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Sample records for arterial transit time

  1. Pulse transit time as a surrogate measure of changes in systolic arterial pressure in children during sleep.

    PubMed

    Vlahandonis, Anna; Biggs, Sarah N; Nixon, Gillian M; Davey, Margot J; Walter, Lisa M; Horne, Rosemary S C

    2014-08-01

    Pulse transit time has been proposed as a surrogate measure of systolic arterial pressure, as it is dependent upon arterial stiffness. Past research has shown that pulse transit time has a significant inverse relationship to systolic arterial pressure in adults; however, studies in children are limited. This study aimed to explore the relationship between systolic arterial pressure and pulse transit time in children during sleep. Twenty-five children (13.1 ± 1.6 years, 48% male) underwent overnight polysomnography (PSG) with a simultaneous recording of continuous systolic arterial pressure and photoplethysmography. Pulse transit time was calculated as the time delay between the R-wave peak of the electrocardiogram (ECG) to the 50% point of the upstroke of the corresponding photoplethysmography waveform; 500 beats of simultaneous systolic arterial pressure and pulse transit time were analysed in each sleep stage for each child. Pulse transit time was normalized to each subject's mean wake pulse transit time. The ability of pulse transit time to predict systolic arterial pressure change was determined by linear mixed-effects modelling. Significant negative correlations between pulse transit time and systolic arterial pressure were found for individual children for each sleep stage [mean correlations for cohort: non-rapid eye movement (NREM) sleep 1 and 2 r = -0.57, slow wave sleep (SWS) r = -0.76, REM r = -0.65, P < 0.01 for all]. Linear mixed-model analysis demonstrated that changes in pulse transit time were a significant predictor of changes in systolic arterial pressure for each sleep stage (P < 0.001). The model of pulse transit time-predicted systolic arterial pressure closely tracked actual systolic arterial pressure changes over time. This study demonstrated that pulse transit time was accurate in tracking systolic arterial pressure changes over time. Thus, the use of pulse transit time as a surrogate measure of changes in systolic arterial pressure in

  2. Pulmonary pulse wave transit time is associated with right ventricular–pulmonary artery coupling in pulmonary arterial hypertension

    PubMed Central

    Weir, E. Kenneth; Archer, Stephen L.; Markowitz, Jeremy; Rose, Lauren; Pritzker, Marc; Madlon-Kay, Richard; Thenappan, Thenappan

    2016-01-01

    Abstract Pulmonary pulse wave transit time (pPTT), defined as the time for the systolic pressure pulse wave to travel from the pulmonary valve to the pulmonary veins, has been reported to be reduced in pulmonary arterial hypertension (PAH); however, the underlying mechanism of reduced pPTT is unknown. Here, we investigate the hypothesis that abbreviated pPTT in PAH results from impaired right ventricular–pulmonary artery (RV-PA) coupling. We quantified pPTT using pulsed-wave Doppler ultrasound from 10 healthy age- and sex-matched controls and 36 patients with PAH. pPTT was reduced in patients with PAH compared with controls. Univariate analysis revealed the following significant predictors of reduced pPTT: age, right ventricular fractional area change (RV FAC), tricuspid annular plane excursion (TAPSE), pulmonary arterial pressures (PAP), diastolic pulmonary gradient, transpulmonary gradient, pulmonary vascular resistance, and RV-PA coupling (defined as RV FAC/mean PAP or TAPSE/mean PAP). Although the correlations between pPTT and invasive markers of pulmonary vascular disease were modest, RV FAC (r = 0.64, P < 0.0001), TAPSE (r = 0.67, P < 0.0001), and RV-PA coupling (RV FAC/mean PAP: r = 0.72, P < 0.0001; TAPSE/mean PAP: r = 0.74, P < 0.0001) had the strongest relationships with pPTT. On multivariable analysis, only RV FAC, TAPSE, and RV-PA coupling were independent predictors of pPTT. We conclude that shortening of pPTT in patients with PAH results from altered RV-PA coupling, probably occurring as a result of reduced pulmonary arterial compliance. Thus, pPTT allows noninvasive determination of the status of both the pulmonary vasculature and the response of the RV in patients with PAH, thereby allowing monitoring of disease progression and regression. PMID:28090301

  3. Improved pulse transit time estimation by system identification analysis of proximal and distal arterial waveforms.

    PubMed

    Xu, Da; Ryan, Kathy L; Rickards, Caroline A; Zhang, Guanqun; Convertino, Victor A; Mukkamala, Ramakrishna

    2011-10-01

    We investigated the system identification approach for potentially improved estimation of pulse transit time (PTT), a popular arterial stiffness marker. In this approach, proximal and distal arterial waveforms are measured and respectively regarded as the input and output of a system. Next, the system impulse response is identified from all samples of the measured input and output. Finally, the time delay of the impulse response is detected as the PTT estimate. Unlike conventional foot-to-foot detection techniques, this approach is designed to provide an artifact robust estimate of the true PTT in the absence of wave reflection. The approach is also applicable to arbitrary types of arterial waveforms. We specifically applied a parametric system identification technique to noninvasive impedance cardiography (ICG) and peripheral arterial blood pressure waveforms from 15 humans subjected to lower-body negative pressure. We assessed the technique through the correlation coefficient (r) between its 1/PTT estimates and measured diastolic pressure (DP) per subject and the root mean squared error (RMSE) of the DP predicted from these estimates and measured DP. The technique achieved average r and RMSE values of 0.81 ± 0.16 and 4.3 ± 1.3 mmHg. For comparison, the corresponding values were 0.59 ± 0.37 (P < 0.05) and 5.9 ± 2.5 (P < 0.01) mmHg for the conventional technique applied to the same waveforms and 0.28 ± 0.40 (P < 0.001) and 7.2 ± 1.8 (P < 0.001) mmHg for the conventional technique with the ECG waveform substituted for the ICG waveform. These results demonstrate, perhaps for the first time, that the system identification approach can indeed improve PTT estimation.

  4. Noninvasive pulse transit time measurement for arterial stiffness monitoring in microgravity.

    PubMed

    McCall, Corey; Rostosky, Rea; Wiard, Richard M; Inan, Omer T; Giovangrandi, Laurent; Cuttino, Charles Marsh; Kovacs, Gregory T A

    2015-01-01

    The use of a noninvasive hemodynamic monitor to estimate arterial stiffness, by measurement of pulse transit time (PTT), was demonstrated in microgravity. The monitor's utility for space applications was shown by establishing the correlation between ground-based and microgravity-based measurements. The system consists of a scale-based ballistocardiogram (BCG) and a toe-mounted photoplethysmogram (PPG). PTT was measured from the BCG I-wave to the intersecting tangents of the first trough and maximum first derivative of the PPG waveforms of each subject. The system was tested on a recent series of parabolic flights in which the PTT of nine subjects was measured on the ground and in microgravity. An average of 60.2 ms PTT increase from ground to microgravity environments was shown, and was consistent across all test subjects (standard deviation = 32.9 ms). This increase in PTT could be explained by a number of factors associated with microgravity and reported in previous research, including elimination of hydrostatic pressure, reduction of intrathoracic pressure, and reduction of mean arterial pressure induced by vasodilation.

  5. Improved Pulse Transit Time Estimation by System Identification Analysis of Proximal and Distal Arterial Waveforms

    DTIC Science & Technology

    2011-10-01

    only), electrical im- pedance, pulse oximetry, and even noncontact laser Doppler vibrometry (8). The disadvantage of the approach is that it may not...Morbiducci U, Scalise L, Tomasini EP, Delbeke D, Baets R, Van Bortel LM, Segers P. A noncontact approach for the evaluation of large artery stiffness: a...management of arterial hypertension: the Task Force for the management of arterial hypertension of the European Society of Hypertension (ESH) and of the

  6. Determining arterial wave transit time from a single aortic pressure pulse in rats: vascular impulse response analysis

    PubMed Central

    Chang, Ru-Wen; Chang, Chun-Yi; Lai, Liang-Chuan; Wu, Ming-Shiou; Young, Tai-Horng; Chen, Yih-Sharng; Wang, Chih-Hsien; Chang, Kuo-Chu

    2017-01-01

    Arterial wave transit time (τw) in the lower body circulation is an effective biomarker of cardiovascular risk that substantially affects systolic workload imposed on the heart. This study evaluated a method for determining τw from the vascular impulse response on the basis of the measured aortic pressure and an assumed triangular flow (Qtri). The base of the unknown Qtri was constructed with a duration set equal to ejection time. The timing of the peak triangle was derived using a fourth-order derivative of the pressure waveform. Values of τws obtained using Qtri were compared with those obtained from the measure aortic flow wave (Qm). Healthy rats (n = 27), rats with chronic kidney disease (CKD; n = 22), and rats with type 1 (n = 22) or type 2 (n = 11) diabetes were analyzed. The cardiovascular conditions in the CKD rats and both diabetic groups were characterized by a decrease in τws. The following significant relation was observed (P < 0.0001): τwtriQ = −1.5709 + 1.0604 × τwmQ (r2 = 0.9641). Our finding indicates that aortic impulse response can be an effective method for the estimation of arterial τw by using a single pressure recording together with the assumed Qtri. PMID:28102355

  7. Determining arterial wave transit time from a single aortic pressure pulse in rats: vascular impulse response analysis.

    PubMed

    Chang, Ru-Wen; Chang, Chun-Yi; Lai, Liang-Chuan; Wu, Ming-Shiou; Young, Tai-Horng; Chen, Yih-Sharng; Wang, Chih-Hsien; Chang, Kuo-Chu

    2017-01-19

    Arterial wave transit time (τw) in the lower body circulation is an effective biomarker of cardiovascular risk that substantially affects systolic workload imposed on the heart. This study evaluated a method for determining τw from the vascular impulse response on the basis of the measured aortic pressure and an assumed triangular flow (Q(tri)). The base of the unknown Q(tri) was constructed with a duration set equal to ejection time. The timing of the peak triangle was derived using a fourth-order derivative of the pressure waveform. Values of τws obtained using Q(tri) were compared with those obtained from the measure aortic flow wave (Q(m)). Healthy rats (n = 27), rats with chronic kidney disease (CKD; n = 22), and rats with type 1 (n = 22) or type 2 (n = 11) diabetes were analyzed. The cardiovascular conditions in the CKD rats and both diabetic groups were characterized by a decrease in τws. The following significant relation was observed (P < 0.0001): τw(triQ) = -1.5709 + 1.0604 × τw(mQ) (r(2) = 0.9641). Our finding indicates that aortic impulse response can be an effective method for the estimation of arterial τw by using a single pressure recording together with the assumed Q(tri).

  8. SU-D-18C-05: Variable Bolus Arterial Spin Labeling MRI for Accurate Cerebral Blood Flow and Arterial Transit Time Mapping

    SciTech Connect

    Johnston, M; Jung, Y

    2014-06-01

    Purpose: Arterial spin labeling (ASL) is an MRI perfusion imaging method from which quantitative cerebral blood flow (CBF) maps can be calculated. Acquisition with variable post-labeling delays (PLD) and variable TRs allows for arterial transit time (ATT) mapping and leads to more accurate CBF quantification with a scan time saving of 48%. In addition, T1 and M0 maps can be obtained without a separate scan. In order to accurately estimate ATT and T1 of brain tissue from the ASL data, variable labeling durations were invented, entitled variable-bolus ASL. Methods: All images were collected on a healthy subject with a 3T Siemens Skyra scanner. Variable-bolus Psuedo-continuous ASL (PCASL) images were collected with 7 TI times ranging 100-4300ms in increments of 700ms with TR ranging 1000-5200ms. All boluses were 1600ms when the TI allowed, otherwise the bolus duration was 100ms shorter than the TI. All TI times were interleaved to reduce sensitivity to motion. Voxel-wise T1 and M0 maps were estimated using a linear least squares fitting routine from the average singal from each TI time. Then pairwise subtraction of each label/control pair and averaging for each TI time was performed. CBF and ATT maps were created using the standard model by Buxton et al. with a nonlinear fitting routine using the T1 tissue map. Results: CBF maps insensitive to ATT were produced along with ATT maps. Both maps show patterns and averages consistent with literature. The T1 map also shows typical T1 contrast. Conclusion: It has been demonstrated that variablebolus ASL produces CBF maps free from the errors due to ATT and tissue T1 variations and provides M0, T1, and ATT maps which have potential utility. This is accomplished with a single scan in a feasible scan time (under 6 minutes) with low sensivity to motion.

  9. Arterial Transit Time Effects in Pulsed Arterial Spin Labeling CBF Mapping: Insight From a PET and MR Study in Normal Human Subjects

    PubMed Central

    Qiu, Maolin; Maguire, R. Paul; Arora, Jagriti; Planeta-Wilson, Beata; Weinzimmer, David; Wang, Jinghua; Wang, Yuenan; Kim, Hyeonjin; Rajeevan, Nallakkandi; Huang, Yiyun; Carson, Richard E.; Constable, R. Todd

    2010-01-01

    Arterial transit time (ATT), a key parameter required to calculate absolute cerebral blood flow in arterial spin labeling (ASL), is subject to much uncertainty. In this study, ASL ATTs were estimated on a per-voxel basis using data measured by both ASL and positron emission tomography in the same subjects. The mean ATT increased by 260 ± 20 (standard error of the mean) ms when the imaging slab shifted downwards by 54 mm, and increased from 630 ± 30 to 1220 ± 30 ms for the first slice, with an increase of 610 ± 20 ms over a four-slice slab when the gap between the imaging and labeling slab increased from 20 to 74 mm. When the per-slice ATTs were employed in ASL cerebral blood flow quantification and the in-slice ATT variations ignored, regional cerebral blood flow could be significantly different from the positron emission tomography measures. ATT also decreased with focal activation by the same amount for both visual and motor tasks (~80 ms). These results provide a quantitative relationship between ATT and the ASL imaging geometry and yield an assessment of the assumptions commonly used in ASL imaging. These findings should be considered in the interpretation of, and comparisons between, different ASL-based cerebral blood flow studies. The results also provide spatially specific ATT data that may aid in optimizing the ASL imaging parameters. PMID:19953506

  10. Techniques and standards in intraoperative graft verification by transit time flow measurement after coronary artery bypass graft surgery: a critical review.

    PubMed

    Niclauss, Lars

    2017-01-01

    Transit time flow measurement (TTFM) is a quality control tool for intraoperative graft evaluation in coronary artery bypass graft (CABG) surgery. A critical review of the literature available using TTFM in CABG surgery is the focus of this article. The main objectives will be to detail precise parameters for flow evaluation, to show limitations of TTFM and to prove its predictive impact on postoperative graft failure rate. Publications listed in the PubMed database were reviewed, searching for intraoperative graft verification in coronary surgery by TTFM, with postoperative imaging follow-up (FU) modality and with a special focus on publications released after European guidelines from 2010. Nine included publications revealed an overall graft failure rate of ∼12%. Mean graft flow had a positive predictive value in the largest study, and cut-offs, of at least 20 ml/min for internal mammary artery (IMA) grafts, therein partially confirming guidelines, and 30-40 ml/min for saphenous venous grafts (SVGs) were proposed. An explicit correlation between graft flow, patency rate and severity of coronary stenosis, by indicating the fractional flow reserve, was found for IMA grafts. Increased pulsatility index and increased systolic reverse flow probably predict worse outcome and may help identifying competitive flow. Diastolic filling, rarely indicated, could not be confirmed as the predictive marker. No significant correlation of TTFM and graft failure rate for radial and other arterial grafts could be found, partially due to the small number of these types of grafts analysed. Larger target vessels and lower postoperative CK-MB levels may predict better graft patency rates. Low sensitivity for TTFM to reliably detect graft failure is certainly a major issue, as found in randomized analyses. However, methodical limitations and varying threshold values for TTFM render a general consensus difficult. Influence of quantity (vessel territory distribution) and quality

  11. Three-dimensional whole-brain perfusion quantification using pseudo-continuous arterial spin labeling MRI at multiple post-labeling delays: accounting for both arterial transit time and impulse response function.

    PubMed

    Qin, Qin; Huang, Alan J; Hua, Jun; Desmond, John E; Stevens, Robert D; van Zijl, Peter C M

    2014-02-01

    Measurement of the cerebral blood flow (CBF) with whole-brain coverage is challenging in terms of both acquisition and quantitative analysis. In order to fit arterial spin labeling-based perfusion kinetic curves, an empirical three-parameter model which characterizes the effective impulse response function (IRF) is introduced, which allows the determination of CBF, the arterial transit time (ATT) and T(1,eff). The accuracy and precision of the proposed model were compared with those of more complicated models with four or five parameters through Monte Carlo simulations. Pseudo-continuous arterial spin labeling images were acquired on a clinical 3-T scanner in 10 normal volunteers using a three-dimensional multi-shot gradient and spin echo scheme at multiple post-labeling delays to sample the kinetic curves. Voxel-wise fitting was performed using the three-parameter model and other models that contain two, four or five unknown parameters. For the two-parameter model, T(1,eff) values close to tissue and blood were assumed separately. Standard statistical analysis was conducted to compare these fitting models in various brain regions. The fitted results indicated that: (i) the estimated CBF values using the two-parameter model show appreciable dependence on the assumed T(1,eff) values; (ii) the proposed three-parameter model achieves the optimal balance between the goodness of fit and model complexity when compared among the models with explicit IRF fitting; (iii) both the two-parameter model using fixed blood T1 values for T(1,eff) and the three-parameter model provide reasonable fitting results. Using the proposed three-parameter model, the estimated CBF (46 ± 14 mL/100 g/min) and ATT (1.4 ± 0.3 s) values averaged from different brain regions are close to the literature reports; the estimated T(1,eff) values (1.9 ± 0.4 s) are higher than the tissue T1 values, possibly reflecting a contribution from the microvascular arterial blood compartment.

  12. Transit Timing Variations

    NASA Video Gallery

    The animation shows the difference between planet transit timing of single and multiple planet system. In tightly packed planetary systems, the gravitational pull of the planets among themselves ca...

  13. Transit satellite system timing capabilities

    NASA Technical Reports Server (NTRS)

    Finsod, T. D.

    1978-01-01

    Current time transfer capabilities of the Transit Satellite System are reviewed. Potential improvements in the changes in equipment and operational procedures using operational satellites are discussed.

  14. [Long time regulation of arterial blood pressure: facts and hypothesis].

    PubMed

    Tsyrlin, V A

    2013-01-01

    The date about long time increase of blood pressure in conditions of excessive salt intake, constriction of renal artery in animals with initial low baroreceptor reflex is presented. Arterial hypertension in this case is accompanied by increase activity of sympathetic nervous system. The supposition that arterial baroreceptor reflex place a role in long time regulation of arterial blood pressure is expressed.

  15. Transit Timing Study of Kepler Planets

    NASA Astrophysics Data System (ADS)

    Xie, Jiwei

    2015-08-01

    Kepler space telescope has found over 4000 transiting planet candidates. Transit timing is a powerful tool to study these transit planet candidates. In this talk, I will talk about two transit timing techniques, i.e., transit timing variation (TTV) and transit duration (TD), which enable confirming their planetary nature and obtaining insight into their orbital properties.

  16. Transit times in turbulent flows.

    PubMed

    Pécseli, H L; Trulsen, J

    2010-04-01

    Statistics of the motion of passively convected point particles in turbulent flows are studied. The database used is obtained by direct numerical solution of the Navier-Stokes equation. We estimate the probability distribution of the transit times of such particles through reference volumes with given forms and sizes. A selected position within the reference volume is moving with the local flow velocity, thus determining the motion of the entire surface. The transit time is defined as the interval between entrance and exit times of surrounding particles convected through the volume by the turbulent motions. Spherical as well as hemispherical surfaces are studied. Scale sizes in the inertial as well as in the viscous subranges of the turbulence are considered. Simple, and seemingly universal, scaling laws are obtained for the probability density of the transit times in terms of the basic properties of the turbulent flow and the geometry. In the present formulation, the results of the analysis are relevant for chemical reactions, but also for understanding details of the feeding rate of micro-organisms in turbulent waters, for instance.

  17. Analyses of some exoplanets' transits and transit timing variations

    NASA Astrophysics Data System (ADS)

    Püsküllü, ćaǧlar; Soydugan, Faruk

    2017-02-01

    We present solutions of the transit light curves and transit timing variations (TTVs) analyses of the exoplanets HAT-P-5b, HAT-P-9b and HAT-P-25b. Transit light curves were collected at Çanakkale Onsekiz Mart University Observatory and TUBITAK National Observatory. The models were produced by WINFITTER program and stellar, planetary and orbital properties were obtained and discussed. We gave new transit times and generated TTVs with them by appending additional data based on Exoplanet Transit Database (ETD). Significant signals at the TTVs were also investigated.

  18. NO TRANSIT TIMING VARIATIONS IN WASP-4

    SciTech Connect

    Petrucci, R.; Schwartz, M.; Buccino, A. P.; Mauas, P. J. D.; Jofré, E.; Cúneo, V.; Gómez, M.; Martínez, C.

    2013-12-20

    We present six new transits of the system WASP-4. Together with 28 light curves published in the literature, we perform a homogeneous study of its parameters and search for variations in the transits' central times. The final values agree with those previously reported, except for a slightly lower inclination. We find no significant long-term variations in i or R{sub P} /R {sub *}. The O-C mid-transit times do not show signs of transit timing variations greater than 54 s.

  19. An advanced protocol-driven transition from parenteral prostanoids to inhaled trepostinil in pulmonary arterial hypertension

    PubMed Central

    Agarwal, Manyoo; Rischard, Franz; De Marco, Teresa

    2016-01-01

    Abstract Patients with pulmonary arterial hypertension (PAH) often require parenteral prostanoids to improve symptoms and signs of PAH. Complications of parenteral prostanoids—such as catheter-related infections and intolerable adverse effects—may develop, prompting transition to inhaled prostanoids. We report a prospective, protocol-driven transition from parenteral prostanoids to inhaled prostanoids with monitoring of exercise gas exchange and acute hemodynamics. Three PAH centers recruited patients transitioning from parenteral prostanoids to inhaled trepostinil. Rigid inclusion criteria were used, including parenteral prostanoid dose < 30 ng/kg/min, New York Heart Association functional class (FC) < 3, and pulmonary vascular resistance (PVR) < 6 Wood units. Of the 9 patients meeting initial inclusion criteria, 3 were excluded. In the remaining patients, the parenteral prostanoid was reduced and the inhaled prostanoid was increased over 24–36 hours with continuous hemodynamic monitoring. Exercise capacity and FC were measured at baseline and weeks 1, 4, and 12. All patients were successfully weaned from parenteral prostanoids. An acute PVR decrease was seen with most inhaled prostanoid doses, but PVR varied throughout the transition. Patients tolerated inhaled prostanoids for 9–12 breaths 4 times a day with no treatment-limiting adverse events. At week 12, FC was unchanged, and all patients continued to receive inhaled prostanoids without serious adverse events or additional PAH therapy. In 5 of 6 patients, 6-minute walk distance and peak V˙O2 were within 10% of baseline. Using a strict transition protocol and rigid patient selection criteria, the parenteral prostanoid to inhaled prostanoid transition appeared safe and well tolerated and did not result in clinical deterioration over 12 weeks. Hemodynamic variability noted acutely during transition in our study did not adversely affect successful transition. (Trial registration: Clinical

  20. Rapid Transition from Inhaled Iloprost to Inhaled Treprostinil in Patients with Pulmonary Arterial Hypertension

    PubMed Central

    Bourge, Robert C; Tapson, Victor F; Safdar, Zeenat; Benza, Raymond L; Channick, Richard N; Rosenzweig, Erika B; Shapiro, Shelley; White, Richard James; McSwain, Christopher Shane; Gotzkowsky, Stephen Karl; Nelsen, Andrew C; Rubin, Lewis J

    2013-01-01

    Background Inhaled treprostinil is a prostacyclin analog approved for the treatment of pulmonary arterial hypertension (PAH) that may provide a more convenient treatment option for patients receiving inhaled iloprost while maintaining the clinical benefit of inhaled prostacyclin therapy. Aims In this open-label safety study, 73 PAH patients were enrolled with primarily World Health Organization Class II (56%) or III (42%) symptoms. At baseline, most patients (93%) were receiving 5 μg of iloprost per dose but 38% of patients reported a dosing frequency below the labeled rate of 6–9 times daily. Patients initiated inhaled treprostinil at 3 breaths four times daily (qid) at the immediate next scheduled iloprost dose. The primary objective was to assess the safety of rapid transition from iloprost to inhaled treprostinil; clinical status and quality of life were also assessed. Results Most patients (84%) achieved the target treprostinil dose of 9 breaths qid and remained on study until transition to commercial therapy (89%). The most frequent adverse events (AEs) were cough (74%), headache (44%), and nausea (30%), and five patients prematurely discontinued study drug due to AE (n = 3), disease progression (n = 1), or death (n = 1). At week 12, the time spent on daily treatment activities was reduced compared to baseline, with a mean total savings of 1.4 h per day. Improvements were also observed at week 12 for 6-min walk distance (+16.0; P < 0.001), N-terminal pro-B-type natriuretic peptide (−74 pg/mL; P = 0.001), and the Cambridge Pulmonary Hypertension Outcome Review (all domains P < 0.001). Conclusions Pulmonary arterial hypertension patients can be safely transitioned from inhaled iloprost to inhaled treprostinil while maintaining clinical status. PMID:22970909

  1. An Exoplanet Radius and Transit Timing Survey

    NASA Astrophysics Data System (ADS)

    Deming, Drake; Jennings, Jonald; Sada, Pedro

    2010-02-01

    Many exoplanet systems contain Jupiter-mass planets on close-in orbits. Theories of planetary system formation account for these hot Jupiters as being end states of inward migration. Variants of those theories also predict terrestrial planets to be captured in mean motion resonance with the hot Jupiters. A continuing explosion of discoveries by transit surveys have given us a sample of 45 hot Jupiters transiting planets brighter than V=13. A transit timing survey of these systems could detect hot Earths in resonance, via the large (~ 180 second) perturbations they induce on the giant planet transits. Moreover, the discovery photometry for these systems usually provides only relatively coarse photometric precision, but larger-aperture follow-up can determine the giant planet radius to a precision limited only by knowledge of the stellar mass, and thereby reveal the diversity of giant exoplanet structure, such as the presence of heavy element cores. The relatively large sample now available means that a radius- and transit timing-survey is well matched to classical observing and telescope scheduling. We propose continued observations to perform transit photometry using FLAMINGOS on the 2.1-meter in the J-band, where stellar limb darkening is minimal and transit photometry has excellent sensitivity to planetary radii and shifts in transit time.

  2. An Exoplanet Radius and Transit Timing Survey

    NASA Astrophysics Data System (ADS)

    Deming, Drake; Jennings, Jonald; Sada, Pedro

    2009-08-01

    Many exoplanet systems contain Jupiter-mass planets on close-in orbits. Theories of planetary system formation account for these hot Jupiters as being end states of inward migration. Variants of those theories also predict terrestrial planets to be captured in mean motion resonance with the hot Jupiters. A recent explosion of discoveries by transit surveys have given us a sample of 37 hot Jupiters transiting planets brighter than V=13. A transit timing survey of these systems could detect hot Earths in resonance, via the large (~ 180 second) perturbations they induce on the giant planet transits. Moreover, the discovery photometry for these systems usually provides only relatively coarse photometric precision, but larger-aperture follow-up can determine the giant planet radius to a precision limited only by knowledge of the stellar mass, and thereby reveal the diversity of giant exoplanet structure, such as the presence of heavy element cores. The relatively large sample now available means that a radius- and transit timing-survey is well matched to classical observing and telescope scheduling. We propose continued observations to perform transit photometry using FLAMINGOS on the 2.1-meter in the J-band, where stellar limb darkening is minimal and transit photometry has excellent sensitivity to planetary radii and shifts in transit time.

  3. Magnetic transit-time flowmeter

    DOEpatents

    Forster, George A.

    1976-07-06

    The flow rate of a conducting fluid in a stream is determined by disposing two permanent-magnet flowmeters in the stream, one downstream of the other. Flow of the conducting fluid causes the generation of both d-c and a-c electrical signals, the a-c comprising flow noise. Measurement of the time delay between similarities in the a-c signals by cross-correlation methods provides a measure of the rate of flow of the fluid.

  4. Decreasing Transition Times in a Second Grade Classroom: Scientific Support for the Timely Transitions Game

    ERIC Educational Resources Information Center

    Yarrough, Jamie L.; Skinner, Christopher H.; Lee, Young Ju; Lemmons, Cathy

    2004-01-01

    Campbell and Skinner used an A-B design to evaluate the effects of the Timely Transitions Game (TTG) on room-to-room transitions in a sixth-grade classroom. The TTG incorporated explicit timing, publicly posted feedback, and an interdependent group contingency with randomly selected transitions and criteria. The purpose of the current study was to…

  5. Late-time cosmological phase transitions

    NASA Technical Reports Server (NTRS)

    Schramm, David N.

    1991-01-01

    It is shown that the potential galaxy formation and large scale structure problems of objects existing at high redshifts (Z approx. greater than 5), structures existing on scales of 100 M pc as well as velocity flows on such scales, and minimal microwave anisotropies ((Delta)T/T) (approx. less than 10(exp -5)) can be solved if the seeds needed to generate structure form in a vacuum phase transition after decoupling. It is argued that the basic physics of such a phase transition is no more exotic than that utilized in the more traditional GUT scale phase transitions, and that, just as in the GUT case, significant random Gaussian fluctuations and/or topological defects can form. Scale lengths of approx. 100 M pc for large scale structure as well as approx. 1 M pc for galaxy formation occur naturally. Possible support for new physics that might be associated with such a late-time transition comes from the preliminary results of the SAGE solar neutrino experiment, implying neutrino flavor mixing with values similar to those required for a late-time transition. It is also noted that a see-saw model for the neutrino masses might also imply a tau neutrino mass that is an ideal hot dark matter candidate. However, in general either hot or cold dark matter can be consistent with a late-time transition.

  6. Late-time cosmological phase transitions

    SciTech Connect

    Schramm, D.N. Fermi National Accelerator Lab., Batavia, IL )

    1990-11-01

    It is shown that the potential galaxy formation and large-scale structure problems of objects existing at high redshifts (Z {approx gt} 5), structures existing on scales of 100M pc as well as velocity flows on such scales, and minimal microwave anisotropies ({Delta}T/T) {approx lt} 10{sup {minus}5} can be solved if the seeds needed to generate structure form in a vacuum phase transition after decoupling. It is argued that the basic physics of such a phase transition is no more exotic than that utilized in the more traditional GUT scale phase transitions, and that, just as in the GUT case, significant random gaussian fluctuations and/or topological defects can form. Scale lengths of {approximately}100M pc for large-scale structure as well as {approximately}1 M pc for galaxy formation occur naturally. Possible support for new physics that might be associated with such a late-time transition comes from the preliminary results of the SAGE solar neutrino experiment, implying neutrino flavor mixing with values similar to those required for a late-time transition. It is also noted that a see-saw model for the neutrino masses might also imply a tau neutrino mass that is an ideal hot dark matter candidate. However, in general either hot or cold dark matter can be consistent with a late-time transition. 47 refs., 2 figs.

  7. Umbilical arterial S-nitrosothiols in stressed newborns: role in perinatal circulatory transition.

    PubMed

    Gaston, B; Fry, E; Sears, S; Heroman, W M; Ignarro, L; Stamler, J S

    1998-12-30

    S-Nitrosothiols are potent endogenous vasodilators recently found to be in greater concentrations in fetal umbilical venous than arterial blood. We hypothesized that neonatal increases in SNOs may be involved in the normal human perinatal circulatory transition. Paired human umbilical artery and vein plasma samples were collected after birth. S-Nitrosothiol concentrations were measured as NO after photolysis--and NO3- after reduction in vanadium chloride--by chemiluminescence. Normal umbilical arterial serum SNO levels were nearly twice those of matched venous samples but were low in infants who did not transition normally to neonatal circulation. There was no difference in the concentration of NO3- between the normal and depressed infants. The parallel failure of some fetuses to switch both to a normal arteriovenous SNO relationship and a normal clinical post-partum state suggests that SNOs may be involved in the perinatal circulatory transition.

  8. Numerical analysis of the effect of turbulence transition on the hemodynamic parameters in human coronary arteries

    PubMed Central

    Gawandalkar, Udhav Ulhas; Kini, Girish; Buradi, Abdulrajak; Araki, Tadashi; Ikeda, Nobutaka; Nicolaides, Andrew; Laird, John R.; Saba, Luca; Suri, Jasjit S.

    2016-01-01

    Background Local hemodynamics plays an important role in atherogenesis and the progression of coronary atherosclerosis disease (CAD). The primary biological effect due to blood turbulence is the change in wall shear stress (WSS) on the endothelial cell membrane, while the local oscillatory nature of the blood flow affects the physiological changes in the coronary artery. In coronary arteries, the blood flow Reynolds number ranges from few tens to several hundreds and hence it is generally assumed to be laminar while calculating the WSS calculations. However, the pulsatile blood flow through coronary arteries under stenotic condition could result in transition from laminar to turbulent flow condition. Methods In the present work, the onset of turbulent transition during pulsatile flow through coronary arteries for varying degree of stenosis (i.e., 0%, 30%, 50% and 70%) is quantitatively analyzed by calculating the turbulent parameters distal to the stenosis. Also, the effect of turbulence transition on hemodynamic parameters such as WSS and oscillatory shear index (OSI) for varying degree of stenosis is quantified. The validated transitional shear stress transport (SST) k-ω model used in the present investigation is the best suited Reynolds averaged Navier-Stokes turbulence model to capture the turbulent transition. The arterial wall is assumed to be rigid and the dynamic curvature effect due to myocardial contraction on the blood flow has been neglected. Results Our observations shows that for stenosis 50% and above, the WSSavg, WSSmax and OSI calculated using turbulence model deviates from laminar by more than 10% and the flow disturbances seems to significantly increase only after 70% stenosis. Our model shows reliability and completely validated. Conclusions Blood flow through stenosed coronary arteries seems to be turbulent in nature for area stenosis above 70% and the transition to turbulent flow begins from 50% stenosis. PMID:27280084

  9. Transition Path Time Distribution, Tunneling Times, Friction, and Uncertainty

    NASA Astrophysics Data System (ADS)

    Pollak, Eli

    2017-02-01

    A quantum mechanical transition path time probability distribution is formulated and its properties are studied using a parabolic barrier potential model. The average transit time is well defined and readily calculated. It is smaller than the analogous classical mechanical average transit time, vanishing at the crossover temperature. It provides a direct route for determining tunneling times. The average time may be also used to define a coarse grained momentum of the system for the passage from one side of the barrier to the other. The product of the uncertainty in this coarse grained momentum with the uncertainty in the location of the particle is shown under certain conditions to be smaller than the ℏ/2 formal uncertainty limit. The model is generalized to include friction in the form of a bilinear interaction with a harmonic bath. Using an Ohmic friction model one finds that increasing the friction, increases the transition time. Only moderate values of the reduced friction coefficient are needed for the quantum transition time and coarse grained uncertainty to approach the classical limit which is smaller than ℏ/2 when the friction is not too small. These results show how one obtains classical dynamics from a pure quantum system without invoking any further assumptions, approximations, or postulates.

  10. Pulse transit time differential measurement by fiber Bragg grating pulse recorder.

    PubMed

    Umesh, Sharath; Padma, Srivani; Ambastha, Shikha; Kalegowda, Anand; Asokan, Sundarrajan

    2015-05-01

    The present study reports a noninvasive technique for the measurement of the pulse transit time differential (PTTD) from the pulse pressure waveforms obtained at the carotid artery and radial artery using fiber Bragg grating pulse recorders (FBGPR). PTTD is defined as the time difference between the arrivals of a pulse pressure waveform at the carotid and radial arterial sites. The PTTD is investigated as an indicator of variation in the systolic blood pressure. The results are validated against blood pressure variation obtained from a Mindray Patient Monitor. Furthermore, the pulse wave velocity computed from the obtained PTTD is compared with the pulse wave velocity obtained from the color Doppler ultrasound system and is found to be in good agreement. The major advantage of the PTTD measurement via FBGPRs is that the data acquisition system employed can simultaneously acquire pulse pressure waveforms from both FBGPRs placed at carotid and radial arterial sites with a single time scale, which eliminates time synchronization complexity.

  11. Linking age, survival, and transit time distributions

    NASA Astrophysics Data System (ADS)

    Calabrese, Salvatore; Porporato, Amilcare

    2015-10-01

    Although the concepts of age, survival, and transit time have been widely used in many fields, including population dynamics, chemical engineering, and hydrology, a comprehensive mathematical framework is still missing. Here we discuss several relationships among these quantities by starting from the evolution equation for the joint distribution of age and survival, from which the equations for age and survival time readily follow. It also becomes apparent how the statistical dependence between age and survival is directly related to either the age dependence of the loss function or the survival-time dependence of the input function. The solution of the joint distribution equation also allows us to obtain the relationships between the age at exit (or death) and the survival time at input (or birth), as well as to stress the symmetries of the various distributions under time reversal. The transit time is then obtained as a sum of the age and survival time, and its properties are discussed along with the general relationships between their mean values. The special case of steady state case is analyzed in detail. Some examples, inspired by hydrologic applications, are presented to illustrate the theory with the specific results. This article was corrected on 11 Nov 2015. See the end of the full text for details.

  12. Real-time vascular mechanosensation through ex vivo artery perfusion

    PubMed Central

    2014-01-01

    Background Cell-based perfusion studies have provided great insight into fluid-sensing mechanisms, such as primary cilia in the renal and vascular systems. However, the intrinsic limitations of in vitro cell culture, such as the inability to reflect cellular organization within tissues, has distanced observed paradigms from possible clinical developments. Here we describe a protocol that applies ex vivo artery perfusion and calcium imaging to observe real-time cellular responses to fluid-shear stress. Results Through our ex vivo artery perfusion method, we were able to simulate physiological flow and initiate distinct fluid shear stress mechanosensory responses, as well as induced acetylcholine responses in mouse aortic tissue. The observed calcium profiles confirm results found through previous in vitro cell culture experiments. The overall procedure, including dissection, sample preparation and perfusion, takes around 3 hours to complete. Conclusion Through our unique method, we are able to induce laminar flow within intact mouse aortic tissue and illicit subsequent cellular responses. This method of ex vivo artery perfusion provides the opportunity to bridge the novel findings of in vitro studies with subsequent physiological models of fluid-shear stress mechanosensation in vascular tissues. PMID:24685068

  13. Transit Timing Study with Kepler and its synergy with LAMOST

    NASA Astrophysics Data System (ADS)

    Xie, Jiwei; Dong, Subo; Zhu, Zhaohuan; Luo, A.-Li; Zhou, Ji-Lin

    2015-12-01

    Kepler space telescope has found over 4000 transiting planet candidates. Transit timing is a powerful tool to study these transit planet candidates. The Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST: http://www.lamost.org) provides mass and radius measurements of the stars thus helps with modeling transit timing. Here, we will show two transit timing techniques, i.e., transit timing variation (TTV) and transit duration (TD), which enable confirming their planetary nature and obtaining insight into their orbital properties by combining Kepler and LAMOST.

  14. Stiffness Indices and Fractal Dimension relationship in Arterial Pressure and Diameter Time Series in-Vitro

    NASA Astrophysics Data System (ADS)

    Cymberknop, L.; Legnani, W.; Pessana, F.; Bia, D.; Zócalo, Y.; Armentano, R. L.

    2011-12-01

    The advent of vascular diseases, such as hypertension and atherosclerosis, is associated to significant alterations in the physical properties of arterial vessels. Evaluation of arterial biomechanical behaviour is related to the assessment of three representative indices: arterial compliance, arterial distensibility and arterial stiffness index. Elasticity is the most important mechanical property of the arterial wall, whose natures is strictly non-linear. Intervention of elastin and collagen fibres, passive constituent elements of the arterial wall, is related to the applied wall stress level. Concerning this, appropriate tools are required to analyse the temporal dynamics of the signals involved, in order to characterize the whole phenomenon. Fractal geometry can be mentioned as one of those techniques. The aim of this study consisted on arterial pressure and diameter signals processing, by means of nonlinear techniques based on fractal geometry. Time series morphology was related to different arterial stiffness states, generated by means of blood flow variations, during experiences performed in vitro.

  15. Transit Timing Variations In Binary Star Systems

    NASA Astrophysics Data System (ADS)

    Sansone, Eric; Haghighipour, N.

    2012-01-01

    We present the results of a study of the effect of a stellar companion on the transit timing variations (TTV) of a planetary system. The purpose of our study is to determine the ranges of the orbital elements of a secondary star for which the amplitude of a currently existing TTV is enhanced. We chose the system of Kepler 9 as this system represents the first planetary system detected by the transit timing variation method, and studied its TTVs by considering a hypothetical secondary star in this system. By varying the mass, semi-major axis, and eccentricity of the fictitious binary companion, we tested the stability of the known planets Kepler-9c and Kepler-9b and identified the region of the parameter-space for which the binary planetary system would be stable. We calculated TTVs for the two planets of the system for different values of the orbital elements of the secondary star and calculated its difference with the system's already existing TTVs. Results of our study indicate that the effect of the binary companion is significant only when the secondary star is in a highly eccentric orbit and/or the planets of the system are within the range of Super-Earth or terrestrial sizes. This work was funded by the National Science Foundation in the form of a Research Experience for Undergraduates program at the University of Hawaii at Manoa.

  16. Arterial spin labelling reveals prolonged arterial arrival time in idiopathic Parkinson's disease

    PubMed Central

    Al-Bachari, Sarah; Parkes, Laura M.; Vidyasagar, Rishma; Hanby, Martha F.; Tharaken, Vivek; Leroi, Iracema; Emsley, Hedley C.A.

    2014-01-01

    Idiopathic Parkinson's disease (IPD) is the second most common neurodegenerative disease, yet effective disease modifying treatments are still lacking. Neurodegeneration involves multiple interacting pathological pathways. The extent to which neurovascular mechanisms are involved is not well defined in IPD. We aimed to determine whether novel magnetic resonance imaging (MRI) techniques, including arterial spin labelling (ASL) quantification of cerebral perfusion, can reveal altered neurovascular status (NVS) in IPD. Fourteen participants with IPD (mean ± SD age 65.1 ± 5.9 years) and 14 age and cardiovascular risk factor matched control participants (mean ± SD age 64.6 ± 4.2 years) underwent a 3T MRI scan protocol. ASL images were collected before, during and after a 6 minute hypercapnic challenge. FLAIR images were used to determine white matter lesion score. Quantitative images of cerebral blood flow (CBF) and arterial arrival time (AAT) were calculated from the ASL data both at rest and during hypercapnia. Cerebrovascular reactivity (CVR) images were calculated, depicting the change in CBF and AAT relative to the change in end-tidal CO2. A significant (p = 0.005) increase in whole brain averaged baseline AAT was observed in IPD participants (mean ± SD age 1532 ± 138 ms) compared to controls (mean ± SD age 1335 ± 165 ms). Voxel-wise analysis revealed this to be widespread across the brain. However, there were no statistically significant differences in white matter lesion score, CBF, or CVR between patients and controls. Regional CBF, but not AAT, in the IPD group was found to correlate positively with Montreal cognitive assessment (MoCA) scores. These findings provide further evidence of alterations in NVS in IPD. PMID:25379411

  17. Bilateral transit time assessment of upper and lower limbs as a surrogate ankle brachial index marker.

    PubMed

    Foo, Jong Yong Abdiel

    2008-01-01

    Ankle brachial index is useful in monitoring the pathogenesis of peripheral arterial occlusive diseases. Sphygmomanometer is the standard instrument widely used but frequent prolonged monitoring can be less comfortable for patients. Pulse transit time is known to be inversely correlated with blood pressure and a ratio-based pulse transit time measurement has been proposed as a surrogate ankle brachial index marker. In this study, 17 normotensive adults (9 men; aged 25.4 +/- 3.9 years) were recruited. Two postural change test activities were performed to induce changes in the stiffness of the arterial wall of the moved periphery. Results showed that only readings from the limbs that adopted a new posture registered significant blood pressure and pulse transit time changes (P < .05). Furthermore, there was significant correlation between the ankle brachial index and pulse transit time ratio measure for both test activities (R(2) > or = 0.704). The findings herein suggest that pulse transit time ratio is a surrogate and accommodating ankle brachial index marker.

  18. Evaluation of blood pressure changes using vascular transit time.

    PubMed

    Foo, Jong Yong Abdiel; Lim, Chu Sing; Wang, Ping

    2006-08-01

    Imbalance of the human haemodynamic system can provide a prognosis of syncope, dizziness or hypertension. This can be assessed by monitoring its responses to postural change. Examining variations in blood pressure (BP) is deemed an effective means to identify symptoms of this associated condition. However, conventional methods do not promote prolonged monitoring due to the discomfort caused to patients. Established correlations between BP and pulse wave transmission have shown its usefulness in clinical applications. In this study, photoplethysmography and phonocardiography were used to estimate BP changes via observed variations in delay transmission or vascular transit time (VTT) at the upper limb. Thirty-one healthy adults (21 male) were recruited to perform three test activities, namely the arm held at heart level, fully raised up and held down. Association of the three BP indices and heart rate variations with transit time changes was then computed. The results showed that observed VTT changes were related to systolic BP (R(2) = 0.820; p < 0.05), diastolic BP (R(2) = 0.517; p < 0.05), mean arterial pressure (R(2) = 0.673; p < 0.05) and heart rate (R(2) = 0.000; p > 0.05). As systolic BP had the strongest correlation, a regression equation was formulated to associate the two parameters. The non-invasive measuring nature of VTT can be more accommodating to patients, especially during continual monitoring. Moreover, it has the added advantage that the pre-ejection period is not included in its time-related derivations.

  19. Time Domain Estimation of Arterial Parameters using the Windkessel Model and the Monte Carlo Method

    NASA Astrophysics Data System (ADS)

    Gostuski, Vladimir; Pastore, Ignacio; Rodriguez Palacios, Gaspar; Vaca Diez, Gustavo; Moscoso-Vasquez, H. Marcela; Risk, Marcelo

    2016-04-01

    Numerous parameter estimation techniques exist for characterizing the arterial system using electrical circuit analogs. However, they are often limited by their requirements and usually high computational burdain. Therefore, a new method for estimating arterial parameters based on Monte Carlo simulation is proposed. A three element Windkessel model was used to represent the arterial system. The approach was to reduce the error between the calculated and physiological aortic pressure by randomly generating arterial parameter values, while keeping constant the arterial resistance. This last value was obtained for each subject using the arterial flow, and was a necessary consideration in order to obtain a unique set of values for the arterial compliance and peripheral resistance. The estimation technique was applied to in vivo data containing steady beats in mongrel dogs, and it reliably estimated Windkessel arterial parameters. Further, this method appears to be computationally efficient for on-line time-domain estimation of these parameters.

  20. TRANSIT TIMING OBSERVATIONS FROM KEPLER. VIII. CATALOG OF TRANSIT TIMING MEASUREMENTS OF THE FIRST TWELVE QUARTERS

    SciTech Connect

    Mazeh, Tsevi; Nachmani, Gil; Holczer, Tomer; Sokol, Gil; Fabrycky, Daniel C.; Ford, Eric B.; Ragozzine, Darin; Sanchis-Ojeda, Roberto; Rowe, Jason F.; Lissauer, Jack J.; Zucker, Shay; Agol, Eric; Carter, Joshua A.; Quintana, Elisa V.; Steffen, Jason H.; Welsh, William

    2013-10-01

    Following the works of Ford et al. and Steffen et al. we derived the transit timing of 1960 Kepler objects of interest (KOIs) using the pre-search data conditioning light curves of the first twelve quarters of the Kepler data. For 721 KOIs with large enough signal-to-noise ratios, we obtained also the duration and depth of each transit. The results are presented as a catalog for the community to use. We derived a few statistics of our results that could be used to indicate significant variations. Including systems found by previous works, we have found 130 KOIs that showed highly significant times of transit variations (TTVs) and 13 that had short-period TTV modulations with small amplitudes. We consider two effects that could cause apparent periodic TTV—the finite sampling of the observations and the interference with the stellar activity, stellar spots in particular. We briefly discuss some statistical aspects of our detected TTVs. We show that the TTV period is correlated with the orbital period of the planet and with the TTV amplitude.

  1. Transit Timing Observations from Kepler. VIII. Catalog of Transit Timing Measurements of the First Twelve Quarters

    NASA Astrophysics Data System (ADS)

    Mazeh, Tsevi; Nachmani, Gil; Holczer, Tomer; Fabrycky, Daniel C.; Ford, Eric B.; Sanchis-Ojeda, Roberto; Sokol, Gil; Rowe, Jason F.; Zucker, Shay; Agol, Eric; Carter, Joshua A.; Lissauer, Jack J.; Quintana, Elisa V.; Ragozzine, Darin; Steffen, Jason H.; Welsh, William

    2013-10-01

    Following the works of Ford et al. and Steffen et al. we derived the transit timing of 1960 Kepler objects of interest (KOIs) using the pre-search data conditioning light curves of the first twelve quarters of the Kepler data. For 721 KOIs with large enough signal-to-noise ratios, we obtained also the duration and depth of each transit. The results are presented as a catalog for the community to use. We derived a few statistics of our results that could be used to indicate significant variations. Including systems found by previous works, we have found 130 KOIs that showed highly significant times of transit variations (TTVs) and 13 that had short-period TTV modulations with small amplitudes. We consider two effects that could cause apparent periodic TTV—the finite sampling of the observations and the interference with the stellar activity, stellar spots in particular. We briefly discuss some statistical aspects of our detected TTVs. We show that the TTV period is correlated with the orbital period of the planet and with the TTV amplitude.

  2. Transition of Stable Pediatric Patients With Pulmonary Arterial Hypertension from Intravenous Epoprostenol to Intravenous Treprostinil

    PubMed Central

    Ivy, D. Dunbar; Claussen, Lori; Doran, Aimee

    2007-01-01

    Intravenous epoprostenol was the first agent approved by the United States Food and Drug Administration for the management of pulmonary arterial hypertension (PAH). However, epoprostenol therapy carries the risks of a short half-life (<6 minutes) and side effects, including jaw pain, flushing, and headache. Recently, intravenous treprostinil has been studied, primarily in adults with PAH, and found to provide effective therapy. The effects of continuous intravenous treprostinil were retrospectively evaluated in 13 children with stable PAH who had been treated with epoprostenol for >1 year. Children were transitioned in the hospital over 24 hours using a rapid or slow strategy. The children were a mean age of 11 years (range 3 to 17) and were transitioned to treprostinil from August 2004 to August 2005. The baseline 6-minute walking distance was on average 516 ± 115 m (n = 9) and did not change after transition. Patients were treated with treprostinil for 1.1 ± 0.5 years. There were 2 deaths, and 2 patients transitioned to other therapy. Seven patients experienced ≥1 central-line infection. Despite a higher dose of treprostinil, the side effects were subjectively diminished. In conclusion, treprostinil provides an alternative therapy in children with PAH, with fewer side effects. However, evaluation regarding rates of infection requires further exploration. PMID:17317374

  3. Transit timing analysis in the HAT-P-32 system

    NASA Astrophysics Data System (ADS)

    Seeliger, M.; Dimitrov, D.; Kjurkchieva, D.; Mallonn, M.; Fernandez, M.; Kitze, M.; Casanova, V.; Maciejewski, G.; Ohlert, J. M.; Schmidt, J. G.; Pannicke, A.; Puchalski, D.; Göğüş, E.; Güver, T.; Bilir, S.; Ak, T.; Hohle, M. M.; Schmidt, T. O. B.; Errmann, R.; Jensen, E.; Cohen, D.; Marschall, L.; Saral, G.; Bernt, I.; Derman, E.; Gałan, C.; Neuhäuser, R.

    2014-06-01

    We present the results of 45 transit observations obtained for the transiting exoplanet HAT-P-32b. The transits have been observed using several telescopes mainly throughout the YETI (Young Exoplanet Transit Initiative) network. In 25 cases, complete transit light curves with a timing precision better than 1.4 min have been obtained. These light curves have been used to refine the system properties, namely inclination i, planet-to-star radius ratio Rp/Rs, and the ratio between the semimajor axis and the stellar radius a/Rs. First analyses by Hartman et al. suggests the existence of a second planet in the system, thus we tried to find an additional body using the transit timing variation (TTV) technique. Taking also the literature data points into account, we can explain all mid-transit times by refining the linear ephemeris by 21 ms. Thus, we can exclude TTV amplitudes of more than ˜1.5 min.

  4. Pulse transit times to the capillary bed evaluated by laser Doppler flowmetry.

    PubMed

    Bernjak, Alan; Stefanovska, Aneta

    2009-03-01

    The pulse transit time (PTT) of a wave over a specified distance along a blood vessel provides a simple non-invasive index that can be used for the evaluation of arterial distensibility. Current methods of measuring the PTT determine the propagation times of pulses only in the larger arteries. We have evaluated the pulse arrival time (PAT) to the capillary bed, through the microcirculation, and have investigated its relationship to the arterial PAT to a fingertip. To do so, we detected cardiac-induced pulse waves in skin microcirculation using laser Doppler flowmetry (LDF). Using the ECG as a reference, PATs to the microcirculation were measured on the four extremities of 108 healthy subjects. Simultaneously, PATs to the radial artery of the left index finger were obtained from blood pressure recordings using a piezoelectric sensor. Both PATs correlate in similar ways with heart rate and age. That to the microcirculation is shown to be sensitive to local changes in skin perfusion induced by cooling. We introduce a measure for the PTT through the microcirculation. We conclude that a combination of LDF and pressure measurements enables simultaneous characterization of the states of the macro and microvasculature. Information about the microcirculation, including an assessment of endothelial function, may be obtained from the responses to perturbations in skin perfusion, such as temperature stress or vasoactive substances.

  5. Mean first-passage time of quantum transition processes

    NASA Astrophysics Data System (ADS)

    Qiu, Rong-Tao; Dai, Wu-Sheng; Xie, Mi

    2012-10-01

    In this paper, we consider the problem of mean first-passage time (MFPT) in quantum mechanics; the MFPT is the average time of the transition from a given initial state, passing through some intermediate states, to a given final state for the first time. We apply the method developed in statistical mechanics for calculating the MFPT of random walks to calculate the MFPT of a transition process. As applications, we (1) calculate the MFPT for multiple-state systems, (2) discuss transition processes occurring in an environmental background, (3) consider a roundabout transition in a hydrogen atom, and (4) apply the approach to laser theory.

  6. Transit light curves with finite integration time: Fisher information analysis

    SciTech Connect

    Price, Ellen M.; Rogers, Leslie A.

    2014-10-10

    Kepler has revolutionized the study of transiting planets with its unprecedented photometric precision on more than 150,000 target stars. Most of the transiting planet candidates detected by Kepler have been observed as long-cadence targets with 30 minute integration times, and the upcoming Transiting Exoplanet Survey Satellite will record full frame images with a similar integration time. Integrations of 30 minutes affect the transit shape, particularly for small planets and in cases of low signal to noise. Using the Fisher information matrix technique, we derive analytic approximations for the variances and covariances on the transit parameters obtained from fitting light curve photometry collected with a finite integration time. We find that binning the light curve can significantly increase the uncertainties and covariances on the inferred parameters when comparing scenarios with constant total signal to noise (constant total integration time in the absence of read noise). Uncertainties on the transit ingress/egress time increase by a factor of 34 for Earth-size planets and 3.4 for Jupiter-size planets around Sun-like stars for integration times of 30 minutes compared to instantaneously sampled light curves. Similarly, uncertainties on the mid-transit time for Earth and Jupiter-size planets increase by factors of 3.9 and 1.4. Uncertainties on the transit depth are largely unaffected by finite integration times. While correlations among the transit depth, ingress duration, and transit duration all increase in magnitude with longer integration times, the mid-transit time remains uncorrelated with the other parameters. We provide code in Python and Mathematica for predicting the variances and covariances at www.its.caltech.edu/∼eprice.

  7. Accuracy of PET rCBF measurements: Effect of transit time delay

    SciTech Connect

    Dhawan, V.; Conti, J.; Mernyk, M.; Jarden, J.; Rottenberg, D.A.

    1984-01-01

    Analytic expressions were derived for estimating the error in PET rCBF measurements associated with the time lag between brain and blood radioactivity (1) following 0-15 water injection and (2) during non-steady-state 0-15 CO/sub 2/ inhalation. This lag time reflects the physiological difference in arrival times of 0-15 activity at brain and radial arterial sampling site as well as the experimentally introduced resistance to flow offered by the arterial catheter/stopcock assembly. Multiple measurements of transit time delay were made in 2 patients using Rb-82. The arrival of radioactivity in the brain was detected by a pair of PET detectors operating in coincidence. The arrival of radioactivity at the radial arterial catheter was estimated from consecutive 5-sec blood samples (catheter flow rate 7-10 ml/min). Transit time delays varied between 1 and 8 sec. For non-steady-state 0-15 CO/sub 2//PET measurements, estimated errors in rCBF ranged from 0.02 to 30% for delays of 2-8 sec and scan lengths of 30-180 sec. In the range 20-100 ml/min/100 g, variations in rCBF only marginally affected these errors. Errors increased with scan length and with longer delays but decreased sharply with scan duration > 60 sec. For 30-180 sec scans, even larger errors are associated with the 0-15 water injection technique (peak blood activity at 10 sec): 1-60% for delays of 2-8 sec. A ''slow'' bolus peaking at 20 sec decreased the error by 40%. For the 0-15 water method it is essential to determine the transit time delay to within 2 sec if accurate flow measurements (error < 5%) are to be obtained from 40-60 sec scans.

  8. Evaluation of transit-time and electromagnetic flow measurement in a chronically instrumented nonhuman primate model

    NASA Technical Reports Server (NTRS)

    Koenig, S. C.; Reister, C. A.; Schaub, J.; Swope, R. D.; Ewert, D.; Fanton, J. W.; Convertino, V. A. (Principal Investigator)

    1996-01-01

    The Physiology Research Branch at Brooks AFB conducts both human and nonhuman primate experiments to determine the effects of microgravity and hypergravity on the cardiovascular system and to identify the particular mechanisms that invoke these responses. Primary investigative efforts in our nonhuman primate model require the determination of total peripheral resistance, systemic arterial compliance, and pressure-volume loop characteristics. These calculations require beat-to-beat measurement of aortic flow. This study evaluated accuracy, linearity, biocompatability, and anatomical features of commercially available electromagnetic (EMF) and transit-time flow measurement techniques. Five rhesus monkeys were instrumented with either EMF (3 subjects) or transit-time (2 subjects) flow sensors encircling the proximal ascending aorta. Cardiac outputs computed from these transducers taken over ranges of 0.5 to 2.0 L/min were compared to values obtained using thermodilution. In vivo experiments demonstrated that the EMF probe produced an average error of 15% (r = .896) and 8.6% average linearity per reading, and the transit-time flow probe produced an average error of 6% (r = .955) and 5.3% average linearity per reading. Postoperative performance and biocompatability of the probes were maintained throughout the study. The transit-time sensors provided the advantages of greater accuracy, smaller size, and lighter weight than the EMF probes. In conclusion, the characteristic features and performance of the transit-time sensors were superior to those of the EMF sensors in this study.

  9. Evaluation of transit-time and electromagnetic flow measurement in a chronically instrumented nonhuman primate model.

    PubMed

    Koenig, S C; Reister, C A; Schaub, J; Swope, R D; Ewert, D; Fanton, J W

    1996-01-01

    The Physiology Research Branch at Brooks AFB conducts both human and nonhuman primate experiments to determine the effects of microgravity and hypergravity on the cardiovascular system and to identify the particular mechanisms that invoke these responses. Primary investigative efforts in our nonhuman primate model require the determination of total peripheral resistance, systemic arterial compliance, and pressure-volume loop characteristics. These calculations require beat-to-beat measurement of aortic flow. This study evaluated accuracy, linearity, biocompatability, and anatomical features of commercially available electromagnetic (EMF) and transit-time flow measurement techniques. Five rhesus monkeys were instrumented with either EMF (3 subjects) or transit-time (2 subjects) flow sensors encircling the proximal ascending aorta. Cardiac outputs computed from these transducers taken over ranges of 0.5 to 2.0 L/min were compared to values obtained using thermodilution. In vivo experiments demonstrated that the EMF probe produced an average error of 15% (r = .896) and 8.6% average linearity per reading, and the transit-time flow probe produced an average error of 6% (r = .955) and 5.3% average linearity per reading. Postoperative performance and biocompatability of the probes were maintained throughout the study. The transit-time sensors provided the advantages of greater accuracy, smaller size, and lighter weight than the EMF probes. In conclusion, the characteristic features and performance of the transit-time sensors were superior to those of the EMF sensors in this study.

  10. WASP-14 b: transit timing analysis of 19 light curves

    NASA Astrophysics Data System (ADS)

    Raetz, St.; Maciejewski, G.; Seeliger, M.; Marka, C.; Fernández, M.; Güver, T.; Göğüş, E.; Nowak, G.; Vaňko, M.; Berndt, A.; Eisenbeiss, T.; Mugrauer, M.; Trepl, L.; Gelszinnis, J.

    2015-08-01

    Although WASP-14 b is one of the most massive and densest exoplanets on a tight and eccentric orbit, it has never been a target of photometric follow-up monitoring or dedicated observing campaigns. We report on new photometric transit observations of WASP-14 b obtained within the framework of Transit Timing Variations @ Young Exoplanet Transit Initiative (TTV@YETI). We collected 19 light curves of 13 individual transit events using six telescopes located in five observatories distributed in Europe and Asia. From light-curve modelling, we determined the planetary, stellar, and geometrical properties of the system and found them in agreement with the values from the discovery paper. A test of the robustness of the transit times revealed that in case of a non-reproducible transit shape the uncertainties may be underestimated even with a wavelet-based error estimation methods. For the timing analysis, we included two publicly available transit times from 2007 and 2009. The long observation period of seven years (2007-2013) allowed us to refine the transit ephemeris. We derived an orbital period 1.2 s longer and 10 times more precise than the one given in the discovery paper. We found no significant periodic signal in the timing-residuals and, hence, no evidence for TTV in the system.

  11. A novel continuous cardiac output monitor based on pulse wave transit time.

    PubMed

    Sugo, Yoshihiro; Ukawa, Teiji; Takeda, Sunao; Ishihara, Hironori; Kazama, Tomiei; Takeda, Junzo

    2010-01-01

    Monitoring cardiac output (CO) is important for the management of patient circulation in an operation room (OR) or intensive care unit (ICU). We assumed that the change in pulse wave transit time (PWTT) obtained from an electrocardiogram (ECG) and a pulse oximeter wave is correlated with the change in stroke volume (SV), from which CO is derived. The present study reports the verification of this hypothesis using a hemodynamic analysis theory and animal study. PWTT consists of a pre-ejection period (PEP), the pulse transit time through an elasticity artery (T(1)), and the pulse transit time through peripheral resistance arteries (T(2)). We assumed a consistent negative correlation between PWTT and SV under all conditions of varying circulatory dynamics. The equation for calculating SV from PWTT was derived based on the following procedures. 1. Approximating SV using a linear equation of PWTT. 2. The slope and y-intercept of the above equation were determined under consideration of vessel compliance (SV was divided by Pulse Pressure (PP)), animal type, and the inherent relationship between PP and PWTT. Animal study was performed to verify the above-mentioned assumption. The correlation coefficient of PWTT and SV became r = -0.710 (p 〈 0.001), and a good correlation was admitted. It has been confirmed that accurate continuous CO and SV measurement is only possible by monitoring regular clinical parameters (ECG, SpO2, and NIBP).

  12. Pharyngeal Pressure and Timing During Bolus Transit.

    PubMed

    Walczak, Chelsea C; Jones, Corinne A; McCulloch, Timothy M

    2017-02-01

    Determining intrabolus pressure (IBP) at the upper esophageal sphincter (UES) and in the esophagus has given compelling evidence that IBP can be a predictor for swallowing dysfunction. Studies have looked most superiorly at the low hypopharynx region but there has been no inquiry into what IBP measures throughout the entire pharynx can tell us. We present a study to describe the pressures within and surrounding the moving bolus throughout the pharynx and into the UES. Simultaneous high-resolution manometry (HRM) and videofluoroscopy were performed in ten healthy subjects swallowing ten 10 mL thin-liquid barium boluses. Three events surrounding bolus movement were tracked via videofluoroscopy, and two additional events were found using manometric measures. As the bolus passes through the pharynx, low pressure is created at and below the head of the bolus. A modest pressure increase is seen as the bolus passes through the pharynx, and finally, high pressure is observed at the bolus tail, followed by an even larger pressure generation of a clearance event. HRM allows for greater resolution in data collection in the pharynx and in this study, aided in identifying semi-unique characteristics around the hypopharynx and the UES which are consistent with the complex anatomy of the regions and the transition of the UES from active closure to relaxed opening. In the future, additional studies designed to look at aged and diseased populations may lead to better understanding of disease etiology, and treatment options.

  13. Who will be active? Predicting exercise stage transitions after hospitalization for coronary artery disease.

    PubMed

    Reid, Robert D; Tulloch, Heather; Kocourek, Jana; Morrin, Louise I; Beaton, Louise J; Papadakis, Sophia; Blanchard, Chris M; Riley, Dana L; Pipe, Andrew L

    2007-01-01

    We describe transitions between exercise stages of change in people with coronary artery disease (CAD) over a 6-month period following a CAD-related hospitalization and evaluate constructs from Protection Motivation Theory, Theory of Planned Behavior, Social Cognitive Theory, the Ecological Model, and participation in cardiac rehabilitation as correlates of stage transition. Seven hundred eighty-two adults hospitalized with CAD were recruited and administered a baseline survey including assessments of theory-based constructs and exercise stage of change. Mailed surveys were used to gather information concerning exercise stage of change and participation in cardiac rehabilitation 6 months later. Progression from pre-action stages between baseline and 6 month follow-up was associated with greater perceived efficacy of exercise to reduce risk of future disease, fewer barriers to exercise, more access to home exercise equipment, and participation in cardiac rehabilitation. Regression from already active stages between baseline and 6 month follow-up was associated with increased perceived susceptibility to a future CAD-related event, fewer intentions to exercise, lower self-efficacy, and more barriers to exercise.

  14. Correcting transit time distributions in coarse MODFLOW-MODPATH models.

    PubMed

    Abrams, Daniel

    2013-01-01

    In low to medium resolution MODFLOW models, the area occupied by sink cells often far exceeds the surface area of the streams they represent. As a result, MODPATH will calculate inaccurate particle traces and transit times. A frequency distribution of transit times for a watershed will also be in error. Such a distribution is used to assess the long-term impact of nonpoint source pollution on surface waters and wells. Although the inaccuracies for individual particles can only be avoided by increased model grid resolution or other advanced modeling techniques, the frequency distribution can be improved by scaling the particle transit times by an adjustment factor during post-processing.

  15. Transition path time distribution and the transition path free energy barrier.

    PubMed

    Pollak, Eli

    2016-10-19

    The recent experimental measurement of the transition path time distributions of proteins presents several challenges to theory. Firstly, why do the fits of the experimental data to a theoretical expression lead to barrier heights which are much lower than the free energies of activation of the observed transitions? Secondly, there is the theoretical question of determining the transition path time distribution, without invoking the Smoluchowski limit. In this paper, we derive an exact expression for a transition path time distribution which is valid for arbitrary memory friction using the normal mode transformation which underlies Kramers' rate theory. We then recall that for low barriers, there is a noticeable difference between the transition path time distribution obtained with absorbing boundary conditions and free boundary conditions. For the former, the transition times are shorter, since recrossings of the boundaries are disallowed. As a result, if one uses the distribution based on absorbing boundary conditions to fit the experimental data, one will find that the transition path barrier will be larger than the values found based on a theory with free boundary conditions. We then introduce the paradigm of a transition path barrier height, and show that one should always expect it to be much smaller than the activation energy.

  16. TRANSIT TIMING OBSERVATIONS FROM KEPLER. V. TRANSIT TIMING VARIATION CANDIDATES IN THE FIRST SIXTEEN MONTHS FROM POLYNOMIAL MODELS

    SciTech Connect

    Ford, Eric B.; Ragozzine, Darin; Holman, Matthew J.; Rowe, Jason F.; Barclay, Thomas; Borucki, William J.; Bryson, Stephen T.; Caldwell, Douglas A.; Kinemuchi, Karen; Koch, David G.; Lissauer, Jack J.; Still, Martin; Tenenbaum, Peter; Steffen, Jason H.; Batalha, Natalie M.; Fabrycky, Daniel C.; and others

    2012-09-10

    Transit timing variations provide a powerful tool for confirming and characterizing transiting planets, as well as detecting non-transiting planets. We report the results of an updated transit timing variation (TTV) analysis for 1481 planet candidates based on transit times measured during the first sixteen months of Kepler observations. We present 39 strong TTV candidates based on long-term trends (2.8% of suitable data sets). We present another 136 weaker TTV candidates (9.8% of suitable data sets) based on the excess scatter of TTV measurements about a linear ephemeris. We anticipate that several of these planet candidates could be confirmed and perhaps characterized with more detailed TTV analyses using publicly available Kepler observations. For many others, Kepler has observed a long-term TTV trend, but an extended Kepler mission will be required to characterize the system via TTVs. We find that the occurrence rate of planet candidates that show TTVs is significantly increased ({approx}68%) for planet candidates transiting stars with multiple transiting planet candidates when compared to planet candidates transiting stars with a single transiting planet candidate.

  17. AMON: Transition to real-time operations

    NASA Astrophysics Data System (ADS)

    Cowen, D. F.; Keivani, A.; Tešić, G.

    2016-04-01

    The Astrophysical Multimessenger Observatory Network (AMON) will link the world's leading high-energy neutrino, cosmic-ray, gamma-ray and gravitational wave observatories by performing real-time coincidence searches for multimessenger sources from observatories' subthreshold data streams. The resulting coincidences will be distributed to interested parties in the form of electronic alerts for real-time follow-up observation. We will present the science case, design elements, current and projected partner observatories, status of the AMON project, and an initial AMON-enabled analysis. The prototype of the AMON server has been online since August 2014 and processing archival data. Currently, we are deploying new high-uptime servers and will be ready to start issuing alerts as early as winter 2015/16.

  18. Pulse wave transit time for monitoring respiration rate.

    PubMed

    Johansson, A; Ahlstrom, C; Lanne, T; Ask, P

    2006-06-01

    In this study, we investigate the beat-to-beat respiratory fluctuations in pulse wave transit time (PTT) and its subcomponents, the cardiac pre-ejection period (PEP) and the vessel transit time (VTT) in ten healthy subjects. The three transit times were found to fluctuate in pace with respiration. When applying a simple breath detecting algorithm, 88% of the breaths seen in a respiration air-flow reference could be detected correctly in PTT. Corresponding numbers for PEP and VTT were 76 and 81%, respectively. The performance during hypo- and hypertension was investigated by invoking blood pressure changes. In these situations, the error rates in breath detection were significantly higher. PTT can be derived from signals already present in most standard monitoring set-ups. The transit time technology thus has prospects to become an interesting alternative for respiration rate monitoring.

  19. Developments in Planet Detection using Transit Timing Variations

    SciTech Connect

    Steffen, Jason H.; Agol, Eric; /Washington U., Seattle, Astron. Dept.

    2006-12-01

    In a transiting planetary system, the presence of a second planet will cause the time interval between transits to vary. These transit timing variations (TTV) are particularly large near mean-motion resonances and can be used to infer the orbital elements of planets with masses that are too small to detect by any other means. The author presents the results of a study of simulated data where they show the potential that this planet detection technique has to detect and characterize secondary planets in transiting systems. These results have important ramifications for planetary transit searches since each transiting system presents an opportunity for additional discoveries through a TTV analysis. They present such an analysis for 13 transits of the HD 209458 system that were observed with the Hubble Space Telescope. This analysis indicates that a putative companion in a low-order, mean-motion resonance can be no larger than the mass of the Earth and constitutes, to date, the most sensitive probe for extrasolar planets that orbit main sequence stars. The presence or absence of small planets in low-order, mean-motion resonances has implications for theories of the formation and evolution of planetary systems. Since TTV is most sensitive in these regimes, it should prove a valuable tool not only for the detection of additional planets in transiting systems, but also as a way to determine the dominant mechanisms of planet formation and the evolution of planetary systems.

  20. Domain wall formation in late-time phase transitions

    NASA Technical Reports Server (NTRS)

    Kolb, Edward W.; Wang, Yun

    1992-01-01

    We examine domain wall formulation in late time phase transitions. We find that in the invisible axion domain wall phenomenon, thermal effects alone are insufficient to drive different parts of the disconnected vacuum manifold. This suggests that domain walls do not form unless either there is some supplemental (but perhaps not unreasonable) dynamics to localize the scalar field responsible for the phase transition to the low temperature maximum (to an extraordinary precision) before the onset of the phase transition, or there is some non-thermal mechanism to produce large fluctuations in the scalar field. The fact that domain wall production is not a robust prediction of late time transitions may suggest future directions in model building.

  1. Oral transit time: a critical review of the literature

    PubMed Central

    SOARES, Thais Jacóe; MORAES, Danielle Pedroni; de MEDEIROS, Gisele Chagas; SASSI, Fernanda Chiarion; ZILBERSTEIN, Bruno; de ANDRADE, Claudia Regina Furquim

    2015-01-01

    Introduction Oral transit time is one of the parameters observed during the clinical assessment of the swallowing function. The importance of this parameter is due to its impact on the total duration of a meal, whose consequence can be an unfavorable nutritional prognostic. Objective To document scientific papers that measure oral transit time in healthy subjects. Method The review followed the steps proposed by the Cochrane Handbook. The search was done via the PubMed database through the use of descriptors related to the oral phase of swallowing, as well as to types of food consistency. Results The articles on the theme had different definitions for oral transit time, as well as heterogeneity of tested volumes, age and gender of the participants. The times found varied from 0.35 s to 1.54 s for liquids, from 0.39 s to 1.05 s for pasty foods and from 1 s to 12.8 s for solid foods. Also, regardless of volume or consistency, oral transit time in elderly people is significantly longer than in adults. Conclusion There's no consensus in the literature about oral transit time in healthy subjects. However, this parameter should be valued during the assessment of the swallowing function due to its negative impact on the dynamics of swallowing, which can cause high energy expenditure during feeding. PMID:26176255

  2. TTVFaster: First order eccentricity transit timing variations (TTVs)

    NASA Astrophysics Data System (ADS)

    Agol, Eric; Deck, Katherine

    2016-04-01

    TTVFaster implements analytic formulae for transit time variations (TTVs) that are accurate to first order in the planet-star mass ratios and in the orbital eccentricities; the implementations are available in several languages, including IDL, Julia, Python and C. These formulae compare well with more computationally expensive N-body integrations in the low-eccentricity, low mass-ratio regime when applied to simulated and to actual multi-transiting Kepler planet systems.

  3. Nonadiabatic transitions in finite-time adiabatic rapid passage

    NASA Astrophysics Data System (ADS)

    Lu, T.; Miao, X.; Metcalf, H.

    2007-06-01

    To apply the adiabatic rapid passage process repetitively [T. Lu, X. Miao, and H. Metcalf, Phys. Rev. A 71, 061405(R) (2005)], the nonadiabatic transition probability of a two-level atom subject to chirped light pulses over a finite period of time needs to be calculated. Using a unitary first-order perturbation method in the rotating adiabatic frame, an approximate formula has been derived for such transition probabilities in the entire parameter space of the pulses.

  4. A multicenter, retrospective study of patients with pulmonary arterial hypertension transitioned from parenteral prostacyclin therapy to inhaled iloprost

    PubMed Central

    Channick, Richard N.; Frantz, Robert P.; Kawut, Steven M.; Palevsky, Harold; Tumuluri, Ramagopal; Sulica, Roxana; Lauto, Paula O.; Benton, Wade W.; de Boisblanc, Bennett

    2013-01-01

    Pulmonary arterial hypertension (PAH) is characterized by progressive increases in pulmonary vascular resistance, leading to right heart failure and death. Guidelines recommend customization of treatment, necessitating the development of effective strategies for transitioning patients among treatments. In this study, we characterized our experience with patient transitions from parenteral prostacyclin to inhaled iloprost. We retrospectively assessed records from 11 centers of 37 consecutive patients with PAH aged ≥ 18 years who were treated with intravenous (IV) or subcutaneous (SC) prostacyclin analogues and transitioned to inhaled iloprost. The transition period began on the first day of inhaled iloprost with the intent of discontinuing parenteral prostacyclin and ended on the first day on inhaled iloprost free of parenteral prostacyclin. Persistence was defined as the absence of (1) parenteral prostacyclin while remaining on inhaled iloprost during post-transition Days 1-90 and (2) no reinitiation of parenteral prostacyclin during post-transition Days 90-365. All patients were clinically stable before transitioning to inhaled iloprost. The mean age was 46.5 years, 70.3% were female, 51.4% had idiopathic PAH, and 43.0% were in New York Heart Association Functional Class III. Among patients with an overlapping transition, the mean transition period was 10.5 days. A transition dosing algorithm was used in 10 patients (27.0%). At one year, 78.4% of the patients remained persistent on inhaled iloprost and 81.1% were free of clinical worsening. In selected patients on background oral PAH therapy, transitioning from parenteral prostacyclin to inhaled iloprost appears safe and feasible and is associated with long-term success. Further study is needed to define the optimal patient selection criteria and transition algorithm. PMID:24015339

  5. Transit time and charge storage measurements in heavily doped emitters

    NASA Technical Reports Server (NTRS)

    Neugroschel, A.; Park, J. S.; Hwang, B. Y.

    1986-01-01

    A first direct measurement of the minority-carrier transit time in a transparent heavily doped emitter layer is reported. The value was obtained by a high-frequency conductance method recently developed and used for low-doped Si. The transit time coupled with the steady-state current enables the determination of the quasi-static charge stored in the emitter and the quasi-static emitter capacitance. Using a transport model, from the measured transit time, the value for the minority-carrier diffusion coefficient and mobility is estimated. The measurements were done using a heavily doped emitter of the Si p(+)-n-p bipolar transistor. The new result indicates that the position-averaged minority-carrier diffusion coefficients may be much smaller than the corresponding majority-carrier values for emitters having a concentration ranging from about 3 x 10 to the 19th per cu cm to 10 to the 20th per cu cm.

  6. Noise-induced transition in human reaction times

    NASA Astrophysics Data System (ADS)

    Medina, José M.; Díaz, José A.

    2016-09-01

    The human reaction/response time can be defined as the time elapsed from the onset of stimulus presentation until a response occurs in many sensory and cognitive processes. A reaction time model based on Piéron’s law is investigated. The model shows a noise-induced transition in the moments of reaction time distributions due to the presence of strong additive noise. The model also demonstrates that reaction times do not follow fluctuation scaling between the mean and the variance but follow a generalized version between the skewness and the kurtosis. The results indicate that noise-induced transitions in the moments govern fluctuations in sensory-motor transformations and open an insight into the macroscopic effects of noise in human perception and action. The conditions that lead to extreme reaction times are discussed based on the transfer of information in neurons.

  7. Reliable estimation of capillary transit time distributions using DSC-MRI

    PubMed Central

    Mouridsen, Kim; Hansen, Mikkel Bo; Østergaard, Leif; Jespersen, Sune Nørhøj

    2014-01-01

    The regional availability of oxygen in brain tissue is traditionally inferred from the magnitude of cerebral blood flow (CBF) and the concentration of oxygen in arterial blood. Measurements of CBF are therefore widely used in the localization of neuronal response to stimulation and in the evaluation of patients suspected of acute ischemic stroke or flow-limiting carotid stenosis. It was recently demonstrated that capillary transit time heterogeneity (CTH) limits maximum oxygen extraction fraction (OEFmax) that can be achieved for a given CBF. Here we present a statistical approach for determining CTH, mean transit time (MTT), and CBF using dynamic susceptibility contrast magnetic resonance imaging (DSC-MRI). Using numerical simulations, we demonstrate that CTH, MTT, and OEFmax can be estimated with low bias and variance across a wide range of microvascular flow patterns, even at modest signal-to-noise ratios. Mean transit time estimated by singular value decomposition (SVD) deconvolution, however, is confounded by CTH. The proposed technique readily identifies malperfused tissue in acute stroke patients and appears to highlight information not detected by the standard SVD technique. We speculate that this technique permits the non-invasive detection of tissue with impaired oxygen delivery in neurologic disorders such as acute ischemic stroke and Alzheimer's disease during routine diagnostic imaging. PMID:24938401

  8. Transit Timing Variations for Eccentric and Inclined Exoplanets

    NASA Astrophysics Data System (ADS)

    Nesvorný, David

    2009-08-01

    The Transit Timing Variation (TTV) method relies on monitoring changes in timing of transits of known exoplanets. Nontransiting planets in the system can be inferred from TTVs by their gravitational interactions with the transiting planet. The TTV method is sensitive to low-mass planets that cannot be detected by other means. Inferring the orbital elements and mass of the nontransiting planets from TTVs, however, is more challenging than for other planet detection schemes. It is a difficult inverse problem. Here, we extended the new inversion method proposed by Nesvorný & Morbidelli to eccentric transiting planets and inclined orbits. We found that the TTV signal can be significantly amplified for hierarchical planetary systems with substantial orbital inclinations and/or for an eccentric transiting planet with anti-aligned orbit of the planetary companion. Thus, a fortuitous orbital setup of an exoplanetary system may significantly enhance our chances of TTV detection. We also showed that the detailed shape of the TTV signal is sensitive to the orbital inclination of the nontransiting planetary companion. The TTV detection method may thus provide important constraints on the orbital inclination of exoplanets and be used to test theories of planetary formation and evolution.

  9. TRANSIT TIMING VARIATIONS FOR ECCENTRIC AND INCLINED EXOPLANETS

    SciTech Connect

    Nesvorny, David

    2009-08-20

    The Transit Timing Variation (TTV) method relies on monitoring changes in timing of transits of known exoplanets. Nontransiting planets in the system can be inferred from TTVs by their gravitational interactions with the transiting planet. The TTV method is sensitive to low-mass planets that cannot be detected by other means. Inferring the orbital elements and mass of the nontransiting planets from TTVs, however, is more challenging than for other planet detection schemes. It is a difficult inverse problem. Here, we extended the new inversion method proposed by Nesvorny and Morbidelli to eccentric transiting planets and inclined orbits. We found that the TTV signal can be significantly amplified for hierarchical planetary systems with substantial orbital inclinations and/or for an eccentric transiting planet with anti-aligned orbit of the planetary companion. Thus, a fortuitous orbital setup of an exoplanetary system may significantly enhance our chances of TTV detection. We also showed that the detailed shape of the TTV signal is sensitive to the orbital inclination of the nontransiting planetary companion. The TTV detection method may thus provide important constraints on the orbital inclination of exoplanets and be used to test theories of planetary formation and evolution.

  10. Transit timing velocimetry /TTV/ for two-phase reacting flows

    SciTech Connect

    Holve, D.J.

    1982-10-01

    A simple single-beam transit timing velocimetry (TTV) method has been developed for determining particle size and mean speed measurements. The method uses a single-beam light scattering system with the addition of two commercial nuclear instrumentation modules to obtain timing information from the trailing edge of the scattering pulses. Results of test studies show that the modal value of transit time remained constant over a wide range of particle sizes, even for particles approaching 50% of the total beam width. Applications of the TTV method to combustion systems include studies of liquid-fuel laminar flames, where integrated reaction times, and thus local droplet velocities, are needed in addition to particle size information.

  11. External beam irradiation in angioplasted arteries of hypercholesterolemic rabbits The dose and time effect

    SciTech Connect

    Kalef-Ezra, J.; Michalis, L.K.; Malamou-Mitsi, V.; Tsekeris, P.; Katsouras, C.; Boziari, A.; Toumpoulis, I.; Bozios, G.; Charchanti, A.; Sideris, D.A

    2002-03-01

    Purpose: To study the dose and time effect of external beam irradiation on the morphometry of both angioplasted and nonangioplasted arteries in a hypercholesterolemic rabbit model. Methods and materials: Eight groups of rabbit femoral arteries were studied: arteries (a) with no intervention, (b) irradiated with a 12-Gy 6 MV X-ray dose, (c) with a 18-Gy, (d) treated with balloon angioplasty, (e) dosed with 12-Gy half an hour post-angioplasty, (f) dosed with 18-Gy half an hour post-angioplasty, (g) dosed with 12-Gy 48 h post angioplasty, (g) dosed with 18-Gy 48 h post angioplasty. Results: External irradiation at either 12 or 18 Gy was not found to change vessel morphometry in noninjured arteries. The 12-Gy dose given soon after angioplasty further increased percentage stenosis (63% on the average), despite the preservation of the lumen cross-sectional area. Positive remodeling was not observed in arteries given 18-Gy half an hour post angioplasty to counterbalance the increased neointimal formation. Therefore, this treatment resulted in a drastic reduction in lumen area and in enhancement of percentage stenosis (84% on the average). On the contrary, the delayed irradiation of the angioplasted arteries at either 12 or 18 Gy was not found to influence any of the studied morphometric parameters 5 weeks after angioplasty. Conclusions: Uniform external beam irradiation up to 18 Gy was well tolerated by intact femoral arteries. Prompt 12- or 18-Gy irradiations accentuated percentage stenosis. However the lumen cross-sectional area was preserved only at the lower dose point. Delayed irradiation at any dose did not influence the restenosis process.

  12. Radial electron-beam-breakup transit-time oscillator

    SciTech Connect

    Mostrom, M.A.; Kwan, T.J.T.

    1995-01-01

    A new radially-driven electron-beam-breakup transit-time oscillator has been investigated analytically and through computer simulation as a compact low-impedance high-power microwave generator. In a 1MV, 50kA device 35cm in radius and 15cm long, with no external magnetic field, 5GW of extracted power and a growth rate of 0.26/ns have been observed. Theoretical maximum efficiencies are several times higher.

  13. Transit timing at Toruń Center for Astronomy

    NASA Astrophysics Data System (ADS)

    Bykowski, W.; Maciejewski, G.

    2011-01-01

    The transit monitoring is one of well-known methods for discovering and observing new extrasolar planets. Among various advantages, this way of searching other worlds does not require complex and expensive equipment -- it can be performed with a relatively small telescope and high-quality CCD camera. At the Center for Astronomy of Nicolaus Copernicus University in Toruń, Poland, we collect observational data using the 60-cm Cassegrain telescope hoping that it would be possible to discover new objects in already known planetary systems using the transit timing variation method. Our observations are a part of a bigger cooperation between observatories from many countries.

  14. Brief communications: visualization of coronary arteries in rats by 3-dimensional real-time contrast echocardiography.

    PubMed

    Ishikura, Fuminobu; Hirayama, Hideo; Iwata, Akiko; Toshida, Tsutomu; Masuda, Kasumi; Otani, Kentaro; Asanuma, Toshihiko; Beppu, Shintaro

    2008-05-01

    Angiogenesis is under intense investigation to advance the treatment of various ischemic diseases. Small animals, such as mice and rats, are often used for this purpose. However, evaluating the structure of coronary arteries in small animals in situ is not easy. We succeeded in visualizing the coronary artery in rats on 3-dimensional real-time contrast echocardiography using a high-frequency transducer. These methods will be applied for more convenient assessment in a new study, examining issues such as angiogenesis using rats in situ.

  15. Time delay between cardiac and brain activity during sleep transitions

    NASA Astrophysics Data System (ADS)

    Long, Xi; Arends, Johan B.; Aarts, Ronald M.; Haakma, Reinder; Fonseca, Pedro; Rolink, Jérôme

    2015-04-01

    Human sleep consists of wake, rapid-eye-movement (REM) sleep, and non-REM (NREM) sleep that includes light and deep sleep stages. This work investigated the time delay between changes of cardiac and brain activity for sleep transitions. Here, the brain activity was quantified by electroencephalographic (EEG) mean frequency and the cardiac parameters included heart rate, standard deviation of heartbeat intervals, and their low- and high-frequency spectral powers. Using a cross-correlation analysis, we found that the cardiac variations during wake-sleep and NREM sleep transitions preceded the EEG changes by 1-3 min but this was not the case for REM sleep transitions. These important findings can be further used to predict the onset and ending of some sleep stages in an early manner.

  16. Psychiatric and Familial Predictors of Transition Times Between Smoking Stages

    PubMed Central

    Sartor, Carolyn E.; Xian, Hong; Scherrer, Jeffrey F.; Lynskey, Michael T.; Duncan, Alexis E.; Haber, J. Randolph; Grant, Julia D.; Bucholz, Kathleen K.; Jacob, Theodore

    2008-01-01

    The modifying effects of psychiatric and familial risk factors on age at smoking initiation, rate of progression from first cigarette to regular smoking, and transition time from regular smoking to nicotine dependence (ND) were examined in 1,269 offspring of male twins from the Vietnam Era Twin Registry. Mean age of the sample was 20.1 years. Cox proportional hazard regression analyses adjusting for paternal alcohol dependence and ND status and maternal ND were conducted. Both early age at first cigarette and rapid transition from initiation to regular smoking were associated with externalizing disorders, alcohol consumption, and cannabis use. Rapid escalation from regular smoking to ND was also predicted by externalizing disorders, but in contrast to earlier transitions, revealed a strong association with internalizing disorders and no significant relationship with use of other substances. Findings characterize a rarely examined aspect of the course of ND development and highlight critical distinctions in risk profiles across stages of tobacco involvement. PMID:17900819

  17. Visual Analysis and Comparison of Kepler Transit Timing Variations with Mutli-Transiting System Applications

    NASA Astrophysics Data System (ADS)

    Kane, Mackenzie; Ragozzine, Darin; Flowers, Xzavier

    2016-10-01

    By noticing the dimming and brightening of the star as an exoplanet transit occurs, NASA's Kepler Space Telescope records the times when the exoplanet passes in front of its star. If other planets are gravitationally influencing the transiting planet, the planet might transit late or early; these deviations from a perfectly periodic set of transits are called transit timing variations (TTVs). Therefore, Kepler TTVs have been very useful in determining exoplanet masses which can be hard to measure in other ways.We visually analyzed the TTV data of all ~6000 Kepler objects of interest (KOIs) to determine whether interesting TTV signals would be missed by purely statistical analyses. Using data from Rowe et al. 2014 and Holczer et al. 2016, we examined TTV plots, periodograms, and folded quadratic+sinusoid fits. To find the most likely KOIs containing visible TTVs and to organize the over 6000 KOIs analyzed, a rating system was developed based on numerous visual factors. By sorting KOIs as such, we were able to compare our findings of the strongest candidates with the same KOIs statistically analyzed by Holczer et al. 2016. It was found that the majority of our findings matched those of Holczer et al. 2016, with only small discrepancies that were understandable based on our different methodologies. Still, our visual inspection of the full list of KOIs contributed multiple planets that were not identified statistically.We combined all of these results with planet properties from the NASA Exoplanet Archive, confirmed and cumulative, to investigate the demographics of planetary systems with and without TTVs. We investigated multi-transiting systems with TTVs not attributable to any of the known planets in the system to better understand exoplanetary system architectures in cases where not all of the planets are transiting.

  18. Visual Analysis and Comparison of Kepler Transit Timing Variations

    NASA Astrophysics Data System (ADS)

    Kane, Mackenzie; Ragozzine, Darin; Holczer, Tomer; Mazeh, Tsevi; Rowe, Jason

    2016-01-01

    NASA's Kepler Space Telescope is designed to find extrasolar planets by watching a section of the sky and observing if an object transits in front its parent star. By noticing the dimming and brightening of the star as a prospective transit occurs, Kepler records the times when the planet moves in front of its star. If other planets are gravitationally influencing the transiting planet, the planet might transit late or early; these deviations from a perfectly periodic set of transits are called "transit timing variations (TTVs). Therefore, Kepler TTVs are useful in determining exoplanet masses which are hard to measure in other ways.We decided to visually analyze the TTV data of all ~6000 Kepler objects of interest (KOIs) to determine whether interesting TTV signals would be missed by purely statistical analyses. Using data from Rowe et al. 2014 and Holczer et al. 2015, submitted, we created combined TTV plots, periodigrams, and folded quadratic+sinusoid fits. The raw TTV data and ancillary plots were visually inspected for each of the ~6000 KOIs. To find the most likely KOIs containing visible TTVs and to organize the over 6000 KOIs analyzed, a rating system was developed based on numerous visual factors. These rating factors include the amount of outliers, if there is a clear sinusoidal period within the folded plots, and if there is a clear peak in the periodigram. By sorting KOIs as such, we were able to compare our findings of the strongest candidates with the same KOIs statistically analyzed by Holczer et al. 2015 (submitted, see also Mazeh et al. 2013).It was found that the majority of our findings matched those of Holczer et al. 2015, with only small discrepancies that were understandable based on our different methodologies. Our visual inspection of the full list of KOIs contributed multiple systems that were not included in the initial list of KOIs with significant TTVs identified statistically.

  19. Electron transit time measurements of 5-in photomultiplier tubes

    NASA Astrophysics Data System (ADS)

    Richards, T.; Peatross, J.; Ware, M.; Rees, L.

    2016-08-01

    We investigated the uniformity of electron transit times for two 5-in photomultiplier tubes: the Hamamatsu R1250 and the Adit B133D01S. We focused a highly attenuated short-pulse laser on the tubes while they were mounted on a programmable stage. The stage translated the tubes relative to the incident beam so that measurements could be made with light focused at points along a grid covering the entire photocathodes. A portion of the incident light was split from the incident beam and measured and recorded by a fast photodiode. Electron transit times were measured by computing the time delay between the recorded photodiode signal and photomultiplier signal using software constant-fraction discrimination. The Hamamatsu tube exhibited a uniform timing response that varied by no more than 1.7 ns. The Adit tube was much less uniform, with transit times that varied by as much as 57 ns. The Adit response also exhibited a spatially varying double-peak structure in its response. The technique described in this paper could be usefully employed by photomultiplier tube manufacturers to characterize the performance of their products.

  20. New contributions to transit-time damping in multidimensional systems

    NASA Technical Reports Server (NTRS)

    Robinson, P. A.

    1989-01-01

    The existence of two previously unrecognized contributions to transit-time damping in systems of more than one dimension is demonstrated and discussed. It is shown that these contributions cannot be treated by one-dimensional analyses unless it is assumed that the gradient of the field perpendicular to itself always vanishes. Such an assumption is unjustified in general and the new contributions can dominate damping by fast particles in more general situations. Analytic expressions obtained using a Born approximation are found to be in excellent agreement with numerical test-particle calculations of transit-time damping for a variety of field configurations. These configurations include those of a resonance layer and of a spherical wave packet, which approximates a collapsing wave packet in a strongly turbulent plasma. It is found that the fractional power absorption can be strongly enhanced in non-slablike field configurations.

  1. Coupling of transit time instabilities in electrostatic confinement fusion devices

    SciTech Connect

    Gruenwald, J. Fröhlich, M.

    2015-07-15

    A model of the behavior of transit time instabilities in an electrostatic confinement fusion reactor is presented in this letter. It is demonstrated that different modes are excited within the spherical cathode of a Farnsworth fusor. Each of these modes is dependent on the fusion products as well as the acceleration voltage applied between the two electrodes and they couple to a resulting oscillation showing non-linear beat phenomena. This type of instability is similar to the transit time instability of electrons between two resonant surfaces but the presence of ions and the occurring fusion reactions alter the physics of this instability considerably. The physics of this plasma instability is examined in detail for typical physical parameter ranges of electrostatic confinement fusion devices.

  2. The time of a photoinduced spin-Peierls phase transition

    SciTech Connect

    Semenov, A. L.

    2015-02-15

    The time τ of the spin-Peierls phase transition is analyzed theoretically as a function of the duration τ{sub p} of the exciting light pulse and the average number x{sub 0} of absorbed photons per magnetic ion after the transmission of the pulse. It is shown that the phase transition occurs at x{sub 0} > x{sub c}. The critical value x{sub c} is determined as a function of the duration τ{sub p} of the light pulse. A photoinduced variation in the optical reflection coefficient R is calculated as a function of time t. The results of calculation are compared with experimental data on ultrafast photoinduced melting of the low-temperature spin-Peierls phase into potassium tetracyanoquinodimethan (K-TCNQ)

  3. Studying time-like baryonic transitions with HADES

    NASA Astrophysics Data System (ADS)

    Ramstein, B.

    2016-05-01

    Recent results of the HADES collaboration are presented with emphasis on the e+e- production in elementary reactions. Via the Dalitz decay of baryonic resonances (R →Ne+e-), access is given to the time-like electromagnetic structure of baryonic transitions. This process could be measured for the first time for Δ(1232) in pp reactions at 1.25 GeV. At higher energies, the sensitivity of e+e- emission to transition form factors of the Vector Dominance type has been demonstrated. Very recently, experiments with the GSI pion beam started, allowing for more direct studies of baryonic resonances Dalitz decays. In addition, the measurement of hadronic channels provides a new data base for baryon spectroscopy issues, in particular in the 2πN channel.

  4. Weighing Scale-Based Pulse Transit Time is a Superior Marker of Blood Pressure than Conventional Pulse Arrival Time

    NASA Astrophysics Data System (ADS)

    Martin, Stephanie L.-O.; Carek, Andrew M.; Kim, Chang-Sei; Ashouri, Hazar; Inan, Omer T.; Hahn, Jin-Oh; Mukkamala, Ramakrishna

    2016-12-01

    Pulse transit time (PTT) is being widely pursued for cuff-less blood pressure (BP) monitoring. Most efforts have employed the time delay between ECG and finger photoplethysmography (PPG) waveforms as a convenient surrogate of PTT. However, these conventional pulse arrival time (PAT) measurements include the pre-ejection period (PEP) and the time delay through small, muscular arteries and may thus be an unreliable marker of BP. We assessed a bathroom weighing scale-like system for convenient measurement of ballistocardiography and foot PPG waveforms – and thus PTT through larger, more elastic arteries – in terms of its ability to improve tracking of BP in individual subjects. We measured “scale PTT”, conventional PAT, and cuff BP in humans during interventions that increased BP but changed PEP and smooth muscle contraction differently. Scale PTT tracked the diastolic BP changes well, with correlation coefficient of ‑0.80 ± 0.02 (mean ± SE) and root-mean-squared-error of 7.6 ± 0.5 mmHg after a best-case calibration. Conventional PAT was significantly inferior in tracking these changes, with correlation coefficient of ‑0.60 ± 0.04 and root-mean-squared-error of 14.6 ± 1.5 mmHg (p < 0.05). Scale PTT also tracked the systolic BP changes better than conventional PAT but not to an acceptable level. With further development, scale PTT may permit reliable, convenient measurement of BP.

  5. Weighing Scale-Based Pulse Transit Time is a Superior Marker of Blood Pressure than Conventional Pulse Arrival Time

    PubMed Central

    Martin, Stephanie L.-O.; Carek, Andrew M.; Kim, Chang-Sei; Ashouri, Hazar; Inan, Omer T.; Hahn, Jin-Oh; Mukkamala, Ramakrishna

    2016-01-01

    Pulse transit time (PTT) is being widely pursued for cuff-less blood pressure (BP) monitoring. Most efforts have employed the time delay between ECG and finger photoplethysmography (PPG) waveforms as a convenient surrogate of PTT. However, these conventional pulse arrival time (PAT) measurements include the pre-ejection period (PEP) and the time delay through small, muscular arteries and may thus be an unreliable marker of BP. We assessed a bathroom weighing scale-like system for convenient measurement of ballistocardiography and foot PPG waveforms – and thus PTT through larger, more elastic arteries – in terms of its ability to improve tracking of BP in individual subjects. We measured “scale PTT”, conventional PAT, and cuff BP in humans during interventions that increased BP but changed PEP and smooth muscle contraction differently. Scale PTT tracked the diastolic BP changes well, with correlation coefficient of −0.80 ± 0.02 (mean ± SE) and root-mean-squared-error of 7.6 ± 0.5 mmHg after a best-case calibration. Conventional PAT was significantly inferior in tracking these changes, with correlation coefficient of −0.60 ± 0.04 and root-mean-squared-error of 14.6 ± 1.5 mmHg (p < 0.05). Scale PTT also tracked the systolic BP changes better than conventional PAT but not to an acceptable level. With further development, scale PTT may permit reliable, convenient measurement of BP. PMID:27976741

  6. Watching excitons move: the time-dependent transition density matrix

    NASA Astrophysics Data System (ADS)

    Ullrich, Carsten

    2012-02-01

    Time-dependent density-functional theory allows one to calculate excitation energies and the associated transition densities in principle exactly. The transition density matrix (TDM) provides additional information on electron-hole localization and coherence of specific excitations of the many-body system. We have extended the TDM concept into the real-time domain in order to visualize the excited-state dynamics in conjugated molecules. The time-dependent TDM is defined as an implicit density functional, and can be approximately obtained from the time-dependent Kohn-Sham orbitals. The quality of this approximation is assessed in simple model systems. A computational scheme for real molecular systems is presented: the time-dependent Kohn-Sham equations are solved with the OCTOPUS code and the time-dependent Kohn-Sham TDM is calculated using a spatial partitioning scheme. The method is applied to show in real time how locally created electron-hole pairs spread out over neighboring conjugated molecular chains. The coupling mechanism, electron-hole coherence, and the possibility of charge separation are discussed.

  7. Tunnel transit-time (TUNNETT) devices for terahertz sources

    NASA Technical Reports Server (NTRS)

    Haddad, G. I.; East, J. R.; Kidner, C.

    1991-01-01

    The potential and capabilities of tunnel transit-time (TUNNETT) devices for power generation in the 100-1000 GHz range are presented. The basic properties of these devices and the important material parameters which determine their properties are discussed and criteria for designing such devices are presented. It is shown from a first-order model that significant amounts of power can be obtained from these devices in the terahertz frequency range.

  8. Arterial Stiffness is Associated with Increase in Blood Pressure Over Time in Treated Hypertensives

    PubMed Central

    Coutinho, T; Bailey, KR; Turner, ST; Kullo, IJ

    2014-01-01

    Background Arterial stiffness is associated with incident hypertension. We hypothesized that arterial stiffness would predict increases in systolic (SBP), mean (MAP) and pulse pressure (PP) over time in treated hypertensives. Methods Blood pressure (BP) was measured a mean of 8.5±0.9 years apart in 414 non-Hispanic white hypertensives (mean age 60±8 years, 55% women). The average of 3 supine right brachial BPs was recorded. Measures of arterial stiffness including carotid-femoral pulse wave velocity (cfPWV), aortic augmentation index (AIx) and central pulse pressure (CPP) were obtained at baseline by applanation tonometry. We performed stepwise multivariable linear regression analyses adjusting for potential confounders to assess the associations of arterial stiffness parameters with BP changes over time. Results Systolic, mean and pulse pressure increased in 80% of participants. After adjustment for the covariates listed above, cfPWV was significantly associated with increases in SBP (β±SE: 0.71±0.31) and PP (β±SE: 1.09±0.27); AIx was associated with increases in SBP (β±SE: 0.23±0.10) and MAP (β±SE: 0.27±0.07); and CPP was associated with increases in SBP (β±SE: 0.44±0.07), MAP (β±SE: 0.24±0.05) and PP (β±SE: 0.42±0.06) over time (P≤0.02 for all). Conclusions Baseline arterial stiffness measures were associated with longitudinal increases in SBP, MAP and PP in treated hypertensives. PMID:24952654

  9. Estimation of liquid volume fraction using ultrasound transit time spectroscopy

    NASA Astrophysics Data System (ADS)

    Al-Qahtani, Saeed M.; Langton, Christian M.

    2016-12-01

    It has recently been proposed that the propagation of an ultrasound wave through complex structures, consisting of two-materials of differing ultrasound velocity, may be considered as an array of parallel ‘sonic rays’, the transit time of each determined by their relative proportion; being a minimum (t min) in entire higher velocity material, and a maximum (t max) in entire lower velocity material. An ultrasound transit time spectrum (UTTS) describes the proportion of sonic rays at an individual transit time. It has previously been demonstrated that the solid volume fraction of a solid:liquid composite, specifically acrylic step-wedges immersed in water, may be reliably estimated from the UTTS. The aim of this research was to investigate the hypothesis that the volume fraction of a two-component liquid mixture, of unequal ultrasound velocity, may also be estimated by UTTS. A through-transmission technique incorporating two 1 MHz ultrasound transducers within a horizontally-aligned cylindrical tube-housing was utilised, the proportion of silicone oil to water being varied from 0% to 100%. The liquid volume fraction was estimated from the UTTS at each composition, the coefficient of determination (R 2%) being 98.9  ±  0.7%. The analysis incorporated a novel signal amplitude normalisation technique to compensate for absorption within the silicone oil. It is therefore envisaged that the parallel sonic ray concept and the derived UTTS may be further applied to the quantification of liquid mixture composition assessment.

  10. Kepler Planet Masses and Eccentricities from Transit Timing Variations

    NASA Astrophysics Data System (ADS)

    Hadden, Sam; Lithwick, Yoram

    2017-01-01

    The Kepler mission’s census of transiting exoplanets has shown that planets between one and four times the radius of Earth with short orbital periods are extremely common. Given their small sizes, the properties of these planets can be difficult or impossible to constrain via radial velocity observations. Mutual gravitational interactions in multi-planet systems induce variations in the arrival times of planets’ transits. These variations can used to probe planets’ masses and eccentricities, which in turn constrain their compositions and formation histories. I will discuss the results of our analysis of the transit timing variations (TTVs) of 145 Kepler planets from 55 multi-planet systems. Bulk densities inferred from TTVs imply that many of these planets are covered in gaseous envelopes ranging from a few percent to ~20% of their total mass. Eccentricities in these systems are small but in a many instances definitively non-zero. These results support theoretical predictions for super-Earth/sub-Neptune planets accreting their envelopes from a depleting proto-planetary disk.

  11. Biomechanics of Ergometric Stress Test: regional and local effects on elastic, transitional and muscular human arteries

    NASA Astrophysics Data System (ADS)

    Valls, G.; Torrado, J.; Farro, I.; Bia, D.; Zócalo, Y.; Lluberas, S.; Craiem, D.; Armentano, Rl

    2011-09-01

    Ergometric exercise stress tests (EST) give important information about the cardiovascular (CV) response to increased demands. The expected EST-related changes in variables like blood pressure and heart rate are known, but those in the arterial biomechanics are controversial and incompletely characterized. In this context, this work aims were to characterize the regional and local arterial biomechanical behaviour in response to EST; to evaluate its temporal profile in the post-EST recovery phase; and to compare the biomechanical response of different to EST. Methods: In 16 non-trained healthy young subjects the carotid-femoral pulse wave velocity and the carotid, femoral and brachial arterial distensibility were non-invasively evaluated before (Rest) and after EST. Main results: The EST resulted in an early increase in the arterial stiffness, evidenced by both, regional and local parameters (pulse wave velocity increase and distensibility reduction). When analyzing conjunctly the different post-EST recovery stages there were quali-quantitative differences among the arterial local stiffness response to EST. The biomechanical changes could not be explained only by blood pressure variations.

  12. Masses of Kepler-46b, c from Transit Timing Variations

    NASA Astrophysics Data System (ADS)

    Saad-Olivera, Ximena; Nesvorný, David; Kipping, David M.; Roig, Fernando

    2017-04-01

    We use 16 quarters of the Kepler mission data to analyze the transit timing variations (TTVs) of the extrasolar planet Kepler-46b (KOI-872). Our dynamical fits confirm that the TTVs of this planet (period P={33.648}-0.005+0.004 days) are produced by a non-transiting planet Kepler-46c (P={57.325}-0.098+0.116 days). The Bayesian inference tool MultiNest is used to infer the dynamical parameters of Kepler-46b and Kepler-46c. We find that the two planets have nearly coplanar and circular orbits, with eccentricities ≃ 0.03 somewhat higher than previously estimated. The masses of the two planets are found to be {M}b={0.885}-0.343+0.374 and {M}c={0.362}-0.016+0.016 Jupiter masses, with M b being determined here from TTVs for the first time. Due to the precession of its orbital plane, Kepler-46c should start transiting its host star a few decades from now.

  13. Beta blockade increases pulmonary and systemic transit time heterogeneity: evaluation based on indocyanine green kinetics in healthy volunteers.

    PubMed

    Weiss, Michael; Krejcie, Tom C; Avram, Michael J

    2017-05-01

    Knowledge of factors influencing the heterogeneity of blood transit times is important in cardiovascular physiology. The aim of the study was to investigate the effect of beta-adrenergic blockade on blood transit time dispersion in awake, anxious volunteers. Recirculatory modelling of the disposition of intravascular markers using parametric forms for transit time distributions, such as the inverse Gaussian distribution, provides the opportunity to estimate the systemic and pulmonary transit time dispersion in vivo. The latter is determined by the flow heterogeneity in the microcirculatory network. Using this approach, we have analysed indocyanine green (ICG) disposition data obtained in four subjects by frequent early arterial blood sampling before and after beta-adrenergic blockade by propranolol. Propranolol decreased cardiac output from 9·3 ± 2·8 l min(-1) to 3·5 ± 0·47 l min(-1) (P<0·05). This reduction was accompanied by a 4·5 ± 0·6-fold and 2·1 ± 0·3-fold increase (P<0·001) in the relative dispersion (dimensionless variance) of blood transit times through the systemic and pulmonary circulation, respectively.

  14. Detection of artery interfaces: a real-time system and its clinical applications

    NASA Astrophysics Data System (ADS)

    Faita, Francesco; Gemignani, Vincenzo; Bianchini, Elisabetta; Giannarelli, Chiara; Ghiadoni, Lorenzo; Demi, Marcello

    2008-03-01

    Analyzing the artery mechanics is a crucial issue because of its close relationship with several cardiovascular risk factors, such as hypertension and diabetes. Moreover, most of the work can be carried out by analyzing image sequences obtained with ultrasounds, that is with a non-invasive technique which allows a real-time visualization of the observed structures. For this reason, therefore, an accurate temporal localization of the main vessel interfaces becomes a central task for which the manual approach should be avoided since such a method is rather unreliable and time consuming. Real-time automatic systems are advantageously used to automatically locate the arterial interfaces. The automatic measurement reduces the inter/intra-observer variability with respect to the manual measurement which unavoidably depends on the experience of the operator. The real-time visual feedback, moreover, guides physicians when looking for the best position of the ultrasound probe, thus increasing the global robustness of the system. The automatic system which we developed is a stand-alone video processing system which acquires the analog video signal from the ultrasound equipment, performs all the measurements and shows the results in real-time. The localization algorithm of the artery tunics is based on a new mathematical operator (the first order absolute moment) and on a pattern recognition approach. Various clinical applications have been developed on board and validated through a comparison with gold-standard techniques: the assessment of intima-media thickness, the arterial distension, the flow-mediated dilation and the pulse wave velocity. With this paper, the results obtained on clinical trials are presented.

  15. Time-resolved PIV measurements of the flow field in a stenosed, compliant arterial model

    NASA Astrophysics Data System (ADS)

    Geoghegan, P. H.; Buchmann, N. A.; Soria, J.; Jermy, M. C.

    2013-05-01

    Compliant (flexible) structures play an important role in several biological flows including the lungs, heart and arteries. Coronary heart disease is caused by a constriction in the artery due to a build-up of atherosclerotic plaque. This plaque is also of major concern in the carotid artery which supplies blood to the brain. Blood flow within these arteries is strongly influenced by the movement of the wall. To study these problems experimentally in vitro, especially using flow visualisation techniques, can be expensive due to the high-intensity and high-repetition rate light sources required. In this work, time-resolved particle image velocimetry using a relatively low-cost light-emitting diode illumination system was applied to the study of a compliant flow phantom representing a stenosed (constricted) carotid artery experiencing a physiologically realistic flow wave. Dynamic similarity between in vivo and in vitro conditions was ensured in phantom construction by matching the distensibility and the elastic wave propagation wavelength and in the fluid system through matching Reynolds ( Re) and Womersley number ( α) with a maximum, minimum and mean Re of 939, 379 and 632, respectively, and a α of 4.54. The stenosis had a symmetric constriction of 50 % by diameter (75 % by area). Once the flow rate reached a critical value, Kelvin-Helmholtz instabilities were observed to occur in the shear layer between the main jet exiting the stenosis and a reverse flow region that occurred at a radial distance of 0.34 D from the axis of symmetry in the region on interest 0-2.5 D longitudinally downstream from the stenosis exit. The instability had an axis-symmetric nature, but as peak flow rate was approached this symmetry breaks down producing instability in the flow field. The characteristics of the vortex train were sensitive not only to the instantaneous flow rate, but also to whether the flow was accelerating or decelerating globally.

  16. Predictable Patterns in Planetary Transit Timing Variations and Transit Duration Variations Due to Exomoons

    NASA Technical Reports Server (NTRS)

    Heller, Rene; Hippke, Michael; Placek, Ben; Angerhausen, Daniel; Agol, Eric

    2016-01-01

    We present new ways to identify single and multiple moons around extrasolar planets using planetary transit timing variations (TTVs) and transit duration variations (TDVs). For planets with one moon, measurements from successive transits exhibit a hitherto undescribed pattern in the TTV-TDV diagram, originating from the stroboscopic sampling of the planet's orbit around the planet-moon barycenter. This pattern is fully determined and analytically predictable after three consecutive transits. The more measurements become available, the more the TTV-TDV diagram approaches an ellipse. For planets with multiple moons in orbital mean motion resonance (MMR), like the Galilean moon system, the pattern is much more complex and addressed numerically in this report. Exomoons in MMR can also form closed, predictable TTV-TDV figures, as long as the drift of the moons' pericenters is suciently slow.We find that MMR exomoons produce loops in the TTV-TDV diagram and that the number of these loops is equal to the order of the MMR, or the largest integer in the MMR ratio.We use a Bayesian model and Monte Carlo simulations to test the discoverability of exomoons using TTV-TDV diagrams with current and near-future technology. In a blind test, two of us (BP, DA) successfully retrieved a large moon from simulated TTV-TDV by co-authors MH and RH, which resembled data from a known Kepler planet candidate. Single exomoons with a 10 percent moon-to-planet mass ratio, like to Pluto-Charon binary, can be detectable in the archival data of the Kepler primary mission. Multi-exomoon systems, however, require either larger telescopes or brighter target stars. Complementary detection methods invoking a moon's own photometric transit or its orbital sampling effect can be used for validation or falsification. A combination of TESS, CHEOPS, and PLATO data would offer a compelling opportunity for an exomoon discovery around a bright star.

  17. Detection and Characterization of Non-Transiting Planets from Transit Timing Variations

    NASA Astrophysics Data System (ADS)

    Nesvorny, David; Kipping, David; Terrell, Dirk

    2014-11-01

    The Transit Timing Variations (TTVs) can be used as a diagnostic of gravitational interactions between planets in a multi-planet system. Here we conduct a photo-dynamical analysis of several Kepler Objects of Interest (KOIs) that exhibit significant TTVs. We show that KOI-142, KOI-227 and KOI-319 are (at least) two planet systems. KOI-142.01's TTVs uniquely detect a non-transiting companion with a mass 0.63 that of Jupiter. KOI-142.01's mass inferred from the TTVs is consistent with the measured transit depth, suggesting a Neptune-class planet. The orbital period ratio 2.03 indicates that the two planets are just wide of the 2:1 resonance. For KOI-319 and KOI-884, the observed TTVs of the inner transiting planet are used to detect an outer non-transiting planet. The outer planet in KOI-884 is 2.6 Jupiter masses and has the orbital period just narrow of the 3:1 resonance with the inner planet (orbital period ratio 2.93). The distribution of parameters inferred from KOI-319.01's TTVs is bimodal with either a 1.6 Neptune-mass planet wide of the 5:3 resonance (period 80.1 d) or a Saturn-mass planet wide of the 7:3 resonance (period 109.2 d). The radial velocity measurements can be used in this case to determine which of these parameter modes is correct. We discuss how the orbital architecture of KOI-142, KOI-227 and KOI-319 systems constrains their formation.

  18. Predictable patterns in planetary transit timing variations and transit duration variations due to exomoons

    NASA Astrophysics Data System (ADS)

    Heller, René; Hippke, Michael; Placek, Ben; Angerhausen, Daniel; Agol, Eric

    2016-06-01

    We present new ways to identify single and multiple moons around extrasolar planets using planetary transit timing variations (TTVs) and transit duration variations (TDVs). For planets with one moon, measurements from successive transits exhibit a hitherto undescribed pattern in the TTV-TDV diagram, originating from the stroboscopic sampling of the planet's orbit around the planet-moon barycenter. This pattern is fully determined and analytically predictable after three consecutive transits. The more measurements become available, the more the TTV-TDV diagram approaches an ellipse. For planets with multiple moons in orbital mean motion resonance (MMR), like the Galilean moon system, the pattern is much more complex and addressed numerically in this report. Exomoons in MMR can also form closed, predictable TTV-TDV figures, as long as the drift of the moons' pericenters is sufficiently slow. We find that MMR exomoons produce loops in the TTV-TDV diagram and that the number of these loops is equal to the order of the MMR, or the largest integer in the MMR ratio. We use a Bayesian model and Monte Carlo simulations to test the discoverability of exomoons using TTV-TDV diagrams with current and near-future technology. In a blind test, two of us (BP, DA) successfully retrieved a large moon from simulated TTV-TDV by co-authors MH and RH, which resembled data from a known Kepler planet candidate. Single exomoons with a 10% moon-to-planet mass ratio, like to Pluto-Charon binary, can be detectable in the archival data of the Kepler primary mission. Multi-exomoon systems, however, require either larger telescopes or brighter target stars. Complementary detection methods invoking a moon's own photometric transit or its orbital sampling effect can be used for validation or falsification. A combination of TESS, CHEOPS, and PLATO data would offer a compelling opportunity for an exomoon discovery around a bright star.

  19. Times of transition: elder abuse and neglect in Israel.

    PubMed

    Lowenstein, Ariela; Doron, Israel

    2008-01-01

    The present paper addresses the advancement of research, policies, legislation, and practice experiences designed to deal with the phenomenon of elder abuse and neglect in Israel in times of transition. The paper presents a short overview of the demographic scene, reflecting population characteristics and needs that impact care giving as well as elder abuse and neglect. The developments of scientific knowledge and its accumulation, especially the empirical data from the first national survey on elder abuse and neglect are discussed. Further, legislative developments relating to four generational laws and the advancement of policies and innovative practice experiences are described and analyzed. Finally, future challenges in the field are identified.

  20. Radial electron-beam-breakup transit-time oscillator

    DOEpatents

    Kwan, Thomas J. T.; Mostrom, Michael A.

    1998-01-01

    A radial electron-beam-breakup transit-time oscillator (RBTO) provides a compact high power microwave generator. The RBTO includes a coaxial vacuum transmission line having an outer conductor and an inner conductor. The inner conductor defines an annular cavity with dimensions effective to support an electromagnetic field in a TEM.sub.00m mode. A radial field emission cathode is formed on the outer conductor for providing an electron beam directed toward the annular cavity electrode. Microwave energy is then extracted from the annular cavity electrode.

  1. Time-Delayed Theory of the Neolithic Transition in Europe

    NASA Astrophysics Data System (ADS)

    Fort, Joaquim; Méndez, Vicenç

    1999-01-01

    The classical wave-of-advance model of the neolithic transition (i.e., the shift from hunter-gatherer to agricultural economies) is based on Fisher's reaction-diffusion equation. Here we present an extension of Einstein's approach to Fickian diffusion, incorporating reaction terms. On this basis we show that second-order terms in the reaction-diffusion equation, which have been neglected up to now, are not in fact negligible but can lead to important corrections. The resulting time-delayed model agrees quite well with observations.

  2. Numerical and Analytical Modeling of Transit Timing Variations

    NASA Astrophysics Data System (ADS)

    Hadden, Sam; Lithwick, Yoram

    2016-09-01

    We develop and apply methods to extract planet masses and eccentricities from observed transit timing variations (TTVs). First, we derive simple analytic expressions for the TTV that include the effects of both first- and second-order resonances. Second, we use N-body Markov chain Monte Carlo simulations, as well as the analytic formulae, to measure the masses and eccentricities of 10 planets discovered by Kepler that have not previously been analyzed. Most of the 10 planets have low densities. Using the analytic expressions to partially circumvent degeneracies, we measure small eccentricities of a few percent or less.

  3. Controllability of timed continuous Petri nets with uncontrollable transitions

    NASA Astrophysics Data System (ADS)

    Vázquez, C. Renato; Ramírez-Treviño, Antonio; Silva, Manuel

    2014-03-01

    This paper is concerned with controllability of Timed Continuous Petri nets, under infinite server semantics, with uncontrollable transitions, which are a class of hybrid systems (piecewise-linear). This class of hybrid systems is suitable for representing biological systems, high traffic information networks, heavily loaded supply chains, etc. By adopting a Control Theory approach, the contribution of this paper is the characterisation of controllability over sets of equilibrium markings (potential equilibrium points), first inside a single marking region (or linear mode) and later extended to several regions.

  4. Measurements Of Coronary Mean Transit Time And Myocardial Tissue Blood Flow By Deconvolution Of Intravasal Tracer Dilution Curves

    NASA Astrophysics Data System (ADS)

    Korb, H.; Hoeft, A.; Hellige, G.

    1984-10-01

    Previous studies have shown that intramyocardial blood volume does not vary to a major extent even during extreme variation of hemodynamics and coronary vascular tone. Based on a constant intramyocardial blood volume it is therefore possible to calculate tissue blood flow from the mean transit time of an intravascular tracer. The purpose of this study was to develop a clinically applicable method for measurement of coronary blood flow. The new method was based on indocyanine green, a dye which is bound to albumin and intravasally detectable by means of a fiberoptic catheter device. One fiberoptic catheter was placed in the aortic root and another in the coronary sinus. After central venous dye injection the resulting arterial and coronary venous dye dilution curves were processed on-line by a micro-computer. The mean transit time as well as myocardial blood flow were calculated from the step response function of the deconvoluted arterial and coronary venous signals. Reference flow was determined with an extracorporeal electromagnetic flowprobe within a coronary sinus bypass system. 38 steady states with coronary blood flow ranging from 49 - 333 ml/min*100g were analysed in 5 dogs. Mean transit times varied from 2.9 to 16.6 sec. An average intracoronary blood volume of 13.9 -7 1.8 m1/100g was calculated. The correlation between flow determined by the dye dilution technique and flow measured with the reference method was 0.98. According to these results determination of coronary blood flow with a double fiberoptic system and indocyanine green should be possible even under clinical conditions. Furthermore, the arterial and coronary venous oxygen saturation can be monitored continuously by the fiberoptic catheters. Therefore, additional information about the performance of the heart such as myocardial oxygen consumption and myocardial efficiency is available with the same equipment.

  5. Analytical approximation of transit time scattering due to magnetosonic waves

    NASA Astrophysics Data System (ADS)

    Bortnik, J.; Thorne, R. M.; Ni, B.; Li, J.

    2015-03-01

    Recent test particle simulations have shown that energetic electrons traveling through fast magnetosonic (MS) wave packets can experience an effect which is specifically associated with the tight equatorial confinement of these waves, known as transit time scattering. However, such test particle simulations can be computationally cumbersome and offer limited insight into the dominant physical processes controlling the wave-particle interactions, that is, in determining the effects of the various wave parameters and equatorial confinement on the particle scattering. In this paper, we show that such nonresonant effects can be effectively captured with a straightforward analytical treatment that is made possible with a set of reasonable, simplifying assumptions. It is shown that the effect of the wave confinement, which is not captured by the standard quasi-linear theory approach, acts in such a way as to broaden the range of particle energies and pitch angles that can effectively resonate with the wave. The resulting diffusion coefficients can be readily incorporated into global diffusion models in order to test the effects of transit time scattering on the dynamical evolution of radiation belt fluxes.

  6. Delivering on the promise of transit timing variations

    NASA Astrophysics Data System (ADS)

    Agol, Eric; Deck, Katherine

    2015-01-01

    Transiting timing variations (TTVs) have held the promise of enabling the measurement of planet masses and radii in multi-transiting planet systems found with the Kepler spacecraft. However, when a single TTV frequency is detected, a degeneracy commonly exists between the eccentricities and masses of the planets (Lithwick, Xie & Wu 2012), making the masses and eccentricities indeterminate. In some cases this degeneracy has been broken with n-body integrations, but this enshrouds the answer in complex numerics. It may also be broken statistically, but this still does not provide measurements for individual planets.We show how this degeneracy may be broken with a measurement of TTV at the synodic frequency, which has an amplitude that depends strongly on the planet-star mass ratios and on the planets' semi-major axis ratio, yet weakly on their eccentricities. This "chopping" signal is generally modest in amplitude, but when it is detected it can provide the primary constraint upon planet masses, such as in Kepler 11d&e and KOI-872c. We show by example how harmonic analysis of TTVs combined with analytic formulae can break the eccentricity-mass degeneracy without the need for dynamical integrations, thus delivering on the promise of TTVs, while at the same time clarifying the origin of the planetary mass constraints resulting from TTV analysis.

  7. Excitation signal's influence on ultrasonic transit time flow meter's performance

    NASA Astrophysics Data System (ADS)

    Svilainis, L.; Kabisius, P.; Aleksandrovas, A.; Chaziachmetovas, A.

    2012-12-01

    Ultrasonic flow meter performance was analyzed. Ultrasound transit time was used for flow rate estimation. Time of flight was measured using cross correlation processing. Simultaneous channels excitation was used. Ultrasonic signals were excited using low voltage (4V pp) signal generator, received signals were amplified 30 dB and simultaneously acquired by 100 Ms/s 10 bit analog-to-digit converters. Subsample delay estimation was used. Flow rate was varied from 10 l/h to 200 l/h. Measurement channel diameter 8 mm was used. It is complicated to obtain the unbiased reference signal for correlation processing. Various combinations of signals travelling in measurement channel were used for cross-correlation processing. Performance of correlation function and time of flight estimator variance were studied. Variable gain amplifier usually is used for signal dynamic range matching to A/D converter input. Gain influence on time of flight was a subject to study. It has been concluded that gain control introduces systematic errors in time of flight estimator. Influence of the temperature of electronics (pulser, receiver, A/D converter, reference clock etc.) and ultrasonic transducers on the delay estimator was studied. It was concluded that the major temperature-related systematic error comes from the pulser. Performance of the meter was studied when narrowband and spread spectrum signals were used for ultrasound excitation across temperature and flow rate range. It has been concluded that spread spectrum signal allows for better zero flow stability over temperature and lower time of flight variation.

  8. Space and time renormalization in phase transition dynamics

    DOE PAGES

    Francuz, Anna; Dziarmaga, Jacek; Gardas, Bartłomiej; ...

    2016-02-18

    Here, when a system is driven across a quantum critical point at a constant rate, its evolution must become nonadiabatic as the relaxation time τ diverges at the critical point. According to the Kibble-Zurek mechanism (KZM), the emerging post-transition excited state is characterized by a finite correlation length ξˆ set at the time tˆ=τˆ when the critical slowing down makes it impossible for the system to relax to the equilibrium defined by changing parameters. This observation naturally suggests a dynamical scaling similar to renormalization familiar from the equilibrium critical phenomena. We provide evidence for such KZM-inspired spatiotemporal scaling by investigatingmore » an exact solution of the transverse field quantum Ising chain in the thermodynamic limit.« less

  9. Space and time renormalization in phase transition dynamics

    SciTech Connect

    Francuz, Anna; Dziarmaga, Jacek; Gardas, Bartłomiej; Zurek, Wojciech H.

    2016-02-18

    Here, when a system is driven across a quantum critical point at a constant rate, its evolution must become nonadiabatic as the relaxation time τ diverges at the critical point. According to the Kibble-Zurek mechanism (KZM), the emerging post-transition excited state is characterized by a finite correlation length ξˆ set at the time tˆ=τˆ when the critical slowing down makes it impossible for the system to relax to the equilibrium defined by changing parameters. This observation naturally suggests a dynamical scaling similar to renormalization familiar from the equilibrium critical phenomena. We provide evidence for such KZM-inspired spatiotemporal scaling by investigating an exact solution of the transverse field quantum Ising chain in the thermodynamic limit.

  10. RSRM Chamber Pressure Oscillations: Transit Time Models and Unsteady CFD

    NASA Technical Reports Server (NTRS)

    Nesman, Tom; Stewart, Eric

    1996-01-01

    Space Shuttle solid rocket motor low frequency internal pressure oscillations have been observed since early testing. The same type of oscillations also are present in the redesigned solid rocket motor (RSRM). The oscillations, which occur during RSRM burn, are predominantly at the first three motor cavity longitudinal acoustic mode frequencies. Broadband flow and combustion noise provide the energy to excite these modes at low levels throughout motor burn, however, at certain times during burn the fluctuating pressure amplitude increases significantly. The increased fluctuations at these times suggests an additional excitation mechanism. The RSRM has inhibitors on the propellant forward facing surface of each motor segment. The inhibitors are in a slot at the segment field joints to prevent burning at that surface. The aft facing segment surface at a field joint slot burns and forms a cavity of time varying size. Initially the inhibitor is recessed in the field joint cavity. As propellant burns away the inhibitor begins to protrude into the bore flow. Two mechanisms (transit time models) that are considered potential pressure oscillation excitations are cavity-edge tones, and inhibitor hole-tones. Estimates of frequency variation with time of longitudinal acoustic modes, cavity edge-tones, and hole-tones compare favorably with frequencies measured during motor hot firing. It is believed that the highest oscillation amplitudes occur when vortex shedding frequencies coincide with motor longitudinal acoustic modes. A time accurate computational fluid dynamic (CFD) analysis was made to replicate the observations from motor firings and to observe the transit time mechanisms in detail. FDNS is the flow solver used to detail the time varying aspects of the flow. The fluid is approximated as a single-phase ideal gas. The CFD model was an axisymmetric representation of the RSRM at 80 seconds into burn.Deformation of the inhibitors by the internal flow was determined

  11. TRANSIT TIMING VARIATIONS FOR INCLINED AND RETROGRADE EXOPLANETARY SYSTEMS

    SciTech Connect

    Payne, Matthew J.; Ford, Eric B.; Veras, Dimitri

    2010-03-20

    We perform numerical calculations of the expected transit timing variations (TTVs) induced on a hot-Jupiter by an Earth-mass perturber. Motivated by the recent discoveries of retrograde transiting planets, we concentrate on an investigation of the effect of varying relative planetary inclinations, up to and including completely retrograde systems. We find that planets in low-order (e.g., 2:1) mean-motion resonances (MMRs) retain approximately constant TTV amplitudes for 0 deg. < i < 170 deg., only reducing in amplitude for i>170 deg. Systems in higher order MMRs (e.g., 5:1) increase in TTV amplitude as inclinations increase toward 45 deg., becoming approximately constant for 45 deg. < i < 135 deg., and then declining for i>135 deg. Planets away from resonance slowly decrease in TTV amplitude as inclinations increase from 0 deg. to 180 deg., whereas planets adjacent to resonances can exhibit a huge range of variability in TTV amplitude as a function of both eccentricity and inclination. For highly retrograde systems (135 deg. < i {<=} 180 deg.), TTV signals will be undetectable across almost the entirety of parameter space, with the exceptions occurring when the perturber has high eccentricity or is very close to an MMR. This high inclination decrease in TTV amplitude (on and away from resonance) is important for the analysis of the known retrograde and multi-planet transiting systems, as inclination effects need to be considered if TTVs are to be used to exclude the presence of any putative planetary companions: absence of evidence is not evidence of absence.

  12. Transit times of baseflow in New Zealand rivers

    NASA Astrophysics Data System (ADS)

    Morgenstern, Uwe; Stewart, Mike; Daughney, Chris; Townsend, Dougal

    2015-04-01

    Water quantity and quality responses of catchments to climate and land-use changes are difficult to understand and predict due to complexities of subsurface water flow paths and potentially large groundwater stores. It is difficult to relate the hydrologic responses of catchments to measurable catchment properties. Tritium is ideally suited to provide a measurable parameter of hydrologic response. Tritium, a component of meteoric water, decays with a half-life of 12.32 years after the water enters the groundwater system, and can therefore provide information on transit time of water through the groundwater system over the time range 0 to 200 years mean residence time (MRT). Transit time of the water discharge is one of the most crucial parameters for understanding the response of catchments. In recent years it has become possible to use tritium in a straightforward way for dating of stream and river water due to the decay of the bomb-tritium from atmospheric thermo-nuclear weapons testing, and to improved measurement accuracy for the extremely low natural tritium concentrations. Tritium dating of river water during baseflow conditions from over 120 sites throughout New Zealand show consistent patterns and a good correlation between geology and residence times of the water discharges. Basement rock catchments (greywacke, schist) have very young water of MRT less than 1year, sand-, mud-, limestone catchments have moderately old water of MRT 3-15 years, and porous ignimbrite catchments have very old water of MRT greater than 100 years. For example, the tritium data indicate MRT of 6 - 7 years in the Whanganui River, 3 - 3.5 years in the Rangitikei River, and 9 - 11 years in the large discharges from the Tertiary sediments in the Manawatu catchment. The discharges from the greywacke Ruahine and Tararua Ranges contain very young water with MRT of 0 - 2 years. Associated groundwater stores for the Rangitikei, Manawatu, and Whanganui Rivers are 1, 2, and 5 x 109 m3 of

  13. Analytic formulae for transit timing variations of planets

    NASA Astrophysics Data System (ADS)

    Deck, Katherine Michele; Agol, Eric

    2015-12-01

    Gravitational interactions between planets in transiting exoplanetary systems lead to variations in the times of transit (TTVs) that are diagnostic of the planetary masses and the dynamical state of the system. I will present analytic formulae for TTVs which can be applied to planetary systems with nearly circular orbits which are not caught in a mean motion resonance. The formulae relate physical parameters, like masses and orbital elements, to direct TTV observables, including shape, amplitude, and timescales. Importantly, the formulae highlight which components of TTVs break degeneracies to allow for unique measurements of planet masses and eccentricities. Additionally, modeling of TTV data using our analytic formulae can be nearly 4 orders of magnitude faster compared with n-body integration. For a number of Kepler systems with TTVs, I will show that our formulae lead to accurate mass and orbital element measurements without full dynamical analyses involving direct integration of the equations of motion. The analytic formulae may ultimately allow for a homogenous analysis of the TTVs (or lack thereof) of many multi-planet systems.

  14. Racial Differences in the Association between Carotid Plaque and Aortic and Coronary Artery Calcification Among Women Transitioning the Menopause

    PubMed Central

    Woodard, Genevieve A.; Narla, Vinod V.; Ye, Rong; Cauley, Jane A.; Thompson, Trina; Matthews, Karen A.; Sutton-Tyrrell, Kim

    2011-01-01

    Background Carotid atherosclerosis is a marker for atherosclerotic disease in other vascular beds; however, racial differences in this association have not been fully examined. The purpose of this report is to evaluate racial differences in the relationship between carotid plaque and calcification in the aorta and coronary arteries among women transitioning the menopause. Methods 540 African American and White women with a median age of 50 years were evaluated from the Study of Women’s Health Across the Nation. Carotid plaque (none versus any) was assessed with B-mode ultrasound and aortic (AC; 0, >0–100, >100) and coronary artery calcification (CAC; 0, >0–10, >10) with computed tomography. Results For the total cohort, higher prevalence of plaque was significantly associated with higher levels of AC, but not CAC. The interaction of race and carotid plaque was significant in models with AC and CAC as dependent variables (p=0.03, 0.002, respectively). Among African Americans, there was an inverse relationship, although not significant, between carotid plaque and high AC (>100) (OR 0.75, 95%CI: 0.10–5.48), and between plaque and high CAC (>10) (OR 0.20, 95%CI: 0.03–1.52) in fully adjusted models. In contrast, for Whites, significant positive associations existed between carotid plaque and high AC (OR 4.12, 95%CI: 1.29–13.13) and borderline for high CAC (OR 1.83, 95%CI: 0.66–5.19). Conclusions This study demonstrated the presence of carotid plaque appeared to be a marker for AC and potentially CAC in White women during the menopause transition, but not African American middle-aged women. PMID:22037218

  15. Time-Distance Seismology and the Solar Transition Region

    NASA Astrophysics Data System (ADS)

    Hansen, Shelley C.; Cally, Paul S.

    2014-12-01

    Time-Distance `travel time' perturbations (as inferred from wave phase) are calculated relative to the quiet-Sun as a function of wave orientation and field inclination in a uniform inclined magnetic field. Modelling indicates that the chromosphere-corona Transition Region (TR) profoundly alters travel times at inclinations from the vertical θ for which the ramp-reduced acoustic cutoff frequency ω c cos θ is similar to the wave frequency ω. At smaller inclinations phase shifts are much smaller as the waves are largely reflected before reaching the TR. At larger inclinations, the shifts resume their quiet-Sun values, although with some resonant oscillatory behaviour. Changing the height of the TR in the model atmosphere has some effect, but the thickness and temperature jump do not change the results substantially. There is a strong correspondence between travel-time shifts and the Alfvén flux that emerges at the top of the modelled region as a result of fast/Alfvén mode conversion. We confirm that the TR transmission coefficient for Alfvén waves generated by mode conversion in the chromosphere is far larger (typically 30 % or more) than for Alfvén waves injected from the photosphere.

  16. The Timing of School Transitions and Early Adolescent Problem Behavior

    ERIC Educational Resources Information Center

    Lippold, Melissa A.; Powers, Christopher J.; Syvertsen, Amy K.; Feinberg, Mark E.; Greenberg, Mark T.

    2013-01-01

    This longitudinal study investigates whether rural adolescents who transition to a new school in sixth grade have higher levels of risky behavior than adolescents who transition in seventh grade. Our findings indicate that later school transitions had little effect on problem behavior between sixth and ninth grades. Cross-sectional analyses found…

  17. Toward a Smartphone Application for Estimation of Pulse Transit Time

    PubMed Central

    Liu, He; Ivanov, Kamen; Wang, Yadong; Wang, Lei

    2015-01-01

    Pulse transit time (PTT) is an important physiological parameter that directly correlates with the elasticity and compliance of vascular walls and variations in blood pressure. This paper presents a PTT estimation method based on photoplethysmographic imaging (PPGi). The method utilizes two opposing cameras for simultaneous acquisition of PPGi waveform signals from the index fingertip and the forehead temple. An algorithm for the detection of maxima and minima in PPGi signals was developed, which includes technology for interpolation of the real positions of these points. We compared our PTT measurements with those obtained from the current methodological standards. Statistical results indicate that the PTT measured by our proposed method exhibits a good correlation with the established method. The proposed method is especially suitable for implementation in dual-camera-smartphones, which could facilitate PTT measurement among populations affected by cardiac complications. PMID:26516861

  18. Detecting nonstationarity and state transitions in a time series

    NASA Astrophysics Data System (ADS)

    Gao, J. B.

    2001-06-01

    One cause of complexity in a time series may be due to nonstationarity and transience. In this paper, we analyze the nonstationarity and transience in a number of dynamical systems. We find that the nonstationarity in the metastable chaotic Lorenz system is due to nonrecurrence. The latter determines a lack of fractal structure in the signal. In 1/fα noise, we find that the associated correlation dimension are local graph dimensions calculated from sojourn points. We also design a transient Lorenz system with a slowly oscillating controlling parameter, and a transient Rossler system with a slowly linearly increasing parameter, with parameter ranges covering a sequence of chaotic dynamics with increased phase incoherence. State transitions, from periodic to chaotic, and vice versa, are identified, together with different facets of nonstationarity in each phase.

  19. Factors influencing stream baseflow transit times in tropical montane watersheds

    NASA Astrophysics Data System (ADS)

    Muñoz-Villers, Lyssette E.; Geissert, Daniel R.; Holwerda, Friso; McDonnell, Jeffrey J.

    2016-04-01

    Stream water mean transit time (MTT) is a fundamental hydrologic parameter that integrates the distribution of sources, flow paths, and storages present in catchments. However, in the tropics little MTT work has been carried out, despite its usefulness for providing important information on watershed functioning at different spatial scales in (largely) ungauged basins. In particular, very few studies have quantified stream MTTs or have related these to catchment characteristics in tropical montane regions. Here we examined topographic, land use/cover and soil hydraulic controls on baseflow transit times for nested catchments (0.1-34 km2) within a humid mountainous region, underlain by volcanic soil (Andisols) in central Veracruz (eastern Mexico). We used a 2-year record of bi-weekly isotopic composition of precipitation and stream baseflow data to estimate MTT. Land use/cover and topographic parameters (catchment area and form, drainage density, slope gradient and length) were derived from geographic information system (GIS) analysis. Soil water retention characteristics, and depth and permeability of the soil-bedrock interface were obtained from intensive field measurements and laboratory analysis. Results showed that baseflow MTTs ranged between 1.2 and 2.7 years across the 12 study catchments. Overall, MTTs across scales were mainly controlled by catchment slope and the permeability observed at the soil-bedrock interface. In association with topography, catchment form and the depth to the soil-bedrock interface were also identified as important features influencing baseflow MTTs. The greatest differences in MTTs were found both within groups of small (0.1-1.5 km2) and large (14-34 km2) catchments. Interestingly, the longest stream MTTs were found in the headwater cloud forest catchments.

  20. Effect of electrical forepaw stimulation on capillary transit-time heterogeneity (CTH).

    PubMed

    Gutiérrez-Jiménez, Eugenio; Cai, Changsi; Mikkelsen, Irene Klærke; Rasmussen, Peter Mondrup; Angleys, Hugo; Merrild, Mads; Mouridsen, Kim; Jespersen, Sune Nørhøj; Lee, Jonghwan; Iversen, Nina Kerting; Sakadzic, Sava; Østergaard, Leif

    2016-12-01

    Functional hyperemia reduces oxygen extraction efficacy unless counteracted by a reduction of capillary transit-time heterogeneity of blood. We adapted a bolus tracking approach to capillary transit-time heterogeneity estimation for two-photon microscopy and then quantified changes in plasma mean transit time and capillary transit-time heterogeneity during forepaw stimulation in anesthetized mice (C57BL/6NTac). In addition, we analyzed transit time coefficient of variance = capillary transit-time heterogeneity/mean transit time, which we expect to remain constant in passive, compliant microvascular networks. Electrical forepaw stimulation reduced, both mean transit time (11.3% ± 1.3%) and capillary transit-time heterogeneity (24.1% ± 3.3%), consistent with earlier literature and model predictions. We observed a coefficient of variance reduction (14.3% ± 3.5%) during functional activation, especially for the arteriolar-to-venular passage. Such coefficient of variance reduction during functional activation suggests homogenization of capillary flows beyond that expected as a passive response to increased blood flow by other stimuli. This finding is consistent with an active neurocapillary coupling mechanism, for example via pericyte dilation. Mean transit time and capillary transit-time heterogeneity reductions were consistent with the relative change inferred from capillary hemodynamics (cell velocity and flux). Our findings support the important role of capillary transit-time heterogeneity in flow-metabolism coupling during functional activation.

  1. Acute Appendicitis as Complication of Colon Transit Time Study; A Case Report

    PubMed Central

    Ghahramani, Leila; Roshanravan, Reza; Khodaei, Shahin; Rahimi Kazerooni, Salar; Moslemi, Sam

    2015-01-01

    Colon transit time study with radio opaque markers is a simple method for assessment of colon motility disorder in patients with chronic idiopathic constipation. We report a case of acute appendicitis that was induced by impaction of radio opaque markers after colon transit time study. We think that this case report is first significant complication of colon transit time study until now PMID:26396723

  2. Remotely detected differential pulse transit time as a stress indicator

    NASA Astrophysics Data System (ADS)

    Kaur, Balvinder; Tarbox, Elizabeth; Cissel, Marty; Moses, Sophia; Luthra, Megha; Vaidya, Misha; Tran, Nhien; Ikonomidou, Vasiliki N.

    2015-05-01

    The human cardiovascular system, controlled by the autonomic nervous system (ANS), is one of the first sites where one can see the "fight-or-flight" response due to the presence of external stressors. In this paper, we investigate the possibility of detecting mental stress using a novel measure that can be measured in a contactless manner: Pulse transit time (dPTT), which refers to the time that is required for the blood wave (BW) to cover the distance from the heart to a defined remote location in the body. Loosely related to blood pressure, PTT is a measure of blood velocity, and is also implicated in the "fight-or-flight" response. We define the differential PTT (dPTT) as the difference in PTT between two remote areas of the body, such as the forehead and the palm. Expanding our previous work on remote BW detection from visible spectrum videos, we built a system that remotely measures dPTT. Human subject data were collected under an IRB approved protocol from 15 subjects both under normal and stress states and are used to initially establish the potential use of remote dPPT detection as a stress indicator.

  3. Digital image correlation for full-field time-resolved assessment of arterial stiffness

    NASA Astrophysics Data System (ADS)

    Campo, Adriaan; Soons, Joris; Heuten, Hilde; Ennekens, Guy; Goovaerts, Inge; Vrints, Christiaan; Lava, Pascal; Dirckx, Joris

    2014-01-01

    Pulse wave velocity (PWV) of the arterial system is a very important parameter to evaluate cardiovascular health. Currently, however, there is no golden standard for PWV measurement. Digital image correlation (DIC) was used for full-field time-resolved assessment of displacement, velocity, acceleration, and strains of the skin in the neck directly above the common carotid artery. By assessing these parameters, propagation of the pulse wave could be tracked, leading to a new method for PWV detection based on DIC. The method was tested on five healthy subjects. As a means of validation, PWV was measured with ultrasound (US) as well. Measured PWV values were between 3.68 and 5.19 m/s as measured with DIC and between 5.14 and 6.58 m/s as measured with US, with a maximum absolute difference of 2.78 m/s between the two methods. DIC measurements of the neck region can serve as a test base for determining a robust strategy for PWV detection, they can serve as reference for three-dimensional fluid-structure interaction models, or they may even evolve into a screening method of their own. Moreover, full-field, time-resolved DIC can be adapted for other applications in biomechanics.

  4. Real-time frequency-domain fiber optic sensor for intra-arterial blood oxygen measurements

    NASA Astrophysics Data System (ADS)

    Alcala, J. R.; Scott, Ian L.; Parker, Jennifer W.; Atwater, Beauford W.; Yu, Clement; Fischer, Russell; Bellingrath, K.

    1993-05-01

    A real time frequency domain phosphorimeter capable of measuring precise and accurate excited state lifetimes for determining oxygen is described. This frequency domain instrument does not make use of cross correlation techniques traditionally used in frequency domain fluorometers. Instead, the electrical signal from the detector is filtered to contain only the first several harmonics. This filtered signal is then sampled and averaged over a few thousand cycles. The absolute phase and absolute modulation of each sampled harmonic of the excitation and of the luminescence is computed by employing fast Fourier transform algorithms. The phase delay and the modulation ratio is then calculated at each harmonic frequency. A least squares fit is performed in the frequency domain to obtain the lifetimes of discrete exponentials. Oxygen concentrations are computed from these lifetimes. Prototypes based on these techniques were built employing commercially available components. Results from measurements in saline solution and in the arterial blood of dogs show that oxygen concentrations can be determined reproducibly. The system drift is less than 1% in over 100 hours of continuous operation. The performance of fiber optic sensors was evaluated in dogs over a period of 10 hours. The sensors tracked changes in arterial oxygen tension over the course of the experiment without instabilities. The overall response of the system was about 90 seconds. The update time was 3 seconds.

  5. MOST Space-based Photometry of the Transiting Exoplanet System HD 209458: Transit Timing to Search for Additional Planets

    NASA Astrophysics Data System (ADS)

    Miller-Ricci, Eliza; Rowe, Jason F.; Sasselov, Dimitar; Matthews, Jaymie M.; Guenther, David B.; Kuschnig, Rainer; Moffat, Anthony F. J.; Rucinski, Slavek M.; Walker, Gordon A. H.; Weiss, Werner W.

    2008-07-01

    We report on the measurement of transit times for the HD 209458 planetary system from photometry obtained with the MOST (Microvariability and Oscillations of Stars) space telescope. Deviations from a constant orbital period can indicate the presence of additional planets in the system that are yet undetected, potentially with masses approaching an Earth mass. The MOST data sets of HD 209458 from 2004 and 2005 represent unprecedented time coverage with nearly continuous observations spanning 14 and 43 days and monitoring three transits and 12 consecutive transits, respectively. The transit times that we obtain show no variations on three scales: (1) no long-term change in P since before 2004 at 25 ms level, (2) no trend in transit timings during the 2005 run, and (3) no individual transit timing deviations above 80 s level. Together with previously published transit times from Agol & Steffen, this allows us to place limits on the presence of additional close-in planets in the system, in some cases down to below an Earth mass. This result, along with previous radial velocity work, now eliminates the possibility that a perturbing planet could be responsible for the additional heat source needed to explain HD 209458b's anomalous low density.

  6. Arterial endothelial function measurement method and apparatus

    DOEpatents

    Maltz, Jonathan S; Budinger, Thomas F

    2014-03-04

    A "relaxoscope" (100) detects the degree of arterial endothelial function. Impairment of arterial endothelial function is an early event in atherosclerosis and correlates with the major risk factors for cardiovascular disease. An artery (115), such as the brachial artery (BA) is measured for diameter before and after several minutes of either vasoconstriction or vasorelaxation. The change in arterial diameter is a measure of flow-mediated vasomodification (FMVM). The relaxoscope induces an artificial pulse (128) at a superficial radial artery (115) via a linear actuator (120). An ultrasonic Doppler stethoscope (130) detects this pulse 10-20 cm proximal to the point of pulse induction (125). The delay between pulse application and detection provides the pulse transit time (PTT). By measuring PTT before (160) and after arterial diameter change (170), FMVM may be measured based on the changes in PTT caused by changes in vessel caliber, smooth muscle tone and wall thickness.

  7. A Transit Timing Posterior Distribution Catalog for all Kepler Planet Candidates

    NASA Astrophysics Data System (ADS)

    Montet, Benjamin; Becker, Juliette; Johnson, John

    2015-01-01

    Thanks to the unprecedented precision of Kepler, the first unambiguous observations of transit timing variations (TTVs) are now in hand. TTVs have afforded us the ability to precisely characterize both transiting and non-transiting exoplanets by observing dynamical interactions in multi-transiting systems. Catalogs attempting to publish transit times of large numbers of Kepler systems exist. However, these catalogs are incomplete: for each event only a point estimate and assumed Gaussian uncertainity of the transit time is included. Moreover, published catalogs only include long-cadence data, do not cover the full Kepler observing baseline, and assume the Kepler noise is perfectly uncorrelated. Here, we present a complete TTV catalog, in which we produce full posterior distributions on the time of each transit for every Kepler planet candidate without any assumptions of Gaussianity in the transit times.

  8. Deconfinement phase transition in an expanding quark system in the relaxation time approximation

    NASA Astrophysics Data System (ADS)

    Yang, Zhenwei; Zhuang, Pengfei

    2004-03-01

    We investigated the effects of nonequilibrium and collision terms on the deconfinement phase transition of an expanding quark system in Friedberg-Lee model in relaxation time approximation. By calculating the effective quark potential, the critical temperature of the phase transition is dominated by the mean field, while the collisions among quarks and mesons change the time structure of the phase transition significantly.

  9. Conductivity and transit time estimates of a soil liner

    USGS Publications Warehouse

    Krapac, I.G.; Cartwright, K.; Panno, S.V.; Hensel, B.R.; Rehfeldt, K.H.; Herzog, B.L.

    1990-01-01

    A field-scale soil linear was built to assess the feasibilty of constructing a liner to meet the saturated hydraulic conductivity requirement of the U.S. EPA (i.e., less than 1 ?? 10-7 cm/s), and to determine the breakthrough and transit times of water and tracers through the liner. The liner, 8 ?? 15 ?? 0.9 m, was constructed in 15-cm compacted lifts using a 20,037-kg pad-foot compactor and standard engineering practices. Estimated saturated hydraulic conductivities were 2.4 ?? 10-9 cm/s, based on data from large-ring infiltrometers; 4.0 ?? 10-8 cm/s from small-ring infiltrometers; and 5.0 ?? 10-8 cm/s from a water-balance analysis. These estimates were derived from 1 year of monitoring water infiltration into the linear. Breakthrough of tracers at the base of the liner was estimated to be between 2 and 13 years, depending on the method of calculation and the assumptions used in the calculation.

  10. Pulse transit time and heart rate variability in sleep staging.

    PubMed

    Shahrbabaki, Sobhan Salari; Ahmed, Beena; Penzel, Thomas; Cvetkovic, Dean

    2016-08-01

    This paper presents a new and robust algorithm for detection of sleep stages by using the lead I of the Electrocardiography (ECG) and a fingertip Photoplethysmography (PPG) sensor, validated using multiple overnight PSG recordings consisting of 20 human subjects (9 insomniac and 11 healthy). Heart Rate Variability (HRV) and Pulse Transit Time (PTT) biomarkers which were extracted from ECG and PPG biosignals then employed to extract features. Distance Weighted k-Nearest Neighbours (DWk-NN) was used as classifier to differentiate sleep epochs. The validation of the algorithm was evaluated by Leave-One-Out-Cross-Validation method. The average accuracy of 73.4% with standard deviation of 6.4 was achieved while the algorithm could distinguish stages 2, 3 of non-rapid eye movement sleep by average sensitivity of almost 80%. The lowest mean sensitivity of 53% was for stage 1. These results demonstrate that an algorithm based on PTT and HRV spectral analysis is able to classify and distinguish sleep stages with high accuracy and sensitivity. In addition the proposed algorithm is capable to be improved and implemented as a wearable, comfortable and cheap instrument for sleep screening.

  11. Transit time kinetics in ordered and disordered vascular trees.

    PubMed

    Karshafian, Raffi; Burns, Peter N; Henkelman, Mark R

    2003-10-07

    Imaging modalities exploit tracer-dilution methods to measure bulk haemodynamic parameters such as blood flow and volume at the level of the microcirculation. Here, we ask the question of whether the kinetics of a tracer can reveal morphological information about the vessels through which the tracers flow. The goal is to relate the acquired time-intensity characteristic to details of the vascular structure that lies below the imaging resolution. Two fractal vascular models are developed that represent organized 'kidney-like' and disorganized 'tumour-like' structures. The models are generated using simple rules of branching and fractal geometry in two dimensions. Blood flow and tracer kinetics are simulated using fundamental laws of haemodynamics. The flow conditions are matched in the two models. The fractal box dimensions of the kidney (D(B) = 1.67 +/- 0.01) and the tumour (D(B) = 1.80 +/- 0.01) vasculatures fall in the range given in the literature (D(B) = 1.61 +/- 0.06 and D(B) = 1.84 +/- 0.04, respectively). The tracer kinetic curves of the kidney and the tumour vasculatures have the same initial slope and final asymptote, corresponding to the same flow rate and vascular volume, but have different forms. The difference in the two curves is related to the distribution function of transit times of the vascular models, and is a consequence of the randomness introduced in vessel diameter and length. In principle, the form of the tracer kinetic curve from a contrast imaging study may offer information relating not only to vascular volume and flow rate, but also to the organization of a microvascular network.

  12. A wearable vital signs monitor at the ear for continuous heart rate and pulse transit time measurements.

    PubMed

    Winokur, Eric S; He, David Da; Sodini, Charles G

    2012-01-01

    A continuous, wearable and wireless vital signs monitor at the ear is demonstrated. The device has the form factor of a hearing aid and is wirelessly connected to a PC for data recording and analysis. The device monitors the electrocardiogram (ECG) in a single lead configuration, the ballistocardiogram (BCG) with a MEMS triaxial accelerometer, and the photoplethysmograms (PPG) with 660 nm and 940 nm LED sources and a static photocurrent subtraction analog front end. Clinical tests are conducted, including Valsalva and head-up tilt maneuvers. Peak timing intervals between the ECG, BCG and PPG are extracted and are shown to relate to pre-ejection period and mean arterial blood pressure (MAP). Pulse Transit Time (PTT) extracted from cross-correlation between the PPG and BCG shows improved results compared to the pulse arrival time (PAT) method for tracking changes in MAP.

  13. A Wearable Vital Signs Monitor at the Ear for Continuous Heart Rate and Pulse Transit Time Measurements

    PubMed Central

    Winokur, Eric S.; Da He, David; Sodini, Charles G.

    2015-01-01

    A continuous, wearable and wireless vital signs monitor at the ear is demonstrated. The device has the form factor of a hearing aid and is wirelessly connected to a PC for data recording and analysis. The device monitors the electrocardiogram (ECG) in a single lead configuration, the ballistocardiogram (BCG) with a MEMS triaxial accelerometer, and the photoplethysmograms (PPG) with 660nm and 940nm LED sources and a static photocurrent subtraction analog front end. Clinical tests are conducted, including Valsalva and head-up tilt maneuvers. Peak timing intervals between the ECG, BCG and PPG are extracted and are shown to relate to pre-ejection period and mean arterial blood pressure (MAP). Pulse Transit Time (PTT) extracted from cross-correlation between the PPG and BCG shows improved results compared to the pulse arrival time (PAT) method for tracking changes in MAP. PMID:23366488

  14. Modeling hyporheic exchange and in-stream transport with time-varying transit time distributions

    NASA Astrophysics Data System (ADS)

    Ball, A.; Harman, C. J.; Ward, A. S.

    2014-12-01

    Transit time distributions (TTD) are used to understand in-stream transport and exchange with the hyporheic zone by quantifying the probability of water (and of dissolved material) taking time T to traverse the stream reach control volume. However, many studies using this method assume a TTD that is time-invariant, despite the time-variability of the streamflow. Others assume that storage is 'randomly sampled' or 'well-mixed' with a fixed volume or fixed exchange rate. Here we present a formulation for a time-variable TTD that relaxes both the time-invariant and 'randomly sampled' assumptions and only requires a few parameters. The framework is applied to transient storage, representing some combination of in-stream and hyporheic storage, along a stream reach. This approach does not assume that hyporheic and dead-zone storage is fixed or temporally-invariant, and allows for these stores to be sampled in more physically representative ways determined by the system itself. Instead of using probability distributions of age, probability distributions of storage (ranked by age) called Ω functions are used to describe how the off-stream storage is sampled in the outflow. Here the Ω function approach is used to describe hyporheic exchange during diurnal fluctuations in streamflow in a gaining reach of the H.J. Andrews Experimental Forest. The breakthrough curves of salt slugs injected four hours apart over a 28-hour period show a systematic variation in transit time distribution. This new approach allows us to relate these salt slug TTDs to a corresponding time-variation in the Ω function, which can then be related to changes in in-stream storage and hyporheic zone mobilization under varying flow conditions. Thus, we can gain insights into how channel storage and hyporheic exchange are changing through time without having to specify difficult to measure or unmeasurable quantities of our system, such as total storage.

  15. Instantaneous frequency time analysis of physiology signals: The application of pregnant women’s radial artery pulse signals

    NASA Astrophysics Data System (ADS)

    Su, Zhi-Yuan; Wang, Chuan-Chen; Wu, Tzuyin; Wang, Yeng-Tseng; Tang, Feng-Cheng

    2008-01-01

    This study used the Hilbert-Huang transform, a recently developed, instantaneous frequency-time analysis, to analyze radial artery pulse signals taken from women in their 36th week of pregnancy and after pregnancy. The acquired instantaneous frequency-time spectrum (Hilbert spectrum) is further compared with the Morlet wavelet spectrum. Results indicate that the Hilbert spectrum is especially suitable for analyzing the time series of non-stationary radial artery pulse signals since, in the Hilbert-Huang transform, signals are decomposed into different mode functions in accordance with signal’s local time scale. Therefore, the Hilbert spectrum contains more detailed information than the Morlet wavelet spectrum. From the Hilbert spectrum, we can see that radial artery pulse signals taken from women in their 36th week of pregnancy and after pregnancy have different patterns. This approach could be applied to facilitate non-invasive diagnosis of fetus’ physiological signals in the future.

  16. Real-time functional MRI using pseudo-continuous arterial spin labeling.

    PubMed

    Hernandez-Garcia, Luis; Jahanian, Hesamoddin; Greenwald, Mark K; Zubieta, Jon-Kar; Peltier, Scott J

    2011-06-01

    The first implementation of real-time acquisition and analysis of arterial spin labeling-based functional magnetic resonance imaging time series is presented in this article. The implementation uses a pseudo-continuous labeling scheme followed by a spiral k-space acquisition trajectory. Real-time reconstruction of the images, preprocessing, and regression analysis of the functional magnetic resonance imaging data were implemented on a laptop computer interfaced with the MRI scanner. The method allows the user to track the current raw data, subtraction images, and the cumulative t-statistic map overlaid on a cumulative subtraction image. The user is also able to track the time course of individual time courses and interactively selects a region of interest as a nuisance covariate. The pulse sequence allows the user to adjust acquisition and labeling parameters while observing their effect on the image within two successive pulse repetition times. This method is demonstrated by two functional imaging experiments: a simultaneous finger-tapping and visual stimulation paradigm, and a bimanual finger-tapping task.

  17. Real-Time Functional MRI Using Pseudo-Continuous Arterial Spin Labeling

    PubMed Central

    Hernandez-Garcia, Luis; Jahanian, Hesamoddin; Greenwald, Mark K.; Zubieta, Jon-Kar; Peltier, Scott J.

    2011-01-01

    The first implementation of real-time acquisition and analysis of Arterial Spin Labeling (ASL) based functional MRI time series is presented in this article. The implementation uses a pseudo-continuous labeling scheme followed by a spiral k-space acquisition trajectory. Real-time reconstruction of the images, preprocessing and regression analysis of the fMRI data were implemented on a laptop computer interfaced with the MRI scanner. The method allows the user to track the current raw data, subtraction images, and the cumulative t-statistic map overlaid on a cumulative subtraction image. The user is also able to track the time course of individual time courses, and interactively select an ROI as a nuisance covariate. The pulse sequence allows the user to adjust acquisition and labeling parameters while observing their effect on the image within two successive TRs. This method is illustrated on a stimulation paradigm consisting of simultaneous finger-tapping and visual stimulation and on a bimanual finger tapping task alternating hands. PMID:21446035

  18. Real-time ultrasound: Key factor in identifying celiac artery compression syndrome.

    PubMed

    Tembey, Raina Anil; Bajaj, Aneeta S; Wagle, Prasad K; Ansari, Abdul Samad

    2015-01-01

    The median arcuate ligament syndrome (MALS) or celiac artery compression syndrome (CACS) is a rare entity, presenting clinically with postprandial abdominal pain and weight loss. The diagnosis is made on computed tomography (CT) angiography, which reveals extrinsic compression of the proximal part of the celiac artery by the median arcuate ligament, producing a characteristic hooked appearance. We report a case of the celiac artery compression syndrome, diagnosed by Doppler USG evaluation.

  19. TRANSIT MONITORING IN THE SOUTH (TraMoS) PROJECT: DISCARDING TRANSIT TIMING VARIATIONS IN WASP-5b

    SciTech Connect

    Hoyer, S.; Rojo, P.; Lopez-Morales, M. E-mail: pato@das.uchile.cl

    2012-03-20

    We report nine new transit epochs of the extrasolar planet WASP-5b, observed in the Bessell I band with the Southern Astrophysical Research Telescope at the Cerro Pachon Observatory and with the SMARTS 1 m Telescope at the Cerro Tololo Inter-American Observatory, between 2008 August and 2009 October. The new transits have been combined with all previously published transit data for this planet to provide a new Transit Timing Variation (TTV) analysis of its orbit. We find no evidence of TTV rms variations larger than 1 minute over a 3 year time span. This result discards the presence of planets more massive than about 5 M{sub Circled-Plus }, 1 M{sub Circled-Plus }, and 2 M{sub Circled-Plus} around the 1:2, 5:3, and 2:1 orbital resonances, respectively. These new detection limits exceed by {approx}5-30 times the limits imposed by current radial velocity observations in the mean motion resonances of this system. Our search for the variation of other parameters, such as orbital inclination and transit depth, also yields negative results over the total time span of the transit observations. This result supports formation theories that predict a paucity of planetary companions to hot Jupiters.

  20. Discovering the space-time dimensions of schedule padding and delay from GTFS and real-time transit data

    NASA Astrophysics Data System (ADS)

    Wessel, Nate; Widener, Michael J.

    2017-01-01

    Schedule padding is the extra time added to transit schedules to reduce the risk of delay. Where there is more random delay, there should be more schedule padding. While schedule padding is a product of transit planners, a method for detecting when and where it exists could provide valuable feedback as transit agencies continually develop their networks. By analyzing transit schedules and real-time vehicle location data at the level of stop-to-stop segments, we can locate padding in space and time and identify the places that may be most effected by stochastic delay. Such information could be used to target delay-reduction interventions such as fare prepayment or transit-only rights of way. The Toronto Transit Commission is used as a case study, and initial results suggest that highly delayed segments appear mostly in the expected, but some surprising, places.

  1. Colonic transit time is related to bacterial metabolism and mucosal turnover in the gut.

    PubMed

    Roager, Henrik M; Hansen, Lea B S; Bahl, Martin I; Frandsen, Henrik L; Carvalho, Vera; Gøbel, Rikke J; Dalgaard, Marlene D; Plichta, Damian R; Sparholt, Morten H; Vestergaard, Henrik; Hansen, Torben; Sicheritz-Pontén, Thomas; Nielsen, H Bjørn; Pedersen, Oluf; Lauritzen, Lotte; Kristensen, Mette; Gupta, Ramneek; Licht, Tine R

    2016-06-27

    Little is known about how colonic transit time relates to human colonic metabolism and its importance for host health, although a firm stool consistency, a proxy for a long colonic transit time, has recently been positively associated with gut microbial richness. Here, we show that colonic transit time in humans, assessed using radio-opaque markers, is associated with overall gut microbial composition, diversity and metabolism. We find that a long colonic transit time associates with high microbial richness and is accompanied by a shift in colonic metabolism from carbohydrate fermentation to protein catabolism as reflected by higher urinary levels of potentially deleterious protein-derived metabolites. Additionally, shorter colonic transit time correlates with metabolites possibly reflecting increased renewal of the colonic mucosa. Together, this suggests that a high gut microbial richness does not per se imply a healthy gut microbial ecosystem and points at colonic transit time as a highly important factor to consider in microbiome and metabolomics studies.

  2. Transitive Lie groups on S^1\\times S^{2m}

    NASA Astrophysics Data System (ADS)

    Gorbatsevich, Vladimir V.

    2007-10-01

    The structure of Lie groups acting transitively on the direct product of a circle and an even-dimensional sphere is described. For products of two spheres of dimension >1 a similar problem has already been solved by other authors. The minimal transitive Lie groups on S^1 and S^{2m} are also indicated. As an application of these results, the structure of the automorphism group of one class of geometric structures, generalized quadrangles (a special case of Tits buildings) is considered. A conjecture put forward by Kramer is proved: the automorphism group of a connected generalized quadrangle of type (1,2m) always contains a transitive subgroup that is the direct product of a compact simple Lie group and a one-dimensional Lie group. Bibliography: 16 titles.

  3. Transit Timing Observations from Kepler: III. Confirmation of 4 Multiple Planet Systems by a Fourier-Domain Study of Anti-correlated Transit Timing Variations

    SciTech Connect

    Steffen, Jason H.; Fabrycky, Daniel C.; Ford, Eric B.; Carter, Joshua A.; Fressin, Francois; Holman, Matthew J.; Lissauer, Jack J.; Rowe, Jason F.; Ragozzine, Darin; Welsh, William F.; Borucki, William J.; /NASA, Ames /UC, Santa Barbara

    2012-01-01

    We present a method to confirm the planetary nature of objects in systems with multiple transiting exoplanet candidates. This method involves a Fourier-domain analysis of the deviations in the transit times from a constant period that result from dynamical interactions within the system. The combination of observed anticorrelations in the transit times and mass constraints from dynamical stability allow us to claim the discovery of four planetary systems, Kepler-25, Kepler-26, Kepler-27 and Kepler-28, containing eight planets and one additional planet candidate.

  4. Decreasing Transition Times in Elementary School Classrooms: Using Computer-Assisted Instruction to Automate Intervention Components

    ERIC Educational Resources Information Center

    Hine, Jeffrey F.; Ardoin, Scott P.; Foster, Tori E.

    2015-01-01

    Research suggests that students spend a substantial amount of time transitioning between classroom activities, which may reduce time spent academically engaged. This study used an ABAB design to evaluate the effects of a computer-assisted intervention that automated intervention components previously shown to decrease transition times. We examined…

  5. Measurement of vascular water transport in human subjects using time-resolved pulsed arterial spin labelling.

    PubMed

    Bibic, Adnan; Knutsson, Linda; Schmidt, Anders; Henningsson, Erik; Månsson, Sven; Abul-Kasim, Kasim; Åkeson, Jonas; Gunther, Matthias; Ståhlberg, Freddy; Wirestam, Ronnie

    2015-08-01

    Most approaches to arterial spin labelling (ASL) data analysis aim to provide a quantitative measure of the cerebral blood flow (CBF). This study, however, focuses on the measurement of the transfer time of blood water through the capillaries to the parenchyma (referred to as the capillary transfer time, CTT) as an alternative parameter to characterise the haemodynamics of the system. The method employed is based on a non-compartmental model, and no measurements need to be added to a common time-resolved ASL experiment. Brownian motion of labelled spins in a potential was described by a one-dimensional general Langevin equation as the starting point, and as a Fokker-Planck differential equation for the averaged distribution of labelled spins at the end point, which takes into account the effects of flow and dispersion of labelled water by the pseudorandom nature of the microvasculature and the transcapillary permeability. Multi-inversion time (multi-TI) ASL data were acquired in 14 healthy subjects on two occasions in a test-retest design, using a pulsed ASL sequence and three-dimensional gradient and spin echo (3D-GRASE) readout. Based on an error analysis to predict the size of a region of interest (ROI) required to obtain reasonably precise parameter estimates, data were analysed in two relatively large ROIs, i.e. the occipital lobe (OC) and the insular cortex (IC). The average values of CTT in OC were 260 ± 60 ms in the first experiment and 270 ± 60 ms in the second experiment. The corresponding IC values were 460 ± 130 ms and 420 ± 139 ms, respectively. Information related to the water transfer time may be important for diagnostics and follow-up of cerebral conditions or diseases characterised by a disrupted blood-brain barrier or disturbed capillary blood flow.

  6. Transitions into and out of daylight saving time compromise sleep and the rest-activity cycles

    PubMed Central

    Lahti, Tuuli A; Leppämäki, Sami; Lönnqvist, Jouko; Partonen, Timo

    2008-01-01

    Background The aim of this study was to analyze the effects of transition out of and into daylight saving time on the rest-activity cycles and sleep. Rest-activity cycles of nine healthy participants aged 20 to 40 years were measured around transitions out of and into daylight saving time on fall 2005 and spring 2006 respectively. Rest-activity cycles were measured using wrist-worn accelerometers. The participants filled in the Morningness-Eveningness and Seasonal Pattern Assessment Questionnaires before starting the study and kept a sleep diary during the study. Results Fall transition was more disturbing for the more morning type and spring transition for the more evening type of persons. Individuals having a higher global seasonality score suffered more from the transitions. Conclusion Transitions out of and into daylight saving time enhanced night-time restlessness and thereby compromised the quality of sleep. PMID:18269740

  7. Regional Gastrointestinal Transit Times in Patients With Carcinoid Diarrhea: Assessment With the Novel 3D-Transit System

    PubMed Central

    Gregersen, Tine; Haase, Anne-Mette; Schlageter, Vincent; Gronbaek, Henning; Krogh, Klaus

    2015-01-01

    Background/Aims The paucity of knowledge regarding gastrointestinal motility in patients with neuroendocrine tumors and carcinoid diarrhea restricts targeted treatment. 3D-Transit is a novel, minimally invasive, ambulatory method for description of gastrointestinal motility. The system has not yet been evaluated in any group of patients. We aimed to test the performance of 3D-Transit in patients with carcinoid diarrhea and to compare the patients’ regional gastrointestinal transit times (GITT) and colonic motility patterns with those of healthy subjects. Methods Fifteen healthy volunteers and seven patients with neuroendocrine tumor and at least 3 bowel movements per day were investigated with 3D-Transit and standard radiopaque markers. Results Total GITT assessed with 3D-Transit and radiopaque markers were well correlated (Spearman’s rho = 0.64, P = 0.002). Median total GITT was 12.5 (range: 8.5–47.2) hours in patients versus 25.1 (range: 13.1–142.3) hours in healthy (P = 0.007). There was no difference in gastric emptying (P = 0.778). Median small intestinal transit time was 3.8 (range: 1.4–5.5) hours in patients versus 4.4 (range: 1.8–7.2) hours in healthy subjects (P = 0.044). Median colorectal transit time was 5.2 (range: 2.9–40.1) hours in patients versus 18.1 (range: 5.0–134.0) hours in healthy subjects (P = 0.012). Median frequency of pansegmental colonic movements was 0.45 (range: 0.03–1.02) per hour in patients and 0.07 (range: 0–0.61) per hour in healthy subjects (P = 0.045). Conclusions Three-dimensional Transit allows assessment of regional GITT in patients with diarrhea. Patients with carcinoid diarrhea have faster than normal gastrointestinal transit due to faster small intestinal and colorectal transit times. The latter is caused by an increased frequency of pansegmental colonic movements. PMID:26130638

  8. Hillslope permeability architecture controls on subsurface transit time distribution and flow paths

    NASA Astrophysics Data System (ADS)

    Ameli, A. A.; Amvrosiadi, N.; Grabs, T.; Laudon, H.; Creed, I. F.; McDonnell, J. J.; Bishop, K.

    2016-12-01

    Defining the catchment transit time distribution remains a challenge. Here, we used a new semi-analytical physically-based integrated subsurface flow and advective-dispersive particle movement model to assess the subsurface controls on subsurface water flow paths and transit time distributions. First, we tested the efficacy of the new model for simulation of the observed groundwater dynamics at the well-studied S-transect hillslope (Västrabäcken sub-catchment, Sweden). This system, like many others, is characterized by exponential decline in saturated hydraulic conductivity and porosity with soil depth. The model performed well relative to a tracer-based estimate of transit time distribution as well as observed groundwater depth-discharge relationship within 30 m of the stream. Second, we used the model to assess the effect of changes in the subsurface permeability architecture on flow pathlines and transit time distribution in a set of virtual experiments. Vertical patterns of saturated hydraulic conductivity and porosity with soil depth significantly influenced hillslope transit time distribution. Increasing infiltration rates significantly decreased mean groundwater age, but not the distribution of transit times relative to mean groundwater age. The location of hillslope hydrologic boundaries, including the groundwater divide and no-flow boundary underlying the hillslope, changed the transit time distribution less markedly. These results can guide future decisions on the degree of complexity that is warranted in a physically-based rainfall-runoff model to efficiently and explicitly estimate time invariant subsurface pathlines and transit time distribution.

  9. Hydrogen breath test assessment of orocecal transit time: comparison with barium meal study.

    PubMed

    Hirakawa, M; Iida, M; Kohrogi, N; Fujishima, M

    1988-12-01

    Orocecal transit time was measured simultaneously by the hydrogen breath test and a barium meal study in 12 hospitalized patients, the objective being to determine whether the former test accurately represents the orocecal transit time, and to establish an adequate criterion for the transit time, based on the former test. Two definitions of orocecal transit time by the hydrogen breath test were evaluated: the time from lactulose ingestion to a sustained increase of over 5 ppm above fasting levels in the end-expiratory hydrogen concentration (definition A) and the interval to that of over 10 ppm (definition B). The orocecal transit time measured by the radiologic method was 63 +/- 9 min (mean +/- SEM), whereas that using definition A of the hydrogen breath test was 74 +/- 9 min, and that using definition B was 87 +/- 10 min. Transit times determined by both definitions closely correlated with that obtained by the radiologic method (A, r = 0.86, p less than 0.01; B, r = 0.81, p less than 0.01). Therefore, elevation of end-expiratory hydrogen concentrations seemed to coincide with cecal appearance of the head of the lactulose load. When the mean transit times were compared with findings in case of the radiologic method, definition A rather than B appeared to be more appropriate to determine orocecal transit time.

  10. The physical origins of transit time measurements for rapid, single cell mechanotyping.

    PubMed

    Nyberg, Kendra D; Scott, Michael B; Bruce, Samuel L; Gopinath, Ajay B; Bikos, Dimitri; Mason, Thomas G; Kim, Jin Woong; Choi, Hong Sung; Rowat, Amy C

    2016-08-16

    The mechanical phenotype or 'mechanotype' of cells is emerging as a potential biomarker for cell types ranging from pluripotent stem cells to cancer cells. Using a microfluidic device, cell mechanotype can be rapidly analyzed by measuring the time required for cells to deform as they flow through constricted channels. While cells typically exhibit deformation timescales, or transit times, on the order of milliseconds to tens of seconds, transit times can span several orders of magnitude and vary from day to day within a population of single cells; this makes it challenging to characterize different cell samples based on transit time data. Here we investigate how variability in transit time measurements depends on both experimental factors and heterogeneity in physical properties across a population of single cells. We find that simultaneous transit events that occur across neighboring constrictions can alter transit time, but only significantly when more than 65% of channels in the parallel array are occluded. Variability in transit time measurements is also affected by the age of the device following plasma treatment, which could be attributed to changes in channel surface properties. We additionally investigate the role of variability in cell physical properties. Transit time depends on cell size; by binning transit time data for cells of similar diameters, we reduce measurement variability by 20%. To gain further insight into the effects of cell-to-cell differences in physical properties, we fabricate a panel of gel particles and oil droplets with tunable mechanical properties. We demonstrate that particles with homogeneous composition exhibit a marked reduction in transit time variability, suggesting that the width of transit time distributions reflects the degree of heterogeneity in subcellular structure and mechanical properties within a cell population. Our results also provide fundamental insight into the physical underpinnings of transit measurements

  11. Primary Pulmonary Artery Sarcoma on Dual-Time Point FDG PET/CT Imaging.

    PubMed

    Li, Juan; Zhao, Qian; He, Lirong; Zhuang, Xiaoqing; Li, Fang

    2016-08-01

    A 59-year-old man presented cough, chest pain, and shortness of breath for 2 weeks and fever for 4 days. A contrast chest CT revealed a large right pulmonary artery filling defect, suggestive of pulmonary embolism that failed to respond to anticoagulation therapy. FDG PET/CT was performed to evaluate possible malignancy, which revealed intense activity in the right main pulmonary artery without any extrathoracic abnormality. The ratio of the SUVmax of this lesion to the liver was significantly increased in the delayed PET images. The pathological examination demonstrated primary pulmonary artery sarcoma.

  12. Regularity and stability of transition fronts in nonlocal equations with time heterogeneous ignition nonlinearity

    NASA Astrophysics Data System (ADS)

    Shen, Wenxian; Shen, Zhongwei

    2017-03-01

    The present paper is devoted to the investigation of various properties of transition fronts in one-dimensional nonlocal equations in heterogeneous media of ignition type, whose existence has been established by the authors of the present paper in a previous work. It is first shown that transition fronts are continuously differentiable in space with uniformly bounded and uniformly Lipschitz continuous space partial derivative. This is the first time that space regularity of transition fronts in nonlocal equations is ever studied. It is then shown that transition fronts are uniformly steep. Finally, asymptotic stability, in the sense of exponentially attracting front-like initial data, of transition fronts is studied.

  13. Orbital parameter estimation of extrasolar multi-planet systems by Transit Time Variation

    NASA Astrophysics Data System (ADS)

    Korth, J.; Grziwa, S.; Pätzold, M.

    2014-04-01

    Transit Time Variation (TTV) is the earlier or later occurrence of a planetary transit relative to the time of a reference transit. TTV may be dominantly caused by the gravitational perturbation of the orbit of the transiting planet by another still unknown planet(s) inside or outside of the orbit of the known transiting planet. Gravitational interactions perturb the velocity of the transiting planet in its orbit which manifests in the periodical perturbation of the revolution period. Measurements of the transit times and the identification of differences from a mean transit period may then indicate the presence of another unknown planet and is therefore proof for the existence of further planets. The estimation of the mass of the transiting planet and the orbital parameters of the undetected planet(s) are constrained by the amplitude of the periodical variation of the transit times. Simulations of known multi-planet systems which show TTV shall be presented. The resulting TTV amplitude is analyzed with regard to the main dependencies: mass of the perturbing planet and the orbit eccentricities.

  14. Integral definition of transition time in the Landau-Zener model

    SciTech Connect

    Yan Yue; Wu Biao

    2010-02-15

    We give a general definition for the transition time in the Landau-Zener model. This definition allows us to compute numerically the Landau-Zener transition time at any sweeping rate without ambiguity in both diabatic and adiabatic bases. With this new definition, analytical results are obtained in both the adiabatic limit and the sudden limit.

  15. Genetic associations for activated partial thromboplastin time and prothrombin time, their gene expression profiles, and risk of coronary artery disease.

    PubMed

    Tang, Weihong; Schwienbacher, Christine; Lopez, Lorna M; Ben-Shlomo, Yoav; Oudot-Mellakh, Tiphaine; Johnson, Andrew D; Samani, Nilesh J; Basu, Saonli; Gögele, Martin; Davies, Gail; Lowe, Gordon D O; Tregouet, David-Alexandre; Tan, Adrian; Pankow, James S; Tenesa, Albert; Levy, Daniel; Volpato, Claudia B; Rumley, Ann; Gow, Alan J; Minelli, Cosetta; Yarnell, John W G; Porteous, David J; Starr, John M; Gallacher, John; Boerwinkle, Eric; Visscher, Peter M; Pramstaller, Peter P; Cushman, Mary; Emilsson, Valur; Plump, Andrew S; Matijevic, Nena; Morange, Pierre-Emmanuel; Deary, Ian J; Hicks, Andrew A; Folsom, Aaron R

    2012-07-13

    Activated partial thromboplastin time (aPTT) and prothrombin time (PT) are clinical tests commonly used to screen for coagulation-factor deficiencies. One genome-wide association study (GWAS) has been reported previously for aPTT, but no GWAS has been reported for PT. We conducted a GWAS and meta-analysis to identify genetic loci for aPTT and PT. The GWAS for aPTT was conducted in 9,240 individuals of European ancestry from the Atherosclerosis Risk in Communities (ARIC) study, and the GWAS for PT was conducted in 2,583 participants from the Genetic Study of Three Population Microisolates in South Tyrol (MICROS) and the Lothian Birth Cohorts (LBC) of 1921 and 1936. Replication was assessed in 1,041 to 3,467 individuals. For aPTT, previously reported associations with KNG1, HRG, F11, F12, and ABO were confirmed. A second independent association in ABO was identified and replicated (rs8176704, p = 4.26 × 10(-24)). Pooling the ARIC and replication data yielded two additional loci in F5 (rs6028, p = 3.22 × 10(-9)) and AGBL1 (rs2469184, p = 3.61 × 10(-8)). For PT, significant associations were identified and confirmed in F7 (rs561241, p = 3.71 × 10(-56)) and PROCR/EDEM2 (rs2295888, p = 5.25 × 10(-13)). Assessment of existing gene expression and coronary artery disease (CAD) databases identified associations of five of the GWAS loci with altered gene expression and two with CAD. In summary, eight genetic loci that account for ∼29% of the variance in aPTT and two loci that account for ∼14% of the variance in PT were detected and supported by functional data.

  16. Genetic Associations for Activated Partial Thromboplastin Time and Prothrombin Time, their Gene Expression Profiles, and Risk of Coronary Artery Disease

    PubMed Central

    Tang, Weihong; Schwienbacher, Christine; Lopez, Lorna M.; Ben-Shlomo, Yoav; Oudot-Mellakh, Tiphaine; Johnson, Andrew D.; Samani, Nilesh J.; Basu, Saonli; Gögele, Martin; Davies, Gail; Lowe, Gordon D.O.; Tregouet, David-Alexandre; Tan, Adrian; Pankow, James S.; Tenesa, Albert; Levy, Daniel; Volpato, Claudia B.; Rumley, Ann; Gow, Alan J.; Minelli, Cosetta; Yarnell, John W.G.; Porteous, David J.; Starr, John M.; Gallacher, John; Boerwinkle, Eric; Visscher, Peter M.; Pramstaller, Peter P.; Cushman, Mary; Emilsson, Valur; Plump, Andrew S.; Matijevic, Nena; Morange, Pierre-Emmanuel; Deary, Ian J.; Hicks, Andrew A.; Folsom, Aaron R.

    2012-01-01

    Activated partial thromboplastin time (aPTT) and prothrombin time (PT) are clinical tests commonly used to screen for coagulation-factor deficiencies. One genome-wide association study (GWAS) has been reported previously for aPTT, but no GWAS has been reported for PT. We conducted a GWAS and meta-analysis to identify genetic loci for aPTT and PT. The GWAS for aPTT was conducted in 9,240 individuals of European ancestry from the Atherosclerosis Risk in Communities (ARIC) study, and the GWAS for PT was conducted in 2,583 participants from the Genetic Study of Three Population Microisolates in South Tyrol (MICROS) and the Lothian Birth Cohorts (LBC) of 1921 and 1936. Replication was assessed in 1,041 to 3,467 individuals. For aPTT, previously reported associations with KNG1, HRG, F11, F12, and ABO were confirmed. A second independent association in ABO was identified and replicated (rs8176704, p = 4.26 × 10−24). Pooling the ARIC and replication data yielded two additional loci in F5 (rs6028, p = 3.22 × 10−9) and AGBL1 (rs2469184, p = 3.61 × 10−8). For PT, significant associations were identified and confirmed in F7 (rs561241, p = 3.71 × 10−56) and PROCR/EDEM2 (rs2295888, p = 5.25 × 10−13). Assessment of existing gene expression and coronary artery disease (CAD) databases identified associations of five of the GWAS loci with altered gene expression and two with CAD. In summary, eight genetic loci that account for ∼29% of the variance in aPTT and two loci that account for ∼14% of the variance in PT were detected and supported by functional data. PMID:22703881

  17. Restrictive hemodynamics are present at the time of diagnosis of allograft coronary artery disease in children.

    PubMed

    Law, Yuk; Boyle, Gerard; Miller, Susan; Clendaniel, James; Ettedgui, Jose; Beerman, Lee; Counihan, Peter; Webber, Steven

    2006-12-01

    Clinical recognition of allograft coronary artery disease (ACAD) is challenging. We examined whether right heart hemodynamics can aid its diagnosis in pediatric recipients. We retrospective analyzed hemodynamic data of recipients with ACAD versus age and date-of-transplant matched controls. From 1982-2001, 18 cases fulfilled study entry criteria. Median age at transplant was 12 years for subjects and 8 years for controls. Median time to diagnosis of ACAD was 65 months (14.5-124 months) and 67 months (16-140 months) to arteriography for controls. The median right ventricular end-diastolic pressure (RVEDP) at diagnosis was 11.0 vs. 6.0 mmHg for controls (p = 0.003). Pulmonary capillary wedge pressure (PCWP) at diagnosis was 14.0 vs. 8.0 mmHg for controls (p = 0.001). When subdivided by severity of ACAD, the difference was greater in the moderate/severe group. Compared to the previous catheterization (median interval 10 months for subjects, 12.0 for controls ), there was an increase of 4.0 mmHg in RVEDP in ACAD subjects (n = 13, p = .003) versus 0 mmHg in controls (p = 0.042), and an increase in PCWP of 5.5 in subjects (p = .002) versus 0 mmHg in controls (p = 0.066). The presence of elevated filling pressures plus an interim increase should alert to the presence of ACAD and help guide further investigation.

  18. Generalizing memories over time: sleep and reinforcement facilitate transitive inference.

    PubMed

    Werchan, Denise M; Gómez, Rebecca L

    2013-02-01

    The use of reinforcement and rewards is known to enhance memory retention. However, the impact of reinforcement on higher-order forms of memory processing, such as integration and generalization, has not been directly manipulated in previous studies. Furthermore, there is evidence that sleep enhances the integration and generalization of memory, but these studies have only used reinforcement learning paradigms and have not examined whether reinforcement impacts or is critical for memory integration and generalization during sleep. Thus, the aims of the current study were to examine: (1) whether reinforcement during learning impacts the integration and generalization of memory; and (2) whether sleep and reinforcement interact to enhance memory integration and generalization. We investigated these questions using a transitive inference (TI) task, which is thought to require the integration and generalization of disparate relational memories in order to make novel inferences. To examine whether reinforcement influences or is required for the formation of inferences, we compared performance using a reinforcement or an observation based TI task. We examined the impact of sleep by comparing performance after a 12-h delay containing either wake or sleep. Our results showed that: (1) explicit reinforcement during learning is required to make transitive inferences and that sleep further enhances this effect; (2) sleep does not make up for the inability to make inferences when reinforcement does not occur during learning. These data expand upon previous findings and suggest intriguing possibilities for the mechanisms involved in sleep-dependent memory transformation.

  19. Investigation of Timing to Switch Control Mode in Powered Knee Prostheses during Task Transitions

    PubMed Central

    Zhang, Fan; Liu, Ming; Huang, He

    2015-01-01

    Current powered prosthetic legs require switching control modes according to the task the user is performing (e.g. level-ground walking, stair climbing, walking on slopes, etc.). To allow prosthesis users safely and seamlessly transition between tasks, it is critical to determine when to switch the prosthesis control mode during task transitions. Our previous study defined critical timings for different types of task transitions in ambulation; however, it is unknown whether it is the unique timing that allows safe and seamless transitions. The goals of this study were to (1) systematically investigate the effects of mode switch timing on the prosthesis user’s performance in task transitions, and (2) identify appropriate timing to switch the prosthesis control mode so that the users can seamlessly transition between different locomotion tasks. Five able-bodied (AB) and two transfemoral (TF) amputee subjects were tested as they wore a powered knee prosthesis. The prosthesis control mode was switched manually at various times while the subjects performed different types of task transitions. The subjects’ task transition performances were evaluated by their walking balance and success in performing seamless task transitions. The results demonstrated that there existed a time window within which switching the prosthesis control mode neither interrupted the subjects’ task transitions nor disturbed their walking balance. Therefore, the results suggested the control mode switching of a lower limb prosthesis can be triggered within an appropriate time window instead of a specific timing or an individual phase. In addition, a generalized criterion to determine the appropriate mode switch timing was proposed. The outcomes of this study could provide important guidance for future designs of neurally controlled powered knee prostheses that are safe and reliable to use. PMID:26197084

  20. Time Resolved Phase Transitions via Dynamic Transmission Electron Microscopy

    SciTech Connect

    Reed, B W; Armstrong, M R; Blobaum, K J; Browning, N D; Burnham, A K; Campbell, G H; Gee, R; Kim, J S; King, W E; Maiti, A; Piggott, W T; Torralva, B R

    2007-02-22

    The Dynamic Transmission Electron Microscope (DTEM) project is developing an in situ electron microscope with nanometer- and nanosecond-scale resolution for the study of rapid laser-driven processes in materials. We report on the results obtained in a year-long LDRD-supported effort to develop DTEM techniques and results for phase transitions in molecular crystals, reactive multilayer foils, and melting and resolidification of bismuth. We report the first in situ TEM observation of the HMX {beta}-{delta} phase transformation in sub-{micro}m crystals, computational results suggesting the importance of voids and free surfaces in the HMX transformation kinetics, and the first electron diffraction patterns of intermediate states in fast multilayer foil reactions. This project developed techniques which are applicable to many materials systems and will continue to be employed within the larger DTEM effort.

  1. Time-Series Interactions of Gene Expression, Vascular Growth and Hemodynamics during Early Embryonic Arterial Development

    PubMed Central

    Goktas, Selda; Uslu, Fazil E.; Kowalski, William J.; Ermek, Erhan; Keller, Bradley B.

    2016-01-01

    The role of hemodynamic forces within the embryo as biomechanical regulators for cardiovascular morphogenesis, growth, and remodeling is well supported through the experimental studies. Furthermore, clinical experience suggests that perturbed flow disrupts the normal vascular growth process as one etiology for congenital heart diseases (CHD) and for fetal adaptation to CHD. However, the relationships between hemodynamics, gene expression and embryonic vascular growth are poorly defined due to the lack of concurrent, sequential in vivo data. In this study, a long-term, time-lapse optical coherence tomography (OCT) imaging campaign was conducted to acquire simultaneous blood velocity, pulsatile micro-pressure and morphometric data for 3 consecutive early embryonic stages in the chick embryo. In conjunction with the in vivo growth and hemodynamics data, in vitro reverse transcription polymerase chain reaction (RT-PCR) analysis was performed to track changes in transcript expression relevant to histogenesis and remodeling of the embryonic arterial wall. Our non-invasive extended OCT imaging technique for the microstructural data showed continuous vessel growth. OCT data coupled with the PIV technique revealed significant but intermitted increases in wall shear stress (WSS) between first and second assigned stages and a noticeable decrease afterwards. Growth rate, however, did not vary significantly throughout the embryonic period. Among all the genes studied, only the MMP-2 and CASP-3 expression levels remained unchanged during the time course. Concurrent relationships were obtained among the transcriptional modulation of the genes, vascular growth and hemodynamics-related changes. Further studies are indicated to determine cause and effect relationships and reversibility between mechanical and molecular regulation of vasculogenesis. PMID:27552150

  2. Frequency of close companions among Kepler planets—a transit time variation study

    SciTech Connect

    Xie, Ji-Wei; Wu, Yanqin; Lithwick, Yoram E-mail: wu@astro.utoronto.ca

    2014-07-10

    A transiting planet exhibits sinusoidal transit time variations (TTVs) if perturbed by a companion near a mean-motion resonance. We search for sinusoidal TTVs in more than 2600 Kepler candidates, using the publicly available Kepler light curves (Q0-Q12). We find that the TTV fractions rise strikingly with the transit multiplicity. Systems where four or more planets transit enjoy a TTV fraction that is roughly five times higher than those where a single planet transits, and about twice as high as those for doubles and triples. In contrast, models in which all transiting planets arise from similar dynamical configurations predict comparable TTV fractions among these different systems. One simple explanation for our results is that there are at least two different classes of Kepler systems, one closely packed and one more sparsely populated.

  3. Frequency of Close Companions among Kepler Planets—a Transit Time Variation Study

    NASA Astrophysics Data System (ADS)

    Xie, Ji-Wei; Wu, Yanqin; Lithwick, Yoram

    2014-07-01

    A transiting planet exhibits sinusoidal transit time variations (TTVs) if perturbed by a companion near a mean-motion resonance. We search for sinusoidal TTVs in more than 2600 Kepler candidates, using the publicly available Kepler light curves (Q0-Q12). We find that the TTV fractions rise strikingly with the transit multiplicity. Systems where four or more planets transit enjoy a TTV fraction that is roughly five times higher than those where a single planet transits, and about twice as high as those for doubles and triples. In contrast, models in which all transiting planets arise from similar dynamical configurations predict comparable TTV fractions among these different systems. One simple explanation for our results is that there are at least two different classes of Kepler systems, one closely packed and one more sparsely populated.

  4. The use of transit timing to detect terrestrial-mass extrasolar planets.

    PubMed

    Holman, Matthew J; Murray, Norman W

    2005-02-25

    Future surveys for transiting extrasolar planets are expected to detect hundreds of jovian-mass planets and tens of terrestrial-mass planets. For many of these newly discovered planets, the intervals between successive transits will be measured with an accuracy of 0.1 to 100 minutes. We show that these timing measurements will allow for the detection of additional planets in the system (not necessarily transiting) by their gravitational interaction with the transiting planet. The transit-time variations depend on the mass of the additional planet, and in some cases terrestrial-mass planets will produce a measurable effect. In systems where two planets are seen to transit, the density of both planets can be determined without radial-velocity observations.

  5. TEE, an estimator for the precision of eclipse and transit minimum times

    NASA Astrophysics Data System (ADS)

    Deeg, H. J.; Tingley, B.

    2017-03-01

    Context. Transit or eclipse timing variations have proven to be a valuable tool in exoplanet research. However, no simple way to estimate the potential precision of such timing measures has been presented yet, nor are guidelines available regarding the relation between timing errors and sampling rate. Aims: A timing error estimator (TEE) equation is presented that requires only basic transit parameters as input. With the TEE, estimating timing precision for actual data and for future instruments, such as the TESS and PLATO space missions, is straightforward. Methods: A derivation of the timing error based on a trapezoidal transit shape is given. We also verify the TEE on realistically modelled transits using Monte Carlo simulations and determine its validity range, exploring in particular the interplay between ingress/egress times and sampling rates. Results: The simulations show that the TEE gives timing errors very close to the correct value, as long as the temporal sampling is faster than transit ingress/egress durations and transits with very low S/N are avoided. Conclusions: The TEE is a useful tool for estimating eclipse or transit timing errors in actual and future data sets. In combination with a previously published equation to estimate period-errors, predictions for the ephemeris precision of long-coverage observations are possible as well. The tests for the TEE's validity range also led to implications for instrumental design. Temporal sampling has to be faster than transit ingress or egress durations, or a loss in timing precision will occur. An application to the TESS mission shows that transits close to its detection limit will have timing uncertainties that exceed 1 h within a few months of their acquisition. Prompt follow-up observations will be needed to avoid "losing" their ephemerides.

  6. Not ready for prime time: transitional events in the extremely preterm infant.

    PubMed

    Armentrout, Debra

    2014-01-01

    Successful transition from intrauterine to extrauterine life involves significant physiologic changes. The majority of these changes occur relatively quickly during those first moments following delivery; however, transition for the extremely preterm infant occurs over a longer period of time. Careful assessment and perceptive interventions on the part of neonatal care providers is essential as the extremely preterm infant adjusts to life outside the womb. This article will focus on respiratory, cardiovascular, gastrointestinal, and neurologic transitional events experienced by the extremely premature infant.

  7. Comparing Intra-Arterial Chemotherapy Combined With Intravesical Chemotherapy Versus Intravesical Chemotherapy Alone: A Randomised Prospective Pilot Study for T1G3 Bladder Transitional Cell Carcinoma After Bladder-Preserving Surgery

    SciTech Connect

    Chen, Junxing Yao, Zhijun Qiu, Shaopeng Chen, Lingwu; Wang, Yu Yang, Jianyong Li, Jiaping

    2013-12-15

    Purpose: To compare the efficacy of intra-arterial chemotherapy combined with intravesical chemotherapy versus intravesical chemotherapy alone for T1G3 bladder transitional cell carcinoma (BTCC) followed by bladder-preserving surgery. Materials and Methods: Sixty patients with T1G3 BTCC were randomly divided into two groups. After bladder-preserving surgery, 29 patients (age 30-80 years, 24 male and 5 female) received intra-arterial chemotherapy in combination with intravesical chemotherapy (group A), whereas 31 patients (age 29-83 years, 26 male and 5 female) were treated with intravesical chemotherapy alone (group B). Twenty-nine patients were treated with intra-arterial epirubicin (50 mg/m{sup 2}) + cisplatin (60 mg/m{sup 2}) chemotherapy 2-3 weeks after bladder-preserving surgery once every 4-6 weeks. All of the patients received the same intravesical chemotherapy: An immediate prophylactic was administered in the first 6 h. After that, therapy was administered one time per week for 8 weeks and then one time per month for 8 months. The instillation drug was epirubicin (50 mg/m{sup 2}) and lasted for 30-40 min each time. The end points were tumour recurrence (stage Ta, T1), tumour progression (to T2 or greater), and disease-specific survival. During median follow-up of 22 months, the overall survival rate, tumour-specific death rate, recurrence rate, progression rate, time to first recurrence, and adverse reactions were compared between groups. Results: The recurrence rates were 10.3 % (3 of 29) in group A and 45.2 % (14 of 31) in group B, and the progression rates were 0 % (0 of 29) in group A and 22.6 % (7 of 31) in group B. There was a significant difference between the two groups regarding recurrence (p = 0.004) and progression rates (p = 0.011). Median times to first recurrence in the two groups were 15 and 6.5 months, respectively. The overall survival rates were 96.6 and 87.1 %, and the tumour-specific death rates were 0 % (0 of 29) and 13.5 % (4 of 31

  8. The role of hillslopes in stream flow response: connectivity, flow path, and transit time

    NASA Astrophysics Data System (ADS)

    McGuire, K. J.; McDonnell, J. J.

    2006-12-01

    Subsurface flow from hillslopes is widely recognized as an important contributor to stream flow generation; however, processes that control how and when hillslopes connect to streams remain unclear. Much of the difficulty in deciphering hillslope response in the stream is due to riparian zone modulation of these inputs. We investigated stream and hillslope runoff dynamics in a 10 ha catchment in the western Cascades of Oregon where the riparian zone has been removed by debris flows, providing an unambiguous hillslope hydrologic signal to the stream channel. Water transit time was used as a framework to develop a conceptual stream flow generation model for the small basin. We based our conceptualization on observations of hydrometric, stable isotope, and applied tracer responses and computed transit times for multiple runoff components using a simple linear systems model. Event water mean transit times (8 to 34 h) and rapid breakthrough from applied hillslope tracer additions, demonstrated that contributing areas extend far upslope during events. Despite rapid hillslope transport processes during events, vadose zone water and runoff mean transit times during non-storm conditions were greater than the timescale of storm events. Vadose zone water mean transit times ranged between 10 and 25 days. Hillslope seepage and catchment baseflow mean transit times were between 1 and 2 years. We describe a conceptual model that captures variable physical flow pathways and transit times through changing antecedent wetness conditions that illustrate the different stages of hillslope and stream connectivity.

  9. Solid volume fraction estimation of bone:marrow replica models using ultrasound transit time spectroscopy.

    PubMed

    Wille, Marie-Luise; Langton, Christian M

    2016-02-01

    The acceptance of broadband ultrasound attenuation (BUA) for the assessment of osteoporosis suffers from a limited understanding of both ultrasound wave propagation through cancellous bone and its exact dependence upon the material and structural properties. It has recently been proposed that ultrasound wave propagation in cancellous bone may be described by a concept of parallel sonic rays; the transit time of each ray defined by the proportion of bone and marrow propagated. A Transit Time Spectrum (TTS) describes the proportion of sonic rays having a particular transit time, effectively describing the lateral inhomogeneity of transit times over the surface aperture of the receive ultrasound transducer. The aim of this study was to test the hypothesis that the solid volume fraction (SVF) of simplified bone:marrow replica models may be reliably estimated from the corresponding ultrasound transit time spectrum. Transit time spectra were derived via digital deconvolution of the experimentally measured input and output ultrasonic signals, and compared to predicted TTS based on the parallel sonic ray concept, demonstrating agreement in both position and amplitude of spectral peaks. Solid volume fraction was calculated from the TTS; agreement between true (geometric calculation) with predicted (computer simulation) and experimentally-derived values were R(2)=99.9% and R(2)=97.3% respectively. It is therefore envisaged that ultrasound transit time spectroscopy (UTTS) offers the potential to reliably estimate bone mineral density and hence the established T-score parameter for clinical osteoporosis assessment.

  10. How to assess regional and whole gut transit time with wireless motility capsule.

    PubMed

    Lee, Yeong Yeh; Erdogan, Askin; Rao, Satish S C

    2014-04-30

    Assessment of transit through the gastrointestinal tract provides useful information regarding gut physiology and patho-physiology. Although several methods are available, each has distinct advantages and limitations. Recently, an ingestible wire-less motility capsule (WMC), similar to capsule video endoscopy, has become available that offers a less-invasive, standardized, radiation-free and office-based test. The capsule has 3 sensors for measurement of pH, pressure and temperature, and collec-tively the information provided by these sensors is used to measure gastric emptying time, small bowel transit time, colonic transit time and whole gut transit time. Current approved indications for the test include the evaluation of gastric emptying in gastroparesis, colonic transit in constipation and evaluation of generalised dysmotility. Rare capsule retention and malfunc-tion are known limitations and some patients may experience difficulty with swallowing the capsule. The use of WMC has been validated for the assessment of gastrointestinal transit. The normal range for transit time includes the following: gastric empty-ing (2-5 hours), small bowel transit (2-6 hours), colonic transit (10-59 hours) and whole gut transit (10-73 hours). Besides avoiding the use of multiple endoscopic, radiologic and functional gastrointestinal tests, WMC can provide new diagnoses, leads to a change in management decision and help to direct further focused work-ups in patients with suspected disordered motility. In conclusion, WMC represents a significant advance in the assessment of segmental and whole gut transit and mo-tility, and could prove to be an indispensable diagnostic tool for gastrointestinal physicians worldwide.

  11. The acceleration of energetic particles in the interplanetary medium by transit-time damping

    NASA Technical Reports Server (NTRS)

    Fisk, L. A.

    1976-01-01

    Transit time damping is examined as a possible means for accelerating low energy particles in co-rotating streams and interstellar ions. Data show that: the protons in co-rotating streams may be accelerated by transient-time damping the small-scale variations in the field magnitude that are observed at a low level in the inner solar system. The interstellar ions may be accelerated by transit time damping large-scale field variations in the outer solar system.

  12. Time-Varying Transition Probability Matrix Estimation and Its Application to Brand Share Analysis

    PubMed Central

    Chiba, Tomoaki; Akaho, Shotaro; Murata, Noboru

    2017-01-01

    In a product market or stock market, different products or stocks compete for the same consumers or purchasers. We propose a method to estimate the time-varying transition matrix of the product share using a multivariate time series of the product share. The method is based on the assumption that each of the observed time series of shares is a stationary distribution of the underlying Markov processes characterized by transition probability matrices. We estimate transition probability matrices for every observation under natural assumptions. We demonstrate, on a real-world dataset of the share of automobiles, that the proposed method can find intrinsic transition of shares. The resulting transition matrices reveal interesting phenomena, for example, the change in flows between TOYOTA group and GM group for the fiscal year where TOYOTA group’s sales beat GM’s sales, which is a reasonable scenario. PMID:28076383

  13. Time-Varying Transition Probability Matrix Estimation and Its Application to Brand Share Analysis.

    PubMed

    Chiba, Tomoaki; Hino, Hideitsu; Akaho, Shotaro; Murata, Noboru

    2017-01-01

    In a product market or stock market, different products or stocks compete for the same consumers or purchasers. We propose a method to estimate the time-varying transition matrix of the product share using a multivariate time series of the product share. The method is based on the assumption that each of the observed time series of shares is a stationary distribution of the underlying Markov processes characterized by transition probability matrices. We estimate transition probability matrices for every observation under natural assumptions. We demonstrate, on a real-world dataset of the share of automobiles, that the proposed method can find intrinsic transition of shares. The resulting transition matrices reveal interesting phenomena, for example, the change in flows between TOYOTA group and GM group for the fiscal year where TOYOTA group's sales beat GM's sales, which is a reasonable scenario.

  14. Deriving the time-variant transit time distributions of an Austrian karst system by a semi-distributed karst model

    NASA Astrophysics Data System (ADS)

    Hartmann, Andreas; Kobler, Johannes; Kralik, Martin; Dirnboeck, Thomas; Humer, Franko; Weiler, Markus

    2014-05-01

    Karst systems contribute around 50% to Austria's drinking water supply. Distributions of transit times of water and hence other water quality parameters can be highly valuable when assessing the risk of contamination of a karst aquifer. In this study we assess the transit time distributions of a dolomite karst system in Austria. Using a new type of semi-distributed model that considers the spatial heterogeneity of the karst system by distribution functions we simulated a range of spatially variable pathways through the karst system. To assure a reliable calibration of the model we used observations of discharge at 2 different locations and 3 time series of solute concentrations (DOC, NO3 and SO4). We benchmarked the model with a split sample test using all 5 types of observations. Having enough indication for a realistic representation of the system and its flow and storage behaviour, the range of simulated pathways through the karst system was used to derive transit time distributions for different initial conditions. We use experimentally derived information about transit times (water ages, O 18 observations, tracer experiments) to evaluate the simulated residence time distributions. Finally, the process-based structure of the model allows to attribute the different transit time distributions to physical processes and pathways in the karst system and to assess the system's vulnerability on contamination.

  15. An efficient tracer experimental design for measuring time-variable transit time distributions in periodic hydrodynamic systems

    NASA Astrophysics Data System (ADS)

    Harman, Ciaran; Kim, Minseok

    2014-05-01

    The time-varying transport dynamics of complex hydrodynamic systems with long transit times are difficult to observe even in experimental systems due to the need for multiple tracer injections. Where only one or two distinct tracers are available, overprinting in the output concentrations limits the injection frequency. We will present an experimental method (the PERiodic Tracer Hierarchy - PERTH) that allows overprinted breakthrough curves to be decomposed into contributions from multiple injections of the same tracer, so long as the transporting flow is periodic. This method allows the time varying transit time distributions to be observed efficiently while making no a priori assumptions about the transport processes operating in the system. Simulations of transport through a soil column subject to a periodic sequence of irrigation events demonstrate that the distinct transit time distributions associated with each irrigation event can be retrieved almost exactly.

  16. Critical capacity, travel time delays and travel time distribution of rapid mass transit systems

    NASA Astrophysics Data System (ADS)

    Legara, Erika Fille; Monterola, Christopher; Lee, Kee Khoon; Hung, Gih Guang

    2014-07-01

    We set up a mechanistic agent-based model of a rapid mass transit system. Using empirical data from Singapore's unidentifiable smart fare card, we validate our model by reconstructing actual travel demand and duration of travel statistics. We subsequently use this model to investigate two phenomena that are known to significantly affect the dynamics within the RTS: (1) overloading in trains and (2) overcrowding in the RTS platform. We demonstrate that by varying the loading capacity of trains, a tipping point emerges at which an exponential increase in the duration of travel time delays is observed. We also probe the impact on the rail system dynamics of three types of passenger growth distribution across stations: (i) Dirac delta, (ii) uniform and (iii) geometric, which is reminiscent of the effect of land use on transport. Under the assumption of a fixed loading capacity, we demonstrate the dependence of a given origin-destination (OD) pair on the flow volume of commuters in station platforms.

  17. Psychosocial Adversities and Timing of Adolescent Transitions: A Comparison of the Former East and West Germanies.

    ERIC Educational Resources Information Center

    Silbereisen, Rainer K.; And Others

    This study was conducted to examine the timing of adolescent transitions. Its first aim was to investigate the hypothesis that cumulated family adversities during childhood would predict earlier transitions in domains such as behavioral autonomy and friendship formation during adolescence. Subjects (N=1,631) were adolescents between the ages of 13…

  18. Supporting Students in Military Families during Times of Transition: A Call for Awareness and Action

    ERIC Educational Resources Information Center

    Cole, Rebekah F.

    2016-01-01

    Throughout their time in school, students in military families face many challenging periods of transition, which include deployments, relocations, and the family's separation from the military. During these transitions, students in military families may be especially susceptible to social, emotional, and academic challenges both in their home…

  19. The use of content and timing to predict turn transitions

    PubMed Central

    Garrod, Simon; Pickering, Martin J.

    2015-01-01

    For addressees to respond in a timely fashion, they cannot simply process the speaker's utterance as it occurs and wait till it finishes. Instead, they predict both when the speaker will conclude and what linguistic forms will be used. While doing this, they must also prepare their own response. To explain this, we draw on the account proposed by Pickering and Garrod (2013a), in which addressees covertly imitate the speaker's utterance and use this to determine the intention that underlies their upcoming utterance. They use this intention to predict when and how the utterance will end, and also to drive their own production mechanisms for preparing their response. Following Arnal and Giraud (2012), we distinguish between mechanisms that predict timing and content. In particular, we propose that the timing mechanism relies on entrainment of low-frequency oscillations between speech envelope and brain. This constrains the context that feeds into the determination of the speaker's intention and hence the timing and form of the upcoming utterance. This approach typically leads to well-timed contributions, but also provides a mechanism for resolving conflicts, for example when there is unintended speaker overlap. PMID:26124728

  20. First-time viewers' comprehension of films: bridging shot transitions.

    PubMed

    Ildirar, Sermin; Schwan, Stephan

    2015-02-01

    Which perceptual and cognitive prerequisites must be met in order to be able to comprehend a film is still unresolved and a controversial issue. In order to gain some insights into this issue, our field experiment investigates how first-time adult viewers extract and integrate meaningful information across film cuts. Three major types of commonalities between adjacent shots were differentiated, which may help first-time viewers with bridging the shots: pictorial, causal, and conceptual. Twenty first-time, 20 low-experienced and 20 high-experienced viewers from Turkey were shown a set of short film clips containing these three kinds of commonalities. Film clips conformed also to the principles of continuity editing. Analyses of viewers' spontaneous interpretations show that first-time viewers indeed are able to notice basic pictorial (object identity), causal (chains of activity), as well as conceptual (links between gaze direction and object attention) commonalities between shots due to their close relationship with everyday perception and cognition. However, first-time viewers' comprehension of the commonalities is to a large degree fragile, indicating the lack of a basic notion of what constitutes a film.

  1. The use of content and timing to predict turn transitions.

    PubMed

    Garrod, Simon; Pickering, Martin J

    2015-01-01

    For addressees to respond in a timely fashion, they cannot simply process the speaker's utterance as it occurs and wait till it finishes. Instead, they predict both when the speaker will conclude and what linguistic forms will be used. While doing this, they must also prepare their own response. To explain this, we draw on the account proposed by Pickering and Garrod (2013a), in which addressees covertly imitate the speaker's utterance and use this to determine the intention that underlies their upcoming utterance. They use this intention to predict when and how the utterance will end, and also to drive their own production mechanisms for preparing their response. Following Arnal and Giraud (2012), we distinguish between mechanisms that predict timing and content. In particular, we propose that the timing mechanism relies on entrainment of low-frequency oscillations between speech envelope and brain. This constrains the context that feeds into the determination of the speaker's intention and hence the timing and form of the upcoming utterance. This approach typically leads to well-timed contributions, but also provides a mechanism for resolving conflicts, for example when there is unintended speaker overlap.

  2. Using a physically-based transit time distribution function to estimate the hydraulic parameters and hydraulic transit times of an unconfined aquifer from tritium measurements

    NASA Astrophysics Data System (ADS)

    Farlin, Julien; Maloszewski, Piotr; Schneider, Wilfried; Gallé, Tom

    2014-05-01

    Groundwater transit time is of interest in environmental studies pertaining to the transport of pollutants from its source to the aquifer outlet (spring or pumping well) or to an observation well. Different models have been proposed to describe the distribution of transit times within groundwatersheds, the most common being the dispersion model, the exponential-piston-flow model (EPM) both proposed by Maloszewski and Zuber (Maloszewski and Zuber, 1982) and the (two or three parameter) gamma model (Amin and Campana, 1996; Kirchner et al., 1999). Choosing which function applies best is a recurrent and controversial problem in hydrogeology. The object of this study is to revisit the applicability of the EPM for unconfined aquifers, and to introduce an alternative model based explicitly on groundwater hydraulics. The alternative model is based on the transit time of water from any point at the groundwater table to the aquifer outlet, and is used to calculate inversely the hydraulic parameters of a fractured unconfined sandstone aquifer from tritium measurements made in a series of contact springs. This model is compared to the EPM, which is usually adopted to describe the transit time distribution of confined and unconfined aquifers alike. Both models are tested against observations, and it is shown that the EPM fails the test for some of the springs, and generally seems to overestimate the older water component. Amin, I. E., and M. E. Campana (1996), A general lumped parameter model for the interpretation of tracer data and transit time calculation in hydrologic systems, Journal of Hydrology, 179, 1-21, doi: 10.1016/0022-1694(95)02880-3. Kirchner, J. W., X. H. Feng, and C. Neal (1999), Fractal stream chemistry and its implications for contaminant transport in catchments, Nature physics, 403, 524-527, doi: 10.1038/35000537. Maloszewski, P., and A. Zuber (1982), Determining the turnover time of groundwater systems with the aid of environmental tracers, Journal of

  3. [Synchonization of the blood flow rate in arterial with the changing rate of space of blood pressure with time].

    PubMed

    Zhang, Shenghua; Qin, Renjia

    2012-10-01

    In physiology-related books, there are many relationship curves about blood flow rate in arteries and blood pressure changes with time, but there are not much explanation about such relationship. This is the very the question that the present article tries to answer. We clarified the relations between blood flow rate and blood pressure gradient using the experimental curves as the basis, using Poiseuille Law and relative knowledge of phisics and mathematics, and using analysis and reasoning. Based on the study, it can be concluded that in every course of cardiac cycle, the blood flow rate of any section in artery blood vessel is roughly synchronized with changing rate of space and time of the blood pressure, but blood flow rate is not synchronized with blood pressure.

  4. TTVFast: An efficient and accurate code for transit timing inversion problems

    SciTech Connect

    Deck, Katherine M.; Agol, Eric; Holman, Matthew J.; Nesvorný, David

    2014-06-01

    Transit timing variations (TTVs) have proven to be a powerful technique for confirming Kepler planet candidates, for detecting non-transiting planets, and for constraining the masses and orbital elements of multi-planet systems. These TTV applications often require the numerical integration of orbits for computation of transit times (as well as impact parameters and durations); frequently tens of millions to billions of simulations are required when running statistical analyses of the planetary system properties. We have created a fast code for transit timing computation, TTVFast, which uses a symplectic integrator with a Keplerian interpolator for the calculation of transit times. The speed comes at the expense of accuracy in the calculated times, but the accuracy lost is largely unnecessary, as transit times do not need to be calculated to accuracies significantly smaller than the measurement uncertainties on the times. The time step can be tuned to give sufficient precision for any particular system. We find a speed-up of at least an order of magnitude relative to dynamical integrations with high precision using a Bulirsch-Stoer integrator.

  5. TTVFast: An Efficient and Accurate Code for Transit Timing Inversion Problems

    NASA Astrophysics Data System (ADS)

    Deck, Katherine M.; Agol, Eric; Holman, Matthew J.; Nesvorný, David

    2014-06-01

    Transit timing variations (TTVs) have proven to be a powerful technique for confirming Kepler planet candidates, for detecting non-transiting planets, and for constraining the masses and orbital elements of multi-planet systems. These TTV applications often require the numerical integration of orbits for computation of transit times (as well as impact parameters and durations); frequently tens of millions to billions of simulations are required when running statistical analyses of the planetary system properties. We have created a fast code for transit timing computation, TTVFast, which uses a symplectic integrator with a Keplerian interpolator for the calculation of transit times. The speed comes at the expense of accuracy in the calculated times, but the accuracy lost is largely unnecessary, as transit times do not need to be calculated to accuracies significantly smaller than the measurement uncertainties on the times. The time step can be tuned to give sufficient precision for any particular system. We find a speed-up of at least an order of magnitude relative to dynamical integrations with high precision using a Bulirsch-Stoer integrator.

  6. Methods for Detecting Early Warnings of Critical Transitions in Time Series Illustrated Using Simulated Ecological Data

    PubMed Central

    Dakos, Vasilis; Carpenter, Stephen R.; Brock, William A.; Ellison, Aaron M.; Guttal, Vishwesha; Ives, Anthony R.; Kéfi, Sonia; Livina, Valerie; Seekell, David A.; van Nes, Egbert H.; Scheffer, Marten

    2012-01-01

    Many dynamical systems, including lakes, organisms, ocean circulation patterns, or financial markets, are now thought to have tipping points where critical transitions to a contrasting state can happen. Because critical transitions can occur unexpectedly and are difficult to manage, there is a need for methods that can be used to identify when a critical transition is approaching. Recent theory shows that we can identify the proximity of a system to a critical transition using a variety of so-called ‘early warning signals’, and successful empirical examples suggest a potential for practical applicability. However, while the range of proposed methods for predicting critical transitions is rapidly expanding, opinions on their practical use differ widely, and there is no comparative study that tests the limitations of the different methods to identify approaching critical transitions using time-series data. Here, we summarize a range of currently available early warning methods and apply them to two simulated time series that are typical of systems undergoing a critical transition. In addition to a methodological guide, our work offers a practical toolbox that may be used in a wide range of fields to help detect early warning signals of critical transitions in time series data. PMID:22815897

  7. Studies in Transition and Time Varying Turbulent Flows

    NASA Technical Reports Server (NTRS)

    Grosch, Chester E.

    2004-01-01

    The research focused on two areas: (a) the dynamics of forced turbulent flows and (b) time filtered Large Eddy Simulations (TLES). The dynamics of turbulent flows arising from external forcing of the turbulence are poorly understood. In particular, here are many unanswered questions relating the basic dynamical balances and the existence or nonexistence of statistical equilibrium of forced turbulent flows. The research used direct numerical simulations to explore these questions. The properties of the temporally filtered Navier-Stokes equations were also studied.

  8. FAST INVERSION METHOD FOR DETERMINATION OF PLANETARY PARAMETERS FROM TRANSIT TIMING VARIATIONS

    SciTech Connect

    Nesvorny, David; Beauge, Cristian

    2010-01-20

    The transit timing variation (TTV) method relies on monitoring changes in timing of transits of known exoplanets. Non-transiting planets in the system can be inferred from TTVs by their gravitational interaction with the transiting planet. The TTV method is sensitive to low-mass planets that cannot be detected by other means. Here we describe a fast algorithm that can be used to determine the mass and orbit of the non-transiting planets from the TTV data. We apply our code, ttvim.f, to a wide variety of planetary systems to test the uniqueness of the TTV inversion problem and its dependence on the precision of TTV observations. We find that planetary parameters, including the mass and mutual orbital inclination of planets, can be determined from the TTV data sets that should become available in near future. Unlike the radial velocity technique, the TTV method can therefore be used to characterize the inclination distribution of multi-planet systems.

  9. Time-course of ventilation, arterial and pulmonary CO(2) tension during CO (2) increase in humans.

    PubMed

    Satoh, Toru; Okada, Yasumasa; Hara, Yasushi; Sakamaki, Fumio; Kyotani, Shingo; Tomita, Takeshi; Nagaya, Noritoshi; Nakanishi, Norifumi

    2012-01-01

    A change of ventilation (VE), PaCO( 2 ) (arterial CO( 2 ) tension) and PvCO( 2 ) (pulmonary arterial CO( 2 ) tension) with time was not evaluated precisely during exercise or CO( 2 ) rebreathing in humans. In this study, changes of these variables with time were fitted to exponential curves {y = Exp ( x/ T + A ) + k} and compared. When exercise pulmonary hemodynamics was examined in 15 cardiac patients to decide therapies, we asked the patients to undergo CO( 2 ) rebreathing using air with supplementation of consumed O( 2 ). Arterial and pulmonary blood was drawn every minute. During exercise, T was 28.2 ± 8.4 and 26.8 ± 12.4, and A was 0.80 ± 0.50 and 0.50 ± 0.90 in VE and PvCO( 2 ), respectively, with no statistical differences. During CO( 2 ) rebreathing, T was 18.6 ± 5.8, 41.8 ± 38.0 and 21.6 ± 9.7 and A was 0.39 ± 0.67, 1.64 ± 1.35 and 0.17 ± 0.83 in VE, PaCO( 2 ) and PvCO( 2 ), respectively, with statistical difference of PaCO( 2 ) from other variables, suggesting that VE and PvCO( 2 ) showed same mode of change according to time but PaCO( 2 ) did not.

  10. Scintigraphic determination of small intestinal transit time: Comparison with the hydrogen breath technique

    SciTech Connect

    Caride, V.J.; Prokop, E.K.; Troncale, F.J.; Buddoura, W.; Winchenbach, K.; McCallum, R.W.

    1984-04-01

    The hydrogen breath test was used as a standard against which a scintigraphic method for determination of small intestinal transit time was evaluated and compared. A total of 19 male volunteers ranging in age from 23 to 28 yr participated in the study. The subjects ingested an isosmotic lactulose solution containing /sup 99m/technetium-diethylenetriaminepentaacetic acid (Sn) and then remained supine under a large field of view gamma-camera that interfaced with a computer system. Data were visually analyzed and then quantified to determine gastric emptying and small intestinal transit time. The small intestinal transit time ranged from 31 to 139 min with the scintigraphic method and 30 to 190 min with the hydrogen breath test (r . 0.77). The mean small intestinal transit time for 20 individual determinations with the scintigraphic method, 73.0 +/- 6.5 min (mean +/- SEM), was similar to the results from the hydrogen breath test technique, 75.1 +/- 8.3 min. Thirteen volunteers underwent two studies with the scintigraphic method separated by intervals ranging from 2 days to 8 wk. Individual variations in small intestinal transit time were significantly correlated with individual variations in gastric emptying (p less than 0.05). We conclude that the scintigraphic method allows accurate determination of gastrocecal time and is a noninvasive technique which may be a useful clinical test for small intestinal transit time as well as for providing information on the pathophysiology and pharmacology of intestinal motility.

  11. Using Dielectric Relaxation Spectroscopy to Characterize the Glass Transition Time of Polydextrose.

    PubMed

    Buehler, Martin G; Kindle, Michael L; Carter, Brady P

    2015-06-01

    Dielectric relaxation spectroscopy was used to characterize the glass transition time, tg , of polydextrose, where the glass transition temperature, Tg , and water activity, aw (relative humidity), were held constant during polydextrose relaxation. The tg was determined from a shift in the peak frequency of the imaginary capacitance spectrum with time. It was found that when the peak frequency reaches 30 mHz, polydextrose undergoes glass transition. Glass transition time, tg , is the time for polydextrose to undergo glass transition at a specific Tg and aw . Results lead to a modified state diagram, where Tg is depressed with increasing aw . This curve forms a boundary: (a) below the boundary, polydextrose does not undergo glass transition and (b) above the boundary, polydextrose rapidly undergoes glass transition. As the boundary curve is specified by a tg value, it can assist in the selection of storage conditions. An important point on the boundary curve is at aw = 0, where Tg0 = 115 °C. The methodology can also be used to calculate the stress-relaxation viscosity of polydextrose as a function of Tg and aw , which is important when characterizing the flow properties of polydextrose initially in powder form.

  12. Transit Timing Observations from Kepler: VII. Potentially interesting candidate systems from Fourier-based statistical tests

    SciTech Connect

    Steffen, Jason H.; Ford, Eric B.; Rowe, Jason F.; Fabrycky, Daniel C.; Holman, Matthew J.; Welsh, William F.; Borucki, William J.; Batalha, Natalie M.; Bryson, Steve; Caldwell, Douglas A.; Ciardi, David R.; /Caltech /NASA, Ames /SETI Inst., Mtn. View

    2012-01-01

    We analyze the deviations of transit times from a linear ephemeris for the Kepler Objects of Interest (KOI) through Quarter six (Q6) of science data. We conduct two statistical tests for all KOIs and a related statistical test for all pairs of KOIs in multi-transiting systems. These tests identify several systems which show potentially interesting transit timing variations (TTVs). Strong TTV systems have been valuable for the confirmation of planets and their mass measurements. Many of the systems identified in this study should prove fruitful for detailed TTV studies.

  13. VizieR Online Data Catalog: 4 Kepler systems transit timing observations (Steffen+, 2012)

    NASA Astrophysics Data System (ADS)

    Steffen, J. H.; Fabrycky, D. C.; Ford, E. B.; Carter, J. A.; Desert, J.-M.; Fressin, F.; Holman, M. J.; Lissauer, J. J.; Moorhead, A. V.; Rowe, J. F.; Ragozzine, D.; Welsh, W. F.; Batalha, N. M.; Borucki, W. J.; Buchhave, L. A.; Bryson, S.; Caldwell, D. A.; Charbonneau, D.; Ciardi, D. R.; Cochran, W. D.; Endl, M.; Everett, M. E.; Gautier, T. N., III; Gilliland, R. L.; Girouard, F. R.; Jenkins, J. M.; Horch, E.; Howell, S. B.; Isaacson, H.; Klaus, T. C.; Koch, D. G.; Latham, D. W.; Li, J.; Lucas, P.; MacQueen, P. J.; Marcy, G. W.; McCauliff, S.; Middour, C. K.; Morris, R. L.; Mullally, F. R.; Quinn, S. N.; Quintana, E. V.; Shporer, A.; Still, M.; Tenenbaum, P.; Thompson, S. E.; Twicken, J. D.; van Cleve, J.

    2013-03-01

    We present a method to confirm the planetary nature of objects in systems with multiple transiting exoplanet candidates. This method involves a Fourier-domain analysis of the deviations in the transit times from a constant period that result from dynamical interactions within the system. The combination of observed anticorrelations in the transit times and mass constraints from dynamical stability allow us to claim the discovery of four planetary systems, Kepler-25, Kepler-26, Kepler-27 and Kepler-28, containing eight planets and one additional planet candidate. (4 data files).

  14. TRANSIT TIMING OBSERVATIONS FROM KEPLER. VI. POTENTIALLY INTERESTING CANDIDATE SYSTEMS FROM FOURIER-BASED STATISTICAL TESTS

    SciTech Connect

    Steffen, Jason H.; Ford, Eric B.; Rowe, Jason F.; Borucki, William J.; Bryson, Steve; Caldwell, Douglas A.; Jenkins, Jon M.; Koch, David G.; Sanderfer, Dwight T.; Seader, Shawn; Twicken, Joseph D.; Fabrycky, Daniel C.; Welsh, William F.; Batalha, Natalie M.; Ciardi, David R.; Prsa, Andrej

    2012-09-10

    We analyze the deviations of transit times from a linear ephemeris for the Kepler Objects of Interest (KOI) through quarter six of science data. We conduct two statistical tests for all KOIs and a related statistical test for all pairs of KOIs in multi-transiting systems. These tests identify several systems which show potentially interesting transit timing variations (TTVs). Strong TTV systems have been valuable for the confirmation of planets and their mass measurements. Many of the systems identified in this study should prove fruitful for detailed TTV studies.

  15. Scintigraphic Small Intestinal Transit Time and Defaecography in Patients with J-Pouch.

    PubMed

    Kjaer, Mie Dilling; Simonsen, Jane Angel; Hvidsten, Svend; Kjeldsen, Jens; Gerke, Oke; Qvist, Niels

    2015-10-10

    Objective methods for examination of pouch function are warranted for a better understanding of the functional result and treatment of dysfunction. The objective of this study was to evaluate the results of scintigraphic intestinal transit time and defaecography compared to the results of pouch function, mucosal condition and a questionnaire on quality of life (QoL). This cross-sectional study included 21 patients. Scintigraphic transit time and defaecography was determined with the use of Tc-99m. Pouch function was assessed by number of bowel movements, pouch volume, and continence. Pouch mucosal condition was evaluated by endoscopy and histology. Median transit time was 189 min (105-365). Median ejection fraction at defaecography (EF) was 49% (3-77) and 62% (17-98) after first and second defecation. Median pouch volume was 223 mL (100-360). A median daily stool frequency of nine (4-25) was reported and three (14%) patients suffered from daytime incontinence. No patients had symptomatic or endoscopic pouchitis; however, the histology showed unspecific inflammation in 19 (90%) patients. There was no correlation between transit time, evacuation fraction (EF) and pouch function in univariate analysis. However, we found a high body mass index (BMI) and a low bowel movement frequency to be associated with a longer transit time by multivariate analysis. Scintigraphic determination of transit time and defaecography are feasible methods in patients with ileal pouch anal anastomosis, but the clinical relevance is yet doubtful.

  16. Scintigraphic Small Intestinal Transit Time and Defaecography in Patients with J-Pouch

    PubMed Central

    Kjaer, Mie Dilling; Simonsen, Jane Angel; Hvidsten, Svend; Kjeldsen, Jens; Gerke, Oke; Qvist, Niels

    2015-01-01

    Objective methods for examination of pouch function are warranted for a better understanding of the functional result and treatment of dysfunction. The objective of this study was to evaluate the results of scintigraphic intestinal transit time and defaecography compared to the results of pouch function, mucosal condition and a questionnaire on quality of life (QoL). This cross-sectional study included 21 patients. Scintigraphic transit time and defaecography was determined with the use of Tc-99m. Pouch function was assessed by number of bowel movements, pouch volume, and continence. Pouch mucosal condition was evaluated by endoscopy and histology. Median transit time was 189 min (105–365). Median ejection fraction at defaecography (EF) was 49% (3–77) and 62% (17–98) after first and second defecation. Median pouch volume was 223 mL (100–360). A median daily stool frequency of nine (4–25) was reported and three (14%) patients suffered from daytime incontinence. No patients had symptomatic or endoscopic pouchitis; however, the histology showed unspecific inflammation in 19 (90%) patients. There was no correlation between transit time, evacuation fraction (EF) and pouch function in univariate analysis. However, we found a high body mass index (BMI) and a low bowel movement frequency to be associated with a longer transit time by multivariate analysis. Scintigraphic determination of transit time and defaecography are feasible methods in patients with ileal pouch anal anastomosis, but the clinical relevance is yet doubtful. PMID:26854162

  17. Effects of alpha-glucosidase inhibitors on mouth to caecum transit time in humans.

    PubMed

    Ladas, S D; Frydas, A; Papadopoulos, A; Raptis, S A

    1992-09-01

    The alpha-glucosidase inhibitors acarbose and miglitol have been successfully used to control postprandial hyperglycaemia in diabetics. They probably work by slowing carbohydrate digestion and absorption, but their effect on mouth to caecum transit time has not been studied. The effect acarbose (100 mg), miglitol (100 mg), and placebo on mouth to caecum transit time (380 kcal breakfast with 20 g of lactulose) was investigated in 18 normal volunteers using breath hydrogen analysis. Both miglitol and acarbose significantly increased breath hydrogen excretion (F2,34 = 6.31, p = 0.005) and shortened the mouth to caecum transit time (F2,34 = 3.49, p = 0.04) after breakfast compared with placebo. There was a significant negative correlation between breath hydrogen excretion and mouth to caecum transit time suggesting that with shorter transit times significantly more carbohydrates were spilled into the colon. These results indicate that alpha-glucosidase inhibitors accelerate mouth to caecum transit time by inducing carbohydrate malabsorption.

  18. Quantitative measurement of blood flow in paediatric brain tumours—a comparative study of dynamic susceptibility contrast and multi time-point arterial spin labelled MRI

    PubMed Central

    Abernethy, Laurence; Pizer, Barry; Avula, Shivaram; Parkes, Laura M

    2016-01-01

    Objective: Arterial spin-labelling (ASL) MRI uses intrinsic blood water to quantify the cerebral blood flow (CBF), removing the need for the injection of a gadolinium-based contrast agent used for conventional perfusion imaging such as dynamic susceptibility contrast (DSC). Owing to the non-invasive nature of the technique, ASL is an attractive option for use in paediatric patients. This work compared DSC and multi-timepoint ASL measures of CBF in paediatric brain tumours. Methods: Patients (n = 23; 20 low-grade tumours and 3 high-grade tumours) had DSC and multi-timepoint ASL with and without vascular crushers (VC). VC removes the contribution from larger vessel blood flow. Mean perfusion metrics were extracted from control and T1-enhanced tumour regions of interest (ROIs): arterial arrival time (AAT) and CBF from the ASL images with and without VC, relative cerebral blood flow (rCBF), relative cerebral blood volume, delay time (DT) and mean transit time (MTT) from the DSC images. Results: Significant correlations existed for: AAT and DT (r = 0.77, p = 0.0002) and CBF and rCBF (r = 0.56, p = 0.02) in control ROIs for ASL-noVC. No significant correlations existed between DSC and ASL measures in the tumour region. Significant differences between control and tumour ROI were found for MTT (p < 0.001) and rCBF (p < 0.005) measures. Conclusion: Significant correlations between ASL-noVC and DSC measures in the normal brain suggest that DSC is most sensitive to macrovascular blood flow. The absence of significant correlations within the tumour ROI suggests that ASL is sensitive to different physiological mechanisms compared with DSC measures. Advances in knowledge: ASL provides information which is comparable with that of DSC in healthy tissues, but appears to reflect a different physiology in tumour tissues. PMID:26975495

  19. TRANSIT TIMING OBSERVATIONS FROM KEPLER. I. STATISTICAL ANALYSIS OF THE FIRST FOUR MONTHS

    SciTech Connect

    Ford, Eric B.; Rowe, Jason F.; Caldwell, Douglas A.; Jenkins, Jon M.; Li Jie; Fabrycky, Daniel C.; Lissauer, Jack J.; Borucki, William J.; Bryson, Steve; Koch, David G.; Steffen, Jason H.; Batalha, Natalie M.; Dunham, Edward W.; Gautier, Thomas N.; Marcy, Geoffrey W.; McCauliff, Sean

    2011-11-01

    The architectures of multiple planet systems can provide valuable constraints on models of planet formation, including orbital migration, and excitation of orbital eccentricities and inclinations. NASA's Kepler mission has identified 1235 transiting planet candidates. The method of transit timing variations (TTVs) has already confirmed seven planets in two planetary systems. We perform a transit timing analysis of the Kepler planet candidates. We find that at least {approx}11% of planet candidates currently suitable for TTV analysis show evidence suggestive of TTVs, representing at least {approx}65 TTV candidates. In all cases, the time span of observations must increase for TTVs to provide strong constraints on planet masses and/or orbits, as expected based on N-body integrations of multiple transiting planet candidate systems (assuming circular and coplanar orbits). We find the fraction of planet candidates showing TTVs in this data set does not vary significantly with the number of transiting planet candidates per star, suggesting significant mutual inclinations and that many stars with a single transiting planet should host additional non-transiting planets. We anticipate that Kepler could confirm (or reject) at least {approx}12 systems with multiple transiting planet candidates via TTVs. Thus, TTVs will provide a powerful tool for confirming transiting planets and characterizing the orbital dynamics of low-mass planets. If Kepler observations were extended to at least seven years, then TTVs would provide much more precise constraints on the dynamics of systems with multiple transiting planets and would become sensitive to planets with orbital periods extending into the habitable zone of solar-type stars.

  20. Alterations of calf venous and arterial compliance following acclimation to heat administered at a fixed daily time in humans

    NASA Astrophysics Data System (ADS)

    Maruyama, Megumi; Hara, Toshiko; Hashimoto, Michio; Koga, Miki; Shido, Osamu

    2006-05-01

    We investigated the effects of heat acclimation on venous and arterial compliance in humans. Four male and four female volunteers were exposed to an ambient temperature of 40°C and relative humidity of 40% for 4 h (1330 1730 hours) per day for 9 10 consecutive days. The calf venous compliance (CV) was estimated using venous occlusion plethysmography with a mercury-in-silastic strain gauge placed around the right calf at its maximum girth. The compliance of the small (CSA) and large (CLA) arteries were assessed by reflective and capacitance compliance by analyzing the radial artery blood pressure waveforms, basing on the use of a modified Windkessel model. The calf CV, CSA, CLA, systolic and diastolic blood pressures, heart rate and core temperature were determined twice a day, 0930 1100 hours (AM test) and 1500 1630 hours (PM test), in both heat-acclimated and non-heat-acclimated (control) conditions. Heat acclimation appeared to decrease blood pressures, heart rate and significantly lowered core temperature only in the PM test. In the control condition, the calf CV was not affected by the time of day and the CSA was significantly depressed in the PM test. After acclimation to heat, the calf CV significantly increased and the CSA did not decrease in the PM test. The results presented suggest that repeated heat exposure in humans, for 4 h at a fixed time daily, increases the calf CV and the CSA particularly during the period when the subjects were previously exposed to heat.

  1. Timing of the maturation transition in haddock Melanogrammus aeglefinus.

    PubMed

    Tobin, D; Wright, P J; O'Sullivan, M

    2010-10-01

    The timing of maturation in haddock Melanogrammus aeglefinus was examined using changes in gonad development, follicle stimulating hormone β (FSH-β) transcript expression profile, growth and condition of 1 year old females held under a common environment between the summer and winter solstices. The circumnuclear ring, cortical alveolus and vitellogenic oocyte stages were first observed in August, October and November, respectively. FSH-β transcript levels did not change significantly until September but increased markedly thereafter in maturing fish. A combined analysis of the mean oocyte diameter of the leading cohort, histological staging and FSH-β transcript profile provided evidence of a commitment to maturation by October or November. Contrary to that previously proposed for gadoid species, histological analysis of field-caught immature M. aeglefinus during the spawning season indicated that cortical alveolar, rather than circumnuclear ring, stage oocytes provided definitive evidence of maturation. A decrease in relative liver size following the summer solstice suggested a possible link between energy status and maturation.

  2. Chronic Obstructive Pulmonary Disease Subtypes. Transitions over Time

    PubMed Central

    Esteban, Cristóbal; Arostegui, Inmaculada; Aburto, Myriam; Moraza, Javier; Quintana, José M.; García-Loizaga, Amaia; Basualdo, Luis V.; Aramburu, Amaia; Aizpiri, Susana; Uranga, Ane; Capelastegui, Alberto

    2016-01-01

    Background Although subtypes of chronic obstructive pulmonary disease are recognized, it is unknown what happens to these subtypes over time. Our objectives were to assess the stability of cluster-based subtypes in patients with stable disease and explore changes in clusters over 1 year. Methods Multiple correspondence and cluster analysis were used to evaluate data collected from 543 stable patients included consecutively from 5 respiratory outpatient clinics. Results Four subtypes were identified. Three of them, A, B, and C, had marked respiratory profiles with a continuum in severity of several variables, while the fourth, subtype D, had a more systemic profile with intermediate respiratory disease severity. Subtype A was associated with less dyspnea, better health-related quality of life and lower Charlson comorbidity scores, and subtype C with the most severe dyspnea, and poorer pulmonary function and quality of life, while subtype B was between subtypes A and C. Subtype D had higher rates of hospitalization the previous year, and comorbidities. After 1 year, all clusters remained stable. Generally, patients continued in the same subtype but 28% migrated to another cluster. Together with movement across clusters, patients showed changes in certain characteristics (especially exercise capacity, some variables of pulmonary function and physical activity) and changes in outcomes (quality of life, hospitalization and mortality) depending on the new cluster they belonged to. Conclusions Chronic obstructive pulmonary disease clusters remained stable over 1 year. Most patients stayed in their initial subtype cluster, but some moved to another subtype and accordingly had different outcomes. PMID:27611911

  3. The effect of conjunctions on the transit timing variations of exoplanets

    SciTech Connect

    Nesvorný, David; Vokrouhlický, David E-mail: vokrouhl@cesnet.cz

    2014-07-20

    We develop an analytic model for transit timing variations produced by orbital conjunctions between gravitationally interacting planets. If the planetary orbits have tight orbital spacing, which is a common case among the Kepler planets, the effect of a single conjunction can be best described as: (1) a step-like change of the transit timing ephemeris with subsequent transits of the inner planet being delayed and those of the outer planet being sped up, and (2) a discrete change in sampling of the underlying oscillations from eccentricity-related interaction terms. In the limit of small orbital eccentricities, our analytic model gives explicit equations for these effects as a function of the mass and orbital separation of planets. We point out that a detection of the conjunction effect in real data is of crucial importance for the physical characterization of planetary systems from transit timing variations.

  4. Landau level transitions in doped graphene in a time dependent magnetic field

    NASA Astrophysics Data System (ADS)

    Ardenghi, J. S.; Bechthold, P.; Jasen, P.; Gonzalez, E.; Nagel, O.

    2013-10-01

    The aim of this work is to describe the Landau level transitions of Bloch electrons in doped graphene with an arbitrary time dependent magnetic field in the long wavelength approximation. In particular, transitions from the m Landau level to the m±1 and m±2 Landau levels are studied using the time dependent perturbation theory. Time intervals are computed in which transition probabilities tend to zero at a low order in the coupling constant. In particular, Landau level transitions are studied in the case of Bloch electrons traveling in the direction of the applied magnetic force and the results are compared with classical and revival periods of electrical current in graphene. Finally, current probabilities are computed for the n=0 and n=1 Landau levels showing expected oscillating behavior with modified cyclotron frequency.

  5. THE IMPACT OF CIRCUMPLANTARY JETS ON TRANSIT SPECTRA AND TIMING OFFSETS FOR HOT JUPITERS

    SciTech Connect

    Dobbs-Dixon, Ian; Agol, Eric; Burrows, Adam

    2012-06-01

    We present theoretical wavelength-dependent transit light curves for the giant planet HD 209458b based on a number of state-of-the-art three-dimensional radiative hydrodynamical models. By varying the kinematic viscosity in the model, we calculate observable signatures associated with the emergence of a super-rotating circumplanetary jet that strengthens with decreased viscosity. We obtain excellent agreement between our mid-transit transit spectra and existing data from Hubble and Spitzer, finding the best fit for intermediate values of viscosity. We further exploit dynamically driven differences between eastern and western hemispheres to extract the spectral signal imparted by a circumplanetary jet. We predict that (1) the transit depth should decrease as the jet becomes stronger; (2) the measured transit times should show timing offsets of up to 6 s at wavelengths with higher opacity, which increases with jet strength; (3) wavelength-dependent differences between ingress and egress spectra increase with jet strength; and (4) the color-dependent transit shape should exhibit stronger asymmetry for planets with stronger jets. These techniques and trends should be valid for other hot Jupiters as well. Observations of transit timing offsets may be accessible with current instrumentation, though the other predictions may require the capabilities of the James Webb Space Telescope and other future missions. Hydrodynamical models utilized solve the three-dimensional Navier-Stokes equations together with decoupled thermal and radiative energy equations and wavelength-dependent stellar heating.

  6. Transit Timing Variations as a Tool for the Bayesian Characterization of Exoplanets

    NASA Astrophysics Data System (ADS)

    Ford, Eric B.; Jontof-Hutter, Daniel; Dawson, Rebekah; Fabrycky, Daniel; Mills, Sean; Ragozzine, Darin; Rogers, Leslie Anne; Shabram, Megan

    2015-08-01

    NASA's Kepler mission has revolutionized time-domain photometry with its photometric precision, high duty cycle, and long observing baseline. In addition to discovering thousands of planet candidates that pass in front of their host star, Kepler's has enabled the precise measurement of transit timing variations (TTV), deviations of transit times from a Keplerian ephemeris due to gravitational interactions among planets (or more massive bodies in the same planetary system). For dozens of planets, TTVs enable the precise characterization of planet masses and orbits, including many planets for which characterization via Doppler observations is impractical.For example, TTVs have: 1) characterized of masses of planets in systems with 2-6 transiting exoplanets, 2) measured densities for low-mass, low-density mass planets that orbit stars with periods of ~50-200 days, and provided precise measurements of orbital eccentricities even in the challenging regime of e<0.1. In addition to characterizing properties of individual planets, analysing the transit times for populations of transiting planets (including those for which no deviations from Keplerian orbits are detected) enable the characterization of the exoplanet distribution function.In both cases, attention to details of the statistical model and computational methods are essential for drawing robust conclusions. I will present selected TTV success stories, describing how these studies dealt with various statistical and computational challenges. Finally, I will describe opportunities for further improvements in the statistical analyses of transit timing variations and the potential science return.

  7. Daylight saving time transitions and hospital treatments due to accidents or manic episodes

    PubMed Central

    Lahti, Tuuli A; Haukka, Jari; Lönnqvist, Jouko; Partonen, Timo

    2008-01-01

    Background Daylight saving time affects millions of people annually but its impacts are still widely unknown. Sleep deprivation and the change of circadian rhythm can trigger mental illness and cause higher accident rates. Transitions into and out of daylight saving time changes the circadian rhythm and may cause sleep deprivation. Thus it seems plausible that the prevalence of accidents and/or manic episodes may be higher after transition into and out of daylight saving time. The aim of this study was to explore the effects of transitions into and out of daylight saving time on the incidence of accidents and manic episodes in the Finnish population during the years of 1987 to 2003. Methods The nationwide data were derived from the Finnish Hospital Discharge Register. From the register we obtained the information about the hospital-treated accidents and manic episodes during two weeks before and two weeks after the transitions in 1987–2003. Results The results were negative, as the transitions into or out of daylight saving time had no significant effect on the incidence of accidents or manic episodes. Conclusion One-hour transitions do not increase the incidence of manic episodes or accidents which require hospital treatment. PMID:18302734

  8. Transition.

    ERIC Educational Resources Information Center

    Thompson, Sandy, Ed.; And Others

    1990-01-01

    This "feature issue" focuses on transition from school to adult life for persons with disabilities. Included are "success stories," brief program descriptions, and a list of resources. Individual articles include the following titles and authors: "Transition: An Energizing Concept" (Paul Bates); "Transition…

  9. Exploring business process modelling paradigms and design-time to run-time transitions

    NASA Astrophysics Data System (ADS)

    Caron, Filip; Vanthienen, Jan

    2016-09-01

    The business process management literature describes a multitude of approaches (e.g. imperative, declarative or event-driven) that each result in a different mix of process flexibility, compliance, effectiveness and efficiency. Although the use of a single approach over the process lifecycle is often assumed, transitions between approaches at different phases in the process lifecycle may also be considered. This article explores several business process strategies by analysing the approaches at different phases in the process lifecycle as well as the various transitions.

  10. Transit times and age distributions for reservoir models represented as nonlinear non-autonomuous systems

    NASA Astrophysics Data System (ADS)

    Müller, Markus; Meztler, Holger; Glatt, Anna; Sierra, Carlos

    2016-04-01

    We present theoretical methods to compute dynamic residence and transit time distributions for non-autonomous systems of pools governed by coupled nonlinear differential equations. Although transit time and age distributions have been used to describe reservoir models for a long time, a closer look to their assumptions reveals two major restrictions of generality in previous studies. First, the systems are assumed to be in equilibrium; and second, the equations under consideration are assumed to be linear. While both these assumptions greatly ease the computation and interpretation of transit time and age distributions they are not applicable to a wide range of problems. Moreover, the transfer of previous results learned from linear systems in steady state to the more complex nonlinear non-autonomous systems that do not even need to have equilibria, can be dangerously misleading. Fortunately the topic of time dependent age and transit time distributions has received some attention recently in hydrology, we aim to compute these distributions for systems of multiple reservoirs. We will discuss how storage selection functions can augment the information represented in an ODE system describing a system of reservoirs. We will present analytical and numerical algorithms and a Monte Carlo simulator to compute solutions for system transit time and age distributions for system-wide storage selection functions including the most simple, but important case of well mixed pools.

  11. A multivariate time-frequency method to characterize the influence of respiration over heart period and arterial pressure

    NASA Astrophysics Data System (ADS)

    Orini, Michele; Bailón, Raquel; Laguna, Pablo; Mainardi, Luca T.; Barbieri, Riccardo

    2012-12-01

    Respiratory activity introduces oscillations both in arterial pressure and heart period, through mechanical and autonomic mechanisms. Respiration, arterial pressure, and heart period are, generally, non-stationary processes and the interactions between them are dynamic. In this study we present a methodology to robustly estimate the time course of cross spectral indices to characterize dynamic interactions between respiratory oscillations of heart period and blood pressure, as well as their interactions with respiratory activity. Time-frequency distributions belonging to Cohen's class are used to estimate time-frequency (TF) representations of coherence, partial coherence and phase difference. The characterization is based on the estimation of the time course of cross spectral indices estimated in specific TF regions around the respiratory frequency. We used this methodology to describe the interactions between respiration, heart period variability (HPV) and systolic arterial pressure variability (SAPV) during tilt table test with both spontaneous and controlled respiratory patterns. The effect of selective autonomic blockade was also studied. Results suggest the presence of common underling mechanisms of regulation between cardiovascular signals, whose interactions are time-varying. SAPV changes followed respiratory flow both in supine and standing positions and even after selective autonomic blockade. During head-up tilt, phase differences between respiration and SAPV increased. Phase differences between respiration and HPV were comparable to those between respiration and SAPV during supine position, and significantly increased during standing. As a result, respiratory oscillations in SAPV preceded respiratory oscillations in HPV during standing. Partial coherence was the most sensitive index to orthostatic stress. Phase difference estimates were consistent among spontaneous and controlled breathing patterns, whereas coherence was higher in spontaneous breathing

  12. Finite-time quantum-to-classical transition for a Schroedinger-cat state

    SciTech Connect

    Paavola, Janika; Hall, Michael J. W.; Paris, Matteo G. A.; Maniscalco, Sabrina

    2011-07-15

    The transition from quantum to classical, in the case of a quantum harmonic oscillator, is typically identified with the transition from a quantum superposition of macroscopically distinguishable states, such as the Schroedinger-cat state, into the corresponding statistical mixture. This transition is commonly characterized by the asymptotic loss of the interference term in the Wigner representation of the cat state. In this paper we show that the quantum-to-classical transition has different dynamical features depending on the measure for nonclassicality used. Measures based on an operatorial definition have well-defined physical meaning and allow a deeper understanding of the quantum-to-classical transition. Our analysis shows that, for most nonclassicality measures, the Schroedinger-cat state becomes classical after a finite time. Moreover, our results challenge the prevailing idea that more macroscopic states are more susceptible to decoherence in the sense that the transition from quantum to classical occurs faster. Since nonclassicality is a prerequisite for entanglement generation our results also bridge the gap between decoherence, which is lost only asymptotically, and entanglement, which may show a ''sudden death''. In fact, whereas the loss of coherences still remains asymptotic, we emphasize that the transition from quantum to classical can indeed occur at a finite time.

  13. The detection and characterization of a nontransiting planet by transit timing variations.

    PubMed

    Nesvorný, David; Kipping, David M; Buchhave, Lars A; Bakos, Gáspár Á; Hartman, Joel; Schmitt, Allan R

    2012-06-01

    The Kepler mission is monitoring the brightness of ~150,000 stars, searching for evidence of planetary transits. As part of the Hunt for Exomoons with Kepler (HEK) project, we report a planetary system with two confirmed planets and one candidate planet discovered with the publicly available data for KOI-872. Planet b transits the host star with a period P(b) = 33.6 days and exhibits large transit timing variations indicative of a perturber. Dynamical modeling uniquely detects an outer nontransiting planet c near the 5:3 resonance (P(c) = 57.0 days) with a mass 0.37 times that of Jupiter. Transits of a third planetary candidate are also found: a 1.7-Earth radius super-Earth with a 6.8-day period. Our analysis indicates a system with nearly coplanar and circular orbits, reminiscent of the orderly arrangement within the solar system.

  14. Attenuation of systolic blood pressure and pulse transit time hysteresis during exercise and recovery in cardiovascular patients.

    PubMed

    Liu, Qing; Yan, Bryan P; Yu, Cheuk-Man; Zhang, Yuan-Ting; Poon, Carmen C Y

    2014-02-01

    Pulse transit time (PTT) is a cardiovascular parameter of emerging interest due to its potential to estimate blood pressure (BP) continuously and without a cuff. Both linear and nonlinear equations have been used in the estimation of BP based on PTT. This study, however, demonstrates that there is a hysteresis phenomenon between BP and PTT during and after dynamic exercise. A total of 46 subjects including 16 healthy subjects, 13 subjects with one or more cardiovascular risk factors, and 17 patients with cardiovascular disease underwent graded exercise stress test. PTT was measured from electrocardiogram and photoplethysmogram of the left index finger of the subject, i.e., a pathway that includes predominately aorta, brachial, and radial arteries. The results of this study showed that, for the same systolic BP (SBP), PTT measured during exercise was significantly larger than PTT measured during recovery for all subject groups. This hysteresis was further quantified as both normalized area bounded by the SBP-PTT relationship (AreaN) and SBP difference at PTT during peak exercise plus 20 ms (ΔSBP20). Significant attenuation of both AreaN (p <; 0.05) and ΔSBP20 (p <; 0.01) is observed in cardiovascular patients compared with healthy subjects, independent of resting BP. Since the SBP-PTT relationship are determined by the mechanical properties of arterial wall, which is predominately mediated by the sympathetic nervous system through altered vascular smooth muscle (VSM) tone during exercise, results of this study are consistent with the previous findings of autonomic nervous dysfunction in cardiovascular patients. We further conclude that VSM tone has a nonnegligible influence on the BP-PTT relationship and thus should be considered in the PTT-based BP estimation.

  15. Transit times and mean ages for nonautonomous and autonomous compartmental systems

    SciTech Connect

    Rasmussen, Martin; Hastings, Alan; Smith, Matthew J.; Agusto, Folashade B.; Chen-Charpentier, Benito M.; Hoffman, Forrest M.; Jiang, Jiang; Todd-Brown, Katherine E. O.; Wang, Ying; Wang, Ying -Ping; Luo, Yiqi

    2016-04-01

    In this study, we develop a theory for transit times and mean ages for nonautonomous compartmental systems. Using the McKendrick–von Förster equation, we show that the mean ages of mass in a compartmental system satisfy a linear nonautonomous ordinary differential equation that is exponentially stable. We then define a nonautonomous version of transit time as the mean age of mass leaving the compartmental system at a particular time and show that our nonautonomous theory generalises the autonomous case. We apply these results to study a nine-dimensional nonautonomous compartmental system modeling the terrestrial carbon cycle, which is a modification of the Carnegie–Ames–Stanford approach model, and we demonstrate that the nonautonomous versions of transit time and mean age differ significantly from the autonomous quantities when calculated for that model.

  16. Transit times and mean ages for nonautonomous and autonomous compartmental systems

    DOE PAGES

    Rasmussen, Martin; Hastings, Alan; Smith, Matthew J.; ...

    2016-04-01

    In this study, we develop a theory for transit times and mean ages for nonautonomous compartmental systems. Using the McKendrick–von Förster equation, we show that the mean ages of mass in a compartmental system satisfy a linear nonautonomous ordinary differential equation that is exponentially stable. We then define a nonautonomous version of transit time as the mean age of mass leaving the compartmental system at a particular time and show that our nonautonomous theory generalises the autonomous case. We apply these results to study a nine-dimensional nonautonomous compartmental system modeling the terrestrial carbon cycle, which is a modification of themore » Carnegie–Ames–Stanford approach model, and we demonstrate that the nonautonomous versions of transit time and mean age differ significantly from the autonomous quantities when calculated for that model.« less

  17. The Ebb and Flow of Filipino First-Time Fatherhood Transition Space: A Grounded Theory Study.

    PubMed

    Villamor, Neil Jupiter E; de Guzman, Allan B; Matienzo, Evangeline T

    2016-11-01

    Fatherhood, as a developmental process, is both a human experience and a text that needs to be read. For developing nations like the Philippines, little is known about the process undergone by first-time fathers on their transition to fatherhood, and how nurses can play a significant role in assisting them. This grounded theory study purported to conceptualize the multifaceted process of transition from the lens of Filipino first-time fathers' lived experiences. A total of 20 first-time fathers from Metro Manila, Philippines, were purposively selected to take part in an individual, semistructured, and in-depth interview. The Glaserian (classical) method of analysis was specifically used, and field texts were inductively analyzed using a repertory grid. Member checking and correspondence were done to validate the findings of the study. Six surfacing stages emerged relative to the process of transition. Interestingly, The B.R.I.D.G.E. Theory of First-Time Fatherhood Transition Space describes how these fathers progress from the beholding, reorganizing, inhibiting, delivering, grasping, and embracing phases toward successful transition. This emerged theoretical model can be used in framing health care programs where the needs of fathers during this period are met and addressed. Finally, it can also be used in guiding nurses in their provision of a more empathetic care for first-time fathers.

  18. Timing of Parenthood in Relation to Other Life Transitions and Adult Social Functioning

    ERIC Educational Resources Information Center

    Kokko, Katja; Pulkkinen, Lea; Mesiainen, Paivi

    2009-01-01

    The timing of having one's first child, in relation to the timing of other transitions into adulthood and to social functioning, was investigated based on the Finnish Jyvaskyla Longitudinal Study of Personality and Social Development, conducted from age 8 (173 females and 196 males) to 42. Results showed that in women, relatively early (less than…

  19. Spontaneous rupture of aneurysms of the ovarian artery at times remote from pregnancy.

    PubMed

    Kodaira, Yuzo; Iwamura, Taro; Hoshino, Hiroki; Takahashi, Ken; Kawahigashi, Yutaka; Matsumoto, Koshi

    2014-01-01

    Spontaneous rupture of an aneurysm of the ovarian artery is usually considered a rare complication of pregnancy and the puerperium. However, we observed this emergent condition in a 51-year-old postmenopausal woman. We report here our experiences and consider lessons about diagnosis and management that can be drawn from this case and 5 other published cases in multiparous middle-aged women. These lessons include application of contrast-enhanced computed tomography to focus emergent care, surgical intervention, and association with systemic inflammatory response syndrome. We also consider how the cases might shed new light on the pathogenesis and evolution of this condition.

  20. Pulse-echo ultrasound transit time spectroscopy: A comparison of experimental measurement and simulation prediction.

    PubMed

    Wille, Marie-Luise; Almualimi, Majdi A; Langton, Christian M

    2016-01-01

    Considering ultrasound propagation through complex composite media as an array of parallel sonic rays, a comparison of computer-simulated prediction with experimental data has previously been reported for transmission mode (where one transducer serves as transmitter, the other as receiver) in a series of 10 acrylic step-wedge samples, immersed in water, exhibiting varying degrees of transit time inhomogeneity. In this study, the same samples were used but in pulse-echo mode, where the same ultrasound transducer served as both transmitter and receiver, detecting both 'primary' (internal sample interface) and 'secondary' (external sample interface) echoes. A transit time spectrum was derived, describing the proportion of sonic rays with a particular transit time. A computer simulation was performed to predict the transit time and amplitude of various echoes created, and compared with experimental data. Applying an amplitude-tolerance analysis, 91.7% ± 3.7% of the simulated data were within ±1 standard deviation of the experimentally measured amplitude-time data. Correlation of predicted and experimental transit time spectra provided coefficients of determination (R(2)%) ranging from 100.0% to 96.8% for the various samples tested. The results acquired from this study provide good evidence for the concept of parallel sonic rays. Furthermore, deconvolution of experimental input and output signals has been shown to provide an effective method to identify echoes otherwise lost due to phase cancellation. Potential applications of pulse-echo ultrasound transit time spectroscopy include improvement of ultrasound image fidelity by improving spatial resolution and reducing phase interference artefacts.

  1. Determining the architecture of the Kepler-297 system using transit timing variations

    NASA Astrophysics Data System (ADS)

    Diamond-Lowe, Hannah; Stevenson, Kevin B.; Fabrycky, Daniel; Ballard, Sarah; Agol, Eric; Bean, Jacob; Holman, Matthew J.; Ragozzine, Darin

    2015-01-01

    It is essential to explore the architectures of exoplanetary systems as we attempt to understand planet formation histories and determine the rate of occurrence of habitable-zone rocky planets. We focus on the Kepler-297 system which hosts three transiting planets, Kepler-297b, Kepler-297c, and KOI-1426.03. We re-analyze extant Kepler data of the system, as well as new Spitzer data of Kepler-297c, to constrain the transit time variations (TTVs) of the three transiting planets in the system. We feed these results into a dynamical analysis in which the TTVs of the transiting planets constrain their orbital parameters, as well as those of potential non-transiting planets. The gravitational interactions between the Kepler-297 planets allow us to derive their mass ratios. We find that the orbital parameters of the three transiting planets are well-fit by a model that includes a non-transiting fourth planet outside of the three transitors. We are also able to constrain the orbital parameters of the outer-most transitor, thereby confirming it as the planet Kepler-297d.

  2. First Experiences in Percutaneous Arterial Chemoembolization of Malignant Liver Lesions by Means of Real-Time CT Fluoroscopy

    SciTech Connect

    Kirchner, Johannes; Laufer, Ulf; Kickuth, Ralph; Schilling, Esther M.; Scherf, Claudia; Liermann, Dieter

    1999-11-15

    Computed tomography fluoroscopy (CTF) allows real-time display (continuous imaging) and has been increasingly used in interventional procedures. We wished to demonstrate the usefulness of CTF in chemoembolization of the liver. Twenty-one patients with primary or secondary malignant lesions of the liver underwent CTF-guided chemoembolization after angiographic positioning of a catheter in the hepatic artery. Embolization materials such as Lipiodol and mitomycin C were administered under continuous CT scanning. CTF led to a change of the method (correction of catheter position, application of norepinephrine) in nine of 21 cases. There were no fatal complications.

  3. Complexity of cerebral blood flow velocity and arterial blood pressure in subarachnoid hemorrhage using time-frequency analysis.

    PubMed

    Placek, Michal M; Wachel, Pawel; Czosnyka, Marek; Soehle, Martin; Smielewski, Peter; Kasprowicz, Magdalena

    2015-01-01

    We investigated changes of time-frequency (TF) complexity, in terms of Rényi entropy and a measure of concentration, of middle cerebral blood flow velocity (CBFV) and arterial blood pressure in relation to the development of cerebral vasospasm in 15 patients after aneurysmal subarachnoid hemorrhage. Interhemispheric differences in the period of no vasospasm and vasospasm were also compared. Results show reduced complexity of TF representations of CBFV on the side of aneurysm before vasospasm was identified. This potentially can serve as an early-warning indicator of future derangement of cerebral circulation.

  4. Finite-time H∞ control for stochastic time-delayed Markovian switching systems with partly known transition rates and nonlinearity

    NASA Astrophysics Data System (ADS)

    Qi, Wenhai; Gao, Xianwen

    2016-01-01

    This paper focuses on the problem of finite-time H∞ control for stochastic time-delayed Markovian switching systems with partly known transition rates and nonlinearity. By employing an appropriate Lyapunov function and some appropriate free-weighting matrices, a state feedback controller is designed to ensure H∞ finite-time boundedness of the resulting closed-loop system that contains time-varying delay, admissible external disturbance, It ?-type stochastic disturbance and nonlinearity. All the proposed conditions are established in the form of linear matrix inequalities. Finally, an example is given to demonstrate the validity of the main results.

  5. Transition state geometry of driven chemical reactions on time-dependent double-well potentials.

    PubMed

    Junginger, Andrej; Craven, Galen T; Bartsch, Thomas; Revuelta, F; Borondo, F; Benito, R M; Hernandez, Rigoberto

    2016-11-09

    Reaction rates across time-dependent barriers are difficult to define and difficult to obtain using standard transition state theory approaches because of the complexity of the geometry of the dividing surface separating reactants and products. Using perturbation theory (PT) or Lagrangian descriptors (LDs), we can obtain the transition state trajectory and the associated recrossing-free dividing surface. With the latter, we are able to determine the exact reactant population decay and the corresponding rates to benchmark the PT and LD approaches. Specifically, accurate rates are obtained from a local description regarding only direct barrier crossings and to those obtained from a stability analysis of the transition state trajectory. We find that these benchmarks agree with the PT and LD approaches for obtaining recrossing-free dividing surfaces. This result holds not only for the local dynamics in the vicinity of the barrier top, but also for the global dynamics of particles that are quenched at the reactant or product wells after their sojourn over the barrier region. The double-well structure of the potential allows for long-time dynamics related to collisions with the outside walls that lead to long-time returns in the low-friction regime. This additional global dynamics introduces slow-decay pathways that do not result from the local transition across the recrossing-free dividing surface associated with the transition state trajectory, but can be addressed if that structure is augmented by the population transfer of the long-time returns.

  6. Decreasing transition times in elementary school classrooms: Using computer-assisted instruction to automate intervention components.

    PubMed

    Hine, Jeffrey F; Ardoin, Scott P; Foster, Tori E

    2015-09-01

    Research suggests that students spend a substantial amount of time transitioning between classroom activities, which may reduce time spent academically engaged. This study used an ABAB design to evaluate the effects of a computer-assisted intervention that automated intervention components previously shown to decrease transition times. We examined the effects of the intervention on the latency to on-task behavior of 4 students in 2 classrooms. Data also were collected on students' on-task behavior during activities and teachers' use of prompts and praise statements. Implementation of the intervention substantially decreased students' latencies to on-task behavior and increased on-task behavior overall. Further, the 2 teachers used fewer prompts to cue students to transition and stay on task and provided more praise during intervention phases. We discuss how automating classroom interventions may affect student and teacher behavior as well as how it may increase procedural fidelity.

  7. The Transit-Time Distribution from the Northern Hemisphere Midlatitude Surface

    NASA Technical Reports Server (NTRS)

    Orbe, Clara; Waugh, Darryn W.; Newman, Paul A.; Strahan, Susan; Steenrod, Stephen

    2015-01-01

    The distribution of transit times from the Northern Hemisphere (NH) midlatitude surface is a fundamental property of tropospheric transport. Here we present an analysis of the transit time distribution (TTD) since air last contacted the northern midlatitude surface layer, as simulated by the NASA Global Modeling Initiative Chemistry Transport Model. We find that throughout the troposphere the TTD is characterized by long flat tails that reflect the recirculation of old air from the Southern Hemisphere and results in mean ages that are significantly larger than the modal age. Key aspects of the TTD -- its mode, mean and spectral width -- are interpreted in terms of tropospheric dynamics, including seasonal shifts in the location and strength of tropical convection and variations in quasi-isentropic transport out of the northern midlatitude surface layer. Our results indicate that current diagnostics of tropospheric transport are insufficient for comparing model transport and that the full distribution of transit times is a more appropriate constraint.

  8. Transit time of a freely falling quantum particle in a background gravitational field

    NASA Astrophysics Data System (ADS)

    Davies, P. C. W.

    2004-12-01

    Using a model quantum clock, I evaluate an expression for the time of a non-relativistic quantum particle to transit a piecewise geodesic path in a background gravitational field with small spacetime curvature (gravity gradient), in the case in which the apparatus is in free fall. This calculation complements and extends an earlier one (Davies 2004) in which the apparatus is fixed to the surface of the Earth. The result confirms that, for particle velocities not too low, the quantum and classical transit times coincide, in conformity with the principle of equivalence. I also calculate the quantum corrections to the transit time when the de Broglie wavelengths are long enough to probe the spacetime curvature. The results are compared with the calculation of Chiao and Speliotopoulos (2003), who propose an experiment to measure the foregoing effects.

  9. Finite-time thermodynamics and the gas-liquid phase transition

    NASA Astrophysics Data System (ADS)

    Santoro, M.; Schön, J. C.; Jansen, M.

    2007-12-01

    In this paper, we study the application of the concept of finite-time thermodynamics to first-order phase transitions. As an example, we investigate the transition from the gaseous to the liquid state by modeling the liquification of the gas in a finite time. In particular, we introduce, state, and solve an optimal control problem in which we aim at achieving the gas-liquid first-order phase transition through supersaturation within a fixed time in an optimal fashion, in the sense that the work required to supersaturate the gas, called excess work, is minimized by controlling the appropriate thermodynamic parameters. The resulting set of coupled nonlinear differential equations is then solved for three systems, nitrogen N2 , oxygen O2 , and water vapor H2O .

  10. Nonlinear light behaviors near phase transition in non-parity-time-symmetric complex waveguides.

    PubMed

    Nixon, Sean; Yang, Jianke

    2016-06-15

    Many classes of non-parity-time (PT)-symmetric waveguides with arbitrary gain and loss distributions still possess all-real linear spectrum or exhibit phase transition. In this Letter, nonlinear light behaviors in these complex waveguides are probed analytically near a phase transition. Using multi-scale perturbation methods, a nonlinear ordinary differential equation (ODE) is derived for the light's amplitude evolution. This ODE predicts that a single class of these non-PT-symmetric waveguides supports soliton families and amplitude-oscillating solutions both above and below linear phase transition, in close analogy with PT-symmetric systems. For the other classes of waveguides, the light's intensity always amplifies under the effect of nonlinearity, even if the waveguide is below the linear phase transition. These analytical predictions are confirmed by direct computations of the full system.

  11. Reconciling transition path time and rate measurements in reactions with large entropic barriers

    NASA Astrophysics Data System (ADS)

    Makarov, Dmitrii E.

    2017-02-01

    Recent experiments and simulation studies showed that protein/DNA folding barriers inferred from folding rates or from potentials of mean force are often much higher than the barriers estimated from the distributions of transition path times. Here a toy model is used to explain a possible origin of this effect: It is shown that when the transition in question involves an entropic barrier, the one-dimensional Langevin model commonly used to interpret experimental data, while adequately predicting the transition rate, fails to describe the properties of the subset of the trajectories that form the transition path ensemble; the latter may still be describable in terms of a one-dimensional model, but with a different potential, just as observed experimentally.

  12. Determination of erythrocyte transit times through micropores. II. Influence of experimental and physicochemical factors.

    PubMed

    Koutsouris, D; Guillet, R; Wenby, R B; Meiselman, H J

    1989-01-01

    A new red blood cell filtration system, termed the Cell Transit Time Analyzer (CTTA), has been developed in order to measure the individual transit times of a large number of cells through cylindrical micropores in special "oligopore" filters; the system operates on the electrical conductometric principle and employs special computer software to provide several measures of the resulting transit time histogram. Using this system with filters having pore diameters of 4.5 or 5.0 microns and length to diameter ratios of 3.0 to 4.7, we have evaluated the effects of several experimental factors on the flow behavior of normal and modified human RBC. Our results indicate: 1) linear RBC pressure-flow behavior over a driving pressure range of 2 to 10.5 cm H2O with zero velocity intercepts at delta P = 0, thus suggesting the Poiseuille-like nature of the flow; 2) resistance to flow or "apparent viscosities" for normal RBC which are between 3.1 to 3.9 cPoise and are independent of driving pressure and pore geometry; 3) increased flow resistance (i.e., increased transit times) for old versus young RBC and for RBC made less deformable by DNP-induced crenation or by heat treatment at 48 degrees C; 4) increased mean transit time and poorer reproducibility when using EDTA rather than heparin as the anticoagulant agent. Further, using mixtures of heat-treated and normal RBC and various percentile values of the transit time histogram, we have been able to demonstrate the presence of sub-populations of rigid cells and thus the value of measurements which allow statistical analyses of RBC populations.

  13. Mean transit times in contrasting headwater catchments from southeast Australia determined using Tritium

    NASA Astrophysics Data System (ADS)

    Cartwright, Ian; Morgenstern, Uwe; Irvine, Dylan

    2016-04-01

    Headwater streams contribute a significant proportion of the total discharge of many river systems. However, despite their importance, the time taken for rainfall to pass through the catchment into the streams (the transit time) in headwater catchments is largely unknown as are the catchment characteristics (such as drainage density, topography, landuse, or geology) that determine variations in transit times. Because the peak in Tritium activities in rainfall produced by atmospheric nuclear tests in the1950's and 1960's (the "bomb-pulse") was several orders of magnitude lower in the southern hemisphere than in the northern hemisphere, Tritium activities of remnant bomb pulse water in the southern hemisphere have decayed below those of modern rainfall. This allows mean transit times to be estimated from single Tritium measurements. Here we use Tritium to estimate transit times of water contributing to perennial streams in the adjacent upper catchments of the Yarra and Latrobe Rivers (southeast Australia). Samples were collected at varying flow from six headwater tributary sites in the Latrobe catchment, which is largely forested and four tributaries in the Yarra catchment which has been extensively cleared for dryland agriculture. The lowest Tritium activities were recorded during summer baseflow conditions and are between 1.25 and 1.75 TU, these are significantly below the Tritium activity of local rainfall (~2.8 TU). Mean transit times calculated using an exponential-piston flow lumped parameter model are 21 to 47 years. Tritium activities during the recession periods following winter high flows are higher (1.54 to 2.1 TU), which may reflect either the dilution of a baseflow component with recent surface runoff or mobilisation of different stores of water with different residence times (e.g., from the soils or the regolith) from within the catchment. The variation of major ion concentrations with discharge suggests it is more likely that that different stores of

  14. Nonlinear ion dynamics in Hall thruster plasma source by ion transit-time instability

    NASA Astrophysics Data System (ADS)

    Lim, Youbong; Choe, Wonho; Mazouffre, Stéphane; Park, Jae Sun; Kim, Holak; Seon, Jongho; Garrigues, L.

    2017-03-01

    High-energy tail formation in an ion energy distribution function (IEDF) is explained in a Hall thruster plasma with the stationary crossed electric and magnetic fields whose discharge current is oscillated at the ion transit-time scale with a frequency of 360 kHz. Among ions in different charge states, singly charged Xe ions (Xe+) have an IEDF that is significantly broadened and shifted toward the high-energy side, which contributes to tail formation in the entire IEDF. Analytical and numerical investigations confirm that the IEDF tail is due to nonlinear ion dynamics in the ion transit-time oscillation.

  15. Application of transit timing variation method (TTV) to exoplanet system TrES-3

    NASA Astrophysics Data System (ADS)

    Kuznyetsova, Yu.; Shliakhetskaya, Y.; Matsiaka, O.; Krushevska, V.; Romanyuk, Ya.

    2015-10-01

    On the basis of the original photometric data, the light curves of several transits in the exoplanet system TrES-3 were simulated by Monte Carlo method. Using these curves, the estimates of precise values of mid-transit time were calculated to assess the possibility of finding new planets by timing method in already known exoplanet systems using ground-based observations at small telescopes. More accurate values of the some orbital and physical parameters of TrES-3 system were also obtained including following the planet-star radius ratio (RP/R*), the angle of the planet orbital plane inclination (i).

  16. Study of the transit time of pressure propagation in an acoustic delay line

    NASA Astrophysics Data System (ADS)

    Song, Yunn-Fang; Chen, Ching-Iue; Chang, Chu-Nan; You, Jean-Luh; Hwang, Fu-Kwun; Hsu, Chih-Ying

    1986-12-01

    A fast sensor was used as a vacuum gauge to measure the transit time of a gas pressure through an acoustic delay line (ADL). The results were compared with the predictions of two theoretical models. We found that in the rupture pressure range of 101 to 104 Pa, the predictions of Jean and Rauss' model, based on the assumption that the flow of gas be a gas fluid, set lower boundaries for the observed transit times; while the predictions of our model, based on the molecular motion, set the upper ones.

  17. Gender Transitions in Later Life: The Significance of Time in Queer Aging

    PubMed Central

    Fabbre, Vanessa D.

    2014-01-01

    Concepts of time are ubiquitous in studies of aging. This article integrates an existential perspective on time with a notion of queer time based on the experiences of older transgender persons who contemplate or pursue a gender transition in later life. Interviews were conducted with male-to-female identified persons aged 50 years or older (N=22), along with participant observation at three national transgender conferences (N=170 hours). Interpretive analyses suggest that an awareness of “time left to live” and a feeling of “time served” play a significant role in later life development and help expand gerontological perspectives on time and queer aging. PMID:24798691

  18. Hydroclimatic influences on non-stationary transit time distributions in a boreal headwater catchment

    NASA Astrophysics Data System (ADS)

    Peralta-Tapia, A.; Soulsby, C.; Tetzlaff, D.; Sponseller, R.; Bishop, K.; Laudon, H.

    2016-12-01

    Understanding how water moves through catchments - from the time it enters as precipitation to when it exits via streamflow - is of fundamental importance to understanding hydrological and biogeochemical processes. A basic descriptor of this routing is the Transit Time Distribution (TTD) which is derived from the input-output behavior of conservative tracers, the mean of which represents the average time elapsed between water molecules entering and exiting a flow system. In recent decades, many transit time studies have been conducted, but few of these have focused on snow-dominated catchments. We assembled a 10-year time series of isotopic data (δ18O and δ2H) for precipitation and stream water to estimate the characteristics of the transit time distribution in a boreal catchment in northern Sweden. We applied lumped parameter models using a gamma distribution to calculate the Mean Transit Time (MTT) of water over the entire period of record and to evaluate how inter-annual differences in transit times relate to hydroclimatic variability. The best fit MTT for the complete 10-year period was 650 days (Nash-Sutcliff Efficiency = 0.65), while the best fit inter-annual MTT ranged from 300 days up to 1200 days. Whilst there was a weak negative correlation between mean annual total precipitation and the annual MTT, this relationship was stronger (r2 = 0.53, p = 0.02) for the annual rain water input. This strong connection between the MTT and annual rainfall, rather than snowmelt, has strong implications for understanding future hydrological and biogeochemical processes in boreal regions, given that predicted warmer winters would translate into a greater proportion of precipitation falling as rain and thus shorter MTT in catchments. Such a change could have direct implications for the export of solutes and pollutants.

  19. QUANTIFYING THE CHALLENGES OF DETECTING UNSEEN PLANETARY COMPANIONS WITH TRANSIT TIMING VARIATIONS

    SciTech Connect

    Veras, Dimitri; Ford, Eric B.; Payne, Matthew J.

    2011-02-01

    Both ground- and space-based transit observatories are poised to significantly increase the number of known transiting planets and the number of precisely measured transit times. The variation in a planet's transit times may be used to infer the presence of additional planets. Deducing the masses and orbital parameters of such planets from transit time variations (TTVs) alone is a rich and increasingly relevant dynamical problem. In this work, we evaluate the extent of the degeneracies in this process, systematically explore the dependence of TTV signals on several parameters, and provide phase space plots that could aid observers in planning future observations. Our explorations are focused on a likely-to-be prevalent situation: a known transiting short-period Neptune- or Jupiter-sized planet and a suspected external low-mass perturber on a nearly coplanar orbit. Through {approx}10{sup 7} N-body simulations, we demonstrate how TTV signal amplitudes may vary by orders of magnitude due to slight variations in any one orbital parameter (10{sup -3} AU in a semimajor axis, 0.005 in eccentricity, or a few degrees in orbital angles), and quantify the number of consecutive transit observations necessary in order to obtain a reasonable opportunity of characterizing the unseen planet ({approx}>50 observations). Planets in or near period commensurabilities of the form p:q, where p {<=} 20 and q {<=} 3, produce distinct TTV signatures, regardless of whether the planets are actually locked in a mean motion resonance. We distinguish these systems from the secular systems in our explorations. Additionally, we find that computing the autocorrelation function of a TTV signal can provide a useful diagnostic for identifying possible orbits for additional planets and suggest that this method could aid integration of TTV signals in future studies of particular exosystems.

  20. A Time Integration Algorithm Based on the State Transition Matrix for Structures with Time Varying and Nonlinear Properties

    NASA Technical Reports Server (NTRS)

    Bartels, Robert E.

    2003-01-01

    A variable order method of integrating the structural dynamics equations that is based on the state transition matrix has been developed. The method has been evaluated for linear time variant and nonlinear systems of equations. When the time variation of the system can be modeled exactly by a polynomial it produces nearly exact solutions for a wide range of time step sizes. Solutions of a model nonlinear dynamic response exhibiting chaotic behavior have been computed. Accuracy of the method has been demonstrated by comparison with solutions obtained by established methods.

  1. Can we measure the spiral and uterine artery blood flow by real-time sonography and Doppler indices to predict spontaneous miscarriage in a normal-risk population?

    PubMed

    Özkan, Mehmet Burak; Ozyazici, Elif; Emiroglu, Baris; Özkara, Enis

    2015-05-01

    Introduction: The predictive value of spiral artery flow Doppler measurements of a subsequent early miscarriage in first trimester pregnancy is explored here. Objective: The aim of this study is to determine uterine and spiral artery blood flow changes in first trimester subsequent miscarriages and correlate within the mechanisms of the Doppler indicies. Study design: The uterine artery and spiral artery pulsatility and resistance indexes, systolic and diastolic ratios, acceleration times, and blood flow of both the right and left uterine arteries were obtained by trans vaginal color Doppler ultrasonography in consecutive viable pregnancies between 5 and 12 gestational week. Women were subsequently classified as having continuing pregnancies or pregnancy loss before 20 weeks gestation. To predict subsequent pregnancy loss, Doppler findings were adjusted for maternal age, history of previous abortion, presence of subchorionic hematoma, embryonic bradycardia, and gestational age by means of multivariate logistic regression analysis. The cut-off values are used for the ROC curve. Results: Twenty-five pregnancies (11.7%) were spontaneously aborted before 20 weeks of gestational age. In 29 (13.6%) cases there were previously abortion history, 30 (14%) had bradycardia, and 37 (17.3%) had subchoronic hematoma. Regarding the parameters of uterine and spiral artery pulsatility and resistive index, acceleration time, systolic/diastolic ratios and blood flows, only uterine artery S/D low values were significantly associated with pregnancy loss in the multivariate logistic regression analysis (P = 0.0001,95% CI: 4.968-55.675). Conclusion: The uterine artery systolic/diastolic ratios have a predictive value for early pregnancy loss and seem to be useful as a marker. On the other hand, spiral artery changes could be so local that they cannot be determined by the parameters of spectral Doppler techniques. This suggests that uterine vascular bed alterations should be measured to

  2. Can we measure the spiral and uterine artery blood flow by real‐time sonography and Doppler indices to predict spontaneous miscarriage in a normal‐risk population?

    PubMed Central

    Ozyazici, Elif; Emiroglu, Baris; Özkara, Enis

    2015-01-01

    Abstract Introduction: The predictive value of spiral artery flow Doppler measurements of a subsequent early miscarriage in first trimester pregnancy is explored here. Objective: The aim of this study is to determine uterine and spiral artery blood flow changes in first trimester subsequent miscarriages and correlate within the mechanisms of the Doppler indicies. Study design: The uterine artery and spiral artery pulsatility and resistance indexes, systolic and diastolic ratios, acceleration times, and blood flow of both the right and left uterine arteries were obtained by trans vaginal color Doppler ultrasonography in consecutive viable pregnancies between 5 and 12 gestational week. Women were subsequently classified as having continuing pregnancies or pregnancy loss before 20 weeks gestation. To predict subsequent pregnancy loss, Doppler findings were adjusted for maternal age, history of previous abortion, presence of subchorionic hematoma, embryonic bradycardia, and gestational age by means of multivariate logistic regression analysis. The cut‐off values are used for the ROC curve. Results: Twenty‐five pregnancies (11.7%) were spontaneously aborted before 20 weeks of gestational age. In 29 (13.6%) cases there were previously abortion history, 30 (14%) had bradycardia, and 37 (17.3%) had subchoronic hematoma. Regarding the parameters of uterine and spiral artery pulsatility and resistive index, acceleration time, systolic/diastolic ratios and blood flows, only uterine artery S/D low values were significantly associated with pregnancy loss in the multivariate logistic regression analysis (P = 0.0001,95% CI: 4.968–55.675). Conclusion: The uterine artery systolic/diastolic ratios have a predictive value for early pregnancy loss and seem to be useful as a marker. On the other hand, spiral artery changes could be so local that they cannot be determined by the parameters of spectral Doppler techniques. This suggests that uterine vascular bed alterations should

  3. Time-dependency of improvements in arterial oxygenation during partial liquid ventilation in experimental acute respiratory distress syndrome

    PubMed Central

    Max, Martin; Kuhlen, Ralf; Dembinski, Rolf; Rossaint, Rolf

    2000-01-01

    Background: The mechanisms by which partial liquid ventilation (PLV) can improve gas exchange in acute lung injury are still unclear. Therefore, we examined the time- and dose-dependency of the improvements in arterial oxygen tension (PaO2) due to PLV in eight pigs with experimental lung injury, in order to discriminate increases due to oxygen dissolved in perfluorocarbon before its intrapulmonary instillation from a persistent diffusion of the respiratory gas through the liquid column. Results: Application of four sequential doses of perfluorocarbon resulted in a dose-dependent increase in PaO2. Comparison of measurements 5 and 30 min after instillation of each dose revealed a time-dependent decrease in PaO2 for doses that approximated the functional residual capacity of the animals. Conclusion: Although oxygen dissolved in perfluorocarbon at the onset of PLV can cause a short-term improvement in arterial oxygenation, diffusion of oxygen through the liquid may not be sufficient to maintain the initially observed increase in PaO2. PMID:11056747

  4. Transit times from rainfall to baseflow in headwater catchments estimated using tritium: the Ovens River, Australia

    NASA Astrophysics Data System (ADS)

    Cartwright, I.; Morgenstern, U.

    2015-06-01

    Headwater streams contribute a significant proportion of the total flow to many river systems, especially during summer low-flow periods. However, despite their importance, the time taken for water to travel through headwater catchments and into the streams (the transit time) is poorly constrained. Here, 3H activities of stream water are used to define transit times of water contributing to streams from the upper reaches of the Ovens River in southeast Australia at varying flow conditions. 3H activities of the stream water varied from 1.63 to 2.45 TU, which are below the average 3H activity of modern local rainfall (~3 TU). The highest 3H activities were recorded following higher winter flows and the lowest 3H activities were recorded at summer low-flow conditions. Variations of major ion concentrations and 3H activities with streamflow imply that different stores of water from within the catchment (e.g. from the soil or regolith) are mobilised during rainfall events rather than there being simple dilution of an older groundwater component by event water. Mean transit times calculated using an exponential-piston flow model range between 5 and 31 years and are higher at summer low-flow conditions. Mean transit times calculated using other flow models (e.g. exponential flow or dispersion) are similar. There are broad correlations between 3H activities and the percentage of rainfall exported from each catchment and between 3H activities and Na and Cl concentrations that allow first-order estimates of mean transit times in adjacent catchments or at different times in these catchments to be made. Water from the upper Ovens River has similar mean transit times to the headwater streams implying there is no significant input of old water from the alluvial gravels. The observation that the water contributing to the headwater streams in the Ovens catchment has a mean transit time of years to decades implies that these streams are buffered against rainfall variations on

  5. Transit times from rainfall to baseflow in headwater catchments estimated using tritium: the Ovens River, Australia

    NASA Astrophysics Data System (ADS)

    Cartwright, I.; Morgenstern, U.

    2015-09-01

    Headwater streams contribute a significant proportion of the total flow to many river systems, especially during summer low-flow periods. However, despite their importance, the time taken for water to travel through headwater catchments and into the streams (the transit time) is poorly understood. Here, 3H activities of stream water are used to define transit times of water contributing to streams from the upper reaches of the Ovens River in south-east Australia at varying flow conditions. 3H activities of the stream water varied from 1.63 to 2.45 TU, which are below the average 3H activity of modern local rainfall (2.85 to 2.99 TU). The highest 3H activities were recorded following higher winter flows and the lowest 3H activities were recorded at summer low-flow conditions. Variations of major ion concentrations and 3H activities with streamflow imply that different stores of water from within the catchment (e.g. from the soil or regolith) are mobilised during rainfall events rather than there being simple dilution of an older groundwater component by event water. Mean transit times calculated using an exponential-piston flow model range from 4 to 30 years and are higher at summer low-flow conditions. Mean transit times calculated using other flow models (e.g. exponential flow or dispersion) are similar. There are broad correlations between 3H activities and the percentage of rainfall exported from each catchment and between 3H activities and Na and Cl concentrations that allow first-order estimates of mean transit times in adjacent catchments or at different times in these catchments to be made. Water from the upper Ovens River has similar mean transit times to the headwater streams implying there is no significant input of old water from the alluvial gravels. The observation that the water contributing to the headwater streams in the Ovens catchment has a mean transit time of years to decades implies that these streams are buffered against rainfall variations on

  6. The Real Time Disintegration of an Asteroid Transiting a White Dwarf

    NASA Astrophysics Data System (ADS)

    Xu, Siyi; Rappaport, Saul; DeVore, John; Ivanov, Valentin; Debes, John; Provencal, Judith; Vanderburg, Andrew; Croll, Bryce; Dufour, Patrick; Zuckerman, Ben

    2016-08-01

    There is strong evidence that an actively disintegrating asteroid is orbiting the white dwarf WD 1145+017. This scenario is supported by several observations, including: (i) transits from multiple objects within the white dwarf's tidal radius; (ii) infrared excess from a circumstellar dust disk; (iii) ubiquitous high-velocity absorption lines from circumstellar gas; (iv) a heavily polluted atmosphere from the accretion of the circumstellar material. We were awarded Spitzer DDT time to perform photometric observation simultaneously with a few other telescopes on March 29, 2016. Our preliminary analysis has returned the first detection of a color-dependent transit. Here, we propose to monitor this system over the next two years to understand the change of the transiting material as well as the possible change of the dust disk. This system provides a unique window to study the real time disintegration of an asteroid around a white dwarf.

  7. Transition time of nonlinear Landau-Zener model in adiabatic limit

    NASA Astrophysics Data System (ADS)

    Liu, Xuan-Zuo; Tian, Dong-Ping; Chong, Bo

    2016-06-01

    The impact of nonlinear interaction on the loop structure of lower energy level and on the time evolution curve of canonical momentum which corresponds to the lower eigenstate are analyzed respectively. We find that the curve changes from single-valued to multi-valued as nonlinear interaction grows. The fascinating part is that the time range delimited by turning points in the loop of energy level and the period between two inflexion points on the multi-valued part of the evolution curve of canonical momentum are the same. Therefore, we propose a characteristic time in the transition process of nonlinear Landau-Zener model in adiabatic limit. Last, the physical meaning of the transition time as a measure of how much time the system experiences a structural change which directly results in the breakdown of adiabaticity is discussed.

  8. Hepatic transit time analysis using contrast-enhanced ultrasound with BR1: A prospective study comparing patients with liver metastases from colorectal cancer with healthy volunteers.

    PubMed

    Hohmann, Joachim; Müller, Christine; Oldenburg, Anja; Skrok, Jan; Frericks, Bernd B; Wolf, Karl-Jürgen; Albrecht, Thomas

    2009-09-01

    We prospectively compared hepatic transit time (HTT) measurements in subjects with liver metastases from colorectal cancer (group a) and healthy volunteers (group b) using contrast-enhanced ultrasound with BR1. The purpose of this study was to verify our hypothesis that the hemodynamic changes of the liver, which occur during metastasis seeding, would shorten the HTT, and we expect that such changes could be used for the detection of occult liver metastases from colorectal cancer in the future. The study had institutional review board approval and all subjects gave informed written consent. Group a and group b consisted of 22 subjects each. Baseline and post contrast images were acquired starting 10 s before and ending 40 s after administration of BR1, using nonlinear imaging at a frame rate of 5/s. The baseline images were used to determine the signal intensity without contrast enhancement as the reference signal. Arrival times (AT) of the contrast agent for the hepatic artery, the portal vein and one hepatic vein were determined using (i) quantitative analysis and (ii) subjective analysis by two blinded readers. HTT was calculated based on arrival time measurements. Quantitative and subjective analysis showed significantly shorter arterial to venous and portal to venous HTT in group a compared with group b (p < 0.001). Arterial to venous HTT (quantitative analysis) was < or = 9 s in 19 of 22 subjects of group a and >9 s in 18 of 22 subjects of group b (sensitivity 86%, specificity 82%, positive predictive value 83%, negative predictive value 86%, area under the curve [AUC] 0.87). Portal to venous HTT (quantitative analysis) was < 7 s in 21 of 22 subjects of group a and > 7s in 15 of 22 subjects of group b (sensitivity 95%, specificity 68%, PPV 75%, NPV 94%, AUC 0.85). There was an inverse relation with number of liver segments involved for arterial to venous and portal to venous HTT in group a (p < 0.05), but no correlation between HTT and overall volume of

  9. Measuring the Masses and Radii of Sub-Neptunes with Transit Timing Variations

    NASA Astrophysics Data System (ADS)

    Jontof-Hutter, Daniel; Lissauer, J. J.; Rowe, J. F.; Fabrycky, D.

    2013-10-01

    The bounty of sub-Neptunes discovered by Kepler enables us to study a regime in planetary size and mass that is absent from the Solar System. This regime includes a transition from rocky planets to those with substantial amounts of volatiles-- in either ice mantles or deep atmospheres. Characterizing these worlds by their bulk densities can probe this transition, and this requires mass and radius determinations. Outside our solar system, there is a small sample of planets with known masses and radii, mostly hot jupiters whose radii are known from transit depths, and whose masses are determined from radial velocity spectroscopy (RV). In the absence of mass determinations via RV observations, transit timing variations (TTVs) offer a chance to probe perturbations between planets that pass close to one another or are near resonance, and hence dynamical fits to observed transit times can measure planetary masses and orbital parameters. Such modelling can probe planetary masses at longer orbital periods than RV targets, although not without some challenges. For example, in modeling pairwise planetary perturbations, a degeneracy between eccentricity and mass exists that limits the accuracy of mass determinations. Nevertheless, in several compact multiplanet systems, fitting complex TTV signals can break the degeneracy, permitting useful mass determinations. The precision in measuring the radius of a transiting planet rests on the uncertainty in the stellar radius, which is typically ~10% for targets with spectral follow-up. With dynamical fits, however, solutions for the orbital parameters including the eccentricity vectors can, alongside the transit lightcurves, tightly constrain the stellar density and radius. Revisiting the six-planet system of Kepler-11, our dynamical fits to TTVs, alongside spectroscopic data on the host star, reduced the stellar and hence planetary radius uncertainties to just 2%, permitting useful planetary density determinations. In the case of

  10. Long-term transit timing monitoring and homogenous study of WASP-32

    NASA Astrophysics Data System (ADS)

    Sun, Lei-Lei; Gu, Sheng-Hong; Wang, Xiao-Bin; Collier Cameron, Andrew; Cao, Dong-Tao; Wang, Yi-Bo; Xiang, Yue; Hui, Ho-Keung; Kwok, Chi-Tai; Yeung, Bill; Leung, Kam-Cheung

    2015-01-01

    We report new photometric observations of the transiting exoplanetary system WASP-32 made by using CCD cameras at Yunnan Observatories and Ho Koon Nature Education cum Astronomical Centre, China from 2010 to 2012. Following our usual procedure, the observed data are corrected for systematic errors according to the coarse decorrelation and SYSREM algorithms so as to enhance the signal of the transit events. Combined with radial velocity data presented in the literature, our newly observed data and earlier photometric data in the literature are simultaneously analyzed to derive the physical parameters describing the system by employing the Markov chain Monte Carlo technique. The derived parameters are consistent with the result published in the original paper about WASP-32b, but the uncertainties of the new parameters are smaller than those in the original paper. Moreover, our modeling result supports a circular orbit for WASP-32b. Through the analysis of all available mid-transit times, we have refined the orbital period of WASP-32b; no evident transit timing variation is found in these transit events.

  11. Transit Timing Observations from Kepler. IX. Catalog of the Full Long-cadence Data Set

    NASA Astrophysics Data System (ADS)

    Holczer, Tomer; Mazeh, Tsevi; Nachmani, Gil; Jontof-Hutter, Daniel; Ford, Eric B.; Fabrycky, Daniel; Ragozzine, Darin; Kane, Mackenzie; Steffen, Jason H.

    2016-07-01

    We present a new transit timing catalog of 2599 Kepler Objects of Interest (KOIs), using the PDC-MAP long-cadence light curves that include the full 17 quarters of the mission (ftp://wise-ftp.tau.ac.il/pub/tauttv/TTV/ver_112). The goal is to produce an easy-to-use catalog that can stimulate further analyses of interesting systems. For 779 KOIs with high enough S/N, we derived the timing, duration, and depth of 69,914 transits. For 1820 KOIs with lower SNR, we derived only the timing of 225,273 transits. After removal of outlier timings, we derived various statistics for each KOI that were used to indicate significant variations. Including systems found by previous works, we have detected 260 KOIs that showed significant TTVs with long-term variations (>100 days), and another 14 KOIs with periodic modulations shorter than 100 days and small amplitudes. For five of those, the periodicity is probably due to the crossing of rotating stellar spots by the transiting planets.

  12. The Measurement of Time: Children's Construction of Transitivity, Unit Iteration, and Conservation of Speed.

    ERIC Educational Resources Information Center

    Long, Kathy; Kamii, Constance

    2001-01-01

    Interviews 120 children in kindergarten and grades 2, 4, and 6 with five Piagetian tasks to determine the grade level at which most have constructed transitive reasoning, unit iteration, and conservation of speed. Indicates that construction of the logic necessary to make sense of the measurement of time is generally not complete before sixth…

  13. The Influence of Unpaid Work on the Transition out of Full-Time Paid Work

    ERIC Educational Resources Information Center

    Carr, Dawn C.; Kail, Ben Lennox

    2013-01-01

    Purpose: Continued employment after retirement and engagement in unpaid work are both important ways of diminishing the negative economic effects of the retirement of baby boomer cohorts on society. Little research, however, examines the relationship between paid and unpaid work at the transition from full-time work. Using a resource perspective…

  14. The Importance of Timing of Transitions for Risk of Regular Smoking and Nicotine Dependence

    PubMed Central

    Dierker, Lisa; He, Jianping; Kalaydjian, Amanda; Swendsen, Joel; Degenhardt, Louisa; Glantz, Meyer; Conway, Kevin; Anthony, James; Chiu, Wai Tat; Sampson, Nancy A.; Kessler, Ronald; Merikangas, Kathleen

    2009-01-01

    Purpose To investigate the association between the timing and speed of transition among major smoking milestones (onset, weekly and daily smoking) and onset and recovery from nicotine dependence. Method Analyses are based on data from The National Comorbidity Survey-Replication (NCS-R), a nationally representative face-to-face household survey conducted between February 2001 and April 2003. Results Of those who had ever smoked (n=5,692), 71.3% had reached weekly smoking levels and 67.5% had reached daily smoking. Four in ten who had ever smoked met criteria for nicotine dependence. A shorter time since the onset of weekly and daily smoking was associated with a transition to both daily smoking and nicotine dependence, respectively. The risk for each smoking transition was highest within the year following the onset of the preceding milestone. Recovery was associated with a longer period of time between smoking initiation and the development of dependence and a later age of smoking onset. Conclusions These findings shed light on the clinical course of smoking and nicotine dependence. Given the importance of timing of smoking transitions, prevalence may be further reduced through intervention targeted at adolescents and young adults in the months most proximal to smoking initiation. PMID:18704617

  15. The Family Transition Program: Implementation and Early Impacts of Florida's Initial Time-Limited Welfare Program.

    ERIC Educational Resources Information Center

    Bloom, Dan; And Others

    Florida's Family Transition Program (FTP) combines a welfare time limit of 24-36 months with services, requirements, and financial incentives designed to help welfare recipients find and hold jobs. Aid to Families with Dependent Children (AFDC) applicants who were not incapacitated, disabled, or otherwise exempt from the FTP program were randomly…

  16. Dating Violence, Bullying, and Sexual Harassment: Longitudinal Profiles and Transitions over Time

    ERIC Educational Resources Information Center

    Miller, Shari; Williams, Jason; Cutbush, Stacey; Gibbs, Deborah; Clinton-Sherrod, Monique; Jones, Sarah

    2013-01-01

    Although there is growing recognition of the problem of dating violence, little is known about how it unfolds among young adolescents who are just beginning to date. This study examined classes (subgroups) and transitions between classes over three time points based on dating violence, bullying, and sexual harassment perpetration and victimization…

  17. Coronary Arteries

    MedlinePlus

    ... and animations for grades K-6. The Coronary Arteries Coronary Circulation The heart muscle, like every other ... into two main coronary blood vessels (also called arteries). These coronary arteries branch off into smaller arteries, ...

  18. The barrier method: a technique for calculating very long transition times.

    PubMed

    Adams, D A; Sander, L M; Ziff, R M

    2010-09-28

    In many dynamical systems, there is a large separation of time scales between typical events and "rare" events which can be the cases of interest. Rare-event rates are quite difficult to compute numerically, but they are of considerable practical importance in many fields, for example, transition times in chemical physics and extinction times in epidemiology can be very long, but are quite important. We present a very fast numerical technique that can be used to find long transition times (very small rates) in low-dimensional systems, even if they lack detailed balance. We illustrate the method for a bistable nonequilibrium system introduced by Maier and Stein and a two-dimensional (in parameter space) epidemiology model.

  19. Establishment of a Protocol for Determining Gastrointestinal Transit Time in Mice Using Barium and Radiopaque Markers

    PubMed Central

    Myagmarjalbuu, Bolormaa; Moon, Myeong Ju; Heo, Suk Hee; Jeong, Seo In; Park, Jong-Seong; Jun, Jae Yeoul; Kang, Heoung Keun

    2013-01-01

    Objective The purpose of this study was to establish a minimally invasive and reproducible protocol for estimating the gastrointestinal (GI) transit time in mice using barium and radiopaque markers. Materials and Methods Twenty 5- to 6-week-old Balb/C female mice weighing 19-21 g were used. The animals were divided into three groups: two groups that received loperamide and a control group. The control group (n = 10) animals were administered physiological saline (1.5 mL/kg) orally. The loperamide group I (n = 10) and group II (n = 10) animals were administered 5 mg/kg and 10 mg/kg loperamide orally, respectively. Thirty minutes after receiving the saline or loperamide, the mice was administered 80 µL of barium solution and six iron balls (0.5 mm) via the mouth and the upper esophagus by gavage, respectively. Afterwards, the mice were continuously monitored with fluoroscopic imaging in order to evaluate the swallowing of the barium solution and markers. Serial fluoroscopic images were obtained at 5- or 10-min intervals until all markers had been excreted from the anal canal. For analysis, the GI transit times were subdivided into intestinal transit times (ITTs) and colon transit times (CTTs). Results The mean ITT was significantly longer in the loperamide groups than in the control group (p < 0.05). The mean ITT in loperamide group II (174.5 ± 32.3) was significantly longer than in loperamide group I (133.2 ± 24.2 minute) (p < 0.05). The mean CTT was significantly longer in loperamide group II than in the control group (p < 0.05). Also, no animal succumbed to death after the experimental procedure. Conclusion The protocol for our study using radiopaque markers and barium is reproducible and minimally invasive in determining the GI transit time of the mouse model. PMID:23323030

  20. Changes in Sleep Duration and Sleep Timing Associated with Retirement Transitions

    PubMed Central

    Hagen, Erika W.; Barnet, Jodi H.; Hale, Lauren; Peppard, Paul E.

    2016-01-01

    Study Objectives: Investigate whether retirement transitions are associated with changes in sleep duration and sleep timing, and whether these associations are modified by age, sex, mental health, or circadian preference. Methods: The Retirement and Sleep Trajectories (REST) study is a longitudinal study consisting of four annual mailed surveys that collected information about employment, sleep, and health. Differences in reported sleep duration, bedtime and wake time between successive surveys were calculated to estimate change over 1, 2, and 3 y. Linear regression models were used to estimate changes in these sleep parameters associated with retirement 1, 2, and 3 y posttransition. Results: Retiring from full-time work was associated with bedtimes that were 30, 31, and 36 min later 1, 2, and 3 y postretirement; wake times that were 63, 69, and 78 min later; and sleep durations that were 15, 16, and 22 min longer 1, 2, and 3 y postretirement. These associations did not differ by sex or mental health status. Age and circadian preference modified the associations between retirement and change in sleep parameters; the increase in sleep duration was shorter and the wake time extension was lesser with advancing retirement age; those with evening preference had longer wake time extensions than those with morning preference. Conclusion: Transitioning to retirement is associated with longer sleep duration, later bedtimes, and later wake times. These changes were detectable about 1 y postwork transition and were persistent up to 3 y later. Citation: Hagen EW, Barnet JH, Hale L, Peppard PE. Changes in sleep duration and sleep timing associated with retirement transitions. SLEEP 2016;39(3):665–673. PMID:26564125

  1. Late time cosmological phase transitions 1: Particle physics models and cosmic evolution

    NASA Technical Reports Server (NTRS)

    Frieman, Joshua A.; Hill, Christopher T.; Watkins, Richard

    1991-01-01

    We described a natural particle physics basis for late-time phase transitions in the universe. Such a transition can seed the formation of large-scale structure while leaving a minimal imprint upon the microwave background anisotropy. The key ingredient is an ultra-light pseudo-Nambu-Goldstone boson with an astronomically large (O(kpc-Mpc)) Compton wavelength. We analyze the cosmological signatures of and constraints upon a wide class of scenarios which do not involve domain walls. In addition to seeding structure, coherent ultra-light bosons may also provide unclustered dark matter in a spatially flat universe, omega sub phi approx. = 1.

  2. Linear and nonlinear theory of the proton beam transit-time oscillator (TTO)

    NASA Astrophysics Data System (ADS)

    Walsh, John E.; Mostrom, Michael A.; Clark, Randy M.; Arman, M. Joseph; Campbell, Mark M.

    1989-07-01

    A theoretical characterization is presented for both the small- and large-amplitude behaviors of the intense beam-driven transit-time oscillator device which encompasses the effects of the beam self-fields and space-charge effects. The theory has been employed in the development of expressions for comparison with particle simulation results. Attention is given to the effect of beam-plasma frequency on gain, saturation growth in the monotron, the effects of space-charge depression on the transit angle, and the dependence of monotron performance on beam energy.

  3. The Diversity of Low-mass Exoplanets Characterized via Transit Timing

    NASA Astrophysics Data System (ADS)

    Jontof-Hutter, Daniel; Ford, Eric B.; Rowe, Jason F.; Lissauer, Jack. J.; Fabrycky, Daniel C.

    2016-10-01

    Transit timing variations (TTV) in multi-transiting systems enables precise characterizations of low-mass planets and their orbits. The range of orbital periods and incident fluxes with detailed TTV constraints complements the radial velocity sample for low-mass planets, pushing exoplanet characterization to the regime sub-Earth size planets and out to Mercury-like distances. This has revealed an astonishing diversity in the density of super-Earth mass planets. We summarize these and other contributions to exoplanet science from TTVs.

  4. LONG-TERM TRANSIT TIMING MONITORING AND REFINED LIGHT CURVE PARAMETERS OF HAT-P-13b

    SciTech Connect

    Fulton, Benjamin J.; Shporer, Avi; Winn, Joshua N.; Holman, Matthew J.; Pal, Andras; Zachary Gazak, J.

    2011-09-15

    We present 10 new transit light curves of the transiting hot Jupiter HAT-P-13b, obtained during two observational seasons by three different telescopes. When combined with 12 previously published light curves, we have a sample consisting of 22 transit light curves, spanning 1041 days across four observational seasons. We use this sample to examine the recently observed large-amplitude transit timing variations (TTVs) by Pal et al. and give refined system parameters. We find that the transit times are consistent with a linear ephemeris, with the exception of a single transit time, from UT 2009 November 5, for which the measured mid-transit time significantly deviates from our linear ephemeris. The nature of this deviation is not clear, and the rest of the data do not show any significant TTVs.

  5. [SPRINT on clinical practice: It's time to change the management of arterial hypertension in Latin America?

    PubMed

    Galvez-Olortegui, José Kelvin; Condor-Rojas, Yudy; Galvez-Olortegui, Tomas Vladimir; Camacho-Saavedra, Luis

    This paper analyzes the feasibility of the implementation of SPRINT trial results, the need to rethink the clinical practice guidelines(CPG) for the management of arterial hypertension and associated costs with daily practice applicability. SPRINT is a clinical trial comparing systolic blood pressure control <120mmHg and <140mmHg over cardiovascular complications, generating a great worldwide impact followed by publication of several studies that addressed relevance, usefulness, applicability and controversial aspects of SPRINT from different perspectives. Achieving blood pressure goals is one of the most discussed issue in widely used hypertension CPG around the world and in Latin American. SPRINT has generated and will generate a great impact on CPG, being necessary the reassessment of blood pressure goals and inclusion in future CPG, as has been considered in 2016 Canadian guideline and will be considered in NICE guideline update scheduled for June. The SPRINT trial raises new evidence for the management of hypertension, useful in people over 50 years, from urban populations, with defined cardiovascular risk without associated comorbidities. The applicability of SPRINT in Latin America is limited by increased costs associated with hypertensive patients' integrated health care, low care coverage, and lack of integrated care programs.

  6. Radiographic analysis of the effect of dietary fibers on rat colonic transit time

    SciTech Connect

    Lupton, J.R.; Meacher, M.M. )

    1988-11-01

    The effect of different fiber sources on colonic transit time was charted using serial radiographs. Sixty male Sprague-Dawley rats, 10 rats per group, were provided with either a fiber-free control diet or the control diet uniformly diluted to provide 8% dietary fiber from guar, pectin, cellulose, wheat bran, or oat bran. At surgery, radiopaque markers were inserted at defined distances in the mesentary closest to the large bowel. Three weeks postsurgery, the animals were intubated with 0.5 ml of a radiopaque marker, and radiographs were taken at 15-min intervals. Of the two poorly fermented fibers, cellulose was as slow as and wheat bran was faster than the fiber-free controls at five out of the six bowel segments measured. The fermentable fibers (pectin, guar, and oat bran) were fast through some bowel segments and slow through others. This study provides in vivo data on colonic transit time and shows that neither 24-h fecal weight nor total transit time is a good predictor of the rate of transit through particular gut segments.

  7. Measurement of Planet Masses with Transit Timing Variations Due to Synodic “Chopping” Effects

    NASA Astrophysics Data System (ADS)

    Deck, Katherine M.; Agol, Eric

    2015-04-01

    Gravitational interactions between planets in transiting exoplanetary systems lead to variations in the times of transit that are diagnostic of the planetary masses and the dynamical state of the system. Here we show that synodic “chopping” contributions to these transit timing variations (TTVs) can be used to uniquely measure the masses of planets without full dynamical analyses involving direct integration of the equations of motion. We present simple analytic formulae for the chopping signal, which are valid (generally \\lt 10% error) for modest eccentricities e≲ 0.1. Importantly, these formulae primarily depend on the mass of the perturbing planet, and therefore the chopping signal can be used to break the mass/free-eccentricity degeneracy, which can appear for systems near first-order mean motion resonances. Using a harmonic analysis, we apply these TTV formulae to a number of Kepler systems, which had been previously modeled with full dynamical analyses. We show that when chopping is measured, the masses of both planets can be determined uniquely, in agreement with previous results, but without the need for numerical orbit integrations. This demonstrates how mass measurements from TTVs may primarily arise from an observable chopping signal. The formula for chopping can also be used to predict the number of transits and timing precision required for future observations, such as those made by TESS or PLATO, in order to infer planetary masses through analysis of TTVs.

  8. Dating violence, bullying, and sexual harassment: longitudinal profiles and transitions over time.

    PubMed

    Miller, Shari; Williams, Jason; Cutbush, Stacey; Gibbs, Deborah; Clinton-Sherrod, Monique; Jones, Sarah

    2013-04-01

    Although there is growing recognition of the problem of dating violence, little is known about how it unfolds among young adolescents who are just beginning to date. This study examined classes (subgroups) and transitions between classes over three time points based on dating violence, bullying, and sexual harassment perpetration and victimization experienced by youth. The sample was ethnically diverse, consisting of 795 seventh-grade students from schools that were part of a multi-site, longitudinal evaluation of a dating violence initiative (50 % female; 27 % White, 32 % African American, 25 % Latino, 16 % other or multiple races). Results from latent transition analyses revealed five classes of students with distinct behavioral profiles: multi-problem (victimization and perpetration), bullying and sexual harassment (victimization and perpetration), bullying (victimization and perpetration) and sexual harassment (victimization only), bullying (victimization and perpetration), and a least problem group. The majority of classes were characterized by reports of both perpetration and victimization for at least one behavior. Girls were more likely to be in the less problematic classes. Class membership was fairly stable across the three time points. When students transitioned to a different class, the shift was most often from a more problematic to a less problematic class, particularly for girls. The findings support understanding dating violence within a dynamic, developmental process that recognizes related behaviors within and across individuals. Overall, the findings highlight the utility of person-oriented approaches to enhance our understanding of longitudinal profiles and transitions over time for dating violence and related behaviors.

  9. Simulation of Electron Cloud Density Distributions in RHIC Dipoles at Injection and Transition and Estimates for Scrubbing Times

    SciTech Connect

    He,P.; Blaskiewicz, M.; Fischer, W.

    2009-01-02

    In this report we summarize electron-cloud simulations for the RHIC dipole regions at injection and transition to estimate if scrubbing over practical time scales at injection would reduce the electron cloud density at transition to significantly lower values. The lower electron cloud density at transition will allow for an increase in the ion intensity.

  10. Transit time estimation using tritium and stable isotopes in a Mediterranean mountain catchment

    NASA Astrophysics Data System (ADS)

    Roig-Planasdemunt, Maria; Stewart, Mike; Latron, Jérôme; Llorens, Pilar; Morgenstern, Uwe

    2015-04-01

    Water resources of Mediterranean regions mainly depend on runoff generated in mountain areas. Therefore, study of the time water spends travelling through Mediterranean mountains is important for water resources management as it reflects the ability of catchments to retain and release water. Natural isotopes (tritium and stable isotopes) have been used in different environments to quantify the ages of water within catchments. However, there are relatively few studies of water transit times in Mediterranean mountain regions. Additionally, tritium dating is more common in Southern Hemisphere streams because they were less affected by tritium produced mainly in the North Hemisphere by nuclear weapons testing in the 1950s and 60s. With the aim of improving knowledge of the hydrological catchment functioning of Mediterranean mountain areas, this work estimates water transit times in spring water, groundwater and stream water using tritium and stable isotope (δ18O and δ2H) measurements in the Vallcebre Research Catchments (NE Spain, 42° 12'N, 1° 49'E). Tritium measurements from a previous study carried out in 1996-1998 (Herrmann et al., 1999) were supplemented by new samples collected on 3 November 2013. Difficulties with the age interpretation of the tritium measurements arise from the determination of the tritium input function, the different accuracies of the tritium measurements and the ambiguous ages resulting from past input of tritium from nuclear testing to the atmosphere. Water stable isotope samples were collected in rainfall, spring water, groundwater and streamwater at baseflow conditions every 15 days over a 27 month period. Detailed distributed hydrometric measurements (precipitation, potential evapotranspiration, discharge and water table level) were obtained during the same period. Preliminary results using δ18O, δ2H and tritium show that mean transit times in the Cal Rodó catchment (4.2 km2) ranged between 1.3 and 11.6 years. The lowest mean

  11. Single-point position and transition defects in continuous time quantum walks

    PubMed Central

    Li, Z. J.; Wang, J. B.

    2015-01-01

    We present a detailed analysis of continuous time quantum walks (CTQW) with both position and transition defects defined at a single point in the line. Analytical solutions of both traveling waves and bound states are obtained, which provide valuable insight into the dynamics of CTQW. The number of bound states is found to be critically dependent on the defect parameters, and the localized probability peaks can be readily obtained by projecting the state vector of CTQW on to these bound states. The interference between two bound states are also observed in the case of a transition defect. The spreading of CTQW probability over the line can be finely tuned by varying the position and transition defect parameters, offering the possibility of precision quantum control of the system. PMID:26323855

  12. POSSIBLE TRANSIT TIMING VARIATIONS OF THE TrES-3 PLANETARY SYSTEM

    SciTech Connect

    Jiang, Ing-Guey; Wu, Yu-Ting; Chien, Ping; Lin, Yi-Ling; Chen, Hong-Yu; Hu, Juei-Hwa; Yeh, Li-Chin; Thakur, Parijat; Sun Zhao; Ji Jianghui

    2013-03-15

    Five newly observed transit light curves of the TrES-3 planetary system are presented. Together with other light-curve data from the literature, 23 transit light curves in total, which cover an overall timescale of 911 epochs, have been analyzed through a standard procedure. From these observational data, the system's orbital parameters are determined and possible transit timing variations (TTVs) are investigated. Given that a null TTV produces a fit with reduced {chi}{sup 2} = 1.52, our results agree with previous work, that TTVs might not exist in these data. However, a one-frequency oscillating TTV model, giving a fit with a reduced {chi}{sup 2} = 0.93, does possess a statistically higher probability. It is thus concluded that future observations and dynamical simulations for this planetary system will be very important.

  13. Possible Transit Timing Variations of the TrES-3 Planetary System

    NASA Astrophysics Data System (ADS)

    Jiang, Ing-Guey; Yeh, Li-Chin; Thakur, Parijat; Wu, Yu-Ting; Chien, Ping; Lin, Yi-Ling; Chen, Hong-Yu; Hu, Juei-Hwa; Sun, Zhao; Ji, Jianghui

    2013-03-01

    Five newly observed transit light curves of the TrES-3 planetary system are presented. Together with other light-curve data from the literature, 23 transit light curves in total, which cover an overall timescale of 911 epochs, have been analyzed through a standard procedure. From these observational data, the system's orbital parameters are determined and possible transit timing variations (TTVs) are investigated. Given that a null TTV produces a fit with reduced χ2 = 1.52, our results agree with previous work, that TTVs might not exist in these data. However, a one-frequency oscillating TTV model, giving a fit with a reduced χ2 = 0.93, does possess a statistically higher probability. It is thus concluded that future observations and dynamical simulations for this planetary system will be very important.

  14. [Effects of various prokinetic drugs on gastrointestinal transit times in patients with progressive systemic scleroderma].

    PubMed

    Folwaczny, C; Läritz, M; Meurer, M; Endres, S P; König, A; Schindlbeck, N

    1997-10-01

    The intestine is involved in about half of the cases with progressive-systemic sclerosis. Intestinal transit disturbances which are caused by neuropathy of the enteric nerve system occur frequently. However, upto-date only few studies which determined the effect of prokinetic drugs exist. Patients with intestinal involvement caused by progressive-systemic sclerosis were treated with the prokinetic drugs cisapride (20 mg, TID; n = 9), erythromycin (250 mg, TID; n = 7) and octreotide (50 micrograms s. c., at night time; n = 5) over a period of four weeks. At study entry and after each treatment period the transit times through the stomach, small and large intestine were evaluated by use of the metal-detector test. Gastric emptying was only accelerated by erythromycin (42 +/- 3 min vs. 54 +/- 6 min; p = 0.0422), whereas treatment with cisapride and octreotide did not result in significant changes (48 +/- 4 min; p = 0.3743 and 44 +/- 4 min; p = 0.1975; resp.). Small intestinal transit times were not altered significantly by cisapride (108 +/- 15 min vs. 108 +/- 9 min; p = 0.2733), crythromycin (92 +/- 8 min; p = 0.0707) or octreotide (106 +/- 12 min; p = 0.8927). Furthermore colonic transit was not fastened by none of the prokinetic agents (study entry: 68 +/- 12 h; cisapride: 88 +/- 12 h; p = 0.0569; erythromycin 77 +/- 14 h; p = 0.7349; octreotide 107 +/- 14 h; p = 0.8927). Four patients were withdrawn from the study because of diarrhea. Prokinetic drugs do not seem to have a major impact on intestinal transit times in patients with progressive-systemic sclerosis. The use of these drugs is limited because of frequent side effects.

  15. Transit Timing Variation analysis with Kepler light curves of KOI 227 and Kepler 93b

    NASA Astrophysics Data System (ADS)

    Dulz, Shannon; Reed, Mike

    2017-01-01

    By searching for transit signals in approximately 150,000 stars, NASA’s Kepler Space telescope found thousands of exoplanets over its primary mission from 2009 to 2013 (Tenenbaum et al. 2014, ApJS, 211, 6). Yet, a detailed follow-up examination of Kepler light curves may contribute more evidence on system dynamics and planetary atmospheres of these objects. Kepler’s continuous observing of these systems over the mission duration produced light curves of sufficient duration to allow for the search for transit timing variations. Transit timing variations over the course of many orbits may indicate a precessing orbit or the existence of a non-transiting third body such as another exoplanet. Flux contributions of the planet just prior to secondary eclipse may provide a measurement of bond albedo from the day-side of the transiting planet. Any asymmetries of the transit shape may indicate thermal asymmetries which can measure upper atmosphere motion of the planet. These two factors can constrain atmospheric models of close orbiting exoplanets. We first establish our procedure with the well-documented TTV system, KOI 227 (Nesvorny et al. 2014, ApJ, 790, 31). Using the test case of KOI 227, we analyze Kepler-93b for TTVs and day-side flux contributions. Kepler-93b is likely a rocky planet with R = 1.50 ± 0.03 Earth Radii and M = 2.59 ± 2.0 Earth Masses (Marcy et al. 2014, ApJS, 210, 20). This research is funded by a NASA EPSCoR grant.

  16. The mass of the Mars-sized exoplanet Kepler-138 b from transit timing.

    PubMed

    Jontof-Hutter, Daniel; Rowe, Jason F; Lissauer, Jack J; Fabrycky, Daniel C; Ford, Eric B

    2015-06-18

    Extrasolar planets that pass in front of their host star (transit) cause a temporary decrease in the apparent brightness of the star, providing a direct measure of the planet's size and orbital period. In some systems with multiple transiting planets, the times of the transits are measurably affected by the gravitational interactions between neighbouring planets. In favourable cases, the departures from Keplerian orbits (that is, unaffected by gravitational effects) implied by the observed transit times permit the planetary masses to be measured, which is key to determining their bulk densities. Characterizing rocky planets is particularly difficult, because they are generally smaller and less massive than gaseous planets. Therefore, few exoplanets near the size of Earth have had their masses measured. Here we report the sizes and masses of three planets orbiting Kepler-138, a star much fainter and cooler than the Sun. We determine that the mass of the Mars-sized inner planet, Kepler-138 b, is 0.066(+0.059)(-0.037) Earth masses. Its density is 2.6(+2.4)(-1.5) grams per cubic centimetre. The middle and outer planets are both slightly larger than Earth. The middle planet's density (6.2(+5.8)(-3.4) grams per cubic centimetre) is similar to that of Earth, and the outer planet is less than half as dense at 2.1(+2.2)(-1.2) grams per cubic centimetre, implying that it contains a greater portion of low-density components such as water and hydrogen.

  17. Relations between transit time, fermentation products, and hydrogen consuming flora in healthy humans.

    PubMed Central

    El Oufir, L; Flourié, B; Bruley des Varannes, S; Barry, J L; Cloarec, D; Bornet, F; Galmiche, J P

    1996-01-01

    BACKGROUND/AIMS: To investigate whether transit time could influence H2 consuming flora and certain indices of colonic bacterial fermentation. METHODS: Eight healthy volunteers (four methane excretors and four non-methane excretors) were studied for three, three week periods during which they received a controlled diet alone (control period), and then the same diet with cisapride or loperamide. At the end of each period, mean transit time (MTT) was estimated, an H2 lactulose breath test was performed, and stools were analysed. RESULTS: In the control period, transit time was inversely related to faecal weight, sulphate reducing bacteria counts, concentrations of total short chain fatty acids (SCFAs), propionic and butyric acids, and H2 excreted in breath after lactulose ingestion. Conversely, transit time was positively related to faecal pH and tended to be related to methanogen counts. Methanogenic bacteria counts were inversely related to those of sulphate reducing bacteria and methane excretors had slower MTT and lower sulphate reducing bacteria counts than non-methane excretors. Compared with the control period, MTT was significantly shortened (p < 0.05) by cisapride and prolonged (p < 0.05) by loperamide (73 (11) hours, 47 (5) hours and 147 (12) hours for control, cisapride, and loperamide, respectively, mean (SD)). Cisapride reduced transit time was associated with (a) a significant rise in faecal weight, sulphate reducing bacteria, concentrations of total SCFAs, and propionic and butyric acids and breath H2 as well as (b) a significant fall in faecal pH and breath CH4 excretion, and (c) a non-significant decrease in the counts of methanogenic bacteria. Reverse relations were roughly the same during the loperamide period including a significant rise in the counts of methanogenic bacteria and a significant fall in those of sulphate reducing bacteria. CONCLUSIONS: Transit time differences between healthy volunteers are associated with differences in H2

  18. Non-invasive quantification of peripheral arterial volume distensibility and its non-linear relationship with arterial pressure.

    PubMed

    Zheng, Dingchang; Murray, Alan

    2009-05-29

    Arterial wall function is associated with different physiological and clinical factors. Changes in arterial pressure cause major changes in the arterial wall. This study presents a simple non-invasive method to quantify arterial volume distensibility changes with different arterial pressures. The electrocardiogram, finger and ear photoplethysmogram were recorded from 15 subjects with the right arm at five different positions (90 degrees , 45 degrees , 0 degrees , -45 degrees and -90 degrees referred to the horizontal level). Arm pulse propagation time was determined by subtracting ear pulse transit time from finger pulse transit time, and was used to obtain arterial volume distensibility. The mean arterial blood pressure with the arm at the horizontal level was acquired, and changes with position were calculated using the hydrostatic principle that blood pressure in the arm is linearly related to its vertical distance from the horizontal level. The mean arm pulse propagation times for the five different positions were 88, 72, 57, 54 and 52ms, with the corresponding mean arterial volume distensibility of 0.234%, 0.158%, 0.099%, 0.088% and 0.083% per mmHg. For all consecutive changes in arm position, arm pulse propagation time and arterial volume distensibility, were significantly different (all probability P<0.05). The slopes of arm pulse propagation time and arterial volume distensibility against arterial pressure decreased significantly between each consecutive arm position from 90 degrees to -45 degrees (all P<0.01), indicating significant non-linearity. The experimental results fitted the physiological exponential model and Langewouters' arctangent model well, and were also comparable to published data with arterial volume distensibility approximately tripling for transmural pressure changes from 101 to 58mmHg. In conclusion, the inverse and non-linear relationship between arterial volume distensibility and arterial pressure has been quantified using a simple

  19. Time Course of Isoflurane-Induced Vasodilation: A Doppler Ultrasound Study of the Left Coronary Artery in Mice.

    PubMed

    Lenzarini, Francesca; Di Lascio, Nicole; Stea, Francesco; Kusmic, Claudia; Faita, Francesco

    2016-04-01

    Isoflurane is widely used as vasodilator in studies of coronary flow reserve (CFR) in small animals, but the protocols have not been standardized. This study assessed the time course of the increase in isoflurane-induced flow in the mouse coronary artery by pulsed-wave Doppler measurements at 1% isoflurane concentration maintained for 6 min and then increased to 2.5% for 30 min. Velocity-time integral and velocity peak values were best fitted by the sigmoid model, which allowed derivation of the mean time (Tt90 = 14 min) of high-isoflurane needed to reach 90% of the hyperemic plateau value. In subsequent experiments, CFR was measured at 4 min (mean time of literature data) and 14 min of hyperemic response. The 4-min CFR was significantly lower than the 14 -min CFR, and the Bland-Altman plot revealed significant bias of the 4-min CFR against the 14-min CFR. This result suggests that measurements of flow velocity at times shorter than 14 min may be inappropriate for expressing the effective value of CFR.

  20. Transition from lognormal to χ2-superstatistics for financial time series

    NASA Astrophysics Data System (ADS)

    Xu, Dan; Beck, Christian

    2016-07-01

    Share price returns on different time scales can be well modelled by a superstatistical dynamics. Here we provide an investigation which type of superstatistics is most suitable to properly describe share price dynamics on various time scales. It is shown that while χ2-superstatistics works well on a time scale of days, on a much smaller time scale of minutes the price changes are better described by lognormal superstatistics. The system dynamics thus exhibits a transition from lognormal to χ2 superstatistics as a function of time scale. We discuss a more general model interpolating between both statistics which fits the observed data very well. We also present results on correlation functions of the extracted superstatistical volatility parameter, which exhibits exponential decay for returns on large time scales, whereas for returns on small time scales there are long-range correlations and power-law decay.

  1. Potential for quantification of regionally altered myocardial perfusion by analysis of rubidium and thallium mean transit times in the rabbit heart

    SciTech Connect

    Marshall, R.C.; Taylor, S.E.; Powers-Risius, P.

    1995-05-01

    Quantitative estimation of regionally altered perfusion could result in improved clinical care for patients with coronary artery disease. We hypothesized that myocardial blood flow (F) and mean transit time (T{sub mtt}) should vary reciprocally for potassium analogs, such as rubidium and thallium, based on the relationship V{sub d}/F=T{sub mtt}. Twelve isolated blood-perfused rabbit hearts were studied at flows ranging from 0.7 to 2.92 ml/gm min{sup -1}. Bolus injections of Rb-83, Tl-201 and I-125 albumin were followed by subsequent venous ampling for 20 to 30 minutes. T{sub mtt} was estimated using two methods which compensate for the dispersion of the bolus in the blood vessels. In Method A, the I-125 albumin venous concentration curve was convolved with a Dirac delta function and one or more exponentials, and fit to the Rb-83 and Tl-201 venous concentration curves. Mean transit times of the Rb-83 and Tl-201 were computed as the weighted sums of the fitted components. In B, all three venous concentration curves were extrapolated by fitting a straight line to the tail of the semi-log plot of each curve. Extrapolated curves were then normalized to unit area, weighted by time, and numerically integrated to obtain gross mean transit times. Net mean transit times for Rb-83 and Tl-201 were then obtained by subtracting the gross mean transit time for I-125 albumin from those for Rb-83 and Tl-201. T{sub mtt} ranged from 4.0 to 15.5 min for Rb-83 and 6.0 to 29.7 min for Tl-=201. Correlations between 1/T{sub mtt} and F for Tl-201 were y = 0.064x - 0.005, r = 0.87 (Method A) and y = 0.049x + 0.011, r = 0.80 (Method B). The correlation for Rb-83 and Method B was y = 0.07x + 0.03, r = 0.89 which was significantly superior to Method A. Results are consistent with the hypothesis that F and T{sub mtt} vary inversely and suggest that T{sub mtt} could be used to quantitatively estimate regional perfusion in vivo after subtraction of the mean transit time of the input function.

  2. Tracer sampling frequency influences estimates of young water fraction and streamwater transit time distribution

    NASA Astrophysics Data System (ADS)

    Stockinger, Michael P.; Bogena, Heye R.; Lücke, Andreas; Diekkrüger, Bernd; Cornelissen, Thomas; Vereecken, Harry

    2016-10-01

    The streamwater transit time distribution (TTD) of a catchment is used to derive insights into the movement of precipitation water via various flow paths to the catchment's stream. Typically, TTDs are estimated by using the convolution integral to model a weekly tracer signal measured in streamflow. Another approach for evaluating the transit time of water to the catchment stream is the fraction of young water (Fyw) in streamflow that is younger than a certain threshold age, which also relies on tracer data. However, few studies used tracer data with a higher sampling frequency than weekly. To investigate the influence of the sampling frequency of tracer data on estimates of TTD and Fyw, we estimated both indicators for a humid, mesoscale catchment in Germany using tracer data of weekly and higher sampling frequency. We made use of a 1.5 year long time series of daily to sub-daily precipitation and streamwater isotope measurements, which were aggregated to create the weekly resolution data set. We found that a higher sampling frequency improved the stream isotope simulation compared to a weekly one (0.35 vs. 0.24 Nash-Sutcliffe Efficiency) and showed more pronounced short-term dynamics in the simulation result. The TTD based on the high temporal resolution data was considerably different from the weekly one with a shift towards faster transit times, while its corresponding mean transit time of water particles was approximately reduced by half (from 9.5 to 5 years). Similar to this, Fyw almost doubled when applying high resolution data compared to weekly one. Thus, the different approaches yield similar results and strongly support each other. This indicates that weekly isotope tracer data lack information about faster water transport mechanisms in the catchment. Thus, we conclude that a higher than weekly sampling frequency should be preferred when investigating a catchment's water transport characteristics. When comparing TTDs or Fyw of different catchments, the

  3. Assessing the effect of the time since transition to organic farming on plants and butterflies.

    PubMed

    Jonason, Dennis; Andersson, Georg K S; Ockinger, Erik; Rundlöf, Maj; Smith, Henrik G; Bengtsson, Jan

    2011-06-01

    1.Environmental changes may not always result in rapid changes in species distributions, abundances or diversity. In order to estimate the effects of, for example, land-use changes caused by agri-environment schemes (AES) on biodiversity and ecosystem services, information on the time-lag between the application of the scheme and the responses of organisms is essential.2.We examined the effects of time since transition (TST) to organic farming on plant species richness and butterfly species richness and abundance. Surveys were conducted in cereal fields and adjacent field margins on 60 farms, 20 conventional and 40 organic, in two regions in Sweden. The organic farms were transferred from conventional management between 1 and 25 years before the survey took place. The farms were selected along a gradient of landscape complexity, indicated by the proportion of arable land, so that farms with similar TST were represented in all landscape types. Organism responses were assessed using model averaging.3.Plant and butterfly species richness was c.20% higher on organic farms and butterfly abundance was about 60% higher, compared with conventional farms. Time since transition affected butterfly abundance gradually over the 25-year period, resulting in a 100% increase. In contrast, no TST effect on plant or butterfly species richness was found, indicating that the main effect took place immediately after the transition to organic farming.4.Increasing landscape complexity had a positive effect on butterfly species richness, but not on butterfly abundance or plant species richness. There was no indication that the speed of response to organic farming was affected by landscape complexity.5.Synthesis and applications. The effect of organic farming on diversity was rapid for plant and butterfly species richness, whereas butterfly abundance increased gradually with time since transition. If time-lags in responses to AESs turn out to be common, long-term effects would need to be

  4. Fluctuation of similarity (FLUS) to detect transitions between distinct dynamical regimes in short time series

    PubMed Central

    Malik, Nishant; Marwan, Norbert; Zou, Yong; Mucha, Peter J.; Kurths, Jürgen

    2016-01-01

    A method to identify distinct dynamical regimes and transitions between those regimes in a short univariate time series was recently introduced [1], employing the computation of fluctuations in a measure of nonlinear similarity based on local recurrence properties. In the present work, we describe the details of the analytical relationships between this newly introduced measure and the well known concepts of attractor dimensions and Lyapunov exponents. We show that the new measure has linear dependence on the effective dimension of the attractor and it measures the variations in the sum of the Lyapunov spectrum. To illustrate the practical usefulness of the method, we identify various types of dynamical transitions in different nonlinear models. We present testbed examples for the new method’s robustness against noise and missing values in the time series. We also use this method to analyze time series of social dynamics, specifically an analysis of the U.S. crime record time series from 1975 to 1993. Using this method, we find that dynamical complexity in robberies was influenced by the unemployment rate until the late 1980’s. We have also observed a dynamical transition in homicide and robbery rates in the late 1980’s and early 1990’s, leading to increase in the dynamical complexity of these rates. PMID:25019852

  5. Fluctuation of similarity to detect transitions between distinct dynamical regimes in short time series

    NASA Astrophysics Data System (ADS)

    Malik, Nishant; Marwan, Norbert; Zou, Yong; Mucha, Peter J.; Kurths, Jürgen

    2014-06-01

    A method to identify distinct dynamical regimes and transitions between those regimes in a short univariate time series was recently introduced [N. Malik et al., Europhys. Lett. 97, 40009 (2012), 10.1209/0295-5075/97/40009], employing the computation of fluctuations in a measure of nonlinear similarity based on local recurrence properties. In this work, we describe the details of the analytical relationships between this newly introduced measure and the well-known concepts of attractor dimensions and Lyapunov exponents. We show that the new measure has linear dependence on the effective dimension of the attractor and it measures the variations in the sum of the Lyapunov spectrum. To illustrate the practical usefulness of the method, we identify various types of dynamical transitions in different nonlinear models. We present testbed examples for the new method's robustness against noise and missing values in the time series. We also use this method to analyze time series of social dynamics, specifically an analysis of the US crime record time series from 1975 to 1993. Using this method, we find that dynamical complexity in robberies was influenced by the unemployment rate until the late 1980s. We have also observed a dynamical transition in homicide and robbery rates in the late 1980s and early 1990s, leading to increase in the dynamical complexity of these rates.

  6. Fluctuation of similarity to detect transitions between distinct dynamical regimes in short time series.

    PubMed

    Malik, Nishant; Marwan, Norbert; Zou, Yong; Mucha, Peter J; Kurths, Jürgen

    2014-06-01

    A method to identify distinct dynamical regimes and transitions between those regimes in a short univariate time series was recently introduced [N. Malik et al., Europhys. Lett. 97, 40009 (2012)], employing the computation of fluctuations in a measure of nonlinear similarity based on local recurrence properties. In this work, we describe the details of the analytical relationships between this newly introduced measure and the well-known concepts of attractor dimensions and Lyapunov exponents. We show that the new measure has linear dependence on the effective dimension of the attractor and it measures the variations in the sum of the Lyapunov spectrum. To illustrate the practical usefulness of the method, we identify various types of dynamical transitions in different nonlinear models. We present testbed examples for the new method's robustness against noise and missing values in the time series. We also use this method to analyze time series of social dynamics, specifically an analysis of the US crime record time series from 1975 to 1993. Using this method, we find that dynamical complexity in robberies was influenced by the unemployment rate until the late 1980s. We have also observed a dynamical transition in homicide and robbery rates in the late 1980s and early 1990s, leading to increase in the dynamical complexity of these rates.

  7. Transit Timing Observations from Kepler: IV. Confirmation of 4 Multiple Planet Systems by Simple Physical Models

    SciTech Connect

    Fabrycky, Daniel C.; Ford, Eric B.; Steffen, Jason H.; Rowe, Jason F.; Carter, Joshua A.; Moorhead, Althea V.; Batalha, Natalie M.; Borucki, William J.; Bryson, Steve; Buchhave, Lars A.; Christiansen, Jessie L.; /SETI Inst., Mtn. View /NASA, Ames /Caltech

    2012-01-01

    Eighty planetary systems of two or more planets are known to orbit stars other than the Sun. For most, the data can be sufficiently explained by non-interacting Keplerian orbits, so the dynamical interactions of these systems have not been observed. Here we present 4 sets of lightcurves from the Kepler spacecraft, which each show multiple planets transiting the same star. Departure of the timing of these transits from strict periodicity indicates the planets are perturbing each other: the observed timing variations match the forcing frequency of the other planet. This confirms that these objects are in the same system. Next we limit their masses to the planetary regime by requiring the system remain stable for astronomical timescales. Finally, we report dynamical fits to the transit times, yielding possible values for the planets masses and eccentricities. As the timespan of timing data increases, dynamical fits may allow detailed constraints on the systems architectures, even in cases for which high-precision Doppler follow-up is impractical.

  8. Characterizing Low-Mass Planets in Kepler's Multi-Planet Systems with Transit Timing

    NASA Astrophysics Data System (ADS)

    Jontof-Hutter, Daniel; Lissauer, Jack; Rowe, Jason; Fabrycky, Daniel

    2014-11-01

    The Kepler mission has revealed an abundance of planets in a regime of mass and size that is absent from the Solar System. This includes systems of high multiplicity within 1 AU, where low-mass volatile-rich planets have been observed in compact orbital configurations. Smaller, rocky planets have also been observed in such systems. The existing sample of characterized planets on the mass-radius diagram shows no abrupt transition from rocky planets to those that must be volatile-rich, but characteristic trends are beginning to emerge. More precise characterizations of planets by mass, radius, and incident flux will aid in revealing fundamental properties of a common class of exoplanets. There is a small sample of exoplanets with known masses and radii, mostly hot jupiters whose radii are known from transit depths, and whose masses are determined from radial velocity spectroscopy (RV). In the absence of mass determinations via RV observations, transit timing variations (TTVs) offer a chance to probe perturbations between planets that pass close to one another or are near resonance, and hence dynamical fits to observed transit times can be used to measure planetary masses and orbital parameters. Such modelling with Kepler data probes planetary masses over orbital periods ranging from ~5-100 days, complementing the sample of RV detections. Furthermore, in select cases, dynamical fits to observed TTVs can tightly constrain the orbital eccentricity vectors, which can, alongside the transit light curve, tightly constrain the density and radius of the host star, and hence reduce the uncertainty on planetary radius. TTV studies have revealed a class of low-mass low-density objects with a substantial mass fraction in the form of a voluminous H-rich atmosphere. To these we add precise mass measurements of the outer planets of Kepler-33, a compact system with five known transiting planets, three of which show detectable transit timing variations. These results will be placed

  9. Does the Timing of Transition Matter? Comparison of German Students' Self-Perceptions before and after Transition to Secondary School

    ERIC Educational Resources Information Center

    Arens, A. Katrin; Yeung, Alexander Seeshing; Craven, Rhonda G.; Watermann, Rainer; Hasselhorn, Marcus

    2013-01-01

    The often observed decline in students' self-perceptions across transition to secondary school after grade 6 is often attributed to students' entry to puberty. This study aims to examine whether lowered self-perceptions can be observed after transition in Germany which occurs after grade 4 and thus takes place before puberty. Fifth graders (N =…

  10. Time-gated single-photon detection module with 110 ps transition time and up to 80 MHz repetition rate

    SciTech Connect

    Buttafava, Mauro Boso, Gianluca; Ruggeri, Alessandro; Tosi, Alberto; Dalla Mora, Alberto

    2014-08-15

    We present the design and characterization of a complete single-photon counting module capable of time-gating a silicon single-photon avalanche diode with ON and OFF transition times down to 110 ps, at repetition rates up to 80 MHz. Thanks to this sharp temporal filtering of incoming photons, it is possible to reject undesired strong light pulses preceding (or following) the signal of interest, allowing to increase the dynamic range of optical acquisitions up to 7 decades. A complete experimental characterization of the module highlights its very flat temporal response, with a time resolution of the order of 30 ps. The instrument is fully user-configurable via a PC interface and can be easily integrated in any optical setup, thanks to its small and compact form factor.

  11. Universal space-time scaling symmetry in the dynamics of bosons across a quantum phase transition

    NASA Astrophysics Data System (ADS)

    Clark, Logan W.; Feng, Lei; Chin, Cheng

    2016-11-01

    The dynamics of many-body systems spanning condensed matter, cosmology, and beyond are hypothesized to be universal when the systems cross continuous phase transitions. The universal dynamics are expected to satisfy a scaling symmetry of space and time with the crossing rate, inspired by the Kibble-Zurek mechanism. We test this symmetry based on Bose condensates in a shaken optical lattice. Shaking the lattice drives condensates across an effectively ferromagnetic quantum phase transition. After crossing the critical point, the condensates manifest delayed growth of spin fluctuations and develop antiferromagnetic spatial correlations resulting from the sub-Poisson distribution of the spacing between topological defects. The fluctuations and correlations are invariant in scaled space-time coordinates, in support of the scaling symmetry of quantum critical dynamics.

  12. High-power transit-time oscillator: Onset of oscillation and saturation

    NASA Astrophysics Data System (ADS)

    Luginsland, J. W.; Arman, M. J.; Lau, Y. Y.

    1997-12-01

    A simple circuit model is used to investigate the transit-time oscillator (TTO) driven by a high-current diode. A novel condition for the onset of oscillation is derived in terms of the diode impedance. It is shown that a low impedance is required for the production of high-power microwaves in a TTO. The initial growth is calculated, and the saturation level is numerically computed using the one-dimensional model. These one-dimensional (1-D) results are in excellent agreement with a full scale two-dimensional Particle-in-Cell simulation. The success of the much simpler 1-D model allows a close examination of the roles played by the convection current and by the displacement current, as well as the modification in the transit time due to the intense space charge within the gap.

  13. Universal space-time scaling symmetry in the dynamics of bosons across a quantum phase transition.

    PubMed

    Clark, Logan W; Feng, Lei; Chin, Cheng

    2016-11-04

    The dynamics of many-body systems spanning condensed matter, cosmology, and beyond are hypothesized to be universal when the systems cross continuous phase transitions. The universal dynamics are expected to satisfy a scaling symmetry of space and time with the crossing rate, inspired by the Kibble-Zurek mechanism. We test this symmetry based on Bose condensates in a shaken optical lattice. Shaking the lattice drives condensates across an effectively ferromagnetic quantum phase transition. After crossing the critical point, the condensates manifest delayed growth of spin fluctuations and develop antiferromagnetic spatial correlations resulting from the sub-Poisson distribution of the spacing between topological defects. The fluctuations and correlations are invariant in scaled space-time coordinates, in support of the scaling symmetry of quantum critical dynamics.

  14. Lagrangian Descriptors of Thermalized Transition States on Time-Varying Energy Surfaces

    NASA Astrophysics Data System (ADS)

    Craven, Galen T.; Hernandez, Rigoberto

    2015-10-01

    Thermalized chemical reactions driven under dynamical load are characteristic of activated dynamics for arbitrary nonautonomous systems. Recent generalizations of transition state theory to obtain formally exact rates have required the construction of a time-dependent transition state trajectory. Here, we show that Lagrangian descriptors can be used to obtain this structure directly. By developing a phase space separatrix that is void of recrossings, these constructs allow for the principal criterion in the implementation of modern rate theories to be satisfied. Thus, the reactive flux over a time-varying barrier can be determined without ambiguity in chemical reactions. The generality of the formalism suggests that this approach is applicable to any activated system subjected to arbitrary driving and thermal fluctuations.

  15. Real-Time Ophthalmoscopic Findings of Super-Selective Intra-Ophthalmic Artery Chemotherapy in a Non-Human Primate Model

    PubMed Central

    Wilson, Matthew W.; Jackson, John S.; Phillips, Blanca X.; Buchanan, Jacquelyn; Frase, Sharon; Wang, Fan; Steinle, Jena J.; Stewart, Clinton F.; Mandrell, Timothy D.; Haik, Barrett G.; Williams, J. Scott

    2012-01-01

    Objectives To report real-time ophthalmoscopic findings during super-selective intra-ophthalmic artery chemotherapy (SSIOAC) in a non-human primate (NHP) model. Methods Six adult male Rhesus macaques (Macacca mulatta) were randomly assigned into one of two treatment cohorts; MEL treated with 5 mg/30 mL melphalan, and CBP treated with 30 mg/30 mL carboplatin. Each animal underwent three separate SSIOAC procedures at three-week intervals. Digital retinal images were obtained during each infusion. Intravenous fluorescein angiography was performed immediately after each procedure. Results All SSIOAC procedures were successfully completed. Toxicities were equally distributed between drug cohorts. Systemic toxicities included mild bone marrow suppression in all animals and anorexia in one. One animal had greater than 50% narrowing of the treated ophthalmic artery after its second infusion. All 18 procedures (100%) resulted in pulsatile optic nerve and choroid blanching, retinal artery narrowing, and retinal edema. Retinal artery sheathing was found during 17 (of 18, 94%) procedures, and retinal artery precipitates were seen in 10 (of 18, 56%). Choroidal hypoperfusion (18 of 18, 100%) was seen by fluorescein angiogram. Conclusions Real-time ophthalmic investigations are useful and, in our NHP model, indicate prevalent, acute ocular vascular toxicities during SSIOAC. Clinical Relevance Real-time retinal imaging is feasible in an NHP model of SSIOAC. Application to SSIOAC in children may shed insight into reported vascular toxicities. PMID:22084215

  16. Using Latent Transition Analysis in Nursing Research to Explore Change Over Time

    PubMed Central

    Roberts, Tonya J.; Ward, Sandra E.

    2011-01-01

    Background Latent transition analysis is a method of modeling change over time in categorical variables. It has been used in the social sciences for many years, but not in nursing research. Objective To illustrate the utility of latent transition analysis for nursing research by presenting a case example (a secondary analysis of data from a previously conducted randomized control trial testing the effectiveness of a tailored psychoeducational intervention to decrease patient-related attitudinal barriers to cancer pain management) and to understand for whom, and in what direction, the tailored intervention resulted in change with respect to attitudinal barriers and pain symptoms. Method The model was developed by (a) defining a class structure based on individuals’ barrier patterns, (b) adding demographic predictors and distal pain outcomes, and (c) modeling and testing transitions across classes. Results There were two classes of individuals: Low Barriers and High Barriers. Older, less educated individuals were more likely to be in the High Barriers class at time 1. Individuals in either class did not have different pain outcomes at the end of the study. Of those individuals that transitioned across classes, those who received the intervention were statistically more likely to move in a favorable direction (to the Low Barriers class). Furthermore, there is evidence that some individuals in the control group had unfavorable outcomes. Discussion The results from the example provide useful information about for whom, and in what direction, the intervention resulted in change. Latent transition analysis is a valuable procedure for nurse researchers because it collapses large arrays of categorical data into meaningful patterns. It is a flexible modeling procedure with extensions allowing further understanding of a change process. PMID:21127448

  17. Measuring the masses, radii and orbital eccentricities of sub-Neptunes with transit timing variations.

    NASA Astrophysics Data System (ADS)

    Jontof-Hutter, Daniel; Lissauer, Jack J.; Rowe, Jason; Fabrycky, Daniel C.

    2014-05-01

    Outside our solar system, there is a small sample of planets with known masses and radii, mostly hot jupiters whose radii are known from transit depths, and whose masses are determined from radial velocity spectroscopy (RV). In the absence of mass determinations via RV observations, transit timing variations (TTVs) offer a chance to probe perturbations between planets that pass close to one another or are near resonance, and hence dynamical fits to observed transit times can measure planetary masses and orbital parameters. Such modeling can probe planetary masses at longer orbital periods than RV targets, although not without some challenges. For example, in modeling pairwise planetary perturbations near first order mean motion resonances, a degeneracy between eccentricity and mass exists that limits the accuracy of mass determinations. Nevertheless, in several compact multiplanet systems, fitting complex TTV signals can break the degeneracy, permitting useful mass constraints, and precise measures of small but non-zero eccentricity.The precision in measuring the radius of a transiting planet rests on the uncertainty in the stellar radius, which is typically ~10% for targets with spectral follow-up. With dynamical fits, however, solutions for the orbital parameters including the eccentricity vectors can, alongside the transit light curves, tightly constrain the stellar density and radius. Alongside spectroscopic data, our dynamical fits to TTVs reduced the stellar and hence planetary radius uncertainties at Kepler-11 and Kepler-79 to just 2%, permitting useful planetary density determinations. In the case of Kepler-79, planetary bulk densities are remarkably low given the planetary masses. Indeed, several multiplanet systems characterized by TTV show much lower planetary densities than typical RV determinations in the same mass range. While this reflects the detection biases of both techniques, it also represents a growing sample of characterized systems of

  18. Comparison of time-frequency distribution techniques for analysis of simulated Doppler ultrasound signals of the femoral artery.

    PubMed

    Guo, Z; Durand, L G; Lee, H C

    1994-04-01

    The time-frequency distribution of the Doppler ultrasound blood flow signal is normally computed by using the short-time Fourier transform or autoregressive modeling. These two techniques require stationarity of the signal during a finite interval. This requirement imposes some limitations on the distribution estimate. In the present study, three new techniques for nonstationary signal analysis (the Choi-Williams distribution, a reduced interference distribution, and the Bessel distribution) were tested to determine their advantages and limitations for analysis of the Doppler blood flow signal of the femoral artery. For the purpose of comparison, a model stimulating the quadrature Doppler signal was developed, and the parameters of each technique were optimized based on the theoretical distribution. Distributions computed using these new techniques were assessed and compared with those computed using the short-time Fourier transform and autoregressive modeling. Three indexes, the correlation coefficient, the integrated squared error, and the normalized root-mean-squared error of the mean frequency waveform, were used to evaluate the performance of each technique. The results showed that the Bessel distribution performed the best, but the Choi-Williams distribution and autoregressive modeling are also techniques which can generate good time-frequency distributions of Doppler signals.

  19. Real-Time 12-Lead High-Frequency QRS Electrocardiography for Enhanced Detection of Myocardial Ischemia and Coronary Artery Disease

    NASA Technical Reports Server (NTRS)

    Schlegel, Todd T.; Kulecz, Walter B.; DePalma, Jude L.; Feiveson, Alan H.; Wilson, John S.; Rahman, M. Atiar; Bungo, Michael W.

    2004-01-01

    Several studies have shown that diminution of the high-frequency (HF; 150-250 Hz) components present within the central portion of the QRS complex of an electrocardiogram (ECG) is a more sensitive indicator for the presence of myocardial ischemia than are changes in the ST segments of the conventional low-frequency ECG. However, until now, no device has been capable of displaying, in real time on a beat-to-beat basis, changes in these HF QRS ECG components in a continuously monitored patient. Although several software programs have been designed to acquire the HF components over the entire QRS interval, such programs have involved laborious off-line calculations and postprocessing, limiting their clinical utility. We describe a personal computer-based ECG software program developed recently at the National Aeronautics and Space Administration (NASA) that acquires, analyzes, and displays HF QRS components in each of the 12 conventional ECG leads in real time. The system also updates these signals and their related derived parameters in real time on a beat-to-beat basis for any chosen monitoring period and simultaneously displays the diagnostic information from the conventional (low-frequency) 12-lead ECG. The real-time NASA HF QRS ECG software is being evaluated currently in multiple clinical settings in North America. We describe its potential usefulness in the diagnosis of myocardial ischemia and coronary artery disease.

  20. Tunnel injection transit-time diodes for W-band power generation

    NASA Technical Reports Server (NTRS)

    Kidner, C.; Eisele, H.; Haddad, G. I.

    1992-01-01

    GaAs p(+ +)n(+)n(-)n(+) single-drift tunnel injection transit-time (TUNNETT) diodes for W-band operation have been successfully designed and tested. An output power of 32 mW at 93.5 GHz with a dc to RF conversion efficiency of 2.6 percent was obtained. The oscillations have a clean spectrum in a conventional waveguide cavity.

  1. Some properties of asymmetric Hopfield neural networks with finite time of transition between states

    NASA Astrophysics Data System (ADS)

    Suleimenov, Ibragim; Mun, Grigoriy; Panchenko, Sergey; Pak, Ivan

    2016-11-01

    There were implemented samples of asymmetric Hopfield neural networks which have finite time of transition from one state to another. It was shown that in such systems, various oscillation modes could occur. It was revealed that the oscillation of the output signal of certain neuron could be treated as extra logical variable, which describes the state of the neuron. Asymmetric Hopfield neural networks are described in terms of ternary logic. Such logic may be employed in image recognition procedure.

  2. The effects of capillary transit time heterogeneity (CTH) on brain oxygenation

    PubMed Central

    Angleys, Hugo; Østergaard, Leif; Jespersen, Sune N

    2015-01-01

    We recently extended the classic flow–diffusion equation, which relates blood flow to tissue oxygenation, to take capillary transit time heterogeneity (CTH) into account. Realizing that cerebral oxygen availability depends on both cerebral blood flow (CBF) and capillary flow patterns, we have speculated that CTH may be actively regulated and that changes in the capillary morphology and function, as well as in blood rheology, may be involved in the pathogenesis of conditions such as dementia and ischemia-reperfusion injury. The first extended flow–diffusion equation involved simplifying assumptions which may not hold in tissue. Here, we explicitly incorporate the effects of oxygen metabolism on tissue oxygen tension and extraction efficacy, and assess the extent to which the type of capillary transit time distribution affects the overall effects of CTH on flow–metabolism coupling reported earlier. After incorporating tissue oxygen metabolism, our model predicts changes in oxygen consumption and tissue oxygen tension during functional activation in accordance with literature reports. We find that, for large CTH values, a blood flow increase fails to cause significant improvements in oxygen delivery, and can even decrease it; a condition of malignant CTH. These results are found to be largely insensitive to the choice of the transit time distribution. PMID:25669911

  3. A New Method for Increasing Output Power of a Three-Cavity Transit-Time Oscillator

    NASA Astrophysics Data System (ADS)

    He, Jun-Tao; Zhong, Hui-Huang; Qian, Bao-Liang; Liu, Yong-Gui

    2004-07-01

    We propose a new method to increase the output power of a three-cavity transit-time oscillator (TC-TTO). Conventional transit-time effect oscillators, such as the split-cavity oscillator (SCO), super-Reltron, and TC-TTO (or double-foil SCO), etc., have a common feature that the span of any modulating cavity is uniform. The new method is to vary the three-cavity spans from uniform to nonuniform. Its configuration is called the nonuniform three-cavity transit-time oscillator (NTC-TTO). Numerical simulations show that the electron-beam is modulated more deeply in certain NTC-TTOs than that in the TC-TTO with the same whole modulating length, and the output microwave power in certain NTC-TTOs is higher than that in the TC-TTO. The experimental results are in agreement with those of the numerical simulations. The results show that the new method can increase the output power of a microwave tube based on the TC-TTO.

  4. Influence of temperature on transit times and microwave noise performances of SiGe HBT

    NASA Astrophysics Data System (ADS)

    Diaz-Albarran, L. M.; Ramirez-Garcia, E.; Zerounian, N.; Aniel, F.; Rodriguez-Mendez, L. M.; Valdez-Perez, D.; Galaz-Larios, M. C.; Enciso-Aguilar, M. A.

    2016-03-01

    The influence of temperature (300 K and 40 K) on intrinsic transit times and microwave noise performances of silicon germanium (SiGe) heterojunction bipolar transistors (HBTs) is investigated. At 300 K, we compared measured and modelled S-parameters and four noise parameters, and we found a good agreement. At 40 K, we compared measured and modelled S-parameters, and we deduced noise performances from the S-parameter measurements. The electric model includes correlated junction noise sources and a proper extraction of the transit times involved in these sources. Moreover, the microwave noise model considers all the physical phenomena that impact noise performances in SiGe HBTs. We analysed three devices having different Ge content (10%-20%, 10%-25% and 10%-30%). At 40 K, the device with 10%-25% reaches one of the lowest base transit times (τ B), the lowest minimum noise figure (NFmin), and the lowest equivalent noise resistance (R n), for operation frequencies up to the maximum device dynamic performances (f ≈ f T) These results demonstrate the excellent potential to develop cryogenic applications of SiGe HBTs.

  5. Performance of the Time Expansion Chamber / Transition Radiation Detector in PHENIX Experiment at RHIC

    NASA Astrophysics Data System (ADS)

    Luiz Silva, Cesar

    2004-10-01

    The Time Expansion Chamber / Transition Radiation Detector (TEC/TRD) in the PHENIX Experiment at RHIC measures ionization losses (dE/dX) and transition radiation from charged particles produced by beam collisions. It is designed to perform tracking and identification for charged particles on very high particle multiplicity environment. The TEC/TRD consists of 24 wire chambers readout on both sides filled with recycled Xe-based gas mixture. This wire chamber configuration, besides providing measurements of ionization losses for charged particles, can absorb X-Ray photons generated by transition radiation from incident particles with γ>1000 crossing fiber radiators placed at the entrance of the chambers. This allows TEC/TRD to distinguish electrons from the huge pion signal produced over a broad momentum range (1GeV/ctimes every collision providing the drift time as an additional variable to determine points for the charged particle's track. In this presentation we will show results on e/π separation for momentum above 1 GeV/c and momentum resolution using TEC/TRD in Au-Au collisions at √s=200 GeV/c and √s=62.4 GeV/c.

  6. Efficient Transition Probability Computation for Continuous-Time Branching Processes via Compressed Sensing

    PubMed Central

    Xu, Jason; Minin, Vladimir N.

    2016-01-01

    Branching processes are a class of continuous-time Markov chains (CTMCs) with ubiquitous applications. A general difficulty in statistical inference under partially observed CTMC models arises in computing transition probabilities when the discrete state space is large or uncountable. Classical methods such as matrix exponentiation are infeasible for large or countably infinite state spaces, and sampling-based alternatives are computationally intensive, requiring integration over all possible hidden events. Recent work has successfully applied generating function techniques to computing transition probabilities for linear multi-type branching processes. While these techniques often require significantly fewer computations than matrix exponentiation, they also become prohibitive in applications with large populations. We propose a compressed sensing framework that significantly accelerates the generating function method, decreasing computational cost up to a logarithmic factor by only assuming the probability mass of transitions is sparse. We demonstrate accurate and efficient transition probability computations in branching process models for blood cell formation and evolution of self-replicating transposable elements in bacterial genomes. PMID:26949377

  7. Validation of thermal techniques for measurement of pelvic organ blood flows in the nonpregnant sheep: comparison with transit-time ultrasonic and microsphere measurements of blood flow

    SciTech Connect

    Randall, N.J.; Beard, R.W.; Sutherland, I.A.; Figueroa, J.P.; Drost, C.J.; Nathanielsz, P.W.

    1988-03-01

    Data obtained from a thermal system capable of measuring changes in organ temperature as well as tissue thermal clearance in the uterus and vagina have been compared with blood flow measured continuously with a transit-time ultrasound volume-flow sensor placed around the common internal iliac artery and intermittently with radioactive microspheres in the chronically instrumented nonpregnant sheep. Temperature changes in both the uterus and the vagina correlated well with blood flow changes measured by both techniques after intravenous administration of estradiol or norepinephrine. Thermal clearance did not correlate well with blood flow in the vagina or uterus. These methods may have value in the investigation of blood flow patterns in various clinical situations such as the pelvic pain syndrome and early pregnancy.

  8. Method of optical self-mixing for pulse wave transit time in comparison with other methods and correlation with blood pressure

    NASA Astrophysics Data System (ADS)

    Meigas, Kalju; Lass, Jaanus; Kattai, Rain; Karai, Deniss; Kaik, Juri

    2004-07-01

    This paper is a part of research to develop convenient method for continuous monitoring of arterial blood pressure by non-invasive and non-oscillometric way. A simple optical method, using self-mixing in a diode laser, is used for detection of skin surface vibrations near the artery. These vibrations, which can reveal the pulsate propagation of blood pressure waves along the vasculature, are used for pulse wave registration. The registration of the Pulse Wave Transit Time (PWTT) is based on computing the time delay in different regions of the human body using an ECG as a reference signal. In this study, the comparison of method of optical self-mixing with other methods as photoplethysmographic (PPG) and bioimpedance (BI) for PWTT is done. Also correlation of PWTT, obtained with different methods, with arterial blood pressure is calculated. In our study, we used a group of volunteers (34 persons) who made the bicycle exercise test. The test consisted of cycling sessions of increasing workloads during which the HR changed from 60 to 180 beats per minute. In addition, a blood pressure (NIBP) was registered with standard sphygmomanometer once per minute during the test and all NIBP measurement values were synchronized to other signals to find exact time moments where the systolic blood pressure was detected (Korotkoff sounds starting point). Computer later interpolated the blood pressure signal in order to get individual value for every heart cycle. The other signals were measured continuously during all tests. At the end of every session, a recovery period was included until person's NIBP and heart rate (HR) normalized. As a result of our study it turned out that time intervals that were calculated from plethysmographic (PPG) waveforms were in the best correlation with systolic blood pressure. The diastolic pressure does not correlate with any of the parameters representing PWTT. The pulse wave signals measured by laser and piezoelectric transducer are very similar

  9. The Life Course in the Making: Gender and the Development of Adolescents' Expected Timing of Adult Role Transitions

    ERIC Educational Resources Information Center

    Crockett, Lisa J.; Beal, Sarah J.

    2012-01-01

    Adolescents' expectations about the timing of adult role transitions have the potential to shape their actual transitions, setting the stage for their adult lives. Although expectations about timing emerge by early adolescence, little is known about how these expectations develop across adolescence. This longitudinal study examined developmental…

  10. Transition in the mechanism of flow-mediated dilation with aging and development of coronary artery disease.

    PubMed

    Beyer, Andreas M; Zinkevich, Natalya; Miller, Bradley; Liu, Yanping; Wittenburg, April L; Mitchell, Michael; Galdieri, Ralph; Sorokin, Andrey; Gutterman, David D

    2017-01-01

    In microvessels of patients with coronary artery disease (CAD), flow-mediated dilation (FMD) is largely dependent upon the endothelium-derived hyperpolarizing factor H2O2. The goal of this study is to examine the influence of age and presence or absence of disease on the mechanism of FMD. Human coronary or adipose arterioles (~150 µm diameter) were prepared for videomicroscopy. The effect of inhibiting COX [indomethacin (Indo) or NOS (L-NAME), eliminating H2O2 (polyethylene glycol-catalase (PEG-CAT)] or targeting a reduction in mitochondrial ROS with scavengers/inhibitors [Vitamin E (mtVitamin E); phenylboronic acid (mtPBA)] was determined in children aged 0-18 years; young adults 19-55 years; older adults >55 years without CAD, and similarly aged adults with CAD. Indo eliminated FMD in children and reduced FMD in younger adults. This response was mediated mainly by PGI2, as the prostacyclin-synthase-inhibitor trans-2-phenyl cyclopropylamine reduced FMD in children and young adults. L-NAME attenuated dilation in children and younger adults and eliminated FMD in older adults without CAD, but had no effect on vessels from those with CAD, where mitochondria-derived H2O2 was the primary mediator. The magnitude of dilation was reduced in older compared to younger adults independent of CAD. Exogenous treatment with a sub-dilator dose of NO blocked FMD in vessels from subjects with CAD, while prolonged inhibition of NOS in young adults resulted in a phenotype similar to that observed in disease. The mediator of coronary arteriolar FMD evolves throughout life from prostacyclin in youth, to NO in adulthood. With the onset of CAD, NO-inhibitable release of H2O2 emerges as the exclusive mediator of FMD. These findings have implications for use of pharmacological agents, such as nonsteroidal anti-inflammatory agents in children and the role of microvascular endothelium in cardiovascular health.

  11. Glass transition temperature of PIB, PDMS and PMMA from small-time simulations

    NASA Astrophysics Data System (ADS)

    Duki, Solomon; Tsige, Mesfin; Taylor, Philip

    2009-03-01

    We have applied some new techniques to obtain predictions of the glass transition temperatures Tg of poly(isobutylene), poly(dimethyl-siloxane), and poly(methyl methacrylate) from small-time atomistic molecular dynamics simulations. The different fragilities of these materials are reflected in the results of the simulations. One approach involved measurement of the apparent softening of the ``cage'' in which a monomer is bound, while another involved studying autocorrelation of a convolution of the velocity with a smoothing function in order to detect the frequency of escapes from the ``cage.'' To check the accuracy of the short-time methods, the Tg of the polymers was also found using conventional diffusion simulations in which the rate of increase of the root mean squared displacement of an atom, monomer, or molecule is measured at very long times. The economical short-time simulations yielded results for Tg that were identical to those of the computer-intensive long-time simulations.

  12. An analytical solution for ground water transit time through unconfined aquifers.

    PubMed

    Chesnaux, R; Molson, J W; Chapuis, R P

    2005-01-01

    An exact, closed-form analytical solution is developed for calculating ground water transit times within Dupuit-type flow systems. The solution applies to steady-state, saturated flow through an unconfined, horizontal aquifer recharged by surface infiltration and discharging to a downgradient fixed-head boundary. The upgradient boundary can represent, using the same equation, a no-flow boundary or a fixed head. The approach is unique for calculating travel times because it makes no a priori assumptions regarding the limit of the water table rise with respect to the minimum saturated aquifer thickness. The computed travel times are verified against a numerical model, and examples are provided, which show that the predicted travel times can be on the order of nine times longer relative to existing analytical solutions.

  13. Transit Times In A Shallow Aquifer From Tracer Measurements In The Aquifer And A Gaining Stream

    NASA Astrophysics Data System (ADS)

    Solomon, D. K.; Genereux, D. P.; Gilmore, T. E.; Solder, J. E.

    2015-12-01

    The mean transit time (MTT) is a fundamental property of a groundwater flow system that is related to recharge rate and storage volume. However, estimating the MTT using environmental tracers is problematic as flow-weighted samples over the full spectrum of transit times are needed and computed MTTs depend on the transit time distribution (TTD) that is not usually determined directly. We studied the TTD and MTT in the baseflow of a gaining stream (West Bear Creek) and in the surrounding shallow aquifer in the North Carolina Coastal Plain. Groundwater seepage to the stream was quantified using the dilution of an injected Br tracer, velocity-area flow measurements, seepage meters, and Darcy calculations from discrete point measurements of vertical K and gradient. Environmental tracers concentrations (CFCs, SF6, 3H-3He) were measured in multi-level monitoring wells, in streambed piezometers, seepage meters, and stream samples. Apparent (piston flow) ages from monitoring wells are generally consistent with an exponential TTD. Discrete samples from streambed piezometers have concentrations from multiple age-dating tracers suggesting that mixing of a wide range of groundwater ages was not occurring as groundwater converged below the streambed and that piston flow apparent ages were reasonable estimates of the transit time of groundwater. Stream water samples that are corrected for exchange with the atmosphere yield SF6 concentrations that are similar to flow weighted values from streambed piezometers. The MTT of 25-30 years derived from well samples is similar to that based on streambed piezometer samples and the exchange-corrected stream samples. The flow-weighted cumulative distribution of apparent ages from streambed samples can be modeled with a gamma distribution having a shape factor (α) that is greater than 1. Numerical modeling of some ideal cases indicates that spatial variations in recharge might be discerned from the cumulative TTD with α >1 for recharge

  14. Anthropogenic carbon estimates in the Weddell Sea using an optimized CFC based transit time distribution approach

    NASA Astrophysics Data System (ADS)

    Huhn, Oliver; Hauck, Judith; Hoppema, Mario; Rhein, Monika; Roether, Wolfgang

    2010-05-01

    We use a 20 year time series of chlorofluorocarbon (CFC) observations along the Prime Meridian to determine the temporal evolution of anthropogenic carbon (Cant) in the two deep boundary currents which enter the Weddell Basin in the south and leave it in the north. The Cant is inferred from transit time distributions (TTDs), with parameters (mean transit time and dispersion) adjusted to the observed mean CFC histories in these recently ventilated deep boundary currents. We optimize that "classic" TTD approach by accounting for water exchange of the boundary currents with an old but not CFC and Cant free interior reservoir. This reservoir in turn, is replenished by the boundary currents, which we parameterize as first order mixing. Furthermore, we account for the time-dependence of the CFC and Cant source water saturation. A conceptual model of an ideal saturated mixed layer and exchange with adjacent water is adjusted to observed CFC saturations in the source regions. The time-dependence for the CFC saturation appears to be much weaker than for Cant. We find a mean transit time of 14 years and an advection/dispersion ratio of 5 for the deep southern boundary current. For the northern boundary current we find a mean transit time of 8 years and a much advection/dispersion ratio of 140. The fractions directly supplied by the boundary currents are in both cases in the order of 10%, while 90% are admixed from the interior reservoirs, which are replenished with a renewal time of about 14 years. We determine Cant ~ 11 umol/kg (reference year 2006) in the deep water entering the Weddell Sea in the south (~2.1 Sv), and 12 umol/kg for the deep water leaving the Weddell Sea in the north (~2.7 Sv). These Cant estimates are, however, upper limits, considering that the Cant source water saturation is likely to be lower than that for the CFCs. Comparison with Cant intrusion estimates based on extended multiple linear regression (using potential temperature, salinity, oxygen, and

  15. Simple magneto-optic transition metal models for time-domain simulations.

    PubMed

    Wolff, Christian; Rodríguez-Oliveros, Rogelio; Busch, Kurt

    2013-05-20

    Efficient modelling of the magneto-optic effects of transition metals such as nickel, cobalt and iron is a topic of growing interest within the nano-optics community. In this paper, we present a general discussion of appropriate material models for the linear dielectric properties for such metals, provide parameter fits and formulate the anisotropic response in terms of auxiliary differential equations suitable for time-domain simulations. We validate both our material models and their implementation by comparing numerical results obtained with the Discontinuous Galerkin time-domain (DGTD) method to analytical results and previously published experimental data.

  16. Transit timing variations for planets co-orbiting in the horseshoe regime

    SciTech Connect

    Vokrouhlický, David; Nesvorný, David E-mail: davidn@boulder.swri.edu

    2014-08-10

    Although not yet detected, pairs of exoplanets in 1:1 mean motion resonance probably exist. Low eccentricity, near-planar orbits, which in the comoving frame follow horseshoe trajectories, are one of the possible stable configurations. Here we study transit timing variations (TTVs) produced by mutual gravitational interaction of planets in this orbital architecture, with the goal to develop methods that can be used to recognize this case in observational data. In particular, we use a semi-analytic model to derive parametric constraints that should facilitate data analysis. We show that characteristic traits of the TTVs can directly constrain the (1) ratio of planetary masses and (2) their total mass (divided by that of the central star) as a function of the minimum angular separation as seen from the star. In an ideal case, when transits of both planets are observed and well characterized, the minimum angular separation can also be inferred from the data. As a result, parameters derived from the observed transit timing series alone can directly provide both planetary masses scaled to the central star mass.

  17. Transit Timing Variations for Planets Co-orbiting in the Horseshoe Regime

    NASA Astrophysics Data System (ADS)

    Vokrouhlický, David; Nesvorný, David

    2014-08-01

    Although not yet detected, pairs of exoplanets in 1:1 mean motion resonance probably exist. Low eccentricity, near-planar orbits, which in the comoving frame follow horseshoe trajectories, are one of the possible stable configurations. Here we study transit timing variations (TTVs) produced by mutual gravitational interaction of planets in this orbital architecture, with the goal to develop methods that can be used to recognize this case in observational data. In particular, we use a semi-analytic model to derive parametric constraints that should facilitate data analysis. We show that characteristic traits of the TTVs can directly constrain the (1) ratio of planetary masses and (2) their total mass (divided by that of the central star) as a function of the minimum angular separation as seen from the star. In an ideal case, when transits of both planets are observed and well characterized, the minimum angular separation can also be inferred from the data. As a result, parameters derived from the observed transit timing series alone can directly provide both planetary masses scaled to the central star mass.

  18. Microscopic dynamics of the glass transition investigated by time-resolved fluorescence measurements of doped chromophores

    NASA Astrophysics Data System (ADS)

    Ye, Jing Yong; Hattori, Toshiaki; Nakatsuka, Hiroki; Maruyama, Yoshihiro; Ishikawa, Mitsuru

    1997-09-01

    The microscopic dynamics of several monomeric and polymeric glass-forming materials has been investigated by time-resolved fluorescence measurements of doped malachite green molecules in a wide temperature region. For monomers, 1-propanol, propylene glycol, and glycerol, and a polymer without side chains, poly- butadiene, the temperature dependence of nonradiative decay time of doped malachite green molecules behaves in a similar way through the glass-transition region. Besides a kink around the calorimetric glass-transition temperature Tg, another crossover at a critical temperature Tc about 30-50 K above Tg has been clearly observed. This experimental finding is in agreement with the prediction of the mode-coupling theory that a dynamical transition exists well above Tg. On the other hand, for the complex polymers with side chains, poly(vinyl acetate), poly(methyl acrylate), and poly(ethyl methacrylate), the crossover at Tg is less pronounced than those for the monomers and the polymer without side chains. Moreover, although we could not distinguish any singularities above Tg for these complex polymers, we observed another kink below Tg, which may be attributed to the side-chain motions.

  19. VizieR Online Data Catalog: Kepler transit timing observations. VIII. (Mazeh+, 2013)

    NASA Astrophysics Data System (ADS)

    Mazeh, T.; Nachmani, G.; Holczer, T.; Fabrycky, D. C.; Ford, E. B.; Sanchis-Ojeda, R.; Sokol, G.; Rowe, J. F.; Zucker, S.; Agol, E.; Carter, J. A.; Lissauer, J. J.; Quintana, E. V.; Ragozzine, D.; Steffen, J. H.; Welsh, W.

    2013-10-01

    Following the works of Ford et al. (2011, Cat. J/ApJS/197/2; 2012ApJ...756..185F) and Steffen et al. (2012ApJ...756..186S) we derived the transit timing of 1960 Kepler objects of interest (KOIs) using the pre-search data conditioning light curves of the first twelve quarters of the Kepler data. For 721 KOIs with large enough signal-to-noise ratios, we obtained also the duration and depth of each transit. The results are presented as a catalog for the community to use. We derived a few statistics of our results that could be used to indicate significant variations. Including systems found by previous works, we have found 130 KOIs that showed highly significant times of transit variations (TTVs) and 13 that had short-period TTV modulations with small amplitudes. We consider two effects that could cause apparent periodic TTV -- the finite sampling of the observations and the interference with the stellar activity, stellar spots in particular. We briefly discuss some statistical aspects of our detected TTVs. We show that the TTV period is correlated with the orbital period of the planet and with the TTV amplitude. (7 data files).

  20. Comprehensive time series analysis of the transiting extrasolar planet WASP-33b

    NASA Astrophysics Data System (ADS)

    Kovács, G.; Kovács, T.; Hartman, J. D.; Bakos, G. Á.; Bieryla, A.; Latham, D.; Noyes, R. W.; Regály, Zs.; Esquerdo, G. A.

    2013-05-01

    Context. HD 15082 (WASP-33) is the hottest and fastest rotating star known to harbor a transiting extrasolar planet (WASP-33b). The lack of high precision radial velocity (RV) data stresses the need for precise light curve analysis and gathering further RV data. Aims: By using available photometric and RV data, we perform a blend analysis, compute more accurate system parameters, confine the planetary mass, and, attempt to cast light on the observed transit anomalies. Methods: We combined the original HATNet observations and various followup data to jointly analyze the signal content and extract the transit component and used our RV data to aid the global parameter determination. Results: The blend analysis of the combination of multicolor light curves yields the first independent confirmation of the planetary nature of WASP-33b. We clearly identify three frequency components in the 15-21 d-1 regime with amplitudes 7-5 mmag. These frequencies correspond to the δ Scuti-type pulsation of the host star. None of these pulsation frequencies or their low-order linear combinations are in close resonance with the orbital frequency. We show that these pulsation components explain some but not all of the observed transit anomalies. The grand-averaged transit light curve shows that there is a ~1.5 mmag brightening shortly after the planet passes the mid-transit phase. Although the duration and amplitude of this brightening varies, it is visible even through the direct inspections of the individual transit events (some 40-60% of the followup light curves show this phenomenon). We suggest that the most likely explanation of this feature is the presence of a well-populated spot belt which is highly inclined to the orbital plane. This geometry is consistent with the inference from the spectroscopic anomalies. Finally, we constrain the planetary mass to Mp = 3.27 ± 0.73 MJ by using our RV data collected by the TRES spectrograph. Appendix A is available in electronic form at http

  1. Distributional behavior of diffusion coefficients obtained by single trajectories in annealed transit time model

    NASA Astrophysics Data System (ADS)

    Akimoto, Takuma; Yamamoto, Eiji

    2016-12-01

    Local diffusion coefficients in disordered systems such as spin glass systems and living cells are highly heterogeneous and may change over time. Such a time-dependent and spatially heterogeneous environment results in irreproducibility of single-particle-tracking measurements. Irreproducibility of time-averaged observables has been theoretically studied in the context of weak ergodicity breaking in stochastic processes. Here, we provide rigorous descriptions of equilibrium and non-equilibrium diffusion processes for the annealed transit time model, which is a heterogeneous diffusion model in living cells. We give analytical solutions for the mean square displacement (MSD) and the relative standard deviation of the time-averaged MSD for equilibrium and non-equilibrium situations. We find that the time-averaged MSD grows linearly with time and that the time-averaged diffusion coefficients are intrinsically random (irreproducible) even in the long-time measurements in non-equilibrium situations. Furthermore, the distribution of the time-averaged diffusion coefficients converges to a universal distribution in the sense that it does not depend on initial conditions. Our findings pave the way for a theoretical understanding of distributional behavior of the time-averaged diffusion coefficients in disordered systems.

  2. Bianchi type-I transit cosmological models with time dependent gravitational and cosmological constants: reexamined

    NASA Astrophysics Data System (ADS)

    Pradhan, A.; Saha, B.; Rikhvitsky, V.

    2015-05-01

    The Einstein's field equations with variable gravitational and cosmological "constants" for a spatially homogeneous and anisotropic Bianchi type-I space-time are obtained in present study. To study the transit behaviour of Universe, we consider a law of variation of scale factor a(t) = ( tk et) ^{1/n}, which yields a time dependent deceleration parameter q = -1 + nk/(k + t)2, comprising a class of models that depicts a transition of the universe from the early decelerated phase to the recent accelerating phase. We find that the time dependent deceleration parameter is reasonable for the present day Universe and gives an appropriate description of the evolution of the universe. For n = 0.27k, we obtain q0 = -0.73, which is similar to observed value of deceleration parameter at present epoch. It is also observed that for n ≥ 2 and k = 1, we obtain a class of transit models of the universe from early decelerating to present accelerating phase. For k = 0, the universe has non-singular origin. In these models, we arrive at the decision that, from the structure of the field equations, the behaviour of cosmological and gravitational constants and are related. Taking into consideration the observational data, we conclude that the cosmological constant behaves as a positive decreasing function of time, whereas gravitational constant is increasing and tends to a constant value at late time. H(z)/(1+z) data (32 points) and model prediction as a function of redshift for different k and n are successfully presented by using recent data. Some physical and geometric properties of the models are also discussed.

  3. Using long-term data sets to understand transit times in contrasting headwater catchments

    NASA Astrophysics Data System (ADS)

    Hrachowitz, M.; Soulsby, C.; Tetzlaff, D.; Dawson, J. J. C.; Dunn, S. M.; Malcolm, I. A.

    2009-04-01

    SummaryLong-term tracer data collected over an 8 year period were analyzed to explore the transit times of two small (˜1 km 2), contrasting headwater catchments in the uplands of Scotland. At Loch Ard, the catchment was characterized by low permeability gleyed soils overlying metamorphic geology. At Sourhope, more freely draining podzolic soils were dominant, which mantled fractured and faulted volcanic rocks. Hydrometric data and chemically-based hydrograph separations indicated that Loch Ard was a flashy catchment dominated by runoff processes in the upper soil horizons. In contrast, around 77% of annual flow at Sourhope was sustained by well-buffered groundwater sources. Weekly Cl - time series in precipitation and stream flow revealed similar variability in inputs at both sites, but much greater damping in outputs at Sourhope. Despite this, both catchments filtered white noise frequencies in precipitation inputs into 1/ f outputs. These input-output relationships were modeled with a range of transit time distributions (TTD). At the responsive Loch Ard catchment, mean transit times (MTT) for the study period were estimated at 135-202 days. Models based on a gamma distribution or two parallel linear reservoirs were best able to capture the short- and long-term fluctuations in stream water in response to input variations. At Sourhope, the highly damped tracer signal in stream waters was poorly captured by all the TTDs used. Resulting MTT estimates of 1830-1970 days are based on weak model fits and poorly identifiable parameter sets, indicating that natural tracers such as Cl - are inadequate for catchments where MTTs are greater than a few years. At both sites, estimates of MTT using moving windows over the 8 year data sets revealed sensitivity to precipitation amounts and the length of monitoring period. It is concluded that time series of around 4 years are required to adequately constrain MTT estimates.

  4. Thermodynamic glass transition in a spin glass without time-reversal symmetry

    PubMed Central

    Baños, Raquel Alvarez; Cruz, Andres; Fernandez, Luis Antonio; Gil-Narvion, Jose Miguel; Gordillo-Guerrero, Antonio; Guidetti, Marco; Iñiguez, David; Maiorano, Andrea; Marinari, Enzo; Martin-Mayor, Victor; Monforte-Garcia, Jorge; Muñoz Sudupe, Antonio; Navarro, Denis; Parisi, Giorgio; Perez-Gaviro, Sergio; Ruiz-Lorenzo, Juan Jesus; Schifano, Sebastiano Fabio; Seoane, Beatriz; Tarancon, Alfonso; Tellez, Pedro; Tripiccione, Raffaele; Yllanes, David

    2012-01-01

    Spin glasses are a longstanding model for the sluggish dynamics that appear at the glass transition. However, spin glasses differ from structural glasses in a crucial feature: they enjoy a time reversal symmetry. This symmetry can be broken by applying an external magnetic field, but embarrassingly little is known about the critical behavior of a spin glass in a field. In this context, the space dimension is crucial. Simulations are easier to interpret in a large number of dimensions, but one must work below the upper critical dimension (i.e., in d < 6) in order for results to have relevance for experiments. Here we show conclusive evidence for the presence of a phase transition in a four-dimensional spin glass in a field. Two ingredients were crucial for this achievement: massive numerical simulations were carried out on the Janus special-purpose computer, and a new and powerful finite-size scaling method. PMID:22493229

  5. Improvements in Low-cost Ultrasonic Measurements of Blood Flow in "by-passes" Using Narrow & Broad Band Transit-time Procedures

    NASA Astrophysics Data System (ADS)

    Ramos, A.; Calas, H.; Diez, L.; Moreno, E.; Prohías, J.; Villar, A.; Carrillo, E.; Jiménez, A.; Pereira, W. C. A.; Von Krüger, M. A.

    The cardio-pathology by ischemia is an important cause of death, but the re-vascularization of coronary arteries (by-pass operation) is an useful solution to reduce associated morbidity improving quality of life in patients. During these surgeries, the flow in coronary vessels must be measured, using non-invasive ultrasonic methods, known as transit time flow measurements (TTFM), which are the most accurate option nowadays. TTFM is a common intra-operative tool, in conjunction with classic Doppler velocimetry, to check the quality of these surgery processes for implanting grafts in parallel with the coronary arteries. This work shows important improvements achieved in flow-metering, obtained in our research laboratories (CSIC, ICIMAF, COPPE) and tested under real surgical conditions in Cardiocentro-HHA, for both narrowband NB and broadband BB regimes, by applying results of a CYTED multinational project (Ultrasonic & computational systems for cardiovascular diagnostics). mathematical models and phantoms were created to evaluate accurately flow measurements, in laboratory conditions, before our new electronic designs and low-cost implementations, improving previous ttfm systems, which include analogic detection, acquisition & post-processing, and a portable PC. Both regimes (NB and BB), with complementary performances for different conditions, were considered. Finally, specific software was developed to offer facilities to surgeons in their interventions.

  6. User-guided automated segmentation of time-series ultrasound images for measuring vasoreactivity of the brachial artery induced by flow mediation

    NASA Astrophysics Data System (ADS)

    Sehgal, Chandra M.; Kao, Yen H.; Cary, Ted W.; Arger, Peter H.; Mohler, Emile R.

    2005-04-01

    Endothelial dysfunction in response to vasoactive stimuli is closely associated with diseases such as atherosclerosis, hypertension and congestive heart failure. The current method of using ultrasound to image the brachial artery along the longitudinal axis is insensitive for measuring the small vasodilatation that occurs in response to flow mediation. The goal of this study is to overcome this limitation by using cross-sectional imaging of the brachial artery in conjunction with the User-Guided Automated Boundary Detection (UGABD) algorithm for extracting arterial boundaries. High-resolution ultrasound imaging was performed on rigid plastic tubing, on elastic rubber tubing phantoms with steady and pulsatile flow, and on the brachial artery of a healthy volunteer undergoing reactive hyperemia. The area of cross section of time-series images was analyzed by UGABD by propagating the boundary from one frame to the next. The UGABD results were compared by linear correlation with those obtained by manual tracing. UGABD measured the cross-sectional area of the phantom tubing to within 5% of the true area. The algorithm correctly detected pulsatile vasomotion in phantoms and in the brachial artery. A comparison of area measurements made using UGABD with those made by manual tracings yielded a correlation of 0.9 and 0.8 for phantoms and arteries, respectively. The peak vasodilatation due to reactive hyperemia was two orders of magnitude greater in pixel count than that measured by longitudinal imaging. Cross-sectional imaging is more sensitive than longitudinal imaging for measuring flow-mediated dilatation of brachial artery, and thus may be more suitable for evaluating endothelial dysfunction.

  7. Arterial insufficiency

    MedlinePlus

    ... the most common causes of arterial insufficiency is atherosclerosis or "hardening of the arteries." Fatty material (called ... Images Arteries of the brain Developmental process of atherosclerosis References Hansson GK, Hamsten A. Atherosclerosis, thrombosis, and ...

  8. Feasibility of real time dual-energy imaging based on a flat panel detector for coronary artery calcium quantification.

    PubMed

    Xu, Tong; Ducote, Justin L; Wong, Jerry T; Molloi, Sabee

    2006-06-01

    The feasibility of a real-time dual-energy imaging technique with dynamic filtration using a flat panel detector for quantifying coronary arterial calcium was evaluated. In this technique, the x-ray beam was switched at 15 Hz between 60 kVp and 120 kVp with the 120 kVp beam having an additional 0.8 mm silver filter. The performance of the dynamic filtration technique was compared with a static filtration technique (4 mm Al+0.2 mm Cu for both beams). The ability to quantify calcium mass was evaluated using calcified arterial vessel phantoms with 20-230 mg of hydroxylapatite. The vessel phantoms were imaged over a Lucite phantom and then an anthropomorphic chest phantom. The total thickness of Lucite phantom ranges from 13.5-26.5 cm to simulate patient thickness of 16-32 cm. The calcium mass was measured using a densitometric technique. The effective dose to patient was estimated from the measured entrance exposure. The effects of patient thickness on contrast-to-noise ratio (CNR), effective dose, and the precision of calcium mass quantification (i.e., the frame to frame variability) were studied. The effects of misregistration artifacts were also measured by shifting the vessel phantoms manually between low- and high-energy images. The results show that, with the same detector signal level, the dynamic filtration technique produced 70% higher calcium contrast-to-noise ratio with only 4% increase in patient dose as compared to the static filtration technique. At the same time, x-ray tube loading increased by 30% with dynamic filtration. The minimum detectability of calcium with anatomical background was measured to be 34 mg of hydroxyapatite. The precision in calcium mass measurement, determined from 16 repeated dual-energy images, ranges from 13 mg to 41 mg when the patient thickness increased from 16 to 32 cm. The CNR was found to decrease with the patient thickness linearly at a rate of (-7%/cm). The anatomic background produced measurement root-mean-square (RMS

  9. Feasibility of real time dual-energy imaging based on a flat panel detector for coronary artery calcium quantification

    SciTech Connect

    Xu Tong; Ducote, Justin L.; Wong, Jerry T.; Molloi, Sabee

    2006-06-15

    The feasibility of a real-time dual-energy imaging technique with dynamic filtration using a flat panel detector for quantifying coronary arterial calcium was evaluated. In this technique, the x-ray beam was switched at 15 Hz between 60 kVp and 120 kVp with the 120 kVp beam having an additional 0.8 mm silver filter. The performance of the dynamic filtration technique was compared with a static filtration technique (4 mm Al+0.2 mm Cu for both beams). The ability to quantify calcium mass was evaluated using calcified arterial vessel phantoms with 20-230 mg of hydroxylapatite. The vessel phantoms were imaged over a Lucite phantom and then an anthropomorphic chest phantom. The total thickness of Lucite phantom ranges from 13.5-26.5 cm to simulate patient thickness of 16-32 cm. The calcium mass was measured using a densitometric technique. The effective dose to patient was estimated from the measured entrance exposure. The effects of patient thickness on contrast-to-noise ratio (CNR), effective dose, and the precision of calcium mass quantification (i.e., the frame to frame variability) were studied. The effects of misregistration artifacts were also measured by shifting the vessel phantoms manually between low- and high-energy images. The results show that, with the same detector signal level, the dynamic filtration technique produced 70% higher calcium contrast-to-noise ratio with only 4% increase in patient dose as compared to the static filtration technique. At the same time, x-ray tube loading increased by 30% with dynamic filtration. The minimum detectability of calcium with anatomical background was measured to be 34 mg of hydroxyapatite. The precision in calcium mass measurement, determined from 16 repeated dual-energy images, ranges from 13 mg to 41 mg when the patient thickness increased from 16 to 32 cm. The CNR was found to decrease with the patient thickness linearly at a rate of (-7%/cm). The anatomic background produced measurement root-mean-square (RMS

  10. Groundwater transit time distribution and transfer of nitrates from soils to river network

    NASA Astrophysics Data System (ADS)

    Michalczyk, Tomasz; Bar-Michalczyk, Dominika; Duliński, Marek; Kania, Jarosław; Malina, Grzegorz; Różański, Kazimierz; Szklarczyk, Tadeusz; Wachniew, Przemysław; Witczak, Stanisław; Zięba, Damian; Żurek, Anna

    2016-04-01

    Measures undertaken to reduce nitrate loadings of agricultural origin to surface waters have to take into account delays associated with pollution transport between the root zone and groundwater abstraction wells or natural discharge zones. Parts of an important fissured-carbonate aquifer (Major Groundwater Basin No. 326) located in southern Poland are polluted, with concentrations of nitrates significantly exceeding the European Union limit of 50 mg/L. The polluted groundwater discharges to the streams of the Kocinka river catchment affecting their water quality. The MODFLOW and MT3DMS codes were used to model flow and transport of contaminants in the aquifer. Transport of conservative solutes was performed in a transient mode, with the steady-state flow field calibrated using present-day distribution of hydraulic heads and discharges of streams draining the aquifer. Time series of tritium data available for 21 production wells and springs, some of them extending over the period of 30 years, were used for calibration of flow and transport model resulting in significant changes in the original conceptual framework of this groundwater system. The regional-scale numerical model of flow and transport allowed for identification of the gaining stream reaches and for estimation of groundwater contributions to streamflow. Observations of in stable isotope composition and stream water chemistry confirmed the results of the numerical model for these particular stream reaches. The numerical model provided also the transit time distribution of groundwater flow through the saturated zone with an average value of 8 years and dominant transit times in the range from 3 to 20 years. Transit times of water through the unsaturated zone are in the range from less than 5 to 25 years with an average value of 10 years. Because of these delays, the results of measures aimed at reducing nitrate loads to the river network will be visible only within the relevant timescales.

  11. The importance of water transit time and mineral dissolution kinetics for the flux of weathering products

    NASA Astrophysics Data System (ADS)

    Erlandsson, Martin; Bishop, Kevin; Köhler, Stephan; Amvrosiadi, Nino

    2016-04-01

    Soil mineral weathering is one of the major sources of base cations (BC), which play a dual role for a forest ecosystem; they function both as plant nutrients, and for buffering against acidification of catchment runoff. On a long-term basis, the soil weathering rates will determine the highest sustainable forest productivity without causing acidification. It is believed that the hydrologic residence time play a key role in determining weathering rates on a landscape scale. In this study, we investigate the significance of the water transit residence time (WTT) distribution for the transport of base cations to catchment runoff. By modelling hillslope flowpaths with different transit times, using the geochemical computing code PHREEQC, we demonstrate how in-stream dynamics as exemplified by elemental ratios can be explained by mineral dissolution kinetics and equilibria. Specifically, we hypothesize that equilibrium of plagioclase regulates the delivery of base cations and silica to catchment runoff. These patters can be seen in field data from 10 years of sampling from a nested-catchment, where the Na+/BC and the Si/BC-ratios vary systematically with WTT on both a temporal and a spatial scale. This behavior has implications for the total transport of products from mineral dissolution to catchment runoff. As the water entering the stream is a mixture of water with different transit times, the composition of stream water will not only be dependent on the average WTT, but also on the shape of the WTT distribution. For the base cations associated with minerals that becomes supersaturated or with precipitating secondary phases within the range of WTT, i.e. Na+ and K+, the tails of "old water" of the WRT-distribution will not contribute to any extra transport of these elements. Finally, we use the derived relationships to estimate the transport of weathering products from a forested hillslope, given the modelled WRT distribution.

  12. Arterial stump pressure: a determinant of arterial patency?

    PubMed

    Nunley, J A; Goldner, R D; Koman, L A; Gelberman, R; Urbaniak, J R

    1987-03-01

    Twenty-seven patients with acute injuries to the radial or ulnar arteries had arterial repairs using microvascular techniques. No patient had an ischemic hand secondary to his arterial injury. The overall patency rate for all repaired vessels was 56%. For sharp, clean lacerations, the success rate for repairs was 55%. Repairs of acute, sharp lacerations yielded no better results than delayed reconstructions. The average distal end arterial stump pressure for patent arteries was 66% of mean, while for thrombosed vessels it was 76% of mean; this was not a statistically significant difference (p = 0.9). There was no statistical correlation between forearm arterial patency, age, sex, vessel injured, mechanism of injury, time of repair, or clinically measured distal arterial stump pressure. At the present time, it does not appear to be possible to predict arterial patency by measuring arterial stump pressure at the time of definitive repair.

  13. Time-varying coupling functions: Dynamical inference and cause of synchronization transitions

    NASA Astrophysics Data System (ADS)

    Stankovski, Tomislav

    2017-02-01

    Interactions in nature can be described by their coupling strength, direction of coupling, and coupling function. The coupling strength and directionality are relatively well understood and studied, at least for two interacting systems; however, there can be a complexity in the interactions uniquely dependent on the coupling functions. Such a special case is studied here: synchronization transition occurs only due to the time variability of the coupling functions, while the net coupling strength is constant throughout the observation time. To motivate the investigation, an example is used to present an analysis of cross-frequency coupling functions between delta and alpha brain waves extracted from the electroencephalography recording of a healthy human subject in a free-running resting state. The results indicate that time-varying coupling functions are a reality for biological interactions. A model of phase oscillators is used to demonstrate and detect the synchronization transition caused by the varying coupling functions during an invariant coupling strength. The ability to detect this phenomenon is discussed with the method of dynamical Bayesian inference, which was able to infer the time-varying coupling functions. The form of the coupling function acts as an additional dimension for the interactions, and it should be taken into account when detecting biological or other interactions from data.

  14. Time-varying coupling functions: Dynamical inference and cause of synchronization transitions.

    PubMed

    Stankovski, Tomislav

    2017-02-01

    Interactions in nature can be described by their coupling strength, direction of coupling, and coupling function. The coupling strength and directionality are relatively well understood and studied, at least for two interacting systems; however, there can be a complexity in the interactions uniquely dependent on the coupling functions. Such a special case is studied here: synchronization transition occurs only due to the time variability of the coupling functions, while the net coupling strength is constant throughout the observation time. To motivate the investigation, an example is used to present an analysis of cross-frequency coupling functions between delta and alpha brain waves extracted from the electroencephalography recording of a healthy human subject in a free-running resting state. The results indicate that time-varying coupling functions are a reality for biological interactions. A model of phase oscillators is used to demonstrate and detect the synchronization transition caused by the varying coupling functions during an invariant coupling strength. The ability to detect this phenomenon is discussed with the method of dynamical Bayesian inference, which was able to infer the time-varying coupling functions. The form of the coupling function acts as an additional dimension for the interactions, and it should be taken into account when detecting biological or other interactions from data.

  15. Being in transit and in transition: the experience of time at the place, when living with severe incurable disease--a phenomenological study.

    PubMed

    Ellingsen, Sidsel; Roxberg, Åsa; Kristoffersen, Kjell; Rosland, Jan Henrik; Alvsvåg, Herdis

    2014-09-01

    The aim of this study is to describe the experience of time as it presents itself at the place being situated when living with severe incurable disease and receiving palliative care. The empirical data consist of 26 open-ended interviews with 23 patients receiving palliative care at home, at a palliative day care, in a palliative bed unit in hospital or in a nursing home in Norway. A common meaning of a shifting space for living emerged from the analysis and was revealed through three different aspects: (i) Transition from a predictable to an unpredictable time: To live with severe incurable disease marks a transition to a changed life involving an ongoing weakened and altered body with bothersome symptoms making experience of time different and unpredictable. (ii) Transition between a safe and unsafe time: When time is unpredictable, feeling safe is revealed as essential to how time is experienced at the place being situated. (iii) To be in transition from a homely to a homeless existence: In a time of increased bodily weakness, unpredictable ailments and displacements, the sense of belonging to the place is revealed as significant to the experience of time. Not knowing where to be in a time of change is like an existential cry of distress where the foothold in existence is lost. The findings are discussed and interpreted as an embodied experience originating from the passage of time continually affecting life sometimes so fundamentally that it marks a transition to a changed space of life that is reflected in the experience of time.

  16. Effects of sacral nerve stimulation with acupuncture on gut transit time and c-kit expression in colon of rats with slow transit constipation.

    PubMed

    Zhang, Y G; Shao, W J; Gu, Y F; Qiu, J F; Yuan, L; Li, G D

    2016-09-23

    Sacral nerve stimulation (SNS) is an alternative surgical approach to alleviate fecal incontinence and constipation. This study aimed to explore the effects and underlying mechanisms of SNS with acupuncture on gut transit time and colon c-kit protein expression in rats with slow transit constipation (STC). Fifty Sprague-Dawley rats were randomly divided into five groups: blank control, SNS, Mosapride, sham SNS, and STC model control group. The STC model was established by subcutaneous injection of morphine. Each group was treated over a 15-day period. Gut transit time was measured 1 day before the treatment started and after 5, 10, and 15 days of treatment. After the 15-day treatment, animals were sacrificed and colonic tissues were collected for analysis of c-kit protein expression, using western blot analysis. We found significant differences in gut transit time in the SNS group compared with the Mosapride group after 5 (P = 0.001) and 10 (P = 0.004) days of treatment. After 15 days of treatment, there were no differences in gut transit time among the SNS, Mosapride, and blank control groups. However, significant differences were observed when comparing the SNS and Mosapride groups with the STC model and sham SNS groups. A decreased c-kit protein expression was observed in the STC model control, sham SNS, and Mosapride groups, compared with the SNS group (P = 0.001). Our data indicate that SNS can decrease gut transit time and increase the expression of c-kit protein in rats with STC to improve colon transit function.

  17. Colonic Transit Time Is a Driven Force of the Gut Microbiota Composition and Metabolism: In Vitro Evidence

    PubMed Central

    Tottey, William; Feria-Gervasio, David; Gaci, Nadia; Laillet, Brigitte; Pujos, Estelle; Martin, Jean-François; Sebedio, Jean-Louis; Sion, Benoit; Jarrige, Jean-François; Alric, Monique; Brugère, Jean-François

    2017-01-01

    Background/Aims Human gut microbiota harbors numerous metabolic properties essential for the host’s health. Increased intestinal transit time affects a part of the population and is notably observed with human aging, which also corresponds to modifications of the gut microbiota. Thus we tested the metabolic and compositional changes of a human gut microbiota induced by an increased transit time simulated in vitro. Methods The in vitro system, Environmental Control System for Intestinal Microbiota, was used to simulate the environmental conditions of 3 different anatomical parts of the human colon in a continuous process. The retention times of the chemostat conditions were established to correspond to a typical transit time of 48 hours next increased to 96 hours. The bacterial communities, short chain fatty acids and metabolite fingerprints were determined. Results Increase of transit time resulted in a decrease of biomass and of diversity in the more distal compartments. Short chain fatty acid analyses and metabolite fingerprinting revealed increased activity corresponding to carbohydrate fermentation in the proximal compartments while protein fermentations were increased in the lower parts. Conclusions This study provides the evidence that the increase of transit time, independently of other factors, affects the composition and metabolism of the gut microbiota. The transit time is one of the factors that explain some of the modifications seen in the gut microbiota of the elderly, as well as patients with slow transit time. PMID:27530163

  18. Impact of Timing of Eptifibatide Administration on Preprocedural Infarct-Related Artery Patency in Acute STEMI Patients Undergoing Primary PCI.

    PubMed

    Dharma, Surya; Firdaus, Isman; Danny, Siska Suridanda; Juzar, Dafsah A; Wardeh, Alexander J; Jukema, J Wouter; van der Laarse, Arnoud

    2014-09-01

    The appropriate timing of eptifibatide initiation for acute ST segment elevation myocardial infarction (STEMI) patients undergoing primary percutaneous coronary intervention (PCI) remains unclear. This study aimed to analyze the impact of timing of eptifibatide administration on infarct-related artery (IRA) patency in STEMI patients undergoing primary PCI. Acute STEMI patients who underwent primary PCI (n = 324) were enrolled in this retrospective study; 164 patients received eptifibatide bolus ≤ 30 minutes after emergency department (ED) admission (group A) and 160 patients received eptifibatide bolus > 30 minutes after ED admission (group B). The primary endpoint was preprocedural IRA patency. Most patients in group A (90%) and group B (89%) were late presenters (> 2 hours after symptom onset). The two groups had similar preprocedural thrombolysis in myocardial infarction 2 or 3 flow of the IRA (26 vs. 24%, p = not significant [NS]), similar creatine kinase-MB (CK-MB) levels at 8 hours after admission (339 vs. 281 U/L, p = NS), similar left ventricular ejection fraction (LVEF) (52 vs. 50%, p = NS), and similar 30-day mortality (2 vs. 7%, p = NS). Compared with group B, patients in group A had shorter door-to-device time (p < 0.001) and shorter procedural time (p = 0.004), without increased bleeding risk (13 vs. 18%, p = NS). Earlier intravenous administration of eptifibatide before primary PCI did not improve preprocedural IRA patency, CK-MB level at 8 hours after admission, LVEF and 30-day mortality compared with patients who received intravenous eptifibatide that was administered later.

  19. Critical space-time networks and geometric phase transitions from frustrated edge antiferromagnetism.

    PubMed

    Trugenberger, Carlo A

    2015-12-01

    Recently I proposed a simple dynamical network model for discrete space-time that self-organizes as a graph with Hausdorff dimension d(H)=4. The model has a geometric quantum phase transition with disorder parameter (d(H)-d(s)), where d(s) is the spectral dimension of the dynamical graph. Self-organization in this network model is based on a competition between a ferromagnetic Ising model for vertices and an antiferromagnetic Ising model for edges. In this paper I solve a toy version of this model defined on a bipartite graph in the mean-field approximation. I show that the geometric phase transition corresponds exactly to the antiferromagnetic transition for edges, the dimensional disorder parameter of the former being mapped to the staggered magnetization order parameter of the latter. The model has a critical point with long-range correlations between edges, where a continuum random geometry can be defined, exactly as in Kazakov's famed 2D random lattice Ising model but now in any number of dimensions.

  20. On the Frequency of Additional Planets in Short Period Hot Jupiter Systems from Transit Timing Variations

    NASA Astrophysics Data System (ADS)

    Dittmann, Jason; Close, L.; Scuderi, L.

    2011-05-01

    The large number of hot Jupiter planets allows one to probe these systems for additional unseen planets via transit timing variations (TTVs). Even relatively small terrestrial planets, when placed in an energetically favorable mean motion resonance (MMR), can cause detectable TTVs with an amplitude of several minutes (Holman and Murray 2005, Agol et al. 2005). In an effort to discover and characterize such companions, we have embarked on a systematic study of known transiting hot Jupiters, utilizing the 1.55 meter Kuiper telescope on Mt. Bigelow to measure multiple individual transits in an observing season to within 30 second precision, and constrain the nature of any planetary companions. Here, we present current and preliminary results on this study, and show that the systems HAT-P-5, HAT- P-6, HAT-P-8, HAT-P-9, WASP-11/HAT-P-10, HAT-P-11, TrES-2, and WASP-10 do not contain small mass companions in MMRs, or moderate mass companions in close enough proximity to induce TTVs on the order of 1.5 minutes.

  1. Critical space-time networks and geometric phase transitions from frustrated edge antiferromagnetism

    NASA Astrophysics Data System (ADS)

    Trugenberger, Carlo A.

    2015-12-01

    Recently I proposed a simple dynamical network model for discrete space-time that self-organizes as a graph with Hausdorff dimension dH=4 . The model has a geometric quantum phase transition with disorder parameter (dH-ds) , where ds is the spectral dimension of the dynamical graph. Self-organization in this network model is based on a competition between a ferromagnetic Ising model for vertices and an antiferromagnetic Ising model for edges. In this paper I solve a toy version of this model defined on a bipartite graph in the mean-field approximation. I show that the geometric phase transition corresponds exactly to the antiferromagnetic transition for edges, the dimensional disorder parameter of the former being mapped to the staggered magnetization order parameter of the latter. The model has a critical point with long-range correlations between edges, where a continuum random geometry can be defined, exactly as in Kazakov's famed 2D random lattice Ising model but now in any number of dimensions.

  2. Comparing Transition-Edge Sensor Response Times in a Modified Contact Scheme with Different Support Beams

    NASA Astrophysics Data System (ADS)

    Beyer, A. D.; Kenyon, M. E.; Bumble, B.; Runyan, M. C.; Echternach, P. E.; Holmes, W. A.; Bock, J. J.; Bradford, C. M.

    2014-08-01

    We present measurements of the thermal conductance, G, and effective time constants, , of three transition-edge sensors (TESs) populated in arrays operated from 80-87 mK with T 120 mK. Our TES arrays include several variations of thermal architecture enabling determination of the architecture that demonstrates the minimum noise equivalent power, the lowest , and the trade-offs among designs. The three TESs we report here have identical Mo/Cu bilayer thermistors and wiring structures, while the thermal architectures are: (1) a TES with straight support beams of 1 mm length, (2) a TES with meander support beams of total length 2 mm and with two phonon-filter blocks per beam, and (3) a TES with meander support beams of total length 2 mm and with six phonon-filter blocks per beam. Our wiring scheme aims to lower the thermistor normal state resistance R and increase the sharpness of the transition dlogR/dlogT at the transition temperature T. We find an upper limit of given by (), and G values of 200 fW/K for (1), 15 fW/K for (2), and 10 fW/K for (3). The value of can be improved by slightly increasing the length of our thermistors.

  3. A mechanism-based approach for absorption modeling: the Gastro-Intestinal Transit Time (GITT) model.

    PubMed

    Hénin, Emilie; Bergstrand, Martin; Standing, Joseph F; Karlsson, Mats O

    2012-06-01

    Absorption models used in the estimation of pharmacokinetic drug characteristics from plasma concentration data are generally empirical and simple, utilizing no prior information on gastro-intestinal (GI) transit patterns. Our aim was to develop and evaluate an estimation strategy based on a mechanism-based model for drug absorption, which takes into account the tablet movement through the GI transit. This work is an extension of a previous model utilizing tablet movement characteristics derived from magnetic marker monitoring (MMM) and pharmacokinetic data. The new approach, which replaces MMM data with a GI transit model, was evaluated in data sets where MMM data were available (felodipine) or not available (diclofenac). Pharmacokinetic profiles in both datasets were well described by the model according to goodness-of-fit plots. Visual predictive checks showed the model to give superior simulation properties compared with a standard empirical approach (first-order absorption rate + lag-time). This model represents a step towards an integrated mechanism-based NLME model, where the use of physiological knowledge and in vitro–in vivo correlation helps fully characterize PK and generate hypotheses for new formulations or specific populations.

  4. Photo-dynamical analysis of three Kepler objects of interest with significant transit timing variations

    SciTech Connect

    Nesvorný, David; Terrell, Dirk; Kipping, David; Feroz, Farhan

    2014-07-20

    KOI-227, KOI-319 and KOI-884 are identified here as (at least) two planet systems. For KOI-319 and KOI-884, the observed Transit Timing Variations (TTVs) of the inner transiting planet are used to detect an outer non-transiting planet. The outer planet in KOI-884 is ≅2.6 Jupiter masses and has the orbital period just narrow of the 3:1 resonance with the inner planet (orbital period ratio 2.93). The distribution of parameters inferred from KOI-319.01's TTVs is bimodal with either a ≅1.6 Neptune-mass (M{sub N}) planet wide of the 5:3 resonance (period 80.1 days) or a ≅1 Saturn-mass planet wide of the 7:3 resonance (period 109.2 days). The radial velocity measurements can be used in this case to determine which of these parameter modes is correct. KOI-227.01's TTVs with large ≅10 hr amplitude can be obtained for planetary-mass companions in various major resonances. Based on the Bayesian evidence, the current TTV data favor the outer 2:1 resonance with a companion mass ≅1.5 M{sub N}, but this solution implies a very large density of KOI-227.01. The inner and outer 3:2 resonance solutions with sub-Neptune-mass companions are physically more plausible, but will need to be verified.

  5. Comparing Transition-Edge Sensor Response Times in a Modified Contact Scheme with Different Support Beams

    NASA Technical Reports Server (NTRS)

    Beyer, A. D.; Kenyon, M. E.; Bumble, B.; Runyan, M. C.; Echternach, P. E.; Holmes, W. A.; Bock, J. J.; Bradford, C. M.

    2013-01-01

    We present measurements of the thermal conductance, G, and effective time constants, tau, of three transition-edge sensors (TESs) populated in arrays operated from 80-87mK with T(sub C) approximately 120mK. Our TES arrays include several variations of thermal architecture enabling determination of the architecture that demonstrates the minimum noise equivalent power (NEP), the lowest tau and the trade-offs among designs. The three TESs we report here have identical Mo/Cu bilayer thermistors and wiring structures, while the thermal architectures are: 1) a TES with straight support beams of 1mm length, 2) a TES with meander support beams of total length 2mm and with 2 phononfilter blocks per beam, and 3) a TES with meander support beams of total length 2mm and with 6 phonon-filter blocks per beam. Our wiring scheme aims to lower the thermistor normal state resistance R(sub N) and increase the sharpness of the transition alpha=dlogR/dlogT at the transition temperature T(sub C). We find an upper limit of given by (25+/-10), and G values of 200fW/K for 1), 15fW/K for 2), and 10fW/K for 3). The value of alpha can be improved by slightly increasing the length of our thermistors.

  6. Photo-dynamical Analysis of Three Kepler Objects of Interest with Significant Transit Timing Variations

    NASA Astrophysics Data System (ADS)

    Nesvorný, David; Kipping, David; Terrell, Dirk; Feroz, Farhan

    2014-07-01

    KOI-227, KOI-319 and KOI-884 are identified here as (at least) two planet systems. For KOI-319 and KOI-884, the observed Transit Timing Variations (TTVs) of the inner transiting planet are used to detect an outer non-transiting planet. The outer planet in KOI-884 is sime2.6 Jupiter masses and has the orbital period just narrow of the 3:1 resonance with the inner planet (orbital period ratio 2.93). The distribution of parameters inferred from KOI-319.01's TTVs is bimodal with either a sime1.6 Neptune-mass (M N) planet wide of the 5:3 resonance (period 80.1 days) or a sime1 Saturn-mass planet wide of the 7:3 resonance (period 109.2 days). The radial velocity measurements can be used in this case to determine which of these parameter modes is correct. KOI-227.01's TTVs with large sime10 hr amplitude can be obtained for planetary-mass companions in various major resonances. Based on the Bayesian evidence, the current TTV data favor the outer 2:1 resonance with a companion mass sime1.5 M N, but this solution implies a very large density of KOI-227.01. The inner and outer 3:2 resonance solutions with sub-Neptune-mass companions are physically more plausible, but will need to be verified.

  7. Phase transitions in optimal search times: How random walkers should combine resetting and flight scales.

    PubMed

    Campos, Daniel; Méndez, Vicenç

    2015-12-01

    Recent works have explored the properties of Lévy flights with resetting in one-dimensional domains and have reported the existence of phase transitions in the phase space of parameters which minimizes the mean first passage time (MFPT) through the origin [L. Kusmierz et al., Phys. Rev. Lett. 113, 220602 (2014)]. Here, we show how actually an interesting dynamics, including also phase transitions for the minimization of the MFPT, can also be obtained without invoking the use of Lévy statistics but for the simpler case of random walks with exponentially distributed flights of constant speed. We explore this dynamics both in the case of finite and infinite domains, and for different implementations of the resetting mechanism to show that different ways to introduce resetting consistently lead to a quite similar dynamics. The use of exponential flights has the strong advantage that exact solutions can be obtained easily for the MFPT through the origin, so a complete analytical characterization of the system dynamics can be provided. Furthermore, we discuss in detail how the phase transitions observed in random walks with resetting are closely related to several ideas recurrently used in the field of random search theory, in particular, to other mechanisms proposed to understand random search in space as mortal random walks or multiscale random walks. As a whole, we corroborate that one of the essential ingredients behind MFPT minimization lies in the combination of multiple movement scales (regardless of their specific origin).

  8. Mean Transit Time as a Predictor of Groundwater Discharge Response in the Upper Colorado River Basin

    NASA Astrophysics Data System (ADS)

    Solder, J. E.; Heilweil, V. M.; Stolp, B. J.; Susong, D.

    2015-12-01

    The Colorado River and its tributaries support 40 million municipal water users and 5.5 million acres of agriculture in the south western United States (U.S. Bureau of Reclamation, 2012). Recent estimates by Rumsey et al. (2015) suggest that a significant portion (about 50 percent) of surface water flow in the Upper Colorado River Basin (UCRB) is sustained by groundwater discharge to streams. Predicted climate variation (Cook et al., 2015) and increased water demand (U.S. Bureau of Reclamation, 2012) within the UCRB suggest future decreases in groundwater discharge, however transient groundwater responses are not well understood. In this study we calculate groundwater mean transit time (MTT) and transit time distribution (TTD) as predictors of the pattern and timing of groundwater response to hydraulic stress. Samples from nineteen large springs within the UCRB were analyzed for environmental tracers to determine MTT and TTD. The predictive value of the MTT is examined by a statistical analysis of MTT, historical spring discharge records, and the Palmer Hydrological Drought Index. MTTs of the 19 springs range from 10 to 15,000 years with a flow-weighted average of 1,650 years. The composite TTD of the 19 springs suggest that flowpaths representing 45 percent of their combined discharge have transit times greater than 100 years. However, spring discharge records indicate that flow responds to drought on much shorter (0.5 - 6 year) time scales, indicative of a hydraulic pressure response. Springs with shorter MTTs (< 100) generally correlated with larger discharge variations and faster responses to drought indicating MTT can be used for estimating the relative magnitude and timing of groundwater response. Previous study (e.g., Manga, 1999) has shown groundwater responds on shorter time scales than the MTT, but of interest the results presented here indicate that relatively stable and old springs with long MTTs (> 100) also show a hydraulic pressure response. While

  9. [Abdominal artery aneurysm and associated surgical abdominal diseases: towards optimal timing].

    PubMed

    Stilo, Francesco; Mirenda, Francesco; Mandolfino, Tommaso; La Spada, Michele; D'Alfonso, Mario; Carmignani, Amedeo; De Caridi, Giovanni; Benedetto, Filippo; Spinelli, Francesco

    2003-01-01

    The purpose of this study was to assess which modalities offered the best timing in the treatment of abdominal aortic aneurysms associated with other abdominal surgical diseases. From January 1984 to December 2002, 372 patients underwent surgery for abdominal aortic aneurysms, 350 men (94%) and 22 women (6%), mean age 72 years. Of these 10% were operated on urgently. The traditional open technique was used in 307 patients, and the endovascular method in the remaining 65 cases. In 40 patients (11%) we observed other associated abdominal diseases which were treated during the same operation in 34 cases (85%). We had three deaths in the 34 cases treated in the same operation (9%). In the remaining cases no perioperative mortality was registered. There were no cases of prosthesis infection. The mean hospital stay was 9 days. Simultaneous treatment appears, on the one hand, to carry an increased operative risk and increased mortality and, on the other, to present the advantage of having to perform only one surgical procedure. The advent of the endovascular method allows us to postpone the treatment of the associated disease without increasing the technical difficulty of the second operation.

  10. How does landscape structure influence catchment transit time across different geomorphic provinces?

    USGS Publications Warehouse

    Tetzlaff, D.; Seibert, J.; McGuire, K.J.; Laudon, H.; Burns, Douglas A.; Dunn, S.M.; Soulsby, C.

    2009-01-01

    Despite an increasing number of empirical investigations of catchment transit times (TTs), virtually all are based on individual catchments and there are few attempts to synthesize understanding across different geographical regions. Uniquely, this paper examines data from 55 catchments in five geomorphic provinces in northern temperate regions (Scotland, United States of America and Sweden). The objective is to understand how the role of catchment topography as a control on the TTs differs in contrasting geographical settings. Catchment inverse transit time proxies (ITTPs) were inferred by a simple metric of isotopic tracer damping, using the ratio of standard deviation of ??18O in streamwater to the standard deviation of ??18O in precipitation. Quantitative landscape analysis was undertaken to characterize the catchments according to hydrologically relevant topographic indices that could be readily determined from a digital terrain model (DTM). The nature of topographic controls on transit times varied markedly in different geomorphic regions. In steeper montane regions, there are stronger gravitational influences on hydraulic gradients and TTs tend to be lower in the steepest catchments. In provinces where terrain is more subdued, direct topographic control weakened; in particular, where flatter areas with less permeable soils give rise to overland flow and lower TTs. The steeper slopes within this flatter terrain appear to have a greater coverage of freely draining soils, which increase sub-surface flow, therefore increasing TTs. Quantitative landscape analysis proved a useful tool for intercatchment comparison. However, the critical influence of sub-surface permeability and connectivity may limit the transferability of predictive tools of hydrological function based on topographic parameters alone. Copyright ?? 2009 John Wiley & Sons, Ltd.

  11. Swallowing transit times and valleculae residue in stable chronic obstructive pulmonary disease

    PubMed Central

    2014-01-01

    Background Breathing and swallowing are physiologically linked to ensure effortless gas exchange during oronasal breathing and to prevent aspiration during swallowing. Studies have indicated consistent aspiration in chronic obstructive pulmonary disease, mainly related to delayed swallowing reflex and problems with lingual propulsion and pharyngeal peristalsis as a result of bilateral weakness and incoordination of the related muscles. The purpose of the present study was to evaluate swallowing transit times and valleculae residue characteristics of stable COPD patients who have no swallowing complaints. Methods Our study population included 20 stable patients with COPD and no swallowing complaints and 20 healthy controls. Swallowing was assessed through videofluoroscopic examination and involved the analysis of the following parameters: (1) pharyngeal stages of deglutition; (2) the duration of bolus movement through the oral cavity and pharynx (i.e. transit times); (3) valleculae residue ratio; (4) penetration/aspiration. Results Participants of the study did not present any signs of penetration-aspiration for any of the tested consistencies. Patients with COPD presented longer pharyngeal transit times during the ingestion of the liquid consistency and during the ingestion of the paste consistency. Regarding the duration of tongue base contact with the posterior pharyngeal wall, COPD patients also presented longer durations for the liquid and paste consistencies. No significant difference was observed for the distribution of individuals among the different valleculae residue severity levels. Conclusions Our study suggests that stable COPD patients may present physiological adaptations as a protective swallowing maneuver to avoid aspiration/penetration of pharyngeal contents. Moreover, valleculae residue cannot be seen as an isolated factor when trying to explain swallowing alterations in this population. PMID:24739506

  12. Are transit times key process-based tools for regional classification and prediction in ungauged basins?

    NASA Astrophysics Data System (ADS)

    Tetzlaff, D.; Soulsby, C.; Hrachowitz, M.; Speed, M.

    2009-04-01

    In recent years, transit times (TTs) have been increasingly explored as a process-based tools for conceptualising hydrological processes in an integrated manner at a range of scales. Traditionally the identification of the appropriate transit time distribution (TTD) for a hydrological system (e.g. hillslope or catchment), and the derivation of metrics such as the mean transit time (MTT) have required quantitative assessment of input-output relationships for conservative tracers using lumped parameter models. Such work has allowed the main landscape controls on TTs to be identified and facilitated the prediction of MTT in ungauged basins in particular geomorphic provinces. This has shown TT to be a useful diagnostic index of similarity that can be valuable in process-based catchment classification. In this contribution, we used well-constrained MTT estimates (with uncertainty) from 32 experimental catchments (1 to 250km2 in area) with contrasting geologic, topographic, pedologic and climatic characteristics in Scotland. The MTT was highly variable ranging from 30 days to ca. 1200 days for individual catchments. Moreover, MTT was also found to be closely correlated with key hydrometric design statistics such as the Q95, Q5, Mean Annual Flood (MAF) and the slope of the hydrograph recession curve. Analysis of the TT estimates, in conjunction with GIS-based quantitative assessment of key landscape controls, showed that MTT could be predicted to within 25% for ungauged basins from catchment soil cover, drainage density and topographic wetness index. For ungauged basins it was found that the hydrometric design statistics (Q95, Q5, MAF and the recession slope) could be more simply and accurately forecasted from MTT predictions than a single set of catchment characteristics. We demonstrate that TTs - predicted from mapped landscape characteristics - are useful integrating diagnostic metrics for regional classification, prediction and process assessment in ungauged montane

  13. A deconvolution method for deriving the transit time spectrum for ultrasound propagation through cancellous bone replica models.

    PubMed

    Langton, Christian M; Wille, Marie-Luise; Flegg, Mark B

    2014-04-01

    The acceptance of broadband ultrasound attenuation for the assessment of osteoporosis suffers from a limited understanding of ultrasound wave propagation through cancellous bone. It has recently been proposed that the ultrasound wave propagation can be described by a concept of parallel sonic rays. This concept approximates the detected transmission signal to be the superposition of all sonic rays that travel directly from transmitting to receiving transducer. The transit time of each ray is defined by the proportion of bone and marrow propagated. An ultrasound transit time spectrum describes the proportion of sonic rays having a particular transit time, effectively describing lateral inhomogeneity of transit times over the surface of the receiving ultrasound transducer. The aim of this study was to provide a proof of concept that a transit time spectrum may be derived from digital deconvolution of input and output ultrasound signals. We have applied the active-set method deconvolution algorithm to determine the ultrasound transit time spectra in the three orthogonal directions of four cancellous bone replica samples and have compared experimental data with the prediction from the computer simulation. The agreement between experimental and predicted ultrasound transit time spectrum analyses derived from Bland-Altman analysis ranged from 92% to 99%, thereby supporting the concept of parallel sonic rays for ultrasound propagation in cancellous bone. In addition to further validation of the parallel sonic ray concept, this technique offers the opportunity to consider quantitative characterisation of the material and structural properties of cancellous bone, not previously available utilising ultrasound.

  14. Intradural Procedural Time to Assess Technical Difficulty of Superciliary Keyhole and Pterional Approaches for Unruptured Middle Cerebral Artery Aneurysms

    PubMed Central

    Choi, Yeon-Ju; Son, Wonsoo; Park, Ki-Su

    2016-01-01

    Objective This study used the intradural procedural time to assess the overall technical difficulty involved in surgically clipping an unruptured middle cerebral artery (MCA) aneurysm via a pterional or superciliary approach. The clinical and radiological variables affecting the intradural procedural time were investigated, and the intradural procedural time compared between a superciliary keyhole approach and a pterional approach. Methods During a 5.5-year period, patients with a single MCA aneurysm were enrolled in this retrospective study. The selection criteria for a superciliary keyhole approach included : 1) maximum diameter of the unruptured MCA aneurysm <15 mm, 2) neck diameter of the MCA aneurysm <10 mm, and 3) aneurysm location involving the sphenoidal or horizontal segment of MCA (M1) segment and MCA bifurcation, excluding aneurysms distal to the MCA genu. Meanwhile, the control comparison group included patients with the same selection criteria as for a superciliary approach, yet who preferred a pterional approach to avoid a postoperative facial wound or due to preoperative skin trouble in the supraorbital area. To determine the variables affecting the intradural procedural time, a multiple regression analysis was performed using such data as the patient age and gender, maximum aneurysm diameter, aneurysm neck diameter, and length of the pre-aneurysm M1 segment. In addition, the intradural procedural times were compared between the superciliary and pterional patient groups, along with the other variables. Results A total of 160 patients underwent a superciliary (n=124) or pterional (n=36) approach for an unruptured MCA aneurysm. In the multiple regression analysis, an increase in the diameter of the aneurysm neck (p<0.001) was identified as a statistically significant factor increasing the intradural procedural time. A Pearson correlation analysis also showed a positive correlation (r=0.340) between the neck diameter and the intradural procedural time

  15. Kepler’s Low-Mass, Low Density Planets Characterized via Transit Timing

    NASA Astrophysics Data System (ADS)

    Jontof-Hutter, Daniel; Ford, Eric B.; Lissauer, Jack; Rowe, Jason; Fabrycky, Daniel

    2015-08-01

    The Kepler mission has revealed an abundance of planets in a regime of mass and size that is absent from the Solar System. This includes systems of high multiplicity within 1 AU, where low-mass volatile-rich planets have been observed in compact orbital configurations, as have smaller, rocky planets. The existing sample of characterized planets on the mass-radius diagram shows no abrupt transition from rocky planets to those that must be volatile-rich, but characteristic trends are beginning to emerge. More precise characterizations of planets by mass, radius, and incident flux are revealing fundamental properties of a common class of exoplanets.There is a small sample of low mass exoplanets with known masses and radii, whose radii are known from transit depths, and whose masses are determined from radial velocity spectroscopy (RV). In the super-Earth mass range, detectability limits this sample to planets that have short orbital periods, and high incident fluxes.In the absence of mass determinations via RV observations, transit timing variations (TTVs) offer a chance to probe perturbations between planets that pass close to one another or are near resonance, and hence dynamical fits to observed transit times can be used to measure planetary masses and orbital parameters. Such modeling with Kepler data probes planetary masses over orbital periods ranging from ~5-200 days, complementing the sample of RV detections, but also with some overlap.In addition, dynamical fits to observed TTVs can tightly constrain the orbital eccentricity vectors in select cases, which can, alongside the transit light curve, tightly constrain the density and radius of the host star, and hence reduce the uncertainty on planetary radius.TTV studies have revealed a class of low-mass, low-density objects with a substantial mass fraction in the form of a voluminous H-rich atmosphere. We will present new precise planetary mass characterizations from TTVs. We find that super-Earth mass planets

  16. Search for Time-Independent Lorentz Violation using Muon Neutrino to Muon Antineutrino Transitions in MINOS

    SciTech Connect

    Adamson, P.; et al.

    2016-05-10

    Data from the MINOS experiment has been used to search for mixing between muon neutrinos and muon antineutrinos using a time-independent Lorentz-violating formalism derived from the Standard-Model Extension (SME). MINOS is uniquely capable of searching for muon neutrino-antineutrino mixing given its long baseline and ability to distinguish between neutrinos and antineutrinos on an event-by-event basis. Neutrino and antineutrino interactions were observed in the MINOS Near and Far Detectors from an exposure of 10.56$\\times10^{20}$ protons-on-target from the NuMI neutrino-optimized beam. No evidence was found for such transitions and new, highly stringent limits were placed on the SME coefficients governing them. We place the first limits on the SME parameters $(c_{L})^{TT}_{\\mu\\mu} $ and $(c_{L})^{TT}_{\\tau\\tau}$ at $-8.4\\times10^{-23} < (c_{L})^{TT}_{\\mu\\mu} < 8.0\\times10^{-23}$ and $-8.0\\times10^{-23} < (c_{L})^{TT}_{\\tau\\tau} < 8.4\\times10^{-23}$, and the world's best limits on the $\\tilde{g}^{ZT}_{\\mu\\overline{\\mu}}$ and $\\tilde{g}^{ZT}_{\\tau\\overline{\\tau}}$ parameters at $|\\tilde{g}^{ZT}_{\\mu\\overline{\\mu}}| < 3.3\\times 10^{-23}$ and $|\\tilde{g}^{ZT}_{\\tau\\overline{\\tau}}| < 3.3\\times 10^{-23}$, all limits quoted at $3\\sigma$.

  17. Renal blood flow transit time in the study of renal transplants

    SciTech Connect

    Sfakianakis, G.; Ihmeidan, I.; Kyriakides, G.; Martinez, B.; Hourani, M.; Miller, J.; Serafini, A.

    1985-05-01

    Radio-hippurate scintigraphy has been used to study renal transplant function because of its unique advantages over other noninvasive methods. Despite a great sensitivity in diagnosing the existence of a functional problem the test lacks in specificity. In an effort to differentiate between acute tubular necrosis (ATN) and graft rejection (RJ) the authors preceded hippurate scintigraphy by measurements of renal flow transit time (TT). After an intravenous injection of 8 mCi of Tc-99m-sulfur-colloid flow curves from the kidney and the abdominal aorta in 1 sec intervals for 1 min were obtained. Renal transit time was mathematically calculated and corrected for bolus and circulatory differences by dividing it with the corresponding Aortic TT (corrected Renal TT(cRTT). Radiohippuran (O-I-131-Hippurate), 150 ..mu..Ci was injected subsequently and of the different computer generated parameters the 30 min net cortical residual (% of the peak) activity (Hippuran Residual Activity, HRA) was found more sensitive and reproducible for comparisons. Results of documented cases showed a statistically significant difference. Uncomplicated cases (usually on antirejection therapy) showed a tendency to increasing the cRTTs with time (not significantly) but their HRAs were significantly lower than in ATN and RJ (p< 0.001).

  18. A portable method for assessing gastrointestinal motility by simultaneously measuring transit time and contraction frequency.

    PubMed

    Li, H; Yan, G

    2008-01-01

    To portably monitor the motility of the total GI tract, a method for assessing GI motility by simultaneously measuring transit time and contraction frequency is put forward. The portable monitoring system is composed of a swallowable telemetric capsule, a portable recorder, magnetizing coils deposited in vitro, and workstation for data processing. The transit time and contraction frequency of the GI tract are deduced by analysing the variation of the position and orientation angles of a telemetric capsule in time domain and frequency domain. AC electromagnetic localization method is used to determine the position and orientation of the telemetric capsule in vivo. In the paper, the localization model based on a quasi-static magnetic field, the method of monitoring GI motility and the set-up of the monitoring system are detailed. Then from static and dynamic experiments, the performances of the system including the accuracy and dynamic response are evaluated. Finally, the electromagnetic safety of the system is verified by simulating electromagnetic radiation to the human body.

  19. A general stochastic model for studying time evolution of transition networks

    NASA Astrophysics Data System (ADS)

    Zhan, Choujun; Tse, Chi K.; Small, Michael

    2016-12-01

    We consider a class of complex networks whose nodes assume one of several possible states at any time and may change their states from time to time. Such networks represent practical networks of rumor spreading, disease spreading, language evolution, and so on. Here, we derive a model describing the dynamics of this kind of network and a simulation algorithm for studying the network evolutionary behavior. This model, derived at a microscopic level, can reveal the transition dynamics of every node. A numerical simulation is taken as an "experiment" or "realization" of the model. We use this model to study the disease propagation dynamics in four different prototypical networks, namely, the regular nearest-neighbor (RN) network, the classical Erdös-Renyí (ER) random graph, the Watts-Strogátz small-world (SW) network, and the Barabási-Albert (BA) scalefree network. We find that the disease propagation dynamics in these four networks generally have different properties but they do share some common features. Furthermore, we utilize the transition network model to predict user growth in the Facebook network. Simulation shows that our model agrees with the historical data. The study can provide a useful tool for a more thorough understanding of the dynamics networks.

  20. Changes in sleep duration, timing, and quality as children transition to kindergarten.

    PubMed

    Cairns, Alyssa; Harsh, John

    2014-01-01

    Sleep can be seen as a biologically driven behavior shaped by cultural context. A "poor fit" occurs when contextual demands for the timing and duration sleep periods are incompatible with the underlying biology. Such contextual factors are well-known for adults, yet little is known of the contextual factors that shape young children's sleep health and to what degree such factors impact sleep duration, timing, and quality. This study attempted to identify how the transition to kindergarten was associated with changes in sleep timing, duration, and quality for children enrolled in preschool prior to attending kindergarten vs. those who were not. Wrist actigraphy in 38 5-year-old children was collected at three longitudinal points before and after the start of kindergarten. Our data suggested that the transition to kindergarten was associated with a reduction in weekday sleep (mostly due to lost napping) and an advance in the weekday nocturnal sleep period that was most pronounced for children not enrolled in preschool prior to kindergarten. These sleep changes paralleled objective and caregiver-reported data of increased sleep pressure that lasted well into the first month of kindergarten.

  1. Predicting critical transitions in dynamical systems from time series using nonstationary probability density modeling

    NASA Astrophysics Data System (ADS)

    Kwasniok, Frank

    2013-11-01

    A time series analysis method for predicting the probability density of a dynamical system is proposed. A nonstationary parametric model of the probability density is estimated from data within a maximum likelihood framework and then extrapolated to forecast the future probability density and explore the system for critical transitions or tipping points. A full systematic account of parameter uncertainty is taken. The technique is generic, independent of the underlying dynamics of the system. The method is verified on simulated data and then applied to prediction of Arctic sea-ice extent.

  2. Predicting critical transitions in dynamical systems from time series using nonstationary probability density modeling.

    PubMed

    Kwasniok, Frank

    2013-11-01

    A time series analysis method for predicting the probability density of a dynamical system is proposed. A nonstationary parametric model of the probability density is estimated from data within a maximum likelihood framework and then extrapolated to forecast the future probability density and explore the system for critical transitions or tipping points. A full systematic account of parameter uncertainty is taken. The technique is generic, independent of the underlying dynamics of the system. The method is verified on simulated data and then applied to prediction of Arctic sea-ice extent.

  3. Correcting for non-compliance when determining colonic transit time with radio-opaque markers

    PubMed Central

    Ibarra, Alvin; Olli, Kaisa; Ouwehand, Arthur C

    2017-01-01

    The use of radio-opaque markers and abdominal X-ray is the standard method for determining colonic transit time (CTT). However, when there are deviations in the intake of these markers by participants in clinical trials it is desirable to improve observations by introducing corrections, where possible. To date, there is no standard procedure to adjust for such deviations. This report proposes a series of alternatives based on possible scenarios for deviations from the intended intake of radio-opaque markers. The proposed method to correct for missed or delayed consumption of radio-opaque markers can help to increase the accuracy of the CTT measurements in clinical trials. PMID:28216983

  4. Transition from time-dependent to stationary flow patterns in the Taylor-Dean system

    NASA Astrophysics Data System (ADS)

    Mutabazi, Innocent; Andereck, C. David

    1991-11-01

    The flow between two horizontal coaxial cylinders with a partially filled gap, the Taylor-Dean system, is investigated for the case in which the outer cylinder rotates while the inner cylinder remains at rest. The initial instability is to a mixed state of both traveling inclined rolls and laminar base flow. At a larger rotation rate, the entire flow becomes time dependent. At a still larger rotation rate, the flow undergoes a subcritical transition to a stationary roll pattern, a process previously observed only in binary fluid mixtures.

  5. Using Isotopes to Assess Transit Times and Pollution Risk in Mesoscale Catchments

    NASA Astrophysics Data System (ADS)

    McGrane, S. J.; Tetzlaff, D.; Essery, R.; Soulsby, C.

    2011-12-01

    The use of environmental tracers to discern dominant runoff sources has become an increasingly popular approach in the field of hydrology. Developing an understanding of both geographical water sources and the timing of water passage through a catchment provides an avenue to characterise both the spatial and temporal dynamics of water fluxes in rainfall-runoff transformation. Understanding these dynamics can provide invaluable insight into the the nature of pollution risk and longevity of natural clean-up times in different catchment landscapes. Here, we present results from a study investigating catchment behaviour across eight heterogeneous mesoscale (104-488 km2) catchments in the north east of Scotland. Weekly samples were taken of both streamwater and precipitation for stable isotopes (2H and 18O) to facilitate Mean Transit Time (MTT) estimates at the catchment scale. Streamwater samples were also analysed for alkalinity which was used as a hydrochemical tracer to determine runoff sources. Estimates of MTT were conducted using a gamma distribution convolution integral model and controlling catchment characteristics were identified using multiple regression using a GIS of landscape properties. A range of MTTs were estimated for the study catchments. In more upland catchments these were in the order of 2 years as waters were mainly derived from near surface soil horizons, but in more lowland catchments the transit times increased to over 4 years as groundwater became a more significant contributor to flow. In such lowland catchments, a legacy of fertilizer applications has contaminated groundwater sources which impacts on macronutrient levels in stream waters. Clean up times are likely to be decadal, and meantime short residence time, clean upland waters provide a critical ecosystem service in diluting downstream sources and maintaining stream water quality.

  6. Estimating transition rates in aggregated Markov models of ion channel gating with loops and with nearly equal dwell times

    PubMed Central

    Wagner, M.; Michalek, S.; Timmer, J.

    1999-01-01

    A typical task in the application of aggregated Markov models to ion channel data is the estimation of the transition rates between the states. Realistic models for ion channel data often have one or more loops. We show that the transition rates of a model with loops are not identifiable if the model has either equal open or closed dwell times. This non-identifiability of the transition rates also has an effect on the estimation of the transition rates for models which are not subject to the constraint of either equal open or closed dwell times. If a model with loops has nearly equal dwell times, the Hessian matrix of its likelihood function will be ill-conditioned and the standard deviations of the estimated transition rates become extraordinarily large for a number of data points which are typically recorded in experiments.

  7. Direct simulation of groundwater transit-time distributions using the reservoir theory

    NASA Astrophysics Data System (ADS)

    Etcheverry, David; Perrochet, Pierre

    Groundwater transit times are of interest for the management of water resources, assessment of pollution from non-point sources, and quantitative dating of groundwaters by the use of environmental isotopes. The age of water is the time water has spent in an aquifer since it has entered the system, whereas the transit time is the age of water as it exits the system. Water at the outlet of an aquifer is a mixture of water elements with different transit times, as a consequence of the different flow-line lengths. In this paper, transit-time distributions are calculated by coupling two existing methods, the reservoir theory and a recent age-simulation method. Based on the derivation of the cumulative age distribution over the whole domain, the approach accounts for the whole hydrogeological framework. The method is tested using an analytical example and its applicability illustrated for a regional layered aquifer. Results show the asymmetry and multimodality of the transit-time distribution even in advection-only conditions, due to the aquifer geometry and to the velocity-field heterogeneity. Résumé Les temps de transit des eaux souterraines sont intéressants à connaître pour gérer l'évaluation des ressources en eau dans le cas de pollution à partir de sources non ponctuelles, et aussi pour dater quantitativement les eaux souterraines au moyen des isotopes du milieu. L'âge de l'eau est le temps qu'elle a passé dans un aquifère depuis qu'elle est entrée dans le système, alors que le temps de transit est l'âge de l'eau au moment où elle quitte le système. L'eau à la sortie d'un aquifère est un mélange d'eaux possédant différents temps de transit, du fait des longueurs différentes des lignes de courant suivies. Dans ce papier, les distributions des temps de transit sont calculées en couplant deux méthodes, la théorie du réservoir et une méthode récente de simulation des âges. Basée sur la dérivation de la distribution cumulées des âges sur

  8. Real-time ultrasound-tagging to track the 2D motion of the common carotid artery wall in vivo

    SciTech Connect

    Zahnd, Guillaume; Salles, Sébastien; Liebgott, Hervé; Vray, Didier; Sérusclat, André; Moulin, Philippe

    2015-02-15

    Purpose: Tracking the motion of biological tissues represents an important issue in the field of medical ultrasound imaging. However, the longitudinal component of the motion (i.e., perpendicular to the beam axis) remains more challenging to extract due to the rather coarse resolution cell of ultrasound scanners along this direction. The aim of this study is to introduce a real-time beamforming strategy dedicated to acquire tagged images featuring a distinct pattern in the objective to ease the tracking. Methods: Under the conditions of the Fraunhofer approximation, a specific apodization function was applied to the received raw channel data, in real-time during image acquisition, in order to introduce a periodic oscillations pattern along the longitudinal direction of the radio frequency signal. Analytic signals were then extracted from the tagged images, and subpixel motion tracking of the intima–media complex was subsequently performed offline, by means of a previously introduced bidimensional analytic phase-based estimator. Results: The authors’ framework was applied in vivo on the common carotid artery from 20 young healthy volunteers and 6 elderly patients with high atherosclerosis risk. Cine-loops of tagged images were acquired during three cardiac cycles. Evaluated against reference trajectories manually generated by three experienced analysts, the mean absolute tracking error was 98 ± 84 μm and 55 ± 44 μm in the longitudinal and axial directions, respectively. These errors corresponded to 28% ± 23% and 13% ± 9% of the longitudinal and axial amplitude of the assessed motion, respectively. Conclusions: The proposed framework enables tagged ultrasound images of in vivo tissues to be acquired in real-time. Such unconventional beamforming strategy contributes to improve tracking accuracy and could potentially benefit to the interpretation and diagnosis of biomedical images.

  9. On reducible nonlinear time-delayed stochastic systems: fluctuation dissipation relations, transitions to bistability, and secondary transitions to non-stationarity

    NASA Astrophysics Data System (ADS)

    Patanarapeelert, K.; Frank, T. D.; Friedrich, R.; Tang, I. M.

    2005-12-01

    We show the conditions under which nonlinear time-delayed dynamical systems with multiplicative noise sources can be transformed into linear time-delayed systems with additive noise sources. We show that, for such reducible systems, analytical expressions for stationary distributions can be obtained. We demonstrate that fluctuation-dissipation relations of reducible systems become trivial and we show that reducible systems may exhibit delay- and noise-induced transitions to bistability and secondary transitions to non-stationarity. Our general findings are exemplified for three models: a Gompertz model, a Hongler model and a model involving a 1 - x2 noise amplitude.

  10. Insights into the water mean transit time in a high-elevation tropical ecosystem

    NASA Astrophysics Data System (ADS)

    Mosquera, Giovanny M.; Segura, Catalina; Vaché, Kellie B.; Windhorst, David; Breuer, Lutz; Crespo, Patricio

    2016-07-01

    This study focuses on the investigation of the mean transit time (MTT) of water and its spatial variability in a tropical high-elevation ecosystem (wet Andean páramo). The study site is the Zhurucay River Ecohydrological Observatory (7.53 km2) located in southern Ecuador. A lumped parameter model considering five transit time distribution (TTD) functions was used to estimate MTTs under steady-state conditions (i.e., baseflow MTT). We used a unique data set of the δ18O isotopic composition of rainfall and streamflow water samples collected for 3 years (May 2011 to May 2014) in a nested monitoring system of streams. Linear regression between MTT and landscape (soil and vegetation cover, geology, and topography) and hydrometric (runoff coefficient and specific discharge rates) variables was used to explore controls on MTT variability, as well as mean electrical conductivity (MEC) as a possible proxy for MTT. Results revealed that the exponential TTD function best describes the hydrology of the site, indicating a relatively simple transition from rainfall water to the streams through the organic horizon of the wet páramo soils. MTT of the streams is relatively short (0.15-0.73 years, 53-264 days). Regression analysis revealed a negative correlation between the catchment's average slope and MTT (R2 = 0.78, p < 0.05). MTT showed no significant correlation with hydrometric variables, whereas MEC increases with MTT (R2 = 0.89, p < 0.001). Overall, we conclude that (1) baseflow MTT confirms that the hydrology of the ecosystem is dominated by shallow subsurface flow; (2) the interplay between the high storage capacity of the wet páramo soils and the slope of the catchments provides the ecosystem with high regulation capacity; and (3) MEC is an efficient predictor of MTT variability in this system of catchments with relatively homogeneous geology.

  11. Eccentricity Inferences in Multi-planet systems with Transit Timing: Degeneracies and Apsidal Alignment

    NASA Astrophysics Data System (ADS)

    Jontof-Hutter, Daniel; Van Laerhoven, Christa L.; Ford, Eric B.

    2016-05-01

    Hundreds of multi-transiting systems discovered by the Kepler mission show Transit Timing Variations (TTV). In cases where the TTVs are uniquely attributable to transiting planets, the TTVs enable precise measurements of planetary masses and orbital parameters. Of particular interest are the constraints on eccentricity vectors that can be inferred in systems of low-mass exoplanets.The TTVs in these systems are dominated by a signal caused by near-resonant mean motions. This causes the well-known near-degeneracy between planetary masses and orbital eccentricities. In addition, it causes a degeneracy between the eccentricities of interacting planet pairs.For many systems, the magnitude of individual eccentricities are weakly constrained, yet the data typically provide a tight constraint on the posterior joint distribution for the eccentricity vector components. This permits tight constraints on the relative eccentricity and degree of alignment of interacting planets.For a sample of two and three-planet systems with TTVs, we highlight the effects of these correlations. While the most eccentric orbital solutions for these systems show apsidal alignment, this is often due to the degeneracy that causes correlated constraints on the eccentricity vector components. We compare the likelihood of apsidal alignment for two choices of eccentricity prior: a wide prior using a Rayleigh distribution of scale length 0.1 and a narrower prior with scale length 0.02. In all cases the narrower prior decreased the fraction of samples that exhibited apsidal alignment. However, apsidal alignment persisted in the majority of cases with a narrower eccentricity prior. For a sample of our TTV solutions, we ran simulations of these systems over secular timescales, and decomposed their eccentricity eigenmodes over time, confirming that in most cases, the eccentricities were dominated by parallel eigenmodes which favor apsidal alignment.

  12. Real-time observation of fluctuations at the driven-dissipative Dicke phase transition

    PubMed Central

    Brennecke, Ferdinand; Mottl, Rafael; Baumann, Kristian; Landig, Renate; Donner, Tobias; Esslinger, Tilman

    2013-01-01

    We experimentally study the influence of dissipation on the driven Dicke quantum phase transition, realized by coupling external degrees of freedom of a Bose–Einstein condensate to the light field of a high-finesse optical cavity. The cavity provides a natural dissipation channel, which gives rise to vacuum-induced fluctuations and allows us to observe density fluctuations of the gas in real-time. We monitor the divergence of these fluctuations over two orders of magnitude while approaching the phase transition, and observe a behavior that deviates significantly from that expected for a closed system. A correlation analysis of the fluctuations reveals the diverging time scale of the atomic dynamics and allows us to extract a damping rate for the external degree of freedom of the atoms. We find good agreement with our theoretical model including dissipation via both the cavity field and the atomic field. Using a dissipation channel to nondestructively gain information about a quantum many-body system provides a unique path to study the physics of driven-dissipative systems. PMID:23818599

  13. On the dispersion relation of the transit time instability in inverted fireballs

    SciTech Connect

    Gruenwald, J.

    2014-08-15

    Recently discovered inverted fireballs are non-linear plasma phenomena, which are formed in hollow grid anodes with high transparency in an existing background plasma. If a sufficiently large potential is applied, accelerated electrons from the bulk start to oscillate through the grid. Experimental investigations have shown that they produce different types of plasma instabilities. One of those oscillations is a transit time instability which originates from strong electron beams that travel through the inverted fireball. This type of instability is similar to vircator reflex oscillations and produces radio frequency waves. Hence, it is suitable to convert DC signals into signals oscillating in the MHz range. This paper analyses the dispersion relation of the transit time instability for three different plasma regimes. The regimes can be divided into a collision less regime, a regime with high collisionality and one in between those former two. It is demonstrated that the plasma properties of the surrounding background plasma have a strong influence on the behavior of the instability itself.

  14. Transit time instabilities in an inverted fireball. II. Mode jumping and nonlinearities

    SciTech Connect

    Stenzel, R. L.; Gruenwald, J.; Fonda, B.; Ionita, C.; Schrittwieser, R.

    2011-01-15

    A fireball is formed inside a highly transparent spherical grid immersed in a dc discharge plasma. The ambient plasma acts as a cathode and the positively biased grid as an anode. A strong nearly current-free double layer separates the two plasmas. Electrons are accelerated into the fireball, ionize, and establish a discharge plasma with plasma potential near the grid potential. Ions are ejected from the fireball. Since electrons are lost at the same rate as ions, most electrons accelerated into the fireball just pass through it. Thus, the electron distribution contains radially counterstreaming electrons. High-frequency oscillations are excited with rf period given by the electron transit time through the fireball. Since the frequency is well below the electron plasma frequency, no eigenmodes other than a beam space-charge wave exists. The instability is an inertial transit-time instability similar to the sheath-plasma instability or the reflex vircator instability. In contrast to vircators, there is no electron reflection from a space-charge layer but counterstreaming arises from spherical convergence and divergence of electrons. While the basic instability properties have been presented in a companion paper [R. L. Stenzel et al., Phys. Plasmas 18, 012104 (2011)], the present paper focuses on observed mode jumping and nonlinear effects. The former produce frequency jumps and different potential profiles, the latter produce harmonics associated with electron bunching at large amplitudes. In situ probe measurements are presented and interpreted.

  15. Effects of anatomical position on esophageal transit time: A biomagnetic diagnostic technique

    PubMed Central

    Cordova-Fraga, Teodoro; Sosa, Modesto; Wiechers, Carlos; la Roca-Chiapas, Jose Maria De; Moreles, Alejandro Maldonado; Bernal-Alvarado, Jesus; Huerta-Franco, Raquel

    2008-01-01

    AIM: To study the esophageal transit time (ETT) and compare its mean value among three anatomical inclinations of the body; and to analyze the correlation of ETT to body mass index (BMI). METHODS: A biomagnetic technique was implemented to perform this study: (1) The transit time of a magnetic marker (MM) through the esophagus was measured using two fluxgate sensors placed over the chest of 14 healthy subjects; (2) the ETT was assessed in three anatomical positions (at upright, fowler, and supine positions; 90º, 45º and 0º, respectively). RESULTS: ANOVA and Tuckey post-hoc tests demonstrated significant differences between ETT mean of the different positions. The ETT means were 5.2 ± 1.1 s, 6.1 ± 1.5 s, and 23.6 ± 9.2 s for 90º, 45º and 0º, respectively. Pearson correlation results were r = -0.716 and P < 0.001 by subjects’ anatomical position, and r = -0.024 and P > 0.05 according the subject’s BMI. CONCLUSION: We demonstrated that using this biomagnetic technique, it is possible to measure the ETT and the effects of the anatomical position on the ETT. PMID:18837088

  16. Transit timing of TrES-2: a combined analysis of ground- and space-based photometry

    NASA Astrophysics Data System (ADS)

    Raetz, St.; Maciejewski, G.; Ginski, Ch.; Mugrauer, M.; Berndt, A.; Eisenbeiss, T.; Adam, Ch.; Raetz, M.; Roell, T.; Seeliger, M.; Marka, C.; Vaňko, M.; Bukowiecki, Ł.; Errmann, R.; Kitze, M.; Ohlert, J.; Pribulla, T.; Schmidt, J. G.; Sebastian, D.; Puchalski, D.; Tetzlaff, N.; Hohle, M. M.; Schmidt, T. O. B.; Neuhäuser, R.

    2014-10-01

    Homogeneous observations and careful analysis of transit light curves can lead to the identification of transit timing variations (TTVs). TrES-2 is one of few exoplanets, which offer the matchless possibility to combine long-term ground-based observations with continuous satellite data. Our research aimed at the search for TTVs that would be indicative of perturbations from additional bodies in the system. We also wanted to refine the system parameters and the orbital elements. We obtained 44 ground-based light curves of 31 individual transit events of TrES-2. Eight 0.2-2.2-m telescopes located at six observatories in Germany, Poland and Spain were used. In addition, we analysed 18 quarters (Q0-Q17) of observational data from NASA's space telescope Kepler including 435 individual transit events and 11 publicly available ground-based light curves. Assuming different limb darkening (LD) laws we performed an analysis for all light curves and redetermined the parameters of the system. We also carried out a joint analysis of the ground- and space-based data. The long observation period of seven years (2007-2013) allowed a very precise redetermination of the transit ephemeris. For a total of 490 transit light curves of TrES-2, the time of transit mid-point was determined. The transit times support neither variations on long time-scale nor on short time-scales. The nearly continuous observations of Kepler show no statistically significant increase or decrease in the orbital inclination i and the transit duration D. Only the transit depth shows a slight increase which could be an indication of an increasing stellar activity. In general, system parameters obtained by us were found to be in agreement with previous studies but are the most precise values to date.

  17. A TRANSIT TIMING ANALYSIS OF NINE RISE LIGHT CURVES OF THE EXOPLANET SYSTEM TrES-3

    SciTech Connect

    Gibson, N. P.; Pollacco, D.; Simpson, E. K.; Barros, S.; Joshi, Y. C.; Todd, I.; Keenan, F. P.; Skillen, I.; Benn, C.; Christian, D.; Hrudkova, M.; Steele, I. A.

    2009-08-01

    We present nine newly observed transits of TrES-3, taken as part of a transit timing program using the RISE instrument on the Liverpool Telescope. A Markov-Chain Monte Carlo analysis was used to determine the planet-star radius ratio and inclination of the system, which were found to be R{sub p} /R {sub *} = 0.1664{sup +0.0011} {sub -0.0018} and i = 81.73{sup +0.13} {sub -0.04}, respectively, consistent with previous results. The central transit times and uncertainties were also calculated, using a residual-permutation algorithm as an independent check on the errors. A re-analysis of eight previously published TrES-3 light curves was conducted to determine the transit times and uncertainties using consistent techniques. Whilst the transit times were not found to be in agreement with a linear ephemeris, giving {chi}{sup 2} = 35.07 for 15 degrees of freedom, we interpret this to be the result of systematics in the light curves rather than a real transit timing variation. This is because the light curves that show the largest deviation from a constant period either have relatively little out-of-transit coverage or have clear systematics. A new ephemeris was calculated using the transit times and was found to be T{sub c} (0) = 2454632.62610 {+-} 0.00006 HJD and P = 1.3061864 {+-} 0.0000005 days. The transit times were then used to place upper mass limits as a function of the period ratio of a potential perturbing planet, showing that our data are sufficiently sensitive to have probed sub-Earth mass planets in both interior and exterior 2:1 resonances, assuming that the additional planet is in an initially circular orbit.

  18. Bryostatin extends tPA time window to 6 hours following middle cerebral artery occlusion in aged female rats

    PubMed Central

    Tan, Zhenjun; Lucke-Wold, Brandon P.; Logsdon, Aric F.; Turner, Ryan C.; Tan, Cong; Li, Xinlan; Hongpaison, Jarin; Alkon, Daniel L.; Simpkins, James W.; Rosen, Charles L.; Huber, Jason D.

    2015-01-01

    Background and Purpose Blood-brain barrier (BBB) disruption and hemorrhagic transformation (HT) following ischemic/reperfusion injury contributes to post-stroke morbidity and mortality. Bryostatin, a potent protein kinase C (PKC) modulator, has shown promise in treating neurological injury. In the present study, we tested the hypothesis that administration of bryostatin would reduce BBB disruption and HT following acute ischemic stroke; thus, prolonging the time window for administering recombinant tissue plasminogen activator (r-tPA). Methods Acute cerebral ischemia was produced by reversible occlusion of the right middle cerebral artery (MCAO) in 18–20-month-old female rats using an autologous blood clot with delayed r-tPA reperfusion. Bryostatin (or vehicle) was administered at 2 hours post-MCAO and r-tPA was administered at 6 hours post-MCAO. Functional assessment, lesion volume, and hemispheric swelling measurements were performed at 24 hours post-MCAO. Assessment of BBB permeability, measurement of hemoglobin, assessment of matrix metalloproteinase (MMP) levels by gel zymography, and measurement of PKCε, PKCα, PKCδ expression by western blot were conducted at 24 hours post-MCAO. Results Rats treated with bryostatin prior to r-tPA administration had decreased mortality and hemispheric swelling when compared with rats treated with r-tPA alone. Administration of bryostatin also limited BBB disruption and HT and down-regulated MMP-9 expression while up-regulating PKCε expression at 24 hours post-MCAO. Conclusions Bryostatin administration ameliorates BBB disruption and reduces the risk of HT by down-regulating MMP-9 activation and up-regulating PKCε. In this proof-of-concept study, bryostatin treatment lengthened the time-to-treatment window and enhanced the efficacy and safety of thrombolytic therapy. PMID:26189021

  19. Sport Transition of JPSS VIIRS Imagery for Night-time Applications

    NASA Technical Reports Server (NTRS)

    Fuell, Kevin; LeRoy, Anita; Smith, Matt; Miller, Steve; Kann, Diedre; Bernhardt, David; Reydell, Nezette; Cox, Robert

    2014-01-01

    The NASA/Short-term Prediction, Research, and Transition (SPoRT) Program and NOAA/Cooperative Institute for Research in the Atmosphere (CIRA) work within the NOAA/Joint Polar Satellite System (JPSS) Proving Ground to demonstrate the unique capabilities of the VIIRS instrument. Very similar to MODIS, the VIIRS instrument provides many high-resolution visible and infrared channels in a broad spectrum. In addition, VIIRS is equipped with a low-light sensor that is able to detect light emissions from the land and atmosphere as well as reflected sunlight by the lunar surface. This band is referred to as the Day-Night Band due to the sunlight being used at night to see cloud and topographic features just as one would typically see in day-time visible imagery. NWS forecast offices that collaborate with SPoRT and CIRA have utilized MODIS imagery in operations, but have longed for more frequent passes of polar-orbiting data. The VIIRS instrument enhances SPoRT collaborations with WFOs by providing another day and night-time pass, and at times two additional passes due to its large swath width. This means that multi-spectral, RGB imagery composites are more readily available to prepare users for their use in GOES-R era and high-resolution imagery for use in high-latitudes is more frequently able to supplement standard GOES imagery within the SPoRT Hybrid GEO-LEO product. The transition of VIIRS also introduces the new Day-Night Band capability to forecast operations. An Intensive Evaluation Period (IEP) was conducted in Summer 2013 with a group of "Front Range" NWS offices related to VIIRS night-time imagery. VIIRS single-channel imagery is able to better analyze the specific location of fire hotspots and other land features, as well as provide a more true measurement of various cloud and aerosol properties than geostationary measurements, especially at night. Viewed within the SPoRT Hybrid imagery, the VIIRS data allows forecasters to better interpret the more frequent, but

  20. Complex networks approach to geophysical time series analysis: Detecting paleoclimate transitions via recurrence networks

    NASA Astrophysics Data System (ADS)

    Donner, R. V.; Zou, Y.; Donges, J. F.; Marwan, N.; Kurths, J.

    2009-12-01

    We present a new approach for analysing structural properties of time series from complex systems. Starting from the concept of recurrences in phase space, the recurrence matrix of a time series is interpreted as the adjacency matrix of an associated complex network which links different points in time if the evolution of the considered states is very similar. A critical comparison of these recurrence networks with similar existing techniques is presented, revealing strong conceptual benefits of the new approach which can be considered as a unifying framework for transforming time series into complex networks that also includes other methods as special cases. Based on different model systems, we demonstrate that there are fundamental interrelationships between the topological properties of recurrence networks and the statistical properties of the phase space density of the underlying dynamical system. Hence, the network description yields new quantitative characteristics of the dynamical complexity of a time series, which substantially complement existing measures of recurrence quantification analysis. Finally, we illustrate the potential of our approach for detecting hidden dynamical transitions from geoscientific time series by applying it to different paleoclimate records. In particular, we are able to resolve previously unknown climatic regime shifts in East Africa during the last about 4 million years, which might have had a considerable influence on the evolution of hominids in the area.

  1. Spectral analysis of finite-time correlation matrices near equilibrium phase transitions

    NASA Astrophysics Data System (ADS)

    Vinayak; Prosen, T.; Buča, B.; Seligman, T. H.

    2014-10-01

    We study spectral densities for systems on lattices, which, at a phase transition display, power-law spatial correlations. Constructing the spatial correlation matrix we prove that its eigenvalue density shows a power law that can be derived from the spatial correlations. In practice time series are short in the sense that they are either not stationary over long time intervals or not available over long time intervals. Also we usually do not have time series for all variables available. We shall make numerical simulations on a two-dimensional Ising model with the usual Metropolis algorithm as time evolution. Using all spins on a grid with periodic boundary conditions we find a power law, that is, for large grids, compatible with the analytic result. We still find a power law even if we choose a fairly small subset of grid points at random. The exponents of the power laws will be smaller under such circumstances. For very short time series leading to singular correlation matrices we use a recently developed technique to lift the degeneracy at zero in the spectrum and find a significant signature of critical behavior even in this case as compared to high temperature results which tend to those of random matrix models.

  2. Extended Coherence Time on the Clock Transition of Optically Trapped Rubidium

    NASA Astrophysics Data System (ADS)

    Kleine Büning, G.; Will, J.; Ertmer, W.; Rasel, E.; Arlt, J.; Klempt, C.; Ramirez-Martinez, F.; Piéchon, F.; Rosenbusch, P.

    2011-06-01

    Optically trapped ensembles are of crucial importance for frequency measurements and quantum memories but generally suffer from strong dephasing due to inhomogeneous density and light shifts. We demonstrate a drastic increase of the coherence time to 21 s on the magnetic field insensitive clock transition of Rb87 by applying the recently discovered spin self-rephasing [C. Deutsch , Phys. Rev. Lett. 105, 020401 (2010)PRLTAO0031-900710.1103/PhysRevLett.105.020401]. This result confirms the general nature of this new mechanism and thus shows its applicability in atom clocks and quantum memories. A systematic investigation of all relevant frequency shifts and noise contributions yields a stability of 2.4×10-11τ-1/2, where τ is the integration time in seconds. Based on a set of technical improvements, the presented frequency standard is predicted to rival the stability of microwave fountain clocks in a potentially much more compact setup.

  3. Direct and real time probe of photoinduced structure transition in colossal magnetoresistive material

    DOE PAGES

    Li, Junjie; Wang, Xuan; Zhou, Haidong; ...

    2016-07-29

    Here, we report a direct and real time measurement of photoinduced structure phase transition in single crystal La0.84Sr0.16MnO3 using femtosecond electron diffraction. The melting of orthorhombic lattice ordering under femtosecond optical excitation is found involving two distinct processes with different time scales, an initial fast melting of orthorhombic phase in about 4 ps and a subsequent slower transformation in 90 ps and longer timescales. Furthermore, the fast process is designated as the initial melting of orthorhombic phase induced by the Mn-O bond change that is most likely driven by the quenching of the dynamic Jahn-Teller distortion following the photo-excitation. Wemore » attribute the slow process to the growing of newly formed structure domain from the photo-excited sites to the neighboring non-excited orthorhombic sites.« less

  4. Direct and real time probe of photoinduced structure transition in colossal magnetoresistive material

    NASA Astrophysics Data System (ADS)

    Li, Junjie; Wang, Xuan; Zhou, Haidong; Zhou, Jun; Cheng, J. G.; Cao, Jianming

    2016-07-01

    We report a direct and real time measurement of photoinduced structure phase transition in single crystal La0.84Sr0.16MnO3 using femtosecond electron diffraction. The melting of orthorhombic lattice ordering under femtosecond optical excitation is found involving two distinct processes with different time scales, an initial fast melting of orthorhombic phase in about 4 ps and a subsequent slower transformation in 90 ps and longer timescales. The fast process is designated as the initial melting of orthorhombic phase induced by the Mn-O bond change that is most likely driven by the quenching of the dynamic Jahn-Teller distortion following the photo-excitation. The slow process is attributed to the growing of newly formed structure domain from the photo-excited sites to the neighboring non-excited orthorhombic sites.

  5. Thermoluminescence and nuclear particle tracks in ALHA-81005 Evidence for a brief transit time

    NASA Astrophysics Data System (ADS)

    Sutton, S. R.; Crozaz, G.

    1983-09-01

    Thermoluminescence and nuclear particle track measurements were made on the Antarctic meteorite ALHA-81005. No nuclear particle tracks were found in lithic fragments indicating that the clast material never resided at the very surface of the parent body. The unusually low natural thermoluminescence of this material is interpreted as being due to a combination of anomalous fading and thermal decay. The thermal decay could be due to very long terrestrial age or heating either during atmospheric entry, in a near sun orbit or during a parent body impact event. Impact heating is considered the more likely of these possibilities for this meteorite. If the impact heating interpretation is correct the thermoluminescence data constrains the space exposure time of the object to be less than 2,500 years. Such a brief earth transit time is consistent with a lunar origin for this meteorite.

  6. Direct and real time probe of photoinduced structure transition in colossal magnetoresistive material

    SciTech Connect

    Li, Junjie; Wang, Xuan; Zhou, Haidong; Zhou, Jun; Cheng, J. G.; Cao, Jianming

    2016-07-29

    Here, we report a direct and real time measurement of photoinduced structure phase transition in single crystal La0.84Sr0.16MnO3 using femtosecond electron diffraction. The melting of orthorhombic lattice ordering under femtosecond optical excitation is found involving two distinct processes with different time scales, an initial fast melting of orthorhombic phase in about 4 ps and a subsequent slower transformation in 90 ps and longer timescales. Furthermore, the fast process is designated as the initial melting of orthorhombic phase induced by the Mn-O bond change that is most likely driven by the quenching of the dynamic Jahn-Teller distortion following the photo-excitation. We attribute the slow process to the growing of newly formed structure domain from the photo-excited sites to the neighboring non-excited orthorhombic sites.

  7. Extended coherence time on the clock transition of optically trapped rubidium.

    PubMed

    Büning, G Kleine; Will, J; Ertmer, W; Rasel, E; Arlt, J; Klempt, C; Ramirez-Martinez, F; Piéchon, F; Rosenbusch, P

    2011-06-17

    Optically trapped ensembles are of crucial importance for frequency measurements and quantum memories but generally suffer from strong dephasing due to inhomogeneous density and light shifts. We demonstrate a drastic increase of the coherence time to 21 s on the magnetic field insensitive clock transition of (87)Rb by applying the recently discovered spin self-rephasing [C. Deutsch et al., Phys. Rev. Lett. 105, 020401 (2010)]. This result confirms the general nature of this new mechanism and thus shows its applicability in atom clocks and quantum memories. A systematic investigation of all relevant frequency shifts and noise contributions yields a stability of 2.4×10(-11)τ(-1/2), where τ is the integration time in seconds. Based on a set of technical improvements, the presented frequency standard is predicted to rival the stability of microwave fountain clocks in a potentially much more compact setup.

  8. The [Formula: see text] transition form factor from space- and time-like experimental data.

    PubMed

    Escribano, R; Masjuan, P; Sanchez-Puertas, P

    The [Formula: see text] transition form factor is analyzed for the first time in both space- and time-like regions at low and intermediate energies in a model-independent approach through the use of rational approximants. The [Formula: see text] experimental data provided by the A2 Collaboration in the very low-energy region of the dielectron invariant mass distribution allows for the extraction of the most precise up-to-date slope and curvature parameters of the form factors as well as their values at zero and infinity. The impact of these new results on the mixing parameters of the [Formula: see text]-[Formula: see text] system, together with the role played by renormalization dependent effects, and on the determination of the [Formula: see text] couplings from [Formula: see text] and [Formula: see text] radiative decays is also discussed.

  9. Extended Coherence Time on the Clock Transition of Optically Trapped Rubidium

    SciTech Connect

    Kleine Buening, G.; Will, J.; Ertmer, W.; Rasel, E.; Klempt, C.; Arlt, J.; Ramirez-Martinez, F.; Rosenbusch, P.; Piechon, F.

    2011-06-17

    Optically trapped ensembles are of crucial importance for frequency measurements and quantum memories but generally suffer from strong dephasing due to inhomogeneous density and light shifts. We demonstrate a drastic increase of the coherence time to 21 s on the magnetic field insensitive clock transition of {sup 87}Rb by applying the recently discovered spin self-rephasing [C. Deutsch et al., Phys. Rev. Lett. 105, 020401 (2010)]. This result confirms the general nature of this new mechanism and thus shows its applicability in atom clocks and quantum memories. A systematic investigation of all relevant frequency shifts and noise contributions yields a stability of 2.4x10{sup -11{tau}-1/2}, where {tau} is the integration time in seconds. Based on a set of technical improvements, the presented frequency standard is predicted to rival the stability of microwave fountain clocks in a potentially much more compact setup.

  10. Pulse wave transit time measured by imaging photoplethysmography in upper extremities

    NASA Astrophysics Data System (ADS)

    Volynsky, M. A.; Mamontov, O. V.; Sidorov, I. S.; Kamshilin, A. A.

    2016-08-01

    We describe highly reliable measurement method of the pulse wave transit time (PWTT) to human limbs by using simultaneous recordings of imaging photoplethysmography and electrocardiography. High accuracy of measurements was achieved by access to a larger number of statistically independent data obtained simultaneously in different points. The method is characterized by higher diagnostic reliability because of automatic selection of the regions less affected by environmental noise. The technique was tested in the group of 12 young healthy subjects aged from 21 to 33 years. Even though PWTT in right and left hands was comparable after averaging over the whole group of subjects, significant difference in the time delay of pulse wave between the hands was found in several individuals. The technique can be used for early-stage diagnostics of various vascular diseases.

  11. Short-time Lyapunov exponent analysis and the transition to chaos in Taylor-Couette flow

    NASA Technical Reports Server (NTRS)

    Vastano, John A.; Moser, Robert D.

    1991-01-01

    The physical mechanism driving the weakly chaotic Taylor-Couette flow is investigated using the short-time Liapunov exponent analysis. In this procedure, the transition from quasi-periodicity to chaos is studied using direct numerical 3D simulations of axially periodic Taylor-Couette flow, and a partial Liapunov exponent spectrum for the flow is computed by simultaneously advancing the full solution and a set of perturbations. It is shown that the short-time Liapunov exponent analysis yields more information on the exponents and dimension than that obtained from the common Liapunov exponent calculations. Results show that the chaotic state studied here is caused by a Kelvin-Helmholtz-type instability of the outflow boundary jet of Taylor vortices.

  12. Cortical Phase Transitions, Nonequilibrium Thermodynamics and the Time-Dependent Ginzburg-Landau Equation

    NASA Astrophysics Data System (ADS)

    Freeman, Walter J.; Livi, Roberto; Obinata, Masashi; Vitiello, Giuseppe

    The formation of amplitude modulated and phase modulated assemblies of neurons is observed in the brain functional activity. The study of the formation of such structures requires that the analysis has to be organized in hierarchical levels, microscopic, mesoscopic, macroscopic, each with its characteristic space-time scales and the various forms of energy, electric, chemical, thermal produced and used by the brain. In this paper, we discuss the microscopic dynamics underlying the mesoscopic and the macroscopic levels and focus our attention on the thermodynamics of the nonequilibrium phase transitions. We obtain the time-dependent Ginzburg-Landau equation for the nonstationary regime and consider the formation of topologically nontrivial structures such as the vortex solution. The power laws observed in functional activities of the brain is also discussed and related to coherent states characterizing the many-body dissipative model of brain.

  13. Understanding Flow Pathways, Mixing and Transit Times for Water Quality Modelling

    NASA Astrophysics Data System (ADS)

    Dunn, S. M.; Bacon, J. R.; Soulsby, C.; Tetzlaff, D.

    2007-12-01

    Water quality modelling requires representation of the physical processes controlling the movement of solutes and particulates at an appropriate level of detail to address the objective of the model simulations. To understand and develop mitigation strategies for diffuse pollution at catchment scales, it is necessary for models to be able to represent the sources and age of water reaching rivers at different times. Experimental and modelling studies undertaken on several catchments in the north east of Scotland have used natural hydrochemical and isotopic tracers as a means of obtaining spatially integrated information about mixing processes. Methods for obtaining and integrating appropriate data are considered together with the implications of neglecting it. The tracer data have been incorporated in a conceptual hydrological model to study the sensitivity of the modelled tracer response to factors that may not affect runoff simulations but do affect mixing and transit times of the water. Results from the studies have shown how model structural and parameter uncertainties can lead to errors in the representation of: the flow pathways of water; the degree to which these flow pathways have mixed and the length of time for which water has been stored within the soil / groundwater system. It has been found to be difficult to eliminate structural uncertainty regarding the mechanisms of mixing, and parameter uncertainty regarding the role of groundwater. Simulations of nitrate pollution, resulting from the application of agricultural fertilisers, have been undertaken to demonstrate the sensitivity of water quality simulations to the potential errors in physical transport mechanisms, inherent in models that fail to account correctly for flow pathways, mixing and transit times.

  14. Factors controlling inter-catchment variation of mean transit time with consideration of temporal variability

    NASA Astrophysics Data System (ADS)

    Ma, Wenchao; Yamanaka, Tsutomu

    2016-03-01

    The catchment transit time, a lumped descriptor reflecting both time scale and spatial structure of catchment hydrology can provide useful insights into chemical/nuclear pollution risks within a catchment. Despite its importance, factors controlling spatial variation of mean transit time (MTT) are not yet well understood. In this study, we estimated time-variant MTTs for about ten years (2003-2012) in five mesoscale sub-catchments of the Fuji River catchment, central Japan, to establish the factors controlling their inter-catchment variation with consideration of temporal variability. For this purpose, we employed a lumped hydrological model that was calibrated and validated by hydrometric and isotopic tracer observations. Temporal variation patterns of estimated MTT were similar in all sub-catchments, but with differing amplitudes. Inter-catchment variation of MTT was greater in dry periods than wet periods, suggesting spatial variation of MTT is controlled by water 'stock' rather than by 'flow'. Although the long-term average MTT (LAMTT) in each catchment was correlated with mean slope, coverage of forest (or conversely, other land use types), coverage of sand-shale conglomerate, and groundwater storage, the multiple linear regression revealed that inter-catchment variation of LAMTT is principally controlled by the amount of groundwater storage. This is smaller in mountainous areas covered mostly by forests and greater in plain areas with less forest coverage and smaller slope. This study highlights the topographic control of MTT via groundwater storage, which might be a more important factor in mesoscale catchments, including both mountains and plains, rather than in smaller catchments dominated by mountainous topography.

  15. Laminar microvascular transit time distribution in the mouse somatosensory cortex revealed by Dynamic Contrast Optical Coherence Tomography.

    PubMed

    Merkle, Conrad W; Srinivasan, Vivek J

    2016-01-15

    The transit time distribution of blood through the cerebral microvasculature both constrains oxygen delivery and governs the kinetics of neuroimaging signals such as blood-oxygen-level-dependent functional Magnetic Resonance Imaging (BOLD fMRI). However, in spite of its importance, capillary transit time distribution has been challenging to quantify comprehensively and efficiently at the microscopic level. Here, we introduce a method, called Dynamic Contrast Optical Coherence Tomography (DyC-OCT), based on dynamic cross-sectional OCT imaging of an intravascular tracer as it passes through the field-of-view. Quantitative transit time metrics are derived from temporal analysis of the dynamic scattering signal, closely related to tracer concentration. Since DyC-OCT does not require calibration of the optical focus, quantitative accuracy is achieved even deep in highly scattering brain tissue where the focal spot degrades. After direct validation of DyC-OCT against dilution curves measured using a fluorescent plasma label in surface pial vessels, we used DyC-OCT to investigate the transit time distribution in microvasculature across the entire depth of the mouse somatosensory cortex. Laminar trends were identified, with earlier transit times and less heterogeneity in the middle cortical layers. The early transit times in the middle cortical layers may explain, at least in part, the early BOLD fMRI onset times observed in these layers. The layer-dependencies in heterogeneity may help explain how a single vascular supply manages to deliver oxygen to individual cortical layers with diverse metabolic needs.

  16. Comments on "Improving estimates of the basic reproductive ratio: using both the mean and the dispersal of transition times".

    PubMed

    Nadarajah, Saralees

    2008-03-01

    Comments on Heffernan, J. M., Wahl, L. M. (2006). Improving estimates of the basic reproductive ratio: Using both the mean and the dispersal of transition times. Theoretical Population Biology, 70, 135-145.

  17. Dynamic contrast optical coherence tomography: quantitative measurement of microvascular transit-time distributions in vivo (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Merkle, Conrad W.; Srinivasan, Vivek J.

    2016-03-01

    Transit time is a fundamental microcirculatory parameter that is critical in determining oxygen delivery from capillaries to surrounding tissue. Recently, it was demonstrated theoretically that capillary transit-time heterogeneity potentially leads to non-uniform oxygen extraction in micro-domains. However, in spite of its importance, capillary transit-time distribution has been challenging to quantify comprehensively and efficiently at the microscopic level. Here, we introduce a method, called Dynamic Contrast Optical Coherence Tomography (DyC-OCT), based on dynamic cross-sectional OCT imaging of the kinetics of an intravascular tracer during its passage through the field-of-view. DyC-OCT is used to quantitatively measure the transit-time distribution in microvascular networks in cross-section at the single-capillary level. Transit-time metrics are derived from analysis of the temporal characteristics of the dynamic scattering signal, related to tracer concentration, using indicator-dilution theory. Since DyC-OCT does not require calibration of the optical focus, quantitative accuracy is achieved even deep in highly scattering brain tissue where the focal spot degrades. After direct validation of DyC-OCT against the dilution curves measured using a fluorescent plasma label in the surface pial vessels of a mouse brain, imaged through a thinned-skull, glass coverslip-reinforced cranial window, the laminar transit-time distribution was investigated in microvasculature across the entire depth of the mouse somatosensory cortex. Laminar trends were identified, with the earliest transit times in the middle cortical layers, and the lowest heterogeneity in cortical layer 4. The new DyC-OCT technique affords a novel perspective of microvascular networks, with the unique capability of performing simultaneous measurements of transit-time distributions across cortical laminae.

  18. Effect of variation in signal amplitude and transit time on reliability analysis of ultrasonic time of flight diffraction characterization of vertical and inclined cracks.

    PubMed

    Nath, S K

    2014-03-01

    The variation of amplitude and transit time of the diffracted signal from the crack-tip in complex geometry components and their resulting effect on the probability of detection (POD) and probability of sizing (POS) was studied. The diffracted signal amplitude has been evaluated from the standard expressions for diffraction coefficient, spatial attenuation and the transit time from the respective mathematical models for both vertical and inclined cracks. The same parameters namely the signal amplitude and the transit time have been measured through experiments conducted on simulated test specimens. It has been observed that the analytical and experimental results compare well with each other. Based on this result the trend and shape (width of the transition zone) of the POD/POS curves can be predicted.

  19. Validation of a Single-Time-Point Measurement of Total Abdominal Counts to Simplify Small Bowel and Colon Transit Analyses.

    PubMed

    Maurer, Alan H; Parupalli, Rahul; Orthey, Perry; Parkman, Henry P

    2016-12-01

    The Society of Nuclear Medicine and Molecular Imaging and European Association of Nuclear Medicine procedure guide on gastrointestinal transit currently indicates that the mean of total abdominal counts of 7 time points (0-360 min) is used to define the total abdominal counts for bowel transit studies. The purpose of this study was to investigate the variability of total abdominal counts during the initial 6 h of bowel transit and to determine whether a simplified, single-time-point measurement can be used.

  20. The scintigraphic determination of small intestinal transit time in patients with irritable bowel syndrome

    SciTech Connect

    Marano, A.R.; Caride, V.J.; Shah, R.V.; Prokop, E.K.; Troncale, F.J.; McCallum, R.W.

    1984-01-01

    Diffuse disturbance in gastrointestinal motility may be present in patients with irritable bowel syndrome (IBS). To further investigate small intestinal motility in IBS patients small intestinal transit time (SITT) was determined and related to the symptom status. 11 female patients with IBS (mean age 29 years) were divided into those whose predominate symptom was diarrhea (N=6), and those with only constipation (N=5). All subjects ingested an isosmotic solution of lactulose (10 gm in 150cc of water) labeled with 99m-Tc-DTPA (Sn). The patient was studied supine under a 25 inch gamma camera with data collected at 1 frame per minute for 180 minutes or until activity appeared in the ascending colon. Regions of interest were selected over the cecum and ascending colon. The time of first appearance of radioactivity in the region of the cecum was taken as the small intestinal transit time. SITT in the 5 normal females was 98.7 +- 13 min (mean +- SEM). SITT in the IBS patients with diarrhea, 67.3 +- 7 min was significantly faster (p< 0.08). SITT in the constipated IBS patients, 126 +- 12 min, was slower than normals and significantly different from diarrhea patients (p< 0.001). These studies show that IBS patients with diarrhea have significantly faster SITT than normals while constipated IBS patients have significantly slower SITT than the diarrhea subgroup. Further, this study emphasizes the need to study the various symptomatic subgroups of IBs patients independently and indicates a possible role for abnormal SITT in the pathogenesis of IBS.

  1. Transitions in Smoking Status Over Time in a Population-Based Panel Study of Smokers

    PubMed Central

    Victor, J. Charles; Diemert, Lori M.; Mecredy, Graham C.; Chaiton, Michael; Brown, K. Stephen; Cohen, Joanna E.; McDonald, Paul W.; Ferrence, Roberta; Garcia, John M.; Selby, Peter; Schwartz, Robert

    2013-01-01

    Introduction: Few studies have examined the transitions of smokers in the general population through multiple periods of daily, occasional smoking, or abstinence over time. Transitions from daily to occasional smoking are particularly of interest as these may be steps toward cessation. Methods: The Ontario Tobacco Survey panel study followed 4,355 baseline smokers, semiannually for up to 3 years. Probabilities of all possible changes in smoking status more than 6 months were estimated using 13,000 repeated measures observations generated from sets of 3 consecutive interviews (n = 9,932 daily smokers, 1,245 occasion smokers, and 1,823 abstinent for at least 30 days, at Time 1). Results: For initial daily smokers, an estimated 83% remained daily smokers more than 2 follow-ups. The majority of those who had been abstinent for 30 days at 1 interview, were also former smokers at the following interview. In contrast, occasional smoking status was unstable and future smoking status was dependent upon smoking history and subjective dependence. Among daily smokers who became occasional smokers 6 months later, an estimated 20% became a former smoker, at the next interview, but 50% returned to daily smoking. Daily, turned occasional smokers who rebounded back to daily smoking were more likely to describe themselves as addicted at Time 1. Continuing occasional smokers were somewhat less likely to intend to quit, or have tried, despite considering themselves less addicted. Conclusions: Reducing to occasional smoking can be a stepping stone toward cessation but entails a greater risk of return to daily smoking, compared with complete abstinence. PMID:23231826

  2. Pulse transit time variability analysis in an animal model of endotoxic shock.

    PubMed

    Tang, Collin H H; Chan, Gregory S H; Middleton, Paul M; Cave, Grant; Harvey, Martyn; Javed, Faizan; Savkin, Andrey V; Lovell, Nigel H

    2010-01-01

    The use of non-invasively measured pulse transit time (PTT) to monitor the cardiovascular systems in critically ill patients, like sepsis, can be of significant clinical value. In this study, the potential of PTT and its variability in cardiovascular system monitoring in a mechanically ventilated and anesthetized rabbit model of endotoxic shock was assessed. Eight adult New Zealand white rabbits, which were treated with endotoxin bolus infusion, were studied. Measurements of PTT, pre-ejection period (PEP), and vascular transit time (VTT) were obtained in pre- and post-intervention stages (before and 90 minutes after the administration of endotoxin). The decrease in mean PTT (p < 0.05) and PEP (p < 0.01) in the post-intervention stage reflected sympathetic activation, whilst the increase in respiratory variation in PTT (p < 0.01), PEP (p 〈 0.01), and VTT (p < 0.01) could be attributed to an enhancement of respiratory variation in stroke volume associated with hypovolemia in endotoxic shock. The relationship between beat-to-beat variability in PTT and all other cardiovascular time series were further investigated through linear regression analysis, which revealed that PTT was most strongly correlated with VTT (R(2) ≥ 0.84 with positive slope). Computation of coherence and phase shift in the ventilating frequency band (HF: 0.50 - 0.75 Hz) showed that the respiratory variation in PTT was synchronized with both PEP and VTT (coherence > 0.84 with phase shift less than one cardiac beat). These results highlighted the potential value of PTT and its respiratory variation in characterizing the pathophysioloigcal hemodynamic change in endotoxic shock.

  3. A phase transition model for the speed-accuracy trade-off in response time experiments.

    PubMed

    Dutilh, Gilles; Wagenmakers, Eric-Jan; Visser, Ingmar; van der Maas, Han L J

    2011-03-01

    Most models of response time (RT) in elementary cognitive tasks implicitly assume that the speed-accuracy trade-off is continuous: When payoffs or instructions gradually increase the level of speed stress, people are assumed to gradually sacrifice response accuracy in exchange for gradual increases in response speed. This trade-off presumably operates over the entire range from accurate but slow responding to fast but chance-level responding (i.e., guessing). In this article, we challenge the assumption of continuity and propose a phase transition model for RTs and accuracy. Analogous to the fast guess model (Ollman, 1966), our model postulates two modes of processing: a guess mode and a stimulus-controlled mode. From catastrophe theory, we derive two important predictions that allow us to test our model against the fast guess model and against the popular class of sequential sampling models. The first prediction--hysteresis in the transitions between guessing and stimulus-controlled behavior--was confirmed in an experiment that gradually changed the reward for speed versus accuracy. The second prediction--bimodal RT distributions--was confirmed in an experiment that required participants to respond in a way that is intermediate between guessing and accurate responding.

  4. Transition to parenthood and mental health in first-time parents.

    PubMed

    Parfitt, Ylva; Ayers, Susan

    2014-01-01

    This study aimed to examine the transition to parenthood and mental health in first-time parents in detail and explore any differences in this transition in the context of parental gender and postpartum mental health. Semistructured clinical interviews (Birmingham Interview for Maternal Mental Health) were carried out with 46 women and 40 men, 5 months after birth. Parents were assessed on pre- and postpartum anxiety, depression, and postpartum posttraumatic stress disorder (PTSD), and a range of adjustment and relationship variables. One fourth of the men and women reported anxiety in pregnancy, reducing to 21% of women and 8% of men after birth. Pregnancy and postpartum depression rates were roughly equal, with 11% of women and 8% of men reporting depression. Postpartum PTSD was experienced by 5% of parents. Postpartum mental health problems were significantly associated with postpartum sleep deprivation (odds ratio [OR] = 7.5), complications in labor (OR = 5.1), lack of postpartum partner support (OR = 8.0), feelings of parental unworthiness (OR = 8.3), and anger toward the infant (OR = 4.4). Few gender differences were found for these variables. This study thus highlights the importance of focusing interventions on strengthening the couple's relationship and avoiding postnatal sleep deprivation, and to address parents' feelings of parental unworthiness and feelings of anger toward their baby.

  5. Probing phase transitions in simvastatin with terahertz time-domain spectroscopy.

    PubMed

    Tan, Nicholas Y; Zeitler, J Axel

    2015-03-02

    Simvastatin is known to exist in at least three polymorphic forms. The nature of polymorphism in simvastatin is ambiguous, as the crystal structures of the polymorphs do not show any significant change in crystal packing or molecular conformation. We utilize terahertz time-domain spectroscopy to characterize each of the polymorphs and probe the phase transitions in the range of 0.2-3.0 THz and for temperatures ranging from 90 to 390 K. In form III, vibrational modes are observed at 1.0, 1.25, and 1.7 THz. For form I, we find that the spectrum is dominated by a baseline corresponding to libration-vibration motions coupled to the dielectric relaxations, which is characteristic of a disordered hydrogen bonding material but with additional broad vibrational modes at 0.8 and 1.4 THz. In addition, the baseline shifts with temperature similar to that observed in disordered materials. This background absorption exhibits pronounced changes around the phase transition temperatures at 232 and 272 K. The results are in agreement with molecular dynamics simulations, which indicate that changes in the rotational freedom of the ester tail in the molecule govern the polymorphism in simvastatin.

  6. Transit Timing Variation of Near-resonance Planetary Pairs: Confirmation of 12 Multiple-planet Systems

    NASA Astrophysics Data System (ADS)

    Xie, Ji-Wei

    2013-10-01

    We extract transit timing variation (TTV) signals for 12 pairs of transiting planet candidates that are near first-order mean motion resonances (MMR), using publicly available Kepler light curves (Q0-Q14). These pairs show significant sinusoidal TTVs with theoretically predicted periods, which demonstrate these planet candidates are orbiting and interacting in the same system. Although individual masses cannot be accurately extracted based only on TTVs because of the well-known degeneracy between mass and eccentricity, TTV phases and amplitudes can still place upper limits on the masses of the candidates, confirming their planetary nature. Furthermore, the mass ratios of these planet pairs can be relatively tightly constrained using these TTVs. The planetary pair in KOI 880 seems to have particularly high mass and density ratios, which might indicate very different internal compositions of these two planets. Some of these newly confirmed planets are also near MMR with other candidates in the system, forming unique resonance chains (e.g., KOI 500).

  7. TRANSIT TIMING VARIATION OF NEAR-RESONANCE PLANETARY PAIRS: CONFIRMATION OF 12 MULTIPLE-PLANET SYSTEMS

    SciTech Connect

    Xie, Ji-Wei E-mail: jwxie@astro.utoronto.ca

    2013-10-01

    We extract transit timing variation (TTV) signals for 12 pairs of transiting planet candidates that are near first-order mean motion resonances (MMR), using publicly available Kepler light curves (Q0-Q14). These pairs show significant sinusoidal TTVs with theoretically predicted periods, which demonstrate these planet candidates are orbiting and interacting in the same system. Although individual masses cannot be accurately extracted based only on TTVs because of the well-known degeneracy between mass and eccentricity, TTV phases and amplitudes can still place upper limits on the masses of the candidates, confirming their planetary nature. Furthermore, the mass ratios of these planet pairs can be relatively tightly constrained using these TTVs. The planetary pair in KOI 880 seems to have particularly high mass and density ratios, which might indicate very different internal compositions of these two planets. Some of these newly confirmed planets are also near MMR with other candidates in the system, forming unique resonance chains (e.g., KOI 500)

  8. A Continuous Time Random Walk Description of Monodisperse, Hard-Sphere Colloids below the Ordering Transition

    NASA Astrophysics Data System (ADS)

    Lechman, Jeremy; Pierce, Flint

    2012-02-01

    Diffusive transport is a ubiquitous process that is typically understood in terms of a classical random walk of non-interacting particles. Here we present the results for a model of hard-sphere colloids in a Newtonian incompressible solvent at various volume fractions below the ordering transition (˜50%). We numerically simulate the colloidal systems via Fast Lubrication Dynamics -- a Brownian Dynamics approach with corrected mean-field hydrodynamic interactions. Colloid-colloid interactions are also included so that we effectively solve a system of interacting Langevin equations. The results of the simulations are analyzed in terms of the diffusion coefficient as a function of time with the early and late time diffusion coefficients comparing well with experimental results. An interpretation of the full time dependent behavior of the diffusion coefficient and mean-squared displacement is given in terms of a continuous time random walk. Therefore, the deterministic, continuum diffusion equation which arises from the discrete, interacting random walkers is presented. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  9. Transit time of electrons and gas gain effects in P-10 and Ar+CO2

    NASA Astrophysics Data System (ADS)

    Orchard, Gloria M.; Waker, Anthony J.

    2014-11-01

    An Electron Mobility Spectrometer (EMS) has been designed to measure the transit time and electron attachment effects in proportional counter fill gases. The aim of the EMS is to observe how electron parameters including the drift velocity, pulse formation time, multiplication gain and electron attachment depend on the gas composition and operating parameters of the EMS. The operating parameters of interest for the EMS include the applied high voltage and gas pressure. Current research interests include the measurement of the time between the generation of the electron-ion pairs and arrival of the electrons at the wire anode in P-10 and Ar+CO2 gases. Additionally, the study of the multiplication properties of the detector as a function of pulse formation time in the two gases and as a function of applied electric field will be presented. The overall objective of this work is to investigate if the gas-gain of a proportional counter can be optimized by minimizing electron attachment with oxygen to improve the measurement of tritium in air.

  10. Noninvasive measurement of cerebrospinal fluid flow using an ultrasonic transit time flow sensor: a preliminary study.

    PubMed

    Pennell, Thomas; Yi, Juneyoung L; Kaufman, Bruce A; Krishnamurthy, Satish

    2016-03-01

    OBJECT Mechanical failure-which is the primary cause of CSF shunt malfunction-is not readily diagnosed, and the specific reasons for mechanical failure are not easily discerned. Prior attempts to measure CSF flow noninvasively have lacked the ability to either quantitatively or qualitatively obtain data. To address these needs, this preliminary study evaluates an ultrasonic transit time flow sensor in pediatric and adult patients with external ventricular drains (EVDs). One goal was to confirm the stated accuracy of the sensor in a clinical setting. A second goal was to observe the sensor's capability to record real-time continuous CSF flow. The final goal was to observe recordings during instances of flow blockage or lack of flow in order to determine the sensor's ability to identify these changes. METHODS A total of 5 pediatric and 11 adult patients who had received EVDs for the treatment of hydrocephalus were studied in a hospital setting. The primary EVD was connected to a secondary study EVD that contained a fluid-filled pressure transducer and an in-line transit time flow sensor. Comparisons were made between the weight of the drainage bag and the flow measured via the sensor in order to confirm its accuracy. Data from the pressure transducer and the flow sensor were recorded continuously at 100 Hz for a period of 24 hours by a data acquisition system, while the hourly CSF flow into the drip chamber was recorded manually. Changes in the patient's neurological status and their time points were noted. RESULTS The flow sensor demonstrated a proven accuracy of ± 15% or ± 2 ml/hr. The flow sensor allowed real-time continuous flow waveform data recordings. Dynamic analysis of CSF flow waveforms allowed the calculation of the pressure-volume index. Lastly, the sensor was able to diagnose a blocked catheter and distinguish between the blockage and lack of flow. CONCLUSIONS The Transonic flow sensor accurately measures CSF output within ± 15% or ± 2 ml

  11. The application of intraoperative transit time flow measurement to accurately assess anastomotic quality in sequential vein grafting

    PubMed Central

    Yu, Yang; Zhang, Fan; Gao, Ming-Xin; Li, Hai-Tao; Li, Jing-Xing; Song, Wei; Huang, Xin-Sheng; Gu, Cheng-Xiong

    2013-01-01

    OBJECTIVES Intraoperative transit time flow measurement (TTFM) is widely used to assess anastomotic quality in coronary artery bypass grafting (CABG). However, in sequential vein grafting, the flow characteristics collected by the conventional TTFM method are usually associated with total graft flow and might not accurately indicate the quality of every distal anastomosis in a sequential graft. The purpose of our study was to examine a new TTFM method that could assess the quality of each distal anastomosis in a sequential graft more reliably than the conventional TTFM approach. METHODS Two TTFM methods were tested in 84 patients who underwent sequential saphenous off-pump CABG in Beijing An Zhen Hospital between April and August 2012. In the conventional TTFM method, normal blood flow in the sequential graft was maintained during the measurement, and the flow probe was placed a few centimetres above the anastomosis to be evaluated. In the new method, blood flow in the sequential graft was temporarily reduced during the measurement by placing an atraumatic bulldog clamp at the graft a few centimetres distal to the anastomosis to be evaluated, while the position of the flow probe remained the same as in the conventional method. This new TTFM method was named the flow reduction TTFM. Graft flow parameters measured by both methods were compared. RESULTS Compared with the conventional TTFM, the flow reduction TTFM resulted in significantly lower mean graft blood flow (P < 0.05); in contrast, yielded significantly higher pulsatility index (P < 0.05). Diastolic filling was not significantly different between the two methods and was >50% in both cases. Interestingly, the flow reduction TTFM identified two defective middle distal anastomoses that the conventional TTFM failed to detect. Graft flows near the defective distal anastomoses were improved substantially after revision. CONCLUSIONS In this study, we found that temporary reduction of graft flow during TTFM seemed to

  12. Life Course Transitions and Housework: Marriage, Parenthood, and Time on Housework

    ERIC Educational Resources Information Center

    Baxter, Janeen; Hewitt, Belinda; Haynes, Michele

    2008-01-01

    We examine the effects of transitions in marital and parenthood status on 1,091 men's and women's housework hours using two waves of data from an Australian panel survey titled Negotiating the Life Course. We examine transitions between cohabitation and marriage, and from cohabitation or marriage to separation, as well as transitions to first and…

  13. Numerical approach to time-dependent quantum transport and dynamical Kondo transition.

    PubMed

    Zheng, Xiao; Jin, Jinshuang; Welack, Sven; Luo, Meng; Yan, YiJing

    2009-04-28

    An accurate and efficient numerical approach is developed for the transient electronic dynamics of open quantum systems at low temperatures. The calculations are based on a formally exact hierarchical equations of motion quantum dissipation theory [J. S. Jin et al., J. Chem. Phys. 128, 234703 (2008)]. We propose a hybrid scheme that combines the Matsubara expansion technique and a frequency dispersion treatment to account for reservoir correlation functions. The new scheme not just admits various forms of reservoir spectral functions but also greatly reduces the computational cost of the resulting hierarchical equations, especially in the low temperature regime. Dynamical Kondo effects are obtained and the cotunneling induced Kondo transitions are resolved in the transient current in response to time-dependent external voltages.

  14. Time-Resolved Emittance Characterization of an Induction Linac Beam using Optical Transition Radiation

    SciTech Connect

    Le Sage, G P

    2002-11-05

    An induction linac is used by Lawrence Livermore National Laboratory to perform radiographic testing at the Flash X-ray Radiography facility. Emittance characterization is important since x-ray spot size impacts the resolution of shadow-graphs. Due to the long pulse length, high current, and beam energy, emittance measurement using Optical Transition Radiation is an attractive alternative for reasons that will be described in the text. The utility of OTR-based emittance measurement has been well demonstrated for both RF and induction linacs. We describe the time-resolved emittance characterization of an induction linac electron beam. We have refined the optical collection system for the induction linac application, and have demonstrated a new technique for probing the divergence of a subset of the beam profile. The experimental apparatus, data reduction, and conclusions will be presented. Additionally, a new scheme for characterizing the correlation between beam divergence and spatial coordinates within the beam profile will be described.

  15. [ASA classification : Transition in the course of time and depiction in the literature].

    PubMed

    Irlbeck, T; Zwißler, B; Bauer, A

    2017-01-01

    The American Society of Anesthesiologists classification of physical status (ASA PS) is a widely used system for categorizing the preoperative status of patients. The ASA class is a good independent predictor of perioperative morbidity and mortality. The definitions of the ASA classes have been amended several times since 1941, resulting in inconsistent and confusing usage in the current literature. Conflicting definitions of ASA PS exist, particularly for classes III, IV and V. The high variability of individual classifications by different anesthesiologist, however, can be explained by the previous lack of examples for diagnoses. In 2014, the ASA has added a catalogue of examples for a simplified definition for classification of the ASA PS. This has so far received limited attention in German-speaking countries. This article describes the transition of the ASA classification over the past 75 years und summarizes the currently valid definitions.

  16. Towards Ubiquitous Blood Pressure Monitoring via Pulse Transit Time: Theory and Practice

    PubMed Central

    Hahn, Jin-Oh; Inan, Omer T.; Mestha, Lalit K.; Kim, Chang-Sei; Töreyin, Hakan; Kyal, Survi

    2015-01-01

    Ubiquitous blood pressure (BP) monitoring is needed to improve hypertension detection and control and is becoming feasible due to recent technological advances such as in wearable sensing. Pulse transit time (PTT) represents a well-known, potential approach for ubiquitous BP monitoring. The goal of this review is to facilitate the achievement of reliable, ubiquitous BP monitoring via PTT. We explain the conventional BP measurement methods and their limitations; present models to summarize the theory of the PTT-BP relationship; outline the approach while pinpointing the key challenges; overview the previous work towards putting the theory to practice; make suggestions for best practice and future research; and discuss realistic expectations for the approach. PMID:26057530

  17. Monte Carlo simulations of the short time dynamics of a first-order irreversible phase transition

    NASA Astrophysics Data System (ADS)

    Albano, Ezequiel V.

    2001-09-01

    The ZGB model (Ziff-Gulari-Barshad, Phys. Rev. Lett. 56 (1986) 2553) for the catalytic oxidation of carbon monoxide has a single parameter given by the normalized partial pressure of CO molecules ( PCO). For PCO⩾ PCOCoex≃0.52583 the surface of the catalyst becomes irreversibly covered by CO molecules and the system cannot escape from this state. However, for PCO slightly below PCOCoex the system reaches an active stationary state. So, just at PCOCoex a sharp first-order irreversible phase transition is observed. It is shown that a study of the short time dynamics of the ZGB model allows to obtain a fairly accurate evaluation of the upper spinodal point given by PCOUsp≃0.52675(5). This figure is in excellent agreement with extensive simulations performed using the constant coverage ensemble.

  18. Further time-resolved electron-beam characterizations with optical transition radiation

    SciTech Connect

    Lumpkin, A.H. . Advanced Photon Source Accelerator Systems Div.); Wilke, M.D. )

    1992-01-01

    Time-resolved characterizations of electron beams using optical transition radiation (OTR) as a prompt conversion mechanism have recently been extended on the Los Alamos Free-electron Laser (FEL) facility 40-MeV linac. Two key timescales for rf-linac driven FELs are the micropulse (10 ps) and the macropulse (5 [mu]s to 1 ms). In the past we have used gated, intensified cameras to select a single or few micropulses (25 to 400 ns gate width) out of the pulse train to evaluate submacropulse effects. Recently, we have obtained some of the first measurements of micropulse bunch length (7 to 10 ps) and submacropulse spatialposition and profile using OTR and a Hamamatsu streak camera. Additionally, micropulse elongation effects and head-to-tail transverse kick effects are reported as a function of charge.

  19. Time-resolved electron-beam characterizations with optical transition radiation

    SciTech Connect

    Lumpkin, A.H. ); Wilke, M.D. )

    1992-01-01

    Time-resolved characterizations of electron beams using optical transition radiation (OTR) as a prompt conversion mechanism have recently been extended on the Los Alamos Free-electron Laser (FEL) facility 40-MeV linac. Two key timescales for rf-linac driven FELs are the micropulse (10 ps) and the macropulse (5 {mu}s to 1 ms). In the past we have used gated, intensified cameras to select a single or few micropulses (25 to 400 ns gate width) out of the pulse train to evaluate submacropulse effects. Recently, we have obtained some of the first measurements of micropulse bunch length (7 to 10 ps) and submacropulse spatial position and profile using OTR and a Hamamatsu streak camera. Additionally, micropulse elongation effects and head-to-tail transverse kicks are reported as a function of charge.

  20. Time-resolved electron-beam characterizations with optical transition radiation

    SciTech Connect

    Lumpkin, A.H.; Wilke, M.D.

    1992-09-01

    Time-resolved characterizations of electron beams using optical transition radiation (OTR) as a prompt conversion mechanism have recently been extended on the Los Alamos Free-electron Laser (FEL) facility 40-MeV linac. Two key timescales for rf-linac driven FELs are the micropulse (10 ps) and the macropulse (5 {mu}s to 1 ms). In the past we have used gated, intensified cameras to select a single or few micropulses (25 to 400 ns gate width) out of the pulse train to evaluate submacropulse effects. Recently, we have obtained some of the first measurements of micropulse bunch length (7 to 10 ps) and submacropulse spatial position and profile using OTR and a Hamamatsu streak camera. Additionally, micropulse elongation effects and head-to-tail transverse kicks are reported as a function of charge.

  1. Further time-resolved electron-beam characterizations with optical transition radiation

    SciTech Connect

    Lumpkin, A.H.; Wilke, M.D.

    1992-12-31

    Time-resolved characterizations of electron beams using optical transition radiation (OTR) as a prompt conversion mechanism have recently been extended on the Los Alamos Free-electron Laser (FEL) facility 40-MeV linac. Two key timescales for rf-linac driven FELs are the micropulse (10 ps) and the macropulse (5 {mu}s to 1 ms). In the past we have used gated, intensified cameras to select a single or few micropulses (25 to 400 ns gate width) out of the pulse train to evaluate submacropulse effects. Recently, we have obtained some of the first measurements of micropulse bunch length (7 to 10 ps) and submacropulse spatialposition and profile using OTR and a Hamamatsu streak camera. Additionally, micropulse elongation effects and head-to-tail transverse kick effects are reported as a function of charge.

  2. Toward Ubiquitous Blood Pressure Monitoring via Pulse Transit Time: Theory and Practice.

    PubMed

    Mukkamala, Ramakrishna; Hahn, Jin-Oh; Inan, Omer T; Mestha, Lalit K; Kim, Chang-Sei; Töreyin, Hakan; Kyal, Survi

    2015-08-01

    Ubiquitous blood pressure (BP) monitoring is needed to improve hypertension detection and control and is becoming feasible due to recent technological advances such as in wearable sensing. Pulse transit time (PTT) represents a well-known potential approach for ubiquitous BP monitoring. The goal of this review is to facilitate the achievement of reliable ubiquitous BP monitoring via PTT. We explain the conventional BP measurement methods and their limitations; present models to summarize the theory of the PTT-BP relationship; outline the approach while pinpointing the key challenges; overview the previous work toward putting the theory to practice; make suggestions for best practice and future research; and discuss realistic expectations for the approach.

  3. Anomalous parity-time-symmetry transition away from an exceptional point

    NASA Astrophysics Data System (ADS)

    Ge, Li

    2016-07-01

    Parity-time (PT ) symmetric systems have two distinguished phases, e.g., one with real-energy eigenvalues and the other with complex-conjugate eigenvalues. To enter one phase from the other, it is believed that the system must pass through an exceptional point, which is a non-Hermitian degenerate point with coalesced eigenvalues and eigenvectors. Here we reveal an anomalous PT transition that takes place away from an exceptional point in a nonlinear system: as the nonlinearity increases, the original linear system evolves along two distinct PT -symmetric trajectories, each of which can have an exceptional point. However, the two trajectories collide and vanish away from these exceptional points, after which the system is left with a PT -broken phase. We first illustrate this phenomenon using a coupled-mode theory and then exemplify it using paraxial wave propagation in a transverse periodic potential.

  4. Intestinal permeability and orocaecal transit time in elderly patients with Parkinson's disease.

    PubMed Central

    Davies, K. N.; King, D.; Billington, D.; Barrett, J. A.

    1996-01-01

    The aetiology of weight loss in patients with Parkinson's disease is likely to be multifactorial. We studied 15 patients with Parkinson's disease and 15 age- and sex-matched controls and looked for evidence of malabsorption due to small bowel bacterial overgrowth or alteration of intestinal permeability. There was a marked increase in orocaecal transit time in the patients with Parkinson's disease, although lactulose hydrogen breath testing did not show evidence of small bowel bacterial contamination. Intestinal permeability measured by the differential sugar absorption test was also deranged. There was reduced absorption of mannitol in patients with Parkinson's disease while lactulose absorption was similar in both groups, suggesting decreased non-mediated uptake across the enterocyte brush border membrane in patients with Parkinson's disease. PMID:8731708

  5. TASTE. III. A homogeneous study of transit time variations in WASP-3b

    NASA Astrophysics Data System (ADS)

    Nascimbeni, V.; Cunial, A.; Murabito, S.; Sada, P. V.; Aparicio, A.; Piotto, G.; Bedin, L. R.; Milone, A. P.; Rosenberg, A.; Zurlo, A.; Borsato, L.; Damasso, M.; Granata, V.; Malavolta, L.

    2013-01-01

    The TASTE project is searching for low-mass planets with the transit timing variation (TTV) technique by gathering high-precision, short-cadence light curves for a selected sample of transiting exoplanets. It has been claimed that the "hot Jupiter" WASP-3b could be perturbed by a second planet. Presenting eleven new light curves (secured at the IAC80 and UDEM telescopes) and re-analyzing thirty-eight archival light curves in a homogeneous way, we show that new data do not confirm the previously claimed TTV signal. However, we bring evidence that measurements are not consistent with a constant orbital period, though no significant periodicity can be detected. Additional dynamical modeling and follow-up observations are planned to constrain the properties of the perturber or to put upper limits to it. We provide a refined ephemeris for WASP-3b and improved orbital/physical parameters. A contact eclipsing binary, serendipitously discovered among field stars, is reported here for the first time. This article is based on observations made with the IAC80 telescope operated on the island of Tenerife by the Instituto de Astrofísica de Canarias (IAC) in the Spanish Observatorio del Teide.Tables 1 and 3 and Appendix A are available in electronic form at http://www.aanda.orgPhotometric data are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/549/A30

  6. Relation of pathways and transit times of recharge water to nitrate concentrations using stable isotopes

    USGS Publications Warehouse

    Landon, M.K.; Delin, G.N.; Komor, S.C.; Regan, C.P.

    2000-01-01

    Oxygen and hydrogen stable isotope values of precipitation, irrigation water, soil water, and ground water were used with soil-moisture contents and water levels to estimate transit times and pathways of recharge water in the unsaturated zone of a sand and gravel aquifer. Nitrate-nitrogen (nitrate) concentrations in ground water were also measured to assess their relation to seasonal recharge. Stable isotope values indicated that recharge water usually had a transit time through the unsaturated zone of several weeks to months. However, wetting fronts usually moved through the unsaturated zone in hours to weeks. The much slower transit of isotopic signals than that of wetting fronts indicates that recharge was predominantly composed of older soil water that was displaced downward by more recent infiltrating water. Comparison of observed and simulated isotopic values from pure-piston flow and mixing-cell water and isotope mass balance models indicates that soil water isotopic values were usually highly mixed. Thus, movement of recharge water did not occur following a pure piston-flow displacement model but rather follows a hydrid model involving displacement of mixed older soil water with new infiltration water. An exception to this model occurred in a topographic depression, where movement of water along preferential flowpaths to the water table occurred within hours to days following spring thaw as result of depression-focused infiltration of snow melt. In an adjacent upland area, recharge of snow melt occurred one to two months later. Increases in nitrate concentrations at the water table during April-May 1993 and 1994 in a topographic lowland within a corn field were related to recharge of water that had infiltrated the previous summer and was displaced from the unsaturated zone by spring infiltration. Increases in nitrate concentrations also occurred during July-August 1994 in response to recharge of water that infiltrated during May-August 1994. These results

  7. Relation of pathways and transit times of recharge water to nitrate concentrations using stable isotopes

    SciTech Connect

    Landon, M.K.; Delin, G.N.; Komor, S.C.; Regan, C.P.

    2000-06-01

    Oxygen and hydrogen stable isotope values of precipitation, irrigation water, soil water, and ground water were used with soil-moisture contents and water levels to estimate transit times and pathways of recharge water in the unsaturated zone of a sand and gravel aquifer. Nitrate-nitrogen (nitrate) concentrations in ground water were also measured to assess their relation to seasonal recharge. Stable isotope values indicated that recharge water usually had a transit time through the unsaturated zone of several weeks to months. However, wetting fronts usually moved through the unsaturated zone in hours to weeks. The much slower transit of isotopic signals than that of wetting fronts indicates that recharge was predominantly composed of older soil water that was displaced downward by more recent infiltrating water. Comparison of observed and simulated isotopic values from pure-piston flow and mixing-cell water and isotope mass balance models indicates that soil water isotopic values were usually highly mixed. Thus, movement of recharge water did not occur following a pure piston-flow displacement model but rather follows a hybrid model involving displacement of mixed older soil water with new infiltration water. An exception to this model occurred in a topographic depression, where movement of water along preferential flowpaths to the water table occurred within hours to days following spring thaw as result of depression-focused infiltration of snow melt. In an adjacent upland area, recharge of snow melt occurred one to two months later. Increases in nitrate concentrations at the water table during April-May 1993 and 1994 in a topographic low-land within a corn field were related to recharge of water that had infiltrated the previous summer and was displaced from the unsaturated zone by spring infiltration. Increases in nitrate concentrations also occurred during July-August 1994 in response to recharge of water that infiltrated during May-August 1994. These results

  8. Spike-timing-dependent plasticity enhanced synchronization transitions induced by autapses in adaptive Newman-Watts neuronal networks.

    PubMed

    Gong, Yubing; Wang, Baoying; Xie, Huijuan

    2016-12-01

    In this paper, we numerically study the effect of spike-timing-dependent plasticity (STDP) on synchronization transitions induced by autaptic activity in adaptive Newman-Watts Hodgkin-Huxley neuron networks. It is found that synchronization transitions induced by autaptic delay vary with the adjusting rate Ap of STDP and become strongest at a certain Ap value, and the Ap value increases when network randomness or network size increases. It is also found that the synchronization transitions induced by autaptic delay become strongest at a certain network randomness and network size, and the values increase and related synchronization transitions are enhanced when Ap increases. These results show that there is optimal STDP that can enhance the synchronization transitions induced by autaptic delay in the adaptive neuronal networks. These findings provide a new insight into the roles of STDP and autapses for the information transmission in neural systems.

  9. Transit and residence times in the Adriatic Sea surface as derived from drifter data and Lagrangian numerical simulations

    NASA Astrophysics Data System (ADS)

    Poulain, P.-M.; Hariri, S.

    2013-08-01

    Statistics of transit and residence times in the Adriatic Sea surface, a semi-enclosed basin of the Mediterranean, are estimated from drifter data and Lagrangian numerical simulations. The results obtained from the drifters are generally underestimated given their short operating lifetimes (half life of ∼40 days) compared to the transit and residence times. This bias can be removed by considering a large amount of numerical particles whose trajectories are integrated over a long time (750 days) with a statistical advection-dispersion model of the Adriatic surface circulation. Numerical particles indicate that the maximum transit time to exit the basin is about 216-260 days for particles released near the northern tip of the Adriatic, and that a particle entering on the eastern Otranto Channel will typically exit on the other side of the channel after 170-185 days. A duration of 150-168 days is estimated as the residence time in the Adriatic Basin.

  10. Transit and residence times in the surface Adriatic Sea as derived from drifter data and Lagrangian numerical simulations

    NASA Astrophysics Data System (ADS)

    Poulain, P.-M.; Hariri, S.

    2013-01-01

    Statistics of transit and residence times in the surface Adriatic Sea, a semi-enclosed basin of the Mediterranean, are estimated from drifter data and Lagrangian numerical simulations. The results obtained from the drifters are generally underestimated given their short operating lifetimes (half life of ~ 40 days) compared to the transit and residence times. This bias can be removed by considering a large amount of numerical particles whose trajectories are integrated over a long time (750 days) with a statistical advection-diffusion model of the Adriatic surface circulation. Numerical particles indicate that the maximum transit time to exit the basin is about 216-260 days for objects released near the northern tip of the Adriatic, and that a particle entering on the eastern Otranto Channel will typically exit on the other side of the Channel after 170-185 days. A value of 150-168 days is estimated for the residence time in the Adriatic basin.

  11. Analysis of small intestinal transit and colon arrival times of non-disintegrating tablets administered in the fasted state.

    PubMed

    Pišlar, Mitja; Brelih, Hana; Mrhar, Aleš; Bogataj, Marija

    2015-07-30

    In this study individual data on tablet gastrointestinal transit times (i.e. gastric emptying, small intestinal transit, ileocecal junction residence, and colon arrival times) were obtained from literature in order to present and analyze their distributions and relationships. The influence of the time of food intake after tablet administration in fasted state on gastrointestinal transit times was additionally evaluated. There were 114 measurements from subjects who received the first meal at 4h after tablet administration. Approximately 32% of the tablets arrived into the colon before the meal intake at 4h. An evident increase in the frequency of colon arrival of tablets within 40min after the meal intake at 4h post-dose was observed, where approximately 39% of all tablets arrived into the colon. This is in accordance with findings described in literature where a meal ingested several hours post-dose accelerates tablet transit through the terminal ileum and shortens the transit through the small intestine. The median (min, max) of gastric emptying, small intestinal transit, and colon arrival times in the group where the first meal intake was at 4h post-dose is 35 (0,192), 215 (60,544), and 254 (117,604) minutes, respectively. The dependence of colon arrival times on gastric emptying times was described by the nonparametric regression curve, and compared with the presumed interval of colon arrival times, calculated by summation of observed gastric emptying times and frequently cited small intestinal transit time interval, i.e. 3-4h. For shorter gastric emptying times the trend of colon arrival times was within the presumed interval. At short gastric emptying times many observation points are also within the presumed interval since this interval coincides with short period after meal intake at 4h post-dose. Additionally, in numerous occasions relatively long ileocecal junction residence times were obtained, which may be important information from the point of view of

  12. Different mRNAs have different nuclear transit times in Dictyostelium discoideum aggregates.

    PubMed Central

    Mangiarotti, G; Zuker, C; Chisholm, R L; Lodish, H F

    1983-01-01

    Nuclear processing of mRNA precursors in differentiating multicellular Dictyostelium discoideum aggregates is markedly slower than in growing amoebae. Thus, we have been able to determine the time of nuclear processing of individual mRNA species in postaggregating cells by following the incorporation of 32PO4 into nuclear and cytoplasmic RNA complementary to cloned cDNAs. Precursors of mRNAs synthesized during both growth and differentiation remain in the nucleus for about 25 to 60 min. By contrast, typical mRNAs which are synthesized only by postaggregative cells have nuclear processing times between 50 and 100 min. Depending on the particular mRNA, between 20 and 60% of nuclear transcripts are converted into cytoplasmic mRNA. A third class of mRNAs are transcribed from a set of repetitive DNA segments and are expressed predominantly during differentiation. Nuclear precursors of these mRNAs are extensively degraded within the nucleus or very rapidly after transport to the cytoplasm. Those sequences that are stable in the cytoplasm exit from the nucleus only after a lag of over 2 h. Thus, mRNAs encoded by different genes that are subject to different types of developmental controls display different times of transit to the cytoplasm and different efficiencies of nuclear processing. Differential nuclear processing may contribute to the regulation of the level of individual cytoplasmic mRNAs. Images PMID:6621537

  13. Residence and transit times of MinD in E. coli bacterial cells

    NASA Astrophysics Data System (ADS)

    Giuliani, Maximiliano; Kelly, Corey; Dutcher, John

    2012-02-01

    A key step in the life of a bacterial cell is its division into two daughters cells of equal size. This process is carefully controlled and regulated so that an equal partitioning of the main cell components is obtained, which is critical for the viability of the daughter cells. In E. coli this regulation is accomplished in part by the Min protein system, that determines the localization of the division machinery. Of particular interest is the MinD protein that exhibits an oscillation between the poles in the rod shaped bacteria. The oscillation relies on a ATP mediated dimerization of the MinD protein that allows its insertion into the inner membrane at one of the poles of the cell, followed by an interaction with the MinE protein, which releases the MinD from the membrane, allowing it to travel to the other pole of the cell where the cycle is repeated. We have studied the spatio-temporal characteristics of the MinD oscillation from which we extract the average times for the two main processes that determine the oscillation period: the residence time in the membrane and the transit time to travel the length of the cell. Additionally, we explore how these two timescales are affected by stresses on the bacterial cells due to unfavorable physiological conditions.

  14. Motion artefact reduction of the photoplethysmographic signal in pulse transit time measurement.

    PubMed

    Foo, J Y A; Wilson, S J; Williams, G R; Harris, M; Cooper, D M

    2004-12-01

    Motion artefact is a common occurrence that contaminates photoplethysmographic (PPG) measurements. To extract timing information from signals during artefact is challenging. PPG signal is very sensitive to artefacts and can be used in applications like, pulse transit time (PTT) as part of the polysomnographic studies. A correlation cancellation or signal processing approach is implemented with the adaptive cancelling filter concept and a triaxial accelerometry. PPG signals obtained from a Masimo (Reference) pulse oximeter is used as reference to compare with the reconstructed PPG signals. Different hands are used for each PPG source, one stationary while the other involves typical movements during sleep. A second Masimo pulse oximeter is used to register intensity of timing errors on commercial PPG signals. 108 PTT measurements are recorded in three different movements with PTT estimates from unprocessed PPG signals showing 35.51+/-27.42%, Masimo 50.02+/-29.40% and reconstructed 4.32+/-3.59% difference against those from the Reference PPG. The triaxial accelerometry can be used to detect the presence of artefact on PPG signals. This is useful in PTT measurements when signal contaminated with artefacts are required for further analysis, especially after and during arousals in sleep. The suggested filtering model can then reconstruct these corrupted PPG signals.

  15. Effect of the unsaturated zone thickness on the distribution of water mean transit times in a porous aquifer

    NASA Astrophysics Data System (ADS)

    Schwientek, M.; Maloszewski, P.; Einsiedl, F.

    2009-07-01

    SummaryThe mean transit time of groundwater is commonly expected to increase gradually with increasing depth below water table. The present study provides evidence that the theoretical distribution of transit times may be significantly altered depending on the thickness of the unsaturated zone. An unconfined porous groundwater system formed by Tertiary sediments (Test Field Scheyern close to Munich in southern Germany) is overlain by an unsaturated zone with variable thickness between 4 and 60 m. Between 1992 and 2007 the groundwater system has been repeatedly sampled for tritium contents at different depths using two high-resolved wells. Modelled tritium concentrations by using a lumped parameter approach yielded depth profiles of mean transit times of tracer. In one well the profile was characterized by two local transit time maxima, each of approximately 100 years. A moving particle approach (MPA) developed in this study was used on the streamlines between the recharge zones linked to different sampling depths in the well. This suggested that the observed transit time in the profile was mainly governed by variable travel distances of the tracer through the unsaturated zone at the points of recharge. This finding was confirmed at a second multi-level well of the test site. The lumped parameter modelling of chlorofluorocarbon data yielded lower transit times as compared to those obtained from tritium data. This effect was explained by the different behaviour of tritium and chlorofluorocarbons in the unsaturated zone. The study clearly shows that the impact of a variable thickness of the unsaturated zone may overweigh the effect of local heterogeneities. Such transit time distributions of water in porous aquifers as observed in the present study can only be achieved with the help of environmental tracer data.

  16. Two Eyes on the Prize: Revealing the Complete Architectures of Planetary Systems through Transit Timing with Kepler and Spitzer

    NASA Astrophysics Data System (ADS)

    Fabrycky, Daniel; Stevenson, Kevin; Ballard, Sarah; Agol, Eric; Holman, Matthew; Bean, Jacob; Ragozzine, Darin

    2013-11-01

    The transit timing variation (TTV) technique has recently become a crucial method for determining the complete architectures (i.e., planet masses, orbital eccentricities, inclinations, and resonant properties) of extrasolar planetary systems. This technique has blossomed because of the Kepler mission's discovery of systems with multiple transiting planets and individual planets exhibiting very large TTVs. All of Kepler's results in this area so far have been for relatively short-period planets, but Kepler has also discovered dynamically-interacting systems with planets that have longer periods, similar to those of the Solar System. However, the ill-timed failure of the Kepler telescope has left us with an incomplete picture of these systems due to a lack of the required time baseline. Fortunately, Spitzer is positioned to leverage the unique potential that these planets offer, by extending the time baseline of transit observations. We propose to observe transits of seven Kepler-discovered planets in four particularly compelling systems to precisely determine their transit times. Combining the legacy Kepler transit times with the new times from Spitzer will give us the baseline that is needed to confirm and characterize these dynamically interacting systems of planets. This information will allow us to assess the complete architectures of these systems -- we will discover planets that do not transit and determine the masses and orbital properties of all the planets. For 6 planets in these systems, the TTVs will allow us to measure the planetary masses to better than 20%, which will approximately double the number of cool giant planets with known masses and radii. Several of the systems have mean-motion resonances between the planets, and characterizing these interactions yields information on the formation and migration of giant planets. The required precision and duration of these observations render Spitzer the only remaining instrument capable of such study.

  17. Simulation of contrast agent transport in arteries with multilayer arterial wall: impact of arterial transmural transport on the bolus delay and dispersion.

    PubMed

    Xu, Min; Liu, Xiao; Li, Ang; Fan, Yubo; Sun, Anqiang; Deng, Xiaoyan; Li, Deyu

    2014-01-01

    One assumption of DSC-MRI is that the injected contrast agent is kept totally intravascular and the arterial wall is impermeable to contrast agent. The assumption is unreal for such small contrast agent as Gd-DTPA can leak into the arterial wall. To investigate whether the unreal assumption is valid for the estimation of the delay and dispersion of the contrast agent bolus, we simulated flow and Gd-DTPA transport in a model with multilayer arterial wall and analyzed the bolus delay and dispersion qualified by mean vascular transit time (MVTT) and the variance of the vascular transport function. Factors that may affect Gd-DTPA transport hence the delay and dispersion were further investigated, such as integrity of endothelium and disturbed flow. The results revealed that arterial transmural transport would slightly affect MVTT and moderately increase the variance. In addition, although the integrity of endothelium can significantly affect the accumulation of contrast agent in the arterial wall, it had small effects on the bolus delay and dispersion. However, the disturbed flow would significantly increase both MVTT and the variance. In conclusion, arterial transmural transport may have a small effect on the bolus delay and dispersion when compared to the flow pattern in the artery.

  18. Simulation of Contrast Agent Transport in Arteries with Multilayer Arterial Wall: Impact of Arterial Transmural Transport on the Bolus Delay and Dispersion

    PubMed Central

    Xu, Min; Liu, Xiao; Li, Ang; Sun, Anqiang; Li, Deyu

    2014-01-01

    One assumption of DSC-MRI is that the injected contrast agent is kept totally intravascular and the arterial wall is impermeable to contrast agent. The assumption is unreal for such small contrast agent as Gd-DTPA can leak into the arterial wall. To investigate whether the unreal assumption is valid for the estimation of the delay and dispersion of the contrast agent bolus, we simulated flow and Gd-DTPA transport in a model with multilayer arterial wall and analyzed the bolus delay and dispersion qualified by mean vascular transit time (MVTT) and the variance of the vascular transport function. Factors that may affect Gd-DTPA transport hence the delay and dispersion were further investigated, such as integrity of endothelium and disturbed flow. The results revealed that arterial transmural transport would slightly affect MVTT and moderately increase the variance. In addition, although the integrity of endothelium can significantly affect the accumulation of contrast agent in the arterial wall, it had small effects on the bolus delay and dispersion. However, the disturbed flow would significantly increase both MVTT and the variance. In conclusion, arterial transmural transport may have a small effect on the bolus delay and dispersion when compared to the flow pattern in the artery. PMID:25692178

  19. Time course of the diameter of the major cerebral arteries after subarachnoid hemorrhage using corrosion cast technique.

    PubMed

    Ono, Shigeki; Date, Isao; Onoda, Keisuke; Ohmoto, Takashi

    2003-06-01

    In this report, we examined whether corrosion cast method is also applicable for the measurement and estimation of the rat major arteries in which subarachnoid hemorrhage (SAH) is produced. Additionally, we have examined the diameters of the rat major arteries following SAH. A total of 0.3 ml autologous blood was injected into the cisterna magna of male Sprague-Dawley rats for the SAH model. A perfusion of a semi-polymerized casting medium was performed, 10 min, 30 min, 1 h, 4 h, 8 h, 1 day, 2 days, 3 days, 5 days, and 7 days after SAH. The brains were corroded in a 10% NaOH solution. The BA and the other major arteries were then measured using scanning electron microscopy (SEM). Macroscopic observation and hematoxylin-eosin (HE) staining were also performed. Using the corrosion cast method, the biphasic contractile response was observed in the BA; 8.3% and 11.6% contractions were observed 30 min and 1 day after SAH, respectively. In addition, there was almost no smooth muscle or adventitial thickening in the chronic stage. In contrast, the dilative response was observed in the internal carotid artery and middle cerebral artery 10 min after SAH. Macroscopic findings and HE staining revealed that the extensive basal subarachnoid hematoma had almost disappeared by day 2. These results indicate that in this model, the minimal spasm, which occurs one day after SAH, can be explained by the small capacity of the rat subarachnoid space and the rapid cerebrospinal fluid washout around major vessels at the cerebral base. Moreover, the present data also show the compensatory dilatation in the ICA and MCA in the early stage after SAH.

  20. Arterial waveform analysis.

    PubMed

    Esper, Stephen A; Pinsky, Michael R

    2014-12-01

    The bedside measurement of continuous arterial pressure values from waveform analysis has been routinely available via indwelling arterial catheterization for >50 years. Invasive blood pressure monitoring has been utilized in critically ill patients, in both the operating room and critical care units, to facilitate rapid diagnoses of cardiovascular insufficiency and monitor response to treatments aimed at correcting abnormalities before the consequences of either hypo- or hypertension are seen. Minimally invasive techniques to estimate cardiac output (CO) have gained increased appeal. This has led to the increased interest in arterial waveform analysis to provide this important information, as it is measured continuously in many operating rooms and intensive care units. Arterial waveform analysis also allows for the calculation of many so-called derived parameters intrinsically created by this pulse pressure profile. These include estimates of left ventricular stroke volume (SV), CO, vascular resistance, and during positive-pressure breathing, SV variation, and pulse pressure variation. This article focuses on the principles of arterial waveform analysis and their determinants, components of the arterial system, and arterial pulse contour. It will also address the advantage of measuring real-time CO by the arterial waveform and the benefits to measuring SV variation. Arterial waveform analysis has gained a large interest in the overall assessment and management of the critically ill and those at a risk of hemodynamic deterioration.

  1. Arterial Catheterization

    MedlinePlus

    ... The arterial catheter allows accurate, second-to-second measurement of the blood pressure; repeated meas- urement is ... pressure must be lowered gradually in steps, and measurements with an arterial catheter help guide the treatment. ■ ...

  2. Effects of Cereal, Fruit and Vegetable Fibers on Human Fecal Weight and Transit Time: A Comprehensive Review of Intervention Trials.

    PubMed

    de Vries, Jan; Birkett, Anne; Hulshof, Toine; Verbeke, Kristin; Gibes, Kernon

    2016-03-02

    Cereal fibers are known to increase fecal weight and speed transit time, but far less data are available on the effects of fruits and vegetable fibers on regularity. This study provides a comprehensive review of the impact of these three fiber sources on regularity in healthy humans. We identified English-language intervention studies on dietary fibers and regularity and performed weighted linear regression analyses for fecal weight and transit time. Cereal and vegetable fiber groups had comparable effects on fecal weight; both contributed to it more than fruit fibers. Less fermentable fibers increased fecal weight to a greater degree than more fermentable fibers. Dietary fiber did not change transit time in those with an initial time of <48 h. In those with an initial transit time ≥48 h, transit time was reduced by approximately 30 min per gram of cereal, fruit or vegetable fibers, regardless of fermentability. Cereal fibers have been studied more than any other kind in relation to regularity. This is the first comprehensive review comparing the effects of the three major food sources of fiber on bowel function and regularity since 1993.

  3. Comparison of active-set method deconvolution and matched-filtering for derivation of an ultrasound transit time spectrum.

    PubMed

    Wille, M-L; Zapf, M; Ruiter, N V; Gemmeke, H; Langton, C M

    2015-06-21

    The quality of ultrasound computed tomography imaging is primarily determined by the accuracy of ultrasound transit time measurement. A major problem in analysis is the overlap of signals making it difficult to detect the correct transit time. The current standard is to apply a matched-filtering approach to the input and output signals. This study compares the matched-filtering technique with active set deconvolution to derive a transit time spectrum from a coded excitation chirp signal and the measured output signal. The ultrasound wave travels in a direct and a reflected path to the receiver, resulting in an overlap in the recorded output signal. The matched-filtering and deconvolution techniques were applied to determine the transit times associated with the two signal paths. Both techniques were able to detect the two different transit times; while matched-filtering has a better accuracy (0.13 μs versus 0.18 μs standard deviations), deconvolution has a 3.5 times improved side-lobe to main-lobe ratio. A higher side-lobe suppression is important to further improve image fidelity. These results suggest that a future combination of both techniques would provide improved signal detection and hence improved image fidelity.

  4. Effects of Cereal, Fruit and Vegetable Fibers on Human Fecal Weight and Transit Time: A Comprehensive Review of Intervention Trials

    PubMed Central

    de Vries, Jan; Birkett, Anne; Hulshof, Toine; Verbeke, Kristin; Gibes, Kernon

    2016-01-01

    Cereal fibers are known to increase fecal weight and speed transit time, but far less data are available on the effects of fruits and vegetable fibers on regularity. This study provides a comprehensive review of the impact of these three fiber sources on regularity in healthy humans. We identified English-language intervention studies on dietary fibers and regularity and performed weighted linear regression analyses for fecal weight and transit time. Cereal and vegetable fiber groups had comparable effects on fecal weight; both contributed to it more than fruit fibers. Less fermentable fibers increased fecal weight to a greater degree than more fermentable fibers. Dietary fiber did not change transit time in those with an initial time of <48 h. In those with an initial transit time ≥48 h, transit time was reduced by approximately 30 min per gram of cereal, fruit or vegetable fibers, regardless of fermentability. Cereal fibers have been studied more than any other kind in relation to regularity. This is the first comprehensive review comparing the effects of the three major food sources of fiber on bowel function and regularity since 1993. PMID:26950143

  5. Measuring spatial effects in time to event data: a case study using months from angiography to coronary artery bypass graft (CABG).

    PubMed

    Crook, Angela M; Knorr-Held, Leonhard; Hemingway, Harry

    2003-09-30

    The application of Bayesian hierarchical models to measure spatial effects in time to event data has not been widely reported. This case study aims to estimate the effect of area of residence on waiting times to coronary artery bypass graft (CABG) and to assess the role of important individual specific covariates (age, sex and disease severity). The data involved all patients with definite coronary artery disease who were referred to one cardiothoracic unit from five contiguous health authorities covering 488 electoral wards (areas). Time to event was the waiting time in months from angiography (diagnosis) to CABG (event). A number of discrete time survival models were fitted to the data. A discrete baseline hazard was estimated by fitting waiting time non-parametrically into the models. Ward was fitted as a spatial effect using a Gaussian Markov random field prior. Individual specific covariates considered were age, sex and number of diseased vessels. The recently proposed DIC criteria was used for comparing models. Results showed a marked spatial effect on time to bypass surgery after including age, sex and disease severity in the model. Notably this spatial effect was not apparent when these covariates were not included in the model. The observed small area spatial variation in time to CABG warrants further investigation.

  6. Enhancing pairwise state-transition weights: A new weighting scheme in simulated tempering that can minimize transition time between a pair of conformational states

    NASA Astrophysics Data System (ADS)

    Qiao, Qin; Zhang, Hou-Dao; Huang, Xuhui

    2016-04-01

    Simulated tempering (ST) is a widely used enhancing sampling method for Molecular Dynamics simulations. As one expanded ensemble method, ST is a combination of canonical ensembles at different temperatures and the acceptance probability of cross-temperature transitions is determined by both the temperature difference and the weights of each temperature. One popular way to obtain the weights is to adopt the free energy of each canonical ensemble, which achieves uniform sampling among temperature space. However, this uniform distribution in temperature space may not be optimal since high temperatures do not always speed up the conformational transitions of interest, as anti-Arrhenius kinetics are prevalent in protein and RNA folding. Here, we propose a new method: Enhancing Pairwise State-transition Weights (EPSW), to obtain the optimal weights by minimizing the round-trip time for transitions among different metastable states at the temperature of interest in ST. The novelty of the EPSW algorithm lies in explicitly considering the kinetics of conformation transitions when optimizing the weights of different temperatures. We further demonstrate the power of EPSW in three different systems: a simple two-temperature model, a two-dimensional model for protein folding with anti-Arrhenius kinetics, and the alanine dipeptide. The results from these three systems showed that the new algorithm can substantially accelerate the transitions between conformational states of interest in the ST expanded ensemble and further facilitate the convergence of thermodynamics compared to the widely used free energy weights. We anticipate that this algorithm is particularly useful for studying functional conformational changes of biological systems where the initial and final states are often known from structural biology experiments.

  7. Aggregation in environmental systems: seasonal tracer cycles quantify young water fractions, but not mean transit times, in spatially heterogeneous catchments

    NASA Astrophysics Data System (ADS)

    Kirchner, J. W.

    2015-03-01

    Environmental heterogeneity is ubiquitous, but environmental systems are often analyzed as if they were homogeneous instead, resulting in aggregation errors that are rarely explored and almost never quantified. Here I use simple benchmark tests to explore this general problem in one specific context: the use of seasonal cycles in chemical or isotopic tracers (such as Cl-, δ18O, or δ2H) to estimate timescales of storage in catchments. Timescales of catchment storage are typically quantified by the mean transit time, meaning the average time that elapses between parcels of water entering as precipitation and leaving again as streamflow. Longer mean transit times imply greater damping of seasonal tracer cycles. Thus, the amplitudes of tracer cycles in precipitation and streamflow are commonly used to calculate catchment mean transit times. Here I show that these calculations will typically be wrong by several hundred percent, when applied to catchments with realistic degrees of spatial heterogeneity. This aggregation bias arises from the strong nonlinearity in the relationship between tracer cycle amplitude and mean travel time. I propose an alternative storage metric, the young water fraction in streamflow, defined as the fraction of runoff with transit times of less than roughly 0.2 years. I show that this young water fraction (not to be confused with event-based "new water" in hydrograph separations) is accurately predicted by seasonal tracer cycles within a precision of a few percent, across the entire range of mean transit times from almost zero to almost infinity. Importantly, this relationship is also virtually free from aggregation error. That is, seasonal tracer cycles also accurately predict the young water fraction in runoff from highly heterogeneous mixtures of subcatchments with strongly contrasting transit time distributions. Thus, although tracer cycle amplitudes yield biased and unreliable estimates of catchment mean travel times in heterogeneous

  8. Transition into and out of daylight saving time and spontaneous delivery: a population-based study

    PubMed Central

    László, Krisztina D; Cnattingius, Sven; Janszky, Imre

    2016-01-01

    Objective To investigate whether the circadian rhythm disruption following the transition into and out of daylight saving time (DST) is associated with an increased risk of spontaneous delivery. Design We compared the number of spontaneous deliveries in the Swedish Medical Birth Register during the week after the change to and the week after the change from DST (exposure periods) with the average number of spontaneous deliveries in the control period, defined as the week before and the week after each exposure period. Setting Sweden, 1993–2006. Primary and secondary outcome measures The primary outcomes were the weekly and the daily number of spontaneous deliveries in the exposure and the control periods. In secondary analyses we also compared the mean length of pregnancy of the women with spontaneous deliveries in the exposure and control periods. Results The number of deliveries during the week after the transition into or out of DST was similar to that in the comparison period (18 519 observed vs 18 434 expected in case of the spring shift and 19 073 observed vs 19 122 expected in case of the autumn shift); the corresponding incidence ratio and 95% CIs were 1.005 (0.990 to 1.019) and 0.997 (0.983 to 1.012), respectively. There were no differences in the length of gestation of the deliveries in the exposure and the control periods. Conclusions Our results do not support the hypothesis that a minor circadian rhythm disruption is associated with an increased short-term risk of spontaneous delivery. PMID:27630067

  9. Enzymatically Modified Starch Favorably Modulated Intestinal Transit Time and Hindgut Fermentation in Growing Pigs

    PubMed Central

    Newman, M. A.; Zebeli, Q.; Velde, K.; Grüll, D.; Molnar, T.; Kandler, W.; Metzler-Zebeli, B. U.

    2016-01-01

    Aside from being used as stabilizing agents in many processed foods, chemically modified starches may act as functional dietary ingredients. Therefore, development of chemically modified starches that are less digestible in the upper intestinal segments and promote fermentation in the hindgut receives considerable attention. This study aimed to investigate the impact of an enzymatically modified starch (EMS) on nutrient flow, passage rate, and bacterial activity at ileal and post-ileal level. Eight ileal-cannulated growing pigs were fed 2 diets containing 72% purified starch (EMS or waxy cornstarch as control) in a cross-over design for 10 d, followed by a 4-d collection of feces and 2-d collection of ileal digesta. On d 17, solid and liquid phase markers were added to the diet to determine ileal digesta flow for 8 h after feeding. Reduced small intestinal digestion after the consumption of the EMS diet was indicated by a 10%-increase in ileal flow and fecal excretion of dry matter and energy compared to the control diet (P<0.05). Moreover, EMS feeding reduced ileal transit time of both liquid and solid fractions compared to the control diet (P<0.05). The greater substrate flow to the large intestine with the EMS diet increased the concentrations of total and individual short-chain fatty acids (SCFA) in feces (P<0.05). Total bacterial 16S rRNA gene abundance was not affected by diet, whereas the relative abundance of the Lactobacillus group decreased (P<0.01) by 50% and of Enterobacteriaceae tended (P<0.1) to increase by 20% in ileal digesta with the EMS diet compared to the control diet. In conclusion, EMS appears to resemble a slowly digestible starch by reducing intestinal transit and increasing SCFA in the distal large intestine. PMID:27936165

  10. Changes in antimicrobial resistance in fecal bacteria associated with pig transit and holding times at slaughter plants.

    PubMed Central

    Molitoris, E; Fagerberg, D J; Quarles, C L; Krichevsky, M I

    1987-01-01

    Fecal coliforms, fecal streptococci, and antimicrobial resistance (AMR) associated with various pig transit and holding times were investigated at slaughter plants. Changes in the relative abundance of two biotypes of Streptococcus faecium were associated with transit and holding of pigs, although approximately 20% of the isolates were unidentified. The greatest variety of coliforms was isolated from porcine feces after short transit (2 h) or holding (3 h) times and was qualitatively similar to those from pigs on farms. Isolates from pigs with longer average transit or holding times were almost all Escherichia coli (four biotypes). Streptococcal resistance to most antimicrobial agents was significantly greater (P less than 0.05) in isolates from live pigs at slaughter plants than in those from pigs at farms and was apparent after a short transit time (2 h). Streptococci from pigs held an average of 15 h were less resistant to most antimicrobial agents than those from pigs held 3 or 43 h. When compared with short transit times, moderate transit times (6 h) were associated with significantly decreased (P less than 0.05) coliform resistance and decreased resistance transfer but a greater diversity of AMR patterns. Holding pigs overnight (14 h) was associated with lowered coliform resistance to several antimicrobial agents, compared with the resistance of isolates from pigs held 3 or 39 h. A substantial increase (18 to 48%) in the ability to transfer streptomycin resistance was demonstrated in coliforms from pigs held 39 h, when compared with those from pigs held 3 h.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:3606107

  11. Time-saving screening for diabetes in patients with coronary artery disease: a report from EUROASPIRE IV

    PubMed Central

    Gyberg, Viveca; De Bacquer, Dirk; Kotseva, Kornelia; De Backer, Guy; Schnell, Oliver; Tuomilehto, Jaakko; Wood, David; Rydén, Lars

    2016-01-01

    Background WHO advocates 2-hour oral glucose tolerance test (OGTT) for detecting diabetes mellitus (DM). OGTT is the most sensitive method to detect DM in patients with coronary artery disease (CAD). Considered time consuming, the use of OGTT is unsatisfactory. A 1-hour plasma glucose (1hPG) test has not been evaluated as an alternative in patients with CAD. Objectives To create an algorithm based on glycated haemoglobin (HbA1c), fasting plasma glucose (FPG) and 1hPG limiting the need of a 2-hour plasma glucose (2hPG) in patients with CAD. Methods 951 patients with CAD without DM underwent OGTT. A 2hPG≥11.1 mmol/L was the reference for undiagnosed DM. The yield of HbA1c, FPG and 1hPG was compared with that of 2hPG. Results Mean FPG was 6.2±0.9 mmol/L, and mean HbA1c 5.8±0.4%. Based on 2hPG≥11.1 mmol/L 122 patients (13%) had DM. There was no value for the combination of HbA1c and FPG to rule out or in DM (HbA1c≥6.5%; FPG≥7.0 mmol/L). In receiver operating characteristic analysis a 1hPG≥12 mmol/L balanced sensitivity and specificity for detecting DM (both=82%; positive and negative predictive values 40% and 97%). A combination of FPG<6.5 mmol/L and 1hPG<11 mmol/L excluded 99% of DM. A combination of FPG>8.0 mmol/L and 1hPG>15 mmol/L identified 100% of patients with DM. Conclusions Based on its satisfactory accuracy to detect DM an algorithm is proposed for screening for DM in patients with CAD decreasing the need for a 2-hour OGTT by 71%. PMID:27932342

  12. Pulmonary transit time measurement by contrast-enhanced ultrasound in left ventricular dyssynchrony

    PubMed Central

    Saporito, Salvatore; Mischi, Massimo; van Assen, Hans C; Bouwman, R Arthur; de Lepper, Anouk G W; van den Bosch, Harrie C M; Korsten, Hendrikus H M; Houthuizen, Patrick

    2016-01-01

    Background Pulmonary transit time (PTT) is an indirect measure of preload and left ventricular function, which can be estimated using the indicator dilution theory by contrast-enhanced ultrasound (CEUS). In this study, we first assessed the accuracy of PTT-CEUS by comparing it with dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI). Secondly, we tested the hypothesis that PTT-CEUS correlates with the severity of heart failure, assessed by MRI and N-terminal pro-B-type natriuretic peptide (NT-proBNP). Methods and results Twenty patients referred to our hospital for cardiac resynchronization therapy (CRT) were enrolled. DCE-MRI, CEUS, and NT-proBNP measurements were performed within an hour. Mean transit time (MTT) was obtained by estimating the time evolution of indicator concentration within regions of interest drawn in the right and left ventricles in video loops of DCE-MRI and CEUS. PTT was estimated as the difference of the left and right ventricular MTT. Normalized PTT (nPTT) was obtained by multiplication of PTT with the heart rate. Mean PTT-CEUS was 10.5±2.4s and PTT-DCE-MRI was 10.4±2.0s (P=0.88). The correlations of PTT and nPTT by CEUS and DCE-MRI were strong; r=0.75 (P=0.0001) and r=0.76 (P=0.0001), respectively. Bland–Altman analysis revealed a bias of 0.1s for PTT. nPTT-CEUS correlated moderately with left ventricle volumes. The correlations for PTT-CEUS and nPTT-CEUS were moderate to strong with NT-proBNP; r=0.54 (P=0.022) and r=0.68 (P=0.002), respectively. Conclusions (n)PTT-CEUS showed strong agreement with that by DCE-MRI. Given the good correlation with NT-proBNP level, (n)PTT-CEUS may provide a novel, clinically feasible measure to quantify the severity of heart failure. Clinical Trial Registry: NCT01735838 PMID:27249553

  13. Mean Transit Times in Seven Upland Catchments, Otway Basin, Southeast Australia

    NASA Astrophysics Data System (ADS)

    Howcroft, William; Cartwright, Ian; Morgenstern, Uwe

    2016-04-01

    The timescales over which precipitation is transmitted into upland streams (the mean transit times, MTTs) are poorly understood, as are the physical processes and controls that govern the variation in mean transit times. In this study, we use tritium (3H), major ion geochemistry and discharge data to investigate the MTTs in upland streams of the Otway Basin of southeast Australia. Samples were collected under varying discharge conditions from seven catchments of varying size whose land use varies from relatively pristine eucalyptus forest to a mixture of pasture, grazing, and production forestry. This allows the controls on MTTs to be assessed. Tritium activities within the streams varied from 0.20 to 2.35 TU, which are below that of local rainfall (~2.7 TU). The highest tritium activities were generally reported in samples collected during periods of high winter discharge, while the lowest tritium activities were reported in samples collected during low, summer discharge. However, at several of the streams, there appears to be a discharge threshold above which tritium activities do not increase appreciably with increased discharge. In general, streams with larger catchment areas and relatively simple geology have less variable but higher tritium activities. In contrast, the lowest and most variable tritium activities were reported in streams having small catchment areas and a greater complexity in geology. MTTs calculated using an exponential-piston flow model ranged between 8 and 180 years; MTTs calculated using other flow models were generally similar, except where the tritium activities were less than around 1 TU. Major ion concentrations generally increased with a corresponding increase in MTT. However, in those streams having more variable MTTs, the opposite often held true, which most likely reflects the variable contribution to flow by water from different geologic units under differing flow conditions. By contrast, land use does not appear to impart a

  14. Transit Timing Variations of TrES-2: a combined analysis of ground- and space-based photometry

    NASA Astrophysics Data System (ADS)

    Raetz, St.; Ginski, Ch.; Mugrauer, M.; Berndt, A.; Eisenbeiss, T.; Adam, Ch.; Raetz, M.; Roell, T.; Seeliger, M.; Maciejewski, G.; Marka, C.; Vanko, M.; Bukowiecki, L.; Errmann, R.; Kitze, M.; Ohlert, J.; Pribulla, T.; Schmidt, J. G.; Sebastian, D.; Tetzlaff, N.; Hohle, M. M.; Schmidt, T. O. B.; Neuhäuser, R.

    2013-07-01

    TrES-2 is one of the few exoplanets, which offer the matchless possibility to combine long-term ground-based observations with continuous satellite data. TrES-2 is a target of our "Transit Timing Variations @ YETI" (TTV@YETI) project which is dedicated to detect and characterize signals of transit timing variations. We observed 43 ground-based light curves of 30 individual transit events of TrES-2. We used seven 0.2 - 2.2m telescopes located at five observatories in Germany and Spain. In addition, we analyzed 16 quarters (Q0-Q15) of observational data from NASA's space telescope Kepler including 424 individual transit events. The continuous monitoring of Kepler allows to determine the system parameters of each of the 424 transits and search for possible changes of these quantities. Here we present a first indication of an increasing stellar activity of the TrES-2 host star and provide new limits on possible transit timing variations.

  15. Following Molecular Transitions with Single Residue Spatial and Millisecond Time Resolution

    SciTech Connect

    Shcherbakova,I.; Mitra, S.; Beer, R.; Brenowitz, M.

    2008-01-01

    'Footprinting' describes assays in which ligand binding or structure formation protects polymers such as nucleic acids and proteins from either cleavage or modification; footprinting allows the accessibility of individual residues to be mapped in solution. Equilibrium and time-dependent footprinting links site-specific structural information with thermodynamic and kinetic transitions, respectively. The hydroxyl radical ({center_dot}OH) is a uniquely insightful footprinting probe by virtue of it being among the most reactive chemical oxidants; it reports the solvent accessibility of reactive sites on macromolecules with as fine as a single residue resolution. A novel method of millisecond time-resolved {center_dot}OH footprinting is presented based on the Fenton reaction, Fe(II) + H2O2 {yields} Fe(III) + {center_dot}OH + OH-. It is implemented using a standard three-syringe quench-flow mixer. The utility of this method is demonstrated by its application to the studies on RNA folding. Its applicability to a broad range of biological questions involving the function of DNA, RNA, and proteins is discussed.

  16. Capillary transit time heterogeneity and flow-metabolism coupling after traumatic brain injury

    PubMed Central

    Østergaard, Leif; Engedal, Thorbjørn S; Aamand, Rasmus; Mikkelsen, Ronni; Iversen, Nina K; Anzabi, Maryam; Næss-Schmidt, Erhard T; Drasbek, Kim R; Bay, Vibeke; Blicher, Jakob U; Tietze, Anna; Mikkelsen, Irene K; Hansen, Brian; Jespersen, Sune N; Juul, Niels; Sørensen, Jens CH; Rasmussen, Mads

    2014-01-01

    Most patients who die after traumatic brain injury (TBI) show evidence of ischemic brain damage. Nevertheless, it has proven difficult to demonstrate cerebral ischemia in TBI patients. After TBI, both global and localized changes in cerebral blood flow (CBF) are observed, depending on the extent of diffuse brain swelling and the size and location of contusions and hematoma. These changes vary considerably over time, with most TBI patients showing reduced CBF during the first 12 hours after injury, then hyperperfusion, and in some patients vasospasms before CBF eventually normalizes. This apparent neurovascular uncoupling has been ascribed to mitochondrial dysfunction, hindered oxygen diffusion into tissue, or microthrombosis. Capillary compression by astrocytic endfeet swelling is observed in biopsies acquired from TBI patients. In animal models, elevated intracranial pressure compresses capillaries, causing redistribution of capillary flows into patterns argued to cause functional shunting of oxygenated blood through the capillary bed. We used a biophysical model of oxygen transport in tissue to examine how capillary flow disturbances may contribute to the profound changes in CBF after TBI. The analysis suggests that elevated capillary transit time heterogeneity can cause critical reductions in oxygen availability in the absence of ‘classic' ischemia. We discuss diagnostic and therapeutic consequences of these predictions. PMID:25052556

  17. Automation from pictures: Producing real time code from a state transition diagram

    SciTech Connect

    Kozubal, A.J.

    1991-01-01

    The state transition diagram (STD) model has been helpful in the design of real time software, especially with the emergence of graphical computer aided software engineering (CASE) tools. Nevertheless, the translation of the STD to real time code has in the past been primarily a manual task. At Los Alamos we have automated this process. The designer constructs the STD using a CASE tool (Cadre Teamwork) using a special notation for events and actions. A translator converts the STD into an intermediate state notation language (SNL), and this SNL is compiled directly into C code (a state program). Execution of the state program is driven by external events, allowing multiple state programs to effectively share the resources of the host processor. Since the design and the code are tightly integrated through the CASE tool, the design and code never diverge, and we avoid design obsolescence. Furthermore, the CASE tool automates the production of formal technical documents from the graphic description encapsulated by the CASE tool. 10 refs., 3 figs.

  18. Eight planets in four multi-planet systems via transit timing variations in 1350 days

    SciTech Connect

    Yang, Ming; Liu, Hui-Gen; Zhang, Hui; Yang, Jia-Yi; Zhou, Ji-Lin E-mail: huigen@nju.edu.cn

    2013-12-01

    Analysis of the transit timing variations (TTVs) of candidate pairs near mean-motion resonances (MMRs) is an effective method to confirm planets. Hitherto, 68 planets in 34 multi-planet systems have been confirmed via TTVs. We analyze the TTVs of all candidates from the most recent Kepler data with a time span of upto about 1350 days (Q0-Q15). The anti-correlations of TTV signals and the mass upper limits of candidate pairs in the same system are calculated using an improved method suitable for long-period TTVs. If the false alarm probability of a candidate pair is less than 10{sup –3} and the mass upper limit for each candidate is less than 13 M {sub J}, we confirm them as planets in the same system. Finally, eight planets in four multi-planet systems are confirmed via analysis of their TTVs. All of the four planet pairs are near first-order MMRs, including KOI-2672 near 2:1 MMR and KOI-1236, KOI-1563, and KOI-2038 near 3:2 MMR. Four planets have relatively long orbital periods (>35 days). KOI-2672.01 has an orbital period of 88.51658 days and a fit mass of 17 M {sub ⊕}. To date, it is the longest-period planet confirmed near a first-order MMR via TTVs.

  19. Space Competition and Time Delays in Human Range Expansions. Application to the Neolithic Transition

    PubMed Central

    Isern, Neus; Fort, Joaquim; Vander Linden, Marc

    2012-01-01

    Space competition effects are well-known in many microbiological and ecological systems. Here we analyze such an effect in human populations. The Neolithic transition (change from foraging to farming) was mainly the outcome of a demographic process that spread gradually throughout Europe from the Near East. In Northern Europe, archaeological data show a slowdown on the Neolithic rate of spread that can be related to a high indigenous (Mesolithic) population density hindering the advance as a result of the space competition between the two populations. We measure this slowdown from a database of 902 Early Neolithic sites and develop a time-delayed reaction-diffusion model with space competition between Neolithic and Mesolithic populations, to predict the observed speeds. The comparison of the predicted speed with the observations and with a previous non-delayed model show that both effects, the time delay effect due to the generation lag and the space competition between populations, are crucial in order to understand the observations. PMID:23251430

  20. Eight Planets in Four Multi-planet Systems via Transit Timing Variations in 1350 Days

    NASA Astrophysics Data System (ADS)

    Yang, Ming; Liu, Hui-Gen; Zhang, Hui; Yang, Jia-Yi; Zhou, Ji-Lin

    2013-12-01

    Analysis of the transit timing variations (TTVs) of candidate pairs near mean-motion resonances (MMRs) is an effective method to confirm planets. Hitherto, 68 planets in 34 multi-planet systems have been confirmed via TTVs. We analyze the TTVs of all candidates from the most recent Kepler data with a time span of upto about 1350 days (Q0-Q15). The anti-correlations of TTV signals and the mass upper limits of candidate pairs in the same system are calculated using an improved method suitable for long-period TTVs. If the false alarm probability of a candidate pair is less than 10-3 and the mass upper limit for each candidate is less than 13 M J, we confirm them as planets in the same system. Finally, eight planets in four multi-planet systems are confirmed via analysis of their TTVs. All of the four planet pairs are near first-order MMRs, including KOI-2672 near 2:1 MMR and KOI-1236, KOI-1563, and KOI-2038 near 3:2 MMR. Four planets have relatively long orbital periods (>35 days). KOI-2672.01 has an orbital period of 88.51658 days and a fit mass of 17 M ⊕. To date, it is the longest-period planet confirmed near a first-order MMR via TTVs.

  1. The Transits of Venus and New Technologies: A Time to Reflect

    NASA Astrophysics Data System (ADS)

    Brashear, Ron

    2005-01-01

    In the recent history of astronomy there have been occasions where `New Astronomies' have been introduced. In the spirit of the recent excitement of the 2004 transit of Venus, I have used the periods around the historical transits to reflect on the `New Astronomies' of those eras. Johannes Kepler's Astronomia Nova is a fine representation of the New Astronomy of the 1631-1639 transit pair and Pierre Simon, Marquis de Laplace's Traité de Mécanique Céleste reflects the New Astronomy of the 1761-1769 transit pair. A combination of Samuel P. Langley's The New Astronomy and James E. Keeler's 1897 paper on astrophysics have been chosen as the exemplars of the New Astronomy of the 1874-1882 transit pair. I am open to suggestions for the works that best represent the 2004-2012 transit pairs.

  2. Transit Timing Observations from Kepler: II. Confirmation of Two Multiplanet Systems via a Non-parametric Correlation Analysis

    SciTech Connect

    Ford, Eric B.; Fabrycky, Daniel C.; Steffen, Jason H.; Carter, Joshua A.; Fressin, Francois; Holman, Matthew J.; Lissauer, Jack J.; Moorhead, Althea V.; Morehead, Robert C.; Ragozzine, Darin; Rowe, Jason F.; /NASA, Ames /SETI Inst., Mtn. View /San Diego State U., Astron. Dept.

    2012-01-01

    We present a new method for confirming transiting planets based on the combination of transit timing variations (TTVs) and dynamical stability. Correlated TTVs provide evidence that the pair of bodies are in the same physical system. Orbital stability provides upper limits for the masses of the transiting companions that are in the planetary regime. This paper describes a non-parametric technique for quantifying the statistical significance of TTVs based on the correlation of two TTV data sets. We apply this method to an analysis of the transit timing variations of two stars with multiple transiting planet candidates identified by Kepler. We confirm four transiting planets in two multiple planet systems based on their TTVs and the constraints imposed by dynamical stability. An additional three candidates in these same systems are not confirmed as planets, but are likely to be validated as real planets once further observations and analyses are possible. If all were confirmed, these systems would be near 4:6:9 and 2:4:6:9 period commensurabilities. Our results demonstrate that TTVs provide a powerful tool for confirming transiting planets, including low-mass planets and planets around faint stars for which Doppler follow-up is not practical with existing facilities. Continued Kepler observations will dramatically improve the constraints on the planet masses and orbits and provide sensitivity for detecting additional non-transiting planets. If Kepler observations were extended to eight years, then a similar analysis could likely confirm systems with multiple closely spaced, small transiting planets in or near the habitable zone of solar-type stars.

  3. Violation of the transit-time limit toward generation of ultrashort electron bunches with controlled velocity chirp

    PubMed Central

    Jeon, Seok-Gy; Shin, Dongwon; Hur, Min Sup

    2016-01-01

    Various methods to generate ultrashort electron bunches for the ultrafast science evolved from the simple configuration of two-plate vacuum diodes to advanced technologies such as nanotips or photocathodes excited by femtosecond lasers. In a diode either in vacuum or of solid-state, the transit-time limit originating from finite electron mobility has caused spatiotemporal bunch-collapse in ultrafast regime. Here, we show for the first time that abrupt exclusion of transit-phase is a more fundamental origin of the bunch-collapse than the transit-time limit. We found that by significantly extending the cathode-anode gap distance, thereby violating the transit-time limit, the conventional transit-time-related upper frequency barrier in diodes can be removed. Furthermore, we reveal how to control the velocity chirp of bunches leading to ballistic bunch-compression. Demonstration of 0.707 THz-, 46.4 femtosecond-bunches from a 50 μm-wide diode in three-dimensional particle-in-cell simulations shows a way toward simple and compact sources of ultrafast electron bunches for diverse ultrafast sciences. PMID:27653458

  4. Violation of the transit-time limit toward generation of ultrashort electron bunches with controlled velocity chirp.

    PubMed

    Jeon, Seok-Gy; Shin, Dongwon; Hur, Min Sup

    2016-09-22

    Various methods to generate ultrashort electron bunches for the ultrafast science evolved from the simple configuration of two-plate vacuum diodes to advanced technologies such as nanotips or photocathodes excited by femtosecond lasers. In a diode either in vacuum or of solid-state, the transit-time limit originating from finite electron mobility has caused spatiotemporal bunch-collapse in ultrafast regime. Here, we show for the first time that abrupt exclusion of transit-phase is a more fundamental origin of the bunch-collapse than the transit-time limit. We found that by significantly extending the cathode-anode gap distance, thereby violating the transit-time limit, the conventional transit-time-related upper frequency barrier in diodes can be removed. Furthermore, we reveal how to control the velocity chirp of bunches leading to ballistic bunch-compression. Demonstration of 0.707 THz-, 46.4 femtosecond-bunches from a 50 μm-wide diode in three-dimensional particle-in-cell simulations shows a way toward simple and compact sources of ultrafast electron bunches for diverse ultrafast sciences.

  5. Violation of the transit-time limit toward generation of ultrashort electron bunches with controlled velocity chirp

    NASA Astrophysics Data System (ADS)

    Jeon, Seok-Gy; Shin, Dongwon; Hur, Min Sup

    2016-09-01

    Various methods to generate ultrashort electron bunches for the ultrafast science evolved from the simple configuration of two-plate vacuum diodes to advanced technologies such as nanotips or photocathodes excited by femtosecond lasers. In a diode either in vacuum or of solid-state, the transit-time limit originating from finite electron mobility has caused spatiotemporal bunch-collapse in ultrafast regime. Here, we show for the first time that abrupt exclusion of transit-phase is a more fundamental origin of the bunch-collapse than the transit-time limit. We found that by significantly extending the cathode-anode gap distance, thereby violating the transit-time limit, the conventional transit-time-related upper frequency barrier in diodes can be removed. Furthermore, we reveal how to control the velocity chirp of bunches leading to ballistic bunch-compression. Demonstration of 0.707 THz-, 46.4 femtosecond-bunches from a 50 μm-wide diode in three-dimensional particle-in-cell simulations shows a way toward simple and compact sources of ultrafast electron bunches for diverse ultrafast sciences.

  6. New BSN nurses' perspectives on the transition to practice in changing economic times.

    PubMed

    Craig, Carol; Moscato, Susan; Moyce, Sally

    2012-04-01

    Helping nursing graduates transition to practice is a concern for nursing educators and employers. This article reports graduates' perceptions of transition both when jobs were plentiful and when jobs were scarce. Survey results from comparison of 2008 and 2010 graduates demonstrated few differences. Key indicators of successful transition were positive feedback at the work site, increased self-confidence on the part of the new graduate, and acceptance by the care team. Presence of good role models, ability to ask questions safely, and ongoing feedback on performance assisted successful transition.

  7. Transiting Primary Eclipse Photometric Follow-up Observations and Transit Timing Variations Studies of WASP-43 b and TrES-3 b

    NASA Astrophysics Data System (ADS)

    Sun, Z.; Ji, J. H.; Dong, Y.

    2016-11-01

    Two photometric follow-up observations for transiting primary eclipse of WASP-43 b and four for TrES-3 b are performed using the Xuyi Near-Earth Object Survey Telescope. After differential photometry and light curve analysis, physical parameters of the two systems are obtained and are in good match with the literatures. Combining with transit data from many literatures, the residuals (O-C) of observations of both systems transits are fitted with the linear and quadratic terms. With the linear fitting, the periods and transit timing variations (TTVs) of the planets are obtained, and no obvious periodic TTV signal is found in either system after analysis. The maximum mass of perturbing planet located at 1:2 mean motion resonance (MMR) of WASP-43 b and TrES-3 b are estimated to be 1.826 and 1.504 Earth mass, respectively. By quadratic fitting, it is confirmed that WASP-43 b may have long-term TTV which means an orbital decay. The decay rate is shown to be dot{P} =(-0.005248 ± 0.001714) s\\cdotyr^{-1}, and is compared with the previous results. Based on this, the lower limit of the stellar tidal quality parameter of WASP-43 is calculated to be Q'_{*} ≥ 1.5×10^5, and the remaining lifetime of the planets of both systems is presented for different Q'_{*} values accordingly.

  8. Measurement of absolute arterial cerebral blood volume in human brain without using a contrast agent.

    PubMed

    Hua, Jun; Qin, Qin; Pekar, James J; van Zijl, Peter C M

    2011-12-01

    Arterial cerebral blood volume (CBV(a) ) is a vital indicator of tissue perfusion and vascular reactivity. We extended the recently developed inflow vascular-space-occupancy (iVASO) MRI technique, which uses spatially selective inversion to suppress the signal from blood flowing into a slice, with a control scan to measure absolute CBV(a) using cerebrospinal fluid (CSF) for signal normalization. Images were acquired at multiple blood nulling times to account for the heterogeneity of arterial transit times across the brain, from which both CBV(a) and arterial transit times were quantified. Arteriolar CBV(a) was determined separately by incorporating velocity-dependent bipolar crusher gradients. Gray matter (GM) CBV(a) values (n=11) were 2.04 ± 0.27 and 0.76 ± 0.17 ml blood/100 ml tissue without and with crusher gradients (b=1.8 s/mm(2) ), respectively. Arterial transit times were 671 ± 43 and 785 ± 69 ms, respectively. The arterial origin of the signal was validated by measuring its T(2) , which was within the arterial range. The proposed approach does not require exogenous contrast agent administration, and provides a non-invasive alternative to existing blood volume techniques for mapping absolute CBV(a) in studies of brain physiology and neurovascular diseases.

  9. Radiopaque markers to evaluate gastric emptying and small intestinal transit time in healthy cats.

    PubMed

    Chandler, M L; Guilford, G; Lawoko, C R

    1997-01-01

    Determinations of gastric emptying time (GET) and small intestinal transit time (SITT) are useful in detecting gastrointestinal motility disorders and partial obstructions of the pylorus or small intestine. Barium-impregnated, polyethylene radiopaque spheres with diameters of 1.5 mm and 5.0 mm have been developed for quantitative assessment of gastrointestinal transit. The purpose of this study was to evaluate GET and SITT using these radiopaque spheres in 10 healthy cats. The cats were randomly assigned to 1 of 3 treatment groups: fasted, fed, and fed plus sedation (acetylpromazine maleate 0.10 mg/kg subcutaneously). A repeated measures study design was used. The mean GETs of 50%, 75%, and 90% of the 1.5-mm and the 5-mm spheres in the unfed cats were 0.36, 0.58, and 0.74 hours, and 0.41, 0.68, and 1.02 hours, respectively. These values were significantly (P < or = .05) more rapid than the GETs of 50%, 75%, and 90% of the 1.5-mm and 5-mm spheres of either the sedated fed cats (4.39, 5.68, 6.65 and 5.15, 5.99, 6.91 hours) or the unsedated fed cats (6.43, 8.12, 9.06 and 7.49, 8.49, 9.22 hours). The mean GETs of 50% and 75% of the 1.5-mm and 5-mm and of 90% of the 1.5-mm spheres were significantly (P < or = .05) more rapid in sedated than in unsedated fed cats. The GET of 50% of the 1.5-mm spheres was significantly more rapid (P < or = .05) than that of the 5-mm spheres in the fed cats. The mean SITTs, which ranged from 2.25 to 3.05 hours, were not significantly different (P > .05) among the treatment groups or between the 1.5-mm and 5-mm spheres. The GET of spheres given to fasted cats is significantly more rapid than that of fed cats. Subcutaneous injection of acetylpromazine speeds GET in fed cats. The SITT of small and large spheres was not influenced by feeding or by acetylpromazine injection.

  10. Temporal alignment of tissue and arterial data and selection of integration start times for the H[sub 2] [sup 15]O autoradiographic CBF model in PET

    SciTech Connect

    Muzic, R.F. Jr. . Dept. of Biomedical Engineering); Nelson, A.D.; Miraldi, F. . Div. of Nuclear Medicine)

    1993-09-01

    A technique has been developed and tested that provides an automated method of temporally aligning the PET tissue activity curve with the arterial activity curve for quantification of cerebral blood flow using the H[sub 2] [sup 15]O autoradiographic model. This technique not only determines the relative time delay between the two curves, but also provides the start time of integration. Variability in computing global cerebral blood flow using this technique is shown to be less than that obtained by trained observers manually selecting parameters and at least as good as that obtained by using another automated alignment technique.

  11. Comparison of efficacy of cryotherapy and chlorhexidine to oral nutrition transition time in chemotherapy-induced oral mucositis.

    PubMed

    Erden, Y; Ipekcoban, G

    2016-05-01

    The aim of this study was to compare the efficacy of cryotherapy and chlorhexidine to oral nutrition transition time in chemotherapy-induced oral mucositis. This randomised controlled trial with random assignments to the experimental and control groups was conducted with cancer patients. Study data were collected from 90 cancer patients. The first experimental group (n = 30) received chlorhexidine mouthwash, the second experimental group (n = 30) received oral cryotherapy and the control group (n = 30) received routine care. To collect data we used the 'Mucositis Rating Index'. Changes in patients' oral mucosa in each group were checked and oral feeding transition periods were recorded. There was an important statistical difference between the times of transition to oral nutrition for patients (P < 0.01). Oral nutrition transition time of patients in the first experimental group who had applied chlorhexidine was shorter than in other groups. Following the tests, we detected a significant shortening in oral nutrition transition time of patients in first group who used chlorhexidine gargle as compared to the second group and control group. There was no significant difference between cryotherapy application and control group. In parallel with these findings, we detected that the degree of oral mucositis decreased.

  12. Mesenteric Artery Insufficiency

    PubMed Central

    Coles, John C.; Walker, John B.; Gergely, N. F.; Buttigliero, Jorge

    1963-01-01

    The syndromes of superior mesenteric artery insufficiency are briefly reviewed. Three cases associated with infarction of bowel which were treated with restoration of arterial flow and resection of residual irretrievable bowel are reported. In two patients an embolectomy and in one patient a bypass graft were used to restore arterial continuity. The importance of the recognition and removal of irretrievable bowel at the time of vascular reconstruction is emphasized. Success is not necessarily predicated by the time factor alone, although the importance of early diagnosis and surgical intervention cannot be denied. PMID:14042788

  13. Carotid Artery Screening

    MedlinePlus

    ... plaque and the injury it causes is called atherosclerosis . Over time, the walls of affected arteries thicken ... disease (CAD) obesity physical inactivity family history of atherosclerosis and/or stroke Screening Recommendations Carotid Duplex US ...

  14. Transit Timing Variation Measurements of WASP-12b and Qatar-1b: No Evidence Of Additional Planets

    NASA Astrophysics Data System (ADS)

    Collins, Karen A.; Kielkopf, John F.; Stassun, Keivan G.

    2017-02-01

    WASP-12b and Qatar-1b are transiting hot Jupiters for which previous works have suggested the presence of transit timing variations (TTVs) indicative of additional bodies in these systems—an Earth-mass planet in WASP-12 and a brown-dwarf mass object in Qatar-1. Here, we present 23 new WASP-12b and 18 new Qatar-1b complete (or nearly complete) transit observations. We perform global system fits to all of our light curves for each system, as well as RV and stellar spectroscopic parameters from the literature. The global fits provide refined system parameters and uncertainties for each system, including precise transit center times for each transit. The transit model residuals of the combined and five minute binned light curves have an rms of 183 and 255 parts per million (ppm) for WASP-12b and Qatar-1b, respectively. Most of the WASP-12b system parameter values from this work are consistent with values from previous studies, but have ∼40%–50% smaller uncertainties. Most of the Qatar-1b system parameter values and uncertainties from this work are consistent with values recently reported in the literature. We find no convincing evidence for sinusoidal TTVs with a semi-amplitude of more than ∼35 and ∼25 s in the WASP-12b and Qatar-1b systems, respectively.

  15. 77 FR 77180 - Notice of Transportation Services' OMB Designation, timely return of excess transit benefits to...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-12-31

    ... of the Federal internal controls that now govern the Transit Benefit Program to prevent future... that federal agencies strengthen internal controls to ensure compliance with the Federal Transit... with the security controls identified in the DOT's System of Records Notice, DOT/ALL 8...

  16. Adolescents' Changing Future Expectations Predict the Timing of Adult Role Transitions