46 CFR 164.120-7 - Acceptance criteria.

Code of Federal Regulations, 2013 CFR

2013-10-01

... Mechanical & Physical Properties of Glass Cloth Base Plastic Laminate (Lengthwise direction of test specimens is parallel to the warp direction of glass fabric.) (1) Tested Under Standard Conditions: (i... ASTM D 695 241 MPa (35,000 ln/in2). (v) Fire retardant MSC Circ. 1006 Pass. (vi) Water absorption, 24...

46 CFR 164.120-7 - Acceptance criteria.

Code of Federal Regulations, 2014 CFR

2014-10-01

... Mechanical & Physical Properties of Glass Cloth Base Plastic Laminate (Lengthwise direction of test specimens is parallel to the warp direction of glass fabric.) (1) Tested Under Standard Conditions: (i... ASTM D 695 241 MPa (35,000 ln/in2). (v) Fire retardant MSC Circ. 1006 Pass. (vi) Water absorption, 24...

46 CFR 164.120-7 - Acceptance criteria.

Code of Federal Regulations, 2012 CFR

2012-10-01

... Mechanical & Physical Properties of Glass Cloth Base Plastic Laminate (Lengthwise direction of test specimens is parallel to the warp direction of glass fabric.) (1) Tested Under Standard Conditions: (i... ASTM D 695 241 MPa (35,000 ln/in2). (v) Fire retardant MSC Circ. 1006 Pass. (vi) Water absorption, 24...

Absorption properties and graphitic carbon emission factors of forest fire aerosols

Treesearch

E.M. Patterson; Charles K. McMahon; D.E. Ward

1986-01-01

Abstract. Data on the optical absorption properties (expressed as a specific absorption, Ba) of the smoke emissions from fires with forest fuels have been determined for a series of low-intensity field fires and a series of laboratory scale fires. The B, data have been used to estimate the emission factors for graphitic...

Triple-effect absorption refrigeration system with double-condenser coupling

DOEpatents

DeVault, R.C.; Biermann, W.J.

1993-04-27

A triple effect absorption refrigeration system is provided with a double-condenser coupling and a parallel or series circuit for feeding the refrigerant-containing absorbent solution through the high, medium, and low temperature generators utilized in the triple-effect system. The high temperature condenser receiving vaporous refrigerant from the high temperature generator is double coupled to both the medium temperature generator and the low temperature generator to enhance the internal recovery of heat within the system and thereby increase the thermal efficiency thereof.

Triple-effect absorption refrigeration system with double-condenser coupling

DOEpatents

DeVault, Robert C.; Biermann, Wendell J.

1993-01-01

A triple effect absorption refrigeration system is provided with a double-condenser coupling and a parallel or series circuit for feeding the refrigerant-containing absorbent solution through the high, medium, and low temperature generators utilized in the triple-effect system. The high temperature condenser receiving vaporous refrigerant from the high temperature generator is double coupled to both the medium temperature generator and the low temperature generator to enhance the internal recovery of heat within the system and thereby increase the thermal efficiency thereof.

Multiphoton near-infrared femtosecond laser pulse-induced DNA damage with and without the photosensitizer proflavine.

PubMed

Shafirovich, V; Dourandin, A; Luneva, N P; Singh, C; Kirigin, F; Geacintov, N E

1999-03-01

The excitation of pBr322 supercoiled plasmid DNA with intense near-IR 810 nm fs laser pulses by a simultaneous multiphoton absorption mechanism results in single-strand breaks after treatment of the irradiated samples with Micrococcus luteus UV endonuclease. This enzyme cleaves DNA strands at sites of cyclobutane dimers that are formed by the simultaneous absorption of three (or more) 810 nm IR photons (pulse width approximately 140 fs, 76 MHz pulse repetition, average power output focused through 10x microscope objective is approximately 1.2 MW/cm2). Direct single-strand breaks (without treatment with M. luteus) were not observed under these conditions. However, in the presence of 6 microM of the intercalator proflavine (PF), both direct single- and double-strand breaks are observed under conditions where substantial fractions of undamaged supercoiled DNA molecules are still present. The fraction of direct double-strand breaks is 30 +/- 5% of all measurable strand cleavage events, is independent of dosage (up to 6.4 GJ/cm2) and is proportional to In, where I is the average power/area of the 810 nm fs laser pulses, and n = 3 +/- 1. The nicking of two DNA strands in the immediate vicinity of the excited PF molecules gives rise to this double-strand cleavage. In contrast, excitation of the same samples under low-power, single-photon absorption conditions (approximately 400-500 nm) gives rise predominantly to single-strand breaks, but some double-strand breaks are observed at the higher dosages. Thus, single-photon excitation with 400-500 nm light and multiphoton activation of PF by near-IR fs laser pulses produces different distributions of single- and double-strand breaks. These results suggest that DNA strand cleavage originates from unrelaxed, higher excited states when PF is excited by simultaneous IR multiphoton absorption processes.

Mobile SO2 and NO2 DIAL Lidar system for enforcement use

NASA Astrophysics Data System (ADS)

Cunningham, David L.; Pence, William H.; Moody, Stephen E.

1994-06-01

A self-contained mobile differential absorption lidar (DIAL) system intended for measuring SO2 and NO2 concentrations from stationary combustion sources has been completed for enforcement use. The system uses tunable Ti:sapphire laser technology, with nonlinear conversion to the blue and UV absorption wavelengths. Separate tunable laser oscillators at slightly offset wavelengths are pumped on alternate pulses of a 20 Hz doubled Nd:YAG pump laser; the outputs are amplified in a common amplifier, doubled or tripled, and transmitted toward a target region via a two-mirror beam director. Scattered atmospheric returns are collected in a 0.27-m-diameter telescope, detected with a filtered photomultiplier, and digitized and stored for analysis. Extensive software-based control and display windows are provided for operator interaction with the system. The DIAL system is built into a small motor coach. Gasoline- powered electrical generation, laser cooling, and air conditioning services are present. Separate computers are provided for simultaneous data collection and data analysis activities, with shared data base access. A laser printer supplies hardcopy output. The system includes the capability for automatic data collection at a series of scanner angles, and computer processing to present results in a variety of formats. Plumes from coal-fired and mixed-fuel-fired combusters have been examined for NO2 and SO2 content. Noise levels of a few parts per million are reached with averaging times of less than one minute.

Molten Salt Promoting Effect in Double Salt CO2 Absorbents

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Keling; Li, Xiaohong S.; Chen, Haobo

2016-01-01

The purpose of this paper is to elaborate on the concept of molten salts as catalysts for CO2 absorption by MgO, and extend these observations to the MgO-containing double salt oxides. We will show that the phenomena involved with CO2 absorption by MgO and MgO-based double salts are similar and general, but with some important differences. This paper focuses on the following key concepts: i) identification of conditions that favor or disfavor participation of isolated MgO during double salt absorption, and investigation of methods to increase the absorption capacity of double salt systems by including MgO participation; ii) examination ofmore » the relationship between CO2 uptake and melting point of the promoter salt, leading to the recognition of the role of pre-melting (surface melting) in these systems; and iii) extension of the reaction pathway model developed for the MgO-NaNO3 system to the double salt systems. This information advances our understanding of MgO-based CO2 absorption systems for application with pre-combustion gas streams.« less

Optical bandgap of semiconductor nanostructures: Methods for experimental data analysis

NASA Astrophysics Data System (ADS)

Raciti, R.; Bahariqushchi, R.; Summonte, C.; Aydinli, A.; Terrasi, A.; Mirabella, S.

2017-06-01

Determination of the optical bandgap (Eg) in semiconductor nanostructures is a key issue in understanding the extent of quantum confinement effects (QCE) on electronic properties and it usually involves some analytical approximation in experimental data reduction and modeling of the light absorption processes. Here, we compare some of the analytical procedures frequently used to evaluate the optical bandgap from reflectance (R) and transmittance (T) spectra. Ge quantum wells and quantum dots embedded in SiO2 were produced by plasma enhanced chemical vapor deposition, and light absorption was characterized by UV-Vis/NIR spectrophotometry. R&T elaboration to extract the absorption spectra was conducted by two approximated methods (single or double pass approximation, single pass analysis, and double pass analysis, respectively) followed by Eg evaluation through linear fit of Tauc or Cody plots. Direct fitting of R&T spectra through a Tauc-Lorentz oscillator model is used as comparison. Methods and data are discussed also in terms of the light absorption process in the presence of QCE. The reported data show that, despite the approximation, the DPA approach joined with Tauc plot gives reliable results, with clear advantages in terms of computational efforts and understanding of QCE.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sierra Thermal /Fluid Team

The SIERRA Low Mach Module: Fuego along with the SIERRA Participating Media Radiation Module: Syrinx, henceforth referred to as Fuego and Syrinx, respectively, are the key elements of the ASCI fire environment simulation project. The fire environment simulation project is directed at characterizing both open large-scale pool fires and building enclosure fires. Fuego represents the turbulent, buoyantly-driven incompressible flow, heat transfer, mass transfer, combustion, soot, and absorption coefficient model portion of the simulation software. Syrinx represents the participating-media thermal radiation mechanics. This project is an integral part of the SIERRA multi-mechanics software development project. Fuego depends heavily upon the coremore » architecture developments provided by SIERRA for massively parallel computing, solution adaptivity, and mechanics coupling on unstructured grids.« less

Application of petrographic examination techniques to the assessment of fire-damaged concrete and masonry structures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ingham, Jeremy P., E-mail: inghamjp@halcrow.com

The number of building fires has doubled over the last 50 years. There has never been a greater need for structures to be assessed for fire damage to ensure safety and enable appropriate repairs to be planned. Fortunately, even after a severe fire, concrete and masonry structures are generally capable of being repaired rather than demolished. By allowing direct examination of microcracking and mineralogical changes, petrographic examination has become widely used to determine the depth of fire damage for reinforced concrete elements. Petrographic examination can also be applied to fire-damaged masonry structures built of materials such as stone, brick andmore » mortar. Petrography can ensure accurate detection of damaged geomaterials, which provides cost savings during building repair and increased safety reassurance. This paper comprises a review of the role of petrography in fire damage assessments, drawing on a range of actual fire damage investigations.« less

Enhancement of pump absorption efficiency by bending and twisting of double clad rare earth doped fibers (Conference Presentation)

NASA Astrophysics Data System (ADS)

Koška, Pavel; Peterka, Pavel; Doya, Valérie; Aubrecht, Jan; Kasik, Ivan; Podrazký, Ondřej

2017-05-01

High-power operation of fiber lasers was enabled by the invention of cladding-pumping in a double-clad fiber structure. Because of existence of so called skew rays in the inner clad of the fiber, pump absorption saturates along the fiber and pumping becomes inefficient. First studies of pump absorption efficiency enhancement were focused on fibers with broken circular symmetry of inner cladding eliminating skew rays [1,2]. Later, techniques of unconventional fiber coiling were proposed [3]. However, theoretical studies were limited to the assumption of a straight fiber. Even recently, the rigorous model accounting for fiber bending and twisting was described [4-6]. It was found that bending of the fiber influences modal spectra of the pump radiation and twisting provides quite efficient mode-scrambling. These effects in a synergic manner significantly enhances pump absorption rate in double clad fibers and improves laser system efficiency. In our contribution we review results of numerical modelling of pump absorption in various types of double-clad fibers, e.g., with cross section shape of hexagon, stadium, and circle; two-fiber bundle (so-called GTWave fiber structure) a panda fibers are also analyzed. We investigate pump field modal spectra evolution in hexagonally shaped fiber in straight, bended, and simultaneously bended and twisted fiber which brings new quality to understanding of the mode-scrambling and pump absorption enhancement. Finally, we evaluate the impact of enhanced pump absorption on signal gain in the fiber. These results can have practical impact in construction of fiber lasers: with pump absorption efficiency optimized by our new model (the other models did not take into account fiber twist), the double-clad fiber of shorter length can be used in the fiber lasers and amplifiers. In such a way the harmful influence of background losses and nonlinear effects can be minimized. [1] Doya, V., Legrand, O., Mortessagne, F., "Optimized absorption in a chaotic double-clad fiber amplifier," Opt. Lett., vol. 26, no. 12, pp. 872-874, (2001). [2] Kouznetsov, D., Moloney, J. V., "Efficiency of pump absorption in double-clad fiber amplifiers. II. Broken circular symmetry," J. Opt. Soc. Am. B, vol. 19, no. 6, pp. 1259-1263, June 2002. [3] Li, Y., Jackson, S. D., Fleming, S., "High absorption and low splice loss properties of hexagonal double-clad fiber," IEEE Photonics Technol. Lett., vol 16, no. 11, pp. 2502-2504, Nov. 2004. [4] Ko\\vska, P. and Peterka, P., "Numerical analysis of pump propagation and absorption in specially tailored double-clad rare-earth doped fiber," Optical and Quantum Electronics, vol. 47, no. 9, pp. 3181-3191 (2015). [5] Ko\\vska, P., Peterka, P., and Doya, V., "Numerical modeling of pump absorption in coiled and twisted double-clad fibers," IEEE J. Sel. Top. Quantum Electron., vol. 22, no. 2 (2016). [6] Ko\\vska, P., Peterka, P., Aubrecht, J., Podrazký, O., Todorov, F., Becker, M., Baravets, Y., Honzátko, P., and Kašík, I., "Enhanced pump absorption efficiency in coiled and twisted double-clad thulium-doped fibers," Opt. Express, vol. 24, no. 1, pp. 102-107 (2016).

Simulations of microphysical, radiative, and dynamical processes in a continental-scale forest fire smoke plume

NASA Technical Reports Server (NTRS)

Westphal, Douglas L.; Toon, Owen B.

1991-01-01

The impact of a large forest fire smoke plume on atmospheric processes is studied through a numerical model of meteorology, aerosols, and radiative transfer. The simulated smoke optical depths at 0.63-micron wavelength are in agreement with analyses of satellite data and show values as high as 1.8. The smoke has an albedo of 35 percent, or more than double the clear-sky value, and cools the surface by as much as 5 K. An imaginary refractive index, n sub im, of 0.01 yields results which closely match the observed cooling, single scattering albedo, and the Angstrom wavelength exponent. An n exp im of 0.1, typical of smoke from urban fires, produces 9 K cooling. Coagulation causes the geometric mean radius by number to increase from the initial value of 0.08 micron to a final value of 0.15 micron, while the specific extinction and absorption increase by 40 and 25 percent, respectively.

Quantifying the role of fire in the Earth system - Part 2: Impact on the net carbon balance of global terrestrial ecosystems for the 20th century

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Fang; Bond-Lamberty, Benjamin; Levis, Samuel

Fire is the primary terrestrial ecosystem disturbance agent on a global scale. It affects carbon balance of global terrestrial ecosystems by emitting carbon to atmosphere directly and immediately from biomass burning (i.e., fire direct effect), and by changing net ecosystem productivity and land-use carbon loss in post-fire regions due to biomass burning and fire-induced vegetation mortality (i.e., fire indirect effect). Here, we provide the first quantitative assessment about the impact of fire on the net carbon balance of global terrestrial ecosystems for the 20th century, and investigate the roles of fire direct and indirect effects. This study is done bymore » quantifying the difference between the 20th century fire-on and fire-off simulations with NCAR community land model CLM4.5 as the model platform. Results show that fire decreases net carbon gain of the global terrestrial ecosystems by 1.0 Pg C yr-1 average across the 20th century, as a results of fire direct effect (1.9 Pg C yr-1) partly offset by indirect effect (-0.9 Pg C yr-1). Fire generally decreases the average carbon gains of terrestrial ecosystems in post-fire regions, which are significant over tropical savannas and part of forests in North America and the east of Asia. The general decrease of carbon gains in post-fire regions is because fire direct and indirect effects have similar spatial patterns and the former (to decrease carbon gain) is generally stronger. Moreover, the effect of fire on net carbon balance significantly declines prior to ~1970 with trend of 8 Tg C yr-1 due to increasing fire indirect effect and increases afterward with trend of 18 Tg C yr-1 due to increasing fire direct effect.« less

AMMONIA ABSORPTION/AMMONIUM BISULFATE REGENERATION PILOT PLANT FOR FLUE GAS DESULFURIZATION

EPA Science Inventory

The report gives results of a pilot-plant study of the ammonia absorption/ammonium bisulfate regeneration process for removing SO2 from the stack gas of coal-fired power plants. Data were developed on the effects of such operating variable in the absorption of SO2 by ammoniacal l...

Parameters on plant absortion of double-stranded Ribonucleic acid, dsRNA

USDA-ARS?s Scientific Manuscript database

Efficient absorption of double-stranded Ribonucleic acid, dsRNA, into citrus is critical for effective psyllid management by RNA interference, RNAi. Parameters which might affect absorption into citrus trees and subsequent ingestion by Asian citrus psyllid were evaluated. Age of leaves, variety of c...

Progress on the FIReTIP Diagnostic on NSTX-U

NASA Astrophysics Data System (ADS)

Scott, Evan; Barchfeld, Robert; Riemenschneider, Paul; Muscatello, Chris; Sohrabi, Mohammad; Domier, Calvin; Ren, Yang; Kaita, Robert; Luhmann, Neville, Jr.; NSTX-U Team

2016-10-01

The Far-infrared Tangential Interferometer/Polarimeter (FIReTIP) system on NSTX-U at the PPPL aims to provide robust, line-averaged electron density measurements. The system consists of three optically-pumped 119 µm methanol lasers, one of which can be tuned via Stark broadening, allowing for uniquely high intermediate frequencies and time resolutions. One of the major goals of FIReTIP is to incorporate it into the NSTX-U plasma control system (PCS) for real-time plasma density feedback control. The front-end optics mounted to Bay G, which shape and position the beam going into the plasma, and internal retroreflector located near Bay B, which facilitates double-pass measurements, are hard-mounted to the NSTX-U vacuum vessel. Because interferometric density measurements are sensitive to vibrational effects, FIReTIP has been upgraded to a two-color interferometer system with the inclusion of a 633 nm laser interferometer for the direct measurement of vibrations and a field programmable gate array (FPGA) for the subsequent subtraction of vibrational effects from the density measurement in real-time. This work is supported by the U.S. Department of Energy Grant DE-FG02-99ER54518.

Temperature sensitivity of differential absorption lidar measurements of water vapor in the 720-nm region

NASA Technical Reports Server (NTRS)

Browell, Edward V.; Ismail, Syed; Grossmann, Benoist E.

1991-01-01

Recently measured properties of water vapor (H2O) absorption lines have been used in calculations to evalute the temperature sensitivity of differential absorption lidar (Dial) H2O measurements. This paper estimates the temperature sensitivity of H2O lines in the 717-733-nm region for both H2O mixing ratio and number density measurements, and discusses the influence of the H2O line ground state energies E-double-prime, the H2O absorption linewidths, the linewidth temperature dependence parameter, and the atmospheric temperature and pressure variations with altitude and location on the temperature sensitivity calculations. Line parameters and temperature sensitivity calculations for 67 H2O lines in the 720-nm band are given which can be directly used in field experiments. Water vapor lines with E-double-prime values in the 100-300/cm range were found to be optimum for Dial measurements of H2O number densities, while E-double-prime values in the 250-500/cm range were found to be optimum for H2O mixing ratio measurements.

DOE Fire Protection Handbook, Volume I

DOE Office of Scientific and Technical Information (OSTI.GOV)

NONE

The Department of Energy (DOE) Fire Protection Program is delineated in a number of source documents including; the Code of Federal Regulations (CFR), DOE Policy Statements and Orders, DOE and national consensus standards (such as those promulgated by the National Fire Protection Association), and supplementary guidance, This Handbook is intended to bring together in one location as much of this material as possible to facilitate understanding and ease of use. The applicability of any of these directives to individual Maintenance and Operating Contractors or to given facilities and operations is governed by existing contracts. Questions regarding applicability should be directedmore » to the DOE Authority Having Jurisdiction for fire safety. The information provided within includes copies of those DOE directives that are directly applicable to the implementation of a comprehensive fire protection program. They are delineated in the Table of Contents. The items marked with an asterisk (*) are included on the disks in WordPerfect 5.1 format, with the filename noted below. The items marked with double asterisks are provided as hard copies as well as on the disk. For those using MAC disks, the files are in Wordperfect 2.1 for MAC.« less

Quantifying the role of fire in the Earth system - Part 2: Impact on the net carbon balance of global terrestrial ecosystems for the 20th century

NASA Astrophysics Data System (ADS)

Li, F.; Bond-Lamberty, B.; Levis, S.

2014-03-01

Fire is the primary form of terrestrial ecosystem disturbance on a global scale. It affects the net carbon balance of terrestrial ecosystems by emitting carbon directly and immediately into the atmosphere from biomass burning (the fire direct effect), and by changing net ecosystem productivity and land-use carbon loss in post-fire regions due to biomass burning and fire-induced vegetation mortality (the fire indirect effect). Here, we provide the first quantitative assessment of the impact of fire on the net carbon balance of global terrestrial ecosystems during the 20th century, and investigate the roles of fire's direct and indirect effects. This is done by quantifying the difference between the 20th century fire-on and fire-off simulations with the NCAR Community Land Model CLM4.5 (prescribed vegetation cover and uncoupled from the atmospheric model) as a model platform. Results show that fire decreases the net carbon gain of global terrestrial ecosystems by 1.0 Pg C yr-1 averaged across the 20th century, as a result of the fire direct effect (1.9 Pg C yr-1) partly offset by the indirect effect (-0.9 Pg C yr-1). Post-fire regions generally experience decreased carbon gains, which is significant over tropical savannas and some North American and East Asian forests. This decrease is due to the direct effect usually exceeding the indirect effect, while they have similar spatial patterns and opposite sign. The effect of fire on the net carbon balance significantly declines until ∼1970 with a trend of 8 Tg C yr-1 due to an increasing indirect effect, and increases subsequently with a trend of 18 Tg C yr-1 due to an increasing direct effect. These results help constrain the global-scale dynamics of fire and the terrestrial carbon cycle.

Fire behavior, fuel treatments, and fire suppression on the Hayman Fire - Part 4: Relation of roads to burn severity

Treesearch

Charles W. McHugh; Mark A. Finney

2003-01-01

Effects of roads on fire behavior intensity and severity can be studied directly or indirectly. A direct study of road effects would include uses by fire suppression, burnout operations, and delay of fire progress at the roadside. Interpretations after the fire burns are easily confounded by the unknown nature of suppression activities and fire arrival time, and fire...

Supplementation with 1000 IU vitamin D/d leads to parathyroid hormone suppression, but not increased fractional calcium absorption, in 4-8-y-old children: A double-blind randomized controlled trial

USDA-ARS?s Scientific Manuscript database

The effects of vitamin D supplementation in healthy prepubertal children on physiologic outcomes have not been investigated. The objective was to evaluate the effects of supplementation with 1000 IU vitamin D(3)/d on calcium absorption. In a double-blind, placebo-controlled trial, we randomly assign...

Limited direct effects of a massive wildfire on its sagebrush steppe bee community

USDA-ARS?s Scientific Manuscript database

Fire can affect bees directly, through exposure to heating and smoke during the combustion phase. Direct effects include mortality, injury and displacement affecting at most two generations of bees—adults and any progeny produced prior to the fire event. To study the direct effects of fire on a bee ...

Determination of gold in geologic materials by solvent extraction and atomic-absorption spectrometry

USGS Publications Warehouse

Huffman, Claude; Mensik, J.D.; Riley, L.B.

1967-01-01

The two methods presented for the determination of traces of gold in geologic materials are the cyanide atomic-absorption method and the fire-assay atomic-absorption method. In the cyanide method gold is leached with a sodium-cyanide solution. The monovalent gold is then oxidized to the trivalent state and concentrated by extracting into methyl isobutyl ketone prior to estimation by atomic absorption. In the fire-assay atomic-absorption method, the gold-silver bead obtained from fire assay is dissolved in nitric and hydrochloric acids. Gold is then concentrated by extracting into methyl isobutyl ketone prior to determination by atomic absorption. By either method concentrations as low as 50 parts per billion of gold can be determined in a 15-gram sample.

SIERRA Low Mach Module: Fuego User Manual Version 4.46.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sierra Thermal/Fluid Team

2017-09-01

The SIERRA Low Mach Module: Fuego along with the SIERRA Participating Media Radiation Module: Syrinx, henceforth referred to as Fuego and Syrinx, respectively, are the key elements of the ASCI fire environment simulation project. The fire environment simulation project is directed at characterizing both open large-scale pool fires and building enclosure fires. Fuego represents the turbulent, buoyantly-driven incompressible flow, heat transfer, mass transfer, combustion, soot, and absorption coefficient model portion of the simulation software. Syrinx represents the participating-media thermal radiation mechanics. This project is an integral part of the SIERRA multi-mechanics software development project. Fuego depends heavily upon the coremore » architecture developments provided by SIERRA for massively parallel computing, solution adaptivity, and mechanics coupling on unstructured grids.« less

SIERRA Low Mach Module: Fuego Theory Manual Version 4.44

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sierra Thermal /Fluid Team

2017-04-01

The SIERRA Low Mach Module: Fuego along with the SIERRA Participating Media Radiation Module: Syrinx, henceforth referred to as Fuego and Syrinx, respectively, are the key elements of the ASCI fire environment simulation project. The fire environment simulation project is directed at characterizing both open large-scale pool fires and building enclosure fires. Fuego represents the turbulent, buoyantly-driven incompressible flow, heat transfer, mass transfer, combustion, soot, and absorption coefficient model portion of the simulation software. Syrinx represents the participating-media thermal radiation mechanics. This project is an integral part of the SIERRA multi-mechanics software development project. Fuego depends heavily upon the coremore » architecture developments provided by SIERRA for massively parallel computing, solution adaptivity, and mechanics coupling on unstructured grids.« less

SIERRA Low Mach Module: Fuego Theory Manual Version 4.46.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sierra Thermal/Fluid Team

The SIERRA Low Mach Module: Fuego along with the SIERRA Participating Media Radiation Module: Syrinx, henceforth referred to as Fuego and Syrinx, respectively, are the key elements of the ASCI fire environment simulation project. The fire environment simulation project is directed at characterizing both open large-scale pool fires and building enclosure fires. Fuego represents the turbulent, buoyantly-driven incompressible flow, heat transfer, mass transfer, combustion, soot, and absorption coefficient model portion of the simulation software. Syrinx represents the participating-media thermal radiation mechanics. This project is an integral part of the SIERRA multi-mechanics software development project. Fuego depends heavily upon the coremore » architecture developments provided by SIERRA for massively parallel computing, solution adaptivity, and mechanics coupling on unstructured grids.« less

Feasibility study on utilization of palm fibre waste into fired clay brick

NASA Astrophysics Data System (ADS)

Kadir, A. A.; Sarani, N. A.; Zaman, N. N.; Abdullah, Mohd Mustafa Al Bakri

2017-04-01

Malaysia is the second largest of palm oil producer after Indonesia, which contribute to 50 % of palm oil production. With this demand, the increasing of palm oil plantation over the years has led to the large production of agricultural waste, for example palm fibre waste. This study investigates different percentages of palm fibre (0 %, 1 %, 5 % and 10 %) to be incorporated into fired clay brick. Manufactured bricks were fired at 1 °C/min heating rate up to 1050 °C. The effects of manufacture bricks on the physical and mechanical properties of manufactured brick were also determined. All brick samples were tested due to the physical and mechanical properties which include dry density, firing shrinkage, initial rate of suction (IRS), water absorption, porosity and compressive strength. Findings show that increasing palm fibre waste affected the properties of brick, which decreased their density, besides increased firing shrinkage, IRS, water absorption, porosity and compressive strength. However, all the manufactured brick still followed the requirement.

Effects of body formulation and firing temperature to properties of ceramic tile incorporated with electric arc furnace (EAF) slag waste

NASA Astrophysics Data System (ADS)

Sharif, Nurulakmal Mohd; Lim, Chi Yang; Teo, Pao Ter; Seman, Anasyida Abu

2017-07-01

Significant quantities of sludge and slag are generated as waste materials or by-products from steel industries. One of the by-products is Electric Arc Furnace (EAF) steel slag which consists of oxides such as CaO, Al2O3 and FeO. This makes it possible for slag to partially replace the raw materials in ceramic tile production. In our preliminary assessment of incorporating the EAF slag into ceramic tile, it was revealed that at fixed firing temperature of 1150°C, the tile of composition 40 wt.% EAF slag - 60 wt.% ball clay has comparable properties with commercial ceramic tile. Thus, this current study would focus on effects of body formulation (different weight percentages of K-feldspar and silica) and different firing temperatures to properties of EAF slag added ceramic tile. EAF slag from Southern Steel Berhad (SSB) was crushed into micron size (EAF slag content was 40 wt.%) and milled with ball clay, K-feldspar and silica before compacted and fired at 1125°C and 1150°C. The EAF slag added tile was characterized in terms of water absorption, apparent porosity, bulk density, modulus of rupture (MOR) and phase analysis via X-ray diffraction (XRD). The composition of 40 wt.% EAF slag - 30 wt.% ball clay - 10 wt.% K-feldspar - 20 wt.% silica (10F_20S), fired at 1150°C showed the lowest water absorption, apparent porosity and highest bulk density due to enhancement of densification process during firing. However, the same composition of ceramic tile (10F_20S) had the highest MOR at lower firing temperature of 1125°C, contributed by presence of the highest total amount of anorthite and wollastonite reinforcement crystalline phases (78.40 wt.%) in the tile. Overall, both the water absorption and MOR of all ceramic tiles surpassed the requirement regulated by MS ISO 13006:2014 Standard (Annex G: Dry-pressed ceramic tile with low water absorption, Eb ≤ 0.50 % and minimum MOR of 35 MPa).

Direct and indirect effects of climate change on projected future fire regimes in the western United States.

PubMed

Liu, Zhihua; Wimberly, Michael C

2016-01-15

We asked two research questions: (1) What are the relative effects of climate change and climate-driven vegetation shifts on different components of future fire regimes? (2) How does incorporating climate-driven vegetation change into future fire regime projections alter the results compared to projections based only on direct climate effects? We used the western United States (US) as study area to answer these questions. Future (2071-2100) fire regimes were projected using statistical models to predict spatial patterns of occurrence, size and spread for large fires (>400 ha) and a simulation experiment was conducted to compare the direct climatic effects and the indirect effects of climate-driven vegetation change on fire regimes. Results showed that vegetation change amplified climate-driven increases in fire frequency and size and had a larger overall effect on future total burned area in the western US than direct climate effects. Vegetation shifts, which were highly sensitive to precipitation pattern changes, were also a strong determinant of the future spatial pattern of burn rates and had different effects on fire in currently forested and grass/shrub areas. Our results showed that climate-driven vegetation change can exert strong localized effects on fire occurrence and size, which in turn drive regional changes in fire regimes. The effects of vegetation change for projections of the geographic patterns of future fire regimes may be at least as important as the direct effects of climate change, emphasizing that accounting for changing vegetation patterns in models of future climate-fire relationships is necessary to provide accurate projections at continental to global scales. Copyright © 2015 Elsevier B.V. All rights reserved.

Dual-circuit, multiple-effect refrigeration system and method

DOEpatents

DeVault, Robert C.

1995-01-01

A dual circuit absorption refrigeration system comprising a high temperature single-effect refrigeration loop and a lower temperature double-effect refrigeration loop separate from one another and provided with a double-condenser coupling therebetween. The high temperature condenser of the single-effect refrigeration loop is double coupled to both of the generators in the double-effect refrigeration loop to improve internal heat recovery and a heat and mass transfer additive such as 2-ethyl-1-hexanol is used in the lower temperature double-effect refrigeration loop to improve the performance of the absorber in the double-effect refrigeration loop.

The double slit experiment and the time reversed fire alarm

NASA Astrophysics Data System (ADS)

Halabi, Tarek

2011-03-01

When both slits of the double slit experiment are open, closing one paradoxically increases the detection rate at some points on the detection screen. Feynman famously warned that temptation to "understand" such a puzzling feature only draws us into blind alleys. Nevertheless, we gain insight into this feature by drawing an analogy between the double slit experiment and a time reversed fire alarm. Much as closing the slit increases probability of a future detection, ruling out fire drill scenarios, having heard the fire alarm, increases probability of a past fire (using Bayesian inference). Classically, Bayesian inference is associated with computing probabilities of past events. We therefore identify this feature of the double slit experiment with a time reversed thermodynamic arrow. We believe that much of the enigma of quantum mechanics is simply due to some variation of time's arrow.

Development of Polyimide Foam for Aircraft Sidewall Applications

NASA Technical Reports Server (NTRS)

Silcox, Richard; Cano, Roberto J.; Howerton, Brian M.; Bolton, J. Stuart; Kim, Nicholas N.

2013-01-01

In this paper, the use of polyimide foam as a lining in double panel applications is considered. It is being investigated here as a replacement for aircraft grade glass fiber and has a number of attractive functional attributes, not the least of which is its high fire resistance. The test configuration studied here consisted of two 1mm (0.04 in.) thick, flat aluminum panels separated by 12.7 cm (5.0 in.) with a 7.6 cm (3.0 in.) thick layer of foam centered in that space. Random incidence transmission loss measurements were conducted on this buildup, and conventional poro-elastic models were used to predict the performance of the lining material. Results from two densities of foam are considered. The Biot parameters of the foam were determined by a combination of direct measurement (for density, flow resistivity and Young s modulus) and inverse characterization procedures (for porosity, tortuosity, viscous and thermal characteristic length, Poisson s ratio and loss factor). The inverse characterization procedure involved matching normal incidence standing wave tube measurements of absorption coefficient and transmission loss of the isolated foam with finite element predictions. When the foam parameters determined in this way were used to predict the performance of the complete double panel system, reasonable agreement was obtained between the measured transmission loss and predictions made using a commercial statistical energy analysis code.

Development of a 2-micron Pulsed Direct Detection IPDA Lidar for CO2 Measurement

NASA Astrophysics Data System (ADS)

Yu, J.; Petros, M.; Singh, U. N.

2013-12-01

NASA Langley is developing a 2-micron pulsed Integrated Path Differential Absorption (IPDA) lidar for atmospheric CO2 measurements. The high pulse energy, direct detection lidar operating at CO2 2-micron absorption band provides an alternate approach to measure CO2 concentrations with significant advantages. The objective of this development is to integrate an existing high energy double-pulsed 2-micron laser transmitter with a direct detection receiver and telescope to enable a first proof of principle demonstration of airborne direct detection CO2 measurements at 2-micron wavelength. It is expected to provide high-precision measurement capability by unambiguously eliminating contamination from aerosols and clouds that can bias the IPDA measurement. The system is scheduled to fly on NASA UC12 or B200 research aircrafts before the end of 2013. This paper will describe the design of the airborne 2-micron pulsed IPDA lidar system; the lidar operation parameters; the wavelength pair selection; laser transmitter energy, pulse rate, beam divergence, double pulse generation and accurate frequency control; detector characterization; telescope design; lidar structure design; and lidar signal to noise ratio estimation.

Studies of Sound Absorption by and Transmission Through Layers of Elastic Noise Control Foams: Finite Element Modeling and Effects of Anisotropy

NASA Astrophysics Data System (ADS)

Kang, Yeon June

In this thesis an elastic-absorption finite element model of isotropic elastic porous noise control materials is first presented as a means of investigating the effects of finite dimension and edge constraints on the sound absorption by, and transmission through, layers of acoustical foams. Methods for coupling foam finite elements with conventional acoustic and structural finite elements are also described. The foam finite element model based on the Biot theory allows for the simultaneous propagation of the three types of waves known to exist in an elastic porous material. Various sets of boundary conditions appropriate for modeling open, membrane-sealed and panel-bonded foam surfaces are formulated and described. Good agreement was achieved when finite element predictions were compared with previously established analytical results for the plane wave absorption coefficient and transmission loss in the case of wave propagation both in foam-filled waveguides and through foam-lined double panel structures of infinite lateral extent. The primary effect of the edge constraints of a foam layer was found to be an acoustical stiffening of the foam. Constraining the ends of the facing panels in foam-lined double panel systems was also found to increase the sound transmission loss significantly in the low frequency range. In addition, a theoretical multi-dimensional model for wave propagation in anisotropic elastic porous materials was developed to study the effect of anisotropy on the sound transmission of foam-lined noise control treatments. The predictions of the theoretical anisotropic model have been compared with experimental measurements for the random incidence sound transmission through double panel structure lined with polyimide foam. The predictions were made by using the measured and estimated macroscopic physical parameters of polyimide foam samples which were known to be anisotropic. It has been found that the macroscopic physical parameters in the direction normal to the face of foam layer play the principal role in determining the acoustical behavior of polyimide foam layers, although more satisfactory agreement between experimental measurements and theoretical predictions of transmission loss is obtained when the anisotropic properties are allowed in the model.

Advancement of Double Effect Absorption Cycle by Input of Low Temperature Waste Heat

NASA Astrophysics Data System (ADS)

Kojima, Hiroshi; Edera, Masaru; Nakamura, Makoto; Oka, Masahiro; Akisawa, Atsushi; Kashiwagi, Takao

Energy conservation is becoming important for global environmental protection. New simple techniques of more efficient1y using the waste heat of gas co-generation systems for refrigerationare required. In first report, a new method of using the low temperature waste heat for refrigeration was proposed, and the basic characteristics of the promising methods of recovering waste heat were c1arified. In this report, the more detailed simulation model of the series flow type double effect absorption refrigerator with auxiliary heat exchanger was constructed and the static characteristics were investigated. Then experiments on this advanced absorption refrigerator were carried out, and the results of the calculation and experiments were compared and discussed. Moreover, the betterment of the simulation model of this advanced absorption refrigerator was carried out.

Modulation of intersubband light absorption and interband photoluminescence in double GaAs/AlGaAs quantum wells under strong lateral electric fields

DOE Office of Scientific and Technical Information (OSTI.GOV)

Balagula, R. M., E-mail: rmbal@spbstu.ru; Vinnichenko, M. Ya., E-mail: mvin@spbstu.ru; Makhov, I. S.

The effect of a lateral electric field on the mid-infrared absorption and interband photoluminescence spectra in double tunnel-coupled GaAs/AlGaAs quantum wells is studied. The results obtained are explained by the redistribution of hot electrons between quantum wells and changes in the space charge in the structure. The hot carrier temperature is determined by analyzing the intersubband light absorption and interband photoluminescence modulation spectra under strong lateral electric fields.

Effect of interdiffusion and external magnetic field on electronic states and light absorption in Gaussian-shaped double quantum ring

NASA Astrophysics Data System (ADS)

Aziz-Aghchegala, V. L.; Mughnetsyan, V. N.; Kirakosyan, A. A.

2018-02-01

The effect of interdiffusion and magnetic field on confined states of electron and heavy hole as well as on interband absorption spectrum in a Ga1-xAlxAs/GaAs Gaussian-shaped double quantum ring are investigated. It is shown that both interdiffusion and magnetic field lead to the change of the charge carriers' quantum states arrangement by their energies. The oscillating behavior of the electron ground state energy as a function of magnetic field induction gradually disappears with the increase of diffusion parameter due to the enhanced tunneling of electron to the central region of the ring. For the heavy hole the ground state energy oscillations are not observable in the region of the values of magnetic field induction B = 0 - 10 T . For considered transitions both the magnetic field and the interdiffusion lead to a blue-shift of the absorption spectrum and to decreasing of the absorption intensity. The obtained results indicate on the opportunity of purposeful manipulation of energy states and absorption spectrum of a Gaussian-shaped double quantum ring by means of the post growth annealing and the external magnetic field.

Cavity ring-down spectroscopy in the liquid phase

NASA Astrophysics Data System (ADS)

Xu, Shucheng; Sha, Guohe; Xie, Jinchun

2002-02-01

A new application for cavity ring-down spectroscopic (CRDS) technique using a pulsed polarized light source has been developed in the absorption measurement of liquids for "colorless" organic compounds using both a single sample cell and double sample cells inserted in an optical cavity at Brewster angle. At present an experimental capability of measuring absorption coefficients as small as 2-5×10-7 cm-1 has been demonstrated by measurement of the absorption baselines. The first spectra for CRDS in the liquid phase, the C-H stretching fifth vibrational overtones of benzene in the pure liquid and hexane solution are obtained. The optical absorption length for liquids in both a single sample cell and double sample cells of 1 cm length is up to 900 cm due to multipass of light within an optical cavity. Compared to the thermal lens and optoacoustic spectroscopic techniques, the sensitivity for CRDS mainly depends on the optical absorption path of the sample (single passing path of the sample times multipass times), is not determined by the laser power and the length of the sample cell. The absolute absorption coefficient and band intensity for the sample are determined directly by the spectroscopy.

Airborne 2-Micron Double Pulsed Direct Detection IPDA Lidar for Atmospheric CO2 Measurement

NASA Technical Reports Server (NTRS)

Yu, Jirong; Petros, Mulugeta; Refaat, Tamer F.; Reithmaier, Karl; Remus, Ruben; Singh, Upendra; Johnson, Will; Boyer, Charlie; Fay, James; Johnston, Susan;

Column CO2 Measurement From an Airborne Solid-State Double-Pulsed 2-Micron Integrated Path Differential Absorption Lidar

NASA Technical Reports Server (NTRS)

Singh, U. N.; Yu, J.; Petros, M.; Refaat, T. F.; Remus, R.; Fay, J.; Reithmaier, K.

2014-01-01

NASA LaRC is developing and integrating a double-Pulsed 2-micron direct detection IPDA lidar for CO2 column measurement from an airborne platform. The presentation will describe the development of the 2-micrometers IPDA lidar system and present the airborne measurement of column CO2 and will compare to in-situ measurement for various ground target of different reflectivity.

Aerosol Optical Properties and Trace Gas Emissions From Laboratory-Simulated Western US Wildfires

NASA Astrophysics Data System (ADS)

Selimovic, V.; Yokelson, R. J.; Warneke, C.; Roberts, J. M.; De Gouw, J. A.; Reardon, J.; Griffith, D. W. T.

2017-12-01

Western wildfires have a major impact on air quality in the US. In the fall of 2016, 107 fires were burned in the large-scale combustion facility at the US Forest Service Missoula Fire Sciences Laboratory as part of the Fire Influence on Regional and Global Environments Experiment (FIREX). Canopy, litter, duff, dead wood, and other fuels from various widespread coniferous and chaparral ecosystems were burned in combinations to represent relevant configurations in the field and as pure components to investigate the effects of individual fuels. The smoke emissions were characterized by a large suite of state-of-the-art instruments. In this study we report emission factor (EF, g compound emitted per kg fuel burned) measurements in fresh smoke of a diverse suite of critically-important trace gases measured by open-path Fourier transform infrared spectroscopy (OP-FTIR). We also report aerosol optical properties (absorption EF, single scattering albedo (SSA) and Ångström absorption exponent (AAE)) as well as black carbon (BC) EF measured by photoacoustic extinctiometers (PAX) at 870 and 401 nm. A careful comparison with available field measurements of wildfires confirms that representative data can be extracted from the lab fire data. The OP-FTIR data show that ammonia (1.65 g kg-1), acetic acid (2.44 g kg-1), and other trace gases are significant emissions not previously measured for US wildfires. The PAX measurements show that brown carbon (BrC) absorption is most dominant for combustion of duff (AAE 7.13) and rotten wood (AAE 4.60): fuels that are consumed in greater amounts during wildfires than prescribed fires. We confirm that about 86% of the aerosol absorption at 401 nm in typical fresh wildfire smoke is due to BrC.

Direct stratospheric injection of biomass burning emissions: a case study of the 2009 Australian bushfires using the NASA GISS ModelE2 composition-climate model

NASA Astrophysics Data System (ADS)

Field, Robert; From, Mike; Voulgarakis, Apostolos; Shindell, Drew; Flannigan, Mike; Bernath, Peter

2014-05-01

Direct stratospheric injection (DSI) of forest fire smoke represents a direct biogeochemical link between the land surface and stratosphere. DSI events occur regularly in the northern and southern extratropics, and have been observed across a wide range of measurements, but their fate and effects are not well understood. DSIs result from explosive, short-lived fires, and their plumes stand out from background concentrations immediately. This makes it easier to associate detected DSIs to individual fires and their estimated emissions. Because the emissions pulses are brief, chemical decay can be more clearly assessed, and because the emissions pulses are so large, a wide range of rare chemical species can be detected. Observational evidence suggests that they can persist in the stratosphere for several months, enhance ozone production, and be self-lofted to the middle stratosphere through shortwave absorption and diabatic heating. None of these phenomena have been evaluated, however, with a physical model. To that end, we are simulating the smoke plumes from the February 2009 Australia 'Black Saturday' bushfires using the NASA GISS ModelE2 composition-climate model, nudged toward horizontal winds from reanalysis. To-date, this is the best-observed DSI in the southern hemisphere. Chemical and aerosol signatures of the plume were observed in a wide array of limb and nadir satellite retrievals. Detailed estimates of fuel consumption and injection height have been made because of the severity of the fires. Uncommon among DSIs events was a large segment of the plume that entrained into the upper equatorial easterlies. Preliminary modeling results show that the relative strengths of the equatorial and extratropical plume segments are sensitive to the plume's initial injection height. This highlights the difficulty in reconciling uncertainty in the reanalysis over the Southern Hemisphere with fairly-well constrained estimates of fire location and injection height at the source.

Water vapour emission in vegetable fuel: absorption cell measurements and detection limits of our CO II Dial system

NASA Astrophysics Data System (ADS)

Bellecci, C.; De Leo, L.; Gaudio, P.; Gelfusa, M.; Lo Feudo, T.; Martellucci, S.; Richetta, M.

2006-09-01

Forest fires can be the cause of serious environmental and economic damages. For this reason a considerable effort has been directed toward the forest protection and fire fighting. In the early forest fire detection, Lidar technique present considerable advantages compared to the passive detection methods based on infrared cameras currently in common use, due its higher sensitivity and ability to accurately locate the fire. The combustion phase of the vegetable matter causes a great amount of water vapour emission, thus the water molecule behaviour will be studied to obtain a fire detection system ready and efficient also before the flame propagation. A first evaluation of increment of the water vapour concentration compared to standard one will be estimated by a numerical simulation. These results will be compared with the experimental measurements carried out into a cell with a CO II Dial system, burning different kinds of vegetable fuel. Our results and their comparison will be reported in this paper.

Forage nutritive quality in the Serengeti ecosystem: The roles of fire and herbivory

USGS Publications Warehouse

Anderson, T.M.; Ritchie, M.E.; Mayemba, E.; Eby, S.; Grace, J.B.; McNaughton, S.J.

2007-01-01

Fire and herbivory are important determinants of nutrient availability in savanna ecosystems. Fire and herbivory effects on the nutritive quality of savanna vegetation can occur directly, independent of changes in the plant community, or indirectly, via effects on the plant community. Indirect effects can be further subdivided into those occurring because of changes in plant species composition or plant abundance (i.e., quality versus quantity). We studied relationships between fire, herbivory, rainfall, soil fertility, and leaf nitrogen (N), phosphorus (P), and sodium (Na) at 30 sites inside and outside of Serengeti National Park. Using structural equation modeling, we asked whether fire and herbivory influences were largely direct or indirect and how their signs and strengths differed within the context of natural savanna processes. Herbivory was associated with enhanced leaf N and P through changes in plant biomass and community composition. Fire was associated with reduced leaf nutrient concentrations through changes in plant community composition. Additionally, fire had direct positive effects on Na and nonlinear direct effects on P that partially mitigated the indirect negative effects. Key mechanisms by which fire reduced plant nutritive quality were through reductions of Na-rich grasses and increased abundance of Themeda triandra, which had below-average leaf nutrients. ?? 2007 by The University of Chicago. All rights reserved.

Realizing high-performance metamaterial absorber based on the localized surface plasmon resonance in the terahertz regime

NASA Astrophysics Data System (ADS)

Yunfeng, Lin; Xiaoqi, Hu; Lin, Hu

2018-04-01

A composite structure design metamaterial absorber is designed and simulated. The proposed composite structure consists of a double-hole sub-structure and a double-metallic particle sub-structure. The damping constant of bulk gold layer is optimized to eliminate the adverse effects of the grain boundary and the surface scattering of thin films on the absorption property. Two absorption peaks (A1 = 58%, A2 = 23%) are achieved based on the localized surface plasmon (LSP) modes resonance. Moreover, the plasmonic hybridization phenomenon between LSP modes is found, which leads to the absorption enhancement between two absorption peaks. The proposed metamaterial absorber holds the property of wide-angle incidence.

Lithogeochemistry of mineralized and altered rock samples from the northern Talkeetna Mountains, south-central Alaska

USGS Publications Warehouse

Light, Thomas D.; Schmidt, Jeanine M.

2011-01-01

Mineralized and altered rock samples collected from the northern Talkeetna Mountains, Alaska, were analyzed by two different inductively coupled plasma atomic-emission spectrometry (ICP-AES) methods for as many as 44 elements; by fire assay and either direct-coupled plasma (DCP) or atomic absorption spectrophotometry (AAS) for gold (Au); by cold vapor atomic absorption (CVAA) for mercury (Hg); and by irradiated neutron activation analysis (INAA) for tungsten (W). The analytical results showed that some samples contain high values of multiple elements and may be potential indicators of hydrothermal mineralization in the area.

Synergic use of TOMS and Aeronet Observations for Characterization of Aerosol Absorption

NASA Technical Reports Server (NTRS)

Torres, O.; Bhartia, P. K.; Dubovik, O.; Holben, B.; Siniuk, A.

2003-01-01

The role of aerosol absorption on the radiative transfer balance of the earth-atmosphere system is one of the largest sources of uncertainty in the analysis of global climate change. Global measurements of aerosol single scattering albedo are, therefore, necessary to properly assess the radiative forcing effect of aerosols. Remote sensing of aerosol absorption is currently carried out using both ground (Aerosol Robotic Network) and space (Total Ozone Mapping Spectrometer) based observations. The satellite technique uses measurements of backscattered near ultraviolet radiation. Carbonaceous aerosols, resulting from the combustion of biomass, are one of the most predominant absorbing aerosol types in the atmosphere. In this presentation, TOMS and AERONET retrievals of single scattering albedo of carbonaceous aerosols, are compared for different environmental conditions: agriculture related biomass burning in South America and Africa and peat fires in Eastern Europe. The AERONET and TOMS derived aerosol absorption information are in good quantitative agreement. The most absorbing smoke is detected over the African Savanna. Aerosol absorption over the Brazilian rain forest is less absorbing. Absorption by aerosol particles resulting from peat fires in Eastern Europe is weaker than the absorption measured in Africa and South America. This analysis shows that the near UV satellite method of aerosol absorption characterization has the sensitivity to distinguish different levels of aerosol absorption. The analysis of the combined AERONET-TOMS observations shows a high degree of synergy between satellite and ground based observations.

Introduction: Strengthening the foundation of wildland fire Effects prediction for research and management

Treesearch

Matthew B. Dickinson; Kevin C. Ryan

2010-01-01

As prescribed fire use increases and the options for responding to wildfires continue to expand beyond suppression, the need for improving fire effects prediction capabilities be¬comes increasingly apparent. The papers in this Fire Ecology special issue describe recent advances in fire effects prediction for key classes of direct (first-order) fire effects. Important...

Research on structural integration of thermodynamic system for double reheat coal-fired unit with CO2 capture

NASA Astrophysics Data System (ADS)

Wang, Lanjing; Shao, Wenjing; Wang, Zhiyue; Fu, Wenfeng; Zhao, Wensheng

2018-02-01

Taking the MEA chemical absorption carbon capture system with 85% of the carbon capture rate of a 660MW ultra-super critical unit as an example,this paper puts forward a new type of turbine which dedicated to supply steam to carbon capture system. The comparison of the thermal systems of the power plant under different steam supply schemes by using the EBSILON indicated optimal extraction scheme for Steam Extraction System in Carbon Capture System. The results show that the cycle heat efficiency of the unit introduced carbon capture turbine system is higher than that of the usual scheme without it. With the introduction of the carbon capture turbine, the scheme which extracted steam from high pressure cylinder’ s steam input point shows the highest cycle thermal efficiency. Its indexes are superior to other scheme, and more suitable for existing coal-fired power plant integrated post combustion carbon dioxide capture system.

Structural parameter effect of porous material on sound absorption performance of double-resonance material

NASA Astrophysics Data System (ADS)

Fan, C.; Tian, Y.; Wang, Z. Q.; Nie, J. K.; Wang, G. K.; Liu, X. S.

2017-06-01

In view of the noise feature and service environment of urban power substations, this paper explores the idea of compound impedance, fills some porous sound-absorption material in the first resonance cavity of the double-resonance sound-absorption material, and designs a new-type of composite acoustic board. We conduct some acoustic characterizations according to the standard test of impedance tube, and research on the influence of assembly order, the thickness and area density of the filling material, and back cavity on material sound-absorption performance. The results show that the new-type of acoustic board consisting of aluminum fibrous material as inner structure, micro-porous board as outer structure, and polyester-filled space between them, has good sound-absorption performance for low frequency and full frequency noise. When the thickness, area density of filling material and thickness of back cavity increase, the sound absorption coefficient curve peak will move toward low frequency.

Bilayer synergetic coupling double negative acoustic metasurface and cloak.

PubMed

Ma, Fuyin; Huang, Meng; Xu, Yicai; Wu, Jiu Hui

2018-04-12

In this paper, we propose a bilayer plate-type lightweight double negative metasurface based on a new synergetic coupling design concept, by which the perfect absorption, double negative bands, free manipulation of phase shifts with a 2π span and acoustic cloak can be successively realized. Firstly, the synergetic behavior between resonant and anti-resonant plates is presented to construct a bilayer unit in which each component respectively provides a pre-defined function in realizing the perfect absorption. Based on this bilayer structure, a double negative band with simultaneously negative effective mass density and bulk modulus is obtained, which, as a metasurface, can obtain continuous phase shifts almost completely covering a 2π range, thus facilitating the design of a three-dimensional (3D) acoustic cloak. In addition, based on this strong sound absorption concept, a two-dimensional (2D) omnidirectional broadband acoustical dark skin, covering between 800 to 6000 Hz, is also demonstrated through the proposed bilayer plate-type structure form. The proposed design concepts and metasurfaces have widespread potential application values in strong sound attenuation, filtering, superlens, imaging, cloak, and extraordinary wave steering, in which the attributes of strong absorption, double negative parameters or continuous phase shifts with full 2π span are required to realize the expected extraordinary physical features.

Optical Properties of Black and Brown Carbon Aerosols from Laboratory Combustion of Wildland Fuels

NASA Astrophysics Data System (ADS)

Beres, N. D.; Molzan, J.

2015-12-01

Aerosol light absorption in the solar spectral region (300 nm - 2300 nm) of the atmosphere is key for the direct aerosol radiative forcing, which is determined by aerosol single scattering albedo (SSA), asymmetry parameter, and by the albedo of the underlying surface. SSA is of key importance for the sign and quantity of aerosol direct radiative forcing; that is, does the aerosol make the earth look darker (heating) or whiter (cooling)? In addition, these optical properties are needed for satellite retrievals of aerosol optical depth and properties. During wildland fires, aerosol optical absorption is largely determined by black carbon (BC) and brown carbon (BrC) emissions. BC is strongly absorbing throughout the solar spectrum, while BrC absorption strongly increases toward shorter wavelength and can be neglected in the red and infrared. Optical properties of BrC emitted from wildland fires are poorly understood and need to be studied as function of fuel type and moisture content and combustion conditions. While much more is known about BC optical properties, knowledge for the ultraviolet (UV) spectral region is still lacking and critically needed for satellite remote sensing (e.g., TOMS, OMI) and for modeling of tropospheric photochemistry. Here, a project to better characterize biomass burning aerosol optical properties is described. It utilizes a laboratory biomass combustion chamber to generate aerosols through combustion of different wildland fuels of global and regional importance. Combustion aerosol optics is characterized with an integrating nephelometer to measure aerosol light scattering and a photoacoustic instrument to measure aerosol light absorption. These measurements will yield optical properties that are needed to improve qualitative and quantitative understanding of aerosol radiative forcing and satellite retrievals for absorbing carbonaceous aerosols from combustion of wildland fuels.

Fire effects in northeastern forests: oak.

Treesearch

Cary Rouse

1986-01-01

Effects of fire on the oak timber type are reviewed. Many oak stands of today originated under severe fire regimes. Fire can ill or injure oak trees. Factors determining direct injury or mortality from fire include: season of year; bark characteristics; size, vigor and form of tree; fire characteristics and stocking level.

Correlation between water absorption and mechanical properties of polyamide 6 filled with layered double hydroxides (LDH)

NASA Astrophysics Data System (ADS)

Botan, R.; Pinheiro, I. F.; Ferreira, F. V.; Lona, L. M. F.

2018-06-01

Polyamide 6 (PA6)/layered double hydroxide (LDH) nanocomposites were prepared by in situ polymerization with different amount (1, 2, 3 wt%) and type (Zn/Cr-L and Zn/Cr-P) of LDHs. The thermal and mechanical properties and water absorption capacity of PA6/LDH nanocomposites were investigated and have shown that the addition of LDHs increases the crystallinity of the polymer and improves their mechanical properties, while decreases the water absorption capacity due to a barrier effect of LDHs. A correlation between mechanical properties and water absorption capacity was observed and discussed. This study provides new strategies for tuning PA6-based nanocomposite properties, leading a progress in the development on the advanced polymer materials.

Evaluation of direct-exchange areas for a cylindrical enclosure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sika, J.

1991-11-01

This paper reports on a method for calculating the radiative heat transfer direct-exchange areas for surface-to-surface, volume-to-surface, and volume-to-volume pairs of zones in axisymmetric cylindrical geometries. With this method the calculation of the direct-exchange areas can be transformed from the original four-, five-, and sixfold integrals in the defining relations to just single and/or double integrals. Gray gas with absorption coefficient K is assumed.

A preliminary investigation of projectile shape effects in hypervelocity impact of a double-sheet structure

NASA Technical Reports Server (NTRS)

Morrison, R. H.

1972-01-01

Impact tests of a sphere and several cylinders of various masses and fineness ratios, all of aluminum, fired into an aluminum double-sheet structure at velocities near 7 km/sec, show that a cylinder, impacting in the direction of its axis, is considerably more effective as a penetrator than a sphere. Impacts of three cylinders of equal mass, but different fineness ratios, produced holes through the structures' rear sheet, whereas impact of a sphere of the same mass did not. Moreover, it was found that to prevent rear-sheet penetration, the mass of the 1/2-fineness-ratio cylinder had to be reduced by a factor greater than three. Further tests wherein the cylinder diameter was held constant while the cylinder length was systematically reduced showed that a cylinder with a fineness ratio of 0.07 and a mass of only 1/7 that of the sphere was still capable of producing a hole in the rear sheet.

Fire extinguishing agents for oxygen-enriched atmospheres

NASA Astrophysics Data System (ADS)

Plugge, M. A.; Wilson, C. W.; Zallen, D. M.; Walker, J. L.

1985-12-01

Fire-suppression agent requirements for extinguishing fires in oxygen-enriched atmospheres were determined employing small-, medium-, large-, and full-scale test apparatuses. The small- and medium-scale tests showed that a doubling of the oxygen concentration required five times more HALON for extinguishment. For fires of similar size and intensity, the effect of oxygen enrichment of the diluent volume in the HC-131A was not as grate as in the smaller compartments of the B-52 which presented a higher damage scenario. The full-scale tests showed that damage to the airframe was as important a factor in extinguishment as oxygen enrichment.

Effects of prescribed fire and season of burn on direct and indirect levels of tree mortality in Ponderosa and Jeffrey Pine Forests in California, USA.

Treesearch

Christopher Fettig; Stephen McKelvey; Daniel Cluck; Smith Sheri; William Otrosina

2010-01-01

Many forests that historically experienced frequent low-intensity wildfires have undergone extensive alterations during the past century. Prescribed fire is now commonly used to restore these fire-adapted forest ecosystems. In this study, we examined the influence of prescribed burn season on levels of tree mortality attributed to prescribed fire effects (direct...

Research of glass fibre used in the electromagnetic wave shielding and absorption composite material

NASA Astrophysics Data System (ADS)

Xu, M.; Jia, F.; Bao, H. Q.; Cui, K.; Zhang, F.

2016-07-01

Electromagnetic shielding and absorption composite material plays an important role in the defence and economic field. Comparing with other filler, Glass fibre and its processed product—metal-coated glass fibre can greatly reduce the material's weight and costs, while it still remains the high strength and the electromagnetic shielding effectiveness. In this paper, the electromagnetic absorption mechanism and the reflection mechanism have been investigated as a whole, and the shielding effectiveness of the double-layer glass fibre composite material is mainly focused. The relationship between the shielding effectiveness and the filled glass fibre as well as its metal-coated product's parameters has also been studied. From the subsequent coaxial flange and anechoic chamber analysis, it can be confirmed that the peak electromagnetic shielding effectiveness of this double-layer material can reach -78dB while the bandwidth is from 2GHz to 18GHz.

Optical characterization of tissue mimicking phantoms by a vertical double integrating sphere system

NASA Astrophysics Data System (ADS)

Han, Yilin; Jia, Qiumin; Shen, Shuwei; Liu, Guangli; Guo, Yuwei; Zhou, Ximing; Chu, Jiaru; Zhao, Gang; Dong, Erbao; Allen, David W.; Lemaillet, Paul; Xu, Ronald

2016-03-01

Accurate characterization of absorption and scattering properties for biologic tissue and tissue-simulating materials enables 3D printing of traceable tissue-simulating phantoms for medical spectral device calibration and standardized medical optical imaging. Conventional double integrating sphere systems have several limitations and are suboptimal for optical characterization of liquid and soft materials used in 3D printing. We propose a vertical double integrating sphere system and the associated reconstruction algorithms for optical characterization of phantom materials that simulate different human tissue components. The system characterizes absorption and scattering properties of liquid and solid phantom materials in an operating wavelength range from 400 nm to 1100 nm. Absorption and scattering properties of the phantoms are adjusted by adding titanium dioxide powder and India ink, respectively. Different material compositions are added in the phantoms and characterized by the vertical double integrating sphere system in order to simulate the human tissue properties. Our test results suggest that the vertical integrating sphere system is able to characterize optical properties of tissue-simulating phantoms without precipitation effect of the liquid samples or wrinkling effect of the soft phantoms during the optical measurement.

The Electronic and Optical Properties of Au Doped Single-Layer Phosphorene

NASA Astrophysics Data System (ADS)

Zhu, Ziqing; Chen, Changpeng; Liu, Jiayi; Han, Lu

2018-01-01

The electronic properties and optical properties of single and double Au-doped phosphorene have been comparatively investigated using the first-principles plane-wave pseudopotential method based on density functional theory. The decrease from direct band gap 0.78 eV to indirect band gap 0.22 and 0.11 eV are observed in the single and double Au-doped phosphorene, respectively. The red shifts of absorbing edge occur in both doped systems, which consequently enhance the absorbing of infrared light in phosphorene. Band gap engineering can, therefore, be used to directly tune the optical absorption of phosphorene system by substitutional Au doping.

10 CFR Appendix H to Part 73 - Weapons Qualification Criteria

Code of Federal Regulations, 2014 CFR

2014-01-01

... position Shotgun 1 1 7 yards 2 Double 0 buck-shot 4 seconds At low ready position fire 2 rounds standing Minimum qualifying = 70%. 2 12 15 yards 4 Double 0 buck-shot 15 seconds At low ready position fire 2 rounds standing, reload and fire 2 rounds 3 12 25 yards 4 rifled slugs or 00 buck-shot 20 seconds On...

10 CFR Appendix H to Part 73 - Weapons Qualification Criteria

Code of Federal Regulations, 2011 CFR

2011-01-01

... position Shotgun 1 1 7 yards 2 Double 0 buck-shot 4 seconds At low ready position fire 2 rounds standing Minimum qualifying = 70%. 2 12 15 yards 4 Double 0 buck-shot 15 seconds At low ready position fire 2 rounds standing, reload and fire 2 rounds 3 12 25 yards 4 rifled slugs or 00 buck-shot 20 seconds On...

10 CFR Appendix H to Part 73 - Weapons Qualification Criteria

Code of Federal Regulations, 2012 CFR

2012-01-01

... position Shotgun 1 1 7 yards 2 Double 0 buck-shot 4 seconds At low ready position fire 2 rounds standing Minimum qualifying = 70%. 2 12 15 yards 4 Double 0 buck-shot 15 seconds At low ready position fire 2 rounds standing, reload and fire 2 rounds 3 12 25 yards 4 rifled slugs or 00 buck-shot 20 seconds On...

10 CFR Appendix H to Part 73 - Weapons Qualification Criteria

Code of Federal Regulations, 2010 CFR

2010-01-01

... position Shotgun 1 1 7 yards 2 Double 0 buck-shot 4 seconds At low ready position fire 2 rounds standing Minimum qualifying = 70%. 2 12 15 yards 4 Double 0 buck-shot 15 seconds At low ready position fire 2 rounds standing, reload and fire 2 rounds 3 12 25 yards 4 rifled slugs or 00 buck-shot 20 seconds On...

10 CFR Appendix H to Part 73 - Weapons Qualification Criteria

Code of Federal Regulations, 2013 CFR

2013-01-01

... position Shotgun 1 1 7 yards 2 Double 0 buck-shot 4 seconds At low ready position fire 2 rounds standing Minimum qualifying = 70%. 2 12 15 yards 4 Double 0 buck-shot 15 seconds At low ready position fire 2 rounds standing, reload and fire 2 rounds 3 12 25 yards 4 rifled slugs or 00 buck-shot 20 seconds On...

Fire and bird communities in the South

Treesearch

James G. Dickson

2002-01-01

Fire has long been a natural and anthropogenic force shaping southern forests and their fauna. Some species are attracted to recent burns. There is little direct mortality of adult birds by fire, but growing season fires may consume some nests. Fire affects bird communities mainly through effects on vegetation. Fires effective enough to limit understory hardwood...

Military Utility of Multispectral and Hyperspectral Sensors

DTIC Science & Technology

1994-11-01

Resolution) ........ 5-12 5-2. Actual and Modeled Target and Conifer Background Signatures. (a) In the MWIR and (b) in the LW IR...absorption in CO2 at 2.7, 4.2, and 15 Pm, and absorption in silicon dioxide between 8.5 and 10 pm. 2.4 DIRECTIONAL REFLECTANCE, BIDIRECTIONAL...3.39 pm), Nd:YAG (1.06 pm), and CO2 (10.6 pm or 5.3 gm doubled). With a typical goniometric facility, a sample is mounted on a 3 axis platform so that

Confirmation of theoretical colour predictions for layering dental composite materials.

PubMed

Mikhail, Sarah S; Johnston, William M

2014-04-01

The aim of this study is to confirm the theoretical colour predictions for single and double layers of dental composite materials on an opaque backing. Single and double layers of composite resins were fabricated, placed in optical contact with a grey backing and measured for spectral radiance. The spectral reflectance and colour were directly determined. Absorption and scattering coefficients as previously reported, the measured thickness of the single layers and the effective reflectance of the grey backing were utilized to theoretically predict the reflectance of the single layer using corrected Kubelka-Munk reflectance theory. For double layers the predicted effective reflectance of the single layer was used as the reflectance of the backing of the second layer and the thickness of the second layer was used to predict the reflectance of the double layer. Colour differences, using both the CIELAB and CIEDE2000 formulae, measured the discrepancy between each directly determined colour and its corresponding theoretical colour. The colour difference discrepancies generally ranged around the perceptibility threshold but were consistently below the respective acceptability threshold. This theory can predict the colour of layers of composite resin within acceptability limits and generally also within perceptibility limits. This theory could therefore be incorporated into computer-based optical measuring instruments that can automate the shade selections for layers of a more opaque first layer under a more translucent second layer for those clinical situations where an underlying background colour and a desirable final colour can be measured. Copyright © 2014 Elsevier Ltd. All rights reserved.

Direct radiative effect of carbonaceous aerosols from crop residue burning during the summer harvest season in East China

NASA Astrophysics Data System (ADS)

Yao, Huan; Song, Yu; Liu, Mingxu; Archer-Nicholls, Scott; Lowe, Douglas; McFiggans, Gordon; Xu, Tingting; Du, Pin; Li, Jianfeng; Wu, Yusheng; Hu, Min; Zhao, Chun; Zhu, Tong

2017-04-01

East China experiences extensive crop residue burnings in fields during harvest season. The direct radiative effect (DRE) of carbonaceous aerosols from crop residue burning in June 2013 in East China was investigated using the Weather Research and Forecasting Model coupled with Chemistry (WRF-Chem). Absorption of organic aerosol (OA) in the presence of brown carbon was considered using the parameterization of Saleh et al. (2014), in which the imaginary part of the OA refractive index is a function of wavelength and the ratio of black carbon (BC) and OA. The carbonaceous emissions from crop fires were estimated using the Moderate Resolution Imaging Spectroradiometer (MODIS) fire radiative power (FRP) product with a localized crop-burning-sourced BC-to-organic carbon (OC) ratio emission ratio of 0.27. Evaluation of the model results with in situ measurements of particulate matter with aerodynamic diameter less than 2.5 µm (PM2. 5) chemical composition, MODIS aerosol optical depth (AOD) detections and meteorological observations showed that this model was able to reproduce the magnitude, spatial variation and optical characteristics of carbonaceous aerosol pollution. The observed BC and OC peak concentrations at the site in Suixi, Anhui province, during the 2013 wheat burning season reached 55.3 µg m-3 and 157.9 µg m-3. WRF-Chem simulations reproduced these trends with a correlation coefficient of 0.74, estimating that crop residue burning contributed 86 and 90 % of peak BC and OC, respectively. The simulated hourly DRE from crop residue burning at the top of atmosphere (TOA) reached a maximum of +22.66 W m-2 at the Suixi site. On average, the simulations showed that the crop residue burning introduced a net positive DRE of +0.14 W m-2 at TOA throughout East China, with BC from this source as the main heating contributor (+0.79 W m-2). The OA DRE from crop burning (-0.22 W m-2) was a combined effect of the positive DRE of absorption (+0.21 W m-2) and a stronger negative DRE of scattering (-0.43 W m-2). Sensitivity tests showed that the DRE of OA absorption strongly depended on the imaginary part of the OA refractive index, the BC-to-OA emission ratio from crop residue burning and the assumed mixing state of the aerosol, whereby the volume mixing treatment resulted in a higher positive DRE compared to the core-shell treatment. The BC mixing state and associated absorption enhancement during BC aging processes will be investigated in detail in future research.

Catalysts for cleaner combustion of coal, wood and briquettes sulfur dioxide reduction options for low emission sources

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smith, P.V.

1995-12-31

Coal fired, low emission sources are a major factor in the air quality problems facing eastern European cities. These sources include: stoker-fired boilers which feed district heating systems and also meet local industrial steam demand, hand-fired boilers which provide heat for one building or a small group of buildings, and masonary tile stoves which heat individual rooms. Global Environmental Systems is marketing through Global Environmental Systems of Polane, Inc. catalysts to improve the combustion of coal, wood or fuel oils in these combustion systems. PCCL-II Combustion Catalysts promotes more complete combustion, reduces or eliminates slag formations, soot, corrosion and somemore » air pollution emissions and is especially effective on high sulfur-high vanadium residual oils. Glo-Klen is a semi-dry powder continuous acting catalyst that is injected directly into the furnace of boilers by operating personnel. It is a multi-purpose catalyst that is a furnace combustion catalyst that saves fuel by increasing combustion efficiency, a cleaner of heat transfer surfaces that saves additional fuel by increasing the absorption of heat, a corrosion-inhibiting catalyst that reduces costly corrosion damage and an air pollution reducing catalyst that reduces air pollution type stack emissions. The reduction of sulfur dioxides from coal or oil-fired boilers of the hand fired stoker design and larger, can be controlled by the induction of the Glo-Klen combustion catalyst and either hydrated lime or pulverized limestone.« less

Photovoltaic and photothermoelectric effect in a double-gated WSe2 device.

PubMed

Groenendijk, Dirk J; Buscema, Michele; Steele, Gary A; Michaelis de Vasconcellos, Steffen; Bratschitsch, Rudolf; van der Zant, Herre S J; Castellanos-Gomez, Andres

2014-10-08

Tungsten diselenide (WSe2), a semiconducting transition metal dichalcogenide (TMDC), shows great potential as active material in optoelectronic devices due to its ambipolarity and direct bandgap in its single-layer form. Recently, different groups have exploited the ambipolarity of WSe2 to realize electrically tunable PN junctions, demonstrating its potential for digital electronics and solar cell applications. In this Letter, we focus on the different photocurrent generation mechanisms in a double-gated WSe2 device by measuring the photocurrent (and photovoltage) as the local gate voltages are varied independently in combination with above- and below-bandgap illumination. This enables us to distinguish between two main photocurrent generation mechanisms, the photovoltaic and photothermoelectric effect. We find that the dominant mechanism depends on the defined gate configuration. In the PN and NP configurations, photocurrent is mainly generated by the photovoltaic effect and the device displays a maximum responsivity of 0.70 mA/W at 532 nm illumination and rise and fall times close to 10 ms. Photocurrent generated by the photothermoelectric effect emerges in the PP configuration and is a factor of 2 larger than the current generated by the photovoltaic effect (in PN and NP configurations). This demonstrates that the photothermoelectric effect can play a significant role in devices based on WSe2 where a region of strong optical absorption, caused by, for example, an asymmetry in flake thickness or optical absorption of the electrodes, generates a sizable thermal gradient upon illumination.

Design optimization of the S-frame to improve crashworthiness

NASA Astrophysics Data System (ADS)

Liu, Shu-Tian; Tong, Ze-Qi; Tang, Zhi-Liang; Zhang, Zong-Hua

2014-08-01

In this paper, the S-frames, the front side rail structures of automobile, were investigated for crashworthiness. Various cross-sections including regular polygon, non-convex polygon and multi-cell with inner stiffener sections were investigated in terms of energy absorption of S-frames. It was determined through extensive numerical simulation that a multi-cell S-frame with double vertical internal stiffeners can absorb more energy than the other configurations. Shape optimization was also carried out to improve energy absorption of the S-frame with a rectangular section. The center composite design of experiment and the sequential response surface method (SRSM) were adopted to construct the approximate design sub-problem, which was then solved by the feasible direction method. An innovative double S-frame was obtained from the optimal result. The optimum configuration of the S-frame was crushed numerically and more plastic hinges as well as shear zones were observed during the crush process. The energy absorption efficiency of the structure with the optimal configuration was improved compared to the initial configuration.

Cattaneo-Christov double-diffusion theory for three-dimensional flow of viscoelastic nanofluid with the effect of heat generation/absorption

NASA Astrophysics Data System (ADS)

Hayat, Tasawar; Qayyum, Sajid; Shehzad, Sabir Ali; Alsaedi, Ahmed

2018-03-01

The present research article focuses on three-dimensional flow of viscoelastic(second grade) nanofluid in the presence of Cattaneo-Christov double-diffusion theory. Flow caused is due to stretching sheet. Characteristics of heat transfer are interpreted by considering the heat generation/absorption. Nanofluid theory comprises of Brownian motion and thermophoresis. Cattaneo-Christov double-diffusion theory is introduced in the energy and concentration expressions. Such diffusions are developed as a part of formulating the thermal and solutal relaxation times framework. Suitable variables are implemented for the conversion of partial differential systems into a sets of ordinary differential equations. The transformed expressions have been explored through homotopic algorithm. Behavior of sundry variables on the velocities, temperature and concentration are scrutinized graphically. Numerical values of skin friction coefficients are also calculated and examined. Here thermal field enhances for heat generation parameter while reverse situation is noticed for heat absorption parameter.

Experimental study of refrigeration performance based on linear Fresnel solar thermal photovoltaic system

NASA Astrophysics Data System (ADS)

Song, Jinghui; Yuan, Hui; Xia, Yunfeng; Kan, Weimin; Deng, Xiaowen; Liu, Shi; Liang, Wanlong; Deng, Jianhua

2018-03-01

This paper introduces the working principle and system constitution of the linear Fresnel solar lithium bromide absorption refrigeration cycle, and elaborates several typical structures of absorption refrigeration cycle, including single-effect, two-stage cycle and double-effect lithium bromide absorption refrigeration cycle A 1.n effect absorption chiller system based on the best parameters was introduced and applied to a linear Fresnel solar absorption chiller system. Through the field refrigerator performance test, the results show: Based on this heat cycle design and processing 1.n lithium bromide absorption refrigeration power up to 35.2KW, It can meet the theoretical expectations and has good flexibility and reliability, provides guidance for the use of solar thermal energy.

The Impact of Fire on Active Layer Thicknes

NASA Astrophysics Data System (ADS)

Schaefer, K. M.; Parsekian, A.; Natali, S.; Ludwig, S.; Michaelides, R. J.; Zebker, H. A.; Chen, J.

2016-12-01

Fire influences permafrost thermodynamics by darkening the surface to increase solar absorption and removing insulating moss and organic soil, resulting in an increase in Active Layer Thickness (ALT). The summer of 2015 was one of the worst fire years on record in Alaska with multiple fires in the Yukon-Kuskokwim (YK) Delta. To understand the impacts of fire on permafrost, we need large-scale, extensive measurements of ALT both within and outside the fire zones. In August 2016, we surveyed ALT across multiple fire zones in the YK Delta using Ground Penetrating Radar (GPR) and mechanical probing. GPR uses pulsed, radio-frequency electromagnetic waves to noninvasively image the subsurface and is an effective tool to quickly map ALT over large areas. We supplemented this ALT data with measurements of Volumetric Water Content (VWC), Organic Layer Thickness (OLT), and burn severity. We quantified the impacts of fire by statistically comparing the measurements inside and outside the fire zones and statistically regressing ALT against VWC, change in OLT, and burn severity.

Enhancing sound absorption and transmission through flexible multi-layer micro-perforated structures.

PubMed

Bravo, Teresa; Maury, Cédric; Pinhède, Cédric

2013-11-01

Theoretical and experimental results are presented into the sound absorption and transmission properties of multi-layer structures made up of thin micro-perforated panels (ML-MPPs). The objective is to improve both the absorption and insulation performances of ML-MPPs through impedance boundary optimization. A fully coupled modal formulation is introduced that predicts the effect of the structural resonances onto the normal incidence absorption coefficient and transmission loss of ML-MPPs. This model is assessed against standing wave tube measurements and simulations based on impedance translation method for two double-layer MPP configurations of relevance in building acoustics and aeronautics. Optimal impedance relationships are proposed that ensure simultaneous maximization of both the absorption and the transmission loss under normal incidence. Exhaustive optimization of the double-layer MPPs is performed to assess the absorption and/or transmission performances with respect to the impedance criterion. It is investigated how the panel volumetric resonances modify the excess dissipation that can be achieved from non-modal optimization of ML-MPPs.

Competitive effects of fire-resistant saplings on their fire-sensitive neighbors are greater than the reverse

Treesearch

J. Stephen Brewer

2015-01-01

Although repeated fires are generally thought to reduce competition, direct tests of this hypothesis are rare. Furthermore, recent theory predicts that fires can increase competitive effects of fireresistant species on fire-sensitive species and thus create stable assemblages dominated by the former. In this study, I quantified competition between saplings of fire-...

Super-hydrophilic copper sulfide films as light absorbers for efficient solar steam generation under one sun illumination

NASA Astrophysics Data System (ADS)

Guo, Zhenzhen; Ming, Xin; Wang, Gang; Hou, Baofei; Liu, Xinghang; Mei, Tao; Li, Jinhua; Wang, Jianying; Wang, Xianbao

2018-02-01

Solar steam technology is one of the simplest, most direct and effective ways to harness solar energy through water evaporation. Here, we report the development using super-hydrophilic copper sulfide (CuS) films with double-layer structures as light absorbers for solar steam generation. In the double-layer structure system, a porous mixed cellulose ester (MCE) membrane is used as a supporting layer, which enables water to get into the CuS light absorbers through a capillary action to provide continuous water during solar steam generation. The super-hydrophilic property of the double-layer system (CuS/MCE) leads to a thinner water film close to the air-water interface where the surface temperature is sufficiently high, leading to more efficient evaporation (˜80 ± 2.5%) under one sun illumination. Furthermore, the evaporation efficiencies still keep a steady value after 15 cycles of testing. The super-hydrophilic CuS film is promising for practical application in water purification and evaporation as a light absorption material.

Forest Fire Finder - DOAS application to long-range forest fire detection

NASA Astrophysics Data System (ADS)

Valente de Almeida, Rui; Vieira, Pedro

2017-06-01

Fires are an important factor in shaping Earth's ecosystems. Plant and animal life, in almost every land habitat, are at least partially dependent on the effects of fire. However, their destructive force, which has often proven uncontrollable, is one of our greatest concerns, effectively resulting in several policies in the most important industrialised regions of the globe. This paper aims to comprehensively characterise the Forest Fire Finder (FFF), a forest fire detection system based mainly upon a spectroscopic technique called differential optical absorption spectroscopy (DOAS). The system is designed and configured with the goal of detecting higher-than-the-horizon smoke columns by measuring and comparing scattered sunlight spectra. The article covers hardware and software, as well as their interactions and specific algorithms for day mode operation. An analysis of data retrieved from several installations deployed in the course of the last 5 years is also presented. Finally, this paper features a discussion on the most prominent future improvements planned for the system, as well as its ramifications and adaptations, such as a thermal imaging system for short-range fire seeking or environmental quality control.

The impact of biogenic carbon emissions on aerosol absorption inMexico City

DOE Office of Scientific and Technical Information (OSTI.GOV)

Marley, N; Gaffney, J; Tackett, M J

2009-02-24

In order to determine the wavelength dependence of atmospheric aerosol absorption in the Mexico City area, the absorption angstrom exponents (AAEs) were calculated from aerosol absorption measurements at seven wavelengths obtained with a seven-channel aethalometer during two field campaigns, the Mexico City Metropolitan Area study in April 2003 (MCMA 2003) and the Megacity Initiative: Local and Global Research Observations in March 2006 (MILAGRO). The AAEs varied from 0.76 to 1.56 in 2003 and from 0.54 to 1.52 in 2006. The AAE values determined in the afternoon were consistently higher than the corresponding morning values, suggesting the photochemical formation of absorbingmore » secondary organic aerosols (SOA) in the afternoon. The AAE values were compared to stable and radiocarbon isotopic measurements of aerosol samples collected at the same time to determine the sources of the aerosol carbon. The fraction of modern carbon (fM) in the aerosol samples, as determined from {sup 14}C analysis, showed that 70% of the carbonaceous aerosols in Mexico City were from modern sources, indicating a significant impact from biomass burning during both field campaigns. The {sup 13}C/{sup 12}C ratios of the aerosol samples illustrate the significant impact of Yucatan forest fires (C-3 plants) in 2003 and local grass fires (C-4 plants) at site T1 in 2006. A direct comparison of the fM values, stable carbon isotope ratios, and calculated aerosol AAEs suggested that the wavelength dependence of the aerosol absorption was controlled by the biogenically derived aerosol components.« less

Elucidating the effects of solar panel waste glass substitution on the physical and mechanical characteristics of clay bricks.

PubMed

Lin, Kae-Long; Huang, Long-Sheng; Shie, Je-Lueng; Cheng, Ching-Jung; Lee, Ching-Hwa; Chang, Tien-Chin

2013-01-01

This study deals with the effect of solar panel waste glass on fired clay bricks. Brick samples were heated to temperatures which varied from 700-1000 degrees C for 6 h, with a heating rate of 10 degrees C min(-1). The material properties of the resultant material were then determined, including speciation variation, loss on ignition, shrinkage, bulk density, 24-h absorption rate, compressive strength and salt crystallization. The results indicate that increasing the amount of solar panel waste glass resulted in a decrease in the water absorption rate and an increase in the compressive strength of the solar panel waste glass bricks. The 24-h absorption rate and compressive strength of the solar panel waste glass brick made from samples containing 30% solar panel waste glass sintered at 1000 degrees C all met the Chinese National Standard (CNS) building requirements for first-class brick (compressive strengths and water absorption of the bricks were 300 kg cm(-2) and 10% of the brick, respectively). The addition of solar panel waste glass to the mixture reduced the degree of firing shrinkage. The salt crystallization test and wet-dry tests showed that the addition of solar panel waste glass had highly beneficial effects in that it increased the durability of the bricks. This indicates that solar panel waste glass is indeed suitable for the partial replacement of clay in bricks.

Pump absorption in coiled and twisted double-clad hexagonal fiber: effect of launching conditions and core location

NASA Astrophysics Data System (ADS)

Dalidet, Romain; Peterka, Pavel; Doya, Valérie; Aubrecht, Jan; Koška, Pavel

2018-02-01

Ever extending applications of fiber lasers require energy efficient, high-power, small footprint and reliable fiber lasers and laser wavelength versatility. To meet these demands, next generation of active fibers for high-power fiber lasers is coming out that will eventually offer tailored spectroscopic properties, high robustness and reduced cooling requirements and improved efficiency through tailored pump absorption. We report on numerical modelling of the efficiency of the pump absorption in double clad active fibers with hexagonal shape of the inner cladding cross section and rare-earth-doped core. We analyze both the effect of different radii of the spool on which the fiber is coiled and different fiber twisting rates. Two different launching conditions were investigated: the Gaussian input pump beam and a speckle pattern that mimics the output of the pump laser diode pigtail. We have found that by asymmetric position of the rare-earth-doped core we can significantly improve the pump absorption.

Validation of a Polyimide Foam Model for Use in Transmission Loss Applications

NASA Technical Reports Server (NTRS)

Hong, Kwanwoo; Bolton, J. Stuart; Cano, Roberto J.; Weiser, Erik S.; Jensen, Brian J.; Silcox, Rich; Howerton, Brian M.; Maxon, John; Wang, Tongan; Lorenzi, Tyler

2010-01-01

The work described in this paper was focused on the use of a new polyimide foam in a double wall sound transmission loss application. Recall that polyimide foams are functionally attractive, compared to polyurethane foams, for example, owing to their fire resistance. The foam considered here was found to have a flow resistivity that was too high for conventional acoustical applications, and as a result, it was processed by partial crushing to lower the flow resistivity into an acceptable range. Procedures for measuring the flow resistivity and Young s modulus of the material have been described, as was an inverse characterization procedure for estimating the remaining Biot parameters based on standing wave tube measurements of transmission loss and absorption coefficient. The inverse characterization was performed using a finite element model implementation of the Biot poro-elastic material theory. Those parameters were then used to predict the sound transmission loss of a double panel system lined with polyimide foam, and the predictions were compared with full-scale transmission loss measurements. The agreement between the two was reasonable, especially in the high and low frequency limits; however, it was found that the SEA model resulted in an under-prediction of the transmission loss in the mid-frequency range. Nonetheless, it was concluded that the performance of polyimide foam could be predicted using conventional poro-elastic material models and that polyimide foam may offer an attractive alternative to other double wall linings in certain situations: e.g., when fire resistance is a key issue. Future work will concentrate on reducing the density of the foam to values similar to those used in current aircraft sidewall treatments, and developing procedures to improve the performance of the foam in transmission loss applications.

A view of microstructure with technological behavior of waste incorporated ceramic bricks.

PubMed

Nirmala, G; Viruthagiri, G

2015-01-25

Production of ceramic bricks from mixtures of ceramic industry wastes (up to 50 wt%) from the area of Vriddhachalam, Cuddalore district, Tamilnadu, India and kaolinitic clay from Thiruvananthapuram district, Kerala were investigated. The firing behavior of the ceramic mixtures was studied by determining their changes in mineralogy and basic ceramic properties such as water absorption, porosity, compressive strength and firing shrinkage at temperatures ranging from 900 to 1200 °C in short firing cycles. The effect of the rejects addition gradually up to 50 wt% was analyzed with the variation of temperature on the mechanical properties and microstructure of the bricks. The highest compressive strength and lowest water absorption is observed for the sample with 40% rejects at 1100 °C which is supported by the results of SEM analysis. The resulting ceramic bricks exhibit features that suggest possibilities of using the ceramic rejects in the conventional brick making methods. Copyright © 2014 Elsevier B.V. All rights reserved.

Line by Line Analysis of Carbon Dioxide Absorption for Predicting Global Warming

NASA Astrophysics Data System (ADS)

Smith, D. C.

2010-12-01

The anthropologic cause of global warming rests on the impact of CO2 on the green house effect. Previous derivations of the increase in the CO2 Forcing Function caused by doubling of atmospheric CO2 from 320 ppm to 640 ppm reported a value of 4 W/M2( Ramananathan,V,et al, J.of Geophysical Research Vol 84, C8,p4949, Aug.1979) This value leads to a calculated temperature rise of 1 deg.K (Charney,J. et al,”Carbon Dioxide and Climate: A Scientific Assessment”, National Academy of Science, Washington D.C., 1979). This increase in global temperature leads to an increase in water vapor if it is assumed that the relative humidity is constant. This ampflication leads to a calculated temperature rise of an additional 2 deg.K. Different arguments as to the effects of the earth’s albido change, clouds, and the oceans also impact the earths global warming with predictions of total temperature rise of as high as 6 deg.K { IPCC,2007 Summary for Policymakers. In: Climate Change 2007: The Physical Sciences Basis. Contributions of Working Group 1 to the Fourth Assessment Report of the IPCC [ Solomon,S,D. et al (eds)] Cambridge University Press, NY,USA}. Regardless of the other effects, the only way that man can be held responsible for global warming is by CO2 emissions and the resulting increase in the Forcing Function. This paper challenges the magnitude of the 4 W/M2 Forcing Function. The earth radiates in the 4 to 30 micron wavelength range. CO2 has absorption bands in the 4, 10, and 15 micron wavelengths (Hertzberg G. Molecular Spectra & Molecular Structure,Norstrand Co.,1960). McClatchey has tabulated the line stengths for all CO2 transitions and they are used to calculate the atmospheric absorption (McClatchey,R, et al “AFCRL Atmospheric Absorption Line Parameter Compilation”,AFCRL-TR-0096,1973). Detailed calculations of the CO2 line absorption in the 8 to 12 micron atmospheric window shows an increase of 0.3 W/M2 for CO2 doubling. The increase in absorbed fluence in the 12 to 20 micron range is 0.8 W/M2. The increase in the 4 micron band is 0.01 W/M2. (The very strong absorption lines are saturated at CO2 levels of 320 ppm). The total increase in absorbed IR fluence for doubling CO2 is 1.1 W/M2 Detailed calculations of how this absorbed energy heats the earth and what fraction escapes to space must be done for a definitive answer as to what the increase in the Forcing Function is for doubled CO2. Even if all of the absorbed radiation were delivered to the earth, the temperature rise due to doubling CO2 would be 0.26 deg.K. Up to 1/2 the absorbed fluence can be convected/radiated to outer space, which would lead to a temperature rise of 0.13 deg.K. (There is the amplification factor due to increased water vapor that must be added to the direct CO2 contribution but this is also signicantly reduced relative to the 2 deg.K presently accepted). The important difference between the results of this study and the previous predictions, (4W/M2), is probably due to the saturation of the lines which is obscured by band model calculations and is not in the line by line calculations. The conclusion is that man’s contribution to global warming is small.

Potential climate change impacts on fire intensity and key wildfire suppression thresholds in Canada

NASA Astrophysics Data System (ADS)

Wotton, B. M.; Flannigan, M. D.; Marshall, G. A.

2017-09-01

Much research has been carried out on the potential impacts of climate change on forest fire activity in the boreal forest. Indeed, there is a general consensus that, while change will vary regionally across the vast extent of the boreal, in general the fire environment will become more conducive to fire. Land management agencies must consider ways to adapt to these new conditions. This paper examines the impact of that changed fire environment on overall wildfire suppression capability. We use multiple General Circulation Models and carbon emission pathways to generate future fire environment scenarios for Canada’s forested region. We then use these scenarios with the Canadian Forest Fire Behaviour Prediction System and spatial coverages of the current forest fuel composition across the landscape to examine potential variation in key fire behaviour outputs that influence whether fire management resources can effectively suppress fire. Specifically, we evaluate how the potential for crown fire occurrence and active growth of fires changes with the changing climate. We also examine future fire behaviour through the lens of operational fire intensity thresholds used to guide decisions about resources effectiveness. Results indicate that the proportion of days in fire seasons with the potential for unmanageable fire will increase across Canada’s forest, more than doubling in some regions in northern and eastern boreal forest.

Strain-induced changes of the electronic properties of B -site ordered double-perovskite Sr2CoIrO6 thin films

NASA Astrophysics Data System (ADS)

Esser, S.; Chang, C. F.; Kuo, C.-Y.; Merten, S.; Roddatis, V.; Ha, T. D.; Jesche, A.; Moshnyaga, V.; Lin, H.-J.; Tanaka, A.; Chen, C. T.; Tjeng, L. H.; Gegenwart, P.

2018-05-01

B -site ordered thin films of double perovskite Sr2CoIrO6 were epitaxially grown by a metalorganic aerosol deposition technique on various substrates, actuating different strain states. X-ray diffraction, transmission electron microscopy, and polarized far-field Raman spectroscopy confirm the strained epitaxial growth on all used substrates. Polarization-dependent Co L2 ,3 x-ray absorption spectroscopy reveals a change of the magnetic easy axis of the antiferromagnetically ordered (high-spin) Co3 + sublattice within the strain series. By reversing the applied strain direction from tensile to compressive, the easy axis changes abruptly from in-plane to out-of-plane orientation. The low-temperature magnetoresistance changes its sign respectively and is described by a combination of weak antilocalization and anisotropic magnetoresistance effects.

Effects of Climate and Fuels Management on Wildfire Occurrence, Size, Severity and Emissions in the Sierra Nevada

NASA Astrophysics Data System (ADS)

Westerling, A. L.; Fites, J. A.; Keyser, A.

2015-12-01

Annual wildfire burned area in federally managed Sierra Nevada forests has increased by more than 10,000 ha per decade since the early 1970s. At the same time, recent years have seen some extremely large fires compared to the historical record, with significant areas of moderate to high severity fire (e.g., McNally 2002, Rim 2013, King 2014 fires). Changes to fuels and fire regimes due to fire suppression and land use, as well as warming temperatures and the occurrence of drought, are thought to be significant factors contributing to increased risks of large, severe fires in Sierra Nevada forests. Over 70% of the vegetated area in federally managed forests in the Sierra Nevada is classified as having altered fuels and fire regimes, while average annual temperature in the Sierra Nevada has been above the long term mean for all but four years in the past two decades. As climate is expected to continue warming for decades to come, we explored fuels management scenarios as the primary tools available to modify risks of large, severe wildfires. We developed experimental statistical models of fire occurrence, fire size, and high severity burned area, to explore the interaction between climate and altered fuels conditions. These models were applied to historical climate conditions, a sample of future climate projections, and to both current fuels conditions and a range of scenarios for fuels treatments. Emissions from wildfires were estimated using the Fire Inventory from the National Center for Atmospheric Research. Our models project that average annual burned area in the Sierra Nevada will more than double by mid-century. Similarly, particulate and other pollution emissions from Sierra Nevada wildfires are projected to more than double, even if future fire severity does not change. Fuels treatment scenarios significantly reduced simulated future burned area and emissions below untreated projections. High severity burned area responded to both climate and fuels treatments. A sensitivity analysis indicated that in areas where the fraction of highly altered fuels is high, successfully restoring fuels to prehistoric conditions could more than compensate for expected climate change effects on fire severity by mid-century.

Fire control method and analytical model for large liquid hydrocarbon pool fires

NASA Technical Reports Server (NTRS)

Fenton, D. L.

1986-01-01

The dominate parameter governing the behavior of a liquid hydrocarbon (JP-5) pool fire is wind speed. The most effective method of controlling wind speed in the vicinity of a large circular (10 m dia.) pool fire is a set of concentric screens located outside the perimeter. Because detailed behavior of the pool fire structure within one pool fire diameter is unknown, an analytical model supported by careful experiments is under development. As a first step toward this development, a regional pool fire model was constructed for the no-wind condition consisting of three zones -- liquid fuel, combustion, and plume -- where the predicted variables are mass burning rate and characteristic temperatures of the combustion and plume zones. This zone pool fire model can be modified to incorporate plume bending by wind, radiation absorption by soot particles, and a different ambient air flow entrainment rate. Results from the zone model are given for a pool diameter of 1.3 m and are found to reproduce values in the literature.

Effects of fire damage on the structural properties of steel bridge elements.

DOT National Transportation Integrated Search

2011-04-30

It is well known that fire can cause severe damage to steel bridges. There are documented cases where fire has directly led to the collapse or significant sagging of a steel bridge. However, when the damage is less severe, the effects of the fire, if...

Taking the Pulse of PyroCumulus Clouds

NASA Technical Reports Server (NTRS)

Gatebe, C. K.; Varnai, T.; Poudyal, R.; Ichoku, C.; King, M. D.

2012-01-01

Forest fires can burn large areas, but can also inject smoke into the upper troposphere/lower stratosphere (UT/LS), where stakes are even higher for climate, because emissions tend to have a longer lifetime, and can produce significant regional and even global climate effects, as is the case with some volcanoes. Large forest fires are now believed to be more common in summer, especially in the boreal regions, where pyrocumulus (pyroCu), and occasionally pyrocumuionimbus (pyroCb) clouds are formed, which can transport emissions into the UT/LS. A major difficulty in developing realistic fire plume models is the lack of observational data within fire plumes that resolves structure at a few 100 m scales, which can be used to validate these models. Here, we report detailed airborne radiation measurements within strong pyroCu taken over boreal forest fires in Saskatchewan, Canada during the Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) summer field campaign in 2008. We find that the angular distribution of radiance within the pyroCu is closely related to the diffusion domain in water clouds and can be described by very similar simple cosine functions. We demonstrate with Monte Carlo simulations that radiation transport in pyroCu is inherently a 3D phenomenon and must account for particle absorption. However, the simple cosine function promises to offer an easy solution for climate models. The presence of a prominent smoke core, defined by strong extinction in the UV, VIS and NIR, suggests that the core might be an important pathway for emission transport to the upper troposphere and lower stratosphere. We speculate that this plume injection core is generated and sustained by complex processes not yet well understood, but not necessarily related directly to the intense fires that originally initiated the plume rise.

Modeling investigation of light-absorbing aerosols in the Amazon Basin during the wet season

NASA Astrophysics Data System (ADS)

Wang, Qiaoqiao; Saturno, Jorge; Chi, Xuguang; Walter, David; Lavric, Jost; Moran-Zuloaga, Daniel; Ditas, Florian; Pöhlker, Christopher; Brito, Joel; Carbone, Samara; Artaxo, Paulo; Andreae, Meinrat

2017-04-01

We use a global chemical transport model (GEOS-Chem) to interpret observed light-absorbing aerosols in Amazonia during the wet season. Observed aerosol properties, including black carbon (BC) concentration and light absorption, at the Amazon Tall Tower Observatory (ATTO) site in the central Amazon have relatively low background levels but frequently show high peaks during the study period of January-April 2014. With daily temporal resolution for open fire emissions and modified aerosol optical properties, our model successfully captures the observed variation in fine/coarse aerosol and BC concentrations as well as aerosol light absorption and its wavelength dependence over the Amazon Basin. The source attribution in the model indicates the important influence of open fire on the observed variances of aerosol concentrations and absorption, mainly from regional sources (northern South America) and from northern Africa. The contribution of open fires from these two regions is comparable, with the latter becoming more important in the late wet season. The analysis of correlation and enhancement ratios of BC versus CO suggests transport times of < 3 days for regional fires and 11 days for African plumes arriving at ATTO during the wet season. The model performance of long-range transport of African plumes is also evaluated with observations from AERONET, MODIS, and CALIOP. Simulated absorption aerosol optical depth (AAOD) averaged over the wet season is lower than 0.0015 over the central Amazon, including the ATTO site. We find that more than 50% of total absorption at 550 nm is from BC, except for the northeastern Amazon and the Guianas, where the influence of dust becomes significant (up to 35 %). The brown carbon contribution is generally between 20 and 30 %. The distribution of absorption Ångström exponents (AAE) suggests more influence from fossil fuel combustion in the southern part of the basin (AAE 1) but more open fire and dust influence in the northern part (AAE > 1.8). Uncertainty analysis shows that accounting for absorption due to secondary organic aerosol (SOA) and primary biogenic aerosol (PBA) particles could result in differences of < 8 and 5-40% in total absorption, respectively.

Assessment of Energy Storage Technologies for Army Facilities.

DTIC Science & Technology

1986-05-01

units, and the other on tandem units with separate multistage pump and Pelton impulse turbine . The third scheme was a double-drop type based on the...used to drive the turbine /generator. Exhaust gas from the low-pressure turbine may be used to preheat inlet air to the high-pressure turbine . Storage...for firing CAES plant turbines . A Battelle publication summarizes reservoir stability criteria and research directed toward minimizing or eliminating

An infrared scattering by evaporating droplets at the initial stage of a pool fire suppression by water sprays

NASA Astrophysics Data System (ADS)

Dombrovsky, Leonid A.; Dembele, Siaka; Wen, Jennifer X.

2018-06-01

The computational analysis of downward motion and evaporation of water droplets used to suppress a typical transient pool fire shows local regions of a high volume fraction of relatively small droplets. These droplets are comparable in size with the infrared wavelength in the range of intense flame radiation. The estimated scattering of the radiation by these droplets is considerable throughout the entire spectrum except for a narrow region in the vicinity of the main absorption peak of water where the anomalous refraction takes place. The calculations of infrared radiation field in the model pool fire indicate the strong effect of scattering which can be observed experimentally to validate the fire computational model.

The design and performance of the nano-carbon based double layers flexible coating for tunable and high-efficiency microwave absorption

NASA Astrophysics Data System (ADS)

Zhang, Danfeng; Hao, Zhifeng; Qian, Yannan; Zeng, Bi; Zhu, Haiping; Wu, Qibai; Yan, Chengjie; Chen, Muyu

2018-05-01

Nanocarbon-based materials are outstanding microwave absorbers with good dielectric properties. In this study, double-layer silicone resin flexible absorbing coatings, composed of carbon-coated nickel nanoparticles (Ni@C) and carbon nanotubes (CNTs), with low loading and a total thickness of 2 mm, were prepared. The reflection loss (RL) of the double-layer absorbing coatings has measured for frequencies between 2 and 18 GHz using the Arch reflecting testing method. The effects of the thickness and electromagnetic parameters of each layer and of the layer sequence on the absorbing properties were investigated. It is found that the measured bandwidth (RL ≤ - 10 dB) of the optimum double-layer structure in our experiment range achieves 3.70 GHz. The results indicated that the double coating structure composed of different materials has greater synergistic absorption effect on impedance matching than that of same materials with different loading. The maximum RL of S1 (5 wt% CNTs)/S3 (60 wt% Ni@C) double-layer absorbing coating composed of different materials (S1 and S3) was larger than the one achieved using either S1 or S3 alone with the same thickness. This was because double-layer coating provided a suitable matching layer and improve the interfacial impedance. It was also shown that absorbing peak value and frequency position can be adjusted by double-layer coating structure.

Design of Miniaturized Double-Negative Material for Specific Absorption Rate Reduction in Human Head

PubMed Central

Faruque, Mohammad Rashed Iqbal; Islam, Mohammad Tariqul

2014-01-01

In this study, a double-negative triangular metamaterial (TMM) structure, which exhibits a resounding electric response at microwave frequency, was developed by etching two concentric triangular rings of conducting materials. A finite-difference time-domain method in conjunction with the lossy-Drude model was used in this study. Simulations were performed using the CST Microwave Studio. The specific absorption rate (SAR) reduction technique is discussed, and the effects of the position of attachment, the distance, and the size of the metamaterials on the SAR reduction are explored. The performance of the double-negative TMMs in cellular phones was also measured in the cheek and the tilted positions using the COMOSAR system. The TMMs achieved a 52.28% reduction for the 10 g SAR. These results provide a guideline to determine the triangular design of metamaterials with the maximum SAR reducing effect for a mobile phone. PMID:25350398

Design of miniaturized double-negative material for specific absorption rate reduction in human head.

PubMed

Faruque, Mohammad Rashed Iqbal; Islam, Mohammad Tariqul

2014-01-01

In this study, a double-negative triangular metamaterial (TMM) structure, which exhibits a resounding electric response at microwave frequency, was developed by etching two concentric triangular rings of conducting materials. A finite-difference time-domain method in conjunction with the lossy-Drude model was used in this study. Simulations were performed using the CST Microwave Studio. The specific absorption rate (SAR) reduction technique is discussed, and the effects of the position of attachment, the distance, and the size of the metamaterials on the SAR reduction are explored. The performance of the double-negative TMMs in cellular phones was also measured in the cheek and the tilted positions using the COMOSAR system. The TMMs achieved a 52.28% reduction for the 10 g SAR. These results provide a guideline to determine the triangular design of metamaterials with the maximum SAR reducing effect for a mobile phone.

Fire and the herbaceous layer of eastern oak forests

Treesearch

Todd Hutchinson

2006-01-01

Across oak forest landscapes, the herbaceous layer supports the great majority of plant diversity. As the use of prescribed fire increases, it is important to better understand its effects on biodiversity. This paper reviews the current ?state of the knowledge? regarding fire effects on herbaceous layer vegetation. In typical dormant-season fires, direct heating...

Fire-induced Carbon Emissions and Regrowth Uptake in Western U.S. Forests: Documenting Variation Across Forest Types, Fire Severity, and Climate Regions

NASA Technical Reports Server (NTRS)

Ghimire, Bardan; Williams, Christopher A.; Collatz, George James; Vanderhoof, Melanie

2012-01-01

The forest area in the western United States that burns annually is increasing with warmer temperatures, more frequent droughts, and higher fuel densities. Studies that examine fire effects for regional carbon balances have tended to either focus on individual fires as examples or adopt generalizations without considering how forest type, fire severity, and regional climate influence carbon legacies. This study provides a more detailed characterization of fire effects and quantifies the full carbon impacts in relation to direct emissions, slow release of fire-killed biomass, and net carbon uptake from forest regrowth. We find important variations in fire-induced mortality and combustion across carbon pools (leaf, live wood, dead wood, litter, and duff) and across low- to high-severity classes. This corresponds to fire-induced direct emissions from 1984 to 2008 averaging 4 TgC/yr and biomass killed averaging 10.5 TgC/yr, with average burn area of 2723 sq km/yr across the western United States. These direct emission and biomass killed rates were 1.4 and 3.7 times higher, respectively, for high-severity fires than those for low-severity fires. The results show that forest regrowth varies greatly by forest type and with severity and that these factors impose a sustained carbon uptake legacy. The western U.S. fires between 1984 and 2008 imposed a net source of 12.3 TgC/yr in 2008, accounting for both direct fire emissions (9.5 TgC/yr) and heterotrophic decomposition of fire-killed biomass (6.1 TgC yr1) as well as contemporary regrowth sinks (3.3 TgC/yr). A sizeable trend exists toward increasing emissions as a larger area burns annually.

Properties of fired clay brick incorporating with sewage sludge waste

NASA Astrophysics Data System (ADS)

Kadir, Aeslina Abdul; Salim, Nurul Salhana Abdul; Sarani, Noor Amira; Rahmat, Nur Aqma Izurin; Abdullah, Mohd Mustafa Al Bakri

2017-09-01

The production of sludge in wastewater treatment plant is about to increase every year and most of the sludge was directly disposed to landfill. In addition, the constraint to treat sludge is very high in cost and time- consuming could be disadvantages to the responsible parties. Therefore, this research was conducted to utilize sludge produced from the wastewater treatment plant into fired clay brick as one of the alternatives of disposal method. In this study, the research attempt to incorporate sewage sludge waste (SSW) into fired clay brick. The sewage sludge brick (SSB) mixtures were incorporated with 0%, 1%, 5%, 10%, and 20% of SSW. The manufactured bricks were fired at 1050°C with heating rate of 1°C/min. Physical and mechanical properties test were conducted such as shrinkage, density, water absorption and compressive strength. As the conclusion, brick with utilization 5% of SSW is acceptable to produce good quality of brick. This study shows by using SSW in fired clay brick could be an alternative method to dispose of the SSW and also could act as a replacement material for brick manufacturing with appropriate mix and design.

Recent changes in the fire regime across the North American boreal region-Spatial and temporal patterns of burning across Canada and Alaska

NASA Astrophysics Data System (ADS)

Kasischke, Eric S.; Turetsky, Merritt R.

2006-05-01

We used historic records from 1959-99 to explore fire regime characteristics at ecozone scales across the entire North American boreal region (NABR). Shifts in the NABR fire regime between the 1960s/70s and the 1980s/90s were characterized by a doubling of annual burned area and more than a doubling of the frequency of larger fire years because of more large fire events (>1,000 km2). The proportion of total burned area from human-ignited fires decreased over this same time period, while the proportion of burning during the early and late- growing-seasons increased. Trends in increased burned area were consistent across the NABR ecozones, though the western ecozones experienced greater increases in larger fire years compared to the eastern ecozones. Seasonal patterns of burning differed among ecozones. Along with the climate warming, changes in the fire regime characteristics may be an important driver of future ecosystem processes in the NABR.

Self-double-emulsifying drug delivery system (SDEDDS): a new way for oral delivery of drugs with high solubility and low permeability.

PubMed

Qi, Xiaole; Wang, Lishuang; Zhu, Jiabi; Hu, Zhenyi; Zhang, Jie

2011-05-16

Water-in-oil-in-water (w/o/w) double emulsions are potential for enhancing oral bioavailability of drugs with high solubility and low permeability, but their industrial application is limited due to the instability. Herein, we developed a novel formulation, self-double-emulsifying drug delivery systems (SDEDDS) by formulating mixtures of hydrophilic surfactants and water-in-oil (w/o) emulsions, which were easier to be stable through formulations optimization. SDEDDS can spontaneously emulsify to water-in-oil-in-water (w/o/w) double emulsions in the mixed aqueous gastrointestinal environment, with drugs encapsulated in the internal water phase of the double emulsions. We employed SDEDDS to improve the oral absorption of pidotimod, a peptide-like drug with high solubility and low permeability. The optimized pidotimod-SDEDDS were found to be stable up to 6 months under 25°C. Plasma concentration-time profiles from pharmacokinetic studies in rats dosed with SDEDDS showed 2.56-fold (p<0.05) increased absorption of pidotimod, compared to the pidotimod solution. Histopathologic studies confirmed that SDEDDS exerted absorption promoting effect without serious local damages. These studies demonstrate that SDEDDS may be a promising strategy for peroral delivery of peptide and peptidomimetic drugs. Copyright © 2011 Elsevier B.V. All rights reserved.

Direct effects of fire on endangered Mount Graham red squirrels

Treesearch

John L. Koprowski; Katherine M. Leonard; Claire A. Zugmeyer; Julia L. Jolley

2006-01-01

Direct mortality of forest wildlife due to fire is rarely documented. In June and July 2004, the Nuttall Complex Fire burned 11,898 ha in the Pinaleno Mountains, southeastern Arizona. Portions of these mountains serve as the only habitat of endangered Mount Graham red squirrels (Tamiasciurus hudsonicus grahamensis). Survival of radio-collared red...

Direct and indirect responses of tallgrass prairie butterflies to prescribed burning

USGS Publications Warehouse

Vogel, Jennifer A.; Koford, Rolf R.; Debinski, Diane M.

2010-01-01

Fire is an important tool in the conservation and restoration of tallgrass prairie ecosystems. We investigated how both the vegetation composition and butterfly community of tallgrass prairie remnants changed in relation to the elapsed time (in months) since prescribed fire. Butterfly richness and butterfly abundance were positively correlated with the time since burn. Habitat-specialist butterfly richness recovery time was greater than 70 months post-fire and habitat-specialist butterfly abundance recovery time was approximately 50 months post-fire. Thus, recovery times for butterfly populations after prescribed fires in our study were potentially longer than those previously reported. We used Path Analysis to evaluate the relative contributions of the direct effect of time since fire and the indirect effects of time since fire through changes in vegetation composition on butterfly abundance. Path models highlighted the importance of the indirect effects of fire on habitat features, such as increases in the cover of bare ground. Because fire return intervals on managed prairie remnants are often less than 5 years, information on recovery times for habitat-specialist insect species are of great importance. ?? 2010 Springer Science+Business Media B.V.

Vibration effects of the space shuttle main engine high pressure oxidizer turbopump bellows

NASA Technical Reports Server (NTRS)

Harp, J. A.

1978-01-01

A welded metal bellows was subjected to a series of vibration tests in a 400 psi oxygen environment to evaluate the effects of the bellows convolutes rubbing on the damper ring in the high pressure oxidizer turbopump of the space shuttle main engine. The bellows was subjected to approximately 2 million cycles at 0.007 in. double amplitude displacement during this series of tests, at a frequency of 400 Hz. Intrumentation of the test specimen revealed no significant heat buildup caused by the rubbing of the bellows convolutes on the damper ring. A final destruct test was made to determine if a fire would result if the bellows ruptured in the 400 psi oxygen environment, thus exposing a fresh metal surface. The vibration input was changed to 0.8 in. double amplitude displacement at 20 Hz to intentionally rupture the bellows. Failure occurred after 2.5 sec; no fire or heat buildup was encountered.

Modeling of exposure to carbon monoxide in fires

NASA Technical Reports Server (NTRS)

Cagliostro, D. E.

1980-01-01

A mathematical model is developed to predict carboxyhemoglobin concentrations in regions of the body for short exposures to carbon monoxide levels expected during escape from aircraft fires. The model includes the respiratory and circulatory dynamics of absorption and distribution of carbon monoxide and carboxyhemoglobin. Predictions of carboxyhemoglobin concentrations are compared to experimental values obtained for human exposures to constant high carbon monoxide levels. Predictions are within 20% of experimental values. For short exposure times, transient concentration effects are predicted. The effect of stress is studied and found to increase carboxyhemoglobin levels substantially compared to a rest state.

Study report on a double isotope method of calcium absorption

NASA Technical Reports Server (NTRS)

1978-01-01

Some of the pros and cons of three methods to study gastrointestinal calcium absorption are briefly discussed. The methods are: (1) a balance study; (2) a single isotope method; and (3) a double isotope method. A procedure for the double isotope method is also included.

Quantifying the effect of fuel reduction treatments on fire behavior in boreal forests

Treesearch

B.W. Butler; R.D. Ottmar; T.S. Rupp; R. Jandt; E. Miller; K. Howard; R. Schmoll; S. Theisen; R.E. Vihnanek; D. Jimenez

2013-01-01

Mechanical (e.g., shearblading) and manual (e.g., thinning) fuel treatments have become the preferred strategy of many fire managers and agencies for reducing fire hazard in boreal forests. This study attempts to characterize the effectiveness of four fuel treatments through direct measurement of fire intensity and forest floor consumption during a single prescribed...

First Order Fire Effects Model: FOFEM 4.0, user's guide

Treesearch

Elizabeth D. Reinhardt; Robert E. Keane; James K. Brown

1997-01-01

A First Order Fire Effects Model (FOFEM) was developed to predict the direct consequences of prescribed fire and wildfire. FOFEM computes duff and woody fuel consumption, smoke production, and fire-caused tree mortality for most forest and rangeland types in the United States. The model is available as a computer program for PC or Data General computer.

A Comprehensive X-Ray Absorption Model for Atomic Oxygen

NASA Technical Reports Server (NTRS)

Gorczyca, T. W.; Bautista, M. A.; Hasoglu, M. F.; Garcia, J.; Gatuzz, E.; Kaastra, J. S.; Kallman, T. R.; Manson, S. T.; Mendoza, C.; Raassen, A. J. J.;

Equivalent Black Carbon measurements and spectral analysis of absorption coefficient during a biomass burning episode in the city of Bogotá, Colombia.

NASA Astrophysics Data System (ADS)

Quirama, M.; Morales, R.

2016-12-01

Light-absorbing carbonaceous aerosol is recognized as a significant short lived climate pollutant that can contribute to direct and indirect radiative forcing. In urban environments, black carbon is an important contributor to the deterioration of local air quality. In this study, we report measurements of equivalent Black Carbon performed during the months of January, February, and March 2016 in the city of Bogotá, Colombia. During this period, a persistent condition of atmospheric stability lead to high concentrations of particulate matter throughout the city. During the month of February, the city was further impacted by a series of small-scale forest fires that took place on hills neighboring the city center. Equivalent Black Carbon (eBC) concentrations were monitored before, during, and after a mayor forest fire episode with a 7-wavelength Aethalometer. The monitoring instruments were located at a traffic impacted site, 18.3 km from the forest fire. To evaluate the contribution of biomass burning to the light-absorbing aerosol particle concentration, spectral analysis of the absorption coefficient of the sampled aerosol particles was performed. When the biomass burning plume directly impacted the monitoring station during the night of February 4, eBC concentrations of up to 40 µg/m3 were observed at nighttime. This concentration was significantly higher than average nighttime concentrations of eBC, observed to be 4 µg/m3 at the site. However, during the period most intensely affected by the biomass burning plume, the angstrom exponent computed between the 450nm and the 970 nm channel, was found to be close to 1. Angstrom exponent close to 1 is an indication that the contribution from traffic generated black carbon is dominant compared to the contribution of biomass burning. The data set collected during this period suggests that despite the significant contribution of the fresh biomass burning plume to the particulate matter concentration in the city, the spectral analysis of the light-absorption coefficient proved insufficient to detect the presence of UV absorbing carbonaceous material during this episode.

Facile fabrication of high-efficiency near-infrared absorption film with tungsten bronze nanoparticle dense layer

NASA Astrophysics Data System (ADS)

Lee, Seong Yun; Kim, Jae Young; Lee, Jun Young; Song, Ho Jun; Lee, Sangkug; Choi, Kyung Ho; Shin, Gyojic

2014-06-01

An excellent transparent film with effective absorption property in near-infrared (NIR) region based on cesium-doped tungsten oxide nanoparticles was fabricated using a facile double layer coating method via the theoretical considerations. The optical performance was evaluated; the double layer-coated film exhibited 10% transmittance at 1,000 nm in the NIR region and over 80% transmittance at 550 nm in the visible region. To optimize the selectivity, the optical spectrum of this film was correlated with a theoretical model by combining the contributions of the Mie-Gans absorption-based localized surface plasmon resonance and reflections by the interfaces of the heterogeneous layers and the nanoparticles in the film. Through comparison of the composite and double layer coating method, the difference of the nanoscale distances between nanoparticles in each layer was significantly revealed. It is worth noting that the nanodistance between the nanoparticles decreased in the double layer film, which enhanced the optical properties of the film, yielding a haze value of 1% or less without any additional process. These results are very attractive for the nanocomposite coating process, which would lead to industrial fields of NIR shielding and thermo-medical applications.

Microprocessor-controlled laser tracker for atmospheric sensing

NASA Technical Reports Server (NTRS)

Johnson, R. A.; Webster, C. R.; Menzies, R. T.

1985-01-01

An optical tracking system comprising a visible HeNe laser, an imaging detector, and a microprocessor-controlled mirror, has been designed to track a moving retroreflector located up to 500 m away from an atmospheric instrument and simultaneously direct spectrally tunable infrared laser radiation to the retroreflector for double-ended, long-path absorption measurements of atmospheric species. The tracker has been tested during the recent flight of a balloon-borne tunable diode laser absorption spectrometer which monitors the concentrations of stratospheric species within a volume defined by a 0.14-m-diameter retroreflector lowered 500 m below the instrument gondola.

The effect of urban growth on landscape-scale restoration for a fire-dependent songbird

USGS Publications Warehouse

Pickens, Bradley A.; Marcus, Jeffrey F.; Carpenter, John P.; Anderson, Scott; Taillie, Paul J.; Collazo, Jaime A.

2017-01-01

A landscape-scale perspective on restoration ecology has been advocated, but few studies have informed restoration with landscape metrics or addressed broad-scale threats. Threats such as urban growth may affect restoration effectiveness in a landscape context. Here, we studied longleaf pine savanna in the rapidly urbanizing southeastern United States where a habitat-specialist bird, Bachman's sparrow (Peucaea aestivalis), is closely associated with savanna vegetation structure and frequent fire. Our objectives were to construct a species distribution model for Bachman's sparrow, determine the relationship between fire and urbanization, quantify the urban growth effect (2010–2090), identify potential restoration areas, and determine the interaction between restoration potential and urban growth by 2050. Number of patches, patch size, and isolation metrics were used to evaluate scenarios. The species distribution model was 88% accurate and emphasized multiscale canopy cover characteristics, fire, and percent habitat. Fires were less common <600 m from urban areas, and this fire suppression effect exacerbated urban growth effects. For restoration scenarios, canopy cover reduction by 30% resulted in nearly double the amount of habitat compared to the prescribed fire scenario; canopy cover reduction resulted in larger patch sizes and less patch isolation compared to current conditions. The effect of urban growth on restoration scenarios was unequal. Seventy-four percent of restoration areas from the prescribed fire scenario overlapped with projected urban growth, whereas the canopy cover reduction scenario only overlapped by 9%. We emphasize the benefits of simultaneously considering the effects of urban growth and landscape-scale restoration potential to promote a landscape with greater patch sizes and less isolation.

Does fire affect amphibians and reptiles in eastern U.S. oak forests?

Treesearch

Rochelle B. Renken

2006-01-01

Current information about the effect of fire on amphibians and reptiles in oak forests of the Eastern and Central United States is reviewed. Current data suggest that fire results in little direct mortality of amphibians and reptiles. Fire has no effect on overall amphibian abundance, diversity, and number of species in comparisons of burned and unburned plots, though...

Human impacts on 20th century fire dynamics and implications for global carbon and water trajectories

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Fang; Lawrence, David M.; Bond-Lamberty, Ben

Fire is a fundamental Earth system process and the primary ecosystem disturbance on the global scale. It affects carbon and water cycles through changing terrestrial ecosystems, and at the same time, is regulated by weather and climate, vegetation characteristics, and, importantly, human ignitions and suppression (i.e., the direct human effect on fire). Here, we utilize the Community Land Model version 4.5 (CLM4.5) to quantify the impacts of changes in human ignition and suppression on fire dynamics and associated carbon and water cycles. We find that the impact is to significantly reduce the 20th century global burned area by a centurymore » average of 38 Mha/yr and by 103 Mha/yr at the end of the century. Land carbon gain is weakened by 17% over the 20th century, mainly due to increased human deforestation fires and associated escape fires (i.e., degradation fires) in the tropical humid forests, even though the decrease in burned area in many other regions due to human fire suppression acts to increase land carbon gain. The direct human effect on fire weakens the upward trend in global runoff throughout the century by 6% and enhances the upward trend in global evapotranspiration since ~ 1945 by 7%. In addition, the above impacts in densely populated, highly developed (if population density > 0.1 person/km2), or moderately populated and developed regions are of opposite sign to those in other regions. Our study suggests that particular attention should be paid to human deforestation and degradation fires in the tropical humid forests when reconstructing and projecting fire carbon emissions and net atmosphere-land carbon exchange and estimating resultant impacts of direct human effect on fire.« less

Human impacts on 20th century fire dynamics and implications for global carbon and water trajectories

NASA Astrophysics Data System (ADS)

Li, Fang; Lawrence, David M.; Bond-Lamberty, Ben

2018-03-01

Fire is a fundamental Earth system process and the primary ecosystem disturbance on the global scale. It affects carbon and water cycles through changing terrestrial ecosystems, and at the same time, is regulated by weather and climate, vegetation characteristics, and, importantly, human ignitions and suppression (i.e., the direct human effect on fire). Here, we utilize the Community Land Model version 4.5 (CLM4.5) to quantify the impacts of changes in human ignition and suppression on fire dynamics and associated carbon and water cycles. We find that the impact is to significantly reduce the 20th century global burned area by a century average of 38 Mha/yr and by 103 Mha/yr at the end of the century. Land carbon gain is weakened by 17% over the 20th century, mainly due to increased human deforestation fires and associated escape fires (i.e., degradation fires) in the tropical humid forests, even though the decrease in burned area in many other regions due to human fire suppression acts to increase land carbon gain. The direct human effect on fire weakens the upward trend in global runoff throughout the century by 6% and enhances the upward trend in global evapotranspiration since 1945 by 7%. In addition, the above impacts in densely populated, highly developed (if population density > 0.1 person/km2), or moderately populated and developed regions are of opposite sign to those in other regions. Our study suggests that particular attention should be paid to human deforestation and degradation fires in the tropical humid forests when reconstructing and projecting fire carbon emissions and net atmosphere-land carbon exchange and estimating resultant impacts of direct human effect on fire.

Incipient fire detection system

DOEpatents

Brooks, Jr., William K.

1999-01-01

A method and apparatus for an incipient fire detection system that receives gaseous samples and measures the light absorption spectrum of the mixture of gases evolving from heated combustibles includes a detector for receiving gaseous samples and subjecting the samples to spectroscopy and determining wavelengths of absorption of the gaseous samples. The wavelengths of absorption of the gaseous samples are compared to predetermined absorption wavelengths. A warning signal is generated whenever the wavelengths of absorption of the gaseous samples correspond to the predetermined absorption wavelengths. The method includes receiving gaseous samples, subjecting the samples to light spectroscopy, determining wavelengths of absorption of the gaseous samples, comparing the wavelengths of absorption of the gaseous samples to predetermined absorption wavelengths and generating a warning signal whenever the wavelengths of absorption of the gaseous samples correspond to the predetermined absorption wavelengths. In an alternate embodiment, the apparatus includes a series of channels fluidically connected to a plurality of remote locations. A pump is connected to the channels for drawing gaseous samples into the channels. A detector is connected to the channels for receiving the drawn gaseous samples and subjecting the samples to spectroscopy. The wavelengths of absorption are determined and compared to predetermined absorption wavelengths is provided. A warning signal is generated whenever the wavelengths correspond.

Parametric Study of Fire Performance of Concrete Filled Hollow Steel Section Columns with Circular and Square Cross-Section

NASA Astrophysics Data System (ADS)

Nurfaidhi Rizalman, Ahmad; Tahir, Ng Seong Yap Mahmood Md; Mohammad, Shahrin

2018-03-01

Concrete filled hollow steel section column have been widely accepted by structural engineers and designers for high rise construction due to the benefits of combining steel and concrete. The advantages of concrete filled hollow steel section column include higher strength, ductility, energy absorption capacity, and good structural fire resistance. In this paper, comparison on the fire performance between circular and square concrete filled hollow steel section column is established. A three-dimensional finite element package, ABAQUS, was used to develop the numerical model to study the temperature development, critical temperature, and fire resistance time of the selected composite columns. Based on the analysis and comparison of typical parameters, the effect of equal cross-sectional size for both steel and concrete, concrete types, and thickness of external protection on temperature distribution and structural fire behaviour of the columns are discussed. The result showed that concrete filled hollow steel section column with circular cross-section generally has higher fire resistance than the square section.

Radiant flux density, energy density, and fuel consumption in mixed-oak forest surface fires

Treesearch

R.L. Kremens; M.B. Dickinson; A.S. Bova

2012-01-01

Closing the wildland fire heat budget involves characterising the heat source and energy dissipation across the range of variability in fuels and fire behaviour. Meeting this challenge will lay the foundation for predicting direct ecological effects of fires and fire-atmosphere coupling. In this paper, we focus on the relationships between the fire radiation field, as...

Chapter 14: Chiller Evaluation Protocol. The Uniform Methods Project: Methods for Determining Energy Efficiency Savings for Specific Measures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kurnik, Charles W; Tiessen, Alex

This protocol defines a chiller measure as a project that directly impacts equipment within the boundary of a chiller plant. A chiller plant encompasses a chiller - or multiple chillers - and associated auxiliary equipment. This protocol primarily covers electric-driven chillers and chiller plants. It does not include thermal energy storage and absorption chillers fired by natural gas or steam, although a similar methodology may be applicable to these chilled water system components.

Acoustic contributions of a sound absorbing blanket placed in a double panel structure: absorption versus transmission.

PubMed

Doutres, Olivier; Atalla, Noureddine

2010-08-01

The objective of this paper is to propose a simple tool to estimate the absorption vs. transmission loss contributions of a multilayered blanket unbounded in a double panel structure and thus guide its optimization. The normal incidence airborne sound transmission loss of the double panel structure, without structure-borne connections, is written in terms of three main contributions; (i) sound transmission loss of the panels, (ii) sound transmission loss of the blanket and (iii) sound absorption due to multiple reflections inside the cavity. The method is applied to four different blankets frequently used in automotive and aeronautic applications: a non-symmetric multilayer made of a screen in sandwich between two porous layers and three symmetric porous layers having different pore geometries. It is shown that the absorption behavior of the blanket controls the acoustic behavior of the treatment at low and medium frequencies and its transmission loss at high frequencies. Acoustic treatment having poor sound absorption behavior can affect the performance of the double panel structure.

Direct observation of double exchange in ferromagnetic La0.7Sr0.3CoO3 by broadband ellipsometry

NASA Astrophysics Data System (ADS)

Friš, P.; Munzar, D.; Caha, O.; Dubroka, A.

2018-01-01

We present results of our broadband ellipsometry measurements of the optical response of ferromagnetic La0.7Sr0.3CoO3 . Our data show that the ferromagnetic transition is accompanied by a transfer of optical spectral weight from an absorption band centered at 1.5 eV to a narrow component of the Drude-like peak. The associated reduction of the intraband kinetic energy is significantly larger than kBTc , confirming that the double exchange plays a major role in the ferromagnetism of doped cobaltites. In conjunction with results of recent theoretical studies, the temperature dependence of the Drude-like peak suggests that the double exchange is mediated by t2 g orbitals.

Effects of fire on chaparral soils in Arizona and California and postfire management implications

Treesearch

Leonard F. DeBano

1989-01-01

Wildfires and prescribed burns are common throughout Arizona and California chaparral. Predicting fire effects requires understanding fire behavior, estimating soil heating, and predicting changes in soil properties. Substantial quantities of some nutrients, particularly nitrogen and phosphorus, are lost directly during combustion. Highly available nutrients released...

2-micron Pulsed Direct Detection IPDA Lidar for Atmospheric CO2 Measurements

NASA Astrophysics Data System (ADS)

Yu, J.; Singh, U.; Petros, M.

2012-12-01

A 2-micron high energy, pulsed Integrated Path Differential Absorption (IPDA) lidar is being developed for atmospheric CO2 measurements. Development of this lidar heavily leverages the 2-micron laser technologies developed in LaRC over the last decade. The high pulse energy, direct detection lidar operating at CO2 2-micron absorption band provides an alternate approach to measure CO2 concentrations with significant advantages. It is expected to provide high-precision measurement capability by unambiguously eliminating contamination from aerosols and clouds that can bias the IPDA measurement. Our objective is to integrate an existing high energy double-pulsed 2-micron laser transmitter with a direct detection receiver and telescope to enable an airborne capability to perform a first proof of principle demonstration of airborne direct detection CO2 measurements. The 2-micron transmitter provides 100mJ at 10Hz with double pulse format specifically designed for DIAL/IPDA instrument. The compact, rugged, highly reliable transceiver is based on unique Ho:Tm:YLF high-energy 2-micron pulsed laser technology. All the optical mounts are custom designed and have space heritage. A 16-inch diameter telescope has been designed and being manufactured for the direct detection lidar. The detector is an InGaAs Positive-Intrinsic-Negative (PIN) photodiode manufactured by Hamamatsu Corporation. The performance of the detector is characterized at various operating temperatures and bias voltages for spectral response, NEP, response time, dynamic range, and linearity. A collinear lidar structure is designed to be integrated to NASA UC12 or B200 research aircrafts. This paper will describe the design of the airborne 2-micron pulsed IPDA lidar system; the lidar operation parameters; the wavelength pair selection; laser transmitter energy, pulse rate, beam divergence, double pulse generation and accurate frequency control; detector characterization; telescope design; lidar structure design; and lidar signal to noise ratio estimation. The first engineering flight is scheduled at the end of next year.

XAS AND XPS CHARACTERIZATION OF MERCURY BINDING ON BROMINATED ACTIVATED CARBON

EPA Science Inventory

Brominated powdered activated carbon sorbents have been shown to e quite effective for mercury capture when injected into the flue gas duct at coal-fired power plants and are especially useful when buring Western low-chlorine subbituminous coals. X-ray absorption spectroscopy (X...

Fire and vegetation dynamics in the Cross Timbers forests of south-central North America

Treesearch

Steve W. Hallgren; Ryan D. DeSantis; Jesse A. Burton

2012-01-01

The vegetation of the Cross Timbers forests was maintained for thousands of years by fire; the historic fire return interval was likely 1 to 10 years. Fire suppression over the past century led to a doubling of stand basal area, increased diversity of tree species, reduced dominance of oak, and increased mesic species intolerant of fire. Dendrochronological studies...

Numerical modeling of heat transfer during hydrogen absorption in thin double-layered annular ZrCo beds

NASA Astrophysics Data System (ADS)

Cui, Yehui; Zeng, Xiangguo; Kou, Huaqin; Ding, Jun; Wang, Fang

2018-06-01

In this work a three-dimensional (3D) hydrogen absorption model was proposed to study the heat transfer behavior in thin double-layered annular ZrCo beds. Numerical simulations were performed to investigate the effects of conversion layer thickness, thermal conductivity, cooling medium and its flow velocity on the efficiency of heat transfer. Results reveal that decreasing the layer thickness and improving the thermal conductivity enhance the ability of heat transfer. Compared with nitrogen and helium, water appears to be a better medium for cooling. In order to achieve the best efficiency of heat transfer, the flow velocity needs to be maximized.

Lessons learned from prescribed fire in ponderosa pine forests of the southern Sierra Nevada

Treesearch

Karen E. Bagne; Kathryn L. Purcell

2009-01-01

Prescribed fire is a commonly used management tool in fire-suppressed ponderosa pine (Pinus ponderosa) forests, but effects of these fires on birds are largely unstudied. We investigated both direct and indirect impacts on breeding birds in ponderosa pine forests of the southern Sierra Nevada where fires were applied in the spring. Following...

Precision Strike 2008 Summer Forum

DTIC Science & Technology

2008-01-11

extended ranges, 360--mounted and dismounted Technical fire direction and limited tactical fire direction on all delivery systems Delivery systems that...can rapidly emplace/displace with high rates of fire Accurate on demand, meteorological data to delivery system ranges All munitions with less than 50M...CEP at all ranges Munitions that provide a variety of effects in any environment To achieve this, Field Artillery needs these “enablers” Target

Effect of Autoclaved Aerated Concrete Modification with High-Impact Polystyrene on Sound Insulation

NASA Astrophysics Data System (ADS)

Brelak, Sylwia; Dachowski, Ryszard

2017-10-01

Autoclaved aerated concrete is one of the most commonly used building materials. Its advantages include low density, high thermal insulation capacity and high fire resistance. It has a relatively high compressive strength, though not high enough to be able to compete with other building materials in this respect. One of the directions leading to the improvement of physical and mechanical properties of autoclaved aerated concrete is the modification of its composition. A noticeable effect of pulverized high-impact polystyrene (improved compressive strength and water absorption) was relevant for the decision to continue the study of its effects. This paper discusses the effect of high-impact polystyrene on sound insulation in AAC products. The tests demonstrated a positive influence of the modifier on AAC sound insulation enhancement. Results from the tests performed on HIPS-modified AAC products were showed and compared with the properties of conventional products. The effect of the polymer on the microstructure of the products obtained was described briefly.

Modelling thermal radiation from one-meter diameter methane pool fires

NASA Astrophysics Data System (ADS)

Consalvi, J. L.; Demarco, R.

2012-06-01

The first objective of this article is to implement a comprehensive radiation model in order to predict the radiant fractions and radiative fluxes on remote surfaces in large-scale methane pool fires. The second aim is to quantify the importance of Turbulence-Radiation Interactions (TRIs) in such buoyant flames. The fire-induced flow is modelled by using a buoyancy-modified k-ɛ model and the Steady Laminar Flamelet (SLF) model coupled with a presumed probability density function (pdf) approach. Spectral radiation is modelled by using the Full-Spectrum Correlated-k (FSCK) method. TRIs are taken into account by considering the Optically-Thin Fluctuation Approximation (OTFA). The emission term and the mean absorption coefficient are closed by using a presumed pdf of the mixture fraction, scalar dissipation rate and enthalpy defect. Two 1m-diameter fires with Heat Release Rates (HRR) of 49 kW and 162 kW were simulated. Predicted radiant fractions and radiative heat fluxes are found in reasonable agreement with experimental data. The importance of TRIs is evidenced, computed radiant fractions and radiative heat fluxes being considerably higher than those obtained from calculations based on mean properties. Finally, model results show that the complete absorption coefficient-Planck function correlation should be considered in order to properly take into account the influence of TRIs on the emission term, whereas the absorption coefficient self-correlation in the absorption term reduces significantly the radiant fractions.

Wildfires in Siberian Mountain Forest

NASA Astrophysics Data System (ADS)

Kharuk, V.; Ponomarev, E. I.; Antamoshkina, O.

2017-12-01

The annual burned area in Russia was estimated as 0.55 to 20 Mha with >70% occurred in Siberia. We analyzed Siberian wildfires distribution with respect to elevation, slope steepness and exposure. In addition, wildfires temporal dynamic and latitudinal range were analyzed. We used daily thermal anomalies derived from NOAA/AVHRR and Terra/MODIS satellites (1990-2016). Fire return intervals were (FRI) calculated based on the dendrochronology analysis of samples taken from trees with burn marks. Spatial distribution of wildfires dependent on topo features: relative burned area increase with elevation increase (ca. 1100 m), switching to following decrease. The wildfires frequency exponentially decreased within lowlands - highlands transition. Burned area is increasing with slope steepness increase (up to 5-10°). Fire return intervals (FRI) on the southfacing slopes are about 30% longer than on the north facing. Wildfire re-occurrence is decreasing exponentially: 90% of burns were caused by single fires, 8.5% by double fires, 1% burned three times, and on about 0.05% territory wildfires occurred four times (observed period: 75 yr.). Wildfires area and number, as well as FRI, also dependent on latitude: relative burned area increasing exponentially in norward direction, whereas relative fire number is exponentially decreasing. FRI increases in the northward direction: from 80 years at 62°N to 200 years at the Arctic Circle, and to 300 years at the northern limit of closed forests ( 71+°N). Fire frequency, fire danger period and FRI are strongly correlated with incoming solar radiation (r = 0.81 - 0.95). In 21-s century, a positive trend of wildfires number and area observed in mountain areas in all Siberia. Thus, burned area and number of fires in Siberia are significantly increased since 1990th (R2 =0.47, R2 =0.69, respectively), and that increase correlated with air temperatures and climate aridity increases. However, wildfires are essential for supporting fire-resistant species (e.g., Larix sibirica, L, dahurica and Pinus silvestris) reforestation and completion with non-fire-resistant species. This work was supported by the Russian Foundation for Basic Research, the Government of the Krasnoyarsk krai, the Krasnoyarsk Fund for Support of Scientific and Technological Activities (N 17-41-240475)

Simulation of a 20-ton LiBr/H{sub 2}O absorption cooling system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wardono, B.; Nelson, R.M.

The possibility of using solar energy as the main heat input for cooling systems has led to several studies of available cooling technologies that use solar energy. The results show that double-effect absorption cooling systems give relatively high performance. To further study absorption cooling systems, a computer code was developed for a double-effect lithium bromide/water (LiBr/H{sub 2}O) absorption system. To evaluate the performance, two objective functions were developed including the coefficient of performance (COP) and the system cost. Based on the system cost, an optimization to find the minimum cost was performed to determine the nominal heat transfer areas ofmore » each heat exchanger. The nominal values of other system variables, such as the mass flow rates and inlet temperatures of the hot water, cooling water, and chilled water, are specified as commonly used values for commercial machines. The results of the optimization show that there are optimum heat transfer areas. In this study, hot water is used as the main energy input. Using a constant load of 20 tons cooling capacity, the effects of various variables including the heat transfer ares, mass flow rates, and inlet temperatures of hot water, cooling water, and chilled water are presented.« less

Fire effects on Gambel oak in southwestern ponderosa pine-oak forests

Treesearch

Scott R. Abella; Peter Z. Fulé

2008-01-01

Gambel oak (Quercus gambelii) is ecologically and aesthetically valuable in southwestern ponderosa pine (Pinus ponderosa) forests. Fire effects on Gambel oak are important because fire may be used in pine-oak forests to manage oak directly or to accomplish other management objectives. We used published literature to: (1) ascertain...

The effect of urban growth on landscape-scale restoration for a fire-dependent songbird.

PubMed

Pickens, Bradley A; Marcus, Jeffrey F; Carpenter, John P; Anderson, Scott; Taillie, Paul J; Collazo, Jaime A

2017-04-15

A landscape-scale perspective on restoration ecology has been advocated, but few studies have informed restoration with landscape metrics or addressed broad-scale threats. Threats such as urban growth may affect restoration effectiveness in a landscape context. Here, we studied longleaf pine savanna in the rapidly urbanizing southeastern United States where a habitat-specialist bird, Bachman's sparrow (Peucaea aestivalis), is closely associated with savanna vegetation structure and frequent fire. Our objectives were to construct a species distribution model for Bachman's sparrow, determine the relationship between fire and urbanization, quantify the urban growth effect (2010-2090), identify potential restoration areas, and determine the interaction between restoration potential and urban growth by 2050. Number of patches, patch size, and isolation metrics were used to evaluate scenarios. The species distribution model was 88% accurate and emphasized multiscale canopy cover characteristics, fire, and percent habitat. Fires were less common <600 m from urban areas, and this fire suppression effect exacerbated urban growth effects. For restoration scenarios, canopy cover reduction by 30% resulted in nearly double the amount of habitat compared to the prescribed fire scenario; canopy cover reduction resulted in larger patch sizes and less patch isolation compared to current conditions. The effect of urban growth on restoration scenarios was unequal. Seventy-four percent of restoration areas from the prescribed fire scenario overlapped with projected urban growth, whereas the canopy cover reduction scenario only overlapped by 9%. We emphasize the benefits of simultaneously considering the effects of urban growth and landscape-scale restoration potential to promote a landscape with greater patch sizes and less isolation. Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.

First-order fire effects on herbs and Shrubs: present knowledge and process modeling needs

Treesearch

Kirsten Stephan; Melanie Miller; Matthew B. Dickinson

2010-01-01

Herbaceous plants and shrubs have received little attention in terms of fire effects modeling despite their critical role in ecosystem integrity and resilience after wildfires and prescribed burns. In this paper, we summarize current knowledge of direct effects of fire on herb and shrub (including cacti) vegetative tissues and seed banks, propose key components for...

Response of reptile and amphibian communities to the reintroduction of fire in an oak/hickory forest

Treesearch

Steven J. Hromada; Christopher A.F. Howey; Matthew B. Dickinson; Roger W. Perry; Willem M. Roosenburg; C.M. Gienger

2018-01-01

Fire can have diverse effects on ecosystems, including direct effects through injury and mortality and indirect effects through changes to available resources within the environment. Changes in vegetation structure such as a decrease in canopy cover or an increase in herbaceous cover from prescribed fire can increase availability of preferred microhabitats for some...

Bifurcation and Firing Patterns of the Pancreatic β-Cell

NASA Astrophysics Data System (ADS)

Wang, Jing; Liu, Shenquan; Liu, Xuanliang; Zeng, Yanjun

Using a model of individual isolated pancreatic β-cells, we investigated bifurcation diagrams of interspike intervals (ISIs) and largest Lyapunov exponents (LLE), which clearly demonstrated a wide range of transitions between different firing patterns. The numerical simulation results revealed the effect of different time constants and ion channels on the neuronal discharge rhythm. Furthermore, an individual cell exhibited tonic spiking, square-wave bursting, and tapered bursting. Additionally, several bifurcation phenomena can be observed in this paper, such as period-doubling, period-adding, inverse period-doubling and inverse period-adding scenarios. In addition, we researched the mechanisms underlying two kinds of bursting (tapered and square-wave bursting) by use of fast-slow dynamics analysis. Finally, we analyzed the codimension-two bifurcation of the fast subsystem and studied cusp bifurcation, generalized Hopf (or Bautin) bifurcation and Bogdanov-Takens bifurcation.

Human impacts on 20th century fire dynamics and implications for global carbon and water trajectories

NASA Astrophysics Data System (ADS)

Li, F.; Lawrence, D. M.; Bond-Lamberty, B. P.

2017-12-01

Fire is a fundamental Earth system process and the primary ecosystem disturbance on the global scale. It affects carbon and water cycles through its impact on terrestrial ecosystems, and at the same time, is regulated by weather and climate, vegetation characteristics, and, importantly, human ignition and efforts to suppress fires (i.e., the direct human effect on fire). Here, we utilize the Community Land Model version 4.5 (CLM4.5) to generate a quantitative understanding of the impacts on fire dynamics and associated carbon and water cycling that can be attributed to changes in human ignition and suppression over the 20th century. We find that the net impact of increases in human ignition and suppression significantly reduce the 20th century averaged global burned area by 38 Mha/yr. The reduction increases since 1920, rising to 103 Mha/yr less burned area at the end of the century. Land carbon gain is weakened by 17% over the 20th century, mainly due to increased human deforestation fires and associated escape fires (i.e., degradation fires) in the tropical humid forests, even though the decrease in burned area in many other regions due to human fire suppression acts to increase land carbon gain. The direct human effect on fire also weakens the 20th century upward trend of global runoff by 6%, and enhances the upward trend in global evaportranspiration since 1945 by 7%. In addition, the above impacts in densely populated, highly developed (if population density > 0.1 person/km2), or moderately populated and developed regions are of opposite sign to those in other regions. Our study suggests that particular attention should be paid to human deforestation and degradation fires in the tropical humid forests when reconstructing and projecting fire carbon emissions and net atmosphere-land carbon exchange and estimating resultant impacts of direct human effect on fire.

Optimization of the preparation conditions of ceramic products using drinking water treatment sludges.

PubMed

Zamora, R M Ramirez; Ayala, F Espesel; Garcia, L Chavez; Moreno, A Duran; Schouwenaars, R

2008-11-01

The aim of this work is to optimize, via Response Surface Methodology, the values of the main process parameters for the production of ceramic products using sludges obtained from drinking water treatment in order to valorise them. In the first experimental stage, sludges were collected from a drinking water treatment plant for characterization. In the second stage, trials were carried out to elaborate thin cross-section specimens and fired bricks following an orthogonal central composite design of experiments with three factors (sludge composition, grain size and firing temperature) and five levels. The optimization parameters (Y(1)=shrinking by firing (%), Y(2)=water absorption (%), Y(3)=density (g/cm(3)) and Y(4)=compressive strength (kg/cm(2))) were determined according to standardized analytical methods. Two distinct physicochemical processes were active during firing at different conditions in the experimental design, preventing the determination of a full response surface, which would allow direct optimization of production parameters. Nevertheless, the temperature range for the production of classical red brick was closely delimitated by the results; above this temperature, a lightweight ceramic with surprisingly high strength was produced, opening possibilities for the valorisation of a product with considerably higher added value than what was originally envisioned.

Aircraft Carrier Flight Deck Fire Fighting Tactics and Equipment Evaluation Tests

DTIC Science & Technology

1987-02-26

pattern nozzles; 8. proper fire fighting techniques for possible titanium ignition in an F-14 crash (deleted later by direction of FLSC, being studied ...separately); 9. effect of full fire involvement of "ready for flight" aircraft (deleted later by direction of FLSC, being studied separately). The...to refine and identify specific hardware and tactical requirements generated from the studies conducted during the scoping tests; 3. concept

Crush analysis of the foam-filled bitubal circular tube under oblique impact

NASA Astrophysics Data System (ADS)

Djamaluddin, F.; Abdullah, S.; Arrifin, A. K.; Nopiah, Z. M.

2018-02-01

This paper presents crashworthiness analysis of bitubal cylindrical tubes under different impact angular. The numerical solution of double cylindrical tubes are determined by finite element analysis (FEA). Moreover, the structure was impacted by mass block as impactor respect to longitudinal direction of the tubes. The model of structure was developed by non-linear ABAQUS sofware with variations of load angle and dimensions of tube. The outcome of this study is the respons parameters such as the peak crusing force (PCF), energy absorption (EA) and specific energy absorption (SEA), thus it can be expected this tube as the great energy absorber.

Biomass consumption during prescribed fires in big sagebrush ecosystems

Treesearch

Clinton S. Wright; Susan J. Prichard

2006-01-01

Big sagebrush (Artemisia tridentata) ecosystems typically experience stand replacing fires during which some or all of the ignited biomass is consumed. Biomass consumption is directly related to the energy released during a fire, and is an important factor that determines smoke production and the effects of fire on other resources. Consumption of...

Mesoscale Simulations During the Double Trouble State Park Wildfire in East-Central New Jersey on June 2, 2002

Treesearch

Joseph J. Charney; Xindi Bian; Brian E. Potter; Warren E. Heilman

2003-01-01

The 2000 fire season brought to the forefront the issue of severe wildland fires in the United States. To address the need for new research and for the development of predictive tools for the management of wildland fires, Congress allocated funding under the National Fire Plan (NFP) to better equip government agencies to fight and study forest fires. As part of the NFP...

Simulations of Forest Fires by the Cellular Automata Model "ABBAMPAU"

NASA Astrophysics Data System (ADS)

di Gregorio, S.; Bendicenti, E.

2003-04-01

Forest fires represent a serious environmental problem, whose negative impact is becoming day by day more worrisome. Forest fires are very complex phenomena; that need an interdisciplinary approach. The adopted method to modelling involves the definition of local rules, from which the global behaviour of the system can emerge. The paradigm of Cellular Automata was applied and the model ABBAMPAU was projected to simulate the evolution of forest fires. Cellular Automata features (parallelism and a-centrism) seem to match the system "forest fire"; the parameters, describing globally a forest fire, i.e. propagation rate, flame length and direction, fireline intensity, fire duration time et c. are mainly depending on some local characteristics i.e. vegetation type (live and dead fuel), relative humidity, fuel moisture, heat, territory morphology (altitude, slope), et c.. The only global characteristic is given by wind velocity and direction, but wind velocity and direction is locally altered according to the morphology; therefore wind has also to be considered at local level. ABBAMPAU accounts for the following aspects of the phenomenon: effects of combustion in surface and crown fire inside the cell, crown fire triggering off; surface and crown fire spread, determination of the local wind rate and direction. A validation of ABBAMPAU was tested on a real case of forest fire, in the territory of Villaputzu, Sardinia island, August 22nd, 1998. First simulations account for the main characteristics of the phenomenon and agree with the observations. The results show that the model could be applied for the forest fire preventions, the productions of risk scenarios and the evaluation of the forest fire environmental impact.

Fire and fish: A synthesis of observation and experience

Treesearch

Bruce Rieman; Robert Gresswell; John Rinne

2012-01-01

The effects of wildfire on aquatic systems and fishes occurring in them has been linked to the direct or immediate influence of the fire on water quality and the indirect or subsequent effects on watershed characteristics and processes that influence water quality and quantity, stream channels, and aquatic biota (Gresswell 1999). Early research linking fire and aquatic...

Airborne 2-Micron Double-Pulsed Integrated Path Differential Absorption Lidar for Column CO2 Measurement

NASA Technical Reports Server (NTRS)

Singh, Upendra N.; Yu, Jirong; Petros, Mulugeta; Refaat, Tamer F.; Remus, Ruben G.; Fay, James J.; Reithmaier, Karl

2014-01-01

Double-pulse 2-micron lasers have been demonstrated with energy as high as 600 millijouls and up to 10 Hz repetition rate. The two laser pulses are separated by 200 microseconds and can be tuned and locked separately. Applying double-pulse laser in DIAL system enhances the CO2 measurement capability by increasing the overlap of the sampled volume between the on-line and off-line. To avoid detection complicity, integrated path differential absorption (IPDA) lidar provides higher signal-to-noise ratio measurement compared to conventional range-resolved DIAL. Rather than weak atmospheric scattering returns, IPDA rely on the much stronger hard target returns that is best suited for airborne platforms. In addition, the IPDA technique measures the total integrated column content from the instrument to the hard target but with weighting that can be tuned by the transmitter. Therefore, the transmitter could be tuned to weight the column measurement to the surface for optimum CO2 interaction studies or up to the free troposphere for optimum transport studies. Currently, NASA LaRC is developing and integrating a double-Pulsed 2-micron direct detection IPDA lidar for CO2 column measurement from an airborne platform. The presentation will describe the development of the 2-micron IPDA lidar system and present the airborne measurement of column CO2 and will compare to in-situ measurement for various ground target of different reflectivity.

Double negative acoustic metastructure for attenuation of acoustic emissions

NASA Astrophysics Data System (ADS)

Kumar, Sanjay; Bhushan, Pulak; Prakash, Om; Bhattacharya, Shantanu

2018-03-01

Acoustic metamaterials hold great potential for attenuation of low frequency acoustic emissions. However, a fundamental challenge is achieving high transmission loss over a broad frequency range. In this work, we report a double negative acoustic metastructure for absorption of low frequency acoustic emissions in an aircraft. This is achieved by utilizing a periodic array of hexagonal cells interconnected with a neck and mounted with an elastic membrane on both ends. An average transmission loss of 56 dB under 500 Hz and an overall absorption of over 48% have been realized experimentally. The negative mass density is derived from the dipolar resonances created as a result of the in-phase movement of the membranes. Further, the negative bulk modulus is ascribed to the combined effect of out-of-phase acceleration of the membranes and the Helmholtz resonator. The proposed metastructure enables absorption of low frequency acoustic emissions with improved functionality that is highly desirable for varied applications.

Modelling Middle Infrared Thermal Imagery from Observed or Simulated Active Fire

NASA Astrophysics Data System (ADS)

Paugam, R.; Gastellu-Etchegorry, J. P.; Mell, W.; Johnston, J.; Filippi, J. B.

2016-12-01

The Fire Radiative Power (FRP) is used in the atmospheric and fire communities to estimate fire emission. For example, the current version of the emission inventory GFAS is using FRP observation from the MODIS sensors to derive daily global distribution of fire emissions. Although the FRP product is widely accepted, most of its theoretical justifications are still based on small scale burns. When up-scaling to large fires effects of view angle, canopy cover, or smoke absorption are still unknown. To cover those questions, we are building a system based on the DART radiative transfer model to simulate the middle infrared radiance emitted by a propagating fire front and propagating in the surrounding scene made of ambient vegetation and plume aerosols. The current version of the system was applied to fire ranging from a 1m2 to 7ha. The 3D fire scene used as input in DART is made of the flame, the vegetation (burnt and unburnt), and the plume. It can be either set up from [i] 3D physical based model scene (ie WFDS, mainly applicable for small scale burn), [ii] coupled 2D fire spread - atmospheric models outputs (eg ForeFire-MesoNH) or [iii] derived from thermal imageries observations (here plume effects are not considered). In the last two cases, as the complexity of physical processes occurring in the flame (in particular soot formation and emission) is not to solved, the flames structures are parameterized with (a) temperature and soot concentration based on empirical derived profiles and (b) 3D triangular shape hull interpolated at the fire front location. Once the 3D fire scene is set up, DART is then used to render thermal imageries in the middle infrared. Using data collected from burns conducted at different scale, the modelled thermal imageries are compared against observations, and effects of view angle are discussed.

Study on Fired Clay Bricks by Replacing Clay with Palm Oil Waste: Effects on Physical and Mechanical Properties

NASA Astrophysics Data System (ADS)

Kadir, A. A.; Sarani, N. A.; Abdullah, M. M. A. B.; Perju, M. C.; Sandu, A. V.

2017-06-01

Palm oil is one of the major agricultural industries in Malaysia. Due to the poor management system, the discarded palm oil waste has always been linked to the environment issues. During processing of palm oil, a considerable amount of solid waste by-products in the form of fibres, shells, empty fruit bunches and fly ashes are produce rapidly. Therefore, this study was conducted to incorporate 1%, 5% and 10% of palm oil waste into fired clay brick. Samples of brick were fired at 1050°C temperature with heating rates of 1°C/min. Manufactured bricks were tested with physical and mechanical properties including firing shrinkage, dry density, water absorption and compressive strength. The results demonstrated that the replacement of 1% up to 5% of palm oil waste had improved several properties, although, a decrease of performance in certain aspects has also been observed. As a result, palm oil waste can be utilized in an environmentally safe way into fired clay brick thus providing adequate properties of fired clay brick.

Global Change Impacts on Future Fire Regimes: Distinguishing Between Climate-limited vs Ignition-Limited Landscapes

NASA Astrophysics Data System (ADS)

Keeley, J. E.; Syphard, A. D.

2016-12-01

Global warming is expected to exacerbate fire impacts. Predicting how climates will impact future fire regimes requires an understanding of how temperature and precipitation interact to control fire activity. Inevitably this requires historical analyses that relate annual burning to climate variation. Within climatically homogeneous subregions, montane forested landscapes show strong relationships between annual fluctuations in temperature and precipitation with area burned, however, this is strongly seasonal dependent; e.g., winter temperatures have very little or no effect but spring and summer temperatures are critical. Climate models are needed that predict future seasonal temperature changes if we are to forecast future fire regimes in these forests. Climate does not appear to be a major determinant of fire activity on all landscapes. Lower elevations and lower latitudes show little or no increase in fire activity with hotter and drier conditions. On these landscapes climate is not usually limiting to fires but these vegetation types are ignition-limited, and because they are closely juxtaposed with human habitations fire regimes are more strongly controlled by other direct anthropogenic impacts. Predicting future fire regimes is not rocket science, it is far more complicated than that. Climate change is not relevant on some landscapes, but where climate is relevant the relationship will change due to direct climate effects on vegetation trajectories, as well as by feedback processes of fire effects on vegetation distribution, plus policy changes in how we manage ecosystems.

Study of Interesting Solidification Phenomena on the Ground and in Space (MEPHISTO)

NASA Technical Reports Server (NTRS)

Alexander, J. Iwan D.; Favier, J.-J.; Garandet, J.-P.

1999-01-01

Real-time Seebeck voltage variations in a Sn-Bi melt during directional solidification in the MEPHISTO spaceflight experiment flown on the USMP-3 mission, have been correlated with well-characterized thruster firings and an Orbiter Main System (OMS) burn. The Seebeck voltage measurement is related to the response of the instantaneous average melt composition at the melt-crystal interface. This allowed us to make a direct comparison of numerical simulations with the experimentally obtained Seebeck signals. Based on the results of preflight and real-time computations, several well-defined thruster firing events were programmed to occur at specific times during the experiment. In particular, we simulated the effects of the thruster firings on melt and crystal composition in a directionally solidifying Sn-Bi alloy. The relative accelerations produced by the firings were simulated by impulsive accelerations of the same magnitude, duration and orientation as the requested firings. A comparison of the simulation results with the Seebeck signal indicates that there is a good agreement between the two. This unique opportunity allows us to make the first quantitative characterization of actual g-jitter effects on an actual crystal growth experiment and to calibrate our models of g-jitter effects on crystal growth.

Study of Interesting Solidification Phenomena on the Ground and in Space (MEPHISTO)

NASA Technical Reports Server (NTRS)

Favier, J.-J.; Iwan, J.; Alexander, D.; Garandet, J.-P.

1998-01-01

Real-time Seebeck voltage variations in a Sn-Bi melt during directional solidification in the MEPHISTO spaceflight experiment flown on the USMP-3 mission, can be correlated with well characterized thruster firings and an Orbiter Main System (OMS) burn. The Seebeck voltage measurement is related to the response of the instantaneous average melt composition at the melt-crystal interface. This allowed us to make a direct comparison of numerical simulations with the experimentally obtained Seebeck signals. Based on the results of preflight and real-time computations, several well-defined thruster firing events were programmed to occur at specific times during the experiment. In particular, we simulated the effects of the thruster firings on melt and crystal composition in a directionally solidifying Sn-Bi alloy. The relative accelerations produced by the firings were simulated by impulsive accelerations of the same magnitude, duration and orientation as the requested firings. A comparison of the simulation results with the Seebeck signal indicates that there is a good agreement between the two. This unique opportunity allows us, for the first time, to quantitatively characterize actual g-jitter effects on an actual crystal growth experiment and to properly calibrate our models of g-jitter effects on crystal growth.

[Responses of boreal forest landscape in northern Great Xing'an Mountains of Northeast China to climate change].

PubMed

Li, Xiao-Na; He, Hong-Shi; Wu, Zhi-Wei; Liang, Yu

2012-12-01

With the combination of forest landscape model (LANDIS) and forest gap model (LINKAGES), this paper simulated the effects of climate change on the boreal forest landscape in the Great Xing'an Mountains, and compared the direct effects of climate change and the effects of climate warming-induced fires on the forest landscape. The results showed that under the current climate conditions and fire disturbances, the forest landscape in the study area could maintain its dynamic balance, and Larix gmelinii was still the dominant tree species. Under the future climate and fire disturbances scenario, the distribution area of L. gmelinii and Pinus pumila would be decreased, while that of Betula platyphylla, Populus davidiana, Populus suaveolens, Chosenia arbutifolia, and Pinus sylvestris var. mongolica would be increased, and the forest fragmentation and forest diversity would have an increase. The changes of the forest landscape lagged behind climate change. Climate warming would increase the growth of most tree species except L. gmelinii, while the increased fires would increase the distribution area of P. davidiana, P. suaveolens, and C. arbutifolia and decrease the distribution area of L. gmelinii, P. sylvestris var. mongolica, and P. pumila. The effects of climate warming-induced fires on the forest landscape were almost equal to the direct effects of climate change, and aggravated the direct effects of climate change on forest composition, forest landscape fragmentation, and forest landscape diversity.

Are Invasive Species Stressful? The Glucocorticoid Profile of Native Lizards Exposed to Invasive Fire Ants Depends on the Context.

PubMed

Graham, Sean P; Freidenfelds, Nicole A; Thawley, Christopher J; Robbins, Travis R; Langkilde, Tracy

Invasive species represent a substantial threat to native species worldwide. Research on the impacts of invasive species on wild living vertebrates has focused primarily on population-level effects. The sublethal, individual-level effects of invaders may be equally important but are poorly understood. We investigated the effects of invasive fire ants (Solenopsis invicta) on the physiological stress response of a native lizard (Sceloporus undulatus) within two experimental contexts: directly exposing lizards to a fire ant attack and housing lizards with fire ants in seminatural field enclosures. Lizards directly exposed to brief attack by fire ants had elevated concentrations of the stress hormone corticosterone (CORT), suggesting that these encounters can be physiologically stressful. However, lizards exposed for longer periods to fire ants in field enclosures had lower concentrations of CORT. This may indicate that the combined effects of confinement and fire ant exposure have pushed lizards into allostatic overload. However, lizards from fire ant enclosures appeared to have intact negative feedback controls of the stress response, evidenced by functioning adrenocorticotropic hormone responsiveness and lack of suppression of innate immunity (plasma bactericidal capacity). We review previous studies examining the stress response of wild vertebrates to various anthropogenic stressors and discuss how these-in combination with our results-underscore the importance of considering context (the length, frequency, magnitude, and types of threat) when assessing these impacts.

Prescribed fire, soil inorganic nitrogen dynamics, and plant responses in a semiarid grassland

Treesearch

David J. Augustine; Paul Brewer; Dana M. Blumenthal; Justin D. Derner; Joseph C. von Fischer

2014-01-01

In arid and semiarid ecosystems, fire can potentially affect ecosystem dynamics through changes in soil moisture, temperature, and nitrogen cycling, as well as through direct effects on plant meristem mortality. We examined effects of annual and triennial prescribed fires conducted in early spring on soil moisture, temperature, and N, plant growth, and plant N content...

Application of Graph Theory to Cost-Effective Fire Protection of Chemical Plants During Domino Effects.

PubMed

Khakzad, Nima; Landucci, Gabriele; Reniers, Genserik

2017-09-01

In the present study, we have introduced a methodology based on graph theory and multicriteria decision analysis for cost-effective fire protection of chemical plants subject to fire-induced domino effects. By modeling domino effects in chemical plants as a directed graph, the graph centrality measures such as out-closeness and betweenness scores can be used to identify the installations playing a key role in initiating and propagating potential domino effects. It is demonstrated that active fire protection of installations with the highest out-closeness score and passive fire protection of installations with the highest betweenness score are the most effective strategies for reducing the vulnerability of chemical plants to fire-induced domino effects. We have employed a dynamic graph analysis to investigate the impact of both the availability and the degradation of fire protection measures over time on the vulnerability of chemical plants. The results obtained from the graph analysis can further be prioritized using multicriteria decision analysis techniques such as the method of reference point to find the most cost-effective fire protection strategy. © 2016 Society for Risk Analysis.

Self-motion improves head direction cell tuning

PubMed Central

Shinder, Michael E.

2014-01-01

Head direction (HD) cells respond when an animal faces a particular direction in the environment and form the basis for the animal's perceived directional heading. When an animal moves through its environment, accurate updating of the HD signal is required to reflect the current heading, but the cells still maintain a representation of HD even when the animal is motionless. This finding suggests that the HD system holds its current state in the absence of input, a view that we tested by rotating a head-restrained rat in the presence of a prominent visual landmark and then stopping it suddenly when facing the cell's preferred firing direction (PFD). Firing rates were unchanged for the first 100 ms, but then progressively decreased over the next 4 s and stabilized at ∼42% of their initial values. When the rat was stopped facing away from the PFD, there was no initial effect of braking, but the firing rate then increased steadily over 4 s and plateaued at ∼14% of its peak firing rate, substantially above initial background firing rates. In experiment 2, the rat was serially placed facing one of eight equidistant directions over 360° and held there for 30 s. Compared with the cell's peak firing rate during a passive rotation session, firing rates were reduced (51%) for in-PFD directions and increased (∼300%) from background levels for off-PFD directions, values comparable to those observed in the braking protocol. These differential HD cell responses demonstrate the importance of self-motion to the HD signal integrity. PMID:24671528

U-shaped, double-tapered, fiber-optic sensor for effective biofilm growth monitoring.

PubMed

Zhong, Nianbing; Zhao, Mingfu; Li, Yishan

2016-02-01

To monitor biofilm growth on polydimethylsiloxane in a photobioreactor effectively, the biofilm cells and liquids were separated and measured using a sensor with two U-shaped, double-tapered, fiber-optic probes (Sen. and Ref. probes). The probes' Au-coated hemispherical tips enabled double-pass evanescent field absorption. The Sen. probe sensed the cells and liquids inside the biofilm. The polyimide-silica hybrid-film-coated Ref. probe separated the liquids from the biofilm cells and analyzed the liquid concentration. The biofilm structure and active biomass were also examined to confirm the effectiveness of the measurement using a simulation model. The sensor was found to effectively respond to the biofilm growth in the adsorption through exponential phases at thicknesses of 0-536 μm.

Analysis of solid propellant combustion in a closed vessel including secondary reaction

NASA Technical Reports Server (NTRS)

Benreuven, M.; Summerfield, M.

1980-01-01

A theory for combustion of solid propellants in a closed vessel is presented allowing for residual exothermic chemical reaction in the bulk of the gas in the vessel. Particular attention is given to propellants exhibiting thick gaseous flame zones such as nitrocellulose, double-base and nitramine propellants. For these, the reaction at high pressures is assumed to involve mainly the oxidation of residual hydrocarbons by NO. It is shown that the direct dynamic coupling between the exothermicity, the molecular weight reduction and the changing pressure can influence the dp/dt-p traces obtained, in a manner not directly related to mass burning rate of the solid. Energy and species conservation equations are derived for the bulk of the vessel in differential form; the system is solved numerically. The results show the effect of extended chemical reaction upon measurable combustion characteristics such as dp/dt-p and burn rate pressure exponent, demonstrating its potential importance in interpretation of closed vessel firing data, depending on the pace of the residual gas phase reactions.

Issues in the analyze of low content gold mining samples by fire assay technique

NASA Astrophysics Data System (ADS)

Cetean, Valentina

2016-04-01

The classic technique analyze of samples with low gold content - below 0.1 g/t (=100 ppb = parts per billion), either ore or gold sediments, involves the preparation of sample by fire assay extraction, followed by the chemical attack with aqua regia (hydrochloric and nitric acid) and measuring the gold content by atomic absorption spectrometry or inductively coupled mass spectrometry. The issues raised by this analysis are well known for the world laboratories, commercial or research ones. The author's knowledge regarding this method of determining the gold content, accumulated in such laboratory from Romania (with more than 40 years of experience, even if not longer available from 2014) confirms the obtaining of reliable results required a lot of attention, amount of work and the involving of an experienced fire assayer specialist. The analytical conclusion for a research laboratory is that most reliable and statistically valid results are till reached for samples with more than 100 ppb gold content; the degree of confidence below this value is lower than 90%. Usually, for samples below 50 ppb, it does not exceed 50-70 %, unless without very strictly control of each stage, that involve additional percentage of hours allocated for successive extracting tests and knowing more precisely the other compounds that appear in the sample (Cu, Sb, As, sulfur / sulphides, Te, organic matter, etc.) or impurities. The most important operation is the preparation, namely: - grinding and splitting of sample (which can cause uneven distribution of gold flakes in the double samples for analyzed); - pyro-metallurgical recovery of gold = fire assay stage, involving the more precise temperature control in furnace during all stages (fusion and cupellation) and adjusting of the fire assay flux components to produce a successful fusion depending of the sample matrix and content; - reducing the sample weight to decrease the amount of impurities that can be concentrated in the lead button during oxidation stage. The better metal recovery and the decreasing of the amount of errors for low gold content samples are controlled in this case by: - the management of the quantity of one or more components of the flux, depending on the chemical composition of the sample (sometimes just by observing the behavior and the visual characteristics of lead Au + Ag button/bead and the resulted slag); - addition of gold-free silver, which will be removed by chemical reduction with aqua regia after the fire assay stage. Regarding the instrumental analyze stage of the samples with less than 100 ppb gold content, there were obtained similar values by both techniques: atomic absorption and inductively coupled mass spectrometry, taking into account each of them has different detection limit. It is mandatory the quality control with a certified reference material with known content, both in the fire assay stage and the reading instrumental stage. This abstract are written in the frame of the SUSMIN project: "Tools for sustainable gold mining in EU".

Theoretical analysis of optical poling and frequency doubling effect based on classical model

NASA Astrophysics Data System (ADS)

Feng, Xi; Li, Fuquan; Lin, Aoxiang; Wang, Fang; Chai, Xiangxu; Wang, Zhengping; Zhu, Qihua; Sun, Xun; Zhang, Sen; Sun, Xibo

2018-03-01

Optical poling and frequency doubling effect is one of the effective manners to induce second order nonlinearity and realize frequency doubling in glass materials. The classical model believes that an internal electric field is built in glass when it's exposed by fundamental and frequency-doubled light at the same time, and second order nonlinearity appears as a result of the electric field and the orientation of poles. The process of frequency doubling in glass is quasi phase matched. In this letter, the physical process of poling and doubling process in optical poling and frequency doubling effect is deeply discussed in detail. The magnitude and direction of internal electric field, second order nonlinear coefficient and its components, strength and direction of frequency doubled output signal, quasi phase matched coupled wave equations are given in analytic expression. Model of optical poling and frequency doubling effect which can be quantitatively analyzed are constructed in theory, which set a foundation for intensive study of optical poling and frequency doubling effect.

Femtosecond Chirp-Free Transient Absorption Method And Apparatus

DOEpatents

McBranch, Duncan W.; Klimov, Victor I.

2001-02-20

A method and apparatus for femtosecond transient absorption comprising phase-sensitive detection, spectral scanning and simultaneous controlling of a translation stage to obtain TA spectra information having at least a sensitivity two orders of magnitude higher than that for single-shot methods, with direct, simultaneous compensation for chirp as the data is acquired. The present invention includes a amplified delay translation stage which generates a splittable frequency-doubled laser signal at a predetermined frequency f, a controllable means for synchronously modulating one of the laser signals at a repetition rate of f/2, applying the laser signals to a material to be sample, and acquiring data from the excited sample while simultaneously controlling the controllable means for synchronously modulating.

Radiative characteristics of aerosol during extreme fire event over Siberia in summer 2012

NASA Astrophysics Data System (ADS)

Zhuravleva, Tatiana B.; Kabanov, Dmitriy M.; Nasrtdinov, Ilmir M.; Russkova, Tatiana V.; Sakerin, Sergey M.; Smirnov, Alexander; Holben, Brent N.

2017-01-01

Microphysical and optical properties of aerosol were studied during a mega-fire event in summer 2012 over Siberia using ground-based measurements of spectral solar radiation at the AERONET site in Tomsk and satellite observations. The data were analysed using multi-year (2003-2013) measurements of aerosol characteristics under background conditions and for less intense fires, differing in burning biomass type, stage of fire, remoteness from observation site, etc. (ordinary smoke). In June-August 2012, the average aerosol optical depth (AOD, 500 nm) had been 0.95 ± 0.86, about a factor of 6 larger than background values (0.16 ± 0.08), and a factor of 2.5 larger than in ordinary smoke. The AOD values were extremely high on 24-28 July and reached 3-5. A comparison with satellite observations showed that ground-based measurements in the region of Tomsk not only reflect the local AOD features, but are also characteristic for the territory of Western Siberia as a whole. Single scattering albedo (SSA, 440 nm) in this period ranged from 0.91 to 0.99 with an average of ˜ 0.96 in the entire wavelength range of 440-1020 nm. The increase in absorptance of aerosol particles (SSA(440 nm) = 0.92) and decrease in SSA with wavelength observed in ordinary smoke agree with the data from multi-year observations in analogous situations in the boreal zone of USA and Canada. Volume aerosol size distribution in extreme and ordinary smoke had a bimodal character with significant prevalence of fine-mode particles, but in summer 2012 the mean median radius and the width of the fine-mode distribution somewhat increased. In contrast to data from multi-year observations, in summer 2012 an increase in the volume concentration and median radius of the coarse mode was observed with growing AOD. The calculations of the average radiative effects of smoke and background aerosol are presented. Compared to background conditions and ordinary smoke, under the extreme smoke conditions the cooling effect of aerosol considerably intensifies: direct radiative effects (DRE) at the bottom (BOA) and at the top of the atmosphere (TOA) are -13, -35, and -60 W m-2 and -5, -14, and -35 W m-2 respectively. The maximal values of DRE were observed on 27 July (AOD(500 nm) = 3.5), when DRE(BOA) reached -150 W m-2, while DRE(TOA) and DRE of the atmosphere were -75 W m-2. During the fire event in summer 2012 the direct radiative effect efficiency varied in range: at the BOA it was -80-40 W m-2, at the TOA it was -50-20 W m-2 and in the atmosphere it was -35-20 W m-2.

Prereplicative complexes assembled in vitro support origin-dependent and independent DNA replication

PubMed Central

On, Kin Fan; Beuron, Fabienne; Frith, David; Snijders, Ambrosius P; Morris, Edward P; Diffley, John F X

2014-01-01

Eukaryotic DNA replication initiates from multiple replication origins. To ensure each origin fires just once per cell cycle, initiation is divided into two biochemically discrete steps: the Mcm2-7 helicase is first loaded into prereplicative complexes (pre-RCs) as an inactive double hexamer by the origin recognition complex (ORC), Cdt1 and Cdc6; the helicase is then activated by a set of “firing factors.” Here, we show that plasmids containing pre-RCs assembled with purified proteins support complete and semi-conservative replication in extracts from budding yeast cells overexpressing firing factors. Replication requires cyclin-dependent kinase (CDK) and Dbf4-dependent kinase (DDK). DDK phosphorylation of Mcm2-7 does not by itself promote separation of the double hexamer, but is required for the recruitment of firing factors and replisome components in the extract. Plasmid replication does not require a functional replication origin; however, in the presence of competitor DNA and limiting ORC concentrations, replication becomes origin-dependent in this system. These experiments indicate that Mcm2-7 double hexamers can be precursors of replication and provide insight into the nature of eukaryotic DNA replication origins. PMID:24566989

Climatic warming strengthens a positive feedback between alpine shrubs and fire.

PubMed

Camac, James S; Williams, Richard J; Wahren, Carl-Henrik; Hoffmann, Ary A; Vesk, Peter A

2017-08-01

Climate change is expected to increase fire activity and woody plant encroachment in arctic and alpine landscapes. However, the extent to which these increases interact to affect the structure, function and composition of alpine ecosystems is largely unknown. Here we use field surveys and experimental manipulations to examine how warming and fire affect recruitment, seedling growth and seedling survival in four dominant Australian alpine shrubs. We found that fire increased establishment of shrub seedlings by as much as 33-fold. Experimental warming also doubled growth rates of tall shrub seedlings and could potentially increase their survival. By contrast, warming had no effect on shrub recruitment, postfire tussock regeneration, or how tussock grass affected shrub seedling growth and survival. These findings indicate that warming, coupled with more frequent or severe fires, will likely result in an increase in the cover and abundance of evergreen shrubs. Given that shrubs are one of the most flammable components in alpine and tundra environments, warming is likely to strengthen an existing feedback between woody species abundance and fire in these ecosystems. © 2017 John Wiley & Sons Ltd.

Effects of Degree of Curing on Fire Spread

NASA Astrophysics Data System (ADS)

Chaivaranont, W.; Evans, J. P.; Liu, Y.

2016-12-01

During extreme summer conditions in Australia, bushfire can become an uncontrollable natural hazard. Various factors, such as geographical and meteorological parameters greatly influence the magnitude of bushfire. In a grassland fire, there is an important factor that affects the severity of fire called the degree of curing. Degree of curing is a percentage measurement of the proportion of dead material in grassland where a 100% curing indicates a totally dead grass field. It is usually assumed constant due to the cost and difficulty in obtaining accurate field observations.To examine the importance of curing, the Phoenix RapidFire fire spread model was used to observe the magnitude and direction of grassland fire spread due to variations in the degree of curing. Idealised experiments and experiments based on 3 past fire events in Australia were conducted, where the 100 by 200 km study area is considered to be all grassland. In the idealised experiments, homogeneous curing data in various patterns were used along with extreme climate data and prescribed topography. In the past fire event experiments, satellite-derived estimated curing data, observed climate data from the nearest weather stations, and real elevation maps were used. A remotely sensed burned area map (MODIS MCD64A1 product) is also used to compare the simulated burned area of past fire events with the satellite observation.The results from both experiments showed that: 1) the rate of spread of grassland fire is significantly impeded when curing is below 75%, 2) topography has insignificant effect on fire spread direction and speed, 3) wind and curing both influence the direction and speed of spread, and 4) the model can only recreate the burned area in one out of three of the past fire events due to various causes including the fact that all past events used here were not exclusively grassland fire.

Design and dosimetric analysis of a 385 MHz TETRA head exposure system for use in human provocation studies.

PubMed

Schmid, Gernot; Bolz, Thomas; Uberbacher, Richard; Escorihuela-Navarro, Ana; Bahr, Achim; Dorn, Hans; Sauter, Cornelia; Eggert, Torsten; Danker-Hopfe, Heidi

2012-10-01

A new head exposure system for double-blind provocation studies investigating possible effects of terrestrial trunked radio (TETRA)-like exposure (385 MHz) on central nervous processes was developed and dosimetrically analyzed. The exposure system allows localized exposure in the temporal brain, similar to the case of operating a TETRA handset at the ear. The system and antenna concept enables exposure during wake and sleep states while an electroencephalogram (EEG) is recorded. The dosimetric assessment and uncertainty analysis yield high efficiency of 14 W/kg per Watt of accepted antenna input power due to an optimized antenna directly worn on the subject's head. Beside sham exposure, high and low exposure at 6 and 1.5 W/kg (in terms of maxSAR10g in the head) were implemented. Double-blind control and monitoring of exposure is enabled by easy-to-use control software. Exposure uncertainty was rigorously evaluated using finite-difference time-domain (FDTD)-based computations, taking into account anatomical differences of the head, the physiological range of the dielectric tissue properties including effects of sweating on the antenna, possible influences of the EEG electrodes and cables, variations in antenna input reflection coefficients, and effects on the specific absorption rate (SAR) distribution due to unavoidable small variations in the antenna position. This analysis yielded a reasonable uncertainty of <±45% (max to min ratio of 4.2 dB) in terms of maxSAR10g in the head and a variability of <±60% (max to min ratio of 6 dB) in terms of mass-averaged SAR in different brain regions, as demonstrated by a brain region-specific absorption analysis. Copyright © 2012 Wiley Periodicals, Inc.

26 CFR 1.1312-2 - Double allowance of a deduction or credit.

Code of Federal Regulations, 2010 CFR

2010-04-01

... return for 1950 claimed and was allowed a deduction for destruction of timber by a forest fire. Subsequently, it was discovered that the forest fire occurred in 1951 rather than 1950. After the expiration of... refund for 1951 based upon a deduction for the fire loss in that year. The Commissioner in 1955 allows...

26 CFR 1.1312-2 - Double allowance of a deduction or credit.

Code of Federal Regulations, 2011 CFR

2011-04-01

... taxpayer in his return for 1950 claimed and was allowed a deduction for destruction of timber by a forest fire. Subsequently, it was discovered that the forest fire occurred in 1951 rather than 1950. After the... claim for refund for 1951 based upon a deduction for the fire loss in that year. The Commissioner in...

Combining Multi-Sensor Measurements and Models to Constrain Time-Varying Aerosol Fire Emissions

NASA Astrophysics Data System (ADS)

Cohen, J. B.

2013-12-01

A significant portion of global Black Carbon (BC) and Organic Carbon (OC) aerosols are emitted into the atmosphere due to fires. However, due to their spatially and temporally heterogeneous nature, quantifying these emissions has proven to be difficult. Some of the problems stem from variability over multiple spatial and temporal scales: ranging from kilometers in size to thousands of kilometers in impact, and from month-to-month variations in the burning season to interannual variation in overall fire strength which follows such global phenomena as El-Nino. Yet, because of the unique absorbing properties that these aerosols have, they leave a distinct impact on the regional and global climate system, as well as the ability to intensely impact human health in downwind areas, proper quantification of the emissions is absolutely essential. To achieve such a critical understanding of their emissions in space and time, a start-of-the art modelling system of their chemical and physical processing, transport, and removal is implemented. This system is capable of effectively and uniquely simulating many impacts important in the atmosphere, including: enhanced absorption associated with internal mixing, mass and number conservation, the direct and semi-direct effects on atmospheric dynamics and circulation, and appropriate non-linear consideration of urban-scale chemical and physical processing. This modelling system has been used in connection with 3 separate sources of data, to achieve an end product that is heavily dependent on both. First of all, the model has been run in a data-assimilation mode to constrain the annual-average emissions of BC using the Kalman Filter technique. This global constraint, the first of its type, relies heavily on ground-based sensors from NASA as well as other organizations. Secondly, data of the decadal-scale variation in aerosol optical depth, surface reflectance, and radiative power have been obtained from the MODIS and MISR sensors. This data has been used in connection with a new analytical technique to derive the temporally and spatially varying component of the emissions. Combining this result with the Kalman Filter annual base emissions and the modelling system shows that fires can be reproduced more accurately than many other methods, including using straight Fire Radiative Power estimations. Finally, this new combined product is analyzed using measurements from the CALIPSO sensor to quantify further properties of these fires, particularly in terms of radiative forcing and vertical distribution. The results are compared against other studies of fires and the impacts on the radiative balance are quantified. One conclusion is that emissions of both BC and OC from these fires are currently underestimated and this method provides a means by which to quantify this underestimation, both in terms of absolute amount as well as space and time. A second conclusion is that this method provides a strong rationale for why relying solely on a Fire Radiative Power approach may not be appropriate, especially in a cloud-covered region such as Southeast Asia. Finally, the limitations of the use of multiple-sensors and this approach in general are detailed by looking more in-depth at the massive biomass-burning episode in June of 2013 that occurred in Southeast Asia.

Assessing the Role and Impact of Geospatial Data for Wildland Fire Management Decisions

NASA Astrophysics Data System (ADS)

Klein, E. A.; Lev, S. M.

2016-12-01

The 2015 Wildland and Fire Science and Technology Task Force Final Report, produced by the National Science and Technology Council, Committee on Environment, Natural Resources, and Sustainability, Subcommittee on Disaster Reduction, highlighted the increasing frequency of large wildfires and the growing demand for science to inform critical resource decisions to manage, mitigate, respond to, and recover from wildland fires. Federal spending on fire suppression from 2005-2015 has more than doubled despite policy changes that prioritize the mitigation of fire risks through the use of fuel treatments, prescribed fire, and management of naturally occurring wildfires to protect life and property. Fire suppression policies over the last century have created forests primed for severe fire, and in the face of a changing climate, the benefits of re-introducing fire into once fire-resilient ecosystems are clear. There are a range of complex factors and regional variation associated with wildland fire risk that complicate our understanding and effective management of this hazard. Data derived from Earth-observing (EO) systems and networks are a crucial input for managers when making decisions about fire suppression and fuel management. EO data can also be used to develop pre- and post-fire metrics that can aid in the evaluating the effectiveness of wildland fire management decisions. A value-tree method for mapping the role of EO systems and networks in delivering societal benefit through key Federal objectives related to wildland fire management will be presented. The value-tree methodology utilizes input from subject matter experts to assess the availability and usability of data and data products and to evaluate the impact of individual EO data inputs for achieving wildland fire management objectives. The results provide a qualitative assessment of the value of the data for the objectives described and identify critical gaps and continuity issues associated with improvements to and continuous delivery of societal benefit.

Effects of biotic feedback and harvest management on boreal forest fire activity under climate change.

PubMed

Krawchuk, Meg A; Cumming, Steve G

2011-01-01

Predictions of future fire activity over Canada's boreal forests have primarily been generated from climate data following assumptions that direct effects of weather will stand alone in contributing to changes in burning. However, this assumption needs explicit testing. First, areas recently burned can be less likely to burn again in the near term, and this endogenous regulation suggests the potential for self-limiting, negative biotic feedback to regional climate-driven increases in fire. Second, forest harvest is ongoing, and resulting changes in vegetation structure have been shown to affect fire activity. Consequently, we tested the assumption that fire activity will be driven by changes in fire weather without regulation by biotic feedback or regional harvest-driven changes in vegetation structure in the mixedwood boreal forest of Alberta, Canada, using a simulation experiment that includes the interaction of fire, stand dynamics, climate change, and clear cut harvest management. We found that climate change projected with fire weather indices calculated from the Canadian Regional Climate Model increased fire activity, as expected, and our simulations established evidence that the magnitude of regional increase in fire was sufficient to generate negative feedback to subsequent fire activity. We illustrate a 39% (1.39-fold) increase in fire initiation and 47% (1.47-fold) increase in area burned when climate and stand dynamics were included in simulations, yet 48% (1.48-fold) and 61% (1.61-fold) increases, respectively, when climate was considered alone. Thus, although biotic feedbacks reduced burned area estimates in important ways, they were secondary to the direct effect of climate on fire. We then show that ongoing harvest management in this region changed landscape composition in a way that led to reduced fire activity, even in the context of climate change. Although forest harvesting resulted in decreased regional fire activity when compared to unharvested conditions, forest composition and age structure was shifted substantially, illustrating a trade-off between management goals to minimize fire and conservation goals to emulate natural disturbance.

A review of fire effects on bats and bat habitat in the eastern oaks region

Treesearch

Roger W. Perry

2012-01-01

Fire is increasingly being used in oak forests to promote oak regeneration, improve wildlife habitat, and reduce hazardous fuel loads. Although recent research has begun to shed light on the relationships among fire, bats, and bat habitat, these interactions are not yet fully understood. Fire may affect bats directly through heat and smoke during the burning process or...

A review of fire effects on bats and bat habitat in the eastern oak region

Treesearch

Roger W. Perry

2012-01-01

Fire is increasingly being used in oak forests to promote oak regeneration, improve wildlife habitat, and reduce hazardous fuel loads. Although recent research has begun to shed light on the relationships among fire, bats, and bat habitat, these interactions are not yet fully understood. Fire may affect bats directly through heat and smoke during the burning process or...

Linking sediment-charcoal records and ecological modeling to understand causes of fire-regime change in boreal forests

Treesearch

Linda B. Brubaker; Philip E. Higuera; T. Scott Rupp; Mark A. Olson; Patricia M. Anderson; Feng Sheng. Hu

2009-01-01

Interactions between vegetation and fire have the potential to overshadow direct effects of climate change on fire regimes in boreal forests of North America. We develop methods to compare sediment-charcoal records with fire regimes simulated by an ecological model, ALFRESCO (Alaskan Frame-based Ecosystem Code) and apply these methods to evaluate potential causes of a...

Post-fire regeneration in a Mediterranean pine forest with historically low fire frequency

NASA Astrophysics Data System (ADS)

Buhk, Constanze; Götzenberger, Lars; Wesche, Karsten; Gómez, Pedro Sánchez; Hensen, Isabell

2006-11-01

Species of Mediterranean vegetation are known to regenerate directly after fire. The phenomenon of autosuccession (direct regeneration) has been found to be often combined with an increase of species richness during the first years after fire due to the high abundance of short-lived herbaceous plants facilitated by plentiful nutrients and light. The high degree of vegetation resilience, which is expressed in terms of autosuccession, has been explained by the selective pressure of fire in historic times. According to existing palaeoecological data, however, the Pinus halepensis forests in the Ricote Mountains (Province of Murcia, SE Spain) did not experience substantial fire impact before the presence of man nor are they especially fire-prone today. Therefore, we studied post-fire regeneration to find out if direct succession is present or if species from pre-fire vegetation are absent during the post-fire regeneration stages. Patterns of succession were deduced from observations made in sample plots on sites of a known regeneration age as well as in adjacent unburnt areas. The results of the vegetation analyses, including a Detrended Correspondence Analysis, indicate that Pinus halepensis forest regeneration after fire resembles autosuccession. As regards the presence of woody species, there is a high percentage similarity on north (83%) and south (70%) facing slopes during the first year after fire vs. reference areas which is due, for example, to direct regeneration of the resprouting Quercus coccifera or seeders like Pinus halepensis or Fumana laevipes. However, if herbaceous species are included in the comparison, the similarity on north-facing sites decreases (to 53%) with the presence of additional species, mainly ruderals like Anagallis arvensis or Reseda phyteuma, and even woody species on the burnt plots. This effect indicates "enhanced autosuccession", which was not found on south-facing sites where overall species richness was very high irrespective of the impact of fire. Locally we found limited regeneration of some species, for example Pinus halepensis at high altitudes (1000 m), even 22 years after fire. As we assume that historical fires did not play an important role in the area and direct succession is present nevertheless, our results support the theory that autosuccession is not a process restricted to fire-prone areas. Fire has been only one of several selective forces since human settlement that probably led to a set of species pre-adapted against recurrent disturbance.

U-shaped, double-tapered, fiber-optic sensor for effective biofilm growth monitoring

PubMed Central

Zhong, Nianbing; Zhao, Mingfu; Li, Yishan

2016-01-01

To monitor biofilm growth on polydimethylsiloxane in a photobioreactor effectively, the biofilm cells and liquids were separated and measured using a sensor with two U-shaped, double-tapered, fiber-optic probes (Sen. and Ref. probes). The probes’ Au-coated hemispherical tips enabled double-pass evanescent field absorption. The Sen. probe sensed the cells and liquids inside the biofilm. The polyimide–silica hybrid-film-coated Ref. probe separated the liquids from the biofilm cells and analyzed the liquid concentration. The biofilm structure and active biomass were also examined to confirm the effectiveness of the measurement using a simulation model. The sensor was found to effectively respond to the biofilm growth in the adsorption through exponential phases at thicknesses of 0–536 μm. PMID:26977344

Variable thickness double-refracting plate

DOEpatents

Hadeishi, Tetsuo

1976-01-01

This invention provides an A.C., cyclic, current-controlled, phase retardation plate that uses a magnetic clamp to produce stress birefringence. It was developed for an Isotope-Zeeman Atomic Absorption Spectrometer that uses polarization modulation to effect automatic background correction in atomic absorption trace-element measurements. To this end, the phase retardation plate of the invention is a variable thickness, photoelastic, double-refracting plate that is alternately stressed and released by the magnetic clamp selectively to modulate specific components selected from the group consisting of circularly and plane polarized Zeeman components that are produced in a dc magnetic field so that they correspond respectively to Zeeman reference and transmission-probe absorption components. The polarization modulation changes the phase of these polarized Zeeman components, designated as .sigma. reference and .pi. absorption components, so that every half cycle the components change from a transmission mode to a mode in which the .pi. component is blocked and the .sigma. components are transmitted. Thus, the Zeeman absorption component, which corresponds in amplitude to the amount of the trace element to be measured in a sample, is alternately transmitted and blocked by a linear polarizer, while the circularly polarized reference components are continuously transmitted thereby. The result is a sinusoidally varying output light amplitude whose average corresponds to the amount of the trace element present in the sample.

Ultra-Lightweight Mirror Manufacturing and Radiation Response Study

DTIC Science & Technology

1981-08-01

Mismatch vs Firing Plateau for Single and Double Fired U-A Frit ................ ..................... 10 2.1.1-2 Channel-Strip Method for Core-Plate... Firing Furnace ..... .............. ... 25 2.2.1-1 Location of Vac-U-Lift Pads ..... ............... .... 30 2.2.1-2 Cross Section of Vacuum Pad...the second plate is then put in place. If the mirror is to be a plano-plano, it is fired front plate up, removed from the furnace, turned over, then

Improvements to Shortwave Absorption in the GFDL General Circulation Model Radiation Code

NASA Astrophysics Data System (ADS)

Freidenreich, S.

2015-12-01

The multiple-band shortwave radiation parameterization used in the GFDL general circulation models is being revised to better simulate the disposition of the solar flux in comparison with line-by-line+doubling-adding reference calculations based on the HITRAN 2012 catalog. For clear skies, a notable deficiency in the older formulation is an underestimate of atmospheric absorption. The two main reasons for this is the neglecting of both H2O absorption for wavenumbers < 2500 cm-1 and the O2 continuum. Further contributions to this underestimate are due to neglecting the effects of CH4, N2O and stratospheric H2O absorption. These issues are addressed in the revised formulation and result in globally average shortwave absorption increasing from 74 to 78 Wm-2. The number of spectral bands considered remains the same (18), but the number of pseudomonochromatic intervals (based mainly on the exponential-sum-fit technique) for the determination of H2O absorption is increased from 38 to 74, allowing for more accuracy in its simulation. Also, CO2 absorption is now determined by the exponential-sum-fit technique, replacing an algebraic absorptivity expression in the older parameterization; this improves the simulation of the heating in the stratosphere. Improvements to the treatment of multiple scattering are currently being tested. This involves replacing the current algorithm, which consists of the two stream delta-Eddington, with a four stream algorithm. Initial results show that in most, but not all cases these produce better agreement with the reference doubling-adding results.

Abrupt climate-independent fire regime changes

USGS Publications Warehouse

Pausas, Juli G.; Keeley, Jon E.

2014-01-01

Wildfires have played a determining role in distribution, composition and structure of many ecosystems worldwide and climatic changes are widely considered to be a major driver of future fire regime changes. However, forecasting future climatic change induced impacts on fire regimes will require a clearer understanding of other drivers of abrupt fire regime changes. Here, we focus on evidence from different environmental and temporal settings of fire regimes changes that are not directly attributed to climatic changes. We review key cases of these abrupt fire regime changes at different spatial and temporal scales, including those directly driven (i) by fauna, (ii) by invasive plant species, and (iii) by socio-economic and policy changes. All these drivers might generate non-linear effects of landscape changes in fuel structure; that is, they generate fuel changes that can cross thresholds of landscape continuity, and thus drastically change fire activity. Although climatic changes might contribute to some of these changes, there are also many instances that are not primarily linked to climatic shifts. Understanding the mechanism driving fire regime changes should contribute to our ability to better assess future fire regimes.

One-way Z→E isomerization around the double bond of N-methoxy- 1- (2-anthryl) ethanimine in the excited triplet state. Direct observation of one-way isomerization from Z triplet to E triplet of the C dbnd N bond

NASA Astrophysics Data System (ADS)

Arai, Tatsuo; Furuya, Yasunori; Furuuchi, Hideo; Tokumaru, Katsumi

1993-09-01

On direct as well as benzil-sensitized irradiation in degassed benzene N-methoxy-1-(2-anthryl) ethanimine ( I), ArC (CH 3) dbnd N sbnd OCH 3 (Ar: 2-anthryl), underwent one-way Z→E isomerization through a quantum chain process. The barrier to Z→E isomerization of I in the excited triplet state was determined by directly observing the change of T—T absorption spectra from the Z triplet to the E triplet. Based on these results the potential energy surface of photoisomerization of I is discussed.

Climate change and future fire regimes: Examples from California

USGS Publications Warehouse

Keeley, Jon E.; Syphard, Alexandra D.

2016-01-01

Climate and weather have long been noted as playing key roles in wildfire activity, and global warming is expected to exacerbate fire impacts on natural and urban ecosystems. Predicting future fire regimes requires an understanding of how temperature and precipitation interact to control fire activity. Inevitably this requires historical analyses that relate annual burning to climate variation. Fuel structure plays a critical role in determining which climatic parameters are most influential on fire activity, and here, by focusing on the diversity of ecosystems in California, we illustrate some principles that need to be recognized in predicting future fire regimes. Spatial scale of analysis is important in that large heterogeneous landscapes may not fully capture accurate relationships between climate and fires. Within climatically homogeneous subregions, montane forested landscapes show strong relationships between annual fluctuations in temperature and precipitation with area burned; however, this is strongly seasonal dependent; e.g., winter temperatures have very little or no effect but spring and summer temperatures are critical. Climate models that predict future seasonal temperature changes are needed to improve fire regime projections. Climate does not appear to be a major determinant of fire activity on all landscapes. Lower elevations and lower latitudes show little or no increase in fire activity with hotter and drier conditions. On these landscapes climate is not usually limiting to fires but these vegetation types are ignition-limited. Moreover, because they are closely juxtaposed with human habitations, fire regimes are more strongly controlled by other direct anthropogenic impacts. Predicting future fire regimes is not rocket science; it is far more complicated than that. Climate change is not relevant to some landscapes, but where climate is relevant, the relationship will change due to direct climate effects on vegetation trajectories, as well as by feedback processes of fire effects on vegetation distribution, plus policy changes in how we manage ecosystems.

The physical properties of black carbon and other light-absorbing material emitted from prescribed fires in the United States

NASA Astrophysics Data System (ADS)

McMeeking, G. R.; Kreidenweis, S. M.; Yokelson, R. J.; Sullivan, A. P.; Lee, T.; Collett, J. L.; Fortner, E.; Onasch, T. B.; Akagi, S. K.; Taylor, J.; Coe, H.

2012-12-01

Black carbon (BC) aerosol emitted from fires absorbs light, leading to visibility degradation as well as regional and global climate impacts. Fires also emit a wide range of trace gases and particulates that can interact with emitted BC and alter its optical properties and atmospheric lifetime. Non-BC particulate species emitted by fires can also scatter and absorb light, leading to additional effects on visibility. Recent work has shown that certain organic species can absorb light strongly at shorter wavelengths, giving it a brown or yellow color. This material has been classified as brown carbon, though it is not yet well defined. Land managers must find a balance between the negative impacts of prescribed fire emissions on visibility and air quality and the need to prevent future catastrophic wildfire as well as manage ecosystems for habitat restoration or other purposes. This decision process requires accurate assessments of the visibility impacts of fire emissions, including BC and brown carbon, which in turn depend on their optical properties. We present recent laboratory and aircraft measurements of black carbon and aerosol optical properties emitted from biomass burning. All measurement campaigns included a single particle soot photometer (SP2) instrument capable of providing size-resolved measurements of BC mass and number distributions and mixing state, which are needed to separate the BC and brown carbon contributions to total light absorption. The laboratory experiments also included a three-wavelength photoacoustic spectrometer that provided accurate measurements of aerosol light absorption. The laboratory systems also characterized emissions after they had been treated with a thermal denuder to remove semi-volatile coatings, allowing an assessment of the role of non-BC coatings on bulk aerosol optical properties. Emissions were also aged in an environmental smog chamber to examine the role of secondary aerosol production on aerosol optical properties.

Chemical Properties of Brown Carbon Aerosol Generated at the Missoula Fire Sciences Laboratory

NASA Astrophysics Data System (ADS)

Washenfelder, R. A.; Womack, C.; Franchin, A.; Middlebrook, A. M.; Wagner, N.; Manfred, K.

2017-12-01

Aerosol scattering and absorption are still among the largest uncertainties in quantifying radiative forcing. Biomass burning is a major source of light-absorbing carbonaceous aerosol in the United States. These aerosol are generally classified into two categories: black carbon (graphitic-like aerosol that absorbs broadly across the ultraviolet and visible spectral regions) and brown carbon (organic aerosol that absorbs strongly in the ultraviolet and near-visible spectral regions). The composition, volatility, and chemical aging of brown carbon are poorly known, but are important to understanding its radiative effects. We deployed three novel instruments to the Missoula Fire Sciences Laboratory in 2016 to measure brown carbon absorption: a photoacoustic spectrometer, broadband cavity enhanced spectrometer, and particle-into-liquid sampler coupled to a liquid waveguide capillary cell. The instruments sampled from a shared inlet with well-characterized dilution and thermal denuding. We sampled smoke from 32 controlled burns of fuels relevant to western U.S. wildfires. We use these measurements to determine the volatility of water-soluble brown carbon, and compare this to the volatility of water-soluble organic aerosol and total organic aerosol. We further examine the wavelength-dependence of the water-soluble brown carbon absorption as a function of denuder temperature. Together this gives new information about the solubility, volatility, and chemical composition of brown carbon.

Smoke, Clouds, and Radiation-Brazil (SCAR-B) Experiment

NASA Technical Reports Server (NTRS)

Kaufman, Y. J.; Hobbs, P. V.; Kirchoff, V. W. J. H.; Artaxo, P.; Remer, L. A.; Holben, B. N.; King, M. D.; Ward, D. E.; Prins, E. M.; Longo, K. M.;

Enhanced optical limiting effects in a double-decker bis(phthalocyaninato) rare earth complex using radially polarized beams

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, Jia-Lu; Gu, Bing, E-mail: gubing@seu.edu.cn; Liu, Dahui

2014-10-27

Optical limiting (OL) effects can be enhanced by exploiting various limiting mechanisms and by designing nonlinear optical materials. In this work, we present the large enhancement of OL effects by manipulating the polarization distribution of the light field. Theoretically, we develop the Z-scan and nonlinear transmission theories on a two-photon absorber under the excitation of cylindrical vector beams. It is shown that both the sensitivity of Z-scan technique and the OL effect using radially polarized beams have the large enhancement compared with that using linearly polarized beams (LPBs). Experimentally, we investigate the nonlinear absorption properties of a double-decker Pr[Pc(OC{sub 8}H{submore » 17}){sub 8}]{sub 2} rare earth complex by performing Z-scan measurements with femtosecond-pulsed radially polarized beams at 800 nm wavelength. The observed two-photon absorption process, which originates from strong intramolecular π–π interaction, is exploited for OL application. The results demonstrate the large enhancement of OL effects using radially polarized beams instead of LPBs.« less

Structural studies on serum albumins under green light irradiation.

PubMed

Comorosan, Sorin; Polosan, Silviu; Popescu, Irinel; Ionescu, Elena; Mitrica, Radu; Cristache, Ligia; State, Alina Elena

2010-10-01

This paper presents two new experimental results: the protective effect of green light (GL) on ultraviolet (UV) denaturation of proteins, and the effect of GL on protein macromolecular structures. The protective effect of GL was revealed on two serum albumins, bovine (BSA) and human (HSA), and recorded by electrophoresis, absorption, and circular dichroism spectra. The effect of GL irradiation on protein structure was recorded by using fluorescence spectroscopy and electrophoresis. These new effects were modeled by quantum-chemistry computation using Gaussian 03 W, leading to good fit between theoretical and experimental absorption and circular dichroism spectra. A mechanism for these phenomena is suggested, based on a double-photon absorption process. This nonlinear effect may lead to generation of long-lived Rydberg macromolecular systems, capable of long-range interactions. These newly suggested systems, with macroscopic quantum coherence behaviors, may block the UV denaturation processes.

Representation of Non-Spatial and Spatial Information in the Lateral Entorhinal Cortex

PubMed Central

Deshmukh, Sachin S.; Knierim, James J.

2011-01-01

Some theories of memory propose that the hippocampus integrates the individual items and events of experience within a contextual or spatial framework. The hippocampus receives cortical input from two major pathways: the medial entorhinal cortex (MEC) and the lateral entorhinal cortex (LEC). During exploration in an open field, the firing fields of MEC grid cells form a periodically repeating, triangular array. In contrast, LEC neurons show little spatial selectivity, and it has been proposed that the LEC may provide non-spatial input to the hippocampus. Here, we recorded MEC and LEC neurons while rats explored an open field that contained discrete objects. LEC cells fired selectively at locations relative to the objects, whereas MEC cells were weakly influenced by the objects. These results provide the first direct demonstration of a double dissociation between LEC and MEC inputs to the hippocampus under conditions of exploration typically used to study hippocampal place cells. PMID:22065409

Design and measure of a tunable double-band metamaterial absorber in the THz spectrum

NASA Astrophysics Data System (ADS)

Guiming, Han

2018-04-01

We demonstrate and measure a hybrid double-band tunable metamaterial absorber in the terahertz region. The measured metamaterial absorber contains of a hybrid dielectric layer structure: a SU-8 layer and a VO2 layer. Near perfect double-band absorption performances are achieved by optimizing the SU-8 layer thickness at room temperature 25 °C. Measured results show that the phase transition can be observed when the measured temperature reaches 68 °C. Further measured results indicate that the resonance frequency and absorption amplitude of the proposed metamaterial absorber are tunable through increasing the measured temperature, while structural parameters unchanged. The proposed hybrid metamaterial absorber shows many advantages, such as frequency agility, absorption amplitude tunable, and simple fabrication.

Protein recycling in growing rabbits: contribution of microbial lysine to amino acid metabolism.

PubMed

Belenguer, Alvaro; Balcells, Joaquim; Guada, Jose A; Decoux, Marc; Milne, Eric

2005-11-01

To study the absorption of microbial lysine in growing rabbits, a labelled diet (supplemented with (15)NH4Cl) was administered to six animals (group ISOT); a control group (CTRL, four rabbits) received a similar, but unlabelled, diet. Diets were administered for 30 d. An additional group of six animals were fed the unlabelled diet for 20 d and then the labelled diet for 10 d while wearing a neck collar to avoid caecotrophy (group COLL), in order to discriminate it from direct intestinal absorption. At day 30 animals were slaughtered and caecal bacteria and liver samples taken. The (15)N enrichment in amino acids of caecal bacteria and liver were determined by GC-combustion/isotope ratio MS. Lysine showed a higher enrichment in caecal microflora (0.925 atom% excess, APE) than liver (0.215 APE) in group ISOT animals, confirming the double origin of body lysine: microbial and dietary. The COLL group showed a much lower enrichment in tissue lysine (0.007 (se 0.0029) APE for liver). Any enrichment in the latter animals was due to direct absorption of microbial lysine along the digestive tract, since recycling of microbial protein (caecotrophy) was avoided. In such conditions liver enrichment was low, indicating a small direct intestinal absorption. From the ratio of [(15)N]lysine enrichment between liver and bacteria the contribution of microbes to body lysine was estimated at 23 %, with 97 % of this arising through caecotrophy. Absorption of microbial lysine through caecotrophy was 119 (se 4.0) mg/d, compared with 406 (se 1.8) mg/d available from the diet. This study confirms the importance of caecotrophy in rabbit nutrition (15 % of total protein intake).

Assessment of the non-Gaussianity and non-linearity levels of simulated sEMG signals on stationary segments.

PubMed

Messaoudi, Noureddine; Bekka, Raïs El'hadi; Ravier, Philippe; Harba, Rachid

2017-02-01

The purpose of this paper was to evaluate the effects of the longitudinal single differential (LSD), the longitudinal double differential (LDD) and the normal double differential (NDD) spatial filters, the electrode shape, the inter-electrode distance (IED) on non-Gaussianity and non-linearity levels of simulated surface EMG (sEMG) signals when the maximum voluntary contraction (MVC) varied from 10% to 100% by a step of 10%. The effects of recruitment range thresholds (RR), the firing rate (FR) strategy and the peak firing rate (PFR) of motor units were also considered. A cylindrical multilayer model of the volume conductor and a model of motor unit (MU) recruitment and firing rate were used to simulate sEMG signals in a pool of 120 MUs for 5s. Firstly, the stationarity of sEMG signals was tested by the runs, the reverse arrangements (RA) and the modified reverse arrangements (MRA) tests. Then the non-Gaussianity was characterised with bicoherence and kurtosis, and non-linearity levels was evaluated with linearity test. The kurtosis analysis showed that the sEMG signals detected by the LSD filter were the most Gaussian and those detected by the NDD filter were the least Gaussian. In addition, the sEMG signals detected by the LSD filter were the most linear. For a given filter, the sEMG signals detected by using rectangular electrodes were more Gaussian and more linear than that detected with circular electrodes. Moreover, the sEMG signals are less non-Gaussian and more linear with reverse onion-skin firing rate strategy than those with onion-skin strategy. The levels of sEMG signal Gaussianity and linearity increased with the increase of the IED, RR and PFR. Copyright © 2016 Elsevier Ltd. All rights reserved.

Aerosol optical properties and trace gas emissions by PAX and OP-FTIR for laboratory-simulated western US wildfires during FIREX

NASA Astrophysics Data System (ADS)

Selimovic, Vanessa; Yokelson, Robert J.; Warneke, Carsten; Roberts, James M.; de Gouw, Joost; Reardon, James; Griffith, David W. T.

2018-03-01

Western wildfires have a major impact on air quality in the US. In the fall of 2016, 107 test fires were burned in the large-scale combustion facility at the US Forest Service Missoula Fire Sciences Laboratory as part of the Fire Influence on Regional and Global Environments Experiment (FIREX). Canopy, litter, duff, dead wood, and other fuel components were burned in combinations that represented realistic fuel complexes for several important western US coniferous and chaparral ecosystems including ponderosa pine, Douglas fir, Engelmann spruce, lodgepole pine, subalpine fir, chamise, and manzanita. In addition, dung, Indonesian peat, and individual coniferous ecosystem fuel components were burned alone to investigate the effects of individual components (e.g., duff) and fuel chemistry on emissions. The smoke emissions were characterized by a large suite of state-of-the-art instruments. In this study we report emission factor (EF, grams of compound emitted per kilogram of fuel burned) measurements in fresh smoke of a diverse suite of critically important trace gases measured using open-path Fourier transform infrared spectroscopy (OP-FTIR). We also report aerosol optical properties (absorption EF; single-scattering albedo, SSA; and Ångström absorption exponent, AAE) as well as black carbon (BC) EF measured by photoacoustic extinctiometers (PAXs) at 870 and 401 nm. The average trace gas emissions were similar across the coniferous ecosystems tested and most of the variability observed in emissions could be attributed to differences in the consumption of components such as duff and litter, rather than the dominant tree species. Chaparral fuels produced lower EFs than mixed coniferous fuels for most trace gases except for NOx and acetylene. A careful comparison with available field measurements of wildfires confirms that several methods can be used to extract data representative of real wildfires from the FIREX laboratory fire data. This is especially valuable for species rarely or not yet measured in the field. For instance, the OP-FTIR data alone show that ammonia (1.62 g kg-1), acetic acid (2.41 g kg-1), nitrous acid (HONO, 0.61 g kg-1), and other trace gases such as glycolaldehyde (0.90 g kg-1) and formic acid (0.36 g kg-1) are significant emissions that were poorly characterized or not characterized for US wildfires in previous work. The PAX measurements show that the ratio of brown carbon (BrC) absorption to BC absorption is strongly dependent on modified combustion efficiency (MCE) and that BrC absorption is most dominant for combustion of duff (AAE 7.13) and rotten wood (AAE 4.60): fuels that are consumed in greater amounts during wildfires than prescribed fires. Coupling our laboratory data with field data suggests that fresh wildfire smoke typically has an EF for BC near 0.2 g kg-1, an SSA of ˜ 0.91, and an AAE of ˜ 3.50, with the latter implying that about 86 % of the aerosol absorption at 401 nm is due to BrC.

[Results for SHEBA/FIRE

NASA Technical Reports Server (NTRS)

Valero, Francisco P. J.

2003-01-01

The Atmospheric Research Laboratory's Radiation Measurement System (RAMS) was on the NCAR C-130 aircraft in May and July 1998, collecting radiometric data on the science flights conducted in the vicinity of the Surface Heat Budget of the Arctic Ocean (SHEBA) ship. These measurements were part of the FIRE Arctic Cloud Experiment (FIRE ACE). Analysis of some of the data focused on the absorption, reflection, and transmittance of Arctic clouds, especially compared to model results. In order to assess the absorption of solar radiation by the clear and cloudy atmosphere in the Arctic the measurements from the radiometers were combined in pairs of above-cloud segments and below-cloud segments. To get these pairs, the data for all sixteen of the flights (8 in May and 8 in July) were examined for occurrences of low-altitude segments in proximity to high-altitude segments. The low-altitude data are then treated as measurements of the bottom of a layer and the high-altitude data are taken as measurements of the top of the layer. With measurements of the upwelling and downwelling irradiances above and below a layer one can determine the reflectance, transmittance, and absorptance of the layer. Attachment: Doelling, D.R., P. Minnis, D.A. Spangenberg, V. Chakrapani, A. Mahesh, S.K. Pope, and F.P.J. Valero, Cloud radiative forcing at the top of the atmosphere during FIRE ACE derived from AVHRR data, J. Geophys. Res. 106, 15,279-15,296,2001. Minnis, P., D.R. Doelling, D.A. Spangenberg, A. Mahesh, S.K. Pope, and F.P.J. Valero, AVHRR-derived cloud radiative forcing over the ARM NSA and SHEBA site during FIRE ACE, abstract submitted to the ARM Science Team Meeting, San Antonio, TX, M a . 13-17,2000. Pope, S.K., and F.P.J. Valero, Measured and modeled radiometric fluxes in the Arctic during FIRE-ACE, presented as a poster at the American Geophysical Union meeting, San Francisco, CA, Dec. 13-17, 1999. Pope, S.K., and F.P.J. Valero, Measured and modeled radiometric fluxes in the Arctic during FIRE-ACEy paper presented at SHEBA/FIRE Workshop, National Center for Atmospheric Research, Boulder, Colo., Apr. 17-20,2000.

Conference Proceedings of Energy Absorption of Aircraft Structures as an Aspect Crashworthiness (66th) Held in Luxembourg on 1-6 May 1988

DTIC Science & Technology

1988-12-01

efforts dans les f~murs ou dans la colonne vert~brale. 2.1.3. Jauges 11 peut s’agir de jauges simples, doubles ou de rosettes 3 directions. Les jauges ...34, -acc~l~rombtres mannequin en "classe 180", -efforts en "classe 180", - jauges en "classe 180", -r~sultantes efforts en "classe 180", -sommes des

Predissociation of tif by tunneling

NASA Astrophysics Data System (ADS)

Wolf, U.; Tiemann, E.

1987-01-01

The UV spectra of the B 3Π 1-X 1Σ + transition in TIF were recorded applying frequency-doubled laser radiation and fluorescence or direct absorption detection. The observed J' -dependent predissociation in the upper levels v' = 2 and v' = 3 is explained quantitatively by invoking tunneling through a potential hump. The line positions and widths are fitted to a potential curve of the B 3Π 1 state using the semiclassical approximation for bound and quasibound levels.

Space Launch System Base Heating Test: Tunable Diode Laser Absorption Spectroscopy

NASA Technical Reports Server (NTRS)

Parker, Ron; Carr, Zak; MacLean, Matthew; Dufrene, Aaron; Mehta, Manish

2016-01-01

This paper describes the Tunable Diode Laser Absorption Spectroscopy (TDLAS) measurement of several water transitions that were interrogated during a hot-fire testing of the Space Launch Systems (SLS) sub-scale vehicle installed in LENS II. The temperature of the recirculating gas flow over the base plate was found to increase with altitude and is consistent with CFD results. It was also observed that the gas above the base plate has significant velocity along the optical path of the sensor at the higher altitudes. The line-by-line analysis of the H2O absorption features must include the effects of the Doppler shift phenomena particularly at high altitude. The TDLAS experimental measurements and the analysis procedure which incorporates the velocity dependent flow will be described.

Far-infrared-light shadowgraphy for high extraction efficiency of extreme ultraviolet light from a CO2-laser-generated tin plasma

NASA Astrophysics Data System (ADS)

Matsukuma, Hiraku; Hosoda, Tatsuya; Suzuki, Yosuke; Yogo, Akifumi; Yanagida, Tatsuya; Kodama, Takeshi; Nishimura, Hiroaki

2016-08-01

The two-color, double-pulse method is an efficient scheme to generate extreme ultraviolet light for fabricating the next generation semiconductor microchips. In this method, a Nd:YAG laser pulse is used to expand a several-tens-of-micrometers-scale tin droplet, and a CO2 laser pulse is subsequently directed at the expanded tin vapor after an appropriate delay time. We propose the use of shadowgraphy with a CO2 laser probe-pulse scheme to optimize the CO2 main-drive laser. The distribution of absorption coefficients is derived from the experiment, and the results are converted to a practical absorption rate for the CO2 main-drive laser.

Synergetic effect of double-step blocking layer for the perovskite solar cell

NASA Astrophysics Data System (ADS)

Kim, Jinhyun; Hwang, Taehyun; Lee, Sangheon; Lee, Byungho; Kim, Jaewon; Kim, Jaewook; Gil, Bumjin; Park, Byungwoo

2017-10-01

In an organometallic CH3NH3PbI3 (MAPbI3) perovskite solar cell, we have demonstrated a vastly compact TiO2 layer synthesized by double-step deposition, through a combination of sputter and solution deposition to minimize the electron-hole recombination and boost the power conversion efficiency. As a result, the double-step strategy allowed outstanding transmittance of blocking layer. Additionally, crystallinity and morphology of the perovskite film were significantly modified, provoking enhanced photon absorption and solar cell performance with the reduced recombination rate. Thereby, this straightforward double-step strategy for the blocking layer exhibited 12.31% conversion efficiency through morphological improvements of each layer.

The 27-28 October 1986 FIRE IFO cirrus case study: Comparison of satellite and aircraft derived particle size

NASA Technical Reports Server (NTRS)

Wielicki, Bruce A.; Suttles, J. T.; Heymsfield, Andrew J.; Welch, Ronald M.; Spinhirne, James D.; Wu, Man-Li C.; Starr, David; Parker, Lindsay; Arduini, Robert F.

1990-01-01

Theoretical calculations predict that cloud reflectance in near infrared windows such as those at 1.6 and 2.2 microns should give lower reflectances than at visible wavelengths. The reason for this difference is that ice and liquid water show significant absorption at those wavelengths, in contrast to the nearly conservative scattering at wavelengths shorter than 1 micron. In addition, because the amount of absorption scales with the path length of radiation through the particle, increasing cloud particle size should lead to decreasing reflectances at 1.6 and 2.2 microns. Measurements at these wavelengths to date, however, have often given unpredicted results. Twomey and Cocks found unexpectedly high absorption (factors of 3 to 5) in optically thick liquid water clouds. Curran and Wu found expectedly low absorption in optically thick high clouds, and postulated the existence of supercooled small water droplets in place of the expected large ice particles. The implications of the FIRE data for optically thin cirrus are examined.

Solid oxide fuel cell/gas turbine trigeneration system for marine applications

NASA Astrophysics Data System (ADS)

Tse, Lawrence Kar Chung; Wilkins, Steven; McGlashan, Niall; Urban, Bernhard; Martinez-Botas, Ricardo

2011-03-01

Shipping contributes 4.5% to global CO2 emissions and is not covered by the Kyoto Agreement. One method of reducing CO2 emissions on land is combined cooling heating and power (CCHP) or trigeneration, with typical combined thermal efficiencies of over 80%. Large luxury yachts are seen as an ideal entry point to the off-shore market for this developing technology considering its current high cost. This paper investigates the feasibility of combining a SOFC-GT system and an absorption heat pump (AHP) in a trigeneration system to drive the heating ventilation and air conditioning (HVAC) and electrical base-load systems. A thermodynamic model is used to simulate the system, with various configurations and cooling loads. Measurement of actual yacht performance data forms the basis of this system simulation. It is found that for the optimum configuration using a double effect absorption chiller in Ship 1, the net electric power increases by 47% relative to the electrical power available for a conventional SOFC-GT-HVAC system. This is due to more air cooled to a lower temperature by absorption cooling; hence less electrical cooling by the conventional HVAC unit is required. The overall efficiency is 12.1% for the conventional system, 34.9% for the system with BROAD single effect absorption chiller, 43.2% for the system with double effect absorption chiller. This shows that the overall efficiency of a trigeneration system is far higher when waste heat recovery happens. The desiccant wheel hardly reduces moisture from the outdoor air due to a relative low mass flow rate of fuel cell exhaust available to dehumidify a very large mass flow rate of HVAC air, Hence, desiccant wheel is not recommended for this application.

Modeling flame structure in wildland fires using the one-dimensional turbulence model

Treesearch

David O. Lignell; Elizabeth I. Monson; Mark A. Finney

2010-01-01

The mechanism of flame propagation in wildland fire fuel beds is of critical importance for understanding and quantifying fire spread rates. Recent observations and experiments have indicated the dominance of flame propagation by direct contact between flames and unburnt fuel, as opposed to propagation via radiative heating alone. It is postulated that effects of...

76 FR 31798 - Airworthiness Directives; L'Hotellier Portable Halon 1211 Fire Extinguishers

Federal Register 2010, 2011, 2012, 2013, 2014

2011-06-02

... Airworthiness Directives; L'Hotellier Portable Halon 1211 Fire Extinguishers AGENCY: Federal Aviation... directive (AD) for the specified fire extinguishers. This action requires replacing each unairworthy portable fire extinguisher with an airworthy portable fire extinguisher. This amendment is prompted by an...

Seasonal-to-interannual variation in biomass burning over the contiguous United States

NASA Astrophysics Data System (ADS)

Kim, K. M.; Lau, W. K. M.; Ichoku, I.; Pereira, G.; Darmenov, A.; da Silva, A. M., Jr.; Ellison, L.

2017-12-01

The intensity and frequency of wildfires are strongly affected by climatic factors, such as droughts and heat waves, which are governed by weather and climate dynamics. . Climatic impacts on wildfire and biomass burning can be complex involving not only natural variability, but also human activities. In this study, we examine the seasonality of occurrences and intensity of fires and climatic impact as a function of underlying biomes over the CONUS, using fire pixel data from MODIS instruments on-board Terra and Aqua. Results show that there are three distinct fire seasons, i.e., summer (June to August), spring (March-April), and Fall (September-October). In the evergreen needle leaf region where most fires occur, the fire season peaks in mid boreal summer. In this region, fires tend to start early (June) in southern US, and late (August) in northern US. Double peaks are distinctive features in grass land and crop land. Double peaks in crop land (spring and fall) appear to be associated with agricultural practices. However, the two peaks in grass land (spring and summer) are due to natural wildfires, associated with changes in seasonal weather pattern. To better understand the potential climatic impact on fire, we examine relationships between fire weather index (FWI) and fire pixel counts. Fire pixel count has a strong correlation with FWI in evergreen needle leaf forest, deciduous broad leaf forest, and open shrub land. However, no significant linear relations are found in crop land, grass land, and mixed forest. The implications of these findings, and possible impacts of atmospheric teleconnecon on the fire season in the CONUS will also be discussed.

Vibrational and optical properties of MoS2: From monolayer to bulk

NASA Astrophysics Data System (ADS)

Molina-Sánchez, Alejandro; Hummer, Kerstin; Wirtz, Ludger

2015-12-01

Molybdenum disulfide, MoS2, has recently gained considerable attention as a layered material where neighboring layers are only weakly interacting and can easily slide against each other. Therefore, mechanical exfoliation allows the fabrication of single and multi-layers and opens the possibility to generate atomically thin crystals with outstanding properties. In contrast to graphene, it has an optical gap of ~1.9 eV. This makes it a prominent candidate for transistor and opto-electronic applications. Single-layer MoS2 exhibits remarkably different physical properties compared to bulk MoS2 due to the absence of interlayer hybridization. For instance, while the band gap of bulk and multi-layer MoS2 is indirect, it becomes direct with decreasing number of layers. In this review, we analyze from a theoretical point of view the electronic, optical, and vibrational properties of single-layer, few-layer and bulk MoS2. In particular, we focus on the effects of spin-orbit interaction, number of layers, and applied tensile strain on the vibrational and optical properties. We examine the results obtained by different methodologies, mainly ab initio approaches. We also discuss which approximations are suitable for MoS2 and layered materials. The effect of external strain on the band gap of single-layer MoS2 and the crossover from indirect to direct band gap is investigated. We analyze the excitonic effects on the absorption spectra. The main features, such as the double peak at the absorption threshold and the high-energy exciton are presented. Furthermore, we report on the the phonon dispersion relations of single-layer, few-layer and bulk MoS2. Based on the latter, we explain the behavior of the Raman-active A1g and E2g1 modes as a function of the number of layers. Finally, we compare theoretical and experimental results of Raman, photoluminescence, and optical-absorption spectroscopy.

Clarifying the role of fire heat and daily temperature fluctuations as germination cues for Mediterranean Basin obligate seeders.

PubMed

Santana, Victor M; Baeza, M Jaime; Blanes, M Carmen

2013-01-01

This study aims to determine the role that both direct effects of fire and subsequent daily temperature fluctuations play in the seed bank dynamics of obligate seeders from the Mediterranean Basin. The short yet high soil temperatures experienced due to passage of fire are conflated with the lower, but longer, temperatures experienced by daily fluctuations which occur after removing vegetation. These germination cues are able to break seed dormancy, but it is difficult to assess their specific level of influence because they occur consecutively after summer fires, just before the flush of germination in the wet season (autumn). By applying experimental fires, seed treatments were imposed that combined fire exposure/non-fire exposure with exposure to microhabitats under a gradient of disturbance (i.e. gaps opened by fire, mechanical brushing and intact vegetation). The seeds used were representative of the main families of obligate seeders (Ulex parviflorus, Cistus albidus and Rosmarinus officinalis). Specifically, an assessment was made of (1) the proportion of seeds killed by fire, (2) seedling emergence under field conditions and (3) seeds which remained ungerminated in soil. For the three species studied, the factors that most influenced seedling emergence and seeds remaining ungerminated were microhabitats with higher temperature fluctuations after fire (gaps opened by fire and brushing treatments). The direct effect of fire decreased the seedling emergence of U. parviflorus and reduced the proportion of seeds of R. officinalis remaining ungerminated. The relevance of depleting vegetation (and subsequent daily temperature fluctuation in summer) suggests that studies focusing on lower temperature thresholds for breaking seed dormancy are required. This fact also supports the hypothesis that the seeding capacity in Mediterranean Basin obligate seeders may have evolved as a response to a wide range of disturbances, and not exclusively to fire.

The Effects of Thermophysical Properties and Environmental Conditions on Fire Performance of Intumescent Coatings on Glass Fibre-Reinforced Epoxy Composites

PubMed Central

Kandola, Baljinder K.; Luangtriratana, Piyanuch; Duquesne, Sophie; Bourbigot, Serge

2015-01-01

Intumescent coatings are commonly used as passive fire protection systems for steel structures. The purpose of this work is to explore whether these can also be used effectively on glass fibre-reinforced epoxy (GRE) composites, considering the flammability of the composites compared to non-flammable steel substrate. The thermal barrier and reaction-to-fire properties of three commercial intumescent coatings on GRE composites have been studied using a cone calorimeter. Their thermophysical properties in terms of heating rate and/or temperature dependent char expansion ratios and thermal conductivities have been measured and correlated. It has been suggested that these two parameters can be used to design coatings to protect composite laminates of defined thicknesses for specified periods of time. The durability of the coatings to water absorption, peeling, impact, and flexural loading were also studied. A strong adhesion between all types of coatings and the substrate was observed. Water soaking had a little effect on the fire performance of epoxy based coatings. All types of 1 mm thick coatings on GRE helped in retaining ~90% of the flexural property after 2 min exposure to 50 kW/m2 heat flux whereas the uncoated laminate underwent severe delamination and loss in structural integrity after 1 min. PMID:28793500

Optical Realization of Double-Continuum Fano Interference and Coherent Control in Plasmonic Metasurfaces

NASA Astrophysics Data System (ADS)

Arju, Nihal; Ma, Tzuhsuan; Khanikaev, Alexander; Purtseladze, David; Shvets, Gennady

2015-06-01

Classical realization of a ubiquitous quantum mechanical phenomenon of double-continuum Fano interference using metasurfaces is experimentally demonstrated by engineering the near-field interaction between two bright and one dark plasmonic modes. The competition between the bright modes, one of them effectively suppressing the Fano interference for the orthogonal light polarization, is discovered. Coherent control of optical energy concentration and light absorption by the ellipticity of the incident light is theoretically predicted.

A Review of the CMOS Buried Double Junction (BDJ) Photodetector and its Applications

PubMed Central

Feruglio, Sylvain; Lu, Guo-Neng; Garda, Patrick; Vasilescu, Gabriel

2008-01-01

A CMOS Buried Double Junction PN (BDJ) photodetector consists of two vertically-stacked photodiodes. It can be operated as a photodiode with improved performance and wavelength-sensitive response. This paper presents a review of this device and its applications. The CMOS implementation and operating principle are firstly described. This includes the description of several key aspects directly related to the device performances, such as surface reflection, photon absorption and electron-hole pair generation, photocurrent and dark current generation, etc. SPICE modelling of the detector is then presented. Next, design and process considerations are proposed in order to improve the BDJ performance. Finally, several BDJ-detector-based image sensors provide a survey of their applications. PMID:27873887

Cotton Rats Alter Foraging in Response to an Invasive Ant.

PubMed

Darracq, Andrea K; Conner, L Mike; Brown, Joel S; McCleery, Robert A

We assessed the effects of red imported fire ants (Solenopsis invicta; hereafter fire ant) on the foraging of hispid cotton rats (Sigmodon hispidus). We used a manipulative experiment, placing resource patches with a known amount of millet seed within areas with reduced (RIFA [-]) or ambient (RIFA [+]) numbers of fire ants. We measured giving up densities (the amount of food left within each patch) within the resource patches for 4 days to quantify the effects of fire ants on cotton rat foraging. We assessed the effects of fire ant treatment (RIFA), Day, and their interaction on cotton rat giving up densities. Giving up densities on RIFA [+] grids were nearly 2.2 times greater across all foraging days and ranged from 1.6 to 2.3 times greater from day 1 to day 4 than the RIFA [-] grids. From day 1 to day 4, mean giving up densities decreased significantly faster for the RIFA [-] than RIFA [+] treatments, 58% and 13%, respectively. Our results demonstrate that cotton rats perceive a risk of injury from fire ants, which is likely caused by interference competition, rather than direct predation. Envenomation from ants likely decrease the foraging efficiency of cotton rats resulting in more time spent foraging. Increased time spent foraging is likely stressful in terms of the opportunity for direct injury and encounters with other predators. These indirect effects may reduce an individual cotton rat's fitness and translate into lowered population abundances.

Surface preparation for high purity alumina ceramics enabling direct brazing in hydrogen atmospheres

DOEpatents

Cadden, Charles H.; Yang, Nancy Yuan Chi; Hosking, Floyd M.

2001-01-01

The present invention relates to a method for preparing the surface of a high purity alumina ceramic or sapphire specimen that enables direct brazing in a hydrogen atmosphere using an active braze alloy. The present invention also relates to a method for directly brazing a high purity alumina ceramic or sapphire specimen to a ceramic or metal member using this method of surface preparation, and to articles produced by this brazing method. The presence of silicon, in the form of a SiO.sub.2 -containing surface layer, can more than double the tensile bond strength in alumina ceramic joints brazed in a hydrogen atmosphere using an active Au-16Ni-0.75 Mo-1.75V filler metal. A thin silicon coating applied by PVD processing can, after air firing, produce a semi-continuous coverage of the alumina surface with a SiO.sub.2 film. Room temperature tensile strength was found to be proportional to the fraction of air fired surface covered by silicon-containing films. Similarly, the ratio of substrate fracture versus interface separation was also related to the amount of surface silicon present prior to brazing. This process can replace the need to perform a "moly-manganese" metallization step.

Exploring the observational constraints on the simulation of brown carbon

NASA Astrophysics Data System (ADS)

Wang, X.; Heald, C. L.; Liu, J.; Weber, R. J.; Campuzano-Jost, P.; Jimenez, J. L.; Schwarz, J. P.; Perring, A. E.

2017-12-01

Brown carbon (BrC) is the component of organic aerosols (OA) which strongly absorbs solar radiation in the near-UV range of the spectrum. However the sources, evolution, and optical properties of BrC remain highly uncertain, and therefore constitute a large source of uncertainty in estimating the global direct radiative effect (DRE) of aerosols. Previous modeling studies of BrC optical properties and DRE have been unable to fully evaluate the skill of their simulations, given the lack of direct measurements of organic aerosol absorption. In this study, we develop a global model simulation (GEOS-Chem) of BrC and test it against BrC absorption measurements from two aircraft campaigns in the U.S. (SEAC4RS and DC3). To our knowledge, this is the first study to compare simulated BrC absorption with direct, continuous ambient measurements. We show that the laboratory-based BrC absorption properties from biomass burning overestimate the aircraft measurements of ambient BrC. In addition, applying a photochemical whitening scheme to simulated BrC is better able to represent the observed BrC absorption. These observations are consistent with a mass absorption coefficient (MAC) of freshly emitted biomass burning OA of 0.57m2g-1. Using the RRTMG model integrated with GEOS-Chem, we estimate that the all-sky top-of-atmosphere direct radiative effect (DRE) of OA is -0.350 Wm-2, 10% higher than that without consideration of BrC absorption. Therefore, our best estimate of the absorption DRE of BrC is +0.042 Wm-2. We suggest that the DRE of BrC has been overestimated previously due to the lack of observational constraints from direct measurements as well as neglect of the effects of photochemical whitening.

The Lasting Effect of Wildfire and Fire Extent on the Chlorine Reactivity of Dissolved Organic Matter after the 2002 Hayman Fire, Colorado

NASA Astrophysics Data System (ADS)

Tsai, K. P.; Chow, A. T.; Rhoades, C.; Fegel, T.; Pierson, D.

2016-12-01

Forest fires commonly affect short-term water quality by altering quantity and quality of dissolved organic matter (DOM), an important precursor of hazardous disinfection byproducts (DBPs) during drinking water disinfection. However, the long-term effect of wildfire on water quality and water treatability remains unclear. We have studied stream water quality in watersheds affected to varying extent by the 2002 Hayman Fire. Since October 2014, we have analyzed monthly water samples from unburned watersheds and those with moderate and high wildfire extent (> 35% and > 80%, respectively) using absorption spectroscopy and chlorine-based specific DBP formation potential experiments. More than a decade after the Hayman Fire, dissolved organic carbon (DOC) concentration, DOM aromaticity, and specific trihalomethanes formation potential (STHMs-FP) were higher in stream water from moderately-burned watersheds than from other areas. For example, DOC concentration was 1.93 ± 1.19, 3.14 ± 2.18, and 1.27 ± 0.64 mg/L, SUVA254 was 2.75 ± 1.32, 3.52 ± 1.40, and 2.29 ± 0.99 L/mg/m, and STHMs-FP was 51.68 ± 33.85, 65.33 ± 29.49, and 46.44 ± 25.17 µg-THMs/mg-DOC for unburned watersheds and those with moderate and high wildfire extent, respectively. STHMs-FP was well correlated with SUVA254 regardless of wildfire extent (R2 = 0.58, 0.62, and 0.76, respectively). Our data document the lasting effect of Hayman Fire on stream water DOC concentration and DBP formation potential, and suggest that these effects are most pronounced for watersheds burned to moderate extent.

Investigation into the origin of parasitic absorption in GaInP|GaAs double heterostructures

NASA Astrophysics Data System (ADS)

Giannini, Nathan; Yang, Zhou; Albrecht, Alexander R.; Sheik-Bahae, Mansoor

2017-02-01

Despite achievements of extremely high external quantum efficiency (EQE), 99.5%, the net cooling of GaInP|GaAs double heterostructures (DHS) has never been realized. This is due to an unknown source of parasitic absorption. Prior studies have ruled out the possibility of the bulk absorption from the GaAs layer. Thus it is thought to be either at the air- GaInP interface, through the presence of dangling bonds, or in bulk GaInP through impurities. Using two-color thermallens calorimetry (based on the Z-scan technique), this study indicates that that the parasitic absorption likely originates from the GaInP bulk layers.

Particulate matter and black carbon optical properties and emission factors from prescribed fires in the southeastern United States

EPA Science Inventory

The aerosol emissions from prescribed fires in the Southeastern United States were measured and compared to emissions from laboratory burns with fuels collected from the site. Fine particulate matter (PM2.5), black carbon, and aerosol light scattering and absorption were characte...

Prescribed fire and timber harvest effects on terrestrial salamander abundance, detectability, and microhabitat use

Treesearch

Katherine M. O' Donnell; Frank R. Thompson; Raymond D. Semlitsch

2015-01-01

Prescribed fire and timber harvest are anthropogenic disturbances that modify resource availability and ecosystem structure, and can affect wildlife both directly and indirectly. Terrestrial salamanders are effective indicators of forest health due to their high abundance and sensitivity to microclimatic conditions. Given their ecological importance, it is critical to...

Chapter 3: Plant invasions and fire regimes

Treesearch

Matthew L. Brooks

2008-01-01

The alteration of fire regimes is one of the most significant ways that plant invasions can affect ecosystems (Brooks and others 2004; D'Antonio 2000; D'Antonio and Vitousek 1992; Vitousek 1990). The suites of changes that can accompany an invasion include both direct effects of invaders on native plants through competitive interference, and indirect effects...

Health hazard evaluation report HETA 90-168-2248, Independence Police Department Indoor Range, Independence, Missouri

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rinehart, R.D.; Almaguer, D.; Klein, M.K.

1992-08-01

On February 14, 1990, the National Institute for Occupational Safety and Health (NIOSH) received a request from a management representative of the Independence, Missouri, Police Department Headquarters for a Health Hazard Evaluation. The Police Department requested NIOSH to evaluate the effectiveness of a newly redesigned air handling system installed inside their indoor firing range. On August 6, 1991, NIOSH investigators met with the firing range supervisor and toured the facility. On August 8, ten personal breathing-zone (PBZ) air samples and 3 area air samples were collected on filters inside the range and the filters were subsequently analyzed for lead bymore » atomic absorption spectroscopy (AAS). Surface lead contamination inside the firing range was measured in two locations and hand (dermal) lead contamination was measured on two instructors and two field officers. These samples were also analyzed for lead by AAS.« less

Fire, herbicide, and chainsaw felling effects on arthropods in fire-suppressed longleaf pine sandhills at Eglin Air Force Base, Florida

Treesearch

Louis Provencher; Krista E. M. Galley; Andrea R. Litt; Doria R. Gordon; Leonard A. Brennan; George W. Tanner; Jeffrey L. Hardesty

2002-01-01

Experimentally evaluating the success of hardwood reduction techniques against a "model" reference condition of longleaf pine sandhill communities is not directly possible because reference sites are not randomized or replicated. We addressed this issue by measuring the similarity of arthropods in treatment (fire, herbicide, felling/girdling, and control) and...

OH-initiated Aging of Biomass Burning Aerosol during FIREX

NASA Astrophysics Data System (ADS)

Lim, C. Y.; Hagan, D. H.; Cappa, C. D.; Kroll, J. H.; Coggon, M.; Koss, A.; Sekimoto, K.; De Gouw, J. A.; Warneke, C.

2017-12-01

Biomass burning emissions represent a major source of fine particulate matter to the atmosphere, and this source will likely become increasingly important in the future due to changes in the Earth's climate. Understanding the effects that increased fire emissions have on both air quality and climate requires understanding the composition of the particles emitted, since chemical and physical composition directly impact important particle properties such as absorptivity, toxicity, and cloud condensation nuclei activity. However, the composition of biomass burning particles in the atmosphere is dynamic, as the particles are subject to the condensation of low-volatility vapors and reaction with oxidants such as the hydroxyl radical (OH) during transport. Here we present a series of laboratory chamber experiments on the OH-initiated aging of biomass burning aerosol performed at the Fire Sciences Laboratory in Missoula, MT as part of the Fire Influences on Regional and Global Environments Experiment (FIREX) campaign. We describe the evolution of biomass burning aerosol produced from a variety of fuels operating the chamber in both particle-only and gas + particle mode, focusing on changes to the organic composition. In particle-only mode, gas-phase biomass burning emissions are removed before oxidation to focus on heterogeneous oxidation, while gas + particle mode includes both heterogeneous oxidation and condensation of oxidized volatile organic compounds onto the particles (secondary organic aerosol formation). Variability in fuels and burning conditions lead to differences in aerosol loading and secondary aerosol production, but in all cases aging results in a significant and rapid increases in the carbon oxidation state of the particles.

Holographic Solar Photon Thrusters

NASA Technical Reports Server (NTRS)

Johnson, Les; Matloff, Greg

2006-01-01

A document discusses a proposal to incorporate holographic optical elements into solar photon thrusters (SPTs). First suggested in 1990, SPTs would be systems of multiple reflective, emissive, and absorptive surfaces (solar sails) that would be attached to spacecraft orbiting the Earth to derive small propulsive forces from radiation pressures. An SPT according to the proposal would include, among other things, a main sail. One side of the sail would be highly emissive and would normally face away from the Earth. The other side would be reflective and would be covered by white-light holographic images that would alternately become reflective, transmissive, and absorptive with small changes in the viewing angle. When the spacecraft was at a favorable orbital position, the main sail would be oriented to reflect sunlight in a direction to maximize the solar thrust; when not in a favorable position, the main sail would be oriented to present a substantially absorptive/emissive aspect to minimize the solar drag. By turning the main sail slightly to alternate between the reflective and absorptive/ emissive extremes, one could achieve nearly a doubling or halving of the radiational momentum transfer and, hence, of the solar thrust.

Importance of the green color, absorption gradient, and spectral absorption of chloroplasts for the radiative energy balance of leaves.

PubMed

Kume, Atsushi

2017-05-01

Terrestrial green plants absorb photosynthetically active radiation (PAR; 400-700 nm) but do not absorb photons evenly across the PAR waveband. The spectral absorbance of photosystems and chloroplasts is lowest for green light, which occurs within the highest irradiance waveband of direct solar radiation. We demonstrate a close relationship between this phenomenon and the safe and efficient utilization of direct solar radiation in simple biophysiological models. The effects of spectral absorptance on the photon and irradiance absorption processes are evaluated using the spectra of direct and diffuse solar radiation. The radiation absorption of a leaf arises as a consequence of the absorption of chloroplasts. The photon absorption of chloroplasts is strongly dependent on the distribution of pigment concentrations and their absorbance spectra. While chloroplast movements in response to light are important mechanisms controlling PAR absorption, they are not effective for green light because chloroplasts have the lowest spectral absorptance in the waveband. With the development of palisade tissue, the incident photons per total palisade cell surface area and the absorbed photons per chloroplast decrease. The spectral absorbance of carotenoids is effective in eliminating shortwave PAR (<520 nm), which contains much of the surplus energy that is not used for photosynthesis and is dissipated as heat. The PAR absorptance of a whole leaf shows no substantial difference based on the spectra of direct or diffuse solar radiation. However, most of the near infrared radiation is unabsorbed and heat stress is greatly reduced. The incident solar radiation is too strong to be utilized for photosynthesis under the current CO 2 concentration in the terrestrial environment. Therefore, the photon absorption of a whole leaf is efficiently regulated by photosynthetic pigments with low spectral absorptance in the highest irradiance waveband and through a combination of pigment density distribution and leaf anatomical structures.

Contributions of wildland fire to terrestrial ecosystem carbon dynamics in North America from 1990 to 2012

USGS Publications Warehouse

Chen, Guangsheng; Hayes, Daniel J.; McGuire, A. David

2017-01-01

Burn area and the frequency of extreme fire events have been increasing during recent decades in North America, and this trend is expected to continue over the 21st century. While many aspects of the North American carbon budget have been intensively studied, the net contribution of fire disturbance to the overall net carbon flux at the continental scale remains uncertain. Based on national scale, spatially explicit and long-term fire data, along with the improved model parameterization in a process-based ecosystem model, we simulated the impact of fire disturbance on both direct carbon emissions and net terrestrial ecosystem carbon balance in North America. Fire-caused direct carbon emissions were 106.55 ± 15.98 Tg C/yr during 1990–2012; however, the net ecosystem carbon balance associated with fire was −26.09 ± 5.22 Tg C/yr, indicating that most of the emitted carbon was resequestered by the terrestrial ecosystem. Direct carbon emissions showed an increase in Alaska and Canada during 1990–2012 as compared to prior periods due to more extreme fire events, resulting in a large carbon source from these two regions. Among biomes, the largest carbon source was found to be from the boreal forest, primarily due to large reductions in soil organic matter during, and with slower recovery after, fire events. The interactions between fire and environmental factors reduced the fire-caused ecosystem carbon source. Fire disturbance only caused a weak carbon source as compared to the best estimate terrestrial carbon sink in North America owing to the long-term legacy effects of historical burn area coupled with fast ecosystem recovery during 1990–2012.

Reward Expectancy Strengthens CA1 Theta and Beta Band Synchronization and Hippocampal-Ventral Striatal Coupling.

PubMed

Lansink, Carien S; Meijer, Guido T; Lankelma, Jan V; Vinck, Martin A; Jackson, Jadin C; Pennartz, Cyriel M A

2016-10-12

The use of information from the hippocampal memory system in motivated behavior depends on its communication with the ventral striatum. When an animal encounters cues that signal subsequent reward, its reward expectancy is raised. It is unknown, however, how this process affects hippocampal dynamics and their influence on target structures, such as ventral striatum. We show that, in rats, reward-predictive cues result in enhanced hippocampal theta and beta band rhythmic activity during subsequent action, compared with uncued goal-directed navigation. The beta band component, also labeled theta's harmonic, involves selective hippocampal CA1 cell groups showing frequency doubling of firing periodicity relative to theta rhythmicity and it partitions the theta cycle into segments showing clear versus poor spike timing organization. We found that theta phase precession occurred over a wider range than previously reported. This was apparent from spikes emitted near the peak of the theta cycle exhibiting large "phase precessing jumps" relative to spikes in foregoing cycles. Neither this phenomenon nor the regular manifestation of theta phase precession was affected by reward expectancy. Ventral striatal neuronal firing phase-locked not only to hippocampal theta, but also to beta band activity. Both hippocampus and ventral striatum showed increased synchronization between neuronal firing and local field potential activity during cued compared with uncued goal approaches. These results suggest that cue-triggered reward expectancy intensifies hippocampal output to target structures, such as the ventral striatum, by which the hippocampus may gain prioritized access to systems modulating motivated behaviors. Here we show that temporally discrete cues raising reward expectancy enhance both theta and beta band activity in the hippocampus once goal-directed navigation has been initiated. These rhythmic activities are associated with increased synchronization of neuronal firing patterns in the hippocampus and the connected ventral striatum. When transmitted to downstream target structures, this expectancy-related state of intensified processing in the hippocampus may modulate goal-directed action. Copyright © 2016 the authors 0270-6474/16/3610598-13$15.00/0.

Effect of olive mill waste addition on the properties of porous fired clay bricks using Taguchi method.

PubMed

Sutcu, Mucahit; Ozturk, Savas; Yalamac, Emre; Gencel, Osman

2016-10-01

Production of porous clay bricks lightened by adding olive mill waste as a pore making additive was investigated. Factors influencing the brick manufacturing process were analyzed by an experimental design, Taguchi method, to find out the most favorable conditions for the production of bricks. The optimum process conditions for brick preparation were investigated by studying the effects of mixture ratios (0, 5 and 10 wt%) and firing temperatures (850, 950 and 1050 °C) on the physical, thermal and mechanical properties of the bricks. Apparent density, bulk density, apparent porosity, water absorption, compressive strength, thermal conductivity, microstructure and crystalline phase formations of the fired brick samples were measured. It was found that the use of 10% waste addition reduced the bulk density of the samples up to 1.45 g/cm(3). As the porosities increased from 30.8 to 47.0%, the compressive strengths decreased from 36.9 to 10.26 MPa at firing temperature of 950 °C. The thermal conductivities of samples fired at the same temperature showed a decrease of 31% from 0.638 to 0.436 W/mK, which is hopeful for heat insulation in the buildings. Increasing of the firing temperature also affected their mechanical and physical properties. This study showed that the olive mill waste could be used as a pore maker in brick production. Copyright © 2016 Elsevier Ltd. All rights reserved.

Theta phase precession of grid and place cell firing in open environments

PubMed Central

Jeewajee, A.; Barry, C.; Douchamps, V.; Manson, D.; Lever, C.; Burgess, N.

2014-01-01

Place and grid cells in the rodent hippocampal formation tend to fire spikes at successively earlier phases relative to the local field potential theta rhythm as the animal runs through the cell's firing field on a linear track. However, this ‘phase precession’ effect is less well characterized during foraging in two-dimensional open field environments. Here, we mapped runs through the firing fields onto a unit circle to pool data from multiple runs. We asked which of seven behavioural and physiological variables show the best circular–linear correlation with the theta phase of spikes from place cells in hippocampal area CA1 and from grid cells from superficial layers of medial entorhinal cortex. The best correlate was the distance to the firing field peak projected onto the animal's current running direction. This was significantly stronger than other correlates, such as instantaneous firing rate and time-in-field, but similar in strength to correlates with other measures of distance travelled through the firing field. Phase precession was stronger in place cells than grid cells overall, and robust phase precession was seen in traversals through firing field peripheries (although somewhat less than in traversals through the centre), consistent with phase coding of displacement along the current direction. This type of phase coding, of place field distance ahead of or behind the animal, may be useful for allowing calculation of goal directions during navigation. PMID:24366140

Potential Evaluation of Solar Heat Assisted Desiccant Hybrid Air Conditioning System

NASA Astrophysics Data System (ADS)

Tran, Thien Nha; Hamamoto, Yoshinori; Akisawa, Atsushi; Kashiwagi, Takao

The solar thermal driven desiccant dehumidification-absorption cooling hybrid system has superior advantage in hot-humid climate regions. The reasonable air processing of desiccant hybrid air conditioning system and the utility of clean and free energy make the system environment friendly and energy efficient. The study investigates the performance of the desiccant dehumidification air conditioning systems with solar thermal assistant. The investigation is performed for three cases which are combinations of solar thermal and absorption cooling systems with different heat supply temperature levels. Two solar thermal systems are used in the study: the flat plate collector (FPC) and the vacuum tube with compound parabolic concentrator (CPC). The single-effect and high energy efficient double-, triple-effect LiBr-water absorption cooling cycles are considered for cooling systems. COP of desiccant hybrid air conditioning systems are determined. The evaluation of these systems is subsequently performed. The single effect absorption cooling cycle combined with the flat plate collector solar system is found to be the most energy efficient air conditioning system.

Oxygen-induced recombination centers in as-grown Czochralski silicon crystals

NASA Technical Reports Server (NTRS)

Nauka, K.; Gatos, H. C.; Lagowski, J.

1983-01-01

Simultaneous quantitative microprofiles of the interstitial oxygen concentration and of the excess carrier lifetime are obtained in Czochralski-grown Si crystals employing double laser absorption scanning. It is found that oxygen concentration maxima and minima along the crystal growth direction coincide with lifetime minima and maxima, respectively. Another finding is that the magnitude of oxygen-induced lifetime changes increases dramatically in going from the center to the periphery of the crystal. The findings discussed imply that 'as-grown' oxygen precipitates figure in lifetime-limiting processes.

Research and development supporting risk-based wildfire effects prediction for fuels and fire management: Status and needs

Treesearch

Kevin Hyde; Matthew B. Dickinson; Gil Bohrer; David Calkin; Louisa Evers; Julie Gilbertson-Day; Tessa Nicolet; Kevin Ryan; Christina Tague

2013-01-01

Wildland fire management has moved beyond a singular focus on suppression, calling for wildfire management for ecological benefit where no critical human assets are at risk. Processes causing direct effects and indirect, long-term ecosystem changes are complex and multidimensional. Robust risk-assessment tools are required that account for highly variable effects on...

A comparison of three approaches for simulating fine-scale surface winds in support of wildland fire management. Part II. An exploratory study of the effect of simulated winds on fire growth simulations

Treesearch

Jason M. Forthofer; Bret W. Butler; Charles W. McHugh; Mark A. Finney; Larry S. Bradshaw; Richard D. Stratton; Kyle S. Shannon; Natalie S. Wagenbrenner

2014-01-01

The effect of fine-resolution wind simulations on fire growth simulations is explored. The wind models are (1) a wind field consisting of constant speed and direction applied everywhere over the area of interest; (2) a tool based on the solution of the conservation of mass only (termed mass-conserving model) and (3) a tool based on a solution of conservation of mass...

Responses of prairie arthropod communities to fire and fertilizer: Balancing plant and arthropod conservation

USGS Publications Warehouse

Hartley, M.K.; Rogers, W.E.; Siemann, E.; Grace, J.

2007-01-01

Fire is an important tool for limiting woody plant invasions into prairies, but using fire management to maintain grassland plant communities may inadvertently reduce arthropod diversity. To test this, we established twenty-four 100 m2 plots in a tallgrass prairie in Galveston County, Texas, in spring 2000. Plots were assigned a fire (no burn, one time burn [2000], two time burn [2000, 2001]) and fertilization treatment (none, NPK addition) in a full factorial design. Fertilization treatments allowed us to examine the effects of fire at a different level of productivity. We measured plant cover by species and sampled arthropods with sweep nets during the 2001 growing season. Path analysis indicated that fertilization reduced while annual fires increased arthropod diversity via increases and decreases in woody plant abundance, respectively. There was no direct effect of fire on arthropod diversity or abundance. Diptera and Homoptera exhibited particularly strong positive responses to fires. Lepidoptera had a negative response to nutrient enrichment. Overall, the negative effects of fire on the arthropod community were minor in contrast to the strong positive indirect effects of small-scale burning on arthropod diversity if conservation of particular taxa is not a priority. The same fire regime that minimized woody plant invasion also maximized arthropod diversity.

Management of spent shea waste: An instrumental characterization and valorization in clay bricks construction.

PubMed

Adazabra, A N; Viruthagiri, G; Shanmugam, N

2017-06-01

This work studies the reuse of spent shea waste as an economic construction material in improving fired clay bricks manufacture aside providing a novel approach to ecofriendly managing its excessive generated from the shea agroindustry. For this purpose, the influence of spent shea waste addition on the chemical, mineralogical, molecular bonding and technological properties (i.e. compressive strength and water absorption) of the fired clay bricks were extensively investigated. The results indicated that the chemical, mineralogical, phase transformations, molecular bonding and thermal behavior of the produced bricks were practically unaffected by the addition of spent shea waste. However, spent shea waste addition increased the compressive strengths and water absorptions of the brick products. Potential performance benefits of reusing spent shea waste was improved fluxing agents, energy-contribution reaction, excellent porosifying effect, reduced thermal conductivity and enhanced compressive strengths of the brick products. This research has therefore provided compelling evidence that could create newfound route for the synergistic ecofriendly reuse of spent shea waste to enhance clay brick construction aside being a potential mainstream disposal option. Copyright © 2017 Elsevier Ltd. All rights reserved.

Direct and indirect effects of fires on the carbon balance of tropical forest ecosystems (Invited)

NASA Astrophysics Data System (ADS)

Randerson, J. T.; Tosca, M. G.; Ward, D. S.; Kasibhatla, P. S.; Mahowald, N. M.; Hess, P. G.

2013-12-01

Fires influence the carbon budget of tropical forests directly because they account for a significant component of net emissions from deforestation and forest degradation. They also have indirect effects on nearby intact forests by modifying regional climate, atmospheric composition, and patterns of nutrient deposition. These latter pathways are not well understood and are often ignored in climate mitigation efforts such as the United Nations Program on Reducing Emissions from Deforestation and forest Degradation (REDD+). Here we used the Community Atmosphere Model (CAM5) and the Global Fire Emissions Database (GFED3) to quantify the impacts of fire-emitted aerosols on the productivity of tropical forests. Across the tropical forest biome, fire-emitted aerosols reduced surface temperatures and increased the diffuse solar insolation fraction. These changes in surface meteorology increased gross primary production (GPP) in the Community Land Model. However, these drivers were more than offset in many regions by reductions in soil moisture and total solar radiation. The net effect of fire aerosols caused GPP to decrease by approximately 8% in equatorial Asia and 6% in the central Africa. In the Amazon, decreases in photosynthesis in the western part of the basin were nearly balanced by increases in the south and east. Using additional CAM5 and GEOS-Chem model simulations, we estimated fire contributions to surface concentrations of ozone. Using empirical relationships between ozone exposure and GPP from field studies and models, we estimated how tropical forest GPP was further modified by fire-induced ozone. Our results suggest that efforts to reduce the fire component of tropical land use fluxes may have sustainability benefits that extend beyond the balance sheet for greenhouse gases.

The Doctrine of Double Effect as an Ineffective Tool in War Theory

DTIC Science & Technology

2014-06-01

interesting exercise but not practical or even effective. Pressure changes thought processes. What a person believes his intent will be under fire...obligated to seek one and avoid the other – are malleable and vary based on culture, upbringing , understanding of the universe, etc. What one person...authority to evaluate whether an action is morally sound? As a purely intellectual 16 exercise , DDE has the luxury of attempting to whittle down

Effect of ceanothus brush on western yellow pine plantations in the northern Rocky Mountains

Treesearch

W. G. Wahlenberg

1930-01-01

Forest planting in the northern Rocky Mountain region is largely confined to areas that have been burned over twice, the second burning occurring during recent years. Planting crews can operate on these "double burns'' with relative ease because the fires have removed shrubs and other obstructions. Unfortunately planting activity on forest lands is not...

iss031e146306

NASA Image and Video Library

2012-06-27

ISS031-E-146306 (27 June 2012) --- An Expedition 31 crew member aboard the International Space Station, flying approximately 240 miles (386 kilometers) above Earth, captured this view of the Fontenelle fire on June 27, 2012. The fire, burning in Wyoming 18 miles (29 kilometers) west of Big Piney, was discovered on June 24. [Editor?s update --- By the morning of June 28, the fire had burned 25,000 acres (101 square kilometers). By July 6, the area burned had more than doubled to 57,324 acres (232 square kilometers), and the fire was 25 percent contained].

Inhibited flammability and surface inactivation of wood irradiated by low energy hydrogen ion showers (LEHIS)

NASA Astrophysics Data System (ADS)

Blantocas, Gene Q.; Mateum, Philip Edward R.; Orille, Ross William M.; Ramos, Rafael Julius U.; Monasterial, Jonathan Lee C.; Ramos, Henry J.; Bo-ot, Luis Ma. T.

2007-06-01

Changes on the properties of wood irradiated by low energy hydrogen ion showers (LEHIS) were examined. The experimental facility employed was an in-house constructed, compact gas discharge ion source with beam energies maintained approximately in the 1 keV range fixed at 1 mA discharge current, 3 mTorr gas filling pressure. Wood specimens used were of species endemic in the Philippines namely Shorea sp., Shorea polysperma and Cocos nucifera. Results showed the processed samples manifested characteristics of inhibited flammability, and became relatively hydrophobic after the treatment. In the fire resistance test, it was also observed during initial flaming that the processed surfaces accumulated less soot attesting to a much lower smoldering rate, i.e. lesser combustibility. To assess the increase in fire endurance time for the processed wood against the control substrates, a non-directional, two-tailed t-test was utilized. Significant at the 0.05 level, the t-statistic measured 9.164 as opposed to only 4.303 in its corresponding critical value at two degrees of freedom. Hence, the treatment appeared to show strong statistical evidence of being effective in enhancing fire resistance. The processed specimens also exhibited moisture absorptive inhibition time of more than 10 min versus an average absorption period of just 8 s for the unprocessed samples. Spectroscopy using a cast steel mass analyzer indicated a predominance of H+ with faint signals of H2+in the ion showers. It is hypothesized that the monatomic ion plays an essential participatory role in the surface modification process. Data from an earlier work using Narra wood (Pterocarpus indicus) [G.Q. Blantocas, H.J. Ramos, M. Wada, Jpn. J. Appl. Phys. 45 (2006) 8498] was extended in the current study to substantiate this hypothesis. The data is now presented as current density ratio H+ /H2+versus the change rate constant K of the wetting model equation. It is shown that wood affinity to water decreased as the proportion of H+ increased, i.e. higher flux density ratios favored surface inactivation. It is further demonstrated using hardwood samples that a dominance of H+ also improved fire resistance. H+ ions seemed to be the initiator in the formation of hydrophobic and flame resistant wood surfaces. In contrast, high energy showers (⩾900 eV) resulted in lower H+ /H2+ratios. Samples exposed to showers in these energy ranges showed decreased flame resistance. They degraded more rapidly during flaming. Finally, a comparison of SEM images showed surface smoothening of the processed samples. The LEHIS method proved benign showing no unfavorable effects on paint adherence and original texture and color. This plasma-based procedure could probably be developed as an alternative mode of wood preservation.

Future inhibition of ecosystem productivity by increasing wildfire pollution over boreal North America

NASA Astrophysics Data System (ADS)

Yue, X.; Strada, S.; Unger, N.

2017-12-01

Biomass burning is an important source of tropospheric ozone (O3) and aerosols, which can affect vegetation photosynthesis through stomatal uptake (for O3) and light scattering and meteorological variations (for aerosols). Climate change will significantly increase wildfire activity in boreal North America by the midcentury, while little is known about the impacts of enhanced emissions on the terrestrial carbon budget. Here, combining site-level and satellite observations and a carbon-chemistry-climate model, we estimate the impacts of fire emitted O3 and aerosols on net primary productivity (NPP) over boreal North America. Fire emissions are calculated based on an ensemble projection from 13 climate models. In the present day, wildfire enhances surface O3 by 2 ppbv (7%) and aerosol optical depth (AOD) at 550 nm by 0.03 (26%) in the summer. By midcentury, boreal area burned is predicted to increase by 66%, contributing more O3 (13%) and aerosols (37%). Fire O3 causes negligible impacts on NPP because ambient O3 concentration is far below the damaging thresholds. Fire aerosols reduce surface solar radiation but enhance atmospheric absorption, resulting in enhanced air stability and intensified regional drought. The domain of this drying is confined to the North in the present day, but extends southward by 2050 due to increased fire emissions. Consequently, wildfire aerosols enhance NPP by 72 Tg C yr-1 in the present day but decrease NPP by 118 Tg C yr-1 in the future, mainly because of the soil moisture perturbations. Our results suggest that future wildfire may accelerate boreal carbon loss, not only through direct emissions, but also through the biophysical impacts of fire aerosols.

Revised (Mixed-Effects) Estimation for Forest Burning Emissions of Gases and Smoke, Fire/Emission Factor Typologies, and Potential Remote Sensing Classification of Types for Use in Ozone and Absorbing-Carbon Simulation

NASA Astrophysics Data System (ADS)

Chatfield, R. B.; Segal-Rosenhaimer, M.

2014-12-01

We summarize recent progress (a) in correcting biomass burning emissions factors deduced from airborne sampling of forest fire plumes, (b) in understanding the variability in reactivity of the fresh plumes sampled in ARCTAS (2008), DC3 (2012), and SEAC4RS (2013) airborne missions, and (c) in a consequent search for remotely sensed quantities that help classify forest-fire plumes. Particle properties, chemical speciation, and smoke radiative properties are related and mutually informative, as pictures below suggest (slopes of lines of same color are similar). (a) Mixed-effects (random-effects) statistical modeling provides estimates of both emission factors and a reasonable description of carbon-burned simultaneously. Different fire plumes will have very different contributions to volatile organic carbon reactivity; this may help explain differences of free NOx(both gas- and particle-phase), and also of ozone production, that have been noted for forest-fire plumes in California. Our evalualations check or correct emission factors based on sequential measurements (e.g., the Normalized Ratio Enhancement and similar methods). We stress the dangers of methods relying on emission-ratios to CO. (b) This work confirms and extends many reports of great situational variability in emissions factors. VOCs vary in OH reactivity and NOx-binding. Reasons for variability are not only fuel composition, fuel condition, etc, but are confused somewhat by rapid transformation and mixing of emissions. We use "unmixing" (distinct from mixed-effects) statistics and compare briefly to approaches like neural nets. We focus on one particularly intense fire the notorious Yosemite Rim Fire of 2013. In some samples, NOx activity was not so surpressed by binding into nitrates as in other fires. While our fire-typing is evolving and subject to debate, the carbon-burned Δ(CO2+CO) estimates that arise from mixed effects models, free of confusion by background-CO2 variation, should provide a solid base for discussion. (c) We report progress using promising links we find between emissions-related "fire types" and promising features deducible from remote observations of plumes, e.g., single scatter albedo, Ångström exponent of scattering, Ångström exponent of absorption, (CO column density)/(aerosol optical depth).

Revised (Mixed-Effects) Estimation for Forest Burning Emissions of Gases and Smoke, Fire/Emission Factor Typology, and Potential Remote Sensing Classification of Types for Ozone and Black-Carbon Simulation

NASA Technical Reports Server (NTRS)

Chatfield, Robert B.; Segal Rozenhaimer, M.

2014-01-01

We summarize recent progress (a) in correcting biomass burning emissions factors deduced from airborne sampling of forest fire plumes, (b) in understanding the variability in reactivity of the fresh plumes sampled in ARCTAS (2008), DC3 (2012), and SEAC4RS (2013) airborne missions, and (c) in a consequent search for remotely sensed quantities that help classify forest-fire plumes. Particle properties, chemical speciation, and smoke radiative properties are related and mutually informative, as pictures below suggest (slopes of lines of same color are similar). (a) Mixed-effects (random-effects) statistical modeling provides estimates of both emission factors and a reasonable description of carbon-burned simultaneously. Different fire plumes will have very different contributions to volatile organic carbon reactivity; this may help explain differences of free NOx(both gas- and particle-phase), and also of ozone production, that have been noted for forest-fire plumes in California. Our evaluations check or correct emission factors based on sequential measurements (e.g., the Normalized Ratio Enhancement and similar methods). We stress the dangers of methods relying on emission-ratios to CO. (b) This work confirms and extends many reports of great situational variability in emissions factors. VOCs vary in OH reactivity and NOx-binding. Reasons for variability are not only fuel composition, fuel condition, etc., but are confused somewhat by rapid transformation and mixing of emissions. We use "unmixing" (distinct from mixed-effects) statistics and compare briefly to approaches like neural nets. We focus on one particularly intense fire the notorious Yosemite Rim Fire of 2013. In some samples, NOx activity was not so suppressed by binding into nitrates as in other fires. While our fire-typing is evolving and subject to debate, the carbon-burned delta(CO2+CO) estimates that arise from mixed effects models, free of confusion by background-CO2 variation, should provide a solid base for discussion. (c) We report progress using promising links we find between emissions-related "fire types" and promising features deducible from remote observations of plumes, e.g., single scatter albedo, Angstrom exponent of scattering, Angstrom exponent of absorption, (CO column density)/(aerosol optical depth).

Absorption of Carbon Dioxide in Aqueous Solutions of N-methyldiethanolamine Mixtures

NASA Astrophysics Data System (ADS)

Ma’mun, S.; Svendsen, H. F.

2018-05-01

Carbon dioxide (CO2) is one of the greenhouse gases (GHG) that has contributed to the global warming problem. Carbon dioxide is produced in large quantity from coal-fired power plants, iron and steel production, cement production, chemical and petrochemical industries, natural gas purification, and transportation. Some efforts to reduce the CO2 emissions to the atmosphere are then required. Amine-based absorption may be an option for post-combustion capture. The objective of this study is to measure the effect of promoter addition as well as MDEA concentration for the CO2 absorption into the aqueous solutions of MDEA to improve its performances, i.e. increasing the absorption rate and the absorption capacity. Absorption of CO2 in aqueous solutions of MDEA mixtures were measured at 40 °C in a bubble tank reactor. The systems tested were the mixtures of 30 wt% MDEA with 5 and 10 wt% BEA and the mixtures of 40 and 50 wt% MDEA with 6 wt% AEEA. It was found that for MDEA-BEA-H2O mixtures, the higher the promoter concentraation the higher the CO2 absorption rate, while for the MDEA-AEEA-H2O mixtures, the higher the MDEA concentration the lower the CO2 absorption rate.

Exploring the observational constraints on the simulation of brown carbon

NASA Astrophysics Data System (ADS)

Wang, Xuan; Heald, Colette L.; Liu, Jiumeng; Weber, Rodney J.; Campuzano-Jost, Pedro; Jimenez, Jose L.; Schwarz, Joshua P.; Perring, Anne E.

2018-01-01

Organic aerosols (OA) that strongly absorb solar radiation in the near-UV are referred to as brown carbon (BrC). The sources, evolution, and optical properties of BrC remain highly uncertain and contribute significantly to uncertainty in the estimate of the global direct radiative effect (DRE) of aerosols. Previous modeling studies of BrC optical properties and DRE have been unable to fully evaluate model performance due to the lack of direct measurements of BrC absorption. In this study, we develop a global model simulation (GEOS-Chem) of BrC and test it against BrC absorption measurements from two aircraft campaigns in the continental US (SEAC4RS and DC3). To the best of our knowledge, this is the first study to compare simulated BrC absorption with direct aircraft measurements. We show that BrC absorption properties estimated based on previous laboratory measurements agree with the aircraft measurements of freshly emitted BrC absorption but overestimate aged BrC absorption. In addition, applying a photochemical scheme to simulate bleaching/degradation of BrC improves model skill. The airborne observations are therefore consistent with a mass absorption coefficient (MAC) of freshly emitted biomass burning OA of 1.33 m2 g-1 at 365 nm coupled with a 1-day whitening e-folding time. Using the GEOS-Chem chemical transport model integrated with the RRTMG radiative transfer model, we estimate that the top-of-the-atmosphere all-sky direct radiative effect (DRE) of OA is -0.344 Wm-2, 10 % higher than that without consideration of BrC absorption. Therefore, our best estimate of the absorption DRE of BrC is +0.048 Wm-2. We suggest that the DRE of BrC has been overestimated previously due to the lack of observational constraints from direct measurements and omission of the effects of photochemical whitening.

On the use of satellite VEGETATION time series for monitoring post fire vegetation recovery

NASA Astrophysics Data System (ADS)

de Santis, F.; Didonna, I.

2009-04-01

Fire is one of the most critical factors of disturbance in worldwide ecosystems. The effects of fires on soil, plants, landscape and ecosystems depend on many factors, among them fire frequency, fire severity and plant resistance. The characterization of vegetation post-fire behaviour is a fundamental issue to model and evaluate the fire resilience, which the ability of vegetation to recover after fire. Recent changes in fire regime, due to abandonment of local land use practice and climate change, can induce significant variations in vegetation fire resilience. In the Mediterranean-type communities, post fire vegetation trends have been analysed in a wide range of habitats, although pre- and post-fire investigation has been widely performed at stand level. But, factors controlling regeneration at the landscape scale are less well known. In this study, a time series of normalized difference vegetation index (NDVI) data derived from SPOT-VEGETATION was used to examine the recovery characteristics of fire affected vegetation in some test areas of the Mediterranean ecosystems of Southern Italy. The vegetation indices operate by contrasting intense chlorophyll pigment absorption in the red against the high reflectance of leaf mesophyll in the near infrared. SPOT-VEGETATION Normalized Difference Vegetation Index (NDVI) data from 1998 to 2005 were analyzed in order to evaluate the resilient effects in a some significant test sites of southern Italy. In particular, we considered: (i) one stable area site, one site affected by one fire during the investigated time window, (iii) one site affected by two consecutive fires during the investigated time window. In order to eliminate the phenological fluctuations, for each decadal composition of each pixel, we focused on the departure NDVId = [NDVI - ]/, where is the decadal mean and  is the decadal standard deviation. The decadal mean and the standard deviation were calculated for each decade, e.g. 1st decade of January, by averaging over all years in the record. We analyzed both: 1) Time variation of NDVI from 1998 to 2005 of pixels for the fire affected and fire unaffected areas. 2) Post-fire NDVI spatial patterns on each image date were compared to the pre-fire pattern to determine the extent to which the pre-fire pattern was re-established, and the rate of this recovery. Results show the ability of vegetation to recovery after a single fire. Nevertheless, such ability can be strongly reduced by successive fires. The recursive fire occurrence can significantly diminish the green biomass especially when disturbances occur at short intervals of time.

Fire Frequency and Vegetation Composition Influence Soil Nitrogen Cycling and Base Cations in an Oak Savanna Ecosystem

NASA Astrophysics Data System (ADS)

McLauchlan, K. K.; Nelson, D. M.; Perakis, S.; Marcotte, A. L.

2017-12-01

Fire frequency is crucial for maintaining savannas in the transition between forests and grasslands. In general, increasing fire frequency has two effects: it increases herbaceous plant cover more than woody plant cover, and it lowers soil organic matter stocks. These effects have been demonstrated at a long-term prescribed fire experiment in an oak savanna ecosystem at Cedar Creek Ecosystem Science Reserve, Minnesota, U.S.A. The fire experiment began in 1964 and oak savannas are burned at various frequencies ranging from every year to not at all. This has led to changes in vegetation ranging from almost 100% grassland to 100% oak forest. Additionally, nitrogen stocks almost doubled in the sites that were not burned, as it accumulated in the trees, leaf litter, and soil. We addressed additional soil changes taking place at this experiment by asking the question: How have fire and oak-grass balance affected soil nutrients, specifically nitrogen and base cations? Surface soils were collected from 12 plots on the oak savanna burn experiment. Soils were collected in increments to 100 cm depth, from under grass-dominated vegetation and from under tree-dominated vegetation. We non-destructively estimated soil base cations by measuring elemental concentrations of dried soil subsamples with a handheld x-ray fluorescence analyzer. We also measured carbon and nitrogen concentrations and isotopic composition of the soil samples. Soils in plots with high fire frequency had higher concentrations of calcium than soils in unburned plots (low fire frequency). Similar trends were seen for soil potassium, magnesium, and phosphorus concentrations. In contrast, soils in plots with high fire frequency had dramatically lowered nitrogen cycling rates and stocks across the oak savanna. The contrast between the responses of different nutrients to changing fire frequency has important implications for the consequences of fire and tree-grass composition on nutrient cycling dynamics.

Vegetation fires and air pollution in Vietnam.

PubMed

Le, Thanh Ha; Thanh Nguyen, Thi Nhat; Lasko, Kristofer; Ilavajhala, Shriram; Vadrevu, Krishna Prasad; Justice, Chris

2014-12-01

Forest fires are a significant source of air pollution in Asia. In this study, we integrate satellite remote sensing data and ground-based measurements to infer fire-air pollution relationships in selected regions of Vietnam. We first characterized the active fires and burnt areas at a regional scale from MODIS satellite data. We then used satellite-derived active fire data to correlate the resulting atmospheric pollution. Further, we analyzed the relationship between satellite atmospheric variables and ground-based air pollutant parameters. Our results show peak fire activity during March in Vietnam, with hotspots in the Northwest and Central Highlands. Active fires were significantly correlated with UV Aerosol Index (UVAI), aerosol extinction absorption optical depth (AAOD), and Carbon Monoxide. The use of satellite aerosol optical thickness improved the prediction of Particulate Matter (PM) concentration significantly. Copyright © 2014 Elsevier Ltd. All rights reserved.

75 FR 221 - Airworthiness Directives; Fire Fighting Enterprises Limited Portable Halon 1211 Fire...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-01-05

... Airworthiness Directives; Fire Fighting Enterprises Limited Portable Halon 1211 Fire Extinguishers as Installed... specification, have been supplied to the aviation industry for use in fire extinguishing equipment. * * * * * * * * * * * This Halon 1211 has subsequently been used to fill certain FFE [Fire Fighting Enterprises] portable...

Depositional characteristics and sediment availability resulting from the post-Schultz Fire floods of 2010

Treesearch

Karen A. Koestner; Mike D. Carroll; Daniel G. Neary; Peter E. Koestner; Ann Youberg

2011-01-01

Wildfire is a major land management concern due to direct impacts of fire on forest resources, and potentially negative effects on landscape processes by increasing rates of runoff, erosion, downstream sedimentation, and overall site degradation (DeBano et al. 1998, Neary et al. 2005, Robichaud et al. 2010). In the United States the number of fires has been increasing...

Soil and vegetation changes in a pinyon-juniper area in central Arizona after prescribed fire

Treesearch

Steven T. Overby; Will H. Moir; George T. Robertson

2000-01-01

Prescribed fire has been used as an inexpensive and rapid method for disposing of slash following fuelwood sales in pinyon-juniper sites. Soil heating during a fire has a direct effect on soil nutrients and microbial activity. The potential for understory cover quantity and quality, along with soil nutrient changes should be the determining factors in management...

Fire management and carbon sequestration in Pine Barren Forests

Treesearch

Kenneth L. Clark; Nicholas Skowronski; Michael Gallagher

2015-01-01

Prescribed burning is the major viable option that land managers have for reducing hazardous fuels and ensuring the regeneration of fire-dependent species in a cost-effective manner in Pine Barren ecosystems. Fuels management activities are directly linked to carbon (C) storage and rates of C sequestration by forests. To evaluate the effects of prescribed burning on...

Airborne Measurements of CO2 Column Concentration and Range Using a Pulsed Direct-Detection IPDA Lidar

NASA Technical Reports Server (NTRS)

Abshire, James B.; Ramanathan, Anand; Riris, Haris; Mao, Jianping; Allan, Graham R.; Hasselbrack, William E.; Weaver, Clark J.; Browell, Edward V.

2013-01-01

We have previously demonstrated a pulsed direct detection IPDA lidar to measure range and the column concentration of atmospheric CO2. The lidar measures the atmospheric backscatter profiles and samples the shape of the 1,572.33 nm CO2 absorption line. We participated in the ASCENDS science flights on the NASA DC-8 aircraft during August 2011 and report here lidar measurements made on four flights over a variety of surface and cloud conditions near the US. These included over a stratus cloud deck over the Pacific Ocean, to a dry lake bed surrounded by mountains in Nevada, to a desert area with a coal-fired power plant, and from the Rocky Mountains to Iowa, with segments with both cumulus and cirrus clouds. Most flights were to altitudes >12 km and had 5-6 altitude steps. Analyses show the retrievals of lidar range, CO2 column absorption, and CO2 mixing ratio worked well when measuring over topography with rapidly changing height and reflectivity, through thin clouds, between cumulus clouds, and to stratus cloud tops. The retrievals shows the decrease in column CO2 due to growing vegetation when flying over Iowa cropland as well as a sudden increase in CO2 concentration near a coal-fired power plant. For regions where the CO2 concentration was relatively constant, the measured CO2 absorption lineshape (averaged for 50 s) matched the predicted shapes to better than 1% RMS error. For 10 s averaging, the scatter in the retrievals was typically 2-3 ppm and was limited by the received signal photon count. Retrievals were made using atmospheric parameters from both an atmospheric model and from in situ temperature and pressure from the aircraft. The retrievals had no free parameters and did not use empirical adjustments, and >70% of the measurements passed screening and were used in analysis. The differences between the lidar-measured retrievals and in situ measured average CO2 column concentrations were <1.4 ppm for flight measurement altitudes >6 km.

Semiempirical modeling of Ag nanoclusters: New parameters for optical property studies enable determination of double excitation contributions to plasmonic excitation

DOE PAGES

Gieseking, Rebecca L.; Ratner, Mark A.; Schatz, George C.

2016-06-03

Quantum mechanical studies of Ag nanoclusters have shown that plasmonic behavior can be modeled in terms of excited states where collectivity among single excitations leads to strong absorption. However, new computational approaches are needed to provide understanding of plasmonic excitations beyond the single-excitation level. We show that semiempirical INDO/CI approaches with appropriately selected parameters reproduce the TD-DFT optical spectra of various closed-shell Ag clusters. The plasmon-like states with strong optical absorption comprise linear combinations of many singly excited configurations that contribute additively to the transition dipole moment, whereas all other excited states show significant cancellation among the contributions to themore » transition dipole moment. The computational efficiency of this approach allows us to investigate the role of double excitations at the INDO/SDCI level. The Ag cluster ground states are stabilized by slight mixing with doubly excited configurations, but the plasmonic states generally retain largely singly excited character. The consideration of double excitations in all cases improves the agreement of the INDO/CI absorption spectra with TD-DFT, suggesting that the SDCI calculation effectively captures some of the ground-state correlation implicit in DFT. Furthermore, these results provide the first evidence to support the commonly used assumption that single excitations are in many cases sufficient to describe the optical spectra of plasmonic excitations quantum mechanically.« less

Cavity ring-down spectroscopy (CRDS) system for measuring atmospheric mercury using differential absorption

NASA Astrophysics Data System (ADS)

Pierce, A.; Obrist, D.; Moosmuller, H.; Moore, C.

2012-04-01

Atmospheric elemental mercury (Hg0) is a globally pervasive element that can be transported and deposited to remote ecosystems where it poses — particularly in its methylated form — harm to many organisms including humans. Current techniques for measurement of atmospheric Hg0 require several liters of sample air and several minutes for each analysis. Fast-response (i.e., 1 second or faster) measurements would improve our ability to understand and track chemical cycling of mercury in the atmosphere, including high frequency Hg0 fluctuations, sources and sinks, and chemical transformation processes. We present theory, design, challenges, and current results of our new prototype sensor based on cavity ring-down spectroscopy (CRDS) for fast-response measurement of Hg0 mass concentrations. CRDS is a direct absorption technique that implements path-lengths of multiple kilometers in a compact absorption cell using high-reflectivity mirrors, thereby improving sensitivity and reducing sample volume compared to conventional absorption spectroscopy. Our sensor includes a frequency-doubled, dye-laser emitting laser pulses tunable from 215 to 280 nm, pumped by a Q-switched, frequency tripled Nd:YAG laser with a pulse repetition rate of 50 Hz. We present how we successfully perform automated wavelength locking and stabilization of the laser to the peak Hg0 absorption line at 253.65 nm using an external isotopically-enriched mercury (202Hg0) cell. An emphasis of this presentation will be on the implementation of differential absorption measurement whereby measurements are alternated between the peak Hg0 absorption wavelength and a nearby wavelength "off" the absorption line. This can be achieved using a piezo electric tuning element that allows for pulse-by-pulse tuning and detuning of the laser "online" and "offline" of the Hg absorption line, and thereby allows for continuous correction of baseline extinction losses. Unexpected challenges with this approach included different efficiencies of laser performance (e.g., frequency doubling) at the two wavelengths and temperature dependence. We will discuss improvements on the control of our system to eliminate drift due to conversion efficiency and temperature dependence. We will detail complications with operating this instrument from a mobile platform for in situ measurements in the field. Finally, we will present data acquisition and processing approaches along with results of calibration curves, and comparisons to conventional mercury analyzers (i.e., a Tekran 2537 mercury vapor analyzer) during ambient air measurements.

Field Measurements of Trace Gases and Aerosols Emitted by Undersampled Combustion Sources Including Wood and Dung Cooking Fires, Garbage and Crop Residue Burning, and Indonesian Peat Fires

NASA Astrophysics Data System (ADS)

Stockwell, C.; Jayarathne, T. S.; Goetz, D.; Simpson, I. J.; Selimovic, V.; Bhave, P.; Blake, D. R.; Cochrane, M. A.; Ryan, K. C.; Putra, E. I.; Saharjo, B.; Stone, E. A.; DeCarlo, P. F.; Yokelson, R. J.

2017-12-01

Field measurements were conducted in Nepal and in the Indonesian province of Central Kalimantan to improve characterization of trace gases and aerosols emitted by undersampled combustion sources. The sources targeted included cooking with a variety of stoves, garbage burning, crop residue burning, and authentic peat fires. Trace gas and aerosol emissions were studied using a land-based Fourier transform infrared spectrometer, whole air sampling, photoacoustic extinctiometers (405 and 870nm), and filter samples that were analyzed off-line. These measurements were used to calculate fuel-based emission factors (EFs) for up to 90 gases, PM2.5, and PM2.5 constituents. The aerosol optical data measured included EFs for the scattering and absorption coefficients, the single scattering albedo (at 870 and 405 nm), as well as the absorption Ångström exponent. The emissions varied significantly by source, although light absorption by both brown and black carbon (BrC and BC, respectively) was important for all non-peat sources. For authentic peat combustion, the emissions of BC were negligible and absorption was dominated by organic aerosol. The field results from peat burning were in reasonable agreement with recent lab measurements of smoldering Kalimantan peat and compare well to the limited data available from other field studies. The EFs can be used with estimates of fuel consumption to improve regional emissions inventories and assessments of the climate and health impacts of these undersampled sources.

Cotton Rats Alter Foraging in Response to an Invasive Ant

PubMed Central

Darracq, Andrea K.; Conner, L. Mike; Brown, Joel S.; McCleery, Robert A.

2016-01-01

We assessed the effects of red imported fire ants (Solenopsis invicta; hereafter fire ant) on the foraging of hispid cotton rats (Sigmodon hispidus). We used a manipulative experiment, placing resource patches with a known amount of millet seed within areas with reduced (RIFA [–]) or ambient (RIFA [+]) numbers of fire ants. We measured giving up densities (the amount of food left within each patch) within the resource patches for 4 days to quantify the effects of fire ants on cotton rat foraging. We assessed the effects of fire ant treatment (RIFA), Day, and their interaction on cotton rat giving up densities. Giving up densities on RIFA [+] grids were nearly 2.2 times greater across all foraging days and ranged from 1.6 to 2.3 times greater from day 1 to day 4 than the RIFA [–] grids. From day 1 to day 4, mean giving up densities decreased significantly faster for the RIFA [–] than RIFA [+] treatments, 58% and 13%, respectively. Our results demonstrate that cotton rats perceive a risk of injury from fire ants, which is likely caused by interference competition, rather than direct predation. Envenomation from ants likely decrease the foraging efficiency of cotton rats resulting in more time spent foraging. Increased time spent foraging is likely stressful in terms of the opportunity for direct injury and encounters with other predators. These indirect effects may reduce an individual cotton rat’s fitness and translate into lowered population abundances. PMID:27655320

Chemical treatment of wastewater from flue gas desulphurisation

NASA Astrophysics Data System (ADS)

Pasiecznik, Iwona; Szczepaniak, Włodzimierz

2017-11-01

The article presents results of laboratory tests of removing boron and arsenium from non-ideal solutions using double-layered magnesium/aluminium hydroxides (Mg/Al Double-Layered Hydroxide - DLH) produced with nitrate-chloride method. In research, wastewater from an installation for flue gas desulfurization was examined. Double-layered hydroxides are perfect absorbents for anionic compounds. The research proved high effectiveness of preparation with reference to arsenium, as well as confirmed the effect of presence of sulfatic and arsenate ions on the effectiveness of boron removal. On the basis of research on absorption kinetics a theoretical dose of DLH/NO3-Cl/M preparation was calculated and compared with a dose that ensures emimination of boron below the limit standarized by the national regulations. Application of double-layered magnesium/aluminium hydroxides for boron elimination from industrial wastewater requires significantly higher doses of preparation than those calculated in model investigations. It is due to the priority of removal of multivalent ions, such as sulfatic, arsenate or phosphate ions, by DLH/NO3-Cl/M.

Land cover, more than monthly fire weather, drives fire-size distribution in Southern Québec forests: Implications for fire risk management.

PubMed

Marchal, Jean; Cumming, Steve G; McIntire, Eliot J B

2017-01-01

Fire activity in North American forests is expected to increase substantially with climate change. This would represent a growing risk to human settlements and industrial infrastructure proximal to forests, and to the forest products industry. We modelled fire size distributions in southern Québec as functions of fire weather and land cover, thus explicitly integrating some of the biotic interactions and feedbacks in a forest-wildfire system. We found that, contrary to expectations, land-cover and not fire weather was the primary driver of fire size in our study region. Fires were highly selective on fuel-type under a wide range of fire weather conditions: specifically, deciduous forest, lakes and to a lesser extent recently burned areas decreased the expected fire size in their vicinity compared to conifer forest. This has large implications for fire risk management in that fuels management could reduce fire risk over the long term. Our results imply, for example, that if 30% of a conifer-dominated landscape were converted to hardwoods, the probability of a given fire, occurring in that landscape under mean fire weather conditions, exceeding 100,000 ha would be reduced by a factor of 21. A similarly marked but slightly smaller effect size would be expected under extreme fire weather conditions. We attribute the decrease in expected fire size that occurs in recently burned areas to fuel availability limitations on fires spread. Because regenerating burned conifer stands often pass through a deciduous stage, this would also act as a negative biotic feedback whereby the occurrence of fires limits the size of nearby future for some period of time. Our parameter estimates imply that changes in vegetation flammability or fuel availability after fires would tend to counteract shifts in the fire size distribution favoring larger fires that are expected under climate warming. Ecological forecasts from models neglecting these feedbacks may markedly overestimate the consequences of climate warming on fire activity, and could be misleading. Assessments of vulnerability to climate change, and subsequent adaptation strategies, are directly dependent on integrated ecological forecasts. Thus, we stress the need to explicitly incorporate land-cover's direct effects and feedbacks in simulation models of coupled climate-fire-fuels systems.

Effect of room absorption on human vocal output in multitalker situations.

PubMed

Nijs, Lau; Saher, Konca; den Ouden, Daniël

2008-02-01

People increase their vocal output in noisy environments. This is known as the Lombard effect. The aim of the present study was to measure the effect as a function of the absorption coefficient. The noise source was generated by using other talkers in the room. A-weighted sound levels were measured in a 108 m(3) test room. The number of talkers varied from one to four and the absorption coefficients from 0.12 to 0.64. A model was introduced based on the logarithmic sum of the level found in an anechoic room plus the increasing portion of noise levels up to 80 dB. Results show that the model fits the measurements when a maximum slope of 0.5 dB per 1.0 dB increase in background level is used. Hence Lombard slopes vary from 0.2 dBdB at 50 dB background level to 0.5 dBdB at 80 dB. In addition, both measurements and the model predict a decrease of 5.5 dB per doubling of absorbing area in a room when the number of talkers is constant. Sound pressure levels increase for a doubling of talkers from 3 dB for low densities to 6 dB for dense crowds. Finally, there was correspondence between the model estimation and previous measurements reported in the literature.

Gas-phase infrared spectroscopy for determination of double bond configuration of monounsaturated compounds.

PubMed

Attygalle, A B; Svatos, A; Wilcox, C; Voerman, S

1994-05-15

Gas-phase Fourier-transform infrared spectra allow unambiguous determination of the configuration of the double bonds of long-chain unsaturated compounds bearing RCH=CHR' type bonds. Although the infrared absorption at 970-967 cm-1 has been used previously for the identification of trans bonds, the absorption at 3028-3011 cm-1 is conventionally considered to be incapable of distinguishing cis and trans isomers. In this paper, we present a large number of gas-phase spectra of monounsaturated long-chain acetates which demonstrate that an absorption, highly characteristic for the cis configuration, occurs at 3013-3011 cm-1, while trans compounds fail to show any bands in this region. However, if a double bond is present at the C-2 or C-3 carbon atoms, this cis=CH stretch absorption shows a hypsochromic shift to 3029-3028 and 3018-3017 cm-1, respectively. Similarly, if a cis double bond is present at the penultimate carbon atom, this band appears at 3022-3021 cm-1. All the spectra of trans alkenyl acetates showed the expected C-H wag absorption at 968-964 cm-1. In addition, the spectra of (E)-2-alkenyl acetates show a unique three-peak "finger-print" pattern which allows the identification of the position and configuration of this bond. Furthermore, by synthesizing and obtaining spectra of appropriate deuteriated compounds, we have proved that the 3013-3011 cm-1 band is representative of the C-H stretching vibration of cis compounds of RCH=CHR' type.

Larch Forests of Middle Siberia: Long-Term Trends in Fire Return Intervals

NASA Technical Reports Server (NTRS)

Kharuk, Viacheslav I.; Dvinskaya, Mariya L.; Petrov, Ilya A.; Im, Sergei T.; Ranson, Kenneth J.

2016-01-01

Fire history within the northern larch forests of Central Siberia was studied (65+degN). Fires within this area are predominantly caused by lightning strikes rather than human activity. Mean fire return intervals (FRIs) were found to be 112 +/- 49 years (based on firescars) and 106 +/- 36 years (based on firescars and tree natality dates). FRIs were increased with latitude increase and observed to be about 80 years at 64N, about 200 years near the Arctic Circle and about 300 years nearby the northern range limit of larch stands (approx.71+degN). Northward FRIs increase correlated with incoming solar radiation (r = -0.95). Post- Little Ice Age (LIA) warming (after 1850) caused approximately a doubling of fire events (in comparison with a similar period during LIA). The data obtained support a hypothesis of climate-induced fire frequency increase. Keywords Fire ecology Fire history Fire frequency Siberian wildfires Larch forests Climate change

The Big Burn: C Emissions from the Northern Rockies 1910 Fires

NASA Astrophysics Data System (ADS)

Walsh, E.; Hudiburg, T. W.

2017-12-01

The forest fires in August of 1910 were one of the greatest fire events in modern U.S. history. The Big Burn of northern Idaho and northwest Montana overwhelmed the burgeoning U.S. Forest Service suppression efforts and would ultimately harden the policy of fire suppression in the United States that prevails today. The fire burned 12k km2 (approximately the size of Connecticut) in two days with an estimated loss of 8 billion board feet of timber valued at $329 million (2016 dollars). Though one of the greatest natural events in U.S. history, little research has focused on the effect of the fires on CO2 emissions and forest successional pathways of this region. Based on fire extents and timber mortality reports, we estimate the fire resulted in 11 Mg/ha in dead woody biomass and potentially as much as 52 Tg C (191 Tg CO2) released as direct emissions. This is 58%-116% above the average yearly direct carbon emissions due to fire during 2002-2012 in the CONUS. We modeled the subsequent fires and change in species composition providing a measure of the observed shift from white pine (Pinus monticola), western larch (Larix occidentalis) and fir (Abies spp.) to lodgepole pine (Pinus contorta). These models can provide biogeochemical and forest successional pathway context for future changes in forest composition and fire severity/extent due to climate change.

Dirty snow after nuclear war

NASA Technical Reports Server (NTRS)

Warren, S. G.; Wiscombe, W. J.

1985-01-01

It is shown that smoke from fires started by nuclear explosions could continue to cause significant disruption even after it has fallen from the atmosphere, by lowering the reflectivity of snow and sea ice surfaces, with possible effects on climate in northern latitudes caused by enhanced absorption of sunlight. The reduced reflectivity could persist for several years on Arctic sea ice and on the ablation area of the Greenland ice sheet.

Land cover, more than monthly fire weather, drives fire-size distribution in Southern Québec forests: Implications for fire risk management

PubMed Central

Marchal, Jean; Cumming, Steve G.; McIntire, Eliot J. B.

2017-01-01

Fire activity in North American forests is expected to increase substantially with climate change. This would represent a growing risk to human settlements and industrial infrastructure proximal to forests, and to the forest products industry. We modelled fire size distributions in southern Québec as functions of fire weather and land cover, thus explicitly integrating some of the biotic interactions and feedbacks in a forest-wildfire system. We found that, contrary to expectations, land-cover and not fire weather was the primary driver of fire size in our study region. Fires were highly selective on fuel-type under a wide range of fire weather conditions: specifically, deciduous forest, lakes and to a lesser extent recently burned areas decreased the expected fire size in their vicinity compared to conifer forest. This has large implications for fire risk management in that fuels management could reduce fire risk over the long term. Our results imply, for example, that if 30% of a conifer-dominated landscape were converted to hardwoods, the probability of a given fire, occurring in that landscape under mean fire weather conditions, exceeding 100,000 ha would be reduced by a factor of 21. A similarly marked but slightly smaller effect size would be expected under extreme fire weather conditions. We attribute the decrease in expected fire size that occurs in recently burned areas to fuel availability limitations on fires spread. Because regenerating burned conifer stands often pass through a deciduous stage, this would also act as a negative biotic feedback whereby the occurrence of fires limits the size of nearby future for some period of time. Our parameter estimates imply that changes in vegetation flammability or fuel availability after fires would tend to counteract shifts in the fire size distribution favoring larger fires that are expected under climate warming. Ecological forecasts from models neglecting these feedbacks may markedly overestimate the consequences of climate warming on fire activity, and could be misleading. Assessments of vulnerability to climate change, and subsequent adaptation strategies, are directly dependent on integrated ecological forecasts. Thus, we stress the need to explicitly incorporate land-cover’s direct effects and feedbacks in simulation models of coupled climate–fire–fuels systems. PMID:28609467

Informing the network: Improving communication with interface communities during wildland fire

USGS Publications Warehouse

Taylor, J.G.; Gillette, S.C.; Hodgson, R.W.; Downing, J.L.; Burns, M.R.; Chavez, D.J.; Hogan, J.T.

2007-01-01

An interagency research team studied fire communications that took place during different stages of two wildfires in southern California: one small fire of short duration and one large fire of long duration. This "quick- response" research showed that pre-fire communication planning was particularly effective for smaller fire events and parts of that planning proved invaluable for the large fire event as well. Information seeking by the affected public relied on locally convenient sources during the small fire. During the large fire, widespread evacuations disrupted many of the local informal communication networks. Residents' needs were for "real-time, " place-specific information: precise location, severity, size, and direction of spread of the fires. Fire management agencies must contribute real-time, place-specific fire information when it is most needed by the affected public, as they try to make sense out of the chaos of a wildland fire. Disseminating fire information as broadly as possible through multiple pathways will maximize the probability of the public finding the information they need. ?? Society for Human Ecology.

Quantitative analysis of intramolecular exciplex and electron transfer in a double-linked zinc porphyrin-fullerene dyad.

PubMed

Al-Subi, Ali Hanoon; Niemi, Marja; Tkachenko, Nikolai V; Lemmetyinen, Helge

2012-10-04

Photoinduced charge transfer in a double-linked zinc porphyrin-fullerene dyad is studied. When the dyad is excited at the absorption band of the charge-transfer complex (780 nm), an intramolecular exciplex is formed, followed by the complete charge separated (CCS) state. By analyzing the results obtained from time-resolved transient absorption and emission decay measurements in a range of solvents with different polarities, we derived a dependence between the observable lifetimes and internal parameters controlling the reaction rate constants based on the semiquantum Marcus electron-transfer theory. The critical value of the solvent polarity was found to be ε(r) ≈ 6.5: in solvents with higher dielectric constants, the energy of the CCS state is lower than that of the exciplex and the relaxation takes place via the CCS state predominantly, whereas in solvents with lower polarities the energy of the CCS state is higher and the exciplex relaxes directly to the ground state. In solvents with moderate polarities the exciplex and the CCS state are in equilibrium and cannot be separated spectroscopically. The degree of the charge shift in the exciplex relative to that in the CCS state was estimated to be 0.55 ± 0.02. The electronic coupling matrix elements for the charge recombination process and for the direct relaxation of the exciplex to the ground state were found to be 0.012 ± 0.001 and 0.245 ± 0.022 eV, respectively.

Determining the cost effectiveness of a smoke alarm give-away program using data from a randomized controlled trial.

PubMed

Ginnelly, Laura; Sculpher, Mark; Bojke, Chris; Roberts, Ian; Wade, Angie; Diguiseppi, Carolyn

2005-10-01

In 2001, 486 deaths and 17,300 injuries occurred in domestic fires in the UK. Domestic fires represent a significant cost to the UK economy, with the value of property loss alone estimated at pounds 375 million in 1999. In 2001 in the US, there were 383 500 home fires, resulting in 3110 deaths, 15,200 injuries and dollar 5.5 billion in direct property damage. A cluster RCT was conducted to determine whether a smoke alarm give-away program, directed to an inner-city UK population, is effective and cost-effective in reducing the risk of fire-related deaths/injuries. Forty areas were randomized to the give-away or control group. The number of injuries/deaths and the number of fires in each ward were collected prospectively. Cost-effectiveness analysis was undertaken to relate the number of deaths/injuries to resource use (damage, fire service, healthcare and give-away costs). Analytical methods were used which reflected the characteristics of the trial data including the cluster design of the trial and a large number of zero costs and effects. The mean cost for a household in a give-away ward, including the cost of the program, was pounds 12.76, compared to pounds 10.74 for the control ward. The total mean number of deaths and injuries was greater in the intervention wards then the control wards, 6.45 and 5.17. When an injury/death avoided is valued at pounds 1000, a smoke alarm give-away has a probability of being cost effective of 0.15. A smoke alarm give-away program, as administered in the trial, is unlikely to represent a cost-effective use of resources.

Strong anisotropic optical conductivity in two-dimensional puckered structures: The role of the Rashba effect

NASA Astrophysics Data System (ADS)

Saberi-Pouya, S.; Vazifehshenas, T.; Salavati-fard, T.; Farmanbar, M.; Peeters, F. M.

2017-08-01

We calculate the optical conductivity of an anisotropic two-dimensional system with Rashba spin-flip excitation within the Kubo formalism. We show that the anisotropic Rashba effect caused by an external field significantly changes the magnitude of the spin splitting. Furthermore, we obtain an analytical expression for the longitudinal optical conductivity associated with interband transitions as a function of the frequency for arbitrary polarization angle. We find that the diagonal components of the optical conductivity tensor are direction dependent and the optical absorption spectrum exhibits a strongly anisotropic absorption window. The height and width of this absorption window are very sensitive to the anisotropy of the system. While the height of absorption peak increases with increasing effective mass anisotropy ratio, the peak intensity is larger when the light polarization is along the armchair direction. Moreover, the absorption peak width becomes broader as the density-of-states mass or Rashba interaction is enhanced. These features in the optical absorption spectrum can be used to determine parameters relevant for spintronics.

Modeling climate change, urbanization, and fire effects on Pinus palustris ecosystems of the southeastern U.S.

USGS Publications Warehouse

Costanza, Jennifer; Terando, Adam J.; McKerrow, Alexa; Collazo, Jaime A.

2015-01-01

Managing ecosystems for resilience and sustainability requires understanding how they will respond to future anthropogenic drivers such as climate change and urbanization. In fire-dependent ecosystems, predicting this response requires a focus on how these drivers will impact fire regimes. Here, we use scenarios of climate change, urbanization and management to simulate the future dynamics of the critically endangered and fire-dependent longleaf pine (Pinus palustris) ecosystem. We investigated how climate change and urbanization will affect the ecosystem, and whether the two conservation goals of a 135% increase in total longleaf area and a doubling of fire-maintained open-canopy habitat can be achieved in the face of these drivers. Our results show that while climatic warming had little effect on the wildfire regime, and thus on longleaf pine dynamics, urban growth led to an 8% reduction in annual wildfire area. The management scenarios we tested increase the ecosystem's total extent by up to 62% and result in expansion of open-canopy longleaf by as much as 216%, meeting one of the two conservation goals for the ecosystem. We find that both conservation goals for this ecosystem, which is climate-resilient but vulnerable to urbanization, are only attainable if a greater focus is placed on restoration of non-longleaf areas as opposed to maintaining existing longleaf stands. Our approach demonstrates the importance of accounting for multiple relevant anthropogenic threats in an ecosystem-specific context in order to facilitate more effective management actions.

Influence of CdS nanoparticles grain morphology on laser-induced absorption

NASA Astrophysics Data System (ADS)

Ebothé, Jean; Michel, Jean; Kityk, I. V.; Lakshminarayana, G.; Yanchuk, O. M.; Marchuk, O. V.

2018-06-01

Using external illumination of a 7 nanosecond (ns) doubled frequency Nd: YAG laser emitting at λ = 532 nm with frequency repetition 10 Hz it was established a possibility of significant changes of the absorption at the probing wavelength 1150 nm of continuous wave (cw) He-Ne laser for the CdS nanoparticles embedded into the PVA polymer matrix. The effect is observed only during the two beam laser coherent treatment and this effect is a consequence of interference of two coherent beams. It is shown a principal role of the grain morphology in the efficiency of the process, which is more important than the nanoparticle sizes. The photoinduced absorption is manifested in the space distribution of the probing laser beam. The principal role of the grain interfaces between the nanoparticle interfaces and the surrounding polymer matrix is shown. The effect is almost independent of the nanoparticle sizes. It may be used for laser operation by nanocomposites.

Saliency Detection and Deep Learning-Based Wildfire Identification in UAV Imagery.

PubMed

Zhao, Yi; Ma, Jiale; Li, Xiaohui; Zhang, Jie

2018-02-27

An unmanned aerial vehicle (UAV) equipped with global positioning systems (GPS) can provide direct georeferenced imagery, mapping an area with high resolution. So far, the major difficulty in wildfire image classification is the lack of unified identification marks, the fire features of color, shape, texture (smoke, flame, or both) and background can vary significantly from one scene to another. Deep learning (e.g., DCNN for Deep Convolutional Neural Network) is very effective in high-level feature learning, however, a substantial amount of training images dataset is obligatory in optimizing its weights value and coefficients. In this work, we proposed a new saliency detection algorithm for fast location and segmentation of core fire area in aerial images. As the proposed method can effectively avoid feature loss caused by direct resizing; it is used in data augmentation and formation of a standard fire image dataset 'UAV_Fire'. A 15-layered self-learning DCNN architecture named 'Fire_Net' is then presented as a self-learning fire feature exactor and classifier. We evaluated different architectures and several key parameters (drop out ratio, batch size, etc.) of the DCNN model regarding its validation accuracy. The proposed architecture outperformed previous methods by achieving an overall accuracy of 98%. Furthermore, 'Fire_Net' guarantied an average processing speed of 41.5 ms per image for real-time wildfire inspection. To demonstrate its practical utility, Fire_Net is tested on 40 sampled images in wildfire news reports and all of them have been accurately identified.

Improvable method for Halon 1301 concentration measurement based on infrared absorption

NASA Astrophysics Data System (ADS)

Hu, Yang; Lu, Song; Guan, Yu

2015-09-01

Halon 1301 has attached much interest because of its pervasive use as an effective fire suppressant agent in aircraft related fires, and the study of fire suppressant agent concentration measurement is especially of interest. In this work, a Halon 1301 concentration measurement method based on the Beer-Lambert law is developed. IR light is transmitted through mixed gas, and the light intensity with and without the agent present is measured. The intensity ratio is a function of the volume percentage of Halon 1301, and the voltage output of the detector is proportional to light intensity. As such, the relationship between the volume percentage and voltage ratio can be established. The concentration measurement system shows a relative error of the system less than ±2.50%, and a full scale error within 1.20%. This work also discusses the effect of temperature and relative humidity (RH) on the calibration. The experimental results of voltage ratio versus Halon 1301 volume percentage relationship show that the voltage ratio drops significantly as temperature rises from 25 to 100 °C, and it decreases as RH rises from 0% to 100%.

Fire and amphibians in North America

USGS Publications Warehouse

Pilliod, D.S.; Bury, R.B.; Hyde, E.J.; Pearl, C.A.; Corn, P.S.

2003-01-01

Information on amphibian responses to fire and fuel reduction practices is critically needed due to potential declines of species and the prevalence of new, more intensive fire management practices in North American forests. The goals of this review are to summarize the known and potential effects of fire and fuels management on amphibians and their aquatic habitats, and to identify information gaps to help direct future scientific research. Amphibians as a group are taxonomically and ecologically diverse; in turn, responses to fire and associated habitat alteration are expected to vary widely among species and among geographic regions. Available data suggest that amphibian responses to fire are spatially and temporally variable and incompletely understood. Much of the limited research has addressed short-term (1–3 years) effects of prescribed fire on terrestrial life stages of amphibians in the southeastern United States. Information on the long-term negative effects of fire on amphibians and the importance of fire for maintaining amphibian communities is sparse for the majority of taxa in North America. Given the size and severity of recent wildland fires and the national effort to reduce fuels on federal lands, future studies are needed to examine the effects of these landscape disturbances on amphibians. We encourage studies to address population-level responses of amphibians to fire by examining how different life stages are affected by changes in aquatic, riparian, and upland habitats. Research designs need to be credible and provide information that is relevant for fire managers and those responsible for assessing the potential effects of various fuel reduction alternatives on rare, sensitive, and endangered amphibian species.

A high-resolution oxygen A-band spectrometer (HABS) and its radiation closure

NASA Astrophysics Data System (ADS)

Min, Q.; Yin, B.; Li, S.; Berndt, J.; Harrison, L.; Joseph, E.; Duan, M.; Kiedron, P.

2014-02-01

The pressure dependence of oxygen A-band absorption enables the retrieval of the vertical profiles of aerosol and cloud properties from oxygen A-band spectrometry. To improve the understanding of oxygen A-band inversions and utility, we developed a high-resolution oxygen A-band spectrometer (HABS), and deployed it at Howard University Beltsville site during the NASA Discover Air-Quality Field Campaign in July 2011. The HABS has the ability to measure solar direct-beam and zenith diffuse radiation through a telescope automatically. It exhibits excellent performance: stable spectral response ratio, high signal-to-noise ratio (SNR), high spectrum resolution (0.16 nm), and high Out-of-Band Rejection (10-5). To evaluate the spectra performance of HABS, a HABS simulator has been developed by combing the discrete ordinates radiative transfer (DISORT) code with the High Resolution Transmission (HTRAN) database HITRAN2008. The simulator uses double-k approach to reduce the computational cost. The HABS measured spectra are consistent with the related simulated spectra. For direct-beam spectra, the confidence intervals (95%) of relative difference between measurements and simulation are (-0.06, 0.05) and (-0.08, 0.09) for solar zenith angles of 27° and 72°, respectively. The main differences between them occur at or near the strong oxygen absorption line centers. They are mainly caused by the noise/spikes of HABS measured spectra, as a result of combined effects of weak signal, low SNR, and errors in wavelength registration and absorption line parameters. The high-resolution oxygen A-band measurements from HABS can constrain the active radar retrievals for more accurate cloud optical properties, particularly for multi-layer clouds and for mixed-phase clouds.

Hyperpolarization-Activated Current Induces Period-Doubling Cascades and Chaos in a Cold Thermoreceptor Model

PubMed Central

Xu, Kesheng; Maidana, Jean P.; Caviedes, Mauricio; Quero, Daniel; Aguirre, Pablo; Orio, Patricio

2017-01-01

In this article, we describe and analyze the chaotic behavior of a conductance-based neuronal bursting model. This is a model with a reduced number of variables, yet it retains biophysical plausibility. Inspired by the activity of cold thermoreceptors, the model contains a persistent Sodium current, a Calcium-activated Potassium current and a hyperpolarization-activated current (Ih) that drive a slow subthreshold oscillation. Driven by this oscillation, a fast subsystem (fast Sodium and Potassium currents) fires action potentials in a periodic fashion. Depending on the parameters, this model can generate a variety of firing patterns that includes bursting, regular tonic and polymodal firing. Here we show that the transitions between different firing patterns are often accompanied by a range of chaotic firing, as suggested by an irregular, non-periodic firing pattern. To confirm this, we measure the maximum Lyapunov exponent of the voltage trajectories, and the Lyapunov exponent and Lempel-Ziv's complexity of the ISI time series. The four-variable slow system (without spiking) also generates chaotic behavior, and bifurcation analysis shows that this is often originated by period doubling cascades. Either with or without spikes, chaos is no longer generated when the Ih is removed from the system. As the model is biologically plausible with biophysically meaningful parameters, we propose it as a useful tool to understand chaotic dynamics in neurons. PMID:28344550

Clarifying the role of fire heat and daily temperature fluctuations as germination cues for Mediterranean Basin obligate seeders

PubMed Central

Santana, Victor M.; Baeza, M. Jaime; Blanes, M. Carmen

2013-01-01

Background and Aims This study aims to determine the role that both direct effects of fire and subsequent daily temperature fluctuations play in the seed bank dynamics of obligate seeders from the Mediterranean Basin. The short yet high soil temperatures experienced due to passage of fire are conflated with the lower, but longer, temperatures experienced by daily fluctuations which occur after removing vegetation. These germination cues are able to break seed dormancy, but it is difficult to assess their specific level of influence because they occur consecutively after summer fires, just before the flush of germination in the wet season (autumn). Methods By applying experimental fires, seed treatments were imposed that combined fire exposure/non-fire exposure with exposure to microhabitats under a gradient of disturbance (i.e. gaps opened by fire, mechanical brushing and intact vegetation). The seeds used were representative of the main families of obligate seeders (Ulex parviflorus, Cistus albidus and Rosmarinus officinalis). Specifically, an assessment was made of (1) the proportion of seeds killed by fire, (2) seedling emergence under field conditions and (3) seeds which remained ungerminated in soil. Key Results For the three species studied, the factors that most influenced seedling emergence and seeds remaining ungerminated were microhabitats with higher temperature fluctuations after fire (gaps opened by fire and brushing treatments). The direct effect of fire decreased the seedling emergence of U. parviflorus and reduced the proportion of seeds of R. officinalis remaining ungerminated. Conclusions The relevance of depleting vegetation (and subsequent daily temperature fluctuation in summer) suggests that studies focusing on lower temperature thresholds for breaking seed dormancy are required. This fact also supports the hypothesis that the seeding capacity in Mediterranean Basin obligate seeders may have evolved as a response to a wide range of disturbances, and not exclusively to fire. PMID:23129044

Fire, Carbon and Climate Change in Boreal Forests

NASA Astrophysics Data System (ADS)

Flannigan, M. D.; Amiro, B. D.; Logan, K. A.

2005-12-01

Disturbances are the major stand-renewing agents for much of the circumboreal forest. In Canada, fire has received much of the attention in carbon cycle science because it affects about 3 million ha of Canadian forest annually, impacts air quality, and can threaten life, property and infrastructure. Fire affects the carbon balance through three processes. First, carbon and other greenhouse gases are emitted to the atmosphere during the combustion process. We estimate this to average about 27 Tg C/year in Canada over the past 40 years, which is close to 20% of industrial carbon emissions. However, in some years this can exceed 100 Tg C. Efforts are underway to estimate global fire activity and greenhouse gas emissions using observations, remote sensing and modelling. The second process is the decomposition of fire-killed vegetation. This forms a pool of coarse woody debris that can take decades to decompose, or can be quite rapid, depending on the post-fire environment. The third process is succession of vegetation following fire, a dynamic process that involves the interplay among species establishment and competition. Weather and climate affects all of these processes. Estimates of the future environment indicate that much of boreal Canada will experience warmer and drier conditions, although there will be regional differences and transient effects. The projections suggest that we may experience a doubling of area burned over the next century because of anthropogenic climate changes. This may have further implications to the global carbon budget by increasing atmospheric carbon dioxide concentrations. This increase in fire activity may lead to a positive feedback cycle with the increased release of greenhouse gases. A run-away scenario is unlikely because young successional boreal vegetation often does not burn as readily and would limit the positive feedback cycle. Also, changes to the forest composition following fire increases surface albedo and alters the energy balance; effects that may cause climate cooling. However, the impacts of landscape feedbacks and human intervention limiting future fire are not well known.

Soil carbon in Australian fire-prone forests determined by climate more than fire regimes.

PubMed

Sawyer, Robert; Bradstock, Ross; Bedward, Michael; Morrison, R John

2018-10-15

Knowledge of global C cycle implications from changes to fire regime and climate are of growing importance. Studies on the role of the fire regime in combination with climate change on soil C pools are lacking. We used Bayesian modelling to estimate the soil % total C (% C Tot ) and % recalcitrant pyrogenic C (% RPC) from field samples collected using a stratified sampling approach. These observations were derived from the following scenarios: 1. Three fire frequencies across three distinctive climate regions in a homogeneous dry sclerophyll forest in south-eastern Australia over four decades. 2. The effects of different fire intensity combinations from successive wildfires. We found climate had a stronger effect than fire frequency on the size of the estimated mineral soil C pool. The largest soil C pool was estimated to occur under a wet and cold (WC) climate, via presumed effects of high precipitation, an adequate growing season temperature (i.e. resulting in relatively high NPP) and winter conditions sufficiently cold to retard seasonal soil respiration rates. The smallest soil C pool was estimated in forests with lower precipitation but warmer mean annual temperature (MAT). The lower precipitation and higher temperature was likely to have retarded NPP and litter decomposition rates but may have had little effect on relative soil respiration. Small effects associated with fire frequency were found, but both their magnitude and direction were climate dependent. There was an increase in soil C associated with a low intensity fire being followed by a high intensity fire. For both fire frequency and intensity the response of % RPC mirrored that of % C Tot : i.e. it was effectively a constant across all combinations of climate and fire regimes sampled. Copyright © 2018. Published by Elsevier B.V.

Real-time, in situ, continuous monitoring of CO in a pulverized-coal-fired power plant with a 2.3 μm laser absorption sensor

NASA Astrophysics Data System (ADS)

Chao, Xing; Jeffries, Jay B.; Hanson, Ronald K.

2013-03-01

A real-time, in situ CO sensor using 2.3 μm DFB diode laser absorption, with calibration-free wavelength-modulation-spectroscopy, was demonstrated for continuous monitoring in the boiler exhaust of a pulverized-coal-fired power plant up to temperatures of 700 K. The sensor was similar to a design demonstrated earlier in laboratory conditions, now refined to accommodate the harsh conditions of utility boilers. Measurements were performed across a 3 m path in the particulate-laden economizer exhaust of the coal-fired boiler. A 0.6 ppm detection limit with 1 s averaging was estimated from the results of a continuous 7-h-long measurement with varied excess air levels. The measured CO concentration exhibited expected inverse trends with the excess O2 concentration, which was varied between 1 and 3 %. Measured CO concentrations ranged between 6 and 200 ppm; evaluation of the data suggested a dynamic range from 6 to 10,000 ppm based on a minimum signal-to-noise ratio of ten and maximum absorbance of one. This field demonstration of a 2.3 μm laser absorption sensor for CO showed great potential for real-time combustion exhaust monitoring and control of practical combustion systems.

Diffraction-limited 577 nm true-yellow laser by frequency doubling of a tapered diode laser

NASA Astrophysics Data System (ADS)

Christensen, Mathias; Vilera, Mariafernanda; Noordegraaf, Danny; Hansen, Anders K.; Buß, Thomas; Jensen, Ole B.; Skovgaard, Peter M. W.

2018-02-01

A wide range of laser medical treatments are based on coagulation of blood by absorption of the laser radiation. It has, therefore, always been a goal of these treatments to maximize the ratio of absorption in the blood to that in the surrounding tissue. For this purpose lasers at 577 nm are ideal since this wavelength is at the peak of the absorption in oxygenated hemoglobin. Furthermore, 577 nm has a lower absorption in melanin when compared to green wavelengths (515 - 532 nm), giving it an advantage when treating at greater penetration depth. Here we present a laser system based on frequency doubling of an 1154 nm Distributed Bragg Reflector (DBR) tapered diode laser, emitting 1.1 W of single frequency and diffraction limited yellow light at 577 nm, corresponding to a conversion efficiency of 30.5%. The frequency doubling is performed in a single pass configuration using a cascade of two bulk non-linear crystals. The system is power stabilized over 10 hours with a standard deviation of 0.13% and the relative intensity noise is measured to be 0.064 % rms.

Transition metal atomic multiplets in the ligand K-edge x-ray absorption spectra and multiple oxidation states in the L2,3 emission of strongly correlated compounds

NASA Astrophysics Data System (ADS)

Jiménez-Mier, J.; Olalde-Velasco, P.; Yang, W.-L.; Denlinger, J.

2014-07-01

We present results that show that atomic multiplet ligand field calculations are in very good agreement with experimental x-ray absorption spectra at the L2,3 edge of transition metal (TM) di-fluorides (MF2, MCrCu). For chromium more than one TM oxidation state is needed to achieve such an agreement. We also show that signature of the TM atomic multiplet can be found at the pre-edge of the fluorine K-edge x-ray absorption spectra. TM atomic multiplet ligand field calculations with a structureless core hole show good agreement with the observed pre-edges in the experimental fluorine absorption spectra. Preliminary results for the comparison between calculated and experimental resonant x-ray emission spectra for nominal CrF2 with more than one oxidation state indicate the presence of three chromium oxidation states in the bulk.

Hydrocarbon characterization experiments in fully turbulent fires.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ricks, Allen; Blanchat, Thomas K.

As the capabilities of numerical simulations increase, decision makers are increasingly relying upon simulations rather than experiments to assess risks across a wide variety of accident scenarios including fires. There are still, however, many aspects of fires that are either not well understood or are difficult to treat from first principles due to the computational expense. For a simulation to be truly predictive and to provide decision makers with information which can be reliably used for risk assessment the remaining physical processes must be studied and suitable models developed for the effects of the physics. The model for the fuelmore » evaporation rate in a liquid fuel pool fire is significant because in well-ventilated fires the evaporation rate largely controls the total heat release rate from the fire. A set of experiments are outlined in this report which will provide data for the development and validation of models for the fuel regression rates in liquid hydrocarbon fuel fires. The experiments will be performed on fires in the fully turbulent scale range (> 1 m diameter) and with a number of hydrocarbon fuels ranging from lightly sooting to heavily sooting. The importance of spectral absorption in the liquid fuels and the vapor dome above the pool will be investigated and the total heat flux to the pool surface will be measured. The importance of convection within the liquid fuel will be assessed by restricting large scale liquid motion in some tests. These data sets will provide a sound, experimentally proven basis for assessing how much of the liquid fuel needs to be modeled to enable a predictive simulation of a fuel fire given the couplings between evaporation of fuel from the pool and the heat release from the fire which drives the evaporation.« less

Effect of wood smoke exposure on vascular function and thrombus formation in healthy fire fighters.

PubMed

Hunter, Amanda L; Unosson, Jon; Bosson, Jenny A; Langrish, Jeremy P; Pourazar, Jamshid; Raftis, Jennifer B; Miller, Mark R; Lucking, Andrew J; Boman, Christoffer; Nyström, Robin; Donaldson, Kenneth; Flapan, Andrew D; Shah, Anoop S V; Pung, Louis; Sadiktsis, Ioannis; Masala, Silvia; Westerholm, Roger; Sandström, Thomas; Blomberg, Anders; Newby, David E; Mills, Nicholas L

2014-12-09

Myocardial infarction is the leading cause of death in fire fighters and has been linked with exposure to air pollution and fire suppression duties. We therefore investigated the effects of wood smoke exposure on vascular vasomotor and fibrinolytic function, and thrombus formation in healthy fire fighters. In a double-blind randomized cross-over study, 16 healthy male fire fighters were exposed to wood smoke (~1 mg/m³ particulate matter concentration) or filtered air for one hour during intermittent exercise. Arterial pressure and stiffness were measured before and immediately after exposure, and forearm blood flow was measured during intra-brachial infusion of endothelium-dependent and -independent vasodilators 4-6 hours after exposure. Thrombus formation was assessed using the ex vivo Badimon chamber at 2 hours, and platelet activation was measured using flow cytometry for up to 24 hours after the exposure. Compared to filtered air, exposure to wood smoke increased blood carboxyhaemoglobin concentrations (1.3% versus 0.8%; P < 0.001), but had no effect on arterial pressure, augmentation index or pulse wave velocity (P > 0.05 for all). Whilst there was a dose-dependent increase in forearm blood flow with each vasodilator (P < 0.01 for all), there were no differences in blood flow responses to acetylcholine, sodium nitroprusside or verapamil between exposures (P > 0.05 for all). Following exposure to wood smoke, vasodilatation to bradykinin increased (P = 0.003), but there was no effect on bradykinin-induced tissue-plasminogen activator release, thrombus area or markers of platelet activation (P > 0.05 for all). Wood smoke exposure does not impair vascular vasomotor or fibrinolytic function, or increase thrombus formation in fire fighters. Acute cardiovascular events following fire suppression may be precipitated by exposure to other air pollutants or through other mechanisms, such as strenuous physical exertion and dehydration.

Gas Fride Heat Pumps : The Present and Future

NASA Astrophysics Data System (ADS)

Kurosawa, Shigekichi; Ogura, Masao

In japan techniques for saving energy is an important goal since energy resources such as oil and nuclear power are limited. Recently gas fired absorption heat pumps and gas engine driven heat pumps have been installed in facilifies such as hotels, swimming pools and offices.
In this article recent techniques, applications and future aspects for gas fired heat pumps are explained.

The Effects of Triggering Mechanisms on the Energy Absorption Capability of Circular Jute/Epoxy Composite Tubes under Quasi-Static Axial Loading

NASA Astrophysics Data System (ADS)

Sivagurunathan, Rubentheran; Lau Tze Way, Saijod; Sivagurunathan, Linkesvaran; Yaakob, Mohd. Yuhazri

2018-01-01

The usage of composite materials have been improving over the years due to its superior mechanical properties such as high tensile strength, high energy absorption capability, and corrosion resistance. In this present study, the energy absorption capability of circular jute/epoxy composite tubes were tested and evaluated. To induce the progressive crushing of the composite tubes, four different types of triggering mechanisms were used which were the non-trigger, single chamfered trigger, double chamfered trigger and tulip trigger. Quasi-static axial loading test was carried out to understand the deformation patterns and the load-displacement characteristics for each composite tube. Besides that, the influence of energy absorption, crush force efficiency, peak load, mean load and load-displacement history were examined and discussed. The primary results displayed a significant influence on the energy absorption capability provided that stable progressive crushing occurred mostly in the triggered tubes compared to the non-triggered tubes. Overall, the tulip trigger configuration attributed the highest energy absorption.

Low-lying singlet states of carotenoids having 8-13 conjugated double bonds as determined by electronic absorption spectroscopy

NASA Astrophysics Data System (ADS)

Wang, Peng; Nakamura, Ryosuke; Kanematsu, Yasuo; Koyama, Yasushi; Nagae, Hiroyoshi; Nishio, Tomohiro; Hashimoto, Hideki; Zhang, Jian-Ping

2005-07-01

Electronic absorption spectra were recorded at room temperature in solutions of carotenoids having different numbers of conjugated double bonds, n = 8-13, including a spheroidene derivatives, neurosporene, spheroidene, lycopene, anhydrorhodovibrin and spirilloxanthin. The vibronic states of 1Bu+(v=0-4), 2Ag-(v=0-3), 3Ag- (0) and 1Bu- (0) were clearly identified. The arrangement of the four electronic states determined by electronic absorption spectroscopy was identical to that determined by measurement of resonance Raman excitation profiles [K. Furuichi et al., Chem. Phys. Lett. 356 (2002) 547] for carotenoids in crystals.

Mechanical Energy and Propulsion in Ergometer Double Poling by Cross-country Skiers.

PubMed

Danielsen, Jørgen; Sandbakk, Øyvind; Holmberg, Hans-Christer; Ettema, Gertjan

2015-12-01

This study aims to investigate fluctuations in total mechanical energy of the body (Ebody) in relation to external ergometer work (Werg) during the poling and recovery phases of simulated double-poling cross-country skiing. Nine male cross-country skiers (mean ± SD age, 24 ± 5 yr; mean ± SD body mass, 81.7 ± 6.5 kg) performed 4-min submaximal tests at low-intensity, moderate-intensity, and high-intensity levels and a 3-min all-out test on a ski ergometer. Motion capture analysis and load cell recordings were used to measure body kinematics and dynamics. From these, Werg, Ebody (sum of the translational, rotational, and gravitational potential energies of all segments), and their time differentials (power P) were calculated. Ptot--the rate of energy absorption or generation by muscles-tendons--was defined as the sum of Pbody and Perg. Ebody showed large fluctuations over the movement cycle, decreasing during poling and increasing during the recovery phase. The fluctuation in Pbody was almost perfectly out of phase with Perg. Some muscle-tendon energy absorption was observed at the onset of poling. For the rest of poling and throughout the recovery phase, muscles-tendons generated energy to do Werg and to increase Ebody. Approximately 50% of cycle Ptot occurred during recovery for all intensity levels. In double poling, the extensive contribution of the lower extremities and trunk to whole-body muscle-tendon work during recovery facilitates a "direct" transfer of Ebody to Werg during the poling phase. This observation reveals that double poling involves a unique movement pattern different from most other forms of legged terrestrial locomotion, which are characterized primarily by inverted pendulum or spring-mass types of movement.

[Influence of different designs and porcelain/glaze firing on the marginal and internal fit of implant-supported zirconia crowns].

PubMed

Cuiling, Liu; Xu, Gao; Yuping, Qi; Liyuan, Yang

2016-02-01

This study investigated the influence of different designs and porcelain/glaze firing on the marginal and internal fit of three kinds of computer aided design/computer aided manufacturing (CAD/CAM) zirconia ceramic implant-supported crowns. Three groups of zirconia ceramic implant-supported crowns with different designs were produced from copings by using a Cercon CAD/CAM system (n = 8). The first two groups comprised double-layer crowns (zirconia coping + veneer) with regular (Group A) and full circumferential zirconia-collar marginal designs (Group B). The third group was composed of anatomic single-layer zirconia crowns without cores (Group C). Initially, the marginal and internal gaps of the copings and crowns were individually replicated by light-body silicon and then measured by micro-computed tomography scanning before and after porcelain/glaze firing. Five measurements were employed: vertical marginal gap (MG); horizontal marginal discrepancy (HMD); chamfer area (CA); axial wall (AW); and axial-occlusal transition area (AOT). Statistical analyses were performed by SPSS 17.0. HMD measurements in Group A were statistically higher than those in Groups B and C (P < 0.05), regardless of whether the values were obtained before or after porcelain/glaze firing. By contrast, the HIMD measurements in Groups B and C showed no significant difference (P > 0.05). Moreover, no differences were noted in MG, CA, AW, and AOT among the three groups (P > 0.05). All the measurements in the three groups showed no significant change after porcelain/glaze firing (P > 0.05), except for MG in Group A, which significantly decreased (P < 0.05). The marginal fits of the double-layer crowns with full circumferential zirconia-collar and the anatomic single-layer zirconia crowns were superior to that of the double-layer crowns with regular margins. The MG of the crowns with regular margins was obviously influenced by porcelain firing.

Larch Forests of Middle Siberia: Long-Term Trends in Fire Return Intervals

NASA Technical Reports Server (NTRS)

Kharuk, Viacheslav I.; Dvinskaya, Mariya L.; Petrov, Ilya A.; Im, Sergei T.; Ranson, Kenneth J.

2016-01-01

Fire history within the northern larch forests of Central Siberia was studied (65 + deg N). Fires within this area are predominantly caused by lightning strikes rather than human activity. Mean fire return intervals (FRIs) were found to be 112 ± 49 years (based on fire scars) and 106 ± 36 years (based on fire scars and tree natality dates). FRI were increased with latitude increase and observed to be about 80 years at 64 deg N, about 200 years near the Arctic Circle and about 300 years nearby the northern range limit of larch stands (approximately 71 deg + N). Northward FRI increase correlated with incoming solar radiation (r = -0.95). Post Little Ice Age (LIA) warming (after 1850) caused approximately a doubling of fire events (in comparison with a similar period during LIA). The data obtained support a hypothesis of climate-induced fire frequency increase.

Larch Forests of Middle Siberia: Long-Term Trends in Fire Return Intervals

PubMed Central

Kharuk, Viacheslav I.; Dvinskaya, Mariya L.; Petrov, Ilya A.; Im, Sergei T.; Ranson, Kenneth J.

2017-01-01

Fire history within the northern larch forests of Central Siberia was studied (65+°N). Fires within this area are predominantly caused by lightning strikes rather than human activity. Mean fire return intervals (FRI) were found to be 112 ± 49 years (based on fire scars) and 106 ± 36 years (based on fire scars and tree natality dates). FRI were increased with latitude increase, and observed to be about 80 years at 64°N, about 200 years near the Arctic Circle, and about 300 years nearby the northern range limit of larch stands (~71°+N). Northward FRI increase correlated with incoming solar radiation (r = − 0.95). Post Little Ice Age (LIA) warming (after 1850) caused approximately a doubling of fire events (in comparison with a similar period during LIA). The data obtained support a hypothesis of climate-induced fire frequency increase. PMID:28966554

Commercial Absorption Heat Pump Water Heater: Beta Prototype Evaluation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Geoghegan, Patrick; Ally, Moonis; Sharma, Vishaldeep

2016-10-14

The Beta version of the Commercial Absorption Heat Pump (CAHP) water heater was evaluated in the environmental chambers at Oak Ridge National Laboratory. Ambient air conditions ranged from 17 to 75 oF and inlet water temperatures ranged from 100 to 120oF in order to capture trends in performance. The unit was operated under full fire (100%) and partial fire (55%). The unit was found to perform at 90% of the project goal at the design conditions of 47oF ambient and 100oF water temperatures. The trends across the full range of environmental conditions were as expected for ambient air temperatures abovemore » 32oF. Below this temperature and for the full fire condition, frost accumulated on the evaporator coil. In future work a defrost strategy will be enabled, the unit will be thoroughly cleaned of an oil contamination and the rectifier will be reconfigured in order to meet the design goals and have a field test unit ready in early 2017.« less

Estimating the direct radiative forcing due to haze from the 1997 forest fires in Indonesia

NASA Astrophysics Data System (ADS)

Davison, P. S.; Roberts, D. L.; Arnold, R. T.; Colvile, R. N.

2004-05-01

The El Niño event of 1997-1998 caused a severe reduction of rainfall in Indonesia that promoted the spread of forest fires, leading to a pervasive haze in the region. Here we use fire coverage data from the 1997 World Fire Atlas with a review of other available data and literature to estimate the distribution of particulate emissions from August to November 1997 and the particle size and radiative properties. Our preferred estimate of the total particulate emissions is approximately 41 Tg. The emissions have been used to drive an atmospheric model to simulate the distribution of the haze and its direct radiative effect, with and without allowing for the effects of the smoke on the atmospheric evolution. Model diagnostics of the aerosol and its radiative impact are compared with measurements and output from other models. Large decreases in the incident solar flux at the surface are obtained in the region. The simulated global mean shortwave radiative forcing at the top of the atmosphere, averaged over the 4 months, is -0.32 Wm-2. The accuracy of this calculation is discussed, and the importance of the Indonesian fires in particular and of biomass burning in general is assessed.

Transmission loss of orthogonally rib-stiffened double-panel structures with cavity absorption.

PubMed

Xin, F X; Lu, T J

2011-04-01

The transmission loss of sound through infinite orthogonally rib-stiffened double-panel structures having cavity-filling fibrous sound absorptive materials is theoretically investigated. The propagation of sound across the fibrous material is characterized using an equivalent fluid model, and the motions of the rib-stiffeners are described by including all possible vibrations, i.e., flexural displacements, bending, and torsional rotations. The effects of fluid-structure coupling are account for by enforcing velocity continuity conditions at fluid-panel interfaces. By taking full advantage of the periodic nature of the double-panel, the space-harmonic approach and virtual work principle are applied to solve the sets of resultant governing equations, which are eventually truncated as a finite system of simultaneous algebraic equations and numerically solved insofar as the solution converges. To validate the proposed model, a comparison between the present model predictions and existing numerical and experimental results for a simplified version of the double-panel structure is carried out, with overall agreement achieved. The model is subsequently employed to explore the influence of the fluid-structure coupling between fluid in the cavity and the two panels on sound transmission across the orthogonally rib-stiffened double-panel structure. Obtained results demonstrate that this fluid-structure coupling affects significantly sound transmission loss (STL) at low frequencies and cannot be ignored when the rib-stiffeners are sparsely distributed. As a highlight of this research, an integrated optimal algorithm toward lightweight, high-stiffness and superior sound insulation capability is proposed, based on which a preliminary optimal design of the double-panel structure is performed.

The federal wildland policy: opportunities for wilderness fire management

Treesearch

G. Thomas Zimmerman; David L. Bunnell

2000-01-01

The Federal Wildland Fire Management Policy and Program Review represents the latest stage in the evolution of wildland fire management. This policy directs changes that consolidate past fire management practices into a single direction to achieve multidimensional objectives and creates increased opportunities for wilderness fire management. Objectives previously...

`Fingerprint' Fine Structure in the Solar Decametric Radio Spectrum Solar Physics

NASA Astrophysics Data System (ADS)

Zlotnik, E. Y.; Zaitsev, V. V.; Melnik, V. N.; Konovalenko, A. A.; Dorovskyy, V. V.

2015-07-01

We study a unique fine structure in the dynamic spectrum of the solar radio emission discovered by the UTR-2 radio telescope (Kharkiv, Ukraine) in the frequency band of 20 - 30 MHz. The structure was observed against the background of a broadband type IV radio burst and consisted of parallel drifting narrow bands of enhanced emission and absorption on the background emission. The observed structure differs from the widely known zebra pattern at meter and decimeter wavelengths by the opposite directions of the frequency drift within a single stripe at a given time. We show that the observed properties can be understood in the framework of the radiation mechanism by virtue of the double plasma resonance effect in a nonuniform coronal magnetic trap. We propose a source model providing the observed frequency drift of the stripes.

Design of butterfly type organic dye sensitizers with double electron donors: The first principle study

NASA Astrophysics Data System (ADS)

Yang, Zhenqing; Shao, Di; Li, Juan; Tang, Lian; Shao, Changjin

2018-05-01

In this work, we designed a series of butterfly type organic dyes, named ME07-ME13 by introducing such as triphenylamine, phenothiazine, coumarin groups etc. as electron donors and further investigated their absorption spectra using density functional theory (DFT) and time-dependent DFT (TDDFT). All designed dyes cover the entire visible absorption spectrum from 300 to 800 nm. It's fascinating that ME13 molecule has two absorption peak and the molar coefficient of two absorption peaks are above 4.645 × 104 M-1·cm-1. The light absorption area of ME13 exhibits an increment of 16.5-19.1% compared to ME07-ME12. Furthermore, we performed a detailed analysis on their geometrical and electronic properties, including molecular structures, energy levels, light harvesting efficiency (LHE), driving force (ΔGinject), regeneration (ΔGregen),electron dipole moments (μnormal), intermolecular electron transfer and dye/(TiO2)38 system electron transitions. The results of calculation reveal that double coumarin donors in ME13 are promising functional groups for butterfly type organic dye sensitizers. It is expected that the design of double donors can provide a new strategy and guidance for the investigation in high efficiency dye-sensitized devices.

Analyzing post-fire topography at the hillslope-channel interface with terrestrial LiDAR: contrasting geomorphic responses from the 2012 Waldo Canyon Fire of Colorado and the 2013 Springs Fire of California

NASA Astrophysics Data System (ADS)

Storesund, R.; Chin, A.; Florsheim, J. L.; O'Hirok, L.; Williams, K.; Austin, K. E.

2014-12-01

Mountains areas are increasingly susceptible to wildfires because of warming climates. Although knowledge of the hydro-geomorphological impacts of wildfire has advanced in recent years, much is still unknown regarding how environmental fluxes move through burned watersheds. Because of the loss of vegetation and hydrophobic soils, flash floods often accompany elevated runoff events from burned watersheds, making direct process measurements challenging. Direct measurements are also only partly successful at capturing the spatial variations of post-fire effects. Coupled with short temporal windows for observing such responses, opportunities are often missed for collecting data needed for developing predictive models. Terrestrial LiDAR scanning (TLS) of burned areas allows detailed documentation of the post-fire topography to cm-level accuracy, providing pictures of geomorphic responses not previously possible. This paper reports a comparative study of hillslope-channel interactions, using repeat TLS, in two contrasting environments. Burned by the 2012 Waldo Canyon Fire and 2013 Springs Fire, in Colorado and California respectively, the study sites share many similarities including steep erosive slopes, small drainage areas, and step-pool channel morphologies. TLS provided a tool to test the central hypothesis that, dry ravel, distinct in the California Mediterranean environment, would prompt a greater sedimentological response from the Springs Fire compared to the Waldo Canyon Fire. At selected sites in each area, TLS documented baseline conditions immediately following the fire. Repeat scanning after major storms allowed detection of changes in the landscape. Results show a tendency for sedimentation in river channels in the study sites interacting with dry ravel on hillslopes, whereas erosion dominated the response from the Waldo Canyon Fire with an absence of dry ravel. These data provide clues to developing generalizations for post-fire effects at regional scales, which could assist with managing hazards from wildfires. TLS provides a promising tool to expand the range of studies concerning environmental responses through burned landscapes.

Interplay of coupling and superradiant emission in the optical response of a double quantum dot

NASA Astrophysics Data System (ADS)

Sitek, Anna; Machnikowski, Paweł

2009-09-01

We study theoretically the optical response of a double quantum dot structure to an ultrafast optical excitation. We show that the interplay of a specific type of coupling between the dots and their collective interaction with the radiative environment leads to very characteristic features in the time-resolved luminescence as well as in the absorption spectrum of the system. For a sufficiently strong coupling, these effects survive even if the transition energy mismatch between the two dots exceeds by far the emission linewidth.

Full Spectrum LAR

DTIC Science & Technology

2008-01-01

Emerson 901 TOW Under Armor (TUA) weapons system. When reliably operational, the Emerson 901 turret can still provide effective anti-armor fires as...the rear of the LAV-R thus there is no available space to carry ammunition resupplies, food, or under armor ambulance kits. On the other hand, the...the LAR battalion; however, the LAV-EFSS cannot be fired under armor protection or in the direct firing mode. Both the LAV-120 AMS and the LAV-EFSS

Assessment of the Influence of Fractures on the Dynamics of Coal Seam Fires by Numerical Experiments

NASA Astrophysics Data System (ADS)

Wuttke, Manfred W.; Zeng, Qiang

2016-04-01

Uncontrolled burning coal seam fires still constitute major problems for the coal industry by destroying the resource, a serious hazard for the local people by severe environmental pollution, and a tremendous threat to the global environment by the emission of greenhouse gases and aerosols. In particular when the seams are lying shallow the alteration of the immediate surrounding of the coal seam fire feeds back on the dynamics of the fire. Thermal stress induced fracturing produces direct connections of the fire zone with the atmosphere. This influences the supply with oxygen, the venting of the exhaust gases, and the dissipation of heat. The first two processes are expected to enhance the fire propagation whereas the latter effect should slow it down. With our dedicated coal seam fire code ACME ("Amendable Coal-fire Modeling Exercise") we study these coupled effects of fractures in simulations of typical coal seam fire scenarios based on data from Xinjiang, China. Fractures are predefined as 1D/2D objects in a 2D/3D model geometry and are opened depending on the passage of the heat wave produced by the coal seam fire.

Direct estimation of diffuse gaseous emissions from coal fires: current methods and future directions

USGS Publications Warehouse

Engle, Mark A.; Olea, Ricardo A.; O'Keefe, Jennifer M. K.; Hower, James C.; Geboy, Nicholas J.

2013-01-01

Coal fires occur in nature spontaneously, contribute to increases in greenhouse gases, and emit atmospheric toxicants. Increasing interest in quantifying coal fire emissions has resulted in the adaptation and development of specialized approaches and adoption of numerical modeling techniques. Overview of these methods for direct estimation of diffuse gas emissions from coal fires is presented in this paper. Here we take advantage of stochastic Gaussian simulation to interpolate CO2 fluxes measured using a dynamic closed chamber at the Ruth Mullins coal fire in Perry County, Kentucky. This approach allows for preparing a map of diffuse gas emissions, one of the two primary ways that gases emanate from coal fires, and establishing the reliability of the study both locally and for the entire fire. Future research directions include continuous and automated sampling to improve quantification of gaseous coal fire emissions.

The Detection Method of Fire Abnormal Based on Directional Drilling in Complex Conditions of Mine

NASA Astrophysics Data System (ADS)

Huijun, Duan; Shijun, Hao; Jie, Feng

2018-06-01

In the light of more and more urgent hidden fire abnormal detection problem in complex conditions of mine, a method which is used directional drilling technology is put forward. The method can avoid the obstacles in mine, and complete the fire abnormal detection. This paper based on analyzing the trajectory control of directional drilling, measurement while drilling and the characteristic of open branch process, the project of the directional drilling is formulated combination with a complex condition mine, and the detection of fire abnormal is implemented. This method can provide technical support for fire prevention, which also can provide a new way for fire anomaly detection in the similar mine.

Factors affecting fuel break effectiveness in the control of large fires on the Los Padres National Forest, California

USGS Publications Warehouse

Syphard, Alexandra D.; Keeley, Jon E.; Brennan, Teresa J.

2011-01-01

As wildfires have increased in frequency and extent, so have the number of homes developed in the wildland-urban interface. In California, the predominant approach to mitigating fire risk is construction of fuel breaks, but there has been little empirical study of their role in controlling large fires.We constructed a spatial database of fuel breaks on the Los Padres National Forest in southern California to better understand characteristics of fuel breaks that affect the behaviour of large fires and to map where fires and fuel breaks most commonly intersect. We evaluated whether fires stopped or crossed over fuel breaks over a 28-year period and compared the outcomes with physical characteristics of the sites, weather and firefighting activities during the fire event. Many fuel breaks never intersected fires, but others intersected several, primarily in historically fire-prone areas. Fires stopped at fuel breaks 46% of the time, almost invariably owing to fire suppression activities. Firefighter access to treatments, smaller fires and longer fuel breaks were significant direct influences, and younger vegetation and fuel break maintenance indirectly improved the outcome by facilitating firefighter access. This study illustrates the importance of strategic location of fuel breaks because they have been most effective where they provided access for firefighting activities.

Determination of iridium in mafic rocks by atomic absorption

USGS Publications Warehouse

Grimaldi, F.S.; Schnepfe, M.M.

1970-01-01

Iridium is determined in mineralized mafic rocks by atomic absorption after fire-assay concentration into a gold bead. Interelement interferences in the atomic-absorption determination are removed and Ir sensitivity is increased by buffering the solutions with a mixture of copper and sodium sulphates. Substantial amounts of Ag, Al, Au, Bi, Ca, Cd, Co, Cr, Fe, Ho, Hg, K, La, Mg, Mn, Mo, Ni, Pb, Te, Ti, V, Y, Zn and platinum metals can be tolerated in the atomic-absorption determination. The sensitivity and detection limits are 3.2 and 0.25 ppm of Ir, respectively. ?? 1970.

Assessing post-fire ground cover in Mediterranean shrublands with field spectrometry and digital photography

NASA Astrophysics Data System (ADS)

Montorio Llovería, Raquel; Pérez-Cabello, Fernando; García-Martín, Alberto

2016-09-01

Fire severity can be assessed by identifying and quantifying the fractional abundance of post-fire ground cover types, an approach with great capacity to predict ecosystem response. Focused on shrubland formations of Mediterranean-type ecosystems, three burned areas (Ibieca and Zuera wildfires and Peñaflor experimental fire) were sampled in the summers of 2006 and 2007. Two different ground measurements were made for each of the 356 plots: (i) 3-band high spatial resolution photography (HSRP) and (ii) the hemispherical-conical reflectance factor (HCRF) in the visible to near-infrared spectral range (VNIR, 400-900 nm). Stepwise multiple lineal regression (SMLR) models were fitted to spectral variables (HCRF, first derivative spectra or FDS, and four absorption indices) to estimate the fractional cover of seven post-fire ground cover types (vegetation and soil - unburned and charred components - and ash - char and ash, individually and as a combined category). Models were developed and validated at the Peñaflor site (training, n = 217; validation, n = 88) and applied to the samples from the Ibieca and Zuera sites (n = 51). The best results were observed for the abundance estimations of green vegetation (Radj.20.70-0.90), unburned soil (Radj.20.40-0.75), and the combination of ashes (Radj.20.65-0.80). In comparison of spectral data, FDS outperforms reflectance or absorption data because of its higher accuracy levels and, importantly, its greater capacity to yield generalizable models. Future efforts should be made to improve the estimation of intermediate severity levels and upscaling the developed models. In the context of fire severity assessment, our study demonstrates the potential of hyperspectral data to estimate in a quick and objective manner post-fire ground cover fractions and thus provide valuable information to guide management responses.

Constraining Carbonaceous Aerosol Climate Forcing by Bridging Laboratory, Field and Modeling Studies

NASA Astrophysics Data System (ADS)

Dubey, M. K.; Aiken, A. C.; Liu, S.; Saleh, R.; Cappa, C. D.; Williams, L. R.; Donahue, N. M.; Gorkowski, K.; Ng, N. L.; Mazzoleni, C.; China, S.; Sharma, N.; Yokelson, R. J.; Allan, J. D.; Liu, D.

2014-12-01

Biomass and fossil fuel combustion emits black (BC) and brown carbon (BrC) aerosols that absorb sunlight to warm climate and organic carbon (OC) aerosols that scatter sunlight to cool climate. The net forcing depends strongly on the composition, mixing state and transformations of these carbonaceous aerosols. Complexities from large variability of fuel types, combustion conditions and aging processes have confounded their treatment in models. We analyse recent laboratory and field measurements to uncover fundamental mechanism that control the chemical, optical and microphysical properties of carbonaceous aerosols that are elaborated below: Wavelength dependence of absorption and the single scattering albedo (ω) of fresh biomass burning aerosols produced from many fuels during FLAME-4 was analysed to determine the factors that control the variability in ω. Results show that ω varies strongly with fire-integrated modified combustion efficiency (MCEFI)—higher MCEFI results in lower ω values and greater spectral dependence of ω (Liu et al GRL 2014). A parameterization of ω as a function of MCEFI for fresh BB aerosols is derived from the laboratory data and is evaluated by field data, including BBOP. Our laboratory studies also demonstrate that BrC production correlates with BC indicating that that they are produced by a common mechanism that is driven by MCEFI (Saleh et al NGeo 2014). We show that BrC absorption is concentrated in the extremely low volatility component that favours long-range transport. We observe substantial absorption enhancement for internally mixed BC from diesel and wood combustion near London during ClearFlo. While the absorption enhancement is due to BC particles coated by co-emitted OC in urban regions, it increases with photochemical age in rural areas and is simulated by core-shell models. We measure BrC absorption that is concentrated in the extremely low volatility components and attribute it to wood burning. Our results support enhanced light absorption by internally mixed BC parameterizations in models and identify mixed biomass and fossil combustion regions where this effect is large. We unify the treatment of carbonaceous aerosol components and their interactions to simplify and verify their representation in climate models, and re-evaluate their direct radiative forcing.

Absorption, Transmission and Amplification in a Double-Cavity Optomechanical System with Coulomb-Interaction

NASA Astrophysics Data System (ADS)

Geng, H.; Liu, H. D.

2018-04-01

We explore three interesting phenomena in a double-cavity optomechanical system: coherent perfect absorption, coherent perfect transmission and output signal amplification, and find that these phenomena can be realized and controlled by the coulomb-interaction between the dissipative oscillator locates in the cavity and the gain oscillator locates outside. They originate from the efficient hybrid coupling of optical and mechanical modes, and can be used for realizing novel photonic devices in quantum information networks.

SOXAL{trademark} pilot plant demonstration at Niagara Mohawk`s Dunkirk Station

DOE Office of Scientific and Technical Information (OSTI.GOV)

Strangway, P.K.

This paper describes a six-month, nominal three megawatt (3 MW) pilot plant demonstration of the SOXAL{trademark} regenerative flue gas desulfurization (FGD) process at Niagara Mohawk Power Corporation`s Dunkirk, NY coal-fired power station. Using a slip-stream of flue gas from an actual coal-fired boiler, the pilot plant successfully demonstrated the absorption of sulfur dioxide and the simultaneous regeneration of sodium-based scrubbing liquor via bipolar membrane electrodialysis. Sulfur dioxide removal efficiency of greater than 98% was routinely achieved. The absorption and regeneration stages were both proven reliable and controllable. The pilot plant was successfully operated in both continuous and decoupled modes ofmore » operation, thus demonstrating the flexibility of this process.« less

Development of fly ash boards with thermal, acoustic and fire insulation properties.

PubMed

Leiva, C; Arenas, C; Vilches, L F; Alonso-Fariñas, B; Rodriguez-Galán, M

2015-12-01

This paper presents an experimental analysis on a new board composed of gypsum and fly ashes from coal combustion, which are mutually compatible. Physical and mechanical properties, sound absorption coefficient, thermal properties and leaching test have been obtained. The mechanical properties showed similar values to other commercial products. As far as the acoustic insulation characteristics are concerned, sound absorption coefficients of 0.3 and 0.8 were found. The board presents a low thermal conductivity and a fire resistance higher than 50 min (for 4 cm of thickness). The leaching of trace elements was below the leaching limit values. These boards can be considered as suitable to be used in building applications as partitions. Copyright © 2015 Elsevier Ltd. All rights reserved.

Low Reynolds Number Droplet Combustion In CO2 Enriched Atmospheres In Microgravity

NASA Technical Reports Server (NTRS)

Hicks, M. C.

2003-01-01

The effect of radiative feedback from the gas phase in micro-gravity combustion processes has been of increasing concern because of the implications in the selection and evaluation of appropriate fire suppressants. The use of CO2, an optically thick gas in the infrared region of the electromagnetic spectrum, has garnered widespread acceptance as an effective fire suppressant for most ground based applications. Since buoyant forces often dominate the flow field in 1-g environments the temperature field between the flame front and the fuel surface is not significantly affected by gas phase radiative absorption and re-emission as these hot gases are quickly swept downstream. However, in reduced gravity environments where buoyant-driven convective flows are negligible and where low-speed forced convective flows may be present at levels where gas phase radiation becomes important, then changes in environment that enhance gas phase radiative effects need to be better understood. This is particularly true in assessments of flammability limits and selection of appropriate fire suppressants for future space applications. In recognition of this, a ground-based investigation has been established that uses a droplet combustion configuration to systematically study the effects of enhanced gas phase radiation on droplet burn rates, flame structure, and radiative output from the flame zone.

Resistance of the boreal forest to high burn rates.

PubMed

Héon, Jessie; Arseneault, Dominique; Parisien, Marc-André

2014-09-23

Boreal ecosystems and their large carbon stocks are strongly shaped by extensive wildfires. Coupling climate projections with records of area burned during the last 3 decades across the North American boreal zone suggests that area burned will increase by 30-500% by the end of the 21st century, with a cascading effect on ecosystem dynamics and on the boreal carbon balance. Fire size and the frequency of large-fire years are both expected to increase. However, how fire size and time since previous fire will influence future burn rates is poorly understood, mostly because of incomplete records of past fire overlaps. Here, we reconstruct the length of overlapping fires along a 190-km-long transect during the last 200 y in one of the most fire-prone boreal regions of North America to document how fire size and time since previous fire will influence future fire recurrence. We provide direct field evidence that extreme burn rates can be sustained by a few occasional droughts triggering immense fires. However, we also show that the most fire-prone areas of the North American boreal forest are resistant to high burn rates because of overabundant young forest stands, thereby creating a fuel-mediated negative feedback on fire activity. These findings will help refine projections of fire effect on boreal ecosystems and their large carbon stocks.

Resistance of the boreal forest to high burn rates

PubMed Central

Héon, Jessie; Arseneault, Dominique; Parisien, Marc-André

2014-01-01

Boreal ecosystems and their large carbon stocks are strongly shaped by extensive wildfires. Coupling climate projections with records of area burned during the last 3 decades across the North American boreal zone suggests that area burned will increase by 30–500% by the end of the 21st century, with a cascading effect on ecosystem dynamics and on the boreal carbon balance. Fire size and the frequency of large-fire years are both expected to increase. However, how fire size and time since previous fire will influence future burn rates is poorly understood, mostly because of incomplete records of past fire overlaps. Here, we reconstruct the length of overlapping fires along a 190-km-long transect during the last 200 y in one of the most fire-prone boreal regions of North America to document how fire size and time since previous fire will influence future fire recurrence. We provide direct field evidence that extreme burn rates can be sustained by a few occasional droughts triggering immense fires. However, we also show that the most fire-prone areas of the North American boreal forest are resistant to high burn rates because of overabundant young forest stands, thereby creating a fuel-mediated negative feedback on fire activity. These findings will help refine projections of fire effect on boreal ecosystems and their large carbon stocks. PMID:25201981

Self-Extinguishing Lithium Ion Batteries Based on Internally Embedded Fire-Extinguishing Microcapsules with Temperature-Responsiveness.

PubMed

Yim, Taeeun; Park, Min-Sik; Woo, Sang-Gil; Kwon, Hyuk-Kwon; Yoo, Jung-Keun; Jung, Yeon Sik; Kim, Ki Jae; Yu, Ji-Sang; Kim, Young-Jun

2015-08-12

User safety is one of the most critical issues for the successful implementation of lithium ion batteries (LIBs) in electric vehicles and their further expansion in large-scale energy storage systems. Herein, we propose a novel approach to realize self-extinguishing capability of LIBs for effective safety improvement by integrating temperature-responsive microcapsules containing a fire-extinguishing agent. The microcapsules are designed to release an extinguisher agent upon increased internal temperature of an LIB, resulting in rapid heat absorption through an in situ endothermic reaction and suppression of further temperature rise and undesirable thermal runaway. In a standard nail penetration test, the temperature rise is reduced by 74% without compromising electrochemical performances. It is anticipated that on the strengths of excellent scalability, simplicity, and cost-effectiveness, this novel strategy can be extensively applied to various high energy-density devices to ensure human safety.

Contrasting fire responses to climate and management: insights from two Australian ecosystems.

PubMed

King, Karen J; Cary, Geoffrey J; Bradstock, Ross A; Marsden-Smedley, Jonathan B

2013-04-01

This study explores effects of climate change and fuel management on unplanned fire activity in ecosystems representing contrasting extremes of the moisture availability spectrum (mesic and arid). Simulation modelling examined unplanned fire activity (fire incidence and area burned, and the area burned by large fires) for alternate climate scenarios and prescribed burning levels in: (i) a cool, moist temperate forest and wet moorland ecosystem in south-west Tasmania (mesic); and (ii) a spinifex and mulga ecosystem in central Australia (arid). Contemporary fire activity in these case study systems is limited, respectively, by fuel availability and fuel amount. For future climates, unplanned fire incidence and area burned increased in the mesic landscape, but decreased in the arid landscape in accordance with predictions based on these limiting factors. Area burned by large fires (greater than the 95th percentile of historical, unplanned fire size) increased with future climates in the mesic landscape. Simulated prescribed burning was more effective in reducing unplanned fire activity in the mesic landscape. However, the inhibitory effects of prescribed burning are predicted to be outweighed by climate change in the mesic landscape, whereas in the arid landscape prescribed burning reinforced a predicted decline in fire under climate change. The potentially contrasting direction of future changes to fire will have fundamentally different consequences for biodiversity in these contrasting ecosystems, and these will need to be accommodated through contrasting, innovative management solutions. © 2012 Blackwell Publishing Ltd.

[Euthanasia and the doctrine of double effect].

PubMed

Klein, Martin

2005-01-01

Direct active euthanasia is prohibited in most countries while passive and indirect is not. However, many arguments against the legalization of voluntary active euthanasia are flawed. Ethical differences between active and passive or indirect euthanasia are difficult to maintain especially when the passivity of the actor causes death. The crucial point is not activity or passivity but respect for the autonomy of individual human beings. In particular there appears to be little ethical difference between active and indirect euthanasia. Indirect euthanasia has often been justified by the principle of double effect, which traces back to Thomas Aquinas. But resorting to this rule contains a logical fallacy. The principle of double effect does not allow foreseen and unwanted adverse effects of an action to occur when they are avoidable. In terminal sedation, an example for indirect euthanasia, hypoxemia and dehydration can easily be prevented by respirator therapy and fluid administration. Therefore the rule of double effect is not applicable. Indirect and direct active euthanasia cannot be ethically distinguished by resorting to the principle of double effect.

At the nexus of fire, water and society

USGS Publications Warehouse

Martin, Deborah

2016-01-01

The societal risks of water scarcity and water-quality impairment have received considerable attention, evidenced by recent analyses of these topics by the 2030 Water Resources Group, the United Nations and the World Economic Forum. What are the effects of fire on the predicted water scarcity and declines in water quality? Drinking water supplies for humans, the emphasis of this exploration, are derived from several land cover types, including forests, grasslands and peatlands, which are vulnerable to fire. In the last two decades, fires have affected the water supply catchments of Denver (CO) and other southwestern US cities, and four major Australian cities including Sydney, Canberra, Adelaide and Melbourne. In the same time period, several, though not all, national, regional and global water assessments have included fire in evaluations of the risks that affect water supplies. The objective of this discussion is to explore the nexus of fire, water and society with the hope that a more explicit understanding of fire effects on water supplies will encourage the incorporation of fire into future assessments of water supplies, into the pyrogeography conceptual framework and into planning efforts directed at water resiliency.

Enhanced absorption cycle computer model

NASA Astrophysics Data System (ADS)

Grossman, G.; Wilk, M.

1993-09-01

Absorption heat pumps have received renewed and increasing attention in the past two decades. The rising cost of electricity has made the particular features of this heat-powered cycle attractive for both residential and industrial applications. Solar-powered absorption chillers, gas-fired domestic heat pumps, and waste-heat-powered industrial temperature boosters are a few of the applications recently subjected to intensive research and development. The absorption heat pump research community has begun to search for both advanced cycles in various multistage configurations and new working fluid combinations with potential for enhanced performance and reliability. The development of working absorption systems has created a need for reliable and effective system simulations. A computer code has been developed for simulation of absorption systems at steady state in a flexible and modular form, making it possible to investigate various cycle configurations with different working fluids. The code is based on unit subroutines containing the governing equations for the system's components and property subroutines containing thermodynamic properties of the working fluids. The user conveys to the computer an image of his cycle by specifying the different subunits and their interconnections. Based on this information, the program calculates the temperature, flow rate, concentration, pressure, and vapor fraction at each state point in the system, and the heat duty at each unit, from which the coefficient of performance (COP) may be determined. This report describes the code and its operation, including improvements introduced into the present version. Simulation results are described for LiBr-H2O triple-effect cycles, LiCl-H2O solar-powered open absorption cycles, and NH3-H2O single-effect and generator-absorber heat exchange cycles. An appendix contains the user's manual.

Wildfires and animal extinctions at the Cretaceous/Tertiary boundary

NASA Astrophysics Data System (ADS)

Adair, Robert K.

2010-06-01

Persuasive models of the ejection of material at high velocities from the Chicxulub asteroid impact marking the Cretaceous/Tertiary boundary have led to the conclusion that upon return, that material, heated in passage through the upper atmosphere, generated a high level of infrared energy density over the Earth's surface. That radiant energy has been considered to be a direct source of universal wildfires, which were presumed to be a major cause of plant and animal species extinctions. The extinction of many animal species, especially the dinosaurs, has also been attributed to the immediate lethal effects of the radiation. I find that the absorption of the radiation by the atmosphere, by cloud formations, and by ejecta drifting in the lower atmosphere reduced the radiation at the surface to a level that cannot be expected to have generated universal fires. Although the reduced radiation will have likely caused severe injuries to many animals, such insults alone seem unlikely to have generated the overall species extinctions that have been deduced.

Interactive effects of historical logging and fire exclusion on ponderosa pine forest structure in the northern Rockies.

PubMed

Naficy, Cameron; Sala, Anna; Keeling, Eric G; Graham, Jon; DeLuca, Thomas H

2010-10-01

Increased forest density resulting from decades of fire exclusion is often perceived as the leading cause of historically aberrant, severe, contemporary wildfires and insect outbreaks documented in some fire-prone forests of the western United States. Based on this notion, current U.S. forest policy directs managers to reduce stand density and restore historical conditions in fire-excluded forests to help minimize high-severity disturbances. Historical logging, however, has also caused widespread change in forest vegetation conditions, but its long-term effects on vegetation structure and composition have never been adequately quantified. We document that fire-excluded ponderosa pine forests of the northern Rocky Mountains logged prior to 1960 have much higher average stand density, greater homogeneity of stand structure, more standing dead trees and increased abundance of fire-intolerant trees than paired fire-excluded, unlogged counterparts. Notably, the magnitude of the interactive effect of fire exclusion and historical logging substantially exceeds the effects of fire exclusion alone. These differences suggest that historically logged sites are more prone to severe wildfires and insect outbreaks than unlogged, fire-excluded forests and should be considered a high priority for fuels reduction treatments. Furthermore, we propose that ponderosa pine forests with these distinct management histories likely require distinct restoration approaches. We also highlight potential long-term risks of mechanical stand manipulation in unlogged forests and emphasize the need for a long-term view of fuels management.

A multi-satellite analysis of the direct radiative effects of absorbing aerosols above clouds

NASA Astrophysics Data System (ADS)

Chang, Y. Y.; Christopher, S. A.

2015-12-01

Radiative effects of absorbing aerosols above liquid water clouds in the southeast Atlantic as a function of fire sources are investigated using A-Train data coupled with the Visible Infrared Imaging Radiometer Suite (VIIRS) onboard Suomi National Polar-orbiting Partnership (Suomi NPP). Both the VIIRS Active Fire product and the Aqua Moderate Resolution Imaging Spectroradiometer (MODIS) Thermal Anomalies product (MYD14) are used to identify the biomass burning fire origin in southern Africa. The Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) are used to assess the aerosol type, aerosol altitude, and cloud altitude. We use back trajectory information, wind data, and the Fire Locating and Modeling of Burning Emissions (FLAMBE) product to infer the transportation of aerosols from the fire source to the CALIOP swath in the southeast Atlantic during austral winter.

Fire Suppression Properties of Very Fine Water Mist

DTIC Science & Technology

2005-01-01

with the University of Heidelberg, developed an in situ oxygen sensor based on tunable diode laser absorption spectroscopy ( TDLAS ) to provide absolute... oxygen number densities in the presence of mist.3 Th e TDLAS oxygen sensor provides real-time, calibra- tion-free, quantitative oxygen ...Determination of Molecular Oxygen Concentrations in Full-Scale Fire Suppression Tests Using TDLAS ,” Proc. Combust. Inst. 29, 353-360 (2002).

Saliency Detection and Deep Learning-Based Wildfire Identification in UAV Imagery

PubMed Central

Zhao, Yi; Ma, Jiale; Li, Xiaohui

2018-01-01

An unmanned aerial vehicle (UAV) equipped with global positioning systems (GPS) can provide direct georeferenced imagery, mapping an area with high resolution. So far, the major difficulty in wildfire image classification is the lack of unified identification marks, the fire features of color, shape, texture (smoke, flame, or both) and background can vary significantly from one scene to another. Deep learning (e.g., DCNN for Deep Convolutional Neural Network) is very effective in high-level feature learning, however, a substantial amount of training images dataset is obligatory in optimizing its weights value and coefficients. In this work, we proposed a new saliency detection algorithm for fast location and segmentation of core fire area in aerial images. As the proposed method can effectively avoid feature loss caused by direct resizing; it is used in data augmentation and formation of a standard fire image dataset ‘UAV_Fire’. A 15-layered self-learning DCNN architecture named ‘Fire_Net’ is then presented as a self-learning fire feature exactor and classifier. We evaluated different architectures and several key parameters (drop out ratio, batch size, etc.) of the DCNN model regarding its validation accuracy. The proposed architecture outperformed previous methods by achieving an overall accuracy of 98%. Furthermore, ‘Fire_Net’ guarantied an average processing speed of 41.5 ms per image for real-time wildfire inspection. To demonstrate its practical utility, Fire_Net is tested on 40 sampled images in wildfire news reports and all of them have been accurately identified. PMID:29495504

Limitations imposed on fire PRA methods as the result of incomplete and uncertain fire event data.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nowlen, Steven Patrick; Hyslop, J. S.

2010-04-01

Fire probabilistic risk assessment (PRA) methods utilize data and insights gained from actual fire events in a variety of ways. For example, fire occurrence frequencies, manual fire fighting effectiveness and timing, and the distribution of fire events by fire source and plant location are all based directly on the historical experience base. Other factors are either derived indirectly or supported qualitatively based on insights from the event data. These factors include the general nature and intensity of plant fires, insights into operator performance, and insights into fire growth and damage behaviors. This paper will discuss the potential methodology improvements thatmore » could be realized if more complete fire event reporting information were available. Areas that could benefit from more complete event reporting that will be discussed in the paper include fire event frequency analysis, analysis of fire detection and suppression system performance including incipient detection systems, analysis of manual fire fighting performance, treatment of fire growth from incipient stages to fully-involved fires, operator response to fire events, the impact of smoke on plant operations and equipment, and the impact of fire-induced cable failures on plant electrical circuits.« less

Hydrocarbon characterization experiments in fully turbulent fires : results and data analysis.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Suo-Anttila, Jill Marie; Blanchat, Thomas K.

As the capabilities of numerical simulations increase, decision makers are increasingly relying upon simulations rather than experiments to assess risks across a wide variety of accident scenarios including fires. There are still, however, many aspects of fires that are either not well understood or are difficult to treat from first principles due to the computational expense. For a simulation to be truly predictive and to provide decision makers with information which can be reliably used for risk assessment the remaining physical processes must be studied and suitable models developed for the effects of the physics. The model for the fuelmore » evaporation rate in a liquid fuel pool fire is significant because in well-ventilated fires the evaporation rate largely controls the total heat release rate from the fire. This report describes a set of fuel regression rates experiments to provide data for the development and validation of models. The experiments were performed with fires in the fully turbulent scale range (> 1 m diameter) and with a number of hydrocarbon fuels ranging from lightly sooting to heavily sooting. The importance of spectral absorption in the liquid fuels and the vapor dome above the pool was investigated and the total heat flux to the pool surface was measured. The importance of convection within the liquid fuel was assessed by restricting large scale liquid motion in some tests. These data sets provide a sound, experimentally proven basis for assessing how much of the liquid fuel needs to be modeled to enable a predictive simulation of a fuel fire given the couplings between evaporation of fuel from the pool and the heat release from the fire which drives the evaporation.« less

The sociology of landowner interest in restoring fire-adapted, biodiverse habitats in the wildland-urban interface of Oregon's Willamette Valley ecoregion

Treesearch

Max Nielsen-Pincus; Robert G. Ribe; Bart R. Johnson

2011-01-01

In many parts of the world, the combined effects of wildfire, climate change, and population growth in the wildland-urban interface pose increasing risks to both people and biodiversity. These risks are exemplified in western Oregon's Willamette Valley Ecoregion, where population is projected to double by 2050 and climate change is expected to increase wildfire...

Effect of air velocity and direction for indirect evaporative cooling in tropical area

NASA Astrophysics Data System (ADS)

Ayodha Ajiwiguna, Tri; Nugraha Rismi, Fadhlin; Ramdlan Kirom, Mukhammad

2017-06-01

In this research, experimental study of heat absorption rate caused by indirect evaporative cooling is performed by varying the velocity and direction of air. The ambient is at average temperature and relative humidity of 28.7 °C and 78% respectively. The experiment is conducted by attaching wet medium on the top of material reference plate with the dimension of 14 x 8 cm with 5 mm thickness. To get evaporative cooling effect, the air flow is directed to the wet medium with velocity from 1.6 m/s to 3.4 m/s with the increment of 0.2 m/s. The direction of air is set 0° (parallel), 45° (inclined), and 90° (perpendicular) to the wet medium surface. While the experiment is being performed, the air temperature, top and bottom of plate temperature are measured simultaneously after steady state condition is established. Based on the measurement result, heat absorption is calculated by analysing the heat conduction on the material reference. The result shows that the heat absorption rate is increased by higher velocity. Perpendicular direction of air flow results the highest cooling capacity compared with other direction. The maximum heat absorption rate is achieved at 13.9 Watt with 3.4 m/s velocity and perpendicular direction of air.

Soft pair excitations and double-log divergences due to carrier interactions in graphene

NASA Astrophysics Data System (ADS)

Lewandowski, Cyprian; Levitov, L. S.

2018-03-01

Interactions between charge carriers in graphene lead to logarithmic renormalization of observables mimicking the behavior known in (3+1)-dimensional quantum electrodynamics (QED). Here we analyze soft electron-hole (e -h ) excitations generated as a result of fast charge dynamics, a direct analog of the signature QED effect—multiple soft photons produced by the QED vacuum shakeup. We show that such excitations are generated in photon absorption, when a photogenerated high-energy e -h pair cascades down in energy and gives rise to multiple soft e -h excitations. This fundamental process is manifested in a double-log divergence in the emission rate of soft pairs and a characteristic power-law divergence in their energy spectrum of the form 1/ω ln(ω/Δ ) . Strong carrier-carrier interactions make pair production a prominent pathway in the photoexcitation cascade.

[Analysis on the long-term effects of modified double endobutton technique in the treatment of Tossy type III acromioclavicular joint dislocations].

PubMed

Yan, Rui-Jian; Lu, Jian-Wei; Zhang, Chun

2014-01-01

To investigate the long-term clinical effects of modified double Endobutton technique for the treatment of acromioclavicular joint dislocations of Tossy type III. A retrospective study was done in 42 patients with acromioclavicular joint dislocations of Tossy type III treated with modified double Endobutton technique from December 2008 to December 2010. There were 24 males and 18 females, ranging in age from 21 to 56 years old (averaged, 32.5 years old). All the patients were treated with open reduction, coracoclavicular ligament reconstruction using double Endobutton technique, and repair of acromioclavicular ligament. The Karlsson system was used to evaluate therapeutic effects. The distance from coracoid to clavicle was measured to evaluate reduction loss. All the patients were followed up, and the duration ranged from 2.0 to 3.2 years (averaged,2.4 years). According to Karlsson system, 32 patients got an A degree and 10 patients got a B degree at three months post-operatively; 26 patients got an A degree and 16 patients got a B degree at the latest follow-up; 6 patients got an A degree at 3 months after operation lowered to B degree at the latest follow-up. The coracoid-clavicle distance increased from (26.91 +/- 0.91) mm at 3 months after operation to (27.41 +/- 1.10) mm at the latest follow-up. Te patients treated with over-reduction during operation or with heavy physical labour work after operation had obvious widened coracoid-clavicle distance. Bone absorption was found around the plate in most cases, mainly in the clavicular side. Treatment for acromioclavicular joint dislocations of Tossy type III with modified double Endobutton technique has satisfactory early clinical results. But with time passing, loss of reduction and bone absorption around the plate could be observed, and clinical outcomes of some cases downgrade during the long-term follow-up.

Diode Lasers and Practical Trace Analysis.

ERIC Educational Resources Information Center

Imasaka, Totaro; Nobuhiko, Ishibashi

1990-01-01

Applications of lasers to molecular absorption spectrometry, molecular fluorescence spectrometry, visible semiconductor fluorometry, atomic absorption spectrometry, and atomic fluorescence spectrometry are discussed. Details of the use of the frequency-doubled diode laser are provided. (CW)

Influence of absorption by environmental water vapor on radiation transfer in wildland fires

Treesearch

D. Frankman; B. W. Webb; B. W. Butler

2008-01-01

The attenuation of radiation transfer from wildland flames to fuel by environmental water vapor is investigated. Emission is tracked from points on an idealized flame to locations along the fuel bed while accounting for absorption by environmental water vapor in the intervening medium. The Spectral Line Weighted-sum-of-gray-gases approach was employed for treating the...

Damage Caused to Polyurethane Foams by Aging, Simulated Sunlight Exposure, Heat and Fire

DTIC Science & Technology

1984-07-01

vented configuration ............ .................. 11 4 Sample of the tan-colored solid formed upon pyrolysis of blue foam ..... .............. .. 21...54 26 Infrared absorption spectrum of the solid, tan-colored pyrolysis product formed from blue polyurethane foam ..... .............. .. 55 27...Infrared absorption spectrum of the liquid, brown-colored pyrolysis product formed from blue polyurethane foam ..... .............. .. 56 28 Fuel vent

Optoelectronic and photoacoustic studies of an organic dye synthesized through green route

NASA Astrophysics Data System (ADS)

Vijayakumar, S.; Sreelatha, S.; Hatamimoslehabadi, M.; Yelleswarappu, C. S.

2017-10-01

An azo dye was prepared through an environmentally benign and economically feasible synthesis route with cardanol as a starting material. Cardanol is a cost-effective and renewable natural source obtained from Cashew Nut Shell Liquid, a by-product of the cashew industry. The dye was spectrally characterized by IR, UV-Vis, NMR and fluorescence studies. UV-Vis absorption showed a bathochromic shift between solvents of lower and higher polarities. Nonlinear optical and photoacoustic properties were studied using a frequency doubled Nd:YAG laser producing 532 nm laser pulses of 3 ns pulse width. Results show that the nonlinear absorption coefficient decreases with the increase of on-axis intensity, suggesting excited state absorption as the principal mechanism. The observed nonlinearity has applications in optoelectronics.

Patterns of Canopy and Surface Layer Consumption in a Boreal Forest Fire from Repeat Airborne Lidar

NASA Technical Reports Server (NTRS)

Alonzo, Michael; Morton, Douglas C.; Cook, Bruce D.; Andersen, Hans-Erik; Babcock, Chad; Pattison, Robert

2017-01-01

Fire in the boreal region is the dominant agent of forest disturbance with direct impacts on ecosystem structure, carbon cycling, and global climate. Global and biome-scale impacts are mediated by burn severity, measured as loss of forest canopy and consumption of the soil organic layer. To date, knowledge of the spatial variability in burn severity has been limited by sparse field sampling and moderate resolution satellite data. Here, we used pre- and post-fire airborne lidar data to directly estimate changes in canopy vertical structure and surface elevation for a 2005 boreal forest fire on Alaskas Kenai Peninsula. We found that both canopy and surface losses were strongly linked to pre-fire species composition and exhibited important fine-scale spatial variability at sub-30m resolution. The fractional reduction in canopy volume ranged from 0.61 in lowland black spruce stands to 0.27 in mixed white spruce and broad leaf forest. Residual structure largely reflects standing dead trees, highlighting the influence of pre-fire forest structure on delayed carbon losses from above ground biomass, post-fire albedo, and variability in understory light environments. Median loss of surface elevation was highest in lowland black spruce stands (0.18 m) but much lower in mixed stands (0.02 m), consistent with differences in pre-fire organic layer accumulation. Spatially continuous depth-of-burn estimates from repeat lidar measurements provide novel information to constrain carbon emissions from the surface organic layer and may inform related research on post-fire successional trajectories. Spectral measures of burn severity from Landsat were correlated with canopy (r = 0.76) and surface (r = -0.71) removal in black spruce stands but captured less of the spatial variability in fire effects for mixed stands (canopy r = 0.56, surface r = -0.26), underscoring the difficulty in capturing fire effects in heterogeneous boreal forest landscapes using proxy measures of burn severity from Landsat.

Patterns of canopy and surface layer consumption in a boreal forest fire from repeat airborne lidar

NASA Astrophysics Data System (ADS)

Alonzo, Michael; Morton, Douglas C.; Cook, Bruce D.; Andersen, Hans-Erik; Babcock, Chad; Pattison, Robert

2017-05-01

Fire in the boreal region is the dominant agent of forest disturbance with direct impacts on ecosystem structure, carbon cycling, and global climate. Global and biome-scale impacts are mediated by burn severity, measured as loss of forest canopy and consumption of the soil organic layer. To date, knowledge of the spatial variability in burn severity has been limited by sparse field sampling and moderate resolution satellite data. Here, we used pre- and post-fire airborne lidar data to directly estimate changes in canopy vertical structure and surface elevation for a 2005 boreal forest fire on Alaska’s Kenai Peninsula. We found that both canopy and surface losses were strongly linked to pre-fire species composition and exhibited important fine-scale spatial variability at sub-30 m resolution. The fractional reduction in canopy volume ranged from 0.61 in lowland black spruce stands to 0.27 in mixed white spruce and broadleaf forest. Residual structure largely reflects standing dead trees, highlighting the influence of pre-fire forest structure on delayed carbon losses from aboveground biomass, post-fire albedo, and variability in understory light environments. Median loss of surface elevation was highest in lowland black spruce stands (0.18 m) but much lower in mixed stands (0.02 m), consistent with differences in pre-fire organic layer accumulation. Spatially continuous depth-of-burn estimates from repeat lidar measurements provide novel information to constrain carbon emissions from the surface organic layer and may inform related research on post-fire successional trajectories. Spectral measures of burn severity from Landsat were correlated with canopy (r = 0.76) and surface (r = -0.71) removal in black spruce stands but captured less of the spatial variability in fire effects for mixed stands (canopy r = 0.56, surface r = -0.26), underscoring the difficulty in capturing fire effects in heterogeneous boreal forest landscapes using proxy measures of burn severity from Landsat.

Double-blind comparison of the two hallucinogens psilocybin and dextromethorphan: similarities and differences in subjective experiences.

PubMed

Carbonaro, Theresa M; Johnson, Matthew W; Hurwitz, Ethan; Griffiths, Roland R

2018-02-01

Although psilocybin and dextromethorphan (DXM) are hallucinogens, they have different receptor mechanisms of action and have not been directly compared. This study compared subjective, behavioral, and physiological effects of psilocybin and dextromethorphan under conditions that minimized expectancy effects. Single, acute oral doses of psilocybin (10, 20, 30 mg/70 kg), DXM (400 mg/70 kg), and placebo were administered under double-blind conditions to 20 healthy participants with histories of hallucinogen use. Instructions to participants and staff minimized expectancy effects. Various subjective, behavioral, and physiological effects were assessed after drug administration. High doses of both drugs produced similar increases in participant ratings of peak overall drug effect strength, with similar times to maximal effect and time-course. Psilocybin produced orderly dose-related increases on most participant-rated subjective measures previously shown sensitive to hallucinogens. DXM produced increases on most of these same measures. However, the high dose of psilocybin produced significantly greater and more diverse visual effects than DXM including greater movement and more frequent, brighter, distinctive, and complex (including textured and kaleidoscopic) images and visions. Compared to DXM, psilocybin also produced significantly greater mystical-type and psychologically insightful experiences and greater absorption in music. In contrast, DXM produced larger effects than psilocybin on measures of disembodiment, nausea/emesis, and light-headedness. Both drugs increased systolic blood pressure, heart rate, and pupil dilation and decreased psychomotor performance and balance. Psilocybin and DXM produced similar profiles of subjective experiences, with psilocybin producing relatively greater visual, mystical-type, insightful, and musical experiences, and DXM producing greater disembodiment.

Fire severity and tree regeneration following bark beetle outbreaks: the role of outbreak stage and burning conditions.

PubMed

Harvey, Brian J; Donato, Daniel C; Romme, William H; Turner, Monica G

The degree to which recent bark beetle (Dendroctonus ponderosae) outbreaks may influence fire severity and postfire tree regeneration is of heightened interest to resource managers throughout western North America, but empirical data on actual fire effects are lacking. Outcomes may depend on burning conditions (i.e., weather during fire), outbreak severity, or intervals between outbreaks and subsequent fire. We studied recent fires that burned through green-attack/red-stage (outbreaks <3 years before fire) and gray-stage (outbreaks 3–15 years before fire) subalpine forests dominated by lodgepole pine (Pinus contorta var. latifolia) in Greater Yellowstone, Wyoming, USA, to determine if fire severity was linked to prefire beetle outbreak severity and whether these two disturbances produced compound ecological effects on postfire tree regeneration. With field data from 143 postfire plots that burned under different conditions, we assessed canopy and surface fire severity, and postfire tree seedling density against prefire outbreak severity. In the green-attack/red stage, several canopy fire-severity measures increased with prefire outbreak severity under moderate burning conditions. Under extreme conditions, few fire-severity measures were related to prefire outbreak severity, and effect sizes were of marginal biological significance. The percentage of tree stems and basal area killed by fire increased with more green-attack vs. red-stage trees (i.e., the earliest stages of outbreak). In the gray stage, by contrast, most fire-severity measures declined with increasing outbreak severity under moderate conditions, and fire severity was unrelated to outbreak severity under extreme burning conditions. Postfire lodgepole pine seedling regeneration was unrelated to prefire outbreak severity in either post-outbreak stage, but increased with prefire serotiny. Results suggest bark beetle outbreaks can affect fire severity in subalpine forests under moderate burning conditions, but have little effect on fire severity under extreme burning conditions when most large wildfires occur in this system. Thus, beetle outbreak severity was moderately linked to fire severity, but the strength and direction of the linkage depended on both endogenous (outbreak stage) and exogenous (fire weather) factors. Closely timed beetle outbreak and fire did not impart compound effects on tree regeneration, suggesting the presence of a canopy seedbank may enhance resilience to their combined effects.

Model of large pool fires.

PubMed

Fay, J A

2006-08-21

A two zone entrainment model of pool fires is proposed to depict the fluid flow and flame properties of the fire. Consisting of combustion and plume zones, it provides a consistent scheme for developing non-dimensional scaling parameters for correlating and extrapolating pool fire visible flame length, flame tilt, surface emissive power, and fuel evaporation rate. The model is extended to include grey gas thermal radiation from soot particles in the flame zone, accounting for emission and absorption in both optically thin and thick regions. A model of convective heat transfer from the combustion zone to the liquid fuel pool, and from a water substrate to cryogenic fuel pools spreading on water, provides evaporation rates for both adiabatic and non-adiabatic fires. The model is tested against field measurements of large scale pool fires, principally of LNG, and is generally in agreement with experimental values of all variables.

Total Iron Absorption by Young Women from Iron-Biofortified Pearl Millet Composite Meals Is Double That from Regular Millet Meals but Less Than That from Post-Harvest Iron-Fortified Millet Meals123

PubMed Central

Cercamondi, Colin I.; Egli, Ines M.; Mitchikpe, Evariste; Tossou, Felicien; Zeder, Christophe; Hounhouigan, Joseph D.; Hurrell, Richard F.

2013-01-01

Iron biofortification of pearl millet (Pennisetum glaucum) is a promising approach to combat iron deficiency (ID) in the millet-consuming communities of developing countries. To evaluate the potential of iron-biofortified millet to provide additional bioavailable iron compared with regular millet and post-harvest iron-fortified millet, an iron absorption study was conducted in 20 Beninese women with marginal iron status. Composite test meals consisting of millet paste based on regular-iron, iron-biofortified, or post-harvest iron-fortified pearl millet flour accompanied by a leafy vegetable sauce or an okra sauce were fed as multiple meals for 5 d. Iron absorption was measured as erythrocyte incorporation of stable iron isotopes. Fractional iron absorption from test meals based on regular-iron millet (7.5%) did not differ from iron-biofortified millet meals (7.5%; P = 1.0), resulting in a higher quantity of total iron absorbed from the meals based on iron-biofortified millet (1125 vs. 527 μg; P < 0.0001). Fractional iron absorption from post-harvest iron-fortified millet meals (10.4%) was higher than from regular-iron and iron-biofortified millet meals (P < 0.05 and P < 0.01, respectively), resulting in a higher quantity of total iron absorbed from the post-harvest iron-fortified millet meals (1500 μg; P < 0.0001 and P < 0.05, respectively). Results indicate that consumption of iron-biofortified millet would double the amount of iron absorbed and, although fractional absorption of iron from biofortification is less than that from fortification, iron-biofortified millet should be highly effective in combatting ID in millet-consuming populations. PMID:23884388

At the nexus of fire, water and society

PubMed Central

2016-01-01

The societal risks of water scarcity and water-quality impairment have received considerable attention, evidenced by recent analyses of these topics by the 2030 Water Resources Group, the United Nations and the World Economic Forum. What are the effects of fire on the predicted water scarcity and declines in water quality? Drinking water supplies for humans, the emphasis of this exploration, are derived from several land cover types, including forests, grasslands and peatlands, which are vulnerable to fire. In the last two decades, fires have affected the water supply catchments of Denver (CO) and other southwestern US cities, and four major Australian cities including Sydney, Canberra, Adelaide and Melbourne. In the same time period, several, though not all, national, regional and global water assessments have included fire in evaluations of the risks that affect water supplies. The objective of this discussion is to explore the nexus of fire, water and society with the hope that a more explicit understanding of fire effects on water supplies will encourage the incorporation of fire into future assessments of water supplies, into the pyrogeography conceptual framework and into planning efforts directed at water resiliency. This article is part of the themed issue ‘The interaction of fire and mankind’. PMID:27216505

Landscape-scale quantification of fire-induced change in canopy cover following mountain pine beetle outbreak and timber harvest

USGS Publications Warehouse

McCarley, T. Ryan; Kolden, Crystal A.; Vaillant, Nicole M.; Hudak, Andrew T.; Smith, Alistair M.S.; Kreitler, Jason R.

2017-01-01

Across the western United States, the three primary drivers of tree mortality and carbon balance are bark beetles, timber harvest, and wildfire. While these agents of forest change frequently overlap, uncertainty remains regarding their interactions and influence on specific subsequent fire effects such as change in canopy cover. Acquisition of pre- and post-fire Light Detection and Ranging (LiDAR) data on the 2012 Pole Creek Fire in central Oregon provided an opportunity to isolate and quantify fire effects coincident with specific agents of change. This study characterizes the influence of pre-fire mountain pine beetle (MPB; Dendroctonus ponderosae) and timber harvest disturbances on LiDAR-estimated change in canopy cover. Observed canopy loss from fire was greater (higher severity) in areas experiencing pre-fire MPB (Δ 18.8%CC) than fire-only (Δ 11.1%CC). Additionally, increasing MPB intensity was directly related to greater canopy loss. Canopy loss was lower for all areas of pre-fire timber harvest (Δ 3.9%CC) than for fire-only, but among harvested areas, the greatest change was observed in the oldest treatments and the most intensive treatments [i.e., stand clearcut (Δ 5.0%CC) and combination of shelterwood establishment cuts and shelterwood removal cuts (Δ 7.7%CC)]. These results highlight the importance of accounting for and understanding the impact of pre-fire agents of change such as MPB and timber harvest on subsequent fire effects in land management planning. This work also demonstrates the utility of multi-temporal LiDAR as a tool for quantifying these landscape-scale interactions.

Selective ablation of sub- and supragingival calculus with a frequency-doubled Alexandrite laser

NASA Astrophysics Data System (ADS)

Rechmann, Peter; Hennig, Thomas

1995-05-01

In a preceding trial the absorption characteristics of subgingival calculus were calculated using fluorescence emission spectroscopy (excitation laser: N2-laser, wavelength 337 nm, pulse duration 4 ns). Subgingival calculus seems to contain chromophores absorbing in the ultraviolet spectral region up to 420 nm. The aim of the actual study was the ablation of sub- and supragingival calculus using a frequency doubled Alexandrite-laser (wavelength 377 nm, pulse duration 100 ns, repetition rate 110 Hz). Extracted human teeth presenting sub- and supragingival calculus were irradiated perpendicular to their axis with a laser fluence of 1 Jcm-2. Using a standard application protocol calculus was irradiated at the enamel surface, at the junction between enamel and root, and at the root surface (located on dentin or on cementum). During the irradiation procedure an effective water cooling-system was engaged. For light microscopical investigations undecalcified histological sections were prepared after treatment. The histological sections revealed that a selective and total removal of calculus is possible at all locations without ablation of healthy enamel, dentin or cementum. Even low fluences provide us with a high effectiveness for the ablation of calculus. Thus, based on different absorption characteristics and ablation thresholds, engaging a frequency doubled Alexandrite-laser a fast and, even more, a selective ablation of sub- and supragingival calculus is possible without adverse side effects to the surrounding tissues. Even more, microbial dental plaque can be perfectly removed.

High-energy long duration frequency-doubled Nd:YAG laser and application to venous occlusion

NASA Astrophysics Data System (ADS)

Zhang, Laiming; Yang, Guilong; Li, Dianjun; Lu, Qipeng; Gu, Huadong; Zhu, Linlin; Zhao, Zhenwu; Li, Xin; Tang, Yuguo; Guo, Jin

2005-01-01

Laser treatment represents an attractive option to other methods of vessel diseases especially varicose veins. A long pulse (30~50ms) 532nm laser (Fig.1) is used in our experiments with the pulse duration matching the thermal relaxation time of the vessels and the green laser matching the absorption spectrum peak of the blood. Laser irradiates nude vein vessels directly or exterior skin to finish operation faster and to acquire the practical data for upper enteron varicose vein treatment in several animal experiments performed in vivo. The 5J-energy pulse allows us to finely occlude rabbit or dog"s vein vessels up to 2 mm in diameter when irradiating them off external skin (Fig.2). Blood vessels are occluded at once and later biopsy specimens show the immediate and long-term lasting occlusion effect. While irradiating vessels directly (Fig.3), the vessels are usually irradiated to perforate, detailed causes are still under investigation. Animal experiments show long pulse green laser therapy is a safe and effective solution to the vein"s occlusion, which promises such laser with high energy of each pulse and 30~50 ms duration is an ideal candidate for vessel diseases treatment.

Simulation of a double-effect LiBr/H{sub 2}O absorption cooling system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wardono, B.; Nelson, R.

1996-10-01

Since commercially-available, double-effect, absorption cooling systems give relatively high performance for using solar energy or other medium-temperature sources, their performance was simulated and studied. To evaluate the cooling system performance, two objective functions were established: the system performance (COP) and the system cost. The system cost was used as the objective function to determine the optimum design of the system, while the COP was used to evaluate the effects of each variable on the system performance. The system optimization shows that there is an economic optimum heat-transfer area for each heat exchanger. Further study shows that this is a globalmore » minimum cost of the system. The best COPs that could be achieved by changing the heat-transfer areas and the inlet hot water temperature vary between 1.4 and 1.5. Higher COPs of approximately 1.6 were achieved if higher chilled water inlet temperatures or lower cooling water temperatures are used. These conditions are not desirable since higher chilled water inlet temperatures are not useful for cooling, and lower cooling water inlet temperatures are not usually available.« less

Double core-hole emissivity of transient aluminum plasmas produced in the interaction with ultra-intense x-ray laser pulse

NASA Astrophysics Data System (ADS)

Gao, Cheng; Zeng, Jiaolong; Yuan, Jianmin

2015-11-01

Emissivity of single core-hole (SCH) and double core-hole (DCH) states of aluminum plasmas produced in the interaction with ultra-intense x-ray laser pulse interaction are investigated systematically by solving the time-dependent rate equation implemented in the detailed level accounting approximation. We first demonstrated the plasma density effects on level populations and charge state distribution. Compared with recent experiments, it is shown that the plasma density effects play important roles in the evolution dynamics. Then we systematically investigated the emissivity of the transient aluminum plasmas produced by the x-ray laser pulses with a few photon energies above the threshold photon energy to create DCH states. For the laser photon energy where there are resonant absorptions (RA), 1s-np transitions with both full 1s and SCH 1s states play important roles in time evolution of the population and DCH emission spectroscopy. The significant RA effects are illustrated in detail for x-ray pulses, which creates the 1s-2p resonant absorption from the SCH states of Al VII. With the increase of the photon energy, the emissions from lower charge states become larger.

Effects of prescribed fire, supplemental feeding, and mammalian predator exclusion on hispid cotton rat populations.

PubMed

Morris, Gail; Hostetler, Jeffrey A; Conner, L Mike; Oli, Madan K

2011-12-01

Predation and food resources can strongly affect small mammal population dynamics directly by altering vital rates or indirectly by influencing behaviors. Fire may also strongly influence population dynamics of species inhabiting fire-adapted habitats because fire can alter food and cover availability. We used capture-mark-recapture and radio-telemetry studies to experimentally examine how supplemental feeding, mammalian predator exclusion, and prescribed fire affected survival, abundance, and reproduction of hispid cotton rats (Sigmodon hispidus) in southwestern Georgia, USA. Prescribed fire reduced survival, abundance, and rates of transitions to reproductive states. Food supplementation increased survival, transitions to reproductive states, and abundance, but was not sufficient to prevent post-fire declines in any of these parameters. Mammalian predator exclusion did not strongly affect any of the considered parameters. Our results show that fire strongly influenced cotton rat populations in our study site, primarily by reducing cover and increasing predation risk from non-mammalian predators.

78 FR 23698 - Airworthiness Directives; Sikorsky Aircraft Corporation Helicopters

Federal Register 2010, 2011, 2012, 2013, 2014

2013-04-22

... fire extinguisher discharge tube (No. 1 engine tube). This proposed AD is prompted by the discovery that the No. 1 engine tube installed on the helicopters is too long to ensure that a fire could be effectively extinguished on a helicopter. The proposed actions are intended to ensure the No. 1 engine tube...

78 FR 60656 - Airworthiness Directives; Sikorsky Aircraft Corporation Helicopters

Federal Register 2010, 2011, 2012, 2013, 2014

2013-10-02

... firewall center fire extinguisher discharge tube (No. 1 engine tube) and inspecting the outboard discharge tube to determine if it is correctly positioned. This AD was prompted by the discovery that the No. 1 engine tube installed on the helicopters is too long to ensure that a fire could be effectively...

[Lightning-caused fire, its affecting factors and prediction: a review].

PubMed

Zhang, Ji-Li; Bi, Wu; Wang, Xiao-Hong; Wang, Zi-Bo; Li, Di-Fei

2013-09-01

Lightning-caused fire is the most important natural fire source. Its induced forest fire brings enormous losses to human beings and ecological environment. Many countries have paid great attention to the prediction of lightning-caused fire. From the viewpoint of the main factors affecting the formation of lightning-caused fire, this paper emphatically analyzed the effects and action mechanisms of cloud-to-ground lightning, fuel, meteorology, and terrain on the formation and development process of lightning-caused fire, and, on the basis of this, summarized and reviewed the logistic model, K-function, and other mathematical methods widely used in prediction research of lightning-caused fire. The prediction methods and processes of lightning-caused fire in America and Canada were also introduced. The insufficiencies and their possible solutions for the present researches as well as the directions of further studies were proposed, aimed to provide necessary theoretical basis and literature reference for the prediction of lightning-caused fire in China.

Fire regime, not time-since-fire, affects soil fungal community diversity and composition in temperate grasslands.

PubMed

Egidi, Eleonora; McMullan-Fisher, Sapphire; Morgan, John W; May, Tom; Zeeman, Ben; Franks, Ashley E

2016-09-01

Frequent burning is commonly undertaken to maintain diversity in temperate grasslands of southern Australia. How burning affects below-ground fungal community diversity remains unknown. We show, using a fungal rDNA metabarcoding approach (Illumina MiSeq), that the fungal community composition was influenced by fire regime (frequency) but not time-since-fire. Fungal community composition was resilient to direct fire effects, most likely because grassland fires transfer little heat to the soil. Differences in the fungal community composition due to fire regime was likely due to associated changes that occur in vegetation with recurrent fire, via the break up of obligate symbiotic relationships. However, fire history only partially explains the observed dissimilarity in composition among the soil samples, suggesting a distinctiveness in composition in each grassland site. The importance of considering changes in soil microbe communities when managing vegetation with fire is highlighted. © FEMS 2016. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

The effect of fire on soil organic matter--a review.

PubMed

González-Pérez, José A; González-Vila, Francisco J; Almendros, Gonzalo; Knicker, Heike

2004-08-01

The extent of the soil organic carbon pool doubles that present in the atmosphere and is about two to three times greater than that accumulated in living organisms in all Earth's terrestrial ecosystems. In such a scenario, one of the several ecological and environmental impacts of fires is that biomass burning is a significant source of greenhouse gases responsible for global warming. Nevertheless, the oxidation of biomass is usually incomplete and a range of pyrolysis compounds and particulate organic matter (OM) in aerosols are produced simultaneously to the thermal modification of pre-existing C forms in soil. These changes lead to the evolution of the OM to "pyromorphic humus", composed by rearranged macromolecular substances of weak colloidal properties and an enhanced resistance against chemical and biological degradation. Hence the occurrence of fires in both undisturbed and agricultural ecosystems may produce long-lasting effects on soils' OM composition and dynamics. Due to the large extent of the C pool in soils, small deviations in the different C forms may also have a significant effect in the global C balance and consequently on climate change. This paper reviews the effect of forest fires on the quantity and quality of soils' OM. It is focused mainly on the most stable pool of soil C; i.e., that having a large residence time, composed of free lipids, colloidal fractions, including humic acids (HA) and fulvic acids (FA), and other resilient forms. The main transformations exerted by fire on soil humus include the accumulation of new particulate C forms highly resistant to oxidation and biological degradation including the so-called "black carbon" (BC). Controversial environmental implications of such processes, specifically in the stabilisation of C in soil and their bearing on the global C cycle are discussed.

Seven years later: effects of wildfire in a young stand of Virginia pine and hardwoods

Treesearch

Richard H. Fenton

1960-01-01

In November 1952 a hot surface fire burned through part of a 30-year-old Virginia pine-hardwood stand near Beltsville, Md. Observations were made for the next 2 years to evaluate the effects of this type of fire under these stand conditions. The main direct effects during the 2 years, as reported by Church in 1955, were: 45 percent mortality of trees 1 inch d.b.h. and...

Triple effect absorption cycles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Erickson, D.C.; Potnis, S.V.; Tang, J.

1996-12-31

Triple effect absorption chillers can achieve 50% COP improvement over double-effect systems. However, to translate this potential into cost-effective hardware, the most promising embodiments must be identified. In this study, 12 generic triple effect cycles and 76 possible hermetic loop arrangements of those 12 generic cycles were identified. The generic triple effect cycles were screened based on their pressure and solubility field requirements, generic COPs, risk involved in the component design, and number of components in a high corrosive environment. This screening identified four promising arrangements: Alkitrate Topping cycle, Pressure Staged Envelope cycle, High Pressure Overlap cycle, and Dual Loopmore » cycle. All of these arrangements have a very high COP ({approximately} 1.8), however the development risk and cost involved is different for each arrangement. Therefore, the selection of a particular arrangement will depend upon the specific situation under consideration.« less

Tuned Normalization Explains the Size of Attention Modulations

PubMed Central

Ni, Amy M.; Ray, Supratim; Maunsell, John H. R.

2012-01-01

SUMMARY The effect of attention on firing rates varies considerably within a single cortical area. The firing rate of some neurons is greatly modulated by attention while others are hardly affected. The reason for this variability across neurons is unknown. We found that the variability in attention modulation across neurons in area MT of macaques can be well explained by variability in the strength of tuned normalization across neurons. The presence of tuned normalization also explains a striking asymmetry in attention effects within neurons: when two stimuli are in a neuron’s receptive field, directing attention to the preferred stimulus modulates firing rates more than directing attention to the non-preferred stimulus. These findings show that much of the neuron-to-neuron variability in modulation of responses by attention depends on variability in the way the neurons process multiple stimuli, rather than differences in the influence of top-down signals related to attention. PMID:22365552

Tuned normalization explains the size of attention modulations.

PubMed

Ni, Amy M; Ray, Supratim; Maunsell, John H R

2012-02-23

The effect of attention on firing rates varies considerably within a single cortical area. The firing rate of some neurons is greatly modulated by attention while others are hardly affected. The reason for this variability across neurons is unknown. We found that the variability in attention modulation across neurons in area MT of macaques can be well explained by variability in the strength of tuned normalization across neurons. The presence of tuned normalization also explains a striking asymmetry in attention effects within neurons: when two stimuli are in a neuron's receptive field, directing attention to the preferred stimulus modulates firing rates more than directing attention to the nonpreferred stimulus. These findings show that much of the neuron-to-neuron variability in modulation of responses by attention depends on variability in the way the neurons process multiple stimuli, rather than differences in the influence of top-down signals related to attention. Copyright © 2012 Elsevier Inc. All rights reserved.

Determination of trace elements in dairy milk collected from the environment of coal-fired power plant.

PubMed

Ramamurthy, N; Thillaivelavan, K

2005-01-01

In the present study the environmental effects on herbivores mammals in and around Coal-fired power plant were studied by collecting the various milk samples of Cow and Buffalo in clean polyethylene bottles. Milk samples collected at five different locations along the banks of the Paravanaru river in and around Neyveli area. These samples were prepared for trace metal determination. The concentration of trace metals (Cu, Zn, Ni, Cd, Cr, Mn, Co and Hg) were determined by Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES) and Cold Vapour Atomic Absorption Spectrometry (CVAAS). It is observed that the samples contain greater amounts of trace metals than that in the unexposed areas. Obviously the milk samples are contaminated with these metals due to fly ash released in such environment.

Utilizing NASA Airborne Data to Investigate the Influence of Fuel Type on Biomass Burning Aerosol Properties

NASA Astrophysics Data System (ADS)

Odwuor, A.; Corr, C.; Griffin, R. J.; Pusede, S.; Anderson, B.; Beyersdorf, A. J.; Campuzano Jost, P.; Chen, G.; Day, D. A.; Diskin, G. S.; Jimenez, J. L.; Moore, R.; Nault, B.; Schwarz, J. P.; Shook, M.; Thornhill, K. L., II; Winstead, E.; Armin, W.; Ziemba, L. D.

2017-12-01

Climate models and satellite aerosol classification retrievals rely on well-characterized aerosol optical properties (e.g., scattering and absorption coefficients) that vary with aerosol type. However, generalized parameterizations of aerosol optical properties are weakened by actual variability in aerosol chemical and physical properties that arises from factors independent of aerosol source (e.g., meteorology). This is particularly true for biomass burning (BB) aerosol, which can vary in composition and size depending on burn conditions (e.g., smoldering versus flaming) and fuel. This work investigates the relationships between BB aerosol chemical, physical, and optical properties and fuel. We compare BB aerosol measured in fire plumes associated with distinct fuel types sampled during three NASA airborne research campaigns: boreal forest fires during the Arctic Research of the Troposphere from Aircraft and Satellites (ARCTAS) mission in Saskatchewan, Canada in July 2008; agricultural fires during the Studies of Emissions and Atmospheric Composition, Clouds, and Climate Coupling by Regional Surveys (SEAC4RS) over the continental U.S. in August/September 2013; and scrubland fires during the Student Airborne Research Program (SARP) mission in Southern California, U.S. in June 2016. Mean modified combustion efficiency values between 0.9 and 0.92 for the agricultural plumes and between 0.92 and 0.99 for the boreal and scrubland plumes indicate a significant flaming component to these fires. Despite similarities in burn conditions, SSA at 550nm was consistently lower for the agricultural and scrubland fires ( 0.92) compared to the boreal forest ( 0.96). While the ratio of black carbon to organic aerosol (OA) was similar among fires, differences in the OA were noted; f44/f60 ratios derived from Aerosol Mass Spectrometer OA measurements were consistently higher (>5) in scrubland and agricultural fires compared to boreal forest fires (<5). This suggests the amount of oxidized OA relative to fresh BB aerosol in fire plumes under flaming conditions may vary with fuel type and influence plume optical properties. The relationship between size distributions and optical properties is also explored in this work, with particular attention on the role of the coarse mode in aerosol absorption.

Disk MHD generator study

NASA Technical Reports Server (NTRS)

Retallick, F. D.

1980-01-01

Directly-fired, separately-fired, and oxygen-augmented MHD power plants incorporating a disk geometry for the MHD generator were studied. The base parameters defined for four near-optimum-performance MHD steam power systems of various types are presented. The finally selected systems consisted of (1) two directly fired cases, one at 1920 K (2996F) preheat and the other at 1650 K (2500 F) preheat, (2) a separately-fired case where the air is preheated to the same level as the higher temperature directly-fired cases, and (3) an oxygen augmented case with the same generator inlet temperature of 2839 (4650F) as the high temperature directly-fired and separately-fired cases. Supersonic Mach numbers at the generator inlet, gas inlet swirl, and constant Hall field operation were specified based on disk generator optimization. System pressures were based on optimization of MHD net power. Supercritical reheat stream plants were used in all cases. Open and closed cycle component costs are summarized and compared.

On the key role of droughts in the dynamics of summer fires in Mediterranean Europe.

PubMed

Turco, Marco; von Hardenberg, Jost; AghaKouchak, Amir; Llasat, Maria Carmen; Provenzale, Antonello; Trigo, Ricardo M

2017-03-06

Summer fires frequently rage across Mediterranean Europe, often intensified by high temperatures and droughts. According to the state-of-the-art regional fire risk projections, in forthcoming decades climate effects are expected to become stronger and possibly overcome fire prevention efforts. However, significant uncertainties exist and the direct effect of climate change in regulating fuel moisture (e.g. warmer conditions increasing fuel dryness) could be counterbalanced by the indirect effects on fuel structure (e.g. warmer conditions limiting fuel amount), affecting the transition between climate-driven and fuel-limited fire regimes as temperatures increase. Here we analyse and model the impact of coincident drought and antecedent wet conditions (proxy for the climatic factor influencing total fuel and fine fuel structure) on the summer Burned Area (BA) across all eco-regions in Mediterranean Europe. This approach allows BA to be linked to the key drivers of fire in the region. We show a statistically significant relationship between fire and same-summer droughts in most regions, while antecedent climate conditions play a relatively minor role, except in few specific eco-regions. The presented models for individual eco-regions provide insights on the impacts of climate variability on BA, and appear to be promising for developing a seasonal forecast system supporting fire management strategies.

Carbon loss from an unprecedented Arctic tundra wildfire.

PubMed

Mack, Michelle C; Bret-Harte, M Syndonia; Hollingsworth, Teresa N; Jandt, Randi R; Schuur, Edward A G; Shaver, Gaius R; Verbyla, David L

2011-07-27

Arctic tundra soils store large amounts of carbon (C) in organic soil layers hundreds to thousands of years old that insulate, and in some cases maintain, permafrost soils. Fire has been largely absent from most of this biome since the early Holocene epoch, but its frequency and extent are increasing, probably in response to climate warming. The effect of fires on the C balance of tundra landscapes, however, remains largely unknown. The Anaktuvuk River fire in 2007 burned 1,039 square kilometres of Alaska's Arctic slope, making it the largest fire on record for the tundra biome and doubling the cumulative area burned since 1950 (ref. 5). Here we report that tundra ecosystems lost 2,016 ± 435 g C m(-2) in the fire, an amount two orders of magnitude larger than annual net C exchange in undisturbed tundra. Sixty per cent of this C loss was from soil organic matter, and radiocarbon dating of residual soil layers revealed that the maximum age of soil C lost was 50 years. Scaled to the entire burned area, the fire released approximately 2.1 teragrams of C to the atmosphere, an amount similar in magnitude to the annual net C sink for the entire Arctic tundra biome averaged over the last quarter of the twentieth century. The magnitude of ecosystem C lost by fire, relative to both ecosystem and biome-scale fluxes, demonstrates that a climate-driven increase in tundra fire disturbance may represent a positive feedback, potentially offsetting Arctic greening and influencing the net C balance of the tundra biome.

Directed evolution of an ultrastable carbonic anhydrase for highly efficient carbon capture from flue gas

DOE PAGES

Alvizo, Oscar; Nguyen, Luan J.; Savile, Christopher K.; ...

2014-11-03

Carbonic anhydrase (CA) is one of nature’s fastest enzymes and can dramatically improve the economics of carbon capture under demanding environments such as coal-fired power plants. The use of CA to accelerate carbon capture is limited by the enzyme’s sensitivity to the harsh process conditions. Using directed evolution, the properties of a β-class CA from Desulfovibrio vulgaris were dramatically enhanced. Iterative rounds of library design, library generation, and high-throughput screening identified highly stable CA variants that tolerate temperatures of up to 107 °C in the presence of 4.2 M alkaline amine solvent at pH >10.0. This increase in thermostability andmore » alkali tolerance translates to a 4,000,000-fold improvement over the natural enzyme. In conclusion, at pilot scale, the evolved catalyst enhanced the rate of CO2 absorption 25-fold compared with the noncatalyzed reaction.« less

Directed evolution of an ultrastable carbonic anhydrase for highly efficient carbon capture from flue gas

PubMed Central

Alvizo, Oscar; Nguyen, Luan J.; Savile, Christopher K.; Bresson, Jamie A.; Lakhapatri, Satish L.; Solis, Earl O. P.; Fox, Richard J.; Broering, James M.; Benoit, Michael R.; Zimmerman, Sabrina A.; Novick, Scott J.; Liang, Jack; Lalonde, James J.

2014-01-01

Carbonic anhydrase (CA) is one of nature’s fastest enzymes and can dramatically improve the economics of carbon capture under demanding environments such as coal-fired power plants. The use of CA to accelerate carbon capture is limited by the enzyme’s sensitivity to the harsh process conditions. Using directed evolution, the properties of a β-class CA from Desulfovibrio vulgaris were dramatically enhanced. Iterative rounds of library design, library generation, and high-throughput screening identified highly stable CA variants that tolerate temperatures of up to 107 °C in the presence of 4.2 M alkaline amine solvent at pH >10.0. This increase in thermostability and alkali tolerance translates to a 4,000,000-fold improvement over the natural enzyme. At pilot scale, the evolved catalyst enhanced the rate of CO2 absorption 25-fold compared with the noncatalyzed reaction. PMID:25368146

Ghrelin decreases firing activity of gonadotropin-releasing hormone (GnRH) neurons in an estrous cycle and endocannabinoid signaling dependent manner.

PubMed

Farkas, Imre; Vastagh, Csaba; Sárvári, Miklós; Liposits, Zsolt

2013-01-01

The orexigenic peptide, ghrelin is known to influence function of GnRH neurons, however, the direct effects of the hormone upon these neurons have not been explored, yet. The present study was undertaken to reveal expression of growth hormone secretagogue receptor (GHS-R) in GnRH neurons and elucidate the mechanisms of ghrelin actions upon them. Ca(2+)-imaging revealed a ghrelin-triggered increase of the Ca(2+)-content in GT1-7 neurons kept in a steroid-free medium, which was abolished by GHS-R-antagonist JMV2959 (10 µM) suggesting direct action of ghrelin. Estradiol (1nM) eliminated the ghrelin-evoked rise of Ca(2+)-content, indicating the estradiol dependency of the process. Expression of GHS-R mRNA was then confirmed in GnRH-GFP neurons of transgenic mice by single cell RT-PCR. Firing rate and burst frequency of GnRH-GFP neurons were lower in metestrous than proestrous mice. Ghrelin (40 nM-4 μM) administration resulted in a decreased firing rate and burst frequency of GnRH neurons in metestrous, but not in proestrous mice. Ghrelin also decreased the firing rate of GnRH neurons in males. The ghrelin-evoked alterations of the firing parameters were prevented by JMV2959, supporting the receptor-specific actions of ghrelin on GnRH neurons. In metestrous mice, ghrelin decreased the frequency of GABAergic mPSCs in GnRH neurons. Effects of ghrelin were abolished by the cannabinoid receptor type-1 (CB1) antagonist AM251 (1µM) and the intracellularly applied DAG-lipase inhibitor THL (10 µM), indicating the involvement of retrograde endocannabinoid signaling. These findings demonstrate that ghrelin exerts direct regulatory effects on GnRH neurons via GHS-R, and modulates the firing of GnRH neurons in an ovarian-cycle and endocannabinoid dependent manner.

Tripartite counterfactual entanglement distribution.

PubMed

Chen, Yuanyuan; Gu, Xuemei; Jiang, Dong; Xie, Ling; Chen, Lijun

2015-08-10

We propose two counterfactual schemes for tripartite entanglement distribution without any physical particles travelling through the quantum channel. One scheme arranges three participators to connect with the absorption object by using switch. Using the "chained" quantum Zeno effect, three participators can accomplish the task of entanglement distribution with unique counterfactual interference probability. Another scheme uses Michelson-type interferometer to swap two entanglement pairs such that the photons of three participators are entangled. Moreover, the distance of entanglement distribution is doubled as two distant absorption objects are used. We also discuss the implementation issues to show that the proposed schemes can be realized with current technology.

Optical and Probe Diagnostics Applied to Reacting Flows

NASA Technical Reports Server (NTRS)

Ticich, Thomas M.

2003-01-01

The general theme of the research my NASA colleague and I have planned is "Optical and probe diagnostics applied to reacting flows". We plan to explore three major threads during the fellowship period. The first interrogates the flame synthesis of carbon nanotubes using aerosol catalysts. Having demonstrated the viability of the technique for nanotube synthesis, we seek to understand the details of this reacting system which are important to its practical application. Laser light scattering will reveal changes in particle size at various heights above the burner. Analysis of the flame gas by mass spectroscopy will reveal the chemical composition of the mixture. Finally, absorption measurements will map the nanotube concentration within the flow. The second thread explores soot oxidation kinetics. Despite the impact of soot on engine performance, fire safety and pollution, models for its oxidation are inhibited by uncertainty in the values of the oxidation rate. We plan to employ both optical and microscopic measurements to refine this rate. Cavity ring-down absorption measurements of the carbonaceous aerosol can provide a measure of the mass concentration with time and, hence, an oxidation rate. Spectroscopic and direct probe measurements will provide the temperature of the system needed for subsequent modeling. These data will be benchmarked against changes in soot nanostructures as revealed by transmission electron microscopic images from directly sampled material.

Electric and magnetic field modulated energy dispersion, conductivity and optical response in double quantum wire with spin-orbit interactions

NASA Astrophysics Data System (ADS)

Karaaslan, Y.; Gisi, B.; Sakiroglu, S.; Kasapoglu, E.; Sari, H.; Sokmen, I.

2018-02-01

We study the influence of electric field on the electronic energy band structure, zero-temperature ballistic conductivity and optical properties of double quantum wire. System described by double-well anharmonic confinement potential is exposed to a perpendicular magnetic field and Rashba and Dresselhaus spin-orbit interactions. Numerical results show up that the combined effects of internal and external agents cause the formation of crossing, anticrossing, camel-back/anomaly structures and the lateral, downward/upward shifts in the energy dispersion. The anomalies in the energy subbands give rise to the oscillation patterns in the ballistic conductance, and the energy shifts bring about the shift in the peak positions of optical absorption coefficients and refractive index changes.

Corridors promote fire via connectivity and edge effects.

PubMed

Brudvig, Lars A; Wagner, Stephanie A; Damschen, Ellen I

2012-04-01

Landscape corridors, strips of habitat that connect otherwise isolated habitat patches, are commonly employed during management of fragmented landscapes. To date, most reported effects of corridors have been positive; however, there are long-standing concerns that corridors may have unintended consequences. Here, we address concerns over whether corridors promote propagation of disturbances such as fire. We collected data during prescribed fires in the world's largest and best replicated corridor experiment (Savannah River Site, South Carolina, USA), six -50-ha landscapes of open (shrubby/herbaceous) habitat within a pine plantation matrix, to test several mechanisms for how corridors might influence fire. Corridors altered patterns of fire temperature through a direct connectivity effect and an indirect edge effect. The connectivity effect was independent of fuel levels and was consistent with a hypothesized wind-driven "bellows effect." Edges, a consequence of corridor implementation, elevated leaf litter (fuel) input from matrix pine trees, which in turn increased fire temperatures. We found no evidence for corridors or edges impacting patterns of fire spread: plots across all landscape positions burned with similar probability. Impacts of edges and connectivity on fire temperature led to changes in vegetation: hotter-burning plots supported higher bunch grass cover during the field season after burning, suggesting implications for woody/herbaceous species coexistence. To our knowledge, this represents the first experimental evidence that corridors can modify landscape-scale patterns of fire intensity. Corridor impacts on fire should be carefully considered during landscape management, both in the context of how corridors connect or break distributions of fuels and the desired role of fire as a disturbance, which may range from a management tool to an agent to be suppressed. In our focal ecosystem, longleaf pine woodland, corridors might provide a previously unrecognized benefit during prescribed burning activities, by promoting fire intensity, which may assist in promoting plant biodiversity.

Crab regulation of cross-ecosystem resource transfer by marine foraging fire ants.

PubMed

Garcia, Erica A; Bertness, Mark D; Alberti, Juan; Silliman, Brian R

2011-08-01

Permeability of boundaries in biological systems is regulated by biotic and/or abiotic factors. Despite this knowledge, the role of biotic factors in regulating resource transfer across ecosystem boundaries has received little study. Additionally, little is known about how cross-ecosystem resource transfer affects source populations. We used experiments, observations and stable isotopes, to evaluate: (1) the proportion of intertidal-foraging black fire ant (Solenopsis richteri) diet derived from marine sources, (2) how black fire ant cross-ecosystem resource transfer is altered by the dominant bioengineer in the intertidal, a burrowing crab (Neohelice granulata), (3) the top-down impact of these terrestrial ants on a marine resource, and (4) the effect of marine resources on recipient black fire ants. We found that more than 85% of the black fire ant diet is derived from marine sources, the number of intertidal foraging ants doubles in the absence of crab burrows, and that ants cause a 50% reduction in intertidal polychaetes. Also, ant mound density is three times greater adjacent to marine systems. This study reveals that cross-ecosystem foraging terrestrial ants can clearly have strong impacts on marine resources. Furthermore, ecosystem engineers that modify and occupy habitat in these ecosystem boundaries can strongly regulate the degree of cross-ecosystem resource transfer and resultant top down impacts.

Singapore’s willingness to pay for mitigation of transboundary forest-fire haze from Indonesia

NASA Astrophysics Data System (ADS)

Lin, Yuan; Wijedasa, Lahiru S.; Chisholm, Ryan A.

2017-02-01

Haze pollution over the past four decades in Southeast Asia is mainly a result of forest and peatland fires in Indonesia. The economic impacts of haze include adverse health effects and disruption to transport and tourism. Previous studies have used a variety of approaches to assess the economic impacts of haze and the forest fires more generally. But no study has used contingent valuation to assess non-market impacts of haze on individuals. Here we apply contingent valuation to estimate impacts of haze on Singapore, one of most severely affected countries. We used a double-bounded dichotomous-choice survey design and the Kaplan-Meier-Turnbull method to infer the distribution of Singaporeans’ willingness to pay (WTP) for haze mitigation. Our estimate of mean individual WTP was 0.97% of annual income (n = 390). To calculate total national WTP, we stratified by income, the demographic variable most strongly related to individual WTP. The total WTP estimate was 643.5 million per year (95% CI [527.7 million, 765.0 million]). This estimate is comparable in magnitude to previously estimated impacts of Indonesia’s fires and also to the estimated costs of peatland protection and restoration. We recommend that our results be incorporated into future cost-benefit analyses of the fires and mitigation strategies.

Pharmacokinetic and metabolism studies of the antiarrhythmic drug meobentine (N-(4-methoxybenzyl)-N prime , N double prime -dimethylguanidine) and its N-(4-trifluoromethyoxybenzyl)-N prime , N double prime - dimethylguanidine analogue, fluorobentine in the rat, dog and man

DOE Office of Scientific and Technical Information (OSTI.GOV)

Warren, J.T.

1988-01-01

A radioimmunoassay (RIA) was developed that was able to detect 40 pg meobentine (M) in 0.1 ml plasma. Cross-reactivity of suspected M metabolites was very low. This RIA was later also used to assay for fluorobentine (F), a fluorine analogue of M. M exhibits three-compartment open model iv kinetics in the rat, dog, and man. Terminal drug half-life in the rat, dog, and man; total-body clearance in the rat, dog, and man; and terminal-phase volume of distribution in the rat, dog, and man were determined. (14C)-M absorption is essentially complete in the rat and dog, but this parameter could notmore » be directly ascertained in man. Relative oral drug bioavailability is linear in the rat and dog but falls off between 5-10 mg/kg in man. F was synthesized in an attempt to counteract suspected problems with M's poor absorption or extensive metabolism that might be affecting its efficacy in humans. F would likely be unavailable for O-demethylation, might well be more lipophilic than M, and yet still be active.« less

Climate-induced variations in global wildfire danger from 1979 to 2013

PubMed Central

Jolly, W. Matt; Cochrane, Mark A.; Freeborn, Patrick H.; Holden, Zachary A.; Brown, Timothy J.; Williamson, Grant J.; Bowman, David M. J. S.

2015-01-01

Climate strongly influences global wildfire activity, and recent wildfire surges may signal fire weather-induced pyrogeographic shifts. Here we use three daily global climate data sets and three fire danger indices to develop a simple annual metric of fire weather season length, and map spatio-temporal trends from 1979 to 2013. We show that fire weather seasons have lengthened across 29.6 million km2 (25.3%) of the Earth's vegetated surface, resulting in an 18.7% increase in global mean fire weather season length. We also show a doubling (108.1% increase) of global burnable area affected by long fire weather seasons (>1.0 σ above the historical mean) and an increased global frequency of long fire weather seasons across 62.4 million km2 (53.4%) during the second half of the study period. If these fire weather changes are coupled with ignition sources and available fuel, they could markedly impact global ecosystems, societies, economies and climate. PMID:26172867

Development of the Lidar Atmospheric Sensing Experiment (LASE): An Advanced Airborne DIAL Instrument

NASA Technical Reports Server (NTRS)

Moore, Alvah S., Jr.; Brown, Kevin E.; Hall, William M.; Barnes, James C.; Edwards, William C.; Petway, Larry B.; Little, Alan D.; Luck, William S., Jr.; Jones, Irby W.; Antill, Charles W., Jr.

1997-01-01

The Lidar Atmospheric Sensing Experiment (LASE) Instrument is the first fully-engineered, autonomous Differential Absorption Lidar (DIAL) System for the measurement of water vapor in the troposphere (aerosol and cloud measurements are included). LASE uses a double-pulsed Ti:Sapphire laser for the transmitter with a 30 ns pulse length and 150 mJ/pulse. The laser beam is "seeded" to operate on a selected water vapor absorption line in the 815-nm region using a laser diode and an onboard absorption reference cell. A 40 cm diameter telescope collects the backscattered signals and directs them onto two detectors. LASE collects DIAL data at 5 Hz while onboard a NASA/Ames ER-2 aircraft flying at altitudes from 16-21 km. LASE was designed to operate autonomously within the environment and physical constraints of the ER-2 aircraft and to make water vapor profile measurements across the troposphere to better than 10% accuracy. LASE has flown 19 times during the development of the instrument and the validation of the science data. This paper describes the design, operation, and reliability of the LASE Instrument.

Defect-induced band-edge reconstruction of a bismuth-halide double perovskite for visible-light absorption

DOE PAGES

Slavney, Adam H.; Leppert, Linn; Bartesaghi, Davide; ...

2017-03-29

In this study, halide double perovskites have recently been developed as less toxic analogs of the lead perovskite solar-cell absorbers APbX 3 (A = monovalent cation; X = Br or I). However, all known halide double perovskites have large bandgaps that afford weak visible-light absorption. The first halide double perovskite evaluated as an absorber, Cs 2AgBiBr 6 (1), has a bandgap of 1.95 eV. Here, we show that dilute alloying decreases 1’s bandgap by ca. 0.5 eV. Importantly, time-resolved photoconductivity measurements reveal long-lived carriers with microsecond lifetimes in the alloyed material, which is very promising for photovoltaic applications. The alloyedmore » perovskite described herein is the first double perovskite to show comparable bandgap energy and carrier lifetime to those of (CH 3NH 3)PbI 3. By describing how energy- and symmetry-matched impurity orbitals, at low concentrations, dramatically alter 1’s band edges, we open a potential pathway for the large and diverse family of halide double perovskites to compete with APbX 3 absorbers.« less

Influence of radiation absorption by environmental water vapor on radiation transfer in wildland fires

Treesearch

David Frankman; Brent W. Webb; Bret W. Butler

2007-01-01

Thermal radiation emission from a simulated black flame surface to a fuel bed is analyzed by a ray-tracing technique, tracking emission from points along the flame to locations along the fuel bed while accounting for absorption by environmental water vapor in the intervening medium. The Spectral Line Weighted-sum-of-gray-gases approach was adopted for treating the...

Strong spectral variation of biomass smoke light absorption and single scattering albedo observed with a novel dual-wavelength photoacoustic instrument

Treesearch

Kristin Lewis; William P. Arnott; Hans Moosmuller; Cyle E. Wold

2008-01-01

A dual-wavelength photoacoustic instrument operating at 405 and 870 nm was used during the 2006 Fire Lab at Missoula Experiment to measure light scattering and absorption by smoke from the combustion of a variety of biomass fuels. Simultaneous measurements of aerosol light scattering by reciprocal nephelometry within the instrument's acoustic resonator accompany...

The Effects of Void Geometry and Contact Angle on the Absorption of Liquids into Porous Calcium Carbonate Structures.

PubMed

Ridgway, Cathy J.; Schoelkopf, Joachim; Matthews, G. Peter; Gane, Patrick A. C.; James, Philip W.

2001-07-15

The absorption (permeation) of alcohols into porous blocks of calcium carbonate has been studied experimentally and with a computer model. The experimental measurement was of change in apparent weight of a block with time after contact with liquid. The modeling used the previously developed 'Pore-Cor' model, based on unit cells of 1000 cubic pores connected by cylindrical throats. To gain some insight into absorption into voids of complex geometry, and to provide a representation of heterogeneities in surface interaction energy, the cylindrical throats were converted to double cones. Relative to cylinders, such geometries caused hold-ups of the percolation of nonwetting fluids with respect to increasing applied pressure, and a change in the rate of absorption of wetting fluids. Both the measured absorption of the alcohols and the simulated absorption of the alcohols and of water showed significant deviations from that predicted by an effective hydraulic radius approximation. The simulation demonstrated the development of a highly heterogeneous wetting front, and of preferred wetting pathways that were perturbed by inertial retardation. The findings are useful in the design of high-performance, low-waste pigments for paper coatings, and environmentally friendly printing inks, as well as in wider industrial, environmental, and geological contexts. Copyright 2001 Academic Press.

Emission Rates and Optical Properties of Pollutants Emitted from a Traditional and an Improved Wood-Burning Cookstove

NASA Astrophysics Data System (ADS)

Kirchstetter, T.; Hadley, O. L.; Preble, C.; Gadgil, A.

2010-12-01

Traditional cooking methods in developing regions of the world generate gas and particle phase pollutants that endanger the lives of more than a billion people and contribute appreciably to the burden of climate-changing particles in the atmosphere. This presentation compares pollutant emissions from the traditional “three-stone fire” and an improved cookstove developed for refugees in Darfur: the Berkeley-Darfur Stove (BDS). The BDS was designed for increased fuel efficiency to decrease the risk of assault that women often face when gathering fuel wood. Reduced pollutant exposure and climate impact are potential co-benefits. Testing of these stoves at the Lawrence Berkeley National Laboratory facility includes 1-Hz measurements of concentrations of particulate matter, black carbon, carbon monoxide, and carbon dioxide; coefficients of particle light absorption and scattering; and absorption Angstrom exponent. Absorption and scattering coefficients were measured at 532 nm using a photoacoustic absorption instrument equipped with a reciprocal nephelometer. The BDS heated food faster and consumed less wood in cooking tests compared to the three-stone fire. The BDS emitted less carbon monoxide and particulate matter but comparable mass of black carbon compared to the three-stone fire for the same cooking task. Values of the absorption Angstrom exponent ranged from about 1 - 3, indicating the emission of both black carbon and light-absorbing organic carbon (i.e., brown carbon). Values of (dry) aerosol single scattering albedo were mostly in the range of 0.25 - 0.55, indicating that the emitted particles tend to absorb more light than they scatter. Our analysis considered the variability of pollutant emissions during different phases of the fire. Particulate matter emissions were highest during the first several minutes of cooking, which included igniting the wood, whereas carbon monoxide emissions were highest during the last several minutes of cooking when smoldering became more dominant. Comparison of photoacoustic absorption and aethalometer black carbon provided an easy means of correcting black carbon concentrations, which were low by a factor of 2 at the end of the aethalometer sampling cycle if uncorrected.

Effects of partial replacement of dietary fat by olestra on dietary cholesterol absorption in man

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jandacek, R.J.; Ramirez, M.M.; Crouse, J.R. III

1990-08-01

Olestra, a nonabsorbable fat substitute comprising long-chain fatty acid esters of sucrose, had been previously shown to reduce cholesterol absorption in humans when ingested at a level of 50 g/d. To determine whether or not a lower level of dietary olestra would also reduce cholesterol absorption, we studied the effect of 7 g of olestra twice a day in 20 normocholesterolemic male inpatients in a double-blind, crossover trial. Two 6-day diet treatment and stool collection periods were separated by a 14-day washout period. Half of the subjects received butter, and half, a butter-olestra blend during each treatment period according tomore » a crossover design. All subjects ingested trace amounts of 3H-cholesterol and 14C-beta-sitosterol with the butter or the butter-olestra blend. Cholesterol absorption was determined from the 3H/14C ratios in the diet and in saponified and extracted stools according to previously validated methodology. Cholesterol absorption during the butter regimen was significantly greater than that during the olestra regimen (56.1% +/- 1.6% v 46.7% +/- 1.1%, P less than .01).« less

Double-pulse 1.57  μm integrated path differential absorption lidar ground validation for atmospheric carbon dioxide measurement.

PubMed

Du, Juan; Zhu, Yadan; Li, Shiguang; Zhang, Junxuan; Sun, Yanguang; Zang, Huaguo; Liu, Dan; Ma, Xiuhua; Bi, Decang; Liu, Jiqiao; Zhu, Xiaolei; Chen, Weibiao

2017-09-01

A ground-based double-pulse integrated path differential absorption (IPDA) instrument for carbon dioxide (CO 2 ) concentration measurements at 1572 nm has been developed. A ground experiment was implemented under different conditions with a known wall located about 1.17 km away acting as the scattering hard target. Off-/offline testing of a laser transmitter was conducted to estimate the instrument systematic and random errors. Results showed a differential absorption optical depth (DAOD) offset of 0.0046 existing in the instrument. On-/offline testing was done to achieve the actual DAOD resulting from the CO 2 absorption. With 18 s pulses average, it demonstrated that a CO 2 concentration measurement of 432.71±2.42  ppm with 0.56% uncertainty was achieved. The IPDA ranging led to a measurement uncertainty of 1.5 m.

Wavelength-modulation-spectroscopy for real-time, in situ NO detection in combustion gases with a 5.2 μm quantum-cascade laser

NASA Astrophysics Data System (ADS)

Chao, X.; Jeffries, J. B.; Hanson, R. K.

2012-03-01

A mid-infrared absorption strategy with calibration-free wavelength-modulation-spectroscopy (WMS) has been developed and demonstrated for real-time, in situ detection of nitric oxide in particulate-laden combustion-exhaust gases up to temperatures of 700 K. An external-cavity quantum-cascade laser (ECQCL) near 5.2 μm accessed the fundamental absorption band of NO, and a wavelength-scanned, 1 f-normalized WMS with second-harmonic detection (WMS-2 f/1 f) strategy was developed. Due to the external-cavity laser architecture, large nonlinear intensity modulation (IM) was observed when the wavelength was modulated by injection-current modulation, and the IM indices were also found to be strongly wavelength-dependent as the center wavelength was scanned with piezoelectric tuning of the cavity. A quantitative model of the 1 f-normalized WMS-2 f signal was developed and validated under laboratory conditions. A sensor was subsequently designed, built and demonstrated for real-time, in situ measurements of NO across a 3 m path in the particulate-laden exhaust of a pulverized-coal-fired power plant boiler. The 1 f-normalized WMS-2 f method proved to have better noise immunity for non-absorption transmission, than wavelength-scanned direct absorption. A 0.3 ppm-m detection limit was estimated using the R15.5 transition near 1927 cm-1 with 1 s averaging. Mid-infrared QCL-based NO absorption with 1 f-normalized WMS-2 f detection shows excellent promise for practical sensing in the combustion exhaust.

Reversible unidirectional reflection and absorption of PT-symmetry structure under electro-optical modulation

NASA Astrophysics Data System (ADS)

Fang, Yun-tuan; Zhang, Yi-chi; Xia, Jing

2018-06-01

In order to obtain tunable unidirectional device, we assumed an ideal periodic layered Parity-Time (PT) symmetry structure inserted by doped LiNbO3 (LN) interlayers. LN is a typical electro-optical material of which the refractive index depends on the external electric field. In our work, we theoretically investigate the modulation effect of the external electric field on the transmittance and reflectance of the structure through numerical method. Through selected structural parameters, the one-way enhanced reflection and high absorption (above 0.9) behaviors are found. Within a special frequency band (not a single frequency), our theoretical model performs enhanced reflection in one incidence direction and high absorption in the other direction. Furthermore, the directions of enhanced reflection and absorption can be reversed through reversing the direction of applied electric field. Such structure with reversible properties has the potential in designing new optical devices.

[Simulating the effects of climate change and fire disturbance on aboveground biomass of boreal forests in the Great Xing'an Mountains, Northeast China].

PubMed

Luo, Xu; Wang, Yu Li; Zhang, Jin Quan

2018-03-01

Predicting the effects of climate warming and fire disturbance on forest aboveground biomass is a central task of studies in terrestrial ecosystem carbon cycle. The alteration of temperature, precipitation, and disturbance regimes induced by climate warming will affect the carbon dynamics of forest ecosystem. Boreal forest is an important forest type in China, the responses of which to climate warming and fire disturbance are increasingly obvious. In this study, we used a forest landscape model LANDIS PRO to simulate the effects of climate change on aboveground biomass of boreal forests in the Great Xing'an Mountains, and compared direct effects of climate warming and the effects of climate warming-induced fires on forest aboveground biomass. The results showed that the aboveground biomass in this area increased under climate warming scenarios and fire disturbance scenarios with increased intensity. Under the current climate and fire regime scenario, the aboveground biomass in this area was (97.14±5.78) t·hm -2 , and the value would increase up to (97.93±5.83) t·hm -2 under the B1F2 scenario. Under the A2F3 scenario, aboveground biomass at landscape scale was relatively higher at the simulated periods of year 100-150 and year 150-200, and the value were (100.02±3.76) t·hm -2 and (110.56±4.08) t·hm -2 , respectively. Compared to the current fire regime scenario, the predicted biomass at landscape scale was increased by (0.56±1.45) t·hm -2 under the CF2 scenario (fire intensity increased by 30%) at some simulated periods, and the aboveground biomass was reduced by (7.39±1.79) t·hm -2 in CF3 scenario (fire intensity increased by 230%) at the entire simulation period. There were significantly different responses between coniferous and broadleaved species under future climate warming scenarios, in that the simulated biomass for both Larix gmelinii and Betula platyphylla showed decreasing trend with climate change, whereas the simulated biomass for Pinus sylvestris var. mongolica, Picea koraiensis and Populus davidiana showed increasing trend at different degrees during the entire simulation period. There was a time lag for the direct effect of climate warming on biomass for coniferous and broadleaved species. The response time of coniferous species to climate warming was 25-30 years, which was longer than that for broadleaf species. The forest landscape in the Great Xing'an Mountains was sensitive to the interactive effect of climate warming (high CO 2 emissions) and high intensity fire disturbance. Future climate warming and high intensity forest fire disturbance would significantly change the composition and structure of forest ecosystem.

Determination of palladium and platinum by atomic absorption

USGS Publications Warehouse

Schnepfe, M.M.; Grimaldi, F.S.

1969-01-01

Palladium and platinum are determined by atomic absorption after fire-assay concentration into a gold bead. The limit of determination is ~0??06 ppm in a 20-g sample. Serious depressive interelement interferences are removed by buffering the solutions with a mixture of cadmium and copper sulphates with cadmium and copper concentrations each at 0??5%. Substantial amounts of Ag, Al, Au, Bi, Ca, Co, Cr, Fe, Hg, K, La, Mg, Mn, Mo, Na, Ni, Pb, Te, Ti, V, Y, Zn, and the platinum metals do not interfere in the atomic-absorption determination. ?? 1969.

Computer program for calculating and plotting fire direction and rate of spread.

Treesearch

James E. Eenigenburg

1987-01-01

Presents an analytical procedure that uses a FORTRAN 77 program to estimate fire direction and rate of spread. The program also calculates the variability of these parameters, both for subsections of the fire and for the fires as a whole. An option in the program allows users with a CALCOMP plotter to obtain a map of the fire with spread vectors.

Outlook for metal lasers

NASA Technical Reports Server (NTRS)

Russell, G. R.

1976-01-01

Lasers utilizing atomic metallic vapors are considered with emphasis on a double discharge technique and multiply pulsed experiments. Data are presented on the effect of time delay after the first electrical discharge and the effect of lasant temperature along with results of absorption measurements utilizing a 13 mm diameter laser tube. Data obtained from multiply pulsed experiments for discharge diameters varying from 1 to 4 cm indicate that the efficiency increases with the pulsing rate.

Nonreciprocal optical properties based on magneto-optical materials: n-InAs, GaAs and HgCdTe

NASA Astrophysics Data System (ADS)

Wang, Han; Wu, Hao; Zhou, Jian-qiu

2018-02-01

Compared with reciprocal optical materials, nonreciprocal materials can break the time reversal and detailed balance due to special nonreciprocal effect, while how its characteristics performing on infrared wavelength have not been paid enough attention. In this paper, the optical properties of three magneto-optical materials was investigated in infrared band, that are n-InAs, GaAs, HgCdTe, based on Finite Difference Time Domain (FDTD) method. The equations of dielectric constant tensor are present and the effect of magnetic field intensity and frequency has been studied in detail. Additionally, the effect of incidence angle at positive and negative directions to the nonreciprocal absorptivity is also investigated. It is found that the nonreciprocal effect is obvious in infrared wavelength, and the nonreciprocal effect could adjust the absorption characteristic, thus be able to tune the absorption for the specific frequency of incident light. In addition to modeling the directional radiative properties at various angles of incidence, the absorption peaks of three materials under different incident angles are also calculated to understand the light absorption and to facilitate the optimal design of high-performance photovoltaic and optical instrument.

Formation and evolution of Tar Balls from Northwestern US wildfires

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sedlacek III, Arthur J.; Buseck, Peter R.; Adachi, Kouji

Biomass burning is a major source of light-absorbing black and brown carbonaceous particles. Brown carbon is a poorly characterized mixture that includes tar balls (TBs), a type of carbonaceous particle apparently unique to biomass burning. Here we describe the first atmospheric observations of the formation and evolution of TBs from forest fires. Aerosol particles were collected on TEM grids during aircraft transects at various downwind distances from the Colockum Tarp wildland fire. TB mass fractions, derived from TEM and in-situ measurements, increased from < 1 % near the fire to 31–45 % downwind, with little change in TB diameter. Single-scatteringmore » albedo determined from scattering and absorption measurements increased slightly with downwind distance. Similar TEM and SSA results were observed sampling multiple wildfires. Mie calculations are consistent with weak light absorbance by TBs (m = 1.56–0.02i) but not consistent with order-of-magnitude stronger absorption observed in different settings. The field-derived TB mass fractions reported here indicate that this particle type should be accounted for in biomass-burn emission inventories.« less

Formation and evolution of Tar Balls from Northwestern US wildfires

DOE PAGES

Sedlacek III, Arthur J.; Buseck, Peter R.; Adachi, Kouji; ...

2018-01-30

Biomass burning is a major source of light-absorbing black and brown carbonaceous particles. Brown carbon is a poorly characterized mixture that includes tar balls (TBs), a type of carbonaceous particle apparently unique to biomass burning. Here we describe the first atmospheric observations of the formation and evolution of TBs from forest fires. Aerosol particles were collected on TEM grids during aircraft transects at various downwind distances from the Colockum Tarp wildland fire. TB mass fractions, derived from TEM and in-situ measurements, increased from < 1 % near the fire to 31–45 % downwind, with little change in TB diameter. Single-scatteringmore » albedo determined from scattering and absorption measurements increased slightly with downwind distance. Similar TEM and SSA results were observed sampling multiple wildfires. Mie calculations are consistent with weak light absorbance by TBs (m = 1.56–0.02i) but not consistent with order-of-magnitude stronger absorption observed in different settings. The field-derived TB mass fractions reported here indicate that this particle type should be accounted for in biomass-burn emission inventories.« less

Effects of fire and fuels management on water quality in eastern North America

Treesearch

R. K. Kolka

2012-01-01

Fuels management, especially prescribed fire, can have direct impacts on aquatic resources through deposition of ash to surface waters. On the terrestrial side, fuels management leads to changes in vegetative structure and potentially soil properties that affect ecosystem cycling of water and inorganic and organic constituents. Because surface water systems (streams,...

Effectiveness of Forestry Agency Personnel as Fire Prevention Contactors

Treesearch

M.L. Doolittle

1980-01-01

A major responsibility of county forest rangers in North Carolina is fire prevention. Personal contact with the public is essential to the successful performance of this function. A survey of 50 North Carolina rangers revealed that the degree of success for each ranger was directly related to the specific effort put forth as a contactor.

Long-term ecosystem nitrogen storage and soil nitrogen availability in post-fire lodgepole pine ecosystems

Treesearch

Erica A. H. Smithwick; Daniel M. Kashian; Michael G. Ryan; Monica G.  Turner

2009-01-01

Long-term, landscape patterns in inorganic nitrogen (N) availability and N stocks following infrequent, stand-replacing fire are unknown but are important for interpreting the effect of disturbances on ecosystem function. Here, we present results from a replicated chronosequence study in the Greater Yellowstone Ecosystem (Wyoming, USA) directed at measuring inorganic N...

The theory, direction, and magnitude of ecosystem fire probability as constrained by precipitation and temperature

Treesearch

Richard Guyette; Michael C. Stambaugh; Daniel Dey; Rose Marie Muzika; Ben Bond-Lamberty

2017-01-01

The effects of climate on wildland fire confronts society across a range of different ecosystems. Water and temperature affect the combustion dynamics, irrespective of whether those are associated with carbon fueled motors or ecosystems, but through different chemical, physical, and biological processes. We use an ecosystem combustion equation developed with the...

Use of a thermocouple-datalogger system to evaluate overstory mortality

Treesearch

Lucy Brudnak; Thomas A. Waldrop; Ross J. Phillips

2010-01-01

In the past, it was difficult to accurately measure dynamic fire behavior during prescribed burns. Peak temperature, flaming duration, and total heat output may be directly related to first-order fire effects such as fuel consumption and vegetative mortality; however, little is known about which of these variables is most closely associated with, and therefore the best...

Modeling effects of climate change and fire management on western white pine (Pinus monticola) in the northern Rocky Mountains, USA

Treesearch

Rachel A. Loehman; Jason A. Clark; Robert E. Keane

2011-01-01

Climate change is projected to profoundly influence vegetation patterns and community compositions, either directly through increased species mortality and shifts in species distributions or indirectly through disturbance dynamics such as increased wildfire activity and extent, shifting fire regimes, and pathogenesis. Mountainous landscapes have been shown to be...

A conservation paradox in the Great Basin—Altering sagebrush landscapes with fuel breaks to reduce habitat loss from wildfire

USGS Publications Warehouse

Shinneman, Douglas J.; Aldridge, Cameron L.; Coates, Peter S.; Germino, Matthew J.; Pilliod, David S.; Vaillant, Nicole M.

2018-03-15

Interactions between fire and nonnative, annual plant species (that is, “the grass/fire cycle”) represent one of the greatest threats to sagebrush (Artemisia spp.) ecosystems and associated wildlife, including the greater sage-grouse (Centrocercus urophasianus). In 2015, U.S. Department of the Interior called for a “science-based strategy to reduce the threat of large-scale rangeland fire to habitat for the greater sage-grouse and the sagebrush-steppe ecosystem.” An associated guidance document, the “Integrated Rangeland Fire Management Strategy Actionable Science Plan,” identified fuel breaks as high priority areas for scientific research. Fuel breaks are intended to reduce fire size and frequency, and potentially they can compartmentalize wildfire spatial distribution in a landscape. Fuel breaks are designed to reduce flame length, fireline intensity, and rates of fire spread in order to enhance firefighter access, improve response times, and provide safe and strategic anchor points for wildland fire-fighting activities. To accomplish these objectives, fuel breaks disrupt fuel continuity, reduce fuel accumulation, and (or) increase plants with high moisture content through the removal or modification of vegetation in strategically placed strips or blocks of land.Fuel breaks are being newly constructed, enhanced, or proposed across large areas of the Great Basin to reduce wildfire risk and to protect remaining sagebrush ecosystems (including greater sage-grouse habitat). These projects are likely to result in thousands of linear miles of fuel breaks that will have direct ecological effects across hundreds of thousands of acres through habitat loss and conversion. These projects may also affect millions of acres indirectly because of edge effects and habitat fragmentation created by networks of fuel breaks. Hence, land managers are often faced with a potentially paradoxical situation: the need to substantially alter sagebrush habitats with fuel breaks to ultimately reduce a greater threat of their destruction from wildfire. However, there is relatively little published science that directly addresses the ability of fuel breaks to influence fire behavior in dryland landscapes or that addresses the potential ecological effects of the construction and maintenance of fuel breaks on sagebrush ecosystems and associated wildlife species.This report is intended to provide an initial assessment of both the potential effectiveness of fuel breaks and their ecological costs and benefits. To provide this assessment, we examined prior studies on fuel breaks and other scientific evidence to address three crucial questions: (1) How effective are fuel breaks in reducing or slowing the spread of wildfire in arid and semi-arid shrubland ecosystems? (2) How do fuel breaks affect sagebrush plant communities? (3) What are the effects of fuel breaks on the greater sage-grouse, other sagebrush obligates, and sagebrush-associated wildlife species? We also provide an overview of recent federal policies and management directives aimed at protecting remaining sagebrush and greater sage-grouse habitat; describe the fuel conditions, fire behavior, and fire trends in the Great Basin; and suggest how scientific inquiry and management actions can improve our understanding of fuel breaks and their effects in sagebrush landscapes.

Experimental demonstration of tunable directional excitation of surface plasmon polaritons with a subwavelength metallic double slit

NASA Astrophysics Data System (ADS)

Li, Xiaowei; Tan, Qiaofeng; Bai, Benfeng; Jin, Guofan

2011-06-01

We demonstrate experimentally the directional excitation of surface plasmon polaritons (SPPs) on a metal film by a subwavelength double slit under backside illumination, based on the interference of SPPs generated by the two slits. By varying the incident angle, the SPPs can be tunably directed into two opposite propagating directions with a predetermined splitting ratio. Under certain incident angle, unidirectional SPP excitation can be achieved. This compact directional SPP coupler is potentially useful for many on-chip applications. As an example, we show the integration of the double-slit couplers with SPP Bragg mirrors, which can effectively realize selective coupling of SPPs into different ports in an integrated plasmonic chip.

Simulating fire regimes in the Amazon in response to climate change and deforestation.

PubMed

Silvestrini, Rafaella Almeida; Soares-Filho, Britaldo Silveira; Nepstad, Daniel; Coe, Michael; Rodrigues, Hermann; Assunção, Renato

2011-07-01

Fires in tropical forests release globally significant amounts of carbon to the atmosphere and may increase in importance as a result of climate change. Despite the striking impacts of fire on tropical ecosystems, the paucity of robust spatial models of forest fire still hampers our ability to simulate tropical forest fire regimes today and in the future. Here we present a probabilistic model of human-induced fire occurrence for the Amazon that integrates the effects of a series of anthropogenic factors with climatic conditions described by vapor pressure deficit. The model was calibrated using NOAA-12 night satellite hot pixels for 2003 and validated for the years 2002, 2004, and 2005. Assessment of the fire risk map yielded fitness values > 85% for all months from 2002 to 2005. Simulated fires exhibited high overlap with NOAA-12 hot pixels regarding both spatial and temporal distributions, showing a spatial fit of 50% within a radius of 11 km and a maximum yearly frequency deviation of 15%. We applied this model to simulate fire regimes in the Amazon until 2050 using IPCC's A2 scenario climate data from the Hadley Centre model and a business-as-usual (BAU) scenario of deforestation and road expansion from SimAmazonia. Results show that the combination of these scenarios may double forest fire occurrence outside protected areas (PAs) in years of extreme drought, expanding the risk of fire even to the northwestern Amazon by midcentury. In particular, forest fires may increase substantially across southern and southwestern Amazon, especially along the highways slated for paving and in agricultural zones. Committed emissions from Amazon forest fires and deforestation under a scenario of global warming and uncurbed deforestation may amount to 21 +/- 4 Pg of carbon by 2050. BAU deforestation may increase fires occurrence outside PAs by 19% over the next four decades, while climate change alone may account for a 12% increase. In turn, the combination of climate change and deforestation would boost fire occurrence outside PAs by half during this period. Our modeling results, therefore, confirm the synergy between the two Ds of REDD (Reducing Emissions from Deforestation and Forest Degradation in Developing Countries).

First principles electron-correlated calculations of optical absorption in magnesium clusters★

NASA Astrophysics Data System (ADS)

Shinde, Ravindra; Shukla, Alok

2017-11-01

In this paper, we report large-scale configuration interaction (CI) calculations of linear optical absorption spectra of various isomers of magnesium clusters Mgn (n = 2-5), corresponding to valence transitions. Geometry optimization of several low-lying isomers of each cluster was carried out using coupled-cluster singles doubles (CCSD) approach, and these geometries were subsequently employed to perform ground and excited state calculations using either the full-CI (FCI) or the multi-reference singles-doubles configuration interaction (MRSDCI) approach, within the frozen-core approximation. Our calculated photoabsorption spectrum of magnesium dimer (Mg2) is in excellent agreement with the experiments both for peak positions, and intensities. Owing to the sufficiently inclusive electron-correlation effects, these results can serve as benchmarks against which future experiments, as well as calculations performed using other theoretical approaches, can be tested. Supplementary material in the form of one pdf fille available from the Journal web page at http://https://doi.org/10.1140/epjd/e2017-80356-6.

The physics of heterodyne detection in the far-infrared: Transition from electric-field to photon-absorption detection in a simple system

NASA Technical Reports Server (NTRS)

Teich, M. C.

1980-01-01

The history of heterodyne detection is reviewed from the radiowave to the optical regions of the electromagnetic spectrum with emphasion the submillimeter/far infrared. The transition from electric field to photon absorption detection in a simple system is investigated. The response of an isolated two level detector to a coherent source of incident radiation is calculated for both heterodyne and video detection. When the processes of photon absorption and photon emission cannot be distinguished, the relative detected power at double- and sum-frequencies is found to be multiplied by a coefficient, which is less than or equal to unity, and which depends on the incident photon energy and on the effective temperature of the system.

Demonstration Report, Munitions Management Projects, ESTCP Project MR-200809, ALLTEM Multi-Axis Electromagnetic Induction System Demonstration and Validation, Aberdeen Proving Ground Standardized UXO Technology Demonstration Site, Version 1.0

DTIC Science & Technology

2011-11-17

to emulate typical impact area conditions. The Open Field area is now divided into four subareas: Legacy, Indirect fire, Direct fire, and Challenge...that could be typically found at an impact area of an indirect fire weapons range. These are 81 mm and 60 mm mortars and 105 ALLTEM APG...munitions. • Open field (direct fire) The direct fire subarea contains only three munition types that could be typically found at an impact area of

The core-double-shell microcapsules flame retardant: Synthesis and its application for polyvinyl chloride composites

NASA Astrophysics Data System (ADS)

Zhang, Bin; Jiang, Yujie; Han, Jian

2017-12-01

The core-double-shell microcapsules flame retardant has been regarded as a promising additive for improving the fire safety of PVC. In this article, melamine-formaldehyde resin (MF)/silicon dioxide (SiO2)/zinc hydroxystannate (ZHS) microcapsule was prepared. The effect of synthetic parameters (such as pH, agitation speed, reaction time and reaction temperature) on the morphologies and sizes of the SiO2/ZHS microcapsules were investigated in details. MF/SiO2/ZHS microcapsule was introduced into PVC to prepare biofunctional composites with excellent fire resistance and smoke suppression. The flammability of PVC composites was characterized by limiting oxygen index (LOI), smoke density (SDR), cone calorimeter test. The results showed that the sample containing 16.4% MF/SiO2/ZHS microcapsule (the mass ratio of MF:SiO2:ZHS = 2.5:2:8) achieved the maximal LOI value of 35.6%, minimal SDR value of 21.2%, and significantly decreased the peak heat release rate from 179.7 kW/m2 of neat PVC to 108.3 kW/m2. The thermal behaviors of PVC composites and the morphologies of residues were characterized.

The role of fire-return interval and season of burn in snag dynamics in a south Florida slash pine forest

USGS Publications Warehouse

Lloyd, John D.; Slater, Gary L.; Snyder, James R.

2012-01-01

Standing dead trees, or snags, are an important habitat element for many animal species. In many ecosystems, fire is a primary driver of snag population dynamics because it can both create and consume snags. The objective of this study was to examine how variation in two key components of the fire regime—fire-return interval and season of burn—affected population dynamics of snags. Using a factorial design, we exposed 1 ha plots, located within larger burn units in a south Florida slash pine (Pinus elliottii var. densa Little and Dorman) forest, to prescribed fire applied at two intervals (approximately 3-year intervals vs. approximately 6-year intervals) and during two seasons (wet season vs. dry season) over a 12- to 13-year period. We found no consistent effect of fire season or frequency on the density of lightly to moderately decayed or heavily decayed snags, suggesting that variation in these elements of the fire regime at the scale we considered is relatively unimportant in the dynamics of snag populations. However, our confidence in these findings is limited by small sample sizes, potentially confounding effects of unmeasured variation in fire behavior and effects (e.g., intensity, severity, synergy with drought cycles) and wide variation in responses within a treatment level. The generalizing of our findings is also limited by the narrow range of treatment levels considered. Future experiments incorporating a wider range of fire regimes and directly quantifying fire intensity would prove useful in identifying more clearly the role of fire in shaping the dynamics of snag populations.

Modeling the impact of common noise inputs on the network activity of retinal ganglion cells

PubMed Central

Ahmadian, Yashar; Shlens, Jonathon; Pillow, Jonathan W.; Kulkarni, Jayant; Litke, Alan M.; Chichilnisky, E. J.; Simoncelli, Eero; Paninski, Liam

2013-01-01

Synchronized spontaneous firing among retinal ganglion cells (RGCs), on timescales faster than visual responses, has been reported in many studies. Two candidate mechanisms of synchronized firing include direct coupling and shared noisy inputs. In neighboring parasol cells of primate retina, which exhibit rapid synchronized firing that has been studied extensively, recent experimental work indicates that direct electrical or synaptic coupling is weak, but shared synaptic input in the absence of modulated stimuli is strong. However, previous modeling efforts have not accounted for this aspect of firing in the parasol cell population. Here we develop a new model that incorporates the effects of common noise, and apply it to analyze the light responses and synchronized firing of a large, densely-sampled network of over 250 simultaneously recorded parasol cells. We use a generalized linear model in which the spike rate in each cell is determined by the linear combination of the spatio-temporally filtered visual input, the temporally filtered prior spikes of that cell, and unobserved sources representing common noise. The model accurately captures the statistical structure of the spike trains and the encoding of the visual stimulus, without the direct coupling assumption present in previous modeling work. Finally, we examined the problem of decoding the visual stimulus from the spike train given the estimated parameters. The common-noise model produces Bayesian decoding performance as accurate as that of a model with direct coupling, but with significantly more robustness to spike timing perturbations. PMID:22203465

Millimeter waves thermally alter the firing rate of the Lymnaea pacemaker neuron

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alekseev, S.I.; Kochetkova, N.V.; Ziskin, M.C.

1997-05-01

The effects of millimeter waves (mm-waves, 75 GHz) and temperature elevation on the firing rate of the BP-4 pacemaker neuron of the pond snail Lymnaea stagnalis were studied by using microelectrode techniques. The open end of a rectangular waveguide covered with a thin Teflon film served as a radiator. Specific absorption rates (SARs), measured in physiological solution at the radiator outlet, ranged from 600 to 4,200 W/kg, causing temperature rises from 0.3 to 2.2 C, respectively. Irradiation at an SAR of 4,200 W/kg caused a biphasic change in the firing rate, i.e., a transient decrease in the firing rate followedmore » by a gradual increase to a new level that was 68 {+-} 21% above control. The biphasic changes in the firing rate were reproduced by heating under the condition that the magnitude (2 C) and the rate of temperature rise were equal to those produced by the irradiation. The addition of 0.05 mM of ouabain caused the disappearance of transient responses of the neuron to the irradiation. It was shown that the rate of temperature rise played an important role in the development of a transient neuronal response. The threshold stimulus for a transient response of the BP-4 neutron found in warming experiments was a temperature rise of 0.0025 C/s.« less

Effects of wild fires on the emissions of reactive gases from boreal and subarctic soils

NASA Astrophysics Data System (ADS)

Zhang-Turpeinen, Huizhong; Pumpanen, Jukka; Kivimäenpää, Minna

2017-04-01

Wild fire has long-term effects on the ecosystem and biological processes of boreal forest, and the frequency of wild fires is increasing as a consequence of climate change. Boreal forests lie largely on permafrost area, and the increase in fire frequency or intensity will affect the depth of the active layer on top of permafrost. The thawing of permafrost soils and increase in the active layer depth could induce significant reactive trace gas emissions. Biogenic volatile organic compounds (BVOCs) and nitrous acid (HONO) are closely associated with air chemistry in the troposphere. They react easily with ozone, hydroxyl radicals, and the reaction products may condense into aerosol particles or affect the growth of atmospheric aerosols which act as cloud condensation nuclei. Forests, and in particular permafrost soils, could be potentially large sources of BVOCs and HONO, because of the large amount of decomposing litter and soil organic matter. However, the forest soil BVOC emissions are poorly known, in contrast to BVOCs emitted from branch and canopy levels in boreal forests. The production rates of HONO in various soils are also poorly known. We studied BVOC and HONO fluxes from boreal forest soils and the effects of wild fires and the time since the last fire on them. We measured BVOCs emissions in west Siberia larch forest stands on permafrost soil in a fire chronosequence where the last forest fires had occurred 2, 24, and more than 100 years ago. HONO emissions in northern boreal subarctic Scots pine forest stands in Eastern Lapland in Finland in a fire chronosequence where the last fires had occurred 7, 47, 72 and 157 years ago. BVOC flux measurements were carried out by drawing air samples from chamber headspace into a steel adsorbent tube containing Tenax TA and carbopack B. The sampling tubes were analyzed on gas chromatography-mass spectrometry (GC-MS). Soil samples were measured for HONO flux in laboratory with LOPAP (Long path absorption photometer). According to our preliminary results the influence and the duration of the impact of forest fires were not observed in HONO emissions. However, the HONO emissions were sensitive to soil moisture. The unexpectedly high rate of release of isoprene measured in the middle age forest sites with warm scenario. Environmental parameters were correlated with the presence of BVOCs. We compared the BVOC fluxes with environmental parameters such as temperature, humidity and PAR, and with ground vegetation coverage and with litter input. The BVOC data is under processing still and more detail results is coming later.

Dynamics of a modified Hindmarsh-Rose neural model with random perturbations: Moment analysis and firing activities

NASA Astrophysics Data System (ADS)

Mondal, Argha; Upadhyay, Ranjit Kumar

2017-11-01

In this paper, an attempt has been made to understand the activity of mean membrane voltage and subsidiary system variables with moment equations (i.e., mean, variance and covariance's) under noisy environment. We consider a biophysically plausible modified Hindmarsh-Rose (H-R) neural system injected by an applied current exhibiting spiking-bursting phenomenon. The effects of predominant parameters on the dynamical behavior of a modified H-R system are investigated. Numerically, it exhibits period-doubling, period halving bifurcation and chaos phenomena. Further, a nonlinear system has been analyzed for the first and second order moments with additive stochastic perturbations. It has been solved using fourth order Runge-Kutta method and noisy systems by Euler's scheme. It has been demonstrated that the firing properties of neurons to evoke an action potential in a certain parameter space of the large exact systems can be estimated using an approximated model. Strong stimulation can cause a change in increase or decrease of the firing patterns. Corresponding to a fixed set of parameter values, the firing behavior and dynamical differences of the collective variables of a large, exact and approximated systems are investigated.

At the nexus of fire, water and society.

PubMed

Martin, Deborah A

2016-06-05

The societal risks of water scarcity and water-quality impairment have received considerable attention, evidenced by recent analyses of these topics by the 2030 Water Resources Group, the United Nations and the World Economic Forum. What are the effects of fire on the predicted water scarcity and declines in water quality? Drinking water supplies for humans, the emphasis of this exploration, are derived from several land cover types, including forests, grasslands and peatlands, which are vulnerable to fire. In the last two decades, fires have affected the water supply catchments of Denver (CO) and other southwestern US cities, and four major Australian cities including Sydney, Canberra, Adelaide and Melbourne. In the same time period, several, though not all, national, regional and global water assessments have included fire in evaluations of the risks that affect water supplies. The objective of this discussion is to explore the nexus of fire, water and society with the hope that a more explicit understanding of fire effects on water supplies will encourage the incorporation of fire into future assessments of water supplies, into the pyrogeography conceptual framework and into planning efforts directed at water resiliency.This article is part of the themed issue 'The interaction of fire and mankind'. © 2016 The Author(s).

Different fire-climate relationships on forested and non-forested landscapes in the Sierra Nevada ecoregion

USGS Publications Warehouse

Keeley, Jon E.; Syphard, Alexandra D.

2015-01-01

In the California Sierra Nevada region, increased fire activity over the last 50 years has only occurred in the higher-elevation forests on US Forest Service (USFS) lands, and is not characteristic of the lower-elevation grasslands, woodlands and shrublands on state responsibility lands (Cal Fire). Increased fire activity on USFS lands was correlated with warmer and drier springs. Although this is consistent with recent global warming, we found an equally strong relationship between fire activity and climate in the first half of the 20th century. At lower elevations, warmer and drier conditions were not strongly tied to fire activity over the last 90 years, although prior-year precipitation was significant. It is hypothesised that the fire–climate relationship in forests is determined by climatic effects on spring and summer fuel moisture, with hotter and drier springs leading to a longer fire season and more extensive burning. In contrast, future fire activity in the foothills may be more dependent on rainfall patterns and their effect on the herbaceous fuel load. We predict spring and summer warming will have a significant impact on future fire regimes, primarily in higher-elevation forests. Lower elevation ecosystems are likely to be affected as much by global changes that directly involve land-use patterns as by climate change.

Energy Analysis and Environmental Impacts of Hybrid Giant Napier (Pennisetum Hydridum) Direct-fired Power Generation in South China

NASA Astrophysics Data System (ADS)

Liao, Yanfen; Fang, Hailin; Zhang, Hengjin; Yu, Zhaosheng; Liu, Zhichao; Ma, Xiaoqian

2017-05-01

To meet with the demand of energy conservation and emission reduction policies, the method of life cycle assessment (LCA) was used to assess the feasibility of Hybrid Giant Napier (HGN) direct-fired power generation in this study. The entire life cycle is consisted of five stages (cultivation and harvesting, transportation, drying and comminuting, direct-fired power generation, constructing and decommissioning of biomass power plant). Analytical results revealed that to generate 10000kWh electricity, 10.925 t of customized HGN fuel (moisture content: 30 wt%) and 6659.430 MJ of energy were required. The total environmental impact potential was 0.927 PET2010 (person equivalents, targeted, in 2010) and the global warming (GW), acidification (AC), and nutrient (NE) emissions were 339.235 kg CO2-eq, 22.033 kg SO2-eq, and 25.486 kg NOx-eq respectively. The effect of AC was the most serious among all calculated category impacts. The energy requirements and environmental impacts were found to be sensitive to single yield, average transport distance, cutting frequency, and moisture content. The results indicated that HGN direct-fired power generation accorded well with Chinese energy planning; in addition, HGN proved to be a promising contribution to reducing non-renewable energy consumption and had encouraging prospects as a renewable energy plant.

Validation of double-pulse 1572 nm integrated path differential absorption lidar measurement of carbon dioxide

NASA Astrophysics Data System (ADS)

Du, Juan; Liu, Jiqiao; Bi, Decang; Ma, Xiuhua; Hou, Xia; Zhu, Xiaolei; Chen, Weibiao

2018-04-01

A ground-based double-pulse 1572 nm integrated path differential absorption (IPDA) lidar was developed for carbon dioxide (CO2) column concentrations measurement. The lidar measured the CO2 concentrations continuously by receiving the scattered echo signal from a building about 1300 m away. The other two instruments of TDLAS and in-situ CO2 analyzer measured the CO2 concentrations on the same time. A CO2 concentration measurement of 430 ppm with 1.637 ppm standard error was achieved.

Preparation of sintered foam materials by alkali-activated coal fly ash.

PubMed

Zhao, Yelong; Ye, Junwei; Lu, Xiaobin; Liu, Mangang; Lin, Yuan; Gong, Weitao; Ning, Guiling

2010-02-15

Coal fly ash from coal fired power stations is a potential raw material for the production of ceramic tiles, bricks and blocks. Previous works have demonstrated that coal fly ash consists mainly of glassy spheres that are relatively resistant to reaction. An objective of this research was to investigate the effect of alkali on the preparation process of the foam material. Moreover, the influence of foam dosage on the water absorption, apparent density and compressive strength was evaluated. The experimental results showed that homogenous microstructures of interconnected pores could be obtained by adding 13 wt.% foaming agent at 1050 degrees C, leading to foams presenting water absorption, apparent density and compressive strength values of about 126.5%, 0.414 g/cm(3), 6.76 MPa, respectively.

Quantifying the effects of climate and post-fire landscape change on hydrologic processes

NASA Astrophysics Data System (ADS)

Steimke, A.; Han, B.; Brandt, J.; Som Castellano, R.; Leonard, A.; Flores, A. N.

2016-12-01

Seasonally snow-dominated, forested mountain watersheds supply water to many human populations globally. However, the timing and magnitude of water delivery from these watersheds has already and will continue to change as the climate warms. Changes in vegetation also affect the runoff response of watersheds. The largest driver of vegetation change in many mountainous regions is wildfire, whose occurrence is affected by both climate and land management decisions. Here, we quantify how direct (i.e. changes in precipitation and temperature) and indirect (i.e. changing fire regimes) effects of climate change influence hydrologic parameters such as dates of peak streamflow, annual discharge, and snowpack levels. We used the Boise River Basin, ID as a model laboratory to calculate the relative magnitude of change stemming from direct and indirect effects of climate change. This basin is relevant to study as it is well-instrumented and major drainages have experienced burning at different spatial and temporal intervals, aiding in model calibration. We built a hydrology-based integrated model of the region using a multiagent simulation framework, Envision. We used a modified HBV (Hydrologiska Byråns Vattenbalansavdelning) rainfall-runoff model and calibrated it to historic streamflow and snowpack observations. We combined a diverse set of climate projections with wildfire scenarios (low vs. high) representing two distinct intervals in the regional historic fire record. In fire simulations, we altered land cover coefficients to reflect a burned state post-fire, which decreased overall evapotranspiration rates and increased water yields. However, direct climate effects had a larger signal on annual variations of hydrologic parameters. By comparing and analyzing scenario outputs, we identified links and sensitivities between land cover and regional hydrology in the context of a changing climate, with potential implications for local land and water managers. In future research, this framework will support investigations of climate-aware land management actions on basin hydrologic response.

Activity and stability of immobilized carbonic anhydrase for promoting CO2 absorption into a carbonate solution for post-combustion CO2 capture

USGS Publications Warehouse

Zhang, S.; Zhang, Z.; Lu, Y.; Rostam-Abadi, M.; Jones, A.

2011-01-01

An Integrated Vacuum Carbonate Absorption Process (IVCAP) currently under development could significantly reduce the energy consumed when capturing CO2 from the flue gases of coal-fired power plants. The biocatalyst carbonic anhydrase (CA) has been found to effectively promote the absorption of CO2 into the potassium carbonate solution that would be used in the IVCAP. Two CA enzymes were immobilized onto three selected support materials having different pore structures. The thermal stability of the immobilized CA enzymes was significantly greater than their free counterparts. For example, the immobilized enzymes retained at least 60% of their initial activities after 90days at 50??C compared to about 30% for their free counterparts under the same conditions. The immobilized CA also had significantly improved resistance to concentrations of sulfate (0.4M), nitrate (0.05M) and chloride (0.3M) typically found in flue gas scrubbing liquids than their free counterparts. ?? 2011 Elsevier Ltd.

A Landscape-Scale, Applied Fire Management Experiment Promotes Recovery of a Population of the Threatened Gouldian Finch, Erythrura gouldiae, in Australia's Tropical Savannas.

PubMed

Legge, Sarah; Garnett, Stephen; Maute, Kim; Heathcote, Joanne; Murphy, Steve; Woinarski, John C Z; Astheimer, Lee

2015-01-01

Fire is an integral part of savanna ecology and changes in fire patterns are linked to biodiversity loss in savannas worldwide. In Australia, changed fire regimes are implicated in the contemporary declines of small mammals, riparian species, obligate-seeding plants and grass seed-eating birds. Translating this knowledge into management to recover threatened species has proved elusive. We report here on a landscape-scale experiment carried out by the Australian Wildlife Conservancy (AWC) on Mornington Wildlife Sanctuary in northwest Australia. The experiment was designed to understand the response of a key savanna bird guild to fire, and to use that information to manage fire with the aim of recovering a threatened species population. We compared condition indices among three seed-eating bird species--one endangered (Gouldian finch) and two non-threatened (long-tailed finch and double-barred finch)--from two large areas (> 2,830 km2) with initial contrasting fire regimes ('extreme': frequent, extensive, intense fire; versus 'benign': less frequent, smaller, lower intensity fires). Populations of all three species living with the extreme fire regime had condition indices that differed from their counterparts living with the benign fire regime, including higher haematocrit levels in some seasons (suggesting higher levels of activity required to find food), different seasonal haematocrit profiles, higher fat scores in the early wet season (suggesting greater food uncertainty), and then lower muscle scores later in the wet season (suggesting prolonged food deprivation). Gouldian finches also showed seasonally increasing stress hormone concentrations with the extreme fire regime. Cumulatively, these patterns indicated greater nutritional stress over many months for seed-eating birds exposed to extreme fire regimes. We tested these relationships by monitoring finch condition over the following years, as AWC implemented fire management to produce the 'benign' fire regime throughout the property. The condition indices of finch populations originally living with the extreme fire regime shifted to resemble those of their counterparts living with the benign fire regime. This research supports the hypothesis that fire regimes affect food resources for savanna seed-eating birds, with this impact mediated through a range of grass species utilised by the birds over different seasons, and that fire management can effectively moderate that impact. This work provides a rare example of applied research supporting the recovery of a population of a threatened species.

Current and future patterns of fire-induced forest degradation in Amazonia

NASA Astrophysics Data System (ADS)

De Faria, Bruno L.; Brando, Paulo M.; Macedo, Marcia N.; Panday, Prajjwal K.; Soares-Filho, Britaldo S.; Coe, Michael T.

2017-09-01

Amazon droughts directly increase forest flammability by reducing forest understory air and fuel moisture. Droughts also increase forest flammability indirectly by decreasing soil moisture, triggering leaf shedding, branch loss, and tree mortality—all of which contribute to increased fuel loads. These direct and indirect effects can cause widespread forest fires that reduce forest carbon stocks in the Amazon, with potentially important consequences for the global carbon cycle. These processes are expected to become more widespread, common, and intense as global climate changes, yet the mechanisms linking droughts, wildfires, and associated changes in carbon stocks remain poorly understood. Here, we expanded the capabilities of a dynamic forest carbon model to better represent (1) drought effects on carbon and fuel dynamics and (2) understory fire behavior and severity. We used the refined model to quantify changes in Pan-Amazon live carbon stocks as a function of the maximum climatological water deficit (MCWD) and fire intensity, under both historical and future climate conditions. We found that the 2005 and 2010 droughts increased potential fire intensity by 226 kW m-1 and 494 kW m-1, respectively. These increases were due primarily to increased understory dryness (109 kW m-1 in 2005; 124 kW m-1 in 2010) and altered forest structure (117 kW m-1 in 2005; 370 kW m-1 in 2010) effects. Combined, these historic droughts drove total simulated reductions in live carbon stocks of 0.016 (2005) and 0.027 (2010) PgC across the Amazon Basin. Projected increases in future fire intensity increased simulated carbon losses by up to 90% per unit area burned, compared with modern climate. Increased air temperature was the primary driver of changes in simulated future fire intensity, while reduced precipitation was secondary, particularly in the eastern portion of the Basin. Our results show that fire-drought interactions strongly affect live carbon stocks and that future climate change, combined with the synergistic effects of drought on forest flammability, may strongly influence the stability of tropical forests in the future.

Characteristics of Borneo and Sumatra fire plume heights and smoke clouds and their impact on regional El Niño-induced drought

NASA Astrophysics Data System (ADS)

Tosca, Michael; Randerson, James; Zender, Charles; Flanner, Mark; Nelson, David; Diner, David; Rasch, Phil; Logan, Jennifer

2010-05-01

During the dry season, anthropogenic fires burn the tropical forests and peatlands of equatorial Asia and produce regionally expansive smoke clouds. We estimated the altitude of smoke from these fires, characterized the sensitivity of this smoke to regional drought and El Niño variability, and investigated its effect on climate. We used the MISR satellite product and MISR INteractive eXplorer (MINX) software to estimate the heights of 382 smoke plumes (smoke with a visible surface source and transport direction) on Borneo and 121 plumes on Sumatra for 2001-2009. In addition, we estimated the altitudes of 10 smoke clouds (opaque regions of smoke with no detectable surface source or transport direction) on Borneo for 2006. Most smoke plumes (80%) were observed during El Niño events (2002, 2004, 2006, 2009); this is consistent with higher aerosol optical depths observed during El Niño-induced drought. Annually averaged plume heights on Borneo were positively correlated to the Oceanic Niño Index (ONI), an indicator of El Niño (r2 = 0.53). The mean plume height for all El Niño years was 765.8 ± 19.7m, compared to 711.4 ± 28.7 for non-El Niño years. The median altitude of all 10 smoke clouds observed on Borneo during 2006 was 1313m, compared to a median 787m for smoke plume grid cells. The area covered by all smoke plumes from 2006 corresponded to approximately three individual smoke clouds. We investigated the climate response to these expansive smoke clouds using the Community Atmosphere Model (CAM). Climate variables from two 30 year simulations were compared: one simulation was forced with fire emissions typical of a dry (El Niño) burning year, while the other was forced with emissions typical of a low (La Niña) burning year. Fire aerosols reduced net shortwave radiation at the surface during August-October by an average of 10% in the region encompassing most of Sumatra and Borneo (90°E-120°E, 5°S-5°N). The reductions in net radiation cooled both ocean (0.5 ± 0.3°C) and land (0.4 ± 0.2°C) temperatures during these months. Tropospheric heating from black carbon (BC) absorption increased substantially (20.5 ± 9.3 W m-2), but was balanced by an overall reduction in latent heating. The combination of decreased SSTs and increased atmospheric heating reduced regional precipitation by 0.9 ± 0.6 mm d-1 (10%). This implies that the vulnerability of ecosystems to fire was increased because the reductions in precipitation exceeded those for evapotranspiration. Together, the satellite and modeling results imply a possible positive feedback loop in which anthropogenic burning in the region intensifies drought stress during El Niño.

Airborne Double Pulsed 2-Micron IPDA Lidar for Atmospheric CO2 Measurement

NASA Technical Reports Server (NTRS)

Yu, Jirong; Petros, Mulugeta; Refaat, Tamer; Singh, Upendra

2015-01-01

We have developed an airborne 2-micron Integrated Path Differential Absorption (IPDA) lidar for atmospheric CO2 measurements. The double pulsed, high pulse energy lidar instrument can provide high-precision CO2 column density measurements.

Development of Double-Pulsed Two-Micron Laser for Atmospheric Carbon Dioxide Measurements

NASA Technical Reports Server (NTRS)

Petros, Mulugeta; Singh, Upendra N.; Yu, Jirong; Refaat, Tamer F.

2017-01-01

A CO2 lidar double-pulse two-micron high-energy transmitter, tuned to on- and off-line absorption wavelengths, has been developed. Transmitter operation and performance has been verified on ground and airborne platform.

A high pressure La K-edge X-ray absorption fine structure spectroscopy investigation of La1/3NbO3

NASA Astrophysics Data System (ADS)

Marini, C.; Joseph, B.; Noked, O.; Shuker, R.; Kennedy, B. J.; Mathon, O.; Pascarelli, S.; Sterer, E.

2018-01-01

La K-edge X-ray absorption spectroscopy has been used to elucidate the changes in the local electronic and lattice structure that occur in the A-site deficient double perovskite La?NbO? up to 6 GPa. The pressure evolution of the oxygen dodecahedrum around the A-site has been examined. XANES (X-ray absorption near edge structure) data show modifications ascribed to the increase of bands overlapping as a consequence of the bond distance contraction, which has been directly probed by EXAFS (extended x-ray absorption fine structure) spectra. The La-O Debye Waller factors (DWFs) tend to increase whereas the La-Nb bond DWFs show only a tendency to decrease indicating the robustness of the crystal lattice structure, even in presence of the oxygen disordering. This permits the system to reverse back to its original conditions in this pressure range as evident from the measurements upon pressure release. The present results have been interpreted in the light of charge transfer related to the two-step reduction mechanism acting at the Nb site (with niobium ions passing from Nb? to Nb?) which also results in the elongation of the Nb-O bond distances in the octahedra, in agreement with the Nb K-edge results reported earlier.

Effects of fire and CO2 on biogeography and primary production in glacial and modern climates.

PubMed

Martin Calvo, Maria; Prentice, Iain Colin

2015-11-01

Dynamic global vegetation models (DGVMs) can disentangle causes and effects in the control of vegetation and fire. We used a DGVM to analyse climate, CO2 and fire influences on biome distribution and net primary production (NPP) in last glacial maximum (LGM) and pre-industrial (PI) times. The Land surface Processes and eXchanges (LPX) DGVM was run in a factorial design with fire 'off' or 'on', CO2 at LGM (185 ppm) or PI (280 ppm) concentrations, and LGM (modelled) or recent climates. Results were analysed by Stein-Alpert decomposition to separate primary effects from synergies. Fire removal causes forests to expand and global NPP to increase slightly. Low CO2 greatly reduces forest area (dramatically in a PI climate; realistically under an LGM climate) and global NPP. NPP under an LGM climate was reduced by a quarter as a result of low CO2 . The reduction in global NPP was smaller at low temperatures, but greater in the presence of fire. Global NPP is controlled by climate and CO2 directly through photosynthesis, but also through biome distribution, which is strongly influenced by fire. Future vegetation simulations will need to consider the coupled responses of vegetation and fire to CO2 and climate. © 2015 The Authors. New Phytologist © 2015 New Phytologist Trust.

Exploiting simultaneous observational constraints on mass and absorption to estimate the global direct radiative forcing of black carbon and brown carbon

NASA Astrophysics Data System (ADS)

Wang, X.; Heald, C. L.; Ridley, D. A.; Schwarz, J. P.; Spackman, J. R.; Perring, A. E.; Coe, H.; Liu, D.; Clarke, A. D.

2014-10-01

Atmospheric black carbon (BC) is a leading climate warming agent, yet uncertainties on the global direct radiative forcing (DRF) remain large. Here we expand a global model simulation (GEOS-Chem) of BC to include the absorption enhancement associated with BC coating and separately treat both the aging and physical properties of fossil-fuel and biomass-burning BC. In addition we develop a global simulation of brown carbon (BrC) from both secondary (aromatic) and primary (biomass burning and biofuel) sources. The global mean lifetime of BC in this simulation (4.4 days) is substantially lower compared to the AeroCom I model means (7.3 days), and as a result, this model captures both the mass concentrations measured in near-source airborne field campaigns (ARCTAS, EUCAARI) and surface sites within 30%, and in remote regions (HIPPO) within a factor of 2. We show that the new BC optical properties together with the inclusion of BrC reduces the model bias in absorption aerosol optical depth (AAOD) at multiple wavelengths by more than 50% at AERONET sites worldwide. However our improved model still underestimates AAOD by a factor of 1.4 to 2.8 regionally, with the largest underestimates in regions influenced by fire. Using the RRTMG model integrated with GEOS-Chem we estimate that the all-sky top-of-atmosphere DRF of BC is +0.13 Wm-2 (0.08 Wm-2 from anthropogenic sources and 0.05 Wm-2 from biomass burning). If we scale our model to match AERONET AAOD observations we estimate the DRF of BC is +0.21 Wm-2, with an additional +0.11 Wm-2 of warming from BrC. Uncertainties in size, optical properties, observations, and emissions suggest an overall uncertainty in BC DRF of -80%/+140%. Our estimates are at the lower end of the 0.2-1.0 Wm-2 range from previous studies, and substantially less than the +0.6 Wm-2 DRF estimated in the IPCC 5th Assessment Report. We suggest that the DRF of BC has previously been overestimated due to the overestimation of the BC lifetime (including the effect on the vertical profile) and the incorrect attribution of BrC absorption to BC.

State Defense Force Monograph Series. Fall 2007, Special Units

DTIC Science & Technology

2007-01-01

authors and the visual panorama of artists and film makers. Those World War Two soldiers for whom “taps” has not yet been sounded may still remember the...Defense Force Monograph Series, Fall 2007, SPECIAL UNITS The Primary Zone will encompass the direct blast and thermal effects of the detonation and also...structural damage and the immediate fires from the thermal effects, although there may be secondary fires outside the Primary Zone. For a 10kt

Quantitative calculations of fluorescence polarization and absorption anisotropy kinetics of double- and triple-chromophore complexes with energy transfer.

PubMed Central

Demidov, A A

1994-01-01

A new method is presented for calculation of the fluorescence depolarization and kinetics of absorption anisotropy for molecular complexes with a limited number of chromophores. The method considers absorption and emission of light by both chromophores, and also energy transfer between them, with regard to their mutual orientations. The chromophores in each individual complex are rigidly positioned. The complexes are randomly distributed and oriented in space, and there is no energy transfer between them. The new "practical" formula for absorption anisotropy and fluorescence depolarization kinetics, P(t) = [3B(t) - 1 + 2A(t)]/[3 + B(t) + 4A(t)], is derived both for double- and triple-chromophore complexes with delta-pulse excitation. The parameter B(t) is given by (a) B(t) = cos2(theta) for double-chromophore complexes, and (b) B(t) = q12(t)cos2(theta 12) + q13(t)-cos2(theta 13) + q23(t)cos2(theta 23) for triple-chromophore complexes, where q12(t) + q13(t) + q23(t) = 1. Here theta ij are the angles between the chromophore transition dipole moments in the individual molecular complex. The parameters qij(t) and A(t) are dependent on chromophore spectroscopic features and on the rates of energy transfer. PMID:7696461

Contribution of inter-muscular synchronization in the modulation of tremor intensity in Parkinson's disease.

PubMed

He, Xin; Hao, Man-Zhao; Wei, Ming; Xiao, Qin; Lan, Ning

2015-12-01

Involuntary central oscillations at single and double tremor frequencies drive the peripheral neuromechanical system of muscles and joints to cause tremor in Parkinson's disease (PD). The central signal of double tremor frequency was found to correlate more directly to individual muscle EMGs (Timmermann et al. 2003). This study is aimed at investigating what central components of oscillation contribute to inter-muscular synchronization in a group of upper extremity muscles during tremor in PD patients. 11 idiopathic, tremor dominant PD subjects participated in this study. Joint kinematics during tremor in the upper extremity was recorded along with EMGs of six upper arm muscles using a novel experimental apparatus. The apparatus provided support for the upper extremity on a horizontal surface with reduced friction, so that resting tremor in the arm can be recorded with a MotionMonitor II system. In each subject, the frequencies of rhythmic firings in upper arm muscles were determined using spectral analysis. Paired and pool-averaged coherence analyses of EMGs for the group of muscles were performed to correlate the level of inter-muscular synchronization to tremor amplitudes at shoulder and elbow. The phase shift between synchronized antagonistic muscle pairs was calculated to aid coherence analysis in the muscle pool. Recorded EMG revealed that rhythmic firings were present in most recorded muscles, which were either synchronized to form phase-locked bursting cycles at a subject specific frequency, or unsynchronized with a random phase distribution. Paired coherence showed a stronger synchronization among a subset of recorded arm muscles at tremor frequency than that at double tremor frequency. Furthermore, the number of synchronized muscles in the arm was positively correlated to tremor amplitudes at elbow and shoulder. Pool-averaged coherence at tremor frequency also showed a better correlation with the amplitude of resting tremor than that of double tremor frequency, indicating that the neuromechanical coupling in peripheral neuromuscular system was stronger at tremor frequency. Both paired and pool-averaged coherences are more consistent indexes to correlate to tremor intensity in a group of upper extremity muscles of PD patients. The central drive at tremor frequency contributes mainly to synchronize peripheral muscles in the modulation of tremor intensity.

Biochemical resistance of pyrogenic organic matter in fire-affected mineral soils of Southern Europe

NASA Astrophysics Data System (ADS)

Knicker, H.; González Vila, F. J.; Clemente Salas, L.

2012-04-01

Incorporated into the soil, naturally formed pyrogenic organic matter (PyOM) is considered as highly recalcitrant, but direct estimation of PyOM decomposition rates are scarce. With this aim in mind, we subjected organic matter (OM) of fire-affected and unaffected soils to biochemical degradation under laboratory conditions and monitored CO2 production over a period of seven months. The soils derived from fire affected and unaffected areas of the Sierra de Aznalcóllar and the Doñana National Park, Southern Spain. Virtual fractionation of the solid-state 13C nuclear magnetic resonance (NMR) spectra of the fire affected soils into fire-unaffected soil organic matter (SOM) and PyOM yielded charcoal C contributions of 30 to 50% to the total organic C (Corg) of the sample derived from the Aznalcóllar region. Fitting the respiration data with a double exponential decay model revealed a fast carbon flush during the first three weeks of the experiment. Solid-state 13C NMR spectroscopy evidenced the contribution of aromatic moieties of the PyOM to this initial carbon release and to the biosynthesis of new microbial biomass. The input of PyOM resulted in an increase of the mean residence time (MRT) of the slow OM pool of the soil by a factor of 3 to 4 to approximately 40 years which rises doubts rises doubts about the presumed big influence of PyOM as an additional C-sink in soils. On the other hand, although being small the difference in turnover rates is evident and has some major implication with respect to long-term alteration of the chemical composition of OM in fire-affected soils. Based on the obtained results and the analysis of PyOM in other soil systems, a conceptual model is presented which can explain the different behavior of PyOM under different soil conditions.

Ultrahigh contrast from a frequency-doubled chirped-pulse-amplification beamline.

PubMed

Hillier, David; Danson, Colin; Duffield, Stuart; Egan, David; Elsmere, Stephen; Girling, Mark; Harvey, Ewan; Hopps, Nicholas; Norman, Michael; Parker, Stefan; Treadwell, Paul; Winter, David; Bett, Thomas

2013-06-20

This paper describes frequency-doubled operation of a high-energy chirped-pulse-amplification beamline. Efficient type-I second-harmonic generation was achieved using a 3 mm thick 320 mm aperture KDP crystal. Shots were fired at a range of energies achieving more than 100 J in a subpicosecond, 527 nm laser pulse with a power contrast of 10(14).

The 27-28 October 1986 FIRE IFO cirrus case study - Cloud optical properties determined by High Spectral Resolution Lidar

NASA Technical Reports Server (NTRS)

Grund, C. J.; Eloranta, E. W.

1990-01-01

The High Spectral Resolution Lidar (HSRL) was operated from a roof-top site in Madison, Wisconsin. The transmitter configuration used to acquire the case study data produces about 50 mW of ouput power and achieved eye-safe, direct optical depth, and backscatter cross section measurements with 10 min averaging times. A new continuously pumped, injection seeded, frequency doubled Nd:YAG laser transmitter reduces time-averaging constraints by a factor of about 10, while improving the aerosol-molecular signal separation capabilities and wavelength stability of the instrument. The cirrus cloud backscatter-phase functions have been determined for the October 27-28, 1986 segment of the HSRL FIRE dataset. Features exhibiting backscatter cross sections ranging over four orders of magnitude have been observed within this 33 h period. During this period, cirrus clouds were observed with optical thickness ranging from 0.01 to 1.4. The altitude relationship between cloud top and bottom boundaries and the optical center of the cloud is influenced by the type of formation observed.

Gas Chromatographic Determination of Fatty Acids in Oils with Regard to the Assessment of Fire Hazard

NASA Astrophysics Data System (ADS)

Bartošová, Alica; Štefko, Tomáš

2017-06-01

The aim of the paper was to study and research the application of processing gas chromatographic method for the rapid and accurate determination of the composition of different types of oils, such as substances with the possibility of an adverse event spontaneous combustion or self-heating. Tendency to spontaneous combustion is chemically characterized mainly by the amount of unsaturated fatty acids, which have one or more double bonds in their molecule. Vegetable oils essentially consist of the following fatty acids: palmitic, stearic, oleic, linoleic, and linoleic. For the needs of assessment, the fire hazard must be known, in which the double bond is present, as well as their number in a molecule. As an analytical method, GCMS was used for determination of oils content. Three types of oil were used - rapeseed, sunflower, and coconut oil. Owing to the occurrence of linoleic acid C18:2 (49.8 wt.%) and oleic acid C18:1 (43.3 wt.%) with double bonds, sunflower oil is the most prone to self-heating. The coconut and rapeseed oils contain double bond FAME in lesser amount, and their propensity to self-heating is relatively low.

Development of lacosamide for the treatment of partial-onset seizures

PubMed Central

Doty, Pamela; Hebert, David; Mathy, Francois-Xavier; Byrnes, William; Zackheim, James; Simontacchi, Kelly

2013-01-01

Lacosamide is an antiepileptic drug (AED) available in multiple formulations that was first approved in 2008 as adjunctive therapy for partial-onset seizures (POS) in adults. Unlike traditional sodium channel blockers affecting fast inactivation, lacosamide selectively enhances sodium channel slow inactivation. This mechanism of action results in stabilization of hyperexcitable neuronal membranes, inhibition of neuronal firing, and reduction in long-term channel availability without affecting physiological function. Lacosamide has a well-characterized and favorable pharmacokinetic profile, including a fast absorption rate, minimal or no interaction with cytochrome P-450 izoenzymes, and a low potential for drug–drug interactions. Lacosamide clinical development included three placebo-controlled, double-blind, randomized trials conducted in more than 1300 patients, each demonstrating safety and efficacy of lacosamide compared to placebo as adjunctive therapy for adults with POS. The clinical use of lacosamide may broaden, pending results of trials evaluating its use as monotherapy for POS in adults, as treatment for epilepsy in pediatric subjects, and as adjunctive treatment for uncontrolled primary generalized tonic–clonic seizures in those with idiopathic generalized epilepsy. PMID:23859801

Fire and shade effects on ground cover structure in Kirtland's warbler habitat

Treesearch

John R. Probst; Deahn DonnerWright

2003-01-01

Researchers and managers have suggested that a narrow range of ground-cover structure resulting from fire might be necessary for suitable Kirtland`s warbler nesting conditions. Yet, Kirtland`s warblers have bred successfully in numerous unburned stands and there is little direct evidence to indicate that ground cover structure is a limiting factor for nest sites or...

Measurement of the muon antineutrino double-differential cross section for quasielastic-like scattering on hydrocarbon at Eν˜3.5 GeV

NASA Astrophysics Data System (ADS)

Patrick, C. E.; Aliaga, L.; Bashyal, A.; Bellantoni, L.; Bercellie, A.; Betancourt, M.; Bodek, A.; Bravar, A.; Budd, H.; Caceres v., G. F. R.; Carneiro, M. F.; Chavarria, E.; da Motta, H.; Dytman, S. A.; Díaz, G. A.; Felix, J.; Fields, L.; Fine, R.; Gago, A. M.; Galindo, R.; Gallagher, H.; Ghosh, A.; Gran, R.; Han, J. Y.; Harris, D. A.; Henry, S.; Hurtado, K.; Jena, D.; Kleykamp, J.; Kordosky, M.; Le, T.; Lu, X.-G.; Maher, E.; Manly, S.; Mann, W. A.; Marshall, C. M.; McFarland, K. S.; McGowan, A. M.; Messerly, B.; Miller, J.; Mislivec, A.; Morfín, J. G.; Mousseau, J.; Naples, D.; Nelson, J. K.; Norrick, A.; Nowak, G. M.; Nuruzzaman, Paolone, V.; Perdue, G. N.; Peters, E.; Ramírez, M. A.; Ransome, R. D.; Ray, H.; Ren, L.; Rodrigues, P. A.; Ruterbories, D.; Schellman, H.; Solano Salinas, C. J.; Sultana, M.; Sánchez Falero, S.; Teklu, A. M.; Valencia, E.; Wolcott, J.; Wospakrik, M.; Yaeggy, B.; Zhang, D.; Miner ν A Collaboration

2018-03-01

We present double-differential measurements of antineutrino charged-current quasielastic scattering in the MINERvA detector. This study improves on a previous single-differential measurement by using updated reconstruction algorithms and interaction models and provides a complete description of observed muon kinematics in the form of a double-differential cross section with respect to muon transverse and longitudinal momentum. We include in our signal definition zero-meson final states arising from multinucleon interactions and from resonant pion production followed by pion absorption in the primary nucleus. We find that model agreement is considerably improved by a model tuned to MINERvA inclusive neutrino scattering data that incorporates nuclear effects such as weak nuclear screening and two-particle, two-hole enhancements.

Preventing deaths and injuries from house fires: a cost–benefit analysis of a community-based smoke alarm installation programme

PubMed Central

Yellman, Merissa A; Peterson, Cora; McCoy, Mary A; Stephens-Stidham, Shelli; Caton, Emily; Barnard, Jeffrey J; Padgett, Ted O; Florence, Curtis; Istre, Gregory R

2017-01-01

Background Operation Installation (OI), a community-based smoke alarm installation programme in Dallas, Texas, targets houses in high-risk urban census tracts. Residents of houses that received OI installation (or programme houses) had 68% fewer medically treated house fire injuries (non-fatal and fatal) compared with residents of non-programme houses over an average of 5.2 years of follow-up during an effectiveness evaluation conducted from 2001 to 2011. Objective To estimate the cost–benefit of OI. Methods A mathematical model incorporated programme cost and effectiveness data as directly observed in OI. The estimated cost per smoke alarm installed was based on a retrospective analysis of OI expenditures from administrative records, 2006–2011. Injury incidence assumptions for a population that had the OI programme compared with the same population without the OI programme was based on the previous OI effectiveness study, 2001–2011. Unit costs for medical care and lost productivity associated with fire injuries were from a national public database. Results From a combined payers’ perspective limited to direct programme and medical costs, the estimated incremental cost per fire injury averted through the OI installation programme was $128,800 (2013 US$). When a conservative estimate of lost productivity among victims was included, the incremental cost per fire injury averted was negative, suggesting long-term cost savings from the programme. The OI programme from 2001 to 2011 resulted in an estimated net savings of $3.8 million, or a $3.21 return on investment for every dollar spent on the programme using a societal cost perspective. Conclusions Community smoke alarm installation programmes could be cost-beneficial in high-fire-risk neighbourhoods. PMID:28183740

Quantum interference effects on the intensity of the G modes in double-walled carbon nanotubes

DOE PAGES

Tran, Huy Nam; Blancon, Jean-Christophe Robert; Arenal, Raul; ...

2017-05-08

The effects of quantum interferences on the excitation dependence of the intensity of G modes have been investigated on single-walled carbon nanotubes [Duque et al., Phys. Rev. Lett.108, 117404 (2012)]. In this work, by combining optical absorption spectroscopy and Raman scattering on individual index identified double-walled carbon nanotubes, we examine the experimental excitation dependence of the intensity of longitudinal optical and transverse optical G modes of the constituent inner and outer single-walled carbon nanotubes. The observed striking dependencies are understood in terms of quantum interference effects. Considering such effects, the excitation dependence of the different components of the G modesmore » permit to unambiguously assign each of them as originating from the longitudinal or transverse G modes of inner and outer tubes.« less

Quantum interference effects on the intensity of the G modes in double-walled carbon nanotubes

NASA Astrophysics Data System (ADS)

Tran, H. N.; Blancon, J.-C.; Arenal, R.; Parret, R.; Zahab, A. A.; Ayari, A.; Vallée, F.; Del Fatti, N.; Sauvajol, J.-L.; Paillet, M.

2017-05-01

The effects of quantum interferences on the excitation dependence of the intensity of G modes have been investigated on single-walled carbon nanotubes [Duque et al., Phys. Rev. Lett. 108, 117404 (2012), 10.1103/PhysRevLett.108.117404]. In this work, by combining optical absorption spectroscopy and Raman scattering on individual index identified double-walled carbon nanotubes, we examine the experimental excitation dependence of the intensity of longitudinal optical and transverse optical G modes of the constituent inner and outer single-walled carbon nanotubes. The observed striking dependencies are understood in terms of quantum interference effects. Considering such effects, the excitation dependence of the different components of the G modes permits us to unambiguously assign each of them as originating from the longitudinal or transverse G modes of inner and outer tubes.

Quantum interference effects on the intensity of the G modes in double-walled carbon nanotubes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tran, Huy Nam; Blancon, Jean-Christophe Robert; Arenal, Raul

The effects of quantum interferences on the excitation dependence of the intensity of G modes have been investigated on single-walled carbon nanotubes [Duque et al., Phys. Rev. Lett.108, 117404 (2012)]. In this work, by combining optical absorption spectroscopy and Raman scattering on individual index identified double-walled carbon nanotubes, we examine the experimental excitation dependence of the intensity of longitudinal optical and transverse optical G modes of the constituent inner and outer single-walled carbon nanotubes. The observed striking dependencies are understood in terms of quantum interference effects. Considering such effects, the excitation dependence of the different components of the G modesmore » permit to unambiguously assign each of them as originating from the longitudinal or transverse G modes of inner and outer tubes.« less

Linear and nonlinear optical absorption coefficients and refractive index changes in GaN/Al{sub x}Ga{sub (1−x)}N double quantum wells operating at 1.55 μm

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dakhlaoui, Hassen

2015-04-07

In the present paper, the linear and nonlinear optical absorption coefficients and refractive index changes between the ground and the first excited states in double GaN/Al{sub x}Ga{sub (1−x)}N quantum wells are studied theoretically. The electronic energy levels and their corresponding wave functions are obtained by solving Schrödinger-Poisson equations self-consistently within the effective mass approximation. The obtained results show that the optical absorption coefficients and refractive index changes can be red- and blue-shifted through varying the left quantum well width and the aluminum concentration x{sub b2} of the central barrier, respectively. These structural parameters are found to present optimum values formore » carrying out the transition of 0.8 eV (1.55 μm). Furthermore, we show that the desired transition can also be achieved by replacing the GaN in the left quantum well with Al{sub y}Ga{sub (1−y)}N and by varying the aluminum concentration y{sub Al}. The obtained results give a new degree of freedom in optoelectronic device applications such as optical fiber telecommunications operating at (1.55 μm)« less

Indirect-fired gas turbine bottomed with fuel cell

DOEpatents

Micheli, P.L.; Williams, M.C.; Parsons, E.L.

1995-09-12

An indirect-heated gas turbine cycle is bottomed with a fuel cell cycle with the heated air discharged from the gas turbine being directly utilized at the cathode of the fuel cell for the electricity-producing electrochemical reaction occurring within the fuel cell. The hot cathode recycle gases provide a substantial portion of the heat required for the indirect heating of the compressed air used in the gas turbine cycle. A separate combustor provides the balance of the heat needed for the indirect heating of the compressed air used in the gas turbine cycle. Hot gases from the fuel cell are used in the combustor to reduce both the fuel requirements of the combustor and the NOx emissions therefrom. Residual heat remaining in the air-heating gases after completing the heating thereof is used in a steam turbine cycle or in an absorption refrigeration cycle. Some of the hot gases from the cathode can be diverted from the air-heating function and used in the absorption refrigeration cycle or in the steam cycle for steam generating purposes. 1 fig.

Indirect-fired gas turbine bottomed with fuel cell

DOEpatents

Micheli, Paul L.; Williams, Mark C.; Parsons, Edward L.

1995-01-01

An indirect-heated gas turbine cycle is bottomed with a fuel cell cycle with the heated air discharged from the gas turbine being directly utilized at the cathode of the fuel cell for the electricity-producing electrochemical reaction occurring within the fuel cell. The hot cathode recycle gases provide a substantial portion of the heat required for the indirect heating of the compressed air used in the gas turbine cycle. A separate combustor provides the balance of the heat needed for the indirect heating of the compressed air used in the gas turbine cycle. Hot gases from the fuel cell are used in the combustor to reduce both the fuel requirements of the combustor and the NOx emissions therefrom. Residual heat remaining in the air-heating gases after completing the heating thereof is used in a steam turbine cycle or in an absorption refrigeration cycle. Some of the hot gases from the cathode can be diverted from the air-heating function and used in the absorption refrigeration cycle or in the steam cycle for steam generating purposes.

Fructo-oligosaccharides and calcium absorption and retention in adolescent girls.

PubMed

Martin, Berdine R; Braun, Michelle M; Wigertz, Karin; Bryant, Rebecca; Zhao, Yongdong; Lee, WangHee; Kempa-Steczko, Ania; Weaver, Connie M

2010-08-01

Several studies have shown a positive effect of fructo-oligosaccharides on calcium absorption and retention in animals and humans. Effects of levels of these pre-biotics that can be functionally incorporated into manufactured foods, have not been studied in controlled feeding studies. This study was designed to evaluate the effect of 9 g/d of fructo-oligosaccharides as part of a controlled diet on calcium absorption and retention in adolescent girls. Fourteen healthy adolescent girls aged 11-13 y were studied in a metabolic setting for two 3-week periods separated by a 2-week washout period. In a randomized, double-blinded, crossover design, the teens received a diet containing either 9 g/d oligofructose-enriched inulin in a calcium-fortified cereal or the control cereal with no inulin. Both diets contained ~1500 mg calcium daily. Calcium retention was determined on the third week of each period. On day 14 of the diet period, fractional calcium absorption was determined from the enrichment of (44)Ca in 4-day urine collections. Calcium absorption (67 ± 3 vs. 66 ± 3%) and retention (409 ± 394 vs. 464 ± 241 mg/d) were not significantly different when diets contained 9 g/d oligofructose-enriched inulin or not in a calcium-fortified cereal. Daily consumption of cereal containing a combination of short- and long-chain fructo-oligosaccharides as part of a controlled diet did not benefit calcium absorption or retention in adolescent girls. Lack of response to the prebiotic in this cohort may relate to their already high calcium absorption efficiency.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Erga, O.; Finborud, A.

Cost-effective FGD processes with high SO{sub 2} removal efficiencies are required for fossil-fired power plants. With high-sulfur fuel, conventional limestone processes are less ideal, and regenerative processes with SO{sub 2} recovery may offer important advantages. The Elsorb process, which is being developed by the Norwegian company Elkem Technology a.s., is a regenerable SO{sub 2} recovery process which operates on the principle of chemical absorption followed by regeneration by evaporation. The process is based on the use of a chemical stable sodium phosphate buffer in high concentration. It combines high cleaning efficiency with high cyclic absorption capacity, moderate energy requirement, andmore » very little oxidation losses. The process produces SO{sub 2} (g) which can be converted into liquid SO{sub 2}, sulfuric acid or elemental sulfur. The Elsorb process has been pilot tested on flue gas from a coal-fired boiler with very promising results, concerning cleaning efficiency and oxidation losses of SO{sub 2}. The first commercial Elsorb plant has been installed for treating incinerated Claus tail gas. Preliminary data regarding cleaning efficiency are in accordance with the pilot tests. However, unexpected high consumption of make-up chemicals were encountered. The existing incinerator is now to be modified. Complete data for the Elsorb plant should be available later this year. 1 fig.« less

Evidence for structural plasticity in the supraoptic nucleus of the rat hypothalamus in relation to gestation and lactation.

PubMed

Theodosis, D T; Poulain, D A

1984-01-01

Supraoptic nuclei of lactating rats present a particular anatomical organization that could serve to facilitate the synchronization of neuronal firing observed during suckling-induced reflex milk ejections. Although magnocellular neurones are usually separated by neuropil elements, particularly glial fibers, in lactating rats, numerous neurosecretory soma and dendritic profiles are in direct apposition, without glial interposition. Concomitantly, there is also a higher incidence of presynaptic terminals contacting two neurosecretory elements in the same plane of section ("double" synapses). In the present study, a quantitative ultrastructural analysis was used to trace the evolution of the structural reorganization of the nucleus at different stages of the reproductive cycle. The percentage of neurosecretory soma and dendritic profiles in direct apposition was low two weeks after the beginning of pregnancy, but the day prior to parturition, as during lactation, over 40% of all neurosecretory profiles were directly in contact and involved about 10% of the total neuronal surface membrane measured (a 5-fold increase over the corresponding frequencies recorded in virgin rats at oestrus). The contiguous neuronal membranes and associated intercellular space appeared unmodified, except for the presence of attachment plaques, that also increased in frequency at late gestation and lactation. The incidence of "double" synapses also increased by late gestation, so that at lactation, they bridged 8% of all the recorded neurosecretory somata and dendrites, (as compared to 1% in the virgin rats). Similar changes were observed during a first and second gestation and lactation. The incidence of direct appositions and "double" synapses then diminished gradually after weaning: 2 months after the end of lactation, the ultrastructure of the nucleus resembled that of virgin animals. These observations demonstrate a plasticity in the structural organization of the supraoptic nucleus that appears closely related to changing physiological states of the animal and that involves both neurone-glial relationships and the neurones' synaptic configuration.

Risk for large-scale fires in boreal forests of Finland under changing climate

NASA Astrophysics Data System (ADS)

Lehtonen, I.; Venäläinen, A.; Kämäräinen, M.; Peltola, H.; Gregow, H.

2015-08-01

The target of this work was to assess the impact of projected climate change on the number of large forest fires (over 10 ha fires) and burned area in Finland. For this purpose, we utilized a strong relationship between fire occurrence and the Canadian fire weather index (FWI) during 1996-2014. We used daily data from five global climate models under representative concentration pathway RCP4.5 and RCP8.5 scenarios. The model data were statistically downscaled onto a high-resolution grid using the quantile-mapping method before performing the analysis. Our results suggest that the number of large forest fires may double or even triple during the present century. This would increase the risk that some of the fires could develop into real conflagrations which have become almost extinct in Finland due to active and efficient fire suppression. Our results also reveal substantial inter-model variability in the rate of the projected increase in forest-fire danger. We moreover showed that the majority of large fires occur within a relatively short period in May and June due to human activities and that FWI correlates poorer with the fire activity during this time of year than later in summer when lightning is more important cause of fires.

The two-photon absorptivity of rotational transitions in the A2 Sigma hyperon + (v prime = O) - X-2 pion (v prime prime = O) gamma band of nitric oxide

NASA Technical Reports Server (NTRS)

Gross, K. P.; Mckenzie, R. L.

1982-01-01

A predominantly single-mode pulsed dye laser system giving a well characterized spatial and temporal output suitable for absolute two-photon absorptivity measurements was used to study the NO gamma(0,0) S11 + R21 (J double prime = 7-1/2) transition. Using a calibrated induced-fluorescence technique, an absorptivity parameter of 2.8 + or - 1.4 x 10 to the minus 51st power cm to the 6th power was obtained. Relative strengths of other rotational transitions in the gamma(0,0) band were also measured and shown to compare well with predicted values in all cases except the O12 (J double prime = 10-1/2) transition.

Experimental demonstration of tunable directional excitation of surface plasmon polaritons with a subwavelength metallic double slit

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li Xiaowei; Tsinghua-Foxconn Nanotechnology Research Center, Tsinghua University, Beijing 100084; Tan Qiaofeng

2011-06-20

We demonstrate experimentally the directional excitation of surface plasmon polaritons (SPPs) on a metal film by a subwavelength double slit under backside illumination, based on the interference of SPPs generated by the two slits. By varying the incident angle, the SPPs can be tunably directed into two opposite propagating directions with a predetermined splitting ratio. Under certain incident angle, unidirectional SPP excitation can be achieved. This compact directional SPP coupler is potentially useful for many on-chip applications. As an example, we show the integration of the double-slit couplers with SPP Bragg mirrors, which can effectively realize selective coupling of SPPsmore » into different ports in an integrated plasmonic chip.« less

Modelling effects on grid cells of sensory input during self‐motion

PubMed Central

Raudies, Florian; Hinman, James R.

2016-01-01

Abstract The neural coding of spatial location for memory function may involve grid cells in the medial entorhinal cortex, but the mechanism of generating the spatial responses of grid cells remains unclear. This review describes some current theories and experimental data concerning the role of sensory input in generating the regular spatial firing patterns of grid cells, and changes in grid cell firing fields with movement of environmental barriers. As described here, the influence of visual features on spatial firing could involve either computations of self‐motion based on optic flow, or computations of absolute position based on the angle and distance of static visual cues. Due to anatomical selectivity of retinotopic processing, the sensory features on the walls of an environment may have a stronger effect on ventral grid cells that have wider spaced firing fields, whereas the sensory features on the ground plane may influence the firing of dorsal grid cells with narrower spacing between firing fields. These sensory influences could contribute to the potential functional role of grid cells in guiding goal‐directed navigation. PMID:27094096

Fire Influences on Atmospheric Composition, Air Quality, and Climate

NASA Technical Reports Server (NTRS)

Voulgarakis, Apostolos; Field, Robert D.

2015-01-01

Fires impact atmospheric composition through their emissions, which range from long-lived gases to short-lived gases and aerosols. Effects are typically larger in the tropics and boreal regions but can also be substantial in highly populated areas in the northern mid-latitudes. In all regions, fire can impact air quality and health. Similarly, its effect on large-scale atmospheric processes, including regional and global atmospheric chemistry and climate forcing, can be substantial, but this remains largely unexplored. The impacts are primarily realised in the boundary layer and lower free troposphere but can also be noticeable in upper troposphere/lower stratosphere (UT/LS) region, for the most intense fires. In this review, we summarise the recent literature on findings related to fire impact on atmospheric composition, air quality and climate. We explore both observational and modelling approaches and present information on key regions and on the globe as a whole. We also discuss the current and future directions in this area of research, focusing on the major advances in emission estimates, the emerging efforts to include fire as a component in Earth system modelling and the use of modelling to assess health impacts of fire emissions.

Physical and optical properties of aged biomass burning aerosol from wildfires in Siberia and the Western USA at the Mt. Bachelor Observatory

NASA Astrophysics Data System (ADS)

Laing, James R.; Jaffe, Daniel A.; Hee, Jonathan R.

2016-12-01

The summer of 2015 was an extreme forest fire year in the Pacific Northwest. Our sample site at the Mt. Bachelor Observatory (MBO, 2.7 km a.s.l.) in central Oregon observed biomass burning (BB) events more than 50 % of the time during August. In this paper we characterize the aerosol physical and optical properties of 19 aged BB events during August 2015. Six of the 19 events were influenced by Siberian fires originating near Lake Baikal that were transported to MBO over 4-10 days. The remainder of the events resulted from wildfires in Northern California and Southwestern Oregon with transport times to MBO ranging from 3 to 35 h. Fine particulate matter (PM1), carbon monoxide (CO), aerosol light scattering coefficients (σscat), aerosol light absorption coefficients (σabs), and aerosol number size distributions were measured throughout the campaign. We found that the Siberian events had a significantly higher Δσabs/ΔCO enhancement ratio, higher mass absorption efficiency (MAE; Δσabs/ΔPM1), lower single scattering albedo (ω), and lower absorption Ångström exponent (AAE) when compared with the regional events. We suggest that the observed Siberian events represent that portion of the plume that has hotter flaming fire conditions and thus enabled strong pyroconvective lofting and long-range transport to MBO. The Siberian events observed at MBO therefore represent a selected portion of the original plume that would then have preferentially higher black carbon emissions and thus an enhancement in absorption. The lower AAE values in the Siberian events compared to regional events indicate a lack of brown carbon (BrC) production by the Siberian fires or a loss of BrC during transport. We found that mass scattering efficiencies (MSE) for the BB events ranged from 2.50 to 4.76 m2 g-1. We measured aerosol size distributions with a scanning mobility particle sizer (SMPS). Number size distributions ranged from unimodal to bimodal and had geometric mean diameters (Dpm) ranging from 138 to 229 nm and geometric standard deviations (σg) ranging from 1.53 to 1.89. We found MSEs for BB events to be positively correlated with the geometric mean of the aerosol size distributions (R2 = 0.73), which agrees with Mie theory. We did not find any dependence on event size distribution to transport time or fire source location.

When smoke comes to town - effects of biomass burning smoke on air quality down under

NASA Astrophysics Data System (ADS)

Keywood, Melita; Cope, Martin; (C. P) Meyer, Mick; Iinuma, Yoshi; Emmerson, Kathryn

2014-05-01

Annually, biomass burning results in the emission of quantities of trace gases and aerosol to the atmosphere. Biomass burning emissions have a significant effect on atmospheric chemistry due to the presence of reactive species. Biomass burning aerosols influence the radiative balance of the earth-atmosphere system directly through the scattering and absorption of radiation, and indirectly through their influence on cloud microphysical processes, and therefore constitute an important forcing in climate models. They also reduce visibility, influence atmospheric photochemistry and can be inhaled into the deepest parts of the lungs, so that they can have a significant effect on human health. Australia experiences bushfires on an annual basis. In most years fires are restricted to the tropical savannah forests of Northern Australia. However in the summer of 2006/2007 (December 2006 - February 2007), South Eastern Australia was affected by the longest recorded fires in its history. During this time the State of Victoria was ravaged by 690 separate bushfires, including the major Great Divide Fire, which devastated 1,048,238 hectares over 69 days. On several occasions, thick smoke haze was transported to the Melbourne central business district and PM10 concentrations at several air quality monitoring stations peaked at over 200 µg m-3 (four times the National Environment Protection Measure PM10 24 hour standard). During this period, a comprehensive suite of air quality measurements was carried out at a location 25 km south of the Melbourne CBD, including detailed aerosol microphysical and chemical composition measurements. Here we examine the chemical and physical properties of the smoke plume as it impacted Melbourne's air shed and discuss its impact on air quality over the city. We estimate the aerosol emission rates of the source fires, the age of the plumes and investigate the transformation of the smoke as it progressed from its source to the Melbourne airshed. We show that the smoke plumes that reached Melbourne during the summer of 2006/2007 resulted in elevated concentrations of particles and gases relative to non-fire impacted periods. The age of the plume was greater when smoke reached Melbourne (note that in our calculation of the plume age we do not distinguish between smoke and anthropogenic plumes). In addition, the older smoke plumes (30 hours) displayed higher concentrations of a number of gaseous and aerosol species relative to the younger smoke plumes (3 hours), particularly secondary reaction products, while the younger smoke plumes had higher concentrations of biomass burning marker compounds. This suggests that the enhanced photochemical activity in the smoke plumes significantly changes the aerosol composition of the smoke, potentially affecting the optical and thus radiative properties of the aerosol. This has implications for the modelling of aged smoke in chemical transport and climate models.

Grid cell mechanisms and function: Contributions of entorhinal persistent spiking and phase resetting

PubMed Central

Hasselmo, Michael E.

2008-01-01

This article presents a model of grid cell firing based on the intrinsic persistent firing shown experimentally in neurons of entorhinal cortex. In this model, the mechanism of persistent firing allows individual neurons to hold a stable baseline firing frequency. Depolarizing input from speed modulated head direction cells transiently shifts the frequency of firing from baseline, resulting in a shift in spiking phase in proportion to the integral of velocity. The convergence of input from different persistent firing neurons causes spiking in a grid cell only when the persistent firing neurons are within similar phase ranges. This model effectively simulates the two-dimensional firing of grid cells in open field environments, as well as the properties of theta phase precession. This model provides an alternate implementation of oscillatory interference models. The persistent firing could also interact on a circuit level with rhythmic inhibition and neurons showing membrane potential oscillations to code position with spiking phase. These mechanisms could operate in parallel with computation of position from visual angle and distance of stimuli. In addition to simulating two-dimensional grid patterns, models of phase interference can account for context-dependent firing in other tasks. In network simulations of entorhinal cortex, hippocampus and postsubiculum, the reset of phase effectively replicates context-dependent firing by entorhinal and hippocampal neurons during performance of a continuous spatial alternation task, a delayed spatial alternation task with running in a wheel during the delay period, and a hairpin maze task. PMID:19021258

Effect of intravenous ranitidine and omeprazole on intestinal absorption of water, sodium, and macronutrients in patients with intestinal resection

PubMed Central

Jeppesen, P; Staun, M; Tjellesen, L; Mortensen, P

1998-01-01

Background—H2 receptor blockers and proton pump inhibitors reduce intestinal output in patients with short bowel syndrome. 
Aims—To evaluate the effect of intravenous omeprazole and ranitidine on water, electrolyte, macronutrient, and energy absorption in patients with intestinal resection. 
Methods—Thirteen patients with a faecal weight above 1.5 kg/day (range 1.7-5.7 kg/day and a median small bowel length of 100cm were studied. Omeprazole 40 mg twice daily or ranitidine 150mg twice daily were administered for five days in a randomised, double blind, crossover design followed by a three day control period with no treatment. Two patients with a segment of colon in continuation were excluded from analysis which, however, had no influence on the results. 
Results—Omeprazole increased median intestinal wet weight absorption compared with no treatment and ranitidine (p<0.03). The effect of ranitidine was not significant. Four patients with faecal volumes below 2.6 kg/day did not respond to omeprazole; in two absorption increased by 0.5-1 kg/day; and in five absorption increased by 1−2 kg/day. Absorption of sodium, calcium, magnesium, nitrogen, carbohydrate, fat, and total energy was unchanged. Four high responders continued on omeprazole for 12-15 months, but none could be weaned from parenteral nutrition. 
Conclusion—Omeprazole increased water absorption in patients with faecal output above 2.50 kg/day. The effect varied significantly and was greater in patients with a high output, but did not allow parenteral nutrition to be discontinued. Absorption of energy, macronutrients, electrolytes, and divalent cations was not improved. The effect of ranitidine was not significant, possibly because the dose was too low. 

 Keywords: short bowel syndrome; human; diarrhoea; ranitidine; omeprazole PMID:9824602

Spatial cell firing during virtual navigation of open arenas by head-restrained mice.

PubMed

Chen, Guifen; King, John Andrew; Lu, Yi; Cacucci, Francesca; Burgess, Neil

2018-06-18

We present a mouse virtual reality (VR) system which restrains head-movements to horizontal rotations, compatible with multi-photon imaging. This system allows expression of the spatial navigation and neuronal firing patterns characteristic of real open arenas (R). Comparing VR to R: place and grid, but not head-direction, cell firing had broader spatial tuning; place, but not grid, cell firing was more directional; theta frequency increased less with running speed; whereas increases in firing rates with running speed and place and grid cells' theta phase precession were similar. These results suggest that the omni-directional place cell firing in R may require local-cues unavailable in VR, and that the scale of grid and place cell firing patterns, and theta frequency, reflect translational motion inferred from both virtual (visual and proprioceptive) and real (vestibular translation and extra-maze) cues. By contrast, firing rates and theta phase precession appear to reflect visual and proprioceptive cues alone. © 2018, Chen et al.

The impact of antecedent fire area on burned area in southern California coastal ecosystems

USGS Publications Warehouse

Price, Owen F.; Bradstock, Ross A.; Keeley, Jon E.; Syphard, Alexandra D.

2012-01-01

Frequent wildfire disasters in southern California highlight the need for risk reduction strategies for the region, of which fuel reduction via prescribed burning is one option. However, there is no consensus about the effectiveness of prescribed fire in reducing the area of wildfire. Here, we use 29 years of historical fire mapping to quantify the relationship between annual wildfire area and antecedent fire area in predominantly shrub and grassland fuels in seven southern California counties, controlling for annual variation in weather patterns. This method has been used elsewhere to measure leverage: the reduction in wildfire area resulting from one unit of prescribed fire treatment. We found little evidence for a leverage effect (leverage = zero). Specifically our results showed no evidence that wildfire area was negatively influenced by previous fires, and only weak relationships with weather variables rainfall and Santa Ana wind occurrences, which were variables included to control for inter-annual variation. We conclude that this is because only 2% of the vegetation burns each year and so wildfires rarely encounter burned patches and chaparral shrublands can carry a fire within 1 or 2 years after previous fire. Prescribed burning is unlikely to have much influence on fire regimes in this area, though targeted treatment at the urban interface may be effective at providing defensible space for protecting assets. These results fit an emerging global model of fire leverage which position California at the bottom end of a continuum, with tropical savannas at the top (leverage = 1: direct replacement of wildfire by prescribed fire) and Australian eucalypt forests in the middle (leverage ∼ 0.25).

Pattern and process of prescribed fires influence effectiveness at reducing wildfire severity in dry coniferous forests

USGS Publications Warehouse

Arkle, Robert S.; Pilliod, David S.; Welty, Justin L.

2012-01-01

We examined the effects of three early season (spring) prescribed fires on burn severity patterns of summer wildfires that occurred 1–3 years post-treatment in a mixed conifer forest in central Idaho. Wildfire and prescribed fire burn severities were estimated as the difference in normalized burn ratio (dNBR) using Landsat imagery. We used GIS derived vegetation, topography, and treatment variables to generate models predicting the wildfire burn severity of 1286–5500 30-m pixels within and around treated areas. We found that wildfire severity was significantly lower in treated areas than in untreated areas and significantly lower than the potential wildfire severity of the treated areas had treatments not been implemented. At the pixel level, wildfire severity was best predicted by an interaction between prescribed fire severity, topographic moisture, heat load, and pre-fire vegetation volume. Prescribed fire severity and vegetation volume were the most influential predictors. Prescribed fire severity, and its influence on wildfire severity, was highest in relatively warm and dry locations, which were able to burn under spring conditions. In contrast, wildfire severity peaked in cooler, more mesic locations that dried later in the summer and supported greater vegetation volume. We found considerable evidence that prescribed fires have landscape-level influences within treatment boundaries; most notable was an interaction between distance from the prescribed fire perimeter and distance from treated patch edges, which explained up to 66% of the variation in wildfire severity. Early season prescribed fires may not directly target the locations most at risk of high severity wildfire, but proximity of these areas to treated patches and the discontinuity of fuels following treatment may influence wildfire severity and explain how even low severity treatments can be effective management tools in fire-prone landscapes.

The impact of antecedent fire area on burned area in southern California coastal ecosystems.

PubMed

Price, Owen F; Bradstock, Ross A; Keeley, Jon E; Syphard, Alexandra D

2012-12-30

Frequent wildfire disasters in southern California highlight the need for risk reduction strategies for the region, of which fuel reduction via prescribed burning is one option. However, there is no consensus about the effectiveness of prescribed fire in reducing the area of wildfire. Here, we use 29 years of historical fire mapping to quantify the relationship between annual wildfire area and antecedent fire area in predominantly shrub and grassland fuels in seven southern California counties, controlling for annual variation in weather patterns. This method has been used elsewhere to measure leverage: the reduction in wildfire area resulting from one unit of prescribed fire treatment. We found little evidence for a leverage effect (leverage = zero). Specifically our results showed no evidence that wildfire area was negatively influenced by previous fires, and only weak relationships with weather variables rainfall and Santa Ana wind occurrences, which were variables included to control for inter-annual variation. We conclude that this is because only 2% of the vegetation burns each year and so wildfires rarely encounter burned patches and chaparral shrublands can carry a fire within 1 or 2 years after previous fire. Prescribed burning is unlikely to have much influence on fire regimes in this area, though targeted treatment at the urban interface may be effective at providing defensible space for protecting assets. These results fit an emerging global model of fire leverage which position California at the bottom end of a continuum, with tropical savannas at the top (leverage = 1: direct replacement of wildfire by prescribed fire) and Australian eucalypt forests in the middle (leverage ~ 0.25). Copyright © 2012 Elsevier Ltd. All rights reserved.

Unexpected solvent effects on the UV/Vis absorption spectra of o-cresol in toluene and benzene: in contrast with non-aromatic solvents

PubMed Central

Zheng, Dong; Yuan, Xiang-Ai; Ma, Haibo; Li, Xiaoxiong; Wang, Xizhang; Liu, Ziteng

2018-01-01

Cresol is a prototype molecule in understanding intermolecular interactions in material and biological systems, because it offers different binding sites with various solvents and protonation states under different pH values. It is found that the UV/Vis absorption spectra of o-cresol in aromatic solvents (benzene, toluene) are characterized by a sharp peak, unlike the broad double-peaks in 11 non-aromatic solvents. Both molecular dynamics simulations and electronic structure calculations revealed the formation of intermolecular π-complexation between o-cresol and aromatic solvents. The thermal movements of solvent and solute molecules render the conformations of o-cresol changing between trans and cis isomers. The π-interaction makes the cis configuration a dominant isomer, hence leading to the single keen-edged UV/Vis absorption peak at approximately 283 nm. The free conformation changes between trans and cis in aqueous solution rationalize the broader absorption peaks in the range of 260–280 nm. The pH dependence of the UV/Vis absorption spectra in aqueous solutions is also rationalized by different protonation states of o-cresol. The explicit solvent model with long-ranged interactions is vital to describe the effects of π-complexation and electrostatic interaction on the UV/Vis absorption spectra of o-cresol in toluene and alkaline aqueous (pH > 10.3) solutions, respectively. PMID:29657794

Unexpected solvent effects on the UV/Vis absorption spectra of o-cresol in toluene and benzene: in contrast with non-aromatic solvents.

PubMed

Zheng, Dong; Yuan, Xiang-Ai; Ma, Haibo; Li, Xiaoxiong; Wang, Xizhang; Liu, Ziteng; Ma, Jing

2018-03-01

Cresol is a prototype molecule in understanding intermolecular interactions in material and biological systems, because it offers different binding sites with various solvents and protonation states under different pH values. It is found that the UV/Vis absorption spectra of o -cresol in aromatic solvents (benzene, toluene) are characterized by a sharp peak, unlike the broad double-peaks in 11 non-aromatic solvents. Both molecular dynamics simulations and electronic structure calculations revealed the formation of intermolecular π-complexation between o -cresol and aromatic solvents. The thermal movements of solvent and solute molecules render the conformations of o -cresol changing between trans and cis isomers. The π-interaction makes the cis configuration a dominant isomer, hence leading to the single keen-edged UV/Vis absorption peak at approximately 283 nm. The free conformation changes between trans and cis in aqueous solution rationalize the broader absorption peaks in the range of 260-280 nm. The pH dependence of the UV/Vis absorption spectra in aqueous solutions is also rationalized by different protonation states of o -cresol. The explicit solvent model with long-ranged interactions is vital to describe the effects of π-complexation and electrostatic interaction on the UV/Vis absorption spectra of o -cresol in toluene and alkaline aqueous (pH > 10.3) solutions, respectively.

Relative importance of black carbon, brown carbon, and absorption enhancement from clear coatings in biomass burning emissions

NASA Astrophysics Data System (ADS)

Pokhrel, Rudra P.; Beamesderfer, Eric R.; Wagner, Nick L.; Langridge, Justin M.; Lack, Daniel A.; Jayarathne, Thilina; Stone, Elizabeth A.; Stockwell, Chelsea E.; Yokelson, Robert J.; Murphy, Shane M.

2017-04-01

A wide range of globally significant biomass fuels were burned during the fourth Fire Lab at Missoula Experiment (FLAME-4). A multi-channel photoacoustic absorption spectrometer (PAS) measured dry absorption at 405, 532, and 660 nm and thermally denuded (250 °C) absorption at 405 and 660 nm. Absorption coefficients were broken into contributions from black carbon (BC), brown carbon (BrC), and lensing following three different methodologies, with one extreme being a method that assumes the thermal denuder effectively removes organics and the other extreme being a method based on the assumption that black carbon (BC) has an Ångström exponent of unity. The methodologies employed provide ranges of potential importance of BrC to absorption but, on average, there was a difference of a factor of 2 in the ratio of the fraction of absorption attributable to BrC estimated by the two methods. BrC absorption at shorter visible wavelengths is of equal or greater importance to that of BC, with maximum contributions of up to 92 % of total aerosol absorption at 405 nm and up to 58 % of total absorption at 532 nm. Lensing is estimated to contribute a maximum of 30 % of total absorption, but typically contributes much less than this. Absorption enhancements and the estimated fraction of absorption from BrC show good correlation with the elemental-carbon-to-organic-carbon ratio (EC / OC) of emitted aerosols and weaker correlation with the modified combustion efficiency (MCE). Previous studies have shown that BrC grows darker (larger imaginary refractive index) as the ratio of black to organic aerosol (OA) mass increases. This study is consistent with those findings but also demonstrates that the fraction of total absorption attributable to BrC shows the opposite trend: increasing as the organic fraction of aerosol emissions increases and the EC / OC ratio decreases.

A WebGIS-based command control system for forest fire fighting

NASA Astrophysics Data System (ADS)

Yang, Jianyu; Ming, Dongping; Zhang, Xiaodong; Huang, Haitao

2006-10-01

Forest is a finite resource and fire prevention is crucial work. However, once a forest fire or accident occurs, timely and effective fire-fighting is the only necessary measure. The aim of this research is to build a computerized command control system based on WEBGIS to direct fire-fighting. Firstly, this paper introduces the total technique flow and functional modules of the system. Secondly, this paper analyses the key techniques for building the system, and they are data obtaining, data organizing & management, architecture of WebGIS and sharing & interoperation technique. In the end, this paper demonstrates the on line martial symbol editing function to show the running result of system. The practical application of this system showed that it played very important role in the forest fire fighting work. In addition, this paper proposes some strategic recommendations for the further development of the system.

Soluble Corn Fiber Increases Calcium Absorption Associated with Shifts in the Gut Microbiome: A Randomized Dose-Response Trial in Free-Living Pubertal Females.

PubMed

Whisner, Corrie M; Martin, Berdine R; Nakatsu, Cindy H; Story, Jon A; MacDonald-Clarke, Claire J; McCabe, Linda D; McCabe, George P; Weaver, Connie M

2016-07-01

Soluble corn fiber (SCF; 12 g fiber/d) is shown to increase calcium absorption efficiency, associated with shifts in the gut microbiota in adolescent males and females who participated in a controlled feeding study. We evaluated the dose response of 0, 10, and 20 g fiber/d delivered by PROMITOR SCF 85 (85% fiber) on calcium absorption, biochemical bone properties, and the fecal microbiome in free-living adolescents. Healthy adolescent females (n = 28; aged 11-14 y) randomly assigned into a 3-phase, double-blind, crossover study consumed SCF for 4 wk at each dose (0, 10, and 20 g fiber/d from SCF) alongside their habitual diet and were followed by 3-d clinical visits and 3-wk washout periods. Stable isotope ((44)Ca and (43)Ca) enrichment in pooled urine was measured by inductively coupled plasma mass spectrometry. Fecal microbial community composition was assessed by high-throughput sequencing (Illumina) of polymerase chain reaction-amplified 16S rRNA genes. Mixed model ANOVA and Friedman analysis were used to determine effects of SCF on calcium absorption and to compare mean microbial proportions, respectively. Calcium absorption increased significantly with 10 (13.3% ± 5.3%; P = 0.042) and 20 g fiber/d (12.9% ± 3.6%; P = 0.026) from SCF relative to control. Significant differences in fecal microbial community diversity were found after consuming SCF (operational taxonomic unit measures of 601.4 ± 83.5, 634.5 ± 83.8, and 649.6 ± 75.5 for 0, 10, and 20 g fiber/d, respectively; P < 0.05). Proportions of the genus Parabacteroides significantly increased with SCF dose (1.1% ± 0.8%, 2.1% ± 1.6%, and 3.0% ± 2.0% for 0, 10, and 20 g fiber/d from SCF, respectively; P < 0.05). Increases in calcium absorption positively correlated with increases in Clostridium (r = 0.44, P = 0.023) and unclassified Clostridiaceae (r = 0.40, P = 0.040). SCF, a nondigestible carbohydrate, increased calcium absorption in free-living adolescent females. Two groups of bacteria may be involved, one directly fermenting SCF and the second fermenting SCF metabolites further, thereby promoting increased calcium absorption. This trial was registered at clinicaltrials.gov as NCT01660503. © 2016 American Society for Nutrition.

Indirect effects of phorid fly parasitoids on the mechanisms of interspecific competition among ants.

PubMed

Morrison, Lloyd W

1999-10-01

Indirect effects, which occur when the impact of one species upon another requires the existence of an intermediary species, are apparently very common and may be of greater magnitude than direct effects. Behaviorally mediated indirect effects occur when one species affects the behavior of a second, which in turn affects how that species interacts with a third. I studied behaviorally mediated indirect effects on the mechanisms of competition in two congeneric fire ant species in the presence and absence of parasitoid phorid flies, which parasitized only one ant species. In observational and experimental field studies, the presence of native Texas phorid flies in the genus Pseudacteon decreased food retrieval by their host, Solenopsis geminata (F.), by as much as 50%. In the presence of phorid flies, many S. geminata workers assumed a stationary, curled defensive posture and did not forage. Although the phorid parasitoids had a relatively large effect on exploitative competition, there was no measurable effect on interference competition. Fierce interspecific aggression was observed between S. geminata and S. invicta Buren, and the presence of phorids had no effect on the outcome of these contests. The indirect effects of Pseudacteon parasitoids on Solenopsis fire ant resource retrieval appear to be larger than the direct effect of mortality. Some aspects of the foraging behavior of these Solenopsis species may be, in part, evolutionary adaptations to phorid parasitoid pressure. Because of the relatively large indirect effects, South American Pseudacteon phorids may be promising biocontrol agents of imported fire ants, S. invicta, in the USA. In a laboratory study, a single South American Pseudacteon female was able to significantly decrease food retrieval rates of a North American population of the imported fire ant, S. invicta.

Pathway-Specific Striatal Substrates for Habitual Behavior.

PubMed

O'Hare, Justin K; Ade, Kristen K; Sukharnikova, Tatyana; Van Hooser, Stephen D; Palmeri, Mark L; Yin, Henry H; Calakos, Nicole

2016-02-03

The dorsolateral striatum (DLS) is implicated in habit formation. However, the DLS circuit mechanisms underlying habit remain unclear. A key role for DLS is to transform sensorimotor cortical input into firing of output neurons that project to the mutually antagonistic direct and indirect basal ganglia pathways. Here we examine whether habit alters this input-output function. By imaging cortically evoked firing in large populations of pathway-defined striatal projection neurons (SPNs), we identify features that strongly correlate with habitual behavior on a subject-by-subject basis. Habitual behavior correlated with strengthened DLS output to both pathways as well as a tendency for action-promoting direct pathway SPNs to fire before indirect pathway SPNs. In contrast, habit suppression correlated solely with a weakened direct pathway output. Surprisingly, all effects were broadly distributed in space. Together, these findings indicate that the striatum imposes broad, pathway-specific modulations of incoming activity to render learned motor behaviors habitual. Copyright © 2016 Elsevier Inc. All rights reserved.

Cloud fraction, layer, and direction of movement results from sky cameras during the FIRE IFO, Coffeyville, Kansas, experiment for the period Nov. 12 through Dec. 9, 1991

NASA Technical Reports Server (NTRS)

Purgold, Gerald C.; Wheeler, Robert J.; Whitlock, Charles H.

1992-01-01

Tables and figures are presented which show local site observations of cloud fractions, the number of cloud layers, direction of movement, and precipitation data collected during the FIRE (First ISCCP Regional Experiment) Phase 2 Cirrus Intensive Field Observations (IFO) conducted in Coffeyville, Kansas during November and December, 1991. Selected data are also presented at the times of the TIROS Operational Vertical Sounder (TOVS) satellite overpass. Several major scientific projects have used surface-based observations of clouds to compare directly with those being observed from satellites. Characterizing the physical properties of clouds is extremely useful in obtaining a more accurate analysis of the effect of clouds and their movements on weather and climate. It is the purpose of this paper to report data collected during the FIRE Phase 2 IFO experiment and to provide a brief history of such a surface-based system and the technical information required for recording local cloud parameters.

Effect of Oral Lipid Matrix Supplement on Fat Absorption in Cystic Fibrosis: A Randomized Placebo-Controlled Trial.

PubMed

Stallings, Virginia A; Schall, Joan I; Maqbool, Asim; Mascarenhas, Maria R; Alshaikh, Belal N; Dougherty, Kelly A; Hommel, Kevin; Ryan, Jamie; Elci, Okan U; Shaw, Walter A

2016-12-01

Pancreatic enzyme therapy does not normalize dietary fat absorption in patients with cystic fibrosis and pancreatic insufficiency. Efficacy of LYM-X-SORB (LXS), an easily absorbable lipid matrix that enhances fat absorption, was evaluated in a 12-month randomized, double-blinded, placebo-controlled trial with plasma fatty acids (FA) and coefficient of fat absorption (CFA) outcomes. A total of 110 subjects (age 10.4 ± 3.0 years) were randomized. Total FA increased with LXS at 3 and 12 months (+1.58, +1.14 mmol/L) and not with placebo (P = 0.046). With LXS, linoleic acid (LA) increased at 3 and 12 months (+298, +175 nmol/mL, P ≤ 0.046), with a 6% increase in CFA (P < 0.01). LA increase was significant in LXS versus placebo (445 vs 42 nmol/mL, P = 0.038). Increased FA and LA predicted increased body mass index Z scores. In summary, the LXS treatment improved dietary fat absorption compared with placebo as indicated by plasma FA and LA and was associated with better growth status.

Generalization of the event-based Carnevale-Hines integration scheme for integrate-and-fire models.

PubMed

van Elburg, Ronald A J; van Ooyen, Arjen

2009-07-01

An event-based integration scheme for an integrate-and-fire neuron model with exponentially decaying excitatory synaptic currents and double exponential inhibitory synaptic currents has been introduced by Carnevale and Hines. However, the integration scheme imposes nonphysiological constraints on the time constants of the synaptic currents, which hamper its general applicability. This letter addresses this problem in two ways. First, we provide physical arguments demonstrating why these constraints on the time constants can be relaxed. Second, we give a formal proof showing which constraints can be abolished. As part of our formal proof, we introduce the generalized Carnevale-Hines lemma, a new tool for comparing double exponentials as they naturally occur in many cascaded decay systems, including receptor-neurotransmitter dissociation followed by channel closing. Through repeated application of the generalized lemma, we lift most of the original constraints on the time constants. Thus, we show that the Carnevale-Hines integration scheme for the integrate-and-fire model can be employed for simulating a much wider range of neuron and synapse types than was previously thought.

Mesoscale Modeling of Smoke Particles Distribution and Their Radiative Feedback over Northern Sub-Saharan African Region

NASA Astrophysics Data System (ADS)

Yue, Y.; Wang, J.; Ichoku, C. M.; Ellison, L.

2015-12-01

Stretching from southern boundary of Sahara to the equator and expanding west to east from Atlantic Ocean coasts to the India Ocean coasts, the northern sub-Saharan African (NSSA) region has been subject to intense biomass burning. Comprised of savanna, shrub, tropical forest and a number of agricultural crops, the extensive fires burn belt covers central and south of NSSA during dry season (from October to March) contributes to one of the highest biomass burning rate per km2 in the world. Due to smoke particles' absorption effects of solar radiation, they can modify the surface and atmosphere temperature and thus change atmospheric stability, height of the boundary layer, regional atmospheric circulation, evaporation rate, cloud formation, and precipitation. Hence, smoke particles emitted from biomass burning over NSSA region has a significant influence to the air quality, weather and climate variability. In this study, the first version of this Fire Energetics and Emissions Research (FEER.v1) emissions of several smoke constituents including light-absorbing organic carbon (OC) and black carbon (BC) are applied to a state-of-science meteorology-chemistry model as NOAA Weather Research and Forecasting Model with Chemistry (WRF-Chem). We analyzed WRF-Chem simulations of surface and vertical distribution of various pollutants and their direct radiative effects in conjunction with satellite observation data from Moderate Resolution Imaging Spectroradiometer (MODIS) and Cloud-Aerosol Lidar data with Orthogonal Polarization (CALIPSO) to strengthen the importance of combining space measured emission products like FEER.v1 emission inventory with mesoscale model over intense biomass burning region, especially in area where ground-based air-quality and radiation-related observations are limited or absent.

Near-infrared light absorption by brown carbon in the ambient atmosphere

NASA Astrophysics Data System (ADS)

Chung, C.; Hoffer, A.; Beres, N. D.; Moosmüller, H.; Liu, C.; Green, M.; Kim, S. W.; Engelbrecht, J. P.; Gelencser, A.

2017-12-01

Organic aerosols have been assumed to have little-to-no absorption in the red and near-infrared spectral regions of solar radiation, even though a class of organic aerosols were shown to absorb significantly in these spectral regions. Here, we show that ambient atmospheric data from commonly-used 7-wavelength aethalometers contain evidence of abundant near-infrared light absorption by organic aerosol. This evidence comes from the absorption Ångström exponent over 880 950 nm, which often exceeds values explainable by fresh or coated black carbon, or mineral dust. This evidence is not due to an artifact from the instrument random errors or biases, either. The best explanation for these large 880/950 nm absorption Ångström exponent values in the aethalometer data is near-infrared light absorption by tar balls. Tar balls are among common particles from forest fire.

Climatic and human controls on the late Holocene fire history of northern Israel

NASA Astrophysics Data System (ADS)

Quintana Krupinski, N. B.; Nishri, A.; Street, J. H.; Paytan, A.

2011-12-01

Long-term fire histories provide insight into the effects of climate, ecology and human influence on fire activity. Fire records can be expanded beyond the period of historical record using accumulation rates of large charcoal particles and soot black carbon (BC) in lacustrine sediments: charcoal accumulation peaks indicate local to regional fire events, while increased deposition of BC may document regional-scale burning. To determine which factors exert the greatest control over changes in fire frequency at different times, this study compares late Holocene fire records from Lake Kinneret (the Sea of Galilee), Israel to local and regional records of climate and human activity. We show that fire frequency decreased during the past 3010 years from 3-4 fire events per 400 years between 3010 - 2620 y.b.p. to 0-2 fire events per 400 years from 750 y.b.p. to present. Human modification of the landscape during periods of high population (e.g. forest clearing, agriculture, settlement expansion and industry) appears to have been the greatest contributor to increased fire activity in the semi-arid southern Levant region during the late Holocene, though aridity may also have contributed to higher fire activity. However, during much of the study period, climate and human activity were interrelated, so while human activity may have been the greater control on fire activity, the effect of climate may have been both direct and indirect (through climate-related changes in population), making it sometimes difficult to distinguish the two controls. Projections of increasing aridification of the region combined with a heavy impact on the landscape from a large modern population suggest that increased fire activity may occur in the region in the near future.

Fire severity and ecosytem responses following crown fires in California shrublands

USGS Publications Warehouse

Keeley, J.E.; Brennan, T.; Pfaff, A.H.

2008-01-01

Chaparral shrublands burn in large high-intensity crown fires. Managers interested in how these wildfires affect ecosystem processes generally rely on surrogate measures of fire intensity known as fire severity metrics. In shrublands burned in the autumn of 2003, a study of 250 sites investigated factors determining fire severity and ecosystem responses.Using structural equation modeling we show that stand age, prefire shrub density, and the shortest interval of the prior fire history had significant direct effects on fire severity, explaining >50% of the variation in severity.Fire severity per se is of interest to resource managers primarily because it is presumed to be an indicator of important ecosystem processes such as vegetative regeneration, community recovery, and erosion. Fire severity contributed relatively little to explaining patterns of regeneration after fire. Two generalizations can be drawn: fire severity effects are mostly short-lived, i.e., by the second year they are greatly diminished, and fire severity may have opposite effects on different functional types.Species richness exhibited a negative relationship to fire severity in the first year, but fire severity impacts were substantially less in the second postfire year and varied by functional type. Much of this relationship was due to alien plants that are sensitive to high fire severity; at all scales from 1 to 1000 m2, the percentage of alien species in the postfire flora declined with increased fire severity. Other aspects of disturbance history are also important determinants of alien cover and richness as both increased with the number of times the site had burned and decreased with time since last fire.A substantial number of studies have shown that remote-sensing indices are correlated with field measurements of fire severity. Across our sites, absolute differenced normalized burn ratio (dNBR) was strongly correlated with field measures of fire severity and with fire history at a site but relative dNBR was not. Despite being correlated with fire severity, absolute dNBR showed little or no relationship with important ecosystem responses to wildfire such as shrub resprouting or total vegetative regeneration. These findings point to a critical need for further research on interpreting remote sensing indices as applied to postfire management of these shrublands.

Fire severity and ecosytem responses following crown fires in California shrublands.

PubMed

Keeley, Jon E; Brennan, Teresa; Pfaff, Anne H

2008-09-01

Chaparral shrublands burn in large high-intensity crown fires. Managers interested in how these wildfires affect ecosystem processes generally rely on surrogate measures of fire intensity known as fire severity metrics. In shrublands burned in the autumn of 2003, a study of 250 sites investigated factors determining fire severity and ecosystem responses. Using structural equation modeling we show that stand age, prefire shrub density, and the shortest interval of the prior fire history had significant direct effects on fire severity, explaining > 50% of the variation in severity. Fire severity per se is of interest to resource managers primarily because it is presumed to be an indicator of important ecosystem processes such as vegetative regeneration, community recovery, and erosion. Fire severity contributed relatively little to explaining patterns of regeneration after fire. Two generalizations can be drawn: fire severity effects are mostly shortlived, i.e., by the second year they are greatly diminished, and fire severity may have opposite effects on different functional types. Species richness exhibited a negative relationship to fire severity in the first year, but fire severity impacts were substantially less in the second postfire year and varied by functional type. Much of this relationship was due to alien plants that are sensitive to high fire severity; at all scales from 1 to 1000 m2, the percentage of alien species in the postfire flora declined with increased fire severity. Other aspects of disturbance history are also important determinants of alien cover and richness as both increased with the number of times the site had burned and decreased with time since last fire. A substantial number of studies have shown that remote-sensing indices are correlated with field measurements of fire severity. Across our sites, absolute differenced normalized burn ratio (dNBR) was strongly correlated with field measures of fire severity and with fire history at a site but relative dNBR was not. Despite being correlated with fire severity, absolute dNBR showed little or no relationship with important ecosystem responses to wildfire such as shrub resprouting or total vegetative regeneration. These findings point to a critical need for further research on interpreting remote sensing indices as applied to postfire management of these shrublands.

Optical effects in artificial opals infiltrated with gold nanoparticles

NASA Astrophysics Data System (ADS)

Comoretto, Davide; Morandi, Valentina; Marabelli, Franco; Amendola, Vincenzo; Meneghetti, Moreno

2006-04-01

Polystyrene artificial opals are directly grown with embedded gold nanoparticles (NpAu) in their interstices. Reflectance spectra of samples having different sphere diameters and nanoparticles load clearly show a red shift of the photonic band gap as well as a reduction of its width without showing direct evidence of NpAu absorption. The case of transmission spectra is instead more complicated: here, overlapped to a broad NpAu absorption, a structure having unusual lineshape is detected. The infiltration of opal with NpAu removes the polarization dependence of the photonic band structure observed in bare opals. The lineshape of the absorption spectra suggest a spatial localization of the electromagnetic field in the volume where NpAu are confined thus enhancing its local intensity. This effect seems to be effective to stimulate optical nonlinearities of NpAu. Nanosecond transient absorption measurements on NpAu infiltrated opals indicate that a variation of transmission of about 10% is observed. Since this effect takes place within the pump pulse and since NpAu photoluminescence has been subtracted to the signal, we attribute it to an optical switching process.

The effect of soot modeling on thermal radiation in buoyant turbulent diffusion flames

NASA Astrophysics Data System (ADS)

Snegirev, A.; Kokovina, E.; Tsoy, A.; Harris, J.; Wu, T.

2016-09-01

Radiative impact of buoyant turbulent diffusion flames is the driving force in fire development. Radiation emission and re-absorption is controlled by gaseous combustion products, mainly CO2 and H2O, and by soot. Relative contribution of gas and soot radiation depends on the fuel sooting propensity and on soot distribution in the flame. Soot modeling approaches incorporated in big commercial codes were developed and calibrated for momentum-dominated jet flames, and these approaches must be re-evaluated when applied to the buoyant flames occurring in fires. The purpose of this work is to evaluate the effect of the soot models available in ANSYS FLUENT on the predictions of the radiative fluxes produced by the buoyant turbulent diffusion flames with considerably different soot yields. By means of large eddy simulations, we assess capability of the Moss-Brooks soot formation model combined with two soot oxidation submodels to predict methane- and heptane-fuelled fires, for which radiative flux measurements are available in the literature. We demonstrate that the soot oxidation models could be equally important as soot formation ones to predict the soot yield in the overfire region. Contribution of soot in the radiation emission by the flame is also examined, and predicted radiative fluxes are compared to published experimental data.

Influence of forest and rangeland management on anadromous fish habitat in Western North America: forest chemicals.

Treesearch

L.A. Norris; H.W. Lorz; S.V. Gregory

1983-01-01

Herbicides, insecticides, fertilizers, and fire retardants are chemicals used to protect or enhance certain forest resources. Their use may directly affect anadromous fish by exposing them to toxic amounts of the chemical. Indirect effects are also possible through chemically induced alteration of habitat, including direct effects on fish-food organisms.Data...

Development of gas fire detection system using tunable diode laser absorption spectroscopy

NASA Astrophysics Data System (ADS)

Jiang, Y. L.; Li, G.; Yang, T.; Wang, J. J.

2017-01-01

The conventional fire detection methods mainly produce an alarm through detecting the changes in smoke concentration, flame radiation, heat and other physical parameters in the environment, but are unable to provide an early warning of a fire emergency. We have designed a gas fire detection system with a high detection sensitivity and high selectivity using the tunable semiconductor diode laser as a light source and combining wavelength modulation and harmonic detection technology. This system can invert the second harmonic signal obtained to obtain the concentration of carbon monoxide gas (a fire characteristic gas) so as to provide an early warning of fire. We reduce the system offset noise and the background noise generated due to the laser interference by deducting the system background spectrum lines from the second harmonic signal. This can also eliminate the interference of other gas spectral lines to a large extent. We detected the concentration of the carbon monoxide gas generated in smoldering sandalwood fire and open beech wood fire with the homemade fire simulator, and tested the lowest detectable limit of system. The test results show that the lowest detectable limit can reach 5×10-6 the system can maintain stable operation for a long period of time and can automatically trigger a water mist fire extinguishing system, which can fully meet the needs of early fire warning.

THE IMPACT OF ACCURATE EXTINCTION MEASUREMENTS FOR X-RAY SPECTRAL MODELS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smith, Randall K.; Valencic, Lynne A.; Corrales, Lia, E-mail: lynne.a.valencic@nasa.gov

Interstellar extinction includes both absorption and scattering of photons from interstellar gas and dust grains, and it has the effect of altering a source's spectrum and its total observed intensity. However, while multiple absorption models exist, there are no useful scattering models in standard X-ray spectrum fitting tools, such as XSPEC. Nonetheless, X-ray halos, created by scattering from dust grains, are detected around even moderately absorbed sources, and the impact on an observed source spectrum can be significant, if modest, compared to direct absorption. By convolving the scattering cross section with dust models, we have created a spectral model asmore » a function of energy, type of dust, and extraction region that can be used with models of direct absorption. This will ensure that the extinction model is consistent and enable direct connections to be made between a source's X-ray spectral fits and its UV/optical extinction.« less

Photoacoustics of single laser-trapped nanodroplets for the direct observation of nanofocusing in aerosol photokinetics

NASA Astrophysics Data System (ADS)

Cremer, Johannes W.; Thaler, Klemens M.; Haisch, Christoph; Signorell, Ruth

2016-03-01

Photochemistry taking place in atmospheric aerosol droplets has a significant impact on the Earth's climate. Nanofocusing of electromagnetic radiation inside aerosols plays a crucial role in their absorption behaviour, since the radiation flux inside the droplet strongly affects the activation rate of photochemically active species. However, size-dependent nanofocusing effects in the photokinetics of small aerosols have escaped direct observation due to the inability to measure absorption signatures from single droplets. Here we show that photoacoustic measurements on optically trapped single nanodroplets provide a direct, broadly applicable method to measure absorption with attolitre sensitivity. We demonstrate for a model aerosol that the photolysis is accelerated by an order of magnitude in the sub-micron to micron size range, compared with larger droplets. The versatility of our technique promises broad applicability to absorption studies of aerosol particles, such as atmospheric aerosols where quantitative photokinetic data are critical for climate predictions.

Photoacoustics of single laser-trapped nanodroplets for the direct observation of nanofocusing in aerosol photokinetics

PubMed Central

Cremer, Johannes W.; Thaler, Klemens M.; Haisch, Christoph; Signorell, Ruth

2016-01-01

Photochemistry taking place in atmospheric aerosol droplets has a significant impact on the Earth's climate. Nanofocusing of electromagnetic radiation inside aerosols plays a crucial role in their absorption behaviour, since the radiation flux inside the droplet strongly affects the activation rate of photochemically active species. However, size-dependent nanofocusing effects in the photokinetics of small aerosols have escaped direct observation due to the inability to measure absorption signatures from single droplets. Here we show that photoacoustic measurements on optically trapped single nanodroplets provide a direct, broadly applicable method to measure absorption with attolitre sensitivity. We demonstrate for a model aerosol that the photolysis is accelerated by an order of magnitude in the sub-micron to micron size range, compared with larger droplets. The versatility of our technique promises broad applicability to absorption studies of aerosol particles, such as atmospheric aerosols where quantitative photokinetic data are critical for climate predictions. PMID:26979973

Modeling the influence of the BRDF characteristics of vegetation on the retrieval of solar-induced chlorophyll fluorescence under different illumination conditions

NASA Astrophysics Data System (ADS)

Liu, Xinjie; Liu, Liangyun

2017-04-01

The Fraunhofer Line Discrimination (FLD) principle is the main approach used for the retrieval of solar-induced chlorophyll fluorescence (SIF). The basic assumption of the FLD principle is that the apparent reflectance spectra without SIF in-filling are smooth in the region of the absorption bands. However, in fact, this assumption is not valid due to the so-called "direct radiation in-filling" effect caused by the non-linear contribution of direct and diffuse radiation at the oxygen absorption bands, which are widely used for ground-based SIF retrieval. In this study, we first analyzed the physical mechanism of the direct radiation in-filling effect on the oxygen absorption bands and found that the bias in the SIF retrieval caused by the direct radiation in-filling effect at the O2-A band was less than 20% based on the use of a simulated dataset. Secondly, we established a simple correction model of the direct radiation in-filling effect. We found that the direct radiation in-filling effect at the O2-A band was directly proportional to the difference between the reflectance of the direct and diffuse radiation, and that the coefficient of proportionality was well correlated with the diffuse-to-global radiation ratio in the form of a quadratic function. The coefficient of determination (R-squared) for this correlation was 0.97. Finally, the model was validated using both simulated and field datasets. The validation results show that the bias in the SIF retrieval caused by the direct radiation in-filling effect can be efficiently corrected using the model proposed in this paper. This study thus provides a possible approach to estimating and correcting for the direct radiation-infilling effect using prior knowledge of the BRDF characteristics of direct and diffuse radiation for specific targets.

Remote sensing of fire severity: linking post-fire reflectance data with physiological responses in two western conifer species

NASA Astrophysics Data System (ADS)

Sparks, A. M.; Smith, A. M.; Kolden, C.; Apostol, K. G.; Boschetti, L.

2014-12-01

Fire is a common disturbance in forested ecosystems in the western U.S. and can be responsible for long-term impacts on vegetation and soil. An improved understanding of how ecosystems recover after fire is necessary so that land managers can plan for and mitigate the effects of these disturbances. Although several studies have attempted to link fire intensity with severity, direct links between spectral indices of severity and key physiological changes in vegetation are not well understood. We conducted an assessment of how two western conifer species respond to four fire radiative energy treatments, with spectra acquired pre- and up to a month post-burn. After transforming the spectral data into Landsat 8 equivalent reflectance, burn severity indices commonly used in the remote sensing community were compared to concurrent physiological measurements including gas exchange and photosynthetic rate. Preliminary results indicate significant relationships between several fire severity indices and physiological responses measured in the conifer seedlings.