An infrared measurement of chemical desorption from interstellar ice analogues

In molecular clouds at temperatures as low as 10 K, all species except hydrogen and helium should be locked in the heterogeneous ice on dust grain surfaces. Nevertheless, astronomical observations have detected over 150 different species in the gas phase in these clouds. The mechanism by which molecules are released from the dust surface below thermal desorption temperatures to be detectable in the gas phase is crucial for understanding the chemical evolution in such cold clouds. Chemical desorption, caused by the excess energy of an exothermic reaction, was first proposed as a key molecular release mechanism almost 50 years ago. Chemical desorption can, in principle, take place at any temperature, even below the thermal desorption temperature. Therefore, astrochemical net- work models commonly include this process. Although there have been a few previous experimental efforts, no infrared measurement of the surface (which has a strong advantage to quantify chemical desorption) has been performed. Here, we report the first infrared in situ measurement of chemical desorption during the reactions H + H2S -> HS + H2 (reaction 1) and HS + H -> H2S (reaction 2), which are key to interstellar sulphur chemistry. The present study clearly demonstrates that chemical desorption is a more efficient process for releasing H2S into the gas phase than was previously believed. The obtained effective cross-section for chemical desorption indicates that the chemical desorption rate exceeds the photodesorption rate in typical interstellar environments

The small-scale structure of photospheric convection retrieved by a deconvolution technique applied to Hinode/SP data

Solar granules are bright patterns surrounded by dark channels called intergranular lanes in the solar photosphere and are a manifestation of overshooting convection. Observational studies generally find stronger upflows in granules and weaker downflows in intergranular lanes. This trend is, however, inconsistent with the results of numerical simulations in which downflows are stronger than upflows through the joint action of gravitational acceleration/deceleration and pressure gradients. One cause of this discrepancy is the image degradation caused by optical distortion and light diffraction and scattering that takes place in an imaging instrument. We apply a deconvolution technique to Hinode/SP data in an attempt to recover the original solar scene. Our results show a significant enhancement in both, the convective upflows and downflows, but particularly for the latter. After deconvolution, the up- and downflows reach maximum amplitudes of -3.0 km/s and +3.0 km/s at an average geometrical height of roughly 50 km, respectively. We found that the velocity distributions after deconvolution match those derived from numerical simulations. After deconvolution the net LOS velocity averaged over the whole FOV lies close to zero as expected in a rough sense from mass balance.Comment: 32 pages, 13 figures, accepted for publication in Ap

Geoforensic Analysis of Agba Bridge Failure, Abakaliki, Ebonyi State

A geoforensic analysis of Agba bridge, in Abakaliki, Ebonyi State was carried out using a combination of geotechnical, geophysical and hydrological techniques. The results indicate a highly geotechnically variable, partially weathered meta-sediments as foundation. The weathered profile as confirmed by VES indicated a much thicker weathered soft soil to the south-west.  An initial shallow foundation for the South-West Abutment was thus inadequate, leading subsequently to sliding movement, which displaced the reinforced concrete piers. Hydrological analysis of the Agba river revealed critical flow velocities capable of generating local scour of up to 3.5m deep, that equally threaten stability of shallow pier foundation. Accordingly, bored piles extended to 15m have been recommended for the second half of the bridge to the south-west as a remedial measure to guaranty the stability of the structure. Keywords: Geoforensic analysis, bridge failure, scour, geo-electrical sounding, geotechnica

Characterization Studies and Yield Attributes of Some Varieties of Cowpea (\u3cem\u3eVigna unguiculata\u3c/em\u3e L.)

Investigations were carried out on sixteen improved varieties of cowpea (Vigna unguiculata L walp) obtained from International Institute for Tropical Agriculture, Ibadan. These varieties were grown in the Department of Biological Sciences Garden, of the University of Ilorin. Qualitative and quantitative characters were observed for the study. Positive correlations were obtained between leaf number and stem diameter, leaf number and number of seeds per pod, number of branches and plant height. Negative correlation existed between number of pods per plant and number of seed per pod. Analysis of variance (ANOVA) showed significant difference in all the quantitative characters analyzed among the varieties. Each character was also analyzed using Duncan test and F-LSD. The result showed that IT99K-529-1, IT99K – 429 – 2, IT97K – 461 – 4, IT98K – 506 – 1 and IT99K- 1122 were outstanding in term of vegetative and yield performances in Ilorin, Kwara State of Nigeria

Solar polarimetry through the K I lines at 770 nm

We characterize the K I D1 & D2 lines in order to determine whether they could complement the 850 nm window, containing the Ca II infrared triplet lines and several Zeeman sensitive photospheric lines, that was studied previously. We investigate the effect of partial redistribution on the intensity profiles, their sensitivity to changes in different atmospheric parameters, and the spatial distribution of Zeeman polarization signals employing a realistic magnetohydrodynamic simulation. The results show that these lines form in the upper photosphere at around 500 km and that they are sensitive to the line of sight velocity and magnetic field strength at heights where neither the photospheric lines nor the Ca II infrared lines are. However, at the same time, we found that their sensitivity to the temperature essentially comes from the photosphere. Then, we conclude that the K I lines provide a complement to the lines in the 850 nm window for the determination of atmospheric parameters in the upper photosphere, especially for the line of sight velocity and the magnetic field.Comment: 10 pages, 9 figures, main journal publicatio