Politically engaged artistic practice: Strategies and tactics

This paper explores political forms of artistic practice operating within Tate Exchange broadly and within the authors’ creative practice specifically. It identifies the tensions and obstacles inherent to socially engaged artistic practice and forms of expertise, and proposes a method of practice that is grounded in prefiguration and solidarity

Chlorinated organic contaminants in breast milk of New Zealand women.

Breast milk samples from 38 women in New Zealand were analyzed for organochlorine pesticides, polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins (PCDDs), and polychlorinated dibenzofurans (PCDFs) as part of a World Health Organization collaborative study of breast-milk contaminants. The women were recruited from two urban areas (Auckland and Christchurch) and two rural areas (Northland and North Canterbury) in the North and South Islands of New Zealand. The best predictor of contaminant concentrations in breast milk was found to be the age of the mother. Regional differences were found for hexachlorobenzene, dieldrin, and pp-DDE, reflecting historical use patterns. Urban-rural differences were found for several PCBs, PCDDs, and PCDFs when contaminant concentrations were calculated on a whole-milk basis. However, these differences could be attributed to variation in breast-milk fat concentrations between urban and rural mothers. Urban mothers had about 50% more breast-milk fat than rural mothers. Evidence suggests that breast-milk consumption by babies is regulated by caloric intake. Almost all of the caloric content of milk is in the fat fraction. This suggests that breast-milk contaminant levels calculated on a whole-milk basis do not necessarily reflect the relative levels of exposure of infants to these contaminants. However, the factors that influence breast-milk fat concentration deserve further study

Using airborne laser altimetry to improve river flood extents delineated from SAR data

Flood extent maps derived from SAR images are a useful source of data for validating hydraulic models of river flood flow. The accuracy of such maps is reduced by a number of factors, including changes in returns from the water surface caused by different meteorological conditions and the presence of emergent vegetation. The paper describes how improved accuracy can be achieved by modifying an existing flood extent delineation algorithm to use airborne laser altimetry (LiDAR) as well as SAR data. The LiDAR data provide an additional constraint that waterline (land-water boundary) heights should vary smoothly along the flooded reach. The method was tested on a SAR image of a flood for which contemporaneous aerial photography existed, together with LiDAR data of the un-flooded reach. Waterline heights of the SAR flood extent conditioned on both SAR and LiDAR data matched the corresponding heights from the aerial photo waterline significantly more closely than those from the SAR flood extent conditioned only on SAR data

C*-algebras of labelled graphs II - Simplicity results

We prove simplicity and pure infiniteness results for a certain class of labelled graph $C^*$-algebras. We show, by example, that this class of unital labelled graph $C^*$-algebras is strictly larger than the class of unital graph $C^*$-algebras.Comment: 18 pages, 4 figure

Effects of Altitude on Step Test Performance

Please view abstract in the attached PDF file

Strong Shift Equivalence of C∗C^*-correspondences

We define a notion of strong shift equivalence for $C^*$-correspondences and show that strong shift equivalent $C^*$-correspondences have strongly Morita equivalent Cuntz-Pimsner algebras. Our analysis extends the fact that strong shift equivalent square matrices with non-negative integer entries give stably isomorphic Cuntz-Krieger algebras.Comment: 26 pages. Final version to appear in Israel Journal of Mathematic

Influence of particle size and chemistry on the cloud nucleating properties of aerosols

International audienceThe ability of an aerosol particle to act as a cloud condensation nuclei (CCN) is a function of the size of the particle, its composition and mixing state, and the supersaturation of the cloud. In-situ data from field studies provide a means to assess the relative importance of these parameters. During the 2006 Texas Air Quality ? Gulf of Mexico Atmospheric Composition and Climate Study (TexAQS-GoMACCS), the NOAA RV Ronald~H.~Brown encountered a wide variety of aerosol types ranging from marine near the Florida panhandle to urban and industrial in the Houston-Galveston area. These varied sources provided an opportunity to investigate the role of aerosol sources, chemistry, and size in the activation of particles to form cloud droplets. Measurements were made of CCN concentrations, aerosol chemical composition in the size range relevant for particle activation, and aerosol size distributions. Variability in aerosol composition was parameterized by the mass fraction of Hydrocarbon-like Organic Aerosol (HOA) for particle diameters less than 200 nm (vacuum aerodynamic). The HOA mass fraction in this size range was lowest for marine aerosol and highest for aerosol sampled close to anthropogenic sources. Combining all data from the experiment reveals that composition (defined by HOA mass fraction) explains 40% of the variance in the critical diameter for particle activation at 0.44% supersaturation (S). Correlations between HOA mass fraction and aerosol mean diameter show that these two parameters are essentially independent of one another for this data set. We conclude that, based on the variability of the HOA mass fraction observed during TexAQS-GoMACCS, composition played a significant role in determining the fraction of particles that could activate to form cloud droplets. In addition, we estimate the error that results in calculated CCN concentrations if the HOA mass fraction is neglected (i.e., a fully soluble composition of (NH4)2SO4 is assumed) for the range of mass fractions and mean diameters observed during the experiment. This error is then related to the source of the aerosol. At 0.22 and 0.44% S, the error is considerable (>50%) for anthropogenic aerosol sampled near the source region as this aerosol had, on average, a high HOA mass fraction in the sub-200 nm diameter size range (vacuum aerodynamic). The error is lower for aerosol distant from anthropogenic source regions as it had a lower HOA mass fraction. Hence, the percent error in calculated CCN concentration is larger for organic-rich aerosol sampled near the source and smaller for aerosol sampled away from sources of anthropogenic particulate organic matter (POM)