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The documentation and understanding of variations in the Earth's magnetic field through time is fundamental for several disciplines, but current geomagnetic models rely on datasets heavily biased toward the mid‐ and high northern latitudes. The African continent and surrounding islands and oceans are particularly underrepresented. Here, we present a new record of paleo‐secular variation (PSV) of the inclinations over the last 23 ka from Lake Chala, situated at 3°S near Mt Kilimanjaro in eastern equatorial Africa. This groundwater‐fed crater lake is characterized by a high sedimentation rate (ca. 1 cm/10 years) and a particularly well‐constrained age model based on 210Pb and 14C dating. The magnetic mineralogy of the sediments is tested with rock magnetic analyses. The Lake Chala inclination record shows four highs and lows over 20 ka and compares well with that of Lake Malawi (10°S) between 20 and 16.2 ka, and from 9.8 to 2.6 ka. This record is linked to PSV records at Lakes Victoria and Malawi using a sequence slotting technique to generate a composite PSV model for east Africa. Analyzed at best‐possible resolutions up to 200 years, the Lake Chala PSV record not only represents an important contribution to improve our understanding of local and global features of the Earth's magnetic field. It also expands the utility of paleomagnetism as a key tool for dating and correlation both for archeological sites throughout East Africa and the many volcanoes, active or dormant, of the East African Rift System. Plain Language Summary: The understanding of the behavior of the Earth's Magnetic field in the geological past is based on an even spatial and temporal distribution of data collections. Nonetheless, data from large areas, such as from the African continent, remain sparse. In this study, we present new data from Lake Chala in equatorial East Africa, near Mount Kilimanjaro. The new inclination data are measured in lacustrine sediments covering the last 23 ka. We combine the data from Lake Chala with other data from Lake Victoria and Lake Malawi to produce a composite record for east African Lakes, using sequence slotting which improves the coherence between the records, whilst still constrained by the sediment age models. The composite record, centered on Lake Chala, improves our understanding of how the Earth's magnetic field changed in the recent past and can serve as an independent tool for dating nearby archeological sites as well as volcanic deposits from the African Rift emplaced in the last 23 ka. Key Points: Lake Chala contains an exceptionally well‐dated paleosecular variation record for east AfricaSequence slotting is used to refine a match to other secular variation records from east African lakesA composite paleosecular variation for equatorial east Africa is produced utilizing the combined set of control dates and magnetic records [ABSTRACT FROM AUTHOR]

The Hazar Basin is a 25 km-long, 7 km-wide and 216 m-deep depression located on the central section of the East Anatolian Fault zone (eastern Turkey) and predominantly overlain by Lake Hazar. This basin has been described previously as a pull-apart basin because of its rhombic shape and an apparent fault step-over between the main fault traces situated at the southwestern and northeastern ends of the lake. However, detailed structural investigation beneath Lake Hazar has not been undertaken previously to verify this interpretation. Geophysical and sedimentological data from Lake Hazar were collected during field campaigns in 2006 and 2007. The analysis of this data reveals that the main strand of the East Anatolian Fault (the Master Fault) is continuous across the Hazar Basin, connecting the two segments previously assumed to be the sidewall faults of a pull-apart structure. In the northeastern part of the lake, an asymmetrical subsiding sub-basin, bounded by two major faults, is cross-cut by the Master Fault, which forms a releasing bend within the lake. Comparison of the structure revealed by this study with analogue models produced for transtensional step-overs suggests that the Hazar Basin structure represents a highly evolved pull-apart basin, to the extent that the previous asperity has been bypassed by a linking fault. The absence of a step-over structure at the Hazar Basin means that no significant segmentation boundary is recognised on the East Anatolian Fault between Palu and Sincik. Therefore, this fault segment is capable of causing larger earthquakes than recognised previously. [ABSTRACT FROM AUTHOR]

A regularization procedure for linear systems of the type &Sigmat=1n fi (Zj)Xi = g(zj). J = 1, 2, .... n is presented, which is particularly useful in the case when z1, z2..... zn are close to each other. The associated numerical algorithm was tested on several examples for which analytic solutions do exist and was found to yield highly accurate results. [ABSTRACT FROM AUTHOR]

Granulocyte-macrophage colony-stimulating factor (GM-CSF) has proliferation- and differentiation-inducing effects on immature myeloid cells in the bone marrow, and it can modulate the function of several types of mature myeloid cells. We have stimulated purified human T cells with immobilized anti-CD3 or mitogenic anti-CD2 (a combination of monoclonal antibodies 9-1 and 9.6) which could induce GM-CSF production. The cytokines interleukin-1β (IL-1β) and IL-2 strongly enhanced GM-CSF production, while IL-4, IL-6, GM-CSF, interferon-γ (IFN-γ) and turnout necrosis factor (TNF) had no effect. Activation of protein kinase C by phorbol myristate acetate or triggering of CD28 on T cells by monoclonal antibody 9.3 provided accessory signals for enhanced GM-CSF production in activated T cells. Most important, the addition of mouse cells transfected with human B7-1 (CD80), a natural ligand for CD28, provided a potent accessory signal for GM-CSF production by activated T cells, which could not be blocked by cyclosporin A. The effect of IL-1β was in fact indirect, and resulted from enhanced IL-2 production, while the effect of B7 resulted from both IL-2-dependent and IL-2-independent pathways. We conclude that antigen-presenting cells (APC) can up-regulate GM-CSF production through IL-1β and through CD28 triggering by B7 molecules. As GM-CSF itself up-regulates B7 expression and IL-1β production by APC, a bidirectional regulatory feedback pathway between APC and T cells seems to modulate GM-CSF production. [ABSTRACT FROM AUTHOR]

Fc-γ receptor III (FcγRIII, CD16) type A is expressed on natural killer cells, on a small subset of peripheral blood monocytes and on mature macrophages. Along with differentiation into macrophages, monocytes will expresses FcγRIII when cultured with transforming growth factor-β (TGF-β). In view of the involvement of granulocyte-macrophage colony-stimulating factor (GM-CSF) in myeloid cell differentiation, we investigated the effect of this cytokine on FcγRIII expression in cultures of peripheral blood monocytes. GM-CSF antagonized TGF-β-induced expression of FcγRIII on monocytes in vitro in a dose-dependent way. The effect of GM-CSF persisted in cultures until at least day 7. The suppression was at the mRNA level, as shown by Northern analyses with a CD16 specific probe, and the signaling pathway involved tyrosine kinase activity. Interferon-γ and interleukin-2 had no effect on the induced expression of FcγRIII by TGF-γ, while interleukin-4, similar to GM-CSF, antagonized this induction. Our findings suggest that regulatory cytokine networks can drive monocytes into different effector functions and differentiation pathways. [ABSTRACT FROM AUTHOR]