Strength Degradation and Failure Mechanisms of Electron-Beam Physical-Vapor-Deposited Thermal Barrier Coatings

Failure mechanisms were determined for electron-beam physical-vapor-deposited thermal barrier coating (TBC) systems from the degradation of mechanical properties and microstructural changes in a furnace cycle test. Bond strength degradation for TBCs resulted from the initiation and growth of interfacial delamination defects between the yttria-stabilized zirconia topcoat and the thermally grown alumina (TGO). It is proposed that defects started from concave depressions in the bondcoat surface created by the grit-blast-cleaning process and that defect growth was driven by the reduction in compressive strain in the TGO as the alumina deformed into and displaced the bondcoat during the cooling cycles. Inclusion of yttrium in the substrate resulted in a doubling of the furnace cycle life of the TBCs because of enhanced fracture toughness of the TGO-bondcoat interface.     

Correspondence

This paper proposes a rhetorical approach to planning, then applies it to the City of Chicago's effort from 1985 to 1991 to explore alternatives to remaining dependent on a single, privately owned electric utility. Arguing that surveys, models, and forecasts act as tropes (or rhetorical devices) in planning arguments, the paper focuses on a survey of Chicago businesses and their responses to the city's exploration of new energy planning options. It examines a meeting in which the survey researcher attempted to persuade a quasi-political task force of the accuracy of his survey “results.” The paper discusses how a rhetorical approach could improve the theory, pedagogy, and practice of planning.     

Predicting the fracture character of weak layers from snowpack penetrometer signals

Digital penetrometers provide reliable assessments of snow penetration resistance with depth. However, extracting useful information from the signals relating to snow stability has proved to be challenging. In this study, penetrometer profiles were collected in close proximity to compression tests. A scheme for predicting the fracture character of weak layers in the compression tests from the penetrometer signals is presented. When a two-group classification between sudden (Q1) (an indicator of instability) and other fracture character groups was performed, potential failure layers were correctly classified 80% of the time. The variables offering the best discrimination between sudden and other categories were weak layer thickness, average force gradient above the weak layer, and both the average and the maximum force gradient below the weak layer. The effect of introducing randomly selected layers into the prediction scheme was also investigated. When such layers were introduced, the classification rate dropped to 67%, indicating that more effective fracture character prediction occurred when weak layers were manually pre-identified. This suggests that this scheme should be used in conjunction with a weak layer detection model rather than as a stand alone analytical technique for the purpose of critical weak layer identification. The classification rate dropped further to 55% when a more detailed, four-group classification scheme was used.     

Gold nanoparticles induce cytotoxicity in the alveolar type-II cell lines A549 and NCIH441

Background  

During the last years engineered nanoparticles (NPs) have been extensively used in different technologies and consequently many questions have arisen about the risk and the impact on human health following exposure to nanoparticles. Nevertheless, at present knowledge about the cytotoxicity induced by NPs is still largely incomplete. In this context, we have investigated the cytotoxicity induced by gold nanoparticles (AuNPs), which differed in size and purification grade (presence or absence of sodium citrate residues on the particle surface) in vitro, in the human alveolar type-II (ATII)-like cell lines A549 and NCIH441.     

Reactive and non-reactive transport modelling in partially water saturated argillaceous porous media around the ventilation experiment, Mont Terri

At Mont Terri Underground Research Laboratory (URL) Switzerland, a specific experiment has been performed in a tunnel, in order to investigate the hydro-mechano-chemical (HMC) perturbations induced in the argillaceous formation by forced ventilation. This experiment has been selected in the international project DECOVALEX to be used for process model development and validation. The numerical simulation of the geochemical response to the ventilation experiment (VE) is the object of the present paper, focusing on the transport of chloride as a conservative species and sulphate as a reactive species. Utilising the validated hydro-mechanical (HM) results from earlier steps of the DECOVALEX task, reactive and non-reactive transport models, incorporating the current understanding of the geochemistry at the site, were successfully constructed for the whole experimental period. The associated parametric and process uncertainty analyses clearly demonstrate that the basic HM understanding must be sound. However, to demonstrate this degree of robustness, the explicit inclusion of process representations of water desaturation, liquid vaporisation, species exclusion porosity, and redox processes, is required.     

Geometric mean vs. Arithmetic mean in extrusion residence time studies

Geometric mean residence time was compared with the arithmetic mean residence time for a residence time distribution study conducted on a twin‐screw extruder using a salt tracer and electrical conductivity measurements. Electrical conductivity of the cornmeal melt was measured at the die exit. All RTD curves obtained during the study were skewed to the right with very long tails that resulted in inflated arithmetic mean residence times. In order to alleviate the problem of long tails, different approaches were considered. Among these approaches, logarithmic transformation of the time scale to calculate the geometric mean residence time was shown to best represent the residence time distribution in terms of mean residence time and spread of the RTD. The log transformation of the time scale alleviates the problem of inappropriate shifting of the mean residence time due to long tails. The difference between the upper limits and lower limits for the log transformed data was found to be more appropriate to define the spreads of the distributions as the untransformed data resulted in quite variable spreads.     

THE RELATIONSHIP OF CONTROL AND LEARNING TO PROJECT PERFORMANCE

ABSTRACT

Management controls can be divided into two types that can have opposite effects on organizational learning: behavioral controls, which promote efficiency but also stifle much of the learning opportunity, and outcome controls, which foster interaction among stakeholders can add to the learning environment. This article reports on a study that confirms these observations and explores the nature of their direct and indirect influences on project performance. Data from a sample of software development professionals confirms that behavioral controls and learning directly influence project performance, while outcome controls contribute only indirectly through their impact on learning.     

Similarity between class A and class B G-protein-coupled receptors exemplified through calcitonin gene-related peptide receptor modelling and mutagenesis studies

Modelling class B G-protein-coupled receptors (GPCRs) using class A GPCR structural templates is difficult due to lack of homology. The plant GPCR, GCR1, has homology to both class A and class B GPCRs. We have used this to generate a class A–class B alignment, and by incorporating maximum lagged correlation of entropy and hydrophobicity into a consensus score, we have been able to align receptor transmembrane regions. We have applied this analysis to generate active and inactive homology models of the class B calcitonin gene-related peptide (CGRP) receptor, and have supported it with site-directed mutagenesis data using 122 CGRP receptor residues and 144 published mutagenesis results on other class B GPCRs. The variation of sequence variability with structure, the analysis of polarity violations, the alignment of group-conserved residues and the mutagenesis results at 27 key positions were particularly informative in distinguishing between the proposed and plausible alternative alignments. Furthermore, we have been able to associate the key molecular features of the class B GPCR signalling machinery with their class A counterparts for the first time. These include the [K/R]KLH motif in intracellular loop 1, [I/L]xxxL and KxxK at the intracellular end of TM5 and TM6, the NPXXY/VAVLY motif on TM7 and small group-conserved residues in TM1, TM2, TM3 and TM7. The equivalent of the class A DRY motif is proposed to involve Arg^2.39, His^2.43 and Glu^3.46, which makes a polar lock with T^6.37. These alignments and models provide useful tools for understanding class B GPCR function.