Postrevolutionary land encroachments in Cairo: Rhizomatic urban space making and the line of flight from illegality

After the January 2011 revolution, new and unpermitted constructions on previously empty land went up across Cairo at striking speed. This paper explores a case of such land encroachments carried out by waste collectors in the neighbourhood of Manshiet Nasser in Cairo, Egypt. It begins with theoretical debates about the production of urban space, arguing that the de Certeauian paradigm, in which urban marginals poach or hijack others' spaces evanescently, fails to account for the way such encroachments produce permanent new spaces rhizomatically alongside the pre‐existing order. The paper then turns to a close examination of the events in Manshiet Nasser. Although in a broad view the actors are marginals living in the ‘informal’ city, the conditions enabling the encroachments were such that only the wealthiest and most powerful members of the ‘community’ benefitted. In a context of generalized ‘illegality’, the squatters rely on practical norms and de facto recognitions to obtain some degree of tenure security. Since these efforts rely on and play off legal norms even as the squatters violate them, the paper argues that property rights in this context should be understood not in classificatory terms based on the legal/illegal binary, but rather through a trajectory of ‘becoming‐legal’: a ‘line of flight’ that approaches legality asymptotically.     

A fungal epizootic in mussels at a deep-sea hydrothermal vent

Mass mortalities due to disease are important determinants of population and community structure in marine ecosystems, but the speed at which an epizootic may sweep through a population, combined with rapid selection for disease‐resistant stocks, can mask the ecological impact of disease in all but the most closely monitored populations. We document an emergent epizootic event in the deep sea that is occurring in mussels (Bathymodiolus brevior) at the Mussel Hill hydrothermal vent in Fiji Basin and we identify the causal agent as a black yeast (order Chaetothyriales) that elicits a pronounced host immune response and is associated with tissue deterioration. The yeast was not observed in other invertebrate taxa (the gastropods Ifremeria nautilei, Alviniconcha aff. hessleri; the limpets Lepetodrilus schrolli, Symmetromphalus aff. hageni; the polychaetes Branchipolynoe pettiboneae, Amphisamytha cf. galapagensis) associated with the mussel bed, nor in mussels (Bathymodiolus brevior) collected from adjacent Lau Basin mussel beds. Massive mussel mortality resulting from the fungal infection is anticipated at the Mussel Hill site in Fiji Basin; we expect that epizootic outbreaks in dense invertebrate communities have the potential to be major determinants of community structure in deep‐sea chemosynthetic ecosystems. The possibility that submersible assets may serve as vectors for transport of the fungus warrants further attention.     

Investigating cross-contamination of aquifers

Shallow aquifers can cross-contaminate deeper aquifers through penetration of an intervening aquitard, via sandy intervals in the aquitard, along well casings, across long well screens, or around aquitard pinchouts. Distinguishing among these potential pathways requires the use of evaluation tools that may support or eliminate certain pathways. These tools include groundwater gradient and aquitard penetration calculations, aquifer pumping test interpretation techniques, chemical concentration plots and statistical methods, hydraulic conductivity-based travel time calculations, pumping-concentration tests, methods for evaluating leaky wells, and methods for evaluating aquitard continuity. Based on analysis of several of these techniques at three sites experiencing aquifer cross-contamination, the authors conclude that calculation of flow rates for various pathways is the single most useful method to confirm or refute specific pathways. Evaluation of leaky wells and aquitard continuity generally must be coupled with other tools to adequately test specific pathways. While fingerprinting, statistical analysis or ratio analysis of contaminants from various sources and receptors was not completed for any of the evaluated sites, the authors believe that these techniques have strong potential for confirming or eliminating pathways. Future research in this area is suggested. Furthermore, the interpretation of pumping-concentration tests is not well developed and needs further assessment.

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Resumen Acuíferos someros pueden ocasionar contaminación transversal de acuíferos profundos mediante la penetración de un acuitardo intermedio, a través de intervalos arenosos en el acuitardo, a lo largo del revestimiento de pozos, o en las inmediaciones de lentes de acuitardos. Para distinguir entre estas trayectorias potenciales se requiere el uso de herramientas de evaluación que pueden apoyar o eliminar ciertas trayectorias. Estas herramientas incluyen cálculos de gradientes de agua subterránea y penetración de acuitardos, técnicas de interpretación de pruebas de bombeo de acuíferos, diagramas de concentración química y métodos estadísticos, estimaciones de conductividad hidráulica en base al tiempo de viaje, pruebas de concentración de bombeo, métodos para evaluar pozos con fugas, y métodos para evaluar la continuidad de acuitardos. Basándose en el análisis de varias de estas técnicas en tres sitios que experimentan contaminación transversal de acuíferos, los autores concluyen que la estimación de ritmos de flujo para varias trayectorias es el único método más útil para confirmar o rechazar trayectorias de flujo específicas. La evaluación de pozos con fugas y continuidad de acuitardos generalmente debe estar acompañada con otras herramientas para probar adecuadamente trayectorias específicas. Aunque no se completó para ninguno de los sitios evaluados técnicas de huellas, análisis estadístico o análisis de relaciones de contaminantes de varias fuentes y receptores, los autores creen que estas técnicas tienen fuerte potencial en la confirmación o eliminación de trayectorias. Se sugiere investigación futura en esta área. Además, la interpretación de pruebas de concentración de bombeo no se ha desarrollado bien y necesita evaluación posterior.

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Résumé Les aquifères de surface peuvent contaminer les aquifères plus profonds à travers un aquitard, un intersection sableuse dans laquitard, le long des forages et de leur crépines, ou de la terminaison biseautée des aquitards. Distinguer et sélectionner ces différents modes de contamination nécessite lutilisation doutils dévaluation. Ces outils incluent le gradient découlement des eaux souterraines et le calcul de pénétration des aquitards, les techniques dinterprétation des essais de pompage, les méthodes dinterprétation chimiques et de traitement statistique, les calculs des temps de transferts sur base de la conductivité, les tests de pompage couplé aux analyses de concentration, les méthodes pour évaluer linfiltration directe alimentant les forages, et les méthodes permettant dévaluer la continuité des aquitards. Basé sur lanalyse de plusieurs de ces techniques sur trois sites expérimentales présentant des contaminations transversale, les auteurs concluent que le calcul des rapports découlement est la méthode la plus simple pour confirmer ou refuser les voies spécifiques. Alors que le traçage, les analyses statistiques et les analyses de la contamination provenant de différentes sources et récepteurs nétait pas complètes pour la plus part des différents sites évalués nétaient pas compléments certains, les auteurs croient que ces techniques ont un potentiel fort pour confirmer ou éliminer ces techniques. Des recherches futures dans cette zone est suggérée. Par ailleurs, linterprétation des tests de pompage couplés à lanalyse des concentrations nest pas développée et nécessite de meilleurs estimations.

     

STAGES: the Space Telescope A901/2 Galaxy Evolution Survey

We present an overview of the Space Telescope A901/2 Galaxy Evolution Survey (STAGES). STAGES is a multiwavelength project designed to probe physical drivers of galaxy evolution across a wide range of environments and luminosity. A complex multicluster system at   z ∼ 0.165  has been the subject of an 80-orbit F606W Hubble Space Telescope (HST) /Advanced Camera for Surveys (ACS) mosaic covering the full     span of the supercluster. Extensive multiwavelength observations with XMM–Newton , GALEX, Spitzer , 2dF, Giant Metrewave Radio Telescope and the 17-band COMBO-17 photometric redshift survey complement the HST imaging. Our survey goals include simultaneously linking galaxy morphology with other observables such as age, star formation rate, nuclear activity and stellar mass. In addition, with the multiwavelength data set and new high-resolution mass maps from gravitational lensing, we are able to disentangle the large-scale structure of the system. By examining all aspects of an environment we will be able to evaluate the relative importance of the dark matter haloes, the local galaxy density and the hot X-ray gas in driving galaxy transformation. This paper describes the HST imaging, data reduction and creation of a master catalogue. We perform the Sérsic fitting on the HST images and conduct associated simulations to quantify completeness. In addition, we present the COMBO-17 photometric redshift catalogue and estimates of stellar masses and star formation rates for this field. We define galaxy and cluster sample selection criteria, which will be the basis for forthcoming science analyses, and present a compilation of notable objects in the field. Finally, we describe the further multiwavelength observations and announce public access to the data and catalogues.     

Discourse and desalination: Potential impacts of proposed climate change adaptation interventions in the Arizona–Sonora border region

The specter of climate change threatens fresh water resources along the U.S.–Mexico border. Water managers and planners on both sides of the border are promoting desalination—the conversion of seawater or brackish groundwater to fresh water—as an adaptation response that can help meet growing water demands and buffer against the negative impacts of climate change on regional water supplies. However, the uneven distribution of costs and benefits of this expensive, energy-intensive technology is likely to exacerbate existing social inequalities in the border zone. In this paper, we examine the discourses employed in the construction of the climate problem and proposed solutions. We focus our analysis on a proposed Arizona–Sonora binational desalination project and use insights from risk and hazards literature to analyze how, why, and to what effect desalination is emerging as a preferred climate change adaptation response. Our risk analysis shows that while desalination technology can reduce some vulnerabilities (e.g., future water supply), it can also introduce new vulnerabilities by compounding the water-energy nexus, increasing greenhouse gas emissions, inducing urban growth, producing brine discharge and chemical pollutants, shifting geopolitical relations of water security, and increasing water prices. Additionally, a high-tech and path-dependent response will likely result in increased reliance on technical expertise, less opportunity for participatory decision-making and reduced flexibility. The paper concludes by proposing alternative adaptation responses that can offer greater flexibility, are less path dependent, incorporate social learning, and target the poorest and most vulnerable members of the community. These alternatives can build greater adaptive capacity and ensure equity.     

Vertical soil water movement in a tropical rainforest catchment in northeast queensland

In a tropical rainforest catchment, shallow piezometers respond almost instantaneously to rainfall, but the dominant ground water recharge mechanisms are not well understood. To improve understanding, the downward movement of soil water on a runoff plot was traced using tritiated water injected at 0·20 m below the surface which marks the lower boundary of active subsurface storm flow. The tritium pulse was translated slowly down the profile, apparently dominated by interstitial piston flow on the lines described by Zimmermann's theoretical model. This recharge mechanism accounted for about 35 per cent of rainfall or 50 per cent of throughfall. The pulse's advance may have also been delayed by the upward movement of soil water indicated by the distribution of hydraulic potential under different hydrological conditions. The result was an increase in soil water transit time particularly below 1·0 m. There was also evidence in the tracer profiles for rapid by-pass flow but the volumes concerned could not be quantified in this experiment.     

Xenon isotopes in size separated nanodiamonds from Efremovka: Xe*, Xe-P3, and Xe-P6

Xenon isotopic data were acquired by high resolution step pyrolysis and combined step pyrolysis/combustion of aliquots of size separated nanodiamonds. ¹²⁹Xe excess (¹²⁹Xe*) from in situ decay of ¹²⁹I is preferentially associated with the larger grain size separates. This observation rules out trapping by recoil from surrounding material. The releases of Xe-P3 and ¹²⁹Xe occur in the same low temperature pyrolysis steps and exhibit similar distributions among the size separates. These observations imply a common site for the components and, in consequence, suggest a common incorporation event.Whether one component or two, our observations require that ¹²⁹Xe* and Xe-P3 were incorporated into a subpopulation of nanodiamonds before nanodiamonds were mixed and incorporated into parent bodies. Their susceptibilities to loss during heating in the laboratory are similar, but the ratio of ¹²⁹Xe* to Xe-P3 varies among nanodiamond separates from different meteorites (literature data). We conclude that the ¹²⁹Xe* we observe today was present as ¹²⁹I during parent body processing. Furthermore, the range of ¹²⁹Xe*/¹³²Xe_P3 ratios across all the separates requires that even nanodiamonds from CI chondrites were at least 5-10× more rich in Xe-P3 during ¹²⁹I decay than they are today.We present a simple model involving one degassing event per parent body between incorporation of nanodiamonds and final decay of ¹²⁹I. The observed variations among parent bodies require degassing events separated by several ¹²⁹I half lives (∼50Ma), consistent with low-temperature processing on parent bodies but longer than expected for nebular processing. In this model, nanodiamonds from ALHA77307 degassed at an unusually early stage, suggesting they alone may retain the signature of processing in the nebula in their P3 and ¹²⁹Xe* abundances.The isotopic signature associated with Xe-P6 is also found only in the larger size separates. Concentration of Xe-HL increases with increasing grain size, but its relative abundance with respect to Xe-P3 and P6 is higher in smaller grain-size fractions. We argue that Xe-P6 is best seen as a variant of Xe-HL, and that they are both mixtures of a “normal” component akin to solar xenon and a slightly variable exotic component. We show that both current models of Xe-H formation can account for the observed variability, and propose a scenario according to which Xe-HL and P6 were implanted into separate diamond populations before incorporation of Xe-P3 and ¹²⁹I.