Allosteric Regulation Alters Carrier Domain Translocation in Pyruvate Carboxylase

Pyruvate carboxylase (PC) catalyzes the ATP-dependent carboxylation of pyruvate to oxaloacetate. The reaction occurs in two separate catalytic domains, coupled by the long-range translocation of a biotinylated carrier domain (BCCP). Here, we use a series of hybrid PC enzymes to examine multiple BCCP translocation pathways in PC. These studies reveal that the BCCP domain of PC adopts a wide range of translocation pathways during catalysis. Furthermore, the allosteric activator, acetyl CoA, promotes one specific intermolecular carrier domain translocation pathway. These results provide a basis for the ordered thermodynamic state and the enhanced carboxyl group transfer efficiency in the presence of acetyl CoA, and reveal that the allosteric effector regulates enzyme activity by altering carrier domain movement. Given the similarities with enzymes involved in the modular synthesis of natural products, the allosteric regulation of carrier domain movements in PC is likely to be broadly applicable to multiple important enzyme systems

Influence of convection and biomass burning outflow on tropospheric chemistry over the tropical Pacific

Observations over the tropics from the Pacific Exploratory Mission-Tropics A Experiment are analyzed using a one-dimensional model with an explicit formulation for convective transport. Adopting tropical convective mass fluxes from a general circulation model (GCM) yields a large discrepancy between observed and simulated CH3I concentrations. Observations of CH3I imply the convective mass outflux to be more evenly distributed with altitude over the tropical ocean than suggested by the GCM. We find that using a uniform convective turnover lifetime of 20 days in the upper and middle troposphere enables the model to reproduce CH3I observations. The model reproduces observed concentrations of H2O2 and CH3OOH. Convective transport of CH3OOH from the lower troposphere is estimated to account for 40-80% of CH3OOH concentrations in the upper troposphere. Photolysis of CH3OOH transported by convection more than doubles the primary HOx source and increases OH concentrations and O3 production by 10-50% and 0.4 ppbv d-1, respectively, above 11 km. Its effect on the OH concentration and O3 production integrated over the tropospheric column is, however, small. The effects of pollutant import from biomass burning regions are much more dominant. Using C2H2 as a tracer, we estimate that biomass burning outflow enhances O3 concentrations, O3 production, and concentrations of NOx and OH by 60%, 45%, 75%, and 7%, respectively. The model overestimates HNO3 concentrations by about a factor of 2 above 4 km for the upper one-third quantile of C2H2 data while it generally reproduces HNO3 concentrations for the lower and middle one-third quantiles of C2H2 data. Copyright 2000 by the American Geophysical Union

The Role of Simple Rules in the Conduct of Canadian Monetary Policy

The third strategy employed by the Bank when dealing with uncertainty is the consideration of appropriate simple reaction functions or "rules" for the setting of the policy interest rate. Since John Taylor's presentation of his much-discussed rule, research on simple policy rules has exploded. Simple rules have several advantages. In particular, they are easy to construct and communicate and are believed by some to be robust, in the sense of generating good results in a variety of economic models. This article provides an overview of the recent research regarding the usefulness and robustness of simple monetary policy rules, particularly in models of the Canadian economy. It also describes and explains the role of simple rules in the conduct of monetary policy in Canada.

Quadtree based mouse trajectory analysis for efficacy evaluation of voice-enabled CAD

Voice-enabled applications have caught considerable research interest in recent years. It is generally believed that voice based interactions can improve the working efficiencies and the overall productivities. Quantitative evaluations on the performance boost by using such Human-Computer interactions (HCI) are therefore necessary to justify the claimed efficacies and the usefulness of the HCI system. In this paper, a quadtree based approach is proposed to analyze the mouse movement distributions in the proposed Voice-enabled Computer-Aided Design (VeCAD) system. The mouse tracker keeps a record of all the mouse movement during the solid modeling process, and a quadtree based approach is applied to analyze the mouse trajectory distributions in both the traditional CAD and the VeCAD system. Our experiments show that the mouse movement is significantly reduced when voice is used to activate CAD modeling commands. ©2009 IEEE.published_or_final_versionThe IEEE International Conference on Virtual Environments, Human-Computer Interfaces, and Measurements Systems (VECIMS) 2009, Hong Kong, 11-13 May 2009. In Conference Proceedings, 2009, p. 196-20

Formation of misfit dislocations in strained-layer GaAs/In_xGa_1–xAs/GaAs heterostructures during postfabrication thermal processing

It is demonstrated that relaxation of GaAs/InxGa1–xAs/GaAs strained-layer heterostructures can be brought about by postfabrication thermal processing. Misfit dislocations are introduced into the structure during thermal processing, even though the thickness of the strained layer is well below the critical value predicted by the Matthews–Blakeslee model. The misfit dislocations are observed to be of both 60° mixed type and 90° pure edge type. As no relaxation occurs at the lower temperatures encountered during fabrication by molecular-beam epitaxy, it can be inferred that the critical condition for the formation of misfit dislocations is not only a function of strained-layer thickness and composition, but also of temperature. This observation cannot be accounted for by differential thermal expansion or diffusion across the strained-layer interfaces, but the temperature-dependent Peierls force may offer an explanation. The high temperature required to produce relaxation of these structures suggests that they are sufficiently thermally stable for most practical applications

Antitumor activity of epidermal growth factor receptor tyrosine kinase inhibitors in human hepatocellular carcinoma cell lines

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The Battleground of Translation: Making Equal in a Global Structure of Inequality

In her interview published in the Cairol based journal ALIF, Lydia H. Liu reflects on the centrality of translation to the circulation of all knowledge. She emphasizes, in particular, new ways of understanding translation beyond semantics: What role does the supersign play in the making of concepts in translation? How do we analyze the logic of equivalency that simultaneously determines the "translables" and "untranslables"? Why is nonsense inseparable from sense? How do we analyze the conditions of the universal in translation? etc

A versatile interface model for thermal conduction phenomena and its numerical implementation by XFEM

A general interface model is presented for thermal conduction and characterized by two jump relations. The first one expresses that the temperature jump across an interface is proportional to the interfacial average of the normal heat flux while the second one states that the normal heat flux jump is proportional to the surface Laplacian of the interfacial average of the temperature. By varying the two scalar proportionality parameters, not only the Kapitza resistance and highly conducting interface models can be retrieved but also all the intermediate cases can be covered. The general interface model is numerically implemented by constructing its weak form and by using the level-set method and XFEM. The resulting numerical procedure, whose accuracy and robustness are thoroughly tested and discussed with the help of a benchmark problem, is shown to be efficient for solving the problem of thermal conduction in particulate composites with various imperfect interfaces