Stochastic Block Model and Community Detection in the Sparse Graphs: A spectral algorithm with optimal rate of recovery

In this paper, we present and analyze a simple and robust spectral algorithm for the stochastic block model with $k$ blocks, for any $k$ fixed. Our algorithm works with graphs having constant edge density, under an optimal condition on the gap between the density inside a block and the density between the blocks. As a co-product, we settle an open question posed by Abbe et. al. concerning censor block models

Technical Change and the Wage Structure During the Second Industrial Revolution: Evidence from the Merchant Marine, 1865-1912

Using a large, individual-level wage data set, we examine the impact of a major technological innovation the steam engine on skill demand and the wage structure in the merchant shipping industry. We find that the technical change created a new demand for skilled workers, the engineers, while destroying demand for workers with skills relevant only to sail. It had a deskilling effect on production work able-bodied seamen (essentially, artisans) were replaced by unskilled engine room operatives. On the other hand, mates and able-bodied seamen employed on steam earned a premium relative to their counterparts on sail. A wholesale switch from sail to steam would increase the 90/10 wage ratio by 40%, with most of the rise in inequality coming from the creation of the engineer occupation.

Technical Change and the Wage Structure During the Second Industrial Revolution: Evidence from the Merchant Marine, 1865-1912

Using a large, individual-level wage data set, we examine the impact of a major technological innovation—the steam engine—on skill demand and the wage structure in the merchant shipping industry. We find that the technical change created a new demand for skilled workers, the engineers, while destroying demand for workers with skills relevant only to sail. It had a deskilling effect on production work—able-bodied seamen (essentially, artisans) were replaced by unskilled engine room operatives. On the other hand, mates and able-bodied seamen employed on steam earned a premium relative to their counterparts on sail. A wholesale switch from sail to steam would increase the 90/10 wage ratio by 40%, with most of the rise in inequality coming from the creation of the engineer occupation.

Technical Change and the Wage Structure During the Second Industrial Revolution: Evidence from the Merchant Marine, 1865-1912

Using a large, individual-level wage data set, we examine the impact of a major technological innovation — the development of powerful and economical steam engines — on skill demand and the wage structure among the merchant marine. Our data reveal a complex range of responses to the new technology. The new technology created a new demand for skilled workers, the engineers, while destroying other skills relevant only to sail. There were also contradictory effects among the less skilled. On the one hand, technological innovation may have been deskilling for production work since many experienced able-bodied seamen were replaced by laborers in the engine room. On the other hand, able-bodied seamen employed on steam earned a premium relative to their counterparts on sail. Our data allow us to identify this steam premium as a skill premium rather than a compensating differential. At the managerial level, we identify a skill premium on steam for mates, whose job became more complex on the larger vessels, but not for bosuns whose job did not. In aggregate, there is little change traditional measures of the skill premium, but such measures are too crude to illuminate the rich wage dynamics induced by a major technical innovation.steam power, wage inequality, skill premium, technical change, merchant marine, Canada

Some Guidance on Conducting and Reporting Qualitative Studies

This paper sets out to address the problem of the imbalance between the number of quantitative and qualitative articles published in highly ranked research journals, by providing guidelines for the design, implementation and reporting of qualitative research. Clarification is provided of key terms (such as quantitative and qualitative) and the interrelationships between them. The relative risks and benefits of using guidelines for qualitative research are considered, and the importance of using any such guidelines flexibly is highlighted. The proposed guidelines are based on a synthesis of existing guidelines and syntheses of guidelines from a range of fields

Simple Priorities and Core Stability in Hedonic Games

In this paper we study hedonic games where each player views every other player either as a friend or as an enemy. Two simple priority criteria for comparison of coalitions are suggested, and the corresponding preference restrictions based on appreciation of friends and aversion to enemies are considered. It turns out that the first domain restriction guarantees non-emptiness of the strong core and the second domain restriction ensures non-emptiness of the weak core of the corresponding hedonic games. Moreover, an element of the strong core under friends appreciation can be found in polynomial time, while finding an element of the weak core under enemies aversion is NP-hard. We examine also the relationship between our domain restrictions and some sufficient conditions for non-emptiness of the core already known in the literature.Additive separability, Coalition formation, Core stability, Hedonic games, NP-completeness, Priority

Probing the mystery of Chinese medicine meridian channels with special emphasis on the connective tissue interstitial fluid system, mechanotransduction, cells durotaxis and mast cell degranulation

This article hypothesizes that the Chinese medicine meridian system is a special channel network comprising of skin with abundant nerves and nociceptive receptors of various types, and deeper connective tissues inside the body with the flowing interstitial fluid system. These meridian channels provide efficient migratory tracks mainly due to durotaxis (also including chemotaxis) for mast cells, fibroblasts and other cells to migrate and carry out a number of physiological functions. Acupuncture acting on meridian channel causes cytoskeletal remodeling through mechanotransduction, leading to regulation of gene expression and the subsequent production of related proteins. Also, stimulation on cell surface can trigger Ca2+ activities, resulting in a cascade of intra- and inter-cellular signaling. Moreover, nerve endings in the meridian channels interact with mast cells and induce the degranulation of these cells, leading to the release of many specific biomolecules needed for homeostasis, immune surveillance, wound healing and tissue repair. Acupoint along a meridian channel is a functional site to trigger the above functions with specificity and high efficiency