Morphology of F-region vertical E×B drifts in the African sector using ionosonde measurements

F-region vertical velocities are derived from the ground-based ionosonde data for Ibadan (7.4°N, 3.9°E; dip 6°S: an equatorial station in the African zone), to study the general characteristics of electrodynamics of equatorial ionosphere, such as their variation with season, solar cycle, and magnetic activity at different local time sectors. The results show profound seasonal and geomagnetic effects. Except for equinoctial period, there is an excellent consistency in the magnitudes (nearly 20 m/s) and patterns of upward daytime F-region drifts at low and high solar activity periods. Evening F-region exhibits strong motion with absolute mean value for quiet-time (15 m/s) greater than on disturbed-time (10 m/s). The average downward quiet midnight-early morning hours sector value is well below than 10 m/s. The evening reversal time is earliest and latest during solstitial periods. Prereversal peak is season dependent and varies strongly with magnetic activity. We show that prereversal peak, daytime, and nighttime maximum drifts saturate at particular values of F10.7 cm solar radio flux index, effects not noticed with corresponding sunspot number. Our observations confirm several previous results from other equatorial sites utilizing different experimental techniques

A study of evolution/suppression parameters of equatorial postsunset plasma instability

Evening equatorial pre-reversal vertical ion <I><B>E</B></I>×<I><B>B</B</I> drift (<I>V<sub>ZP</sub></I>) and the peak of the ionospheric F2 maximum altitude (<I>hm</I>F2<I><sub>P</sub></I>) of the postsunset equatorial F-layer, which are the essential parameters requisite for the generation or inhibition of postsunset bottomside equatorial irregularities were deduced from ionosonde observations made in the Africa region (Ouagadougou: ~3° N dip latitude) between January 1987 and December 1990 for solar activity minimum, medium, and maxima (F<sub>10.7</sub>=85, 141, 214, and 190, respectively) for quiet geomagnetic conditions. We investigate variations of evening equatorial pre-reversal drift and the corresponding altitude at four levels of solar activity. Our observations show strong variations with solar variability. Correlation analysis between these parameters indicates that the correlation coefficient value between <I>hm</I>F2<I><sub>P</sub></I> versus <I>V<sub>ZP</sub></I> decreases considerably with increasing solar flux value. There seems to be no significant link between these parameters under high solar activity, especially for solar intensity F<sub>10.7</sub>>200 units. We conclude that meridional neutral wind in the F-region contributes substantially to the variations of the pre-reversal vertical plasma drifts enhancement and the peak <I>hm</I>F2, particularly the electrodynamics during twilight high solar flux conditions

The consequence of societal secrecy for the financial constraints faced by firms

This is the author accepted manuscriptDoes the level of societal secrecy aggravate or alleviate access to finance? We explore this question for 51,249 firms in 39, predominantly developing, countries, from 2006 to 2015. We find a strong positive relationship between cultural orientation towards secrecy in a country and financial constraints faced by its firms. Our results are robust to several considerations and emphasize the adverse consequence of societal secrecy for perpetuating financing obstacles for firms

Nocturnal variations of F-region vertical ionization velocities near the magnetic equator

227-233 F-region vertical plasma drifts at the magnetic equatorial station, Ibadan (7.4 °N, 3.9 °E; 6 °S dip) are inferred from the time variation of the hourly-recorded ionosonde virtual height (h'F) of F-layer data; obtained during 1957/58 International Geophysical Year (IGY) period under geomagnetically quiet and disturbed nights. Prominent nocturnal vertical drift characteristics are presented at African longitudinal sector. Seasonal effects appeared to be pronounced during undisturbed and disturbed nighttime conditions. Also, pre-reversal peak velocity obviously varies considerably with season. In addition, pre-reversal peak velocity exhibits significant variability with 10.7 cm Solar Flux Index and average Zurich monthly sunspot numbers. Furthermore the threshold parameters, such as, E × B vertical drifts and virtual height (h'F) required to cause spread-F irregularities are determined to be approximately 30 m/s and 400 km, respectively. Results obtained by the authors are in good accord with those for other low-latitude regions that employ other observational techniques. There are several likely processes responsible for the quiet and disturbed times plasma drift variability in the night hours at equatorial regions. </smarttagtype

Morphology of F-region vertical E×B drifts in the African sector using ionosonde measurements

F-region vertical velocities are derived from the ground-based ionosonde data for Ibadan (7.4°N, 3.9°E; dip 6°S: an equatorial station in the African zone), to study the general characteristics of electrodynamics of equatorial ionosphere, such as their variation with season, solar cycle, and magnetic activity at different local time sectors. The results show profound seasonal and geomagnetic effects. Except for equinoctial period, there is an excellent consistency in the magnitudes (nearly 20 m/s) and patterns of upward daytime F-region drifts at low and high solar activity periods. Evening F-region exhibits strong motion with absolute mean value for quiet-time (15 m/s) greater than on disturbed-time (10 m/s). The average downward quiet midnight-early morning hours sector value is well below than 10 m/s. The evening reversal time is earliest and latest during solstitial periods. Prereversal peak is season dependent and varies strongly with magnetic activity. We show that prereversal peak, daytime, and nighttime maximum drifts saturate at particular values of F10.7 cm solar radio flux index, effects not noticed with corresponding sunspot number. Our observations confirm several previous results from other equatorial sites utilizing different experimental techniques

Vertical drift velocity in the daytime F-region at Ibadan estimated from ionosonde data

9-13Electron drifts distributions obtained from ionosonde measurements at Ibadan (lat. 7.4oN, long. 3.9oE; magn lat. 3.0°S), Nigeria, have been used to estimate daytime F-region vertical drift velocities during periods of low and high solar activity. Values of the drift velocity near 300 km altitude at Ibadan are shown to be in good agreement with the results of experiments carried out at other equatorial stations. The proposed method may be relevant to the bottomside ionosphere for estimating vertical drift velocities, especially, at locations close to the magnetic equator where measurements are not carried out on a continuous basis. <br

Kinetic analysis of biological sulphate reduction using lactate as carbon source and electron donor across a range of sulphate concentrations

This study investigated the effect of feed sulphate concentration on the kinetics of anaerobic sulphate reduction by a mixed SRB culture, using lactate as the sole carbon source and electron donor. Chemostat cultures were operated across a range of residence times (0.5–5 d) and feed sulphate concentrations (1.0–10.0 g l−1). Similar phenomena were observed at feed sulphate concentrations of 1.0 and 10.0 g l−1 with the volumetric sulphate reduction rate increasing linearly with increasing volumetric sulphate loading rate. These reactors were characterised by higher specific volumetric sulphate reduction rates with maximum values of 0.24 and 0.20 g h−1 g−1. Contrastingly, the reactors fed with sulphate concentrations of 2.5 and 5.0 g l−1 showed distinctly different trends in which the volumetric sulphate reduction rate passed through a maximum at the dilution rates of 0.014 and 0.021 h−1, respectively, followed by a decline with further increase in sulphate loading rate. The maximum specific volumetric sulphate reduction rates observed were 2–6-fold lower than those observed at 1.0 and 10.0 g l−1 feed sulphate concentrations. Profiles of specific volumetric sulphate reduction rate and biomass concentration suggested a shift in lactate utilisation from oxidation to fermentation at high dilution rates, implying a change in the dominant components of the microbial consortium. The data suggest that population structure was influenced by lactate affinity and dissolved sulphide concentration. The trends observed were attributed to the greater ability of lactate oxidisers to scavenge lactate under limiting concentrations of the substrate and their greater resilience to dissolved sulphide species in comparison to lactate fermenters

Investigation of initial configuration on the dynamic properties of Lennard-Jones fluid by method of molecular dynamics

428-432<span style="font-size:14.0pt;line-height: 115%;font-family:" times="" new="" roman";mso-fareast-font-family:"times="" roman";="" color:black;mso-ansi-language:en-in;mso-fareast-language:en-in;mso-bidi-language:="" hi"="" lang="EN-IN">The system of 500 spheres interacting with a Lennard-Jones potential and obeying classical equations of motion has been studied on a digital computer to simulate molecular dynamics in liquid argon at various values of temperature and density. The dependence of temperature and density on dynamic properties and the time-dependent correlation function is described and discussed for face-centered cubic (FCC) and simple cubic (SC) crystalline lattice structure.</span