Features of Trifolium rubens (Leguminosae) ontomorphogenesis in conditions of Ukraine

The necessary basis for studying the structure and dynamics of populations is an investigation of ontomophogenetic peculiarities and establishment of ontogenetic stages of individuals. Information about ontomorphogenesis is especially important for protected species of plants. The minimal amount of data on morphology of plants in the different periods of ontogenesis complicates plant identification and evaluation of population state conditions in nature and culture. Trifolium rubens L. is a perennial Central European plant listed in the Red Book of Ukraine as a rare species. The objective of this research is to analyze the peculiarities of ontomorphogenesis of T. rubens, to establish diagnostic signs of age stages and the sequence of their passage for identification of the multivariance of development. The results of the study on T. rubens ontomorphogeny at the M. M. Gryshko National Botanical Garden оf the National Academy of Sciences of Ukraine and in the natural population in Zakarpattya are represented in this article. The terms “age stage” and “age period” are used to describe the degree of ontogenetic development of individuals. Diagnostic features of the age periods: latent, pregenerative, generative and senile are established. Detailed morphological descriptions of plants in different stages of ontogenesis are presented. The study shows a multivariate development that reveals different sequences of passing ontogenesis stages by individuals and, accordingly, the rate of their aging and life expectancy. It was found that during the first year of vegetation the plants undergo two periods (latent and pregenerative) and 5 stages of ontogeny (latent, seedlings, juvenile, immature and virginile). The first bloom in plants appears mainly in the second year of vegetation. The research showed the change of the leaf blade shape in ontogeny from simple to compound. There is a difference in the pubescence of leaf parts, and leaf shape indicates that these features are age-old. It was concluded that the aboveground part of the immature, virginile, generative individuals during the flowering period of plants differ from subsenile and senile in shape and number of leaves. In the generative period of ontogeny in dense plantings or in the natural population, it is difficult to reliably determine the boundaries of an individual by the aboveground part. The correlation between vegetative shoots of different type and generative shoots in the individual or group of plants can be used as an indicator to estimate the ontogenetic status of a particular locus or population. Successful growth of T. rubens in culture outside the natural range indicates good prospects for its ex situ protection and the implementation of measures for repatriation and restoration of populations in nature. The data of the research may be used for evaluation of the age structure of T. rubens populations

Observation of total omnidirectional reflection from a one-dimensional dielectric lattice

We show that under certain conditions one-dimensional dielectric lattice possesses total omnidirectional reflection of incident light. The predictions are verified experimentally using Na3AlF6/ZnSe multilayer structure developed by means of standard optical technology. The structure was found to exhibit reflection coefficient more then 99% in the range of incident angles 0-86 (degree) at the wavelength of 632.8 nm for s-polarization. The results are believed to stimulate new experiments on photonic crystals and controlled spontaneous emission.Comment: 4 pages, 5 figures; submitted to Applied Physics

All-dielectric one-dimensional periodic structures for total omnidirectional reflection and partial spontaneous emission control

A remarkable property of one-dimensional all-dielectric periodic structures has recently been reported, namely a one-dimensional lattice can totally reflect electromagnetic wave of any polarization at all angles within a prescribed frequency region. Unlike their metallic counterpart, such all-dielectric omnidirectional mirrors are nearly free of loss at optical frequencies. Here we discuss the physics, design criteria and applications of the thin-film all-dielectric omnidirectional mirror. The experimental demonstration of the mirror is presented at optical frequencies.Comment: 6 pages, 9 figures; submitted to IEEE Journal of Lightwave Technolog

Constraints on transmission, dispersion, and density of states in dielectric multilayers and stepwise potential barriers with arbitrary layer arrangement

Normal-incidence transmission and dispersion properties of optical multilayers and one-dimensional stepwise potential barriers in the non-tunneling regime are analytically investigated. The optical paths of every constituent layer in a multilayer structure, as well as the parameters of every step of the stepwise potential barrier, are constrained by a generalized quarter-wave condition. No other restrictions on the structure geometry is imposed, i.e., the layers are arranged arbitrarily. We show that the density of states (DOS) spectra of the multilayer or barrier in question are subject to integral conservation rules similar to the Barnett-Loudon sum rule but ocurring within a finite frequency or energy interval. In the optical case, these frequency intervals are regular. For the potential barriers, only non-periodic energy intervals can be present in the spectrum of any given structure, and only if the parameters of constituent potential steps are properly chosen. Abstract The integral conservation relations derived analytically have also been verified numerically. The relations can be used in dispersion-engineered multilayer-based devices, e.g., ultrashort pulse compressors or ultracompact optical delay lines, as well as to design multiple-quantum-well electronic heterostructures with engineered DOS.Comment: 10 pages, 5 figures, to be submitted to PR

Josephson surface plasmons in spatially confined cuprate superconductors

In this work, we generalize the theory of localized surface plasmons to the case of high-Tc cuprate superconductors, spatially confined in the form of small spherical particles. At variance from ordinary metals, cuprate superconductors are characterized by a low-energy bulk excitation known as the Josephson plasma wave (JPW), arising from interlayer tunneling of the condensate along the c-axis. The effect of the JPW is revealed in a characteristic spectrum of surface excitations, which we call Josephson surface plasmons. Our results, which apply to any material with a strongly anisotropic electromagnetic response, are worked out in detail for the case of multilayered superconductors supporting both low-frequency (acoustic) and transverse-optical JPW. Spatial confinement of the Josephson plasma waves may represent a new degree of freedom to engineer their frequencies and to explore the link between interlayer tunnelling and high-Tc superconductivity

Coherently tunable third-order nonlinearity in a nanojunction

A possibility of tuning the phase of the third-order Kerr-type nonlinear susceptibility in a system consisting of two interacting metal nanospheres and a nonlinearly polarizable molecule is investigated theoretically and numerically. It is shown that by varying the relative inter-sphere separation, it is possible to tune the phase of the effective nonlinear susceptibility \chi^{(3)}(\omega;\omega,\omega,-\omega)$in the whole range from 0 to$2\pi$.Comment: 10 pages 5 figure

Bleak House. No. 12

https://scholarexchange.furman.edu/bleak-house/1011/thumbnail.jp