Daily variation in cellular content of UV-absorbing compounds mycosporine-like amino acids in the marine dinoflagellate Scrippsiella sweeneyae

Sudden exposure experiments to high PAR (photosynthetically available radiation) or high PAR+UVR (ultraviolet radiation) were conducted for the marine dinoflagellate Scrippsiella sweeneyae acclimated to either low PAR or high PAR to determine the induction of cellular mycosporine-like amino acid (MAA) in relation to photosynthesis status. When the exposure to high PAR (30.8 Wm(-2)) was provided at different time in the light period for S. sweeneyae acclimated to low PAR (7.7 Wm(-2)) which suppressed photosynthesis, S. sweeneyae could enhance the induction of MAA but it only occurred in the first half of the light period. When UVR exposure was provided for the culture acclimated to high PAR which enhanced photosynthesis, cellular MAA content did not increase during the entire light period, but displayed daily variation similar to the control for two and half days. Daily variation of cellular MAA content did not synchronized with that of cell volume and cellular chlorophyll a content. The individual MAAs also revealed similar daily variations with different phase, which increased for a few hours in the beginning of the light period, except for cellular palythine content. Thus the total cellular MAA content revealed daily variation with changing the relative composition within a few hours. As one of the biological protective strategies against harmful UVR in sunlight, the daily vertical migration in the bloom forming dinoflagellates might be accompanied by the daily variation of cellular MAA content for a photosynthesis at daytime.     

Combustion process in a spark ignition engine: analysis of cyclic peak pressure and peak pressure angle oscillations

In this paper we analyze the cycle-to-cycle variations of peak pressure p _max and peak pressure angle α _pmax in a four-cylinder spark ignition engine. We examine the experimental time series of p _max and α _pmax for three different spark advance angles. Using standard statistical techniques such as return maps and histograms we show that depending on the spark advance angle, there are significant differences in the fluctuations of p _max and α _pmax . We also calculate the multiscale entropy of the various time series to estimate the effect of randomness in these fluctuations. Finally, we explain how the information on both p _max and α _pmax can be used to develop optimal strategies for controlling the combustion process and improving engine performance.     

Clustering Coefficient of a Spatial Preferential Attachment Model

The clustering structure of a graph in a spatial preferential attachment model whose similarity to real-world networks has been shown in many aspects is considered. The behavior of the local clustering coefficient is studied. Namely, the asymptotic behavior of its average value over all graph vertices of a certain degree as the graph size tends to infinity is examined. This characteristic has not been previously analyzed in the SPA model, and it reflects the typical dependence of the clustering structure near some vertex on its degree in the graph. Additionally, it is shown that, with a high probability, there is a vertex for which the value of the clustering coefficient differs from its average.     

Hybrid photonics structures with grating and prism couplers based on ZnO waveguides

This paper presents the results of investigations concerning input-output systems of an electromagnetic wave in the visible and near visible spectrum for their application in structures of integrated optics. The input-output structures used in described planar optical waveguides are in a form of prism and grating couplers. The first part of the paper contains numerical analysis of grating couplers aiming at an optimization of their geometrical parameters, strictly — the depth of the grooves in the grating coupler. The second part presents the practical realization, as well as experimental tests of the planar optical waveguide with the hybrid input-output system. As the input system of the electromagnetic wave, a prism coupler was used, and in the case of the output system — a photonic structure with grating coupler was applied. The investigated planar wave guides with the input-output structures were made of a wide energy band gap semiconductor — zinc oxide (ZnO).     

Synthesis of a new class of highly fluorescent aryl-vinyl benzo[1,2-b:4,5-b′]difuran derivatives

The synthesis of 2-(2-arylvinyl)- and 2,6-di(2-arylvinyl)dibenzo[1,2-b:4,5-b′]furan derivatives for application in optoelectronics is described. Wittig reaction of the triphenylphosphonium bromides derived from diethyl 2,6-dimethylbenzofuro[5,6-b]furan-3,7-dicarboxylate with aryl aldehydes gave the products in 70-99% yield. The corresponding products derived from furfural and cinnamic aldehyde were also obtained. The prepared products reveal UV-Vis fluorescence with quantum yields, varying from 1% to 100%, and may be used as organic small molecule materials for organic light-emitting devices (OLED).     

Space and surface-state effects in multiphoton emission

We investigate multiphoton emission of electrons from solid surfaces in the presence of nonperturbative monochromatic laser fields. We study the dependence of transmission probabilities on surface states, the penetration depth of laser fields in solids and the size of the laser focus in vacuum. To this end we present a one-space-dimensional model which permits to study these problems and develop a numerically stable algorithm for solving the corresponding time-dependent Schrödinger equation.