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Papers by K. Kostov
Surface and Coatings Technology, 2004
Surface modification of ultra-high molecular weight polyethylene (UHMWPE) has been explored by us... more Surface modification of ultra-high molecular weight polyethylene (UHMWPE) has been explored by using the non-line-of-sight plasma immersion ion implantation (PIII) technique. The polymer specimens, immersed in nitrogen plasma, were pulsed through a metallic grid at repetition rate of 100 Hz with negative high-voltage pulse of 15 kV magnitude and 10 As duration. The UHMWPE's structural changes induced by the PIII were analyzed by laser Raman spectroscopy (LRS) at 514.5 nm, X-ray photoelectron spectroscopy (XPS) and optical microscopy. From the Raman spectra it is observed that the chain structure of UHMWPE has been damaged due to ion bombardment and a layer of hydrogenated amorphous carbon is formed. The ratio of sp 3 /sp 2 bonded carbon in the modified layer was obtained by suitable fitting of the XPS C 1s energy peak, using a four-curve fitting procedure, which recognizes a portion of C -O and CMO surface bonding. The XPS results for N 1s peak show that the implanted nitrogen ions form chemical bonds with the polymer instead of forming precipitates by self-clustering. D
Biotechnology & Biotechnological Equipment, 2010
In the present study the microsatellite marker Xgwm261, linked to Rht 8 gene as well as allele sp... more In the present study the microsatellite marker Xgwm261, linked to Rht 8 gene as well as allele specific markers for , and the gibberellic acid (GA) test were employed to examine the distribution of semi-dwarf and photoperiod response and vernalization genes in 21 old and modern Bulgarian, 4 introduced cultivars and 11 advanced breeding lines from the wheat germplasm collections of DAI, General Toshevo, Institute of Genetics, Sofia and IPGR, Sadovo. Several allele variants were identified at locus Xgwm261, among which the 192 bp allele can serve as a diagnostic marker for the presence of Rht 8 gene. The Ppd-D1a, vrn-A1 and vrn-D1 alleles were found in almost all wheat genotypes illustrating the relationship between the photoperiod and vernalization response and the adaptability to the regional environments. The photoperiod insensitivity allele (Ppd-D1a) was found in 93.
Surface and Coatings Technology, 2004
Surface modification of ultra-high molecular weight polyethylene (UHMWPE) has been explored by us... more Surface modification of ultra-high molecular weight polyethylene (UHMWPE) has been explored by using the non-line-of-sight plasma immersion ion implantation (PIII) technique. The polymer specimens, immersed in nitrogen plasma, were pulsed through a metallic grid at repetition rate of 100 Hz with negative high-voltage pulse of 15 kV magnitude and 10 As duration. The UHMWPE's structural changes induced by the PIII were analyzed by laser Raman spectroscopy (LRS) at 514.5 nm, X-ray photoelectron spectroscopy (XPS) and optical microscopy. From the Raman spectra it is observed that the chain structure of UHMWPE has been damaged due to ion bombardment and a layer of hydrogenated amorphous carbon is formed. The ratio of sp 3 /sp 2 bonded carbon in the modified layer was obtained by suitable fitting of the XPS C 1s energy peak, using a four-curve fitting procedure, which recognizes a portion of C -O and CMO surface bonding. The XPS results for N 1s peak show that the implanted nitrogen ions form chemical bonds with the polymer instead of forming precipitates by self-clustering. D
Biotechnology & Biotechnological Equipment, 2010
In the present study the microsatellite marker Xgwm261, linked to Rht 8 gene as well as allele sp... more In the present study the microsatellite marker Xgwm261, linked to Rht 8 gene as well as allele specific markers for , and the gibberellic acid (GA) test were employed to examine the distribution of semi-dwarf and photoperiod response and vernalization genes in 21 old and modern Bulgarian, 4 introduced cultivars and 11 advanced breeding lines from the wheat germplasm collections of DAI, General Toshevo, Institute of Genetics, Sofia and IPGR, Sadovo. Several allele variants were identified at locus Xgwm261, among which the 192 bp allele can serve as a diagnostic marker for the presence of Rht 8 gene. The Ppd-D1a, vrn-A1 and vrn-D1 alleles were found in almost all wheat genotypes illustrating the relationship between the photoperiod and vernalization response and the adaptability to the regional environments. The photoperiod insensitivity allele (Ppd-D1a) was found in 93.