Rolf Werner

Cyclic patterns of malaria incidence in Burundi

Best available descriptions of malaria incidence and mortality dynamics are important to improve and evaluate the implementation of programs to monitor (e.g., remote sensing) and control disease, especially in endemic zones. High-frequency (e.g., semi-annual and seasonal) cycles in malaria incidence have been observed in various countries and they coincide with cycles in the natural environment (e.g., temperature, heliogeophysical activity, etc.). However, neither trend nor cyclical oscillations beyond a 6-month (0.5-year) period for this vector-borne disease were reported in a recent analysis on monthly notifications in Burundi for the years 1997–2003. Since the examination of graphical plots indicated an eventual existence of trans-year (multiannual) variations, we further analyzed the same data in more detail. Here we explore whether low-frequency cycles (beyond seasonality) might exist (e.g., trans-year cycles with periods of 13–24 months or longer). Monthly incidence rate per 100 inhabitants from the Province of Karuzi, Burundi, over the years 1997–2003 was analysed. The exploration of underlying chronomes (time structures) was done by linear and non-linear parametric regression models, autocorrelation, spectral analysis (e.g., fast Fourier transforms), periodogram regression analysis (PRA) and wavelet transform (WT). By using a periodogram regression analysis, we describe a multicomponent cyclic chronome with periods T>12 months (19 and 86 months, all at P<0.05). Notably, the strongest cyclic pattern in the periodogram of the detrended malaria rates (whereas the peak was suppressed and beyond the semi-annual cycle of 6 months) was ≈1.5–1.6 years (T=19.0 months, R=0.32). A dynamic pattern of “shortening” of the length (period) of the cycles was observed during the pre-epidemic interval (from 8–9 to 5–6 months and from 20–22 to 16–18 months in years 1997–2000) that can be used to anticipate a forthcoming incidence increase and epidemic levels of malaria at a regional level. Indeed, these cycles in malaria incidence correspond to cyclic components of heliogeophysical activity (HGA) such as the sunspot cycle impulses of 0.5–2.0 years as well as the quasi-biennial solar magnetic cycle of 1.5–2.5 years and further, detailed analyses are warranted to investigate such relationships. A multicomponent dynamic cyclical pattern of malaria incidence variations in Burundi (1997–2003) exists thus allowing further, more specific analyses and modelling as well as correlations with similar environmental cycles to be explored. These results might also contribute to better estimates for forecasting, prevention and understanding of malaria dynamics and aetiology.

Stratosphere NO2 observation at mid- and high latitude performed with ground-based spectrometers

UV-visible ground-based spectrometers were developed at the ISAO Institute and they are used for application of differential optical absorption spectroscopy (DOAS) methodology to detect stratospheric trace gases involved in the ozone cycle such as NO2, OClO, and BrO. Observations of the light scattered from the zenith-sky were performed with the instrumentation above mentioned, in various stations situated in both the hemispheres. Some problematics connected to data validation and results analysis are introduced. Considerations about the temperature dependency of the cross-section used for the determination of the trace gases slant column are carried out. Results for nitrogen dioxide abundances at different season and various Solar Zenith Angle in their seasonal and diurnal variation are presented and discussed. Finally, the behavior of the sunrise nitrogen dioxide abundance over the sunset slant column is shown and examined.

Cyclic patterns of cerebral malaria admissions in Papua New Guinea for the years 1987-1996.

Data on the dynamics of malaria incidence, admissions and mortality and their best possible description are very important to better forecast and assess the implementation of programmes to register, monitor (e.g. by remote sensing) and control the disease, especially in endemic zones. Semi-annual and seasonal cycles in malaria rates have been observed in various countries and close similarity with cycles in the natural environment (temperature, heliogeophysical activity, etc.), host immunity and/or virulence of the parasite suggested. This study aimed at confirming previous results on malaria cyclicity by exploring whether trans-year and/or multiannual cycles might exist. The exploration of underlying chronomes (time structures) was done with raw data (without smoothing) by linear and nonlinear parametric regression models, autocorrelation, spectral (Fourier) and periodogram regression analysis. The strongest cyclical patterns of detrended malaria admissions were (i) annual period of 1·0 year (12 months or seasonality); (ii) quasi-biennial cycle of about 2·25 years; and (iii) infrannual, circadecennial cycle of about 10·3 years. The seasonal maximum occurred in May with the minimum in September. Notably, these cycles corresponded to similar cyclic components of heliogeophysical activity such as sunspot seasonality and solar activity cyclicities and well-known climate/weather oscillations. Further analyses are thus warranted to investigate such similarities. In conclusion, multicomponent cyclical dynamics of cerebral malaria admissions in Papua New Guinea were observed thus allowing more specific analyses and modelling as well as correlations with environmental factors of similar cyclicity to be explored. Such further results might also contribute to and provide more precise estimates for the forecasting and prevention, as well as the better understanding, of the dynamics and aetiology of this vector-borne disease.

Substorm observations by THEMIS D and ground-based observations by MAIN camera system in Apatity - a case study

In this work we studied the development of a substorm during the geomagnetic storm on 23 December 2014 using data of THEMIS D (THD) satellite, ground based magnetic field measurements and auroras observations by the Multiscale Aurora Imaging Network (MAIN) in Apatity. Solar wind and interplanetary magnetic field parameters were taken from the OMNI data base. THD was located at ~ 7Re from 18:30 to 19:30 UT in the time interval 23-24 December 2014 and the projection of its orbit crossed Kola Peninsula in this time. A substorm was observed over Apatity from 19:19:50 UT on 24 December 2014. A comparative analysis between ground based and satellite data was carried out. High energy electrons (1-10 keV) injections and reduction of the less energetic electrons flux (~100 eV) were observed during the substorm. Particles density reduction was found at the time about the auroras intensifications. Plasma fast flows were identified during the consecutive auroras intensifications. The time delay between the beginning of the different parameters disturbances registered by THD and the ground based observed ones is about 1.0 ÷ 1.5 min.

Investigation of Halley's Comet dust size distribution by Vega-2 interplanetary station visual spectra analysis

Spectra in the visible region measured on board the Vega-2 station are analyzed to obtain the solar spectrum continuum reflected by the dust particles in the Halley comet coma. It is suggested to determine the continuum level for every individual spectrum. By the time of Vega encounter, the concentration and distribution of particles around the comet has changed. This resulted in a different spectral indices for spectra measured in different time. The cumulative size index has been calculated for each specific spectrum by linear regression on the basis of a random number of dust points. Eleven dust continuum wavelengths are selected. The spectral index shows the mean particle size in the line of sight column around the nucleus (values calculated for 1019 spectra are in the interval of 2.85 - 3.48). Its change with the radial distance to the nucleus is discussed. The continuum spectra are calculated with the obtained values of the spectral index and are normalized to the real spectra on the minimum of interval of +/- 15 pixels in relation to the specific dust intensity, with the help of a linear regression. The continuum spectrum follows well the course of the specific Halleys comet spectrum.