The relative volatility of commodity prices : a reappraisal

This paper studies the volatility of commodity prices on the basis of a large dataset of monthly prices observed in international trade data from the United States over the period 2002 to 2011. The conventional wisdom in academia and policy circles is that primary commodity prices are more volatile than those of manufactured products, although most of the existing evidence does not actually attempt to measure the volatility of prices of individual goods or commodities. The literature tends to focus on trends in the evolution and volatility of ratios of price indexes composed of multiple commodities and products. This approach can be misleading. Indeed, the evidence presented in this paper suggests that on average prices of individual primary commodities are less volatile than those of individual manufactured goods. However, the challenges of managing terms of trade volatility in developing countries with concentrated export baskets remain.Markets and Market Access,Emerging Markets,Commodities,E-Business,Access to Markets

The Relative Volatility of Commodity Prices: A Reappraisal

This paper studies the volatility of commodity prices on the basis of a large dataset of monthly prices observed in international trade data from the United States over the period 2002 to 2011. The conventional wisdom in academia and policy circles is that primary commodity prices are more volatile than those of manufactured products, although most of the existing evidence does not actually attempt to measure the volatility of prices of individual goods or commodities. The literature tends to focus on trends in the evolution and volatility of ratios of price indexes composed of multiple commodities and products. This approach can be misleading. Indeed, the evidence presented in this paper suggests that on average prices of individual primary commodities are less volatile than those of individual manufactured goods. However, the challenges of managing terms of trade volatility in developing countries with concentrated export baskets remain.international commodity prices, volatility, manufactured product prices

A full contraction-reaction-diffusion model for pattern formation in geometrically confined microtissues

The reaction-diffusion models have been extensively applied to explain the mechanism of pattern formations in early embryogenesis based on geometrically confined microtissues consisting of human pluripotent stem cells. Recently, mechanical cues, such as the cellular stresses and strains, have been found to dictate the pattern formation in human stem cell differentiation. As a result, the traditional reaction-diffusion models are modified by adding mechanically related terms to consider the role played by the mechanical cues. However, these models either do not consider the activeness of the cellular tissues or neglect their poroelastic nature that biological tissues are made by both cells and interstitial fluid. Hence, the current models suffer from the lacks of biophysical relevance. Here we propose a modified reaction-diffusion model that couples with the active contraction of cellular tissues. The cellular tissue is modelled as a piece of biphasic poroelastic material, where mechanical forces naturally regulate the transport of chemical cues. Such chemical cues direct cell fate and hence yield certain types of pattern formations observed in previous experiments

The Influence of Class Teachers’ Leadership Behavior and Personal Characteristics on Student Academic Performance: A Study of Fuzzy Set Qualitative Comparative Analysis Citing H Middle School as a Case Study

Leadership behavior of classroom teachers has a significant impact on students’ academic success. However, little empirical research on this subject has been undertaken in China. By developing truth tables and doing necessary computations, this study examines the influence of differential combinations of parameters connected to class teachers’ qualities and leadership behavior on student academic performance. It has been discovered that the democratic leadership behavior displayed by class teachers is the most popular among students and is helpful to student academic achievement; the numerous combinations of linked characteristics have varying effects on student academic performance. The study compensates for a dearth of empirical research on the subject and sheds light on the process by which class teacher leadership influences student academic progress

Sludge transforms into biochar: Doping calcium induces phosphorus transforming into a plant-available speciation

The mass-produced sewage sludge (SS) worldwide is regarded as an important phosphorus (P) pool with a P-content of 2-3% (dry basis). Pyrolytic conversion of SS into P-rich biochar has multiple environmental benefits: toxicity elimination, carbon sequestration and soil fertilization. It has been proved that P transforms into insoluble speciation such as Ca2P2O7 during pyrolysis, and this would be influenced significantly by inherent minerals such as Ca, Mg, Fe, Al, etc [1, 2]. With a purpose of enhancing biochar’s fertilizer efficiency to plant, we selected calcium (Ca) as an additive to SS and expected their thermal-chemical interaction would induce P transforming into a plant-available speciation. The sequential extraction experiments showed that after pyrolysis (biochar: SS500) the percent of the insoluble phosphates (HCl-extracted P) increased significantly from 8.28% to 76.6%, while the readily soluble P species being extracted by water, NaHCO3 and NaOH decreased sharply. Doping CaCl2 strengthened this transformation and the produced biochars at pyrolysis temperature of 500oC with 20% (w/w) Ca-doping (biochar: SS-Ca500) contained 84.1% insoluble phosphates and 5.28% Fe/Al mineral adsorbed P (NaOH-extracted P). It indicated that Ca could compete for more P than Fe/Al during pyrolysis. Instrumental analysis (XRD, NMR) showed that Ca promoted more formation of pyrophosphate and short-chain polyphosphates such as Ca5(PO4)3(OH), Ca5(PO4)3Cl, which are species facilitating plant-uptake while avoiding dissolution loss. This study gave an insight into P speciation transformation during biochar formation and suggested that P availability in biochars are controllable by doping minerals to structure a safe slow-release P fertilizer benefiting plant growth. Please click Additional Files below to see the full abstract