Showing papers by "Virginia Tech published in 2007"

Scientific aspects of polymer electrolyte fuel cell durability and degradation.

Abstract: Rod Borup is a Team Leader in the fuel cell program at Los Alamos National Lab in Los Alamos, New Mexico. He received his B.S.E. in Chemical Engineering from the University of Iowa in 1988 and his Ph.D. from the University of Washington in 1993. He has worked on fuel cell technology since 1994, working in the areas of hydrogen production and PEM fuel cell stack components. He has been awarded 12 U.S. patents, authored over 40 papers related to fuel cell technology, and presented over 50 oral papers at national meetings. His current main research area is related to water transport in PEM fuel cells and PEM fuel cell durability. Recently, he was awarded the 2005 DOE Hydrogen Program R&D Award for the most significant R&D contribution of the year for his team's work in fuel cell durability and was the Principal Investigator for the 2004 Fuel Cell Seminar (San Antonio, TX, USA) Best Poster Award. Jeremy Meyers is an Assistant Professor of materials science and engineering and mechanical engineering at the University of Texas at Austin, where his research focuses on the development of electrochemical energy systems and materials. Prior to joining the faculty at Texas, Jeremy workedmore » as manager of the advanced transportation technology group at UTC Power, where he was responsible for developing new system designs and components for automotive PEM fuel cell power plants. While at UTC Power, Jeremy led several customer development projects and a DOE-sponsored investigation into novel catalysts and membranes for PEM fuel cells. Jeremy has coauthored several papers on key mechanisms of fuel cell degradation and is a co-inventor of several patents. In 2006, Jeremy and several colleagues received the George Mead Medal, UTC's highest award for engineering achievement, and he served as the co-chair of the Gordon Research Conference on fuel cells. Jeremy received his Ph.D. in Chemical Engineering from the University of California at Berkeley and holds a Bachelor's Degree in Chemical Engineering from Stanford University. Bryan Pivovar received his B.S. in Chemical Engineering from the University of Wisconsin in 1994. He completed his Ph.D. in Chemical Engineering at the University of Minnesota in 2000 under the direction of Profs. Ed Cussler and Bill Smyrl, studying transport properties in fuel cell electrolytes. He continued working in the area of polymer electrolyte fuel cells at Los Alamos National Laboratory as a post-doc (2000-2001), as a technical staff member (2001-2005), and in his current position as a team leader (2005-present). In this time, Bryan's research has expanded to include further aspects of fuel cell operation, including electrodes, subfreezing effects, alternative polymers, hydroxide conductors, fuel cell interfaces, impurities, water transport, and high-temperature membranes. Bryan has served at various levels in national and international conferences and workshops, including organizing a DOE sponsored workshop on freezing effects in fuel cells and an ARO sponsored workshop on alkaline membrane fuel cells, and he was co-chair of the 2007 Gordon Research Conference on Fuel Cells. Minoru Inaba is a Professor at the Department of Molecular Science and Technology, Faculty of Engineering, Doshisha University, Japan. He received his B.Sc. from the Faculty of Engineering, Kyoto University, in 1984 and his M.Sc. in 1986 and his Dr. Eng. in 1995 from the Graduate School of Engineering, Kyoto University. He has worked on electrochemical energy conversion systems including fuel cells and lithium-ion batteries at Kyoto University (1992-2002) and at Doshisha University (2002-present). His primary research interest is the durability of polymer electrolyte fuel cells (PEFCs), in particular, membrane degradation, and he has been involved in NEDO R&D research projects on PEFC durability since 2001. He has authored over 140 technical papers and 30 review articles. Kenichiro Ota is a Professor of the Chemical Energy Laboratory at the Graduate School of Engineering, Yokohama National University, Japan. He received his B.S.E. in Applied Chemistry from the University of Tokyo in 1968 and his Ph.D. from the University of Tokyo in 1973. He has worked on hydrogen energy and fuel cells since 1974, working on materials science for fuel cells and water electrolysis. He has published more than 150 original papers, 70 review papers, and 50 scientific books. He is now the president of the Hydrogen Energy Systems Society of Japan, the chairman of the Fuel Cell Research Group of the Electrochemical Society of Japan, and the chairman of the National Committee for the Standardization of the Stationary Fuel Cells. ABSTRACT TRUNCATED« less

A review of power harvesting using piezoelectric materials (2003–2006)

Abstract: The field of power harvesting has experienced significant growth over the past few years due to the ever-increasing desire to produce portable and wireless electronics with extended lifespans. Current portable and wireless devices must be designed to include electrochemical batteries as the power source. The use of batteries can be troublesome due to their limited lifespan, thus necessitating their periodic replacement. In the case of wireless sensors that are to be placed in remote locations, the sensor must be easily accessible or of a disposable nature to allow the device to function over extended periods of time. Energy scavenging devices are designed to capture the ambient energy surrounding the electronics and convert it into usable electrical energy. The concept of power harvesting works towards developing self-powered devices that do not require replaceable power supplies. A number of sources of harvestable ambient energy exist, including waste heat, vibration, electromagnetic waves, wind, flowing water, and solar energy. While each of these sources of energy can be effectively used to power remote sensors, the structural and biological communities have placed an emphasis on scavenging vibrational energy with piezoelectric materials. This article will review recent literature in the field of power harvesting and present the current state of power harvesting in its drive to create completely self-powered devices.

Decoupled Double Synchronous Reference Frame PLL for Power Converters Control

Abstract: This paper deals with a crucial aspect in the control of grid-connected power converters, i.e., the detection of the fundamental-frequency positive-sequence component of the utility voltage under unbalanced and distorted conditions. Specifically, it proposes a positive-sequence detector based on a new decoupled double synchronous reference frame phase-locked loop (DDSRF-PLL), which completely eliminates the detection errors of conventional synchronous reference frame PLL's (SRF-PLL). This is achieved by transforming both positive- and negative-sequence components of the utility voltage into the double SRF, from which a decoupling network is developed in order to cleanly extract and separate the positive- and negative-sequence components. The resultant DDSRF-PLL conducts then to a fast, precise, and robust positive-sequence voltage detection even under unbalanced and distorted grid conditions. The paper presents a detailed description and derivation of the proposed detection method, together with an extensive evaluation using simulation and experimental results from a digital signal processor-based laboratory prototype in order to verify and validate the excellent performance achieved by the DDSRF-PLL

Genome sequence of Aedes aegypti, a major arbovirus vector

Abstract: We present a draft sequence of the genome of Aedes aegypti, the primary vector for yellow fever and dengue fever, which at approximately 1376 million base pairs is about 5 times the size of the genome of the malaria vector Anopheles gambiae. Nearly 50% of the Ae. aegypti genome consists of transposable elements. These contribute to a factor of approximately 4 to 6 increase in average gene length and in sizes of intergenic regions relative to An. gambiae and Drosophila melanogaster. Nonetheless, chromosomal synteny is generally maintained among all three insects, although conservation of orthologous gene order is higher (by a factor of approximately 2) between the mosquito species than between either of them and the fruit fly. An increase in genes encoding odorant binding, cytochrome P450, and cuticle domains relative to An. gambiae suggests that members of these protein families underpin some of the biological differences between the two mosquito species.

Virtual Reality: How Much Immersion Is Enough?

Abstract: Solid evidence of virtual reality's benefits has graduated from impressive visual demonstrations to producing results in practical applications. Further, a realistic experience is no longer immersion's sole asset. Empirical studies show that various components of immersion provide other benefits - full immersion is not always necessary. The goal of immersive virtual environments (VEs) was to let the user experience a computer-generated world as if it were real - producing a sense of presence, or "being there," in the user's mind.

Fractionating recalcitrant lignocellulose at modest reaction conditions.

Abstract: Effectively releasing the locked polysaccharides from recalcitrant lignocellulose to fermentable sugars is among the greatest technical and economic barriers to the realization of lignocellulose biorefineries because leading lignocellulose pre-treatment technologies suffer from low sugar yields, and/or severe reaction conditions, and/or high cellulase use, narrow substrate applicability, and high capital investment, etc. A new lignocellulose pre-treatment featuring modest reaction conditions (50 degrees C and atmospheric pressure) was demonstrated to fractionate lignocellulose to amorphous cellulose, hemicellulose, lignin, and acetic acid by using a non-volatile cellulose solvent (concentrated phosphoric acid), a highly volatile organic solvent (acetone), and water. The highest sugar yields after enzymatic hydrolysis were attributed to no sugar degradation during the fractionation and the highest enzymatic cellulose digestibility ( approximately 97% in 24 h) during the hydrolysis step at the enzyme loading of 15 filter paper units of cellulase and 60 IU of beta-glucosidase per gram of glucan. Isolation of high-value lignocellulose components (lignin, acetic acid, and hemicellulose) would greatly increase potential revenues of a lignocellulose biorefinery.

Porcine circovirus type 2-associated disease: Update on current terminology, clinical manifestations, pathogenesis, diagnosis, and intervention strategies

Abstract: Porcine circovirus type 2 (PCV2)-associated disease (PCVAD) continues to be an important differential diagnosis on pig farms in the United States and worldwide. Case trend analyses indicate that the incidence of PCVAD is on the rise in the United States. Accurate diagnosis is important in order to implement appropriate intervention strategies. PCVAD can manifest as a systemic disease, as part of the respiratory disease complex, as an enteric disease, as porcine dermatitis and nephropathy syndrome, or as reproductive problems. PCVAD may be only a sporadic individual animal diagnosis; however, PCVAD may also manifest as a severe herd problem accelerated and enhanced by concurrent virus or bacterial infections. This article is intended to discuss the most common disease manifestations, pathogenesis, diagnostic approaches, and intervention strategies associated with PCVAD in North America.

Exposure to Hurricane-Related Stressors and Mental Illness After Hurricane Katrina

Abstract: Context Uncertainty exists about the prevalence, severity, and correlates of mental disorders among people exposed to Hurricane Katrina. Objective To estimate the prevalence and associations between DSM-IV anxiety-mood disorders and hurricane-related stressors separately among prehurricane residents of the New Orleans metropolitan area and the remainder of the areas in Alabama, Louisiana, and Mississippi affected by Katrina. Design Community survey. Setting and Participants A probability sample of 1043 English-speaking prehurricane residents of the areas affected by Hurricane Katrina was administered via telephone survey between January 19 and March 31, 2006. The survey assessed hurricane-related stressors and screened for 30-day DSM-IV anxiety-mood disorders. Main Outcome Measures The K6 screening scale of anxiety-mood disorders and the Trauma Screening Questionnaire scale for posttraumatic stress disorder (PTSD), both calibrated against blinded structured clinical reappraisal interviews to approximate the 30-day prevalence of DSM-IV disorders. Results Prehurricane residents of the New Orleans metropolitan area were estimated to have a 49.1% 30-day prevalence of any DSM-IV anxiety-mood disorder (30.3% estimated prevalence of PTSD) compared with 26.4% (12.5% PTSD) in the remainder of the sample. The vast majority of respondents reported exposure to hurricane-related stressors. Extent of stressor exposure was more strongly related to the outcomes in the New Orleans metropolitan area subsample than the remainder of the sample. The stressors most strongly related to these outcomes were physical illness/injury and physical adversity in the New Orleans metropolitan area subsample and property loss in the remainder of the sample. Sociodemographic correlates were not explained either by differential exposure or reactivity to hurricane-related stressors. Conclusions The high prevalence of DSM-IV anxiety-mood disorders, the strong associations of hurricane-related stressors with these outcomes, and the independence of sociodemographics from stressors argue that the practical problems associated with ongoing stressors are widespread and must be addressed to reduce the prevalence of mental disorders in this population.

Theory of neutrinos: a white paper

Abstract: This paper is a review of the present status of neutrino mass physics, which grew out of an APS sponsored study of neutrinos in 2004. After a discussion of the present knowledge of neutrino masses and mixing and some popular ways to probe the new physics implied by recent data, it summarizes what can be learned about neutrino interactions as well as the nature of new physics beyond the Standard Model from the various proposed neutrino experiments. The intriguing possibility that neutrino mass physics may be at the heart of our understanding of a long standing puzzle of cosmology, i.e. the origin of matter?antimatter asymmetry is also discussed.

Fluorescently labeled cellulose nanocrystals for bioimaging applications.

Abstract: Cellulose nanocrystals are promising candidates for applications in nanomedicine. To enable the use of fluorescence techniques in in vitro and in vivo studies, cellulose nanocrystals were labeled with fluorescein-5‘-isothiocyanate (FITC) via a three-step reaction, involving epoxy activation of the nanocrystal surface, opening of the epoxy rings with ammonium hydroxide, and coupling of FITC molecules to the primary amino groups. The FITC content of the labeled cellulose nanocrystals was determined by UV/vis spectroscopy. A FITC content of 0.03 mmol/g of cellulose, equivalent to 5 FITC moieties per 1000 anhydroglucose units, was obtained using the described method.

Self-regulation, self-efficacy, outcome expectations, and social support: social cognitive theory and nutrition behavior.

Abstract: Background: Understanding the need for and accessibility to healthier foods have not improved the overall diets of the U.S. population. Social cognitive theory (SCT) may explain how other variables, such as self-regulation and self-efficacy, may be key to integrating healthier nutrition into U.S. lifestyles.Purpose: To determine how SCT accounts for the nutritional content of food purchases and consumption among adults in a health promotion study.Methods: Participants were 712 churchgoers (18% African American, 66% female, 79% overweight or obese) from 14 churches in southwestern Virginia participating in the baseline phase of a larger health promotion study. Data were collected on the nutrition related social support, self-efficacy, outcome expectations, and self-regulation components of SCT, as well as on the fat, fiber, fruit, and vegetable content of food-shopping receipts and food frequency questionnaires. These data were used to test the fit of models ordered as prescribed by SCT and subjected to structural equation analysis.Results: SCT provided a good fit to the data explaining 35%, 52%, and 59% of observed variance in percent calories from fat, fiber g/1000 kcals and fruit and vegetable servings/1000 kcals. Participants’ age, gender, socioeconomic status, social support, self-efficacy, negative outcome expectations, and self-regulation made important contributions to their nutrition behavior—a configuration of influences consistent with SCT.Conclusions: These results suggest a pivotal role for self-regulatory behavior in the healthier food choices of adults. Interventions effective at garnering family support, increasing nutrition related self-efficacy, and overcoming negative outcome expectations should be more successful at helping adults enact the self-regulatory behaviors essential to buying and eating healthier foods.

Improvement of water use efficiency in rice by expression of HARDY, an Arabidopsis drought and salt tolerance gene

Abstract: Freshwater is a limited and dwindling global resource; therefore, efficient water use is required for food crops that have high water demands, such as rice, or for the production of sustainable energy biomass. We show here that expression of the Arabidopsis HARDY (HRD) gene in rice improves water use efficiency, the ratio of biomass produced to the water used, by enhancing photosynthetic assimilation and reducing transpiration. These drought-tolerant, low-water-consuming rice plants exhibit increased shoot biomass under well irrigated conditions and an adaptive increase in root biomass under drought stress. The HRD gene, an AP2/ERF-like transcription factor, identified by a gain-of-function Arabidopsis mutant hrd-D having roots with enhanced strength, branching, and cortical cells, exhibits drought resistance and salt tolerance, accompanied by an enhancement in the expression of abiotic stress associated genes. HRD overexpression in Arabidopsis produces thicker leaves with more chloroplast-bearing mesophyll cells, and in rice, there is an increase in leaf biomass and bundle sheath cells that probably contributes to the enhanced photosynthesis assimilation and efficiency. The results exemplify application of a gene identified from the model plant Arabidopsis for the improvement of water use efficiency coincident with drought resistance in the crop plant rice.

Effective hydrostatic limits of pressure media for high-pressure crystallographic studies

Abstract: The behavior of a number of commonly used pressure media, including nitrogen, argon, 2-propanol, a 4:1 methanol–ethanol mixture, glycerol and various grades of silicone oil, has been examined by measuring the X-ray diffraction maxima from quartz single crystals loaded in a diamond-anvil cell with each of these pressure media in turn. In all cases, the onset of non-hydrostatic stresses within the medium is detectable as the broadening of the rocking curves of X-ray diffraction peaks from the single crystals. The onset of broadening of the rocking curves of quartz is detected at ∼9.8 GPa in a 4:1 mixture of methanol and ethanol and at ∼4.2 GPa in 2-propanol, essentially at the same pressures as the previously reported hydrostatic limits determined by other techniques. Gigahertz ultrasonic interferometry was also used to detect the onset of the glass transition in 4:1 methanol–ethanol and 16:3:1 methanol–ethanol–water, which were observed to support shear waves above ∼9.2 and ∼10.5 GPa, respectively, at 0.8–1.2 GHz. By contrast, peak broadening is first detected at ∼3 GPa in nitrogen, ∼1.9 GPa in argon, ∼1.4 GPa in glycerol and ∼0.9 GPa in various grades of silicone oil. These pressures, which are significantly lower than hydrostatic limits quoted in the literature, should be considered as the practical maximum limits to the hydrostatic behavior of these pressure media at room temperature.

Cyclostationary Approaches to Signal Detection and Classification in Cognitive Radio

Abstract: Spectrum awareness is currently one of the most challenging problems in cognitive radio (CR) design. Detection and classification of very low SNR signals with relaxed information on the signal parameters being detected is critical for proper CR functionality as it enables the CR to react and adapt to the changes in its radio environment. In this work, the cycle frequency domain profile (CDP) is used for signal detection and preprocessing for signal classification. Signal features are extracted from CDP using a threshold-test method. For classification, a Hidden Markov Model (HMM) has been used to process extracted signal features due to its robust pattern-matching capability. We also investigate the effects of varied observation length on signal detection and classification. It is found that the CDP-based detector and the HMM-based classifier can detect and classify incoming signals at a range of low SNRs.

Dynamic pull-in phenomenon in MEMS resonators

Abstract: We study the pull-in instability in microelectromechanical (MEMS) resonators and find that characteristics of the pull-in phenomenon in the presence of AC loads differ from those under purely DC loads. We analyze this phenomenon, dubbed dynamic pull-in, and formulate safety criteria for the design of MEMS resonant sensors and filters excited near one of their natural frequencies. We also utilize this phenomenon to design a low-voltage MEMS RF switch actuated with a combined DC and AC loading. The new switch uses a voltage much lower than the traditionally used DC voltage. Either the frequency or the amplitude of the AC loading can be adjusted to reduce the driving voltage and switching time. The new actuation method has the potential of solving the problem of high driving voltages of RF MEMS switches.

Search for electron neutrino appearance at the Δm2∼1eV2 Scale

Abstract: The MiniBooNE Collaboration reports first results of a search for {nu}{sub e} appearance in a {nu}{sub {mu}} beam. With two largely independent analyses, we observe no significant excess of events above the background for reconstructed neutrino energies above 475 MeV. The data are consistent with no oscillations within a two-neutrino appearance-only oscillation model.

The Metabolomics Standards Initiative

Abstract: In 2005, the Metabolomics Standards Initiative has been formed. An outline and general introduction is provided to inform about the history, structure, working plan and intentions of this initiative. Comments on any of the suggested minimal reporting standards are welcome to be sent to the open email list Msi-workgroups-feedback@lists.sourceforge.net

The Development of Pine Plantation Silviculture in the Southern United States

Abstract: In the 1950s there were vast acreages of cutover forestland and degraded agricultural land across the South. Less than 2 million ac of southern pine plantations existed at that time. By the end of the 20th century, there were 32 million ac of southern pine plantations in the US South and this region is the wood basket of the world. The success story that is southern pine forestry was facilitated by the application of research results generated through cooperative work of the US Forest Service, southern forestry schools, state forestry agencies, and forest industry. This article reviews the contributions of applied silvicultural research in tree improvement, nursery management, site preparation, weed control, and fertilization to plantation forestry in the South. These practices significantly increased productivity of southern pine plantations. Plantations established in the 1950s and 1960s, which produced less than 90 ft 3 ac 1y r 1 , have been replaced by plantations established in the 2000s, which may produce in excess of 400 ft 3 ac 1y r 1 . Currently, southern pine plantations are among the most intensively managed forests in the world. Growth of plantations managed using modern, integrated, site-specific silvicultural regimes now can rival that of plantations of fast-growing exotic species in the Southern Hemisphere.

Phytophthora sojae: root rot pathogen of soybean and model oomycete

Abstract: SUMMARY Phytophthora sojae is an oomycete pathogen of soybean, classified in the kingdom Stramenopiles It causes ‘damping off’ of seedlings and root rot of older plants, with an annual cost worldwide of $1–2 billion Owing to its economic importance, this species, along with P infestans, has been developed as a model species for the study of oomycete plant pathogens It is readily transformed with DNA enabling over-expression and silencing of selected genes, genetic maps have been constructed and large expressed sequence tag sequence libraries have been developed A draft genome sequence has recently been completed This review briefly summarizes current information about the pathogenicity, evolution, molecular biology and genomics of P sojae Taxonomy: Phytophthora sojae (Kaufman & Gerdman): superkingdom Eukaryota; kingdom Stramenopila; phylum Oomycota; class Peronosporomycetidae; order Pythiales; family Pythiaceae; genus Phytophthora Host range: Soybean is the only economically important host Several species of lupins have also been reported as hosts Disease symptoms and signs: All parts of the soybean plant are susceptible to infection by P sojae, from germinating seedlings to mature plants In the field, P sojae causes damping off of soybean seedlings and a root and stem rot of established plants Leaves can be infected in the field as a result of rain splash or by deliberate inoculation in the laboratory Damping off can affect germinating seeds or emerged seedlings and is most severe when the spring is very wet and warm (25–30 °C) Established plants can become infected when the soil is wet for extended periods, especially if the soil is poorly drained Both the cortex and the vascular tissue are colonized by P sojae, and the infection can spread rapidly along the vascular tissues in susceptible cultivars Useful websites: http://pmgnvbivtedu, http://phytophthoravbivtedu, http://wwwjgidoegov/Psojae, http://wwwjgidoegov/Pramorum, http://wwwpfgdorg, http://pamgovbivtedu, http://soyvbivtedu, https://wwwvbivtedu/article/articleview/78, http://plantpathosuedu/faculty/dorrancephp

Size-dependent structural transformations of hematite nanoparticles. 1. Phase transition.

Abstract: Using Fourier Transform InfraRed (FTIR) spectroscopy, Raman spectroscopy, X-ray diffraction (XRD), and Transmission Electron Microscopy (TEM), we characterize the structure and/or morphology of hematite (α-Fe2O3) particles with sizes of 7, 18, 39 and 120 nm. It is found that these nanoparticles possess maghemite (γ-Fe2O3)-like defects in the near surface regions, to which a vibrational mode at 690 cm−1, active both in FTIR and Raman spectra, is assigned. The fraction of the maghemite-like defects and the net lattice disorder are inversely related to the particle size. However, the effect is opposite for nanoparticles grown by sintering of smaller hematite precursors under conditions when the formation of a uniform hematite-like structure throughout the aggregate is restricted by kinetic issues. This means that not only particle size but also the growth kinetics determines the structure of the nanoparticles. The observed structural changes are interpreted as size-induced α-Fe2O3 ↔ γ-Fe2O3 phase transitions. We develop a general model that considers spinel defects and absorbed/adsorbed species (in our case, hydroxyls) as dominant controls on structural changes with particle size in hematite nanoparticles, including solid-state phase transitions. These changes are represented by trajectories in a phase diagram built in three phase coordinates—concentrations of spinel defects, absorbed impurities, and adsorbed species. The critical size for the onset of the α → γ phase transition depends on the particle environment, and for the dry particles used in this study is about 40 nm. The model supports the existence of intermediate phases (protohematite and hydrohematite) during dehydration of goethite. We also demonstrate that the hematite structure is significantly less defective when the nanoparticles are immersed in water or KBr matrix, which is explained by the effects of the electrochemical double layer and increased rigidity of the particle environment. Finally, we revise the problem of applicability of IR spectroscopy to the lattice vibrations of hematite nanoparticles, demonstrating that structural comparison of different samples is much more reliable if it is based on the Eu band at about 460 cm−1 and the spinel band at 690 cm−1, instead of the A2u/Eu band at about 550 cm−1 used in previous work. The new methodology is applied to analysis of the reported IR spectra of Martian hematite.

Optimizing the Distribution of Resources between Enzymes of Carbon Metabolism Can Dramatically Increase Photosynthetic Rate: A Numerical Simulation Using an Evolutionary Algorithm

Abstract: The distribution of resources between enzymes of photosynthetic carbon metabolism might be assumed to have been optimized by natural selection. However, natural selection for survival and fecundity does not necessarily select for maximal photosynthetic productivity. Further, the concentration of a key substrate, atmospheric CO(2), has changed more over the past 100 years than the past 25 million years, with the likelihood that natural selection has had inadequate time to reoptimize resource partitioning for this change. Could photosynthetic rate be increased by altered partitioning of resources among the enzymes of carbon metabolism? This question is addressed using an "evolutionary" algorithm to progressively search for multiple alterations in partitioning that increase photosynthetic rate. To do this, we extended existing metabolic models of C(3) photosynthesis by including the photorespiratory pathway (PCOP) and metabolism to starch and sucrose to develop a complete dynamic model of photosynthetic carbon metabolism. The model consists of linked differential equations, each representing the change of concentration of one metabolite. Initial concentrations of metabolites and maximal activities of enzymes were extracted from the literature. The dynamics of CO(2) fixation and metabolite concentrations were realistically simulated by numerical integration, such that the model could mimic well-established physiological phenomena. For example, a realistic steady-state rate of CO(2) uptake was attained and then reattained after perturbing O(2) concentration. Using an evolutionary algorithm, partitioning of a fixed total amount of protein-nitrogen between enzymes was allowed to vary. The individual with the higher light-saturated photosynthetic rate was selected and used to seed the next generation. After 1,500 generations, photosynthesis was increased substantially. This suggests that the "typical" partitioning in C(3) leaves might be suboptimal for maximizing the light-saturated rate of photosynthesis. An overinvestment in PCOP enzymes and underinvestment in Rubisco, sedoheptulose-1,7-bisphosphatase, and fructose-1,6-bisphosphate aldolase were indicated. Increase in sink capacity, such as increase in ADP-glucose pyrophosphorylase, was also indicated to lead to increased CO(2) uptake rate. These results suggest that manipulation of partitioning could greatly increase carbon gain without any increase in the total protein-nitrogen investment in the apparatus for photosynthetic carbon metabolism.

An integrative framework capturing experiential and utilitarian shopping experience

Abstract: Purpose – In line with changes in consumer demand, models used in empirical study of the shopping experience have expanded. Reflecting the integrative (experiential and utilitarian) nature of shopping experience, the paper aims to propose an overarching stimulus‐organism‐response based shopping experience framework.Design/methodology/approach – This conceptual paper offers a framework that integrates components of both the hedonic experience related consciousness‐emotion‐value model and the utilitarian experience‐related cognition‐affect‐behavior model. In this paper, articles crossing hedonic and utilitarian boundaries are briefly presented, and the array of variables used in empirical studies of shopping experience, with an emphasis on brick‐and‐mortar shopping experiences, are synthesized for each component of the framework.Findings – The resulting framework is an inclusive overarching structure that explains the consumer shopping experience. This framework is useful for both academia and industry. It ...

Instrument development tools and activities for measure validation using Rasch models: part II--validation activities.

Abstract: Accumulation of validity evidence is an important part of the instrument development process. In Part I of a two-part series, we provided an overview of validity concepts and described how instrument development efforts can be conducted to facilitate the development of validity arguments. In this, Part II of the series, we identify how analyses, especially those conducted within a Rasch measurement framework, can be used to provide evidence to support validity arguments that are founded during the instrument development process.