Scholarly Works, Civil and Environmental Engineering

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Sediment-Water Column Oxygen and Nutrient Fluxes in Nearshore Environments of the Lower Delmarva Peninsula, USA
Reay, William G.; Gallagher, Daniel L.; Simmons, George M. Jr. (Inter-Research, 1995)
Sediment-water column exchanges of oxygen, dissolved inorganic nitrogen (DIN) and dissolved inorganic phosphorus (DIP) were measured in situ over an annual cycle for sandy and silt-clay sediment types in a shallow Chesapeake Bay (USA) inlet. Benthic oxygen and inorganic nutrient fluxes differed between sediment types. Based on metabolic rate estimates and photosynthetic pigment concentrations, nearshore sandy sediments were more productive than silt-clay sediments. Overall benthic community respiration rates were 872 mu mol m(-2) h(-1) for sandy sediments and 2220 mu mol m(-2) h(-1) for silt-clay sediments. Elevated ammonium and DIP sediment fluxes were associated with silt-clay sediments. Sandy and silt-clay sediment ammonium fluxes ranged from -44 to 358 and -30 to 615 mu mol m(-2) h(-1) respectively, with DIP fluxes ranging from -5.3 to 42.0 and -3.3 to 35.7 mu mol m(-2) h(-1). Negative nutrient flux values denote sediment uptake. Sediment ammonium and DIP fluxes were dependent on benthic aerobic respiration rates for silt-clay sediments. In contrast, sandy sediment ammonium fluxes were less dependent and DIP fluxes showed no relationship to benthic aerobic respiration rates. Ammonium and DIP flux rates were significantly reduced in transparent chambers as compared to opaque chambers indicating the importance of the benthic microalgal community. On an annual basis, sandy sediments could supply 11% of the phosphorus and 6% of the phytoplankton nitrogen requirements based on gross productivity estimates, whereas silt-clay sediments could supply 11 and 14%, respectively. Positive correlations between sandy and silt-clay sediment DIN fluxes and phytoplankton DIN assimilatory demands emphasize the importance and interdependence of sediment heterotrophic and water column autotrophic processes. Short water column DIN and DIP turnover times, on the order of hours, were characteristic of summer conditions when water column nutrient concentrations were low and silt-clay sediment nutrient fluxes high. Conversely, nutrient turnover times on the order of days were characteristic of winter conditions when water column nutrient concentrations were high and sediment nutrient fluxes low.
Dietary phosphorus effects on characteristics of mechanically separated dairy manure
Knowlton, Katharine F.; Love, Nancy G.; Parsons, C. A. (American Society of Agricultural and Biological Engineers, 2005)
One approach to reduce nutrient losses from livestock farms is to apply biological waste treatment systems such as biological nitrogen (N) removal or enhanced biological phosphorus (P) removal (EBPR) to reduce the nutrient content of land-applied waste. The EBPR process takes advantage of the ability of P-accumulating organisms (PAOs) to sequester excess P as polyphosphate granules in their cytoplasms, yielding a P-depleted liquid effluent and a P-enriched biomass. Biological N removal systems result in the conversion of organic or ammonia-N to innocuous N-2 gas. Understanding the variation in parameters such as chemical oxygen demand (COD), total and volatile suspended solids (TSS and VSS), and ammonia-N (NH3-N) is necessary to design these systems. Our objectives were to evaluate the effects of diet and manure separation on parameters important to reactor design. Waste was collected from nine cows fed a high P diet (0.47% P), a low P diet (0.32 % P), or low P with exogenous phytase plus cellulase (0.32 % P), in a replicated Latin square design (three 3 X 3 squares). Total collection of milk, urine, and feces was conducted on days 19 to 21 of each period, a mixed slurry (urine, feces, and water) was created, and slurry was separated mechanically to generate liquid effluent. Slurry contained more COD, solids, N, and P than liquid effluent, but the COD:P ratio was similar in the two wastes. The ratio of COD:N was higher in slurry than in separator effluent, but the ratio in both wastes was sufficient to support biological N removal. The P content of slurry, liquid effluent, and manure solids from cows fed low P was lower than from cows fed high P, and the COD content of effluent was higher with the low P diet. The COD:P ratio of all wastes was sufficient to support EBPR and biological N removal, but variation was observed with diet. Waste from cows fed low P had a higher COD:P ratio than that of cows fed high P, and waste from cows fed the enzyme-supplemented diet had a lower COD:N ration than that of cows fed the control diet. Dairy manure slurry and effluent will support EBPR and biological N removal. Dietary effects on parameters important to the design of advanced waste treatment systems were observed, but were not of a magnitude that would affect reactor design.
Experimental Snap Loading of Synthetic Ropes
Hennessey, C. M.; Pearson, N. J.; Plaut, Raymond H. (Hindawi, 2005-01-01)
Large tensile forces, known as snap loads, can occur when a slack rope becomes taut. Such forces may damage the rope or masses connected to it. Experiments are described in which one end of a rope is attached to the top of a drop tower and the bottom end is attached to a weight. The weight is raised to a certain height and then released. The force at the top of the rope and the acceleration of the weight are recorded during the first snap load that occurs. Repeated drop tests are performed on each rope. The effects of the type of rope, drop height, drop weight, whether the rope has been subjected to static precycling, and the number of previous dynamic tests are examined. A mathematical model is proposed for the rope force as a function of the displacement and velocity of the weight.
Vehicle fleet emissions of black carbon, polycyclic aromatic hydrocarbons, and other pollutants measured by a mobile laboratory in Mexico City
Jiang, M.; Marr, Linsey C.; Dunlea, E. J.; Herndon, S. C.; Jayne, John T.; Kolb, C. E.; Knighton, W. B.; Rogers, T. M.; Zavala, M.; Molina, L. T.; Molina, M. J. (Copernicus Publications, 2005-12-01)
Black carbon ( BC) and polycyclic aromatic hydrocarbons (PAHs) are of concern due to their effects on climate and health. The main goal of this research is to provide the first estimate of emissions of BC and particle-phase PAHs (PPAHs) from motor vehicles in Mexico City. The emissions of other pollutants including carbon monoxide ( CO), oxides of nitrogen (NOx), volatile organic compounds (VOCs), and particulate matter of diameter 2.5 mu m and less (PM2.5) are also estimated. As a part of the Mexico City Metropolitan Area field campaign in April 2003 (MCMA-2003), a mobile laboratory was driven throughout the city. The laboratory was equipped with a comprehensive suite of gas and particle analyzers, including an aethalometer that measured BC and a photoionization aerosol sensor that measured PPAHs. While driving through traffic, the mobile lab continuously sampled exhaust plumes from the vehicles around it. We have developed a method of automatically identifying exhaust plumes, which are then used as the basis for calculation of fleet-average emissions. In the approximately 75 h of on-road sampling during the field campaign, we have identified similar to 30 000 exhaust measurement points that represent a variety of vehicle types and driving conditions. The large sample provides a basis for estimating fleet-average emission factors and thus the emission inventory. Motor vehicles in the Mexico City area are estimated to emit 1700 +/- 200 metric tons BC, 57 +/- 6 tons PPAHs, 1 190 000 +/- 40 000 tons CO, 120 000 +/- 3000 tons NOx, 240 000 +/- 50 000 tons VOCs, and 4400 +/- 400 tons PM2.5 per year, not including cold start emissions. The estimates for CO, NOx, and PPAHs may be low by up to 10% due to the slower response time of analyzers used to measure these species. Compared to the government's official motor vehicle emission inventory for the year 2002, the estimates for CO, NOx, VOCs, and PM2.5 are 38% lower, 23% lower, 27% higher, and 25% higher, respectively. The distributions of emission factors of BC, PPAHs, and PM2.5 are highly skewed, i.e. asymmetric, while those for benzene, measured as a surrogate for total VOCs, and NOx are less skewed. As a result, the total emissions of BC, PPAHs, and PM2.5 could be reduced by approximately 50% if the highest 20% of data points were removed, but "super polluters" are less influential on overall NOx and VOC emissions.
Sources and transformations of particle-bound polycyclic aromatic hydrocarbons in Mexico City
Marr, Linsey C.; Dzepina, K.; Jimenez, Jose L.; Reisen, F.; Bethel, H. L.; Arey, J.; Gaffney, J. S.; Marley, N. A.; Molina, L. T.; Molina, M. J. (Copernicus Publications, 2006-05-01)
Understanding sources, concentrations, and transformations of polycyclic aromatic hydrocarbons (PAHs) in the atmosphere is important because of their potent mutagenicity and carcinogenicity. The measurement of particle-bound PAHs by three different methods during the Mexico City Metropolitan Area field campaign in April 2003 presents a unique opportunity for characterization of these compounds and intercomparison of the methods. The three methods are ( 1) collection and analysis of bulk samples for time-integrated gas- and particle-phase speciation by gas chromatography/ mass spectrometry; ( 2) aerosol photoionization for fast detection of PAHs on particles' surfaces; and ( 3) aerosol mass spectrometry for fast analysis of size and chemical composition. This research represents the first time aerosol mass spectrometry has been used to measure ambient PAH concentrations and the first time that fast, real-time methods have been used to quantify PAHs alongside traditional filter-based measurements in an extended field campaign. Speciated PAH measurements suggest that motor vehicles and garbage and wood burning are important sources in Mexico City. The diurnal concentration patterns captured by aerosol photoionization and aerosol mass spectrometry are generally consistent. Ambient concentrations of particle-phase PAHs typically peak at similar to 110 ng m(-3) during the morning rush hour and rapidly decay due to changes in source activity patterns and dilution as the boundary layer rises, although surface-bound PAH concentrations decay faster. The more rapid decrease in surface versus bulk PAH concentrations during the late morning suggests that freshly emitted combustion-related particles are quickly coated by secondary aerosol material in Mexico City's atmosphere and may also be transformed by heterogeneous reactions.
Resistance to IT Change in the AEC Industry: An Individual Assessment Tool
Davis, Kirsten A.; Songer, Anthony D. (2008)
Numerous IT adoption studies within the AEC industry identify issues with individuals resisting IT changes. Current change models often only look at organizations and tasks and frequently neglect the individuals involved. The limitations in existing change models and the criticality of people issues in the successful implementation of change necessitates the investigation of individual resistance to IT change. Change management theory and attitude-behavior connections provide a framework to study variables associated with impeding/promoting the use of technologies. Data collected from a 50-person sample of the AEC population allowed reductions of the attitudes, fears, and beliefs variables. Reducing the variables indicative of resistance to information technology change facilitated the creation of a detailed social architecture factor model. Subsequently, a Resistance to Change Index (RTCI) was created, enabling estimations of the intensity of resistance an individual is likely to exhibit using the personality traits and behavioral characteristics identified in the revised social architecture factor model. The RTCI assists practitioners in developing new technology implementation plans. The RTCI also enables researchers to understand how individual participants resist and adapt to change allowing the development of enhanced organizational adoption models for new technology implementation within the building industry.
Spatial and temporal variability of particulate polycyclic aromatic hydrocarbons in Mexico City
Thornhill, D. A.; de Foy, B.; Herndon, S. C.; Onasch, T. B.; Wood, E. C.; Zavala, M.; Molina, L. T.; Gaffney, J. S.; Marley, N. A.; Marr, Linsey C. (Copernicus Publications, 2008)
As part of the Megacities Initiative: Local and Global Research Observations (MILAGRO) study in the Mexico City Metropolitan Area in March 2006, we measured particulate polycyclic aromatic hydrocarbons (PAHs) and other gaseous species and particulate properties, including light absorbing carbon or effective black carbon (BC), at six locations throughout the city. The measurements were intended to support the following objectives: to describe spatial and temporal patterns in PAH concentrations, to gain insight into sources and transformations of PAHs and BC, and to quantify the relationships between PAHs and other pollutants. Total particulate PAHs at the Instituto Mexicano del Petroleo (T0 supersite) located near downtown averaged 50 ng m(-3), and aerosol active surface area averaged 80 mm(2) m(-3). PAHs were also measured on board the Aerodyne Mobile Laboratory, which visited six sites encompassing a mixture of different land uses and a range of ages of air parcels transported from the city core. A combination of analyses of time series, back trajectories, concentration fields, pollutant ratios, and correlation coefficients supports the concept of T0 as an urban source site, T1 as a receptor site with strong local sources, Pedregal and PEMEX as intermediate sites, Pico Tres Padres as a vertical receptor site, and Santa Ana as a downwind receptor site. Weak intersite correlations suggest that local sources are important and variable and that exposure to PAHs and BC cannot be represented by a single regional-scale value. The relationships between PAHs and other pollutants suggest that a variety of sources and ages of particles are present. Among carbon monoxide, nitrogen oxides (NO(x)), and carbon dioxide, particulate PAHs are most strongly correlated with NO(x). Mexico City's PAH/BC mass ratio of 0.01 is similar to that found on a freeway loop in the Los Angeles area and approximately 8-30 times higher than that found in other cities. Evidence also suggests that primary combustion particles are rapidly coated by secondary aerosol in Mexico City. If so, their optical properties may change, and the lifetime of PAHs may be prolonged if the coating protects them against photodegradation or heterogeneous reactions.
Forecasting Model for Air Taxi, Commercial Airline, and Automobile Demand in the United States
Baik, Hojong; Trani, Antonio A.; Hinze, Nicolas; Swingle, Howard; Ashiabor, Senanu; Seshadri, Anand (Transportation Research Board of the National Academies, 2008)
A nationwide model predicts the annual county-to-county person roundtrips for air taxi, commercial airline, and automobile at 1-year intervals through 2030. The transportation systems analysis model (TSAM) uses the four-step transportation systems modeling process to calculate trip generation, trip distribution, and mode choice for each county origin–destination pair. Network assignment is formulated for commercial airline and air taxi demand. TSAM classifies trip rates by trip purpose, household income group, and type of metropolitan statistical area from which the round-trip started. A graphical user interface with geographic information systems capability is included in the model. Potential applications of the model are nationwide impact studies of transportation policies and technologies, such as those envisioned with the introduction of extensive air taxi service using very light jets, the next-generation air transportation system, and the introduction of new aerospace technologies.
An Optimal Constrained Pruning Strategy for Decision Trees
Sherali, Hanif D.; Hobeika, Antoine G.; Jeenanunta, Chawalit (INFORMS, 2009)
This paper is concerned with the optimal constrained pruning of decision trees. We present a novel 0-1 programming model for pruning the tree to minimize some general penalty function based on the resulting leaf nodes, and show that this model possesses a totally unimodular structure that enables it to be solved as a shortest-path problem on an acyclic graph. Moreover, we prove that this problem can be solved in strongly polynomial time while incorporating an additional constraint on the number of residual leaf nodes. Furthermore, the framework of the proposed modeling approach renders it suitable to accommodate different (multiple) objective functions and side-constraints, and we identify various such modeling options that can be applied in practice. The developed methodology is illustrated using a numerical example to provide insights, and some computational results are presented to demonstrate the efficacy of solving generically constrained problems of this type. We also apply this technique to a large-scale transportation analysis and simulation system (TRANSIMS), and present related computational results using real data to exhibit the flexibility and effectiveness of the proposed approach.
Evaluation of mobile emissions contributions to Mexico City's emissions inventory using on-road and cross-road emission measurements and ambient data
Zavala, M.; Herndon, S. C.; Wood, E. C.; Onasch, T. B.; Knighton, W. B.; Marr, Linsey C.; Kolb, C. E.; Molina, L. T. (Copernicus Publications, 2009)
Mobile emissions represent a significant fraction of the total anthropogenic emissions burden in the Mexico City Metropolitan Area (MCMA) and, therefore, it is crucial to use top-down techniques informed by on-road exhaust measurements to evaluate and improve traditional bottom-up official emissions inventory (EI) for the city. We present the measurements of on-road fleet-average emission factors obtained using the Aerodyne mobile laboratory in the MCMA in March 2006 as part of the MILAGRO/MCMA-2006 field campaign. A comparison of our on-road emission measurements with those obtained in 2003 using essentially the same measurement techniques and analysis methods indicates that, in the three year span, NO emission factors remain within the measured variability ranges whereas emission factors of aldehydes and aromatics species were reduced for all sampled driving conditions. We use a top-down fuel-based approach to evaluate the mobile emissions from the gasoline fleet estimated in the bottom-up official 2006 MCMA mobile sources. Within the range of measurement uncertainties, we found probable slight overpredictions of mean EI estimates on the order of 20-28% for CO and 14-20% for NO. However, we identify a probable EI discrepancy of VOC mobile emissions between 1.4 and 1.9; although estimated benzene and toluene mobile emissions in the inventory seem to be well within the uncertainties of the corresponding emissions estimates. Aldehydes mobile emissions in the inventory, however, seem to be underpredicted by factors of 3 for HCHO and 2 for CH(3)CHO. Our on-road measurement-based estimate of annual emissions of organic mass from PM(1) particles suggests a severe underprediction (larger than a factor of 4) of PM(2.5) mobile emissions in the inventory. Analyses of ambient CO, NO(x) and CO/NO(x) concentration trends in the MCMA indicate that the early morning ambient CO/NO(x) ratio has decreased at a rate of about 1.9 ppm/ppm/year over the last two decades due to reductions in CO levels rather than by NO(x). These trends, together with the analysis of fuel sales and fleet size, suggest that the relative contribution of diesel vehicles to overall NO(x) levels has increased over time in the city. Despite the impressive increase in the size of the vehicle fleet between 2000 and 2006, the early morning ambient concentrations of CO and NO(x) have not increased accordingly, probably due to the reported low removal rates of older vehicles, which do not have emissions control technologies, and partially due to the much lower emissions from newer gasoline vehicles. This indicates that an emission-based air quality improvement strategy targeting large reductions of emissions from mobile sources should be directed towards a significant increase of the removal rate of older, highly-polluting, vehicles.
Application of positive matrix factorization to on-road measurements for source apportionment of diesel- and gasoline-powered vehicle emissions in Mexico City
Thornhill, D. A.; Williams, A. E.; Onasch, T. B.; Wood, E.; Herndon, S. C.; Kolb, C. E.; Knighton, W. B.; Zavala, M.; Molina, L. T.; Marr, Linsey C. (Copernicus Publications, 2010)
The goal of this research is to quantify diesel- and gasoline-powered motor vehicle emissions within the Mexico City Metropolitan Area (MCMA) using on-road measurements captured by a mobile laboratory combined with positive matrix factorization (PMF) receptor modeling. During the MCMA-2006 ground-based component of the MILAGRO field campaign, the Aerodyne Mobile Laboratory (AML) measured many gaseous and particulate pollutants, including carbon dioxide, carbon monoxide (CO), nitrogen oxides (NOx), benzene, toluene, alkylated aromatics, formaldehyde, acetaldehyde, acetone, ammonia, particle number, fine particulate mass (PM2.5), and black carbon (BC). These serve as inputs to the receptor model, which is able to resolve three factors corresponding to gasoline engine exhaust, diesel engine exhaust, and the urban background. Using the source profiles, we calculate fuel-based emission factors for each type of exhaust. The MCMA's gasoline-powered vehicles are considerably dirtier, on average, than those in the US with respect to CO and aldehydes. Its diesel-powered vehicles have similar emission factors of NOx and higher emission factors of aldehydes, particle number, and BC. In the fleet sampled during AML driving, gasoline-powered vehicles are found to be responsible for 97% of total vehicular emissions of CO, 22% of NOx, 95-97% of each aromatic species, 72-85% of each carbonyl species, 74% of ammonia, negligible amounts of particle number, 26% of PM2.5, and 2% of BC; diesel-powered vehicles account for the balance. Because the mobile lab spent 17% of its time waiting at stoplights, the results may overemphasize idling conditions, possibly resulting in an underestimate of NOx and overestimate of CO emissions. On the other hand, estimates of the inventory that do not correctly account for emissions during idling are likely to produce bias in the opposite direction.The resulting fuel-based estimates of emissions are lower than in the official inventory for CO and NOx and higher for VOCs. For NOx, the fuel-based estimates are lower for gasoline-powered vehicles but higher for diesel-powered ones compared to the official inventory. While conclusions regarding the inventory should be interpreted with care because of the small sample size, 3.5 h of driving, the discrepancies with the official inventory agree with those reported in other studies.
Spatial distribution of imperviousness and the space-time variability of rainfall, runoff generation, and routing
Mejia, Alfonso I.; Moglen, Glenn E. (American Geophysical Union, 2010-07-01)
We study the relationship between the spatial distribution of imperviousness and the space-time variability of rainfall, runoff generation, and hydrologic response. For this study we follow an analytical framework that is able to represent space-time variability and use it to determine relationships for quantities commonly used in hydrology, for example, the amount of rainfall excess, the total runoff from a storm, the runoff ratio of developed land use to undeveloped land use, and the mean time and variance of the runoff time. The relationships are derived such that the space-time variability of rainfall, runoff, and the hydrologic response, and their relative importance, can be identified and compared. In addition, the method allows the separation of pervious and impervious contributions to runoff and the estimation of their relative influence on the hydrologic response. We illustrate the estimation of the relationships from available data and apply them to two cases. In the first case, the space-time variability of rainfall and its interaction with impervious cover is investigated. In the second case, we examine the impacts of the imperviousness pattern on runoff relationships. We find that the imperviousness and rainfall pattern can interact to either increase or decrease the average amount of rainfall excess. We also find that the influence of pervious and impervious contributions on the response can depend on the form of the overall imperviousness pattern. The proposed framework can be a useful tool for identifying the importance of different space-time hydrologic components in mixed pervious-impervious landscapes.
The effects of dietary protein content and manure handling technique on ammonia emissions during short-term storage of dairy cow manure
Sparks, J. A.; Ogejo, Jactone Arogo; Cyriac, J.; Hanigan, Mark D.; Knowlton, Katharine F.; Gay, S. W.; Marr, Linsey C. (American Society of Agricultural and Biological Engineers, 2011)
An improved understanding of the potential for dietary protein manipulation to reduce ammonia emissions from dairy farms during various stages of manure handling is needed for both modeling and policy-making efforts. The objective of this study was to assess the effects of dietary protein manipulation on ammonia emissions from relatively freshly voided dairy cow manure in three types of removal systems: scraped manure removal systems, flushed manure removal systems, and flushed manure removal systems with a solids separator. Emissions were measured using a dynamic flux chamber for 12 h or more. Ammonia fluxes and emission factors per mass of manure were not affected by dietary protein content because fluxes depended mainly on total ammoniacal nitrogen (TAN) concentration, which did not vary with diet. However, emissions on a per-cow basis were 12% lower with the diet containing 15.0% crude protein as compared to the one with 17.8% (a change in crude protein of 16%) due to reduced urine output. The largest absolute impact of dietary protein manipulation would be with separated liquids because their emission factor was approximately four times higher than for the other types of manure. While dietary protein manipulation can reduce ammonia emissions from manure during long-term storage, its effectiveness in the hours immediately after manure is excreted is limited because emissions are more sensitive to other factors, including temperature and extent of mixing of the manure, that vary widely under real operating conditions on a farm.
A Case Study: Educating Transportation Engineers with Simulation Software
Luken, Brittany Lynn; Hotle, Susan; Alemdar, Meltem; Garrow, Laurie A. (2011 ASEE Annual Conference & Exposition, 2011)
Evaluation of Resiliency of Transportation Networks After Disasters
Freckleton, Derek; Heaslip, Kevin Patrick; Louisell, William; Collura, John (The National Academies of Sciences, Engineering, and Medicine, 2012)
The resiliency of infrastructure, particularly as related to transportation networks, is essential to any society. This resiliency is especially vital in the aftermath of disasters. Recent events around the globe, including Hurricane Katrina and significant seismic events in Haiti, Chile, and Japan, have increased the awareness and the importance of resiliency. Transportation systems are key to response and recovery. These systems must withstand stress, maintain baseline service levels, and be stout enough in physical design and operational concept to provide restoration to the system. Analysis of a transportation network’s resiliency before a disruptive event will help decision makers identify specific weaknesses within the network so that investments and improvement projects are prioritized appropriately. Previous research in quantification of network resiliency was expanded into a proposed methodology, through which understanding and applying concepts of network resiliency could preclude many devastating effects of destabilizing events and preserve the quality of life and economic stability.
Excretion of antibiotic resistance genes by dairy calves fed milk replacers with varying doses of antibiotics
Thames, Callie H.; Pruden, Amy; James, Robert E.; Ray, Partha P.; Knowlton, Katharine F. (Frontiers, 2012-01-01)
Elevated levels of antibiotic resistance genes (ARGs) in soil and water have been linked to livestock farms and in some cases feed antibiotics may select for antibiotic resistant gut microbiota. The purpose of this study was to examine the establishment of ARGs in the feces of calves receiving milk replacer containing no antibiotics versus subtherapeutic or therapeutic doses of tetracycline and neomycin. The effect of antibiotics on calf health was also of interest.
Role of coexisting tetragonal regions in the rhombohedral phase of Na0.5Bi0.5TiO3-xat.%BaTiO3 crystals on enhanced piezoelectric properties on approaching the morphotropic phase boundary
Yao, Jianjun; Monsegue, Niven; Murayama, Mitsuhiro; Leng, W. N.; Reynolds, William T. Jr.; Zhang, Qinhui; Luo, Haosu; Li, Jiefang; Ge, Wenwei; Viehland, Dwight D. (AIP Publishing, 2012-01-01)
The ferroelectric domain and local structures of Na0.5Bi0.5TiO3-xat.%BaTiO3 (NBT-x%BT) crystals for x = 0, 4.5, and 5.5 have been investigated by transmission electron microscopy. The results show that the size of polar nano-regions was refined with increasing xat. %BT. The tetragonal phase volume fraction, as identified by in-phase octahedral tilting, was found to be increased with BT. The findings indicate that the large electric field induced strains in morphotropic phase boundary compositions of NBT-x%BT originate not only from polarization rotation but also polarization extension. (C) 2012 American Institute of Physics. [doi: 10.1063/1.3673832]
Relationship between Humidity and Influenza A Viability in Droplets and Implications for Influenza's Seasonality
Yang, Wan; Elankumaran, Subbiah; Marr, Linsey C. (PLOS, 2012-10-03)
Humidity has been associated with influenza’s seasonality, but the mechanisms underlying the relationship remain unclear. There is no consistent explanation for influenza’s transmission patterns that applies to both temperate and tropical regions. This study aimed to determine the relationship between ambient humidity and viability of the influenza A virus (IAV) during transmission between hosts and to explain the mechanisms underlying it. We measured the viability of IAV in droplets consisting of various model media, chosen to isolate effects of salts and proteins found in respiratory fluid, and in human mucus, at relative humidities (RH) ranging from 17% to 100%. In all media and mucus, viability was highest when RH was either close to 100% or below ,50%. When RH decreased from 84% to 50%, the relationship between viability and RH depended on droplet composition: viability decreased in saline solutions, did not change significantly in solutions supplemented with proteins, and increased dramatically in mucus. Additionally, viral decay increased linearly with salt concentration in saline solutions but not when they were supplemented with proteins. There appear to be three regimes of IAV viability in droplets, defined by humidity: physiological conditions (,100% RH) with high viability, concentrated conditions (50% to near 100% RH) with lower viability depending on the composition of media, and dry conditions (,50% RH) with high viability. This paradigm could help resolve conflicting findings in the literature on the relationship between IAV viability in aerosols and humidity, and results in human mucus could help explain influenza’s seasonality in different regions.
Experimental determination of the oral bioavailability and bioaccessibility of lead particles
Deshommes, Elise; Tardif, Robert; Edwards, Marc A.; Sauvé, Sébastien; Prévost, Michèle (2012-11-22)
In vivo estimations of Pb particle bioavailability are costly and variable, because of the nature of animal assays. The most feasible alternative for increasing the number of investigations carried out on Pb particle bioavailability is in vitro testing. This testing method requires calibration using in vivo data on an adapted animal model, so that the results will be valid for childhood exposure assessment. Also, the test results must be reproducible within and between laboratories. The Relative Bioaccessibility Leaching Procedure, which is calibrated with in vivo data on soils, presents the highest degree of validation and simplicity. This method could be applied to Pb particles, including those in paint and dust, and those in drinking water systems, which although relevant, have been poorly investigated up to now for childhood exposure assessment.
Dietary biomarkers: advances, limitations and future directions
Hedrick, Valisa E.; Dietrich, Andrea M.; Estabrooks, Paul A.; Savla, Jyoti S.; Serrano, Elena L.; Davy, Brenda M. (Biomed Central, 2012-12-14)
The subjective nature of self-reported dietary intake assessment methods presents numerous challenges to obtaining accurate dietary intake and nutritional status. This limitation can be overcome by the use of dietary biomarkers, which are able to objectively assess dietary consumption (or exposure) without the bias of self-reported dietary intake errors. The need for dietary biomarkers was addressed by the Institute of Medicine, who recognized the lack of nutritional biomarkers as a knowledge gap requiring future research. The purpose of this article is to review existing literature on currently available dietary biomarkers, including novel biomarkers of specific foods and dietary components, and assess the validity, reliability and sensitivity of the markers. This review revealed several biomarkers in need of additional validation research; research is also needed to produce sensitive, specific, cost-effective and noninvasive dietary biomarkers. The emerging field of metabolomics may help to advance the development of food/nutrient biomarkers, yet advances in food metabolome databases are needed. The availability of biomarkers that estimate intake of specific foods and dietary components could greatly enhance nutritional research targeting compliance to national recommendations as well as direct associations with disease outcomes. More research is necessary to refine existing biomarkers by accounting for confounding factors, to establish new indicators of specific food intake, and to develop techniques that are cost-effective, noninvasive, rapid and accurate measures of nutritional status.

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