Microstructural evolution in Grade 91(9CR-1MoVNb) power plant steels

The aim of this research project was to gam a complete, quantified, understanding of microstructural changes in high Cr ferritic-martensitic power plant steels, as a function of preservice heat treatment, stress, time and temperature. The creep strength, which is the main design criteria for this class of alloys, depends on the stability of the microstructure, which consists of tempered martensite and a fine dispersion of carbide precipitates. An understanding of the changes of these two features forms an essential process towards the creation of a physically or microstructural-based model, which may improve the current approaches towards the prediction of remanent operational lifetime of these materials in service in conventional fossil-fired power plant... cont'd

Platform Procedure: Using Technology to Facilitate (Efficient) Civil Settlement.

In this chapter, we explore the ability of courts to enhance the role of substantive law in case outcomes by reducing party litigation costs. When it becomes less costly for parties to engage actively in dispute resolution, the shadow of substantive law should, in theory, become more pronounced and case outcomes should change (and hopefully become more accurate/efficient on average). To empirically investigate this hypothesis, we examine the consequences of a large state court’s implementation of court-assisted online dispute resolution (ODR) tools for its small claims docket. A central goal of this technology is to reduce litigation costs of all sorts so that parties are able to communicate easily and negotiate settlements quickly in the shadow of what is —or could be—efficient substantive law, thereby avoiding inefficient status quo outcomes, like default judgments. ODR tools enhance court efficiency and litigant satisfaction by giving parties on‐demand, inexpensive access to a private and secure platform to negotiate an agreement that fully resolves their dispute. We find that, by reducing costs, eliminating procedural inefficiencies, and placing decision-making power in the hands of the parties, platform technology reduces the likelihood of default and likely improves the substantive outcome of disputes

Social Capital, Trust and Entrepreneurial Productivity

With an incomplete panel data from 63 countries over 25 years this paper finds that the average number of employees per entrepreneur increases with the countries'' levels of social capital. This evidence is in line with predictions from occupational choice models, where the equilibrium average size of firms increases with lower internal costs of growth, when social capital supported trust reduces these costs facilitating the delegation of decision power in firms. We also find that the influence of social capital in self-employed rates differs if the self-employed have employees or not so entrepreneurs should be treated as a heterogeneous group

Organization of production and the distribution of labor income in Spain

This paper examines evidences of market labor income inequality in Spain, as if they were the outcome of the market equilibrium from occupational choices of individuals with different general skills. We find that the parameters of the distribution of skills, production technology, and internal organization of firms that match the observed organization of production (number of persons occupied as employees, entrepreneurs-managers and solo self-employed, distribution of firm sizes) in Spain, also explain reasonably well the distribution of market labor income, within groups and for all occupied individuals together. The proposed model can be of use in evaluating the potential consequences for labor income inequality of changes in the organization of production

New Trends and Future Opportunities in the Enzymatic Formation of C-C, C-N, and C-O bonds

Organic chemistry provides society with fundamental products we use daily. Concerns about the impact that the chemical industry has over the environment is propelling major changes in the way we manufacture chemicals. Biocatalysis offers an alternative to other synthetic approaches as it employs enzymes, Nature''s catalysts, to carry out chemical transformations. Enzymes are biodegradable, come from renewable sources, operate under mild reaction conditions, and display high selectivities in the processes they catalyse. As a highly multidisciplinary field, biocatalysis benefits from advances in different areas, and developments in the fields of molecular biology, bioinformatics, and chemical engineering have accelerated the extension of the range of available transformations (E. L. Bell et al., Nat. Rev. Meth. Prim. 2021, 1, 1–21). Recently, we surveyed advances in the expansion of the scope of biocatalysis via enzyme discovery and protein engineering (J. R. Marshall et al., Tetrahedron 2021, 82, 131926). Herein, we focus on novel enzymes currently available to the broad synthetic community for the construction of new C-C, C-N and C-O bonds, with the purpose of providing the non-specialist with new and alternative tools for chiral and sustainable chemical synthesis. © 2021 The Authors. ChemBioChem published by Wiley-VCH GmbH

The effect of simulated post weld heat treatment temperature overshoot on microstructural evolution in P91 and P92 power plant steels

Creep strength enhanced ferritic (CSEF) steels, in particular modified 9Cr steels Grade 91 and 92, are becoming more widely used in the electrical power generation industry for the construction of header and steam piping in advanced coal-fired power plants. They typically enter service having received a standard high temperature normalizing treatment following by a lower temperature tempering treatment designed to produce an optimum microstructural condition. However, situations may arise in practice, particularly during welding operations for example, whereby the component may receive an additional heat treatment which briefly exceeds the Ac, and possibly the Ac , temperature before stabilizing at the tempering temperature. In this research, simulated post weld heat treatments (PWHT) have been applied to Grade 91 and 92 materials using carefully controlled heating and cooling rates within a dilatometer. Peak temperatures applied were below Ac, between Ac and Ac, and above Ac, prior to a subsequent heat treatment at 750°C for 2 hours. Hardness measurements demonstrated a significant reduction once the Ac temperature was exceeded. Advanced electron microscopy has been carried out to investigate the effect of the PWHT excursions on subsequent microstructural evolution. Electron back scatter diffraction has been used to quantify the nature of the martensite laths and grain structure changes as a function of temperature. The detailed size distribution of carbides within the microstructure has also been determined using both scanning and transmission electron microscopy. These results are discussed in respect of the likely consequences of such a PWHT overshoot on subsequent mechanical properties during high temperature service. Copyright © 2011 Electric Power Research Institute Distributed by ASM International®. All rights reserved

Shifts in Growth Responses to Climate and Exceeded Drought-Vulnerability Thresholds Characterize Dieback in Two Mediterranean Deciduous Oaks

Drought stress has induced dieback episodes affecting many forest types and tree species worldwide. However, there is scarce information regarding drought-triggered growth decline and canopy dieback in Mediterranean deciduous oaks. These species face summer drought but have to form new foliage every spring which can make them vulnerable to hotter and drier conditions during that season. Here, we investigated two stands dominated byQuercus frainettoTen. andQuercus canariensisWilld. and situated in southern Italy and Spain, respectively, showing drought-induced dieback since the 2000s. We analyzed how radial growth and its responses to climate differed between non-declining (ND) and declining (D) trees, showing different crown defoliation and coexisting in each stand by: (i) characterizing growth variability and its responsiveness to climate and drought through time, and (ii) simulating growth responses to soil moisture and temperature thresholds using the Vaganov-Shashkin VS-lite model. Our results show how growth responsiveness to climate and drought was higher in D trees for both oak species. Growth has become increasingly limited by warmer-drier climate and decreasing soil moisture availability since the 1990s. These conditions preceded growth drops in D trees indicating they were more vulnerable to warming and aridification trends. Extremely warm and dry conditions during the early growing season trigger dieback. Changes in the seasonal timing of water limitations caused contrasting effects on long-term growth trends of D trees after the 1980s inQ. frainettoand during the 1990s inQ. canariensis. Using growth models allows identifying early-warning signals of vulnerability, which can be compared with shifts in the growth responses to warmer and drier conditions. Our approach facilitates establishing drought-vulnerability thresholds by combining growth models with field records of dieback

Theory of Melting and the Optical Properties of Gold/DNA Nanocomposites

We describe a simple model for the melting and optical properties of a DNA/gold nanoparticle aggregate. The optical properties at fixed wavelength change dramatically at the melting transition, which is found to be higher and narrower in temperature for larger particles, and much sharper than that of an isolated DNA link. All these features are in agreement with available experiments. The aggregate is modeled as a cluster of gold nanoparticles on a periodic lattice connected by DNA bonds, and the extinction coefficient is computed using the discrete dipole approximation. Melting takes place as an increasing number of these bonds break with increasing temperature. The melting temperature corresponds approximately to the bond percolation threshold.Comment: 5 pages, 4 figure. To be published in Phys. Rev.

Solving the Social Choice problem under equality constraints

Suppose that a number of equally qualified agents want to choose collectively an element from a set of alternatives defined by equality constraints. Each agent may well prefer a different element, and the social choice problem consists in deciding whether it is possible to design a rule to aggregate all the agents’ preferences into a social choice in an egalitarian way. In this paper we obtain criteria that solve this problem in terms of conditions that are explicitly computable from the constraints. As a theoretical consequence, we show that the only way to avoid running into a social choice paradox consists in designing (if possible) the set of alternatives satisfying certain optimality condition on the constraints, that is, in the natural way from the point of view of economics

The Puzzling Stability of Monatomic Gold Wires

We have examined theoretically the spontaneous thinning process of tip-suspended nanowires, and subsequently studied the structure and stability of the monatomic gold wires recently observed by Transmission Electron Microscopy (TEM). The methods used include thermodynamics, classical many-body force simulations, Local Density (LDA) and Generalized Gradient (GGA) electronic structure calculations as well as ab-initio simulations including the two tips. The wire thinning is well explained in terms of a thermodynamic tip suction driving migration of surface atoms from the wire to the tips. For the same reason the monatomic wire becomes progressively stretched. Surprisingly, however, all calculations so far indicate that the stretched monatomic gold wire should be unstable against breaking, contrary to the apparent experimental stability. The possible reasons for the observed stability are discussed.Comment: 4 figure