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Prevalence, Risk Factors and Consequent Effect of Dystocia in Holstein Dairy Cows in Iran
Atashi, Hadi,Abdolmohammadi, Alireza,Dadpasand, Mohammad,Asaadi, Anise Asian Australasian Association of Animal Productio 2012 Animal Bioscience Vol.25 No.4
The objective of this research was to determine the prevalence, risk factors and consequent effect of dystocia on lactation performance in Holstein dairy cows in Iran. The data set consisted of 55,577 calving records on 30,879 Holstein cows in 30 dairy herds for the period March 2000 to April 2009. Factors affecting dystocia were analyzed using multivariable logistic regression models through the maximum likelihood method in the GENMOD procedure. The effect of dystocia on lactation performance and factors affecting calf birth weight were analyzed using mixed linear model in the MIXED procedure. The average incidence of dystocia was 10.8% and the mean (SD) calf birth weight was 42.13 (5.42) kg. Primiparous cows had calves with lower body weight and were more likely to require assistance at parturition (p<0.05). Female calves had lower body weight, and had a lower odds ratio for dystocia than male calves (p<0.05). Twins had lower birth weight, and had a higher odds ratio for dystocia than singletons (p<0.05). Cows which gave birth to a calf with higher weight at birth experienced more calving difficulty (OR (95% CI) = 1.1(1.08-1.11). Total 305-d milk, fat and protein yield was 135 (23), 3.16 (0.80) and 6.52 (1.01) kg less, in cows that experienced dystocia at calving compared with those that did not (p<0.05).
Atashi, Hossein,Motahari, Kazem,Tabrizi, Farshad Farshchi,Sarkari, Majid,Fazlollahi, Farhad Korean Chemical Society 2011 대한화학회지 Vol.55 No.1
비닐 아세트산염 합성에 대한 1족 알칼리금속 아세트산염의 촉진 효과를 조사하였다. Pd-Au/$SiO_2$ 촉매를 사용한 경우와 사용하지 않은 경우에 대해 에틸렌과 아세트산 간의 기체상 반응에 대해 생성물 선택성과 에틸렌 전환을 비교하였다. 촉진제가 촉매 표면을 안정화시켰으며, 생성물 선택성과 에틸렌 전환을 촉진하였다. 이 촉매 효과는 1족에서 위에서 아래로 내려갈수록 증가하였다. 이것은 아세트산염의 공통이온효과 때문이다. The effect of Group I alkali acetate promoters on vinyl acetate (VA) synthesis was evaluated. Catalyst product selectivity and ethylene conversion are compared to the unpromoted catalyst in the fixed-bed reactor with oxidation reaction of ethylene and acetic acid in gaseous phase over Pd-Au/$SiO_2$ catalyst. It was found that: a) the promoters were stabilized on the catalyst surface, b) common effect for the alkali promoted Pd-Au catalysts increaseed in product selectivity and ethylene conversion compared to unpromoted catalyst (these effects increase from top to the bottom of Group I). These promoting effect is due to the common-ion effect of acetate, present in the reaction, resulting in an increase in the activity of the catalyst. In addition a complementary theory for the effect of Au in the structure of the catalyst is proposed the imposition of distribution of palladium particles through decreasing the particle's diameter.
Kinetic study of Fischer–Tropsch process on titania-supported cobalt–manganese catalyst
H. Atashi,F. Siami,A.A. Mirzaei,M. Sarkari 한국공업화학회 2010 Journal of Industrial and Engineering Chemistry Vol.16 No.6
An active cobalt–manganese catalyst was prepared by co-precipitation method, and was also tested for hydrogenation of carbon monoxide to light olefins. The catalyst was characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM) and Brunauer–Emmett–Teller (BET) surface area techniques. The kinetic experiments on a well-characterized Co–Mn/TiO2 catalyst were performed in a fixed-bed micro-reactor, and were also conducted in a temperature range of 190–280 8C, pressure range of 1–10 bar, H2/CO feed ratio (mol/mol) range of 1–3 and a space velocity range of 2700–5200 h1. Two kinetic expressions based on Langmuir–Hinshelwood–Houngen–Watson (LHHW) mechanism were observed to fit the experimental data accurately for Fischer–Tropsch synthesis reaction. The kinetic parameters were estimated with non-linear regression method. Activation energies obtained were 35.131 and 44.613 kJ/mol for optimal kinetics models.
Intrinsic kinetics of the Fischer-Tropsch synthesis over an impregnated cobalt-potassium catalyst
Hossein Atashi,Mohsen Mansouri,Seyyed Hossein Hosseini,Mohammad Khorram,Ali Akbar Mirzaei,Masoud Karimi,Ghobad Mansouri 한국화학공학회 2012 Korean Journal of Chemical Engineering Vol.29 No.3
The optimal amount of 15 wt%Co/10 wt%K/Al2O3 catalyst was prepared using the impregnation technique in order to study the kinetics of the Fischer-Tropsch synthesis. The rate of synthesis was measured in a fixed-bed micro reactor with H2/CO feed ratio of 1-3 and space velocity in the range of 2,700-5,200 h−1 under reactor pressure of 8 bar and a temperature range of 210-240 oC. The experimental data were best fitted by a Langmuir-Hinshelwood-Hougen-Watson (LHHW) approach rate in the form of −rCO=(k2K1PCOPH2)/(1+K1PCO). Furthermore, the data were fitted fairly well by a power law equation in the form of −rCO=kPCO 1.32PH21.42. The activation energies for LHHW approach model and power law equation were obtained as 138.5 kJ/mol and 87.39 kJ/mol, respectively.
Hossein Atashi,Kazem Motahari,Farshad Farshchi Tabrizi,Farhad Fazlollahi,Majid Sarkari 대한화학회 2011 대한화학회지 Vol.55 No.1
The effect of Group I alkali acetate promoters on vinyl acetate (VA) synthesis was evaluated. Catalyst product selectivity and ethylene conversion are compared to the unpromoted catalyst in the fixed-bed reactor with oxidation reaction of ethylene and acetic acid in gaseous phase over Pd-Au/SiO_2 catalyst. It was found that: a) the promoters were stabilized on the catalyst surface, b) common effect for the alkali promoted Pd-Au catalysts increaseed in product selectivity and ethylene conversion compared to unpromoted catalyst (these effects increase from top to the bottom of Group I). These promoting effect is due to the common-ion effect of acetate, present in the reaction, resulting in an increase in the activity of the catalyst. In addition a complementary theory for the effect of Au in the structure of the catalyst is proposed the imposition of distribution of palladium particles through decreasing the particle’s diameter.
Moradi, Hiresh,Atashi, Peyman,Amelirad, Omid,Yang, Jae-Kyu,Chang, Yoon-Young,Kamranifard, Telma Techno-Press 2022 Advances in nano research Vol.12 No.4
Silica nanoparticles, which have a broad range of sizes and specific surface features, have been used in many industrial applications. This study was conducted to synthesize monodispersed silica nanoparticles directly from tetraethyl orthosilicate (TEOS) with an alkaline catalyst (NH<sub>3</sub>) based on the sol-gel process and the Stöber method. A central composite design (CCD) is used to build a second-order (quadratic) model for the response variables without requiring a complete three-level factorial experiment. The process was then optimized to achieve the minimum particle size with the lowest concentration of TEOS. Dynamic light scattering and scanning electron microscopy were used to analyze the size, dispersity, and morphology of the synthesized nanoparticles. After optimization, a confirmation test was carried out to evaluate the confidence level of the software prediction. The results revealed that the predicted optimization is consistent with experimental procedures, and the model is significant at the 95% confidence level.
Mansouri, Mohsen,Atashi, Hossein,Khalilipour, Mir Mohammad,Setareshenas, Naimeh,Shahraki, Farhad Korean Chemical Society 2013 대한화학회지 Vol.57 No.6
The effect of operating conditions (temperature and the partial pressures of H2 and CO) on the reaction rate of Fischer-Tropsch synthesis (FTS) were investigated by carrying out experiments according to a Box-Behnken design (BBD), and were mathematically modeled by using response surface methodology (RSM). The catalyst used was a nano-structured cobalt/manganese oxide catalyst, which was prepared by thermal decomposition. The rate of synthesis was measured in a fixed-bed micro reactor with $H_2/CO$ molar feed ratio of 0.32-3.11 and reactor pressure in the range of 3-9.33 bar at space velocity of $3600h^{-1}$ and a temperature range of 463.15-503.15 K, under differential conditions (CO conversion below 2%). The results indicated that in the present experimental setup, the temperature and the partial pressure of CO were the most significant variables affecting reaction rate. Based on statistical analysis the quadratic model of reaction rate of FTS was highly significant as p-value 0.0002.
M. Shiva,H. Atashi,F. Farshchi Tabrizi,A.A. Mirzaei 한국공업화학회 2012 Journal of Industrial and Engineering Chemistry Vol.18 No.3
Combined UBI-QEP/LHHW methodology was employed for kinetic modeling of carbon monoxide hydrogenation to light olefins on a bimetallic Fe–Co catalysis in a fixed bed micro-reactor. In combination with apparent activation energies obtained from UBI-QEP approach, the experimental data from central composite designs were employed to fit several LH/ER rate equations. A new rate equation for CO consumption and a new mechanism based on parallel formyl/carbide with two RDS elementary reactions was concluded. It was also concluded that CO* is MARI on Fe–Co catalysis surface and its coverage on the catalyst was estimated to be 0.5 ml.
Bioleaching kinetics of copper from copper smelters dust
Fereshteh Bakhtiari,Hossein Atashi,Mortaza Zivdar,Seyedali Seyedbagheri,Mohammad Hassan Fazaelipoor 한국공업화학회 2011 Journal of Industrial and Engineering Chemistry Vol.17 No.1
The smelting factory of Sarcheshmeh Copper Complex in Iran produces about 50 tons per day of copper dust containing 36% Cu, 22.2% Fe and 12.2% S. The dust is currently recycled to the smelters. Thismethod is not desirable in terms of operation, and energy consumption. A mixed culture of mesophilic bacteria was used to examine the bioleaching of copper from the dust. The effect of various parameters such as pulp density, nutrients, temperature, and the amount of pyrite added to the bioleaching media were examined in the dust bioleaching tests. It was shown that the bacteria contributed effectively in the leaching of copper from the dust. The collected data showed that at pH 1.8 and the pulp density less than 7%, the dissolution of copper followed shrinking core kinetic model and the process was limited by diffusion of lixiviant. With the pulp density of 7%, however, the process showed to be reaction limited.
Mehdi Shiva,Hossein Atashi,Farhad Farshchi Tabrizi,Ali Akbar Mirzaei,Maryam Arsalanfar 한국공업화학회 2013 Journal of Industrial and Engineering Chemistry Vol.19 No.1
The study addresses an enhanced approach for study of kinetics and mechanism of CO hydrogenation over Fe–Co catalyst. Kinetic models for rate of methane, paraffin and olefin formation have been developed by LHHW approach and information that obtained from UBI_QEP calculations.