Conditional-moment Closure with Differential Diffusion for Soot Evolution in Fire

The conditional-moment closure (CMC) equation for the evolution of a large Lewis number scalar, soot, is derived starting from the joint probability density function (pdf) equation for the gas-phase mixture fraction, ξ g , and the soot mass fraction, Y s . Unlike previous approaches starting with the joint pdf, the residual terms that result from the typical closure models were retained. A new formulation of the one-dimensional turbulence (ODT) model suitable for spatially evolving flows with buoyant acceleration and radiative transport in participating media was employed to carry out simulations of a prototypical ethene fire. The resulting ODT evolution of ξ g and Y s was used to assess the significance of various terms in the CMC equation including the residual correlations. The terms involving differential diffusion are found to be important along with the soot source terms and the large-scale evolution of both ξ g and Y s . Of particular importance in the regions in mixture-fraction space around the soot production and consumption is a residual term, not previously identified, related to the correlation between the differential diffusion and Y s . This term results in a diffusion-like behavior of Y s in the mixture fraction coordinate that has an apparent Lewis number near unity. In scenarios where the large Lewis number component is a non-negligible component of the mixture fraction (i.e., large soot loading), it is found easier to employ a mixture fraction neglecting this component. Such a mixture-fraction variable has a chemical source term, but this appears easier to model than the differential diffusion and dissipation terms that result when the large Lewis number component is retained in the mixture-fraction definition

Difficult encounters around "monkey cheeks": Farmers' interests and the design of flood retention areas in Thailand

Flood retention areas are being increasingly promoted for flood risk management. People living in these areas will accept them if their interests are taken into account. The present study analyses the extent to which farmers' interests were taken into account in two flood retention projects in Thailand. A feasibility study was conducted in preparation for the first project which included public participation. The second project was a pilot project implemented in the same zone at a small scale. Participants in the public participation process and farmers living in proposed flood retention areas were interviewed for the purpose of the present study. Agreement could have been reached between the farmers and the public agencies concerning the flood retention areas. However, the participation process did not enable frank discussion about the conditions under which farmers would accept the project. The second project was designed without public participation and offered very little compensation to farmers. In countries marked by power imbalances in water resources management, public agencies may impose flood retention areas, but the absence of agreements with farmers can reduce the effectiveness of the measure. Reaching such agreements requires challenging the imbalanced power relationships between farmers and public agencies

An S2 Fluorescence Model for Interpreting High-Resolution Cometary Spectra. I. Model Description and Initial Results

A new versatile model providing S2 fluorescence spectrum as a function of time is developed with the aim of interpreting high resolution cometary spectra. For the S2 molecule, it is important to take into account both chemical and dynamic processes because S2 has a short lifetime and is confined in the inner coma where these processes are most important. The combination of the fluorescence model with a global coma model allows for the comparison with observations of column densities taken through an aperture and for the analysis of S2 fluorescence in different parts of the coma. Moreover, the model includes the rotational structure of the molecule. Such a model is needed for interpreting recent high spectral resolution observations of cometary S2. A systematic study of the vibrational-rotational spectrum of S2 is undertaken, including relevant effects, such as non-equilibrium state superposition and the number density profile within the coma due to dynamics and chemistry, to investigate the importance of the above effects on the scale length and abundance of S2 in comets.Comment: 20 pages, 7 figure

Photorefractive Laser Ultrasound Spectroscopy for Materials Characterization

Ultrasonic elastic wave motion is often used to measure or characterize material properties. Through the years, many optical techniques have been developed for applications requiring noncontacting ultrasonic measurement. Most of these methods have similar sensitivities and are based on time domain processing using interferometry. Wide bandwidth is typically employed to obtain real- time surface motion under transient conditions. However, some applications, such as structural analysis, are well served by measurements in the frequency domain that record the randomly or continuously excited vibrational resonant spectrum. A significant signal-to-noise ratio improvement is achieved by the reduced bandwidth of the measurement at the expense of measurement speed compared to the time domain methods. Complications often arise due to diffuse surfaces producing speckle that introduces an arbitrary phase component onto the optical wavefront to be recorded. Methods that correct for this effect are actively being investigated today

Evidence for Quantum Interference in SAMs of Arylethynylene Thiolates in Tunneling Junctions with Eutectic Ga-In (EGaIn) Top-Contacts

This paper compares the current density (J) versus applied bias (V) of self-assembled monolayers (SAMs) of three different ethynylthiophenol-functionalized anthracene derivatives of approximately the same thickness with linear-conjugation (AC), cross-conjugation (AQ), and broken-conjugation (AH) using liquid eutectic Ga-In (EGaIn) supporting a native skin (~1 nm thick) of Ga2O3 as a nondamaging, conformal top-contact. This skin imparts non-Newtonian rheological properties that distinguish EGaIn from other top-contacts; however, it may also have limited the maximum values of J observed for AC. The measured values of J for AH and AQ are not significantly different (J ≈ 10-1 A/cm2 at V = 0.4 V). For AC, however, J is 1 (using log averages) or 2 (using Gaussian fits) orders of magnitude higher than for AH and AQ. These values are in good qualitative agreement with gDFTB calculations on single AC, AQ, and AH molecules chemisorbed between Au contacts that predict currents, I, that are 2 orders of magnitude higher for AC than for AH at 0 < |V| < 0.4 V. The calculations predict a higher value of I for AQ than for AH; however, the magnitude is highly dependent on the position of the Fermi energy, which cannot be calculated precisely. In this sense, the theoretical predictions and experimental conclusions agree that linearly conjugated AC is significantly more conductive than either cross-conjugated AQ or broken conjugate AH and that AQ and AH cannot necessarily be easily differentiated from each other. These observations are ascribed to quantum interference effects. The agreement between the theoretical predictions on single molecules and the measurements on SAMs suggest that molecule-molecule interactions do not play a significant role in the transport properties of AC, AQ, and AH.

Diesel Exhaust Induces Mitochondrial Dysfunction, Hyperlipidemia, and Liver Steatosis.

ObjectiveAir pollution is associated with increased cardiovascular morbidity and mortality, as well as dyslipidemia and metabolic syndrome. Our goal was to dissect the mechanisms involved. Approach and Results: We assessed the effects of exposure to air pollution on lipid metabolism in mice through assessment of plasma lipids and lipoproteins, oxidized fatty acids 9-HODE (9-hydroxyoctadecadienoic) and 13-HODE (13-hydroxyoctadecadienoic), lipid, and carbohydrate metabolism. Findings were corroborated, and mechanisms were further assessed in HepG2 hepatocytes in culture. ApoE knockout mice exposed to inhaled diesel exhaust (DE, 6 h/d, 5 days/wk for 16 weeks) exhibited elevated plasma cholesterol and triglyceride levels, increased hepatic triglyceride content, and higher hepatic levels of 9-HODE and 13-HODE, as compared to control mice exposed to filtered air. A direct effect of DE exposure on hepatocytes was demonstrated by treatment of HepG2 cells with a methanol extract of DE particles followed by loading with oleic acid. As observed in vivo, this led to increased triglyceride content and significant downregulation of ACAD9 mRNA expression. Treatment of HepG2 cells with DE particles and oleic acid did not alter de novo lipogenesis but inhibited total, mitochondrial, and ATP-linked oxygen consumption rate, indicative of mitochondrial dysfunction. Treatment of isolated mitochondria, prepared from mouse liver, with DE particles and oleic acid also inhibited mitochondrial complex activity and β-oxidation.ConclusionsDE exposure leads to dyslipidemia and liver steatosis in ApoE knockout mice, likely due to mitochondrial dysfunction and decreased lipid catabolism

Estimating the Impact of Newly Arrived Foreign-Born Persons on Tuberculosis in the United States

Background: Among approximately 163.5 million foreign-born persons admitted to the United States annually, only 500,000 immigrants and refugees are required to undergo overseas tuberculosis (TB) screening. It is unclear what extent of the unscreened nonimmigrant visitors contributes to the burden of foreign-born TB in the United States. Methodology/Principal Findings: We defined foreign-born persons within 1 year after arrival in the United States as ‘‘newly arrived’’, and utilized data from U.S. Department of Homeland Security, U.S. Centers for Disease Control and Prevention, and World Health Organization to estimate the incidence of TB among newly arrived foreign-born persons in the United States. During 2001 through 2008, 11,500 TB incident cases, including 291 multidrug-resistant TB incident cases, were estimated to occur among 20,989,738 person-years for the 1,479,542,654 newly arrived foreign-born persons in the United States. Of the 11,500 estimated TB incident cases, 41.6 % (4,783) occurred among immigrants and refugees, 36.6 % (4,211) among students/ exchange visitors and temporary workers, 13.8 % (1,589) among tourists and business travelers, and 7.3 % (834) among Canadian and Mexican nonimmigrant visitors without an I-94 form (e.g., arrival-departure record). The top 3 newly arrived foreign-born populations with the largest estimated TB incident cases per 100,000 admissions were immigrants and refugees from high-incidence countries (e.g., 2008 WHO-estimated TB incidence rate of $100 cases/100,000 population/ year; 235.8 cases/100,000 admissions, 95 % confidence interval [CI], 228.3 to 243.3), students/exchange visitors an