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S Atanassova

Publications and source records attributed to S Atanassova.

8 recordsLinked to original sources
PubMed2005

Chlorsulfuron resistant transgenic tobacco as a tool for broomrape control.

Broomrape (Orobanche ramosa L.) is the most important parasitic plant that infests tobacco (Nicotiana tabacum L.). Chemical treatment of the soil is not effective and crop rotation is not acceptable to solve this problem because of the long viability period of Orobanche seeds in the soil. Application of systemic herbicides in the field with herbicide resistant tobacco could be a successful tool for broomrape control. Several tobacco cultivars were transformed with a mutant ahas3R gene for resistance to the herbicide chlorsulfuron (Glean, DuPont). Transformed plants were selfed and the segregation of resistance was followed in the next generation. The efficiency of the herbicide was demonstrated in greenhouse and field trials. An Orobanche/tobacco growth system was used in order to prove the lethal effect of the herbicide to the attached broomrape plants.

Agrobacterium tumefaciens↗
PubMed2001

Somatic cell count determination in cow's milk by near-infrared spectroscopy: a new diagnostic tool.

The potential of near-infrared spectroscopy (NIR) in the region from 1,100 to 2,500 nm to measure somatic cell count (SCC) content of cow's milk was investigated. A total of 196 milk samples from seven Holstein cows were collected for 28, consecutive days, starting from 7th d after calving, and analyzed for fat, protein, lactose, and SCC. Three of the cows were healthy, and the remainder had periods of mastitis during the experiment. Near-infrared transflectance milk spectra were obtained using an InfraAlyzer 500 spectrophotometer. The calibration for logSCC was performed using partial least square (PLS) regression and different spectral data pretreatment. The best accuracy of determination was found for an equation that was obtained using smoothed absorbance data and 10 PLS factors. The standard error of calibration was 0.361, the calibration coefficient of multiple correlation was 0.868, the standard error of prediction for independent validation set of samples was 0.382, the correlation coefficient was 0.854, and the coefficient of variation was 7.63%. The accuracy of logSCC determination by NIR spectroscopy would allow health screening of cows and differentiation between healthy and mastitic milk samples. It has been found that SCC determination by NIR milk spectra is based on the related changes in milk composition. The most significant factors that simultaneously influenced milk spectra with the elevation of SCC were alteration of milk proteins and changes in ionic concentration of milk.

Animals↗
PubMed2000

Near infrared spectroscopy for biomonitoring: cow milk composition measurement in a spectral region from 1,100 to 2,400 nanometers.

The potential of near infrared spectroscopy (NIRS; 1,100 to 2,400 nm) to measure fat, total protein, and lactose content of nonhomogenized milk during milking and the influence of individual characteristics of each cow's milk on the accuracy of determination were studied. Milk fractions were taken during milking, twice per month, for 6 mo. Samples were taken every 2nd and 4th wk at the morning and the evening milkings. Teatcups were removed at each 3 L of milk yield as determined with a fractional sampling milk meter. A total of 260 milk samples were collected and analyzed with an NIRSystem 6500 spectrophotometer with 1-mm sample thickness. Partial least squares (PLS) regression was used to develop calibration models for the examined milk components. The comparison with the reference method was based on standard error of cross validation (SECV). The obtained SECV varied from .107 to .138% for fat content, from .092 to .125% for total protein, and from .066 to .096% for lactose content, and the accuracy of the reference method (AOAC, 1990, method No 972.16) was .05% for all measured milk components. The obtained models had lower SECV when an individual cow's spectral data were used for calibration. The reduction of SECV for each cow's individual calibration, when compared with SECV for the set of all samples, differed with the different constituents. For fat content determination, the reduction reached 22.46%, for protein 26.40%, and for lactose 31.25%. This phenomena was investigated and explained by principle component analysis (PCA) and by comparing loading of PLS factors that account for the most spectral variations for each cow and the measured milk components, respectively. The results of this study indicated that NIRS (1,100 to 2,500 nm, 1-mm sample thickness) was satisfactory for nonhomogenized milk compositional analysis of milk fractions taken in the process of milking.

Animals↗
PubMed1999

Near-infrared spectroscopy for dairy management: measurement of unhomogenized milk composition.

The potential of near-infrared spectroscopy to measure fat, total protein, and lactose contents of unhomogenized milk was studied for use in dairy management, as a new tool for on-line milk analysis in the process of milking. Influence of the spectral region, sample thickness, and spectral data treatment on the accuracy of determination was investigated. Transmittance spectra of 258 milk samples, collected at different stages of the milking process, were obtained with a spectrophotometer (NIRSystems 6500; FOSS-NIRSystems, Silver Spring, MD) in the wavelength range from 400 to 2500 nm with sample thicknesses of 1 mm, 4 mm, and 10 mm. The spectral region and sample thickness were found to be significant factors for milk fat and total protein determination but not the lactose determination. The best accuracy was obtained with the 1100 to 2400 nm region, 1-mm sample thickness, and the first derivative data transformation. For the spectral region from 700 to 1100 nm, close accuracy was obtained for fat with a 10-mm sample and for total protein with a 1-mm sample thickness. The sample thickness did not change significantly the accuracy of lactose determination. Different treatments of spectral data did not improve the calibrations for fat and protein. For the region from 700 to 1100 nm, where inexpensive on-line sensors could be used, the highest positive coefficients for fat were at 930, 968, 990, 1026, 1076, and 1092 nm; for lactose were at 734, 750, 786, 812, 908, 974, 982, and 1064 nm; and for total protein were at 776, 880, 902, 952, and 1034 nm.

Animals↗
PubMed1998

Spatiotemporal impulse response and cortical magnification.

According to a model of the spatiotemporal weighting function (Manahilov, V. Spatiotemporal visual response at suprathreshold stimuli. Vision Research, 1995, 35, 227-237; and Triphasic temporal impulse responses and Mach bands in time. Vision Research, 38, 447-458) the waveform of the temporal-impulse response and the cortical spread of the spatial-impulse response should not depend on the retinal site of stimulation. To verify these model predictions, the spatiotemporal responses to brief near-threshold lines presented in the fovea and the near retinal periphery were studied. The effect of an inducing stimulus on the threshold for pattern detection of a test stimulus was measured, assuming that the pattern-detection threshold was determined by the test peak response. The spatial spread of the line response expressed in visual-field units was increased with eccentricity. The temporal-impulse responses to foveal and peripheral stimuli were similar. The model of the weighting function was used to evaluate the relative magnification factor for the retinal location tested. The calculated cortical spatial-impulse responses did not depend on the stimulation site. The data obtained are in line with the cortical magnification theory of peripheral vision.

Humans↗
PubMed1993

Solubility, inhibited growth and dissolution kinetics of calcium oxalate crystals in solutions, containing hippuric acid.

An analysis of crystal growth and dissolution of slightly soluble salts in physiological solutions in the presence of complexing ions was carried out, simulating conditions typical in human urine. It was found that hippuric acid, a normal physiological constituent of urine, acts at increased concentrations as a dissolving agent with respect to calcium oxalate (CaOx) and CaOx calculi. The kinetics of dissolution of crystalline CaOx calculi in physiological solutions containing hippuric acid at different concentrations were studied, using the change in the Archimedean weight of samples immersed in the solution. Analysis of the experimental results enabled the determination of the increased solubility of CaOx in the presence of hippuric acid and the quantitative characterization of this substance as a new and promising agent for dissolving CaOx calculi in human urine. The possible effect of hippuric acid as a natural regulator of CaOx supersaturation and crystallization in human and mammalian urine is also discussed.

Calcium Oxalate↗