A five-year epidemiologic study of patients attending a malaria clinic in Delhi was conducted to find the relapse rate of infections with Plasmodium vivax, its seasonal correlation between the primary infection and subsequent relapses, the duration of the incubation period, and the patterns of relapse. By our definition, the relapse rate ranged from 23% to 44% depending on the duration of follow-up. The relapse pattern observed in the study clearly suggests the existence of both tropical and temperate zone types of P. vivax in the population characterized by distinct incubation periods and the possible existence of P. vivax subpopulations characterized by primary long incubation periods. The implication of different incubating forms of P. vivax on the epidemiology and control of malaria is also discussed. Plasmodium vivax malaria constitutes about 60-65% of total malaria cases in India with, pronounced morbidity particularly in the economically weaker sections of the society. 1 The clinicoepidemiologic picture of P. vivax is not well understood due to the phenomenon of latency/relapse. Due to the persistence of the hepatic or hypnozoite form of the parasite, relapses occur in P. vivax infections and it is difficult to predict their timing. 2 Plasmodium vivax exhibits two primary types of incubation/relapse patterns that apparently depend on their tropical or temperate zone origin. 3-5 The classic example of the tropical type is the Chesson strain (New Guinea-South Pacific), characterized by an early primary attack, followed by a short latent period before appearance of frequent relapses during the next year or more, whereas the St. Elizabeth (United States) strain of the temperate type exhibits an early primary attack, followed by a long latent period of 6-14 months, and thereafter succeeded by a series of relapses at short intervals. The present study is an attempt to understand the composition of P. vivax populations exhibiting different types of incubations in relation to the phenomenon of latency and relapses to elucidate their transmission dynamics for planning vector control strategies and chemotherapeutic measures in P. vivax foci. MATERIALS AND METHODS Study site. The malaria clinic of the Malaria Research Centre, at 2-Nanak Enclave, Delhi is located in northeastern Delhi. The clinic attracts patients mostly from 8-9 periurban villages that are 4-5 km from the clinic and have an area of approximately 25 km 2. The Yamuna River is located approximately 3-4 km from these villages. The inhabitants belong mainly to low socioeconomic strata and are employed in small-scale industries as laborers. The climate of Delhi is divided into three distinct seasons: summer (April-June), monsoon (July-October), and winter (November-March). The average temperature, rainfall, and relative humidity during the three seasons are as follows:

The purpose of this study was to choose an appropriate head scatter source model for the fast and accurate independent planar dose calculation for intensity-modulated radiation therapy (IMRT) with MLC. The performance of three different head scatter source models regarding their ability to model head scatter and facilitate planar dose calculation was evaluated. A three-source model, a two-source model and a single-source model were compared in this study. In the planar dose calculation algorithm, in-air fluence distribution was derived from each of the head scatter source models while considering the combination of Jaw and MLC opening. Fluence perturbations due to tongue-and-groove effect, rounded leaf end and leaf transmission were taken into account explicitly. The dose distribution was calculated by convolving the in-air fluence distribution with an experimentally determined pencil-beam kernel. The results were compared with measurements using a diode array and passing rates with 2%/2 mm and 3%/3 mm criteria were reported. It was found that the two-source model achieved the best agreement on head scatter factor calculation. The three-source model and single-source model underestimated head scatter factors for certain symmetric rectangular fields and asymmetric fields, but similar good agreement could be achieved when monitor back scatter effect was incorporated explicitly. All the three source models resulted in comparable average passing rates (>97%) when the 3%/3 mm criterion was selected. The calculation with the single-source model and two-source model was slightly faster than the three-source model due to their simplicity.

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The article contains topical issues regarding the need of methodological support for the efficiency of enterprises. The article considers the theoretical and practical aspects of assessing the effectiveness of enterprises. It is determined that the enterprises of the telecommunication sphere belong to the important components of the national economy. It is offered to consider the efficiency increase of the enterprises activity as the tool of rational use of their resources and potential. The article defines modern and effective concepts of stimulation and increase of the enterprise efficiency. It is determined that currently the most important stages are the concept of digital business, the concept of project management, the concept of business process management, the concept of a system of balanced exponents. The determining factors of production are provided. They include objects of labor, personnel and means of labor. Their characteristics are given. It is noted that ensuring high efficiency of labor and new technology is an integral part of the overall problem of improving the efficiency of financial and economic activities of the enterprise. It is determined that in modern conditions of various crises, competition and uncertainty, economic and political problems, improving the efficiency of production of enterprises in the telecommunications sector is a priority in solving the problems of enterprise viability. It is noted that as well as traditional efficiency indicators, such as return on operating activities, return on assets, return on equity; operating profitability of sales; return on investment in today's transformational environment of industry 4.0 the return on innovation (new technologies) should be added to the list. The characteristics of the main approaches to determine the efficiency of the enterprise are given. General economic analysis of the telecommunications enterprise efficiency is presented. Methodological approaches to increase the activity of these enterprises are suggested and explained.

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