bluuebunny/crossref_metadata_2025 huggingface dataset:
Ultra-low-emission diesel engine fuelled with dimethoxymethane—diesel fuel blends
Authors: Zhu R J , Wang X B , Miao H Y , Huang Z H
Published: April 2009

The influences of dimethoxymethane (DMM content), exhaust gas recirculation (EGR) and post-processor on combustion and emission were studied experimentally, and the approaches to meet the Euro III regulation were discussed. Results showed that, for diesel blending fuel with 50 per cent DMM volume fraction, on setting the EGR rate at 28 per cent for low and medium loads and at 7 per cent at high loads, nitrogen oxide and soot emissions are both reduced markedly; a diesel oxidation catalyst (DOC) reduces hydrocarbon and carbon monoxide emissions. Comparison of the combustion process with diesel fuel indicated that application of DMM—diesel blended fuel increases both premixed and diffusion combustion, leading to a higher peak pressure and a pressure rise. EGR does not lengthen the combustion duration significantly. A naturally aspirated diesel engine in the test fuelled with a high percentage of DMM component in the blend, together with EGR and DOC, makes it possible to meet the Euro III emission standard for a vehicle diesel engine.
Comparative thermal stress analysis of gasketed and non-gasketed flange joints for safe operating conditions
Authors: Abid M , Iqbal M , Ullah B
Published: April 2009

The performance of a flanged joint is characterized mainly by its ‘strength’ and ‘sealing capability’. A number of analytical and experimental studies have been conducted to study these characteristics under only internal pressure loading. However, with the advent of new technological trends for high temperature and high-pressure applications, an increased demand for more complex analysis is recognized. The effect of steady-state thermal loading is a well-recognized problem and makes the analysis more complex. To investigate joint strength and sealing capability under combined internal pressure and different steady-state thermal loadings, a comparative three-dimensional non-linear finite-element analysis of gasketed and non-gasketed flange joints is carried out and their behaviour is discussed. To determine the safe operating conditions or actual joint load capacity, both the flange joints are further analysed for different internal pressures and temperatures.
Medium earth orbit and inclined geosynchronous orbit satellite control strategies optimization based on the function approximation method
Authors: Tan W , Jen T-C , Gao M
Published: April 2009

The article proposes an optimization method based on the function approximation in control strategies design of medium earth orbit (MEO) and inclined geosynchronous orbit (IGSO) satellites. As an extension of the functional approximation method (FAM), this method is suitable to solve a single-variable or a multivariable optimization question with equality or inequality constraints. This ensures that the optimal control strategies for MEO and IGSO satellites to manoeuvre along the ideal control arc can be easily determined, and finally make satellites enter the designed orbits as soon as possible after satellites being launched under restrictions of the limited propellant and number of revolutions around the earth. In the current article, the basic FAM model is first introduced, and then the method applications and the simulation results are discussed in detail. Compared with the conventionally adopted exhaust search in the process of the optimal strategy design for the MEO and IGSO satellites, this method has the advantages of simplicity, less dependence on the initial parameter range, and requires much less computational effort.
On the mean characteristics of the juncture vortex in cross-flow planes
Authors: Khan M J , Ahmed A
Published: April 2009

Juncture flow of wings with leading edge sweep angles of 0°, ±15°, ±30°, and ±45° mounted on a flat plate for a turbulent approach boundary layer was investigated using laser Doppler velocimetry (LDV) in a subsonic wind tunnel. Time-averaged measurements in the cross-flow planes indicated incompletely formed vortical structures. Additionally, in the cross-flow plane at the airfoil maximum thickness location, measured velocity directions were inconsistent with vortex rotation. Complex motion of the juncture vortex system in the cross-flow direction was observed during flow visualization of the configuration in a water tunnel, suggesting masking of the mean vortex structure by the global motion of the structures. The mean vortex signature with correct rotational direction was ‘frozen’ by subtracting a constant cross-flow velocity component from the LDV mean measurements. Vorticity contours in the cross-flow planes were calculated using a finite differencing scheme on the measured data. Good comparison of vortex core estimated locations between the ‘frozen’ vortex and from vorticity contours was observed. Another artefact of the measurements was asymmetry in the vertical velocities, which is attributed to motion of the vortex core towards the flat plate in the maximum thickness plane and away from it in the 80 per cent chord plane. The horizontal location of the vortex core was observed to be influenced by wing sweep; however, the vertical location was insensitive to this parameter.
Vibration detection of local gear damage by advanced demodulation and residual techniques
Authors: Combet F , Gelman L , Anuzis P , Slater R
Published: April 2009

Damage detection in a gearbox is reported based on analysis of vibration signals measured on a running aircraft engine on a test bed. The experiment was stopped due to material being found on the magnetic chip detectors in the oil system. Subsequent inspection found a significant damage to a bevel gear inside the drive train system. Three damage detection techniques are applied to the vibration signals: advanced demodulation, advanced residual technique, and the classical residual technique. Fault indicators are defined from each technique and trended over time. Results show that these techniques have the ability to provide early damage detection; however, with some noticeable difference in their feature evolution. The advantages of the techniques are compared and discussed.
Effects of satellite dimensions in the solar pressure formulation for formation flying
Authors: Capó-Lugo P A , Bainum P M
Published: April 2009

In highly elliptical orbits, the solar pressure can perturb the motion of a constellation through the entire orbit because of the longer exposure of the satellites to the Sun. The Tschauner—Hempel equations for a perturbed motion will be used to explain the motion of a pair of satellites about the Earth in a highly elliptical orbit. In this set of equations, the solar pressure formulation will be written differently to determine how the satellite dimensions can affect the control effort to perform the drift correction. To maintain the separation distance constraints, the authors developed a hierarchical control scheme, in discrete format, that takes care of the perturbation effects of the Earth and the Sun. In summary, this article will show how the differences of the satellite dimensions in the solar pressure formulation can cause variations in the control effort.
The stability analysis of a discrete-time control algorithm for the Canadian advanced nanospace eXperiment-4&5 formation flying nanosatellites
Authors: Eyer J K , Damaren C J
Published: April 2009

The development of an LQR-based control algorithm for the Canadian advanced nanospace eXperiment (CanX)-4&5 formation flying nanosatellite mission is described. To facilitate an analytical stability proof of the algorithm, elements of the non-linear and continuous system are linearized and discretized. A suitable state for the system is selected and the algorithm is converted into a discrete linear time-varying system that is very nearly periodic. The stability of the system is then determined by means of discrete Floquet theory. This analysis is applied to the CanX-4&5 algorithm during its primary mission of testing along track orbit formations and projected circular orbit formations. The analysis is also applied to the algorithm while executing a quasi J2-invariant formation. The results in all cases indicate stability. Finally, for the quasi J2-invariant formation the control authority of the algorithm is reduced until the stability limit is approached and the minimum Δ V required to maintain the formation is found.
Evaluation of the relationship between exhaust gas temperature and operational parameters in CFM56-7B engines
Authors: Yılmaz İ
Published: April 2009

This study presents the relationship between exhaust gas temperature (EGT) and engine operational parameters at two different power settings, including maximum continuous and take-off, in the CFM56-7B turbofan engine. The ground measurements of engine operational parameters including net thrust, fuel flow, low rotational speed, core rotational speed, pressure ratio, air temperature at engine fan inlet, take-off margin temperature, and thrust-specific fuel consumption of 51 different CFM56-7B engines are used to find the relationship mentioned in the study. This engine type is selected due to its common use by the civil aviation sector. In accordance with the results of multiple linear regression analysis, it was shown that EGT is affected by the engine operational parameters in different rate. The relationship between EGT and the operational parameters used in the maximum continuous power setting is slightly stronger than that of take-off power setting, R2=0.73 and 0.69, respectively. The fuel flow, thrust-specific fuel consumption, and take-off margin temperature are determined to be the most significant operational parameters in the correlations used to predict the EGT of 51 CFM56-7B turbofan engines in maximum continuous and take-off power settings, R2=0.28, 0.23, and 0.35 and R2=0.27, 0.14, and 0.60, respectively. It is found that there are good agreements between the predicted and measured values of EGT in the study. It can be concluded that the proposed technique is an effective tool for the EGT estimation of the turbofan engine.
An experimental investigation of the cold flowfield in a model scramjet combustor
Authors: Zhao Z , Song W Y , Xiao Y L , Le J L
Published: April 2009

In order to obtain the cold flow structures inside a model scramjet combustor, direct-connected experiments have been conducted on the inlet Mach number of 2.0. The length to height ratio of the isolator is 6 and 8. The static pressure along the wall is measured with varied back pressure. The Schlieren technique is employed for visualizing the typical shock train structures in the model. The results indicate that the flowfield in the scramjet combustor is rather complicated because of shock wave/boundary layer interaction. The first shock of the normal shock train is bifurcated at the foot, while the subsequent shocks are seen to be of nearly normal shock. Each successive shock is weaker. The shock train moves towards the isolator entrance as back pressure increases. The position of the leading edge of shock train is sensitive to the pressure variation. The isolator of Liso/ h=8 can sustain pressure rise better than Liso/ h=6.
Statistical estimation of multiple faults in aircraft gas turbine engines
Authors: Sarkar S , Rao C , Ray A
Published: April 2009

This article presents estimation of multiple faults in aircraft gas-turbine engines, based on a statistical pattern recognition tool called symbolic dynamic filtering. The underlying concept is formulated by statistical analysis of evidences to estimate anomalies (i.e. deviations from the nominal values) in multiple critical parameters of the engine system; it also presents a framework for sensor information fusion. The fault estimation algorithm is validated on a numerical simulation test-bed that is built upon the NASA C-MAPSS model of a generic commercial aircraft engine.
Multifunctional materials and structures for autonomic systems
Authors: Lee B-L , Inman D J
Published: April 2009

The authors' vision of the way forward in multifunctional materials and structures is presented. Their opinion reflects the growth of research activities in the subject area evolved from those of smart materials and adaptive structures. Their ultimate goal is to create the knowledge to enable a new concept of multifunctional materials and structures for autonomic systems, which captures a deeper level of integration of functions between control, transduction, and structure.
Experimental definition of a failure model for the tribological behaviour of polytetrafluoroethylene bronze compounds
Authors: Gódor I , Major Z , Vezér Sz , Grün F
Published: April 2009

Because of their high chemical and thermal resistance and advantageous friction behaviour, polytetrafluoroethylene (PTFE) compounds are frequently used in various engineering applications, especially for pressurized seals. To adjudge the applicability, and to establish a reliable ranking of various compounds with similar composition and micro-structure for tribological systems, a number of bronze-particle-filled PTFE materials (PTFE-Bz compounds) were investigated with a seal test system at the component level. The two best performing materials in these component tests, termed PTFE-Bz9 and PTFE-Bz14 in this article, were then selected for further, more detailed thermo-mechanical and tribological investigations on a laboratory specimen level. Furthermore, extensive failure analysis of both the worn seals and the test specimens were carried out using laser confocal and scanning electron microscopy techniques. Finally, based on the experimental results a model for describing the functionality and of the failure behaviour of these materials was developed and described.
Numerical lubrication simulation of metal-on-metal artificial hip joint replacements: Ball-in-socket model and ball-on-plane model
Authors: Wang W-Z , Wang F-C , Jin Z-M , Dowson D , Hu Y-Z
Published: April 2009

Long-term successful function of artificial hip joint replacements strongly depends on the design parameters of the bearing such as the diameters of femoral head and acetabular cup and the corresponding radial clearance, which determine the lubrication regime experienced in the prostheses. Generally, there are two types of numerical models for elastohydrodynamic lubrication (EHL) analysis of the bearing in the hip joint replacements: ball-in-socket model and effective ball-on-plane model. As the real hip joint is in ball-in-socket configuration, the ball-in-socket lubrication model should be the reasonable approximation to the real bearing. The ball-in-socket model solves a lubrication problem in spherical coordinates, which means all of governing equations, including Reynolds equation, film thickness and load balance equation, should be written in the spherical coordinate forms. In addition, the calculation of the elastic deformation of the bearing surfaces in artificial joints is not a trial problem. Complex spherical geometries in the joint bearing often require employing the finite-element method to determine/extract the displacement influence coefficients at first, and then the deformation is evaluated through using an equivalent discrete spherical convolution model. Fortunately, the fast Fourier transform-based approach is recently developed to speed up the deformation calculation. In comparison with the ball-in-socket model, the effective ball-on-plane model is simple and easy to conduct EHL analysis. The main characteristic of the effective ball-on-plane model is that the elastic deformation was evaluated under an assumption of semi-infinite solid and certainly without the consideration of the curvature effect associated with the ball-in-socket configuration. In the present study, some typical cases of EHL analysis for hip joint replacements were conducted to systematically demonstrate the capability of these two models. It was found that both models were able to provide quite close results in most situations, and the difference may only take place when the head is positioned near the edge of the cup bearing surface.
Models for predicting friction coefficient and parameters with influence in elastohydrodynamic lubrication
Authors: Morgado P Lafont , Otero J Echávarri , Lejarraga J B Sánchez-Peñuela , Sanz J L Muñoz , Lantada A Díaz , Munoz-Guijosa J M , Yustos H Lorenzo , Wiña P Leal , García J Muñoz
Published: April 2009

This article shows different friction prediction models applicable to lubricants in point contacts under an elastohydrodynamic regime. The types of models used are two variations of the Newtonian theory, the Limiting Shear Stress model and the one based on Carreau's equation. The article sets out the theoretical calculation procedures and the ensuing equations for calculating the friction coefficient.

The aims of the article are to study the effect of the parameters with influence on friction and to compare the model's results with those given by an experimental stage performed on a mini traction machine. This test system allows the measurement of friction coefficient in point contacts (ball—disc) under a wide range of variation of parameters such as temperature, slide-roll ratio, lubricant, material, load, or velocity.
Thermal behaviours of metallic materials under very high-speed sliding
Authors: Zhang Y Z , Qiu M
Published: April 2009

Heat produced by friction influences tribological properties greatly, especially under high-speed dry sliding, where the temperature is high enough to cause obvious changes in the microstructure of the materials. Based on the above suggestions, researches were carried out on several metallic pairs with different thermal properties. The experiments were carried out under the condition of sliding speed ranging from 30 to 60 m/s, contacting pressure ranging from 0.13 to 1.33 MPa, and the surrounding temperatures ranging from room temperature to 500 °C. The testing results have indicated that thermal behaviours influence tribological characteristics in a very complicated way. It seems that tribological properties behaviours are different among different metallic pairs under high-speed dry sliding, which seems to be related to heat conductivity; tribological properties are also sensitive to surface temperature. All measures to improve the friction heat conduction help to increase the tribological properties. Surrounding temperature also influences the tribological property greatly; it seems that the existence of oxygen is beneficial to obtain better tribological properties.
Solving active wrench of limited-degree of freedom parallel manipulators based on translational/rotational Jacobian matrices
Authors: Lu Y , Hu B , Yu J
Published: April 2009

A methodology is proposed for unified solving active wrench of the limited-degree of freedom (DOF) parallel manipulators (PMs). First, the geometric constraints and the inverse displacement kinematics are analysed. Second, the formulae for unified solving the inverse/forward velocity and the translational/rotational Jacobian matrices and inverse/forward Jacobian matrices are derived. Third, the analytic formulae for unified solving the active wrench of limited-DOF PMs are derived based on the principle of virtual work. Finally, a 3-DOF PM with linear/rotational active legs is presented to illustrate the use of the methodology.
Improvement of premixed charge compression ignition-based combustion by two-stage injection
Authors: Horibe N , Harada S , Ishiyama T , Shioji M
Published: April 2009

The objective of this study is to find strategies for extending the load range of premixed charge compression ignition-based combustion while improving thermal efficiency and reducing combustion noise and exhaust emission levels. Experiments were performed using a single-cylinder direct-injection diesel engine equipped with a common-rail injection system and a cooled EGR system. First, experiments were carried out with single-stage injection. The results indicated a notable improvement of NO x and smoke emissions by selecting lower EGR rates and later injection timings according to the increase in injection quantity. However, the problems of high pressure rise rates and levels of unburned species emissions developed. To solve these problems, two-stage injection was applied. These additional experiments started with injection and EGR conditions that were based on the results of the single-stage injection tests, and modifications were made to mitigate the increased emissions and decreased thermal efficiency. As a result, judicious selection of injection and EGR conditions for two-stage injection provided a drastic improvement in exhaust emissions with a sufficiently low pressure rise rate to be equivalent to pilot-diesel operation.
A single C. elegans PUF protein binds RNA in multiple modes
Authors: Koh Yvonne Yiling , Opperman Laura , Stumpf Craig , Mandan Arpita , Keles Sunduz , Wickens Marvin
Published: April 2009

PUF proteins specifically bind mRNAs to regulate their stability and translation. Here we focus on the RNA-binding specificity of a C. elegans PUF protein, PUF-11. Our findings reveal that PUF-11 binds RNA in multiple modes, in which the protein can accommodate variable spacings between two distinct recognition elements. We propose a structural model in which flexibility in the central region of the protein enables the protein to adopt at least two distinct structures, one of which results in base flipping.
Regulation of NAB2 mRNA 3′-end formation requires the core exosome and the Trf4p component of the TRAMP complex
Authors: Roth Kelly M. , Byam Joel , Fang Feng , Butler J. Scott
Published: April 2009

The nuclear exosome functions in a variety of pathways catalyzing formation of mature RNA 3′-ends or the destruction of aberrant RNA transcripts. The RNA 3′-end formation activity of the exosome appeared restricted to small noncoding RNAs. However, the nuclear exosome controls the level of the mRNA encoding the poly(A)-binding protein Nab2p in a manner requiring an A26 sequence in the mRNA 3′ untranslated regions (UTR), and the activities of Nab2p and the exosome-associated exoribonuclease Rrp6p. Here we show that the A26 sequence inhibits normal 3′-end processing of NAB2 mRNA in vivo and in vitro, and makes formation of the mature 3′-end dependent on trimming of the transcript by the core exosome and the Trf4p component of the TRAMP complex from a downstream site. The detection of mature, polyadenylated transcripts ending at, or within, the A26 sequence indicates that exosome trimming sometimes gives way to polyadenylation of the mRNA. Alternatively, Rrp6p and the TRAMP-associated Mtr4p degrade these transcripts thereby limiting the amount of Nab2p in the cell. These findings suggest that NAB2 mRNA 3′-end formation requires the exosome and TRAMP complex, and that competition between polyadenylation and Rrp6p-dependent degradation controls the level of this mRNA.
An Extension of the Internal Rate of Return to Stochastic Cash Flows
Authors: Hazen Gordon
Published: April 2009

The internal rate of return (IRR) is a venerable technique for evaluating deterministic cash flow streams. Part of the difficulty in extending this measure to stochastic cash flows is the lack of coherent methods for accounting for multiple or nonexistent internal rates of return in deterministic streams. Recently such a coherent theory has been developed, and we examine its implications for stochastic cash flows. We devise an extension of the deterministic IRR, which we call the stochastic rate of return on mean investment. It has significant computational and conceptual advantages over the stochastic internal rate. For instance, in the deterministic case, the standard result is that under proper conditions a cash flow stream is acceptable (in the sense of positive present value) if its internal rate exceeds the interest rate. We show that a stochastic cash flow stream is acceptable (in the sense of positive certainty equivalent expected value) if the rate of return on mean investment has a suitably defined certainty equivalent exceeding the risk-free interest rate.
Pioneering Plus a Broad Product Line Strategy: Higher Profits or Deeper Losses?
Authors: Boulding William , Christen Markus
Published: April 2009

Previous research suggests firms can build a market share advantage by preempting later entrants with a broad product line and expanding rapidly into related markets. Whether such a strategy leads to a pioneering profit advantage relative to followers also depends on its cost effects. In this paper, we examine when the market share advantage of a pioneering firm with a broad product line strategy translates into a profit advantage by examining the cost effects of this strategy. Using the profit impact of marketing strategies data and an estimation method that controls for various unobserved factors, we find significant differences between different industry settings. From these contrasting findings, we generate an emerging theoretical framework that we subject to empirical testing. We conjecture, and empirically verify, that creating a broad product line with a versioning strategy—creating variety from a standard product in anticipating customer demand—does not increase the pioneering cost disadvantage, and thus results in a pioneering profit advantage. On the other hand, with a tailoring strategy—creating variety by customizing a product to actual customer demand—a broad product line substantially increases the pioneering cost disadvantage, thereby making a preemption strategy counterproductive.
Jackknife Estimator for Tracking Error Variance of Optimal Portfolios
Authors: Basak Gopal K. , Jagannathan Ravi , Ma Tongshu
Published: April 2009

We develop a jackknife estimator for the conditional variance of a minimum tracking error variance portfolio constructed using estimated covariances. We empirically evaluate the performance of our estimator using an optimal portfolio of 200 stocks that has the lowest tracking error with respect to the S&P 500 benchmark when three years of daily return data are used for estimating covariances. We find that our jackknife estimator provides more precise estimates and suffers less from in-sample optimism when compared to conventional estimators.
Barter Markets for Conjoint Analysis
Authors: Ding Min , Park Young-Hoon , Bradlow Eric T.
Published: April 2009

We propose a new alternative preference measurement method, barter conjoint, to contrast with traditional choice-based conjoint (CBC) approaches. Barter conjoint collects a substantially larger amount of data compared to CBC and allows for information diffusion among respondents. We conducted two empirical studies that compare CBC (with and without incentive alignment) and barter conjoint. The studies employed a total of three product categories, each with two validation tasks (one follows immediately and one conducted two weeks later). Our results confirmed prior research that incentive alignment, in general, substantially improves out-of-sample predictive performance of CBC. Furthermore, we found barter conjoint performs substantially better than the incentive-aligned CBC. However, in the spirit of “no free lunch,” barter conjoint is more taxing (in various ways) than CBC, suggesting a potential trade-off between consumer resource allocation (at the time of the task) and (managerial) predictive accuracy downstream. Given that this is the first study on barter conjoint, we discuss various limitations of the current implementation and fruitful directions for future research.
Brand and Price Advertising in Online Markets
Authors: Baye Michael R. , Morgan John
Published: April 2009

We model an environment where e-retailers sell similar products and endogenously engage in both brand advertising (to create loyal customers) and price advertising (to attract “shoppers”). In contrast to models where loyalty is exogenous, endogenizing the creation of loyal customers by allowing firms to engage in brand advertising leads to a continuum of symmetric equilibria; however, there is a unique equilibrium in secure strategies, and the set of equilibria converges to this unique equilibrium as the number of potential e-retailers grows arbitrarily large. Price dispersion is a key feature of all of these equilibria, including the limit equilibrium. Branding tightens the range of prices and reduces the value of the price information provided by a comparison site, and this reduces profits for platforms (such as an Internet price comparison site) where firms advertise prices. Data from a leading price comparison site are shown to be consistent with several predictions of the model.
A Novel Approach to CFTR Mutation Testing by Pyrosequencing-Based Assay Panels Adapted to Ethnicities
Authors: Bickmann Julia K , Kamin Wolfgang , Wiebel Matthias , Häuser Friederike , Wenzel Jürgen J , Neukirch Carolin , Stuhrmann Manfred , Lackner Karl J , Rossmann Heidi
Published: April 2009

Background: Cystic fibrosis (CF) is a common autosomal recessive genetic disorder caused by a variety of sequence alterations in the CFTR gene [cystic fibrosis transmembrane conductance regulator (ATP-binding cassette sub-family C, member 7)]. Because the relative prevalence of mutations strongly depends on the ethnic background, first-level testing of CF as defined by recent consensus recommendations ought to be adaptable to the ethnicity of patients.

Methods: We therefore developed and implemented a diagnostic approach to first-level testing for CF based on published mutation frequencies and Pyrosequencing (PSQ) technology that we complemented with standard procedures of mutation detection at the second level.

Results: The current test system of PSQ assays for 46 target CF mutations [including CFTRdele2,3 (21 kb) and 1342-6 (T)n (5T/7T/9T)] permits recombinations of single assays to optimize sensitivities for certain ethnicities. By easy expansion of the original mutation panel, the first-level test sensitivities with other ethnic groups would be increased, provided that the mutation frequencies are known. The test was validated with our local, ethnically mixed, but mainly German population (155 patients). The mutation-detection rate for the 92 patients whose CF was confirmed by the sweat test was 89.0% for the patients of German descent (73 of the 92 patients) and 73.7% for the patients of any other origin (19 of the 92 patients). Ethnicity-adapted testing panels for our foreign CF patients would increase the sensitivities for the respective groups by approximately 5%.

Conclusions: PSQ-based genotyping is a reliable, convenient, highly flexible, and inexpensive alternative to conventional methods for first-level testing of CFTR, facilitating flexible adaptation of the analyzed mutation panel to any local ethnic group.
Measurement and Quality Control Issues in Multiplex Protein Assays: A Case Study
Authors: Ellington Allison A , Kullo Iftikhar J , Bailey Kent R , Klee George G
Published: April 2009

Background: Multiplex arrays are increasingly used for measuring protein biomarkers. Advantages of this approach include specimen conservation, limited sample handling, and decreased time and cost, but the challenges of optimizing assay format for each protein, selecting common dilution factors, and establishing robust quality control algorithms are substantial. Here, we use measurements of 15 protein biomarkers from a large study to illustrate processing, analytic, and quality control issues with multiplexed immunoassays.

Methods: We contracted with ThermoScientific for duplicate measurements of 15 proteins in 2322 participants from a community-based cohort, a plasma control, and recombinant protein controls using 2 custom planar microarrays with 6 (panel A) or 9 (panel B) capture antibodies printed in each well. We selected constituent analytes in each panel based on endogenous concentrations and assay availability. Protocols were standardized for sample processing, storage, and freeze-thaw exposures. We analyzed data for effects of deviations from processing protocols, precision, and bias.

Results: Measurements were within reportable ranges for each of the assays; however, concentrations for 7 of the 15 proteins were not centered on the dose–response curves. An additional freeze-thaw cycle and erroneous sample dilution for a subset of samples produced significantly different results. Measurements with large differences between duplicates were seen to cluster by analyte, plate, and participant. Conventional univariate quality control algorithms rejected many plates. Plate-specific medians of cohort and plasma control data significantly covaried, an observation important for development of alternative quality control algorithms.

Conclusions: Multiplex measurements present difficult challenges that require further analytical and statistical developments.
Developing Multiplexed Assays for Troponin I and Interleukin-33 in Plasma by Peptide Immunoaffinity Enrichment and Targeted Mass Spectrometry
Authors: Kuhn Eric , Addona Terri , Keshishian Hasmik , Burgess Michael , Mani D R , Lee Richard T , Sabatine Marc S , Gerszten Robert E , Carr Steven A
Published: April 2009

Background: Protein biomarker candidates from discovery proteomics must be quantitatively verified in patient samples before they can progress to clinical validation. Here we demonstrate that peptide immunoaffinity enrichment coupled with stable isotope dilution mass spectrometry (SISCAPA-MRM) can be used to configure assays with performance suitable for candidate biomarker verification. As proof of principle, we configured SISCAPA assays for troponin I (cTnI), an established biomarker of cardiac injury, and interleukin 33 (IL-33), an emerging immunological and cardiovascular marker for which robust immunoassays are currently not available.

Methods: We configured individual and multiplexed assays in which peptides were enriched from digested human plasma using antipeptide antibodies. Assay performance was established using response curves for peptides and proteins spiked into normal plasma. We quantified proteins using labeled peptides as internal standards, and we measured levels of cTnI in patients who underwent a planned myocardial infarction for hypertrophic obstructive cardiomyopathy.

Results: Measurement of cTnI and IL-33 proteins from trypsin-digested plasma was linear from 1.5 to 5000 μg/L, with imprecision <13% for both proteins, processed individually or multiplexed. Results correlated well (R = 0.89) with a commercial immunoassay.

Conclusions: We used an established biomarker of cardiac injury and an emerging biomarker to demonstrate how SISCAPA can detect and quantify changes in concentration of proteins present at 1–10 μg/L in plasma. Our results demonstrate that these assays can be multiplexed and retain the necessary precision, reproducibility, and sensitivity to be applied to new and uncharacterized candidate biomarkers for verification of low-abundance proteins in blood. .
Vulnerability and Resilience in Natural Disasters: A Marketing and Public Policy Perspective
Authors: Baker Stacey Menzel
Published: April 2009

This essay addresses how the definitions of disaster and vulnerability serve as guides for market and policy responses and shows how a fundamental lack of understanding of what creates a disaster and what constitutes human (and consumer) vulnerability constrains the ability of individuals, communities, and institutions to mitigate and/or recover from natural hazards and the responses that follow. The essay outlines the current state of affairs on conceptualizations of disaster and vulnerability, distinguishes between risk and vulnerability, and notes ten paradoxes of disaster that create constraints on resilience. Fundamentally, the perspective taken here is that disaster is socially constructed and that vulnerability is a dynamic process that depends on a host of contextual factors. The essay shows that sustainable models of economic, social, and environmental development are at the heart of disaster and vulnerability analysis. Furthermore, it argues that market and policy responses must consider both the resource deficits and adaptive capacities of disaster survivors and the characteristics of the environments in which they live to cocreate opportunities for resilience.
The Paradoxical Relationships between Marketing and Vulnerability
Authors: Shultz Clifford J. , Holbrook Morris B.
Published: April 2009

Marketing both reduces and contributes to consumer vulnerability. In this essay, the authors explore this paradoxical relationship. Complexities and nuances captured in existing definitions are revisited. The authors then share a more expansive perspective; they offer a new typology with hopes of drawing attention to multifaceted and conflicting challenges so as to stimulate fresh thinking. Several points are raised so that policy makers and marketers might be inspired to invoke systemic solutions that increase the security and well-being of consumers who are subject to various vulnerabilities.
Overcoming Consumption Constraints through Social Entrepreneurship
Authors: Bloom Paul N.
Published: April 2009

This essay examines the potential of social entrepreneurship efforts to contribute to poverty alleviation. In analyzing this potential, the author pays particular attention to the roles of marketing thinking and academic research in supporting social entrepreneurial initiatives to combat poverty.
Understanding Markets as Online Public Places: Insights from Consumers with Visual Impairments
Authors: Kaufman-Scarborough Carol , Childers Terry L.
Published: April 2009

More than 20% of the U.S. population is composed of people with disabilities. When such people interact with certain marketplaces, such as commercial Web sites, some become “consumers with constraints,” and others become liberated, experiencing the freedom to search for information independently for the first time. While accessibility in physical stores is mandated by the Americans with Disabilities Act, commercial Web sites do not fall under its jurisdiction, because they are not considered “public places.” This research challenges this view and examines whether actual consumers interpret Web sites as public places. The authors examine this question in the context of experiences of consumers with visual impairments in online shopping. The authors apply the concepts of consumer normalcy and consumer vulnerability to the technology acceptance model as theoretical lenses through which to interpret this context. The findings form the basis for recommendations to policy makers to develop and enforce standards for Web site accessibility and to the marketplace to create a level playing field for people with visual impairments.
The Philosophy and Methods of Deliberative Democracy: Implications for Public Policy and Marketing
Authors: Ozanne Julie L. , Corus Canan , Saatcioglu Bige
Published: April 2009

Urgent social problems increasingly arise at the intersection of the interests of business leaders, policy makers, and consumers. The authors argue that deliberative democracy offers a fruitful approach for understanding marketing's impact on society by revealing the complex and often conflicting network of interests among stakeholders. Deliberative methods hold promise for easing constraints on civic engagement and increasing consumer empowerment. The authors explore the historical and philosophical underpinnings of deliberative democracy. Specifically, they evaluate popular methods and applications of deliberative democracy and examine the implications for public policy and marketing.
The Nutrition Elite: Do Only the Highest Levels of Caloric Knowledge, Obesity Knowledge, and Motivation Matter in Processing Nutrition Ad Claims and Disclosures?
Authors: Andrews J. Craig , Netemeyer Richard G. , Burton Scot
Published: April 2009

This study examines the role of the highest levels of caloric knowledge, obesity consequences knowledge, and motivation to search for nutrition information in the processing of relative nutrient content claims in advertisements, such as “half the calories” or “half the fat,” for products relatively high in total calorie levels. After controlling for the impact of demographics, dietary habits, body mass index, relative ad claims and disclosures, perceived weight gain risk, and other variables, the authors find curvilinear (quadratic) effects for caloric knowledge, obesity consequences knowledge, and motivation to search for nutrition information on intent to buy an advertised, high-calorie snack bar. This suggests a strengthening of the negative relationship for intent for consumers at the highest levels of caloric knowledge, obesity consequences knowledge, and motivation (i.e., the “nutrition elite”). The authors offer public policy implications, including whether achieving such exceedingly high levels of nutrition knowledge and motivation is realistic for the general public in light of other policy alternatives, such as market-based solutions (e.g., reducing serving sizes, standardized front-of-package icons).
The Unique Relationship between Quality of Life and Consumer Trust in Market-Related Institutions among Financially Constrained Consumers in a Developing Country
Authors: Ekici Ahmet , Peterson Mark
Published: April 2009

This study focuses on how relationships among constructs representing (1) consumer trust in market-related institutions (CTMRI), (2) distrust for individuals (DFI), and (3) subjective quality of life (QOL) differ across groups separated by the poverty line in a developing country (Turkey). A comparison of models across the two groups using multisample confirmatory factor analysis indicates that there is a correlation only between CTMRI and QOL for consumers below the poverty line (r = .43); there are no correlations between any of the three constructs for consumers above the poverty line. Accordingly, there is a unique relationship between QOL and CTMRI among financially constrained consumers in a developing country. Below the poverty line, consumers with lower trust in market-related institutions tend to report lower QOL, while those with higher trust in market-related institutions tend to report higher QOL.
Price, Scarcity, and Consumer Willingness to Purchase Pirated Media Products
Authors: Miyazaki Anthony D. , Rodriguez Alexandra Aguirre , Langenderfer Jeff
Published: April 2009

Worldwide purchases of pirated media products continue to rise despite various industry and government efforts to quell their growth. Academic research examining consumer decisions underlying the purchase of pirated media has been limited in its approach by focusing almost exclusively on main-effects relationships and by using noncausal research designs. This article addresses these shortcomings by examining how various factors that consumers may perceive as constraining their ability to purchase genuine products (e.g., high price, stockouts, low income, lack of channel access, government restrictions) lead them to acquire pirated products and to condone such behavior in others. The authors report the results of three studies (two of which are experimental) that test three moderators of the consumption constraint effects using various settings, stimuli, and consumer types. The findings support the hypotheses that factors that may be perceived as limiting consumption can lead to higher piracy-related activity and are moderated by ethical beliefs, interpersonal social influence, and trait psychological reactance. The authors discuss the results in terms of implications for policy makers, managers, and future research opportunities.
Health Care Choices in the United States and the Constrained Consumer: A Marketing Systems Perspective on Access and Assortment in Health Care
Authors: Mittelstaedt John D. , Duke Charles R. , Mittelstaedt Robert A.
Published: April 2009

One of the great American success stories of the twentieth century was the victory of medicine over disease. Its success relied on the emergence of a marketing system that delivered and managed health care. Yet, for all the success of the U.S. health care marketing system, there persists a consumption constraint of access—namely, access for whom and access to what. The purpose of this essay is to explore the effects of marketing systems on provisioning and constraining consumption and to understand the role of public policy in overcoming the constraints in marketing systems.
Parallel downregulation of retinol-binding protein-4 and adiponectin expression in subcutaneous adipose tissue of non-morbidly obese subjects
Authors: Broch Montserrat , Auguet Maria Teresa , Ramírez Rafael , Olona Montserrat , Aguilar Carmen , Megia Ana , Alcaide Maria José , Pastor Rosa , Martínez Salomé , Caubet Enric , Garcia-España Antonio , Richart Cristóbal
Published: April 2009

Context and objective

Adipokines are involved in the etiopathology of obesity-related disorders. Since the role of adipokine retinol-binding protein-4 (RBP4) in obesity remains uncertain and its relationship with other adipokines and inflammatory markers has not been examined in detail, we investigated the relationships of RBP4 mRNA expression and circulating protein levels with obesity, anthropometric and metabolic variables, as well as with obesity-related inflammatory markers adiponectin and C-reactive protein.

Subjects and methods

One-hundred and twenty-five subjects participated, 36 lean (body mass index (BMI): <25 kg/m2) and 89 obese (overweight/obese; BMI: ≥25<40) whose anthropometric and metabolic variables were assessed. mRNA expression was quantified by real-time PCR in subcutaneous adipose tissue (s.c.-AT) of 46 subjects.

Results

There was a tendency for circulating RBP4 levels to positively correlate with waist circumference (β=0.29, P=0.08; R2=0.08), but there was no significant association with the obesity-related parameters analysed. RBP4 and adiponectin mRNA expression levels were similarly downregulated in the s.c.-AT of obese subjects (0.5-fold); however, RBP4 downregulation did not affect its circulating protein levels. The expression of RBP4 and adiponectin was positively correlated even after controlling for confounding factors (β=0.59, P<0.0001; R2=0.40).

Conclusions

In our population, RBP4 circulating levels were not significantly correlated with obesity-related parameters, although a tendency to correlate with waist circumference suggests a relationship with insulin resistance and other metabolic disorders. In addition, our results suggest that the production of RBP4 by other tissues such as liver, rather than s.c.-AT, may be involved in regulating RBP4 circulating levels.
Oral hypoglycaemic agents, insulin resistance and cardiovascular disease in patients with type 2 diabetes
Authors: Hemmingsen Bianca , Lund Søren S , Wetterslev Jørn , Vaag Allan
Published: April 2009

This article is a narrative review of the current evidence of the effects on cardiovascular disease (CVD) of oral hypoglycaemic agents that increase insulin sensitivity in patients with type 2 diabetes (T2D). In overweight T2D patients, metformin has been demonstrated to reduce CVD risk, and this beneficial effect may be conserved with the combination of metformin and insulin treatment. However, the effect of glitazones on CVD is uncertain. There is conflicting evidence from large randomized trials to support a protective effect against CVD of lowering blood glucose per se but a systematic review with meta-analysis is lacking. It may be reasonable to aim for an intervention targeting multiple CVD risk factors such as dyslipidaemia, hypertension and albuminuria in T2D patients.