F region echo occurrence rates for the Polar Dual Auroral Radar Network (PolarDARN) HF radars at Inuvik (INV), Rankin Inlet (RKN), and Clyde River (CLY) are compared for observations in 2013. The CLY radar shows somewhat smaller echo occurrence rates consistent with its more poleward geographic and geomagnetic location. For all three radars, the winter occurrence rates are roughly twice that of the corresponding summer rates. For observations in the midnight sector, strong equinoctial maxima are evident. In terms of season and local time, echo occurrence patterns are found to be roughly the same for all radars: seasonally, clear maxima are found near noon during both winter and summer, while, diurnally, enhancements are found during equinoctial dusk. A comparison of data from roughly the same scattering area shows that having strong electron density in the scattering volume is not sufficient for getting an HF echo: propagation conditions along the propagation path are also important. Diurnal variations in the F region electron density and electric field (both measured by Canadian Advanced Digital Ionosonde) are compared to those of RKN echo occurrence rates for observations over Resolute Bay (RB) located at a geomagnetic latitude of 83°N. These results show a reasonable correlation between occurrence and electron density for both winter and summer periods and correlation between occurrence and electric field during summer periods.

Abstract. The occurrence of F region ionospheric echoes observed by a number of SuperDARN HF radars is analyzed statistically in order to infer solar cycle, seasonal, and diurnal trends. The major focus is on Saskatoon radar data for 1994-2012. The distribution of the echo occurrence rate is presented in terms of month of observation and magnetic local time. Clear repetitive patterns are identified during periods of solar maximum and solar minimum. For years near solar maximum, echoes are most frequent near midnight during winter. For years near solar minimum, echoes occur more frequently near noon during winter, near dusk and dawn during equinoxes and near midnight during summer. Similar features are identified for the Hankasalmi and Prince George radars in the northern hemisphere and the Bruny Island TIGER radar in the southern hemisphere. Echo occurrence for the entire SuperDARN network demonstrates patterns similar to patterns in the echo occurrence for the Saskatoon radar and for other radars considered individually. In terms of the solar cycle, the occurrence rate of nightside echoes is shown to increase by a factor of at least 3 toward solar maximum while occurrence of the near-noon echoes does not significantly change with the exception of a clear depression during the declining phase of the solar cycle.

Joint observations of the Rankin Inlet and Inuvik Super Dual Auroral Radar Network HF radars and Resolute Bay (RB) Canadian Advanced Digital Ionosonde are used to assess the electron density at the F region peak and the electric field magnitude as factors affecting echo detection over RB. We demonstrate that the radars show similar diurnal and seasonal variations in ionospheric echo occurrence. During nighttime and at radar frequencies of~12 MHz, optimum densities for both radars are shown to be ∼ 1.4 × 10 5 cm À 3 , 1.8 × 10 5 cm À 3 , and~2.0 × 10 5 cm À 3 for winter, equinox, and summer, respectively. During daytime, optimum densities are larger by (0.2 À 0.3) × 10 5 cm À 3 . Observations at lower radar frequencies of 10 MHz show smaller required densities during nighttime, by~0.3 × 10 5 cm À 3 . Optimum electric fields for the moments of echo detection over RB are found to be 5-25 mV/m with no clear threshold effect and any seasonal dependence. The presented data suggest that for echo detection, favorable propagation conditions along the entire path of radio waves toward the scattering volume are important.

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Background: Proteomics is considered a new era in neurophysiological/ neuropathological research including brain tumors. Gliomas which are derived from glial cells are the most common type of brain tumor in humans. Methods: In the present study the total protein content of healthy cells of the brain and brain tumor cells was extracted, purified and quantified by Bradford assay. Two-dimensional electrophoresis were used for protein separation followed by statistical analysis. Primary protein detection was performed based on the differences in isoelectric pH, molecular weight of proteins and protein data banks, which was further confirmed by MALDI-TOF/TOF mass spectrometry (MS). Results: Our results showed elevated levels of beta-actin protein expression in glioma brain tumor cells. It is important to know when a cell is transformed and when it becomes malignant. Here we evaluated the beta-actin expression in malignant cells. Conclusion: Since structural changes are highly involved in tumor cell malignancy, beta-actin elevations can contribute in glioma tumor cell invasiveness.