Measuring Community and University Impacts of Critical Civic Geography: Insights from Chicago

Geographers have increasingly adopted community-based learning and research into their teaching and scholarly activities since Bunge and Harvey called for an applied public geography that is both useful and challenges societal inequalities. With few exceptions, however, there has been little discussion of methods for measuring this work. Many published assessments focus on the impacts of projects on students but overlook the impacts on community partners. Impacts on faculty and the larger university community are also often ignored. This article discusses literature on the evaluation of community–university research and service learning from a critical perspective. A discussion of service learning and community-based research (CBR) projects at two Chicago universities, DePaul and Chicago State, is presented. In both cases challenges were encountered to achieve full evaluation of projects, yet both included an evaluation of university and community partners that allowed for assessment of the projects’ value to all partners.     

Tectonic control of fan size: the importance of spatially variable subsidence rates

We study the geophysical controls on the size of alluvial fans. Simple relationships between catchment characteristics, sediment yield, subsidence patterns and fan size are developed. As predicting fan size is essentially a conservation of mass problem, our analysis is general, applying to all types of fan landform. The importance of spatially variable subsidence rates has gone largely unrecognized in previous studies of modern fans. Here we stress that the distribution of subsidence rates in the depositional basin is a primary control on relative fan size. Both free coefficients in the oft-cited power-law correlation of fan area and catchment area can be shown to be set primarily by the tectonic setting, taken to include source area uplift rate and the subsidence distribution in the depositional basin. In the case of a steady-state landscape, relative fan size is shown to be independent of both climate and source lithology; only during times of significant departure from steady state can relative fan size be expected to vary with either climate or source lithology. Transients associated with (1) a sudden increase in rock uplift rate, (2) a sudden change in climate and (3) the unroofing of strata with greatly differing erodibilities may produce variation of relative fan areas with both climate and source lithology. Variation of relative fan size with climate or lithology, however, requires that catchment–fan system response to perturbations away from steady state is sensitive to climate and lithology. Neither the strength of transient system responses nor their sensitivity to climate or lithology are known at present. Furthermore, internal feedbacks can significantly dampen any climatic or lithological effect. Thus theoretical considerations of the importance of climatic and lithological variables are inconclusive, but suggest that climatic and lithological effects are probably of secondary importance to tectonic effects. Field data from an unsteady landscape in Owens Valley, California, support and illustrate theoretical predictions regarding tectonic control of fan size. Field data from Owens Valley allow, but do not prove, a secondary dependence on source lithology. In addition, the Owens Valley field data indicate no relationship between relative fan size and climate. Headward catchment growth and enhanced sediment bypassing of fans during times of increased sediment yield (glacial) are put forward as plausible explanations.     

Simulations of deep pencil-beam redshift surveys

We create mock pencil-beam redshift surveys from very large cosmological N -body simulations of two cold dark matter (CDM) cosmogonies, an Einstein–de Sitter model ( τ CDM) and a flat model with Ω₀=0.3 and a cosmological constant (ΛCDM). We use these to assess the significance of the apparent periodicity discovered by Broadhurst et al. Simulation particles are tagged as 'galaxies' so as to reproduce observed present-day correlations. They are then identified along the past light-cones of hypothetical observers to create mock catalogues with the geometry and the distance distribution of the Broadhurst et al. data. We produce 1936 (2625) quasi-independent catalogues from our τ CDM (ΛCDM) simulation. A couple of large clumps in a catalogue can produce a high peak at low wavenumbers in the corresponding one-dimensional power spectrum, without any apparent large-scale periodicity in the original redshift histogram. Although the simulated redshift histograms frequently display regularly spaced clumps, the spacing of these clumps varies between catalogues and there is no 'preferred' period over our many realizations. We find only a 0.72 (0.49) per cent chance that the highest peak in the power spectrum of a τ CDM (ΛCDM) catalogue has a peak-to-noise ratio higher than that in the Broadhurst et al. data. None of the simulated catalogues with such high peaks shows coherently spaced clumps with a significance as high as that of the real data. We conclude that in CDM universes, the regularity on a scale of ∼130  h ⁻¹ Mpc observed by Broadhurst et al. has a priori probability well below 10⁻³.     

Ellipticity of Nearby Elliptical Galaxies Identified with Extended Extragalactic Radio Sources

The dependence of the ellipticity of nearby optical galaxies associated with extragalactic radio sources on the type of radio galaxy is considered. It is shown that elliptical galaxies identified with radio galaxies of the FRI type and with radio sources having a radio image with a small elongation have a smaller ellipticity, on the average, than those associated with radio galaxies of the FRII type and with radio sources with greater elongation. As one possible explanation for this phenomenon, one can assume that the optical galaxies associated with radio galaxies of type FRI and with radio sources of small elongation are oriented in space so that they are observed edge-on relatively rarely.     

Short gamma-ray bursts from SGR giant flares and neutron star mergers: two populations are better than one

There is increasing evidence of a local population of short duration gamma-ray bursts (sGRB), but it remains to be seen whether this is a separate population to higher redshift bursts. Here we choose plausible luminosity functions (LFs) for both neutron star binary mergers and giant flares from soft gamma repeaters (SGR), and combined with theoretical and observed Galactic intrinsic rates we examine whether a single progenitor model can reproduce both the overall Burst and Transient Source Experiment (BATSE) sGRB number counts and a local population, or whether a dual progenitor population is required. Though there are large uncertainties in the intrinsic rates, we find that at least a bimodal LF consisting of lower and higher luminosity populations is required to reproduce both the overall BATSE sGRB number counts and a local burst distribution. Furthermore, the best-fitting parameters of the lower luminosity population agree well with the known properties of SGR giant flares, and the predicted numbers are sufficient to account for previous estimates of the local sGRB population.     

Molekular Connectivity Indizes als strukturchemische Stoffparameter ökotoxikologischer Relevanz

The molecular connectivity index developed by Randic as a numerical expression characterizes the position and bond of atoms in the molecular structure. Since significant correlations between the molar refraction as well as electron polarizability and ecotoxicologically relevant parameters of substances were determined in the preceding investigations, such connections are investigated also for this index and sorption coefficients, bioconcentration factors and toxicity data. By the example of 56 differentiated organic substances, significant regression relations are demonstrated between bioconcentration factors, sorption coefficients and toxicity data as well as the valency molecular connectivity indices. By these regressions it is possible to determine essential distribution and action parameters of chemical substances from the structure for assesing an ecotoxicological risk. The possibilities resulting from this for predicting ecotoxicologically relevant parameters of substances are discussed.     

The OSIRIS‐REx target asteroid (101955) Bennu: Constraints on its physical,geological, and dynamical nature from astronomical observations

We review the results of an extensive campaign to determine the physical, geological, and dynamical properties of asteroid (101955) Bennu. This investigation provides information on the orbit, shape, mass, rotation state, radar response, photometric, spectroscopic, thermal, regolith, and environmental properties of Bennu. We combine these data with cosmochemical and dynamical models to develop a hypothetical timeline for Bennu's formation and evolution. We infer that Bennu is an ancient object that has witnessed over 4.5 Gyr of solar system history. Its chemistry and mineralogy were established within the first 10 Myr of the solar system. It likely originated as a discrete asteroid in the inner Main Belt approximately 0.7–2 Gyr ago as a fragment from the catastrophic disruption of a large (approximately 100‐km), carbonaceous asteroid. It was delivered to near‐Earth space via a combination of Yarkovsky‐induced drift and interaction with giant‐planet resonances. During its journey, YORP processes and planetary close encounters modified Bennu's spin state, potentially reshaping and resurfacing the asteroid. We also review work on Bennu's future dynamical evolution and constrain its ultimate fate. It is one of the most Potentially Hazardous Asteroids with an approximately 1‐in‐2700 chance of impacting the Earth in the late 22nd century. It will most likely end its dynamical life by falling into the Sun. The highest probability for a planetary impact is with Venus, followed by the Earth. There is a chance that Bennu will be ejected from the inner solar system after a close encounter with Jupiter. OSIRIS‐REx will return samples from the surface of this intriguing asteroid in September 2023.