EFFECT OF CARBON NANOTUBES ON THE ELECTRICAL PROPERTIES OF THE POLYMERIC COMPOSITES

Experimental study of single-wall carbon nabotubes (CNT) effect on the electrical properties of polymeric composite materials based on epoxy matrix has been carried out. Direct-current (DC) as well as alternating-current (AC) electrical conductivity of nanocomposites with different CNT concentrations have been investigated in the temperature interval from 293 K to 373 K. Measurements of Seebeck coefficient confirm n-type conductivity of composite with CNTs. Percolation threshold of the composite material under study has been estimated. It has been found that addition of single-wall CNT at low concentration causes hysteresis of current-voltage characteristics and the temperature dependences of electrical conductivity as well as its anisotropy in the samples under study. No noticeable frequency dependence of the AC electrical conductivity has been found in the frequency range from 100 Hz to 300 kHz

Three New Species of Placoneis Mereschkowsky (Bacillariophyceae: Cymbellales) with Comments on Cryptic Diversity in the P. elginensis-Group

Using genetic markers 18S V4 rDNA and rbcL and morphological investigation of the diatom genus Placoneis, we described three new species. The new species, Placoneis baikaloelginensis sp. nov., Placoneis subundulata sp. nov., Placoneis neohambergii sp. nov. were isolated from Russia (Lake Baikal) and Vietnam (waterbodies of C&aacute;t Ti&ecirc;n National Park (Đồng Nai Province) and Kh&aacute;nh H&ograve;a Province). We examine relationships within the Cymbellales and show that the genera Placoneis, Paraplaconeis and Geissleria are phylogenetically independent. We discuss the importance of careful identification of strains used for phylogenetic analysis and we show the history of identification of several different Placoneis elginensis strains. After careful identification of Placoneis elginensis vouchers, we found that we have a few independent species. The question of cryptic or pseudocryptic species in this context is discussed.</p

Diversity of Silica-Scaled Chrysophytes in Central Vietnam

This paper focuses on the flora of scale-bearing chrysophytes from eight provinces located in the central part of Vietnam. Khanh Hoa, Phu Yen, Binh Dinh, Thua Thien Hue, Quang Tri, and Quang Binh provinces are located in the coastal area of Vietnam. Lam Dong and Dak Lak provinces represent mountain territories with an elevation of 500–2000 metres above sea level. In total, 212 water bodies of different origins were studied. Samples were obtained from swamp areas, lakes, rivers, reservoirs, ponds, and small temporary water bodies. In total, 76 taxa were identified by electron microscopic observations of samples. A total of 54 taxa were found in the mountainous provinces, while 73 were found in the coastal provinces. Of these, 51 species are common for both areas. The most diverse was the genus Mallomonas with 66 species, varieties, and forms; followed by Synura with 7 taxa; Chrysosphaerella with 2; and Spiniferomonas with 1. Seven taxa of the genus Mallomonas were not identified to the lower rank. All these unidentified specimens may potentially represent new species for science. Ten taxa are reported for the first time in Vietnam

Silica-Scaled Chrysophytes of Teletskoye Lake and Adjacent Area with a Description of a New Species from the Genus <i>Mallomonas</i>

The silica-scaled chrysophyte flora of some lakes and rivers of the Altai Mountains was investigated by means of electron microscopy. Teletskoye Lake; the Biya, Chulyshman, and Katun Rivers; and small lakes around the area were studied. A total of sixteen taxa were recorded, including eight belonging to Mallomonas, five to Synura, and three to Paraphysomonas. A revision of previously reported taxa of scaled chrysophytes in this region was carried out. One species new to science from the genus Mallomonas was found and described. Mallomonas altaica sp. nov. belongs to the section Striatae and is characterised by scales with ribs covering only the anterior part of the shield and a posterior flange almost completely covered with the secondary siliceous layer. This species was discovered only at Teletskoye Lake

Description of a New Species of the Genus Cryptomonas (Cryptophyceae: Cryptomonadales), Isolated from Soils in a Tropical Forest

A new species, Cryptomonas tropica sp. nov., is described from Cat Tien National Park (Vietnam) based on morphological and molecular data. Strains of the new species were isolated from soil, which is an unusual environment for photosynthetic cryptomonads. This species has elliptical cells in ventral view and a single plastid notched into several irregular lobes without microscopically visible pyrenoids. Phylogenetic relationships inferred from nuclear-encoded SSU, LSU, ITS2 rDNA and psbA cpDNA show that the new species forms an independent branch on the phylogenetic tree of the genus Cryptomonas. In all phylogenetic analyses, this lineage was sister to clades containing other small-celled, pyrenoid-less species: Cryptomonas erosa, C. parmana, C. macilenta, C. obovoidea and C. commutata. C. tropica has been observed in two distant localities in Cat Tien National Park

New forms of botanical collections of tropical and subtropical plants in Russia

Cultivation of tropical plants in conditions of protected soil has significant risks associated with the damages of technical communications, finance termination, human factor, etc. To provide continous preservation and sustainable development of the collections, we offer new approaches to keeping private and state botanical collections jointly. This can significantly improve communication between collectors and help reduce risks of degradation or death of the rarest plants. Each collection can be presented as a separate section – such sections can be combined into a cluster structure. We have identified three types of cluster collections – state, distributed and private. State cluster collections are still at the starting phase of their formation that are united by the Council of Botanical Gardens of Russia and the Information and Analytical System (IAS) "Botanical Collections of Russia"(http://garden.karelia.ru/look/ru, http://hortusbotanicus.ru). Distributed cluster collections are the most stable – most of their plants are kept in greenhouses of botanical gardens, and a small part in private collections; such collections are more resistant to global risks, they are interchangeable, extensive and mobile. The cluster of private collections allows to cover several mono-type amateur collections. Such kind of collections can be divided into parts and can be kept and preserved by several collectors. Distributed keeping of plant funds can be recommended to any botanical collections, including open-ground collections, in vitro, seed banks, herbariums, etc

Description of a New Species of the Genus <i>Cryptomonas</i> (Cryptophyceae: Cryptomonadales), Isolated from Soils in a Tropical Forest

A new species, Cryptomonas tropica sp. nov., is described from Cat Tien National Park (Vietnam) based on morphological and molecular data. Strains of the new species were isolated from soil, which is an unusual environment for photosynthetic cryptomonads. This species has elliptical cells in ventral view and a single plastid notched into several irregular lobes without microscopically visible pyrenoids. Phylogenetic relationships inferred from nuclear-encoded SSU, LSU, ITS2 rDNA and psbA cpDNA show that the new species forms an independent branch on the phylogenetic tree of the genus Cryptomonas. In all phylogenetic analyses, this lineage was sister to clades containing other small-celled, pyrenoid-less species: Cryptomonas erosa, C. parmana, C. macilenta, C. obovoidea and C. commutata. C. tropica has been observed in two distant localities in Cat Tien National Park

Diversity of Silica-Scaled Chrysophytes in the Steppe Zone of the Southern Urals with a Description of a New Species from the Genus <i>Mallomonas</i>

This paper is devoted to the study of the flora of silica-scaled chrysophytes in water bodies of the steppe zone of the Southern Urals (Russia). Twenty-four taxa were identified via scanning and transmission electron microscopy, twenty of which are representatives of the genus Mallomonas Perty, while four are species of the genus Synura Ehrenberg. In the course of the study, a species new to science from the genus Mallomonas, M. baturinae sp. nov., was described. This species belongs to the section Papillosae. The stomatocyst of M. doignonii was described. For the first time in Russia and for the third time since description, M. phasma and M. solea-ferrea var. irregularis were reported in the studied area. Here, their extended description is provided with illustrations of their scales in detail. Some rare taxa for the flora of Russia have been identified: M. doignonii, M. pillula f. exannulata, and M. pillula f. valdiviana. One taxon of the genus Mallomonas has not been identified to a species level and is probably a taxon new to science

Phylogenetic position of the diatom genus Geissleria Lange-Bertalot &amp; Metzeltin and description of two new species from Siberian mountain lakes

Two new Geissleria species from Siberian mountain lakes Baikal and Frolikha are described based on molecular and morphological data. The two new species are Geissleria baicalosimilis Kulikovskiy, Gusev, Andreeva & Annenkova sp. nov. and G. frolikhiensis Kulikovskiy, Gusev, Andreeva & Annenkova sp. nov. According to partial 18S rDNA and rbcL gene fragment analyses, Geissleria does not belong to the large catch-all genus Navicula as it was previously thought. Morphological features such as slit like areolae without hymenes, presence of one isolated pore near the central nodule and presence of props in areolae and an annulus structure support this conclusion. Plastid morphology of Geissleria species is typical for the Cymbellales, with one large chloroplast divided into two plates lying one against each valve, connected by a broad column. All of our data show that Geissleria is most closely to the genus Placoneis, with which they share naviculoid symmetry. Given these results, Geissleria should be included in the order Cymbellales