A systematic review of the scientifically demonstrated effects of densification

One of the current dominant strategies proposed for sustainable urban development is densification. UN Habitat prescribes a density of over 150 inhabitants per hectare to realize the UN Sustainable Development Goals. While some authors advocate the very reasonable benefits of density, others emphasize the potential drawbacks. The main goal of this paper is to provide a systematic review of international research on urban density and its potential benefits and drawbacks for sustainable urban development. 1208 articles were selected from Web of Science and after the screening of abstracts, 330 papers were found eligible to be included in the quantitative synthesis. Results show that the effects of densification that dominate literature are transport related studies (41%), followed by studies focusing on economics (14%), social effects (12%) and human health (11%). Least studied effects are resource efficiency (1%), service (3%) and urban environment (4%). Positive correlations with higher density are reported for transport and economics, while ecology, social impact and health show mainly negative correlations with higher density. The findings reported are generic as similar trends are found in North America, Asia and Europe and only minor differences in outcome are found in studies using different measures of density, unit or scale of analysis

MONEY AND MACRO MODELS

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Probabilistic formulation of conservation of cosmogenic nuclides: Effect of surface elevation fluctuations on approach to steady state. Earth Surf. Process

Abstract Cosmogenic nuclides have provided a powerful tool for determining rates of landscape erosion. Once a steady-state profile of cosmogenic nuclides is reached, the erosion rate becomes inversely proportional to the concentration of cosmogenic nuclides in the eroded sediment. Erosional landscapes are, however, subject to varying degrees of elevation fluctuations due to e.g. gullying, landsliding and bioturbation. Here elevation fluctuation is described in terms of a probability density of deviation from mean elevation. A probabilistic formulation for the conservation of cosmogenic nuclides is derived so as to include the effect of the fluctuations. At steady state, the relation between the mean erosion rate and the concentration of cosmogenic radionucides in the eroded material becomes identical to that which would prevail in the absence of fluctuations. The * Corresponding author. E-mail address: [email protected] (G. Parker) 2 fluctuations, however, can significantly lengthen the time required to reach steady state. Here the approach to steady state is studied in terms of a) an impulsive increase in erosion rate starting from an antecedent steady state, and b) a constant erosion rate but the initial absence of any cosmogenic nuclides. The problem allows an analytical solution. The effect of the fluctuations increases monotonically with increase in the ratio of the standard deviation of elevation fluctuations to the e-folding penetration length of cosmic rays. Of prime importance to the practitioner is whether or not the concentration of cosmogenic nuclides in the eroded material has reached its steady-state value. The central result of this paper is a simple plot allowing estimation of the time required to reach within a specified tolerance of the steady-state value of this concentration. The time increases markedly with increase in the ratio defined above. Sample applications to the field are given in the text

Efficient Investment Portfolios in a Real-Value Environment: Implications for Portfolio Managers and Bond Yields

ABSTRACT In early 1997 the U.S. Treasury began issuing inflation-indexed securities. This paper compares efficient portfolios containing an inflation-indexed security to portfolios without such a security. Inflation risk premiums that are required for traditional, nominal, non-indexed debt assets to replace an inflation-indexed security in efficient portfolios are estimated. Results are calculated and compared for the period

Slip Rate of the Calico Fault: Implications for Geologic Versus Geodetic Rate Discrepancy in the Eastern California Shear Zone

Long-term (10(5) years) fault slip rates test the scale of discrepancy between infrequent paleoseismicity and relatively rapid geodetic rates of dextral shear in the Eastern California Shear Zone (ECSZ). The Calico fault is one of a family of dextral faults that traverse the Mojave Desert portion of the ECSZ. Its slip rate is determined from matching and dating incised Pleistocene alluvial fan deposits and surfaces displaced by fault slip. A high-resolution topographic base acquired via airborne laser swath mapping aids in identification and mapping of deformed geomorphic features. The oldest geomorphically preserved alluvial fan, unit B, is displaced 900 +/- 200 m from its source at Sheep Springs Wash in the northern Rodman Mountains. This fan deposit contains the first preserved occurrence of basalt clasts derived from the Pipkin lava field and overlies Quaternary conglomerate deposits lacking these clasts. The Ar-40/Ar-39 dating of two flows from this field yields consistent ages of 770 +/- 40 ka and 735 +/- 9 ka. An age of 650 +/- 100 ka is assigned to this fan deposit based on these ages and on the oldest cosmogenic He-3 exposure date of 653 +/- 20 ka on a basalt boulder from the surface of unit B. This assigned age and offset together yield a mid-Pleistocene to present average slip rate of 1.4 +/- 0.4 mm/yr. A younger fan surface, unit K, records 100 +/- 10 m of dextral displacement and preserves original depositional morphology of its surface. Granitic boulders and pavement samples from this surface yield an average age of 56.4 +/- 7.7 ka after taking into account minimal cosmogenic inheritance of granitic clasts. The displaced and dated K fans yield a slip rate of 1.8 +/- 0.3 mm/yr. Distributed deformation of the region surrounding the fault trace, if active, could increase the overall displacement rate to 2.1 +/- 0.5 mm/yr. Acceleration of slip rate from an average of 1.4 mm/yr prior to similar to 50 ka to 1.8 mm/yr since similar to 50 ka is possible, though a single time-averaged slip rate of 1.6 +/- 0.2 mm/yr satisfies the data. These rates are faster than any other paleoseismic or long-term slip rate yet determined for other dextral faults in the Mojave Desert and imply that fault slip rates and earthquake productivity are heterogeneous across this portion of the ECSZ. Total displacement across the Calico fault diminishes northward as shear is distributed into folding and sinistral faults in the Calico Mountains. This pattern is consistent with an approximately threefold drop in geologic slip rate as the Calico fault steps over onto the Blackwater fault and demonstrates the significance of fault interaction for understanding the pattern of present-day strain accumulation in the ECSZ.Earth and Planetary Science