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Search Results: 1 - 10 of 1549 matches for " Petra Hna uková "
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Geochemical distribution and mobility of heavy metals in sediments of urban streams affected by combined sewer overflows
Petra Hna uková
Journal of Hydrology and Hydromechanics , 2011, DOI: 10.2478/v10098-011-0007-7
Abstract: This study was undertaken to assess the impact of combined sewer overflows (CSOs) on distribution and potential mobility of heavy metals in sediments of urban streams in Prague, Czech Republic. Contents of total and extractable heavy metals (Cu, Zn, Pb, Cd, Cr and Ni), mineralogical phases and other sediment properties were measured in 44 surficial sediment samples. Total metal concentrations were obtained after microwave-assisted digestion whilst extractable metal contents were obtained following a sequential extraction scheme (acid soluble, reducible, oxidisable and residual fraction). The multivariate statistics of cluster analysis was used to identify specific areas of contamination and to evaluate the impact of CSOs. The observed mobility order of metals was Cd > Zn > Ni > Cu > Pb > Cr. There was a considerable increase in Zn mobility and increase of Cu associated with the oxidisable fraction in the sediments below CSO discharges. Cd was revealed as the most mobile heavy metal with percentages of extraction of approximately 40-60% in acid soluble fraction. Pb was mainly found in reducible fraction associated with Fe/Mn (oxi)hydroxides, which is indicative of anthropogenic pollution. In terms of environmental significance, Cd and Zn can be particularly mobile and bioavailable under acidic conditions, because they are predominantly bound in labile fractions. However, potential changes of redox state and pH may remobilize the metals bound to carbonates, reducible, and/or organic matter.
Likelihood Inference of Non-Constant Diversification Rates with Incomplete Taxon Sampling
Sebastian H?hna
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0084184
Abstract: Large-scale phylogenies provide a valuable source to study background diversification rates and investigate if the rates have changed over time. Unfortunately most large-scale, dated phylogenies are sparsely sampled (fewer than 5% of the described species) and taxon sampling is not uniform. Instead, taxa are frequently sampled to obtain at least one representative per subgroup (e.g. family) and thus to maximize diversity (diversified sampling). So far, such complications have been ignored, potentially biasing the conclusions that have been reached. In this study I derive the likelihood of a birth-death process with non-constant (time-dependent) diversification rates and diversified taxon sampling. Using simulations I test if the true parameters and the sampling method can be recovered when the trees are small or medium sized (fewer than 200 taxa). The results show that the diversification rates can be inferred and the estimates are unbiased for large trees but are biased for small trees (fewer than 50 taxa). Furthermore, model selection by means of Akaike's Information Criterion favors the true model if the true rates differ sufficiently from alternative models (e.g. the birth-death model is recovered if the extinction rate is large and compared to a pure-birth model). Finally, I applied six different diversification rate models – ranging from a constant-rate pure birth process to a decreasing speciation rate birth-death process but excluding any rate shift models – on three large-scale empirical phylogenies (ants, mammals and snakes with respectively 149, 164 and 41 sampled species). All three phylogenies were constructed by diversified taxon sampling, as stated by the authors. However only the snake phylogeny supported diversified taxon sampling. Moreover, a parametric bootstrap test revealed that none of the tested models provided a good fit to the observed data. The model assumptions, such as homogeneous rates across species or no rate shifts, appear to be violated.
The time-dependent reconstructed evolutionary process with a key-role for mass-extinction events
Sebastian H?hna
Quantitative Biology , 2013,
Abstract: The homogeneous reconstructed evolutionary process is a birth-death process without observed extinct lineages. Each species evolves independently with the same diversification rates (speciation rate $\lambda(t)$ and extinction rate $\mu(t)$) that may change over time. The process is commonly applied to model species diversification where the data are reconstructed phylogenies, e.g., trees reconstructed from present-day molecular data, and used to infer diversification rates. In the present paper I develop the general probability density of a reconstructed tree under any time-dependent birth-death process. I elaborate on how to adapt this probability density if conditioned on survival of one or two initial lineages, or having sampled $n$ species and show how to transform between the probability density of a reconstructed and the probability density of the speciation times. I demonstrate the use of the general time-dependent probability density functions by deriving the probability density of a reconstructed tree under a birth-death-shift model with explicit mass-extinction events. I enrich this compendium by providing and discussing several special cases, including: the pure birth process, the pure death process, the birth-death process and the critical branching process. Thus, I provide here most of the commonly used birth-death models in a unified framework (e.g., same condition and same data) with common notation.
In vitro and in situ absorption studies of vasicine in rats
Ram HNA,Shirwaikar Annie,Shirwaikar A
Indian Journal of Pharmaceutical Sciences , 2007,
Abstract: Vasicine is a pyrralazoquinazoline monobasic alkaloid obtained from the plant Adhatoda zeylanica. In the current experiment, we have made an attempt to determine the sites of absorption for the bioactive component vasicine from the various segments of small intestine (duodenum, jejunum and ileum) and colon. Everted intestinal sac method was used to assess the in vitro absorption of vasicine. The absorption of standard vasicine, vasicine from methanol and ethanol extracts of vasaka from the small intestine of rats was studied using the Doluisio technique. Maximum absorption of 87.3±5.256% of vasicine was observed in the duodenal region, whilst the colon showed the minimum absorption of 42.6±7.314%. The jejunum and ileum showed 77.2±3.415% and 46.9±3.271% absorption of vasicine respectively. The luminal disappearance of vasicine by Doluisio technique was determined from the standard curve. Absorption of vasicine was found to be better from the ethanol extract than from the methanol extract. Standard vasicine has revealed steady absorption as evidenced by a typical sigmoidal curve. The absorption rate was found to be of the first order for the tested samples.
The Religiosity of Japanese Migrants in the Czech Republic  [PDF]
Petra Tlcimukova
Open Journal of Social Sciences (JSS) , 2014, DOI: 10.4236/jss.2014.21002
Abstract: This study examines the role of religion in lives of the Japanese migrants in the Czech Republic. Scholars have been dealing with issues concerning both the religiosity and migration for a long time. The contemporary sociology of religion offers various theoretical and methodological tools to approach both social phenomena; nevertheless, regarding the transformative character of both of them, it remains difficult to characterize the nexus of the various modes of religiosity and migration development. Based on critics of contemporary research on migrants religiosity, I propose a qualitative approach that builds upon the postulates of theories of transnationalism and draws on Jean-Claude Kaufmann’s method of understanding interviews. The method of gaining and analysing the interviews conducted with the Japanese living long-term in the Czech Republic allowed me to observe the process of religious identity construction, or in other words to uncover the deeper levels of claims concerning their relationship with religion. The results of my empirical investigation and analysis show that 1) not all migrants create transnational identities, 2) the method of understanding interview allowed some respondents to construct their own individualized and fragmented religious identities, 3) not all religious identities of migrants can be interpreted as transnational.
Effect of Cultural Differences in Reaction of Students to Ambiguous Art Stimulus  [PDF]
Petra Potmesilova, Petra Sobkova, Marcela Fojtikova Roubalova
Open Journal of Social Sciences (JSS) , 2014, DOI: 10.4236/jss.2014.211008
Abstract:

Reconstruction is one of the basic methods used in art therapy and the artphiletic approach to work with a client. The method of Reconstruction can be used in practice not only for development of imagination, but also as a means of obtaining information about the ways clients react to ambiguous stimuli. The present article compares reactions of students of Palacky University in Olomouc and students of Sichuan University at Chengdu to an ambiguous stimulus using the reconstruction method.

Physical Activity Improves Mental Rotation Performance  [PDF]
Petra Jansen, Stefanie Pietsch
Creative Education (CE) , 2010, DOI: 10.4236/ce.2010.11009
Abstract: Even there seemed to be general knowledge that physical activity enhanced spatial cognitive performance almost none experimental studies on this influence exist. For that the influence of physical activity on mental rotation per-formance is investigated in this study. Mental rotation is the ability to imagine how an object would look if rotated away from the original orientation. Two groups of 44 students of educational science each solved a psychometrical mental rotation task with three-dimensional block figures. After this, the participants of the physical activity group took part in a sport lesson, whereas the participants of the cognitive activity group attended an oral lesson of kinematics. Both lessons took 45 minutes. Thereafter, all participants solved the mental rotation task again. The results showed that the participants of the physical activity group improved their mental rotation performance whereas the participants of the cognitive activity showed no improvement.
Collective Actions in the European Union—American or European Model?  [PDF]
Verica Trstenjak, Petra Weingerl
Beijing Law Review (BLR) , 2014, DOI: 10.4236/blr.2014.53015
Abstract: Collective redress is a procedural mechanism that allows for reasons of procedural economy and efficiency of enforcement many similar legal claims to be combined into a single court action. Consumers and investors encounter problems with the enforcement of their rights through the individual redress, especially in times of the financial crisis. If a substantial number of harmed individuals decide not to pursue their, usually low, claims, the unduly gained profits of the opposite party can be extremely high. Thus, collective redress mechanisms can represent better option for consumers and investors, as their claims tend to be much less burdensome in case of the collective action. However, such mechanisms can trigger the abuse of the procedures, with the most commonly quoted threat being the example of American regulation of class actions. Negative characteristics of American model are the reasons that EU decided to shape its own concept of collective redress mechanisms. The binding act in this field in the EU is directive on injunctions for the protection of consumers’ interests; however, there is no binding act yet regarding compensatory actions. In June 2013, the European Commission published the Recommendation on common principles for injunctive and compensatory collective redress mechanisms in the Member States concerning violations of rights granted under Union Law. It is not binding on Member States, however, it can serve as a guideline to improve their existing legislations, especially the regulation of collective compensatory actions. In so doing, consumers and investors might be given the possibility to use more efficient mechanism to compensate the harm suffered.
The Relation between Performance and Flows of Mutual Funds: Case of the Croatian Fund Market  [PDF]
Darko Brborovic, Petra Posedel
Applied Mathematics (AM) , 2014, DOI: 10.4236/am.2014.519292
Abstract: With pre 2008 euphoria and present depression, inflows to open investment funds and outflows from it shaped general market conditions on the Croatian fund market. This article studies the relationship between performance of open ended investment funds and inflows (outflows) to them on Croatian funds data in an environment without long fund data history, with small number of funds and relatively illiquid underlying equity market. The results suggest that the driving forces behind funds’ flows encompass the combined influence of present month fund’s performance and persistency of past performances. At the end of our analysis we test the significance of the introduced explanatory variables on the data sets that include data for each particular fund. The significance of the introduced explanatory variables varies among different funds, although a general level of the explanatory power is maintained on average.
Non-monophyly and intricate morphological evolution within the avian family Cettiidae revealed by multilocus analysis of a taxonomically densely sampled dataset
Per Alstr?m, Sebastian H?hna, Magnus Gelang, Per GP Ericson, Urban Olsson
BMC Evolutionary Biology , 2011, DOI: 10.1186/1471-2148-11-352
Abstract: There are many topological incongruences among the single-locus trees, although none of these is strongly supported. The multi-locus tree inferred using concatenated sequences and the species tree agree well with each other, and are overall well resolved and well supported by the data. The main discrepancy between these trees concerns the most basal split. Both methods infer the genus Cettia to be highly non-monophyletic, as it is scattered across the entire family tree. Deep intraspecific divergences are revealed, and one or two species and one subspecies are inferred to be non-monophyletic (differences between methods).The molecular phylogeny presented here is strongly inconsistent with the traditional, morphology-based classification. The remarkably high degree of non-monophyly in the genus Cettia is likely to be one of the most extraordinary examples of misconceived relationships in an avian genus. The phylogeny suggests instances of parallel evolution, as well as highly unequal rates of morphological divergence in different lineages. This complex morphological evolution apparently misled earlier taxonomists. These results underscore the well-known but still often neglected problem of basing classifications on overall morphological similarity. Based on the molecular data, a revised taxonomy is proposed. Although the traditional and species tree methods inferred much the same tree in the present study, the assumption by species tree methods that all species are monophyletic is a limitation in these methods, as some currently recognized species might have more complex histories.In a study of large-scale relationships within the avian superfamily Sylvioidea, Alstr?m et al. [1] found, based on mitochondrial cytochrome b and nuclear myoglobin intron 2 sequence data, that two species of Cettia and one species each of Urosphena, Tesia, Abroscopus and Tickellia, and Orthotomus cucullatus formed a clade, well separated from a broad selection of other passerines. They pro
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