The Czech Academy of Sciences
Recent publications
Hyaluronan is a natural carbohydrate polymer with a negative charge that fosters gel-like conditions crucial for its cellular functions and industrial applications. As a recognized ligand for proteins, understanding their mutual interactions provides solid ground to tune hyaluronan's gel properties using biocompatible peptides. This work employs NMR and molecular dynamics simulations to identify molecular motifs relevant to hyaluronan–peptide interactions using arginine, lysine, and glycine oligopeptides. Arginine-rich peptides exhibit the strongest binding to hyaluronan according to chemical shift perturbation measurements, followed distantly by the similarly charged lysine. This difference highlights the significance of electrostatics and the peculiarities of the guanidinium side chain in arginine, capable of non-polar interactions that further stabilize the binding. Additional nuclear Overhauser effect measurements do not show stable interaction partners, precluding strong and well-defined complexes. Finally, molecular simulations support our findings and show an extended but significant interaction region, especially for arginine, responsible for the observed enhanced binding, which can also promote cross-linking of hyaluronan polymers. Our findings pave the way for optimizing biocompatible peptides to alter hyaluronan gels' properties efficiently and also explain why hyaluronan–protein interaction typically involves positively charged arginine-rich regions also capable of forming hydrogen bonds and non-polar interactions.
As in the work of Tartar [59], we develop here some new results on nonlinear interpolation of α-Hölderian mappings between normed spaces, by studying the action of the mappings on K-functionals and between interpolation spaces with logarithm functions. We apply these results to obtain some regularity results on the gradient of the solutions to quasilinear equations of the form where V is a nonlinear potential and f belongs to non-standard spaces like Lorentz–Zygmund spaces. We show several results; for instance, that the mapping \(\cal{T}:\cal{T}f=\nabla u\) is locally or globally α-Hölderian under suitable values of α and appropriate hypotheses on V and â.
Cerrenaceae is a small family of polypores and hydnoid fungi in the order Polyporales (Basidiomycota). The family consists of white-rot fungi, some of which are serious tree pathogens. Combining morphological evidence with a phylogenetic dataset of six genetic markers, we revise generic concepts in the family and propose a seven-genus classification system for the family. Two genera are introduced as new: the monotypic Acanthodontia for Radulodon cirrhatinus, and Lividopora for the Rigidoporus vinctus complex. We re-introduce the name Somion for the Spongipellis delectans complex. Other recognized genera in the family are Cerrena, Irpiciporus, Pseudolagarobasidium, and Radulodon. New species introduced are Irpiciporus branchiformis from Tanzania, Lividopora armeniaca, and L. facilis from Southeast Asia, and Somion strenuum from East Asia. We provide nomenclatural comments on all the names combined to the above Cerrenaceae genera and typify Cerrena unicolor, C. zonata, Polyporus carneopallens (= L. vincta), Somion occarium, and S. unicolor. The genus Hyphoradulum belongs to Cystostereaceae (Agaricales), and we transfer the type species H. conspicuum to Crustomyces. Our study highlights the importance of integrating different basidiocarp types in analyses when revising genus classification in macrofungi
Main conclusion Adaptive traits in rice responding to flooding, a compound stress, are associated with morpho-anatomical and physiological changes which are regulated at the genetic level. Therefore, understanding submergence stress tolerance in rice will help development of adapted cultivars that can help mitigate agricultural losses. Abstract Rice is an important dietary component of daily human consumption and is cultivated as a staple crop worldwide. Flooding is a compound stress which imposes significant financial losses to farmers. Flood-affected rainfed rice ecosystems led to the development of various adaptive traits in different cultivars for their optimal growth and survival. Some cultivars can tolerate hypoxia by temporarily arresting elongation and conserving their energy sources, which they utilize to regrow after the stress conditions subside. However, few other cultivars rapidly elongate to escape hypoxia using carbohydrate resources. These contrasting characters are regulated at the genetic level through different quantitative trait loci that contain ERF transcription factors (TFs), Submergence and Snorkels. TFs can simultaneously activate the transcription of various genes involved in stress and development responses. These TFs are of prime importance because the introgressed and near-isogenic lines showed promising results with increased submergence tolerance without affecting yield or quality. However, the entire landscape of submergence tolerance is not entirely depicted, and further exploration in the field is necessary to understand the mechanism in rice completely. Therefore, this review will highlight the significant adaptive traits observed in flooded rice varieties and how they are regulated mechanistically.
Mobility is highly species-specific and individual species mobility can be predicted by species traits, yet this topic remains largely understudied. We analyzed data on species presences/absences in permanent subplots (1m × 1m) within 15 main plots 10m × 10m) over 24 years originating from a grassland biodiversity experiment in Czechia. Plots differed in initial species richness and composition. We estimated mean individual species persistence and searched for any relationship with individual species traits. We also tested the effect of sowing richness/composition on species persistence and community mobility. Our results show that individual species have very different mobilities which vary in time and can be predicted by species traits, most importantly by leaf traits, clonal traits, and traits characterizing species life forms. Trait syndrome corresponding to the traveler part of the mobility gradient typically includes annuals having a taproot, long-lasting seedbank, and high SLA. Trait syndrome of sitters includes perennial hemicryptophytes with effective clonal reproduction and transient seedbank. Importantly, trait association with species mobility is spatial scale dependent, whereas studies on the spatial scale of 0.01m² show that clonality increases mobility, in our case clonality increases the persistence of species in 1m² units. In contrast with an evident linkage between mobility and traits, the effect of community richness/composition on species/community mobility was weak and detectable in the very first years of the experiment only.
For mechanical properties of titanium, oxygen content is important. In re-certifying O mass fraction in the Ti certified reference material ERM-EB090b, instrumental photon activation analysis (IPAA) was used as an alternative to the inert gas fusion technique. IPAA utilizes 15O measurable only via the nonspecific annihilation gamma line 511 keV. Interferences from other radionuclides can be suppressed by optimizing photon energy and irradiation-decay-counting times, and for most interfering radionuclides corrected via their specific gamma lines. The present re-evaluated IPAA results for O content 3.56 ± 0.59 g/kg matches closely the assigned certified value 3.57 ± 0.19 g/kg.
Self-assembly of organic molecules represents a fascinating playground to create various liquid crystalline nanostructures. In this Letter, we study layer undulations on micrometer scale in smectic A phases for achiral compounds, experimentally demonstrated as regular stripe patterns induced by thermal treatment. Undulations, including their anharmonic properties, are evaluated by means of polarimetric imaging and light diffraction experiments in cells with various thicknesses. The key role in stripe formation is played by high negative values of the thermal expansion coefficient.
We study the complexities of isometry and isomorphism classes of separable Banach spaces in the Polish spaces of Banach spaces, recently introduced and investigated by the authors in [14]. We obtain sharp results concerning the most classical separable Banach spaces. We prove that the infinite-dimensional separable Hilbert space is characterized as the unique separable infinite-dimensional Banach space whose isometry class is closed, and also as the unique separable infinite-dimensional Banach space whose isomorphism class is $F_\sigma $ . For $p\in \left [1,2\right )\cup \left (2,\infty \right )$ , we show that the isometry classes of $L_p[0,1]$ and $\ell _p$ are $G_\delta $ -complete sets and $F_{\sigma \delta }$ -complete sets, respectively. Then we show that the isometry class of $c_0$ is an $F_{\sigma \delta }$ -complete set. Additionally, we compute the complexities of many other natural classes of separable Banach spaces; for instance, the class of separable $\mathcal {L}_{p,\lambda +}$ -spaces, for $p,\lambda \geq 1$ , is shown to be a $G_\delta $ -set, the class of superreflexive spaces is shown to be an $F_{\sigma \delta }$ -set, and the class of spaces with local $\Pi $ -basis structure is shown to be a $\boldsymbol {\Sigma }^0_6$ -set. The paper is concluded with many open problems and suggestions for a future research.
Flutter of turbine and compressor blades represents a serious problem for designers of large turbomachines. In real machines, measurements of flutter conditions are hardly possible. Therefore, tests on linear blade cascades with movable blades play important role in investigations of flutter. In the current research, a simple blade cascade for controlled flutter testing was developed. The blades in this test rig undergo high-frequency oscillations which induce inertial forces. The influence of the elastic deformation of the blade on the flow field is studied in this work by means of experiments and numerical simulations. First, the computational and experimental modal analysis was done to obtain eigenfrequencies and modal damping. The deformed shape of the blade due to high-frequency oscillation was acquired by structural transient analysis. The influence of the elastic deformation on the flow field was then studied by CFD analysis for two incidence angles both for the deformed (elastic) and undeformed (idealized rigid) blade. Flow field was only very weakly distorted due to the blade elastic deformation. The total torque induced by aerodynamic and inertial forces was evaluated. The inertial loading is an order of magnitude larger than loading due to fluid flow.
The article informs about the discovery of the remains of a circular structure called a rondel, in this case featuring a double rondel in ‘Padělky’ field near Uherský Ostroh (SE Moravia, Czech Republic) and offers the results of non-destructive methods of research performed there in 2016–2020. The double circular complex was discovered during an analysis of satellite images of the Earth’s surface and subsequently verified by geophysical prospection. The resulting magnetogram revealed two ditches interrupted by five presumptive entrances at the site, along with dozens of anomalies that can be interpreted as potential archaeological features. Multiple-phase prehistoric occupation at the site was later proved by surface surveys. Occupation of the earlier phase of the Linear Pottery culture and the Lengyel culture has been documented. The age of the rondel itself remains an open question for the time being, however; it can only be clarified by a regular excavation. The present study discusses the existing possibilities of dating from various perspectives. Besides a probable dating the rondel to the Lengyel culture, a later, Early Eneolithic or Early Bronze Age, dating cannot be ruled out either.
Lucas sequences are constant-recursive integer sequences with a long history of applications in cryptography, both in the design of cryptographic schemes and cryptanalysis. In this work, we study the sequential hardness of computing Lucas sequences over an RSA modulus. First, we show that modular Lucas sequences are at least as sequentially hard as the classical delay function given by iterated modular squaring proposed by Rivest, Shamir, and Wagner (MIT Tech. Rep. 1996) in the context of time-lock puzzles. Moreover, there is no obvious reduction in the other direction, which suggests that the assumption of sequential hardness of modular Lucas sequences is strictly weaker than that of iterated modular squaring. In other words, the sequential hardness of modular Lucas sequences might hold even in the case of an algorithmic improvement violating the sequential hardness of iterated modular squaring. Second, we demonstrate the feasibility of constructing practically-efficient verifiable delay functions based on the sequential hardness of modular Lucas sequences. Our construction builds on the work of Pietrzak (ITCS 2019) by leveraging the intrinsic connection between the problem of computing modular Lucas sequences and exponentiation in an appropriate extension field.
We describe the formation of swift heavy ion tracks in polyethylene (PE) by combining the Monte Carlo code TREKIS, which models electronic excitation in nanometric proximity of the ion trajectory, with the molecular dynamics simulating a response of the atomic system to the excitation. The model predicts circular tracks in amorphous PE but elliptical ones in crystalline PE caused by preferential propagation of excitation along polymer chains during the cooling stage. The obtained track sizes and shapes agree well with the high-resolution transmission microscopy of tracks in PE with colorant. The velocity effect in PE is shown: the track parameters differ for ions with the same linear energy losses but different velocities. Graphical abstract
The Strongyloides genus of parasitic nematodes have a fascinating life cycle and biology, but are also important pathogens of people and a World Health Organization-defined neglected tropical disease. Here, a community of Strongyloides researchers have posed thirteen major questions about Strongyloides biology and infection that sets a Strongyloides research agenda for the future. This article is part of the Theo Murphy meeting issue ‘Strongyloides: omics to worm-free populations’.
Primates are an important source of infectious disease in humans. Strongyloidiasis affects an estimated 600 million people worldwide, with a global distribution and hotspots of infection in tropical and subtropical regions. Recently added to the list of neglected tropical diseases, global attention has been demanded in the drive for its control. Through a literature review of Strongyloides in humans and non-human primates (NHP), we analysed the most common identification methods and gaps in knowledge about this nematode genus. The rise of molecular-based methods for Strongyloides detection is evident in both humans and NHP and provides an opportunity to analyse all data available from primates. Dogs were also included as an important host species of Strongyloides and a potential bridge host between humans and NHP. This review highlights the lack of molecular data across all hosts—humans, NHP and dogs—with the latter highly underrepresented in the database. Despite the cosmopolitan nature of Strongyloides, there are still large gaps in our knowledge for certain species when considering transmission and pathogenicity. We suggest that a unified approach to Strongyloides detection be taken, with an optimized, repeatable molecular-based method to improve our understanding of this parasitic infection. This article is part of the Theo Murphy meeting issue ‘Strongyloides: omics to worm-free populations’.
The electronic structure and magnetism of an individual Dy atom adsorbed on the MgO(001) substrate is investigated using a combination of the density functional theory with the Hubbard-I approximation to the Anderson impurity model. The divalent Dy2+ adatom in f10 configuration is found. The calculated x-ray absorption and magnetic circular dichroism spectra are compared to the experimental data. Quantum tunneling between degenerate |J=8.0,Jz=±4.0〉 states leads to the formation of a |J=8.0,Jz=0.0〉 ground state with an in-plane orientation of the magnetic moment. It explains the absence of remanent magnetization in a Dy adatom on the top of the MgO(001) substrate. Our studies can provide a viable route for further investigation and prediction of the rare-earth single-atom magnets.
Fine (J Philos Log 43:549–577, 2014) developed a truthmaker semantics for intuitionistic logic, which is also called exact semantics, since it is based on a relation of exact verification between states and formulas. A natural question arises as to what are the limits of Fine’s approach and whether an exact semantics of similar kind can be constructed for other important non-classical logics. In our paper, we will generalize Fine’s approach and develop an exact semantics for some substructural logics. In particular, we will provide a truthmaker semantics for the Non-associative Lambek calculus and some of its extensions. This generalization will reveal some interesting connections between Fine’s recent work on truthmaker semantics and his early work on relevant logic.
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3,268 members
Thibault JY. Derrien
  • Institute of Physics
Holger Kruse
  • Institute of Biophysics
Jaroslav Hlinka
  • Institute of Computer Sciences, Department of Complex Systems
Pod Vodárenskou věží 2, 18207, Prague, Czechia
Head of institution
prof. RNDr. Eva Zažímalová, CSc
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