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Sample records for oximetry wave variation

  1. Pulse Oximetry Wave Variation as a Noninvasive Tool to Assess Volume Status in Cardiac Surgery

    PubMed Central

    Westphal, Glauco A; Silva, Eliezer; Gonçalves, Anderson Roman; Filho, Milton Caldeira; Poli-de-Figueiredo, Luíz F

    2009-01-01

    OBJECTIVE: To compare variations of plethysmographic wave amplitude (ΔPpleth) and to determine the percent difference between inspiratory and expiratory pulse pressure (ΔPp) cutoff values for volume responsiveness in a homogenous population of postoperative cardiac surgery patients. INTRODUCTION: Intra-thoracic pressure variations interfere with stroke volume variation. Pulse pressure variations through arterial lines during mechanical ventilation have been recommended for the estimation of fluid responsiveness. Pulse oximetry may offer a non-invasive plethysmographic method to evaluate pulse pressure; this may be useful for guiding fluid replacement. METHODS: Controlled, prospective study in cardiac surgery patients under controlled ventilation. Simultaneous digital recordings of arterial pressure and plethysmographic waves were performed. ΔPp, systolic pressure (ΔPs), ΔPpleth, and systolic component (ΔSpleth) were calculated. A ΔPp ≥ 13% identified fluid-responsive patients. Volume expansion was performed in responsive subjects. Systolic and amplitude components of pressure and plethysmographic waves were compared. RESULTS: In 50 measurements from 43 patients, ΔPp was correlated with (Ppleth (r=0.90, p<0.001), (Ps (r=0.90, p<0.001), and (Spleth (r=0.73, p<0.001). An aArea under ROC curve (AUC) identified the fluid responsiveness thresholds: (Ppleth of 11% (AUC = 0.95±0.04), (Ps of 8% (AUC=0.93±0.05), and (Spleth of 32% (AUC=0.82±0.07). A (Ppleth value ≥ 11% predicted (Pp ≥ 13% with 100% specificity and 91% sensitivity. Volume expansion, performed in 20 patients, changed (Pp, (Ppleth, (Ps and (Spleth significantly (p<0.008). CONCLUSIONS: ΔPpleth is well correlated with ΔPp and constitutes a simple and non-invasive method for assessing fluid responsiveness in patients following cardiac surgery. PMID:19488592

  2. Relation between respiratory variations in pulse oximetry plethysmographic waveform amplitude and arterial pulse pressure in ventilated patients

    PubMed Central

    Cannesson, Maxime; Besnard, Cyril; Durand, Pierre G; Bohé, Julien; Jacques, Didier

    2005-01-01

    Introduction Respiratory variation in arterial pulse pressure is a reliable predictor of fluid responsiveness in mechanically ventilated patients with circulatory failure. The main limitation of this method is that it requires an invasive arterial catheter. Both arterial and pulse oximetry plethysmographic waveforms depend on stroke volume. We conducted a prospective study to evaluate the relationship between respiratory variation in arterial pulse pressure and respiratory variation in pulse oximetry plethysmographic (POP) waveform amplitude. Method This prospective clinical investigation was conducted in 22 mechanically ventilated patients. Respiratory variation in arterial pulse pressure and respiratory variation in POP waveform amplitude were recorded simultaneously in a beat-to-beat evaluation, and were compared using a Spearman correlation test and a Bland–Altman analysis. Results There was a strong correlation (r2 = 0.83; P < 0.001) and a good agreement (bias = 0.8 ± 3.5%) between respiratory variation in arterial pulse pressure and respiratory variation in POP waveform amplitude. A respiratory variation in POP waveform amplitude value above 15% allowed discrimination between patients with respiratory variation in arterial pulse pressure above 13% and those with variation of 13% or less (positive predictive value 100%). Conclusion Respiratory variation in arterial pulse pressure above 13% can be accurately predicted by a respiratory variation in POP waveform amplitude above 15%. This index has potential applications in patients who are not instrumented with an intra-arterial catheter. PMID:16277719

  3. Higher temporal resolution is necessary for continuous-wave near -infrared spectrophotometric monitors in both cerebral and muscular tissue oximetry

    NASA Astrophysics Data System (ADS)

    Chihara, Eiichi; Shiga, Toshikazu; Tanabe, Kazuhisa; Tanaka, Yoshifumi

    1997-12-01

    Conventional near infrared spectrophotometric monitors have temporal resolution of less than about 1 Hz. However, physiological Hb signals such as pulsation and muscle contraction have higher frequency than 1 Hz. Insufficient sampling rates inevitably lead aliasing of the recorded signals in tissue oximetry for both brain and muscle. Cerebral Hb signals (57 y.o. female artificially ventilated under general anesthesia) and thigh muscle (22 y.o. male with 20 W - 240 W exercise at 1 Hz cycling in semirecumbent ergometer) were measured with NIRS monitor with temporal resolution of 10 Hz (OMRON Co. Ltd., Japan). The detail of physiological fluctuations such as pulsation, ventilation, and muscle pumping was clearly recognized with a 10 Hz sampling. The comparison with recalculated waveforms at slower sampling rate (0.5 Hz, 1 Hz, 2 Hz) revealed that with slower sampling than 1 Hz cerebral respiratory waves were deformed by pulsation, and that magnitudes of muscle pumping could not be properly evaluated in dynamic exercise. In both pulsatile and muscle contractile cycle a phase delay between oxygenated component and deoxygenated one was also detected, which has been overlooked by conventional NIRS monitoring.

  4. Higher temporal resolution is necessary for continuous-wave near -infrared spectrophotometric monitors in both cerebral and muscular tissue oximetry

    NASA Astrophysics Data System (ADS)

    Chihara, Eiichi; Shiga, Toshikazu; Tanabe, Kazuhisa; Tanaka, Yoshifumi

    1998-01-01

    Conventional near infrared spectrophotometric monitors have temporal resolution of less than about 1 Hz. However, physiological Hb signals such as pulsation and muscle contraction have higher frequency than 1 Hz. Insufficient sampling rates inevitably lead aliasing of the recorded signals in tissue oximetry for both brain and muscle. Cerebral Hb signals (57 y.o. female artificially ventilated under general anesthesia) and thigh muscle (22 y.o. male with 20 W - 240 W exercise at 1 Hz cycling in semirecumbent ergometer) were measured with NIRS monitor with temporal resolution of 10 Hz (OMRON Co. Ltd., Japan). The detail of physiological fluctuations such as pulsation, ventilation, and muscle pumping was clearly recognized with a 10 Hz sampling. The comparison with recalculated waveforms at slower sampling rate (0.5 Hz, 1 Hz, 2 Hz) revealed that with slower sampling than 1 Hz cerebral respiratory waves were deformed by pulsation, and that magnitudes of muscle pumping could not be properly evaluated in dynamic exercise. In both pulsatile and muscle contractile cycle a phase delay between oxygenated component and deoxygenated one was also detected, which has been overlooked by conventional NIRS monitoring.

  5. Respiratory variations in the photoplethysmographic waveform amplitude depend on type of pulse oximetry device.

    PubMed

    Høiseth, Lars Øivind; Hoff, Ingrid Elise; Hagen, Ove Andreas; Kirkebøen, Knut Arvid; Landsverk, Svein Aslak

    2016-06-01

    Respiratory variations in the photoplethysmographic waveform amplitude predict fluid responsiveness under certain conditions. Processing of the photoplethysmographic signal may vary between different devices, and may affect respiratory amplitude variations calculated by the standard formula. The aim of the present analysis was to explore agreement between respiratory amplitude variations calculated using photoplethysmographic waveforms available from two different pulse oximeters. Analysis of registrations before and after fluid loads performed before and after open-heart surgery (aortic valve replacement and/or coronary artery bypass grafting) with patients on controlled mechanical ventilation. Photoplethysmographic (Nellcor and Masimo pulse oximeters) and arterial pressure waveforms were recorded. Amplitude variations induced by ventilation were calculated and averaged over ten respiratory cycles. Agreements for absolute values are presented in scatterplots (with least median square regression through the origin, LMSO) and Bland-Altman plots. Agreement for trending presented in a four-quadrant plot. Agreement between respiratory photoplethysmographic amplitude variations from the two pulse oximeters was poor with LMSO ΔPOPNellc = 1.5 × ΔPOPMas and bias ± limits of agreement 7.4 ± 23 %. Concordance rate with a fluid load was 91 %. Agreement between respiratory variations in the photoplethysmographic waveform amplitude calculated from the available signals output by two different pulse oximeters was poor, both evaluated by LMSO and Bland-Altman plot. Respiratory amplitude variations from the available signals output by these two pulse oximeters are not interchangeable. PMID:26067403

  6. Pulse oximetry in pediatric practice.

    PubMed

    Fouzas, Sotirios; Priftis, Kostas N; Anthracopoulos, Michael B

    2011-10-01

    The introduction of pulse oximetry in clinical practice has allowed for simple, noninvasive, and reasonably accurate estimation of arterial oxygen saturation. Pulse oximetry is routinely used in the emergency department, the pediatric ward, and in pediatric intensive and perioperative care. However, clinically relevant principles and inherent limitations of the method are not always well understood by health care professionals caring for children. The calculation of the percentage of arterial oxyhemoglobin is based on the distinct characteristics of light absorption in the red and infrared spectra by oxygenated versus deoxygenated hemoglobin and takes advantage of the variation in light absorption caused by the pulsatility of arterial blood. Computation of oxygen saturation is achieved with the use of calibration algorithms. Safe use of pulse oximetry requires knowledge of its limitations, which include motion artifacts, poor perfusion at the site of measurement, irregular rhythms, ambient light or electromagnetic interference, skin pigmentation, nail polish, calibration assumptions, probe positioning, time lag in detecting hypoxic events, venous pulsation, intravenous dyes, and presence of abnormal hemoglobin molecules. In this review we describe the physiologic principles and limitations of pulse oximetry, discuss normal values, and highlight its importance in common pediatric diseases, in which the principle mechanism of hypoxemia is ventilation/perfusion mismatch (eg, asthma exacerbation, acute bronchiolitis, pneumonia) versus hypoventilation (eg, laryngotracheitis, vocal cord dysfunction, foreign-body aspiration in the larynx or trachea). Additional technologic advancements in pulse oximetry and its incorporation into evidence-based clinical algorithms will improve the efficiency of the method in daily pediatric practice. PMID:21930554

  7. Pathway to Retinal Oximetry

    PubMed Central

    Beach, James

    2014-01-01

    Events and discoveries in oxygen monitoring over the past two centuries are presented as the background from which oximetry of the human retina evolved. Achievements and the people behind them are discussed, showing parallels between the work in tissue measurements and later in the eye. Developments in the two-wavelength technique for oxygen saturation measurements in retinal vessels are shown to exploit the forms of imaging technology available over time. The last section provides a short summary of the recent research in retinal diseases using vessel oximetry. PMID:25237591

  8. Variational modelling of nonlinear water waves

    NASA Astrophysics Data System (ADS)

    Kalogirou, Anna; Bokhove, Onno

    2015-11-01

    Mathematical modelling of water waves is demonstrated by investigating variational methods. A potential flow water wave model is derived using variational techniques and extented to include explicit time-dependence, leading to non-autonomous dynamics. As a first example, we consider the problem of a soliton splash in a long wave channel with a contraction at its end, resulting after a sluice gate is removed at a finite time. The removal of the sluice gate is included in the variational principle through a time-dependent gravitational potential. A second example involving non-autonomous dynamics concerns the motion of a free surface in a vertical Hele-Shaw cell. Explicit time-dependence now enters the model through a linear damping term due to the effect of wall friction and a term representing the motion of an artificially driven wave pump. In both cases, the model is solved numerically using a Galerkin FEM and the numerical results are compared to wave structures observed in experiments. The water wave model is also adapted to accommodate nonlinear ship dynamics. The novelty is this case is the coupling between the water wave dynamics, the ship dynamics and water line dynamics on the ship. For simplicity, we consider a simple ship structure consisting of V-shaped cross-sections.

  9. Photonic textiles for pulse oximetry.

    PubMed

    Rothmaier, Markus; Selm, Bärbel; Spichtig, Sonja; Haensse, Daniel; Wolf, Martin

    2008-08-18

    Biomedical sensors, integrated into textiles would enable monitoring of many vitally important physiological parameters during our daily life. In this paper we demonstrate the design and performance of a textile based pulse oximeter, operating on the forefinger tip in transmission mode. The sensors consisted of plastic optical fibers integrated into common fabrics. To emit light to the human tissue and to collect transmitted light the fibers were either integrated into a textile substrate by embroidery (producing microbends with a nominal diameter of 0.5 to 2 mm) or the fibers inside woven patterns have been altered mechanically after fabric production. In our experiments we used a two-wavelength approach (690 and 830 nm) for pulse wave acquisition and arterial oxygen saturation calculation. We have fabricated different specimens to study signal yield and quality, and a cotton glove, equipped with textile based light emitter and detector, has been used to examine movement artifacts. Our results show that textile-based oximetry is feasible with sufficient data quality and its potential as a wearable health monitoring device is promising. PMID:18711536

  10. Lanczos steps to improve variational wave functions

    NASA Astrophysics Data System (ADS)

    Becca, Federico; Hu, Wen-Jun; Iqbal, Yasir; Parola, Alberto; Poilblanc, Didier; Sorella, Sandro

    2015-09-01

    Gutzwiller-projected fermionic states can be efficiently implemented within quantum Monte Carlo calculations to define extremely accurate variational wave functions for Heisenberg models on frustrated two-dimensional lattices, not only for the ground state but also for low-energy excitations. The application of few Lanczos steps on top of these states further improves their accuracy, allowing calculations on large clusters. In addition, by computing both the energy and its variance, it is possible to obtain reliable estimations of exact results. Here, we report the cases of the frustrated Heisenberg models on square and Kagome lattices.

  11. Variational wave functions for homogenous Bose systems

    SciTech Connect

    Sueto, Andras; Szepfalusy, Peter

    2008-02-15

    We study variational wave functions of the product form, factorizing according to the wave vectors k, for the ground state of a system of bosons interacting via positive pair interactions with a positive Fourier transform. Our trial functions are members of different orthonormal bases in Fock space. Each basis contains a quasiparticle vacuum state and states with an arbitrary finite number of quasiparticles. One of the bases is that of Valatin and Butler (VB), introduced fifty years ago and parametrized by an infinite set of variables determining Bogoliubov's canonical transformation for each k. In another case, inspired by Nozieres and Saint James the canonical transformation for k=0 is replaced by a shift in the creation/annihilation operators. For the VB basis we prove that the lowest energy is obtained in a state with {approx}{radical}(volume) quasiparticles in the zero mode. The number of k=0 physical particles is of the order of the volume and its fluctuation is anomalously large, resulting in an excess energy. The same fluctuation is normal in the second type of optimized bases, the minimum energy is smaller and is attained in a vacuum state. Associated quasiparticle theories and questions about the gap in their spectrum are also discussed.

  12. Optimal filter bandwidth for pulse oximetry

    NASA Astrophysics Data System (ADS)

    Stuban, Norbert; Niwayama, Masatsugu

    2012-10-01

    Pulse oximeters contain one or more signal filtering stages between the photodiode and microcontroller. These filters are responsible for removing the noise while retaining the useful frequency components of the signal, thus improving the signal-to-noise ratio. The corner frequencies of these filters affect not only the noise level, but also the shape of the pulse signal. Narrow filter bandwidth effectively suppresses the noise; however, at the same time, it distorts the useful signal components by decreasing the harmonic content. In this paper, we investigated the influence of the filter bandwidth on the accuracy of pulse oximeters. We used a pulse oximeter tester device to produce stable, repetitive pulse waves with digitally adjustable R ratio and heart rate. We built a pulse oximeter and attached it to the tester device. The pulse oximeter digitized the current of its photodiode directly, without any analog signal conditioning. We varied the corner frequency of the low-pass filter in the pulse oximeter in the range of 0.66-15 Hz by software. For the tester device, the R ratio was set to R = 1.00, and the R ratio deviation measured by the pulse oximeter was monitored as a function of the corner frequency of the low-pass filter. The results revealed that lowering the corner frequency of the low-pass filter did not decrease the accuracy of the oxygen level measurements. The lowest possible value of the corner frequency of the low-pass filter is the fundamental frequency of the pulse signal. We concluded that the harmonics of the pulse signal do not contribute to the accuracy of pulse oximetry. The results achieved by the pulse oximeter tester were verified by human experiments, performed on five healthy subjects. The results of the human measurements confirmed that filtering out the harmonics of the pulse signal does not degrade the accuracy of pulse oximetry.

  13. Cerebral oximetry and cardiac arrest.

    PubMed

    Skhirtladze-Dworschak, Keso; Dworschak, Martin

    2013-12-01

    Cerebral oximetry is a Food and Drug Administration-approved technology that allows monitoring of brain oxygen saturation in accessible superficial brain cortex regions, which are amongst the most vulnerable in regard to ischemic or hypoxic injury. Since most oxygen in the area of interest is located in the venous compartment, the determined regional brain oxygen saturation approximately reflects the local balance between oxygen delivery and oxygen consumption. Major systemic alterations in blood oxygen content and oxygen delivery will be accompanied by corresponding changes in regional brain saturation. This systematic review, which is based on a Medline search, focuses on the characteristic changes in regional cerebral oxygen saturation that occur, when global oxygen supply to the brain ceases. It further highlights the potential application of cerebral oximetry in the management of cardiac arrest victims, the predictability of clinical outcome after global cerebral ischemia, and it also indicates possible potentials for the management of cerebral reperfusion after having instituted return of spontaneous circulation. PMID:23782549

  14. Pulse oximetry in sickle cell disease.

    PubMed

    Weston Smith, S G; Glass, U H; Acharya, J; Pearson, T C

    1989-01-01

    The place of pulse oximetry in monitoring arterial oxygen saturation in sickle cell disease has been evaluated. In four admissions of patients with sickle cell anaemia with varying degrees of arterial haemoglobin oxygen desaturation, pulse oximetry was compared with a simultaneous assessment of oxygen saturation by arterial blood gas measurement and oxygen dissociation curve (ODC) analysis. Close agreement was found between the oxygen saturation measured by pulse oximetry and that calculated from the measured arterial partial pressure of oxygen (PaO2) with reference to the patient's own ODC. Calculation of oxygen saturation by the blood gas analyser assuming a normal ODC was erroneous. Pulse oximetry is an accurate and effective non-invasive method for monitoring the arterial oxygen saturation in sickle cell disease. PMID:2591150

  15. Pulse oximetry in bronchiolitis: is it needed?

    PubMed Central

    Hendaus, Mohamed A; Jomha, Fatima A; Alhammadi, Ahmed H

    2015-01-01

    Infants admitted to health-care centers with acute bronchiolitis are frequently monitored with a pulse oximeter, a noninvasive method commonly used for measuring oxygen saturation. The decision to hospitalize children with bronchiolitis has been largely influenced by pulse oximetry, despite its questionable diagnostic value in delineating the severity of the illness. Many health-care providers lack the appropriate clinical fundamentals and limitations of pulse oximetry. This deficiency in knowledge might have been linked to changes in the management of bronchiolitis. The aim of this paper is to provide the current evidence on the role of pulse oximetry in bronchiolitis. We discuss the history, fundamentals of operation, and limitations of the apparatus. A search of the Google Scholar, Embase, Medline, and PubMed databases was carried out for published articles covering the use of pulse oximetry in bronchiolitis. PMID:26491341

  16. Variational Water Wave Modelling: from Continuum to Experiment

    NASA Astrophysics Data System (ADS)

    Bokhove, Onno; Kalogirou, Anna

    2015-04-01

    Variational methods are investigated asymptotically and numerically to model water waves in tanks with wave generators. A modified Benney-Luke model is derived using variational techniques including a time-dependent gravitional potential mimicking a removable "sluice gate". As a validation, our modelling results using (dis)continuous Galerkin finite elements will be compared to a soliton splash event resulting after a sluice gate is removed during a finite time in a long water channel with a contraction at its end. Future work will explore these methods for wave-energy devices and ships in modest to heavy seas.

  17. Geomagnetic field variations in seismic waves traveling across a fault

    NASA Astrophysics Data System (ADS)

    Lukishov, B. G.; Spivak, A. A.; Ter-Semenov, A. A.

    2012-01-01

    The results of regular instrumental observations over geomagnetic field variations in the zones of influence of tectonic faults during movement of seismic waves of varied intensity are presented. It has been shown that seismic waves with an amplitude more than 5-10 μm/s, traveling across the fault zone, always produced geomagnetic field variations. At weaker seismic disturbances, geomagnetic field variations are of the "glimmer" character, and the relative frequency of appearance of the effect drops as the seismic wave amplitude decreases. The quantitative dependence between the maximal value of the full vector of variations in geomagnetic field induction in a fault zone and the amplitude of the seismic disturbance has been found for the first time.

  18. Variational principle for nonlinear wave propagation in dissipative systems.

    PubMed

    Dierckx, Hans; Verschelde, Henri

    2016-02-01

    The dynamics of many natural systems is dominated by nonlinear waves propagating through the medium. We show that in any extended system that supports nonlinear wave fronts with positive surface tension, the asymptotic wave-front dynamics can be formulated as a gradient system, even when the underlying evolution equations for the field variables cannot be written as a gradient system. The variational potential is simply given by a linear combination of the occupied volume and surface area of the wave front and changes monotonically over time. PMID:26986334

  19. Solitary Waves of the MRLW Equation by Variational Iteration Method

    SciTech Connect

    Hassan, Saleh M.; Alamery, D. G.

    2009-09-09

    In a recent publication, Soliman solved numerically the modified regularized long wave (MRLW) equation by using the variational iteration method (VIM). In this paper, corrected numerical results have been computed, plotted, tabulated, and compared with not only the exact analytical solutions but also the Adomian decomposition method results. Solitary wave solutions of the MRLW equation are exactly obtained as a convergent series with easily computable components. Propagation of single solitary wave, interaction of two and three waves, and also birth of solitons have been discussed. Three invariants of motion have been evaluated to determine the conservation properties of the problem.

  20. Spatial variations in Achilles tendon shear wave speed

    PubMed Central

    DeWall, Ryan J.; Slane, Laura C.; Lee, Kenneth S.; Thelen, Darryl G.

    2014-01-01

    Supersonic shear imaging (SSI) is an ultrasound imaging modality that can provide insight into tissue mechanics by measuring shear wave propagation speed, a property that depends on tissue elasticity. SSI has previously been used to characterize the increase in Achilles tendon shear wave speed that occurs with loading, an effect attributable to the strain-stiffening behavior of the tissue. However, little is known about how shear wave speed varies spatially, which is important, given the anatomical variation that occurs between the calcaneus insertion and the gastrocnemius musculotendon junction. The purpose of this study was to investigate spatial variations in shear wave speed along medial and lateral paths of the Achilles tendon for three different ankle postures: resting ankle angle (R, i.e. neutral), plantarflexed (P; R − 15 deg), and dorsiflexed (D; R + 15 deg). We observed significant spatial and posture variations in tendon shear wave speed in ten healthy young adults. Shear wave speeds in the Achilles free tendon averaged 12 ± 1.2 m/s in a resting position, but decreased to 7.2 ± 1.8 m/s with passive plantarflexion. Distal tendon shear wave speeds often reached the maximum tracking limit (16.3 m/s) of the system when the ankle was in the passively dorsiflexed posture (+15 deg from R). At a fixed posture, shear wave speeds decreased significantly from the free tendon to the gastrocnemius musculotendon junction, with slightly higher speeds measured on the medial side than on the lateral side. Shear wave speeds were only weakly correlated with the thickness and depth of the tendon, suggesting that the distal-to-proximal variations may reflect greater compliance in the aponeurosis relative to the free tendon. The results highlight the importance of considering both limb posture and transducer positioning when using SSI for biomechanical and clinical assessments of the Achilles tendon. PMID:24933528

  1. Variational formulation of covariant eikonal theory for vector waves

    SciTech Connect

    Kaufman, A.N.; Ye, H.; Hui, Y.

    1986-10-01

    The eikonal theory of wave propagation is developed by means of a Lorentz-covariant variational principle, involving functions defined on the natural eight-dimensional phase space of rays. The wave field is a four-vector representing the electromagnetic potential, while the medium is represented by an anisotropic, dispersive nonuniform dielectric tensor D/sup ..mu nu../(k,x). The eikonal expansion yields, to lowest order, the Hamiltonian ray equations, which define the Lagrangian manifold k(x), and the wave-action conservation law, which determines the wave-amplitude transport along the rays. The first-order contribution to the variational principle yields a concise expression for the transport of the polarization phase. The symmetry between k-space and x-space allows for a simple implementation of the Maslov transform, which avoids the difficulties of caustic singularities.

  2. Hurricane Directional Wave Spectrum Spatial Variation at Landfall

    NASA Technical Reports Server (NTRS)

    Walsh, E. J.; Wright, C. W.; Vandemark, D.; Krabill, W. B.; Garcia, A. W.

    1999-01-01

    On 26 August 1998, hurricane Bonnie was making landfall near Wilmington, NC. The NASA airborne scanning radar altimeter (SRA) carried aboard one of the NOAA WP-3D hurricane hunter aircraft at 2.2 km height documented the sea surface directional wave spectrum in the region between Charleston, SC and Cape Hatteras, NC. The aircraft ground track included both segments along the shoreline and Pamlico Sound as well as far offshore. An animation of the directional wave spectrum spatial variation at landfall will be presented and contrasted with the spatial variation when Bonnie was in the open ocean on 24 August 1998.

  3. Hurricane Directional Wave Spectrum Spatial Variation at Landfall

    NASA Technical Reports Server (NTRS)

    Walsh, Edward J.; Wright, C. Wayne; Vandemark, Douglas C.; Krabill, William B.; Garcia, Andrew W.; Houston, Samuel H.; Powell, Mark D.; Black, Peter G.; Marke, Frank D.; Busalacchi, Antonio J. (Technical Monitor)

    2000-01-01

    On 26 August 1998, hurricane Bonnie was making landfall near Wilmington, NC. The NASA airborne scanning radar altimeter (SRA) carried aboard one of the NOAA WP-3D hurricane hunter aircraft at 2.2 km height documented the sea surface directional wave spectrum in the region between Charleston, SC and Cape Hatteras, NC. The aircraft ground track included both segments along the shoreline and Pamlico Sound as well as far offshore. An animation of the directional wave spectrum spatial variation at landfall will be presented and contrasted with the spatial variation when Bonnie was in the open ocean on 24 August 1998.

  4. Pulse oximetry performance in mechanically ventilated newborn infants.

    PubMed

    Solevåg, Anne L; Solberg, Marianne T; Šaltytė-Benth, Jūratė

    2015-08-01

    Pulse oximetry is widely used to target oxygenation in newborn infants. In a retrospective chart review of 138 mechanically ventilated infants, pulse oximetry overestimated blood oxygen saturation compared to arterial blood gas analyses. Despite improvements in pulse oximeter technology, pulse oximetry performance in sick newborns should still be under scrutiny. PMID:26067867

  5. Using pulse oximetry to assess oxygen levels.

    PubMed

    Olive, Sandra

    Abstract Olive S (2016) Using pulse oximetry to assess oxygen levels. Detecting low oxygen levels in patients is important but not always easy; central cyanosis--when a patient's lips, tongue and mucus membranes acquire a blue tinge--can be missed, even by skilled observers, until significant hypoxaemia is present. Pulse oximetry can be undertaken to measure a patient's oxygen levels and help identify earlier when action must be taken. This article outlines the procedure and its limitations, as well as the circumstances in which it should be used. PMID:27295798

  6. Improved variational wave functions for few-body nuclei

    SciTech Connect

    Wiringa, R.B.; Arriaga, A.; Pandharipande, V.R.

    1995-08-01

    We continued to work on improvements to our variational wave functions for use in Monte Carlo calculations of few-body nuclei. These trial functions include central, spin, isospin, tensor, and spin-orbit two-body correlations and three-body correlations for the three-nucleon potential. In the last two years we studied a variety of extra three-body correlations. Our search for possible forms was guided by comparisons made with 34-channel Faddeev wave functions provided by the Los Alamos-Iowa group. The new trial functions reduce the discrepancy with exact Faddeev calculations in {sup 3}H and Green`s Function Monte Carlo (GFMC) calculations in {sup 4}He by about 40%. This work is now being written up for publication. We hope to use similar comparisons with GFMC calculations in the six-body nuclei to find further improvements for the light p-shell nuclei, where the variational wave functions are not as good.

  7. Simulating and understanding sand wave variation: A case study of the Golden Gate sand waves

    USGS Publications Warehouse

    Sterlini, F.; Hulscher, S.J.M.H.; Hanes, D.M.

    2009-01-01

    In this paper we present a detailed comparison between measured features of the Golden Gate sand wave field and the results of a nonlinear sand wave model. Because the Golden Gate sand waves exhibit large variation in their characteristics and in their environmental physics, this area gives us the opportunity to study sand wave variation between locations, within one well-measured, large area. The nonlinear model used in this paper is presently the only tool that provides information on the nonlinear evolution of large-amplitude sand waves. The model is used to increase our understanding of the coupling between the variability in environmental conditions and the sand wave characteristics. Results show that the model is able to describe the variation in the Golden Gate sand waves well when both the local oscillating tidal current and the residual current are taken into account. Current and water depth seem to be the most important factors influencing sand wave characteristics. The simulation results give further confidence in the underlying model hypothesis and assumptions. Copyright 2009 by the American Geophysical Union.

  8. On Variational Methods in the Physics of Plasma Waves

    SciTech Connect

    I.Y. Dodin

    2013-03-08

    A fi rst-principle variational approach to adiabatic collisionless plasma waves is described. The focus is made on one-dimensional electrostatic oscillations, including phase-mixed electron plasma waves (EPW) with trapped particles, such as Bernstein-Greene-Kruskal modes. The well known Whitham's theory is extended by an explicit calculation of the EPW Lagrangian, which is related to the oscillation-center energies of individual particles in a periodic fi eld, and those are found by a quadrature. Some paradigmatic physics of EPW is discussed for illustration purposes. __________________________________________________

  9. Assessment of the calibration curve for transmittance pulse-oximetry

    NASA Astrophysics Data System (ADS)

    Doronin, A.; Fine, I.; Meglinski, I.

    2011-11-01

    Optical/laser modalities provide a broad variety of practical solutions for clinical diagnostics and therapy in a range from imaging of single cells and molecules to non-invasive biopsy of specific biological tissues and organs tomography. Near-infrared transmittance pulse oximetry with laser diodes is the accepted standard in current clinical practice and widely used for noninvasive monitoring of oxygen saturation in arterial blood hemoglobin. Conceptual design of practical pulse oximetry systems requires careful selection of various technical parameters, including intensity, wavelength, beam size and profile of incident laser radiation, size, numerical aperture of the detector, as well as a clear understanding of how the spatial and temporal structural alterations in biological tissues can be linked with and can be distinguished by variations of these parameters. In current letter utilizing state-of-the-art NVIDEA CUDA technology, a new object oriented programming paradigm and on-line solutions we introduce a computational tool applied for human finger transmittance spectra simulation and assessment of calibration curve for near-infrared transmitted pulseoximetry.

  10. New spectral imaging techniques for blood oximetry in the retina

    NASA Astrophysics Data System (ADS)

    Alabboud, Ied; Muyo, Gonzalo; Gorman, Alistair; Mordant, David; McNaught, Andrew; Petres, Clement; Petillot, Yvan R.; Harvey, Andrew R.

    2007-07-01

    Hyperspectral imaging of the retina presents a unique opportunity for direct and quantitative mapping of retinal biochemistry - particularly of the vasculature where blood oximetry is enabled by the strong variation of absorption spectra with oxygenation. This is particularly pertinent both to research and to clinical investigation and diagnosis of retinal diseases such as diabetes, glaucoma and age-related macular degeneration. The optimal exploitation of hyperspectral imaging however, presents a set of challenging problems, including; the poorly characterised and controlled optical environment of structures within the retina to be imaged; the erratic motion of the eye ball; and the compounding effects of the optical sensitivity of the retina and the low numerical aperture of the eye. We have developed two spectral imaging techniques to address these issues. We describe first a system in which a liquid crystal tuneable filter is integrated into the illumination system of a conventional fundus camera to enable time-sequential, random access recording of narrow-band spectral images. Image processing techniques are described to eradicate the artefacts that may be introduced by time-sequential imaging. In addition we describe a unique snapshot spectral imaging technique dubbed IRIS that employs polarising interferometry and Wollaston prism beam splitters to simultaneously replicate and spectrally filter images of the retina into multiple spectral bands onto a single detector array. Results of early clinical trials acquired with these two techniques together with a physical model which enables oximetry map are reported.

  11. Rogue wave variational modelling through the interaction of two solitary waves

    NASA Astrophysics Data System (ADS)

    Gidel, Floriane; Bokhove, Onno

    2016-04-01

    The extreme and unexpected characteristics of Rogue waves have made them legendary for centuries. It is only on the 1st of January 1995 that these mariners' tales started to raise scientist's curiosity, when such a wave was recorded in the North Sea; a sudden wall of water hit the Draupner offshore platform, more than twice higher than the other waves, providing evidence of the existence of rogue or freak waves. Since then, studies have shown that these surface gravity waves of high amplitude (at least twice the height of the other sea waves [Dyste et al., 2008]) appear in non-linear dispersive water motion [Drazin and Johnson, 1989], at any depth, and have caused a lot of damage in recent years [Nikolkina and Didenkulova, 2011 ]. So far, most of the studies have tried to determine their probability of occurrence, but no conclusion has been achieved yet, which means that we are currently unenable to predict or avoid these monster waves. An accurate mathematical and numerical water-wave model would enable simulation and observation of this external forcing on boats and offshore structures and hence reduce their threat. In this work, we aim to model rogue waves through a soliton splash generated by the interaction of two solitons coming from different channels at a specific angle. Kodama indeed showed that one way to produce extreme waves is through the intersection of two solitary waves, or one solitary wave and its oblique reflection on a vertical wall [Yeh, Li and Kodama, 2010 ]. While he modelled Mach reflection from Kadomtsev-Petviashvili (KP) theory, we aim to model rogue waves from the three-dimensional potential flow equations and/or their asymptotic equivalent described by Benney and Luke [Benney and Luke, 1964]. These theories have the advantage to allow wave propagation in several directions, which is not the case with KP equations. The initial solitary waves are generated by removing a sluice gate in each channel. The equations are derived through a

  12. EPR Oximetry in Three Spatial Dimensions using Sparse Spin Distribution

    PubMed Central

    Som, Subhojit; Potter, Lee C.; Ahmad, Rizwan; Vikram, Deepti S.; Kuppusamy, Periannan

    2008-01-01

    A method is presented to use continuous wave electron paramagnetic resonance imaging for rapid measurement of oxygen partial pressure in three spatial dimensions. A particulate paramagnetic probe is employed to create a sparse distribution of spins in a volume of interest. Information encoding location and spectral linewidth is collected by varying the spatial orientation and strength of an applied magnetic gradient field. Data processing exploits the spatial sparseness of spins to detect voxels with nonzero spin and to estimate the spectral linewidth for those voxels. The parsimonious representation of spin locations and linewidths permits an order of magnitude reduction in data acquisition time, compared to four-dimensional tomographic reconstruction using traditional spectral-spatial imaging. The proposed oximetry method is experimentally demonstrated for a lithium octa-n-butoxy naphthalocyanine (LiNc-BuO) probe using an L-band EPR spectrometer. PMID:18538600

  13. Shear-wave velocity variation in jointed rock: an attempt to measure tide-induced variations

    SciTech Connect

    Beem, L.I.

    1987-08-01

    The use of the perturbation of seismic wave velocities by solid earth tides as a possible method of exploration for fractured media is discussed. Velocity of compressional seismic waves in fractured homogeneous rock has been observed to vary through solid earth tide cycles by a significant 0.5-0.9%. This variation of seismic velocities may be attributed to the opening and closing of joints by tidal stresses. In an attempt to see if shear-wave velocities show a similar velocity variation, a pneumatic shear-wave generator was used for the source. The 5 receivers, 3-component, 2.0 Hz, moving-coil geophones, were connected to a GEOS digital recorder. The two receivers located 120 m and 110 m from the source showed large shear-to-compression amplitude ratio and a high signal-to-noise ratio. A glaciated valley was chosen for the experiment site, since topography is flat and the granodiorite is jointed by a set of nearly orthogonal vertical joints, with superimposed horizontal sheeting joints. A slight velocity variation was noted in the first 200 consecutive firings; after which, the amplitude of the shear-wave begun to increase. This increase has been attributed to the compacting of the soil beneath the shear-wave generator (SWG). In the future, the soil will be compacted prior to placing the SWG or the SWG will be coupled directly to the rock to alleviate the amplitude fluctuation problem. This research may have application in exploration for fracture permeability in the rock mass between existing wells, by measuring seismic velocities from well to well through the tidal cycle.

  14. Solar cycle variation of gravity waves observed in OH airglow

    NASA Astrophysics Data System (ADS)

    Gelinas, L. J.; Hecht, J. H.; Walterscheid, R. L.; Reid, I. M.; Woithe, J.; Vincent, R. A.

    2013-12-01

    Airglow imaging provides a unique means by which to study many wave-related phenomena in the 80 to 100 km altitude regime. Two-dimensional image observations reveal quasi-monochromatic disturbances associated with atmospheric gravity waves (AGWs) as well as small-scale instabilities, often called ripples. Image-averaged temperature and intensity measurements can be used to study the response of the airglow layer to tides and planetary waves, as well as monitor longer-term climatological variations. Here we present results of low and mid-latitude OH airglow observations beginning near solar max of solar cycle 23 and continuing through solar max of cycle 24. Aerospace imagers deployed at Alice Springs (23o42'S, 133o53'E) and Adelaide (34o55'S, 138o36'E) have been operating nearly continuously since ~2001. The imagers employ filters measuring OH Meinel (6, 2) and O2 Atmospheric (0, 1) band emission intensities and temperatures, as well as atmospheric gravity wave parameters. The Aerospace Corporation's Infrared Camera deployed at Maui, HI (20.7N,156.3W), collected more than 700 nights of airglow images from 2002-2005. The camera measures the OH Meinel (4,2) emission at 1.6 um using a 1 second exposure at a 3 second cadence, which allows the study of AGW and ripple features over very short temporal and spatial scales. The camera was relocated to Cerro Pachon, Chile (30.1 S, 70.8 W) and has been operating continuously since 2010. Temperature, intensity and gravity wave climatologies derived from the two Australian airglow imagers span a full solar cycle (solar max to solar max). Emission intensities have been calibrated using background stars, and temperatures have been calibrated with respect to TIMED/SABER temperatures, reducing the influence of instrument degradation on the solar cycle climatology. An automated wave detection algorithm is used to identify quasi monochromatic wave features in the airglow data, including wavelength, wave period and propagation

  15. Longitudinal variation and waves in Jupiter's south equatorial wind jet

    NASA Astrophysics Data System (ADS)

    Simon-Miller, Amy A.; Rogers, John H.; Gierasch, Peter J.; Choi, David; Allison, Michael D.; Adamoli, Gianluigi; Mettig, Hans-Joerg

    2012-04-01

    A detailed study of the chevron-shaped dark spots on the strong southern equatorial wind jet near 7.5°S planetographic latitude shows variations in velocity with longitude and time. The presence of the large anticyclonic South Equatorial Disturbance (SED) has a profound effect on the chevron velocity, causing slower velocities to its east and increasing with distance from the disturbance. The chevrons move with velocities near the maximum wind jet velocity of ˜140 m/s, as deduced by the history of velocities at this latitude and the magnitude of the symmetric wind jet near 7°N latitude. Their repetitive nature is consistent with a gravity-inertia wave (n = 75-100) with phase speed up to 25 m/s, relative to the local flow, but the identity of this wave mode is not well constrained. However, for the first time, high spatial resolution movies from Cassini images show that the chevrons oscillate in latitude with a 6.7 ± 0.7-day period. This oscillating motion has a wavelength of ˜20° and a speed of 101 ± 3 m/s, following a pattern similar to that seen in the Rossby wave plumes of the North Equatorial Zone, and possibly reinforced by it. All dates show chevron latitude variability, but it is unclear if this larger wave is present during other epochs, as there are no other suitable time series movies that fully delineate it. In the presence of multiple wave modes, the difference in dominant cloud appearance between 7°N and 7.5°S is likely due to the presence of the Great Red Spot, either through changes in stratification and stability or by acting as a wave boundary.

  16. Longitudinal Variation and Waves in Jupiter's South Equatorial Wind Jet

    NASA Technical Reports Server (NTRS)

    Simon-Miller, Amy A.; Choi, David; Rogers, John H.; Gierasch, Peter J.; Allison, Michael D.; Adamoli, Gianluigi; Mettig, Hans-Joerg

    2012-01-01

    A detailed study of the chevron-shaped dark spots on the strong southern equatorial wind jet near 7.5 S planetographic latitude shows variations in velocity with longitude and time. The presence of the large anticyclonic South Equatorial Disturbance (SED) has a profound effect on the chevron velocity, causing slower velocities to its east and accelerations over distance from the disturbance. The chevrons move with velocities near the maximum wind jet velocity of approx 140 m/s, as deduced by the history of velocities at this latitude and the magnitude of the symmetric wind jet near 7 N latitude. Their repetitive nature is consistent with a gravity-inertia wave (n = 75 to 100) with phase speed up to 25 m/s, relative to the local flow, but the identity of this wave mode is not well constrained. However, for the first time, high spatial resolution movies from Cassini images show that the chevrons oscillate in latitude with a 6.7 +/- 0.7-day period. This oscillating motion has a wavelength of approx 20 and a speed of 101 +/- 3 m/s, following a pattern similar to that seen in the Rossby wave plumes of the North Equatorial Zone, and possibly reinforced by it. All dates show chevron latitude variability, but it is unclear if this larger wave is present during other epochs, as there are no other suitable time series movies that fully delineate it. In the presence of mUltiple wave modes, the difference in dominant cloud appearance between 7 deg N and 7.5 deg S is likely due to the presence of the Great Red Spot, either through changes in stratification and stability or by acting as a wave boundary.

  17. Seasonal variation of solitary wave properties in Lake Constance

    NASA Astrophysics Data System (ADS)

    Preusse, M.; Freistühler, H.; Peeters, F.

    2012-04-01

    The properties of internal solitary waves (ISWs) depend on the stratification of the water body. In most climatic regions the stratification in lakes and oceans varies during the year, and hence the properties of the ISWs can also be expected to change over the seasons. On the basis of a long-term temperature time series recorded over 6 years, this paper investigates seasonal changes in the characteristic properties of ISWs in Lake Überlingen, a subbasin of Lake Constance. A large number of ISWs with amplitudes ranging from 3 m to 30 m were identified. More than 15% of the leading ISWs of a wave train were associated with density inversions, often indicating shear instabilities or trapped cores. For all waves the propagation depth and the value of a nonlinearity index nlp providing the degree of nonlinearity were determined, propagation depth being the rest height of the isotherm undergoing maximum displacement and nlp the ratio between wave amplitude and propagation depth. The index nlp was found to be a good parameter for predicting the occurrence of inversions. The statistical analysis of the wave properties derived from the observations revealed that the degree of nonlinearity of the ISWs changes with season. Complementary to the statistical analysis, the seasonally averaged ISW properties were compared with wave prototypes obtained numerically from the Dubreil-Jacotin-Long (DJL) and the stratified Korteweg-deVries (KdV) models. The simulations indicate that the typical stratification and its seasonal variation are responsible for the degree and the seasonality of nonlinearity of the ISWs.

  18. Esophageal pulse oximetry utilizing reflectance photoplethysmography.

    PubMed

    Kyriacou, Panayiotis A; Powell, Sarah; Langford, Richard M; Jones, Deric P

    2002-11-01

    Peripheral perfusion is often poor and barely pulsatile in patients undergoing prolonged major surgery. Hence, the arterial blood oxygen saturation (SpO2) readings from commercial finger pulse oximeters can become unreliable or cease when they are most needed. To overcome this limitation, the esophagus has been investigated as an alternative measurement site, as perfusion may be preferentially preserved centrally. A reflectance esophageal pulse oximeter probe, and a processing system implemented in LabVIEW were developed. The system was evaluated in clinical measurements on 49 cardiothoracic surgery patients. The SpO2 values from the esophagus were in good agreement with arterial blood oxygen saturation (SaO2) values obtained from blood gas analysis and CO-oximetry. The means (+/-SD) of the differences between the esophageal SpO2 and SaO2 results from blood gas analysis and CO-oximetry were 0.02 +/- 0.88% and -0.73 +/- 0.72%, respectively. In five (10.2%) of the patients, the finger pulse oximeter failed for at least 10 min while the esophageal SpO2 readings remained reliable. The results confirm that the esophagus may be used as an alternative monitoring site for pulse oximetry even in patients with compromised peripheral perfusion. PMID:12450366

  19. Tissue oximetry in anaesthesia and intensive care.

    PubMed

    Biedrzycka, Aleksandra; Lango, Romuald

    2016-01-01

    Conventional monitoring during surgery and intensive care is not sufficiently sensitive to detect acute changes in vital organs perfusion, while its good quality is critical for maintaining their function. Disturbed vital organ perfusion may lead to the development of postoperative complications, including neurological sequel and renal failure. Near-infra-red spectroscopy (NIRS) represents one of up-to-date techniques of patient monitoring which is commonly used for the assessment of brain oximetry in thoracic aorta surgery, and - increasingly more often -in open-heart surgery. Algorithms for maintaining adequate brain saturation may result in a decrease of neurological complications and cognitive dysfunction following cardiac surgery. The assessment of kidney and visceral perfusion with tissue oximetry is gaining increasing interest during pediatric cardiac surgery. Attempts at decreasing complications by the use of brain oximetry during carotid endarterectomy, as well as thoracic and abdominal surgery demonstrated conflicting results. In recent years NIRS technique was proposed as a tool for muscle perfusion assessment under short term ischemia and reperfusion, referred to as vascular occlusion test (VOT). This monitoring extension allows for the identification of early disturbances in tissue perfusion. Results of recent studies utilizing VOT suggest that the muscle saturation decrease rate is reduced in septic shock patients, while decreased speed of saturation recovery on reperfusion is related to disturbed microcirculation. Being non-invasive and feasible technique, NIRS offers an improvement of preoperative risk assessment in cardiac surgery and promises more comprehensive intraoperative and ICU patient monitoring allowing for better outcome. PMID:26966109

  20. Variational stereo imaging of oceanic waves with statistical constraints.

    PubMed

    Gallego, Guillermo; Yezzi, Anthony; Fedele, Francesco; Benetazzo, Alvise

    2013-11-01

    An image processing observational technique for the stereoscopic reconstruction of the waveform of oceanic sea states is developed. The technique incorporates the enforcement of any given statistical wave law modeling the quasi-Gaussianity of oceanic waves observed in nature. The problem is posed in a variational optimization framework, where the desired waveform is obtained as the minimizer of a cost functional that combines image observations, smoothness priors and a weak statistical constraint. The minimizer is obtained by combining gradient descent and multigrid methods on the necessary optimality equations of the cost functional. Robust photometric error criteria and a spatial intensity compensation model are also developed to improve the performance of the presented image matching strategy. The weak statistical constraint is thoroughly evaluated in combination with other elements presented to reconstruct and enforce constraints on experimental stereo data, demonstrating the improvement in the estimation of the observed ocean surface. PMID:23807444

  1. Variational structure of inverse problems in wave propagation and vibration

    SciTech Connect

    Berryman, J.G.

    1995-03-01

    Practical algorithms for solving realistic inverse problems may often be viewed as problems in nonlinear programming with the data serving as constraints. Such problems are most easily analyzed when it is possible to segment the solution space into regions that are feasible (satisfying all the known constraints) and infeasible (violating some of the constraints). Then, if the feasible set is convex or at least compact, the solution to the problem will normally lie on the boundary of the feasible set. A nonlinear program may seek the solution by systematically exploring the boundary while satisfying progressively more constraints. Examples of inverse problems in wave propagation (traveltime tomography) and vibration (modal analysis) will be presented to illustrate how the variational structure of these problems may be used to create nonlinear programs using implicit variational constraints.

  2. Pulse oximetry in the evaluation of peripheral vascular disease.

    PubMed

    Jawahar, D; Rachamalla, H R; Rafalowski, A; Ilkhani, R; Bharathan, T; Anandarao, N

    1997-08-01

    The role of pulse oximetry in the evaluation of peripheral vascular disease (PVD) was investigated. In addition, the value of elevating the limb to improve the sensitivity of detection of PVD by the pulse oximeter was also determined. Pulse oximetry reading in the toes were obtained in 40 young, healthy volunteers and in 40 randomly selected patients referred to the vascular investigation laboratory over a period of two months. All 40 healthy volunteers had normal pulse oximetry readings. Normal pulse oximetry reading in the toes was defined as > 95% O2 Sat and +/-2 of finger pulse oximetry reading. In all 40 patients, pulse oximetry readings were either normal or not detected at all. Since there was no gradation in decrease in the pulse oximetry reading with severity of disease or with elevation of the patient's lower extremity, an absent or no reading was considered as an abnormal result from the test. The frequency of abnormal pulse oximetry readings increased significantly in groups with abnormal ankle-brachial pressure index (ABPI) and also varied significantly with elevation of the patients' lower limbs. In patients with no PVD detected by Doppler (ABPI > 0.9), pulse oximetry readings were normal in all. However, in patients with moderate PVD (ABPI, 0.5-0.9), 84% of the patients' lower limbs had normal pulse oximetry readings and 16% had an abnormal reading at baseline level (flat). An additional 12% of the lower limbs in this group had an abnormal reading on elevation of the limb to 12 inches. In patients with severe PVD (ABPI < 0.5), 54% of the patients' lower limbs had an abnormal reading at baseline and an additional 23% had an abnormal reading at elevation of the limb to 12 inches. In conclusion, pulse oximetry was not a sensitive test for detecting early PVD. PMID:9269142

  3. Planetary Wave Influence on Wintertime OH Meinel Longitudinal Variation?

    NASA Astrophysics Data System (ADS)

    Winick, J. R.; Picard, R. H.; Wintersteiner, P. P.; Mlynczak, M. G.; Russell, J. M.; Gordley, L.

    2009-05-01

    We report on very unusual conditions in the upper mesosphere during the boreal winters of 2004 and 2006. Unusually bright OH volume emissions, as measured by TIMED/SABER, occurred in the region north of 60N. These emissions also occurred at unusually low altitudes, while at the same time very high temperatures characterized the upper mesosphere. These large perturbations allowed us to see more clearly longitudinal spatial and temporal variations that were present in the emissions. The affected areas varied in size and location on time scales of a few days and had a distinct planetary-wave wave-1 structure. We present data demonstrating the variability in the emissions and temperatures throughout the polar region and the correlations among them, and we contrast their behavior with that in normal years. The underlying cause of the correlations and longitudinal structure appears to be greatly enhanced downwelling in the upper mesosphere, which in turn was produced by unusual dynamical conditions in the lower atmosphere, consisting of stratospheric warmings and perturbations of wave structures within the polar vortex.

  4. The impact of crustal density variations on seismic wave propagation

    NASA Astrophysics Data System (ADS)

    Plonka, A.; Fichtner, A.

    2014-12-01

    Lateral density variations are the source of mass transport in the Earth at all scales, acting as drivers of convective motion. However, the density structure of the Earth remains largely unknown since classic seismic observables and gravity provide only weak constraints with strong trade-offs. Current density models are therefore often based on velocity scaling, making strong assumptions on the origin of structural heterogeneities, which may not necessarily be correct.We propose to develop a seismic tomography technique that directly inverts for density, using complete seismograms rather than arrival times of certain waves only. The first task in this challenge is to systematically study the imprints of density on synthetic seismograms.To compute the full seismic wavefield in a 3D heterogeneous medium without making significant approximations, we usenumerical wave propagation based on a spectral-element discretization of the seismic wave equation. We consider a 2000 by 1000 km wide and 500 km deep spherical section, with the 1D Earth model PREM (with 40 km crust thickness) as a background. Onto this (in the uppermost 40 km) we superimpose 3D randomly generated velocity and density heterogeneities of various magnitudes and correlation lenghts. We use different random realizations of heterogeneity distribution.We compare the synthetic seismograms for 3D velocity and density structure with 3D velocity structure and with the 1D background, calculating relative amplitude differences and timeshifts as functions of time and frequency.Our analyses indicate that reasonably sized density variations within the crust can leave a strong imprint on both traveltimes and amplitudes. This suggests (1) that crustal tomography can be significantly biased when density heterogeneities are not properly accounted for, and (2) that the solution of the seismic inverse problem for density may become feasible.

  5. Pulse Oximetry as a Medical Physics Practical on School Trips

    ERIC Educational Resources Information Center

    Gibson, Adam P.; Chandra, Elizabeth; Chandra, Manik

    2009-01-01

    We have measured blood oxygenation levels in a group of 14 people (8 young people and 6 adults) on a physically demanding expedition to Mt Kenya. Blood oxygenation was measured at 11 different altitudes between 1910 and 4985 m using pulse oximetry. We found that pulse oximetry was suitable for use on a youth expedition and we were able to show…

  6. Longitudinal Variations of Low-Latitude Gravity Waves and Their Impacts on the Ionosphere

    NASA Astrophysics Data System (ADS)

    Cullens, C. Y.; England, S.; Immel, T. J.

    2014-12-01

    The lower atmospheric forcing has important roles in the ionospheric variability. However, influences of lower atmospheric gravity waves on the ionospheric variability are still not clear due to the simplified gravity wave parameterizations and the limited knowledge of gravity wave distributions. In this study, we aim to study the longitudinal variations of gravity waves and their impacts of longitudinal variations of low-latitude gravity waves on the ionospheric variability. Our SABER results show that longitudinal variations of gravity waves at the lower boundary of TIME-GCM are the largest in June-August and January-February. We have implemented these low-latitude gravity wave variations from SABER instrument into TIME-GCM model. TIME-GCM simulation results of ionospheric responses to longitudinal variations of gravity waves and physical mechanisms will be discussed.

  7. Retinal Oximetry in a Healthy Japanese Population

    PubMed Central

    Nakano, Yuki; Shimazaki, Takeru; Kobayashi, Nobuko; Miyoshi, Yukiko; Ono, Aoi; Kobayashi, Mamoru; Shiragami, Chieko; Hirooka, Kazuyuki; Tsujikawa, Akitaka

    2016-01-01

    Purpose To establish the normative database of retinal oximetry using Oxymap T1 in a healthy Japanese population, and study the reproducibility of the measurements in Japanese. Methods We measured oxygen saturation in the major retinal vessels with Oxymap T1 in 252 eyes of 252 healthy Japanese subjects. Fundus images acquired using Oxymap T1 were processed using built-in Oxymap Analyzer software. Reproducibility of retinal oximetry was investigated using 20 eyes of 20 healthy subjects. Results The mean retinal oxygen saturation of 4 quadrants in healthy Japanese was 97.0 ± 6.9% in arteries and 52.8 ± 8.3% in veins. The mean arteriovenous difference in oxygen saturation was 44.2 ± 9.2%. Both arterial and venous oxygen saturation were significantly lower in the temporal side of the retina, especially in the temporal-inferior vessels. However, the arteriovenous difference in oxygen saturation was limited in the 4 quadrants. Interphotograph, intervisit, and interevaluator intraclass correlation coefficients were 0.936–0.979, 0.809–0.837, and 0.732–0.947, respectively. In the major retinal arteries, oxygen saturation increased with age (r = 0.18, p<0.01), at a rate of 0.67% per 10 years. However, venous oxygen saturation showed no correlation with age. Conclusions This study provides the normative database for the Japanese population. The arterial saturation value appears to be higher than other previous studies. Mean retinal oximetry in 4 quadrants with Oxymap T1 has high reproducibility. PMID:27434373

  8. Control of Periodic Variations in Saturn's Magnetosphere By Compressional Waves

    NASA Astrophysics Data System (ADS)

    Jia, X.; Kivelson, M.

    2014-12-01

    Many of the periodic variations observed in Saturn's magnetosphere can be linked directly to the presence of a rotating pattern of field-aligned currents that link the northern and southern ionospheres with each other and with the magnetosphere. Such a current system is incorporated in a magnetohydrodynamic simulation that has previously been shown to reproduce many of the observed periodic properties of the system (Jia et al., 2012; Jia and Kivelson, 2012). Here the simulation is used to investigate a range of phenomena that can be attributed to the effects of compressional waves launched from the rotating current sources. The compressional waves are found to drive the flapping of the plasma sheet and the expansion and contraction of the magnetopause in each rotation period. Because the compressional perturbations weaken as they rotate from morning to evening around the day side of the magnetosphere, the boundary develops a strong morning-evening asymmetry. A fit to the shape is provided that may be useful in further investigation of magnetopause properties, but there is already evidence of the proposed asymmetry in the Cassini observations of Clarke et al. [2010].

  9. Control of periodic variations in Saturn's magnetosphere by compressional waves

    NASA Astrophysics Data System (ADS)

    Kivelson, Margaret Galland; Jia, Xianzhe

    2014-10-01

    Many of the periodic variations observed in Saturn's magnetosphere can be linked directly to the presence of a rotating pattern of field-aligned currents that link the northern and southern ionospheres with each other and with the magnetosphere. Such a current system is incorporated in a magnetohydrodynamic simulation that has previously been shown to reproduce many of the observed periodic properties of the system. Here the simulation is used to investigate a range of phenomena that can be attributed to the effects of compressional waves launched from the rotating current sources. The compressional waves are found to drive the flapping of the plasma sheet and the expansion and contraction of the magnetopause in each rotation period. Because the compressional perturbations weaken as they rotate from morning to evening around the dayside of the magnetosphere, the boundary develops a strong morning-evening asymmetry. A fit to the shape is provided that may be useful in further investigation of magnetopause properties, but there is already evidence of the proposed asymmetry in the observations of Clarke et al. (2010a).

  10. Modeling photon transport in transabdominal fetal oximetry

    NASA Astrophysics Data System (ADS)

    Jacques, Steven L.; Ramanujam, Nirmala; Vishnoi, Gargi; Choe, Regine; Chance, Britton

    2000-07-01

    The possibility of optical oximetry of the blood in the fetal brain measured across the maternal abdomen just prior to birth is under investigated. Such measurements could detect fetal distress prior to birth and aid in the clinical decision regarding Cesarean section. This paper uses a perturbation method to model photon transport through a 8- cm-diam fetal brain located at a constant 2.5 cm below a curved maternal abdominal surface with an air/tissue boundary. In the simulation, a near-infrared light source delivers light to the abdomen and a detector is positioned up to 10 cm from the source along the arc of the abdominal surface. The light transport [W/cm2 fluence rate per W incident power] collected at the 10 cm position is Tm equals 2.2 X 10-6 cm-2 if the fetal brain has the same optical properties as the mother and Tf equals 1.0 X 10MIN6 cm-2 for an optically perturbing fetal brain with typical brain optical properties. The perturbation P equals (Tf - Tm)/Tm is -53% due to the fetal brain. The model illustrates the challenge and feasibility of transabdominal oximetry of the fetal brain.

  11. Review of splanchnic oximetry in clinical medicine.

    PubMed

    Bailey, Sean M; Mally, Pradeep V

    2016-09-01

    Global tissue perfusion and oxygenation are important indicators of physiologic function in humans. The monitoring of splanchnic oximetry through the use of near-infrared spectroscopy (NIRS) is an emerging method used to assess tissue oxygenation status. Splanchnic tissue oxygenation (SrSO2) is thought to be potentially of high value in critically ill patients because gastrointestinal organs can often be the first to suffer ischemic injury. During conditions of hypovolemia, cardiac dysfunction, or decreased oxygen-carrying capacity, blood flow is diverted toward vital organs, such as the brain and the heart at the expense of the splanchnic circulation. While monitoring SrSO2 has great potential benefit, there are limitations to the technology and techniques. SrSO2 has been found to have a relatively high degree of variability that can potentially make it difficult to interpret. In addition, because splanchnic organs only lie near the skin surface in children and infants, and energy from currently available sensors only penetrates a few centimeters deep, it can be difficult to use clinically in a noninvasive manner in adults. Research thus far is showing that splanchnic oximetry holds great promise in the ability to monitor patient oxygenation status and detect disease states in humans, especially in pediatric populations. PMID:27165703

  12. Effect of gravity wave temperature variations on homogeneous ice nucleation

    NASA Astrophysics Data System (ADS)

    Dinh, Tra; Podglajen, Aurélien; Hertzog, Albert; Legras, Bernard; Plougonven, Riwal

    2015-04-01

    Observations of cirrus clouds in the tropical tropopause layer (TTL) have shown various ice number concentrations (INC) (e.g., Jensen et al. 2013), which has lead to a puzzle regarding their formation. In particular, the frequently observed low numbers of ice crystals seemed hard to reconcile with homogeneous nucleation knowing the ubuquity of gravity waves with vertical velocity of the order of 0.1 m/s. Using artificial time series, Spichtinger and Krämer (2013) have illustrated that the variation of vertical velocity during a nucleation event could terminate it and limit the INC. However, their study was limited to constructed temperature time series. Here, we carry out numerical simulations of homogeneous ice nucleation forced by temperature time series data collected by isopycnic balloon flights near the tropical tropopause. The balloons collected data at high frequency (30 s), so gravity wave signals are well resolved in the temperature time series. With the observed temperature time series, the numerical simulations with homogeneous freezing show a full range of ice number concentrations (INC) as previously observed in the tropical upper troposphere. The simulations confirm that the dynamical time scale of temperature variations (as seen from observations) can be shorter than the nucleation time scale. They show the existence of two regimes for homogeneous ice nucleation : one limited by the depletion of water vapor by the nucleated ice crystals (those we name vapor events) and one limited by the reincrease of temperature after its initial decrease (temperature events). Low INC may thus be obtained for temperature events when the gravity wave perturbations produce a non-persistent cooling rate (even with large magnitude) such that the absolute change in temperature remains small during nucleation. This result for temperature events is explained analytically by a dependence of the INC on the absolute drop in temperature (and not on the cooling rate). This

  13. Variational symplectic particle-in-cell simulation of nonlinear mode conversion from extraordinary waves to Bernstein waves

    SciTech Connect

    Xiao, Jianyuan; Liu, Jian; Qin, Hong; Yu, Zhi; Xiang, Nong

    2015-09-15

    In this paper, the nonlinear mode conversion of extraordinary waves in nonuniform magnetized plasmas is studied using the variational symplectic particle-in-cell simulation. The accuracy of the nonlinear simulation is guaranteed by the long-term accuracy and conservativeness of the symplectic algorithm. The spectra of the electromagnetic wave, the evolution of the wave reflectivity, the energy deposition profile, and the parameter-dependent properties of radio-frequency waves during the nonlinear mode conversion are investigated. It is illustrated that nonlinear effects significantly modify the physics of the radio-frequency injection in magnetized plasmas. The evolutions of the radio-frequency wave reflectivity and the energy deposition are observed, as well as the self-interaction of the Bernstein waves and mode excitations. Even for waves with small magnitude, nonlinear effects can also become important after continuous wave injections, which are common in the realistic radio-frequency wave heating and current drive experiments.

  14. Four-wavelength retinal vessel oximetry

    NASA Astrophysics Data System (ADS)

    Drewes, Jonathan Jensen

    1999-11-01

    This dissertation documents the design and construction of a four-wavelength retinal vessel oximeter, the Eye Oximeter (EOX). The EOX scans low-powered laser beams (at 629, 678, 821 and 899 nm) into the eye and across a targeted retinal vessel to measure the transmittance of the blood within the vessel. From the transmittance measurements, the oxygen saturation of the blood within the vessel is computed. Retinal vessel oxygen saturation has been suggested as a useful parameter for monitoring a wide range of conditions including occult blood loss and a variety of ophthalmic diseases. An artificial eye that simulates the geometry of a human retinal vessel was constructed and used to calibrate the EOX saturation measurement. A number of different oximetry equations were developed and tested. From measurements made on whole human blood in the artificial eye, an oximetry equation that places a linear wavelength dependance on the scattering losses (3% decrease from 629 to 899 nm) is found to best calibrate the EOX oxygen saturation measurement. This calibration also requires that an adjustment be made to the absorption coefficient of hemoglobin at 629 nm that has been reported in the literature. More than 4,000 measurements were made in the eyes of three human subjects during the development of the EOX. Applying the oximetry equation developed through the in vitro experiments to human data, the average human retinal venous oxygen saturation is estimated to be 0.63 +/- 0.07 and the average human retinal arterial oxygen saturation is 0.99 +/- 0.03. Furthermore, measurements made away from the optic disk resulted in a larger variance in the calculated saturation when compared to measurements made on the optic disk. A series of EOX experiments using anesthetized swine helped to verify the sensitivity of the EOX measurement of oxygen saturation. It is found that the calibration in swine differed from the calibration in the artificial eye. An empirical calibration from the

  15. Transillumination waveform simulator for pulse oximetry

    NASA Astrophysics Data System (ADS)

    Vazquez-Jaccaud, Camille; Paez, Gonzalo; Strojnik, Marija

    2009-08-01

    Pulse oximetry technique is a non invasive method useful to monitor the quantity of oxygen in hemoglobin, used in medical diagnosis and clinical decision-making. It is based on the ratio between the red and infrared light absorbance corresponding to the oxygenated (HbO2) and non-oxygenated (Hb) state of the hemoglobin. We develop the mathematical model to obtain the oxygen saturation value observing that it depends on four known parameters: two transillumination values assessed at the common pulse oximetry wavelengths (λ1 = 660 nm y λ2 = 940 nm), and the extinction coefficients for the oxy- and deoxy-hemoglobin at these given wavelengths. Analyzing the extinction curves for oxy- and deoxy-hemoglobin we note that at λ equal to 660 nm the HbO2 component almost does not contribute to the attenuation of incidance when we transilluminate tissue (7.479x10-5 cm-1M-1). In this case is the Hb component that gives the significant attenuation value (7.863x10-4 cm-1M-1). In 940 nm the extinction coefficient of the Hb is 2.589x10-5 cm-1M-1 and we can ignore it when we count attenuation. At this λ we assume that the pulsate component is only affected by the HbO2 (2.099x10-4 cm-1M-1). This analysis of hemoglobin extinction coefficients in the absorption curves highlights the signal to noise ratio between these two oxygen dependent elements. We are interested in accentuate the better contrast interval (λ pair), where this signal-to-noise ratio is higher, looking for more transillumination information and more precise SO2 value. We propose to use a transillumination waveform simulator to study the different effects (respiration, artifact body movement, absorption, low perfusion, etc) presented in complex physiological signals and to know the optical path-integrated behavior when we transilluminate tissue. This is practical for acquisition and processing transillumination signals. The present work is the first part of a λ selection method to guaratee the optimum S/N for

  16. Assessing the orbital selective Mott transition with variational wave functions

    NASA Astrophysics Data System (ADS)

    Tocchio, Luca F.; Arrigoni, Federico; Sorella, Sandro; Becca, Federico

    2016-03-01

    We study the Mott metal-insulator transition in the two-band Hubbard model with different hopping amplitudes t 1 and t 2 for the two orbitals on the two-dimensional square lattice by using non-magnetic variational wave functions, similarly to what has been considered in the limit of infinite dimensions by dynamical mean-field theory. We work out the phase diagram at half filling (i.e. two electrons per site) as a function of R={{t}2}/{{t}1} and the on-site Coulomb repulsion U, for two values of the Hund’s coupling J  =  0 and J/U  =  0.1. Our results are in good agreement with previous dynamical mean-field theory calculations, demonstrating that the non-magnetic phase diagram is only slightly modified from infinite to two spatial dimensions. Three phases are present: a metallic one, for small values of U, where both orbitals are itinerant; a Mott insulator, for large values of U, where both orbitals are localized because of the Coulomb repulsion; and the so-called orbital-selective Mott insulator (OSMI), for small values of R and intermediate Us, where one orbital is localized while the other one is still itinerant. The effect of the Hund’s coupling is two-fold: on one side, it favors the full Mott phase over the OSMI; on the other side, it stabilizes the OSMI at larger values of R.

  17. Longitudinal Variation and Waves in Jupiter's South Equatorial Wind Jet

    NASA Astrophysics Data System (ADS)

    Simon-Miller, A. A.; Rogers, J. H.; Gierasch, P. J.; Choi, D.; Allison, M. D.; Adamoli, G.; Mettig, H.-J.

    2012-03-01

    Jupiter's south equatorial winds and clouds are consistent with a high frequency, gravity-inertia, wave. A second, westward-moving, Rossby wave was also identified. Asymmetry with the north equatorial clouds are likely due to the Great Red Spot.

  18. Interseasonal Variations in the Middle Atmosphere Forced by Gravity Waves

    NASA Technical Reports Server (NTRS)

    Mayr, H. G.; Mengel, J. G.; Drob, D. P.; Porter, H. S.; Bhartia, P. K. (Technical Monitor)

    2002-01-01

    In our Numerical Spectral Model (NSM), which incorporates Hines' Doppler Spread Parameterization, gravity waves (GW) propagating in the east/west direction can generate the essential features of the observed equatorial oscillations of the zonal circulation and in particular the QBO (quasi-biennial oscillation) extending from the stratosphere into the upper mesosphere. We report here that the NSM also produces inter-seasonal variations in the zonally symmetric meridional circulation. A distinct meridional oscillation (MO) is generated, which appears to be the counterpart to the QBO. With a vertical grid-point resolution of about 0.5 km, the NSM produces the MO through momentum deposition of GW's propagating in the north/south direction. This process is inherently non-linear, of third (odd) order, which enables the oscillation. Since the meridional winds are relatively small compared to the zonal winds, the vertical wavelength required to maintain the MO is also smaller, i.e., only about 10 km instead of the 30 km for the QBO. The corresponding viscous stress is then larger, and the period of the MO is thus short compared with that of the QBO, i.e., only about 3 to 4 months. Depending on the strength of the GW forcing, the computed amplitudes of the meridional wind oscillation are typically 5 m/s in the upper stratosphere and mesosphere, and the associated temperature amplitudes are between about 2 and 3 K. These amplitudes may be observable with the instruments on the TIMED spacecraft. Extended computer simulations with the NSM in 2D and 3D reveal that the MO at low latitudes is modulated by the QBO and in turn can influence it to produce a hemispherically asymmetric component. The annual circulation from the summer to the winter hemisphere is likely to play an important role.

  19. Interseasonal Variations in the Middle Atmosphere Forced by Gravity Waves

    NASA Technical Reports Server (NTRS)

    Mayr, H. G.; Mengel, J. G.; Drob, D. P.; Porter, H. S.; Chan, K. L.; Bhartia, P. K. (Technical Monitor)

    2002-01-01

    In our Numerical Spectral Model (NSM), which incorporates Hines' Doppler Spread Parameterization, gravity waves (GW) propagating in the east/west direction can generate the essential features of the observed equatorial oscillations in the zonal circulation and in particular the QBO (quasi-biennial oscillation) extending from the stratosphere into the upper mesosphere. We report here that the NSM also produces inter-seasonal variations in the zonally symmetric (m = 0) meridional circulation. A distinct but variable meridional wind oscillation (MWO) is generated, which appears to be the counterpart to the QBO. With a vertical grid-point resolution of about 0.5 km, the NSM produces the MWO through momentum deposition of GWs propagating in the north/south direction. The resulting momentum source represents a third (generally odd) order non-linear function of the meridional winds, and this enables the oscillation, as in the case of the QBO for the zonal winds. Since the meridional winds are relatively small compared to the zonal winds, however, the vertical wavelength that maintains the MWO is much smaller, i.e., only about 10 km instead of 40 km for the QBO. Consistent with the associated increase of the viscous stress, the period of the MWO is then short compared with that of the QBO, i.e., only about two to four months. Depending on the strength of the GW forcing, the computed amplitudes of the MWO are typically 4 m/s in the upper stratosphere and mesosphere, and the associated temperature amplitudes are between about 2 and 3 K. These amplitudes may be observable with the instruments on the TIMED spacecraft. Extended computer simulations with the NSM in 2D (two-dimensional) and 3D (three-dimensional) reveal that the MWO is modulated by and in turn influences the QBO.

  20. Theory of spin wave modes in tangentially magnetized thin cylindrical dots: A variational approach

    NASA Astrophysics Data System (ADS)

    Zivieri, R.; Stamps, R. L.

    2006-04-01

    We present a theoretical study of the quantized spin wave spectrum in tangentially magnetized cylindrical thin magnetic dots. Low-energy spin waves in magnetic dots may be subdivided into four families: Damon-Eshbach like, backward like, mixed, and end modes. Frequencies and mode profiles are found using a variational approach based on carefully chosen trial functions. The variational method has the advantage that it can be used for large dots that are not practical to treat using numerical finite-element methods. Results for small dots generated using the variational method compare well with micromagnetic results. The variational method is demonstrated with an analysis of data obtained from experimental Brillouin light scattering data from saturated thin cylindrical Permalloy dots. Our approach allows for the definition of parameters describing important contributions to the spin wave energies. As an example, we show that a variational parameter γ provides a measure of spin wave localization near the dot border for one class of modes.

  1. Stationary Planetary Wave and Nonmigrating Tidal Composition of Ionospheric Wave-3 & Wave-4 variations in 2007-2011 FORMOSAT-3/COSMIC observations

    NASA Astrophysics Data System (ADS)

    Chang, L. C.; Lin, C.; Yue, J.; Liu, J. G.; Lin, J.

    2013-12-01

    The wave-3 and wave-4 modulations of the Equatorial Ionization Anomalies (EIAs) are a robust feature of the low latitude ionosphere, when viewed in a constant local time reference frame. Although initially associated respectively with the DE2 and DE3 nonmigrating diurnal tides coupling upwards from the mesosphere and lower thermosphere (MLT) region alone, recent results have suggested that the wave-3 and wave-4 components may also have significant contributions from other nonmigrating tidal and stationary planetary wave (SPW) components. In this study, we present observations of tidal and SPW components comprising the ionospheric wave-3 and wave-4 structures from FORMOSAT-3 / COSMIC Total Electron Content (TEC) from 2007-2011. We find that the wave-3 (wave-4) feature is comprised predominately by DE2 (DE3) and SPW3 (SPW4) throughout the entire five year period, with contributions from SE1 (SE2) being less significant. Additionally, the wave-3 component also has recurring contributions from a DW4 component during December/January. The absolute amplitudes of all the aforementioned components are positively correlated to the level of solar activity, as well as the semiannual variation in zonal mean TEC. After normalizing by the zonal mean TEC, the relative amplitudes of the wave-4 related components show an anti-correlation to solar activity through 2010, which is not seen with the wave-3 related components. The seasonal variation and phase relations of the main constituents of wave-3 and wave-4 are consistent from year to year, as evidenced by the inter-annual recurrence in the peak and trough locations of the ionospheric wave-3 and wave-4. Relative amplitudes of DE3 (black) and SPW4 (blue) in COSMIC TECs as a function of time at 15°N (a) and 15°S (b). Units % of maximum daily zonal mean TEC. Range of uncertainties denoted by dotted lines.

  2. Examiner's finger-mounted fetal tissue oximetry

    NASA Astrophysics Data System (ADS)

    Kanayama, Naohiro; Niwayama, Masatsugu

    2014-06-01

    The best way to assess fetal condition is to observe the oxygen status of the fetus (as well as to assess the condition of infants, children, and adults). Previously, several fetal oximeters have been developed; however, no instrument has been utilized in clinical practice because of the low-capturing rate of the fetal oxygen saturation. To overcome the problem, we developed a doctor's finger-mounted fetal tissue oximeter, whose sensor volume is one hundredth of the conventional one. Additionally, we prepared transparent gloves. The calculation algorithm of the hemoglobin concentration was derived from the light propagation analysis based on the transport theory. We measured neonatal and fetal oxygen saturation (StO2) with the new tissue oximeter. Neonatal StO was measured at any position of the head regardless of amount of hair. Neonatal StO was found to be around 77%. Fetal StO was detected in every position of the fetal head during labor regardless of the presence of labor pain. Fetal StO without labor pain was around 70% in the first stage of labor and around 60% in the second stage of labor. We concluded that our new concept of fetal tissue oximetry would be useful for detecting fetal StO in any condition of the fetus.

  3. Occurring Conditions of Atmospheric Electricity Variation during Seismic Wave Propagation

    NASA Astrophysics Data System (ADS)

    Okubo, Kan; Yamamoto, Keisuke; Takayama, Masakazu; Takeuchi, Nobunao

    We have observed the co-seismic electromagnetic phenomena such as earth potential difference (EPD) variation and atmospheric electricity (AE) variation at three observation sites in Akita Prefecture. In the strong earthquake of December 2nd, 2001, we observed clear signals of the EPD and the AE variation at all three sites. However, the amplitude of both observed signals at three sites are very different though with almost equal quake intensity at each site. The AE signal amplitude is increasing with the EPD signal one at each site. The model how both variation signals appear is proposed to explain the observed data.

  4. A phantom with pulsating artificial vessels for non-invasive fetal pulse oximetry.

    PubMed

    Laqua, Daniel; Pollnow, Stefan; Fischer, Jan; Ley, Sebastian; Husar, Peter

    2014-01-01

    Arterial oxygen saturation of the fetus is an important parameter for monitoring its physical condition. During labor and delivery the transabdominal non-invasive fetal pulse oximetry could minimize the risk for mother and fetus, compared to other existing invasive examination methods. In this contribution, we developed a physical-like phantom to investigate new sensor circuits and algorithms of a non-invasive diagnostic method for fetal pulse oximetry. Hence, the developed artificial vascular system consists of two independent tube systems representing the maternal and fetal vessel system. The arterial blood pressure is reproduced with a pre-pressure and an artificial vascular system. Each pulse wave can be reproduced, by digital control of a proportional valve, adjustable viscoelastic elements, and resistances. The measurements are performed by pressure transducers, optical sensor units, and a coplanar capacitive sensor. Transmission and reflection measurements have shown that the fetal and maternal pulse waves can be reproduced qualitatively. The measured light represents the transabdominal modulated signal on an abdomen of a pregnant woman. PMID:25571272

  5. Variational space-time (dis)continuous Galerkin method for nonlinear free surface water waves

    NASA Astrophysics Data System (ADS)

    Gagarina, E.; Ambati, V. R.; van der Vegt, J. J. W.; Bokhove, O.

    2014-10-01

    A new variational finite element method is developed for nonlinear free surface gravity water waves using the potential flow approximation. This method also handles waves generated by a wave maker. Its formulation stems from Miles' variational principle for water waves together with a finite element discretization that is continuous in space and discontinuous in time. One novel feature of this variational finite element approach is that the free surface evolution is variationally dependent on the mesh deformation vis-à-vis the mesh deformation being geometrically dependent on free surface evolution. Another key feature is the use of a variational (dis)continuous Galerkin finite element discretization in time. Moreover, in the absence of a wave maker, it is shown to be equivalent to the second order symplectic Störmer-Verlet time stepping scheme for the free-surface degrees of freedom. These key features add to the stability of the numerical method. Finally, the resulting numerical scheme is verified against nonlinear analytical solutions with long time simulations and validated against experimental measurements of driven wave solutions in a wave basin of the Maritime Research Institute Netherlands.

  6. Variational Approach to Yang-Mills Theory with non-Gaussian Wave Functionals

    NASA Astrophysics Data System (ADS)

    Campagnari, Davide R.; Reinhardt, Hugo

    2011-05-01

    A general method for treating non-Gaussian wave functionals in quantum field theory is presented and applied to the Hamiltonian approach to Yang-Mills theory in Coulomb gauge in order to include a three-gluon kernel in the exponential of the vacuum wave functional. The three-gluon vertex is calculated using the propagators found in the variational approach with a Gaussian trial wave functional as input.

  7. Experience of pulse oximetry in children with croup.

    PubMed

    Stoney, P J; Chakrabarti, M K

    1991-04-01

    We report our experience with 199 patients requiring admission with a diagnosis of croup over an 18 month period. The value of using pulse oximetry to monitor these children was critically examined. Twenty-nine patients with clinically significant stridor were monitored for an average of 12 hours. There was poor correlation of clinical status and respiratory rate with hypoxia as shown by the technique, with frequent dips in oxygen saturation being caused by technical problems such as movement artefact. Pulse oximetry is a useful adjunct to the clinical assessment of croup, but cannot be relied upon solely for monitoring these labile patients. PMID:2026945

  8. Low-frequency wave modulations in an electronegative dusty plasma in the presence of charge variations.

    PubMed

    Ghosh, Samiran; Sarkar, Subrata; Khan, Manoranjan; Gupta, M R

    2011-12-01

    The effects of dust charge variations on low-frequency wave modulations in an electronegative dusty plasma are investigated. The dynamics of the modulated wave is governed by a nonlinear Schrödinger equation with a dissipative term. The dissipation arises due to the nonsteady (nonadiabatic) dust charge variations. Theoretical and numerical investigations predict the formation of dissipative bright (envelope) and dark solitons. The nonsteady charge-variation-induced dissipation reduces the modulational instability growth rate and introduces a characteristic time scale to observe bright solitons. Results are discussed in the context of electronegative dusty plasma experiments. PMID:22304202

  9. The correlation of VLF propagation variations with atmospheric planetary-scale waves

    NASA Technical Reports Server (NTRS)

    Cavalieri, D. J.; Deland, R. J.; Potemra, T. A.; Gavin, R. F.

    1973-01-01

    Variations in the received daytime phase of long distance, cesium-controlled, VLF transmission were compared to the height variations of the 10-mb isobaric surface during the first three months of 1965 and 1969. The VLF phase values are also compared to height variations of constant electron densities in the E-region and to variations of f-min which have been shown to be well correlated with planetary-scale variations in the stratosphere by Deland and Cavalieri (1973). The VLF phase variations show good correlation with these previous ionospheric measurements and with the 10-mb surfaces. The planetary scale waves in the stratosphere are shown to be travelling on the average eastward in 1965 and westward in 1969. These correlations are interpreted as due to the propagation of travelling planetary scale waves with westward tilted wave fronts. Upward energy transport due to the vertical structure of those waves is also discussed. These correlations provide further evidence for the coupling between the lower ionosphere at about 70 km altitude (the daytime VLF reflection height and the stratosphere, and they demonstrate the importance of planetary wave phenomena to VLF propagation.

  10. Longitudinal Variation and Waves in Jupiter's South Equatorial Wind Jet

    NASA Technical Reports Server (NTRS)

    Simon-Miller, A. A.; Rogers, John H.; Gierasch, Peter J.; Choi, David; Allison, Michael; Adamoli, Gianluigi; Mettig, Hans-Joerg

    2012-01-01

    We have conducted a detailed study of the cloud features in the strong southern equatorial wind jet near 7.5 S planetographic latitude. To understand the apparent variations in average zonal wind jet velocity at this latitude [e.g.. 1,2,3], we have searched for variations iIi both feature latitude and velocity with longitude and time. In particular, we focused on the repetitive chevron-shaped dark spots visible on most dates and the more transient large anticyclonic system known as the South Equatorial Disturbance (SED). These small dark spots are interpreted as cloud holes, and are often used as material tracers of the wind field.

  11. Noncontact simultaneous dual wavelength photoplethysmography: A further step toward noncontact pulse oximetry

    NASA Astrophysics Data System (ADS)

    Humphreys, Kenneth; Ward, Tomas; Markham, Charles

    2007-04-01

    We present a camera-based device capable of capturing two photoplethysmographic (PPG) signals at two different wavelengths simultaneously, in a remote noncontact manner. The system comprises a complementary metal-oxide semiconductor camera and dual wavelength array of light emitting diodes (760 and 880nm). By alternately illuminating a region of tissue with each wavelength of light, and detecting the backscattered photons with the camera at a rate of 16frames/wavelengths, two multiplexed PPG wave forms are simultaneously captured. This process is the basis of pulse oximetry, and we describe how, with the inclusion of a calibration procedure, this system could be used as a noncontact pulse oximeter to measure arterial oxygen saturation (SpO2) remotely. Results from an experiment on ten subjects, exhibiting normal SpO2 readings, that demonstrate the instrument's ability to capture signals from a range of subjects under realistic lighting and environmental conditions are presented. We compare the signals captured by the noncontact system to a conventional PPG signal captured concurrently from a finger, and show by means of a J. Bland and D. Altman [Lancet 327, 307 (1986); Statistician 32, 307 (1983)] test, the noncontact device to be comparable to a contact device as a monitor of heart rate. We highlight some considerations that should be made when using camera-based "integrative" sampling methods and demonstrate through simulation, the suitability of the captured PPG signals for application of existing pulse oximetry calibration procedures.

  12. Effect of nonadiabaticity of dust charge variation on dust acoustic waves: generation of dust acoustic shock waves.

    PubMed

    Gupta, M R; Sarkar, S; Ghosh, S; Debnath, M; Khan, M

    2001-04-01

    The effect of nonadiabaticity of dust charge variation arising due to small nonzero values of tau(ch)/tau(d) has been studied where tau(ch) and tau(d) are the dust charging and dust hydrodynamical time scales on the nonlinear propagation of dust acoustic waves. Analytical investigation shows that the propagation of a small amplitude wave is governed by a Korteweg-de Vries (KdV) Burger equation. Notwithstanding the soliton decay, the "soliton mass" is conserved, but the dissipative term leads to the development of a noise tail. Nonadiabaticity generated dissipative effect causes the generation of a dust acoustic shock wave having oscillatory behavior on the downstream side. Numerical investigations reveal that the propagation of a large amplitude dust acoustic shock wave with dust density enhancement may occur only for Mach numbers lying between a minimum and a maximum value whose dependence on the dusty plasma parameters is presented. PMID:11308955

  13. Seasonal variations in lower stratospheric gravity wave energy above the Falkland Islands

    NASA Astrophysics Data System (ADS)

    Moffat-Griffin, T.; Jarvis, M. J.; Colwell, S. R.; Kavanagh, A. J.; Manney, G. L.; Daffer, W. H.

    2013-10-01

    gravity wavefield in the lower stratosphere (between 15 km and 22 km altitude) above Mount Pleasant Airport (51°49'S, 58°26'W) on the Falkland Islands is studied using over 2100 high-resolution radiosonde soundings from 2002 to 2010. The seasonal variation in vertical direction of propagation shows a small decrease in numbers of upward propagating waves that is related to critical level filtering; however, there is a very large increase in numbers of downward propagating waves between July and September; this is attributed to the proximity of the edge of the polar vortex. There is a seasonal variation in gravity wave energy density, with a large peak during the austral autumn equinox; this is markedly different to results in the literature both from Rothera, on the Antarctic Peninsula, and stations on the main Antarctic continent. This seasonal pattern has been shown to be linked to variations in the sources of upward propagating gravity waves. The seasonal variation in gravity wave characteristics above Mount Pleasant Airport seen in our results suggests that the gravity wavefield in this region is determined by a combination of different gravity wave sources located above and below the lower stratosphere.

  14. Detection of pulsus paradoxus by pulse oximetry in pediatric patients after cardiac surgery.

    PubMed

    Amoozgar, Hamid; Ghodsi, Hossein; Borzoee, Mohammad; Amirghofran, Ahmad Ali; Ajami, Gholamhossein; Serati, Zahra

    2009-01-01

    The presence or absence of pulsus paradoxus (PP), defined as an inspiratory decrease greater than 10 mmHg in systolic blood pressure, can have significant diagnostic and therapeutic implications for many clinical conditions including acute asthma, pericardial tamponade, heart failure, hypovolemia, shock states, and the like. However, PP may be difficult to measure in children. Indwelling arterial catheters facilitate the measurement of PP, but this invasive technique generally is reserved for critically ill patients. This study aimed to assess the use of the pulse oximetry plethysmographic waveform (POPW) for the detection of PP in pediatric patients after cardiac surgery. The study enrolled 40 pediatric patients 18 years of age and younger who had invasive blood pressure monitoring with an intraarterial cannula. Systolic pressure variability (SPV) and changes in POPW amplitude (DeltaPOPW%), calculated using five consecutive snapshots from every patient's monitor, were compared using linear regression, Pearson product-moment correlation, the Spearman rank method, and receiver operating characteristic (ROC) curve analysis. A strong correlation existed between respiratory SPV and DeltaPOPW% for the detection of PP (r = 0.682; p < 0.0001). A respiratory variation in DeltaPOPW% exceeding 25.44% (about one-fourth the amplitude of the tallest POP waveform) allowed detection of PP with a sensitivity of 86.7% and a specificity of 88%. Pulse oximetry is a readily available and easily performed noninvasive means for detecting PP in children. PMID:18665417

  15. Middle-aged adults exhibit altered spatial variations in Achilles tendon wave speed

    PubMed Central

    Slane, Laura Chernak; DeWall, Ryan; Martin, Jack; Lee, Kenneth; Thelen, Darryl G.

    2016-01-01

    The purpose of this study was to investigate spatial variations in measured wave speed in the relaxed and stretched Achilles tendons of young and middle-aged adults. Wave speed was measured from the distal Achilles tendon, soleus aponeurosis, medial gastrocnemius aponeurosis and medial gastrocnemius muscle in healthy young (n = 15, aged 25 ± 4 years) and middle-aged (n = 10, aged 49 ± 4 years) adults in resting, dorsiflexed and plantarflexed postures. In both age groups, Achilles tendon wave speed decreased proximally, with the lowest wave speed measured in the gastrocnemius aponeurosis. Measured wave speed increased with passive dorsiflexion, reflecting the strain-stiffening behavior of tendons. There were no significant aging effects on wave speed in the free tendon or soleus aponeurosis. However, a significant, inverse relationship between gastrocnemius aponeurosis wave speed and age was observed in the dorsiflexed posture. We also observed significantly lower wave speeds in the gastrocnemius muscles of middle-aged adults when compared with young adults. These results suggest that Achilles tendon compliance increases in a distal-to-proximal pattern, with middle-aged adults exhibiting greater compliance in the distal gastrocnemius muscle and tendinous structures. An age-related change in the spatial variation in Achilles tendon compliance could affect localised tissue deformation patterns and injury potential within the triceps surae muscle-tendon units. PMID:26020294

  16. Variational principle in optics II: Dissipative wave equations.

    PubMed

    Rubinstein, Jacob; Wolansky, Gershon

    2016-08-01

    The problem of phase retrieval from intensity measurements is examined for the case of dissipative wave equations. Unlike the conservative case, it is not clear if and when the problem is solvable at all. We provide two solutions. First, it is shown that, for a certain class of dissipating potentials, the problem can be fully solved by converting it through a simple transformation to the framework of the weighted least action principle. Second, for all other dissipating potentials, a deep result from the theory of elliptic partial differential equations is used to show that the problem is always solvable up to a scaling of one of the measured intensities. Moreover, the solution in this general case can be obtained by solving a Monge-Ampere type differential equation. Two numerical examples are given to illustrate some of the theoretical considerations. PMID:27505643

  17. Variation of wave velocity and porosity of sandstone after high temperature heating

    NASA Astrophysics Data System (ADS)

    Sun, Qiang; Zhang, ·Weiqiang; Su, Tianming; Zhu, Shuyun

    2016-05-01

    This paper reports the variations of mass, porosity, and wave velocity of sandstone after high temperature heating. The range of temperature to which the sandstone specimens have been exposed is 25-850°C, in a heating furnace. It has been shown that below 300°C, porosity and wave velocity change very little. Above 300°C, there is a rapid increase in porosity, but the wave velocity decreases significantly. The results of thermo gravimetric analysis (TGA), differential scanning calorimetry (DSC) and mercury intrusion porosimetry (MIP) suggest that a series of changes occurred between 400 and 600°C in sandstone could be responsible for the different patterns of variation in porosity and wave velocity.

  18. sup 4 He- sup 4 He elastic scattering and variational wave functions

    SciTech Connect

    Usmani, A.A.; Ahmad, I. ); Usmani, Q.N. )

    1992-01-01

    We calculate differential cross sections for {sup 4}He-{sup 4}He elastic scattering at 4.32 GeV/{ital c} in the framework of Glauber multiple scattering theory using correlated variational wave functions as given by the two-nucleon Urbana {ital v}{sub 14} potential and the spin-isospin averaged Melfleit-Tjon force {ital V}. These wave functions are found to give fairly satisfactory results.

  19. Optical beam shaping and diffraction free waves: A variational approach

    NASA Astrophysics Data System (ADS)

    Gemmer, John A.; Venkataramani, Shankar C.; Durfee, Charles G.; Moloney, Jerome V.

    2014-08-01

    We investigate the problem of shaping radially symmetric annular beams into desired intensity patterns along the optical axis. Within the Fresnel approximation, we show that this problem can be expressed in a variational form equivalent to the one arising in phase retrieval. Using the uncertainty principle we prove various rigorous lower bounds on the functional; these lower bounds estimate the L2 error for the beam shaping problem in terms of the design parameters. We also use the method of stationary phase to construct a natural ansatz for a minimizer in the short wavelength limit. We illustrate the implications of our results by applying the method of stationary phase coupled with the Gerchberg-Saxton algorithm to beam shaping problems arising in the remote delivery of beams and pulses.

  20. A normalized wave number variation parameter for acoustic black hole design.

    PubMed

    Feurtado, Philip A; Conlon, Stephen C; Semperlotti, Fabio

    2014-08-01

    In recent years, the concept of the Acoustic Black Hole has been developed as an efficient passive, lightweight absorber of bending waves in plates and beams. Theory predicts greater absorption for a higher thickness taper power. However, a higher taper power also increases the violation of an underlying theory smoothness assumption. This paper explores the effects of high taper power on the reflection coefficient and spatial change in wave number and discusses the normalized wave number variation as a spatial design parameter for performance, assessment, and optimization. PMID:25096139

  1. Analysis of Wave Propagation in Mechanical Continua Using a New Variational Approach

    NASA Astrophysics Data System (ADS)

    Chakraborty, Goutam

    2016-06-01

    In this paper a new variational principle is presented for studying various wave propagation phenomena without explicitly deriving the equations of motion. The method looks for steady state solutions of linear or non-linear partial differential equations that admit wave-like solutions. Dispersion relations of plane waves propagating in unbounded continuous media, transmission and reflection coefficients of wave incident on the boundary of two semi-infinite media and wave impedance and mobility in an excited medium are studied with the help of the same principle. Numerous examples are given to clarify the method adopted showing distinct advantages over the traditional methods. The scientific insights that this principle provides are also highlighted.

  2. Hurricane Directional Wave Spectrum Spatial Variation in the Open Ocean and at Landfall

    NASA Technical Reports Server (NTRS)

    Walsh, E. J.; Wright, C. W.; Vandemark, D.; Krabill, W. B.; Garcia, A. W.; Houston, S. H.; Powell, M. D.; Black, P. G.; Marks, F. D.; Busalacchi, Antonio J. (Technical Monitor)

    2000-01-01

    The sea surface directional wave spectrum was measured for the first time in all quadrants of a hurricane in open water using the NASA airborne scanning radar altimeter (SRA) carried aboard one of the NOAA WP-3D hurricane hunter aircraft at 1.5 km height. The SRA measures the energetic portion of the directional wave spectrum by generating a topographic map of the sea surface. At 8 Hz, the SRA sweeps a radar beam of 1 E half-power width (two-way) across the aircraft ground track over a swath equal to 0.8 of the aircraft height, simultaneously measuring the backscattered power at its 36 GHz (8.3 mm) operating frequency and the range to the sea surface at 64 positions. These slant ranges are multiplied by the cosine of the incidence angles to determine the vertical distances from the aircraft to the sea surface. Subtracting these distances from the aircraft height produces the sea surface elevation map. The sea surface topography is interpolated to a uniform grid, transformed by a two-dimensional FFT, and Doppler corrected. The open-ocean data were acquired on 24 August 1998 when hurricane Bonnie was east of the Bahamas and moving slowly to the north. Individual waves with heights up to 18 m were observed and the spatial variation of the wave field was dramatic. The dominant waves generally propagated at significant angles to the downwind direction. At some positions there were three different wave fields of comparable energy crossing each other. The NOAA aircraft spent over five hours within 180 km of the hurricane Bonnie eye, and made five eye penetrations. A 3-minute animation of the directional wave spectrum spatial variation over this period will be shown as well as summary plots of the wave field spatial variation. On 26 August 1998, the NOAA aircraft flew at 2.2 km height when hurricane Bonnie was making landfall near Wilmington, NC, documenting the directional wave spectrum in the region between Charleston, SC and Cape Hatteras, NC. The aircraft ground track

  3. Full-wave calculation of fast-wave current drive in tokamaks including k sub parallel variations

    SciTech Connect

    Jaeger, E.F; Batchelor, D.B.

    1991-01-01

    When fast waves propagate inward from the edge of a tokamak toward the plasma center, the k{perpendicular} spectrum produced by the antenna is not maintained but is shifted and deformed due to the presence of the finite poloidal magnetic field. This k{perpendicular} shift causes a variation in the parallel phase speed of the wave and can therefore have a strong effect on electron damping and current drive efficiency. In this paper, we include this effect in a new full-wave calculation (PICES) which represents the wave fields as a superposition of poloidal modes, thereby reducing k{perpendicular} to an algebraic operator. The wave equation is solved in general flux coordinates, including a full (non-perturbative) solution for E{perpendicular} and a reduced-order dielectric formulation to eliminate short-wavelength ion Bernstein modes. A simplified current drive model which includes particle trapping is used to estimate the effect of the k{perpendicular} shift on current drive efficiency in ITER and D3-D. Results suggest that when single-pass absorption is weak, reflected power may drive current nearly as efficiently as that absorbed on the first pass. 15 refs., 5 figs.

  4. Lunar Brightness Variations with Phase at 4.3-MM Wave Length

    NASA Technical Reports Server (NTRS)

    Coates, Robert J.

    1961-01-01

    The lunar radio observations and interpretations of Piddington and Minnett (1949) and Gibson (1958) show that the lunar brightness variation with phase at millimeter wave lengths can be used to determine the physical properties of the lunar surface. They found that the millimeter-wave brightness lagged the optical phase, and their interpretation was that the millimeter radiation originates below a surface layer that is a very good thermal insulator. The thickness of this layer could not be determined from observations at one frequency. Observations at different frequencies give different results because of the wave-length dependence of the radio absorption by the surface material. The attenuation in the material increases with decreasing wave length, and therefore it is possible, in principle, to determine surface layer thickness from radio observations at several wave lengths. For this reason, observations of lunar radiation were started at the Naval Research Laboratory at a wave length of 4.3 mm. This is half the wave length used by Gibson (1958) in his earlier studies. The radio telescope used for these observations has been described in detail in a previous publication (Coates 1958). The antenna is a parabolic reflector 10 feet in diameter, and it has a beam width of 6.7 minutes of arc at the wave length of 4.3 mm. This is about one-fifth the diameter of the moon. The receiver was a Dicke-type radiometer.

  5. Transcutaneous oximetry: normal values for the lower limb.

    PubMed

    2016-03-01

    Consistent with the Committee on Publication Ethics guidelines, we the above authors are initiating the retraction of our paper: Blake DF, Young DA, Brown LH: Transcutaneous oximetry: normal values for the lower limb. Diving Hyperb Med. 2014 September;44(3):146-153. We wish to make the following statement: "The authors voluntarily retract this article after discovering a critical error associated with the instrumentation used in the study, namely the fitting of incorrect sensor membranes on the electrodes of the transcutaneous oximetry device used in the study. This resulted in transcutaneous oxygen tension (PtcO₂) measurements that were consistently lower than those that would be recorded with the correct electrode membranes in place, which we recently confirmed by comparing the two membrane types once we discovered the error. We are in the process of replicating our work using the correct PtcO₂ specific membranes." PMID:27044466

  6. Transcutaneous oximetry measurement: normal values for the upper limb.

    PubMed

    2016-03-01

    Consistent with the Committee on Publication Ethics guidelines, we the above authors are initiating the retraction of our paper: Young DA, Blake DF, Brown LH: Transcutaneous oximetry measurement: normal values for the upper limb. Diving Hyperb Med. 2012;42(4):208-213. We wish to make the following statement: "The authors voluntarily retract this article after discovering a critical error associated with the instrumentation used in the study, namely the fitting of incorrect sensor membranes on the electrodes of the transcutaneous oximetry device used in the study. This resulted in transcutaneous oxygen tension (PtcO₂) measurements that were consistently lower than those that would have been recorded with the correct electrode membranes in place. We recently confirmed this by comparing the two membrane types once we discovered the error. We are in the process of replicating our work using the correct PtcO₂ specific membranes." PMID:27044465

  7. Improving pulse oximetry pitch perception with multisensory perceptual training.

    PubMed

    Schlesinger, Joseph J; Stevenson, Ryan A; Shotwell, Matthew S; Wallace, Mark T

    2014-06-01

    The pulse oximeter is a critical monitor in anesthesia practice designed to improve patient safety. Here, we present an approach to improve the ability of anesthesiologists to monitor arterial oxygen saturation via pulse oximetry through an audiovisual training process. Fifteen residents' abilities to detect auditory changes in pulse oximetry were measured before and after perceptual training. Training resulted in a 9% (95% confidence interval, 4%-14%, P = 0.0004, t(166) = 3.60) increase in detection accuracy, and a 72-millisecond (95% confidence interval, 40-103 milliseconds, P < 0.0001, t(166) = -4.52) speeding of response times in attentionally demanding and noisy conditions that were designed to simulate an operating room. This study illustrates the benefits of multisensory training and sets the stage for further work to better define the role of perceptual training in clinical anesthesiology. PMID:24846194

  8. Effect of Helical Slow-Wave Circuit Variations on TWT Cold-Test Characteristics

    NASA Technical Reports Server (NTRS)

    Kory, Carol L.; Dayton, James A., Jr.

    1997-01-01

    Recent advances in the state of the art of computer modeling offer the possibility for the first time to evaluate the effect that slow-wave structure parameter variations, such as manufacturing tolerances, have on the cold-test characteristics of helical traveling-wave tubes (TWT's). This will enable manufacturers to determine the cost effectiveness of controlling the dimensions of the component parts of the TWT, which is almost impossible to do experimentally without building a large number of tubes and controlling several parameters simultaneously. The computer code MAFIA is used in this analysis to determine the effect on dispersion and on-axis interaction impedance of several helical slow-wave circuit parameter variations, including thickness and relative dielectric constant of the support rods, tape width, and height of the metallized films deposited on the dielectric rods. Previous computer analyses required so many approximations that accurate determinations of the effect of many relevant dimensions on tube performance were practically impossible.

  9. Effect of Helical Slow-Wave Circuit Variations on TWT Cold-Test Characteristics

    NASA Technical Reports Server (NTRS)

    Kory, Carol L.; Dayton, J. A., Jr.

    1998-01-01

    Recent advances in the state of the art of computer modeling offer the possibility for the first time to evaluate the effect that slow-wave structure parameter variations, such as manufacturing tolerances, have on the cold-test characteristics of helical traveling-wave tubes (TWT's). This will enable manufacturers to determine the cost effectiveness of controlling the dimensions of the component parts of the TWT, which is almost impossible to do experimentally without building a large number of tubes and controlling several parameters simultaneously. The computer code MAFIA is used in this analysis to determine the effect on dispersion and on-axis interaction impedance of several helical slow-wave circuit parameter variations, including thickness and relative dielectric constant of the support rods, tape width, and height of the metallized films deposited on the dielectric rods. Previous computer analyzes required so many approximations that accurate determinations of the effect of many relevant dimensions on tube performance were practically impossible.

  10. The influence of temperature variations on ultrasonic guided waves in anisotropic CFRP plates.

    PubMed

    Putkis, O; Dalton, R P; Croxford, A J

    2015-07-01

    Carbon Fibre Reinforced Polymer (CFRP) materials are lightweight and corrosion-resistant and therefore are increasingly used in aerospace, automotive and construction industries. In Structural Health Monitoring (SHM) applications of CFRP materials, ultrasonic guided waves potentially offer large area inspection or inspection from a remote location. This paper addresses the effect of temperature variation on guided wave propagation in highly anisotropic CFRP materials. Temperature variations cause changes in guided wave velocity that can in turn compromise the baseline subtraction procedures employed by many SHM systems for damage detection. A simple model that describes the dependence of elastic properties of the CFRP plates on temperature is presented in this paper. The model can be used to predict anisotropic velocity changes and baseline subtraction performance under varying thermal conditions. The results produced by the model for unidirectional and 0/90 CFRP plates are compared with experimental measurements. PMID:25812468

  11. Temperature variation effects on sparse representation of guided-waves for damage diagnosis in pipelines

    NASA Astrophysics Data System (ADS)

    Eybpoosh, Matineh; Berges, Mario; Noh, Hae Young

    2015-04-01

    Multiple ultrasonic guided-wave modes propagating along a pipe travel with different velocities which are themselves a function of frequency. Reflections from the features of the structure (e.g., boundaries, pipe welding, damage, etc.), and their complex superposition, adds to the complexity of guided-waves. Guided-wave based damage diagnosis of pipelines becomes even more challenging when environmental and operational conditions (EOCs) vary (e.g., temperature, flow rate, inner pressure, etc.). These complexities make guided-wave based damage diagnosis of operating pipelines a challenging task. This paper reviews the approaches to-date addressing these challenges, and highlights the preferred characteristics of a method that simplifies guided-wave signals for damage diagnosis purposes. A method is proposed to extract a sparse subset of guided-wave signals in time-domain, while retaining optimal damage information for detection purpose. In this paper, the general concept of this method is proved through an extensive set of experiments. Effects of temperature variation on detection performance of the proposed method, and on discriminatory power of the extracted damage-sensitive features are investigated. The potential of the proposed method for real-time damage detection is illustrated, for wide range of temperature variation scenarios (i.e., temperature difference between training and test data varying between -2°C and 13°C).

  12. Finger blood content, light transmission, and pulse oximetry errors.

    PubMed

    Craft, T M; Lawson, R A; Young, J D

    1992-01-01

    The changes in light emitting diode current necessary to maintain a constant level of light incident upon a photodetector were measured in 20 volunteers at the two wavelengths employed by pulse oximeters. Three states of finger blood content were assessed; exsanguinated, hyperaemic, and normal. The changes in light emitting diode current with changes in finger blood content were small and are not thought to represent a significant source of error in saturation as measured by pulse oximetry. PMID:1536406

  13. Optoelectronic blood oximetry as a tool of health safety monitoring

    NASA Astrophysics Data System (ADS)

    Cysewska-Sobusiak, Anna

    2001-08-01

    A metrological approach of some selected problems connected with the significant field of biomedical optics i.e., monitoring of arterial blood oxygenation by use of the tissues as optical media exposed to the controlled light action, has been presented. The subject of the measurements based on utilization of the selection absorption properties of blood is the hemoglobin oxygen saturation. Using optoelectronic sensing allows to convert sophisticated effects of noninvasive light-living tissue interaction to electrical signals which may be convenient to measure. Pulse oximetry which is based upon such a way of sensing and processing, is the recent advance in noninvasive oximetry. The unique advantages of that marvelous diagnostic technique have caused to recommend pulse oximeters as standard equipment in intensive care and other critical situations impending hypoxemia appearance. However, end-users of the pulse oximeters not always are aware of that these devices fall under specific limitations, of both physiological and technical nature. The author of this paper is a metrologist and deals mainly with various interdisciplinary problems of a measurement reliability including the aspects such as uncertainty of an outcome accessible to the user, causes affecting sensitivity, resolution and repeatability of processing function, and response time and stability of results. Referring to the subject discussed herein, and taking into account some open questions, the author's contribution is her own experience in modeling as well as in in vivo measuring of transilluminated living objects. A proposed novel use of the known pulse oximetry concept may be considered as complementary results against a general review background of the achievements obtained in oximetry as the state-of-the-art, and furthermore, the developing studies which are still in progress.

  14. Regional synchrony of temperature variation and internal wave forcing along the Florida Keys reef tract

    NASA Astrophysics Data System (ADS)

    Leichter, James J.; Stokes, M. Dale; Vilchis, L. Ignacio; Fiechter, Jerome

    2014-01-01

    Analysis of 10 year temperature records collected along the Florida Keys reef tract (FLKRT) reveals strong, regional-scale synchrony in high-frequency temperature variation suggestive of internal wave forcing at predominately semidiurnal frequencies. In each year and at all sites, the amplitude of semidiurnal temperature variation was greatest from March to September, and markedly lower from October to February. Comparisons of the semidiurnal component of the temperature variation among sites suggest complex patterns in the arrival of internal waves, with highest cross correlation among closely spaced sites and synchrony in periods of enhanced internal wave activity across the length of the FLKRT, particularly in summer. The periods of enhanced semidiurnal temperature variation at the 20 and 30 m isobaths on the reef slopes appear to be associated with the dynamics of the Florida Current and the onshore movement of warm fronts preceding the passage of Florida Current frontal eddies. Regional-scale satellite altimetry observations suggest temporal linkages to sea surface height anomalies in the Loop Current (upstream of the Florida Current) and setup of the Tortugas Gyre. The synchronized forcing of cool water onto the reef slope sites across the FLKRT is likely to affect physiological responses to temperature variation in corals and other ectothermic organisms, as well as larval transport and nutrient dynamics with the potential for regionally coherent pulses of larvae and nutrients arriving on reef slopes across the FLKRT.

  15. Retinal oximeter for the blue-green oximetry technique

    NASA Astrophysics Data System (ADS)

    Denninghoff, Kurt R.; Sieluzycka, Katarzyna B.; Hendryx, Jennifer K.; Ririe, Tyson J.; Deluca, Lawrence; Chipman, Russell A.

    2011-10-01

    Retinal oximetry offers potential for noninvasive assessment of central venous oxyhemoglobin saturation (SO2) via the retinal vessels but requires a calibrated accuracy of +/-3% saturation in order to be clinically useful. Prior oximeter designs have been hampered by poor saturation calibration accuracy. We demonstrate that the blue-green oximetry (BGO) technique can provide accuracy within +/-3% in swine when multiply scattered light from blood within a retinal vessel is isolated. A noninvasive on-axis scanning retinal oximeter (ROx-3) is constructed that generates a multiwavelength image in the range required for BGO. A field stop in the detection pathway is used in conjunction with an anticonfocal bisecting wire to remove specular vessel reflections and isolate multiply backscattered light from the blood column within a retinal vessel. This design is tested on an enucleated swine eye vessel and a retinal vein in a human volunteer with retinal SO2 measurements of ~1 and ~65%, respectively. These saturations, calculated using the calibration line from earlier work, are internally consistent with a standard error of the mean of +/-2% SO2. The absolute measures are well within the expected saturation range for the site (-1 and 63%). This is the first demonstration of noninvasive on-axis BGO retinal oximetry.

  16. A hand-held EPR scanner for transcutaneous oximetry

    NASA Astrophysics Data System (ADS)

    Wolfson, Helen; Ahmad, Rizwan; Twig, Ygal; Blank, Aharon; Kuppusamy, Periannan

    2015-03-01

    Cutaneous (skin) oxygenation is an important prognostic factor for the treatment of chronic wounds, skin cancer, diabetes side effects, and limb amputation. Currently, there are no reliable methods for measuring this parameter. Oximetry, using electron paramagnetic resonance (EPR) spectroscopy, is emerging as a potential tool for clinical oximetry, including cutaneous applications. The problem with EPR oximetry, however, is that the conventional EPR design requires the use of a large magnet that can generate homogeneous field across the sample, making it unattractive for clinical practice. We present a novel approach that makes use of a miniature permanent magnet, combined with a small microwave resonator, to enable the acquisition of EPR signals from paramagnetic species placed on the skin. The instrumentation consists of a hand-held, modular, cylindrical probehead with overall dimensions of 36-mm diameter and 24-mm height, with 150-g weight. The probehead includes a Halbach array of 16 pieces (4×4×8 mm3) of Sm-Co permanent magnet and a loop-gap resonator (2.24 GHz). Preliminary measurements using a Hahn-echo pulse sequence (800 echos in 20 ms) showed a signalto- noise ratio of ~70 compared to ~435 in a homogenous magnet under identical settings. Further work is in progress to improve the performance of the probehead and to optimize the hand-held system for clinical use

  17. Accuracy of retinal oximetry: a Monte Carlo investigation

    PubMed Central

    Liu, Wenzhong; Jiao, Shuliang

    2013-01-01

    Abstract. Retinal hemoglobin oxygen saturation (sO2) level is believed to be associated with the pathophysiology of several leading blinding diseases. Methods to properly measure retinal sO2 have been investigated for decades; however, the accuracy of retinal oximetry is still considered to be limited. The Monte Carlo simulation of photon transport in retina to examine how the accuracy of retinal oximetry is affected by local parameters is discussed. Fundus photography was simulated in a multilayer retinal model, in which a single vessel segment with 0.7  sO2 was embedded, at six optical wavelengths. Then, 200 million photons were traced in each simulation to ensure statistically stable results. The optical reflectance and energy deposit were recorded to measure sO2 using both the reflection method (existing retinal oximetry) and a new absorption method, photoacoustic ophthalmoscopy (PAOM). By varying the vessel diameter and melanin concentration in the retinal pigment epithelium, the relative error of sO2 measurement in the reflection method increased with increasing vessel diameter and melanin concentration; in comparison, the sO2 measurement was insensitive to these two parameters in PAOM. The results suggest that PAOM potentially can be a more accurate tool in quantifying retinal sO2. PMID:23733019

  18. Advances in Probes and Methods for Clinical EPR Oximetry

    PubMed Central

    Hou, Huagang; Khan, Nadeem; Jarvis, Lesley A.; Chen, Eunice Y.; Williams, Benjamin B.; Kuppusamy, Periannan

    2015-01-01

    EPR oximetry, which enables reliable, accurate, and repeated measurements of the partial pressure of oxygen in tissues, provides a unique opportunity to investigate the role of oxygen in the pathogenesis and treatment of several diseases including cancer, stroke, and heart failure. Building on significant advances in the in vivo application of EPR oximetry for small animal models of disease, we are developing suitable probes and instrumentation required for use in human subjects. Our laboratory has established the feasibility of clinical EPR oximetry in cancer patients using India ink, the only material presently approved for clinical use. We now are developing the next generation of probes, which are both superior in terms of oxygen sensitivity and biocompatibility including an excellent safety profile for use in humans. Further advances include the development of implantable oxygen sensors linked to an external coupling loop for measurements of deep-tissue oxygenations at any depth, overcoming the current limitation of 10 mm. This paper presents an overview of recent developments in our ability to make meaningful measurements of oxygen partial pressures in human subjects under clinical settings. PMID:24729217

  19. Global oximetry: an international anaesthesia quality improvement project.

    PubMed

    Walker, I A; Merry, A F; Wilson, I H; McHugh, G A; O'Sullivan, E; Thoms, G M; Nuevo, F; Whitaker, D K

    2009-10-01

    Pulse oximetry is mandatory during anaesthesia in many countries, a standard endorsed by the World Health Organization 'Safe Surgery Saves Lives' initiative. The Association of Anaesthetists of Great Britain and Ireland, the World Federation of Societies of Anaesthesiologists and GE Healthcare collaborated in a quality improvement project over a 15-month period to investigate pulse oximetry in four pilot sites in Uganda, Vietnam, India and the Philippines, using 84 donated pulse oximeters. A substantial gap in oximeter provision was demonstrated at the start of the project. Formal training was essential for oximeter-naïve practitioners. After introduction of oximeters, logbook data were collected from over 8000 anaesthetics, and responses to desaturation were judged appropriate. Anaesthesia providers believed pulse oximeters were essential for patient safety and defined characteristics of the ideal oximeter for their setting. Robust systems for supply and maintenance of low-cost oximeters are required for sustained uptake of pulse oximetry in low- and middle-income countries. PMID:19735394

  20. Accuracy of retinal oximetry: a Monte Carlo investigation

    NASA Astrophysics Data System (ADS)

    Liu, Wenzhong; Jiao, Shuliang; Zhang, Hao F.

    2013-06-01

    Retinal hemoglobin oxygen saturation (sO2) level is believed to be associated with the pathophysiology of several leading blinding diseases. Methods to properly measure retinal sO have been investigated for decades; however, the accuracy of retinal oximetry is still considered to be limited. The Monte Carlo simulation of photon transport in retina to examine how the accuracy of retinal oximetry is affected by local parameters is discussed. Fundus photography was simulated in a multilayer retinal model, in which a single vessel segment with 0.7 sO2 was embedded, at six optical wavelengths. Then, 200 million photons were traced in each simulation to ensure statistically stable results. The optical reflectance and energy deposit were recorded to measure sO using both the reflection method (existing retinal oximetry) and a new absorption method, photoacoustic ophthalmoscopy (PAOM). By varying the vessel diameter and melanin concentration in the retinal pigment epithelium, the relative error of sO measurement in the reflection method increased with increasing vessel diameter and melanin concentration; in comparison, the sO measurement was insensitive to these two parameters in PAOM. The results suggest that PAOM potentially can be a more accurate tool in quantifying retinal sO.

  1. ROx3: Retinal oximetry utilizing the blue-green oximetry method

    NASA Astrophysics Data System (ADS)

    Parsons, Jennifer Kathleen Hendryx

    The ROx is a retinal oximeter under development with the purpose of non-invasively and accurately measuring oxygen saturation (SO2) in vivo. It is novel in that it utilizes the blue-green oximetry technique with on-axis illumination. ROx calibration tests were performed by inducing hypoxia in live anesthetized swine and comparing ROx measurements to SO 2 values measured by a CO-Oximeter. Calibration was not achieved to the precision required for clinical use, but limiting factors were identified and improved. The ROx was used in a set of sepsis experiments on live pigs with the intention of tracking retinal SO2 during the development of sepsis. Though conclusions are qualitative due to insufficient calibration of the device, retinal venous SO2 is shown to trend generally with central venous SO2 as sepsis develops. The novel sepsis model developed in these experiments is also described. The method of cecal ligation and perforation with additional soiling of the abdomen consistently produced controllable severe sepsis/septic shock in a matter of hours. In addition, the ROx was used to collect retinal images from a healthy human volunteer. These experiments served as a bench test for several of the additions/modifications made to the ROx. This set of experiments specifically served to illuminate problems with various light paths and image acquisition. The analysis procedure for the ROx is under development, particularly automating the process for consistency, accuracy, and time efficiency. The current stage of automation is explained, including data acquisition processes and the automated vessel fit routine. Suggestions for the next generation of device minimization are also described.

  2. Possible variations of E-layer electromagnetic fields by acoustic waves above earthquake preparation regions

    NASA Astrophysics Data System (ADS)

    Meister, C.-V.; Mayer, B.; Hoffmann, D. H. H.

    2012-04-01

    The many-fluid magnetohydrodynamic theory is applied to describe the modification of the electromagnetic field of the ionospheric E-layer by acoustic-type waves. These waves originate from lower altitudes and may be caused by earthquake preparation processes. In comparison to former works, the different stratification of the positively and negatively charged ionospheric particles and of the neutral constituents is taken into account. There also the influence of the mean electric field on the different hight scales of the plasma parameters is discussed. Besides, the hight scales of the electric and magnetic wave fields are modeled. It is shown that at E-layer altitudes the acoustic waves may be converted into Alfvén waves. The dependence of these waves on the height scales of the plasma parameters of the particles and on the momentum transport between the charged and neutral particles is analysed. First estimates of the temperature variations within the E-layer because of the assumed acoustic-type waves of seismic origin are made.

  3. Coherent molecular transistor: Control through variation of the gate wave function

    SciTech Connect

    Ernzerhof, Matthias

    2014-03-21

    In quantum interference transistors (QUITs), the current through the device is controlled by variation of the gate component of the wave function that interferes with the wave function component joining the source and the sink. Initially, mesoscopic QUITs have been studied and more recently, QUITs at the molecular scale have been proposed and implemented. Typically, in these devices the gate lead is subjected to externally adjustable physical parameters that permit interference control through modifications of the gate wave function. Here, we present an alternative model of a molecular QUIT in which the gate wave function is directly considered as a variable and the transistor operation is discussed in terms of this variable. This implies that we specify the gate current as well as the phase of the gate wave function component and calculate the resulting current through the source-sink channel. Thus, we extend on prior works that focus on the phase of the gate wave function component as a control parameter while having zero or certain discrete values of the current. We address a large class of systems, including finite graphene flakes, and obtain analytic solutions for how the gate wave function controls the transistor.

  4. Seasonal variation of gravity waves in the Equatorial Middle Atmosphere: results from ISRO's Middle Atmospheric Dynamics (MIDAS) program

    NASA Astrophysics Data System (ADS)

    Ramkumar, G.; Antonita, T. M.; Bhavani Kumar, Y.; Venkata Kumar, H.; Narayana Rao, D.

    2006-10-01

    Altitude profiles of temperature in the stratospheric and mesopheric region from lidar observations at NARL, Gadanki, India, during December 2002-April 2005, as part of ISRO's Middle Atmospheric Dynamics - "MIDAS (2002-2005)" program are used to study the characteristics of gravity waves and their seasonal variation. Month-to-month variation of the gravity wave activity observed during the period of December 2002-April 2005 show maximum wave activity, with primary peaks in May 2003, August 2004 and March 2005 and secondary peaks in February 2003 and November 2004. This month-to-month variation in gravity wave activity is linked to the variation in the strength of the sources, viz. convection and wind shear, down below at the tropospheric region, estimated from MST radar measurements at the same location. Horizontal wind shear is found to be mostly correlated with wave activity than convection, and sometimes both sources are found to contribute towards the wave activity.

  5. Retinal Oximetry with Scanning Laser Ophthalmoscope in Infants

    PubMed Central

    Vehmeijer, Wouter B.; Magnusdottir, Vigdis; Eliasdottir, Thorunn S.; Hardarson, Sveinn Hakon; Schalij-Delfos, Nicoline E.; Stefánsson, Einar

    2016-01-01

    Purpose Dual wavelength retinal oximetry has been developed for adults, but is not available for infants. Retinal oximetry may provide insight into the pathophysiology of oxygen-mediated diseases like retinopathy of prematurity. More insight in the oxygen metabolism of the retina in infants may provide valuable clues for better understanding and subsequent prevention or treatment of the disease. The measurements of oxygen saturation are obtained with two fundus images simultaneously captured in two different wavelengths of light. The comparison in light absorption of oxygenated and deoxygenated hemoglobin can be used to estimate the oxygen saturation within the retinal vessels by means of a software algorithm. This study aims to make retinal oximetry available for neonates. The first step towards estimating retinal oxygen saturation is determining the optical density ratio. Therefore, the purpose of this study is to image healthy newborn infants with a scanning laser ophthalmoscope and determine the optical density ratio for retinal oximetry analysis. Methods Images of the retina of full-term healthy infants were obtained with an SLO, Optomap 200Tx (Optos), with two laser wavelengths (532nm and 633nm). The infant lay face down on the lower arm of the parent, while the parent supported the chest and chin with one hand, and stabilized the back with the other hand. No mydriatics or eyelid specula were used during this study. The images were analyzed with modified Oxymap Analyzer software for calculation of the Optical Density Ratio (ODR) and vessel width. The ODR is inversely and approximately linearly related to the oxygen saturation. Measurements were included from the superotemporal vessel pair. A paired t-test was used for statistical analysis. Results Fifty-nine infants, (58% female), were included with mean gestational age of 40 ± 1.3 weeks (mean ± SD) and mean post-natal age of 16 ± 4.8 days. A total of 28 images were selected for retinal oximetry analysis

  6. Schwinger variational principle calculations of wave scattering from conducting cylinders using physically motivated trial functions

    NASA Astrophysics Data System (ADS)

    Stoyanov, B. J.; Farrell, R. A.

    1996-02-01

    The Schwinger variational principle for the scattering amplitude is applied to two related test problems: an infinitely long perfectly conducting circular cylinder and a hemicylindrically embossed plane illuminated by a normally incident plane wave whose magnetic field is perpendicular to the cylinder axis (TM polarization). It is demonstrated that the variational principle yields very good results with trial functions containing only a few variational parameters, provided the trial functions mimic not only the correct boundary conditions on the scatterer surface but also the expected shadowing effects of the obstacle. A variety of analytical variational limits for both low and high frequencies are derived, which, together with the numerical results for intermediate frequencies, compare very favorably with the available exact solutions.

  7. Seasonal variation in Rayleigh-to-Love wave ratio in the secondary microseism

    NASA Astrophysics Data System (ADS)

    Tanimoto, T.; Hadziioannou, C.; Igel, H.; Wassermann, J. M.; Schreiber, U.; Gebauer, A.; Chow, B.

    2015-12-01

    The Ring Laser (the G-ring) at Wettzell (WET), Germany, is a rotation-measurement instrument that can monitor tiny variations in seismic noise. It essentially records only SH-type signals. Combined with a co-located seismograph (three-component seismograph STS-2), we can monitor the amount of Love waves from this instrument and that of Rayleigh waves from the STS seismograph. We report on seasonal variation of Rayleigh-to-Love wave ratio in the secondary microseism. The first step in our analysis is to obtain stacked Fourier spectra that were least affected by earthquakes. We used two earthquake catalogues to do this; the GCMT (Global Centroid Moment Tensor, Earthquakes M > 5.5) catalogue and the EMSC (European-Mediterranean Seismic Centre) catalogue for regional earthquakes (distance < 1000 km) with M > 4.5. We then created monthly averages of noise Fourier spectra for the frequency range 0.13-0.30 Hz using both the G-ring and STS data from 2009 to 2015. Monthly spectra show clear seasonal variations for the secondary microseism. We obtained surface vertical acceleration from STS and surface transverse acceleration from G-ring from which we can directly measure the Rayleigh-to-Love wave ratio. The procedure is the same with an account in our recent GRL paper (Tanimoto et al., 2015). Comparison between vertical acceleration and transverse acceleration shows that Rayleigh-wave surface amplitudes are about 20 percent larger than Love waves but in terms of kinetic energy this ratio will be different. We converted these ratios of surface amplitude to those of kinetic energy using an available earth model (Fichtner et al., 2013). The averaged ratio over the frequency band 0.13-0.30 Hz shows is in the range 0.6-0.8 in spring, autumn and winter but it increases to about 1.2 in summer. Except for the summer, the amount of Love waves are higher but the amount of Rayleigh waves increases in summer and appears to exceed that of Love waves.

  8. Structure of Ground state Wave Functions for the Fractional Quantum Hall Effect: A Variational Approach

    NASA Astrophysics Data System (ADS)

    Mukherjee, Sutirtha; Mandal, Sudhansu

    The internal structure and topology of the ground states for fractional quantum Hall effect (FQHE) are determined by the relative angular momenta between all the possible pairs of electrons. Laughlin wave function is the only known microscopic wave function for which these relative angular momenta are homogeneous (same) for any pair of electrons and depend solely on the filling factor. Without invoking any microscopic theory, considering only the relationship between number of flux quanta and particles in spherical geometry, and allowing the possibility of inhomogeneous (different) relative angular momenta between any two electrons, we develop a general method for determining a closed-form ground state wave function for any incompressible FQHE state. Our procedure provides variationally obtained very accurate wave functions, yet having simpler structure compared to any other known complex microscopic wave functions for the FQHE states. This method, thus, has potential in predicting a very accurate ground state wave function for the puzzling states such as the state at filling fraction 5/2. We acknowledge support from Department of Science and Technology, India.

  9. Gaussian variational ansatz in the problem of anomalous sea waves: Comparison with direct numerical simulation

    SciTech Connect

    Ruban, V. P.

    2015-05-15

    The nonlinear dynamics of an obliquely oriented wave packet on a sea surface is analyzed analytically and numerically for various initial parameters of the packet in relation to the problem of the so-called rogue waves. Within the Gaussian variational ansatz applied to the corresponding (1+2)-dimensional hyperbolic nonlinear Schrödinger equation (NLSE), a simplified Lagrangian system of differential equations is derived that describes the evolution of the coefficients of the real and imaginary quadratic forms appearing in the Gaussian. This model provides a semi-quantitative description of the process of nonlinear spatiotemporal focusing, which is one of the most probable mechanisms of rogue wave formation in random wave fields. The system of equations is integrated in quadratures, which allows one to better understand the qualitative differences between linear and nonlinear focusing regimes of a wave packet. Predictions of the Gaussian model are compared with the results of direct numerical simulation of fully nonlinear long-crested waves.

  10. Adjustable fetal phantom for pulse oximetry

    NASA Astrophysics Data System (ADS)

    Stubán, Norbert; Niwayama, Masatsugu

    2009-05-01

    As the measuring head of a fetal pulse oximeter must be attached to the head of the fetus inside the mother's uterus during labor, testing, and developing of fetal pulse oximeters in real environment have several difficulties. A fetal phantom could enable evaluation of pulse oximeters in a simulated environment without the restrictions and difficultness of medical experiments in the labor room. Based on anatomic data we developed an adjustable fetal head phantom with three different tissue layers and artificial arteries. The phantom consisted of two arteries with an inner diameter of 0.2 and 0.4 mm. An electronically controlled pump produced pulse waves in the arteries. With the phantom we investigated the sensitivity of a custom-designed wireless pulse oximeter at different pulsation intensity and artery diameters. The results showed that the oximeter was capable of identifying 4% and 2% changes in diameter between the diastolic and systolic point in arteries of over 0.2 and 0.4 mm inner diameter, respectively. As the structure of the phantom is based on reported anatomic values, the results predict that the investigated custom-designed wireless pulse oximeter has sufficient sensitivity to detect the pulse waves and to calculate the R rate on the fetal head.

  11. Variation of particle size distribution in Saturn's rings and search for density waves in Uranus rings

    SciTech Connect

    Yanamandra-Fisher, P.A.

    1988-01-01

    A bimodal size distribution for particles in Saturn's rings has been determined via an analysis of PPS, UVS and RSS occultation data. The variation of the size distribution in featureless regions indicates that the dust variation is nearly constant in the Saturn's rings and exhibits a slight anti-correlation with 1 cm sized particles. Sub-centimeter sized particles increase outward in the rings, with a maximum in the B ring, similar to the variation of 1 cm sized particles. However, the ratio of subcentimeter sized particles to 1 cm sized particles does not vary significantly in the rings. Janus 5:4 density wave differs significantly from the featureless regions. The amount of dust is greater by a factor of about 2. Both dust and sub-centimeter sized particles are strongly anti-correlated with 1 cm sized particles. Partial formation of gaps is evident for both sub- and supra-centimeter sized particles, consistent with the predictions of Goldreich and Tremaine (1978). Dust is insensitive to the gravitational torque associated with the resonance. The results are also consistent with Dones (1987). In wave regions, large particles collide and produce dust and do not break up into smaller particles. The author searched the Uranian rings, via time series analysis methods, to identify periodic phenomena in the rings. A possible wave-like feature has been identified in both the {epsilon} and the {delta} rings of Uranus. A density wave has been identified in the inner half of the {delta} ring. It implies the existence of a moonlet between the {gamma} and {delta} rings and a possible shepherd for the outer edge of the {gamma} ring and an inner shepherd for the {delta} ring. Comparison of density waves in the two ring systems are similar, indicating the similarity of the local ring environments.

  12. Data fusion for compensation of temperature variations in Lamb-wave based SHM systems

    NASA Astrophysics Data System (ADS)

    Dworakowski, Ziemowit; Ambrozinski, Lukasz; Stepinski, Tadeusz

    2015-03-01

    Temperature variations affect Lamb wave propagation and therefore in this way they can severely limit application of baseline signals in SHM systems. Various techniques are proposed in the paper to solve this problem. New method based on an interpretation of multiple signals acquired in distinct points of the structure is introduced and compared with other widely used approaches. Data fusion is used to merge a number of methods into one with a substantially increased efficiency.

  13. Coda wave interferometry for the measurement of thermally induced ultrasonic velocity variations in CFRP laminates

    NASA Astrophysics Data System (ADS)

    Livings, Richard; Dayal, Vinay; Barnard, Dan

    2016-02-01

    Ultrasonic velocity measurement is a well-established method to measure properties and estimate strength as well as detect and locate damage. Determination of accurate and repeatable ultrasonic wave velocities can be difficult due to the influence of environmental and experimental factors. Diffuse fields created by a multiple scattering environment have been shown to be sensitive to homogeneous strain fields such as those caused by temperature variations, and Coda Wave Interferometry has been used to measure the thermally induced ultrasonic velocity variation in concrete, aluminum, and the Earth's crust. In this work, we analyzed the influence of several parameters of the experimental configuration on the measurement of thermally induced ultrasonic velocity variations in a carbon-fiber reinforced polymer plate. Coda Wave Interferometry was used to determine the relative velocity change between a baseline signal taken at room temperature and the signal taken at various temperatures. The influence of several parameters of the experimental configuration, such as the material type, the receiver aperture size, and fiber orientation on the results of the processing algorithm was evaluated in order to determine the optimal experimental configuration.---This work is supported by the NSF Industry/University Cooperative Research Program of the Center for Nondestructive Evaluation at Iowa State University.

  14. Visible-light optical coherence tomography for retinal oximetry.

    PubMed

    Yi, Ji; Wei, Qing; Liu, Wenzhong; Backman, Vadim; Zhang, Hao F

    2013-06-01

    We applied a visible-light spectroscopic optical coherence tomography (vis-OCT) for in vivo retinal oximetry. To extract hemoglobin oxygen saturation (sO(2)) in individual retinal vessels, we established a comprehensive analytical model to describe optical absorption, optical scattering, and blood cell packing factor in the whole blood and fit the acquired vis-OCT signals from the bottom of each imaged vessel. We found that averaged sO(2) values in arterial and venous bloods were 95% and 72%, respectively. PMID:23722747

  15. Spatial variations of ocean wave directional spectra from the Seasat synthetic aperture radar

    NASA Technical Reports Server (NTRS)

    Beal, R. C.; Gerling, T. W.; Irvine, D. E.; Monaldo, F. M.; Tilley, D. G.

    1986-01-01

    Seasat synthetic aperture radar ocean wave spectra for a 900-km pass are analyzed and interpreted in the context of both their probable generation sources and their surface current and bathymetric modifiers. Systematic vector wavenumber variations of several times the standard error of determination (about 1.5 percent in magnitude and 0.9 deg in direction) occur along the entire 900-km pass. The large-scale spatial variation of a 200-m swell system can be accurately accounted for as a result of dispersion from a distant storm. The more local variations are qualitatively well correlated in position with known currents and bathymetry but show systematic biases that appear partly due to an environmentally dependent instrument transfer function in the regions of high current and highest sea state. There is also substantial evidence that a large angular deviation in the center of the pass is the result of a mesoscale eddy just to the east.

  16. Explanation of the Normal Winter Anomaly from the Seasonal Variation of Short Wave Absorption

    NASA Technical Reports Server (NTRS)

    Velinov, P. J.; Smirnova, N. V.; Vlaskov, V. A.

    1984-01-01

    The frequency dependence of the winter anomaly (WA) of radio wave absorption indicates the altitude range where the considered seasonal variation of absorption, L, takes place: 75-95 km. In this height region considerable seasonal variations of ionic composition and effective recombination coefficient, alpha sub e, exist, which can cause seasonal variations of electron concentration, N, and absorption, L. An attempt to render a qualitative estimation of the normal WA, i.e., the increased ratio of winter over summer absorption, L sub w/L sub s, at medium latitudes 40 deg and 50 deg, for solar zenith angles CHi = 60 deg and 75 deg is made. This is compared with existing experimental data.

  17. Laboratory coda wave interferometry for the monitoring of rock property variations

    NASA Astrophysics Data System (ADS)

    Schmittbuhl, Jean; Chaintreuil, Marie; Lengliné, Olivier; Griffiths, Luke; Heap, Mike; Baud, Patrick

    2016-04-01

    A significant effort is on-going in the community to continuously monitor deep geothermal reservoirs using ambient seismic noise tomography (e.g. Calo et al, 2013; Lehujeur et al, 2015). It is a method that determines the Green's function between a pair of receivers by correlating sufficiently long seismic noise records. Very small changes of the medium are accessible using this new monitoring technique (significantly smaller than those deduced from direct arrivals). In particular, very small variations of seismic velocities are shown to appear both in time and space during the stimulation of the reservoir. A central question is how to interpret these transient or lateral variations of the seismic velocities for a precise 4D tomography of the reservoir properties. In this study, we address the direct problem of monitoring small variations in seismic velocities when small variations in stress or temperature are slowly applied to the sample. We use a network of piezo-electric sensors on laboratory samples (sandstone and granite from Soultz-sous-Forêts core samples) to perform coda wave interferometry from the multiple scattering of well-controlled seismic pulses (Grêt et al, 2006). The data collected are estimates of the relative variation of travel time. We combine acoustic measurements and strain gauges to differentiate between travel time variations due to seismic velocity changes and those due to deformation effects. We expect this approach to provide useful information for large scale seismic tomography despite the significant difference of considered wavelengths.

  18. A new global model for P wave speed variations in Earth's mantle

    NASA Astrophysics Data System (ADS)

    Li, Chang; van der Hilst, Robert D.; Engdahl, E. Robert; Burdick, Scott

    2008-05-01

    We document our tomographic method and present a new global model of three-dimensional (3-D) variations in mantle P wave velocity. The model is parameterized by means of rectangular cells in latitude, longitude, and radius, the size of which adapts to sampling density by short-period (1 Hz) data. The largest single data source is ISC/NEIC data reprocessed by Engdahl and coworkers, from which we use routinely picked, short-period P, Pg, Pn, pP, and pwP data (for earthquakes during the period 1964˜2007). To improve the resolution in the lowermost and uppermost mantle, we use differential times of core phases (PKPAB - PKPDF, PKPAB - PKPBC, Pdiff - PKPDF) and surface-reflected waves (PP-P). The low-frequency differential times (Pdiff, PP) are measured by waveform cross correlation. Approximate 3-D finite frequency kernels are used to integrate the long-period data (Pdiff, PP) and short-period (P, pP, PKP) data. This global data set is augmented with data from regional catalogs and temporary seismic arrays. A crust correction is implemented to mitigate crustal smearing into the upper mantle. We invert the data for 3-D variations in P wave speed and effects of hypocenter mislocation subject to norm and gradient regularization. Spatial resolution is ˜100 km in the best sampled upper mantle regions. Our model, which is available online and which will be updated periodically, reveals in unprecedented detail the rich variation in style of subduction of lithospheric slabs into the mantle. The images confirm the structural complexity of downwellings in the transition zone discussed in previous papers and show with more clarity the structure of slab fragments stagnant in the transition zone beneath east Asia. They also reveal low wave speed beneath major hot spots, such as Iceland, Afar, and Hawaii, but details of these structures are not well resolved by the data used.

  19. Can the Tibetan Plateau snow cover influence the interannual variations of Eurasian heat wave frequency?

    NASA Astrophysics Data System (ADS)

    Wu, Zhiwei; Zhang, Peng; Chen, Hua; Li, Yun

    2016-06-01

    The Eurasian continent has experienced significant year-to-year variations of summer heat waves during the past decades. Several possible factors, such as ocean temperature, soil moisture, and changes in land use and greenhouse gases, have been identified in previous studies, but the mechanisms are still unclear. In this study, it is found that the Tibetan Plateau snow cover (TPSC) is closely linked to the interannual variations of summer heat waves over Eurasia. The TPSC variability explains more than 30 % of the total variances of heat wave variability in the southern Europe and northeastern Asia (SENA) region. A set of numerical experiments reveal that the reduced TPSC may induce a distinct teleconnection pattern across the Eurasian continent, with two anomalous high pressure centers in the upper troposphere over the SENA region, which may lead to a reduction of the cloud formation near the surface. The less cloud cover tends to increase the net shortwave radiation and favor a stronger surface sensible heat flux in the dry surface condition over the SENA region, resulting in a deeper, warmer and drier atmospheric boundary layer that would further inhibit the local cloud formation. Such a positive land-atmosphere feedback may dry the surface even further, heat the near-surface atmosphere and thereby intensify the local heat waves. The above dynamical processes also operate on interdecadal time scales. Given the reduction of the TPSC could become more pronounced with increasing levels of greenhouse gases in a warming climate, we infer that the TPSC may play an increasingly important role in shaping the summer heat waves over the SENA region in next decades.

  20. Studies on gravity waves momentum flux variations in different seasons using MST radar

    NASA Astrophysics Data System (ADS)

    I, V.; Y-H, C.; v, S.; D, N.; S, V.

    2006-12-01

    MST radars are the best tools to study the high frequency gravity waves and its associated momentum fluxes because of excellent temporal and spatial resolutions. The upward propagating gravity waves transport energy and momentum in different regions of the atmosphere along with their propagation to produce effects at upper heights. The estimation of the vertical flux of horizontal momentum in the troposphere and lower stratosphere involves two methods, using three beams V one vertical and two oblique, and using four beams V two pairs of oblique beams systematically offset from the vertical. The rapid steerability of the Indian MST radar allows to make three and four beam measurements simultaneously. The objective of this study is to examine the variations of zonal and meridional momentum fluxes with height, variation of momentum fluxes with wave periods and body forces. We choose frequency bands corresponding to periods of 30 min-2h, 2-8 h, and 2-16h. Vertical profiles of the zonal and meridional flux in each frequency band were found to be consistent, in general, with the total flux. The study also compares momentum fluxes computed with three and four beam methods. Zonal fluxes were small at lower levels and increasingly negative (westward) at higher heights. The dominant contributions to the meridional flux occur in the lower-frequency band. The large vertical momentum flux values observed around the 16 km altitude on most of the observations are due to the presence of large zonal wind shears at that altitude. Due to their persistent southward direction of propagation the meridional momentum flux during winter and summer shows southward direction of propagation and long period waves make contributions to the momentum flux in the lower stratosphere which is comparable to that of short period waves. The detailed discussion will be presented in the meeting.

  1. Effect of Helical Slow-Wave Circuit Variations on TWT Cold-Test Characteristics

    NASA Technical Reports Server (NTRS)

    Kory, Carol L.; Dayton, James A., Jr.

    1998-01-01

    Recent advances in the state of the art of computer modeling offer the possibility for the first time to evaluate the effect that slow-wave structure parameter variations, such'as manufacturing tolerances, have on the cold-test characteristics of helical traveling-wave tubes (TWT's). This will enable manufacturers to determine the cost effectiveness of controlling the dimensions of the component parts of the TWT, which is almost impossible to do experimentally without building a large number of tubes and controlling several parameters simultaneously. The computer code MAxwell's equations by the Finite Integration Algorithm (MAFIA) is used in this analysis to determine the effect on dispersion and on-axis interaction impedance of several helical slow-wave circuit parameter variations, including thickness and relative dielectric constant of the support rods, tape width, and height of the metallized films deposited on the dielectric rods. Previous computer analyzes required so many approximations that accurate determinations of the effect of many relevant dimensions on tube performance were practically impossible.

  2. Detection of the optimal region of interest for camera oximetry.

    PubMed

    Karlen, Walter; Ansermino, J Mark; Dumont, Guy A; Scheffer, Cornie

    2013-01-01

    The estimation of heart rate and blood oxygen saturation with an imaging array on a mobile phone (camera oximetry) has great potential for mobile health applications as no additional hardware other than a camera and LED flash enabled phone are required. However, this approach is challenging as the configuration of the camera can negatively influence the estimation quality. Further, the number of photons recorded with the photo detector is largely dependent on the optical path length, resulting in a non-homogeneous image. In this paper we describe a novel method to automatically detect the optimal region of interest (ROI) for the captured image to extract a pulse waveform. We also present a study to select the optimal camera settings, notably the white balance. The experiments show that the incandescent white balance mode is the preferable setting for camera oximetry applications on the tested mobile phone (Samsung Galaxy Ace). Also, the ROI algorithm successfully identifies the frame regions which provide waveforms with the largest amplitudes. PMID:24110175

  3. Assessing diabetic foot ulcer development risk with hyperspectral tissue oximetry

    NASA Astrophysics Data System (ADS)

    Yudovsky, Dmitry; Nouvong, Aksone; Schomacker, Kevin; Pilon, Laurent

    2011-02-01

    Foot ulceration remains a serious health concern for diabetic patients and has a major impact on the cost of diabetes treatment. Early detection and preventive care, such as offloading or improved hygiene, can greatly reduce the risk of further complications. We aim to assess the use of hyperspectral tissue oximetry in predicting the risk of diabetic foot ulcer formation. Tissue oximetry measurements are performed during several visits with hyperspectral imaging of the feet in type 1 and 2 diabetes mellitus subjects that are at risk for foot ulceration. The data are retrospectively analyzed at 21 sites that ulcerated during the course of our study and an ulceration prediction index is developed. Then, an image processing algorithm based on this index is implemented. This algorithm is able to predict tissue at risk of ulceration with a sensitivity and specificity of 95 and 80%, respectively, for images taken, on average, 58 days before tissue damage is apparent to the naked eye. Receiver operating characteristic analysis is also performed to give a range of sensitivity/specificity values resulting in a Q-value of 89%.

  4. Clinical hyperbaric oxygen therapy, wound perfusion, and transcutaneous oximetry.

    PubMed

    Niinikoski, Juha H A

    2004-03-01

    Hyperbaric oxygen therapy (HBOT) is an important adjunct in the management of problem wounds which exist in chronic oxygen deficiency and in which the local oxygen tension is below optimal for healing. In the treatment of hypoxic and ischemic wounds, the most important effects of hyperbaric oxygenation are the stimulation of fibroblast proliferation and differentiation, increased collagen formation and cross-linking, augmented neovascularization, and the stimulation of leukocyte microbial killing. Ischemic soft tissues also benefit from hyperoxygenation through improved preservation of energy metabolism and reduction of edema. Hyperbaric oxygen is administered in either a multiplace or a monoplace hyperbaric chamber. Normally, pressures of 2 to 2.5 ATA are used for a period of 90 minutes once or twice daily. For an objective assessment of wound perfusion and oxygenation, transcutaneous oximetry provides a simple, reliable, noninvasive, diagnostic technique. It can be used for assessment of tissue perfusion in the vicinity of the problem wound. Transcutaneous oximetry may be used in the assessment of wound healing potential, selection of amputation level, and patient selection for HBOT. In diabetic patients with chronic foot ulcers peri-wound transcutaneous oxygen tensions (TcP(O2)) over 400 mmHg in 2.5 ATA hyperbaric oxygen or over 50 mmHg in normobaric pure oxygen predict healing success with adjuncted HBOT with high accuracy. PMID:14961187

  5. HIGH LIFE: High altitude fatalities led to pulse oximetry.

    PubMed

    Severinghaus, John W

    2016-01-15

    In 1875, Paul Bert linked high altitude danger to the low partial pressure of oxygen when 2 of 3 French balloonists died euphorically at about 8,600 m altitude. World War I fatal crashes of high altitude fighter pilots led to a century of efforts to use oximetry to warn pilots. The carotid body, discovered in 1932 to be the hypoxia detector, led to most current physiologic understanding of the body's respiratory responses to hypoxia and CO2. The author describes some of his UCSF group's work: In 1963, we reported both the brain's ventral medullary near-surface CO2 (and pH) chemosensors and the role of cerebrospinal fluid in acclimatization to altitude. In 1966, we reported the effect of altitude on cerebral blood flow and later the changes of carotid body sensitivity at altitude and the differences in natives of high altitude. In 1973, pulse oximetry was invented when Japanese biophysicist Takuo Aoyagi read and applied to pulses a largely forgotten 35-year-old discovery by English medical student J. R. Squire of a method of computing oxygen saturation from red and infrared light passing through both perfused and blanched tissue. PMID:26251514

  6. The light-tissue interaction of pulse oximetry.

    PubMed

    Mannheimer, Paul D

    2007-12-01

    The underlying science of pulse oximetry is based on a simple manipulation of the Lambert-Beer law, which describes the attenuation of light traveling through a mixture of absorbers. Signals from detected red and infrared light that has traveled through blood-perfused tissues are used to estimate the underlying arterial hemoglobin oxygen saturation. However, light scatters in tissue and influences some of the simplifications made in determining this relationship. Under most clinical circumstances, the empirical process that manufacturers use to calibrate the system during its design readily accommodates this and results in accurate readings. The same tissue light scattering properties allow sensors to be configured for use on opposing or adjacent surfaces, provided that the placement sites offer sufficient signal strength and are absent factors known to influence accuracy. In this paper I review the light-tissue interaction in pulse oximetry and describe some of the assumptions made and their implications. Certain deviations from the nominal conditions, whether clinical in nature or misuse of the product, can affect system performance. Consequently, users should be cautious in modifying sensors and/or using them on tissue sites not intended by the manufacturer (off-label use). While perhaps helpful for obtaining pulsatile signals or extending the lifetime of a sensor, some practices can disrupt the optical integrity of the measurement and negatively impact the oxygen saturation reading accuracy. PMID:18048891

  7. Differential shear wave attenuation and its lateral variation in the North Atlantic region

    NASA Technical Reports Server (NTRS)

    Sheehan, Anne F.; Solomon, Sean C.

    1992-01-01

    A digital data base of over 150 seismograms and a spectral radio technique are used to measure SS-S differential attenuation in the North Atlantic region. Differential attenuation is positively correlated with SS-S travel time residual, and both differential attentuation and travel time residual decrease with increasing seafloor age. Models are developed for seismic Q in which lateral variations include contributions from the asthenospheric low-Q zone as well as from lithospheric cooling. The Q models obtained under this assumption are in good agreement with those obtained from surface wave studies and are therefore preferred over those models with lateral variations confined to the upper 125 km. Systematic long-wavelength (1000-7000 km) variations in differential attenuation, corrected for seafloor age, are evident along the axis of the Mid-Atlantic Ridge. These variations can be qualitatively correlated with long-wavelength variations in SS-S differential travel time residuals and are attributed to along-axis differences in upper mantle temperature.

  8. Effects of temperature variations on guided waves propagating in composite structures

    NASA Astrophysics Data System (ADS)

    Shoja, Siavash; Berbyuk, Viktor; Boström, Anders

    2016-04-01

    Effects of temperature on guided waves propagating in composite materials is a well-known problem which has been investigated in many studies. The majority of the studies is focused on effects of high temperature. Understanding the effects of low temperature has major importance in composite structures and components which are operating in cold climate conditions such as e.g. wind turbines operating in cold climate regions. In this study first the effects of temperature variations on guided waves propagating in a composite plate is investigated experimentally in a cold climate chamber. The material is a common material used to manufacture rotor blades of wind turbines. The temperature range is 25°C to -25°C and effects of temperature variations on amplitude and phase shift of the received signal are investigated. In order to apply the effects of lowering the temperature on the received signal, the Baseline Signal Stretch (BSS) method is modified and used. The modification is based on decomposing the signal into symmetric and asymmetric modes and applying two different stretch factors on each of them. Finally the results obtained based on the new method is compared with the results of application of BSS with one stretch factor and experimental measurements. Comparisons show that an improvement is obtained using the BSS with the mode decomposition method at temperature variations of more than 25°C.

  9. Theory on excitations of drift Alfvén waves by energetic particles. I. Variational formulation

    SciTech Connect

    Zonca, Fulvio; Chen, Liu

    2014-07-15

    A unified theoretical framework is presented for analyzing various branches of drift Alfvén waves and describing their linear and nonlinear behaviors, covering a wide range of spatial and temporal scales. Nonlinear gyrokinetic quasineutrality condition and vorticity equation, derived for drift Alfvén waves excited by energetic particles in fusion plasmas, are cast in integral form, which is generally variational in the linear limit; and the corresponding gyrokinetic energy principle is obtained. Well known forms of the kinetic energy principle are readily recovered from this general formulation. Furthermore, it is possible to demonstrate that the general fishbone like dispersion relation, obtained within the present theoretical framework, provides a unified description of drift Alfvén waves excited by energetic particles as either Alfvén eigenmodes or energetic particle modes. The advantage of the present approach stands in its capability of extracting underlying linear and nonlinear physics as well as spatial and temporal scales of the considered fluctuation spectrum. For these reasons, this unified theoretical framework can help understanding experimental observations as well as numerical simulation and analytic results with different levels of approximation. Examples and applications are given in Paper II [F. Zonca and L. Chen, “Theory on excitations of drift Alfvén waves by energetic particles. II. The general fishbone-like dispersion relation,” Phys. Plasmas 21, 072121 (2014)].

  10. Overhauser Magnetometers Development and Some Magnetic Field Variation and Long-wave Seismic Synchronous Registration Results

    NASA Astrophysics Data System (ADS)

    Kusonsky, O.; Sapunov, V.; Denisova, O.

    Creation experience and advantages of the cyclic Overhauser magnetometers with double polarization by magnetostatic and high-frequency magnetic fields (DC-HF OVH magnetometers) are discussed for some geophysical tasks. In particular, DC- HF OVH method provides: · The high sensitivity (0.01-0.05nT) is achievable even for the bottom geomagnetic field range (10000-40000nT), is due to the simple ESR-structure of the radical in bias DC field, and that is especially useful for applications in equatorial conditions an d space. · The record gradient tolerance (up to 40000 nT/m) useful for borehole applications is reached, that is caused by an opportunity of adaptive reduction of the proton precession signal time registration. · The high-sensitivity registration of magnetic field variations up to 0.001 nT at rate about 10 seconds and high stability (0.05 nT/year), and absolute (up to 0.1 nT) measurements are possible that is useful at ground seismic researches. Addressing this last advantage of DC-HF OVH magnetometer, the magnetic field variation and long-wave seismic synchronous investigations at the Ural magnetic observatory ARTY has been made. Magnetometer POS-1 and digital seismic station IRIS/IDA recording elastic fluctuation from 0,1 up to 1000 sec and more duration were used. The observable correlation of elastic waves and geomagnetic variations, and also superlong-wave emission can testify that the Earth crust has high strain -sensing characteristics where supervision was carried out. The latter is peculiar to lithospher ic areas at astable condition near to a destruction barrier.

  11. A Variational Formulation for the Finite Element Analysis of Sound Wave Propagation in a Spherical Shell

    NASA Technical Reports Server (NTRS)

    Lebiedzik, Catherine

    1995-01-01

    Development of design tools to furnish optimal acoustic environments for lightweight aircraft demands the ability to simulate the acoustic system on a workstation. In order to form an effective mathematical model of the phenomena at hand, we have begun by studying the propagation of acoustic waves inside closed spherical shells. Using a fully-coupled fluid-structure interaction model based upon variational principles, we have written a finite element analysis program and are in the process of examining several test cases. Future investigations are planned to increase model accuracy by incorporating non-linear and viscous effects.

  12. Variational integrators for the dynamics of thermo-elastic solids with finite speed thermal waves

    SciTech Connect

    Mata, Pablo

    2014-01-15

    This paper formulates variational integrators for finite element discretizations of deformable bodies with heat conduction in the form of finite speed thermal waves. The cornerstone of the construction consists in taking advantage of the fact that the Green–Naghdi theory of type II for thermo-elastic solids has a Hamiltonian structure. Thus, standard techniques to construct variational integrators can be applied to finite element discretizations of the problem. The resulting discrete-in-time trajectories are then consistent with the laws of thermodynamics for these systems: for an isolated system, they exactly conserve the total entropy, and nearly exactly conserve the total energy over exponentially long periods of time. Moreover, linear and angular momenta are also exactly conserved whenever the exact system does. For definiteness, we construct an explicit second-order accurate algorithm for affine tetrahedral elements in two and three dimensions, and demonstrate its performance with numerical examples.

  13. Diurnal Variation in Gravity Wave Activity at Low and Middle Latitudes

    NASA Technical Reports Server (NTRS)

    Andrioli, V. F.; Fritts, D. C.; Batista, P. P.; Clemesha, B. R.; Janches, Diego

    2013-01-01

    We employ a modified composite day extension of the Hocking (2005) analysis method to study gravity wave (GW) activity in the mesosphere and lower thermosphere using 4 meteor radars spanning latitudes from 7deg S to 53.6deg S. Diurnal and semidiurnal modulations were observed in GW variances over all sites. Semidiurnal modulation with downward phase propagation was observed at lower latitudes mainly near the equinoxes. Diurnal modulations occur mainly near solstice and, except for the zonal component at Cariri (7deg S), do not exhibit downward phase propagation. At a higher latitude (SAAMER, 53.6deg S) these modulations are only observed in the meridional component where we can observe diurnal variation from March to May, and semidiurnal, during January, February, October (above 88 km) and November. Some of these modulations with downward phase progression correlate well with wind shear. When the wind shear is well correlated with the maximum of the variances the diurnal tide has its largest amplitudes, i.e., near equinox. Correlations exhibiting variations with tidal phases suggest significant GW-tidal interactions that have different characters depending on the tidal components and possible mean wind shears. Modulations that do not exhibit phase variations could be indicative of diurnal variations in GW sources.

  14. Relativistic blast-wave model for the rapid flux variations of AO 0235+164 and other compact radio sources

    NASA Technical Reports Server (NTRS)

    Marscher, A. P.

    1978-01-01

    A relativistic blast-wave version of a signal-screen model is developed which can adequately explain the details of the flux-density and structural variations of compact extragalactic radio sources. The relativistic motion implied by flux variations is analyzed with respect to the synchrotron spectrum of the BL Lac object AO 0235+164 observed during outbursts, and a signal-screen model for rapidly expanding shells produced by ultrarelativistic blast waves is examined. The approximate observed structure of the blast wave at three stages in its evolution is illustrated, each stage is described, and the model is applied to the flux density outburst in AO 0235+164 observed in late 1975. The results show that a relativistic blast-wave model can in general reproduce the main features of the observed flux variations in compact sources. Some problems with the proposed model are briefly discussed.

  15. The effects of nonadiabatic dust charge variation and ultraviolet irradiation on the modulational instability of dust ion acoustic waves

    SciTech Connect

    Wang Yunliang; Guo Chunxia; Ni Xiaodong; Qian Ping; Shen Jiang; Jiang Xiangqian; Zhou Zhongxiang

    2010-11-15

    The effects of nonadiabatic dust charge fluctuation on the nonlinear propagation of the dust ion acoustic (DIA) waves in the dusty plasma with positively charged dust grains have been investigated. By using the reductive perturbation technique, a three-dimensional modified nonlinear Schroedinger equation (mNLSE) governing the nonlinear envelope DIA waves was derived and the approximate solitary wave solution of the mNLSE was also obtained in the weak effect of nonadiabatic dust charge fluctuation limit, which shows that the amplitude of the DIA solitary wave exponentially decreases with time due to the collisionless dissipation caused by the nonadiabatic dust charge variation. The frequency, instability growth rate, and the critical modulational wave number of the small amplitude modulation are all dependent on photoelectron generated by ultraviolet irradiation and time due to the presence of nonadiabatic dust charge variation. The transverse perturbation plays an important role in the modulational instability region.

  16. Global and seasonal variations in three-dimensional gravity wave momentum flux from satellite limb-sounding temperatures

    NASA Astrophysics Data System (ADS)

    Alexander, M. Joan

    2015-08-01

    Satellite limb-sounding methods provide the best global temperature data available for simultaneous measurement of gravity wave horizontal and vertical structures needed to estimate momentum flux and constrain wave effects on general circulation. Gravity waves vary in the three spatial dimensions and time, so the ideal measurement observes all three dimensions at high resolution nearly simultaneously. High Resolution Dynamics Limb Sounder (HIRDLS) measurements give near-simultaneous profiles in close proximity and at high vertical resolution, but these coincident profiles lie only along the plane of the measurement track. Here we combine HIRDLS and radio occultation data sets to obtain three-dimensional properties of gravity waves on a global scale as well as seasonal variations. The results show dramatic changes from previous estimates using either data set alone. Changes include much larger momentum fluxes and latitudinal variations in propagation direction that support an enhanced role for gravity wave forcing of middle atmosphere circulation.

  17. A physical model study of converted wave amplitude variation in a reservoir of systematically aligned vertical fractures

    NASA Astrophysics Data System (ADS)

    Chang, C.; Sun, L.; Lin, C.; Chang, Y.; Tseng, P.

    2013-12-01

    The existence of fractures not only provides spaces for the residence of oils and gases reside, but it also creates pathways for migration. Characterizing a fractured reservoir thus becomes an important subject and has been widely studied by exploration geophysicists and drilling engineers. In seismic anisotropy, a reservoir of systematically aligned vertical fractures (SAVF) is often treated as a transversely isotropic medium (TIM) with a horizontal axis of symmetry (HTI). Subjecting to HTI, physical properties vary in azimuth. P-wave reflection amplitude, which is susceptible to vary in azimuth, is one of the most popular seismic attributes which is widely used to delineate the fracture strike of an SAVF reservoir. Instead of going further on analyzing P-wave signatures, in this study, we focused on evaluating the feasibility of orienting the fracture strike of an SAVF reservoir using converted (C-) wave amplitude. For a C-wave is initiated by a downward traveling P-wave that is converted on reflection to an upcoming S-wave; the behaviors of both P- and S-waves should be theoretically woven in a C-wave. In our laboratory work, finite offset reflection experiments were carried out on the azimuthal plane of a HTI model at two different offset intervals. To demonstrate the azimuthal variation of C-wave amplitude in a HTI model, reflections were acquired along the principal symmetry directions and the diagonal direction of the HTI model. Inheriting from phenomenon of S-wave splitting in a transversely isotropic medium (TIM), P-waves get converted into both the fast (S1) and slow (S2) shear modes at all azimuths outside the vertical symmetry planes, thus producing split PS-waves (PS1 and PS2). In our laboratory data, the converted PS1- (C1-) wave were observed and identified. As the azimuth varies from the strike direction to the strike normal, C1-wave amplitude exhibits itself in a way of weakening and can be view from the common-reflection-point (CRP) gathers

  18. Understanding the variation in the millimeter-wave emission of Venus

    NASA Technical Reports Server (NTRS)

    Fahd, Antoine K.; Steffes, Paul G.

    1992-01-01

    Recent observations of the millimeter-wave emission from Venus at 112 GHz (2.6 mm) have shown significant variations in the continuum flux emission that may be attributed to the variability in the abundances of absorbing constituents in the Venus atmosphere. Such constituents include gaseous H2SO4, SO2, and liquid sulfuric acid (cloud condensates). Recently, Fahd and Steffes have shown that the effects of liquid H, SO4, and gaseous SO2 cannot completely account for this measured variability in the millimeter-wave emission of Venus. Thus, it is necessary to study the effect of gaseous H2SO4 on the millimeter-wave emission of Venus. This requires knowledge of the millimeter-wavelength (MMW) opacity of gaseous H2SO4, which unfortunately has never been determined for Venus-like conditions. We have measured the opacity of gaseous H2SO4 in a CO2 atmosphere at 550, 570, and 590 K, at 1 and 2 atm total pressure, and at a frequency of 94.1 GHz. Our results, in addition to previous centimeter-wavelength results are used to verify a modeling formalism for calculating the expected opacity of this gaseous mixture at other frequencies. This formalism is incorporated into a radiative transfer model to study the effect of gaseous H2SO4 on the MMW emission of Venus.

  19. Spatial variation of Lg-wave attenuation in the Iberian Peninsula

    NASA Astrophysics Data System (ADS)

    Noriega, Raquel; Ugalde, Arantza; Villaseñor, Antonio; José Jurado, María

    2014-05-01

    Within a global context, the Iberian Peninsula is a region where low to moderate (Mw < 5.5) earthquakes occur, most of them at shallow depths (h < 40 km). Seismicity concentrates mainly around the Pyrenean Range, the northwestern part of the peninsula, and the southern deformation zone that includes the Betics, the Alborán Sea and the Gulf of Cádiz. In recent years, considerable improvements in seismic data quality and geographic coverage have been made by the deployment of new permanent and portable broadband seismic stations in the Iberian Peninsula. The dense accumulation of seismic data has allowed us to investigate lateral variation of crustal seismic attenuation to develop the first regional 2D Lg-wave attenuation model for the entire Iberian Peninsula and its frequency dependence. Seismic data used consist of 71 events with magnitudes 3 ≤ mbLg ≤ 5.4 focal depths less than 30 km and epicentral distances from 100 to 1000 km which were recorded by 343 seismic stations between January 2008 and October 2013. To avoid confusion with fundamental-mode Love-wave energy on the transverse components, we only analyzed vertical component recordings. Among all the methods proposed to measure Lg attenuation, we considered the reliable Two-Station Method that allows removing the common source term by taking the ratio of Lg amplitudes recorded at two different stations along the same great-circle path from the same event. It requires, however, strict source-station configuration and dense event and station coverage. The spectral ratios collected over high-quality interstation paths were used to determine 1 Hz Lg Q (Q0) and its frequency dependence η. Then, the lateral variations of the attenuation parameters were mapped using inversion. Lg-wave propagation was found to be inefficient or blocked for most of the paths crossing the Mediterranean Sea, the western Alborán Sea and the Strait of Gibraltar. Our results reflect large variations in Q0 values across the Iberian

  20. Pulse oximetry in a cohort study of sickle cell disease.

    PubMed

    Homi, J; Levee, L; Higgs, D; Thomas, P; Serjeant, G

    1997-03-01

    Oxygen saturation was determined by pulse oximetry in a representative sample of Jamaican patients with steady-state sickle cell disease in a cohort study from birth. There were 220 with homozygous sickle cell (SS) disease and 142 with sickle cell-haemoglobin C (SC) disease aged 9-18 years, and 122 with a normal haemoglobin (AA) genotype aged 15-18 years. Pulse oximetry (SpO2) values were lower in SS disease (mean [95% confidence interval], 92.5 [92.0-93.0]) than in SC disease (96.7[96.5-96.9]) or AA controls (97.1 [96.8-97.3]). Inhalation of 100% oxygen in SS patients with O2 saturations below 90% consistently increased saturation to 99-100%. In SS disease, SpO2 correlated positively with haemoglobin and fetal haemoglobin and negatively with reticulocyte counts but not with MCHC, MCV or bilirubin level. Mean SpO2 in SS subjects with a normal alpha globin gene complement (mean [SD], 91.7 [3.9]%) was lower than in heterozygotes (93.4 [4.0]%) or homozygotes (96.1 [3.0]%) for alpha+ thalassaemia, the effects of alpha-thalassaemia not being explained by differences in haemoglobin or MCHC. In SS disease, SpO2 levels were not associated with age (within this age range), sex, number of sick clinic visits or number of hospital admissions. Higher SpO2 levels were associated with greater height and weight, more frequent painful crises and less frequent acute chest syndrome, but these associations were not significant after adjustment for haemoglobin level. Desaturation is common in steady-state SS disease and knowledge of the individual's steady-state value may be important in the interpreting low values during acute complications. PMID:9146942

  1. Spin label oximetry to assess extracellular oxygen during myocardial ischemia.

    PubMed

    Baker, J E; Froncisz, W; Joseph, J; Kalyanaraman, B

    1997-01-01

    We describe real-time measurement of myocardial oxygen consumption during ischemia in the intact heart. Measurement of extracellular oxygen concentration during myocardial ischemia by spin label oximetry has been limited by ischemia-induced reduction of the neutral, water-soluble nitroxide TEMPONE. We have overcome this problem by encapsulating the nitroxides. Isolated immature (7-10 d old) rabbit hearts (n = 8) were perfused aerobically within the cavity of a loop gap resonator with bicarbonate buffer containing an oxygen-sensitive, lipid-soluble nitroxide (14N-TEMPO laurate in FC-43 perfluorocarbon micelles) and a much less oxygen-sensitive and positively charged nitroxide (15N-TEMPO choline in multilamellar vesicles) as an internal standard. The ratio of the ESR signal amplitudes of these nitroxides was used as a sensitive index of oxygen concentration. Sequestration of the nitroxides decreased their reduction rate by ascorbate in comparison with nonsequestered nitroxides. Hearts were subjected to 60 min of global no-flow ischemia at 20 degrees C. Extracellular oxygen content (mean +/- SD) during aerobic perfusion was 1195 +/- 55 mumol/liter. The electron spin resonance signal from TEMPO laurate increased with the onset and progression of ischemia, consistent with a decrease in extracellular oxygen, while the signal for TEMPO choline was relatively unchanged. Extracellular oxygen content after 40 and 60 min of ischemia was reduced to 393 +/- 27 mumol/liter (p < .05) and 61 +/- 5 mumol/liter (p < .05), respectively. We conclude that spin-label oximetry can directly and precisely measure myocardial oxygen consumption at constant temperature during ischemia in the intact heart. PMID:8958135

  2. Variation of Fundamental Mode Surface Wave Group Velocity Dispersion in Iran and the Surrounding Region

    NASA Astrophysics Data System (ADS)

    Rham, D. J.; Preistley, K.; Tatar, M.; Paul, A.

    2006-12-01

    We present group velocity dispersion results from a study of regional fundamental mode Rayleigh and Love waves propagating across Iran and the surrounding region. Data for these measurements comes from field deployments within Iran by the University of Cambridge (GBR) and the Universite Joseph-Fourier (FRA) in conjunction with International Institute of Earthquake Engineering and Seismology (Iran), in addition to data from IRIS and Geofone. 1D path- averaged dispersion measurements have been made for ~5500 source-receiver paths using multiple filter analysis. We combine these observations in a tomographic inversion to produce group velocity images between 10 and 60 s period. Because of the dense path coverage, these images have substantially higher lateral resolution for this region than is currently available from global and regional group velocity studies. We observe variations in short-period wave group velocity which is consistent with the surface geology. Low group velocities (2.00-2.55 km/s) at short periods (10-20 s), for both Rayleigh and Love waves are observed beneath thick sedimentary deposits; The south Caspian Basin, Black Sea, the eastern Mediterranean, the Persian Gulf, the Makran, the southern Turan shield, and the Indus and Gangetic basins. Somewhat higher group velocity (2.80-3.15 km/s for Rayleigh, and 3.00-3.40 km/s for Love) at these periods occur in sediment poor regions, such as; the Turkish-Iranian plateau, the Arabian shield, and Kazakhstan. At intermediate periods (30-40 s) group velocities over most of the region are low (2.65-3.20 km/s for Rayleigh, and 2.80-3.45 km/s for love) compared to Arabia (3.40-3.70 km/s Rayleigh, 3.50-4.0 km/s Love). At longer periods (50-60 s) Love wave group velocities remain low (3.25-3.70 km/s) over most of Iran, but there are even lower velocities (2.80-3.00 km/s) still associated with the thick sediments of the south Caspian basin, the surrounding shield areas have much higher group velocities (3

  3. Near-infrared spectral imaging of the female breast for quantitative oximetry in optical mammography

    SciTech Connect

    Yu Yang; Liu Ning; Sassaroli, Angelo; Fantini, Sergio

    2009-04-01

    We present a hybrid continuous-wave, frequency-domain instrument for near-infrared spectral imaging of the female breast based on a tandem, planar scanning of one illumination optical fiber and one collection optical fiber configured in a transmission geometry. The spatial sampling rate of 25 points/cm{sup 2} is increased to 400 points/cm{sup 2} by postprocessing the data with a 2D cubic spline interpolation. We then apply a previously developed spatial second-derivative algorithm to an edge-corrected intensity image (N-image) to enhance the visibility and resolution of optical inhomogeneities in breast tissue such as blood vessels and tumors. The spectral data at each image pixel consist of 515-point spectra over the 650-900 nm wavelength range, thus featuring a spectral density of two data points per nanometer. We process the measured spectra with a paired-wavelength spectral analysis method to quantify the oxygen saturation of detected optical inhomogeneities, under the assumption that they feature a locally higher hemoglobin concentration. Our initial measurements on two healthy human subjects have generated high-resolution optical mammograms displaying a network of blood vessels with values of hemoglobin saturation typically falling within the 60%-95% range, which is physiologically reasonable. This approach to spectral imaging and oximetry of the breast has the potential to efficiently exploit the high intrinsic contrast provided by hemoglobin in breast tissue and to contribute a useful tool in the detection, diagnosis, and monitoring of breast pathologies.

  4. Pulse oximetry screening: a review of diagnosing critical congenital heart disease in newborns

    PubMed Central

    Engel, Melissa S; Kochilas, Lazaros K

    2016-01-01

    Congenital heart disease (CHD) is one of the most common birth defects, with an incidence of nine out of every 1,000 live births. The mortality of infants with CHD has decreased over the past 3 decades, but significant morbidity and mortality continue to occur if not diagnosed shortly after birth. Pulse oximetry was recommended as a screening tool to detect critical CHD in 2011 by the American Academy of Pediatrics and the American Heart Association. Pulse oximetry is a tool to measure oxygen saturation, and based on the presence of hypoxemia, many cardiac lesions are detected. Due to its ease of application to the patient, providing results in a timely manner and without the need for calibrating the sensor probe, pulse oximetry offers many advantages as a screening tool. However, pulse oximetry has also important limitations of which physicians should be aware to be able to assess the significance of the pulse oximetry measurement for a given patient. This review aims to highlight the benefits and shortcomings of pulse oximetry within the context of screening for critical CHD and suggests future avenues to cover existing gaps in current practices. PMID:27468253

  5. Pediatric OSAS: Oximetry can provide answers when polysomnography is not available.

    PubMed

    Kaditis, Athanasios; Kheirandish-Gozal, Leila; Gozal, David

    2016-06-01

    Overnight polysomnography is the gold standard tool for the diagnosis of obstructive sleep apnea syndrome (OSAS) in habitually snoring children, but it is expensive and not always available. Nocturnal oximetry has been proposed as an abbreviated and low-cost testing modality for the diagnosis of OSAS. In this systematic review, 25 original articles were evaluated to: (i) summarize reference values of nocturnal oximetry parameters in healthy children; (ii) identify abnormal oximetry patterns that predict OSAS in habitually snoring children; (iii) delineate abnormalities in oximetry that can predict responses to treatment interventions for OSAS and potential complications. Nocturnal SpO2 drops <90%, more than two clusters of desaturation events (≥4%) and oxyhemoglobin desaturation (≥4%) index (ODI4) >2.2 episodes/h are unusual in children without OSAS. At least three clusters of desaturation events, and at least three SpO2 drops below 90% in a nocturnal oximetry recording are indicative of moderate-to-severe OSAS. An ODI4 >2 episodes/h combined with OSAS symptoms also exhibits high positive predictive value for apnea-hypopnea index >1 episode/h. Children without clusters of desaturation events have low risk of major respiratory complications following adenotonsillectomy. Thus, nocturnal oximetry emerges as a valuable tool that can facilitate treatment decisions when polysomnography is not available. PMID:26146027

  6. Pulse oximetry versus transcutaneous pO2 in sick newborn infants.

    PubMed

    Wimberley, P D; Helledie, N R; Friis-Hansen, B; Fogh-Andersen, N; Olesen, H

    1987-01-01

    A pulse oximeter (Ohmeda Biox 3700) and two transcutaneous systems (Radiometer TCM3) were applied simultaneously to 18 newborn infants with respiratory insufficiency. All infants had either an umbilical catheter placed in the mid thoracic aorta or a radial artery catheter. The average monitoring time was 2 hours. Arterial blood pO2, pCO2 and pH (Radiometer ABL300), arterial sO2, HbCO and metHb (Radiometer OSM3), erythrocyte 2,3 DPG concentration, and fetal hemoglobin fraction (alkali denaturation kinetic method) were measured. Using arterial sO2 and pO2 as reference, the analytical bias of pulse oximetry (-0.5 +/- 1.0%, mean +/- 1 SD) corresponded in magnitude, when converted to pO2, to that of transcutaneous - pO2 (0.6 +/- 1.4 kPa for combined O2-CO2 electrode and -0.1 +/- 2.3 kPa for single O2 electrode). Transcutaneous pCO2 showed the smallest bias (0.3 +/- 0.3 kPa). Both pulse oximetry and transcutaneous pO2 electrodes were good as trend monitors detecting rapid changes in the infants' oxygenation status. The pulse oximeter offers certain advantages in not requiring calibration or heating. The variations in the levels of fetal hemoglobin fraction (44 to 97%), pH (7.27 to 7.49), pCO2 (3.3 to 6.8 kPa) and 2,3 diphosphoglycerate concentration (1.6 to 5.9 mmol/l) between the infants studied, resulted in a variable pO2-sO2 relation (p50 2.5 to 3.5 kPa). This presents difficulties in interpreting sO2 values in sick newborn infants, and we therefore recommend caution in using a pulse oximeter to apply strict limits for avoiding hypoxia and hyperoxia in this population. PMID:2453078

  7. Reproducibility of transcutaneous oximetry and laser Doppler flowmetry in facial skin and gingival tissue.

    PubMed

    Svalestad, J; Hellem, S; Vaagbø, G; Irgens, A; Thorsen, E

    2010-01-01

    Laser Doppler flowmetry (LDF) and transcutaneous oximetry (TcPO(2)) are non-invasive techniques, widely used in the clinical setting, for assessing microvascular blood flow and tissue oxygen tension, e.g. recording vascular changes after radiotherapy and hyperbaric oxygen therapy. With standardized procedures and improved reproducibility, these methods might also be applicable in longitudinal studies. The aim of this study was to evaluate the reproducibility of facial skin and gingival LDF and facial skin TcPO(2). The subjects comprised ten healthy volunteers, 5 men, aged 31-68 years. Gingival perfusion was recorded with the LDF probe fixed to a custom made, tooth-supported acrylic splint. Skin perfusion was recorded on the cheek. TcPO(2) was recorded on the forehead and cheek and in the second intercostal space. The reproducibility of LDF measurements taken after vasodilation by heat provocation was greater than for basal flow in both facial skin and mandibular gingiva. Pronounced intraday variations were observed. Interweek reproducibility assessed by intraclass correlation coefficient ranged from 0.74 to 0.96 for LDF and from 0.44 to 0.75 for TcPO(2). The results confirm acceptable reproducibility of LDF and TcPO(2) in longitudinal studies in a vascular laboratory where subjects serve as their own controls. The use of thermoprobes is recommended. Repeat measurements should be taken at the same time of day. PMID:19837098

  8. Depth variations of P-wave azimuthal anisotropy beneath Mainland China.

    PubMed

    Wei, Wei; Zhao, Dapeng; Xu, Jiandong; Zhou, Bengang; Shi, Yaolin

    2016-01-01

    A high-resolution model of P-wave anisotropic tomography beneath Mainland China and surrounding regions is determined using a large number of arrival-time data recorded by the China seismic network, the International Seismological Centre (ISC) and temporary seismic arrays deployed on the Tibetan Plateau. Our results provide important new insights into the subducted Indian plate and mantle dynamics in East Asia. Our tomographic images show that the northern limit of the subducting Indian plate has reached the Jinsha River suture in eastern Tibet. A striking variation of P-wave azimuthal anisotropy is revealed in the Indian lithosphere: the fast velocity direction (FVD) is NE-SW beneath the Indian continent, whereas the FVD is arc parallel beneath the Himalaya and Tibetan Plateau, which may reflect re-orientation of minerals due to lithospheric extension, in response to the India-Eurasia collision. There are multiple anisotropic layers with variable FVDs in some parts of the Tibetan Plateau, which may be the cause of the dominant null splitting measurements in these regions. A circular pattern of FVDs is revealed around the Philippine Sea slab beneath SE China, which reflects asthenospheric strain caused by toroidal mantle flow around the edge of the subducting slab. PMID:27432744

  9. Depth variations of P-wave azimuthal anisotropy beneath Mainland China

    PubMed Central

    Wei, Wei; Zhao, Dapeng; Xu, Jiandong; Zhou, Bengang; Shi, Yaolin

    2016-01-01

    A high-resolution model of P-wave anisotropic tomography beneath Mainland China and surrounding regions is determined using a large number of arrival-time data recorded by the China seismic network, the International Seismological Centre (ISC) and temporary seismic arrays deployed on the Tibetan Plateau. Our results provide important new insights into the subducted Indian plate and mantle dynamics in East Asia. Our tomographic images show that the northern limit of the subducting Indian plate has reached the Jinsha River suture in eastern Tibet. A striking variation of P-wave azimuthal anisotropy is revealed in the Indian lithosphere: the fast velocity direction (FVD) is NE-SW beneath the Indian continent, whereas the FVD is arc parallel beneath the Himalaya and Tibetan Plateau, which may reflect re-orientation of minerals due to lithospheric extension, in response to the India-Eurasia collision. There are multiple anisotropic layers with variable FVDs in some parts of the Tibetan Plateau, which may be the cause of the dominant null splitting measurements in these regions. A circular pattern of FVDs is revealed around the Philippine Sea slab beneath SE China, which reflects asthenospheric strain caused by toroidal mantle flow around the edge of the subducting slab. PMID:27432744

  10. Numerical Assessment of Four-Port Through-Flow Wave Rotor Cycles with Passage Height Variation

    NASA Technical Reports Server (NTRS)

    Paxson, D. E.; Lindau, Jules W.

    1997-01-01

    The potential for improved performance of wave rotor cycles through the use of passage height variation is examined. A Quasi-one-dimensional CFD code with experimentally validated loss models is used to determine the flowfield in the wave rotor passages. Results indicate that a carefully chosen passage height profile can produce substantial performance gains. Numerical performance data are presented for a specific profile, in a four-port, through-flow cycle design which yielded a computed 4.6% increase in design point pressure ratio over a comparably sized rotor with constant passage height. In a small gas turbine topping cycle application, this increased pressure ratio would reduce specific fuel consumption to 22% below the un-topped engine; a significant improvement over the already impressive 18% reductions predicted for the constant passage height rotor. The simulation code is briefly described. The method used to obtain rotor passage height profiles with enhanced performance is presented. Design and off-design results are shown using two different computational techniques. The paper concludes with some recommendations for further work.

  11. Depth variations of P-wave azimuthal anisotropy beneath Mainland China

    NASA Astrophysics Data System (ADS)

    Wei, Wei; Zhao, Dapeng; Xu, Jiandong; Zhou, Bengang; Shi, Yaolin

    2016-07-01

    A high-resolution model of P-wave anisotropic tomography beneath Mainland China and surrounding regions is determined using a large number of arrival-time data recorded by the China seismic network, the International Seismological Centre (ISC) and temporary seismic arrays deployed on the Tibetan Plateau. Our results provide important new insights into the subducted Indian plate and mantle dynamics in East Asia. Our tomographic images show that the northern limit of the subducting Indian plate has reached the Jinsha River suture in eastern Tibet. A striking variation of P-wave azimuthal anisotropy is revealed in the Indian lithosphere: the fast velocity direction (FVD) is NE-SW beneath the Indian continent, whereas the FVD is arc parallel beneath the Himalaya and Tibetan Plateau, which may reflect re-orientation of minerals due to lithospheric extension, in response to the India-Eurasia collision. There are multiple anisotropic layers with variable FVDs in some parts of the Tibetan Plateau, which may be the cause of the dominant null splitting measurements in these regions. A circular pattern of FVDs is revealed around the Philippine Sea slab beneath SE China, which reflects asthenospheric strain caused by toroidal mantle flow around the edge of the subducting slab.

  12. Quantum variational measurement and the optical lever intracavity topology of gravitational-wave detectors

    SciTech Connect

    Khalili, F. Ya.

    2007-04-15

    The intracavity topologies of laser gravitational-wave detectors proposed several years ago are the promising way to obtain sensitivity of these devices significantly better than the Standard Quantum Limit (SQL). In essence, the intracavity detector is a two-stage device where the end mirrors displacement created by the gravitational wave is transferred to the displacement of an additional local mirror by means of the optical rigidity. The local mirror positions have to be monitored by an additional local meter. It is evident that the local meter precision defines the sensitivity of the detector. To overcome the SQL, the quantum variational measurement can be used in the local meter. In this method a frequency-dependent correlation between the meter backaction noise and measurement noise is introduced, which allows us to eliminate the backaction noise component from the meter output signal. This correlation is created by means of an additional filter cavity. In this article the sensitivity limitations of this scheme imposed by the optical losses both in the local meter itself and in the filter cavity are estimated. It is shown that the main sensitivity limitation stems from the filter cavity losses. In order to overcome it, it is necessary to increase the filter cavity length. In a preliminary prototype experiment, an approximate 10 m long filter cavity can be used to obtain sensitivity approximately 2-3 times better than the SQL. For future Quantum Non-Demolition (QND) gravitational-wave detectors with sensitivity about 10 times better than the SQL, the filter cavity length should be within kilometer range.

  13. Variations in Shear Wave Splitting Beneath Southern Arabia and the Gulf of Aden

    NASA Astrophysics Data System (ADS)

    Gallacher, R. J.; Eakin, C. M.; Keir, D.; Leroy, S. D.; Stuart, G. W.; Harmon, N.; Ahmed, A.

    2015-12-01

    Mantle flow beneath Southern Arabia and the Gulf of Aden remains enigmatic due to a paucity of seismic measurements in the region. Potential processes contributing to mantle flow include northward progression of the African Superplume, radial flow from the Afar plume and vertical flow from small-scale convection along the margins of the Gulf of Aden. These would result in characteristic mantle flow directions, creating mantle anisotropy that can be detected by shear wave splitting. We analyse SKS, SKKS & PKS phases for shear wave splitting at 141 stations deployed throughout Yemen, Oman and Socotra along the margins of the Gulf of Aden. Large numbers of null measurements from a range of back azimuths are found beneath the entire region. These may indicate that vertical anisotropy is present in the upper mantle beneath the region, consistent with models of small-scale convection. The null measurements may also be due to complicated layering of crustal anisotropy interfering destructively and precluding measurement of shear wave splitting. Splitting measurements bordering the Red Sea show North-South orientations that may result from shallow aligned melt along the Red Sea or from variations in lower mantle flow. Fast polarization directions of splitting measurements along the Northern margin of the Gulf of Aden are rift parallel suggesting a shallow source such as rift related faulting might be responsible. These results show that anisotropy beneath the region is not controlled by the northward progression of the African Superplume or radial flow from the Afar plume. Upper mantle flow is likely vertical with splitting occurring either in the crust or the lower mantle.

  14. Explicitly correlated wave functions for atoms and singly charged ions from Li through Sr: Variational and Diffusion Monte Carlo results

    NASA Astrophysics Data System (ADS)

    Buendía, E.; Gálvez, F. J.; Maldonado, P.; Sarsa, A.

    2014-11-01

    Total energies calculated from explicitly correlated wave functions for the ground state of the atoms Li to Sr and their singly charged anions and cations are obtained. Accurate all electron, non-relativistic Variational and Diffusion Monte Carlo energies are reported. The quality of the results, when comparing with exact estimations and experimental electron affinities and ionization potential is similar for all of the atoms studied. The parameterization of the explicitly correlated wave functions for all of the atomic systems studied is provided.

  15. Spatial variations of shear wave anisotropy near the San Jacinto Fault Zone in Southern California

    NASA Astrophysics Data System (ADS)

    Li, Zefeng; Peng, Zhigang; Ben-Zion, Yehuda; Vernon, Frank L.

    2015-12-01

    We examine crustal anisotropy at several scales along and across the San Jacinto Fault Zone (SJFZ) by systematically measuring shear wave splitting (SWS) parameters. The analyzed data are recorded by 86 stations during 2012-2014, including five linear dense arrays crossing the SJFZ at different locations and other autonomous stations within 15 km from the main fault trace. Shear phase arrivals and SWS parameters (fast directions and delay times) are obtained with automated methods. The measurement quality is then assessed using multiple criteria, resulting in 23,000 high-quality measurements. We find clear contrast of fast directions between the SW and NE sides of the SJFZ. Stations on the SW side have fast directions consistent overall with the maximum horizontal compression direction (SHmax), while stations on the NE side show mixed patterns likely reflecting lithological/topographic variations combined with fault zone damage. The fast directions in the Anza gap section with relatively simple fault geometry agree with the inferred SHmax, and the delay times at an array within that section are smaller than those observed at other across-fault arrays. These indications of less pronounced damage zone in the Anza section compared to other segments of the SJFZ are correlated generally with geometrical properties of the surface traces. Significant variations of fast directions on several across-fault arrays, with station spacing on the orders of a few tens of meters, suggest that shallow fault structures and near-surface layers play an important role in controlling the SWS parameters.

  16. Seasonal variations in the Rayleigh-to-Love wave ratio in the secondary microseism from colocated ring laser and seismograph

    NASA Astrophysics Data System (ADS)

    Tanimoto, Toshiro; Hadziioannou, Céline; Igel, Heiner; Wassermann, Joachim; Schreiber, Ulrich; Gebauer, André; Chow, Bryant

    2016-04-01

    Monthly variations in the ratio of Rayleigh-to-Love waves in the secondary microseism are obtained from a colocated ring laser and an STS-2 seismograph at Wettzell, Germany. Two main conclusions are derived for the Rayleigh-to-Love wave kinetic energy ratios in the secondary microseism; first, the energy ratio is in the range 0.8-0.9 (<1.0) throughout a year except for June and July. It means that Love wave energy is larger than Rayleigh wave energy most of the year by about 10-20%. Second, this ratio suddenly increases to 1.0-1.2 in June and July, indicating a larger fraction of Rayleigh wave energy. This change suggests that the locations and behaviors of excitation sources are different in these months.

  17. Investigation of coastal wave field variations with TerraSAR-X

    NASA Astrophysics Data System (ADS)

    Jacobsen, Sven; Lehner, Susanne; Bruck, Miguel; Gies, Tobias; Pleskachevsky, Andrey; Rosenthal, Wolfgang; Bruns, Thomas

    2014-05-01

    Spaceborne Synthetic Aperture Radar (SAR) is a uniquely powerful sensor providing two-dimensional information of the ocean surface like a broad spectrum of meteo-marine parameters such as windfields, significant wave height, peak wavelength and other seastate characteristics. SAR is particularly suitable for many oceanographic observations due to its high resolution in combination with global coverage and the independence of daylight and cloud conditions. The data has been amongst others used to investigate geophysical processes and for numerical model validation. It has also so been found to be a valuable contribution regarding data assimilation into meteorological, marine and coupled models. The X-band radar of the TerraSAR-X (TS-X) satellite acquires images of the sea surface with a high resolution up to 1m. Due to a lower platform altitude and a higher signal frequency, nonlinear imaging effects of the moving ocean surface are reduced when compared to previous C-band sensors and thus individual ocean waves with wavelengths below 30m are detectable. Minor importance of nonlinear effects in the wave imaging process also gives rise to new empirical model functions to derive sea state parameters directly from the SAR image spectrum properties and thus minimizing data processing time. This is of special interest with regard to the development of near-real-time (NRT) data products often favorable for maritime safety and security applications particularly . The latest generation of the empirical algorithm for TS-X seastate analysis XWAVE has been tuned with hundreds of collocated buoy measurements over the open ocean and subsequent validation exhibits a very good agreement with in-situ data. However, in contrast to the open ocean where seastate parameters do not change significantly on the scale of kilometers, coastal waters exhibit a large spacial variablility owing to ,inter alia, subsurface topography influence. The lateral variation complicates the extraction of

  18. Oscillations in sympatho-vagal balance oppose variations in delta-wave activity and the associated renin release.

    PubMed

    Charloux, A; Otzenberger, H; Gronfier, C; Lonsdorfer-Wolf, E; Piquard, F; Brandenberger, G

    1998-05-01

    To determine the potential role of the sympathetic nervous system in the generation of the oscillations in PRA over the 24-h period, we used the autocorrelation coefficient of RR interval (rRR), a new tool to evaluate the sympatho-vagal balance continuously. We determined the influence of the sympathetic nervous system both on the nocturnal PRA oscillations associated to increases in delta-wave activity and on the daytime oscillations that occur randomly in awake subjects. PRA and rRR were determined every 10 min during 24 h in nine healthy subjects under continuous bed rest. Electroencephalographic spectral analysis was used to establish the variations in delta-wave activity during sleep, from 2300-0700 h. The overnight profiles in PRA, rRR and delta-wave activity were analyzed using a modified version of the pulse detection program ULTRA. The temporal link among the profiles of rRR, PRA, and delta-wave activity was quantified using cross-correlation analysis. During sleep, large oscillations in PRA were strongly linked to variations in delta-wave activity. They were preceded by opposite oscillations in rRR, decreases in rRR reflecting predominant vagal activity, and increases in rRR reflecting sympathetic dominance. During the waking periods, the levels of rRR were higher, with smaller variations. The daytime PRA oscillations were not associated with any significant changes in rRR, and conversely, significant oscillations in rRR were not followed by any significant changes in PRA. In conclusion, the sympathetic nervous system is not directly involved in the generation of renin oscillations observed under basal conditions. During sleep, the oscillations in sympatho-vagal balance are inversely related to the variations in delta-wave activity and the associated renin release. The processes that give the intermittent signal for concomitant increases in slow wave activity and renin release from the kidney remain to be identified. PMID:9589649

  19. All-organic optoelectronic sensor for pulse oximetry

    NASA Astrophysics Data System (ADS)

    Lochner, Claire M.; Khan, Yasser; Pierre, Adrien; Arias, Ana C.

    2014-12-01

    Pulse oximetry is a ubiquitous non-invasive medical sensing method for measuring pulse rate and arterial blood oxygenation. Conventional pulse oximeters use expensive optoelectronic components that restrict sensing locations to finger tips or ear lobes due to their rigid form and area-scaling complexity. In this work, we report a pulse oximeter sensor based on organic materials, which are compatible with flexible substrates. Green (532 nm) and red (626 nm) organic light-emitting diodes (OLEDs) are used with an organic photodiode (OPD) sensitive at the aforementioned wavelengths. The sensor’s active layers are deposited from solution-processed materials via spin-coating and printing techniques. The all-organic optoelectronic oximeter sensor is interfaced with conventional electronics at 1 kHz and the acquired pulse rate and oxygenation are calibrated and compared with a commercially available oximeter. The organic sensor accurately measures pulse rate and oxygenation with errors of 1% and 2%, respectively.

  20. All-organic optoelectronic sensor for pulse oximetry.

    PubMed

    Lochner, Claire M; Khan, Yasser; Pierre, Adrien; Arias, Ana C

    2014-01-01

    Pulse oximetry is a ubiquitous non-invasive medical sensing method for measuring pulse rate and arterial blood oxygenation. Conventional pulse oximeters use expensive optoelectronic components that restrict sensing locations to finger tips or ear lobes due to their rigid form and area-scaling complexity. In this work, we report a pulse oximeter sensor based on organic materials, which are compatible with flexible substrates. Green (532 nm) and red (626 nm) organic light-emitting diodes (OLEDs) are used with an organic photodiode (OPD) sensitive at the aforementioned wavelengths. The sensor's active layers are deposited from solution-processed materials via spin-coating and printing techniques. The all-organic optoelectronic oximeter sensor is interfaced with conventional electronics at 1 kHz and the acquired pulse rate and oxygenation are calibrated and compared with a commercially available oximeter. The organic sensor accurately measures pulse rate and oxygenation with errors of 1% and 2%, respectively. PMID:25494220

  1. A model for seasonal changes in GPS positions and seismic wave speeds due to thermoelastic and hydrologic variations

    USGS Publications Warehouse

    Tsai, V.C.

    2011-01-01

    It is known that GPS time series contain a seasonal variation that is not due to tectonic motions, and it has recently been shown that crustal seismic velocities may also vary seasonally. In order to explain these changes, a number of hypotheses have been given, among which thermoelastic and hydrology-induced stresses and strains are leading candidates. Unfortunately, though, since a general framework does not exist for understanding such seasonal variations, it is currently not possible to quickly evaluate the plausibility of these hypotheses. To fill this gap in the literature, I generalize a two-dimensional thermoelastic strain model to provide an analytic solution for the displacements and wave speed changes due to either thermoelastic stresses or hydrologic loading, which consists of poroelastic stresses and purely elastic stresses. The thermoelastic model assumes a periodic surface temperature, and the hydrologic models similarly assume a periodic near-surface water load. Since all three models are two-dimensional and periodic, they are expected to only approximate any realistic scenario; but the models nonetheless provide a quantitative framework for estimating the effects of thermoelastic and hydrologic variations. Quantitative comparison between the models and observations is further complicated by the large uncertainty in some of the relevant parameters. Despite this uncertainty, though, I find that maximum realistic thermoelastic effects are unlikely to explain a large fraction of the observed annual variation in a typical GPS displacement time series or of the observed annual variations in seismic wave speeds in southern California. Hydrologic loading, on the other hand, may be able to explain a larger fraction of both the annual variations in displacements and seismic wave speeds. Neither model is likely to explain all of the seismic wave speed variations inferred from observations. However, more definitive conclusions cannot be made until the model

  2. Generation of the cosmic rays flux variations due to surfatron acceleration of charges by electromagnetic waves in space plasma

    NASA Astrophysics Data System (ADS)

    Erokhin, Nikolay; Loznikov, Vladimir; Shkevov, Rumen; Zolnikova, Nadezhda; Mikhailovskaya, Ludmila

    2016-07-01

    The analysis of experimental data on the spectra of cosmic rays (CR) has shown their variability on time scales of a few years, in particular, CR variations observed in E / Z range from TeV to 10000 TeV, where E is the energy of the particle, Z is its charge number. Consequently, the source of these variations must be located at a distance of no more than 1 parsec from the sun in the closest local interstellar clouds. As a mechanism of such variations appearance it is considered the surfatron acceleration of CR particles by electromagnetic wave in a relatively quiet space plasma. On the basis of developed model the numerical calculations were performed for particle capture dynamics (electrons, protons, helium and iron nuclei) in the wave effective potential well with a following growth their energy by 3-6 orders of magnitude. Optimal conditions for the implementation of charged particles surfatron acceleration in space plasma, the rate of trapped particles energy growth, the dynamics of wave phase on the captured particle trajectory, a temporal dynamics of components for charge impulse momentum and speed were studied. It is indicated that the capture of a small fraction of particles by wave for energies about TeV and less followed by their surfatron acceleration to an energy of about 10000 TeV will lead to a significant increase in the CR flux at such high energies. Thus CL flow variations are conditioned by changes in the space weather parameters

  3. Low renal oximetry correlates with acute kidney injury after infant cardiac surgery.

    PubMed

    Owens, Gabe E; King, Karen; Gurney, James G; Charpie, John R

    2011-02-01

    Acute kidney injury (AKI) is a frequent complication after cardiopulmonary bypass surgery during infancy. Standard methods for evaluating renal function are not particularly sensitive nor are proximate indicators of renal dysfunction that allow intervention in real time. Near-infrared spectroscopy (NIRS) is a newer noninvasive technology that continuously evaluates regional oximetry and may correlate with renal injury and adverse outcomes after cardiac surgery in infants. This prospective observational study enrolled 40 infants (age, <12 months) undergoing biventricular repair. Continuous renal oximetry data were collected for the first 48 postoperative hours and correlated with postoperative course, standard laboratory data, and the occurrence of acute renal injury. Subjects with low renal oximetry (below 50% for >2 h) had significantly higher postoperative peak creatinine levels by 48 h (0.8 ± 0.4 vs. 0.52 ± 0.2; p = 0.003) and a higher incidence of AKI (50 vs. 3.1%; p = 0.003) than those with normal renal oximetry. These subjects also required more ventilator days and greater vasoactive support, and they had elevated lactate levels. Prolonged low renal near-infrared oximetry appears to correlate with renal dysfunction, decreased systemic oxygen delivery, and the overall postoperative course in infants with congenital heart disease undergoing biventricular repair. PMID:21085945

  4. Clinical use of pulse oximetry: official guidelines from the Thoracic Society of Australia and New Zealand.

    PubMed

    Pretto, Jeffrey J; Roebuck, Teanau; Beckert, Lutz; Hamilton, Garun

    2014-01-01

    Pulse oximetry provides a simple, non-invasive approximation of arterial oxygenation in a wide variety of clinical settings including emergency and critical-care medicine, hospital-based and ambulatory care, perioperative monitoring, inpatient and outpatient settings, and for specific diagnostic applications. Pulse oximetry is of utility in perinatal, paediatric, adult and geriatric populations but may require use of age-specific sensors in these groups. It plays a role in the monitoring and treatment of respiratory dysfunction by detecting hypoxaemia and is effective in guiding oxygen therapy in both adult and paediatric populations. Pulse oximetry does not provide information about the adequacy of ventilation or about precise arterial oxygenation, particularly when arterial oxygen levels are very high or very low. Arterial blood gas analysis is the gold standard in these settings. Pulse oximetry may be inaccurate as a marker of oxygenation in the presence of dyshaemoglobinaemias such as carbon monoxide poisoning or methaemoglobinaemia where arterial oxygen saturation values will be overestimated. Technical considerations such as sensor position, signal averaging time and data sampling rates may influence clinical interpretation of pulse oximetry readings. PMID:24251722

  5. Dust-acoustic solitary waves and double layers in a magnetized dusty plasma with nonthermal ions and dust charge variation

    SciTech Connect

    El-Taibany, W.F.; Sabry, R.

    2005-08-15

    The effect of nonthermal ions and variable dust charge on small-amplitude nonlinear dust-acoustic (DA) waves is investigated. It is found that both compressive and rarefactive solitons exist and depend on the nonthermal parameter a. Using a reductive perturbation theory, a Zakharov-Kuznetsov (ZK) equation is derived. At critical value of a, a{sub c}, a modified ZK equation with third- and fourth-order nonlinearities, is obtained. Depending on a, the solution of the evolution equation reveals whether there is coexistence of both compressive and rarefactive solitary waves or double layers (DLs) with the possibility of their two kinds. In addition, for certain plasma parameters, the solitary wave disappears and a DL is expected. The variation of dust charge number, wave velocity, and soliton amplitude and its width against system parameters is investigated for the DA solitary waves. It is shown that the incorporation of both the adiabatic dust-charge variation and the nonthermal distributed ions modifies significantly the nature of DA solitary waves and DA DLs. The findings of this investigation may be useful in understanding the ion acceleration mechanisms close to the Moon and also enhances our knowledge on pickup ions around unmagnetized bodies, such as comets, Mars, and Venus.

  6. The nonadiabatic dust charge variation on dust acoustic solitary and shock waves in strongly coupled dusty plasmas

    NASA Astrophysics Data System (ADS)

    Wang, Yunliang; Guo, Xiaoyan; Lu, Yanzhen; Wang, Xiaodan

    2016-01-01

    The combined effects of nonadiabatic dust charge fluctuation and strongly coupled dust particles on the nonlinear propagation of dust acoustic (DA) waves in dusty plasma consisting of nonthermal electrons and trapped ions with vortex-like distribution are presented here. We use generalized viscoelastic hydrodynamic model for dust particles. In the weak nonlinearity limit, a modified Korteweg-de Vries (KdV) equation with a damping term and a KdV-Burger equation have been derived in the kinetic regime and hydrodynamic regime, respectively. The approximate analytical solitary solution of modified KdV equation is derived in the weak nonadiabatic dust charge variation limit, which shows that the amplitude of DA solitary waves decreases with time. The presence of viscosity due to strong coupling stands for the formation of DA shock waves in the hydrodynamic regime. The results show that the DA shock waves will be oscillating one for weak viscosity and will become monotonic ones for large viscosity.

  7. Longitudinal frequency variation of long-lasting EMIC Pc1-Pc2 waves localized in the inner magnetosphere

    NASA Astrophysics Data System (ADS)

    Kim, K.-H.; Shiokawa, K.; Mann, I. R.; Park, J.-S.; Kwon, H.-J.; Hyun, K.; Jin, H.; Connors, M.

    2016-02-01

    Long-lasting (> 20 h) electromagnetic ion cyclotron (EMIC) Pc1-Pc2 waves were observed by the Athabasca (L =˜ 4.6) induction magnetometer and Canadian Array for Realtime Investigations of Magnetic Activity (L =˜ 4-6) fluxgate magnetometers on 5 April 2007. These waves showed a systematic frequency change with local time, the minimum frequency near dusk, and the maximum frequency near dawn. Assuming the plasmapause as a potential source region of the waves, we estimated the plasmapause location from localized proton enhancement (LPE) events observed at NOAA-Polar Orbiting Environmental Satellites and METOP-2 satellites. We found that the longitudinal frequency variation of EMIC waves has a clear correlation with the estimated plasmapause location and that the waves are in the frequency band between the equatorial helium and oxygen gyrofrequencies at the estimated plasmapause. With our analysis results we suggest that the LPE events are caused by wave-particle interaction with the helium band EMIC waves generated near the plasmapause.

  8. A Novel Free Flap Monitoring System Using Tissue Oximetry with Text Message Alerts.

    PubMed

    Ricci, Joseph A; Vargas, Christina R; Lin, Samuel J; Tobias, Adam M; Taghinia, Amir H; Lee, Bernard T

    2016-06-01

    Background The time to detection of vascular compromise is a significant predictor of free flap salvage outcomes as early reexploration improves salvage rates. Continuous transcutaneous near-infrared tissue oximetry is an objective, quantitative method of detecting flap vascular compromise and has been shown to allow earlier reexploration and higher salvage rates than clinical assessment alone. We designed a novel text messaging system to improve communication using tissue oximetry monitoring. Methods A retrospective review was performed of a prospectively collected database of all microsurgical breast reconstructions from 2008 to 2015. A novel text messaging system was introduced in 2013 and programmed to send text messages alert when the tissue oximetry readings suggested potential flap compromise based on established thresholds. Patient demographics and complications, including rate of reexploration and flap loss were assessed. Results There were 900 autologous microsurgical breast free flaps during the study period: 614 were monitored with standard clinical monitoring and tissue oximetry compared with 286 flaps with the additional text messaging system. There were 27 unplanned returns to the operating room in the tissue oximetry group and 5 in the text messaging group with 1 complete flap loss in each group. Reexploration occurred sooner as a result of these text message alerts (17.5 vs. 26.6 hours postoperatively), however, it did not achieve statistical significance. Conclusions We were able to demonstrate the use of a novel text messaging system for tissue oximetry. This alert system shows promise in identifying impending flap loss with rapid notification of the surgical team. PMID:27135144

  9. Combining transcutaneous blood gas measurement and pulse oximetry.

    PubMed

    Eberhard, Patrick; Gisiger, P A; Gardaz, J P; Spahn, D R

    2002-01-01

    We are describing the preliminary results of tests performed in adult volunteers and in adult patients during and after general anesthesia with a miniaturized single sensor combining the continuous and non-invasive measurement of oxygen saturaiton by pulse oximetry (SpO2) and transcutaneous PCO2 (OxiCarbo sensor). The sensor is heated to 42 degrees C to arterialize the cutaneous tissue and is applied at the ear lobe with a special low-pressure clip. The results indicate a good agreement between ear lobe PCO2 and arterial PCO2 in the range 35 to 70 mmHg (10 patients, number of measurements 104, regression line TcPCO2 = 1.01 PaCO2 + 0.59 mmHg, bias 1.22 mmHg, SD 3.69 mmHg) and between ear lobe SpO2 and SaO2 (bias 0.44% with SD 0.77% in the range 80% to 100%, bias 1.39% with SD 1.43% in the range 60% to 80%). The ear lobe OxiCarbog sensor detects the SpO2 change 5 to 37 sec faster than a finger sensor and the PCO2 change 9 to 48 sec faster than a transcutaneous sensor fixed at the upper arm. Further improvements versus single sensors are a higher stability of the SpO2 signal and the possibility of performing long term SpO2 and PCO2 measurement at the ear lobe. PMID:11900043

  10. Pulse Oximetry in the Physics Lab: A Colorful Alternative to Traditional Optics Curricula

    NASA Astrophysics Data System (ADS)

    Kutschera, Ellynne; Dunlap, Justin C.; Byrd, Misti; Norlin, Casey; Widenhorn, Ralf

    2013-11-01

    We designed a physics laboratory exercise around pulse oximetry, a noninvasive medical technique used to assess a patient's blood oxygen saturation. An alternative to a traditional optics and light lab, this exercise teaches the principles of light absorption, spectroscopy, and the properties of light, while simultaneously studying a common medical device. Pulse oximeters are ubiquitous in clinical environments; many people who have undergone surgery or visited a hospital environment have experienced the use of this device, making it a good candidate for an investigative lab. The experiment elicits the creative process of device development from students as they conduct measurements using a blood analog that reconstructs the principles of pulse oximetry.

  11. Overnight Pulse Oximetry for Evaluation of Sleep Apnea among Children with Trisomy 21

    PubMed Central

    Coverstone, Andrea M.; Bird, Merielle; Sicard, Melissa; Tao, Yu; Grange, Dorothy K.; Cleveland, Claudia; Molter, David; Kemp, James S.

    2014-01-01

    Study Objectives: For children with trisomy 21, polysomnography at age 4 to assess obstructive sleep disordered breathing (OSDB) is the standard of care. Oximetry alone has been used to screen for disease among children without trisomy 21. This study evaluates the potential usefulness of oximetry scoring in diagnosing OSDB among children with trisomy 21. Methods: A McGill oximetry score from 1 to 4 was derived from a full overnight PSG done on 119 consecutive pediatric subjects with trisomy 21. Most were referred to the sleep laboratory because of suspicion for OSDB. Oximetry scorers were blinded to the child's full PSG and clinical course. Results of the complete PSG were then compared to oximetry scores. Results: Obstructive apnea-hypopnea index (OAHI) was ≥ 2.5 for 50% of all subjects. Fifty-nine subjects (49.6%) had McGill Score 1 (“inconclusive”); median OAHI was 1.0 (IQR 0.4–3.3). McGill Score was 2 for 43 subjects (36.1%); median OAHI was 4.5 (IQR 1.3-8.8). Seventeen subjects (14.3%) had McGill Scores of 3 or 4; median OAHI was 16.1 (IQR 9.3–45.5, range 2.1 to 101.1). Ten percent of subjects had a considerable number of central events (≥ 2.5 respiratory events/h but OAHI < 2.5), including 7 with McGill Score 2. Conclusions: In a retrospective cohort of children with trisomy 21, McGill oximetry scores of 3 or 4 reliably identified patients with marked OSDB. The possibility of central apneas causing hypoxemia must be considered in those with McGill Score 2. With these caveats, oximetry screening should be considered when developing streamlined protocols for early intervention to treat OSDB in this population. Citation: Coverstone AM, Bird M, Sicard M, Tao Y, Grange DK, Cleveland C, Molter D, Kemp JS. Overnight pulse oximetry for evaluation of sleep apnea among children with trisomy 21. J Clin Sleep Med 2014;10(12):1309-1315. PMID:25325597

  12. Pulse Oximetry Screening for Critical Congenital Heart Disease: Bringing Evidence Into Practice.

    PubMed

    Amsbaugh, Sarah; Scott, Shannon D; Foss, Karen

    2015-01-01

    Congenital heart disease is the most common and serious type of infant birth defect. Pulse oximetry screening has been supported in the literature as a valuable tool to aid in the prompt detection of critical defects. Pulse oximetry is easily accessible, inexpensive, and noninvasive, and can be readily performed by clinical nurses at the infant's bedside; however, it remains a technology that is underutilized in newborns. Nurses can be leaders in addressing the need to translate knowledge into practice to improve the morbidity and mortality rates in the newborn population. PMID:25458107

  13. Variational full wave calculation of fast wave current drive in DIII-D using the ALCYON code

    SciTech Connect

    Becoulet, A.; Moreau, D.

    1992-04-01

    Initial fast wave current drive simulations performed with the ALCYON code for the 60 MHz DIII-D experiment are presented. Two typical shots of the 1991 summer campaign were selected with magnetic field intensities of 1 and 2 teslas respectively. The results for the wave electromagnetic field in the plasma chamber are displayed. They exhibit a strong enrichment of the poloidal mode number m-spectrum which leads to the upshift of the parallel wavenumber, {kappa}{perpendicular}, and to the wave absorption. The m-spectrum is bounded when the local poloidal wavenumber reaches the Alfven wavenumber and the {kappa}{perpendicular} upshifts do not destroy the wave directionality. Linear estimations of the driven current are made. The current density profiles are found to be peaked and we find that about 88 kA can be driven in the 1 tesla/1.7 keV phase with 1.7 MW coupled to the electrons. In the 2 tesla/3.4 keV case, 47 kA are driven with a total power of 1.5 MW, 44% of which are absorbed on the hydrogen minority, through the second harmonic ion cyclotron resonance. The global efficiency is then 0.18 {times} 10{sup 19} A m{sup {minus}2}W{sup {minus}1} if one considers only the effective power going to the electrons.

  14. Variation of fundamental mode Rayleigh wave group velocity dispersion in Iran and the surrounding region

    NASA Astrophysics Data System (ADS)

    Rham, D.; Priestley, K.; Tatar, M.; Paul, A.; Hatzfeld, D.; Radjaee, A.; Nowrouzi, G.; Kaviani, A.; Tiberi, C.

    2005-12-01

    We present group velocity dispersion results from a study of regional fundamental mode Rayleigh waves propagating across Iran and the surrounding region. Data for these measurements come from field deployments within Iran by the University of Cambridge (UK) and the Universite Joseph-Fourier (FRA) in conjunction with International Institute of Earthquake Engineering and Seismology (Iran), within Oman by the Universite Pierre et Marie Curie-Paris (FRA), in addition to data from IRIS and Geofone. 1D path-averaged dispersion measurements have been made for ~800 source-receiver paths using multiple filter analysis. We combine these observations in a tomographic inversion to produce group velocity images between 15 and 60~s period. Because of the dense path coverage, these images have substantially higher lateral resolution for this region than is currently available from global and regional group velocity studies. We observe variations in short-period group velocity which is consistent with the surface geology. Low group velocity (2.45-2.55~km/s) at short periods (15-20~s) is observed beneath the south Caspian Basin, northern Iran, the Persian Gulf, the Zagros, the Makran, northern Afghanistan and southern Pakistan. Somewhat higher group velocity (2.60-2.70~km/s) at these periods occurs in central Iran. At intermediate periods (30-40~s) group velocities over most of the region are low (2.90-3.10~km/s) compared to Arabia. At longer periods (50-60~s) group velocities remain low (3.35-3.45~km/s) over most of Iran but there is a suggestion of higher group velocities beneath the northern and central Zagros.

  15. Decomposing variations of geopotential height in the troposphere and stratosphere into stationary and travelling waves

    NASA Astrophysics Data System (ADS)

    Guryanov, Vladimir; Eliseev, Alexey

    2016-07-01

    The ERA-Interim geopotential height in the Northern Hemisphere from November to March, 1992-2015 in the layer from between pressure levels 1000 mb and 1 mb is expanded into stationary and travelling zonal waves with zonal wavenumbers, k, from 1 to 10, and with periods, T, from 2 to 156 days (the so called Hayashi spectra). Among the studied waves, the largest amplitude is attained by the stationary and travelling waves with zonal wavenumber k=1 and with periods from 3 to 4 weeks in the upper stratosphere over the latitudinal belt 60-70oN. The stationary waves with k from 1 to 3 and with T from 2 to 3 weeks are most pronounced in the stratosphere. In turn, the largest amplitudes of the travelling waves with zonal wavenumbers k ≥ 5 are found in the troposphere. The dominant periods of the latter waves are about 1 week or slightly higher, and this dominant period basically decrease with increasing wavenumber. In the upper stratosphere, the eastward travelling waves generally dominate over westward ones. The only exception is the longest zonal mode with k=1, for which the amplitude of the westward travelling wave is larger than that for the eastward one. The period of the travelling waves dominating in the upper stratosphere is close to 3 weeks. In the upper troposphere, the amplitudes of the eastward waves with k from 4 to 10 is several-fold larger than those for their westward counterparts. The latter is reflected in the larger average wavenumber of the eastward travelling wave in comparison to that of the westarward one. The period of the gravest of the dominant travelling waves in the upper troposphere is close to one week, and it decreases to 2-4 days for the dominant travelling waves with k=8-10.

  16. [Nocturnal monitoring of home non-invasive ventilation: Contribution of simple tools such as pulse-oximetry, capnography, built-in ventilator software and autonomic markers of sleep fragmentation].

    PubMed

    Janssens, J-P; Borel, J-C; Pépin, J-L

    2014-02-01

    Complex respiratory events, which may have a detrimental effect on both quality of sleep and control of nocturnal hypoventilation, occur during sleep in patients treated by non-invasive ventilation (NIV). Among these events are patient-ventilator asynchrony, increases in upper airway resistance with or without increased respiratory drive, and leaks. Detection of these events is important in order to select the most appropriate ventilator settings and interface. Simple tools can provide important information when monitoring NIV. Pulse-oximetry is important to ensure that an adequate SpO2 is provided, and to detect either prolonged or short and recurrent desaturations. However, the specificity of pulse-oximetry tracings under NIV is low. Transcutaneous capnography discriminates between hypoxemia related to V/Q mismatch and hypoventilation, documents correction of nocturnal hypoventilation, and may detect ventilator-induced hyperventilation, a possible cause for central apnea/hypopnea and glottic closure. Data provided by ventilator software helps the clinician by estimating ventilation, tidal volume, leaks, rate of inspiratory or expiratory triggering by the patient, although further validation of these signals by independent studies is indicated. Finally, autonomic markers of sympathetic tone using signals such as pulse wave amplitude of the pulse-oximetry signal can provide reliable information of sleep fragmentation. PMID:24602678

  17. Geomagnetic Pulsation Amplitude and Spectrum Variations Accompanying the Ionospheric Heating by High-Power Radio waves from the Sura Facility

    NASA Astrophysics Data System (ADS)

    Chernogor, L. F.; Frolov, V. L.

    2014-10-01

    Aperiodic and quasiperiodic variations in the geomagnetic pulsation amplitude in a range of periods from 40 to 1000 s, which accompany the quasicontinuous and periodic impact on the ionospheric plasma by high-power radio waves from the SURA facility near Nizhny Novgorod (Russia) were recorded near Kharkov (Ukraine) using a magnetometer-fluxmeter. The main parameters of aperiodic and quasiperiodic disturbances of the geomagnetic field are determined. The mechanisms for generation and propagation of detected disturbances are discussed.

  18. On the variation and growth of wave-slope spectra in the capillary-gravity range with increasing wind

    NASA Technical Reports Server (NTRS)

    Long, S. R.; Huang, N. E.

    1976-01-01

    A new laser device has been used to make direct wave-slope measurements in the capillary-gravity range. Owing to the design principles, the digital nature of the system and the use of a laser beam as a probe, the earlier problems of intensity variations and meniscus effects were avoided. Using this new technique, wave-slope spectra both down and across the channel were obtained for different wind conditions, along with corresponding mean-square slope values. Comparisons are made with existing data. The results indicate that a quasi-equilibrium state may exist for each wind speed and that it increases in intensity with increasing wind, which may imply an asymptotic nature for the equilibrium-range coefficient. From the data, two significant frictional velocities, 17.5 and 31 cm/s respectively, are identified as critical values for different ranges of wave development.

  19. Effects of water depth and spectral bandwidth on Stokes drift estimation based on short-term variation of wave conditions

    NASA Astrophysics Data System (ADS)

    Myrhaug, Dag; Wang, Hong; Holmedal, Lars Erik

    2016-04-01

    The Stokes drift represents an important transport component of ocean circulation models. Locally it is responsible for transport of e.g. contaminated ballast water from ships, oil spills, plankton and larvae. It also plays an important role in mixing processes across the interphase between the atmosphere and the ocean. The Stokes drift is the mean Lagrangian velocity obtained from the water particle trajectory in the wave propagation direction; it is maximum at the surface, decreasing rapidly with the depth below the surface. The total mean mass transport is obtained by integrating the Stokes drift over the water depth; this is also referred to as the volume Stokes transport. The paper provides a simple analytical method which can be used to give estimates of the Stokes drift in moderate intermediate water depth based on short-term variation of wave conditions. This is achieved by using a joint distribution of individual wave heights and wave periods together with an explicit solution of the wave dispersion equation. The mean values of the surface Stokes drift and the volume Stokes transport for individual random waves within a sea state are presented, and the effects of water depth and spectral bandwidth parameter are discussed. Furthermore, example of results corresponding to typical field conditions are presented to demonstrate the application of the method, including the Stokes drift profile in the water column beneath the surface. Thus, the present analytical method can be used to estimate the Stokes drift in moderate intermediate water depth for random waves within a sea state based on available wave statistics.

  20. Wave run up statistics on a meso-tidal, steeply-sloping beach: effect of wave forcing and tidal variations

    NASA Astrophysics Data System (ADS)

    Vousdoukas, M. I.; Kirupakaramoorthy, T.; Ferreira, O.

    2012-12-01

    Understanding the probability distributions of shoreline elevation, swash height and swash maxima is important for several applications like numerical modeling of dune erosion and stochastic modeling of swash zone processes. In the present contribution we analyze wave run-up time series obtained from a total of 456 timestack images and acquired, during a 2 years period, from a coastal video monitoring station installed at Faro Beach, S. Portugal. All transformations from image to world coordinates took place considering the daily beach topography measured during 40 RTK-DGPS surveys and the timestack images were processed in an open-access, freely-available Graphical User Interface software (Vousdoukas et al. 2012, Oc. Dyn., 62), developed to extract and process time-series of the cross-shore position of the swash extrema. The shoreline elevation probability distribution was found to be in good agreement with Rayleigh distribution, while comparisons with a standard normal PDF showed no statistically significant match. The Kumaraswamy distribution was found to reproduce even better the measured probability distributions. Following, the 456 swash series were separated into classes according to the significant wave height and water level, among others, and ensemble average distributions were generated for each 'bin'. Low wave height distributions were shown to be better represented by power-law PDFs and only more energetic conditions resulted in good match with the Rayleigh distribution. High tide series were characterized by lower kurtosis compared to low tide ones. The Kumaraswamy distribution (f(x)=pqxp-1(1-xp)q-1) was found to reproduce better all the probability distributions of the different cases, as it is a very versatile due to the 2 shape coefficients p, q. Preliminary results showed that it is possible to parameterize the 2 Kumaraswamy distribution shape coefficients as a function of the wave and tidal parameters (p=0.28Hs+0.27ηs; q=0.85Hs+1.16ηs), in

  1. Spin-label oximetry at Q- and W-band

    NASA Astrophysics Data System (ADS)

    Subczynski, W. K.; Mainali, L.; Camenisch, T. G.; Froncisz, W.; Hyde, J. S.

    2011-04-01

    Spin-lattice relaxation times ( T1s) of small water-soluble spin-labels in the aqueous phase as well as lipid-type spin-labels in membranes increase when the microwave frequency increases from 2 to 35 GHz (Hyde, et al., J. Phys. Chem. B 108 (2004) 9524-9529). The T1s measured at W-band (94 GHz) for the water-soluble spin-labels CTPO and TEMPONE (Froncisz, et al., J. Magn. Reson. 193 (2008) 297-304) are, however, shorter than when measured at Q-band (35 GHz). In this paper, the decreasing trends at W-band have been confirmed for commonly used lipid-type spin-labels in model membranes. It is concluded that the longest values of T1 will generally be found at Q-band, noting that long values are advantageous for measurement of bimolecular collisions with oxygen. The contribution of dissolved molecular oxygen to the relaxation rate was found to be independent of microwave frequency up to 94 GHz for lipid-type spin-labels in membranes. This contribution is expressed in terms of the oxygen transport parameter W=T1-1 (Air)-T1-1 (N), which is a function of both concentration and translational diffusion of oxygen in the local environment of a spin-label. The new capabilities in measurement of the oxygen transport parameter using saturation-recovery (SR) EPR at Q- and W-band have been demonstrated in saturated (DMPC) and unsaturated (POPC) lipid bilayer membranes with the use of stearic acid ( n-SASL) and phosphatidylcholine ( n-PC) spin-labels, and compared with results obtained earlier at X-band. SR EPR spin-label oximetry at Q- and W-band has the potential to be a powerful tool for studying samples of small volume, ˜30 nL. These benefits, together with other factors such as a higher resonator efficiency parameter and a new technique for canceling free induction decay signals, are discussed.

  2. Desaturation Patterns Detected by Oximetry in a Large Population of Athletes

    ERIC Educational Resources Information Center

    Garrido-Chamorro, Raul P.; Gonzalez-Lorenzo, Marta; Sirvent-Belando, Jose; Blasco-Lafarga, Cristina; Roche, Enrique

    2009-01-01

    Optimal exercise performance in well trained athletes can be affected by arterial oxygen saturation failure. Noninvasive detection of this phenomenon when performing a routine ergometric test can be a valuable tool for subsequent planning of the athlete's training, recovery, and nutrition. Oximetry has been used to this end. The authors studied…

  3. Pulse Oximetry in the Physics Lab: A Colorful Alternative to Traditional Optics Curricula

    ERIC Educational Resources Information Center

    Kutschera, Ellynne; Dunlap, Justin C.; Byrd, Misti; Norlin, Casey; Widenhorn, Ralf

    2013-01-01

    We designed a physics laboratory exercise around pulse oximetry, a noninvasive medical technique used to assess a patient's blood oxygen saturation. An alternative to a traditional optics and light lab, this exercise teaches the principles of light absorption, spectroscopy, and the properties of light, while simultaneously studying a common…

  4. Should pulse oximetry be included in GPs’ assessment of patients with obstructive lung disease?

    PubMed Central

    Dalbak, Lene G.; Straand, Jørund; Melbye, Hasse

    2015-01-01

    Objective: To explore the associations between decreased pulse oximetry values (SpO2) and clinical, laboratory, and demographic variables in general practice patients diagnosed with asthma or chronic obstructive pulmonary disease (COPD), including those with both COPD and asthma in combination. Design/setting: A cross-sectional study in seven Norwegian general practices of patients aged 40 years or over who were diagnosed by their general practitioner (GP) with asthma and/or COPD. The patients were examined during a stable phase of their disease. Patients diagnosed with COPD (including those with combined COPD/asthma) and those diagnosed with asthma only were analysed separately. Main outcome measures: Decreased SpO2 values (≤ 95% and ≤ 92%). Results: Of 372 patients included (mean age 61.5 years, 62% women), 82 (22.0%) had SpO2 ≤ 95%, of which 11 had SpO2 ≤ 92%. In both asthma and COPD patients, SpO2 ≤ 95% was significantly associated with reduced lung function (spirometry), a diagnosis of coronary heart disease and older age (≥ 65 years). In the COPD group, haemoglobin above normal was associated with SpO2 ≤ 95%. These associations were confirmed by multivariable logistic regression, where FEV1% predicted < 50 was the strongest predictor of SpO2 ≤ 95% (odds ratio 6.8, 95% confidence interval 2.8–16.4). Conclusion. Pulse oximetry represents a useful diagnostic adjunct for assessing the severity of obstructive pulmonary disease. Decreased pulse oximetry values in stable-phase patients with asthma and/or COPD should prompt the GP to consider revising the diagnosis and treatment and to look for co-morbidities.Key PointsDespite its common use in general practice, the diagnostic benefits of pulse oximetry remain to be established.Decreased pulse oximetry values are associated with both reduced lung function (spirometry) and with a diagnosis of coronary heart disease.Decreased pulse oximetry values may reflect suboptimal

  5. Evaluating the impact of pulse oximetry on childhood pneumonia mortality in resource-poor settings.

    PubMed

    Floyd, Jessica; Wu, Lindsey; Hay Burgess, Deborah; Izadnegahdar, Rasa; Mukanga, David; Ghani, Azra C

    2015-12-01

    It is estimated that pneumonia is responsible for 15% of childhood deaths worldwide. Recent research has shown that hypoxia and malnutrition are strong predictors of mortality in children hospitalized for pneumonia. It is estimated that 15% of children under 5 who are hospitalized for pneumonia have hypoxaemia and that around 1.5 million children with severe pneumonia require oxygen treatment each year. We developed a deterministic compartmental model that links the care pathway to disease progression to assess the impact of introducing pulse oximetry as a prognostic tool to distinguish severe from non-severe pneumonia in under-5 year olds across 15 countries with the highest burden worldwide. We estimate that, assuming access to supplemental oxygen, pulse oximetry has the potential to avert up to 148,000 deaths if implemented across the 15 countries. By contrast, integrated management of childhood illness alone has a relatively small impact on mortality owing to its low sensitivity. Pulse oximetry can significantly increase the incidence of correctly treated severe cases as well as reduce the incidence of incorrect treatment with antibiotics. We also found that the combination of pulse oximetry with integrated management of childhood illness is highly cost-effective, with median estimates ranging from US$2.97 to $52.92 per disability-adjusted life year averted in the 15 countries analysed. This combination of substantial burden reduction and favourable cost-effectiveness makes pulse oximetry a promising candidate for improving the prognosis for children with pneumonia in resource-poor settings. PMID:26633766

  6. Pulse Wave Variation during the Menstrual Cycle in Women with Menstrual Pain.

    PubMed

    Jeon, Soo Hyung; Kim, Kyu Kon; Lee, In Seon; Lee, Yong Tae; Kim, Gyeong Cheol; Chi, Gyoo Yong; Cho, Hye Sook; Kang, Hee Jung; Kim, Jong Won

    2016-01-01

    Objective. This study is performed to obtain objective diagnostic indicators associated with menstrual pain using pulse wave analysis. Methods. Using a pulse diagnostic device, we measured the pulse waves of 541 women aged between 19 and 30 years, placed in either an experimental group with menstrual pain (n = 329) or a control group with little or no menstrual pain (n = 212). Measurements were taken during both the menstrual and nonmenstrual periods, and comparative analysis was performed. Results. During the nonmenstrual period, the experimental group showed a significantly higher value in the left radial artery for the radial augmentation index (RAI) (p = 0.050) but significantly lower values for pulse wave energy (p = 0.021) and time to first peak from baseline (T1) (p = 0.035) in the right radial artery. During the menstrual period, the experimental group showed significantly lower values in the left radial artery for cardiac diastole and pulse wave area during diastole and significantly higher values for pulse wave area during systole, ratio of systolic phase to the full heartbeat, and systolic-diastolic ratio. Conclusion. We obtained indicators of menstrual pain in women during the menstrual period, including prolonged systolic and shortened diastolic phases, increases in pulse wave energy and area of representative pulse wave, and increased blood vessel resistance. PMID:27579304

  7. Pulse Wave Variation during the Menstrual Cycle in Women with Menstrual Pain

    PubMed Central

    Jeon, Soo Hyung; Kim, Kyu Kon; Lee, In Seon; Lee, Yong Tae; Kim, Gyeong Cheol; Chi, Gyoo Yong; Cho, Hye Sook; Kang, Hee Jung

    2016-01-01

    Objective. This study is performed to obtain objective diagnostic indicators associated with menstrual pain using pulse wave analysis. Methods. Using a pulse diagnostic device, we measured the pulse waves of 541 women aged between 19 and 30 years, placed in either an experimental group with menstrual pain (n = 329) or a control group with little or no menstrual pain (n = 212). Measurements were taken during both the menstrual and nonmenstrual periods, and comparative analysis was performed. Results. During the nonmenstrual period, the experimental group showed a significantly higher value in the left radial artery for the radial augmentation index (RAI) (p = 0.050) but significantly lower values for pulse wave energy (p = 0.021) and time to first peak from baseline (T1) (p = 0.035) in the right radial artery. During the menstrual period, the experimental group showed significantly lower values in the left radial artery for cardiac diastole and pulse wave area during diastole and significantly higher values for pulse wave area during systole, ratio of systolic phase to the full heartbeat, and systolic-diastolic ratio. Conclusion. We obtained indicators of menstrual pain in women during the menstrual period, including prolonged systolic and shortened diastolic phases, increases in pulse wave energy and area of representative pulse wave, and increased blood vessel resistance. PMID:27579304

  8. The seasonal variation of the D region as inferred from propagation characteristics of LF radio waves

    NASA Technical Reports Server (NTRS)

    Ishimine, T.; Ishii, T.; Echizenya, Y.

    1985-01-01

    The propagation data of JG2AS 40 kHz (Japanese Standard Frequency), Loran C 100 kHz radio waves, and meteorological data were analyzed to study the association of propagation characteristics of LF radio waves with the atmospheric circulation in the mesosphere. The monthly averaged electric fields were depicted on the complex plane for typical summer and winter months, June and November. The locus traced out by the electric field vector during daytime is nearly circular. This is because during daytime the amplitude of the sky wave remains nearly constant while its phase changes in accord with the height change of the reflection layer, and thus the electric field vector traces out a circular locus with its center at the tip of the supposed ground wave vector. The locus has a loop during the sunrise or sunset period, which seems to arise from interference of two waves reflected by two different layers. In June the amplitude of the sky wave decreases rapidly before the dawn or increases after the dusk. In November such rapid change is not observed. During nighttime, the sky wave phase changes in such a way as to suggest that the reflection height moves upwards with time before midnight or lowers after midnight in November. In June it changes similarly before midnight, but after midnight it varies erratically. These characteristics are closely related to the structure of the D region, which is clearly shown by simulating the loci traced out by electric fields.

  9. Regional variations of the shear-wave polarization anisotropy in the crust and mantle wedge beneath the Tohoku district

    NASA Astrophysics Data System (ADS)

    Watanabe, Mitsumi; Oda, Hitoshi

    2014-10-01

    We investigated the regional variations of the shear-wave polarization anisotropy in the upper crust, lower crust, and mantle wedge beneath the Tohoku district in the northeast Japan arc. The shear-wave splitting parameters (fast polarization direction (FPD) and split time) for the upper and lower crusts are estimated by shear-wave splitting analysis of the Ps phases, which are generated by the conversion of a P wave into an S wave at the Conrad and Moho discontinuity interfaces. The splitting parameters for the mantle wedge are determined by splitting analysis of the slab Ps phase converted at the oceanic crust on the subducting Pacific slab and the direct S waves from deep focus earthquakes located just below seismic stations. The Ps phases are identified on the P-wave receiver functions constructed from the teleseismic records. To accurately determine the splitting parameters for the lower crust from the Moho Ps phase, the Ps phase should be corrected for the shear-wave splitting effect in the upper crust. Similarly, to estimate the mantle wedge anisotropy, the direct S wave and slab Ps phase must be corrected for the splitting effect in the crust. The anisotropies of the crust and mantle wedge are estimated from the corrected Ps phases and direct S waves. The anisotropy of the upper crust exhibits a regional variation where FPD of the split shear wave is predominant in the N-S direction in the Pacific coast area and in the E-W direction in the rest of the Tohoku district. The split time is less than 0.2 s. The upper crustal anisotropy is attributed to the alignment of vertical cracks induced in the upper crust by tectonic stress. In the lower crust, FPD is predominant in the E-W direction with a split time similar to that in the upper crust, and the anisotropy of the lower crust is due to the lattice preferred orientation of rock-forming minerals. In the mantle wedge, FPD is predominant in the N-S direction (trench-parallel) in the fore-arc side of the volcanic

  10. Models for electrostatic drift waves with density variations along magnetic field lines

    NASA Astrophysics Data System (ADS)

    Garcia, O. E.; Pécseli, H. L.

    2013-11-01

    Drift waves with vertical magnetic fields in gravitational ionospheres are considered where the unperturbed plasma density is enhanced in a magnetic flux tube. The gravitational field gives rise to an overall decrease of plasma density for increasing altitude. Simple models predict that drift waves with finite vertical wave vector components can increase in amplitude merely due to a conservation of energy density flux of the waves. Field-aligned currents are some of the mechanisms that can give rise to fluctuations that are truly unstable. We suggest a self-consistent generator or "battery" mechanism that in the polar ionospheres can give rise to magnetic field-aligned currents even in the absence of electron precipitation. The free energy here is supplied by steady state electric fields imposed in the direction perpendicular to the magnetic field in the collisional lower parts of the ionosphere or by neutral winds that have similar effects.

  11. Variation of Langmuir wave polarization with electron beam speed in type III radio bursts

    SciTech Connect

    Malaspina, David M.; Cairns, Iver H.; Ergun, Robert E.

    2013-06-13

    Observations by the twin STEREO spacecraft of in-situ electric field waveforms and radio signatures associated with type III radio bursts have demonstrated that the polarization of electron beam-driven waves near the local plasma frequency depends strongly on the speed of the driving electron beam. We expand upon a previous study by including all radio bursts with in-situ waveforms observed by STEREO in 2011. The expanded data set contains five times more radio bursts (35 up from 7) and three times as many Langmuir waves (663 up from 168). While this expanded study supports the results of the original study, that faster (slower) beam electrons drive waves with strong (weak) electric fields perpendicular to the local magnetic field, the larger data set emphasizes that the observation of strong perpendicular electric fields at high electron beam speeds is probabilistic rather than definite. This property supports the interpretation of wave polarization dependence on beam speed as Langmuir/z-mode waves shifted to small wave number through interaction with turbulent solar wind density fluctuations.

  12. Variational Optimization of the Second-Order Density Matrix Corresponding to a Seniority-Zero Configuration Interaction Wave Function.

    PubMed

    Poelmans, Ward; Van Raemdonck, Mario; Verstichel, Brecht; De Baerdemacker, Stijn; Torre, Alicia; Lain, Luis; Massaccesi, Gustavo E; Alcoba, Diego R; Bultinck, Patrick; Van Neck, Dimitri

    2015-09-01

    We perform a direct variational determination of the second-order (two-particle) density matrix corresponding to a many-electron system, under a restricted set of the two-index N-representability P-, Q-, and G-conditions. In addition, we impose a set of necessary constraints that the two-particle density matrix must be derivable from a doubly occupied many-electron wave function, i.e., a singlet wave function for which the Slater determinant decomposition only contains determinants in which spatial orbitals are doubly occupied. We rederive the two-index N-representability conditions first found by Weinhold and Wilson and apply them to various benchmark systems (linear hydrogen chains, He, N2, and CN(-)). This work is motivated by the fact that a doubly occupied many-electron wave function captures in many cases the bulk of the static correlation. Compared to the general case, the structure of doubly occupied two-particle density matrices causes the associate semidefinite program to have a very favorable scaling as L(3), where L is the number of spatial orbitals. Since the doubly occupied Hilbert space depends on the choice of the orbitals, variational calculation steps of the two-particle density matrix are interspersed with orbital-optimization steps (based on Jacobi rotations in the space of the spatial orbitals). We also point to the importance of symmetry breaking of the orbitals when performing calculations in a doubly occupied framework. PMID:26575902

  13. Diffuse Optical Imaging and Spectroscopy of the Human Breast for Quantitative Oximetry with Depth Resolution

    NASA Astrophysics Data System (ADS)

    Yu, Yang

    Near-infrared spectral imaging for breast cancer diagnostics and monitoring has been a hot research topic for the past decade. Here we present instrumentation for diffuse optical imaging of breast tissue with tandem scan of a single source-detector pair with broadband light in transmission geometry for tissue oximetry. The efforts to develop the continuous-wave (CW) domain instrument have been described, and a frequency-domain (FD) system is also used to measure the bulk tissue optical properties and the breast thickness distribution. We also describe the efforts to improve the data processing codes in the 2D spatial domain for better noise suppression, contrast enhancement, and spectral analysis. We developed a paired-wavelength approach, which is based on finding pairs of wavelength that feature the same optical contrast, to quantify the tissue oxygenation for the absorption structures detected in the 2D structural image. A total of eighteen subjects, two of whom were bearing breast cancer on their right breasts, were measured with this hybrid CW/FD instrument and processed with the improved algorithms. We obtained an average tissue oxygenation value of 87% +/- 6% from the healthy breasts, significantly higher than that measured in the diseased breasts (69% +/- 14%) (p < 0.01). For the two diseased breasts, the tumor areas bear hypoxia signatures versus the remainder of the breast, with oxygenation values of 49 +/- 11% (diseased region) vs. 61 +/- 16% (healthy regions) for the breast with invasive ductal carcinoma, and 58 +/- 8% (diseased region) vs 77 +/- 11% (healthy regions) for ductal carcinoma in situ. Our subjects came from various ethnical/racial backgrounds, and two-thirds of our subjects were less than thirty years old, indicating a potential to apply the optical mammography to a broad population. The second part of this thesis covers the topic of depth discrimination, which is lacking with our single source-detector scan system. Based on an off

  14. Effects of planetary-scale waves on temporal wind variations in the Venusian thermosphere

    NASA Astrophysics Data System (ADS)

    Hoshino, N.; Fujiwara, H.; Takagi, M.; Takahashi, Y.; Kasaba, Y.

    2008-12-01

    In recent years, the importance of planetary-scale waves for dynamics of the Venusian upper atmosphere has been recognized. For example, Forbes and Knopliv [2007] suggested propagations of planetary-scale waves originated in the cloud deck to the thermosphere from reanalysis of the Magellan spacecraft data. In addition, recent simulation studies suggest importance of tidal waves for the superrotation in the Venusian cloud deck [Takagi and Matsuda, 2007]. Venus Climate Orbiter (VCO), which will be launched in 2010 as the second Japanese planetary mission, is expected to provide precious information about upward propagating planetary scale-waves which can't be obtained by Venus Express because of the polar orbit and the close-up observations. In order to understand effects of the planetary-scale waves propagating from the cloud top on the thermospheric circulation, we have developed a new general circulation model (GCM) which includes about 80-200 km altitude region. The GCM solves the primitive equations for momentum, energy and composition. The solar EUV heating, NIR heating and 15μm Radiative cooling are considered. We also consider O, CO and CO2 as the major composition of the Venusian mesosphere and thermosphere. The horizontal and vertical resolutions are 10° in longitude, 20° in latitude, and 0.5 scale height in altitude, respectively. In this study, we perform GCM simulations with use of global distributions of planetary-scale waves taking into account the recent simulation results [e.g., Takagi and Matsuda, 2007] and the past observations [e.g., Del genio and Rossow, 1990]. We will also develop a method for GCM simulations with the VCO data.

  15. Improved techniques for outgoing wave variational principle calculations of converged state-to-state transition probabilities for chemical reactions

    NASA Technical Reports Server (NTRS)

    Mielke, Steven L.; Truhlar, Donald G.; Schwenke, David W.

    1991-01-01

    Improved techniques and well-optimized basis sets are presented for application of the outgoing wave variational principle to calculate converged quantum mechanical reaction probabilities. They are illustrated with calculations for the reactions D + H2 yields HD + H with total angular momentum J = 3 and F + H2 yields HF + H with J = 0 and 3. The optimization involves the choice of distortion potential, the grid for calculating half-integrated Green's functions, the placement, width, and number of primitive distributed Gaussians, and the computationally most efficient partition between dynamically adapted and primitive basis functions. Benchmark calculations with 224-1064 channels are presented.

  16. A statistical study of variations of internal gravity wave energy characteristics in meteor zone

    NASA Technical Reports Server (NTRS)

    Gavrilov, N. M.; Kalov, E. D.

    1987-01-01

    Internal gravity wave (IGW) parameters obtained by the radiometer method have been considered by many other researchers. The results of the processing of regular radiometeor measurements taken during 1979 to 1980 in Obninsk (55.1 deg N, 36.6 deg E) are presented.

  17. Seascape-level variation in turbulence- and wave-generated hydrodynamic signals experienced by plankton

    NASA Astrophysics Data System (ADS)

    Fuchs, Heidi L.; Gerbi, Gregory P.

    2016-02-01

    Plankton exhibit diverse and dramatic responses to fluid motions, and these behaviors are likely critical for survival and fitness. Fluid motions can be generated by organisms or by physical processes, including turbulence and surface gravity waves. Physical processes vary geographically in their intensity and generate hydrodynamic signals experienced by plankton as fluid forces on their sensory receptors. In this synthesis, we review how turbulence and waves vary in space, the scales and statistics of their motions, and the forces exerted on plankton. We then quantify the hydrodynamic signals produced by turbulence and waves in four seascape types - surf zones, inlets and estuaries, the continental shelf, and the open ocean - using published dissipation rates, wind and wave data from buoys, and observations from two coastal sites in Massachusetts, USA. We relate these geographic patterns in signals to the observed behaviors of example species and to the forces sensed by typical plankters with different receptor types. Turbulence-generated shears are largest in the surf zone, inlets and estuaries, while wave-generated accelerations are larger offshore; as a result, each seascape exhibits some range of combined shears and accelerations that is distinct. These signals generate forces on plankton that vary among habitats and with plankton size and swimming speed. Spatial patterns in fluid forces create a potential mechanism for dispersing larvae to distinguish habitats by their hydrodynamic signatures. However, turbulence can be strong in all seascapes and may cause widespread interference in signaling among predators and prey. Plankton with a single receptor type could identify nearshore habitats, while those with multiple receptor types potentially could distinguish inshore vs. offshore seascapes or decode signals produced by physical processes and by other organisms.

  18. Comparison of dysphagics and nondysphagics on pulse oximetry during oral feeding.

    PubMed

    Colodny, N

    2000-01-01

    This study was designed to determine whether significant differences in SpO(2) levels existed among elderly individuals with dysphagia, and, more specifically, whether pulse oximetry can discriminate dysphagic from nondysphagic individuals. In addition, differences in SpO(2) between liquid aspirators, solid aspirators, laryngeal penetrators, and normals was investigated in a sample of 181 subjects, 104 of whom were dysphagic. Results indicated that aspirators had lower SpO(2) levels before, during, and after feeding compared with nonaspirators. Solid aspirators were the most compromised. No relation was found between SpO(2) levels and aspiration. Pulse levels rose for all subjects from before to during feeding, declining slightly thereafter. These data were consistent with previous findings that dysphagics have compromised pulmonary systems but at variance with studies that indicated changes in pulse oximetry during aspiration. PMID:10758188

  19. Theoretical considerations to optimize transabdominal monitoring of fetal arterial blood oxygenation using pulse oximetry

    NASA Astrophysics Data System (ADS)

    Zourabian, Anna; Boas, David A.

    2001-06-01

    Pulse oximetry (oxygen saturation monitoring) has markedly improved medical care in many fields, including anesthesiology, intensive care, and newborn intensive care. In obstetrics, fetal heart rate monitoring remains the standard for intrapartum assessment of fetal well being. Fetal oxygen saturation monitoring is a new technique currently under development. It is potentially superior to electronic fetal heart rate monitoring (cardiotocography) because it allows direct assessment of both fetal oxygen status and fetal tissue perfusion. Here we present the analysis for determining the most optimal wavelength selection for pulse oximetry. The wavelengths we chose as the most optimal are: the first in the range of 670-720nm and the second in the range of 825-925nm. Further we discuss the possible systematic errors during our measurements, and their contribution to the obtained saturation results.

  20. Pulse oximetry error in a patient with a Santa Ana haemoglobinopathy.

    PubMed

    Robertson, Alistair; Rahemtulla, Amin

    2016-01-01

    A young man with a rare unstable haemoglobinopathy presented with a high fever, worsening shortness of breath and abdominal pain. At triage his pulse oximetry (SpO2) suggested that his blood oxygen saturation was 84% at room air. However, an arterial blood gas (ABG) oxygen saturation reading (SaO2) was 100%. The significant disparity between the two measurements demonstrates that using pulse oximetry in some unstable haemoglobinopathies may significantly underestimate the actual reading. This error is most probably due to the structural differences in the variant haemoglobin causing light to be absorbed at a different wavelength beyond the normal range of the oximeter. Haemoglobinopathies affect about 7% of the world's population and is often asymptomatic; so, there may be many more undiagnosed cases. Therefore, clinicians may confirm low SpO2 readings with an ABG and, where there is significant disparity with no obvious extrinsic cause, they should consider haemoglobinopathies. PMID:27599809

  1. Pulse oximetry: A reliable and cost effective screening tool in children with pneumonia for developing countries.

    PubMed

    Hamid, Muhammad Akhter; Chandna, Ayesha; Siddiqui, Sohaib; Fayyaz, Jabeen

    2016-08-01

    The infant mortality rates are high in developing countries and, according to World Health Organisation (WHO), statistics show that the main contributors are acute respiratory infections and pneumonia. In children hypoxaemia is an ominous sign associated with respiratory tract infections. Hypoxia can be detected easily with pulse oximetry. It is a non-invasive, readily available and cost-effective way to identify hypoxaemia. If we identify hypoxaemia at the primary care level, especially in a low-income setting, we can make early referral to tertiary care settings. This will subsequently have a positive impact in saving lives. A detailed search of Medline database was conducted through PubMed from 1990 to date, to review the literature on the usefulness of pulse oximetry at primary care centres in developing countries. Such information will become vital in formulating guidelines for income-poor countries in order to stratify high-risk children with hypoxaemia. PMID:27524539

  2. Type III home sleep testing versus pulse oximetry: is the respiratory disturbance index better than the oxygen desaturation index to predict the apnoea-hypopnoea index measured during laboratory polysomnography?

    PubMed Central

    Dawson, Arthur; Loving, Richard T; Gordon, Robert M; Abel, Susan L; Loewy, Derek; Kripke, Daniel F; Kline, Lawrence E

    2015-01-01

    Objectives In its guidelines on the use of portable monitors to diagnose obstructive sleep apnoea, the American Academy of Sleep Medicine endorses home polygraphy with type III devices recording at a minimum airflow the respiratory effort and pulse oximetry, but advises against simple pulse oximetry. However, oximetry is widely available and simple to use in the home. This study was designed to compare the ability of the oxygen desaturation index (ODI) based on oximetry alone with a stand-alone pulse oximeter (SPO) and from the oximetry channel of the ApneaLink Plus (ALP), with the respiratory disturbance index (RDI) based on four channels from the ALP to predict the apnoea–hypopnoea index (AHI) from laboratory polysomnography. Design Cross-sectional diagnostic accuracy study. Setting Sleep medicine practice of a multispecialty clinic. Participants Patients referred for laboratory polysomnography with suspected sleep apnoea. We enrolled 135 participants with 123 attempting the home sleep testing and 73 having at least 4 hours of satisfactory data from SPO and ALP. Interventions Participants had home testing performed simultaneously with both a SPO and an ALP. The 2 oximeter probes were worn on different fingers of the same hand. The ODI for the SPO was calculated using Profox software (ODISOX). For the ALP, RDI and ODI were calculated using both technician scoring (RDIMAN and ODIMAN) and the ALP computer scoring (RDIRAW and ODIRAW). Results The receiver–operator characteristic areas under the curve for AHI ≥5 were RDIMAN 0.88 (95% confidence limits 0.81–0.96), RDIRAW 0.86 (0.76–0.94), ODIMAN 0.86 (0.77–0.95), ODIRAW 0.84 (0.75–0.93) and ODISOX 0.83 (0.73–0.93). Conclusions We conclude that the RDI and the ODI, measured at home on the same night, give similar predictions of the laboratory AHI, measured on a different night. The differences between the two methods are small compared with the reported night-to-night variation of the AHI. PMID

  3. Functional muscle studies by dual-wavelength eight-channel time-resolved oximetry

    NASA Astrophysics Data System (ADS)

    Cubeddu, Rinaldo; Biscotti, Giovanni; Pifferi, Antonio; Taroni, Paola; Torricelli, Alessandro; Ferrari, Marco; Quaresima, Valentina

    2003-10-01

    A portable instrument for tissue oximetry based on time-resolved reflectance spectroscopy was developed. The performances of the system were tested on phantoms in terms of stability, reproducibility among channels, and accuracy in the determination of the optical properties. Preliminary in vivo measurements were performed on healthy volunteers to monitor spatial changes in calf (medial and lateral gastrocnemius) oxygen hemoglobin saturation and blood volume during dynamic plantar flexion exercise.

  4. Peri-operative pulse oximetry in low-income countries: a cost–effectiveness analysis

    PubMed Central

    Chilton, Peter J; Gawande, Atul A; Lilford, Richard J

    2014-01-01

    Abstract Objective To evaluate the cost–effectiveness of pulse oximetry – compared with no peri-operative monitoring – during surgery in low-income countries. Methods We considered the use of tabletop and portable, hand-held pulse oximeters among patients of any age undergoing major surgery in low-income countries. From earlier studies we obtained baseline mortality and the effectiveness of pulse oximeters to reduce mortality. We considered the direct costs of purchasing and maintaining pulse oximeters as well as the cost of supplementary oxygen used to treat hypoxic episodes identified by oximetry. Health benefits were measured in disability-adjusted life-years (DALYs) averted and benefits and costs were both discounted at 3% per year. We used recommended cost–effectiveness thresholds – both absolute and relative to gross domestic product (GDP) per capita – to assess if pulse oximetry is a cost–effective health intervention. To test the robustness of our results we performed sensitivity analyses. Findings In 2013 prices, tabletop and hand-held oximeters were found to have annual costs of 310 and 95 United States dollars (US$), respectively. Assuming the two types of oximeter have identical effectiveness, a single oximeter used for 22 procedures per week averted 0.83 DALYs per annum. The tabletop and hand-held oximeters cost US$ 374 and US$ 115 per DALY averted, respectively. For any country with a GDP per capita above US$ 677 the hand-held oximeter was found to be cost–effective if it prevented just 1.7% of anaesthetic-related deaths or 0.3% of peri-operative mortality. Conclusion Pulse oximetry is a cost–effective intervention for low-income settings. PMID:25552770

  5. A rapid Look-Locker imaging sequence for quantitative tissue oximetry

    NASA Astrophysics Data System (ADS)

    Vidya Shankar, Rohini; Kodibagkar, Vikram D.

    2015-03-01

    Tissue oximetry studies using magnetic resonance imaging are increasingly contributing to advances in the imaging and treatment of cancer. The non-invasive measurement of tissue oxygenation (pO2) may facilitate a better understanding of the pathophysiology and prognosis of diseases, particularly in the assessment of the extensive hypoxic regions associated with cancerous lesions. The availability of tumor hypoxia maps could help quantify and predict tumor response to intervention and therapy. The PISTOL (Proton Imaging of Siloxanes to map Tissue Oxygenation Levels) oximetry technique maps the T1 of administered hexamethyldisiloxane (HMDSO), an 1H NMR pO2 reporter molecule in about 3 ½ min. This allows us to subsequently monitor static and dynamic changes in the tissue pO2 (in response to intervention) at various locations due to the linear relationship between 1/T1 and pO2. In this work, an HMDSO-selective Look-Locker imaging sequence with EPI readout has been developed to enable faster PISTOL acquisitions. The new sequence incorporates the fast Look-Locker measurement method to enable T1, and hence, pO2 mapping of HMDSO in under one minute. To demonstrate the application of this pulse sequence in vivo, 50 μL of neat HMDSO was administered to the thigh muscle of a healthy rat (Fischer F344, n=4). Dynamic changes in the mean pO2 of the thigh muscle were measured using both PISTOL and the developed LL oximetry sequence in response to oxygen challenge and compared. Results demonstrate the efficacy of the new sequence in rapidly mapping the pO2 changes, leading to advances in fast quantitative 1H MR oximetry.

  6. Cerebral oximetry in preterm infants: an agenda for research with a clear clinical goal.

    PubMed

    Greisen, Gorm; Andresen, Bjørn; Plomgaard, Anne Mette; Hyttel-Sørensen, Simon

    2016-07-01

    Preterm birth constitutes a major cause of death before 5 years of age and it is a major cause of neurodevelopmental impairment across the world. Preterm infants are most unstable during the transition between fetal and newborn life during the first days of life and most brain damage occurs in this period. The brain of the preterm infant is accessible for tissue oximetry by near-infrared spectroscopy. Cerebral oximetry has the potential to improve the long-term outcome by helping to tailor the support of respiration and circulation to the individual infant's needs, but the evidence is still lacking. The goals for research include testing the benefit and harms of cerebral oximetry in large-scale randomized trials, improved definition of the hypoxic threshold, better understanding the effects of intensive care on cerebral oxygenation, as well as improved precision of oximeters and calibration among devices or standardization of values in the hypoxic range. These goals can be pursued in parallel. PMID:27158632

  7. Trans-abdominal monitoring of fetal arterial blood oxygenation using pulse oximetry

    NASA Astrophysics Data System (ADS)

    Zourabian, Anna; Siegel, Andrew M.; Chance, Britton; Ramanujam, Nirmala; Rode, Martha; Boas, David A.

    2000-10-01

    Pulse oximetry (oxygen saturation monitoring) has markedly improved medical care in many fields, including anesthesiology, intensive care, and newborn intensive care. In obstetrics, fetal heart rate monitoring remains the standard for intrapartum assessment of fetal well being. Fetal oxygen saturation monitoring is a new technique currently under development. It is potentially superior to electronic fetal heart rate monitoring (cardiotocography) because it allows direct assessment of both the fetal oxygen status and fetal tissue perfusion. Here we present the analysis for determining the most optimal wavelength selection for pulse oximetry. The wavelengths we chose as the most optimal are the first in the range of 670 - 720 nm and the second in the range of 825 - 925 nm. Further, we discuss the possible systematic errors during our measurements and their contribution to the obtained saturation results. We present feasibility studies for fetal pulse oximetry, monitored noninvasively through the maternal abdomen. Our preliminary experiments show that the fetal pulse can be discriminated from the maternal pulse and thus, in principle, the fetal arterial oxygen saturation can be obtained. We present the methodology for obtaining these data, and discuss the dependence of our measurements on the fetal position with respect to the optode assembly.

  8. Evaluation of cerebral oximetry during endovascular treatment of carotid-cavernous fistula

    NASA Astrophysics Data System (ADS)

    Dujovny, Manuel; Misra, Mukesh; Alp, M. Serdar; Debrun, Gerard; Charbel, F. T.; Aletich, Victor; Ausman, James I.

    1997-08-01

    Endovascular treatment of carotid cavernous fistula is done routinely in our institution. We have been monitoring these patients with transcranial cerebral oximetry. The transcranial cerebral oximeter is a reliable, low-cost, non-invasive device that provides real-time evaluation of regional brain oxygen saturation during and after endovascular treatment of cerebrovascular diseases. We used the INVOS 3100A (Somanetics, Troy, MI) in our study. We discuss seven patients with carotid-cavernous fistulas treated by endovascular balloon occlusion, each monitored continuously before, during, and after the procedure with transcranial cerebral oximetry. The cerebral oxygen saturation depicted was directly related to the side of the venous drainage of the fistula, with the brain oxygen saturation 15 - 20% higher on the side of the venous drainage. Following endovascular occlusion of the fistula, oxygen saturation gradually became equal on both sides. In our patients treated for carotid-cavernous fistula, we evaluated the sensitivity and usefulness of cerebral oximetry as an important non-invasive monitoring tool for the endovascular treatment of carotid-cavernous fistula.

  9. Variation of P-Wave Velocity before the Bear Valley, California, Earthquake of 24 February 1972.

    PubMed

    Robinson, R; Wesson, R L; Ellsworth, W L

    1974-06-21

    Residuals for P-wave traveltimes at a seismnograph station near Bear Valley, California, for small, precisely located local earthquakes at distances of 20 to 70 kilometers show a sharp increase of nearly 0.3 second about 2 months before a magnitude 5.0 earthquake that occurred within a few kilometers of the station. This indicates that velocity changes observed elsewhere premonitory to earthquakes, possibly related to dilatancy, occur along the central section of the San Andreas fault system. PMID:17784227

  10. Modeling Mars Cyclogenesis and Frontal Waves: Seasonal Variations and Implications on Dust Activity

    NASA Technical Reports Server (NTRS)

    Hollingsworth, J. L.; Kahre, M. A.

    2014-01-01

    Between late autumn through early spring,middle and high latitudes onMars exhibit strong equator-to-polemean temperature contrasts (i.e., "baroclinicity"). Data collected during the Viking era and observations from both the Mars Global Surveyor (MGS) and Mars Reconnaissance Orbiter (MRO) indicate that such strong baroclinicity supports vigorous, large-scale eastward traveling weather systems (i.e., transient synoptic period waves) [1, 2]. For a rapidly rotating, differentially heated, shallow atmosphere such as on Earth and Mars, these large-scale, extratropical weather disturbances are critical components of the global circulation. The wave-like disturbances serve as agents in the transport of heat and momentum between low and high latitudes of the planet. Through cyclonic/anticyclonic winds, intense shear deformations, contractions-dilatations in temperature and density, and sharp perturbations amongst atmospheric tracers (i.e., dust, volatiles (e.g., water vapor) and condensates (e.g., water-ice cloud particles)), Mars' extratropical weather systems have significant sub-synoptic scale ramifications by supporting atmospheric frontal waves (Fig. 1).

  11. Variation of shear and compressional wave modulus upon saturation for pure pre-compacted sands

    NASA Astrophysics Data System (ADS)

    Bhuiyan, M. H.; Holt, R. M.

    2016-04-01

    Gassmann's fluid substitution theory is commonly used to predict seismic velocity change upon change in saturation, and is hence essential for 4D seismic and AVO studies. This paper addresses the basics assumptions of the Gassmann theory, in order to see how well they are fulfilled in controlled laboratory experiments. Our focus is to investigate the sensitivity of shear modulus to fluid saturation, and the predictability of Gassmann's fluid substitution theory for P-wave modulus. Ultrasonic P- and S-wave velocities in dry and saturated (3.5wt% NaCl) unconsolidated clean sands (Ottawa and Columbia) were measured in an oedometer test system (uniaxial strain conditions) over a range of 0.5 MPa to 10 MPa external vertical stress. This study shows shear modulus hardening upon brine saturation, which is consistent with previous data found in the literature. Analysis of the data shows that most of the hardening of the ultrasonic shear modulus may be explained by Biot dispersion. Isotropic Gassmann's fluid substitution is found to underestimate the P-wave modulus upon fluid saturation. However, adding the Biot dispersion effect improves the prediction. More work is required to obtain good measurements of parameters influencing dispersion, such as tortuosity, which is very ambiguous and challenging to measure accurately.

  12. Variation of shear and compressional wave modulus upon saturation for pure pre-compacted sands

    NASA Astrophysics Data System (ADS)

    Bhuiyan, M. H.; Holt, R. M.

    2016-07-01

    Gassmann's fluid substitution theory is commonly used to predict seismic velocity change upon change in saturation, and is hence essential for 4-D seismic and AVO studies. This paper addresses the basics assumptions of the Gassmann theory, in order to see how well they are fulfilled in controlled laboratory experiments. Our focus is to investigate the sensitivity of shear modulus to fluid saturation, and the predictability of Gassmann's fluid substitution theory for P-wave modulus. Ultrasonic P- and S-wave velocities in dry and saturated (3.5 wt per cent NaCl) unconsolidated clean sands (Ottawa and Columbia) were measured in an oedometer test system (uniaxial strain conditions) over a range of 0.5-10 MPa external vertical stress. This study shows shear modulus hardening upon brine saturation, which is consistent with previous data found in the literature. Analysis of the data shows that most of the hardening of the ultrasonic shear modulus may be explained by Biot dispersion. Isotropic Gassmann's fluid substitution is found to underestimate the P-wave modulus upon fluid saturation. However, adding the Biot dispersion effect improves the prediction. More work is required to obtain good measurements of parameters influencing dispersion, such as tortuosity, which is very ambiguous and challenging to measure accurately.

  13. Monthly variation of some parameters about internal solitary waves in the South China sea

    NASA Astrophysics Data System (ADS)

    Cai, Shuqun; Xie, Jieshuo; Xu, Jiexin; Wang, Dongxiao; Chen, Zhiwu; Deng, Xiaodong; Long, Xiaomin

    2014-02-01

    In this paper, by non-dimensional analysis, it is found that finite-depth theory is more appropriate to the study of internal solitary waves (ISWs) in the South China Sea (SCS) than shallow-water theory. The 1-degree grid data of monthly mean temperature and salinity data at standard levels in the SCS are used to solve the linearized vertical eigenvalue problem. The nonlinear parameter and the wave phase speed are computed, then the nonlinear phase speed and the characteristic half-width of ISWs are calculated respectively by two different theories to investigate the difference between these two parameters in the SCS. The nonlinearity is the strongest near the continental slope of the SCS or islands where the bottom topography changes sharply, it is stronger in summer than that in winter; it increases (decreases) as pycnocline depth deepens (shallows), stratification strengthens (weakens) and pycnocline thickness thins (thickens). The nonlinear wave phase speed and the characteristic half-width are the largest in deep sea area, they then reduce peripherally in shallower water. The nonlinear wave phase speed in the SCS changes slightly with time, but the characteristic half-width changes somewhat larger with time. In most of the SCS basin, the nonlinear wave phase speed derived from shallow-water theory is very close to that derived from finite-depth theory, but the characteristic half-width derived from shallow-water theory is about 0.2-0.6 times larger than that derived from finite-depth theory. The ISW induced horizontal current velocity derived from shallow-water theory is larger than that derived from finite-depth theory. Some observed and numerical modeled ISW characteristic half-widths are compared with those derived from shallow-water and finite-depth theories, respectively. It is shown that, the characteristic half-widths derived from finite-depth theory agree better with observational and numerical modeled results than those derived from shallow

  14. Variation in crossover frequency of EMIC waves in plasmasphere estimated from ion cyclotron whistler waves observed by Van Allen Probe A

    NASA Astrophysics Data System (ADS)

    Matsuda, Shoya; Kasahara, Yoshiya; Kletzing, Craig A.

    2016-01-01

    We report variations in the propagation of the H+ band ion cyclotron whistlers observed by Van Allen Probe A. Ion cyclotron whistlers are one of the EMIC (electromagnetic ion cyclotron) waves generated by mode conversion from lightning whistlers. Crossover frequency is an important frequency for the ion cyclotron whistlers, which is a function of the variations in the local heavy-ion composition. We surveyed waveform data obtained by the Electric and Magnetic Field Instrument and Integrated Science instrument and found that 3461 H+ band ion cyclotron whistlers were observed from 572 km to 5992 km in altitude. The main finding is that the crossover frequencies of the observed events decreased with increasing altitude. These results support the hypothesis that the total heavy-ion density decreases with increasing altitude. Furthermore, in 96% of all observed events, the crossover frequencies exceeded 0.5fH+, which suggests that the EMIC dispersion relation contains a frequency gap of around 0.5fH+.

  15. The Effects of Variations in Jet Width on the Growth of Baroclinic Waves: Implications for Midwinter Pacific Storm Track Variability.

    NASA Astrophysics Data System (ADS)

    Harnik, Nili; Chang, Edmund K. M.

    2004-01-01

    The effects of variations in jet width on the downstream growth of baroclinic waves are studied, using a simple quasigeostrophic model with a vertically varying basic state and variable channel width, as well as a simplified primitive equation model with a basic state that varies in latitude and height. This study is motivated by observations that in midwinter in the Pacific the storm track is weaker and the jet is narrower during years when the jet is strong.The linear models are able to reproduce the observed decrease of spatial growth rate with shear, if the narrowing of the jet is accounted for by assuming it decreases the meridional wavelength of the perturbations, which hampers their growth. A common suggestion has been that perturbations are weaker when the jet is strong because they move faster out of the unstable storm track region. The authors find that one needs to take into account that the jet narrows when it strengthens; otherwise, the increase of growth rate is strong enough to counteract the effect of increased advection speed.It is also found that, when the model basic state is Eady-like (small or zero meridional potential vorticity gradients in the troposphere), the short-wave cutoff for instability moves to large-scale waves as shear is increased, due to the accompanying increase in meridional wavenumber. This results in a transition from a regime where upper-level perturbations spin up a surface circulation very rapidly, and normal-mode growth ensues, to a regime where the initial perturbations take a very long time to excite growth. Since waves slow down when a surface perturbation develops, this can explain the observations that the storm track perturbations are more “upper level” during strong jet years and their group velocities increase faster than linearly with shear.

  16. NDSC millimeter wave ozone observations at Lauder, New Zealand, 1992-1998: Improved methodology, validation, and variation study

    NASA Astrophysics Data System (ADS)

    Tsou, J. J.; Connor, B. J.; Parrish, A.; Pierce, R. B.; Boyd, I. S.; Bodeker, G. E.; Chu, W. P.; Russell, J. M.; Swart, D. P. J.; McGee, T. J.

    2000-01-01

    A ground-based millimeter wave radiometer for the Network for the Detection of Stratospheric Change (NDSC) was installed at Lauder, New Zealand (45°S, 169.7°E) in November 1992. It has been monitoring the middle atmospheric ozone with nearly continuous operation since then. Owing to special complications in the observing conditions at this southern midlatitude site, three refinements to the data analysis and calibration techniques were proposed: (1) the use of a radiative model of local tropospheric climate adopted to the low surface elevation of the observing site, (2) the correction of observing angle measurements due to the settling of the foundation of the site, and (3) the improved method of radiometric temperature determination of calibration sources. All data from 1992 to 1998 were reprocessed with these modifications implemented. The retrieved ozone profiles are compared to sonde, two lidars, and satellite (Halogen Occultation Experiment (HALOE), Stratospheric Aerosol and Gas Experiment (SAGE II)) overpass measurements. The agreement is very good, with mean differences from 56 to 1 mbar of generally 2-3% for the comparisons with sonde, HALOE, and SAGE II, and generally <5% for the comparisons with lidars when large samples are considered. The root-mean-square scatter about the mean differences is mostly consistent with the expected (combined) precision. In comparisons with these correlative measurements, the millimeter wave ozone observations are found to have no seasonal bias, no comparison bias due to the a priori profiles used in millimeter wave data retrievals, and no observable instrument drift from 1992 to 1998. Better agreement is found in the comparison with sonde data if suspected vertical shifts in the sonde profiles are considered. The variations seen in the 6 year millimeter wave ozone data are shown to be mostly in line with photochemistry and dynamic transport processes in the mid austral latitudes. These processes, however, are apparently

  17. Effects of the planetary-scale waves on the temporal variations of the O2-1.27μm nightglow in the Venusian upper atmosphere

    NASA Astrophysics Data System (ADS)

    Hoshino, N.; Fujiwara, H.; Takagi, M.; Kasaba, Y.; Takahashi, Y.

    2009-12-01

    The O2-1.27 μm nightglow distribution, which has the peak intensity in the depression region of the day-to-night flow, gives us information of the wind field at about 95 km in Venus. The past nightglow observations [Crisp et al., 1996] showed that the intensity of the nightglow in the brightness region changed by 20 % in about one hour, and the brightness region disappeared in less than one day. The observation results obtained by Venus Express (VEX) also showed the temporal variations of the nightglow emission. Some simulation studies suggested contributions of gravity waves generated in the cloud deck (50-70 km) to the temporal variations. However, the causes of the temporal variations are still unknown. In recent years, the importance of planetary-scale waves for the dynamics of the Venusian atmosphere has been recognized. For example, Takagi and Matsuda [2006] suggested that the atmospheric superrotation was driven by the momentum transport due to the vertical propagation of the thermal tides generated in the Venus cloud deck. In order to estimate effects of the planetary-scale waves on the temporal variations of the nightglow, we have performed numerical simulations with a general circulation model (GCM), which includes the altitude region of 80 - about 200 km. The planetary-scale waves (thermal tides, Kelvin wave and Rosbby wave) are imposed at the lower boundary. The amplitudes and phase velocities of the waves are assumed from the study by Del Genio and Rossow [1990]. The nightglow intensity and its global distribution are calculated from the GCM results assuming the chemical equilibration. In this study, we investigate contributions of the planetary-scale waves on the temporal variations of the nightglow shown by past observations. In addition, we show the characteristics of the wave propagation and the interactions between the waves in the Venusian upper atmosphere. Venus Climate Orbiter (VCO), which will be launched in 2010 as the second Japanese

  18. In vivo oximetry of human bulbar conjunctival and episcleral microvasculature using snapshot multispectral imaging.

    PubMed

    MacKenzie, L E; Choudhary, T R; McNaught, A I; Harvey, A R

    2016-08-01

    Multispectral imaging (MSI) is a well-established technique for non-invasive oximetry of retinal blood vessels, which has contributed to the understanding of a variety of retinal conditions, including glaucoma, diabetes, vessel occlusion, and retinal auto-regulation. We report the first study to use snapshot multi-spectral imaging (SMSI) for oximetry of the bulbar conjunctival and episcleral microvasculature in the anterior segment of the eye. We report the oxygen dynamics of the bulbar conjunctival and episcleral microvasculature at normoxia and at acute mild hypoxia conditions. A retinal-fundus camera fitted with a custom Image-Replicating Imaging Spectrometer was used to image the bulbar conjunctival and episcleral microvasculature in ten healthy human subjects at normoxia (21% Fraction of Inspired Oxygen [FiO2]) and acute mild hypoxia (15% FiO2) conditions. Eyelid closure was used to control oxygen diffusion between ambient air and the sclera surface. Four subjects were imaged for 30 seconds immediately following eyelid opening. Vessel diameter and Optical Density Ratio (ODR: a direct proxy for oxygen saturation) of vessels was computed automatically. Oximetry capability was validated using a simple phantom that mimicked the scleral vasculature. Acute mild hypoxia resulted in a decrease in blood oxygen saturation (SO2) (i.e. an increase in ODR) when compared with normoxia in both bulbar conjunctival (p < 0.001) and episcleral vessels (p = 0.03). Average episcleral diameter increased from 78.9 ± 8.7 μm (mean ± standard deviation) at normoxia to 97.6 ± 14.3 μm at hypoxia (p = 0.02). Diameters of bulbar conjunctival vessels showed no significant change from 80.1 ± 7.6 μm at normoxia to 80.6 ± 7.0 μm at hypoxia (p = 0.89). When exposed to ambient air, hypoxic bulbar conjunctival vessels rapidly reoxygenated due to oxygen diffusion from ambient air. Reoxygenation occured in an exponential manner, and SO2 reached normoxia baseline levels. The average

  19. Mass variation of a thin liquid film driven by an acoustic wave

    NASA Astrophysics Data System (ADS)

    Batson, W.; Agnon, Y.; Oron, A.

    2015-06-01

    In this work, we investigate the dynamics of a thin liquid film subjected to an acoustic field in its bounding vapor space. For large acoustic wavelengths, the field imposes a spatially uniform, temporally periodic temperature and pressure at the vapor side of the film interface, which leads to a periodic driving force for mass exchange with the vapor. Neglecting the dynamics of the vapor space, we adopt the "one-sided" model for evaporation/condensation of thin liquid films. In the interest of determining the effect of oscillatory mass exchange on film stability, we consider films in thermodynamic equilibrium with the mean vapor conditions. The effects of oscillatory phase change on both linear stability and nonlinear dynamics are investigated for slightly inclined ceiling films that are destabilized by gravity and subject to thermocapillary effects. At linear order, this mass exchange is not found to alter the band of unstable wave numbers and only marginally affects the growth rates. Additionally, the mass exchanged during evaporation is balanced by condensation so that the total mass of the liquid film is conserved. However, due to nonlinear effects, we find that traveling waves encouraged by the inclination are subject to net mass loss. It is then found that normal thermocapillary effects enhance this loss, and that anomalous thermocapillarity mitigates or even reverses the loss to a mass gain.

  20. Variational properties and orbital stability of standing waves for NLS equation on a star graph

    NASA Astrophysics Data System (ADS)

    Adami, Riccardo; Cacciapuoti, Claudio; Finco, Domenico; Noja, Diego

    2014-11-01

    We study standing waves for a nonlinear Schrödinger equation on a star graph G, i.e. N halflines joined at a vertex. At the vertex an interaction occurs described by a boundary condition of delta type with strength α⩽0. The nonlinearity is of focusing power type. The dynamics is given by an equation of the form iddtΨt=HΨt-|2μΨt, where H is the Hamiltonian operator which generates the linear Schrödinger dynamics. We show the existence of several families of standing waves for every sign of the coupling at the vertex for every ω>α2N2. Furthermore, we determine the ground states, as minimizers of the action on the Nehari manifold, and order the various families. Finally, we show that the ground states are orbitally stable for every allowed ω if the nonlinearity is subcritical or critical, and for ω<ω* otherwise.

  1. Mass variation of a thin liquid film driven by an acoustic wave

    SciTech Connect

    Batson, W.; Agnon, Y.; Oron, A.

    2015-06-15

    In this work, we investigate the dynamics of a thin liquid film subjected to an acoustic field in its bounding vapor space. For large acoustic wavelengths, the field imposes a spatially uniform, temporally periodic temperature and pressure at the vapor side of the film interface, which leads to a periodic driving force for mass exchange with the vapor. Neglecting the dynamics of the vapor space, we adopt the “one-sided” model for evaporation/condensation of thin liquid films. In the interest of determining the effect of oscillatory mass exchange on film stability, we consider films in thermodynamic equilibrium with the mean vapor conditions. The effects of oscillatory phase change on both linear stability and nonlinear dynamics are investigated for slightly inclined ceiling films that are destabilized by gravity and subject to thermocapillary effects. At linear order, this mass exchange is not found to alter the band of unstable wave numbers and only marginally affects the growth rates. Additionally, the mass exchanged during evaporation is balanced by condensation so that the total mass of the liquid film is conserved. However, due to nonlinear effects, we find that traveling waves encouraged by the inclination are subject to net mass loss. It is then found that normal thermocapillary effects enhance this loss, and that anomalous thermocapillarity mitigates or even reverses the loss to a mass gain.

  2. Variation of coda wave attenuation in the Alborz region and central Iran

    NASA Astrophysics Data System (ADS)

    Rahimi, H.; Motaghi, K.; Mukhopadhyay, S.; Hamzehloo, H.

    2010-06-01

    More than 340 earthquakes recorded by the Institute of Geophysics, University of Tehran (IGUT) short period stations from 1996 to 2004 were analysed to estimate the S-coda attenuation in the Alborz region, the northern part of the Alpine-Himalayan orogen in western Asia, and in central Iran, which is the foreland of this orogen. The coda quality factor, Qc, was estimated using the single backscattering model in frequency bands of 1-25 Hz. In this research, lateral and depth variation of Qc in the Alborz region and central Iran are studied. It is observed that in the Alborz region there is absence of significant lateral variation in Qc. The average frequency relation for this region is Qc = 79 +/- 2f1.07+/-0.08. Two anomalous high-attenuation areas in central Iran are recognized around the stations LAS and RAZ. The average frequency relation for central Iran excluding the values of these two stations is Qc = 94 +/- 2f0.97+/-0.12. To investigate the attenuation variation with depth, Qc value was calculated for 14 lapse times (25, 30, 35,... 90s) for two data sets having epicentral distance range R < 100 km (data set 1) and 100 < R < 200 km (data set 2) in each area. It is observed that Qc increases with depth. However, the rate of increase of Qc with depth is not uniform in our study area. Beneath central Iran the rate of increase of Qc is greater at depths less than 100 km compared to that at larger depths indicating the existence of a high attenuation anomalous structure under the lithosphere of central Iran. In addition, below ~180 km, the Qc value does not vary much with depth under both study areas, indicating the presence of a transparent mantle under them.

  3. Fiber-optic voltage sensor with cladded fiber and evanescent wave variation detection

    DOEpatents

    Wood, Charles B.

    1992-01-01

    A fiber optic voltage sensor is described which includes a source of light, a reference fiber for receiving a known percentage of the light and an electrostrictive element having terminals across which is applied, a voltage to be measured. The electrostrictive element is responsive to the applied voltage to assume an altered physical state. A measuring fiber also receives a known percentage of light from the light source and is secured about the electrostrictive element. The measuring fiber is provided with a cladding and exhibits an evanescent wave in the cladding. The measuring fiber has a known length which is altered when the electrostrictive element assumes its altered physical state. A differential sensor is provided which senses the intensity of light in both the reference fiber and the measuring fiber and provides an output indicative of the difference between the intensities.

  4. Fiber-optic voltage sensor with cladded fiber and evanescent wave variation detection

    DOEpatents

    Wood, C.B.

    1992-12-15

    A fiber optic voltage sensor is described which includes a source of light, a reference fiber for receiving a known percentage of the light and an electrostrictive element having terminals across which is applied, a voltage to be measured. The electrostrictive element is responsive to the applied voltage to assume an altered physical state. A measuring fiber also receives a known percentage of light from the light source and is secured about the electrostrictive element. The measuring fiber is provided with a cladding and exhibits an evanescent wave in the cladding. The measuring fiber has a known length which is altered when the electrostrictive element assumes its altered physical state. A differential sensor is provided which senses the intensity of light in both the reference fiber and the measuring fiber and provides an output indicative of the difference between the intensities. 3 figs.

  5. Shear wave velocity variation across the Taupo Volcanic Zone, New Zealand, from receiver function inversion

    USGS Publications Warehouse

    Bannister, S.; Bryan, C.J.; Bibby, H.M.

    2004-01-01

    The Taupo Volcanic Zone (TVZ), New Zealand is a region characterized by very high magma eruption rates and extremely high heat flow, which is manifest in high-temperature geothermal waters. The shear wave velocity structure across the region is inferred using non-linear inversion of receiver functions, which were derived from teleseismic earthquake data. Results from the non-linear inversion, and from forward synthetic modelling, indicate low S velocities at ???6- 16 km depth near the Rotorua and Reporoa calderas. We infer these low-velocity layers to represent the presence of high-level bodies of partial melt associated with the volcanism. Receiver functions at other stations are complicated by reverberations associated with near-surface sedimentary layers. The receiver function data also indicate that the Moho lies between 25 and 30 km, deeper than the 15 ?? 2 km depth previously inferred for the crust-mantle boundary beneath the TVZ. ?? 2004 RAS.

  6. Accuracy and precision of MR blood oximetry based on the long paramagnetic cylinder approximation of large vessels.

    PubMed

    Langham, Michael C; Magland, Jeremy F; Epstein, Charles L; Floyd, Thomas F; Wehrli, Felix W

    2009-08-01

    An accurate noninvasive method to measure the hemoglobin oxygen saturation (%HbO(2)) of deep-lying vessels without catheterization would have many clinical applications. Quantitative MRI may be the only imaging modality that can address this difficult and important problem. MR susceptometry-based oximetry for measuring blood oxygen saturation in large vessels models the vessel as a long paramagnetic cylinder immersed in an external field. The intravascular magnetic susceptibility relative to surrounding muscle tissue is a function of oxygenated hemoglobin (HbO(2)) and can be quantified with a field-mapping pulse sequence. In this work, the method's accuracy and precision was investigated theoretically on the basis of an analytical expression for the arbitrarily oriented cylinder, as well as experimentally in phantoms and in vivo in the femoral artery and vein at 3T field strength. Errors resulting from vessel tilt, noncircularity of vessel cross-section, and induced magnetic field gradients were evaluated and methods for correction were designed and implemented. Hemoglobin saturation was measured at successive vessel segments, differing in geometry, such as eccentricity and vessel tilt, but constant blood oxygen saturation levels, as a means to evaluate measurement consistency. The average standard error and coefficient of variation of measurements in phantoms were <2% with tilt correction alone, in agreement with theory, suggesting that high accuracy and reproducibility can be achieved while ignoring noncircularity for tilt angles up to about 30 degrees . In vivo, repeated measurements of %HbO(2) in the femoral vessels yielded a coefficient of variation of less than 5%. In conclusion, the data suggest that %HbO(2) can be measured reproducibly in vivo in large vessels of the peripheral circulation on the basis of the paramagnetic cylinder approximation of the incremental field. PMID:19526517

  7. Systematic variation in anisotropy beneath the mantle wedge in the Java-Sumatra subduction system from shear-wave splitting

    NASA Astrophysics Data System (ADS)

    Hammond, J. O. S.; Wookey, J.; Kaneshima, S.; Inoue, H.; Yamashina, T.; Harjadi, P.

    2010-02-01

    The tectonic context of south-east Asia is dominated by subduction. One such major convergent boundary is the Java-Sunda trench, where the Australian-Indian plates are being subducted beneath the Eurasian plate. We measure shear-wave splitting in local and teleseismic data from 12 broadband stations across Sumatra and Java to study the anisotropic characteristics of this subduction system, which can provide important constraints on dynamical processes involved. Splitting in S-waves from local earthquakes between 75 and 300 km deep show roughly trench parallel fast directions, and with time-lags 0.1-1.3 s (92% ≤0.6 s). Splitting from deeper local events and SKS, however, shows larger time-lags (0.8-2.0 s) and significant variation in fast direction. In order to infer patterns of deformation in the slab we apply a hybrid modelling scheme. We raytrace through an isotropic subduction zone velocity model, obtaining event to station raypaths in the upper mantle. We then apply appropriately rotated olivine elastic constants to various parts of the subduction zone, and predict the shear-wave splitting accrued along the raypath. Finally, we perform grid searches for orientation of deformation, and attempt to minimise the misfit between predicted and observed shear-wave splitting. Splitting from the shallow local events is best explained by anisotropy confined to a 40 km over-riding plate with horizontal, trench parallel deformation. However, in order to explain the larger lag times from SKS and deeper events, we must consider an additional region of seismic anisotropy in or around the slab. The slab geometry in the model is constrained by seismicity and regional tomography models, and many SKS raypaths travel large distances within the slab. Models placing anisotropy in the slab produce smaller misfits than those with anisotropy outside for most stations. There is a strong indication that inferred flow directions are different for sub-Sumatran stations than for sub

  8. Variational solution of the three-dimensional Schrödinger equation using plane waves in adaptive coordinates.

    PubMed

    Pérez-Jordá, José M

    2011-11-28

    A series of improvements for the solution of the three-dimensional Schrödinger equation over a method introduced by Gygi [F. Gygi, Europhys. Lett. 19, 617 (1992); F. Gygi, Phys. Rev. B 48, 11692 (1993)] are presented. As in the original Gygi's method, the solution (orbital) is expressed by means of plane waves in adaptive coordinates u, where u is mapped from Cartesian coordinates, u=f(r). The improvements implemented are threefold. First, maps are introduced that allow the application of the method to atoms and molecules without the assistance of the supercell approximation. Second, the electron-nucleus singularities are exactly removed, so that pseudo-potentials are no longer required. Third, the sampling error during integral evaluation is made negligible, which results in a true variational, second-order energy error procedure. The method is tested on the hydrogen atom (ground and excited states) and the H(2)(+) molecule, resulting in milli-Hartree accuracy with a moderate number of plane waves. PMID:22128925

  9. Mixed augmented variational formulation (MAVF) for lower hybrid full-wave calculations

    NASA Astrophysics Data System (ADS)

    Peysson, Y.; Roche, J. R.; Bertrand, P.; Chatenet, J.-H.; Kirsch, C.; Mokrani, A.; Labrunie, S.

    2009-11-01

    In the continuation of the works led in cylindrical geometry [2], a full toroidal description for an arbitrary poloidal cross-section of the plasma has been developed. For simulation purpose a mixed augmented variational formulation (MAVF), which is particularly well suited for solving Maxwell equations, is considered [4]. The discretization of the MAVF is carried out using Taylor-Hood P2-iso-P1 finite elements. This formulation provide a natural implementation for parallel processing, a particularly important aspect when simulations for plasmas of large size must be considered. Details on the specific application of the MAVF to the LH problem are presented, as well as the structure of the corresponding matrices. A first application to a realistic small tokamak configuration is considered.

  10. Interannual variation of the quasi-two-day wave at 22.7 S

    NASA Astrophysics Data System (ADS)

    Lima, Lourivaldo; Jacobi, Christoph; Batista, Paulo; Rodrigues de Araujo, Luciana; Rodrigues, Chayenny E. S.; Lilienthal, Friederike

    2016-07-01

    In the present investigation, the mesosphere/lower thermosphere winds at Cachoeira Paulista (22.7° S, 45.0° W) obtained by a VHF all sky interferometric meteor radar have been used to investigate the interannual variability of the quasi-two-day wave (QTDW) amplitudes at a low latitude in the Southern Hemisphere. The wind data were obtained from December 1999 to July 2006, from September 2007 to October 2008 and from December 2013 to April 2015. The analysis shows that meridional amplitudes for QTDW are larger than zonal amplitudes and the strongest amplitudes occur after austral summer solstice in January-February. Besides semiannual and annual oscillations, the QTDW amplitudes in the meridional winds also show weak quasi-biennial oscillation (QBO). The summer QTDW in the meridional winds also shows a possible correlation with solar activity. The amplitudes are nearly in phase with the 11 year solar cycle, and the solar maxima leads the QTDW maxima by one year. Finally, larger QTDW amplifications have been observed during 2003, 2004, 2006 and 2015 summers. The unusual major sudden stratospheric warming (SSW) event suggests a coupling between QTDW amplification and SSW during Jan-Feb 2006. The mechanistic global circulation model MUAM of the middle and upper atmosphere has been used to simulate the dynamic configuration during January major and minor SSW events.

  11. Toward efficient light diffraction and intensity variations by using wide bandwidth surface acoustic wave

    NASA Astrophysics Data System (ADS)

    Lee, Young Ok; Chen, Fu; Lee, Kee Keun

    2016-06-01

    We have developed acoustic-optic (AO) based display units for implementing a handheld hologram display by modulating light deflection through wide bandwidth surface acoustic wave (SAW). The developed AO device consists of a metal layer, a ZnS waveguide layer, SAW inter digital transducers (IDTs), and a screen for display. When RF power with a particular resonant frequency was applied to IDTs, SAW was radiated and interfered with confined beam propagating along ZnS waveguide layer. The AO interacted beam was deflected laterally toward a certain direction depending on Bragg diffraction condition, exited out of the waveguide layer and then directed to the viewing screen placed at a certain distance from the device to form a single pixel. The deflected angles was adjusted by modulating the center frequency of the SAW IDT (SAW grating), the RF power of SAW, and the angles between propagating light beam path along waveguide and radiating SAW. The diffraction efficiency was also characterized in terms of waveguide thickness, SAW RF input power, and aperture length. Coupling of mode (COM) modeling was fulfilled to find optimal device parameters prior to fabrication. All the parameters affecting the deflection angle and efficiency to form a pixel for a three-dimensional (3D) hologram image were characterized and then discussed.

  12. Influence of resonant transducer variations on long range guided wave monitoring of rail track

    NASA Astrophysics Data System (ADS)

    Loveday, Philip W.; Long, Craig S.

    2016-02-01

    The ability of certain guided wave modes to propagate long distances in continuously welded rail track is exploited in permanently installed monitoring systems. Previous work demonstrated that reflections from thermite welds could be measured at distances of the order of 1 km from a transducer array. The availability of numerous thermite welds is useful during the development of a monitoring system as real defects are not available. Measurements of reflections from welds were performed over an eleven month period with two permanently installed transducers. Phased array processing was performed and the true location of a weld is indicated by a strong reflection but there is generally also a smaller, spurious replica reflection, at the same distance but in the incorrect direction. In addition, the relative reflection from different welds appears to change over time. The influence of differences between the two resonant transducers was investigated using a model. It was found that estimating the attenuation in either direction and scaling the reflections in either direction decreased the variability in the reflection measurements. Transducer interaction effects, where the transducer closer to the weld records a greater reflection than the second transducer were observed and can be used to determine the direction of a weld. This feature was used to demonstrate a simple alternative to phased array processing that can be used with resonant transducers.

  13. A comprehensive survey of atmospheric quasi 3 day planetary-scale waves and their impacts on the day-to-day variations of the equatorial ionosphere

    NASA Astrophysics Data System (ADS)

    Liu, Guiping; England, Scott L.; Immel, Thomas J.; Frey, Harald U.; Mannucci, Anthony J.; Mitchell, Nicholas J.

    2015-04-01

    This study reports a comprehensive survey of quasi 3 day (2.5-4.5 day period) planetary-scale waves in the low-latitude mesosphere and lower thermosphere using the temperature observations from Thermosphere Ionosphere and Mesosphere Electric Dynamics/Sounding of the Atmosphere using Broadband Emission Radiometry throughout 2002-2012. Occurrences and properties of the waves, including the eastward propagating zonal wave numbers of 1-3 (E1-E3) and vertical wavelengths, are determined for each case. The impacts of these waves on the equatorial ionosphere are investigated by searching for the corresponding variations with the same periods and wave numbers in total electron content (TEC) from the concurrent observations of the ground-based GPS network. For a threshold amplitude of 4 K in temperature, a total of 300 waves are identified, of which there are 186 E1, 63 E2, and 51 E3 events. The mean amplitudes and vertical wavelengths of these waves are calculated to be about 7.9 K and 34 km for the E1, 5.7 K and 29 km for the E2, and 5.1 K and 27 km for the E3, having the standard deviations of 1.5 K and 6.5 km, 0.6 K and 5.6 km, and 0.5 K and 6.7 km. Occurrences of the E1 cases are not observed to depend on season, but the large-amplitude (>8 K) cases occur more often during solstices than at equinoxes. Similarly, the E2 and E3 cases are observed to occur most often in January-February and May-August. Among these waves, 199 cases (66%) are found to have the corresponding variations in the equatorial ionosphere with amplitudes ≥4.2% relative to the mean TEC values (corresponding to 90th percentile). Most of these waves have long vertical wavelengths and large amplitudes (˜3 times more than short vertical wavelength and small-amplitude waves). Because no seasonal or solar cycle dependence on the frequency at which these waves have corresponding variations in the ionosphere at this TEC perturbation threshold is observed, we conclude that there is no seasonal and solar

  14. Nadir sensitivity of passive millimeter and submillimeter wave channels to clear air temperature and water vapor variations

    NASA Astrophysics Data System (ADS)

    Klein, Marian; Gasiewski, Albin J.

    2000-07-01

    The upwelling microwave-to-submillimeter wave brightness temperature observed from above the Earth's atmosphere is sensitive to parameters such as pressure, temperature, water vapor, and hydrometeor content, and this sensitivity has been successfully used for passive vertical sounding of temperature and water vapor profiles. To determine optimal satellite observation strategies for future passive microwave instruments operating at frequencies above those now used, a study of the potential clear-air vertical sounding capabilities of all significant microwave oxygen and water vapor absorption lines in the frequency range from approximately 10 to 1000 GHz has been performed. The study is based on a second-order statistical climatological model covering four seasons, three latitudinal zones, and altitudes up to ˜70 km. The climatological model was developed by comparing data from three sources: the Upper Atmosphere Research Satellite Halogen Occultation Experiment (UARS HALOE) instrument, the TIROS Operational Vertical Sounder (TOVS) Initial Guess Retrieval radiosonde set, and the NOAA advanced microwave sounder unit (AMSU) radiosonde set. The Liebe MPM87 absorption model is used for water vapor and oxygen absorption and considers the effects of ozone and isotope absorption. Variations in the vertical sounding capabilities due to statistical variations of water vapor and temperature with latitude and season around each line are considered, and useful channel sets for geostationary microwave vertical sounding are suggested.

  15. Local time variation of high-frequency gravity wave momentum flux and its relationship with background wind derived from LIDAR measurements

    NASA Astrophysics Data System (ADS)

    Agner, R. M.; Liu, A. Z.

    2013-12-01

    Gravity waves and atmospheric tides have strong interactions in the mesopause region and is a major contributor to the large variabilities in this region. How these two large perturbations interact with each other is not well understood. Observational studies of their relationships are needed to help clarify some contradictory results from modeling studies. Due to large differences in temporal and spatial scales between gravity waves and tides, they are not easily observed simultaneously and consistently with extended periods of time. In this work, we use four-hundred hours of Na LIDAR observation at Starfire Optical Range (SOR, 35.0 N, 106.5 W), New Mexico to derive the local time variation of gravity wave momentum flux and corresponding background wind. Their relationship is then examined in detail. The effects of gravity waves on the background wind at the tidal time scale are deduced. These results are explained through gravity wave propagation in a varying background atmosphere.

  16. Spatiotemporal current variation of coastal-trapped waves west of the Noto Peninsula measured by using fishing boats

    NASA Astrophysics Data System (ADS)

    Fukudome, Ken-ichi; Igeta, Yosuke; Senjyu, Tomoharu; Okei, Noriyuki; Watanabe, Tatsuro

    2016-03-01

    Spatiotemporal current variations of coastal-trapped waves (CTWs) were investigated by using a current dataset obtained from daily fishing operations west of the Noto Peninsula (NTP), Japan. Cross-shore lines located in southern, middle, and northern parts of the west coast of the NTP were designed to detect characteristics of CTWs with a time interval of a few days and about 5-km resolution in the cross-shore direction. Accuracy validation by using moored current meter data and sea level data demonstrated that the established dataset expresses accurate variations with periods of several days. The generation and propagation of a CTW event associated with a low-pressure zone passing north of the study area in late May 2010 were analyzed. Along-shore currents with the coast on the right strengthened in every line simultaneously with the domination of the southerly wind, and then weakened in order from south to north simultaneously with weakening of the southerly wind. Although the along-shore currents of the CTWs linearly decreased heading offshore along the south and middle lines, these currents broadened within about 50 km from the coast along the north line, with small variations in the cross-shelf direction, with an increase in shelf width. These generation, propagation and current structure characteristics are clarified and interpreted by the characteristics of the estimated possible CTWs west of the NTP and numerical experiments, which reproduce wind-induced freely propagating CTWs. A change in the propagation characteristics and the structure of the CTWs associated with bottom topography indicates the possibility that adjustments can occur on the order of a few dozen kilometers.

  17. Pediatric obstructive sleep apnea assessment using pulse oximetry and dual RIP bands.

    PubMed

    Mason, David G; Iyer, Kartik; Terrill, Philip I; Wilson, Stephen J; Suresh, Sadasivam

    2010-01-01

    The diagnosis of Obstructive Sleep Apnea (OSA) in children presents a challenging diagnostic problem given the high prevalence (2-3%), the resource intensity of the overnight polysomnography investigation, and the realisation that OSA poses a serious threat to the healthy growth and development of children. Previous attempts to develop OSA diagnostic systems using home pulse oximetry studies have failed to meet the accuracy requirements - particularly the low false normal rate (FNR) - required for a pre-PSG screening test. Thus the aim of this study is to investigate the feasibility of an OSA severity diagnostic system based on both oximetry and dual respiratory inductance plethysmography (RIP) bands. A total of 90 PSG studies (30 each of normal, mild/moderate and severe OSA) were retrospectively analyzed. Quantifications of oxygen desaturations (S), respiratory events (E) and heart rate arousals (A) were calculated and extracted and an empirical rule-based SEA classifier model for normal, mild/moderate and severe OSA defined and developed. In addition, an automated classifier using a decision tree algorithm was trained and tested using a 10-fold cross-validation. The empirical classification system showed a correct classification rate (CCR) of 0.83 (Cohen's Kappa κ=0.81, FNR=0.08), and the decision tree classifier achieved a CCR of 0.79 (κ=0.73, FNR=0.08) when compared to gold standard PSG assessment. The relatively high CCR, and low FNR indicate that a OSA severity system based on dual RIP and oximetry is feasible for application as a pre-PSG screening tool. PMID:21097147

  18. Nanofiber-based paramagnetic probes for rapid, real-time biomedical oximetry.

    PubMed

    Bhallamudi, Vidya P; Xue, Ruipeng; Purser, Carola M; Presley, Kayla F; Banasavadi-Siddegowda, Yeshavanth K; Hwang, Jinwoo; Kaur, Balveen; Hammel, P Chris; Poirier, Michael G; Lannutti, John J; Pandian, Ramasamy P

    2016-04-01

    EPR (electron paramagnetic resonance) based biological oximetry is a powerful tool that accurately and repeatedly measures tissue oxygen levels. In vivo determination of oxygen in tissues is crucial for the diagnosis and treatment of a number of diseases. Here, we report the first successful fabrication and remarkable properties of nanofiber sensors for EPR-oximetry applications. Lithium octa-n-butoxynaphthalocyanine (LiNc- BuO), an excellent paramagnetic oxygen sensor, was successfully encapsulated in 300-500 nm diameter fibers consisting of a core of polydimethylsiloxane (PDMS) and a shell of polycaprolactone (PCL) by electrospinning. This core-shell nanosensor (LiNc-BuO-PDMS-PCL) shows a linear dependence of linewidth versus oxygen partial pressure (pO2). The nanofiber sensors have response and recovery times of 0.35 s and 0.55 s, respectively, these response and recovery times are ~12 times and ~218 times faster than those previously reported for PDMS-LiNc-BuO chip sensors. This greater responsiveness is likely due to the high porosity and excellent oxygen permeability of the nanofibers. Electrospinning of the structurally flexible PDMS enabled the fabrication of fibers having tailored spin densities. Core-shell encapsulation ensures the non-exposure of embedded LiNc-BuO and mitigates potential biocompatibility concerns. In vitro evaluation of the fiber performed under exposure to cultured cells showed that it is both stable and biocompatible. The unique combination of biocompatibility due to the PCL 'shell,' the excellent oxygen transparency of the PDMS core, and the excellent oxygen-sensing properties of LiNc-BuO makes LiNc-BuO-PDMS-PCL platform promising for long-term oximetry and repetitive oxygen measurements in both biological systems and clinical applications. PMID:27106026

  19. Acute Variations in Retinal Vascular Oxygen Content in a Rabbit Model of Retinal Venous Occlusion

    PubMed Central

    Saati, Saloomeh; Martin, Gabriel; Chader, Gerald; Humayun, Mark S.

    2012-01-01

    Purpose To study the variation in intravascular oxygen saturation (oximetry) during an acute retinal vein occlusion (RVO) using hyperspectral computed tomographic spectroscopy based oximetry measurements. Methods Thirty rabbits were dilated and anesthetized for experiments. Baseline oximetry measurements were made using a custom-made hyperspectral computed tomographic imaging spectrometer coupled to a fundus camera. RVO were induced using argon green laser following an intravenous injection of Rose Bengal. RVO induction was confirmed by fluorescein angiography. Retinal oximetry measurements were repeated in arterial and venous branches one hour after RVO induction and up to 4 weeks afterwards. Comparison of retinal oximetry before and after vein occlusion was made using the Student T-test. Results One hour after RVO induction, we observed statistically significant reductions in the intravascular oxygen saturation in temporal retinal arteries (85.1±6.1% vs. 80.6±6.6%; p<0.0001) and veins (71.4±5.5% vs. 64.0±4.7%; p<0.0001). This decrease was reversible in animals that spontaneously recannulated the vein occlusion. There were no statistically significant differences in oxygen saturation in the nasal control arteries and veins before and after temporal vein RVO induction. Conclusions We demonstrate, for the first time, acute changes in the intravascular oxygen content of retinal vessels 1 hour after RVO. These changes are reversible upon spontaneous recannulation of retinal vessels. This study demonstrates that hyperspectral computer tomographic spectroscopy based oximetry can detect physiological variations in intravascular retinal oxygen saturation. The study also provides the first qualitative and quantitative evidence of the variation in retinal vascular oxygen content directly attributable to an acute retinal vein occlusion. PMID:23185567

  20. A New Global Model for 3-D variations in P Wave Speed in Earth's Mantle

    NASA Astrophysics Data System (ADS)

    Karason, H.; van der Hilst, R. D.; Li, C.

    2003-12-01

    In an effort to improve the resolution of mantle structure we have combined complementary data sets of short- and long period (absolute and differential) travel time residuals. Our new model is based on short period P (N\\~7.7x10**6), pP (N\\~2.3x10**5), and PKP (N\\~16x10**4) data from the catalog by Engdahl et al (BSSA, 1998), short-period PKP differential times (N\\~1600) measured by McSweeney & Creager, and long-period differential PP-P times - N\\~20,000 measured by Bolton & Masters and N\\~18,000 by Ritsema - and Pdiff-PKP (N\\~560) measured by Wysession. Inversion tests, spectral analysis, and comparison with geology indicate that the large-scale upper mantle structure is better constrained with the addition of PP-P, whereas the Pdiff and PKP data help constrain deep mantle structure (Karason & Van der Hilst, JGR, 2001). The long period data were measured by cross-correlation. We solved the system of equations using 400 iterations of the iterative algorithm LSQR For the short period (1 Hz) data we use a high frequency approximation and trace rays through a fine grid of constant slowness cells to invert for mantle structure. For low frequency Pdiff and PP data we account for sensitivity to structure away from the optical ray path with 3-D Frechet derivatives (sensitivity kernels) estimated from single forward scattering and projected onto basis functions (constant slowness blocks) used for model parameterization. With such kernels the low frequency data can constrain long wavelength heterogeneity without keeping the short period data from mapping details in densely sampled regions. In addition to finite frequency sensitivity kernels we optimized the localization by using a parameterization that adapts to spatial resolution, with small cells in regions of dense sampling and larger cells in regions where sampling is more sparse (the total number of cells was \\~ 350,000). Finally, we corrected all travel times and surface reflections for lateral variations in

  1. Features of amplitude and Doppler frequency variation of ELF/VLF waves generated by "beat-wave" HF heating at high latitudes

    NASA Astrophysics Data System (ADS)

    Tereshchenko, E. D.; Shumilov, O. I.; Kasatkina, E. A.; Gomonov, A. D.

    2014-07-01

    Observations of extremely low frequency (ELF, 3-3000 Hz) radio waves generated by a "beat-wave" (BW) high frequency (~ 4.04-4.9 MHz) ionospheric heating are presented. ELF waves were registered with the ELF receiver located at Lovozero (68°N, 35°E), 660 km east from the European Incoherent Scatter Tromso heating facility (69.6°N, 19.2°E). Frequency shifts between the generated beat-wave and received ELF waves were detected in all sessions. It is shown that the amplitudes of ELF waves depend on the auroral electrojet current strength. Our results showing a strong dependence of ELF signal intensities on the substorm development seem to support the conclusion that electrojet currents may affect the BW generation of ELF/VLF waves.

  2. Effects of the gravitational waves emission on the orbit of the binary neutron stars considering the mass variation.

    NASA Astrophysics Data System (ADS)

    Mabrouk, Zeinab; Rahoma, W. A.

    2016-07-01

    Gravitational waves which have been announced finally to be detected in February 11, 2016 are believed to be emitted from many sources and phenomena in the universe, the binary neutron stars systems specially the inspirals are one kind of them. In this paper we are going to calculate the effects of this emission on the elements of the elliptical orbits of such binary neutron stars before the onset of the mass exchange. We based our work on the Imshennik and Popov (1994) paper then we do some modifications. The main and important results that Imshennik and Popov get were the rate of change of the eccentricity e, the rate of change of the semi major axis a, and the monotonic dependence between them a=a(e). Finally they concluded the smallness of the final eccentricity which make the orbits to be near-circular due to the emission of the gravitational waves. Our modification is to consider the masses of the two binary stars to be varied using the famous Eddington-Jeams law, then we expand them around the time t using Taylor expansion. we do this variation first for one mass with the constancy of the second one, then we let both mosses to vary together. We start the algorithm from the beginning substituting with our new series of masses in the two main equations, the average rate of change of the total energy of the system (dE/dt) , and the average rate of change of the angular momentum (dJ/dt). This modification leads to new expressions of the previous mentioned rate of changes of the orbital elements obtained by Imshennik and Popov, some of them we obtained and still working in the rest.

  3. Seismicity, Vp/Vs and shear wave anisotropy variations during the 2011 unrest at Santorini caldera, southern Aegean

    NASA Astrophysics Data System (ADS)

    Konstantinou, K. I.; Evangelidis, C. P.; Liang, W.-T.; Melis, N. S.; Kalogeras, I.

    2013-11-01

    The Santorini caldera has been the focus of several large explosive eruptions in the past, the last of which occurred in the early 1950s. The volcano was dormant until early 2011 when increasing number of earthquakes accompanied significant intra-caldera uplift. This seismic activity was recorded by 8 temporary as well as 19 permanent seismic stations that were installed on Santorini and nearby islands after the onset of the unrest. Using data from January 2011 until June 2012 we calculated accurate relative locations for 490 events utilizing both catalog and waveform cross-correlation differential travel times of P- and S-phases. The distribution of relocated events exhibits a large cluster between Thera and Nea Kameni islands along the caldera rim, suggesting the activation of a preexisting ring fault. All hypocenters are located between 5 and 11 km resulting in a sharp cutoff of seismicity above and below these depths. We also used P and S travel times in order to calculate average Vp/Vs ratios and estimated shear wave splitting parameters (fast direction φ, delay time δt) for events within the shear wave window. The Vp/Vs ratios at several stations exhibit a majority of values consistently below the regional one (~ 1.77). Their temporal variations can be explained as periods of gas influx and depletion in the upper crust beneath the caldera. A comparison of δt for a number of earthquake doublets shows a progressive decrease of delay times towards the end of the unrest probably as a result of cracks closing owing to stress relaxation. The seismological observations presented here are compatible with petrological models that suggest the existence of a deep (11-14 km) dacitic magma reservoir and a shallower (< 5 km) rhyolitic magma chamber.

  4. Development and initial testing of a pulse oximetry prototype for measuring dental pulp vitality

    NASA Astrophysics Data System (ADS)

    Cerqueira, M.; Ferreira, M.; Caramelo, F.

    2015-05-01

    The guiding principle of endodontic treatment is to preserve teeth while maintaining its aesthetic and functional roles. To accomplish this goal the assessment of teeth pulp vitality is very important since it will determine the procedures that should be adopted and define the therapy strategy. Currently, the most commonly tests for determining dental pulp state are the thermal and the electrical tests, which are based on nerve response and, because of that, have a relatively high rate of false positives and false negatives cases. In this work we present a simple test to be used in the clinical setting for evaluating noninvasively the existence of blood perfusion in dental pulp. This test is based on pulse oximetry principle that was devised to indirectly measure the amount of oxygen in blood. Although pulse oximetry has already demonstrated its usefulness in clinical environment its usage for the determination of dental pulp vitality has been frustrated by several factors, notably the absence of a suitable sensor to the complex shape of the various coronary teeth. We developed a suitable sensor and present the first trials with promising results, regarding the ability for distinguish teeth with and without blood perfusion.

  5. Skeletal Muscle Oxygenation Measured by EPR Oximetry Using a Highly Sensitive Polymer-Encapsulated Paramagnetic Sensor.

    PubMed

    Hou, H; Khan, N; Nagane, M; Gohain, S; Chen, E Y; Jarvis, L A; Schaner, P E; Williams, B B; Flood, A B; Swartz, H M; Kuppusamy, P

    2016-01-01

    We have incorporated LiNc-BuO, an oxygen-sensing paramagnetic material, in polydimethylsiloxane (PDMS), which is an oxygen-permeable, biocompatible, and stable polymer. We fabricated implantable and retrievable oxygen-sensing chips (40 % LiNc-BuO in PDMS) using a 20-G Teflon tubing to mold the chips into variable shapes and sizes for in vivo studies in rats. In vitro EPR measurements were used to test the chip's oxygen response. Oxygen induced linear and reproducible line broadening with increasing partial pressure (pO2). The oxygen response was similar to that of bare (unencapsulated) crystals and did not change significantly on sterilization by autoclaving. The chips were implanted in rat femoris muscle and EPR oximetry was performed repeatedly (weekly) for 12 weeks post-implantation. The measurements showed good reliability and reproducibility over the period of testing. These results demonstrated that the new formulation of OxyChip with 40 % LiNc-BuO will enable the applicability of EPR oximetry for long-term measurement of oxygen concentration in tissues and has the potential for clinical applications. PMID:27526163

  6. A paramagnetic implant containing lithium naphthalocyanine microcrystals for high-resolution biological oximetry

    NASA Astrophysics Data System (ADS)

    Meenakshisundaram, Guruguhan; Pandian, Ramasamy P.; Eteshola, Edward; Lee, Stephen C.; Kuppusamy, Periannan

    2010-03-01

    Lithium naphthalocyanine (LiNc) is a microcrystalline EPR oximetry probe with high sensitivity to oxygen [R.P. Pandian, M. Dolgos, C. Marginean, P.M. Woodward, P.C. Hammel, P.T. Manoharan, P. Kuppusamy, Molecular packing and magnetic properties of lithium naphthalocyanine crystal: hollow channels enabling permeability and paramagnetic sensitivity to molecular oxygen J. Mater. Chem. 19 (2009) 4138-4147]. However, direct implantation of the crystals in the tissue for in vivo oxygen measurements may be hindered by concerns associated with their direct contact with the tissue/cells and loss of EPR signal due to particle migration in the tissue. In order to address these concerns, we have developed encapsulations (chips) of LiNc microcrystals in polydimethyl siloxane (PDMS), an oxygen-permeable, bioinert polymer. Oximetry evaluation of the fabricated chips revealed that the oxygen sensitivity of the crystals was unaffected by encapsulation in PDMS. Chips were stable against sterilization procedures or treatment with common biological oxidoreductants. In vivo oxygen measurements established the ability of the chips to provide reliable and repeated measurements of tissue oxygenation. This study establishes PDMS-encapsulated LiNc as a potential probe for long-term and repeated measurements of tissue oxygenation.

  7. Diagnostic accuracy of a mathematical model to predict apnea–hypopnea index using nighttime pulse oximetry

    NASA Astrophysics Data System (ADS)

    Ebben, Matthew R.; Krieger, Ana C.

    2016-03-01

    The intent of this study is to develop a predictive model to convert an oxygen desaturation index (ODI) to an apnea-hypopnea index (AHI). This model will then be compared to actual AHI to determine its precision. One thousand four hundred and sixty-seven subjects given polysomnograms with concurrent pulse oximetry between April 14, 2010, and February 7, 2012, were divided into model development (n=733) and verification groups (n=734) in order to develop a predictive model of AHI using ODI. Quadratic regression was used for model development. The coefficient of determination (r2) between the actual AHI and the predicted AHI (PredAHI) was 0.80 (r=0.90), which was significant at a p<0.001. The areas under the receiver operating characteristic curve ranged from 0.96 for AHI thresholds of ≥10 and ≥15/h to 0.97 for thresholds of ≥5 and ≥30/h. The algorithm described in this paper provides a convenient and accurate way to convert ODI to a predicted AHI. This tool makes it easier for clinicians to understand oximetry data in the context of traditional measures of sleep apnea.

  8. Regularity analysis of nocturnal oximetry recordings to assist in the diagnosis of sleep apnoea syndrome.

    PubMed

    Marcos, J Víctor; Hornero, Roberto; Nabney, Ian T; Álvarez, Daniel; Gutiérrez-Tobal, Gonzalo C; del Campo, Félix

    2016-03-01

    The relationship between sleep apnoea-hypopnoea syndrome (SAHS) severity and the regularity of nocturnal oxygen saturation (SaO2) recordings was analysed. Three different methods were proposed to quantify regularity: approximate entropy (AEn), sample entropy (SEn) and kernel entropy (KEn). A total of 240 subjects suspected of suffering from SAHS took part in the study. They were randomly divided into a training set (96 subjects) and a test set (144 subjects) for the adjustment and assessment of the proposed methods, respectively. According to the measurements provided by AEn, SEn and KEn, higher irregularity of oximetry signals is associated with SAHS-positive patients. Receiver operating characteristic (ROC) and Pearson correlation analyses showed that KEn was the most reliable predictor of SAHS. It provided an area under the ROC curve of 0.91 in two-class classification of subjects as SAHS-negative or SAHS-positive. Moreover, KEn measurements from oximetry data exhibited a linear dependence on the apnoea-hypopnoea index, as shown by a correlation coefficient of 0.87. Therefore, these measurements could be used for the development of simplified diagnostic techniques in order to reduce the demand for polysomnographies. Furthermore, KEn represents a convincing alternative to AEn and SEn for the diagnostic analysis of noisy biomedical signals. PMID:26719242

  9. Inaccurate pulse CO-oximetry of carboxyhemoglobin due to digital clubbing: case report.

    PubMed

    Harlan, Nicole; Weaver, Lindell K; Deru, Kayla

    2016-01-01

    Newer pulse CO-oximeters provide a non-invasive and quick means of measuring oxyhemoglobin, carboxyhemoglobin and methemoglobin. Clubbing has been reported to cause inaccuracy in pulse oximeters. We present a case of inaccurate carboxy-hemoglobin measurement by pulse CO-oximetry due to digital clubbing. An 18-year-old man with a history of cystic fibrosis presented after a suicide attempt by inhalation of exhaust. At the initial emergency department evaluation, his blood carboxyhemoglobin was 33%. He was intubated, placed on 100% oxygen and transferred to our facility. Upon arrival, we placed three different pulse CO-oximeters on different fingers and toes. Carboxyhemoglobin levels measured by these meters ranged from 9%-11%. A venous blood gas drawn on arrival showed a carboxyhemoglobin level of 2.3% after four hours on 100% oxygen by endotracheal tube. Thirty minutes later, we checked arterial blood gas, which revealed a COHb level of 0.9%. Again, non-invasive carboxyhemoglobin measurements read 10%. The patient was treated with hyperbaric oxygen for carbon monoxide poisoning. This case suggests that non-invasive measurements of carboxyhemoglobin should be correlated with the clinic history and with an arterial or venous blood gas oximetry analysis. PMID:27000014

  10. Introduction of a new patient monitoring system during dental procedures: pulse oximetry.

    PubMed

    Luotio, K; Mattila, M A; Kotilainen, R M

    1993-01-01

    This paper describes three cases of early detection of hypoxia with pulse oximeter during intravenous sedation. In the main study group over 40 patients were monitored by pulse oximetry during large dental operation under iv-sedation. Diatsepam with soybean oily solvent and midatsolam were used as intravenous sedative agents in this study. The first signs of hypoxia were seen by pulse oximetry. In three healthy patients some periods of remarkable hypoxia was detected and those cases are reported in this paper. Two of the patients were treated by a surgical operation and one patient underwent large conservative dental treatment under sedation because of dental care fobia. During the dental treatment period external oxygen was added for all these three patients to avoid more complications as a result of hypoxia. Two of the patients received an injection of bentsodiatsepine antagonist, too. One patient needed further follow up but non of these patients developed any additional complications. As a conclusion pulse oximetric monitoring was found to be extremely sensitive as a predictor for coming complications as well as allowing early intervention in ventilation problems. PMID:8935103

  11. Variational solution of the Schrödinger equation using plane waves in adaptive coordinates: The radial case.

    PubMed

    Pérez-Jordá, José M

    2010-01-14

    A new method for solving the Schrödinger equation is proposed, based on the following details. First, a map u=u(r) from Cartesian coordinates r to a new coordinate system u is chosen. Second, the solution (orbital) psi(r) is written in terms of a function U depending on u so that psi(r)=/J(u)/(-1/2)U(u), where /J(u)/ is the Jacobian determinant of the map. Third, U is expressed as a linear combination of plane waves in the u coordinate, U(u)= sum (k)c(k)e(ik x u). Finally, the coefficients c(k) are variationally optimized to obtain the best energy, using a generalization of an algorithm originally developed for the Coulomb potential [J. M. Perez-Jorda, Phys. Rev. B 58, 1230 (1998)]. The method is tested for the radial Schrödinger equation in the hydrogen atom, resulting in micro-Hartree accuracy or better for the energy of ns and np orbitals (with n up to 5) using expansions of moderate length. PMID:20095666

  12. Interdecadal variations and trends of the Urban Heat Island in Athens (Greece) and its response to heat waves

    NASA Astrophysics Data System (ADS)

    Founda, D.; Pierros, F.; Petrakis, M.; Zerefos, C.

    2015-07-01

    The study explores the interdecadal and seasonal variability of the urban heat island (UHI) intensity in the city of Athens. Daily air temperature data from a set of urban and surrounding non urban stations over the period 1970-2004 were used. Nighttime and daytime heat island revealed different characteristics as regards the mean amplitude, seasonal variability and temporal variation and trends. The difference of the annual mean air temperature between urban and rural stations exhibited a progressive statistically significant increase over the studied period, with rates equal to + 0.2 °C/decade. A gradual and constant increase of the daytime UHI intensity was detected, in contrast to the nighttime UHI intensity which increases only in summer, after the mid 1980s. UHI phenomenon was found to be related to higher increasing rates of hot days frequency at the urban stations. It was found that the interaction between heat waves and heat island in Athens, results to pronounced amplification of nocturnal UHI intensity under exceptionally hot weather.

  13. Lower Hybrid Wave Induced SOL Emissivity Variation at High Density on the Alcator C-Mod Tokamak

    SciTech Connect

    Faust, I.; Terry, J. L.; Reinke, M. L.; Meneghini, O.; Shiraiwa, S.; Wallace, G. M.; Parker, R. R.; Schmidt, A. E.; Wilson, J. R.

    2011-12-23

    Lower Hybrid Current Drive (LHCD) in the Alcator C-Mod tokamak provides current profile control for the generation of Advanced Tokamak (AT) plasmas. Non-thermal electron bremsstrahlung emission decreases dramatically at n-bar{sub e}>1{center_dot}10{sup 20}[m{sup -3}] for diverted discharges, indicating low current drive efficiency. It is suggested that Scrape-Off-Layer (SOL) collisional absorption of LH waves is the cause for the absence of non-thermal electrons at high density. VUV and visible spectroscopy in the SOL provide direct information on collision excitation processes. Deuterium Balmer-, Lyman- and He-I transition emission measurements were used for initial characterization of SOL electron-neutral collisional absorption. Data from Helium and Deuterium LHCD discharges were characterized by an overall increase in the emissivity as well as an outward radial shift in the emissivity profile with increasing plasma density and applied LHCD power. High-temperature, high-field (T{sub e} = 5keV,B{sub t} = 8T) helium discharges at high density display increased non-thermal signatures as well as reduced SOL emissivity. Variations in emissivity due to LHCD were seen in SOL regions not magnetically connected to the LH Launcher, indicating global SOL effects due to LHCD.

  14. Cerebral oximetry improves detection of sickle cell patients at risk for nocturnal cerebral hypoxia.

    PubMed

    Raj, Ashok B; O'brien, Louise M; Bertolone, Salvatore J; Gozal, David; Edmonds, Harvey L

    2006-11-01

    We previously used cerebral oximetry to identify low cerebral venous oxygen saturation in waking children with sickle cell disease (SCD). Because arterial oxyhemoglobin desaturation is common during sleep in SCD patients, this study compared both waking and sleeping systemic arterial and cerebral venous oxygenation dynamics in children with and without SCD. Seventeen African-American (AA) children with homozygous SCD [8 (4-15) years; 29% male; normal transcranial Doppler velocities] were compared with a control cohort (CON) comprised of six healthy AA children [9 (4-16) years, 33% male]. Standard all-night polysomnographic recordings were performed, including measurement of arterial oxygen saturation by pulse oximetry (SpO(2)). Regional cerebral oxygen saturation (rSO(2)) was measured non-invasively with cerebral oximetry. Intra-cohort comparisons examined the influence of sleep on SpO(2) and rSO(2) in the subjects. Inter-cohort comparisons of SpO(2), rSO(2,) and the rSO(2)/SpO(2) ratio assessed the impact of SCD on systemic and cerebral oxygenation during wakefulness and sleep. Cohort differences in SpO(2) were not statistically significant in either wakefulness or sleep. However, only in the SCD cohort was the magnitude of SpO(2) change statistically significant (P = 0.002). In contrast, both waking and sleep rSO(2) cohort median values did differ significantly [awake: CON 76 (67-86) vs. SCD 62 (58-71), P = 0.01; sleep: CON 65 (60-77) vs. SCD 55 (48-61), P = 0.01)]. The waking rSO(2)/SpO(2) ratio was also significantly lower in the SCD group [CON 0.78 (0.68-0.88) vs. SCD of 0.66 (0.61-0.72); P = 0.015]. During sleep, the ratio was also significantly lower in the SCD group [CON 0.71 (0.66-0.81) vs. SCD 0.59 (0.52-0.65); P = 0.011]. Our findings suggest that SCD patients may be at increased risk of cerebral hypoxia during both wakefulness and sleep. PMID:16998929

  15. Pulse Oximetry

    MedlinePlus

    ... www.thoracic.org amount of gases (oxygen and carbon dioxide) that are in your blood. To get an ... Also, a pulse oximeter does not measure your carbon dioxide level. How accurate is the pulse oximeter? The ...

  16. Energies and wave functions of an off-centre donor in hemispherical quantum dot: Two-dimensional finite difference approach and ritz variational principle

    NASA Astrophysics Data System (ADS)

    Nakra Mohajer, Soukaina; El Harouny, El Hassan; Ibral, Asmaa; El Khamkhami, Jamal; Assaid, El Mahdi

    2016-09-01

    Eigenvalues equation solutions of a hydrogen-like donor impurity, confined in a hemispherical quantum dot deposited on a wetting layer and capped by an insulating matrix, are determined in the framework of the effective mass approximation. Conduction band alignments at interfaces between quantum dot and surrounding materials are described by infinite height barriers. Ground and excited states energies and wave functions are determined analytically and via one-dimensional finite difference approach in case of an on-center donor. Donor impurity is then moved from center to pole of hemispherical quantum dot and eigenvalues equation is solved via Ritz variational principle, using a trial wave function where Coulomb attraction between electron and ionized donor is taken into account, and by two-dimensional finite difference approach. Numerical codes developed enable access to variations of donor total energy, binding energy, Coulomb correlation parameter, spatial extension and radial probability density with respect to hemisphere radius and impurity position inside the quantum dot.

  17. Nano-emulsions of fluorinated trityl radicals as sensors for EPR oximetry

    NASA Astrophysics Data System (ADS)

    Charlier, N.; Driesschaert, B.; Wauthoz, N.; Beghein, N.; Préat, V.; Amighi, K.; Marchand-Brynaert, J.; Gallez, B.

    2009-04-01

    This article reports the development and evaluation of two nano-emulsions (F45T-03/HFB and F15T-03/PFOB) containing fluorinated trityl radicals dissolved in perfluorocarbons. Preparation with a high-pressure homogenizer conferred sub-micronic size to both nano-emulsions. In vitro and in vivo EPR spectroscopy showed that the nano-emulsions had much greater oxygen sensitivity than the hydrophilic trityl, CT-03. In vivo experiments in rodents confirmed the ability of the nano-emulsions to follow the changes in oxygen concentration after induced ischemia. Histological evaluation of the tissue injected with the nano-emulsions revealed some acute toxicity for the F45T-03/HFB nano-emulsion but none for the F15T-03/PFOB nano-emulsion. These new formulations should be considered for further EPR oximetry experiments in pathophysiological situations where subtle changes in tissue oxygenation are expected.

  18. Nano-emulsions of fluorinated trityl radicals as sensors for EPR oximetry.

    PubMed

    Charlier, N; Driesschaert, B; Wauthoz, N; Beghein, N; Préat, V; Amighi, K; Marchand-Brynaert, J; Gallez, B

    2009-04-01

    This article reports the development and evaluation of two nano-emulsions (F45T-03/HFB and F15T-03/PFOB) containing fluorinated trityl radicals dissolved in perfluorocarbons. Preparation with a high-pressure homogenizer conferred sub-micronic size to both nano-emulsions. In vitro and in vivo EPR spectroscopy showed that the nano-emulsions had much greater oxygen sensitivity than the hydrophilic trityl, CT-03. In vivo experiments in rodents confirmed the ability of the nano-emulsions to follow the changes in oxygen concentration after induced ischemia. Histological evaluation of the tissue injected with the nano-emulsions revealed some acute toxicity for the F45T-03/HFB nano-emulsion but none for the F15T-03/PFOB nano-emulsion. These new formulations should be considered for further EPR oximetry experiments in pathophysiological situations where subtle changes in tissue oxygenation are expected. PMID:19128993

  19. Is Pulse Oximetry Useful for Screening Neonates for Critical Congenital Heart Disease at High Altitudes?

    PubMed

    Hoffman, Julien I E

    2016-06-01

    Now that pulse oximetry is used widely to screen for critical congenital heart disease, it is time to consider whether this screening method is applicable to those who live at high altitudes. Consideration of basic physical principles and reports from the literature indicate that not only is the 95 % cutoff point for arterial oxygen saturation incorrect at high altitudes, but the lower saturations are accompanied by greater variability and therefore there is the possibility of a greater percentage of false-positive screening tests at high altitudes. Because of ethnic differences in response to high altitudes, normative data will have to be collected separately in different countries and perhaps for different ethnic groups. PMID:27090652

  20. An ECG oximetry system for identifying obstructive and central apnoea events.

    PubMed

    de Chazal, Philip; Sadr, Nadi; Jayawardhana, Madhuka

    2015-08-01

    An automatic algorithm for processing simultaneously acquired electrocardiogram (ECG) and oximetry signals that identifies epochs of pure central apnoea, epochs containing obstructive apnoea and epochs of normal breathing is presented. The algorithm uses time and spectral features from the ECG derived heart-rate and respiration information, as well as features capturing desaturations from the oximeter sensor. Evaluation of performance of the system was achieved by using leave-one-record-out cross validation on the St. Vincent's University Hospital / University College Dublin Sleep Apnea Database from the Physionet collections of recorded physiologic signals. When classifying the three epoch types, our system achieved a specificity of 80%, a sensitivity to central apnoea of 44% and sensitivity to obstructive apnoea of 35%. A sensitivity of 81% was achieved when the central and obstructive epochs were combined into one class. PMID:26738069

  1. Universal Pulse Oximetry Screening for Early Detection of Critical Congenital Heart Disease

    PubMed Central

    Kumar, Praveen

    2016-01-01

    Critical congenital heart disease (CCHD) is a major cause of infant death and morbidity worldwide. An early diagnosis and timely intervention can significantly reduce the likelihood of an adverse outcome. However, studies from the United States and other developed countries have shown that as many as 30%–50% of infants with CCHD are discharged after birth without being identified. This diagnostic gap is likely to be even higher in low-resource countries. Several large randomized trials have shown that the use of universal pulse-oximetry screening (POS) at the time of discharge from birth hospital can help in early diagnosis of these infants. The objective of this review is to share data to show that the use of POS for early detection of CCHD meets the criteria necessary for inclusion to the universal newborn screening panel and could be adopted worldwide. PMID:27279759

  2. Application of Electron Paramagnetic Resonance (EPR) Oximetry to Monitor Oxygen in Wounds in Diabetic Models

    PubMed Central

    Desmet, Céline M.; Lafosse, Aurore; Vériter, Sophie; Porporato, Paolo E.; Sonveaux, Pierre; Dufrane, Denis; Levêque, Philippe; Gallez, Bernard

    2015-01-01

    A lack of oxygen is classically described as a major cause of impaired wound healing in diabetic patients. Even if the role of oxygen in the wound healing process is well recognized, measurement of oxygen levels in a wound remains challenging. The purpose of the present study was to assess the value of electron paramagnetic resonance (EPR) oximetry to monitor pO2 in wounds during the healing process in diabetic mouse models. Kinetics of wound closure were carried out in streptozotocin (STZ)-treated and db/db mice. The pO2 was followed repeatedly during the healing process by 1 GHz EPR spectroscopy with lithium phthalocyanine (LiPc) crystals used as oxygen sensor in two different wound models: a full-thickness excisional skin wound and a pedicled skin flap. Wound closure kinetics were dramatically slower in 12-week-old db/db compared to control (db/+) mice, whereas kinetics were not statistically different in STZ-treated compared to control mice. At the center of excisional wounds, measurements were highly influenced by atmospheric oxygen early in the healing process. In pedicled flaps, hypoxia was observed early after wounding. While reoxygenation occurred over time in db/+ mice, hypoxia was prolonged in the diabetic db/db model. This observation was consistent with impaired healing and microangiopathies observed using intravital microscopy. In conclusion, EPR oximetry using LiPc crystals as the oxygen sensor is an appropriate technique to follow wound oxygenation in acute and chronic wounds, in normal and diabetic animals. Nevertheless, the technique is limited for measurements in pedicled skin flaps and cannot be applied to excisional wounds in which diffusion of atmospheric oxygen significantly affects the measurements. PMID:26659378

  3. Elevated Carboxyhaemoglobin Concentrations by Pulse CO-Oximetry is Associated with Severe Aluminium Phosphide Poisoning.

    PubMed

    Mashayekhian, Mohammad; Hassanian-Moghaddam, Hossein; Rahimi, Mitra; Zamani, Nasim; Aghabiklooei, Abbas; Shadnia, Shahin

    2016-09-01

    In pulse CO-oximetry of aluminium phosphide (ALP)-poisoned patients, we discovered that carboxyhaemoglobin (CO-Hb) level was elevated. We aimed to determine whether a higher CO level was detected in patients with severe ALP poisoning and if this could be used as a prognostic factor in these patients. In a prospective case-control study, 96 suspected cases of ALP poisoning were evaluated. In the ALP-poisoned group, demographic characteristics, gastric and exhalation silver nitrate test results, average CO-Hb saturation, methaemoglobin saturation, and blood pressure and blood gas analysis until death/discharge were recorded. Severely poisoned patients were defined as those with systolic blood pressure ≤80 mmHg, pH ≤7.2, or HCO3 ≤15 meq/L or those who died, while patients with minor poisoning were those without any of these signs/symptoms. A control group (37 patients) was taken from other medically ill patients to detect probable effects of hypotension and metabolic acidosis on CO-Hb and methaemoglobin saturations. Of 96 patients, 27 died and 37 fulfilled the criteria for severe poisoning. All patients with carbon monoxide saturation >18% met the criteria to be included in the severe poisoning group and all with a SpCO >25% died. Concerning all significant variables in univariate analysis of severe ALP toxicity, the only significant variable which could independently predict death was carbon monoxide saturation. Due to high mortality rate and need for intensive care support, early prediction of outcome is vital for choosing an appropriate setting (ICU or ordinary ward). CO-oximetry is a good diagnostic and prognostic factor in patients with ALP poisoning even before any clinical evidence of toxicity will develop. PMID:26899262

  4. Transcutaneous oximetry in clinical practice: consensus statements from an expert panel based on evidence.

    PubMed

    Fife, C E; Smart, D R; Sheffield, P J; Hopf, H W; Hawkins, G; Clarke, D

    2009-01-01

    Transcutaneous oximetry (PtcO2) is finding increasing application as a diagnostic tool to assess the peri-wound oxygen tension of wounds, ulcers, and skin flaps. It must be remembered that PtcO2 measures the oxygen partial pressure in adjacent areas of a wound and does not represent the actual partial pressure of oxygen within the wound, which is extremely difficult to perform. To provide clinical practice guidelines, an expert panel was convened with participants drawn from the transcutaneous oximetry workshop held on June 13, 2007, in Maui, Hawaii. Important consensus statements were (a) tissue hypoxia is defined as a PtcO2 <40 mm Hg; (b) in patients without vascular disease, PtcO2 values on the extremity increase to a value >100 mm Hg when breathing 100% oxygen under normobaric pressures; (c) patients with critical limb ischemia (ankle systolic pressure of < or =50 mm Hg or toe systolic pressure of < or =30 mm Hg) breathing air will usually have a PtcO2 <30 mm Hg; (d) low PtcO2 values obtained while breathing normobaric air can be caused by a diffusion barrier; (e) a PtcO2 <40 mm Hg obtained while breathing normobaric air is associated with a reduced likelihood of amputation healing; (f) if the baseline PtcO2 increases <10 mm Hg while breathing 100% normobaric oxygen, this is at least 68% accurate in predicting failure of healing post-amputation; (g) an increase in PtcO2 to >40 mm Hg during normobaric air breathing after revascularization is usually associated with subsequent healing, although the increase in PtcO2 may be delayed; (h) PtcO2 obtained while breathing normobaric air can assist in identifying which patients will not heal spontaneously. PMID:19341127

  5. Screening by Pulse CO-Oximetry for Environmental Tobacco Smoke Exposure in Preanesthetic Children

    PubMed Central

    Cardwell, Kathryn; Pan, Zhaoxing; Boucher, Rebecca; Zuk, Jeannie; Friesen, Robert H.

    2012-01-01

    Objective The purpose of this study was to evaluate the ability of multiple wavelength pulse CO-oximetry (SpCO) to screen for environmental tobacco smoke (ETS) exposure in children. Background Exposure to ETS is associated with an increased risk of perioperative respiratory complications in children. It is often difficult to obtain an accurate history for ETS exposure, so a preoperative screening tool is desirable. Carbon monoxide is a measurable product of tobacco combustion. Multiple wavelength pulse CO-oximetry is a recently developed point-of-care monitor. Methods Following IRB approval and parental consent, 220 children aged 1–16 years having outpatient surgical procedures were enrolled. SpCO was measured preoperatively 3 times with the Radical-7 Rainbow SET CO-oximeter (Masimo, Irvine, CA). Immediately following induction of anesthesia, a blood sample for laboratory measurement of carboxyhemoglobin (COHb) and serum cotinine was obtained. Regression analysis determined the correlation of SpCO with serum cotinine values. Receiver operator characteristic (ROC) curves analyzed the discriminating ability of SpCO or COHb to predict ETS exposure based on cotinine cutoff values known to be present in children exposed to ETS. Agreement of SpCO and COHb values was assessed using Bland-Altman plots. Results SpCO did not correlate with cotinine (R2=0.005). Both SpCO and COHb had poor discriminating ability for ETS exposure (area under the ROC curve = 0.606 and 0.562, respectively). SpCO values had poor agreement with COHb values. Conclusions The point-of-care multiple wavelength pulse CO-oximeter does not appear to be a useful preoperative screening tool for ETS exposure in children. PMID:22587734

  6. Application of Electron Paramagnetic Resonance (EPR) Oximetry to Monitor Oxygen in Wounds in Diabetic Models.

    PubMed

    Desmet, Céline M; Lafosse, Aurore; Vériter, Sophie; Porporato, Paolo E; Sonveaux, Pierre; Dufrane, Denis; Levêque, Philippe; Gallez, Bernard

    2015-01-01

    A lack of oxygen is classically described as a major cause of impaired wound healing in diabetic patients. Even if the role of oxygen in the wound healing process is well recognized, measurement of oxygen levels in a wound remains challenging. The purpose of the present study was to assess the value of electron paramagnetic resonance (EPR) oximetry to monitor pO2 in wounds during the healing process in diabetic mouse models. Kinetics of wound closure were carried out in streptozotocin (STZ)-treated and db/db mice. The pO2 was followed repeatedly during the healing process by 1 GHz EPR spectroscopy with lithium phthalocyanine (LiPc) crystals used as oxygen sensor in two different wound models: a full-thickness excisional skin wound and a pedicled skin flap. Wound closure kinetics were dramatically slower in 12-week-old db/db compared to control (db/+) mice, whereas kinetics were not statistically different in STZ-treated compared to control mice. At the center of excisional wounds, measurements were highly influenced by atmospheric oxygen early in the healing process. In pedicled flaps, hypoxia was observed early after wounding. While reoxygenation occurred over time in db/+ mice, hypoxia was prolonged in the diabetic db/db model. This observation was consistent with impaired healing and microangiopathies observed using intravital microscopy. In conclusion, EPR oximetry using LiPc crystals as the oxygen sensor is an appropriate technique to follow wound oxygenation in acute and chronic wounds, in normal and diabetic animals. Nevertheless, the technique is limited for measurements in pedicled skin flaps and cannot be applied to excisional wounds in which diffusion of atmospheric oxygen significantly affects the measurements. PMID:26659378

  7. Seasonal variation of wave activities near the mesopause region observed at King Sejong Station (62.22°S, 58.78°W), Antarctica

    NASA Astrophysics Data System (ADS)

    Lee, Changsup; Kim, Yong Ha; Kim, Jeong-Han; Jee, Geonhwa; Won, Young-In; Wu, Dong L.

    2013-12-01

    We analyzed the neutral wind data at altitudes of 80-100 km obtained from a VHF meteor radar at King Sejong Station (KSS, 62.22°S, 58.78°W), a key location to study wave activities above the stratospheric vortex near the Antarctic Peninsula. The seasonal behavior of the semidiurnal tides is generally consistent with the prediction of Global Scale Wave Model (GSWM02) except in the altitude region above ~96 km. Gravity wave (GW) activities inferred from the neutral wind variances show a seasonal variation very similar to the semidiurnal tide amplitudes, suggesting a strong interaction between gravity waves and the tide. Despite the consistent seasonal variations of the GW wind variances observed at the adjacent Rothera station, the magnitudes of the wind variance obtained at KSS are much larger than those at Rothera, especially during May-September. The enhanced GW activity at KSS is also observed by Aura Microwave Limb Sounder (MLS) from space in its temperature variance. The observed large wind variances at KSS imply that the Antarctic vortex in the stratosphere may act as an effective filter and source for the GWs in the upper atmosphere.

  8. Evaluating future flooding risks by using a probabilistic approach to include wave height distributions in sea level variations

    NASA Astrophysics Data System (ADS)

    Leijala, Ulpu; Björkqvist, Jan-Victor; Kahma, Kimmo K.; Johansson, Milla M.; Pellikka, Hilkka; Särkkä, Jani

    2016-04-01

    Assessing sea flood risks has an essential role in future coastal planning as climate change drives forward the global sea level rise. Safe planning of land utilization and building in coastal areas requires capability to estimate sea level behaviour all the way to 100-200 years ahead. The coastal effect of the sea level is always affected also by the wave conditions, which may vary greatly depending on location. An archipelago acts as an efficient shield against the largest waves penetrating to the shoreline. However, part of the energy of the waves passes through the archipelago and coastal wave height conditions, depending for example on the shape of the shoreline and topography of the seabed, must be evaluated close to the shore separately. The probability of high sea level and wind generated high waves occurring simultaneously is lower than the probability of one of the components occurring alone. Summing the maximum sea level and maximum wave height components together can thus lead to an overestimation of the joint effect. For this reason a method based on probability distributions is reasonable and preferable. In this study, a method of combining sea level and wave height distributions using a location specific probability approach is introduced. First estimates of the joint effect of high sea level and high waves at several locations at the archipelago area on the southern coast of Finland are presented. Constructing sea level scenarios including the effect of wind waves until the end of the century demands knowledge of both sea level and wave height variability in the past, and global mean sea level predictions for the future. In our study, an estimate of short-term sea level variability is based on 30 years (1982-2011) of hourly data from the Helsinki tide gauge located on the coast of the Gulf of Finland. Future predictions for the long-term mean sea level changes at Helsinki are based on scenarios taking into account the global mean sea level rise

  9. The 27-day versus 13.5-day variations in the solar Lyman-alpha radiation and the radio wave absorption in the lower ionosphere over Europe

    NASA Technical Reports Server (NTRS)

    Delamorena, B. A.; Lastovicka, Jan; Rapoport, Z. TS.; Alberca, L.

    1989-01-01

    In order to clarify the question of solar periods in absorption, the pattern was studied of the solar Lyman-alpha radiation (the principal ionizing agent of the lower ionosphere) and of the radio wave absorption at five widely spaced places in Europe. When the solar Lyman-alpha flux variability is very well developed, then it dominates in the lower ionospheric variability. The most pronounced Lyman-alpha variation on time scale day-month is the solar rotation variation (about 27 days). When the Lyman-alpha variability is developed rather poorly, as it is typical for periods dominated by the 13.5 day variability, then the lower ionospheric variability appears to be dominated by variations of meteorological origin. The conclusions hold for all five widely spaced placed in Europe.

  10. Effect of spatial density variation and O+ concentration on the growth and evolution of electromagnetic ion cyclotron waves

    DOE PAGESBeta

    Denton, R. E.; Jordanova, V. K.; Fraser, B. J.

    2014-10-01

    We simulate electromagnetic ion cyclotron (EMIC) wave growth and evolution within three regions, the plasmasphere (or plasmaspheric plume), the plasmapause, and the low-density plasmatrough outside the plasmapause. First, we use a ring current simulation with a plasmasphere model to model the particle populations that give rise to the instability for conditions observed on 9 June 2001. Then, using two different models for the cold ion composition, we do a full scale hybrid code simulation in dipole coordinates of the EMIC waves on a meridional plane at MLT = 18 and at 1900 UT within a range of L shell frommore » L = 4.9 to 6.7. EMIC waves were observed during June 9, 2001 by Geostationary Operational Environmental Satellite (GOES) spacecraft. While an exact comparison between observed and simulated spectra is not possible here, we do find significant similarities between the two, at least at one location within the region of largest wave growth. We find that the plasmapause is not a preferred region for EMIC wave growth, though waves can grow in that region. The density gradient within the plasmapause does, however, affect the orientation of wave fronts and wave vector both within the plasmapause and in adjacent regions. There is a preference for EMIC waves to be driven in the He+ band (frequencies between the O+ and He+ gyrofrequencies) within the plasmasphere, although they can also grow in the plasmatrough. If present, H+ band waves are more likely to grow in the plasmatrough. This fact, plus L dependence of the frequency and possible time evolution toward lower frequency waves, can be explained by a simple model. Large O+ concentration limits the frequency range of or even totally quenches EMIC waves. This is more likely to occur in the plasmatrough at solar maximum. Such large O+ concentration significantly affects the H+ cutoff frequency and hence the width in frequency of the stop band above the He+ gyrofrequency. EMIC wave surfaces predicted by cold

  11. Effect of spatial density variation and O+ concentration on the growth and evolution of electromagnetic ion cyclotron waves

    SciTech Connect

    Denton, R. E.; Jordanova, V. K.; Fraser, B. J.

    2014-10-01

    We simulate electromagnetic ion cyclotron (EMIC) wave growth and evolution within three regions, the plasmasphere (or plasmaspheric plume), the plasmapause, and the low-density plasmatrough outside the plasmapause. First, we use a ring current simulation with a plasmasphere model to model the particle populations that give rise to the instability for conditions observed on 9 June 2001. Then, using two different models for the cold ion composition, we do a full scale hybrid code simulation in dipole coordinates of the EMIC waves on a meridional plane at MLT = 18 and at 1900 UT within a range of L shell from L = 4.9 to 6.7. EMIC waves were observed during June 9, 2001 by Geostationary Operational Environmental Satellite (GOES) spacecraft. While an exact comparison between observed and simulated spectra is not possible here, we do find significant similarities between the two, at least at one location within the region of largest wave growth. We find that the plasmapause is not a preferred region for EMIC wave growth, though waves can grow in that region. The density gradient within the plasmapause does, however, affect the orientation of wave fronts and wave vector both within the plasmapause and in adjacent regions. There is a preference for EMIC waves to be driven in the He+ band (frequencies between the O+ and He+ gyrofrequencies) within the plasmasphere, although they can also grow in the plasmatrough. If present, H+ band waves are more likely to grow in the plasmatrough. This fact, plus L dependence of the frequency and possible time evolution toward lower frequency waves, can be explained by a simple model. Large O+ concentration limits the frequency range of or even totally quenches EMIC waves. This is more likely to occur in the plasmatrough at solar maximum. Such large O+ concentration significantly affects the H+ cutoff frequency and hence the width in frequency of the stop band above the He+ gyrofrequency. EMIC wave surfaces predicted by cold plasma theory

  12. Evidence for MAC waves at the top of Earth's core and implications for variations in length of day

    NASA Astrophysics Data System (ADS)

    Buffett, Bruce; Knezek, Nicholas; Holme, Richard

    2016-03-01

    Earth's liquid core hosts a diverse set of waves with periods ranging from days to thousands of years. One class of waves with periods of several decades is known to arise from an interplay between magnetic, Archimedes and Coriolis forces. These so-called MAC waves are thought to be relevant for interpreting historical fluctuations in the geomagnetic field. In this study, we show that MAC waves provide a good description of time-dependent zonal flow at the top of the core. The same collection of waves also offers a simple explanation for observed fluctuations in the dipole field. Both of these predictions require a stratified layer at the top of the core with a thickness of 130-140 km and a buoyancy frequency comparable to Earth's rotation rate. We extend these predictions to include changes in the length of day (LOD) and find that MAC waves can account for about half of the observed fluctuation at decadal periods. Larger fluctuations are possible when electromagnetic stresses couple MAC waves to flow in the interior of the core. In fact, an idealized model for the coupled motion overestimates the LOD fluctuations, probably reflecting limitations in this idealized model. Our results offer support for stable stratification at the top of the core and suggest a common origin for decadal fluctuations in the geomagnetic field and the LOD.

  13. Coupling alongshore variations in wave energy to beach morphologic change using the SWAN wave model at Ocean Beach, San Francisco, CA

    USGS Publications Warehouse

    Eshleman, Jodi L.; Barnard, Patrick L.; Erikson, Li H.; Hanes, Daniel M.

    2007-01-01

    Coastal managers have faced increasing pressure to manage their resources wisely over the last century as a result of heightened development and changing environmental forcing. It is crucial to understand seasonal changes in beach volume and shape in order to identify areas vulnerable to accelerated erosion. Shepard (1950) was among the first to quantify seasonal beach cycles. Sonu and Van Beek (1971) and Wright et al. (1985) described commonly occurring beach states. Most studies utilize widest spaced 2-D cross shore profiles or shorelines extracted from aerial photographs (e.g. Winant et al. 1975; Aubrey, 1979, Aubrey and Ross, 1985; Larson and Kraus, 1994; Jimenez et al., 1977; Lacey and Peck, 1998; Guillen et al., 1999; Norcorss et al., 2002) to analyzed systematic changes in beach evolution. But with the exception of established field stations, such as Duck, NC (Birkemeier and Mason, 1984), ans Hazaki Oceanographical Research Station (HORS) in Japan (Katoh, 1997), there are very few beach change data sets with high temporal and spatial resolutions (e.g. Dail et al., 2000; Ruggiero et al., 2005; Yates et al., in press). Comprehensive sets of nearshore morphological data and local in situ measurements outside of these field stations are very rare and virtually non-existent high-energy coasts. Studied that have attempted to relate wave statistics to beach morphology change require some knowledge of the nearshore wave climate, and have had limited success using offshore measurement (Sonu and Van Beek, 1971; Dail et al., 2000). The primary objective of this study is to qualitatively compare spatially variable nearshore wave predictions to beach change measurements in order to understand the processes responsible for a persistent erosion 'hotspot' at Ocean Beach, San Francisco, CA. Local wave measurements are used to calibrate and validate a wave model that provides nearshore wave prediction along the beach. The model is run for thousands of binned offshore wave

  14. Is pulse oximetry an essential tool or just another distraction? The role of the pulse oximeter in modern anesthesia care.

    PubMed

    Shah, Amit; Shelley, Kirk H

    2013-06-01

    Since the discovery of anesthetic agents, patient monitoring has been considered one of the core responsibilities of the anesthesiologist. As depicted in Robert Hinckley's famous painting, The First Operation with Ether, one observes William Thomas Green Morton carefully watching over his patient. Since its founding in 1905, 'Vigilance' has been the motto of the American Society of Anesthesiologists (ASA). Over a hundred years have passed, and one would think we would be clear regarding what we are watching for and how we should be watching. On the contrary, the introduction of new technology and outcome research is requiring us to re-examine our fundamental assumptions regarding what is and what is not important in the care of the patient. A vast majority of anesthesiologists would refuse to proceed with an anesthetic without the presence of a pulse oximeter. On the other hand, outcome studies have failed to demonstrate an improvement in patient care with their use. For that matter, it can be argued that outcome studies have yet to demonstrate an unambiguous role for any monitor of any type (i.e. blood pressure cuff or ECG), as outcome studies may fail to capture rare events. Because of the increased safety that has been attributed to pulse oximetry, it is unlikely that further studies can or will be conducted. As we enter a new era of clinical monitoring, with an emphasis on noninvasive cardiovascular monitoring, it might be of benefit to examine the role of the pulse oximeter in clinical care. This article reviews the available evidence for pulse oximetry. Further, it discusses contemporary issues, events, and perceptions that may help to explain how and why pulse oximetry may have been adopted as a standard of care despite the lack of supportive. Lastly, it discusses less obvious benefits of pulse oximetry that may have further implications on the future of anesthesia care and perhaps even automated anesthesia. PMID:23314807

  15. Repetitive Tissue PO2 Measurements by Electron Paramagnetic Resonance Oximetry: Current Status and Future Potential for Experimental and Clinical Studies

    PubMed Central

    KHAN, NADEEM; WILLIAMS, BENJAMIN B.; HOU, HUAGANG; LI, HONGBIN; SWARTZ, HAROLD M.

    2010-01-01

    Tissue oxygen plays a crucial role in maintaining tissue viability and in various diseases, including responses to therapy. Useful knowledge has been gained by methods that can give limited snapshots of tissue oxygen (e.g., oxygen electrodes) or evidence of a history of tissue hypoxia (e.g., EF5) or even indirect evidence by monitoring oxygen availability in the circulatory system (e.g., NMR methods). Each of these methods has advantages and significant limitations. EPR oximetry is a technique for direct measurement of tissue pO2, which has several advantages over the other existing methods for applications in which the parameter of interest is the pO2 of tissues, and information is needed over a time course of minutes to hours, and/or for repetitive measurements over days or weeks or years. The aim of this article is to provide an overview of EPR oximetry using particulates to readers who are not familiar with this technique and its potential in vivo and clinical applications. The data presented here are from the experiments currently being carried out in our laboratory. We are confident that in vivo EPR oximetry will play a crucial role in the understanding and clinical management of various pathologies in the years to come. PMID:17536960

  16. Diurnal variations and modulation by easterly waves of the size distribution of convective cloud clusters over West Africa and the Atlantic Ocean

    SciTech Connect

    Machado, L.A.T.; Duvel, J.Ph.; Desbois, M. )

    1993-01-01

    Short time-scale fluctuations of the size distribution of tropical convective cloud clusters for July to September 1989 were studied using Meteosat data. A cluster at a given brightness-temperature threshold was defined as the area covered by adjacent cloudy pixels with brightness temperature lower than the threshold. The clusters were classified according to the area covered and the position of their center of mass. Over land regions of West Africa the size distribution underwent a coherent diurnal behavior with development of small cells between noon and 1500 LST. Over the Atlantic Ocean, the highest cloudiness had a weak maximum extent in early morning, while cloudiness at lower levels was more extended in the afternoon. This diurnal behavior was primarily due to large cloud clusters, suggesting that the diurnal variation over the ocean resulted from internal variations of large convective systems and not from the initiation of convection at a given hour of the day. This was confirmed by the analysis of 15 large convective systems propagating over the ocean. The authors have ascertained that the high cloud cover was maximized within the trough of eastrly waves. The cluster size was dependent upon the wave amplitude with a larger mean cluster size when the amplitude was largr. The trough phase of the wave was found to promote the development of large clusters more than it favored the initial stage of convection. 30 refs., 11 figs.

  17. Spatio-temporal variations in the structure of the attenuation field of the S-wave in the region of Nevada nuclear test site

    NASA Astrophysics Data System (ADS)

    Kopnichev, Yu. F.; Sokolova, I. N.; Sokolov, K. N.

    2013-11-01

    The characteristics of the attenuation field of short-period shear waves in the region of Nevada nuclear test site (NNTS) are studied. The seismograms of underground nuclear explosions (UNEs) and earthquakes recorded by three seismic stations in 1975-2012 at the epicentral distances of up to 1000 km are processed by the methods based on the analysis of the amplitude ratios of Sn to Pn and Lg to Pg waves, as well as the S-coda envelopes for close events. It is shown that the structure of the attenuation field in the Earth's crust and upper mantle in the NNTS region experienced significant temporal variations during the interval of nuclear operations. The strongest variations were associated with UNEs conducted in the Pahute Mesa area, which held about two-thirds of the most intense explosions. Our data indicate that temporal variations in the structure of the attenuation field are related to the migration of deep fluids. A comparison of the general characteristics of the attenuation field in the regions of the three large nuclear test sites is presented.

  18. In vivo evidence of methamphetamine induced attenuation of brain tissue oxygenation as measured by EPR oximetry

    SciTech Connect

    Weaver, John; Yang, Yirong; Purvis, Rebecca; Weatherwax, Theodore; Rosen, Gerald M.; Liu, Ke Jian

    2014-03-01

    Abuse of methamphetamine (METH) is a major and significant societal problem in the US, as a number of studies have suggested that METH is associated with increased cerebrovascular events, hemorrhage or vasospasm. Although cellular and molecular mechanisms involved in METH-induced toxicity are not completely understood, changes in brain O{sub 2} may play an important role and contribute to METH-induced neurotoxicity including dopaminergic receptor degradation. Given that O{sub 2} is the terminal electron acceptor for many enzymes that are important in brain function, the impact of METH on brain tissue pO{sub 2}in vivo remains largely uncharacterized. This study investigated striatal tissue pO{sub 2} changes in male C57BL/6 mice (16–20 g) following METH administration using EPR oximetry, a highly sensitive modality to measure pO{sub 2}in vivo, in situ and in real time. We demonstrate that 20 min after a single injection of METH (8 mg/kg i.v.), the striatal pO{sub 2} was reduced to 81% of the pretreatment level and exposure to METH for 3 consecutive days further attenuated striatal pO{sub 2} to 64%. More importantly, pO{sub 2} did not recover fully to control levels even 24 h after administration of a single dose of METH and continual exposure to METH exacerbates the condition. We also show a reduction in cerebral blood flow associated with a decreased brain pO{sub 2} indicating an ischemic condition. Our findings suggests that administration of METH can attenuate brain tissue pO{sub 2}, which may lead to hypoxic insult, thus a risk factor for METH-induced brain injury and the development of stroke in young adults. - Highlights: • Explored striatal tissue pO{sub 2}in vivo after METH administration by EPR oximetry. • pO{sub 2} was reduced by 81% after a single dose and 64% after 3 consecutive daily doses. • pO{sub 2} did not recover fully to control levels even 24 h after a single dose. • Decrease in brain tissue pO{sub 2} may be associated with a decrease in

  19. EPR Oximetry for Investigation of Hyperbaric O2 Pre-treatment for Tumor Radiosensitization.

    PubMed

    Williams, Benjamin B; Hou, Huagang; Coombs, Rachel; Swartz, Harold M

    2016-01-01

    A number of studies have reported benefits associated with the application of hyperbaric oxygen treatment (HBO) delivered immediately prior to radiation therapy. While these studies provide evidence that pre-treatment with HBO may be beneficial, no measurements of intratumoral pO2 were carried out and they do not directly link the apparent benefits to decreased hypoxic fractions at the time of radiation therapy. While there is empirical evidence and some theoretical basis for HBO to enhance radiation therapy, without direct and repeated measurements of its effects on pO2, it is unlikely that the use of HBO can be understood and optimized for clinical applications. In vivo EPR oximetry is a technique uniquely capable of providing repeated direct measurements of pO2 through a non-invasive procedure in both animal models and human patients. In order to evaluate the ability of pretreatment with HBO to elevate tumor pO2, a novel small animal hyperbaric chamber system was constructed that allows simultaneous in vivo EPR oximetry. This chamber can be placed within the EPR magnet and is equipped with a variety of ports for multiplace gas delivery, thermoregulation, delivery of anesthesia, physiologic monitoring, and EPR detection. Initial measurements were performed in a subcutaneous RIF-1 tumor model in C3H/HeJ mice. The mean baseline pO2 value was 6.0 ± 1.2 mmHg (N = 7) and responses to two atmospheres absolute pressure HBO varied considerably across subjects, within tumors, and over time. When an increase in pO2 was observed, the effect was transient in all but one case, with durations lasting from 5 min to over 20 min, and returned to baseline levels during HBO administration. These results indicate that without direct measurements of pO2 in the tissue of interest, it is likely to be difficult to know the effects of HBO on actual tissue pO2. PMID:27526165

  20. Recognition of wave-dominated, tide-influenced shoreline systems in the rock record: Variations from a microtidal shoreline model

    NASA Astrophysics Data System (ADS)

    Vakarelov, Boyan K.; Ainsworth, R. Bruce; MacEachern, James A.

    2012-11-01

    Existing wave-dominated facies models are based on microtidal coastlines and do not adequately address wave-dominated environments influenced by significant tidal ranges. Observations from modern environments show that such systems are abundant along tide-influenced shorelines facing wide shelves and large embayments, such as much of the northern Australia coast; yet equivalent deposits have been rarely recognized from the ancient record. Geomorphological literature shows that tidal influence on wave-dominated shorelines has the effect of shifting the shoaling, breaking, and swash wave zones up and down the beach profile; when the tidal range is appreciable, sedimentation is affected significantly. Many macrotidal, wave-dominated systems (tidal range > 4 m), for example, are non-barred and are characterized by poor development of dune-scale bedforms in the subtidal zone and along the beach profile. Other systems do develop cross stratification, but this occurs in the intertidal zone rather than the subtidal zone as is implied in existing wave-dominated facies models. The association of many wave-dominated, tide-influenced environments with shallow shelves also suggests that major storms may be capable of reworking sediment significant distances from the shoreline. We present an ancient example of a wave-dominated, tide-influenced, fluvial-affected system (Wtf) from the Campanian Bearpaw to Horseshoe Canyon Formation transition near Drumheller, Alberta, Canada, which has been described in closely spaced outcrop exposures and core. Wave domination in the coarsening-upward interval is unambiguous and is represented by abundance of micro-hummocky cross stratification and other storm beds in the mudstone-dominated portions, a well-defined swaley cross stratified sandstone interval, and an up to four meter thick, horizontal planar stratified interval interpreted to have been formed by swash waves. Tide influence is suggested by common double carbonaceous and mud drapes

  1. Study of stress-induced velocity variation in concrete under direct tensile force and monitoring of the damage level by using thermally-compensated Coda Wave Interferometry.

    PubMed

    Zhang, Yuxiang; Abraham, Odile; Grondin, Frédéric; Loukili, Ahmed; Tournat, Vincent; Le Duff, Alain; Lascoup, Bertrand; Durand, Olivier

    2012-12-01

    In this paper, we describe an experimental study of concrete behavior under a uniaxial tensile load by use of the thermally-compensated Coda Wave Interferometry (CWI) analysis. Under laboratory conditions, uniaxial tensile load cycles are imposed on a cylindrical concrete specimen, with continuous ultrasonic measurements being recorded within the scope of bias control protocols. A thermally-compensated CWI analysis of multiple scattering waves is performed in order to evaluate the stress-induced velocity variation. Concrete behavior under a tensile load can then be studied, along with CWI results from both its elastic performance (acoustoelasticity) and plastic performance (microcracking corresponding to the Kaiser effect). This work program includes a creep test with a sustained, high tensile load; the acoustoelastic coefficients are estimated before and after conducting the creep test and then used to demonstrate the effect of creep load. PMID:22989948

  2. Study of obliquely propagating dust acoustic solitary waves in magnetized tropical mesospheric plasmas with effect of dust charge variations and rotation of the plasma

    SciTech Connect

    Mushtaq, A.; Shah, H.A.; Rubab, N.; Murtaza, G.

    2006-06-15

    The characteristics of obliquely propagating Dust Acoustic Waves (DAWs) in rotating and magnetized dusty plasma in the dayside tropical mesosphere are examined by incorporating adiabatic dust charge fluctuations. A Korteweg-de Vries equation is derived, which may support a nonlinear dust acoustic wave on a very slow time scale. The meteoritic dust in mesospheric plasmas on the dayside is charged positively due to photo- and thermionic emissions. The dynamics of the DAW with electronic, ionic, thermionic, and photoelectric currents along with obliqueness and effective gyrofrequency are studied. It is observed that the amplitude of the soliton depends directly on the obliqueness {theta} and dust charge variation, respectively, while the width is modified inversely with these parameters. It is also observed that the effective gyrofrequency modifies the width inversely.

  3. Nitrate Effects on Nodule Oxygen Permeability and Leghemoglobin (Nodule Oximetry and Computer Modeling).

    PubMed Central

    Denison, R. F.; Harter, B. L.

    1995-01-01

    Two current hypotheses to explain nitrate inhibition of nodule function both involve decreased O2 supply for respiration in support of N2 fixation. This decrease could result from either (a) decreased O2 permeability (PO) of the nodule cortex, or (b) conversion of leghemoglobin (Lb) to an inactive, nitrosyl form. These hypotheses were tested using alfalfa (Medicago sativa L. cv Weevlchek) and birdsfoot trefoil (Lotus corniculatus L. cv Fergus) plants grown in growth pouches under controlled conditions. Nodulated roots were exposed to 10 mM KNO3 or KCI. Fractional oxygenation of Lb under air (FOLair), relative concentration of functional Lb, apparent PO, and O2-saturated central zone respiration rate were all monitored by nodule oximetry. Apparent PO and FOLair in nitrate-treated nodules decreased to <50% of values for KCI controls within 24 h, but there was no decrease in functional Lb concentration during the first 72 h. In nitrate-treated alfalfa, but not in birdsfoot trefoil, FOLair, apparent PO, and O2-saturated central zone respiration rate decreased during each light period and recovered somewhat during the subsequent dark period. This species difference could be explained by greater reliance on photoreduction of nitrate in alfalfa than in birdsfoot trefoil. Computer simulations extended the experimental results, showing that previously reported decreases in apparent PO of Glycine max nodules with nitrate exposure cannot be explained by hypothetical decreases in the concentration or O2 affinity of Lb. PMID:12228439

  4. Oximetry system performance assessment with POM (acetal) phantoms incorporating hemoglobin calibration standards and customized saturation levels

    NASA Astrophysics Data System (ADS)

    Jang, Hyounguk; Singh, Karam; Wang, Hsing-Wen; Pfefer, T. J.; Chen, Yu

    2015-03-01

    Standardized approaches for performance assessment of biophotonic devices have the potential to facilitate system development and intercomparison, clinical trial standardization, recalibration, manufacturing quality control and quality assurance during clinical use. Evaluation of devices based on near-infrared spectroscopy (NIRS) for detection of hemoglobin (Hb) content and oxygenation have often involved tissue-simulating phantoms incorporating artificial dyes or flow systems. Towards the development of simple, effective techniques for objective, quantitative evaluation of basic NIRS system performance, we have developed and evaluated two test methods. These methods are based on cuvette inserts in solid turbid phantoms for measuring commercially-available Hb oximetry standards and custom-formulated oxy/deoxy-Hb solutions. Both approaches incorporate solid acetal, or polyoxymethylene (POM), as a tissue-simulating matrix material. First, inverse-adding-doubling (IAD) based on measurements with a spectrophotometer and an integrating sphere was used to measure POM optical properties and their stability over time. Second, two fiberopticprobe- based NIRS systems were used to measure concentration change of oxy- and deoxy-Hb in standard Hb solutions and customized Hb solutions by adding yeast. Differences in system performance were likely due to differences in light source outputs and fiberoptic probe design. Our preliminary results indicate that simple phantom-based approaches based on commercially available polymers and inclusions containing Hb standards, or controlled oxygenation levels may be useful for benchtop assessment of NIRS device quality for a variety of biophotonic devices.

  5. Preliminary investigation of multispectral retinal tissue oximetry mapping using a hyperspectral retinal camera.

    PubMed

    Desjardins, Michèle; Sylvestre, Jean-Philippe; Jafari, Reza; Kulasekara, Susith; Rose, Kalpana; Trussart, Rachel; Arbour, Jean Daniel; Hudson, Chris; Lesage, Frédéric

    2016-05-01

    Oximetry measurement of principal retinal vessels represents a first step towards understanding retinal metabolism, but the technique could be significantly enhanced by spectral imaging of the fundus outside of main vessels. In this study, a recently developed Hyperspectral Retinal Camera was used to measure relative oximetric (SatO2) and total hemoglobin (HbT) maps of the retina, outside of large vessels, in healthy volunteers at baseline (N = 7) and during systemic hypoxia (N = 11), as well as in patients with glaucoma (N = 2). Images of the retina, on a field of view of ∼30°, were acquired between 500 and 600 nm with 2 and 5 nm steps, in under 3 s. The reflectance spectrum from each pixel was fitted to a model having oxy- and deoxyhemoglobin as the main absorbers and scattering modeled by a power law, yielding estimates of relative SatO2 and HbT over the fundus. Average optic nerve head (ONH) saturation over 8 eyes was 68 ± 5%. During systemic hypoxia, mean ONH saturation decreased by 12.5% on average. Upon further development and validation, the relative SatO2 and HbT maps of microvasculature obtained with this imaging system could ultimately contribute to the diagnostic and management of diseases affecting the ONH and retina. PMID:27060375

  6. Evaluation of pulse-oximetry oxygen saturation taken through skin protective covering

    PubMed Central

    James, Jyotsna; Tiwari, Lokesh; Upadhyay, Pramod; Sreenivas, Vishnubhatla; Bhambhani, Vikas; Puliyel, Jacob M

    2006-01-01

    Background The hard edges of adult finger clip probes of the pulse oximetry oxygen saturation (POOS) monitor can cause skin damage if used for prolonged periods in a neonate. Covering the skin under the probe with Micropore surgical tape or a gauze piece might prevent such injury. The study was done to see if the protective covering would affect the accuracy of the readings. Methods POOS was studied in 50 full-term neonates in the first week of life. After obtaining consent from their parents the neonates had POOS readings taken directly (standard technique) and through the protective covering. Bland-Altman plots were used to compare the new method with the standard technique. A test of repeatability for each method was also performed. Results The Bland-Altman plots suggest that there is no significant loss of accuracy when readings are taken through the protective covering. The mean difference was 0.06 (SD of 1.39) and 0.04 (SD 1.3) with Micropore and gauze respectively compared to the standard method. The mean difference was 0.22 (SD 0.23) on testing repeatability with the standard method. Conclusion Interposing Micropore or gauze does not significantly affect the accuracy of the POOS reading. The difference between the standard method and the new method was less than the difference seen on testing repeatability of the standard method. PMID:16677394

  7. Intracellular hypoxia of tumor tissue estimated by noninvasive electron paramagnetic resonance oximetry technique using paramagnetic probes.

    PubMed

    Matsumoto, Atsuko; Matsumoto, Ken-ichiro; Matsumoto, Shingo; Hyodo, Fuminori; Sowers, Anastasia L; Koscielniak, Janusz W; Devasahayam, Nallathamby; Subramanian, Sankaran; Mitchell, James B; Krishna, Murali C

    2011-01-01

    Electron paramagnetic resonance (EPR) oximetry at 700 MHz operating frequency employing a surface coil resonator is used to assess tissue partial pressure of oxygen (pO(2)) using paramagnetic media whose linewidth and decay constant are related to oxygen concentration. Differences in extracellular and intracellular pO(2) in squamous cell carcinoma (SCC) tumor tissue were tested using several types of water-soluble paramagnetic media, which localize extracellularly or permeate through the cell membrane. The nitroxide carboxy-PROXYL (CxP) can only be distributed in blood plasma and extracellular fluids whereas the nitroxides carbamoyl-PROXYL (CmP) and TEMPOL (TPL) can permeate cell membranes and localize intracellularly. EPR signal decay constant and the linewidth of the intravenously administered nitroxides in SCC tumor tissues implanted in mouse thigh and the contralateral normal muscle of healthy mice breathing gases with different pO(2) were compared. The pO(2) in the blood can depend on the oxygen content in the breathing gas while tissue pO(2) was not directly influenced by pO(2) in the breathing gas. The decay constants of CmP and TPL in tumor tissue were significantly larger than in the normal muscles, and lower linewidths of CmP and TPL in tumor tissue was observed. The SCC tumor showed intracellular hypoxia even though the extracellular pO(2) is similar to normal tissue in the peripheral region. PMID:21212532

  8. Impact of Intraoperative Events on Cerebral Tissue Oximetry in Patients Undergoing Cardiopulmonary Bypass.

    PubMed

    Ševerdija, Ervin E; Vranken, Nousjka P A; Teerenstra, Steven; Ganushchak, Yuri M; Weerwind, Patrick W

    2015-03-01

    Previous studies showed that decreased cerebral saturation during cardiac surgery is related to adverse postoperative outcome. Therefore, we investigated the influence of intraoperative events on cerebral tissue saturation in patients undergoing cardiac surgery with cardiopulmonary bypass (CPB). A total of 52 adult patients who underwent cardiac surgery using pulsatile CPB were included in this prospective explorative study. Cerebral tissue oxygen saturation (SctO2) was measured in both the left and right cerebral hemisphere. Intraoperative events, involving interventions performed by anesthesiologist, surgeon, and clinical perfusionist, were documented. Simultaneously, in-line hemodynamic parameters (partial oxygen pressure, partial carbon dioxide pressure, hematocrit, arterial blood pressure, and CPB flow rates) were recorded. Cerebral tissue saturation was affected by anesthetic induction (p < .001), placement of the sternal retractor (p < .001), and initiation (p < .001) as well as termination of CPB (p < .001). Placement (p < .001) and removal of the aortic cross-clamp (p = .026 for left hemisphere, p = .048 for right hemisphere) led to changes in cerebral tissue saturation. In addition, when placing the aortic crossclamp, hematocrit (p < .001) as well as arterial (p = .007) and venous (p < .001) partial oxygen pressures changed. Cerebral tissue oximetry effectively identifies changes related to surgical events or vulnerable periods during cardiac surgery. Future studies are needed to identify methods of mitigating periods of reduced cerebral saturation. PMID:26390677

  9. Newborn Critical Congenital Heart Disease Screening Using Pulse Oximetry: Nursing Aspects.

    PubMed

    Hom, Lisa A; Martin, Gerard R

    2016-09-01

    Congenital heart disease (CCHD) is the most common birth defect. Screening for the most critical forms (CCHD) using pulse oximetry was added to the Recommended Uniform Screening Panel in the United States in 2011. Since then, CCHD screening has become nearly universal in the United States. Nurses are ideally situated to contribute to the development of best practices for implementation and provide education to families on CCHD screening. Much of the standardization, advocacy, and development of national recommendations occurred with key input from nurses. Nurses often have responsibility for educating parents, performing the screening, interpreting the screening algorithm, and the documentation of results. The nurse role often includes implementing follow-up quality improvement initiatives to ensure that systematic and accurate screening occurs. Smooth implementation can be achieved by identifying champions early, obtaining input from a multidisciplinary team including both physician and nursing leaders, and identifying ways to integrate screening into already existing workflow. By knowing the basics of why screening is important, how to screen, current recommendations on the follow-up for positive screens and the limitations of CCHD screening, nurses can advocate for their patients and positively impact outcomes for infants born with CCHD through early identification before discharge. PMID:27603538

  10. Comparison of NIRS, laser Doppler flowmetry, photoplethysmography, and pulse oximetry during vascular occlusion challenges.

    PubMed

    Abay, T Y; Kyriacou, P A

    2016-04-01

    Monitoring changes in blood volume, blood flow, and oxygenation in tissues is of vital importance in fields such as reconstructive surgery and trauma medicine. Near infrared spectroscopy (NIRS), laser Doppler (LDF) flowmetry, photoplethysmography (PPG), and pulse oximetry (PO) contribute to such fields due to their safe and noninvasive nature. However, the techniques have been rarely investigated simultaneously or altogether. The aim of this study was to investigate all the techniques simultaneously on healthy subjects during vascular occlusion challenges. Sensors were attached on the forearm (NIRS and LDF) and fingers (PPG and PO) of 19 healthy volunteers. Different degrees of vascular occlusion were induced by inflating a pressure cuff on the upper arm. The responses of tissue oxygenation index (NIRS), tissue haemoglobin index (NIRS), flux (LDF), perfusion index (PPG), and arterial oxygen saturation (PO) have been recorded and analyzed. Moreover, the optical densities were calculated from slow varying dc PPG, in order to distinguish changes in venous blood volumes. The indexes showed significant changes (p  <  0.05) in almost all occlusions, either venous or over-systolic occlusions. However, differentiation between venous and arterial occlusion by LDF may be challenging and the perfusion index (PI) may not be adequate to indicate venous occlusions. Optical densities may be an additional tool to detect venous occlusions by PPG. PMID:26963349

  11. Neural networks and wavelet analysis in the computer interpretation of pulse oximetry data

    SciTech Connect

    Dowla, F.U.; Skokowski, P.G.; Leach, R.R. Jr.

    1996-03-01

    Pulse oximeters determine the oxygen saturation level of blood by measuring the light absorption of arterial blood. The sensor consists of red and infrared light sources and photodetectors. A method based on neural networks and wavelet analysis is developed for improved saturation estimation in the presence of sensor motion. Spectral and correlation functions of the dual channel oximetry data are used by a backpropagation neural network to characterize the type of motion. Amplitude ratios of red to infrared signals as a function of time scale are obtained from the multiresolution wavelet decomposition of the two-channel data. Motion class and amplitude ratios are then combined to obtain a short-time estimate of the oxygen saturation level. A final estimate of oxygen saturation is obtained by applying a 15 s smoothing filter on the short-time measurements based on 3.5 s windows sampled every 1.75 s. The design employs two backpropagation neural networks. The first neural network determines the motion characteristics and the second network determines the saturation estimate. Our approach utilizes waveform analysis in contrast to the standard algorithms that are based on the successful detection of peaks and troughs in the signal. The proposed algorithm is numerically efficient and has stable characteristics with a reduced false alarm rate with a small loss in detection. The method can be rapidly developed on a digital signal processing platform.

  12. Oximetry Signal Processing Identifies REM Sleep-Related Vulnerability Trait in Asthmatic Children

    PubMed Central

    Perez, Geovanny F.; Gutierrez, Maria J.; Huseni, Shehlanoor; Pancham, Khrisna; Rodriguez-Martinez, Carlos E.; Nino, Cesar L.; Nino, Gustavo

    2013-01-01

    Rationale. The sleep-related factors that modulate the nocturnal worsening of asthma in children are poorly understood. This study addressed the hypothesis that asthmatic children have a REM sleep-related vulnerability trait that is independent of OSA. Methods. We conducted a retrospective cross-sectional analysis of pulse-oximetry signals obtained during REM and NREM sleep in control and asthmatic children (n = 134). Asthma classification was based on preestablished clinical criteria. Multivariate linear regression model was built to control for potential confounders (significance level P ≤ 0.05). Results. Our data demonstrated that (1) baseline nocturnal respiratory parameters were not significantly different in asthmatic versus control children, (2) the maximal % of SaO2 desaturation during REM, but not during NREM, was significantly higher in asthmatic children, and (3) multivariate analysis revealed that the association between asthma and REM-related maximal % SaO2 desaturation was independent of demographic variables. Conclusion. These results demonstrate that children with asthma have a REM-related vulnerability trait that impacts oxygenation independently of OSA. Further research is needed to delineate the REM sleep neurobiological mechanisms that modulate the phenotypical expression of nocturnal asthma in children. PMID:24288619

  13. Effect of latitudinal variations in low-level baroclinicity on eddy life cycles and upper-tropospheric wave-breaking processes

    NASA Astrophysics Data System (ADS)

    Rivière, G.

    2009-09-01

    Storm tracks play a crucial role in the dynamics of the general circulation of the atmosphere and particularly of the teleconnections such as the North Atlantic Oscillation (NAO). Baroclinic waves may displace the large-scale jets during their breaking with anticyclonic and cyclonic wave breaking leading generally to a northward and southward displacement of the jets respectively. For example, it has been recently shown by different authors that the positive and the negative phases of the NAO are closely related to anticyclonic and cyclonic wave breaking respectively. The purpose of our study is to look at the reverse side: the impact of the jet latitude onto wave-breaking processes by performing idealized numerical simulations using a primitive-equation model on the sphere (the PUMA model). We first focus on normal mode analysis. By prescribing different types of jets, we study the effects of their latitude on normal mode structures and their breaking using nonlinear simulations. A second stage consists in forcing the model by relaxing the temperature field toward a given restoration temperature. Sensitivity runs are performed by using different restoration temperature fields to look at the effect of the latitude of the low-level baroclinicity on eddy life cycles. Implication for the eddy feedback onto the large-scale circulation is more precisely investigated. Our results reveal that eddies exert a positive feedback onto the latitudinal variations of the large-scale jets. Finally, these results are used to interpret some wave-breaking processes found in the observations of the Northern Hemisphere.

  14. Diurnal ozone variations in the stratosphere revealed in observations from the Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES) on board the International Space Station (ISS)

    NASA Astrophysics Data System (ADS)

    Sakazaki, Takatoshi; Fujiwara, Masatomo; Mitsuda, Chihiro; Imai, Koji; Manago, Naohiro; Naito, Yoko; Nakamura, Tetsu; Akiyoshi, Hideharu; Kinnison, Douglas; Sano, Takuki; Suzuki, Makoto; Shiotani, Masato

    2013-04-01

    Considerable uncertainties remain in the global pattern of diurnal variation in stratospheric ozone, particularly lower to middle stratospheric ozone, which is the principal contributor to total column ozone. The Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES) attached to the Japanese Experiment Module (JEM) on board the International Space Station (ISS) was developed to gather high-quality global measurements of stratospheric ozone at various local times, with the aid of superconducting mixers cooled to 4K by a compact mechanical cooler. Using the SMILES dataset, as well as data from nudged chemistry-climate models (MIROC3.2-CTM and SD-WACCM), we show that the SMILES observational data have revealed the global pattern of diurnal ozone variations throughout the stratosphere. We also found that these variations can be explained by both photochemistry and dynamics. The peak-to-peak difference in the stratospheric ozone mixing ratio (total column ozone) reached 8% (1%) over the course of a day. This variation needs to be considered when merging ozone data from different satellite measurements and even from measurements made using one specific instrument at different local times.

  15. Diurnal ozone variations in the stratosphere revealed in observations from the Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES) onboard the International Space Station (ISS)

    NASA Astrophysics Data System (ADS)

    Sakazaki, Takatoshi; Fujiwara, Masatomo; Mitsuda, Chihiro; Imai, Koji; Manago, Naohiro; Naito, Yoko; Nakamura, Tetsu; Akiyoshi, Hideharu; Kinnison, Douglas; Sano, Takuki; Suzuki, Makoto; Shiotani, Masato

    2013-04-01

    Considerable uncertainties remain in the global pattern of diurnal variation in stratospheric ozone, particularly lower to middle stratospheric ozone, which is the principal contributor to total column ozone. The Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES) attached to the Japanese Experiment Module (JEM) on board the International Space Station (ISS), was developed to gather high-quality global measurements of stratospheric ozone at various local times, with the aid of superconducting mixers cooled to 4 K by a compact mechanical cooler. Using the SMILES dataset, as well as data from nudged chemistry-climate models (MIROC3.2-CTM and SD-WACCM), we show that the SMILES observational data have revealed the global pattern of diurnal ozone variations throughout the stratosphere. We also found that these variations can be explained by both photochemistry and dynamics. The peak-to-peak difference in the stratospheric ozone mixing ratio (total column ozone) reached 8% (1%) over the course of a day. This variation needs to be considered when merging ozone data from different satellite measurements and even from measurements made using one specific instrument at different local times.

  16. On the altitude-variation of electron acceleration by HF radio-waves in the F-region

    NASA Astrophysics Data System (ADS)

    Gustavsson, Bjorn

    2016-07-01

    I will talk about artificial aurora, the descending layers we have observed at HAARP and the altitude-variations we have observed in enhanced ion and plasma-lines with the EISCAT UHF-radar, and present an empirical model describing these phenomena.

  17. Can we Replace Arterial Blood Gas Analysis by Pulse Oximetry in Neonates with Respiratory Distress Syndrome, who are Treated According to INSURE Protocol?

    PubMed Central

    Niknafs, Pedram; Norouzi, Elahe; Bahman Bijari, Bahareh; Baneshi, Mohammad Reza

    2015-01-01

    Neonates with respiratory distress syndrome (RDS), who are treated according to INSURE protocol; require arterial blood gas (ABG) analysis to decide on appropriate management. We conducted this study to investigate the validity of pulse oximetry instead of frequent ABG analysis in the evaluation of these patients. From a total of 193 blood samples obtained from 30 neonates <1500 grams with RDS, 7.2% were found to have one or more of the followings: acidosis, hypercapnia, or hypoxemia. We found that pulse oximetry in the detection of hyperoxemia had a good validity to appropriately manage patients without blood gas analysis. However, the validity of pulse oximetry was not good enough to detect acidosis, hypercapnia, and hypoxemia. PMID:25999627

  18. Numerical simulation of surface wave dynamics of liquid metal MHD flow on an inclined plane in a magnetic field with spatial variation

    NASA Astrophysics Data System (ADS)

    Gao, Donghong

    Interest in utilizing liquid metal film flows to protect the plasma-facing solid structures places increasing demand on understanding the magnetohydrodynamics (MHD) of such flows in a magnetic field with spatial variation. The field gradient effect is studied by a two-dimensional (2D) model in Cartesian coordinates. The thin film flow down an inclined plane in spanwise (z-direction) magnetic field with constant streamwise gradient and applied current is analyzed. The solution to the equilibrium flow shows forcefully the M-shaped velocity profile and dependence of side layer thickness on Ha-1/2 whose definition is based on field gradient. The major part of the dissertation is the numerical simulation of free surface film flows and understanding the results. The VOF method is employed to track the free surface, and the CSF model is combined with VOF method to account for surface dynamics condition. The code is validated with respect to Navier-Stokes solver and MHD implementation by computations of ordinary wavy films, MHD flat films and a colleague proposed film flow. The comparisons are performed against respective experimental, theoretical or numerical solutions, and the results are well matched with them. It is found for the ordinary water falling films, at low frequency and high flowrate, the small forcing disturbance at inlet flowrate develops into big roll waves preceded by small capillary bow waves; at high frequency and low Re, it develops into nearly sinusoidal waves with small amplitude and without fore-running capillary waves. The MHD surface instability is investigated for two kinds of film flows in constant streamwise field gradient: one with spatial disturbance and without surface tension, the other with inlet forcing disturbance and with surface tension. At no surface tension condition, the finite amplitude disturbance is rapidly amplified and degrades to irregular shape. With surface tension to maintain smooth interface, finite amplitude regular waves

  19. Direct Measurements of Oxygen Gradients in Spheroid Culture System Using Electron Parametric Resonance Oximetry.

    PubMed

    Langan, Laura M; Dodd, Nicholas J F; Owen, Stewart F; Purcell, Wendy M; Jackson, Simon K; Jha, Awadhesh N

    2016-01-01

    Advanced in vitro culture from tissues of different origin includes three-dimensional (3D) organoid micro structures that may mimic conditions in vivo. One example of simple 3D culture is spheroids; ball shaped structures typically used as liver and tumour models. Oxygen is critically important in physiological processes, but is difficult to quantify in 3D culture: and the question arises, how small does a spheroid have to be to have minimal micro-environment formation? This question is of particular importance in the growing field of 3D based models for toxicological assessment. Here, we describe a simple non-invasive approach modified for the quantitative measurement and subsequent evaluation of oxygen gradients in spheroids developed from a non-malignant fish cell line (i.e. RTG-2 cells) using Electron Paramagnetic Resonance (EPR) oximetry. Sonication of the paramagnetic probe Lithium phthalocyanine (LiPc) allows for incorporation of probe particulates into spheroid during its formation. Spectra signal strength after incorporation of probe into spheroid indicated that a volume of 20 μl of probe (stock solution: 0.10 mg/mL) is sufficient to provide a strong spectra across a range of spheroid sizes. The addition of non-toxic probes (that do not produce or consume oxygen) report on oxygen diffusion throughout the spheroid as a function of size. We provide evidence supporting the use of this model over a range of initial cell seeding densities and spheroid sizes with the production of oxygen distribution as a function of these parameters. In our spheroid model, lower cell seeding densities (∼2,500 cells/spheroid) and absolute size (118±32 μm) allow control of factors such as pre-existing stresses (e.g. ∼ 2% normoxic/hypoxic interface) for more accurate measurement of treatment response. The applied methodology provides an elegant, widely applicable approach to directly characterize spheroid (and other organoid) cultures in biomedical and toxicological

  20. Direct Measurements of Oxygen Gradients in Spheroid Culture System Using Electron Parametric Resonance Oximetry

    PubMed Central

    Langan, Laura M.; Dodd, Nicholas J. F.; Owen, Stewart F.; Purcell, Wendy M.; Jackson, Simon K.; Jha, Awadhesh N.

    2016-01-01

    Advanced in vitro culture from tissues of different origin includes three-dimensional (3D) organoid micro structures that may mimic conditions in vivo. One example of simple 3D culture is spheroids; ball shaped structures typically used as liver and tumour models. Oxygen is critically important in physiological processes, but is difficult to quantify in 3D culture: and the question arises, how small does a spheroid have to be to have minimal micro-environment formation? This question is of particular importance in the growing field of 3D based models for toxicological assessment. Here, we describe a simple non-invasive approach modified for the quantitative measurement and subsequent evaluation of oxygen gradients in spheroids developed from a non-malignant fish cell line (i.e. RTG-2 cells) using Electron Paramagnetic Resonance (EPR) oximetry. Sonication of the paramagnetic probe Lithium phthalocyanine (LiPc) allows for incorporation of probe particulates into spheroid during its formation. Spectra signal strength after incorporation of probe into spheroid indicated that a volume of 20 μl of probe (stock solution: 0.10 mg/mL) is sufficient to provide a strong spectra across a range of spheroid sizes. The addition of non-toxic probes (that do not produce or consume oxygen) report on oxygen diffusion throughout the spheroid as a function of size. We provide evidence supporting the use of this model over a range of initial cell seeding densities and spheroid sizes with the production of oxygen distribution as a function of these parameters. In our spheroid model, lower cell seeding densities (∼2,500 cells/spheroid) and absolute size (118±32 μm) allow control of factors such as pre-existing stresses (e.g. ∼ 2% normoxic/hypoxic interface) for more accurate measurement of treatment response. The applied methodology provides an elegant, widely applicable approach to directly characterize spheroid (and other organoid) cultures in biomedical and toxicological

  1. Screening for Critical Congenital Heart Defects with Pulse Oximetry: Medical Aspects.

    PubMed

    Ewer, Andrew K

    2016-09-01

    The detection of newborn babies with potentially life-threatening, critical congenital heart defects (CCHDs) before they collapse or expire remains an important clinical challenge. The absence of physical signs and the difficulty assessing mild cyanosis means that the newborn baby check misses up to a third of babies. Fetal anomaly ultrasound scanning identifies an increasing proportion, but this screen is operator-dependent and therefore highly variable; although some units report very high detection rates, overall most babies with CCHD are still missed. Pulse oximetry screening (POS) is an additional test that meets the criteria for universal screening. POS increases overall detection of CCHD to over 90% and also identifies babies with noncardiac, hypoxemic conditions (such as congenital pneumonia, early-onset sepsis, and pulmonary hypertension), which are usually included in the false positives. There is a wealth of published data on the POS, both in a research setting and more recently in routine clinical practice, and consideration of POS is becoming increasingly widespread particularly among high-income countries. But a degree of controversy still remains, and debate continues regarding the most appropriate time to screen, the most effective screening pathway, and screening outside the well-baby nursery. So, should all newborn babies be screened with POS, if so, when and where should screening take place, what saturations are acceptable, and which conditions are we trying to identify? This review will look at the available evidence and try to suggest the way forward for those considering its introduction into their clinical practice. PMID:27603536

  2. Transcutaneous Oximetry May Predict Wound Healing Complications In Preoperatively Radiated Soft Tissue Sarcoma

    PubMed Central

    Nystrom, Lukas M; Miller, Benjamin J

    2016-01-01

    Background Preoperative radiation is frequently used in management of soft tissue sarcoma. We hypothesize that anoxic tissue from preoperative radiation contributes to surgical wound complications and that transcutaneous oximetry (TcO2) measurements made preoperatively can predict wounds at risk. Methods Ten consecutive patients were prospectively enrolled. TcO2 was recorded at five time points. Wound complications (defined as major or minor) and healing outcomes were recorded out to 120 days postoperatively. Means between groups with and without wound complications were compared by use of a Student’s t-test (p < 0.05). Results There were three major and one minor wound complication. During the time from radiation to surgery, patients with wound complications had a 13.1 mmHg decrease in mean TcO2 while those who healed uneventfully had an increase of 2.3 mm Hg (p=0.09). Patients with complications had a low preoperative TcO2 of 18.7 mmHg compared to those without complications (18.7 vs. 33.4 mmHg; p=0.09). No patient with a TcO2 greater than 25 mmHg immediately preoperatively developed a wound complication. Conclusions This data suggests an earlier recovery of tissue oxygenation in patients that healed without complication. The TcO2 measurement immediately preceding surgery seems to be the most important in predicting wound complications. Larger scale investigation may determine if TcO2 measurement is a viable clinical tool to aid in risk assessment for potential wound complications. PMID:27528847

  3. Visible light optical coherence tomography for microvascular oximetry in ocular circulation (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Chen, Siyu; Yi, Ji; Zhang, Hao F.

    2016-03-01

    Visible light optical coherence tomography (vis-OCT) is intrinsically capable of optical determination of blood oxygen saturation (sO2). Thanks to its 3D sectioning ability, confounding factors that plaque multi-wavelength fundus photography can be avoided. We further supplemented it with motion-enhanced angiography (vis-OCTA), which allowed us to resolve retinal micro vessels without losing spectral information. As a result, spectroscopic vis-OCTA can extract microvascular sO2 which are generally inaccessible. Here we extend the theoretical formulation of vis-OCTA oximetry to include optical attenuation, scattering and motion contrast. The model allows robust estimation of sO2, while also promising reduction of illuminating power to 1/3 of current value of ~1 mW. To demonstrate the capability of our approach, we performed oxygen challenge while taking vis-OCTA measurements on rat ocular circulation in vivo. We supplied the experiment animal with the following gas mixture: normal air, 5% CO2 air, pure O2 and 10% O2 air. For each inhalation gas, the OCTA measurements were compared with peripheral capillary sO2 (spO2) provided by a pulse oximeter. The retinal artery sO2 measurements corresponded well with spO2 reading as expected (R2 = 0.87). We found that both retinal and choroidal circulation sO2 moderately increased when we supplied 5% CO2 air. 100% O2 inhalation significantly increased both artery and vein oxygenation. On the contrary, 10% O2 air could deplete the oxygen reservoir in the circulation and lead to low sO2 readings.

  4. Diurnal variations of the propagation conditions of short-wave signals on a high-latitude path in the winter

    NASA Astrophysics Data System (ADS)

    Mingalev, V. S.; Orlova, M. I.; Evlashina, M. L.; Krivilev, V. N.; Mingaleva, G. I.

    1987-08-01

    The propagation trajectories of short waves on a path from the North Magnetic Pole to Murmansk in the course of a complete winter day is calculated on the basis of the electron density distribution determined using a numerical model of the convective polar ionosphere. It is shown that the propagation of the signals may be impossible at certain hours of local time, while, at those hours when it is possible, the ray trajectories can be of different types: beat, channeled between the E and F layers, ricocheting with chord propagation, and their combinations.

  5. Noise, transient dynamics, and the generation of realistic interspike interval variation in square-wave burster neurons.

    PubMed

    Marin, Bóris; Pinto, Reynaldo Daniel; Elson, Robert C; Colli, Eduardo

    2014-10-01

    First return maps of interspike intervals for biological neurons that generate repetitive bursts of impulses can display stereotyped structures (neuronal signatures). Such structures have been linked to the possibility of multicoding and multifunctionality in neural networks that produce and control rhythmical motor patterns. In some cases, isolating the neurons from their synaptic network reveals irregular, complex signatures that have been regarded as evidence of intrinsic, chaotic behavior. We show that incorporation of dynamical noise into minimal neuron models of square-wave bursting (either conductance-based or abstract) produces signatures akin to those observed in biological examples, without the need for fine tuning of parameters or ad hoc constructions for inducing chaotic activity. The form of the stochastic term is not strongly constrained and can approximate several possible sources of noise, e.g., random channel gating or synaptic bombardment. The cornerstone of this signature generation mechanism is the rich, transient, but deterministic dynamics inherent in the square-wave (saddle-node and homoclinic) mode of neuronal bursting. We show that noise causes the dynamics to populate a complex transient scaffolding or skeleton in state space, even for models that (without added noise) generate only periodic activity (whether in bursting or tonic spiking mode). PMID:25375534

  6. Geomagnetically conjugate observations of ionospheric and thermospheric variations accompanied with a midnight brightness wave at low latitudes

    NASA Astrophysics Data System (ADS)

    Fukushima, D.; Shiokawa, K.; Otsuka, Y.; Kubota, M.; Yokoyama, T.; Nishioka, M.; Komonjinda, S.; Yatini, C. Y.

    2014-12-01

    A midnight brightness wave (MBW) is the phenomenon that the OI (630-nm) airglow enhancement propagates poleward once at local midnight. In this study, we first conducted geomagnetically conjugate observations of 630nm airglow for an MBW at conjugate stations. An airglow enhancement which is considered to be an MBW was observed in the 630-nm airglow images at Kototabang, Indonesia (geomagnetic latitude (MLAT): 10.0S) at around local midnight from 1540 to 1730 UT (from 2240 to 2430 LT) on 7 February 2011. This MBW was propagating south-southwestward, which is geomagnetically poleward, with a velocity of 290 m/s. However, similar wave was not observed in the 630-nm airglow images at Chiang Mai, Thailand (MLAT: 8.9N), which is close to being conjugate point of Kototabang. This result indicates that the MBW does not have geomagnetic conjugacy. We simultaneously observed thermospheric neutral winds observed by a co-located Fabry-Perot interferometer at Kototabang. The observed meridional winds turned from northward (geomagnetically equatorward) to southward (geomagnetically poleward) just before the MBW was observed. The bottomside ionospheric heights observed by ionosondes rapidly decreased at Kototabang and slightly increased at Chiang Mai simultaneously with the MBW passage. In the presentation, we discuss the MBW generation by the observed poleward neutral winds at Kototabang, and the cause of the coinciding small height increase at Chiang Mai by the polarization electric field inside the observed MBW at Kototabang.

  7. Measurements of Diurnal Variations of Upper Stratospheric ClO with a Ground-based Millimeter-wave Radiometer at Atacama, Chile

    NASA Astrophysics Data System (ADS)

    Kuwahara, T.; Mizuno, A.; Nagahama, T.; Maezawa, H.; Toriyama, N.; Kojima, Y.

    2010-12-01

    We present the first results of measuring the stratospheric chlorine monoxide (ClO) with a ground-based millimeter-wave radiometer at Atacama highland (23S, 68W, Alt. 4800 m), Chile. The chlorine chemistry plays an essential role in the ozone depletion in the upper stratosphere, and ClO is a key molecule for better understandings of the chlorines chemistry and the ozone recovery processes. However, measurements of the ClO distribution in the upper stratosphere are still limited at present because the ClO spectrum can be measured only in millimeter-wave region and its intensity is considerably weak. Therefore, we had newly installed a ground-based millimeter-wave radiometer equipped with a high sensitivity receiver at Atacama highland, Chile in 2004, and started monitoring the vertical profiles of the stratospheric ClO in 2008. Atacama highland is in a desert area of the northern part of Chile, being one of the most suitable places for millimeter-wave observations. Our instrument equips a superconducting (SIS) mixer receiver whose noise temperature is 170 K in double sideband at 204 GHz and a digital FFT spectrometer covering 1 GHz bandwidth with 70 kHz frequency resolution. We had continuously observed ClO spectra in 204 GHz band every 2 minutes from December 2009 to January 2010, and had obtained 11466 spectra. Vertical profiles of ClO in the upper stratosphere were retrieved from the spectra integrated every 2 hours in local time (LT) taken during 4 and 16 December. From these data, we have clearly detected a diurnal variation of ClO at 40 km. Comparing ClO mixing ratio obtained with our radiometer with those of AURA/MLS taken over our site at 12:00 - 15:00 LT, we had confirmed that they are consistent in range of errors. In this presentation, we will show the details of the diurnal variations of upper stratospheric ClO and comparisons among our results, AURA/MLS and JEM/SMILES.

  8. Determination of Bedrock Variations and S-wave Velocity Structure in the NW part of Turkey for Earthquake Hazard Mitigation

    NASA Astrophysics Data System (ADS)

    Ozel, A. O.; Arslan, M. S.; Aksahin, B. B.; Genc, T.; Isseven, T.; Tuncer, M. K.

    2015-12-01

    Tekirdag region (NW Turkey) is quite close to the North Anatolian Fault which is capable of producing a large earthquake. Therefore, earthquake hazard mitigation studies are important for the urban areas close to the major faults. From this point of view, integration of different geophysical methods has important role for the study of seismic hazard problems including seismotectonic zoning. On the other hand, geological mapping and determining the subsurface structure, which is a key to assist management of new developed areas, conversion of current urban areas or assessment of urban geological hazards can be performed by integrated geophysical methods. This study has been performed in the frame of a national project, which is a complimentary project of the cooperative project between Turkey and Japan (JICA&JST), named as "Earthquake and Tsunami Disaster Mitigation in the Marmara Region and Disaster Education". With this principal aim, this study is focused on Tekirdag and its surrounding region (NW of Turkey) where some uncertainties in subsurface knowledge (maps of bedrock depth, thickness of quaternary sediments, basin geometry and seismic velocity structure,) need to be resolved. Several geophysical methods (microgravity, magnetic and single station and array microtremor measurements) are applied and the results are evaluated to characterize lithological changes in the region. Array microtremor measurements with several radiuses are taken in 30 locations and 1D-velocity structures of S-waves are determined by the inversion of phase velocities of surface waves, and the results of 1D structures are verified by theoretical Rayleigh wave modelling. Following the array measurements, single-station microtremor measurements are implemented at 75 locations to determine the predominant frequency distribution. The predominant frequencies in the region range from 0.5 Hz to 8 Hz in study area. On the other hand, microgravity and magnetic measurements are performed on

  9. Reflection-induced linear polarization rotation and phase modulation between orthogonal waves for refractive index variation measurement.

    PubMed

    Twu, Ruey-Ching; Wang, Jhao-Sheng

    2016-04-01

    An optical phase interrogation is proposed to study reflection-induced linear polarization rotation in a common-path homodyne interferometer. This optical methodology can also be applied to the measurement of the refractive index variation of a liquid solution. The performance of the refractive index sensing structure is discussed theoretically, and the experimental results demonstrated a very good ability based on the proposed schemes. Compared with a conventional common-path heterodyne interferometer, the proposed homodyne interferometer with only a single channel reduced the usage of optic elements. PMID:27192320

  10. Thermospheric gravity waves near the source - Comparison of variations in neutral temperature and vertical velocity at Sondre Stromfjord

    NASA Technical Reports Server (NTRS)

    Herrero, F. A.; Mayr, H. G.; Harris, I.; Varosi, F.; Meriwether, J. W., Jr.

    1984-01-01

    Theoretical predictions of thermospheric gravity wave oscillations are compared with observed neutral temperatures and velocities. The data were taken in February 1983 using a Fabry-Perot interferometer located on Greenland, close to impulse heat sources in the auroral oval. The phenomenon was modeled in terms of linearized equations of motion of the atmosphere on a slowly rotating sphere. Legendre polynomials were used as eigenfunctions and the transfer function amplitude surface was characterized by maxima in the wavenumber frequency plane. Good agreement for predicted and observed velocities and temperatures was attained in the 250-300 km altitude. The amplitude of the vertical velocity, however, was not accurately predicted, nor was the temperature variability. The vertical velocity did exhibit maxima and minima in response to corresponding temperature changes.

  11. Measurement of time-resolved oxygen concentration changes in photosynthetic systems by nitroxide-based EPR oximetry.

    PubMed

    Strzalka, K; Walczak, T; Sarna, T; Swartz, H M

    1990-09-01

    The application of recent developments of EPR oximetry to photosynthetic systems is described and used to study rapid processes in isolated thylakoid membranes from spinach and in intact photoautotrophic soybean cells. Using the peak heights of 15N perdeuterated Tempone and two microwave power levels oxygen evolution and consumption were measured. The method measured time-resolved oxygen concentration changes in the micromolar range. Oxygen evolution was linearly proportionate to the chlorophyl concentration of thylakoid membrane over the range studied (0-2 mg/ml). Oxygen evolution associated with single turnover light pulses was consistent with the four state model. The time (t1/2) to reach equilibrium of oxygen concentrations after a single turnover pulse was 0.4-0.5 ms, indicating that the evolution of oxygen coupled to the S4-S0 transition may be shorter than reported previously. The time for equilibrium of oxygen after single turnover pulses in soybean cells was relatively long (400 ms), which suggests that there are significant barriers to the free diffusion of oxygen in this system. The method also was used to study oxygen consumption by the electron transport chain of photosystem I and photosystem II. We conclude that EPR oximetry can provide quantitative and time-resolved data on oxygen concentrations with a sensitivity that is useful for studies of such systems. PMID:2168161

  12. Evaluation of oxygen-response times of phthalocyanine-based crystalline paramagnetic spin probes for EPR oximetry

    PubMed Central

    Vikram, Deepti S.; Ahmad, Rizwan; Pandian, Ramasamy P.; Petryakov, Sergey; Kuppusamy, Periannan

    2009-01-01

    The goal of the present study was to evaluate the temporal response of particulate-based EPR oximetry probes to changes in partial pressure of oxygen (pO2). In order to accurately evaluate the oxygen-response time, we developed a method for rapid modulation of pO2 in a chamber containing the probe using an oscillator-driven speaker–diaphragm setup. The apparatus was capable of producing sinusoidal changes in pO2 at frequencies up to 300 Hz or more. The pressure-modulation setup was used to evaluate the temporal response of some of the most commonly used phthalocyanine-based particulate probes. For validation, the time-response of the probes was compared to that of a high sensitivity pressure sensor. The results revealed that some particulate probes could respond to changes in pO2 with a temporal response of 3.3 ms (300 Hz). The observations were interpreted in the light of their crystalline packing in favor of oxygen diffusion. The results of the present study should enable the selection of probes for oximetry applications requiring high temporal resolution. PMID:18479953

  13. A novel analytical method to evaluate directly catalase activity of microorganisms and mammalian cells by ESR oximetry.

    PubMed

    Nakamura, Keisuke; Kanno, Taro; Mokudai, Takayuki; Iwasawa, Atsuo; Niwano, Yoshimi; Kohno, Masahiro

    2010-09-01

    Electron spin resonance (ESR) oximetry technique was applied for analysis of catalase activity in the present study. Catalase activity was evaluated by measuring oxygen from the reaction between hydrogen peroxide (H(2)O(2)) and catalase-positive cells. It was demonstrated that the ESR spectra of spin-label probes, 4-hydroxy-2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPOL), 4-oxo-2,2,6,6-tetramethyl-1-piperidinyloxy (4-oxo-TEMPO) and 4-maleimido-2,2,6,6-tetramethyl-1-piperidinyloxy (4-maleimido-TEMPO) in the presence of H(2)O(2) were broadened with the concentrations of catalase. It was possible to make a calibration curve for catalase activity by peak widths of the spectra of each spin-label probe, which are broadened dependently on catalase concentrations. The broadened ESR spectra were also observed when the catalase-positive micro-organisms or the mammalian cells originally from circulating monocytes/macrophages were mixed with TEMPOL and H(2)O(2). Meanwhile, catalase-negative micro-organisms caused no broadening change of ESR spectra. The present study indicates that it is possible to evaluate directly the catalase activity of various micro-organisms and mammalian cells by using an ESR oximetry technique. PMID:20815766

  14. Modeling the variations of reflection coefficient of Earth's lower ionosphere using very low frequency radio wave data by artificial neural network

    NASA Astrophysics Data System (ADS)

    Ghanbari, Keyvan; Khakian Ghomi, Mehdi; Mohammadi, Mohammad; Marbouti, Marjan; Tan, Le Minh

    2016-08-01

    The ionized atmosphere lying from 50 to 600 km above surface, known as ionosphere, contains high amount of electrons and ions. Very Low Frequency (VLF) radio waves with frequencies between 3 and 30 kHz are reflected from the lower ionosphere specifically D-region. A lot of applications in long range communications and navigation systems have been inspired by this characteristic of ionosphere. There are several factors which affect the ionization rate in this region, such as: time of day (presence of sun in the sky), solar zenith angle (seasons) and solar activities. Due to nonlinear response of ionospheric reflection coefficient to these factors, finding an accurate relation between these parameters and reflection coefficient is an arduous task. In order to model these kinds of nonlinear functionalities, some numerical methods are employed. One of these methods is artificial neural network (ANN). In this paper, the VLF radio wave data of 4 sudden ionospheric disturbance (SID) stations are given to a multi-layer perceptron ANN in order to simulate the variations of reflection coefficient of D region ionosphere. After training, validation and testing the ANN, outputs of ANN and observed values are plotted together for 2 random cases of each station. By evaluating the results using 2 parameters of pearson correlation coefficient and root mean square error, a satisfying agreement was found between ANN outputs and real observed data.

  15. Short baseline variations in site response and wave-propagation effects and their structural causes: Four examples in and around the santa clara valley, California

    USGS Publications Warehouse

    Hartzell, S.; Ramirez-Guzman, L.; Carver, D.; Liu, P.

    2010-01-01

    Ground motion records of local and regional events from a portable array are used to investigate the structural causes of variations in ground motion over distances of a few hundred meters to a few kilometers in the sedimentary basin environment of the Santa Clara Valley, California, and its margins. Arrays of portable seismic stations are used to target four study areas with different ground motion patterns: (1) an edge of the alluvial basin extending up onto a marginal ridge (Blossom Hill), (2) a Cenozoic basin with a nearly flat bottom (Cupertino Basin), (3) a long, narrow Cenozoic basin with a steep V profile (Evergreen Basin), and (4) a line perpendicular to the trace of the Hayward fault. Average peak velocities on Blossom Hill from local earthquakes are a factor of 2.5 times higher than nearby valley sites. Three-dimensional (3D) modeling is used to conclude that the majority of the amplification is due to lower shear-wave velocities along a local fault zone (Shannon–Berrocal). Site amplification over the Cupertino Basin in the frequency band 0.5–4 Hz is generally low (less than 2.0 relative to a Mesozoic rock site) and spatially uniform. This response is attributed to the shallow, flat-bottomed shape of the basin and the uniform, flat-laying sedimentary fill. In contrast, site amplification in the Evergreen Basin generally exceeds 3.0 and is attributed to the deep, V-shaped geometry of the basin and younger sedimentary fill. 3D waveform modeling shows the elongated shape of the Evergreen Basin causes more efficient trapping of long-period waves for sources along the long axis of the basin. A low-velocity zone is postulated along the Hayward fault with a width between 100 and 200 m, based on elevated site response along the fault trace and 4.5-Hz fault zone guided waves on the horizontal components of stations near the fault.

  16. SWDreader: A Wavelet-Based Algorithm Using Spectral Phase to Characterize Spike-Wave Morphological Variation in Genetic Models of Absence Epilepsy

    PubMed Central

    Richard, CD; Tanenbaum, A; Audit, B; Arneodo, A; Khalil, A; Frankel, WN

    2014-01-01

    Background Spike-wave discharges (SWD) found in neuroelectrical recordings are pathognomonic to absence epilepsy. The characteristic spike-wave morphology of the spike-wave complex (SWC) constituents of SWDs can be mathematically described by a subset of possible spectral power and phase values. Morlet wavelet transform (MWT) generates time-frequency representations well-suited to identifying this SWC-associated subset. New method MWT decompositions of SWDs reveal spectral power concentrated at harmonic frequencies. The phase relationships underlying SWC morphology were identified by calculating the differences between phase values at SWD fundamental frequency and the 2nd, 3rd and 4th harmonics. The three phase differences were then used as coordinates to generate a density distribution in a {360° × 360° × 360°} phase difference space. Strain-specific density distributions were generated from SWDs of mice carrying the Gria4, Gabrg2 or Scn8a mutations to determine whether SWC morphological variants reliably mapped to the same regions of the distribution, and if distribution values could be used to detect SWD. Comparison with existing methods To the best of our knowledge, this algorithm is the first to employ spectral phase to quantify SWC morphology, making it possible to computationally distinguish SWC subtypes and detect SWDs. Results/conclusions Proof-of-concept testing of the SWDreader algorithm shows: (1) a major pattern of variation in SWC morphology maps to one axis of the phase difference distribution, (2) variability between the strain-specific distributions reflects differences in the proportion of SWC subtypes generated during SWD, and (3) regularities in the spectral power and phase profiles of SWCs can be used to detect waveforms possessing SWC-like morphology. PMID:25549550

  17. Application of TVD schemes for the Euler equations of gas dynamics. [method of Total Variation Diminishing for shock wave computation

    NASA Technical Reports Server (NTRS)

    Yee, H. C.; Warming, R. F.; Harten, A.

    1985-01-01

    Highly accurate and yet stable shock-capturing finite difference schemes have been designed for the computation of the Euler equations of gas dynamics. Four different principles for the construction of high resolution total variation diminishing (TVD) schemes are available, including hybrid schemes, a second-order extension of Godunov's scheme by van Leer (1979), the modified flux approach of Harten (1983, 1984), and the numerical fluctuation approach of Roe (1985). The present paper has the objective to review the class of second-order TVD schemes via the modified flux approach. Attention is given to first-order TVD schemes, a second-order accurate explicit TVD scheme, the global order of accuracy of the second-order TVD scheme, extensions to systems and two-dimensional conservation laws, numerical experiments with a second-order explicit TVD scheme, implicit TVD schemes, and second-order implicit TVD schemes.

  18. Rejection of Erroneous Saturation Data in Optical Pulse Oximetry in Newborn Patients

    NASA Astrophysics Data System (ADS)

    Scalise, L.; Marchionni, Paolo; Carnielli, Virgilio P.

    2011-08-01

    Pulse oximetry (PO) is extensively used in intensive care unit (ICU); this is mainly due to the fact that it is a non-invasive and real-time monitoring method. PO allows to measure arterial oxygen saturation (SaO2) and in particular hemoglobin oxygenation. Optical PO is typically realized by the use of a clip (to be applied on the ear or on the finger top) containing a couple of monochromatic LED sources and a photodiode. The main drawback with the use of PO is the presence of movement artifacts or disturbance due to optical sources and skin, causing erroneous saturation data. The aim of this work is to present the measurement procedure based on a specially developed algorithm able to reject erroneous oxygen saturation data during long lasting monitoring of patients in ICU and to compare measurement data with reference data provided by EGA. We have collected SaO2 data from a standard PO and used an intensive care unit monitor to collect data. This device was connected to our acquisition system and heart rate (HR) and SaO2 data were acquired and processed by our specially developed algorithm and directly reproduced on the PC screen for use by the clinicians. The algorithm here used for the individuation and rejection of erroneous saturation data is based on the assessment of the difference between the Heart Rate (HR) measured by respectively by the ECG and PO. We have used an emogasanalyzer (EGA) for comparison of the measured data. The study was carried out in a neonatal intensive care unit (NICU), using 817 data coming from 24 patients and the observation time was of about 10000 hours. Results show a reduction in the maximum difference between the SaO2 data measured, simultaneously, on the same patient by the EGA and by the proposed method of 14.20% and of the 4.76% in average over the 817 samples. The measurement method proposed is therefore able to individuate and eliminate the erroneous saturation data due to motion artifacts and reported by the pulse oxymeter

  19. Craniofacial tissue oxygen saturation is associated with blood pH using an examiner's finger-mounted tissue oximetry in mice

    NASA Astrophysics Data System (ADS)

    Uchida, Toshiyuki; Kanayama, Naohiro; Kawai, Kenta; Niwayama, Masatsugu

    2016-04-01

    Although fetal scalp blood sampling is an examination to assess fetal acidosis during the intrapartum period, it has not been widely used by obstetricians because of its invasiveness. We have developed a small, portable oximetry with a sensor attached to the examiner's finger. Our previous report using this oximetry concluded that fetal head tissue oxygen saturation (StO2) correlated with umbilical cord artery blood pH. We investigated whether the association between StO2 and blood pH in mice could be validated using this oximetry. Eleven the Institute for Cancer Research (ICR) mice were measured using a near-infrared spectroscopy probe at the craniofacial site in a closed polyethylene bag while changing the oxygen concentration. A total of nine blood samples were collected and analyzed for pH. The StO2 and tissue blood pH showed a strong positive correlation (r=0.90 and P=0.0009). The StO2 and total hemoglobin index also showed a positive correlation (r=0.84 and P=0.0049). Thus, the results of the present study support those of our previous report on clinical cases and allow examiners to easily check the status of fetal acidosis. Fetal management using this oximetry might gain popularity with obstetricians in the near future.

  20. Utility of the pediatric sleep questionnaire and pulse oximetry as screening tools in pediatric patients with suspected obstructive sleep apnea syndrome.

    PubMed

    Peña-Zarza, Jose A; Osona-Rodriguez de Torres, Borja; Gil-Sanchez, Jose Antonio; Figuerola-Mulet, Joan

    2012-01-01

    Objective. To assess the screening tools in snoring patients. Material and Methods. A retrospective review of data was conducted from children between 2 and 15 years old who were referred on suspicion of obstructive sleep apnea-hypopnea (OSAH) between June 2008 and June 2011. We excluded patients with significant comorbidities. Pediatric Sleep Questionnaire (PSQ), physical exam (PE), and pulse-oximetry data were collected and correlated with the results of the nightly polygraph at home. Results. We selected 98 patients. The 22-item version of the PSQ had sensitivity of 96% and specificity of 36.8%. The overall value of the clinic predictor of OSAH (PSQ and PE together) exhibited an increased specificity 57.6% with 94.6% of sensitivity. The nocturnal home oximetry method used alone was very specific, 92.1%, but had a lower sensitivity, 77.1%. The set of clinical assessment tools used together with pulse-oximetry screening provided excellent specificity 98.1% and a positive predictive value 94.1% globally. The performance of this screening tool is related with the severity of OSAH and accuracy is better in moderate and severe cases. Conclusion. The combination of clinical assessment and pulse-oximetry screening can provide a sufficient diagnostic approach for pediatric patients with suspected OSAH at least in moderate and severe cases. PMID:23471006

  1. Skeletal muscle and glioma oxygenation by carbogen inhalation in rats: a longitudinal study by EPR oximetry using single-probe implantable oxygen sensors.

    PubMed

    Hou, Huagang; Khan, Nadeem; Lariviere, Jean; Hodge, Sassan; Chen, Eunice Y; Jarvis, Lesley A; Eastman, Alan; Williams, Benjamin B; Kuppusamy, Periannan; Swartz, Harold M

    2014-01-01

    The feasibility of EPR oximetry using a single-probe implantable oxygen sensor (ImOS) was tested for repeated measurement of pO₂ in skeletal muscle and ectopic 9L tumors in rats. The ImOS (50 mm length) were constructed using nickel-chromium alloy wires, with lithium phthalocyanine (LiPc, oximetry probe) crystals loaded in the sensor loop and coated with AF 2400(®) Teflon. These ImOS were implanted into the skeletal muscle in the thigh and subcutaneous 9L tumors. Dynamic changes in tissue pO₂ were assessed by EPR oximetry at baseline, during tumor growth, and repeated hyperoxygenation with carbogen breathing. The mean skeletal muscle pO₂ of normal rats was stable and significantly increased during carbogen inhalation in experiments repeated for 12 weeks. The 9L tumors were hypoxic with a tissue pO₂ of 12.8 ± 6.4 mmHg on day 1; however, the response to carbogen inhalation varied among the animals. A significant increase in the glioma pO₂ was observed during carbogen inhalation on day 9 and day 14 only. In summary, EPR oximetry with ImOS allowed direct and longitudinal oxygen measurements in deep muscle tissue and tumors. The heterogeneity of 9L tumors in response to carbogen highlights the need to repeatedly monitor pO₂ to confirm tumor oxygenation so that such changes can be taken into account in planning therapies and interpreting results. PMID:24729220

  2. Beyond Critical Congenital Heart Disease: Newborn Screening Using Pulse Oximetry for Neonatal Sepsis and Respiratory Diseases in a Middle-Income Country

    PubMed Central

    Ang, Hak-Lee; Omar, Asma

    2015-01-01

    Background Studies on pulse oximetry screening for neonatal sepsis and respiratory disease in a middle-income country are lacking. Newborn screening for critical congenital heart disease (CCHD) using pulse oximetry is an effective and life-saving strategy in developed countries. While most studies have reported false-positive results during CCHD screening, they have not elaborated on the detected disease types. We studied the effectiveness and outcomes of pulse oximetry newborn screening for non-cardiac hypoxemic diseases such as neonatal sepsis, respiratory diseases, and CCHD in a middle-income country. Methods and Findings In a pilot study performed at the University Malaya Medical Centre (UMMC), Malaysia, all apparently healthy term newborns, delivered at UMMC were screened pre-discharge using pulse oximetry. Echocardiography was performed for newborns that had positive screening results on two separate occasions, 1-h apart. Newborns with normal echocardiograms were evaluated and treated for other non-cardiac diseases. Fifteen of 5247 term newborns had positive screening results. The median age at screening was 20 h. Thirteen newborns (0.24%) had significant non-cardiac diseases: sepsis (n = 2) and respiratory diseases (n = 11) that required hospitalization and treatment. The remaining two newborns with normal antenatal ultrasonograms had positive screening test and confirmed to have CCHD. Another 18 newborns with negative screening test were later admitted for treatment of sepsis (n = 16) and penumonia (n = 2). All newborns were treated and alive at the end of the study. The sensitivity and specificity of pulse oximetry screening for non-cardiac diseases were 42% and 99.9% respectively, and 100% and 99.7% for CCHD, respectively. Conclusions Routine pulse oximetry screening test was effective in identifying newborns with CCHD and other hypoxemia illnesses, which may led to potential life-threatening condition. This study showed that the expanded use of pulse

  3. On the variational computation of a large number of vibrational energy levels and wave functions for medium-sized molecules.

    PubMed

    Mátyus, Edit; Simunek, Ján; Császár, Attila G

    2009-08-21

    In a recent publication [J. Chem. Phys. 127, 084102 (2007)], the nearly variational DEWE approach (DEWE denotes Discrete variable representation of the Watson Hamiltonian using the Eckart frame and an Exact inclusion of a potential energy surface expressed in arbitrarily chosen coordinates) was developed to compute a large number of (ro)vibrational eigenpairs for medium-sized semirigid molecules having a single well-defined minimum. In this publication, memory, CPU, and hard disk usage requirements of DEWE, and thus of any DEWE-type approach, are carefully considered, analyzed, and optimized. Particular attention is paid to the sparse matrix-vector multiplication, the most expensive part of the computation, and to rate-determining steps in the iterative Lanczos eigensolver, including spectral transformation, reorthogonalization, and restart of the iteration. Algorithmic improvements are discussed in considerable detail. Numerical results are presented for the vibrational band origins of the (12)CH(4) and (12)CH(2)D(2) isotopologues of the methane molecule. The largest matrix handled on a personal computer during these computations is of the size of (4x10(8))x(4x10(8)). The best strategy for determining vibrational eigenpairs depends largely on the actual details of the required computation. Nevertheless, for a usual scenario requiring a large number of the lowest eigenpairs of the Hamiltonian matrix the combination of the thick-restart Lanczos method, shift-fold filtering, and periodic reorthogonalization appears to result in the computationally most feasible approach. PMID:19708731

  4. Photodynamic treatment of the RIF-1 tumor with verteporfin with online monitoring of tissue oxygen using electron paramagnetic resonance oximetry

    NASA Astrophysics Data System (ADS)

    Pogue, Brian W.; O'Hara, Julia A.; Liu, Ke J.; Hasan, Tayyaba; Swartz, Harold

    1999-06-01

    In this study, treatment of the RIF-1 tumor was examined with photodynamic therapy using Verteprofin (formerly benzoporphyrin derivative, BPD). The effects of two different optical dose rates were examined, with no detectable difference in the tumor regrowth time. Oxygen consumption during PDT could reliably be monitored with electron paramagnetic resonance (EPR) oximetry using an implanted paramagnetic material within the tumor. A reduction of the tumor pO2 was detected in the animals that were followed after treatment, suggesting that there was a compromise to the tumor vasculature that persisted throughout the measurements. At high total doses some of the tumors did not regrow. Altogether these results are indicative of the tumor destruction being caused by destruction of the blood vessels from the treatment.

  5. Pulse Oximetry: A Non-Invasive, Novel Marker for the Quality of Chest Compressions in Porcine Models of Cardiac Arrest

    PubMed Central

    Han, Fei; Li, Yan; Walline, Joseph; Fu, Yangyang; Yao, Dongqi; Zhang, Xiaocui; Zhang, Hui; Zhu, Huadong; Guo, Shubin; Wang, Zhong; Yu, Xuezhong

    2015-01-01

    Objective Pulse oximetry, which noninvasively detects the blood flow of peripheral tissue, has achieved widespread clinical use. We have noticed that the better the quality of cardiopulmonary resuscitation (CPR), the better the appearance of pulse oximetry plethysmographic waveform (POP). We investigated whether the area under the curve (AUC) and/or the amplitude (Amp) of POP could be used to monitor the quality of CPR. Design Prospective, randomized controlled study. Setting Animal experimental center in Peking Union Medical Collage Hospital, Beijing, China. Subjects Healthy 3-month-old male domestic swine. Interventions 34 local pigs were enrolled in this study. After 4 minutes of untreated ventricular fibrillation, animals were randomly assigned into two resuscitation groups: a “low quality” group (with a compression depth of 3cm) and a “high quality” group (with a depth of 5cm). All treatments between the two groups were identical except for the depth of chest compressions. Hemodynamic parameters [coronary perfusion pressure (CPP), partial pressure of end-tidal carbon dioxide (PETCO2)] as well as AUC and Amp of POP were all collected and analyzed. Measurements and Findings There were statistical differences between the “high quality” group and the “low quality” group in AUC, Amp, CPP and PETCO2 during CPR (P<0.05). AUC, Amp and CPP were positively correlated with PETCO2, respectively (P<0.01). There was no statistical difference between the heart rate calculated according to the POP (FCPR) and the frequency of mechanical CPR at the 3rd minute of CPR. The FCPR was lower than the frequency of mechanical CPR at the 6th and the 9th minute of CPR. Conclusions Both the AUC and Amp of POP correlated well with CPP and PETCO2 in animal models. The frequency of POP closely matched the CPR heart rate. AUC and Amp of POP might be potential noninvasive quality monitoring markers for CPR. PMID:26485651

  6. Variational wave functions for the S =1/2 Heisenberg model on the anisotropic triangular lattice: Spin liquids and spiral orders

    NASA Astrophysics Data System (ADS)

    Ghorbani, Elaheh; Tocchio, Luca F.; Becca, Federico

    2016-02-01

    By using variational wave functions and quantum Monte Carlo techniques, we investigate the complete phase diagram of the Heisenberg model on the anisotropic triangular lattice, where two out of three bonds have superexchange couplings J and the third one has instead J'. This model interpolates between the square lattice and the isotropic triangular one, for J'/J ≤1 , and between the isotropic triangular lattice and a set of decoupled chains, for J /J'≤1 . We consider all the fully symmetric spin liquids that can be constructed with the fermionic projective-symmetry group classification (Zhou and Wen, arXiv:cond-mat/0210662) and we compare them with the spiral magnetic orders that can be accommodated on finite clusters. Our results show that, for J'/J ≤1 , the phase diagram is dominated by magnetic orderings, even though a spin-liquid state may be possible in a small parameter window, i.e., 0.7 ≲J'/J ≲0.8 . In contrast, for J /J'≤1 , a large spin-liquid region appears close to the limit of decoupled chains, i.e., for J /J'≲0.6 , while magnetically ordered phases with spiral order are stabilized close to the isotropic point.

  7. Gravitational wave detection by a spherical antenna: The angular sensitivity of resonators in the truncated icosahedral gravitational wave antenna configuration and its variation with sidereal time and galactic longitude

    NASA Astrophysics Data System (ADS)

    Gasparini, Maria Alice

    2005-11-01

    Experimental projects using spherical antennas to detect gravitational waves are nowadays a concrete reality. The main purpose of this paper is to give a possible way of interpreting output data from such a system. Responses of the five fundamental quadrupole modes and of the six resonators in truncated icosahedral gravitational wave antenna (TIGA) collocations are shown as a function of the incoming direction of the incident wave. Then, for a source lying in the galactic plane, sidereal time and galactic longitude dependence is given. Thus, once a candidate source of gravitational waves is considered, we can exactly predict the resonators’ response as a function of time.

  8. Wave form variations in auditory event-related potentials evoked by a memory-scanning task and their relationship with tests of intellectual function.

    PubMed

    Pelosi, L; Holly, M; Slade, T; Hayward, M; Barrett, G; Blumhardt, L D

    1992-01-01

    The inter-subject wave form variability of auditory event-related potentials (ERPs) evoked by digit probe identification in a memory-scanning task (Sternberg paradigm) and the effects of reaction time (RT) and task difficulty were studied in 26 healthy subjects. The response wave forms were compared with the performance of psychological tests of intelligence and memory. ERPs to 1-digit sets consisted of a sequence of waves identified as P100, N170, P250, N290, P400, P560 and N640. The major inter-subject difference in the response wave form was either the presence or absence of the late parietal positive wave P560. This wave occurred significantly more often in responses associated with larger memory sets and slow RT, suggesting that its presence reflects subjective difficulty in performing a task. With increasing set size, the P400 showed variable effects in different subjects, ranging from relative preservation of amplitude, through attenuation, to replacement or overlap by a broad surface-negative wave. This predominantly 'negative-going' effect of increasing task difficulty on the P400 was significantly correlated with scores of psychological tests; the greater the amplitude difference between the responses to easy and more difficult tasks, the better the scores, suggesting that these wave form changes reflect a more effective cognitive processing mechanism. PMID:1378004

  9. Oximetry: a reflective tool for the detection of physiological expression of emotions in a science education classroom

    NASA Astrophysics Data System (ADS)

    Calderón, Olga

    2016-07-01

    The pulse oximeter is a device that measures the oxygen concentration (or oxygen saturation—SpO2); heart rate, and heartbeat of a person at any given time. This instrument is commonly used in medical and aerospace fields to monitor physiological outputs of a patient according to health conditions or physiological yields of a flying pilot according to changes in altitude and oxygen availability in the atmosphere. Nonetheless, the uses for pulse oximetry may expand to other fields where there is human interaction and where physiological outputs reflect fluctuations mediated by arising emotions. A classroom, for instance is filled with a plethora of emotions, but very often participants in this space are unaware of others' or their own sentiments as these arise as a result of interactions and responses to class discussions. In this paper I describe part of a larger study-taking place at Brooklyn College of the City University of New York. The focus is on the exploration of emotions and mindfulness in the science classroom. The oximeter is used in this study as a reflexive tool to detect emotions emerging among participants of a graduate History and Philosophy of Science Education course offered in the spring of 2012. Important physiological information of class participants provided by the oximeter is used to analyze the role of emotions in the classroom as sensitive and controversial topics in science education are discussed every week.

  10. Real-Time, In Vivo Determination of Dynamic Changes in Lung and Heart Tissue Oxygenation Using EPR Oximetry

    PubMed Central

    Rivera, Brian K.; Naidu, Shan K.; Subramanian, Kamal; Joseph, Matthew; Hou, Huagang; Khan, Nadeem; Swartz, Harold M.

    2015-01-01

    The use of electron paramagnetic resonance (EPR) oximetry for oxygen measurements in deep tissues (>1 cm) is challenging due to the limited penetration depth of the microwave energy. To overcome this limitation, implantable resonators, having a small (0 5 mm diameter) sensory loop containing the oxygen-sensing paramagnetic material connected by a pair of twisted copper wire to a coupling loop (8–10 mm diameter), have been developed, which enable repeated measurements of deep-tissue oxygen levels (pO2, partial pressure of oxygen) in the brain and tumors of rodents. In this study, we have demonstrated the feasibility of measuring dynamic changes in pO2 in the heart and lung of rats using deep-tissue implantable oxygen sensors. The sensory loop of the resonator contained lithium octa-n-butoxynaphthalocyanine (LiNc-BuO) crystals embedded in polydimethylsiloxane (PDMS) polymer and was implanted in the myocardial tissue or lung pleura. The external coupling loop was secured subcutaneously above chest. The rats were exposed to different breathing gas mixtures while undergoing EPR measurements. The results demonstrated that implantable oxygen sensors provide reliable measurements of pO2 in deep tissues such as heart and lung under adverse conditions of cardiac and respiratory motions. PMID:24729218

  11. Melodic algorithms for pulse oximetry to allow audible discrimination of abnormal systolic blood pressures.

    PubMed

    Chima, Ranjit S; Ortega, Rafael; Connor, Christopher W

    2014-12-01

    An anesthesiologist must remain vigilant of the patient's clinical status, incorporating many independent physiological measurements. Oxygen saturation and heart rate are represented by continuous audible tones generated by the pulse oximeter, a mandated monitoring device. Other important clinical parameters--notably blood pressure--lack any audible representation beyond arbitrarily-configured threshold alarms. Attempts to introduce further continuous audible tones have apparently foundered; the complexity and interaction of these tones have exceeded the ability of clinicians to interpret them. Instead, we manipulate the tonal and rhythmic structure of the accepted pulse oximeter tone pattern melodically. Three melodic algorithms were developed to apply tonal and rhythmic variations to the continuous pulse oximeter tone, dependent on the systolic blood pressure. The algorithms distort the original audible pattern minimally, to facilitate comprehension of both the underlying pattern and the applied variations. A panel of anesthesia practitioners (attending anesthesiologists, residents and nurse anesthetists) assessed these algorithms in characterizing perturbations in cardiopulmonary status. Twelve scenarios, incorporating combinations of oxygen desaturation, bradycardia, tachycardia, hypotension and hypertension, were tested. A rhythmic variation in which additional auditory information was conveyed only at halftime intervals, with every other "beat" of the pulse oximeter, was strongly favored. The respondents also strongly favored the use of musical chords over single tones. Given three algorithms of tones embedded in the pulse oximeter signal, anesthesiologists preferred a melodic tone to signal a significant change in blood pressure. PMID:24474369

  12. Adaptive re-tracking algorithm for retrieval of water level variations and wave heights from satellite altimetry data for middle-sized inland water bodies

    NASA Astrophysics Data System (ADS)

    Troitskaya, Yuliya; Lebedev, Sergey; Soustova, Irina; Rybushkina, Galina; Papko, Vladislav; Baidakov, Georgy; Panyutin, Andrey

    by the improved threshold algorithm. The possibility of determination of significant wave height (SWH) in the lakes through a two-step adaptive retracking is also studied. Calculation of the parameter SWH for Gorky Reservoir from May 2010 to March 2014 showed the anomalously high values of SWH, derived from altimetry data [15], which means that the calibration of this SWH for inland waters is required. Calibration ground measurements were performed at Gorky reservoir in 2011-2013, when wave height, wind speed and air temperature were collected by equipment placed on a buoy [15] collocated with Jason-1 and Jason-2 altimetry data acquisition. The results obtained on the basis of standard algorithm and method for adaptive re-tracking at Rybinsk , Gorky , Kuibyshev , Saratov and Volgograd reservoirs and middle-sized lakes of Russia: Chany, Segozero, Hanko, Oneko, Beloye, water areas of which are intersected by the Jason-1,2 tracks, were compared and their correlation with the observed data of hydrological stations in reservoirs and lakes was investigated. It was noted that the Volgograd reservoir regional re-tracking to determine the water level , while the standard GDR data are practically absent. REFERENCES [1] AVISO/Altimetry. User Handbook. Merged TOPEX/ POSEIDON Products. Edition 3.0. AVISO. Toulouse., 1996. [2] C.M. Birkett et al., “Surface water dynamics in the Amazon Basin: Application of satellite radar altimetry,” J. Geophys. Res., vol. 107, pp. 8059, 2002. [3] G. Brown, “The average impulse response of a rough surface and its applications,” IEEE Trans. Antennas Propagat., vol. 25, pp. 67-74, 1977. [4] I.O. Campos et al., “Temporal variations of river basin waters from Topex/Poseidon satellite altimetry. Application to the Amazon basin,” Earth and Planetary Sciences, vol. 333, pp. 633-643, 2001. [5] A.V. Kouraev et al., “Ob’ river discharge from TOPEX/Poseidon satellite altimetry (1992-2002),” Rem. Sens. Environ., vol. 93, pp. 238-245, 2004

  13. Localized parallel parametric generation of spin waves in a Ni{sub 81}Fe{sub 19} waveguide by spatial variation of the pumping field

    SciTech Connect

    Brächer, T.; Pirro, P.; Heussner, F.; Serga, A. A.; Hillebrands, B.

    2014-03-03

    We present the experimental observation of localized parallel parametric generation of spin waves in a transversally in-plane magnetized Ni{sub 81}Fe{sub 19} magnonic waveguide. The localization is realized by combining the threshold character of parametric generation with a spatially confined enhancement of the amplifying microwave field. The latter is achieved by modulating the width of the microstrip transmission line which is used to provide the pumping field. By employing microfocussed Brillouin light scattering spectroscopy, we analyze the spatial distribution of the generated spin waves and compare it with numerical calculations of the field distribution along the Ni{sub 81}Fe{sub 19} waveguide. This provides a local spin-wave excitation in transversally in-plane magnetized waveguides for a wide wave-vector range which is not restricted by the size of the generation area.

  14. Seasonal and height variations of gravity waves in the middle atmosphere over Syowa Station (69S, 40E) in the Antarctic using Rayleigh/Raman lidar

    NASA Astrophysics Data System (ADS)

    Nakamura, Takuji; Tsutsumi, Masaki; Ejiri, Mitsumu K.; Nishiyama, Takanori; Tomikawa, Yoshihiro; Kogure, Masaru

    2016-07-01

    Gravity waves generated in the lower atmosphere, or near the surface, propagate upward and transfer significant momentum and energy into the middle atmosphere/lower thermosphere. Recently it is known gravity waves are extensively generated in the high latitudes in the southern hemisphere, but not many have been reported on the generation, propagation and dissipation of such waves. In this study, we investigated gravity wave profiles in the high latitude southern hemisphere by potential energy (Ep) in the height range of 15-70 km from May 2011 to October 2013 by using Rayleigh/Raman lidar located at Syowa station (69S, 40E), in the Antarctic. Above 35km altitude, Ep was maximized during winter. The seasonal dependence of Ep over Syowa was similar to those observed at Davis (69S,79E) [Alexander et al., 2011]. Below 35 km altitude, Ep was enhanced in around May, and did not decrease in September. Almost all monthly mean profiles showed similar growth rate (corresponding scale height of about 12-14 km) above 30 km altitude. Furthermore, almost all Ep profiles have a local minimum around 25 km altitude and a local maximum around 20 km altitude, suggesting significant loss of the gravity waves between 20-25 km. In October 2012, The profile of Ep in October 2012 was quite different from those in the other months. Comparisons with zonal wind in the NASA/MERRA reanalysis data suggests that a height region of weak zonal winds descended earlier in 2012 than in the other years. This also suggests gravity waves below stratosphere include waves with slow phase speed.

  15. Dynamic changes in oxygenation of intracranial tumor and contralateral brain during tumor growth and carbogen breathing: A multisite EPR oximetry with implantable resonators

    NASA Astrophysics Data System (ADS)

    Hou, Huagang; Dong, Ruhong; Li, Hongbin; Williams, Benjamin; Lariviere, Jean P.; Hekmatyar, S. K.; Kauppinen, Risto A.; Khan, Nadeem; Swartz, Harold

    2012-01-01

    IntroductionSeveral techniques currently exist for measuring tissue oxygen; however technical difficulties have limited their usefulness and general application. We report a recently developed electron paramagnetic resonance (EPR) oximetry approach with multiple probe implantable resonators (IRs) that allow repeated measurements of oxygen in tissue at depths of greater than 10 mm. MethodsThe EPR signal to noise ( S/ N) ratio of two probe IRs was compared with that of LiPc deposits. The feasibility of intracranial tissue pO 2 measurements by EPR oximetry using IRs was tested in normal rats and rats bearing intracerebral F98 tumors. The dynamic changes in the tissue pO 2 were assessed during repeated hyperoxia with carbogen breathing. ResultsA 6-10 times increase in the S/ N ratio was observed with IRs as compared to LiPc deposits. The mean brain pO 2 of normal rats was stable and increased significantly during carbogen inhalation in experiments repeated for 3 months. The pO 2 of F98 glioma declined gradually, while the pO 2 of contralateral brain essentially remained the same. Although a significant increase in the glioma pO 2 was observed during carbogen inhalation, this effect declined in experiments repeated over days. ConclusionEPR oximetry with IRs provides a significant increase in S/ N ratio. The ability to repeatedly assess orthotopic glioma pO 2 is likely to play a vital role in understanding the dynamics of tissue pO 2 during tumor growth and therapies designed to modulate tumor hypoxia. This information could then be used to optimize chemoradiation by scheduling treatments at times of increased glioma oxygenation.

  16. Intraoperative prediction of ischaemic injury of the bowel: a comparison of laser Doppler flowmetry and tissue oximetry to histological analysis.

    PubMed

    Krohg-Sørensen, K; Line, P D; Haaland, T; Horn, R S; Kvernebo, K

    1992-09-01

    Intraoperative diagnosis of inadequate colonic perfusion would contribute to prevention of ischaemic colitis after abdominal aortic reconstructions. The aim of this study was to evaluate laser Doppler flowmetry (LDF) and tissue oximetry (TpO2) as predictors of the development of bowel necrosis. Devascularised loops of colon and ileum in anaesthetised pigs were divided into 10-20 mm segments and measurements of laser Doppler flux and TpO2 were performed in each segment. After 7 h of ischaemia the segments were resected for histological and biochemical analysis. In 65 colonic and 58 ileal segments a significantly lower flux was found in segments with necrosis of greater than or equal to 30% of the mucosal thickness compared to segments with necrosis of less than or equal to 10% (p less than 0.01). The discriminant flux value was 50 perfusion units, confirming a previous clinical study. The specificity was 0.96 and the sensitivity 0.94. Flux was inversely correlated to tissue lactate concentration. Significantly lower TpO2 was found in 19 colonic segments with necrosis of greater than or equal to 30% of mucosa compared to 19 colonic segments with necrosis of less than or equal to 10% (p less than 0.01). Using a discriminant value of 5kPa, a specificity of 0.79, and a sensitivity of 0.95 were calculated. In 27 ileum segments no significant difference in TpO2 between different histological groups was found (p greater than 0.30). The results show that LDF and TpO2 can predict ischaemic injury of the colon, and LDF also of the small bowel. PMID:1397347

  17. Respiratory rate and pulse oximetry derived information as predictors of hospital admission in young children in Bangladesh: a prospective observational study

    PubMed Central

    Garde, Ainara; Zhou, Guohai; Raihana, Shahreen; Dunsmuir, Dustin; Karlen, Walter; Dekhordi, Parastoo; Huda, Tanvir; Arifeen, Shams El; Larson, Charles; Kissoon, Niranjan; Dumont, Guy A; Ansermino, J Mark

    2016-01-01

    Objective Hypoxaemia is a strong predictor of mortality in children. Early detection of deteriorating condition is vital to timely intervention. We hypothesise that measures of pulse oximetry dynamics may identify children requiring hospitalisation. Our aim was to develop a predictive tool using only objective data derived from pulse oximetry and observed respiratory rate to identify children at increased risk of hospital admission. Setting Tertiary-level hospital emergency department in Bangladesh. Participants Children under 5 years (n=3374) presenting at the facility (October 2012–April 2013) without documented chronic diseases were recruited. 1-minute segments of pulse oximetry (photoplethysmogram (PPG), blood oxygen saturation (SpO2) and heart rate (HR)) and respiratory rate were collected with a mobile app. Primary outcome The need for hospitalisation based on expert physician review and follow-up. Methods Pulse rate variability (PRV) using pulse peak intervals of the PPG signal and features extracted from the SpO2 signal, all derived from pulse oximetry recordings, were studied. A univariate age-adjusted logistic regression was applied to evaluate differences between admitted and non-admitted children. A multivariate logistic regression model was developed using a stepwise selection of predictors and was internally validated using bootstrapping. Results Children admitted to hospital showed significantly (p<0.01) decreased PRV and higher SpO2 variability compared to non-admitted children. The strongest predictors of hospitalisation were reduced PRV-power in the low frequency band (OR associated with a 0.01 unit increase, 0.93; 95% CI 0.89 to 0.98), greater time spent below an SpO2 of 98% and 94% (OR associated with 10 s increase, 1.4; 95% CI 1.3 to 1.4 and 1.5; 95% CI 1.4 to 1.6, respectively), high respiratory rate, high HR, low SpO2, young age and male sex. These variables provided a bootstrap-corrected AUC of the receiver operating characteristic

  18. Coupled wind-forced controls of the Bering-Chukchi shelf circulation and the Bering Strait throughflow: Ekman transport, continental shelf waves, and variations of the Pacific-Arctic sea surface height gradient

    NASA Astrophysics Data System (ADS)

    Danielson, Seth L.; Weingartner, Thomas J.; Hedstrom, Katherine S.; Aagaard, Knut; Woodgate, Rebecca; Curchitser, Enrique; Stabeno, Phyllis J.

    2014-06-01

    We develop a conceptual model of the closely co-dependent Bering shelf, Bering Strait, and Chukchi shelf circulation fields by evaluating the effects of wind stress over the North Pacific and western Arctic using atmospheric reanalyses, current meter observations, satellite-based sea surface height (SSH) measurements, hydrographic profiles, and numerical model integrations. This conceptual model suggests Bering Strait transport anomalies are primarily set by the longitudinal location of the Aleutian Low, which drives oppositely signed anomalies at synoptic and annual time scales. Synoptic time scale variations in shelf currents result from local wind forcing and remotely generated continental shelf waves, whereas annual variations are driven by basin scale adjustments to wind stress that alter the magnitude of the along-strait (meridional) pressure gradient. In particular, we show that storms centered over the Bering Sea excite continental shelf waves on the eastern Bering shelf that carry northward velocity anomalies northward through Bering Strait and along the Chukchi coast. The integrated effect of these storms tends to decrease the northward Bering Strait transport at annual to decadal time scales by imposing cyclonic wind stress curl over the Aleutian Basin and the Western Subarctic Gyre. Ekman suction then increases the water column density through isopycnal uplift, thereby decreasing the dynamic height, sea surface height, and along-strait pressure gradient. Storms displaced eastward over the Gulf of Alaska generate an opposite set of Bering shelf and Aleutian Basin responses. While Ekman pumping controls Canada Basin dynamic heights (Proshutinsky et al., 2002), we do not find evidence for a strong relation between Beaufort Gyre sea surface height variations and the annually averaged Bering Strait throughflow. Over the western Chukchi and East Siberian seas easterly winds promote coastal divergence, which also increases the along-strait pressure head, as

  19. Evidence for a chemical-thermal structure at base of mantle from sharp lateral P-wave variations beneath Central America

    PubMed Central

    Sun, Xinlei; Song, Xiaodong; Zheng, Sihua; Helmberger, Don V.

    2007-01-01

    Compressional waves that sample the lowermost mantle west of Central America show a rapid change in travel times of up to 4 s over a sampling distance of 300 km and a change in waveforms. The differential travel times of the PKP waves (which traverse Earth's core) correlate remarkably well with predictions for S-wave tomography. Our modeling suggests a sharp transition in the lowermost mantle from a broad slow region to a broad fast region with a narrow zone of slowest anomaly next to the boundary beneath the Cocos Plate and the Caribbean Plate. The structure may be the result of ponding of ancient subducted Farallon slabs situated near the edge of a thermal and chemical upwelling. PMID:17182740

  20. Non-invasive measurement of peripheral venous oxygen saturation using a new venous oximetry method: evaluation during bypass in heart surgery.

    PubMed

    Echiadis, A S; Crabtree, V P; Bence, J; Hadjinikolaou, L; Alexiou, C; Spyt, T J; Hu, S

    2007-08-01

    Monitoring of mixed venous oxygen saturation (SvO(2)) is currently performed using invasive fibre-optic catheters. This procedure is not without risk as complications may arise from catheterization. This paper describes an alternative, non-invasive method of monitoring peripheral venous oxygen saturation (SxvO(2)) which, although it cannot replace pulmonary artery catheters, can serve as an adjunct/early warning indicator of when there is an imbalance in oxygen supply and demand. The technique requires the generation of an artificial venous pulse at the finger, thereby causing modulation of the venous blood volume within the digit. The blood volume changes are monitored using an optical sensor. Just as pulse oximetry utilizes the natural arterial pulse to perform a spectrophotometric analysis of the peripheral blood in order to estimate the arterial blood oxygen saturation, the proposed venous oximetry technique uses the artificially generated venous pulse to estimate SxvO(2). A prototype device was tested in a pilot study with patients undergoing heart surgery. Data from this study support the notion that the method is capable of tracking haemodynamic changes and suggests the technique is worthy of further development and evaluation. PMID:17664681

  1. Lateral variation in upper mantle temperature and composition beneath mid-ocean ridges inferred from shear-wave propagation, geoid, and bathymetry. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Sheehan, Anne Francis

    1991-01-01

    Resolution of both the extent and mechanism of lateral heterogeneity in the upper mantle constraints the nature and scales of mantle convection. Oceanic regions are of particular interest as they are likely to provide the closest glimpse at the patterns of temperature anomalies and convective flow in the upper mantle because of their young age and simple crustal structure relative to continental regions. Lateral variations were determined in the seismic velocity and attenuation structure of the lithosphere and astenosphere beneath the oceans, and these seismological observations were combined with the data and theory of geoid and bathymetry anomalies in order to test and improve current models for seafloor spreading and mantle convection. Variations were determined in mantle properties on a scale of about 1000 km, comparable to the thickness of the upper mantle. Seismic velocity, geoid, and bathymetry anomalies are all sensitive to variations in upper mantle density, and inversions were formulated to combine quantitatively these different data and to search for a common origin. Variations in mantle density can be either of thermal or compositional origin and are related to mantle convection or differentiation.

  2. Wave propagation in solids and fluids

    SciTech Connect

    Davis, J. L.

    1988-01-01

    The fundamental principles of mathematical analysis for wave phenomena in gases, solids, and liquids are presented in an introduction for scientists and engineers. Chapters are devoted to oscillatory phenomena, the physics of wave propagation, partial differential equations for wave propagation, transverse vibration of strings, water waves, and sound waves. Consideration is given to the dynamics of viscous and inviscid fluids, wave propagation in elastic media, and variational methods in wave phenomena. 41 refs.

  3. Temperature Variation and Heat Wave and Cold Spell Impacts on Years of Life Lost Among the Urban Poor Population of Nairobi, Kenya

    PubMed Central

    Egondi, Thaddaeus; Kyobutungi, Catherine; Rocklöv, Joacim

    2015-01-01

    Weather extremes are associated with adverse health outcomes, including mortality. Studies have investigated the mortality risk of temperature in terms of excess mortality, however, this risk estimate may not be appealing to policy makers assessing the benefits expected for any interventions to be adopted. To provide further evidence of the burden of extreme temperatures, we analyzed the effect of temperature on years of life lost (YLL) due to all-cause mortality among the population in two urban informal settlements. YLL was generated based on the life expectancy of the population during the study period by applying a survival analysis approach. Association between daily maximum temperature and YLL was assessed using a distributed lag nonlinear model. In addition, cold spell and heat wave effects, as defined according to different percentiles, were investigated. The exposure-response curve between temperature and YLL was J-shaped, with the minimum mortality temperature (MMT) of 26 °C. An average temperature of 21 °C compared to the MMT was associated with an increase of 27.4 YLL per day (95% CI, 2.7–52.0 years). However, there was no additional effect for extended periods of cold spells, nor did we find significant associations between YLL to heat or heat waves. Overall, increased YLL from all-causes were associated with cold spells indicating the need for initiating measure for reducing health burdens. PMID:25739007

  4. MHD Wave in Sunspots

    NASA Astrophysics Data System (ADS)

    Sych, Robert

    2016-02-01

    The study of magnetohydrodynamic (MHD) waves and oscillations in the solar atmosphere is one of the fastest developing fields in solar physics, and lies in the mainstream of using solar instrumentation data. This chapter first addresses the spatial frequency morphology of sources of sunspot oscillations and waves, including their localization, size, oscillation periods, and height localization with the mechanism of cutoff frequency that forms the observed emission variability. Then, it presents a review dynamic of sunspot wave processes, provides the information about the structure of wave fronts and their time variations, and investigates the oscillation frequency transformation depending on the wave energy. The chapter also addresses the initializing solar flares caused by trigger agents like magnetoacoustic waves, accelerated particle beams, and shocks. Special attention is paid to the relation between the flare reconnection periodic initialization and the dynamics of sunspot slow magnetoacoustic waves.

  5. An overview of millimeter-wave spectroscopic measurements of chlorine monoxide at Thule, Greenland, February-March, 1992: Vertical profiles, diurnal variation, and longer-term trends

    NASA Technical Reports Server (NTRS)

    De Zafra, R. L.; Emmons, L. K.; Reeves, J. M.; Shindell, D. T.

    1994-01-01

    Measurements of chlorine monoxide in the stratosphere over Thule, Greenland (73.6 N, 68.4 W) were made quasi-continuously during the period February 8 to March 24, 1992, using a high-sensitivity ground based mm-wave spectrometer. These observations give diurnal, short term, and long term changes in the mixing ratio and vertical distribution of ClO. At an equivalent time after the Antarctic winter solstice, very large concentrations (up to approximately 1.5 ppbv) occur in lower stratospheric ClO, resulting in massive ozone destruction. We saw no evidence for large (approximately 1 top 1.5 ppbv) amounts of ClO in the 16-25 km range over Thule in February or March, in agreement with UARS (satellite) observations by the MLS mm-wave spectrometer for this period, and in marked contrast to UARS/MLS and ER-2 aircraft measurements over northern Europe and eastern Canada, respectively, during January, 1992. We have evidence for smaller enhancements (approximately 0.2 to 0.5 ppbv) in the 18-30 km range during late February-early March, which could result from transport of residual low NO2 air following earlier polar stratospheric cloud (PSC) processing (the last of which occurred at least one month earlier, however) or the result of chemical processing by Pinatubo aerosols. Direct influence of Pinatubo aerosols on Arctic ozone during the spring of 1992 has been difficult to assess, and this enhancement of low-altitude ClO might be a significant indicator of aerosol effects.

  6. Skin oxygenation after topical application of liposome-entrapped benzyl nicotinate as measured by EPR oximetry in vivo: influence of composition and size.

    PubMed

    Kristl, Julijana; Abramović, Zrinka; Sentjurc, Marjeta

    2003-01-01

    New and improved drug delivery systems are the important subject of much scientific research. The development of formulations that increase skin oxygenation and of methods for measuring oxygen levels in skin are important for dealing with healing processes affected by the level of oxygen. We have used EPR oximetry in vivo to compare the influence of liposomal formulations of different size and composition with that of hydrogel with respect to the action of the entrapped benzyl nicotinate (BN). Following the topical application of BN onto the skin of mice, pO2 increase was measured by low-frequency EPR as a function of time. The effect of BN was evaluated by 3 different parameters: lag-time, time needed for maximum pO2 increase, and overall effectiveness expressed by the area under the response-time curve. An increase in skin oxygenation was observed after BN application. The results show that the effect of BN incorporated in liposomes is achieved more rapidly than the effect from hydrophilic gel. The composition of the liposomes significantly affects the time at which BN starts to act and, to a lesser extent, the maximum increase of pO2 in skin and the effectiveness of BN action. However, the size of the liposomes influences both the effectiveness of BN action and the time at which BN starts to act. After repeated application of liposomes, the pO2 baseline increased and the response of the skin tissue was faster. Our results demonstrate that EPR oximetry is a useful method for evaluating oxygen changes after drug application and for following the time course of their action. PMID:12713274

  7. MJO-related intraseasonal variation of gravity waves in the Southern Hemisphere tropical stratosphere revealed by high-resolution AIRS observations

    NASA Astrophysics Data System (ADS)

    Tsuchiya, Chikara; Sato, Kaoru; Alexander, M. Joan; Hoffmann, Lars

    2016-07-01

    The intraseasonal variability of gravity waves (GWs) in the austral summer middle stratosphere was examined using dedicated high-resolution temperature retrieval from the Atmospheric Infrared Sounder data. Composite maps were made of stratospheric GW temperature variances, large-scale zonal winds around the tropopause, and precipitation based on the real-time multivariate Madden-Julian Oscillation (MJO) index. Regional distributions of these quantities are synchronized with the MJO: The GW variances are larger for stronger precipitation and for more strongly westward wind around the tropopause at a given precipitation. These results suggest that the GWs observed by Atmospheric Infrared Sounder (AIRS) in the stratosphere originate from convection. Moreover, it is shown that the zonal wind around the tropopause likely controls the GW propagation into the stratosphere by a critical level filtering mechanism and/or the GW generation by an obstacle source effect. This means that the MJO can modulate the middle atmospheric circulation by regulating the GWs in two ways, namely, generation and propagation.

  8. Evidence for Chiral d-Wave Superconductivity in URu2Si2 from the Field-Angle Variation of Its Specific Heat

    NASA Astrophysics Data System (ADS)

    Kittaka, Shunichiro; Shimizu, Yusei; Sakakibara, Toshiro; Haga, Yoshinori; Yamamoto, Etsuji; Ōnuki, Yoshichika; Tsutsumi, Yasumasa; Nomoto, Takuya; Ikeda, Hiroaki; Machida, Kazushige

    2016-03-01

    Low-energy quasiparticle (QP) excitations in the heavy-fermion superconductor URu2Si2 were investigated by specific-heat C(T,H,φ ,θ ) measurements of a high-quality single crystal. The occurrence of QP excitations due to the Doppler-shift effect was detected regardless of the field direction in C(H) of the present clean sample, which is in sharp contrast to a previous report. Furthermore, the polar-angle-dependent C(θ) measured under a rotating magnetic field within the ac plane exhibits a shoulder-like anomaly at θ ˜ 45° and a sharp dip at θ = 90° (H || a) in the moderate-field region. These features are supported by theoretical analyses based on microscopic calculations assuming the gap symmetry of kz(kx + iky), whose gap structure is characterized by a combination of a horizontal line node at the equator and point nodes at the poles. The present results have settled the previous controversy over the gap structure of URu2Si2 and have authenticated its chiral d-wave superconductivity.

  9. Conservation laws of wave action and potential enstrophy for Rossby waves in a stratified atmosphere

    NASA Technical Reports Server (NTRS)

    Straus, D. M.

    1983-01-01

    The evolution of wave energy, enstrophy, and wave motion for atmospheric Rossby waves in a variable mean flow are discussed from a theoretical and pedagogic standpoint. In the absence of mean flow gradients, the wave energy density satisfies a local conservation law, with the appropriate flow velocity being the group velocity. In the presence of mean flow variations, wave energy is not conserved, but wave action is, provided the mean flow is independent of longitude. Wave enstrophy is conserved for arbitrary variations of the mean flow. Connections with Eiiassen-Palm flux are also discussed.

  10. Conservation laws of wave action and potential enstrophy for Rossby waves in a stratified atmosphere

    NASA Technical Reports Server (NTRS)

    Straus, D. M.

    1983-01-01

    The evolution of wave energy, enstrophy, and wave motion for atmospheric Rossby waves in a variable mean flow are discussed from a theoretical and pedagogic standpoint. In the absence of mean flow gradients, the wave energy density satisfies a local conservation law, with the appropriate flow velocity being the group velocity. In the presence of mean flow variations, wave energy is not conserved, but wave action is, provided the mean flow is independent of longitude. Wave enstrophy is conserved for arbitrary variations of the mean flow. Connections with Eliassen-Palm flux are also discussed.

  11. Electromagnetic wave energy converter

    NASA Technical Reports Server (NTRS)

    Bailey, R. L. (Inventor)

    1973-01-01

    Electromagnetic wave energy is converted into electric power with an array of mutually insulated electromagnetic wave absorber elements each responsive to an electric field component of the wave as it impinges thereon. Each element includes a portion tapered in the direction of wave propagation to provide a relatively wideband response spectrum. Each element includes an output for deriving a voltage replica of the electric field variations intercepted by it. Adjacent elements are positioned relative to each other so that an electric field subsists between adjacent elements in response to the impinging wave. The electric field results in a voltage difference between adjacent elements that is fed to a rectifier to derive dc output power.

  12. The structure of irregular mesospheric variations.

    NASA Technical Reports Server (NTRS)

    Justus, C. G.

    1972-01-01

    The daily difference method developed by Woodrum and Justus (1968) has been used to analyze the existing data in the height range from 50 to 200 km for irregular variations which could be due to gravity waves. The results presented establish the magnitude as well as the vertical and latitudinal structure of the irregular atmospheric variations. It is pointed out that results obtained by Theon et al. (1969) indicate strong seasonal variation in the magnitude of upper atmospheric waves at high latitudes.

  13. Kinesthetic Transverse Wave Demonstration

    NASA Astrophysics Data System (ADS)

    Pantidos, Panagiotis; Patapis, Stamatis

    2005-09-01

    This is a variation on the String and Sticky Tape demonstration "The Wave Game," suggested by Ron Edge. A group of students stand side by side, each one holding a card chest high with both hands. The teacher cues the first student to begin raising and lowering his card. When he starts lowering his card, the next student begins to raise his. As succeeding students move their cards up and down, a wave such as that shown in the figure is produced. To facilitate the process, students' motions were synchronized with the ticks of a metronome (without such synchronization it was nearly impossible to generate a satisfactory wave). Our waves typically had a frequency of about 1 Hz and a wavelength of around 3 m. We videotaped the activity so that the students could analyze the motions. The (17-year-old) students had not received any prior instruction regarding wave motion and did not know beforehand the nature of the exercise they were about to carry out. During the activity they were asked what a transverse wave is. Most of them quickly realized, without teacher input, that while the wave propagated horizontally, the only motion of the transmitting medium (them) was vertical. They located the equilibrium points of the oscillations, the crests and troughs of the waves, and identified the wavelength. The teacher defined for them the period of the oscillations of the motion of a card to be the total time for one cycle. The students measured this time and then several asserted that it was the same as the wave period. Knowing the length of the waves and the number of waves per second, the next step can easily be to find the wave speed.

  14. Random focusing of tsunami waves

    NASA Astrophysics Data System (ADS)

    Degueldre, Henri; Metzger, Jakob J.; Geisel, Theo; Fleischmann, Ragnar

    2016-03-01

    Tsunamis exhibit surprisingly strong height fluctuations. An in-depth understanding of the mechanisms that lead to these variations in wave height is a prerequisite for reliable tsunami forecasting. It is known, for example, that the presence of large underwater islands or the shape of the tsunami source can affect the wave heights. Here we show that the consecutive effect of even tiny fluctuations in the profile of the ocean floor (the bathymetry) can cause unexpectedly strong fluctuations in the wave height of tsunamis, with maxima several times higher than the average wave height. A novel approach combining stochastic caustic theory and shallow water wave dynamics allows us to determine the typical propagation distance at which the strongly focused waves appear. We demonstrate that owing to this mechanism the small errors present in bathymetry measurements can lead to drastic variations in predicted tsunami heights. Our results show that a precise knowledge of the ocean's bathymetry is absolutely indispensable for reliable tsunami forecasts.

  15. WINDII atmospheric wave airglow imaging

    SciTech Connect

    Armstrong, W.T.; Hoppe, U.-P.; Solheim, B.H.; Shepherd, G.G.

    1996-12-31

    Preliminary WINDII nighttime airglow wave-imaging data in the UARS rolldown attitude has been analyzed with the goal to survey gravity waves near the upper boundary of the middle atmosphere. Wave analysis is performed on O[sub 2](0,0) emissions from a selected 1[sup 0] x 1[sup 0] oblique view of the airglow layer at approximately 95 km altitude, which has no direct earth background and only an atmospheric background which is optically thick for the 0[sub 2](0,0) emission. From a small data set, orbital imaging of atmospheric wave structures is demonstrated, with indication of large variations in wave activity across land and sea. Comparison ground-based imagery is discussed with respect to similarity of wave variations across land/sea boundaries and future orbital mosaic image construction.

  16. Arterial input function of an optical tracer for dynamic contrast enhanced imaging can be determined from pulse oximetry oxygen saturation measurements

    NASA Astrophysics Data System (ADS)

    Elliott, Jonathan T.; Wright, Eric A.; Tichauer, Kenneth M.; Diop, Mamadou; Morrison, Laura B.; Pogue, Brian W.; Lee, Ting-Yim; St. Lawrence, Keith

    2012-12-01

    In many cases, kinetic modeling requires that the arterial input function (AIF)—the time-dependent arterial concentration of a tracer—be characterized. A straightforward method to measure the AIF of red and near-infrared optical dyes (e.g., indocyanine green) using a pulse oximeter is presented. The method is motivated by the ubiquity of pulse oximeters used in both preclinical and clinical applications, as well as the gap in currently available technologies to measure AIFs in small animals. The method is based on quantifying the interference that is observed in the derived arterial oxygen saturation (SaO2) following a bolus injection of a light-absorbing dye. In other words, the change in SaO2 can be converted into dye concentration knowing the chromophore-specific extinction coefficients, the true arterial oxygen saturation, and total hemoglobin concentration. A simple error analysis was performed to highlight potential limitations of the approach, and a validation of the method was conducted in rabbits by comparing the pulse oximetry method with the AIF acquired using a pulse dye densitometer. Considering that determining the AIF is required for performing quantitative tracer kinetics, this method provides a flexible tool for measuring the arterial dye concentration that could be used in a variety of applications.

  17. Wave turbulence

    NASA Astrophysics Data System (ADS)

    Nazarenko, Sergey

    2015-07-01

    Wave turbulence is the statistical mechanics of random waves with a broadband spectrum interacting via non-linearity. To understand its difference from non-random well-tuned coherent waves, one could compare the sound of thunder to a piece of classical music. Wave turbulence is surprisingly common and important in a great variety of physical settings, starting with the most familiar ocean waves to waves at quantum scales or to much longer waves in astrophysics. We will provide a basic overview of the wave turbulence ideas, approaches and main results emphasising the physics of the phenomena and using qualitative descriptions avoiding, whenever possible, involved mathematical derivations. In particular, dimensional analysis will be used for obtaining the key scaling solutions in wave turbulence - Kolmogorov-Zakharov (KZ) spectra.

  18. Assessment of oxygen saturation in retinal vessels of normal subjects and diabetic patients with and without retinopathy using Flow Oximetry System

    PubMed Central

    Ibrahim, Mohamed A.; Annam, Rachel E.; Sepah, Yasir J.; Luu, Long; Bittencourt, Millena G.; Jang, Hyun S.; Lemaillet, Paul; Munoz, Beatriz; Duncan, Donald D.; West, Sheila; Nguyen, Quan Dong

    2015-01-01

    Purpose To assess oxygen saturation (StO2) in retinal vessels of normal subjects and diabetic patients with and without retinopathy using the modified version of the Flow Oximetry System (FOS) and a novel assessment software. Methods The FOS and novel assessment software were used to determine StO2 levels in arteries and veins located between 1 and 2 mm from the margin of the optic disc and in the macular area. Results Eighteen normal subjects, 15 diabetics without diabetic retinopathy (DM no DR), and 11 with non-proliferative diabetic retinopathy (NPDR) were included in final analysis. The mean [± standard deviation (SD)] StO2 in retinal arteries was 96.9%±3.8% in normal subjects; 97.4%±3.7% in DM no DR; and 98.4%±2.0% in NPDR. The mean venous StO2 was 57.5%±6.8% in normal subjects; 57.4%±7.5% in DM no DR; and 51.8%±6.8% in NPDR. The mean arterial and venous StO2 across the three groups were not statistically different (P=0.498 and P=0.071, respectively). The arterio-venous differences between the three study groups, however, were found to be statistically significant (P=0.015). Pairwise comparisons have demonstrated significant differences when comparing the A-V difference in the NPDR group to either normal subjects (P=0.02) or diabetic patients without DR (P=0.04). Conclusions The arterio-venous difference was greater, and statistically significant, in patients with NPDR when compared to normal subjects and to patients with diabetes and no retinopathy. The mean venous StO2 was lower, but not statistically significant, in NPDR compared with diabetics without retinopathy and with normal subjects. PMID:25694958

  19. Pulse Oximetry for the Detection of Obstructive Sleep Apnea Syndrome: Can the Memory Capacity of Oxygen Saturation Influence Their Diagnostic Accuracy?

    PubMed Central

    Nigro, Carlos A.; Dibur, Eduardo; Rhodius, Edgardo

    2011-01-01

    Objective. To assess the diagnostic ability of WristOx 3100 using its three different recording settings in patients with suspected obstructive sleep apnea syndrome (OSAS). Methods. All participants (135) performed the oximetry (three oximeters WristOx 3100) and polysomnography (PSG) simultaneously in the sleep laboratory. Both recordings were interpreted blindly. Each oximeter was set to one of three different recording settings (memory capabilities 0.25, 0.5, and 1 Hz). The software (nVision 5.1) calculated the adjusted O2 desaturation index-mean number of O2 desaturation per hour of analyzed recording ≥2, 3, and 4% (ADI2, 3, and 4). The ADI2, 3, and 4 cutoff points that better discriminated between subjects with or without OSAS arose from the receiver-operator characteristics (ROCs) curve analysis. OSAS was defined as a respiratory disturbance index (RDI) ≥ 5. Results. 101 patients were included (77 men, mean age 52, median RDI 22.6, median BMI 27.4 kg/m2). The area under the ROCs curves (AUC-ROCs) of ADI2, 3, and 4 with different data storage rates were similar (AUC-ROCs with data storage rates of 0.25/0.5/1 Hz: ADI2: 0.958/0.948/0.965, ADI3: 0.961/0.95/0.966, and ADI4: 0.957/0.949/0.963, P NS). Conclusions. The ability of WristOx 3100 to detect patients with OSAS was not affected by the data storage rate of the oxygen saturation signal. Both memory capacity of 0.25, 0.5, or 1 Hz showed a similar performance for the diagnosis of OSAS. PMID:23471171

  20. Variational Method for Two-Electron Atoms

    ERIC Educational Resources Information Center

    Srivastava, M. K.; Bhaduri, R. K.

    1977-01-01

    Proposes a simple two-parameter trial wave function for the helium atom and helium-like ions. Shows that a variational calculation for the ground-state energy yields better results than the usual one-parameter example. (MLH)

  1. Heat Waves

    MedlinePlus

    Heat Waves Dangers we face during periods of very high temperatures include: Heat cramps: These are muscular pains and spasms due ... that the body is having trouble with the heat. If a heat wave is predicted or happening… - ...

  2. Upper atmospheric planetary-wave and gravity-wave observations

    NASA Technical Reports Server (NTRS)

    Justus, C. G.; Woodrum, A.

    1973-01-01

    Previously collected data on atmospheric pressure, density, temperature and winds between 25 and 200 km from sources including Meteorological Rocket Network data, ROBIN falling sphere data, grenade release and pitot tube data, meteor winds, chemical release winds, satellite data, and others were analyzed by a daily-difference method, and results on the magnitude of atmospheric perturbations interpreted as gravity waves and planetary waves are presented. Traveling planetary-wave contributions in the 25-85 km range were found to have significant height and latitudinal variation. It was found that observed gravity-wave density perturbations and wind are related to one another in the manner predicted by gravity-wave theory. It was determined that, on the average, gravity-wave energy deposition or reflection occurs at all altitudes except the 55-75 km region of the mesosphere.

  3. Gravity Waves

    Atmospheric Science Data Center

    2013-04-19

    article title:  Gravity Waves Ripple over Marine Stratocumulus Clouds ... Imaging SpectroRadiometer (MISR), a fingerprint-like gravity wave feature occurs over a deck of marine stratocumulus clouds. Similar ... that occur when a pebble is thrown into a still pond, such "gravity waves" sometimes appear when the relatively stable and stratified air ...

  4. Common Genetic Variation in the 3-BCL11B Gene Desert Is Associated With Carotid-Femoral Pulse Wave Velocity and Excess Cardiovascular Disease Risk The AortaGen Consortium

    PubMed Central

    Mitchell, Gary F.; Verwoert, Germaine C.; Tarasov, Kirill V.; Isaacs, Aaron; Smith, Albert V.; Yasmin; Rietzschel, Ernst R.; Tanaka, Toshiko; Liu, Yongmei; Parsa, Afshin; Najjar, Samer S.; O’Shaughnessy, Kevin M.; Sigurdsson, Sigurdur; De Buyzere, Marc L.; Larson, Martin G.; Sie, Mark P.S.; Andrews, Jeanette S.; Post, Wendy S.; Mattace-Raso, Francesco U.S.; McEniery, Carmel M.; Eiriksdottir, Gudny; Segers, Patrick; Vasan, Ramachandran S.; van Rijn, Marie Josee E.; Howard, Timothy D.; McArdle, Patrick F.; Dehghan, Abbas; Jewell, Elizabeth; Newhouse, Stephen J.; Bekaert, Sofie; Hamburg, Naomi M.; Newman, Anne B.; Hofman, Albert; Scuteri, Angelo; De Bacquer, Dirk; Ikram, Mohammad Arfan; Psaty, Bruce; Fuchsberger, Christian; Olden, Matthias; Wain, Louise V.; Elliott, Paul; Smith, Nicholas L.; Felix, Janine F.; Erdmann, Jeanette; Vita, Joseph A.; Sutton-Tyrrell, Kim; Sijbrands, Eric J.G.; Sanna, Serena; Launer, Lenore J.; De Meyer, Tim; Johnson, Andrew D.; Schut, Anna F.C.; Herrington, David M.; Rivadeneira, Fernando; Uda, Manuela; Wilkinson, Ian B.; Aspelund, Thor; Gillebert, Thierry C.; Van Bortel, Luc; Benjamin, Emelia J.; Oostra, Ben A.; Ding, Jingzhong; Gibson, Quince; Uitterlinden, André G.; Abecasis, Gonçalo R.; Cockcroft, John R.; Gudnason, Vilmundur; De Backer, Guy G.; Ferrucci, Luigi; Harris, Tamara B.; Shuldiner, Alan R.; van Duijn, Cornelia M.; Levy, Daniel; Lakatta, Edward G.; Witteman, Jacqueline C.M.

    2012-01-01

    Background Carotid-femoral pulse wave velocity (CFPWV) is a heritable measure of aortic stiffness that is strongly associated with increased risk for major cardiovascular disease events. Methods and Results We conducted a meta-analysis of genome-wide association data in 9 community-based European ancestry cohorts consisting of 20,634 participants. Results were replicated in 2 additional European ancestry cohorts involving 5,306 participants. Based on a preliminary analysis of 6 cohorts, we identified a locus on chromosome 14 in the 3′-BCL11B gene desert that is associated with CFPWV (rs7152623, minor allele frequency = 0.42, beta=−0.075±0.012 SD/allele, P = 2.8 x 10−10; replication beta=−0.086±0.020 SD/allele, P = 1.4 x 10−6). Combined results for rs7152623 from 11 cohorts gave beta=−0.076±0.010 SD/allele, P=3.1x10−15. The association persisted when adjusted for mean arterial pressure (beta=−0.060±0.009 SD/allele, P = 1.0 x 10−11). Results were consistent in younger (<55 years, 6 cohorts, N=13,914, beta=−0.081±0.014 SD/allele, P = 2.3 x 10−9) and older (9 cohorts, N=12,026, beta=−0.061±0.014 SD/allele, P=9.4x10−6) participants. In separate meta-analyses, the locus was associated with increased risk for coronary artery disease (hazard ratio [HR]=1.05, confidence interval [CI]=1.02 to 1.08, P=0.0013) and heart failure (HR=1.10, CI=1.03 to 1.16, P=0.004). Conclusions Common genetic variation in a locus in the BCL11B gene desert that is thought to harbor one or more gene enhancers is associated with higher CFPWV and increased risk for cardiovascular disease. Elucidation of the role this novel locus plays in aortic stiffness may facilitate development of therapeutic interventions that limit aortic stiffening and related cardiovascular disease events. PMID:22068335

  5. Oximetry: a new non-invasive method to detect metabolic effects induced by a local application of mechanical vibration

    NASA Astrophysics Data System (ADS)

    Felici, A.; Trombetta, C.; Abundo, P.; Foti, C.; Rosato, N.

    2012-10-01

    Mechanical vibrations application is increasingly common in clinical practice due to the effectiveness induced by these stimuli on the human body. Local vibration (LV) application allows to apply and act only where needed, focusing the treatment on the selected body segment. An experimental device for LV application was used to generate the vibrations. The aim of this study was to detect and analyze the metabolic effects induced by LV on the brachial bicep muscle by means of an oximeter. This device monitors tissue and muscle oxygenation using NIRS (Near Infrared Spectroscopy) and is able to determine the concentration of haemoglobin and oxygen saturation in the tissue. In a preliminary stage we also investigated the effects induced by LV application, by measuring blood pressure, heart rate, oxygen saturation and temperature. These data confirmed that the effects induced by LV application are actually localized. The results of the measurements obtained using the oximeter during the vibration application, have shown a variation of the concentrations. In particular an increase of oxygenate haemoglobin was shown, probably caused by an increased muscle activity and/or a rise in local temperature detected during the application.

  6. Equatorial waves in the stratosphere of Uranus

    NASA Technical Reports Server (NTRS)

    Hinson, David P.; Magalhaes, Julio A.

    1991-01-01

    Analyses of radio occultation data from Voyager 2 have led to the discovery and characterization of an equatorial wave in the Uranus stratosphere. The observed quasi-periodic vertical atmospheric density variations are in close agreement with theoretical predictions for a wave that propagates vertically through the observed background structure of the stratosphere. Quantitative comparisons between measurements obtained at immersion and at emersion yielded constraints on the meridional and zonal structure of the wave; the fact that the two sets of measurements are correlated suggests a wave of planetary scale. Two equatorial wave models are proposed for the wave.

  7. Amplitude, phase, and period variations of the quasi 2-day wave in the mesosphere and lower thermosphere over London, Canada (43°N, 81°W), during 1993 and 1994

    NASA Astrophysics Data System (ADS)

    Thayaparan, T.; Hocking, W. K.; MacDougall, J.

    1997-04-01

    Because there is as yet no conclusive evidence pointing to the source of the quasi 2-day wave, further observations are required in order to resolve questions about the generating mechanism as well as to better understand the role of the wave in the middle atmosphere. In this paper we investigate the period, amplitude, phase, and vertical wavelength for the quasi 2-day wave in the mesosphere and lower thermosphere, using the University of Western Ontario 2 MHz radar near London, Canada, and in addition, we look at possible coupling with atmospheric tides. The results of the present study bring out certain new aspects of the quasi 2-day wave at midlatitude in the northern hemisphere that have not been previously reported. In particular, we show that the period of the quasi 2-day wave determined from our study is smaller (46-47 hours) than the 51- to 52-h period generally suggested by other northern hemisphere results, and our periods also showed variability as a function of time. We also draw attention to the annual variability and especially highlight the occurrence of the wave in nonsummer months. For example, a brief occurrence in April is not uncommon. Our study also contributes additional midlatitude geographical data that should aid in developing a better picture of the quasi 2-day wave.

  8. The Schwinger Variational Method

    NASA Technical Reports Server (NTRS)

    Huo, Winifred M.

    1995-01-01

    Variational methods have proven invaluable in theoretical physics and chemistry, both for bound state problems and for the study of collision phenomena. The application of the Schwinger variational (SV) method to e-molecule collisions and molecular photoionization has been reviewed previously. The present chapter discusses the implementation of the SV method as applied to e-molecule collisions. Since this is not a review of cross section data, cross sections are presented only to server as illustrative examples. In the SV method, the correct boundary condition is automatically incorporated through the use of Green's function. Thus SV calculations can employ basis functions with arbitrary boundary conditions. The iterative Schwinger method has been used extensively to study molecular photoionization. For e-molecule collisions, it is used at the static exchange level to study elastic scattering and coupled with the distorted wave approximation to study electronically inelastic scattering.

  9. SURFACE ALFVEN WAVES IN SOLAR FLUX TUBES

    SciTech Connect

    Goossens, M.; Andries, J.; Soler, R.; Van Doorsselaere, T.; Arregui, I.; Terradas, J.

    2012-07-10

    Magnetohydrodynamic (MHD) waves are ubiquitous in the solar atmosphere. Alfven waves and magneto-sonic waves are particular classes of MHD waves. These wave modes are clearly different and have pure properties in uniform plasmas of infinite extent only. Due to plasma non-uniformity, MHD waves have mixed properties and cannot be classified as pure Alfven or magneto-sonic waves. However, vorticity is a quantity unequivocally related to Alfven waves as compression is for magneto-sonic waves. Here, we investigate MHD waves superimposed on a one-dimensional non-uniform straight cylinder with constant magnetic field. For a piecewise constant density profile, we find that the fundamental radial modes of the non-axisymmetric waves have the same properties as surface Alfven waves at a true discontinuity in density. Contrary to the classic Alfven waves in a uniform plasma of infinite extent, vorticity is zero everywhere except at the cylinder boundary. If the discontinuity in density is replaced with a continuous variation of density, vorticity is spread out over the whole interval with non-uniform density. The fundamental radial modes of the non-axisymmetric waves do not need compression to exist unlike the radial overtones. In thin magnetic cylinders, the fundamental radial modes of the non-axisymmetric waves with phase velocities between the internal and the external Alfven velocities can be considered as surface Alfven waves. On the contrary, the radial overtones can be related to fast-like magneto-sonic modes.

  10. Tunnel effect wave energy detection

    NASA Technical Reports Server (NTRS)

    Kaiser, William J. (Inventor); Waltman, Steven B. (Inventor); Kenny, Thomas W. (Inventor)

    1995-01-01

    Methods and apparatus for measuring gravitational and inertial forces, magnetic fields, or wave or radiant energy acting on an object or fluid in space provide an electric tunneling current through a gap between an electrode and that object or fluid in space and vary that gap with any selected one of such forces, magnetic fields, or wave or radiant energy acting on that object or fluid. These methods and apparatus sense a corresponding variation in an electric property of that gap and determine the latter force, magnetic fields, or wave or radiant energy in response to that corresponding variation, and thereby sense or measure such parameters as acceleration, position, particle mass, velocity, magnetic field strength, presence or direction, or wave or radiant energy intensity, presence or direction.

  11. Satellite observations of the QBO wave driving by Kelvin waves and gravity waves

    NASA Astrophysics Data System (ADS)

    Ern, Manfred; Preusse, Peter; Kalisch, Silvio; Riese, Martin

    2014-05-01

    The quasi-biennial oscillation (QBO) of the zonal wind in the tropical stratosphere is an important process in atmospheric dynamics influencing a wide range of altitudes and latitudes. Effects of the QBO are found also in the mesosphere and in the extra-tropics. The QBO even has influence on the surface weather and climate, for example during winter in the northern hemisphere at midlatitudes. Still, climate models have large difficulties in reproducing a realistic QBO. One reason for this deficiency are uncertainties in the wave driving by planetary waves and, in particular, gravity waves that are usually too small-scale to be resolved in global models. Different global equatorial wave modes (e.g., Kelvin waves) have been identified by longitude-time 2D spectral analysis in Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) satellite temperature data, as well as ECMWF temperatures. We find good agreement between SABER satellite observations and ECMWF wave variances in both QBO-related temporal variations and their magnitude. Slow phase speed waves are strongly modulated by the QBO, higher phase speed waves are almost unaffected by the QBO, and ultra-fast equatorial waves can even reach the MLT region. Momentum fluxes and zonal wind drag due to Kelvin waves are derived, and the relative contribution of Kelvin waves to the QBO wind reversal from westward to eastward wind is estimated to be about 30% of the total wave driving. This is in good agreement with the general assumption that gravity waves (GWs) are probably more important for the QBO driving than global-scale waves. This is further supported by SABER and High Resolution Dynamics Limb Sounder (HIRDLS) satellite observations of gravity wave drag in the equatorial region. These observations are compared with the drag still missing in the ECMWF ERA Interim (ERAI) tropical momentum budget after considering zonal wind tendency, Coriolis force, advection terms and drag of resolved global

  12. Third Wave.

    ERIC Educational Resources Information Center

    Reed, Chris

    2000-01-01

    Third Wave is a Christian charity based in Derby (England) that offers training in vocational skills, preindustrial crafts, horticultural and agricultural skills, environmental education, and woodland survival skills to disadvantaged people at city and farm locations. Third Wave employs a holistic approach to personal development in a community…

  13. Microfluidic waves.

    PubMed

    Utz, Marcel; Begley, Matthew R; Haj-Hariri, Hossein

    2011-11-21

    The propagation of pressure waves in fluidic channels with elastic covers is discussed in view of applications to flow control in microfluidic devices. A theory is presented which describes pressure waves in the fluid that are coupled to bending waves in the elastic cover. At low frequencies, the lateral bending of the cover dominates over longitudinal bending, leading to propagating, non-dispersive longitudinal pressure waves in the channel. The theory addresses effects due to both the finite viscosity and compressibility of the fluid. The coupled waves propagate without dispersion, as long as the wave length is larger than the channel width. It is shown that in channels of typical microfluidic dimensions, wave velocities in the range of a few 10 m s(-1) result if the channels are covered by films of a compliant material such as PDMS. The application of this principle to design microfluidic band pass filters based on standing waves is discussed. Characteristic frequencies in the range of a few kHz are readily achieved with quality factors above 30. PMID:21966667

  14. Joint inversion of shear wave travel time residuals and geoid and depth anomalies for long-wavelength variations in upper mantle temperature and composition along the Mid-Atlantic Ridge

    NASA Technical Reports Server (NTRS)

    Sheehan, Anne F.; Solomon, Sean C.

    1991-01-01

    Measurements were carried out for SS-S differential travel time residuals for nearly 500 paths crossing the northern Mid-Atlantic Ridge, assuming that the residuals are dominated by contributions from the upper mantle near the surface bounce point of the reflected phase SS. Results indicate that the SS-S travel time residuals decrease linearly with square root of age, to an age of 80-100 Ma, in general agreement with the plate cooling model. A joint inversion was formulated of travel time residuals and geoid and bathymetric anomalies for lateral variation in the upper mantle temperature and composition. The preferred inversion solutions were found to have variations in upper mantle temperature along the Mid-Atlantic Ridge of about 100 K. It was calculated that, for a constant bulk composition, such a temperature variation would produce about a 7-km variation in crustal thickness, larger than is generally observed.

  15. Wave-Like Ozone Movements

    NASA Astrophysics Data System (ADS)

    Roldugin, V. C.; Nikulin, G. N.; Henriksen, K.

    The wave-like character of the total ozone variations is examined from the Aral Sea and Karaganda observatories in Middle Asia, and from Tromsø and Murmansk in the Arctic. The waves have a period of 10-20 days and an amplitude of about 20-50 DU. They are seen practically every year when the ozone data do not contain too many gaps. In Middle Asia waves with the same periods are found in geopotential height and tropopause pressure variations. The ozone waves are caused by dynamic meteorological disturbances near the tropopause. The passing of a wave crest in the pressure field causes the convergence of ozone poor air under the tropopause and the divergence of ozone rich air above the tropopause giving rise to a total ozone content decrease. The passing of a wave trough stimulates the opposite process. By crosscorrelation analysis the wave-like movement was determined as eastward for both pairs of stations with a velocity of 11-15 °/day.

  16. Ion Cyclotron Waves in the Solar Wind

    NASA Astrophysics Data System (ADS)

    Wei, H. Y.; Jian, L. K.; Russell, C. T.; Omidi, N.

    2016-02-01

    The ion cyclotron waves (ICWs) refer to electromagnetic transverse waves with nearly field-aligned propagation, circular polarization, and frequencies near the proton gyro-frequency. This chapter presents the ICW studies observed in the solar wind over a wide range of heliocentric distances, at all solar longitudes, and at locations far from planets or comets. To better understand the wave source region, case studies have been performed on a special group of ICW storm events, in which the left-handed (LH) and right-handed (RH) waves were observed simultaneously in the spacecraft frame. The study in the chapter assumes the waves are generated through one possible mechanism (i.e., the temperature anisotropy instability). The variations of the wave properties with heliocentric distances may also provide information on the possible wave generation sources and the effects of the wave to the solar wind plasma.

  17. Atmospheric Waves

    NASA Technical Reports Server (NTRS)

    2007-01-01

    With its Multispectral Visible Imaging Camera (MVIC), half of the Ralph instrument, New Horizons captured several pictures of mesoscale gravity waves in Jupiter's equatorial atmosphere. Buoyancy waves of this type are seen frequently on Earth - for example, they can be caused when air flows over a mountain and a regular cloud pattern forms downstream. In Jupiter's case there are no mountains, but if conditions in the atmosphere are just right, it is possible to form long trains of these small waves. The source of the wave excitation seems to lie deep in Jupiter's atmosphere, below the visible cloud layers at depths corresponding to pressures 10 times that at Earth's surface. The New Horizons measurements showed that the waves move about 100 meters per second faster than surrounding clouds; this is about 25% of the speed of sound on Earth and is much greater than current models of these waves predict. Scientists can 'read' the speed and patterns these waves to learn more about activity and stability in the atmospheric layers below.

  18. Quasitravelling waves

    SciTech Connect

    Beklaryan, Leva A

    2011-02-11

    A finite difference analogue of the wave equation with potential perturbation is investigated, which simulates the behaviour of an infinite rod under the action of an external longitudinal force field. For a homogeneous rod, describing solutions of travelling wave type is equivalent to describing the full space of classical solutions to an induced one-parameter family of functional differential equations of point type, with the characteristic of the travelling wave as parameter. For an inhomogeneous rod, the space of solutions of travelling wave type is trivial, and their 'proper' extension is defined as solutions of 'quasitravelling' wave type. By contrast to the case of a homogeneous rod, describing the solutions of quasitravelling wave type is equivalent to describing the quotient of the full space of impulsive solutions to an induced one-parameter family of point-type functional differential equations by an equivalence relation connected with the definition of solutions of quasitravelling wave type. Stability of stationary solutions is analyzed. Bibliography: 9 titles.

  19. Moreton Waves

    NASA Technical Reports Server (NTRS)

    Thompson, B. J.

    1999-01-01

    "Moreton waves," named for the observer who popularized them, are a solar phenomenon also known in scientific literature as "Moreton-Ramsey wave," "flare waves," "flare-associated waves," "MHD blast waves," "chromospheric shock fronts" and various other combinations of terms which connote violently propagating impulsive disturbances. It is unclear whether all of the observations to which these terms have been applied pertain to a single physical phenomenon: there has perhaps been some overlap between the observations and the assumed physical properties of the observed occurrence. Moreton waves are ideally observed in the wings of H alpha, and appear as semi-circular fronts propagating at speeds ranging from several hundred to over a thousand km/sec. They form an arc, or "brow shape" which can span up to 180 degrees. Extrapolating the speed and locations of the arc indicates that the phenomenon's origin intersects well with the impulsive phase of the associated H alpha flare (if the flare exhibits an impulsive phase). However, the arc may not form or may not be observable until it is tens of megameters from the flaring region, and subsequently can propagate to distances exceeding 100 megameters. The high speeds and distances of propagation, plus the associated radio and energetic particle observations, provided strong evidence of a coronal, rather than a chromospheric origin. The H alpha manifestation of the wave is assumed to be the "ground track" or "skirt" of a three-dimensional disturbance.

  20. Ship waves and lee waves

    NASA Technical Reports Server (NTRS)

    Sharman, R. D.; Wurtele, M. G.

    1983-01-01

    Dynamics analogous to those of surface ship waves on water of finite depth are noted for the three-dimensional trapped lee wave modes produced by an isolated obstacle in a stratified fluid. This vertical trapping of wave energy is modeled by uniform upstream flow and stratification, bounded above by a rigid lid, and by a semiinfinite fluid of uniform stability whose wind velocity increases exponentially with height, representing the atmosphere. While formal asymptotic solutions are produced, limited quantitative usefulness is obtained through them because of the limitations of the approximations and the infinity of modes in the solution. Time-dependent numerical models are accordingly developed for both surface ship waves and internal and atmospheric ship waves, yielding a variety of results.

  1. Wave Propagation in the Vicinities of Rock Fractures Under Obliquely Incident Wave

    NASA Astrophysics Data System (ADS)

    Zou, Yang; Li, Jianchun; He, Lei; laloui, Lyesse; Zhao, Jian

    2016-05-01

    Though obliquely incident plane wave across rock fractures has been extensively investigated by theoretical analysis, the quantitative identification of each wave emerged from fractures has not been achieved either in numerical simulation or laboratory experiment. On the other hand, there are no theoretical results describing the stress/velocity state of the rocks beside a fracture. The superposition of the multiple waves propagating in the media results in the variation of the stress/velocity state. To understand the superposition of the wave components in the adjacent rocks of a facture, based on the geometrical analysis of the wave paths, the lag times among passing waves at an arbitrary point are determined. The normalised critical distances from the fracture to the measuring locations where the corresponding harmonic waves depart from other waves for a certain duration are then derived. Discussion on the correction for an arbitrary incident wave is then carried out considering the changes of the duration of the reflected and transmitted waves. Under the guidance of the analysis, wave superposition is performed for theoretical results and separated waves are obtained from numerical model. They are demonstrated to be consistent with each other. The measurement and the data processing provide an approach for wave separation in a relatively unbounded media. In addition, based on the mechanical analysis on the wave front, an indirect wave separation method is proposed which provides a possibility for laboratory experiments of wave propagation with an arbitrary incident angle.

  2. Dissipation of atmospheric waves: An asymptotic approach

    NASA Astrophysics Data System (ADS)

    Godin, Oleg A.

    2014-05-01

    Wave energy dissipation through irreversible thermodynamic processes is a major factor influencing propagation of acoustic and gravity waves in the Earth's atmosphere. Accurate modeling of the wave dissipation is important in a wide range of problems from understanding the momentum and energy transport by waves into the upper atmosphere to predicting long-range propagation of infrasound to the acoustic remote sensing of mesospheric and thermospheric winds. Variations with height of the mass density, kinematic viscosity, and other physical parameters of the atmosphere have a profound effect on the wave dissipation and its frequency dependence. To characterize the wave dissipation, it is typical to consider an idealized environment, which admits plane-wave solutions. For instance, kinematic viscosity is often assumed to be constant in derivations of dispersion equations of acoustic-gravity waves in the atmosphere. While the assumption of constant shear viscosity coefficient would be much more realistic, it does not lead to plane-wave solutions. Here, we use an asymptotic approach to derivation of dispersion equations of acoustic-gravity waves in dissipative fluids. The approach does not presuppose existence of any plane-wave solutions and relies instead on the assumption that spatial variations of environmental parameters are gradual. The atmosphere is modeled as a neutral, horizontally stratified, moving ideal gas of variable composition. Linearized hydrodynamic equations for compressible fluids in a gravity field are solved asymptotically, leading to a self-consistent version of the Wentzel-Kramers-Brillouin approximation for acoustic-gravity waves. Dissipative processes are found to affect both the eikonal and the geometric (Berry) phase of the wave. Newly found expressions for acoustic-gravity wave attenuation due to viscosity and thermal conductivity of the air are compared to results previously reported in the literature. Effects of the wind on the wave

  3. Coronary venous oximetry using MRI.

    PubMed

    Foltz, W D; Merchant, N; Downar, E; Stainsby, J A; Wright, G A

    1999-11-01

    Based on the Fick law, coronary venous blood oxygen measurements have value for assessing functional parameters such as the coronary flow reserve. At present, the application of this measure is restricted by its invasive nature. This report describes the design and testing of a noninvasive coronary venous blood oxygen measurement using MRI, with a preliminary focus on the coronary sinus. After design optimization including a four-coil phased array and an optimal set of data acquisition parameters, quality tests indicate measurement precision on the order of the gold standard optical measurement (3%O(2)). Comparative studies using catheter sampling suggest reasonable accuracy (3 subjects), with variability dominated by sampling location uncertainty ( approximately 7%O(2)). Intravenous dipyridamole (5 subjects) induces significant changes in sinus blood oxygenation (22 +/- 9% O(2)), corresponding to flow reserves of 1.8 +/- 0.4, suggesting the potential for clinical utility. Underestimation of flow reserve is dominated by right atrial mixing and the systemic effects of dipyridamole. Magn Reson Med 42:837-848, 1999. PMID:10542342

  4. Middle Atmosphere Dynamics with Gravity Wave Interactions in the Numerical Spectral Model: Tides and Planetary Waves

    NASA Technical Reports Server (NTRS)

    Mayr, Hans G.; Mengel, J. G.; Chan, K. L.; Huang, F. T.

    2010-01-01

    As Lindzen (1981) had shown, small-scale gravity waves (GW) produce the observed reversals of the zonal-mean circulation and temperature variations in the upper mesosphere. The waves also play a major role in modulating and amplifying the diurnal tides (DT) (e.g., Waltersheid, 1981; Fritts and Vincent, 1987; Fritts, 1995a). We summarize here the modeling studies with the mechanistic numerical spectral model (NSM) with Doppler spread parameterization for GW (Hines, 1997a, b), which describes in the middle atmosphere: (a) migrating and non-migrating DT, (b) planetary waves (PW), and (c) global-scale inertio gravity waves. Numerical experiments are discussed that illuminate the influence of GW filtering and nonlinear interactions between DT, PW, and zonal mean variations. Keywords: Theoretical modeling, Middle atmosphere dynamics, Gravity wave interactions, Migrating and non-migrating tides, Planetary waves, Global-scale inertio gravity waves.

  5. Micro-scale environmental variation amplifies physiological variation among individual mussels.

    PubMed

    Jimenez, Ana Gabriela; Jayawardene, Sarah; Alves, Shaina; Dallmer, Jeremiah; Dowd, W Wesley

    2015-12-01

    The contributions of temporal and spatial environmental variation to physiological variation remain poorly resolved. Rocky intertidal zone populations are subjected to thermal variation over the tidal cycle, superimposed with micro-scale variation in individuals' body temperatures. Using the sea mussel (Mytilus californianus), we assessed the consequences of this micro-scale environmental variation for physiological variation among individuals, first by examining the latter in field-acclimatized animals, second by abolishing micro-scale environmental variation via common garden acclimation, and third by restoring this variation using a reciprocal outplant approach. Common garden acclimation reduced the magnitude of variation in tissue-level antioxidant capacities by approximately 30% among mussels from a wave-protected (warm) site, but it had no effect on antioxidant variation among mussels from a wave-exposed (cool) site. The field-acclimatized level of antioxidant variation was restored only when protected-site mussels were outplanted to a high, thermally stressful site. Variation in organismal oxygen consumption rates reflected antioxidant patterns, decreasing dramatically among protected-site mussels after common gardening. These results suggest a highly plastic relationship between individuals' genotypes and their physiological phenotypes that depends on recent environmental experience. Corresponding context-dependent changes in the physiological mean-variance relationships within populations complicate prediction of responses to shifts in environmental variability that are anticipated with global change. PMID:26645201

  6. Novel wave power analysis linking pressure-flow waves, wave potential, and the forward and backward components of hydraulic power.

    PubMed

    Mynard, Jonathan P; Smolich, Joseph J

    2016-04-15

    Wave intensity analysis provides detailed insights into factors influencing hemodynamics. However, wave intensity is not a conserved quantity, so it is sensitive to diameter variations and is not distributed among branches of a junction. Moreover, the fundamental relation between waves and hydraulic power is unclear. We, therefore, propose an alternative to wave intensity called "wave power," calculated via incremental changes in pressure and flow (dPdQ) and a novel time-domain separation of hydraulic pressure power and kinetic power into forward and backward wave-related components (ΠP±and ΠQ±). Wave power has several useful properties:1) it is obtained directly from flow measurements, without requiring further calculation of velocity;2) it is a quasi-conserved quantity that may be used to study the relative distribution of waves at junctions; and3) it has the units of power (Watts). We also uncover a simple relationship between wave power and changes in ΠP±and show that wave reflection reduces transmitted power. Absolute values of ΠP±represent wave potential, a recently introduced concept that unifies steady and pulsatile aspects of hemodynamics. We show that wave potential represents the hydraulic energy potential stored in a compliant pressurized vessel, with spatial gradients producing waves that transfer this energy. These techniques and principles are verified numerically and also experimentally with pressure/flow measurements in all branches of a central bifurcation in sheep, under a wide range of hemodynamic conditions. The proposed "wave power analysis," encompassing wave power, wave potential, and wave separation of hydraulic power provides a potent time-domain approach for analyzing hemodynamics. PMID:26873972

  7. Strong acoustic wave action

    NASA Astrophysics Data System (ADS)

    Gokhberg, M. B.

    1983-07-01

    Experiments devoted to acoustic action on the atmosphere-magnetosphere-ionosphere system using ground based strong explosions are reviewed. The propagation of acoustic waves was observed by ground observations over 2000 km in horizontal direction and to an altitude of 200 km. Magnetic variations up to 100 nT were detected by ARIEL-3 satellite near the epicenter of the explosion connected with the formation of strong field aligned currents in the magnetosphere. The enhancement of VLF emission at 800 km altitude is observed.

  8. Ion cyclotron waves at Mars: Occurrence and wave properties

    NASA Astrophysics Data System (ADS)

    Wei, H. Y.; Cowee, M. M.; Russell, C. T.; Leinweber, H. K.

    2014-07-01

    Ion cyclotron waves (ICWs) are generated during the interaction between the solar wind and the Martian exosphere in a process called ion pickup. Mars Global Surveyor (MGS) detected waves near the proton gyrofrequency, indicating pickup of the exospheric hydrogen. To analyze these waves, we first improve the zero levels of the MGS magnetic field data taken during the first aerobreaking phase and then perform a statistical study of the ICWs observed from just outside the Martian bow shock to over 14 Mars radii away. These ICW events typically last for 5 to 30 min but can occasionally last for hours. The wave power decreases slowly with distance on both the upstream and downstream sides. From the variation of wave properties with the strength of the background field, we find that there are likely still remaining offsets in at least some the data sets even after applying our calibration technique. Thus, we use the events with a strong background field to examine the wave properties that depend on an accurate determination of the field direction and strength. We find the pickup angle associated with the largest occurrence rate of ICWs to be around 45°, but neither the wave amplitude, nor wave frequency, nor wave duration appear to vary with pickup angle. Finally, we find the waves with background field strength greater than 4 nT occur on both the positive and negative electric field sides of Mars but have a larger occurrence rate on the side of Mars in the positive electric field direction (which is defined as the direction of the cross product of the magnetic field vector and solar wind flow vector).

  9. Full wave description of VLF wave penetration through the ionosphere

    NASA Astrophysics Data System (ADS)

    Kuzichev, Ilya; Shklyar, David

    2010-05-01

    Of the many problems in whistler study, wave propagation through the ionosphere is among the most important, and the most difficult at the same time. Both satellite and ground-based investigations of VLF waves include considerations of this problem, and it has been in the focus of research since the beginning of whistler study (Budden [1985]; Helliwell [1965]). The difficulty in considering VLF wave passage through the ionosphere is, after all, due to fast variation of the lower ionosphere parameters as compared to typical VLF wave number. This makes irrelevant the consideration in the framework of geometrical optics, which, along with a smooth variations of parameters, is always based on a particular dispersion relation. Although the full wave analysis in the framework of cold plasma approximation does not require slow variations of plasma parameters, and does not assume any particular wave mode, the fact that the wave of a given frequency belongs to different modes in various regions makes numerical solution of the field equations not simple. More specifically, as is well known (e.g. Ginzburg and Rukhadze [1972]), in a cold magnetized plasma, there are, in general, two wave modes related to a given frequency. Both modes, however, do not necessarily correspond to propagating waves. In particular, in the frequency range related to whistler waves, the other mode is evanescent, i.e. it has a negative value of N2 (the refractive index squared). It means that one of solutions of the relevant differential equations is exponentially growing, which makes a straightforward numerical approach to these equations despairing. This well known difficulty in the problem under discussion is usually identified as numerical swamping (Budden [1985]). Resolving the problem of numerical swamping becomes, in fact, a key point in numerical study of wave passage through the ionosphere. As it is typical of work based on numerical simulations, its essential part remains virtually hidden

  10. Comparing the Robustness of High-Frequency Traveling-Wave Tube Slow-Wave Circuits

    NASA Technical Reports Server (NTRS)

    Chevalier, Christine T.; Wilson, Jeffrey D.; Kory, Carol L.

    2007-01-01

    A three-dimensional electromagnetic field simulation software package was used to compute the cold-test parameters, phase velocity, on-axis interaction impedance, and attenuation, for several high-frequency traveling-wave tube slow-wave circuit geometries. This research effort determined the effects of variations in circuit dimensions on cold-test performance. The parameter variations were based on the tolerances of conventional micromachining techniques.

  11. The Accuracy of a Near-Infrared Spectroscopy Cerebral Oximetry Device and Its Potential Value for Estimating Jugular Venous Oxygen Saturation

    PubMed Central

    Ikeda, Keita; MacLeod, David B; Grocott, Hilary P.; Moretti, Eugene W.; Ames, Warwick; Vacchiano, Charles

    2014-01-01

    Background An intriguing potential clinical use of cerebral oximeter measurements (SctO2) is the ability to noninvasively estimate jugular bulb venous oxygen saturation (SjvO2). Our purpose in this study was to determine the accuracy of the FORE-SIGHT® (CAS Medical Systems; Branford, CT), which is calibrated to a weighted average of 70% (SjvO2) and 30% arterial saturation, for Food and Drug Administration pre-market approval 510 (k) certification by adapting an industry standard protocol, ISO 9919:2005 [www.ISO.org] (used for pulse oximeters) and to evaluate the use of SctO2 and SpO2 measurements to noninvasively estimate jugular venous oxygen saturation (SnvO2). Methods Paired blood gas samples from the radial artery and the jugular venous bulb were collected from 20 healthy volunteers undergoing progressive oxygen desaturation from 100 to 70%. The blood sample pairs were analyzed via co-oximetry and used to calculate the approximate mixed vascular cerebral blood oxygen saturation, or reference SctO2 values (refSctO2), during increasing hypoxia. These reference values were compared to bilateral FORE-SIGHT SctO2 values recorded simultaneously with the blood gas draws to determine its accuracy. Bilateral SctO2 and SpO2 measurements were then used to calculate SnvO2 values which were compared to SjvO2. Results Two hundred forty-six arterial and 253 venous samples from 18 subjects were used in the analysis. The ipsilateral FORE-SIGHT SctO2 values showed a tolerance interval (TI) of [−10.72 10.90] Lin’s concordance correlation coefficient (CCC) with standard error (SE) of 0.83 ± 0.073 with the refSctO2 values calculated using arterial and venous blood gases. The combined data had a CCC of 0. 81 + 0.059 with TI of [−9.22 9.40] with overall bias was 0.09% and amplitude of the root mean square of error after it was corrected with random effects analysis was 2.92%. The bias and variability values between the ipsilateral and the contralateral FORE-SIGHT SctO2

  12. Quasi-periodic variations in the Doppler shift of HF signals scattered by artificial ionospheric turbulence

    SciTech Connect

    Belenov, A.F.; Ponomarenko, P.V.; Sinitsyn, V.G.; Yampol`skii, Yu.M.

    1994-06-01

    The results of an experimental study of quasi-periodic variations of the Doppler shift (DS) of decimeter-wave signals scattered by artificial ionospheric turbulence are presented. It is suggested that ionospheric MHD waves of natural origin are a possible cause of such variations. The amplitude of the magnetic component of such waves that leads to observable values of DS variations is estimated to be 1{gamma}.

  13. Quasi-periodic variations in the Doppler shift of HF signals scattered by artificial ionospheric turbulence

    NASA Astrophysics Data System (ADS)

    Belenov, A. F.; Ponomarenko, P. V.; Sinitsyn, V. G.; Yampol'Skii, Yu. M.

    1993-12-01

    The results of an experimental study of quasi-periodic variations of the Doppler shift (DS) of decimeter-wave signals scattered by artificial ionospheric turbulence are presented. It is suggested that ionospheric MHD waves of natural origin are a possible cause of such variations. The amplitude of the magnetic component of such waves that leads to observable values of DS variations is estimated to be 1γ.

  14. Statistics of unidirectional random breaking water-waves

    NASA Astrophysics Data System (ADS)

    Shemer, Lev; Sergeeva, Anna

    2011-11-01

    Quasi-random wave groups were studied experimentally in a 300 m long Large Wave Chanel in Hannover. Multiple realizations of several spectral shapes each having random phases of individual harmonics were excited by a computer-controlled wavemaker. Wave field evolution along the tank was recorded by 28 wave gauges and the variation of waves' statistical parameters with the distance from the wavemaker was analyzed. An attempt was made to identify individual breaking events based on the spectrum variation between consecutive wave gauges. It was concluded that energy decay in the high frequency part of the spectrum can serve as a reliable criterion for breaking localization in each realization. The data processing based on the adopted criterion resulted in constructing separate ensembles of events with and without breaking. Statistical processing of those ensembles enabled to assess the effect of breaking on such wave field characteristics as probability of appearance of extremely steep (rogue, or freak) waves, as well on skewness and kurtosis.

  15. Water wave model with accurate dispersion and vertical vorticity

    NASA Astrophysics Data System (ADS)

    Bokhove, Onno

    2010-05-01

    Cotter and Bokhove (Journal of Engineering Mathematics 2010) derived a variational water wave model with accurate dispersion and vertical vorticity. In one limit, it leads to Luke's variational principle for potential flow water waves. In the another limit it leads to the depth-averaged shallow water equations including vertical vorticity. Presently, focus will be put on the Hamiltonian formulation of the variational model and its boundary conditions.

  16. On shallow water rogue wave formation in strongly inhomogeneous channels

    NASA Astrophysics Data System (ADS)

    Didenkulova, Ira; Pelinovsky, Efim

    2016-05-01

    Rogue wave formation in shallow water is often governed by dispersive focusing and wave-bottom interaction. In this study we try to combine these mechanisms by considering dispersive nonreflecting wave propagation in shallow strongly inhomogeneous channels. Nonreflecting wave propagation provides extreme wave amplification and the transfer of wave energy over large distances, while dispersive effects allow formation of a short-lived wave of extreme height (rogue wave). We found several types of water channels, where this mechanism can be realized, including (i) channels with a monotonically decreasing cross-section (normal dispersion), (ii) an inland basin described by a half of elliptic paraboloid (abnormal dispersion) and (iii) an underwater hill described by a half of hyperbolic paraboloid (normal dispersion). Conditions for variations of local frequency in the wave train providing optimal focusing of the wave train are also found.

  17. On neutron surface waves

    SciTech Connect

    Ignatovich, V. K.

    2009-01-15

    It is shown that neutron surface waves do not exist. The difference between the neutron wave mechanics and the wave physics of electromagnetic and acoustic processes, which allows the existence of surface waves, is analyzed.

  18. Gravity Waves

    NASA Technical Reports Server (NTRS)

    Vanzandt, T. E.

    1985-01-01

    Atmospheric parameters fluctuate on all scales. In the mesoscale these fluctuations are occasionally sinusoidal so that they can be interpreted as gravity waves. Usually, however, the fluctuations are noise like, so that their cause is not immediately evident. Results of mesoscale observations in the 20 to 120 m altitude range that are suitable for incorporation into a model atmosphere are very limited. In the stratosphere and lower mesosphere observations are sparse and very little data has been summarized into appropriate form. There is much more data in the upper mesosphere and lower thermosphere, but again very little of it has been summarized. The available mesoscale spectra of horizontal wind u versus vertical wave number m in the 20 to 120 km altitude range are shown together with a spectrum from the lower atmosphere for comparison. Further information about these spectra is given. In spite of the large range of altitudes and latitudes, the spectra from the lower atmosphere (NASA, 1971 and DEWAN, 1984) are remarkably similar in both shape and amplitude. The mean slopes of -2.38 for the NASA spectrum and -2.7 for the Dewan spectra are supported by the mean slope of -2.75 found by ROSENBERG et al. (1974). The mesospheric spectrum is too short to establish a shape. Its amplitude is about an order of magnitude larger than the NASA spectrum in the same wave number range. The NASA and Dewan spectra suggest that the mesoscale spectra in the lower atmosphere are insensitive to meteorological conditions.

  19. Asymptotic Linear Stability of Solitary Water Waves

    NASA Astrophysics Data System (ADS)

    Pego, Robert L.; Sun, Shu-Ming

    2016-06-01

    We prove an asymptotic stability result for the water wave equations linearized around small solitary waves. The equations we consider govern irrotational flow of a fluid with constant density bounded below by a rigid horizontal bottom and above by a free surface under the influence of gravity neglecting surface tension. For sufficiently small amplitude waves, with waveform well-approximated by the well-known sech-squared shape of the KdV soliton, solutions of the linearized equations decay at an exponential rate in an energy norm with exponential weight translated with the wave profile. This holds for all solutions with no component in (that is, symplectically orthogonal to) the two-dimensional neutral-mode space arising from infinitesimal translational and wave-speed variation of solitary waves. We also obtain spectral stability in an unweighted energy norm.

  20. Waves in a Venus general circulation model

    NASA Astrophysics Data System (ADS)

    Sugimoto, Norihiko; Takagi, Masahiro; Matsuda, Yoshihisa

    2014-11-01

    Waves in the Venus atmosphere are numerically investigated by extending a work of Sugimoto et al. (2014). Fast superrotating zonal flow of 120 m s-1 at the equator is reproduced and maintained by solar heating for more than 10 Earth years. The meridional distribution of the obtained fast zonal flow is quite consistent with observations at the cloud levels. In the cloud layer, baroclinic waves develop continuously with a life cycle of ~25 Earth days at midlatitudes, using available potential energy derived from a baroclinically unstable basic state. Rossby waves observed at the cloud top are generated by the baroclinic waves and induce spatio-temporal variation of the superrotation with amplitude larger than 25 m s-1. Further, Kelvin waves with a period of ˜ 6.2 days appear in the equatorial region below ~50 km. Momentum and heat transports produced by these waves are discussed.

  1. ULF Waves in the Inner Magnetosphere

    NASA Astrophysics Data System (ADS)

    Takahashi, K.

    2016-02-01

    This chapter presents examples that illustrate how recent spacecraft observations allow us to quantitatively understand the mode structure of various magnetohydrodynamic (MHD)-type ultra-low-frequency (ULF) waves propagating into or excited in the inner magnetosphere. In addition, particle observations provide evidence for specific types of wave-particle interaction. The fast mode waves may be free propagating or evanescent, depending on their frequency and wavelength and the spatial variation of the MHD wave speed. The inhomogeneity of the magnetosphere causes the fast mode energy to be transferred to standing Alfven waves through the well-known field line resonance mechanism. The cold plasma MHD equation for axisymmetric plasma with a dipole magnetic field yields two guided mode solutions called the axisymmetric toroidal mode and guided poloidal mode. Although toroidal and poloidal modes are always coupled in the real magnetosphere, the idealized modes are good approximation to the basic features of observed magnetospheric standing Alfven waves.

  2. Bragg reflection of ocean waves from sandbars

    NASA Astrophysics Data System (ADS)

    Elgar, Steve; Raubenheimer, B.; Herbers, T. H. C.

    2003-01-01

    Resonant Bragg reflection of ocean surface waves by a field of natural shore-parallel sandbars was observed in Cape Cod Bay, MA. Waves transmitted through the bars were reflected strongly from the steep shoreline, and the observed cross-shore variations in the onshore- and offshore-directed energy fluxes are consistent with theory for resonant Bragg reflection, including a 20% decay of the incident wave energy flux that is an order of magnitude greater than expected for wave-orbital velocity induced bottom friction. Bragg reflection was observed for a range of incident wave conditions, including storms when sediment transported toward and away from nodes and antinodes caused by the reflecting waves might result in growth and maintenance of the sandbars.

  3. Genomic characteristics of cattle copy number variations

    Technology Transfer Automated Retrieval System (TEKTRAN)

    We performed a systematic analysis of cattle copy number variations (CNVs) using the Bovine HapMap SNP genotyping data, including 539 animals of 21 modern cattle breeds and 6 outgroups. After correcting genomic waves and considering the trio information, we identified 682 candidate CNV regions (CNVR...

  4. Compaction Waves in Granular HMX

    SciTech Connect

    E. Kober; R. Menikoff

    1999-01-01

    Piston driven compaction waves in granular HMX are simulated with a two-dimensional continuum mechanics code in which individual grains are resolved. The constitutive properties of the grains are modeled with a hydrostatic pressure and a simple elastic-plastic model for the shear stress. Parameters are chosen to correspond to inert HMX. For a tightly packed random grain distribution (with initial porosity of 19%) we varied the piston velocity to obtain weak partly compacted waves and stronger fully compacted waves. The average stress and wave speed are compatible with the porous Hugoniot locus for uni- axial strain. However, the heterogeneities give rise to stress concentrations, which lead to localized plastic flow. For weak waves, plastic deformation is the dominant dissipative mechanism and leads to dispersed waves that spread out in time. In addition to dispersion, the granular heterogeneities give rise to subgrain spatial variation in the thermodynamic variables. The peaks in the temperature fluctuations, known as hot spots, are in the range such that they are the critical factor for initiation sensitivity.

  5. Variational calculations of positronium scattering with hydrogen

    NASA Astrophysics Data System (ADS)

    Woods, Denton

    Positronium-hydrogen (Ps-H) scattering is of interest, as it is a fundamental four-body Coulomb problem. We have investigated low-energy Ps-H scattering below the Ps(n=2) excitation threshold using the Kohn variational method and variants of the method with a trial wavefunction that includes highly correlated Hylleraas-type short-range terms. We give an elegant formalism that combines all Kohn-type variational methods into a single form. Along with this, we have also developed a general formalism for Kohn-type matrix elements that allows us to evaluate arbitrary partial waves with a single codebase. Computational strategies we have developed and use in this work will also be discussed. With these methods, we have computed phase shifts for the first six partial waves for both the singlet and triplet states. The 1S and 1P phase shifts are highly accurate results and could potentially be viewed as benchmark results. Resonance positions and widths for the 1S-, 1P-, 1D-, and 1F-waves have been calculated. We present elastic integrated, elastic differential, and momentum transfer cross sections using all six partial waves and note interesting features of each. We use multiple effective range theories, including several that explicitly take into account the long-range van der Waals interaction, to investigate scattering lengths for the 1,3S and 1,3P partial waves and effective ranges for the 1,3S-wave.

  6. Wash waves generated by high speed displacement ships

    NASA Astrophysics Data System (ADS)

    Zhou, Li-lan; Gao, Gao; Huijsmans, R. H. M.

    2015-10-01

    It is difficult to compute far-field waves in a relative large area by using one wave generation model when a large calculation domain is needed because of large dimensions of the waterway and long distance of the required computing points. Variation of waterway bathymetry and nonlinearity in the far field cannot be included in a ship fixed process either. A coupled method combining a wave generation model and wave propagation model is then used in this paper to simulate the wash waves generated by the passing ship. A NURBS-based higher order panel method is adopted as the stationary wave generation model; a wave spectrum method and Boussinesq-type equation wave model are used as the wave propagation model for the constant water depth condition and variable water depth condition, respectively. The waves calculated by the NURBS-based higher order panel method in the near field are used as the input for the wave spectrum method and the Boussinesq-type equation wave model to obtain the far-field waves. With this approach it is possible to simulate the ship wash waves including the effects of water depth and waterway bathymetry. Parts of the calculated results are validated experimentally, and the agreement is demonstrated. The effects of ship wash waves on the moored ship are discussed by using a diffraction theory method. The results indicate that the prediction of the ship induced waves by coupling models is feasible.

  7. Lamb Wave Helical Ultrasonic Tomography

    NASA Astrophysics Data System (ADS)

    Leonard, K. R.; Hinders, M. K.

    2004-02-01

    Ultrasonic guided waves have been used for a wide variety of ultrasonic inspection techniques. We describe here a new variation called helical ultrasound tomography (HUT). This new technique, among other things, has direct application to advanced pipe inspection. HUT uses guided ultrasonic waves along with an adaptation of the tomographic reconstruction algorithms developed by seismologists for what they call "cross borehole" tomography. In HUT, the Lamb-like guided waves travel in various helical crisscross paths between two parallel circumferential transducer arrays instead of the planar crisscross seismic paths between two boreholes. Although the measurement itself is fairly complicated, the output of the tomographic reconstruction is a readily interpretable map of a quantity of interest such as pipe wall thickness. We demonstrate the feasibility of the HUT technique via laboratory scans on steel pipe segments into which controlled thinnings have been introduced.

  8. Stochastic modeling of inhomogeneous ocean waves

    NASA Astrophysics Data System (ADS)

    Smit, P. B.; Janssen, T. T.; Herbers, T. H. C.

    2015-12-01

    Refraction of swell waves in coastal waters can result in fast-scale variations of wave statistics due to wave interference. These variations cannot be resolved by wave models based on the radiative transport equation. More advanced models based on quasi-coherent theory, a generalization of the radiative transfer equation, can be coupled or nested into larger-scale models to resolve such local inhomogeneous effects. However, source terms for quasi-coherent models to account for non-conservative and nonlinear effects are not available, which hampers their operational use. In the present work we revisit the derivation of quasi-coherent theory to consistently include a source term for dissipation associated with depth-induced wave breaking. We demonstrate how general source terms can be incorporated in this class of models and compare model simulations with the new dissipation term to laboratory observations of focusing and breaking waves over a submerged shoal. The results show that a consistent derivation of source terms is essential to accurately capture coherent effects in coastal areas. Specifically, our results show that if coherent effects are ignored in the dissipation term, interference effects are strongly exaggerated. With the development of source terms for quasi-coherent models they can be effectively nested inside or otherwise coupled to larger-scale wave models to efficiently improve operational predictive capability of wave models near the coast.

  9. P-wave Variability and Atrial Fibrillation

    PubMed Central

    Censi, Federica; Corazza, Ivan; Reggiani, Elisa; Calcagnini, Giovanni; Mattei, Eugenio; Triventi, Michele; Boriani, Giuseppe

    2016-01-01

    The analysis of P-wave template has been widely used to extract indices of Atrial Fibrillation (AF) risk stratification. The aim of this paper was to assess the potential of the analysis of the P-wave variability over time in patients suffering from atrial fibrillation. P-wave features extracted from P-wave template together with novel indices of P-wave variability have been estimated in a population of patients suffering from persistent AF and compared to those extracted from control subjects. We quantify the P-wave variability over time using three algorithms and we extracted three novel indices: one based on the cross-correlation coefficients among the P-waves (Cross-Correlation Index, CCI), one associated to variation in amplitude of the P-waves (Amplitude Dispersion Index, ADI), one sensible to the phase shift among P-waves (Warping Index, WI). The control group resulted to be characterized by shorter P-wave duration and by a less amount of fragmentation and variability, respect to AF patients. The parameter CCI shows the highest sensitivity (97.3%) and a good specificity (95%). PMID:27225709

  10. Many-body wave functions

    SciTech Connect

    Chasman, R.R.

    1995-08-01

    In the past few years, we developed many-body variational wave functions that allow one to treat pairing and particle-hole two-body interactions on an equal footing. The complexity of these wave functions depends on the number of levels included in the valence space, but does not depend on the number of nucleons in the system. By using residual interaction strengths (e.g. the quadrupole interaction strength or pairing interaction strength) as generator coordinates, one gets many different wave functions, each having a different expectation value for the relevant interaction mode. These wave functions are particularly useful when one is dealing with a situation in which the mean-field approximation is inadequate. Because the same basis states are used in the construction of the many-body wave functions, it is possible to calculate overlaps and interaction matrix elements for the many-body wave functions (which are not in general orthogonal) easily. The valence space can contain a large number of single-particle basis states, when there are constants of motion that can be used to break the levels up into groups. We added a cranking term to the many-body Hamiltonian and modified the projection procedure to get states of good signature before variation. In our present implementation, each group is limited to eight pairs of single-particle levels. We are working on ways of increasing the number of levels that can be included in each group. We are also working on including particle-particle residual interaction modes, in addition to pairing, in our Hamiltonian.

  11. The relationship between partial pressure of oxygen and perfusion in two murine tumors after X-ray irradiation: a combined gadopentetate dimeglumine dynamic magnetic resonance imaging and in vivo electron paramagnetic resonance oximetry study.

    PubMed

    Goda, F; Bacic, G; O'Hara, J A; Gallez, B; Swartz, H M; Dunn, J F

    1996-07-15

    Changes of partial pressure of oxygen (pO2) and blood perfusion were studied in MTG-B and RIF-1 tumors (n = 5 each) before and after a single 20-Gy dose of X-ray irradiation. Using electron paramagnetic resonance oximetry, we have observed an initial fast decrease of pO2 after irradiation, followed by a slow increase. The time course of these changes was faster in the MTG-B tumors than in the RIF-1 tumors. Gadopentetate dimeglumine (Gd-DTPA) dynamic magnetic resonance imaging studies showed a reduction in uptake of Gd-DTPA at the time of minimum pO2 and a recovery at the time of maximum pO2 in each tumor. Previous work indicates that there is microscopic heterogeneity in tumors, with well-vascularized "capillary regions" being closer to capillaries than poorly vascularized "noncapillary regions." We propose a two-component (slow and fast) model of Gd-DTPA uptake that is designed to quantify the kinetics of these two compartments by analyzing the total tumor uptake kinetics without having to identify specific regions of interest. Total perfusion in the tumors was greatly reduced at the time of minimum oxygenation, and the volume of the slow component increased after irradiation. We conclude that a decrease in blood perfusion is one of the main causes of the decline in pO2 observed after irradiation. PMID:8764132

  12. Parabolic approximation method for fast magnetosonic wave propagation in tokamaks

    SciTech Connect

    Phillips, C.K.; Perkins, F.W.; Hwang, D.Q.

    1985-07-01

    Fast magnetosonic wave propagation in a cylindrical tokamak model is studied using a parabolic approximation method in which poloidal variations of the wave field are considered weak in comparison to the radial variations. Diffraction effects, which are ignored by ray tracing mthods, are included self-consistently using the parabolic method since continuous representations for the wave electromagnetic fields are computed directly. Numerical results are presented which illustrate the cylindrical convergence of the launched waves into a diffraction-limited focal spot on the cyclotron absorption layer near the magnetic axis for a wide range of plasma confinement parameters.

  13. Waves in Plasmas

    SciTech Connect

    Tracy, Eugene R

    2009-09-21

    Quadratic corrections to the metaplectic formulation of mode conversions. In this work we showed how to systematically deal with quadratic corrections beyond the usual linearization of the dispersion matrix at a conversion. The linearization leads to parabolic cylinder functions as the local approximation to the full-wave behavior, but these do not include the variation in amplitude associated with ray refraction in the neighborhood of the conversion. Hence, the region over which they give a good fit to the incoming and outgoing WKB solutions is small. By including higher order corrections it is possible to provide a much more robust matching. We also showed that it was possible, in principle, to extend these methods to arbitrary order. A new normal form for mode conversion. This is based upon our earlier NSF-DOE-funded work on ray helicity. We have begun efforts to apply these new ideas in practical ray tracing algorithms. Group theoretical foundation of path integrals and phase space representations of wave problems. Using the symbol theory of N. Zobin, we developed a new understanding of path integrals on phase space. The initial goal was to find practical computational tools for dealing with non-standard mode conversions. Along the way we uncovered a new way to represent wave functions directly on phase space without the intermediary of a Wigner function. We are exploring the use of these ideas for numerical studies of conversion, with the goal of eventually incorporating kinetic effects. Wave packet studies of gyroresonance crossing. In earlier work, Huanchun Ye and Allan Kaufman -- building upon ideas due to Lazar Friedland -- had shown that gyroresonance crossings could be treated as a double conversion. This perspective is one we have used for many of our papers since then. We are now performing a detailed numerical comparison between full-wave and ray tracing approaches in the study of minority-ion gyroresonance crossing. In this study, a fast magnetosonic

  14. ASTER Waves

    NASA Technical Reports Server (NTRS)

    2000-01-01

    The pattern on the right half of this image of the Bay of Bengal is the result of two opposing wave trains colliding. This ASTER sub-scene, acquired on March 29, 2000, covers an area 18 kilometers (13 miles) wide and 15 kilometers (9 miles) long in three bands of the reflected visible and infrared wavelength region. The visible and near-infrared bands highlight surface waves due to specular reflection of sunlight off of the wave faces.

    Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) is one of five Earth-observing instruments launched December 18, 1999, on NASA's Terra satellite. The instrument was built by Japan's Ministry of International Trade and Industry. A joint U.S./Japan science team is responsible for validation and calibration of the instrument and the data products. Dr. Anne Kahle at NASA's Jet Propulsion Laboratory, Pasadena, California, is the U.S. science team leader; Moshe Pniel of JPL is the project manager. ASTER is the only high-resolution imaging sensor on Terra. The primary goal of the ASTER mission is to obtain high-resolution image data in 14 channels over the entire land surface, as well as black and white stereo images. With revisit time of between 4 and 16 days, ASTER will provide the capability for repeat coverage of changing areas on Earth's surface. Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) is one of five Earth-observing instruments launched December 18, 1999, on NASA's Terra satellite. The instrument was built by Japan's Ministry of International Trade and Industry. A joint U.S./Japan science team is responsible for validation and calibration of the instrument and the data products. Dr. Anne Kahle at NASA's Jet Propulsion Laboratory, Pasadena, California, is the U.S. science team leader; Moshe Pniel of JPL is the project manager. ASTER is the only high-resolution imaging sensor on Terra. The primary goal of the ASTER mission is to obtain high-resolution image data in 14 channels

  15. MHD simple waves and the divergence wave

    SciTech Connect

    Webb, G. M.; Pogorelov, N. V.; Zank, G. P.

    2010-03-25

    In this paper we investigate magnetohydrodynamic (MHD) simple divergence waves in MHD, for models in which nablacentre dotBnot =0. These models are related to the eight wave Riemann solvers in numerical MHD, in which the eighth wave is the divergence wave associated with nablacentre dotBnot =0. For simple wave solutions, all physical variables (the gas density, pressure, fluid velocity, entropy, and magnetic field induction in the MHD case) depend on a single phase function phi. We consider the form of the MHD equations used by both Powell et al. and Janhunen. It is shown that the Janhunen version of the equations possesses fully nonlinear, exact simple wave solutions for the divergence wave, but no physically meaningful simple divergence wave solution exists for the Powell et al. system. We suggest that the 1D simple, divergence wave solution for the Janhunen system, may be useful for the testing and validation of numerical MHD codes.

  16. Autoresonant beat-wave generation

    SciTech Connect

    Lindberg, R. R.; Charman, A. E.; Wurtele, J. S.; Friedland, L.; Shadwick, B. A.

    2006-12-15

    Autoresonance offers an efficient and robust means for the ponderomotive excitation of nonlinear Langmuir waves by phase-locking of the plasma wave to the slowly chirped beat frequency of the driving lasers via adiabatic passage through resonance. This mechanism is analyzed for the case of a cold, relativistic, underdense electron plasma, and its suitability for particle acceleration is discussed. Compared to traditional approaches, this new autoresonant scheme achieves larger accelerating electric fields for given laser intensity; the plasma wave excitation is much more robust to variations in plasma density; it is largely insensitive to the precise choice of chirp rate, provided only that it is sufficiently slow; and the suitability of the resulting plasma wave for accelerator applications is, in some respects, superior. As in previous schemes, modulational instabilities of the ionic background ultimately limit the useful interaction time, but nevertheless peak electric fields approaching the wave-breaking limit seem readily attainable. The total frequency shift required is only of the order of a few percent of the laser carrier frequency, and might be implemented with relatively little additional modification to existing systems based on chirped pulse amplification techniques, or, with somewhat greater technological effort, using a CO{sub 2} or other gas laser system.

  17. Quarkonia with a variational method

    NASA Astrophysics Data System (ADS)

    de Deus, Jorge Dias; Henriques, Alfredo B.; Pulido, João M. R.

    1981-06-01

    A variational method, based in independent minimization of energy levels, is applied to quantum mechanical quarkonium systems. A discussion is presented of the method, with emphasis on quark mass dependence of energy levels (Feynman-Hellman theorem), on the behaviour of wave functions at the origin (Martin's theorem) and on the ordering of energy levels. The potential used in the applications is the Coulomb (4-vector) + Linear (4-scalar) potentials, the fine and hyperfine splittings being included by means of the Fermi-Breit hamiltonian. An attempt is made for an overall treatment of the known splittings (radial s-wave, hyperfine and fine splittings) for all quarkonium systems, using an approximately flavour independent potential. The p-wave splittings, as well as the hyperfine splittings, are shown to be particularly sensitive to the nature and mass dependence of the potential. In particular, asymptotic freedom can be more easily tested there. On the other hand, radial excitations provide the place where the set up of short range potential effects should be first detected. Some results concerning the ordinary mesons are presented, and it is specifically pointed out that strong restrictions exist for the masses of the ρ' and the A 1. Predictions for the toponium family are also presented.

  18. Numerical modeling of the effects of wave energy converter characteristics on nearshore wave conditions

    DOE PAGESBeta

    Chang, G.; Ruehl, K.; Jones, C. A.; Roberts, J.; Chartrand, C.

    2015-12-24

    Modeled nearshore wave propagation was investigated downstream of simulated wave energy converters (WECs) to evaluate overall near- and far-field effects of WEC arrays. Model sensitivity to WEC characteristics and WEC array deployment scenarios was evaluated using a modified version of an industry standard wave model, Simulating WAves Nearshore (SWAN), which allows the incorporation of device-specific WEC characteristics to specify obstacle transmission. The sensitivity study illustrated that WEC device type and subsequently its size directly resulted in wave height variations in the lee of the WEC array. Wave heights decreased up to 30% between modeled scenarios with and without WECs formore » large arrays (100 devices) of relatively sizable devices (26 m in diameter) with peak power generation near to the modeled incident wave height. Other WEC types resulted in less than 15% differences in modeled wave height with and without WECs, with lesser influence for WECs less than 10 m in diameter. Wave directions and periods were largely insensitive to changes in parameters. Furthermore, additional model parameterization and analysis are required to fully explore the model sensitivity of peak wave period and mean wave direction to the varying of the parameters.« less

  19. Numerical modeling of the effects of wave energy converter characteristics on nearshore wave conditions

    SciTech Connect

    Chang, G.; Ruehl, K.; Jones, C. A.; Roberts, J.; Chartrand, C.

    2015-12-24

    Modeled nearshore wave propagation was investigated downstream of simulated wave energy converters (WECs) to evaluate overall near- and far-field effects of WEC arrays. Model sensitivity to WEC characteristics and WEC array deployment scenarios was evaluated using a modified version of an industry standard wave model, Simulating WAves Nearshore (SWAN), which allows the incorporation of device-specific WEC characteristics to specify obstacle transmission. The sensitivity study illustrated that WEC device type and subsequently its size directly resulted in wave height variations in the lee of the WEC array. Wave heights decreased up to 30% between modeled scenarios with and without WECs for large arrays (100 devices) of relatively sizable devices (26 m in diameter) with peak power generation near to the modeled incident wave height. Other WEC types resulted in less than 15% differences in modeled wave height with and without WECs, with lesser influence for WECs less than 10 m in diameter. Wave directions and periods were largely insensitive to changes in parameters. Furthermore, additional model parameterization and analysis are required to fully explore the model sensitivity of peak wave period and mean wave direction to the varying of the parameters.

  20. Mesosphere Dynamics with Gravity Wave Forcing. 2; Planetary Waves

    NASA Technical Reports Server (NTRS)

    Mayr, H. G.; Mengel, J. G.; Chan, K. L.; Porter, H. S.; Einaudi, Franco (Technical Monitor)

    2000-01-01

    We present results from a non-linear, 3D, time dependent numerical spectral model (NSM) which extends from the ground up into the thermosphere and incorporates Hines' Doppler Spread Parameterization for small-scale gravity waves (GW). Our focal point is the mesosphere where wave interactions are playing a dominant role. We discuss planetary waves in the present paper and diurnal and semi-diurnal tides in the companion paper. Without external time dependent energy or momentum sources, planetary waves (PWs) are generated in the model for zonal wavenumbers 1 to 4, which have amplitudes in the mesosphere above 50 km as large as 30 m/s and periods between 2 and 50 days. The waves are generated primarily during solstice conditions, which indicates that the baroclinic instability (associated with the GW driven reversal in the latitudinal temperature gradient) is playing an important role. Results from a numerical experiment show that GWs are also involved directly in generating the PWs. For the zonal wavenumber m = 1, the predominant wave periods in summer are around 4 days and in winter between 6 and 10 days. For m = 2, the periods are in summer and close to 2.5 and 3.5 days respectively For m = 3, 4 the predominant wave periods are in both seasons close to two days. The latter waves have the characteristics of Rossby gravity waves with meridional winds at equatorial latitudes. A common feature of the PWs (m = 1 to 4) generated in summer and winter is that their vertical wavelengths throughout the mesosphere are large which indicates that the waves are not propagating freely but are generated throughout the region. Another common feature is that the PWs propagate preferentially westward in summer and eastward in winter, being launched from the westward and eastward zonal winds that prevail respectively in summer and winter altitudes below 80 km. During spring and fall, for m = 1 and 2 eastward propagating long period PWs are generated that are launched from the smaller

  1. Waves and Tsunami Project

    ERIC Educational Resources Information Center

    Frashure, K. M.; Chen, R. F.; Stephen, R. A.; Bolmer, T.; Lavin, M.; Strohschneider, D.; Maichle, R.; Micozzi, N.; Cramer, C.

    2007-01-01

    Demonstrating wave processes quantitatively in the classroom using standard classroom tools (such as Slinkys and wave tanks) can be difficult. For example, waves often travel too fast for students to actually measure amplitude or wavelength. Also, when teaching propagating waves, reflections from the ends set up standing waves, which can confuse…

  2. Breaking of Longitudinal Akhiezer-Polovin Waves

    NASA Astrophysics Data System (ADS)

    Verma, Prabal Singh; Sengupta, Sudip; Kaw, Predhiman

    2012-03-01

    The breaking of longitudinal Akhiezer-Polovin (AP) waves is demonstrated using a one-dimensional simulation based on the Dawson sheet model. It is found that the AP longitudinal waves break through the process of phase mixing at an amplitude well below the breaking amplitude for AP waves, when subjected to arbitrarily small longitudinal perturbations. Results from the simulation show a good agreement with the Dawson phase mixing formula modified to include relativistic mass variation effects. This result may be of direct relevance to the laser- or particle-beam plasma wakefield experiments.

  3. Turbulent boundary layers under irregular waves and currents: Experiments and the equivalent-wave concept

    NASA Astrophysics Data System (ADS)

    Yuan, Jing

    2016-04-01

    A full-scale experimental study of turbulent boundary layer flows under irregular waves and currents is conducted with the primary objective to investigate the equivalent-wave concept by Madsen (1994). Irregular oscillatory flows following the bottom-velocity spectrum under realistic surface irregular waves are produced over two fixed rough bottoms in an oscillatory water tunnel, and flow velocities are measured using a Particle Image Velocimetry. The root-mean-square (RMS) value and representative phase lead of wave velocities have vertical variations very similar to those of the first-harmonic velocity of periodic wave boundary layers, e.g., the RMS wave velocity follows a logarithmic distribution controlled by the physical bottom roughness in the very near-bottom region. The RMS wave bottom shear stress and the associated representative phase lead can be accurately predicted using the equivalent-wave approach. The spectra of wave bottom shear stress and boundary layer velocity are found to be proportional to the spectrum of free-stream velocity. Currents in the presence of irregular waves exhibit the classic two-log-profile structure with the lower log-profile controlled by the physical bottom roughness and the upper log-profile controlled by a much larger apparent roughness. Replacing the irregular waves by their equivalent sinusoidal waves virtually makes no difference for the coexisting currents. These observations, together with the excellent agreement between measurements and model predictions, suggest that the equivalent-wave representation adequately characterizes the basic wave-current interaction under irregular waves.

  4. Inertio Gravity Waves in the Upper Mesosphere

    NASA Technical Reports Server (NTRS)

    Mayr, H. G.; Mengel, J. G.; Talaat, E. L.; Porter, H. S.; Chan, K. L.

    2003-01-01

    In the polar region of the upper mesosphere, horizontal wind oscillations have been observed with periods around 10 hours (Hernandez et al., 1992). Such waves are generated in our Numerical Spectral Model (NSM) and appear to be inertio gravity waves (IGW). Like the planetary waves (PW) in the model, the IGWs are generated by instabilities that arise in the mean zonal circulation. In addition to stationary waves for m = 0, eastward and westward propagating waves for m = 1 to 4 appear above 70 km that grow in magnitude up to about 110 km, having periods between 9 and 11 hours. The m = 1 westward propagating IGWs have the largest amplitudes, which can reach at the poles 30 m/s. Like PWs, the IGWs are intermittent but reveal systematic seasonal variations, with the largest amplitudes occurring generally in winter and spring. The IGWs propagate upward with a vertical wavelength of about 20 km.

  5. Further SEASAT SAR coastal ocean wave analysis

    NASA Technical Reports Server (NTRS)

    Kasischke, E. S.; Shuchman, R. A.; Meadows, G. A.; Jackson, P. L.; Tseng, Y.

    1981-01-01

    Analysis techniques used to exploit SEASAT synthetic aperture radar (SAR) data of gravity waves are discussed and the SEASAT SAR's ability to monitor large scale variations in gravity wave fields in both deep and shallow water is evaluated. The SAR analysis techniques investigated included motion compensation adjustments and the semicausal model for spectral analysis of SAR wave data. It was determined that spectra generated from fast Fourier transform analysis (FFT) of SAR wave data were not significantly altered when either range telerotation adjustments or azimuth focus shifts were used during processing of the SAR signal histories, indicating that SEASAT imagery of gravity waves is not significantly improved or degraded by motion compensation adjustments. Evaluation of the semicausal (SC) model using SEASAT SAR data from Rev. 974 indicates that the SC spectral estimates were not significantly better than the FFT results.

  6. Spectral wave dissipation over a barrier reef

    NASA Astrophysics Data System (ADS)

    Lowe, Ryan J.; Falter, James L.; Bandet, Marion D.; Pawlak, Geno; Atkinson, Marlin J.; Monismith, Stephen G.; Koseff, Jeffrey R.

    2005-04-01

    A 2 week field experiment was conducted to measure surface wave dissipation on a barrier reef at Kaneohe Bay, Oahu, Hawaii. Wave heights and velocities were measured at several locations on the fore reef and the reef flat, which were used to estimate rates of dissipation by wave breaking and bottom friction. Dissipation on the reef flat was found to be dominated by friction at rates that are significantly larger than those typically observed at sandy beach sites. This is attributed to the rough surface generated by the reef organisms, which makes the reef highly efficient at dissipating energy by bottom friction. Results were compared to a spectral wave friction model, which showed that the variation in frictional dissipation among the different frequency components could be described using a single hydraulic roughness length scale. Surveys of the bottom roughness conducted on the reef flat showed that this hydraulic roughness length was comparable to the physical roughness measured at this site. On the fore reef, dissipation was due to the combined effect of frictional dissipation and wave breaking. However, in this region the magnitude of dissipation by bottom friction was comparable to wave breaking, despite the existence of a well-defined surf zone there. Under typical wave conditions the bulk of the total wave energy incident on Kaneohe Bay is dissipated by bottom friction, not wave breaking, as is often assumed for sandy beach sites and other coral reefs.

  7. Dissipation of acoustic-gravity waves: an asymptotic approach.

    PubMed

    Godin, Oleg A

    2014-12-01

    Acoustic-gravity waves in the middle and upper atmosphere and long-range propagation of infrasound are strongly affected by air viscosity and thermal conductivity. To characterize the wave dissipation, it is typical to consider idealized environments, which admit plane-wave solutions. Here, an asymptotic approach is developed that relies instead on the assumption that spatial variations of environmental parameters are gradual. It is found that realistic assumptions about the atmosphere lead to rather different predictions for wave damping than do the plane-wave solutions. A modification to the Sutherland-Bass model of infrasound absorption is proposed. PMID:25480091

  8. The meridional scale of baroclinic waves with latent heat release

    NASA Technical Reports Server (NTRS)

    Tang, Chung-Muh

    1988-01-01

    The control on the meridional scale of a class of the baroclinic waves exercised by latent heat release is analyzed. A meridional-scale equation is derived, in which the dry model and the moist model without the meridional variation of the baroclinic waves are revealed. It is shown that, in the dry model the stability analysis cannot determine the meridional scale of the baroclinic waves. When latent heat release is included, the meridional variation of the waves either vanishes or is finite. When the waves have the meridional variation with latent heat release, the growth rate increases as the heating increases for a given Froude number, and there are two modes - the first mode has a small ascending region and a large descending region, while the second mode has a small descending region and a large ascending region.

  9. Statistical reconstruction algorithms for continuous wave electron spin resonance imaging

    NASA Astrophysics Data System (ADS)

    Kissos, Imry; Levit, Michael; Feuer, Arie; Blank, Aharon

    2013-06-01

    Electron spin resonance imaging (ESRI) is an important branch of ESR that deals with heterogeneous samples ranging from semiconductor materials to small live animals and even humans. ESRI can produce either spatial images (providing information about the spatially dependent radical concentration) or spectral-spatial images, where an extra dimension is added to describe the absorption spectrum of the sample (which can also be spatially dependent). The mapping of oxygen in biological samples, often referred to as oximetry, is a prime example of an ESRI application. ESRI suffers frequently from a low signal-to-noise ratio (SNR), which results in long acquisition times and poor image quality. A broader use of ESRI is hampered by this slow acquisition, which can also be an obstacle for many biological applications where conditions may change relatively quickly over time. The objective of this work is to develop an image reconstruction scheme for continuous wave (CW) ESRI that would make it possible to reduce the data acquisition time without degrading the reconstruction quality. This is achieved by adapting the so-called "statistical reconstruction" method, recently developed for other medical imaging modalities, to the specific case of CW ESRI. Our new algorithm accounts for unique ESRI aspects such as field modulation, spectral-spatial imaging, and possible limitation on the gradient magnitude (the so-called "limited angle" problem). The reconstruction method shows improved SNR and contrast recovery vs. commonly used back-projection-based methods, for a variety of simulated synthetic samples as well as in actual CW ESRI experiments.

  10. Surface wave tomography

    NASA Technical Reports Server (NTRS)

    Anderson, D. L.

    1984-01-01

    Vertically polarized shear wave velocity (VSV), determined primarily from fundamental mode Rayleigh waves, and the difference between the velocity of horizontally polarized shear waves (VSH) and VSV, therefore a measure of anisotropy, are shown.

  11. Geometrical versus wave optics under gravitational waves

    NASA Astrophysics Data System (ADS)

    Angélil, Raymond; Saha, Prasenjit

    2015-06-01

    We present some new derivations of the effect of a plane gravitational wave on a light ray. A simple interpretation of the results is that a gravitational wave causes a phase modulation of electromagnetic waves. We arrive at this picture from two contrasting directions, namely, null geodesics and Maxwell's equations, or geometric and wave optics. Under geometric optics, we express the geodesic equations in Hamiltonian form and solve perturbatively for the effect of gravitational waves. We find that the well-known time-delay formula for light generalizes trivially to massive particles. We also recover, by way of a Hamilton-Jacobi equation, the phase modulation obtained under wave optics. Turning then to wave optics—rather than solving Maxwell's equations directly for the fields, as in most previous approaches—we derive a perturbed wave equation (perturbed by the gravitational wave) for the electromagnetic four-potential. From this wave equation it follows that the four-potential and the electric and magnetic fields all experience the same phase modulation. Applying such a phase modulation to a superposition of plane waves corresponding to a Gaussian wave packet leads to time delays.

  12. Experimental and Numerical Studies on Wave Breaking Characteristics over a Fringing Reef under Monochromatic Wave Conditions

    PubMed Central

    2014-01-01

    Fringing reefs play an important role in protecting the coastal area by inducing wave breaking and wave energy dissipation. However, modeling of wave transformation and energy dissipation on this topography is still difficult due to the unique structure. In the present study, two-dimensional laboratory experiments were conducted to investigate the cross-shore variations of wave transformation, setup, and breaking phenomena over an idealized fringing reef with the 1/40 reef slope and to verify the Boussinesq model under monochromatic wave conditions. One-layer and two-layer model configurations of the Boussinesq model were used to figure out the model capability. Both models predicted well (r2 > 0.8) the cross-shore variation of the wave heights, crests, troughs, and setups when the nonlinearity is not too high (A0/h0 < 0.07 in this study). However, as the wave nonlinearity and steepness increase, the one-layer model showed problems in prediction and stability due to the error on the vertical profile of fluid velocity. The results in this study revealed that one-layer model is not suitable in the highly nonlinear wave condition over a fringing reef bathymetry. This data set can contribute to the numerical model verification. PMID:25276853

  13. Digital measurements of LF radio wave absorption in the lower ionosphere and inferred gravity wave activity

    NASA Astrophysics Data System (ADS)

    Lastovicka, J.; Boska, J.; Buresova, D.

    1993-10-01

    Low frequency (LF) radio wave absorption in the lower ionosphere has been measured at Pruhonice (approximately 50 deg N) since 1957. A new digital computer-controlled measuring-recording-processing system was introduced in 1988. The A3 method of radio wave absorption measurement, the measuring equipment used for the digital measurements at 270 kHz, is briefly described. The digital nighttime LF A3 measurements allow the use of absorption data for studying and monitoring the gravity wave activity in the upper middle atmosphere in the period range 10 min-3(2) hours. The resulting gravity wave spectra are as expected even though their shapes vary. Individual period bands sometimes exhibit a similar general pattern of variability in gravity wave activity (winter 1990), while in other intervals we observe a shift of gravity wave energy from one period band to another (winter 1991). No strong, pronounced and consistent response to strong geomagnetic storms and midwinter stratospheric warming is found. An apparent seasonal variation with winter minima observed in shorter-period gravity wave activity is an artefact of the changing length of the night. There is no significant seasonal variation of gravity wave activity in the analysed data. The method is very cheap -- the results are a by-product of measurements made for ionospheric purposes.

  14. Experimental and numerical studies on wave breaking characteristics over a fringing reef under monochromatic wave conditions.

    PubMed

    Lee, Jong-In; Shin, Sungwon; Kim, Young-Taek

    2014-01-01

    Fringing reefs play an important role in protecting the coastal area by inducing wave breaking and wave energy dissipation. However, modeling of wave transformation and energy dissipation on this topography is still difficult due to the unique structure. In the present study, two-dimensional laboratory experiments were conducted to investigate the cross-shore variations of wave transformation, setup, and breaking phenomena over an idealized fringing reef with the 1/40 reef slope and to verify the Boussinesq model under monochromatic wave conditions. One-layer and two-layer model configurations of the Boussinesq model were used to figure out the model capability. Both models predicted well (r (2) > 0.8) the cross-shore variation of the wave heights, crests, troughs, and setups when the nonlinearity is not too high (A 0/h 0 < 0.07 in this study). However, as the wave nonlinearity and steepness increase, the one-layer model showed problems in prediction and stability due to the error on the vertical profile of fluid velocity. The results in this study revealed that one-layer model is not suitable in the highly nonlinear wave condition over a fringing reef bathymetry. This data set can contribute to the numerical model verification. PMID:25276853

  15. Global wave modeling of electron interactions with fast magnetosonic waves

    NASA Astrophysics Data System (ADS)

    Jaeger, E. F.; Batchelor, D. B.; Murakami, M.

    Electron interactions with fast magnetosonic waves are of interest for both direct electron heating and fast-wave current drive (FWCD) in tokamaks. Here the authors apply the full-wave ICRF code PICES to examples of both of these applications. To realistically account for the actual D-shaped magnetic geometry of present-day tokamaks, PICES is interfaced with the 3-D MHD equilibrium code VMEC. Likewise, to correctly model the real toroidal structure of both source and image currents in ICRF current drive antennas, PICES is interfaced with the 2-D recessed antenna impedance code RANT. Both current drive and electron heating by fast waves can be strongly altered through modification of the kappa(sub (parallel))-spectrum by the poloidal magnetic field. A poloidal mode expansion in PICES allows such variations in kappa(sub (parallel)) to be included correctly. In this paper, comparisons are made to observations of the direct electron heating profile on TFTR and to the FWCD efficiency on DIII-D. They also extrapolate to make predictions for future tokamaks such as TPX and ITER.

  16. Rossby wave energy dispersion from tropical cyclone in zonal basic flows

    NASA Astrophysics Data System (ADS)

    Shi, Wenli; Fei, Jianfang; Huang, Xiaogang; Liu, Yudi; Ma, Zhanhong; Yang, Lu

    2016-04-01

    This study investigates tropical cyclone energy dispersion under horizontally sheared flows using a nonlinear barotropic model. In addition to common patterns, unusual features of Rossby wave trains are also found in flows with constant vorticity and vorticity gradients. In terms of the direction of the energy dispersion, the wave train can rotate clockwise and elongate southwestward under anticyclonic circulation (ASH), which contributes to the reenhancement of the tropical cyclone (TC). The wave train even splits into two obvious wavelike trains in flows with a southward vorticity gradient (WSH). Energy dispersed from TCs varies over time, and variations in the intensity of the wave train components typically occur in two stages. Wave-activity flux diagnosis and ray tracing calculations are extended to the frame that moves along with the TC to reveal the concrete progress of wave propagation. The direction of the wave-activity flux is primarily determined by the combination of the basic flow and the TC velocity. Along the flux, the distribution of pseudomomentum effectively illustrates the development of wave trains, particularly the rotation and split of wave propagation. Ray tracing involves the quantitative tracing of wave features along rays, which effectively coincide with the wave train regimes. Flows of a constant shear (parabolic meridional variation) produce linear (nonlinear) wave number variations. For the split wave trains, the real and complex wave number waves move along divergent trajectories and are responsible for different energy dispersion ducts.

  17. Visualization of Sound Waves Using Regularly Spaced Soap Films

    ERIC Educational Resources Information Center

    Elias, F.; Hutzler, S.; Ferreira, M. S.

    2007-01-01

    We describe a novel demonstration experiment for the visualization and measurement of standing sound waves in a tube. The tube is filled with equally spaced soap films whose thickness varies in response to the amplitude of the sound wave. The thickness variations are made visible based on optical interference. The distance between two antinodes is…

  18. Wave Energy Converter Effects on Wave Fields: Evaluation of SNL-SWAN and Sensitivity Studies in Monterey Bay CA.

    SciTech Connect

    Roberts, Jesse D.; Chang, Grace; Magalen, Jason; Jones, Craig

    2014-09-01

    A modified version of an indust ry standard wave modeling tool was evaluated, optimized, and utilized to investigate model sensitivity to input parameters a nd wave energy converter ( WEC ) array deployment scenarios. Wave propagation was investigated d ownstream of the WECs to evaluate overall near - and far - field effects of WEC arrays. The sensitivity study illustrate d that wave direction and WEC device type we r e most sensitive to the variation in the model parameters examined in this study . Generally, the changes in wave height we re the primary alteration caused by the presence of a WEC array. Specifically, W EC device type and subsequently their size directly re sult ed in wave height variations; however, it is important to utilize ongoing laboratory studies and future field tests to determine the most appropriate power matrix values for a particular WEC device and configuration in order to improve modeling results .

  19. ADVANCED WAVE-EQUATION MIGRATION

    SciTech Connect

    L. HUANG; M. C. FEHLER

    2000-12-01

    Wave-equation migration methods can more accurately account for complex wave phenomena than ray-tracing-based Kirchhoff methods that are based on the high-frequency asymptotic approximation of waves. With steadily increasing speed of massively parallel computers, wave-equation migration methods are becoming more and more feasible and attractive for imaging complex 3D structures. We present an overview of several efficient and accurate wave-equation-based migration methods that we have recently developed. The methods are implemented in the frequency-space and frequency-wavenumber domains and hence they are called dual-domain methods. In the methods, we make use of different approximate solutions of the scalar-wave equation in heterogeneous media to recursively downward continue wavefields. The approximations used within each extrapolation interval include the Born, quasi-Born, and Rytov approximations. In one of our dual-domain methods, we use an optimized expansion of the square-root operator in the one-way wave equation to minimize the phase error for a given model. This leads to a globally optimized Fourier finite-difference method that is a hybrid split-step Fourier and finite-difference scheme. Migration examples demonstrate that our dual-domain migration methods provide more accurate images than those obtained using the split-step Fourier scheme. The Born-based, quasi-Born-based, and Rytov-based methods are suitable for imaging complex structures whose lateral variations are moderate, such as the Marmousi model. For this model, the computational cost of the Born-based method is almost the same as the split-step Fourier scheme, while other methods takes approximately 15-50% more computational time. The globally optimized Fourier finite-difference method significantly improves the accuracy of the split-step Fourier method for imaging structures having strong lateral velocity variations, such as the SEG/EAGE salt model, at an approximately 30% greater

  20. Internal marine waves and atmospheric depressions

    NASA Astrophysics Data System (ADS)

    Dolgikh, G. I.; Budrin, S. S.; Dolgikh, S. G.; Ovcharenko, V. V.; Chupin, V. A.; Shvets, V. A.; Yakovenko, S. V.

    2015-06-01

    This work describes the results of processing experimental data during synchronous registration of the crust deformations and oscillations of atmospheric and hydrospheric pressures. It was found that internal marine waves with a frequency range from 5 to 20 min are mainly generated by atmospheric disturbances, whose variations are absolutely identical to those of hydrospheric pressure in the shelf zone of the Sea of Japan.

  1. Wave-Turbulence Interactions: a DPIV Study

    NASA Astrophysics Data System (ADS)

    Lang, Amy; Lalinde, David

    1999-11-01

    Previous studies on wave-turbulence interactions, such as the one by Olmez & Milgram (JFM, 1992), supported the hypothesis that the dominant mechanism for the dissipation of non-breaking waves by turbulence is vertical mixing, rather than wave-to-turbulence energy transfer in the wave layer. In this study, Digital Particle Image Velocimetry (DPIV) was used to study the increase in turbulence levels due to the presence of surface waves. Two types of turbulent fields were studied. A grid of cylindrical rods was placed in a water tunnel with smaller scale turbulence resulting in the wake of the grid. The second case used a flat plate grid, with the plates aligned parallel to the free-stream flow. This allowed for a range of scales to be generated within the turbulent flow-field in the test section. Next, a wave-generator was placed in the tunnel allowing waves to propagate into the area studied and interact with the grid-generated turbulence. Variation in wavelength and frequency of the surface waves was performed. Results will be presented.

  2. Radio wave propagation at frequencies exceeding MUF-F2 in the short wave band

    NASA Technical Reports Server (NTRS)

    Ashkaliyev, Y. F.; Bocharov, V. I.

    1972-01-01

    The results of measurements of field strength and signal/noise ratio on experimental ionospheric-scattering short wave radio links are presented. It is shown that the seasonal and diurnal variations of field strength are determined by features of solar and meteoric activity. The role of the sporadic E-layer in propagation of short radio waves at frequencies exceeding MUF-F2 is noted.

  3. Signatures of surface wave/internal wave interactions: Experiment and theory

    NASA Astrophysics Data System (ADS)

    Apel, J. R.; Gasparovic, R. F.; Thompson, D. R.; Gotwols, B. L.

    1988-11-01

    This paper summarizes results from an extended investigation of the physics of surface wave/internal wave interactions. During summer conditions of stratification, internal solitary waves are generated by the semidiurnal tide at the continental shelf break off New York. The waves evolve as packets of solitons having rank-ordered amplitudes, wave spacings, and crest lengths. They propagate toward shore and are ultimately dissipated in the region where the mixed layer intersects the bottom. We have studied their hydrodynamic properties, their interactions with surface waves and with each other, and the scattering of electromagnetic radiation from their accompanying surface roughness variations. Measurement using a towed thermistor chain. CTD casts, and moored current meter arrays have allowed a detailed characterization of the subsurface and near-surface hydrodynamics. Quantitative surface signatures were obtained using: (a) TV Stilwell methods, (b) calibrated airborne synthetic aperture radar at L- and X-bands, and (c) the L-band SIR-B synthetic aperture radar on the space shuttle Challenger. The scattering data have been analyzed using the wave action equation for calculating internal current/surface wave interactions. Hughes' description of the wave relaxation rate has been used to obtain the perturbation to the surface wave spectrum from the internal currents and current straining. Radar backscatter variations from the perturbed surface wave roughness were then calculated using a variant of the Kirchhoff approximation to the scattering integral. Both Bragg scattering and specular point scattering are important in this case. Excellent agreement is obtained between the theory and the observations.

  4. Variation in fracture zone rigidity by dynamic effects

    NASA Astrophysics Data System (ADS)

    Spivak, A. A.; Khazins, V. M.

    2013-03-01

    The coefficient of normal rigidity of different-order fault zones was evaluated from seismic data. The crust tectonic faults were shown to be dynamic systems and nonstatic. Specifically, this is manifested in the variability of their rigidity with time. The value of the rigidity of fault zones varies in time with periods of 13-15 days, 27-32 days, and around 1 year. Here, the coefficient of normal rigidity of different-order fault zones can vary by 1.3 (semimonthly variations) 1.5 (monthly variations), and 2.5 times (annual variations), respectively. These variations are most likely governed by the rate and intensity of the transformation of matter of fault zones and, as a consequence, the variations in their mechanical properties under tidal conditions. Dynamic effects like seismoexplosive waves lead to a reduction in the rigidity of fault zones by 5-50% depending on the amplitude of the compression wave.

  5. Preliminary tests on a new near-infrared continuous-wave tissue oximeter

    NASA Astrophysics Data System (ADS)

    Casavola, Claudia; Cicco, Giuseppe; Pirrelli, Anna; Lugara, Pietro M.

    2000-11-01

    We present a preliminary study, in vitro and in vivo, with a novel device for near-infrared tissue oximetry. The light sources used are two quasi-continuous-wave LEDs, emitting at 656 and 851 nm, and the detector is a photodiode. The data are acquired in back-scattering configuration, thus allowing the non-invasive characterization of thick tissues. Stability tests were performed by placing the optical probe on a tissue- like phantom and acquiring data for periods of time ranging from 5 to 40 minutes. No significant drifts in the DC signal were observed after a warm-up period of no more than 10 minutes. We performed reproducibility tests by repositioning the optical probe on the phantom for a number of times. We found a reproducibility better than 5% in the DC signal. We also present the results of a preliminary study conducted in vivo, on the calf muscle of human subjects. We report a comparison of the results obtained with the near-infrared oximeter with the values of blood oxygenation ctO2 measured with conventional chemical tests.

  6. Wave-current interaction in Willapa Bay

    USGS Publications Warehouse

    Olabarrieta, M.; Warner, J.C.; Kumar, N.

    2011-01-01

    This paper describes the importance of wave-current interaction in an inlet-estuary system. The three-dimensional, fully coupled, Coupled Ocean-Atmosphere-Wave-Sediment Transport (COAWST) modeling system was applied in Willapa Bay (Washington State) from 22 to 29 October 1998 that included a large storm event. To represent the interaction between waves and currents, the vortex-force method was used. Model results were compared with water elevations, currents, and wave measurements obtained by the U.S. Army Corp of Engineers. In general, a good agreement between field data and computed results was achieved, although some discrepancies were also observed in regard to wave peak directions in the most upstream station. Several numerical experiments that considered different forcing terms were run in order to identify the effects of each wind, tide, and wave-current interaction process. Comparison of the horizontal momentum balances results identified that wave-breaking-induced acceleration is one of the leading terms in the inlet area. The enhancement of the apparent bed roughness caused by waves also affected the values and distribution of the bottom shear stress. The pressure gradient showed significant changes with respect to the pure tidal case. During storm conditions the momentum balance in the inlet shares the characteristics of tidal-dominated and wave-dominated surf zone environments. The changes in the momentum balance caused by waves were manifested both in water level and current variations. The most relevant effect on hydrodynamics was a wave-induced setup in the inner part of the estuary. Copyright 2011 by the American Geophysical Union.

  7. Longitudinal nonlinear wave propagation through soft tissue.

    PubMed

    Valdez, M; Balachandran, B

    2013-04-01

    In this paper, wave propagation through soft tissue is investigated. A primary aim of this investigation is to gain a fundamental understanding of the influence of soft tissue nonlinear material properties on the propagation characteristics of stress waves generated by transient loadings. Here, for computational modeling purposes, the soft tissue is modeled as a nonlinear visco-hyperelastic material, the geometry is assumed to be one-dimensional rod geometry, and uniaxial propagation of longitudinal waves is considered. By using the linearized model, a basic understanding of the characteristics of wave propagation is developed through the dispersion relation and in terms of the propagation speed and attenuation. In addition, it is illustrated as to how the linear system can be used to predict brain tissue material parameters through the use of available experimental ultrasonic attenuation curves. Furthermore, frequency thresholds for wave propagation along internal structures, such as axons in the white matter of the brain, are obtained through the linear analysis. With the nonlinear material model, the authors analyze cases in which one of the ends of the rods is fixed and the other end is subjected to a loading. Two variants of the nonlinear model are analyzed and the associated predictions are compared with the predictions of the corresponding linear model. The numerical results illustrate that one of the imprints of the nonlinearity on the wave propagation phenomenon is the steepening of the wave front, leading to jump-like variations in the stress wave profiles. This phenomenon is a consequence of the dependence of the local wave speed on the local deformation of the material. As per the predictions of the nonlinear material model, compressive waves in the structure travel faster than tensile waves. Furthermore, it is found that wave pulses with large amplitudes and small elapsed times are attenuated over shorter spans. This feature is due to the elevated

  8. A Simple Wave Driver

    ERIC Educational Resources Information Center

    Temiz, Burak Kagan; Yavuz, Ahmet

    2015-01-01

    This study was done to develop a simple and inexpensive wave driver that can be used in experiments on string waves. The wave driver was made using a battery-operated toy car, and the apparatus can be used to produce string waves at a fixed frequency. The working principle of the apparatus is as follows: shortly after the car is turned on, the…

  9. Financial Rogue Waves

    NASA Astrophysics Data System (ADS)

    Yan, Zhen-Ya

    2010-11-01

    We analytically give the financial rogue waves in the nonlinear option pricing model due to Ivancevic, which is nonlinear wave alternative of the Black—Scholes model. These rogue wave solutions may he used to describe the possible physical mechanisms for rogue wave phenomenon in financial markets and related fields.

  10. On the physics of waves in the solar atmosphere: Wave heating and wind acceleration

    NASA Technical Reports Server (NTRS)

    Musielak, Z. E.

    1992-01-01

    In the area of solar physics, new calculations of the acoustic wave energy fluxes generated in the solar convective zone was performed. The original theory developed was corrected by including a new frequency factor describing temporal variations of the turbulent energy spectrum. We have modified the original Stein code by including this new frequency factor, and tested the code extensively. Another possible source of the mechanical energy generated in the solar convective zone is the excitation of magnetic flux tube waves which can carry energy along the tubes far away from the region. The problem as to how efficiently those waves are generated in the Sun was recently solved. The propagation of nonlinear magnetic tube waves in the solar atmosphere was calculated, and mode coupling, shock formation, and heating of the local medium was studied. The wave trapping problems and evaluation of critical frequencies for wave reflection in the solar atmosphere was studied. It was shown that the role played by Alfven waves in the wind accelerations and the coronal hole heating is dominant. Presently, we are performing calculations of wave energy fluxes generated in late-type dwarf stars and studying physical processes responsible for the heating of stellar chromospheres and coronae. In the area of physics of waves, a new analytical approach for studying linear Alfven waves in smoothly nonuniform media was recently developed. This approach is presently being extended to study the propagation of linear and nonlinear magnetohydrodynamic (MHD) waves in stratified, nonisothermal and solar atmosphere. The Lighthill theory of sound generation to nonisothermal media (with a special temperature distribution) was extended. Energy cascade by nonlinear MHD waves and possible chaos driven by these waves are presently considered.

  11. Sea water temperature variation east of Taiwan

    NASA Astrophysics Data System (ADS)

    Yin, Fuh

    Temperature, wave and wind data over two years off Ho Peng, Shi Ti and Jang Yuan of east Taiwan are analyzed to study their seasonal variations. A model for predicting the mixed layer thickness is developed by use of wave data. The vertical profile of temperature indicates that there are basically three layers; mixed layer, thermocline layer and deep cold layer. The surface mixed layer appears in winter and disappears in summer. While surface water is warmer in summer than in winter, water at a depth of 50 m is warmer in winter than in summer. The seasonal variation in the deep cold layer is weak. The sea surface temperature is generally higher offshore than nearshore. The surface temperature off east Taiwan is almost equal to that in Taiwan Strait in summer, but in winter it is about 4°C warmer off northeast Taiwan than in the northeast of the Taiwan Strait, if compared at the same latitude. This is an effect of the seasonal variation of the Kuroshio. A model is developed for predicting the mixed layer thickness in terms of the input wave energy. The model successfully accounts for the observed features.

  12. Variational methods for field theories

    SciTech Connect

    Ben-Menahem, S.

    1986-09-01

    Four field theory models are studied: Periodic Quantum Electrodynamics (PQED) in (2 + 1) dimensions, free scalar field theory in (1 + 1) dimensions, the Quantum XY model in (1 + 1) dimensions, and the (1 + 1) dimensional Ising model in a transverse magnetic field. The last three parts deal exclusively with variational methods; the PQED part involves mainly the path-integral approach. The PQED calculation results in a better understanding of the connection between electric confinement through monopole screening, and confinement through tunneling between degenerate vacua. This includes a better quantitative agreement for the string tensions in the two approaches. Free field theory is used as a laboratory for a new variational blocking-truncation approximation, in which the high-frequency modes in a block are truncated to wave functions that depend on the slower background modes (Boron-Oppenheimer approximation). This ''adiabatic truncation'' method gives very accurate results for ground-state energy density and correlation functions. Various adiabatic schemes, with one variable kept per site and then two variables per site, are used. For the XY model, several trial wave functions for the ground state are explored, with an emphasis on the periodic Gaussian. A connection is established with the vortex Coulomb gas of the Euclidean path integral approach. The approximations used are taken from the realms of statistical mechanics (mean field approximation, transfer-matrix methods) and of quantum mechanics (iterative blocking schemes). In developing blocking schemes based on continuous variables, problems due to the periodicity of the model were solved. Our results exhibit an order-disorder phase transition. The transfer-matrix method is used to find a good (non-blocking) trial ground state for the Ising model in a transverse magnetic field in (1 + 1) dimensions.

  13. Gravity wave transmission diagram

    NASA Astrophysics Data System (ADS)

    Tomikawa, Yoshihiro

    2016-07-01

    A possibility of gravity wave propagation from a source region to the airglow layer around the mesopause has been discussed based on the gravity wave blocking diagram taking into account the critical level filtering alone. This paper proposes a new gravity wave transmission diagram in which both the critical level filtering and turning level reflection of gravity waves are considered. It shows a significantly different distribution of gravity wave transmissivity from the blocking diagram.

  14. Photoelectron wave function in photoionization: plane wave or Coulomb wave?

    PubMed

    Gozem, Samer; Gunina, Anastasia O; Ichino, Takatoshi; Osborn, David L; Stanton, John F; Krylov, Anna I

    2015-11-19

    The calculation of absolute total cross sections requires accurate wave functions of the photoelectron and of the initial and final states of the system. The essential information contained in the latter two can be condensed into a Dyson orbital. We employ correlated Dyson orbitals and test approximate treatments of the photoelectron wave function, that is, plane and Coulomb waves, by comparing computed and experimental photoionization and photodetachment spectra. We find that in anions, a plane wave treatment of the photoelectron provides a good description of photodetachment spectra. For photoionization of neutral atoms or molecules with one heavy atom, the photoelectron wave function must be treated as a Coulomb wave to account for the interaction of the photoelectron with the +1 charge of the ionized core. For larger molecules, the best agreement with experiment is often achieved by using a Coulomb wave with a partial (effective) charge smaller than unity. This likely derives from the fact that the effective charge at the centroid of the Dyson orbital, which serves as the origin of the spherical wave expansion, is smaller than the total charge of a polyatomic cation. The results suggest that accurate molecular photoionization cross sections can be computed with a modified central potential model that accounts for the nonspherical charge distribution of the core by adjusting the charge in the center of the expansion. PMID:26509428

  15. Sensitivity of a Wave Structure to Initial Conditions

    NASA Technical Reports Server (NTRS)

    Duval, Walter M. B.; Duval, Walter M. B. (Technical Monitor)

    2000-01-01

    Microgravity experiments aimed at quantifying effects of gentler via controlled sinusoidal forcing transmitted on the interface between two miscible liquids have shown the evolution of a quasi -stationary four-mode wave structure oriented vertically. The sensitivity of the wave structure to phase angle variation is investigated computationally. We show that a slight variation of the phase angle is sufficient to cause a bifurcation to a two-mode structure. The dependence of phase angle on wave structure is attributed to sensitivity on initial conditions due to the strong nonlinearity of the coupled field equations for the parametric space of interest.

  16. Wave propagation into the middle atmosphere

    NASA Technical Reports Server (NTRS)

    Hirota, I.

    1989-01-01

    Recent observations of various types of waves propagating into the middle atmosphere are reviewed. Emphasis is made on the excitation processes in the lower atmosphere and their vertical propagation through the background flow as a function of the latitude, height and season. The following subjects are discussed: (1) Vertical propagation of quasi-stationary forced Rossby waves into the winter stratosphere in connection with the sudden warming; (2) Spectral distribution and seasonal characteristics of normal mode (free) Rossby waves and the asymmetry of the Northern and Southern Hemispheres; and (3) Seasonal variation of internal gravity waves in the middle atmosphere. Further discussions are presented for future studies based on accumulated observational data during the MAP period.

  17. Persistent subplasma-frequency kinetic electrostatic electron nonlinear waves

    SciTech Connect

    Johnston, T. W.; Tyshetskiy, Y.; Ghizzo, A.; Bertrand, P.

    2009-04-15

    Driving a one-dimensional collisionless Maxwellian (Vlasov) plasma with a sufficiently strong longitudinal ponderomotive driver for a sufficiently long time results in a self-sustaining nonsinusoidal wave train with well-trapped electrons even for frequencies well below the plasma frequency, i.e., in the plasma wave spectral gap. Typical phase velocities of these waves are somewhat above the electron thermal velocity. This new nonlinear wave is being termed a kinetic electrostatic electron nonlinear (KEEN) wave. The drive duration must exceed the bounce period {tau}{sub B} of the trapped electrons subject to the drive, as calculated from the drive force and the linear plasma response to the drive. For a given wavenumber a wide range of KEEN wave frequencies can be readily excited. The basic KEEN structure is essentially kinetic, with the trapped electron density variation being almost completely shielded by the free electrons, leaving just enough net charge to support the wave.

  18. Lamb Wave Assessment of Fiber Volume Fraction in Composites

    NASA Technical Reports Server (NTRS)

    Seale, Michael D.; Smith, Barry T.; Prosser, W. H.; Zalameda, Joseph N.

    1998-01-01

    Among the various techniques available, ultrasonic Lamb waves offer a convenient method of examining composite materials. Since the Lamb wave velocity depends on the elastic properties of a material, an effective tool exists to evaluate composites by measuring the velocity of these waves. Lamb waves can propagate over long distances and are sensitive to the desired in-plane elastic properties of the material. This paper discusses a study in which Lamb waves were used to examine fiber volume fraction variations of approximately 0.40-0.70 in composites. The Lamb wave measurements were compared to fiber volume fractions obtained from acid digestion tests. Additionally, a model to predict the fiber volume fraction from Lamb wave velocity values was evaluated.

  19. Wave power extraction from a transient heaving cylinder

    SciTech Connect

    Hudspeth, R. T.; Slotta, L. S.

    1980-01-01

    Wave power extracted from the transient motion of a periodically restrained-released heaving circular cylinder proposed by Falnes and Budal is examined under the limitations of linear wave theory excitation. Numerical estimates for the normalized radiated wave amplitudes required for the waveforce excitation derived by Mei are computed from the computationally efficient variational method developed by Black and Mei for the wave force diffraction regime. Wave power estimates for the rising period only of the heaving motion are given; while the falling period of the motion is neglected. A graphical summary is presented which demonstrates the parametric dependency of the dimensionless wave power rate on the design wave parameters and the body geometry for three general types of transient power systems heaving in deep water conditions. The total power requirements for the complete power extraction system as well as the real fluid viscous effects are not included.

  20. Spectra of Baroclinic Inertia-Gravity Wave Turbulence

    NASA Technical Reports Server (NTRS)

    Glazman, Roman E.

    1996-01-01

    Baroclinic inertia-gravity (IG) waves form a persistent background of thermocline depth and sea surface height oscillations. They also contribute to the kinetic energy of horizontal motions in the subsurface layer. Measured by the ratio of water particle velocity to wave phase speed, the wave nonlinearity may be rather high. Given a continuous supply of energy from external sources, nonlinear wave-wave interactions among IG waves would result in inertial cascades of energy, momentum, and wave action. Based on a recently developed theory of wave turbulence in scale-dependent systems, these cascades are investigated and IG wave spectra are derived for an arbitrary degree of wave nonlinearity. Comparisons with satellite-altimetry-based spectra of surface height variations and with energy spectra of horizontal velocity fluctuations show good agreement. The well-known spectral peak at the inertial frequency is thus explained as a result of the inverse cascade. Finally, we discuss a possibility of inferring the internal Rossby radius of deformation and other dynamical properties of the upper thermocline from the spectra of SSH (sea surface height) variations based on altimeter measurements.

  1. Generating a soliton splash through variational modelling and experiments

    NASA Astrophysics Data System (ADS)

    Kalogirou, Anna; Bokhove, Onno

    2015-11-01

    Mathematical modelling of water waves in tanks with wave generators is demonstrated by investigating variational methods asymptotically and numerically. A reduced potential flow water wave model is derived using variational techniques, which is based on the assumptions of waves with small amplitude and large wavelength. This model consists of a set of modified Benney-Luke equations describing the deviation from the still water surface η (x , y , t) and the bottom potential Φ (x , y , t) , and includes a time-dependent gravitional potential mimicking a removable ``sluice gate''. The asymptotic model is solved numerically using the automated system Firedrake. In particular, a (dis)continuous Galerkin finite element method is used, together with symplectic integrators for the time discretisation. As a validation, the numerical results are compared to a soliton splash experiment in a long water channel with a contraction at its end, resulting after a sluice gate is removed at a finite time.

  2. Shear wave logging using guided waves

    SciTech Connect

    Winbow, G.A.; Chen, S.T.; Rice, J.A.

    1988-09-27

    This patent describes a method for acoustically logging an earth formation surrounding a borehole which contains a liquid where the approximate shear wave velocity v of the formation is known. The method consists of: vibrating a dipole source in the liquid to generate in the liquid a guided wave the frequencies of which include a critical frequency f given by zeta = ..nu..12a where a is the borehole radius, so that the fastest component of the guided wave has velocity substantially equal to ..nu..; and detecting the arrival of the fastest component of the guided wave at least one location in the liquid spaced longitudinally along the borehole from the dipole source.

  3. Internal wave observations made with an airborne synthetic aperture imaging radar

    NASA Technical Reports Server (NTRS)

    Elachi, C.; Apel, J. R.

    1976-01-01

    Synthetic aperture L-band radar flown aboard the NASA CV-990 has observed periodic striations on the ocean surface off the coast of Alaska which have been interpreted as tidally excited oceanic internal waves of less than 500 m length. These radar images are compared to photographic imagery of similar waves taken from Landsat 1. Both the radar and Landsat images reveal variations in reflectivity across each wave in a packet that range from low to high to normal. The variations point to the simultaneous existence of two mechanisms for the surface signatures of internal waves: roughening due to wave-current interactions, and smoothing due to slick formation.

  4. Magneto-atmospheric waves

    NASA Technical Reports Server (NTRS)

    Thomas, J. H.

    1983-01-01

    A theoretical treatment of magneto-atmospheric waves is presented and applied to the modelling of waves in the solar atmosphere. The waves arise in compressible, stratified, electrically conductive atmospheres within gravitational fields when permeated by a magnetic field. Compression, buoyancy, and distortion of the magnetic field all contribute to the existence of the waves. Basic linearized equations are introduced to describe the waves and attention is given to plane-stratified atmospheres and their stability. A dispersion relation is defined for wave propagation in a plane-stratified atmosphere when there are no plane-wave solutions. Solutions are found for the full wave equation in the presence of either a vertical or a horizontal magnetic field. The theory is applied to describing waves in sunspots, in penumbrae, and flare-induced coronal disturbances.

  5. ULF Waves at Mercury

    NASA Astrophysics Data System (ADS)

    Kim, E.-H.; Boardsen, S. A.; Johnson, J. R.; Slavin, J. A.

    2016-02-01

    This chapter provides a brief overview of the observed characteristics of ultra-low-frequency (ULF) waves at Mercury. It shows how field-aligned propagating ULF waves at Mercury can be generated by externally driven fast compressional waves (FWs) via mode conversion at the ion-ion hybrid resonance. Then, the chapter reviews the interpretation that the strong magnetic compressional waves near and its harmonics observed with 20 of Mercury's magnetic equator could be the ion Bernstein wave (IBW) mode. A recent statistical study of ULF waves at Mercury based on MESSENGER data reported the occurrence and polarization of the detected waves. The chapter further introduces the field line resonance and the electromagnetic ion Bernstein waves to explain such waves, and shows that both theories can partially explain the observations.

  6. Fracture channel waves

    SciTech Connect

    Nihei, K.T.; Yi, W.; Myer, L.R.; Cook, N.G.; Schoenberg, M.

    1999-03-01

    The properties of guided waves which propagate between two parallel fractures are examined. Plane wave analysis is used to obtain a dispersion equation for the velocities of fracture channel waves. Analysis of this equation demonstrates that parallel fractures form an elastic waveguide that supports two symmetric and two antisymmetric dispersive Rayleigh channel waves, each with particle motions and velocities that are sensitive to the normal and tangential stiffnesses of the fractures. These fracture channel waves degenerate to shear waves when the fracture stiffnesses are large, to Rayleigh waves and Rayleigh-Lamb plate waves when the fracture stiffnesses are low, and to fracture interface waves when the fractures are either very closely spaced or widely separated. For intermediate fracture stiffnesses typical of fractured rock masses, fracture channel waves are dispersive and exhibit moderate to strong localization of guided wave energy between the fractures. The existence of these waves is examined using laboratory acoustic measurements on a fractured marble plate. This experiment confirms the distinct particle motion of the fundamental antisymmetric fracture channel wave (A{sub 0} mode) and demonstrates the ease with which a fracture channel wave can be generated and detected. {copyright} 1999 American Geophysical Union

  7. Electron scattering by magnetosonic waves in the inner magnetosphere

    NASA Astrophysics Data System (ADS)

    Ma, Qianli; Li, Wen; Thorne, Richard M.; Bortnik, Jacob; Kletzing, C. A.; Kurth, W. S.; Hospodarsky, G. B.

    2016-01-01

    We investigate the importance of electron scattering by magnetosonic waves in the Earth's inner magnetosphere. A statistical survey of the magnetosonic wave amplitude and wave frequency spectrum, as a function of geomagnetic activity, is performed using the Van Allen Probes wave measurements and is found to be generally consistent with the wave distribution obtained from previous spacecraft missions. Outside the plasmapause the statistical frequency distribution of magnetosonic waves follows the variation of the lower hybrid resonance frequency, but this trend is not observed inside the plasmasphere. Drift and bounce averaged electron diffusion rates due to magnetosonic waves are calculated using a recently developed analytical formula. The resulting timescale of electron energization during disturbed conditions (when AE* > 300 nT) is more than 10 days. We perform a 2-D simulation of the electron phase space density evolution due to magnetosonic wave scattering during disturbed conditions. Outside the plasmapause, the waves accelerate electrons with pitch angles between 50° and 70° and form butterfly pitch angle distributions at energies from ~100 keV to a few MeV over a timescale of several days; whereas inside the plasmapause, the electron acceleration is very weak. Our study suggests that intense magnetosonic waves may cause the butterfly distribution of radiation belt electrons especially outside the plasmapause, but electron acceleration due to magnetosonic waves is generally not as effective as chorus wave acceleration.

  8. Power spectra of internal gravity waves

    NASA Astrophysics Data System (ADS)

    Dewan, E. M.

    1990-09-01

    The OH layer located in the region of 85 km altitude emits strong infrared radiation. Gravity waves can be modulate the brightness of this layer over a wide range of spatial scales. Such fluctuations constitute, in effect, a form of IR clutter which could potentially degrade surveillance systems in certain situations. For this reason there is interest in the spatial and temporal variations of atmospheric internal gravity waves. A physical, similitude model of internal gravity waves assumes saturation of the waves and control by cascade processes of the temporal and horizontal scales of the waves. This model contains all the power spectral densities (PSD's) (sometimes merely called spectra) to be found in the formalism of Garrett and Munk. The latter is a purely empirical model for internal gravity waves applicable to the atmosphere and ocean. The main new predictions of the present model are that the dissipation rate controls the amplitudes of the frequency and horizontal wave number spectra. The validity of the proposed model is unknown at this time, and will depend upon the future experimental tests. It is shown, however, that based on 'typical' parametric values, results from the model are encouraging.

  9. Jovimagnetic secular variation

    NASA Technical Reports Server (NTRS)

    Connerney, J. E. P.; Acuna, M. H.

    1982-01-01

    Long term variations of a planetary magnetic field are one of the few observables available in the study of planetary interiors and dynamo theory. While variations of the geomagnetic field were accessible to direct measurement for centuries, knowledge of the secular variations of other planetary dynamos is limited. New limits on Jovimagnetic secular variations were found by comparison of a Jovian internal field model obtained from the Voyager 1 magnetic field observations at epoch 1979.2 with the epoch 1974.9 Pioneer 11 O4 model. No significant secular variation of either the magnitude or position of the Jovidipole is found for the years 1974.9 through 1979.2, although a small Earth-like variation cannot be ruled out.

  10. Analyzing low frequency waves associated with plasma sheet flow channels

    NASA Astrophysics Data System (ADS)

    Xing, X.; Liang, J.; Wang, C. P.; Lyons, L. R.; Angelopoulos, V.

    2014-12-01

    Low frequency (0.006~0.02 Hz) magnetic oscillations are frequently observed to be associated with the substorm-related dipolarization in the near-Earth plasma sheet. It has been suggested that these oscillations are possibly triggered by ballooning instability in the transition region. However, our multi-point observations using THEMIS spacecraft have shown that similar oscillations are observed to be associated with the earthward moving flow channels as they penetrate from middle tail to the transition region. Linear MHD wave analysis suggested that these oscillations ahead of the dipolarization front are magnetosonic waves. For most of the cases, the thermal pressure and magnetic pressures variations are anti-phase, indicating slow mode waves. However, by taking advantage of the spacecraft located very close in X-Y plane and slightly away from the central plasma sheet, we found that for many events the phase relation between the thermal and magnetic pressure variations is Z-dependent, which suggests that the observational evidence for slow mode may not be applicable. In order to further examine these waves, we performed a MHD analysis in inhomogeneous plasma sheet. The calculation shows that for Harris Sheet configuration, the thermal and magnetic pressures variations can be anti-phase for any wave other than slow mode waves where the vertical velocity disturbance reaches its maximum, thus this phase relation may not be used as an identifier of magnetosonic wave modes. We will show the dispersion relation and wave generated disturbances obtained from the numerical calculations.

  11. Particle Acceleration by Cme-driven Shock Waves

    NASA Technical Reports Server (NTRS)

    Reames, Donald V.

    1999-01-01

    In the largest solar energetic particle (SEP) events, acceleration occurs at shock waves driven out from the Sun by coronal mass ejections (CMEs). Peak particle intensities are a strong function of CME speed, although the intensities, spectra, and angular distributions of particles escaping the shock are highly modified by scattering on Alfven waves produced by the streaming particles themselves. Element abundances vary in complex ways because ions with different values of Q/A resonate with different parts of the wave spectrum, which varies with space and time. Just recently, we have begun to model these systematic variations theoretically and to explore other consequences of proton-generated waves.

  12. Controls on flood and sediment wave propagation

    NASA Astrophysics Data System (ADS)

    Bakker, Maarten; Lane, Stuart N.; Costa, Anna; Molnar, Peter

    2015-04-01

    The understanding of flood wave propagation - celerity and transformation - through a fluvial system is of generic importance for flood forecasting/mitigation. In association with flood wave propagation, sediment wave propagation may induce local erosion and sedimentation, which will affect infrastructure and riparian natural habitats. Through analysing flood and sediment wave propagation, we gain insight in temporal changes in transport capacity (the flood wave) and sediment availability and transport (the sediment wave) along the river channel. Heidel (1956) was amongst the first to discuss the progressive lag of sediment concentration behind the corresponding flood wave based on field measurements. Since then this type of hysteresis has been characterized in a number of studies, but these were often based on limited amount of floods and measurement sites, giving insufficient insight into associated forcing mechanisms. Here, as part of a project concerned with the hydrological and geomorphic forcing of sediment transfer processes in alpine environments, we model the downstream propagation of short duration, high frequency releases of water and sediment (purges) from a flow intake in the Borgne d'Arolla River in south-west Switzerland. A total of >50 events were measured at 1 minute time intervals using pressure transducers and turbidity probes at a number of sites along the river. We show that flood and sediment wave propagation can be well represented through simple convection diffusion models. The models are calibrated/validated to describe the set of measured waves and used to explain the observed variation in wave celerity and diffusion. In addition we explore the effects of controlling factors including initial flow depth, flood height, flood duration, bed roughness, bed slope and initial sediment concentration, on the wave propagation processes. We show that the effects of forcing mechanisms on flood and sediment wave propagation will lead to different

  13. Dust-Acoustic Waves: Visible Sound Waves

    SciTech Connect

    Merlino, Robert L.

    2009-11-10

    A historical overview of some of the early theoretical and experimental work on dust acoustic waves is given. The basic physics of the dust acoustic wave and some of the theoretical refinements that have been made, including the effects of collisions, plasma absorption, dust charge fluctuations, particle drifts and strong coupling effects are discussed. Some recent experimental findings and outstanding problems are also presented.

  14. Bounce harmonic Landau damping of plasma waves

    NASA Astrophysics Data System (ADS)

    Anderegg, F.; Affolter, M.; Kabantsev, A. A.; Dubin, D. H. E.; Ashourvan, A.; Driscoll, C. F.

    2016-05-01

    We present measurements of bounce harmonic Landau damping due to z-variations in the plasma potential, created by an azimuthally symmetric "squeeze" voltage Vs applied to the cylindrical wall. Traditional Landau damping on spatially uniform plasma is weak in regimes where the wave phase velocity vp h≡ω/k is large compared to the thermal velocity. However, z-variations in plasma density and potential create higher spatial harmonics, which enable resonant wave damping by particles with bounce-averaged velocities vp h/n , where n is an integer. In our geometry, the applied squeeze predominantly generates a resonance at vp h/3 . Wave-coherent laser induced fluorescence measurements of particle velocities show a distinctive Landau damping signature at vp h/3 , with amplitude proportional to the applied Vs. The measured (small amplitude) wave damping is then proportional to Vs2 , in quantitative agreement with theory over a range of 20 in temperature. Significant questions remain regarding "background" bounce harmonic damping due to ubiquitous confinement fields and regarding the saturation of this damping at large wave amplitudes.

  15. Wave Meteorology and Soaring

    NASA Technical Reports Server (NTRS)

    Wiley, Scott

    2008-01-01

    This viewgraph document reviews some mountain wave turbulence and operational hazards while soaring. Maps, photographs, and satellite images of the meteorological phenomena are included. Additionally, photographs of aircraft that sustained mountain wave damage are provided.

  16. Cold wave lotion poisoning

    MedlinePlus

    ... this page: //medlineplus.gov/ency/article/002693.htm Cold wave lotion poisoning To use the sharing features on this page, please enable JavaScript. Cold wave lotion is a hair care product used ...

  17. Detonation Wave Profile

    SciTech Connect

    Menikoff, Ralph

    2015-12-14

    The Zel’dovich-von Neumann-Doering (ZND) profile of a detonation wave is derived. Two basic assumptions are required: i. An equation of state (EOS) for a partly burned explosive; P(V, e, λ). ii. A burn rate for the reaction progress variable; d/dt λ = R(V, e, λ). For a steady planar detonation wave the reactive flow PDEs can be reduced to ODEs. The detonation wave profile can be determined from an ODE plus algebraic equations for points on the partly burned detonation loci with a specified wave speed. Furthermore, for the CJ detonation speed the end of the reaction zone is sonic. A solution to the reactive flow equations can be constructed with a rarefaction wave following the detonation wave profile. This corresponds to an underdriven detonation wave, and the rarefaction is know as a Taylor wave.

  18. Real-time Ocean Wave Prediction for Optimal Performance of a Wave Energy Converter

    NASA Astrophysics Data System (ADS)

    Cavaglieri, Daniele; Bewley, Thomas

    2013-11-01

    In recent years, there has been a growing interest in renewable energy. Among all the available possibilities, wave energy conversion, due to the huge availability of energy that the ocean could provide, represents nowadays one of the most promising solutions. However, the efficiency of a wave energy converter for ocean wave energy harvesting is still far from making it competitive with more mature fields of renewable energy, such as solar and wind energy. One of the main problems is related to the inability to accurately predict the profile of oncoming waves approaching the wave energy converter. For this reason, we developed a new hybrid method for state estimation of nonlinear systems, which is based on a variational formulation of an ensemble smoother, combined with the formulation of the ensemble Kalman smoother. This method has been employed for the optimal forecasting of ocean waves via sensors placed on an array of wave energy converters. The coupled simulation of ocean waves and energy devices has been carried out leveraging a nonlinear High Order Spectral code.

  19. P-Wave Electron-Hydrogen Scattering

    NASA Technical Reports Server (NTRS)

    Bhtia, Anand

    2012-01-01

    A variational wave function incorporating short range correlations via Hylleraas type functions plus long-range polarization terms of the polarized orbital type but with smooth cut-off factors has been used to calculate P-wave phase shifts for electron-hydrogen scattering. This approach gives the direct r(exp -4) potential and a non-local optical potential which is definite. The resulting phase shifts have rigorous lower bounds and the convergence is much faster than those obtained without the modification of the target function. Final results will be presented at the conference.

  20. Oceanic wave measurement system

    NASA Technical Reports Server (NTRS)

    Holmes, J. F.; Miles, R. T. (Inventor)

    1980-01-01

    An oceanic wave measured system is disclosed wherein wave height is sensed by a barometer mounted on a buoy. The distance between the trough and crest of a wave is monitored by sequentially detecting positive and negative peaks of the output of the barometer and by combining (adding) each set of two successive half cycle peaks. The timing of this measurement is achieved by detecting the period of a half cycle of wave motion.

  1. Variations in Sexual Behavior.

    ERIC Educational Resources Information Center

    Juhasz, Anne McCreary

    1983-01-01

    Questions are raised about the difficulty of defining normal and atypical sexual behavior. Variations from normalcy that students, parents, and educators are most likely to encounter are discussed. The importance of dealing with variations in ways that are best for the individual and the group is emphasized. (PP)

  2. Effect of critical dimension variation on SAW correlator energy.

    SciTech Connect

    Skinner, Jack L.

    2005-04-01

    The effect of critical dimension (CD) variation and metallization ratio on the efficiency of energy conversion of a surface acoustic wave (SAW) correlator is examined. We find that a 10% variation in the width of finger electrodes predicts only a 1% decrease in the efficiency of energy conversion. Furthermore, our model predicts that a metallization ratio of 0.74 represents an optimum value for energy extraction from the SAW by the interdigitated transducer (IDT).

  3. Short and long periodic atmospheric variations between 25 and 200 km

    NASA Technical Reports Server (NTRS)

    Justus, C. G.; Woodrum, A.

    1973-01-01

    Previously collected data on atmospheric pressure, density, temperature and winds between 25 and 200 km from sources including Meteorological Rocket Network data, ROBIN falling sphere data, grenade release and pitot tube data, meteor winds, chemical release winds, satellite data, and others were analyzed by a daily difference method and results on the distribution statistics, magnitude, and spatial structure of gravity wave and planetary wave atmospheric variations are presented. Time structure of the gravity wave variations were determined by the analysis of residuals from harmonic analysis of time series data. Planetary wave contributions in the 25-85 km range were discovered and found to have significant height and latitudinal variation. Long period planetary waves, and seasonal variations were also computed by harmonic analysis. Revised height variations of the gravity wave contributions in the 25 to 85 km height range were computed. An engineering method and design values for gravity wave magnitudes and wave lengths are given to be used for such tasks as evaluating the effects on the dynamical heating, stability and control of spacecraft such as the space shuttle vehicle in launch or reentry trajectories.

  4. Electron acceleration by inertial Alfven waves

    SciTech Connect

    Thompson, B.J.; Lysak, R.L.

    1996-03-01

    Alfven waves reflected by the ionosphere and by inhomogeneities in the Alfven speed can develop an oscillating parallel electric field when electron inertial effects are included. These waves, which have wavelengths of the order of an Earth radius, can develop a coherent structure spanning distances of several Earth radii along geomagnetic field lines. This system has characteristic frequencies in the range of 1 Hz and can exhibit electric fields capable of accelerating electrons in several senses: via Landua resonance, bounce or transit time resonance as discussed by Andre and Eliasson or through the effective potential drop which appears when the transit time of the electrons is much smaller than the wave period, so that the electric fields appear effectively static. A time-dependent model of wave propagation is developed which represents inertial Alfven wave propagation along auroral field lines. The disturbance is modeled as it travels earthward, experiences partial reflections in regions of rapid variation, and finally reflects off a conducting ionosphere to continue propagating antiearthward. The wave experiences partial trapping by the ionospheric and the Alfven speed peaks discussed earlier by Polyakov and Rapoport and Trakhtengerts and Feldstein and later by Lysak. Results of the wave simulation and an accompanying test particle simulation are presented, which indicate that inertial Alfven waves are a possible mechanism for generating electron conic distributions and field-aligned particle precipitation. The model incorporates conservation of energy by allowing electrons to affect the wave via Landau damping, which appears to enhance the effect of the interactions which heat electron populations. 22 refs., 14 figs.

  5. Waves of Hanta

    NASA Astrophysics Data System (ADS)

    Abramson, Guillermo

    2003-03-01

    A spatially extended model of the hantavirus infection in deer mice is analyzed. Traveling waves solutions of the infected and susceptible populations are studied in different regimes, controlled by an environmental parameter. The wave of infection is shown to lag behind the wave of susceptible population, and the delay between the two is analyzed numerically and through a piecewise linearization.

  6. Wave dynamics of a Pacific Atoll with high frictional effects

    NASA Astrophysics Data System (ADS)

    Rogers, Justin S.; Monismith, Stephen G.; Koweek, David A.; Dunbar, Robert B.

    2016-01-01

    We report field measurements of waves and currents made from September 2011 to July 2014 on Palmyra Atoll in the central Pacific that were used in conjunction with the SWAN wave model to characterize the wave dynamics operant on the atoll. Our results indicate that wave energy is primarily from the north during the northern hemisphere winter and from the south in the northern hemisphere summer. Refraction of waves along the reef terraces due to variations in bathymetry leads to focusing of waves in specific locations. Bottom friction, modeled with a modified bottom roughness formulation, is the significant source of wave energy dissipation on the atoll, a result that is consistent with available observations of wave damping on Palmyra. Indeed modeled wave dissipation rates from bottom friction are on average larger than dissipation rates due to breaking and are an order of magnitude larger than what has been observed on other, less geometrically complex reefs, a result which should be corroborated with future in situ measurements. The SWAN wave model with a modified bottom friction formulation better predicts bulk wave energy properties than the existing formulation at our measurement stations. The near bed squared velocity, a proxy for bottom stress, shows strong spatial variability across the atoll and exerts control over geomorphic structure and benthic community composition.

  7. Effects of the Gulf Stream on ocean waves

    NASA Technical Reports Server (NTRS)

    Holthuijsen, L. H.; Tolman, H. L.

    1991-01-01

    In the present study a third-generation numerical wave model is used to study effects of a straight Gulf Stream ring on ocean waves in swell and storm conditions. The model accounts for all relevant processes of propagation, generation, and dissipation of the waves (including current effects) without imposing a priori restraints on the spectral development of the waves. The dominating mechanism affecting the waves appears to be current-induced refraction even though the short-crestedness of the incoming waves tends to mask its effects (also in swell conditions). Depending on wind and wave conditions, refraction may trap locally generated waves in the straight Gulf Stream or it may reflect wave energy back to the open ocean. In the Gulf Stream ring, refraction induces a considerable variation in significant wave height and short-crestedness, but it hardly affects the mean wave direction. In storm conditions the processes of generation and dissipation are considerably enhanced in countercurrent situations and reduced following-current situations.

  8. Influence of flow and pressure on wave propagation in the canine aorta.

    NASA Technical Reports Server (NTRS)

    Histand, M. B.; Anliker, M.

    1973-01-01

    Data on wave speed acquired from 20 anesthetized dogs showed that the thoracic aorta was essentially nondispersive for small artificially generated pressure waves traveling in the downstream or the upstream direction and having frequencies between 40 and 120 Hz. The amplitude of these waves decayed exponentially with the distance traveled. Theoretical studies are cited which have shown that changes in wave speed due to variations in pressure and flow produce marked nonlinear effects in hemodynamics.

  9. Variational symmetries, conserved quantities and identities for several equations of mathematical physics

    SciTech Connect

    Donchev, Veliko

    2014-03-15

    We find variational symmetries, conserved quantities and identities for several equations: envelope equation, Böcher equation, the propagation of sound waves with losses, flow of a gas with losses, and the nonlinear Schrödinger equation with losses or gains, and an electro-magnetic interaction. Most of these equations do not have a variational description with the classical variational principle and we find such a description with the generalized variational principle of Herglotz.

  10. Investigation of Spatial Variation of Sea States Offshore of Humboldt Bay CA Using a Hindcast Model.

    SciTech Connect

    Dallman, Ann Renee; Neary, Vincent Sinclair

    2014-10-01

    Spatial variability of sea states is an important consideration when performing wave resource assessments and wave resource characterization studies for wave energy converter (WEC) test sites and commercial WEC deployments. This report examines the spatial variation of sea states offshore of Humboldt Bay, CA, using the wave model SWAN . The effect of depth and shoaling on bulk wave parameters is well resolved using the model SWAN with a 200 m grid. At this site, the degree of spatial variation of these bulk wave parameters, with shoaling generally perpendicular to the depth contours, is found to depend on the season. The variation in wave height , for example, was higher in the summer due to the wind and wave sheltering from the protruding land on the coastline north of the model domain. Ho wever, the spatial variation within an area of a potential Tier 1 WEC test site at 45 m depth and 1 square nautical mile is almost negligible; at most about 0.1 m in both winter and summer. The six wave characterization parameters recommended by the IEC 6 2600 - 101 TS were compared at several points along a line perpendicular to shore from the WEC test site . As expected, these parameters varied based on depth , but showed very similar seasonal trends.

  11. Wave turbulence in annular wave tank

    NASA Astrophysics Data System (ADS)

    Onorato, Miguel; Stramignoni, Ettore

    2014-05-01

    We perform experiments in an annular wind wave tank at the Dipartimento di Fisica, Universita' di Torino. The external diameter of the tank is 5 meters while the internal one is 1 meter. The tank is equipped by two air fans which can lead to a wind of maximum 5 m/s. The present set up is capable of studying the generation of waves and the development of wind wave spectra for large duration. We have performed different tests including different wind speeds. For large wind speed we observe the formation of spectra consistent with Kolmogorv-Zakharov predictions.

  12. MESSENGER Observations of Upstream Whistler Waves in Mercury's Foreshock Region

    NASA Astrophysics Data System (ADS)

    Le, G.; Chi, P. J.; Blanco-Cano, X.; Boardsen, S. A.; Slavin, J. A.; Anderson, B. J.; Korth, H.

    2012-12-01

    The region upstream from a planetary bow shock is a natural plasma laboratory containing a variety of wave particle phenomena. The study of foreshocks other than the Earth's is important for extending our understanding of collisionless shocks and foreshock physics since the bow shock strength varies with heliocentric distance from the Sun, and the sizes of the bow shocks are different at different planets. The Mercury's bow shock is unique in our solar system as it is produced by low Mach number and low plasma beta solar wind blowing over a small magnetized body with a predominately radial interplanetary magnetic field. Previous observations of Mercury upstream ultra-low frequency (ULF) waves came exclusively from two Mercury flybys of Mariner 10. The MESSENGER orbiter data enable us to study upstream waves in the Mercury's foreshock in depth. This paper reports an overview of upstream ULF waves in the Mercury's foreshock using high-time resolution magnetic field data, 20 samples per second, from the MESSENGER spacecraft. A preliminary study has shown the existence of at least three types of upstream waves: 1) whistler waves at frequencies near 2 Hz, similar to 1-Hz waves at the Earth; 2) waves with frequencies ~ 0.1 Hz, similar to the large-amplitude 30-s waves at the Earth; 3) fluctuations with broad spectral peaks centered at ~ 0.6 Hz. Unlike the Earth's foreshock where the most prominent upstream wave phenomenon is locally generated large-amplitude 30-s waves, the most common foreshock waves are whistler waves generated at the bow shock, with properties similar to the 1-Hz waves in the Earth's foreshock. These "one-Hz" waves are present in both the flyby data and in every orbit of the orbital data we have surveyed. We will discuss their properties, spatial variations, and propagation and occurrence characteristics in this paper.

  13. Wave spectra partitioning and long term statistical distribution

    NASA Astrophysics Data System (ADS)

    Portilla-Yandún, Jesús; Cavaleri, Luigi; Van Vledder, Gerbrant Ph.

    2015-12-01

    A new method is presented for a physically based statistical description of wind wave climatology. The method applies spectral partitioning to identify individual wave systems (partitions) in time series of 2D-wave spectra, followed by computing the probability of occurrence of their (peak) position in frequency-direction space. This distribution can be considered as a spectral density function to which another round of partitioning is applied to obtain spectral domains, each representing a typical wave system or population in a statistical sense. This two-step partitioning procedure allows identifying aggregate wave systems without the need to discuss specific characteristics as wind sea and swell systems. We suggest that each of these aggregate wave systems (populations) is linked to a specific generation pattern opening the way to dedicated analyses. Each population (of partitions) can be subjected to further analyses to add dimension carrying information based on integrated wave parameters of each partition, such as significant wave height, wave age, mean wave period and direction, among others. The new method is illustrated by analysing model spectra from a numerical wave prediction model and measured spectra from a directional wave buoy located in the Southern North Sea. It is shown that these two sources of information yield consistent results. Examples are given of computing the statistical distribution of significant wave height, spectral energy distribution and the spatial variation of wind wave characteristics along a north-south transect in the North Sea. Wind or wave age information can be included as an extra attribute of the members of a population to label them as wind sea or swell systems. Finally, suggestions are given for further applications of this new method.

  14. Shock-wave surfing

    SciTech Connect

    Laurence, Stuart J; Deiterding, Ralf

    2011-01-01

    A phenomenon referred to as shock-wave surfing , in which a body moves in such a way as to follow the shock wave generated by another upstream body, is investigated numerically and theoretically. This process can lead to the downstream body accumulating a significantly higher lateral velocity than would otherwise be possible, and thus is of importance in situations such as meteoroid fragmentation, in which the fragment separation behaviour following disruption is determined to a large extent by aerodynamic effects. The surfing effect is first investigated in the context of interactions between a sphere and a planar oblique shock. Numerical simulations are performed and a simple theoretical model is developed to determine the forces acting on the sphere. A phase-plane description is employed to elucidate features of the system dynamics. The theoretical model is then generalised to the more complex situation of aerodynamic interactions between two spheres, and, through comparisons with further computations, is shown to adequately predict, in particular, the final separation velocity of the surfing sphere in initially touching configurations. Both numerical simulations and theory indicate a strong influence of the body radius ratio on the separation process and predict a critical radius ratio for initially touching fragments that delineates entrainment of the smaller fragment within the larger fragment s shock from expulsion; this critical ratio also results in the most extended surfing. Further, these results show that an earlier prediction for the separation velocity to scale with the square root of the radius ratio does not accurately describe the separation behaviour. The theoretical model is then employed to investigate initial configurations with varying relative sphere positions and initial velocities. A phase-space description is also shown to be useful in elucidating the dynamics of the sphere-sphere system. With regard to meteoroid fragmentation, it is shown

  15. The spartial distribution of the particles of the beam interacting with an inhomogeneous electromagnetic wave

    SciTech Connect

    Serov, A.V.

    1995-12-31

    The time variation of the spartial distribution of an electron beam reflected by an inhomogeneous wave or traverse the wave was investigated. The injected beam is perpendicular to the direction of propagation of the wave. The interaction between an electron beam and an electromagnetic wave not only produces electron oscillation but also substantially changes the electron phase and energy distribution. It is shown that under specific conditions one part of particles are reflected by an electromagnetic wave and other part of particles traverse the wave.

  16. Detectors of gravitational waves

    NASA Astrophysics Data System (ADS)

    Pizzella, G.

    Gravitational waves Motion of test bodies in a g.w. field Energy carried by gravitational waves Gravitational-wave sources Spinning star Double-star systems Fall into a Schwarzschild black hole Radiation from gravitational collapse Gravitational-wave detectors The nonresonant detectors The resonant detectors Electromechnical transducers Piezoelectric ceramic The capacitor The inductor Data analysis The Brownian noise The back-action The wide-band noise, data analysis and optimization The resonant transducer The Wiener-Kolmogoroff filter The cross-section and the effective temperature The antenna bandwidth The gravitational-wave experiments in the world The laser interferometers The resonant detectors

  17. Ion-acoustic cnoidal waves in a quantum plasma

    SciTech Connect

    Mahmood, S.; Haas, F.

    2014-10-15

    Nonlinear ion-acoustic cnoidal wave structures are studied in an unmagnetized quantum plasma. Using the reductive perturbation method, a Korteweg-de Vries equation is derived for appropriate boundary conditions and nonlinear periodic wave solutions are obtained. The corresponding analytical solution and numerical plots of the ion-acoustic cnoidal waves and solitons in the phase plane are presented using the Sagdeev pseudo-potential approach. The variations in the nonlinear potential of the ion-acoustic cnoidal waves are studied at different values of quantum parameter H{sub e} which is the ratio of electron plasmon energy to electron Fermi energy defined for degenerate electrons. It is found that both compressive and rarefactive ion-acoustic cnoidal wave structures are formed depending on the value of the quantum parameter. The dependence of the wavelength and frequency on nonlinear wave amplitude is also presented.

  18. Signatures of Nonlinear Waves in Coronal Plumes and Holes

    NASA Technical Reports Server (NTRS)

    Ofman, Leon

    1999-01-01

    In recent Ultraviolet Coronagraph Spectrometer/Solar and Heliospheric Observatory (UVCS/SOHO) White Light Channel (WLC) observations we found quasi-periodic variations in the polarized brightness (pB) in the polar coronal holes at heliocentric distances of 1.9-2.45 solar radii. The motivation for the observation is the 2.5D Magnetohydrodynamics (MHD) model of solar wind acceleration by nonlinear waves, that predicts compressive fluctuations in coronal holes. To help identify the waves observed with the UVCS/WLC we model the propagation and dissipation of slow magnetosonic waves in polar plumes using 1D MHD code in spherical geometry, We find that the slow waves nonlinearly steepen in the gravitationally stratified plumes. The nonlinear steepening of the waves leads to enhanced dissipation due to compressive viscosity at the wave-fronts.

  19. Remote sensing of nearshore wave interference

    NASA Astrophysics Data System (ADS)

    Smit, P. B.; Bland, R.; Janssen, T. T.; Laughlin, B.

    2016-05-01

    Wave focusing of energetic swell fields can result in small-scale variations associated with coherent interference that can be important for nearshore circulation and beach dynamics. However, coherent interference is difficult to measure with conventional in situ instruments and is not accounted for in operational wave models. As a result, such effects are generally ignored. In this work, we analyze X-band radar observations collected at Ocean Beach, San Francisco using a Wigner-Ville or coupled-mode spectrum, to show how long-dwell remote sensing technology allows us to identify coherent wave interference. Our analysis demonstrates that during energetic swell events, the nearshore wave field consists of two noncollinear, but coherent, swell patterns that originate from the same offshore source but are directionally separated due to refraction over the San Francisco Bar. The length scale of the associated alongshore wave height variability (200 m) is consistent with the wavenumber separation obtained from the coupled mode analysis. This confirms that the small-scale variability is primarily due to coherent interference. In addition, our analysis shows that the shoreline exhibits a strong localized response near the radar site on the 200 m scale, which suggests that coherent interference effects can affect wave-driven nearshore transport processes and localized erosion.

  20. Bound infragravity waves

    NASA Astrophysics Data System (ADS)

    Okihiro, Michele; Guza, R. T.; Seymour, R. J.

    1992-07-01

    Model predictions of bound (i.e., nonlinearly forced by and coupled to wave groups) infragravity wave energy are compared with about 2 years of observations in 8- to 13-m depths at Imperial Beach, California, and Barbers Point, Hawaii. Frequency-directional spectra of free waves at sea and swell frequencies, estimated with a small array of four pressure sensors, are used to predict the bound wave spectra below 0.04 Hz. The predicted total bound wave energy is always less than the observed infragravity energy, and the underprediction increases with increasing water depth and especially with decreasing swell energy. At most half, and usually much less, of the observed infragravity energy is bound. Bound wave spectra are also predicted with data from a single wave gage in 183-m depth at Point Conception, California, and the assumption of unidirectional sea and swell. Even with energetic swell, less than 10% of the total observed infragravity energy in 183-m depth is bound. Free waves, either leaky or edge waves, are more energetic than bound waves at both the shallow and deep sites. The low level of infragravity energy observed in 183-m depth compared with 8- to 13-m depths, with similarly moderate sea and swell energy, suggests that leaky (and very high-mode edge) waves contribute less than 10% of the infragravity energy in 8-13 m. Most of the free infragravity energy in shallow water is refractively trapped and does not reach deep water.