The epidemiology of epidemic parotitis in the USSR.

Morbidity from epidemic parotitis in the USSR in the period from 1958 to 1972 ranged within the limits of 266.6 and 521.7 cases per 100 000 inhabitants. A 3--4 years cyclic recurrence of rises and falls in morbidity was observed. The bulk of cases of disease occur in the winter-spring period. In towns, parotitis is registered 3 times more frequently, in the mean, than in rural districts. More than 95% of patients in the USSR consisted of children under 15, while in Moscow, children aged 3--5 years were the most affected group. In Moscow in the period from February 1, 1972 to January 31, 1973, the morbidity in men was 493.2 per 100 000 and in women 339.5 per 100 000 (ratio 1:1.45).     

Incidence of epidemic parotitis in different countries]

The authors analyzed the incidence of epidemic parotitis in various countries in 1960--1969 on the basis of the data published by the WHO. It can be supposed that there was no significant difference in the morbidity in various countries and that discrepancy in the official data of individual countries was apparently caused by the errors in recording. In the majority of the countries morbidity curve was fluctuating in character with a 4--5-year periodicity. In the countries of the northern hemisphere the greatest number of cases occurred in spring, and in the southern--in autumn. Monthly distribution of cases during the years with a high and low morbidity level displayed no significant changes.     

气象因素对芒果蓟马种群数量动态的影响

明确芒果园中蓟马复合种种群动态与气象因子之间的关系。用粘虫板定期定点监测芒果园中蓟马的种群消长情况;通过相关分析、主成分分析和灰色关联分析,分析其与气象因素的关系。芒果花期蓟马种群数量为全年发生高峰。相关分析结果表明,监测日蓟马种群数量与日平均气温(℃)、日最大风速(m/s)显著正相关,与日最低气温(℃)显著负相关。芒果花期蓟马种群数量与2月降水量(mm)、3月平均风速(m/s)、1-2月平均气温(℃)、2月月均最高、最低气温(℃)、2-3月平均相对湿度(%)及1-3月平均最小相对湿度(%)显著相关。主成分分析表明,月平均温度(℃)和月最低气温(℃)是影响蓟马种群动态的主要因素,对蓟马种群动态的影响达56.0%。灰色关联分析表明,月均最低气温(℃)对芒果蓟马种群数量影响最大。月最低气温(℃)和月平均温度(℃)是影响芒果园中蓟马复合种种群数量动态的主要气象因素。芒果蓟马复合种种群数量受食物、种群扩散、天敌、自身繁殖和气候因素的共同影响。     

Studies on the spread of certain plant viruses in the field

Studies on the spread of potato viruses X and Y and cucumber mosaic virus in the field are described: tobacco was used as the experimental plant. The plants were set out in the form of a cross, one series with the leaves in contact and one with the leaves not touching. No spread of potato virus X was observed, but there was extremely rapid permeation of virus Y throughout the plots. The spread of cucumber mosaic virus was much slower than that of virus Y.     

Effect of certain environmental factors on Bradyrhizobium japonicum

Dependence of motility and chemotaxis was studied in two strains of Bradyrhizobium japonicum upon several environmental factors. In both strains, chemotaxis was found to increase with an increasing concentration of the attractant (glucose) to 5.6 x 10(-2) M. Both motility and chemotaxis reached their maximum in the two- to three-day cultures at neutral pH. The maximum motility of these bacteria occurred at 40 degrees C. The maximum values of chemotaxis in these microorganisms were, however, observed at 20-25 degrees C. Chemotaxis in acidic or alkaline media and at low temperatures was found to be markedly weaker. Nonoptimal values of these parameters in soil may be a limiting factor for the interaction of the given bacteria with soybean roots.     

Phytoecological importance,mutual redundancy and phytological threshold values of certain climatic factors

A combination of methods (intensity of indication, floristic and mesological redundancy analysis, beta-diversity analysis, principal components analysis and Wildi's interactive ranking procedure) were used to evaluate redundancy and relative phytoecological importance among 80 climatic variables in Galicia (N.W. Spain). The information they contained was found to be adequately summarized by just 3 factors thought to play a major role in regulating the distribution of the species considered in the study area and similar areas: Baudiere's QE index, mean minimum temperature in the coldest month and mean temperature range in the coldest month. For these three factors, phytoclimatic thresholds were determined by examining beta-diversity and were used to define phytoclimatic zone types.

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Resumen Se valora la redundancia e importancia fitoecológica relative de 80 variables climáticas en Galicia (N.O. de España) empleando una combinacion de diferentes metodos (intensidad indicadora, análisis de la redundancia florística y mesológica, análisis de beta-diversidad, análisis de componentes principales y el método de ordenación interactiva de Wildi). La información contenida en esta variables es adecuadamente resumida por 3 factores que juegan un papel predominante en regular la distribución de las especies consideradas en el area de estudio y areas similares: el índice QE de Baudiere, la temperatura media de las mínimas del mes más frío y la oscilación térmica del mes más frío. Para estos factores el análisis de la beta-diversidad permitió determinar los umbrales fitoclimáticos utilizados en la definición y cartografía de las zonas fitoclimáticas.

     

A model for the spread of an epidemic

A temporally continuous and spatially discrete stochastic model for the spread of an epidemic within some set of holdings is constructed. A recursion formula is given for the probability that a certain set of holdings is infected at a certain moment. Moreover, under an additional condition (which will always be satisfied in practice) a formula for the expected value and the variance of the moment when a certain holding is infected the first time is given.     

Oscillations in epidemic models with spread of awareness

Journal of Mathematical Biology - We study ODE models of epidemic spreading with a preventive behavioral response that is triggered by awareness of the infection. Previous studies of such models...     

Effect of certain factors on the variability of strains of pertussis microbes

The population of degraded cells having stable changes in some phenotypical properties were isolated after subculturing some laboratory Bordetella pertussis strains in Bordet-Gengou culture medium and casein-charcoal agar with blood, treated with mitomycin C and allowed to proliferate in the spleen of mice injected intravenously with microbial suspensions. The characteristics indicative of cell degradation were the growth of large yellowish-white colonies appearing in 24 hours, the destruction of the agglutinogenic complex and toxic substances causing the atrophy of the spleen in mice, the increased capacity for active proliferation in the spleen. Electron-microscopic study revealed that the variants obtained by subculturing in culture media had the damaged membrane with the formation of cell-wall invaginations having rounded membrane-like formations on their surface, disappearing after treatment with mitomycin C; the treatment of the initial strains with mitomycin C resulted in cytoplasmic damage with the coagulation of the nucleoid.     

Effect of certain environmental factors on zygospore germination ofSpirogyra hyalina

The present study focusses on the effects of pH, temperature, intensity of white, red far-red light on zygospore germination in the filamentous green algaSpirogyra hyalina. Maximum germination of zygospores occurred at pH 8.0 and 25°C. Germination of zygospores was favored by white light at an intensity of 3–4 klx. Red light resulted in higher germination when applied at the beginning or in the middle of the dark period, while far-red light decreased zygospore germination. Red light in the middle of the dark period was found to be most effective for germination. These observations suggest a possible presence of the phytochrome system in the test alga contributing to its morphogenetic response.