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1

Effect of severe plastic deformation by ECAP on corrosion behaviour of aluminium alloy AA 7075

100%

Ilieva M. , Radev R.

Archives of Materials Science and Engineering

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2016

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tom Vol. 81, nr 2

55--61

EN

Purpose: The present study compares the corrosion behaviour of overaged AA 7075 before and after equal channel angular pressing ECAP in two media, containing chlorides, in order to answer the question how grain refinement of aluminium alloys influences their corrosion properties. Design/methodology/approach: The effect of equal channel angular pressing ECAP on corrosion behaviour of aluminium alloy AA 7075 was studied in two water solutions, containing chloride ions: 1) 0.01 M Na2SO4 with addition of 0.01%Cl-, and 2) 3g/l H2O2 and 57g/l NaCl. The changes in electrochemical characteristics, provoked by grain size refinement after equal channel angular pressing ECAP, were found using potentiodynamic polarisation. Steady state potential, corrosion potential, corrosion current density; breakdown (pitting) potential of overaged and deformed by equal channel angular pressing ECAP aluminium alloy AA 7075 were measured. Findings: In the environment with lower chloride concentration equal channel angular pressing ECAP process led to increase in pitting corrosion resistance and in the medium with higher chloride concentration - to decrease in pitting corrosion resistance. That way grain refinement does not demonstrate a uni-directional influence on corrosion resistance of AA 70775. Research limitations/implications: The results suggest the possibility for development of materials having the same chemical composition but with different corrosion resistance to different environments. Originality/value: The paper presents the corrosion behaviour of ultrafine-grained aluminium alloy AA 7075 and the influence of the chloride ions concentration in the corrosion medium on this behaviour.

2

Changes in the rural areas in Bulgaria: processes and prospects

100%

Ilieva M. , Mladenov C.

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tom 76

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nr 1

3

Migratory state: body mass and fat level of some passerine long-distance migrants during autumn migration in North-Eastern Bulgaria

100%

Ilieva M. , Zehtindjiev P.

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nr 1

4

Betalain production in plant in vitro systems

80%

Georgiev V. , Ilieva M. , Bley T. , Pavlov A.

Acta Physiologiae Plantarum

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2008

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tom 30

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nr 5

EN

Betalains have been widely used as natural colorants for many centuries, but their attractiveness for use as colorants of foods (or drugs and cosmetics) has increased recently due to their reportedly high anti-oxidative, free radical scavenging activities and concerns about the use of various synthetic alternatives. The main commercial sources of betalains are powders and concentrates of red beet (Beta vulgaris) or cactus pear (Opuntia ficusindica) extracts. However, in recent years the technical and commercial feasibility of various in vitro systems to produce them biotechnologically has been explored. These research activities have included assessments of novel approaches for cultivating plant cell or tissue cultures, and diverse bioreactor systems for increasing production levels of secondary metabolites. This paper reviews recent progress in plant in vitro systems for producing betalain pigments. In addition, the factors that could be manipulated, the bioreactor systems that could be used, and the strategies that could be applied to improve betalain production are discussed.

5

Directional behaviour of the Sedge Warbler [Acrocephalus schoenobaenus] studied in two types of orientation cages during autumn migration - a case study

80%

Zehtindjiev P. , Ilieva M. , Ozarowska A. , Busse P.

The Ring

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2003

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tom 25

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nr 1-2

6

Occurrence of haemosporidian parasites in the paddyfield warbler, Acrocephalus agricola [Passeriformes, Sylviidae]

61%

Zehtindjiev P. , Ilieva M. , Krizanauskiene A. , Oparina O. , Oparin M. , Bensch S.

Acta Parasitologica

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2009

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tom 54

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nr 4

295-300

EN

The blood parasite diversity was studied in paddyfield warblers (Acrocephalus agricola) breeding in NE Bulgaria, SW Russia and S. Kazakhstan. Nine cytochrome b gene lineages were recorded, 4 belonging to Haemoproteus spp. and 5 to Plasmodium spp. The overall prevalence of haemosporidians was 33.3%. The composition of parasites varied geographically, with six lineages recorded in Russia, five lineages in Bulgaria and two lineages in Kazakhstan. Two lineages are described for the first time, i.e. ACAGR1 (belonging to Plasmodium sp. and recorded from a single bird in Russia) and ACAGR2 (belonging to Haemoproteus sp., recorded from Bulgaria and Russia). The latter lineage is the most widespread parasite in the Bulgarian population, scarce in Russia and absent in Kazakhstan. It is supposed that ACAGR2 has originated from the widespread lineage ACDUM1 differing from it by a single nucleotide. One lineage only (ACDUM2) occurs in all the three populations studied and is a nonspecific parasite known from various passerines. Six of the registered lineages have been found in a single population of A. agricola and also represent non-specific parasites occurring in a wide range of passerine birds. Their records in A. agricola may indicate the high transmission rate of these parasites in the habitats where this host co-occurs with other passerines. The variation of the composition of the haemosporidian parasite communities through the breeding range of A. agricola makes up heterogeneous selection pressures that may drive intraspecific variation in important life-history traits.