Showing papers by "Academy of Sciences of the Czech Republic published in 1998"
TL;DR: A mean-square error lower bound for the discrete-time nonlinear filtering problem is derived based on the van Trees (1968) (posterior) version of the Cramer-Rao inequality and is applicable to multidimensional nonlinear, possibly non-Gaussian, dynamical systems.
Abstract: A mean-square error lower bound for the discrete-time nonlinear filtering problem is derived based on the van Trees (1968) (posterior) version of the Cramer-Rao inequality. This lower bound is applicable to multidimensional nonlinear, possibly non-Gaussian, dynamical systems and is more general than the previous bounds in the literature. The case of singular conditional distribution of the one-step-ahead state vector given the present state is considered. The bound is evaluated for three important examples: the recursive estimation of slowly varying parameters of an autoregressive process, tracking a slowly varying frequency of a single cisoid in noise, and tracking parameters of a sinusoidal frequency with sinusoidal phase modulation.
1,333 citations
TL;DR: Theoretical models of meteoroid interaction with the Earth's atmosphere are given and applied to observational data as discussed by the authors, including radar observations, spectroscopic observations, experiments with artificial meteors and different types of meteor sounds.
Abstract: Meteoroids can be observed at collision with the Earth's atmosphere as meteors. Different methods of observing meteors are presented: besides the traditional counts of individual events, exact methods yield also data on the geometry of the atmospheric trajectory; on the dynamics and ablation of the body in the atmosphere; on radiation; on the spectral distribution of radiation; on ionization; on accompanying sounds; and also data on orbits. Theoretical models of meteoroid interaction with the atmosphere are given and applied to observational data. Attention is paid to radar observations; to spectroscopic observations; to experiments with artificial meteors and to different types of meteor sounds. The proposed composition and structure of meteoroids as well as their orbits link them to meteorites, asteroids and comets. Meteor streams can be observed as meteor showers and storms. The rate of influx of meteoroids of different sizes onto Earth is presented and potential hazards discussed.
752 citations
TL;DR: Molecular mechanisms of the melatonin effects are not clear but may involve at least two parallel transduction pathways, one inhibiting adenylyl cyclase and the other regulating phospholipide metabolism and [Ca2+]i.
Abstract: Vanecek, Jiri. Cellular Mechanisms of Melatonin Action. Physiol. Rev. 78: 687–721, 1998. — The pineal hormone melatonin is involved in photic regulations of various kinds, including adaptation to l...
567 citations
TL;DR: It is shown that the targeted control element adopts an intrastrand fold-back DNA tetraplex, which requires potassium ions for stability in vitro, and proposed a transcription initiation mechanism that explains how anti-gene therapy silence c-myc at the molecular level.
Abstract: The c-myc oncogene is one of the most commonly malfunctioning genes in human cancers, and is an attractive target for anti-gene therapy. Although synthetic oligonucleotides designed to silence c-myc expression via one of its major control elements function well in vitro, their mode of action has been indefinite. Here we show that the targeted control element adopts an intrastrand fold-back DNA tetraplex, which requires potassium ions for stability in vitro. We believe formation of the tetraplex is important for c-myc activation in vivo, and propose a transcription initiation mechanism that explains how anti-gene therapy silence c-myc at the molecular level.
541 citations
TL;DR: Collembola have well differentiated ecomorphological life-forms and feeding guilds which enable the functional role that Collembolas play in ecosystems to be recognised in some degree.
Abstract: More than 6500 species of Collembola are known from throughout the world and these are only a small part of the still undescribed species. There are many checklists and catalogues of Collembola for smaller territories and entire continents. Biogeographical analyses have been made for some genera and smaller territories. The most serious problems for a global biogeographical analysis is the lack of enough records from immense territories of all continents. Local biodiversity of Collembola can be very high, reaching over 100 species in small mountain ranges. Sampling methods do not impede documenting biodiversity on a global scale. Collembola have well differentiated ecomorphological life-forms and feeding guilds which enable the functional role that Collembola play in ecosystems to be recognised in some degree. Collembola play an important role in plant litter decomposition processes and in forming soil microstructure. They are hosts of many parasitic Protozoa, Nematoda, Trematoda and pathogenic bacteria and in turn are attacked by different predators. They utilise as food Protozoa, Nematoda, Rotatoria, Enchytraeidae, invertebrate carrion, bacteria, fungi, algae, plant litter, live plant tissues, and some plant pathogens. Soil acidification, nitrogen supply, global climate change and intensive farming have greatly impacted collembolan diversity.
538 citations
TL;DR: In this paper, the authors provided quantitative information on the occurrence of alien species in Central European cities and analyzed factors determining the richness of alien and native floras in this habitat type.
Abstract: The paper provides quantitative information on the occurrence of alien species in Central European cities and analyses factors determining the richness of alien and native floras in this habitat type. Data for 54 cities (25 Polish, 24 German, 4 Czech and 1 Austrian) were gathered, and the representation of archaeophytes (i.e. aliens introduced before 1500 ad), neophytes (introduced after that date) and native species was expressed. In an average city there were 87.4 archaeophytes (15.2% of the city flora) and 172.4 neophytes (25.2%) giving a total of 259.7 for alien species (40.3%). The number of native species averaged 386.5. The numbers of species in each category of immigration status increased significantly with city size. For neophytes, the species-area relationship showed a higher slope (0.49) on log–log axes than for both archaeophytes (0.16) and native species (0.30). Not only the number, but also the relative contribution of neophytes to the total flora, increased with city size, indicating that neophytes are the group which are most closely associated with human activity. On the other hand, archaeophytes were better represented in smaller cities, as they were confined to rural environment. A step-wise multiple regression was used to test for environmental variables acting as significant predictors, and explained between 40 and 65% of variation in the species numbers for particular categories of immigration status, providing the best fit for neophytes. City size was the best predictor for each characteristic, except of the proportion of total aliens, where the percentage of explained variability was low (8.2%), with latitude being the only significant predictor. Temperature was another highly significant predictor for the number of archaeophytes and total aliens, reflecting the origin of aliens in warmer areas. There was an effect of region on some flora characteristics. Polish cities had significantly higher proportion of archaeophytes and of total aliens than German cities. It is concluded that the occurrence of native and alien species in urban floras follows rather different pattern.
454 citations
TL;DR: The results suggest the “EPR effect” in solid tumor primarily arises from in the difference in clearance rate between the solid tumor and the normal tissues after initial penetration of the polymers into these tissues.
Abstract: The objective of this study was to investigate the molecular weight (MW) and time-dependence of the phenomenon termed "the enhanced permeability and retention" (EPR) effect in solid tumor, in particular to determine and define the early phase accumulation of macromolecules in tumor and normal tissues and the relationship between blood concentration and tissue clearance. As a model, radioiodinated N-(2-hydroxypropyl)methacrylamide (HPMA) copolymers of MW ranging from 4.5 K to 800 K were administered i.v. to mice bearing sarcoma 180 tumor. Within 10 min all HPMA copolymers accumulated effectively in the tumor regardless of MW (1.0-1.5% of injected dose per g of tumor). However, higher MW copolymers (> 50 K) showed significantly increased tumor accumulation after 6 h, while the lower MW copolymers (< 40 K) were cleared rapidly from tumor tissue due to rapid diffusion back into the bloodstream. Blood clearance was also MW-dependent; the lower MW copolymers displayed rapid clearance, with kidney radioactivity of the copolymers of MW < 20 K representing 24% of injected dose per g kidney at 1 min after i.v. administration. Within 10 min these copolymers passed through the kidney and were excreted in the urine. Higher MW copolymers consistently showed kidney levels of 3-5% dose per g kidney in the early phase with no time-dependent accumulation in kidney. There was also no progressive accumulation in muscle or liver, regardless of polymer MW. These results suggest the "EPR effect" in solid tumor primarily arises from in the difference in clearance rate between the solid tumor and the normal tissues after initial penetration of the polymers into these tissues.
444 citations
TL;DR: The principles and practice of sampling are described in relation to the main habitat types encountered in Europe, and it is hoped that these provide a framework that can be adapted to most river types in Europe.
Abstract: Many methods for using diatoms for routine monitoring of water quality have been developed in Europe and, in some countries, these are being used to enforce environmental legislation. In order to facilitate their wider use, particularly with respect to European Union legislation, steps are being taken to harmonize methodology. In this paper, the principles and practice of sampling are described in relation to the main habitat types encountered in Europe. Although details of methods and sampling programmes have to be tailored to particular circumstances and the overall objectives of the monitoring, a number of generalizations can be made. Where available, rocks and other hard surfaces are the preferred substrates and methods for sampling these are described. If such substrata are not available, then introduced ('artificial') substrata have many applications. Various types of introduced substrata can be used successfully, so long as some basic precautions are described. Other types of substrata such as macrophytes and macroalgae may also be useful under certain circumstances, although there is less consensus in the literature on the most appropriate methods, and of the validity of comparisons between indices computed from epiphytic and epilithic communities. When designing surveys, it is recommended that as far as possible, extremes of non-water quality factors (e.g. shade, current speed, etc) are avoided, unless these are characteristic of the system under investigation. Detailed guidelines for sampling epilithon are described. Along with the recommendations for sampling other substrata, it is hoped that these provide a framework that can be adapted to most river types in Europe.
442 citations
TL;DR: The correlation between the geometries of small-molecule crystal structures and the metal-binding sites in metalloproteins was investigated and it follows that the octahedral arrangement is preferred by Co2+ and Ni2+, tetrahedral by Zn2+, square planar by Cu2+.
369 citations
TL;DR: Alien floras of 26 regions distributed over the globe and covering a variety of habitats were analysed to assess the role of plant families and higher taxonomic units and there is no simple morphological, physiological or ecological character that could be generally related to the invasiveness of the family.
Abstract: Alien floras of 26 regions distributed over the globe and covering a variety of habitats were analysed to assess the role of plant families and higher taxonomic units. Alien species were recorded in 164 families. The highest concentration of families containing aliens was recorded in Caryophyllidae (namcly Caryophyllales) and Asteridae. The largest families (Gramineac, Compositae. Leguminosae, Cruciferae) contribute most to the total number of alien species in local floras. In relative tersm, i.e. related to the species pool available as potential invaders. the best invaders belong to Papaveraccac. Chenopodiaceae, Amaranthaceae, Cruciferae, Polygonaceae and Gramineae. Some families depend largely on deliberate introductions of crops and ornamental species. while the representation of others is enhanced when only accidental introductions are considered. The adventive distribution of families, i.e. the regions into which their members tend to invade, reflects their natural distribution. Particular families tend to invade in the regions with conditions similar to those from their native area. The most successful families possess specific features that could be attributed to their invasiveness. Ilowever, there is no simple morphological, physiological or ecological character that could be generally related to the invasiveness of the family.
321 citations
Book•
01 Jan 1998TL;DR: The CTA paradigm: Terminology, methods, and conventions is compared to other paradigms in physiology, psychology, and neurobiology to help clarify the role of emotion and self-consistency in clinical practice.
Abstract: Preface 1. Ethology, physiological psychology, and neurobiology of CTA 2. The CTA paradigm: Terminology, methods, and conventions 3. Neuroanatomy of CTA: Lesions studies 4. Functional ablation studies of CTA 5. Pharmacology of CTA 6. Electrophysiology of CTA 7. Funtional morphology of CTA 8. Transplantation studies 9. Paradoxes, projections, and perspectives of CTA research References Index
TL;DR: In this article, the giant magnetocaloric effect was shown to be associated with a field-induced first-order structural transition from a monoclinic (paramagnetic) to a Pnma orthorhombic (ferromagnetic) structure.
Abstract: We present direct evidence that the giant magnetocaloric effect recently discovered in the ${\mathrm{Gd}}_{5}{(\mathrm{S}\mathrm{i}}_{1.8}{\mathrm{Ge}}_{2.2})$ alloy is associated with a field-induced first-order structural transition from a ${P112}_{1}/a$ monoclinic (paramagnetic) to a Pnma orthorhombic (ferromagnetic) structure. A large volume contraction of $\ensuremath{\Delta}V/V\ensuremath{\cong}0.4%$ takes place spontaneously at the transition temperature, ${T}_{C}\ensuremath{\cong}240\mathrm{K}.$ The reported structural transition can be induced reversibly by application of an external magnetic field, producing strong magnetoelastic effects.
TL;DR: Using the peptide nucleic acid in the biosensor recognition layer greatly increased the specificity of the DNA hybridization biosensor making it possible to detect point mutations (single-base mismatches) in DNA.
TL;DR: These materials appear to have the ability to regulate the physicochemical and biological properties of polycation/DNA complexes, and should find important applications in packaging of nucleic acids for specific biological applications.
TL;DR: This work derives the features for image representation which are invariant with respect to blur regardless of the degradation PSF provided that it is centrally symmetric, and proves that there exist two classes of such features: the first one in the spatial domain and the second in the frequency domain.
Abstract: Analysis and interpretation of an image which was acquired by a nonideal imaging system is the key problem in many application areas. The observed image is usually corrupted by blurring, spatial degradations, and random noise. Classical methods like blind deconvolution try to estimate the blur parameters and to restore the image. We propose an alternative approach. We derive the features for image representation which are invariant with respect to blur regardless of the degradation PSF provided that it is centrally symmetric. As we prove in the paper, there exist two classes of such features: the first one in the spatial domain and the second one in the frequency domain. We also derive so-called combined invariants, which are invariant to composite geometric and blur degradations. Knowing these features, we can recognize objects in the degraded scene without any restoration.
TL;DR: The MN/CA9 protein is a tumorassociated antigen that has been shown to have diagnostic utility in identifying cervical dysplasia and carcinoma as mentioned in this paper, but it is limited to very few normal tissues.
TL;DR: In this paper, the binding energy of the Au(Xe)+ complex has been studied comprehensively by CCSD(T) calculations in order to provide a benchmark for a gold(I) cation affinity scale.
Abstract: Ligation of atomic gold(I) cation Au+ by various inorganic and organic ligands containing heteroatoms has been examined by experimental and theoretical means The Au(Xe)+ complex has been studied comprehensively by CCSD(T) calculations in order to provide a benchmark for a gold(I) cation affinity scale The best theoretical estimate of the binding energy is D0(Au+−Xe) = 301 kcal/mol This value is used to relate calculated and experimentally bracketed binding energies of Au(L)+ complexes with a relative gold(I) cation affinity scale for heteroatom ligands L, ie, Xe < C6F6 < H2O < CO < H2S < CH3CN ≈ C2H4 ≈ NH3 ≈ CH3NC < CH3SCH3 < PH3 In comparison to other transition metal cations, the gold(I) cation is unique in that the binding energies to several ligands are exceptionally large Further, the covalent character of the Au+−L bonds as well as charge transfer from the ligand to gold are significant Finally, the gas-phase behavior of Au+ suggests some implications for possible new approaches to gold(I)
TL;DR: It is speculated that fatty acid-induced uncoupling serves in bioenergetic systems to set the optimum efficiency and tune the degree of coupling of oxidative phosphorylation in mammalian mitochondria and plant mitochondria by PUMP and StUCP.
TL;DR: Water distributions around phosphate groups in 59 B-, A-, and Z-DNA crystal structures were analyzed and it was shown that the waters are concentrated in six hydration sites per phosphate and that the positions and occupancies are dependent on the conformation and type of nucleotide.
TL;DR: The influence of polymerization temperature on molecular weight, crystallinity, and electrical conductivity of polyaniline has been investigated in this article, where aniline was oxidized in aqueous medium with ammonium peroxodisulfate at equimolar and excess concentrations of hydrochloric acid.
TL;DR: Inactivation of both the PCx gene and the PEPCx gene in C. glutamicum WT led to the absence of PCx activity and to negligible growth on lactate, indicating that PCx is essential for growth on this carbon source.
Abstract: In addition to phosphoenolpyruvate carboxylase (PEPCx), pyruvate carboxylase (PCx) has recently been found as an anaplerotic enzyme in the amino-acid-producing bacterium Corynebacterium glutamicum. Using oligonucleotides designed according to conserved regions of PCx amino acid sequences from other organisms, a 200 bp fragment central to the C. glutamicum PCx gene (pyc) was amplified from genomic DNA by PCR. This fragment was then used to identify and to subclone the entire C. glutamicum pyc gene. The cloned pyc gene was expressed in C. glutamicum, as cells harbouring the gene on plasmid showed four- to fivefold higher specific PCx activities when compared to the wild-type (WT). Moreover, increased PCx protein levels in the pyc-plasmid-carrying strain were readily detected after SDS-PAGE of cell-free extracts. DNA sequence analysis of the pyc gene, including its 5' and 3' flanking regions, and N-terminal sequencing of the pyc gene product predicts a PCx polypeptide of 1140 amino acids with an M(r) of 123070. The amino acid sequence of this polypeptide shows between 62% and 45% identity when compared to PCx enzymes from other organisms. Transcriptional analyses revealed that the pyc gene from C. glutamicum is monocistronic (3.5 kb mRNA) and that its transcription is initiated at an A residue 55 bp upstream of the translational start. Inactivation of the chromosomal pyc gene in C. glutamicum WT led to the absence of PCx activity and to negligible growth on lactate, indicating that PCx is essential for growth on this carbon source. Inactivation of both the PCx gene and the PEPCx gene in C. glutamicum led additionally to the inability to grow on glucose, indicating that no further anaplerotic enzymes for growth on carbohydrates exist in this organism.
TL;DR: In this article, a lower stability of bridging hydroxyls of H-ferrierite (3604 cm −1 ) with Si/Al 8.4 and its framework structure compared to those of HZSM-5 (3612 cm − 1 ) withSi/Al 12.6 was found.
TL;DR: In this article, the results of a selected ion flow tube study of the reactions of H 3 O +, NO +, and O 2 + with the 10 aromatic hydrocarbons benzene, toluene, 1,2-, 1,3-, and 1,4-dimethylbenzene, the alkenes 1-pentene and 2-methyl-2-butene, and the dialkene 2 -methyl butadiene (isoprene).
TL;DR: Results suggest that the 42-kDa CCF-1 protein of E. foetida coelomic fluid likely plays a role in the protection of earthworms against microbes.
26 Mar 1998
TL;DR: In this article, a multi-information function assigns to each subset A ⊂ N the relative entropy of the joint distribution of [ξ i ] i ∈ A with respect to the product of distributions of individual random variables.
Abstract: Given a collection of random variables [ξ i ] i ∈ N where N is a finite nonempty set, the corresponding multiinformation function assigns to each subset A ⊂ N the relative entropy of the joint distribution of [ξ i ] i ∈ A with respect to the product of distributions of individual random variables ξ i for i ∈ A. We argue that it is a useful tool for problems concerning stochastic (conditional) dependence and independence (at least in the discrete case).
TL;DR: It is shown that optimal antipredator behavior of prey leads to persistence and reduction of oscillations in population densities and adaptive prey behavior does not lead to a stable equilibrium but to the reduction of population fluctuations.
TL;DR: In this paper, data sets from seven original trait taxonomies from different languages, American English, Dutch, German, Hungarian, Italian, Czech, and Polish, are used for a cross-cultural study.
Abstract: Data sets from seven original trait taxonomies from different languages, American English, Dutch, German, Hungarian, Italian, Czech, and Polish, are used for a cross-cultural study. The taxonomic procedures, involving culling trait terms from the various lexicons and the construction of representative samples of trait terms, are briefly discussed. Factor structures, presumably Big Five structures, within these languages, based on ratings from an average of about 640 subjects on an average of approximately 430 trait variables per language, are used for comparison. Congruence coefficients are calculated for the corresponding factors in the different languages, based on their independent positions and on their positions after rotations, using the American English solution as target. In a relative sense, the congruences show replicability of the first four American English, Big Five factors in the other languages.
TL;DR: In this paper, the structure and energy properties of the guanine−cytosine Watson−Crick DNA base pair and pentahydrated Mg2+, Ca2+, Sr2+, Ba2+, Zn2+, Cd2+, and Hg2+ metal cations were studied.
Abstract: Structures and energetics of complexes between the guanine−cytosine Watson−Crick DNA base pair and pentahydrated Mg2+, Ca2+, Sr2+, Ba2+, Zn2+, Cd2+, and Hg2+ metal cations were studied. Comparison has been made with the data for the unsolvated cations. The complexes were fully optimized within the Hartree−Fock approximation applying the 6-31G* basis set of atomic orbitals, while relativistic pseudopotentials were used for the cations except magnesium. The energetics have been studied with the inclusion of electron correlation using the full second-order Moller−Plesset perturbation theory. The cation with its hydration sphere has been considered as one subsystem in the calculations of interaction energy. Thus, the complete system for a calculation would include the hydrated cation−guanine−cytosine trimer. The interaction between hydrated cation and guanine is significantly reduced compared to the guanine−unsolvated cation interaction. Though the stabilizing three-body contribution has been reduced by almos...
TL;DR: The results suggest that the interaction of daunomycin with DNA anchored at the surface may significantly differ from that with DNA in solution, and electroanalytical methods in studies of DNA–drug interactions are discussed.
TL;DR: The structural bases of UCP transport function and nucleotide inhibition are discussed in light of recent mutagenesis studies and in relationship to the sequences of newly discovered UCPs.