Validation of a Suprasystolic Cuff System for Static and Dynamic Representation of the Central Pressure Waveform

BACKGROUND

Noninvasive pulse waveform analysis is valuable for central cardiovascular assessment, yet controversies persist over its validity in peripheral measurements. Our objective was to compare waveform features from a cuff system with suprasystolic blood pressure hold with an invasive aortic measurement.

METHODS AND RESULTS

This study analyzed data from 88 subjects undergoing concurrent aortic catheterization and brachial pulse waveform acquisition using a suprasystolic blood pressure cuff system. Oscillometric blood pressure (BP) was compared with invasive aortic systolic BP and diastolic BP. Association between cuff and catheter waveform features was performed on a set of 15 parameters inclusive of magnitudes, time intervals, pressure-time integrals, and slopes of the pulsations. The evaluation covered both static (subject-averaged values) and dynamic (breathing-induced fluctuations) behaviors. Peripheral BP values from the cuff device were higher than catheter values (systolic BP-residual, 6.5 mm Hg; diastolic BP-residual, 12.4 mm Hg). Physiological correction for pressure amplification in the arterial system improved systolic BP prediction (r2=0.83). Dynamic calibration generated noninvasive BP fluctuations that reflect those invasively measured (systolic BP Pearson R=0.73, P<0.001; diastolic BP Pearson R=0.53, P<0.001). Static and dynamic analyses revealed a set of parameters with strong associations between catheter and cuff (Pearson R>0.5, P<0.001), encompassing magnitudes, timings, and pressure-time integrals but not slope-based parameters.

CONCLUSIONS

This study demonstrated that the device and methods for peripheral waveform measurements presented here can be used for noninvasive estimation of central BP and a subset of aortic waveform features. These results serve as a benchmark for central cardiovascular assessment using suprasystolic BP cuff-based devices and contribute to preserving system dynamics in noninvasive measurements.

A Pneumatic Low-Pass Filter for High-Fidelity Cuff-Based Pulse Waveform Acquisition

Cuff-based pulse waveform acquisition (CBPWA) devices are reliable solutions for non-invasive cardiovascular diagnostics. However, poor signal resolution has limited clinical applications. This study aims to demonstrate the improved signal quality of CBPWA devices by implementing passive pneumatic low-pass filters (pLPF). Conventionally, pressure sensor output resolution is a percentage of the operating range. Therefore, measurement of small pressure changes in a large range must sacrifice signal resolution to accommodate for the large mean pressures. We design a pLPF to obtain the running mean pressure and combine it with a high-resolution differential pressure sensor for isolating the signal's pulsatile component. Thirty-one volunteers participated in a device proof-of-concept study at Caltech. Volunteers were measured at rest in the supine position on the left arm. The filtering behavior is mathematically modeled and experimentally verified, showing good agreement between measured and predicted cutoff frequencies. In the human study, the device successfully captured high-fidelity pulse waveform measurements for all volunteers: a blood pressure (BP) reading was followed by inflate-and-hold acquisition in diastolic BP (DBP), mean arterial pressure (MAP), and supra systolic BP (sSBP). The study demonstrated the reliability and high signal resolution of pLPF for CBPWA. Considering the widespread use of the brachial cuff, a system for high-resolution CBPWA motivates the clinical implementation of non-invasive pulse waveform analysis (PWA).

Multi-Modal Mobility Morphobot (M4) with appendage repurposing for locomotion plasticity enhancement

Robot designs can take many inspirations from nature, where there are many examples of highly resilient and fault-tolerant locomotion strategies to navigate complex terrains by recruiting multi-functional appendages. For example, birds such as Chukars and Hoatzins can repurpose wings for quadrupedal walking and wing-assisted incline running. These animals showcase impressive dexterity in employing the same appendages in different ways and generating multiple modes of locomotion, resulting in highly plastic locomotion traits which enable them to interact and navigate various environments and expand their habitat range. The robotic biomimicry of animals' appendage repurposing can yield mobile robots with unparalleled capabilities. Taking inspiration from animals, we have designed a robot capable of negotiating unstructured, multi-substrate environments, including land and air, by employing its components in different ways as wheels, thrusters, and legs. This robot is called the Multi-Modal Mobility Morphobot, or M4 in short. M4 can employ its multi-functional components composed of several actuator types to (1) fly, (2) roll, (3) crawl, (4) crouch, (5) balance, (6) tumble, (7) scout, and (8) loco-manipulate. M4 can traverse steep slopes of up to 45 deg. and rough terrains with large obstacles when in balancing mode. M4 possesses onboard computers and sensors and can autonomously employ its modes to negotiate an unstructured environment. We present the design of M4 and several experiments showcasing its multi-modal capabilities.

The Influence of Valve Leaflet Stiffness Variability on Aortic Wall Shear Stress

Aortic stenosis is a common cardiac condition that impacts the aorta's hemodynamics downstream of the affected valve. We sought to better understand how non-uniform stiffening of a stenotic aortic valve would affect the wall shear stress (WSS) experienced by the walls of the aorta and the residence time near the valve. Several experimental configurations were created by individually stiffening leaflets of a polymer aortic valve. These configurations were mounted inside an in vitro experimental setup. Digital particle image velocimetry (DPIV) was used to measure velocity profiles inside a model aorta. The DPIV results were used to estimate the WSS and residence time. Our analysis suggests that leaflet asymmetry greatly affects the amount of WSS by vectoring the systolic jet and stiffened leaflets have an increased residence time. This study indicates that valve leaflets with different stiffness conditions can have a more significant impact on wall shear stress than stenosis caused by the uniform increase in all three leaflets (and the subsequent increased systolic velocity) alone. This finding is promising for creating customizable (patient-specific) prosthetic heart valves tailored to individual patients.

Intrinsic Frequencies of Carotid Pressure Waveforms Predict Heart Failure Events: The Framingham Heart Study

Supplemental Digital Content is available in the text.

Intrinsic frequencies (IFs) derived from arterial waveforms are associated with cardiovascular performance, aging, and prevalent cardiovascular disease (CVD). However, prognostic value of these novel measures is unknown. We hypothesized that IFs are associated with incident CVD risk. Our sample was drawn from the Framingham Heart Study Original, Offspring, and Third Generation Cohorts and included participants free of CVD at baseline (N=4700; mean age 52 years, 55% women). We extracted 2 dominant frequencies directly from a series of carotid pressure waves: the IF of the coupled heart and vascular system during systole (ω₁) and the IF of the decoupled vasculature during diastole (ω₂). Total frequency variation (Δω) was defined as the difference between ω₁ and ω₂. We used Cox proportional hazards regression models to relate IFs to incident CVD events during a mean follow-up of 10.6 years. In multivariable models adjusted for CVD risk factors, higher ω₁ (hazard ratio [HR], 1.14 [95% CI], 1.03–1.26]; P=0.01) and Δω (HR, 1.16 [95% CI, 1.03–1.30]; P=0.02) but lower ω₂ (HR, 0.87 [95% CI, 0.77–0.99]; P=0.03) were associated with higher risk for incident composite CVD events. In similarly adjusted models, higher ω₁ (HR, 1.23 [95% CI, 1.07–1.42]; P=0.004) and Δω (HR, 1.26 [95% CI, 1.05–1.50]; P=0.01) but lower ω₂ (HR, 0.81 [95% CI, 0.66–0.99]; P=0.04) were associated with higher risk for incident heart failure. IFs were not significantly associated with incident myocardial infarction or stroke. Novel IFs may represent valuable markers of heart failure risk in the community.

Thermal Effects on Fluid Mixing in the Eye

Age-related macular degeneration (AMD) is the leading cause of central vision loss in the developed world. Wet AMD can be managed through serial intravitreal injections of anti-vascular endothelial growth factor (anti-VEGF) agents. However, sometimes the treatment is ineffective. Given that the half-life of the drug is limited, inefficient mixing of the injected drug in the vitreous chamber of the eye may contribute to the ineffectiveness. Here, we introduce thermal heating as a means of enhancing the mixing-process in the vitreous chamber and investigate parameters that potentially influence its effectiveness. Our in vitro studies reveal the importance of the heating location on the eye. A significant increase in the mixing and delivery of drugs to the targeted area (the macula) could be achieved by placing heating pads to induce a current, against gravity, in the vitreous. The presented results can potentially help in the development of a better strategy for intravitreal injection, subsequently improving the quality of patient care.

A dynamical model of oncotripsy by mechanical cell fatigue: selective cancer cell ablation by low-intensity pulsed ultrasound

The method of oncotripsy, first proposed in Heyden & Ortiz (Heyden & Ortiz 2016 J. Mech. Phys. Solids 92, 164-175 (doi:10.1016/j.jmps.2016.04.016)), exploits aberrations in the material properties and morphology of cancerous cells in order to ablate them selectively by means of tuned low-intensity pulsed ultrasound. We propose the dynamical model of oncotripsy that follows as an application of cell dynamics, statistical mechanical theory of network elasticity and 'birth-death' kinetics to describe the processes of damage and repair of the cytoskeleton. We also develop a reduced dynamical model that approximates the three-dimensional dynamics of the cell and facilitates parametric studies, including sensitivity analysis and process optimization. We show that the dynamical model predicts-and provides a conceptual basis for understanding-the oncotripsy effect and other trends in the data of Mittelstein et al. (Mittelstein et al. 2019 Appl. Phys. Lett. 116, 013701 (doi:10.1063/1.5128627)), for cells in suspension, including the dependence of cell-death curves on cell and process parameters.

A dynamical model of oncotripsy by mechanical cell fatigue: selective cancer cell ablation by low-intensity pulsed ultrasound

The method of oncotripsy, first proposed in Heyden & Ortiz (Heyden & Ortiz 2016 J. Mech. Phys. Solids 92, 164-175 (doi:10.1016/j.jmps.2016.04.016)), exploits aberrations in the material properties and morphology of cancerous cells in order to ablate them selectively by means of tuned low-intensity pulsed ultrasound. We propose the dynamical model of oncotripsy that follows as an application of cell dynamics, statistical mechanical theory of network elasticity and 'birth-death' kinetics to describe the processes of damage and repair of the cytoskeleton. We also develop a reduced dynamical model that approximates the three-dimensional dynamics of the cell and facilitates parametric studies, including sensitivity analysis and process optimization. We show that the dynamical model predicts-and provides a conceptual basis for understanding-the oncotripsy effect and other trends in the data of Mittelstein et al. (Mittelstein et al. 2019 Appl. Phys. Lett. 116, 013701 (doi:10.1063/1.5128627)), for cells in suspension, including the dependence of cell-death curves on cell and process parameters.

P4627Presentation, management, and outcomes of STEMI in Egypt: results from the European Society of Cardiology registry on ST elevation myocardial infarction

Background

Apart from few small single-center studies there are limited data about STEMI patients in Egypt.

Patients and methods

The European Society of Cardiology (ESC) Registry on ST Elevation Myocardial Infarction is a prospective, multicenter and observational registry. Nineteen Egyptian centers (with and without PCI facilities) participated in this registry with 1356 patients who were compared to 7420 patients from other ESC countries. Patient recruitment started from March 2016 to February 2018.

Aims of the study

The aims of this study was to describe the characteristics of patients with STEMI, to assess STEMI management patterns, to evaluate in-hospital patient outcome and to compare Egyptian patients with other ESC countries.

Results

Compared to other ESC countries, Egyptian patients were younger (mean age 55.4±11.3 vs. 62.9±12.4; P<0.001 and 4.3% vs. 19.4%% were ≥75 years old; P<0.001) with fewer females (18.4% vs. 25.6%; P<0.001). Fewer Egyptian patients had history of myocardial infarction (7.9% vs. 12.6%; P<0.001), chronic heart failure (2.0% vs. 11.5%; P<0.001), but Egyptians had higher prevalence of current smoking (59.0% vs. 42.8% p<0.001), Diabetes mellitus (40.7% vs. 21.9%, p<0.001). Egypt had longer median time between symptoms onset and first medical contact: 120.0 (60.0; 240.0) vs. 100.0 (50.0; 240.0) p<0.001. Self-presentation rather than EMS presentation was the mode of admission in 86.0% in Egypt vs. 25.8% in EU countries (p<0.001). On qualifying ECG, anterior STEMI was in 57.0% in Egypt vs. 45.9% in other countries (p<0.001). Initial reperfusion therapy was 49.1%, 43.0% and 7.2% for Primary PCI, thrombolytic therapy and no reperfusion in Egypt vs. 85.4%, 7.2% and 7.8% for EU countries, respectively. Thrombolysis when given was in the CCU/ICU rather than EMS or ER in 97.2% in Egypt vs. 43.7% in other countries. Compared to thrombolytic therapy, patients who were treated with primary PCI had less Cerebrovascular accident (0.75% vs. 1.3%; P<0.001), killip Class IV (3.0% vs. 5.9%; P<0.001) or AF (2.5% vs. 3.6%; P 0.008). In hospital mortality was 4.6% in Egypt vs. 3.5% in other countries P 0.040 and was 18.7% in No reperfusion vs. 2.1% in Primary PCI vs. 4.9% in Thrombolysis (P<0.001) among Egyptians. Patients were discharged on Aspirin in 98.6%, Clopidogrel in 91.0%, Ticagrelor in 7.1%, DAPT in 97.6%, Beta Blockers in 82.8%, ACE inhibitors in 84.7%, MRAs in 10.0%, and Statins in 99.7%.

Conclusion

Egyptian STEMI patients were younger, more frequently obese, smokers and diabetics had significantly longer delay between symptoms onset and first medical contact with more self-presentation rather than the recommended EMS presentation. Primary PCI was offered to only half of the patients. In hospital mortality was significantly higher and was highest among non-reperfused patients. National plans for primary and secondary prevention are urgently needed in Egypt.

Acknowledgement/Funding

This registry was funded by the ESC. The Egyptian Society of Cardiology was given a grant of €12000 to help with the implementation of this national E

Mobile robot position estimation using Euler-Maruyama algorithm

Mobile robots became very important and more familiar in commercial, industrial and military applications. In many unmanned vehicle applications, sensors and control systems are mounted on mobile robots to identify the surrounding environment for obstacle avoidance. This work aims to estimate the mobile robot location to compensate the time delay problem which appears in teleoperation. According to the stochastic nature of the mobile robot teleoperation, the kinematics equation of mobile robot will be converted into stochastic differential equations (SDEs). Euler-Maruyama algorithm used as it is one of the most popular numerical algorithms to approximate SDEs solution. A simulated results for the solution is produced which seem to be good comparing with mobile robot ideal path simulation.

Experimental trajectory optimization of a flapping fin propulsor using an evolutionary strategy

The experimental optimization of bio-inspired flapping fin trajectories are demonstrated for potential applications as a side or a rear propulsor of an autonomous underwater vehicle. The trajectories are scored based upon their difference from a force set-point and upon their efficiency and are parameterized by 10 variables inspired by fish swimming. The flapping fin is a generic rectangular rigid flat plate with a tapered edge. Optimization occurs as follows. First, a generation of trajectories is created. Second, the trajectories are executed by a spherical parallel manipulator, during which the forces are acquired. Third, the trajectories are scored and a new generation of trajectories is created using the covariance matrix adaptive evolutionary strategy. This loop repeats ad-infinitum until the search converges. Within the first set of searches, two trajectories for optimal side-force generation are found, one is fully three-dimensional while the other is artificially constrained to a line, and one trajectory for optimal thrust generation is found. All searches demonstrate good convergence properties and match the desired force set-point almost immediately. Additional generations primarily improve the efficiency of the maneuver. The two trajectories for generating side-force have a similar efficiency, which shows potential in utilizing a simple trajectory limited to a line. Comparison between the trajectories for generating side-force and thrust suggests that side-force generation is more efficient around Re ~1000, based on the average tip velocity and length of the fin. The second set of searches explores the behavior of the optimal trajectories for generating side-force at a lower force set-point and the third set of searches explores the sensitivity and repeatability of the optimization.

Asymmetry in the jet opening: underwater jet vectoring mechanism by dragonfly larvae

Aquatic Anisopteran dragonfly larvae achieve respiration and propulsion by repetitive water jets flowing through their anal openings. Previous studies have shown that the tri-leaflet anal valves modulate the emerging jet by varying the opening size. We discovered that the valves are also capable of controlling the opening asymmetry by independent retraction of a leaflet. This study shows the effects of their valve asymmetry control on the respiratory and propulsive flows. Furthermore, the effects of size variation are re-evaluated using fluid momentum and power equations. Synchronized dual cameras recorded the valve movement and the flow generated by Aeshnidae sp. During the respiratory jetting, retraction of a single leaflet positions the opening in an off-centred locale, from which diagonally deflected jets emerge. The resulting flow field, together with the opening size modulation, implicates a reduction in the reinhalation of the exhaled jet and partial powering of the refilling process. Instead, during the propulsive jetting, concurrent partial retraction of the three leaflets results in the centred opening. The resulting jet flows straight, which has an implication for lowering form drag. Additionally, the propulsive aperture size control suggests improved thrust production. Our study highlights the significant influence that an asymmetrically positioned jet opening can have on biological jet flow. The findings inspire a new mechanism for jet vectoring that may prove useful for application in the broader engineering field.

Experimental Investigation of the Effect of Non-Newtonian Behavior of Blood Flow in the Fontan Circulation

The Fontan procedure for univentricular heart defects creates a unique circulation where all pulmonary blood flow is passively supplied directly from systemic veins. Computational simulations, aimed at optimizing the surgery, have assumed blood to be a Newtonian fluid without evaluating the potential error introduced by this assumption. We compared flow behavior between a non-Newtonian blood analog (0.04% xanthan gum) and a control Newtonian fluid (45% glycerol) in a simplified model of the Fontan circulation. Particle image velocimetry was used to examine flow behavior at two different cardiac outputs and two caval blood flow distributions. Pressure and flow rates were measured at each inlet and outlet. Velocity, shear strain, and shear stress maps were derived from velocity data. Power loss was calculated from pressure, flow, and velocity data. Power loss was increased in all test conditions with xanthan gum vs. glycerol (mean 10±2.9% vs. 5.6±1.3%, p=0.032). Pulmonary blood flow distribution differed in all conditions, more so at low cardiac output. Caval blood flow mixing patterns and shear stress were also qualitatively different between the solutions in all conditions. We conclude that assuming blood to be a Newtonian fluid introduces considerable error into simulations of the Fontan circulation, where low-shear flow predominates.

On the role of tip curvature on flapping plates

During the flapping motion of a fish's tail, the caudal fin exhibits antero-posterior bending and dorso-ventral bending, the latter of which is referred to as chord-wise bending herein. The impact of chord-wise tip curvature on the hydrodynamic forces for flapping plates is investigated to explore potential mechanisms to improve the maneuverability or the performance of autonomous underwater vehicles. First, actuated chord-wise tip curvature is explored. Comparison of rigid curved geometries to a rigid flat plate as a baseline suggests that an increased curvature decreases the generated forces. An actuated plate with a dynamic tip curvature is created to illustrate a modulation of this decrease in forces. Second, the impact of curvature is isolated using curved plates with an identical planform area. Comparison of rigid curved geometries as a baseline corroborates the result that an increased curvature decreases the generated forces, with the exception that presenting a concave geometry into the flow increases the thrust and the efficiency. A passively-actuated plate is designed to capitalize on this effect by presenting a concave geometry into the flow throughout the cycle. The dynamically and passively actuated plates show potential to improve the maneuverability and the efficiency of autonomous underwater vehicles, respectively.

Shielding calculation and criticality safety analysis of spent fuel transportation cask in research reactors

In this study, shielding calculation and criticality safety analysis were carried out for general material testing reactor (MTR) research reactors interim storage and relevant transportation cask. During these processes, three major terms were considered: source term, shielding, and criticality calculations. The Monte Carlo transport code MCNP5 was used for shielding calculation and criticality safety analysis and ORIGEN2.1 code for source term calculation. According to the results obtained, a cylindrical cask with body, top, and bottom thicknesses of 18, 13, and 13 cm, respectively, was accepted as the dual-purpose cask. Furthermore, it is shown that the total dose rates are below the normal transport criteria that meet the standards specified.

Analyzing the effect of geometric factors on designing neutron radiography system

Neutron radiography is one of the main applications of research reactors. It is a powerful tool to conduct nondestructive testing of materials. The parameters that affect the quality of a radiographic image must be considered during the design of a neutron radiography system. Hence, this study aims to investigate the effect of geometric factors on the quality of the neutron radiography system. The results show that the performance of the mentioned system can be increased by regulating the geometric factors.

Intrinsic Frequency and the Single Wave Biopsy: Implications for Insulin Resistance

Insulin resistance is the hallmark of classical type II diabetes. In addition, insulin resistance plays a central role in metabolic syndrome, which astonishingly affects 1 out of 3 adults in North America. The insulin resistance state can precede the manifestation of diabetes and hypertension by years. Insulin resistance is correlated with a low-grade inflammatory condition, thought to be induced by obesity as well as other conditions. Currently, the methods to measure and monitor insulin resistance, such as the homeostatic model assessment and the euglycemic insulin clamp, can be impractical, expensive, and invasive. Abundant evidence exists that relates increased pulse pressure, pulse wave velocity (PWV), and vascular dysfunction with insulin resistance. We introduce a potential method of assessing insulin resistance that relies on a novel signal-processing algorithm, the intrinsic frequency method (IFM). The method requires a single pulse pressure wave, thus the term " wave biopsy."

Intrinsic frequency for a systems approach to haemodynamic waveform analysis with clinical applications

The reductionist approach has dominated the fields of biology and medicine for nearly a century. Here, we present a systems science approach to the analysis of physiological waveforms in the context of a specific case, cardiovascular physiology. Our goal in this study is to introduce a methodology that allows for novel insight into cardiovascular physiology and to show proof of concept for a new index for the evaluation of the cardiovascular system through pressure wave analysis. This methodology uses a modified version of sparse time-frequency representation (STFR) to extract two dominant frequencies we refer to as intrinsic frequencies (IFs; ω1 and ω2). The IFs are the dominant frequencies of the instantaneous frequency of the coupled heart + aorta system before the closure of the aortic valve and the decoupled aorta after valve closure. In this study, we extract the IFs from a series of aortic pressure waves obtained from both clinical data and a computational model. Our results demonstrate that at the heart rate at which the left ventricular pulsatile workload is minimized the two IFs are equal (ω1 = ω2). Extracted IFs from clinical data indicate that at young ages the total frequency variation (Δω = ω1 - ω2) is close to zero and that Δω increases with age or disease (e.g. heart failure and hypertension). While the focus of this paper is the cardiovascular system, this approach can easily be extended to other physiological systems or any biological signal.

Abstract 355: Calculating Pulse Wave Velocity from a Single Pressure Waveform Using the Intrinsic Frequency Method

INTRODUCTION: Increased aortic stiffness is correlated with many clinically adverse cardiovascular outcomes. The “gold standard” quantitative index for arterial stiffness is the pulse wave velocity (PWV). We have developed a new method called the Intrinsic Frequency ( IF ), which views the arterial pressure waveform as a piecewise combination of two coupled systems, the heart and arterial system which are decoupled upon closure of the aortic valve. Each of these dynamical systems has an inherent frequency of operation (ω 1 and ω 2 ) which gives information about LV function (ω 1 ) as well as arterial dynamics (ω 2 ).

METHODS: IF methodology is based on Sparse Time-Frequency Representation method. It uses an effective L 2 -minimization to extract the second intrinsic frequency (ω 2 ) from an aortic pressure waveform. To examine the clinical relevance of this method, IF was applied to aortic pressure waveforms taken from published works. These aortic waveforms were selected from a healthy population free of any cardiovascular diseases (CVD).

RESULTS: Our results show that ω 2 represents information about the arterial system and that these measurements are highly correlated with PWV ( r=0.9 ).

CONCLUSION: These results show ω 2 can potentially be used to evaluate aortic rigidity and calculate aortic PWV from one pressure waveform. Increased aortic rigidity is a common feature in normal aging and is accelerated in many CVDs including diabetes. One unique advantage of the method is that only a single measurement of the pressure waveform is required to extract the result. Therefore, ω 2 may be employed as a clinically effective noninvasive assessment of cardiovascular health.

Physicochemical characteristics and droplet impact dynamics of superhydrophobic carbon nanotube arrays

The physicochemical and droplet impact dynamics of superhydrophobic carbon nanotube arrays are investigated. These superhydrophobic arrays are fabricated simply by exposing the as-grown carbon nanotube arrays to a vacuum annealing treatment at a moderate temperature. This treatment, which allows a significant removal of oxygen adsorbates, leads to a dramatic change in wettability of the arrays, from mildly hydrophobic to superhydrophobic. Such change in wettability is also accompanied by a substantial change in surface charge and electrochemical properties. Here, the droplet impact dynamics are characterized in terms of critical Weber number, coefficient of restitution, spreading factor, and contact time. Based on these characteristics, it is found that superhydrophobic carbon nanotube arrays are among the best water-repellent surfaces ever reported. The results presented herein may pave a way for the utilization of superhydrophobic carbon nanotube arrays in numerous industrial and practical applications, including inkjet printing, direct injection engines, steam turbines, and microelectronic fabrication.

Carbon nanotube-based substrates for modulation of human pluripotent stem cell fate

We investigated the biological response of human pluripotent stem cells (hPSCs) cultured on a carbon nanotube (CNT) array-based substrate with the long term goal to direct hPSC germ layer specification for a wide variety of tissue engineering applications. CNT arrays were fabricated using a chemical vapor deposition system allowing for control over surface roughness and mechanical stiffness. Our results demonstrated that hPSCs readily attach to hydrophilized and extracellular matrix coated CNT arrays. hPSCs cultured as colonies in conditions supporting self-renewal demonstrated the morphology and marker expression of undifferentiated hPSCs. Conditions inducing spontaneous differentiation lead to hPSC commitment to all three embryonic germ layers as assessed by immunostaining and RT-PCR analysis. Strikingly, the physical characteristics of CNT arrays favored mesodermal specification of hPSCs. This is contradictory to the behavior of hPSCs on traditional tissue culture plastic which promotes the development of ectoderm. Altogether, these results demonstrate the potential of CNT arrays to be used in the generation of new platforms that allow for precise control of hPSC differentiation by tuning the characteristics of their physical microenvironment.

A bio-inspired approach for the reduction of left ventricular workload

Previous studies have demonstrated the existence of optimization criteria in the design and development of mammalians cardiovascular systems. Similarities in mammalian arterial wave reflection suggest there are certain design criteria for the optimization of arterial wave dynamics. Inspired by these natural optimization criteria, we investigated the feasibility of optimizing the aortic waves by modifying wave reflection sites. A hydraulic model that has physical and dynamical properties similar to a human aorta and left ventricle was used for a series of in-vitro experiments. The results indicate that placing an artificial reflection site (a ring) at a specific location along the aorta may create a constructive wave dynamic that could reduce LV pulsatile workload. This simple bio-inspired approach may have important implications for the future of treatment strategies for diseased aorta.

Pathological wave dynamics: a postulate for sudden cardiac death in athletes

Sudden death (SD) in young athletes is a shocking and disturbing event with significant societal impact. Previous studies have demonstrated that sudden cardiac death (SCD) is the leading medical cause of SD in athletes. Various structural and pathological cardiovascular abnormalities have identified as the underlying causes of SCD in young athletes. However, there have been reported cases of SCD in athletes with no structural or pathological cardiovascular disorders. Our proposed hypothesis in this article is that abnormalities in aortic wave dynamics and coronary wave dynamics may be responsible for SCD in these athletes. These abnormal waves-pathological waves-can act as a trigger toward cardiac death in the presence of cardiovascular diseases. These waves may initiate SCD in the absence of apparent cardiovascular abnormalities. In summary, when the aortic and coronary wave dynamics are abnormal, the myocardial oxygen demand can exceed the oxygen delivery during exercise, hence creating acute ischemia which leads to death. It is explained in this article how increased oxygen demand may be the result of pathological aortic waves while reduced oxygen delivery is mainly due to pathological coronary waves. Additionally, our pathological wave hypothesis is able to provide a plausible explanation for Commotio Cordis.

In-vitro investigation of a potential wave pumping effect in human aorta

An impedance pump - also known as Liebau pump - is a simple valveless pump that operates based on the principles of wave propagation and reflection. It has been shown in embryonic zebrafish that a similar mechanism is responsible for the pumping action in the embryonic heart during the early stages before valve formation. Recent studies suggest that the cardiovascular system is designed to take advantage of wave propagation and reflection phenomena in the arterial network. In this study we report the results of an in-vitro study that examines the hypothesis that the adult human aorta acts as a passive pump based on Liebau effect. A hydraulic model with different compliant models of an artificial aorta was used for a series of in-vitro experiments. Our result indicates that wave propagation and reflection can result in a pumping mechanism in a compliant aorta.

Feasibility Study of Carbon Nanotube Microneedles for Rapid Transdermal Drug Delivery

We introduce a new approach for fabricating hollow microneedles using vertically-aligned carbon nanotubes (VA-CNTs) for rapid transdermal drug delivery. Here, we discuss the fabrication of the microneedles emphasizing the overall simplicity and flexibility of the method to allow for potential industrial application. By capitalizing on the nanoporosity of the CNT bundles, uncured polymer can be wicked into the needles ultimately creating a high strength composite of aligned nanotubes and polymer. Flow through the microneedles as well as in vitro penetration of the microneedles into swine skin is demonstrated. Furthermore, we present a trade study comparing the difficulty and complexity of the fabrication process of our CNT-polymer microneedles with other standard microneedle fabrication approaches.

Dry oxidation and vacuum annealing treatments for tuning the wetting properties of carbon nanotube arrays

In this article, we describe a simple method to reversibly tune the wetting properties of vertically aligned carbon nanotube (CNT) arrays. Here, CNT arrays are defined as densely packed multi-walled carbon nanotubes oriented perpendicular to the growth substrate as a result of a growth process by the standard thermal chemical vapor deposition (CVD) technique.(1,2) These CNT arrays are then exposed to vacuum annealing treatment to make them more hydrophobic or to dry oxidation treatment to render them more hydrophilic. The hydrophobic CNT arrays can be turned hydrophilic by exposing them to dry oxidation treatment, while the hydrophilic CNT arrays can be turned hydrophobic by exposing them to vacuum annealing treatment. Using a combination of both treatments, CNT arrays can be repeatedly switched between hydrophilic and hydrophobic.(2) Therefore, such combination show a very high potential in many industrial and consumer applications, including drug delivery system and high power density supercapacitors.(3-5) The key to vary the wettability of CNT arrays is to control the surface concentration of oxygen adsorbates. Basically oxygen adsorbates can be introduced by exposing the CNT arrays to any oxidation treatment. Here we use dry oxidation treatments, such as oxygen plasma and UV/ozone, to functionalize the surface of CNT with oxygenated functional groups. These oxygenated functional groups allow hydrogen bond between the surface of CNT and water molecules to form, rendering the CNT hydrophilic. To turn them hydrophobic, adsorbed oxygen must be removed from the surface of CNT. Here we employ vacuum annealing treatment to induce oxygen desorption process. CNT arrays with extremely low surface concentration of oxygen adsorbates exhibit a superhydrophobic behavior.

The investigation of effects of blood exchange transfusion on selenium in newborn infants by instrumental neutron activation analysis method

OBJECTIVE

The evidence for the effects of blood exchange transfusion on selenium (Se) in newborn infants is unknown. This study was conducted to determine the possible effects of blood exchange transfusion on Se by comparing the Se blood concentrations before and after exchange transfusion in jaundiced neonates.

METHODS

A total of 30 jaundiced term neonates who underwent blood exchange transfusion (EXT) for first time because of idiopathic unconjugated hyperbilirubinemia, were recruited. The Se level of 30 blood bank donors' samples used for EXT were measured and 30 pairs of uncontaminated umbilical cord blood samples were investigated for Se before and after exchange transfusion. The samples were analyzed by instrumental neutron activation analysis method. Serum bilirubin concentrations were measured by venous blood samples before EXT.

FINDINGS

The average of Se concentration before EXT was higher than that after EXT (629.78±283.82 SD ppb versus 454.83±213.75 SD ppb) (P<0.05). There was significant correlation between the blood concentration of Se before and after EXT and also between the blood level of Se before EXT and total serum bilirubin level (P<0.05). There was no significant correlation between the blood concentration of Se before EXT and babies' gender and weight (P>0.05). The average Se level in samples obtained from transfused blood products was 507.90±223.56 SD ppb.

CONCLUSION

Blood exchange transfusion caused a 28% decrease of the blood Se level because the blood donors had lower blood Se levels than the newborns. Furthermore, there was a significant correlation between the blood level of Se before EXT and the total serum bilirubin level.

Characteristics of vortex formation and thrust performance in drag-based paddling propulsion

Several characteristics of drag-based paddling propulsion are studied with a simple mechanical model and a measurement technique for mapping three-dimensional flow fields. In drag-based propulsion, the temporal change of the vortex strength is an important parameter in the relationship between vortex formation and thrust generation. Our results indicate that spanwise flow behind the paddling propulsor significantly affects tip vortex development and thrust generation. The distribution of spanwise flow is dependent on the propulsor shape and the Reynolds number. A delta-shaped propulsor generates strong spanwise flow compared with a rectangular propulsor. For the low Reynolds number case, spanwise flow is not as strong as that for the high Reynolds number case. Without sacrificing total impulse, the flexible propulsor can smooth out thrust peaks during sudden stroke motions, which is favorable for avoiding structural failures and stabilizing body motion. We also explored the role of stopping vortex shedding in efficient thrust generation by determining the relationship between stroke angles and total impulses generated by paddling propulsors.

Aortic wave dynamics and its influence on left ventricular workload

The pumping mechanism of the heart is pulsatile, so the heart generates pulsatile flow that enters into the compliant aorta in the form of pressure and flow waves. We hypothesized that there exists a specific heart rate at which the external left ventricular (LV) power is minimized. To test this hypothesis, we used a computational model to explore the effects of heart rate (HR) and aortic rigidity on left ventricular (LV) power requirement. While both mean and pulsatile parts of the pressure play an important role in LV power requirement elevation, at higher rigidities the effect of pulsatility becomes more dominant. For any given aortic rigidity, there exists an optimum HR that minimizes the LV power requirement at a given cardiac output. The optimum HR shifts to higher values as the aorta becomes more rigid. To conclude, there is an optimum condition for aortic waves that minimizes the LV pulsatile load and consequently the total LV workload.

Reversible tuning of the wettability of carbon nanotube arrays: the effect of ultraviolet/ozone and vacuum pyrolysis treatments

Among diverse types of synthetic materials, arrays of vertically aligned carbon nanotubes have attracted the most attention, mainly because of their exceptional mechanical, electrical, optical, and thermal properties. However, their wetting properties are yet to be understood. In this present study, oxygenated surface functional groups have been identified as a vital factor in controlling the wetting properties of carbon nanotube arrays. The results presented herein indeed show that a combination of ultraviolet/ozone and vacuum pyrolysis treatments can be used to vary the surface concentration of these functional groups such that the carbon nanotube array can be repeatedly switched between hydrophilic and hydrophobic.

Low pulse pressure with high pulsatile external left ventricular power: influence of aortic waves

Elevated pulse pressure (pp) is considered to be a risk factor for adverse cardiovascular events since it is directly related to an elevated myocardial workload. Information about both pressure and flow wave must be provided to assess hemodynamic complexity and true level of external left ventricular power (ELVP). pp value as a single feature of aortic waves cannot identify true level of ELVP. However, it is generally presumed that ELVP (and consequently LV workload) is positively correlated with pp. This study examined this positive correlation. The aim of this study was to test the hypothesis that aortic wave dynamics can create destructive hemodynamic conditions that increase the ELVP even though pp appears to be normal. To test this hypothesis, a computational model of the aorta with physiological properties was used. A Finite Element Method with fluid-structure interaction was employed to solve the equations of the solid and fluid. The aortic wall was assumed to be elastic and isotropic. The blood was assumed to be an incompressible Newtonian fluid. Simulations were performed for various heart rates (HR) and different aortic compliances while keeping the shape of the inlet flow and peripheral resistance constant. As expected, in most of the cases studied here, higher pp was associated with higher LV power demand. However, for a given cardiac output, mean pressure, and location of total reflection site, we have found cases where the above-mentioned trend does not hold. Our results suggest that using pp as a single index can result in an underestimation of the LV power demand under certain conditions related to the altered wave dynamics. Hence, in hypertensive patients, a full analysis of aortic wave dynamics is essential for the prevention and management of left ventricular hypertrophy (LVH) and congestive heart failure.

A physiologically relevant, simple outflow boundary model for truncated vasculature

A realistic outflow boundary condition model for pulsatile flow in a compliant vessel is studied by taking into account physiological effects: compliance, resistance, and wave reflection of the downstream vasculature. The new model extends the computational domain with an elastic tube terminated in a rigid contraction. The contraction ratio, the length, and elasticity of the terminal tube can be adjusted to represent effects of the truncated vasculature. Using the wave intensity analysis method, we apply the model to the test cases of a straight vessel and the aorta and find good agreement with the physiological characteristics of blood flow and pressure. The model is suitable for cardiac transient (non-periodic) events and easily employed using so-called black box software.

Analytical method to measure three-dimensional strain patterns in the left ventricle from single slice displacement data

BACKGROUND

Displacement encoded Cardiovascular MR (CMR) can provide high spatial resolution measurements of three-dimensional (3D) Lagrangian displacement. Spatial gradients of the Lagrangian displacement field are used to measure regional myocardial strain. In general, adjacent parallel slices are needed in order to calculate the spatial gradient in the through-slice direction. This necessitates the acquisition of additional data and prolongs the scan time. The goal of this study is to define an analytic solution that supports the reconstruction of the out-of-plane components of the Lagrangian strain tensor in addition to the in-plane components from a single-slice displacement CMR dataset with high spatio-temporal resolution. The technique assumes incompressibility of the myocardium as a physical constraint.

RESULTS

The feasibility of the method is demonstrated in a healthy human subject and the results are compared to those of other studies. The proposed method was validated with simulated data and strain estimates from experimentally measured DENSE data, which were compared to the strain calculation from a conventional two-slice acquisition.

CONCLUSION

This analytical method reduces the need to acquire data from adjacent slices when calculating regional Lagrangian strains and can effectively reduce the long scan time by a factor of two.