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Sample records for absolute diffusion rates

  1. 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

  2. Absolute Rate Theories of Epigenetic Stability

    NASA Astrophysics Data System (ADS)

    Walczak, Aleksandra M.; Onuchic, Jose N.; Wolynes, Peter G.

    2006-03-01

    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.

  3. Absolute calibration for complex-geometry biomedical diffuse optical spectroscopy

    NASA Astrophysics Data System (ADS)

    Mastanduno, Michael A.; Jiang, Shudong; El-Ghussein, Fadi; diFlorio-Alexander, Roberta; Pogue, Brian W.; Paulsen, Keith D.

    2013-03-01

    We have presented methodology to calibrate data in NIRS/MRI imaging versus an absolute reference phantom and results in both phantoms and healthy volunteers. This method directly calibrates data to a diffusion-based model, takes advantage of patient specific geometry from MRI prior information, and generates an initial guess without the need for a large data set. This method of calibration allows for more accurate quantification of total hemoglobin, oxygen saturation, water content, scattering, and lipid concentration as compared with other, slope-based methods. We found the main source of error in the method to be derived from incorrect assignment of reference phantom optical properties rather than initial guess in reconstruction. We also present examples of phantom and breast images from a combined frequency domain and continuous wave MRI-coupled NIRS system. We were able to recover phantom data within 10% of expected contrast and within 10% of the actual value using this method and compare these results with slope-based calibration methods. Finally, we were able to use this technique to calibrate and reconstruct images from healthy volunteers. Representative images are shown and discussion is provided for comparison with existing literature. These methods work towards fully combining the synergistic attributes of MRI and NIRS for in-vivo imaging of breast cancer. Complete software and hardware integration in dual modality instruments is especially important due to the complexity of the technology and success will contribute to complex anatomical and molecular prognostic information that can be readily obtained in clinical use.

  4. Multidimensional reaction rate theory with anisotropic diffusion.

    PubMed

    Berezhkovskii, Alexander M; Szabo, Attila; Greives, Nicholas; Zhou, Huan-Xiang

    2014-11-28

    An analytical expression is derived for the rate constant that describes diffusive transitions between two deep wells of a multidimensional potential. The expression, in contrast to the Kramers-Langer formula for the rate constant, is valid even when the diffusion is highly anisotropic. Our approach is based on a variational principle for the reactive flux and uses a trial function for the splitting probability or commitor. The theoretical result is validated by Brownian dynamics simulations.

  5. Reaction weakening and emplacement of crystalline thrusts: Diffusion control on reaction rate and strain rate

    NASA Astrophysics Data System (ADS)

    O'Hara, Kieran

    2007-08-01

    In the southern Appalachians, the Blue Ridge-Piedmont crystalline thrust sheet was emplaced onto low-grade Late Precambrian and Paleozoic sedimentary rocks in the footwall along a basal detachment consisting of phyllosilicate-rich mylonites (phyllonites). The phyllonites developed first by mechanical breakdown of feldspar followed by chemical breakdown to white mica in the presence of a pore fluid. Diffusion of solute in the pore fluid is the rate limiting step in controlling reaction rate and also the strain rate. Assuming solute diffusion follows the Stokes-Einstein equation, the shear strain rate is given by ⅆγ/ⅆt=2ωkT/5ηrx for shear stress ≥20 MPa, where n is a constant, ω is a geometric factor, k is Boltzmann's constant, T is absolute temperature, η is water viscosity, r is the atomic radius of the diffusing species, and x is the diffusion distance. A bulk diffusion coefficient in the range of ˜10 -10 to 10 -12 m 2/s over distances of 10-100 m results in strain rates of 10 -14 to 10 -13 s -1 in the temperature range 200-400 °C. It is concluded that greenschist grade crystalline thrust sheets develop on pre-existing basement faults that become weak during reaction softening and localize into high strain phyllonite zones in which pore fluid diffusion controls reaction rate and strain rate.

  6. Apparent exchange rate mapping with diffusion MRI.

    PubMed

    Lasič, Samo; Nilsson, Markus; Lätt, Jimmy; Ståhlberg, Freddy; Topgaard, Daniel

    2011-08-01

    Water exchange through the cell membranes is an important feature of cells and tissues. The rate of exchange is determined by factors such as membrane lipid composition and organization, as well as the type and activity of aquaporins. A method for noninvasively estimating the rate of water exchange would be useful for characterizing pathological conditions, e.g., tumors, multiple sclerosis, and ischemic stroke, expected to be associated with a change of the membrane barrier properties. This study describes the filter exchange imaging method for determining the rate of water exchange between sites having different apparent diffusion coefficients. The method is based on the filter-exchange pulsed gradient spin-echo NMR spectroscopy experiment, which is here modified to be compatible with the constraints of clinical MR scanners. The data is analyzed using a model-free approach yielding maps of the apparent exchange rate, here being introduced in analogy with the concept of the apparent diffusion coefficient. Proof-of-principle experiments are performed on microimaging and whole-body clinical scanners using yeast suspension phantoms. The limitations and appropriate experimental conditions are examined. The results demonstrate that filter exchange imaging is a fast and reliable method for characterizing exchange, and that it has the potential to become a powerful diagnostic tool.

  7. Noninvasive optical quantification of absolute blood flow, blood oxygenation, and oxygen consumption rate in exercising skeletal muscle

    PubMed Central

    Gurley, Katelyn; Shang, Yu

    2012-01-01

    Abstract. 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 (V˙O2) in exercising skeletal muscle. Healthy subjects (n=9) performed a handgrip exercise to increase BF and V˙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 (rV˙O2). The rBF and rV˙O2 signals were calibrated with absolute baseline BF and V˙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. PMID:22894482

  8. Noninvasive optical quantification of absolute blood flow, blood oxygenation, and oxygen consumption rate in exercising skeletal muscle

    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.

  9. 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…

  10. Leak rate estimation of a resistive plate chamber gap by monitoring absolute pressure

    NASA Astrophysics Data System (ADS)

    Mondal, S.; Datar, V. M.; Kalmani, S. D.; Majumder, G.; Mondal, N. K.; Satyanarayana, B.

    2016-11-01

    The differential pressure of a conventional manometer is highly dependent on the atmospheric pressure. The measurements with a manometer for an extended time period show a large variation due to solar atmospheric tides. However, the measurements of absolute pressure, both outside and inside of a resistive plate chamber (RPC), are independent of each other. By monitoring the absolute pressures, both outside and inside of a RPC, along with the temperature, its leakage rate can be estimated. During the test period, the supporting button spacers inside a RPC may get detached due to some manufacturing defect. This effect can be detected clearly by observing the sudden fall of pressure inside the chamber.

  11. 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.

  12. 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.

  13. 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.

  14. Spatially resolved absolute diffuse reflectance measurements for noninvasive determination of the optical scattering and absorption coefficients of biological tissue

    NASA Astrophysics Data System (ADS)

    Kienle, Alwin; Lilge, Lothar; Patterson, Michael S.; Hibst, Raimund; Steiner, Rudolf; Wilson, Brian C.

    1996-05-01

    The absorption and transport scattering coefficients of biological tissues determine the radial dependence of the diffuse reflectance that is due to a point source. A system is described for making remote measurements of spatially resolved absolute diffuse reflectance and hence noninvasive, noncontact estimates of the tissue optical properties. The system incorporated a laser source and a CCD camera. Deflection of the incident beam into the camera allowed characterization of the source for absolute reflectance measurements. It is shown that an often used solution of the diffusion equation cannot be applied for these measurements. Instead, a neural network, trained on the results of Monte Carlo simulations, was used to estimate the absorption and scattering coefficients from the reflectance data. Tests on tissue-simulating phantoms with transport scattering coefficients between 0.5 and 2.0 mm-1 and absorption coefficients between 0.002 and 0.1 mm -1 showed the rms errors of this technique to be 2.6% for the transport scattering coefficient and 14% for the absorption coefficients. The optical properties of bovine muscle, adipose, and liver tissue, as well as chicken muscle (breast), were also measured ex vivo at 633 and 751 nm. For muscle tissue it was found that the Monte Carlo simulation did not agree with experimental measurements of reflectance at distances less than 2 mm from the incident beam. Carlo, neural network.

  15. Absolute rate constant for the reaction of Cl(/sup 2/P) with CINO

    SciTech Connect

    Nesbitt, F.L.; Nava, D.F.; Payne, W.A.; Stief, L.J.

    1987-09-24

    The room temperature rate constant for the reaction Cl + CINO yields Cl/sub 2/ + NO has been measured by the method of discharge flow mass spectrometry. The rate constant was determined from the decay of CINO in the presence of an excess of Cl atoms at a total pressure of 1 Torr. The rate constant obtained was (7.6 +/- 0.8) X 10/sup -11/ cm/sup 3/ s/sup -1/. This result is compared with previous determinations, the values of which ranged by more than an order of magnitude and all of which depended on knowledge of the absolute concentration of CINO. The authors suggest that the lack of agreement is attributable principally to uncertainties in (CINO) resulting from absorption of this reactive species on glass and metal surfaces. Our result does not depend directly on (CINO) and supports the highest values published for this rate constant.

  16. Tomographic imaging of absolute optical absorption coefficient in turbid media using combined photoacoustic and diffusing light measurements.

    PubMed

    Yin, Lu; Wang, Qiang; Zhang, Qizhi; Jiang, Huabei

    2007-09-01

    We present a new method that can provide high resolution images of absolute optical absorption coefficient in heterogeneous turbid media. In this method, acoustic measurements in conventional photoacoustic tomography are combined with diffusing light measurements to separate the product of absorption coefficient and optical fluence or photon density. We validate this method using a series of tissuelike phantom experiments. The experimental results show that targets as small as 0.5 mm in diameter with optical absorption contrasts as low as 1.5 relative to a 50 mm diameter scattering background medium can be clearly detected.

  17. Absolute determination of the Na22(p,γ)Mg23 reaction rate in novae

    NASA Astrophysics Data System (ADS)

    Sallaska, A. L.; Wrede, C.; García, A.; Storm, D. W.; Brown, T. A. D.; Ruiz, C.; Snover, K. A.; Ottewell, D. F.; Buchmann, L.; Vockenhuber, C.; Hutcheon, D. A.; Caggiano, J. A.; José, J.

    2011-03-01

    Gamma-ray telescopes in orbit around the earth are searching for evidence of the elusive radionuclide Na22 produced in novae. Previously published uncertainties in the dominant destructive reaction, Na22(p,γ)Mg23, indicated new measurements in the proton energy range of 150 to 300 keV were needed to constrain predictions. We have measured the resonance strengths, energies, and branches directly and absolutely by using protons from the University of Washington accelerator with a specially designed beam line, which included beam rastering and cold vacuum protection of the Na22 implanted targets. The targets, fabricated at TRIUMF-ISAC, displayed minimal degradation over a ~20 C bombardment as a result of protective layers. We avoided the need to know the absolute stopping power, and hence the target composition, by extracting resonance strengths from excitation functions integrated over proton energy. Our measurements revealed that resonance strengths for Ep=213, 288, 454, and 610 keV are stronger by factors of 2.4-3.2 than previously reported. Upper limits have been placed on proposed resonances at 198, 209, and 232 keV. These substantially reduce the uncertainty in the reaction rate. We have re-evaluated the Na22(p,γ) reaction rate, and our measurements indicate the resonance at 213 keV makes the most significant contribution to Na22 destruction in novae. Hydrodynamic simulations including our rate indicate that the expected abundance of Na22 ejecta from a classical nova is reduced by factors between 1.5 and 2, depending on the mass of the white-dwarf star hosting the nova explosion.

  18. A simple reaction-rate model for turbulent diffusion flames

    NASA Technical Reports Server (NTRS)

    Bangert, L. H.

    1975-01-01

    A simple reaction rate model is proposed for turbulent diffusion flames in which the reaction rate is proportional to the turbulence mixing rate. The reaction rate is also dependent on the mean mass fraction and the mean square fluctuation of mass fraction of each reactant. Calculations are compared with experimental data and are generally successful in predicting the measured quantities.

  19. 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.

  20. Continuous monitoring of absolute cerebral blood flow by combining diffuse correlation spectroscopy and time-resolved near-infrared technology

    NASA Astrophysics Data System (ADS)

    Diop, Mamadou; Lee, Ting-Yim; St. Lawrence, Keith

    2011-02-01

    Continuous bedside monitoring of cerebral blood flow (CBF) in patients recovering from brain injury could improve the detection of impaired substrate delivery, which can exacerbate injury and worsen outcome. Diffuse correlation spectroscopy (DCS) provides the ability to monitor perfusion changes continuously, but it is difficult to quantify absolute blood flow - leading to uncertainties as to whether or not CBF has fallen to ischemic levels. To continuously measure CBF, we propose to calibrate DCS data using a single time-point, time-resolved near-infrared (TR-NIR) technique for measuring absolute CBF. Experiments were conducted on newborn piglets in which CBF was increased by raising the arterial tension of CO2 (40-62 mmHg) and decreased by carotid occlusion. For validation, values of CBF measured by TR-NIR were converted into blood flow changes and compared to CBF changes measured by DCS. A strong correlation between perfusion changes from the two techniques was revealed (slope = 0.98 and R2 = 0.96), suggesting that a single time-point CBF measurement by TR-NIR can be used to convert continuous DCS data into units of CBF (ml/100g/min).

  1. Anesthetic diffusion through lipid membranes depends on the protonation rate.

    PubMed

    Pérez-Isidoro, Rosendo; Sierra-Valdez, F J; Ruiz-Suárez, J C

    2014-12-18

    Hundreds of substances possess anesthetic action. However, despite decades of research and tests, a golden rule is required to reconcile the diverse hypothesis behind anesthesia. What makes an anesthetic to be local or general in the first place? The specific targets on proteins, the solubility in lipids, the diffusivity, potency, action time? Here we show that there could be a new player equally or even more important to disentangle the riddle: the protonation rate. Indeed, such rate modulates the diffusion speed of anesthetics into lipid membranes; low protonation rates enhance the diffusion for local anesthetics while high ones reduce it. We show also that there is a pH and membrane phase dependence on the local anesthetic diffusion across multiple lipid bilayers. Based on our findings we incorporate a new clue that may advance our understanding of the anesthetic phenomenon.

  2. Nitric oxide diffusion rate is reduced in the aortic wall.

    PubMed

    Liu, Xiaoping; Srinivasan, Parthasarathy; Collard, Eric; Grajdeanu, Paula; Zweier, Jay L; Friedman, Avner

    2008-03-01

    Endogenous nitric oxide (NO) plays important physiological roles in the body. As a small diatomic molecule, NO has been assumed to freely diffuse in tissues with a diffusion rate similar to that in water. However, this assumption has not been tested experimentally. In this study, a modified Clark-type NO electrode attached with a customized aorta holder was used to directly measure the flux of NO diffusion across the aortic wall at 37 degrees C. Experiments were carefully designed for accurate measurements of the apparent NO diffusion coefficient D and the partition coefficient alpha in the aortic wall. A mathematical model was presented for analyzing experimental data. It was determined that alpha = 1.15 +/- 0.11 and D = 848 +/- 45 mum(2)/s (n = 12). The NO diffusion coefficient in the aortic wall is nearly fourfold smaller than the reported diffusion coefficient in solution at 37 degrees C, indicating that NO diffusion in the vascular wall is no longer free, but markedly dependent on the environment in the tissue where these NO molecules are. These results imply that the NO diffusion rate in the vascular wall may be upregulated and downregulated by certain physiological and/or pathophysiological processes affecting the composition of tissues.

  3. Reaction rates for reaction-diffusion kinetics on unstructured meshes

    NASA Astrophysics Data System (ADS)

    Hellander, Stefan; Petzold, Linda

    2017-02-01

    The reaction-diffusion master equation is a stochastic model often utilized in the study of biochemical reaction networks in living cells. It is applied when the spatial distribution of molecules is important to the dynamics of the system. A viable approach to resolve the complex geometry of cells accurately is to discretize space with an unstructured mesh. Diffusion is modeled as discrete jumps between nodes on the mesh, and the diffusion jump rates can be obtained through a discretization of the diffusion equation on the mesh. Reactions can occur when molecules occupy the same voxel. In this paper, we develop a method for computing accurate reaction rates between molecules occupying the same voxel in an unstructured mesh. For large voxels, these rates are known to be well approximated by the reaction rates derived by Collins and Kimball, but as the mesh is refined, no analytical expression for the rates exists. We reduce the problem of computing accurate reaction rates to a pure preprocessing step, depending only on the mesh and not on the model parameters, and we devise an efficient numerical scheme to estimate them to high accuracy. We show in several numerical examples that as we refine the mesh, the results obtained with the reaction-diffusion master equation approach those of a more fine-grained Smoluchowski particle-tracking model.

  4. 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.

  5. Thermal /Soret/ diffusion effects on interfacial mass transport rates

    NASA Technical Reports Server (NTRS)

    Rosner, D. E.

    1980-01-01

    It is shown that thermal (Soret) diffusion significantly alters convective mass transport rates and important transition temperatures in highly nonisothermal flow systems involving the transport of 'heavy' species (vapors or particles). Introduction of the Soret transport term is shown to result in mass transfer effects similar to those of 'suction' and a homogeneous chemical 'sink'. It is pointed out that this analogy provides a simple method of correlating and predicting thermal diffusion effects in the abovementioned systems.

  6. Polymer reversal rate calculated via locally scaled diffusion map.

    PubMed

    Zheng, Wenwei; Rohrdanz, Mary A; Maggioni, Mauro; Clementi, Cecilia

    2011-04-14

    A recent study on the dynamics of polymer reversal inside a nanopore by Huang and Makarov [J. Chem. Phys. 128, 114903 (2008)] demonstrated that the reaction rate cannot be reproduced by projecting the dynamics onto a single empirical reaction coordinate, a result suggesting the dynamics of this system cannot be correctly described by using a single collective coordinate. To further investigate this possibility we have applied our recently developed multiscale framework, locally scaled diffusion map (LSDMap), to obtain collective reaction coordinates for this system. Using a single diffusion coordinate, we obtain a reversal rate via Kramers expression that is in good agreement with the exact rate obtained from the simulations. Our mathematically rigorous approach accounts for the local heterogeneity of molecular configuration space in constructing a diffusion map, from which collective coordinates emerge. We believe this approach can be applied in general to characterize complex macromolecular dynamics by providing an accurate definition of the collective coordinates associated with processes at different time scales.

  7. 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.

  8. Absolute amounts and diffusibility of HSP72, HSP25, and αB-crystallin in fast- and slow-twitch skeletal muscle fibers of rat.

    PubMed

    Larkins, Noni T; Murphy, Robyn M; Lamb, Graham D

    2012-01-01

    Heat shock proteins (HSPs) are essential for normal cellular stress responses. Absolute amounts of HSP72, HSP25, and αB-crystallin in rat extensor digitorum longus (EDL) and soleus (SOL) muscle were ascertained by quantitative Western blotting to better understand their respective capabilities and limitations. HSP72 content of EDL and SOL muscle was only ∼1.1 and 4.6 μmol/kg wet wt, respectively, and HSP25 content approximately twofold greater (∼3.4 and ∼8.9 μmol/kg, respectively). αB-crystallin content of EDL muscle was ∼4.9 μmol/kg but in SOL muscle was ∼30-fold higher (∼140 μmol/kg). To examine fiber heterogeneity, HSP content was also assessed in individual fiber segments; every EDL type II fiber had less of each HSP than any SOL type I fiber, whereas the two SOL type II fibers examined were indistinguishable from the EDL type II fibers. Sarcolemma removal (fiber skinning) demonstrated that 10-20% of HSP25 and αB-crystallin was sarcolemma-associated in SOL fibers. HSP diffusibility was assessed from the extent and rate of diffusion out of skinned fiber segments. In unstressed SOL fibers, 70-90% of each HSP was readily diffusible, whereas ∼95% remained tightly bound in fibers from SOL muscles heated to 45°C. Membrane disruption with Triton X-100 allowed dispersion of HSP72 and sarco(endo)plasmic reticulum Ca(2+)-ATPase pumps but did not alter binding of HSP25 or αB-crystallin. The amount of HSP72 in unstressed EDL muscle is much less than the number of its putative binding sites, whereas SOL type I fibers contain large amounts of αB-crystallin, suggesting its importance in normal cellular function without upregulation.

  9. Site-specific hydrogen diffusion rates during clinopyroxene dehydration

    NASA Astrophysics Data System (ADS)

    Ferriss, Elizabeth; Plank, Terry; Walker, David

    2016-06-01

    The rate of hydrogen diffusion in clinopyroxene is relevant to interpreting hydrogen ("water") concentrations in xenoliths, phenocrysts, and clinopyroxene-hosted melt inclusions to provide insight into the deep-earth water cycle and volcanic explosivity. Here, we determine bulk and site-specific hydrogen diffusivities in two diopsides and an augite by heating initially homogeneous water-bearing samples in a 1-atm CO/CO2 gas-mixing furnace at 800-1000 °C and oxygen fugacity at the quartz-fayalite-magnetite buffer and observing H-loss profiles. The O-H stretching range between wavenumbers 3000 and 4000 cm-1 in FTIR spectra is resolved into 4-6 peaks, each of which is assumed to represent a distinct defect site for the hydrogen, to determine peak-specific diffusivities using our previously published whole-block method. For the diopside from the Kunlun Mts. in China, Arrhenius relations are reported for peaks at 3645, 3617, 3540, 3443, and 3355 cm-1 based on measurements at 816, 904, and 1000 °C. Bulk and site-specific diffusivities are determined for the same set of peaks at 904 °C for the second diopside (Jaipur). The augite (PMR-53) was a triangular thin slab, and hydrogen diffusivities were determined for bulk hydrogen and peaks at 3620, 3550, 3460, and 3355 cm-1 in the thickness direction at 800 °C. Bulk hydrogen diffusivity in the Jaipur diopside is consistent with previous work, and hydrogen diffusivity in augite PMR-53 is slightly lower than the fast direction diffusivities measured || [100] and [001]* in Jaipur diopside. Both diopsides show 1-2 orders of magnitude differences in the peaks-specific diffusivities, with the fastest diffusivities at 3450 cm-1 and the slowest at 3645 cm-1. However, the hydrogen diffusivities in Jaipur diopside are 2-4 orders of magnitude higher than those in Kunlun diopside for bulk hydrogen and all peaks. Thus, peak-specific differences cannot by themselves adequately explain the 5 orders of magnitude range in hydrogen

  10. Effective reaction rates for diffusion-limited reaction cycles

    NASA Astrophysics Data System (ADS)

    Nałecz-Jawecki, Paweł; Szymańska, Paulina; Kochańczyk, Marek; Miekisz, Jacek; Lipniacki, Tomasz

    2015-12-01

    Biological signals in cells are transmitted with the use of reaction cycles, such as the phosphorylation-dephosphorylation cycle, in which substrate is modified by antagonistic enzymes. An appreciable share of such reactions takes place in crowded environments of two-dimensional structures, such as plasma membrane or intracellular membranes, and is expected to be diffusion-controlled. In this work, starting from the microscopic bimolecular reaction rate constants and using estimates of the mean first-passage time for an enzyme-substrate encounter, we derive diffusion-dependent effective macroscopic reaction rate coefficients (EMRRC) for a generic reaction cycle. Each EMRRC was found to be half of the harmonic average of the microscopic rate constant (phosphorylation c or dephosphorylation d), and the effective (crowding-dependent) motility divided by a slowly decreasing logarithmic function of the sum of the enzyme concentrations. This implies that when c and d differ, the two EMRRCs scale differently with the motility, rendering the steady-state fraction of phosphorylated substrate molecules diffusion-dependent. Analytical predictions are verified using kinetic Monte Carlo simulations on the two-dimensional triangular lattice at the single-molecule resolution. It is demonstrated that the proposed formulas estimate the steady-state concentrations and effective reaction rates for different sets of microscopic reaction rates and concentrations of reactants, including a non-trivial example where with increasing diffusivity the fraction of phosphorylated substrate molecules changes from 10% to 90%.

  11. Effective reaction rates for diffusion-limited reaction cycles.

    PubMed

    Nałęcz-Jawecki, Paweł; Szymańska, Paulina; Kochańczyk, Marek; Miękisz, Jacek; Lipniacki, Tomasz

    2015-12-07

    Biological signals in cells are transmitted with the use of reaction cycles, such as the phosphorylation-dephosphorylation cycle, in which substrate is modified by antagonistic enzymes. An appreciable share of such reactions takes place in crowded environments of two-dimensional structures, such as plasma membrane or intracellular membranes, and is expected to be diffusion-controlled. In this work, starting from the microscopic bimolecular reaction rate constants and using estimates of the mean first-passage time for an enzyme-substrate encounter, we derive diffusion-dependent effective macroscopic reaction rate coefficients (EMRRC) for a generic reaction cycle. Each EMRRC was found to be half of the harmonic average of the microscopic rate constant (phosphorylation c or dephosphorylation d), and the effective (crowding-dependent) motility divided by a slowly decreasing logarithmic function of the sum of the enzyme concentrations. This implies that when c and d differ, the two EMRRCs scale differently with the motility, rendering the steady-state fraction of phosphorylated substrate molecules diffusion-dependent. Analytical predictions are verified using kinetic Monte Carlo simulations on the two-dimensional triangular lattice at the single-molecule resolution. It is demonstrated that the proposed formulas estimate the steady-state concentrations and effective reaction rates for different sets of microscopic reaction rates and concentrations of reactants, including a non-trivial example where with increasing diffusivity the fraction of phosphorylated substrate molecules changes from 10% to 90%.

  12. Escape rate and diffusion of a Stochastically Driven particle

    PubMed Central

    Piscitelli, Antonio; Pica Ciamarra, Massimo

    2017-01-01

    The dynamical properties of a tracer repeatedly colliding with heat bath particles can be described within a Langevin framework provided that the tracer is more massive than the bath particles, and that the collisions are frequent. Here we consider the escape of a particle from a potential well, and the diffusion coefficient in a periodic potential, without making these assumptions. We have thus investigated the dynamical properties of a Stochastically Driven particle that moves under the influence of the confining potential in between successive collisions with the heat bath. In the overdamped limit, both the escape rate and the diffusion coefficient coincide with those of a Langevin particle. Conversely, in the underdamped limit the two dynamics have a different temperature dependence. In particular, at low temperature the Stochastically Driven particle has a smaller escape rate, but a larger diffusion coefficient. PMID:28120904

  13. Simultaneous estimation of lithospheric uplift rates and absolute sea level change in southwest Scandinavia from inversion of sea level data

    NASA Astrophysics Data System (ADS)

    Nielsen, Lars; Hansen, Jens Morten; Hede, Mikkel Ulfeldt; Clemmensen, Lars B.; Pejrup, Morten; Noe-Nygaard, Nanna

    2014-11-01

    Relative sea level curves contain coupled information about absolute sea level change and vertical lithospheric movement. Such curves may be constructed based on, for example tide gauge data for the most recent times and different types of geological data for ancient times. Correct account for vertical lithospheric movement is essential for estimation of reliable values of absolute sea level change from relative sea level data and vise versa. For modern times, estimates of vertical lithospheric movement may be constrained by data (e.g. GPS-based measurements), which are independent from the relative sea level data. Similar independent data do not exist for ancient times. The purpose of this study is to test two simple inversion approaches for simultaneous estimation of lithospheric uplift rates and absolute sea level change rates for ancient times in areas where a dense coverage of relative sea level data exists and well-constrained average lithospheric movement values are known from, for example glacial isostatic adjustment (GIA) models. The inversion approaches are tested and used for simultaneous estimation of lithospheric uplift rates and absolute sea level change rates in southwest Scandinavia from modern relative sea level data series that cover the period from 1900 to 2000. In both approaches, a priori information is required to solve the inverse problem. A priori information about the average vertical lithospheric movement in the area of interest is critical for the quality of the obtained results. The two tested inversion schemes result in estimated absolute sea level rise of ˜1.2/1.3 mm yr-1 and vertical uplift rates ranging from approximately -1.4/-1.2 mm yr-1 (subsidence) to about 5.0/5.2 mm yr-1 if an a priori value of 1 mm yr-1 is used for the vertical lithospheric movement throughout the study area. In case the studied time interval is broken into two time intervals (before and after 1970), absolute sea level rise values of ˜0.8/1.2 mm yr-1 (before

  14. Diffusion Rates on the Overhead Projector: Amines Compared to HCl.

    ERIC Educational Resources Information Center

    Solomon, Sally; And Others

    1996-01-01

    Describes a method to compare diffusion rates of selected amines to that of HCl. Provides an opportunity to introduce simple organic compounds early in the general chemistry curriculum and can be used to test Graham's Law for several different molar masses. (JRH)

  15. ZGB surface reaction model with high diffusion rates

    NASA Astrophysics Data System (ADS)

    Evans, J. W.

    1993-02-01

    The diffusionless ZGB (monomer-dimer) surface reaction model exhibits a discontinuous transition to a monomer-poisoned state when the fraction of monomer adsorption attempts exceeds 0.525. It has been claimed that this transition shifts to 2/3 with introduction of rapid diffusion of the monomer species, or of both species. We show this is not the case, 2/3 representing the spinodal rather than the transition point. For equal diffusion rates of both species, we find that the transition only shifts to 0.5951±0.0002.

  16. ZGB surface reaction model with high diffusion rates

    SciTech Connect

    Evans, J.W. )

    1993-02-01

    The diffusionless ZGB (monomer--dimer) surface reaction model exhibits a discontinuous transition to a monomer-poisoned state when the fraction of monomer adsorption attempts exceeds 0.525. It has been claimed that this transition shifts to 2/3 with introduction of rapid diffusion of the monomer species, or of both species. We show this is not the case, 2/3 representing the spinodal rather than the transition point. For equal diffusion rates of both species, we find that the transition only shifts to 0.5951[plus minus]0.0002.

  17. Release rates in a salt repository by diffusion

    SciTech Connect

    Hwang, Y.; Lee, W.W.L.; Chambre, P.L.; Pigford, T.H.

    1988-09-01

    In a recent analysis, we predicted extremely small brine migration velocities after emplacement of waste packages. Therefore it is expected that mass transfer of radioactive species dissolved in the brine is likely to be controlled by molecular diffusion. Here we apply the analytic solutions for the rate of diffusive mass transfer of dissolved species through a porous medium predict radionuclide release from waste packages in salt. This analysis shows that for the parameter values selected here, and for containment times of over 300 years, release rates from individual waste packages in sale can meet the US Nuclear Regulatory Commission's (USNRC) performance objective for the engineered barrier system. If many waste packages are actually exposed to brine much sooner than 300 years after emplacement, it will be difficult to meet the release rate for /sup 137/Cs, calculated from the USNRC regulation. In this report we present the analytic solutions and some numerical illustrations of the molecular diffusion analysis. We also compare the results with a different type of diffusion analysis in the Environmental Assessments for the potential repository sites in salt. 21 refs., 4 figs.

  18. Strain-Rate-Free Diffusion Flames: Initiation, Properties, and Quenching

    NASA Technical Reports Server (NTRS)

    Fendell, Francis; Rungaldier, Harald; Gokoglu, Suleyman; Schultz, Donald

    1997-01-01

    For about a half century, the stabilization of a steady planar deflagration on a heat-sink-type flat-flame burner has been of extraordinary service for the theoretical modeling and diagnostic probing of combusting gaseous mixtures. However, most engineering devices and most unwanted fire involve the burning of initially unmixed reactants. The most vigorous burning of initially separated gaseous fuel and oxidizer is the diffusion flame. In this useful idealization (limiting case), the reactants are converted to product at a mathematically thin interface, so no interpenetration of fuel and oxidizer occurs. This limit is of practical importance because it often characterizes the condition of optimal performance (and sometimes environmentally objectionable operation) of a combustor. A steady planar diffusion flame is most closely approached in the laboratory in the counterflow apparatus. The utility of this simple-strain-rate flow for the modeling and probing of diffusion flames was noted by Pandya and Weinberg 35 years ago, though only in the last decade or so has its use become internationally common place. However, typically, as the strain rate a is reduced below about 20 cm(exp -1), and the diffusion-flame limit (reaction rate much faster than the flow rate) is approached, the burning is observed to become unstable in earth gravity. The advantageous steady planar flow is not available in the diffusion-flame limit in earth gravity. This is unfortunate because the typical spatial scale in a counterflow is (k/a)(sup 1/2), where k denotes a characteristic diffusion coefficient; thus, the length scale becomes large, and the reacting flow is particularly amenable to diagnostic probing, as the diffusion-flame limit is approached. The disruption of planar symmetry is owing the fact that, as the strain rate a decreases, the residence time (l/a) of the throughput in the counterflow burner increases. Observationally, when the residence time exceeds about 50 msec, the

  19. Determination of mantle upwelling rate beneath Taiyuan basin by using absolute gravity, GPS, groundwater and GLDAS data

    NASA Astrophysics Data System (ADS)

    Xing, Lelin; Wang, Linhai; Hu, Minzhang

    2017-03-01

    The Taiyuan basin is in the Shanxi rift system of China. Results of tectonic studies indicate that the Moho is uplifted by 2-3 km under the Taiyuan basin. However, there is no quantitative evidence showing whether the rift is still in the status of mantle upwelling. Herein, we estimated mantle upwelling rate of Taiyuan basin by using absolute gravity, GPS, groundwater and GLDAS data in this paper. In order to utilize the absolute gravity measurements in terms of tectonic study it is necessary to reduce all disturbing environmental effects. Many of those can be modeled, such as tide, polar motion, ocean tidal loading and atmospheric mass components. The Taiyuan station located in the Taiyuan basin, and absolute gravity measurements with a FG5 instrument were performed from 2009 to 2014, a secular trend was obtained. In-situ GPS data was used to estimate the vertical motion rate since 2011, and the result indicated a land subsidence. In-situ groundwater level was collected with daily surveys from 2009 to 2015, and local hydrology impact on effect was made. The global terrestrial water storage loading effect on gravity at Taiyuan station was computed by using GLDAS global hydrology model. Furthermore there is a good agreement between GRACE results and GLDAS hydrological model results. Subtracting the gravity change rate attributable to the land subsidence, groundwater level and global hydrology from the absolute gravity change rate, the residual gravity change rate was obtained. It reflects mantle upwelling about 2.1 ± 2.6 cm/yr beneath Taiyuan basin.

  20. The joint dissipation rate for multiple scalars in differential diffusion.

    NASA Astrophysics Data System (ADS)

    Vedula, Prakash; Yeung, P. K.; Fox, R. O.

    1999-11-01

    We continue recent numerical studies of scalar dissipation fluctuations in turbulent mixing, with current emphasis on modeling and extension to differential diffusion for scalars with different molecular diffusivities. Data are taken from high-resolution direct numerical simulations for homogeneous scalar fields with uniform mean gradient. Amplification of scalar gradients by strain rate fluctuations in principal axes is of greatest interest, with a nearly universal time scale slightly less than 2 Kolmogorov time scales. Preferential alignment of scalar gradients with the most compressive strain rate conditioned upon the energy dissipation is observed in studies of both the dissipation rate of each scalar and their joint dissipation rate (which appears in the covariance equation). The gradient correlation between scalars with Schmidt numbers 1/8 to 1 is strongest in the most compressive strain direction. The Lagrangian PDF model for the joint dissipation (Fox 1999, Phys. Fluids 11, 1550) contains closures for each of the terms in the conditional joint dissipation rate balance equation. The DNS data are used to validate and improve the conditional closures, as well as to check for Reynolds and Schmidt number dependencies.

  1. Inertial effects on flow rate spectrum of diffuser micropumps.

    PubMed

    Hsu, Yi-Chu; Le, Ngoc-Bich

    2008-10-01

    This study develops a diffuser micropump and characterizes its output flow rates, such as the parabola shape on the frequency domain and the affecting factors. First, an equivalent circuit using electronic-hydraulic analogies was constructed. Flow rate analysis results were then compared to experimental results to verify the applicability of the circuit simulation. The operational frequency was 800 Hz for both cases and maximum flow rates were 0.078 and 0.075 mul/s for simulation and experimental results, respectively. Maximum flow rate difference between simulation and experiment was 3.7%. The circuit was then utilized to analyze inertial effects of transferred fluid and system components on output flow rates. This work also explained why the flow rate spectrum has a parabolic shape. Analysis results demonstrated that without inertial effects, micropump flow rates are linearly proportional to operational frequency; otherwise flow rate spectrum has parabolic shape. The natural frequency of the actuator-membrane structure was identified using the finite element method to verify whether this parameter affects flow rate characteristics. Experimental and simulation results demonstrated that the frequency of the maximum pumping flow rate was 800 Hz and the first mode natural frequency of actuator-membrane structure was 91.4 kHz, suggesting that the structure natural frequencies of the actuator-membrane structure do not play any role in micropump operations.

  2. Absolute rate constant of the reaction between chlorine /2P/ atoms and hydrogen peroxide from 298 to 424 K

    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.

  3. Determination of diffusion rate parameters in unequilibrated systems

    SciTech Connect

    Kohls, J.F.

    1980-05-06

    A mathematical method of determining the required rate parameters has been developed using the unequilibrated portion of the throughput rate curve. The developed method, termed the stabilized search method, has been verified against both simulated data and actual experimental equilibrated data. Studies performed with simulated permeation data demonstrate that the accuracy of the determined parameters is dependent upon the accuracy of the data used. To quantitatively assess the accuracy of the stabilized search method, several values of diffusivity were used to generate groups of simulated permeation data, each with known solubility and magnitude of random error. The magnitudes of the errors used were chosen to approximate actual experimental permeation rate data. Each group of data was then analyzed using the stabilized search method. The accuracy of the method was evaluated using the calculated diffusivity, solubility, and permeability values in comparison to their actual values. Results showed that the value of diffusivity generated from the data is tolerant of random errors and can be accurately evaluated from data with a 20 percent random error component. The solubility and permeability values are more sensitive to random error. The accuracy to which they can be determined is approximately equal to the random error. Several other modes of error encroachment are discussed and their relative contributions to the possible overall error assessed. A prediction of parameters was made from six sets of experimental permeation data; data was gathered using a leak detector with a 10 to 20% experimental error. Predicted parametric values yield calculated equilibrium throughputs with an average error of 15%.

  4. Reaction rates for a generalized reaction-diffusion master equation

    SciTech Connect

    Hellander, Stefan; Petzold, Linda

    2016-01-19

    It has been established that there is an inherent limit to the accuracy of the reaction-diffusion master equation. Specifically, there exists a fundamental lower bound on the mesh size, below which the accuracy deteriorates as the mesh is refined further. In this paper we extend the standard reaction-diffusion master equation to allow molecules occupying neighboring voxels to react, in contrast to the traditional approach in which molecules react only when occupying the same voxel. We derive reaction rates, in two dimensions as well as three dimensions, to obtain an optimal match to the more fine-grained Smoluchowski model, and show in two numerical examples that the extended algorithm is accurate for a wide range of mesh sizes, allowing us to simulate systems that are intractable with the standard reaction-diffusion master equation. In addition, we show that for mesh sizes above the fundamental lower limit of the standard algorithm, the generalized algorithm reduces to the standard algorithm. We derive a lower limit for the generalized algorithm which, in both two dimensions and three dimensions, is on the order of the reaction radius of a reacting pair of molecules.

  5. Reaction rates for a generalized reaction-diffusion master equation.

    PubMed

    Hellander, Stefan; Petzold, Linda

    2016-01-01

    It has been established that there is an inherent limit to the accuracy of the reaction-diffusion master equation. Specifically, there exists a fundamental lower bound on the mesh size, below which the accuracy deteriorates as the mesh is refined further. In this paper we extend the standard reaction-diffusion master equation to allow molecules occupying neighboring voxels to react, in contrast to the traditional approach, in which molecules react only when occupying the same voxel. We derive reaction rates, in two dimensions as well as three dimensions, to obtain an optimal match to the more fine-grained Smoluchowski model and show in two numerical examples that the extended algorithm is accurate for a wide range of mesh sizes, allowing us to simulate systems that are intractable with the standard reaction-diffusion master equation. In addition, we show that for mesh sizes above the fundamental lower limit of the standard algorithm, the generalized algorithm reduces to the standard algorithm. We derive a lower limit for the generalized algorithm which, in both two dimensions and three dimensions, is of the order of the reaction radius of a reacting pair of molecules.

  6. Reaction rates for a generalized reaction-diffusion master equation

    DOE PAGES

    Hellander, Stefan; Petzold, Linda

    2016-01-19

    It has been established that there is an inherent limit to the accuracy of the reaction-diffusion master equation. Specifically, there exists a fundamental lower bound on the mesh size, below which the accuracy deteriorates as the mesh is refined further. In this paper we extend the standard reaction-diffusion master equation to allow molecules occupying neighboring voxels to react, in contrast to the traditional approach in which molecules react only when occupying the same voxel. We derive reaction rates, in two dimensions as well as three dimensions, to obtain an optimal match to the more fine-grained Smoluchowski model, and show inmore » two numerical examples that the extended algorithm is accurate for a wide range of mesh sizes, allowing us to simulate systems that are intractable with the standard reaction-diffusion master equation. In addition, we show that for mesh sizes above the fundamental lower limit of the standard algorithm, the generalized algorithm reduces to the standard algorithm. We derive a lower limit for the generalized algorithm which, in both two dimensions and three dimensions, is on the order of the reaction radius of a reacting pair of molecules.« less

  7. 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…

  8. Reaction rates for mesoscopic reaction-diffusion kinetics

    DOE PAGES

    Hellander, Stefan; Hellander, Andreas; Petzold, Linda

    2015-02-23

    The mesoscopic reaction-diffusion master equation (RDME) is a popular modeling framework frequently applied to stochastic reaction-diffusion kinetics in systems biology. The RDME is derived from assumptions about the underlying physical properties of the system, and it may produce unphysical results for models where those assumptions fail. In that case, other more comprehensive models are better suited, such as hard-sphere Brownian dynamics (BD). Although the RDME is a model in its own right, and not inferred from any specific microscale model, it proves useful to attempt to approximate a microscale model by a specific choice of mesoscopic reaction rates. In thismore » paper we derive mesoscopic scale-dependent reaction rates by matching certain statistics of the RDME solution to statistics of the solution of a widely used microscopic BD model: the Smoluchowski model with a Robin boundary condition at the reaction radius of two molecules. We also establish fundamental limits on the range of mesh resolutions for which this approach yields accurate results and show both theoretically and in numerical examples that as we approach the lower fundamental limit, the mesoscopic dynamics approach the microscopic dynamics. Finally, we show that for mesh sizes below the fundamental lower limit, results are less accurate. Thus, the lower limit determines the mesh size for which we obtain the most accurate results.« less

  9. Reaction rates for mesoscopic reaction-diffusion kinetics

    SciTech Connect

    Hellander, Stefan; Hellander, Andreas; Petzold, Linda

    2015-02-23

    The mesoscopic reaction-diffusion master equation (RDME) is a popular modeling framework frequently applied to stochastic reaction-diffusion kinetics in systems biology. The RDME is derived from assumptions about the underlying physical properties of the system, and it may produce unphysical results for models where those assumptions fail. In that case, other more comprehensive models are better suited, such as hard-sphere Brownian dynamics (BD). Although the RDME is a model in its own right, and not inferred from any specific microscale model, it proves useful to attempt to approximate a microscale model by a specific choice of mesoscopic reaction rates. In this paper we derive mesoscopic scale-dependent reaction rates by matching certain statistics of the RDME solution to statistics of the solution of a widely used microscopic BD model: the Smoluchowski model with a Robin boundary condition at the reaction radius of two molecules. We also establish fundamental limits on the range of mesh resolutions for which this approach yields accurate results and show both theoretically and in numerical examples that as we approach the lower fundamental limit, the mesoscopic dynamics approach the microscopic dynamics. Finally, we show that for mesh sizes below the fundamental lower limit, results are less accurate. Thus, the lower limit determines the mesh size for which we obtain the most accurate results.

  10. 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

  11. 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.

  12. 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.

  13. Absolute depth-dose-rate measurements for an 192Ir HDR brachytherapy source in water using MOSFET detectors.

    PubMed

    Zilio, Valéry Olivier; Joneja, Om Parkash; Popowski, Youri; Rosenfeld, Anatoly; Chawla, Rakesh

    2006-06-01

    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 192Ir 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.

  14. 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.

  15. 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.

  16. Absolute rate constant for the O plus NO chemiluminescence in the near infrared

    NASA Technical Reports Server (NTRS)

    Golde, M. F.; Roche, A. E.; Kaufman, F.

    1973-01-01

    Infrared chemiluminescence from the process O + NO (+M) NO2 + hv (+M) has been studied between 1.3 and 4.1 micrometer. The wavelength dependence of the continuum between 1.3 and 3.3 micrometer is in fair agreement with previous studies and the measured radiative rate constant at 1.51 micrometer establishes the NO-O glow in this spectral range as a secondary emission standard. Comparison with previous studies of the visible region of the glow implies that the overall radiative rate constant lies in the range (9.4 to 11.2) x 10 to the minus 17 power cu cm sec/1. In the region 3.3 to 4.1 micrometer, the previously observed broad band, peaking at 3.7 micrometer, shows a complex kinetic dependence on O and M.

  17. Absolute rate constants of alkoxyl radical reactions in aqueous solution. [Tert-butyl hydroperoxide

    SciTech Connect

    Erben-Russ, M.; Michel, C.; Bors, W.; Saran, M.

    1987-04-23

    The pulse radiolysis technique was used to generate the alkoxyl radical derived from tert-butyl hydroperoxide (/sup t/BuOOH) in aqueous solution. The reactions of this radical with 2,2'-azinobis(3-ethyl-6-benzothiazolinesulfonate) (ABTS) and promethazine were monitored by kinetic spectroscopy. The unimolecular decay rate constant of the tert-butoxyl radical (/sup t/BuO) was determined to be 1.4 x 10/sup 6/ s/sup -1/. On the basis of this value, the rate constants for /sup t/BuO attack on quercetin, crocin, crocetin, ascorbate, isoascorbate, trolox c, glutathione, thymidine, adenosine, guanosine, and unsaturated fatty acids were determined. In addition, the reaction of /sup t/BuO with the polyunsaturated fatty acids (PUFA) was observed by directly monitoring the formation of the fatty acid pentadienyl radicals. Interestingly, the attack of /sup t/BuO on PUFA was found to be faster by about one order of magnitude as compared to the same reaction in a nonpolar solvent.

  18. Temperature and pressure dependence of the absolute rate constant for the reactions of NH2 radicals with acetylene and ethylene

    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.

  19. Diffusion-controlled growth rate of stepped interfaces

    NASA Astrophysics Data System (ADS)

    Saidi, P.; Hoyt, J. J.

    2015-07-01

    For many materials, the structure of crystalline surfaces or solid-solid interphase boundaries is characterized by an array of mobile steps separated by immobile terraces. Despite the prevalence of step-terraced interfaces a theoretical description of the growth rate has not been completely solved. In this work the boundary element method (BEM) has been utilized to numerically compute the concentration profile in a fluid phase in contact with an infinite array of equally spaced surface steps and, under the assumption that step motion is controlled by diffusion through the fluid phase, the growth rate is computed. It is also assumed that a boundary layer exists between the growing surface and a point in the liquid where complete convective mixing occurs. The BEM results are presented for varying step spacing, supersaturation, and boundary layer width. BEM calculations were also used to study the phenomenon of step bunching during crystal growth, and it is found that, in the absence of elastic strain energy, a sufficiently large perturbation in the position of a step from its regular spacing will lead to a step bunching instability. Finally, an approximate analytic solution using a matched asymptotic expansion technique is presented for the case of a stagnant liquid or equivalently a solid-solid stepped interface.

  20. Diffusion-controlled growth rate of stepped interfaces.

    PubMed

    Saidi, P; Hoyt, J J

    2015-07-01

    For many materials, the structure of crystalline surfaces or solid-solid interphase boundaries is characterized by an array of mobile steps separated by immobile terraces. Despite the prevalence of step-terraced interfaces a theoretical description of the growth rate has not been completely solved. In this work the boundary element method (BEM) has been utilized to numerically compute the concentration profile in a fluid phase in contact with an infinite array of equally spaced surface steps and, under the assumption that step motion is controlled by diffusion through the fluid phase, the growth rate is computed. It is also assumed that a boundary layer exists between the growing surface and a point in the liquid where complete convective mixing occurs. The BEM results are presented for varying step spacing, supersaturation, and boundary layer width. BEM calculations were also used to study the phenomenon of step bunching during crystal growth, and it is found that, in the absence of elastic strain energy, a sufficiently large perturbation in the position of a step from its regular spacing will lead to a step bunching instability. Finally, an approximate analytic solution using a matched asymptotic expansion technique is presented for the case of a stagnant liquid or equivalently a solid-solid stepped interface.

  1. Solid-state track recorder dosimetry device to measure absolute reaction rates and neutron fluence as a function of time

    DOEpatents

    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.

  2. A rare gas optics-free absolute photon flux and energy analyzer to provide absolute photoionization rates of inflowing interstellar neutrals

    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.

  3. 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.

  4. The reaction H + C4H2 - Absolute rate constant measurement and implication for atmospheric modeling of Titan

    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.

  5. The reaction H + C4H2 - Absolute rate constant measurement and implication for atmospheric modeling of Titan

    NASA Astrophysics Data System (ADS)

    Nava, D. F.; Mitchell, M. B.; Stief, L. J.

    1986-04-01

    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.

  6. SAS-2 observations of the diffuse gamma radiation in the galactic latitude interval 10 deg absolute b or equal to 90 deg

    NASA Technical Reports Server (NTRS)

    Fichtel, C. E.; Hartman, R. C.; Kniffen, D. A.; Thompson, D. J.; Oegelman, H. B.; Oezel, M. E.; Tuemer, T.

    1977-01-01

    An analysis of all of the second small astronomy satellite gamma-ray data for galactic latitudes with the absolute value of b 10 deg has shown that the intensity varies with galactic latitude, being larger near 10 deg than 90 deg. For energies above 100 MeV the gamma-ray data are consistent with a latitude distribution of the form I(b) = C sub 1 + C sub 2/sin b, with the second term being dominant. This result suggests that the radiation above 100 MeV is coming largely from local regions of the galactic disk. Between 35 and 100 MeV, a similar equation is also a good representation of the data, but here the two terms are comparable. These results indicate that the diffuse radiation above 35 MeV consists of two parts, one with a relatively hard galactic component and the other an isotropic, steep spectral component which extrapolates back well to the low energy diffuse radiation. The steepness of the diffuse isotropic component places significant constraints on possible theoretical models of this radiation.

  7. Measurements of Transverse Beam Diffusion Rates in the Fermilab Tevatron Collider

    SciTech Connect

    Stancari, G.; Annala, G.; Johnson, T.R.; Still, D.A.; Valishev, A.; /Fermilab

    2011-08-01

    The transverse beam diffusion rate vs. particle oscillation amplitude was measured in the Tevatron using collimator scans. All collimator jaws except one were retracted. As the jaw of interest was moved in small steps, the local shower rates were recorded as a function of time. By using a diffusion model, the time evolution of losses could be related to the diffusion rate at the collimator position. Preliminary results of these measurements are presented.

  8. Note: The effect of viscosity on the rate of diffusion-limited association of nanoparticles.

    PubMed

    Zhdanov, Vladimir P

    2015-10-28

    In the treatments of diffusion-limited association of suspended nanoparticles, their diffusion coefficients are usually considered to be constant and equal to those given by conventional hydrodynamics for diffusion of single nanoparticles. In reality, according to hydrodynamics, these coefficients depend, however, on the distance between nanoparticles. I show how this dependence can influence the association rate.

  9. Calibration of diffuse correlation spectroscopy with a time-resolved near-infrared technique to yield absolute cerebral blood flow measurements

    PubMed Central

    Diop, Mamadou; Verdecchia, Kyle; Lee, Ting-Yim; St Lawrence, Keith

    2011-01-01

    A primary focus of neurointensive care is the prevention of secondary brain injury, mainly caused by ischemia. A noninvasive bedside technique for continuous monitoring of cerebral blood flow (CBF) could improve patient management by detecting ischemia before brain injury occurs. A promising technique for this purpose is diffuse correlation spectroscopy (DCS) since it can continuously monitor relative perfusion changes in deep tissue. In this study, DCS was combined with a time-resolved near-infrared technique (TR-NIR) that can directly measure CBF using indocyanine green as a flow tracer. With this combination, the TR-NIR technique can be used to convert DCS data into absolute CBF measurements. The agreement between the two techniques was assessed by concurrent measurements of CBF changes in piglets. A strong correlation between CBF changes measured by TR-NIR and changes in the scaled diffusion coefficient measured by DCS was observed (R2 = 0.93) with a slope of 1.05 ± 0.06 and an intercept of 6.4 ± 4.3% (mean ± standard error). PMID:21750781

  10. Using genetic data to estimate diffusion rates in heterogeneous landscapes.

    PubMed

    Roques, L; Walker, E; Franck, P; Soubeyrand, S; Klein, E K

    2016-08-01

    Having a precise knowledge of the dispersal ability of a population in a heterogeneous environment is of critical importance in agroecology and conservation biology as it can provide management tools to limit the effects of pests or to increase the survival of endangered species. In this paper, we propose a mechanistic-statistical method to estimate space-dependent diffusion parameters of spatially-explicit models based on stochastic differential equations, using genetic data. Dividing the total population into subpopulations corresponding to different habitat patches with known allele frequencies, the expected proportions of individuals from each subpopulation at each position is computed by solving a system of reaction-diffusion equations. Modelling the capture and genotyping of the individuals with a statistical approach, we derive a numerically tractable formula for the likelihood function associated with the diffusion parameters. In a simulated environment made of three types of regions, each associated with a different diffusion coefficient, we successfully estimate the diffusion parameters with a maximum-likelihood approach. Although higher genetic differentiation among subpopulations leads to more accurate estimations, once a certain level of differentiation has been reached, the finite size of the genotyped population becomes the limiting factor for accurate estimation.

  11. Computation of Rate Constants for Diffusion of Small Ligands to and from Buried Protein Active Sites.

    PubMed

    Wang, P-H; De Sancho, D; Best, R B; Blumberger, J

    2016-01-01

    The diffusion of ligands to actives sites of proteins is essential to enzyme catalysis and many cellular signaling processes. In this contribution we review our recently developed methodology for calculation of rate constants for diffusion and binding of small molecules to buried protein active sites. The diffusive dynamics of the ligand obtained from molecular dynamics simulation is coarse grained and described by a Markov state model. Diffusion and binding rate constants are then obtained either from the reactive flux formalism or by fitting the time-dependent population of the Markov state model to a phenomenological rate law. The method is illustrated by applications to diffusion of substrate and inhibitors in [NiFe] hydrogenase, CO-dehydrogenase, and myoglobin. We also discuss a recently developed sensitivity analysis that allows one to identify hot spots in proteins, where mutations are expected to have the strongest effects on ligand diffusion rates.

  12. Coordinate-dependent diffusion coefficients: Decay rate in open quantum systems

    SciTech Connect

    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.

  13. Anisotropic conductivity tensor imaging in MREIT using directional diffusion rate of water molecules.

    PubMed

    Kwon, Oh In; Jeong, Woo Chul; Sajib, Saurav Z K; Kim, Hyung Joong; Woo, Eung Je

    2014-06-21

    Magnetic resonance electrical impedance tomography (MREIT) is an emerging method to visualize electrical conductivity and/or current density images at low frequencies (below 1 KHz). Injecting currents into an imaging object, one component of the induced magnetic flux density is acquired using an MRI scanner for isotropic conductivity image reconstructions. Diffusion tensor MRI (DT-MRI) measures the intrinsic three-dimensional diffusion property of water molecules within a tissue. It characterizes the anisotropic water transport by the effective diffusion tensor. Combining the DT-MRI and MREIT techniques, we propose a novel direct method for absolute conductivity tensor image reconstructions based on a linear relationship between the water diffusion tensor and the electrical conductivity tensor. We first recover the projected current density, which is the best approximation of the internal current density one can obtain from the measured single component of the induced magnetic flux density. This enables us to estimate a scale factor between the diffusion tensor and the conductivity tensor. Combining these values at all pixels with the acquired diffusion tensor map, we can quantitatively recover the anisotropic conductivity tensor map. From numerical simulations and experimental verifications using a biological tissue phantom, we found that the new method overcomes the limitations of each method and successfully reconstructs both the direction and magnitude of the conductivity tensor for both the anisotropic and isotropic regions.

  14. Effective reaction rates in diffusion-limited phosphorylation-dephosphorylation cycles

    NASA Astrophysics Data System (ADS)

    Szymańska, Paulina; Kochańczyk, Marek; Miekisz, Jacek; Lipniacki, Tomasz

    2015-02-01

    We investigate the kinetics of the ubiquitous phosphorylation-dephosphorylation cycle on biological membranes by means of kinetic Monte Carlo simulations on the triangular lattice. We establish the dependence of effective macroscopic reaction rate coefficients as well as the steady-state phosphorylated substrate fraction on the diffusion coefficient and concentrations of opposing enzymes: kinases and phosphatases. In the limits of zero and infinite diffusion, the numerical results agree with analytical predictions; these two limits give the lower and the upper bound for the macroscopic rate coefficients, respectively. In the zero-diffusion limit, which is important in the analysis of dense systems, phosphorylation and dephosphorylation reactions can convert only these substrates which remain in contact with opposing enzymes. In the most studied regime of nonzero but small diffusion, a contribution linearly proportional to the diffusion coefficient appears in the reaction rate. In this regime, the presence of opposing enzymes creates inhomogeneities in the (de)phosphorylated substrate distributions: The spatial correlation function shows that enzymes are surrounded by clouds of converted substrates. This effect becomes important at low enzyme concentrations, substantially lowering effective reaction rates. Effective reaction rates decrease with decreasing diffusion and this dependence is more pronounced for the less-abundant enzyme. Consequently, the steady-state fraction of phosphorylated substrates can increase or decrease with diffusion, depending on relative concentrations of both enzymes. Additionally, steady states are controlled by molecular crowders which, mostly by lowering the effective diffusion of reactants, favor the more abundant enzyme.

  15. Effective reaction rates in diffusion-limited phosphorylation-dephosphorylation cycles.

    PubMed

    Szymańska, Paulina; Kochańczyk, Marek; Miękisz, Jacek; Lipniacki, Tomasz

    2015-02-01

    We investigate the kinetics of the ubiquitous phosphorylation-dephosphorylation cycle on biological membranes by means of kinetic Monte Carlo simulations on the triangular lattice. We establish the dependence of effective macroscopic reaction rate coefficients as well as the steady-state phosphorylated substrate fraction on the diffusion coefficient and concentrations of opposing enzymes: kinases and phosphatases. In the limits of zero and infinite diffusion, the numerical results agree with analytical predictions; these two limits give the lower and the upper bound for the macroscopic rate coefficients, respectively. In the zero-diffusion limit, which is important in the analysis of dense systems, phosphorylation and dephosphorylation reactions can convert only these substrates which remain in contact with opposing enzymes. In the most studied regime of nonzero but small diffusion, a contribution linearly proportional to the diffusion coefficient appears in the reaction rate. In this regime, the presence of opposing enzymes creates inhomogeneities in the (de)phosphorylated substrate distributions: The spatial correlation function shows that enzymes are surrounded by clouds of converted substrates. This effect becomes important at low enzyme concentrations, substantially lowering effective reaction rates. Effective reaction rates decrease with decreasing diffusion and this dependence is more pronounced for the less-abundant enzyme. Consequently, the steady-state fraction of phosphorylated substrates can increase or decrease with diffusion, depending on relative concentrations of both enzymes. Additionally, steady states are controlled by molecular crowders which, mostly by lowering the effective diffusion of reactants, favor the more abundant enzyme.

  16. The impact of thermal conductivity and diffusion rates on water vapor transport through gas diffusion layers

    NASA Astrophysics Data System (ADS)

    Burlatsky, Sergei F.; Atrazhev, Vadim V.; Gummalla, Mallika; Condit, Dave A.; Liu, Fuqiang

    Proper water management in a hydrogen-fueled polymer electrolyte membrane (PEM) fuel cell is critical for performance and durability. A mathematical model has been developed to elucidate the effect of thermal conductivity and water vapor diffusion coefficient in the gas diffusion layers (GDLs). The fraction of product water removed in the vapor phase through the GDL as a function of GDL properties/set of material and component parameters and operating conditions has been calculated. The current model enables identification of conditions wherein condensation occurs in each GDL component. The model predicts the temperature gradient across various components of a PEM fuel cell, providing insight into the overall mechanism of water transport in a given cell design. The water condensation conditions and transport mode in the GDL components depend on the combination of water vapor diffusion coefficients and thermal conductivities of the GDL components. Different types of GDLs and water transport scenarios are defined in this work, based on water condensation in the GDL and fraction of water that the GDL removes through the vapor phase, respectively.

  17. Diffusive shock acceleration - Acceleration rate, magnetic-field direction and the diffusion limit

    NASA Technical Reports Server (NTRS)

    Jokipii, J. R.

    1992-01-01

    This paper reviews the concept of diffusive shock acceleration, showing that the acceleration of charged particles at a collisionless shock is a straightforward consequence of the standard cosmic-ray transport equation, provided that one treats the discontinuity at the shock correctly. This is true for arbitrary direction of the upstream magnetic field. Within this framework, it is shown that acceleration at perpendicular or quasi-perpendicular shocks is generally much faster than for parallel shocks. Paradoxically, it follows also that, for a simple scattering law, the acceleration is faster for less scattering or larger mean free path. Obviously, the mean free path can not become too large or the diffusion limit becomes inapplicable. Gradient and curvature drifts caused by the magnetic-field change at the shock play a major role in the acceleration process in most cases. Recent observations of the charge state of the anomalous component are shown to require the faster acceleration at the quasi-perpendicular solar-wind termination shock.

  18. Quantifying the cerebral metabolic rate of oxygen by combining diffuse correlation spectroscopy and time-resolved near-infrared spectroscopy.

    PubMed

    Verdecchia, Kyle; Diop, Mamadou; Lee, Ting-Yim; St Lawrence, Keith

    2013-02-01

    Preterm infants are highly susceptible to ischemic brain injury; consequently, continuous bedside monitoring to detect ischemia before irreversible damage occurs would improve patient outcome. In addition to monitoring cerebral blood flow (CBF), assessing the cerebral metabolic rate of oxygen (CMRO2) would be beneficial considering that metabolic thresholds can be used to evaluate tissue viability. The purpose of this study was to demonstrate that changes in absolute CMRO2 could be measured by combining diffuse correlation spectroscopy (DCS) with time-resolved near-infrared spectroscopy (TR-NIRS). Absolute CBF was determined using bolus-tracking TR-NIRS to calibrate the DCS measurements. Cerebral venous blood oxygenation (SvO2) was determined by multiwavelength TR-NIRS measurements, the accuracy of which was assessed by directly measuring the oxygenation of sagittal sinus blood. In eight newborn piglets, CMRO2 was manipulated by varying the anesthetics and by injecting sodium cyanide. No significant differences were found between the two sets of SvO2 measurements obtained by TR-NIRS or sagittal sinus blood samples and the corresponding CMRO2 measurements. Bland-Altman analysis showed a mean CMRO2 difference of 0.0268 ± 0.8340 mLO2/100 g/min between the two techniques over a range from 0.3 to 4 mL O2/100 g/min.

  19. Quantifying the cerebral metabolic rate of oxygen by combining diffuse correlation spectroscopy and time-resolved near-infrared spectroscopy

    NASA Astrophysics Data System (ADS)

    Verdecchia, Kyle; Diop, Mamadou; Lee, Ting-Yim; St. Lawrence, Keith

    2013-02-01

    Preterm infants are highly susceptible to ischemic brain injury; consequently, continuous bedside monitoring to detect ischemia before irreversible damage occurs would improve patient outcome. In addition to monitoring cerebral blood flow (CBF), assessing the cerebral metabolic rate of oxygen (CMRO2) would be beneficial considering that metabolic thresholds can be used to evaluate tissue viability. The purpose of this study was to demonstrate that changes in absolute CMRO2 could be measured by combining diffuse correlation spectroscopy (DCS) with time-resolved near-infrared spectroscopy (TR-NIRS). Absolute CBF was determined using bolus-tracking TR-NIRS to calibrate the DCS measurements. Cerebral venous blood oxygenation (SvO2) was determined by multiwavelength TR-NIRS measurements, the accuracy of which was assessed by directly measuring the oxygenation of sagittal sinus blood. In eight newborn piglets, CMRO2 was manipulated by varying the anesthetics and by injecting sodium cyanide. No significant differences were found between the two sets of SvO2 measurements obtained by TR-NIRS or sagittal sinus blood samples and the corresponding CMRO2 measurements. Bland-Altman analysis showed a mean CMRO2 difference of 0.0268±0.8340 mL O2/100 g/min between the two techniques over a range from 0.3 to 4 mL O2/100 g/min.

  20. Fractional rate of change of swim-bladder volume is reliably related to absolute depth during vertical displacements in teleost fish.

    PubMed

    Taylor, Graham K; Holbrook, Robert Iain; de Perera, Theresa Burt

    2010-09-06

    Fish must orient in three dimensions as they navigate through space, but it is unknown whether they are assisted by a sense of depth. In principle, depth can be estimated directly from hydrostatic pressure, but although teleost fish are exquisitely sensitive to changes in pressure, they appear unable to measure absolute pressure. Teleosts sense changes in pressure via changes in the volume of their gas-filled swim-bladder, but because the amount of gas it contains is varied to regulate buoyancy, this cannot act as a long-term steady reference for inferring absolute pressure. In consequence, it is generally thought that teleosts are unable to sense depth using hydrostatic pressure. Here, we overturn this received wisdom by showing from a theoretical physical perspective that absolute depth could be estimated during fast, steady vertical displacements by combining a measurement of vertical speed with a measurement of the fractional rate of change of swim-bladder volume. This mechanism works even if the amount of gas in the swim-bladder varies, provided that this variation occurs over much longer time scales than changes in volume during displacements. There is therefore no a priori physical justification for assuming that teleost fish cannot sense absolute depth by using hydrostatic pressure cues.

  1. 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.

  2. Application of a diffusion-desorption rate equation model in astrochemistry.

    PubMed

    He, Jiao; Vidali, Gianfranco

    2014-01-01

    Desorption and diffusion are two of the most important processes on interstellar grain surfaces; knowledge of them is critical for the understanding of chemical reaction networks in the interstellar medium (ISM). However, a lack of information on desorption and diffusion is preventing further progress in astrochemistry. To obtain desorption energy distributions of molecules from the surfaces of ISM-related materials, one usually carries out adsorption-desorption temperature programmed desorption (TPD) experiments, and uses rate equation models to extract desorption energy distributions. However, the often-used rate equation models fail to adequately take into account diffusion processes and thus are only valid in situations where adsorption is strongly localized. As adsorption-desorption experiments show that adsorbate molecules tend to occupy deep adsorption sites before occupying shallow ones, a diffusion process must be involved. Thus, it is necessary to include a diffusion term in the model that takes into account the morphology of the surface as obtained from analyses of TPD experiments. We take the experimental data of CO desorption from the MgO(100) surface and of D2 desorption from amorphous solid water ice as examples to show how a diffusion-desorption rate equation model explains the redistribution of adsorbate molecules among different adsorption sites. We extract distributions of desorption energies and diffusion energy barriers from TPD profiles. These examples are contrasted with a system where adsorption is strongly localized--HD from an amorphous silicate surface. Suggestions for experimental investigations are provided.

  3. Structural effects on the beta-scission reaction of alkoxyl radicals. Direct measurement of the absolute rate constants for ring opening of benzocycloalken-1-oxyl radicals.

    PubMed

    Bietti, Massimo; Lanzalunga, Osvaldo; Salamone, Michela

    2005-02-18

    [reaction: see text] The absolute rate constants for beta-scission of a series of benzocycloalken-1-oxyl radicals and of the 2-(4-methylphenyl)-2-butoxyl radical have been measured directly by laser flash photolysis. The benzocycloalken-1-oxyl radicals undergo ring opening with rates which parallel the ring strain of the corresponding cycloalkanes. In the 1-X-indan-1-oxyl radical series, ring opening is observed when X = H, Me, whereas exclusive C-X bond cleavage occurs when X = Et. The factors governing the fragmentation regioselectivity are discussed.

  4. New constraints on upper mantle creep mechanism inferred from silicon grain-boundary diffusion rates

    NASA Astrophysics Data System (ADS)

    Fei, Hongzhan; Koizumi, Sanae; Sakamoto, Naoya; Hashiguchi, Minako; Yurimoto, Hisayoshi; Marquardt, Katharina; Miyajima, Nobuyoshi; Yamazaki, Daisuke; Katsura, Tomoo

    2016-01-01

    The creep in the Earth's interior is dominated either by diffusion creep which causes Newtonian mantle flow, or by dislocation creep which results in non-Newtonian mantle flow. Although previous deformation studies on olivine claimed a transition from dislocation creep to diffusion creep with depth in the upper mantle, they might misunderstand the creep rates due to experimental difficulties. Since creep in olivine is controlled by silicon diffusion, we measured the silicon grain-boundary diffusion coefficient in well-sintered iron-free olivine aggregates as a function of temperature, pressure, and water content, showing activation energy, activation volume, and water content exponent of 220 ± 30 kJ /mol, 4.0 ± 0.7 cm3 /mol, and 0.26 ± 0.07, respectively. Our results based on Si diffusion in forsterite predict that diffusion creep dominates at low pressures and low temperatures, whereas dislocation creep dominates under high pressure and high temperature conditions. Water has negligible effects on both diffusion and dislocation creep. There is a transition from diffusion creep in the shallow upper mantle to dislocation creep in deeper regions. This explains the seismic anisotropy increases at the Gutenberg discontinuity beneath oceans and at the mid-lithosphere discontinuity beneath continents.

  5. Estimation of phase diffusion rates in a condensate interferometer using the Gross-Pitaevskii equation

    NASA Astrophysics Data System (ADS)

    Fallon, A.; Leonard, R. H.; Sackett, C. A.

    2015-10-01

    Atom interferometers using Bose-Einstein condensates are fundamentally limited by a phase diffusion process that arises from atomic interactions. Numerical solution of the Gross-Pitaevskii equation is here used to accurately calculate the diffusion rate for a Bragg interferometer. It is seen to agree with a Thomas-Fermi approximation at large atom numbers and a perturbative approximation at low atom numbers. Most experiments to date operate in the crossover region between these two regimes. Even in this case, it is found that that the diffusion time is governed in a simple way by the ratio of the healing length to the size of the condensate.

  6. Determination of subjective similarity for pairs of masses and pairs of clustered microcalcifications on mammograms: Comparison of similarity ranking scores and absolute similarity ratings

    SciTech Connect

    Muramatsu, Chisako; Li Qiang; Schmidt, Robert A.; Shiraishi, Junji; Suzuki, Kenji; Newstead, Gillian M.; Doi, Kunio

    2007-07-15

    The presentation of images that are similar to that of an unknown lesion seen on a mammogram may be helpful for radiologists to correctly diagnose that lesion. For similar images to be useful, they must be quite similar from the radiologists' point of view. We have been trying to quantify the radiologists' impression of similarity for pairs of lesions and to establish a ''gold standard'' for development and evaluation of a computerized scheme for selecting such similar images. However, it is considered difficult to reliably and accurately determine similarity ratings, because they are subjective. In this study, we compared the subjective similarities obtained by two different methods, an absolute rating method and a 2-alternative forced-choice (2AFC) method, to demonstrate that reliable similarity ratings can be determined by the responses of a group of radiologists. The absolute similarity ratings were previously obtained for pairs of masses and pairs of microcalcifications from five and nine radiologists, respectively. In this study, similarity ranking scores for eight pairs of masses and eight pairs of microcalcifications were determined by use of the 2AFC method. In the first session, the eight pairs of masses and eight pairs of microcalcifications were grouped and compared separately for determining the similarity ranking scores. In the second session, another similarity ranking score was determined by use of mixed pairs, i.e., by comparison of the similarity of a mass pair with that of a calcification pair. Four pairs of masses and four pairs of microcalcifications were grouped together to create two sets of eight pairs. The average absolute similarity ratings and the average similarity ranking scores showed very good correlations in the first study (Pearson's correlation coefficients: 0.94 and 0.98 for masses and microcalcifications, respectively). Moreover, in the second study, the correlations between the absolute ratings and the ranking scores were also

  7. Absolute Zero

    NASA Astrophysics Data System (ADS)

    Donnelly, Russell J.; Sheibley, D.; Belloni, M.; Stamper-Kurn, D.; Vinen, W. F.

    2006-12-01

    Absolute Zero is a two hour PBS special attempting to bring to the general public some of the advances made in 400 years of thermodynamics. It is based on the book “Absolute Zero and the Conquest of Cold” by Tom Shachtman. Absolute Zero will call long-overdue attention to the remarkable strides that have been made in low-temperature physics, a field that has produced 27 Nobel Prizes. It will explore the ongoing interplay between science and technology through historical examples including refrigerators, ice machines, frozen foods, liquid oxygen and nitrogen as well as much colder fluids such as liquid hydrogen and liquid helium. A website has been established to promote the series: www.absolutezerocampaign.org. It contains information on the series, aimed primarily at students at the middle school level. There is a wealth of material here and we hope interested teachers will draw their student’s attention to this website and its substantial contents, which have been carefully vetted for accuracy.

  8. Intrinsic absolute bioavailability prediction in rats based on in situ absorption rate constants and/or in vitro partition coefficients: 6-fluoroquinolones.

    PubMed

    Sánchez-Castaño, G; Ruíz-García, A; Bañón, N; Bermejo, M; Merino, V; Freixas, J; Garriguesx, T M; Plá-Delfina, J M

    2000-11-01

    A preliminary study attempting to predict the intrinsic absolute bioavailability of a group of antibacterial 6-fluoroquinolones-including true and imperfect homologues as well as heterologues-was carried out. The intrinsic absolute bioavailability of the test compounds, F, was assessed on permanently cannulated conscious rats by comparing the trapezoidal normalized areas under the plasma concentration-time curves obtained by intravenous and oral routes (n = 8-12). The high-performance liquid chromatography analytical methods used for plasma samples are described. Prediction of the absolute bioavailability of the compounds was based on their intrinsic rat gut in situ absorption rate constant, k(a). The working equation was: where T represents the mean absorbing time. A T value of 0.93 (+/-0.06) h provides the best correlation between predicted and experimentally obtained bioavailabilities (F' and F, respectively) when k(a) values are used (slope a = 1.10; intercept b = -0.05; r = 0.991). The k(a) values can also be expressed in function of the in vitro partition coefficients, P, between n-octanol and a phosphate buffer. In this case, theoretical k(a) values can be determined with the parameters of a standard k(a)/P correlation previously established for a group of model compounds. When P values are taken instead of k(a) values, reliable bioavailability predictions can also be made. These and other relevant features of the method are discussed.

  9. High-accuracy absolute rotation rate measurements with a large ring laser gyro: establishing the scale factor.

    PubMed

    Hurst, Robert B; Mayerbacher, Marinus; Gebauer, Andre; Schreiber, K Ulrich; Wells, Jon-Paul R

    2017-02-01

    Large ring lasers have exceeded the performance of navigational gyroscopes by several orders of magnitude and have become useful tools for geodesy. In order to apply them to tests in fundamental physics, remaining systematic errors have to be significantly reduced. We derive a modified expression for the Sagnac frequency of a square ring laser gyro under Earth rotation. The modifications include corrections for dispersion (of both the gain medium and the mirrors), for the Goos-Hänchen effect in the mirrors, and for refractive index of the gas filling the cavity. The corrections were measured and calculated for the 16  m2 Grossring laser located at the Geodetic Observatory Wettzell. The optical frequency and the free spectral range of this laser were measured, allowing unique determination of the longitudinal mode number, and measurement of the dispersion. Ultimately we find that the absolute scale factor of the gyroscope can be estimated to an accuracy of approximately 1 part in 108.

  10. Adsorption rate of phenol from aqueous solution onto organobentonite: surface diffusion and kinetic models.

    PubMed

    Ocampo-Perez, Raul; Leyva-Ramos, Roberto; Mendoza-Barron, Jovita; Guerrero-Coronado, Rosa M

    2011-12-01

    The concentration decay curves for the adsorption of phenol on organobentonite were obtained in an agitated tank batch adsorber. The experimental adsorption rate data were interpreted with diffusional models as well as first-order, second-order and Langmuir kinetic models. The surface diffusion model adjusted the data quite well, revealing that the overall rate of adsorption was controlled by surface diffusion. Furthermore, the surface diffusion coefficient increased raising the mass of phenol adsorbed at equilibrium and was independent of the particle diameter in the range 0.042-0.0126 cm. It was demonstrated that the overall rate of adsorption was essentially not affected by the external mass transfer. The second-order and the Langmuir kinetic models fitted the experimental data quite well; however, the kinetic constants of both models varied without any physical meaning while increasing the particle size and the mass of phenol adsorbed at equilibrium.

  11. Jump rates for surface diffusion of large molecules from first principles

    SciTech Connect

    Shea, Patrick Kreuzer, Hans Jürgen

    2015-04-21

    We apply a recently developed stochastic model for the surface diffusion of large molecules to calculate jump rates for 9,10-dithioanthracene on a Cu(111) surface. The necessary input parameters for the stochastic model are calculated from first principles using density functional theory (DFT). We find that the inclusion of van der Waals corrections to the DFT energies is critical to obtain good agreement with experimental results for the adsorption geometry and energy barrier for diffusion. The predictions for jump rates in our model are in excellent agreement with measured values and show a marked improvement over transition state theory (TST). We find that the jump rate prefactor is reduced by an order of magnitude from the TST estimate due to frictional damping resulting from energy exchange with surface phonons, as well as a rotational mode of the diffusing molecule.

  12. Rate of energy gain and maximum energy in diffusive shock acceleration. [astrophysical implications

    NASA Technical Reports Server (NTRS)

    Jokipii, J. R.

    1987-01-01

    The problem of diffusive shock acceleration of fast charged particles is reexamined with emphasis on the rate of energy gain, and the maximum energy which can be attained in a given circumstance. The direction of the average magnetic field at the shock is shown to have a large effect. If the perpendicular diffusion coefficient is much smaller than the parallel coefficient, particles can gain much more energy if the shock is quasi-perpendicular than if it is quasi-parallel. The maximum energy attainable can be substantially higher (by a factor of 100 or more) than previous discussions would predict, in cases where the shock is quasi-perpendicular. The energy gain increases as kappa-perpendicular decreases. The principal limitation comes from the requirement that diffusion be a valid approximation to the particle motion, and that the particle be able to diffuse fast enough to encounter the shock many times.

  13. Geometry-Specific Heterogeneity of the Apparent Diffusion Rate of Materials Inside Sperm Cells

    PubMed Central

    Takao, Daisuke; Kamimura, Shinji

    2010-01-01

    Abstract In sea urchin spermatozoa, the energy source powering flagellar motion is provided as ATP produced by mitochondria located at the proximal ends of flagella. However, the bottleneck structure between the sperm head and the flagellar tail seems to restrict the free entry of ATP from mitochondria into the tail region. To test this possibility, we investigated the diffusion properties in sperm cells using fluorescence recovery after photobleaching. We found that the rate of fluorescence recovery in the head region was ∼10% of that observed in the flagellar tail regions. We also found that, even within the tail region, rates varied depending on location, i.e., rates were slower at the more distal regions. Using computational analysis, the rate heterogeneity was shown to be caused mainly by the geometry of the sperm structure, even if little or no difference in diffusion rates through the neck region was assumed. Therefore, we concluded that materials such as ATP would generally diffuse freely between the heads and the flagella of sperm cells. We believe these findings regarding the diffusion properties inside spermatozoa provide further insights into material transportation and chemical signaling inside eukaryotic cilia and flagella. PMID:20409478

  14. Geometry-specific heterogeneity of the apparent diffusion rate of materials inside sperm cells.

    PubMed

    Takao, Daisuke; Kamimura, Shinji

    2010-04-21

    In sea urchin spermatozoa, the energy source powering flagellar motion is provided as ATP produced by mitochondria located at the proximal ends of flagella. However, the bottleneck structure between the sperm head and the flagellar tail seems to restrict the free entry of ATP from mitochondria into the tail region. To test this possibility, we investigated the diffusion properties in sperm cells using fluorescence recovery after photobleaching. We found that the rate of fluorescence recovery in the head region was approximately 10% of that observed in the flagellar tail regions. We also found that, even within the tail region, rates varied depending on location, i.e., rates were slower at the more distal regions. Using computational analysis, the rate heterogeneity was shown to be caused mainly by the geometry of the sperm structure, even if little or no difference in diffusion rates through the neck region was assumed. Therefore, we concluded that materials such as ATP would generally diffuse freely between the heads and the flagella of sperm cells. We believe these findings regarding the diffusion properties inside spermatozoa provide further insights into material transportation and chemical signaling inside eukaryotic cilia and flagella.

  15. 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.

  16. 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.

  17. Absolute Summ

    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. .

  18. Leakage rates and thermal requirements for the diffusion bonding of microchannel arrays via internal convective heating

    SciTech Connect

    Bose, Sumantra; Palo, Daniel R.; Paul, Brian

    2007-07-24

    Diffusion bonding cycle times can be a large cost factor in the production of metal microchannel devices. The challenge is to significantly minimize this cost by reducing the bonding cycle time through rapid and uniform heating and cooling within the bonding process. Heating rates in diffusion bonding processes are typically limited by the need to minimize thermal gradients during bonding. A novel method is described which takes advantage of the internal flow passages within microchannel devices for convective heat transfer during the bonding process. The internal convective heating (ICH) technique makes use of heated inert gas to provide the microchannel assembly with rapid and uniform heat input. This paper will demonstrate the ability to effectively diffusion bond microchannel laminae using the ICH method by investigating the leakage rates.

  19. Diffusion as a Rate Limiting Factor on the Evolution of Strontium Isotope Ratios in Fractured Rock

    NASA Astrophysics Data System (ADS)

    Johnson, E. G.; Holt, R. M.; McLing, T. L.

    2002-12-01

    In recent years, several approaches have been developed to model the evolution of strontium isotope ratios (87Sr/86Sr) in porous media. In fractured rock, however, diffusion limits the rates of reaction between mobile water and mineral surfaces inside fracture-bounded blocks. Diffusion can limit transfer of fluids with differing isotopic ratios between the mobile and immobile zones leading to longer equilibration times. We develop a diffusion-based mathematical approach for modeling the evolution of ratios that includes sorption, ion exchange, and dissolution in fracture bounded blocks of multiple sizes. Traditional models employing isotopic ratios with the advection-dispersion equation are unable to incorporate diffusion because they are limited by the structure of their equation. Modeling the individual isotopic species separately accounts for the effects of diffusion. The general governing equation is robust in that it does not assume chemical equilibrium reactions. Special cases show the importance of diffusion-limited mass transfer on the evolution of isotopes ratios in fractured rock.

  20. The rate of the deoxygenation reaction limits myoglobin- and hemoglobin-facilitated O₂ diffusion in cells.

    PubMed

    Endeward, Volker

    2012-05-01

    A mathematical model describing facilitation of O(2) diffusion by the diffusion of myoglobin and hemoglobin is presented. The equations are solved numerically by a finite-difference method for the conditions as they prevail in cardiac and skeletal muscle and in red cells without major simplifications. It is demonstrated that, in the range of intracellular diffusion distances, the degree of facilitation is limited by the rate of the chemical reaction between myglobin or hemoglobin and O(2). The results are presented in the form of relationships between the degree of facilitation and the length of the diffusion path on the basis of the known kinetics of the oxygenation-deoxygenation reactions. It is concluded that the limitation by reaction kinetics reduces the maximally possible facilitated oxygen diffusion in cardiomyoctes by ∼50% and in skeletal muscle fibers by ∼ 20%. For human red blood cells, a reduction of facilitated O(2) diffusion by 36% is obtained in agreement with previous reports. This indicates that, especially in cardiomyocytes and red cells, chemical equilibrium between myoglobin or hemoglobin and O(2) is far from being established, an assumption that previously has often been made. Although the "O(2) transport function" of myoglobin in cardiac muscle cells thus is severely limited by the chemical reaction kinetics, and to a lesser extent also in skeletal muscle, it is noteworthy that the speed of release of O(2) from MbO(2), the "storage function," is not limited by the reaction kinetics under physiological conditions.

  1. Residue-specific NH exchange rates studied by NMR diffusion experiments

    NASA Astrophysics Data System (ADS)

    Brand, Torsten; Cabrita, Eurico J.; Morris, Gareth A.; Günther, Robert; Hofmann, Hans-Jörg; Berger, Stefan

    2007-07-01

    We present a novel approach to the investigation of rapid (>2 s -1) NH exchange rates in proteins, based on residue-specific diffusion measurements. 1H, 15N-DOSY-HSQC spectra are recorded in order to observe resolved amide proton signals for most residues of the protein. Human ubiquitin was used to demonstrate the proposed method. Exchange rates are derived directly from the decay data of the diffusion experiment by applying a model deduced from the assumption of a two-site exchange with water and the "pure" diffusion coefficients of water and protein. The "pure" diffusion coefficient of the protein is determined in an experiment with selective excitation of the amide protons in order to suppress the influence of magnetization transfer from water to amide protons on the decay data. For rapidly exchanging residues a comparison of our results with the exchange rates obtained in a MEXICO experiment showed good agreement. Molecular dynamics (MD) and quantum mechanical calculations were performed to find molecular parameters correlating with the exchangeability of the NH protons. The RMS fluctuations of the amide protons, obtained from the MD simulations, together with the NH coupling constants provide a bilinear model which shows a good correlation with the experimental NH exchange rates.

  2. The effect of receptor clustering on diffusion-limited forward rate constants.

    PubMed Central

    Goldstein, B; Wiegel, F W

    1983-01-01

    The effect of receptor clustering on the diffusion-limited forward rate constant (k+) is studied theoretically by modeling cell surface receptors by hemispheres distributed on a plane. We give both exact results and bounds. The exact results are obtained using an electrostatic analogue and applying the method of the images. Accurate upper bounds on k+ are found from a variational principle. PMID:6309261

  3. Absolute rate of the reaction of C l(2P) with methane 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 methane have been measured from 200-500K using the flash photolysis-resonance fluorescence technique. When the results from fourteen equally spaced experimental determinations are plotted in Arrhenius form a definite curvature is noted. The results are compared to previous work and are theoretically discussed.

  4. Absolute Photometry

    NASA Astrophysics Data System (ADS)

    Hartig, George

    1990-12-01

    The absolute sensitivity of the FOS will be determined in SV by observing 2 stars at 3 epochs, first in 3 apertures (1.0", 0.5", and 0.3" circular) and then in 1 aperture (1.0" circular). In cycle 1, one star, BD+28D4211 will be observed in the 1.0" aperture to establish the stability of the sensitivity and flat field characteristics and improve the accuracy obtained in SV. This star will also be observed through the paired apertures since these are not calibrated in SV. The stars will be observed in most detector/grating combinations. The data will be averaged to form the inverse sensitivity functions required by RSDP.

  5. 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).

  6. Absolute rate of the reaction of O/3-P/ with hydrogen sulfide over the temperature range 263 to 495 K

    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.

  7. Absolute rate parameters for the reaction of ground state atomic oxygen with carbonyl sulfide. [using O(3P) monitoring

    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 k sub 1 was measured over a temperature range of 263 - 502 K and the data were fitted to an Arrhenuis expression with good linearity.

  8. Accurate and absolute diffusion measurements of Rhodamine 6G in low-concentration aqueous solutions by the PGSE-WATERGATE sequence

    SciTech Connect

    Majer, G.; Zick, K.

    2015-04-28

    A pulsed field gradient spin-echo nuclear magnetic resonance (NMR) sequence with solvent suppression (PGSE-WATERGATE) was applied to accurately measure the diffusion coefficients of Rhodamine 6G (Rh6G) in low-concentration aqueous solutions. Three samples with Rh6G concentrations of C{sub Rh6G} = 1, 4.5, and 25 μM were investigated. The precise determination of the diffusion coefficients in this low-concentration range was made possible by using a cryogenically cooled NMR probe and by the effective solvent suppression of the PGSE-WATERGATE sequence. The present results bridge the gap between diffusion data measured by fluorescence correlation spectroscopy in the single molecule limit and diffusivities obtained by pulsed field gradient NMR (PFG-NMR) without solvent suppression at higher concentrations. To further extend the concentration range, the diffusion coefficient of Rh6G was also measured on a sample with C{sub Rh6G} = 410 μM by PFG-NMR. The overall concentration dependence of the Rh6G diffusion at 25 °C is discussed in terms of dimerization of the Rh6G molecules. The concentration-dependent monomer/dimer proportion is deduced from the diffusion data.

  9. Heritability of white matter microstructure in late middle age: A twin study of tract-based fractional anisotropy and absolute diffusivity indices.

    PubMed

    Vuoksimaa, Eero; Panizzon, Matthew S; Hagler, Donald J; Hatton, Sean N; Fennema-Notestine, Christine; Rinker, Daniel; Eyler, Lisa T; Franz, Carol E; Lyons, Michael J; Neale, Michael C; Tsuang, Ming T; Dale, Anders M; Kremen, William S

    2017-04-01

    There is evidence that differences among individuals in white matter microstructure, as measured with diffusion tensor imaging (DTI), are under genetic control. However, little is known about the relative contribution of genetic and environmental effects on different diffusivity indices among late middle-aged adults. Here, we examined the magnitude of genetic influences for fractional anisotropy (FA), and mean (MD), axial (AD), and radial (RD) diffusivities in male twins aged 56-66 years old. Using an atlas-based registration approach to delineate individual white matter tracts, we investigated mean DTI-based indices within the corpus callosum, 12 bilateral tracts and all these regions of interest combined. All four diffusivity indices had high heritability at the global level (72%-80%). The magnitude of genetic effects in individual tracts varied from 0% to 82% for FA, 0% to 81% for MD, 8% to 77% for AD, and 0% to 80% for RD with most of the tracts showing significant heritability estimates. Despite the narrow age range of this community-based sample, age was correlated with all four diffusivity indices at the global level. In sum, all diffusion indices proved to have substantial heritability for most of the tracts and the heritability estimates were similar in magnitude for different diffusivity measures. Future studies could aim to discover the particular set of genes that underlie the significant heritability of white matter microstructure. Hum Brain Mapp 38:2026-2036, 2017. © 2017 Wiley Periodicals, Inc.

  10. Absolute rate determinations and temperature dependences of the gas-phase reactions of O( 3P) with halogenated propenes

    NASA Astrophysics Data System (ADS)

    Cometto, Pablo M.; Teruel, Mariano A.; Taccone, Raúl A.; Lane, Silvia I.

    2006-01-01

    The rate constants for the gas-phase reactions of ground state oxygen atoms with CF 3CH dbnd CH 2 (1), CF 3CF dbnd CF 2 (2) and CF 3CCl dbnd CCl 2 (3) have been measured directly using a discharge flow tube employing the O( 3P) chemiluminescence titration method. The experiments were carried out under pseudo-first-order conditions with [O( 3P)] 0 ≪ [propene] 0. The temperature dependences of the reactions were studied for the first time in the range 298-363 K. The Arrhenius expressions obtained (in units of cm 3 molecule -1 s -1) were: k1 = (0.28 ± 0.09) × 10 -11 exp[-(10.4 ± 0.9) × 10 3/ RT], k2 = (1.57 ± 0.72) × 10 -11 exp[-(15.6 ± 1.3) × 10 3/ RT], k3 = (2.23 ± 1.27) × 10 -11 exp[-(16.0 ± 1.6) × 10 3/ RT]. All the rate coefficients display a positive temperature dependence which points to the importance of the irreversibility of the addition mechanism for these reactions. Halogen substitution in the alkenes is discussed in terms of reactivity with O( 3P) and its relation with the ionization potential.

  11. An analytical model for estimating water exchange rate in white matter using diffusion MRI.

    PubMed

    Davoodi-Bojd, Esmaeil; Chopp, Michael; Soltanian-Zadeh, Hamid; Wang, Shiyang; Ding, Guangliang; Jiang, Quan

    2014-01-01

    Substantial effort is being expended on using micro-structural modeling of the white matter, with the goal of relating diffusion weighted magnetic resonance imaging (DWMRI) to the underlying structure of the tissue, such as axonal density. However, one of the important parameters affecting diffusion is the water exchange rate between the intra- and extra-axonal space, which has not been fully investigated and is a crucial marker of brain injury such as multiple sclerosis (MS), stroke, and traumatic brain injury (TBI). To our knowledge, there is no diffusion analytical model which includes the Water eXchange Rate (WXR) without the requirement of short gradient pulse (SGP) approximation. We therefore propose a new analytical model by deriving the diffusion signal for a permeable cylinder, assuming a clinically feasible pulse gradient spin echo (PGSE) sequence. Simulations based on Markov Random Walk confirm that the exchange parameter included in our model has a linear correlation (R2>0.88) with the actual WXR. Moreover, increasing WXR causes the estimated values of diameter and volume fraction of the cylinders to increase and decrease, respectively, which is consistent with our findings from histology measurements in tissues near TBI regions. This model was also applied to the diffusion signal acquired from ex vivo brains of 14 male (10 TBI and 4 normal) rats using hybrid diffusion imaging. The estimated values of axon diameter and axonal volume fraction are in agreement with their corresponding histological measurements in normal brains, with 0.96 intra-class correlation coefficient value resulting from consistency analysis. Moreover, a significant increase (p = 0.001) in WXR and diameter and decrease in axonal volume fraction in the TBI boundary were detected in the TBI rats compared with the normal rats.

  12. A quantitative radioluminographic imaging method for evaluating lateral diffusion rates in skin.

    PubMed

    Rush, Allison K; Miller, Matthew A; Smith, Edward D; Kasting, Gerald B

    2015-10-28

    A method is presented for measuring the lateral diffusion coefficients of exogenously applied compounds on excised skin. The method involves sequential high resolution imaging of the spatial distribution of β-radiation associated with [(14)C]-labeled compounds to monitor the development of the concentration profile on the skin surface. It is exemplified by measurements made on three radiolabeled test compounds--caffeine, testosterone, and zinc pyrithione (ZnPT)--administered as solutions. Lateral diffusivity is expected to be an important determinant of the topical bioavailability of ZnPT, which is characteristically administered as a fine suspension and must reach microorganisms in molecular form to exert biocidal activity. Application of the test compounds at levels below and above their estimated saturation doses in the upper stratum corneum allows one to distinguish between diffusion-limited and dissolution rate-limited kinetics. The effective lateral diffusivities of the two chemically stable reference compounds, caffeine and testosterone, were (1-4) × 10(-9) cm(2)/s and (3-9) × 10(-9) cm(2)/s, respectively. Lateral transport of [(14)C] associated with ZnPT was formulation-dependent, with effective diffusivities of (1-2) × 10(-9) cm(2)/s in water and (3-9) × 10(-9) cm(2)/s in a 1% body wash solution. These differences are thought to be related to molecular speciation and/or the presence of a residual surfactant phase on the skin surface. All values were greater than those estimated for the transverse diffusivities of these compounds in stratum corneum by factors ranging from 250 to over 2000. Facile lateral transport on skin, combined with a low transdermal permeation rate, may thus be seen to be a key factor in the safe and effective use of ZnPT as a topical antimicrobial agent.

  13. Diffusion dependence of proton NMR relaxation rates in the presence of ferritin

    NASA Astrophysics Data System (ADS)

    Boss, Michael; Hammel, P. Chris

    2009-03-01

    Ferritin is the predominant iron-storage protein in living organisms. It may serve as an indicator of neurodegenerative diseases such as Alzheimer's. Measuring brain ferritin concentration non-invasively via MRI could enable better diagnoses and treatments of such diseases. Quantitative MRI determination of the ferritin concentration requires an understanding of the NMR relaxation mechanisms of hydrogen protons in the presence of ferritin. In aqueous solutions, ferritin enhances the transverse relaxation rate (R2) of the protons. This is thought to occur due to a diffusive mechanism, where protons diffusing near ferritin pass through a region of elevated magnetic field, and a chemical exchange mechanism, where protons bind to the protein for a period of time, experiencing an even higher magnetic field. These two mechanisms exhibit different dependencies on the self-diffusion coefficient of the protons. By adding glycerol to aqueous solutions, we control the self-diffusion of protons. We measure the R2 of protons in ferritin-containing binary mixtures of water and glycerol using CPMG sequences, and compare the experimental results to theoretical predictions of diffusion dependence in order to distinguish the relative importance of the mechanisms.

  14. Breakdown of the reaction-diffusion master equation with nonelementary rates.

    PubMed

    Smith, Stephen; Grima, Ramon

    2016-05-01

    The chemical master equation (CME) is the exact mathematical formulation of chemical reactions occurring in a dilute and well-mixed volume. The reaction-diffusion master equation (RDME) is a stochastic description of reaction-diffusion processes on a spatial lattice, assuming well mixing only on the length scale of the lattice. It is clear that, for the sake of consistency, the solution of the RDME of a chemical system should converge to the solution of the CME of the same system in the limit of fast diffusion: Indeed, this has been tacitly assumed in most literature concerning the RDME. We show that, in the limit of fast diffusion, the RDME indeed converges to a master equation but not necessarily the CME. We introduce a class of propensity functions, such that if the RDME has propensities exclusively of this class, then the RDME converges to the CME of the same system, whereas if the RDME has propensities not in this class, then convergence is not guaranteed. These are revealed to be elementary and nonelementary propensities, respectively. We also show that independent of the type of propensity, the RDME converges to the CME in the simultaneous limit of fast diffusion and large volumes. We illustrate our results with some simple example systems and argue that the RDME cannot generally be an accurate description of systems with nonelementary rates.

  15. Absolute and relative blindsight.

    PubMed

    Balsdon, Tarryn; Azzopardi, Paul

    2015-03-01

    The concept of relative blindsight, referring to a difference in conscious awareness between conditions otherwise matched for performance, was introduced by Lau and Passingham (2006) as a way of identifying the neural correlates of consciousness (NCC) in fMRI experiments. By analogy, absolute blindsight refers to a difference between performance and awareness regardless of whether it is possible to match performance across conditions. Here, we address the question of whether relative and absolute blindsight in normal observers can be accounted for by response bias. In our replication of Lau and Passingham's experiment, the relative blindsight effect was abolished when performance was assessed by means of a bias-free 2AFC task or when the criterion for awareness was varied. Furthermore, there was no evidence of either relative or absolute blindsight when both performance and awareness were assessed with bias-free measures derived from confidence ratings using signal detection theory. This suggests that both relative and absolute blindsight in normal observers amount to no more than variations in response bias in the assessment of performance and awareness. Consideration of the properties of psychometric functions reveals a number of ways in which relative and absolute blindsight could arise trivially and elucidates a basis for the distinction between Type 1 and Type 2 blindsight.

  16. 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.

  17. Absolute rate constants for hydrogen atom transfer from tertiary amides to the cumyloxyl radical: evaluating the role of stereoelectronic effects.

    PubMed

    Salamone, Michela; Milan, Michela; DiLabio, Gino A; Bietti, Massimo

    2014-08-01

    A time-resolved kinetic study of the hydrogen atom transfer (HAT) reactions from a series of alkanamides to the cumyloxyl radical (CumO(•)) was carried out. With N,N-dialkylformamides HAT preferentially occurs from the formyl C-H bond, while in N-formylpyrrolidine HAT mostly occurs from the ring α-C-H bonds. With the acetamides and the alkanamides almost exclusive HAT from the C-H bonds that are α to nitrogen was observed. The results obtained show that alignment between the C-H bond being broken and the amide π-system can lead to significant increases in the HAT rate constant (kH). This finding points toward the important role of stereoelectronic effects on the HAT reactivity and selectivity. The highest kH values were measured for the reactions of CumO(•) with N-acylpyrrolidines. These substrates have ring α-C-H bonds that are held in a conformation that is optimally aligned with the amide π-system, thus allowing for the relatively facile HAT reaction. The lowest kH value was measured for the reaction of N,N-diisobutylacetamide, wherein the steric bulk associated with the N-isobutyl groups increases the energy barrier required to reach the most suitable conformation for HAT. The experimental results are well supported by the computed BDEs for the C-H bonds of the most representative substrates.

  18. Optically based quantification of absolute cerebral metabolic rate of oxygen (CMRO2) with high spatial resolution in rodents

    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.

  19. The Extinction of Low Strain Rate Diffusion Flames by a Suppressant

    NASA Technical Reports Server (NTRS)

    Hamins, A.; Yang, J.; Puri, I. K.

    1999-01-01

    This paper describes plans for an experimental and computational study on the structure and extinction of low strain rate diffusion flames by a suppressant added to the oxidizer stream. Stable low strain rate flames will be established through ground based reduced gravity experiments using the 2.2 s drop tower. A variety of agents will be investigated, including both physically and chemically acting agents (He, N2, CO2, and CF3Br) for flames burning methane and propane. A computational model of flame structure and extinction will be modified to include radiative losses, which is thought to be a significant heat loss mechanism at low strain rates.

  20. Water has no effect on oxygen self-diffusion rate in forsterite

    NASA Astrophysics Data System (ADS)

    Fei, H.; Yamazaki, D.; Wiedenbeck, M.; Katsura, T.

    2014-12-01

    Water is thought to play an essential role in dynamical processes in the Earth's interior. Even several tens wt. ppm of water may enhance the creep rates in olivine by orders of magnitude based on deformation experiments [1, 2]. High temperature creep in olivine is believed to be controlled by self-diffusion of the slowest species, which is silicon in olivine. However, silicon self-diffusion experiments suggest that the role of water on olivine rheology is overestimated in previous deformation studies because of the experimental difficulties [3].On the other hand, oxygen is the second slowest species with similar diffusion rate as silicon. It may also play an essential role in olivine creep. By comparing the oxygen self-diffusion coefficient (DO) in olivine at ambient pressure and dry conditions [4] with those at 2 GPa and hydrous conditions, it is found that even 30-50 wt. ppm of water could enhance DO by one order of magnitude [5]. However, comparison of experimental results obtained at different pressures could lead to misinterpretations because different experimental setups have different error sources [6]. In this study, we systematically measured DO in an iron-free olivine, namely, forsterite, at 8 GPa and 1600-1800 K over a wide range of water content (CH2O) from <1 up to 800 wt. ppm. Our results show that DO∝(CH2O)0.05±0.06≈(CH2O)0. Thus, water has no significant effect on oxygen self-diffusion rate in forsterite. Since the water content dependence of silicon self-diffusion rate is also very small [3], the role of water on olivine rheology is not as significant as previously thought by assuming the diffusion controlled creep mechanism. [1] Karato &Jung (2003), Philosophical Mag. 83, 401-414.[2] Hirth & Kohlstedt (2003) Geophys. Monogr. 138, 83-105.[3] Fei et al. (2013), Nature 498, 213-215.[4] Dohmen et al. (2002), GRL 29, 2030.[5] Costa & Chakraborty (2008), PEPI 166, 11-29.[6] Fei et al. (2012), EPSL 345, 95-103.

  1. A new method for measuring the oxygen diffusion constant and oxygen consumption rate of arteriolar walls.

    PubMed

    Sasaki, Nobuhiko; Horinouchi, Hirohisa; Ushiyama, Akira; Minamitani, Haruyuki

    2012-01-01

    Oxygen transport is believed to primarily occur via capillaries and depends on the oxygen tension gradient between the vessels and tissues. As blood flows along branching arterioles, the O(2) saturation drops, indicating either consumption or diffusion. The blood flow rate, the O(2) concentration gradient, and Krogh's O(2) diffusion constant (K) of the vessel wall are parameters affecting O(2)delivery. We devised a method for evaluating K of arteriolar wall in vivo using phosphorescence quenching microscopy to measure the partial pressure of oxygen in two areas almost simultaneously. The K value of arteriolar wall (inner diameter, 63.5 ± 11.9 μm; wall thickness, 18.0 ± 1.2 μm) was found to be 6.0 ± 1.2 × 10(-11) (cm(2)/s)(ml O(2)·cm(-3) tissue·mmHg(-1)). The arteriolar wall O(2) consumption rate (M) was 1.5 ± 0.1 (ml O(2)·100 cm(-3) tissue·min(-1)), as calculated using Krogh's diffusion equation. These results suggest that the arteriolar wall consumes a considerable proportion of the O(2) that diffuses through it.

  2. Sandwich mixer-reactor: influence of the diffusion coefficient and flow rate ratios.

    PubMed

    Abonnenc, Mélanie; Josserand, Jacques; Girault, Hubert H

    2009-02-07

    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.

  3. Advances and problems of the nucleation rate measurements by the flow diffusion chamber

    NASA Astrophysics Data System (ADS)

    Anisimov, Michael

    2013-05-01

    The flow diffusion chamber (FDC) presents flow systems for measuring of the vaporgas nucleation rate on the base of primary aerosol concentration measurements and estimation of the nucleation conditions within the axial vapor-gas flow. A particle size distribution can be measured in that experimental scheme as well. FDC decouples aerosol generation volume and aerosol detecting zones, which is useful for growing small critical clusters into optically detectable particles in residual supersaturated vapor.

  4. Effect of Drag Reducing Polymer and Suspended Solid on the Rate of Diffusion Controlled Corrosion in 90° Copper Elbow

    NASA Astrophysics Data System (ADS)

    Fouad, Mohamed Ahmed; Zewail, Taghreed Mohamed; Amine, Nieven Kamal Abbes

    2016-06-01

    Rate of diffusion controlled corrosion in 90° Copper Elbow acidified dichromate has been investigated in relation to the following parameters: effect of solution velocity in the absence and presence of drag- reducing polymer on the rate of diffusion controlled corrosion, and effect of the presence of suspended solids on the rate of diffusion controlled corrosion. It was found that the presence of drag reducing polymer inhibited the rate of mass transfer, while the presence of suspended solid increased significantly the rate of mass transfer.

  5. Mass-loading and diffusion-loss rates of the Io plasma torus

    NASA Technical Reports Server (NTRS)

    Shemansky, D. E.

    1980-01-01

    Limits to the mass-loading and diffusion-loss rates of ions in the Io plasma torus have been calculated on the assumption that observed optical emissions are controlled by electron-ion collisions. Calculations of the yield of emission from the vicinity of Io limit the mass-loading rate to the order of 10 to the 27th per s for S II or O II, on the grounds that electron-excited emissions associated with the location of Io have not been observed in the optical spectrum. This mass-loading limit is dependent on the assumptions that Io is the source of torus particles and that most of the neutral atoms are converted to ions within 1 R(J) of Io. According to the calculations presented below, the observed partitioning of sulfur ion species in the hot torus at the time of Voyager 1 encounter indicates that the diffusion-loss time of the ions is of the order of 1/D = 100 days. The two results limiting the mass-loading and diffusion-loss rates are compatible and suggest that the energy required to maintain the observed radiated power cannot be supplied by acceleration of ions formed at Io in Jupiter's rotating magnetic field.

  6. Planar Strain-Rate-Free Diffusion Flames: Initiation, Properties, and Extinction

    NASA Technical Reports Server (NTRS)

    Fendell, Francis; Gokoglu, Suleyman; Rungaldier, Harald; Schultz, Donald

    1999-01-01

    An effectively strain-rate-free diffusion flame constitutes the most vigorous laminar combustion of initially unmixed reactive gases. Such a diffusion flame is characterized by a relatively long residence time and by a relatively large characteristic length scale. If such a flame were also planar, providing high symmetry, it would be particularly suitable for experimental and theoretical investigations of key combustion phenomena, such as multicomponent diffusion, chemical kinetics, and soot inception, growth, and oxidation. Unfortunately, a planar strain-rate-free diffusion flame is highly disrupted in earth-gravity (e.g., in a counterflow-diffusion-flame apparatus) because of the very rapid onset (approx. 100 ms) of gravity-induced instability. Accordingly, a specially dedicated apparatus was designed, fabricated, and initially checked out for the examination of a planar strain-rate-free diffusion flame in microgravity. Such a diffusion flame may be formed within a hollowed-out squat container (initially configured as 25 cm x 25 cm x 9 cm), with isothermal, noncatalytic, impervious walls. At test initiation, a thin metallic sheet (approx. 1 mm in thickness) that separates the internal volume into two equal portions, each of dimensions 25 cm x 25 cm x 4.5 cm, is withdrawn, by uniform translation (approx. 50 cm/s) in its own plane, through a tightly fitting slit in one side wall. Thereupon, diluted fuel vapor (initially confined to one half-volume of the container) gains access to diluted oxygen (initially with the same pressure, density, and temperature as the fuel, but initially confined to the other half-volume). After a brief delay (approx. 10 ms), to permit limited but sufficient-for-flammability diffusional interpenetration of fuel vapor and oxidizer, burning is initiated by discharge of a line igniter, located along that side wall from which the trailing edge of the separator withdraws. The ignition spawns a triple-flame propagation across the 25 cm x 25 cm

  7. Diffusion Rates for Hydrogen on Pd(111) from Molecular Quantum Dynamics Calculations.

    PubMed

    Firmino, Thiago; Marquardt, Roberto; Gatti, Fabien; Dong, Wei

    2014-12-18

    The van Hove formula for the dynamical structure factor (DSF) related to particle scattering at mobile adsorbates is extended to include the relaxation of the adsorbates' vibrational states. The total rate obtained from the DSF is assumed to be the sum of a diffusion and a relaxation rate. A simple kinetic model to support this assumption is presented. To illustrate its potential applicability, the formula is evaluated using wave functions, energies, and lifetimes of vibrational states obtained for H/Pd(111) from first-principle calculations. Results show that quantum effects can be expected to be important even at room temperature.

  8. Diffusion Rates and Dispersal Patterns of Unfed versus Recently Fed Bed Bugs (Cimex lectularius L.)

    PubMed Central

    Goddard, Jerome; Caprio, Michael; Goddard, Jerome

    2015-01-01

    Bed bug problems have been increasing since the 1980s, and accordingly, there have been intensive efforts to better understand their biology and behavior for control purposes. Understanding bed bug diffusion rates and dispersal patterns from one site to another (or lack thereof) is a key component in prevention and control campaigns. This study analyzed diffusion rates and dispersal patterns in a population of bed bugs, recently fed and unfed, in both one-dimensional and two-dimensional settings. When placed in the middle of a 71 cm × 2.7 cm artificial lane, approximately half of the bugs regardless of feeding status stayed at or near the release point during the 10 min observation periods, while about a fourth of them walked to the end of the lane. When placed in the middle of an arena measuring 51 cm × 76 cm and allowed to walk in any direction, approximately one-fourth of bed bugs, fed or unfed, still remained near their release point (no significant difference between fed or unfed). As for long-distance dispersal, 11/50 (22%) of recently fed bed bugs moved as far as possible in the arena during the 10 min replications, while only 2/50 (4%) unfed bed bugs moved to the maximum distance. This difference was significantly different (p < 0.0038), and indicates that unfed bed bugs did not move as far as recently fed ones. A mathematical diffusion model was used to quantify bed bug movements and an estimated diffusion rate range of 0.00006 cm2/s to 0.416 cm2/s was determined, which is almost no movement to a predicted root mean squared distance of approximately 19 cm per 10 min. The results of this study suggest that bed bugs, upon initial introduction into a new area, would have a difficult time traversing long distances when left alone to randomly disperse. PMID:26466900

  9. Diffusion Rates and Dispersal Patterns of Unfed versus Recently Fed Bed Bugs (Cimex lectularius L.).

    PubMed

    Goddard, Jerome; Caprio, Michael; Goddard, Jerome

    2015-09-24

    Bed bug problems have been increasing since the 1980s, and accordingly, there have been intensive efforts to better understand their biology and behavior for control purposes. Understanding bed bug diffusion rates and dispersal patterns from one site to another (or lack thereof) is a key component in prevention and control campaigns. This study analyzed diffusion rates and dispersal patterns in a population of bed bugs, recently fed and unfed, in both one-dimensional and two-dimensional settings. When placed in the middle of a 71 cm × 2.7 cm artificial lane, approximately half of the bugs regardless of feeding status stayed at or near the release point during the 10 min observation periods, while about a fourth of them walked to the end of the lane. When placed in the middle of an arena measuring 51 cm × 76 cm and allowed to walk in any direction, approximately one-fourth of bed bugs, fed or unfed, still remained near their release point (no significant difference between fed or unfed). As for long-distance dispersal, 11/50 (22%) of recently fed bed bugs moved as far as possible in the arena during the 10 min replications, while only 2/50 (4%) unfed bed bugs moved to the maximum distance. This difference was significantly different (p < 0.0038), and indicates that unfed bed bugs did not move as far as recently fed ones. A mathematical diffusion model was used to quantify bed bug movements and an estimated diffusion rate range of 0.00006 cm²/s to 0.416 cm²/s was determined, which is almost no movement to a predicted root mean squared distance of approximately 19 cm per 10 min. The results of this study suggest that bed bugs, upon initial introduction into a new area, would have a difficult time traversing long distances when left alone to randomly disperse.

  10. Cooling rate estimations based on kinetic modelling of Fe-Mg diffusion in olivine

    NASA Technical Reports Server (NTRS)

    Taylor, L. A.; Onorato, P. I. K.; Uhlmann, D. R.

    1977-01-01

    A finite one-dimensional kinetic model was developed to estimate the cooling rates of lunar rocks. The model takes into consideration the compositional zonation of olivine and applies Buening and Buseck (1973) data on ion diffusion in olivine. Since the 'as-solidified' profile of a given olivine is not known, a step-function, with infinite gradient, is assumed; the position of this step is based on mass balance considerations of the measured compositional profile. A minimum cooling rate would be associated with the preservation of a given gradient. The linear cooling rates of lunar rocks 12002 and 15555 were estimated by use of the olivine cooling-rate indicator to be 10 C/day and 5 C/day, respectively. These values are lower than those obtained by dynamic crystallization studies (10-20 C/day).

  11. Cooling rates for lunar samples determined with a diffusion model for phosphide exsolution

    NASA Technical Reports Server (NTRS)

    Hewins, R. H.; Goldstein, J. I.

    1977-01-01

    A numerical model for diffusion-controlled phase growth has been applied to the exsolution of phosphide lamellae in lunar metal grains. Computer simulations reproduce observed composition profiles, and reveal the influence of cooling rate on dimensional and compositional parameters of phosphide and metal. At lower cooling rates, phosphide lamellae are larger and the concentration of P in the metal host close to the interface is lower. Cooling rates inferred for Apollo 16 samples, based on compositions and dimensions of the phosphide-metal grains, are mostly in the range 1-100 C/day. These rates correspond to burial depths of 5-0.5 m for melt rocks and 3-0.3 m for breccias. This is in good agreement with thicknesses of lunar cooling units determined by other techniques.

  12. Wavy membranes and the growth rate of a planar chemical garden: Enhanced diffusion and bioenergetics

    PubMed Central

    Ding, Yang; Batista, Bruno; Steinbock, Oliver; Cardoso, Silvana S. S.

    2016-01-01

    To model ion transport across protocell membranes in Hadean hydrothermal vents, we consider both theoretically and experimentally the planar growth of a precipitate membrane formed at the interface between two parallel fluid streams in a 2D microfluidic reactor. The growth rate of the precipitate is found to be proportional to the square root of time, which is characteristic of diffusive transport. However, the dependence of the growth rate on the concentrations of hydroxide and metal ions is approximately linear and quadratic, respectively. We show that such a difference in ionic transport dynamics arises from the enhanced transport of metal ions across a thin gel layer present at the surface of the precipitate. The fluctuations in transverse velocity in this wavy porous gel layer allow an enhanced transport of the cation, so that the effective diffusivity is about one order of magnitude higher than that expected from molecular diffusion alone. Our theoretical predictions are in excellent agreement with our laboratory measurements of the growth of a manganese hydroxide membrane in a microfluidic channel, and this enhanced transport is thought to have been needed to account for the bioenergetics of the first single-celled organisms. PMID:27486248

  13. Wavy membranes and the growth rate of a planar chemical garden: Enhanced diffusion and bioenergetics.

    PubMed

    Ding, Yang; Batista, Bruno; Steinbock, Oliver; Cartwright, Julyan H E; Cardoso, Silvana S S

    2016-08-16

    To model ion transport across protocell membranes in Hadean hydrothermal vents, we consider both theoretically and experimentally the planar growth of a precipitate membrane formed at the interface between two parallel fluid streams in a 2D microfluidic reactor. The growth rate of the precipitate is found to be proportional to the square root of time, which is characteristic of diffusive transport. However, the dependence of the growth rate on the concentrations of hydroxide and metal ions is approximately linear and quadratic, respectively. We show that such a difference in ionic transport dynamics arises from the enhanced transport of metal ions across a thin gel layer present at the surface of the precipitate. The fluctuations in transverse velocity in this wavy porous gel layer allow an enhanced transport of the cation, so that the effective diffusivity is about one order of magnitude higher than that expected from molecular diffusion alone. Our theoretical predictions are in excellent agreement with our laboratory measurements of the growth of a manganese hydroxide membrane in a microfluidic channel, and this enhanced transport is thought to have been needed to account for the bioenergetics of the first single-celled organisms.

  14. The prognostic utility and the association of serum light chains (free and total) and absolute lymphocyte count in patients with newly diagnosed diffuse large B-cell lymphoma.

    PubMed

    Han, Xiaohong; Wang, Jianfei; Zhang, Ningning; Yao, Jiarui; Feng, Yun; Li, Dan; Liu, Peng; Yang, Jianliang; Zhou, Shengyu; Qin, Yan; Yang, Sheng; Gui, Lin; He, Xiaohui; Shi, Yuankai

    2014-11-01

    In this study, serum free and total light chains (sFLC/sTLC) were measured in 108 serum samples of therapy-naïve patients with DLBCL. Clinicopathologic data and survival outcomes were analyzed according to the results of sFLC/sTLC measurements. Moreover, the association of sFLC/sTLC with absolute monocyte count (AMC) and absolute lymphocyte count (ALC) was evaluated. Elevated sFLC and abnormal κ/λ ratio was present in 42.6% (51/108) and 4.6% (5/108) of patients, respectively. sTLC was successfully measured in 107 serum samples, abnormal sTLC and abnormal κ/λ ratio was found in 28.0% (30/107) and 26.2% (28/107) of patients, respectively. Patients with elevated sFLC more frequently displayed adverse clinical characteristics, including age (P=0.001), B symptoms (P=0.022), low ALC (P=0.024) and hyperglobulinemia (P=0.012). Patients with elevated sFLC had an inferior overall survival (OS) (P=0.012) and tended to have shorter progression-free survival (PFS) (P=0.061) compared to patients with normal sFLC. Abnormal sTLC or abnormal sTLC ratio showed no significant association with clinical outcomes, with exception of abnormal concurrent κ and λ. Only association of sFLC and ALC with survival remained significant after adjusting for the International Prognostic Index (IPI). The measurement of sFLC and ALC at diagnosis might be useful for the prognostic stratification of patients and sTLC measurement was of little prognostic utility in DLBCL.

  15. Ar-40/Ar-39 dating, Ar diffusion properties, and cooling rate determinations of severely shocked chondrites

    NASA Technical Reports Server (NTRS)

    Bogard, D. D.; Hirsch, W. C.

    1980-01-01

    The ages of Ar-40/Ar-39 chondrites were computed to be 4.29 to 1.0 Gyr, with degassing times of 0.5 to 1.0 Gyr. The values of the diffusion parameter for Ar in Arrhenius plots show linear relationships which correspond to the degassing of different mineral phases with distinct K/Ca ratios and different average temperatures for Ar release. The experimental values of the diffusion parameter for the high-temperature phase of severely shocked chondrites are 10 to the -7th to 10 to the -5th/s for the shock-heating temperatures in the 950-1200 C range; the inferred reheating temperatures and the fraction of the Ar-40 loss during the reheating event suggest post-shock cooling rates and burial depths of 0.01-0.0001 C/s and 0.5-2m, respectively.

  16. Influence of bubble size, diffuser width, and flow rate on the integral behavior of bubble plumes

    NASA Astrophysics Data System (ADS)

    Fraga, Bruño.; Stoesser, Thorsten

    2016-06-01

    A large-eddy simulation based Eulerian-Lagrangian model is employed to quantify the impact of bubble size, diffuser diameter, and gas flow rate on integral properties of bubble plumes, such as the plume's width, centerline velocity, and mass flux. Calculated quantities are compared with experimental data and integral model predictions. Furthermore, the LES data were used to assess the behavior of the entrainment coefficient, the momentum amplification factor, and the bubble-to-momentum spread ratio. It is found that bubble plumes with constant bubble size and smaller diameter behave in accordance with integral plume models. Plumes comprising larger and non-uniform bubble sizes appear to deviate from past observations and model predictions. In multi-diameter bubble plumes, a bubble self-organisation takes place, i.e., small bubbles cluster in the center of the plume whilst large bubbles are found at the periphery of the plume. Multi-diameter bubble plumes also feature a greater entrainment rate than single-size bubble plumes, as well as a higher spread ratio and lower turbulent momentum rate. Once the plume is fully established, the size of the diffuser does not appear to affect integral properties of bubble plumes. However, plume development is affected by the diffuser width, as larger release areas lead to a delayed asymptotic behavior of the plume and consequently to a lower entrainment and higher spread ratio. Finally, the effect of the gas flow rate on the integral plume is studied and is deemed very relevant with regards to most integral plume properties and coefficients. This effect is already fairly well described by integral plume models.

  17. Absolute Determination for the Sodium-22(p,gamma)Magnesium-23 Reaction Rate: Consequences for Nucleosynthesis of Sodium-22 in Novae

    NASA Astrophysics Data System (ADS)

    Sallaska, Anne L.

    2010-11-01

    Hydrodynamic simulations of classical novae on ONe white dwarfs predict substantial production of 22Na. Observation of 22Na decay should be correlated with the corresponding nova because the half life of 22Na is only 2.6 years. The 1275-keV gamma ray from the beta decay of 22Na is, therefore, an excellent diagnostic for the nova phenomenon and a long-sought target of gamma-ray telescopes. Nova simulations determine the maximum 22Na-detection distance to be < 1 kpc for the INTEGRAL spectrometer SPI, consistent with its non-observation to date. However, model estimates are strongly dependent on the thermonuclear rate of the 22Na(p, gamma)23Mg reaction, which is the main destruction mechanism of 22Na in novae. The 22Na(p,gamma)23Mg rate is expected to be dominated by narrow, isolated resonances with Ep < 300 key. The currently employed rate is based on a single set of absolute resonance-strength measurements with Ep ≥ 290 keV, and one relative measurement of resonances with Ep ≥ 214 keV. Recently, a new level has been found in 23Mg which would correspond to a resonance at Ep = 198 keV that might dominate the reaction rate at nova temperatures. We have measured the 22Na(p, gamma) 23Mg resonance strengths directly and absolutely, in addition to resonance energies and branches. Proton beams were produced at the University of Washington and delivered to a specially designed beam line that included rastering and cold vacuum protection of the 22Na-implanted targets (fabricated at TRIUMF-ISAC). Two high-purity germanium detectors were employed and surrounded by anticoincidence shields to reduce cosmic backgrounds. Measurements were made on known 22Na+p resonances, which we observed at laboratory energies Ep = 213, 288, 454, 610 keV and on proposed resonances at Ep = 198, 209, and 232 key. The proposed resonances were not observed, and the upper limit placed on the 198-keV resonance strength indicates that the resonance at Ep = 213 keV still dominates the reaction rate

  18. Skin thickness progression rate: a predictor of mortality and early internal organ involvement in diffuse scleroderma

    PubMed Central

    Domsic, Robyn T; Rodriguez-Reyna, Tatiana; Lucas, Mary; Fertig, Noreen; Medsger, Thomas A

    2013-01-01

    Objective To examine the association of skin thickness progression rate (STPR) with mortality, and as a predictor of future internal organ involvement in an inception cohort of diffuse cutaneous systemic sclerosis (SSc) patients. Methods Diffuse cutaneous SSc patients older than 16 years of age evaluated at the University of Pittsburgh within 2 years of the first evidence of skin thickening between 1980 and 2005 were eligible. The authors calculated the STPR on these patients, and examined the relationship of this variable to the development of early internal organ involvement and short-term mortality using logistic regression. Results 826 patients were included in the analysis. Patients with a rapid STPR experienced significantly reduced short-term survival at 1 and 2 years from the time of first Pittsburgh evaluation (p=0.002). Patients with a rapid STPR were more likely to develop renal crisis within 1–2 years of follow-up. Rapid STPR was found to be an independent predictor of both mortality (OR 1.72; 95% CI 1.13 to 2.62; p=0.01) and ‘renal crisis’ (OR 2.05, 95% CI 1.10 to 3.85; p=0.02) within 2 years from first evaluation. Conclusion The STPR is an easy measure to perform at the time of initial evaluation for identifying those diffuse cutaneous SSc patients who are at increased risk of mortality and the development of renal crisis during the following 2 years. PMID:20679474

  19. Homogeneous nucleation rate measurements of 1-butanol in helium: a comparative study of a thermal diffusion cloud chamber and a laminar flow diffusion chamber.

    PubMed

    Brus, David; Hyvärinen, Antti-Pekka; Zdímal, Vladimír; Lihavainen, Heikki

    2005-06-01

    Isothermal homogeneous nucleation rates of 1-butanol were measured both in a thermal diffusion cloud chamber and in a laminar flow diffusion chamber built recently at the Institute of Chemical Process Fundamentals, Academy of Sciences of the Czech Republic, Prague, Czech Republic. The chosen system 1-butanol-helium can be studied reasonably well in both devices, in the overlapping range of temperatures. The results were compared with those found in the literature and those measured by Lihavainen in a laminar flow diffusion chamber of a similar design. The same isotherms measured with the thermal diffusion cloud chamber occur at highest saturation ratios of the three devices. Isotherms measured with the two laminar flow diffusion chambers are reasonably close together; the measurements by Lihavainen occur at lowest saturation ratios. The temperature dependences observed were similar in all three devices. The molecular content of critical clusters was calculated using the nucleation theorem and compared with the Kelvin equation. Both laminar flow diffusion chambers provided very similar sizes slightly above the Kelvin equation, whereas the thermal diffusion cloud chamber suggests critical cluster sizes significantly smaller. The results found elsewhere in the literature were in reasonable agreement with our results.

  20. Are in vitro estimates of cell diffusivity and cell proliferation rate sensitive to assay geometry?

    PubMed

    Treloar, Katrina K; Simpson, Matthew J; McElwain, D L Sean; Baker, Ruth E

    2014-09-07

    Cells respond to various biochemical and physical cues during wound-healing and tumour progression. in vitro assays used to study these processes are typically conducted in one particular geometry and it is unclear how the assay geometry affects the capacity of cell populations to spread, or whether the relevant mechanisms, such as cell motility and cell proliferation, are somehow sensitive to the geometry of the assay. In this work we use a circular barrier assay to characterise the spreading of cell populations in two different geometries. Assay 1 describes a tumour-like geometry where a cell population spreads outwards into an open space. Assay 2 describes a wound-like geometry where a cell population spreads inwards to close a void. We use a combination of discrete and continuum mathematical models and automated image processing methods to obtain independent estimates of the effective cell diffusivity, D, and the effective cell proliferation rate, λ. Using our parameterised mathematical model we confirm that our estimates of D and λ accurately predict the time-evolution of the location of the leading edge and the cell density profiles for both assay 1 and assay 2. Our work suggests that the effective cell diffusivity is up to 50% lower for assay 2 compared to assay 1, whereas the effective cell proliferation rate is up to 30% lower for assay 2 compared to assay 1.

  1. Evolution of supersaturation of amorphous pharmaceuticals: nonlinear rate of supersaturation generation regulated by matrix diffusion.

    PubMed

    Sun, Dajun D; Lee, Ping I

    2015-04-06

    The importance of rate of supersaturation generation on the kinetic solubility profiles of amorphous systems has recently been shown by us; however, the previous focus was limited to constant rates of supersaturation generation. The objective of the current study is to further examine the effect of nonlinear rate profiles of supersaturation generation in amorphous systems, including (1) instantaneous or infinite rate (i.e., initial degree of supersaturation), (2) first-order rate (e.g., from dissolution of amorphous drug particles), and (3) matrix diffusion regulated rate (e.g., drug release from amorphous solid dispersions (ASDs) based on cross-linked poly(2-hydroxyethyl methacrylate) (PHEMA) hydrogels), on the kinetic solubility profiles of a model poorly soluble drug indomethacin (IND) under nonsink dissolution conditions. The previously established mechanistic model taking into consideration both the crystal growth and ripening processes was extended to predict the evolution of supersaturation resulting from nonlinear rates of supersaturation generation. Our results confirm that excessively high initial supersaturation or a rapid supersaturation generation leads to a surge in maximum supersaturation followed by a rapid decrease in drug concentration owing to supersaturation-induced precipitation; however, an exceedingly low degree of supersaturation or a slow rate of supersaturation generation does not sufficiently raise the supersaturation level, which results in a lower but broader maximum kinetic solubility profile. Our experimental data suggest that an optimal area-under-the-curve of the kinetic solubility profiles exists at an intermediate initial supersaturation level for the amorphous systems studied here, which agrees well with the predicted trend. Our model predictions also support our experimental findings that IND ASD in cross-linked PHEMA exhibits a unique kinetic solubility profile because the resulting supersaturation level is governed by a matrix

  2. Chemical response of methane/air diffusion flames to unsteady strain rate

    SciTech Connect

    Im, H.G.; Chen, J.H.; Chen, J.Y.

    1998-03-01

    Effects of unsteady strain rate on the response of methane/air diffusion flames are studied. The authors use the finite-domain opposed flow configuration in which the nozzle exit velocity is imposed as a function of time. The GRI mechanism v2.11 is used for the detailed methane/air chemistry. The response of individual species to monochromatic oscillation in strain rate with various frequencies reveals that the fluctuation of slow species, such as CO and NO{sub x}, is more rapidly suppressed as the flow time scale decreases. It is also observed that the maximum CO concentration is very insensitive to the variation in the scalar dissipation rate. An extinction event due to an abrupt imposition of high strain rates is also simulated by an impulsive velocity with various frequencies. For a fast impulse, a substantial overshoot in NO{sub 2} concentration is observed after extinction. Finally, the overall fuel burning rate shows a nonmonotonic response to the variation in characteristic unsteady time scale, while the emission indices for NO{sub x} shows monotonic decay in response as frequency is increased.

  3. Determination of oxygen diffusion rates in magnetite from natural isotopic variations

    NASA Astrophysics Data System (ADS)

    Sharp, Z. D.

    1991-06-01

    The oxygen isotope compositions of magnetite grains, hosted in a calcite marble from the Bancroft terrane of the Ontario Grenville province, vary systematically with grain size. The δ18O values of magnetite and corresponding closure temperatures (Tc) based on Δcalcite-magnetite range from δ18O = 2.6‰, Tc = 505 °C for a grain radius of 0.075 mm, to δ18O = 5.5‰ Tc = 660 °C for a grain radius of 1.15 mm. The δ18O of the calcite is constant within a scale of 100 μm at a value of 12.3‰. The observed isotopic variations can be fit to the diffusion model of Dodson by the method of least squares (r = 0.98) to yield an activation energy (Q) = 211 (±20) kJ/mole and a pre-exponential factor (Do) = 4.3 (+3.3, -1.9) x 10-7 cm2/s for a cooling rate of 4 °C/m.y. The activation energy estimate is independent of the assumed cooling rate, but the calculated pre-exponential factor varies as follows: Do (cm2/s) = (dT/dt) x (-1.08 x 10-7). (Note: dT/dt is in °C/m.y.) The activation energy is identical to an experimental determination by Giletti and Hess, but the pre-exponential factor is 100 times lower. The difference is attributed to the water-rich conditions in the experiments and the absence of fluid in the slowly cooled marbles investigated in this study. The strong dependence of diffusion rate on water presence, or fH2O, may be used as a sensor for water-rich fluids during cooling in natural systems.

  4. Collision limited reaction rates for arbitrarily shaped particles across the entire diffusive Knudsen number range.

    PubMed

    Gopalakrishnan, Ranganathan; Thajudeen, Thaseem; Hogan, Christopher J

    2011-08-07

    Aerosol particle reactions with vapor molecules and molecular clusters are often collision rate limited, hence determination of particle-vapor molecule and particle-molecular cluster collision rates are of fundamental importance. These collisions typically occur in the mass transfer transition regime, wherein the collision kernel (collision rate coefficient) is dependent upon the diffusive Knudsen number, Kn(D). While this alone prohibits analytical determination of the collision kernel, aerosol particle- vapor molecule collisions are further complicated when particles are non-spherical, as is often the case for particles formed in high temperature processes (combustion). Recently, through a combination of mean first passage time simulations and dimensional analysis, it was shown that the collision kernel for spherical particles and vapor molecules could be expressed as a dimensionless number, H, which is solely a function of Kn(D). In this work, it is shown through similar mean first passage times and redefinitions of H and Kn(D) that the H(Kn(D)) relationship found for spherical particles applies for particles of arbitrary shape, including commonly encountered agglomerate particles. Specifically, it is shown that to appropriately define H and Kn(D), two geometric descriptors for a particle are necessary: its Smoluchowski radius, which defines the collision kernel in the continuum regime (Kn(D)→0) and its orientationally averaged projected area, which defines the collision kernel in the free molecular regime (Kn(D)→∞). With these two parameters, as well as the properties of the colliding vapor molecule (mass and diffusion coefficient), the particle-vapor molecule collision kernel in the continuum, transition, and free molecular regimes can be simply calculated using the H(Kn(D)) relationship.

  5. 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…

  6. Competing quantum effects in the free energy profiles and diffusion rates of hydrogen and deuterium molecules through clathrate hydrates.

    PubMed

    Cendagorta, Joseph R; Powers, Anna; Hele, Timothy J H; Marsalek, Ondrej; Bačić, Zlatko; Tuckerman, Mark E

    2016-11-30

    Clathrate hydrates hold considerable promise as safe and economical materials for hydrogen storage. Here we present a quantum mechanical study of H2 and D2 diffusion through a hexagonal face shared by two large cages of clathrate hydrates over a wide range of temperatures. Path integral molecular dynamics simulations are used to compute the free-energy profiles for the diffusion of H2 and D2 as a function of temperature. Ring polymer molecular dynamics rate theory, incorporating both exact quantum statistics and approximate quantum dynamical effects, is utilized in the calculations of the H2 and D2 diffusion rates in a broad temperature interval. We find that the shape of the quantum free-energy profiles and their height relative to the classical free energy barriers at a given temperature, as well as the rate of diffusion, are strongly affected by competing quantum effects: above 25 K, zero-point energy (ZPE) perpendicular to the reaction path for diffusion between cavities decreases the quantum rate compared to the classical rate, whereas at lower temperatures tunneling outcompetes the ZPE and as a result the quantum rate is greater than the classical rate.

  7. Absolute rate constants for the quenching of reactive excited states by melanin and related 5,6-dihydroxyindole metabolites: implications for their antioxidant activity.

    PubMed

    Zhang, X; Erb, C; Flammer, J; Nau, W M

    2000-05-01

    The triplet-excited state of benzophenone and the singlet-excited state of 2,3-diazabicyclo[2.2.2]oct-2-ene (Fluorazophore-P) have been employed as kinetic probes to obtain information on the antioxidant activity of the skin and eye pigment melanin and its biogenetic precursors 5,6-dihydroxyindole (DHI) and 5,6-dihydroxyindole-2-carboxylic acid (DHICA). The excited states were generated by the laser-flash photolysis technique and their reaction kinetics was examined by time-resolved transient absorption or fluorescence spectroscopy, respectively. The reaction between triplet benzophenone and DHI produced with unit efficiency the corresponding 6O-centered semiquinone radical, which was characterized by its characteristic transient absorption. The quenching rate constants for DHI (3.1-8.4 x 10(9) M-1 s-1) and DHICA (3.3-5.5 x 10(9) M-1 s-1) were near the diffusion-controlled limit, indicating excellent antioxidant properties. Kinetic solvent effects were observed. The reactivity of synthetic melanin, assessed through the quenching rate constant of Fluorazophore-P and normalized to the number of monomer units, was more than one order of magnitude lower (2.7 x 10(8) M-1 s-1) than that of its precursors. The trend of the quenching rate constants, i.e. DHI > DHICA approximately alpha-tocopherol > melanin, along with the preferential solubility of DHICA in aqueous environments, serves to account for several experimental results from biochemical studies on the inhibition of lipid peroxidation by these natural antioxidants.

  8. Molecular Dynamics and Monte Carlo simulations resolve apparent diffusion rate differences for proteins confined in nanochannels

    NASA Astrophysics Data System (ADS)

    Tringe, J. W.; Ileri, N.; Levie, H. W.; Stroeve, P.; Ustach, V.; Faller, R.; Renaud, P.

    2015-08-01

    We use Molecular Dynamics and Monte Carlo simulations to examine molecular transport phenomena in nanochannels, explaining four orders of magnitude difference in wheat germ agglutinin (WGA) protein diffusion rates observed by fluorescence correlation spectroscopy (FCS) and by direct imaging of fluorescently-labeled proteins. We first use the ESPResSo Molecular Dynamics code to estimate the surface transport distance for neutral and charged proteins. We then employ a Monte Carlo model to calculate the paths of protein molecules on surfaces and in the bulk liquid transport medium. Our results show that the transport characteristics depend strongly on the degree of molecular surface coverage. Atomic force microscope characterization of surfaces exposed to WGA proteins for 1000 s show large protein aggregates consistent with the predicted coverage. These calculations and experiments provide useful insight into the details of molecular motion in confined geometries.

  9. Simulation of chemical reaction via particle tracking: Diffusion-limited versus thermodynamic rate-limited regimes

    NASA Astrophysics Data System (ADS)

    Benson, David A.; Meerschaert, Mark M.

    2008-12-01

    Chemical reactions may be simulated without regard to local concentrations by applying simple probabilistic rules of particle interaction and combination. The forward reaction A + B→ C is coded by calculating the probability that any A and B particles will occupy the same volume over some time interval. This becomes a convolution of the location densities of the two particles. The backward reaction is a simple exponential decay of C particles into A and B particles. When the mixing of reactants is not a limiting process, the classical thermodynamic reaction rates are reproduced. When low mixing (as by diffusion) limits the reaction probabilities, the reaction rates drop significantly, including the rate of approach to global equilibrium. At long enough times, the law of mass action is reproduced exactly in the mean, with some irreducible deviation in the local equilibrium saturations (the equilibrium constant divided by the mass action expression) away from unity. The saturation variability is not sensitive to numerical parameters but depends strongly on how far from equilibrium the system is initiated. This is simply due to a relative paucity of particles of some species as the reaction moves far to one side or the other.

  10. Enhanced International Prognostic Index (NCCN-IPI), Charlson Comorbidity Index and absolute lymphocyte count as predictors for survival of elderly patients with diffuse large B cell lymphoma treated by immunochemotherapy.

    PubMed

    Jelicic, J; Todorovic Balint, M; Sretenovic, D Antic A; Balint, B; Perunicic Jovanovic, M; Andjelic, B; Vukovic, V; Djurasinovic, V; Bila, J; Pavlovic, M; Smiljanic, M; Mihaljevic, B

    2015-01-01

    Diffuse large B cell lymphoma (DLBCL) affects more commonly patients over 60 years. These patients have vast number of comorbidities which can modify survival as well as other clinical parameters. The aim of this study was to evaluate prognostic significance of the National Comprehensive Cancer Network International Prognostic Index (NCCN-IPI), absolute lymphocyte count (ALC), absolute monocyte count (AMC), lymphocyte-to-monocyte ratio (LMR) and comorbidities expressed with Charlson Comorbidity Index (CCI). A total of 182 DLBCL patients 60 years old and older were included, focusing on whole group and patients older than 70. All patients were treated with immunochemotherapy.Overall treatment response was achieved in 84.6% of patients. The NCCN-IPI was of highly prognostic value in the analyzed group (p<0.0001). Survival analysis showed that ALC>1.1x109/L, AMC≤0.59x109/L, and LMR>2.8 were associated with more favorable outcome (p=0.029, p=0.019, p=0.028, respectively). The patients with CCI≥2 had poorer outcome (p=0.008) compared to the patients with CCI 0-1. Multivariate analysis showed that among ALC, AMC, LMR, NCCN-IPI and CCI, the NCCN-IPI was the critical parameter that significantly affected survival (p<0.0001). Furthermore, comorbidities were also valuable independent factors which influenced survival (p=0.031) as well as the ALC (p=0.024). In elderly DLBCL patients, NCCN-IPI and ALC proved their prognostic validity, while poorer outcome could be expected in older patients with high CCI (≥2). Furthermore, mentioned prognostic parameters retained their prognostic value in the group of patients older than 70.

  11. Validation of absolute axial neutron flux distribution calculations with MCNP with 197Au(n,γ)198Au reaction rate distribution measurements at the JSI TRIGA Mark II reactor.

    PubMed

    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.

  12. Comparison of in vitro release rates of acyclovir from cream formulations using vertical diffusion cells.

    PubMed

    Nallagundla, Sumalatha; Patnala, Srinivas; Kanfer, Isadore

    2014-08-01

    Acyclovir, indicated in the treatment of herpes labialis ("cold sores"), is formulated as semisolid topical dosage forms and marketed in numerous countries. Since the formulations of the various acyclovir products may differ from country to country, this study was undertaken to compare the in vitro release of acyclovir from various generic cream products available on the South African and Indian markets using the respective brand/innovator product as the reference product. The in vitro studies were carried out using vertical diffusion cells with a diffusional surface area of 1.767 cm(2) and various commercially available membranes. Normal saline was used as receptor fluid and the temperature maintained at 32 ± 0.5°C. The in vitro release comparisons were based on the recommendations described in the US Food and Drug Administration Draft Guidance for acyclovir ointment and the SUPAC-SS Guidance for non-sterile semisolid dosage forms. The release rates (slope) of the test (T) and the relevant reference product (R) were monitored and compared. The comparative release of acyclovir from the various generic formulations compared with the reference product was found to be within the limits of 75-133.33% with a 90% confidence interval. These experiments indicate that the generic acyclovir cream formulations exhibited release rates that were comparable to the innovator product and could be considered to be bioequivalent.

  13. Rate of diffusion-limited reactions for a fractal aggregate of reactive spheres

    NASA Astrophysics Data System (ADS)

    Tseng, Chin-Yao; Tsao, Heng-Kwong

    2002-08-01

    We study the reaction rate for a fractal cluster of perfectly absorbing, stationary spherical sinks in a medium containing a mobile reactant. The effectiveness factor eta, which is defined as the ratio of the total reaction rate of the cluster to that without diffusional interactions, is calculated. The scaling behavior of eta is derived for arbitrary fractal dimension based on the Kirkwood-Riseman approximation. The asymptotic as well as the finite size scaling of eta are confirmed numerically by the method of multipole expansion, which has been proven to be an excellent approximation. The fractal assembly is made of N spheres with its dimension varying from D<1 to D=3. The number of sinks can be as high as NapproxO(104). The asymptotic scaling behavior of the effectiveness factor is eta][approxN1/D-1 for D>1, eta][approx(ln N)-1 for D=1, and eta][approxN0 for D<1. The crossover behavior indicates that while in the regime of D>1 the screening effect of diffusive interactions grows with the size, for D<1 it is limited in a finite range and decays with decreasing D. The conclusion is also applicable to transport phenomena like dissolution, heat conduction, and sedimentation.

  14. Radiochromic leuco dye micelle hydrogels: II. Low diffusion rate leuco crystal violet gel

    NASA Astrophysics Data System (ADS)

    Babic, Steven; Battista, Jerry; Jordan, Kevin

    2009-11-01

    Radiation-sensitive hydrogels offer the capability of verifying intricate dose distributions in three-dimensional (3D) space conveniently in a single measurement with sub-millimetre spatial resolution. In this study, a new radiochromic hydrogel called leuco crystal violet (LCV) micelle gel is introduced. Upon irradiation, LCV converts to crystal violet (CV+). Triton X-100 micelles are used to provide the required hybrid-interfacing environment to dissolve LCV. The diffusion coefficient of the LCV gel has been measured to be 0.036 ± 0.001 mm2 h-1, which is a factor of 25 times less than the standard radiochromic ferrous xylenol-orange (FX) gel; LCV gels without Triton X-100 micelles have a diffusion coefficient of 0.33 ± 0.02 mm2 h-1. The LCV gel formulation contains: 1 mM LCV, 25 mM trichloroacetic acid, 4 mM Triton X-100 and 4% w/w gelatin. The primary innovative feature of this 3D hydrogel is that the radiation-induced CV+ dye is more soluble in the Triton X-100 micelles than in the surrounding water which consequently leads to more stable post-irradiation dose distributions. A dosimetric characterization revealed that the dose response is reproducible to within 1% over three separate batches, independent of energy, dose rate and dose fractionation but is affected by the temperature (~4% per °C) during irradiation. LCV micelle gels scanned optically with a yellow light source are a promising system for 3D dose verification. They may prove to be, especially, useful for scanning large volume dosimeters (i.e. 20 cm) since they are easily manufactured, transparent and near colourless prior to irradiation.

  15. Radiochromic leuco dye micelle hydrogels: II. Low diffusion rate leuco crystal violet gel.

    PubMed

    Babic, Steven; Battista, Jerry; Jordan, Kevin

    2009-11-21

    Radiation-sensitive hydrogels offer the capability of verifying intricate dose distributions in three-dimensional (3D) space conveniently in a single measurement with sub-millimetre spatial resolution. In this study, a new radiochromic hydrogel called leuco crystal violet (LCV) micelle gel is introduced. Upon irradiation, LCV converts to crystal violet (CV(+)). Triton X-100 micelles are used to provide the required hybrid-interfacing environment to dissolve LCV. The diffusion coefficient of the LCV gel has been measured to be 0.036 +/- 0.001 mm(2) h(-1), which is a factor of 25 times less than the standard radiochromic ferrous xylenol-orange (FX) gel; LCV gels without Triton X-100 micelles have a diffusion coefficient of 0.33 +/- 0.02 mm(2) h(-1). The LCV gel formulation contains: 1 mM LCV, 25 mM trichloroacetic acid, 4 mM Triton X-100 and 4% w/w gelatin. The primary innovative feature of this 3D hydrogel is that the radiation-induced CV(+) dye is more soluble in the Triton X-100 micelles than in the surrounding water which consequently leads to more stable post-irradiation dose distributions. A dosimetric characterization revealed that the dose response is reproducible to within 1% over three separate batches, independent of energy, dose rate and dose fractionation but is affected by the temperature ( approximately 4% per degree C) during irradiation. LCV micelle gels scanned optically with a yellow light source are a promising system for 3D dose verification. They may prove to be, especially, useful for scanning large volume dosimeters (i.e. 20 cm) since they are easily manufactured, transparent and near colourless prior to irradiation.

  16. Evaluation and comparison of diffusion MR methods for measuring apparent transcytolemmal water exchange rate constant

    NASA Astrophysics Data System (ADS)

    Tian, Xin; Li, Hua; Jiang, Xiaoyu; Xie, Jingping; Gore, John C.; Xu, Junzhong

    2017-02-01

    Two diffusion-based approaches, CG (constant gradient) and FEXI (filtered exchange imaging) methods, have been previously proposed for measuring transcytolemmal water exchange rate constant kin, but their accuracy and feasibility have not been comprehensively evaluated and compared. In this work, both computer simulations and cell experiments in vitro were performed to evaluate these two methods. Simulations were done with different cell diameters (5, 10, 20 μm), a broad range of kin values (0.02-30 s-1) and different SNR's, and simulated kin's were directly compared with the ground truth values. Human leukemia K562 cells were cultured and treated with saponin to selectively change cell transmembrane permeability. The agreement between measured kin's of both methods was also evaluated. The results suggest that, without noise, the CG method provides reasonably accurate estimation of kin especially when it is smaller than 10 s-1, which is in the typical physiological range of many biological tissues. However, although the FEXI method overestimates kin even with corrections for the effects of extracellular water fraction, it provides reasonable estimates with practical SNR's and more importantly, the fitted apparent exchange rate AXR showed approximately linear dependence on the ground truth kin. In conclusion, either CG or FEXI method provides a sensitive means to characterize the variations in transcytolemmal water exchange rate constant kin, although the accuracy and specificity is usually compromised. The non-imaging CG method provides more accurate estimation of kin, but limited to large volume-of-interest. Although the accuracy of FEXI is compromised with extracellular volume fraction, it is capable of spatially mapping kin in practice.

  17. Role of hydraulic diffusivity in the decrease of weathering rates over time

    NASA Astrophysics Data System (ADS)

    Pacheco, Fernando A. L.; Van der Weijden, Cornelis H.

    2014-05-01

    Springs emerging within massifs of crystalline rocks were monitored for discharge rate (Q), and the Q values combined with geomorphic and hydrographic parameters in a hydrologic model to calculate hydraulic conductivity (K) and effective porosity (ne) of the spring watersheds. The spring waters, several borehole waters and rain water were analyzed for major dissolved compounds, strontium and isotopes (δ18O, δ2H, δ13C and 87Sr/86Sr). With a shift to less negative values, δ18O and δ2H were fitted by a line approximately parallel to the GMWL, but no significant dependence on altitude was found. The δ18O and δ2H values correlate better with those of precipitation amount. The 87Sr/86Sr ratios in drilled well waters correlate positively with the depth of water circulation reported in the borehole logs. The corresponding regression equations were used to extrapolate the depth of hydraulic circuits within the spring watersheds. The previous data, together with groundwater travel times calculated by a water balance model, and with reactions of granite/metassediment plagioclase and biotite precipitating halloysite, gibbsite and vermiculite, were assembled in a mass balance model to calculate solute-flux weathering rates of plagioclase (WPl). The WPl's were described as a function of √{D}∝√{K/n}, where D is the hydraulic diffusivity. The discrepancies between the WPl values and solid-state rates, based on the differences between elemental, isotopic and mineral compositions measured in present-day regoliths and in the assumed protolith, were assigned to a decrease in D over time, from values in the protolith to values in the weathered aquifer.

  18. Evaluation and comparison of diffusion MR methods for measuring apparent transcytolemmal water exchange rate constant.

    PubMed

    Tian, Xin; Li, Hua; Jiang, Xiaoyu; Xie, Jingping; Gore, John C; Xu, Junzhong

    2017-02-01

    Two diffusion-based approaches, CG (constant gradient) and FEXI (filtered exchange imaging) methods, have been previously proposed for measuring transcytolemmal water exchange rate constant kin, but their accuracy and feasibility have not been comprehensively evaluated and compared. In this work, both computer simulations and cell experiments in vitro were performed to evaluate these two methods. Simulations were done with different cell diameters (5, 10, 20μm), a broad range of kin values (0.02-30s(-1)) and different SNR's, and simulated kin's were directly compared with the ground truth values. Human leukemia K562 cells were cultured and treated with saponin to selectively change cell transmembrane permeability. The agreement between measured kin's of both methods was also evaluated. The results suggest that, without noise, the CG method provides reasonably accurate estimation of kin especially when it is smaller than 10s(-1), which is in the typical physiological range of many biological tissues. However, although the FEXI method overestimates kin even with corrections for the effects of extracellular water fraction, it provides reasonable estimates with practical SNR's and more importantly, the fitted apparent exchange rate AXR showed approximately linear dependence on the ground truth kin. In conclusion, either CG or FEXI method provides a sensitive means to characterize the variations in transcytolemmal water exchange rate constant kin, although the accuracy and specificity is usually compromised. The non-imaging CG method provides more accurate estimation of kin, but limited to large volume-of-interest. Although the accuracy of FEXI is compromised with extracellular volume fraction, it is capable of spatially mapping kin in practice.

  19. The time-periodic diffusive competition models with a free boundary and sign-changing growth rates

    NASA Astrophysics Data System (ADS)

    Wang, Mingxin; Zhang, Yang

    2016-10-01

    To understand the spreading of invasive and native species, in this paper we consider the diffusive competition models with a free boundary in the heterogeneous time-periodic environments, in which the variable intrinsic growth rates of these two species change signs and may be very negative in some large regions. We study the spreading-vanishing dichotomy, long-time dynamical behavior of solution, sharp criteria for spreading and vanishing, and estimates of the asymptotic spreading speed of the free boundary. Moreover, we establish the existence of positive solutions to a T-periodic boundary value problem of the diffusive competition system with sign-changing growth rates in the half line.

  20. Rényi entropy and improved equilibration rates to self-similarity for nonlinear diffusion equations

    NASA Astrophysics Data System (ADS)

    Carrillo, J. A.; Toscani, G.

    2014-12-01

    We investigate the large-time asymptotics of nonlinear diffusion equations ut = Δup in dimension n ⩾ 1, in the exponent interval p > n/(n + 2), when the initial datum u0 is of bounded second moment. Precise rates of convergence to the Barenblatt profile in terms of the relative Rényi entropy are demonstrated for finite-mass solutions defined in the whole space when they are re-normalized at each time t > 0 with respect to their own second moment, as proposed by Carrillo et al (2006 Arch. Ration. Mech. Anal. 180 127-49) and Toscani (2005 J. Evol. Eqns 5 185-203). The analysis shows that, in the range p > max((n - 1)/n, n/(n + 2)), the relative Rényi entropy exhibits a better decay, for intermediate times, with respect to the standard Ralston-Newman entropy. The result follows by a suitable use of sharp Gagliardo-Nirenberg-Sobolev inequalities considered by Dolbeault and Toscani (2013 Ann. Inst. Henri Poincare (C) Non Linear Anal. 30 917-34), and their information-theoretical proof (Savaré and Toscani 2014 IEEE Trans. Inform. Theory 60 2687-93), known as concavity of Rényi entropy power.

  1. Growth rate of crystalline ice and the diffusivity of supercooled water from 126 to 262 K

    NASA Astrophysics Data System (ADS)

    Xu, Yuntao; Petrik, Nikolay G.; Smith, R. Scott; Kay, Bruce D.; Kimmel, Greg A.

    2016-12-01

    Understanding deeply supercooled water is key to unraveling many of water’s anomalous properties. However, developing this understanding has proven difficult due to rapid and uncontrolled crystallization. Using a pulsed-laser–heating technique, we measure the growth rate of crystalline ice, G(T), for 180 K < T < 262 K, that is, deep within water’s “no man’s land” in ultrahigh-vacuum conditions. Isothermal measurements of G(T) are also made for 126 K ≤ T ≤ 151 K. The self-diffusion of supercooled liquid water, D(T), is obtained from G(T) using the Wilson–Frenkel model of crystal growth. For T > 237 K and P ˜ 10‑8 Pa, G(T) and D(T) have super-Arrhenius (“fragile”) temperature dependences, but both cross over to Arrhenius (“strong”) behavior with a large activation energy in no man’s land. The fact that G(T) and D(T) are smoothly varying rules out the hypothesis that liquid water’s properties have a singularity at or near 228 K at ambient pressures. However, the results are consistent with a previous prediction for D(T) that assumed no thermodynamic transitions occur in no man’s land.

  2. Growth rate of crystalline ice and the diffusivity of supercooled water from 126 to 262 K

    SciTech Connect

    Xu, Yuntao; Petrik, Nikolay G.; Smith, R. Scott; Kay, Bruce D.; Kimmel, Greg A.

    2016-12-12

    Understanding deeply supercooled water is key to unraveling many of water’s anomalous properties. However, this has proven difficult due to rapid and uncontrolled crystallization. Using a pulsed laser heating technique, we measure the growth rate of crystalline ice, G(T), for 180 K < T < 262 K, i.e. deep within water’s “no man’s land.” The self-diffusion of supercooled liquid water, D(T), is obtained from G(T) using the Wilson-Frenkel model of crystal growth. For T > 237 K, G(T) and D(T) have super-Arrhenius (“fragile”) temperature dependences, but both crossover to Arrhenius (“strong”) behavior with a large activation energy in “no man’s land.” The fact that G(T) and D(T) are smoothly varying rules out the hypothesis that liquid water’s properties have a singularity at or near 228 K. However the results are consistent with a previous prediction for D(T) that assumed no thermodynamic transitions occur in “no man’s land.

  3. Modeling exposure close to air pollution sources in naturally ventilated residences: association of turbulent diffusion coefficient with air change rate.

    PubMed

    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.

  4. Absolutely classical spin states

    NASA Astrophysics Data System (ADS)

    Bohnet-Waldraff, F.; Giraud, O.; Braun, D.

    2017-01-01

    We introduce the concept of "absolutely classical" spin states, in analogy to absolutely separable states of bipartite quantum systems. Absolutely classical states are states that remain classical (i.e., a convex sum of projectors on coherent states of a spin j ) under any unitary transformation applied to them. We investigate the maximal size of the ball of absolutely classical states centered on the maximally mixed state and derive a lower bound for its radius as a function of the total spin quantum number. We also obtain a numerical estimate of this maximal radius and compare it to the case of absolutely separable states.

  5. Diffusion-driven and excitation-dependent recombination rate in blue InGaN/GaN quantum well structures

    SciTech Connect

    Aleksiejūnas, R.; Gelžinytė, K.; Nargelas, S. Jarašiūnas, K.; Vengris, M.; Armour, E. A.; Byrnes, D. P.; Arif, R. A.; Lee, S. M.; Papasouliotis, G. D.

    2014-01-13

    We report on diffusion-driven and excitation-dependent carrier recombination rate in multiple InGaN/GaN quantum wells by using photoluminescence, light-induced absorption, and diffraction techniques. We demonstrate gradually increasing with excitation carrier diffusivity and its correlation with the recombination rate. At low carrier densities, an increase in radiative emission and carrier lifetime was observed due to partial saturation of non-radiative recombination centers. However, at carrier densities above ∼5 × 10{sup 18} cm{sup −3}, a typical value of photoluminescence efficiency droop, a further increase of diffusivity forces the delocalized carriers to face higher number of fast non-radiative recombination centers leading to an increase of non-radiative losses.

  6. Vertical and horizontal eddy diffusivities and oxygen dissipation rate in the subtropical Northwest Pacific

    NASA Astrophysics Data System (ADS)

    Kawabe, Masaki

    2008-03-01

    KV and may form the maximum of KV at 2000-2500 m. The contribution of Rossby waves to KV should be examined further, although instability of the bottom current formed by Rossby waves was suggested. The diffusive pseudo-velocity Wd(≡-∂ KV/∂ z) is a downwelling of 0.5×10 -5 cm s -1 in the deep layer at A0-C0, which may depress vertical advection because of the upwelling of deep water. The value of KH decreases with increasing depth: 1.7×10 7 cm 2 s -1 at 750-2000 m, 3.5×10 6 at 2250-4000 m, and 7.3×10 5 at 4250-5000 m. The oxygen dissipation rate, estimated using the obtained KV and KH, also decreases with increasing depth; it is 0.33 ml l -1 year -1 at the oxygen minimum and 0.12, 0.020, and 0.0090 in the upper, middle, and lower deep layers, respectively. These values are larger than past results by 1 order of magnitude or more at depths less than 3750 m and a few times at depths greater than 4250 m.

  7. 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.

  8. Diffusion of Innovation Theory and Xbox Live: Examining Minority Gamers' Responses and Rate of Adoption to Changes in Xbox Live

    ERIC Educational Resources Information Center

    Gray, Kishonna L.

    2012-01-01

    This article examines the response of minority gamers as they adopt new innovations in Xbox Live. Using diffusion of innovation theory, specific attention is given to gamers' rate of adoption of the new Xbox Live environment, which was a recent update to the Xbox Live interface. By employing virtual ethnography, observations, and interviews reveal…

  9. Determination of H{sub 2} Diffusion Rates through Various Closures on TRU Waste Bag-Out Bags

    SciTech Connect

    Phillip D. Noll, Jr.; E. Larry Callis; Kirsten M. Norman

    1999-06-01

    The amount of H{sub 2} diffusion through twist and tape (horse-tail), wire tie, plastic tie, and heat sealed closures on transuranic (TRU) waste bag-out bags has been determined. H{sub 2} diffusion through wire and plastic tie closures on TRU waste bag-out bags has not been previously characterized and, as such, TRU waste drums containing bags with these closures cannot be certified and/or shipped to the Waste Isolation Pilot Plant (WIPP). Since wire ties have been used at Los Alamos National Laboratory (LANL) from 1980 to 1991 and the plastic ties from 1991 to the present, there are currently thousands of waste drums that cannot be shipped to the WIPP site. Repackaging the waste would be prohibitively expensive. Diffusion experiments performed on the above mentioned closures show that the diffusion rates of plastic tie and horse-tail closures are greater than the accepted value presented in the TRU-PACT 11 Safety Analysis Report (SAR). Diffusion rates for wire tie closures are not statistically different from the SAR value. Thus, drums containing bags with these closures can now potentially be certified which would allow for their consequent shipment to WIPP.

  10. Diffusion of myosin light chain kinase on actin: A mechanism to enhance myosin phosphorylation rates in smooth muscle.

    PubMed

    Hong, Feng; Brizendine, Richard K; Carter, Michael S; Alcala, Diego B; Brown, Avery E; Chattin, Amy M; Haldeman, Brian D; Walsh, Michael P; Facemyer, Kevin C; Baker, Josh E; Cremo, Christine R

    2015-10-01

    Smooth muscle myosin (SMM) light chain kinase (MLCK) phosphorylates SMM, thereby activating the ATPase activity required for muscle contraction. The abundance of active MLCK, which is tightly associated with the contractile apparatus, is low relative to that of SMM. SMM phosphorylation is rapid despite the low ratio of MLCK to SMM, raising the question of how one MLCK rapidly phosphorylates many SMM molecules. We used total internal reflection fluorescence microscopy to monitor single molecules of streptavidin-coated quantum dot-labeled MLCK interacting with purified actin, actin bundles, and stress fibers of smooth muscle cells. Surprisingly, MLCK and the N-terminal 75 residues of MLCK (N75) moved on actin bundles and stress fibers of smooth muscle cell cytoskeletons by a random one-dimensional (1-D) diffusion mechanism. Although diffusion of proteins along microtubules and oligonucleotides has been observed previously, this is the first characterization to our knowledge of a protein diffusing in a sustained manner along actin. By measuring the frequency of motion, we found that MLCK motion is permitted only if acto-myosin and MLCK-myosin interactions are weak. From these data, diffusion coefficients, and other kinetic and geometric considerations relating to the contractile apparatus, we suggest that 1-D diffusion of MLCK along actin (a) ensures that diffusion is not rate limiting for phosphorylation, (b) allows MLCK to locate to areas in which myosin is not yet phosphorylated, and (c) allows MLCK to avoid getting "stuck" on myosins that have already been phosphorylated. Diffusion of MLCK along actin filaments may be an important mechanism for enhancing the rate of SMM phosphorylation in smooth muscle.

  11. Diffusion kinetics of samarium and neodymium in garnet, and a method for determining cooling rates of rocks

    PubMed

    Ganguly; Tirone; Hervig

    1998-08-07

    Experimental determinations of the diffusion coefficients of samarium and neodymium in almandine garnet and theoretical considerations show that one cannot assign a sufficiently restricted range of closure temperature, TC, to the samarium-neodymium decay system in garnet for the purpose of constraining the cooling rate. However, it is shown that the samarium-neodymium cooling age of garnet can be used to calculate both cooling rate and TC if the temperature and age at the peak metamorphic conditions are known.

  12. UNBIASED MOMENT-RATE SPECTRA AND ABSOLUTE SITE EFFECTS IN THE KACHCHH BASIN, INDIA, FROM THE ANALYSIS OF THE AFTERSHOCKS OF THE 2001 Mw 7.6 BHUJ EARTHQUAKE

    SciTech Connect

    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

  13. Functional imaging and assessment of the glucose diffusion rate in epithelial tissues in optical coherence tomography

    SciTech Connect

    Larin, K V; Tuchin, V V

    2008-06-30

    Functional imaging, monitoring and quantitative description of glucose diffusion in epithelial and underlying stromal tissues in vivo and controlling of the optical properties of tissues are extremely important for many biomedical applications including the development of noninvasive or minimally invasive glucose sensors as well as for therapy and diagnostics of various diseases, such as cancer, diabetic retinopathy, and glaucoma. Recent progress in the development of a noninvasive molecular diffusion biosensor based on optical coherence tomography (OCT) is described. The diffusion of glucose was studied in several epithelial tissues both in vitro and in vivo. Because OCT provides depth-resolved imaging of tissues with high in-depth resolution, the glucose diffusion is described not only as a function of time but also as a function of depth. (special issue devoted to application of laser technologies in biophotonics and biomedical studies)

  14. Magma ascent rate and initial water concentration inferred from diffusive water loss from olivine-hosted melt inclusions

    NASA Astrophysics Data System (ADS)

    Chen, Yang; Provost, Ariel; Schiano, Pierre; Cluzel, Nicolas

    2013-03-01

    As the water concentration in magma decreases during magma ascent, olivine-hosted melt inclusions will reequilibrate with the host magma through hydrogen diffusion in olivine. Previous models showed that for a single spherical melt inclusion in the center of a spherical olivine, the rate of diffusive reequilibration depends on the partition coefficient and diffusivity of hydrogen in olivine, the radius of the melt inclusion, and the radius of the olivine. This process occurs within a few hours and must be considered when interpreting water concentration in olivine-hosted melt inclusions. A correlation is expected between water concentration and melt inclusion radius, because small melt inclusions are more rapidly reequilibrated than large ones when the other conditions are the same. This study investigates the effect of diffusive water loss in natural samples by exploring such a correlation between water concentration and melt inclusion radius, and shows that the correlation can be used to infer the initial water concentration and magma ascent rate. Raman and Fourier transform infrared spectroscopy measurements show that 31 melt inclusions (3.6-63.9 μm in radius) in six olivines from la Sommata, Vulcano Island, Aeolian Islands, have 0.93-5.28 wt% water, and the host glass has 0.17 wt% water. The water concentration in the melt inclusions shows larger variation than the data in previous studies (1.8-4.52 wt%). It correlates positively with the melt inclusion radius, but does not correlate with the major element concentrations in the melt inclusions, which is consistent with the hypothesis that the water concentration has been affected by diffusive water loss. In a simplified hypothetical scenario of magma ascent, the initial water concentration and magma ascent rate are inferred by numerical modeling of the diffusive water loss process. The melt inclusions in each olivine are assumed to have the same initial water concentration and magma ascent rate. The melt

  15. Rates and mechanisms of conversion of ice nanocrystals to hydrates of HCl and HBr: acid diffusion in the ionic hydrates.

    PubMed

    Devlin, J Paul; Gulluru, Dheeraj B; Buch, Victoria

    2005-03-03

    This FTIR study focuses on solid-state chemistry associated with formation and interconversion of the ionic HX (X = Cl, Br) hydrates. Kinetic data are reported for conversions of ice nanocrystal arrays exposed to the saturation pressure of the acids in the 110 approximately 125 K range. The product is amorphous acid dihydrate in the case of HBr, and amorphous monohydrate for HCl. The rate-determining step is identified as HX diffusion through the hydrate product crust toward the interfacial reaction zone, rather than diffusion through ice, as commonly believed. Slowing of the conversion process is thus observed with increasing thickness of the crust. The diffusion coefficient (D(e)) and activation energy values for HX diffusion through the hydrates were evaluated with the help of the shrinking-core model. Hydrate crystallization occurs as a separate step, upon heating above 130 K. Subsequently, rates of reversible transitions between crystal di- and monohydrates were observed upon exposure to acid vapor and acid evacuation. In conversion from di- to monohydrate, the rate slows after fast formation of several layers; subsequently, diffusion through the product crust appears to be the rate-controlling step. The activation energy for HBr diffusion through crystal dihydrate is found to be significantly higher than that for the amorphous analogue. Conjecture is offered for a molecular mechanism of HX transport through the crystal hydrate, based on (i) spectroscopic/computational evidence for the presence of molecular HX bonded to X(-) in each of the ionic hydrate phases and (ii) the relative E(a) values found for HBr and HCl diffusion. Monte Carlo modeling suggests acid transport to the reaction zone along boundaries between "nanocrystallites" generated by multiple hydrate nucleation events at the particle surfaces. The reverse conversion, of crystalline monohydrate particles to the dihydrate phase, as well as dihydrate to trihydrate, displays nearly constant rate

  16. Absolute nuclear material assay

    DOEpatents

    Prasad, Manoj K [Pleasanton, CA; Snyderman, Neal J [Berkeley, CA; Rowland, Mark S [Alamo, CA

    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.

  17. Absolute nuclear material assay

    DOEpatents

    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.

  18. Zero-Order Antibiotic Release from Multilayer Contact Lenses: Nonuniform Drug and Diffusivity Distributions Produce Constant-Rate Drug Delivery.

    PubMed

    Guzman, Gustavo; Es-Haghi, Siamak Shams; Nugay, Turgut; Cakmak, Mukerrem

    2017-02-01

    A novel approach to zero-order constant-rate drug delivery from contact lenses is presented. Quasi-Case II non-Fickian transport is achieved by nonuniform drug and diffusivity distributions within three-layer bimodal amphiphilic conetworks (β-APCNs). The center layer is a highly oxygen permeable β-APCN matrix, which contains the drug and exhibits a high drug diffusivity. The outer β-APCN layers contain no-drug and are loaded with vitamin E, which slows diffusion. In contrast to single-layer neat-polymer and vitamin E-loaded films that display first-order "burst" kinetics, it is demonstrated experimentally and by modeling that the combined effect of nonuniform distribution of drug loading and diffusion constants within the three-layer lens maintains low local drug concentration at the lens-fluid interface and yields zero-order drug delivery. The release rates of topical antibiotics provide constant-rate therapeutic-level delivery with appropriate oxygen permeability for at least 30 h, at which time ≈25% of the drug was released.

  19. Impact of water boundary layer diffusion on the nitrification rate of submerged biofilter elements from a recirculating aquaculture system.

    PubMed

    Prehn, Jonas; Waul, Christopher K; Pedersen, Lars-Flemming; Arvin, Erik

    2012-07-01

    Total ammonia nitrogen (TAN) removal by microbial nitrification is an essential process in recirculating aquaculture systems (RAS). In order to protect the aquatic environment and fish health, it is important to be able to predict the nitrification rates in RAS's. The aim of this study was to determine the impact of hydraulic film diffusion on the nitrification rate in a submerged biofilter. Using an experimental batch reactor setup with recirculation, active nitrifying biofilter units from a RAS were exposed to a range of hydraulic flow velocities. Corresponding nitrification rates were measured following ammonium chloride, NH₄Cl, spikes and the impact of hydraulic film diffusion was quantified. The nitrification performance of the tested biofilter could be significantly increased by increasing the hydraulic flow velocity in the filter. Area based first order nitrification rate constants ranged from 0.065 m d⁻¹ to 0.192 m d⁻¹ for flow velocities between 2.5 m h⁻¹ and 40 m h⁻¹ (18 °C). This study documents that hydraulic film diffusion may have a significant impact on the nitrification rate in fixed film biofilters with geometry and hydraulic flows corresponding to our experimental RAS biofilters. The results may thus have practical implications in relation to the design, operational strategy of RAS biofilters and how to optimize TAN removal in fixed film biofilter systems.

  20. Measurement of lateral diffusion rates in membranes by pulsed magnetic field gradient, magic angle spinning-proton nuclear magnetic resonance.

    PubMed

    Gawrisch, Klaus; Gaede, Holly C

    2007-01-01

    Membrane organization, including the presence of domains, can be characterized by measuring lateral diffusion rates of lipids and membrane-bound substances. Magic angle spinning (MAS) yields well-resolved proton nuclear magnetic resonance (NMR) of lipids in biomembranes. When combined with pulsed-field gradient NMR (rendering what is called "pulsed magnetic field gradients-MAS-NMR"), it permits precise diffusion measurements on the micrometer lengths scale for any substance with reasonably well-resolved proton MAS-NMR resonances, without the need of preparing oriented samples. Sample preparation procedures, the technical requirements for the NMR equipment, and spectrometer settings are described. Additionally, equations for analysis of diffusion data obtained from unoriented samples, and a method for correcting the data for liposome curvature are provided.

  1. Opposed jet diffusion flames of nitrogen-diluted hydrogen vs air - Axial LDA and CARS surveys; fuel/air rates at extinction

    SciTech Connect

    Pellett, G.L.; Northam, G.B.; Wilson, L.G.; Jarrett, O. Jr.; Antcliff, R.R.

    1989-01-01

    An experimental study of H-air counterflow diffusion flames (CFDFs) is reported. Coaxial tubular opposed jet burners were used to form dish-shaped CFDFs centered by opposing laminar jets of H2/N2 and air in an argon bath at 1 atm. Jet velocities for extinction and flame restoration limits are shown versus input H2 concentration. LDA velocity data and CARS temperature and absolute N2, O2 density data give detailed flame structure on the air side of the stagnation point. The results show that air jet velocity is a more fundamental and appropriate measure of H2-air CFDF extinction than input H2 mass flux or fuel jet velocity. It is proposed that the observed constancy of air jet velocity for fuel mixtures containing 80 to 100 percent H2 measure a maximum, kinetically controlled rate at which the CFDF can consume oxygen in air. Fuel velocity mainly measures the input jet momentum required to center an H2/N2 versus air CFDF. 42 refs.

  2. Opposed jet diffusion flames of nitrogen-diluted hydrogen vs air - Axial LDA and CARS surveys; fuel/air rates at extinction

    NASA Technical Reports Server (NTRS)

    Pellett, G. L.; Northam, G. B.; Wilson, L. G.; Jarrett, Olin, Jr.; Antcliff, R. R.

    1989-01-01

    An experimental study of H-air counterflow diffusion flames (CFDFs) is reported. Coaxial tubular opposed jet burners were used to form dish-shaped CFDFs centered by opposing laminar jets of H2/N2 and air in an argon bath at 1 atm. Jet velocities for extinction and flame restoration limits are shown versus input H2 concentration. LDA velocity data and CARS temperature and absolute N2, O2 density data give detailed flame structure on the air side of the stagnation point. The results show that air jet velocity is a more fundamental and appropriate measure of H2-air CFDF extinction than input H2 mass flux or fuel jet velocity. It is proposed that the observed constancy of air jet velocity for fuel mixtures containing 80 to 100 percent H2 measure a maximum, kinetically controlled rate at which the CFDF can consume oxygen in air. Fuel velocity mainly measures the input jet momentum required to center an H2/N2 versus air CFDF.

  3. Expansion Rate Measurements at Moderate Pressure of Nonneutral Electron Plasmas in the Electron Diffusion Gauge (EDG) Experiment

    SciTech Connect

    Morrison, Kyle A.; Davidson, Ronald C.; Paul, Stephen F.; Belli, Emily A.; and Chao, Edward H.

    2001-05-18

    Measurements of the expansion rate of pure-electron plasmas have been performed on the Electron Diffusion Gauge (EDG) device at background helium gas pressures in the 5 x 10(superscript -8) Torr to 1 x 10(superscript -5) Torr range, where plasma expansion due to electron-neutral collisions dominates over plasma expansion due to trap asymmetries. It is found that the expansion rate, defined as the time rate of change of the particles' mean-square radius, scales approximately linearly with pressure and inversely as the square of the magnetic field strength in this regime, in agreement with classical predictions.

  4. Effect of Diffusion on Resonance Energy Transfer Rate Distributions: Implications for Distance Measurements.

    PubMed

    Toptygin, Dmitri; Chin, Alexander F; Hilser, Vincent J

    2015-10-01

    Intrinsically disordered protein regions and many other biopolymers lack the three-dimensional structure that could be determined by X-ray crystallography or NMR, which encourages the application of alternative experimental methods. Time-resolved resonance energy transfer data are often used to measure distances between two fluorophores attached to a flexible biopolymer. This is complicated by the rotational and translational diffusion of the fluorophores and by nonmonoexponential donor decay in the absence of the acceptor. Equation I(DA)(t) = I(D)(t)·F(t) is derived here, which is applicable regardless of whether I(D)(t) is monoexponential. I(D)(t) and I(DA)(t) are the δ-excitation donor emission decays in the absence and in the presence of the acceptor; F(t) contains information about energy transfer, donor-acceptor distance distribution, and diffusion dynamics. It is shown that in the absence of rotational and translational diffusion, F(t) is a continuous distribution of exponentials, whereas in the presence of rotational and translational diffusion, F(t) is a sum of discrete exponentials. For each case it is shown how F(t) is related to the distance distribution. Experimental data obtained with a flexible tetradecapeptide in aqueous solution clearly demonstrate that F(t) is a sum of discrete exponential terms. A partial differential equation describing resonance energy transfer in the presence of both rotational and translational diffusion of the donor and acceptor tethered to the ends of a semiflexible chain is solved in this work using a combination of analytical and numerical methods; the solution is used to fit time-resolved emission of the donor, which makes it possible to determine the model parameters: contour length, persistence length, and the end-to-end translational diffusion coefficient.

  5. Radial expansion rates and tumor growth kinetics predict malignant transformation in contrast-enhancing low-grade diffuse astrocytoma

    PubMed Central

    Hathout, Leith; Pope, Whitney B; Lai, Albert; Nghiemphu, Phioanh L; Cloughesy, Timothy F; Ellingson, Benjamin M

    2015-01-01

    Summary Background Contrast-enhancing low-grade diffuse astrocytomas are an understudied, aggressive subtype at increased risk because of few radiographic indications of malignant transformation. In the current study, we tested whether tumor growth kinetics could identify tumors that undergo malignant transformation to higher grades. Methods Thirty patients with untreated diffuse astrocytomas (WHO II) that underwent tumor progression were enrolled. Contrast-enhancing and T2 hyperintense tumor regions were segmented and the radius of tumor at two time points leading to progression was estimated. Radial expansion rates were used to estimate proliferation and invasion rates using a biomathematical model. Results Radial expansion rates for both contrast-enhancing (p = 0.0040) and T2 hyperintense regions (p = 0.0016) were significantly higher in WHO II–IV tumors compared with nontransformers. Similarly, model estimates showed a significantly higher proliferation (p = 0.0324) and invasion rate (p = 0.0050) in WHO II–IV tumors compared with nontransformers. Conclusion Tumor growth kinetics can identify contrast-enhancing diffuse astrocytomas undergoing malignant transformation. PMID:26095141

  6. Temperature dependence for the absolute rate constant for the reaction CH/sub 2/OH + O/sub 2/. -->. HO/sub 2/ + H/sub 2/CO from 215 to 300 K

    SciTech Connect

    Nesbitt, F.L.; Payne, W.A.; Stief, L.J.

    1988-07-14

    The absolute rate constant for the reaction CH/sub 2/OH + O/sub 2/ ..-->.. HO/sub 2/ + H/sub 2/CO has been determined from 215 to 300 K in a discharge flow system at 1-Torr pressure. The decay of CH/sub 2/OH was monitored in excess O/sub 2/ by collision-free sampling mass spectrometry. The temperature dependence observed is quite different from the usual Arrhenius form. For the 215-250 K interval, an activation energy of 3.4 kcal/mol is obtained. Above 250 K, the rate constant increases at a slower rate; previous high-temperature studies (1000-2000 K) again show a faster increase in the rate constant. A possible explanation for these observations is that the reaction mechanism changes from addition at low temperature to direct abstraction at high temperatures.

  7. Mechanobiology of LDL mass transport in the arterial wall under the effect of magnetic field, part I: Diffusion rate

    NASA Astrophysics Data System (ADS)

    Aminfar, Habib; Mohammadpourfard, Mousa; Khajeh, Kosar

    2017-03-01

    It is well-known that the Low Density Lipoprotein (LDL) can accumulate and penetrate into the arterial wall. Here, we have investigated the diffusion rate of macromolecules across the porous layer of blood vessel under the effects of magnetic force. By using a finite volume technique, it was found that magnetic field makes alterations in diffusion rate of LDLs, also surface concentration of macromolecules on the walls. As well, the influence of different value of Re and Sc number in the presence of a magnetic field have shown as nondimensional concentration profiles. Magnetic field considered as a body force, porous layer simulated by using Darcy's law and the blood regarded as nano fluid which was examined as a single phase model.

  8. Energy landscape analysis of native folding of the prion protein yields the diffusion constant, transition path time, and rates.

    PubMed

    Yu, Hao; Gupta, Amar Nath; Liu, Xia; Neupane, Krishna; Brigley, Angela M; Sosova, Iveta; Woodside, Michael T

    2012-09-04

    Protein folding is described conceptually in terms of diffusion over a configurational free-energy landscape, typically reduced to a one-dimensional profile along a reaction coordinate. In principle, kinetic properties can be predicted directly from the landscape profile using Kramers theory for diffusive barrier crossing, including the folding rates and the transition time for crossing the barrier. Landscape theory has been widely applied to interpret the time scales for protein conformational dynamics, but protein folding rates and transition times have not been calculated directly from experimentally measured free-energy profiles. We characterized the energy landscape for native folding of the prion protein using force spectroscopy, measuring the change in extension of a single protein molecule at high resolution as it unfolded/refolded under tension. Key parameters describing the landscape profile were first recovered from the distributions of unfolding and refolding forces, allowing the diffusion constant for barrier crossing and the transition path time across the barrier to be calculated. The full landscape profile was then reconstructed from force-extension curves, revealing a double-well potential with an extended, partially unfolded transition state. The barrier height and position were consistent with the previous results. Finally, Kramers theory was used to predict the folding rates from the landscape profile, recovering the values observed experimentally both under tension and at zero force in ensemble experiments. These results demonstrate how advances in single-molecule theory and experiment are harnessing the power of landscape formalisms to describe quantitatively the mechanics of folding.

  9. Poisson-Nernst-Planck equations for simulating biomolecular diffusion-reaction processes II: size effects on ionic distributions and diffusion-reaction rates.

    PubMed

    Lu, Benzhuo; Zhou, Y C

    2011-05-18

    The effects of finite particle size on electrostatics, density profiles, and diffusion have been a long existing topic in the study of ionic solution. The previous size-modified Poisson-Boltzmann and Poisson-Nernst-Planck models are revisited in this article. In contrast to many previous works that can only treat particle species with a single uniform size or two sizes, we generalize the Borukhov model to obtain a size-modified Poisson-Nernst-Planck (SMPNP) model that is able to treat nonuniform particle sizes. The numerical tractability of the model is demonstrated as well. The main contributions of this study are as follows. 1), We show that an (arbitrarily) size-modified PB model is indeed implied by the SMPNP equations under certain boundary/interface conditions, and can be reproduced through numerical solutions of the SMPNP. 2), The size effects in the SMPNP effectively reduce the densities of highly concentrated counterions around the biomolecule. 3), The SMPNP is applied to the diffusion-reaction process for the first time, to our knowledge. In the case of low substrate density near the enzyme reactive site, it is observed that the rate coefficients predicted by SMPNP model are considerably larger than those by the PNP model, suggesting both ions and substrates are subject to finite size effects. 4), An accurate finite element method and a convergent Gummel iteration are developed for the numerical solution of the completely coupled nonlinear system of SMPNP equations.

  10. First experimental determination of the absolute gas-phase rate coefficient for the reaction of OH with 4-hydroxy-2-butanone (4H2B) at 294 K by vapor pressure measurements of 4H2B.

    PubMed

    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.

  11. Electrochemistry of cations in diopsidic melt - Determining diffusion rates and redox potentials from voltammetric curves

    NASA Technical Reports Server (NTRS)

    Colson, Russell O.; Haskin, Larry A.; Crane, Daniel

    1990-01-01

    Results are presented on determinations of reduction potentials and their temperature dependence of selected ions in diopsidic melt, by using linear sweep voltammetry. Diffusion coefficients were measured for cations of Eu, Mn, Cr, and In. Enthalpies and entropies of reduction were determined for the cations V(V), Cr(3+), Mn(2+), Mn(3+), Fe(2+), Cu(2+), Mo(VI), Sn(IV), and Eu(3+). Reduction potentials were used to study the structural state of cations in the melt.

  12. Optical tracer size differences allow quantitation of active pumping rate versus Stokes-Einstein diffusion in lymphatic transport

    NASA Astrophysics Data System (ADS)

    DSouza, Alisha V.; Marra, Kayla; Gunn, Jason R.; Samkoe, Kimberley S.; Pogue, Brian W.

    2016-10-01

    Lymphatic uptake of interstitially administered agents occurs by passive convective-diffusive inflow driven by interstitial concentration and pressure, while the downstream lymphatic transport is facilitated by active propulsive contractions of lymphatic vessel walls. Near-infrared fluorescence imaging in mice was used to measure these central components of lymphatic transport for the first time, using two different-sized molecules-methylene blue (MB) and fluorescence-labeled antibody immunoglobulin G (IgG)-IRDye 680RD. This work confirms the hypothesis that lymphatic passive inflow and active propulsion rates can be separated based upon the relative differences in Stokes-Einstein diffusion coefficient. This coefficient specifically affects the passive-diffusive uptake when the interstitial volume and pressure are constant. Parameters such as mean time-to-peak signal, overall fluorescence signal intensities, and number of active peristaltic pulses, were estimated from temporal imaging data. While the mean time to attain peak signal representative of diffusion-dominated flow in the lymph vessels was 0.6±0.2 min for MB and 8±6 min for IgG, showing a size dependence, the active propulsion rates were 3.4±0.8 pulses/min and 3.3±0.5 pulses/min, respectively, appearing size independent. The propulsion rates for both dyes decreased with clearance from the interstitial injection-site, indicating intrinsic control of the smooth muscles in response to interstitial pressure. This approach to size-comparative agent flow imaging of lymphatic function can enable noninvasive characterization of diseases related to uptake and flow in lymph networks.

  13. Measuring radon exhalation rate in two cycles avoiding the effects of back-diffusion and chamber leakage.

    PubMed

    Tan, Yanliang; Xiao, Detao

    2013-10-01

    This paper will present a simple method for measuring the radon exhalation rate from the medium surface in two cycles and also avoiding the effects of back-diffusion and chamber leakage. The method is based on a combination of the "accumulation chamber" technique and a radon monitor. The radon monitor performs the measurement of the radon concentration inside the accumulation chamber, and then the radon exhalation rate can be obtained by simple calculation. For reducing the systematic error and the statistical uncertainty, too short of total measurement time is not appropriate, and the first cycle time should be about 70 % of the total measurement. The radon exhalation rate from the medium surface obtained through this method is in good agreement with the reference value. This simple method can be applied to develop and improve the instruments for measuring radon exhalation rate.

  14. A new approach to the correlation of boundary layer mass transfer rates with thermal diffusion and/or variable properties

    NASA Technical Reports Server (NTRS)

    Srivastava, R.; Rosner, D. E.

    1979-01-01

    A rational approach to the correlation of boundary layer mass transport rates, applicable to many commonly encountered laminar flow conditions with thermal diffusion and/or variable properties, is outlined. The correlation scheme builds upon already available constant property blowing/suction solutions by introducing appropriate correction factors to account for the additional ('pseudo' blowing and source) effects identified with variable properties and thermal diffusion. Applications of the scheme to the particular laminar boundary layer mass transfer problems considered herein (alkali and transition metal compound vapor transport) indicates satisfactory accuracy up to effective blowing factors equivalent to about one third of the 'blow off' value. As a useful by-product of the variable property correlation, we extend the heat-mass transfer analogy, for a wide range of Lewis numbers, to include variable property effects.

  15. Determination of plate wave velocities and diffuse field decay rates with braod-band acousto-ultrasonic signals

    NASA Technical Reports Server (NTRS)

    Kautz, Harold E.

    1993-01-01

    Lowest symmetric and lowest antisymmetric plate wave modes were excited and identified in broad-band acousto-ultrasonic (AU) signals collected from various high temperature composite materials. Group velocities have been determined for these nearly nondispersive modes. An algorithm has been developed and applied to determine phase velocities and hence dispersion curves for the frequency ranges of the broad-band pulses. It is demonstrated that these data are sensitive to changes in the various stiffness moduli of the materials, in agreement by analogy, with the theoretical and experimental results of Tang and Henneke on fiber reinforced polymers. Diffuse field decay rates have been determined in the same specimen geometries and AU configuration as for the plate wave measurements. These decay rates are of value in assessing degradation such as matrix cracking in ceramic matrix composites. In addition, we verify that diffuse field decay rates respond to fiber/matrix interfacial shear strength and density in ceramic matrix composites. This work shows that velocity/stiffness and decay rate measurements can be obtained in the same set of AU experiments for characterizing materials and in specimens with geometries useful for mechanical measurements.

  16. Estimating Absolute Site Effects

    SciTech Connect

    Malagnini, L; Mayeda, K M; Akinci, A; Bragato, P L

    2004-07-15

    The authors use previously determined direct-wave attenuation functions as well as stable, coda-derived source excitation spectra to isolate the absolute S-wave site effect for the horizontal and vertical components of weak ground motion. They used selected stations in the seismic network of the eastern Alps, and find the following: (1) all ''hard rock'' sites exhibited deamplification phenomena due to absorption at frequencies ranging between 0.5 and 12 Hz (the available bandwidth), on both the horizontal and vertical components; (2) ''hard rock'' site transfer functions showed large variability at high-frequency; (3) vertical-motion site transfer functions show strong frequency-dependence, and (4) H/V spectral ratios do not reproduce the characteristics of the true horizontal site transfer functions; (5) traditional, relative site terms obtained by using reference ''rock sites'' can be misleading in inferring the behaviors of true site transfer functions, since most rock sites have non-flat responses due to shallow heterogeneities resulting from varying degrees of weathering. They also use their stable source spectra to estimate total radiated seismic energy and compare against previous results. they find that the earthquakes in this region exhibit non-constant dynamic stress drop scaling which gives further support for a fundamental difference in rupture dynamics between small and large earthquakes. To correct the vertical and horizontal S-wave spectra for attenuation, they used detailed regional attenuation functions derived by Malagnini et al. (2002) who determined frequency-dependent geometrical spreading and Q for the region. These corrections account for the gross path effects (i.e., all distance-dependent effects), although the source and site effects are still present in the distance-corrected spectra. The main goal of this study is to isolate the absolute site effect (as a function of frequency) by removing the source spectrum (moment-rate spectrum) from

  17. Diffusion Rate Limitations in Actin-Based Propulsion of Hard and Deformable Particles

    PubMed Central

    Dickinson, Richard B.; Purich, Daniel L.

    2006-01-01

    The mechanism by which actin polymerization propels intracellular vesicles and invasive microorganisms remains an open question. Several recent quantitative studies have examined propulsion of biomimetic particles such as polystyrene microspheres, phospholipid vesicles, and oil droplets. In addition to allowing quantitative measurement of parameters such as the dependence of particle speed on its size, these systems have also revealed characteristic behaviors such a saltatory motion of hard particles and oscillatory deformation of soft particles. Such measurements and observations provide tests for proposed mechanisms of actin-based motility. In the actoclampin filament end-tracking motor model, particle-surface-bound filament end-tracking proteins are involved in load-insensitive processive insertion of actin subunits onto elongating filament plus-ends that are persistently tethered to the surface. In contrast, the tethered-ratchet model assumes working filaments are untethered and the free-ended filaments grow as thermal ratchets in a load-sensitive manner. This article presents a model for the diffusion and consumption of actin monomers during actin-based particle propulsion to predict the monomer concentration field around motile particles. The results suggest that the various behaviors of biomimetic particles, including dynamic saltatory motion of hard particles and oscillatory vesicle deformations, can be quantitatively and self-consistently explained by load-insensitive, diffusion-limited elongation of (+)-end-tethered actin filaments, consistent with predictions of the actoclampin filament-end tracking mechanism. PMID:16731556

  18. Poisson-Nernst-Planck Equations for Simulating Biomolecular Diffusion-Reaction Processes II: Size Effects on Ionic Distributions and Diffusion-Reaction Rates

    PubMed Central

    Lu, Benzhuo; Zhou, Y.C.

    2011-01-01

    The effects of finite particle size on electrostatics, density profiles, and diffusion have been a long existing topic in the study of ionic solution. The previous size-modified Poisson-Boltzmann and Poisson-Nernst-Planck models are revisited in this article. In contrast to many previous works that can only treat particle species with a single uniform size or two sizes, we generalize the Borukhov model to obtain a size-modified Poisson-Nernst-Planck (SMPNP) model that is able to treat nonuniform particle sizes. The numerical tractability of the model is demonstrated as well. The main contributions of this study are as follows. 1), We show that an (arbitrarily) size-modified PB model is indeed implied by the SMPNP equations under certain boundary/interface conditions, and can be reproduced through numerical solutions of the SMPNP. 2), The size effects in the SMPNP effectively reduce the densities of highly concentrated counterions around the biomolecule. 3), The SMPNP is applied to the diffusion-reaction process for the first time, to our knowledge. In the case of low substrate density near the enzyme reactive site, it is observed that the rate coefficients predicted by SMPNP model are considerably larger than those by the PNP model, suggesting both ions and substrates are subject to finite size effects. 4), An accurate finite element method and a convergent Gummel iteration are developed for the numerical solution of the completely coupled nonlinear system of SMPNP equations. PMID:21575582

  19. 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.

  20. Lipid composition affects the rate of photosensitized dissipation of cross-membrane diffusion potential on liposomes

    PubMed Central

    Ytzhak, Shany; Wuskell, Joseph P.; Loew, Leslie M.; Ehrenberg, Benjamin

    2010-01-01

    Hydrophobic or amphiphilic tetrapyrrole sensitizers are taken up by cells and are usually located in cellular lipid membranes. Singlet oxygen is photogenerated by the sensitizer and it diffuses in the membrane and causes oxidative damage to membrane components. This damage can occur to membrane lipids and to membrane-localized proteins. Depolarization of the Nernst electric potential on cells’ membranes has been observed in cellular photosensitization, but it was not established whether lipid oxidation is a relevant factor leading to abolishing the resting potential of cells’ membranes and to their death. In this work we studied the effect of liposomes’ lipid composition on the kinetics of hematoporphyrin-photosensitized dissipation of K+-diffusion electric potential that was generated across the membranes. We employed an electrochromic voltage-sensitive spectroscopic probe that possesses a high fluorescence signal response to the potential. We found a correlation between the structure and unsaturation of lipids and the leakage of the membrane, following photosensitization. As the extent of non-conjugated unsaturation of the lipids is increased from 1 to 6 double bonds, the kinetics of depolarization become faster. We also found that the kinetics of depolarization is affected by the percentage of the unsaturated lipids in the liposome: as the fraction of the unsaturated lipids increases the leakage trough the membrane is enhanced. When liposomes are composed of a lipid mixture similar to that of natural membranes and photosensitization is being carried out under usual photodynamic therapy (PDT) conditions, photodamage to the lipids is not likely to cause enhanced permeability of ions through the membrane, which would have been a mechanism that leads to cell death. PMID:20536150

  1. Absolute neutrino mass scale

    NASA Astrophysics Data System (ADS)

    Capelli, Silvia; Di Bari, Pasquale

    2013-04-01

    Neutrino oscillation experiments firmly established non-vanishing neutrino masses, a result that can be regarded as a strong motivation to extend the Standard Model. In spite of being the lightest massive particles, neutrinos likely represent an important bridge to new physics at very high energies and offer new opportunities to address some of the current cosmological puzzles, such as the matter-antimatter asymmetry of the Universe and Dark Matter. In this context, the determination of the absolute neutrino mass scale is a key issue within modern High Energy Physics. The talks in this parallel session well describe the current exciting experimental activity aiming to determining the absolute neutrino mass scale and offer an overview of a few models beyond the Standard Model that have been proposed in order to explain the neutrino masses giving a prediction for the absolute neutrino mass scale and solving the cosmological puzzles.

  2. Ignition and structure of a laminar diffusion flame in a compressible mixing layer with finite rate chemistry

    NASA Technical Reports Server (NTRS)

    Grosch, C. E.; Jackson, T. L.

    1991-01-01

    The ignition and structure of a reacting compressible mixing layer is considered using finite rate chemistry lying between two streams of reactants with different freestream speeds and temperatures. Numerical integration of the governing equations show that the structure of the reacting flow can be quite complicated depending on the magnitude of the Zeldovich number. An analysis of both the ignition a diffusion flame regimes is presented using a combination of large Zeldovich number asymptotics and numerics. This allows to analyze the behavior of these regimes as a function of the parameters of the problem.

  3. Ignition and structure of a laminar diffusion flame in a compressible mixing layer with finite rate chemistry

    NASA Technical Reports Server (NTRS)

    Grosch, C. E.; Jackson, T. L.

    1991-01-01

    The ignition and structure of a reacting compressible mixing layer is considered using finite rate chemistry lying between two streams of reactants with different freestream speeds and temperatures. Numerical integration of the governing equations show that the structure of the reacting flow can be quite complicated depending on the magnitude of the Zeldovich number. An analysis of both the ignition and diffusion flame regimes is presented using a combination of large Zeldovich number asymptotics and numerics. This allows to analyze the behavior of these regimes as a function of the parameters of the problem.

  4. Kinetics of O(1D) + H2O and O(1D) + H2: absolute rate coefficients and O(3P) yields between 227 and 453 K.

    PubMed

    Vranckx, Stijn; Peeters, Jozef; Carl, Shaun

    2010-08-28

    The rate coefficients for the crucial atmospheric reactions of O((1)D) with H(2)O and H(2), k(1) and k(2), were measured over a wide temperature range using O((1)D) detection based on the chemiluminescence reaction of O((1)D) with C(2)H. Analyzing the decays of the chemiluminescence intensities yielded a value for k(1)(T) of (1.70 x 10(-10)exp[36 K/T]) cm(3) s(-1). Multiplying or dividing k(1)(T) by a factor f(T) = 1.04 exp(5.59(|1 K/T- 1/287|)), gives the 95% confidence limits; our new determination, in good agreement with previous studies, further reduces the uncertainty in k(1). An extended study of k(2) yielded a temperature independent rate constant of (1.35 +/- 0.05) x 10(-10) cm(3) s(-1). This precise value, based on an extended set of determinations with very low scatter, is significantly larger than the current recommendations, as were two other recent k(2) determinations. Secondly, the fractions of O((1)D) quenched to O((3)P) by H(2)O and H(2), k(1b)/k(1) and k(2b)/k(2), were precisely determined from fits to chemiluminescence decays. A temperature-independent value for k(1b)/k(1) of 0.010 +/- 0.003 was found. For the quenching fraction k(2b)/k(2) a value of 0.007 +/- 0.007 was obtained at room temperature. Both determinations are significantly smaller than values and upper limits from previous studies.

  5. The absolute path command

    SciTech Connect

    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.

  6. Estimation of slow diffusion rates in confined systems: CCl4 in zeolite NaA

    NASA Astrophysics Data System (ADS)

    Ghorai, Pradip Kr.; Yashonath, S.; Lynden-Bell, R. M.

    Often the rate of passage of gaseous molecules through model zeolites is too small to be computed directly. An estimate for the rate of passage of CCl4 through the 8-ring window in a model of zeolite A has been obtained by combining a direct evaluation of the free energy profile and an adaptation of the rare events method. First the free energy profile is found from a direct evaluation of the canonical partition function at high dilution and the transition state theory rate constant obtained. The dynamic correction factor is then estimated from molecular dynamics runs and used to compute the actual rate keff. The method is used to estimate the rate of passage through the 8-ring window in a rigid model of zeolite A, and the results are compared with those obtained from rigid models with expanded windows and from the flexible model. Even a small expansion in the 8-ring window diameter increases the rate significantly, but the changes associated with a flexible cage are small.

  7. The American Foreign Exchange Option in Time-Dependent One-Dimensional Diffusion Model for Exchange Rate

    SciTech Connect

    Rehman, Nasir Shashiashvili, Malkhaz

    2009-06-15

    The classical Garman-Kohlhagen model for the currency exchange assumes that the domestic and foreign currency risk-free interest rates are constant and the exchange rate follows a log-normal diffusion process.In this paper we consider the general case, when exchange rate evolves according to arbitrary one-dimensional diffusion process with local volatility that is the function of time and the current exchange rate and where the domestic and foreign currency risk-free interest rates may be arbitrary continuous functions of time. First non-trivial problem we encounter in time-dependent case is the continuity in time argument of the value function of the American put option and the regularity properties of the optimal exercise boundary. We establish these properties based on systematic use of the monotonicity in volatility for the value functions of the American as well as European options with convex payoffs together with the Dynamic Programming Principle and we obtain certain type of comparison result for the value functions and corresponding exercise boundaries for the American puts with different strikes, maturities and volatilities.Starting from the latter fact that the optimal exercise boundary curve is left continuous with right-hand limits we give a mathematically rigorous and transparent derivation of the significant early exercise premium representation for the value function of the American foreign exchange put option as the sum of the European put option value function and the early exercise premium.The proof essentially relies on the particular property of the stochastic integral with respect to arbitrary continuous semimartingale over the predictable subsets of its zeros. We derive from the latter the nonlinear integral equation for the optimal exercise boundary which can be studied by numerical methods.

  8. Rate Limited Diffusion and Dissolution of Multicomponent Nonaqueous Phase Liquids (NAPLs) and Effects on Mass Discharge in Groundwater

    NASA Astrophysics Data System (ADS)

    Padgett, M.; Tick, G.; Carroll, K. C.

    2014-12-01

    Remediation efforts and contaminant transport predictions generally neglect the complicated dissolution and transport behavior associated with multicomponent NAPL (Non-aqueous phase liquid) sources. Therefore, it is important to understand the diffusion and dissolution processes occurring in these multicomponent systems as a function of mole fraction, molecular similarity/dissimilarity, hydraulic, or nonideal factors. A series of laboratory scale NAPL-aqueous phase dissolution experiments were conducted to assess dissolution and intra-NAPL diffusion as a function of multicomponent NAPL composition (i.e. mole fraction) for both trichloroethene and toluene. These target compounds were selected as representative contaminants as they are commonly components of NAPL mixtures and they define both classes of NAPL (dense-DNAPL and light-LNAPL). Predetermined volumes of target NAPL were mixed with an insoluble n-hexadecane NAPL to create mixtures that vary by NAPL composition. The ideality of resulting target compound dissolution was evaluated by quantifying NAPL-phase activity coefficient through Raoult's Law analysis. The results show that dissolution from the NAPL mixtures behave ideally for mole fractions above 0.2. As the target compound fraction of the NAPL mixture get smaller, the dissolution behavior becomes increasingly more nonideal (i.e. greater NAPL-phase activity coefficients). Overall, the time-series batch experiments show that dissolution rates were consistent for various mole fraction ratios, indicating that intra-NAPL diffusion is not the rate-limiting control over aqueous concentrations or is not significantly controlled by NAPL composition-dependent factors. The results of this work will improve transport predictions, remediation design, and risk assessments especially for sites contaminated by complex NAPL mixtures.

  9. Diffuse shear wave imaging: toward passive elastography using low-frame rate spectral-domain optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Nguyen, Thu-Mai; Zorgani, Ali; Lescanne, Maxime; Boccara, Claude; Fink, Mathias; Catheline, Stefan

    2016-12-01

    Optical coherence tomography (OCT) can map the stiffness of biological tissue by imaging mechanical perturbations (shear waves) propagating in the tissue. Most shear wave elastography (SWE) techniques rely on active shear sources to generate controlled displacements that are tracked at ultrafast imaging rates. Here, we propose a noise-correlation approach to retrieve stiffness information from the imaging of diffuse displacement fields using low-frame rate spectral-domain OCT. We demonstrated the method on tissue-mimicking phantoms and validated the results by comparison with classic ultrafast SWE. Then we investigated the in vivo feasibility on the eye of an anesthetized rat by applying noise correlation to naturally occurring displacements. The results suggest a great potential for passive elastography based on the detection of natural pulsatile motions using conventional spectral-domain OCT systems. This would facilitate the transfer of OCT-elastography to clinical practice, in particular, in ophthalmology or dermatology.

  10. Effect of competition between catalytic particles C on the rate of the reversible diffusion-controlled reaction A+C⇌B+C

    NASA Astrophysics Data System (ADS)

    Felderhof, B. U.; Jones, R. B.

    1999-11-01

    The effect of competition between catalytic particles C on the rate of the reversible diffusion-controlled reaction A+C⇌B+C is studied in a self-consistent approximation. The C-particles are assumed static with random configuration. The A- and B-particles diffuse in a fluid or solid background medium. Frequency-dependent effective rate coefficients are calculated as a function of the volume fraction of C-particles.

  11. Analysis of turbulent free jet hydrogen-air diffusion flames with finite chemical reaction rates

    NASA Technical Reports Server (NTRS)

    Sislian, J. P.

    1978-01-01

    The nonequilibrium flow field resulting from the turbulent mixing and combustion of a supersonic axisymmetric hydrogen jet in a supersonic parallel coflowing air stream is analyzed. Effective turbulent transport properties are determined using the (K-epsilon) model. The finite-rate chemistry model considers eight reactions between six chemical species, H, O, H2O, OH, O2, and H2. The governing set of nonlinear partial differential equations is solved by an implicit finite-difference procedure. Radial distributions are obtained at two downstream locations of variables such as turbulent kinetic energy, turbulent dissipation rate, turbulent scale length, and viscosity. The results show that these variables attain peak values at the axis of symmetry. Computed distributions of velocity, temperature, and mass fraction are also given. A direct analytical approach to account for the effect of species concentration fluctuations on the mean production rate of species (the phenomenon of unmixedness) is also presented. However, the use of the method does not seem justified in view of the excessive computer time required to solve the resulting system of equations.

  12. Functional mapping of flow and back-diffusion rate of N-isopropyl-p-iodoamphetamine in human brain.

    PubMed

    Yonekura, Y; Nishizawa, S; Mukai, T; Iwasaki, Y; Fukuyama, H; Ishikawa, M; Tamaki, N; Konishil, J

    1993-05-01

    Iodine-123-labeled N-isopropyl-p-iodoamphetamine (IMP) has been reported to be an excellent tracer for mapping cerebral blood flow with single-photon emission computed tomography (SPECT). Clinical interpretation of these SPECT images, however, requires further understanding of the kinetics of IMP in the human brain. In order to evaluate the kinetic behavior of IMP in normal and diseased areas, we measured flow and back-diffusion rates with serial dynamic SPECT scans following an intravenous bolus injection of IMP using a multi-detector SPECT scanner. Arterial input function was determined by octanol extracted radioactivity of serial arterial blood samples. Average values for influx rate (K1) and back-diffusion rate (k2) were 0.43 ml/g/min and 0.014 min-1 in the normal cerebral cortex, 0.43 and 0.013 in the basal ganglia, 0.28 and 0.012 in the white matter and 0.48 and 0.016 in the cerebellar hemisphere. The partition coefficient (K1/k2 ratio) was 32.4 ml/g in the cerebral cortex, 35.3 in the basal ganglia, 24.7 in the white matter and 30.4 in the cerebellum. The K1-to-k2 ratio in the infarcted and ischemic regions as well as in the tumor was smaller than that of the normal cortex. Accurate measurement of local cerebral blood flow (LCBF) based on the microsphere model was possible only on the early SPECT images, but a relative pattern of LCBF can be assessed with SPECT images obtained within 1 hr after injection except for tumors.

  13. Solid Propellant Kinetics. V. Fuel-Oxidizer Reaction Rates from Heterogeneous Opposed Flow Diffusion Flame

    DTIC Science & Technology

    1974-12-01

    species i and the V1 and v are i i i stoichiometric ratios. Then w = W (V -V ( 8 where W is the molecular weight of species i and molar reaction rate...where W is a constant molecular weight. Then the conservation equations 0 read L (0) L (Y) W Wi T o where 01 = Y W /W (V" - Vi ) i i oi i i T = C T/Q...Let W be the average molecular weight, IV = I/(Y i/Wi Then X = Y W/W so that the X. can be eliminated. Neglecting the variation in W allows one to

  14. Is the surface oxygen exchange rate linked to bulk ion diffusivity in mixed conducting Ruddlesden-Popper phases?

    PubMed

    Tomkiewicz, Alex C; Tamimi, Mazin A; Huq, Ashfia; McIntosh, Steven

    2015-01-01

    The possible link between oxygen surface exchange rate and bulk oxygen anion diffusivity in mixed ionic and electronic conducting oxides is a topic of great interest and debate. While a large body of experimental evidence and theoretical analyses support a link, observed differences between bulk and surface composition of these materials are hard to reconcile with this observation. This is further compounded by potential problems with simultaneous measurement of both parameters. Here we utilize separate techniques, in situ neutron diffraction and pulsed isotopic surface exchange, to examine bulk ion mobility and surface oxygen exchange rates of three Ruddlesden-Popper phases, general form A(n-1)A(2)'B(n)O(3n+1), A(n-1)A(2)'B(n)X(3n+1); LaSrCo(0.5)Fe(0.5)O(4-δ) (n = 1), La(0.3)Sr(2.7)CoFeO(7-δ) (n = 2) and LaSr3Co(1.5)Fe(1.5)O(10-δ) (n = 3). These measurements are complemented by surface composition determination via high sensitivity-low energy ion scattering. We observe a correlation between bulk ion mobility and surface exchange rate between materials. The surface exchange rates vary by more than one order of magnitude with high anion mobility in the bulk of an oxygen vacancy-rich n = 2 Ruddlesden-Popper material correlating with rapid oxygen exchange. This is in contrast with the similar surface exchange rates which we may expect due to similar surface compositions across all three samples. We conclude that experimental limitations lead to inherent convolution of surface and bulk rates, and that surface exchange steps are not likely to be rate limiting in oxygen incorporation.

  15. Is the surface oxygen exchange rate linked to bulk ion diffusivity in mixed conducting Ruddlesden–Popper phases?

    DOE PAGES

    Tomkiewicz, Alex C.; Tamimi, Mazin A.; Huq, Ashfia; ...

    2015-03-02

    There is a possible link between oxygen surface exchange rate and bulk oxygen anion diffusivity in mixed ionic and electronic conducting oxides; it is a topic of great interest and debate. While a large body of experimental evidence and theoretical analyses support a link, observed differences between bulk and surface composition of these materials are hard to reconcile with this observation. This is further compounded by potential problems with simultaneous measurement of both parameters. Here we utilize separate techniques, in situ neutron diffraction and pulsed isotopic surface exchange, to examine bulk ion mobility and surface oxygen exchange rates of threemore » Ruddlesden-Popper phases, general form An-1A2'BnO3n+1, An-1A2'BnX3n+1; LaSrCo0.5Fe0.5O4-δ (n = 1), La0.3Sr2.7CoFeO7-δ (n = 2) and LaSr3Co1.5Fe1.5O10-δ (n = 3). These measurements are complemented by surface composition determination via high sensitivity-low energy ion scattering. We observe a correlation between bulk ion mobility and surface exchange rate between materials. The surface exchange rates vary by more than one order of magnitude with high anion mobility in the bulk of an oxygen vacancy-rich n = 2 Ruddlesden-Popper material correlating with rapid oxygen exchange. Furthermore this is in contrast with the similar surface exchange rates which we may expect due to similar surface compositions across all three samples. This paper conclude that experimental limitations lead to inherent convolution of surface and bulk rates, and that surface exchange steps are not likely to be rate limiting in oxygen incorporation.« less

  16. Analysis of turbulent free-jet hydrogen-air diffusion flames with finite chemical reaction rates

    NASA Technical Reports Server (NTRS)

    Sislian, J. P.; Glass, I. I.; Evans, J. S.

    1979-01-01

    A numerical analysis is presented of the nonequilibrium flow field resulting from the turbulent mixing and combustion of an axisymmetric hydrogen jet in a supersonic parallel ambient air stream. The effective turbulent transport properties are determined by means of a two-equation model of turbulence. The finite-rate chemistry model considers eight elementary reactions among six chemical species: H, O, H2O, OH, O2 and H2. The governing set of nonlinear partial differential equations was solved by using an implicit finite-difference procedure. Radial distributions were obtained at two downstream locations for some important variables affecting the flow development, such as the turbulent kinetic energy and its dissipation rate. The results show that these variables attain their peak values on the axis of symmetry. The computed distribution of velocity, temperature, and mass fractions of the chemical species gives a complete description of the flow field. The numerical predictions were compared with two sets of experimental data. Good qualitative agreement was obtained.

  17. Kalman Filtering and Smoothing of the Van Allen Probes Observations to Estimate the Radial, Energy and Pitch Angle Diffusion Rates

    NASA Astrophysics Data System (ADS)

    Podladchikova, T.; Shprits, Y.; Kellerman, A. C.

    2015-12-01

    The Kalman filter technique combines the strengths of new physical models of the Earth's radiation belts with long-term spacecraft observations of electron fluxes and therefore provide an extremely useful method for the analysis of the state and evolution of the electron radiation belts. However, to get the reliable data assimilation output, the Kalman filter application is confronted with a set of fundamental problems. E.g., satellite measurements are usually limited to a single location in space, which confines the reconstruction of the global evolution of the radiation environment. The uncertainties arise from the imperfect description of the process dynamics and the presence of observation errors, which may cause the failure of data assimilation solution. The development of adaptive Kalman filter that combines the Van Allen Probes data and 3-D VERB code, its accurate customizations in the reconstruction of model describing the phase space density (PSD) evolution, extension of the possibilities to use measurement information, and the model adjustment by developing the identification techniques of model and measurement errors allowed us to reveal hidden and implicit regularities of the PSD dynamics and obtain quantitative and qualitative estimates of radial, energy and pitch angle diffusion characteristics from satellite observations. In this study we propose an approach to estimate radial, energy and pitch angle diffusion rates, as well as the direction of their propagation.

  18. Combustion rate limits of hydrogen plus hydrocarbon fuel: Air diffusion flames from an opposed jet burner technique

    NASA Technical Reports Server (NTRS)

    Pellett, Gerald L.; Guerra, Rosemary; Wilson, Lloyd G.; Reeves, Ronald N.; Northam, G. Burton

    1987-01-01

    Combustion of H2/hydrocarbon (HC) fuel mixtures may be considered in certain volume-limited supersonic airbreathing propulsion applications. Effects of HC addition to H2 were evaluated, using a recent argon-bathed, coaxial, tubular opposed jet burner (OJB) technique to measure the extinction limits of counterflow diffusion flames. The OJB flames were formed by a laminar jet of (N2 and/or HC)-diluted H2 mixture opposed by a similar jet of air at ambient conditions. The OJB data, derived from respective binary mixtures of H2 and methane, ethylene, or propane HCs, were used to characterize BLOWOFF and RESTORE. BLOWOFF is a sudden breaking of the dish-shaped OJB flame to a stable torus or ring shape, and RESTORE marks sudden restoration of the central flame by radial inward flame propagation. BLOWOFF is a measure of kinetically-limited flame reactivity/speed under highly stretched, but relatively ideal impingement flow conditions. RESTORE measures inward radial flame propagation rate, which is sensitive to ignition processes in the cool central core. It is concluded that relatively small molar amounts of added HC greatly reduce the reactivity characteristics of counterflow hydrogen-air diffusion flames, for ambient initial conditions.

  19. The Influence of Dimensionality on the Rate of Diffusive Escape From an Energy Well.

    PubMed

    Freund, L B

    2012-05-01

    A commonly used idealization when describing separation of a chemical bond between molecules is that of an energy well which prescribes the dependence of energy of interaction between the molecules in terms of a reaction coordinate. The energy difference between the peak to be overcome and the root of the well is the so-called activation energy, and the overall shape of the well dictates the kinetics of separation through a constitutive assumption concerning transport. An assumption tacit in this description is that the state of the bond evolves with only a single degree of freedom-the reaction coordinate-as the system explores its energy environment under random thermal excitation. In this discussion we will consider several bonds described by one and the same energy profile. The cases differ in that the energy profile varies along a line extending from the root of the well in the first case, along any radial line in a plane extending from the root of the well in a second case, and along any radial line in space extending from the root of the well in a third case. To focus the discussion we determine the statistical rate of escape of states from the well in each case, requiring that the profile of the well is the same in all three cases. It is found that the rates of escape each depend exponentially on the depth of the well but that the coefficients of the exponential vary with depth of the well differently in the three cases considered.

  20. Equal impact of diffusion and DNA binding rates on the potential spatial distribution of nuclear factor κB transcription factor inside the nucleus.

    PubMed

    Sycheva, A M; Kel, A; Nikolaev, E N; Moshkovskii, S A

    2014-06-01

    There are two physical processes that influence the spatial distribution of transcription factor molecules entering the nucleus of a eukaryotic cell, the binding to genomic DNA and the diffusion throughout the nuclear volume. Comparison of the DNA-protein association rate constant and the protein diffusion constant may determine which one is the limiting factor. If the process is diffusion-limited, transcription factor molecules are captured by DNA before their even distribution in the nuclear volume. Otherwise, if the reaction rate is limiting, these molecules diffuse evenly and then find their binding sites. Using well-studied human NF-κB dimer as an example, we calculated its diffusion constant using the Debye-Smoluchowski equation. The value of diffusion constant was about 10(-15) cm(3)/s, and it was comparable to the NF-κB association rate constant for DNA binding known from previous studies. Thus, both diffusion and DNA binding play an equally important role in NF-κB spatial distribution. The importance of genome 3D-structure in gene expression regulation and possible dependence of gene expression on the local concentration of open chromatin can be hypothesized from our theoretical estimate.

  1. Factors associated with the diffusion rate of innovations: a pilot study from the perspective of the Brazilian Unified National Health System.

    PubMed

    Schneiders, Roberto Eduardo; Ronsoni, Ricardo de March; Sarti, Flávia Mori; Nita, Marcelo Eidi; Bastos, Ediane de Assis; Zimmermann, Ivan Ricardo; Ferreira, Fernando Fagundes

    2016-10-10

    Budget Impact Analyses require a set of essential information on health technology innovation, including expected rates of adoption. There is an absence of studies investigating trends, magnitude of budgetary effects and determinants of diffusion rates for health technology innovations worldwide during the last decades. The present study proposes a pilot assessment on main determinants influencing diffusion rates of pharmaceutical innovations within the Brazilian Unified National Health System (SUS). Data from the Brazilian Health Informatics Department (DATASUS) was gathered to establish the main determinants of diffusion rates of health technology innovations in Brazil, specifically referring to pharmaceutical innovations incorporated in the Brazilian Program for Specialized Pharmaceutical Services (CEAF) at SUS. Information was retrieved on DATASUS relating to patients who had used one of the medicines incorporated into CEAF at least three years prior to the beginning of the study (2015) for treatment of each health condition available. Thus, data from patients adopting 10 different medicines were analyzed in the study. Results from the zero-one inflated beta model showed a higher influence on diffusion rates of pharmaceutical innovations due to: number of pharmaceutical competitors for treatment of the same disease available at CEAF (negative); medicine used in combination with other medication (positive); and innovative medicine within the SUS (positive). Further research on diffusion rates of health technology innovations is required, including wider scope of diseases and medications, potential confusion factors and other variables that may influence rates of adoption in different health systems.

  2. Homogenous nucleation rates of n-propanol measured in the Laminar Flow Diffusion Chamber at different total pressures

    NASA Astrophysics Data System (ADS)

    Görke, Hanna; Neitola, Kimmo; Hyvärinen, Antti-Pekka; Lihavainen, Heikki; Wölk, Judith; Strey, Reinhard; Brus, David

    2014-05-01

    Nucleation rates of n-propanol were investigated in the Laminar Flow Diffusion Chamber. Nucleation temperatures between 270 and 300 K and rates between 100 and 106 cm-3 s-1 were achieved. Since earlier measurements of n-butanol and n-pentanol suggest a dependence of nucleation rates on carrier gas pressure, similar conditions were adjusted for these measurements. The obtained data fit well to results available from literature. A small positive pressure effect was found which strengthen the assumption that this effect is attributed to the carbon chain length of the n-alcohol [D. Brus, A. P. Hyvärinen, J. Wedekind, Y. Viisanen, M. Kulmala, V. Ždímal, J. Smolík, and H. Lihavainen, J. Chem. Phys. 128, 134312 (2008)] and might be less intensive for substances in the homologous series with higher equilibrium vapor pressure. A comparison with the theoretical approach by Wedekind et al. [Phys. Rev. Lett. 101, 12 (2008)] shows that the effect goes in the same direction but that the intensity is much stronger in experiments than in theory.

  3. Quantifying the rate of biofilm growth of S. meliloti strains in microfluidics via the diffusion coefficient of microspheres

    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.

  4. Variations of boundary reaction rate and particle size on the diffusion-induced stress in a phase separating electrode

    SciTech Connect

    Zhang, Lei; He, Linghui; Ni, Yong; Song, Yicheng

    2014-10-14

    In contrast to the case of single-phase delithiation wherein faster discharging leads to higher diffusion-induced stress (DIS), this paper reports nonmonotonous dependency of the boundary reaction rate on the DIS in nanosized spherical electrode accompanying phase separation. It is attributed to a transition from two-phase to single-phase delithiation driven by increase of the boundary reaction rate leading to narrowing and vanishing of the miscibility gap in a range of the particle size. The profiles of lithium concentration and the DIS are identified during the transition based on a continuum model. The resultant maximum DIS first decreases in the region of two-phase delithiation and later returns to increase in the region of single-phase delithiation with the increase of the boundary reaction rate. A map for the failure behavior in the spherical electrode particle is constructed based on the Tresca failure criterion. These results indicate that the failure caused by the DIS can be avoided by appropriate selection of the said parameters in such electrodes.

  5. Electronic Absolute Cartesian Autocollimator

    NASA Technical Reports Server (NTRS)

    Leviton, Douglas B.

    2006-01-01

    An electronic absolute Cartesian autocollimator performs the same basic optical function as does a conventional all-optical or a conventional electronic autocollimator but differs in the nature of its optical target and the manner in which the position of the image of the target is measured. The term absolute in the name of this apparatus reflects the nature of the position measurement, which, unlike in a conventional electronic autocollimator, is based absolutely on the position of the image rather than on an assumed proportionality between the position and the levels of processed analog electronic signals. The term Cartesian in the name of this apparatus reflects the nature of its optical target. Figure 1 depicts the electronic functional blocks of an electronic absolute Cartesian autocollimator along with its basic optical layout, which is the same as that of a conventional autocollimator. Referring first to the optical layout and functions only, this or any autocollimator is used to measure the compound angular deviation of a flat datum mirror with respect to the optical axis of the autocollimator itself. The optical components include an illuminated target, a beam splitter, an objective or collimating lens, and a viewer or detector (described in more detail below) at a viewing plane. The target and the viewing planes are focal planes of the lens. Target light reflected by the datum mirror is imaged on the viewing plane at unit magnification by the collimating lens. If the normal to the datum mirror is parallel to the optical axis of the autocollimator, then the target image is centered on the viewing plane. Any angular deviation of the normal from the optical axis manifests itself as a lateral displacement of the target image from the center. The magnitude of the displacement is proportional to the focal length and to the magnitude (assumed to be small) of the angular deviation. The direction of the displacement is perpendicular to the axis about which the

  6. Absolute airborne gravimetry

    NASA Astrophysics Data System (ADS)

    Baumann, Henri

    This work consists of a feasibility study of a first stage prototype airborne absolute gravimeter system. In contrast to relative systems, which are using spring gravimeters, the measurements acquired by absolute systems are uncorrelated and the instrument is not suffering from problems like instrumental drift, frequency response of the spring and possible variation of the calibration factor. The major problem we had to resolve were to reduce the influence of the non-gravitational accelerations included in the measurements. We studied two different approaches to resolve it: direct mechanical filtering, and post-processing digital compensation. The first part of the work describes in detail the different mechanical passive filters of vibrations, which were studied and tested in the laboratory and later in a small truck in movement. For these tests as well as for the airborne measurements an absolute gravimeter FG5-L from Micro-G Ltd was used together with an Inertial navigation system Litton-200, a vertical accelerometer EpiSensor, and GPS receivers for positioning. These tests showed that only the use of an optical table gives acceptable results. However, it is unable to compensate for the effects of the accelerations of the drag free chamber. The second part describes the strategy of the data processing. It is based on modeling the perturbing accelerations by means of GPS, EpiSensor and INS data. In the third part the airborne experiment is described in detail, from the mounting in the aircraft and data processing to the different problems encountered during the evaluation of the quality and accuracy of the results. In the part of data processing the different steps conducted from the raw apparent gravity data and the trajectories to the estimation of the true gravity are explained. A comparison between the estimated airborne data and those obtained by ground upward continuation at flight altitude allows to state that airborne absolute gravimetry is feasible and

  7. Absolute-structure reports.

    PubMed

    Flack, Howard D

    2013-08-01

    All the 139 noncentrosymmetric crystal structures published in Acta Crystallographica Section C between January 2011 and November 2012 inclusive have been used as the basis of a detailed study of the reporting of absolute structure. These structure determinations cover a wide range of space groups, chemical composition and resonant-scattering contribution. Defining A and D as the average and difference of the intensities of Friedel opposites, their level of fit has been examined using 2AD and selected-D plots. It was found, regardless of the expected resonant-scattering contribution to Friedel opposites, that the Friedel-difference intensities are often dominated by random uncertainty and systematic error. An analysis of data collection strategy is provided. It is found that crystal-structure determinations resulting in a Flack parameter close to 0.5 may not necessarily be from crystals twinned by inversion. Friedifstat is shown to be a robust estimator of the resonant-scattering contribution to Friedel opposites, very little affected by the particular space group of a structure nor by the occupation of special positions. There is considerable confusion in the text of papers presenting achiral noncentrosymmetric crystal structures. Recommendations are provided for the optimal way of treating noncentrosymmetric crystal structures for which the experimenter has no interest in determining the absolute structure.

  8. Is the surface oxygen exchange rate linked to bulk ion diffusivity in mixed conducting Ruddlesden–Popper phases?

    SciTech Connect

    Tomkiewicz, Alex C.; Tamimi, Mazin A.; Huq, Ashfia; McIntosh, Steven

    2015-03-02

    There is a possible link between oxygen surface exchange rate and bulk oxygen anion diffusivity in mixed ionic and electronic conducting oxides; it is a topic of great interest and debate. While a large body of experimental evidence and theoretical analyses support a link, observed differences between bulk and surface composition of these materials are hard to reconcile with this observation. This is further compounded by potential problems with simultaneous measurement of both parameters. Here we utilize separate techniques, in situ neutron diffraction and pulsed isotopic surface exchange, to examine bulk ion mobility and surface oxygen exchange rates of three Ruddlesden-Popper phases, general form An-1A2'BnO3n+1, An-1A2'BnX3n+1; LaSrCo0.5Fe0.5O4-δ (n = 1), La0.3Sr2.7CoFeO7-δ (n = 2) and LaSr3Co1.5Fe1.5O10-δ (n = 3). These measurements are complemented by surface composition determination via high sensitivity-low energy ion scattering. We observe a correlation between bulk ion mobility and surface exchange rate between materials. The surface exchange rates vary by more than one order of magnitude with high anion mobility in the bulk of an oxygen vacancy-rich n = 2 Ruddlesden-Popper material correlating with rapid oxygen exchange. Furthermore this is in contrast with the similar surface exchange rates which we may expect due to similar surface compositions across all three samples. This paper conclude that experimental limitations lead to inherent convolution of surface and bulk rates, and that surface exchange steps are not likely to be rate limiting in oxygen incorporation.

  9. Deduction of the rates of radial diffusion of protons from the structure of the Earth's radiation belts

    NASA Astrophysics Data System (ADS)

    Kovtyukh, Alexander S.

    2016-11-01

    From the data on the fluxes and energy spectra of protons with an equatorial pitch angle of α0 ≈ 90° during quiet and slightly disturbed (Kp ≤ 2) periods, I directly calculated the value DLL, which is a measure of the rate of radial transport (diffusion) of trapped particles. This is done by successively solving the systems (chains) of integrodifferential equations which describe the balance of radial transport/acceleration and ionization losses of low-energy protons of the stationary belt. This was done for the first time. For these calculations, I used data of International Sun-Earth Explorer 1 (ISEE-1) for protons with an energy of 24 to 2081 keV at L = 2-10 and data of Explorer-45 for protons with an energy of 78.6 to 872 keV at L = 2-5. Ionization losses of protons (Coulomb losses and charge exchange) were calculated on the basis of modern models of the plasmasphere and the exosphere. It is shown that for protons with μ from ˜ 0.7 to ˜ 7 keV nT-1 at L ≈ 4.5-10, the functions of DLL can be approximated by the following equivalent expressions: DLL ≈ 4.9 × 10-14μ-4.1L8.2 or DLL ≈ 1.3 × 105(EL)-4.1 or DLL ≈ 1.2 × 10-9fd-4.1, where fd is the drift frequency of the protons (in mHz), DLL is measured in s-1, E is measured in kiloelectronvolt and μ is measured in kiloelectronvolt per nanotesla. These results are consistent with the radial diffusion of particles under the action of the electric field fluctuations (pulsations) in the range of Pc6 and contradict the mechanism of the radial diffusion of particles under the action of sudden impulses (SIs) of the magnetic field and also under the action of substorm impulses of the electric field. During magnetic storms DLL increases, and the expressions for DLL obtained here can change completely.

  10. Towards Stable Lithium-Sulfur Batteries with a Low Self-Discharge Rate: Ion Diffusion Modulation and Anode Protection.

    PubMed

    Xu, Wen-Tao; Peng, Hong-Jie; Huang, Jia-Qi; Zhao, Chen-Zi; Cheng, Xin-Bing; Zhang, Qiang

    2015-09-07

    The self-discharge of a lithium-sulfur cell decreases the shelf-life of the battery and is one of the bottlenecks that hinders its practical applications. New insights into both the internal chemical reactions in a lithium-sulfur system and effective routes to retard self-discharge for highly stable batteries are crucial for the design of lithium-sulfur cells. Herein, a lithium-sulfur cell with a carbon nanotube/sulfur cathode and lithium-metal anode in lithium bis(trifluoromethanesulfonyl)imide/1,3-dioxolane/dimethyl ether electrolyte was selected as the model system to investigate the self-discharge behavior. Both lithium anode passivation and polysulfide anion diffusion suppression strategies are applied to reduce self-discharge of the lithium-sulfur cell. When the lithium-metal anode is protected by a high density passivation layer induced by LiNO3 , a very low shuttle constant of 0.017 h(-1) is achieved. The diffusion of the polysulfides is retarded by an ion-selective separator, and the shuttle constants decreased. The cell with LiNO3 additive maintained a discharge capacity of 97 % (961 mAh g(-1) ) of the initial capacity after 120 days at open circuit, which was around three times higher than the routine cell (32 % of initial capacity, corresponding to 320 mAh g(-1) ). It is expected that lithium-sulfur batteries with ultralow self-discharge rates may be fabricated through a combination of anode passivation and polysulfide shuttle control, as well as optimization of the lithium-sulfur cell configuration.

  11. Experimental Methodology for Estimation of Local Heat Fluxes and Burning Rates in Steady Laminar Boundary Layer Diffusion Flames.

    PubMed

    Singh, Ajay V; Gollner, Michael J

    2016-06-01

    Modeling the realistic burning behavior of condensed-phase fuels has remained out of reach, in part because of an inability to resolve the complex interactions occurring at the interface between gas-phase flames and condensed-phase fuels. The current research provides a technique to explore the dynamic relationship between a combustible condensed fuel surface and gas-phase flames in laminar boundary layers. Experiments have previously been conducted in both forced and free convective environments over both solid and liquid fuels. A unique methodology, based on the Reynolds Analogy, was used to estimate local mass burning rates and flame heat fluxes for these laminar boundary layer diffusion flames utilizing local temperature gradients at the fuel surface. Local mass burning rates and convective and radiative heat feedback from the flames were measured in both the pyrolysis and plume regions by using temperature gradients mapped near the wall by a two-axis traverse system. These experiments are time-consuming and can be challenging to design as the condensed fuel surface burns steadily for only a limited period of time following ignition. The temperature profiles near the fuel surface need to be mapped during steady burning of a condensed fuel surface at a very high spatial resolution in order to capture reasonable estimates of local temperature gradients. Careful corrections for radiative heat losses from the thermocouples are also essential for accurate measurements. For these reasons, the whole experimental setup needs to be automated with a computer-controlled traverse mechanism, eliminating most errors due to positioning of a micro-thermocouple. An outline of steps to reproducibly capture near-wall temperature gradients and use them to assess local burning rates and heat fluxes is provided.

  12. Experimental Methodology for Estimation of Local Heat Fluxes and Burning Rates in Steady Laminar Boundary Layer Diffusion Flames

    PubMed Central

    Singh, Ajay V.; Gollner, Michael J.

    2016-01-01

    Modeling the realistic burning behavior of condensed-phase fuels has remained out of reach, in part because of an inability to resolve the complex interactions occurring at the interface between gas-phase flames and condensed-phase fuels. The current research provides a technique to explore the dynamic relationship between a combustible condensed fuel surface and gas-phase flames in laminar boundary layers. Experiments have previously been conducted in both forced and free convective environments over both solid and liquid fuels. A unique methodology, based on the Reynolds Analogy, was used to estimate local mass burning rates and flame heat fluxes for these laminar boundary layer diffusion flames utilizing local temperature gradients at the fuel surface. Local mass burning rates and convective and radiative heat feedback from the flames were measured in both the pyrolysis and plume regions by using temperature gradients mapped near the wall by a two-axis traverse system. These experiments are time-consuming and can be challenging to design as the condensed fuel surface burns steadily for only a limited period of time following ignition. The temperature profiles near the fuel surface need to be mapped during steady burning of a condensed fuel surface at a very high spatial resolution in order to capture reasonable estimates of local temperature gradients. Careful corrections for radiative heat losses from the thermocouples are also essential for accurate measurements. For these reasons, the whole experimental setup needs to be automated with a computer-controlled traverse mechanism, eliminating most errors due to positioning of a micro-thermocouple. An outline of steps to reproducibly capture near-wall temperature gradients and use them to assess local burning rates and heat fluxes is provided. PMID:27285827

  13. Absolute Equilibrium Entropy

    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.

  14. Absolute multilateration between spheres

    NASA Astrophysics Data System (ADS)

    Muelaner, Jody; Wadsworth, William; Azini, Maria; Mullineux, Glen; Hughes, Ben; Reichold, Armin

    2017-04-01

    Environmental effects typically limit the accuracy of large scale coordinate measurements in applications such as aircraft production and particle accelerator alignment. This paper presents an initial design for a novel measurement technique with analysis and simulation showing that that it could overcome the environmental limitations to provide a step change in large scale coordinate measurement accuracy. Referred to as absolute multilateration between spheres (AMS), it involves using absolute distance interferometry to directly measure the distances between pairs of plain steel spheres. A large portion of each sphere remains accessible as a reference datum, while the laser path can be shielded from environmental disturbances. As a single scale bar this can provide accurate scale information to be used for instrument verification or network measurement scaling. Since spheres can be simultaneously measured from multiple directions, it also allows highly accurate multilateration-based coordinate measurements to act as a large scale datum structure for localized measurements, or to be integrated within assembly tooling, coordinate measurement machines or robotic machinery. Analysis and simulation show that AMS can be self-aligned to achieve a theoretical combined standard uncertainty for the independent uncertainties of an individual 1 m scale bar of approximately 0.49 µm. It is also shown that combined with a 1 µm m‑1 standard uncertainty in the central reference system this could result in coordinate standard uncertainty magnitudes of 42 µm over a slender 1 m by 20 m network. This would be a sufficient step change in accuracy to enable next generation aerospace structures with natural laminar flow and part-to-part interchangeability.

  15. Understanding supported reactions in spherical compartments: a general algorithm to model and determine rate constants, diffusion coefficients, and spatial product distributions.

    PubMed

    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.

  16. Modeling of Pickup Ion Distributions in the Halley Cometo-Sheath: Empirical Rates of Ionization, Diffusion, Loss and Creation of Fast Neutral Atoms

    NASA Technical Reports Server (NTRS)

    Huddleston, D.; Neugebauer, M.; Goldstein, B.

    1994-01-01

    The shape of the velocity distribution of water-group ions observed by the Giotto ion mass spectrometer on its approach to comet Halley is modeled to derive empirical values for the rates on ionization, energy diffusion, and loss in the mid-cometosheath.

  17. Convergence rate calculation of simultaneous iterative reconstruction technique algorithm for diffuse optical tomography image reconstruction: A feasibility study

    NASA Astrophysics Data System (ADS)

    Chuang, Ching-Cheng; Tsai, Jui-che; Chen, Chung-Ming; Yu, Zong-Han; Sun, Chia-Wei

    2012-04-01

    Diffuse optical tomography (DOT) is an emerging technique for functional biological imaging. The imaging quality of DOT depends on the imaging reconstruction algorithm. The SIRT has been widely used for DOT image reconstruction but there is no criterion to truncate based on any kind of residual parameter. The iteration loops will always be decided by experimental rule. This work presents the CR calculation that can be great help for SIRT optimization. In this paper, four inhomogeneities with various shapes of absorption distributions are simulated as imaging targets. The images are reconstructed and analyzed based on the simultaneous iterative reconstruction technique (SIRT) method. For optimization between time consumption and imaging accuracy in reconstruction process, the numbers of iteration loop needed to be optimized with a criterion in algorithm, that is, the root mean square error (RMSE) should be minimized in limited iterations. For clinical applications of DOT, the RMSE cannot be obtained because the measured targets are unknown. Thus, the correlations between the RMSE and the convergence rate (CR) in SIRT algorithm are analyzed in this paper. From the simulation results, the parameter CR reveals the related RMSE value of reconstructed images. The CR calculation offers an optimized criterion of iteration process in SIRT algorithm for DOT imaging. Based on the result, the SIRT can be modified with CR calculation for self-optimization. CR reveals an indicator of SIRT image reconstruction in clinical DOT measurement. Based on the comparison result between RMSE and CR, a threshold value of CR (CRT) can offer an optimized number of iteration steps for DOT image reconstruction. This paper shows the feasibility study by utilizing CR criterion for SIRT in simulation and the clinical application of DOT measurement relies on further investigation.

  18. Surface diffusion in reversed-phase liquid chromatography

    SciTech Connect

    Miyabe, Kanji; Guiochon, Georges A

    2010-01-01

    More than 40 years ago, Giddings pointed out in 'Dynamics of Chromatography' that surface diffusion should become an important research topic in the kinetics of chromatographic phenomena. However, few studies on surface diffusion in adsorbents used in chromatography were published since then. Most scientists use ordinary rate equations to study mass transfer kinetics in chromatography. They take no account of surface diffusion and overlook the significant contributions of this mass transfer process to chromatographic behavior and to column efficiency at high mobile phase flow rate. Only recently did the significance of surface diffusion in separation processes begin to be recognized in connection with the development of new techniques of fast flow, high efficiency chromatography. In this review, we revisit the reports on experimental data on surface diffusion and introduce a surface-restricted molecular diffusion model, derived as a first approximation for the mechanism of surface diffusion, on the basis of the absolute rate theory. We also explain how this model accounts for many intrinsic characteristics of surface diffusion that cannot properly be explained by the conventional models of surface diffusion.

  19. Fe Mg interdiffusion in wadsleyite: The role of pressure, temperature and composition and the magnitude of jump in diffusion rates at the 410 km discontinuity

    NASA Astrophysics Data System (ADS)

    Holzapfel, C.; Chakraborty, S.; Rubie, D. C.; Frost, D. J.

    2009-01-01

    The limited stability range of wadsleyite seriously impedes our ability to constrain kinetic parameters (e.g. activation energy, activation volume) using experiments carried out over a wide range of temperature and pressure. We have carried out a new measurement to extend the experimental temperature range of the dataset of Chakraborty et al. [Chakraborty, S., Knoche, R., Schulze, H., Rubie, D.C., Dobson, D., Ross, N.L., Angel, R.J., 1999. Enhancement of cation diffusion rates across the 410-kilometer discontinuity in Earth's mantle. Science 283, 362-365] to the maximum possible limit for that experimental setup. This result allows us to (i) obtain a better constrained value for activation energy for Fe-Mg diffusion in wadsleyite at 15 GPa (˜230 kJ/mol), and (ii) characterize the compositional dependence of Fe-Mg diffusion in wadsleyite. Evaluation of all data available in the literature [i.e. this study; Chakraborty et al., 1999; Farber, D.L., Williams, Q., Ryerson, F.J., 2000. Divalent cation diffusion in Mg 2SiO 4 spinel (ringwoodite), β-phase (wadsleyite), and olivine: implications for the electrical conductivity of the mantle. J. Geophys. Res. 105, 513-529; Kubo, T., Shimojuko, A., Ohtani, E., 2004. Fe-Mg interdiffusion rates in wadsleyite and the diffusivity jump at the 410 km discontinuity. Phys. Chem. Miner. 31, 456-464] reveals that there is a strong pressure dependence of the diffusion coefficient (activation volume ≈14 cm 3/mol). The expression D (m/s)=1.24×10-6 exp[11.8(0.86-X)] exp{-[]229,000+(P-15)×13.9×10 J/mol}/{RT} is an excellent description of all experimentally measured diffusion coefficients in wadsleyite and points to consistency between the various studies from different laboratories that used different methods. This expression should provide a robust basis for extrapolation of diffusion data for wadsleyite to conditions removed from the experimental ones, e.g. for modeling processes in the interiors of cold subducting slabs. Moreover

  20. Garnet-biotite diffusion mechanisms in complex high-grade orogenic belts: Understanding and constraining petrological cooling rates in granulites from Ribeira Fold Belt (SE Brazil)

    NASA Astrophysics Data System (ADS)

    Bento dos Santos, Telmo M.; Tassinari, Colombo C. G.; Fonseca, Paulo E.

    2014-12-01

    Cooling rates based on the retrograde diffusion of Fe2+ and Mg between garnet and biotite inclusions commonly show two contrasting scenarios: a) narrow closure temperature range with apparent absence of retrograde diffusion; or b) high result dispersion due to compositional variations in garnet and biotite. Cooling rates from migmatites, felsic and mafic granulites from Ribeira Fold Belt (SE Brazil) also show these two scenarios. Although the former can be explained by very fast cooling, the latter is often the result of open-system behaviour caused by deformation. Retrogressive cooling during the exhumation of granulite-facies rocks is often processed by thrusting and shearing which may cause plastic deformation, fractures and cracks in the garnet megablasts, allowing chemical diffusion outside the garnet megablast - biotite inclusion system. However, a careful use of garnets and biotites with large Fe/Mg variation and software that reduces result dispersion provides a good correlation between closure temperatures and the size of biotite inclusions which are mostly due to diffusion and compositional readjustment to thermal evolution during retrogression. Results show that felsic and mafic granulites have low cooling rates (1-2 °C/Ma) at higher temperatures and high cooling rates (˜100 °C/Ma) at lower temperatures, suggesting a two-step cooling/exhumation process, whereas migmatites show a small decrease in cooling rates during cooling (from 2.0 to 0.5 °C/Ma). These results agree with previously obtained thermochronological data, which indicates that this method is a valid tool to obtain meaningful petrological cooling rates in complex high-grade orogenic belts, such as the Ribeira Fold Belt.

  1. Modeling of pickup ion distributions in the Halley cometosheath: Empirical limits on rates of ionization, diffusion, loss and creation of fast neutral atoms

    NASA Technical Reports Server (NTRS)

    Huddleston, D. E.; Neugebauer, M.; Goldstein, B. E.

    1994-01-01

    The shape of the velocity distribution of water group ions observed by the Giotto ion mass spectrometer on its approach to comet Halley is modeled to derive empirical values for the rates of ionization, energy diffusion, and loss in the midcometosheath. The model includes the effect of rapid pitch angle scattering into a bispherical shell distribution as well as the effect of the magnetization of the plasma on the charge exchange loss rate. It is found that the average rate of ionization of cometary neutrals in this region of the cometosheath appears to be of the order of a factor 3 faster than the `standard' rates approx. 1 x 10(exp -6)/s that are generally assumed to model the observations in most regions of the comet environment. For the region of the coma studied in the present work (approx. 1 - 2 x 10(exp 5) km from the nucleus), the inferred energy diffusion coefficient is D(sub 0) approx. equals 0.0002 to 0.0005 sq km/cu s, which is generally lower than values used in other models. The empirically obtained loss rate appears to be about an order of magnitude greater than can be explained by charge exchange with the `standard' cross section of approx. 2 x 10(exp -15)sq cm. However such cross sections are not well known and for water group ion/water group neutral interactions, rates as high as 8 x 10(exp -15) sq cm have previously been suggested in the literature. Assuming the entire loss rate is due to charge exchange yields a rate of creation of fast neutral atoms of the order of approx. 10(exp -4)/s or higher, depending on the level of velocity diffusion. The fast neutrals may, in turn, be partly responsible for the higher-than-expected ionization rate.

  2. Measurements of the effective diffusion coefficient of dissolved oxygen and oxidation rate of pyrite by dissolved oxygen in compacted sodium bentonite

    SciTech Connect

    Manaka, Mitsuo; Kawasaki, Manabu; Honda, Akira

    2000-05-01

    The redox condition of the near field is expected to affect the performance of engineered barrier systems. In particular, the oxygen initially existing in the pore spaces of compacted bentonites strongly affects the redox condition of the near field. To assess the influence of the oxygen, research was done to assess its transport parameters in the compacted bentonite and consumption process. To understand the diffusion of dissolved oxygen (DO) in compacted bentonite and to predict the effect of the DO, the measurements of the effective diffusion coefficient of DO in compacted sodium bentonite were made by electro-chemistry. As a result, the following relationship between the dry density of compacted sodium bentonite and the effective diffusion coefficient of DO in compacted sodium bentonite was derived: D{sub e} = 3.0 {+-} 0.5 {times} 10{sup {minus}9} exp({minus}3.7 {+-} 0.2 {times} 10{sup -3}p), where D{sub e} is the effective diffusion coefficient (m{sup 2}s{sup -1}) of DO in compacted sodium bentonite and p is the dry density (kg m{sup -3})of compacted sodium bentonite. The oxygen concentration in the bentonite is expected to be controlled by the oxidation of pyrite as an impurity in the bentonite. To investigate this idea, the rates of pyrite oxidation by DO in compacted sodium bentonite were estimated from the experimental data in pyrite-bentonite systems using the obtained effective diffusion coefficient of DO. The results show that the average of the rate constants of pyrite oxidation by DO in compacted sodium bentonite was 1.16 {+-} 0.35 {times} 10{sup {minus}8}m s{sup {minus}1}, whereas the rate constant in a carbonate-buffered solution (pH = 9.24) was 1.46 {+-} 0.09 {times}10{sup {minus}9}m s{sup {minus}1}.

  3. Upwelling Rates and Vertical Diffusivities Determined During the 2013 US GEOTRACES Eastern Tropical Pacific Zonal Transect: Results from 7Be Analysis

    NASA Astrophysics Data System (ADS)

    Kadko, D. C.

    2014-12-01

    Upwelling is an important physical process affecting biogeochemical cycling within the global ocean. Direct measurements are difficult because of the relatively small velocities involved, and must therefore be inferred by indirect methods such as those provided by tracer observations. Measurements of the cosmogenic radioisotope 7Be (half-life = 53.3 d) were used to derive upwelling rates and upper thermocline vertical diffusivities during the 2013 US GEOTRACES Eastern Tropical Pacific Zonal Transect. In the eastern, upwelling zone of this transect, the 7Be activity in the mixed layer varied between low values of 63 dpm/m3 in areas with the coldest sea surface temperatures (SSTs) to values of 190 dpm/m3 associated with warm SSTs. The 7Be inventory in the coldest water was only 5,150 dpm/m2 while that in the warmer water was 19,000 dpm/m2. The decrease in mixed layer 7Be with decrease in temperature occurs as 7Be ''dead'', cold water is upwelled from below. The deficit of the 7Be inventory relative to the non-upwelling stations provides a measure of the upwelling rate. For the eastern-most station with the lowest SST (17.6 deg C) an upwelling rate of 2.56 m/d was derived. Towards the west, as SST increased, derived upwelling rates decreased. At SST of 20.9 deg C, upwelling was zero. With knowledge of upwelling rates, 7Be and temperature profiles were used to constrain vertical diffusivity within the upper thermocline. Diffusivities derived from 7Be profiles were approximately twice that derived from temperature, likely reflecting the difference in vertical resolution of these measurements. Diffusivities derived from temperature were on the order of 1-4 x 10-4 m2/s. These parameters will be applied to profiles of nutrients and trace elements to derive fluxes of these species into the mixed layer.

  4. Developing a new simplified method to determine diffusive uptake rates of volatile organic compounds in workplaces based on a fractional factorial designs approach.

    PubMed

    Estève, Williams; Lhuillier, Francine; Ravera, Christel; Grzebyck, Michel; Langlois, Eddy

    2013-01-01

    Exposure to organic vapors in the workplace is a source of occupational risk. Admissible exposure levels are tightly regulated and must be closely monitored. However, the complexity and slowness of the existing complete protocols to determine diffusive uptake rates through passive sampling have limited the use of this tool despite obvious advantages. In this study, we experimentally validate two simplified protocols to determine diffusive uptake rates with passive sampling. The proposed 2(6-3) and 2(6-2) fractional factorial designs were validated for toluene sampling using a (Gas Adsorbent Badge for Individual Exposure) GABIE-activated charcoal sampler in a controlled atmosphere. The uptake rate for this sampler had been determined previously using a full protocol. The uptake rates for all three protocols were similar, indicating that the proposed new designs can be substituted for classical full protocols. After validation of our protocols, uptake rates for new substances used as fuel additives (methyl and ethyl tert-butyl ethers, MTBE and ETBE) were determined on the same sampler using the 2(6-2) design. In these experiments, temperature appears to have a non-negligible influence on the uptake rates measured for these compounds. With some precautions of usage (ambient temperature below a determined limit temperature or at least exposure time ≥4 h) and storage (storage temperature = 4°C) of the sampler, the experimental diffusive uptake rates determined by this method can be used with good confidence. Field experiments confirmed the experimental results, showing good agreement between active and passive sampling using the experimentally determined uptake rates.

  5. Rate of Contamination Removal of Two Phyto-remediation Sites at the DOE Portsmouth Gaseous Diffusion Plant

    SciTech Connect

    Lewis, A.C.; Baird, D.R.

    2006-07-01

    This paper describes applications of phyto-remediation at the Portsmouth Gaseous Diffusion Plant (PORTS), a Department of Energy (DOE) Facility that enriched uranium from the early 1950's until 2000. Phyto-remediation has been implemented to assist in the removal of TCE (trichloroethylene) in the groundwater at two locations at the PORTS facility: the X-740 area and the X-749/X-120 area. Phyto-remediation technology is based on the ability of certain plants species (in this case hybrid poplar trees) and their associated rhizo-spheric microorganisms to remove, degrade, or contain chemical contaminants located in the soil, sediment, surface water, groundwater, and possibly even the atmosphere. Phyto-remediation technology is a promising clean-up solution for a wide variety of pollutants and sites. Mature trees, such as the hybrid poplar, can consume up to 3,000 gallons of groundwater per acre per day. Organic compounds are captured in the trees' root systems. These organic compounds are degraded by ultraviolet light as they are transpired along with the water vapor through the leaves of the trees. The phyto-remediation system at the X-740 area encompasses 766 one-year old hybrid poplar trees (Populus nigra x nigra, Populus nigra x maximowiczii, and Populus deltoides x nigra) that were planted 10 feet apart in rows 10 feet to 20 feet apart, over an area of 2.6 acres. The system was installed to manage the VOC contaminant plume. At the X749/X-120 area, a phyto-remediation system of 2,640 hybrid poplar trees (Populus nigra x maximowiczii) was planted in seven areas/zones to manage the VOC contaminant plume. The objectives of these systems are to remove contamination from the groundwater and to prevent further migration of contaminants. The goal of these remediation procedures is to achieve completely mature and functional phyto-remediation systems within two years of the initial planting of the hybrid poplar trees at each planting location. There is a direct

  6. The relative diffusive transport rate of SrI2 in water changes over the nanometer length scale as measured by coherent quasielastic neutron scattering.

    PubMed

    Rubinson, Kenneth A; Faraone, Antonio

    2016-05-14

    X-ray and neutron scattering have been used to provide insight into the structures of ionic solutions for over a century, but the probes have covered distances shorter than 8 Å. For the non-hydrolyzing salt SrI2 in aqueous solution, a locally ordered lattice of ions exists that scatters slow neutrons coherently down to at least 0.1 mol L(-1) concentration, where the measured average distance between scatterers is over 18 Å. To investigate the motions of these scatterers, coherent quasielastic neutron scattering (CQENS) data on D2O solutions with SrI2 at 1, 0.8, 0.6, and 0.4 mol L(-1) concentrations was obtained to provide an experimental measure of the diffusive transport rate for the motion between pairs of ions relative to each other. Because CQENS measures the motion of one ion relative to another, the frame of reference is centered on an ion, which is unique among all diffusion measurement methods. We call the measured quantity the pairwise diffusive transport rate Dp. In addition to this ion centered frame of reference, the diffusive transport rate can be measured as a function of the momentum transfer q, where q = (4π/λ)sin θ with a scattering angle of 2θ. Since q is related to the interion distance (d = 2π/q), for the experimental range 0.2 Å(-1)≤q≤ 1.0 Å(-1), Dp is, then, measured over interion distances from 40 Å to ≈6 Å. We find the measured diffusional transport rates increase with increasing distance between scatterers over the entire range covered and interpret this behavior to be caused by dynamic coupling among the ions. Within the model of Fickian diffusion, at the longer interionic distances Dp is greater than the Nernst-Hartley value for an infinitely dilute solution. For these nm-distance diffusional transport rates to conform with the lower, macroscopically measured diffusion coefficients, we propose that local, coordinated counter motion of at least pairs of ions is part of the transport process.

  7. Low temperature diffusion coefficients in the Fe-Ni and FeNiP systems: Application to meteorite cooling rates

    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.

  8. Cryogenic, Absolute, High Pressure Sensor

    NASA Technical Reports Server (NTRS)

    Chapman, John J. (Inventor); Shams. Qamar A. (Inventor); Powers, William T. (Inventor)

    2001-01-01

    A pressure sensor is provided for cryogenic, high pressure applications. A highly doped silicon piezoresistive pressure sensor is bonded to a silicon substrate in an absolute pressure sensing configuration. The absolute pressure sensor is bonded to an aluminum nitride substrate. Aluminum nitride has appropriate coefficient of thermal expansion for use with highly doped silicon at cryogenic temperatures. A group of sensors, either two sensors on two substrates or four sensors on a single substrate are packaged in a pressure vessel.

  9. 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.

  10. Experimental determination of the velocity and strain rate field in a laminar H2/Air counter-flow diffusion flame via LDA

    NASA Technical Reports Server (NTRS)

    Yeo, S. H.; Dancey, C. L.

    1991-01-01

    Measurements of the axial and radial components of velocity on the air side of stagnation in an axisymmetric H2/Air laminar counter-flow diffusion flame are reported. Results include the two-dimensional velocity field and computed velocity gradients (strain rates) along the stagnation streamline at two 'characteristic' strain rates, below the extinction limit. The measurements generally verify the modeling assumptions appropriate to the model of Kee et al. (1988). The 'traditional' potential flow model is not consistent with the measured results.

  11. Single Molecule Microscopy Reveals an Increased Hyaluronan Diffusion Rate in Synovial Fluid from Knees Affected by Osteoarthritis

    PubMed Central

    Kohlhof, Hendrik; Gravius, Sascha; Kohl, Sandro; Ahmad, Sufian S.; Randau, Thomas; Schmolders, Jan; Rommelspacher, Yorck; Friedrich, Max; Kaminski, Tim P.

    2016-01-01

    Osteoarthritis is a common and progressive joint disorder. Despite its widespread, in clinical practice only late phases of osteoarthritis that are characterized by severe joint damage are routinely detected. Since osteoarthritis cannot be cured but relatively well managed, an early diagnosis and thereby early onset of disease management would lower the burden of osteoarthritis. Here we evaluated if biophysical parameters of small synovial fluid samples extracted by single molecule microscopy can be linked to joint damage. In healthy synovial fluid (ICRS-score < 1) hyaluronan showed a slower diffusion (2.2 μm2/s, N = 5) than in samples from patients with joint damage (ICRS-score > 2) (4.5 μm2/s, N = 16). More strikingly, the diffusion coefficient of hyaluronan in healthy synovial fluid was on average 30% slower than expected by sample viscosity. This effect was diminished or missing in samples from patients with joint damage. Since single molecule microscopy needs only microliters of synovial fluid to extract the viscosity and the specific diffusion coefficient of hyaluronan this method could be of use as diagnostic tool for osteoarthritis. PMID:26868769

  12. Single Molecule Microscopy Reveals an Increased Hyaluronan Diffusion Rate in Synovial Fluid from Knees Affected by Osteoarthritis.

    PubMed

    Kohlhof, Hendrik; Gravius, Sascha; Kohl, Sandro; Ahmad, Sufian S; Randau, Thomas; Schmolders, Jan; Rommelspacher, Yorck; Friedrich, Max; Kaminski, Tim P

    2016-02-12

    Osteoarthritis is a common and progressive joint disorder. Despite its widespread, in clinical practice only late phases of osteoarthritis that are characterized by severe joint damage are routinely detected. Since osteoarthritis cannot be cured but relatively well managed, an early diagnosis and thereby early onset of disease management would lower the burden of osteoarthritis. Here we evaluated if biophysical parameters of small synovial fluid samples extracted by single molecule microscopy can be linked to joint damage. In healthy synovial fluid (ICRS-score < 1) hyaluronan showed a slower diffusion (2.2 μm(2)/s, N = 5) than in samples from patients with joint damage (ICRS-score > 2) (4.5 μm(2)/s, N = 16). More strikingly, the diffusion coefficient of hyaluronan in healthy synovial fluid was on average 30% slower than expected by sample viscosity. This effect was diminished or missing in samples from patients with joint damage. Since single molecule microscopy needs only microliters of synovial fluid to extract the viscosity and the specific diffusion coefficient of hyaluronan this method could be of use as diagnostic tool for osteoarthritis.

  13. Passive absolute age and temperature history sensor

    DOEpatents

    Robinson, Alex; Vianco, Paul T.

    2015-11-10

    A passive sensor for historic age and temperature sensing, including a first member formed of a first material, the first material being either a metal or a semiconductor material and a second member formed of a second material, the second material being either a metal or a semiconductor material. A surface of the second member is in contact with a surface of the first member such that, over time, the second material of the second member diffuses into the first material of the first member. The rate of diffusion for the second material to diffuse into the first material depends on a temperature of the passive sensor. One of the electrical conductance, the electrical capacitance, the electrical inductance, the optical transmission, the optical reflectance, or the crystalline structure of the passive sensor depends on the amount of the second material that has diffused into the first member.

  14. Cation diffusion in the electrical double layer enhances the mass transfer rates for Sr2+, Co2+ and Zn2+ in compacted illite

    NASA Astrophysics Data System (ADS)

    Glaus, M. A.; Aertsens, M.; Appelo, C. A. J.; Kupcik, T.; Maes, N.; Van Laer, L.; Van Loon, L. R.

    2015-09-01

    Enhanced mass transfer rates have been frequently observed in diffusion studies with alkaline and earth alkaline elements in compacted clay minerals and clay rocks. Whether this phenomenon - often termed surface diffusion - is also relevant for more strongly sorbing species is an open question. We therefore investigated the diffusion of Sr2+, Co2+ and Zn2+ in compacted illite with respect to variations of the concentration of the background electrolyte, pH and carbonate. New experimental techniques were developed in order to avoid artefacts stemming from the confinement of the clay sample. A distinct dependence of the effective diffusion coefficients on the concentration of the background electrolyte was observed for all three elements. A similar correlation was found for the sorption distribution ratio (Rd) derived from tracer breakthrough in the case of Sr2+, while this dependence was much weaker for Co2+ and Zn2+. Model calculations using Phreeqc resulted in a good agreement with the experimental data when it was assumed that the cationic species, present in the electrical double layer (EDL) of the charged clay surface, are mobile. Species bound to the specific surface complexation sites at the clay edges were assumed to be immobile. An assessment of the mobility of the type of cationic elements studied here in argillaceous media thus requires an analysis of their distribution among specifically sorbed surface species and species in the EDL. The normal approach of deriving unknown effective diffusion coefficients from reference values of an uncharged water tracer may significantly underestimate the mobility of metal cations in argillaceous media.

  15. The origin of low water vapor transmission rates through Al2O3/ZrO2 nanolaminate gas-diffusion barriers grown by atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Meyer, J.; Schmidt, H.; Kowalsky, W.; Riedl, T.; Kahn, A.

    2010-06-01

    This paper reports on thin film gas-diffusion barriers consisting of Al2O3/ZrO2 nanolaminates (NL) grown by low-temperature (80 °C) atomic layer deposition. We show that reliable barriers with water vapor transmission rates of 3.2×10-4 g/(m2 day), measured at 80 °C and 80% relative humidity, can be realized with very thin layers down to 40 nm. We determine that ZrO2 acts as anticorrosion element in our NL. Furthermore, we demonstrate by x-ray photoemission spectroscopy that an aluminate phase is formed at the interfaces between Al2O3 and ZrO2 sublayers, which additionally improves the gas-diffusion barrier due to a densification of the layer system. These Al2O3/ZrO2 NLs prepared at low temperatures hold considerable promises for application in organic electronics and beyond.

  16. Demonstrating Diffusion

    ERIC Educational Resources Information Center

    Foy, Barry G.

    1977-01-01

    Two demonstrations are described. Materials and instructions for demonstrating movement of molecules into cytoplasm using agar blocks, phenolphthalein, and sodium hydroxide are given. A simple method for demonstrating that the rate of diffusion of a gas is inversely proportional to its molecular weight is also presented. (AJ)

  17. Experimental and computational results on exciton/free-carrier ratio, hot/thermalized carrier diffusion, and linear/nonlinear rate constants affecting scintillator proportionality

    SciTech Connect

    Williams, Richard; Grim, Joel; Li, Qi; Ucer, K. B.; Bizarri, G. A.; Kerisit, Sebastien N.; Gao, Fei; Bhattacharya, Pijush; Tupitsyn, Eugene; Rowe, Emmanuel; Buliga, Vladimir M.; Burger, Arnold

    2013-10-01

    Models of nonproportional response in scintillators have highlighted the importance of parameters such as branching ratios, carrier thermalization times, diffusion, kinetic order of quenching, associated rate constants, and radius of the electron track. For example, the fraction ηeh of excitations that are free carriers versus excitons was shown by Payne and coworkers to have strong correlation with the shape of electron energy response curves from Compton-coincidence studies. Rate constants for nonlinear quenching are implicit in almost all models of nonproportionality, and some assumption about track radius must invariably be made if one is to relate linear energy deposition dE/dx to volume-based excitation density n (eh/cm3) in terms of which the rates are defined. Diffusion, affecting time-dependent track radius and thus density of excitations, has been implicated as an important factor in nonlinear light yield. Several groups have recently highlighted diffusion of hot electrons in addition to thermalized carriers and excitons in scintillators. However, experimental determination of many of these parameters in the insulating crystals used as scintillators has seemed difficult. Subpicosecond laser techniques including interband z scan light yield, fluence-dependent decay time, and transient optical absorption are now yielding experimental values for some of the missing rates and ratios needed for modeling scintillator response. First principles calculations and Monte Carlo simulations can fill in additional parameters still unavailable from experiment. As a result, quantitative modeling of scintillator electron energy response from independently determined material parameters is becoming possible on an increasingly firmer data base. This paper describes recent laser experiments, calculations, and numerical modeling of scintillator response.

  18. Experimental and computational results on exciton/free-carrier ratio, hot/thermalized carrier diffusion, and linear/nonlinear rate constants affecting scintillator proportionality

    SciTech Connect

    Williams, R. T.; Grim, Joel Q.; Li, Qi; Ucer, K. B.; Bizarri, G. A.; Kerisit, S.; Gao, Fei; Bhattacharya, P.; Tupitsyn, E.; Rowe, E.; Buliga, V. M.; Burger, A.

    2013-09-26

    Models of nonproportional response in scintillators have highlighted the importance of parameters such as branching ratios, carrier thermalization times, diffusion, kinetic order of quenching, associated rate constants, and radius of the electron track. For example, the fraction ηeh of excitations that are free carriers versus excitons was shown by Payne and coworkers to have strong correlation with the shape of electron energy response curves from Compton-coincidence studies. Rate constants for nonlinear quenching are implicit in almost all models of nonproportionality, and some assumption about track radius must invariably be made if one is to relate linear energy deposition dE/dx to volume-based excitation density n (eh/cm3) in terms of which the rates are defined. Diffusion, affecting time-dependent track radius and thus density of excitations, has been implicated as an important factor in nonlinear light yield. Several groups have recently highlighted diffusion of hot electrons in addition to thermalized carriers and excitons in scintillators. However, experimental determination of many of these parameters in the insulating crystals used as scintillators has seemed difficult. Subpicosecond laser techniques including interband z scan light yield, fluence-dependent decay time, and transient optical absorption are now yielding experimental values for some of the missing rates and ratios needed for modeling scintillator response. First principles calculations and Monte Carlo simulations can fill in additional parameters still unavailable from experiment. As a result, quantitative modeling of scintillator electron energy response from independently determined material parameters is becoming possible on an increasingly firmer data base. This study describes recent laser experiments, calculations, and numerical modeling of scintillator response.

  19. Experimental and computational results on exciton/free-carrier ratio, hot/thermalized carrier diffusion, and linear/nonlinear rate constants affecting scintillator proportionality

    DOE PAGES

    Williams, R. T.; Grim, Joel Q.; Li, Qi; ...

    2013-09-26

    Models of nonproportional response in scintillators have highlighted the importance of parameters such as branching ratios, carrier thermalization times, diffusion, kinetic order of quenching, associated rate constants, and radius of the electron track. For example, the fraction ηeh of excitations that are free carriers versus excitons was shown by Payne and coworkers to have strong correlation with the shape of electron energy response curves from Compton-coincidence studies. Rate constants for nonlinear quenching are implicit in almost all models of nonproportionality, and some assumption about track radius must invariably be made if one is to relate linear energy deposition dE/dx tomore » volume-based excitation density n (eh/cm3) in terms of which the rates are defined. Diffusion, affecting time-dependent track radius and thus density of excitations, has been implicated as an important factor in nonlinear light yield. Several groups have recently highlighted diffusion of hot electrons in addition to thermalized carriers and excitons in scintillators. However, experimental determination of many of these parameters in the insulating crystals used as scintillators has seemed difficult. Subpicosecond laser techniques including interband z scan light yield, fluence-dependent decay time, and transient optical absorption are now yielding experimental values for some of the missing rates and ratios needed for modeling scintillator response. First principles calculations and Monte Carlo simulations can fill in additional parameters still unavailable from experiment. As a result, quantitative modeling of scintillator electron energy response from independently determined material parameters is becoming possible on an increasingly firmer data base. This study describes recent laser experiments, calculations, and numerical modeling of scintillator response.« less

  20. Database applicaton for absolute spectrophotometry

    NASA Astrophysics Data System (ADS)

    Bochkov, Valery V.; Shumko, Sergiy

    2002-12-01

    32-bit database application with multidocument interface for Windows has been developed to calculate absolute energy distributions of observed spectra. The original database contains wavelength calibrated observed spectra which had been already passed through apparatus reductions such as flatfielding, background and apparatus noise subtracting. Absolute energy distributions of observed spectra are defined in unique scale by means of registering them simultaneously with artificial intensity standard. Observations of sequence of spectrophotometric standards are used to define absolute energy of the artificial standard. Observations of spectrophotometric standards are used to define optical extinction in selected moments. FFT algorithm implemented in the application allows performing convolution (deconvolution) spectra with user-defined PSF. The object-oriented interface has been created using facilities of C++ libraries. Client/server model with Windows Socket functionality based on TCP/IP protocol is used to develop the application. It supports Dynamic Data Exchange conversation in server mode and uses Microsoft Exchange communication facilities.

  1. Absolute classification with unsupervised clustering

    NASA Technical Reports Server (NTRS)

    Jeon, Byeungwoo; Landgrebe, D. A.

    1992-01-01

    An absolute classification algorithm is proposed in which the class definition through training samples or otherwise is required only for a particular class of interest. The absolute classification is considered as a problem of unsupervised clustering when one cluster is known initially. The definitions and statistics of the other classes are automatically developed through the weighted unsupervised clustering procedure, which is developed to keep the cluster corresponding to the class of interest from losing its identity as the class of interest. Once all the classes are developed, a conventional relative classifier such as the maximum-likelihood classifier is used in the classification.

  2. Computer Program for the Calculation of Multicomponent Convective Diffusion Deposition Rates from Chemically Frozen Boundary Layer Theory

    NASA Technical Reports Server (NTRS)

    Gokoglu, S. A.; Chen, B. K.; Rosner, D. E.

    1984-01-01

    The computer program based on multicomponent chemically frozen boundary layer (CFBL) theory for calculating vapor and/or small particle deposition rates is documented. A specific application to perimter-averaged Na2SO4 deposition rate calculations on a cylindrical collector is demonstrated. The manual includes a typical program input and output for users.

  3. Optical coherent tomography measurements of the diffusion rate of water and drugs in an isolated and whole cornea

    SciTech Connect

    Larin, Kirill V; Ghosn, M G

    2006-12-31

    The passive diffusion of drugs through the epithelial surfaces of an eye (the most widespread method for medical treatment of various diseases) is considered. The permeability of water and drugs through rabbit cornea was measured in the isolated cornea (separate from an eye) and in the whole cornea. The permeability coefficients of water and dexamethasone were estimated by the method of optical coherence tomography (OCT). Because multiple photon scattering introduces noise and distortions to the OCT signal, measurements were performed at depths up to 500 {mu}m where most likely single scattering of light occurs in cornea. It is shown that the permeability coefficients in the isolated and whole cornea strongly differ from each other. For example, the water permeability in the isolated and whole cornea is (7.09{+-}0.12)x10{sup -5} and (1.71{+-}0.51)x10{sup -5} cm s{sup -1}, respectively. (special issue devoted to multiple radiation scattering in random media)

  4. Understanding the Low Photosynthetic Rates of Sun and Shade Coffee Leaves: Bridging the Gap on the Relative Roles of Hydraulic, Diffusive and Biochemical Constraints to Photosynthesis

    PubMed Central

    Martins, Samuel C. V.; Galmés, Jeroni; Cavatte, Paulo C.; Pereira, Lucas F.; Ventrella, Marília C.; DaMatta, Fábio M.

    2014-01-01

    It has long been held that the low photosynthetic rates (A) of coffee leaves are largely associated with diffusive constraints to photosynthesis. However, the relative limitations of the stomata and mesophyll to the overall diffusional constraints to photosynthesis, as well as the coordination of leaf hydraulics with photosynthetic limitations, remain to be fully elucidated in coffee. Whether the low actual A under ambient CO2 concentrations is associated with the kinetic properties of Rubisco and high (photo)respiration rates also remains elusive. Here, we provide a holistic analysis to understand the causes associated with low A by measuring a variety of key anatomical/hydraulic and photosynthetic traits in sun- and shade-grown coffee plants. We demonstrate that leaf hydraulic architecture imposes a major constraint on the maximisation of the photosynthetic gas exchange of coffee leaves. Regardless of the light treatments, A was mainly limited by stomatal factors followed by similar limitations associated with the mesophyll and biochemical constraints. No evidence of an inefficient Rubisco was found; rather, we propose that coffee Rubisco is well tuned for operating at low chloroplastic CO2 concentrations. Finally, we contend that large diffusive resistance should lead to large CO2 drawdown from the intercellular airspaces to the sites of carboxylation, thus favouring the occurrence of relatively high photorespiration rates, which ultimately leads to further limitations to A. PMID:24743509

  5. Dispersion of Relaxation Rates in the Rotating Frame Under the Action of Spin-Locking Pulses and Diffusion in Inhomogeneous Magnetic Fields

    PubMed Central

    Spear, John T.; Zu, Zhongliang; Gore, John C.

    2013-01-01

    Purpose A method is described for characterizing magnetically inhomogeneous media and the spatial scales of intrinsic susceptibility variations within samples. The rate of spin-lattice relaxation in the rotating frame, R1ρ, is affected by diffusion effects to a degree that depends on the magnitude of an applied spin-locking field. Appropriate analysis of the dispersion of R1ρ with locking field may be used to characterize susceptibility variations in inhomogeneous tissues. Theory and Methods The contribution of diffusion to R1ρ is quantified by an analytic expression derived by analyzing of the effects of diffusion through periodic variations of magnetic susceptibility and is used to predict the effects of inhomogeneities in simple phantoms. The theory is further applied to imaging to derive parametric images that portray the dimensions of susceptibility inhomogeneities independent of their magnitude. Results Significant dispersion of R1ρ with locking field was predicted and measured experimentally for suspensions of microspheres ranging from 1 to 90 µm in diameter. For scales of practical interest, these dispersion effects occur at much lower locking fields than the range in which chemical exchange effects cause similar dispersion. Conclusion There is good agreement between theory and experiment, and the method has potential for quantitative tissue characterization and functional imaging. PMID:23804212

  6. Hydrodynamic enhancement of the diffusion rate in the region between two fluctuating membranes in close opposition: a theoretical and computational study.

    PubMed

    Pannuzzo, Martina; Grassi, Antonio; Raudino, Antonio

    2014-07-24

    Periodic variation of the distance between two weakly adhering bodies gives rise to a huge tangential motions of the sandwiched solvent layer (squeezing flow). Oscillations either can be induced by an external applied field or can spontaneously arise from the coupling with the solvent heat bath. First we calculated by the Navier-Stokes equation the components of the fluid velocity near two oscillating juxtaposed plates. Then we evaluated the influence of plate oscillations on the transport properties of a trace diffusant dissolved at t = 0 in the outer medium for both deterministic and stochastic excitations. By employing both analytical (Fokker-Planck) and coarse-grained molecular dynamics (MD) simulations, we proved that the entry and migration rates of the diffusant sharply increases with the oscillation amplitudes. Enhancement was related to relevant parameters like oscillation frequency, fluid layer thickness, fluid viscosity, and temperature. An extension to the case of oscillating multistacked lamellae has been also made. Theoretical and MD results suggest a significant enhancement of the diffusant flux even in the worse situation of thermally excited small amplitude fluctuations. Excitation arising from other sources (e.g., microwave or ultrasound irradiation of solid-fluid layered systems) could have a dramatic effect on the transport phenomena. Possible implications to relevant biological problems have been discussed.

  7. 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.-

  8. 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)

  9. Absolute Standards for Climate Measurements

    NASA Astrophysics Data System (ADS)

    Leckey, J.

    2016-10-01

    In a world of changing climate, political uncertainty, and ever-changing budgets, the benefit of measurements traceable to SI standards increases by the day. To truly resolve climate change trends on a decadal time scale, on-orbit measurements need to be referenced to something that is both absolute and unchanging. One such mission is the Climate Absolute Radiance and Refractivity Observatory (CLARREO) that will measure a variety of climate variables with an unprecedented accuracy to definitively quantify climate change. In the CLARREO mission, we will utilize phase change cells in which a material is melted to calibrate the temperature of a blackbody that can then be observed by a spectrometer. A material's melting point is an unchanging physical constant that, through a series of transfers, can ultimately calibrate a spectrometer on an absolute scale. CLARREO consists of two primary instruments: an infrared (IR) spectrometer and a reflected solar (RS) spectrometer. The mission will contain orbiting radiometers with sufficient accuracy to calibrate other space-based instrumentation and thus transferring the absolute traceability. The status of various mission options will be presented.

  10. An Effective Continuum Model for the Liquid-to-Gas Phase Change in a Porous Medium Driven by Solute Diffusion: II. Constant Liquid Withdrawal Rates

    SciTech Connect

    Tsimpanogiannis, Ioannis N.; Yortsos, Yanis C.

    2001-08-15

    This report describes the development of an effective continuum model to describe the nucleation and subsequent growth of a gas phase from a supersaturated, slightly compressible binary liquid in a porous medium, driven by solute diffusion.This report also focuses on the processes resulting from the withdrawal of the liquid at a constant rate. As before, the model addresses two stages before the onset of bulk gas flow, nucleation and gas phase growth. Because of negligible gradients due to gravity or viscous forces, the critical gas saturation, is only a function of the nucleation fraction.

  11. Raman measurement of mixing and finite-rate chemistry in a supersonic hydrogen-air diffusion flame

    SciTech Connect

    Cheng, T.S.; Wehrmeyer, J.A.; Pitz, R.W. . Dept. of Mechanical Engineering); Jarrett, O. Jr.; Northam, G.B. . Langley Research Center)

    1994-10-01

    Ultraviolet (UV) spontaneous vibrational Raman scattering and laser-induced predissociative fluorescence (LIPF) from a KrF excimer laser are combined to simultaneously measure temperature, major species concentrations (H[sub 2], O[sub 2], N[sub 2], H[sub 2]O), and OH radical concentration in a supersonic lifted co-flowing hydrogen-air diffusion flame. The axisymmetric flame is formed when a sonic jet of hydrogen mixes with a Mach 2 annular jet of vitiated air. Mean and rms profiles of temperature, species concentrations, and mixture fraction are obtained throughout the supersonic flame. Simultaneous measurements of the chemical species and temperature are compared with frozen chemistry and equilibrium chemistry limits to assess the local state of the mixing and chemistry. Upstream of the lifted flame base, a very small amount of reaction occurs form mixing with hot vitiated air. Downstream of the lifted flame base, strong turbulent mixing leads to sub equilibrium values of temperature and OH concentration. Due to the interaction of velocity and temperature in supersonic compressible flames, the fluctuations of temperature and species concentrations are found to be higher than subsonic flames. Farther downstream, slow three-body recombination reactions result in super equilibrium OH concentrations that depress temperatures below their equilibrium values.

  12. Counterflow diffusion flames of hydrogen, and hydrogen plus methane, ethylene, propane, and silane vs. air - Strain rates at extinction

    NASA Technical Reports Server (NTRS)

    Pellett, G. L.; Northam, G. Burton; Wilson, L. G.

    1991-01-01

    Five coaxial tubular opposed jet burners (OJBs) with tube diameter D(T) of 1.8-10 mm and 5 mm conical nozzles were used to form dish-shaped counterflow diffusion flames centered by opposing laminar jets of nitrogen and hydrocarbon-diluted H2 versus air in an argon-purged chamber at 1 atm. Area-averaged air jet velocities at blowoff of the central flame, U(air), characterized extinction of the airside flame as functions of input H2 concentration on the fuelside. A master plot of extensive U(air) data at blowoff versus D(T) shows that U(air) varies linearly with D(T). This and other data sets are used to find that nozzle OJB results for U(air)/diameter average 4.24 + or - 0.28 times larger than tubular OJB results for the same fuel compositions. Critical radial velocity gradients consistent with one-dimensional stagnation point boundary theory and with plug flow inputs are estimated. The results compare favorably with published numerical results based only on potential flow.

  13. Probabilistic diffusion tractography: a potential tool to assess the rate of disease progression in amyotrophic lateral sclerosis.

    PubMed

    Ciccarelli, O; Behrens, T E; Altmann, D R; Orrell, R W; Howard, R S; Johansen-Berg, H; Miller, D H; Matthews, P M; Thompson, A J

    2006-07-01

    The goal of probabilistic tractography is to obtain a connectivity index along a white matter pathway that reflects fibre organization and is sensitive to pathological abnormalities contributing to disability. Here, we present the development of voxel-based connectivity measures along the tractography-derived corticospinal tract (CST). We investigated whether these connectivity measures are different in patients with amyotrophic lateral sclerosis (ALS) and correlate with the rate of disease progression. We also investigated whether fractional anisotropy (FA), which reflects directional coherence of fibre tracts, is reduced in the CST of ALS patients and relates to disease progression rate. Thirteen patients with probable or definite ALS and 19 healthy subjects were studied. The probabilistic tractography algorithm segmented the bilateral CST, along which FA and connectivity values were obtained. To take into account the asymmetric distribution of connectivity values, two summary statistic measures that focused on voxels with higher connectivity values were selected and then used in the analysis, together with the mean connectivity and the mean FA. To complete the analysis, the same summary measures for FA were included. Differences in all these indices between patients with moderate or rapid disease progression rate and controls were investigated using linear regression, adjusted for age and white matter fraction. The association between FA or connectivity in the CST and the disease progression rate was assessed using linear regression. Patients with a rapid disease progression rate had significantly lower summary connectivity measures than controls in the left CST, but there was only a borderline statistical difference in mean connectivity. Patients with rapid progression had a significantly lower mean FA, and any other FA measure, in both CSTs than controls. When only patients were considered, strong associations between the rate of disease progression and all

  14. Quantum effect of intramolecular high-frequency vibrational modes on diffusion-controlled electron transfer rate: From the weak to the strong electronic coupling regions

    SciTech Connect

    Zhu, Wenjuan; Zhao, Yi

    2007-05-14

    The Sumi-Marcus theory is extended by introducing two approaches to investigate electron transfer reactions from weak-to-strong electronic coupling regime. One of these approaches is the quantum R-matrix theory, useful for dealing with the intramolecular vibrational motions in the whole electronic coupling domain. The other is the split operator approach that is employed to solve the reaction-diffusion equation. The approaches are then applied to electron transfer in the Marcus inverted regime to investigate the nuclear tunneling effect on the long time rate and the survival probabilities. The numerical results illustrate that the adiabatic suppression obtained from the R-matrix approach is much smaller than that from the Landau-Zener theory whereas it cannot be predicted by the perturbation theory. The jointed effects of the electronic coupling and solvent relaxation time on the rates are also explored.

  15. Absolute calibration of optical flats

    DOEpatents

    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.

  16. Physics of negative absolute temperatures

    NASA Astrophysics Data System (ADS)

    Abraham, Eitan; Penrose, Oliver

    2017-01-01

    Negative absolute temperatures were introduced into experimental physics by Purcell and Pound, who successfully applied this concept to nuclear spins; nevertheless, the concept has proved controversial: a recent article aroused considerable interest by its claim, based on a classical entropy formula (the "volume entropy") due to Gibbs, that negative temperatures violated basic principles of statistical thermodynamics. Here we give a thermodynamic analysis that confirms the negative-temperature interpretation of the Purcell-Pound experiments. We also examine the principal arguments that have been advanced against the negative temperature concept; we find that these arguments are not logically compelling, and moreover that the underlying "volume" entropy formula leads to predictions inconsistent with existing experimental results on nuclear spins. We conclude that, despite the counterarguments, negative absolute temperatures make good theoretical sense and did occur in the experiments designed to produce them.

  17. Why does hydronium diffuse faster than hydroxide in liquid water?

    NASA Astrophysics Data System (ADS)

    Zheng, Lixin; Santra, Biswajit; Distasio, Robert; Klein, Michael; Car, Roberto; Wu, Xifan

    Experiments show that the hydronium ion (H3O+) diffuses much faster than the hydroxide ion (OH-) in liquid water. ab initio molecular dynamics (AIMD) simulations correctly associated the diffusion mechanism to proton transfer (PT) but have been unable so far to clearly identify the reason for the faster diffusion of hydronium compared to hydroxide, as the diffusion rate was found to depend sensitively on the adopted functional approximation. We carried out AIMD simulations of the solvated water ions using a van der Waals (vdW) inclusive PBE0 hybrid density functional. It is found that not only hydronium diffuses faster than hydroxide but also the absolute rates agree with experiment. The fast diffusion of H3O+ occurs via concerted PT that enables the ion to jump across several H-bonded molecules in successful transfer events; in contrast, such concerted motion is significantly hindered in OH- where the ion is easily trapped in a hyper-coordination configuration (a local solvation structure that forbids PT). As a result multiple PT events are rare and the diffusion of OH- is significantly slowed down. Such a clear difference between the two ions results from the combined effect of vdW interactions and self-interaction correction. Doe SciDac: DE-SC0008626 and DE-SC0008726.

  18. Tactile perception of thermal diffusivity.

    PubMed

    Tiest, Wouter M Bergmann; Kappers, Astrid M L

    2009-04-01

    The thermal diffusivity of an object is a parameter that controls the rate at which heat is extracted from the hand when it touches that object. It is an important feature for distinguishing materials by means of touch. In order to quantitatively describe the ability of human observers to discriminate between materials on the basis of heat extraction rate, we conducted an experiment in which this heat extraction was performed in a controlled way. In different conditions, subjects were repeatedly asked to select from two stimuli the one that cooled faster. The discrimination threshold was around 43% of the extraction rate. A rate that was twice as slow also yielded twice the absolute threshold. When we halved the temperature difference between the beginning and end of the stimulus, the threshold did not change as much. In separate experiments, we investigated the different cues that were available in the stimulus: initial cooling rate and end temperature. Both cues were used for discrimination, but cooling rate seemed to be the most important.

  19. Rocket observations of the diffuse ultraviolet background

    NASA Technical Reports Server (NTRS)

    Jakobsen, P.; Bowyer, S.; Kimble, R.; Jelinsky, P.; Grewing, M.; Kraemer, G.; Wulf-Mathies, C.

    1984-01-01

    The objective of the experiment reported here was to obtain additional information on the absolute intensity level and spatial variation of the diffuse ultraviolet background and thereby gain insight into the origin of this radiation. The experiment used three ultraviolet sensitive photometers placed in the focal plane of a 95-cm, f/2.8 normal incidence telescope flown on board an Aries sounding rocket. The measured intensities clearly refute the hypothesis of an isotropic background, the intensities of the high galactic latitude being definitely lower than the intensities seen at intermediate latitudes. Moreover, the count rates in all three channels along the slow scan exhibit local enhancements as well as an overall trend. In general, the spatial variations exhibited by the data correlate with the line of sight of neutral hydrogen column density as determined from 21-cm radio observations. This fact demonstrates that there is a galactic component to the diffuse ultraviolet radiation field.

  20. Microfabricated diffusion source

    DOEpatents

    Oborny, Michael C.; Frye-Mason, Gregory C.; Manginell, Ronald P.

    2008-07-15

    A microfabricated diffusion source to provide for a controlled diffusion rate of a vapor comprises a porous reservoir formed in a substrate that can be filled with a liquid, a headspace cavity for evaporation of the vapor therein, a diffusion channel to provide a controlled diffusion of the vapor, and an outlet to release the vapor into a gas stream. The microfabricated diffusion source can provide a calibration standard for a microanalytical system. The microanalytical system with an integral diffusion source can be fabricated with microelectromechanical systems technologies.

  1. Shaken and Stirred: A Combined Reaction-Diffusion and Random Rate Model for the Temporal Evolution and Earthquake-induced Hydrodynamics of Silicate Mineral Weathering

    NASA Astrophysics Data System (ADS)

    Evaristo, J. A.; Willenbring, J.

    2013-12-01

    The time dependency of silicate mineral weathering has been explored in the literature in terms of processes and features that are intrinsic and extrinsic to the mineral [1]. However, although the advent of sophisticated reactive transport models has allowed for coupling increasingly complex reaction and transport processes [2,3], a simple and fundamental understanding of the temporal evolution of weathering is lacking. Here, we propose that a purely deterministic approach may not be sufficient given the inherent differences in reactivity over space and time. Therefore, we explore how a combined reaction-diffusion and random rate model - informed by a stochastic distribution of weathering rates K (T-1) - might be able to explain not only the temporal evolution but also the hydrodynamics of weathering during earthquakes; the latter being purportedly described by time-dependent property permeability (L2). Preliminary model results show that (1) an increase in dimensionless quantity βrp, where β is the diffusion length (L-1) and rp is the distance between pores (L), leads to a decrease in minimum reaction rate with time from the relation Kmin ∝ e-βrp/rp ; (2) at a given porosity, a time-dependent decrease in reactivity arises as permeability decreases due to decreasing pore size (and therefore increasing rp), which in turn may be related to the time-dependent feedback between dissolution and precipitation; (3) while permeability is lower in older soils, transient stresses as during earthquakes [4], may induce more efficient "declogging" of pores in these soils than in younger soils due to higher hydrodynamic viscous shear stress, thereby, resulting in a coseismic change in stream discharge Q; and (4) subsequent weathering beyond t~Kmin-1 exhibits a fall in rates, marking the cessation of logarithmic decay possibly due to dissolution-precipitation feedback. [1] White and Brantley (2003), Chem. Geol. 202, 479. [2] Lichtner P.C. (1996), Mineralogical Society of

  2. Diffusion and Monod kinetics model to determine in vivo human corneal oxygen-consumption rate during soft contact lens wear

    PubMed Central

    Del Castillo, Luis F.; da Silva, Ana R. Ferreira; Hernández, Saul I.; Aguilella, M.; Andrio, Andreu; Mollá, Sergio; Compañ, Vicente

    2014-01-01

    Purpose We present an analysis of the corneal oxygen consumption Qc from non-linear models, using data of oxygen partial pressure or tension (pO2) obtained from in vivo estimation previously reported by other authors.1 Methods Assuming that the cornea is a single homogeneous layer, the oxygen permeability through the cornea will be the same regardless of the type of lens that is available on it. The obtention of the real value of the maximum oxygen consumption rate Qc,max is very important because this parameter is directly related with the gradient pressure profile into the cornea and moreover, the real corneal oxygen consumption is influenced by both anterior and posterior oxygen fluxes. Results Our calculations give different values for the maximum oxygen consumption rate Qc,max, when different oxygen pressure values (high and low pO2) are considered at the interface cornea-tears film. Conclusion Present results are relevant for the calculation on the partial pressure of oxygen, available at different depths into the corneal tissue behind contact lenses of different oxygen transmissibility. PMID:25649636

  3. C2H2 absolutely optical frequency-stabilized and 40 GHz repetition-rate-stabilized, regeneratively mode-locked picosecond erbium fiber laser at 1.53 microm.

    PubMed

    Nakazawa, Masataka; Kasai, Keisuke; Yoshida, Masato

    2008-11-15

    We have succeeded in the simultaneous stabilization of the optical frequency and repetition rate of a regeneratively mode-locked picosecond erbium-doped fiber ring laser. The optical frequency was locked to the molecular absorption of C2H2 in the 1.5 microm band, and the repetition rate was stabilized to a 40 GHz synthesizer by using a microwave phase-locked loop. The optical frequency stability of the pulse train reached 2x10(-11) for tau=10-100 s. The key to success is the independent control of the repetition rate without disturbing the optical cavity condition.

  4. Diffusion-Based Density-Equalizing Maps: an Interdisciplinary Approach to Visualizing Homicide Rates and Other Georeferenced Statistical Data

    NASA Astrophysics Data System (ADS)

    Mazzitello, Karina I.; Candia, Julián

    2012-12-01

    In every country, public and private agencies allocate extensive funding to collect large-scale statistical data, which in turn are studied and analyzed in order to determine local, regional, national, and international policies regarding all aspects relevant to the welfare of society. One important aspect of that process is the visualization of statistical data with embedded geographical information, which most often relies on archaic methods such as maps colored according to graded scales. In this work, we apply nonstandard visualization techniques based on physical principles. We illustrate the method with recent statistics on homicide rates in Brazil and their correlation to other publicly available data. This physics-based approach provides a novel tool that can be used by interdisciplinary teams investigating statistics and model projections in a variety of fields such as economics and gross domestic product research, public health and epidemiology, sociodemographics, political science, business and marketing, and many others.

  5. Absolute calibration of optical tweezers

    SciTech Connect

    Viana, N.B.; Mazolli, A.; Maia Neto, P.A.; Nussenzveig, H.M.; Rocha, M.S.; Mesquita, O.N.

    2006-03-27

    As a step toward absolute calibration of optical tweezers, a first-principles theory of trapping forces with no adjustable parameters, corrected for spherical aberration, is experimentally tested. Employing two very different setups, we find generally very good agreement for the transverse trap stiffness as a function of microsphere radius for a broad range of radii, including the values employed in practice, and at different sample chamber depths. The domain of validity of the WKB ('geometrical optics') approximation to the theory is verified. Theoretical predictions for the trapping threshold, peak position, depth variation, multiple equilibria, and 'jump' effects are also confirmed.

  6. A Numerical Investigation of the Extinction of Low Strain Rate Diffusion Flames by an Agent in Microgravity

    NASA Technical Reports Server (NTRS)

    Puri, Ishwar K.

    2004-01-01

    Our goal has been to investigate the influence of both dilution and radiation on the extinction process of nonpremixed flames at low strain rates. Simulations have been performed by using a counterflow code and three radiation models have been included in it, namely, the optically thin, the narrowband, and discrete ordinate models. The counterflow flame code OPPDIFF was modified to account for heat transfer losses by radiation from the hot gases. The discrete ordinate method (DOM) approximation was first suggested by Chandrasekhar for solving problems in interstellar atmospheres. Carlson and Lathrop developed the method for solving multi-dimensional problem in neutron transport. Only recently has the method received attention in the field of heat transfer. Due to the applicability of the discrete ordinate method for thermal radiation problems involving flames, the narrowband code RADCAL was modified to calculate the radiative properties of the gases. A non-premixed counterflow flame was simulated with the discrete ordinate method for radiative emissions. In comparison with two other models, it was found that the heat losses were comparable with the optically thin and simple narrowband model. The optically thin model had the highest heat losses followed by the DOM model and the narrow-band model.

  7. Some like it hot: Linking diffuse X-ray luminosity, baryonic mass, and star formation rate in compact groups of galaxies

    SciTech Connect

    Desjardins, Tyler D.; Gallagher, Sarah C.; Hornschemeier, Ann E.; Tzanavaris, Panayiotis; Walker, Lisa May; Johnson, Kelsey E.; Brandt, William N.; Charlton, Jane C.

    2014-08-01

    We present an analysis of the diffuse X-ray emission in 19 compact groups (CGs) of galaxies observed with Chandra. The hottest, most X-ray luminous CGs agree well with the galaxy cluster X-ray scaling relations in L{sub X} -T and L{sub X} -σ, even in CGs where the hot gas is associated with only the brightest galaxy. Using Spitzer photometry, we compute stellar masses and classify Hickson CGs 19, 22, 40, and 42, and RSCGs 32, 44, and 86 as fossil groups using a new definition for fossil systems that includes a broader range of masses. We find that CGs with total stellar and H I masses ≳ 10{sup 11.3} M{sub ☉} are often X-ray luminous, while lower-mass CGs only sometimes exhibit faint, localized X-ray emission. Additionally, we compare the diffuse X-ray luminosity against both the total UV and 24 μm star formation rates of each CG and optical colors of the most massive galaxy in each of the CGs. The most X-ray luminous CGs have the lowest star formation rates, likely because there is no cold gas available for star formation, either because the majority of the baryons in these CGs are in stars or the X-ray halo, or due to gas stripping from the galaxies in CGs with hot halos. Finally, the optical colors that trace recent star formation histories of the most massive group galaxies do not correlate with the X-ray luminosities of the CGs, indicating that perhaps the current state of the X-ray halos is independent of the recent history of stellar mass assembly in the most massive galaxies.

  8. Some Like it Hot: Linking Diffuse X-Ray Luminosity, Baryonic Mass, and Star Formation Rate in Compact Groups of Galaxies

    NASA Technical Reports Server (NTRS)

    Desjardins, Tyler D.; Gallagher, Sarah C.; Hornschemeier, Ann E.; Mulchaey, John S.; Walker, Lisa May; Brandt, Willian N.; Charlton, Jane C.; Johnson, Kelsey E.; Tzanavaris, Panayiotis

    2014-01-01

    We present an analysis of the diffuse X-ray emission in 19 compact groups (CGs) of galaxies observed with Chandra. The hottest, most X-ray luminous CGs agree well with the galaxy cluster X-ray scaling relations in L(x-T) and (L(x-sigma), even in CGs where the hot gas is associated with only the brightest galaxy. Using Spitzer photometry, we compute stellar masses and classify Hickson CGs 19, 22, 40, and 42, and RSCGs 32, 44, and 86 as fossil groups using a new definition for fossil systems that includes a broader range of masses. We find that CGs with total stellar and Hi masses are great than or equal to 10(sup (11.3) solar mass are often X-ray luminous, while lower-mass CGs only sometimes exhibit faint, localized X-ray emission. Additionally, we compare the diffuse X-ray luminosity against both the total UV and 24 micron star formation rates of each CG and optical colors of the most massive galaxy in each of the CGs. The most X-ray luminous CGs have the lowest star formation rates, likely because there is no cold gas available for star formation, either because the majority of the baryons in these CGs are in stars or the X-ray halo, or due togas stripping from the galaxies in CGs with hot halos. Finally, the optical colors that trace recent star formation histories of the most massive group galaxies do not correlate with the X-ray luminosities of the CGs, indicating that perhaps the current state of the X-ray halos is independent of the recent history of stellar mass assembly in the most massive galaxies.

  9. Determination of convective diffusion heat/mass transfer rates to burner rig test targets comparable in size to cross-stream jet diameter

    NASA Technical Reports Server (NTRS)

    Gokoglu, S. A.; Santoro, G. J.

    1985-01-01

    Two sets of experiments have been performed to be able to predict the convective diffusion heat/mass transfer rates to a cylindrical target whose height and diameter are comparable to, but less than, the diameter of the circular cross-stream jet, thereby simulating the same geometric configuration as a typical burner rig test specimen located in the cross-stream of the combustor exit nozzle. The first set exploits the naphthalene sublimation technique to determine the heat/mass transfer coefficient under isothermal conditions for various flow rates (Reynolds numbers). The second set, conducted at various combustion temperatures and Reynolds numbers, utilized the temperature variation along the surface of the above-mentioned target under steady-state conditions to estimate the effect of cooling (dilution) due to the entrainment of stagnant room temperature air. The experimental information obtained is used to predict high temperature, high velocity corrosive salt vapor deposition rates in burner rigs on collectors that are geometrically the same. The agreement with preliminary data obtained from Na2SO4 vapor deposition experiments is found to be excellent.

  10. Determination of convective diffusion heat/mass transfer rates to burner rig test targets comparable in size to cross-stream jet diameter

    NASA Technical Reports Server (NTRS)

    Gokoglu, S. A.; Santoro, G. J.

    1986-01-01

    Two sets of experiments have been performed to be able to predict the convective diffusion heat/mass transfer rates to a cylindrical target whose height and diameter are comparable to, but less than, the diameter of the circular cross-stream jet, thereby simulating the same geometric configuration as a typical burner rig test specimen located in the cross-stream of the combustor exit nozzlle. The first set exploits the naphthalene sublimation technique to detetermine the heat/mass transfer coefficient under isothermal conditions for various flow rates (Reynolds numbers). The second set, conducted at various combustion temperatures and Reynolds numbers, utilized the temperature variation along the surface of the above-mentioned target under steady-state conditions to estimate the effect of cooling (dilution) due to the entrainment of stagnant room temperature air. The experimental information obtained is used to predict high temperature, high velocity corrosive salt vapor deposition rates in burner rigs on collectors that are geometrically the same. The agreement with preliminary data obtained from Na2S04 vapor deposition experiments is found to be excellent.

  11. The Effective Diffusion Coefficient of Dissolved Oxygen and Oxidation Rate of Pyrite by Dissolved Oxygen in Compacted Purified and Crude Sodium Bentonites in Carbonate Buffered Solution

    SciTech Connect

    Manaka, Mitsuo

    2003-09-15

    Immediately after the geological disposal of high-level radioactive waste, the oxygen initially existing in the repository is expected to strongly affect the redox condition of the near field. The oxygen dissolves in the groundwater, is transported by diffusion through it, and is consumed by the oxidation of pyrite as an impurity in bentonite. To assess the influence of the oxygen, this study was conducted to estimate the diffusion of dissolved oxygen (DO) and the rate of pyrite oxidation by DO in compacted purified and crude sodium bentonites (SBs) in more detail than the Manaka et al. study. The effective diffusion coefficient (De) of DO in the compacted purified SB was measured in low ionic strength solution (carbonate buffered solution with pH {approx} 9) using the electrochemical method. The empirical equation between De value of DO and dry density (0.5 x 10{sup 3}-1.8 x 10{sup 3} kg m{sup -3}) of purified SB was obtained as follows:De{sub DO}{sup Kunipia-F} = 8.2 {+-} 1.5 x 10{sup -10}x exp(-2.6 {+-} 0.2 x10{sup -3}{rho},where De{sub DO}{sup Kunipia-F} is the De of DO in compacted purified SB (Kunipia F) (m{sup 2} s{sup -1}) and {rho} is the dry density of the SB (kg m{sup -3}).On the other hand, the De value of DO in the compacted crude SB was estimated using the relationship between De values of tritiated water in compacted purified and crude SBs. The empirical equation between the De value of DO and dry density (0.5 x 10{sup 3}-1.8 x 10{sup 3} kg m{sup -3}) of crude SB was derived as follows:De{sub DO}{sup Kunigel-V1} = 2.04 x 10{sup -9} exp(-2.6 x 10{sup -3}{rho}),where De{sub DO}{sup Kunigel-V1} is the De of DO in compacted crude SB (Kunigel V1) (m{sup 2} s{sup -1}) and {rho} is the dry density of the SB (kg m{sup -3}).The rates of pyrite oxidation by DO were estimated from the experimental data in pyrite-purified SB systems using the obtained De values of DO. The relation between rate constant (k') of pyrite oxidation by DO and dry density ({rho}) of

  12. The absolute threshold of cone vision

    PubMed Central

    Koeing, Darran; Hofer, Heidi

    2013-01-01

    We report measurements of the absolute threshold of cone vision, which has been previously underestimated due to sub-optimal conditions or overly strict subjective response criteria. We avoided these limitations by using optimized stimuli and experimental conditions while having subjects respond within a rating scale framework. Small (1′ fwhm), brief (34 msec), monochromatic (550 nm) stimuli were foveally presented at multiple intensities in dark-adapted retina for 5 subjects. For comparison, 4 subjects underwent similar testing with rod-optimized stimuli. Cone absolute threshold, that is, the minimum light energy for which subjects were just able to detect a visual stimulus with any response criterion, was 203 ± 38 photons at the cornea, ∼0.47 log units lower than previously reported. Two-alternative forced-choice measurements in a subset of subjects yielded consistent results. Cone thresholds were less responsive to criterion changes than rod thresholds, suggesting a limit to the stimulus information recoverable from the cone mosaic in addition to the limit imposed by Poisson noise. Results were consistent with expectations for detection in the face of stimulus uncertainty. We discuss implications of these findings for modeling the first stages of human cone vision and interpreting psychophysical data acquired with adaptive optics at the spatial scale of the receptor mosaic. PMID:21270115

  13. 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.

  14. Age and forgetfulness: absolute versus comparison decisions about capability.

    PubMed

    Erber, J T; Prager, I G

    1997-01-01

    Perceivers were assigned to one of two decision conditions. In an absolute decision condition, perceivers rated how likely they would be to allow a young or old highly forgetful, slightly forgetful, or nonforgetful target to perform a challenging task. In a comparison decision condition, perceivers rated two targets, one young and one old, who had a similar level of forgetfulness. Separate Decision Type x Target Forgetfulness analyses of variance were conducted on ratings of the two target age groups. Young targets received higher ratings in the comparison than in the absolute condition, whereas old targets were rated the same in the two conditions. There was some preference for young targets in a comparison situation, but it was concluded that forgetfulness was a more important factor than age in perceivers' ratings.

  15. Reinvestigation of the laser-initiated Cl/sub 2//HBr chain reaction: absolute rate constants and the v = 2/v = 1 ratio from Cl + HBr. -->. HCl(v) + Br

    SciTech Connect

    Dolson, D.A.; Leone, S.R.

    1987-06-18

    The Cl/sub 2//HBr chain reaction is reinvestigated by using real time state-selected observations of ..delta..v = -1 chemiluminescence from the HCl(V) products following pulsed laser photolysis of Cl/sub 2/. These state-selected observations are analyzed with a more complete kinetic treatment to obtain room temperature rate constants for the chain propagation steps and the vibrational deactivation of HCl(V = 1,2) by HBr. The chain propagation rate constants are k/sub R1/ = (1.02 +/- 0.15) x 10/sup -11/ and k/sub R2/ = (1.1 +/- 0.4) x 10/sup -15/ cm/sup 3/ molecule/sup -1/ s/sup -1/, respectively, for Cl + HBr ..-->../sup kR1/ HCl(v) + Br and Br + Cl/sub 2/ ..-->../sup kR2/ BrCl + Cl. Rate constants for vibrational deactivation of HCl(v=1) and HCl(v=2) by HBr are k/sub V1/ = (1.06 +/- 0.16) x 10/sup -12/ and k/sub V2/ = (2.09 +/- 0.50) x 10/sup -12/ cm/sup 3/ molecule/sup -1/ s/sup -1/. Relative intensity measurements of the HCl v = 2 ..-->.. 1 and 1 ..-->.. 0 vibrational fluorescence are used to obtain an HCl(v) product branching ratio, N/sub v=2//N/sub v=1/ = 0.40 +/- 0.06. The kinetic analysis indicates that broad-band observations of infrared chemiluminescence may lead to erroneous rate constant determinations because of vibrational cascade, whereas the detection of individual vibrational states leads to correct results.

  16. The reaction NH2 + PH3 yields NH3 + PH2 - Absolute rate constant measurement and implication for NH3 and PH3 photochemistry in the atmosphere of Jupiter

    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.

  17. The reaction NH2 + PH3 yields NH3 + PH2: Absolute rate constant measurement and implication for NH3 and PH3 photochemistry in the atmosphere of Jupiter

    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.

  18. 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.

  19. Modeling tumor growth in the presence of a therapy with an effect on rate growth and variability by means of a modified Gompertz diffusion process.

    PubMed

    Román-Román, Patricia; Román-Román, Sergio; Serrano-Pérez, Juan José; Torres-Ruiz, Francisco

    2016-10-21

    In experimental studies on tumor growth, whenever the time evolution of the relative volume of a tumor in an untreated (control) group can be fitted by a Gompertz diffusion process there is a possibility that an antiproliferative therapy, which modifies the growth rate of the process that fits the treated group, may also affect its variability. The present paper proposes several procedures for the estimation of the time function included in the infinitesimal variance of the new process, as well as the time function affecting the growth rate (which is included in the infinitesimal mean). Also, a hypothesis testing is designed to confirm or refute the need for including such a time-dependent function in the infinitesimal variance. In order to validate and compare the proposed procedures a simulation study has been carried out. In addition, a proposal is made for a strategy aimed at finding the optimal combination of procedures for each case. A real data application concerning the effects of cisplatin on a patient-derived xenograft (PDX) tumor model showcases the advantages of this model over others that have been used in the past.

  20. An interpretation of fluctuations in enzyme catalysis rate, spectral diffusion, and radiative component of lifetimes in terms of electric field fluctuations.

    PubMed

    Prakash, Meher K; Marcus, R A

    2007-10-09

    Time-dependent fluctuations in the catalysis rate (deltak(t)) observed in single-enzyme experiments were found in a particular study to have an autocorrelation function decaying on the same time scale as that of spectral diffusion deltaomega(0)(t). To interpret this similarity, the present analysis focuses on a factor in enzyme catalysis, the local electrostatic interaction energy (E) at the active site and its effect on the activation free energy barrier. We consider the slow fluctuations of the electrostatic interaction energy (deltaE(t)) as a contributor to deltak(t) and relate the latter to deltaomega(0)(t). The resulting relation between deltak(t) and deltaomega(0)(t) is a dynamic analog of the solvatochromism used in interpreting solvent effects on organic reaction rates. The effect of the postulated deltaE(t) on fluctuations in the radiative component (deltagamma(r)(-1)(t)) of the fluorescence decay of chromophores in proteins also is examined, and a relation between deltagamma(r)(-1)(t) and deltaomega(0)(t) is obtained. Experimental tests will determine whether the correlation functions for deltak(t), deltaomega(0)(t), and deltagamma(r)(-1) are indeed similar for any enzyme. Measurements of dielectric dispersion, epsilon(omega), for the enzyme discussed elsewhere will provide further insight into the correlation function for deltaE(t). They also will determine whether fluctuations in the nonradiative component gamma(nr)(-1) of the lifetime decay has a different origin, fluctuations in distance for example.

  1. Recommendations for a Kalman filter to estimate and control freeze and sublime rates of gaseous diffusion plant freezer/sublimer systems

    SciTech Connect

    Ruppel, F.R.

    1992-09-01

    A signal is required to control the flow of UF{sub 6} in gaseous diffusion plant freezer/sublimer systems. The original strategy envisioned for deriving a flow signal was to take the derivative of the freezer/sublimer weigh cell signal. However, the derivative of the digitized weight signal is noisy, preventing good control. In addition, a disturbance is introduced into the weight derivative signal because a refrigerant is circulated through a shell-and-tube heat exchanger inside the freezer/sublimer. The weight of the refrigerant is included in the weight measured by the weigh cell. If the circulation rate of the refrigerant is not steady state, a disturbance exists. Measurements of upstream pressure, vessel pressure, and output to the system control valve are available to the control system. Thus, if the flow through the control valve is characterized properly by these measurements, a Kalman filter can be used in conjunction with these auxiliary inputs and the weigh cell input to overcome the noise and disturbance problem and provide an improved estimate of flow rate. A discussion of the development of a Kalman filter that could be used for this application is given, and recommendations are given for its implementation.

  2. Accurate absolute GPS positioning through satellite clock error estimation

    NASA Astrophysics Data System (ADS)

    Han, S.-C.; Kwon, J. H.; Jekeli, C.

    2001-05-01

    An algorithm for very accurate absolute positioning through Global Positioning System (GPS) satellite clock estimation has been developed. Using International GPS Service (IGS) precise orbits and measurements, GPS clock errors were estimated at 30-s intervals. Compared to values determined by the Jet Propulsion Laboratory, the agreement was at the level of about 0.1 ns (3 cm). The clock error estimates were then applied to an absolute positioning algorithm in both static and kinematic modes. For the static case, an IGS station was selected and the coordinates were estimated every 30 s. The estimated absolute position coordinates and the known values had a mean difference of up to 18 cm with standard deviation less than 2 cm. For the kinematic case, data obtained every second from a GPS buoy were tested and the result from the absolute positioning was compared to a differential GPS (DGPS) solution. The mean differences between the coordinates estimated by the two methods are less than 40 cm and the standard deviations are less than 25 cm. It was verified that this poorer standard deviation on 1-s position results is due to the clock error interpolation from 30-s estimates with Selective Availability (SA). After SA was turned off, higher-rate clock error estimates (such as 1 s) could be obtained by a simple interpolation with negligible corruption. Therefore, the proposed absolute positioning technique can be used to within a few centimeters' precision at any rate by estimating 30-s satellite clock errors and interpolating them.

  3. Variation in the electrical properties of 100 V/100 a rated mesh and stripe TDMOSFETs (Trench Double-Diffused MOSFETs) for motor drive applications

    NASA Astrophysics Data System (ADS)

    Na, Kyoung-Il; Kah, Dong-Ha; Kim, Sang-Gi; Koo, Jin-Gun; Kim, Jongdae; Yang, Yil-Suk; Lee, Jin-Ho

    2012-05-01

    The vertical power metal-oxide semiconductor field-effect transistors (MOSFETs) with deep trench structures are the most promising candidates to overcome the trade-off relationship between the ON-resistance (R ON ) and the blocking voltage (BV DS ). Especially, 100 V/100 A rated trench power MOSFETs are used in components of many power systems, such as motors and LED lighting drive ICs, DC-DC converters in electric vehicles, and so on. In this work, we studied variations of the electrical characteristics, such as threshold voltage (V TH ), BV DS , and drain current drivability, with p-well doping concentration via the SILVACO simulator. From simulation results, we found the BV DS and the drain current (I D ) as functions of the p-well doping concentration at an ion implantation energy of 80 keV. With increasing of p-well doping concentration in the guard ring region, both V TH and BV DS slowly increased, but I D decreased, because the boron lateral diffusion during the fabrication process below gate trench region affected the doping concentration of the p-body at the active region. Additionally, 100 V/100 A rated trench double-diffused MOSFETs (TDMOSFETs) with meshes and stripes were successfully developed by using a silicon deep etching process. The variations in the electrical properties, such as V TH , BV DS , and drain current drivability, of the two different kinds of fabricated devices, with cell design and density in TDMOSFETs were also studied. The BV DS and the V TH in the stripe-type TDMOSFET were 110 and 3 V, respectively. However, the V TH of mesh-type device was smaller 0.5 V than that of stripe-type because of corner effect. The BV DS improved about 20 V compared to stripe-type TDMOSFET due to edge termination, and the maximum drain current (I D.MAX ) was improved by about 10% due to an increase in the gate width at the same chip size. These effects were reflected in devices with different cell densities. When the cell density was increased, however

  4. 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.

  5. The role of external electric fields in enhancing ion mobility, drift velocity, and drift-diffusion rates in aqueous electrolyte solutions

    NASA Astrophysics Data System (ADS)

    Murad, Sohail

    2011-03-01

    Molecular simulations have been carried out using the method of molecular dynamics to investigate the role of external electric fields on the ion mobility, drift velocity, and drift-diffusion rate of ions in aqueous electrolyte solutions. These properties are critical for a range of processes including electrodialysis, electro-deionization, electrophoresis, and electroosmosis. Our results show that external electric fields relax the hydrated ion structure at significantly larger time scales (between 300 and 800 ps), than most other relaxation processes in solutions (generally of the order of 1 ps). Previous studies that did not account for the much longer relaxation times did not observe this behavior for ions even with very high electric fields. External electric fields must also overcome several (at least two or more) activation energy barriers to significantly change the structure of hydrated ions. As a result, the dynamic behavior changes almost in bands as a function of electric field strengths, rather than linearly. Finally, the effect of the field is much less dramatic on water than the ions. Thus electric fields will be of more significance in processes that involve the transport of ions (such as electro-deionization) than the transport of water (electroosmosis).

  6. Absolute GPS Positioning Using Genetic Algorithms

    NASA Astrophysics Data System (ADS)

    Ramillien, G.

    A new inverse approach for restoring the absolute coordinates of a ground -based station from three or four observed GPS pseudo-ranges is proposed. This stochastic method is based on simulations of natural evolution named genetic algorithms (GA). These iterative procedures provide fairly good and robust estimates of the absolute positions in the Earth's geocentric reference system. For comparison/validation, GA results are compared to the ones obtained using the classical linearized least-square scheme for the determination of the XYZ location proposed by Bancroft (1985) which is strongly limited by the number of available observations (i.e. here, the number of input pseudo-ranges must be four). The r.m.s. accuracy of the non -linear cost function reached by this latter method is typically ~10-4 m2 corresponding to ~300-500-m accuracies for each geocentric coordinate. However, GA can provide more acceptable solutions (r.m.s. errors < 10-5 m2), even when only three instantaneous pseudo-ranges are used, such as a lost of lock during a GPS survey. Tuned GA parameters used in different simulations are N=1000 starting individuals, as well as Pc=60-70% and Pm=30-40% for the crossover probability and mutation rate, respectively. Statistical tests on the ability of GA to recover acceptable coordinates in presence of important levels of noise are made simulating nearly 3000 random samples of erroneous pseudo-ranges. Here, two main sources of measurement errors are considered in the inversion: (1) typical satellite-clock errors and/or 300-metre variance atmospheric delays, and (2) Geometrical Dilution of Precision (GDOP) due to the particular GPS satellite configuration at the time of acquisition. Extracting valuable information and even from low-quality starting range observations, GA offer an interesting alternative for high -precision GPS positioning.

  7. Diffusion coefficients significant in modeling the absorption rate of carbon dioxide into aqueous blends of N-methyldiethanolamine and diethanolamine and of hydrogen sulfide into aqueous N-methyldiethanolamine

    SciTech Connect

    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.

  8. What is Needed for Absolute Paleointensity?

    NASA Astrophysics Data System (ADS)

    Valet, J. P.

    2015-12-01

    Many alternative approaches to the Thellier and Thellier technique for absolute paleointensity have been proposed during the past twenty years. One reason is the time consuming aspect of the experiments. Another reason is to avoid uncertainties in determinations of the paleofield which are mostly linked to the presence of multidomain grains. Despite great care taken by these new techniques, there is no indication that they always provide the right answer and in fact sometimes fail. We are convinced that the most valid approach remains the original double heating Thellier protocol provided that natural remanence is controlled by pure magnetite with a narrow distribution of small grain sizes, mostly single domains. The presence of titanium, even in small amount generates biases which yield incorrect field values. Single domain grains frequently dominate the magnetization of glass samples, which explains the success of this selective approach. They are also present in volcanic lava flows but much less frequently, and therefore contribute to the low success rate of most experiments. However the loss of at least 70% of the magnetization at very high temperatures prior to the Curie point appears to be an essential prerequisite that increases the success rate to almost 100% and has been validated from historical flows and from recent studies. This requirement can easily be tested by thermal demagnetization while low temperature experiments can document the detection of single domain magnetite using the δFC/δZFC parameter as suggested (Moskowitz et al, 1993) for biogenic magnetite.

  9. 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.

  10. ON A SUFFICIENT CONDITION FOR ABSOLUTE CONTINUITY.

    DTIC Science & Technology

    The formulation of a condition which yields absolute continuity when combined with continuity and bounded variation is the problem considered in the...Briefly, the formulation is achieved through a discussion which develops a proof by contradiction of a sufficiently theorem for absolute continuity which uses in its hypothesis the condition of continuity and bounded variation .

  11. 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…

  12. Monolithically integrated absolute frequency comb laser system

    SciTech Connect

    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.

  13. Overspecification of color, pattern, and size: salience, absoluteness, and consistency

    PubMed Central

    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

  14. 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.

  15. An estimate of the irradiation creep rate in α-Fe based on computer simulation of vacancy pipe diffusion along <100> ?010? dislocations

    NASA Astrophysics Data System (ADS)

    Borodin, V. A.; Kevorkyan, Yu. R.; Kolomytkin, V. V.; Ryazanov, A. I.

    1992-04-01

    The effect of external loading on vacancy pipe diffusion along a dislocation line is studied. It is shown that the external load leads to orientational dependence of dislocation sink strengths due to polarization of vacancies in the dislocation core. Computer calculations of the dipole tensor for vacancy diffusion in the core of a [100](010) dislocation in α-Fe are performed to obtain an estimate of the irradiation creep compliance value.

  16. 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.

  17. Absolute quantitation of protein posttranslational modification isoform.

    PubMed

    Yang, Zhu; Li, Ning

    2015-01-01

    Mass spectrometry has been widely applied in characterization and quantification of proteins from complex biological samples. Because the numbers of absolute amounts of proteins are needed in construction of mathematical models for molecular systems of various biological phenotypes and phenomena, a number of quantitative proteomic methods have been adopted to measure absolute quantities of proteins using mass spectrometry. The liquid chromatography-tandem mass spectrometry (LC-MS/MS) coupled with internal peptide standards, i.e., the stable isotope-coded peptide dilution series, which was originated from the field of analytical chemistry, becomes a widely applied method in absolute quantitative proteomics research. This approach provides more and more absolute protein quantitation results of high confidence. As quantitative study of posttranslational modification (PTM) that modulates the biological activity of proteins is crucial for biological science and each isoform may contribute a unique biological function, degradation, and/or subcellular location, the absolute quantitation of protein PTM isoforms has become more relevant to its biological significance. In order to obtain the absolute cellular amount of a PTM isoform of a protein accurately, impacts of protein fractionation, protein enrichment, and proteolytic digestion yield should be taken into consideration and those effects before differentially stable isotope-coded PTM peptide standards are spiked into sample peptides have to be corrected. Assisted with stable isotope-labeled peptide standards, the absolute quantitation of isoforms of posttranslationally modified protein (AQUIP) method takes all these factors into account and determines the absolute amount of a protein PTM isoform from the absolute amount of the protein of interest and the PTM occupancy at the site of the protein. The absolute amount of the protein of interest is inferred by quantifying both the absolute amounts of a few PTM

  18. When Is a Diffusion Profile Not a Diffusion Profile? the Importance of Initial State Assumptions in Diffusion Modelling

    NASA Astrophysics Data System (ADS)

    Morgan, D. J.; Chamberlain, K. J.; Kahl, M.; Potts, N. J.; Pankhurst, M. J.; Wilson, C. J. N.

    2014-12-01

    Over the past 20 years, diffusion chronometers have evolved from a niche tool into one of routine application, with more practitioners, new tools and increasingly large datasets. As we expand the horizons of diffusional geochronometry, it is worth taking stock of developments in methodologies and data acquisition, and taking time to revisit the underpinnings of the technique. Data collected as part of recent projects on Campi Flegrei, the Bishop Tuff and Fimmvörðuháls-Eyjafjallajökull are here used to investigate the initial state assumption, an absolutely vital aspect underpinning most diffusional work and one that is rarely evaluated despite its fundamental importance. To illustrate the nature of the problem we consider two widely-used element-mineral systems for felsic and mafic systems, respectively. First, barium and strontium profiles within sanidine crystals, modelled independently, can give strongly contrasting timescales from the same crystal zone. We can reconcile the datasets only for a situation where the initial boundary within the crystal was not a sharp step function, but relatively fuzzy before diffusion onset. This fuzziness effectively starts both chronometers off with an apparent, and false, pre-existing timescale, impacting the slower-diffusing barium much more strongly than the faster-diffusing strontium, yielding thousands of years of non-existent diffusion history. By combining both elements, a starting width of tens of microns can be shown, shortening the true diffusive timescales from tens of thousands of years to hundreds. Second, in olivine, we encounter different growth-related problems. Here, Fe-Mg interdiffusion occurs at a rate comparable to growth, with the compound nature of zonation making it difficult to extract the diffusion component. This requires a treatment of changing boundary conditions and sequential growth to generate the curvature seen in natural data, in order to recover timescales for anything but the outermost

  19. Absolute realization of low BRDF value

    NASA Astrophysics Data System (ADS)

    Liu, Zilong; Liao, Ningfang; Li, Ping; Wang, Yu

    2010-10-01

    Low BRDF value is widespread used in many critical domains such as space and military fairs. These values below 0.1 Sr-1 . So the Absolute realization of these value is the most critical issue in the absolute measurement of BRDF. To develop the Absolute value realization theory of BRDF , defining an arithmetic operators of BRDF , achieving an absolute measurement Eq. of BRDF based on radiance. This is a new theory method to solve the realization problem of low BRDF value. This theory method is realized on a self-designed common double orientation structure in space. By designing an adding structure to extend the range of the measurement system and a control and processing software, Absolute realization of low BRDF value is achieved. A material of low BRDF value is measured in this measurement system and the spectral BRDF value are showed within different angles allover the space. All these values are below 0.4 Sr-1 . This process is a representative procedure about the measurement of low BRDF value. A corresponding uncertainty analysis of this measurement data is given depend on the new theory of absolute realization and the performance of the measurement system. The relative expand uncertainty of the measurement data is 0.078. This uncertainty analysis is suitable for all measurements using the new theory of absolute realization and the corresponding measurement system.

  20. The EM-POGO: A simple, absolute velocity profiler

    NASA Astrophysics Data System (ADS)

    Terker, S. R.; Sanford, T. B.; Dunlap, J. H.; Girton, J. B.

    2013-01-01

    Electromagnetic current instrumentation has been added to the Bathy Systems, Inc. POGO transport sondes to produce a free-falling absolute velocity profiler called EM-POGO. The POGO is a free-fall profiler that measures a depth-averaged velocity using GPS fixes at the beginning and end of a round trip to the ocean floor (or a preset depth). The EM-POGO adds a velocity profile determined from measurements of motionally induced electric fields generated by the ocean current moving through the vertical component of the Earth's magnetic field. In addition to providing information about the vertical structure of the velocity, the depth-dependent measurements improve transport measurements by correcting for the non-constant fall-rate. Neglecting the variable fall rate results in errors O (1 cm s-1). The transition from POGO to EM-POGO included electrically isolating the POGO and electric-field-measuring circuits, installing a functional GPS receiver, finding a pressure case that provided an optimal balance among crush-depth, price and size, and incorporating the electrodes, electrode collar, and the circuitry required for the electric field measurement. The first EM-POGO sea-trial was in July 1999. In August 2006 a refurbished EM-POGO collected 15 absolute velocity profiles; relative and absolute velocity uncertainty was ˜1cms-1 and 0.5-5 cm s-1, respectively, at a vertical resolution of 25 m. Absolute velocity from the EM-POGO compared to shipboard ADCP measurements differed by ˜ 1-2 cm s-1, comparable to the uncertainty in absolute velocity from the ADCP. The EM-POGO is thus a low-cost, easy to deploy and recover, and accurate velocity profiler.

  1. Geomorphological Dating Using an Improved Scarp Degradation Model: Is This a Reliable Approach Compared With Common Absolute Dating Methods?

    NASA Astrophysics Data System (ADS)

    Oemisch, M.; Hergarten, S.; Neugebauer, H. J.

    2002-12-01

    Geomorphological dating of a certain landform or geomorphological structure is based on the evolution of the landscape itself. In this context it is difficult to use common absolute dating techniques such as luminescence and radiocarbon dating because they require datable material which is often not available. Additionally these methods do not always date the time since the formation of these structures. For these reasons the application of geomorphological dating seems one reliable possibility to date certain geomorphological features. The aim of our work is to relate present-day shapes of fault scarps and terrace risers to their ages. The time span since scarp formation ceased is reflected by the stage of degradation as well as the rounding of the profile edges due to erosive processes. It is assumed that the average rate of downslope soil movement depends on the local slope angle and can be described in terms of a diffusion equation. On the basis of these assumptions we present a model to simulate the temporal development of scarp degradation by erosion. A diffusivity reflecting the effects of soil erosion, surface runoff and detachability of particles as well as present-day shapes of scarps are included in the model. As observations of present-day scarps suggest a higher diffusivity at the toe than at the head of a slope, we suggest a linear approach with increasing diffusivities in downslope direction. First results show a better match between simulated and observed profiles of the Upper Rhine Graben in comparison to models using a constant diffusivity. To date the scarps the model has to be calibrated. For this purpose we estimate diffusivities by fitting modelled profiles to observed ones of known age. Field data have been collected in the area around Bonn, Germany and in the Alps, Switzerland. It is a matter of current research to assess the quality of this dating technique and to compare the results and the applicability with some of the absolute dating

  2. Diffusion MRI

    NASA Astrophysics Data System (ADS)

    Fukuyama, Hidenao

    Recent advances of magnetic resonance imaging have been described, especially stressed on the diffusion sequences. We have recently applied the diffusion sequence to functional brain imaging, and found the appropriate results. In addition to the neurosciences fields, diffusion weighted images have improved the accuracies of clinical diagnosis depending upon magnetic resonance images in stroke as well as inflammations.

  3. Consistent set of nuclear parameters values for absolute INAA

    SciTech Connect

    Heft, R.E.

    1980-01-01

    Gamma spectral analysis of irradiated material can be used to determine absolute disintegration rates for specific radionuclides. These data, together with measured values for the thermal and epithermal neutron fluxes, and irradiation, cooling and counting time values, are all the experimental information required to do absolute Instrumental Neutron Activation Analysis. The calculations required to go from product photon emission rate to target nuclide amount depend upon values used for the thermal neutron capture cross-section, the resonance absorption integral, the half-life and photon branching ratios. Values for these parameters were determined by irradiating and analyzing a series of elemental standards. The results of these measurements were combined with values reported by other workers to arrive at a set of recommended values for the constants. Values for 114 nuclides are listed.

  4. Absolute pitch and pupillary response: effects of timbre and key color.

    PubMed

    Schlemmer, Kathrin B; Kulke, Franziska; Kuchinke, Lars; Van Der Meer, Elke

    2005-07-01

    The pitch identification performance of absolute pitch possessors has previously been shown to depend on pitch range, key color, and timbre of presented tones. In the present study, the dependence of pitch identification performance on key color and timbre of musical tones was examined by analyzing hit rates, reaction times, and pupillary responses of absolute pitch possessors (n = 9) and nonpossessors (n = 12) during a pitch identification task. Results revealed a significant dependence of pitch identification hit rate but not reaction time on timbre and key color in both groups. Among absolute pitch possessors, peak dilation of the pupil was significantly dependent on key color whereas the effect of timbre was marginally significant. Peak dilation of the pupil differed significantly between absolute pitch possessors and nonpossessors. The observed effects point to the importance of learning factors in the acquisition of absolute pitch.

  5. 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)

  6. Magnifying absolute instruments for optically homogeneous regions

    SciTech Connect

    Tyc, Tomas

    2011-09-15

    We propose a class of magnifying absolute optical instruments with a positive isotropic refractive index. They create magnified stigmatic images, either virtual or real, of optically homogeneous three-dimensional spatial regions within geometrical optics.

  7. 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)

  8. Absolute cross sections of compound nucleus reactions

    NASA Astrophysics Data System (ADS)

    Capurro, O. A.

    1993-11-01

    The program SEEF is a Fortran IV computer code for the extraction of absolute cross sections of compound nucleus reactions. When the evaporation residue is fed by its parents, only cumulative cross sections will be obtained from off-line gamma ray measurements. But, if one has the parent excitation function (experimental or calculated), this code will make it possible to determine absolute cross sections of any exit channel.

  9. Kelvin and the absolute temperature scale

    NASA Astrophysics Data System (ADS)

    Erlichson, Herman

    2001-07-01

    This paper describes the absolute temperature scale of Kelvin (William Thomson). Kelvin found that Carnot's axiom about heat being a conserved quantity had to be abandoned. Nevertheless, he found that Carnot's fundamental work on heat engines was correct. Using the concept of a Carnot engine Kelvin found that Q1/Q2 = T1/T2. Thermometers are not used to obtain absolute temperatures since they are calculated temperatures.

  10. Griffith diffusers

    NASA Technical Reports Server (NTRS)

    Yang, T.-T.; Nelson, C. D.

    1979-01-01

    Contoured wall diffusers are designed by using an inverse method. The prescribed wall velocity distribution(s) was taken from the high lift airfoil designed by A. A. Griffith in 1938; therefore, such diffusers are named Griffith diffusers. First the formulation of the inverse problem and the method of solution are outlined. Then the typical contour of a two-dimensional diffuser and velocity distributions across the flow channel at various stations are presented. For a Griffith diffuser to operate as it is designed, boundary layer suction is necessary. Discussion of the percentage of through-flow required to be removed for the purpose of boundary layer control is given. Finally, reference is made to the latest version of a computer program for a two-dimensional diffuser requiring only area ratio, nondimensional length and suction percentage as inputs.

  11. 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.

  12. Jasminum flexile flower absolute from India--a detailed comparison with three other jasmine absolutes.

    PubMed

    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.

  13. Diffusion of Botulinum Toxins

    PubMed Central

    Brodsky, Matthew A.; Swope, David M.; Grimes, David

    2012-01-01

    Background It is generally agreed that diffusion of botulinum toxin occurs, but the extent of the spread and its clinical importance are disputed. Many factors have been suggested to play a role but which have the most clinical relevance is a subject of much discussion. Methods This review discusses the variables affecting diffusion, including protein composition and molecular size as well as injection factors (e.g., volume, dose, injection method). It also discusses data on diffusion from comparative studies in animal models and human clinical trials that illustrate differences between the available botulinum toxin products (onabotulinumtoxinA, abobotulinumtoxinA, incobotulinumtoxinA, and rimabotulinumtoxinB). Results Neither molecular weight nor the presence of complexing proteins appears to affect diffusion; however, injection volume, concentration, and dose all play roles and are modifiable. Both animal and human studies show that botulinum toxin products are not interchangeable, and that some products are associated with greater diffusion and higher rates of diffusion-related adverse events than others. Discussion Each of the botulinum toxins is a unique pharmacologic entity. A working knowledge of the different serotypes is essential to avoid unwanted diffusion-related adverse events. In addition, clinicians should be aware that the factors influencing diffusion may range from properties intrinsic to the drug to accurate muscle selection as well as dilution, volume, and dose injected. PMID:23440162

  14. Multispecies diffusion models: A study of uranyl species diffusion

    NASA Astrophysics Data System (ADS)

    Liu, Chongxuan; Shang, Jianying; Zachara, John M.

    2011-12-01

    , where intragranular diffusion is a rate-limiting process controlling U(VI) adsorption and desorption. The grain-scale reactive diffusion model was able to describe U(VI) adsorption/desorption kinetics that had been previously described using a semiempirical, multirate model. Compared with the multirate model, the diffusion models have the advantage to provide spatiotemporal speciation evolution within the diffusion domains.

  15. Surface diffusion of Au on √{ 3} ×√{ 3} Si(111)-Au studied by nucleation-rate and Ostwald-ripening analysis

    NASA Astrophysics Data System (ADS)

    Curiotto, S.; Cheynis, F.; Leroy, F.; Müller, P.

    2016-05-01

    The surface diffusion energy of Au on the √{ 3} ×√{ 3} Au-Si(111) reconstructed surface is determined from low energy electron microscopy experiments. We have used two methods, one based on the nucleation of Au particles, the other one on the island growth by Ostwald ripening. The two methods give Ed = 1.10 ± 0.34 eV and Ed = 1.56 ± 0.31 eV respectively and with a weighted mean we obtain Ed = 1.3 ± 0.2 eV. We suggest that this high activation energy could be due to a mechanism of diffusion by exchange.

  16. 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.

  17. Quantitative standards for absolute linguistic universals.

    PubMed

    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.

  18. Absolute Distance Measurement with the MSTAR Sensor

    NASA Technical Reports Server (NTRS)

    Lay, Oliver P.; Dubovitsky, Serge; Peters, Robert; Burger, Johan; Ahn, Seh-Won; Steier, William H.; Fetterman, Harrold R.; Chang, Yian

    2003-01-01

    The MSTAR sensor (Modulation Sideband Technology for Absolute Ranging) is a new system for measuring absolute distance, capable of resolving the integer cycle ambiguity of standard interferometers, and making it possible to measure distance with sub-nanometer accuracy. The sensor uses a single laser in conjunction with fast phase modulators and low frequency detectors. We describe the design of the system - the principle of operation, the metrology source, beamlaunching optics, and signal processing - and show results for target distances up to 1 meter. We then demonstrate how the system can be scaled to kilometer-scale distances.

  19. Absolutely relative or relatively absolute: violations of value invariance in human decision making.

    PubMed

    Teodorescu, Andrei R; Moran, Rani; Usher, Marius

    2016-02-01

    Making decisions based on relative rather than absolute information processing is tied to choice optimality via the accumulation of evidence differences and to canonical neural processing via accumulation of evidence ratios. These theoretical frameworks predict invariance of decision latencies to absolute intensities that maintain differences and ratios, respectively. While information about the absolute values of the choice alternatives is not necessary for choosing the best alternative, it may nevertheless hold valuable information about the context of the decision. To test the sensitivity of human decision making to absolute values, we manipulated the intensities of brightness stimuli pairs while preserving either their differences or their ratios. Although asked to choose the brighter alternative relative to the other, participants responded faster to higher absolute values. Thus, our results provide empirical evidence for human sensitivity to task irrelevant absolute values indicating a hard-wired mechanism that precedes executive control. Computational investigations of several modelling architectures reveal two alternative accounts for this phenomenon, which combine absolute and relative processing. One account involves accumulation of differences with activation dependent processing noise and the other emerges from accumulation of absolute values subject to the temporal dynamics of lateral inhibition. The potential adaptive role of such choice mechanisms is discussed.

  20. Molecular Diffusion through Cyanobacterial Septal Junctions

    PubMed Central

    Nieves-Morión, Mercedes

    2017-01-01

    ABSTRACT Heterocyst-forming cyanobacteria grow as filaments in which intercellular molecular exchange takes place. During the differentiation of N2-fixing heterocysts, regulators are transferred between cells. In the diazotrophic filament, vegetative cells that fix CO2 through oxygenic photosynthesis provide the heterocysts with reduced carbon and heterocysts provide the vegetative cells with fixed nitrogen. Intercellular molecular transfer has been traced with fluorescent markers, including calcein, 5-carboxyfluorescein, and the sucrose analogue esculin, which are observed to move down their concentration gradient. In this work, we used fluorescence recovery after photobleaching (FRAP) assays in the model heterocyst-forming cyanobacterium Anabaena sp. strain PCC 7120 to measure the temperature dependence of intercellular transfer of fluorescent markers. We find that the transfer rate constants are directly proportional to the absolute temperature. This indicates that the “septal junctions” (formerly known as “microplasmodesmata”) linking the cells in the filament allow molecular exchange by simple diffusion, without any activated intermediate state. This constitutes a novel mechanism for molecular transfer across the bacterial cytoplasmic membrane, in addition to previously characterized mechanisms for active transport and facilitated diffusion. Cyanobacterial septal junctions are functionally analogous to the gap junctions of metazoans. PMID:28049144

  1. Molecular Diffusion through Cyanobacterial Septal Junctions.

    PubMed

    Nieves-Morión, Mercedes; Mullineaux, Conrad W; Flores, Enrique

    2017-01-03

    Heterocyst-forming cyanobacteria grow as filaments in which intercellular molecular exchange takes place. During the differentiation of N2-fixing heterocysts, regulators are transferred between cells. In the diazotrophic filament, vegetative cells that fix CO2 through oxygenic photosynthesis provide the heterocysts with reduced carbon and heterocysts provide the vegetative cells with fixed nitrogen. Intercellular molecular transfer has been traced with fluorescent markers, including calcein, 5-carboxyfluorescein, and the sucrose analogue esculin, which are observed to move down their concentration gradient. In this work, we used fluorescence recovery after photobleaching (FRAP) assays in the model heterocyst-forming cyanobacterium Anabaena sp. strain PCC 7120 to measure the temperature dependence of intercellular transfer of fluorescent markers. We find that the transfer rate constants are directly proportional to the absolute temperature. This indicates that the "septal junctions" (formerly known as "microplasmodesmata") linking the cells in the filament allow molecular exchange by simple diffusion, without any activated intermediate state. This constitutes a novel mechanism for molecular transfer across the bacterial cytoplasmic membrane, in addition to previously characterized mechanisms for active transport and facilitated diffusion. Cyanobacterial septal junctions are functionally analogous to the gap junctions of metazoans.

  2. Effects of H2O, CO2, and N2 air contaminants on critical airside strain rates for extinction of hydrogen-air counterflow diffusion flames

    NASA Technical Reports Server (NTRS)

    Pellett, G. L.; Northam, G. B.; Wilson, L. G.; Guerra, Rosemary

    1989-01-01

    Dish-shaped counterflow diffusion flames centered by opposing laminar jets of H2 and clean and contaminant O2/N2 mixtures in an argon bath at 1 atm were used to study the effects of contaminants on critical airside strain. The jet velocities for both flame extinction and restoration are found for a wide range of contaminant and O2 concentrations in the air jet. The tests are also conducted for a variety of input H2 concentrations. The results are compared with those from several other studies.

  3. Comparative vs. Absolute Judgments of Trait Desirability

    ERIC Educational Resources Information Center

    Hofstee, Willem K. B.

    1970-01-01

    Reversals of trait desirability are studied. Terms indicating conservativw behavior appeared to be judged relatively desirable in comparative judgement, while traits indicating dynamic and expansive behavior benefited from absolute judgement. The reversal effect was shown to be a general one, i.e. reversals were not dependent upon the specific…

  4. New Techniques for Absolute Gravity Measurements.

    DTIC Science & Technology

    1983-01-07

    Hammond, J.A. (1978) Bollettino Di Geofisica Teorica ed Applicata Vol. XX. 8. Hammond, J. A., and Iliff, R. L. (1979) The AFGL absolute gravity system...International Gravimetric Bureau, No. L:I-43. 7. Hammond. J.A. (1978) Bollettino Di Geofisica Teorica ed Applicata Vol. XX. 8. Hammond, J.A., and

  5. An Absolute Electrometer for the Physics Laboratory

    ERIC Educational Resources Information Center

    Straulino, S.; Cartacci, A.

    2009-01-01

    A low-cost, easy-to-use absolute electrometer is presented: two thin metallic plates and an electronic balance, usually available in a laboratory, are used. We report on the very good performance of the device that allows precise measurements of the force acting between two charged plates. (Contains 5 footnotes, 2 tables, and 6 figures.)

  6. 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…

  7. Absolute Positioning Using the Global Positioning System

    DTIC Science & Technology

    1994-04-01

    Global Positioning System ( GPS ) has becom a useful tool In providing relativ survey...Includes the development of a low cost navigator for wheeled vehicles. ABSTRACT The Global Positioning System ( GPS ) has become a useful tool In providing...technique of absolute or point positioning involves the use of a single Global Positioning System ( GPS ) receiver to determine the three-dimenslonal

  8. Diffusion tensor imaging and tractography of the white matter in normal aging: The rate-of-change differs between segments within tracts.

    PubMed

    Mårtensson, J; Lätt, J; Åhs, F; Fredrikson, M; Söderlund, H; Schiöth, H B; Kok, J; Kremer, B; van Westen, Danielle; Larsson, E-M; Nilsson, M

    2017-03-27

    Knowledge concerning the normal aging of cerebral white matter will improve our understanding of abnormal changes in neurodegenerative diseases. The microstructural basis of white matter maturation and aging can be investigated using diffusion tensor imaging (DTI). Generally, diffusion anisotropy increases during childhood and adolescence followed by a decline in middle age. However, this process is subject to spatial variations between tracts. The aim of this study was to investigate to what extent age-related variations also occur within tracts. DTI parameters were compared between segments of two white matter tracts, the cingulate bundle (CB) and the inferior fronto-occipital fasciculus (IFO), in 257 healthy individuals between 13 and 84years of age. Segments of the CB and the IFO were extracted and parameters for each segment were averaged across the hemispheres. The data was analysed as a function of age. Results show that age-related changes differ both between and within individual tracts. Different age trajectories were observed in all segments of the analysed tracts for all DTI parameters. In conclusion, aging does not affect white matter tracts uniformly but is regionally specific; both between and within white matter tracts.

  9. Absolute magnetic helicity and the cylindrical magnetic field

    SciTech Connect

    Low, B. C.

    2011-05-15

    evolution; (iii) twist as a topological property of solenoidal fields versus the linkage properties of open and closed discrete curves treated by Gauss, Caligarneau, Berger, and Prior; and (iv) the change of absolute helicity by resistive diffusion. These are important hydromagnetic properties of twisted magnetic fields in the million-degree hot, highly conducting corona of the Sun.

  10. THE ABSOLUTE MAGNITUDES OF TYPE Ia SUPERNOVAE IN THE ULTRAVIOLET

    SciTech Connect

    Brown, Peter J.; Roming, Peter W. A.; Ciardullo, Robin; Gronwall, Caryl; Hoversten, Erik A.; Pritchard, Tyler; Milne, Peter; Bufano, Filomena; Mazzali, Paolo; Elias-Rosa, Nancy; Filippenko, Alexei V.; Li Weidong; Foley, Ryan J.; Hicken, Malcolm; Kirshner, Robert P.; Gehrels, Neil; Holland, Stephen T.; Immler, Stefan; Phillips, Mark M.; Still, Martin

    2010-10-01

    We examine the absolute magnitudes and light-curve shapes of 14 nearby (redshift z = 0.004-0.027) Type Ia supernovae (SNe Ia) observed in the ultraviolet (UV) with the Swift Ultraviolet/Optical Telescope. Colors and absolute magnitudes are calculated using both a standard Milky Way extinction law and one for the Large Magellanic Cloud that has been modified by circumstellar scattering. We find very different behavior in the near-UV filters (uvw1{sub rc} covering {approx}2600-3300 A after removing optical light, and u {approx} 3000-4000 A) compared to a mid-UV filter (uvm2 {approx}2000-2400 A). The uvw1{sub rc} - b colors show a scatter of {approx}0.3 mag while uvm2-b scatters by nearly 0.9 mag. Similarly, while the scatter in colors between neighboring filters is small in the optical and somewhat larger in the near-UV, the large scatter in the uvm2 - uvw1 colors implies significantly larger spectral variability below 2600 A. We find that in the near-UV the absolute magnitudes at peak brightness of normal SNe Ia in our sample are correlated with the optical decay rate with a scatter of 0.4 mag, comparable to that found for the optical in our sample. However, in the mid-UV the scatter is larger, {approx}1 mag, possibly indicating differences in metallicity. We find no strong correlation between either the UV light-curve shapes or the UV colors and the UV absolute magnitudes. With larger samples, the UV luminosity might be useful as an additional constraint to help determine distance, extinction, and metallicity in order to improve the utility of SNe Ia as standardized candles.

  11. Absolute Radiation Thermometry in the NIR

    NASA Astrophysics Data System (ADS)

    Bünger, L.; Taubert, R. D.; Gutschwager, B.; Anhalt, K.; Briaudeau, S.; Sadli, M.

    2017-04-01

    A near infrared (NIR) radiation thermometer (RT) for temperature measurements in the range from 773 K up to 1235 K was characterized and calibrated in terms of the "Mise en Pratique for the definition of the Kelvin" (MeP-K) by measuring its absolute spectral radiance responsivity. Using Planck's law of thermal radiation allows the direct measurement of the thermodynamic temperature independently of any ITS-90 fixed-point. To determine the absolute spectral radiance responsivity of the radiation thermometer in the NIR spectral region, an existing PTB monochromator-based calibration setup was upgraded with a supercontinuum laser system (0.45 μm to 2.4 μm) resulting in a significantly improved signal-to-noise ratio. The RT was characterized with respect to its nonlinearity, size-of-source effect, distance effect, and the consistency of its individual temperature measuring ranges. To further improve the calibration setup, a new tool for the aperture alignment and distance measurement was developed. Furthermore, the diffraction correction as well as the impedance correction of the current-to-voltage converter is considered. The calibration scheme and the corresponding uncertainty budget of the absolute spectral responsivity are presented. A relative standard uncertainty of 0.1 % (k=1) for the absolute spectral radiance responsivity was achieved. The absolute radiometric calibration was validated at four temperature values with respect to the ITS-90 via a variable temperature heatpipe blackbody (773 K ...1235 K) and at a gold fixed-point blackbody radiator (1337.33 K).

  12. Thorium Diffusion in Monazite

    NASA Astrophysics Data System (ADS)

    Cherniak, D. J.

    2006-05-01

    Diffusion of thorium has been characterized in synthetic monazite under dry conditions. The synthetic monazites (either pure CePO4, NdPO4, or a mixed LREE phosphate containing Ce, Nd, and Sm) were grown via a Na2CO3-MoO3 flux method. The source of diffusant for the experiments were either synthesized ThSiO4 or CaTh(PO4)2 powders. Experiments were performed by placing source and monazite in Pt capsules and annealing capsules in 1 atm furnaces for times ranging from 10 days to a few hours, at temperatures from 1400 to 1550C. The Th distributions in the monazite were profiled by Rutherford Backscattering Spectrometry (RBS). The following Arrhenius relation was obtained for diffusion in monazite: DSm = 7.2x103 exp(-814 kJ mol-1/RT) m2sec-1 The diffusivity of Th was similar for monazites containing a single REE and the mixed LREE phosphates. Th diffusion was also similar for experiments run using the Th silicate and Ca-Th phosphate sources, suggesting that the substitutional mechanism for Th in monazite, i.e, Th+4 + Si+4 for REE+3 + P+5 with the ThSiO4 source, and Th+4 + Ca+2 for 2REE+3 with the CaTh(PO4)2 source, does not significantly affect Th diffusivities, and that Th is likely the rate-limiting species. Th diffusion in monazite is about 4 orders of magnitude slower than Pb diffusion (Cherniak et al., 2004). This contrasts with findings of Gardes et al. (2005) who determined that Pb, Th and REE diffusivities in monazite are similar. Th diffusion in zircon (Cherniak et al., 1997) is about an order of magnitude slower than in monazite, but with similar activation energy for diffusion. The smaller diffusivities in zircon may be a consequence of the larger disparity in size between Th and the Zr site in zircon as compared with Th and the REE site in monazite. Nonetheless, Th is essentially immobile in monazite with respect to exchange by volume diffusion under most geologic conditions; these findings may have implications for containment of high- level actinide

  13. Diffusion barriers

    NASA Technical Reports Server (NTRS)

    Nicolet, M. A.

    1983-01-01

    The choice of the metallic film for the contact to a semiconductor device is discussed. One way to try to stabilize a contact is by interposing a thin film of a material that has low diffusivity for the atoms in question. This thin film application is known as a diffusion barrier. Three types of barriers can be distinguished. The stuffed barrier derives its low atomic diffusivity to impurities that concentrate along the extended defects of a polycrystalline layer. Sacrificial barriers exploit the fact that some (elemental) thin films react in a laterally uniform and reproducible fashion. Sacrificial barriers have the advantage that the point of their failure is predictable. Passive barriers are those most closely approximating an ideal barrier. The most-studied case is that of sputtered TiN films. Stuffed barriers may be viewed as passive barriers whose low diffusivity material extends along the defects of the polycrystalline host.

  14. Diffuse radiation

    NASA Technical Reports Server (NTRS)

    1981-01-01

    A diffuse celestial radiation which is isotropic at least on a course scale were measured from the soft X-ray region to about 150 MeV, at which energy the intensity falls below that of the galactic emission for most galactic latitudes. The spectral shape, the intensity, and the established degree of isotropy of this diffuse radiation already place severe constraints on the possible explanations for this radiation. Among the extragalactic theories, the more promising explanations of the isotropic diffuse emission appear to be radiation from exceptional galaxies from matter antimatter annihilation at the boundaries of superclusters of galaxies of matter and antimatter in baryon symmetric big bang models. Other possible sources for extragalactic diffuse gamma radiation are discussed and include normal galaxies, clusters of galaxies, primordial cosmic rays interacting with intergalactic matter, primordial black holes, and cosmic ray leakage from galaxies.

  15. SPECIAL ISSUE DEVOTED TO MULTIPLE RADIATION SCATTERING IN RANDOM MEDIA: Optical coherent tomography measurements of the diffusion rate of water and drugs in an isolated and whole cornea

    NASA Astrophysics Data System (ADS)

    Larin, Kirill V.; Ghosn, M. G.

    2006-12-01

    The passive diffusion of drugs through the epithelial surfaces of an eye (the most widespread method for medical treatment of various diseases) is considered. The permeability of water and drugs through rabbit cornea was measured in the isolated cornea (separate from an eye) and in the whole cornea. The permeability coefficients of water and dexamethasone were estimated by the method of optical coherence tomography (OCT). Because multiple photon scattering introduces noise and distortions to the OCT signal, measurements were performed at depths up to 500 μm where most likely single scattering of light occurs in cornea. It is shown that the permeability coefficients in the isolated and whole cornea strongly differ from each other. For example, the water permeability in the isolated and whole cornea is (7.09±0.12)×10-5 and (1.71±0.51)×10-5 cm s-1, respectively.

  16. Method of differential-phase/absolute-amplitude QAM

    DOEpatents

    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.

  17. Method of differential-phase/absolute-amplitude QAM

    DOEpatents

    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.

  18. Method of differential-phase/absolute-amplitude QAM

    DOEpatents

    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.

  19. Method of differential-phase/absolute-amplitude QAM

    SciTech Connect

    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.

  20. Method of differential-phase/absolute-amplitude QAM

    DOEpatents

    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.

  1. Quantum bath refrigeration towards absolute zero: challenging the unattainability principle.

    PubMed

    Kolář, M; Gelbwaser-Klimovsky, D; Alicki, R; Kurizki, G

    2012-08-31

    A minimal model of a quantum refrigerator, i.e., a periodically phase-flipped two-level system permanently coupled to a finite-capacity bath (cold bath) and an infinite heat dump (hot bath), is introduced and used to investigate the cooling of the cold bath towards absolute zero (T=0). Remarkably, the temperature scaling of the cold-bath cooling rate reveals that it does not vanish as T→0 for certain realistic quantized baths, e.g., phonons in strongly disordered media (fractons) or quantized spin waves in ferromagnets (magnons). This result challenges Nernst's third-law formulation known as the unattainability principle.

  2. Transdermal diffusion of xenon in vitro using diffusion cells

    NASA Astrophysics Data System (ADS)

    Verkhovsky, A.; Petrov, E.

    2015-11-01

    The aim of this research was to study the diffusion rate of xenon through guinea pig skin and how viscosity of cosmetic component capryl/capric triglyceride (CCT) facilitates to deliver xenon to surface of skin patches. They were placed in Franz cell for 24 hours and diffusion rate and permeability of xenon were calculated. Thus diffusion rate was 0.031 mg/hour*cm2 and permeability was 0.003 cm/hour. Using Brookfield viscometer it was shown that viscosity of CCT decreased upon increasing xenon concentration. Obtained results can be utilized in developing of new xenon containing drugs for topical administration.

  3. 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.

  4. Consistent thermostatistics forbids negative absolute temperatures

    NASA Astrophysics Data System (ADS)

    Dunkel, Jörn; Hilbert, Stefan

    2014-01-01

    Over the past 60 years, a considerable number of theories and experiments have claimed the existence of negative absolute temperature in spin systems and ultracold quantum gases. This has led to speculation that ultracold gases may be dark-energy analogues and also suggests the feasibility of heat engines with efficiencies larger than one. Here, we prove that all previous negative temperature claims and their implications are invalid as they arise from the use of an entropy definition that is inconsistent both mathematically and thermodynamically. We show that the underlying conceptual deficiencies can be overcome if one adopts a microcanonical entropy functional originally derived by Gibbs. The resulting thermodynamic framework is self-consistent and implies that absolute temperature remains positive even for systems with a bounded spectrum. In addition, we propose a minimal quantum thermometer that can be implemented with available experimental techniques.

  5. Absolute measurement of length with nanometric resolution

    NASA Astrophysics Data System (ADS)

    Apostol, D.; Garoi, F.; Timcu, A.; Damian, V.; Logofatu, P. C.; Nascov, V.

    2005-08-01

    Laser interferometer displacement measuring transducers have a well-defined traceability route to the definition of the meter. The laser interferometer is de-facto length scale for applications in micro and nano technologies. However their physical unit -half lambda is too large for nanometric resolution. Fringe interpolation-usual technique to improve the resolution-lack of reproducibility could be avoided using the principles of absolute distance measurement. Absolute distance refers to the use of interferometric techniques for determining the position of an object without the necessity of measuring continuous displacements between points. The interference pattern as produced by the interference of two point-like coherent sources is fitted to a geometric model so as to determine the longitudinal location of the target by minimizing least square errors. The longitudinal coordinate of the target was measured with accuracy better than 1 nm, for a target position range of 0.4μm.

  6. 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.

  7. Computer processing of spectrograms for absolute intensities.

    PubMed

    Guttman, A; Golden, J; Galbraith, H J

    1967-09-01

    A computer program was developed to process photographically recorded spectra for absolute intensity. Test and calibration films are subjected to densitometric scans that provide digitally recorded densities on magnetic tapes. The nonlinear calibration data are fitted by least-squares cubic polynomials to yield a good approximation to the monochromatic H&D curves for commonly used emulsions (2475 recording film, Royal-X, Tri-X, 4-X). Several test cases were made. Results of these cases show that the machine processed absolute intensities are accurate to within 15%o. Arbitrarily raising the sensitivity threshold by 0.1 density units above gross fog yields cubic polynomial fits to the H&D curves that are radiometrically accurate within 10%. In addition, curves of gamma vs wavelength for 2475, Tri-X, and 4-X emulsions were made. These data show slight evidence of the photographic Purkinje effect in the 2475 emulsion.

  8. 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.

  9. Probing absolute spin polarization at the nanoscale.

    PubMed

    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.

  10. Absolute and relative dosimetry for ELIMED

    NASA Astrophysics Data System (ADS)

    Cirrone, G. A. P.; Cuttone, G.; Candiano, G.; Carpinelli, M.; Leonora, E.; Lo Presti, D.; Musumarra, A.; Pisciotta, P.; Raffaele, L.; Randazzo, N.; Romano, F.; Schillaci, F.; Scuderi, V.; Tramontana, A.; Cirio, R.; Marchetto, F.; Sacchi, R.; Giordanengo, S.; Monaco, V.

    2013-07-01

    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.

  11. Silicon Absolute X-Ray Detectors

    SciTech Connect

    Seely, John F.; Korde, Raj; Sprunck, Jacob; Medjoubi, Kadda; Hustache, Stephanie

    2010-06-23

    The responsivity of silicon photodiodes having no loss in the entrance window, measured using synchrotron radiation in the 1.75 to 60 keV range, was compared to the responsivity calculated using the silicon thickness measured using near-infrared light. The measured and calculated responsivities agree with an average difference of 1.3%. This enables their use as absolute x-ray detectors.

  12. Photon diffusion in a homogeneous medium bounded externally or internally by an infinitely long circular cylindrical applicator. III. Synthetic study of continuous-wave photon fluence rate along unique spiral paths.

    PubMed

    Zhang, Anqi; Piao, Daqing; Bunting, Charles F

    2012-04-01

    This is Part III of the work that examines photon diffusion in a scattering-dominant medium enclosed by a "concave" circular cylindrical applicator or enclosing a "convex" circular cylindrical applicator. In Part II of this work Zhang et al. [J. Opt. Soc. Am. A, 66 (2011)] predicted that, on the tissue-applicator interface of either "concave" or "convex" geometry, there exists a unique set of spiral paths, along which the steady-state photon fluence rate decays at a rate equal to that along a straight line on a planar semi-infinite interface, for the same line-of-sight source-detector distance. This phenomenon of steady-state photon diffusion is referred to as "straight-line-resembling-spiral paths" (abbreviated as "spiral paths"). This Part III study develops analytic approaches to the spiral paths associated with geometry of a large radial dimension and presents spiral paths found numerically for geometry of a small radial dimension. This Part III study also examines whether the spiral paths associated with a homogeneous medium are a good approximation for the medium containing heterogeneity. The heterogeneity is limited to an anomaly that is aligned azimuthally with the spiral paths and has either positive or negative contrast of the absorption or scattering coefficient over the background medium. For a weak-contrast anomaly the perturbation by it to the photon fluence rate along the spiral paths is found by applying a well-established perturbation analysis in cylindrical coordinates. For a strong-contrast anomaly the change by it to the photon fluence rate along the spiral paths is computed using the finite-element method. For the investigated heterogeneous-medium cases the photon fluence rate along the homogeneous-medium associated spiral paths is macroscopically indistinguishable from, and microscopically close to, that along a straight line on a planar semi-infinite interface.

  13. Advanced manufacturing: Technology diffusion

    SciTech Connect

    Tesar, A.

    1995-12-01

    In this paper we examine how manufacturing technology diffuses rom the developers of technology across national borders to those who do not have the capability or resources to develop advanced technology on their own. None of the wide variety of technology diffusion mechanisms discussed in this paper are new, yet the opportunities to apply these mechanisms are growing. A dramatic increase in technology diffusion occurred over the last decade. The two major trends which probably drive this increase are a worldwide inclination towards ``freer`` markets and diminishing isolation. Technology is most rapidly diffusing from the US In fact, the US is supplying technology for the rest of the world. The value of the technology supplied by the US more than doubled from 1985 to 1992 (see the Introduction for details). History shows us that technology diffusion is inevitable. It is the rates at which technologies diffuse to other countries which can vary considerably. Manufacturers in these countries are increasingly able to absorb technology. Their manufacturing efficiency is expected to progress as technology becomes increasingly available and utilized.

  14. Negative absolute temperature for mobile particles

    NASA Astrophysics Data System (ADS)

    Braun, Simon; Ronzheimer, Philipp; Schreiber, Michael; Hodgman, Sean; Bloch, Immanuel; Schneider, Ulrich

    2013-05-01

    Absolute temperature is usually bound to be strictly positive. However, negative absolute temperature states, where the occupation probability of states increases with their energy, are possible in systems with an upper energy bound. So far, such states have only been demonstrated in localized spin systems with finite, discrete spectra. We realized a negative absolute temperature state for motional degrees of freedom with ultracold bosonic 39K atoms in an optical lattice, by implementing the attractive Bose-Hubbard Hamiltonian. This new state strikingly revealed itself by a quasimomentum distribution that is peaked at maximum kinetic energy. The measured kinetic energy distribution and the extracted negative temperature indicate that the ensemble is close to degeneracy, with coherence over several lattice sites. The state is as stable as a corresponding positive temperature state: The negative temperature stabilizes the system against mean-field collapse driven by negative pressure. Negative temperatures open up new parameter regimes for cold atoms, enabling fundamentally new many-body states. Additionally, they give rise to several counterintuitive effects such as heat engines with above unity efficiency.

  15. 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.

  16. System for absolute measurements by interferometric sensors

    NASA Astrophysics Data System (ADS)

    Norton, Douglas A.

    1993-03-01

    The most common problem of interferometric sensors is their inability to measure absolute path imbalance. Presented in this paper is a signal processing system that gives absolute, unambiguous reading of optical path difference for almost any style of interferometric sensor. Key components are a wide band (incoherent) optical source, a polychromator, and FFT electronics. Advantages include no moving parts in the signal processor, no active components at the sensor location, and the use of standard single mode fiber for sensor illumination and signal transmission. Actual absolute path imbalance of the interferometer is determined without using fringe counting or other inferential techniques. The polychromator extracts the interference information that occurs at each discrete wavelength within the spectral band of the optical source. The signal processing consists of analog and digital filtering, Fast Fourier analysis, and a peak detection and interpolation algorithm. This system was originally designed for use in a remote pressure sensing application that employed a totally passive fiber optic interferometer. A performance qualification was made using a Fabry-Perot interferometer and a commercially available laser interferometer to measure the reference displacement.

  17. Chemical composition of French mimosa absolute oil.

    PubMed

    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.

  18. Constrained Least Absolute Deviation Neural Networks

    PubMed Central

    Wang, Zhishun; Peterson, Bradley S.

    2008-01-01

    It is well known that least absolute deviation (LAD) criterion or L1-norm used for estimation of parameters is characterized by robustness, i.e., the estimated parameters are totally resistant (insensitive) to large changes in the sampled data. This is an extremely useful feature, especially, when the sampled data are known to be contaminated by occasionally occurring outliers or by spiky noise. In our previous works, we have proposed the least absolute deviation neural network (LADNN) to solve unconstrained LAD problems. The theoretical proofs and numerical simulations have shown that the LADNN is Lyapunov-stable and it can globally converge to the exact solution to a given unconstrained LAD problem. We have also demonstrated its excellent application value in time-delay estimation. More generally, a practical LAD application problem may contain some linear constraints, such as a set of equalities and/or inequalities, which is called constrained LAD problem, whereas the unconstrained LAD can be considered as a special form of the constrained LAD. In this paper, we present a new neural network called constrained least absolute deviation neural network (CLADNN) to solve general constrained LAD problems. Theoretical proofs and numerical simulations demonstrate that the proposed CLADNN is Lyapunov stable and globally converges to the exact solution to a given constrained LAD problem, independent of initial values. The numerical simulations have also illustrated that the proposed CLADNN can be used to robustly estimate parameters for nonlinear curve fitting, which is extensively used in signal and image processing. PMID:18269958

  19. Ammonia diffusion through Nalophan™ bags.

    PubMed

    Sironi, Selena; Eusebio, Lidia; Dentoni, Licinia; Capelli, Laura; Del Rosso, Renato

    2014-01-01

    The aim of the work is to verify the diffusion rate of ammonia through the Nalophan™ film that constitutes the sampling bag, considering storage times ranging from 1 to 26 h. The ammonia decay over time was evaluated using gas-chromatography for the quantification of ammonia concentration inside the bag. The research assesses the roles of both of ammonia and water concentration gradients at the polymeric film interface on the diffusion process. The results show that both the ammonia concentration gradient and, in a less pronounced way, the water concentration gradient are the main 'engines' of ammonia diffusion. Double bags seem to represent a simple solution for preventing ammonia losses during storage. Another interesting result concerns the role of the bag surface on the ammonia diffusion rate: the higher the surface/volume (S/V) ratio, the higher the ammonia diffusion rate through the polymeric film.

  20. Influence of high voltage electric fields applied across a horizontal liquid-liquid interface on the rate of metal extraction using a rotating diffusion cell

    SciTech Connect

    Kuipa, P.K.; Hughes, M.A.

    1999-09-01

    The effect of an applied electrical field across a plane liquid-liquid interface on the rate of metal extraction using hydroxyoximes and dialkylphosphoric acids as extractants is examined. The results indicate that applied electric fields have no marked influence on the observed rate of metal extraction when aliphatic hydrocarbons are employed as the diluents in the organic phase. Increases in mass transfer rates of up to 250% were observed when mixtures of octanol and an aliphatic hydrocarbon were employed as the diluent in the organic phase. The mechanism of transfer is thought to be a combination of movement of charges in the bulk of the nonconducting organic phase and electrohydrodynamic flows due to local variations in the effective interfacial tension as a result of the applied electric fields.

  1. Absolute rotation detection by Coriolis force measurement using optomechanics

    NASA Astrophysics Data System (ADS)

    Davuluri, Sankar; Li, Yong

    2016-10-01

    In this article, we present an application of the optomechanical cavities for absolute rotation detection. Two optomechanical cavities, one in each arm, are placed in a Michelson interferometer. The interferometer is placed on a rotating table and is moved with a uniform velocity of \\dot{\\bar{y}} with respect to the rotating table. The Coriolis force acting on the interferometer changes the length of the optomechanical cavity in one arm, while the length of the optomechanical cavity in the other arm is not changed. The phase shift corresponding to the change in the optomechanical cavity length is measured at the interferometer output to estimate the angular velocity of the absolute rotation. An analytic expression for the minimum detectable rotation rate corresponding to the standard quantum limit of measurable Coriolis force in the interferometer is derived. Squeezing technique is discussed to improve the rotation detection sensitivity by a factor of \\sqrt{{γ }m/{ω }m} at 0 K temperature, where {γ }m and {ω }m are the damping rate and angular frequency of the mechanical oscillator. The temperature dependence of the rotation detection sensitivity is studied.

  2. Feasibility of interstitial diffuse optical tomography using cylindrical diffusing fiber for prostate PDT

    PubMed Central

    Liang, Xing; Wang, Ken Kang-Hsin; Zhu, Timothy C.

    2013-01-01

    Interstitial diffuse optical tomography (DOT) has been used to characterize spatial distribution of optical properties for prostate photodynamic therapy (PDT) dosimetry. We have developed an interstitial DOT method using cylindrical diffuse fibers (CDFs) as light sources, so that the same light sources can be used for both DOT measurement and PDT treatment. In this novel interstitial CDF-DOT method, absolute light fluence per source strength (in unit of 1/cm2) is used to separate absorption and scattering coefficients. A mathematical phantom and a solid prostate phantom including anomalies with known optical properties were used, respectively, to test the feasibility of reconstructing optical properties using interstitial CDF-DOT. Three dimension spatial distributions of the optical properties were reconstructed for both scenarios. Our studies show that absorption coefficient can be reliably extrapolated while there are some cross talks between absorption and scattering properties. Even with the suboptimal reduced scattering coefficients, the reconstructed light fluence rate agreed with the measured values to within ±10%, thus the proposed CDF-DOT allows greatly improved light dosimetry calculation for interstitial PDT. PMID:23629149

  3. Diffusion in natural ilmenite

    NASA Astrophysics Data System (ADS)

    Stenhouse, Iona; O'Neill, Hugh; Lister, Gordon

    2010-05-01

    Diffusion rates in natural ilmenite of composition Fe0.842+ Fe0.163+Mn0.07Mg0.01Ti 0.92O3 from the Vishnevye Mountains (Urals, Russia) have been measured at 1000° C. Experiments were carried out in a one atmosphere furnace with oxygen fugacity controlled by flow of a CO-CO2 gas mixture, over a period of four hours. The diffusant source was a synthetic ilmenite (FeTiO3) powder doped with trace amounts of Mg, Co, Ni, Zr, Hf, V, Nb, Ta, Al, Cr, Ga and Y. Since, the natural ilmenite crystal contained Mn it was also possible to study diffusion of Mn from the ilmenite crystal. The experiments were analysed using the electron microprobe and scanning laser ablation ICP-MS. Diffusion profiles were measured for Al, Mg, Mn, Co, Ni, Ga, and Y. Diffusion of Cr, Hf, Zr, V, Nb and Ta was too slow to allow diffusion profiles to be accurately measured for the times and temperatures studied so far. The preliminary results show that diffusion in ilmenite is fast, with the diffusivity determined in this study on the order of 10-13 to 10-16 m2s-1. For comparison, Chakraborty (1997) found interdiffusion of Fe and Mg in olivine at 1000° C on the order of 10-17 to 10-18m2s-1 and Dieckmann (1998) found diffusivity of Fe, Mg, Co in magnetite at 1200° C to be on the order of 10-13 to 10-14 m2s-1. The order in which the diffusivity of the elements decreases is Mn > Co > Mg ≥ Ni > Al ≥ Y ≥ Ga, that is to say that Mn diffuses the fastest and Ga the slowest. Overall, this study intends to determine diffusion parameters such as frequency factor, activation energy and activation volume as a function of temperature and oxygen fugacity. This research is taking place in the context of a larger study focusing on the use of the garnet-ilmenite system as a geospeedometer. Examination of the consequences of simultaneous diffusion of multiple elements is a necessity if we are to develop an understanding of the crystal-chemical controls on diffusion (cf Spandler & O'Neill, in press). Chakraborty

  4. Comparison of the Rates of Uni- and Bi-Molecular Diffusion Controlled Reactions on Circular, Filled Aggregate and DLA Fractal Aggregate in Two Dimensions.

    DTIC Science & Technology

    1987-05-07

    CLASSIFICATION Of THIS PAGIL(Whan Data Entered) It is found that the reaction rates of OLA agigregates are comnatible with * that of circular aggregates with...NOSC Wayne State University Code 521 Detroit, Michigan 49207 San Diego, California 91232 Or. W.E. Moerner I.B.M. Corporation Almaden Research Center 650

  5. Increased rate of apoptosis and diminished phagocytic ability of human neutrophils infected with Afa/Dr diffusely adhering Escherichia coli strains.

    PubMed

    Brest, Patrick; Bétis, Frédéric; Cuburu, Nicolas; Selva, Eric; Herrant, Magali; Servin, Alain; Auberger, Patrick; Hofman, Paul

    2004-10-01

    The proinflammatory effect of Afa/Dr diffusely adhering Escherichia coli (Afa/Dr DAEC) strains have been recently demonstrated in vitro by showing that polymorphonuclear leukocyte (PMN) transepithelial migration is induced after bacterial colonization of apical intestinal monolayers. The effect of Afa/Dr DAEC-PMN interaction on PMN behavior has been not investigated. Because of the putative virulence mechanism of PMN apoptosis during infectious diseases and taking into account the high level of expression of the decay-accelerating factor (DAF, or CD55), the receptor of Afa/Dr DAEC on PMNs, we sought to determine whether infection of PMNs by Afa/Dr DAEC strains could promote cell apoptosis. We looked at the behavior of PMNs incubated with Afa/Dr DAEC strains once they had transmigrated across polarized monolayers of intestinal (T84) cells. Infection of PMNs by Afa/Dr DAEC strains induced PMN apoptosis characterized by morphological nuclear changes, DNA fragmentation, caspase activation, and a high level of annexin V expression. However, transmigrated and nontransmigrated PMNs incubated with Afa/Dr DAEC strains showed similar elevated global caspase activities. PMN apoptosis depended on their agglutination, induced by Afa/Dr DAEC, and was still observed after preincubation of PMNs with anti-CD55 and/or anti-CD66 antibodies. Low levels of phagocytosis of Afa/Dr DAEC strains were observed both in nontransmigrated and in transmigrated PMNs compared to that observed with the control E. coli DH5alpha strain. Taken together, these data strongly suggest that interaction of Afa/Dr DAEC with PMNs may increase the bacterial virulence both by inducing PMN apoptosis through an agglutination process and by diminishing their phagocytic capacity.

  6. Effects of H2O, CO2, and N2 Air Contaminants on Critical Airside Strain Rates for Extinction of Hydrogen-Air Counterflow Diffusion Flames

    NASA Technical Reports Server (NTRS)

    Pellett, G. L.; Wilson, L. G.; Northam, G. B.; Guerra, Rosemary

    1989-01-01

    Coaxial tubular opposed jet burners (OJB) were used to form dish shaped counterflow diffusion flames (CFDF), centered by opposing laminar jets of H2, N2 and both clean and contaminated air (O2/N2 mixtures) in an argon bath at 1 atm. Jet velocities for flame extinction and restoration limits are shown versus wide ranges of contaminant and O2 concentrations in the air jet, and also input H2 concentration. Blowoff, a sudden breaking of CFDF to a stable ring shape, occurs in highly stretched stagnation flows and is generally believed to measure kinetically limited flame reactivity. Restore, a sudden restoration of central flame, is a relatively new phenomenon which exhibits a H2 dependent hysteresis from Blowoff. For 25 percent O2 air mixtures, mole for mole replacement of 25 percent N2 contaminant by steam increased U(air) or flame strength at Blowoff by about 5 percent. This result is consistent with laminar burning velocity results from analogous substitution of steam for N2 in a premixed stoichiometric H2-O2-N2 (or steam) flame, shown by Koroll and Mulpuru to promote a 10 percent increase in experimental and calculated laminar burning velocity, due to enhanced third body efficiency of water in: H + O2 + M yields HO2 + M. When the OJB results were compared with Liu and MacFarlane's experimental laminar burning velocity of premixed stoichiometric H2 + air + steam, a crossover occurred, i.e., steam enhanced OJB flame strength at extinction relative to laminar burning velocity.

  7. High levels of periostin correlate with increased fracture rate, diffuse MRI pattern, abnormal bone remodeling and advanced disease stage in patients with newly diagnosed symptomatic multiple myeloma

    PubMed Central

    Terpos, E; Christoulas, D; Kastritis, E; Bagratuni, T; Gavriatopoulou, M; Roussou, M; Papatheodorou, A; Eleutherakis-Papaiakovou, E; Kanellias, N; Liakou, C; Panagiotidis, I; Migkou, M; Kokkoris, P; Moulopoulos, L A; Dimopoulos, M A

    2016-01-01

    Periostin is an extracellular matrix protein that is implicated in the biology of normal bone remodeling and in different cancer cell growth and metastasis. However, there is no information on the role of periostin in multiple myeloma (MM). Thus, we evaluated periostin in six myeloma cell lines in vitro; in the bone marrow plasma and serum of 105 newly diagnosed symptomatic MM (NDMM) patients and in the serum of 23 monoclonal gammopathy of undetermined significance (MGUS), 33 smoldering MM (SMM) patients, 30 patients at the plateau phase post-first-line therapy, 30 patients at first relapse and 30 healthy controls. We found high levels of periostin in the supernatants of myeloma cell lines compared with ovarian cancer cell lines that were not influenced by the incubation with the stromal cell line HS5. In NDMM patients the bone marrow plasma periostin was almost fourfold higher compared with the serum levels of periostin and correlated with the presence of fractures and of diffuse magnetic resonance imaging pattern of marrow infiltration. Serum periostin was elevated in NDMM patients compared with healthy controls, MGUS and SMM patients and correlated with advanced disease stage, high lactate dehydrogenase, increased activin-A, increased bone resorption and reduced bone formation. Patients at first relapse had also elevated periostin compared with healthy controls, MGUS and SMM patients, while even patients at the plateau phase had elevated serum periostin compared with healthy controls. These results support an important role of periostin in the biology of myeloma and reveal periostin as a possible target for the development of antimyeloma drugs. PMID:27716740

  8. Landsat-7 ETM+ radiometric stability and absolute calibration

    USGS Publications Warehouse

    Markham, B.L.; Barker, J.L.; Barsi, J.A.; Kaita, E.; Thome, K.J.; Helder, D.L.; Palluconi, Frank Don; Schott, J.R.; Scaramuzza, P.; ,

    2002-01-01

    Launched in April 1999, the Landsat-7 ETM+ instrument is in its fourth year of operation. The quality of the acquired calibrated imagery continues to be high, especially with respect to its three most important radiometric performance parameters: reflective band instrument stability to better than ??1%, reflective band absolute calibration to better than ??5%, and thermal band absolute calibration to better than ??0.6 K. The ETM+ instrument has been the most stable of any of the Landsat instruments, in both the reflective and thermal channels. To date, the best on-board calibration source for the reflective bands has been the Full Aperture Solar Calibrator, which has indicated changes of at most -1.8% to -2.0% (95% C.I.) change per year in the ETM+ gain (band 4). However, this change is believed to be caused by changes in the solar diffuser panel, as opposed to a change in the instrument's gain. This belief is based partially on ground observations, which bound the changes in gain in band 4 at -0.7% to +1.5%. Also, ETM+ stability is indicated by the monitoring of desert targets. These image-based results for four Saharan and Arabian sites, for a collection of 35 scenes over the three years since launch, bound the gain change at -0.7% to +0.5% in band 4. Thermal calibration from ground observations revealed an offset error of +0.31 W/m 2 sr um soon after launch. This offset was corrected within the U. S. ground processing system at EROS Data Center on 21-Dec-00, and since then, the band 6 on-board calibration has indicated changes of at most +0.02% to +0.04% (95% C.I.) per year. The latest ground observations have detected no remaining offset error with an RMS error of ??0.6 K. The stability and absolute calibration of the Landsat-7 ETM+ sensor make it an ideal candidate to be used as a reference source for radiometric cross-calibrating to other land remote sensing satellite systems.

  9. Defusing Diffusion

    ERIC Educational Resources Information Center

    Dou, Remy; Hogan, DaNel; Kossover, Mark; Spuck, Timothy; Young, Sarah

    2013-01-01

    Diffusion has often been taught in science courses as one of the primary ways by which molecules travel, particularly within organisms. For years, classroom teachers have used the same common demonstrations to illustrate this concept (e.g., placing drops of food coloring in a beaker of water). Most of the time, the main contributor to the motion…

  10. NASA/DoD Aerospace knowledge diffusion research project. III - The impact of a sponsor letter on mail survey response rates

    NASA Technical Reports Server (NTRS)

    Kennedy, John M.; Pinelli, Thomas E.

    1990-01-01

    The paper describes the impact of two interventions in the design of mail surveys. The interventions were devised to increase response rates and to clarify sample eligibility. To test their effectiveness, interventions occurred at different points in each of three surveys. One intervention was a letter from the research sponsor (NASA) supporting the research. The other intervention was the inclusion of a postcard that could be used by the respondent to indicate that the questionnaire was not appropriate for him/her. The sample was drawn from the membership of the American Institute for Aeronautics and Astronautics research society. The results indicate that the sponsor letter improved response rates under certain conditions described in the paper. The postcards assisted in identifying noneligible persons particularly when they accompanied a pre-survey letter. The implications for survey costs are discussed.

  11. NASA/DOD Aerospace Knowledge Diffusion Research Project. Paper 3: The impact of a sponsor letter on mail survey response rates

    NASA Technical Reports Server (NTRS)

    Kennedy, John M.; Pinelli, Thomas E.

    1990-01-01

    We describe the impact of two interventions in the design of mail surveys. The interventions were devised to increase response rates and to clarify sample eligibility. To test their effectiveness, the interventions occurred at different points in each of three surveys. One intervention was a letter from the research sponsor (NASA) supporting the research. The other intervention was the inclusion of a postcard that could be used by the respondent to indicate that the questionnaire was not appropriate for him/her. The sample was drawn from the membership of a professional aerospace research society, the American Institute for Aeronautics and Astronautics (AIAA). Scientists and engineers are difficult to survey for two reasons. First, there are significant problems with the definition of scientists and engineers. Second, typically there are low response rates in surveys of this group. These two problems were found in the NASA surveys. The results indicate that the sponsor letter improved response rates under certain conditions described here. The postcards assisted in identifying non-eligible persons, particularly when the postcards accompanied a pre-survey letter. The implications for survey costs are discussed.

  12. Effect of channelling on water balance, oxygen diffusion and oxidation rate in mine waste rock with an inclined multilayer soil cover

    NASA Astrophysics Data System (ADS)

    Song, Qing; Yanful, Ernest K.

    2010-05-01

    Engineered soil covers provide an option to mitigate acid rock drainage through reduced water flow and gaseous oxygen influx to underlying mine waste. Channels such as fissures, cracks or fractures developed in the barrier may influence the long-term performance of the soil cover. However, limited published information is available on the extent to which soil cover performance is impacted by these fissures and cracks. This study was conducted to investigate the effect of channelling in a barrier layer on water flow and oxygen transport in a soil cover. Two inclined (a slope of 20%) multilayer soil covers were examined under laboratory conditions. One cover had a 10-cm wide sand-filled channel in a compacted barrier layer (silty clay) at the upslope section, while the other cover was a normal one without the channel pathway. The soil covers were installed in plastic boxes measuring 120 cm × 120 cm × 25 cm (width × height × thickness). The sand-filled channel was designed to represent the aggregate of fissures and cracks that may be present in the compacted barrier. The soil covers were subjected to controlled drying and wetting periods selected to simulate field situation at the Whistle mine site near Capreol, Ontario, Canada. The measured results indicated that interflow decreased from 72.8% of the total precipitation in the soil cover without channel flow to 35.3% in the cover with channel flow, and percolation increased from zero in the normal soil cover to 43.0% of the total precipitation in the cover with channel flow. Gaseous oxygen transfer into the waste rock below the cover soils was 1091 times greater in the cover with channel than in the soil cover without channel. The channel pathway present in the barrier layer acted as a major passage for water movement and gaseous oxygen diffusion into the waste rock layer, thus decreasing the performance of the soil cover. The spacing of the channel with respect to the length of the test box is similar to those

  13. 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.

  14. 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.

  15. 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.

  16. Review of enhanced vapor diffusion in porous media

    SciTech Connect

    Webb, S.W.; Ho, C.K.

    1998-08-01

    Vapor diffusion in porous media in the presence of its own liquid has often been treated similar to gas diffusion. The gas diffusion rate in porous media is much lower than in free space due to the presence of the porous medium and any liquid present. However, enhanced vapor diffusion has also been postulated such that the diffusion rate may approach free-space values. Existing data and models for enhanced vapor diffusion, including those in TOUGH2, are reviewed in this paper.

  17. Brownian motion: Absolute negative particle mobility

    NASA Astrophysics Data System (ADS)

    Ros, Alexandra; Eichhorn, Ralf; Regtmeier, Jan; Duong, Thanh Tu; Reimann, Peter; Anselmetti, Dario

    2005-08-01

    Noise effects in technological applications, far from being a nuisance, can be exploited with advantage - for example, unavoidable thermal fluctuations have found application in the transport and sorting of colloidal particles and biomolecules. Here we use a microfluidic system to demonstrate a paradoxical migration mechanism in which particles always move in a direction opposite to the net acting force (`absolute negative mobility') as a result of an interplay between thermal noise, a periodic and symmetric microstructure, and a biased alternating-current electric field. This counterintuitive phenomenon could be used for bioanalytical purposes, for example in the separation and fractionation of colloids, biological molecules and cells.

  18. Arbitrary segments of absolute negative mobility

    NASA Astrophysics Data System (ADS)

    Chen, Ruyin; Nie, Linru; Chen, Chongyang; Wang, Chaojie

    2017-01-01

    In previous research work, investigators have reported only one or two segments of absolute negative mobility (ANM) in a periodic potential. In fact, many segments of ANM also occur in the system considered here. We investigate transport of an inertial particle in a gating ratchet periodic potential subjected to a constant bias force. Our numerical results show that its mean velocity can decrease with the bias force increasing, i.e. ANM phenomenon. Furthermore, the ANM can take place arbitrary segments, even up to more than thirty. Intrinsic physical mechanism and conditions for arbitrary segments of ANM to occur are discussed in detail.

  19. Absolute quantification of myocardial blood flow.

    PubMed

    Yoshinaga, Keiichiro; Manabe, Osamu; Tamaki, Nagara

    2016-07-21

    With the increasing availability of positron emission tomography (PET) myocardial perfusion imaging, the absolute quantification of myocardial blood flow (MBF) has become popular in clinical settings. Quantitative MBF provides an important additional diagnostic or prognostic information over conventional visual assessment. The success of MBF quantification using PET/computed tomography (CT) has increased the demand for this quantitative diagnostic approach to be more accessible. In this regard, MBF quantification approaches have been developed using several other diagnostic imaging modalities including single-photon emission computed tomography, CT, and cardiac magnetic resonance. This review will address the clinical aspects of PET MBF quantification and the new approaches to MBF quantification.

  20. An absolute radius scale for Saturn's rings

    NASA Technical Reports Server (NTRS)

    Nicholson, Philip D.; Cooke, Maren L.; Pelton, Emily

    1990-01-01

    Radio and stellar occultation observations of Saturn's rings made by the Voyager spacecraft are discussed. The data reveal systematic discrepancies of almost 10 km in some parts of the rings, limiting some of the investigations. A revised solution for Saturn's rotation pole has been proposed which removes the discrepancies between the stellar and radio occultation profiles. Corrections to previously published radii vary from -2 to -10 km for the radio occultation, and +5 to -6 km for the stellar occultation. An examination of spiral density waves in the outer A Ring supports that the revised absolute radii are in error by no more than 2 km.

  1. Absolute method of measuring magnetic susceptibility

    USGS Publications Warehouse

    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.

  2. 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.

  3. New Chorus Diffusion Matrix

    NASA Astrophysics Data System (ADS)

    Horne, Richard B.; Kersten, Tobias; Glauert, Sarah A.; Meredith, Nigel P.; Boscher, Daniel; Sicard, Angelica; Maget, Vincent

    2013-04-01

    Whistler mode chorus waves play a major role in the loss and acceleration of electrons in the Earth's radiation belts. While high time resolution satellite data show that these waves are highly structured in frequency and time, at present their effects on the electron distribution can only be assessed on a global scale by using quasi-linear diffusion theory. Here we present new quasi-linear diffusion coefficients for upper and lower band chorus waves for use in global radiation belt models. Using data from DE 1 CRRES, Cluster 1, Double Star TC1 and THEMIS, we have constructed a database of wave properties and used this to construct new diffusion coefficients for L* = 1.5 to 10 in steps of 0.5, 10 latitude bins between 0o and 60o ,8 bins in MLT and 5 levels of geomagnetic activity as measured by Kp. We find that the peak frequency of lower band chorus is close to 0.2 fce, which is lower than that used in previous models. The combined upper and lower band chorus diffusion shows structure that should result in an energy dependent pitch angle anisotropy, particularly between 1 keV and 100 keV. The diffusion rates suggest that wave-particle interactions should still be very important outside geostationary orbit, out to at least L* = 8. We find significant energy diffusion near 1 keV near the loss cone, consistent with wave growth. By including the new chorus diffusion matrix into the BAS radiation belt (BRB) model we compare the effects on the evolution of the radiation belts against previous models.

  4. Absolute bioavailability and absorption characteristics of divalproex sodium extended-release tablets in healthy volunteers.

    PubMed

    Dutta, Sandeep; Reed, Ronald C; Cavanaugh, John H

    2004-07-01

    Conventional delayed-release, enteric-coated divalproex sodium tablet has an absolute bioavailability of approximately 100%. Divalproex sodium extended-release (ER) tablet is a novel formulation of valproic acid (VPA) designed to release the drug slowly at a constant zero-order rate. The purpose of this study was to evaluate the absolute bioavailability and absorption characteristics of divalproex ER. Healthy adult volunteers (n = 16) received divalproex ER and intravenous VPA in crossover fashion. Absolute bioavailability was calculated as the divalproex ER/intravenous VPA ratio of area under the curve extrapolated to infinity. The duration and rate of absorption of VPA from divalproex ER tablets were determined by deconvolution analysis. The geometric mean absolute bioavailability of divalproex ER was 0.896. The mean (coefficient of variation) duration of drug absorption from divalproex ER was 21.8 (17%) hours, and the zero-order absorption rate was 21.6 (24%) mg/h for a 500-mg tablet. Divalproex ER has a lower absolute bioavailability than conventional divalproex tablets but exhibits good extended-release characteristics without any dose dumping.

  5. Absolute Spectrophotometry of 237 Open Cluster Stars

    NASA Astrophysics Data System (ADS)

    Clampitt, L.; Burstein, D.

    1994-12-01

    We present absolute spectrophotometry of 237 stars in 7 nearby open clusters: Hyades, Pleiades, Alpha Persei, Praesepe, Coma Berenices, IC 4665, and M 39. The observations were taken using the Wampler single-channel scanner (Wampler 1966) on the Crossley 0.9m telescope at Lick Observatory from July 1973 through December 1974. 21 bandpasses spanning the spectral range 3500 Angstroms to 7780 Angstroms were observed for each star, with bandwiths ranging from 32Angstroms to 64 Angstroms. Data are standardized to the Hayes--Latham (1975) system. Our measurements are compared to filter colors on the Johnson BV, Stromgren ubvy, and Geneva U V B_1 B_2 V_1 G systems, as well as to spectrophotometry of a few stars published by Gunn, Stryker & Tinsley and in the Spectrophotometric Standards Catalog (Adelman; as distributed by the NSSDC). Both internal and external comparisons to the filter systems indicate a formal statistical accuracy per bandpass of 0.01 to 0.02 mag, with apparent larger ( ~ 0.03 mag) differences in absolute calibration between this data set and existing spectrophotometry. These data will comprise part of the spectrophotometry that will be used to calibrate the Beijing-Arizona-Taipei-Connecticut Color Survey of the Sky (see separate paper by Burstein et al. at this meeting).

  6. Linear ultrasonic motor for absolute gravimeter.

    PubMed

    Jian, Yue; Yao, Zhiyuan; Silberschmidt, Vadim V

    2017-02-01

    Thanks to their compactness and suitability for vacuum applications, linear ultrasonic motors are considered as substitutes for classical electromagnetic motors as driving elements in absolute gravimeters. Still, their application is prevented by relatively low power output. To overcome this limitation and provide better stability, a V-type linear ultrasonic motor with a new clamping method is proposed for a gravimeter. In this paper, a mechanical model of stators with flexible clamping components is suggested, according to a design criterion for clamps of linear ultrasonic motors. After that, an effect of tangential and normal rigidity of the clamping components on mechanical output is studied. It is followed by discussion of a new clamping method with sufficient tangential rigidity and a capability to facilitate pre-load. Additionally, a prototype of the motor with the proposed clamping method was fabricated and the performance tests in vertical direction were implemented. Experimental results show that the suggested motor has structural stability and high dynamic performance, such as no-load speed of 1.4m/s and maximal thrust of 43N, meeting the requirements for absolute gravimeters.

  7. Why to compare absolute numbers of mitochondria.

    PubMed

    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.

  8. [Estimation of absolute risk for fracture].

    PubMed

    Fujiwara, Saeko

    2009-03-01

    Osteoporosis treatment aims to prevent fractures and maintain the QOL of the elderly. However, persons at high risk of future fracture cannot be effectively identified on the basis of bone density (BMD) alone, although BMD is used as an diagnostic criterion. Therefore, the WHO recommended that absolute risk for fracture (10-year probability of fracture) for each individual be evaluated and used as an index for intervention threshold. The 10-year probability of fracture is calculated based on age, sex, BMD at the femoral neck (body mass index if BMD is not available), history of previous fractures, parental hip fracture history, smoking, steroid use, rheumatoid arthritis, secondary osteoporosis and alcohol consumption. The WHO has just announced the development of a calculation tool (FRAX: WHO Fracture Risk Assessment Tool) in February this year. Fractures could be prevented more effectively if, based on each country's medical circumstances, an absolute risk value for fracture to determine when to start medical treatment is established and persons at high risk of fracture are identified and treated accordingly.

  9. Absolute stereochemistry of altersolanol A and alterporriols.

    PubMed

    Kanamaru, Saki; Honma, Miho; Murakami, Takanori; Tsushima, Taro; Kudo, Shinji; Tanaka, Kazuaki; Nihei, Ken-Ichi; Nehira, Tatsuo; Hashimoto, Masaru

    2012-02-01

    The absolute stereochemistry of altersolanol A (1) was established by observing a positive exciton couplet in the circular dichroism (CD) spectrum of the C3,C4-O-bis(2-naphthoyl) derivative 10 and by chemical correlations with known compound 8. Before the discussion, the relative stereochemistry of 1 was confirmed by X-ray crystallographic analysis. The shielding effect at C7'-OMe group by C1-O-benzoylation established the relative stereochemical relationship between the C8-C8' axial bonding and the C1-C4/C1'-C4' polyol moieties of alterporriols E (3), an atropisomer of the C8-C8' dimer of 1. As 3 could be obtained by dimerization of 1 in vitro, the absolute configuration of its central chirality elements (C1-C4) must be identical to those of 1. Spectral comparison between the experimental and theoretical CD spectra supported the above conclusion. Axial stereochemistry of novel C4-O-deoxy dimeric derivatives, alterporriols F (4) and G (5), were also revealed by comparison of their CD spectra to those of 2 and 3.

  10. 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.

  11. Standardization of the cumulative absolute velocity

    SciTech Connect

    O'Hara, T.F.; Jacobson, J.P. )

    1991-12-01

    EPRI NP-5930, A Criterion for Determining Exceedance of the Operating Basis Earthquake,'' was published in July 1988. As defined in that report, the Operating Basis Earthquake (OBE) is exceeded when both a response spectrum parameter and a second damage parameter, referred to as the Cumulative Absolute Velocity (CAV), are exceeded. In the review process of the above report, it was noted that the calculation of CAV could be confounded by time history records of long duration containing low (nondamaging) acceleration. Therefore, it is necessary to standardize the method of calculating CAV to account for record length. This standardized methodology allows consistent comparisons between future CAV calculations and the adjusted CAV threshold value based upon applying the standardized methodology to the data set presented in EPRI NP-5930. The recommended method to standardize the CAV calculation is to window its calculation on a second-by-second basis for a given time history. If the absolute acceleration exceeds 0.025g at any time during each one second interval, the earthquake records used in EPRI NP-5930 have been reanalyzed and the adjusted threshold of damage for CAV was found to be 0.16g-set.

  12. Swarm's Absolute Scalar Magnetometers Burst Mode Results

    NASA Astrophysics Data System (ADS)

    Coisson, P.; Vigneron, P.; Hulot, G.; Crespo Grau, R.; Brocco, L.; Lalanne, X.; Sirol, O.; Leger, J. M.; Jager, T.; Bertrand, F.; Boness, A.; Fratter, I.

    2014-12-01

    Each of the three Swarm satellites embarks an Absolute Scalar Magnetometer (ASM) to provide absolute scalar measurements of the magnetic field with high accuracy and stability. Nominal data acquisition of these ASMs is 1 Hz. But they can also run in a so-called "burst mode" and provide data at 250 Hz. During the commissioning phase of the mission, seven burst mode acquisition campaigns have been run simultaneously for all satellites, obtaining a total of ten days of burs-mode data. These campaigns allowed the identification of issues related to the operations of the piezo-electric motor and the heaters connected to the ASM, that do not impact the nominal 1 Hz scalar data. We analyze the burst mode data to identify high frequency geomagnetic signals, focusing the analysis in two regions: the low latitudes, where we seek signatures of ionospheric irregularities, and the high latitudes, to identify high frequency signals related to polar region currents. Since these campaigns have been conducted during the initial months of the mission, the three satellites where still close to each other, allowing to analyze the spatial coherency of the signals. Wavelet analysis have revealed 31 Hz signals appearing in the night-side in the equatorial region.

  13. Diffusion bonding

    DOEpatents

    Anderson, Robert C.

    1976-06-22

    1. A method for joining beryllium to beryllium by diffusion bonding, comprising the steps of coating at least one surface portion of at least two beryllium pieces with nickel, positioning a coated surface portion in a contiguous relationship with an other surface portion, subjecting the contiguously disposed surface portions to an environment having an atmosphere at a pressure lower than ambient pressure, applying a force upon the beryllium pieces for causing the contiguous surface portions to abut against each other, heating the contiguous surface portions to a maximum temperature less than the melting temperature of the beryllium, substantially uniformly decreasing the applied force while increasing the temperature after attaining a temperature substantially above room temperature, and maintaining a portion of the applied force at a temperature corresponding to about maximum temperature for a duration sufficient to effect the diffusion bond between the contiguous surface portions.

  14. The origin of low water vapor transmission rates through Al2O3/ZrO2 nanolaminate gas-diffusion barriers grown by atomic layer deposition

    SciTech Connect

    Meyer, Jens; Schmidt, H.; Kowalsky, W.; Riedl, T.; Kahn, Antoine

    2010-01-01

    This paper reports on thin film gas-diffusion barriers consisting of Al2 O3 /ZrO2 nanolaminates (NL) grown by low-temperature (80 °C) atomic layer deposition. We show that reliable barriers with water vapor transmission rates of 3.2×10-4 g/(m2 day) , measured at 80 °C and 80% relative humidity, can be realized with very thin layers down to 40 nm. We determine that ZrO2 acts as anticorrosion element in our NL. Furthermore, we demonstrate by x-ray photoemission spectroscopy that an aluminate phase is formed at the interfaces between Al2 O3 and ZrO2 sublayers, which additionally improves the gas-diffusion barrier due to a densification of the layer system. These Al2 O3 /ZrO2 NLs prepared at low temperatures hold considerable promises for application in organic electronics and beyond.

  15. Extracting infrared absolute reflectance from relative reflectance measurements.

    PubMed

    Berets, Susan L; Milosevic, Milan

    2012-06-01

    Absolute reflectance measurements are valuable to the optics industry for development of new materials and optical coatings. Yet, absolute reflectance measurements are notoriously difficult to make. In this paper, we investigate the feasibility of extracting the absolute reflectance from a relative reflectance measurement using a reference material with known refractive index.

  16. 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…

  17. Central 300 PC of the Galaxy Probed by the Infrared Spectra of H_3^+ and Co: I. Predominance of Warm and Diffuse Gas and High H_2 Ionization Rate

    NASA Astrophysics Data System (ADS)

    Oka, Takeshi; Geballe, Thomas R.; Goto, Miwa; Usuda, Tomonori; Indriolo, Nick

    2016-06-01

    A low-resolution 2.0-2.5 μm survey of ˜500 very red point-like objects in the Central Molecular Zone (CMZ) of our Galaxy, initiated in 2008, has revealed many new bright objects with featureless spectra that are suitable for high resolution absorption spectroscopy of H_3^+ and CO. We now have altogether 48 objects mostly close to the Galactic plane located from 142 pc to the west of Sgr A* to 120 pc east allowing us to probe dense and diffuse gas by H_3^+ and dense gas by CO. Our observations demonstrate that the warm (˜250 K) and diffuse (≤100 cm-3) gas with a large column length (≥30 pc) initially observed toward the brightest star in the CMZ, GCS3-2 of the Quintuplet Cluster, exists throughout the CMZ with the surface filling factor of ˜ 100% dominating the region. The column densities of CO in the CMZ are found to be much less than those in the three foreground spiral arms except in the directions of Sgr B and Sgr E complexes and indicate that the volume filling factor of dense clouds of 10% previously estimated is a gross overestimate for the front half of the CMZ. Nevertheless the predominance of the newly found diffuse molecular gas makes the term "Central Molecular Zone" even more appropriate. The ultra-hot X-rays emitting plasma which some thought to dominate the region must be non existent except near the stars and SNRs. Recently the H_2 fraction f(H_2) in diffuse gas of the CMZ has been reported to be ˜0.6. If we use this value, the cosmic ray H_2 ionization rate ζ of a few times 10-15 s-1 reported earlier^b on the assumption of f(H_2)=1 needs to be increased by a factor of ˜3 since the value is approximately inversely proportional to f(H_2)^2. Geballe, T. R., Oka, T., Lambridges, E., Yeh, S. C. C., Schlegelmilch, B., Goto, M., Westrick, C. W., WI07 at the 70th ISMS, Urbana, IL, USA,2015 Oka, T., Geballe, T. R., Goto, M., Usuda, T., McCall, B. J. 2005, ApJ, 632, 882 Le Petit, F., Ruaud, M., Bron, E., Godard, B., Roueff, E., Languignon, D., Le

  18. Gray- and white-matter anatomy of absolute pitch possessors.

    PubMed

    Dohn, Anders; Garza-Villarreal, Eduardo A; Chakravarty, M Mallar; Hansen, Mads; Lerch, Jason P; Vuust, Peter

    2015-05-01

    Absolute pitch (AP), the ability to identify a musical pitch without a reference, has been examined behaviorally in numerous studies for more than a century, yet only a few studies have examined the neuroanatomical correlates of AP. Here, we used MRI and diffusion tensor imaging to investigate structural differences in brains of musicians with and without AP, by means of whole-brain vertex-wise cortical thickness (CT) analysis and tract-based spatial statistics (TBSS) analysis. APs displayed increased CT in a number of areas including the bilateral superior temporal gyrus (STG), the left inferior frontal gyrus, and the right supramarginal gyrus. Furthermore, we found higher fractional anisotropy in APs within the path of the inferior fronto-occipital fasciculus, the uncinate fasciculus, and the inferior longitudinal fasciculus. The findings in gray matter support previous studies indicating an increased left lateralized posterior STG in APs, yet they differ from previous findings of thinner cortex for a number of areas in APs. Finally, we found a relation between the white-matter results and the CT in the right parahippocampal gyrus. In this study, we present novel findings in AP research that may have implications for the understanding of the neuroanatomical underpinnings of AP ability.

  19. Diffusion of Ca and Mg in Calcite

    SciTech Connect

    Cygan, R.T.; Fisler, D.K.

    1999-02-10

    The self-diffusion of Ca and the tracer diffusion of Mg in calcite have been experimentally measured using isotopic tracers of {sup 25}Mg and {sup 44}Ca. Natural single crystals of calcite were coated with a thermally-sputtered oxide thin film and then annealed in a CO{sub 2} gas at one atmosphere total pressure and temperatures from 550 to 800 C. Diffusion coefficient values were derived from the depth profiles obtained by ion microprobe analysis. The resultant activation energies for Mg tracer diffusion and Ca self-diffusion are respectively: E{sub a}(Mg) = 284 {+-} 74 kJ/mol and E{sub a}(Ca) = 271 {+-} 80 kJ/mol. For the temperature ranges in these experiments, the diffusion of Mg is faster than Ca. The results are generally consistent in magnitude with divalent cation diffusion rates obtained in previous studies and provide a means of interpreting the thermal histories of carbonate minerals, the mechanism of dolomitization, and other diffusion-controlled processes. The results indicate that cation diffusion in calcite is relatively slow and cations are the rate-limiting diffusing species for the deformation of calcite and carbonate rocks. Application of the calcite-dolomite geothermometer to metamorphic assemblages will be constrained by cation diffusion and cooling rates. The direct measurement of Mg tracer diffusion in calcite indicates that dolomitization is unlikely to be accomplished by Mg diffusion in the solid state but by a recrystallization process.

  20. Use of Absolute and Comparative Performance Feedback in Absolute and Comparative Judgments and Decisions

    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…

  1. First Absolutely Calibrated Localized Measurements of Ion Velocity in the MST in Locked and Rotating Plasmas

    NASA Astrophysics Data System (ADS)

    Baltzer, M.; Craig, D.; den Hartog, D. J.; Nornberg, M. D.; Munaretto, S.

    2015-11-01

    An Ion Doppler Spectrometer (IDS) is used on MST for high time-resolution passive and active measurements of impurity ion emission. Absolutely calibrated measurements of flow are difficult because the spectrometer records data within 0.3 nm of the C+5 line of interest, and commercial calibration lamps do not produce lines in this narrow range . A novel optical system was designed to absolutely calibrate the IDS. The device uses an UV LED to produce a broad emission curve in the desired region. A Fabry-Perot etalon filters this light, cutting transmittance peaks into the pattern of the LED emission. An optical train of fused silica lenses focuses the light into the IDS with f/4. A holographic diffuser blurs the light cone to increase homogeneity. Using this light source, the absolute Doppler shift of ion emissions can be measured in MST plasmas. In combination with charge exchange recombination spectroscopy, localized ion velocities can now be measured. Previously, a time-averaged measurement along the chord bisecting the poloidal plane was used to calibrate the IDS; the quality of these central chord calibrations can be characterized with our absolute calibration. Calibration errors may also be quantified and minimized by optimizing the curve-fitting process. Preliminary measurements of toroidal velocity in locked and rotating plasmas will be shown. This work has been supported by the US DOE.

  2. Surface self-diffusion of organic glasses.

    PubMed

    Brian, Caleb W; Yu, Lian

    2013-12-19

    Surface self-diffusion coefficients have been determined for the organic glass Nifedipine using the method of surface grating decay. The flattening of 1000 nm surface gratings occurs by viscous flow at 12 K or more above the glass transition temperature and by surface diffusion at lower temperatures. Surface diffusion is at least 10(7) times faster than bulk diffusion, indicating a highly mobile surface. Nifedipine glasses have faster surface diffusion than the previously studied Indomethacin glasses, despite their similar bulk relaxation times. Both glasses exhibit fast surface crystal growth, and its rate scales with surface diffusivity. The observed rate of surface diffusion implies substantial surface rearrangement during the preparation of low-energy glasses by vapor deposition. The Random First Order Transition Theory and the Coupling Model successfully predict the large surface-enhancement of mobility and its increase on cooling, but disagree with the experimental observation of the faster surface diffusion of Nifedipine.

  3. Absolute nonlocality via distributed computing without communication

    NASA Astrophysics Data System (ADS)

    Czekaj, Ł.; Pawłowski, M.; Vértesi, T.; Grudka, A.; Horodecki, M.; Horodecki, R.

    2015-09-01

    Understanding the role that quantum entanglement plays as a resource in various information processing tasks is one of the crucial goals of quantum information theory. Here we propose an alternative perspective for studying quantum entanglement: distributed computation of functions without communication between nodes. To formalize this approach, we propose identity games. Surprisingly, despite no signaling, we obtain that nonlocal quantum strategies beat classical ones in terms of winning probability for identity games originating from certain bipartite and multipartite functions. Moreover we show that, for a majority of functions, access to general nonsignaling resources boosts success probability two times in comparison to classical ones for a number of large enough outputs. Because there are no constraints on the inputs and no processing of the outputs in the identity games, they detect very strong types of correlations: absolute nonlocality.

  4. In vivo absorption spectroscopy for absolute measurement.

    PubMed

    Furukawa, Hiromitsu; Fukuda, Takashi

    2012-10-01

    In in vivo spectroscopy, there are differences between individual subjects in parameters such as tissue scattering and sample concentration. We propose a method that can provide the absolute value of a particular substance concentration, independent of these individual differences. Thus, it is not necessary to use the typical statistical calibration curve, which assumes an average level of scattering and an averaged concentration over individual subjects. This method is expected to greatly reduce the difficulties encountered during in vivo measurements. As an example, for in vivo absorption spectroscopy, the method was applied to the reflectance measurement in retinal vessels to monitor their oxygen saturation levels. This method was then validated by applying it to the tissue phantom under a variety of absorbance values and scattering efficiencies.

  5. Determining Absolute Zero Using a Tuning Fork

    NASA Astrophysics Data System (ADS)

    Goldader, Jeffrey D.

    2008-04-01

    The Celsius and Kelvin temperature scales, we tell our students, are related. We explain that a change in temperature of 1°C corresponds to a change of 1 Kelvin and that atoms and molecules have zero kinetic energy at zero Kelvin, -273°C. In this paper, we will show how students can derive the relationship between the Celsius and Kelvin temperature scales using a simple, well-known physics experiment. By making multiple measurements of the speed of sound at different temperatures, using the classic physics experiment of determining the speed of sound with a tuning fork and variable-length tube, they can determine the temperature at which the speed of sound is zero—absolute zero.

  6. 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.

  7. An estimate of global absolute dynamic topography

    NASA Technical Reports Server (NTRS)

    Tai, C.-K.; Wunsch, C.

    1984-01-01

    The absolute dynamic topography of the world ocean is estimated from the largest scales to a short-wavelength cutoff of about 6700 km for the period July through September, 1978. The data base consisted of the time-averaged sea-surface topography determined by Seasat and geoid estimates made at the Goddard Space Flight Center. The issues are those of accuracy and resolution. Use of the altimetric surface as a geoid estimate beyond the short-wavelength cutoff reduces the spectral leakage in the estimated dynamic topography from erroneous small-scale geoid estimates without contaminating the low wavenumbers. Comparison of the result with a similarly filtered version of Levitus' (1982) historical average dynamic topography shows good qualitative agreement. There is quantitative disagreement, but it is within the estimated errors of both methods of calculation.

  8. 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.

  9. Absolute measurements of fast neutrons using yttrium.

    PubMed

    Roshan, M V; Springham, S V; Rawat, R S; Lee, P; Krishnan, M

    2010-08-01

    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(n) approximately 4.1x10(-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(8) neutrons per discharge.

  10. Measured and modelled absolute gravity in Greenland

    NASA Astrophysics Data System (ADS)

    Nielsen, E.; Forsberg, R.; Strykowski, G.

    2012-12-01

    Present day changes in the ice volume in glaciated areas like Greenland will change the load on the Earth and to this change the lithosphere will respond elastically. The Earth also responds to changes in the ice volume over a millennial time scale. This response is due to the viscous properties of the mantle and is known as Glaical Isostatic Adjustment (GIA). Both signals are present in GPS and absolute gravity (AG) measurements and they will give an uncertainty in mass balance estimates calculated from these data types. It is possible to separate the two signals if both gravity and Global Positioning System (GPS) time series are available. DTU Space acquired an A10 absolute gravimeter in 2008. One purpose of this instrument is to establish AG time series in Greenland and the first measurements were conducted in 2009. Since then are 18 different Greenland GPS Network (GNET) stations visited and six of these are visited more then once. The gravity signal consists of three signals; the elastic signal, the viscous signal and the direct attraction from the ice masses. All of these signals can be modelled using various techniques. The viscous signal is modelled by solving the Sea Level Equation with an appropriate ice history and Earth model. The free code SELEN is used for this. The elastic signal is modelled as a convolution of the elastic Greens function for gravity and a model of present day ice mass changes. The direct attraction is the same as the Newtonian attraction and is calculated as this. Here we will present the preliminary results of the AG measurements in Greenland. We will also present modelled estimates of the direct attraction, the elastic and the viscous signals.

  11. Absolute bioavailability of quinine formulations in Nigeria.

    PubMed

    Babalola, C P; Bolaji, O O; Ogunbona, F A; Ezeomah, E

    2004-09-01

    This study compared the absolute bioavailability of quinine sulphate as capsule and as tablet against the intravenous (i.v.) infusion of the drug in twelve male volunteers. Six of the volunteers received intravenous infusion over 4 h as well as the capsule formulation of the drug in a cross-over manner, while the other six received the tablet formulation. Blood samples were taken at predetermined time intervals and plasma analysed for quinine (QN) using reversed-phase HPLC method. QN was rapidly absorbed after the two oral formulations with average t(max) of 2.67 h for both capsule and tablet. The mean elimination half-life of QN from the i.v. and oral dosage forms varied between 10 and 13.5 hr and were not statistically different (P > 0.05). On the contrary, the maximum plasma concentration (C(max)) and area under the curve (AUC) from capsule were comparable to those from i.v. (P > 0.05), while these values were markedly higher than values from tablet formulation (P < 0.05). The therapeutic QN plasma levels were not achieved with the tablet formulation. The absolute bioavailability (F) were 73% (C.l., 53.3 - 92.4%) and 39 % (C.I., 21.7 - 56.6%) for the capsule and tablet respectively and the difference was significant (P < 0.05). The subtherapeutic levels obtained from the tablet form used in this study may cause treatment failure during malaria and caution should be taken when predictions are made from results obtained from different formulations of QN.

  12. DIFFUSION PUMP

    DOEpatents

    Levenson, L.

    1963-09-01

    A high-vacuum diffusion pump is described, featuring a novel housing geometry for enhancing pumping speed. An upright, cylindrical lower housing portion is surmounted by a concentric, upright, cylindrical upper housing portion of substantially larger diameter; an uppermost nozzle, disposed concentrically within the upper portion, is adapted to eject downwardly a conical sheet of liquid outwardly to impinge upon the uppermost extremity of the interior wall of the lower portion. Preferably this nozzle is mounted upon a pedestal rising coaxially from within the lower portion and projecting up into said upper portion. (AEC)

  13. ABSOLUTE PROPERTIES OF THE ECLIPSING BINARY STAR V335 SERPENTIS

    SciTech Connect

    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.

  14. Market entry decisions: effects of absolute and relative confidence.

    PubMed

    Bolger, Fergus; Pulford, Briony D; Colman, Andrew M

    2008-01-01

    In a market entry game, the number of entrants usually approaches game-theoretic equilibrium quickly, but in real-world markets business start-ups typically exceed market capacity, resulting in chronically high failure rates and suboptimal industry profits. Excessive entry has been attributed to overconfidence arising when expected payoffs depend partly on skill. In an experimental test of this hypothesis, 96 participants played 24 rounds of a market entry game, with expected payoffs dependent partly on skill on half the rounds, after their confidence was manipulated and measured. The results provide direct support for the hypothesis that high levels of confidence are largely responsible for excessive entry, and they suggest that absolute confidence, independent of interpersonal comparison, rather than confidence about one's abilities relative to others, drives excessive entry decisions when skill is involved.

  15. Ambipolar diffusion in complex plasma.

    PubMed

    Losseva, T V; Popel, S I; Yu, M Y; Ma, J X

    2007-04-01

    A self-consistent model of the ambipolar diffusion of electrons and ions in complex (dusty) plasmas accounting for the local electric fields, the dust grain charging process, and the interaction of the plasma particles with the dust grains and neutrals is presented. The dependence of the diffusion coefficient on the interaction of the electrons and ions with the dust grains as well as with the neutrals are investigated. It is shown that increase of the dust density leads to a reduction of the diffusion scale length, and this effect is enhanced at higher electron densities. The dependence of the diffusion scale length on the neutral gas pressure is found to be given by a power law, where the absolute value of the power exponent decreases with increase of the dust density. The electric field gradient and its effects are shown to be significant and should thus be taken into account in studies of complex plasmas with not very small dust densities. The possibility of observing localized coherent dissipative nonlinear dust ion-acoustic structures in an asymmetrically discharged double plasma is discussed.

  16. Extended source model for diffusive coupling.

    PubMed

    González-Ochoa, Héctor O; Flores-Moreno, Roberto; Reyes, Luz M; Femat, Ricardo

    2016-01-01

    Motivated by the prevailing approach to diffusion coupling phenomena which considers point-like diffusing sources, we derived an analogous expression for the concentration rate of change of diffusively coupled extended containers. The proposed equation, together with expressions based on solutions to the diffusion equation, is intended to be applied to the numerical solution of systems exclusively composed of ordinary differential equations, however is able to account for effects due the finite size of the coupled sources.

  17. Diffusion of polymer gel implants.

    PubMed

    Davis, B K

    1974-08-01

    Crosslinked polyacrylamide and polyvinylpyrrolidone gels have been used to subcutaneously implant (125)I-labeled immunoglobulin, (125)I-labeled luteinizing hormone, (125)I-labeled bovine serum albumin, (125)I-labeled insulin, [(3)H]prostaglandin F(2alpha), and Na(125)I into hamsters. From the rates of absorption of the solutes, their diffusion coefficients were determined. The diffusion coefficients showed a logarithmic dependence on implant polymer concentration and solute molecular weight. Release of the solutes from gel preparations incubated 10 mM phosphate buffer (pH 7.2) at 37 degrees revealed a similar relationship between solute diffusion coefficient, molecular weight, and the concentration of polymer. A general equation was derived that gives the expected diffusion coefficient of a substance in a polymer gel from its molecular weight, diffusion coefficient in solvent, and polymer concentration of the gel.

  18. Cervical Gross Tumor Volume Dose Predicts Local Control Using Magnetic Resonance Imaging/Diffusion-Weighted Imaging—Guided High-Dose-Rate and Positron Emission Tomography/Computed Tomography—Guided Intensity Modulated Radiation Therapy

    SciTech Connect

    Dyk, Pawel; Jiang, Naomi; Sun, Baozhou; DeWees, Todd A.; Fowler, Kathryn J.; Narra, Vamsi; Garcia-Ramirez, Jose L.; Schwarz, Julie K.; Grigsby, Perry W.

    2014-11-15

    Purpose: Magnetic resonance imaging/diffusion weighted-imaging (MRI/DWI)-guided high-dose-rate (HDR) brachytherapy and {sup 18}F-fluorodeoxyglucose (FDG) — positron emission tomography/computed tomography (PET/CT)-guided intensity modulated radiation therapy (IMRT) for the definitive treatment of cervical cancer is a novel treatment technique. The purpose of this study was to report our analysis of dose-volume parameters predicting gross tumor volume (GTV) control. Methods and Materials: We analyzed the records of 134 patients with International Federation of Gynecology and Obstetrics stages IB1-IVB cervical cancer treated with combined MRI-guided HDR and IMRT from July 2009 to July 2011. IMRT was targeted to the metabolic tumor volume and lymph nodes by use of FDG-PET/CT simulation. The GTV for each HDR fraction was delineated by use of T2-weighted or apparent diffusion coefficient maps from diffusion-weighted sequences. The D100, D90, and Dmean delivered to the GTV from HDR and IMRT were summed to EQD2. Results: One hundred twenty-five patients received all irradiation treatment as planned, and 9 did not complete treatment. All 134 patients are included in this analysis. Treatment failure in the cervix occurred in 24 patients (18.0%). Patients with cervix failures had a lower D100, D90, and Dmean than those who did not experience failure in the cervix. The respective doses to the GTV were 41, 58, and 136 Gy for failures compared with 67, 99, and 236 Gy for those who did not experience failure (P<.001). Probit analysis estimated the minimum D100, D90, and Dmean doses required for ≥90% local control to be 69, 98, and 260 Gy (P<.001). Conclusions: Total dose delivered to the GTV from combined MRI-guided HDR and PET/CT-guided IMRT is highly correlated with local tumor control. The findings can be directly applied in the clinic for dose adaptation to maximize local control.

  19. Water vapor diffusion membranes, 2

    NASA Technical Reports Server (NTRS)

    Holland, F. F.; Klein, E.; Smith, J. K.; Eyer, C.

    1976-01-01

    Transport mechanisms were investigated for the three different types of water vapor diffusion membranes. Membranes representing porous wetting and porous nonwetting structures as well as dense diffusive membrane structures were investigated for water permeation rate as a function of: (1) temperature, (2) solids composition in solution, and (3) such hydrodynamic parameters as sweep gas flow rate, solution flow rate and cell geometry. These properties were measured using nitrogen sweep gas to collect the effluent. In addition, the chemical stability to chromic acid-stabilized urine was measured for several of each type of membrane. A technology based on the mechanism of vapor transport was developed, whereby the vapor diffusion rates and relative susceptibility of membranes to fouling and failure could be projected for long-term vapor recovery trials using natural chromic acid-stabilized urine.

  20. Absolute calibration of forces in optical tweezers

    NASA Astrophysics Data System (ADS)

    Dutra, R. S.; Viana, N. B.; Maia Neto, P. A.; Nussenzveig, H. M.

    2014-07-01

    Optical tweezers are highly versatile laser traps for neutral microparticles, with fundamental applications in physics and in single molecule cell biology. Force measurements are performed by converting the stiffness response to displacement of trapped transparent microspheres, employed as force transducers. Usually, calibration is indirect, by comparison with fluid drag forces. This can lead to discrepancies by sizable factors. Progress achieved in a program aiming at absolute calibration, conducted over the past 15 years, is briefly reviewed. Here we overcome its last major obstacle, a theoretical overestimation of the peak stiffness, within the most employed range for applications, and we perform experimental validation. The discrepancy is traced to the effect of primary aberrations of the optical system, which are now included in the theory. All required experimental parameters are readily accessible. Astigmatism, the dominant effect, is measured by analyzing reflected images of the focused laser spot, adapting frequently employed video microscopy techniques. Combined with interface spherical aberration, it reveals a previously unknown window of instability for trapping. Comparison with experimental data leads to an overall agreement within error bars, with no fitting, for a broad range of microsphere radii, from the Rayleigh regime to the ray optics one, for different polarizations and trapping heights, including all commonly employed parameter domains. Besides signaling full first-principles theoretical understanding of optical tweezers operation, the results may lead to improved instrument design and control over experiments, as well as to an extended domain of applicability, allowing reliable force measurements, in principle, from femtonewtons to nanonewtons.

  1. Elevation correction factor for absolute pressure measurements

    NASA Technical Reports Server (NTRS)

    Panek, Joseph W.; Sorrells, Mark R.

    1996-01-01

    With the arrival of highly accurate multi-port pressure measurement systems, conditions that previously did not affect overall system accuracy must now be scrutinized closely. Errors caused by elevation differences between pressure sensing elements and model pressure taps can be quantified and corrected. With multi-port pressure measurement systems, the sensing elements are connected to pressure taps that may be many feet away. The measurement system may be at a different elevation than the pressure taps due to laboratory space or test article constraints. This difference produces a pressure gradient that is inversely proportional to height within the interface tube. The pressure at the bottom of the tube will be higher than the pressure at the top due to the weight of the tube's column of air. Tubes with higher pressures will exhibit larger absolute errors due to the higher air density. The above effect is well documented but has generally been taken into account with large elevations only. With error analysis techniques, the loss in accuracy from elevation can be easily quantified. Correction factors can be applied to maintain the high accuracies of new pressure measurement systems.

  2. Gyrokinetic Statistical Absolute Equilibrium and Turbulence

    SciTech Connect

    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.

  3. 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.

  4. 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

  5. On limits to Jupiter's magnetospheric diffusion rates.

    NASA Technical Reports Server (NTRS)

    Mihalov, J. D.

    1973-01-01

    X-ray fluxes at earth estimated from hypothetical fluxes and spectra of energetic particles trapped in Jupiter's magnetic field are found to be 1/170000 times the upper limit X-ray flux from Jupiter based on published results from a rocket experiment. Detection of the calculated X-ray flux from Jupiter does not necessarily provide information on an energetic trapped proton component because the X-ray flux due to the hypothetical trapped energetic proton fluxes alone is comparable in magnitude to that due alone to trapped energetic electron fluxes as Jupiter.

  6. Dimer motion on a periodic substrate: spontaneous symmetry breaking and absolute negative mobility.

    PubMed

    Speer, David; Eichhorn, Ralf; Evstigneev, Mykhaylo; Reimann, Peter

    2012-06-01

    We consider two coupled particles moving along a periodic substrate potential with negligible inertia effects (overdamped limit). Even when the particles are identical and the substrate spatially symmetric, a sinusoidal external driving of appropriate amplitude and frequency may lead to spontaneous symmetry breaking in the form of a permanent directed motion of the dimer. Thermal noise restores ergodicity and thus zero net velocity, but entails arbitrarily fast diffusion of the dimer for sufficiently weak noise. Moreover, upon application of a static bias force, the dimer exhibits a motion opposite to that force (absolute negative mobility). The key requirement for all these effects is a nonconvex interaction potential of the two particles.

  7. Thorough subcells diagnosis in a multi-junction solar cell via absolute electroluminescence-efficiency measurements.

    PubMed

    Chen, Shaoqiang; Zhu, Lin; Yoshita, Masahiro; Mochizuki, Toshimitsu; Kim, Changsu; Akiyama, Hidefumi; Imaizumi, Mitsuru; Kanemitsu, Yoshihiko

    2015-01-16

    World-wide studies on multi-junction (tandem) solar cells have led to record-breaking improvements in conversion efficiencies year after year. To obtain detailed and proper feedback for solar-cell design and fabrication, it is necessary to establish standard methods for diagnosing subcells in fabricated tandem devices. Here, we propose a potential standard method to quantify the detailed subcell properties of multi-junction solar cells based on absolute measurements of electroluminescence (EL) external quantum efficiency in addition to the conventional solar-cell external-quantum-efficiency measurements. We demonstrate that the absolute-EL-quantum-efficiency measurements provide I-V relations of individual subcells without the need for referencing measured I-V data, which is in stark contrast to previous works. Moreover, our measurements quantify the absolute rates of junction loss, non-radiative loss, radiative loss, and luminescence coupling in the subcells, which constitute the "balance sheets" of tandem solar cells.

  8. Absolute nuclear material assay using count distribution (LAMBDA) space

    DOEpatents

    Prasad, Mano K.; Snyderman, Neal J.; Rowland, Mark S.

    2015-12-01

    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.

  9. Absolute nuclear material assay using count distribution (LAMBDA) space

    DOEpatents

    Prasad, Manoj K [Pleasanton, CA; Snyderman, Neal J [Berkeley, CA; Rowland, Mark S [Alamo, CA

    2012-06-05

    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.

  10. Positioning, alignment and absolute pointing of the ANTARES neutrino telescope

    NASA Astrophysics Data System (ADS)

    Fehr, F.; Distefano, C.; Antares Collaboration

    2010-01-01

    A precise detector alignment and absolute pointing is crucial for point-source searches. The ANTARES neutrino telescope utilises an array of hydrophones, tiltmeters and compasses for the relative positioning of the optical sensors. The absolute calibration is accomplished by long-baseline low-frequency triangulation of the acoustic reference devices in the deep-sea with a differential GPS system at the sea surface. The absolute pointing can be independently verified by detecting the shadow of the Moon in cosmic rays.

  11. Absolute and Convective Instability of a Liquid Jet

    NASA Technical Reports Server (NTRS)

    Lin, S. P.; Hudman, M.; Chen, J. N.

    1999-01-01

    The existence of absolute instability in a liquid jet has been predicted for some time. The disturbance grows in time and propagates both upstream and downstream in an absolutely unstable liquid jet. The image of absolute instability is captured in the NASA 2.2 sec drop tower and reported here. The transition from convective to absolute instability is observed experimentally. The experimental results are compared with the theoretical predictions on the transition Weber number as functions of the Reynolds number. The role of interfacial shear relative to all other relevant forces which cause the onset of jet breakup is explained.

  12. Absolute Measurements Of Methane On Mars: The Current Status.

    NASA Astrophysics Data System (ADS)

    Mumma, Michael J.; Villanueva, G. L.; Novak, R. E.; Hewagama, T.; Bonev, B. P.; DiSanti, M. A.; Smith, M. D.

    2008-09-01

    Our study of methane on Mars now extends over three Mars years, sampling a wide range of seasons with significant spatial coverage. Three spectrometer-telescope combinations were used. With the spectrometer slit oriented North-South on the planet, we obtain simultaneous spectra at latitudes along the central meridian. Successive longitudes are sampled as the planet rotates, and the combination then permits partial mapping of the planet. We earlier reported differential detections of methane and water on Mars. Here, we present absolute extractions of methane, based on improved analytical procedures developed since 2005. We now identify and correct instrumental effects such as variations in resolving power along the slit, second-order optical fringe removal, and correction of (minor) internal scattered light. We synthesize the fully-resolved terrestrial transmittance spectrum, convolve it to the instrumental resolution, and subtract it from the measured Mars-Earth spectrum. Fraunhofer lines are removed from the residual Mars spectra along with spectral lines of water and of (newly identified by us) carbon dioxide isotopomers. The residuals are then inspected for signatures of methane and other possible trace constituents such as HDO and H2O (Villanueva et al., this Conference). On certain dates, the residual spectra display spectral lines at the Doppler-shifted positions expected for methane on Mars. The positive indications favor certain seasons (e.g., Ls = 121° & 155°) and locations. Mixing ratios derived from those residuals (up to 60 ppb) greatly exceed upper limits obtained at other seasons (e.g., < 3ppb at Ls = 17°) these variations could be consistent with episodic release. The CH4 spatial extent requires transport over large distances (coupled with eddy diffusion), and destruction lifetimes of order one year. Details will be presented and implications will be discussed. This work was supported by NASA's Astrobiology, Planetary Astronomy, and Postdoctoral

  13. DEVELOPMENT OF A LASER SYSTEM FOR ABSOLUTE ATMOSPHERIC DIFFUSION MEASUREMENT OF A GASEOUS TRACER MATERIAL.

    DTIC Science & Technology

    laser development . Successful application of the Rayleigh scattering technique awaits idenficiation of a gas with a Rayleigh scattering cross section near 10 to the (-21)st power cm. squared. The fluorescence approach is feasible at this time with hexafluoroacetone as the tracer gas and a nitrogen laser as the light source. Preliminary system design considerations are presented in an appendix.

  14. Cooling rates of LL, L and H chondrites and constraints on the duration of peak thermal conditions: Diffusion kinetic modeling and implications for fragmentation of asteroids and impact resetting of petrologic types

    NASA Astrophysics Data System (ADS)

    Ganguly, Jibamitra; Tirone, Massimiliano; Domanik, Kenneth

    2016-11-01

    We have carried out detailed thermometric and cooling history studies of several LL-, L- and H-chondrites of petrologic types 5 and 6. Among the selected samples, the low-temperature cooling of St. Séverin (LL6) has been constrained in an earlier study by thermochronological data to an average rate of ∼2.6 °C/My below 500 °C. However, numerical simulations of the development of Fe-Mg profiles in Opx-Cpx pairs using this cooling rate grossly misfit the measured compositional profiles. Satisfactory simulation of the latter and low temperature thermochronological constraints requires a two-stage cooling model with a cooling rate of ∼50-200 °C/ky from the peak metamorphic temperature of ∼875 °C down to 450 °C, and then transitioning to very slow cooling with an average rate of ∼2.6 °C/My. Similar rapid high temperature cooling rates (200-600 °C/ky) are also required to successfully model the compositional profiles in the Opx-Cpx pairs in the other samples of L5, L6 chondrites. For the H-chondrite samples, the low temperature cooling rates were determined earlier to be 10-20 °C/My by metallographic method. As in St. Séverin, these cooling rates grossly misfit the compositional profiles in the Opx-Cpx pairs. Modeling of these profiles requires very rapid cooling, ∼200-400 °C/ky, from the peak temperatures (∼810-830 °C), transitioning to the metallographic rates at ∼450-500 °C. We interpret the rapid high temperature cooling rates to the exposure of the samples to surface or near surface conditions as a result of fragmentation of the parent body by asteroidal impacts. Using the thermochronological data, the timing of the presumed impact is constrained to be ∼4555-4560 My before present for St. Séverin. We also deduced similar two stage cooling models in earlier studies of H-chondrites and mesosiderites that could be explained, using the available geochronological data, by impact induced fragmentation at around the same time. Diffusion kinetic

  15. Absolute Plate Velocities from Seismic Anisotropy

    NASA Astrophysics Data System (ADS)

    Kreemer, Corné; Zheng, Lin; Gordon, Richard

    2015-04-01

    The orientation of seismic anisotropy inferred beneath plate interiors may provide a means to estimate the motions of the plate relative to the sub-asthenospheric mantle. Here we analyze two global sets of shear-wave splitting data, that of Kreemer [2009] and an updated and expanded data set, to estimate plate motions and to better understand the dispersion of the data, correlations in the errors, and their relation to plate speed. We also explore the effect of using geologically current plate velocities (i.e., the MORVEL set of angular velocities [DeMets et al. 2010]) compared with geodetically current plate velocities (i.e., the GSRM v1.2 angular velocities [Kreemer et al. 2014]). We demonstrate that the errors in plate motion azimuths inferred from shear-wave splitting beneath any one tectonic plate are correlated with the errors of other azimuths from the same plate. To account for these correlations, we adopt a two-tier analysis: First, find the pole of rotation and confidence limits for each plate individually. Second, solve for the best fit to these poles while constraining relative plate angular velocities to consistency with the MORVEL relative plate angular velocities. The SKS-MORVEL absolute plate angular velocities (based on the Kreemer [2009] data set) are determined from the poles from eight plates weighted proportionally to the root-mean-square velocity of each plate. SKS-MORVEL indicates that eight plates (Amur, Antarctica, Caribbean, Eurasia, Lwandle, Somalia, Sundaland, and Yangtze) have angular velocities that differ insignificantly from zero. The net rotation of the lithosphere is 0.25±0.11° Ma-1 (95% confidence limits) right-handed about 57.1°S, 68.6°E. The within-plate dispersion of seismic anisotropy for oceanic lithosphere (σ=19.2° ) differs insignificantly from that for continental lithosphere (σ=21.6° ). The between-plate dispersion, however, is significantly smaller for oceanic lithosphere (σ=7.4° ) than for continental

  16. Evaluation of the Absolute Regional Temperature Potential

    NASA Technical Reports Server (NTRS)

    Shindell, D. T.

    2012-01-01

    The Absolute Regional Temperature Potential (ARTP) is one of the few climate metrics that provides estimates of impacts at a sub-global scale. The ARTP presented here gives the time-dependent temperature response in four latitude bands (90-28degS, 28degS-28degN, 28-60degN and 60-90degN) as a function of emissions based on the forcing in those bands caused by the emissions. It is based on a large set of simulations performed with a single atmosphere-ocean climate model to derive regional forcing/response relationships. Here I evaluate the robustness of those relationships using the forcing/response portion of the ARTP to estimate regional temperature responses to the historic aerosol forcing in three independent climate models. These ARTP results are in good accord with the actual responses in those models. Nearly all ARTP estimates fall within +/-20%of the actual responses, though there are some exceptions for 90-28degS and the Arctic, and in the latter the ARTP may vary with forcing agent. However, for the tropics and the Northern Hemisphere mid-latitudes in particular, the +/-20% range appears to be roughly consistent with the 95% confidence interval. Land areas within these two bands respond 39-45% and 9-39% more than the latitude band as a whole. The ARTP, presented here in a slightly revised form, thus appears to provide a relatively robust estimate for the responses of large-scale latitude bands and land areas within those bands to inhomogeneous radiative forcing and thus potentially to emissions as well. Hence this metric could allow rapid evaluation of the effects of emissions policies at a finer scale than global metrics without requiring use of a full climate model.

  17. 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.

  18. Kramers turnover: From energy diffusion to spatial diffusion using metadynamics

    PubMed Central

    Tiwary, Pratyush; Berne, B. J.

    2016-01-01

    We consider the rate of transition for a particle between two metastable states coupled to a thermal environment for various magnitudes of the coupling strength using the recently proposed infrequent metadynamics approach [P. Tiwary and M. Parrinello, Phys. Rev. Lett. 111, 230602 (2013)]. We are interested in understanding how this approach for obtaining rate constants performs as the dynamics regime changes from energy diffusion to spatial diffusion. Reassuringly, we find that the approach works remarkably well for various coupling strengths in the strong coupling regime, and to some extent even in the weak coupling regime. PMID:27059558

  19. Diffusion archeology for diffusion progression history reconstruction.

    PubMed

    Sefer, Emre; Kingsford, Carl

    2016-11-01

    Diffusion through graphs can be used to model many real-world processes, such as the spread of diseases, social network memes, computer viruses, or water contaminants. Often, a real-world diffusion cannot be directly observed while it is occurring - perhaps it is not noticed until some time has passed, continuous monitoring is too costly, or privacy concerns limit data access. This leads to the need to reconstruct how the present state of the diffusion came to be from partial diffusion data. Here, we tackle the problem of reconstructing a diffusion history from one or more snapshots of the diffusion state. This ability can be invaluable to learn when certain computer nodes are infected or which people are the initial disease spreaders to control future diffusions. We formulate this problem over discrete-time SEIRS-type diffusion models in terms of maximum likelihood. We design methods that are based on submodularity and a novel prize-collecting dominating-set vertex cover (PCDSVC) relaxation that can identify likely diffusion steps with some provable performance guarantees. Our methods are the first to be able to reconstruct complete diffusion histories accurately in real and simulated situations. As a special case, they can also identify the initial spreaders better than the existing methods for that problem. Our results for both meme and contaminant diffusion show that the partial diffusion data problem can be overcome with proper modeling and methods, and that hidden temporal characteristics of diffusion can be predicted from limited data.

  20. Hybrid diffuse optical techniques for continuous hemodynamic measurement in gastrocnemius during plantar flexion exercise

    NASA Astrophysics Data System (ADS)

    Henry, Brad; Zhao, Mingjun; Shang, Yu; Uhl, Timothy; Thomas, D. Travis; Xenos, Eleftherios S.; Saha, Sibu P.; Yu, Guoqiang

    2015-12-01

    Occlusion calibrations and gating techniques have been recently applied by our laboratory for continuous and absolute diffuse optical measurements of forearm muscle hemodynamics during handgrip exercises. The translation of these techniques from the forearm to the lower limb is the goal of this study as various diseases preferentially affect muscles in the lower extremity. This study adapted a hybrid near-infrared spectroscopy and diffuse correlation spectroscopy system with a gating algorithm to continuously quantify hemodynamic responses of medial gastrocnemius during plantar flexion exercises in 10 healthy subjects. The outcomes from optical measurement include oxy-, deoxy-, and total hemoglobin concentrations, blood oxygen saturation, and relative changes in blood flow (rBF) and oxygen consumption rate (rV˙O2). We calibrated rBF and rV˙O2 profiles with absolute baseline values of BF and V˙O2 obtained by venous and arterial occlusions, respectively. Results from this investigation were comparable to values from similar studies. Additionally, significant correlation was observed between resting local muscle BF measured by the optical technique and whole limb BF measured concurrently by a strain gauge venous plethysmography. The extensive hemodynamic and metabolic profiles during exercise will allow for future comparison studies to investigate the diagnostic value of hybrid technologies in muscles affected by disease.

  1. Hybrid diffuse optical techniques for continuous hemodynamic measurement in gastrocnemius during plantar flexion exercise

    PubMed Central

    Henry, Brad; Zhao, Mingjun; Shang, Yu; Uhl, Timothy; Thomas, D. Travis; Xenos, Eleftherios S.; Saha, Sibu P.; Yu, Guoqiang

    2015-01-01

    Abstract. Occlusion calibrations and gating techniques have been recently applied by our laboratory for continuous and absolute diffuse optical measurements of forearm muscle hemodynamics during handgrip exercises. The translation of these techniques from the forearm to the lower limb is the goal of this study as various diseases preferentially affect muscles in the lower extremity. This study adapted a hybrid near-infrared spectroscopy and diffuse correlation spectroscopy system with a gating algorithm to continuously quantify hemodynamic responses of medial gastrocnemius during plantar flexion exercises in 10 healthy subjects. The outcomes from optical measurement include oxy-, deoxy-, and total hemoglobin concentrations, blood oxygen saturation, and relative changes in blood flow (rBF) and oxygen consumption rate (rV˙O2). We calibrated rBF and rV˙O2 profiles with absolute baseline values of BF and V˙O2 obtained by venous and arterial occlusions, respectively. Results from this investigation were comparable to values from similar studies. Additionally, significant correlation was observed between resting local muscle BF measured by the optical technique and whole limb BF measured concurrently by a strain gauge venous plethysmography. The extensive hemodynamic and metabolic profiles during exercise will allow for future comparison studies to investigate the diagnostic value of hybrid technologies in muscles affected by disease. PMID:26720871

  2. Sentinel-2 diffuser on-ground calibration

    NASA Astrophysics Data System (ADS)

    Mazy, E.; Camus, F.; Chorvalli, V.; Domken, I.; Laborie, A.; Marcotte, S.; Stockman, Y.

    2013-10-01

    The Sentinel-2 multi-spectral instrument (MSI) will provide Earth imagery in the frame of the Global Monitoring for Environment and Security (GMES) initiative which is a joint undertaking of the European Commission and the Agency. MSI instrument, under Astrium SAS responsibility, is a push-broom spectro imager in 13 spectral channels in VNIR and SWIR. The instrument radiometric calibration is based on in-flight calibration with sunlight through a quasi Lambertian diffuser. The diffuser covers the full pupil and the full field of view of the instrument. The on-ground calibration of the diffuser BRDF is mandatory to fulfil the in-flight performances. The diffuser is a 779 x 278 mm2 rectangular flat area in Zenith-A material. It is mounted on a motorised door in front of the instrument optical system entrance. The diffuser manufacturing and calibration is under the Centre Spatial of Liege (CSL) responsibility. The CSL has designed and built a completely remote controlled BRDF test bench able to handle large diffusers in their mount. As the diffuser is calibrated directly in its mount with respect to a reference cube, the error budget is significantly improved. The BRDF calibration is performed directly in MSI instrument spectral bands by using dedicated band-pass filters (VNIR and SWIR up to 2200 nm). Absolute accuracy is better than 0.5% in VNIR spectral bands and 1% in SWIR spectral bands. Performances were cross checked with other laboratories. The first MSI diffuser for flight model was calibrated mid 2013 on CSL BRDF measurement bench. The calibration of the diffuser consists mainly in thermal vacuum cycles, BRDF uniformity characterisation and BRDF angular characterisation. The total amount of measurement for the first flight model diffuser corresponds to more than 17500 BRDF acquisitions. Performance results are discussed in comparison with requirements.

  3. Impact of a federal program on response rate & survival, in a cohort of patients with diffuse large B-cell lymphoma. Analysis in a single national reference institution in México.

    PubMed

    Candelaria, Myrna; Labardini-Mendez, Juan; Ramírez-Ibarguen, Ana F; Avilés-Salas, Alejandro; Estrada-Lobato, Enrique; Meneses-García, Abelardo; Mohar, Alejandro

    2014-01-01

    The actual standard of care of diffuse large B-cell lymphoma (DLBCL) includes rituximab in combination with chemotherapy, with response rates up to 76%. However, this treatment may not be accessible to many patients, particularly in developing countries, where most of the treatment must be paid from the pocket of patients or their families. In México, since 2011 a federal program has fully covered this treatment of patients with DLBCL. At the Instituto Nacional de Cancerología (INCan) in Mexico City, 214 new cases with this disease were treated without cost with the standard of care in 20 months. The mean age at diagnosis was 56.7 ± 15.9 (22-91). This series of cases was compared with a retrospective analysis of cases with DLBCL attended at the INCan between 2006-2009. A total of 264 cases were retrospectively analyzed. No differences were found in demographic and clinical characteristics at time of diagnosis. However a clear positive impact was found in the group that received full treatment thanks to this new social coverage by this new social security program. The follow-up and completion of treatment was 99 %. In contrast; from 264 in the retrospective group (79%) were treated, but only 29 (10.9%) were able to receive an optimal treatment, including rituximab. These differences in treatments had a clearly impact on the response rate: 66.8 vs. 50.7% global response (full treatment vs. retrospective group, respectively). These results demonstrate the importance of social programs that may accessible standard treatment options in countries with limited resources.

  4. Characterization of metallic foil joints using diffusion bonding and diffusion soldering in micro-technology-based energy and chemical systems

    SciTech Connect

    Gabriel, Michael; Paul, B.K.; Wilson, R.D.

    2001-01-01

    The several 316 stainless steel mesoscopic devices were made using diffusing bonding and diffusion soldering. Tensile strength, pressure drop of the devices were measured, and metallurgical examinations were made of the joints. Continuous bonds were observed in both diffusion bonded and diffusion soldered samples. Strengths of the diffusion soldered samples were up to 80% of the strength of the Ag3Sn joint material or 125 MPa. The pressure drop in diffusion soldered samples was 0.76 psi at the highest flow rates of 2.08 L/min. Diffusion bonded joints had strengths of up to 700 MPa but the back pressures were higher at all flow rates.

  5. Characterization of metallic foil joints using diffusion bonding and diffusion soldering in micro-technology-based energy and chemical systems

    SciTech Connect

    Gabriel, Michael; Paul, Brian K.; Wilson, Rick D.; Alman, David E.

    2001-01-10

    The several 316 stainless steel mesoscopic devices were made using diffusing bonding and diffusion soldering. Tensile strength, pressure drop of the devices were measured, and metallurgical examinations were made of the joints. Continuous bonds were observed in both diffusion bonded and diffusion soldered samples. Strengths of the diffusion soldered samples were up to 80% of the strength of the Ag(sub3) Sn joint material or 125 MPa. The pressure drop in diffusion soldered samples was 0.76 psi at the highest flow rates of 2.08 L/min. Diffusion bonded joints had strengths of up to 700 MPa but the back pressures were higher at all flow rates.

  6. Gender equality and women's absolute status: a test of the feminist models of rape.

    PubMed

    Martin, Kimberly; Vieraitis, Lynne M; Britto, Sarah

    2006-04-01

    Feminist theory predicts both a positive and negative relationship between gender equality and rape rates. Although liberal and radical feminist theory predicts that gender equality should ameliorate rape victimization, radical feminist theorists have argued that gender equality may increase rape in the form of male backlash. Alternatively, Marxist criminologists focus on women's absolute socioeconomic status rather than gender equality as a predictor of rape rates, whereas socialist feminists combine both radical and Marxist perspectives. This study uses factor analysis to overcome multicollinearity limitations of past studies while exploring the relationship between women's absolute and relative socioeconomic status on rape rates in major U.S. cities using 2000 census data. The findings indicate support for both the Marxist and radical feminist explanations of rape but no support for the ameliorative hypothesis. These findings support a more inclusive socialist feminist theory that takes both Marxist and radical feminist hypotheses into account.

  7. Determination of Absolute Zero Using a Computer-Based Laboratory

    ERIC Educational Resources Information Center

    Amrani, D.

    2007-01-01

    We present a simple computer-based laboratory experiment for evaluating absolute zero in degrees Celsius, which can be performed in college and undergraduate physical sciences laboratory courses. With a computer, absolute zero apparatus can help demonstrators or students to observe the relationship between temperature and pressure and use…

  8. A Global Forecast of Absolute Poverty and Employment.

    ERIC Educational Resources Information Center

    Hopkins, M. J. D.

    1980-01-01

    Estimates are made of absolute poverty and employment under the hypothesis that existing trends continue. Concludes that while the number of people in absolute poverty is not likely to decline by 2000, the proportion will fall. Jobs will have to grow 3.9% per year in developing countries to achieve full employment. (JOW)

  9. Novalis' Poetic Uncertainty: A "Bildung" with the Absolute

    ERIC Educational Resources Information Center

    Mika, Carl

    2016-01-01

    Novalis, the Early German Romantic poet and philosopher, had at the core of his work a mysterious depiction of the "absolute." The absolute is Novalis' name for a substance that defies precise knowledge yet calls for a tentative and sensitive speculation. How one asserts a truth, represents an object, and sets about encountering things…

  10. Influence of site occupancy on diffusion of hydrogen in vanadium

    NASA Astrophysics Data System (ADS)

    Mooij, Lennard; Huang, Wen; Droulias, Sotirios A.; Johansson, Robert; Hartmann, Ola; Xin, Xiao; Palonen, Heikki; Scheicher, Ralph H.; Wolff, Max; Hjörvarsson, Björgvin

    2017-02-01

    We investigate the effect of site occupancy on the chemical diffusion of hydrogen in strained vanadium. The diffusion rate is found to decrease substantially, when hydrogen is occupying octahedral sites as compared to tetrahedral sites. Profound isotope effects are observed when comparing the diffusion rate of H and D. The changes in the diffusion rate are found to be strongly influenced by the changes in the potential energy landscape, as deduced from first-principles molecular dynamics calculations.

  11. [Study on the absolute spectral irradiation calibration method for far ultraviolet spectrometer in remote sensing].

    PubMed

    Yu, Lei; Lin, Guan-Yu; Chen, Bin

    2013-01-01

    The present paper studied spectral irradiation responsivities calibration method which can be applied to the far ultraviolet spectrometer for upper atmosphere remote sensing. It is difficult to realize the calibration for far ultraviolet spectrometer for many reasons. Standard instruments for far ultraviolet waveband calibration are few, the degree of the vacuum experiment system is required to be high, the stabilities of the experiment are hardly maintained, and the limitation of the far ultraviolet waveband makes traditional diffuser and the integrating sphere radiance calibration method difficult to be used. To solve these problems, a new absolute spectral irradiance calibration method was studied, which can be applied to the far ultraviolet calibration. We build a corresponding special vacuum experiment system to verify the calibration method. The light source system consists of a calibrated deuterium lamp, a vacuum ultraviolet monochromater and a collimating system. We used the calibrated detector to obtain the irradiance responsivities of it. The three instruments compose the calibration irradiance source. We used the "calibration irradiance source" to illuminate the spectrometer prototype and obtained the spectral irradiance responsivities. It realized the absolute spectral irradiance calibration for the far ultraviolet spectrometer utilizing the calibrated detector. The absolute uncertainty of the calibration is 7.7%. The method is significant for the ground irradiation calibration of the far ultraviolet spectrometer in upper atmosphere remote sensing.

  12. Double Diffusive Plumes

    NASA Astrophysics Data System (ADS)

    Sutherland, Bruce; Lee, Brace

    2008-11-01

    Sour gas flares attempt to dispose of deadly H2S gas through combustion. What does not burn rises as a buoyant plume. But the gas is heavier than air at room temperature, so as the rising gas cools eventually it becomes negatively buoyant and descends back to the ground. Ultimately, our intent is to predict the concentrations of the gas at ground level in realistic atmospheric conditions. As a first step towards this goal we have performed laboratory experiments examining the structure of a steady state plume of hot and salty water that rises buoyantly near the source and descends as a fountain after it has cooled sufficiently. We call this a double-diffusive plume because its evolution is dictated by the different (turbulent) diffusivities of heat and salt. A temperature and conductivity probe measures both the salinity and temperature along the centreline of the plume. The supposed axisymmetric structure of the salinity concentration as it changes with height is determined by light-attenuation methods. To help interpret the results, a theory has been successfully adapted from the work of Bloomfield and Kerr (2000), who developed coupled equations describing the structure of fountains. Introducing a new empirical parameter for the relative rates of turbulent heat and salt diffusion, the predictions are found to agree favourably with experimental results.

  13. Absolute radiometric calibration of advanced remote sensing systems

    NASA Technical Reports Server (NTRS)

    Slater, P. N.

    1982-01-01

    The distinction between the uses of relative and absolute spectroradiometric calibration of remote sensing systems is discussed. The advantages of detector-based absolute calibration are described, and the categories of relative and absolute system calibrations are listed. The limitations and problems associated with three common methods used for the absolute calibration of remote sensing systems are addressed. Two methods are proposed for the in-flight absolute calibration of advanced multispectral linear array systems. One makes use of a sun-illuminated panel in front of the sensor, the radiance of which is monitored by a spectrally flat pyroelectric radiometer. The other uses a large, uniform, high-radiance reference ground surface. The ground and atmospheric measurements required as input to a radiative transfer program to predict the radiance level at the entrance pupil of the orbital sensor are discussed, and the ground instrumentation is described.

  14. A developmental study of latent absolute pitch memory.

    PubMed

    Jakubowski, Kelly; Müllensiefen, Daniel; Stewart, Lauren

    2017-03-01

    The ability to recall the absolute pitch level of familiar music (latent absolute pitch memory) is widespread in adults, in contrast to the rare ability to label single pitches without a reference tone (overt absolute pitch memory). The present research investigated the developmental profile of latent absolute pitch (AP) memory and explored individual differences related to this ability. In two experiments, 288 children from 4 to12 years of age performed significantly above chance at recognizing the absolute pitch level of familiar melodies. No age-related improvement or decline, nor effects of musical training, gender, or familiarity with the stimuli were found in regard to latent AP task performance. These findings suggest that latent AP memory is a stable ability that is developed from as early as age 4 and persists into adulthood.

  15. Absolute Position Encoders With Vertical Image Binning

    NASA Technical Reports Server (NTRS)

    Leviton, Douglas B.

    2005-01-01

    Improved optoelectronic patternrecognition encoders that measure rotary and linear 1-dimensional positions at conversion rates (numbers of readings per unit time) exceeding 20 kHz have been invented. Heretofore, optoelectronic pattern-recognition absoluteposition encoders have been limited to conversion rates <15 Hz -- too low for emerging industrial applications in which conversion rates ranging from 1 kHz to as much as 100 kHz are required. The high conversion rates of the improved encoders are made possible, in part, by use of vertically compressible or binnable (as described below) scale patterns in combination with modified readout sequences of the image sensors [charge-coupled devices (CCDs)] used to read the scale patterns. The modified readout sequences and the processing of the images thus read out are amenable to implementation by use of modern, high-speed, ultra-compact microprocessors and digital signal processors or field-programmable gate arrays. This combination of improvements makes it possible to greatly increase conversion rates through substantial reductions in all three components of conversion time: exposure time, image-readout time, and image-processing time.

  16. NIST Diffusion Data Center

    National Institute of Standards and Technology Data Gateway

    NIST Diffusion Data Center (Web, free access)   The NIST Diffusion Data Center is a collection of over 14,100 international papers, theses, and government reports on diffusion published before 1980.

  17. Parallel flow diffusion battery

    DOEpatents

    Yeh, Hsu-Chi; Cheng, Yung-Sung

    1984-08-07

    A parallel flow diffusion battery for determining the mass distribution of an aerosol has a plurality of diffusion cells mounted in parallel to an aerosol stream, each diffusion cell including a stack of mesh wire screens of different density.

  18. Parallel flow diffusion battery

    DOEpatents

    Yeh, H.C.; Cheng, Y.S.

    1984-01-01

    A parallel flow diffusion battery for determining the mass distribution of an aerosol has a plurality of diffusion cells mounted in parallel to an aerosol stream, each diffusion cell including a stack of mesh wire screens of different density.

  19. Transport of absolute angular momentum in quasi-axisymmetric equatorial jet streams

    NASA Technical Reports Server (NTRS)

    Read, P. L.

    1986-01-01

    It is well known that prograde equatorial jet stresses cannot occur in an axisymmetric inviscid fluid, owing to the constraints of local angular momentum conservation. For a viscous fluid, the constraints of mass conservation prevent the formation of any local maximum of absolute angular momentum (m) without a means of transferring m against its gradient (delta m) in the meridional plane. The circumstances under which m can be diffused up-gradient by normal molecular viscosity are derived, and illustrated with reference to numerical simulations of axisymmetric flows in a cylindrical annulus. Viscosity is shown to act so as to tend to expel m from the interior outwards from the rotation axis. Such an effect can produce local super-rotation even in a mechanically isolated fluid. The tendency of viscosity to result in the expulsion of m is shown to be analogous in certain respects to a vorticity-mixing hypothesis for the effects of non-axisymmetric eddies of the zonally-averaged flow. It is shown how the advective and diffusive transport of m by non-axisymmetric eddies can be represented by the Transformed Eulerian Mean meridional circulation and the Eliassen-Palm (EP) flux of Andrews and McIntyre respectively, in the zonal mean. Constraints on the form and direction of the EP flux in an advective/diffusive flow for such eddies are derived, by analogy with similar constraints on the diffusive flux of m due to viscosity.

  20. 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

  1. FRACTIONAL PEARSON DIFFUSIONS.

    PubMed

    Leonenko, Nikolai N; Meerschaert, Mark M; Sikorskii, Alla

    2013-07-15

    Pearson diffusions are governed by diffusion equations with polynomial coefficients. Fractional Pearson diffusions are governed by the corresponding time-fractional diffusion equation. They are useful for modeling sub-diffusive phenomena, caused by particle sticking and trapping. This paper provides explicit strong solutions for fractional Pearson diffusions, using spectral methods. It also presents stochastic solutions, using a non-Markovian inverse stable time change.

  2. FRACTIONAL PEARSON DIFFUSIONS

    PubMed Central

    Leonenko, Nikolai N.; Meerschaert, Mark M.

    2013-01-01

    Pearson diffusions are governed by diffusion equations with polynomial coefficients. Fractional Pearson diffusions are governed by the corresponding time-fractional diffusion equation. They are useful for modeling sub-diffusive phenomena, caused by particle sticking and trapping. This paper provides explicit strong solutions for fractional Pearson diffusions, using spectral methods. It also presents stochastic solutions, using a non-Markovian inverse stable time change. PMID:23626377

  3. Absolute Geodetic Rotation Measurement Using Atom Interferometry

    SciTech Connect

    Stockton, J. K.; Takase, K.; Kasevich, M. A.

    2011-09-23

    We demonstrate a cold-atom interferometer gyroscope which overcomes accuracy and dynamic range limitations of previous atom interferometer gyroscopes. We show how the instrument can be used for precise determination of latitude, azimuth (true north), and Earth's rotation rate. Spurious noise terms related to multiple-path interferences are suppressed by employing a novel time-skewed pulse sequence. Extended versions of this instrument appear capable of meeting the stringent requirements for inertial navigation, geodetic applications of Earth's rotation rate determination, and tests of general relativity.

  4. Absolute calorimetric calibration of low energy brachytherapy sources

    NASA Astrophysics Data System (ADS)

    Stump, Kurt E.

    In the past decade there has been a dramatic increase in the use of permanent radioactive source implants in the treatment of prostate cancer. A small radioactive source encapsulated in a titanium shell is used in this type of treatment. The radioisotopes used are generally 125I or 103Pd. Both of these isotopes have relatively short half-lives, 59.4 days and 16.99 days, respectively, and have low-energy emissions and a low dose rate. These factors make these sources well suited for this application, but the calibration of these sources poses significant metrological challenges. The current standard calibration technique involves the measurement of ionization in air to determine the source air-kerma strength. While this has proved to be an improvement over previous techniques, the method has been shown to be metrologically impure and may not be the ideal means of calbrating these sources. Calorimetric methods have long been viewed to be the most fundamental means of determining source strength for a radiation source. This is because calorimetry provides a direct measurement of source energy. However, due to the low energy and low power of the sources described above, current calorimetric methods are inadequate. This thesis presents work oriented toward developing novel methods to provide direct and absolute measurements of source power for low-energy low dose rate brachytherapy sources. The method is the first use of an actively temperature-controlled radiation absorber using the electrical substitution method to determine total contained source power of these sources. The instrument described operates at cryogenic temperatures. The method employed provides a direct measurement of source power. The work presented here is focused upon building a metrological foundation upon which to establish power-based calibrations of clinical-strength sources. To that end instrument performance has been assessed for these source strengths. The intent is to establish the limits of

  5. Extremely slow intramolecular diffusion in unfolded protein L.

    PubMed

    Waldauer, Steven A; Bakajin, Olgica; Lapidus, Lisa J

    2010-08-03

    A crucial parameter in many theories of protein folding is the rate of diffusion over the energy landscape. Using a microfluidic mixer we have observed the rate of intramolecular diffusion within the unfolded B1 domain of protein L before it folds. The diffusion-limited rate of intramolecular contact is about 20 times slower than the rate in 6 M GdnHCl, and because in these conditions the protein is also more compact, the intramolecular diffusion coefficient decreases 100-500 times. The dramatic slowdown in diffusion occurs within the 250 micros mixing time of the mixer, and there appears to be no further evolution of this rate before reaching the transition state of folding. We show that observed folding rates are well predicted by a Kramers model with a denaturant-dependent diffusion coefficient and speculate that this diffusion coefficient is a significant contribution to the observed rate of folding.

  6. Quantifying protein diffusion and capture on filaments.

    PubMed

    Reithmann, Emanuel; Reese, Louis; Frey, Erwin

    2015-02-17

    The functional relevance of regulating proteins is often limited to specific binding sites such as the ends of microtubules or actin-filaments. A localization of proteins on these functional sites is of great importance. We present a quantitative theory for a diffusion and capture process, where proteins diffuse on a filament and stop diffusing when reaching the filament's end. It is found that end-association after one-dimensional diffusion is the main source for tip-localization of such proteins. As a consequence, diffusion and capture is highly efficient in enhancing the reaction velocity of enzymatic reactions, where proteins and filament ends are to each other as enzyme and substrate. We show that the reaction velocity can effectively be described within a Michaelis-Menten framework. Together, one-dimensional diffusion and capture beats the (three-dimensional) Smoluchowski diffusion limit for the rate of protein association to filament ends.

  7. Entrenched Geographical and Socioeconomic Disparities in Child Mortality: Trends in Absolute and Relative Inequalities in Cambodia

    PubMed Central

    Jimenez-Soto, Eliana; Durham, Jo; Hodge, Andrew

    2014-01-01

    Background Cambodia has made considerable improvements in mortality rates for children under the age of five and neonates. These improvements may, however, mask considerable disparities between subnational populations. In this paper, we examine the extent of the country's child mortality inequalities. Methods Mortality rates for children under-five and neonates were directly estimated using the 2000, 2005 and 2010 waves of the Cambodian Demographic Health Survey. Disparities were measured on both absolute and relative scales using rate differences and ratios, and where applicable, slope and relative indices of inequality by levels of rural/urban location, regions and household wealth. Findings Since 2000, considerable reductions in under-five and to a lesser extent in neonatal mortality rates have been observed. This mortality decline has, however, been accompanied by an increase in relative inequality in both rates of child mortality for geography-related stratifying markers. For absolute inequality amongst regions, most trends are increasing, particularly for neonatal mortality, but are not statistically significant. The only exception to this general pattern is the statistically significant positive trend in absolute inequality for under-five mortality in the Coastal region. For wealth, some evidence for increases in both relative and absolute inequality for neonates is observed. Conclusion Despite considerable gains in reducing under-five and neonatal mortality at a national level, entrenched and increased geographical and wealth-based inequality in mortality, at least on a relative scale, remain. As expected, national progress seems to be associated with the period of political and macroeconomic stability that started in the early 2000s. However, issues of quality of care and potential non-inclusive economic growth might explain remaining disparities, particularly across wealth and geography markers. A focus on further addressing key supply and demand side

  8. ABSOLUTE PROPERTIES OF THE ECLIPSING BINARY STAR BF DRACONIS

    SciTech Connect

    Sandberg Lacy, Claud H.; Torres, Guillermo; Fekel, Francis C.; Sabby, Jeffrey A.; Claret, Antonio E-mail: gtorres@cfa.harvard.edu E-mail: jsabby@siue.edu

    2012-06-15

    BF Dra is now known to be an eccentric double-lined F6+F6 binary star with relatively deep (0.7 mag) partial eclipses. Previous studies of the system are improved with 7494 differential photometric observations from the URSA WebScope and 9700 from the NFO WebScope, 106 high-resolution spectroscopic observations from the Tennessee State University 2 m automatic spectroscopic telescope and the 1 m coude-feed spectrometer at Kitt Peak National Observatory, and 31 accurate radial velocities from the CfA. Very accurate (better than 0.6%) masses and radii are determined from analysis of the two new light curves and four radial velocity curves. Theoretical models match the absolute properties of the stars at an age of about 2.72 Gyr and [Fe/H] = -0.17, and tidal theory correctly confirms that the orbit should still be eccentric. Our observations of BF Dra constrain the convective core overshooting parameter to be larger than about 0.13 H{sub p}. We find, however, that standard tidal theory is unable to match the observed slow rotation rates of the components' surface layers.

  9. Weighted Wilcoxon-type Smoothly Clipped Absolute Deviation Method

    PubMed Central

    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

  10. Cosmic backgrounds of relic gravitons and their absolute normalization

    NASA Astrophysics Data System (ADS)

    Giovannini, Massimo

    2014-11-01

    Provided the consistency relations are not violated, the recent BICEP2 observations pin down the absolute normalization, the spectral slope and the maximal frequency of the cosmic graviton background produced during inflation. The properly normalized spectra are hereby computed from the lowest frequencies (of the order of the present Hubble rate) up to the highest frequency range in the GHz region. Deviations from the conventional paradigm cannot be excluded and are examined by allowing for different physical possibilities including, in particular, a running of the tensor spectral index, an explicit breaking of the consistency relations and a spike in the high-frequency tail of the spectrum coming either from a post-inflationary phase dominated by a stiff fluid or from the contribution of waterfall fields in a hybrid inflationary context. The direct determinations of the tensor to scalar ratio at low frequencies, if confirmed by the forthcoming observations, will also affect and constrain the high-frequency uncertainties. The limits on the cosmic graviton backgrounds coming from wide-band interferometers (such as LIGO/Virgo, LISA and BBO/DECIGO) together with a more accurate scrutiny of the tensor B-mode polarization at low frequencies will set direct bounds on the post-inflationary evolution and on other unconventional completions of the standard lore.

  11. Increased rate of positive biopsies using a combination of MR-Tomography, spectroscopy and diffusion-weighted magnetic resonance imaging prior to prostate biopsies in patients with persistent elevated prostate-specific antigen values: A retrospective analysis

    PubMed Central

    Lunacek, A.; Simon, J.; Bernt, R.; Huber, M.; Plas, E.; Mrstik, C.

    2013-01-01

    Purpose: Persistently elevated prostate-specific antigen (PSA) values following negative biopsies result in a diagnostic dilemma. In order to improve detection rates in patients with former negative biopsies and persistently elevated PSA values, magnetic resonance tomography (MRT), magnetic resonance spectroscopy (MRS), and diffusion-weighted magnetic resonance imaging (DW-MRI) were performed prior to prostate rebiopsies. Materials and Methods: Over a 14-month period, 67 patients (mean age of 66 years) with a history of 1-5 negative biopsies underwent endorectal magnetic resonance imaging (MRI) using T2-weighted MRT MRS and DW-MRI before an additional prostate biopsy was performed. Subsequently, 5 contrast-enhanced transrectal ultrasound-guided biopsies were performed according to a 10-core systematic scheme. Out of the 67 men, 25 patients had positive biopsies and opted for radical prostatectomy. Histological evaluation of cancer localization, PSA, diameters of primary tumors, numbers and diameters of satellite tumors, prostate volume, and staging pathology was performed. These findings were compared with MRI and MRS results. Results: Serum PSA levels ranged from 3.1 to 19.5 g/ml (median level of 7.96 ng/ml). After the 25 patients underwent radical prostatectomy, analysis of 20 whole-mount sections of 25 radical retropubic prostatectomy (RPE) specimens presented results agreeing with the tumor location from MRI and MRS data. Conclusions: The aim of image-guided diagnostics should be to provide more critical information prior to biopsy. Furthermore, the acquisition of such data is important for better risk stratification in therapeutic decisions. PMID:23798861

  12. Mini-implants and miniplates generate sub-absolute and absolute anchorage.

    PubMed

    Consolaro, Alberto

    2014-01-01

    The functional demand imposed on bone promotes changes in the spatial properties of osteocytes as well as in their extensions uniformly distributed throughout the mineralized surface. Once spatial deformation is established, osteocytes create the need for structural adaptations that result in bone formation and resorption that happen to meet the functional demands. The endosteum and the periosteum are the effectors responsible for stimulating adaptive osteocytes in the inner and outer surfaces. Changes in shape, volume and position of the jaws as a result of skeletal correction of the maxilla and mandible require anchorage to allow bone remodeling to redefine morphology, esthetics and function as a result of spatial deformation conducted by orthodontic appliances. Examining the degree of changes in shape, volume and structural relationship of areas where mini-implants and miniplates are placed allows us to classify mini-implants as devices of subabsolute anchorage and miniplates as devices of absolute anchorage.

  13. Absolute dose verifications in small photon fields using BANGTM gel

    NASA Astrophysics Data System (ADS)

    Scheib, S. G.; Schenkel, Y.; Gianolini, S.

    2004-01-01

    Polymer gel dosimeters change their magnetic resonance (MR) and optical properties with the absorbed dose when irradiated and are suitable for narrow photon beam dosimetry in radiosurgery. Such dosimeters enable relative and absolute 3D dose verifications in order to check the entire treatment chain from imaging to dose application during commissioning and quality assurance. For absolute 3D dose verifications in radiosurgery using Gamma Knife B, commercially available BANGTM Gels (BANG 25 Gy and BANG 3 Gy) together with dedicated phantoms were chosen in order to determine the potential of absolute gel dosimetry in radiosurgery.

  14. Measuring the absolute magnetic field using high-Tc SQUID

    NASA Astrophysics Data System (ADS)

    He, D. F.; Itozaki, H.

    2006-06-01

    SQUID normally can only measure the change of magnetic field instead of the absolute value of magnetic field. Using a compensation method, a mobile SQUID, which could keep locked when moving in the earth's magnetic field, was developed. Using the mobile SQUID, it was possible to measure the absolute magnetic field. The absolute value of magnetic field could be calculated from the change of the compensation output when changing the direction of the SQUID in a magnetic field. Using this method and the mobile SQUID, we successfully measured the earth's magnetic field in our laboratory.

  15. Absolute Antenna Calibration at the US National Geodetic Survey

    NASA Astrophysics Data System (ADS)

    Mader, G. L.; Bilich, A. L.

    2012-12-01

    Geodetic GNSS applications routinely demand millimeter precision and extremely high levels of accuracy. To achieve these accuracies, measurement and instrument biases at the centimeter to millimeter level must be understood. One of these biases is the antenna phase center, the apparent point of signal reception for a GNSS antenna. It has been well established that phase center patterns differ between antenna models and manufacturers; additional research suggests that the addition of a radome or the choice of antenna mount can significantly alter those a priori phase center patterns. For the more demanding GNSS positioning applications and especially in cases of mixed-antenna networks, it is all the more important to know antenna phase center variations as a function of both elevation and azimuth in the antenna reference frame and incorporate these models into analysis software. Determination of antenna phase center behavior is known as "antenna calibration". Since 1994, NGS has computed relative antenna calibrations for more than 350 antennas. In recent years, the geodetic community has moved to absolute calibrations - the IGS adopted absolute antenna phase center calibrations in 2006 for use in their orbit and clock products, and NGS's CORS group began using absolute antenna calibration upon the release of the new CORS coordinates in IGS08 epoch 2005.00 and NAD 83(2011,MA11,PA11) epoch 2010.00. Although NGS relative calibrations can be and have been converted to absolute, it is considered best practice to independently measure phase center characteristics in an absolute sense. Consequently, NGS has developed and operates an absolute calibration system. These absolute antenna calibrations accommodate the demand for greater accuracy and for 2-dimensional (elevation and azimuth) parameterization. NGS will continue to provide calibration values via the NGS web site www.ngs.noaa.gov/ANTCAL, and will publish calibrations in the ANTEX format as well as the legacy ANTINFO

  16. Absolute distance measurement by dual-comb nonlinear asynchronous optical sampling.

    PubMed

    Zhang, Hongyuan; Wei, Haoyun; Wu, Xuejian; Yang, Honglei; Li, Yan

    2014-03-24

    A dual-comb nonlinear asynchronous optical sampling method is proposed to simplify determination of the time interval and extend the non-ambiguity range in absolute length measurements. Type II second harmonic generation facilitates curve fitting in determining the time interval between adjacent pulses. Meanwhile, the non-ambiguity range is extended by adjusting the repetition rate of the signal laser. The performance of the proposed method is compared with a heterodyne interferometer. Results show that the system achieves a maximum residual of 100.6 nm and an uncertainty of 1.48 μm in a 0.5 ms acquisition time. With longer acquisition time, the uncertainty can be reduced to 166.6 nm for 50 ms and 82.9 nm for 500 ms. Moreover, the extension of the non-ambiguity range is demonstrated by measuring an absolute distance beyond the inherent range determined by the fixed repetition rate.

  17. A New Absolute Plate Motion Model for Africa

    NASA Astrophysics Data System (ADS)

    Maher, S. M.; Wessel, P.; Müller, D.; Harada, Y.

    2013-12-01

    The India-Eurasia collision, a change in relative plate motion between Australia and Antarctica, and the coeval ages of the Hawaiian Emperor Bend (HEB) and Louisville Bend of ~Chron 22-21 all provide convincing evidence of a global tectonic plate reorganization at ~50 Ma. Yet if it were a truly global event, then there should be a contemporaneous change in Africa absolute plate motion (APM) reflected by physical evidence somewhere on the Africa plate. This evidence might be visible in the Reunion-Mascarene bend, which exhibits many HEB-like features such as a large angular change close to ~50 Ma. Recently, the Reunion hotpot trail has been interpreted as a continental feature with incidental hotspot volcanism. Here we propose the alternative hypothesis that the northern portion of the chain between Saya de Malha and the Seychelles (Mascarene Plateau) formed as the Reunion hotspot was situated on the Carlsberg Ridge, contemporaneously forming the Chagos-Laccadive Ridge on the India plate. We have created a 4-stage model that explores how a simple APM model fitting the Mascarene Plateau can also satisfy the age progressions and geometry of other hotspot trails on the Africa plate. This type of model could explain the apparent bifurcation of the Tristan hotspot chain, the age reversals seen along the Walvis Ridge and the diffuse nature of the St. Helena chain. To test this hypothesis we have made a new African APM model that goes back to ~80 Ma using a modified version of the Hybrid Polygonal Finite Rotation Method. This method uses seamount chains and their associated hotspots as geometric constraints for the model, and seamount age dates to determine its motion through time. The positions of the hotspots can be moved to get the best fit for the model and to explore the possibility that the ~50 Ma bend in the Reunion-Mascarene chain reflects Africa plate motion. We will examine how well this model can predict the key features reflecting Africa plate motion and

  18. Monochromator-Based Absolute Calibration of Radiation Thermometers

    NASA Astrophysics Data System (ADS)

    Keawprasert, T.; Anhalt, K.; Taubert, D. R.; Hartmann, J.

    2011-08-01

    A monochromator integrating-sphere-based spectral comparator facility has been developed to calibrate standard radiation thermometers in terms of the absolute spectral radiance responsivity, traceable to the PTB cryogenic radiometer. The absolute responsivity calibration has been improved using a 75 W xenon lamp with a reflective mirror and imaging optics to a relative standard uncertainty at the peak wavelength of approximately 0.17 % ( k = 1). Via a relative measurement of the out-of-band responsivity, the spectral responsivity of radiation thermometers can be fully characterized. To verify the calibration accuracy, the absolutely calibrated radiation thermometer is used to measure Au and Cu freezing-point temperatures and then to compare the obtained results with the values obtained by absolute methods, resulting in T - T 90 values of +52 mK and -50 mK for the gold and copper fixed points, respectively.

  19. Gibbs Paradox Revisited from the Fluctuation Theorem with Absolute Irreversibility

    NASA Astrophysics Data System (ADS)

    Murashita, Yûto; Ueda, Masahito

    2017-02-01

    The inclusion of the factor ln (1 /N !) in the thermodynamic entropy proposed by Gibbs is shown to be equivalent to the validity of the fluctuation theorem with absolute irreversibility for gas mixing.

  20. 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.