Moving off the farm: Land institutions to facilitate structural transformation and agricultural productivity growth in China

Agriculture has made major contributions to China's economic growth and poverty reduction, but the literature has rarely focused on the institutional factors that might underpin such structural transformation and productivity. This paper aims to fill that gap. Drawing on an 8-year panel of 1,200 households in six key provinces, it explores the impact of government land reallocations and formal land-use certificates on agricultural productivity growth, as well as the likelihood of households to exit from agriculture or send family members to the non-farm sector. It finds that land tenure insecurity, measured by the history of past land reallocations, discourages households from quitting agriculture. The recognitionof land rights through formal certificates encourages the temporary migration of rural labor. Both factors have a large impact on productivity (at about 30 percent each), mainly by encouraging market-based land transfers. A sustained increase in non-agricultural opportunities will likely reinforce the importance of secure land tenure, which is a precondition for successful structural transformation and continued economic attractiveness of rural areas.Labor Policies,Rural Development Knowledge&Information Systems,Economic Theory&Research,Economic Growth,Rural Poverty Reduction

A words-of-interest model of sketch representation for image retrieval

In this paper we propose a method for sketch-based image retrieval. Sketch is a magical medium which is capable of conveying semantic messages for user. It’s in accordance with user’s cognitive psychology to retrieve images with sketch. In order to narrow down the semantic gap between the user and the images in database, we preprocess all the images into sketches by the coherent line drawing algorithm. During the process of sketches extraction, saliency maps are used to filter out the redundant background information, while preserve the important semantic information. We use a variant of Words-of-Interest model to retrieve relevant images for the user according to the query. Words-of-Interest (WoI) model is based on Bag-ofvisual Words (BoW) model, which has been proven successfully for information retrieval. Bag-of-Words ignores the spatial relationships among visual words, which are important for sketch representation. Our method takes advantage of the spatial information of the query to select words of interest. Experimental results demonstrate that our sketch-based retrieval method achieves a good tradeoff between retrieval accuracy and semantic representation of users’ query

Low-Voltage High-Linearity Wideband Current Differencing Transconductance Amplifier and Its Application on Current-Mode Active Filter

A low-voltage high-linearity wideband current differencing transconductance amplifier (CDTA) is presented in this paper. The CDTA consists of a current differencing circuit and a cross-coupling transconductance circuit. The PSPICE simulations of the proposed CDTA show a good performance: -3dB frequency bandwith is about 900 MHz, low power consumption is 2.48 mW, input current linear range is ±100 µA and low current-input resistance is less than 20 Ω, high current-output resistance is more than 3 MΩ. PSpice simulations for a current-mode universal filter and a proposed high-order filter are also conducted, and the results verify the validity of the proposed CDTA

Ramsey numbers involving a triangle: theory and algorithms

Ramsey theory studies the existence of highly regular patterns in large sets of objects. Given two graphs G and H, the Ramsey number R(G, H) is defined to be the smallest integer n such that any graph F with n or more vertices must contain G, or F must contain H. Albeit beautiful, the problem of determining Ramsey numbers is considered to be very difficult. We focus our attention on efficient algorithms for determining Ram sey numbers involving a triangle: R(K3 , G). With the help of theoretical tools, the search space is reduced by using different pruning techniques and linear programming. Efficient operations are also carried out to mathematically glue together small graphs to construct larger critical graphs. Using the algorithms developed in this thesis, we compute all the Ramsey numbers R(Kz,G), where G is any connected graph of order seven. Most of the corresponding critical graphs are also constructed. We believe that the algorithms developed here will have wider applications to other Ramsey-type problems

Nitric Oxide Toxicity Mediated by Peroxynitrite.

The reaction of nitric oxide (NO) with superoxide forms peroxynitrite, an extremely potent oxidant. Peroxynitrite can be synthesized by the ozonation of the azide ion. This preparation of peroxynitrite is essentially free of hydrogen peroxide and does not contain excess alkali. Peroxynitrites synthesized by independent methods contain very different impurities, but give the same results toward the oxidation of methionine (Met), dimethylsulfoxide, and the nitration of phenols. The oxidations of Met and its analog, 2-keto-4-thiomethylbutanoic acid (KTBA), by peroxynitrite proceed by two competing mechanisms. The first is a non-radical, bimolecular reaction yielding methionine sulfoxide (MetS=O). In the second mechanism, methionine or KTBA reacts with peroxynitrite by a one-electron transfer (ET) reaction that produces ethylene; this reaction is first order in peroxynitrite and zero order in Met. Both ceric and peroxydisulfate ions also oxidize KTBA to ethylene, supporting an ET mechanism. Neither the yields of MetS=O nor the yields of ethylene are affected by several hydroxyl radical scavengers, suggesting that a unimolecular homolysis of peroxynitrite to form the hydroxyl radical is not involved in these reactions. We propose that the reaction of methionine with peroxynitrite to form ethylene involves an excited intermediate of peroxynitrite that has a reactivity similar to the hydroxyl radical. Both peroxynitrous acid and its anion react with methionine to form MetS=O; the second-order rate constants at 25\sp\circC are 2060 $\pm$ 120 and 0.20 \rm M\sp{-1}s\sp{-1}, respectively. The first-order rate constants for the decomposition of peroxynitrous acid to give nitric acid is 1.38 \pm 0.02\ {\rm s}\sp{-1}. This rate is sufficiently slow so that methionine can trap peroxynitrous acid before it rearranges to nitric acid. The activation parameters for the bimolecular reaction of peroxynitrite with methionine to form MetS=O are: \Delta{\rm H}\sp\ddagger = 7.6 \pm 0.2 kcal/mol and \Delta{\rm S}\sp\ddagger = -19.8 \pm 1 cal/mol.K at pH 4.7, and \Delta{\rm H}\sp\ddagger = 7.7 \pm 0.4 kcal/mol and \Delta{\rm S}\sp\ddagger = -22.7 \pm 1.3 cal/mol.K at pH 7.4; and the activation parameters for the unimolecular decomposition of peroxynitrous acid to form nitric acid are: \Delta{\rm H}\sp\ddagger = 18.1 \pm 0.7 kcal/mol and \Delta{\rm S}\sp\ddagger = 1.4 \pm 2 cal/mol.K at pH 4.7, and \Delta{\rm H}\sp\ddagger = 17.4 \pm 0.5 kcal/mol and \Delta{\rm S}\sp\ddagger = 0.9 \pm 1.7 cal/mol.K at pH 7.4