Showing papers by "Romanian Academy published in 2000"
TL;DR: It is proved that the P systems with the possibility of objects to cooperate characterize the recursively enumerable sets of natural numbers; moreover, systems with only two membranes suffice.
2,327 citations
TL;DR: It is concluded that using higher taxonomic units in soil food web analysis is problematic and in general not consistent with nature.
Abstract: The structure of the soil food web in two beech (Fagus sylvatica) forests, the Gottinger Wald and the Solling forest (Northern Germany), was investigated using variations in tissue 15N concentrations of animal species or taxa. The Gottinger Wald is located on a limestone plateau and characterized by mull humus with high macrofauna activity, particularly of Lumbricidae, Diplopoda and Isopoda. In contrast, the Solling forest is located on a sandstone mountain range and characterized by moder humus. The soil fauna of this forest is dominated by mesofauna, particularly by Collembola, Enchytraeidae and Oribatida. In June 1995 soil fauna was sampled using heat extraction. Three soil layers were analysed at each of the sites. 15N/14N ratios of bulk material increased strongly with soil depth in both forests. This also applied to the water-soluble fraction at the Gottinger Wald, but not at the Solling. Generally, the water-soluble fraction was more enriched in 15N than the bulk materials. For most animals studied 15N/14N ratios varied little with soil depth. In both forests soil animals could be classified either as saprophages, including microphytophages, or predators. On average, the δ15N of predatory taxa (Chilopoda, Araneida, Gamasina, Staphylinidae) exceeded that of saprophagous or microphytophagous taxa (Lumbricidae, Isopoda, Diplopoda, Collembola, Oribatida, Enchytraeidae) by 4.4 and 3.9‰ for the Gottinger Wald and the Solling, respectively. We assume that most of the saprophagous or microphytophagous taxa studied consist of primary and secondary decomposers and hypothesize that predators prey more on secondary than primary decomposers. Generally, average δ15N values differed little between saprophagous (Lumbricidae, Diplopoda, Isopoda) and microphytophagous taxa (Collembola, Oribatida). The variations in δ15N values of species within these taxa consistently exceeded the variation between them, indicating that the species of each of these taxa form a continuum from primary to secondary decomposers. Also, variations in δ15N values within predatory taxa in most cases exceeded that between taxa excluding top predators like Sorex. We conclude that using higher taxonomic units in soil food web analysis is problematic and in general not consistent with nature. Higher taxonomic units may only be useful for depicting very general trophic groupings such as predators or microbi-detritivores.
343 citations
TL;DR: The interaction between bovine serum albumin (BSA) and several surfactants has been investigated by light scattering as discussed by the authors, showing that cooperative binding of DTAB occurs at higher surfactant concentrations than in comparative solutions of SDS and C12E8.
Abstract: The interaction between bovine serum albumin (BSA) and several surfactants has been investigated by light scattering. Anionic (sodium dodecyl sulfate, SDS), cationic (dodecyl trimethylammonium bromide, DTAB), and nonionic (polyoxyethylene 8 lauryl ether, C12E8) surfactants, all containing a C12 alkyl chain, were used to study the effect of different headgroups on the complex formation. The hydrodynamic radii of the complexes obtained by dynamic light scattering indicate that cooperative binding of DTAB occurs at higher surfactant concentrations than in comparative solutions of SDS and C12E8. The effect of chain length is shown for the cationic surfactants DTAB and cetyl trimethylammonium bromide (CTAB, C16 alkyl chain). The higher surface activity of CTAB results in complex formation at a lower surfactant concentration compared to DTAB. The hydrodynamic radii of the BSA−SDS and BSA−DTAB complexes at saturation were determined as ∼5.9 nm and ∼4.8 nm, respectively. The hydrodynamic radius of the reduced BSA...
220 citations
TL;DR: A local folding mechanism is proposed that can explain the mechanism of inactivation of tyrosinaseN-glycosylation mutants found in certain pigmentation disorders.
119 citations
Book•
28 Oct 2000TL;DR: This paper aims to demonstrate the power of the H-Systems model in the context of quantum computing, and to provide some examples of how this model can be applied to the model of DNA computing.
Abstract: 1. Prerequisites 1.1. Preliminary Notions and Notations 1.2. Operations on Strings and Languages 1.3. A General Computing Framework 1.4. Chomsky Grammars 1.5. Lindenmayer Systems 1.6. Automata and Transducers 1.7. Characterizations of Computably Enumerable Languages 1.8. Universal Turing Machines and Type-0 Grammars 1.9. Complexity 1.10. Bibliographic Notes 2. DNA Computing 2.1 The Structure of DNA 2.2. Complementarity Induces Computational Completeness 2.3. Operations on DNA Molecules 2.4. Adleman's Experiment 2.5. Other DNA Solutions to NP Complete Problems 2.6. A Two-dimensional Generalization 2.7. Computing by Carving 2.8. Sticker Systems 2.9 Extended H-Systems 2.10 Controlled H-Systems 2.11 Distributed H-Systems 2.12 Bibliographic Notes 3. Membrane Computing 3.1 P Systems with Labeled Membranes 3.2. Examples 3.3. The Power of P Systems 3.4. Decidability Results 3.5. Rewriting P Systms 3.6. P Systems with Polarized Membranes 3.7. Normal Forms 3.8. P Systems on Asymmetric Graphs 3.9. P Systems with Active Membranes 3.10. Splicing P Systems 3.11 Variants, Problems, Conjectures 3.12 Bibliographic Notes 4. Quantum Computing 4.1. Church-Turing Thesis 4.2 Computation is Physical 4.3. Reversible Computation 4.4. The Copy Computer 4.5. Maxwell's Demon 4.6. Quantum World 4.7 Bits and Quibits 4.8. Quantum Calculus 4.9. Quibit Evolution 4.10 No Cloning Theorem 4.11. Measurements 4.12 Zeno Machines 4.13 Inexhaustible Uncertainty 4.14. Randomness 4.15. The EPR Conundrum and Bell's Theorem 4.16. Quantum Logic 4.17. Have Quantum Propositions Classical Meaning? 4.18 Quantum Computers 4.19 Quantum Algorithms 4.20 Quantum Complexity 4.21 Quantum Cryptography 4.22 Information and Teleportation 4.23 Computing the Uncomputable 4.24 Bibliographic Notes 5. Final Remarks 6. Bibliography 7. Index
118 citations
TL;DR: In this article, it was shown that the 1 -coordinate distribution of the angles formed with the origin exists, and the repartition function is explicitly expressed as the convolution between the square of the distance from origin function and a certain kernel.
Abstract: Let Ω be a region in the plane which contains the origin, is star-shaped with respect to the origin and has a piecewise C
1 boundary. For each integer Q≥ 1, we consider the integer lattice points from which are visible from the origin and prove that the 1
st
consecutive spacing distribution of the angles formed with the origin exists. This is a probability measure supported on an interval [m
Ω,∞), with m
Ω >0. Its repartition function is explicitly expressed as the convolution between the square of the distance from origin function and a certain kernel.
115 citations
TL;DR: In this paper, the exact internal and boundary controllability of parabolic equations with superlinear nonlinearity was studied, where the authors considered the case where the superlinearity of the equations is unknown.
Abstract: The exact internal and boundary controllability of parabolic equations with superlinear nonlinearity is studied.
114 citations
TL;DR: In this article, it was shown that ∆n≥1nr/p−2P|Sn|≥en1/p∼e−(αp/(α−p))(r/p −1)pr−pE|Z|(α p/(α −p)(r /p−1)n/p+1)as e↘0, for 1 ≤ p < r < α, under the additional assumption that there is normal attraction to G.
111 citations
TL;DR: In this article, the authors studied the initiation of slip instabilities of a finite fault in a homogeneous linear elastic space and derived the first (nondimensional) eigenvalue which depends only on the geometry of the problem.
79 citations
TL;DR: The continued occurrence of sporadic WN infections in southeastern Romania in consecutive years after the 1996 epidemic is consistent with local enzootic transmission of the virus.
Abstract: After an epidemic of West Nile (WN) virus neurologic infections in southeastern Romania in 1996, human and animal surveillance were established to monitor continued transmission of the virus. During 1997 and 1998, neurologic infections were diagnosed serologically as WN encephalitis in 12 of 322 patients in 19 southeastern districts and in 1 of 75 Bucharest patients. In addition, amid a countrywide epidemic of measles, the etiology of the febrile exanthem in 2 of 180 investigated cases was determined serologically to be WN fever; 1 case was complicated by hepatitis. Sentinel chickens placed in Bucharest seroconverted to WN virus during the summer months, indicating their potential value in monitoring transmission. The continued occurrence of sporadic WN infections in southeastern Romania in consecutive years after the 1996 epidemic is consistent with local enzootic transmission of the virus.
79 citations
13 Dec 2000
TL;DR: The aim of this paper is to introduce to the reader the main ideas of Computing with Membranes, a recent branch of (theoretical) Molecular Computing, with emphasis on some variants which can solve computationally hard problems in polynomial time.
Abstract: The aim of this paper is to introduce to the reader the main ideas of Computing with Membranes, a recent branch of (theoretical) Molecular Computing, with emphasis on some variants which can solve computationally hard problems in polynomial (often, linear) time. In short, in a cell-like system (called a P system), multisets of objects (described by symbols or by strings of symbols) evolve in a membrane structure and compute natural numbers as the result of halting sequences of transitions. The model is parallel, distributed, and non-deterministic.
TL;DR: In this paper, the authors define act,ions and coactions for quasi-Hopf algebras and introduce the notion of coactions of quasi-hopf algebra.
Abstract: The construct,ion of quasi-Hopf algebras obtains its importance from its signficance in Physics, cf.[l], 151, 161. Since for usual quantum groups and Hopf algebras actions and coactions of Hopf algebras play an important r81e, it is natmal to try to define act,ions and coactions for quasi-Hopf algebras. Now, coactions of quasi-Hopf algebras have been introduced by I?. Hansser and F. Nil1 in [8], [9]. If H is a quasi-Hopf algebra and B is an (associative) algebra, then, roughly speaking, B is a right H-comodule algebra if there exists an algebra map p : B -+ B @ H which turns B into an \"almost\" H-comodule
TL;DR: Improved techniques for magnetogranulometry analysis and a formula for the magnetoviscous effect were proposed and the area of applicability of some existing models was studied.
TL;DR: The fundamental properties of computations in such P systems with external output are investigated, including the computing power, normal forms, and basic decision problems.
Abstract: A membrane computing system (also called P system) consists of computing cells which are organized hierarchically by the inclusion relation: cells may include cells, which again may include cells, etc Each cell is enclosed by its membrane Each cell is an independent computing agent with its own computing program, which produces objects The interaction between cells consists of the exchange of objects through membranes The output of a computation is a partially ordered set of objects which leave the system through its external membrane The fundamental properties of computations in such P systems with external output are investigated These include the computing power, normal forms, and basic decision problems
TL;DR: In this article, the structure of cellulose fiber is discussed in relation to the relevance of the ligand-receptor concept for dye-fibre binding and calculations of pertinent (electronic, geometric and partition) properties of dye molecules.
TL;DR: In this paper, it was shown that there is a Hopf duality between two Hopf algebras built on rooted trees: the Connes-Kreimer Hopf algebra HR which controls the renormalization in quantum field theory, and the Grossman-Larson hopf algebra A introduced ten years ago through some 'differential' and combinatorial reason.
Abstract: We prove that there is a Hopf duality between two Hopf algebras built on rooted trees: the Connes–Kreimer Hopf algebra HR which controls the renormalization in quantum field theory, and the Grossman–Larson Hopf algebra A introduced ten years ago through some 'differential' and combinatorial reason. We then study two natural operators on A, inspired by similar ones introduced by Connes and Kreimer for HR.
TL;DR: It is proved that P systems are able to characterize the one-letter recursively enumerable languages (equivalently, the recursically enumerable sets of natural numbers), providing that an extra feature is considered: the membranes can be made thicker or thinner and the communication through a membrane is possible only when its thickness is equal to 1.
Abstract: Membrane Computing is a recently introduced area of Molecular Computing, where a computation takes place in a membrane structure where multisets of objects evolve according to given rules (they can also pass through membranes). The obtained computing models were called P systems. In basic variants of P systems, the use of objects evolution rules is regulated by a given priority relation; moreover, each membrane has a label and one can send objects to precise membranes, identified by their labels. We propose here a variant where we get rid of both there rather artificial (non-biochemical) features. Instead, we add to membranes and to objects an "electrical charge" and the objects are passed through membranes according to their charge. We prove that such systems are able to characterize the one-letter recursively enumerable languages (equivalently, the recursively enumerable sets of natural numbers), providing that an extra feature is considered: the membranes can be made thicker or thinner (also dissolved) and the communication through a membrane is possible only when its thickness is equal to 1. Several open problems are formulated.
TL;DR: It is concluded that disulfide bridge burring is crucial for the TRP-1 export, suggesting that although various folding pathways may complete this process, the native form may be acquired only through the normal unperturbed pathway.
TL;DR: Popescu et al. as mentioned in this paper presented a spectrophotometric catalogue of 90 emission-line galaxies (ELGs) discovered during an ob- jective - prism survey that aimed to search for dwarf galax- ies within the voids.
Abstract: We present a spectrophotometric catalogue of 90 emission-line galaxies (ELGs) discovered during an ob- jective - prism survey that aimed to search for dwarf galax- ies within the voids (Popescu et al. 1996, 1998). The paper presents line ratios, equivalent widths and absolute fluxes for the emission-lines seen in the spectra of the galaxies. A list of newly discovered Wolf-Rayet galaxies is presented. Many objects included in the catalogue have low metallic- ity and the extreme cases are proposed as candidates for very low metallicity galaxies.
TL;DR: In this paper, Diacu et al. proposed a phase-space structure and regularization of Manev-type problems for the regularisation of the phase space structure of phase space problems.
Abstract: Phase-space structure and regularization of Manev-type problems Florin Diacu a;∗, Vasile Mioc b, Cristina Stoica c a Department of Mathematics and Statistics, University of Victoria, Victoria, Canada V8W 3P4 b Astronomical Institute of the Romanian Academy, Astronomical Observatory Cluj-Napoca, Str. Cire silor 19, 3400 Cluj-Napoca, Romania c Institute for Gravitation and Space Sciences, Laboratory for Gravitation, Str. Mendeleev 21-25, Bucharest, Romania
TL;DR: In this article, the authors used in vitro ligation methodology to generate a fluorescent semi-synthetic Rab7 protein, which was used to demonstrate a micromolar affinity interaction of Rab7 with the RabGGTase in the absence of Rab escort protein (REP).
TL;DR: In this paper, the authors compare the temporal character of seismic emission from acoustic glories with that from the quiet Sun and show that the latter distribution shows significant saturation, suggesting the operation of a hydromechanical nonlinearity that sets limits on the acoustic power generated by the convection zone.
Abstract: Helioseismic images of multipolar active regions show enhanced seismic emission in 5-mHz oscillations in a halo surrounding the active region called the ‘acoustic glory’ The acoustic glories contain elements that sustain an average seismic emission 50% greater than similar elements in the quiet Sun The most intense seismic emitters tend to form strings in non-magnetic regions, sometimes marking the borders of weak magnetic regions and the separation between weak magnetic regions of opposite polarity This study compares the temporal character of seismic emission from acoustic glories with that from the quiet Sun The power distribution of quiet-Sun seismic emission far from solar activity is exponential, as for random Gaussian noise, and therefore not perceivably episodic The distribution of seismic power emanating from the most intense elements that comprise the acoustic glories is exponential out to approximately 4 times the average power emitted by the quiet Sun Above this threshold the latter distribution shows significant saturation, suggesting the operation of a hydromechanical non-linearity that sets limits on the acoustic power generated by the convection zone This could give us considerable insight into the physical mechanism of seismic emission from the near subphotosphere
TL;DR: In this article, the first cohomology analysis of higher-rank abelian groups with values in a linear Lie group is presented. But the main result is that the corresponding cohomologies trivialize, i.e. that any cocycle from a given class is cohomologous to a constant cocycle.
Abstract: We develop a new technique for calculating the first cohomology of certain classes of actions of higher-rank abelian groups (Z k andR k ,k 2) with values in a linear Lie group. In this paper we consider the discrete-time case. Our results apply to cocycles of different regularity, from Holder to smooth and real-analytic. The main conclusion is that the corresponding cohomology trivializes, i.e. that any cocycle from a given class is cohomologous to a constant cocycle. The principal novel feature of our method is its geometric character; no global information about the action based on harmonic analysis is used. The method can be developed to apply to cocycles with values in certain infinite dimensional groups and to rigidity problems.
TL;DR: In this article, optical data obtained with the 1.05m telescope of the Torino Astronomical Observatory for five X-ray selected BL Lacertae objects were used for better understanding of the properties of these objects.
Abstract: We present optical data obtained with the 1.05 m telescope of the Torino Astronomical Observatory for five X-ray selected BL Lacertae objects. The data are in the Johnson's B , V , and Cousins' R bands. As the observing periods include the pointings of the Satellite per Astronomia X “Beppo” (BeppoSAX), our optical information will be comparable with the X-ray observations for a better understanding of the properties of these objects. The present data also provide optical information on sources that have been rarely observed in the optical band. Variability on short time scales (a few days) was found only for 1ES 1959+650.
TL;DR: In this paper, it was shown that the canonical magnetization admits a thermodynamic limit for all strictly positive ρ, T and B. And the canonical and grand canonical magnetizations are equal up to the surface order corrections.
Abstract: Consider a charged Bose gas without self-interactions, confined in a three dimensional cubic box of side L≥ 1 and subjected to a constant magnetic field B≠ 0. If the bulk density of particles ρ and the temperature T are fixed, then define the canonical magnetization as the partial derivative with respect to B of the reduced free energy. Our main result is that it admits thermodynamic limit for all strictly positive ρ, T and B. It is also proven that the canonical and grand canonical magnetizations (the last one at fixed average density) are equal up to the surface order corrections.
TL;DR: In this paper, it was shown that there is a convex surface S such that for any point x on S and any point y in the set Fx of farthest points from x, there are at most two segments from x to y.
Abstract: We disprove two conjectures of H. Steinhaus by showing that: (1) there is a convex surface S such that for any point x on S and any point y in the set Fx of farthest points from x, there are at most two segments from x to y; (2) the properties \(\left| {Fx} \right| = 1\) and \({F_{F_x } = x}\)do not characterize the sphere.
TL;DR: In this paper, the influence of process variables (e.g., initial mold temperature) on the degree of crystallinity and mechanical properties of the finished moldings was investigated in the direct centrifugal molding of ϵ-caprolactam.
Abstract: Previously synthesized polymers (pellets or powders) and reactive monomers (lactams) can be used as starting materials in direct centrifugal molding for the manufacture of products with a circular section. The direct centrifugal molding of ϵ-caprolactam has been investigated in order to obtain Nylon 6-based products as well as to study the influence of process variables (e.g., initial mold temperature) on the degree of crystallinity and mechanical properties of the finished moldings. At initial mold temperatures greater than 140°C, a significant reduction of the degree of crystallinity, an increase of the Izod impact strength values, as well as a decrease of the flexural modulus values were observed.
TL;DR: It is found that heparin caused a dose-dependent inhibition of specific binding of both human and bovine lactoferrin to human monocytic THP-1 cells, and results suggest thatHeparin binding and monocyte/macrophage binding by lact oferrin both involve interactions between basic regions in the N1 domain of lactof Kerrin and sulphate groups.
21 Aug 2000
TL;DR: In this article, a hierarchy of multiset rewriting devices is introduced to generate macroset families, which are then used to solve algebraic systems of equations, and some results about the power of these devices are proved.
Abstract: A macroset is a (finite or infinite) set of multisets over a finite alphabet. We introduce a Chomsky-like hierarchy of multiset rewriting devices which, therefore, generate macrosets. Some results are proved about the power of these devices and some open problems are formulated. We also present an algebraic characterization of some of the macroset families as least fixed point solutions of algebraic systems of equations.