A comprehensive model to determine the effects of temperature and species fluctuations on reaction rates in turbulent reacting flows

The use of probability theory to determine the effects of turbulent fluctuations on reaction rates in turbulent combustion systems is briefly reviewed. Results are presented for the effect of species fluctuations in particular. It is found that turbulent fluctuations of species act to reduce the reaction rates, in contrast with the temperature fluctuations previously determined to increase Arrhenius reaction rate constants. For the temperature fluctuations, a criterion is set forth for determining if, in a given region of a turbulent flow field, the temperature can be expected to exhibit ramp like fluctuations. Using the above results, along with results previously obtained, a model is described for testing the effects of turbulent fluctuations of temperature and species on reaction rates in computer programs dealing with turbulent reacting flows. An alternative model which employs three variable probability density functions (temperature and two species) and is currently being formulated is discussed as well

MSAT-X electronically steered phased array antenna system

A low profile electronically steered phased array was successfully developed for the Mobile Satellite Experiment Program (MSAT-X). The newly invented cavity-backed printed crossed-slot was used as the radiating element. The choice of this element was based on its low elevation angle gain coverage and low profile. A nineteen-way radial type unequal power divider and eighteen three-bit diode phase shifters constitute the beamformer module which is used to scan the beams electronically. A complete hybrid mode pointing system was also developed. The major features of the antenna system are broad coverage, low profile, and fast acquisition and tracking performance, even under fading conditions. Excellent intersatellite isolation (better than 26 dB) was realized, which will provide good quality mobile satellite communication in the future

When they Come Home: Posttraumatic Stress, Moral Injury, and Spiritual Consequences for Veterans

Clergy supervisors, as they live out their various roles as models, educators, consultants, and direct providers of pastoral care, have powerful opportunities to influence and shape the responses of religious communities to the needs of returning veterans. Four key suggestions are offered to assist in ministry to/with veterans

Information requirements for guidance and control systems

Control or guidance system performance dependency on information handling by subsystem

A comprehensive model to determine the effects of temperature and species fluctuations on reaction rates in turbulent reacting flows

A principal element to be derived from modeling turbulent reacting flows is an expression for the reaction rates of the various species involved in any particular combustion process under consideration. A temperature-derived most-likely probability density function (pdf) was used to describe the effects of temperature fluctuations on the Arrhenius reaction rate constant. A most-likely bivariate pdf described the effects of temperature and species concentrations fluctuations on the reaction rate. A criterion is developed for the use of an "appropriate" temperature pdf. The formulation of models to calculate the mean turbulent Arrhenius reaction rate constant and the mean turbulent reaction rate is considered and the results of calculations using these models are presented

Characterizing ozone production and response under different meteorological conditions in Mexico City

International audienceTropospheric photochemistry, particularly the formation of ozone (O3), depends not only on pollutant emissions, but also on meteorological conditions. In this study a 3-D chemical transport model CAMx was employed to investigate the O3 formation and its response to emission reductions under three distinctively different meteorological conditions ("Cold Surge", "O3-North" and "O3-South") in the Mexico City Metropolitan Area during the MCMA-2003 field measurement campaign. The O3 formation characteristics and sensitivity to emissions changes were found to be weakly dependent on the meteorological conditions. The evolution of O3 formation and sensitivity were also examined along the photochemical plume transport pathway. The midday O3 production was found to undergo a rapid increase in a narrow range of chemical aging, while plumes in the downwind were characterized with low and constant O3 production, and plumes along their transport pathway were featured by a combination of the two. The O3 formation was more VOC sensitive near the source area, but as the plume became chemically aged, O3 formation became progressively VOC insensitive and more NOx sensitive

Characterizing ozone production in the Mexico City Metropolitan Area: a case study using a chemical transport model

International audienceAn episodic simulation is conducted to characterize ozone (O3) photochemical production and investigate its sensitivity to emission changes of ozone precursors in the Mexico City Metropolitan Area (MCMA) using the Comprehensive Air Quality Model with extensions (CAMx). High Ox (O3+NO2) photochemical production rates of 10?80 ppb/h are predicted due to the high reactivity of volatile organic compounds (VOCs) in which alkanes, alkenes, and aromatics exert comparable contributions. The predicted ozone production efficiency is between 4?10 O3 molecules per NOx molecule oxidized, and increases with VOC-to-NO2 reactivity ratio. Process apportionment analyses indicate significant outflow of pollutants such as O3 and peroxyacetyl nitrate (PAN) from the urban area to the surrounding regional environment. PAN is not in chemical-thermal equilibrium during the photochemically active periods. Sensitivity studies of O3 production suggest that O3 formation in the MCMA urban region with less chemical aging (NOz/NOy3 production and its sensitivities to precursors suggest that midday O3 formation during this episode is VOC sensitive in the urban region on the basis of the current emissions inventory. More episodic studies are needed to construct a comprehensive and representative picture of the O3 production characteristics and its response to emission controls

Using 3DVAR data assimilation system to improve ozone simulations in the Mexico City basin

This study investigates the improvement of ozone (O<sub>3</sub>) simulations in the Mexico City basin using a three-dimensional variational (3DVAR) data assimilation system in meteorological simulations during the MCMA-2003 field measurement campaign. Meteorological simulations from the NCAR/Penn State mesoscale model (MM5) are used to drive photochemical simulations with the Comprehensive Air Quality Model with extensions (CAMx) during a four-day episode on 13–16 April 2003. The simulated wind circulation, temperature, and humidity fields in the basin with the data assimilation are found to be more consistent with the observations than those from the reference deterministic forecast. This leads to improved simulations of plume position, peak O<sub>3</sub> timing, and peak O<sub>3</sub> concentrations in the photochemical model. The improvement in O<sub>3</sub> simulations is especially strong during the daytime. The results demonstrate the importance of applying data assimilation in meteorological simulations for air quality studies in the Mexico City basin

Xenosurveillance reflects traditional sampling techniques for the identification of human pathogens: A comparative study in West Africa

BACKGROUND: Novel surveillance strategies are needed to detect the rapid and continuous emergence of infectious disease agents. Ideally, new sampling strategies should be simple to implement, technologically uncomplicated, and applicable to areas where emergence events are known to occur. To this end, xenosurveillance is a technique that makes use of blood collected by hematophagous arthropods to monitor and identify vertebrate pathogens. Mosquitoes are largely ubiquitous animals that often exist in sizable populations. As well, many domestic or peridomestic species of mosquitoes will preferentially take blood-meals from humans, making them a unique and largely untapped reservoir to collect human blood. METHODOLOGY/PRINCIPAL FINDINGS: We sought to take advantage of this phenomenon by systematically collecting blood-fed mosquitoes during a field trail in Northern Liberia to determine whether pathogen sequences from blood engorged mosquitoes accurately mirror those obtained directly from humans. Specifically, blood was collected from humans via finger-stick and by aspirating bloodfed mosquitoes from the inside of houses. Shotgun metagenomic sequencing of RNA and DNA derived from these specimens was performed to detect pathogen sequences. Samples obtained from xenosurveillance and from finger-stick blood collection produced a similar number and quality of reads aligning to two human viruses, GB virus C and hepatitis B virus. CONCLUSIONS/SIGNIFICANCE: This study represents the first systematic comparison between xenosurveillance and more traditional sampling methodologies, while also demonstrating the viability of xenosurveillance as a tool to sample human blood for circulating pathogens

Dramatically Increased Rearrangement and Peripheral Representation of Vβ14 Driven by the 3′Dβ1 Recombination Signal Sequence

AbstractV(D)J recombination is targeted by short recombination signal (RS) sequences that are relatively conserved but exhibit natural sequence variations. To evaluate the potential of RS sequence variations to determine the primary and peripheral TCRβ repertoire, we generated mice containing specific replacement of the endogenous Vβ14 RS with the 3′Dβ1 RS (Vβ14/3′DβRS). These mice exhibited a dramatic increase in Vβ14+ thymocyte numbers at the expense of thymocytes expressing other Vβs. In addition, the percentage of peripheral Vβ14+ αβ T lymphocytes was similarly increased. Strikingly, this altered Vβ repertoire resulted predominantly from a higher relative level of primary Vβ14/3′DβRS rearrangement to DβJβ complexes, despite the ability of the 3′Dβ1 RS to break B12/23 restriction and allow direct rearrangement of Vβ14/3′DβRS to Jβ segments