The present study aims to detect the prevalence and molecular characterization of Bovine Viral Diarrhea, Rota and corona viral diseases as major causes of diarrhea that mainly leads to neonatal deaths among calves in some governorates in Egypt (Kafr El Sheikh, El Menofyia, Sharkia, Bahaira and El-Gharbia). The infection rate of the three examined viral diseases showed non-significant difference between sex and age of cow calves, and the infection more common in female young calves. Selective positive samples undergo sequencing and compared with other strains in GenBank. The results showed that the Egyptian BVD strain is closely related to BVD strain from Argentina (DQ088995) and Colombia (MH198305), while Bovine Rota (BRV) showed high similarity with Bovine Rota strain of South Korea and Turkey, but Bovine Corona virus (BCoV) was closed to Bovine Corona viruses (BCoV) strain isolated from France.

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The heat transfer area of the heater tubes is a significant factor that deeply affects output power and thermal efficiency in Stirling engines. Alpha-type Stirling engine is concerned in this study. Circular section, elliptical section, twisted elliptical section tubes having twist ratios of 2, 3 and 4 are used as heater designs. 3D simulation model using SST K-ω turbulent model is used for simulating airflow through the hot cylinder, heater tubes, regenerator, cooler, and cold cylinder of the Stirling engine, during a complete engine cycle. The results showed that the elliptical section tubes are better than the circular section tubes. The maximum input energy rate, output work and thermal efficiency are achieved by using elliptical section with twist ratio of 2. These values are 4245.87 W, 1225.34 W and 29.55%, respectively with percentage increments of 5.2%, 7.47% and 3.76%, respectively relative to the circular section heater tubes.