Number of results to display per page
Search Results
14972. Check- and Red List of bryophytes of the Czech Republic (2003)
- Creator:
- Kučera, Jan and Váňa, Jiří
- Type:
- article and TEXT
- Subject:
- checklist, Red List, threatened taxa, mosses, liverworts, hornworts, and Czech Republic
- Language:
- English
- Description:
- The second version of the checklist and Red List of bryophytes of the Czech Republic is provided. Generally accepted infraspecific taxa have been incorporated into the checklist for the first time. With respect to the Red List, IUCN criteria version 3.1 has been adopted for evaluation of taxa, and the criteria used for listing in the respective categories are listed under each red-listed taxon. Taxa without recent localities and those where extinction has not been proven are listed as a subset of DD taxa. Little known and rare non-threatened taxa with incomplete knowledge of distribution which are worthy of further investigation are listed on the so-called attention list. In total, 849 species plus 5 subspecies and 19 varieties have been accepted. 23 other historically reported species and one variety were evaluated as doubtful with respect to unproven but possible occurrence in the territory, and 6 other species with proven occurrence require taxonomic clarification. 43 taxa have been excluded from our flora compared to the last checklist version. 48.6 % of evaluated taxa have been listed in either of the Red List categories (EX (RE), CR, EN, VU, LR or DD), which is comparable to other industrialized regions of Central Europe.
- Rights:
- http://creativecommons.org/publicdomain/mark/1.0/
14973. Checking proportional rates in the two-sample transformation model
- Creator:
- Kraus, David
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- Neyman´s smooth test, proportional hazards, proportional odds, survival analysis, transformation model, and two-sample test
- Language:
- English
- Description:
- Transformation models for two samples of censored data are considered. Main examples are the proportional hazards and proportional odds model. The key assumption of these models is that the ratio of transformation rates (e. g., hazard rates or odds rates) is constant in time. A method of verification of this proportionality assumption is developed. The proposed procedure is based on the idea of Neyman's smooth test and its data-driven version. The method is suitable for detecting monotonic as well as nonmonotonic ratios of rates. Keywords:
- Rights:
- http://creativecommons.org/publicdomain/mark/1.0/ and policy:public
14974. Checklist and Red List of lichens of the Czech Republic
- Creator:
- Liška, Jiří, Palice, Zdeněk, and Slavíková, Štěpánka
- Type:
- article and TEXT
- Subject:
- biodiversity, checklist, Czech Republic, lichens, lichenized fungi, Red List, and threatened species
- Language:
- English
- Description:
- This first version of the Red List of lichens of the Czech Republic uses IUCN criteria version 3.1 for evaluating the species (no infraspecific taxa are included). The Red List is at the same time a new version of the checklist of lichens of the Czech Republic. Differences from the previous checklist published in the Catalogue of lichens of the Czech Republic in 1999 are: 98 species are excluded (non-lichenized fungi, species not documented in the Czech Republic, misidentifications, doubtful/dubious records and other errors) and nomenclatural changes are listed in the chapter on synonyms. In total, 1497 species of lichenized fungi (without lichenicolous and lichen-allied fungi) are included. Of these, 120 (8%) suspicious records and taxonomically problematic or not well explored taxa were not evaluated against the IUCN criteria (NE category). In total, 560 species (37.4%) are threatened: 130 (8.7%) are critically endangered (CR), 184 (12.3%) are endangered (EN) and 246 (16.4%) are vulnerable (VU). In addition, 140 species (9.4%) are extinct in the Czech Republic (RE category), 174 species (11.6%) are listed in the category near threatened (NT) and 190 (12.7%) in least concern (LC). In total, 313 species (20.9%) are listed as data deficient (DD) because insufficient data are available for a categorization.
- Rights:
- http://creativecommons.org/publicdomain/mark/1.0/
14975. Chegwidden, W. R., Carter, N. D., Edwards, Y. H. (ed.): The carbonic anhydrases: New horizons
- Creator:
- Květoň, J.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- enzymes
- Language:
- Multiple languages
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
14976. Chemical analysis of interplanetary dust particles with synchrotron radiation
- Creator:
- Antz, Ch., Bavdaz, M., Jessberger, E. K., Knöchel, A., and Wallenwein, R.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- chemical multielement analysis, interplanetary dust particles, and Synchrotron X-ray Fluorescence Analysis (SYXFA)
- Language:
- Czech
- Description:
- Two 10-μm interplanetary dust particles collected in the stratosphere, have been analyzed with X-ray fluorescence excited by white synchrotron radiation (SYXFA) at the HASYLAB (DESY) in Hamburg. The measured abundances of the minor and trace elements with 16 < Z < 76 are in good agreement with abundances determined by PIXE analysis [1] of the same particles. The results demonstrate that SYXFA is indeed a powerful non-destructive technique for multi-element analysis of micron-sized samples. Moreover we find that the combined application of two such techniques, SYXFA and PIXE, to the same valuable particle lends high credibility to the results.
- Rights:
- http://creativecommons.org/publicdomain/mark/1.0/ and policy:public
14977. Chemical cues mediating aphid location by natural enemies
- Creator:
- Michaud, J.P., Hatano, Eduard, Kunert, Grit, and Weisser , W.
- Type:
- article, model:article, and TEXT
- Subject:
- Aphid, natural enemies, host selection, semiochemicals, and infochemical
- Language:
- English
- Description:
- There is increasing evidence that chemical cues play a pivotal role in host selection by the natural enemies of aphids. We use Vinson's (1976) division of the host selection process into habitat location, host location and host acceptance for both parasitoids and predators and review what is known about the role of semiochemicals in aphid selection by natural enemies. For habitat location (i.e. detection of the host plant), volatiles emitted by plants after aphid attack have been described for a number of plant-aphid interactions. These synomones indicate not only the presence of an aphid host plant to the predator or parasitoid, but also the presence of aphids. Volatiles emitted from undamaged host plants are often attractive to aphid parasitoids, but less so for predators. Host location by the natural enemy on the food plant is guided by semiochemicals that mostly originate from the aphids, in particular aphid alarm pheromone, honeydew, or the smell of the aphid itself. Host acceptance is guided by contact chemicals for both predators and parasitoids. In parasitoids, host recognition may be based on visual cues or on contact chemicals on the aphid's cuticle, whereas host acceptance is ultimately based on as yet unknown substances within the aphid's hemolymph. While it appears that many predators and parasitoids are attracted to the same semiochemicals, synergistic and antagonistic interactions among chemical substances have only rarely been investigated. More research into model systems is needed, not only to identify important semiochemicals, but also to determine their range of attraction. Recent progress in the development of analytical techniques has created new opportunities to improve our understanding of the chemical ecology of aphid-natural enemy interactions in the coming years.
- Rights:
- http://creativecommons.org/publicdomain/mark/1.0/ and policy:public
14978. Chemical defence of the warningly coloured caterpillars of Methona themisto (Lepidoptera: Nymphalidae: Ithomiinae)
- Creator:
- Massuda, Kamila F. and Trigo, José R.
- Type:
- article, model:article, and TEXT
- Subject:
- Aposematism, Brunfelsia uniflora, Camponotus crassus, Gallus gallus domesticus, learning, Lycosa erythrognatha, predation, Solanaceae, and unpalatability
- Language:
- English
- Description:
- The caterpillars of the butterfly Methona themisto (Nymphalidae: Ithomiinae) are conspicuously coloured and feed exclusively on Brunfelsia uniflora (Solanaceae), a plant that is rich in secondary plant substances, which suggests the caterpillars are chemically protected against predators. Results of experiments indicate that predators determine the survival of Methona themisto caterpillars in the field and laboratory bioassays that this organism is eaten by ants and spiders but not chicks. Both the conspicuous orange and black striped colouration and chemical compounds of Methona themisto caterpillars seem to be related to protection against predation by visually hunting predators. Chicks ate proportionally more of the cryptically coloured 1st instar caterpillars than of the conspicuously coloured later instar caterpillars. That Methona themisto caterpillars are chemically defended is supported by the activity of the dichloromethanic extract of 5th instars in preventing predation by chicks. Caterpillars of Methona themisto are aposematic as they are both (1) unpalatable, and (2) their warning signal is easily recognized by potential predators. Chicks learned to avoid the aposematic 3rd or 5th instar caterpillars after one encounter. Mealworms painted to look like caterpillars were also rejected by chicks that had previously encountered Methona caterpillars. Naïve chicks did not avoid eating the painted mealworms, which indicates they do not innately avoid this specific colour pattern.
- Rights:
- http://creativecommons.org/publicdomain/mark/1.0/ and policy:public
14979. Chemical evolution of the galaxy and comets
- Creator:
- Vanýsek, V.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- space research, chemical evoluton, and comets
- Language:
- Czech
- Description:
- A possible influence of comets on the growth of heavy elements abundance suggested several years ago by Tinsley and Cameron is shortly reviewed. Such an effect would be significant if the formation of comets produce cometary material equivalent to 0.01 - 0.02 M per one solar mass. In the view of current hypothesis of the formation and structure of cometary nuclei the role of comets should be considered as one of the possible moderators of the Z value variation during the chemical evolution of our Galaxy.
- Rights:
- http://creativecommons.org/publicdomain/mark/1.0/ and policy:public
14980. Chemical stability of assembly pheromone of argasid ticks (Ixodoidea: Argasidae)
- Creator:
- Dusbábek, František, Zahradníčková, Helena, and Šimek, Petr
- Format:
- Type:
- model:internalpart and TEXT
- Subject:
- assembly pheromone, guanine, xanthine, hypoxanthine, uric acid, tick excreta, purine degradation, Argas persicus, and Omithodoros moubata
- Language:
- English
- Description:
- Chemical stability and aggregation activity of assembly pheromone of argasid ticks and its synthetic purine analogues were studied during long-lasting storage at room temperature as the potential components of attractant/acaricide mixtures. Guanine spherules from dry excreta of Omithodoros moubata Murray, 1877 were very stable in their chemical composition and did not suffer from purine degradation. However, an intensive purine conversion into uric acid occurred in samples of the fluid of the excreta of Argas persicus (Oken, 1818) and to a lesser extent also in an artificial mixture of synthetic guanine, xanthine and hypoxanthine in saline. The presence of bacteria Bacillus sp. and the moulds Talaromyces flavus (syn. Pénicillium dangeardii) and Aspergillus carbonarius, isolated from some samples, might explain the enzymic degradation of purines. The suspension of guanine hydrochloride in saline or in saline with ethanol (1 : 1 v/v) as a potential acaricide solvent, and with diatomaceous earth as the pheromone carrier, was very stable and no guanine degradation occurred. This proved to be suitable for potential use mixed with acaricides for tick control. The assembly of A. persicus males, on most of the substrates tested, was very high up to day 77 of experiment but decreased significantly on day 114-119 in samples of synthetic analogue of assembly pheromone variant 1 in which the absolute amount of guanine in solutions strongly decreased or disappeared completely.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public