92 research outputs found
Interesting diatoms from a special habitat
The epiphytic diatoms of the soda ponds of bomb craters were sampled in 2014.
The small ponds (area: 7.1-86.5 m2, depth: 4 to 60 cm) are located in the northern
part of the Kiskunsåg National Park (47°7.403 'N, 19°8.187'E), near the village of
Apaj in Hungary. Their salinity ranges from fresh water to moderately saline levels
(conductivity of 1.3 to 7.1 mS cm-1). This area has patchy surface salinization,
because the flow pattern of groundwater results extensive surface salinization in
those discharge areas where the infiltrating freshwater does not superimpose the
upwelling saline water. The salts origin from the overpressured NaCl-type water
of the Pre-Neogene basement and the NaHCO3-type water of the Neogene
sediments. The ponds can be characterized by different areal extent, depth and
salinity, various conductivity, hydroperiod (1â9 months, the deepest ones do not
dry out in years with high amount of precipitation due to probably more or less
continuous supply by groundwater), plant coverage and width of macrophyte belt.
All of the ponds were sampled except for the ones with very short (shorter than
one month) hydroperiod.
A total of 80 diatom taxa, representing 33 genera, were identified in these ponds.
The genus Nitzschia was represented by the largest number of species (16),
followed by the genus Gomphonema with 9 taxa. IndVal analysis identified 15
species with significant indicator values for ponds. Some interesting, rare or new
diatoms for Hungarian flora have also been recorded, including Gomphonema
jadwigiae, Halamphora dominici, Navicula wiesneri, Nitzschia austriaca, N. vitrea,
Surirella peisonis
Nitzschia austriaca Hustedt: a characteristic diatom of Hungarian inland saline waters including a morphological comparison with the type material
A detailed scanning electron microscopic investigation was carried out to clarify the taxonomic status of a small sigmoid Nitzschia species, a potential indicator of Central European soda waters. We found this taxon to be one of the dominant epiphytic diatoms collected from sodic bomb crater ponds at Apaj (Hungary). The large population allowed for a morphometric comparison based on frustule ultrastructure with the type material of the most similar species, Nitzschia austriaca Hustedt that was originally described from a soda pan in the region. The results clearly demonstrated an overlap between the Apaj population and the type material of N. austriaca (based on NMDS analysis), therefore we argue that they represent the same taxon. An emended diagnosis of N. austriaca is given. Total suspended solids and total phosphorous proved to be the most important factors predicting the occurrence of the species, with possible interactive effects of conductivity and pH. We then expanded the distribution of the species by revisiting data originating from previous large-scale surveys targeting sodic habitats in Hungary. On the basis of our results, N. austriaca is a characteristic species for Central European soda waters, including the protected astatic soda pans, indicating their typical chemical and physical characteristics.</jats:p
THE EFFECTS OF ADDITIVES ON THE PYROELECTRIC PROPERTIES OF T. G. S.
Nous rĂ©sumons l'effet polaire permanent dĂ» Ă la substitution d'alanine L sur les propriĂ©tĂ©s pyroĂ©lectriques de T. G. S. Nous expliquons les effets observĂ©s au moyen d'un modĂšle dans lequel le "switching" ferroĂ©lectrique est gĂȘnĂ© par la perte de symĂ©trie due Ă la substitution d'une molĂ©cule. D'autres additifs actifs et passifs peuvent ĂȘtre proposĂ©s Ă partir de ce modĂšle.The permanent poling effects of L-alanine substitution on the pyroelectric properties of T. G. S. are summarized. The observations are explained in terms of a structural model in which ferroelectric switching is impeded by the lack of the required prototypic symmetry in the substituent molecule. Other active and passive additives may be proposed from the model
A new race of the little owl from Transylvania
Volume: 81Start Page: 51End Page: 5
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