36 research outputs found
Structural and nonlinear optical properties of as-grown and annealed metallophthalocyanine thin films
The paper presents the Third Harmonic Generation investigation of four metallophtalocyanine (MPc, M = Cu, Co, Mg and Zn) thin films. The investigated films were fabricated by Physical Vapor Deposition in high vacuum onto quartz substrates. MPc thin films were annealed after fabrication in ambient atmosphere for 12 h at the temperature equal to 150 °C or 250 °C. The Third Harmonic Generation spectra were measured to investigate the nonlinear optical properties and their dependence on the structure of the thin film after the annealing process. This approach allowed us to determine the electronic contribution of the third-order nonlinear optical susceptibility χ< 3 >elec of these MPc films and to investigate two theoretical models for explanation of the observed results. We find that the annealing process significantly changes the optical and structural properties of MPc thin films
Multiproxy study of anthropogenic and climatic changes in the last two millennia from a small mire in central Poland
The Żabieniec kettle-hole is the first peatland in central Poland analysed quantitatively with four biotic proxies (plant macrofossils, pollen, testate amoebae and chironomids) in order to reconstruct past environmental change. Palaeoecological data were supported by historical and archaeological records. We focused on autogenic vegetation change and human impact in relation to climatic effects. The aims of our study were: (a) to describe the development history of the mire during the last 2000 years, (b) to date and reconstruct the anthropogenic land-use changes, and (c) to discuss a possible climatic signal in the peat archive. The combination of proxies revealed dramatic shifts that took place in the peatland since the Roman Period. Żabieniec was a very wet telmatic habitat until ca AD 600. Then the water table declined and the site transformed into a Sphagnum-dominated mire. This dry shift took place mainly during the Early Medieval Period. Human impact was gradually increasing and it was particularly emphasized by deforestation since AD 1250 (beginning of the Late Medieval Period). Consequently, surface run-off and aeolian transport from the exposed soils caused the eutrophication of the mire. Furthermore, chironomids and testate amoebae reveal the beginning of a wet shift ca AD 1350. Openness considerably increased in the Late Medieval and the Modern Periods. The highest water table during the last 1000 years was recorded between AD 1500 and 1800. This wet event is connected with deforestation but it could be also associated with the Little Ice Age. Our study shows plant succession in the Żabieniec peatland, which can be explained with the recent landscape transformation. However, such changes are also possibly linked with the major climatic episodes during the last two millennia, such as the Medieval Warm Period and the Little Ice Age
Diversity and distribution of Chironomidae (Insecta: Diptera) of protected areas in North Tunisia
In North Africa seasonal streams called wadi are an unique habitats with serve hydrological and thermal regime. Non-biting midges take an important part of freshwater biodiversity in North Africa. We present new data on the distribution and diversity of Chironomidae in North Tunisia. Larvae, pupal exuviae and adult males of chironomids were collected from a various freshwater ecosystems from May 2005 till April 2006. The aim of this study was to recognize the pattern of midge diversity in North Tunisia to estimate ecological value of running waters in the region. In total, 79 taxa were identified. Nearly all of the taxa were typical representatives of the Palaearctic and Mediterranean complexes. The majority of the investigated sites belonged to the protected areas in North Tunisia, such as the Ichkeul National Park, the Kroumerie Mountains and the El Feija National Park, part of the Intercontinental Reserve of the Mediterranean Biosphere. Altitudinal zonation of the communities composition was found in the lowland (250 m a.s.l.) with maximum of 760 m. Whereas among the data 39 species are recorded from Tunisia for the first time, the species richness of Chironomidae is higher than previously estimated
Diversity and distribution of Chironomidae (Insecta: Diptera) of protected areas in North Tunisia
In North Africa seasonal streams called wadi are an unique habitats with serve hydrological and thermal regime. Non-biting midges take an important part of freshwater biodiversity in North Africa. We present new data on the distribution and diversity of Chironomidae in North Tunisia. Larvae, pupal exuviae and adult males of chironomids were collected from a various freshwater ecosystems from May 2005 till April 2006. The aim of this study was to recognize the pattern of midge diversity in North Tunisia to estimate ecological value of running waters in the region. In total, 79 taxa were identified. Nearly all of the taxa were typical representatives of the Palaearctic and Mediterranean complexes. The majority of the investigated sites belonged to the protected areas in North Tunisia, such as the Ichkeul National Park, the Kroumerie Mountains and the El Feija National Park, part of the Intercontinental Reserve of the Mediterranean Biosphere. Altitudinal zonation of the communities composition was found in the lowland (250 m a.s.l.) with maximum of 760 m. Whereas among the data 39 species are recorded from Tunisia for the first time, the species richness of Chironomidae is higher than previously estimated
Optimisation of 2,3-butanediol production by Bacillus licheniformis NCIMB 8059 strain using response surface method
W pracy wykorzystano metodę płaszczyzny odpowiedzi w celu zoptymalizowania biosyntezy 2,3-butanodiolu przez szczep Bacillus licheniformis NCIMB 8059. Oceniono wpływ stężenia ekstraktu drożdżwego oraz jonów CH3COO", Fe2+i Mn2+ na końcową zawartość 2,3-butanodiolu w płynie pohodowlanym. Doświadczenie optymalizacyjne zaprojektowano w oparciu o plan D-optymalny obejmujący 25 wariantów hodowli. Zaobserwowano istotny (p < 0,05) wpływ stężenia ekstraktu drożdżowego oraz jonów CH3COO" i Mn2+na syntezę diolu. Na podstawie analizy statystycznej uzyskano optymalne wartości analizowanych zmiennych, wynoszące (g-dm3): ekstrakt drożdżowy - 4, CH3COONH4- 4, FeS04-7H20 - 0,1 oraz MnS04-H20 - 0,3, które odpowiadały końcowemu stężeniu 2,3-butanodiolu na poziomie 8,9 g-dm-3.Response surface method was used in this work in order to optimise the biosynthesis of 2,3-butanediol by strain Bacillus licheniformis NCIMB 8059. The effect of yeast extract and concentration of CH3COO", Fe2+and Mn2+ ions was evaluated on the final level of 2,3-butanediol in fermentation broth. The optimisation experiment was planned according to D-optimal design and consisted of 25 runs. Obtained results showed significant influence (p < 0,05) of the yeast extract, CH3COO" and Mn2+ concentration on the studied process. On the basis of statistic analysis, optimal values of analyzed variable were determined as follows (g-dm3): yeast extract - 4, CH3COONH4 - 4, FeS04-7 HzO - 0,1, MnS04-H20 - 0,3, that corresponded to 8,9 g-dm-3 final 2,3-butanediol concentration
Ecological patterns of Chironomidae assemblages in Dynaric karst springs
Springs are one of important freshwater habitats in the Dynaric Mountains. Nevertheless,
there were no intensive studies on dipteran communities in the region. Here we present an
ecological analysis of Chironomidae communities recorded from a set of 27 springs along
the Cvrcka River mainstream (the Republic of Srpska, Bosnia and Herzegovina).
Environmental classification of Cvrcka springs divide them into three groups reflecting
the level of human impact. Chironomidae communities divide investigated springs into three
groups more dependent on bottom substrate quality. CCA indicates that the hard bottom and
altitude are primary (significant) factors determining midge assemblages. Secondary
factors influencing communities are oxygen concentration and conductivity. There are clear
differences in diversity and abundance in these three types of spring communities. Type II
aggregates natural sites for Cvrcka valley. Samples characterized by high abundance of
Chironomus seems to be an outliers in Cvrcka canyon. Eucrenon and
hypocrenon communities are distinct, but no differences in the diversity level or the
environmental assemblage relation were recorded for both mesohabitats. This study proves
that solely environmental classification of spring habitats reflects well human impact,
but invertebrate communities may not clearly follow general classification, reacting to a
set of natural and altered conditions