Knowledge exchange, matching, and agglomeration

Despite wide recognition of their significant role in explaining sustained growth and economic development, uncompensated knowledge spillovers have not yet been fully modeled with a microeconomic foundation. The main purpose of this paper is to illustrate the exchange of knowledge as well as its consequences on agglomerative activity in a general-equilibrium search-theoretic framework. Agents, possessing differentiated types of knowledge, search for partners to exchange ideas and create new knowledge in order to improve production efficacy. When individuals’ types of knowledge are too diverse, a match is less likely to generate significant innovations. We demonstrate the extent of agglomeration has significant implications for the patterns of information flows in economies. Further, by simultaneously determining the patterns of knowledge exchange and the spatial agglomeration of an economy we identify additional channels for interaction between agglomerative activity and knowledge exchange. Finally, contrary to previous work in spatial agglomeration, our model suggests that agglomerative environments may be either under-specialized and under-populated or over-specialized and over-populated relative to the social optimum.Econometric models

Knowledge Exchange, Matching, and Agglomeration

Despite wide recognition of their significant role in explaining sustained grwoth and economic development, uncompensated knowledge spillovers have not yet been fully modeled with a microeconomic foundation. The main purpose of this paper is to illustrate the creation of knowledge as well as its consequences for agglomerative activity in a general-equilibrium search-theoretic framework. Agents, possessing differentiated types of knowledge, search for partners to exchange ideas and create new knowledge in order to improve production efficacy. When individuals' types of knowledge are too diverse, a match is less likely to generate significant innovations. We demonstrate that the extent of agglomeration has significant implications for the patterns of information flows in economies. Further, by simultaneously determining the patterns of knowledge exchange and the spatial agglomeration of an economy we identify additional channels for interaction between agglomerative activity and knowledge exchange. Finally, contrary to previous work on spatial agglomeration, our model suggests that agglomerative environments may be either under-specialized and under-populated or over-specialized and over-populated relative to the social optimum.

Knowledge Exchange, Matching, and Agglomeration

Despite wide recognition of their significant role in explaining sustained growth and economic development, uncompensated knowledge spillovers have not yet been fully modeled with a microeconomic foundation. This paper illustrates the exchange of knowledge as well as its consequences for agglomerative activity in a general-equilibrium search-theoretic framework. Agents, possessing differentiated types of knowledge, search for partners to exchange ideas in order to improve production efficacy. Contrary to previous work, we demonstrate that a decentralized equilibrium may be under-populated or over-populated and under-selective or over-selective in knowledge exchange, compared to the social optimum.matching, knowledge exchange and spillovers, agglomerative activity

Knowledge Exchange, Matching, and Agglomeration

Despite wide recognition of their significant role in explaining sustained growth and economic development, uncompensated knowledge spillovers have not yet been fully modeled with a microeconomic foundation. This paper illustrates the exchange of knowledge as well as its consequences for agglomerative activity in a general-equilibrium search-theoretic framework. Agents, possessing differentiated types of knowledge, search for partners to exchange ideas in order to improve production efficacy. When individuals’ types of knowledge are too diverse, a match is less likely to generate significant innovations. We demonstrate that the extent of agglomeration has significant implications for the patterns of information flows in economies. By simultaneously determining the patterns of knowledge exchange and the population agglomeration of an economy, we identify additional channels for interaction between agglomerative activity and knowledge exchange. The main implications of the model are a negative correlation between city population and diversity of knowledge exchange and a positive correlation between city population and per capita knowledge or patent output. Contrary to previous work in urban economics and growth theory, it is possible that a decentralized equilibrium is under-populated or over-populated and under-selective or over-selective in knowledge exchange, compared to the social optimum. By allowing for perpetual knowledge accumulation, we find that population agglomeration is generally accompanied by higher growth. The main findings remain qualitatively unchanged even if we allow individual knowledge types to change over time, though the creation of new types of knowledge may result in multiple equilibria.Matching, Knowledge Exchange and Spillovers, Agglomerative Activity

Labor Market Search and Optimal Retirement Policy

A popular view about social security, dating back to its early days of inception, is that it is a means for young, unemployed workers to 'purchase' jobs from older, employed workers. The question we ask is: Can social security, by encouraging retirement and hence creating job vacancies for the young, improve the allocation of workers to jobs in the labor market? Using a standard model of labor market search, we establish that the equilibrium with no policy-induced retirement can be efficient. Even under worst-case parameterizations of our model, we find that public retirement programs pay the elderly substantially more than labor market search theory implies that their jobs are worth. An important effect, ignored by the popular view, is that the creation of a vacant job by a retirement reduces the value of other vacant jobs.

CKS Proteins Promote Checkpoint Recovery by Stimulating Phosphorylation of Treslin

CKS proteins are small (9-kDa) polypeptides that bind to a subset of the cyclin-dependent kinases. The two paralogs expressed in mammals, Cks1 and Cks2, share an overlapping function that is essential for early development. However, both proteins are frequently overexpressed in human malignancy. It has been shown that CKS protein overexpression overrides the replication stress checkpoint, promoting continued origin firing. This finding has led to the proposal that CKS protein-dependent checkpoint override allows premalignant cells to evade oncogene stress barriers, providing a causal link to oncogenesis. Here, we provide mechanistic insight into how overexpression of CKS proteins promotes override of the replication stress checkpoint. We show that CKS proteins greatly enhance the ability of Cdk2 to phosphorylate the key replication initiation protein treslin in vitro. Furthermore, stimulation of treslin phosphorylation does not occur by the canonical adapter mechanism demonstrated for other substrates, as cyclin-dependent kinase (CDK) binding-defective mutants are capable of stimulating treslin phosphorylation. This effect is recapitulated in vivo, where silencing of Cks1 and Cks2 decreases treslin phosphorylation, and overexpression of wild-type or CDK binding-defective Cks2 prevents checkpoint-dependent dephosphorylation of treslin. Finally, we provide evidence that the role of CKS protein-dependent checkpoint override involves recovery from checkpoint-mediated arrest of DNA replication

Use of Rollover Protective Structures -- Iowa, Kentucky, New York, and Ohio, 1992-1997

Agriculture has one of the highest occupational fatality rates of all industries in the United States (1). Tractors and other types of agricultural equipment account for a large proportion of these fatalities, and farm-tractor rollovers account for approximately 130 work-related deaths each year in the United States (2). Although rollover protective structures (ROPS) are effective in protecting tractor operators from fatal injuries during rollovers (3-5), most tractors in the United States are not equipped with ROPS (4-7). Beginning in 1985, tractor manufacturers in the United Sates agreed to sell only tractors with ROPS; however, many older tractors without ROPS remain in use. To determine the prevalence of the use of ROPS, beginning in 1992, the Farm Family Health and Hazard Surveillance (FFHHS) program * collected state-based data on tractor age and use of ROPS from selected states. As of August 1997, four states had completed collection and analysis of data on farm tractors. This report summarizes the results of that survey, which indicates that 80%-90% of tractors in use in the four states were manufactured before 1985 and that less than 40% are equipped with ROPS

First radial velocity results from the MINiature Exoplanet Radial Velocity Array (MINERVA)

The MINiature Exoplanet Radial Velocity Array (MINERVA) is a dedicated observatory of four 0.7m robotic telescopes fiber-fed to a KiwiSpec spectrograph. The MINERVA mission is to discover super-Earths in the habitable zones of nearby stars. This can be accomplished with MINERVA's unique combination of high precision and high cadence over long time periods. In this work, we detail changes to the MINERVA facility that have occurred since our previous paper. We then describe MINERVA's robotic control software, the process by which we perform 1D spectral extraction, and our forward modeling Doppler pipeline. In the process of improving our forward modeling procedure, we found that our spectrograph's intrinsic instrumental profile is stable for at least nine months. Because of that, we characterized our instrumental profile with a time-independent, cubic spline function based on the profile in the cross dispersion direction, with which we achieved a radial velocity precision similar to using a conventional "sum-of-Gaussians" instrumental profile: 1.8 m s$^{-1}$ over 1.5 months on the RV standard star HD 122064. Therefore, we conclude that the instrumental profile need not be perfectly accurate as long as it is stable. In addition, we observed 51 Peg and our results are consistent with the literature, confirming our spectrograph and Doppler pipeline are producing accurate and precise radial velocities.Comment: 22 pages, 9 figures, submitted to PASP, Peer-Reviewed and Accepte

Emerging Infectious Disease leads to Rapid Population Decline of Common British Birds

Emerging infectious diseases are increasingly cited as threats to wildlife, livestock and humans alike. They can threaten geographically isolated or critically endangered wildlife populations; however, relatively few studies have clearly demonstrated the extent to which emerging diseases can impact populations of common wildlife species. Here, we report the impact of an emerging protozoal disease on British populations of greenfinch Carduelis chloris and chaffinch Fringilla coelebs, two of the most common birds in Britain. Morphological and molecular analyses showed this to be due to Trichomonas gallinae. Trichomonosis emerged as a novel fatal disease of finches in Britain in 2005 and rapidly became epidemic within greenfinch, and to a lesser extent chaffinch, populations in 2006. By 2007, breeding populations of greenfinches and chaffinches in the geographic region of highest disease incidence had decreased by 35% and 21% respectively, representing mortality in excess of half a million birds. In contrast, declines were less pronounced or absent in these species in regions where the disease was found in intermediate or low incidence. Also, populations of dunnock Prunella modularis, which similarly feeds in gardens, but in which T. gallinae was rarely recorded, did not decline. This is the first trichomonosis epidemic reported in the scientific literature to negatively impact populations of free-ranging non-columbiform species, and such levels of mortality and decline due to an emerging infectious disease are unprecedented in British wild bird populations. This disease emergence event demonstrates the potential for a protozoan parasite to jump avian host taxonomic groups with dramatic effect over a short time period

Conserving Coastal Wetlands Despite Sea Level Rise

Coastal wetlands provide valuable services such as flood protection and fisheries production to a global population that is increasingly concentrated near the coast and dependent on its resources. Many of the world\u27s coastal wetlands suffered significant losses during this century, and the creation of new wetland areas is not keeping pace with recent losses. Some destruction of wetland areas can be expected as a consequence of the continual reworking of the coastal zone by dynamic geologic processes. Yet human activities also play a role, both directly by encroaching on coastal wetlands and indirectly by influencing the hydrologic and geologic processes in the coastal zone