Sartre's Postcartesian Ontology: On Negation and Existence

This article maintains that Jean-Paul Sartre’s early masterwork, Being and Nothingness, is primarily concerned with developing an original approach to the being of consciousness. Sartre’s ontology resituates the Cartesian cogito in a complete system that provides a new understanding of negation and a dynamic interpretation of human existence. The article examines the role of consciousness, temporality and the relationship between self and others in the light of Sartre’s arguments against “classical” rationalism. The conclusion suggests that Sartre’s departure from modern foundationalism has “postmodern” implications that emerge in the areas of ontology, existential analytics and the ethics of human freedom

Land tenancy, soybean, actors and transformations in the pampas: a district balance

In Argentina, the recent expansion of agriculture has turned into an extreme process almost completely dominated by soybean. The magnitude and speed of soybean expansion are believed to be the main drivers behind social, organizational and economic changes, including the displacement of small-scale producers out of agriculture. Under these transformations, land leasing is a critical management practice and constitutes a link among agricultural actors. This study analyzes changes in land tenancy patterns considering the recent agriculturization process but also older drivers of change. Our results indicate that the expansion of agriculture affects small- and large-scale farms differently, as land renting practices and productive orientation show clear differences by size. In the land leasing market, local producers are the main tenants while sowing pools rent about one quarter of the leased land. The competition for leasing farmland appears to operate within farm sizes. Small- and medium-scale producers compete among them for land, while large-scale local producers compete with sowing pools for the larger plots. Sowing pools do not appear to be the main drivers of land tenancy changes as they are no more relevant than local actors in the land leasing market. However, results suggest that small-scale landowners renting out their land for several years are the ones with higher probabilities of selling their lands. This segment of producers appears to be the one most negatively affected by soybeanization.Facultad de Ciencias Agrarias y Forestale

TCR and CD28 Concomitant Stimulation Elicits a Distinctive Calcium Response in Naive T Cells

T cell activation is initiated upon ligand engagement of the T cell receptor (TCR) and costimulatory receptors. The CD28 molecule acts as a major costimulatory receptor in promoting full activation of naive T cells. However, despite extensive studies, why naive T cell activation requires concurrent stimulation of both the TCR and costimulatory receptors remains poorly understood. Here, we explore this issue by analyzing calcium response as a key early signaling event to elicit T cell activation. Experiments using mouse naive CD4+ T cells showed that engagement of the TCR or CD28 with the respective cognate ligand was able to trigger a rise in fluctuating calcium mobilization levels, as shown by the frequency and average response magnitude of the reacting cells compared with basal levels occurred in unstimulated cells. The engagement of both TCR and CD28 enabled a further increase of these two metrics. However, such increases did not sufficiently explain the importance of the CD28 pathways to the functionally relevant calcium responses in T cell activation. Through the autocorrelation analysis of calcium time series data, we found that combined but not separate TCR and CD28 stimulation significantly prolonged the average decay time (τ) of the calcium signal amplitudes determined with the autocorrelation function, compared with its value in unstimulated cells. This increasement of decay time (τ) uniquely characterizes the fluctuating calcium response triggered by concurrent stimulation of TCR and CD28, as it could not be achieved with either stronger TCR stimuli or by co-engaging both TCR and LFA-1, and likely represents an important feature of competent early signaling to provoke efficient T cell activation. Our work has thus provided new insights into the interplay between the TCR and CD28 early signaling pathways critical to trigger naive T cell activation