Wyniki wyszukiwania - Biblioteka Nauki

1

Finding an iterated function systems based representation for complex visual structures using an evolutionary algorithm

100%

Bielecki A. , Strug B.

Machine Graphics and Vision

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2007

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tom Vol. 16, No. 1/2

171-189

EN

This paper presents an approach to the IFS inverse problem based on evolutionary computations. Having a bitmap image, we look for a set of functions that can reproduce a good approximation of a given image. A method using a variable number of mappings is proposed. A number of different crossover operators is described and tested. The possibility of enriching evolutionary algorithms by a specific type mechanism characteristic for replication of influenza viruses is discussed. The genetic material of the influenza type A virus consists of eight separate segments. In some types of tasks, such a structure of a genome can be more adequate than representation that consists of one sequence only. If influenza virus strains infect the same cell, then their RNA segments can mix freely, producing progeny viruses which represents the reasortment mechanism. Furthermore, mistakes leading to new mutations are common. The structure of problems for which such viral reproduction mechanisms can be effective are analyzed. The paper ends with some experimental results showing the images we were able to generate with the proposed method. The preliminary experimental results suggest that the introduction of the reasortment operator results in achieving satisfactory images in a smaller number of generations.

2

How RNA viruses exchange their genetic material

100%

Alejska M. , Kurzynska-Kokorniak A. , Broda M. , Kierzek R. , Figlerowicz M.

Acta Biochimica Polonica

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2001

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tom 48

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nr 2

EN

One of the most un usual fea tures of RNA vi ruses is their enor mous ge netic vari ability. Among the dif fer ent pro cesses con trib ut ing to the con tin u ous gen er a tion of new vi ral vari ants RNA re com bi na tion is of spe cial im por tance. This pro cess has been observed for human, animal, plant and bacterial viruses. The collected data reveal a great sus cep ti bil ity of RNA vi ruses to re com bi na tion. They also in di cate that ge netic RNA re com bi na tion (es pe cially the nonhomologous one) is a major fac tor re spon si ble for the emer gence of new vi ral strains or spe cies. Al though the for ma tion and ac cu mu la tion of vi ral recombinants was ob served in numer ous RNA vi ruses, the mo lec u lar ba sis of this phe nom e non was stud ied in only a few vi ral spe cies. Among them, brome mo saic vi rus (BMV), a model (+)RNA vi rus offers the best op por tu ni ties to in ves ti gate var i ous as pects of ge netic RNA re com bi nation in vivo. Unlike any other, the BMV-based system enables homologous and nonhomologous re com bi na tion stud ies at both the pro tein and RNA lev els. As a con sequence, BMV is the vi rus for which the struc tural re quire ments for ge netic RNA re- com bi na tion have been most pre cisely es tab lished. Nev er the less, the pre vi ously proposed model of ge netic re com bi na tion in BMV still had one weak ness: it could not really ex plain the role of RNA struc ture in nonhomologous re com bi na tion. Re cent discoveries concerning the latter problem give us a chance to fill this gap. That is why in this re view we pres ent and thor oughly dis cuss all re sults con cern ing nonhomologous recombination in BMV that have been ob tained un til now.

3

Interplay of viral miRNAs and host mRNAs and proteins

86%

Zhdanov V.

Open Physics

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2011

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tom 9

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nr 5

1366-1371

EN

Recent experiments indicate that several viruses may encode microRNAs (miRNAs) in cells. Such RNAs may interfere with the host mRNAs and proteins. We present a kinetic analysis of this interplay. In our treatment, the viral miRNA is considered to be able to associate with the host mRNA with subsequent degradation. This process may result in a decline of the mRNA population and also in a decline of the population of the protein encoded by this mRNA. With these ingredients, we first show the types of the corresponding steady-state kinetics in the cases of positive and negative regulation of the miRNA synthesis by the protein. In addition, we scrutinize the situation when the protein regulates the virion replication or, in other words, provides a feedback for the replication. For the negative feedback, the replication rate is found to increase with increasing the intracellular virion population. For the positive feedback, the replication rate first increases and then drops. These features may determine the stability of steady states.

4

Viral genomes and their replication strategies

86%

Lisowski P. , Kleczkowski M. , Jakubczak A.

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2004

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tom 09

5

Molecular mechanisms of genome expression of coxsackievirus B3 that belongs to enteroviruses

72%

Dutkiewicz M. , Swiatkowska A. , Ojdowska A. , Smolska B. , Dymarek-Babs T. , Jasinska A. , Ciesiolka J.

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2012

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tom 93

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nr 4

6

The innate cellular responses to HIV-1 invasion: emerging molecules of ancient defense mechanisms

72%

Simm M.

Archivum Immunologiae et Therapiae Experimentalis

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2007

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tom 55

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nr 3

7

Infectious transcripts from cloned cDNA of potato leafroll luteovirus

72%

Sadowy E. , Pluta K. , Gronenborn B. , Hulanicka D.

Acta Biochimica Polonica

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1998

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tom 45

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nr 2

EN

Infectious transcripts play a key role in the research on plant viruses at the molecular level. A number of cDNA clones covering the whole genome of the Polish isolate of potato leafroll virus were constructed. Four overlapping clones were selected and assembled using restriction sites. The full copy was positioned between T7 RNA polymerase promoter and unique ScaI site. The full-length capped transcripts of the sequence of the viral genome synthesised in vitro were able to replicate in protoplasts and to produce the viral coat protein