Transformar políticas de informalidad urbana: el caso de la transición tunecina

Este artículo se ocupa del estudio del «sector informal» o «economía informal» en el discurso sobre desarrollo. La pregunta es: ¿hasta qué punto y por qué la estructura de la economía informal, su predominio en áreas urbanas y su vinculación con sectores marginados de la sociedad justifican la afirmación de que el levantamiento tunecino de 2010-2011 puede considerarse una «revolución informal»? Incorporando debates de la sociología y antropología urbanas, el artículo explora la relación entre la informalidad y la vida cotidiana en las ciudades, conectando el impacto de la globalización, las políticas neoliberales y la gobernanza urbana con las actividades económicas informales de los ciudadanos de áreas urbanas marginadas y segregadas espacialmente. El argumento se ilustra con un estudio de caso del levantamiento tunecino de 2010-2011 que pone de manifiesto el cambiante papel de la informalidad y su influencia sobre la gobernanza urbana de la economía informal, en particular sobre el comercio informal

“Getting By” at the Urban Periphery: Everyday Struggles of Informal Merchants in Tunisia

The article examines the significance of informal economic practices, e.g. street vending and informal commerce, for young merchants from Ettadhamen, a neighborhood situated in the northwestern periphery of the Greater Tunis area. It further addresses cross-border trade in the Tunisian-Libyan and Tunisian-Algerian border regions in which some of these merchants are indirectly involved. Peripheralization therefore does not imply complete socio-spatial exclusion. Peripheries rather offer important, albeit limited possibilities, to acquire resources through practices that are situated in the interstices between legality and illegality. As these possibilities often avoid state regulation and control, the article also addresses the ambivalent nature of the state-society relations that shapes everyday encounters between inhabitants and state agents, especially the police

Intensity of Mercury Lines Excited by Positive Ions

Observations were made concerning the intensity of lines of the mercury spectrum as excited by positive ions. The results were compared with corresponding data on the electron spectrum given by previous observers. Intensity measurements were made with a microphotometer

The Spectrum of Mercury Excited by Canal-Ray Impact

The spectrum of mercury is excited by hydrogen canal rays. The velocity of the canal rays is regulated by the voltage applied to a discharge tube and the canal-ray particles are allowed to shoot through a small hole in the cathode. Spectrograms were taken at voltages ranging from 1000 to 12,000 volts and the general characteristics of the spectra were studied. The spectra thus excited had very much the same characteristics as the electron spectrum just below ionization with the exception that several spark lines appeared at the lower voltages. The spark lines became more prominent as the voltage was increased although the relative intensity of the arc lines did not change appreciably. The polarization of the light was also investigated but no polarization was detected

Experimental evaluation of elemental behavior during LA-ICP-MS: influences of plasma conditions and limits of plasma robustness

Matrix effects are one of the frequently observed and discussed issues challenging the accuracy of LA-ICP-MS results. The specific role of the ICP as a source of elemental fractionation seems not fully understood. We report the results of an experiment using six internationally available reference materials (five silicates, one carbonate) measured under 11 different plasma conditions. The thermal/energetic state of the plasma was estimated based on the ratio of Ar-38(+) and Ar-40(2)+ ions. We show that element specific behavior (volatile vs. refractory) dominates at cool but vanishes under hot plasma conditions. For robust (hot) plasma conditions matrix-tolerance seems to be achieved. Additionally we address the problem of matrix-load with respect to the plasma conditions. We've estimated practical limits for the amount of matrix which can be introduced into the ICP without significantly changing the plasma condition

Rap1, a mercenary among the Ras-like GTPases

AbstractThe small Ras-like GTPase Rap1 is an evolutionary conserved protein that originally gained interest because of its capacity to revert the morphological phenotype of Ras-transformed fibroblasts. Rap1 is regulated by a large number of stimuli that include growth factors and cytokines, but also physical force and osmotic stress. Downstream of Rap1, a plethora of effector molecules has been proposed on the basis of biochemical studies. Here, we present an overview of genetic studies on Rap1 in various model organisms and relate the observed phenotypes to in vitro studies. The picture that emerges is one in which Rap1 is a versatile regulator of morphogenesis, by regulating diverse processes that include establishment of cellular polarity, cell–matrix interactions and cell–cell adhesion. Surprisingly, genetic experiments indicate that in the various model organisms, Rap1 uses distinct effector molecules that impinge upon the actin cytoskeleton and adhesion molecules

Sediment contamination of an urban canal—a case study approach for an integrated assessment of organic sediment contamination

Purpose The pesticide DDT and its metabolites represent a contamination risk for the aquatic environment, especially the polar metabolite DDA. The study provides a quantitative assessment of long-term pollution risks from sedimentary DDT residues with a special focus on DDA. It presents an overview of the contamination range of different DDX compounds in the sediments of a canal in Berlin (Germany), resulting from a former industrial point source that has implications for drinking water resources in the nearby area. The comprehensive analysis scheme provides information on free accessible and potentially metabolized precursors also in the non-extractable residues. This allows a quantitative assessment of the DDA pollution potential derived from the sedimentary DDT residues. Materials and methods The area was investigated for fine-grained sediment by means of a geo-electric mapping. Twelve sediment cores were taken in four areas (three in each section). A wider range of precursor metabolites has been included due to their transformation potential to the polar metabolite DDA. The sediments were analysed quantitatively for extractable and easily releasable fractions by application of a variety of degradation techniques as well as a dispersion extraction procedure on the sediment samples. These extracts were fractionated and subsequently analysed by GC-MS. Results and discussion Concentrations were obtained for extractable and bound metabolites. Different scenarios for the calculation of the amount of contaminated sediment are displayed as a tool for contamination assessment. The formation potential of DDA as the water-soluble metabolite is presented. Several precursor metabolites, e.g. DDD and DDMS, extractable from the sediment organic matter, revealed a high potential for a long-term formation of DDA, especially in the easily releasable fraction (via hydrolysis) with a mean concentration of up to 11,000 mu g g(-1)dry sediment. The resulting DDA contamination potential represents a significant pollution risk for the groundwater from a downstream waterworks area and by remobilisation into the whole ecosystem and adjacent rivers. Conclusions The application of the presented methods provides a tool for a quantitative assessment of the long-term release potential of DDA under different scenarios by a comprehensive analysis of contaminated sediments (and soils). This approach can be transferred to pollutants that are also characterized by a complex metabolism accompanied by bound residue formation

A simplified procedure for the determination of stable chlorine isotope ratios (δ37Cl) using LA-MC-ICP-MS

Stable chlorine isotopes (37Cl, 35Cl) are considered as important tracers of geochemical processes, especially in subduction zone systems. However, high-quality chlorine isotope data are scarcely available. Here we present a comparatively simple procedure for the precise and accurate determination of stable chlorine isotope ratios (δ37Cl) using LA-MC-ICP-MS. Chlorine was extracted from solid samples by pyrohydrolysis. After quantitative precipitation as AgCl the dried precipitates where analysed in a sample-standard bracketing approach using a weak laser ablation (0.3 J/cm2) for sample evaporation. Atlantic Ocean sea salt and the sea water standard IAPSO were used as SMOC (standard mean ocean chloride) for normalisation (δ37Cl = 0 ‰). The precision and accuracy of the presented method was validated analysing the reference materials JB-1a and JB-2. The chlorine isotope ratios of these standards were determined as δ37ClJB-1a = (−0.99 ± 0.06) ‰ and δ37ClJB-2 = (−0.60 ± 0.03) ‰ (errors 2SE), respectively, in accordance with published data. Applying the presented method a total amount of less than 1 μg of chlorine was consumed during a typical measurement including 10 ablation periods on the sample

Motion of K+ Ions in Mercury Vapor

Ionization by positive ion impact was studied in A, Ne, N2 , CO, He, at voltages up to 4000 volts and the results seem to check with those of Sutton (Phys. Rev. 33, 363, 1929) and Beeck (Ann. cl. Phys. 6, 8, 1001, 1930) wherever a check was possible. When the work was extended to an element heavier than K + i.e., Hg. the results are more complicated. The evidence seems to indicate; (a) reflection of K + ions at all voltages, (b) an increase in mean free path with increase in voltage, (c) no ionization below 250 volts, but above 250-350 volts ionization increases with increase in voltage