The Internet of Things (IoT) paradigm allows the connection and exchange of information between millions of smart devices. This paradigm grows and develops exponentially as do the risks and attacks on IoT infrastructures. Security, privacy, reliability, and autonomy are the most important requirements in IoT Systems. If these issues are not guaranteed, the IoT system could be susceptible to malicious users and malicious use. In centralized IoT systems, attacks and risks are greater, especially when data is transmitted between devices and shared with other organizations. To avoid these types of situations, this work presents a decentralized system that guarantees the autonomy and security of an IoT system. The proposed methodology helps to protect data integrity and availability based on the security advantages provided by blockchain and the use of cryptographic tools. The accuracy of the proposed methodology was measured on a temperature and humidity sensing IoT-based Wireless Sensor Network (WSN). The obtained results prove that the proposal fulfils the main requirements of an IoT system. It is autonomous, secure to share and send information between devices and users, has privacy, it is reliable, and the information is available in the infrastructure. Furthermore, this research demonstrates that the proposal is less susceptible to the most frequent attacks against IoT systems, such as linking attack, man in the middle, and Distributed Denial of Service (DDoS) attack.

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Potato (Solanum tuberosum L.) is the fourth most important food crop in the world. It is the most economically valuable and well-known member of the plant family Solanaceae. Potato is the host of many pathogens, including fungi, bacteria, Phytoplasmas, viruses, viroids and nematodes, which cause reductions in the quantity and quality of yield. Apart from the late blight fungus [Phytophthora infestans (Mont.) de Bary] viruses are the most important pathogens, with over 40 viruses and virus-like pathogens infecting cultivated potatoes in the field, among which Potato virus Y (PVY), Potato leaf roll virus (PLRV), Potato virus X (PVX), Potato virus A (PVA), Potato virus S (PVS) and Potato virus M (PVM) are some of the most important viruses in the world. In this review, their characteristics and types of resistance to them will be discussed.

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Th e fi rst part of the newly launched series includes miscellaneous new records from fungi to vascular plants. New Th e present paper includes also the revision of the occurrence of Calamag rostis villosa in Hungary and concludes that it has been extinct in the country.

Exchange rate fluctuation is phenomenal in South Africa. This study thus estimates the impact of exchange fluctuation on the profitability of listed mining and manufacturing companies over 2000-2014. The study controlled for company level factors including liquidity, leverage, firm size, tangibility, the opportunity for growth and interest cover. The macroeconomic factors controlled for were interest rate and economic growth. The study used random effect model for estimation. Profitability was measured as return on asset (ROA). Exchange rate fluctuation had a significant negative impact on return on the asset when both industries are considered. However, exchange rate fluctuation had no significant impact on return on the asset in the mining industry but in the manufacturing industry. Liquidity, Interest cover, and tangibility had a significant positive impact but leverage had a significant negative impact on ROA. At the macro level, interest rate had a significant positive impact but economic growth had no significant impact on ROA. The study recommends that managers of manufacturing companies should adopt strategies such as currency swaps, future contract, and hedging to avert exchange rate fluctuation risk.

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A disease of tomato (Lycopersicon esculentum Mill.) was observed in three greenhouses in Tömörkény in southern Hungary in the autumn of 2007. Thirty percent of the plants were chlorotic and stunted and had mottled leaves with interveinal yellowing and necrosis. Similar symptoms induced by Tomato chlorosis virus (ToCV) on tomato have been reported in other countries (1,2). ToCV is a Crinivirus in the Closteroviridae family, which can cause a decline in plant vigor and reduced fruit yield. ToCV is transmitted by whiteflies (Trialeurodes vaporariorum West., T. abutilonea Hald., and Bemisia tabaci Genn.) and grafting, but cannot be transmitted mechanically. Only T. vaporariorum is known to be present and widespread in Hungary. Virus presence was confirmed by reverse transcription-PCR as described by Louro et al. (2). cDNA synthesis with ToCV specific primers (ToCV-UP 5′-TCATTAAAACTCAATGGGACCGAG-3′ (3) and ToCV-DW 5′-GCGACGTAAATTGAAACCC-3′) was successful and electron microscopy revealed ToCV-like particles. The PCR product has been sequenced (GenBank Accession No. HQ444266) and showed 97 to 99% identity to ToCV isolates in GenBank. According to the symptoms, amplified region, sequence data, and electron microscopy, the tomato samples from Tömörkény were confirmed to be infected with ToCV. The economic losses associated with ToCV were minor. To our knowledge, this is the first report on the occurrence of ToCV in Hungary. References: (1) G. P. Accotto et al. Plant Dis. 85:1208, 2001. (2) D. Louro et al. Eur. J. Plant Pathol. 106:589, 2000 (3) J. Th. J. Verhoven et al. Plant Dis. 87:872, 2003.