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Several viruses have been described to infect sugar beet (Beta vulgaris var. saccharifera L.), but virus yellows disease is one of the most important diseases in many sugar beet growing areas. It is caused by four viruses in either single or mixed infection, including the poleroviruses beet western yellows virus (BWYV), beet mild yellowing virus (BMYV), and beet chlorosis virus (BChV) and a closterovirus, beet yellows virus (BYV) (Hossain et al. 2021; Stevens et al. 2005). In August 2019, five samples of sugar beet plants showing yellowing on interveinal leaf tissue were collected in a sugar beet crop in the Novi Sad locality (Vojvodina Province, Serbia). Double-antibody sandwich (DAS) ELISA commercial antisera (DSMZ, Braunschweig, Germany) were used to test the collected samples for the presence of the most common sugar beet viruses: beet necrotic yellow vein virus (BNYVV), BWYV, BMYV, BChV, and BYV. Commercial positive and negative controls were included in each ELISA test. BYV was serologically detected in all sugar beet samples, but no other viruses tested were found.

Aircrafts powered by piston engine represent the bulk of the fixed wing fleet. Large majorities of these aircrafts are equipped with single, air-cooled, and horizontally opposed, piston engines. The mechanical failure in any of the piston engine components, especially concerning fatigue failure of the cylinder head (CH) made of an aluminum-casting alloy may have serious or fatal consequences to the safety of the crew and the aircraft. Therefore, the aim of this study is to identify the root cause(s) of repetitive premature failures in an aircraft engine CH.Two piston engines of the training aircraft Utva-75 have malfunctioned during the flight mission due to the fatigue cracking of their aluminum cast CHs. Visual inspection revealed that transverse cracking had occurred between the fifth and the sixth deep integral cooling fins. Based on the fractographic analysis, observation of the characteristic ratchet and beach marks indicated the occurrence of fatigue failure. The crack initiated from multiple origins located on the inner flange fillet on the exhaust side of the CHs. The metallographic examination revealed that the fatigue was promoted from pre-existing material defect due to a high concentration of shrinkage pores at the initiation crack site and can be most likely associated with the manufacturing process of casting. The finite element method, utilized to determine the stress state of the cylinder assembly, also confirmed that the crack origin was located at the most stressed area of the cylinder assembly, i.e., on the inner flange fillet of the exhaust side of the CH.

This paper presents an analytical study on the effect of laminate lay-up of composite missile stabilizer structure for achieving a maximum flutter speed without strength penalty. The flexible stabilizer structure in high-velocity flow may experience flutter, an aeroelastic phenomena where vibrations of the structure become unstable and can cause stability loss and flight vehicle failure. Flutter in missiles is mainly affected by the aerodynamic and structural properties of the stabilizers whereas flight vehicle body has a minor role. In the present paper the effect of laminate lay-up on flutter speed of composite missile stabilizers is investigated. Two degrees of freedom (plunge and twist) analytical model of typical fin stabilizer airfoil section is presented. Based on this model the critical flutter speed for the composite missile stabilizer is derived for subsonic flight conditions. It was found that natural stabilizer frequencies (in bending and twisting) highly influence the maximum flutter speed. Natural fin frequencies (in bending and twisting) are calculated using finite element approach based on Lanczos method of frequencies extraction. Several modal frequency models are investigated and results are discussed, since the accurate prediction of natural frequencies plays significant role in overall flutter speed (VF) determination. For the trapezoidal stabilizer shape different laminate lay-up sequences are investigated, flutter speeds calculated and results compared in order to determine maximum flutter speed. The material of interest in this study was carbon based AS/4-3501-6.

Infection of strawberry plants with binucleate Rhizoctonia spp. results in an increase in peroxidase activity and the appearance of new isoforms of the enzyme. In healthy and diseased roots of two different strawberry genotypes seven peroxidase isoenzymes were found. In healthy strawberry cv. Senga Sengana, which was moderately resistant to infection, four isoenzymes (1, 2, 5, and 6) were found. Moreover the activity of these isoenzymes was increased and three new isoenzymes (3, 4, and 7) were found in infected roots. In the strawberry hybrid 3/2/86/88/R, which is very susceptible to infection, only isoenzyme 2 was present in the roots of healthy plants. Following infection, the activity of isoenzyme 2 was increased and five new isoenzymes (1, 4, 5, 6, and 7) were detectable. The results obtained indicate that strawberry resistance to binucleate Rhizoctonia may be correlated with peroxidase isoenzyme profile with particular reference to isoform 3, which is only present in infected roots of the moderately resistant cv., Senga Sengana.