Absolute rate coefficients for the recombination of open f-shell tungsten ions
NASA Astrophysics Data System (ADS)
Krantz, C.; Spruck, K.; Badnell, N. R.; Becker, A.; Bernhardt, D.; Grieser, M.; Hahn, M.; Novotný, O.; Repnow, R.; Savin, D. W.; Wolf, A.; Müller, A.; Schippers, S.
2014-04-01
We have carried out direct measurements of the absolute recombination rate coefficients of four charge states of tungsten in the range from W18+ to W21+ in a heavy ion storage ring. We find that the rich atomic fine structure of the open f-shell leads to very high resonant enhancement of the recombination rate at energies below ~50 eV. Even in the higher energy domain relevant to fusion plasma this leads to a recombination rate coefficient that is more than four times higher than predicted by the commonly used ADAS database of recombination rates. In addition to the experimental measurements we have carried out theoretical calculations using Autostructure. For W20+ these predict a plasma recombination rate coefficient that agrees much better with the measurement than the ADAS model but still fail to reproduce the experimental data in detail.
Absolute rate coefficients for photorecombination of beryllium-like and boron-like silicon ions
NASA Astrophysics Data System (ADS)
Bernhardt, D.; Becker, A.; Brandau, C.; Grieser, M.; Hahn, M.; Krantz, C.; Lestinsky, M.; Novotný, O.; Repnow, R.; Savin, D. W.; Spruck, K.; Wolf, A.; Müller, A.; Schippers, S.
2016-04-01
We report measured rate coefficients for electron-ion recombination of Si10+ forming Si9+ and of Si9+ forming Si8+, respectively. The measurements were performed using the electron-ion merged-beams technique at a heavy-ion storage ring. Electron-ion collision energies ranged from 0 to 50 eV for Si9+ and from 0 to 2000 eV for Si10+, thus, extending previous measurements for Si10+ (Orban et al 2010 Astrophys. J. 721 1603) to much higher energies. Experimentally derived rate coefficients for the recombination of Si9+ and Si10+ ions in a plasma are presented along with simple parameterizations. These rate coefficients are useful for the modeling of the charge balance of silicon in photoionized plasmas (Si9+ and Si10+) and in collisionally ionized plasmas (Si10+ only). In the corresponding temperature ranges, the experimentally derived rate coefficients agree with the latest corresponding theoretical results within the experimental uncertainties.
NASA Astrophysics Data System (ADS)
Badnell, N. R.; Spruck, K.; Krantz, C.; Novotný, O.; Becker, A.; Bernhardt, D.; Grieser, M.; Hahn, M.; Repnow, R.; Savin, D. W.; Wolf, A.; Müller, A.; Schippers, S.
2016-05-01
Experimentally measured and theoretically calculated rate coefficients for the recombination of W19 +([Kr ] 4 d10 4 f9 ) ions with free electrons (forming W18 +) are presented. At low electron-ion collision energies, the merged-beam rate coefficient is dominated by strong, mutually overlapping, recombination resonances as already found previously for the neighboring charge-state ions W18 + and W20 +. In the temperature range where W19 + is expected to form in a collisionally ionized plasma, the experimentally derived recombination rate coefficient deviates by up to a factor of about 20 from the theoretical rate coefficient obtained from the Atomic Data and Analysis Structure database. The present calculations, which employ a Breit-Wigner redistributive partitioning of autoionizing widths for dielectronic recombination via multi-electron resonances, reproduce the experimental findings over the entire temperature range.
Teplukhin, Alexander; Babikov, Dmitri
2016-07-28
Rigorous calculations of scattering resonances in ozone are carried out for a broad range of rotational excitations. The accurate potential energy surface of Dawes is adopted, and a new efficient method for calculations of ro-vibrational energies, wave functions and resonance lifetimes is employed (which uses hyper-spherical coordinates, the sequential diagonalization/truncation approach, grid optimization and complex absorbing potential). A detailed analysis is carried out to characterize distributions of resonance energies and lifetimes, their rotational/vibrational content and their positions with respect to the centrifugal barrier. Emphasis is on the contribution of these resonances to the recombination process that forms ozone. It is found that major contributions come from localized resonances at energies near the top of the barrier. Delocalized resonances at higher energies should also be taken into account, while very narrow resonances at low energies (trapped far behind the centrifugal barrier) should be treated as bound states. The absolute value of the recombination rate coefficient, its pressure and temperature dependencies are obtained using the energy-transfer model developed in the earlier work. Good agreement with experimental data is obtained if one follows the suggestion of Troe, who argued that the energy transfer mechanism of recombination is responsible only for 55% of the recombination rate (with the remaining 45% coming from the competing chaperon mechanism). PMID:27364351
Teplukhin, Alexander; Babikov, Dmitri
2016-07-28
Rigorous calculations of scattering resonances in ozone are carried out for a broad range of rotational excitations. The accurate potential energy surface of Dawes is adopted, and a new efficient method for calculations of ro-vibrational energies, wave functions and resonance lifetimes is employed (which uses hyper-spherical coordinates, the sequential diagonalization/truncation approach, grid optimization and complex absorbing potential). A detailed analysis is carried out to characterize distributions of resonance energies and lifetimes, their rotational/vibrational content and their positions with respect to the centrifugal barrier. Emphasis is on the contribution of these resonances to the recombination process that forms ozone. It is found that major contributions come from localized resonances at energies near the top of the barrier. Delocalized resonances at higher energies should also be taken into account, while very narrow resonances at low energies (trapped far behind the centrifugal barrier) should be treated as bound states. The absolute value of the recombination rate coefficient, its pressure and temperature dependencies are obtained using the energy-transfer model developed in the earlier work. Good agreement with experimental data is obtained if one follows the suggestion of Troe, who argued that the energy transfer mechanism of recombination is responsible only for 55% of the recombination rate (with the remaining 45% coming from the competing chaperon mechanism).
Vetters, B; Dils, B; Nguyen, T L; Vereecken, L; Carl, S A; Peeters, J
2009-06-01
The absolute rate coefficients of the reactions of the carbyne-radical CF(X(2)Pi, nu = 0) with O(2), F(2) and Cl(2) have been measured over extended temperature ranges, using pulsed-laser photodissociation-laser-induced fluorescence (PLP-LIF) techniques. The CF(X(2)Pi) radicals were generated by KrF excimer laser 2-photon photolysis of CF(2)Br(2) at 248 nm and the real-time exponential decays of CF(X(2)Pi, nu = 0) at varying coreactant concentrations, in large excess, were monitored by LIF (A(2)Sigma(+), nu' = 1 <-- X(2)Pi, nu'' = 0 transition). The experimental bimolecular rate coefficients of the CF(X(2)Pi) reactions with F(2) and Cl(2) can be described by simple Arrhenius expressions: k(F2)(295-408 K) = (1.5 +/- 0.2) x 10(-11) exp[-(370 +/- 40)K/T] cm(3) molecule(-1) s(-1); and k(Cl2)(295-392 K) = (6.1 +/- 2.1) x 10(-12) exp[+(280 +/- 120)K/T]. The k(F2)(T) and k(Cl2)(T) results can be rationalized in terms of direct halogen-atom abstraction reactions in which the radical character of CF dominates; a quantum chemical CBS-Q//BHandHLYP/6-311G(d,p) study confirms that the ground state reactants CF(X(2)Pi) + F(2)(X(1)Sigma) connect directly with the ground-state products CF(2)(X(1)A(1)) + F((2)P) via a nearly barrierless F-atom abstraction route. The rate coefficient of CF(X(2)Pi) + O(2) can be represented by a two-term Arrhenius expression: k(O2)(258-780 K) = 1.1 x 10(-11) exp(-850 K/T) + 2.3 x 10(-13) exp(500 K/T), with a standard deviation of 5%. The first term dominates at higher temperatures T and the second at lower T where a negative temperature dependence is observed (<290 K). Quantum chemical computations at the CBS-QB3 and CCSD(T)/aug-cc-pVDZ levels of theory show that the k(O2)(T) behaviour is consistent with a change of the dominant rate-determining mechanism from a carbyne-type insertion into the O-O bond at high T to a radical-radical combination at low T.
Determination of absolute internal conversion coefficients using the SAGE spectrometer
NASA Astrophysics Data System (ADS)
Sorri, J.; Greenlees, P. T.; Papadakis, P.; Konki, J.; Cox, D. M.; Auranen, K.; Partanen, J.; Sandzelius, M.; Pakarinen, J.; Rahkila, P.; Uusitalo, J.; Herzberg, R.-D.; Smallcombe, J.; Davies, P. J.; Barton, C. J.; Jenkins, D. G.
2016-03-01
A non-reference based method to determine internal conversion coefficients using the SAGE spectrometer is carried out for transitions in the nuclei of 154Sm, 152Sm and 166Yb. The Normalised-Peak-to-Gamma method is in general an efficient tool to extract internal conversion coefficients. However, in many cases the required well-known reference transitions are not available. The data analysis steps required to determine absolute internal conversion coefficients with the SAGE spectrometer are presented. In addition, several background suppression methods are introduced and an example of how ancillary detectors can be used to select specific reaction products is given. The results obtained for ground-state band E2 transitions show that the absolute internal conversion coefficients can be extracted using the methods described with a reasonable accuracy. In some cases of less intense transitions only an upper limit for the internal conversion coefficient could be given.
El Dib, Gisèle; Sleiman, Chantal; Canosa, André; Travers, Daniel; Courbe, Jonathan; Sawaya, Terufat; Mokbel, Ilham; Chakir, Abdelkhaleq
2013-01-10
The reaction of the OH radicals with 4-hydroxy-2-butanone was investigated in the gas phase using an absolute rate method at room temperature and over the pressure range 10-330 Torr in He and air as diluent gases. The rate coefficients were measured using pulsed laser photolysis (PLP) of H(2)O(2) to produce OH and laser induced fluorescence (LIF) to measure the OH temporal profile. An average value of (4.8 ± 1.2) × 10(-12) cm(3) molecule(-1) s(-1) was obtained. The OH quantum yield following the 266 nm pulsed laser photolysis of 4-hydroxy-2-butanone was measured for the first time and found to be about 0.3%. The investigated kinetic study required accurate measurements of the vapor pressure of 4-hydroxy-2-butanone, which was measured using a static apparatus. The vapor pressure was found to range from 0.056 to 7.11 Torr between 254 and 323 K. This work provides the first absolute rate coefficients for the reaction of 4-hydroxy-2-butanone with OH and the first experimental saturated vapor pressures of the studied compound below 311 K. The obtained results are compared to those of the literature and the effects of the experimental conditions on the reactivity are examined. The calculated tropospheric lifetime obtained in this work suggests that once emitted into the atmosphere, 4H2B may contribute to the photochemical pollution in a local or regional scale.
Absolute rate theories of epigenetic stability
NASA Astrophysics Data System (ADS)
Walczak, Aleksandra M.; Onuchic, José N.; Wolynes, Peter G.
2005-12-01
Spontaneous switching events in most characterized genetic switches are rare, resulting in extremely stable epigenetic properties. We show how simple arguments lead to theories of the rate of such events much like the absolute rate theory of chemical reactions corrected by a transmission factor. Both the probability of the rare cellular states that allow epigenetic escape and the transmission factor depend on the rates of DNA binding and unbinding events and on the rates of protein synthesis and degradation. Different mechanisms of escape from the stable attractors occur in the nonadiabatic, weakly adiabatic, and strictly adiabatic regimes, characterized by the relative values of those input rates. rate theory | stochastic gene expression | gene switches
The Absolute Rate of LGRB Formation
NASA Astrophysics Data System (ADS)
Graham, J. F.; Schady, P.
2016-06-01
We estimate the long-duration gamma-ray burst (LGRB) progenitor rate using our recent work on the effects of environmental metallically on LGRB formation in concert with supernovae (SNe) statistics via an approach patterned loosely off the Drake equation. Beginning with the cosmic star formation history, we consider the expected number of broad-line Type Ic events (the SNe type associated with LGRBs) that are in low-metallicity host environments adjusted by the contribution of high-metallicity host environments at a much reduced rate. We then compare this estimate to the observed LGRB rate corrected for instrumental selection effects to provide a combined estimate of the efficiency fraction of these progenitors to produce LGRBs and the fraction of which are beamed in our direction. From this we estimate that an aligned LGRB occurs for approximately every 4000 ± 2000 low-metallically broad-lined SNe Ic. Therefore, if one assumes a semi-nominal beaming factor of 100, then only about one such supernova out of 40 produce an LGRB. Finally, we propose an off-axis LGRB search strategy of targeting only broad-line Type Ic events that occur in low-metallicity hosts for radio observation.
Measurement of Disintegration Rates and Absolute {gamma}-ray Intensities
DeVries, Daniel J.; Griffin, Henry C.
2006-03-13
The majority of practical radioactive materials decay by modes that include {gamma}-ray emission. For questions of 'how much' or 'how pure', one must know the absolute intensities of the major radiations. We are using liquid scintillation counting (LSC) to measurements of disintegration rates, coupled with {gamma}-ray spectroscopy to measure absolute {gamma}-ray emission probabilities. Described is a study of the 227Th chain yielding absolute {gamma}-ray intensities with {approx}0.5% accuracy and information on LSC efficiencies.
Rate coefficient for the reaction N + NO
NASA Technical Reports Server (NTRS)
Fox, J. L.
1994-01-01
Evidence has been advanced that the rate coefficient for the reaction N + NO right arrow N2 + O has a small positive temperature dependence at the high temperatures (900 to 1500 K) that prevail in the terrestrial middle and upper thermosphere by Siskind and Rusch (1992), and at the low temperatures (100 to 200 K) of the Martian lower thermosphere by Fox (1993). Assuming that the rate coefficient recommended by the Jet Propulsion Laboratory evaluation (DeMore et al., 1992) is accurate at 300 K, we derive here the low temperature value of the activation energy for this reaction and thus the rate coefficient that best fits the Viking 1 measured NO densities. We find that the fit is acceptable for a rate coefficient of about 1.3 x 10(exp -10)(T/300)(exp 0.5)exp(-400/T) and better for a value of about 2.5 x 10(exp -10)(T/300)(exp 0.5)exp(-600/T)cu cm/s.
Flow rate calibration for absolute cell counting rationale and design.
Walker, Clare; Barnett, David
2006-05-01
There is a need for absolute leukocyte enumeration in the clinical setting, and accurate, reliable (and affordable) technology to determine absolute leukocyte counts has been developed. Such technology includes single platform and dual platform approaches. Derivations of these counts commonly incorporate the addition of a known number of latex microsphere beads to a blood sample, although it has been suggested that the addition of beads to a sample may only be required to act as an internal quality control procedure for assessing the pipetting error. This unit provides the technical details for undertaking flow rate calibration that obviates the need to add reference beads to each sample. It is envisaged that this report will provide the basis for subsequent clinical evaluations of this novel approach. PMID:18770842
Nanoscale Thermoelectrics: A Study of the Absolute Seebeck Coefficient of Thin Films
NASA Astrophysics Data System (ADS)
Mason, Sarah J.
measure, S, as a function of temperature using a micro-machined thermal isolation platform consisting of a suspended, patterned SiN membrane. By measuring a series of thicknesses of metallic films up to the infinitely thin film limit, in which the electrical resistivity is no longer decreasing with increasing film thickness, but still not at bulk values, along with the effective electron mean free path, we are able to show the contribution of the leads needed to measure this property. Having a comprehensive understanding of the background contribution we are able to determine the absolute Seebeck coefficient of a wide variety of thin films. The nature of the design of the SiN membrane also allows the ability to accurately and directly measure thermal and electrical transport of the thin films yielding a comprehensive measurement of the three quantities that characterize a material's efficiency. This can serve to further the development of thermoelectric materials through precise measurements of the material properties that dictate efficiency.
Rate Change Graph Technology: Absolute Value Point Methodology
NASA Astrophysics Data System (ADS)
Strickland, Ken; Duvernois, Michael
2011-10-01
Absolute Value Point Methodology (AVPM) is a new theoretical tool for science research centered on Rate Change Graph Technology (RCGT). The modeling techniques of AVPM surpass conventional methods by extending the geometrical rules of mathematics. Exact geometrical structures of matter and energy become clearer revealing new ways to compile advanced data. RCGT mechanics is realized from geometrical intersections that are the result of plotting changing value vs. changing geometry. RCGT methods ignore size and value to perform an objective analysis in geometry. Value and size are then re-introduced back into the analytical system for a clear and concise solution. Available AVPM applications reveal that a massive amount of data from the Big Bang to vast super-clusters is untouched by human thought. Once scientists learn to design tools from RCGT Mechanics, new and formidable approaches to experimentation and theory may lead to new discoveries. In the creation of AVPM, it has become apparent there is a particle-world that exists between strings and our familiar universe. These unrealized particles in their own nature exhibit inflation like properties and may be the progenitor of the implements of our universe. Thus space, time, energy, motion, space-time and gravity are born from its existence and decay. This announcement will be the beginning of many new ideas from the study of RCGT mechanics.
NASA Astrophysics Data System (ADS)
Madhav, Priti; Li, Christina M.; Tornai, Martin P.
2010-04-01
With advances in 3D in vivo imaging technology, non-invasive procedures can be used to characterize tissues to identify tumors and monitor changes over time. Using a dedicated breast CT system with a quasi-monochromatic cone-beam x-ray source and flat-panel digital detector, this study was performed in an effort to directly characterize different materials in vivo based on their absolute attenuation coefficients. CT acquisitions were first acquired using a multi-material rod phantom with acrylic, delrin, polyethylene, fat-equivalent, and glandular-equivalent plastic rods, and also with a human cadaver breast. Projections were collected with and without a beam stop array for scatter correction. For each projection, the 2D scatter was estimated with cubic spline interpolation of the average values behind the shadow of each beam stop overlapping the object. Scatter-corrected projections were subsequently calculated by subtracting the scatter images containing only the region of the object from corresponding projections (consisting of primary and scatter x-rays) without the beam stop array. Iterative OSTR was used to reconstruct the data and estimate the non-uniform attenuation distribution. Preliminary results show that with reduced beam hardening from the x-ray beam, scatter correction further reduces the cupping artifact, improves image contrast, and yields attenuation coefficients < 8% of narrow-beam values of the known materials (range 1.2 - 7.8%). Peaks in the histogram showed clear separation between the different material attenuation coefficients. These findings indicate that minimizing beam hardening and applying scatter correction make it practical to directly characterize different tissues in vivo using absolute attenuation coefficients.
Explaining the Relative and Absolute LGRB Rate with Metallically
NASA Astrophysics Data System (ADS)
Graham, John
2016-01-01
There is now strong evidence that Long-duration Gamma-Ray Bursts (LGRBs) have an intrinsic preference for low-metallicity environments despite the existence of some exceptions to this trend (Graham & Fruchter 2013). Here I will present a pair of results expanding on this work. First, a detailed effort to quantize magnitude of this effect, and characterized its change as a function of metallicity. Thus we directly address a fundamental question of this subfield: how much more likely is an LGRB to form at one metallicity as compared with another? Then, employing these results, we relate the LGRB rate as a function of redshift to the cosmic star-formation rate and provide a detailed breakdown of the intervening steps and their rate of occurrence. This provides interesting implications for radio search efforts to detect off axis LGRB events which will be discussed.
McCormick, Matthew M.; Madsen, Ernest L.; Deaner, Meagan E.; Varghese, Tomy
2011-01-01
Absolute backscatter coefficients in tissue-mimicking phantoms were experimentally determined in the 5–50 MHz frequency range using a broadband technique. A focused broadband transducer from a commercial research system, the VisualSonics Vevo 770, was used with two tissue-mimicking phantoms. The phantoms differed regarding the thin layers covering their surfaces to prevent desiccation and regarding glass bead concentrations and diameter distributions. Ultrasound scanning of these phantoms was performed through the thin layer. To avoid signal saturation, the power spectra obtained from the backscattered radio frequency signals were calibrated by using the signal from a liquid planar reflector, a water-brominated hydrocarbon interface with acoustic impedance close to that of water. Experimental values of absolute backscatter coefficients were compared with those predicted by the Faran scattering model over the frequency range 5–50 MHz. The mean percent difference and standard deviation was 54% ± 45% for the phantom with a mean glass bead diameter of 5.40 μm and was 47% ± 28% for the phantom with 5.16 μm mean diameter beads. PMID:21877789
Modeling NAPL dissolution fingering with upscaled mass transfer rate coefficients
NASA Astrophysics Data System (ADS)
Imhoff, Paul T.; Farthing, Matthew W.; Miller, Cass T.
2003-10-01
The dissolution of nonaqueous phase liquids (NAPLs) at residual saturation in porous media has sometimes resulted in the development of preferential dissolution pathways or NAPL dissolution fingers. While NAPL dissolution fingering may be modeled using numerical simulators with fine discretization, this approach is computational intensive. We derived an expression for an upscaled mass transfer rate coefficient that accounts for the growth of dissolution fingers within porous media contaminated uniformly with residual NAPL. This expression was closely related to the lengthening of the dissolution front. Data from physical experiments and numerical simulations in two dimensions were used to examine the growth of the dissolution front and the corresponding upscaled mass transfer rate coefficient. Using this upscaled mass transfer rate coefficient, the time when dissolution fingering results in a reduction in the overall mass transfer rate and thus controls the rate of NAPL dissolution was determined. This crossover time is a convenient parameter for assessing the influence of dissolution fingering on NAPL removal. For the physical experiments and numerical simulations analyzed in this study, the crossover time to dissolution fingering control always occurred before the dissolution front had moved 14 cm within NAPL-contaminated porous media, which is small compared to the scale of typical systems of concern. To verify the utility of this approach, data from a three-dimensional physical experiment were predicted reasonably well using an upscaled mass transfer rate coefficient that was determined independently from this experiment.
The Influence of Particle Charge on Heterogeneous Reaction Rate Coefficients
NASA Technical Reports Server (NTRS)
Aikin, A. C.; Pesnell, W. D.
2000-01-01
The effects of particle charge on heterogeneous reaction rates are presented. Many atmospheric particles, whether liquid or solid are charged. This surface charge causes a redistribution of charge within a liquid particle and as a consequence a perturbation in the gaseous uptake coefficient. The amount of perturbation is proportional to the external potential and the square of the ratio of debye length in the liquid to the particle radius. Previous modeling has shown how surface charge affects the uptake coefficient of charged aerosols. This effect is now included in the heterogeneous reaction rate of an aerosol ensemble. Extension of this analysis to ice particles will be discussed and examples presented.
RECOMBINATION RATE COEFFICIENTS OF Be-LIKE Si
Orban, I.; Boehm, S.; Schuch, R.; Loch, S. D.
2010-10-01
Recombination of Be-like Si{sup 10+} over the 0-43 eV electron-ion energy range is measured at the CRYRING electron cooler. In addition to radiative and dielectronic recombination, the recombination spectrum also shows strong contributions from trielectronic recombination. Below 100 meV, several very strong resonances associated with a spin-flip of the excited electron dominate the spectrum and also dominate the recombination in the photoionized plasma. The resonant plasma rate coefficients corrected for the experimental field ionization are in good agreement with calculated results by Gu and with AUTOSTRUCTURE calculations. All other calculations significantly underestimate the plasma rate coefficients at low temperatures.
ROVIBRATIONAL QUENCHING RATE COEFFICIENTS OF HD IN COLLISIONS WITH He
Nolte, J. L.; Stancil, P. C.; Lee, T.-G.; Balakrishnan, N.; Forrey, R. C. E-mail: stancil@physast.uga.edu E-mail: naduvala@unlv.nevada.edu
2012-01-01
Along with H{sub 2}, HD has been found to play an important role in the cooling of the primordial gas for the formation of the first stars and galaxies. It has also been observed in a variety of cool molecular astrophysical environments. The rate of cooling by HD molecules requires knowledge of collisional rate coefficients with the primary impactors, H, He, and H{sub 2}. To improve knowledge of the collisional properties of HD, we present rate coefficients for the He-HD collision system over a range of collision energies from 10{sup -5} to 5 Multiplication-Sign 10{sup 3} cm{sup -1}. Fully quantum mechanical scattering calculations were performed for initial HD rovibrational states of j = 0 and 1 for v = 0-17 which utilized accurate diatom rovibrational wave functions. Rate coefficients of all {Delta}v = 0, -1, and -2 transitions are reported. Significant discrepancies with previous calculations, which adopted a small basis and harmonic HD wave functions for excited vibrational levels, were found for the highest previously considered vibrational state of v = 3. Applications of the He-HD rate coefficients in various astrophysical environments are briefly discussed.
NASA Astrophysics Data System (ADS)
Jentzen, Walter
2010-04-01
The use of recovery coefficients (RCs) in 124I PET lesion imaging is a simple method to correct the imaged activity concentration (AC) primarily for the partial-volume effect and, to a minor extent, for the prompt gamma coincidence effect. The aim of this phantom study was to experimentally investigate a number of various factors affecting the 124I RCs. Three RC-based correction approaches were considered. These approaches differ with respect to the volume of interest (VOI) drawn, which determines the imaged AC and the RCs: a single voxel VOI containing the maximum value (maximum RC), a spherical VOI with a diameter of the scanner resolution (resolution RC) and a VOI equaling the physical object volume (isovolume RC). Measurements were performed using mainly a stand-alone PET scanner (EXACT HR+) and a latest-generation PET/CT scanner (BIOGRAPH mCT). The RCs were determined using a cylindrical phantom containing spheres or rotational ellipsoids and were derived from images acquired with a reference acquisition protocol. For each type of RC, the influence of the following factors on the RC was assessed: object shape, background activity spill in and iterative image reconstruction parameters. To evaluate the robustness of the RC-based correction approaches, the percentage deviation between RC-corrected and true ACs was determined from images acquired with a clinical acquisition protocol of different AC regimes. The observed results of the shape and spill-in effects were compared with simulation data derived from a convolution-based model. The study demonstrated that the shape effect was negligible and, therefore, was in agreement with theoretical expectations. In contradiction to the simulation results, the observed spill-in effect was unexpectedly small. To avoid variations in the determination of RCs due to reconstruction parameter changes, image reconstruction with a pixel length of about one-third or less of the scanner resolution and an OSEM 1 × 32 algorithm or
Fusion Reaction Rate Coefficient for Different Beam and Target Scenarios
NASA Astrophysics Data System (ADS)
Ou, Wei; Zeng, Xian-Jun; Deng, Bai-Quan; Gou, Fu-Jun
2015-02-01
Fusion power output is proportional not only to the fuel particle number densities participating in reaction but also to the fusion reaction rate coefficient (or reactivity), which is dependent on reactant velocity distribution functions. They are usually assumed to be dual Maxwellian distribution functions with the same temperature for thermal nuclear fusion circumstances. However, if high power neutral beam injection and minority ion species ICRF plasma heating, or multi-pinched plasma beam head-on collision, in a converging region are required and investigated in future large scale fusion reactors, then the fractions of the injected energetic fast ion tail resulting from ionization or charge exchange will be large enough and their contribution to the non-Maxwellian distribution functions is not negligible, hence to the fusion reaction rate coefficient or calculation of fusion power. In such cases, beam-target, and beam-beam reaction enhancement effect contributions should play very important roles. In this paper, several useful formulae to calculate the fusion reaction rate coefficient for different beam and target combination scenarios are derived in detail.
Crawford, Charles G.
1985-01-01
The modified tracer technique was used to determine reaeration-rate coefficients in the Wabash River in reaches near Lafayette and Terre Haute, Indiana, at streamflows ranging from 2,310 to 7,400 cu ft/sec. Chemically pure (CP grade) ethylene was used as the tracer gas, and rhodamine-WT dye was used as the dispersion-dilution tracer. Reaeration coefficients determined for a 13.5-mi reach near Terre Haute, Indiana, at streamflows of 3,360 and 7,400 cu ft/sec (71% and 43% flow duration) were 1.4/day and 1.1/day at 20 C, respectively. Reaeration-rate coefficients determined for a 18.4-mile reach near Lafayette, Indiana, at streamflows of 2,310 and 3,420 cu ft/sec (70% and 53 % flow duration), were 1.2/day and 0.8/day at 20 C, respectively. None of the commonly used equations found in the literature predicted reaeration-rate coefficients similar to those measured for reaches of the Wabash River near Lafayette and Terre Haute. The average absolute prediction error for 10 commonly used reaeration equations ranged from 22% to 154%. Prediction error was much smaller in the reach near Terre Haute than in the reach near Lafayette. The overall average of the absolute prediction error for all 10 equations was 22% for the reach near Terre Haute and 128% for the reach near Lafayette. Confidence limits of results obtained from the modified tracer technique were smaller than those obtained from the equations in the literature.
Measurement of diffusion coefficients from solution rates of bubbles
NASA Technical Reports Server (NTRS)
Krieger, I. M.
1979-01-01
The rate of solution of a stationary bubble is limited by the diffusion of dissolved gas molecules away from the bubble surface. Diffusion coefficients computed from measured rates of solution give mean values higher than accepted literature values, with standard errors as high as 10% for a single observation. Better accuracy is achieved with sparingly soluble gases, small bubbles, and highly viscous liquids. Accuracy correlates with the Grashof number, indicating that free convection is the major source of error. Accuracy should, therefore, be greatly increased in a gravity-free environment. The fact that the bubble will need no support is an additional important advantage of Spacelab for this measurement.
Gas-phase rate coefficients of the reaction of ozone with four sesquiterpenes at 295 ± 2 K.
Richters, Stefanie; Herrmann, Hartmut; Berndt, Torsten
2015-05-01
The rate coefficients of the reaction of ozone with the four atmospherically relevant sesquiterpenes β-caryophyllene, α-humulene, α-cedrene and isolongifolene were investigated at 295 ± 2 K and atmospheric pressure by at least two independent experimental investigations for each reaction. Relative rate experiments were carried out in a flow tube using two different experimental approaches with GC-MS detection (RR 1) and PTR-MS analysis (RR 2) as the analytical techniques. Absolute rate coefficients were determined in a stopped-flow experiment following the ozone depletion by means of UV spectroscopy. The average rate coefficients from the combined investigations representing the mean values of the different experimental methods are (unit: cm(3) molecule(-1) s(-1)): k(O3+β-caryophyllene) = (1.1 ± 0.3) × 10(-14) (methods: RR 1, RR 2, absolute), k(O3+α-humulene) = (1.2 ± 0.3) × 10(-14) (RR 1, RR 2), k(O3+α-cedrene) = (1.7 ± 0.5) × 10(-16) (RR 2, absolute) and k(O3+isolongifolene) = (1.1 ± 0.5) × 10(-17) (RR 2, absolute). The high ozonolysis rate coefficients for β-caryophyllene and α-humulene agree well with the results by Shu and Atkinson (Int. J. Chem. Kinet., 1994, 26) and lead to short atmospheric lifetimes of about two minutes with respect to the ozone reaction. The relatively small rate coefficients for α-cedrene and isolongifolene differ from the available literature values by a factor of about 2.5-6. Possible reasons for the deviations are discussed. Finally, calibrated sesquiterpene FT-IR spectra were recorded for the first time.
Gas-phase rate coefficients of the reaction of ozone with four sesquiterpenes at 295 ± 2 K.
Richters, Stefanie; Herrmann, Hartmut; Berndt, Torsten
2015-05-01
The rate coefficients of the reaction of ozone with the four atmospherically relevant sesquiterpenes β-caryophyllene, α-humulene, α-cedrene and isolongifolene were investigated at 295 ± 2 K and atmospheric pressure by at least two independent experimental investigations for each reaction. Relative rate experiments were carried out in a flow tube using two different experimental approaches with GC-MS detection (RR 1) and PTR-MS analysis (RR 2) as the analytical techniques. Absolute rate coefficients were determined in a stopped-flow experiment following the ozone depletion by means of UV spectroscopy. The average rate coefficients from the combined investigations representing the mean values of the different experimental methods are (unit: cm(3) molecule(-1) s(-1)): k(O3+β-caryophyllene) = (1.1 ± 0.3) × 10(-14) (methods: RR 1, RR 2, absolute), k(O3+α-humulene) = (1.2 ± 0.3) × 10(-14) (RR 1, RR 2), k(O3+α-cedrene) = (1.7 ± 0.5) × 10(-16) (RR 2, absolute) and k(O3+isolongifolene) = (1.1 ± 0.5) × 10(-17) (RR 2, absolute). The high ozonolysis rate coefficients for β-caryophyllene and α-humulene agree well with the results by Shu and Atkinson (Int. J. Chem. Kinet., 1994, 26) and lead to short atmospheric lifetimes of about two minutes with respect to the ozone reaction. The relatively small rate coefficients for α-cedrene and isolongifolene differ from the available literature values by a factor of about 2.5-6. Possible reasons for the deviations are discussed. Finally, calibrated sesquiterpene FT-IR spectra were recorded for the first time. PMID:25866852
Absolute and Relative Reliability of Percentage of Syllables Stuttered and Severity Rating Scales
ERIC Educational Resources Information Center
Karimi, Hamid; O'Brian, Sue; Onslow, Mark; Jones, Mark
2014-01-01
Purpose: Percentage of syllables stuttered (%SS) and severity rating (SR) scales are measures in common use to quantify stuttering severity and its changes during basic and clinical research conditions. However, their reliability has not been assessed with indices measuring both relative and absolute reliability. This study was designed to provide…
Szabó, Milán; Wangpraseurt, Daniel; Tamburic, Bojan; Larkum, Anthony W D; Schreiber, Ulrich; Suggett, David J; Kühl, Michael; Ralph, Peter J
2014-10-01
Pulse Amplitude Modulation (PAM) fluorometry has been widely used to estimate the relative photosynthetic efficiency of corals. However, both the optical properties of intact corals as well as past technical constrains to PAM fluorometers have prevented calculations of the electron turnover rate of PSII. We used a new Multi-colour PAM (MC-PAM) in parallel with light microsensors to determine for the first time the wavelength-specific effective absorption cross-section of PSII photochemistry, σII(λ), and thus PAM-based absolute electron transport rates of the coral photosymbiont Symbiodinium both in culture and in hospite in the coral Pocillopora damicornis. In both cases, σII of Symbiodinium was highest in the blue spectral region and showed a progressive decrease towards red wavelengths. Absolute values for σII at 440 nm were up to 1.5-times higher in culture than in hospite. Scalar irradiance within the living coral tissue was reduced by 20% in the blue when compared to the incident downwelling irradiance. Absolute electron transport rates of P. damicornis at 440 nm revealed a maximum PSII turnover rate of ca. 250 electrons PSII(-1) s(-1), consistent with one PSII turnover for every 4 photons absorbed by PSII; this likely reflects the limiting steps in electron transfer between PSII and PSI. Our results show that optical properties of the coral host strongly affect light use efficiency of Symbiodinium. Therefore, relative electron transport rates do not reflect the productivity rates (or indeed how the photosynthesis-light response is parameterised). Here we provide a non-invasive approach to estimate absolute electron transport rates in corals.
Temperature Dependence of the O + HO2 Rate Coefficient
NASA Technical Reports Server (NTRS)
Nicovich, J. M.; Wine, P. H.
1997-01-01
A pulsed laser photolysis technique has been employed to investigate the kinetics of the radical-radical reaction O((sup 3)P) + HO2 OH + O2 over the temperature range 266-391 K in 80 Torr of N2 diluent gas. O((sup 3)P) was produced by 248.5-nm KrF laser photolysis of O3 followed by rapid quenching of O(1D) to O((sup 3)P) while HO2 was produced by simultaneous photolysis of H2O2 to create OH radicals which, in turn, reacted with H2O2 to yield HO2. The O((sup 3)P) temporal profile was monitored by using time-resolved resonance fluorescence spectroscopy. The HO2 concentration was calculated based on experimentally measured parameters. The following Arrhenius expression describes our experimental results: k(sub 1)(T) equals (2.91 +/- 0.70) x 10(exp -11) exp[(228 +/- 75)/T] where the errors are 2 sigma and represent precision only. The absolute uncertainty in k, at any temperature within the range 266-391 K is estimated to be +/- 22 percent. Our results are in excellent agreement with a discharge flow study of the temperature dependence of k(sub 1) in 1 Torr of He diluent reported by Keyser, and significantly reduce the uncertainty in the rate of this important stratospheric reaction at subambient temperatures.
Extended Simulations of Graphene Growth with Updated Rate Coefficients
Whitesides, R; You, X; Frenklach, M
2010-03-18
New simulations of graphene growth in flame environments are presented. The simulations employ a kinetic Monte Carlo (KMC) algorithm coupled to molecular mechanics (MM) geometry optimization to track individual graphenic species as they evolve. Focus is given to incorporation of five-member rings and resulting curvature and edge defects. The model code has been re-written to be more computationally efficient enabling a larger set of simulations to be run, decreasing stochastic fluctuations in the averaged results. The model also includes updated rate coefficients for graphene edge reactions recently published in the literature. The new simulations are compared to results from the previous model as well as to hydrogen to carbon ratios recorded in experiment and calculated with alternate models.
Cosmological Implications of the Uncertainty in Astrochemical Rate Coefficients
NASA Technical Reports Server (NTRS)
Glover, S. C. O.; Savin, D. W.; Jappsen, A.-K.
2006-01-01
The cooling of neutral gas of primordial composition, or with very low levels of metal enrichment, depends crucially on the formation of molecular coolants, such as H2 and HD within the gas. Although the chemical reactions involved in the formation and destruction of these molecules are well known, the same cannot be said for the rate coefficients of these reactions, some of which are uncertain by an order of magnitude. Here we discuss two reactions for which large uncertainties exist the formation of H2 by associative detachment of H- with H and the destruction of H- by mutual neutralization with protons. We show that these uncertainties can have a dramatic impact on the effectiveness of cooling during protogalactic collapse.
Absolute rate of the reaction of hydrogen atoms with ozone from 219-360 K
NASA Technical Reports Server (NTRS)
Lee, J. H.; Michael, J. V.; Payne, W. A.; Stief, L. J.
1978-01-01
Absolute rate constants for the reaction of atomic hydrogen with ozone were obtained over the temperature range 219-360 K by the flash photolysis-resonance fluorescence technique. The results can be expressed in Arrhenius form by K = (1.33 plus or minus 0.32)x10 to the minus 10 power exp (-449 plus or minus 58/T) cu cm/molecule/s (two standard deviations). The present work is compared to two previous determinations and is discussed theoretically.
Viggiano, Albert A; Friedman, Jeffrey F; Shuman, Nicholas S; Miller, Thomas M; Schaffer, Linda C; Troe, Jürgen
2010-05-21
Thermal electron attachment to C(60) has been studied by relative rate measurements in a flowing afterglow Langmuir probe apparatus. The rate coefficients of the attachment k(1) are shown to be close to 10(-6) cm(3) s(-1) with a small negative temperature coefficient. These results supersede measurements from the 1990s which led to much smaller values of k(1) with a large positive temperature coefficient suggesting an activation barrier. Theoretical modeling of k(1) in terms of generalized Vogt-Wannier capture theory shows that k(1) now looks more consistent with measurements of absolute attachment cross sections sigma(at) than before. The comparison of capture theory and experimental rate or cross section data leads to empirical correction factors, accounting for "intramolecular vibrational relaxation" or "electron-phonon coupling," which reduce k(1) below the capture results and which, on a partial wave-selected level, decrease with increasing electron energy.
Viggiano, Albert A; Friedman, Jeffrey F; Shuman, Nicholas S; Miller, Thomas M; Schaffer, Linda C; Troe, Jürgen
2010-05-21
Thermal electron attachment to C(60) has been studied by relative rate measurements in a flowing afterglow Langmuir probe apparatus. The rate coefficients of the attachment k(1) are shown to be close to 10(-6) cm(3) s(-1) with a small negative temperature coefficient. These results supersede measurements from the 1990s which led to much smaller values of k(1) with a large positive temperature coefficient suggesting an activation barrier. Theoretical modeling of k(1) in terms of generalized Vogt-Wannier capture theory shows that k(1) now looks more consistent with measurements of absolute attachment cross sections sigma(at) than before. The comparison of capture theory and experimental rate or cross section data leads to empirical correction factors, accounting for "intramolecular vibrational relaxation" or "electron-phonon coupling," which reduce k(1) below the capture results and which, on a partial wave-selected level, decrease with increasing electron energy. PMID:20499963
NASA Astrophysics Data System (ADS)
Viggiano, Albert A.; Friedman, Jeffrey F.; Shuman, Nicholas S.; Miller, Thomas M.; Schaffer, Linda C.; Troe, Jürgen
2010-05-01
Thermal electron attachment to C60 has been studied by relative rate measurements in a flowing afterglow Langmuir probe apparatus. The rate coefficients of the attachment k1 are shown to be close to 10-6 cm3 s-1 with a small negative temperature coefficient. These results supersede measurements from the 1990s which led to much smaller values of k1 with a large positive temperature coefficient suggesting an activation barrier. Theoretical modeling of k1 in terms of generalized Vogt-Wannier capture theory shows that k1 now looks more consistent with measurements of absolute attachment cross sections σat than before. The comparison of capture theory and experimental rate or cross section data leads to empirical correction factors, accounting for "intramolecular vibrational relaxation" or "electron-phonon coupling," which reduce k1 below the capture results and which, on a partial wave-selected level, decrease with increasing electron energy.
Learning rates of lq coefficient regularization learning with gaussian kernel.
Lin, Shaobo; Zeng, Jinshan; Fang, Jian; Xu, Zongben
2014-10-01
Regularization is a well-recognized powerful strategy to improve the performance of a learning machine and l(q) regularization schemes with 0 < q < ∞ are central in use. It is known that different q leads to different properties of the deduced estimators, say, l(2) regularization leads to a smooth estimator, while l(1) regularization leads to a sparse estimator. Then how the generalization capability of l(q) regularization learning varies with q is worthy of investigation. In this letter, we study this problem in the framework of statistical learning theory. Our main results show that implementing l(q) coefficient regularization schemes in the sample-dependent hypothesis space associated with a gaussian kernel can attain the same almost optimal learning rates for all 0 < q < ∞. That is, the upper and lower bounds of learning rates for l(q) regularization learning are asymptotically identical for all 0 < q < ∞. Our finding tentatively reveals that in some modeling contexts, the choice of q might not have a strong impact on the generalization capability. From this perspective, q can be arbitrarily specified, or specified merely by other nongeneralization criteria like smoothness, computational complexity or sparsity.
Photolysis Rate Coefficient Calculations in Support of SOLVE II
NASA Technical Reports Server (NTRS)
Swartz, William H.
2005-01-01
A quantitative understanding of photolysis rate coefficients (or "j-values") is essential to determining the photochemical reaction rates that define ozone loss and other crucial processes in the atmosphere. j-Values can be calculated with radiative transfer models, derived from actinic flux observations, or inferred from trace gas measurements. The primary objective of the present effort was the accurate calculation of j-values in the Arctic twilight along NASA DC-8 flight tracks during the second SAGE III Ozone Loss and Validation Experiment (SOLVE II), based in Kiruna, Sweden (68 degrees N, 20 degrees E) during January-February 2003. The JHU/APL radiative transfer model was utilized to produce a large suite of j-values for photolysis processes (over 70 reactions) relevant to the upper troposphere and lower stratosphere. The calculations take into account the actual changes in ozone abundance and apparent albedo of clouds and the Earth surface along the aircraft flight tracks as observed by in situ and remote sensing platforms (e.g., EP-TOMS). A secondary objective was to analyze solar irradiance data from NCAR s Direct beam Irradiance Atmospheric Spectrometer (DIAS) on-board the NASA DC-8 and to start the development of a flexible, multi-species spectral fitting technique for the independent retrieval of O3,O2.02, and aerosol optical properties.
Absolute Density Calibration Cell for Laser Induced Fluorescence Erosion Rate Measurements
NASA Technical Reports Server (NTRS)
Domonkos, Matthew T.; Stevens, Richard E.
2001-01-01
Flight qualification of ion thrusters typically requires testing on the order of 10,000 hours. Extensive knowledge of wear mechanisms and rates is necessary to establish design confidence prior to long duration tests. Consequently, real-time erosion rate measurements offer the potential both to reduce development costs and to enhance knowledge of the dependency of component wear on operating conditions. Several previous studies have used laser-induced fluorescence (LIF) to measure real-time, in situ erosion rates of ion thruster accelerator grids. Those studies provided only relative measurements of the erosion rate. In the present investigation, a molybdenum tube was resistively heated such that the evaporation rate yielded densities within the tube on the order of those expected from accelerator grid erosion. This work examines the suitability of the density cell as an absolute calibration source for LIF measurements, and the intrinsic error was evaluated.
Photolysis Rate Coefficient Calculations in Support of SOLVE Campaign
NASA Technical Reports Server (NTRS)
Lloyd, Steven A.; Swartz, William H.
2001-01-01
The objectives for this SOLVE project were 3-fold. First, we sought to calculate a complete set of photolysis rate coefficients (j-values) for the campaign along the ER-2 and DC-8 flight tracks. En route to this goal, it would be necessary to develop a comprehensive set of input geophysical conditions (e.g., ozone profiles), derived from various climatological, aircraft, and remotely sensed datasets, in order to model the radiative transfer of the atmosphere accurately. These j-values would then need validation by comparison with flux-derived j-value measurements. The second objective was to analyze chemistry along back trajectories using the NASA/Goddard chemistry trajectory model initialized with measurements of trace atmospheric constituents. This modeling effort would provide insight into the completeness of current measurements and the chemistry of Arctic wintertime ozone loss. Finally, we sought to coordinate stellar occultation measurements of ozone (and thus ozone loss) during SOLVE using the Midcourse Space Experiment(MSX)/Ultraviolet and Visible Imagers and Spectrographic Imagers (UVISI) satellite instrument. Such measurements would determine ozone loss during the Arctic polar night and represent the first significant science application of space-based stellar occultation in the Earth's atmosphere.
Photolysis Rate Coefficient Calculations in Support of SOLVE Campaign
NASA Technical Reports Server (NTRS)
Lloyd, Steven A.; Swartz, William H.
2001-01-01
The objectives for this SOLVE project were 3-fold. First, we sought to calculate a complete set of photolysis rate coefficients (j-values) for the campaign along the ER-2 and DC-8 flight tracks. En route to this goal, it would be necessary to develop a comprehensive set of input geophysical conditions (e.g., ozone profiles), derived from various climatological, aircraft, and remotely sensed datasets, in order to model the radiative transfer of the atmosphere accurately. These j-values would then need validation by comparison with flux-derived j-value measurements. The second objective was to analyze chemistry along back trajectories using the NASA/Goddard chemistry trajectory model initialized with measurements of trace atmospheric constituents. This modeling effort would provide insight into the completeness of current measurements and the chemistry of Arctic wintertime ozone loss. Finally, we sought to coordinate stellar occultation measurements of ozone (and thus ozone loss) during SOLVE using the MSX/UVISI satellite instrument. Such measurements would determine ozone loss during the Arctic polar night and represent the first significant science application of space-based stellar occultation in the Earth's atmosphere.
Proton Transfer Rate Coefficient Measurements of Selected Volatile Organic Molecules
NASA Astrophysics Data System (ADS)
Brooke, G.; Popović, S.; Vušković, L.
2002-05-01
We have developed an apparatus based on the selected ion flow tube (SIFT)footnote D. Smith and N.G. Adams, Ads. At. Mol. Phys. 24, 1 (1987). that allows the study of proton transfer between various positive ions and volatile organic molecules. Reactions in the flow tube occur at pressures of approximately 300 mTorr, eliminating the requirement of thermal beam production. The proton donor molecule H_3O^+ has been produced using several types of electrical discharges in water vapor, such as a capacitively coupled RF discharge and a DC hollow cathode discharge. Presently we are developing an Asmussen-type microwave cavity discharge using the components of a standard microwave oven that has the advantages of simple design and operation, as well as low cost. We will be presenting the results of the microwave cavity ion source to produce H_3O^+, and compare it to the other studied sources. In addition, we will be presenting a preliminary measurement of the proton transfer rate coefficient in the reaction of H_3O^+ with acetone and methanol.
NASA Astrophysics Data System (ADS)
Hallacoglu, Bertan; Sassaroli, Angelo; Wysocki, Michael; Guerrero-Berroa, Elizabeth; Schnaider Beeri, Michal; Haroutunian, Vahram; Shaul, Merav; Rosenberg, Irwin H.; Troen, Aron M.; Fantini, Sergio
2012-08-01
We present near-infrared spectroscopy measurement of absolute cerebral hemoglobin concentration and saturation in a large sample of 36 healthy elderly (mean age, 85±6 years) and 19 young adults (mean age, 28±4 years). Non-invasive measurements were obtained on the forehead using a commercially available multi-distance frequency-domain system and analyzed using a diffusion theory model for a semi-infinite, homogeneous medium with semi-infinite boundary conditions. Our study included repeat measurements, taken five months apart, on 16 elderly volunteers that demonstrate intra-subject reproducibility of the absolute measurements with cross-correlation coefficients of 0.9 for absorption coefficient (μa), oxy-hemoglobin concentration ([HbO2]), and total hemoglobin concentration ([HbT]), 0.7 for deoxy-hemoglobin concentration ([Hb]), 0.8 for hemoglobin oxygen saturation (StO2), and 0.7 for reduced scattering coefficient (). We found significant differences between the two age groups. Compared to young subjects, elderly subjects had lower cerebral [HbO2], [Hb], [HbT], and StO2 by 10±4 μM, 4±3 μM, 14±5 μM, and 6%±5%, respectively. Our results demonstrate the reliability and robustness of multi-distance near-infrared spectroscopy measurements based on a homogeneous model in the human forehead on a large sample of human subjects. Absolute, non-invasive optical measurements on the brain, such as those presented here, can significantly advance the development of NIRS technology as a tool for monitoring resting/basal cerebral perfusion, hemodynamics, oxygenation, and metabolism.
The Br+HO 2 reaction revisited: Absolute determination of the rate constant at 298 K
NASA Astrophysics Data System (ADS)
Laverdet, G.; Le Bras, G.; Mellouki, A.; Poulet, G.
1990-09-01
The absolute determination of the rate constant for the reaction Br+HO 2→HBr+O 2 has been done at 298 K using the discharge-flor EPR method. The value k1 = (1.5±0.2) × 10 -12 cm 3 molecule -1 s -1 was obtained. Previous indirect measurements of k1 from a discharge-flow, LIF/mass spectrometric study of the Br/H 2CO/O 2 system have been reinterpreted, leading to values for k1 ranging from 1.0 × 10 -12 to 2.2 × 10 -12 cm 3 molecule -1 s -1 at 298 K. These results are discussed and compared with other literature values.
Study on improving the turbidity measurement of the absolute coagulation rate constant.
Sun, Zhiwei; Liu, Jie; Xu, Shenghua
2006-05-23
The existing theories dealing with the evaluation of the absolute coagulation rate constant by turbidity measurement were experimentally tested for different particle-sized (radius = a) suspensions at incident wavelengths (lambda) ranging from near-infrared to ultraviolet light. When the size parameter alpha = 2pi a/lambda > 3, the rate constant data from previous theories for fixed-sized particles show significant inconsistencies at different light wavelengths. We attribute this problem to the imperfection of these theories in describing the light scattering from doublets through their evaluation of the extinction cross section. The evaluations of the rate constants by all previous theories become untenable as the size parameter increases and therefore hampers the applicable range of the turbidity measurement. By using the T-matrix method, we present a robust solution for evaluating the extinction cross section of doublets formed in the aggregation. Our experiments show that this new approach is effective in extending the applicability range of the turbidity methodology and increasing measurement accuracy.
EVAPOTRANSPIRATION RATES AND CROP COEFFICIENTS FOR LOWBUSH BLUEBERRY (Vaccinium angustifolium)
Technology Transfer Automated Retrieval System (TEKTRAN)
Lowbush blueberry (Vaccinium angustifolium) yield is strongly influenced by water availability; however, growers need more specific irrigation recommendations in order to optimize water use efficiency. Weighing lysimeters were used to determine actual evapotranspiration (ET) rates of lowbush bluebe...
Temperature dependences of rate coefficients for electron catalyzed mutual neutralization
Shuman, Nicholas S.; Miller, Thomas M.; Friedman, Jeffrey F.; Viggiano, Albert A.; Maeda, Satoshi; Morokuma, Keiji
2011-07-14
The flowing afterglow technique of variable electron and neutral density attachment mass spectrometry (VENDAMS) has recently yielded evidence for a novel plasma charge loss process, electron catalyzed mutual neutralization (ECMN), i.e., A{sup +}+ B{sup -}+ e{sup -}{yields} A + B + e{sup -}. Here, rate constants for ECMN of two polyatomic species (POCl{sub 3}{sup -} and POCl{sub 2}{sup -}) and one diatomic species (Br{sub 2}{sup -}) each with two monatomic cations (Ar{sup +}and Kr{sup +}) are measured using VENDAMS over the temperature range 300 K-500 K. All rate constants show a steep negative temperature dependence, consistent with that expected for a three body process involving two ions and an electron. No variation in rate constants as a function of the cation type is observed outside of uncertainty; however, rate constants of the polyatomic anions ({approx}1 x 10{sup -18} cm{sup 6} s{sup -1} at 300 K) are measurably higher than that for Br{sub 2}{sup -}[(5.5 {+-} 2) x 10{sup -19} cm{sup 6} s{sup -1} at 300 K].
Reaction of limonene with F2: rate coefficient and products.
Bedjanian, Yuri; Romanias, Manolis N; Morin, Julien
2014-11-01
The kinetics of the reaction of limonene (C10H16) with F2 has been studied using a low pressure (P = 1 Torr) and a high pressure turbulent (P = 100 Torr) flow reactor coupled with an electron impact ionization and chemical ionization mass spectrometers, respectively: F2 + Limonene → products (1). The rate constant of the title reaction was determined under pseudo-first-order conditions by monitoring either limonene or F2 decay in excess of F2 or C10H16, respectively. The reaction rate constant, k1 = (1.15 ± 0.25) × 10(-12) exp(160 ± 70)/T) was determined over the temperature range 278-360 K, independent of pressure between 1 (He) and 100 (N2) Torr. F atom and HF were found to be formed in reaction 1 , with the yields of 0.60 ± 0.13 and 0.39 ± 0.09, respectively, independent of temperature in the range 296-355 K.
Subjective evaluation of HDTV stereoscopic videos in IPTV scenarios using absolute category rating
NASA Astrophysics Data System (ADS)
Wang, K.; Barkowsky, M.; Cousseau, R.; Brunnström, K.; Olsson, R.; Le Callet, P.; Sjöström, M.
2011-03-01
Broadcasting of high definition (HD) stereobased 3D (S3D) TV are planned, or has already begun, in Europe, the US, and Japan. Specific data processing operations such as compression and temporal and spatial resampling are commonly used tools for saving network bandwidth when IPTV is the distribution form, as this results in more efficient recording and transmission of 3DTV signals, however at the same time it inevitably brings quality degradations to the processed video. This paper investigated observers quality judgments of state of the art video coding schemes (simulcast H.264/AVC or H.264/MVC), with or without added temporal and spatial resolution reduction of S3D videos, by subjective experiments using the Absolute Category Rating method (ACR) method. The results showed that a certain spatial resolution reduction working together with high quality video compressing was the most bandwidth efficient way of processing video data when the required video quality is to be judged as "good" quality. As the subjective experiment was performed in two different laboratories in two different countries in parallel, a detailed analysis of the interlab differences was performed.
Coordinate-dependent diffusion coefficients: Decay rate in open quantum systems
Sargsyan, V. V.; Palchikov, Yu. V.; Antonenko, N. V.; Kanokov, Z.; Adamian, G. G.
2007-06-15
Based on a master equation for the reduced density matrix of an open quantum collective system, the influence of coordinate-dependent microscopical diffusion coefficients on the decay rate from a metastable state is treated. For various frictions and temperatures larger than a crossover temperature, the quasistationary decay rates obtained with the coordinate-dependent microscopical set of diffusion coefficients are compared with those obtained with the coordinate-independent microscopical set of diffusion coefficients and coordinate-independent and -dependent phenomenological sets of diffusion coefficients. Neglecting the coordinate dependence of diffusion coefficients, one can strongly overestimate or underestimate the decay rate at low temperature. The coordinate-dependent phenomenological diffusion coefficient in momentum are shown to be suitable for applications.
NASA Astrophysics Data System (ADS)
Wang, C.; Gordon, R. G.; Zheng, L.
2015-12-01
Hotspot tracks have been widely used to estimate the velocities of the plate relative to the lower mantle. Here we analyze the hotspot azimuth data set of Morgan and Phipps Morgan [2007] and show that the errors in plate velocity azimuths inferred from hotspot tracks in any one plate are correlated with the errors of other azimuths in the same plate. We use a two-tier analysis to account for this correlated error. First, we determine an individual best-fitting pole for each plate. Second, we determine the absolute plate velocity by minimizing the misfit while constrained by the MORVEL relative plate velocities [DeMets et al. 2010]. Our preferred model, HS4-MORVEL, uses azimuths from 9 major plates, which are weighted equally. We find that the Pacific plate rotates 0.860.016°Ma-1 right handed about 63.3°S, 96.1°E. Angular velocities of four plates (Amur, Eurasia, Yangtze and Antarctic) differ insignificantly from zero. The net rotation of the lithosphere is 0.24°±0.014° Ma-1 right handed about 52.3S, 56.9E. The angular velocities differ insignificantly from the absolute angular velocities inferred from the orientation of seismic anisotropy [Zheng et al. 2014]. The within-plate dispersion of hotspot track azimuths is 14°, which is comparable to the within-plate dispersion found from orientations of seismic anisotropy. The between-plate dispersion is 6.9±2.4° (95% confidence limits), which is smaller than that found from seismic anisotropy. The between-plate dispersion of 4.5° to 9.3° can be used to place bounds on how fast hotspots under one plate move relative to hotspots under another plate. For an average plate absolute speed of ≈50 mm/yr, the between-plate dispersion indicates a rate of motion of 4 mm/yr to 8 mm/yr for the component of hotspot motion perpendicular to plate motion. This upper bound is consistent with prior work that indicated upper bounds on motion between Pacific hotspots and Indo-Atlantic hotspots over the past 48 Ma of 8-13 mm
Baasandorj, Munkhbayar; Ravishankara, A R; Burkholder, James B
2011-09-29
Rate coefficients, k, for the gas-phase reaction of the OH radical with (Z)-CF(3)CH═CHCF(3) (cis-1,1,1,4,4,4-hexafluoro-2-butene) were measured under pseudo-first-order conditions in OH using pulsed laser photolysis (PLP) to produce OH and laser-induced fluorescence (LIF) to detect it. Rate coefficients were measured over a range of temperatures (212-374 K) and bath gas pressures (20-200 Torr; He, N(2)) and found to be independent of pressure over this range of conditions. The rate coefficient has a non-Arrhenius behavior that is well-described by the expression k(1)(T) = (5.73 ± 0.60) × 10(-19) × T(2) × exp[(678 ± 10)/T] cm(3) molecule(-1) s(-1) where k(1)(296 K) was measured to be (4.91 ± 0.50) × 10(-13) cm(3) molecule(-1) s(-1) and the uncertainties are at the 2σ level and include estimated systematic errors. Rate coefficients for the analogous OD radical reaction were determined over a range of temperatures (262-374 K) at 100 Torr (He) to be k(2)(T) = (4.81 ± 0.20) × 10(-19) × T(2) × exp[(776 ± 15)/T], with k(2)(296 K) = (5.73 ± 0.50) × 10(-13) cm(3) molecule(-1) s(-1). OH radical rate coefficients were also measured at 296, 345, and 375 K using a relative rate technique and found to be in good agreement with the PLP-LIF results. A room-temperature rate coefficient for the O(3) + (Z)-CF(3)CH═CHCF(3) reaction was measured using an absolute method with O(3) in excess to be <6 × 10(-21) cm(3) molecule(-1) s(-1). The atmospheric lifetime of (Z)-CF(3)CH═CHCF(3) due to loss by OH reaction was estimated to be ~20 days. Infrared absorption spectra of (Z)-CF(3)CH═CHCF(3) measured in this work were used to determine a (Z)-CF(3)CH═CHCF(3) global warming potential (GWP) of ~9 for the 100 year time horizon. A comparison of the OH reactivity of (Z)-CF(3)CH═CHCF(3) with other unsaturated fluorinated compounds is presented.
Rate Coefficient Measurements of the Reaction CH3+O2+CH3O+O
NASA Technical Reports Server (NTRS)
Hwang, S. M.; Ryu, Si-Ok; DeWitt, K. J.; Rabinowitz, M. J.
1999-01-01
Rate coefficients for the reaction CH3 + O2 = CH3O + O were measured behind reflected shock waves in a series of lean CH4-O2-Ar mixtures using hydroxyl and methyl radical diagnostics. The rate coefficients are well represented by an Arrhenius expression given as k = (1.60(sup +0.67, -0.47)) X 10(exp 13) exp(- 15813 +/- 587 K/T)cc/mol s. This expression, which is valid in the temperature range 1575-1822 K, supports the downward trend in the rate coefficients that has been reported in recent determinations. All measurements to date, including the present study, have been to some extent affected by secondary reactions. The complications due to secondary reactions, choice of thermochemical data, and shock-boundary layer interactions that affect the determination of the rate coefficients are examined.
Rate Coefficient Measurements of the Reaction CH3 + O2 = CH3O + O
NASA Technical Reports Server (NTRS)
Hwang, S. M.; Ryu, Si-Ok; DeWitt, K. J.; Rabinowitz, M. J.
1999-01-01
Rate coefficients for the reaction CH3 + O2 = CH3O + O were measured behind reflected shock waves in a series of lean CH4-O2-Ar mixtures using hydroxyl and methyl radical diagnostics. The rate coefficients are well represented by an Arrhenius expression given as k = (1.60(sup +0.67, sub -0.47 ) x 10(exp 13) e(-15813 +/- 587 K/T)/cubic cm.mol.s. This expression, which is valid in the temperature range 1575-1822 K, supports the downward trend in the rate coefficients that has been reported in recent determinations. All measurements to date, including the present study, have been to some extent affected by secondary reactions. The complications due to secondary reactions, choice of thermochemical data, and shock-boundary layer interactions that affect the determination of the rate coefficients are examined.
New potential energy surface for the HCS(+)-He system and inelastic rate coefficients.
Dubernet, Marie-Lise; Quintas-Sánchez, Ernesto; Tuckey, Philip
2015-07-28
A new high quality potential energy surface is calculated at a coupled-cluster single double triple level with an aug-cc-pV5Z basis set for the HCS(+)-He system. This potential energy surface is used in low energy quantum scattering calculations to provide a set of (de)-excitation cross sections and rate coefficients among the first 20 rotational levels of HCS(+) by He in the range of temperature from 5 K to 100 K. The paper discusses the impact of the new ab initio potential energy surface on the cross sections at low energy and provides a comparison with the HCO(+)-He system. The HCS(+)-He rate coefficients for the strongest transitions differ by factors of up to 2.5 from previous rate coefficients; thus, analysis of astrophysical spectra should be reconsidered with the new rate coefficients.
Li, Xiqing; Johnson, William P
2005-03-15
The transport of carboxylate-modified polystyrene latex microspheres was examined in packed quartz sand under a variety of environmentally relevant ionic strength and flow conditions. The retained concentrations of microspheres in the sediment increased first, and then decreased with transport distance, indicating that the deposition rate coefficient changed nonmonotonically over the transport distance. This finding demonstrates the ubiquity of spatial variation in deposition rate coefficients under unfavorable deposition conditions, and in addition indicates that the previously recognized monotonic decrease with transport distance is not the sole form of spatial variations in deposition rate coefficients. In contrast, the deposition rate coefficients of similarly sized microspheres with different surface group densities were shown to decrease monotonically with transport distance in the same porous media, indicating that the form of spatial variation in deposition rate coefficient is highly sensitive to system conditions. The ubiquity and sensitivity of the spatial variation of deposition rate coefficients indicate that current practices that utilize log-linear extrapolation of discreet measurements of colloid attenuation to determine colloid removal with distance from source are not valid (for both biological and nonbiological colloids). The retained colloid profiles hold the promise to reveal processes governing colloid deposition under unfavorable conditions that are yet to be identified.
NASA Astrophysics Data System (ADS)
Wojnárovits, László; Takács, Erzsébet
2014-03-01
Rate coefficients published in the literature on hydroxyl radical reactions with pesticides and related compounds are discussed together with the experimental methods and the basic reaction mechanisms. Recommendations are made for the most probable values. Most of the molecules whose rate coefficients are discussed have aromatic ring: their rate coefficients are in the range of 2×109-1×1010 mol-1 dm3 s-1. The rate coefficients show some variation with the electron withdrawing-donating nature of the substituent on the ring. The rate coefficients for triazine pesticides (simazine, atrazine, prometon) are all around 2.5×109 mol-1 dm3 s-1. The values do not show variation with the substituent on the s-triazine ring. The rate coefficients for the non-aromatic molecules which have C=C double bonds or several C-H bonds may also be above 1×109 mol-1 dm3 s-1. However, the values for molecules without C=C double bonds or several C-H bonds are in the 1×107-1×109 mol-1 dm3 s-1 range.
HTO washout model: on the relationship between exchange rate and washout coefficient
Golubev, A.; Balashov, Y.; Mavrin, S.; Golubeva, V.; Galeriu, D.
2015-03-15
Washout coefficient Λ is widely used as a parameter in washout models. These models describes overall HTO washout with rain by a first-order kinetic equation, while washout coefficient Λ depends on the type of rain event and rain intensity and empirical parameters a, b. The washout coefficient is a macroscopic parameter and we have considered in this paper its relationship with a microscopic rate K of HTO isotopic exchange in atmospheric humidity and drops of rainwater. We have shown that the empirical parameters a, b can be represented through the rain event characteristics using the relationships of molecular impact rate, rain intensity and specific rain water content while washout coefficient Λ can be represented through the exchange rate K, rain intensity, raindrop diameter and terminal raindrop velocity.
Calculated diffusion coefficients and the growth rate of olivine in a basalt magma
NASA Technical Reports Server (NTRS)
Donaldson, C. H.
1975-01-01
Concentration gradients in glass adjacent to skeletal olivines in a basalt have been examined by electron probe. The glass is depleted in Mg, Fe, and Cr and enriched in Si, Al, Na, and Ca relative to that far from olivine. Ionic diffusion coefficients for the glass compositions are calculated from temperature, ionic radius and melt viscosity, using the Stokes-Einstein relation. At 1170 C, the diffusion coefficient of Mg(2+) ions in the basalt is 4.5 billionths sq cm per sec. Comparison with measured diffusion coefficients in a mugearite suggests this value may be 16 times too small. The concentration gradient data and the diffusion coefficients are used to calculate instantaneous olivine growth rates. Growth necessarily preceded emplacement such that the composition of the crystals plus the enclosing glass need not be that of a melt. The computed olivine growth rates are compatible with the rate of crystallization deduced for the Skaegaard intrusion.
NASA Astrophysics Data System (ADS)
Yamaguchi, H.; Takamori, K.; Perrier, P.; Graur, I.; Matsuda, Y.; Niimi, T.
2016-09-01
The viscous slip coefficient for helium-argon binary gas mixture is extracted from the experimental values of the mass flow rate through a microtube. The mass flow rate is measured by the constant-volume method. The viscous slip coefficient was obtained by identifying the measured mass flow rate through a microtube with the corresponding analytical expression, which is a function of the Knudsen number. The measurements were carried out in the slip flow regime where the first-order slip boundary condition can be applied. The measured viscous slip coefficients of binary gas mixtures exhibit a concave function of the molar ratio of the mixture, showing a similar profile with numerical results. However, from the detailed comparison between the measured and numerical values with the complete and incomplete accommodation at a surface, it is inappropriate to estimate the viscous slip coefficient for the mixture numerically by employing separately measured tangential momentum accommodation coefficient for each component. The time variation of the molar ratio in the downstream chamber was measured by sampling the gas from the chamber using the quadrupole mass spectrometer. In our measurements, it is indicated that the volume flow rate of argon is larger than that of helium because of the difference in the tangential momentum accommodation coefficient.
Equilibration Rates and Negative Absolute Temperatures for Ultracold Atoms in Optical Lattices
NASA Astrophysics Data System (ADS)
Rapp, Akos; Mandt, Stephan; Rosch, Achim
2010-11-01
As highly tunable interacting systems, cold atoms in optical lattices are ideal to realize and observe negative absolute temperatures, T<0. We show theoretically that, by reversing the confining potential, stable superfluid condensates at finite momentum and T<0 can be created with low entropy production for attractive bosons. They may serve as “smoking gun” signatures of equilibrated T<0. For fermions, we analyze the time scales needed to equilibrate to T<0. For moderate interactions, the equilibration time is proportional to the square of the radius of the cloud and grows with increasing interaction strengths as atoms and energy are transported by diffusive processes.
NASA Astrophysics Data System (ADS)
Song, L.; Balakrishnan, N.; Walker, K. M.; Stancil, P. C.; Thi, W. F.; Kamp, I.; van der Avoird, A.; Groenenboom, G. C.
2015-11-01
We present calculated rate coefficients for ro-vibrational transitions of CO in collisions with H atoms for a gas temperature range of 10 K ≤ T ≤ 3000 K, based on the recent three-dimensional ab initio H-CO interaction potential of Song et al. Rate coefficients for ro-vibrational v=1,j=0-30\\to v\\prime =0,j\\prime transitions were obtained from scattering cross sections previously computed with the close-coupling (CC) method by Song et al. Combining these with the rate coefficients for vibrational v=1-5\\to v\\prime \\lt v quenching obtained with the infinite-order sudden approximation, we propose a new extrapolation scheme that yields the rate coefficients for ro-vibrational v=2-5,j=0-30\\to v\\prime ,j\\prime de-excitation. Cross sections and rate coefficients for ro-vibrational v=2,j=0-30\\to v\\prime =1,j\\prime transitions calculated with the CC method confirm the effectiveness of this extrapolation scheme. Our calculated and extrapolated rates are very different from those that have been adopted in the modeling of many astrophysical environments. The current work provides the most comprehensive and accurate set of ro-vibrational de-excitation rate coefficients for the astrophysical modeling of the H-CO collision system. The application of the previously available and new data sets in astrophysical slab models shows that the line fluxes typically change by 20%-70% in high temperature environments (800 K) with an H/H2 ratio of 1; larger changes occur for lower temperatures.
NASA Technical Reports Server (NTRS)
Keyser, L. F.
1980-01-01
The absolute rate constant of the reaction between chlorine (2P) atoms and hydrogen peroxide was determined from 298 to 424 K, using the discharge flow resonance fluorescence technique. Pseudo-first-order conditions were used with hydrogen peroxide in large excess. A fast flow-sampling procedure limited hydrogen peroxide decomposition to less than 5% over the temperature range studied. At 298 K, the rate constant is (4.1 plus or minus 0.2) x 10 to the minus 13th cu cm/molecule-sec.
Neufeld, David A.
2010-01-01
An artificial neural network (ANN) is investigated as a tool for estimating rate coefficients for the collisional excitation of molecules. The performance of such a tool can be evaluated by testing it on a data set of collisionally induced transitions for which rate coefficients are already known: the network is trained on a subset of that data set and tested on the remainder. Results obtained by this method are typically accurate to within a factor of approx2.1 (median value) for transitions with low excitation rates and approx1.7 for those with medium or high excitation rates, although 4% of the ANN outputs are discrepant by a factor of 10 or more. The results suggest that ANNs will be valuable in extrapolating a data set of collisional rate coefficients to include high-lying transitions that have not yet been calculated. For the asymmetric top molecules considered in this paper, the favored architecture is a cascade-correlation network that creates 16 hidden neurons during the course of training, with three input neurons to characterize the nature of the transition and one output neuron to provide the logarithm of the rate coefficient.
NASA Astrophysics Data System (ADS)
Dransfield, T. J.; Gennaco, M. M.; Huang, Y.; Hannun, R. A.
2011-12-01
We report absolute measurements of the rate constants of the reaction of hydroxyl radical (OH) with cyclopentane and cycloheptane in 6-8 Torr of nitrogen from 230-350 K using Harvard's High Pressure Flow System. Ethane's reactivity was simultaneously measured as a test of experimental performance. Hydroxyl concentrations were measured using Laser-Induced Fluorescence, and alkane concentrations were measured using Fourier-Transform Infrared Spectroscopy. Recent work on this flow system has suggested that cyclohexane has a significantly higher activation energy to reaction with OH than does cyclo-octane, a result which is not suggested by our understanding of hydrocarbon reactivity nor predicted by structure-activity relationships. This work examines the temperature dependent rates for two other similarly-sized cycloalkanes to determine whether they behave as cyclohexane or as cyclooctane. While several previous experiments have studied the reaction with cyclopentane, there is significant scatter in the room temperature rates, and only four absolute rate measurements are available at non-ambient temperatures. There are only two absolute rate measurements available for the reaction with cycloheptane; only one of these reports a temperature dependence, and that study is limited to temperatures above 298 K. Thus, this work significantly expands the available data set for both reactions. The data for the reactions of OH with ethane, cyclopentane, cyclohexane, and cycloheptane are all modeled using a simple Arrhenius fit, and also with a modified Arrhenius equation based on transition state theory, ignoring tunneling. Results from the latter fit indicate that the activation barriers for both title reactions are greater than that of OH + cyclo-octane. The measured activation energy for OH + cyclopentane actually exceeds that of OH + cyclohexane.
Generalized Treanor-Marrone model for state-specific dissociation rate coefficients
NASA Astrophysics Data System (ADS)
Kunova, O.; Kustova, E.; Savelev, A.
2016-08-01
We propose a simple and accurate model for state-specific dissociation rate coefficients based on the widely used Treanor-Marrone model. It takes into account the dependence of its parameter on temperature and vibrational level and can be used with arbitrary vibrational ladder. The model is validated by comparisons with state-specific dissociation rate coefficients of O2 and N2 obtained using molecular dynamics, and its good accuracy is demonstrated. Non-equilibrium kinetics of O2/O and N2/N mixtures under heat bath conditions is studied; applying the optimized Treanor-Marrone model leads to more efficient dissociation and vibrational relaxation.
NASA Technical Reports Server (NTRS)
Wolynes, Peter G.
1987-01-01
Nonadiabatic transitions are central to many areas of chemical and condensed matter physics, ranging from biological electron transfer to the optical properties of one-dimensional conductors. Here, a path integral Monte Carlo method is used to simulate such transitions, based on the observation that nonadiabatic rate coefficients are often dominated by saddle point trajectories that correspond to an imaginary time. Simple analytic theories can be used to continue these imaginary time correlation functions to determine rate coefficients. The advantages and drawbacks of this approach are discussed.
NASA Technical Reports Server (NTRS)
Torr, D. G.; Torr, M. R.
1978-01-01
The large data base of aeronomic parameters measured by the Atmosphere Explorer C, D, and E satellites since December 1973 has been used to determine a number of reaction rate coefficients highly relevant to our understanding of thermospheric chemistry. In this paper the results are reviewed for ionic rate coefficients for recombination of NO(+), O2(+), for reactions of O(+) + N2, N2(+) + O, and O(++) + O, and for various reactions involving O(+)(2D) and O(+)(2P) ions with O and N2.
Kinetic models for coagulation processes: determination of rate coefficients in vivo
NASA Astrophysics Data System (ADS)
Pearce, John A.; Cheong, Wai-Fung; Pandit, Kirit; McMurray, Tom J.; Thomsen, Sharon L.
1991-06-01
Kinetic models of thermal damage in tissues can be used to describe histologic end points obtained with laser irradiation. In this study, thermographic measurements of skin surface temperature distributions during laser impingement were used to derive a temperature history for the lesion site. Lesions were evaluated at 48 h after laser irradiation to determine the radius of purpura formation. The temperature histories at the maximum radius of purpura formation (threshold temperatures) were analyzed and plotted on Arrhenius axes to estimate rate coefficients for the process. As expected, transient in vivo thermal history data yielded a noisy Arrhenius plot; however, estimates of the appropriate rate coefficients for purpura formation in vivo could be made.
Semiempirical method of determining flow coefficients for pitot rake mass flow rate measurements
NASA Technical Reports Server (NTRS)
Trefny, C. J.
1985-01-01
Flow coefficients applicable to area-weighted pitot rake mass flow rate measurements are presented for fully developed, turbulent flow in an annulus. A turbulent velocity profile is generated semiempirically for a given annulus hub-to-tip radius ratio and integrated numerically to determine the ideal mass flow rate. The calculated velocities at each probe location are then summed, and the flow rate as indicated by the rake is obtained. The flow coefficient to be used with the particular rake geometry is subsequently obtained by dividing the ideal flow rate by the rake-indicated flow rate. Flow coefficients ranged from 0.903 for one probe placed at a radius dividing two equal areas to 0.984 for a 10-probe area-weighted rake. Flow coefficients were not a strong function of annulus hub-to-tip radius ratio for rakes with three or more probes. The semiempirical method used to generate the turbulent velocity profiles is described in detail.
Easy Absolute Values? Absolutely
ERIC Educational Resources Information Center
Taylor, Sharon E.; Mittag, Kathleen Cage
2015-01-01
The authors teach a problem-solving course for preservice middle-grades education majors that includes concepts dealing with absolute-value computations, equations, and inequalities. Many of these students like mathematics and plan to teach it, so they are adept at symbolic manipulations. Getting them to think differently about a concept that they…
Dielectronic recombination rate coefficients for the CoI isoelectronic sequence
NASA Astrophysics Data System (ADS)
Meng, Fan-Chang; Zhou, Li; Huang, Min; Chen, Chong-Yang; Wang, Yan-Sen; Zou, Ya-Ming
2009-05-01
In our recent reports (2007 J. Phys. B: At. Mol. Opt. Phys. 40 4269-86 and 2008 J. Quant. Spectrosc. Radiat. Transfer 109 2000-2008), we performed detailed and large-scale ab initio calculations on the total dielectronic recombination (DR) rate coefficients for Co-like gold and tungsten. Here we extend the calculations for another eight ions (Kr9+, Mo15+, Ag20+, Xe27+, Pr32+, Dy39+, At58+ and U65+) along the CoI isoelectronic sequence in the ground state employing the flexible atomic code. The total DR rates mainly come from complex series 3d84ln'l' and 3p53d94ln'l'. The complex series 3p53d10n'l' and 3d85ln'l' also contribute significantly at low (<0.1EI, EI is the ionization energy of the corresponding Ni-like ions) and high (>1.0EI) electron temperatures, respectively. On the basis of the calculated results, a general analytic formula for the total DR rate coefficients of all the ions along the CoI isoelectronic sequence is constructed. This formula can generally reproduce the calculated DR rate coefficients to within 3% for electron temperatures above 0.1EI. Comparisons of the present results with those obtained from the commonly used Burgess-Merts (BM) semiempirical formula show that the BM formula is not adequate to predict the total DR rate coefficients at relatively low electron temperatures and for low-Z ions. In addition, the total DR rate coefficients from the first excited state are also presented.
Global rate coefficients for ionization and recombination of carbon, nitrogen, oxygen, and argon
Annaloro, Julien; Morel, Vincent; Bultel, Arnaud; Omaly, Pierre
2012-07-15
The flow field modeling of planetary entry plasmas, laser-induced plasmas, inductively coupled plasmas, arcjets, etc., requires to use Navier-Stokes codes. The kinetic mechanisms implemented in these codes involve global (effective) rate coefficients. These rate coefficients result from the excited states coupling during a quasi-steady state. In order to obtain these global rate coefficients over a wide electron temperature (T{sub e}) range for ionization and recombination of carbon, nitrogen, oxygen, and argon, the behavior of their excited states is investigated using a zero-dimensional (time-dependent) code. The population number densities of these electronic states are considered as independent species. Their relaxation is studied within the range 3000 K{<=}T{sub e}{<=}20 000 K and leads to the determination of the ionization (k{sub i}) and recombination (k{sub r}) global rate coefficients. Comparisons with existing data are performed. Finally, the ratio k{sub i}/k{sub r} is compared with the Saha equilibrium constant. This ratio increases more rapidly than the equilibrium constant for T{sub e}>15 000 K.
Suleimanov, Yury V.; Aoiz, F. Javier; Guo, Hua
2016-11-03
This Feature Article presents an overview of the current status of ring polymer molecular dynamics (RPMD) rate theory. We first analyze the RPMD approach and its connection to quantum transition-state theory. We then focus on its practical applications to prototypical chemical reactions in the gas phase, which demonstrate how accurate and reliable RPMD is for calculating thermal chemical reaction rate coefficients in multifarious cases. This review serves as an important checkpoint in RPMD rate theory development, which shows that RPMD is shifting from being just one of recent novel ideas to a well-established and validated alternative to conventional techniques formore » calculating thermal chemical rate coefficients. We also hope it will motivate further applications of RPMD to various chemical reactions.« less
Theory and simulation of the time-dependent rate coefficients of diffusion-influenced reactions.
Zhou, H X; Szabo, A
1996-01-01
A general formalism is developed for calculating the time-dependent rate coefficient k(t) of an irreversible diffusion-influenced reaction. This formalism allows one to treat most factors that affect k(t), including rotational Brownian motion and conformational gating of reactant molecules and orientation constraint for product formation. At long times k(t) is shown to have the asymptotic expansion k(infinity)[1 + k(infinity) (pie Dt)-1/2 /4 pie D + ...], where D is the relative translational diffusion constant. An approximate analytical method for calculating k(t) is presented. This is based on the approximation that the probability density of the reactant pair in the reactive region keeps the equilibrium distribution but with a decreasing amplitude. The rate coefficient then is determined by the Green function in the absence of chemical reaction. Within the framework of this approximation, two general relations are obtained. The first relation allows the rate coefficient for an arbitrary amplitude of the reactivity to be found if the rate coefficient for one amplitude of the reactivity is known. The second relation allows the rate coefficient in the presence of conformational gating to be found from that in the absence of conformational gating. The ratio k(t)/k(0) is shown to be the survival probability of the reactant pair at time t starting from an initial distribution that is localized in the reactive region. This relation forms the basis of the calculation of k(t) through Brownian dynamics simulations. Two simulation procedures involving the propagation of nonreactive trajectories initiated only from the reactive region are described and illustrated on a model system. Both analytical and simulation results demonstrate the accuracy of the equilibrium-distribution approximation method. PMID:8913584
Camper, Anne K.; Hayes, Jason T.; Sturman, Paul J.; Jones, Warren L.; Cunningham, Alfred B.
1993-01-01
Three strains of Pseudomonas fluorescens with different motility rates and adsorption rate coefficients were injected into porous-medium reactors packed with l-mm-diameter glass spheres. Cell breakthrough, time to peak concentration, tailing, and cell recovery were measured at three interstitial pore velocities (higher than, lower than, and much lower than the maximal bacterial motility rate). All experiments were done with distilled water to reduce the effects of growth and chemotaxis. Contrary to expectations, motility did not result in either early breakthrough or early time to peak concentration at flow velocities below the motility rate. Bacterial size exclusion effects were shown to affect breakthrough curve shape at the very low flow velocity, but no such effect was seen at the higher flow velocity. The tendency of bacteria to adsorb to porous-medium surfaces, as measured by adsorption rate coefficients, profoundly influenced transport characteristics. Cell recoveries were shown to be correlated with the ratio of advective to adsorptive transport in the reactors. Adsorption rate coefficients were found to be better predictors of microbial transport phenomena than individual characteristics, such as size, motility, or porous-medium hydrodynamics. PMID:16349075
Pressure dependence of the absolute rate constant for the reaction OH + C2H2 from 228 to 413 K
NASA Technical Reports Server (NTRS)
Michael, J. V.; Nava, D. F.; Payne, W. A.; Stief, L. J.; Borkowski, R. P.
1980-01-01
The pressure dependence of the absolute rate constant for the reaction of the hydroxyl radical with acetylene, important in both atmospheric and combustion chemistry, is determined for temperatures between 228 and 413 K. The flash photolysis-resonance fluorescence technique was employed at five temperatures over wide ranges of pressure and acetylene concentrations, with the OH produced by water photolysis and hydroxyl resonance fluorescent photons measured by multiscaling techniques. Results indicate that, except at the lowest temperature, the bimolecular rate constant for the reaction depends strongly on total pressure, with the pressure effect becoming more pronounced with increasing temperature. At limiting high pressures, the rate constant is found to be equal to 6.83 + or - 1.19 x 10 to the -12th exp (-646 + or - 47/T) cu cm/molecule per sec, where T is the temperature. Results thus demonstrate the importance of environmental conditions in theoretical studies of atmospheric and combustion product compositions
Absolute rate parameters for the reaction of ground state atomic oxygen with carbonyl sulfide
NASA Technical Reports Server (NTRS)
Klemm, R. B.; Stief, L. J.
1974-01-01
The rate parameters for the reaction of O(3P) with carbonyl sulfide, O(3P) + OCS yields CO + SO, have been determined directly by monitoring O(3P) using the flash photolysis-resonance fluorescence technique. The value for reaction rate was measured over a temperature range of 263-502 K and the data were fitted to an Arrhenius expression with good linearity. A comparison of the present results with those from previous studies of this reaction is also presented.
NASA Astrophysics Data System (ADS)
Gurley, Katelyn; Shang, Yu; Yu, Guoqiang
2012-07-01
This study investigates a method using novel hybrid diffuse optical spectroscopies [near-infrared spectroscopy (NIRS) and diffuse correlation spectroscopy (DCS)] to obtain continuous, noninvasive measurement of absolute blood flow (BF), blood oxygenation, and oxygen consumption rate (\\Vdot O2) in exercising skeletal muscle. Healthy subjects (n=9) performed a handgrip exercise to increase BF and \\Vdot O2 in forearm flexor muscles, while a hybrid optical probe on the skin surface directly monitored oxy-, deoxy-, and total hemoglobin concentrations ([HbO2], [Hb], and THC), tissue oxygen saturation (StO2), relative BF (rBF), and relative oxygen consumption rate (r\\Vdot O2). The rBF and r\\Vdot O2 signals were calibrated with absolute baseline BF and \\Vdot O2 obtained through venous and arterial occlusions, respectively. Known problems with muscle-fiber motion artifacts in optical measurements during exercise were mitigated using a novel gating algorithm that determined muscle contraction status based on control signals from a dynamometer. Results were consistent with previous findings in the literature. This study supports the application of NIRS/DCS technology to quantitatively evaluate hemodynamic and metabolic parameters in exercising skeletal muscle and holds promise for improving diagnosis and treatment evaluation for patients suffering from diseases affecting skeletal muscle and advancing fundamental understanding of muscle and exercise physiology.
Transitions in genetic toggle switches driven by dynamic disorder in rate coefficients
NASA Astrophysics Data System (ADS)
Chen, Hang; Thill, Peter; Cao, Jianshu
2016-05-01
In biochemical systems, intrinsic noise may drive the system switch from one stable state to another. We investigate how kinetic switching between stable states in a bistable network is influenced by dynamic disorder, i.e., fluctuations in the rate coefficients. Using the geometric minimum action method, we first investigate the optimal transition paths and the corresponding minimum actions based on a genetic toggle switch model in which reaction coefficients draw from a discrete probability distribution. For the continuous probability distribution of the rate coefficient, we then consider two models of dynamic disorder in which reaction coefficients undergo different stochastic processes with the same stationary distribution. In one, the kinetic parameters follow a discrete Markov process and in the other they follow continuous Langevin dynamics. We find that regulation of the parameters modulating the dynamic disorder, as has been demonstrated to occur through allosteric control in bistable networks in the immune system, can be crucial in shaping the statistics of optimal transition paths, transition probabilities, and the stationary probability distribution of the network.
CO2 in the MLT: Constraining the CO2(υ2)-O Quenching Rate Coefficient.
NASA Astrophysics Data System (ADS)
Dawkins, E. C. M.; Kutepov, A. A.; Feofilov, A.; Janches, D.
2015-12-01
Carbon dioxide plays an important role in the terrestrial atmosphere, with infrared emission in the 15 μm CO2 band (I15μm) providing the dominant cooling mechanism in the mesosphere/lower thermosphere (MLT) region via interaction with atomic O. This CO2(υ2)-O quenching rate coefficient is poorly understood and current estimates vary by a factor 3-4, with a significant discrepancy between laboratory measurements and those provided by satellite remote sensing. However, the true value of this rate coefficient is of vital importance in understanding both the energetics of the MLT region and for temperatures retrievals from measurements of I15μm. This work builds upon and extends an existing methodology developed by Feofilov et al. (2012) who used TIMED/SABER satellite instrument data to retrieve the CO2(υ2)-O quenching rate coefficient using a synergy of atmospheric and ground-based lidar temperature measurements. Using the SABER overflights of the Fort Collins (CO) lidar, these authors derived the altitude variation of the CO2(υ2)-O quenching rate. The latter demonstrated deficiency of the current non-LTE model of the 15 μm CO2 emission which obviously misses some so far unknown mechanisms of non-thermal excitation of the CO2(υ2) vibrations. Current work involves several other lidar locations and is aimed at assessing whether there is a spatio-temporal variability component to this rate coefficient, and what this could reveal about these additional energy sources and sinks in the real atmosphere that are currently not accounted for in the non-LTE model.
Graves, D. A.; Greenbaum, E.
1989-01-01
Photosynthetically generated O2 was measured from single algal colonies in a He atmosphere, using an enhanced Hersch galvanic cell. The enhancement consisted of using ultrapure potassium hydroxide as the electrolyte and ultrapure lead as the anode. The galvanic cell was placed in a regulated helium-flow system containing a reaction cuvette with the colonies and an electrolysis cell for calibration. Colonies were individually irradiated using a He-Ne laser. Data collection and laser positioning for colony irradiation were microcomputer controlled. This assay system was capable of detecting O2 production rates of 500 femtomoles per second with a signal to noise ratio of 2, a level of sensitivity that permitted the detection of photoevolved O2 from single algal colonies. This capability provides, for the first time, an approach for quantitatively measuring the absolute rate of photosynthetic O2 evolution from a single algal colony. PMID:16666743
Zilio, Valery Olivier; Joneja, Om Parkash; Popowski, Youri; Rosenfeld, Anatoly; Chawla, Rakesh
2006-06-15
Reported MOSFET measurements concern mostly external radiotherapy and in vivo dosimetry. In this paper, we apply the technique for absolute dosimetry in the context of HDR brachytherapy using an {sup 192}Ir source. Measured radial dose rate distributions in water for different planes perpendicular to the source axis are presented and special attention is paid to the calibration of the R and K type detectors, and to the determination of appropriate correction factors for the sensitivity variation with the increase of the threshold voltage and the energy dependence. The experimental results are compared with Monte Carlo simulated dose rate distributions. The experimental results show a good agreement with the Monte Carlo simulations: the discrepancy between experimental and Monte Carlo results being within 5% for 82% of the points and within 10% for 95% of the points. Moreover, all points except two are found to lie within the experimental uncertainties, confirming thereby the quality of the results obtained.
Absolute rate of the reaction of bromine atoms with ozone from 200-360 K
NASA Technical Reports Server (NTRS)
Michael, J. V.; Lee, J. H.; Payne, W. A.; Stief, L. J.
1978-01-01
The rate constant for the reaction Br + O3 yields BrO + O2 was measured from 200 to 360 K by the technique of flash photolysis coupled to time resolved detection of bromine atoms by resonance fluorescence (FP-RF). Br atoms were produced by the flash photolysis of CH3Br at lambda 165nm.O3 was monitored continuously under reaction conditions by absorption at 253.7 nm. At each of five temperatures the results were independent of substantial variations in O3, total pressure and limited variations in flash intensity. The measured rate constants obeyed the Arrhenius expression, where the error quoted is two standard deviations. Results are compared with previous determinations which employed the discharge flow-mass spectrometric technique.
Absolute rate of the reaction of bromine atoms with ozone from 200 to 360 K
NASA Technical Reports Server (NTRS)
Michael, J. V.; Lee, J. H.; Payne, W. A.; Stief, L. J.
1978-01-01
The rate constant for the reaction Br + O3 yields BrO + O2 has been measured from 200 to 360 K by the technique of flash photolysis coupled to time resolved detection of bromine atoms by resonance fluorescence (FP-RF). Br atoms were produced by the flash photolysis of CH3Br at a wavelength of 165 nm. O3 concentration was monitored continuously under reaction conditions by absorption at 253.7 nm. At each of five temperatures the results were independent of substantial variations in O3 concentration, total pressure (Ar), and limited variations in flash intensity (i.e., initial Br concentration). The measured rate constants obey the Arrhenius expression, k = (7.74 plus or minus 0.50) x 10 to the -12th exp(-603 plus or minus 16/T) cu cm/molecule/sec, where the error quoted is two standard deviations.
Absolute rate constants for the reaction of atomic hydrogen with ketene from 298 to 500 K
NASA Technical Reports Server (NTRS)
Michael, J. V.; Nava, D. F.; Payne, W. A.; Stief, L. J.
1979-01-01
Rate constants for the reaction of atomic hydrogen with ketene have been measured at room temperature by two techniques, flash photolysis-resonance fluorescence and discharge flow-resonance fluorescence. The measured values are (6.19 + or - 1.68) x 10 to the -14th and (7.3 + or - 1.3) x 10 to the -14th cu cm/molecule/s, respectively. In addition, rate constants as a function of temperature have been measured over the range 298-500 K using the FP-RF technique. The results are best represented by the Arrhenius expression k = (1.88 + or - 1.12) x 10 to the -11th exp(-1725 + or - 190/T) cu cm/molecule/s, where the indicated errors are at the two standard deviation level.
Rate-coefficients and polarization results for the electron-impact excitation of Ar+ ion
NASA Astrophysics Data System (ADS)
Srivastava, Rajesh; Dipti, Dipti
2016-05-01
A fully relativistic distorted wave theory has been employed to study the electron impact excitation in Ar+ ion. Results have been obtained for the excitation cross-sections and rate-coefficients for the transitions from the ground state 3p5 (J = 3/2) to fine-structure levels of excited states 3p4 4 s, 3p4 4 p , 3p4 5 s, 3p4 5 p, 3p4 3 d and 3p4 4 d. Polarization of the radiation following the excitation has been calculated using the obtained magnetic sub-level cross-sections. Comparison of the present rate-coefficients is also done with the previously reported theoretical results for some unresolved fine structure transitions. Work is supported by DAE-BRNS Mumbai and CSIR, New Delhi.
Recommended Thermal Rate Coefficients for the C + H3+ Reaction and Some Astrochemical Implications
NASA Astrophysics Data System (ADS)
Vissapragada, Shreyas; Buzard, Cam; Miller, Kenneth A.; O'Connor, Aodh; De Ruette, Nathalie; Urbain, Xavier; Savin, Daniel Wolf
2016-06-01
We have incorporated our experimentally derived thermal rate coefficients for C + H3+ forming CH+ and CH2+ into a commonly used astrochemical model. We find that the Arrhenius-Kooij equation typically used in chemical models does not accurately fit our data and use instead a more versatile fitting formula. At a temperature of 10 K and a density of 104 cm-3, we find no significant differences in the predicted abundances, but at higher temperatures of 50, 100, and 300 K we find up to factor of 2 changes. Additionally, we find that the relatively small error on our measurements (~15%) significantly reduces the uncertainties on the predicted abundances compared to those obtained using the currently implemented Langevin rate coefficient with its estimated factor of 2 uncertainty.
Electron-impact excitation rate-coefficients and polarization of subsequent emission for Ar+ ion
NASA Astrophysics Data System (ADS)
Dipti; Srivastava, Rajesh
2016-06-01
Electron impact excitation in Ar+ ions has been studied by using fully relativistic distorted wave theory. Calculations are performed to obtain the excitation cross-sections and rate-coefficients for the transitions from the ground state 3p5 (J=3/2) to fine-structure levels of excited states 3p44s, 3p44p, 3p45s, 3p45p, 3p43d and 3p44d. Polarization of the radiation following the excitation has been calculated using the obtained magnetic sub-level cross-sections. Comparison of the present rate-coefficients is also done with the previously reported theoretical results for some unresolved fine structure transitions.
NASA Astrophysics Data System (ADS)
Alba, S.; Weldon, R.; Livelybrooks, D.; Schmidt, D. A.
2009-12-01
We present a new uplift rate map for western Washington based on reanalysis of water levels from the 12 major NOAA tide gauges, three new water level series that combine NOAA’s historical records and our temporarily deployed gauges (at Cape Disappointment, Olympia, and Point Grenville), and reinterpretation of repeated 1st and 2nd order NGS leveling lines. As previous studies have concluded, EW gradients in the vertical deformation field are consistent with strain accumulation across the Cascadia subduction zone interface; however, uplift rates are highly variable along the outer Washington coast, ranging from approximately +4 to -2 mm/yr, suggesting significant changes in the depth of locking along strike. Improved measure of uplift rates from water level changes are accomplished by aggressively editing available hourly data and applying a transfer function approach to better remove tides, ocean and atmospheric “noise”. The analysis allows uplift to be determined from shorter and less complete records and in some cases permits the identification of transients like slow earthquakes. As we found in a similar study in Oregon (Burgette et al, JGR, 2009), releveled lines need to be anchored to as many tide gauges as possible to remove systematic error, and repeated releveling (especially of tidal benchmarks) is required to identify the few stable benchmarks that link water levels at the tidal stations to each other through time and to the regional NGS leveling lines. A portion of the westernmost Washington coast, from an approximate latitude of 47.4 to 47.9 N, is subsiding, and tilts suggest that the peak in uplift rate is well onshore, indicating that the locked zone extends onshore, in contrast to most previous studies. To the north, the peak in uplift approximately passes through Neah Bay (the NW corner of the Olympic Peninsula, lat. 48.3 N), and to the south the peak is offshore from Grays Harbor (lat. 47 N) to the Columbia River (lat. 46.2 N). A north
NASA Astrophysics Data System (ADS)
Crawford, J.; Davis, D.; Chen, G.; Shetter, R.; Müller, M.; Barrick, J.; Olson, J.
1999-03-01
An assessment of the effects of clouds on photolysis rate coefficients was carried out using three different experimental methods involving two different aircraft platforms. This evaluation was based on data recorded during NASA's Pacific Exploratory Mission (PEM)-Tropics A program in August-October 1996. On the NASA DC-8, upward and downward looking J(NO2) filter radiometers and spectroradiometers were employed. For the NASA P-3B, the instrumentation consisted of Eppley radiometers. Although each aircraft typically sampled the same geographic region, coincident measurements occurred for only one brief period in the marine boundary layer near Christmas Island (2°N, 157°W). All three methods were compared for this flight period; however, only the J(NO2) filter radiometers and spectroradiometers could be compared for the entire campaign. For the Christmas Island sampling period, all three radiometric measurements disagreed in magnitude but exhibited trends consistent with model-calculated photolysis rate coefficients. Overall, the results showed that the J(NO2) filter radiometers and spectroradiometers exhibited a consistent disagreement of 30%, the J(NO2) filter radiometers being higher. Eppley-derived values of J(NO2) fell between those of the J(NO2) filter radiometers and spectroradiometers. An examination of the variation in J(O1D) and J(NO2) based on the output from the spectroradiometers and J(NO2) filter radiometers suggests that differences between each photolysis rate coefficient's response to cloud effects tend to be smaller than model uncertainties. Thus J(O1D) and other photolysis rate coefficients can be corrected for cloud effects based on the response of J(NO2).
NASA Technical Reports Server (NTRS)
Davidson, J. A.; Sadowski, C. M.; Schiff, H. I.; Howard, C. J.; Schmeltekopf, A. L.; Jennings, D. A.; Streit, G. E.
1976-01-01
Absolute rate constants for the deactivation of O(1D) atoms by some atmospheric gases have been determined by observing the time-resolved emission of O(1D) at 630 nm. O(1D) atoms were produced by the dissociation of ozone via repetitive laser pulses at 266 nm. Absolute rate constants for the relaxation of O(1D) at 298 K are reported for N2, O2, CO2, O3, H2, D2, CH4, HCl, NH3, H2O, N2O, and Ne. The results obtained are compared with previous relative and absolute measurements reported in the literature.
Low-temperature rate coefficients for the reaction of ethynyl radical (C2H) with benzene.
Goulay, Fabien; Leone, Stephen R
2006-02-01
The reaction of the C2H radical with benzene is studied at low temperature using a pulsed Laval nozzle apparatus. The C2H radical is prepared by 193-nm photolysis of acetylene, and the C2H concentration is monitored using CH(A2Delta) chemiluminescence from the C2H + O2 reaction. Measurements at very low photolysis energy are performed using CF3C2H as the C2H precursor to study the influence of benzene photodissociation on the rate coefficient. Rate coefficients are obtained over a temperature range between 105 and 298 K. The average rate coefficient is found to be five times greater than the estimated value presently used in the photochemical modeling of Titan's atmosphere. The reaction exhibits a slight negative temperature dependence which can be fitted to the expression k(cm3 molecule(-1) s(-1)) = 3.28(+/-1.0) x 10(-10) (T/298)(-0.18(+/-0.18)). The results show that this reaction has no barrier and may play an important role in the formation of large molecules and aerosols at low temperature. Our results are consistent with the formation of a short lifetime intermediate that decomposes to give the final products.
NASA Technical Reports Server (NTRS)
Bogan, Denis
1999-01-01
Laboratory measurements have been carried out to determine low temperature chemical rate coefficients of ethynyl radical (C2H) for the atmospheres of the outer planets and their satellites. This effort is directly related to the Cassini mission which will explore Saturn and Titan. A laser-based photolysis/infrared laser probe setup was used to measure the temperature dependence of kinetic rate coefficients from approx. equal to 150 to 350 K for C2H radicals with H2, C2H2, CH4, CD4, C2H4, C2H6, C3H8, n-C4H10, i-C4H10, neo-C5H12, C3H4 (methylacetylene and allene), HCN, and CH3CN. The results revealed discrepancies of an order of magnitude or more compared with the low temperature rate coefficients used in present models. A new Laval nozzle, low Mach number supersonic expansion kinetics apparatus has been constructed, resulting in the first measurements of neutral C2H radical kinetics at 90 K and permitting studies on condensable gases with insufficient vapor pressure at low temperatures. New studies of C 2H with acetylene have been completed.
Absolute rate calculations: atom and proton transfers in hydrogen-bonded systems.
Barroso, Mónica; Arnaut, Luis G; Formosinho, Sebastião J
2005-02-01
We calculate energy barriers of atom- and proton-transfer reactions in hydrogen-bonded complexes in the gas phase. Our calculations do not involve adjustable parameters and are based on bond-dissociation energies, ionization potentials, electron affinities, bond lengths, and vibration frequencies of the reactive bonds. The calculated barriers are in agreement with experimental data and high-level ab initio calculations. We relate the height of the barrier with the molecular properties of the reactants and complexes. The structure of complexes with strong hydrogen bonds approaches that of the transition state, and substantially reduces the barrier height. We calculate the hydrogen-abstraction rates in H-bonded systems using the transition-state theory with the semiclassical correction for tunneling, and show that they are in excellent agreement with the experimental data. H-bonding leads to an increase in tunneling corrections at room temperature. PMID:15751360
NASA Technical Reports Server (NTRS)
Bosco, S. R.; Nava, D. F.; Brobst, W. D.; Stief, L. J.
1984-01-01
The absolute rate constants for the reaction between the NH2 free radical and acetylene and ethylene is measured experimentally using a flash photolysis technique. The constant is considered to be a function of temperature and pressure. At each temperature level of the experiment, the observed pseudo-first-order rate constants were assumed to be independent of flash intensity. The results of the experiment indicate that the bimolecular rate constant for the NH2 + C2H2 reaction increases with pressure at 373 K and 459 K but not at lower temperatures. Results near the pressure limit conform to an Arrhenius expression of 1.11 (+ or -) 0.36 x 10 to the -13th over the temperature range from 241 to 459 K. For the reaction NH2 + C2H4, a smaller rate of increase in the bimolecular rate constant was observed over the temperature range 250-465 K. The implications of these results for current theoretical models of NH2 + C2H2 (or H4) reactions in the atmospheres of Jupiter and Saturn are discussed.
NASA Technical Reports Server (NTRS)
Jameson, A. R.
1990-01-01
The relationship between the rainfall rate (R) obtained from radiometric brightness temperatures and the extinction coefficient (k sub e) is investigated by computing the values of k sub e over a wide range of rainfall rates, for frequencies from 3 to 25 GHz. The results show that the strength of the relation between the R and the k sub e values exhibits considerable variation for frequencies at this range. Practical suggestions are made concerning the selection of particular frequencies for rain measurements to minimize the error in R determinations.
Derivation of the chemical-equilibrium rate coefficient using scattering theory
NASA Technical Reports Server (NTRS)
Mickens, R. E.
1977-01-01
Scattering theory is applied to derive the equilibrium rate coefficient for a general homogeneous chemical reaction involving ideal gases. The reaction rate is expressed in terms of the product of a number of normalized momentum distribution functions, the product of the number of molecules with a given internal energy state, and the spin-averaged T-matrix elements. An expression for momentum distribution at equilibrium for an arbitrary molecule is presented, and the number of molecules with a given internal-energy state is represented by an expression which includes the partition function.
NASA Astrophysics Data System (ADS)
Nilsson, E. J. K.; Joelsson, L. M. T.; Heimdal, J.; Johnson, M. S.; Nielsen, O. J.
2013-12-01
The reaction rate coefficient k(CH3Br + OH) has been determined in the temperature range 298-373 K, using pulse radiolysis/UV kinetic spectroscopy, and at 298 K using a relative rate method. The Arrhenius expression obtained from a fit to the experimental results is (2.9 ± 0.9) × 10-12 exp(-(1230 ± 125)/T) cm3 molecule-1 s-1, which is greater than the expression currently recommended. The relative rate experiments give k(298 K) = (4.13 ± 0.63) × 10-14 cm3 molecule-1 s-1. The results of the absolute and relative rate experiments indicate that the source budget of atmospheric CH3Br should be reinvestigated, as was recently done for CH3Cl.
Recombination and Electron Impact Excitation Rate Coefficients for S XV and S XVI
NASA Astrophysics Data System (ADS)
Mahmood, S.; Ali, S.; Orban, I.; Tashenov, S.; Lindroth, E.; Schuch, R.
2012-08-01
Recombination and electron impact excitation of S14+ and S15+ ions was measured at the Stockholm refrigerated electron beam ion trap. The collision energy range was 1.4-3 keV, in which we covered the KLL, KLM, KLN, and KLO dielectronic recombination resonances resulting in S13+ and S14+ ions. The recombination rates were obtained by detecting the charge state distribution with a newly developed time-of-flight technique. Resonance energies and cross-sections calculated within the relativistic many-body perturbation theory for S15+ agree well with the experimental data. The temperature-dependent rate coefficients were extracted from the measured rates and compared with calculations from the literature used for studies of collisionally ionized astrophysical plasmas. Good agreement for S15+ was obtained, while the plasma rates for S14+ were 23% lower than the current published values. In addition to the time-of-flight spectra, the X-ray spectra, produced mainly by photo-recombination and excitation, were also collected. The combination of these two measurements allowed us to separate the photo-recombination and the excitation spectra, and the excitation rate coefficients for summed intensities with known fractions of S14+ and S15+ ions were extracted.
Gold, Raymond; Roberts, James H.
1989-01-01
A solid state track recording type dosimeter is disclosed to measure the time dependence of the absolute fission rates of nuclides or neutron fluence over a period of time. In a primary species an inner recording drum is rotatably contained within an exterior housing drum that defines a series of collimating slit apertures overlying windows defined in the stationary drum through which radiation can enter. Film type solid state track recorders are positioned circumferentially about the surface of the internal recording drum to record such radiation or its secondary products during relative rotation of the two elements. In another species both the recording element and the aperture element assume the configuration of adjacent disks. Based on slit size of apertures and relative rotational velocity of the inner drum, radiation parameters within a test area may be measured as a function of time and spectra deduced therefrom.
Electron-Ion Recombination Rate Coefficient Measurements in a Flowing Afterglow Plasma
NASA Technical Reports Server (NTRS)
Gougousi, Theodosia; Golde, Michael F.; Johnsen, Rainer
1996-01-01
The flowing-afterglow technique in conjunction with computer modeling of the flowing plasma has been used to determine accurate dissociative-recombination rate coefficients alpha for the ions O2(+), HCO(+), CH5(+), C2H5(+), H3O(+), CO2(+), HCO2(+), HN2O(+), and N2O(+) at 295 K. We find that the simple form of data analysis that was employed in earlier experiments was adequate and we largely confirm earlier results. In the case of HCO(+) ions, published coefficients range from 1.1 X 10(exp -7) to 2.8 x 10(exp -7) cu cm/S, while our measurements give a value of 1.9 x 10(exp -7) cu cm/S.
Technology Transfer Automated Retrieval System (TEKTRAN)
We present near-infrared spectroscopy measurement of absolute cerebral hemoglobin concentration and saturation in a large sample of 36 healthy elderly (mean age, 85 ± 6 years) and 19 young adults (mean age, 28 ± 4 years). Non-invasive measurements were obtained on the forehead using a commercially a...
NASA Technical Reports Server (NTRS)
Leone, Stephen R.
1993-01-01
The objectives are to measure laboratory rate coefficients for key reactions of hydrocarbon molecules and radicals at low temperatures, which are relevant to the atmospheric photochemistry of Saturn, Jupiter, and Titan. Upcoming NASA planetary missions, such as Cassini, will probe the atmosphere of Titan in more detail, offering an excellent opportunity to test kinetic models and to establish fiducial standards for using kinetic models to interpret various parameters of the outer planets. Accurate low temperature kinetic data, which are presently lacking, may require crucial revisions to the rates of formation and destruction and are of utmost importance to the success of these efforts. In this program, several key reactions of ethynyl radicals (C2H) with acetylene (C2H2), methane (CH4), and oxygen (O2), down to temperatures of 170 K were successfully investigated. The experimental apparatus developed in our laboratory for measuring reaction kinetics at low temperatures consists of a laser photolysis/infrared probe laser setup. The rate measurements are carried out as a function of (low) temperature with a transverse flow cell designed specifically for these studies. A 193 nm argon fluoride pulsed excimer laser is used to photolyze a suitable precursor molecule, such as acetylene to produce C2H, and a high resolution, tunable infrared F-center laser (2.3-3.35 mu m) probes the transient concentrations of the radical species directly in absorption to extract the kinetic rate coefficients.
2013-01-01
Background National smoking-specific lung cancer mortality rates are unavailable, and studies presenting estimates are limited, particularly by histology. This hinders interpretation. We attempted to rectify this by deriving estimates indirectly, combining data from national rates and epidemiological studies. Methods We estimated study-specific absolute mortality rates and variances by histology and smoking habit (never/ever/current/former) based on relative risk estimates derived from studies published in the 20th century, coupled with WHO mortality data for age 70–74 for the relevant country and period. Studies with populations grossly unrepresentative nationally were excluded. 70–74 was chosen based on analyses of large cohort studies presenting rates by smoking and age. Variations by sex, period and region were assessed by meta-analysis and meta-regression. Results 148 studies provided estimates (Europe 59, America 54, China 22, other Asia 13), 54 providing estimates by histology (squamous cell carcinoma, adenocarcinoma). For all smoking habits and lung cancer types, mortality rates were higher in males, the excess less evident for never smokers. Never smoker rates were clearly highest in China, and showed some increasing time trend, particularly for adenocarcinoma. Ever smoker rates were higher in parts of Europe and America than in China, with the time trend very clear, especially for adenocarcinoma. Variations by time trend and continent were clear for current smokers (rates being higher in Europe and America than Asia), but less clear for former smokers. Models involving continent and trend explained much variability, but non-linearity was sometimes seen (with rates lower in 1991–99 than 1981–90), and there was regional variation within continent (with rates in Europe often high in UK and low in Scandinavia, and higher in North than South America). Conclusions The indirect method may be questioned, because of variations in definition of smoking and
NASA Technical Reports Server (NTRS)
Judge, Darrell L.
1994-01-01
A prototype spectrometer has been developed for space applications requiring long term absolute EUV photon flux measurements. The energy spectrum of the incoming photons is transformed directly into an electron energy spectrum by taking advantage of the photoelectric effect in one of several rare gases at low pressures. Using an electron energy spectrometer, followed by an electron multiplier detector, pulses due to individual electrons are counted. The overall efficiency of this process can be made essentially independent of gain drifts in the signal path, and the secular degradation of optical components which is often a problem in other techniques is avoided. A very important feature of this approach is its freedom from the problem of overlapping spectral orders that plagues grating EUV spectrometers. An instrument with these features has not been flown before, but is essential to further advances in our understanding of solar EUV flux dynamics, and the coupled dynamics of terrestrial and planetary atmospheres. The detailed characteristics of this optics-free spectrometer are presented in the publications section.
Pressure dependence of the absolute rate constant for the reaction OH + C2H2 from 228 to 413K
NASA Technical Reports Server (NTRS)
Michael, J. V.; Nava, D. F.; Borokowski, R. P.; Payne, W. A.; Stief, L. J.
1980-01-01
The pressure dependence of absolute rate constants for the reaction of OH + C2H2 yields products has been examined at five temperatures ranging from 228 to 413 K. The experimental techniques which was used is flash photolysis-resonance fluoresence. OH was produced by water photolysis and hydroxyl resonance fluorescent photons were measured by multiscaling techniques. The results indicate that the low pressure bimolecular rate constant is 4 x 10 the the minus 13th power cu cm molecule (-1) s(-1) over the temperature range studied. A substantial increase in the bimolecular rate constant with an increase in pressure was observed at all temperatures except 228 K. This indicates the importance of initial adduct formation and subsequent stablization. The high pressure results are well represented by the Arrhenius expression (k sub bi) sub infinity = (6.83 + or - 1.19) x 10 to the minus 12th power exp(-646 + or - 47/T)cu cm molecule (-1) s(-1). The results are compared to previous investigated and are theoretically discussed. The implications of these results on modeling of terrestrial and planetary atmospheres and also in combustion chemistry are discussed.
NASA Technical Reports Server (NTRS)
Nava, D. F.; Mitchell, M. B.; Stief, L. J.
1986-01-01
The absolute rate constant for the reaction H + C4H2 has been measured over the temperature (T) interval 210-423 K, using the technique of flash photolysis-resonance fluorescence. At each of the five temperatures employed, the results were independent of variations in C4H2 concentration, total pressure of Ar or N2, and flash intensity (i.e., the initial H concentration). The rate constant, k, was found to be equal to 1.39 x 10 to the -10th exp (-1184/T) cu cm/s, with an error of one standard deviation. The Arrhenius parameters at the high pressure limit determined here for the H + C4H2 reaction are consistent with those for the corresponding reactions of H with C2H2 and C3H4. Implications of the kinetic carbon chemistry results, particularly those at low temperature, are considered for models of the atmospheric carbon chemistry of Titan. The rate of this reaction, relative to that of the analogous, but slower, reaction of H + C2H2, appears to make H + C4H2 a very feasible reaction pathway for effective conversion of H atoms to molecular hydrogen in the stratosphere of Titan.
Rate coefficients for reaction of OH with acetone between 202 and 395 K
Wollenhaupt, M.; Carl, S.A.; Horowitz, A.; Crowley, J.N.
2000-03-30
The kinetics of the title reaction were investigated between 202 and 395 K and at 20, 50, and 100 Torr of Ar or N{sub 2} bath gas using pulsed laser photolysis (PLP) generation of OH combined with both resonance fluorescence (RF) and laser-induced fluorescence (LIF) detection. OH was generated either by the sequential 439 nm, two-photon dissociation of NO{sub 2} in the presence of H{sub 2}, or by HONO photolysis at 351 nm. The accuracy of the rate constants obtained was enhanced by optical absorption measurements of acetone concentrations both before and after the photolysis reactor. The temperature dependence is not describe by a simple Arrhenius expression but by k{sub 1} (202--395 K) = 8.8 x 10{sup {minus}12} exp({minus}1,320/T) + 1.7 x 10{sup {minus}14} exp(423/T) cm{sup 3} s{sup {minus}1}, indicating that a simple H atom abstraction may not be the only reaction mechanism. The estimated total error (95% confidence) associated wit the rate coefficient derived from this expression is estimated as 5% and is independent of temperature. The curvature in the Arrhenius plot results in a significantly larger rate coefficient at low temperatures than obtained by extrapolation of the previous measurement and implies greater significance for the reaction with OH as a sink for acetone in the upper troposphere than presently assumed.
Rate coefficients, binding probabilities, and related quantities for area reactivity models
Prüstel, Thorsten; Meier-Schellersheim, Martin
2014-01-01
We further develop the general theory of the area reactivity model that describes the diffusion-influenced reaction of an isolated receptor-ligand pair in terms of a generalized Feynman-Kac equation and that provides an alternative to the classical contact reactivity model. Analyzing both the irreversible and reversible reaction, we derive the equation of motion of the survival probability as well as several relationships between single pair quantities and the reactive flux at the encounter distance. Building on these relationships, we derive the equation of motion of the many-particle survival probability for irreversible pseudo-first-order reactions. Moreover, we show that the usual definition of the rate coefficient as the reactive flux is deficient in the area reactivity model. Numerical tests for our findings are provided through Brownian Dynamics simulations. We calculate exact and approximate expressions for the irreversible rate coefficient and show that this quantity behaves differently from its classical counterpart. Furthermore, we derive approximate expressions for the binding probability as well as the average lifetime of the bound state and discuss on- and off-rates in this context. Throughout our approach, we point out similarities and differences between the area reactivity model and its classical counterpart, the contact reactivity model. The presented analysis and obtained results provide a theoretical framework that will facilitate the comparison of experiment and model predictions. PMID:25416882
Gas-phase reaction of ( E)-β-farnesene with ozone: Rate coefficient and carbonyl products
NASA Astrophysics Data System (ADS)
Kourtchev, Ivan; Bejan, Iustinian; Sodeau, John R.; Wenger, John C.
The gas-phase ozonolysis of ( E)-β-farnesene was investigated in a 3.91 m 3 atmospheric simulation chamber at 296 ± 2 K and relative humidity of around 0.1%. The relative rate method was used to determine the reaction rate coefficient of (4.01 ± 0.17) × 10 -16 cm 3 molecule -1 s -1, where the indicated errors are two least-squares standard deviations and do not include uncertainties in the rate coefficients for the reference compounds (γ-terpinene, cis-cyclooctene and 1,5-cyclooctadiene). Gas phase carbonyl products were collected using a denuder sampling technique and analyzed with GC/MS following derivatization with O-(2,3,4,5,6-pentafluorobenzyl) hydroxylamine (PFBHA). The reaction products detected were acetone, 4-oxopentanal, methylglyoxal, 4-methylenehex-5-enal, 6-methylhept-5-en-2-one, and ( E)-4-methyl-8-methylenedeca-4,9-dienal. A detailed mechanism for the gas-phase ozonolysis of ( E)-β-farnesene is proposed, which accounts for all of the products observed in this study. The results of this work indicate that the atmospheric reaction of ( E)-β-farnesene with ozone has a lifetime of around 1 h and is another possible source of the ubiquitous carbonyls, acetone, 4-oxopentanal and 6-methylhept-5-en-2-one in the atmosphere.
Parameterization of the level-resolved radiative recombination rate coefficients for the SPEX code
NASA Astrophysics Data System (ADS)
Mao, Junjie; Kaastra, Jelle
2016-03-01
The level-resolved radiative recombination (RR) rate coefficients for H-like to Na-like ions from H (Z = 1) up to and including Zn (Z = 30) are studied here. For H-like ions, the quantum-mechanical exact photoionization cross sections for nonrelativistic hydrogenic systems are usedto calculate the RR rate coefficients under the principle of detailed balance, while for He-like to Na-like ions, the archival data on ADAS are adopted. Parameterizations are made for the direct capture rates in a wide temperature range. The fitting accuracies are better than 5% for about 99% of the ~3 × 104 levels considered here. The ~1% exceptions include levels from low-charged many-electron ions, and/or high-shell (n ≳ 4) levels are less important in terms of interpreting X-ray emitting astrophysical plasmas. The RR data will be incorporated into the high-resolution spectral analysis package SPEX. Results of the parameterizations are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/587/A84
Rate coefficients, binding probabilities, and related quantities for area reactivity models.
Prüstel, Thorsten; Meier-Schellersheim, Martin
2014-11-21
We further develop the general theory of the area reactivity model that describes the diffusion-influenced reaction of an isolated receptor-ligand pair in terms of a generalized Feynman-Kac equation and that provides an alternative to the classical contact reactivity model. Analyzing both the irreversible and reversible reaction, we derive the equation of motion of the survival probability as well as several relationships between single pair quantities and the reactive flux at the encounter distance. Building on these relationships, we derive the equation of motion of the many-particle survival probability for irreversible pseudo-first-order reactions. Moreover, we show that the usual definition of the rate coefficient as the reactive flux is deficient in the area reactivity model. Numerical tests for our findings are provided through Brownian Dynamics simulations. We calculate exact and approximate expressions for the irreversible rate coefficient and show that this quantity behaves differently from its classical counterpart. Furthermore, we derive approximate expressions for the binding probability as well as the average lifetime of the bound state and discuss on- and off-rates in this context. Throughout our approach, we point out similarities and differences between the area reactivity model and its classical counterpart, the contact reactivity model. The presented analysis and obtained results provide a theoretical framework that will facilitate the comparison of experiment and model predictions. PMID:25416882
NASA Astrophysics Data System (ADS)
Wojnárovits, László; Takács, Erzsébet
1999-08-01
The OH radical induced oligomerization in dilute aqueous solution of ethyl- and 2-hydroxypropyl acrylate, methyl- and 2-hydroxypropyl methacrylate, acrylamide and methacrylamide, ethyl-fumarate and maleate was investigated by pulse- and steady-state radiolysis. In pulse radiolysis the reactions were observed by measuring the absorbance of the α-carboxyalkyl type radicals. At low concentration (⩽1 mmol dm -3) the radicals decay in self-termination. At higher concentration there is a significant deviation from the simple second order behavior due to oligomerization. Computer programs were used to calculate the rate coefficients of propagation and termination at the beginning of oligomerization.
On the accuracy of the rate coefficients used in plasma fluid models for breakdown in air
NASA Astrophysics Data System (ADS)
Kourtzanidis, Konstantinos; Raja, Laxminarayan L.
2016-07-01
The electrical breakdown of air depends on the balance between creation and loss of charged particles. In fluid models, datasets of the rate coefficients used are obtained either from fits to experimental data or by solutions of the Boltzmann equation. Here, we study the accuracy of the commonly used models for ionization and attachment frequencies and their impact on the prediction of the breakdown threshold for air. We show that large errors can occur depending on the model and propose the most accurate dataset available for modeling of air breakdown phenomena.
Xu, Shenghua; Liu, Jie; Sun, Zhiwei
2006-12-01
Turbidity measurement for the absolute coagulation rate constants of suspensions has been extensively adopted because of its simplicity and easy implementation. A key factor in deriving the rate constant from experimental data is how to theoretically evaluate the so-called optical factor involved in calculating the extinction cross section of doublets formed during aggregation. In a previous paper, we have shown that compared with other theoretical approaches, the T-matrix method provides a robust solution to this problem and is effective in extending the applicability range of the turbidity methodology, as well as increasing measurement accuracy. This paper will provide a more comprehensive discussion of the physical insight for using the T-matrix method in turbidity measurement and associated technical details. In particular, the importance of ensuring the correct value for the refractive indices for colloidal particles and the surrounding medium used in the calculation is addressed, because the indices generally vary with the wavelength of the incident light. The comparison of calculated results with experiments shows that the T-matrix method can correctly calculate optical factors even for large particles, whereas other existing theories cannot. In addition, the data of the optical factor calculated by the T-matrix method for a range of particle radii and incident light wavelengths are listed.
On the temperature dependence of the rate coefficient of formation of C2+ from C + CH+
NASA Astrophysics Data System (ADS)
Rampino, S.; Pastore, M.; Garcia, E.; Pacifici, L.; Laganà, A.
2016-08-01
We carry out quasi-classical trajectory calculations for the C + CH+→ C_2^+ + H reaction on an ad hoc computed high-level ab initio potential energy surface. Thermal rate coefficients at the temperatures of relevance in cold interstellar clouds are derived and compared with the assumed, temperature-independent estimates publicly available in kinetic data bases KIDA and UDfA. For a temperature of 10 K the data base value overestimates by a factor of 2 the one obtained by us (thus improperly enhancing the destruction route of CH+ in astrochemical kinetic models) which is seen to double in the temperature range 5-300 K with a sharp increase in the first 50 K. The computed values are fitted via the popular Arrhenius-Kooij formula and best-fitting parameters α = 1.32 × 10-9 cm3 s-1, β = 0.1 and γ = 2.19 K to be included in the online mentioned data bases are provided. Further investigation shows that the temperature dependence of the thermal rate coefficient better conforms to the recently proposed so-called `deformed Arrhenius' law by Aquilanti and Mundim.
NASA Technical Reports Server (NTRS)
Leone, Stephen R.
1995-01-01
The objectives of the research are to measure low temperature laboratory rate coefficients for key reactions relevant to the atmospheres of Titan and Saturn. These reactions are, for example, C2H + H2, CH4, C2H2, and other hydrocarbons which need to be measured at low temperatures, down to approximately 150 K. The results of this work are provided to NASA specialists who study modeling of the hydrocarbon chemistry of the outer planets. The apparatus for this work consists of a pulsed laser photolysis system and a tunable F-center probe laser to monitor the disappearance of C2H. A low temperature cell with a cryogenic circulating fluid in the outer jacket provides the gas handling system for this work. These elements have been described in detail in previous reports. Several new results are completed and the publications are just being prepared. The reaction of C2H with C2H2 has been measured with an improved apparatus down to 154 K. An Arrhenius plot indicates a clear increase in the rate coefficient at the lowest temperatures, most likely because of the long-lived (C4H3) intermediate. The capability to achieve the lowest temperatures in this work was made possible by construction of a new cell and addition of a multipass arrangement for the probe laser, as well as improvements to the laser system.
Behavior of rate coefficients for ion-ion mutual neutralization, 300-550 K
Miller, Thomas M.; Shuman, Nicholas S.; Viggiano, A. A.
2012-05-28
Rate coefficients k{sub MN} have been measured for a number of anion neutralization reactions with Ar{sup +} and Kr{sup +} over the temperature range 300-550 K. For the first time, the data set includes anions of radicals and other short-lived species. In the present paper, we review these results and make note of correlations with reduced mass, electron binding energy of the anion (equivalent to the electron affinity of the corresponding neutral), and temperature, and compare with expectations from absorbing sphere models. An intriguing result is that the data for diatomic anions neutralized by Ar{sup +} and Kr{sup +} have k{sub MN} values close to 3 x 10{sup -8} cm{sup 3} s{sup -1} at 300 K, a figure which is lower than those for all of the polyatomic anions at 300 K except for SF{sub 5}{sup -}+ Kr{sup +}. For the polyatomic anions studied here, neutralized by Ar{sup +} and Kr{sup +}, the reduced mass dependence agrees with theory, on average, but we find a stronger temperature dependence of T{sup -0.9} than expected from the theoretical E{sup -0.5} energy dependence of the rate coefficient at thermal energies. The k{sub MN} show a weak dependence on the electron binding energy of the anion for the polyatomic species studied.
Sandwich mixer-reactor: influence of the diffusion coefficient and flow rate ratios.
Abonnenc, Mélanie; Josserand, Jacques; Girault, Hubert H
2009-02-01
A sandwich mixer consists of mixing two solutions in a channel, one central laminar flow being sandwiched between two outer flow solutions. The present numerical study considers the convection-diffusion of two reacting species A and B, provided respectively by the two incoming solutions. The simulations show how the diffusion coefficient, flow rate and species concentration ratios influence, via the transversal diffusion length and reaction kinetics, the reaction extent at the end of the sandwich mixer. First, this extent can be enhanced up to 60% if the species with the lowest diffusion coefficient is located in the outer solutions where the flow velocity is small compared to that of the central part (higher residence time). Secondly, decreasing the outer flow rates (to confine the reaction close to the walls) and increasing the local concentration to keep the same flux ratio improve the extent by 300%. Comparison with a bi-lamination passive mixer, with an ideal mixer and an electro-osmotic driven flow mixer is presented. These conclusions are also demonstrated for consecutive reactions, showing an amplification of the effects described above. The results are also presented versus the residence time in the mixer-reactor to show the time window for which the gain is appreciable.
Estimating Reaction Rate Coefficients Within a Travel-Time Modeling Framework
Gong, R; Lu, C; Luo, Jian; Wu, Wei-min; Cheng, H.; Criddle, Craig; Kitanidis, Peter K.; Gu, Baohua; Watson, David B; Jardine, Philip M; Brooks, Scott C
2011-03-01
A generalized, efficient, and practical approach based on the travel-time modeling framework is developed to estimate in situ reaction rate coefficients for groundwater remediation in heterogeneous aquifers. The required information for this approach can be obtained by conducting tracer tests with injection of a mixture of conservative and reactive tracers and measurements of both breakthrough curves (BTCs). The conservative BTC is used to infer the travel-time distribution from the injection point to the observation point. For advection-dominant reactive transport with well-mixed reactive species and a constant travel-time distribution, the reactive BTC is obtained by integrating the solutions to advective-reactive transport over the entire travel-time distribution, and then is used in optimization to determine the in situ reaction rate coefficients. By directly working on the conservative and reactive BTCs, this approach avoids costly aquifer characterization and improves the estimation for transport in heterogeneous aquifers which may not be sufficiently described by traditional mechanistic transport models with constant transport parameters. Simplified schemes are proposed for reactive transport with zero-, first-, nth-order, and Michaelis-Menten reactions. The proposed approach is validated by a reactive transport case in a two-dimensional synthetic heterogeneous aquifer and a field-scale bioremediation experiment conducted at Oak Ridge, Tennessee. The field application indicates that ethanol degradation for U(VI)-bioremediation is better approximated by zero-order reaction kinetics than first-order reaction kinetics.
Estimating reaction rate coefficients within a travel-time modeling framework.
Gong, R; Lu, C; Wu, W-M; Cheng, H; Gu, B; Watson, D; Jardine, P M; Brooks, S C; Criddle, C S; Kitanidis, P K; Luo, J
2011-01-01
A generalized, efficient, and practical approach based on the travel-time modeling framework is developed to estimate in situ reaction rate coefficients for groundwater remediation in heterogeneous aquifers. The required information for this approach can be obtained by conducting tracer tests with injection of a mixture of conservative and reactive tracers and measurements of both breakthrough curves (BTCs). The conservative BTC is used to infer the travel-time distribution from the injection point to the observation point. For advection-dominant reactive transport with well-mixed reactive species and a constant travel-time distribution, the reactive BTC is obtained by integrating the solutions to advective-reactive transport over the entire travel-time distribution, and then is used in optimization to determine the in situ reaction rate coefficients. By directly working on the conservative and reactive BTCs, this approach avoids costly aquifer characterization and improves the estimation for transport in heterogeneous aquifers which may not be sufficiently described by traditional mechanistic transport models with constant transport parameters. Simplified schemes are proposed for reactive transport with zero-, first-, nth-order, and Michaelis-Menten reactions. The proposed approach is validated by a reactive transport case in a two-dimensional synthetic heterogeneous aquifer and a field-scale bioremediation experiment conducted at Oak Ridge, Tennessee. The field application indicates that ethanol degradation for U(VI)-bioremediation is better approximated by zero-order reaction kinetics than first-order reaction kinetics.
Determination of the global recombination rate coefficient for the ISX-B Tokamak
Langley, R.A.; Howe, H.C.
1983-01-01
The global recombination rate coefficient for hydrogen has been measured for the ISX-B tokamak vacuum vessel for various surface conditions. The measurements were performed by observing the rate of decrease of gas pressure in the vessel during a glow discharge. The parameters of the glow discharge and the complete experimental method are described. Previously published analytic and numerical models are used for data analysis. The effects of surface contamination on the results are described. For ''unclean'' wall conditions sigmak/sub r/ = 1.8 x 10/sup -28/ cm/sup 4//atom.s at 296 K and increases to sigmak/sub r/ = 4.4 x 10/sup -28/ cm/sup 4//atoms.s for ''clean'' conditions and remains constant until subsequent exposure to air.
NASA Astrophysics Data System (ADS)
Seetha, N.; Majid Hassanizadeh, S.; Mohan Kumar, M. S.; Raoof, Amir
2015-10-01
Nanoparticle deposition behavior observed at the Darcy scale represents an average of the processes occurring at the pore scale. Hence, the effect of various pore-scale parameters on nanoparticle deposition can be understood by studying nanoparticle transport at pore scale and upscaling the results to the Darcy scale. In this work, correlation equations for the deposition rate coefficients of nanoparticles in a cylindrical pore are developed as a function of nine pore-scale parameters: the pore radius, nanoparticle radius, mean flow velocity, solution ionic strength, viscosity, temperature, solution dielectric constant, and nanoparticle and collector surface potentials. Based on dominant processes, the pore space is divided into three different regions, namely, bulk, diffusion, and potential regions. Advection-diffusion equations for nanoparticle transport are prescribed for the bulk and diffusion regions, while the interaction between the diffusion and potential regions is included as a boundary condition. This interaction is modeled as a first-order reversible kinetic adsorption. The expressions for the mass transfer rate coefficients between the diffusion and the potential regions are derived in terms of the interaction energy profile. Among other effects, we account for nanoparticle-collector interaction forces on nanoparticle deposition. The resulting equations are solved numerically for a range of values of pore-scale parameters. The nanoparticle concentration profile obtained for the cylindrical pore is averaged over a moving averaging volume within the pore in order to get the 1-D concentration field. The latter is fitted to the 1-D advection-dispersion equation with an equilibrium or kinetic adsorption model to determine the values of the average deposition rate coefficients. In this study, pore-scale simulations are performed for three values of Péclet number, Pe = 0.05, 5, and 50. We find that under unfavorable conditions, the nanoparticle deposition at
Brummelhuis, Walter J; van Schelven, Leonard J; Boer, Walther H
2008-01-01
Methods to continuously measure absolute refill during dialysis are not available. It would be useful to have such a method because it would allow investigating the mechanism of refill the effect of interventions. We designed a feedback algorithm that adjusts ultrafiltration rate (QUF) according to hemoglobin (Hb) concentration changes in such a way that relative blood volume (BV) remains constant within a narrow target range. In this situation, the generated QUF quantitatively reflects refill. Refill patterns were studied in five hypotension prone patients. In addition, on separate occasions, we studied the effect of antiembolism stockings (AES) and infusion of hydroxy-ethylated starch (HAES) on refill in these patients. Refill during the first hour fell significantly from 21 +/- 3 ml/min to 9 +/- 2 ml/min (p < 0.05). In the second hour, refill decreased further and became zero in four out of five patients. Neither AES nor HAES measurably affected refill. The marked and rapid fall in refill in the early stages of dialysis suggests untimely depletion of the interstitial compartment and underestimation of dry weight. We propose that continuous, online measurement of refill patterns may be of value for accurate estimation of dry weight in dialysis patients. PMID:18204322
Tillmann, Ralf; Saathoff, Harald; Brauers, Theo; Kiendler-Scharr, Astrid; Mentel, Thomas F
2009-04-01
The absolute rate coefficient for the reaction of alpha-pinene with ozone was determined in the temperature range between 243 K and 303 K at atmospheric pressure. In total, 30 experiments were performed in the large (85 m3) temperature-controlled simulation chamber AIDA, where the concentrations of the reactants ozone and alpha-pinene were measured directly. An Arrhenius expression for the alpha-pinene + ozone reaction was derived with a pre-exponential factor of (1.4 +/- 0.4) x 10(-15) cm3 s(-1) and a temperature coefficient of (833 +/- 86) K. This rate coefficient is in good agreement (-5%) with the current IUPAC (IUPAC 2007) recommendation at 298 K. The IUPAC recommendation is significantly larger (+27%), around 243 K where the recommended values were extrapolated from higher temperatures. This finding is relevant for tropical regions where strong updrafts can rapidly transport reactive hydrocarbons like alpha-pinene from the boundary layer into the cold regions of the free troposphere.
Time-dependent methods for calculating thermal rate coefficients using flux correlation functions
NASA Astrophysics Data System (ADS)
Thachuk, Mark; Schatz, George C.
1992-11-01
In this paper we study numerical methods for calculating thermal rate coefficients using flux correlation functions, with the goal of determining optimal methods for producing values with a specified accuracy. In all cases we employ grid based methods for solving the time-dependent Schrödinger equation in one mathematical dimension for a simple barrier potential function. The solutions are used to determine the propagator matrix elements needed to evaluate the flux correlation functions. Within this framework, we examine (1) several time-dependent methods for propagating the wave packets, (2) several procedures for evaluating the action of the Hamiltonian on the wave function, (3) the choice of complex time contours for evaluating the rate coefficient expression, (4) alternatives for estimating the initial short-time evolution of the wave packet (which starts as a δ function), (5) quadrature methods for evaluating the spatial and time integrals appearing in the flux correlation function, and (6) special numerical strategies which can dramatically improve the accuracy of the calculation, particularly at low temperatures. We find that several methods yield rate coefficients accurate to 1% or 0.1% using about the same computational effort. These include (a) split-operator time propagators combined with fast-Fourier-transform evaluations of the wave-function derivatives, and (b) the Chebyshev time propagator combined with either an eleventh-order finite-difference or fifth-order spline evaluation of the wave-function derivatives. These finite-difference and spline methods can also be used competitively with the split-operator approach provided that a Crank-Nicholson approximation is utilized in evaluating the action of the kinetic-energy propagator. It was also found that inaccuracies in estimating the initial short-time behavior of the wave function could limit the effectiveness of the more accurate methods. A multigrid approach based on the split
NASA Technical Reports Server (NTRS)
Chackerian, Charles, Jr.; Freedman, R.; Giver, L. P.; Brown, L. R.
2001-01-01
The rotationless transition moment squared for the x(sup 1) sigma (sup +) v=3 (left arrow) v=0 band of CO is measured to be the absolute value of R (sub 3-0) squared = 1.7127(25)x 10(exp -7) Debye squared. This value is about 8.6 percent smaller than the value assumed for HITRAN 2000. The Herman-Wallis intensity factor of this band is F=1+0.01168(11)m+0.0001065(79)m squared. The determination of self-broadening coefficients is improved with the inclusion of line narrowing; self-shifts are also reported.
Revised rate coefficients for H2 and H- destruction by realistic stellar spectra
NASA Astrophysics Data System (ADS)
Agarwal, Bhaskar; Khochfar, Sadegh
2015-01-01
Understanding the processes that can destroy H2 and H- species is quintessential in governing the formation of the first stars, black holes and galaxies. In this study, we compute the reaction rate coefficients for H2 photodissociation by Lyman-Werner photons (11.2-13.6 eV) and H- photodetachment by 0.76 eV photons emanating from self-consistent stellar populations that we model using publicly available stellar synthesis codes. So far, studies that include chemical networks for the formation of molecular hydrogen take these processes into account by assuming that the source spectra can be approximated by a power-law dependence or a blackbody spectrum at 104 or 105 K. We show that using spectra generated from realistic stellar population models can alter the reaction rates for photodissociation, kdi, and photodetachment, kde, significantly. In particular, kde can be up to ˜2-4 orders of magnitude lower in the case of realistic stellar spectra suggesting that previous calculations have overestimated the impact that radiation has on lowering H2 abundances. In contrast to burst modes of star formation, we find that models with continuous star formation predict increasing kde and kdi, which makes it necessary to include the star formation history of sources to derive self-consistent reaction rates, and that it is not enough to just calculate J21 for the background. For models with constant star formation rate, the change in shape of the spectral energy distribution leads to a non-negligible late-time contribution to kde and kdi, and we present self-consistently derived cosmological reaction rates based on star formation rates consistent with observations of the high-redshift Universe.
Mikitishin, S.I.; Fedorov, V.V.; Sergienko, O.M.; Sokolovskii, O.R.; Spas, Y.M.
1985-07-01
A proposed method of measuring the diffusion coefficient of hydrogen D from the rate of change in electrical resistance in degassing of hydrogenimpregnated specimens is presented. Distinguished by simplicity, the method makes it possible to determine the coefficients with any method of hydrogen impregnation in a broad temperature range.
New potential energy surface for the HCS{sup +}–He system and inelastic rate coefficients
Dubernet, Marie-Lise; Quintas-Sánchez, Ernesto; Tuckey, Philip
2015-07-28
A new high quality potential energy surface is calculated at a coupled-cluster single double triple level with an aug-cc-pV5Z basis set for the HCS{sup +}–He system. This potential energy surface is used in low energy quantum scattering calculations to provide a set of (de)-excitation cross sections and rate coefficients among the first 20 rotational levels of HCS{sup +} by He in the range of temperature from 5 K to 100 K. The paper discusses the impact of the new ab initio potential energy surface on the cross sections at low energy and provides a comparison with the HCO{sup +}–He system. The HCS{sup +}–He rate coefficients for the strongest transitions differ by factors of up to 2.5 from previous rate coefficients; thus, analysis of astrophysical spectra should be reconsidered with the new rate coefficients.
Schwartz, S.E.
1988-10-01
Although it has been recognized for some time that the rate of reactive uptake of gases in cloudwater can depend on the value of the mass-accommodation coefficient (..cap alpha..) describing interfacial mass transport (MT), definitive evaluation of such rates is only now becoming possible with the availability of measurements of ..cap alpha.. for gases of atmospheric interest at air-water interfaces. Examination of MT limitation to the rate of in-cloud aqueous-phase oxidation of SO/sub 2/ by O/sub 3/ and H/sub 2/O/sub 2/ shows that despite the low value of ..cap alpha../sub O3/ (5 /times/ 10/sup /minus/4/), interfacial MT of this species is not limiting under essentially all conditions of interest; the high values of ..cap alpha.. for SO/sub 2/ (greater than or equal to 0.2) and H/sub 2/O/sub 2/ (greater than or equal to 0.08) indicate no interfacial MT limitation for these species also. Although gas- and aqueous-phase MT can be limiting under certain extremes of conditions, treating the system as under chemical kinetic control is generally an excellent approximation. Interfacial MT limitation also is found not to hinder the rate of H/sub 2/O/sub 2/ formation by aqueous-phase disproportionation of HO/sub 2/. Finally, the rapid uptake of N/sub 2/O/sub 5/ by cloud droplets implies that the yield of aqueous HNO/sub 3/ from in-cloud gas-phase oxidation of NO/sub 2/by O/sub 3/ can be substantial even under daytime conditions. This report consists of copies of viewgraphs prepared for this presentation.
Ar II Emission Processes and Emission Rate Coefficients in ASTRAL Helicon Plasmas
NASA Astrophysics Data System (ADS)
Boivin, R. F.; Gardner, A.; Kamar, O.; Kesterson, A.; Loch, S.; Munoz, J.; Ballance, C.
2008-11-01
Emission processes for Ar II line emission are described for low temperature plasmas (Te < 10 eV). It is found that Ar II emission results primarily from Ar ion ground state excitation rather than from any Ar neutral state. This suggests that Ar II emission results from stepping processes which includes ionization and then excitation of the neutral Ar atom filling the vacuum chamber. The Ar II emission rate coefficients are measured in the ASTRAL helicon plasma source using a 0.33 m monochromator and a CCD camera. ASTRAL produces Ar plasmas with the following parameters: ne = 1E11 -- 1E13 cm-3 and Te = 2 - 10 eV, B-field <= 1.3 kGauss, rf power <= 2 kWatt. RF compensated Langmuir probes are used to measure Te and ne. In this experiment, Ar II transitions are monitored as a function of Te while ne is kept constant. Experimental emission rates are obtained as a function of Te and compared to theoretical predictions. Theoretical predictions make use of the ADAS suite of codes as well as recent R-matrix electron-impact excitation calculations that includes pseudo-states contributions. Our collisional-radiative formalism assumes that the excited levels are in quasi-static equilibrium with the ground and metastable populations.
Gómez-Carrasco, Susana; Godard, Benjamin; Lique, François; Bulut, Niyazi; Kłos, Jacek; Roncero, Octavio; Aguado, Alfredo; Aoiz, F. Javier; Castillo, Jesús F.; Goicoechea, Javier R.; Etxaluze, Mireya; Cernicharo, José
2014-10-10
The rate constants required to model the OH{sup +} observations in different regions of the interstellar medium have been determined using state of the art quantum methods. First, state-to-state rate constants for the H{sub 2}(v = 0, J = 0, 1) + O{sup +}({sup 4} S) → H + OH{sup +}(X {sup 3}Σ{sup –}, v', N) reaction have been obtained using a quantum wave packet method. The calculations have been compared with time-independent results to assess the accuracy of reaction probabilities at collision energies of about 1 meV. The good agreement between the simulations and the existing experimental cross sections in the 0.01-1 eV energy range shows the quality of the results. The calculated state-to-state rate constants have been fitted to an analytical form. Second, the Einstein coefficients of OH{sup +} have been obtained for all astronomically significant rovibrational bands involving the X {sup 3}Σ{sup –} and/or A {sup 3}Π electronic states. For this purpose, the potential energy curves and electric dipole transition moments for seven electronic states of OH{sup +} are calculated with ab initio methods at the highest level, including spin-orbit terms, and the rovibrational levels have been calculated including the empirical spin-rotation and spin-spin terms. Third, the state-to-state rate constants for inelastic collisions between He and OH{sup +}(X {sup 3}Σ{sup –}) have been calculated using a time-independent close coupling method on a new potential energy surface. All these rates have been implemented in detailed chemical and radiative transfer models. Applications of these models to various astronomical sources show that inelastic collisions dominate the excitation of the rotational levels of OH{sup +}. In the models considered, the excitation resulting from the chemical formation of OH{sup +} increases the line fluxes by about 10% or less depending on the density of the gas.
Coughlin, Jeffrey L.; Harrison, Thomas E.; Gelino, Dawn M.
2010-11-10
We present a novel technique to determine the absolute inclination of single stars using multi-wavelength submilliarcsecond astrometry. The technique exploits the effect of gravity darkening, which causes a wavelength-dependent astrometric displacement parallel to a star's projected rotation axis. We find that this effect is clearly detectable using SIM Lite for various giant stars and rapid rotators, and present detailed models for multiple systems using the REFLUX code. We also explore the multi-wavelength astrometric reflex motion induced by spots on single stars. We find that it should be possible to determine spot size, relative temperature, and some positional information for both giant and nearby main-sequence stars utilizing multi-wavelength SIM Lite data. These data will be extremely useful in stellar and exoplanet astrophysics, as well as supporting the primary SIM Lite mission through proper multi-wavelength calibration of the giant star astrometric reference frame, and reduction of noise introduced by starspots when searching for extrasolar planets.
Franz, James A.; Kolwaite, Douglas S.; Linehan, John C.; Rosenberg, Edward
2004-02-02
Absolute rate constants for hydrogen atom abstraction by benzyl radical from Os3(m-H)2 (CO)9PPh3(1), Os3 (m-H)(H)(CO)10PPh3(2), Os3(m-H)(CO)9(m3-h2-C9H6N)(3), Os3(m-H)(CO)9(m-h2-C9H6N)PPh3 (5) and Os3(m-H)(CO)10(m-h2-C9H6N) (4) were determined in benzene by competition of the abstraction reaction with the self termination of benzyl radical. Thus, experimental values of kabs/kt1/2 were combined with rate constants for self-termination of benzyl radical in benzene from the expression ln(2kt/M-1s-1= 27.23 - 2952.4/RT), RT in cal/mol, to give absolute rate constants for abstraction, kabs: for Os3(m-H)2 (CO)9PPh3(1) in benzene, log (kabs/M-1s-1)= (8.86 .20) - (6.90 .31)/q; for Os3 (m-H)(H)(CO)(10PPh3) (2) log (kabs/M-1s-1)= (8.15 .49) - (4.41 .72)/q; for Os3(m-H)(CO)9(m3-h2-C9H6N) (3) log (kabs/M-1s-1)= (8.9 2) (8.8 3)/q; value for 4 and for Os3(m-H)(CO9)(m-h2-C9H6N)(PPh3) (5) log (kabs/M-1s-1)= (7.0 .38) - (4.15 .56)/q, q= 2.303RT kcal/mol. The terminal hydride on the Os3 c luster 2 is about 10 times more reactive than bridging hydride in 1. The results show that while m-H bridging retards the rate of hydrogen abstraction relative to terminal hydrogen, the bridging hydrogen remains appreciably reactive in the m-H form. In fact, the highest rate observed was for the bridging hydride in 4, Os3(m-H)(CO)10(m-h2-C9H6N). Temperature dependent kinetics for compound 4 were not determined because of significant CO loss above room temperature. However at 293 K the rate constant of hydrogen atom abstraction from this electron-rich cluster, 5 2 x 104 M-1s-1, is at least twice as fast as that for the terminal hydrogen atom cluster, 2, Os3 (m-H)(H)(CO)10PPh3, kabs (298 K)= 1.8 x 104 M-1s-1. The rate constants for hydrogen atom abstraction by benzyl radical from these osmium clusters increase with increasing electron density on the osmium cluster and decrease with increasing steric bulk of the ligands.
Shaw, A; Takács, I; Pagilla, K R; Murthy, S
2013-10-15
The Monod equation is often used to describe biological treatment processes and is the foundation for many activated sludge models. The Monod equation includes a "half-saturation coefficient" to describe the effect of substrate limitations on the process rate and it is customary to consider this parameter to be a constant for a given system. The purpose of this study was to develop a methodology, and its use to show that the half-saturation coefficient for denitrification is not constant but is in fact a function of the maximum denitrification rate. A 4-step procedure is developed to investigate the dependency of half-saturation coefficients on the maximum rate and two different models are used to describe this dependency: (a) an empirical linear model and (b) a deterministic model based on Fick's law of diffusion. Both models are proved better for describing denitrification kinetics than assuming a fixed K(NO3) at low nitrate concentrations. The empirical model is more utilitarian whereas the model based on Fick's law has a fundamental basis that enables the intrinsic K(NO3) to be estimated. In this study data was analyzed from 56 denitrification rate tests and it was found that the extant K(NO3) varied between 0.07 mgN/L and 1.47 mgN/L (5th and 95th percentile respectively) with an average of 0.47 mgN/L. In contrast to this, the intrinsic K(NO3) estimated for the diffusion model was 0.01 mgN/L which indicates that the extant K(NO3) is greatly influenced by, and mostly describes, diffusion limitations.
Cranor, W.L.; Alvarez, D.A.; Huckins, J.N.; Petty, J.D.
2009-01-01
To fully utilize semipermeable membrane devices (SPMDs) as passive samplers in air monitoring, data are required to accurately estimate airborne concentrations of environmental contaminants. Limited uptake rate constants (kua) and no SPMD air partitioning coefficient (Ksa) existed for vapor-phase contaminants. This research was conducted to expand the existing body of kinetic data for SPMD air sampling by determining kua and Ksa for a number of airborne contaminants including the chemical classes: polycyclic aromatic hydrocarbons, organochlorine pesticides, brominated diphenyl ethers, phthalate esters, synthetic pyrethroids, and organophosphate/organosulfur pesticides. The kuas were obtained for 48 of 50 chemicals investigated and ranged from 0.03 to 3.07??m3??g-1??d-1. In cases where uptake was approaching equilibrium, Ksas were approximated. Ksa values (no units) were determined or estimated for 48 of the chemicals investigated and ranging from 3.84E+5 to 7.34E+7. This research utilized a test system (United States Patent 6,877,724 B1) which afforded the capability to generate and maintain constant concentrations of vapor-phase chemical mixtures. The test system and experimental design employed gave reproducible results during experimental runs spanning more than two years. This reproducibility was shown by obtaining mean kua values (n??=??3) of anthracene and p,p???-DDE at 0.96 and 1.57??m3??g-1??d-1 with relative standard deviations of 8.4% and 8.6% respectively.
Electron Impact Ionization Cross Sections and Rate Coefficients for Single Carbon Freon Molecules
NASA Astrophysics Data System (ADS)
Pal, Satyendra; Kumar, Neeraj
2015-09-01
Single carbon Freon molecules or chlorofluorocarbons (CFCs) are important industrial material with wide-ranging applications as refrigerant, aerosol propellant and semiconductor etchant, etc. The large-scale industrial consumption is of particular environmental concern because of its potential for ozone destruction in the stratosphere. In the present work, we have extended and generalized the modified Jain-Khare (JK) semi-empirical formalism for the evaluation of the total ionization cross sections corresponding to the formation of the cations in the electron impact ionization of molecules to the electron impact ionization of single carbon freon molecules, viz. CFCl3, CF2Cl2 and CF3Cl. The integral partial and the total ionization cross sections as function of incident electron energy are evaluated in the energy range varying from ionization threshold to 1000 eV. In absence of available differential cross sections, the corresponding derived partial and total ionization cross sections revealed a reasonably good agreement with the experimental and theoretical data, wherever available. In addition to the differential and integral ionization cross sections, we have also calculated the ionization rate coefficients using the evaluated partial ionization cross sections and the Maxwell-Boltzmann distribution as a function of electron temperature/energy. The work is supported by DST, New Delhi, India.
Ionization cross sections and rate coefficients for CFCl3 molecule by electron impact
NASA Astrophysics Data System (ADS)
Pal, Satyendra; Kumar, Neeraj
2013-09-01
Chlorofluorocarbons (CFCs) or freons are important industrial material with wide-ranging applications as refrigerant, aerosol propellant and semiconductor etchant, etc. The large-scale industrial consumption is of particular environmental concern because of its potential for ozone destruction in the stratosphere. The present work reports the calculations for differential cross sections as a function of secondary/ ejected electron energy and the scattering angle in the ionization of CFCl3 by electron collision leading to the production of various cations viz. CCl3+,CFCl2+,CCl2+,CFCl+, CCl+, Cl+, CF+, F+, and C+ through direct and dissociative ionization processes at a fixed incident electron energy of 200 eV. A modified Jain-Khare semi-empirical formalism based on oscillator strength has been employed. To the best of our knowledge, no experimental and/or theoretical data is available for comparison of the present results for differential cross sections. The corresponding derived integral cross sections in terms of the partial ionization cross sections corresponding to these cations, in the energy range varying from ionization threshold to 1000 eV, revealed a reasonably good agreement with the experimental and theoretical data, wherever available. In addition to the differential and integral ionization cross sections, we have also calculated the ionization rate coefficients using the evaluated partial ionization cross sections and the Maxwell-Boltzmann distribution as a function of electron energy.
Datsyuk, Vitaly V.; Juodkazis, Saulius; Misawa, Hiroaki
2005-08-15
The rate of spontaneous electromagnetic emission in a cavity is the normalized output radiation rate in the classical electrodynamics and the Einstein A coefficient in a quantum theory. We reveal the difference and similarity between the quantum and classical rates by calculations of the relative output power of the resonant spontaneous electric-dipole emission as a function of light absorption in a high-Q cavity. We show that the relative resonant output power is equal to the relative width of a morphology-dependent resonance in the spectral dependence of the Einstein A coefficient. The validity of the theory is demonstrated by numerical verification of an experimental result on a microsphere.
Rate Coefficients of the HCl + OH → Cl + H2O Reaction from Ring Polymer Molecular Dynamics.
Zuo, Junxiang; Li, Yongle; Guo, Hua; Xie, Daiqian
2016-05-26
Thermal rate coefficients at temperatures between 200 and 1000 K are calculated for the HCl + OH → Cl + H2O reaction on a recently developed permutation invariant potential energy surface, using ring polymer molecular dynamics (RPMD). Large deviations from the Arrhenius limit are found at low temperatures, suggesting significant quantum tunneling. Agreement with available experimental rate coefficients is generally satisfactory, although the deviation becomes larger at lower temperatures. The theory-experiment discrepancy is attributed to the remaining errors in the potential energy surface, which is known to slightly overestimate the barrier. In the deep tunneling region, RPMD performs better than traditional transition-state theory with semiclassical tunneling corrections.
Barbosa, Thaís da Silva; Peirone, Silvina; Barrera, Javier A; Abrate, Juan P A; Lane, Silvia I; Arbilla, Graciela; Bauerfeldt, Glauco Favilla
2015-04-14
The kinetics of the cis-3-hexene + OH reaction were investigated by an experimental relative rate method and at the density functional theory level. The experimental set-up consisted of a 200 L Teflon bag, operated at atmospheric pressure and 298 K. OH radicals were produced by the photolysis of H2O2 at 254 nm. Relative rate coefficients were determined by comparing the decays of the cis-3-hexene and reference compounds (cyclohexene, 2-buten-1-ol and allyl ether). The mean second-order rate coefficient value found was (6.27 ± 0.66) × 10(-11) cm(3) molecule(-1) s(-1), the uncertainty being estimated by propagation of errors. Theoretical calculations for the addition reaction of OH to cis-3-hexene have also been performed, at the BHandHLYP/aug-cc-pVDZ level, in order to investigate the reaction mechanism, to clarify the experimental observations and to model the reaction kinetics. Different conformations of the reactants, pre-barrier complexes and saddle points were considered in our calculations. The individual rate coefficients, calculated for each conformer of the reactant, at 298 K, using a microcanonical variational transition state method, are 4.19 × 10(-11) and 1.23 × 10(-10) cm(3) molecule(-1) s(-1). The global rate coefficient was estimated from the Boltzmann distribution of the conformers to be 8.10 × 10(-11) cm(3) molecule(-1) s(-1), which is in agreement with the experimental value. Rate coefficients calculated over the temperature range from 200-500 K are also given. Our results suggest that the complex mechanism, explicitly considering different conformations for the stationary points, must be taken into account for a proper description of the reaction kinetics.
NASA Technical Reports Server (NTRS)
Laufer, A. H.; Gardner, E. P.; Kwok, T. L.; Yung, Y. L.
1983-01-01
The rate coefficients, including Arrhenius parameters, have been computed for a number of chemical reactions involving hydrocarbon species for which experimental data are not available and which are important in planetary atmospheric models. The techniques used to calculate the kinetic parameters include the Troe and semiempirical bond energy-bond order (BEBO) or bond strength-bond length (BSBL) methods.
NASA Technical Reports Server (NTRS)
Herbst, E.; Leung, C. M.
1986-01-01
In order to incorporate large ion-polar neutral rate coefficients into existing gas phase reaction networks, it is necessary to utilize simplified theoretical treatments because of the significant number of rate coefficients needed. The authors have used two simple theoretical treatments: the locked dipole approach of Moran and Hamill for linear polar neutrals and the trajectory scaling approach of Su and Chesnavich for nonlinear polar neutrals. The former approach is suitable for linear species because in the interstellar medium these are rotationally relaxed to a large extent and the incoming charged reactants can lock their dipoles into the lowest energy configuration. The latter approach is a better approximation for nonlinear neutral species, in which rotational relaxation is normally less severe and the incoming charged reactants are not as effective at locking the dipoles. The treatments are in reasonable agreement with more detailed long range theories and predict an inverse square root dependence on kinetic temperature for the rate coefficient. Compared with the locked dipole method, the trajectory scaling approach results in rate coefficients smaller by a factor of approximately 2.5.
NASA Technical Reports Server (NTRS)
Savin, D. W.; Gwinner, G.; Schwalm, D.; Wolf, A.; Mueller, A.; Schippers, S.
2002-01-01
Low temperature dielectronic recombination (DR) is the dominant recombination mechanism for most ions in X-ray photoionized cosmic plasmas. Reliably modeling and interpreting spectra from these plasmas requires accurate low temperature DR rate Coefficients. Of particular importance are the DR rate coefficients for the iron L-shell ions (Fe XVII-Fe XXIV). These ions are predicted to play an important role in determining the thermal structure and line emission of X-ray photoionized plasmas, which form in the media surrounding accretion powered sources such as X-ray binaries (XRBs), active galactic nuclei (AGN), and cataclysmic variables (Savin et al., 2000). The need for reliable DR data of iron L-shell ions has become particularly urgent after the launches of Chandra and XMM-Newton. These satellites are now providing high-resolution X-ray spectra from a wide range of X-ray photoionized sources. Interpreting the spectra from these sources requires reliable DR rate coefficients. However, at the temperatures relevant, for X-ray photoionized plasmas, existing theoretical DR rate coefficients can differ from one another by factors of two to orders of magnitudes.
NASA Astrophysics Data System (ADS)
Denisov, Vasilii
2016-08-01
In this report, we study sufficient conditions on the lower order coefficients of a parabolic equation guaranteeing the power rate of the uniform stabilization to zero of the solution to the Cauchy problem on every compact K in RN and for any bounded initial function.
Preliminary Report on Use of Self-Ratings to Provide J-Coefficient Data.
ERIC Educational Resources Information Center
Primoff, Ernest S.
This report shows how Beta weights for the J-Coefficient may be easily developed without a formal validity study, and indicates how indications of ability other than tests can be used to measure the same abilities that are measured by tests. See also TM 001 163-64,166 for further information on job elements (J-Scale) procedures. (Author/DLG)
LABORATORY STUDY OF RATE COEFFICIENTS FOR H{sub 2}O:He INELASTIC COLLISIONS BETWEEN 20 AND 120 K
Tejeda, G.; Moreno, E.; Fernández, J. M.; Montero, S.; Carmona-Novillo, E.; Hernández, M. I.
2015-01-01
State-to-state rate coefficients for ortho-H{sub 2}O:He and para-H{sub 2}O:He inelastic collisions in the 20-120 K thermal range are investigated by means of an improved experimental procedure. This procedure is based on the use of a kinetic master equation (MEQ) which describes the evolution of populations of H{sub 2}O rotational levels along a supersonic jet of H{sub 2}O highly diluted in helium. The MEQ is expressed in terms of experimental observables and rate coefficients for H{sub 2}O:He inelastic collisions. The primary experimental observables are the local number density and the populations of the rotational energy levels of H{sub 2}O, quantities which are determined along the jet with unprecedented accuracy by means of Raman spectroscopy with high space resolution. Sets of rate coefficients from the literature and from present close-coupling calculations using two different potential energy surfaces (PESs) have been tested against the experiment. The Green et al. rate coefficients are up to 50% too low compared to the experiment, while most rates calculated here from the Hodges et al. PES and the Patkowski et al. PES are much closer to the experimental values. Experimental rates with an estimated accuracy on the order of 10% have been obtained for ortho-H{sub 2}O:He and para-H{sub 2}O:He inelastic collisions between 20 and 120 K by scaling and averaging the theoretical rates to the experiment.
Cheng, Kai-Chung; Acevedo-Bolton, Viviana; Jiang, Ruo-Ting; Klepeis, Neil E; Ott, Wayne R; Fringer, Oliver B; Hildemann, Lynn M
2011-05-01
For modeling exposure close to an indoor air pollution source, an isotropic turbulent diffusion coefficient is used to represent the average spread of emissions. However, its magnitude indoors has been difficult to assess experimentally due to limitations in the number of monitors available. We used 30-37 real-time monitors to simultaneously measure CO at different angles and distances from a continuous indoor point source. For 11 experiments involving two houses, with natural ventilation conditions ranging from <0.2 to >5 air changes per h, an eddy diffusion model was used to estimate the turbulent diffusion coefficients, which ranged from 0.001 to 0.013 m² s⁻¹. The model reproduced observed concentrations with reasonable accuracy over radial distances of 0.25-5.0 m. The air change rate, as measured using a SF₆ tracer gas release, showed a significant positive linear correlation with the air mixing rate, defined as the turbulent diffusion coefficient divided by a squared length scale representing the room size. The ability to estimate the indoor turbulent diffusion coefficient using two readily measurable parameters (air change rate and room dimensions) is useful for accurately modeling exposures in close proximity to an indoor pollution source.
Bai, Shirong; Davis, Michael J; Skodje, Rex T
2015-11-12
The sensitivity of kinetic observables is analyzed using a newly developed sum over histories representation of chemical kinetics. In the sum over histories representation, the concentrations of the chemical species are decomposed into the sum of probabilities for chemical pathways that follow molecules from reactants to products or intermediates. Unlike static flux methods for reaction path analysis, the sum over histories approach includes the explicit time dependence of the pathway probabilities. Using the sum over histories representation, the sensitivity of an observable with respect to a kinetic parameter such as a rate coefficient is then analyzed in terms of how that parameter affects the chemical pathway probabilities. The method is illustrated for species concentration target functions in H2 combustion where the rate coefficients are allowed to vary over their associated uncertainty ranges. It is found that large sensitivities are often associated with rate limiting steps along important chemical pathways or by reactions that control the branching of reactive flux.
NASA Astrophysics Data System (ADS)
Shizgal, Bernie D.
2016-08-01
Nonclassical quadratures based on a new set of half-range polynomials, Tn(x) , orthogonal with respect to w(x) =e - x - b /√{ x } for x ∈ [ 0 , ∞) are employed in the efficient calculation of the nuclear fusion reaction rate coefficients from cross section data. The parameter b = B /√{kB T } in the weight function is temperature dependent and B is the Gamow factor. The polynomials Tn(x) satisfy a three term recurrence relation defined by two sets of recurrence coefficients, αn and βn. These recurrence coefficients define in turn the tridiagonal Jacobi matrix whose eigenvalues are the quadrature points and the weights are calculated from the first components of the eigenfunctions. For nonresonant nuclear reactions for which the astrophysical function can be expressed as a lower order polynomial in the relative energy, the convergence of the thermal average of the reactive cross section with this nonclassical quadrature is extremely rapid requiring in many cases 2-4 quadrature points. The results are compared with other libraries of nuclear reaction rate coefficient data reported in the literature.
NASA Technical Reports Server (NTRS)
Fang, Z.; Kwong, Victor H. S.
1997-01-01
The charge transfer rate coefficient for the reaction N(2+)(2p(sup 2)P(sup 0)) + He yields products is measured by recording the time dependence of the N(2+) ions stored in an ion trap. A cylindrical radio-frequency ion trap was used to store N(2+) ions produced by laser ablation of a solid titanium nitride target. The decay of the ion signals was analyzed by single exponential least-squares fits to the data. The measured rate coefficient is 8.67(0.76) x 10(exp -11)sq cm/s. The N(2+) ions were at a mean energy of 2.7 eV while He gas was at room temperature, corresponding to an equivalent temperature of 3.9 x 10(exp 3) K. The measured value is in good agreement with a recent calculation.
Caravan, Rebecca L; Shannon, Robin J; Lewis, Thomas; Blitz, Mark A; Heard, Dwayne E
2015-07-16
The low temperature kinetics of the reactions of OH with ethanol and propan-2-ol have been studied using a pulsed Laval nozzle apparatus coupled with pulsed laser photolysis-laser-induced fluorescence (PLP-LIF) spectroscopy. The rate coefficients for both reactions have been found to increase significantly as the temperature is lowered, by approximately a factor of 18 between 293 and 54 K for ethanol, and by ∼10 between 298 and 88 K for OH + propan-2-ol. The pressure dependence of the rate coefficients provides evidence for two reaction channels: a zero pressure bimolecular abstraction channel leading to products and collisional stabilization of a weakly bound OH-alcohol complex. The presence of the abstraction channel at low temperatures is rationalized by a quantum mechanical tunneling mechanism, most likely through the barrier to hydrogen abstraction from the OH moiety on the alcohol.
NASA Astrophysics Data System (ADS)
Burkholder, J. B.; Baasandorj, M.; Fleming, E. L.; Jackman, C. H.
2012-12-01
A key stratospheric loss process for ozone depleting substances (ODSs) and greenhouse gases (GHGs) is their gas-phase reaction with electronically excited oxygen atoms, O(1D). Although numerous O(1D) reactions have been studied in the past, large uncertainties in the recommended rate coefficients and reactive yields, i.e., loss of ODS or GHG, for use in atmospheric modeling still exist for a number of key compounds. Our understanding of the coupling of atmospheric chemistry and climate-change requires the most accurate reaction rate coefficient data to be used in climate-change model calculations. In this presentation, results from an extensive laboratory study of the total reaction rate coefficient, corresponding to loss of O(1D), and reactive rate coefficients, corresponding to the loss of the reactant compound, will be presented for the ODSs: CFCl3 (CFC-11), CF2Cl2 (CFC-12), CFCl2CF2Cl (CFC-113), CF2ClCF2Cl (CFC-114), CF3CF2Cl (CFC-115), HClCF2 (HCFC-22), CH3CClF2 (HCFC-142b); GHGs: CHF3 (HFC-23), CHF2CF3 (HFC-125), CF3CHCF3 (HFC-227ea), and CF3CH3 (HFC-143a); and the persistent (long-lived) GHGs: NF3, SF5CF3, C2F6, c-C4F8, n-C5F12, and n-C6F14. The results from this work will be compared with results from previous studies and discrepancies discussed along with the atmospheric implications of the improved kinetic dataset on the atmospheric lifetimes of these compounds.
Yao, Kangning; Chi, Yong; Wang, Fei; Yan, Jianhua; Ni, Mingjiang; Cen, Kefa
2016-01-01
A commonly used aeration device at present has the disadvantages of low mass transfer rate because the generated bubbles are several millimeters in diameter which are much bigger than microbubbles. Therefore, the effect of a microbubble on gas-liquid mass transfer and wastewater treatment process was investigated. To evaluate the effect of each bubble type, the volumetric mass transfer coefficients for microbubbles and conventional bubbles were determined. The volumetric mass transfer coefficient was 0.02905 s(-1) and 0.02191 s(-1) at a gas flow rate of 0.67 L min(-1) in tap water for microbubbles and conventional bubbles, respectively. The degradation rate of simulated municipal wastewater was also investigated, using aerobic activated sludge and ozone. Compared with the conventional bubble generator, the chemical oxygen demand (COD) removal rate was 2.04, 5.9, 3.26 times higher than those of the conventional bubble contactor at the same initial COD concentration of COD 200 mg L(-1), 400 mg L(-1), and 600 mg L(-1), while aerobic activated sludge was used. For the ozonation process, the rate of COD removal using microbubble generator was 2.38, 2.51, 2.89 times of those of the conventional bubble generator. Based on the results, the effect of initial COD concentration on the specific COD degradation rate were discussed in different systems. Thus, the results revealed that microbubbles could enhance mass transfer in wastewater treatment and be an effective method to improve the degradation of wastewater.
NASA Astrophysics Data System (ADS)
Phillips, Alfred, Jr.
Summ means the entirety of the multiverse. It seems clear, from the inflation theories of A. Guth and others, that the creation of many universes is plausible. We argue that Absolute cosmological ideas, not unlike those of I. Newton, may be consistent with dynamic multiverse creations. As suggested in W. Heisenberg's uncertainty principle, and with the Anthropic Principle defended by S. Hawking, et al., human consciousness, buttressed by findings of neuroscience, may have to be considered in our models. Predictability, as A. Einstein realized with Invariants and General Relativity, may be required for new ideas to be part of physics. We present here a two postulate model geared to an Absolute Summ. The seedbed of this work is part of Akhnaton's philosophy (see S. Freud, Moses and Monotheism). Most important, however, is that the structure of human consciousness, manifest in Kenya's Rift Valley 200,000 years ago as Homo sapiens, who were the culmination of the six million year co-creation process of Hominins and Nature in Africa, allows us to do the physics that we do. .
Absolute rate of the reaction of Cl(p-2) with molecular hydrogen from 200 - 500 K
NASA Technical Reports Server (NTRS)
Whytock, D. A.; Lee, J. H.; Michael, J. V.; Payne, W. A.; Stief, L. J.
1976-01-01
Rate constants for the reaction of atomic chlorine with hydrogen are measured from 200 - 500 K using the flash photolysis-resonance fluorescence technique. The results are compared with previous work and are discussed with particular reference to the equilibrium constant for the reaction and to relative rate data for chlorine atom reactions. Theoretical calculations, using the BEBO method with tunneling, give excellent agreement with experiment.
Absolute rate of the reaction of atomic hydrogen with ethylene from 198 to 320 K at high pressure
NASA Technical Reports Server (NTRS)
Lee, J. H.; Michael, J. V.; Payne, W. A.; Stief, L. J.
1978-01-01
The rate constant for the H+C2H4 reaction has been measured as a function of temperature. Experiments were performed with high pressures of Ar heat bath gas at seven temperatures from 198 to 320 K with the flash photolysis-resonance fluorescence (FP-RF) technique. Pressures were chosen so as to isolate the addition rate constant k1. The results are well represented by an Arrhenius expression. The results are compared with other studies and are theoretically discussed.
NASA Technical Reports Server (NTRS)
Chang, T.; Torr, D. G.; Richards, P. G.; Solomon, S. C.
1993-01-01
O(+)(2P) is an important species for studies of the ionosphere and thermosphere: its emission at 7320 A can be used as a diagnostic of the thermospheric atomic oxygen density. Unfortunately, there are no laboratory measurements of the O and N2 reaction rates which are needed to determine the major sinks of (O+)(2p). We have recalculated the O and N2 reaction rates for O(+) (2P) using recent improvements in the solar EUV flux, cross sections, and photoelectron fluxes. For the standard solar EUV flux, the new N2 reaction rate of 3.4 +/- 1.5 x 10 exp -10 cu cm/s is close to the value obtained by Rusch et al. (1977), but the new O reaction rate of 4.0 +/- 1.9 x 10 exp -10 cu cm/sec is about 8 times larger. These new reaction rates are derived using neutral densities, electron density, and solar EUV fluxes measured by Atmosphere Explorer C in 1974 during solar minimum. The new theoretical emission rates are in good agreement with the data for the two orbits studied by Rusch et al.
NASA Astrophysics Data System (ADS)
Narayanan, S.; Mohan Kumar, M.; Hassanizadeh, S. M.; Raoof, A.
2014-12-01
The colloid deposition behavior observed at the Darcy scale represents an average of the processes occurring at the pore scale. Hence, a better understanding of the processes occurring at the Darcy scale can be obtained by studying colloid transport at the pore-scale and then upscaling the results. In this study, we have developed a mathematical model to simulate the transport of colloids in a cylindrical pore by considering various processes such as advection, diffusion, colloid-soil surface interactions and hydrodynamic wall effects. The pore space is divided into three different regions, namely, the bulk, diffusion and potential regions, based on the dominant processes acting in each of these regions. In the bulk region, colloid transport is governed by advection and diffusion; whereas in the diffusion region, colloid mobility due to diffusion is retarded by hydrodynamic wall effects. Colloid-solid interaction forces dominate the transport in the potential region where colloid deposition occurs and are calculated using DLVO theory. The expressions for mass transfer rate coefficients between the diffusion and potential regions have been derived for different DLVO energy profiles. These are incorporated in the pore-scale equations in the form of a boundary condition at the diffusion-potential region interface. The model results are used to obtain the colloid breakthrough curve at the end of a long pore, and then it is fitted with 1D advection-dispersion-adsorption model so as to determine the averaged attachment and detachment rate coefficients at the scale of a single pore. A sensitivity analysis of the model to six pore-scale parameters (colloid and wall surface potentials, solution ionic strength, average pore-water velocity, colloid radius, and pore radius) is carried out so as to find the relation between the averaged deposition rate coefficients at pore scale vs the pore-scale parameters. We found an hyper exponential relation between the colloid attachment
NASA Astrophysics Data System (ADS)
Huestis, D. L.; Pejaković, D. A.; Copeland, R. A.; Kalogerakis, K. S.
2004-12-01
In the atmospheres of Earth, Venus, and Mars photodissociation of O2 and CO2 produces oxygen atoms that eventually undergo three-body recombination: O + O + M -> O2* + M. The competition between photodissociation, recombination, and diffusive vertical transport controls the atomic and molecular composition of the mesosphere and lower thermosphere. Knowledge of the rate coefficient for recombination of atomic oxygen is essential for modeling atmospheric composition. The most recent measurement of O-atom recombination rate coefficient is over thirty years old [1]. The published values of this rate coefficient have large divergence for both M = O2 and M = N2. For N2 as the third body, the room temperature coefficient varies between about 3 × 10-33 cm6s-1, which is the value recommended in the combustion science community, and 5 × 10-33 cm6s-1, a value used in the atmospheric modeling community. Previous laboratory investigations [2] of the process O + O + N2 -> O2* + N2 shared the same basic approach, which was to use N2 discharge flow system with NO added downstream to generate O-atoms in the absence of O2 through the reaction N + NO -> O + N2. This approach is vulnerable to heterogeneous recombination and other processes that may obscure the reaction of interest, mostly due to the low O-atom densities and, consequently, long reaction times. We employ an F2 laser with up to 50 mJ of 157 nm pulsed output to achieve nearly complete photodissociation of molecular oxygen. In a high-pressure (760 Torr) background of N2 the oxygen atoms recombine in a time scale of several milliseconds. Oxygen atom population is monitored by detecting 845-nm fluorescence, which is induced by the 226 nm output of the second laser via a two-photon process O(2p4 3P) + 2hν -> O(2p33p ^3P). Our measurements give a preliminary value for the O + O + N_2 recombination rate coefficient of approximately 3 \\times 10^{-33} cm^6s^{-1}, which favors the value recommended in the combustion community
Absolute rate constant of the reaction OH + H2O2 yields HO2 + H2O from 245 to 423 K
NASA Technical Reports Server (NTRS)
Keyser, L. F.
1980-01-01
The absolute rate constant of the reaction between the hydroxyl radical and hydrogen peroxide was measured by using the discharge-flow resonance fluorescence technique at total pressure between 1 and 4 torr. At 298 K the result is (1.64 + or - 0.32) x 10 to the -12th cu cm/molecule s. The observed rate constant is independent of pressure, surface-to-volume ratio, the addition of vibrational quenchers, and the source of OH. The temperature dependence has also been determined between 245 and 423 K; the resulting Arrhenius expression is k cu cm/molecule s is equal to (2.51 + or - 0.6) x 10 to the -12th exp(-126 + or - 76/T).
NASA Technical Reports Server (NTRS)
Whytock, D. A.; Timmons, R. B.; Lee, J. H.; Michael, J. V.; Payne, W. A.; Stief, L. J.
1976-01-01
The technique of flash photolysis coupled with time resolved detection of O via resonance fluorescence has been used to obtain rate constants for the reaction of O(3-P) with H2S at temperatures from 263 to 495 K and at pressures in the range 10-400 torr. Under conditions where secondary reactions are avoided, the measured rate constants for the primary step obey the Arrhenius equation k = (7.24 plus or minus 1.07) x 10 to the -12th exp(-3300 plus or minus 100/1.987 T) cu cm/molecules/s. Experiments with D2S show that the reaction exhibits a primary isotope effect, in support of a hydrogen abstraction mechanism.
Nauser, Thomas; Schöneich, Christian
2003-09-01
Free radical damage of DNA is a well-known process affecting biological tissue under conditions of oxidative stress. Thiols can repair DNA-derived radicals. However, the product thiyl radicals may also cause biological damage. To obtain quantitative information on the potential reactivity with DNA components, we measured the rate constant for hydrogen abstraction by cysteamine thiyl radicals from thymine C5-CH(3), k = (1.2 +/- 0.8) x 10(4) M(-1) s(-1), and thymidine-5'-monophosphate, k = (0.9 +/- 0.6) x 10(4) M(-1) s(-1). Hence, the hydrogen abstraction from C5-CH(3) occurs with rate constants similar to the hydrogen abstraction from the carbohydrate moieties. Especially at low oxygen concentration such as that found in skeletal muscle, such hydrogen abstraction processes by thiyl radicals may well compete against other dioxygen-dependent reactions. The rate constants for hydrogen abstraction at thymine C5-CH(3) were compared to those with benzylic substrates, toluenesulfonic acid, and benzyl alcohol.
Storkey, Corin; Pattison, David I; Ignasiak, Marta T; Schiesser, Carl H; Davies, Michael J
2015-12-01
Peroxynitrite (the physiological mixture of ONOOH and its anion, ONOO(-)) is a powerful biologically-relevant oxidant capable of oxidizing and damaging a range of important targets including sulfides, thiols, lipids, proteins, carbohydrates and nucleic acids. Excessive production of peroxynitrite is associated with several human pathologies including cardiovascular disease, ischemic-reperfusion injury, circulatory shock, inflammation and neurodegeneration. This study demonstrates that low-molecular-mass selenols (RSeH), selenides (RSeR') and to a lesser extent diselenides (RSeSeR') react with peroxynitrite with high rate constants. Low molecular mass selenols react particularly rapidly with peroxynitrite, with second order rate constants k2 in the range 5.1 × 10(5)-1.9 × 10(6)M(-1)s(-1), and 250-830 fold faster than the corresponding thiols (RSH) and many other endogenous biological targets. Reactions of peroxynitrite with selenides, including selenosugars are approximately 15-fold faster than their sulfur homologs with k2 approximately 2.5 × 10(3)M(-1)s(-1). The rate constants for diselenides and sulfides were slower with k2 0.72-1.3 × 10(3)M(-1)s(-1) and approximately 2.1 × 10(2)M(-1)s(-1) respectively. These studies demonstrate that both endogenous and exogenous selenium-containing compounds may modulate peroxynitrite-mediated damage at sites of acute and chronic inflammation, with this being of particular relevance at extracellular sites where the thiol pool is limited.
Brown, Samuel M.; Tate, M. Quinn; Jones, Jason P.; Kuttler, Kathryn G.; Lanspa, Michael; Rondina, Matthew T.; Grissom, Colin K.; Mathews, V.J.
2014-01-01
Purpose Determine whether variability of coarsely sample heart rate and blood pressure early in the course of severe sepsis and septic shock predicts successful resuscitation, defined as vasopressor independence at 24 hours after admission. Methods In an observational study of patients admitted with severe sepsis or septic shock from 2009 to 2011 to one of two ICUs at a tertiary-care hospital, in whom blood pressure was measured via an arterial catheter, we sampled heart rate and blood pressure every 30 seconds over the first six hours of ICU admission and calculated coefficient of variability of those measurements. Primary outcome was vasopressor independence at 24 hours; secondary outcome was 28-day mortality. Results We studied 165 patients, of which 97 (59%) achieved vasopressor independence at 24 hours. Overall 28-day mortality was 15%. Significant predictors of vasopressor independence at 24 hours included the coefficient of variation of heart rate, age, APACHE II, the number of increases in vasopressor dose, mean vasopressin dose, mean blood pressure, and time-pressure integral of mean blood pressure below 60mm Hg. Lower sampling frequencies (up to once every 5 minutes) did not affect the findings. Conclusions Increased variability of coarsely sampled heart rate was associated with vasopressor independence at 24 hours after controlling for possible confounders. Sampling frequencies of once in five minutes may be similar to once in 30 seconds. PMID:24578465
NASA Astrophysics Data System (ADS)
Glover, Simon C. O.
2015-11-01
We investigate how uncertainties in the chemical and cooling rate coefficients relevant for a metal-free gas influence our ability to determine the critical ultraviolet field strength required to suppress H2 cooling in high-redshift atomic cooling haloes. The suppression of H2 cooling is a necessary prerequisite for the gas to undergo direct collapse and form an intermediate mass black hole. These black holes can then act as seeds for the growth of the supermassive black holes (SMBHs) observed at redshifts z ˜ 6. The viability of this model for SMBH formation depends on the critical ultraviolet field strength, Jcrit: if this is too large, then too few seeds will form to explain the observed number density of SMBHs. We show in this paper that there are five key chemical reactions whose rate coefficients are uncertain enough to significantly affect Jcrit. The most important of these is the collisional ionization of hydrogen by collisions with other hydrogen atoms, as the rate for this process is very poorly constrained at the low energies relevant for direct collapse. The total uncertainty introduced into Jcrit by this and the other four reactions could in the worst case approach a factor of five. We also show that the use of outdated or inappropriate values for the rates of some chemical reactions in previous studies of the direct collapse mechanism may have significantly affected the values of Jcrit determined by these studies.
Dail, Michelle K; Mezyk, Stephen P
2010-08-19
The beta-lactam antibiotics are some of the most prevalent pharmaceutical contaminants currently being detected in aquatic environments. Because the presence of any trace level of antibiotic in water may adversely affect aquatic ecosystems and contribute to the production of antibiotic-resistant bacteria, active removal by additional water treatments, such as using advanced oxidation and reduction processes (AO/RPs), may be required. However, to ensure that any AOP treatment process occurs efficiently and quantitatively, a full understanding of the kinetics and mechanisms of all of the chemical reactions involved under the conditions of use is necessary. In this study, we report on our kinetic measurements for the hydroxyl-radical-induced oxidation of 11 beta-lactam antibiotics obtained using electron pulse radiolysis techniques. For the 5-member ring species, an average reaction rate constant of (7.9 +/- 0.8) x 10(9) M(-1) s(-1) was obtained, slightly faster than for the analogous 6-member ring containing antibiotics, (6.6 +/- 1.2) x 10(9) M(-1) s(-1). The consistency of these rate constants for each group infers a common reaction mechanism, consisting of the partitioning of the hydroxyl radical between addition to peripheral aromatic rings and reaction with the central double-ring core of these antibiotics.
Absolute rate constants for O + NO + M /= He, Ne, Ar, Kr/ yields NO2 + M from 217-500 K
NASA Technical Reports Server (NTRS)
Michael, J. V.; Payne, W. A.; Whytock, D. A.
1976-01-01
Rate constants for the reaction O + NO + M yields NO2 + M have been obtained at temperatures from 217-500 K in four different rare gases by a method combining flash photolysis with time resolved detection of O(3-P) by resonance fluorescence. The measured rate constants in Arrhenius form are (10.8 plus or minus 1.2) x 10 to the -33rd exp(1040 plus or minus 60/1.987 T) for helium; (9.01 plus or minus 1.16) x 10 to the -33rd exp(1180 plus or minus 70/1.987 T) for argon; (9.33 plus or minus 1.10) x 10 to the -33rd exp(1030 plus or minus 60/1.987 T) for neon; and (9.52 plus or minus 1.10) x 10 to the -33rd exp(1140 plus or minus 70/1.987 T) for krypton in units of cm to the 6th/sq molecule/s.
Tono-oka, T; Kaneko, I
1993-05-01
The daily level of physical activity was estimated using the heart rate monitor, PE3000 (Polar Electro, Finland). The level was expressed with the coefficient of variation (CV) of heart rates recorded from waking time to dinner time. In the course of a day of intense physical activity, CV was confirmed to rise significantly. Then the CV was estimated and compared among 3 age classes, young (10-18 years), middle-aged (30-47 years), and elderly (62-76 years). The CVs of young people were significantly higher than those of middle-aged (P < 0.001) and elderly (P < 0.01), regardless of sex. However there was no significant sex difference in all age classes. These results suggest that the CV is an accurate index of daily physical activity. Thus clinicians can use the CV of heart rates to estimate the level of physical activity of individuals which closely relates to QOL.
Yao, Kangning; Chi, Yong; Wang, Fei; Yan, Jianhua; Ni, Mingjiang; Cen, Kefa
2016-01-01
A commonly used aeration device at present has the disadvantages of low mass transfer rate because the generated bubbles are several millimeters in diameter which are much bigger than microbubbles. Therefore, the effect of a microbubble on gas-liquid mass transfer and wastewater treatment process was investigated. To evaluate the effect of each bubble type, the volumetric mass transfer coefficients for microbubbles and conventional bubbles were determined. The volumetric mass transfer coefficient was 0.02905 s(-1) and 0.02191 s(-1) at a gas flow rate of 0.67 L min(-1) in tap water for microbubbles and conventional bubbles, respectively. The degradation rate of simulated municipal wastewater was also investigated, using aerobic activated sludge and ozone. Compared with the conventional bubble generator, the chemical oxygen demand (COD) removal rate was 2.04, 5.9, 3.26 times higher than those of the conventional bubble contactor at the same initial COD concentration of COD 200 mg L(-1), 400 mg L(-1), and 600 mg L(-1), while aerobic activated sludge was used. For the ozonation process, the rate of COD removal using microbubble generator was 2.38, 2.51, 2.89 times of those of the conventional bubble generator. Based on the results, the effect of initial COD concentration on the specific COD degradation rate were discussed in different systems. Thus, the results revealed that microbubbles could enhance mass transfer in wastewater treatment and be an effective method to improve the degradation of wastewater. PMID:27120652
NASA Astrophysics Data System (ADS)
Lhotka, C.; Reimond, S.; Souchay, J.; Baur, O.
2016-02-01
The aim of this study is first to determine the gravity field of the comet 67P/Churyumov-Gerasimenko and second to derive the solar component of the precession rate and nutation coefficients of the spin-axis of the comet nucleus, i.e. without the direct, usually larger, effect of outgassing. The gravity field and related moments of inertia are obtained from two polyhedra, which are provided by the Optical, Spectroscopic, and Infrared Remote Imaging System (OSIRIS) and NAVigation CAMera (NAVCAM) experiments on Rosetta, and are based on the assumption of uniform density for the comet nucleus. We also calculate the forced precession rate as well as the nutation coefficients on the basis of Kinoshita's theory of rotation of the rigid Earth and adapted it to be able to indirectly include the effect of outgassing on the rotational parameters. The second degree denormalized Stokes coefficients of comet 67P/C-G turn out to be (bracketed numbers refer to second shape model) C20 ≃ -6.74 [-7.93] × 10-2, C22 ≃ 2.60 [2.71] × 10-2, consistent with normalized principal moments of inertia A/MR2 ≃ 0.13 [0.11], B/MR2 ≃ 0.23 [0.22], with polar moment c = C/MR2 ≃ 0.25, depending on the choice of the polyhedron model. The obliquity between the rotation axis and the mean orbit normal is ε ≃ 52°, and the precession rate only due to solar torques becomes dot{ψ }in [20,30] arcsec yr^{-1}. Oscillations in longitude caused by the gravitational pull of the Sun turn out to be of the order of Δψ ≃ 1 arcmin, and oscillations in obliquity can be estimated to be of the order of Δε ≃ 0.5 arcmin.
Drexler, J.Z.; Anderson, F.E.; Snyder, R.L.
2008-01-01
The surface renewal method was used to estimate evapotranspiration (ET) for a restored marsh on Twitchell Island in the Sacramento-San Joaquin Delta, California, USA. ET estimates for the marsh, together with reference ET measurements from a nearby climate station, were used to determine crop coefficients over a 3-year period during the growing season. The mean ET rate for the study period was 6 mm day-1, which is high compared with other marshes with similar vegetation. High ET rates at the marsh may be due to the windy, semi-arid Mediterranean climate of the region, and the permanently flooded nature of the marsh, which results in very low surface resistance of the vegetation. Crop coefficient (Kc) values for the marsh ranged from 0.73 to 1.18. The mean Kc value over the entire study period was 0-95. The daily Kc values for any given month varied from year to year, and the standard deviation of daily Kc values varied between months. Although several climate variables were undoubtedly responsible for this variation, our analysis revealed that wind direction and the temperature of standing water in the wetland were of particular importance in determining ET rates and Kc values.
Anders, R.; Chrysikopoulos, C.V.
2006-01-01
Static and dynamic batch experiments were conducted to study the effects of temperature and the presence of sand on the inactivation of bacteriophage MS2 and PRD1. The experimental data suggested that the inactivation process can be satisfactorily represented by a pseudo-first-order expression with time-dependent rate coefficients. The time-dependent rate coefficients were used to determine pertinent thermodynamic properties required for the analysis of the molecular processes involved in the inactivation of each bacteriophage. A combination of high temperature and the presence of sand appears to produce the greatest disruption to the surrounding protein coat of MS2. However, the lower activation energies for PRD1 indicate a weaker dependence of the inactivation rate on temperature. Instead, the presence of air-liquid and air-solid interfaces appears to produce the greatest damage to specific viral components that are related to infection. These results indicate the importance of using thermodynamic parameters based on the time-dependent inactivation model to better predict the inactivation of viruses in groundwater. ?? 2006 American Chemical Society.
NASA Astrophysics Data System (ADS)
Dash, Manas Ranjan; Rajakumar, B.
2013-11-01
Rate coefficient for the reaction of β-pinene with OH radicals was determined at 298 K and 800 Torr of N2 using the relative rate technique. Isobutylene was used as a reference compound and the concentrations of the organics were followed by gas chromatographic analysis. The rate coefficient for the reaction of β-pinene with OH radical was measured to be (9.35 ± 2.79) × 10-11 cm3 molecule-1 s-1. Theoretical kinetic calculations were also performed for the title reaction using canonical variational transition state theory (CVT) with small-curvature tunneling (SCT). The kinetics data obtained over the temperature range of 200-400 K were used to derive the Arrhenius expression: k(T) = 8.24 × 10-23T3.41 exp[2421/T] cm3 molecule-1 s-1. The OH-driven atmospheric lifetime (τ) and global warming potential (GWP) for β-pinene were computed and concluded that β-pinene is very short lived (2.5 h) in the Earth's atmosphere with a GWP of 1.6 × 10-2 at 20 years horizon of time and which is negligible. The ozone formation potential of β-pinene was also calculated and reported in this present work.
NASA Astrophysics Data System (ADS)
Yaseen, Mohammad A.; Srinivasan, Vivek J.; Sakadžić, Sava; Vinogradov, Sergei A.; Boas, David A.
2010-02-01
Measuring oxygen delivery in brain tissue is important for identifying the pathophysiological changes associated with brain injury and various diseases such as cancer, stroke, and Alzheimer's disease. We have developed a multi-modal imaging system for minimally invasive measurement of cerebral oxygenation and blood flow in small animals with high spatial resolution. The system allows for simultaneous measurement of blood flow using Fourier-domain optical coherence tomography, and oxygen partial pressure (pO2) using either confocal or multiphoton phosphorescence lifetime imaging with exogenous porphyrin-based dyes sensitive to dissolved oxygen. Here we present the changes in pO2 and blood flow in superficial cortical vessels of Sprague Dawley rats in response to conditions such as hypoxia, hyperoxia, and functional stimulation. pO2 measurements display considerable heterogeneity over distances that cannot be resolved with more widely used oxygen-monitoring techniques such as BOLD-fMRI. Large increases in blood flow are observed in response to functional stimulation and hypoxia. Our system allows for quantification of cerebral metabolic rate of oxygen (CMRO2) with high spatial resolution, providing a better understanding of metabolic dynamics during functional stimulation and under various neuropathologies. Ultimately, better insight into the underlying mechanisms of neuropathologies will facilitate the development of improved therapeutic strategies to minimize damage to brain tissue.
Pressure dependence of the absolute rate constant for the reaction Cl + C2H2 from 210-361 K
NASA Technical Reports Server (NTRS)
Brunning, J.; Stief, L. J.
1985-01-01
In recent years, considerable attention has been given to the role of chlorine compounds in the catalytic destruction of stratospheric ozone. However, while some reactions have been studied extensively, the kinetic data for the reaction of Cl with C2H2 is sparse with only three known determinations of the rate constant k3. The reactions involved are Cl + C2H2 yields reversibly ClC2H2(asterisk) (3a) and ClC2H2(asterisk) + M yields ClC2H2 + M (3b). In the present study, flash photolysis coupled with chlorine atomic resonance fluorescence have been employed to determine the pressure and temperature dependence of k3 with the third body M = Ar. Room temperature values are also reported for M = N2. The pressure dependence observed in the experiments confirms the expectation that the reaction involves addition of Cl to the unsaturated C2H2 molecule followed by collisional stabilization of the resulting adduct radical.
NASA Technical Reports Server (NTRS)
Dateo, Christopher E.; Walch, Stephen P.
2002-01-01
As part of NASA Ames Research Center's Integrated Process Team on Device/Process Modeling and Nanotechnology our goal is to create/contribute to a gas-phase chemical database for use in modeling microelectronics devices. In particular, we use ab initio methods to determine chemical reaction pathways and to evaluate reaction rate coefficients. Our initial studies concern reactions involved in the dichlorosilane-hydrogen (SiCl2H2--H2) and trichlorosilane-hydrogen (SiCl2H-H2) systems. Reactant, saddle point (transition state), and product geometries and their vibrational harmonic frequencies are determined using the complete-active-space self-consistent-field (CASSCF) electronic structure method with the correlation consistent polarized valence double-zeta basis set (cc-pVDZ). Reaction pathways are constructed by following the imaginary frequency mode of the saddle point to both the reactant and product. Accurate energetics are determined using the singles and doubles coupled-cluster method that includes a perturbational estimate of the effects of connected triple excitations (CCSD(T)) extrapolated to the complete basis set limit. Using the data from the electronic structure calculations, reaction rate coefficients are obtained using conventional and variational transition state and RRKM theories.
NASA Astrophysics Data System (ADS)
Ivanov, Konstantin L.; Lukzen, Nikita N.; Doktorov, Alexander B.
2016-08-01
Time dependence of the rate coefficients of sterically specific reactions is analyzed theoretically. Generally, such reactions exhibit a non-trivial dependence of their rate constant on the steric factor, f < 1, which is defined as the fraction of reactive surface area. Notably, the rate constant of a diffusion-controlled reaction is proportional not to f but, counter-intuitively, to √{ f } due to partial averaging of the reaction anisotropy by translational diffusion. Here we demonstrate that the effective steric factor of a diffusion-influenced reaction is strongly time-dependent, increasing from f to √{ f } . When reactants have several active sites, these sites "interfere" each other in the sense that the rate constant depends on their relative positions. We demonstrate that such an interference effect is strongly time-dependent as well: it is absent at t = 0 but builds up with time. We argue that the outlined effects are also of importance for calculating the fluorescence quenching rate constants.
Collisional quenching reaction rate coefficients of N2 (A3Σu+) by C2F6 and C3F8
NASA Astrophysics Data System (ADS)
Suzuki, Susumu; Kuboaki, Masaru; Itoh, Haruo
2015-09-01
The collisional quenching reaction rate coefficient of N2 (A3Σu+) by various air pollutant gases were determined from the measurement of the effective lifetime of N2 (A3Σu+) in pure N2 (5-nine) with a small amount of air pollutant gases as an admixture. Derivation of the rate coefficient was performed the waveform analysis of the transient ionization current after turning off the UV light in the Townsend discharge. In this paper, we report that the obtained collisional quenching reaction rate coefficients of N2 (A3Σu+) by C2F6 and C3F8 are (2.3 +/- 1.8) × 10-15 cm3/s and (1.6 +/- 0.8) × 10-14 cm3/s, respectively. Furthermore, we investigate the relationship between the rate coefficient and the mass number of their quenching molecular gases. Firstly, it is confirmed that the rate coefficient take large value with an increase in the mass number of the quenching gases. Secondly, if H atom is included in the gas molecules such as CH4, C2F6 and C3F8 the rate coefficient take large value, but if the molecules including F atom such as C2F6 and C3F8 instead of H atom in this study, more smaller values of the collisional quenching reaction rate coefficient are observed.
Scheibe, Timothy D.; Dong, Hailiang; Xie, YuLong
2007-06-01
It has been widely observed in field experiments that the apparent rate of bacterial attachment, particularly as parameterized by the collision efficiency in filtration-based models, decreases with transport distance (i.e., exhibits scale-dependency). This effect has previously been attributed to microbial heterogeneity; that is, variability in cell-surface properties within a single monoclonal population. We demonstrate that this effect could also be interpreted as a field-scale manifestation of local-scale correlation between physical heterogeneity (hydraulic conductivity variability) and reaction heterogeneity (attachment rate coefficient variability). A field-scale model of bacterial transport developed for the South Oyster field research site located near Oyster, Virginia, and observations from field experiments performed at that site, are used as the basis for this study. Three-dimensional Monte Carlo simulations of bacterial transport were performed under four alternative scenarios: 1) homogeneous hydraulic conductivity (K) and attachment rate coefficient (Kf), 2) heterogeneous K, homogeneous Kf, 3) heterogeneous K and Kf with local correlation based on empirical and theoretical relationships, and 4) heterogeneous K and Kf without local correlation. The results of the 3D simulations were analyzed using 1D model approximations following conventional methods of field data analysis. An apparent decrease with transport distance of effective collision efficiency was observed only in the case where the local properties were both heterogeneous and correlated. This effect was observed despite the fact that the local collision efficiency was specified as a constant in the 3D model, and can therefore be interpreted as a scale effect associated with the local correlated heterogeneity as manifested at the field scale.
NASA Astrophysics Data System (ADS)
Izgorodina, Ekaterina I.; Coote, Michelle L.
2006-05-01
A systematic methodology for calculating accurate propagation rate coefficients in free-radical polymerization was designed and tested for vinyl chloride and acrylonitrile polymerization. For small to medium-sized polymer systems, theoretical reaction barriers are calculated using G3(MP2)-RAD. For larger systems, G3(MP2)-RAD barriers can be approximated (to within 1 kJ mol -1) via an ONIOM-based approach in which the core is studied at G3(MP2)-RAD and the substituent effects are modeled with ROMP2/6-311+G(3df,2p). DFT methods (including BLYP, B3LYP, MPWB195, BB1K and MPWB1K) failed to reproduce the correct trends in the reaction barriers and enthalpies with molecular size, though KMLYP showed some promise as a low cost option for very large systems. Reaction rates are calculated via standard transition state theory in conjunction with the one-dimensional hindered rotor model. The harmonic oscillator approximation was shown to introduce an error of a factor of 2-3, and would be suitable for "order-of-magnitude" estimates. A systematic study of chain length effects indicated that rate coefficients had largely converged to their long chain limit at the dimer radical stage, and the inclusion of the primary substituent of the penultimate unit was sufficient for practical purposes. Solvent effects, as calculated using the COSMO model, were found to be relatively minor. The overall methodology reproduced the available experimental data for both of these monomers within a factor of 2.
Low-Temperature Rate Coefficients of C2H with CH4 and CD4 from 154 to 359 K
NASA Technical Reports Server (NTRS)
Opansky, Brian J.; Leone, Stephen R.
1996-01-01
Rate coefficients for the reaction C2H + CH4 yields C2H2 + CH3 and C2H + CD4 yields C2HD + CD3 are measured over the temperature range 154-359 K using transient infrared laser absorption spectroscopy. Ethynyl radicals are produced by pulsed laser photolysis of C2H2 in a variable temperature flow cell, and a tunable color center laser probes the transient removal of C2H (Chi(exp 2) Sigma(+) (0,0,0)) in absorption. The rate coefficients for the reactions of C2H with CH4 and CD4 both show a positive temperature dependence over the range 154-359 K, which can be expressed as k(sub CH4) = (1.2 +/- 0.1) x 10(exp -11) exp((-491 +/- 12)/T) and k(sub CD4) = (8.7 +/- 1.8) x 10(exp -12) exp((-650 +/- 61)/T) cm(exp 3) molecule(exp -1) s(exp -1), respectively. The reaction of C2H + CH4 exhibits a significant kinetic isotope effect at 300 K of k(sub CH4)/k(sub CD4) = 2.5 +/- 0.2. Temperature dependent rate constants for C2H + C2H2 were also remeasured over an increased temperature range from 143 to 359 K and found to show a slight negative temperature dependence, which can be expressed as k(sub C2H2) = 8.6 x 10(exp -16) T(exp 1.8) exp((474 +/- 90)/T) cm(exp 3) molecule(exp -1) s(exp -1).
Hotop, H; Ruf, M-W; Kopyra, J; Miller, T M; Fabrikant, I I
2011-02-14
Rate coefficients k(T) for dissociative electron attachment (DEA) to molecules in many cases exhibit a more or less strong rise with increasing temperature T (the electron temperature T(e) and the molecular temperature T(G) are assumed to be in thermal equilibrium, i.e., T = T(e) = T(G)). This rise is frequently modeled by the Arrhenius equation k(T) = k(A) exp[-E(a)∕(k(B)T)], and an activation energy E(a) is deduced from fits to the experimental data k(T). This behavior reflects the presence of an energy barrier for the anion on its path to the dissociated products. In a recent paper [J. Kopyra, J. Wnorowska, M. Foryś, and I. Szamrej, Int. J. Mass Spectrom. 268, 60 (2007)] it was suggested that the size of the rate coefficients for DEA reactions at room temperature exhibits an exponential dependence on the activation energy, i.e., k(E(a); T ≈ 300 K) = k(1) exp[-E(a)∕E(0)]. More recent experimental data for molecules with high barriers [T. M. Miller, J. F. Friedman, L. C. Schaffer, and A. A. Viggiano, J. Chem. Phys. 131, 084302 (2009)] are compatible with such a correlation. We investigate the validity and the possible origin of this dependence by analyzing the results of R-matrix calculations for temperature-dependent rate coefficients of exothermic DEA processes with intermediate barrier toward dissociation. These include results for model systems with systematically varied barrier height as well as results of molecule-specific calculations for CH(3)Cl, CH(3)Br, CF(3)Cl, and CH(2)Cl(2) (activation energies above 0.2 eV) involving appropriate molecular parameters. A comparison of the experimental and theoretical results for the considered class of molecules (halogenated alkanes) supports the idea that the exponential dependence of k(T = 300 K) on the activation energy reflects a general phenomenon associated with Franck-Condon factors for getting from the initial neutral vibrational levels to the dissociating final anion state in a direct DEA process
Determination of the Rate Coefficients of the SO2 plus O plus M yields SO3 plus M Reaction
NASA Technical Reports Server (NTRS)
Hwang, S. M.; Cooke, J. A.; De Witt, K. J.; Rabinowitz, M. J.
2010-01-01
Rate coefficients of the title reaction R(sub 31) (SO2 +O+M yields SO3 +M) and R(sub 56) (SO2 + HO2 yields SO3 +OH), important in the conversion of S(IV) to S(VI),were obtained at T =970-1150 K and rho (sub ave) = 16.2 micro mol/cubic cm behind reflected shock waves by a perturbation method. Shock-heated H2/ O2/Ar mixtures were perturbed by adding small amounts of SO2 (1%, 2%, and 3%) and the OH temporal profiles were then measured using laser absorption spectroscopy. Reaction rate coefficients were elucidated by matching the characteristic reaction times acquired from the individual experimental absorption profiles via simultaneous optimization of k(sub 31) and k(sub 56) values in the reaction modeling (for satisfactory matches to the observed characteristic times, it was necessary to take into account R(sub 56)). In the experimental conditions of this study, R(sub 31) is in the low-pressure limit. The rate coefficient expressions fitted using the combined data of this study and the previous experimental results are k(sub 31,0)/[Ar] = 2.9 10(exp 35) T(exp ?6.0) exp(?4780 K/T ) + 6.1 10(exp 24) T(exp ?3.0) exp(?1980 K/T ) cm(sup 6) mol(exp ?2)/ s at T = 300-2500 K; k(sub 56) = 1.36 10(exp 11) exp(?3420 K/T ) cm(exp 3)/mol/s at T = 970-1150 K. Computer simulations of typical aircraft engine environments, using the reaction mechanism with the above k(sub 31,0) and k(sub 56) expressions, gave the maximum S(IV) to S(VI) conversion yield of ca. 3.5% and 2.5% for the constant density and constant pressure flow condition, respectively. Moreover, maximum conversions occur at rather higher temperatures (?1200 K) than that where the maximum k(sub 31,0) value is located (approximately 800 K). This is because the conversion yield is dependent upon not only the k(sup 31,0) and k(sup 56) values (production flux) but also the availability of H, O, and HO2 in the system (consumption flux).
Jaffey, A.H.; Gray, J.; Bentley, W.C.; Lerner, J.L.
1987-09-01
A precision built moveable endplate Geiger-Mueller counter was used to measure the absolute disintegration rate of a beta-emitting radioactive gas. A Geiger-Mueller counter used for measuring gaseous radioactivity has <100% counting efficiency owing to two factors: (1) ''end effect,'' due to decreased and distorted fields at the ends where wire-insulator joints are placed, and (2) ''wall effect,'' due to non-ionization by beta particles emitted near to and heading into the wall. The end effect was evaluated by making one end of the counter movable and measuring counting rates at a number of endplate positions. Much of the wall effect was calculated theoretically, based on known data for primary ionization of electrons as a function of energy and gas composition. Corrections were then made for the ''shakeoff'' effect in beta decay and for backscattering of electrons from the counter wall. Measurements and calculations were made for a sample of /sup 85/Kr (beta energy, 0.67 MeV). The wall effect calculation is readily extendable to other beta energies.
Ballesteros, Bernabé; Ceacero-Vega, Antonio A; Jiménez, Elena; Albaladejo, José
2015-04-01
As the result of biogenic and anthropogenic activities, large quantities of chemical compounds are emitted into the troposphere. Alkanes, in general, and cycloalkanes are an important chemical class of hydrocarbons found in diesel, jet and gasoline, vehicle exhaust emissions, and ambient air in urban areas. In general, the primary atmospheric fate of organic compounds in the gas phase is the reaction with hydroxyl radicals (OH). The oxidation by Cl atoms has gained importance in the study of atmospheric reactions because they may exert some influence in the boundary layer, particularly in marine and coastal environments, and in the Arctic troposphere. The aim of this paper is to study of the atmospheric reactivity of methylcylohexanes with Cl atoms and OH radicals under atmospheric conditions (in air at room temperature and pressure). Relative kinetic techniques have been used to determine the rate coefficients for the reaction of Cl atoms and OH radicals with methylcyclohexane, cis-1,4-dimethylcyclohexane, trans-1,4-dimethylcyclohexane, and 1,3,5-trimethylcyclohexane at 298 ± 2 K and 720 ± 5 Torr of air by Fourier transform infrared) spectroscopy and gas chromatography-mass spectrometry (GC-MS) in two atmospheric simulation chambers. The products formed in the reaction under atmospheric conditions were investigated using a 200-L Teflon bag and employing the technique of solid-phase microextraction coupled to a GC-MS. The rate coefficients obtained for the reaction of Cl atoms with the studied compounds are the following ones (in units of 10(-10) cm(3) molecule(-1) s(-1)): (3.11 ± 0.16), (2.89 ± 0.16), (2.89 ± 0.26), and (2.61 ± 0.42), respectively. For the reactions with OH radicals the determined rate coefficients are (in units of 10(-11) cm(3) molecule(-1) s(-1)): (1.18 ± 0.12), (1.49 ± 0.16), (1.41 ± 0.15), and (1.77 ± 0.23), respectively. The reported error is twice the standard deviation. A detailed
Chicheportiche, Alexandre; Stachoň, Martin; Benhenni, Malika; Gadéa, Florent Xavier; Kalus, René; Yousfi, Mohammed
2014-10-01
Momentum-transfer collision cross-sections and integral collision cross-sections for the collision-induced dissociation are calculated for collisions of ionized argon dimers with argon atoms using a nonadiabatic semiclassical method with the electronic Hamiltonian calculated on the fly via a diatomics-in-molecules semiempirical model as well as inverse-method modeling based on simple isotropic rigid-core potential. The collision cross-sections are then used in an optimized Monte Carlo code for evaluations of the Ar 2 (+) mobility in argon gas, longitudinal diffusion coefficient, and collision-induced dissociation rates. A thorough comparison of various theoretical calculations as well as with available experimental data on the Ar 2 (+) mobility and collision cross-sections is performed. Good agreement is found between both theoretical approaches and the experiment. Analysis of the role of inelastic processes in Ar 2 (+)/Ar collisions is also provided.
NASA Astrophysics Data System (ADS)
Chicheportiche, Alexandre; StachoÅ, Martin; Benhenni, Malika; Gadéa, Florent Xavier; Kalus, René; Yousfi, Mohammed
2014-10-01
Momentum-transfer collision cross-sections and integral collision cross-sections for the collision-induced dissociation are calculated for collisions of ionized argon dimers with argon atoms using a nonadiabatic semiclassical method with the electronic Hamiltonian calculated on the fly via a diatomics-in-molecules semiempirical model as well as inverse-method modeling based on simple isotropic rigid-core potential. The collision cross-sections are then used in an optimized Monte Carlo code for evaluations of the Ar_2^+ mobility in argon gas, longitudinal diffusion coefficient, and collision-induced dissociation rates. A thorough comparison of various theoretical calculations as well as with available experimental data on the Ar_2^+ mobility and collision cross-sections is performed. Good agreement is found between both theoretical approaches and the experiment. Analysis of the role of inelastic processes in Ar_2^+/Ar collisions is also provided.
Bémer, D; Callé, S; Godinot, S; Régnier, R; Dessagne, J M
2000-12-01
A measuring method of the emission rate of an atmospheric pollutant source, based on the use of a tracer gas (helium) and developed in the case of a gaseous source, was tested for an aerosol source. The influence of both particle sedimentation and wall depositions was studied. The transport coefficients of the tracer gas and of alumina particles of various particle sizes (MMAD from 8 to 36 microns) were measured on a vertical axis close to the source, in a 71 m3 room swept by a piston flow. The measurements clearly demonstrated the predominant influence of sedimentation in the case of particles with aerodynamic diameters greater than 10 microns. Particle wall deposition was determined by measuring the gas and particle concentration decay in the ventilated room. To do this, a new tracing method using a fluorescent aerosol was developed. The measured aerosol deposition rates are much higher than those calculated from the formula of Corner for a cubical volume. Aerosol sedimentation and wall deposition are two phenomena limiting the use of a tracer gas to measure the aerosol emission rate. The chemical substances and materials used in work premises are likely to be released into the atmosphere and lead to the formation of pollutants. These emissions stem from either physical or chemical processes (evaporation of a solvent) or from mechanical processes (dispersion of oil droplets at the source of mists).
NASA Astrophysics Data System (ADS)
Dorian, Matthew; Seitaridou, Effrosyni
2014-03-01
Understanding the rate of biofilm growth is essential for studying genes and preventing unwanted biofilms. In this study, the diffusion coefficient (D) of polystyrene microspheres was used to quantify biofilm growth rates of Sinorhizobia meliloti, a nitrogen fixing bacteria that forms a symbiotic relationship with alfalfa plants. Five strains were studied, two wild types (8530 expR+ and 1021) and three mutants in the exopolysaccharide (EPS I, EPS II) synthesis (8530 exoY , 9034 expG , and 9030-2 expA 1); 1021 and 9030-2 expA 1 are known to be unable to form biofilms. Each strain was inserted into a microfluidic channel with the microspheres. As the cultures grew, the spheres' D values were obtained every 24 hours for 4 days using fluorescence microscopy. Although the D values for 9030-2 expA 1 were inconclusive, 8530 expR+ , 8530 exoY , and 9034 expG showed significant decreases in D between 3 days of growth (| z | > 2 . 25 , p < 0 . 025). The data also indicated that 8530 expR+ and 8530 exoY grew at similar rates. There was no significant change in D for 1021 (χ2(2) = 5 . 76 , p > 0 . 05), which shows the lack of a structured biofilm community. Thus, D can be used as an indicator of the presence of a biofilm and its development.
NASA Astrophysics Data System (ADS)
Vranckx, S.; Peeters, J.; Carl, S. A.
2008-10-01
The absolute rate constant for the reaction that is the major source of stratospheric NOx, O(1D)+N2O → products, has been determined in the temperature range 227 K to 719 K, and, in the temperature range 248 K to 600 K, the fraction of the reaction that yields O(3P). Both the rate constants and product yields were determined using a recently-developed chemiluminescence technique for monitoring O(1D) that allows for higher precision determinations for both rate constants, and, particularly, O(3P) yields, than do other methods. We found the rate constant, kR1, to be essentially independent of temperature between 400 K and 227 K, having a value of (1.37±0.11)×10-10 cm3 s-1, and for temperatures greater than 450 K a marked decrease in rate constant was observed, with a rate constant of only (0.94±0.11)×10-10 cm3 s-1 at 719 K. The rate constants determined over the 227 K 400 K range show very low scatter and are significantly greater, by 20% at room temperature and 15% at 227 K, than the current recommended values. The fraction of O(3P) produced in this reaction was determined to be 0.002±0.002 at 250 K rising steadily to 0.010±0.004 at 600 K, thus the channel producing O(3P) can be entirely neglected in atmospheric kinetic modeling calculations. A further result of this study is an expression of the relative quantum yields as a function of temperature for the chemiluminescence reactions (kCL1)C2H + O(1D) → CH(A) + CO and (kCL2)C2H + O(3P) → CH(A) + CO, both followed by CH(A) → CH(X) + hν, as kCL1(T)/kCL2(T)=(32.8T-3050)/(6.29T+398).
NASA Astrophysics Data System (ADS)
Vranckx, S.; Peeters, J.; Carl, S. A.
2008-05-01
We have determined, in the temperature range 227 K to 719 K, the absolute rate constant for the reaction O(1D)+N2O → products and, in the temperature range 248 K to 600 K, the fraction of the reaction that yields O(3P). Both the rate constants and product yields were determined using a recently-developed chemiluminescence technique for monitoring O(1D) that allows for higher precision determinations for both rate constants, and, particularly, O(3P) yields, than do other methods. We found the rate constant, kR1, to be essentially independent of temperature between 400 K and 227 K, having a value of (1.37±0.09)×10-10 cm3 s-1. For temperatures greater than 450 K a marked decrease in value was observed, with a rate constant of only (0.94±0.11)×10-10 cm3 s-1 at 719 K. The rate constants determined over the 227 K-400 K range show very low scatter and are significantly greater, by 20% at room temperature and by 15% at 227 K, than the current recommended values. The fraction of O(3P) produced in this reaction was determined to be 0.002±0.002 at 250 K rising steadily to 0.010±0.004 at 600 K, thus the channel producing O(3P) can be entirely neglected in atmospheric kinetic modeling calculations. A further result of this study is an expression of the relative quantum yields as a function of temperature for the chemiluminescence reactions (kCL1) C2H+O(1D) → CH(A)+CO and (kCL2) C2H+O(3P) → CH(A)+CO, both followed by CH(A) → CH(X)+hν, as kCL1(T)/kCL2(T)=(32.8T-3050)/(6.29T+398).
Kockler, Katrin B; Haehnel, Alexander P; Junkers, Thomas; Barner-Kowollik, Christopher
2016-01-01
Detailed knowledge of the polymerization mechanisms and kinetics of academically and industrially relevant monomers is mandatory for the precision synthesis of tailor-made polymers. The IUPAC-recommended pulsed-laser polymerization-size exclusion chromatography (PLP-SEC) approach is the method of choice for the determination of propagation rate coefficients and the associated Arrhenius parameters for free radical polymerization processes. With regard to specific monomer classes-such as acrylate-type monomers, which are very important from a materials point of view-high laser frequencies of up to 500 Hz are mandatory to prevent the formation of mid-chain radicals and the occurrence of chain-breaking events by chain transfer, if industrially relevant temperatures are to be reached and wide temperature ranges are to be explored (up to 70 °C). Herein the progress and state-of-the-art of high-frequency PLP-SEC with pulse repetition rates of 500 Hz is reported, with a critical collection of to-date investigated 500 Hz data as well as future perspectives for the field. PMID:26479174
G. WOOD
2000-12-01
Published breakthrough time, adsorption rate, and capacity data for components of organic vapor mixtures adsorbed from flows through fixed activated carbon beds have been analyzed. Capacities (as stoichiometric centers of constant pattern breakthrough curves) yielded stoichiometric times {tau}, which are useful for determining elution orders of mixture components. We also calculated adsorption rate coefficients k{sub v} of the Wheeler (or, more general Reaction Kinetic) breakthrough curve equation, when not reported, from breakthrough times and {tau}. Ninety-five k{sub v} (in mixture)/ k{sub v} (single vapor) ratios at similar vapor concentrations were calculated and averaged for elution order categories. For 43 first-eluting vapors the average ratio (1.07) was statistically no different (0.21 standard deviation) than unity, so that we recommend using the single-vapor k{sub v} for such. Forty-seven second-eluting vapor ratios averaged 0.85 (0.24 standard deviation), also not significantly different from unity; however, other evidence and considerations lead us recommend using k{sub v} (in mixture) = 0.85 k{sub v} (single vapor). Five third- and fourth-eluting vapors gave an average of 0.56 (0.16 standard deviation) for a recommended k{sub v} (in mixture) = 0.56 k{sub v} (single vapor) for such.
Kockler, Katrin B; Haehnel, Alexander P; Junkers, Thomas; Barner-Kowollik, Christopher
2016-01-01
Detailed knowledge of the polymerization mechanisms and kinetics of academically and industrially relevant monomers is mandatory for the precision synthesis of tailor-made polymers. The IUPAC-recommended pulsed-laser polymerization-size exclusion chromatography (PLP-SEC) approach is the method of choice for the determination of propagation rate coefficients and the associated Arrhenius parameters for free radical polymerization processes. With regard to specific monomer classes-such as acrylate-type monomers, which are very important from a materials point of view-high laser frequencies of up to 500 Hz are mandatory to prevent the formation of mid-chain radicals and the occurrence of chain-breaking events by chain transfer, if industrially relevant temperatures are to be reached and wide temperature ranges are to be explored (up to 70 °C). Herein the progress and state-of-the-art of high-frequency PLP-SEC with pulse repetition rates of 500 Hz is reported, with a critical collection of to-date investigated 500 Hz data as well as future perspectives for the field.
Pusateri, Elise N.; Morris, Heidi E.; Nelson, Eric M.; Ji, Wei
2015-08-04
Electromagnetic pulse (EMP) events produce low-energy conduction electrons from Compton electron or photoelectron ionizations with air. It is important to understand how conduction electrons interact with air in order to accurately predict EMP evolution and propagation. An electron swarm model can be used to monitor the time evolution of conduction electrons in an environment characterized by electric field and pressure. Here a swarm model is developed that is based on the coupled ordinary differential equations (ODEs) described by Higgins et al. (1973), hereinafter HLO. The ODEs characterize the swarm electric field, electron temperature, electron number density, and drift velocity. Important swarm parameters, the momentum transfer collision frequency, energy transfer collision frequency, and ionization rate, are calculated and compared to the previously reported fitted functions given in HLO. These swarm parameters are found using BOLSIG+, a two term Boltzmann solver developed by Hagelaar and Pitchford (2005), which utilizes updated cross sections from the LXcat website created by Pancheshnyi et al. (2012). We validate the swarm model by comparing to experimental effective ionization coefficient data in Dutton (1975) and drift velocity data in Ruiz-Vargas et al. (2010). In addition, we report on electron equilibrium temperatures and times for a uniform electric field of 1 StatV/cm for atmospheric heights from 0 to 40 km. We show that the equilibrium temperature and time are sensitive to the modifications in the collision frequencies and ionization rate based on the updated electron interaction cross sections.
NASA Astrophysics Data System (ADS)
Pusateri, Elise N.; Morris, Heidi E.; Nelson, Eric M.; Ji, Wei
2015-08-01
Electromagnetic pulse (EMP) events produce low-energy conduction electrons from Compton electron or photoelectron ionizations with air. It is important to understand how conduction electrons interact with air in order to accurately predict EMP evolution and propagation. An electron swarm model can be used to monitor the time evolution of conduction electrons in an environment characterized by electric field and pressure. Here a swarm model is developed that is based on the coupled ordinary differential equations (ODEs) described by Higgins et al. (1973), hereinafter HLO. The ODEs characterize the swarm electric field, electron temperature, electron number density, and drift velocity. Important swarm parameters, the momentum transfer collision frequency, energy transfer collision frequency, and ionization rate, are calculated and compared to the previously reported fitted functions given in HLO. These swarm parameters are found using BOLSIG+, a two term Boltzmann solver developed by Hagelaar and Pitchford (2005), which utilizes updated cross sections from the LXcat website created by Pancheshnyi et al. (2012). We validate the swarm model by comparing to experimental effective ionization coefficient data in Dutton (1975) and drift velocity data in Ruiz-Vargas et al. (2010). In addition, we report on electron equilibrium temperatures and times for a uniform electric field of 1 StatV/cm for atmospheric heights from 0 to 40 km. It is shown that the equilibrium temperature and time are sensitive to the modifications in the collision frequencies and ionization rate based on the updated electron interaction cross sections.
Pusateri, Elise N.; Morris, Heidi E.; Nelson, Eric M.; Ji, Wei
2015-08-04
Electromagnetic pulse (EMP) events produce low-energy conduction electrons from Compton electron or photoelectron ionizations with air. It is important to understand how conduction electrons interact with air in order to accurately predict EMP evolution and propagation. An electron swarm model can be used to monitor the time evolution of conduction electrons in an environment characterized by electric field and pressure. Here a swarm model is developed that is based on the coupled ordinary differential equations (ODEs) described by Higgins et al. (1973), hereinafter HLO. The ODEs characterize the swarm electric field, electron temperature, electron number density, and drift velocity. Importantmore » swarm parameters, the momentum transfer collision frequency, energy transfer collision frequency, and ionization rate, are calculated and compared to the previously reported fitted functions given in HLO. These swarm parameters are found using BOLSIG+, a two term Boltzmann solver developed by Hagelaar and Pitchford (2005), which utilizes updated cross sections from the LXcat website created by Pancheshnyi et al. (2012). We validate the swarm model by comparing to experimental effective ionization coefficient data in Dutton (1975) and drift velocity data in Ruiz-Vargas et al. (2010). In addition, we report on electron equilibrium temperatures and times for a uniform electric field of 1 StatV/cm for atmospheric heights from 0 to 40 km. We show that the equilibrium temperature and time are sensitive to the modifications in the collision frequencies and ionization rate based on the updated electron interaction cross sections.« less
Papadimitriou, Vassileios C; Burkholder, James B
2016-08-25
Rate coefficients, k(T), for the OH radical + (E)-(CF3)2CFCH═CHF ((E)-1,3,4,4,4-pentafluoro-3-(trifluoromethyl)-1-butene, HFO-1438ezy(E)) gas-phase reaction were measured using pulsed laser photolysis-laser-induced fluorescence (PLP-LIF) between 214 and 380 K and 50 and 450 Torr (He or N2 bath gas) and with a relative rate method at 296 K between 100 and 400 Torr (synthetic air). Over the range of pressures included in this study, no pressure dependence in k(T) was observed. k(296 K) obtained using the two techniques agreed to within ∼3% with (3.26 ± 0.26) × 10(-13) cm(3) molecule(-1) s(-1) (2σ absolute uncertainty) obtained using the PLP-LIF technique. k(T) displayed non-Arrhenius behavior that is reproduced by (7.34 ± 0.30) × 10(-19)T(2) exp[(481 ± 10)/T) cm(3) molecule(-1) s(-1). With respect to OH reactive loss, the atmospheric lifetime of HFO-1438ezy(E) is estimated to be ∼36 days and HFO-1438ezy(E) is considered a very short-lived substance (VSLS) (the actual lifetime will depend on the time and location of the HFO-1438ezy(E) emission). On the basis of the HFO-1438ezy(E) infrared absorption spectrum measured in this work and its estimated lifetime, a radiative efficiency of 0.306 W m(-2) ppb(-1) (well-mixed gas) was calculated and its 100-year time-horizon global warming potential, GWP100, was estimated to be 8.6. CF3CFO, HC(O)F, and CF2O were identified using infrared spectroscopy as stable end products in the oxidation of HFO-1438ezy(E) in the presence of O2. Two additional fluorinated products were observed and theoretical calculations of the infrared spectra of likely degradation products are presented. The photochemical ozone creation potential of HFO-1438ezy(E) was estimated to be ∼2.15.
Papadimitriou, Vassileios C; Burkholder, James B
2016-08-25
Rate coefficients, k(T), for the OH radical + (E)-(CF3)2CFCH═CHF ((E)-1,3,4,4,4-pentafluoro-3-(trifluoromethyl)-1-butene, HFO-1438ezy(E)) gas-phase reaction were measured using pulsed laser photolysis-laser-induced fluorescence (PLP-LIF) between 214 and 380 K and 50 and 450 Torr (He or N2 bath gas) and with a relative rate method at 296 K between 100 and 400 Torr (synthetic air). Over the range of pressures included in this study, no pressure dependence in k(T) was observed. k(296 K) obtained using the two techniques agreed to within ∼3% with (3.26 ± 0.26) × 10(-13) cm(3) molecule(-1) s(-1) (2σ absolute uncertainty) obtained using the PLP-LIF technique. k(T) displayed non-Arrhenius behavior that is reproduced by (7.34 ± 0.30) × 10(-19)T(2) exp[(481 ± 10)/T) cm(3) molecule(-1) s(-1). With respect to OH reactive loss, the atmospheric lifetime of HFO-1438ezy(E) is estimated to be ∼36 days and HFO-1438ezy(E) is considered a very short-lived substance (VSLS) (the actual lifetime will depend on the time and location of the HFO-1438ezy(E) emission). On the basis of the HFO-1438ezy(E) infrared absorption spectrum measured in this work and its estimated lifetime, a radiative efficiency of 0.306 W m(-2) ppb(-1) (well-mixed gas) was calculated and its 100-year time-horizon global warming potential, GWP100, was estimated to be 8.6. CF3CFO, HC(O)F, and CF2O were identified using infrared spectroscopy as stable end products in the oxidation of HFO-1438ezy(E) in the presence of O2. Two additional fluorinated products were observed and theoretical calculations of the infrared spectra of likely degradation products are presented. The photochemical ozone creation potential of HFO-1438ezy(E) was estimated to be ∼2.15. PMID:27482844
NASA Astrophysics Data System (ADS)
McGillen, Max R.; Bernard, François; Fleming, Eric L.; Burkholder, James B.
2015-07-01
HCFC-133a (CF3CH2Cl), an ozone-depleting substance, is primarily removed from the atmosphere by gas-phase reaction with OH radicals and by UV photolysis. The rate coefficient, k, for the OH + HCFC-133a reaction was measured between 233 and 379 K and is given by k(T) = (9.32 ± 0.8) × 10-13 exp(-(1296 ± 28)/T), where k(296 K) was measured to be (1.10 ± 0.02) × 10-14 (cm3 molecule-1 s-1) (2σ precision uncertainty). The HCFC-133a UV absorption spectrum was measured between 184.95 and 240 nm at 213-323 K, and a spectrum parameterization is presented. The HCFC-133a atmospheric loss processes, lifetime, ozone depletion potential, and uncertainties were evaluated using a 2-D atmospheric model. The global annually averaged steady state lifetime and ozone depletion potential (ODP) were determined to be 4.45 (4.04-4.90) years and 0.017 (±0.001), respectively, where the ranges are based solely on the 2σ uncertainty in the kinetic and photochemical parameters. The infrared absorption spectrum of HCFC-133a was measured, and its global warming potential was determined to be 380 on the 100 year time horizon.
NASA Technical Reports Server (NTRS)
Feofilov, A. G.; Kutepov, A. A.; She, C. Y.; Smith, A. K.; Pesnell, W. D.; Goldberg, R. A.
2009-01-01
Among the processes governing the energy balance in the mesosphere and lower thermosphere (MLT), the quenching of CO2(V2) vibrational levels in collisions with oxygen atoms plays an important role. However, neither the rate coefficient of this process (k(CO2O)) nor the atomic oxygen concentrations ([O]) in the MLT are well known. The discrepancy between k(CO2O) measured in the lab and retrieved from atmospheric measurements is of about factor of 2.5. At the same time, the discrepancy between [O] in the MLT measured by different instruments is of the same order of magnitude. In this work we used a synergy of a ground based lidar and satellite infrared radiometer to make a further step in understanding of the physics of the region. In this study we apply the night- and daytime temperatures between 80 and 110 km measured by the Colorado State University narrow-band sodium (Na) lidar located at Fort Collins, Colorado for retrieving the product of k(CO2-O) x [O] from the limb radiances in the 15 micron channel measured by the SABER/TIMED instrument for nearly simultaneous common volume measurements of both instruments within +/-1 degree in latitude, +/-2 degrees in longitude and +/-10 minutes in time. We derive k(CO2-O) and its possible variation range from the retrieved product by utilizing the [O] values measured by the SABER and other instruments.
NASA Astrophysics Data System (ADS)
Peirone, Silvina A.; Barrera, Javier A.; Taccone, Raúl A.; Cometto, Pablo M.; Lane, Silvia I.
2014-03-01
The relative rate technique was used to determine the rate coefficients of the reactions of OH radicals with (Z)-2-hexen-1-ol (k1), and (E)-3-hexen-1-ol (k2), at (296 ± 2) K and (750 ± 10) Torr of N2 or pure air. The reactions were investigated using a 200 L Teflon reaction chamber and a gas chromatograph coupled with flame-ionization detection. The following rate coefficients were derived, in units of cm3 mol-1 s-1: k1 = (1.1 ± 0.4) × 10-10 and k2 = (0.8 ± 0.1) × 10-10. This is the first experimental determination of k1 and k2. A comparison between the experimental rate coefficients (kexp) and the calculated rate coefficients using the structure-activity relationship (SAR) method (kSAR), for the reaction of different unsaturated alcohols with OH radicals is presented. The atmospheric lifetimes of the studied alcohols were estimated considering the rate coefficients of their reactions with OH and NO3 radicals. The radiative efficiencies (REs) were obtained from the infrared spectra of the two hexenols and the global warming potentials (GWPs) were then estimated. Atmospheric implications of the alcohols emission are briefly discussed.
Karwat, Darshan M A; Wooldridge, Margaret S; Klippenstein, Stephen J; Davis, Michael J
2015-01-29
Experimental, time-resolved species profiles provide critical tests in developing accurate combustion models for biofuels such as n-butanol. A number of such species profiles measured by Karwat et al. [ Karwat, D. M. A.; et al. J. Phys. Chem. A 2011 , 115 , 4909 ] were discordant with predictions from a well-tested chemical kinetic mechanism developed by Black et al. [ Black, G.; et al. Combust. Flame 2010 , 157 , 363 ]. Since then, significant theoretical and experimental efforts have focused on determining the rate coefficients of primary n-butanol consumption pathways in combustion environments, including H atom abstraction reactions from n-butanol by key radicals such as HO2 and OH, as well as the decomposition of the radicals formed by these H atom abstractions. These reactions not only determine the overall reactivity of n-butanol, but also significantly affect the concentrations of intermediate species formed during n-butanol ignition. In this paper we explore the effect of incorporating new ab initio predictions into the Black et al. mechanism on predictions of ignition delay time and species time histories for the experimental conditions studied by Karwat et al. The revised predictions for the intermediate species time histories are in much improved agreement with the measurements, but some discrepancies persist. A rate of production analysis comparing the effects of various modifications to the Black et al. mechanism shows significant changes in the predicted consumption pathways of n-butanol, and of the hydroxybutyl and butoxy radicals formed by H atom abstraction from n-butanol. The predictions from the newly revised mechanism are in very good agreement with the low-pressure n-butanol pyrolysis product species measurements of Stranic et al. [ Stranic, I.; et al. Combust. Flame 2012 , 159 , 3242 ] for all but one species. Importantly, the changes to the Black et al. mechanism show that concentrations of small products from n-butanol pyrolysis are
Nauser, Thomas; Casi, Giulio; Koppenol, Willem H.; Schöneich, Christian
2008-01-01
The intramolecular reaction of cysteine thiyl radicals with peptide and protein αC-H bonds represents a potential mechanism for irreversible protein oxidation. Here, we have measured absolute rate constants for these reversible hydrogen transfer reactions by means of pulse radiolysis and laser flash photolysis of model peptides. For N-Ac-CysGly6 and N-Ac-CysGly2AspGly3, Cys thiyl radicals abstract hydrogen atoms from Gly with kf = (1.0-1.1)×105 s-1, generating carbon-centered radicals, while the reverse reaction proceeds with kr = (8.0-8.9)×105 s-1. The forward reaction shows a normal kinetic isotope effect of kH/kD = 6.9, while the reverse reaction shows a significantly higher normal kinetic isotope effect of 17.6, suggesting a contribution of tunneling. For N-Ac-CysAla2AspAla3, cysteine thiyl radicals abstract hydrogen atoms from Ala with kf =(0.9-1.0)×104 s-1, while the reverse reaction proceeds with kr = 1.0×105 s-1. The order of reactivity, Gly > Ala, is in accord with previous studies on intermolecular reactions of thiyl radicals with these amino acids. The fact that kf < kr suggests some secondary structure of the model peptides, which prevents the adoption of extended conformations, for which calculations of homolytic bond dissociation energies would have predicted kf > kr. Despite kf < kr, model calculations show that intramolecular hydrogen abstraction by Cys thiyl radicals can lead to significant oxidation of other amino acids in the presence of physiologic oxygen concentrations. PMID:18973367
Teaching Absolute Value Meaningfully
ERIC Educational Resources Information Center
Wade, Angela
2012-01-01
What is the meaning of absolute value? And why do teachers teach students how to solve absolute value equations? Absolute value is a concept introduced in first-year algebra and then reinforced in later courses. Various authors have suggested instructional methods for teaching absolute value to high school students (Wei 2005; Stallings-Roberts…
NASA Astrophysics Data System (ADS)
Pfrang, Christian; King, Martin D.; Canosa-Mas, Carlos E.; Flugge, Mark; Wayne, Richard P.
Gas-phase rate coefficients for the atmospherically important reactions of NO 3, OH and O 3 are predicted for 55 α, β-unsaturated esters and ketones. The rate coefficients were calculated using a correlation described previously [Pfrang, C., King, M.D., C. E. Canosa-Mas, C.E., Wayne, R.P., 2006. Atmospheric Environment 40, 1170-1179]. These rate coefficients were used to extend structure-activity relations for predicting the rate coefficients for the reactions of NO 3, OH or O 3 with alkenes to include α, β-unsaturated esters and ketones. Conjugation of an alkene with an α, β-keto or α, β-ester group will reduce the value of a rate coefficient by a factor of ˜110, ˜2.5 and ˜12 for reaction with NO 3, OH or O 3, respectively. The actual identity of the alkyl group, R, in -C(O)R or -C(O)OR has only a small influence. An assessment of the reliability of the SAR is given that demonstrates that it is useful for reactions involving NO 3 and OH, but less valuable for those of O 3 or peroxy nitrate esters.
Smith, Laurence H.; McCarty, Perry L.; Kitanidis, Peter K.
1998-01-01
A convenient method for evaluation of biochemical reaction rate coefficients and their uncertainties is described. The motivation for developing this method was the complexity of existing statistical methods for analysis of biochemical rate equations, as well as the shortcomings of linear approaches, such as Lineweaver-Burk plots. The nonlinear least-squares method provides accurate estimates of the rate coefficients and their uncertainties from experimental data. Linearized methods that involve inversion of data are unreliable since several important assumptions of linear regression are violated. Furthermore, when linearized methods are used, there is no basis for calculation of the uncertainties in the rate coefficients. Uncertainty estimates are crucial to studies involving comparisons of rates for different organisms or environmental conditions. The spreadsheet method uses weighted least-squares analysis to determine the best-fit values of the rate coefficients for the integrated Monod equation. Although the integrated Monod equation is an implicit expression of substrate concentration, weighted least-squares analysis can be employed to calculate approximate differences in substrate concentration between model predictions and data. An iterative search routine in a spreadsheet program is utilized to search for the best-fit values of the coefficients by minimizing the sum of squared weighted errors. The uncertainties in the best-fit values of the rate coefficients are calculated by an approximate method that can also be implemented in a spreadsheet. The uncertainty method can be used to calculate single-parameter (coefficient) confidence intervals, degrees of correlation between parameters, and joint confidence regions for two or more parameters. Example sets of calculations are presented for acetate utilization by a methanogenic mixed culture and trichloroethylene cometabolism by a methane-oxidizing mixed culture. An additional advantage of application of this
NASA Astrophysics Data System (ADS)
Pamboundom, Mama; Tchakoua, Théophile; Nsangou, Mama
2016-04-01
In this work, inelastic rotational collision of AlCl with helium was studied. The CCSD(T) method was used for the computation of an accurate two dimensional potential energy surface (PES). In the calculation of the PES, Al-Cl bond was frozen at the experimental value 4.02678 a0. The aug-cc-pVQZ basis sets of Dunning was used throughout the computational process. This basis was completed with a set of 3s3p2d2f1g bond functions placed at mid-distance between the center of mass of AlCl and He atom for a better description of the van der Waals interaction energy. The PES of AlCl-He was found to have a global minimum at (R=8.65 a0, θ=0 degree), a local minimum at (R=7.45 a0, θ=82 degree) and a saddle point at (R=7.9 a0, θ=56 degree). The depths of the minima were 20.2 cm^{-1} and 19.8 cm^{-1} respectively for θ=0 and 84 degrees. The height of the saddle point with respect to the global minimum was 1.3 cm^{-1}. The PES, the result of an analytical fit, was expanded in terms of Legendre polynomials, then used for the evaluation of state-to-state rotational integral cross sections for the collision of AlCl with He in the close coupling approach. The collisional cross sections for the transitions occurring among the 17 first rotational levels of AlCl were calculated for kinetic energies up to 4000 cm^{-1}. Collisional rate coefficients between these rotational levels were computed for low and moderate kinetic temperatures ranging from 30 to 500 K. A propensity rule that favors odd Δ j transitions was found.
Rate coefficient for the reaction SiO + Si2O2 at T = 10-1000 K.
Pimentel, André S; Lima, Francisco das C A; da Silva, Albérico B F
2006-12-14
The reaction paths for the formation of Si3O3 molecules have been investigated at high level ab initio quantum chemical calculations by using the QCISD method with the 6-311++G(d,p) basis set. The cis-Si2O2 isomer does not participate in the chemical mechanism for the formation of Si3O3 molecules. Although the SiO + cis-Si2O2 reaction is exothermic and spontaneous, it is not expected to explain the growth mechanism of Si3O3 in the interstellar silicate grains of circumstellar envelopes surrounding M-type giants. The reaction of SiO with cyclic Si2O2 molecules is exothermic, is spontaneous, and has a nonplanar transition state. The Gibbs free energy for the transition state formation, (DeltaG0#), is around 5.5 kcal mol-1 at 298 K. The bimolecular rate coefficient for this reaction, kT, is about 1 x 10-12 cm3 molecule-1 s-1 at 298 K and in the collision limit, 1.5 x 10-10 cm3 molecule-1 s-1, at 500 K. The activation energy, Ea, is about 8 kcal mol-1. The enthalpy of Si3O3 fragmentation is 53.9 kcal mol-1 at 298 K. The SiO + cyclic Si2O2 reaction is expected to be the most prominent reaction path for the Si3O3 formation in interstellar environment and fabrication of silicon nanowires. PMID:17149837
Dong Hongjie Krylov, Nicolai V.
2007-06-15
We consider degenerate parabolic and elliptic fully nonlinear Bellman equations with Lipschitz coefficients in domains. Error bounds of order h{sup 1/2} in the sup norm for certain types of finite-difference schemes are obtained.
Radulović, Vladimir; Štancar, Žiga; Snoj, Luka; Trkov, Andrej
2014-02-01
The calculation of axial neutron flux distributions with the MCNP code at the JSI TRIGA Mark II reactor has been validated with experimental measurements of the (197)Au(n,γ)(198)Au reaction rate. The calculated absolute reaction rate values, scaled according to the reactor power and corrected for the flux redistribution effect, are in good agreement with the experimental results. The effect of different cross-section libraries on the calculations has been investigated and shown to be minor. PMID:24316530
Wood, G O; Lodewyckx, P
2003-01-01
Organic vapor adsorption rates in air-purifying respirator cartridges (and other packed beds of activated carbon granules) need to be known for estimating service lives. The correlation of Lodewyckx and Vansant [AIHAJ 61:501-505 (2000)] for mass transfer coefficients for organic vapor adsorption onto activated carbon was tested with additional data from three sources. It was then extended to better describe all the data, including that for gases. The additional parameter that accomplished this was the square root of molar equilibrium capacity of the vapor or gas on the carbon. This change, along with skew corrections when appropriate, resulted in better correlations with all experimental rate coefficients. PMID:14521430
Papadimitriou, Vassileios C; Lazarou, Yannis G; Talukdar, Ranajit K; Burkholder, James B
2011-01-20
Rate coefficients, k, for the gas-phase reactions of Cl atoms and NO(3) radicals with 2,3,3,3-tetrafluoropropene, CF(3)CF═CH(2) (HFO-1234yf), and 1,2,3,3,3-pentafluoropropene, (Z)-CF(3)CF═CHF (HFO-1225ye), are reported. Cl-atom rate coefficients were measured in the fall-off region as a function of temperature (220-380 K) and pressure (50-630 Torr; N(2), O(2), and synthetic air) using a relative rate method. The measured rate coefficients are well represented by the fall-off parameters k(0)(T) = 6.5 × 10(-28) (T/300)(-6.9) cm(6) molecule(-2) s(-1) and k(∞)(T) = 7.7 × 10(-11) (T/300)(-0.65) cm(3) molecule(-1) s(-1) for CF(3)CF═CH(2) and k(0)(T) = 3 × 10(-27) (T/300)(-6.5) cm(6) molecule(-2) s(-1) and k(∞)(T) = 4.15 × 10(-11) (T/300)(-0.5) cm(3) molecule(-1) s(-1) for (Z)-CF(3)C═CHF with F(c) = 0.6. Reaction product yields were measured in the presence of O(2) to be (98 ± 7)% for CF(3)C(O)F and (61 ± 4)% for HC(O)Cl in the CF(3)CF═CH(2) reaction and (108 ± 8)% for CF(3)C(O)F and (112 ± 8)% for HC(O)F in the (Z)-CF(3)CF═CHF reaction, where the quoted uncertainties are 2σ (95% confidence level) and include estimated systematic errors. NO(3) reaction rate coefficients were determined using absolute and relative rate methods. Absolute measurements yielded upper limits for both reactions between 233 and 353 K, while the relative rate measurements yielded k(3)(295 K) = (2.6 ± 0.25) × 10(-17) cm(3) molecule(-1) s(-1) and k(4)(295 K) = (4.2 ± 0.5) × 10(-18) cm(3) molecule(-1) s(-1) for CF(3)CF═CH(2) and (Z)-CF(3)CF═CHF, respectively. The Cl-atom reaction with CF(3)CF═CH(2) and (Z)-CF(3)CF═CHF leads to decreases in their atmospheric lifetimes and global warming potentials and formation of a chlorine-containing product, HC(O)Cl, for CF(3)CF═CH(2). The NO(3) reaction has been shown to have a negligible impact on the atmospheric lifetimes of CF(3)CF═CH(2) and (Z)-CF(3)CF═CHF. The energetics for the reaction of Cl, NO(3), and OH with CF
Eosinophils; Absolute eosinophil count ... the white blood cell count to give the absolute eosinophil count. ... than 500 cells per microliter (cells/mcL). Normal value ranges may vary slightly among different laboratories. Talk ...
NASA Astrophysics Data System (ADS)
Quack, M.; Humbert, P.; van den Bergh, H.
1980-07-01
The influence of the three parameters (with two degrees of freedom) fluence, intensity, and time on rate coefficients and product yields in collisionless Unimolecular Reactions Induced by Monochromatic Infrared Radiation (URIMIR) is discussed in some detail in terms of the recently proposed logarithmic reactant fluence plots. Model calculations for several archetypes of such plots are presented, based on solutions of the Pauli master equation and solutions of the quantum mechanical equations of motion for spectra involving many states at each level of excitation. Linear diagrams, turnups, and turnovers are found and are discussed systematically. Experimental examples re-evaluated from the literature and new measurements on the laser induced decomposition of CF2HCl are reported which nicely illustrate the various theoretical possibilities. Steady state rate coefficients for six molecules are evaluated and summarized. In some situations the intrinsic nonlinear intensity dependence of the steady state rate coefficients and deviations from simple fluence dependence of the product yields both before and at steady state are shown to be important theoretically and experimentally. The role of the reducibility of the rate coefficient matrix is discussed in connection with turnovers and with the strong influence of initial temperature that is found in the laser induced decomposition of CF2HCl.
Liu, Zhijian; Liu, Kejun; Li, Hao; Zhang, Xinyu; Jin, Guangya; Cheng, Kewei
2015-01-01
Measurements of heat collection rate and heat loss coefficient are crucial for the evaluation of in service water-in-glass evacuated tube solar water heaters. However, conventional measurement requires expensive detection devices and undergoes a series of complicated procedures. To simplify the measurement and reduce the cost, software based on artificial neural networks for measuring heat collection rate and heat loss coefficient of water-in-glass evacuated tube solar water heaters was developed. Using multilayer feed-forward neural networks with back-propagation algorithm, we developed and tested our program on the basis of 915 measured samples of water-in-glass evacuated tube solar water heaters. This artificial neural networks-based software program automatically obtained accurate heat collection rate and heat loss coefficient using simply "portable test instruments" acquired parameters, including tube length, number of tubes, tube center distance, heat water mass in tank, collector area, angle between tubes and ground and final temperature. Our results show that this software (on both personal computer and Android platforms) is efficient and convenient to predict the heat collection rate and heat loss coefficient due to it slow root mean square errors in prediction. The software now can be downloaded from http://t.cn/RLPKF08.
Liu, Zhijian; Liu, Kejun; Li, Hao; Zhang, Xinyu; Jin, Guangya; Cheng, Kewei
2015-01-01
Measurements of heat collection rate and heat loss coefficient are crucial for the evaluation of in service water-in-glass evacuated tube solar water heaters. However, conventional measurement requires expensive detection devices and undergoes a series of complicated procedures. To simplify the measurement and reduce the cost, software based on artificial neural networks for measuring heat collection rate and heat loss coefficient of water-in-glass evacuated tube solar water heaters was developed. Using multilayer feed-forward neural networks with back-propagation algorithm, we developed and tested our program on the basis of 915 measured samples of water-in-glass evacuated tube solar water heaters. This artificial neural networks-based software program automatically obtained accurate heat collection rate and heat loss coefficient using simply "portable test instruments" acquired parameters, including tube length, number of tubes, tube center distance, heat water mass in tank, collector area, angle between tubes and ground and final temperature. Our results show that this software (on both personal computer and Android platforms) is efficient and convenient to predict the heat collection rate and heat loss coefficient due to it slow root mean square errors in prediction. The software now can be downloaded from http://t.cn/RLPKF08. PMID:26624613
ERIC Educational Resources Information Center
Liu, Yan; Wu, Amery D.; Zumbo, Bruno D.
2010-01-01
In a recent Monte Carlo simulation study, Liu and Zumbo showed that outliers can severely inflate the estimates of Cronbach's coefficient alpha for continuous item response data--visual analogue response format. Little, however, is known about the effect of outliers for ordinal item response data--also commonly referred to as Likert, Likert-type,…
Werfelli, Ghofran; Halvick, Philippe; Honvault, Pascal; Kerkeni, Boutheïna; Stoecklin, Thierry
2015-09-21
The observed abundances of the methylidyne cation, CH(+), in diffuse molecular clouds can be two orders of magnitude higher than the prediction of the standard gas-phase models which, in turn, predict rather well the abundances of neutral CH. It is therefore necessary to investigate all the possible formation and destruction processes of CH(+) in the interstellar medium with the most abundant species H, H2, and e(-). In this work, we address the destruction process of CH(+) by hydrogen abstraction. We report a new calculation of the low temperature rate coefficients for the abstraction reaction, using accurate time-independent quantum scattering and a new high-level ab initio global potential energy surface including a realistic model of the long-range interaction between the reactants H and CH(+). The calculated thermal rate coefficient is in good agreement with the experimental data in the range 50 K-800 K. However, at lower temperatures, the experimental rate coefficient takes exceedingly small values which are not reproduced by the calculated rate coefficient. Instead, the latter rate coefficient is close to the one given by the Langevin capture model, as expected for a reaction involving an ion and a neutral species. Several recent theoretical works have reported a seemingly good agreement with the experiment below 50 K, but an analysis of these works show that they are based on potential energy surfaces with incorrect long-range behavior. The experimental results were explained by a loss of reactivity of the lowest rotational states of the reactant; however, the quantum scattering calculations show the opposite, namely, a reactivity enhancement with rotational excitation.
NASA Astrophysics Data System (ADS)
Zhu, Xi-Ming; Cheng, Zhi-Wen; Carbone, Emile; Pu, Yi-Kang; Czarnetzki, Uwe
2016-08-01
Electron-impact excitation processes play an important role in low-temperature plasma physics. Cross section and rate coefficient data for electron-impact processes from the ground state to excited states or between two excited states are required for both diagnostics and modeling works. However, the collisional processes between excited states are much less investigated than the ones involving the ground state due to various experimental challenges. Recently, a method for determining electron excitation rate coefficients between Ar excited states in afterglow plasmas was successfully implemented and further developed to obtain large sets of collisional data. This method combines diagnostics for electron temperature, electron density, and excited species densities and kinetic modeling of excited species, from which the electron excitation rate coefficients from one of the 1s states to the other 1s states or to one of 2p or 3p states are determined (states are in Paschen’s notation). This paper reviews the above method—namely the combined diagnostics and modeling in afterglow plasmas. The results from other important approaches, including electron-beam measurement of cross sections, laser pump-probe technique for measuring rate coefficients, and theoretical calculations by R-matrix and distorted-wave models are also discussed. From a comparative study of these results, a fitted mathematical expression of excitation rate coefficients is obtained for the electron temperature range of 1-5 eV, which can be used for the collisional-radiative modeling of low-temperature Ar plasmas. At last, we report the limitations in the present dataset and give some suggestions for future work in this area.
NASA Astrophysics Data System (ADS)
Zhu, Xi-Ming; Cheng, Zhi-Wen; Carbone, Emile; Pu, Yi-Kang; Czarnetzki, Uwe
2016-08-01
Electron-impact excitation processes play an important role in low-temperature plasma physics. Cross section and rate coefficient data for electron-impact processes from the ground state to excited states or between two excited states are required for both diagnostics and modeling works. However, the collisional processes between excited states are much less investigated than the ones involving the ground state due to various experimental challenges. Recently, a method for determining electron excitation rate coefficients between Ar excited states in afterglow plasmas was successfully implemented and further developed to obtain large sets of collisional data. This method combines diagnostics for electron temperature, electron density, and excited species densities and kinetic modeling of excited species, from which the electron excitation rate coefficients from one of the 1s states to the other 1s states or to one of 2p or 3p states are determined (states are in Paschen’s notation). This paper reviews the above method—namely the combined diagnostics and modeling in afterglow plasmas. The results from other important approaches, including electron-beam measurement of cross sections, laser pump-probe technique for measuring rate coefficients, and theoretical calculations by R-matrix and distorted-wave models are also discussed. From a comparative study of these results, a fitted mathematical expression of excitation rate coefficients is obtained for the electron temperature range of 1–5 eV, which can be used for the collisional-radiative modeling of low-temperature Ar plasmas. At last, we report the limitations in the present dataset and give some suggestions for future work in this area.
NASA Technical Reports Server (NTRS)
Batterson, Sidney A.
1959-01-01
An experimental investigation was made at the Langley landing loads track to obtain data on the maximum spin-up coefficients of friction developed by a landing gear having a static-load rating of 20,000 pounds. The forward speeds ranged from 0 to approximately 180 feet per second and the sinking speeds, from 2.7 feet per second to 9.4 feet per second. The results indicated the variation of the maximum spin-up coefficient of friction with forward speed and vertical load. Data obtained during this investigation are also compared with some results previously obtained for nonrolling tires to show the effect of forward speed.
Liu, Zhijian; Liu, Kejun; Li, Hao; Zhang, Xinyu; Jin, Guangya; Cheng, Kewei
2015-01-01
Measurements of heat collection rate and heat loss coefficient are crucial for the evaluation of in service water-in-glass evacuated tube solar water heaters. However, conventional measurement requires expensive detection devices and undergoes a series of complicated procedures. To simplify the measurement and reduce the cost, software based on artificial neural networks for measuring heat collection rate and heat loss coefficient of water-in-glass evacuated tube solar water heaters was developed. Using multilayer feed-forward neural networks with back-propagation algorithm, we developed and tested our program on the basis of 915measuredsamples of water-in-glass evacuated tube solar water heaters. This artificial neural networks-based software program automatically obtained accurate heat collection rateand heat loss coefficient using simply "portable test instruments" acquired parameters, including tube length, number of tubes, tube center distance, heat water mass in tank, collector area, angle between tubes and ground and final temperature. Our results show that this software (on both personal computer and Android platforms) is efficient and convenient to predict the heat collection rate and heat loss coefficient due to it slow root mean square errors in prediction. The software now can be downloaded from http://t.cn/RLPKF08. PMID:26624613
NASA Astrophysics Data System (ADS)
Liu, K.; Zitzenbacher, G.; Laengauer, M.; Kneidinger, C.
2014-05-01
The influence of the pellet shape on the external coefficient of friction of polypropylene and on the mass flow rate of a single screw extruder is presented in this conference paper. The external coefficient of friction describes the friction between the polymeric bulk material and the screw or the barrel surface. In general, the external coefficient of friction should be rather low at the screw surface and high at the barrel surface in order to achieve a high mass flow rate and sufficient pressure build-up in the conveying zone of a single screw extruder. The measurements of the external coefficient of friction of polypropylene pellets, which are dependent on the shape and the dimensions of the pellets at processing conditions (pressure and velocity), are carried out using a previously developed tribometer. The tests were performed at room temperature on a polished hardened shaft made of screw steel. The effect of the shape of the polypropylene pellets on the mass flow rate is studied using a single screw extruder (Measuring extruder type Dr. Collin E20M). Two different temperature profiles were used for the extrusion experiments. When using the long cylindrical polypropylene pellets a higher extruder output can be achieved compared to the virgin material.
NASA Technical Reports Server (NTRS)
Dean, D. C.; Goldstein, J. I.
1984-01-01
The interdiffusion coefficient of FeNi in fcc taenite (gamma) of Fe-Ni and Fe-Ni-0.2 P alloys was measured as a function of temperature between 600 and 900 C. This temperature range is directly applicable to the nucleation and growth of the Widmanstatten pattern in iron meteorites and metal regions of stony and stony-iron meteorites. Diffusion couples were made from FeNi or FeNiP alloys which ensured that the couples were in the taenite phase at the diffusion temperature. The presence or absence of grain boundary diffusion was determined by measuring the Ni profile normal to the existing grain boundaries with the AEM. Ignoring any variation of interdiffusion coefficient with composition, the measured data was plotted versus the reciprocal of the diffusion temperature. The FeNi data generally follow the extrapolated Goldstein, et al. (1965) data from high temperatures. The FeNiP data indicates that small additions of P (0.2 wt%) cause a 3 to 10 fold increase in the FeNi interdifussion coefficient increasing with decreasing temperature. This increase is about the same as that predicted by Narayan and Goldstein (1983) at the Widmanstatten growth temperature.
Li, Yongle; Suleimanov, Yury V; Green, William H; Guo, Hua
2014-03-20
Thermal rate coefficients and kinetic isotope effect have been calculated for prototypical heavy-light-heavy polyatomic bimolecular reactions Cl + CH4/CD4 → HCl/DCl + CH3/CD3, using a recently proposed quantum dynamics approach: ring polymer molecular dynamics (RPMD). Agreement with experimental rate coefficients, which are quite scattered, is satisfactory. However, differences up to 50% have been found between the RPMD results and those obtained from the harmonic variational transition-state theory on one of the two full-dimensional potential energy surfaces used in the calculations. Possible reasons for such discrepancy are discussed. The present work is an important step in a series of benchmark studies aimed at assessing accuracy for RPMD for chemical reaction rates, which demonstrates that this novel method is a quite reliable alternative to previously developed techniques based on transition-state theory.
Egelhaaf, Hans-Joachim; Rademann, Jörg
2005-01-01
A general algorithm allowing the numerical modeling of the time and space dependence of product formation in spherical reaction volumes is described. The algorithm is described by the complete set of mass balance equations. On the basis of these equations, the effects of the diffusion coefficient, reaction rate, bead size, reagent excess, and packing density of the resin beads on the overall reaction rates are determined for second-order reactions. Experimental data of reaction progress are employed to calculate reaction rates and diffusion coefficients in polymer-supported reactions. In addition, the conditions for shell-like product formation are determined, and various strategies for the radial patterning of resin beads are compared. The effect of diffusion on polymer-supported enzyme-catalyzed reactions of the Michaelis-Menten type is treated, as well. Finally, the effects of typical nonideal solid-phase phenomena, namely, the inhomogeneity of rate constants and the concentration dependence of diffusion coefficients, on overall rates are discussed.
Malagnini, L; Bodin, P; Mayeda, K; Akinci, A
2005-05-04
What can be learned about absolute site effects on ground motions and about earthquake source spectra from recordings at temporary seismic stations, none of which could be considered a 'reference' (hard rock) site, for which no geotechnical information is available, in a very poorly instrumented region? This challenge motivated our current study of aftershocks of the 2001 Mw 7.6 Bhuj earthquake, in Western India. Crustal attenuation and spreading relationships based on the same data used here were determined in an earlier study. In this paper we decouple the ambiguity between absolute source radiation and site effects by first computing robust estimates of moment-rate spectra of about 200 aftershocks in each of two depth ranges. Using these new estimates of sourcespectra, and our understanding of regional wave propagation, we extract the absolute site terms of the sites of the temporary deployment. Absolute site terms (one for each component of the ground motion, for each station) are computed in an average sense, via an L{sub 1}-norm minimization, and results for each site are averaged over wide ranges of azimuths and takeoff angles. The Bhuj deployment is characterized by a variable shallow geology, mostly of soft sedimentary units. Vertical site terms in the region were observed to be almost featureless and slightly < 1.0 within wide frequency ranges. As a result, H/V spectral ratios mimic the absolute behaviors of absolute horizontal site terms, and they generally overpredict them. On the contrary, with respect to the results for sedimentary rock sites (limestone, dolomite) obtained by Malagnini et al. (2004), H/V spectral ratios in their study did not have much in common with absolute horizontal site terms. Spectral ratios between the vector sum of the computed horizontal site terms for the temporary deployment with respect to the same quantity computed at the hardest rock station available, BAC1, are seriously biased by its non-flat, non-unitary site response
Tajima, Satomi; Hayashi, Toshio; Hori, Masaru
2015-02-26
The rate coefficient of F2 + NO → F + FNO is 2 to 5 orders of magnitude higher than that of F2 + NO2 → F + FNO2 even though bond energies of FNO and FNO2 only differ by ∼0.2 eV. To understand the cause of having different rate coefficients of these two reactions, the change in total energies was calculated by varying the stereochemical arrangement of F2 with respect to NOx (x = 1 or 2) by the density functional theory (DFT), using CAM-B3LYP/6-311 G+(d) in the Gaussian program. The permitted approaching angle between the x-axis and the plane consisting of O, N, F, and ϕ plays a key role to restrict the reaction of NO2 and F2 compared to the reaction of NO and F2. This restriction in the reaction space is considered to be the main cause of different rate coefficients depending on the selection of x = 1 or 2 of the reaction of F2 + NOx → F + FNOx, which was also confirmed by the difference in Si etch rate using the F formed by those reactions. PMID:25599135
Tajima, Satomi; Hayashi, Toshio; Hori, Masaru
2015-02-26
The rate coefficient of F2 + NO → F + FNO is 2 to 5 orders of magnitude higher than that of F2 + NO2 → F + FNO2 even though bond energies of FNO and FNO2 only differ by ∼0.2 eV. To understand the cause of having different rate coefficients of these two reactions, the change in total energies was calculated by varying the stereochemical arrangement of F2 with respect to NOx (x = 1 or 2) by the density functional theory (DFT), using CAM-B3LYP/6-311 G+(d) in the Gaussian program. The permitted approaching angle between the x-axis and the plane consisting of O, N, F, and ϕ plays a key role to restrict the reaction of NO2 and F2 compared to the reaction of NO and F2. This restriction in the reaction space is considered to be the main cause of different rate coefficients depending on the selection of x = 1 or 2 of the reaction of F2 + NOx → F + FNOx, which was also confirmed by the difference in Si etch rate using the F formed by those reactions.
Absolute nuclear material assay
Prasad, Manoj K.; Snyderman, Neal J.; Rowland, Mark S.
2012-05-15
A method of absolute nuclear material assay of an unknown source comprising counting neutrons from the unknown source and providing an absolute nuclear material assay utilizing a model to optimally compare to the measured count distributions. In one embodiment, the step of providing an absolute nuclear material assay comprises utilizing a random sampling of analytically computed fission chain distributions to generate a continuous time-evolving sequence of event-counts by spreading the fission chain distribution in time.
Absolute nuclear material assay
Prasad, Manoj K.; Snyderman, Neal J.; Rowland, Mark S.
2010-07-13
A method of absolute nuclear material assay of an unknown source comprising counting neutrons from the unknown source and providing an absolute nuclear material assay utilizing a model to optimally compare to the measured count distributions. In one embodiment, the step of providing an absolute nuclear material assay comprises utilizing a random sampling of analytically computed fission chain distributions to generate a continuous time-evolving sequence of event-counts by spreading the fission chain distribution in time.
Reference Material for Seebeck Coefficients
NASA Astrophysics Data System (ADS)
Edler, F.; Lenz, E.; Haupt, S.
2015-03-01
This paper describes a measurement method and a measuring system to determine absolute Seebeck coefficients of thermoelectric bulk materials with the aim of establishing reference materials for Seebeck coefficients. Reference materials with known thermoelectric properties are essential to allow a reliable benchmarking of different thermoelectric materials for application in thermoelectric generators to convert thermal into electrical energy or vice versa. A temperature gradient (1 to 8) K is induced across the sample, and the resulting voltage is measured by using two differential Au/Pt thermocouples. On the basis of the known absolute Seebeck coefficients of Au and Pt, the unknown Seebeck coefficient of the sample is calculated. The measurements are performed in inert atmospheres and at low pressure (30 to 60) mbar in the temperature range between 300 K and 860 K. The measurement results of the Seebeck coefficients of metallic and semiconducting samples are presented. Achievable relative measurement uncertainties of the Seebeck coefficient are on the order of a few percent.
Li, Yaqin; Sun, Zhigang E-mail: dawesr@mst.edu; Jiang, Bin; Guo, Hua E-mail: dawesr@mst.edu; Xie, Daiqian; Dawes, Richard E-mail: dawesr@mst.edu
2014-08-28
The kinetics and dynamics of several O + O{sub 2} isotope exchange reactions have been investigated on a recently determined accurate global O{sub 3} potential energy surface using a time-dependent wave packet method. The agreement between calculated and measured rate coefficients is significantly improved over previous work. More importantly, the experimentally observed negative temperature dependence of the rate coefficients is for the first time rigorously reproduced theoretically. This negative temperature dependence can be attributed to the absence in the new potential energy surface of a submerged “reef” structure, which was present in all previous potential energy surfaces. In addition, contributions of rotational excited states of the diatomic reactant further accentuate the negative temperature dependence.
NASA Astrophysics Data System (ADS)
McGillen, M. R.; Percival, C. J.; Pieterse, G.; Watson, L. A.; Shallcross, D. E.
2007-02-01
The reactivity of aromatic compounds is of great relevance to pure and applied chemical disciplines, yet existing methods for estimating gas-phase rate coefficients for their reactions with free radicals lack accuracy and universality. Here a novel approach is taken, whereby strong relationships between rate coefficients of aromatic hydrocarbons and a Randić-type topological index are investigated, optimized and developed into a method which requires no specialist software or computing power. Measured gas-phase rate coefficients for the reaction of aromatic hydrocarbons with OH radicals were correlated with a calculated Randić-type index, and optimized by including a term for side chain length. Although this method is exclusively for use with hydrocarbons, it is more diverse than any single existing methodology since it incorporates alkenylbenzenes into correlations, and can be extended towards other radical species such as O(3P) (and tentatively NO3, H and Cl). A comparison (with species common to both techniques) is made between the topological approach advocated here and a popular approach based on electrophilic subsituent constants, where it compares favourably. A modelling study was carried out to assess the impact of using estimated rate coefficients as opposed to measured data in an atmospheric model. The difference in model output was negligible for a range of NOx concentrations, which implies that this method has utility in complex chemical models. Strong relationships (e.g.~for OH, R2 = 0.96) between seemingly diverse compounds including benzene, multisubstituted benzenes with saturated, unsaturated, aliphatic and cyclic substitutions and the nonbenzenoid aromatic, azulene suggests that the Randić-type index presented here represents a new and effective way of describing aromatic reactivity, based on a quantitative structure-activity relationship (QSAR).
NASA Astrophysics Data System (ADS)
McGillen, M. R.; Percival, C. J.; Pieterse, G.; Watson, L. A.; Shallcross, D. E.
2007-07-01
The reactivity of aromatic compounds is of great relevance to pure and applied chemical disciplines, yet existing methods for estimating gas-phase rate coefficients for their reactions with free radicals lack accuracy and universality. Here a novel approach is taken, whereby strong relationships between rate coefficients of aromatic hydrocarbons and a Randić-type topological index are investigated, optimized and developed into a method which requires no specialist software or computing power. Measured gas-phase rate coefficients for the reaction of aromatic hydrocarbons with OH radicals were correlated with a calculated Randić-type index, and optimized by including a term for side chain length. Although this method is exclusively for use with hydrocarbons, it is more diverse than any single existing methodology since it incorporates alkenylbenzenes into correlations, and can be extended towards other radical species such as O(3P) (and tentatively NO3, H and Cl). A comparison (with species common to both techniques) is made between the topological approach advocated here and a popular approach based on electrophilic subsituent constants, where it compares favourably. A modelling study was carried out to assess the impact of using estimated rate coefficients as opposed to measured data in an atmospheric model. The difference in model output was negligible for a range of NOx concentrations, which implies that this method has utility in complex chemical models. Strong relationships (e.g. for OH, R2=0.96) between seemingly diverse compounds including benzene, multisubstituted benzenes with saturated, unsaturated, aliphatic and cyclic substitutions and the nonbenzenoid aromatic, azulene suggests that the Randić-type index presented here represents a new and effective way of describing aromatic reactivity, based on a quantitative structure-activity relationship (QSAR).
NASA Technical Reports Server (NTRS)
Banks, M.; Bridges, N. T.; Benzit, M.
2005-01-01
Knowledge of the rates at which rocks abrade from the impact of saltating sand provides important input into estimating the age and degree of modification of arid surfaces on Earth and Mars. Previous work has relied on measuring mass loss rates in the field and the laboratory. The susceptibility of rocks and other natural materials has been quantified on a relative scale from laboratory studies.
Ramos Fuentes, F; Cardesa García, J J; Arbués Lacadena, J; Espinosa Ruiz-Cabal, J; Pérez González, J
1987-09-01
A prospective study of continual heart rate monitoring is made in 57 normal newborn infants in the first two hours after birth. They were all divided into three groups according to their type of delivery. We have estimated the coefficient of variation, whose value quantifies the heart rate variability, obtained by continual monitoring. It was significantly lower (p less than 0.05) in newborns whose mothers had received anaesthesia during labour than in infants born by non-induced vaginal delivery. These results support the sensitivity of this method in order to assess neonatal cardiac readaptation.
NASA Technical Reports Server (NTRS)
Savin, D. W.; Badnell, N. R.; Bartsch, T.; Brandau, C.; Chen, M. H.; Grieser, M.; Gwinner, G.; Hoffknecht, A.; Kahn, S. M.; Linkemann, J.
2000-01-01
Iron L-shell ions (Fe XVII to Fe XXIV) play an important role in determining the line emission and thermal and ionization structures of photoionized gases. Existing uncertainties in the theoretical low temperature dielectronic recombination (DR) rate coefficients for these ions significantly affects our ability to model and interpret observations of photoionized plasmas. To help address this issue, we have initiated a laboratory program to produce reliable low temperature DR rates. Here, we present some of our recent results and discuss some of their astrophysical implications.
Santos, M V; Sansinena, M; Zaritzky, N; Chirife, J
2012-01-01
In oocyte vitrification, plunging directly into liquid nitrogen favor film boiling and strong nitrogen vaporization. A survey of literature values of heat transfer coefficients (h) for film boiling of small metal objects with different geometries plunged in liquid nitrogen revealed values between 125 to 1000 W per per square m per K. These h values were used in a numerical simulation of cooling rates of two oocyte vitrification devices (open-pulled straw and Cryotop), plunged in liquid and slush nitrogen conditions. Heat conduction equation with convective boundary condition was considered a linear mathematical problem and was solved using the finite element method applying the variational formulation. COMSOL Multiphysics was used to simulate the cooling process of the systems. Predicted cooling rates for OPS and Cryotop when cooled at -196 degree C (liquid nitrogen) or -207 degree C (average for slush nitrogen) for heat transfer coefficients estimated to be representative of film boiling, indicated lowering the cooling temperature produces only a maximum 10 percent increase in cooling rates; confirming the main benefit of plunging in slush over liquid nitrogen does not arise from their temperature difference. Numerical simulations also demonstrated that a hypothetical four-fold increase in the cooling rate of vitrification devices when plunging in slush nitrogen would be explained by an increase in heat transfer coefficient. This improvement in heat transfer (i.e., high cooling rates) in slush nitrogen is attributed to less or null film boiling when a sample is placed in slush (mixture of liquid and solid nitrogen) because it first melts the solid nitrogen before causing the liquid to boil and form a film.
Meng, Qingyong; Chen, Jun; Zhang, Dong H
2015-09-14
The ring polymer molecular dynamics (RPMD) calculations are performed to calculate rate constants for the title reaction on the recently constructed potential energy surface based on permutation invariant polynomial (PIP) neural-network (NN) fitting [J. Li et al., J. Chem. Phys. 142, 204302 (2015)]. By inspecting convergence, 16 beads are used in computing free-energy barriers at 300 K ≤ T ≤ 1000 K, while different numbers of beads are used for transmission coefficients. The present RPMD rates are in excellent agreement with quantum rates computed on the same potential energy surface, as well as with the experimental measurements, demonstrating further that the RPMD is capable of producing accurate rates for polyatomic chemical reactions even at rather low temperatures.
NASA Astrophysics Data System (ADS)
Meng, Qingyong; Chen, Jun; Zhang, Dong H.
2015-09-01
The ring polymer molecular dynamics (RPMD) calculations are performed to calculate rate constants for the title reaction on the recently constructed potential energy surface based on permutation invariant polynomial (PIP) neural-network (NN) fitting [J. Li et al., J. Chem. Phys. 142, 204302 (2015)]. By inspecting convergence, 16 beads are used in computing free-energy barriers at 300 K ≤ T ≤ 1000 K, while different numbers of beads are used for transmission coefficients. The present RPMD rates are in excellent agreement with quantum rates computed on the same potential energy surface, as well as with the experimental measurements, demonstrating further that the RPMD is capable of producing accurate rates for polyatomic chemical reactions even at rather low temperatures.
Kirikae, M.; Diksic, M.; Yamamoto, Y.L.
1988-08-01
An autoradiographic method for the measurement of the rate of valine incorporation into brain proteins is described. The transfer coefficients for valine into and out of the brain and the rate of valine incorporation into normal rat brain proteins are given. The valine incorporation and the transfer constants of valine between different biological compartments are provided for 14 gray matter and 2 white matter structures of an adult rat brain. The rate of valine incorporation varies between 0.52 +/- 0.19 nmol/g/min in white matter and 1.94 +/- 0.47 in inferior colliculus (gray matter). Generally, the rate of valine incorporation is about three to four times higher in the gray matter than in the white matter structures.
Mass transfer between aquifer material and groundwater is often modeled as first-order rate-limited sorption or diffusive exchange between mobile zones and immobile zones with idealized geometries. Recent improvements in experimental techniques and advances in our understanding o...
Rate Coefficient for the (4)Heμ + CH4 Reaction at 500 K: Comparison between Theory and Experiment.
Arseneau, Donald J; Fleming, Donald G; Li, Yongle; Li, Jun; Suleimanov, Yury V; Guo, Hua
2016-03-01
The rate constant for the H atom abstraction reaction from methane by the muonic helium atom, Heμ + CH4 → HeμH + CH3, is reported at 500 K and compared with theory, providing an important test of both the potential energy surface (PES) and reaction rate theory for the prototypical polyatomic CH5 reaction system. The theory used to characterize this reaction includes both variational transition-state (CVT/μOMT) theory (VTST) and ring polymer molecular dynamics (RPMD) calculations on a recently developed PES, which are compared as well with earlier calculations on different PESs for the H, D, and Mu + CH4 reactions, the latter, in particular, providing for a variation in atomic mass by a factor of 36. Though rigorous quantum calculations have been carried out for the H + CH4 reaction, these have not yet been extended to the isotopologues of this reaction (in contrast to H3), so it is important to provide tests of less rigorous theories in comparison with kinetic isotope effects measured by experiment. In this regard, the agreement between the VTST and RPMD calculations and experiment for the rate constant of the Heμ + CH4 reaction at 500 K is excellent, within 10% in both cases, which overlaps with experimental error.
Scheibe, Timothy D.
2002-10-28
In granular porous media, bacterial transport is often modeled using the advection-dispersion transport equation, modified to account for interactions between the bacteria and grain surfaces (attachment and detachment) using a linear kinetic reaction model. In this paper we examine the relationships among the parameters of the above model in the context of bacterial transport for bioaugmentation. In this context, we wish to quantify the distance to which significant concentrations of bacteria can be transported, as well as the uniformity with which they can be distributed within the subsurface. Because kinetic detachment rates (Kr) are typically much smaller than corresponding attachment rates (Kf), the attachment rate exerts primary control on the distance of bacterial transport. Hydraulic conductivity (K) also plays a significant role because of its direct relationship to the advective velocity and its typically high degree of spatial variability at field scales. Because Kf is related to the velocity, grain size, and porosity of the medium, as is K, we expect that there exists correlation between these two parameters. Previous investigators have assumed a form of correlation between Kf and ln(K) based in part on reparameterization of clean-bed filtration equations in terms of published relations between grain size, effective porosity, and ln(K). The hypotheses examined here are that (1) field-scale relationships between K and Kf can be developed by combining a number of theoretical and empirical results in the context of a heterogeneous aquifer flow model (following a similar approach to previous investigators with some extensions), and (2) correlation between K and Kf will enhance the distance of field-scale bacterial transport in granular aquifers. We test these hypotheses using detailed numerical models and observations of field-scale bacterial transport in a shallow sandy aquifer within the South Oyster Site near Oyster, Virginia, USA.
Corman, Gregory Scot; Dean, Anthony John; Tognarelli, Leonardo; Pecchioli, Mario
2005-06-28
A structure for attaching together or sealing a space between a first component and a second component that have different rates or amounts of dimensional change upon being exposed to temperatures other than ambient temperature. The structure comprises a first attachment structure associated with the first component that slidably engages a second attachment structure associated with the second component, thereby allowing for an independent floating movement of the second component relative to the first component. The structure can comprise split rings, laminar rings, or multiple split rings.
NASA Astrophysics Data System (ADS)
Górecki, Kamil; Bala, Piotr; Cios, Grzegorz; Koziel, Tomasz; Stępień, Milena; Wieczerzak, Krzysztof
2016-07-01
An influence of two different cooling rates on the microstructure and dispersion of the components of high-entropy alloy from Al-Ti-Co-Ni-Fe system has been examined. For investigated alloys, the effective partitioning coefficient has been calculated. This factor indicates the degree of segregation of elements and allows for the specification of the differences between dendrites and interdendritic regions. The obtained results allow for the conclusion that the cooling rate substantially affect the growth of dendrites and the volume fraction of interdendritic regions as well as the partitioning of elements in the alloy. Furthermore, the obtained results made it possible to compare the influence of the cooling rate and the chemical composition on the dispersion of the alloying elements.
NASA Technical Reports Server (NTRS)
Hoobler, Ray J.; Leone, Stephen R.
1997-01-01
Rate coefficients for the reactions of C2H + HCN yields products and C2H + CH3CN yields products have been measured over the temperature range 262-360 K. These experiments represent an ongoing effort to accurately measure reaction rate coefficients of the ethynyl radical, C2H, relevant to planetary atmospheres such as those of Jupiter and Saturn and its satellite Titan. Laser photolysis of C2H2 is used to produce C2H, and transient infrared laser absorption is employed to measure the decay of C2H to obtain the subsequent reaction rates in a transverse flow cell. Rate constants for the reaction C2H + HCN yields products are found to increase significantly with increasing temperature and are measured to be (3.9-6.2) x 10(exp 13) cm(exp 3) molecules(exp -1) s(exp -1) over the temperature range of 297-360 K. The rate constants for the reaction C2H + CH3CN yields products are also found to increase substantially with increasing temperature and are measured to be (1.0-2.1) x 10(exp -12) cm(exp 3) molecules(exp -1) s(exp -1) over the temperature range of 262-360 K. For the reaction C2H + HCN yields products, ab initio calculations of transition state structures are used to infer that the major products form via an addition/elimination pathway. The measured rate constants for the reaction of C2H + HCN yields products are significantly smaller than values currently employed in photochemical models of Titan, which will affect the HC3N distribution.
Endres, Eric S; Lakhmanskaya, Olga; Hauser, Daniel; Huber, Stefan E; Best, Thorsten; Kumar, Sunil S; Probst, Michael; Wester, Roland
2014-08-21
In the interstellar medium (ISM) ion–molecule reactions play a key role in forming complex molecules. Since 2006, after the radioastronomical discovery of the first of by now six interstellar anions, interest has grown in understanding the formation and destruction pathways of negative ions in the ISM. Experiments have focused on reactions and photodetachment of the identified negatively charged ions. Hints were found that the reactions of CnH(–) with H2 may proceed with a low (<10(–13) cm(3) s(–1)), but finite rate [Eichelberger, B.; et al. Astrophys. J. 2007, 667, 1283]. Because of the high abundance of molecular hydrogen in the ISM, a precise knowledge of the reaction rate is needed for a better understanding of the low-temperature chemistry in the ISM. A suitable tool to analyze rare reactions is the 22-pole radiofrequency ion trap. Here, we report on reaction rates for Cn(–) and CnH(–) (n = 2, 4, 6) with buffer gas temperatures of H2 at 12 and 300 K. Our experiments show the absence of these reactions with an upper limit to the rate coefficients between 4 × 10(–16) and 5 × 10(–15) cm(3) s(–1), except for the case of C2(–), which does react with a finite rate with H2 at low temperatures. For the cases of C2H(–) and C4H(–), the experimental results were confirmed with quantum chemical calculations. In addition, the possible influence of a residual reactivity on the abundance of C4H(–) and C6H(–) in the ISM were estimated on the basis of a gas-phase chemical model based on the KIDA database. We found that the simulated ion abundances are already unaffected if reaction rate coefficients with H2 were below 10(–14) cm(3) s(–1).
McLeod, Stephen
2014-07-01
Absolute needs (as against instrumental needs) are independent of the ends, goals and purposes of personal agents. Against the view that the only needs are instrumental needs, David Wiggins and Garrett Thomson have defended absolute needs on the grounds that the verb 'need' has instrumental and absolute senses. While remaining neutral about it, this article does not adopt that approach. Instead, it suggests that there are absolute biological needs. The absolute nature of these needs is defended by appeal to: their objectivity (as against mind-dependence); the universality of the phenomenon of needing across the plant and animal kingdoms; the impossibility that biological needs depend wholly upon the exercise of the abilities characteristic of personal agency; the contention that the possession of biological needs is prior to the possession of the abilities characteristic of personal agency. Finally, three philosophical usages of 'normative' are distinguished. On two of these, to describe a phenomenon or claim as 'normative' is to describe it as value-dependent. A description of a phenomenon or claim as 'normative' in the third sense does not entail such value-dependency, though it leaves open the possibility that value depends upon the phenomenon or upon the truth of the claim. It is argued that while survival needs (or claims about them) may well be normative in this third sense, they are normative in neither of the first two. Thus, the idea of absolute need is not inherently normative in either of the first two senses. PMID:23586876
McLeod, Stephen
2014-07-01
Absolute needs (as against instrumental needs) are independent of the ends, goals and purposes of personal agents. Against the view that the only needs are instrumental needs, David Wiggins and Garrett Thomson have defended absolute needs on the grounds that the verb 'need' has instrumental and absolute senses. While remaining neutral about it, this article does not adopt that approach. Instead, it suggests that there are absolute biological needs. The absolute nature of these needs is defended by appeal to: their objectivity (as against mind-dependence); the universality of the phenomenon of needing across the plant and animal kingdoms; the impossibility that biological needs depend wholly upon the exercise of the abilities characteristic of personal agency; the contention that the possession of biological needs is prior to the possession of the abilities characteristic of personal agency. Finally, three philosophical usages of 'normative' are distinguished. On two of these, to describe a phenomenon or claim as 'normative' is to describe it as value-dependent. A description of a phenomenon or claim as 'normative' in the third sense does not entail such value-dependency, though it leaves open the possibility that value depends upon the phenomenon or upon the truth of the claim. It is argued that while survival needs (or claims about them) may well be normative in this third sense, they are normative in neither of the first two. Thus, the idea of absolute need is not inherently normative in either of the first two senses.
Li, Yongle; Suleimanov, Yury V; Guo, Hua
2014-02-20
The thermal rate constants of two prototypical insertion-type reactions, namely, N/O + H2 → NH/OH + H, are investigated with ring polymer molecular dynamics (RPMD) on full-dimensional potential energy surfaces using recently developed RPMDrate code. It is shown that the unique ability of the RPMD approach among the existing theoretical methods to capture the quantum effects, e.g., tunneling and zero-point energy, as well as recrossing dynamics quantum mechanically with ring-polymer trajectories leads to excellent agreement with rigorous quantum dynamics calculations. The present result is encouraging for future applications of the RPMD method and the RPMDrate code to complex-forming chemical reactions involving polyatomic reactants.
NASA Astrophysics Data System (ADS)
Urpi, Luca; Rinaldi, Antonio Pio; Rutqvist, Jonny; Cappa, Frédéric; Spiers, Christopher J.
2016-04-01
Poro-elastic stress and effective stress reduction associated with deep underground fluid injection can potentially trigger shear rupture along pre-existing faults. We modeled an idealized CO2 injection scenario, to assess the effects on faults of the first phase of a generic CO2 aquifer storage operation. We used coupled multiphase fluid flow and geomechanical numerical modeling to evaluate the stress and pressure perturbations induced by fluid injection and the response of a nearby normal fault. Slip-rate dependent friction and inertial effects have been aken into account during rupture. Contact elements have been used to take into account the frictional behavior of the rupture plane. We investigated different scenarios of injection rate to induce rupture on the fault, employing various fault rheologies. Published laboratory data on CO2-saturated intact and crushed rock samples, representative of a potential target aquifer, sealing formation and fault gouge, have been used to define a scenario where different fault rheologies apply at different depths. Nucleation of fault rupture takes place at the bottom of the reservoir, in agreement with analytical poro-elastic stress calculations, considering injection-induced reservoir inflation and the tectonic scenario. For the stress state here considered, the first triggered rupture always produces the largest rupture length and slip magnitude, correlated with the fault rheology. Velocity weakening produces larger ruptures and generates larger magnitude seismic events. Heterogeneous faults have been considered including velocity-weakening or velocity strengthening sections inside and below the aquifer, while upper sections being velocity-neutral. Nucleation of rupture in a velocity strengthening section results in a limited rupture extension, both in terms of maximum slip and rupture length. For a heterogeneous fault with nucleation in a velocity-weakening section, the rupture may propagate into the overlying velocity
Rosická, Dana; Sembera, Jan
2013-01-01
: The need may arise to be able to simulate the migration of groundwater nanoparticles through the ground. Transportation velocities of nanoparticles are different from that of water and depend on many processes that occur during migration. Unstable nanoparticles, such as zero-valent iron nanoparticles, are especially slowed down by aggregation between them. The aggregation occurs when attracting forces outweigh repulsive forces between the particles. In the case of iron nanoparticles that are used for remediation, magnetic forces between particles contribute to attractive forces and nanoparticles aggregate rapidly. This paper describes the addition of attractive magnetic forces and repulsive electrostatic forces between particles (by 'particle', we mean both single nanoparticles and created aggregates) into a basic model of aggregation which is commonly used. This model is created on the basis of the flow of particles in the proximity of observed particles that gives the rate of aggregation of the observed particle. By using a limit distance that has been described in our previous work, the flow of particles around one particle is observed in larger spacing between the particles. Attractive magnetic forces between particles draw the particles into closer proximity and result in aggregation. This model fits more closely with rapid aggregation which occurs between magnetic nanoparticles.
Altitude Variation of the CO2(V2)-O Quenching Rate Coefficient in Mesosphere and Lower Thermosphere
NASA Technical Reports Server (NTRS)
Feofilov, A.; Kutepov, A.; She, C.; Smith, A. K.; Pesnell, W. D.; Goldberg, R. A.
2010-01-01
Among the processes governing the energy balance in the mesosphere and lower thermosphere (MLT), the quenching of CO2(v2) vibrational levels by collisions with oxygen atoms plays an important role. However, the k(CO2-O) values measured in the lab and retrieved from atmospheric measurements vary from 1.5 x 10(exp -12)cu cm/s through 9.0 x 10(exp -12)cu cm/s that requires further studying. In this work we used synergistic data from a ground based lidar and a satellite infrared radiometer to estimate k(CO2-O). We used the night- and daytime temperatures between 80 and 110 km measured by the Colorado State University narrow-band sodium (Na) lidar located at Fort Collins, Colorado (41 N, 255E) as ground truth of the SABER/TIMED nearly simultaneous ( +/-10 minutes) and common volume (within +/-1 degree in latitude, +/-2 degrees in longitude) observations. For each altitude in 80-110 km interval we estimate an 'optimal" value of k(CO2-O) needed to minimize the discrepancy between the simulated 15 micron CO2 radiance and that measured by the SABER/TIMED instrument. The k(CO2-O) obtained in this way varies in altitude from 3.5 x 10(exp -12)cu cm/s at 80 km to 5.2 x 10(exp -12)cu cm/s for altitudes above 95 km. We discuss this variation of the rate constant and its impact on temperature retrievals from 15 pm radiance measurements and on the energy budget of MLT.
Altitude Variation of the CO2 (V2)-O Quenching Rate Coefficient in Mesosphere and Lower Thermosphere
NASA Technical Reports Server (NTRS)
Feofilovi, Artem; Kutepov, Alexander; She, Chiao-Yao; Smith, Anne K.; Pesnell, William Dean; Goldberg, Richard A.
2010-01-01
Among the processes governing the energy balance in the mesosphere and lower thermosphere (mlt), the quenching of CO2(N2) vibrational levels by collisions with oxygen atoms plays an important role. However, the k(CO2-O) values measured in the lab and retrieved from atmospheric measurements vary from 1.5 x 10(exp -12) cubic centimeters per second through 9.0 x 10(exp -12) cubic centimeters per second that requires further studying. In this work we used synergistic data from a ground based lidar and a satellite infrared radiometer to estimate K(CO2-O). We used the night- and daytime temperatures between 80 and 110 km measured by the colorado state university narrow-band sodium (Na) lidar located at fort collins, colorado (41N, 255E) as ground truth of the saber/timed nearly simultaneous (plus or minus 10 minutes) and common volume (within plus or minus 1 degree in latitude, plus or minus 2 degrees in longitude) observations. For each altitude in 80-110 km interval we estimate an "optimal" value of K(CO2-O) needed to minimize the discrepancy between the simulated 15 mm CO2 radiance and that measured by the saber/timed instrument. The K(CO2-O) obtained in this way varies in altitude from 3.5 x 10(exp -12) cubic centimeters per second at 80 km to 5.2 x 10(exp -12) cubic centimeters pers second for altitudes above 95 km. We discuss this variation of the rate constant and its impact on temperature retrievals from 15 mm radiance measurements and on the energy budget of mlt.
NASA Technical Reports Server (NTRS)
Michael, J. V.; Whytock, D. A.; Lee, J. H.; Payne, W. A.; Stief, L. J.
1977-01-01
Rate constants for the reaction of atomic chlorine with hydrogen peroxide were measured from 265-400 K using the flash photolysis-resonance fluorescence technique. Analytical techniques were developed to measure H2O2 under reaction conditions. Due to ambiguity in the interpretation of the analytical results, the data combine to give two equally acceptable representations of the temperature dependence. The results are compared to previous work at 298 K and are theoretically discussed in terms of the mechanism of the reaction. Additional experiments on the H + H2O2 reaction at 298 and 359 K are compared with earlier results from this laboratory and give a slightly revised bimolecular rate constant.
Absolute Value Boundedness, Operator Decomposition, and Stochastic Media and Equations
NASA Technical Reports Server (NTRS)
Adomian, G.; Miao, C. C.
1973-01-01
The research accomplished during this period is reported. Published abstracts and technical reports are listed. Articles presented include: boundedness of absolute values of generalized Fourier coefficients, propagation in stochastic media, and stationary conditions for stochastic differential equations.
NASA Astrophysics Data System (ADS)
Meng, Qingyong; Chen, Jun; Zhang, Dong H.
2016-04-01
To fast and accurately compute rate coefficients of the H/D + CH4 → H2/HD + CH3 reactions, we propose a segmented strategy for fitting suitable potential energy surface (PES), on which ring-polymer molecular dynamics (RPMD) simulations are performed. On the basis of recently developed permutation invariant polynomial neural-network approach [J. Li et al., J. Chem. Phys. 142, 204302 (2015)], PESs in local configuration spaces are constructed. In this strategy, global PES is divided into three parts, including asymptotic, intermediate, and interaction parts, along the reaction coordinate. Since less fitting parameters are involved in the local PESs, the computational efficiency for operating the PES routine is largely enhanced by a factor of ˜20, comparing with that for global PES. On interaction part, the RPMD computational time for the transmission coefficient can be further efficiently reduced by cutting off the redundant part of the child trajectories. For H + CH4, good agreements among the present RPMD rates and those from previous simulations as well as experimental results are found. For D + CH4, on the other hand, qualitative agreement between present RPMD and experimental results is predicted.
NASA Technical Reports Server (NTRS)
Feofilov, A. G.; Kutepov, A. A.; She, C.-Y.; Smith, A. K.; Pesnell, W. D.; Goldberg, R. A.
2012-01-01
Among the processes governing the energy balance in the mesosphere and lower thermosphere (MLT), the quenching of CO2(nu2) vibrational levels by collisions with O atoms plays an important role. However, there is a factor of 3-4 discrepancy between the laboratory measurements of the CO2-O quenching rate coefficient, k(sub VT),and its value estimated from the atmospheric observations. In this study, we retrieve k(sub VT) in the altitude region85-105 km from the coincident SABER/TIMED and Fort Collins sodium lidar observations by minimizing the difference between measured and simulated broadband limb 15 micron radiation. The averaged k(sub VT) value obtained in this work is 6.5 +/- 1.5 X 10(exp -12) cubic cm/s that is close to other estimates of this coefficient from the atmospheric observations.However, the retrieved k(sub VT) also shows altitude dependence and varies from 5.5 1 +/-1 10(exp -12) cubic cm/s at 90 km to 7.9 +/- 1.2 10(exp -12) cubic cm/s at 105 km. Obtained results demonstrate the deficiency in current non-LTE modeling of the atmospheric 15 micron radiation, based on the application of the CO2-O quenching and excitation rates, which are linked by the detailed balance relation. We discuss the possible model improvements, among them accounting for the interaction of the non-thermal oxygen atoms with CO2 molecules.
NASA Technical Reports Server (NTRS)
Georgevic, R. M.
1973-01-01
Closed-form analytic expressions for the time variations of instantaneous orbital parameters and of the topocentric range and range rate of a spacecraft moving in the gravitational field of an oblate large body are derived using a first-order variation of parameters technique. In addition, the closed-form analytic expressions for the partial derivatives of the topocentric range and range rate are obtained, with respect to the coefficient of the second harmonic of the potential of the central body (J sub 2). The results are applied to the motion of a point-mass spacecraft moving in the orbit around the equatorially elliptic, oblate sun, with J sub 2 approximately equal to .000027.
Optomechanics for absolute rotation detection
NASA Astrophysics Data System (ADS)
Davuluri, Sankar
2016-07-01
In this article, we present an application of optomechanical cavity for the absolute rotation detection. The optomechanical cavity is arranged in a Michelson interferometer in such a way that the classical centrifugal force due to rotation changes the length of the optomechanical cavity. The change in the cavity length induces a shift in the frequency of the cavity mode. The phase shift corresponding to the frequency shift in the cavity mode is measured at the interferometer output to estimate the angular velocity of absolute rotation. We derived an analytic expression to estimate the minimum detectable rotation rate in our scheme for a given optomechanical cavity. Temperature dependence of the rotation detection sensitivity is studied.
NASA Astrophysics Data System (ADS)
Bisetti, Fabrizio; El Morsli, Mbark
2014-01-01
The effects of an electric field on the collision rates, energy exchanges and transport properties of electrons in premixed flames are investigated via solutions to the Boltzmann kinetic equation. The case of high electric field strength, which results in high-energy, non-thermal electrons, is analysed in detail at sub-breakdown conditions. The rates of inelastic collisions and the energy exchange between electrons and neutrals in the reaction zone of the flame are characterised quantitatively. The analysis includes attachment, ionisation, impact dissociation, and vibrational and electronic excitation processes. Our results suggest that Townsend breakdown occurs for E/N = 140 Td. Vibrational excitation is the dominant process up to breakdown, despite important rates of electronic excitation of CO, CO2 and N2 as well as impact dissociation of O2 being apparent from 50 Td onwards. Ohmic heating in the reaction zone is found to be negligible (less than 2% of peak heat release rate) up to breakdown field strengths for realistic electron densities equal to 1010 cm-3. The observed trends are largely independent of equivalence ratio. In the non-thermal regime, electron transport coefficients are insensitive to mixture composition and approximately constant across the flame, but are highly dependent on the electric field strength. In the thermal limit, kinetic parameters and transport coefficients vary substantially across the flame due to the spatially inhomogeneous concentration of water vapour. A practical approach for identifying the plasma regime (thermal versus non-thermal) in studies of electric field effects on flames is proposed.
Local carbon diffusion coefficient measurement in the S-1 spheromak
Mayo, R.M.; Levinton, F.M.; Meyerhofer, D.D.; Chu, T.K.; Paul, S.F.; Yamada, M.
1988-10-01
The local carbon diffusion coefficient was measured in the S - 1 spheromak by detecting the radial spread of injected carbon impurity. The radial impurity density profile is determined by the balance of ionization and diffusion. Using measured local electron temperature T/sub e/ and density n/sub e/, the ionization rate is determined from which the particle diffusion coefficient is inferred. The results found in this work are consistent with Bohm diffusion. The absolute magnitude of D/sub /perpendicular// was determined to be (4/approximately/6) /times/ D/sub Bohm/. 25 refs., 13 figs., 2 tabs.
Absolute rate constants of Mo 2 (X 1Σg+) and Mo (a 7S 3) with O 2 at room temperature
NASA Astrophysics Data System (ADS)
Wakabayashi, Tomohiro; Ishikawa, Yo-ichi; Arai, Shigeyoshi
1996-07-01
The gas phase reactivities of ground-state molybdenum dimers and atoms for oxygen molecule have been investigated in a mass-flow controlled cell. Transient concentration of Mo 2 (X 1Σg+, ν = 0) or Mo (a 7S 3) produced by 355 nm multiphoton dissociation (MPD) of Mo(CO) 6 was monitored by a laser-induced fluorescence (LIF). The predictable disturbance caused by free electrons inevitably produced in the MPD of metal carbonyls was examined by an appropriate addition of SF 6 as an electron scavenger. The pseudo-first order decay rates of these molybdenum species were found to depend linearly on O 2 pressure both in the absence and in the presence of SF 6, giving the bimolecular rate constants of (1.1 ± 0.1) × 10 -11 for Mo 2 (X 1Σg+, ν = 0) + O 2 and (1.2 ± 0.1) × 10 -10 cm 3 molecule -1 s -1 for Mo (a 7S 3) + O 2 under the 6.5 Torr total pressure with balance Ar at room temperature.
Papadimitriou, Vassileios C; Spitieri, Christina S; Papagiannakopoulos, Panos; Cazaunau, Mathieu; Lendar, Maria; Daële, Véronique; Mellouki, Abdelwahid
2015-10-14
The rate coefficients for the gas phase reactions of OH radicals, k1, Cl atoms, k2, and O3, k3, with 3,3,3-trifluoro-2(trifluoromethyl)-1-propene ((CF3)2C=CH2, hexafluoroisobutylene, HFIB) were determined at room temperature and atmospheric pressure employing the relative rate method and using two atmospheric simulation chambers and a static photochemical reactor. OH and Cl rate coefficients obtained by both techniques were indistinguishable, within experimental precision, and the average values were k1 = (7.82 ± 0.55) × 10(-13) cm(3) molecule(-1) s(-1) and k2 = (3.45 ± 0.24) × 10(-11) cm(3) molecule(-1) s(-1), respectively. The quoted uncertainties are at 95% level of confidence and include the estimated systematic uncertainties. An upper limit for the O3 rate coefficient was determined to be k3 < 9.0 × 10(-22) cm(3) molecule(-1) s(-1). In global warming potential (GWP) calculations, radiative efficiency (RE) was determined from the measured IR absorption cross-sections and treating HFIB both as long (LLC) and short (SLC) lived compounds, including estimated lifetime dependent factors in the SLC case. The HFIB lifetime was estimated from kinetic measurements considering merely the OH reaction, τOH = 14.8 days and including both OH and Cl chemistry, τeff = 10.3 days. Therefore, GWP(HFIB,OH) and GWP(HFIB,eff) were estimated to be 4.1 (LLC) and 0.6 (SLC), as well as 2.8 (LLC) and 0.3 (SLC) for a hundred year time horizon. Moreover, the estimated photochemical ozone creation potential (ε(POCP)) of HFIB was calculated to be 4.60. Finally, HCHO and (CF3)2C(O) were identified as final oxidation products in both OH- and Cl-initiated oxidation, while HC(O)Cl was additionally observed in the Cl-initiated oxidation. PMID:26372403
2012-05-11
The ap command traveres all symlinks in a given file, directory, or executable name to identify the final absolute path. It can print just the final path, each intermediate link along with the symlink chan, and the permissions and ownership of each directory component in the final path. It has functionality similar to "which", except that it shows the final path instead of the first path. It is also similar to "pwd", but it canmore » provide the absolute path to a relative directory from the current working directory.« less
Moody, A.
2012-05-11
The ap command traveres all symlinks in a given file, directory, or executable name to identify the final absolute path. It can print just the final path, each intermediate link along with the symlink chan, and the permissions and ownership of each directory component in the final path. It has functionality similar to "which", except that it shows the final path instead of the first path. It is also similar to "pwd", but it can provide the absolute path to a relative directory from the current working directory.
NASA Astrophysics Data System (ADS)
Pfrang, C.; Kasyutich, V. L.; Canosa-Mas, C. E.; Vaughan, S.; Wayne, R. P.
2003-04-01
The nitrate radical, NO_3, is a key species in the night-time tropospheric oxidation of a variety of volatile organic compounds (VOCs), including those emitted by living vegetation. In addition to the VOC emissions from intact plants, it is well known that wounding induces the release of a series of C_6 aldehydes and C_6 alcohols, as can be readily sensed in the odour of freshly mown grass. Large emissions of the "leaf alcohol", (Z)-3-hexenol, have been observed after wounding, during drying, and following pathogen attack, while (Z)-2-hexenol has been reported as an emission from clipped clover. Rate coefficients for the gas-phase reactions of the nitrate radical with these two isomeric compounds have been measured using the discharge-flow technique at room temperature. Because of the relatively low volatility of these compounds, it is necessary to employ low concentrations of NO_3 in order to determine the kinetics satisfactorily. To this end, we used a technique not hitherto applied in kinetic experiments on NO_3: that of off-axis continuous-wave cavity-enhanced absorption spectroscopy (CW CEAS) for the detection of NO_3, using a broadband absorption line at λ = 662 nm. A noise-equivalent detection sensitivity of 5.5 × 10^9 molecule cm-3 for the nitrate radical (Kasyutich et al., Appl. Phys. B, 2002, 75, 755--761) enabled us to work with the hexenol compounds in excess over NO_3. The rate coefficients were determined to be (2.80 ± 0.12) × 10-13 cm^3 molecule-1 s-1 and (1.36 ± 0.08) × 10-13 cm^3 molecule-1 s-1, respectively, for (Z)-3-hexenol and (Z)-2-hexenol. The rate constant for reaction with (Z)-3-hexenol lies within the combined error limits of the single measurement of the rate coefficient using relative rate methods of (2.72 ± 0.83) × 10-13 cm^3 molecule-1 s-1 (Atkinson et al., Int. J. Chem. Kinetics, 1995, 27, 941--955). However, for (Z)-3-hexenol there is some evidence for upward curvature of the second-order plot at longer contact times, and
NASA Astrophysics Data System (ADS)
Feofilov, A.; Kutepov, A.; Chu, X.; Smith, A. K.
2012-12-01
Infrared emission in 15 μm CO2 band (I15 μm) is the dominant cooling mechanism in the Earth's mesosphere and lower thermosphere (MLT). On Earth, the magnitude of the MLT cooling affects both the mesopause temperature and height; the stronger the cooling, the colder and higher is the mesopause. This process is also important for the energy budgets of Martian and, especially, Venusian atmospheres, where CO2 cooling compensates for the EUV heating of the dayside upper atmosphere. The I15 μm radiation is used to retrieve vertical temperature distributions T(z) in Earth's atmosphere by a number of satellite instruments. Both the cooling efficiency and I15 μm strongly depend on the rate coefficient of the quenching of the CO2(ν2) vibrational levels by collisions with oxygen atoms. However, there is a factor of 3-4 discrepancy between the laboratory measurements of this rate coefficient, kVT, and its value estimated from the atmospheric observations. In this study, we retrieve kVT in the altitude region 85-105 km from the coincident SABER/TIMED and ground-based lidar observations in different locations by minimizing the difference between measured and simulated broadband limb 15 μm radiation. Obtained results demonstrate the deficiency in current non-LTE modeling of the atmospheric 15 μm radiation, based on the application of the CO2-O quenching and excitation rates, which are linked by the detailed balance relation. We discuss the possible model improvements, among them accounting for the interaction of the "non-thermal" oxygen atoms with CO2 molecules.
Prediction of stream volatilization coefficients
Rathbun, Ronald E.
1990-01-01
Equations are developed for predicting the liquid-film and gas-film reference-substance parameters for quantifying volatilization of organic solutes from streams. Molecular weight and molecular-diffusion coefficients of the solute are used as correlating parameters. Equations for predicting molecular-diffusion coefficients of organic solutes in water and air are developed, with molecular weight and molal volume as parameters. Mean absolute errors of prediction for diffusion coefficients in water are 9.97% for the molecular-weight equation, 6.45% for the molal-volume equation. The mean absolute error for the diffusion coefficient in air is 5.79% for the molal-volume equation. Molecular weight is not a satisfactory correlating parameter for diffusion in air because two equations are necessary to describe the values in the data set. The best predictive equation for the liquid-film reference-substance parameter has a mean absolute error of 5.74%, with molal volume as the correlating parameter. The best equation for the gas-film parameter has a mean absolute error of 7.80%, with molecular weight as the correlating parameter.
NASA Technical Reports Server (NTRS)
Johnsen, R.; Biondi, M. A.
1980-01-01
Rate coefficients which have been measured at thermal energies for the charge transfer reactions of metastable O+/2D/ ions with N2 and O2 are reported. It is found that at an effective temperature of about 550 K, k(n2) = (8 + or - 2) x 10 to the -10 cu cm/sec and k(O2) = (7 + or - 2) x 10 to the -10 cu cm/sec. Drift tube-mass spectrometer measurements employ the reaction He(+) + O2 as the source of metastable O+ ions, showing that the ions produced in this manner are in the 2D state rather than the 2P state, a possible alternative identification. Finally, consideration is given to the ionospheric implications of the laboratory measurements.
Chicheportiche, Alexandre; Benhenni, Malika; Yousfi, Mohammed; Stachoň, Martin; Kalus, René; Gadéa, Florent Xavier
2014-10-07
Momentum-transfer collision cross-sections and integral collision cross-sections for the collision-induced dissociation are calculated for collisions of ionized argon dimers with argon atoms using a nonadiabatic semiclassical method with the electronic Hamiltonian calculated on the fly via a diatomics-in-molecules semiempirical model as well as inverse-method modeling based on simple isotropic rigid-core potential. The collision cross-sections are then used in an optimized Monte Carlo code for evaluations of the Ar{sub 2}{sup +} mobility in argon gas, longitudinal diffusion coefficient, and collision-induced dissociation rates. A thorough comparison of various theoretical calculations as well as with available experimental data on the Ar{sub 2}{sup +} mobility and collision cross-sections is performed. Good agreement is found between both theoretical approaches and the experiment. Analysis of the role of inelastic processes in Ar{sub 2}{sup +}/Ar collisions is also provided.
NASA Astrophysics Data System (ADS)
Feofilov, A. G.; Kutepov, A. A.; She, C.-Y.; Smith, A. K.; Pesnell, W. D.; Goldberg, R. A.
2012-10-01
Among the processes governing the energy balance in the mesosphere and lower thermosphere (MLT), the quenching of CO2(ν2) vibrational levels by collisions with O atoms plays an important role. However, there is a factor of 3-4 discrepancy between the laboratory measurements of the CO2-O quenching rate coefficient, kVT, and its value estimated from the atmospheric observations. In this study, we retrieve kVT in the altitude region 85-105 km from the coincident SABER/TIMED and Fort Collins sodium lidar observations by minimizing the difference between measured and simulated broadband limb 15 μm radiation. The averaged kVT value obtained in this work is 6.5 ± 1.5 × 10-12 cm3 s-1 that is close to other estimates of this coefficient from the atmospheric observations. However, the retrieved kVT also shows altitude dependence and varies from 5.5 ± 1.1 × 10-12 cm3 s-1 at 90 km to 7.9 ± 1.2 × 10-12 cm3 s-1 at 105 km. Obtained results demonstrate the deficiency in current non-LTE modeling of the atmospheric 15 μm radiation, based on the application of the CO2-O quenching and excitation rates, which are linked by the detailed balance relation. We discuss the possible model improvements, among them accounting for the interaction of the "non-thermal" oxygen atoms with CO2 molecules.
Absolute calibration of sniffer probes on Wendelstein 7-X
NASA Astrophysics Data System (ADS)
Moseev, D.; Laqua, H. P.; Marsen, S.; Stange, T.; Braune, H.; Erckmann, V.; Gellert, F.; Oosterbeek, J. W.
2016-08-01
Here we report the first measurements of the power levels of stray radiation in the vacuum vessel of Wendelstein 7-X using absolutely calibrated sniffer probes. The absolute calibration is achieved by using calibrated sources of stray radiation and the implicit measurement of the quality factor of the Wendelstein 7-X empty vacuum vessel. Normalized absolute calibration coefficients agree with the cross-calibration coefficients that are obtained by the direct measurements, indicating that the measured absolute calibration coefficients and stray radiation levels in the vessel are valid. Close to the launcher, the stray radiation in the empty vessel reaches power levels up to 340 kW/m2 per MW injected beam power. Furthest away from the launcher, i.e., half a toroidal turn, still 90 kW/m2 per MW injected beam power is measured.
Absolute calibration of sniffer probes on Wendelstein 7-X.
Moseev, D; Laqua, H P; Marsen, S; Stange, T; Braune, H; Erckmann, V; Gellert, F; Oosterbeek, J W
2016-08-01
Here we report the first measurements of the power levels of stray radiation in the vacuum vessel of Wendelstein 7-X using absolutely calibrated sniffer probes. The absolute calibration is achieved by using calibrated sources of stray radiation and the implicit measurement of the quality factor of the Wendelstein 7-X empty vacuum vessel. Normalized absolute calibration coefficients agree with the cross-calibration coefficients that are obtained by the direct measurements, indicating that the measured absolute calibration coefficients and stray radiation levels in the vessel are valid. Close to the launcher, the stray radiation in the empty vessel reaches power levels up to 340 kW/m(2) per MW injected beam power. Furthest away from the launcher, i.e., half a toroidal turn, still 90 kW/m(2) per MW injected beam power is measured. PMID:27587121
Tanner, D. D.; Kandanarachchi, P.; Das, N. C.; Franz, James A.
2003-04-08
The reactions of vinyl butyl ether and vinyl butyrate with atomic hydrogen and deuterium lead to addition of atomic hydrogen to the terminal position of the olefins. This observation is consistent with the reactions carried out earlier with other olefins. Both the absolute rates of addition to vinylbutyl ether and vinyl butyrate in acetone and hexane were carried out at several temperatures. The relative rates are consistent with only modest stabilization of the transition state of the radical adduct by the ??-o substituent compared with hydrogen atom addition to 1-octene. The relative rates measured in acetone and hexane indicate no significant differential solvation of ground state relative to the transition structures of the hydrogen atom addition. The kinetics reveal that the early transition states of hydrogen atom addition exhibit little selectivity (vinyl ether versus simple olefin) in either abstraction of hydrogen ??- to the oxygen or by terminal addition to the olefinic ether, reflecting the modest influence of the increased enthalpy of reaction associated with resonance stabilization by the oxygen substituent at the developing radical site.
Tanner, D D.; Kandanarachchi, P; Das, N. C.; Franz, James A.
2003-04-08
The reactions of vinyl butyl ether and vinyl butyrate with atomic hydrogen and deuterium lead to addition at the terminal position of the olefins. This observation is consistent with the reactions carried out earlier with other olefins. Both of the absolute rates of addition to vinylbutyl ether and vinyl butyrate, in acetone and hexane, were measured at several temperatures. The relative rates are consistent with only modest stabilization of the transition state of the radical adduct by the R-O substituent compared with that of hydrogen atom addition to 1-octene. The relative rates measured in acetone and hexane indicate no significant differential solvation of the ground state relative to the transition structures of the hydrogen atom addition. The kinetics reveal that the early transition states for hydrogen atom addition exhibit little selectivity (vinyl ether versus simple olefin) in either the abstraction of hydrogen R to the oxygen or by terminal addition to the olefinic ether and reflects the modest influence of the increased enthalpy of reaction associated with resonance stabilization by the oxygen substituent at the developing radical site.
NASA Astrophysics Data System (ADS)
Papadimitriou, V.; Burkholder, J. B.
2015-12-01
Short-lived hydrofluoroolefins (HFOs) are proposed replacement compounds for ozone depleting substances (ODSs) and longer-lived greenhouse gases that are used in various industrial and technological applications. HFOs are not ODSs and the presence of the highly reactive unsaturated bond toward the common atmospheric oxidants (OH, Cl, NO3 and O3) is expected to lead to shorter tropospheric lifetimes relative to those of saturated hydrofluorocarbons. The shorter lifetime reduces their direct contribution to Climate Change. In this study, rate coefficients for the gas-phase reaction of the OH radical with (CF3)2CFCH=CHF (HFO-1438ezy), between 214 and 380 K and 50-450 Torr (He, N2), were measured using pulsed laser photolysis-laser induced fluorescence (PLP/LIF) and relative rate methods. No pressure dependence was observed within this measurement range. The reaction displays a non-Arrhenius temperature dependence over this temperature range with a slightly positive temperature dependence above 280 K and near temperature independence at lower temperatures. The infrared spectrum of HFO-1438ezy was measured as part of this work. On the basis of the present measurements, the atmospheric lifetime of HFO-1438ezy as well as its radiative efficiency, global warming potential and photochemical ozone creation potential were estimated.
Gaspar, A; Strodiot, L; Thonart, P
1998-01-01
To improve xylanase productivity from Penicillium canescens 10-10c culture, an optimization of oxygen supply is required. Because the strain is sensitive to shear forces, leading to lower xylanase productivity as to morphological alteration, vigorous mixing is not desired. The influence of turbine design, agitation speed, and air flow rate on K1a (global mass transfer coefficient, h(-1)) and enzyme production is discussed. K1a values increased with agitation speed and air flow rate, whatever the impeller, in our assay conditions. Agitation had more influence on K1a values than air flow, when a disk-mounted blade's impeller (DT) is used; an opposite result was obtained with a hub-mounted pitched blade's impeller (PBT). Xylanase production appeared as a function of specific power (W/m3), and an optimum was found in 20 and 100 L STRs fitted with DT impellers. On the other hand, the use of a hub-mounted pitched blade impeller (PBT8), instead of a disk-mounted blade impeller (DT4), reduced the lag time of hemicellulase production and increased xylanase productivity 1.3-fold. PMID:18576019
On the solar cycle variation in the barometer coefficients of high latitude neutron monitors
NASA Technical Reports Server (NTRS)
Kusunose, M.; Ogita, N.
1985-01-01
Evaluation of barometer coefficients of neutron monitors located at high latitudes has been performed by using the results of the spherical harmonic analysis based on the records from around twenty stations for twelve years from January 1966 to December 1977. The average of data at eight stations, where continuous records are available for twelve years, show that the absolute value of barometer coefficient is in positive correlation with the cosmic ray neutron intensity. The variation rate of the barometer coefficient to the cosmic ray neutron intensity is influenced by the changes in the cutoff rigidity and in the primary spectrum.
NASA Astrophysics Data System (ADS)
Laporta, V.; Celiberto, R.; Wadehra, J. M.
2012-10-01
Electron-impact vibrational-excitation cross sections, involving rovibrationally excited N2 and NO molecules, are calculated for collisions occurring through the nitrogen resonant electronic state N_2^-(X\\,^2\\!\\Pi_g) , and the three resonant states of nitric oxide NO-(3Σ-, 1Δ, 1Σ+). Complete sets of cross sections have been obtained for all possible transitions involving 68 vibrational levels of N_2(X\\,{}^1\\!\\Sigma_g^+) and 55 levels of NO(X 2Π), for incident electron energy between 0.1 and 10 eV. In order to study the rotational motion in the resonant processes, cross sections have also been computed for rotationally elastic transitions characterized by the rotational quantum number J running from 0 to 150. The calculations are performed within the framework of the local complex potential model, using potential energies and widths optimized to reproduce the experimental cross sections available in the literature. Rate coefficients are calculated for transitions between all vibrational levels by assuming a Maxwellian electron energy distribution function in the temperature range from 0.1 to 100 eV. All numerical data are available at http://users.ba.cnr.it/imip/cscpal38/phys4entry/database.html
NASA Astrophysics Data System (ADS)
Feofilov, A. G.; Kutepov, A. A.; She, C.-Y.; Smith, A. K.; Pesnell, W. D.; Goldberg, R. A.
2011-12-01
Among the processes governing the energy balance in the mesosphere and lower thermosphere (MLT), the quenching of CO2(ν2)-O vibrational levels by collisions with O atoms plays an important role. However, there is a factor of 3-4 discrepancy between various measurements of the CO2-O quenching rate coefficient, kVT. We retrieve kVT in the altitude region 80-110 km from coincident SABER/TIMED and Fort Collins sodium lidar observations by minimizing the difference between measured and simulated broadband limb 15 μm radiances. The retrieved kVT varies from about 5 × 10-12 cm3 s-1 at 87 km to about 7 × 10-12 cm3 s-1 at 104 km. A detailed consideration of retrieval errors and uncertainties indicates deficiency in current understanding the non-LTE formation mechanism of atmospheric 15 μm radiances. An updated mechanism of CO2-O collisional interactions is suggested.
Morales, Sébastien B; Le Picard, Sébastien D; Canosa, André; Sims, Ian R
2010-01-01
The kinetics of the reactions of cyano radical, CN (X2sigma+) with three hydrocarbons, propane (CH3CH2CH3), propene (CH3CH=CH2) and 1-butyne (CH[triple band]CCH2CH3) have been studied over the temperature range of 23-298 K using a CRESU (Cinétique de Réaction en Ecoulement Supersonique Uniforme or Reaction Kinetics in Uniform Supersonic Flow) apparatus combined with the pulsed laser photolysis-laser induced fluorescence technique. These reactions are of interest for the cold atmospheres of Titan, Pluto and Triton, as they might participate in the formation of nitrogen and carbon bearing molecules, including nitriles, that are thought to play an important role in the formation of hazes and biological molecules. All three reactions are rapid with rate coefficients in excess of 10(-10) cm3 molecule(-1) s(-1) at the lowest temperatures of this study and show behaviour characteristic of barrierless reactions. Temperature dependences, different for each reaction, are compared to those used in the most recent photochemical models of Titan's atmosphere. PMID:21302546
Morales, Sébastien B; Le Picard, Sébastien D; Canosa, André; Sims, Ian R
2010-01-01
The kinetics of the reactions of cyano radical, CN (X2sigma+) with three hydrocarbons, propane (CH3CH2CH3), propene (CH3CH=CH2) and 1-butyne (CH[triple band]CCH2CH3) have been studied over the temperature range of 23-298 K using a CRESU (Cinétique de Réaction en Ecoulement Supersonique Uniforme or Reaction Kinetics in Uniform Supersonic Flow) apparatus combined with the pulsed laser photolysis-laser induced fluorescence technique. These reactions are of interest for the cold atmospheres of Titan, Pluto and Triton, as they might participate in the formation of nitrogen and carbon bearing molecules, including nitriles, that are thought to play an important role in the formation of hazes and biological molecules. All three reactions are rapid with rate coefficients in excess of 10(-10) cm3 molecule(-1) s(-1) at the lowest temperatures of this study and show behaviour characteristic of barrierless reactions. Temperature dependences, different for each reaction, are compared to those used in the most recent photochemical models of Titan's atmosphere.
OKADA; BRAVAR, A.; BUNCE, G.; GILL, R.; HUANG, H.; MAKDISI, Y.; NASS, A.; WOOD, J.; ZELENSKI, Z.; ET AL.
2007-09-10
Precise and absolute beam polarization measurements are critical for the RHIC spin physics program. Because all experimental spin-dependent results are normalized by beam polarization, the normalization uncertainty contributes directly to final physics uncertainties. We aimed to perform the beam polarization measurement to an accuracy Of {Delta}P{sub beam}/P{sub beam} < 5%. The absolute polarimeter consists of Polarized Atomic Hydrogen Gas Jet Target and left-right pairs of silicon strip detectors and was installed in the RHIC-ring in 2004. This system features proton-proton elastic scattering in the Coulomb nuclear interference (CNI) region. Precise measurements of the analyzing power A{sub N} of this process has allowed us to achieve {Delta}P{sub beam}/P{sub beam} = 4.2% in 2005 for the first long spin-physics run. In this report, we describe the entire set up and performance of the system. The procedure of beam polarization measurement and analysis results from 2004-2005 are described. Physics topics of AN in the CNI region (four-momentum transfer squared 0.001 < -t < 0.032 (GeV/c){sup 2}) are also discussed. We point out the current issues and expected optimum accuracy in 2006 and the future.
NASA Astrophysics Data System (ADS)
Myers, S.; Johannesson, G.
2012-12-01
Arrival time measurements based on waveform cross correlation are becoming more common as advanced signal processing methods are applied to seismic data archives and real-time data streams. Waveform correlation can precisely measure the time difference between the arrival of two phases, and differential time data can be used to constrain relative location of events. Absolute locations are needed for many applications, which generally requires the use of absolute time data. Current methods for measuring absolute time data are approximately two orders of magnitude less precise than differential time measurements. To exploit the strengths of both absolute and differential time data, we extend our multiple-event location method Bayesloc, which previously used absolute time data only, to include the use of differential time measurements that are based on waveform cross correlation. Fundamentally, Bayesloc is a formulation of the joint probability over all parameters comprising the multiple event location system. The Markov-Chain Monte Carlo method is used to sample from the joint probability distribution given arrival data sets. The differential time component of Bayesloc includes scaling a stochastic estimate of differential time measurement precision based the waveform correlation coefficient for each datum. For a regional-distance synthetic data set with absolute and differential time measurement error of 0.25 seconds and 0.01 second, respectively, epicenter location accuracy is improved from and average of 1.05 km when solely absolute time data are used to 0.28 km when absolute and differential time data are used jointly (73% improvement). The improvement in absolute location accuracy is the result of conditionally limiting absolute location probability regions based on the precise relative position with respect to neighboring events. Bayesloc estimates of data precision are found to be accurate for the synthetic test, with absolute and differential time measurement
Papadimitriou, Vassileios C; Karafas, Emmanuel S; Gierczak, Tomasz; Burkholder, James B
2015-07-16
The gas-phase CH3CO + O2 reaction is known to proceed via a chemical activation mechanism leading to the formation of OH and CH3C(O)OO radicals via bimolecular and termolecular reactive channels, respectively. In this work, rate coefficients, k, for the CH3CO + O2 reaction were measured over a range of temperature (241-373 K) and pressure (0.009-600 Torr) with He and N2 as the bath gas and used to characterize the bi- and ter-molecular reaction channels. Three independent experimental methods (pulsed laser photolysis-laser-induced fluorescence (PLP-LIF), pulsed laser photolysis-cavity ring-down spectroscopy (PLP-CRDS), and a very low-pressure reactor (VLPR)) were used to characterize k(T,M). PLP-LIF was the primary method used to measure k(T,M) in the high-pressure regime under pseudo-first-order conditions. CH3CO was produced by PLP, and LIF was used to monitor the OH radical bimolecular channel reaction product. CRDS, a complementary high-pressure method, measured k(295 K,M) over the pressure range 25-600 Torr (He) by monitoring the temporal CH3CO radical absorption following its production via PLP in the presence of excess O2. The VLPR technique was used in a relative rate mode to measure k(296 K,M) in the low-pressure regime (9-32 mTorr) with CH3CO + Cl2 used as the reference reaction. A kinetic mechanism analysis of the combined kinetic data set yielded a zero pressure limit rate coefficient, kint(T), of (6.4 ± 4) × 10(-14) exp((820 ± 150)/T) cm(3) molecule(-1) s(-1) (with kint(296 K) measured to be (9.94 ± 1.3) × 10(-13) cm(3) molecule(-1) s(-1)), k0(T) = (7.39 ± 0.3) × 10(-30) (T/300)(-2.2±0.3) cm(6) molecule(-2) s(-1), and k∞(T) = (4.88 ± 0.05) × 10(-12) (T/300)(-0.85±0.07) cm(3) molecule(-1) s(-1) with Fc = 0.8 and M = N2. A He/N2 collision efficiency ratio of 0.60 ± 0.05 was determined. The phenomenological kinetic results were used to define the pressure and temperature dependence of the OH radical yield in the CH3CO + O2 reaction. The
NASA Technical Reports Server (NTRS)
Shebalin, John V.
1997-01-01
The entropy associated with absolute equilibrium ensemble theories of ideal, homogeneous, fluid and magneto-fluid turbulence is discussed and the three-dimensional fluid case is examined in detail. A sigma-function is defined, whose minimum value with respect to global parameters is the entropy. A comparison is made between the use of global functions sigma and phase functions H (associated with the development of various H-theorems of ideal turbulence). It is shown that the two approaches are complimentary though conceptually different: H-theorems show that an isolated system tends to equilibrium while sigma-functions allow the demonstration that entropy never decreases when two previously isolated systems are combined. This provides a more complete picture of entropy in the statistical mechanics of ideal fluids.
NASA Astrophysics Data System (ADS)
Tao, Jiangchuan; Zhao, Chunsheng
2016-04-01
Hygroscopic growth of aerosol particles can significantly affect their single-scattering albedo (ω), and consequently alters the aerosol effect on tropospheric photochemistry. In this study, the impact of aerosol hygroscopic growth on ω and its application to the NO2 photolysis rate coefficient (JNO2) are investigated for a typical aerosol particle population in the North China Plain (NCP). The variations of aerosol optical properties with relative humidity (RH) are calculated using a Mie theory aerosol optical model, on the basis of field measurements of number-size distribution and hygroscopic growth factor (at RH values above 90 %) from the 2009 HaChi (Haze in China) project. Results demonstrate that ambient ω has pronouncedly different diurnal patterns from ω measured at dry state, and is highly sensitive to the ambient RHs. Ambient ω in the NCP can be described by a dry state ω value of 0.863, increasing with the RH following a characteristic RH dependence curve. A Monte Carlo simulation shows that the uncertainty ofω from the propagation of uncertainties in the input parameters decreases from 0.03 (at dry state) to 0.015 (RHs > 90 %). The impact of hygroscopic growth on ω is further applied in the calculation of the radiative transfer process. Hygroscopic growth of the studied aerosol particle population generally inhibits the photolysis of NO2 at the ground level, whereas accelerates it above the moist planetary boundary layer. Compared with dry state, the calculated JNO2 at RH of 98 % at the height of 1 km increases by 30.4 %, because of the enhancement of ultraviolet radiation by the humidified scattering-dominant aerosol particles. The increase of JNO2 due to the aerosol hygroscopic growth above the upper boundary layer may affect the tropospheric photochemical processes and this needs to be taken into account in the atmospheric chemical models.
Rate Coefficients of C2H with C2H4, C2H6, and H2 from 150 to 359 K
NASA Technical Reports Server (NTRS)
Opansky, Brian J.; Leone, Stephen R.
1996-01-01
Rate coefficients for the reactions C2H with C2H4, C2H6, and H2 are measured over the temperature range 150-359 K using transient infrared laser absorption spectroscopy. The ethynyl radical is formed by photolysis of C2H2 with a pulsed excimer laser at 193 nm, and its transient absorption is monitored with a color center laser on the Q(sub 11)(9) line of the A(sup 2) Pi-Chi(sup 2) Sigma transition at 3593.68 cm(exp -1). Over the experimental temperature range 150-359 K the rate constants of C2H with C2H4, C2H6, and H2 can be fitted to the Arrhenius expressions k(sub C2H4) = (7.8 +/- 0.6) x 10(exp -11) exp[(134 +/- 44)/T], k(sub C2H6) = (3.5 +/- 0.3) x 10(exp -11) exp[(2.9 +/- 16)/T], and k(sub H2) = (1.2 +/- 0.3) x 10(exp -11) exp[(-998 +/- 57)]/T cm(exp 3) molecule(exp -1) sec(exp -1). The data for C2H with C2H4 and C2H6 indicate a negligible activation energy to product formation shown by the mild negative temperature dependence of both reactions. When the H2 data are plotted together with the most recent high-temperature results from 295 to 854 K, a slight curvature is observed. The H2 data can be fit to the non-Arrhenius form k(sub H2) = 9.2 x 10(exp -18) T(sup 2.17 +/- 0.50) exp[(-478 +/- 165)/T] cm(exp 3) molecules(exp -1) sec(exp -1). The curvature in the Arrhenius plot is discussed in terms of both quantum mechanical tunneling of the H atom from H2 to the C2H radical and bending mode contributions to the partition function.
Absolute neutrino mass measurements
Wolf, Joachim
2011-10-06
The neutrino mass plays an important role in particle physics, astrophysics and cosmology. In recent years the detection of neutrino flavour oscillations proved that neutrinos carry mass. However, oscillation experiments are only sensitive to the mass-squared difference of the mass eigenvalues. In contrast to cosmological observations and neutrino-less double beta decay (0v2{beta}) searches, single {beta}-decay experiments provide a direct, model-independent way to determine the absolute neutrino mass by measuring the energy spectrum of decay electrons at the endpoint region with high accuracy.Currently the best kinematic upper limits on the neutrino mass of 2.2eV have been set by two experiments in Mainz and Troitsk, using tritium as beta emitter. The next generation tritium {beta}-experiment KATRIN is currently under construction in Karlsruhe/Germany by an international collaboration. KATRIN intends to improve the sensitivity by one order of magnitude to 0.2eV. The investigation of a second isotope ({sup 137}Rh) is being pursued by the international MARE collaboration using micro-calorimeters to measure the beta spectrum. The technology needed to reach 0.2eV sensitivity is still in the R and D phase. This paper reviews the present status of neutrino-mass measurements with cosmological data, 0v2{beta} decay and single {beta}-decay.
Jubb, Aaron M; Gierczak, Tomasz; Baasandorj, Munkhbayar; Waterland, Robert L; Burkholder, James B
2014-05-01
Mixtures of methyl-perfluoroheptene-ethers (CH3OC7F13, MPHEs) are currently in use as replacements for perfluorinated alkanes (PFCs) and poly-ether heat transfer fluids, which are persistent greenhouse gases with lifetimes >1000 years. At present, the atmospheric processing and environmental impact from the use of MPHEs is unknown. In this work, rate coefficients at 296 K for the gas-phase reaction of the OH radical with six key isomers (including stereoisomers and enantiomers) of MPHEs used commercially were measured using a relative rate method. Rate coefficients for the six MPHE isomers ranged from ∼ 0.1 to 2.9 × 10(-12) cm(3) molecule(-1) s(-1) with a strong stereoisomer and -OCH3 group position dependence; the (E)-stereoisomers with the -OCH3 group in an α- position relative to the double bond had the greatest reactivity. Rate coefficients measured for the d3-MPHE isomer analogues showed decreased reactivity consistent with a minor contribution of H atom abstraction from the -OCH3 group to the overall reactivity. Estimated atmospheric lifetimes for the MPHE isomers range from days to months. Atmospheric lifetimes, radiative efficiencies, and global warming potentials for these short-lived MPHE isomers were estimated based on the measured OH rate coefficients along with measured and theoretically calculated MPHE infrared absorption spectra. Our results highlight the importance of quantifying the atmospheric impact of individual components in an isomeric mixture.
Kandanarachchi, Pramod H; Autrey, Tom; Franz, James A
2002-11-15
Arrhenius rate expressions were determined for beta-scission of phenoxyl radical from 1-phenyl-2-phenoxyethanol-1-yl, PhC*(OH)CH2OPh (V). Ketyl radical V was competitively trapped by thiophenol to yield PhCH(OH)CH2OPh in competition with beta-scission to yield phenoxyl radical and acetophenone. A basis rate expression for hydrogen atom abstraction by sec-phenethyl alcohol, PhC*(OH)CH3, from thiophenol, log(k(abs)/M(-1) s(-1)) = (8.88 +/- 0.24) - (6.07 +/- 0.34)/theta, theta = 2.303RT, was determined by competing hydrogen atom abstraction with radical self-termination. Self-termination rates for PhC*(OH)CH3 were calculated using the Smoluchowski equation employing experimental diffusion coefficients of the parent alcohol, PhCH(OH)CH3, as a model for the radical. The hydrogen abstraction basis reaction was employed to determine the activation barrier for the beta-scission of phenoxyl from 1-phenyl-2-phenoxyethanol-1-yl (V): log(k beta)/s(-1)) = (12.85 +/- 0.22) - (15.06 +/- 0.38)/theta, k beta (298 K) ca. (64.0 s(-1) in benzene), and log(k beta /s(-1)) = (12.50 +/- 0.18) - (14.46 +/- 0.30)/theta, k beta (298 K) = 78.7 s(-1) in benzene containing 0.8 M 2-propanol. B3LYP/cc-PVTZ electronic structure calculations predict that intramolecular hydrogen bonding between the alpha-OH and the -OPh leaving group of ketyl radical (V) stabilizes both ground- and transition-state structures. The computed activation barrier, 14.9 kcal/mol, is in good agreement with the experimental activation barrier.
Noninvasive absolute cerebral oximetry with frequency-domain near-infrared spectroscopy
NASA Astrophysics Data System (ADS)
Hallacoglu, Bertan
Near-infrared spectroscopy (NIRS) measurements of absolute concentrations of oxy-hemoglobin and deoxy-hemoglobin in the human brain can provide critical information about cerebral physiology in terms of cerebral blood volume, blood flow, oxygen delivery, and metabolic rate of oxygen. We developed several frequency domain NIRS data acquisition and analysis methods aimed at absolute measurements of hemoglobin concentration and saturation in cerebral tissue of adult human subjects. Extensive experimental investigations were carried out in various homogenous and two-layered tissue-mimicking phantoms, and biological tissues. The advantages and limitations of commonly used homogenous models and inversion strategies were thoroughly investigated. Prior to human subjects, extensive studies were carried out in in vivo animal models. In rabbits, absolute hemoglobin oxygen desaturation was shown to depend strongly on surgically induced testicular torsion. Methods developed in this study were then adapted for measurements in the rat brain. Absolute values were demonstrated to discern cerebrovascular impairment in a rat model of diet-induced vascular cognitive impairment. These results facilitated the development of clinically useful optical measures of cerebrovascular health. In a large group of human subjects, employing a homogeneous model for absolute measurements was shown to be reliable and robust. However, it was also shown to be limited due to the relatively thick extracerebral tissue. The procedure we develop in this work and the thesis thereof performs a nonlinear inversion procedure with six unknown parameters with no other prior knowledge for the retrieval of the optical coefficients and top layer thickness with high accuracy on two-layered media. Our absolute measurements of cerebral hemoglobin concentration and saturation are based on the discrimination of extracerebral and cerebral tissue layers, and they can enhance the impact of NIRS for cerebral hemodynamics and
Ng, Maggie; Mok, Daniel K W; Lee, Edmond P F; Dyke, John M
2013-03-15
The minimum energy path (MEP) of the reaction, CF(3)CHFCF(3) + H → transition state (TS) → CF(3)CFCF(3) + H(2), has been computed at different ab initio levels and with density functional theory (DFT) using different functionals. The computed B3LYP/6-31++G**, BH&HLYP/cc-pVDZ, BMK/6-31++G**, M05/6-31+G**, M05-2X/6-31+G**, UMP2/6-31++G**, PUMP2/6-31++G**//UMP2/6-31++G**, RCCSD(T)/aug-cc-pVDZ//UMP2/6-31++G**, RCCSD(T)/aug-cc-pVTZ(spd,sp)//UMP2//6-31++G**, RCCSD(T)/CBS//M05/6-31+G**, and RCCSD(T)/CBS//UMP2/6-31++G** MEPs, and associated gradients and Hessians, were used in reaction rate coefficient calculations based on the transition state theory (TST). Reaction rate coefficients were computed between 300 and 1500 K at various levels of TST, which include conventional TST, canonical variational TST (CVT) and improved CVT (ICVT), and with different tunneling corrections, namely, Wigner, zero-curvature, and small-curvature (SCT). The computed rate coefficients obtained at different ab initio, DFT and TST levels are compared with experimental values available in the 1000-1200 K temperature range. Based on the rate coefficients computed at the ICVT/SCT level, the highest TST level used in this study, the BH&HLYP functional performs best among all the functionals used, while the RCCSD(T)/CBS//MP2/6-31++G** level is the best among all the ab initio levels used. Comparing computed reaction rate coefficients obtained at different levels of theory shows that, the computed barrier height has the strongest effect on the computed reaction rate coefficients as expected. Variational effects on the computed rate coefficients are found to be negligibly small. Although tunneling effects are relatively small at high temperatures (~1500 K), SCT corrections are significant at low temperatures (~300 K), and both barrier heights and the magnitudes of the imaginary frequencies affect SCT corrections.
Jasper, A. W.; Klippenstein, S. J.; Harding, L. B.; Chemistry
2007-09-06
Direct variable reaction coordinate transition state theory (VRC-TST) rate coefficients are reported for the {sup 3}CH{sub 2} + OH, {sup 3}CH{sub 2} + {sup 3}CH{sub 2}, and {sup 3}CH{sub 2} + CH{sub 3} barrierless association reactions. The predicted rate coefficient for the {sup 3}CH{sub 2} + OH reaction ({approx} 1.2 x 10{sup -10} cm{sup 3} molecule{sup -1} s{sup -1} for 300-2500 K) is 4-5 times larger than previous estimates, indicating that this reaction may be an important sink for OH in many combustion systems. The predicted rate coefficients for the {sup 3}CH{sub 2} + CH{sub 3} and {sup 3}CH{sub 2} + {sup 3}CH{sub 2} reactions are found to be in good agreement with the range of available experimental measurements. Product branching in the self-reaction of methylene is discussed, and the C{sub 2}H{sub 2} + 2H and C{sub 2}H{sub 2} + H{sub 2} products are predicted in a ratio of 4:1. The effect of the present set of rate coefficients on modeling the secondary kinetics of methanol decomposition is briefly considered. Finally, the present set of rate coefficients, along with previous VRC-TST determinations of the rate coefficients for the self-reactions of CH{sub 3} and OH and for the CH{sub 3} + OH reaction, are used to test the geometric mean rule for the CH{sub 3}, {sup 3}CH{sub 2}, and OH fragments. The geometric mean rule is found to predict the cross-combination rate coefficients for the {sup 3}CH{sub 2} + OH and {sup 3}CH{sub 2} + CH{sub 3} reactions to better than 20%, with a larger (up to 50%) error for the CH{sub 3} + OH reaction.
Absolute Identification by Relative Judgment
ERIC Educational Resources Information Center
Stewart, Neil; Brown, Gordon D. A.; Chater, Nick
2005-01-01
In unidimensional absolute identification tasks, participants identify stimuli that vary along a single dimension. Performance is surprisingly poor compared with discrimination of the same stimuli. Existing models assume that identification is achieved using long-term representations of absolute magnitudes. The authors propose an alternative…
Be Resolute about Absolute Value
ERIC Educational Resources Information Center
Kidd, Margaret L.
2007-01-01
This article explores how conceptualization of absolute value can start long before it is introduced. The manner in which absolute value is introduced to students in middle school has far-reaching consequences for their future mathematical understanding. It begins to lay the foundation for students' understanding of algebra, which can change…
Werfelli, Ghofran; Halvick, Philippe; Stoecklin, Thierry; Honvault, Pascal; Kerkeni, Boutheïna
2015-09-21
The observed abundances of the methylidyne cation, CH{sup +}, in diffuse molecular clouds can be two orders of magnitude higher than the prediction of the standard gas-phase models which, in turn, predict rather well the abundances of neutral CH. It is therefore necessary to investigate all the possible formation and destruction processes of CH{sup +} in the interstellar medium with the most abundant species H, H{sub 2}, and e{sup −}. In this work, we address the destruction process of CH{sup +} by hydrogen abstraction. We report a new calculation of the low temperature rate coefficients for the abstraction reaction, using accurate time-independent quantum scattering and a new high-level ab initio global potential energy surface including a realistic model of the long-range interaction between the reactants H and CH{sup +}. The calculated thermal rate coefficient is in good agreement with the experimental data in the range 50 K–800 K. However, at lower temperatures, the experimental rate coefficient takes exceedingly small values which are not reproduced by the calculated rate coefficient. Instead, the latter rate coefficient is close to the one given by the Langevin capture model, as expected for a reaction involving an ion and a neutral species. Several recent theoretical works have reported a seemingly good agreement with the experiment below 50 K, but an analysis of these works show that they are based on potential energy surfaces with incorrect long-range behavior. The experimental results were explained by a loss of reactivity of the lowest rotational states of the reactant; however, the quantum scattering calculations show the opposite, namely, a reactivity enhancement with rotational excitation.
Weighted Wilcoxon-type Smoothly Clipped Absolute Deviation Method
Wang, Lan; Li, Runze
2009-01-01
Summary Shrinkage-type variable selection procedures have recently seen increasing applications in biomedical research. However, their performance can be adversely influenced by outliers in either the response or the covariate space. This paper proposes a weighted Wilcoxon-type smoothly clipped absolute deviation (WW-SCAD) method, which deals with robust variable selection and robust estimation simultaneously. The new procedure can be conveniently implemented with the statistical software R. We establish that the WW-SCAD correctly identifies the set of zero coefficients with probability approaching one and estimates the nonzero coefficients with the rate n−1/2. Moreover, with appropriately chosen weights the WW-SCAD is robust with respect to outliers in both the x and y directions. The important special case with constant weights yields an oracle-type estimator with high efficiency at the presence of heavier-tailed random errors. The robustness of the WW-SCAD is partly justified by its asymptotic performance under local shrinking contamination. We propose a BIC-type tuning parameter selector for the WW-SCAD. The performance of the WW-SCAD is demonstrated via simulations and by an application to a study that investigates the effects of personal characteristics and dietary factors on plasma beta-carotene level. PMID:18647294
Adams, M.E.; Marshall, T.L.; Rowley, R.L.
1998-07-01
Absorption rates of gaseous CO{sub 2} into aqueous blends of N-methyldiethanolamine (MDEA) and diethanolamine (DEA) and of gaseous H{sub 2}S into aqueous MDEA were measured in a quiescent, inverted-tube diffusiometer by monitoring the rate of pressure drop. A numerical model for absorption, diffusion, and reaction of CO{sub 2} and H{sub 2}S in blends of MDEA, DEA, and water was developed. The model was used to regress diffusion coefficients of bicarbonate, carbamate, and MDEAH{sub 2}CO{sub 3} for the case of CO{sub 2} absorption and of bisulfide ion for the case of H{sub 2}S absorption from measured absorption rates. CO{sub 2} absorption rates and diffusion coefficients of bicarbonate, carbamate, and MDEAH{sub 2}CO{sub 3} were obtained at 298.2 K and 318.2 K in aqueous solutions containing 50 mass % total amine at DEA:MDEA mole ratios of 1:20, 1:4, 1L3, and 2:3. H{sub 2}S absorption rates and diffusion coefficients of bisulfide ion were obtained at 298.2 K and 318.2 K in aqueous solutions containing 20, 35, and 50 mass % MDEA.
Singular perturbation of absolute stability.
NASA Technical Reports Server (NTRS)
Siljak, D. D.
1972-01-01
It was previously shown (author, 1969) that the regions of absolute stability in the parameter space can be determined when the parameters appear on the right-hand side of the system equations, i.e., the regular case. Here, the effect on absolute stability of a small parameter attached to higher derivatives in the equations (the singular case) is studied. The Lur'e-Postnikov class of nonlinear systems is considered.
Absolute Humidity and the Seasonality of Influenza (Invited)
NASA Astrophysics Data System (ADS)
Shaman, J. L.; Pitzer, V.; Viboud, C.; Grenfell, B.; Goldstein, E.; Lipsitch, M.
2010-12-01
Much of the observed wintertime increase of mortality in temperate regions is attributed to seasonal influenza. A recent re-analysis of laboratory experiments indicates that absolute humidity strongly modulates the airborne survival and transmission of the influenza virus. Here we show that the onset of increased wintertime influenza-related mortality in the United States is associated with anomalously low absolute humidity levels during the prior weeks. We then use an epidemiological model, in which observed absolute humidity conditions temper influenza transmission rates, to successfully simulate the seasonal cycle of observed influenza-related mortality. The model results indicate that direct modulation of influenza transmissibility by absolute humidity alone is sufficient to produce this observed seasonality. These findings provide epidemiological support for the hypothesis that absolute humidity drives seasonal variations of influenza transmission in temperate regions. In addition, we show that variations of the basic and effective reproductive numbers for influenza, caused by seasonal changes in absolute humidity, are consistent with the general timing of pandemic influenza outbreaks observed for 2009 A/H1N1 in temperate regions. Indeed, absolute humidity conditions correctly identify the region of the United States vulnerable to a third, wintertime wave of pandemic influenza. These findings suggest that the timing of pandemic influenza outbreaks is controlled by a combination of absolute humidity conditions, levels of susceptibility and changes in population mixing and contact rates.
Matsuura, H.; Nakao, Y.
2007-05-15
An effect of nuclear elastic scattering on the rate coefficient of fusion reaction between field deuteron and triton in the presence of neutral beam injection heating is studied. Without assuming a Maxwellian for bulk-ion distribution function, the Boltzmann-Fokker-Planck (BFP) equations for field (bulk) deuteron, field (bulk) triton, {alpha}-particle, and beam deuteron are simultaneously solved in an ITER-like deuterium-tritium thermonuclear plasma [R. Aymar, Fusion Eng. Des. 55, 107 (2001)]. The BFP calculation shows that enhancement of the reaction rate coefficient due to knock-on tail formation in fuel-ion distribution functions becomes appreciable, especially in the case of low-density operations.
NASA Technical Reports Server (NTRS)
Jaffe, Richard; Schwenke, David; Chaban, Galina; Panesi, Marco
2014-01-01
Development of High-Fidelity Physics-Based Models to describe hypersonic flight through the atmospheres of Earth and Mars is underway at NASA Ames Research Center. The goal is to construct chemistry models of the collisional and radiative processes that occur in the bow shock and boundary layers of spacecraft during atmospheric entry that are free of empiricism. In this talk I will discuss our philosophy and describe some of our progress. Topics to be covered include thermochemistry, internal energy relaxation, collisional dissociation and radiative emission and absorption. For this work we start by solving the Schrodinger equation to obtain accurate interaction potentials and radiative properties. Then we invoke classical mechanics to compute state-specific heavy particle collision cross sections and reaction rate coefficients. Finally, phenomenological rate coefficients and relaxation times are determined from master equation solutions.
Absolute radiometry and the solar constant
NASA Technical Reports Server (NTRS)
Willson, R. C.
1974-01-01
A series of active cavity radiometers (ACRs) are described which have been developed as standard detectors for the accurate measurement of irradiance in absolute units. It is noted that the ACR is an electrical substitution calorimeter, is designed for automatic remote operation in any environment, and can make irradiance measurements in the range from low-level IR fluxes up to 30 solar constants with small absolute uncertainty. The instrument operates in a differential mode by chopping the radiant flux to be measured at a slow rate, and irradiance is determined from two electrical power measurements together with the instrumental constant. Results are reported for measurements of the solar constant with two types of ACRs. The more accurate measurement yielded a value of 136.6 plus or minus 0.7 mW/sq cm (1.958 plus or minus 0.010 cal/sq cm per min).
On the emission coefficient of uranium plasmas.
NASA Technical Reports Server (NTRS)
Schneider, R. T.; Campbell, H. D.; Mack, J. M.
1973-01-01
The emission coefficient for uranium plasmas (temperature: 8000 K) was measured for the wavelength range from 1200 to 6000 A. The results were compared to theoretical calculations and other measurements. Reasonable agreement between theoretical predictions and our measurements was found in the region from 1200 to 2000 A. Although it was difficult to make absolute comparisons among the different reported measurements, considerable disagreement was found for the higher wavelength region. A short discussion regarding the overall comparisons is given, and final suggestions are made as to the most appropriate emission coefficient values to be used in future design calculations. The absorption coefficient for the same wavelength interval is also reported.
Absolute radiometric calibration of the CCRS SAR
NASA Astrophysics Data System (ADS)
Ulander, Lars M. H.; Hawkins, Robert K.; Livingstone, Charles E.; Lukowski, Tom I.
1991-11-01
Determining the radar scattering coefficients from SAR (synthetic aperture radar) image data requires absolute radiometric calibration of the SAR system. The authors describe an internal calibration methodology for the airborne Canada Centre for Remote Sensing (CCRS) SAR system, based on radar theory, a detailed model of the radar system, and measurements of system parameters. The methodology is verified by analyzing external calibration data acquired over a 6-month period in 1988 by the C-band radar using HH polarization. The results indicate that the overall error is +/- 0.8 dB (1-sigma) for incidence angles +/- 20 deg from antenna boresight. The dominant error contributions are due to the antenna radome and uncertainties in the elevation angle relative to the antenna boresight.
Absolute flux scale for radioastronomy
Ivanov, V.P.; Stankevich, K.S.
1986-07-01
The authors propose and provide support for a new absolute flux scale for radio astronomy, which is not encumbered with the inadequacies of the previous scales. In constructing it the method of relative spectra was used (a powerful tool for choosing reference spectra). A review is given of previous flux scales. The authors compare the AIS scale with the scale they propose. Both scales are based on absolute measurements by the ''artificial moon'' method, and they are practically coincident in the range from 0.96 to 6 GHz. At frequencies above 6 GHz, 0.96 GHz, the AIS scale is overestimated because of incorrect extrapolation of the spectra of the primary and secondary standards. The major results which have emerged from this review of absolute scales in radio astronomy are summarized.
NASA Technical Reports Server (NTRS)
Zhang, Hong Lin; Graziani, Mark; Pradhan, Anil K.
1994-01-01
Collison strengths and maxwellian averaged rate coefficients have been calculated for the 105 transitions among all 15 fine structure levels of the 8 LS terms 2s(sup 2) 2 P(P-2(sup 0 sub 1/, 3/2)), 2s2p(sup 2)(P-4(sub 1/2,3/2,5/2), D-2(sub 3/2, 5/2), S-2(sub 1/2), P-2(sub 1/2, 3/2)), 2p(sup 3)(S-4(sup 0)(sub 3/2), D-2(sup 0 sub 3/2, 5/2), P-2(sup 0 sub 1/2, 3/2)) in highly- charged B-like Ne, Mg, Al, Si, S, Ar, Ca and Fe. Rate coefficients have been tabulated at a wide range of temperatures, depending on the ion charge and abundance in plasma sources. Earlier work for O IV has also been extended to include the high temperature range. A brief discussion of the calculations, sample results, and comparison with earlier works is also given. While much of the new data should be applicable to UV spectral diagnostics, the new rates for the important ground state fine structure transition P-2(sup 0 sub 1/2)-P-2(sup 0 sub 3/2) should result in significant revision of the IR cooling rates in plasmas where B-like ions are prominent constituents, since the new rate coefficients are generally higher by several factors compared with the older data.
Sentinel-2/MSI absolute calibration: first results
NASA Astrophysics Data System (ADS)
Lonjou, V.; Lachérade, S.; Fougnie, B.; Gamet, P.; Marcq, S.; Raynaud, J.-L.; Tremas, T.
2015-10-01
Sentinel-2 is an optical imaging mission devoted to the operational monitoring of land and coastal areas. It is developed in partnership between the European Commission and the European Space Agency. The Sentinel-2 mission is based on a satellites constellation deployed in polar sun-synchronous orbit. It will offer a unique combination of global coverage with a wide field of view (290km), a high revisit (5 days with two satellites), a high resolution (10m, 20m and 60m) and multi-spectral imagery (13 spectral bands in visible and shortwave infra-red domains). CNES is involved in the instrument commissioning in collaboration with ESA. This paper reviews all the techniques that will be used to insure an absolute calibration of the 13 spectral bands better than 5% (target 3%), and will present the first results if available. First, the nominal calibration technique, based on an on-board sun diffuser, is detailed. Then, we show how vicarious calibration methods based on acquisitions over natural targets (oceans, deserts, and Antarctica during winter) will be used to check and improve the accuracy of the absolute calibration coefficients. Finally, the verification scheme, exploiting photometer in-situ measurements over Lacrau plain, is described. A synthesis, including spectral coherence, inter-methods agreement and temporal evolution, will conclude the paper.
Meng, Qingyong Chen, Jun Zhang, Dong H.
2015-09-14
The ring polymer molecular dynamics (RPMD) calculations are performed to calculate rate constants for the title reaction on the recently constructed potential energy surface based on permutation invariant polynomial (PIP) neural-network (NN) fitting [J. Li et al., J. Chem. Phys. 142, 204302 (2015)]. By inspecting convergence, 16 beads are used in computing free-energy barriers at 300 K ≤ T ≤ 1000 K, while different numbers of beads are used for transmission coefficients. The present RPMD rates are in excellent agreement with quantum rates computed on the same potential energy surface, as well as with the experimental measurements, demonstrating further that the RPMD is capable of producing accurate rates for polyatomic chemical reactions even at rather low temperatures.
The contribution of outdoor particles to indoor concentrations is governed by three physical processes: air exchange, penetration, and deposition. Air exchange rates can be measured during field studies, but the other two parameters must be estimated. Over the past few years,...
Branzoli, Francesca; Ercan, Ece; Webb, Andrew; Ronen, Itamar
2014-05-01
The dependence of apparent diffusion coefficients (ADCs) of molecules in biological tissues on an acquisition-specific timescale is a powerful mechanism for studying tissue microstructure. Unlike water, metabolites are confined mainly to intracellular compartments, thus providing higher specificity to tissue microstructure. Compartment-specific structural and chemical properties may also affect molecule transverse relaxation times (T₂). Here, we investigated the correlation between diffusion and relaxation for N-acetylaspartate, creatine and choline compounds in human brain white matter in vivo at 7 T, and compared them with those of water under the same experimental conditions. Data were acquired in a volume of interest in parietal white matter at two different diffusion times, Δ = 44 and 246 ms, using a matrix of three echo times (T(E)) and five diffusion weighting values (up to 4575 s/mm²). Significant differences in the dependence of the ADCs on T(E) were found between water and metabolites, as well as among the different metabolites. A significant decrease in water ADC as a function of TE was observed only at the longest diffusion time (p < 0.001), supporting the hypothesis that at least part of the restricted water pool can be associated with longer T₂, as suggested by previous studies in vitro. Metabolite data showed an increase of creatine (p < 0.05) and N-acetylaspartate (p < 0.05) ADCs with TE at Δ = 44 ms, and a decrease of creatine (p < 0.05) and N-acetylaspartate (p = 0.1) ADCs with TE at Δ = 246 ms. No dependence of choline ADC on TE was observed. The metabolite results suggest that diffusion and relaxation properties are dictated not only by metabolite distribution in different cell types, but also by other mechanisms, such as interactions with membranes, exchange between "free" and "bound" states or interactions with microsusceptibility gradients.
Progress Toward an Absolute Measurement of Electron Impact Excitation of Si^2+
NASA Astrophysics Data System (ADS)
Reisenfeld, D. B.; Janzen, P. H.; Gardner, L. D.; Kohl, J. L.
1997-04-01
We are in the process of measuring the electron impact excitation (EIE) absolute rate coefficients for Si^2+(3s^2 ^1S - 3s3p ^1P) and Si^2+(3s3p ^3P^o - 3p^2 ^3P) for energies near threshold. A beams modulation technique with inclined electron and ion beams is being used. The radiation from the excited ions at λ 120.6 nm and λ 130.0 nm is detected using an absolutely calibrated optical system that subtends slightly over π steradians. The population of the Si^2+(3s3p ^3P^o) metastable state in the incident ion beam is determined by making an absolute measurement of the intensity of the λ 189.2 nm light from the beam due to radiative decay of the metastable state(G. P. Layfatis and J. L. Kohl, Phys. Rev. A 36), 59 (1987).. Because of the high density of overlapping resonances above threshold, the cross sections should exhibit a complex energy dependence(D. C. Griffin et al)., Phys. Rev. A 47, 2871 (1993).. We expect to resolve some of this structure. Research progress and the experimental apparatus will be described. There are no previous measurements of EIE in a Mg-like system, nor of EIE in a metastable ion. This work was supported in part by NASA Supporting Research and Technology Program in Solar Physics grant NAGW-1687 and NASA Training Grant NGT-51081.
Robust control design with real parameter uncertainty using absolute stability theory. Ph.D. Thesis
NASA Technical Reports Server (NTRS)
How, Jonathan P.; Hall, Steven R.
1993-01-01
The purpose of this thesis is to investigate an extension of mu theory for robust control design by considering systems with linear and nonlinear real parameter uncertainties. In the process, explicit connections are made between mixed mu and absolute stability theory. In particular, it is shown that the upper bounds for mixed mu are a generalization of results from absolute stability theory. Both state space and frequency domain criteria are developed for several nonlinearities and stability multipliers using the wealth of literature on absolute stability theory and the concepts of supply rates and storage functions. The state space conditions are expressed in terms of Riccati equations and parameter-dependent Lyapunov functions. For controller synthesis, these stability conditions are used to form an overbound of the H2 performance objective. A geometric interpretation of the equivalent frequency domain criteria in terms of off-axis circles clarifies the important role of the multiplier and shows that both the magnitude and phase of the uncertainty are considered. A numerical algorithm is developed to design robust controllers that minimize the bound on an H2 cost functional and satisfy an analysis test based on the Popov stability multiplier. The controller and multiplier coefficients are optimized simultaneously, which avoids the iteration and curve-fitting procedures required by the D-K procedure of mu synthesis. Several benchmark problems and experiments on the Middeck Active Control Experiment at M.I.T. demonstrate that these controllers achieve good robust performance and guaranteed stability bounds.
Guo, JunJiang; Xu, JiaQi; Li, ZeRong; Tan, NingXin; Li, XiangYuan
2015-04-01
The potential energy surface (PES) for reaction C2H4 + HO2 was examined by using the quantum chemical methods. All rates were determined computationally using the CBS-QB3 composite method combined with conventional transition state theory(TST), variational transition-state theory (VTST) and Rice-Ramsberger-Kassel-Marcus/master-equation (RRKM/ME) theory. The geometries optimization and the vibrational frequency analysis of reactants, transition states, and products were performed at the B3LYP/CBSB7 level. The composite CBS-QB3 method was applied for energy calculations. The major product channel of reaction C2H4 + HO2 is the formation C2H4O2H via an OH(···)π complex with 3.7 kcal/mol binding energy which exhibits negative-temperature dependence. We further investigated the reactions related to this complex, which were ignored in previous studies. Thermochemical properties of the species involved in the reactions were determined using the CBS-QB3 method, and enthalpies of formation of species were compared with literature values. The calculated rate constants are in good agreement with those available from literature and given in modified Arrhenius equation form, which are serviceable in combustion modeling of hydrocarbons. Finally, in order to illustrate the effect for low-temperature ignition of our new rate constants, we have implemented them into the existing mechanisms, which can predict ethylene ignition in a shock tube with better performance.
Guo, JunJiang; Xu, JiaQi; Li, ZeRong; Tan, NingXin; Li, XiangYuan
2015-04-01
The potential energy surface (PES) for reaction C2H4 + HO2 was examined by using the quantum chemical methods. All rates were determined computationally using the CBS-QB3 composite method combined with conventional transition state theory(TST), variational transition-state theory (VTST) and Rice-Ramsberger-Kassel-Marcus/master-equation (RRKM/ME) theory. The geometries optimization and the vibrational frequency analysis of reactants, transition states, and products were performed at the B3LYP/CBSB7 level. The composite CBS-QB3 method was applied for energy calculations. The major product channel of reaction C2H4 + HO2 is the formation C2H4O2H via an OH(···)π complex with 3.7 kcal/mol binding energy which exhibits negative-temperature dependence. We further investigated the reactions related to this complex, which were ignored in previous studies. Thermochemical properties of the species involved in the reactions were determined using the CBS-QB3 method, and enthalpies of formation of species were compared with literature values. The calculated rate constants are in good agreement with those available from literature and given in modified Arrhenius equation form, which are serviceable in combustion modeling of hydrocarbons. Finally, in order to illustrate the effect for low-temperature ignition of our new rate constants, we have implemented them into the existing mechanisms, which can predict ethylene ignition in a shock tube with better performance. PMID:25774424
An agreement coefficient for image comparison
Ji, L.; Gallo, K.
2006-01-01
Combination of datasets acquired from different sensor systems is necessary to construct a long time-series dataset for remotely sensed land-surface variables. Assessment of the agreement of the data derived from various sources is an important issue in understanding the data continuity through the time-series. Some traditional measures, including correlation coefficient, coefficient of determination, mean absolute error, and root mean square error, are not always optimal for evaluating the data agreement. For this reason, we developed a new agreement coefficient for comparing two different images. The agreement coefficient has the following properties: non-dimensional, bounded, symmetric, and distinguishable between systematic and unsystematic differences. The paper provides examples of agreement analyses for hypothetical data and actual remotely sensed data. The results demonstrate that the agreement coefficient does include the above properties, and therefore is a useful tool for image comparison. ?? 2006 American Society for Photogrammetry and Remote Sensing.
Relativistic Absolutism in Moral Education.
ERIC Educational Resources Information Center
Vogt, W. Paul
1982-01-01
Discusses Emile Durkheim's "Moral Education: A Study in the Theory and Application of the Sociology of Education," which holds that morally healthy societies may vary in culture and organization but must possess absolute rules of moral behavior. Compares this moral theory with current theory and practice of American educators. (MJL)
Absolute transition probabilities of phosphorus.
NASA Technical Reports Server (NTRS)
Miller, M. H.; Roig, R. A.; Bengtson, R. D.
1971-01-01
Use of a gas-driven shock tube to measure the absolute strengths of 21 P I lines and 126 P II lines (from 3300 to 6900 A). Accuracy for prominent, isolated neutral and ionic lines is estimated to be 28 to 40% and 18 to 30%, respectively. The data and the corresponding theoretical predictions are examined for conformity with the sum rules.-
The rate coefficient for the reaction NO2 + NO3 yielding NO + NO2 + O2 from 273 to 313 K
NASA Technical Reports Server (NTRS)
Cantrell, Chris A.; Shetter, Richard E.; Mcdaniel, Anthony H.; Calvert, Jack G.
1990-01-01
The ratio of rate constants for the reaction NO3 + NO yielding 2 NO2 (k3) and the reaction NO2 + NO3 yielding NO + NO2 + O2 (k4) were determined by measuring of NO and NO2 concentrations of NO and NO2 in an N2O5/NO2/N2 mixture over the temperature range 273-313 K. The measured ratio was found to be expressed by the equation k3/k4 = 387 exp(-1375/T). The results are consistent with those of Hammer et al. (1986).
McGillen, Max R; Baasandorj, Munkhbayar; Burkholder, James B
2013-06-01
Butanol (C4H9OH) is a potential biofuel alternative in fossil fuel gasoline and diesel formulations. The usage of butanol would necessarily lead to direct emissions into the atmosphere; thus, an understanding of its atmospheric processing and environmental impact is desired. Reaction with the OH radical is expected to be the predominant atmospheric removal process for the four aliphatic isomers of butanol. In this work, rate coefficients, k, for the gas-phase reaction of the n-, i-, s-, and t-butanol isomers with the OH radical were measured under pseudo-first-order conditions in OH using pulsed laser photolysis to produce OH radicals and laser induced fluorescence to monitor its temporal profile. Rate coefficients were measured over the temperature range 221-381 K at total pressures between 50 and 200 Torr (He). The reactions exhibited non-Arrhenius behavior over this temperature range and no dependence on total pressure with k(296 K) values of (9.68 ± 0.75), (9.72 ± 0.72), (8.88 ± 0.69), and (1.04 ± 0.08) (in units of 10(-12) cm(3) molecule(-1) s(-1)) for n-, i-, s-, and t-butanol, respectively. The quoted uncertainties are at the 2σ level and include estimated systematic errors. The observed non-Arrhenius behavior is interpreted here to result from a competition between the available H-atom abstraction reactive sites, which have different activation energies and pre-exponential factors. The present results are compared with results from previous kinetic studies, structure-activity relationships (SARs), and theoretical calculations and the discrepancies are discussed. Results from this work were combined with available high temperature (1200-1800 K) rate coefficient data and room temperature reaction end-product yields, where available, to derive a self-consistent site-specific set of reaction rate coefficients of the form AT(n) exp(-E/RT) for use in atmospheric and combustion chemistry modeling.
Factor Scores, Structure Coefficients, and Communality Coefficients
ERIC Educational Resources Information Center
Goodwyn, Fara
2012-01-01
This paper presents heuristic explanations of factor scores, structure coefficients, and communality coefficients. Common misconceptions regarding these topics are clarified. In addition, (a) the regression (b) Bartlett, (c) Anderson-Rubin, and (d) Thompson methods for calculating factor scores are reviewed. Syntax necessary to execute all four…
Moral absolutism and ectopic pregnancy.
Kaczor, C
2001-02-01
If one accepts a version of absolutism that excludes the intentional killing of any innocent human person from conception to natural death, ectopic pregnancy poses vexing difficulties. Given that the embryonic life almost certainly will die anyway, how can one retain one's moral principle and yet adequately respond to a situation that gravely threatens the life of the mother and her future fertility? The four options of treatment most often discussed in the literature are non-intervention, salpingectomy (removal of tube with embryo), salpingostomy (removal of embryo alone), and use of methotrexate (MXT). In this essay, I review these four options and introduce a fifth (the milking technique). In order to assess these options in terms of the absolutism mentioned, it will also be necessary to discuss various accounts of the intention/foresight distinction. I conclude that salpingectomy, salpingostomy, and the milking technique are compatible with absolutist presuppositions, but not the use of methotrexate.
Moral absolutism and ectopic pregnancy.
Kaczor, C
2001-02-01
If one accepts a version of absolutism that excludes the intentional killing of any innocent human person from conception to natural death, ectopic pregnancy poses vexing difficulties. Given that the embryonic life almost certainly will die anyway, how can one retain one's moral principle and yet adequately respond to a situation that gravely threatens the life of the mother and her future fertility? The four options of treatment most often discussed in the literature are non-intervention, salpingectomy (removal of tube with embryo), salpingostomy (removal of embryo alone), and use of methotrexate (MXT). In this essay, I review these four options and introduce a fifth (the milking technique). In order to assess these options in terms of the absolutism mentioned, it will also be necessary to discuss various accounts of the intention/foresight distinction. I conclude that salpingectomy, salpingostomy, and the milking technique are compatible with absolutist presuppositions, but not the use of methotrexate. PMID:11262641
The Absolute Spectrum Polarimeter (ASP)
NASA Technical Reports Server (NTRS)
Kogut, A. J.
2010-01-01
The Absolute Spectrum Polarimeter (ASP) is an Explorer-class mission to map the absolute intensity and linear polarization of the cosmic microwave background and diffuse astrophysical foregrounds over the full sky from 30 GHz to 5 THz. The principal science goal is the detection and characterization of linear polarization from an inflationary epoch in the early universe, with tensor-to-scalar ratio r much greater than 1O(raised to the power of { -3}) and Compton distortion y < 10 (raised to the power of{-6}). We describe the ASP instrument and mission architecture needed to detect the signature of an inflationary epoch in the early universe using only 4 semiconductor bolometers.
Classification images predict absolute efficiency.
Murray, Richard F; Bennett, Patrick J; Sekuler, Allison B
2005-02-24
How well do classification images characterize human observers' strategies in perceptual tasks? We show mathematically that from the classification image of a noisy linear observer, it is possible to recover the observer's absolute efficiency. If we could similarly predict human observers' performance from their classification images, this would suggest that the linear model that underlies use of the classification image method is adequate over the small range of stimuli typically encountered in a classification image experiment, and that a classification image captures most important aspects of human observers' performance over this range. In a contrast discrimination task and in a shape discrimination task, we found that observers' absolute efficiencies were generally well predicted by their classification images, although consistently slightly (approximately 13%) higher than predicted. We consider whether a number of plausible nonlinearities can account for the slight under prediction, and of these we find that only a form of phase uncertainty can account for the discrepancy.
Absolute calibration of optical flats
Sommargren, Gary E.
2005-04-05
The invention uses the phase shifting diffraction interferometer (PSDI) to provide a true point-by-point measurement of absolute flatness over the surface of optical flats. Beams exiting the fiber optics in a PSDI have perfect spherical wavefronts. The measurement beam is reflected from the optical flat and passed through an auxiliary optic to then be combined with the reference beam on a CCD. The combined beams include phase errors due to both the optic under test and the auxiliary optic. Standard phase extraction algorithms are used to calculate this combined phase error. The optical flat is then removed from the system and the measurement fiber is moved to recombine the two beams. The newly combined beams include only the phase errors due to the auxiliary optic. When the second phase measurement is subtracted from the first phase measurement, the absolute phase error of the optical flat is obtained.
NASA Astrophysics Data System (ADS)
Douglas, Kevin; Slater, Eloise; Blitz, Mark; Plane, John; Heard, Dwayne; Seakins, Paul
2016-04-01
The Cassini-Huygens mission to Titan revealed unexpectedly large amounts of benzene in the troposphere, and confirmed the absence of a global ethane ocean as predicted by photochemical models of methane conversion over the lifetime of the solar system. An important chemical intermediate in both the production and loss of benzene and ethane is the first electronically excited state of methylene, 1CH2. For example, at room temperature an important reaction of 1CH2 is with acetylene (R1a), leading to the formation of propargyl (C3H3)[1]. The subsequent recombination of propargyl radicals is the major suggested route to benzene in Titan's atmosphere (R2)[2]. In addition to reaction of 1CH2 leading to products, there is also competition between inelastic electronic relaxation to form the ground triplet state 3CH2 (R1b). This ground state 3CH2 has a markedly different reactivity to the singlet, reacting primarily with methyl radicals (CH3) to form ethene (R3). As methyl radical recombination is the primary route to ethane (R4)[3], reactions of 1CH2 will also heavily influence the ethane budget on Titan. 1CH2 + C2H2 → C3H3 + H (R1a) 1CH2 + C2H2 → 3CH2 + C2H2 (R1b) C3H3 + C3H3 → C6H6 (R2) 3CH2 + CH3 → C2H4 + H (R3) CH3 + CH3 (+ M) → C2H6 (R4) Thus this competition between chemical reaction and electronic relaxation in the reactions of 1CH2 with H2, CH4, C2H4, and C2H6 will play an important role in determining the benzene and ethane budgets on Titan. Despite this there are no measurements of any rate constants for 1CH2 at temperatures relevant to Titan's atmosphere (60 - 170 K). Using a pulsed Laval nozzle apparatus coupled with pulsed laser photolysis laser-induced fluorescence, the low temperature reaction kinetics for the removal of 1CH2 with nitrogen, hydrogen, methane, ethane, ethene, acetylene, and oxygen, have been studied. The results revealed an increase in the removal rate of 1CH2 at temperatures below 200 K, with a sharp increase of around a factor of
NASA Astrophysics Data System (ADS)
Yang, Kaike
FOR MOLECULES WEAKLY COUPLED TO LEADS THE EXACT ZERO-BIAS KOHN-SHAM CONDUCTANCE CAN BE ORDERS OF MAGNITUDE LARGER THAN THE TRUE CONDUCTANCE DUE TO THE LACK OF DYNAMICAL EXCHANGE-CORRELATION (XC) EFFECTS. RECENTLY, IT HAS BEEN SHOWN HOW THESE DYNAMICAL XC CORRECTIONS CAN BE CALCULATED USING ONLY QUANTITIES OBTAINED FROM STATIC DENSITY FUNCTIONAL THEORY. HERE, WE INVESTIGATE THE THERMOELECTRIC TRANSPORT AND DERIVE THE XC CORRECTION TO THE SEEBECK COEFFICIENT. WE FIND THAT THE DYNAMICAL CORRECTION TO THE SEEBECK COEFFICIENT IS DETERMINANT IN EVALUATING THE THERMOPOWER: THE ABSOLUTE VALUE OF THE DYNAMICAL CORRECTION FOR THE SEEBECK COEFFICIENT IS, FOR CERTAIN VALUES OF GATE VOLTAGE, MUCH LARGER THAN THAT OF THE KOHN-SHAM TERM. FINALLY, WE COMPARE OUR DENSITY FUNCTIONAL CALCULATIONS TO THE RATE EQUATION AND THE EXPERIMENTAL RESULTS
Castro-Palacio, Juan Carlos; Bemish, Raymond J; Meuwly, Markus
2015-03-01
The O((3)P) + NO((2)Π) → O2(X(3)Σg(-)) + N((4)S) reaction is among the N- and O- involving reactions that dominate the energetics of the reactive air flow around spacecraft during hypersonic atmospheric re-entry. In this regime, the temperature in the bow shock typically ranges from 1000 to 20,000 K. The forward and reverse rate coefficients for this reaction derived directly from trajectory calculations over this range of temperature are reported in this letter. Results compare well with the established equilibrium constants for the same reaction from thermodynamic quantities derived from spectroscopy in the gas phase which paves the way for large-scale in silico investigations of equilibrium rates under extreme conditions.
The Absolute Radiometric Calibration of Space - Sensors.
NASA Astrophysics Data System (ADS)
Holm, Ronald Gene
1987-09-01
The need for absolute radiometric calibration of space-based sensors will continue to increase as new generations of space sensors are developed. A reflectance -based in-flight calibration procedure is used to determine the radiance reaching the entrance pupil of the sensor. This procedure uses ground-based measurements coupled with a radiative transfer code to characterize the effects the atmosphere has on the signal reaching the sensor. The computed radiance is compared to the digital count output of the sensor associated with the image of a test site. This provides an update to the preflight calibration of the system and a check on the on-board internal calibrator. This calibration procedure was used to perform a series of five calibrations of the Landsat-5 Thematic Mapper (TM). For the 12 measurements made in TM bands 1-3, the RMS variation from the mean as a percentage of the mean is (+OR-) 1.9%, and for measurements in the IR, TM bands 4,5, and 7, the value is (+OR-) 3.4%. The RMS variation for all 23 measurements is (+OR-) 2.8%. The absolute calibration techniques were put to another test with a series of three calibration of the SPOT-1 High Resolution Visible, (HRV), sensors. The ratio, HRV-2/HRV-1, of absolute calibration coefficients compared very well with ratios of histogrammed data obtained when the cameras simultaneously imaged the same ground site. Bands PA, B1 and B3 agreed to within 3%, while band B2 showed a 7% difference. The procedure for performing a satellite calibration was then used to demonstrate how a calibrated satellite sensor can be used to quantitatively evaluate surface reflectance over a wide range of surface features. Predicted reflectance factors were compared to values obtained from aircraft -based radiometer data. This procedure was applied on four dates with two different surface conditions per date. A strong correlation, R('2) = .996, was shown between reflectance values determined from satellite imagery and low-flying aircraft
NASA Astrophysics Data System (ADS)
Kappatou, A.; Jaspers, R. J. E.; Delabie, E.; Marchuk, O.; Biel, W.; Jakobs, M. A.
2012-10-01
Investigation of impurity transport properties in tokamak plasmas is essential and a diagnostic that can provide information on the impurity content is required. Combining charge exchange recombination spectroscopy (CXRS) and beam emission spectroscopy (BES), absolute radial profiles of impurity densities can be obtained from the CXRS and BES intensities, electron density and CXRS and BES emission rates, without requiring any absolute calibration of the spectra. The technique is demonstrated here with absolute impurity density radial profiles obtained in TEXTOR plasmas, using a high efficiency charge exchange spectrometer with high etendue, that measures the CXRS and BES spectra along the same lines-of-sight, offering an additional advantage for the determination of absolute impurity densities.
The AFGL absolute gravity program
NASA Technical Reports Server (NTRS)
Hammond, J. A.; Iliff, R. L.
1978-01-01
A brief discussion of the AFGL's (Air Force Geophysics Laboratory) program in absolute gravity is presented. Support of outside work and in-house studies relating to gravity instrumentation are discussed. A description of the current transportable system is included and the latest results are presented. These results show good agreement with measurements at the AFGL site by an Italian system. The accuracy obtained by the transportable apparatus is better than 0.1 microns sq sec 10 microgal and agreement with previous measurements is within the combined uncertainties of the measurements.
Familial Aggregation of Absolute Pitch
Baharloo, Siamak; Service, Susan K.; Risch, Neil; Gitschier, Jane; Freimer, Nelson B.
2000-01-01
Absolute pitch (AP) is a behavioral trait that is defined as the ability to identify the pitch of tones in the absence of a reference pitch. AP is an ideal phenotype for investigation of gene and environment interactions in the development of complex human behaviors. Individuals who score exceptionally well on formalized auditory tests of pitch perception are designated as “AP-1.” As described in this report, auditory testing of siblings of AP-1 probands and of a control sample indicates that AP-1 aggregates in families. The implications of this finding for the mapping of loci for AP-1 predisposition are discussed. PMID:10924408
Ng, Maggie; Mok, Daniel K W; Lee, Edmond P F; Dyke, John M
2015-03-21
The reaction between atomic chlorine (Cl) and methyl nitrate (CH3ONO2) is significant in the atmosphere, as Cl is a key oxidant, especially in the marine boundary layer, and alkyl nitrates are important nitrogen-containing organic compounds, which are temporary reservoirs of the reactive nitrogen oxides NO, NO2 and NO3 (NOx). Four reaction channels HCl + CH2ONO2, CH3OCl + NO2, CH3Cl + NO3 and CH3O + ClNO2 were considered. The major channel is found to be the H abstraction channel, to give the products HCl + CH2ONO2. For all channels, geometry optimization and frequency calculations were carried out at the M06-2X/6-31+G** level, while relative electronic energies were improved to the UCCSD(T*)-F12/CBS level. The reaction barrier (ΔE(‡)0K) and reaction enthalpy (ΔH(RX)298K) of the H abstraction channel were computed to be 0.61 and -2.30 kcal mol(-1), respectively, at the UCCSD(T*)-F12/CBS//M06-2X/6-31+G** level. Reaction barriers (ΔE(‡)0K) for the other channels are more positive and these pathways do not contribute to the overall reaction rate coefficient in the temperature range considered (200-400 K). Rate coefficients were calculated for the H-abstraction channel at various levels of variational transition state theory (VTST) including tunnelling. Recommended ICVT/SCT rate coefficients in the temperature range 200-400 K are presented for the first time for this reaction. The values obtained in the 200-300 K region are particularly important as they will be valuable for atmospheric modelling calculations involving reactions with methyl nitrate. The implications of the results to atmospheric chemistry are discussed. Also, the enthalpies of formation, ΔHf,298K, of CH3ONO2 and CH2ONO2 were computed to be -29.7 and 19.3 kcal mol(-1), respectively, at the UCCSD(T*)-F12/CBS level.
Transient absolute robustness in stochastic biochemical networks.
Enciso, German A
2016-08-01
Absolute robustness allows biochemical networks to sustain a consistent steady-state output in the face of protein concentration variability from cell to cell. This property is structural and can be determined from the topology of the network alone regardless of rate parameters. An important question regarding these systems is the effect of discrete biochemical noise in the dynamical behaviour. In this paper, a variable freezing technique is developed to show that under mild hypotheses the corresponding stochastic system has a transiently robust behaviour. Specifically, after finite time the distribution of the output approximates a Poisson distribution, centred around the deterministic mean. The approximation becomes increasingly accurate, and it holds for increasingly long finite times, as the total protein concentrations grow to infinity. In particular, the stochastic system retains a transient, absolutely robust behaviour corresponding to the deterministic case. This result contrasts with the long-term dynamics of the stochastic system, which eventually must undergo an extinction event that eliminates robustness and is completely different from the deterministic dynamics. The transiently robust behaviour may be sufficient to carry out many forms of robust signal transduction and cellular decision-making in cellular organisms. PMID:27581485
Suleimanov, Yury V.; Kong, Wendi J.; Green, William H.; Guo, Hua
2014-12-28
Following our previous study of prototypical insertion reactions of energetically asymmetric type with the RPMD (Ring-Polymer Molecular Dynamics) method [Y. Li, Y. Suleimanov, and H. Guo, J. Phys. Chem. Lett. 5, 700 (2014)], we extend it to two other prototypical insertion reactions with much less exothermicity (near thermoneutral), namely, X + H{sub 2} → HX + H where X = C({sup 1}D), S({sup 1}D), in order to assess the accuracy of this method for calculating thermal rate coefficients for this class of reactions. For both chemical reactions, RPMD displays remarkable accuracy and agreement with the previous quantum dynamic results that make it encouraging for the future application of the RPMD to other barrier-less, complex-forming reactions involving polyatomic reactants with any exothermicity.
Absolute flux measurements for swift atoms
NASA Technical Reports Server (NTRS)
Fink, M.; Kohl, D. A.; Keto, J. W.; Antoniewicz, P.
1987-01-01
While a torsion balance in vacuum can easily measure the momentum transfer from a gas beam impinging on a surface attached to the balance, this measurement depends on the accommodation coefficients of the atoms with the surface and the distribution of the recoil. A torsion balance is described for making absolute flux measurements independent of recoil effects. The torsion balance is a conventional taut suspension wire design and the Young modulus of the wire determines the relationship between the displacement and the applied torque. A compensating magnetic field is applied to maintain zero displacement and provide critical damping. The unique feature is to couple the impinging gas beam to the torsion balance via a Wood's horn, i.e., a thin wall tube with a gradual 90 deg bend. Just as light is trapped in a Wood's horn by specular reflection from the curved surfaces, the gas beam diffuses through the tube. Instead of trapping the beam, the end of the tube is open so that the atoms exit the tube at 90 deg to their original direction. Therefore, all of the forward momentum of the gas beam is transferred to the torsion balance independent of the angle of reflection from the surfaces inside the tube.
Berteloite, Coralie; Le Picard, Sébastien D; Balucani, Nadia; Canosa, André; Sims, Ian R
2010-04-21
The kinetics of the reactions of the linear butadiynyl radical, C4H (CCCCH), with methane, ethane, propane and butane have been studied over the temperature range of 39-300 K using a CRESU (Cinétique de Réaction en Ecoulement Supersonique Uniforme or Reaction Kinetics in Uniform Supersonic Flow) apparatus combined with the pulsed laser photolysis-laser induced fluorescence technique. The rate coefficients, except for the reaction with methane, show a negative temperature dependence and can be fitted with the following expressions over the temperature range of this study: k(C2H6) = 0.289 x 10(-10) (T/298 K)(-1.23) exp(-24.8 K/T) cm3 molecule(-1) s(-1); k(C3H8) = 1.06 x 10(-10) (T/298 K)(-1.36) exp(-56.9 K/T) cm3 molecule(-1) s(-1); k(C4H10) = 2.93 x 10(-10) (T/298 K)(-1.30) exp(-90.1 K/T) cm3 molecule(-1) s(-1). The rate coefficients for the reaction with methane were measured only at 200 K and 300 K yielding a positive temperature dependence: k(CH4) = 1.63 x 10(-11) exp(-610 K/T) cm3 molecule(-1) s(-1). Possible reaction mechanisms and product channels are discussed in detail for each of these reactions. Potential implications of these results for models of low temperature chemical environments, in particular cold interstellar clouds and planetary atmospheres such as that of Titan, are considered.
NASA Astrophysics Data System (ADS)
Sudbø, Aa. S.; Loy, M. M. T.
1982-04-01
Using a pulsed, time resolved IR-UV double resonance technique, we have measured initial and final state specific rates for collision-induced rotational and spin-orbit transitions in NO in its (X 2Π, v = 2) vibronic state. A systematic study of the rates was done for initial and final rotational states with J between 1/2 and 35/2, for both Ω = 1/2 and the Ω = 3/2 spin-orbit components of the X 2Π state. Collision partners were room temperature NO, He, Ar, N2, CO, and SF6. No propensity rules favoring ΔΩ = 0 or ΔJ = 0,±1 were observed, except in NO-He collisions, where ΔΩ = 0 was favored. The state-to-state rates do not vary much with initial state and fall off slowly with increasing ΔJ. Total cross sections for collision-induced rotational transitions were found to be tens of Å2, insensitive to initial state, and correlated with the size of the collision partner.
NASA Technical Reports Server (NTRS)
Bosco, S. R.; Brobst, W. D.; Nava, D. F.; Stief, L. J.
1983-01-01
The rate constant is measured over the temperature interval 218-456 K using the technique of flash photolysis-laser-induced fluorescence. NH2 radicals are produced by the flash photolysis of ammonia highly diluted in argon, and the decay of fluorescent NH2 photons is measured by multiscaling techniques. For each of the five temperatures employed in the study, the results are shown to be independent of variations in PH3 concentration, total pressure (argon), and flash intensity. It is found that the rate constant results are best represented for T between 218 and 456 K by the expression k = (1.52 + or - 0.16) x 10 to the -12th exp(-928 + or - 56/T) cu cm per molecule per sec; the error quoted is 1 standard deviation. This is the first determination of the rate constant for the reaction NH2 + PH3. The data are compared with an estimate made in order to explain results of the radiolysis of NH3-PH3 mixtures. The Arrhenius parameters determined here for NH2 + PH3 are then constrasted with those for the corresponding reactions of H and OH with PH3.
NASA Technical Reports Server (NTRS)
Bosco, S. R.; Brobst, W. D.; Nava, D. F.; Stief, L. J.
1983-01-01
The rate constant is measured over the temperature interval 218-456 K using the technique of flash photolysis-laser-induced fluorescence. NH2 radicals are produced by the flash photolysis of ammonia highly diluted in argon, and the decay of fluorescent NH2 photons is measured by multiscaling techniques. For each of the five temperatures employed in the study, the results are shown to be indepenent of variations in PH3 concentration, total pressure (argon), and flash intensity. It is found that the rate constant results are best represented for T between 218 and 456 K by the expression k = (1.52 + or - 0.16) x 10 to the -12th exp(-928 + or - 56/T) cu cm per molecule per sec; the error quoted is 1 standard deviation. This is the first determination of the rate constant for the reaction NH2 + PH3. The data are compared with an estimate made in order to explain results of the radiolysis of NH3-PH3 mixtures. The Arrhenius parameters determined here for NH2 + PH3 are then contrasted with those for the corresponding reactions of H and OH with PH3.
Channel specific rate constants for reactions of O(1D) with HCl and HBr
NASA Technical Reports Server (NTRS)
Wine, P. H.; Wells, J. R.; Ravishankara, A. R.
1986-01-01
The absolute rate coefficients and product yields for reactions of O(1D) with HCl(1) and HBr(2) at 287 K are presently determined by means of the time-resolved resonance fluorescence detection of O(3P) and H(2S) in conjunction with pulsed laser photolysis of O3/HX/He mixtures. Total rate coefficients for O(1D) removal are found to be, in units of 10 to the -10th cu cm/molecule per sec, k(1) = 1.50 + or - 0.18 and k(2) 1.48 + or - 0.16; the absolute accuracy of these rate coefficients is estimated to be + or - 20 percent.
Cosmology with negative absolute temperatures
NASA Astrophysics Data System (ADS)
Vieira, J. P. P.; Byrnes, Christian T.; Lewis, Antony
2016-08-01
Negative absolute temperatures (NAT) are an exotic thermodynamical consequence of quantum physics which has been known since the 1950's (having been achieved in the lab on a number of occasions). Recently, the work of Braun et al. [1] has rekindled interest in negative temperatures and hinted at a possibility of using NAT systems in the lab as dark energy analogues. This paper goes one step further, looking into the cosmological consequences of the existence of a NAT component in the Universe. NAT-dominated expanding Universes experience a borderline phantom expansion (w < ‑1) with no Big Rip, and their contracting counterparts are forced to bounce after the energy density becomes sufficiently large. Both scenarios might be used to solve horizon and flatness problems analogously to standard inflation and bouncing cosmologies. We discuss the difficulties in obtaining and ending a NAT-dominated epoch, and possible ways of obtaining density perturbations with an acceptable spectrum.
Apparatus for absolute pressure measurement
NASA Technical Reports Server (NTRS)
Hecht, R. (Inventor)
1969-01-01
An absolute pressure sensor (e.g., the diaphragm of a capacitance manometer) was subjected to a superimposed potential to effectively reduce the mechanical stiffness of the sensor. This substantially increases the sensitivity of the sensor and is particularly useful in vacuum gauges. An oscillating component of the superimposed potential induced vibrations of the sensor. The phase of these vibrations with respect to that of the oscillating component was monitored, and served to initiate an automatic adjustment of the static component of the superimposed potential, so as to bring the sensor into resonance at the frequency of the oscillating component. This establishes a selected sensitivity for the sensor, since a definite relationship exists between resonant frequency and sensitivity.
Cosmology with negative absolute temperatures
NASA Astrophysics Data System (ADS)
Vieira, J. P. P.; Byrnes, Christian T.; Lewis, Antony
2016-08-01
Negative absolute temperatures (NAT) are an exotic thermodynamical consequence of quantum physics which has been known since the 1950's (having been achieved in the lab on a number of occasions). Recently, the work of Braun et al. [1] has rekindled interest in negative temperatures and hinted at a possibility of using NAT systems in the lab as dark energy analogues. This paper goes one step further, looking into the cosmological consequences of the existence of a NAT component in the Universe. NAT-dominated expanding Universes experience a borderline phantom expansion (w < -1) with no Big Rip, and their contracting counterparts are forced to bounce after the energy density becomes sufficiently large. Both scenarios might be used to solve horizon and flatness problems analogously to standard inflation and bouncing cosmologies. We discuss the difficulties in obtaining and ending a NAT-dominated epoch, and possible ways of obtaining density perturbations with an acceptable spectrum.
Swarm's Absolute Scalar Magnetometer metrological performances
NASA Astrophysics Data System (ADS)
Leger, J.; Fratter, I.; Bertrand, F.; Jager, T.; Morales, S.
2012-12-01
The Absolute Scalar Magnetometer (ASM) has been developed for the ESA Earth Observation Swarm mission, planned for launch in November 2012. As its Overhauser magnetometers forerunners flown on Oersted and Champ satellites, it will deliver high resolution scalar measurements for the in-flight calibration of the Vector Field Magnetometer manufactured by the Danish Technical University. Latest results of the ground tests carried out to fully characterize all parameters that may affect its accuracy, both at instrument and satellite level, will be presented. In addition to its baseline function, the ASM can be operated either at a much higher sampling rate (burst mode at 250 Hz) or in a dual mode where it also delivers vector field measurements as a by-product. The calibration procedure and the relevant vector performances will be discussed.
Lyons, P.C.; Krogh, T.E.; Kwok, Y.Y.; Zodrow, E.L.
1997-01-01
The Upper Banner tonstein, a kaolinized volcanic ash bed that occurs about 90 m above the base of the Middle Pennsylvanian Series in Virginia, is the oldest known Middle Pennsylvanian tonstein in the Appalachian basin. On the basis of palynostratigraphy, the Upper Banner coal bed correlates approximately with the Langsettian-Duckmantian (ex Westphalian A-B) boundary in Europe. Stratigraphically, the Upper Banner tonstein occurs 440-480 m below the Fire Clay tonstein, which in turn is 25-50 m below the marine Magoffin Member of the Breathitt Formation, the approximate correlative of the Agir Marine Band that marks the Dunckmantian-Bolsovian (ex Westphalian C) boundary in Europe. Six single-crystal U-Pb zircon ages were determined for the Upper Banner tonstein. Of these, four overlap concordia within uncertainties and have 206Pb/238U ages that range from 306 to 310??1 Ma. Another analysis falls in the same group but plots slightly to the right of the curve, whereas a single analysis of a low uranium zircon grain gives an age of 316??1 Ma. Variation in ages is outside of analytical uncertainty; hence, variable amounts of recent Pb loss is implied, and the most probable (minimum) depositional age is given by the oldest value at 316??1 Ma - an age consistent with a mean sanidine 40Ar/39Ar plateau age of 311.2??0.7 Ma for the stratigraphically younger Fire Clay tonstein. Thus, the Upper Banner tonstein-Fire Clay tonstein interval is about 5 ?? 1 m.y. This period of time for the Dunckmantian Stage is in good agreement with the Hess and Lippolt (1986) and Hess et al. (1988) chronology for the Duckmantian based on 40Ar/39Ar plateau methods for Westphalian tonsteins. Also, on the basis of this period of time, calculated sedimentation rates (decompacted) od 66-165 m/m.y. were determined for the lower part of the Middle Pennsylvanian Series in the central Appalachian basin. These rates are consistent with the sedimentation rates for shallow-water marine siliciclastic sediments
Time-resolved Absolute Velocity Quantification with Projections
Langham, Michael C.; Jain, Varsha; Magland, Jeremy F.; Wehrli, Felix W.
2010-01-01
Quantitative information on time-resolved blood velocity along the femoral/popliteal artery can provide clinical information on peripheral arterial disease and complement MR angiography since not all stenoses are hemodynamically significant. The key disadvantages of the most widely used approach to time-resolve pulsatile blood flow by cardiac-gated velocity-encoded gradient-echo imaging are gating errors and long acquisition time. Here we demonstrate a rapid non-triggered method that quantifies absolute velocity on the basis of phase difference between successive velocity-encoded projections after selectively removing the background static tissue signal via a reference image. The tissue signal from the reference image’s center k-space line is isolated by masking out the vessels in the image domain. The performance of the technique, in terms of reproducibility and agreement with results obtained with conventional phase contrast (PC)-MRI was evaluated at 3T field strength with a variable-flow rate phantom and in vivo of the triphasic velocity waveforms at several segments along the femoral and popliteal arteries. Additionally, time-resolved flow velocity was quantified in five healthy subjects and compared against gated PC-MRI results. To illustrate clinical feasibility the proposed method was shown to be able to identify hemodynamic abnormalities and impaired reactivity in a diseased femoral artery. For both phantom and in vivo studies, velocity measurements were within 1.5 cm/s and the coefficient of variation was less than 5% in an in vivo reproducibility study. In five healthy subjects, the average differences in mean peak velocities and their temporal locations were within 1 cm/s and 10 ms compared to gated PC-MRI. In conclusion, the proposed method provides temporally-resolved arterial velocity with a temporal resolution of 20 ms with minimal post-processing. PMID:20677235
Kandanarachchi, Pramod H.; Autrey, S Thomas ); Franz, James A. )
2002-11-15
The lifetime of the lignin radical model compound, 1-phenyl-2-phenoxyethanol-1-yl, PhC?(OH)CH2-OPh is several orders of magnitude greater than suggested by the previous experimental studies. The ketyl radical is competitively trapped by thiophenol to yield PhCH(OH)CH2-OPh in competition with? -scission to yield phenoxyl radical and acetophenone. A basis rate expression, hydrogen atom abstraction by sec-phenethyl alcohol, PhC?(OH)CH3, from thiophenol, log(kabs/M -1 s -1 )=(8.88?0.24)? (6.07?0.34)/? ,?= 2.303RT,was determined by competing reduction and radical termination pathways. The Smoluchowski equation was used to calculate the temperature dependent rate of PhC?(OH)CH3 termination. The hydrogen abstraction pathway was used as a basis reaction to determine the activation barrier for the? -scission of phenoxyl from 1-phenyl-2-phenoxyethanol-1-yl: log(k? -sci/s -1 )= (12.85?0.22)?(15.06?0.38)/?, k? -sci(298K) ca. (64.0s -1 in benzene), log(k? -sci/s -1 )= (12.50?0.18)?(14.46?0.30)/? , k? -sc i(298K) ca. (78.7s -1 in benzene containing 0.8 M 2-propanol).B3LYP/cc-PVZT methods predict intramolecular hydrogen bonding between the? -OH on the ketyl radical and the?OPh leaving group stabilize both the ground state and transition state structures. At this level of theory the activation barrier (14.9 kcal/mol) is in fair agreement with the experimentally determined activation barrier.
Absolute photon-flux measurements in the vacuum ultraviolet
NASA Technical Reports Server (NTRS)
Samson, J. A. R.; Haddad, G. N.
1974-01-01
Absolute photon-flux measurements in the vacuum ultraviolet have extended to short wavelengths by use of rare-gas ionization chambers. The technique involves the measurement of the ion current as a function of the gas pressure in the ion chamber. The true value of the ion current, and hence the absolute photon flux, is obtained by extrapolating the ion current to zero gas pressure. Examples are given at 162 and 266 A. The short-wavelength limit is determined only by the sensitivity of the current-measuring apparatus and by present knowledge of the photoionization processes that occur in the rate gases.
Bunde, R.L.; Rosentreter, J.J.; Liszewski, M.J.
1998-01-01
The rate of strontium sorption and the effects of variable aqueous concentrations of sodium and potassium on strontium sorption were measured as part of an investigation to determine strontium chemical transport properties of a surficial sediment at the Idaho National Engineering Laboratory (INEL), Idaho. Batch experimental techniques were used to determine the rate of strontium sorption and strontium distribution coefficients (K(d)s) between aqueous and solid phases. Rate experiments indicate that strontium in solution reached an apparent equilibrium with the sediment in 26 h. K(d)s were derived using the linear isotherm model at initial sodium concentrations from 100 to 5,000 mg/l and initial potassium concentrations from 2 to 150 mg/l. K(d)s ranged from 56 ?? 2 to 62 ?? 3 ml/g at initial aqueous concentrations of sodium and potassium equal to or less than 300 and 150 mg/l, respectively. K(d)s hinged from 4.7 ?? 0.2 to 19 ?? 1 ml/g with initial aqueous concentrations of sodium between 1,000 and 5,000 mg/l. These data indicate that sodium concentrations greater than 300 mg/l in wastewater increase the availability of strontium for transport beneath waste disposal ponds at the INEL by decreasing strontium sorption on the surficial sediment. Wastewater concentrations of sodium and potassium less than 300 and 150 mg/l, respectively, have little effect on the availability of strontium for transport.The rate of strontium sorption and the effects of variable aqueous concentrations of sodium and potassium on strontium sorption were measured as part of an investigation to determine strontium chemical transport properties of a surficial sediment at the Idaho National Engineering Laboratory (INEL), Idaho. Batch experimental techniques were used to determine the rate of strontium sorption and strontium distribution coefficients (Kds) between aqueous and solid phases. Rate experiments indicate that strontium in solution reached an apparent equilibrium with the sediment in 26
Absolute configuration of isovouacapenol C
Fun, Hoong-Kun; Yodsaoue, Orapun; Karalai, Chatchanok; Chantrapromma, Suchada
2010-01-01
The title compound, C27H34O5 {systematic name: (4aR,5R,6R,6aS,7R,11aS,11bR)-4a,6-dihydroxy-4,4,7,11b-tetramethyl-1,2,3,4,4a,5,6,6a,7,11,11a,11b-dodecahydrophenanthro[3,2-b]furan-5-yl benzoate}, is a cassane furanoditerpene, which was isolated from the roots of Caesalpinia pulcherrima. The three cyclohexane rings are trans fused: two of these are in chair conformations with the third in a twisted half-chair conformation, whereas the furan ring is almost planar (r.m.s. deviation = 0.003 Å). An intramolecular C—H⋯O interaction generates an S(6) ring. The absolute configurations of the stereogenic centres at positions 4a, 5, 6, 6a, 7, 11a and 11b are R, R, R, S, R, S and R, respectively. In the crystal, molecules are linked into infinite chains along [010] by O—H⋯O hydrogen bonds. C⋯O [3.306 (2)–3.347 (2) Å] short contacts and C—H⋯π interactions also occur. PMID:21588364
Frequency-domain analysis of absolute gravimeters
NASA Astrophysics Data System (ADS)
Svitlov, S.
2012-12-01
An absolute gravimeter is analysed as a linear time-invariant system in the frequency domain. Frequency responses of absolute gravimeters are derived analytically based on the propagation of the complex exponential signal through their linear measurement functions. Depending on the model of motion and the number of time-distance coordinates, an absolute gravimeter is considered as a second-order (three-level scheme) or third-order (multiple-level scheme) low-pass filter. It is shown that the behaviour of an atom absolute gravimeter in the frequency domain corresponds to that of the three-level corner-cube absolute gravimeter. Theoretical results are applied for evaluation of random and systematic measurement errors and optimization of an experiment. The developed theory agrees with known results of an absolute gravimeter analysis in the time and frequency domains and can be used for measurement uncertainty analyses, building of vibration-isolation systems and synthesis of digital filtering algorithms.
Absolute V-R colors of trans-Neptunian objects
NASA Astrophysics Data System (ADS)
Alvarez-Candal, Alvaro; Ayala-Loera, Carmen; Ortiz, Jose-Luis; Duffard, Rene; Estela, Fernandez-Valenzuela; Santos-Sanz, Pablo
2016-10-01
The absolute magnitude of a minor body is the apparent magnitude that the body would have if observed from the Sun at a distance of 1AU. Absolute magnitudes are measured using phase curves, showing the change of the magnitude, normalized to unit helio and geo-centric distance, vs. phase angle. The absolute magnitude is then the Y-intercept of the curve. Absolute magnitudes are related to the total reflecting surface of the body and thus bring information of its size, coupled with the reflecting properties.Since 2011 our team has been collecting data from several telescopes spread in Europe and South America. We complemented our data with those available in the literature in order to construct phase curves of trans-Neptunian objects with at least three points. In a first release (Alvarez-Candal et al. 2016, A&A, 586, A155) we showed results for 110 trans-Neptunian objects using V magnitudes only, assuming an overall linear trend and taking into consideration rotational effects, for objects with known light-curves.In this contribution we show results for more than 130 objects, about 100 of them with phase curves in two filters: V and R. We compute absolute magnitudes and phase coefficients in both filters, when available. The average values are HV = 6.39 ± 2.37, βV = (0.09 ± 0.32) mag per degree, HR = 5.38 ± 2.30, and βR = (0.08 ± 0.42) mag per degree.
Measuring Postglacial Rebound with GPS and Absolute Gravity
NASA Technical Reports Server (NTRS)
Larson, Kristine M.; vanDam, Tonie
2000-01-01
We compare vertical rates of deformation derived from continuous Global Positioning System (GPS) observations and episodic measurements of absolute gravity. We concentrate on four sites in a region of North America experiencing postglacial rebound. The rates of uplift from gravity and GPS agree within one standard deviation for all sites. The GPS vertical deformation rates are significantly more precise than the gravity rates, primarily because of the denser temporal spacing provided by continuous GPS tracking. We conclude that continuous GPS observations are more cost efficient and provide more precise estimates of vertical deformation rates than campaign style gravity observations where systematic errors are difficult to quantify.
Dillon, Terry J; Blitz, Mark A; Heard, Dwayne E
2006-06-01
Laser-induced fluorescence spectroscopy via excitation of the A2pi(3/2) <-- X2pi(3/2) (2,0) band at 445 nm was used to monitor IO in the presence of NO2 following its generation in the reactions O(3P) + CF3I and O(3P) + I2. Both photolysis of O3 (248 nm) and NO2 (351 nm) were used to initiate the production of IO. The rate coefficients for the thermolecular reaction IO + NO2 + M --> IONO2 + M were measured in air, N2, and O2 over the range P = 18-760 Torr, covering typical tropospheric conditions, and were found to be in the falloff region. No dependence of k1 upon bath gas identity was observed, and in general, the results are in good agreement with recent determinations. Using a Troe broadening factor of F(B) = 0.4, the falloff parameters k0(1) = (9.5 +/- 1.6) x 10(-31) cm6 molecule(-2) s(-1) and k(infinity)(1) = (1.7 +/- 0.3) x 10(-11) cm3 molecule(-1) s(-1) were determined at 294 K. The temporal profile of IO at elevated temperatures was used to investigate the thermal stability of the product, IONO2, but no evidence was observed for the regeneration of IO, consistent with recent calculations for the IO-NO2 bond strength being approximately 100 kJ mol(-1). Previous modeling studies of iodine chemistry in the marine boundary layer that utilize values of k1 measured in N2 are hence validated by these results conducted in air. The rate coefficient for the reaction O(3P) + NO2 --> O2 + NO at 294 K and in 100 Torr of air was determined to be k2 = (9.3 +/- 0.9) x 10(-12) cm3 molecule(-1) s(-1), in good agreement with recommended values. All uncertainties are quoted at the 95% confidence limit.
Absolute Radiometric Calibration of KOMPSAT-3A
NASA Astrophysics Data System (ADS)
Ahn, H. Y.; Shin, D. Y.; Kim, J. S.; Seo, D. C.; Choi, C. U.
2016-06-01
This paper presents a vicarious radiometric calibration of the Korea Multi-Purpose Satellite-3A (KOMPSAT-3A) performed by the Korea Aerospace Research Institute (KARI) and the Pukyong National University Remote Sensing Group (PKNU RSG) in 2015.The primary stages of this study are summarized as follows: (1) A field campaign to determine radiometric calibrated target fields was undertaken in Mongolia and South Korea. Surface reflectance data obtained in the campaign were input to a radiative transfer code that predicted at-sensor radiance. Through this process, equations and parameters were derived for the KOMPSAT-3A sensor to enable the conversion of calibrated DN to physical units, such as at-sensor radiance or TOA reflectance. (2) To validate the absolute calibration coefficients for the KOMPSAT-3A sensor, we performed a radiometric validation with a comparison of KOMPSAT-3A and Landsat-8 TOA reflectance using one of the six PICS (Libya 4). Correlations between top-of-atmosphere (TOA) radiances and the spectral band responses of the KOMPSAT-3A sensors at the Zuunmod, Mongolia and Goheung, South Korea sites were significant for multispectral bands. The average difference in TOA reflectance between KOMPSAT-3A and Landsat-8 image over the Libya 4, Libya site in the red-green-blue (RGB) region was under 3%, whereas in the NIR band, the TOA reflectance of KOMPSAT-3A was lower than the that of Landsat-8 due to the difference in the band passes of two sensors. The KOMPSAT-3Aensor includes a band pass near 940 nm that can be strongly absorbed by water vapor and therefore displayed low reflectance. Toovercome this, we need to undertake a detailed analysis using rescale methods, such as the spectral bandwidth adjustment factor.
Measuring Terrestrial Water Storage Change Using GPS, Absolute Gravity and GRACE in Scandinavia
NASA Astrophysics Data System (ADS)
Jia, Lulu; Wang, Hansheng; Wang, Xinsheng
2015-04-01
For Scandinavia, terrestrial water storage change estimates from Gravity Recovery and Climate Experiment (GRACE) would be seriously affected by the process of glacial isostatic adjustment (GIA) . The effects of GIA are typically removed using modeled values. However, the uncertainty in current GIA models is very large. To solve this problem, we calculates the measured linear ratio of GIA gravity rates and vertical displacement rates according to the data from collocation stations for absolute gravity and GPS in Scandinavia. Using the linear ratio and uplift field derived from GPS observation network, we get the gravity signal of GIA. Gravity change rates from GRACE RL05 data can be corrected for GIA using independent gravity rates derived from GPS vertical velocities, and then we can calculate corresponding equivalent water thickness in Scandinavia and the uncertainties are evaluated by considering the uncertainties from data. Our method utilizes observational data only and can avoid the enormous uncertainty from GIA models.The results are compared with that of two hydrological models. The ratio of gravity versus uplift obtained by ground-based measurements in Scandinavia is 0.148±0.020μGal/mm, which validates Wahr's approximate theoretical ratio (Wahr et al., 1995) and is very close to the result from North America (Mazzotti et al., 2011). From January 2003 to March 2011, terrestrial water storage shows obvious increase in Scandinavia. The main signal locates at the Vänern lake which is in the southern tip of the peninsula. The rate of total water storage change is 4.6±2.1 Gt/yr and the corresponding cumulative quantity is 38±17 Gt for the period 2003-2011. Results from hydrological models are consistent with our result very well. The correlation coefficient between GRACE and WGHM hydrological model can reach 0.69, while for GLDAS model the correlation coefficient is slightly smaller(0.57)
A gain-coefficient switched Alexandrite laser
NASA Astrophysics Data System (ADS)
Lee, Chris J.; van der Slot, Peter J. M.; Boller, Klaus-J.
2013-01-01
We report on a gain-coefficient switched Alexandrite laser. An electro-optic modulator is used to switch between high and low gain states by making use of the polarization dependent gain of Alexandrite. In gain-coefficient switched mode, the laser produces 85 ns pulses with a pulse energy of 240 mJ at a repetition rate of 5 Hz.
NASA Astrophysics Data System (ADS)
Ricard, André; Oh, Soo-ghee; Guerra, Vasco
2013-06-01
Optical emission spectroscopy line-ratio methods are developed in order to estimate the absolute densities of nitrogen and oxygen atoms and metastable N2(A) molecules in the nitrogen late afterglow of an RF discharge, operating at p = 8 Torr, Q = 1 slm and P = 100 W, in what constitutes an extension of the typical domain of application of these methods. [N] is obtained from the first positive (1+) emission with calibration by NO titration, [O] from the ratio of the NOβ to 1+ bands, and [N2(A)] from the ratios of (i) the NOγ and NOβ bands, (ii) the second positive (2+) and NOβ bands and (iii) the 1+ and 2+ bands. In addition to the determination of the N, O and N2(A) absolute densities, the present investigation gives an indication on the order of magnitude of the rate coefficient of the very important reaction N2(X, v ⩾ 13) + O → NO + N at room temperature.
Absolute Income, Relative Income, and Happiness
ERIC Educational Resources Information Center
Ball, Richard; Chernova, Kateryna
2008-01-01
This paper uses data from the World Values Survey to investigate how an individual's self-reported happiness is related to (i) the level of her income in absolute terms, and (ii) the level of her income relative to other people in her country. The main findings are that (i) both absolute and relative income are positively and significantly…
Investigating Absolute Value: A Real World Application
ERIC Educational Resources Information Center
Kidd, Margaret; Pagni, David
2009-01-01
Making connections between various representations is important in mathematics. In this article, the authors discuss the numeric, algebraic, and graphical representations of sums of absolute values of linear functions. The initial explanations are accessible to all students who have experience graphing and who understand that absolute value simply…
Preschoolers' Success at Coding Absolute Size Values.
ERIC Educational Resources Information Center
Russell, James
1980-01-01
Forty-five 2-year-old and forty-five 3-year-old children coded relative and absolute sizes using 1.5-inch, 6-inch, and 18-inch cardboard squares. Results indicate that absolute coding is possible for children of this age. (Author/RH)
Introducing the Mean Absolute Deviation "Effect" Size
ERIC Educational Resources Information Center
Gorard, Stephen
2015-01-01
This paper revisits the use of effect sizes in the analysis of experimental and similar results, and reminds readers of the relative advantages of the mean absolute deviation as a measure of variation, as opposed to the more complex standard deviation. The mean absolute deviation is easier to use and understand, and more tolerant of extreme…
Monolithically integrated absolute frequency comb laser system
Wanke, Michael C.
2016-07-12
Rather than down-convert optical frequencies, a QCL laser system directly generates a THz frequency comb in a compact monolithically integrated chip that can be locked to an absolute frequency without the need of a frequency-comb synthesizer. The monolithic, absolute frequency comb can provide a THz frequency reference and tool for high-resolution broad band spectroscopy.
Estimating the absolute wealth of households
Gerkey, Drew; Hadley, Craig
2015-01-01
Abstract Objective To estimate the absolute wealth of households using data from demographic and health surveys. Methods We developed a new metric, the absolute wealth estimate, based on the rank of each surveyed household according to its material assets and the assumed shape of the distribution of wealth among surveyed households. Using data from 156 demographic and health surveys in 66 countries, we calculated absolute wealth estimates for households. We validated the method by comparing the proportion of households defined as poor using our estimates with published World Bank poverty headcounts. We also compared the accuracy of absolute versus relative wealth estimates for the prediction of anthropometric measures. Findings The median absolute wealth estimates of 1 403 186 households were 2056 international dollars per capita (interquartile range: 723–6103). The proportion of poor households based on absolute wealth estimates were strongly correlated with World Bank estimates of populations living on less than 2.00 United States dollars per capita per day (R2 = 0.84). Absolute wealth estimates were better predictors of anthropometric measures than relative wealth indexes. Conclusion Absolute wealth estimates provide new opportunities for comparative research to assess the effects of economic resources on health and human capital, as well as the long-term health consequences of economic change and inequality. PMID:26170506
Absolute optical metrology : nanometers to kilometers
NASA Technical Reports Server (NTRS)
Dubovitsky, Serge; Lay, O. P.; Peters, R. D.; Liebe, C. C.
2005-01-01
We provide and overview of the developments in the field of high-accuracy absolute optical metrology with emphasis on space-based applications. Specific work on the Modulation Sideband Technology for Absolute Ranging (MSTAR) sensor is described along with novel applications of the sensor.
Overspecification of color, pattern, and size: salience, absoluteness, and consistency
Tarenskeen, Sammie; Broersma, Mirjam; Geurts, Bart
2015-01-01
The rates of overspecification of color, pattern, and size are compared, to investigate how salience and absoluteness contribute to the production of overspecification. Color and pattern are absolute and salient attributes, whereas size is relative and less salient. Additionally, a tendency toward consistent responses is assessed. Using a within-participants design, we find similar rates of color and pattern overspecification, which are both higher than the rate of size overspecification. Using a between-participants design, however, we find similar rates of pattern and size overspecification, which are both lower than the rate of color overspecification. This indicates that although many speakers are more likely to include color than pattern (probably because color is more salient), they may also treat pattern like color due to a tendency toward consistency. We find no increase in size overspecification when the salience of size is increased, suggesting that speakers are more likely to include absolute than relative attributes. However, we do find an increase in size overspecification when mentioning the attributes is triggered, which again shows that speakers tend to refer in a consistent manner, and that there are circumstances in which even size overspecification is frequently produced. PMID:26594190
Absolute instability of the Gaussian wake profile
NASA Technical Reports Server (NTRS)
Hultgren, Lennart S.; Aggarwal, Arun K.
1987-01-01
Linear parallel-flow stability theory has been used to investigate the effect of viscosity on the local absolute instability of a family of wake profiles with a Gaussian velocity distribution. The type of local instability, i.e., convective or absolute, is determined by the location of a branch-point singularity with zero group velocity of the complex dispersion relation for the instability waves. The effects of viscosity were found to be weak for values of the wake Reynolds number, based on the center-line velocity defect and the wake half-width, larger than about 400. Absolute instability occurs only for sufficiently large values of the center-line wake defect. The critical value of this parameter increases with decreasing wake Reynolds number, thereby indicating a shrinking region of absolute instability with decreasing wake Reynolds number. If backflow is not allowed, absolute instability does not occur for wake Reynolds numbers smaller than about 38.
Son preference in Indian families: absolute versus relative wealth effects.
Gaudin, Sylvestre
2011-02-01
The desire for male children is prevalent in India, where son preference has been shown to affect fertility behavior and intrahousehold allocation of resources. Economic theory predicts less gender discrimination in wealthier households, but demographers and sociologists have argued that wealth can exacerbate bias in the Indian context. I argue that these apparently conflicting theories can be reconciled and simultaneously tested if one considers that they are based on two different notions of wealth: one related to resource constraints (absolute wealth), and the other to notions of local status (relative wealth). Using cross-sectional data from the 1998-1999 and 2005-2006 National Family and Health Surveys, I construct measures of absolute and relative wealth by using principal components analysis. A series of statistical models of son preference is estimated by using multilevel methods. Results consistently show that higher absolute wealth is strongly associated with lower son preference, and the effect is 20%-40% stronger when the household's community-specific wealth score is included in the regression. Coefficients on relative wealth are positive and significant although lower in magnitude. Results are robust to using different samples, alternative groupings of households in local areas, different estimation methods, and alternative dependent variables.
Orion Absolute Navigation System Progress and Challenge
NASA Technical Reports Server (NTRS)
Holt, Greg N.; D'Souza, Christopher
2012-01-01
The absolute navigation design of NASA's Orion vehicle is described. It has undergone several iterations and modifications since its inception, and continues as a work-in-progress. This paper seeks to benchmark the current state of the design and some of the rationale and analysis behind it. There are specific challenges to address when preparing a timely and effective design for the Exploration Flight Test (EFT-1), while still looking ahead and providing software extensibility for future exploration missions. The primary onboard measurements in a Near-Earth or Mid-Earth environment consist of GPS pseudo-range and delta-range, but for future explorations missions the use of star-tracker and optical navigation sources need to be considered. Discussions are presented for state size and composition, processing techniques, and consider states. A presentation is given for the processing technique using the computationally stable and robust UDU formulation with an Agee-Turner Rank-One update. This allows for computational savings when dealing with many parameters which are modeled as slowly varying Gauss-Markov processes. Preliminary analysis shows up to a 50% reduction in computation versus a more traditional formulation. Several state elements are discussed and evaluated, including position, velocity, attitude, clock bias/drift, and GPS measurement biases in addition to bias, scale factor, misalignment, and non-orthogonalities of the accelerometers and gyroscopes. Another consideration is the initialization of the EKF in various scenarios. Scenarios such as single-event upset, ground command, and cold start are discussed as are strategies for whole and partial state updates as well as covariance considerations. Strategies are given for dealing with latent measurements and high-rate propagation using multi-rate architecture. The details of the rate groups and the data ow between the elements is discussed and evaluated.
González, Sergio; Jiménez, Elena; Ballesteros, Bernabé; Martínez, Ernesto; Albaladejo, José
2015-04-01
CF3CH=CH2 (hydrofluoroolefin, HFO-1243zf) is a potential replacement of high global-warming potential (GWP) hydrofluorocarbon (HFC-134a, CF3CFH2). Both the atmospheric lifetime and the radiative efficiency of HFO-1243zf are parameters needed for estimating the GWP of this species. Therefore, the aim of this work is (i) to estimate the atmospheric lifetime of HFO-1243zf from the reported OH rate coefficients, k OH, determined under tropospheric conditions and (ii) to calculate its radiative efficiency from the reported IR absorption cross sections. The OH rate coefficient at 298 K also allows the estimation of the photochemical ozone creation potential (ε(POCP)). The pulsed laser photolysis coupled to a laser-induced fluorescence technique was used to determine k OH for the reaction of OH radicals with HFO-1243zf as a function of pressure (50-650 Torr of He) and temperature (263-358 K). Gas-phase IR spectra of HFO-1243zf were recorded at room temperature using a Fourier transform IR spectrometer between 500 and 4,000 cm(-1). At all temperatures, k OH did not depend on bath gas concentration (i.e., on the total pressure between 50 and 650 Torr of He). A slight but noticeable T dependence of k OH was observed in the temperature range investigated. The observed behavior is well described by the following Arrhenius expression: k OH(T) = (7.65 ± 0.26) × 10(-13) exp [(165 ± 10) / T] cm(3) molecule(-1) s(-1). Negligible IR absorption of HFO-1243zf was observed at wavenumbers greater than 1,700 cm(-1). Therefore, IR absorption cross sections, [Formula: see text], were determined in the 500-1,700 cm(-1) range. Integrated [Formula: see text] were determined between 650 and 1,800 cm(-1) for comparison purposes. The main diurnal removal pathway for HFO-1243zf is the reaction with OH radicals, which accounts for 64% of the overall loss by homogeneous reactions at 298 K. Globally, the lifetime due to OH reaction (τ OH) was estimated to be 8.7 days under
González, Sergio; Jiménez, Elena; Ballesteros, Bernabé; Martínez, Ernesto; Albaladejo, José
2015-04-01
CF3CH=CH2 (hydrofluoroolefin, HFO-1243zf) is a potential replacement of high global-warming potential (GWP) hydrofluorocarbon (HFC-134a, CF3CFH2). Both the atmospheric lifetime and the radiative efficiency of HFO-1243zf are parameters needed for estimating the GWP of this species. Therefore, the aim of this work is (i) to estimate the atmospheric lifetime of HFO-1243zf from the reported OH rate coefficients, k OH, determined under tropospheric conditions and (ii) to calculate its radiative efficiency from the reported IR absorption cross sections. The OH rate coefficient at 298 K also allows the estimation of the photochemical ozone creation potential (ε(POCP)). The pulsed laser photolysis coupled to a laser-induced fluorescence technique was used to determine k OH for the reaction of OH radicals with HFO-1243zf as a function of pressure (50-650 Torr of He) and temperature (263-358 K). Gas-phase IR spectra of HFO-1243zf were recorded at room temperature using a Fourier transform IR spectrometer between 500 and 4,000 cm(-1). At all temperatures, k OH did not depend on bath gas concentration (i.e., on the total pressure between 50 and 650 Torr of He). A slight but noticeable T dependence of k OH was observed in the temperature range investigated. The observed behavior is well described by the following Arrhenius expression: k OH(T) = (7.65 ± 0.26) × 10(-13) exp [(165 ± 10) / T] cm(3) molecule(-1) s(-1). Negligible IR absorption of HFO-1243zf was observed at wavenumbers greater than 1,700 cm(-1). Therefore, IR absorption cross sections, [Formula: see text], were determined in the 500-1,700 cm(-1) range. Integrated [Formula: see text] were determined between 650 and 1,800 cm(-1) for comparison purposes. The main diurnal removal pathway for HFO-1243zf is the reaction with OH radicals, which accounts for 64% of the overall loss by homogeneous reactions at 298 K. Globally, the lifetime due to OH reaction (τ OH) was estimated to be 8.7 days under
On the Absolute Continuity of the Blackwell Measure
NASA Astrophysics Data System (ADS)
Bárány, Balázs; Kolossváry, István
2015-04-01
In 1957, Blackwell expressed the entropy of hidden Markov chains using a measure which can be characterised as an invariant measure for an iterated function system with place-dependent weights. This measure, called the Blackwell measure, plays a central role in understanding the entropy rate and other important characteristics of fundamental models in information theory. We show that for a suitable set of parameter values the Blackwell measure is absolutely continuous for almost every parameter in the case of binary symmetric channels.
NASA Technical Reports Server (NTRS)
Snyder, G. Jeffrey (Inventor)
2015-01-01
A high temperature Seebeck coefficient measurement apparatus and method with various features to minimize typical sources of errors is described. Common sources of temperature and voltage measurement errors which may impact accurate measurement are identified and reduced. Applying the identified principles, a high temperature Seebeck measurement apparatus and method employing a uniaxial, four-point geometry is described to operate from room temperature up to 1300K. These techniques for non-destructive Seebeck coefficient measurements are simple to operate, and are suitable for bulk samples with a broad range of physical types and shapes.
Absolute magnitudes of trans-neptunian objects
NASA Astrophysics Data System (ADS)
Duffard, R.; Alvarez-candal, A.; Pinilla-Alonso, N.; Ortiz, J. L.; Morales, N.; Santos-Sanz, P.; Thirouin, A.
2015-10-01
Accurate measurements of diameters of trans- Neptunian objects are extremely complicated to obtain. Radiomatric techniques applied to thermal measurements can provide good results, but precise absolute magnitudes are needed to constrain diameters and albedos. Our objective is to measure accurate absolute magnitudes for a sample of trans- Neptunian objects, many of which have been observed, and modelled, by the "TNOs are cool" team, one of Herschel Space Observatory key projects grantes with ~ 400 hours of observing time. We observed 56 objects in filters V and R, if possible. These data, along with data available in the literature, was used to obtain phase curves and to measure absolute magnitudes by assuming a linear trend of the phase curves and considering magnitude variability due to rotational light-curve. In total we obtained 234 new magnitudes for the 56 objects, 6 of them with no reported previous measurements. Including the data from the literature we report a total of 109 absolute magnitudes.
A New Gimmick for Assigning Absolute Configuration.
ERIC Educational Resources Information Center
Ayorinde, F. O.
1983-01-01
A five-step procedure is provided to help students in making the assignment absolute configuration less bothersome. Examples for both single (2-butanol) and multi-chiral carbon (3-chloro-2-butanol) molecules are included. (JN)
The Simplicity Argument and Absolute Morality
ERIC Educational Resources Information Center
Mijuskovic, Ben
1975-01-01
In this paper the author has maintained that there is a similarity of thought to be found in the writings of Cudworth, Emerson, and Husserl in his investigation of an absolute system of morality. (Author/RK)
Balaganesh, M; Rajakumar, B
2012-10-11
The rate coefficients of ((E)-CF(3)CH═CHF, (Z)-CF(3)CH═CHF, (E)-CF(3)CF═CHF, and (Z)-CF(3)CF═CHF) + OH reactions were computed using M06-2X/6-31+G(d,p) theory in the temperature range of 200 and 400 K. The possible reaction mechanisms of the ((E)-CF(3)CH═CHF, (Z)-CF(3)CH═CHF, (E)-CF(3)CF═CHF, and (Z)-CF(3)CF═CHF) + OH reactions were examined. The rate coefficients for the addition and abstraction reactions were calculated using canonical variational transition state theory (CVT) and conventional transition state theory (CTST), respectively, and we concluded that abstraction reactions are negligible within the temperature range and addition reactions take the lead role. The small curvature tunnelling (SCT) was included in the computation of the rate coefficients. The temperature dependent rate expressions (in cm(3) molecule(-1) s(-1)) of the (E)-CF(3)CH═CHF, (Z)-CF(3)CH═CHF, (E)-CF(3)CF═CHF, and (Z)-CF(3)CF═CHF + OH reactions between 200 and 400 K are presented. The atmospheric lifetimes and global warming potentials (GWPs) of the test molecules were computed using the rate coefficients obtained in this study, and it is concluded that these molecules are very short-lived in the Earth's atmosphere with low GWPs.
Absolute determination of local tropospheric OH concentrations
NASA Technical Reports Server (NTRS)
Armerding, Wolfgang; Comes, Franz-Josef
1994-01-01
Long path absorption (LPA) according to Lambert Beer's law is a method to determine absolute concentrations of trace gases such as tropospheric OH. We have developed a LPA instrument which is based on a rapid tuning of the light source which is a frequency doubled dye laser. The laser is tuned across two or three OH absorption features around 308 nm with a scanning speed of 0.07 cm(exp -1)/microsecond and a repetition rate of 1.3 kHz. This high scanning speed greatly reduces the fluctuation of the light intensity caused by the atmosphere. To obtain the required high sensitivity the laser output power is additionally made constant and stabilized by an electro-optical modulator. The present sensitivity is of the order of a few times 10(exp 5) OH per cm(exp 3) for an acquisition time of a minute and an absorption path length of only 1200 meters so that a folding of the optical path in a multireflection cell was possible leading to a lateral dimension of the cell of a few meters. This allows local measurements to be made. Tropospheric measurements have been carried out in 1991 resulting in the determination of OH diurnal variation at specific days in late summer. Comparison with model calculations have been made. Interferences are mainly due to SO2 absorption. The problem of OH self generation in the multireflection cell is of minor extent. This could be shown by using different experimental methods. The minimum-maximum signal to noise ratio is about 8 x 10(exp -4) for a single scan. Due to the small size of the absorption cell the realization of an open air laboratory is possible in which by use of an additional UV light source or by additional fluxes of trace gases the chemistry can be changed under controlled conditions allowing kinetic studies of tropospheric photochemistry to be made in open air.
Heat transfer coefficient of cryotop during freezing.
Li, W J; Zhou, X L; Wang, H S; Liu, B L; Dai, J J
2013-01-01
Cryotop is an efficient vitrification method for cryopreservation of oocytes. It has been widely used owing to its simple operation and high freezing rate. Recently, the heat transfer performance of cryotop was studied by numerical simulation in several studies. However, the range of heat transfer coefficient in the simulation is uncertain. In this study, the heat transfer coefficient for cryotop during freezing process was analyzed. The cooling rates of 40 percent ethylene glycol (EG) droplet in cryotop during freezing were measured by ultra-fast measurement system and calculated by numerical simulation at different value of heat transfer coefficient. Compared with the results obtained by two methods, the range of the heat transfer coefficient necessary for the numerical simulation of cryotop was determined, which is between 9000 W/(m(2)·K) and 10000 W/(m (2)·K).
Braun, Norbert A; Kohlenberg, Birgit; Sim, Sherina; Meier, Manfred; Hammerschmidt, Franz-Josef
2009-09-01
Jasminum flexile flower absolute from the south of India and the corresponding vacuum headspace (VHS) sample of the absolute were analyzed using GC and GC-MS. Three other commercially available Indian jasmine absolutes from the species: J. sambac, J. officinale subsp. grandiflorum, and J. auriculatum and the respective VHS samples were used for comparison purposes. One hundred and twenty-one compounds were characterized in J. flexile flower absolute, with methyl linolate, benzyl salicylate, benzyl benzoate, (2E,6E)-farnesol, and benzyl acetate as the main constituents. A detailed olfactory evaluation was also performed.
Enumeration of absolute cell counts using immunophenotypic techniques.
Mandy, F; Brando, B
2001-05-01
Absolute counting of cells or cell subsets has a number of significant clinical applications: monitoring the disease status of HIV-infected patients, enumerating residual white blood cells in leukoreduced blood products, and assessing immunodeficiency in a variety of situations. The single-platform method (flow cytometry alone) has emerged as the method of choice for absolute cell enumeration. This technology counts only the cells of interest in a precisely determined blood volume. Exact cell identification is accomplished by a logical electronic gating algorithm capable of identifying lineage-specific immunofluorescent markers. Exclusion of unwanted cells is automatic. This extensive and detailed unit presents protocols for both volumetric and flow-rate determination of residual white blood cells and of leukocyte subsets. PMID:18770719
Universal Cosmic Absolute and Modern Science
NASA Astrophysics Data System (ADS)
Kostro, Ludwik
The official Sciences, especially all natural sciences, respect in their researches the principle of methodic naturalism i.e. they consider all phenomena as entirely natural and therefore in their scientific explanations they do never adduce or cite supernatural entities and forces. The purpose of this paper is to show that Modern Science has its own self-existent, self-acting, and self-sufficient Natural All-in Being or Omni-Being i.e. the entire Nature as a Whole that justifies the scientific methodic naturalism. Since this Natural All-in Being is one and only It should be considered as the own scientifically justified Natural Absolute of Science and should be called, in my opinion, the Universal Cosmic Absolute of Modern Science. It will be also shown that the Universal Cosmic Absolute is ontologically enormously stratified and is in its ultimate i.e. in its most fundamental stratum trans-reistic and trans-personal. It means that in its basic stratum. It is neither a Thing or a Person although It contains in Itself all things and persons with all other sentient and conscious individuals as well, On the turn of the 20th century the Science has begun to look for a theory of everything, for a final theory, for a master theory. In my opinion the natural Universal Cosmic Absolute will constitute in such a theory the radical all penetrating Ultimate Basic Reality and will substitute step by step the traditional supernatural personal Absolute.
Absolute Humidity and the Seasonal Onset of Influenza in the Continental United States
Shaman, Jeffrey; Pitzer, Virginia E.; Viboud, Cécile; Grenfell, Bryan T.; Lipsitch, Marc
2010-01-01
Much of the observed wintertime increase of mortality in temperate regions is attributed to seasonal influenza. A recent reanalysis of laboratory experiments indicates that absolute humidity strongly modulates the airborne survival and transmission of the influenza virus. Here, we extend these findings to the human population level, showing that the onset of increased wintertime influenza-related mortality in the United States is associated with anomalously low absolute humidity levels during the prior weeks. We then use an epidemiological model, in which observed absolute humidity conditions temper influenza transmission rates, to successfully simulate the seasonal cycle of observed influenza-related mortality. The model results indicate that direct modulation of influenza transmissibility by absolute humidity alone is sufficient to produce this observed seasonality. These findings provide epidemiological support for the hypothesis that absolute humidity drives seasonal variations of influenza transmission in temperate regions. PMID:20186267
A three-axis SQUID-based absolute vector magnetometer
Schönau, T.; Schmelz, M.; Stolz, R.; Anders, S.; Linzen, S.; Meyer, H.-G.; Zakosarenko, V.; Meyer, M.
2015-10-15
We report on the development of a three-axis absolute vector magnetometer suited for mobile operation in the Earth’s magnetic field. It is based on low critical temperature dc superconducting quantum interference devices (LTS dc SQUIDs) with sub-micrometer sized cross-type Josephson junctions and exhibits a white noise level of about 10 fT/Hz{sup 1/2}. The width of superconducting strip lines is restricted to less than 6 μm in order to avoid flux trapping during cool-down in magnetically unshielded environment. The long-term stability of the flux-to-voltage transfer coefficients of the SQUID electronics is investigated in detail and a method is presented to significantly increase their reproducibility. We further demonstrate the long-term operation of the setup in a magnetic field varying by about 200 μT amplitude without the need for recalibration.
A three-axis SQUID-based absolute vector magnetometer.
Schönau, T; Zakosarenko, V; Schmelz, M; Stolz, R; Anders, S; Linzen, S; Meyer, M; Meyer, H-G
2015-10-01
We report on the development of a three-axis absolute vector magnetometer suited for mobile operation in the Earth's magnetic field. It is based on low critical temperature dc superconducting quantum interference devices (LTS dc SQUIDs) with sub-micrometer sized cross-type Josephson junctions and exhibits a white noise level of about 10 fT/Hz(1/2). The width of superconducting strip lines is restricted to less than 6 μm in order to avoid flux trapping during cool-down in magnetically unshielded environment. The long-term stability of the flux-to-voltage transfer coefficients of the SQUID electronics is investigated in detail and a method is presented to significantly increase their reproducibility. We further demonstrate the long-term operation of the setup in a magnetic field varying by about 200 μT amplitude without the need for recalibration.
Quantum theory allows for absolute maximal contextuality
NASA Astrophysics Data System (ADS)
Amaral, Barbara; Cunha, Marcelo Terra; Cabello, Adán
2015-12-01
Contextuality is a fundamental feature of quantum theory and a necessary resource for quantum computation and communication. It is therefore important to investigate how large contextuality can be in quantum theory. Linear contextuality witnesses can be expressed as a sum S of n probabilities, and the independence number α and the Tsirelson-like number ϑ of the corresponding exclusivity graph are, respectively, the maximum of S for noncontextual theories and for the theory under consideration. A theory allows for absolute maximal contextuality if it has scenarios in which ϑ /α approaches n . Here we show that quantum theory allows for absolute maximal contextuality despite what is suggested by the examination of the quantum violations of Bell and noncontextuality inequalities considered in the past. Our proof is not constructive and does not single out explicit scenarios. Nevertheless, we identify scenarios in which quantum theory allows for almost-absolute-maximal contextuality.
Absolute calibration in vivo measurement systems
Kruchten, D.A.; Hickman, D.P.
1991-02-01
Lawrence Livermore National Laboratory (LLNL) is currently investigating a new method for obtaining absolute calibration factors for radiation measurement systems used to measure internally deposited radionuclides in vivo. Absolute calibration of in vivo measurement systems will eliminate the need to generate a series of human surrogate structures (i.e., phantoms) for calibrating in vivo measurement systems. The absolute calibration of in vivo measurement systems utilizes magnetic resonance imaging (MRI) to define physiological structure, size, and composition. The MRI image provides a digitized representation of the physiological structure, which allows for any mathematical distribution of radionuclides within the body. Using Monte Carlo transport codes, the emission spectrum from the body is predicted. The in vivo measurement equipment is calibrated using the Monte Carlo code and adjusting for the intrinsic properties of the detection system. The calibration factors are verified using measurements of existing phantoms and previously obtained measurements of human volunteers. 8 refs.
Stimulus probability effects in absolute identification.
Kent, Christopher; Lamberts, Koen
2016-05-01
This study investigated the effect of stimulus presentation probability on accuracy and response times in an absolute identification task. Three schedules of presentation were used to investigate the interaction between presentation probability and stimulus position within the set. Data from individual participants indicated strong effects of presentation probability on both proportion correct and response times. The effects were moderated by the ubiquitous stimulus position effect. The accuracy and response time data were predicted by an exemplar-based model of perceptual cognition (Kent & Lamberts, 2005). The bow in discriminability was also attenuated when presentation probability for middle items was relatively high, an effect that will constrain future model development. The study provides evidence for item-specific learning in absolute identification. Implications for other theories of absolute identification are discussed. (PsycINFO Database Record
Quantitative standards for absolute linguistic universals.
Piantadosi, Steven T; Gibson, Edward
2014-01-01
Absolute linguistic universals are often justified by cross-linguistic analysis: If all observed languages exhibit a property, the property is taken to be a likely universal, perhaps specified in the cognitive or linguistic systems of language learners and users. In many cases, these patterns are then taken to motivate linguistic theory. Here, we show that cross-linguistic analysis will very rarely be able to statistically justify absolute, inviolable patterns in language. We formalize two statistical methods--frequentist and Bayesian--and show that in both it is possible to find strict linguistic universals, but that the numbers of independent languages necessary to do so is generally unachievable. This suggests that methods other than typological statistics are necessary to establish absolute properties of human language, and thus that many of the purported universals in linguistics have not received sufficient empirical justification.
Absolute photoacoustic thermometry in deep tissue.
Yao, Junjie; Ke, Haixin; Tai, Stephen; Zhou, Yong; Wang, Lihong V
2013-12-15
Photoacoustic thermography is a promising tool for temperature measurement in deep tissue. Here we propose an absolute temperature measurement method based on the dual temperature dependences of the Grüneisen parameter and the speed of sound in tissue. By taking ratiometric measurements at two adjacent temperatures, we can eliminate the factors that are temperature irrelevant but difficult to correct for in deep tissue. To validate our method, absolute temperatures of blood-filled tubes embedded ~9 mm deep in chicken tissue were measured in a biologically relevant range from 28°C to 46°C. The temperature measurement accuracy was ~0.6°C. The results suggest that our method can be potentially used for absolute temperature monitoring in deep tissue during thermotherapy.
Molecular iodine absolute frequencies. Final report
Sansonetti, C.J.
1990-06-25
Fifty specified lines of {sup 127}I{sub 2} were studied by Doppler-free frequency modulation spectroscopy. For each line the classification of the molecular transition was determined, hyperfine components were identified, and one well-resolved component was selected for precise determination of its absolute frequency. In 3 cases, a nearby alternate line was selected for measurement because no well-resolved component was found for the specified line. Absolute frequency determinations were made with an estimated uncertainty of 1.1 MHz by locking a dye laser to the selected hyperfine component and measuring its wave number with a high-precision Fabry-Perot wavemeter. For each line results of the absolute measurement, the line classification, and a Doppler-free spectrum are given.
Uncertainty Analysis for Photovoltaic Degradation Rates (Poster)
Jordan, D.; Kurtz, S.; Hansen, C.
2014-04-01
Dependable and predictable energy production is the key to the long-term success of the PV industry. PV systems show over the lifetime of their exposure a gradual decline that depends on many different factors such as module technology, module type, mounting configuration, climate etc. When degradation rates are determined from continuous data the statistical uncertainty is easily calculated from the regression coefficients. However, total uncertainty that includes measurement uncertainty and instrumentation drift is far more difficult to determine. A Monte Carlo simulation approach was chosen to investigate a comprehensive uncertainty analysis. The most important effect for degradation rates is to avoid instrumentation that changes over time in the field. For instance, a drifting irradiance sensor, which can be achieved through regular calibration, can lead to a substantially erroneous degradation rates. However, the accuracy of the irradiance sensor has negligible impact on degradation rate uncertainty emphasizing that precision (relative accuracy) is more important than absolute accuracy.
Berteloite, Coralie; Le Picard, Sébastien D; Balucani, Nadia; Canosa, André; Sims, Ian R
2010-04-21
The kinetics of the reactions of the linear butadiynyl radical, C4H (CCCCH), with a variety of unsaturated hydrocarbons have been studied over the temperature range of 39-300 K using a CRESU (Cinétique de Réaction en Ecoulement Supersonique Uniforme, or reaction kinetics in uniform supersonic flow) apparatus combined with the pulsed laser photolysis-laser induced fluorescence technique. The rate coefficients for all the reactions studied are found to all be in excess of 10(-10) cm(3) molecule(-1) s(-1) over the entire temperature range. They can be fitted with the following expressions (valid from 39 K to 300 K, with RMS deviations of the experimental points from the predicted values shown, to which should be added 10% possible systematic error) for reaction of C4H with alkenes: k(C2H4) = (1.95 +/- 0.17) x 10(-10) (T/298 K)(-0.40) exp(9.4 K/T) cm3 molecule(-1) s(-1); k(C3H6) = (3.25 +/- 0.12) x 10(-10) (T/298 K)(-0.84) exp(-48.9 K/T) cm3 molecule(-1) s(-1); k(1-C4H8) = (6.30 +/- 0.35) x 10(-10) (T/298 K)(-0.61) exp(-65.0 K/T) cm3 molecule(-1) s(-1), for reaction of C4H with dienes: k(C3H4) = (3.70 +/- 0.34) x 10(-10) (T/298 K)(-1.18) exp(-91.1 K/T) cm3 molecule(-1) s(-1); k(1,3-C4H6) = (5.37 +/- 0.30) x 10(-10) (T/298 K)(-1.25) exp(-116.8 K/T) cm3 molecule(-1) s(-1), and for reaction of C4H with alkynes: k(C2H2) = (1.82 +/- 0.19) x 10(-10) (T/298 K)(-1.06) exp(-65.9 K/T) cm3 molecule(-1) s(-1); k(C3H4) = (3.20 +/- 0.08) x 10(-10) (T/298 K)(-0.82) exp(-47.5 K/T) cm3 molecule(-1) s(-1); k(1-C4H6) = (3.48 +/- 0.14) x 10(-10) (T/298 K)(-0.65) exp(-58.4 K/T) cm3 molecule(-1) s(-1). Possible reaction mechanisms and product channels are discussed in detail for each of these reactions. Potential implications of these results for models of low temperature chemical environments, in particular cold interstellar clouds and star-forming regions, are considered.
Absolute Stability And Hyperstability In Hilbert Space
NASA Technical Reports Server (NTRS)
Wen, John Ting-Yung
1989-01-01
Theorems on stabilities of feedback control systems proved. Paper presents recent developments regarding theorems of absolute stability and hyperstability of feedforward-and-feedback control system. Theorems applied in analysis of nonlinear, adaptive, and robust control. Extended to provide sufficient conditions for stability in system including nonlinear feedback subsystem and linear time-invariant (LTI) feedforward subsystem, state space of which is Hilbert space, and input and output spaces having finite numbers of dimensions. (In case of absolute stability, feedback subsystem memoryless and possibly time varying. For hyperstability, feedback system dynamical system.)
Entropy production rate as a constraint for collisionless fluid closures
Fleurence, E.; Sarazin, Y.; Garbet, X.; Dif-Pradalier, G.; Ghendrih, Ph.; Grandgirard, V.; Ottaviani, M.
2006-11-30
A novel method is proposed to construct collisionless fluid closures accounting for some kinetic properties. The first dropped fluid moment is assumed to be a linear function of the lower order ones. Optimizing the agreement between the fluid and kinetic entropy production rates is used to constrain the coefficients of the linear development. This procedure is applied to a reduced version of the interchange instability. The closure, involving the absolute value of the wave vector, is non-local in real space. In this case, the linear instability thresholds are the same, and the linear growth rates exhibit similar characteristics. Such a method is applicable to other models and classes of instabilities.
NASA Astrophysics Data System (ADS)
Mast, J. C.; Mlynczak, M. G.; Marshall, B. T.; Thompson, R. E.; Mertens, C. J.; Hunt, L. A.; Russell, J. M.; Gordley, L. L.
2011-12-01
We present global distributions of v = 9 + v = 8 nighttime vibrationally excited hydroxyl concentrations as measured by the SABER instrument on board the TIMED spacecraft. These states are formed directly by the reaction of atomic hydrogen and ozone in the terrestrial mesopause region. SABER measures the limb radiance from the delta-v = 2 transitions in a channel centered near 2.0 um, specifically the sum of the 9 -> 7 and 8 -> 6 transitions. The limb radiances are inverted to yield the volume emission rates from the sum of the v = 8 and 9 states of the hydroxyl molecule. The Einstein coefficients for spontaneous emission for these two transitions are essentially identical. Thus dividing the derived volume emission rate by the Einstein coefficient yields the absolute populations of these states (molecules per cubic cm). Nine full years of data are presented in this paper. Over this time the globally averaged OH(v = 8 + v = 9) populations have varied relative to the nine year mean by only a few percent. We conclude that despite substantial solar variability over this time period, the apparently small variation of the highly vibrationally excited hydroxyl populations implies that atomic hydrogen, atomic oxygen, temperature, and density adjust in such a way so as to keep the product of the atomic hydrogen concentration, the ozone concentration, and the rate coefficient for their reaction essentially constant.
Absolute Points for Multiple Assignment Problems
ERIC Educational Resources Information Center
Adlakha, V.; Kowalski, K.
2006-01-01
An algorithm is presented to solve multiple assignment problems in which a cost is incurred only when an assignment is made at a given cell. The proposed method recursively searches for single/group absolute points to identify cells that must be loaded in any optimal solution. Unlike other methods, the first solution is the optimal solution. The…
Absolute partial photoionization cross sections of ozone.
Berkowitz, J.; Chemistry
2008-04-01
Despite the current concerns about ozone, absolute partial photoionization cross sections for this molecule in the vacuum ultraviolet (valence) region have been unavailable. By eclectic re-evaluation of old/new data and plausible assumptions, such cross sections have been assembled to fill this void.
Stimulus Probability Effects in Absolute Identification
ERIC Educational Resources Information Center
Kent, Christopher; Lamberts, Koen
2016-01-01
This study investigated the effect of stimulus presentation probability on accuracy and response times in an absolute identification task. Three schedules of presentation were used to investigate the interaction between presentation probability and stimulus position within the set. Data from individual participants indicated strong effects of…
Teaching Absolute Value Inequalities to Mature Students
ERIC Educational Resources Information Center
Sierpinska, Anna; Bobos, Georgeana; Pruncut, Andreea
2011-01-01
This paper gives an account of a teaching experiment on absolute value inequalities, whose aim was to identify characteristics of an approach that would realize the potential of the topic to develop theoretical thinking in students enrolled in prerequisite mathematics courses at a large, urban North American university. The potential is…
Solving Absolute Value Equations Algebraically and Geometrically
ERIC Educational Resources Information Center
Shiyuan, Wei
2005-01-01
The way in which students can improve their comprehension by understanding the geometrical meaning of algebraic equations or solving algebraic equation geometrically is described. Students can experiment with the conditions of the absolute value equation presented, for an interesting way to form an overall understanding of the concept.
Increasing Capacity: Practice Effects in Absolute Identification
ERIC Educational Resources Information Center
Dodds, Pennie; Donkin, Christopher; Brown, Scott D.; Heathcote, Andrew
2011-01-01
In most of the long history of the study of absolute identification--since Miller's (1956) seminal article--a severe limit on performance has been observed, and this limit has resisted improvement even by extensive practice. In a startling result, Rouder, Morey, Cowan, and Pfaltz (2004) found substantially improved performance with practice in the…
Absolute Radiometric Calibration Of The Thematic Mapper
NASA Astrophysics Data System (ADS)
Slater, P. N.; Biggar, S. F.; Holm, R. G.; Jackson, R. D.; Mao, Y.; Moran, M. S.; Palmer, J. M.; Yuan, B.
1986-11-01
The results are presented of five in-flight absolute radiometric calibrations, made in the period July 1984 to November 1985, at White Sands, New Mexico, of the solar reflective bands of the Landsat-5 Thematic Mapper (TM) . The 23 bandcalibrations made on the five dates show a ± 2.8% RMS variation from the mean as a percentage of the mean.
On Relative and Absolute Conviction in Mathematics
ERIC Educational Resources Information Center
Weber, Keith; Mejia-Ramos, Juan Pablo
2015-01-01
Conviction is a central construct in mathematics education research on justification and proof. In this paper, we claim that it is important to distinguish between absolute conviction and relative conviction. We argue that researchers in mathematics education frequently have not done so and this has lead to researchers making unwarranted claims…
Optical absorption coefficients of pure water
NASA Astrophysics Data System (ADS)
Lu, Zheng; Zhao, Xianzhen; Fry, Edward S.
2002-10-01
The integrating cavity absorption meter(ICAM), which is independent of scattering effect, is used to measure the absolute values of small optical absorption coefficients of liquid. A modified ICAM is being used to measure the absorption of water in the wavelength range 300 to 700 nm. The ultrapure water produced by a two-stages water purification system reaches Type I quality. This is equal to or better than ASTM,CAP and NCCLS water quality standards. To avoid the fact that dissolved oxygen absorbs ultraviolet light due to the photochemical effect, the water sample is delivered through a nitrogen sealed system which will prevent the sample from contacting with oxygen. A compassion of our absorption spectrum with other existing data is given.
Schuler, Friedrich; Schwemmer, Frank; Trotter, Martin; Wadle, Simon; Zengerle, Roland; von Stetten, Felix; Paust, Nils
2015-07-01
Aqueous microdroplets provide miniaturized reaction compartments for numerous chemical, biochemical or pharmaceutical applications. We introduce centrifugal step emulsification for the fast and easy production of monodisperse droplets. Homogenous droplets with pre-selectable diameters in a range from 120 μm to 170 μm were generated with coefficients of variation of 2-4% and zero run-in time or dead volume. The droplet diameter depends on the nozzle geometry (depth, width, and step size) and interfacial tensions only. Droplet size is demonstrated to be independent of the dispersed phase flow rate between 0.01 and 1 μl s(-1), proving the robustness of the centrifugal approach. Centrifugal step emulsification can easily be combined with existing centrifugal microfluidic unit operations, is compatible to scalable manufacturing technologies such as thermoforming or injection moulding and enables fast emulsification (>500 droplets per second and nozzle) with minimal handling effort (2-3 pipetting steps). The centrifugal microfluidic droplet generation was used to perform the first digital droplet recombinase polymerase amplification (ddRPA). It was used for absolute quantification of Listeria monocytogenes DNA concentration standards with a total analysis time below 30 min. Compared to digital droplet polymerase chain reaction (ddPCR), with processing times of about 2 hours, the overall processing time of digital analysis was reduced by more than a factor of 4.
Schuler, Friedrich; Schwemmer, Frank; Trotter, Martin; Wadle, Simon; Zengerle, Roland; von Stetten, Felix; Paust, Nils
2015-07-01
Aqueous microdroplets provide miniaturized reaction compartments for numerous chemical, biochemical or pharmaceutical applications. We introduce centrifugal step emulsification for the fast and easy production of monodisperse droplets. Homogenous droplets with pre-selectable diameters in a range from 120 μm to 170 μm were generated with coefficients of variation of 2-4% and zero run-in time or dead volume. The droplet diameter depends on the nozzle geometry (depth, width, and step size) and interfacial tensions only. Droplet size is demonstrated to be independent of the dispersed phase flow rate between 0.01 and 1 μl s(-1), proving the robustness of the centrifugal approach. Centrifugal step emulsification can easily be combined with existing centrifugal microfluidic unit operations, is compatible to scalable manufacturing technologies such as thermoforming or injection moulding and enables fast emulsification (>500 droplets per second and nozzle) with minimal handling effort (2-3 pipetting steps). The centrifugal microfluidic droplet generation was used to perform the first digital droplet recombinase polymerase amplification (ddRPA). It was used for absolute quantification of Listeria monocytogenes DNA concentration standards with a total analysis time below 30 min. Compared to digital droplet polymerase chain reaction (ddPCR), with processing times of about 2 hours, the overall processing time of digital analysis was reduced by more than a factor of 4. PMID:25947077
NASA Technical Reports Server (NTRS)
Wang, S. Y.; Smith, J. M.
1977-01-01
Measurements of the electrical conductivity in the NASA Lewis cesium seeded, H2-O2 MHD duct made by applying a voltage across the channel from one end electrode to the other, measuring the current, and using the inner electrodes as probes to monitor the voltage distribution along the channel were found to be in good agreement with theory except at low combustion pressures and/or high ratios of seed/oxygen mass flows. To corroborate these measurements and to analyze the possibility of nonuniform seed injection as a cause of the above deviations, a spectroscopic investigation of the plasma conductivity was undertaken. Radial profiles of emission coefficient were obtained from measured transverse profiles of the absolute integrated intensity by Abel inversion. Radial profiles of electrical conductivity were then obtained under two different assumptions. In the first the Cs seed fraction is assumed uniform and equal to the measured flow rate at the time when the temperature and conductivity were obtained. In the second method the local temperature and pressure are taken to be those given by a one-dimensional channel calculation including heat transfer and friction. The results of the two methods are compared to the previously measured conductivity.
NASA Technical Reports Server (NTRS)
Wang, S. Y.; Smith, M.
1977-01-01
Measurements of the electrical conductivity in the NASA Lewis cesium seeded, H2-O2 MHD duct have been previously reported. In order to corroborate the above measurements and to analyze the possibility of nonuniform seed injection as a cause of the deviations, a spectroscopic investigation of the plasma conductivity has been undertaken. Transverse profiles of the absolute integrated intensity were measured from the optically thin lines of CSI-.5664 microns and .5636 microns. Radial profiles of emission coefficient were obtained from the measured transverse profiles of intensity by Abel inversion. Radial profiles of electrical conductivity were then obtained under two different assumptions. In the first, the Cs seed fraction is assumed uniform and equal to the measured flow rate at the time when the temperature and conductivity were obtained. In the second method, the local temperature and pressure are taken to be those given by a one-dimensional channel calculation including heat transfer and friction. In this case profiles of conductivity and seed fractions are obtained. The results of the two methods are compared to the previously measured conductivity.
Method of differential-phase/absolute-amplitude QAM
Dimsdle, Jeffrey William
2007-07-03
A method of quadrature amplitude modulation involving encoding phase differentially and amplitude absolutely, allowing for a high data rate and spectral efficiency in data transmission and other communication applications, and allowing for amplitude scaling to facilitate data recovery; amplitude scale tracking to track-out rapid and severe scale variations and facilitate successful demodulation and data retrieval; 2.sup.N power carrier recovery; incoherent demodulation where coherent carrier recovery is not possible or practical due to signal degradation; coherent demodulation; multipath equalization to equalize frequency dependent multipath; and demodulation filtering.
Method of differential-phase/absolute-amplitude QAM
Dimsdle, Jeffrey William
2008-10-21
A method of quadrature amplitude modulation involving encoding phase differentially and amplitude absolutely, allowing for a high data rate and spectral efficiency in data transmission and other communication applications, and allowing for amplitude scaling to facilitate data recovery; amplitude scale tracking to track-out rapid and severe scale variations and facilitate successful demodulation and data retrieval; 2.sup.N power carrier recovery; incoherent demodulation where coherent carrier recovery is not possible or practical due to signal degradation; coherent demodulation; multipath equalization to equalize frequency dependent multipath; and demodulation filtering.
Method of differential-phase/absolute-amplitude QAM
Dimsdle, Jeffrey William
2007-07-17
A method of quadrature amplitude modulation involving encoding phase differentially and amplitude absolutely, allowing for a high data rate and spectral efficiency in data transmission and other communication applications, and allowing for amplitude scaling to facilitate data recovery; amplitude scale tracking to track-out rapid and severe scale variations and facilitate successful demodulation and data retrieval; 2.sup.N power carrier recovery; incoherent demodulation where coherent carrier recovery is not possible or practical due to signal degradation; coherent demodulation; multipath equalization to equalize frequency dependent multipath; and demodulation filtering.
Method of differential-phase/absolute-amplitude QAM
Dimsdle, Jeffrey William
2007-10-02
A method of quadrature amplitude modulation involving encoding phase differentially and amplitude absolutely, allowing for a high data rate and spectral efficiency in data transmission and other communication applications, and allowing for amplitude scaling to facilitate data recovery; amplitude scale tracking to track-out rapid and severe scale variations and facilitate successful demodulation and data retrieval; 2.sup.N power carrier recovery; incoherent demodulation where coherent carrier recovery is not possible or practical due to signal degradation; coherent demodulation; multipath equalization to equalize frequency dependent multipath; and demodulation filtering.
Method of differential-phase/absolute-amplitude QAM
Dimsdle, Jeffrey William
2009-09-01
A method of quadrature amplitude modulation involving encoding phase differentially and amplitude absolutely, allowing for a high data rate and spectral efficiency in data transmission and other communication applications, and allowing for amplitude scaling to facilitate data recovery; amplitude scale tracking to track-out rapid and severe scale variations and facilitate successful demodulation and data retrieval; 2.sup.N power carrier recovery; incoherent demodulation where coherent carrier recovery is not possible or practical due to signal degradation; coherent demodulation; multipath equalization to equalize frequency dependent multipath; and demodulation filtering.
In-flight absolute calibration of the CBERS-2 CCD sensor data.
Ponzoni, Flávio J; Zullo Junior, Jurandir; Lamparelli, Rubens A C
2008-06-01
Since the first images of the sensors on board of CBERS-2 (China-Brazil Earth Resources Satellite) satellite were made available by the National Institute for Space Research (INPE), users have asked information about the conversion of image digital numbers to physical data (radiance or reflectance). This paper describes the main steps that were carried out to calculate the in-flight absolute calibration coefficients for CBERS-2 CCD level 2 (radiometric and geometric correction) images considering the reflectance-based method. Remarks about the preliminary evaluation of these coefficients application are also presented.
Averaging Internal Consistency Reliability Coefficients
ERIC Educational Resources Information Center
Feldt, Leonard S.; Charter, Richard A.
2006-01-01
Seven approaches to averaging reliability coefficients are presented. Each approach starts with a unique definition of the concept of "average," and no approach is more correct than the others. Six of the approaches are applicable to internal consistency coefficients. The seventh approach is specific to alternate-forms coefficients. Although the…
An absolute measure for a key currency
NASA Astrophysics Data System (ADS)
Oya, Shunsuke; Aihara, Kazuyuki; Hirata, Yoshito
It is generally considered that the US dollar and the euro are the key currencies in the world and in Europe, respectively. However, there is no absolute general measure for a key currency. Here, we investigate the 24-hour periodicity of foreign exchange markets using a recurrence plot, and define an absolute measure for a key currency based on the strength of the periodicity. Moreover, we analyze the time evolution of this measure. The results show that the credibility of the US dollar has not decreased significantly since the Lehman shock, when the Lehman Brothers bankrupted and influenced the economic markets, and has increased even relatively better than that of the euro and that of the Japanese yen.
Probing absolute spin polarization at the nanoscale.
Eltschka, Matthias; Jäck, Berthold; Assig, Maximilian; Kondrashov, Oleg V; Skvortsov, Mikhail A; Etzkorn, Markus; Ast, Christian R; Kern, Klaus
2014-12-10
Probing absolute values of spin polarization at the nanoscale offers insight into the fundamental mechanisms of spin-dependent transport. Employing the Zeeman splitting in superconducting tips (Meservey-Tedrow-Fulde effect), we introduce a novel spin-polarized scanning tunneling microscopy that combines the probing capability of the absolute values of spin polarization with precise control at the atomic scale. We utilize our novel approach to measure the locally resolved spin polarization of magnetic Co nanoislands on Cu(111). We find that the spin polarization is enhanced by 65% when increasing the width of the tunnel barrier by only 2.3 Å due to the different decay of the electron orbitals into vacuum. PMID:25423049
From Hubble's NGSL to Absolute Fluxes
NASA Technical Reports Server (NTRS)
Heap, Sara R.; Lindler, Don
2012-01-01
Hubble's Next Generation Spectral Library (NGSL) consists of R-l000 spectra of 374 stars of assorted temperature, gravity, and metallicity. Each spectrum covers the wavelength range, 0.18-1.00 microns. The library can be viewed and/or downloaded from the website, http://archive.stsci.edu/prepds/stisngsll. Stars in the NGSL are now being used as absolute flux standards at ground-based observatories. However, the uncertainty in the absolute flux is about 2%, which does not meet the requirements of dark-energy surveys. We are therefore developing an observing procedure that should yield fluxes with uncertainties less than 1 % and will take part in an HST proposal to observe up to 15 stars using this new procedure.
Impact of Winko on absolute discharges.
Balachandra, Krishna; Swaminath, Sam; Litman, Larry C
2004-01-01
In Canada, case laws have had a significant impact on the way mentally ill offenders are managed, both in the criminal justice system and in the forensic mental health system. The Supreme Court of Canada's decision with respect to Winko has set a major precedent in the application of the test of significant risk to the safety of the public in making dispositions by the Ontario Review Board and granting absolute discharges to the mentally ill offenders in the forensic health system. Our study examines the impact of the Supreme Court of Canada's decision before and after Winko. The results show that the numbers of absolute discharges have increased post-Winko, which was statistically significant, but there could be other factors influencing this increase.
Asteroid absolute magnitudes and slope parameters
NASA Technical Reports Server (NTRS)
Tedesco, Edward F.
1991-01-01
A new listing of absolute magnitudes (H) and slope parameters (G) has been created and published in the Minor Planet Circulars; this same listing will appear in the 1992 Ephemerides of Minor Planets. Unlike previous listings, the values of the current list were derived from fits of data at the V band. All observations were reduced in the same fashion using, where appropriate, a single basis default value of 0.15 for the slope parameter. Distances and phase angles were computed for each observation. The data for 113 asteroids was of sufficiently high quality to permit derivation of their H and G. These improved absolute magnitudes and slope parameters will be used to deduce the most reliable bias-corrected asteroid size-frequency distribution yet made.
Absolute-magnitude distributions of supernovae
Richardson, Dean; Wright, John; Jenkins III, Robert L.; Maddox, Larry
2014-05-01
The absolute-magnitude distributions of seven supernova (SN) types are presented. The data used here were primarily taken from the Asiago Supernova Catalogue, but were supplemented with additional data. We accounted for both foreground and host-galaxy extinction. A bootstrap method is used to correct the samples for Malmquist bias. Separately, we generate volume-limited samples, restricted to events within 100 Mpc. We find that the superluminous events (M{sub B} < –21) make up only about 0.1% of all SNe in the bias-corrected sample. The subluminous events (M{sub B} > –15) make up about 3%. The normal Ia distribution was the brightest with a mean absolute blue magnitude of –19.25. The IIP distribution was the dimmest at –16.75.
Absolute and relative dosimetry for ELIMED
Cirrone, G. A. P.; Schillaci, F.; Scuderi, V.; Cuttone, G.; Candiano, G.; Musumarra, A.; Pisciotta, P.; Romano, F.; Carpinelli, M.; Presti, D. Lo; Raffaele, L.; Tramontana, A.; Cirio, R.; Sacchi, R.; Monaco, V.; Marchetto, F.; Giordanengo, S.
2013-07-26
The definition of detectors, methods and procedures for the absolute and relative dosimetry of laser-driven proton beams is a crucial step toward the clinical use of this new kind of beams. Hence, one of the ELIMED task, will be the definition of procedures aiming to obtain an absolute dose measure at the end of the transport beamline with an accuracy as close as possible to the one required for clinical applications (i.e. of the order of 5% or less). Relative dosimetry procedures must be established, as well: they are necessary in order to determine and verify the beam dose distributions and to monitor the beam fluence and the energetic spectra during irradiations. Radiochromic films, CR39, Faraday Cup, Secondary Emission Monitor (SEM) and transmission ionization chamber will be considered, designed and studied in order to perform a fully dosimetric characterization of the ELIMED proton beam.
Absolute photoionization cross sections of atomic oxygen
NASA Technical Reports Server (NTRS)
Samson, J. A. R.; Pareek, P. N.
1985-01-01
The absolute values of photoionization cross sections of atomic oxygen were measured from the ionization threshold to 120 A. An auto-ionizing resonance belonging to the 2S2P4(4P)3P(3Do, 3So) transition was observed at 479.43 A and another line at 389.97 A. The experimental data is in excellent agreement with rigorous close-coupling calculations that include electron correlations in both the initial and final states.
Absolute photoionization cross sections of atomic oxygen
NASA Technical Reports Server (NTRS)
Samson, J. A. R.; Pareek, P. N.
1982-01-01
The absolute values of photoionization cross sections of atomic oxygen were measured from the ionization threshold to 120 A. An auto-ionizing resonance belonging to the 2S2P4(4P)3P(3Do, 3So) transition was observed at 479.43 A and another line at 389.97 A. The experimental data is in excellent agreement with rigorous close-coupling calculations that include electron correlations in both the initial and final states.
Relative errors can cue absolute visuomotor mappings.
van Dam, Loes C J; Ernst, Marc O
2015-12-01
When repeatedly switching between two visuomotor mappings, e.g. in a reaching or pointing task, adaptation tends to speed up over time. That is, when the error in the feedback corresponds to a mapping switch, fast adaptation occurs. Yet, what is learned, the relative error or the absolute mappings? When switching between mappings, errors with a size corresponding to the relative difference between the mappings will occur more often than other large errors. Thus, we could learn to correct more for errors with this familiar size (Error Learning). On the other hand, it has been shown that the human visuomotor system can store several absolute visuomotor mappings (Mapping Learning) and can use associated contextual cues to retrieve them. Thus, when contextual information is present, no error feedback is needed to switch between mappings. Using a rapid pointing task, we investigated how these two types of learning may each contribute when repeatedly switching between mappings in the absence of task-irrelevant contextual cues. After training, we examined how participants changed their behaviour when a single error probe indicated either the often-experienced error (Error Learning) or one of the previously experienced absolute mappings (Mapping Learning). Results were consistent with Mapping Learning despite the relative nature of the error information in the feedback. This shows that errors in the feedback can have a double role in visuomotor behaviour: they drive the general adaptation process by making corrections possible on subsequent movements, as well as serve as contextual cues that can signal a learned absolute mapping. PMID:26280315
The absolute spectrophotometric catalog by Anita Cochran
NASA Astrophysics Data System (ADS)
Burnashev, V. I.; Burnasheva, B. A.; Ruban, E. V.; Hagen-Torn, E. I.
2014-06-01
The absolute spectrophotometric catalog by Anita Cochran is presented in a machine-readable form. The catalog systematizes observations acquired at the McDonald Observatory in 1977-1978. The data are compared with other sources, in particular, the calculated broadband stellar magnitudes are compared with photometric observations by other authors, to show that the observational data given in the catalog are reliable and suitable for a variety of applications. Observations of variable stars of different types make Cochran's catalog especially valuable.
Absolute magnitudes and kinematics of barium stars.
NASA Astrophysics Data System (ADS)
Gomez, A. E.; Luri, X.; Grenier, S.; Prevot, L.; Mennessier, M. O.; Figueras, F.; Torra, J.
1997-03-01
The absolute magnitude of barium stars has been obtained from kinematical data using a new algorithm based on the maximum-likelihood principle. The method allows to separate a sample into groups characterized by different mean absolute magnitudes, kinematics and z-scale heights. It also takes into account, simultaneously, the censorship in the sample and the errors on the observables. The method has been applied to a sample of 318 barium stars. Four groups have been detected. Three of them show a kinematical behaviour corresponding to disk population stars. The fourth group contains stars with halo kinematics. The luminosities of the disk population groups spread a large range. The intrinsically brightest one (M_v_=-1.5mag, σ_M_=0.5mag) seems to be an inhomogeneous group containing barium binaries as well as AGB single stars. The most numerous group (about 150 stars) has a mean absolute magnitude corresponding to stars in the red giant branch (M_v_=0.9mag, σ_M_=0.8mag). The third group contains barium dwarfs, the obtained mean absolute magnitude is characteristic of stars on the main sequence or on the subgiant branch (M_v_=3.3mag, σ_M_=0.5mag). The obtained mean luminosities as well as the kinematical results are compatible with an evolutionary link between barium dwarfs and classical barium giants. The highly luminous group is not linked with these last two groups. More high-resolution spectroscopic data will be necessary in order to better discriminate between barium and non-barium stars.
Pre-Launch Absolute Calibration of CCD/CBERS-2B Sensor
Ponzoni, Flávio Jorge; Albuquerque, Bráulio Fonseca Carneiro
2008-01-01
Pre-launch absolute calibration coefficients for the CCD/CBERS-2B sensor have been calculated from radiometric measurements performed in a satellite integration and test hall in the Chinese Academy of Space Technology (CAST) headquarters, located in Beijing, China. An illuminated integrating sphere was positioned in the test hall facilities to allow the CCD/CBERS-2B imagery of the entire sphere aperture. Calibration images were recorded and a relative calibration procedure adopted exclusively in Brazil was applied to equalize the detectors responses. Averages of digital numbers (DN) from these images were determined and correlated to their respective radiance levels in order to calculate the absolute calibration coefficients. It has been the first time these pre-launch absolute calibration coefficients have been calculated considering the Brazilian image processing criteria. Now it will be possible to compare them to those that will be calculated from vicarious calibration campaigns. This comparison will permit the CCD/CBERS-2B monitoring and the frequently data updating to the user community.
Temperature-dependent Absolute Refractive Index Measurements of Synthetic Fused Silica
NASA Technical Reports Server (NTRS)
Leviton, Douglas B.; Frey, Bradley J.
2006-01-01
Using the Cryogenic, High-Accuracy Refraction Measuring System (CHARMS) at NASA's Goddard Space Flight Center, we have measured the absolute refractive index of five specimens taken from a very large boule of Corning 7980 fused silica from temperatures ranging from 30 to 310 K at wavelengths from 0.4 to 2.6 microns with an absolute uncertainty of plus or minus 1 x 10 (exp -5). Statistical variations in derived values of the thermo-optic coefficient (dn/dT) are at the plus or minus 2 x 10 (exp -8)/K level. Graphical and tabulated data for absolute refractive index, dispersion, and thermo-optic coefficient are presented for selected wavelengths and temperatures along with estimates of uncertainty in index. Coefficients for temperature-dependent Sellmeier fits of measured refractive index are also presented to allow accurate interpolation of index to other wavelengths and temperatures. We compare our results to those from an independent investigation (which used an interferometric technique for measuring index changes as a function of temperature) whose samples were prepared from the same slugs of material from which our prisms were prepared in support of the Kepler mission. We also compare our results with sparse cryogenic index data from measurements of this material from the literature.
Chemical composition of French mimosa absolute oil.
Perriot, Rodolphe; Breme, Katharina; Meierhenrich, Uwe J; Carenini, Elise; Ferrando, Georges; Baldovini, Nicolas
2010-02-10
Since decades mimosa (Acacia dealbata) absolute oil has been used in the flavor and perfume industry. Today, it finds an application in over 80 perfumes, and its worldwide industrial production is estimated five tons per year. Here we report on the chemical composition of French mimosa absolute oil. Straight-chain analogues from C6 to C26 with different functional groups (hydrocarbons, esters, aldehydes, diethyl acetals, alcohols, and ketones) were identified in the volatile fraction. Most of them are long-chain molecules: (Z)-heptadec-8-ene, heptadecane, nonadecane, and palmitic acid are the most abundant, and constituents such as 2-phenethyl alcohol, methyl anisate, and ethyl palmitate are present in smaller amounts. The heavier constituents were mainly triterpenoids such as lupenone and lupeol, which were identified as two of the main components. (Z)-Heptadec-8-ene, lupenone, and lupeol were quantified by GC-MS in SIM mode using external standards and represents 6%, 20%, and 7.8% (w/w) of the absolute oil. Moreover, odorant compounds were extracted by SPME and analyzed by GC-sniffing leading to the perception of 57 odorant zones, of which 37 compounds were identified by their odorant description, mass spectrum, retention index, and injection of the reference compound. PMID:20070087
Measurement of absolute gravity acceleration in Firenze
NASA Astrophysics Data System (ADS)
de Angelis, M.; Greco, F.; Pistorio, A.; Poli, N.; Prevedelli, M.; Saccorotti, G.; Sorrentino, F.; Tino, G. M.
2011-01-01
This paper reports the results from the accurate measurement of the acceleration of gravity g taken at two separate premises in the Polo Scientifico of the University of Firenze (Italy). In these laboratories, two separate experiments aiming at measuring the Newtonian constant and testing the Newtonian law at short distances are in progress. Both experiments require an independent knowledge on the local value of g. The only available datum, pertaining to the italian zero-order gravity network, was taken more than 20 years ago at a distance of more than 60 km from the study site. Gravity measurements were conducted using an FG5 absolute gravimeter, and accompanied by seismic recordings for evaluating the noise condition at the site. The absolute accelerations of gravity at the two laboratories are (980 492 160.6 ± 4.0) μGal and (980 492 048.3 ± 3.0) μGal for the European Laboratory for Non-Linear Spectroscopy (LENS) and Dipartimento di Fisica e Astronomia, respectively. Other than for the two referenced experiments, the data here presented will serve as a benchmark for any future study requiring an accurate knowledge of the absolute value of the acceleration of gravity in the study region.
A Methodology for Absolute Isotope Composition Measurement
NASA Astrophysics Data System (ADS)
Shen, J. J.; Lee, D.; Liang, W.
2007-12-01
Double spike technique was a well defined method for isotope composition measurement by TIMS of samples which have natural mass fractionation effect, but it is still a problem to define the isotope composition for double spike itself. In this study, we modified the old double spike technique and found that we could use the modified technique to solve the ¡§true¡¨ isotope composition of double spike itself. According the true isotope composition of double spike, we can measure the absolute isotope composition if the sample has natural fractionation effect. A new vector analytical method has been developed in order to obtain the true isotopic composition of a 42Ca-48Ca double spike, and this is achieved by using two different sample-spike mixtures combined with the double spike and the natural Ca data. Because the natural sample, the two mixtures, and the spike should all lie on a single mixing line, we are able to constrain the true isotopic composition of our double spike using this new approach. This method not only can be used in Ca system but also in Ti, Cr, Fe, Ni, Zn, Mo, Ba and Pb systems. The absolute double spike isotopic ratio is important, which can save a lot of time to check different reference standards. Especially for Pb, radiogenic isotope system, the decay systems embodied in three of four naturally occurring isotopes induce difficult to obtain true isotopic ratios for absolute dating.
Chemical composition of French mimosa absolute oil.
Perriot, Rodolphe; Breme, Katharina; Meierhenrich, Uwe J; Carenini, Elise; Ferrando, Georges; Baldovini, Nicolas
2010-02-10
Since decades mimosa (Acacia dealbata) absolute oil has been used in the flavor and perfume industry. Today, it finds an application in over 80 perfumes, and its worldwide industrial production is estimated five tons per year. Here we report on the chemical composition of French mimosa absolute oil. Straight-chain analogues from C6 to C26 with different functional groups (hydrocarbons, esters, aldehydes, diethyl acetals, alcohols, and ketones) were identified in the volatile fraction. Most of them are long-chain molecules: (Z)-heptadec-8-ene, heptadecane, nonadecane, and palmitic acid are the most abundant, and constituents such as 2-phenethyl alcohol, methyl anisate, and ethyl palmitate are present in smaller amounts. The heavier constituents were mainly triterpenoids such as lupenone and lupeol, which were identified as two of the main components. (Z)-Heptadec-8-ene, lupenone, and lupeol were quantified by GC-MS in SIM mode using external standards and represents 6%, 20%, and 7.8% (w/w) of the absolute oil. Moreover, odorant compounds were extracted by SPME and analyzed by GC-sniffing leading to the perception of 57 odorant zones, of which 37 compounds were identified by their odorant description, mass spectrum, retention index, and injection of the reference compound.
The Carina Project: Absolute and Relative Calibrations
NASA Astrophysics Data System (ADS)
Corsi, C. E.; Bono, G.; Walker, A. R.; Brocato, E.; Buonanno, R.; Caputo, F.; Castellani, M.; Castellani, V.; Dall'Ora, M.; Marconi, M.; Monelli, M.; Nonino, M.; Pulone, L.; Ripepi, V.; Smith, H. A.
We discuss the reduction strategy adopted to perform the relative and the absolute calibration of the Wide Field Imager (WFI) available at the 2.2m ESO/MPI telescope and of the Mosaic Camera (MC) available at the 4m CTIO Blanco telescope. To properly constrain the occurrence of deceptive systematic errors in the relative calibration we observed with each chip the same set of stars. Current photometry seems to suggest that the WFI shows a positional effect when moving from the top to the bottom of individual chips. Preliminary results based on an independent data set collected with the MC suggest that this camera is only marginally affected by the same problem. To perform the absolute calibration we observed with each chip the same set of standard stars. The sample covers a wide color range and the accuracy both in the B and in the V-band appears to be of the order of a few hundredths of magnitude. Finally, we briefly outline the observing strategy to improve both relative and absolute calibrations of mosaic CCD cameras.
Absolute dynamic viscosity measurements of subcooled liquid oxygen from 0.15 MPa to 1.0 MPa
NASA Astrophysics Data System (ADS)
Hilton, D. K.; Van Sciver, S. W.
2008-01-01
New absolute dynamic viscosity measurements of subcooled liquid oxygen are presented which were acquired in the pressure and temperature domains from 0.15 MPa to 1.0 MPa and from 55.20 K to 90.19 K, respectively. The measurements were acquired with an uncertainty of 1% at a 95% confidence level using a pressurized gravitational capillary (PGC) viscometer specifically designed for subcooled liquefied gases. The measurements are summarized by Arrhenius-Eyring plot parameters ( μ = Ae E/ RT), and interpreted with respect to the chemical reaction rate theory of viscosity by Eyring. The Arrhenius-Eyring plot parameters reproduce the dynamic viscosity measurements with only a 2% RMS error, which is remarkable considering just two parameters are involved, A, the factor which includes the weak pressure dependence of the dynamic viscosity, and E/ R, the barrier energy of the flow, where R is the universal gas constant. Although the Arrhenius-Eyring plot parameters do not have a discernible pressure dependence in the present work, the pressure coefficient versus temperature for the dynamic viscosity was determined from line plots of the dynamic viscosity versus pressure. The pressure coefficients suggest that the pressure dependence is very weak, yet positive, and increases with decreasing temperature. Measurements at pressures an order-of-magnitude higher are required to confirm this suggestion.
Measurement of absolute T cell receptor rearrangement diversity.
Baum, Paul D; Young, Jennifer J; McCune, Joseph M
2011-05-31
T cell receptor (TCR) diversity is critical for adaptive immunity. Existing methods for measuring such diversity are qualitative, expensive, and/or of uncertain accuracy. Here, we describe a method and associated reagents for estimating the absolute number of unique TCR Vβ rearrangements present in a given number of cells or volume of blood. Compared to next generation sequencing, this method is rapid, reproducible, and affordable. Diversity of a sample is calculated based on three independent measurements of one Vβ-Jβ family of TCR rearrangements at a time. The percentage of receptors using the given Vβ gene is determined by flow cytometric analysis of T cells stained with anti-Vβ family antibodies. The percentage of receptors using the Vβ gene in combination with the chosen Jβ gene is determined by quantitative PCR. Finally, the absolute clonal diversity of the Vβ-Jβ family is determined with the AmpliCot method of DNA hybridization kinetics, by interpolation relative to PCR standards of known sequence diversity. These three component measurements are reproducible and linear. Using titrations of known numbers of input cells, we show that the TCR diversity estimates obtained by this approach approximate expected values within a two-fold error, have a coefficient of variation of 20%, and yield similar results when different Vβ-Jβ pairs are chosen. The ability to obtain accurate measurements of the total number of different TCR gene rearrangements in a cell sample should be useful for basic studies of the adaptive immune system as well as in clinical studies of conditions such as HIV disease, transplantation, aging, and congenital immunodeficiencies. PMID:21385585
Inbreeding coefficients and coalescence times.
Slatkin, M
1991-10-01
This paper describes the relationship between probabilities of identity by descent and the distribution of coalescence times. By using the relationship between coalescence times and identity probabilities, it is possible to extend existing results for inbreeding coefficients in regular systems of mating to find the distribution of coalescence times and the mean coalescence times. It is also possible to express Sewall Wright's FST as the ratio of average coalescence times of different pairs of genes. That simplifies the analysis of models of subdivided populations because the average coalescence time can be found by computing separately the time it takes for two genes to enter a single subpopulation and time it takes for two genes in the same subpopulation to coalesce. The first time depends only on the migration matrix and the second time depends only on the total number of individuals in the population. This approach is used to find FST in the finite island model and in one- and two-dimensional stepping-stone models. It is also used to find the rate of approach of FST to its equilibrium value. These results are discussed in terms of different measures of genetic distance. It is proposed that, for the purposes of describing the amount of gene flow among local populations, the effective migration rate between pairs of local populations, M, which is the migration rate that would be estimated for those two populations if they were actually in an island model, provides a simple and useful measure of genetic similarity that can be defined for either allozyme or DNA sequence data.
Absolute Radiometric Calibration of EUNIS-06
NASA Technical Reports Server (NTRS)
Thomas, R. J.; Rabin, D. M.; Kent, B. J.; Paustian, W.
2007-01-01
The Extreme-Ultraviolet Normal-Incidence Spectrometer (EUNIS) is a soundingrocket payload that obtains imaged high-resolution spectra of individual solar features, providing information about the Sun's corona and upper transition region. Shortly after its successful initial flight last year, a complete end-to-end calibration was carried out to determine the instrument's absolute radiometric response over its Longwave bandpass of 300 - 370A. The measurements were done at the Rutherford-Appleton Laboratory (RAL) in England, using the same vacuum facility and EUV radiation source used in the pre-flight calibrations of both SOHO/CDS and Hinode/EIS, as well as in three post-flight calibrations of our SERTS sounding rocket payload, the precursor to EUNIS. The unique radiation source provided by the Physikalisch-Technische Bundesanstalt (PTB) had been calibrated to an absolute accuracy of 7% (l-sigma) at 12 wavelengths covering our bandpass directly against the Berlin electron storage ring BESSY, which is itself a primary radiometric source standard. Scans of the EUNIS aperture were made to determine the instrument's absolute spectral sensitivity to +- 25%, considering all sources of error, and demonstrate that EUNIS-06 was the most sensitive solar E W spectrometer yet flown. The results will be matched against prior calibrations which relied on combining measurements of individual optical components, and on comparisons with theoretically predicted 'insensitive' line ratios. Coordinated observations were made during the EUNIS-06 flight by SOHO/CDS and EIT that will allow re-calibrations of those instruments as well. In addition, future EUNIS flights will provide similar calibration updates for TRACE, Hinode/EIS, and STEREO/SECCHI/EUVI.
Clock time is absolute and universal
NASA Astrophysics Data System (ADS)
Shen, Xinhang
2015-09-01
A critical error is found in the Special Theory of Relativity (STR): mixing up the concepts of the STR abstract time of a reference frame and the displayed time of a physical clock, which leads to use the properties of the abstract time to predict time dilation on physical clocks and all other physical processes. Actually, a clock can never directly measure the abstract time, but can only record the result of a physical process during a period of the abstract time such as the number of cycles of oscillation which is the multiplication of the abstract time and the frequency of oscillation. After Lorentz Transformation, the abstract time of a reference frame expands by a factor gamma, but the frequency of a clock decreases by the same factor gamma, and the resulting multiplication i.e. the displayed time of a moving clock remains unchanged. That is, the displayed time of any physical clock is an invariant of Lorentz Transformation. The Lorentz invariance of the displayed times of clocks can further prove within the framework of STR our earth based standard physical time is absolute, universal and independent of inertial reference frames as confirmed by both the physical fact of the universal synchronization of clocks on the GPS satellites and clocks on the earth, and the theoretical existence of the absolute and universal Galilean time in STR which has proved that time dilation and space contraction are pure illusions of STR. The existence of the absolute and universal time in STR has directly denied that the reference frame dependent abstract time of STR is the physical time, and therefore, STR is wrong and all its predictions can never happen in the physical world.
Achieving Climate Change Absolute Accuracy in Orbit
NASA Technical Reports Server (NTRS)
Wielicki, Bruce A.; Young, D. F.; Mlynczak, M. G.; Thome, K. J; Leroy, S.; Corliss, J.; Anderson, J. G.; Ao, C. O.; Bantges, R.; Best, F.; Bowman, K.; Brindley, H.; Butler, J. J.; Collins, W.; Dykema, J. A.; Doelling, D. R.; Feldman, D. R.; Fox, N.; Huang, X.; Holz, R.; Huang, Y.; Jennings, D.; Jin, Z.; Johnson, D. G.; Jucks, K.; Kato, S.; Kratz, D. P.; Liu, X.; Lukashin, C.; Mannucci, A. J.; Phojanamongkolkij, N.; Roithmayr, C. M.; Sandford, S.; Taylor, P. C.; Xiong, X.
2013-01-01
The Climate Absolute Radiance and Refractivity Observatory (CLARREO) mission will provide a calibration laboratory in orbit for the purpose of accurately measuring and attributing climate change. CLARREO measurements establish new climate change benchmarks with high absolute radiometric accuracy and high statistical confidence across a wide range of essential climate variables. CLARREO's inherently high absolute accuracy will be verified and traceable on orbit to Système Internationale (SI) units. The benchmarks established by CLARREO will be critical for assessing changes in the Earth system and climate model predictive capabilities for decades into the future as society works to meet the challenge of optimizing strategies for mitigating and adapting to climate change. The CLARREO benchmarks are derived from measurements of the Earth's thermal infrared spectrum (5-50 micron), the spectrum of solar radiation reflected by the Earth and its atmosphere (320-2300 nm), and radio occultation refractivity from which accurate temperature profiles are derived. The mission has the ability to provide new spectral fingerprints of climate change, as well as to provide the first orbiting radiometer with accuracy sufficient to serve as the reference transfer standard for other space sensors, in essence serving as a "NIST [National Institute of Standards and Technology] in orbit." CLARREO will greatly improve the accuracy and relevance of a wide range of space-borne instruments for decadal climate change. Finally, CLARREO has developed new metrics and methods for determining the accuracy requirements of climate observations for a wide range of climate variables and uncertainty sources. These methods should be useful for improving our understanding of observing requirements for most climate change observations.
Absolute calibration of the Auger fluorescence detectors
Bauleo, P.; Brack, J.; Garrard, L.; Harton, J.; Knapik, R.; Meyhandan, R.; Rovero, A.C.; Tamashiro, A.; Warner, D.
2005-07-01
Absolute calibration of the Pierre Auger Observatory fluorescence detectors uses a light source at the telescope aperture. The technique accounts for the combined effects of all detector components in a single measurement. The calibrated 2.5 m diameter light source fills the aperture, providing uniform illumination to each pixel. The known flux from the light source and the response of the acquisition system give the required calibration for each pixel. In the lab, light source uniformity is studied using CCD images and the intensity is measured relative to NIST-calibrated photodiodes. Overall uncertainties are presently 12%, and are dominated by systematics.
Characterization of the DARA solar absolute radiometer
NASA Astrophysics Data System (ADS)
Finsterle, W.; Suter, M.; Fehlmann, A.; Kopp, G.
2011-12-01
The Davos Absolute Radiometer (DARA) prototype is an Electrical Substitution Radiometer (ESR) which has been developed as a successor of the PMO6 type on future space missions and ground based TSI measurements. The DARA implements an improved thermal design of the cavity detector and heat sink assembly to minimize air-vacuum differences and to maximize thermal symmetry of measuring and compensating cavity. The DARA also employs an inverted viewing geometry to reduce internal stray light. We will report on the characterization and calibration experiments which were carried out at PMOD/WRC and LASP (TRF).
Absolute Priority for a Vehicle in VANET
NASA Astrophysics Data System (ADS)
Shirani, Rostam; Hendessi, Faramarz; Montazeri, Mohammad Ali; Sheikh Zefreh, Mohammad
In today's world, traffic jams waste hundreds of hours of our life. This causes many researchers try to resolve the problem with the idea of Intelligent Transportation System. For some applications like a travelling ambulance, it is important to reduce delay even for a second. In this paper, we propose a completely infrastructure-less approach for finding shortest path and controlling traffic light to provide absolute priority for an emergency vehicle. We use the idea of vehicular ad-hoc networking to reduce the imposed travelling time. Then, we simulate our proposed protocol and compare it with a centrally controlled traffic light system.
Absolute method of measuring magnetic susceptibility
Thorpe, A.; Senftle, F.E.
1959-01-01
An absolute method of standardization and measurement of the magnetic susceptibility of small samples is presented which can be applied to most techniques based on the Faraday method. The fact that the susceptibility is a function of the area under the curve of sample displacement versus distance of the magnet from the sample, offers a simple method of measuring the susceptibility without recourse to a standard sample. Typical results on a few substances are compared with reported values, and an error of less than 2% can be achieved. ?? 1959 The American Institute of Physics.
On determination of sign of the piezo-optic coefficients using torsion method.
Vasylkiv, Yurij; Savaryn, Viktoriya; Smaga, Ihor; Skab, Ihor; Vlokh, Rostyslav
2011-06-10
We have shown that a high-accuracy torsion method recently developed by the authors for measuring piezo-optic coefficients allows determining not only the absolute value of the coefficients but also their sign. The techniques and experimental procedures used for determination of the sign are described in detail and proven based on studies of α-BaB2O4 and LiNbO3 crystals. The piezo-optic coefficients are determined for both crystals, and a combination of the corresponding photoelastic coefficients is determined for the case of α-BaB2O4 crystals.
Coefficient Alpha: A Reliability Coefficient for the 21st Century?
ERIC Educational Resources Information Center
Yang, Yanyun; Green, Samuel B.
2011-01-01
Coefficient alpha is almost universally applied to assess reliability of scales in psychology. We argue that researchers should consider alternatives to coefficient alpha. Our preference is for structural equation modeling (SEM) estimates of reliability because they are informative and allow for an empirical evaluation of the assumptions…
Experimental results for absolute cylindrical wavefront testing
NASA Astrophysics Data System (ADS)
Reardon, Patrick J.; Alatawi, Ayshah
2014-09-01
Applications for Cylindrical and near-cylindrical surfaces are ever-increasing. However, fabrication of high quality cylindrical surfaces is limited by the difficulty of accurate and affordable metrology. Absolute testing of such surfaces represents a challenge to the optical testing community as cylindrical reference wavefronts are difficult to produce. In this paper, preliminary results for a new method of absolute testing of cylindrical wavefronts are presented. The method is based on the merging of the random ball test method with the fiber optic reference test. The random ball test assumes a large number of interferograms of a good quality sphere with errors that are statistically distributed such that the average of the errors goes to zero. The fiber optic reference test utilizes a specially processed optical fiber to provide a clean high quality reference wave from an incident line focus from the cylindrical wave under test. By taking measurements at different rotation and translations of the fiber, an analogous procedure can be employed to determine the quality of the converging cylindrical wavefront with high accuracy. This paper presents and discusses the results of recent tests of this method using a null optic formed by a COTS cylindrical lens and a free-form polished corrector element.
Absolute Electron Extraction Efficiency of Liquid Xenon
NASA Astrophysics Data System (ADS)
Kamdin, Katayun; Mizrachi, Eli; Morad, James; Sorensen, Peter
2016-03-01
Dual phase liquid/gas xenon time projection chambers (TPCs) currently set the world's most sensitive limits on weakly interacting massive particles (WIMPs), a favored dark matter candidate. These detectors rely on extracting electrons from liquid xenon into gaseous xenon, where they produce proportional scintillation. The proportional scintillation from the extracted electrons serves to internally amplify the WIMP signal; even a single extracted electron is detectable. Credible dark matter searches can proceed with electron extraction efficiency (EEE) lower than 100%. However, electrons systematically left at the liquid/gas boundary are a concern. Possible effects include spontaneous single or multi-electron proportional scintillation signals in the gas, or charging of the liquid/gas interface or detector materials. Understanding EEE is consequently a serious concern for this class of rare event search detectors. Previous EEE measurements have mostly been relative, not absolute, assuming efficiency plateaus at 100%. I will present an absolute EEE measurement with a small liquid/gas xenon TPC test bed located at Lawrence Berkeley National Laboratory.
Why to compare absolute numbers of mitochondria.
Schmitt, Sabine; Schulz, Sabine; Schropp, Eva-Maria; Eberhagen, Carola; Simmons, Alisha; Beisker, Wolfgang; Aichler, Michaela; Zischka, Hans
2014-11-01
Prompted by pronounced structural differences between rat liver and rat hepatocellular carcinoma mitochondria, we suspected these mitochondrial populations to differ massively in their molecular composition. Aiming to reveal these mitochondrial differences, we came across the issue on how to normalize such comparisons and decided to focus on the absolute number of mitochondria. To this end, fluorescently stained mitochondria were quantified by flow cytometry. For rat liver mitochondria, this approach resulted in mitochondrial protein contents comparable to earlier reports using alternative methods. We determined similar protein contents for rat liver, heart and kidney mitochondria. In contrast, however, lower protein contents were determined for rat brain mitochondria and for mitochondria from the rat hepatocellular carcinoma cell line McA 7777. This result challenges mitochondrial comparisons that rely on equal protein amounts as a typical normalization method. Exemplarily, we therefore compared the activity and susceptibility toward inhibition of complex II of rat liver and hepatocellular carcinoma mitochondria and obtained significant discrepancies by either normalizing to protein amount or to absolute mitochondrial number. Importantly, the latter normalization, in contrast to the former, demonstrated a lower complex II activity and higher susceptibility toward inhibition in hepatocellular carcinoma mitochondria compared to liver mitochondria. These findings demonstrate that solely normalizing to protein amount may obscure essential molecular differences between mitochondrial populations.
Absolute Proper Motions of Southern Globular Clusters
NASA Astrophysics Data System (ADS)
Dinescu, D. I.; Girard, T. M.; van Altena, W. F.
1996-05-01
Our program involves the determination of absolute proper motions with respect to galaxies for a sample of globular clusters situated in the southern sky. The plates cover a 6(deg) x 6(deg) area and are taken with the 51-cm double astrograph at Cesco Observatory in El Leoncito, Argentina. We have developed special methods to deal with the modelling error of the plate transformation and we correct for magnitude equation using the cluster stars. This careful astrometric treatment leads to accuracies of from 0.5 to 1.0 mas/yr for the absolute proper motion of each cluster, depending primarily on the number of measurable cluster stars which in turn is related to the cluster's distance. Space velocities are then derived which, in association with metallicities, provide key information for the formation scenario of the Galaxy, i.e. accretion and/or dissipational collapse. Here we present results for NGC 1851, NGC 6752, NGC 6584, NGC 6362 and NGC 288.
Relational versus absolute representation in categorization.
Edwards, Darren J; Pothos, Emmanuel M; Perlman, Amotz
2012-01-01
This study explores relational-like and absolute-like representations in categorization. Although there is much evidence that categorization processes can involve information about both the particular physical properties of studied instances and abstract (relational) properties, there has been little work on the factors that lead to one kind of representation as opposed to the other. We tested 370 participants in 6 experiments, in which participants had to classify new items into predefined artificial categories. In 4 experiments, we observed a predominantly relational-like mode of classification, and in 2 experiments we observed a shift toward an absolute-like mode of classification. These results suggest 3 factors that promote a relational-like mode of classification: fewer items per group, more training groups, and the presence of a time delay. Overall, we propose that less information about the distributional properties of a category or weaker memory traces for the category exemplars (induced, e.g., by having smaller categories or a time delay) can encourage relational-like categorization.
NASA Astrophysics Data System (ADS)
Sergievskii, V. V.; Rudakov, A. M.
2016-08-01
The model that considers the nonideality of aqueous solutions of electrolytes with allowance for independent contributions of hydration of ions of various types and electrostatic interactions was substantiated using the cluster ion model. The empirical parameters in the model equations were found to be the hydrophilic and hydrophobic hydration numbers of ions in the standard state and the dispersion of their distribution over the stoichiometric coefficients. A mathematically adequate description of the concentration dependences of the osmotic coefficients and average ion activity coefficients of electrolytes was given for several systems. The difference in the rate of the decrease in the hydrophilic and hydrophobic hydration numbers of ions leads to extremum concentration dependences of the osmotic coefficients, which were determined by other authors from isopiestic data for many electrolytes and did not find explanation.
A Conceptual Approach to Absolute Value Equations and Inequalities
ERIC Educational Resources Information Center
Ellis, Mark W.; Bryson, Janet L.
2011-01-01
The absolute value learning objective in high school mathematics requires students to solve far more complex absolute value equations and inequalities. When absolute value problems become more complex, students often do not have sufficient conceptual understanding to make any sense of what is happening mathematically. The authors suggest that the…
Using, Seeing, Feeling, and Doing Absolute Value for Deeper Understanding
ERIC Educational Resources Information Center
Ponce, Gregorio A.
2008-01-01
Using sticky notes and number lines, a hands-on activity is shared that anchors initial student thinking about absolute value. The initial point of reference should help students successfully evaluate numeric problems involving absolute value. They should also be able to solve absolute value equations and inequalities that are typically found in…
Graph characterization via Ihara coefficients.
Ren, Peng; Wilson, Richard C; Hancock, Edwin R
2011-02-01
The novel contributions of this paper are twofold. First, we demonstrate how to characterize unweighted graphs in a permutation-invariant manner using the polynomial coefficients from the Ihara zeta function, i.e., the Ihara coefficients. Second, we generalize the definition of the Ihara coefficients to edge-weighted graphs. For an unweighted graph, the Ihara zeta function is the reciprocal of a quasi characteristic polynomial of the adjacency matrix of the associated oriented line graph. Since the Ihara zeta function has poles that give rise to infinities, the most convenient numerically stable representation is to work with the coefficients of the quasi characteristic polynomial. Moreover, the polynomial coefficients are invariant to vertex order permutations and also convey information concerning the cycle structure of the graph. To generalize the representation to edge-weighted graphs, we make use of the reduced Bartholdi zeta function. We prove that the computation of the Ihara coefficients for unweighted graphs is a special case of our proposed method for unit edge weights. We also present a spectral analysis of the Ihara coefficients and indicate their advantages over other graph spectral methods. We apply the proposed graph characterization method to capturing graph-class structure and clustering graphs. Experimental results reveal that the Ihara coefficients are more effective than methods based on Laplacian spectra.
Absolute position total internal reflection microscopy with an optical tweezer
Liu, Lulu; Woolf, Alexander; Rodriguez, Alejandro W.; Capasso, Federico
2014-01-01
A noninvasive, in situ calibration method for total internal reflection microscopy (TIRM) based on optical tweezing is presented, which greatly expands the capabilities of this technique. We show that by making only simple modifications to the basic TIRM sensing setup and procedure, a probe particle’s absolute position relative to a dielectric interface may be known with better than 10 nm precision out to a distance greater than 1 μm from the surface. This represents an approximate 10× improvement in error and 3× improvement in measurement range over conventional TIRM methods. The technique’s advantage is in the direct measurement of the probe particle’s scattering intensity vs. height profile in situ, rather than relying on assumptions, inexact system analogs, or detailed knowledge of system parameters for calibration. To demonstrate the improved versatility of the TIRM method in terms of tunability, precision, and range, we show our results for the hindered near-wall diffusion coefficient for a spherical dielectric particle. PMID:25512542
Using absolute gravimeter data to determine vertical gravity gradients
Robertson, D.S.
2001-01-01
The position versus time data from a free-fall absolute gravimeter can be used to estimate the vertical gravity gradient in addition to the gravity value itself. Hipkin has reported success in estimating the vertical gradient value using a data set of unusually good quality. This paper explores techniques that may be applicable to a broader class of data that may be contaminated with "system response" errors of larger magnitude than were evident in the data used by Hipkin. This system response function is usually modelled as a sum of exponentially decaying sinusoidal components. The technique employed here involves combining the x0, v0 and g parameters from all the drops made during a site occupation into a single least-squares solution, and including the value of the vertical gradient and the coefficients of system response function in the same solution. The resulting non-linear equations must be solved iteratively and convergence presents some difficulties. Sparse matrix techniques are used to make the least-squares problem computationally tractable.
THE ABSOLUTE MAGNITUDES OF RED HORIZONTAL BRANCH STARS IN THE ugriz SYSTEM
Chen, Y. Q.; Zhao, G.; Zhao, J. K.
2009-09-10
Based on photometric data of the central parts of eight globular clusters and one open cluster presented by An and his collaborators, we select red horizontal branch (RHB) stars in the (g - r){sub 0}-g {sub 0} diagram and make a statistical study of the distributions of their colors and absolute magnitudes in the SDSS ugriz system. Meanwhile, absolute magnitudes in the Johnson VRI system are calculated through the translation formulae between gri and VRI in the literature. The calibrations of absolute magnitude as functions of metallicity and age are established by linear regressions of the data. It is found that metallicity coefficients in these calibrations decrease, while age coefficients increase, from the blue u filter to the red z filter. The calibration of M{sub i} = 0.06[Fe/H] + 0.040t + 0.03 has the smallest scatter of 0.04 mag, and thus i is the best filter in the ugriz system when RHB stars are used for distance indicators. The comparison of the M{sub I} calibration from our data with that from red clump stars indicates that the previous suggestion that the I filter is better than the V filter in distance determination may not be true because of its significant dependence on age.
ERIC Educational Resources Information Center
Moore, Don A.; Klein, William M. P.
2008-01-01
Which matters more--beliefs about absolute ability or ability relative to others? This study set out to compare the effects of such beliefs on satisfaction with performance, self-evaluations, and bets on future performance. In Experiment 1, undergraduate participants were told they had answered 20% correct, 80% correct, or were not given their…
Absolute calibration of ultraviolet filter photometry
NASA Technical Reports Server (NTRS)
Bless, R. C.; Fairchild, T.; Code, A. D.
1972-01-01
The essential features of the calibration procedure can be divided into three parts. First, the shape of the bandpass of each photometer was determined by measuring the transmissions of the individual optical components and also by measuring the response of the photometer as a whole. Secondly, each photometer was placed in the essentially-collimated synchrotron radiation bundle maintained at a constant intensity level, and the output signal was determined from about 100 points on the objective. Finally, two or three points on the objective were illuminated by synchrotron radiation at several different intensity levels covering the dynamic range of the photometers. The output signals were placed on an absolute basis by the electron counting technique described earlier.
Absolute measurements of fast neutrons using yttrium
Roshan, M. V.; Springham, S. V.; Rawat, R. S.; Lee, P.; Krishnan, M.
2010-08-15
Yttrium is presented as an absolute neutron detector for pulsed neutron sources. It has high sensitivity for detecting fast neutrons. Yttrium has the property of generating a monoenergetic secondary radiation in the form of a 909 keV gamma-ray caused by inelastic neutron interaction. It was calibrated numerically using MCNPX and does not need periodic recalibration. The total yttrium efficiency for detecting 2.45 MeV neutrons was determined to be f{sub n}{approx}4.1x10{sup -4} with an uncertainty of about 0.27%. The yttrium detector was employed in the NX2 plasma focus experiments and showed the neutron yield of the order of 10{sup 8} neutrons per discharge.
Absolute geostrophic currents in global tropical oceans
NASA Astrophysics Data System (ADS)
Yang, Lina; Yuan, Dongliang
2016-11-01
A set of absolute geostrophic current (AGC) data for the period January 2004 to December 2012 are calculated using the P-vector method based on monthly gridded Argo profiles in the world tropical oceans. The AGCs agree well with altimeter geostrophic currents, Ocean Surface Current Analysis-Real time currents, and moored current-meter measurements at 10-m depth, based on which the classical Sverdrup circulation theory is evaluated. Calculations have shown that errors of wind stress calculation, AGC transport, and depth ranges of vertical integration cannot explain non-Sverdrup transport, which is mainly in the subtropical western ocean basins and equatorial currents near the Equator in each ocean basin (except the North Indian Ocean, where the circulation is dominated by monsoons). The identified non-Sverdrup transport is thereby robust and attributed to the joint effect of baroclinicity and relief of the bottom (JEBAR) and mesoscale eddy nonlinearity.
Absolute Measurement of Electron Cloud Density
Covo, M K; Molvik, A W; Cohen, R H; Friedman, A; Seidl, P A; Logan, G; Bieniosek, F; Baca, D; Vay, J; Orlando, E; Vujic, J L
2007-06-21
Beam interaction with background gas and walls produces ubiquitous clouds of stray electrons that frequently limit the performance of particle accelerator and storage rings. Counterintuitively we obtained the electron cloud accumulation by measuring the expelled ions that are originated from the beam-background gas interaction, rather than by measuring electrons that reach the walls. The kinetic ion energy measured with a retarding field analyzer (RFA) maps the depressed beam space-charge potential and provides the dynamic electron cloud density. Clearing electrode current measurements give the static electron cloud background that complements and corroborates with the RFA measurements, providing an absolute measurement of electron cloud density during a 5 {micro}s duration beam pulse in a drift region of the magnetic transport section of the High-Current Experiment (HCX) at LBNL.
Micron Accurate Absolute Ranging System: Range Extension
NASA Technical Reports Server (NTRS)
Smalley, Larry L.; Smith, Kely L.
1999-01-01
The purpose of this research is to investigate Fresnel diffraction as a means of obtaining absolute distance measurements with micron or greater accuracy. It is believed that such a system would prove useful to the Next Generation Space Telescope (NGST) as a non-intrusive, non-contact measuring system for use with secondary concentrator station-keeping systems. The present research attempts to validate past experiments and develop ways to apply the phenomena of Fresnel diffraction to micron accurate measurement. This report discusses past research on the phenomena, and the basis of the use Fresnel diffraction distance metrology. The apparatus used in the recent investigations, experimental procedures used, preliminary results are discussed in detail. Continued research and equipment requirements on the extension of the effective range of the Fresnel diffraction systems is also described.
Absolute calibration of remote sensing instruments
NASA Astrophysics Data System (ADS)
Biggar, S. F.; Bruegge, C. J.; Capron, B. A.; Castle, K. R.; Dinguirard, M. C.; Holm, R. G.; Lingg, L. J.; Mao, Y.; Palmer, J. M.; Phillips, A. L.
1985-12-01
Source-based and detector-based methods for the absolute radiometric calibration of a broadband field radiometer are described. Using such a radiometer, calibrated by both methods, the calibration of the integrating sphere used in the preflight calibration of the Thematic Mapper was redetermined. The results are presented. The in-flight calibration of space remote sensing instruments is discussed. A method which uses the results of ground-based reflectance and atmospheric measurements as input to a radiative transfer code to predict the radiance at the instrument is described. A calibrated, helicopter-mounted radiometer is used to determine the radiance levels at intermediate altitudes to check the code predictions. Results of such measurements for the calibration of the Thematic Mapper on Landsat 5 and an analysis that shows the value of such measurements are described.
Absolute radiometric calibration of the Thematic Mapper
NASA Technical Reports Server (NTRS)
Slater, P. N.; Biggar, S. F.; Holm, R. G.; Jackson, R. D.; Mao, Y.
1986-01-01
Calibration data for the solar reflective bands of the Landsat-5 TM obtained from five in-flight absolute radiometric calibrations from July 1984-November 1985 at White Sands, New Mexico are presented and analyzed. Ground reflectance and atmospheric data were utilized to predict the spectral radiance at the entrance pupil of the TM and the average number of digital counts in each TM band. The calibration of each of the TM solar reflective bands was calculated in terms of average digital counts/unit spectral radiance for each band. It is observed that for the 12 reflectance-based measurements the rms variation from the means as a percentage of the mean is + or - 1.9 percent; for the 11 measurements in the IR bands, it is + or - 3.4 percent; and the rms variation for all 23 measurements is + or - 2.8 percent.
MAGSAT: Vector magnetometer absolute sensor alignment determination
NASA Technical Reports Server (NTRS)
Acuna, M. H.
1981-01-01
A procedure is described for accurately determining the absolute alignment of the magnetic axes of a triaxial magnetometer sensor with respect to an external, fixed, reference coordinate system. The method does not require that the magnetic field vector orientation, as generated by a triaxial calibration coil system, be known to better than a few degrees from its true position, and minimizes the number of positions through which a sensor assembly must be rotated to obtain a solution. Computer simulations show that accuracies of better than 0.4 seconds of arc can be achieved under typical test conditions associated with existing magnetic test facilities. The basic approach is similar in nature to that presented by McPherron and Snare (1978) except that only three sensor positions are required and the system of equations to be solved is considerably simplified. Applications of the method to the case of the MAGSAT Vector Magnetometer are presented and the problems encountered discussed.
THE DIFFUSION COEFFICIENT OF CRYSTALLINE TRYPSIN
Scherp, Henry W.
1933-01-01
The diffusion coefficient of crystalline trypsin in 0.5 saturated magnesium sulfate at 5°C. is 0.020 ±0.001 cm.2 per day, corresponding to a molecular radius of 2.6 x 10–7 cm. The rate of diffusion of the proteolytic activity is the same as that of the protein nitrogen, indicating that these two properties are held together in chemical combination and not in the form of an adsorption complex. PMID:19872740
ABSOLUTE PROPERTIES OF THE ECLIPSING BINARY STAR V335 SERPENTIS
Lacy, Claud H. Sandberg; Fekel, Francis C.; Claret, Antonio E-mail: fekel@evans.tsuniv.edu
2012-08-15
V335 Ser is now known to be an eccentric double-lined A1+A3 binary star with fairly deep (0.5 mag) partial eclipses. Previous studies of the system are improved with 7456 differential photometric observations from the URSA WebScope and 5666 from the NFO WebScope, and 67 high-resolution spectroscopic observations from the Tennessee State University 2 m automatic spectroscopic telescope. From dates of minima, the apsidal period is about 880 years. Accurate (better than 2%) masses and radii are determined from analysis of the two new light curves and the radial velocity curve. Theoretical models match the absolute properties of the stars at an age of about 380 Myr, though the age agreement for the two components is poor. Tidal theory correctly confirms that the orbit should still be eccentric, but we find that standard tidal theory is unable to match the observed asynchronous rotation rates of the components' surface layers.
Absolute properties of the eclipsing binary star IM Persei
Lacy, Claud H. Sandberg; Torres, Guillermo; Fekel, Francis C.; Muterspaugh, Matthew W.; Southworth, John E-mail: gtorres@cfa.harvard.edu E-mail: matthew1@coe.tsuniv.edu
2015-01-01
IM Per is a detached A7 eccentric eclipsing binary star. We have obtained extensive measurements of the light curve (28,225 differential magnitude observations) and radial velocity curve (81 spectroscopic observations) which allow us to fit orbits and determine the absolute properties of the components very accurately: masses of 1.7831 ± 0.0094 and 1.7741 ± 0.0097 solar masses, and radii of 2.409 ± 0.018 and 2.366 ± 0.017 solar radii. The orbital period is 2.25422694(15) days and the eccentricity is 0.0473(26). A faint third component was detected in the analysis of the light curves, and also directly observed in the spectra. The observed rate of apsidal motion is consistent with theory (U = 151.4 ± 8.4 year). We determine a distance to the system of 566 ± 46 pc.
Cytoplasmic hydrogen ion diffusion coefficient.
al-Baldawi, N F; Abercrombie, R F
1992-01-01
The apparent cytoplasmic proton diffusion coefficient was measured using pH electrodes and samples of cytoplasm extracted from the giant neuron of a marine invertebrate. By suddenly changing the pH at one surface of the sample and recording the relaxation of pH within the sample, an apparent diffusion coefficient of 1.4 +/- 0.5 x 10(-6) cm2/s (N = 7) was measured in the acidic or neutral range of pH (6.0-7.2). This value is approximately 5x lower than the diffusion coefficient of the mobile pH buffers (approximately 8 x 10(-6) cm2/s) and approximately 68x lower than the diffusion coefficient of the hydronium ion (93 x 10(-6) cm2/s). A mobile pH buffer (approximately 15% of the buffering power) and an immobile buffer (approximately 85% of the buffering power) could quantitatively account for the results at acidic or neutral pH. At alkaline pH (8.2-8.6), the apparent proton diffusion coefficient increased to 4.1 +/- 0.8 x 10(-6) cm2/s (N = 7). This larger diffusion coefficient at alkaline pH could be explained quantitatively by the enhanced buffering power of the mobile amino acids. Under the conditions of these experiments, it is unlikely that hydroxide movement influences the apparent hydrogen ion diffusion coefficient. PMID:1617134
ERIC Educational Resources Information Center
Halsall, H. B.; Wermeling, J. R.
1982-01-01
Describes an experiment using a high-speed preparative centrifuge and calculator to demonstrate effects of the frictional coefficient of a macromolecule on its rate of transport in a force field and to estimate molecular weight of the macromolecule using an empirical relationship. Background information, procedures, and discussion of results are…
Computing confidence intervals for standardized regression coefficients.
Jones, Jeff A; Waller, Niels G
2013-12-01
With fixed predictors, the standard method (Cohen, Cohen, West, & Aiken, 2003, p. 86; Harris, 2001, p. 80; Hays, 1994, p. 709) for computing confidence intervals (CIs) for standardized regression coefficients fails to account for the sampling variability of the criterion standard deviation. With random predictors, this method also fails to account for the sampling variability of the predictor standard deviations. Nevertheless, under some conditions the standard method will produce CIs with accurate coverage rates. To delineate these conditions, we used a Monte Carlo simulation to compute empirical CI coverage rates in samples drawn from 36 populations with a wide range of data characteristics. We also computed the empirical CI coverage rates for 4 alternative methods that have been discussed in the literature: noncentrality interval estimation, the delta method, the percentile bootstrap, and the bias-corrected and accelerated bootstrap. Our results showed that for many data-parameter configurations--for example, sample size, predictor correlations, coefficient of determination (R²), orientation of β with respect to the eigenvectors of the predictor correlation matrix, RX--the standard method produced coverage rates that were close to their expected values. However, when population R² was large and when β approached the last eigenvector of RX, then the standard method coverage rates were frequently below the nominal rate (sometimes by a considerable amount). In these conditions, the delta method and the 2 bootstrap procedures were consistently accurate. Results using noncentrality interval estimation were inconsistent. In light of these findings, we recommend that researchers use the delta method to evaluate the sampling variability of standardized regression coefficients.
Reliability and validity of quantifying absolute muscle hardness using ultrasound elastography.
Chino, Kentaro; Akagi, Ryota; Dohi, Michiko; Fukashiro, Senshi; Takahashi, Hideyuki
2012-01-01
Muscle hardness is a mechanical property that represents transverse muscle stiffness. A quantitative method that uses ultrasound elastography for quantifying absolute human muscle hardness has been previously devised; however, its reliability and validity have not been completely verified. This study aimed to verify the reliability and validity of this quantitative method. The Young's moduli of seven tissue-mimicking materials (in vitro; Young's modulus range, 20-80 kPa; increments of 10 kPa) and the human medial gastrocnemius muscle (in vivo) were quantified using ultrasound elastography. On the basis of the strain/Young's modulus ratio of two reference materials, one hard and one soft (Young's moduli of 7 and 30 kPa, respectively), the Young's moduli of the tissue-mimicking materials and medial gastrocnemius muscle were calculated. The intra- and inter-investigator reliability of the method was confirmed on the basis of acceptably low coefficient of variations (≤6.9%) and substantially high intraclass correlation coefficients (≥0.77) obtained from all measurements. The correlation coefficient between the Young's moduli of the tissue-mimicking materials obtained using a mechanical method and ultrasound elastography was 0.996, which was equivalent to values previously obtained using magnetic resonance elastography. The Young's moduli of the medial gastrocnemius muscle obtained using ultrasound elastography were within the range of values previously obtained using magnetic resonance elastography. The reliability and validity of the quantitative method for measuring absolute muscle hardness using ultrasound elastography were thus verified.
Fuel Temperature Coefficient of Reactivity
Loewe, W.E.
2001-07-31
A method for measuring the fuel temperature coefficient of reactivity in a heterogeneous nuclear reactor is presented. The method, which is used during normal operation, requires that calibrated control rods be oscillated in a special way at a high reactor power level. The value of the fuel temperature coefficient of reactivity is found from the measured flux responses to these oscillations. Application of the method in a Savannah River reactor charged with natural uranium is discussed.
Wrong Signs in Regression Coefficients
NASA Technical Reports Server (NTRS)
McGee, Holly
1999-01-01
When using parametric cost estimation, it is important to note the possibility of the regression coefficients having the wrong sign. A wrong sign is defined as a sign on the regression coefficient opposite to the researcher's intuition and experience. Some possible causes for the wrong sign discussed in this paper are a small range of x's, leverage points, missing variables, multicollinearity, and computational error. Additionally, techniques for determining the cause of the wrong sign are given.
Diffusion Coefficients in White Dwarfs
NASA Astrophysics Data System (ADS)
Saumon, D.; Starrett, C. E.; Daligault, J.
2015-06-01
Models of diffusion in white dwarfs universally rely on the coefficients calculated by Paquette et al. (1986). We present new calculations of diffusion coefficients based on an advanced microscopic theory of dense plasmas and a numerical simulation approach that intrinsically accounts for multiple collisions. Our method is validated against a state-of-the-art method and we present results for the diffusion of carbon ions in a helium plasma.
Bayes and Empirical Bayes Shrinkage Estimation of Regression Coefficients: A Cross-Validation Study.
ERIC Educational Resources Information Center
Nebebe, Fassil; Stroud, T. W. F.
1988-01-01
Bayesian and empirical Bayes approaches to shrinkage estimation of regression coefficients and uses of these in prediction (i.e., analyzing intelligence test data of children with learning problems) are investigated. The two methods are consistently better at predicting response variables than are either least squares or least absolute deviations.…
Universal organic solvent-water partition coefficient model
Torrens
2000-03-01
A method that permits a semiquantitative estimate of the partitioning of any solute between any two media is presented. As an example, the organic solvent-water partition coefficients P are calculated. Program GSCAP is written as a version of Pascal's SCAP program. The only needed parameters are the dielectric constant and molecular volume of the organic solvent. The log P results are compared with the Pomona database. The average absolute deviation is 1.48 log units and the standard deviation is 1.66 log units.
Castro-Palacio, Juan Carlos; Bemish, Raymond J.; Meuwly, Markus
2015-03-07
The O({sup 3}P) + NO({sup 2}Π) → O{sub 2}(X{sup 3}Σ{sub g}{sup −}) + N({sup 4}S) reaction is among the N- and O- involving reactions that dominate the energetics of the reactive air flow around spacecraft during hypersonic atmospheric re-entry. In this regime, the temperature in the bow shock typically ranges from 1000 to 20 000 K. The forward and reverse rate coefficients for this reaction derived directly from trajectory calculations over this range of temperature are reported in this letter. Results compare well with the established equilibrium constants for the same reaction from thermodynamic quantities derived from spectroscopy in the gas phase which paves the way for large-scale in silico investigations of equilibrium rates under extreme conditions.
Personal dose-equivalent conversion coefficients for 1252 radionuclides.
Otto, Thomas
2016-01-01
Dose conversion coefficients for radionuclides are useful for routine calculations in radiation protection in industry, medicine and research. They give a simple and often sufficient estimate of dose rates during production, handling and storage of radionuclide sources, based solely on the source's activity. The latest compilation of such conversion coefficients dates from 20 y ago, based on nuclear decay data published 30 y ago. The present publication provides radionuclide-specific conversion coefficients to personal dose based on the most recent evaluations of nuclear decay data for 1252 radionuclides and fluence-to-dose-equivalent conversion coefficients for monoenergetic radiations. It contains previously unknown conversion coefficients for >400 nuclides and corrects those conversion coefficients that were based on erroneous decay schemes. For the first time, estimates for the protection quantity Hp(3) are included.
Converting Sabine absorption coefficients to random incidence absorption coefficients.
Jeong, Cheol-Ho
2013-06-01
Absorption coefficients measured by the chamber method are referred to as Sabine absorption coefficients, which sometimes exceed unity due to the finite size of a sample and non-uniform intensity in the reverberation chambers under test. In this study, conversion methods from Sabine absorption coefficients to random incidence absorption coefficients are proposed. The overestimations of the Sabine absorption coefficient are investigated theoretically based on Miki's model for porous absorbers backed by a rigid wall or an air cavity, resulting in conversion factors. Additionally, three optimizations are suggested: An optimization method for the surface impedances for locally reacting absorbers, the flow resistivity for extendedly reacting absorbers, and the flow resistance for fabrics. With four porous type absorbers, the conversion methods are validated. For absorbers backed by a rigid wall, the surface impedance optimization produces the best results, while the flow resistivity optimization also yields reasonable results. The flow resistivity and flow resistance optimization for extendedly reacting absorbers are also found to be successful. However, the theoretical conversion factors based on Miki's model do not guarantee reliable estimations, particularly at frequencies below 250 Hz and beyond 2500 Hz.
Primacy and frequency effects in absolute judgments of visual velocity.
Sokolov, A; Pavlova, M; Ehrenstein, W H
2000-07-01
In absolute judgment tasks, identical stimuli are rated higher (or lower) when presented in a series of more frequent small (or large) stimuli. Using visual stimuli differing in velocity, we show that this conventional frequency effect is largely modulated by the primacy effect--that is, by the stimuli occurring on the early trials of a run. In Experiment 1, a frequency-like primacy effect was obtained with equal-frequent velocities. Identical velocities were rated faster when mainly slow rather than fast ones occurred on initial trials. In Experiment 2, we contrasted the frequency effect and the primacy effect: In runs with frequent slow velocities, mainly fast ones occurred earlier, whereas in runs with infrequent slow velocities, mainly slow ones did so. Lack of differences of ratings in the two conditions suggests that the two effects canceled each other. In Experiment 3, when mainly frequent velocities occurred earlier, the conventional frequency effect was obtained. We conclude that the conventional frequency effect represents a combination of the primacy effect and the pure frequency effect.
NASA Technical Reports Server (NTRS)
Liebert, Curt H.; Ehlers, Robert C.
1961-01-01
Local experimental heat-transfer coefficients were measured in the chamber and throat of a 2400-pound-thrust ammonia-oxygen rocket engine with a nominal chamber pressure of 600 pounds per square inch absolute. Three injector configurations were used. The rocket engine was run over a range of oxidant-fuel ratio and chamber pressure. The injector that achieved the best performance also produced the highest rates of heat flux at design conditions. The heat-transfer data from the best-performing injector agreed well with the simplified equation developed by Bartz at the throat region. A large spread of data was observed for the chamber. This spread was attributed generally to the variations of combustion processes. The spread was least evident, however, with the best-performing injector.
On the absolute alignment of GONG images
NASA Astrophysics Data System (ADS)
Toner, C. G.
2001-01-01
In order to combine data from the six instruments in the GONG network the alignment of all of the images must be known to a fairly high precision (~0°.1 for GONG Classic and ~0°.01 for GONG+). The relative orientation is obtained using the angular cross-correlation method described by (Toner & Harvey, 1998). To obtain the absolute orientation the Project periodically records a day of drift scans, where the image of the Sun is allowed to drift across the CCD repeatedly throughout the day. These data are then analyzed to deduce the direction of Terrestrial East-West as a function of hour angle (i.e., time) for that instrument. The transit of Mercury on Nov. 15, 1999, which was recorded by three of the GONG instruments, provided an independent check on the current alignment procedures. Here we present a comparison of the alignment of GONG images as deduced from both drift scans and the Mercury transit for two GONG sites: Tucson (GONG+ camera) and Mauna Loa (GONG Classic camera). The agreement is within ~0°.01 for both cameras, however, the scatter is substantially larger for GONG Classic: ~0°.03 compared to ~0°.01 for GONG+.
Climate Absolute Radiance and Refractivity Observatory (CLARREO)
NASA Technical Reports Server (NTRS)
Leckey, John P.
2015-01-01
The Climate Absolute Radiance and Refractivity Observatory (CLARREO) is a mission, led and developed by NASA, that will measure a variety of climate variables with an unprecedented accuracy to quantify and attribute climate change. CLARREO consists of three separate instruments: an infrared (IR) spectrometer, a reflected solar (RS) spectrometer, and a radio occultation (RO) instrument. The mission will contain orbiting radiometers with sufficient accuracy, including on orbit verification, to calibrate other space-based instrumentation, increasing their respective accuracy by as much as an order of magnitude. The IR spectrometer is a Fourier Transform spectrometer (FTS) working in the 5 to 50 microns wavelength region with a goal of 0.1 K (k = 3) accuracy. The FTS will achieve this accuracy using phase change cells to verify thermistor accuracy and heated halos to verify blackbody emissivity, both on orbit. The RS spectrometer will measure the reflectance of the atmosphere in the 0.32 to 2.3 microns wavelength region with an accuracy of 0.3% (k = 2). The status of the instrumentation packages and potential mission options will be presented.
Gyrokinetic Statistical Absolute Equilibrium and Turbulence
Jian-Zhou Zhu and Gregory W. Hammett
2011-01-10
A paradigm based on the absolute equilibrium of Galerkin-truncated inviscid systems to aid in understanding turbulence [T.-D. Lee, "On some statistical properties of hydrodynamical and magnetohydrodynamical fields," Q. Appl. Math. 10, 69 (1952)] is taken to study gyrokinetic plasma turbulence: A finite set of Fourier modes of the collisionless gyrokinetic equations are kept and the statistical equilibria are calculated; possible implications for plasma turbulence in various situations are discussed. For the case of two spatial and one velocity dimension, in the calculation with discretization also of velocity v with N grid points (where N + 1 quantities are conserved, corresponding to an energy invariant and N entropy-related invariants), the negative temperature states, corresponding to the condensation of the generalized energy into the lowest modes, are found. This indicates a generic feature of inverse energy cascade. Comparisons are made with some classical results, such as those of Charney-Hasegawa-Mima in the cold-ion limit. There is a universal shape for statistical equilibrium of gyrokinetics in three spatial and two velocity dimensions with just one conserved quantity. Possible physical relevance to turbulence, such as ITG zonal flows, and to a critical balance hypothesis are also discussed.
Swarm Absolute Scalar Magnetometers first in-orbit results
NASA Astrophysics Data System (ADS)
Fratter, Isabelle; Léger, Jean-Michel; Bertrand, François; Jager, Thomas; Hulot, Gauthier; Brocco, Laura; Vigneron, Pierre
2016-04-01
The ESA Swarm mission will provide the best ever survey of the Earth's magnetic field and its temporal evolution. This will be achieved by a constellation of three identical satellites, launched together on the 22nd of November 2013. In order to observe the magnetic field thoroughly, each satellite carries two magnetometers: a Vector Field Magnetometer (VFM) coupled with a star tracker camera, to measure the direction of the magnetic field in space, and an Absolute Scalar Magnetometer (ASM), to measure its intensity. The ASM is the French contribution to the Swarm mission. This new generation instrument was designed by CEA-Leti and developed in close partnership with CNES, with scientific support from IPGP. Its operating principle is based on the atomic spectroscopy of the helium 4 metastable state. It makes use of the Zeeman's effect to transduce the magnetic field into a frequency, the signal being amplified by optical pumping. The primary role of the ASM is to provide absolute measurements of the magnetic field's strength at 1 Hz, for the in-flight calibration of the VFM. As the Swarm magnetic reference, the ASM scalar performance is crucial for the mission's success. Thanks to its innovative design, the ASM offers the best precision, resolution and absolute accuracy ever attained in space, with similar performance all along the orbit. In addition, thanks to an original architecture, the ASM implements on an experimental basis a capacity for providing simultaneously vector measurements at 1 Hz. This new feature makes it the first instrument capable of delivering both scalar and vector measurements simultaneously at the same point. Swarm offers a unique opportunity to validate the ASM vector data in orbit by comparison with the VFM's. Furthermore, the ASM can provide scalar data at a much higher sampling rate, when run in "burst" mode at 250 Hz, with a 100 Hz measurement bandwidth. An analysis of the spectral content of the magnetic field above 1 Hz becomes thus