Performance of ionospheric maps in support of long baseline GNSS kinematic positioning at low latitudes

Ionospheric scintillation occurs mainly at high and low latitude regions of the Earth and may impose serious degradation on GNSS (Global Navigation Satellite System) functionality. The Brazilian territory sits on one of the most affected areas of the globe, where the ionosphere behaves very unpredictably, with strong scintillation frequently occurring in the local postsunset hours. The correlation between scintillation occurrence and sharp variations in the ionospheric total electron content (TEC) in Brazil is demonstrated in Spogli et al. (2013). The compounded effect of these associated ionospheric disturbances on long baseline GNSS kinematic positioning is studied in this paper, in particular when ionospheric maps are used to aid the positioning solution. The experiments have been conducted using data from GNSS reference stations in Brazil. The use of a regional TEC map generated under the CALIBRA (Countering GNSS high-Accuracy applications Limitations due to Ionospheric disturbances in BRAzil) project, referred to as CALIBRA TEC map (CTM), was compared to the use of the Global Ionosphere Map (GIM), provided by the International GNSS Service (IGS). Results show that the use of the CTM greatly improves the kinematic positioning solution as compared with that using the GIM, especially under disturbed ionospheric conditions. Additionally, different hypotheses were tested regarding the precision of the TEC values obtained from ionospheric maps, and its effect on the long baseline kinematic solution evaluated. Finally, this study compares two interpolation methods for ionospheric maps, namely, the Inverse Distance Weight and the Natural Neighbor

Human melanoma-initiating cells express neural crest nerve growth factor receptor CD271.

The question of whether tumorigenic cancer stem cells exist in human melanomas has arisen in the last few years. Here we show that in melanomas, tumour stem cells (MTSCs, for melanoma tumour stem cells) can be isolated prospectively as a highly enriched CD271(+) MTSC population using a process that maximizes viable cell transplantation. The tumours sampled in this study were taken from a broad spectrum of sites and stages. High-viability cells isolated by fluorescence-activated cell sorting and re-suspended in a matrigel vehicle were implanted into T-, B- and natural-killer-deficient Rag2(-/-)gammac(-/-) mice. The CD271(+) subset of cells was the tumour-initiating population in 90% (nine out of ten) of melanomas tested. Transplantation of isolated CD271(+) melanoma cells into engrafted human skin or bone in Rag2(-/-)gammac(-/-) mice resulted in melanoma; however, melanoma did not develop after transplantation of isolated CD271(-) cells. We also show that in mice, tumours derived from transplanted human CD271(+) melanoma cells were capable of metastatsis in vivo. CD271(+) melanoma cells lacked expression of TYR, MART1 and MAGE in 86%, 69% and 68% of melanoma patients, respectively, which helps to explain why T-cell therapies directed at these antigens usually result in only temporary tumour shrinkage

Long-term haematopoietic reconstitution by Trp53(-/-)p16(Ink4a-/-)p19(Arf-/-) multipotent progenitors

Haematopoiesis is maintained by a hierarchical system where haematopoietic stem cells ( HSCs) give rise to multipotent progenitors, which in turn differentiate into all types of mature blood cells1. HSCs maintain themselves for the lifetime of the organism because of their ability to self- renew. However, multipotent progenitors lack the ability to self- renew, therefore their mitotic capacity and expansion potential are limited and they are destined to eventually stop proliferating after a finite number of cell divisions(1,2). The molecular mechanisms that limit the proliferation capacity of multipotent progenitors and other more mature progenitors are not fully understood(2,3). Here we show that bone marrow cells from mice deficient in three genes genetically downstream of Bmi1-p16(Ink4a), p19(Arf) and Trp53 ( triple mutant mice; p16(Ink4a) and p19(Arf) are alternative reading frames of the same gene ( also called Cdkn2a) that encode different proteins) - have an approximately 10-fold increase in cells able to reconstitute the blood long term. This increase is associated with the acquisition of long- term reconstitution capacity by cells of the phenotype c-kit(+)Sca-1(+)Flt3(+)CD150(-)CD48(-)Lin(-), which defines multipotent progenitors in wild- type mice(4-6). The pattern of triple mutant multipotent progenitor response to growth factors resembles that of wild- type multipotent progenitors but not wild- type HSCs. These results demonstrate that p16(Ink4a)/p19(Arf) and Trp53 have a central role in limiting the expansion potential of multipotent progenitors. These pathways are commonly repressed in cancer, suggesting a mechanism by which early progenitor cells could gain the ability to self- renew and become malignant with further oncogenic mutations.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/62767/1/nature06869.pd

Democratic Capabilities Research: Exploring contextual challenges and contributions of participatory research towards epistemic justice

Epistemic justice is central for participatory practices; indeed, social justice is not possible without considering epistemic inequalities in knowledge generation. Nevertheless, although this debate is theoretically clear, we still have little literature exploring and reflecting on how this can be achieved. Thus, this chapter draws on findings from a South African case study called "Democratic Capabilities Research". Using extensive and rich qualitative data collected during the space of one year, the analysis of the findings shows that epistemic justice is not an end for higher education practitioners but rather a way of applying research practices in non-ideal settings, where colonial conversion factors are in place. The chapter concludes by suggesting that the contribution of this DCR project, towards epistemic justice, lies in its impact minimising the adverse consequences of colonial conversion factors in the research participants and the use of different multi-epistemic strategies as a way to balance knowledge inequalities instead of achieving epistemic justice as an end