Wyniki wyszukiwania - Biblioteka Nauki

1

Tree operations in P systems and [lambda]-calculus

100%

Jonoska N. , Margenstern M.

Fundamenta Informaticae

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2004

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tom Vol. 59, nr 1

67-90

EN

In this paper we introduce a membrane system (named lP systems) in which the computation is performed through certain operations on the tree structure of the membranes. The objects within the membranes play the role of catalysts for the operations. The result of the computation is the final configuration of the system. We show that lP systems can simulate pure l-calculus and so they have universal computational power. We also show that NP-complete problems can be solved in polynomial time in this way by showing that 3SAT is solvable in linear time with linear input.

2

Hydrodynamic instabilities in membrane systems

100%

Dworecki K. , Wasik S. , Przestalski S. , Kargol M.

Biophysics of Membrane Transport

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1994

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tom 12

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nr 2

3

Dynamic Meaning Membrane Systems: An Application to the Description of Semantic Change

80%

Bel-Enguix G. , Jiménez-López M. D.

Fundamenta Informaticae

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2007

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tom Vol. 76, nr 3

219-237

EN

An application of membrane systems to natural languages study is presented. Specifically, we show how language change can be explained by using a new variant of membrane systems: Dynamic Meaning Membrane Systems (DMMS). By using DMMS, we model the main concepts of semantics and explain the three basic types of changes in meaning: broadening, narrowing and shift. Finally, we relate the membrane systems' application to language evolution with the suggested application of the so-called cultural grammar systems to the same topic. Collaboration between the two frameworks may provide a useful formalism that, due to its naturalness and simplicity, might offer interesting results in a discipline traditionally far away from any formalization.

4

Multiset-Based Self-Assembly of Graphs

80%

Bernardini F. , Brijder R. , Rozenberg G. , Zandron C.

Fundamenta Informaticae

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2007

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tom Vol. 75, nr 1-4

49-75

EN

We present a model for self-assembly of graphs based on multisets and the formalism of membrane systems. The model deals with aggregates of cells which are defined as undirected graphs where a multiset over a fixed alphabet is assigned to each vertex. The evolution of these aggregates is determined by an application of multiset-based aggregation rules to enlarge the current structure as well as an application of membrane-systems-based communication rules to enable cells to exchange objects alongside the edges of the graph. We compare the generative power of self-assembly membrane systems with and without communication rules, and we characterise properties of the sets of graphs generated by these systems. We also introduce two notions of stability for self-assembly processes that capture the idea of having produced a stable structure. Finally, we investigate self-assembly membrane systems where the alphabet is a singleton.

5

Membrane Systems with Coupled Transport: Universality and Normal Forms

80%

Martin-Vide C. , Paun A. , Paun G. , Rozenberg G.

Fundamenta Informaticae

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2002

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tom Vol. 49, nr 1-3

1-15

EN

This paper continues research on membrane systems which function by communication only, meaning that there are no evolving rules for molecules. The whole computation process relies on passage of molecules through membranes - this provides communication between regions of the membrane system. Next to transport of single molecules through membranes (uniport) we also study a coupled transport of molecules, with two molecules passing either in the same direction (symport) or in opposite directions (antiport). We study the computational power of such membrane systems and prove that using only symport one gets Turing universality. Moreover, we prove that five membranes suffice to get Turing universality, and the number of membranes can be decreased to three if forbidding context conditions for transport are used.

6

DNA and Membrane Algorithms for SAT

70%

Manca V.

Fundamenta Informaticae

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2002

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tom Vol. 49, nr 1-3

205-221

EN

Some DNA algorithms proposed in the literature for propositional satisfiability (SAT) are analyzed. In the class of `extract model' the two sub-classes of `literal string' and `clause string' algorithms are compared and a new formulation of these algorithms is given in terms of membrane systems. Then, the duality between literal string and clause string formulation of SAT is expressed by means of `singleton matrices' that introduce another membrane algorithm for SAT. The analysis developed suggests the perspective of membrane systems as problem-solving agents based on molecule localization, transformation, and propagation.

7

Time and Synchronization in Membrane Systems

70%

Cavaliere M. , Sburlan D.

Fundamenta Informaticae

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2005

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tom Vol. 64, nr 1-4

65-77

EN

Membrane systems are parallel computational devices inspired from the cell functioning. Since the original definition, a standard feature of membrane systems is the fact that each rule of the system is executed in exactly one time-unit. However, this hypothesis seems not to have a counterpart in real world. In fact, in cells, chemical reactions might take different times to be executed. Therefore, a natural step is to associate to each rule of a membrane system a certain time of execution. We are interested in membrane systems, called time-free, working independently from the assigned execution time of the rules. A basic and interesting problem in time-free membrane systems consists in the synchronization of different rules, running in parallel, and having unknown execution times. Here, we present different ways to approach this problem within the framework of membrane systems. Several research proposals are also suggested.

8

Rola grawitacji w ewolucji pola stężeń roztworów elektrolitów w układzie membranowym

60%

Ślęzak A. , Bajdur W. M.

Przemysł Chemiczny

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2019

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tom T. 98, nr 12

1952--1955

PL

Zbadano wpływ stężenia poszczególnych składników roztworów oraz konfiguracji układu membranowego na wartość objętościowych strumieni osmotycznych (Jr vi) w układzie jednomembranowym, w którym membrana polimerowa usytuowana w płaszczyźnie horyzontalnej rozdziela wodę i roztwór składający się z wody, etanolu i/lub CuSO4. Na podstawie otrzymanych wyników pomiarów obliczono współczynnik asymetrii (ki) oraz współczynnik osmotycznej polaryzacji stężeniowej (ζ r i ). Współczynnik ζ r i , poprzez grubość stężeniowej warstwy granicznej (δr i, związano ze stężeniową liczbą Rayleigha (Rr C), tj. parametrem sterującym przejściem ze stanu bezkonwekcyjnego do konwekcyjnego. Wykazano, że liczba ta pełni również funkcję przełącznika między stanami konwekcyjnym i bezkonwekcyjnym. Funkcjonowanie tego przełącznika świadczy o regulatorowej roli grawitacji ziemskiej w odniesieniu do transportu membranowego.

EN

Two cylindrical vessels connected with a horizontally placed membrane were used to det. the osmotic fluxes of aq. and aq.-alc. CuSO4 solns. at 295 K. The tested solns. and water were placed alternately in the upper or lower tank to det. an effect of gravitational acceleration on the osmotic fluxes. Location of the tested solns. in the upper cylinder resulted in an increase in osmotic flux compared to the inverse option. The asymmetry coeffs. of osmotic fluxes and concn. polarization as well as the values of Rayleigh nos. for both types of solns. were calcd.

9

Evaluation of cation exchange membranes for pertraction processes

60%

Szczepański P. , Wódzki R.

Zeszyty Naukowe. Chemia / Politechnika Śląska

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2001

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tom z. 146

235-238

PL

Przedmiotem badań był wpływ fizykochemicznych właściwości kationowymiennych membran polimerowych (CEM) na pertrakcję kationów w wielomembranowym układzie hybrydowym (MHS). Układ składał się z sekwencji membran kationowymiennych z kwasowymi grupami sulfonowymi oraz membrany ciekłej (BLM): CEM-BLM-CEM. Membranę ciekłą stanowił roztwór kwasu di-(2-etyloheksylo) fosforowego w nafcie. Podstawą oceny membran były strumienie kationów Zn2+, Cu2+, Ca2+, Mg2+, K+, Na+ osiągane w procesie transportu konkurencyjnego.

10

Design of integrated membrane system with liquid and polymer membranes

60%

Wódzki R. , Szczepańska G.

Zeszyty Naukowe. Chemia / Politechnika Śląska

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2001

|

tom z. 146

231-234

PL

Opracowano nowy zintegrowany układ membranowy DD-MHS[FLM-PV] wykorzystujący jednocześnie: proces dializy Donnana (DD), pertrakcji w układzie hybrydowym z przepływową membraną ciekłą (FLM) oraz perwaporacji wody akumulowanej w FLM. Działanie układu zintegrowanego porównano z działaniem jego poszczególnych składowych z osobna. Podstawą porównania były strumienie oraz współczynniki separacji takich kationów, jak: Zn2+, Cu2+, Ca2+, Mg2+, K+ oraz Na+.

11

The Kedem-Katchalsky equations as applied for describing substance transport across biological membranes

60%

Kargol A. , Kargol M. , Przestalski S.

Cellular and Molecular Biology Letters

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1997

|

tom 02

|

nr 2

EN

The classical version of the Kedem-Katchalsky equations is suitable for describing substance transport in membrane systems with well-stirred bathing solutions. However, when dealing with biological reality we are faced with a more complicated situation. For instance, in the living cell one can distinguish the central bulk area where the cytoplasm is well stirred due to its natural streaming and a certain relatively thin layer adjacent to the plasma membrane where there is no stirring. In such a situation, the passive transport of substance can be well described using the Kedem-Katchalsky equations in their more general form [1], The equations can, however, be applied provided the membrane boundary unstirred layers of cytoplasm are treated as diffusion layers. This has been shown in detail in the present work.

12

Membrane Systems with Qualitative Evolution Rules

51%

Kleijn J. , Koutny M.

Fundamenta Informaticae

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2011

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tom Vol. 110, nr 1-4

217-230

EN

In membrane systems, biochemical reactions taking place in the compartments of a cell are abstracted to evolution rules that specify which and how many objects are consumed and produced. The recently proposed reaction systems also investigate processes carried by biochemical reactions, but the resulting computational model is remarkably different. A key difference is that in reaction systems, biochemical reactions are modeled using a qualitative rather than a quantitative approach. In this paper, we introduce so-called set membrane systems, a variant of membrane systems with qualitative evolution rules inspired by reaction systems. We then relate set membrane systems to Petri nets which leads to a new class of Petri nets: set-nets with localities. This Petri net model provides a faithful match with the operational semantics of set membrane systems.

13

Molecular dynamics simulation studies of lipid bilayer systems

41%

Pasenkiewicz-Gierula M. , Murzyn K. , Rog T. , Czaplewski C.

Acta Biochimica Polonica

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2000

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tom 47

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nr 3

EN

The main structural element of biological membranes is a liquid-crystalline lipid bilayer. Other constituents, i.e. proteins, sterols and peptides, either intercalate into or loosely attach to the bilayer. We applied a molecular dynamics simulation method to study membrane systems at various levels of compositional complexity. The studies were started from simple lipid bilayers containing a single type phosphatidylcholine (PC) and water molecules (PC bilayers). As a next step, cholesterol (Chol) molecules were introduced to the PC bilayers (PC-Chol bilayers). These studies provided detailed information about the structure and dynamics of the membrane/water interface and the hydrocarbon chain region in bilayers built of various types of PCs and Chol. This enabled studies of membrane systems of higher complexity. They included the investigation of an integral membrane protein in its natural environment of a PC bilayer, and the antibacterial activity of magainin-2. The latter study required the construction of a model bacterial membrane which consisted of two types of phospholipids and counter ions. Whenever published experimental data were available, the results of the simulations were compared with them.

14

Interferometric studies of diffusive unstirred layers generated in graviosmotic systems

41%

Kargol M. , Dworecki K.

|

tom 18

|

nr 2

15

Three-dimensional dynamic structure of the lipid bilayer membranes: An EPR spin label study

41%

Subczynski W. K. , Wisniewska A.

Cellular and Molecular Biology Letters

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1996

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tom 01

|

nr 4

EN

Over the last decade we have investigated the effects of cholesterol, polar carotenoids, and integral proteins (peptides) on the structure, dynamics, and hydrophobicity of saturated and unsaturated phosphatidylcholine (PC) membranes. The major results obtained in our studies can be summarized as follows: (1) The effect of unsaturation on the membrane alkyl chain order and reorientational motion is negligibly small; (2) The translational diffusion of lipids (lateral or vertical) as well as the diffusion of lipid-soluble small molecules is significantly decreased in cis- and trans-unsaturated PC membranes; (3) cis-unsaturated alkyl chains greatly decrease the ordering effect of membrane modifiers (cholesterol, polar carotenoids) as well as their effect on alkyl chain reorientational motion; (4) Introduction of a double bond into the alkyl chain increases the hydrophobicity (decreases water penetration) at all locations in the membrane; (5) Incorporation of cholesterol (30 mol%) decreases hydrophobicity (increases water penetration) from the polar headgroup region to a depth of approximately C7 and C9 for saturated and unsaturated PC membranes, respectively. Membrane hydrophobicity sharply increases at these positions from the level of methanol to the level of pure hexane, and hydrophobicity is constant in the inner region of the membrane.

16

A study on gravielectric polarization in 1-membrane systems

41%

Kargol M. , Ornal B. , Kosztolowicz T.

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tom 18

|

nr 2

17

The structure of the Ca2plus -ATPase of sarcoplasmic reticulum

41%

Martonosi A. N. , Pikula S.

Acta Biochimica Polonica

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2003

|

tom 50

|

nr 2

EN

In this article the morphology of sarcoplasmic reticulum, classification of Ca2+ -ATPase (SERCA) isoenzymes presented in this membrane system, as well as their topology will be reviewed. The focus is on the structure and interactions of Ca2+ -ATPase determined by electron and X-ray crystallog2r+aphy, lamellar X-ray and neutron diffraction analysis of the profile structure of Ca2+ -ATPase in sarcoplasmic reticulum multilayers. In addition, targeting of the Ca2+ -ATPase to the sarcoplasmic reticulum is discussed.