced as more prominent in middle age (the 40s) than in early adulthood (the 30s). We also found that these elements of personality were rated even higher in the 50s than the 40s. Scores seemed to be a function of age more than historical period or particular experiences in social roles. Scores on identity certainty, generativity, and confident power were positively related to well-being, while concern about aging was negatively related to well-being.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44636/1/10804_2004_Article_228798.pd

Multiplication and Composition in Weighted Modulation Spaces

We study the existence of the product of two weighted modulation spaces. For this purpose we discuss two different strategies. The more simple one allows transparent proofs in various situations. However, our second method allows a closer look onto associated norm inequalities under restrictions in the Fourier image. This will give us the opportunity to treat the boundedness of composition operators.Comment: 49 page

The Dirichlet-to-Robin Transform

A simple transformation converts a solution of a partial differential equation with a Dirichlet boundary condition to a function satisfying a Robin (generalized Neumann) condition. In the simplest cases this observation enables the exact construction of the Green functions for the wave, heat, and Schrodinger problems with a Robin boundary condition. The resulting physical picture is that the field can exchange energy with the boundary, and a delayed reflection from the boundary results. In more general situations the method allows at least approximate and local construction of the appropriate reflected solutions, and hence a "classical path" analysis of the Green functions and the associated spectral information. By this method we solve the wave equation on an interval with one Robin and one Dirichlet endpoint, and thence derive several variants of a Gutzwiller-type expansion for the density of eigenvalues. The variants are consistent except for an interesting subtlety of distributional convergence that affects only the neighborhood of zero in the frequency variable.Comment: 31 pages, 5 figures; RevTe

Does wage rank affect employees' well-being?

How do workers make wage comparisons? Both an experimental study and an analysis of 16,000 British employees are reported. Satisfaction and well-being levels are shown to depend on more than simple relative pay. They depend upon the ordinal rank of an individual's wage within a comparison group. “Rank” itself thus seems to matter to human beings. Moreover, consistent with psychological theory, quits in a workplace are correlated with pay distribution skewness