Fachartikel
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2024
Cerebrospinal fluid pressure dynamics across the intra- and postoperative setting: Retrospective study of a spine surgery cohort
Journal of Clinical Neuroscience, 128, 110803 (2024). doi: 10.1016/j.jocn.2024.110803Timely and sufficient decompression are critical objectives in degenerative cervical myelopathy (DCM) and spinal cord injury (SCI). We previously investigated intraoperative cerebrospinal fluid pressure (CSFP) for determining surgical outcomes. However, confounding factors during the intra- and postoperative setting need consideration. These are... more -
Influence of age on the relation between body position and noninvasively acquired intracranial pulse waves
Sci Rep, 14, 5493 (2024). doi: 10.1038/s41598-024-55860-6The capacitive measurement of the head's dielectric properties has been recently proposed as a noninvasive method for deriving surrogates of craniospinal compliance (CC), a parameter used in the evaluation of space-occupying neurological disorders. With the higher prevalence of such disorders in the older compared to the younger population, data... more -
Assessment of liver function by gadoxetic acid avidity in MRI in a model of rapid liver regeneration in rats
HPB, 26(4), 521 - 529 (2024). doi: 10.1016/j.hpb.2023.12.007Background : This animal study investigates the hypothesis of an immature liver growth following ALPPS (associating liver partition and portal vein ligation for staged hepatectomy) by measuring liver volume and function using gadoxetic acid avidity in magnetic resonance imaging (MRI) in models of ALPPS, major liver resection (LR) and portal... more -
Incorporating unresolved stresses in blood damage modeling: Energy dissipation more accurate than Reynolds stress formulation
IEEE Transactions on Biomedical Engineering, 71(2), 563 - 573 (2024). doi: 10.1109/TBME.2023.3309338Objective : Reynolds Averaged Navier Stokes (RANS) models are often used as the basis for modeling blood damage in turbulent flows. To predict blood damage by turbulence stresses that are not resolved in RANS, a stress formulation that represents the corresponding scales is required. Here, we compare two commonly employed stress formulations: a... more -
Current understanding of the anatomy, physiology, and magnetic resonance imaging of neurofluids: Update from the 2022 ISMRM imaging neurofluids study group workshop in Rome
Journal of Magnetic Resonance Imaging , 59(2), 431 - 449 (2024). doi: 10.1002/jmri.28759Neurofluids is a term introduced to define all fluids in the brain and spine such as blood, cerebrospinal fluid, and interstitial fluid. Neuroscientists in the past millennium have steadily identified the several different fluid environments in the brain and spine that interact in a synchronized harmonious manner to assure a healthy... more -
2023
Queckenstedt’s test repurposed for the quantitative assessment of the cerebrospinal fluid pulsatility curve
Acta Neurochirurgica, 165(6), 1533 - 1543 (2023). doi: 10.1007/s00701-023-05583-wPurpose : Before the era of spinal imaging, presence of a spinal canal block was tested through gross changes in cerebrospinal fluid pressure (CSFP) provoked by manual compression of the jugular veins (referred to as Queckenstedt's test; QT). Beyond these provoked gross changes, cardiac-driven CSFP peak-to-valley amplitudes (CSFPp) can be... more -
Terabyte-scale supervised 3D training and benchmarking dataset of the mouse kidney
Scientific Data, 10, 510 (2023). doi: 10.1038/s41597-023-02407-5The performance of machine learning algorithms, when used for segmenting 3D biomedical images, does not reach the level expected based on results achieved with 2D photos. This may be explained by the comparative lack of high-volume, high-quality training datasets, which require state-of-the-art imaging facilities, domain experts for annotation... more -
Radiological feature heterogeneity supports etiological diversity among patient groups in Meniere’s disease
Scientific Reports, 13(1), 10303 (2023). doi: 10.1038/s41598-023-36479-5We aimed to determine the prevalence of radiological temporal bone features that in previous studies showed only a weak or an inconsistent association with the clinical diagnosis of Meniere's disease (MD), in two groups of MD patients (n = 71) with previously established distinct endolymphatic sac pathologies; i.e. the group MD-dg (ES... more -
Assessment of extracranial carotid artery disease using digital twins – A pilot study
NeuroImage: Clinical, 38, 103435 (2023). doi: 10.1016/j.nicl.2023.103435To improve risk stratification in extracranial internal carotid artery disease (CAD), patients who would benefit maximally from revascularization must be identified. In cardiology, the fractional flow reserve (FFR) has become a reference standard for evaluating the functional severity of coronary artery stenosis, and noninvasive surrogates... more -
Evolution of hypoxia and hypoxia-inducible factor asparaginyl hydroxylase (FIH) regulation in chronic kidney disease
Nephrology Dialysis Transplantation, 38(10), 2288 - 2288 (2023). doi: 10.1093/ndt/gfad075The roles of hypoxia and hypoxia inducible factor (HIF) during chronic kidney disease (CKD) are much debated. Interventional studies with HIF-α activation in rodents yielded contradictory results. The HIF pathway is regulated by prolyl and asparaginyl hydroxylases; while prolyl hydroxylase inhibition is a well-known method to stabilize HIF-α,... more -
Cerebrospinal fluid pressure dynamics as a bedside test in traumatic spinal cord injury to assess surgical spinal cord decompression: safety, feasibility, and proof-of-concept
Neurorehabil Neural Repair, 37(4), 171 - 182 (2023). doi: 10.1177/15459683231159662Background : Sufficient and timely spinal cord decompression is a critical surgical objective for neurological recovery in spinal cord injury (SCI). Residual cord compression may be associated with disturbed cerebrospinal fluid pressure (CSFP) dynamics. Objectives : This study aims to assess whether intrathecal CSFP dynamics in SCI... more -
Large-scale morphometry of the subarachnoid space of the optic nerve
Fluids and Barriers of the CNS, 20, 21 (2023). doi: 10.1186/s12987-023-00423-6Background : The meninges, formed by dura, arachnoid and pia mater, cover the central nervous system and provide important barrier functions. Located between arachnoid and pia mater, the cerebrospinal fluid (CSF)-filled subarachnoid space (SAS) features a variety of trabeculae, septae and pillars. Like the arachnoid and the pia mater, these... more -
The effect of body position change on noninvasively acquired intracranial pulse waves
Physiological Measurement, 44, 035014 (2023). doi: 10.1088/1361-6579/acc3d6Objective : Craniospinal compliance (CC) is an important metric for the characterization of space-occupying neurological pathologies. CC is obtained using invasive procedures that carry risks for the patients. Therefore, noninvasive methods for acquiring surrogates of CC have been proposed, most recently based on changes in the head's... more -
Are standing osmotic gradients the main driver of cerebrospinal fluid production? A computational analysis
Fluids and Barriers of the CNS, 20, 18 (2023). doi: 10.1186/s12987-023-00419-2Background : The mechanisms of cerebrospinal fluid (CSF) production by the ventricular choroid plexus (ChP) have not been fully deciphered. One prominent hypothesized mechanism is trans-epithelial water transport mediated by accumulation of solutes at the luminal ChP membrane that produces local osmotic gradients. However, this standing osmotic... more -
Characterising spinal cerebrospinal fuid fow in the pig with phase-contrast magnetic resonance imaging
Fluids and Barriers of the CNS, 20, 5 (2023). doi: 10.1186/s12987-022-00401-4Background : Detecting changes in pulsatile cerebrospinal fluid (CSF) flow may assist clinical management decisions, but spinal CSF flow is relatively understudied. Traumatic spinal cord injuries (SCI) often cause spinal cord swelling and subarachnoid space (SAS) obstruction, potentially causing pulsatile CSF flow changes. Pigs are emerging as... more -
Theory for a non-invasive diagnostic biomarker for craniospinal diseases
NeuroImage: Clinical, 37, 103280 (2023). doi: 10.1016/j.nicl.2022.103280Monitoring intracranial pressure (ICP) and craniospinal compliance (CC) is frequently required in the treatment of patients suffering from craniospinal diseases. However, current approaches are invasive and cannot provide continuous monitoring of CC. Dynamic exchange of blood and cerebrospinal fluid (CSF) between cranial and spinal compartments... more -
2022
Stabilized reduced-order models for unsteady incompressible flows in three-dimensional parametrized domains
Computers & Fluids, 246, 105604 (2022). doi: 10.1016/j.compfluid.2022.105604In this work we derive a parametric reduced-order model (ROM) for the unsteady three-dimensional incompressible Navier–Stokes equations without additional pre-processing on the reduced-order subspaces. Concerning the high-fidelity, full-order model, we start from a streamline-upwind Petrov–Galerkin stabilized finite element discretization of the... more -
Membrane transporters control cerebrospinal fluid formation independently of conventional osmosis to modulate intracranial pressure
Fluids and Barriers of the CNS, 19, 65 (2022). doi: 10.1186/s12987-022-00358-4Background : Disturbances in the brain fluid balance can lead to life-threatening elevation in the intracranial pressure (ICP), which represents a vast clinical challenge. Nevertheless, the details underlying the molecular mechanisms governing cerebrospinal fluid (CSF) secretion are largely unresolved, thus preventing targeted and efficient... more -
Noninvasive monitoring of intracranial pulse waves
IEEE Transactions on Biomedical Engineering, 70(1), 144 - 153 (2022). doi: 10.1109/TBME.2022.3186748Objective : The clinical management of several neurological disorders benefits from the assessment of intracranial pressure and craniospinal compliance. However, the associated procedures are invasive in nature. Here, we aimed to assess whether naturally occurring periodic changes in the dielectric properties of the head could serve as the... more -
Shape trumps size: image-based morphological analysis reveals that the 3D shape discriminates intracranial aneurysm disease status better than aneurysm size
Frontiers in Neurology, 13, 809391 (2022). doi: 10.3389/fneur.2022.809391Background : To date, it remains difficult for clinicians to reliably assess the disease status of intracranial aneurysms. As an aneurysm's 3D shape is strongly dependent on the underlying formation processes, it is believed that the presence of certain shape features mirrors the disease status of the aneurysm wall. Currently, clinicians... more -
Intraoperative monitoring of CSF pressure in patients with degenerative cervical myelopathy (COMP-CORD Study): a prospective cohort study
Journal of Neurotrauma, 39(3-4), 300 - 310 (2022). doi: 10.1089/neu.2021.0310Degenerative cervical myelopathy (DCM) is hallmarked by spinal canal narrowing and related cord compression and myelopathy. CSF pressure dynamics are likely disturbed due to spinal canal stenosis. The study aims to investigate the diagnostic value of continuous intraoperative CSF pressure monitoring during surgical decompression. Prospective... more -
Renal blood flow and oxygenation
European Journal of Physiology, 474, 759 - 770 (2022). doi: 10.1007/s00424-022-02690-yOur kidneys receive about one-fifth of the cardiac output at rest and have a low oxygen extraction ratio, but may sustain, under some conditions, hypoxic injuries that might lead to chronic kidney disease. This is due to large regional variations in renal blood flow and oxygenation, which are the prerequisite for some and the consequence of... more -
Insights into the low rate of in-pump thrombosis with the HeartMate3: does the artificial pulse improve washout?
Frontiers in Cardiovascular Medicine, 9, 775780 (2022). doi: 10.3389/fcvm.2022.775780While earlier studies reported no relevant effect of the HeartMate 3 (HM3) artificial pulse (AP) on bulk pump washout, its effect on regions with prolonged residence times remains unexplored. Using numerical simulations, we compared pump washout in the HM3 with and without AP with a focus on the clearance of the last 5% of the pump volume.... more -
Cerebrospinal fluid pressure dynamics reveal signs of effective spinal canal narrowing in ambiguous spine conditions
Frontiers in Neurology, 13, 951018 (2022). doi: 10.3389/fneur.2022.951018Spinal canal narrowing with consecutive spinal cord compression is considered a key mechanism in degenerative cervical myelopathy (DCM). DCM is a common spine condition associated with progressive neurological disability, and timely decompressive surgery is recommended. However, the clinical and radiological diagnostic workup is often ambiguous,... more -
Virtual histology of an entire mouse brain from formalin fixation to paraffin embedding. Part 2: Volumetric strain fields and local contrast changes
Journal of Neuroscience Methods, 365, 109385 (2022). doi: 10.1016/j.jneumeth.2021.109385Background : Fixation and embedding of post mortem brain tissue is a pre-requisite for both gold-standard conventional histology and X-ray virtual histology. This process alters the morphology and density of the brain microanatomy. New method : To quantify these changes, we employed synchrotron radiation-based hard X-ray tomography with 3... more -
Analysis of L-leucine amino acid transporter species activity and gene expression by human blood brain barrier hCMEC/D3 model reveal potential LAT1, LAT4, B0AT2 and y+LAT1 functional cooperation
Journal of Cerebral Blood Flow & Metabolism, 42(1), 90 - 103 (2022). doi: 10.1177/0271678X211039593In the CNS, amino acid (AA) neurotransmitters and neurotransmitter precursors are subject to tight homeostatic control mediated by blood-brain barrier (BBB) solute carrier amino acid transporters (AATs). Since the BBB is composed of multiple closely apposed cell types and opportunities for human in vivo studies are limited, we used in vitro... more -
2021
Newborn incubators do not protect from high noise levels in the neonatal intensive care unit and are relevant noise sources by themselves
Children, 8(8), 704 (2021). doi: 10.3390/children8080704Background : While meaningful sound exposure has been shown to be important for newborn development, an excess of noise can delay the proper development of the auditory cortex. The aim of this study was to assess the acoustic environment of a preterm baby in an incubator on a newborn intensive care unit (NICU). Methods : An empty but... more -
Virtual histology of an entire mouse brain from formalin fixation to paraffin embedding. Part 1: Data acquisition, anatomical feature segmentation, tracking global volume and density changes
Journal of Neuroscience Methods, 364, 109354 (2021). doi: 10.1016/j.jneumeth.2021.109354Background : Micrometer-resolution neuroimaging with gold-standard conventional histology requires tissue fixation and embedding. The exchange of solvents for the creation of sectionable paraffin blocks modifies tissue density and generates non-uniform brain shrinkage. New method : We employed synchrotron radiation-based X-ray... more -
Thrombotic risk of rotor speed modulation regimes of contemporary centrifugal continuous-flow left ventricular assist devices
ASAIO Journal, 67(7), 737 - 745 (2021). doi: 10.1097/MAT.0000000000001297Contemporary centrifugal continuous-flow left ventricular assist devices (LVADs) incorporate dynamic speed modulation algorithms. Hemocompatibility of these periodic unsteady pump operating conditions has been only partially explored. We evaluated whether speed modulation induces flow alterations associated with detrimental prothrombotic... more -
In vitro testing and comparison of additively manufactured polymer impellers for the centrimag blood pump
ASAIO Journal, 67(3), 306 - 313 (2021). doi: 10.1097/MAT.0000000000001220Additive manufacturing (AM) is an effective tool for accelerating knowledge gain in development processes, as it enables the production of complex prototypes at low cost and with short lead times. In the development of mechanical circulatory support, the use of cheap polymer-based AM techniques for prototype manufacturing allows more design... more -
High-throughput lossy-to-lossless 3D image compression
IEEE Transactions on Medical Imaging, 40(2), 607 - 620 (2021). doi: 10.1109/TMI.2020.3033456The rapid increase in medical and biomedical image acquisition rates has opened up new avenues for image analysis, but has also introduced formidable challenges. This is evident, for example, in selective plane illumination microscopy where acquisition rates of about 1–4 GB/s sustained over several days have redefined the scale of I/O bandwidth... more -
2020
RAQ: A novel surrogate for the craniospinal pressure-volume relationship
Physiological Measurement, 41(9), 094002 (2020). doi: 10.1088/1361-6579/abb145Objective : The intracranial pressure–volume relation contains information relevant for diagnostics of hydrocephalus and other space-occupying pathologies. We aimed to design a noise-resilient surrogate for this relationship that can be calculated from intracranial pressure (ICP) signals. Approach : The new surrogate, termed respiratory... more -
X-ray phase tomography with near-field speckles for three-dimensional virtual histology
Optica, 7(9), 1221 - 1227 (2020). doi: 10.1364/OPTICA.399421High-contrast, high-resolution imaging of biomedical specimens is indispensable for studying organ function and pathologies. Conventional histology, the gold standard for soft-tissue visualization, is limited by its anisotropic spatial resolution, elaborate sample preparation, and lack of quantitative image information. X-ray absorption or phase... more -
Radiomics approach to quantify shape irregularity from crowd-based qualitative assessment of intracranial aneurysms
Computer Methods in Biomechanics and Biomedical Engineering: Imaging & Visualization, 8(5), 538 - 546 (2020). doi: 10.1080/21681163.2020.1728579The morphological assessment of anatomical structures is clinically relevant, but often falls short of quantitative or standardised criteria. Whilst human observers are able to assess morphological characteristics qualitatively, the development of robust shape features remains challenging. In this study, we employ psychometric and radiomic... more -
Shape irregularity of the intracranial aneurysm lumen exhibits diagnostic value
Acta Neurochirurgica, 162, 2261 - 2270 (2020). doi: 10.1007/s00701-020-04428-0Background : Morphological irregularity is linked to intracranial aneurysm wall instability and manifests in the lumen shape. Yet there is currently no consent on how to assess shape irregularity. The aims of this work are to quantify irregularity as perceived by clinicians, to break down irregularity into morphological attributes, and to... more -
Simultaneous three-dimensional vascular and tubular imaging of whole mouse kidneys with X-ray μCT
Microscopy and Microanalysis, 26, 731 - 740 (2020). doi: 10.1017/S1431927620001725Concurrent three-dimensional imaging of the renal vascular and tubular systems on the whole-kidney scale with capillary level resolution is labor-intensive and technically difficult. Approaches based on vascular corrosion casting and X-ray micro computed tomography (μCT), for example, suffer from vascular filling artifacts and necessitate... more -
Hypoxia sensing by hepatic stellate cells leads to VEGF-dependent angiogenesis and may contribute to accelerated liver regeneration
Scientific Reports, 10(1), 4392 (2020). doi: 10.1038/s41598-020-60709-9Portal vein ligation (PVL) induces liver growth prior to resection. Associating liver partition and portal vein ligation (PVL plus transection=ALPPS) or the addition of the prolyl-hydroxylase inhibitor dimethyloxalylglycine (DMOG) to PVL both accelerate growth via stabilization of HIF-α subunits. This study aims at clarifying the crosstalk of... more -
Assessment of the flow field in the HeartMate 3 using three-dimensional particle tracking velocimetry and comparison to computational fluid dynamics
ASAIO Journal, 66(2), 173 - 182 (2020). doi: 10.1097/MAT.0000000000000987Flow fields in rotary blood pumps (RBPs) have a significant influence on hemocompatibility. Because flow characteristics vary with flow rate, different operating conditions play a role. Furthermore, turbulence is crucial in the evaluation of blood damage potential, but the level of turbulence in implantable RBPs is still unknown. In this study,... more -
Crosslinkable polymeric contrast agent for high-resolution X-ray imaging of the vascular system
Chemical Communications, 56, 5885 - 5888 (2020). doi: 10.1039/C9CC09883FX-ray micro computed tomography (µCT) is able to provide 3D data of the vascular system of whole organs and small animals with capillary resolution. Current contrast agents suffer from drawbacks when used for capillary resolution imaging of whole organs ex vivo : Angiography contrast agents are insufficiently retained within the vasculature for... more -
2019
Reduced-order modeling of blood flow for noninvasive functional evaluation of coronary artery disease
Biomechanics and Modeling in Mechanobiology, 18(6), 1867 - 1881 (2019). doi: 10.1007/s10237-019-01182-wWe present a novel computational approach, based on a parametrized reduced-order model, for accelerating the calculation of pressure drop along blood vessels. Vessel lumina are defined by a geometric parametrization using the discrete empirical interpolation method on control points located on the surface of the vessel. Hemodynamics are then... more -
Extending statistical learning for aneurysm rupture assessment to Finnish and Japanese populations using morphology, hemodynamics, and patient characteristics
Neurosurgical Focus, 47(1), E16 (2019). doi: 10.3171/2019.4.FOCUS19145Objective : Incidental aneurysms pose a challenge for physicians, who need to weigh the rupture risk against the risks associated with treatment and its complications. A statistical model could potentially support such treatment decisions. A recently developed aneurysm rupture probability model performed well in the US data used for model... more -
Integrated flow chamber system for live cell microscopy
Frontiers in Bioengineering and Biotechnology, 7, 91 (2019). doi: 10.3389/fbioe.2019.00091In vitro quantification of the effect of mechanical loads on cells by live microscopy requires precise control of load and culture environment. Corresponding systems are often bulky, their setup and maintenance are time consuming, or the cell yield is low. Here, we show the design and initial testing of a new cell culture system that fits on... more -
Propagation of plasma L-phenylalanine concentration fluctuations to the neurovascular unit in phenylketonuria: An in silico study
Frontiers in Physiology, 10, 360 (2019). doi: 10.3389/fphys.2019.00360Phenylketonuria (PKU) is an inherited metabolic disease characterized by abnormally high concentrations of the essential amino acid L-phenylalanine (Phe) in blood plasma caused by reduced activity of phenylalanine hydroxylase (PAH). While numerous studies have shown association between high plasma Phe concentration and intellectual impairment,... more -
Fluid Dynamics in the HeartMate 3: Influence of the Artificial Pulse Feature and Residual Cardiac Pulsation
Artificial Organs, 43(3), 363 - 376 (2019). doi: 10.1111/aor.13346Ventricular assist devices (VADs), among which the HeartMate 3 (HM3) is the latest clinically approved representative, are often the therapy of choice for patients with end‐stage heart failure. Despite advances in the prevention of pump thrombosis, rates of stroke and bleeding remain high. These complications are attributed to the flow field... more -
Generation of renal Epo-producing cell lines by conditional gene tagging reveals rapid HIF-2 driven Epo kinetics, cell autonomous feedback regulation, and a telocyte phenotype
Kidney International, 95, 375 - 387 (2019). doi: 10.1016/j.kint.2018.08.043Erythropoietin (Epo) is essential for erythropoiesis and is mainly produced by the fetal liver and the adult kidney following hypoxic stimulation. Epo regulation is commonly studied in hepatoma cell lines, but differences in Epo regulation between kidney and liver limit the understanding of Epo dysregulation in polycythaemia and anaemia. To... more -
2018
Virtual surgical planning, flow simulation and 3D electro-spinning of patient-specific grafts to optimize Fontan hemodynamics
The Journal of Thoracic and Cardiovascular Surgery, 155(4), 1734 - 1742 (2018). doi: 10.1016/j.jtcvs.2017.11.068Background : Despite advances in the Fontan procedure, there is an unmet clinical need for patient-specific graft designs that are optimized for variations in patient anatomy. The objective of this study is to design and produce patient-specific Fontan geometries, with the goal of improving hepatic flow distribution (HFD) and reducing power... more -
Functional polarity of microvascular brain endothelial cells supported by neurovascular unit computational model of large neutral amino acid homeostasis
Frontiers in Physiology, 9(171), 1 - 14 (2018). doi: 10.3389/fphys.2018.00171The homeostatic regulation of large neutral amino acid (LNAA) concentration in the brain interstitial fluid (ISF) is essential for proper brain function. LNAA passage into the brain is primarily mediated by the complex and dynamic interactions between various solute carrier (SLC) transporters expressed in the neurovascular unit (NVU), among... more -
Blood pump design variations and their influence on hydraulic performance and indicators of hemocompatibility
Annals of Biomedical Engineering, 46(3), 417 - 428 (2018). doi: 10.1007/s10439-017-1951-0Patients with ventricular assist devices still suffer from high rates of adverse events. Since many of these complications are linked to the flow field within the pump, optimization of the device geometry is essential. To investigate design aspects that influence the flow field, we developed a centrifugal blood pump using industrial guidelines.... more -
2017
Barrier dysfunction or drainage reduction: differentiating causes of CSF protein increase
Fluids and Barriers of the CNS, 14(1), (2017). doi: 10.1186/s12987-017-0063-4Background : Cerebrospinal fluid (CSF) protein analysis is an important element in the diagnostic chain for various central nervous system (CNS) pathologies. Among multiple existing approaches to interpreting measured protein levels, the Reiber diagram is particularly robust with respect to physiologic inter-individual variability, as it uses... more -
Is posture-related craniospinal compliance shift caused by jugular vein collapse? A theoretical analysis
Fluids and Barriers of the CNS, 14(5), 1 - 11 (2017). doi: 10.1186/s12987-017-0053-6Background : Postural changes are related to changes in cerebrospinal fluid (CSF) dynamics. While sitting up leads to a decrease in cranial CSF pressure, it also causes shifts in the craniospinal CSF volume and compliance distribution. We hypothesized that jugular vein collapse in upright posture is a major contributor to these shifts in CSF... more -
Influence of standard laboratory procedures on measures of erythrocyte damage
Frontiers in Physiology, 8(731), 1 - 11 (2017). doi: 10.3389/fphys.2017.00731The ability to characterize the mechanical properties of erythrocytes is important in clinical and research contexts: to diagnose and monitor hematologic disorders, as well as to optimize the design of cardiovascular implants and blood circulating devices with respect to blood damage. However, investigation of red blood cell (RBC) properties... more -
Comparison of anti-siphon devices—how do they affect CSF dynamics in supine and upright posture?
Acta Neurochirurgica, 159(8), 1389 - 1397 (2017). doi: 10.1007/s00701-017-3249-2Background : Three different types of anti-siphon devices (ASDs) have been developed to counteract siphoning-induced overdrainage in upright posture. However, it is not known how the different ASDs affect CSF dynamics under the complex pressure environment seen in clinic due to postural changes. We investigated which ASDs can avoid overdrainage... more -
Renal arteriovenous oxygen shunting
Current Opinion in Nephrology and Hypertension, 26(4), 290 - 295 (2017). doi: 10.1097/MNH.0000000000000332Purpose of review : Renal arteriovenous oxygen shunting has been proposed as a mechanism by which oxygen supplied to the kidney can bypass the renal parenchyma. Shunting could, therefore, play a crucial role in renal hypoxia and hyperoxia. In the absence of suitable quantitative experimental methods, computational modeling has been employed in... more -
The breakup of intravascular microbubbles and its impact on the endothelium
Biomechanics and Modeling in Mechanobiology, 16(2), 611 - 624 (2017). doi: 10.1007/s10237-016-0840-zEncapsulated microbubbles (MBs) serve as endovascular agents in a wide range of medical ultrasound applications. The oscillatory response of these agents to ultrasonic excitation is determined by MB size, gas content, viscoelastic shell properties and geometrical constraints. The viscoelastic parameters of the MB capsule vary during an... more -
Rapid adaptation to microgravity in mammalian macrophage cells
Scientific Reports, 7(43), 1 - 13 (2017). doi: 10.1038/s41598-017-00119-6Despite the observed severe effects of microgravity on mammalian cells, many astronauts have completed long term stays in space without suffering from severe health problems. This raises questions about the cellular capacity for adaptation to a new gravitational environment. The International Space Station (ISS) experiment TRIPLE LUX A,... more -
Quantifying the relative contributions of different solute carriers to aggregate substrate transport
Scientific Reports, 7(40628), 1 - 13 (2017). doi: 10.1038/srep40628Determining the contributions of different transporter species to overall cellular transport is fundamental for understanding the physiological regulation of solutes. We calculated the relative activities of Solute Carrier (SLC) transporters using the Michaelis-Menten equation and global fitting to estimate the normalized maximum transport rate... more -
2016
Glymphatic solute transport does not require bulk flow
Scientific Reports, 6(38635 ), 1 - 11 (2016). doi: 10.1038/srep38635Observations of fast transport of fluorescent tracers in mouse brains have led to the hypothesis of bulk water flow directed from arterial to venous paravascular spaces (PVS) through the cortical interstitium. At the same time, there is evidence for interstitial solute transport by diffusion rather than by directed bulk fluid motion. It has been... more -
B-waves revisited
Interdisciplinary Neurosurgery, 6, 13 - 17 (2016). doi: 10.1016/j.inat.2016.03.004Reduced intracranial compliance is a key manifestation common to a number of pathological conditions of the brain. It is encountered in, but not limited to, traumatic brain injury, cerebral edema, and hydrocephalus. There are no clinically accepted methods to measure intracranial compliance available to date. Intracranial pressure (ICP)... more -
The Bohr effect is not a likely promoter of renal preglomerular oxygen shunting
Frontiers in Physiology, 7(482), 1 - 14 (2016). doi: 10.3389/fphys.2016.00482The aim of this study was to evaluate whether possible preglomerular arterial-to-venous oxygen shunting is affected by the interaction between renal preglomerular carbon dioxide and oxygen transport. We hypothesized that a reverse (venous-to-arterial) shunting of carbon dioxide will increase partial pressure of carbon dioxide and decrease pH in... more -
Drug deposition in coronary arteries with overlapping drug-eluting stents
Journal of Controlled Release, 238, 1 - 9 (2016). doi: 10.1016/j.jconrel.2016.07.023Drug-eluting stents are accepted as mainstream endovascular therapy, yet concerns for their safety may be under-appreciated. While failure from restenosis has dropped to below 5%, the risk of stent thrombosis and associated mortality remain relatively high. Further optimization of drug release is required to minimize thrombosis risk while... more -
In vivo characterization of the integration and vascularization of a silk-derived surgical scaffold
Journal of Plastic, Reconstructive & Aesthetic Surgery, 69(8), 1141 - 1150 (2016). doi: 10.1016/j.bjps.2016.01.017Background : The application of acellular matrices, biomaterials, and polymeric scaffolds in reconstructive surgery facilitates postsurgical tissue remodeling and is increasingly used clinically in order to improve tissue healing and implant coverage. This study presents an in vivo investigation of the integration of the knitted, silk-derived... more -
2015
Patient-specific surgical planning, where do we stand? The example of the Fontan procedure
Annals of Biomedical Engineering, 44(1), 174 - 186 (2015). doi: 10.1007/s10439-015-1381-9The Fontan surgery for single ventricle heart defects is a typical example of a clinical intervention in which patient-specific computational modeling can improve patient outcome: with the functional heterogeneity of the presenting patients, which precludes generic solutions, and the clear influence of the surgically-created Fontan connection on... more -
How astrocyte networks may contribute to cerebral metabolite clearance
Scientific Reports, 5, 15024 (2015). doi: 10.1038/srep15024The brain possesses an intricate network of interconnected fluid pathways that are vital to the maintenance of its homeostasis. With diffusion being the main mode of solute transport in cerebral tissue, it is not clear how bulk flow through these pathways is involved in the removal of metabolites. In this computational study, we show that... more -
Continuous positive airway pressure alters cranial blood flow and cerebrospinal fluid dynamics at the craniovertebral junction
Interdisciplinary Neurosurgery, 2(3), 152 - 159 (2015). doi: 10.1016/j.inat.2015.06.004Purpose : To investigate the impact of continuous positive airway pressure (CPAP) applied by a full-face fitted mask at 15 cmH 2 O on total cerebral blood flow (tCBF), jugular venous flow (tJVF) and cerebrospinal fluid (CSF) flow. Materials and methods : Axial 2D phase-contrast MRI measurements were acquired at the C2–C3 vertebral level for... more -
Patient-specific hardware-in-the-loop testing of cerebrospinal fluid shunt systems
IEEE Transactions on Biomedical Engineering, 63(2), 348 - 358 (2015). doi: 10.1109/TBME.2015.2457681Goal : The development of increasingly sophisticated cerebrospinal fluid (CSF) shunts calls for test beds that can reproduce an ever larger range of physiologic and pathophysiologic behaviors. In particular, upcoming smart and active devices will require extensive testing under complex dynamic conditions. Herein, we describe a test bed that... more -
Renal oxygenation: Pre-glomerular vasculature is an unlikely contributor to renal oxygen shunting
American Journal of Physiology – Renal Physiology, 308(7), F671 - F688 (2015). doi: 10.1152/ajprenal.00551.2014The primary aim of this study is to assess the plausibility of pre-glomerular arterial-to-venous oxygen shunting in the kidney. To this end, we have developed a segment-wise three-dimensional computational model that takes into account transport processes in arteries, veins, cortical tissue and capillaries. Our model suggests that the amount of... more -
Frequently asked questions in hypoxia research
Hypoxia, 2015(3), 35 - 43 (2015). doi: 10.2147/HP.S92198“What is the O2 concentration in a normoxic cell culture incubator?” This and other frequently asked questions in hypoxia research will be answered in this review. Our intention is to give a simple introduction to the physics of gases that would be helpful for newcomers to the field of hypoxia research. We will provide background knowledge about... more -
2014
Modeling the interaction of microbubbles: Effects of proximity, confinement, and excitation amplitude
Physics of Fluids, 26, 062106 (2014). doi: 10.1063/1.4883482The interaction of closely spaced microbubbles (MBs) exposed to a transient external pressure field is relevant for a variety of industrial and medical applications. We present a computational framework employing an interface tracking approach to model the transient dynamics of multiple, interacting, insonated MBs in arbitrary settings. In... more -
Complementary X-ray tomography techniques for histology-validated 3D imaging of soft and hard tissues using plaque-containing blood vessels as examples
Nature Protocols, 9, 1401 - 1415 (2014). doi: 10.1038/nprot.2014.091A key problem in X-ray computed tomography is choosing photon energies for postmortem specimens containing both soft and hard tissues. Increasing X-ray energy reduces image artifacts from highly absorbing hard tissues including plaque, but it simultaneously decreases contrast in soft tissues including the endothelium. Therefore, identifying the... more -
Flow induced by ependymal cilia dominates near-wall cerebrospinal fluid dynamics in the lateral ventricles
Journal of the Royal Society Interface, 11, 20131189 (2014). doi: DOI:10.1098/rsif.2013.1189While there is growing experimental evidence that cerebrospinal fluid (CSF) flow induced by the beating of ependymal cilia is an important factor for neuronal guidance, the respective contribution of vascular pulsation-driven macroscale oscillatory CSF flow remains unclear. This work uses computational fluid dynamics to elucidate the interplay... more -
Arterial, venous, and cerebrospinal fluid flow: Simultaneous assessment with Bayesian multipoint velocity-encoded MR Imaging
Radiology, 270(2), 566 - 573 (2014). doi: 10.1148/radiol.13130840Purpose : To measure arterial, venous, and cerebrospinal fluid (CSF) velocities simultaneously by using Bayesian multipoint velocity-encoded magnetic resonance (MR) imaging and to compare interacquisition reproducibility relative to that of standard phase-contrast MR imaging for sequential measurements of arterial, venous, and CSF velocities.... more -
Hemodynamics in coronary arteries with overlapping stents
Journal of Biomechanics, 47(2), 505 - 511 (2014). doi: 10.1016/j.jbiomech.2013.10.048Coronary artery stenosis is commonly treated by stent placement via percutaneous intervention, at times requiring multiple stents that may overlap. Stent overlap is associated with increased risk of adverse clinical outcome. While changes in local blood flow are suspected to play a role therein, hemodynamics in arteries with overlapping stents... more -
2013
Assessment of intracranial dynamics in hydrocephalus: effects of viscoelasticity on the outcome of infusion tests
Journal of Neurosurgery, 119(6), 1511 - 1519 (2013). doi: 10.3171/2013.8.JNS122497The treatment of hydrocephalus requires insight into the intracranial dynamics in the patient. Resistance to CSF outflow (R0) is a clinically obtainable parameter of intracranial fluid dynamics that quantifies the apparent resistance to CSF absorption. It is used as a criterion for the selection of shunt candidates and serves as an indicator of... more -
A robust algorithm for segmenting and tracking clustered cells in time-lapse fluorescent microscopy
IEEE Journal of Biomedical and Health Informatics, 17(4), 862 - 869 (2013). doi: 10.1109/JBHI.2013.2262233We present herein a robust algorithm for cell tracking in a sequence of time-lapse 2D fluorescent microscopy images. Tracking is performed automatically via a multiphase active contours algorithm adapted to the segmentation of clustered nuclei with obscure boundaries. An ellipse fitting method is applied to avoid problems typically associated... more -
Compound ex vivo and in silico method for hemodynamic analysis of stented arteries
PLoS ONE, 8(3), e58147 (2013). doi: 10.1371/journal.pone.0058147Hemodynamic factors such as low wall shear stress have been shown to influence endothelial healing and atherogenesis in stent-free vessels. However, in stented vessels, a reliable quantitative analysis of such relations has not been possible due to the lack of a suitable method for the accurate acquisition of blood flow. The objective of this... more -
Accelerated endothelial wound healing on microstructured substrates under flow
Biomaterials, 34(5), 1488 - 1497 (2013). doi: 10.1016/j.biomaterials.2012.10.007Understanding and accelerating the mechanisms of endothelial wound healing is of fundamental interest for biotechnology and of significant medical utility in repairing pathologic changes to the vasculature induced by invasive medical interventions. We report the fundamental mechanisms that determine the influence of substrate topography and flow... more -
2012
Phosphorylation of VE-cadherin is modulated by haemodynamic forces and contributes to the regulation of vascular permeability in vivo
Nature Communications, 3, 1208 (2012). doi: 10.1038/ncomms2199Endothelial adherens junctions maintain vascular integrity. Arteries and veins differ in their permeability but whether organization and strength of their adherens junctions vary has not been demonstrated in vivo . Here we report that vascular endothelial cadherin, an endothelial specific adhesion protein located at adherens junctions, is... more -
Cell image velocimetry (CIV): boosting the automated quantification of cell migration in wound healing assays
Integrative Biology, 4(11), 1437 - 1447 (2012). doi: 10.1039/C2IB20113ECell migration is commonly quantified by tracking the speed of the cell layer interface in wound healing assays. This quantification is often hampered by low signal to noise ratio, in particular when complex substrates are employed to emulate in vivo cell migration in geometrically complex environments. Moreover, information about the cell... more -
Cutaneous heat transfer and its effect on contact heat evoked brain potentials
Experimental Heat Transfer, 25(4), 341 - 362 (2012). doi: 10.1080/08916152.2012.675800The brain's response to external painful stimuli can be assessed through contact heat evoked cortical potentials that enable the evaluation of the integrity of pain pathways. This work aims to improve the reliability of this diagnostic procedure by decoupling the effects of heat transfer and nerve fiber conduction. It is herein shown... more -
Craniospinal Pressure–Volume Dynamics in Phantom Models
IEEE Transactions on Biomedical Engineering, 59(12), 3482 - 3490 (2012). doi: 10.1109/TBME.2012.2214220Regulation of intracranial pressure (ICP) is vital to proper brain function. Pathologic conditions such as traumatic brain injury and hydrocephalus can cause lethal changes in ICP through an imbalance of fluid passage into and out of the craniospinal space. The relationship between craniospinal volume and pressure determines to a large extent... more -
Age-specific characteristics and coupling of cerebral arterial inflow and cerebrospinal fluid dynamics
PLoS ONE, 7(5), e37502 (2012). doi: 10.1371/journal.pone.0037502The objective of this work is to quantify age-related differences in the characteristics and coupling of cerebral arterial inflow and cerebrospinal fluid (CSF) dynamics. To this end, 3T phase-contrast magnetic resonance imaging blood and CSF flow data of eleven young (24 ± 3 years) and eleven elderly subjects (70 ± 5 years) with a comparable... more -
Choosing the optimal wall shear parameter for the prediction of plaque location – A patient-specific computational study in human left coronary arteries
Atherosclerosis, 221(2), 432 - 437 (2012). doi: 10.1016/j.atherosclerosis.2012.01.018Objective : While the correlation of atherosclerotic plaque locations with local wall shear stress magnitude has been evaluated previously by other investigators in both right (RCA) and left coronary arteries (LCA), the relative performance of average wall shear stress (AWSS), average wall shear stress gradient (AWSSG), oscillatory shear index... more -
Phantom model of physiologic intracranial pressure and cerebrospinal fluid dynamics
IEEE Transactions on Biomedical Engineering, 59(6), 1532 - 1538 (2012). doi: 10.1109/TBME.2012.2187448We describe herein a novel life-size phantom model of the intracranial cavity and its validation. The cerebrospinal fluid (CSF) domains including ventricular, cysternal, and subarachnoid spaces were derived via magnetic resonance imaging. Brain mechanical properties and cranio-spinal compliance were set based on published data. Both bulk and... more -
On ultrasound-induced microbubble oscillation in a capillary blood vessel and its implications for the blood–brain barrier
Physics in Medicine and Biology, 57(4), 1019 - 1045 (2012). doi: 10.1088/0031-9155/57/4/1019The complex interaction between an ultrasound-driven microbubble and an enclosing capillary microvessel is investigated by means of a coupled, multi-domain numerical model using the finite volume formulation. This system is of interest in the study of transient blood–brain barrier disruption (BBBD) for drug delivery applications. The compliant... more -
Topography-mediated apical guidance in epidermal wound healing
Soft Matter, 8(26), 6922 - 6930 (2012). doi: 10.1039/C2SM00030JTopographic modifications of the substrate of a cell culture have the potential to guide cell polarization and migration, through which epidermal wound healing may be accelerated. Classic topographic contact guidance is based on the interaction between cells and a supporting scaffold that interferes with the establishment of focal adhesions,... more -
Prior to 2012
Computed high concentrations of low-density lipoprotein correlate with plaque locations in human coronary arteries
Journal of Biomechanics, 44(13), 2466 - 2471 (2011). doi: 10.1016/j.jbiomech.2011.06.022Subendothelial accumulation of low-density lipoprotein (LDL) in arterial walls is an initiator of atherosclerotic plaque formation. We report here on the correlation between healthy state subendothelial LDL concentration distribution and sites of subsequent plaque formation in coronary arteries of patients with coronary artery disease (CAD). We... more -
Wall stress of the cervical carotid artery in patients with carotid dissection. A case-control study
American Journal of Physiology – Heart and Circulatory Physiology, 300(4), H1451 - H1458 (2011). doi: 10.1152/ajpheart.00871.2010Spontaneous internal carotid artery (ICA) dissection (sICAD) results from an intimal tear located around the distal carotid sinus. The mechanisms causing the tear are unknown. This case-control study tested the hypotheses that head movements increase the wall stress in the cervical ICA and that the stress increase is greater in patients with... more -
Control of initial endothelial spreading by topographic activation of Focal Adhesion Kinase
Soft Matter, 7(16), 7313 - 7324 (2011). doi: 10.1039/C1SM05191AThe time required to re-establish a functioning endothelial cell layer after vascular implant placement is critical to the success of the respective cardiologic or surgical intervention. Topographic modifications of implant surfaces promise to expedite endothelial regeneration by triggering the activation of cellular machineries that facilitate... more -
Cerebrospinal fluid dynamics in the human cranial subarachnoid space – An overlooked mediator of cerebral disease. Part II: In vitro arachnoid outflow model
Royal Society Interface, 7(49), 1205 - 1218 (2010). doi: 10.1098/RSIF.2010.0032The arachnoid membrane (AM) and granulations (AGs) are important in cerebrospinal fluid (CSF) homeostasis, regulating intracranial pressure in health and disease. We offer a functional perspective of the human AM's transport mechanism to clarify the role of AM in the movement of CSF and metabolites. Using cultures of human AG cells and a... more -
Cerebrospinal fluid dynamics in the human cranial subarachnoid space – An overlooked mediator of cerebral disease. Part I: Computational model
Royal Society Interface, 7(49), 1195 - 1204 (2010). doi: 10.1098/RSIF.2010.0033Abnormal cerebrospinal fluid (CSF) flow is suspected to be a contributor to the pathogenesis of neurodegenerative diseases such as Alzheimer's through the accumulation of toxic metabolites, and to the malfunction of intracranial pressure regulation, possibly through disruption of neuroendocrine communication. For the understanding of transport... more -
Choosing the optimal wall shear parameter for the prediction of plaque location – A patient-specific computational study in human right coronary arteries
Atherosclerosis, 211(2), 445 - 450 (2010). doi: 10.1016/j.atherosclerosis.2010.03.001Background : Average wall shear–stress (AWSS), average wall shear–stress gradient (AWSSG), oscillatory shear index (OSI) and relative residence time (RRT) are believed to predict areas vulnerable to plaque formation in the coronary arteries. Our aim was to analyze the correlation of these parameters in patients’ vessels before the onset of... more -
Long-term follow-up, computed tomography and computational fluid dynamics of the cabrol procedure
Journal of Thoracic and Cardiovascular Surgery, 139(6), 1602 - 1608 (2010). doi: 10.1016/j.jtcvs.2009.09.023Objectives : The Cabrol procedure is characterized by insertion of an ascending aortic composite graft with reimplantation of the coronary arteries by the interposition of a graft tube. Our purpose is to report the clinical long-term follow-up and computed tomographic findings in patients having undergone the Cabrol procedure and to determine... more -
A mathematical method for the 3D analysis of rotating deformable systems applied to lumen-forming MDCK cell aggregates
Cytoskeleton, 67(4), 224 - 240 (2010). doi: 10.1002/cm.20438Cell motility contributes to the formation of organs and tissues, into which multiple cells self-organize. However such mammalian cellular motilities are not characterized in a quantitative manner and the systemic consequences are thus unknown. A mathematical tool to decipher cell motility, accounting for changes in cell shape, within a... more -
Ex-vivo and in-vivo coronary ostial locations in humans
Surgical and Radiologic Anatomy, 31(8), 597 - 604 (2009). doi: 10.1007/s00276-009-0488-9Purpose : Knowledge of the normal in vivo distribution and variation of coronary ostial locations is essential in the planning of various interventional and surgical procedures. However, all studies to date have reported the distribution of coronary ostia locations only in cadaver hearts. In this study, we sought to assess the distribution of... more -
Patient-specific three-dimensional simulation of LDL accumulation in a human left coronary artery in its healthy and atherosclerotic states
American Journal of Physiology – Heart and Circulatory Physiology, 296(6), H1969 - H1982 (2009). doi: 10.1152/ajpheart.01182.2008We calculate low-density lipoprotein (LDL) transport from blood into arterial walls in a three-dimensional, patient-specific model of a human left coronary artery. The in vivo anatomy data are obtained from computed tomography images of a patient with coronary artery disease. Models of the artery anatomy in its healthy and diseased states are... more -
Remodelling of the aortic root in severe tricuspid aortic stenosis: Implications for transcatheter aortic valve implantation
European Radiology, 19(6), 1316 - 1323 (2009). doi: 10.1007/s00330-009-1302-0Detailed knowledge of aortic root geometry is a prerequisite to anticipate complications of transcatheter aortic valve (TAV) implantation. We determined coronary ostial locations and aortic root dimensions in patients with aortic stenosis (AS) and compared these values with normal subjects using computed tomography (CT). One hundred consecutive... more -
The role of the carotid sinus in the reduction of arterial wall stresses due to head movements – potential implications for cervical artery dissection
Journal of Biomechanics, 42(6), 755 - 761 (2009). doi: 10.1016/j.jbiomech.2008.12.023Spontaneous dissection of the cervical internal carotid artery (sICAD) is a major cause of stroke in young adults. A tear in the inner part of the vessel wall triggers sICAD as it allows the blood to enter the wall and develop a transmural hematoma. The etiology of the tear is unknown but many patients with sICAD report an initiating trivial... more -
Three-dimensional computational modeling of subject-specific cerebrospinal fluid flow in the subarachnoid space
ASME Journal of Biomechanical Engineering, 131(2), 021010 (2009). doi: 10.1115/1.3005171This study aims at investigating three-dimensional subject-specific cerebrospinal fluid (CSF) dynamics in the inferior cranial space, the superior spinal subarachnoid space (SAS), and the fourth cerebral ventricle using a combination of a finite-volume computational fluid dynamics (CFD) approach and magnetic resonance imaging (MRI) experiments.... more -
Analytical solution for pulsatile viscous flow in a straight elliptic annulus and application to the motion of the cerebrospinal fluid
Physics of Fluids, 20(9), 093607 (2008). doi: 10.1063/1.2988858We present here the analytical solution of transient, laminar, viscous flow of an incompressible, Newtonian fluid driven by a harmonically oscillating pressure gradient in a straight elliptic annulus. The analytical formulation is based on the exact solution of the governing fluid flow equations known as Navier–Stokes equations. We validate the... more -
Computational modeling of coupled blood-wall mass transport of LDL: Effects of local wall shear stress
American Journal of Physiology – Heart and Circulatory Physiology, 294(2), H909 - H919 (2008). doi: 10.1152/ajpheart.01082.2007The work herein represents a novel approach for the modeling of low-density lipoprotein (LDL) transport from the artery lumen into the arterial wall, taking into account the effects of local wall shear stress (WSS) on the endothelial cell layer and its pathways of volume and solute flux. We have simulated LDL transport in an axisymmetric... more -
Mixing and modes of mass transfer in the third cerebral ventricle: A computational analysis
ASME Journal of Biomechanical Engineering, 129(5), 695 - 702 (2007). doi: 10.1115/1.2768376Anatomic, velocimetric, and brain motion MRI scans were combined with a computational fluid dynamics model to investigate cerebrospinal fluid (CSF) mixing in the third cerebral ventricle of a healthy male adult. It was found that advection dominates over diffusion in most of the third ventricle. Three zones where diffusion plays an important... more -
Computational investigation of subject-specific cerebrospinal fluid flow in the third ventricle and aqueduct of Sylvius
Journal of Biomechanics, 40(6), 1235 - 1245 (2007). doi: 10.1016/j.jbiomech.2006.05.031The cerebrospinal fluid flow in the third ventricle of the brain and the aqueduct of Sylvius was studied using computational fluid dynamics (CFD) based on subject-specific boundary conditions derived from magnetic resonance imaging (MRI) scans. The flow domain geometry was reconstructed from anatomical MRI scans by manual image segmentation. The... more -
Purification of metallurgical grade silicon by a solar process
Solar Energy Materials and Solar Cells, 90(14), 2099 - 2106 (2006). doi: 10.1016/j.solmat.2006.02.009The purification of upgraded metallurgical silicon by extraction of boron and phosphorus was experimentally demonstrated using concentrated solar radiation in the temperature range 1550–1700 °C. The process operated with a flow of Ar at reduced pressure (0.05 atm) for elimination of P, and with a flow of H2O for elimination of B. Impurity... more -
Computational modeling of the mechanical behavior of the cerebrospinal fluid system
ASME Journal of Biomechanical Engineering, 127(2), 264 - 269 (2005). doi: 10.1115/1.1865191A computational fluid dynamics (CFD) model of the cerebrospinal fluid system was constructed based on a simplified geometry of the brain ventricles and their connecting pathways. The flow is driven by a prescribed sinusoidal motion of the third ventricle lateral walls, with all other boundaries being rigid. The pressure propagation between the... more