Short Communication: Equatorial electrojet strength in the African sector during high and low solar activity years

The daily variation of the horizontal component (H) of the geomagnetic field for the geomagnetic station at Addis Ababa (AAE)- geomagnetic latitude 5°3' and longitude 109°2', and dip latitude –0.5°- is analyzed for a pair of solar maximum and solar minimum years. The result represents the study of the strength of the electrojet phenomena in the African sector. It is found that the midday peak of .H, which is an indicator of the strength of the equatorial eastward electric field at this station, occurs later in the local summer months than during local winter months. Analysis of delay in the time of occurrence of the peak of .H for the autumnal and equinoctial months show that there is a consistent time delay of one hour between these pair of months. The results emphasize the importance of solar activity and local seasonal variations on the strength of the equatorial electrojet current and are shown to be consistent with the earlier similar work carried out for the American and Indian sectors. Key words/phrases: Autumnal and equinoctial months, equatorial electrojet, solar daily and lunar daily variations SINET: Ethiop. J. Sci Vol.26(1) 2003: 77-8

Geomagnetic secular variation and the 1969–1970 secular jerk at the African observatories

All-day annual mean values of the D, H and Z components of the geomagnetic field from ten observatories in the African continent are used to study long period secular variations, effects of external signals for the variation in the recorded field and for the signatures of geomagnetic jerks in the African region. Polynomials of second or third degree are found to be adequate to represent the secular variation in the field for most of the observatories. This shows that no strong local anomalies exist over much of the continent and the source of the secular variation is deep seated. Departures from these trends are observed over the Southern African region. The residuals in the geomagnetic field components are shown to exhibit parallelism with the periods corresponding to the double solar cycle only for some of the stations. A clear latitudinal distribution in the geomagnetic component that exhibits the 1969–70 secular jerk is shown. The jerk appears in the plots of the first differences in H for the southern most observatories of Hermanus, Hartebeesthoek, and Tsumeb, while the Z plots show the jerk for near equatorial and equatorial stations of Antananarivo, Luanda Belas, Bangui and Addis Ababa. There is some indication for this jerk in the first difference plots of D for the northern stations of M\'Bour and Tamanrasset. The plots of D rather strongly suggest the presence of a jerk around 1980 at most of the stations. Key words/phrases: Magnetic observatories, polynomial fitting, residuals, secular variation, secular jerk SINET: Ethiopian Journal of Science Vol. 27 (2) 2004: 105–12

Empirical analysis of procedures that schedule unit length jobs subject to precedence constraints forming in- and out-stars

This paper addresses the problem of scheduling unit length jobs subject to precedence constraints forming in- and out-stars. There are several different procedures that can be used to solve this problem and our aim in this paper is to compare these procedures empirically. We found that one algorithm that was thought to solve the problem optimally didn't do so for the general set of instances and that all procedures that we tested did not perform well if the number of stars in the instance was close but below the number of machines in the instance

Electrical resistivity tomography and magnetic surveys: applications for building site characterization at Gubre, Wolkite University site, western Ethiopia

A study aimed at evaluating the competence of the near surface formations as foundation materials has been undertaken at the site of the newly established Wolkite University Campus. Integrated geophysical surveys involving 2D Electrical Resistivity Tomography (ert), Vertical Electrical Sounding (ves) and magnetic surveys have been used for the purpose. The ert and ves results show the presence of intermediate to low resistivity top soil, an even lower resistivity second layer of clay and/or high moisture content underlain by weathered and fresh bedrocks, and a number of vertical or near vertical discontinuities and weak zones in the site.  The magnetic anomaly plots, have mapped the weak zones resulting from subsurface structures and the Euler depth map and 2d magnetic modelling specially depicting the depth of the magnetic sources that are associated with the bedrock. The correlation of the magnetic anomaly plot and 2d inverse model resistivity sections are used for the identification of weak zones that need special building design consideration at the site. The work emphasizes the viability of high resolution electrical tomographic surveys in engineering site investigations to augment geotechnical investigations that depend on data from a limited number of points to characterize large areas and complex geologic settings

Metabolism of polyunsaturated fatty acids in human bone marrow derived mesenchymal stromal cells

The application of human bone marrow derived mesenchymal stromal cells (hBMSCs) for regenerative or immunomodulatory therapies, e.g. treatment of the graft-versus-host disease, requires in vitro expansion of the cells. The hBMSCs undergo subtle changes during expansion which may compromise their functionality. In order to evaluate these changes lipidomics techniques were applied and the fatty acid (FA) and glycerophospholipid (GPL) profiles of hBMSCs were determined. During the cell passaging, arachidonic acid (20:4n-6) -containing species of phosphatidylcholine (PC) and phosphatidyl-ethanolamine (PE) accumulated while the species containing monounsaturated fatty acids (MUFA) or n-3 polyunsaturated fatty acids (n-3 PUFAs) decreased. The accumulation of 20:4n-6 and deficiency of n-3 PUFAs correlated with the decreased immunosuppressive capacity of the hBMSCs, which suggests that extensive expansion of hBMSCs harmfully modulates membrane GPLs profiles, affects lipid signaling and eventually impairs the functionality of the cells. Experiments, in which hBMSCs were cultured with different PUFA supplements revealed that the cells may limit the proinflammatory 20:4n-6 signaling by elongating this precursor with high biological activity to the less active precursor, 22:4n-6. It was also found that the ability of hBMSCs to produce long chain highly unsaturated fatty acids from C18 PUFA precursors was limited apparently due to the low desaturase activity of the cells. Thus, when the n-3 PUFA precursor, 18:3n-3, had little potency to reduce the GPL 20:4n-6 content, the eicosapentaenoic (20:5n-3) and docosahexaenoic (22:6n-3) acid supplements efficiently displaced the 20:4n-6 acyls, allowing attenuation of inflammatory signaling. These findings call for specifically designed optimal PUFA supplements for the cultures with sufficiently 20:5n-3 and 22:6n-3 but moderately 20:4n-6. Studies on the dynamics of PUFA incorporation into the major GPL classes revealed that the PUFAs in PC are remodeled at first, then those of the PEs and phosphatidylserines (PS). These results demonstrate that not only the type of PUFA administered but also the treatment time largely determines the resulting composition of the membrane GPL species, which serve as PUFA donors for the synthesis of lipid mediators. This thesis work highlights the importance of using lipidomics data to complement genomics or proteomics approaches when aiming at understanding of the therapeutic mechanisms of stem/stromal cells. The work provides tools to develop the protocols of hBMSCs culture and manipulate the functionality of the cells.Ihmisen luuydinperäisten mesenkymaalisten stroomasolujen (Human Bone Marrow Derived Stem Cells, hBMSC) käyttö regenerointi- ja immunomodulointiterapiamenetelmissä, kuten käänteishyljintäsairauden hoidossa, edellyttää solujen in vitro -viljelyä. Kasvatuksen myötä soluissa tapahtuu pieniä, niiden toiminnallisuutta vaarantavia muutoksia. Jotta muutoksia voitaisiin arvioida, solujen rasvahappo- ja glyserofsosfolipidiprofiilit määritettiin lipidomiikkamenetelmiä soveltaen. Solujen lisäysjakojen myötä arakidonihappoa (20:4n-6) sisältävät fosfatidyylikoliini- (phosphatidylcholine, PC) ja fostaftidyylietanoliaminiinilajit (phosphatidylethanolamine, PE) lisääntyivät, ja monoeeneja sisältävät lajit sekä n-3-ryhmään kuuluvat monityydyttymättömät rasvahapot (polyunsaturated fatty acid, PUFA) vastaavasti laskivat. Havaittu arakidonihapon nousu ja n-3-ryhmän monoeenien lasku korreloivat hBMSC-solujen vähentyneen immunosuppressivisen kyvyn kanssa. Tämä viittaa siihen, että toistuvat lisäysjaot muuttavat solujen glyserofosfolipidiprofiileja haitalliseen suuntaan ja vaikuttavat lipidisignalointiin lopulta heikentäen solujen toiminnallisuutta. Kokeissa, joissa soluja viljeltiin erilaisissa PUFA-täydennetyissä kasvatusliuoksissa, havaittiin, että solut saattavat rajoittaa 20:4n-6­välitteistä proinflammatorista signalointia muokkaamalla tätä prekursoria pidemmäksi ja vähemmän bioaktiiviseksi 22:4n-6-prekursoriksi. Kokeissa havaittiin myös, että solujen kyky tuottaa hyvin pitkiä monityydyttymättömiä rasvahappoja 18-hiilisistä rasvahapoista oli rajoittunutta todennäköisesti alhaisen solujen desaturaasiaktiivisuuden johdosta. Täten havaittiin että 18:3n-3-rasvahappo, joka on n-3-ryhmään kuuluva PUFA-prekursori, ei kyennyt juurikaan vähentämään glyserofosfolipidien arakidonihapposisältöä, kun taas eikosapentaeenihappo (20:5n-3) ja dokosahekaseenihappo (22:6n-3) korvasivat tehokkaasti kalvolipideissä olevan arakidonihapon, mahdollistaen inflammatorisen signaloinnin vaimentumisen. Löydökset peräänkuuluttavat solukasvatukseen erityisesti suunniteltujen rasvahappolisien kehitystä. Kasvatusliuoksen tulisi sisältää riittäviä määriä 20:5n-3- ja 22:6n-3-rasvahappoja, mutta vain maltillinen määrä 20:4n-6-rasvahappoa. Aiemmat tutkimukset monityydyttymättömien rasvahappojen liittämisestä merkittävimpiin glyserofosfolipidiluokkiin ovat osoittaneet, että PC-luokan monityydyttymättömät rasvahapot muokataan ennen PE- ja PS-luokkien monityydyttömättömiä rasvahappoja. Näin ollen rasvahappolisäyksen tyypin lisäksi myös käsittelyaika vaikuttaa pitkälti kalvojen rakennelipidien koostumukseen. Rakennelipidien asyyliketjut toimivat puolestaan luovuttajina, kun lipidisignaloinnissa toimivia monityydyttymättömiä rasvahappoja syntetisoidaan. Tämä väitöskirjatyö korostaa lipidomiikkatekniikoiden käytön tärkeyttä genomiikan ja proteomiikan ohella, kun pyritään selvittämään kanta- ja stroomasolujen terapeuttisia mekanismeja. Työn tulokset tarjoavat välineitä soluviljelymenetelmien kehittämiseen ja solujen toiminnallisuuden muokkaamiseen

Frequency of seizure attack and associated factors among patients with epilepsy at University of Gondar Referral Hospital: a cross-sectional study, Gondar, North West Ethiopia, 2017.

OBJECTIVE: About three-fourth of adults with new-onset epilepsy become seizure-free with current anti-epileptic drugs, but around one-fourth of the patients continue to experience seizure which increases the risk of accident, disability, death and treatment side effects. Therefore, this study aimed to address the gap in determining the magnitude of the number of seizure attacks and identify the factors that provoke a repeated seizure in a patient with epilepsy. RESULTS: A total of 166(40.68%) study participants were experienced seizure attacks with a minimum of one and a maximum of seventeen times attacks. Perceived exposure to noise (adjusted incidence risk ratio (AIRR) = 1.91, 95% confidence interval (CI) [1.46, 2.49]), light (AIRR = 1.48, 95% CI [1.09, 2.00]), head injury (AIRR = 1.71, 95% CI [1.14, 2.57]) and sleep deprivations (AIRR = 1.41, 95% CI [1.02, 1.94]) were associated with increased incidence of seizure, while adherence adjusted odds ratio (AOR) = 18.18, 95% CI [3.49, 94.63]), being in middle wealth index (AOR = 3.52, 95% CI [1.14, 11.02]) and being in rich wealth index (AOR = 4.05, 95% CI [1.54, 10.69]) were associated with inflation of zero count

Integrated geophysical investigations to study thermal zones at Boku volcanic Centre, Main Ethiopian Rift

This paper presents the results of electrical and magnetic surveys carried out over the Boku fumarole sites (Main Ethiopian Rift). On the basis of observed thermal manifestations, surface alterations and geophysical results we suggest that the Boku thermal field is a vapour-dominated, dry type geothermal system tapping heat from the shallow acidic magma chamber of Quaternary volcanic rocks of the Rift floor. The cap rock is formed by the self-sealing process through hydro thermal alterations of the Plio-Quaternary volcanic rocks in the area as witnessed by the surface manifestations of calcite and silica that are suggestive of such an environment. The aquifer system consists of the Quaternary Rift floor ignimbrites that are fractured intensively. The necessary supply for the replenishment of the reservoirs is derived from the closed basin system of the Nazareth watershed and/or from the large open irrigated grounds of the Wonji plantation. The investigations have clearly mapped the Quaternary faults that are the major tectonic structures for the passage of the deep-seated vapour to the surface, and the recharging of the geothermal reservoir. Key words/phrases: Boku caldera, hydrothermal alterations, magnetic anomaly, vapour-dominated geothermal systems, vertical electrical sounding SINET: Ethiopian Journal of Science Vol.25(2) 2002: 253-26

Lipidomics for Human Bone Marrow Mesenchymal Stem Cells

In addition to being structural components of biological membranes and energy storage of cells, lipids have recently been found to participate as essential players in cell signaling, subcellular transport mechanisms, adjusting functions of integral proteins, and regulation of cell growth and apoptosis. In this study electrospray ionization mass spectrometry (ESI-MS) techniques were used to analyze the phospholipid composition of human bone marrow derived mesenchymal stem cells (BMSC). Numerous chemically distinct lipid species were quantified and the changes in their relative amounts i.e. in the cell’s lipid profile after sequential passaging were followed until senescence (usually from passage 4 up to passage 10, in some cases until p14). Subsequently, the total lipids extracted from the cell pellets were analyzed by triple quadrupole ESI-MS equipment and using lipid-class specific scanning modes. The BMSC lines studied originated from ten donors, five of which were young and five elderly individuals. In culture, the BMSC from both young and aged donors showed time-dependent changes in their phospholipid profiles. The clearest marker findings among individual lipid species were that in phosphatidylcholines (PC) and phosphatidylethanolamines (PE), the species 38:4 (acyl chain pair 18:0/20:4n-6) largely increased towards the late passages, which was seen in the BMSC derived from both the young or aged donors. Thus the reserves of 20:4n-6, the precursor of the eicosanoids having antiproliferative, apoptotic and inflammatory cellular reactions, were increased towards late passages. At phospholipid class level, lysophosphatidylcholine (LysoPC) and phosphatidylinositol (PI) totals, and the ratio of total PI to total phosphatidylserine (PI:PS) were increased from early to latest passages. The results provide new lipid biomarkers to be used for stem cell quality control. The accumulation of polyunsaturated lipid species containing 20:4n-6 or the increase of PI: PS ratio could be potential markers for cell aging and the cells’ poor viability and functionality. The results can be used to develop efficient stem cell therapies and improve patient safety