Electronic Absorption Spectra of New y-Keto-dimethine Cyanine Dyes and Apocyanines

New asymmetrical y-keto-dimethine cyanines (2.-f) were prepared through the condensation of phenyl glycosal derivatives (l.-e) with 2-methyl pyridinium (quinolinium)- 2yl salts. Such dyes were converted into the corresponding dyes (3a-g and 4a-d) by cyclocondensation with hydrazines or hydroxylamine hydrochloride under suitable conditions. The new synthesized cyanines were identified by elemental and spectral analyses. The U\u27V-visible absorption spectra of some selected dyes were investigated in pure and mixed solvents as well as in aqueous buffer solutions. Molecular complex formation with ethanol was verified by mixed solvent studies. Electronic transitions were attributed to either locally excited or predominantly charge transfer states. The spectral shifts were discussed in relation to molecular structure and in terms of medium effects. The variation of absorbance with pR was utilized for the determination of the pK. value for aselected compound (2e). The photostability of some selected đyes (2e, 3g and 4d) was investigated

Dystocia in Friesian cows and its effects on postpartum reproductive performance and milk production

A total of 1,243 records for 585 dairy Friesian cows from 1997–2004 were used to study the factors affecting dystocia and its effects on reproductive performance and milk production. The overall incidence of dystocia was 6.9%. The percentage of dystocia decreased with increasing live body weight, age, and parity of cows (P < 0.05); however, it increased with increasing birth weight of calves (P < 0.05). The highest percentage of dystocia was detected in winter season, but the least percentage was in summer season (P < 0.05). The percentage of incidence of dystocia was significantly (P < 0.05) higher with winter feeding compared to summer ration (8.2% vs. 5.1%). The percentage of incidence of dystocia was significantly (P < 0.05) higher with twinning than single calving (15.5% vs. 6.5%), while not significantly affected by the sex of born calves. Incidence of dystocia had adverse effects on reproductive performance and milk yield. The service interval, service period, days open, and calving interval were significantly (P < 0.05) longer in cows afflicted with dystocia compared to normal cows. The conception rate was lower (P < 0.05), but the number of service per conception was higher (P < 0.05) in cows afflicted with dystocia compared to normal cows (60.5% vs. 73.0% and 3.4 vs. 2.7, respectively). Average daily milk yield was lower (P < 0.05) by 1 kg for cows with incidence of dystocia compared to normal cows

Eefect Of Heat Stress On Perfprmance Of Dairy Friesian Cows 1-Milk Production And Composition Researcher

Abstract: A total of 1243 available records were collected for 581 Friesian cows during 8 year period from 1997 to 2004 were used to study heat stress on milk production and composition. Average temperature humidity index (THI) values confirm the presence of heat stress during the period from June to September (summer season). Heat stress during summer season led to significant decrease (P&lt;0.05) in lactation period by 35 day and reduced total, 305 and daily milk yield by 39.00, 31.40 and 29.84% and the percentages of fat, protein, lactose, solids not fat, total solids and ash by 7.92, 4.06, 3.97, 4.03, 5.21 and 5.63% compared with winter season, respectively