Nikolai N. Smirnov

A revision of the genus Camptocercus (Anomopoda, Chydoridae, Aloninae)

The genus Camptocercus is revised. Camptocercus streletskayae sp. n. is described from East Siberia. The status of other species is discussed on the basis of a standard set of morphological features, including the structure of the cephalic region, the post-abdomen and post-abdominal claw, the dorsal keel, denticles at the ventro-posterior angle of valve, and setae on the inner distal lobe of limb I. Geographical distribution of species of this genus is discussed. A key to the species of this genus is composed.

New and little known cladocerans (Crustacea : Anomopoda) from Southeastern Mexico

Mexico represents a transitional area in which two biogeographic regions meet. A survey of the cladocerans collected in true tropical waterbodies from the country revealed a diverse fauna. The environments examined included temporary pools in the forest, rivers, permanent lagoons and karstic sinkholes. New records or little known taxa include: Diaphanosoma brevireme, D. fluviatile, Pseudosida ramosa, Simocephalus mixtus, Onchobunops tuberculatus,Guernella raphaelis, Chydorus nitidilus, Notoalonacf. globulosa, Alonella brasiliensis and Leydigiopsis curvirostris. In contrast to high altitude systems, with clear nearctic affinity, the lowlands of southeastern Mexico showed a striking resemblance with the South and Central American cladoceran fauna. Apparently, orographic barriers control the distribution of the cladoceran taxa in this region.

Synthesis and photophysical properties of soluble polyimides and polyquinazolones containing side-chain chalcones or azo chromophores

Soluble aromatic and carboxyl- and hydroxyl-containing polyimides, mixed polyimides, and polyquinazolones of various chemical structures, as well as a series of new dicyanoazobenzene chromophores, are synthesized. From 20 to 80 mol % of chromophore groups are incorporated into side chains of the polymers. The thermal, photosensitive, and nonlinear optical properties (second-harmonic generation) of the chromophore-containing polymers are investigated. The polymers with covalently attached groups of the dye DR-13 or azo-derivatives of 4-phthalonitrile demonstrate the highest nonlinearity. The T g values of the polyimides vary from 165 to 215°C; their temperatures corresponding to 5% weight loss lie in the range 290–350°C; and the measured coefficients of second-harmonic generation, d 33, for a number of polarized films based on chromophore-containing polymers attain several tens of picometers per volt. The incorporation of chromophore groups into the side chains of the polymers causes an increase in the photosensitivity of polyimides by an order of magnitude relative to that of the parent polymers (S 0.1 = (3−4) × 105 cm2/J in the range of dye absorption).

Some littoral anomopods (Crustacea) from Central Amazonia

Samples collected in Central Amazonia contained 16 species of Chydoridae, 4 species of Macrothricidae and 1 species of Ilyocryptidae. A new chydorid,Celsinotum laticaudatum sp. nov. is described, clearly differing from Australian species of this genus. Variation ofAlona dentifera (Sars, 1901) is commented upon, as well as a peculiar specimen ofAlona.

Pleuroxus -like chydorids (Crustacea: Anomopoda) from South Africa, with the description of Dumontiellus africanus gen. n., sp. n.

Five species of Pleuroxus-like chydorids are found in new material from South Africa or are known from the literature. One species is here described as Dumontiellus africanus gen. n., sp. n., endemic to South Africa.

Reinstatement of the genus Paralona Sramek-Husek et al., 1962, and assessment of morphological variability in the Paralona pigra-group (Anomopoda: Chydoridae)

We studied the morphology of some members of the ‘Chydorus’ piger-group, using populations from Karelia (Russia), France, Germany, the Azores, Magadan (East Siberia), Newfoundland (Canada), Venezuela, Zambia, and Bolivia, and move Chydorus piger Sars, 1861 to the genus Paralona Sramek-Husek et al., 1962, which we redefine using traditional characters (first antenna with subapical and apical esthetascs, second antenna with only six setae, ventral valve rim fully setulated with setae in marginal position except between anterior bend and well-developed anterior flange), as well as structural features of the trunk limbs, especially 1 and 2. Chydorus and Pleuroxus are the nearest relatives of Paralona.The genus presently contains only the species P. pigra (Sars, 1861). This, however, shows considerable morphological variation and might therefore be composed of several related taxa, in need of a closer definition.

Temperature dependence and the dispersion of nonlinear optical properties of chromophore-containing polyimide thin films

Detailed investigations of the quadratic nonlinear response of a series of new polyimides with covalently attached chromophore DR13 are performed by the Maker fringes method in the range of fundamental wavelength from 850 to 1450 nm. Polymer films with thickness of 100–400 nm were spin-coated on glass substrates and corona poled. For these materials, the maximum values of the second harmonic generation coefficients d33 are 80–120 pm/V. A red shift of the nonlinear response dispersion with respect to the linear absorption spectrum was observed for the DR13 chromophore. The temperature dependences of linear absorption and nonlinear coefficients d33 for studied structures are observed. It was found that the temperature changes of the absorption spectra lead to appreciable contribution to the value of the nonlinear coefficient d33. The demonstrated high temperature stability (up to 120 °C) of chromophore-containing polyimide thin films makes it possible to eliminate the degradation of their nonlinear optical ...

Contributions to the Cladocera fauna from Papua New Guinea

Twenty-eight taxa of the Cladocera are identified in collections from Papua New Guinea, 17 being new records for New Guinea, bringing the total number of Cladocera taxa reported for this region to 39. Most of the taxa are circumtropical. One species (Sarsilatona papuana) is endemic to Papua New Guinea and northern Australia. The species list includes two species that are normally listed as Holarctic:Alonella nana andAlona rustica. Widespread genera such asDaphnia, Pleuroxus, Disparalona, Acroperus were strikingly absent from the Papua New Guinean material.

Nonlinear optical properties of chromophore-containing polyimides with covalently attached dyes

Spectral dependences of quadratic nonlinear coefficients of new chromophore-containing polyimides with covalently attached DR13 chromophore molecules are synthesized and studied by the second-harmonic generation method in the fundamental radiation wavelength from 800 to 1400 nm. The obtained record values of quadratic nonlinear coefficients are 80 to 120 pm/V. Dispersions of refractive indices and extinction coefficients in the spectral range from 400 to 800 nm are determined by spectral ellipsometry, resulting in the improved accuracy of nonlinear coefficients..

Streblocerus superserricaudatus sp. nov. from Venezuela

A new species of the genus Streblocerus is described from Venezuela and compared with European, Newfoundland and Australian specimens. The geographical distribution of the genus is discussed.