Urban Structure and Growth ROSSI-HANSBERG, ESTEBAN; WRIGHT, MARK L.J
The Review of economic studies,
04/2007, Letnik:
74, Številka:
2
Journal Article
Recenzirano
Odprti dostop
Most economic activity occurs in cities. This creates a tension between local increasing returns, implied by the existence of cities, and aggregate constant returns, implied by balanced growth. To ...address this tension, we develop a general equilibrium theory of economic growth in an urban environment. In our theory, variation in the urban structure through the growth, birth, and death of cities is the margin that eliminates local increasing returns to yield constant returns to scale in the aggregate. We show that, consistent with the data, the theory produces a city size distribution that is well approximated by Zipf's law, but that also displays the observed systematic underrepresentation of both very small and very large cities. Using our model, we show that the dispersion of city sizes is consistent with the dispersion of productivity shocks found in the data.
PhotoCORMs: CO release moves into the visible Wright, Mark A; Wright, Joseph A
Dalton transactions : an international journal of inorganic chemistry,
04/2016, Letnik:
45, Številka:
16
Journal Article
Recenzirano
The potential of carbon monoxide to act as a therapeutic agent is now well-established. Controlled delivery of CO is best achieved using 'CORMs': molecules which release known amounts of carbon ...monoxide in response to a stimulus. Metal carbonyl complexes will release CO if irradiated with ultraviolet light, but it is only in the past five years that development of true 'photoCORMs' has been explored. Recent exciting developments in this area now show that design of photoCORMs operating well into the visible region is achievable. In this Perspective, we examine the growth of photoCORMs from their origins in the photophysics of metal carbonyls to the latest visible-light agents.
Aluminum (Al) toxicity is a primary limitation to crop productivity on acid soils, and rice has been demonstrated to be significantly more Al tolerant than other cereal crops. However, the mechanisms ...of rice Al tolerance are largely unknown, and no genes underlying natural variation have been reported. We screened 383 diverse rice accessions, conducted a genome-wide association (GWA) study, and conducted QTL mapping in two bi-parental populations using three estimates of Al tolerance based on root growth. Subpopulation structure explained 57% of the phenotypic variation, and the mean Al tolerance in Japonica was twice that of Indica. Forty-eight regions associated with Al tolerance were identified by GWA analysis, most of which were subpopulation-specific. Four of these regions co-localized with a priori candidate genes, and two highly significant regions co-localized with previously identified QTLs. Three regions corresponding to induced Al-sensitive rice mutants (ART1, STAR2, Nrat1) were identified through bi-parental QTL mapping or GWA to be involved in natural variation for Al tolerance. Haplotype analysis around the Nrat1 gene identified susceptible and tolerant haplotypes explaining 40% of the Al tolerance variation within the aus subpopulation, and sequence analysis of Nrat1 identified a trio of non-synonymous mutations predictive of Al sensitivity in our diversity panel. GWA analysis discovered more phenotype-genotype associations and provided higher resolution, but QTL mapping identified critical rare and/or subpopulation-specific alleles not detected by GWA analysis. Mapping using Indica/Japonica populations identified QTLs associated with transgressive variation where alleles from a susceptible aus or indica parent enhanced Al tolerance in a tolerant Japonica background. This work supports the hypothesis that selectively introgressing alleles across subpopulations is an efficient approach for trait enhancement in plant breeding programs and demonstrates the fundamental importance of subpopulation in interpreting and manipulating the genetics of complex traits in rice.
In this article, we review the empirical literature about sovereign debt and default. As we survey the work of economists, historians, and political scientists, we also emphasize parallel ...developments by theorists and recommend steps to improve the correspondence between theory and data.
•Internal rate of returns ranged between 3.51 and 5.57%.•Emissions for the biomass only scenarios range from −28 to −82 g of CO2eq/kWh.•Emissions for the biomass and glycerin scenario range from 358 ...to 400 g of CO2eq/kWh.•Operating capacity and biomass/glycerin factors were most significant.
There is growing interest in the use of anaerobic digestion to increase revenues in rural areas and reduce greenhouse gas emissions. This study evaluates the economic and environmental feasibility of a farm-scale anaerobic digestion (AD) combined heat and power (CHP) plant co-located with a cattle feedlot. The study evaluates two different scenarios with six cases – Biomass Only (BO) scenario and Biomass and Glycerin (BG) scenario, targeting a power capacity of 950 kWe using combinations of manure, biomass, and crude glycerin. Beef cattle manure with approximately 10.15 wt% of biomass and 10 wt% of glycerin is added into the system. The internal rate of return (IRR) and greenhouse gas emissions (GHG) were calculated for six cases. The IRR ranges between 3.51% and 5.57%, and the GHG emissions range between −82.6 and 498.52 g CO2e/kWh. Glycerin reduces the operating cost by 32%. These results indicate that AD CHP could be profitable at the farm-scale depending on various parameters. Sensitivity analysis indicates that power efficiency, operating capacity and waste generation per cattle have the strongest impact on the IRR, affecting it by over 40%, while glycerin and manure emission factors are the most important for GHG emissions affecting it by over 15%. Uncertainty analysis describes the role of feedstock choice and process performance on minimizing commercialization risks.
This study describes a techno-economic analysis to evaluate the economic feasibility of transportation fuel production by hydrothermal liquefaction (HTL) of defatted microalgae followed by ...hydroprocessing of the resulting bio-crude. A 2000 dry tonne per day biorefinery produces 112 dam3 of gasoline-range fuels and 121 dam3 of diesel-range fuels per year. We estimate the total project investment is 504 M$ and the annual operating cost is 158 M$. The minimum fuel-selling price (MFSP) is 679 $ m−3 assuming a 10% internal rate of return assuming 30-year plant life. Sensitivity analysis shows that MFSP is most sensitive to product fuel yield indicating the relative importance of HTL conversion performance. Feedstock cost also strongly influences MFSP, which varied between 584 $ m−3 and 869 $ m−3 for feedstock cost of 33 and 132 $ dry tonne−1, respectively. A Monte-Carlo analysis suggests an 80% probability of MFSP being between 607 and 833 $ m−3.
•Fuel production from defatted microalgae hydrothermal liquefaction was modeled.•Estimated Fixed capital investment of a 2000 dry tonne day−1 facility was 424 M$.•Estimated minimum fuel selling price was 679 $ m−3.•Overall Energy efficiency of the process was 56.3%.•Overall carbon yield of the process was 49.3%.
The stock of sovereign debt is typically measured at face value. Defined as the undiscounted sum of future principal repayments, face values are misleading when debts are issued with different ...contractual forms or maturities. In this paper, we construct alternative measures of the stock of external sovereign debt for 100 developing countries from 1979 through 2006 that correct for differences in contractual form and maturity. We show that our alternative measures: (1) paint a very different quantitative, and in some cases also qualitative, picture of the stock of developing country external sovereign debt; (2) often invert rankings of indebtedness across countries, which historically defined eligibility for debt forgiveness; (3) indicate that the empirical performance of the benchmark quantitative model of sovereign debt deteriorates by roughly 50% once model-consistent measures of debt are used; (4) show how the spread of aggregation clauses in debt contracts that award creditors voting power in proportion to the contractual face value may introduce inefficiencies into the process of restructuring sovereign debts; and (5) illustrate how countries have manipulated their debt issuance to meet fiscal targets written in terms of face values.
•We present new measures of sovereign debt for 100 countries from 1979-2006.•Our measure is model consistent, and invariant to the contractual form of debt.•Differences in contract form sometimes invert rankings of indebtedness.•Benchmark models under-predict indebtedness by 40-70%.•We identify manipulation of the traditional measure of sovereign debt in practice.
After World War II, international capital flowed into slow-growing Latin America rather than fast-growing Asia. This is surprising as, everything else equal, fast growth should imply high capital ...returns. This paper develops a capital flow accounting framework to quantify the role of different factor market distortions in producing these patterns. Surprisingly, we find that distortions in labor markets, rather than domestic or international capital markets, account for the bulk of these flows. Labor market distortions that indirectly depress investment incentives by lowering equilibrium labor supply explain two-thirds of observed flows, while improvement in these distortions over time accounts for much of Asia’s rapid growth.
This paper presents a theory of establishment size dynamics based on the accumulation of industry-specific human capital that simultaneously rationalizes the economy-wide facts on establishment ...growth rates, exit rates, and size distributions. The theory predicts that establishment growth and net exit rates should decline faster with size, and that the establishment size distribution should have thinner tails, in sectors that use specific human capital less intensively. We establish that there is substantial cross-sector heterogeneity in US establishment size dynamics and distributions, which is well explained by relative factor intensities.
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