Pulsatile Waveform Research Articles

Near-Wall Fluid Mechanics Of A Pulsatile Flow Through A Compliant Tube

The demand for heart transplantation far exceeds the supply. This shortage is mainly due to the high percentage of discarded hearts and the narrow time window of only six hours that the current standard preservation method, static cold storage (SCS), allows for completing the entire procedure from donor to recipient patient. An alternative method called ex-vivo heart perfusion (EVHP) maintains a human donor heart beating outside the body for the time preceding transplantation surgery. By keeping the donor heart beating in a quasi-physiological mode of operation and assessing its functions, the organ's health can be monitored so that, ultimately, the transplant time window can be extended to increase the geographic availability of donors. In order to improve and optimize the EVHP system, fundamental understanding of the system physics is needed. To achieve this, the present work aims to investigate the relationship between pulsatile flow and compliance, evaluating the near wall region of a compliant tube with a particular focus on the formation of the viscous boundary layer. Thus, an experimental setup was designed to replicate the flow loop of the EVHP system and an optical transparent compliant tube that mimics the functioning of the body's largest and most compliant artery, the aorta, was custom-made to allow optical access to the flow field matching the refractive index of the working fluid. A pulsatile waveform is generated using a computer-controlled mechanical diaphragm pump, also equipped with a tri-leaf exit valve to simulate the physiological working condition of the heart. In the present work, the flow field is assessed by first performing stereo particle image velocimetry (PIV) on the bulk flow to investigate the large-scale phenomena within a compliant tube and the results of these experiments will be further used as a guide to interrogate smaller near-wall regions of interest in the flow. The preliminary results show, in addition to the general characteristics of a pulsatile flow through a compliant tube, a potential complex fluid-structure relationship between the pulsatile flow and the moving wall of the tube has been observed. The presentation of this work will discuss the experimental setup and review the preliminary results presented here in addition to others findings that are still being analyzed, data processing is underway to do so.

Pulsatile flow in venous perforators of the lower limb.

Teaching traditionally asserts that the arterial pressure pulse is dampened across the capillary bed to the extent that pulsatility is nonexistent in the venous circulation of the lower limbs. Herein, we present evidence of transmission of arterial pulsations across the capillary network into perforator veins in the lower limbs of healthy, heat-stressed humans. Perforator veins are connections from the superficial veins that drain into the deep veins. When assessed using ultrasound at rest, they infrequently demonstrate flow, and a pulsatile flow waveform is not described. We investigated perforator vein pulsatility in 10 young, healthy volunteers who underwent passive heating by +2°C core body temperature via a hot-water-perfused suit, and 5 who also underwent active heating by +2°C via low-intensity cycling while wearing the hot-water-perfused suit. At +0.5°C increments in temperature, blood velocity in an ankle perforator vein was measured using duplex ultrasound. In all perforators with heating, sustained flow was demonstrated, with a pulsatile waveform that was synchronous with the cardiac cycle. The maximum velocity was 30 ± 13 cm/s with passive heating and approximately half with active heating (P = 0.04). The small veins of the skin at the ankle also demonstrated increased perfusion with pulsatility, seen with low-velocity microvascular imaging technology. We consider explanations for this pulsatility and conclude that it is propagated from the arterial inflow through the skin microcirculation as a result of increased dilatation and flow volume and that this is a normal response to increased skin blood flow.

Analysis of Hemodynamic on Different Stent Strut Configurations in Femoral Popliteal Artery

Peripheral arterial disease is a narrowing of the peripheral arteries that might result in blockage if not immediately treated. Normally, an invasive technique called stenting is used at the stenosed arterial region to restore normal blood flow. Furthermore, the impact of physiological stresses on the stented arterial wall may worsen the condition and divert blood away from the main direction of flow. This phenomenon may promote the formation of thrombosis in the stented artery due to the presenting flow recirculation. This study aims to investigate the effect of physiological loads with different hemodynamic factors on the strut configuration in Peripheral arterial. The computational fluid dynamics (CFD) method is governed by continuity and Navier-Stokes equations were implemented. Three-dimensional geometries of the different strut configurations inserted into the peripheral artery are modelled. Each of the struts has different characteristics in terms of strut angle and the number of strut configurations. Due to hemodynamic differences, the pulsatile waveform of the velocity and pressure at the peak systole time were investigated. Hemodynamic factors analysed in this study consist of wall shear stress (WSS), velocity, and pressure. From the result, the prediction of thrombosis formation is around 30% higher for the largest number of strut design. The lowest formation of thrombosis was seen with the fewer strut configurations and the reduction of the strut angle with an overall percentage of 15%.

Measuring Arterial Pulsatility With Dynamic Inflow Magnitude Contrast.

The pulsatility of blood flow through cerebral arteries is clinically important, as it is intrinsically associated with cerebrovascular health. In this study we outline a new MRI approach to measuring the real-time pulsatile flow in cerebral arteries, which is based on the inflow phenomenon associated with fast gradient-recalled-echo acquisitions. Unlike traditional phase-contrast techniques, this new method, which we dub dynamic inflow magnitude contrast (DIMAC), does not require velocity-encoding gradients as sensitivity to flow velocity is derived purely from the inflow effect. We achieved this using a highly accelerated single slice EPI acquisition with a very short TR (15 ms) and a 90° flip angle, thus maximizing inflow contrast. We simulate the spoiled GRE signal in the presence of large arteries and perform a sensitivity analysis. The sensitivity analysis demonstrates that in the regime of high inflow contrast, DIMAC shows much greater sensitivity to flow velocity over blood volume changes. We support this theoretical prediction with in-vivo data collected in two separate experiments designed to demonstrate the utility of the DIMAC signal contrast. We perform a hypercapnia challenge experiment in order to experimentally modulate arterial tone within subjects, and thus modulate the arterial pulsatile flow waveform. We also perform a thigh-cuff release challenge, designed to induce a transient drop in blood pressure, and demonstrate that the continuous DIMAC signal captures the complex transient change in the pulsatile and non-pulsatile components of flow. In summary, this study proposes a new role for a well-established source of MR image contrast and demonstrates its potential for measuring both steady-state and dynamic changes in arterial tone.

An Experimental Set-Up for the <i>in Vitro</i> Simulation of a Physiological Pulsatile Flow in the Abdominal Aorta

In vitro experimental set-up is an important tool for investigating abdominal aortic aneurysm (AAA). Accurate reproduction of the physiological pulsatile flow waveform in the abdominal aorta at various anatomic locations is an important component of these experimental methods. The objective of this study is to establish an experimental set-up to generate a physiological pulsatile flow for in vitro simulations of the abdominal aorta. The physiological flow was established by a computer-controlled peristaltic pump and the flow field in a circular straight pipe is measured under pulsatile flow conditions by a 2-dimensional particle image velocimetry system (2D-PIV). Experimental results show that the in vitro experimental set-up provides a flow with a period of 2 s, a reasonable cross-sectional velocity distribution and an approximate inlet velocity profile that is close to the human abdominal aorta.

Compensatory reserve versus traditional vital signs in the obstetric patient

The Compensatory Reserve Index (CRI) is a new metric, estimated from pulsatile waveforms, that accurately tracks the compensatory phase of central volume loss or gain. It reports values between 1 and 0 to indicate the proportion of central volume loss the subject can tolerate before collapse, or how well the patient is compensating for acute volume loss. While studied in non-obstetrical patients, we sought to demonstrate how CRI compares to traditional vital signs in the obstetric patient at time of delivery.

Constrictive pericarditis: portal, splenic, and femoral venous Doppler pulsatility: a case series.

Pulsatile flow of the portal vein has been implicated as an indicator of right ventricular dysfunction in cardiac patients. In patients with significantly elevated right atrial pressure, pulsatile venous flow may be transmitted to the portal, splenic, renal, and femoral veins. We describe the evolution of these echocardiographic findings in four patients with constrictive pericarditis (CP) undergoing pericardiectomy with simultaneous hemodynamic waveform and cerebral oximetry monitoring in the operating room and in the intensive care unit. Patient 1 presented classic signs of CP, including equalization of left and right diastolic pressures, a "square root" sign on the diastolic portion of the right ventricular pressure curve, and elevated right atrial pressure. Preoperative transesophageal echocardiography showed a hyperdynamic left ventricle and dilated right ventricle with abnormal pulsatile waveforms in the portal and splenic veins. Surgical decompression of the pericardium gradually normalized the Doppler waveforms. Increased venous return following pericardiectomy during surgery in patients 2 and 3 and during the postoperative period in patient 4 resulted in right ventricular (RV) failure due to significantly increased preload. Venous pulsatility was also observed in the portal, splenic, and femoral veins. In patients with CP, changes in hemodynamic and echocardiographic signs of RV dysfunction are rapidly reflected by changes in peripheral venous velocities. Identifying signs of splanchnic and peripheral vascular venous congestion could help identify patients at higher risk of developing postoperative complications following pericardiectomy.

Insufficient sampling frequencies skew heart rate variability estimates: Implications for extracting heart rate metrics from neuroimaging and physiological data

BackgroundWhile cardiac pulsations are widely present within physiological and neuroimaging data, it is unknown the extent this information can provide valid and reliable heart rate and heart rate variability (HRV) estimates. The objective of this study was to demonstrate how a slight temporal shift due to an insufficient sampling frequency can impact the validity/accuracy of deriving cardiac metrics. MethodsTwenty-two participants were instrumented with valid/reliable industry-standard or open-source electrocardiograms. Five-minute lead II recordings were collected at 1000 Hz in an upright orthostatic position. Following artifact removal, the 1000 Hz recording for each participant was downsampled to frequencies ranging 2–500 Hz. The validity of each participant’s downsampled recording was compared against their 1000 Hz recording (“reference-standard”) using Bland-Altman plots with 95 % limits of agreement (LOA), coefficient of variation (CoV), intraclass correlation coefficients, and adjusted r-squared values. ResultsDownsampled frequencies of ≥ 50 and ≥ 90 Hz produced highly robust measures with narrow log-transformed 95 % LOA (<±0.01) and low CoV values (≤3.5 %) for heart rate and HRV metrics, respectively. Below these thresholds, the log-transformed 95 % LOA became wider (LOA range: ±0.1–1.9) and more variable (CoV range: 1.5–111.6 %). ConclusionThese results provide an important consideration for obtaining cardiac information from physiological data. Compared to the “reference-standard” ECG, a seemingly negligible temporal shift of the systolic contraction (R wave) greater than 11-milliseconds (90 Hz) away from its true value, lessened the validity of the HRV. Further research is warranted to determine the minimum sampling frequency required to obtain valid heart rate/HRV metrics from pulsatile waveforms.

Responsiveness and Inter-Rater Reliability of the Pulse Volume Recording Upstroke Ratio (PVRr)

The objective of this study was to evaluate a measure of the responsiveness and reliability of the pulse volume recording upstroke ratio (PVRr). A database of 389 subjects undergoing lower extremity revascularization was analyzed. Subjects were included in the analysis if they had undergone pedal radiographs, had PVRs performed pre- and postlower extremity revascularization, and had regular pulsatile digital waveforms with a pressure recording on both PVRs. The responsiveness of the PVRr was assessed by means of the postoperative percent change in comparison to the digital pressures. A statistically significant negative correlation was observed (Pearson -0.421; p = .007) indicating that as digital pressures increased, the PVRr decreased. Further, measurement of the reliability of the PVRr was performed on a selection of 10 recordings by 2 residents and 3 board-certified surgeons. The observed intraclass correlation coefficient of measurements was 0.960. Results of this investigation provide evidence in support of the responsiveness and inter-rater reliability in the calculation of the pulse volume recording upstroke ratio.

Analysis of Epidural Waveform to Determine Correct Epidural Catheter Placement After CSE Labor Analgesia

BackgroundThe epidural pressure is pulsatile and synchronized with arterial pulsations. Monitoring the epidural waveform has been suggested as a technique to reliably confirm the appropriate localization of the epidural catheter.ObjectiveThe aim of this study was to evaluate the sensitivity and specificity of the Computer Controlled Drug Delivery System with continuous pressure and waveform sensing technology (CCDDS) (CompuFlo® CathCheck™) as an instrument to assess the correct placement of the catheter in the epidural space in parturients who have received combined spinal-epidural technique (CSE) for labor analgesia.MethodsWe enrolled 40 consecutive healthy patients undergoing CSE labor analgesia with successful analgesia. All the cases in which pulsatile waveforms in synchrony with heart rate were detected were considered to be true positives; all the cases in which there was the absence of pulsatile waves were followed up. If these patients had to eventually relocate or manipulate the epidural catheter, they were considered to be true negative. If the absence of pulse waves was observed in the presence of successful analgesia during labor, the patients were considered to be false negatives.ResultsPulsatile waveforms synchronous with heart rate were observed in 33 cases associated with adequate analgesia. In 5 cases, the pulsatile waveforms were absent due to unilateral analgesia or catheter occlusion (true negatives). In 2 cases, the patients had effective analgesia but we were not able to observe a distinct pulsatile waveform. The pressure waveform analysis through the epidural catheter had a sensitivity of 95%, a positive predictive value of 100%, a specificity of 100% and a negative predictive value of 60%.ConclusionPulsatile pressure waveform recording with CCDDS through the epidural catheter resulted in high sensitivity and positive predictive value which can help the proper placement of the epidural catheter.

Development of experimental ground truth and quantification of intracranial aneurysm pulsation in a patient

Aneurysm wall motion has been reported to be associated with rupture. However, its quantification with medical imaging is challenging and should be based on experimental ground-truth to avoid misinterpretation of results. In this work a time-resolved CT angiography (4D-CTA) acquisition protocol is proposed to detect the pulsation of intracranial aneurysms with a low radiation dose. To acquire ground-truth data, the accuracy of volume pulsation detection and quantification in a silicone phantom was assessed by applying pressure sinusoidal waves of increasing amplitudes. These experiments were carried out using a test bench that could reproduce pulsatile waveforms similar to those inside the internal carotid arteries of human subjects. 4D-CTA acquisition parameters (mAs, kVp) were then selected to achieve reliable pulsation detection and quantification with the lowest radiation dose achievable. The resulting acquisition protocol was then used to image an anterior communicating artery aneurysm in a human subject. Data reveals that in a simplified in vitro setting 4D-CTA allows for an effective and reproducible method to detect and quantify aneurysm volume pulsation with an inferior limit as low as 3 mm3 and a background noise of 0.5–1 mm3. Aneurysm pulsation can be detected in vivo with a radiation dose approximating 1 mSv.

The composition of vulnerable plaque and its effect on arterial waveforms

Carotid plaque composition is a key factor of plaque stability and it carries significant prognostic information. The carotid unstable plaques are characterized by a thin fibrous cap (FC) ≤65μm with large lipid core (LC), while stable plaques have a thicker FC and less LC. Identifying the percentage of plaque compositions could help surgeons to make a precise decision for their patients’ treatment protocol. This study aims to distinguish between stable and unstable plaque by defining the relationship between plaque composition and arterial waveform non-invasively. An in-vitro arterial system, composed of a Harvard pulsatile flow pump and artificial circulation system, was used to investigate the effect of the plaque compositions on the pulsatile arterial waveforms. Five types of arterial plaques, composed of the LC, FC, Collagen (Col) and Calcium (Ca), were implemented into the artificial carotid artery to represent the diseased arterial system with 30% of blockage. The pulsatile pressure, velocity and arterial wall movement were measured simultaneously at the site proximal to the plaque. Non-invasive wave intensity analysis (Non-WIA) was used to separate the waves into forward and backward components. The correlation between the plaque compositions and the reflected waveforms was quantitatively analysed. The experimental results indicate that the reflected waveforms are strongly correlated with the plaque compositions, where the percentages of the Col are linearly correlated with the amplitude of the backward diameter (correlation coefficient, r = 0.74) and the lipid content has a strong negative correlation with the backward diameter (r = 0.82). A slight weak correlation exists between the reflected waveform and the percentage of Ca. The strong correlation between the compositions of the plaques with the backward waveforms observed in this study demonstrates that the components of the arterial plaques could be distinguished by the arterial waveforms. This finding might lead to a potential novel non-invasive clinical tool to determine the composition of the plaques and distinguish between stable and vulnerable arterial plaques at the early stage.

Recurrence Plot and Machine Learning for Signal Quality Assessment of Photoplethysmogram in Mobile Environment.

The purpose of this study was to develop a machine learning model that could accurately evaluate the quality of a photoplethysmogram based on the shape of the photoplethysmogram and the phase relevance in a pulsatile waveform without requiring complicated pre-processing. Photoplethysmograms were recorded for 76 participants (5 min for each participant). All recorded photoplethysmograms were segmented for each beat to obtain a total of 49,561 pulsatile segments. These pulsatile segments were manually labeled as ‘good’ and ‘poor’ classes and converted to a two-dimensional phase space trajectory image using a recurrence plot. The classification model was implemented using a convolutional neural network with a two-layer structure. As a result, the proposed model correctly classified 48,827 segments out of 49,561 segments and misclassified 734 segments, showing a balanced accuracy of 0.975. Sensitivity, specificity, and positive predictive values of the developed model for the test dataset with a ‘poor’ class classification were 0.964, 0.987, and 0.848, respectively. The area under the curve was 0.994. The convolutional neural network model with recurrence plot as input proposed in this study can be used for signal quality assessment as a generalized model with high accuracy through data expansion. It has an advantage in that it does not require complicated pre-processing or a feature detection process.

Reduced Pulsatile Trabecular Meshwork Motion in Eyes With Primary Open Angle Glaucoma Using Phase-Sensitive Optical Coherence Tomography.

PurposeThe purpose of this study was to investigate the difference in pulsatile trabecular meshwork (TM) motion between normal and eyes with POAG using phase-sensitive optical coherence tomography (PhS-OCT).MethodsIn this cross-sectional study, eight healthy subjects (16 eyes) and nine patients with POAG (18 eyes) were enrolled. A laboratory-based prototype PhS-OCT system was used to measure pulsatile TM motion. PhS-OCT images were analyzed to obtain parameters of pulsatile TM motion (i.e. maximum velocity [MV] and cumulative displacement [CDisp]). Outflow facility and ocular pulse amplitude were measured using pneumotonography. Detection sensitivity was compared among various parameters by calculating the area under the receiver operating characteristic curves (AUCs).ResultsA pulsatile TM motion waveform synchronous with digital pulse was observed using PhS-OCT in both healthy and POAG eyes. The mean MV in eyes with glaucoma was significantly lower than healthy eyes (P < 0.001). The mean CDisp in POAG eyes was also significantly lower than healthy eyes (P < 0.001). CDisp showed a significant correlation (r = 0.46; P = 0.0088) with ocular pulse amplitude in the study. Compared with the outflow facility, both the MV and CDisp were found to have a better discrimination of glaucoma (P < 0.001 and P = 0.0074, respectively).ConclusionsPulsatile TM motion was reduced in patients with POAG compared to healthy subjects. The underlying mechanism may be due to the altered tissue stiffness or other biomechanical properties of the TM in POAG eyes. Our evidence suggests that the measurement of pulsatile TM motion with PhS-OCT may help in characterizing outflow pathway abnormalities.

Abstract 16439: Is Pulmonary Venous Flow Pulsatility a Critical Determinant of Left Atrial Appendage Blood Stasis Risk?

Introduction: Atrial fibrillation (AF) is the most common arrhythmia that leads to thrombus formation, most commonly in the left atrial appendage (LAA), and a resultant five-fold increase in the risk of ischemic stroke. The current standard of stratifying stroke risk, based on the CHA 2 DS 2 -VASc score, does not consider subject-specific LAA hemodynamics and blood stasis risk. We have developed a methodology for computing mean residence time of blood-borne particles in the LAA ( t m ), an index of LAA blood stasis, using 3D left atrial (LA) and LAA geometries and pulmonary venous (PV) inlet blood flow data. While subject-specific 3D geometry can be obtained readily, it is not easy to measure all LA inlet blood flow waveforms in vivo . Therefore, a sensitivity study of LAA t m to the inlet blood flow waveform characteristics (shape and magnitude) is needed. Hypothesis: PV flow pulsatility does not affect LAA t m . Methods: Cardiac computed tomography images of 10 AF subjects were obtained and LA and LAA geometries were reconstructed in 3D and subsequently meshed for computational fluid dynamics (CFD) analysis. We employed CFD analysis, modeling blood cells as neutrally buoyant tracers transported in the blood and used a systems-based approach, to quantify LAA t m . Each subject was simulated using four PV blood flow characteristics: (1) Normal-S , steady PV flow with cardiac output (CO) of 5.5 L/min; (2) AF-S , steady PV flow with reduced CO of 4.4 L/min; (3) Normal-P , normal pulsatile PV flow with normal CO = 5.5 L/min; and (4) AF-P , a typical AF pulsatile waveform where systolic phase and the reversal phase are diminished with reduced CO of 4.4 L/min. Results: Comparing the two steady flow groups, LAA t m significantly increased as CO was decreased ( Normal-S: 2.6±0.3 s, AF-S: 3.1±0.3 s, P =0.02). However, the presence of pulsatility did not affect LAA t m at both levels of CO: Normal-P: 2.4±0.2 s; Normal-S: 2.6±0.3 s, P =0.2 and AF-P: 2.9±0.3 s; AF-S: 3.1±0.3 s, P =0.3. Conclusions: LAA blood stasis risk, as quantified by LAA t m , is significantly affected by the steady PV flow magnitude (i.e., cardiac output) and not by PV flow pulsatility. Therefore, the subject-specific LAA blood stasis risk can be reliably estimated using subject-specific LA and LAA 3D geometries and subject-specific CO.

Effects of highly pulsatile inflow frequency on surface-mounted bluff body wakes

Abstract

On optimal coupling of the ‘electronic photoreceptors’ into the degenerate retina

ObjectiveTo restore sight in atrophic age-related macular degeneration, the lost photoreceptors can be replaced with electronic implants, which replicate their two major functions: (1) converting light into an electric signal, and (2) transferring visual information to the secondary neurons in the retinal neural network—the bipolar cells (BC). We study the selectivity of BC activation by subretinal implants and dynamics of their response to pulsatile waveforms in order to optimize the electrical stimulation scheme such that retinal signal processing with ‘electronic photoreceptors’ remains as close to natural as possible.ApproachA multicompartmental model of a BC was implemented to simulate responses of the voltage-gated calcium channels and subsequent synaptic vesicle release under continuous and pulsatile stimuli. We compared the predicted response under various frequencies, pulse durations, and alternating gratings to the corresponding experimental measurements. In addition, electric field was computed for various electrode configurations in a 3-d finite element model to assess the stimulation selectivity via spatial confinement of the field.Main resultsThe modeled BC-mediated retinal responses were, in general, in good agreement with previously published experimental results. Kinetics of the calcium pumps and of the neurotransmitter release in ribbon synapses, which underpin the BC’s temporal filtering and rectifying functions, allow mimicking the natural BC response with high frequency pulsatile stimulation, thereby preserving features of the retinal signal processing, such as flicker fusion, adaptation to static stimuli and non-linear summation of subunits in receptive field. Selectivity of the BC stimulation while avoiding direct activation of the downstream neurons (amacrine and ganglion cells—RGCs) is improved with local return electrodes.SignificanceIf the retinal neural network is preserved to a large extent in age-related macular degeneration, selective stimulation of BCs with proper spatial and temporal modulation of the extracellular electric field may retain many features of the natural retinal signal processing and hence allow highly functional restoration of sight.

Effects of Heart Rate on the Pulsatile Flow Characteristics of a Stenotic Aortic Valve Model: An In Vitro Experimental Study

Abstract In this paper, the characteristics of pulsatile flow past a silicone-based artificial stenotic aortic valve under varied heart rates have been studied using particle image velocimetry (PIV). Pulsatile flow waveforms were generated by a closed-loop cardiovascular flow simulator. Phase-locked PIV was employed to quantify the average and turbulent flow field information. Pressure gradient waveforms were recorded to evaluate the severity of the stenosis. Results suggest that as the heart rate increases, the peak pressure gradient across the stenotic aortic valve increases significantly under the same cardiac output. Under the same cardiac output, the aortic valve area (AVA) estimated using Gorlin equation decreases as the heart rate increases, while the trend is reversed using Hakki equation estimation. PIV results suggest that the peak systolic jet velocity downstream of the valve increases as the heart rate increases, implying a longer pressure recovery distance as heart rate increases. While the turbulence at peak systole is higher under the slower heart rate, the faster heart rate contributes to higher turbulence during the late systole and early diastole phases. Based on the comparison with no-valve cases, the differences in turbulence kinetic energy (TKE) was mainly related to the dynamics of leaflets under different heart rates. Overall, the results obtained in this study demonstrate that the hemodynamics of a stenotic aortic valve is complex, and the assessment of AS could be significantly affected by the pulsating rate of the flow.

The advertisement and release call of the Bahia forest frog Macrogenioglottus alipioi (Anura: Odontophrynidae) with comments on its morphometry, from southern Bahia, northeastern Brazil

The advertisement call of Macrogenioglottus alipioi was firstly described 40 years ago from Santa Teresa municipality, Espirito Santo state, Brazil. With the advancement of digital recording and call analysis in bioacoustics, we redescribe the advertisement call of M. alipioi from a population close to its type locality, municipality of Urucuca, Bahia. Additionally, we describe the release call and provide morphometric data. The advertisement call of M. alipioi consists of a simple pulsatile structured call, which can be emitted alone or in a series of 4–9 calls. The mean call duration is 0.46 ± 0.04 s (0.35–0.55 s) and dominant frequency ranges from 344.5 to 430.7 Hz (366.2 ± 37.56 Hz). The release call of M. alipioi usually has a pulsatile spindle-shaped waveform with harmonics and sidebands in the spectrum. The mean call duration is 0.175 s ± 0.067 (0.032–0.314 s) and dominant frequency ranges from 387.60 to 559.90 Hz (420.99 Hz ± 30.63 Hz). Males (95.3 ± 5.5 mm) and females (99.6 ± 7.8 mm) do not differ in body length, although they present significant differences related to morphometric variables of the hind limbs. We provide new bioacoustical and morphometric data of M. alipioi from a population close to its type locality. This information can help future studies that aim to define the range of a species that is widely distributed in the Atlantic Forest.

Particle Residence Time in pulsatile post-stenotic flow

Particle Residence Time (PRT), a measure of a fluid element’s transit time through a region of interest, is a clear indicator of recirculation. The PRT of fluid recirculating downstream of an idealized stenosis geometry is found to vary dramatically under pulsatile flow conditions. Two-dimensional particle tracking velocimetry is used to track particles directly as they exit the stenosis geometry and are entrained into the region of recirculation immediately downstream. A Lagrangian approach permits long pathlines to be drawn, describing each particle’s motion from the instant they enter the domain. PRT along each pathline is compared here for three mean Reynolds numbers; specifically, Rem = 4800, 9600, and 14 400. The pulsatile waveforms are characterized by Strouhal numbers of 0.04, 0.08, and 0.15 and amplitude ratios of 0.50 and 0.95. As the mean Reynolds number is increased, higher fluid velocities are shown to lower PRT. However, the strength of PRT is truly revealed when highlighting the influence pulsatility has on the degree of mixing beyond the stenosis throat. Higher Strouhal numbers correlate with roll-up across the shear layer and increased PRT distribution at all Reynolds numbers in consideration. Similarly, strong temporal velocity gradients generated by a high amplitude ratio carry large volumes of fluid from the jet deep into the recirculation region, contributing to greater PRT.