Sandor Bernad

Romanian Academy -Timisoara Branch

In this article, we investigated the influence of molecular weight (Mw) on particle deposition efficiency after PEG-functionalized (polyethylene glycol-PEG) magnetoresponsive magnetic cluster targeting. In this work, the clusters were obtained by the solvothermal polyol method using polyethylene glycol (PEG) as a coating agent. So, we investigated...

This research aims to investigate the agglomeration processes of magnetoresponsive functionalized nanocluster suspensions in a magnetic field, as well as how these structures impact the behaviour of these suspensions in biomedical applications. The synthesis, shape, colloidal stability, and magnetic characteristics of PEG-functionalized nanocluster...

Based on our prior research, we synthesized iron-oxide nanoparticles (IONPs) in two shapes (spherical and cubic) and sized them for the current inquiry. This research examined the magnetic, rheological, and sedimentation properties of the suspensions containing PEG-coated IONPs, considering that both produced particles are intended to be employed f...

Objective: Omentum involvement resulting from uterine perforation is a rare complication following intrauterine procedures that might require immediate intervention due to severe ischemic consequences. This review examines the prevalence of this complication, risk factors, the mode and timing of diagnosis, the proper management and the outcome. M...

This study presents preliminary computational and experimental findings on two alternative permanent magnet configurations helpful for magnetic drug administration in vivo. A numerical simulation and a direct experimental measurement of the magnetic induction on the magnet system’s surface were used to map the magnetic field. In addition, the ferri...

The complicated abdominal aorta and its branches are a portion of the circulatory system prone to developing atherosclerotic plaque and aneurysms. These disorders are closely connected to the changing blood flow environment that the area's complicated architecture produces (between celiac artery and iliac artery bifurcation); this phenomenon is wid...

Drug therapy for vascular disease has been promoted to inhibit angiogenesis in atherosclerotic plaques and prevent restenosis following surgical intervention. This paper investigates the arterial depositions and distribution of PEG-functionalized magnetic nanocomposite clusters (PEG_MNCs) following local delivery in a stented artery model in a unif...

The Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) pandemic significantly impacted the general population’s health. At times, the infection has unfavorably influenced pregnancy evolution and the result of birth. However, vertical transmission of the virus is rare and generates controversial discussions. The study aimed to highlight th...

The Coronavirus disease 2019 (COVID-19) pandemic has exposed the vulnerable neonatal population to unknown risks. Given that herd immunity is has not been reached, the entire population is susceptible to Severe Acute Respiratory Syndrome Coronavirus 2 Virus(SARS-CoV-2) infection. The arising concern about the vertical transmission of neonatal compl...

Computational Fluid Dynamics (CFD) is a non-invasive in silico technique that can be used for characterizing the blood flow in the cardiovascular system under physiological or pathological conditions with potential applications in the clinical decision-making, therapy planning and strategies or medical device design and optimization. The aim of thi...

The initiation and development of atherosclerosis is strongly related to regions characterized by low values of Wall Shear Stress and altered blood flow field. Computational Fluid Dynamics tools allow to non-invasively analyze the hemodynamic parameters associated with critical regions of the vascular system that are susceptible to atherosclerosis....

Atherosclerosis is a cardiovascular disease that hardens, narrows, and finally blocks the medium and large arteries. Depending on the stenosis severity, different treatments are applied. One of the most common approaches used in moderate stenosis is percutaneous transluminal coronary angioplasty and stent implantation. In this paper, computational...

Vascular stent implantation needs a rapid endothelialization to reduce morbidity and improve patient outcomes. A promising strategy to enhance the artery wall healing is to use the site-specific drug targeting technique to deliver the required medication at the site of injury. This work presents a new concept of using permanent magnet systems to gu...

Stent malapposition has been linked to late and very late stent thrombosis, particularly in case of drug-eluting stents for percutaneous coronary interventions. The presence of gaps between stent struts and vessel wall has been associated with lack of strut coverage and thus incomplete re-endothelialization. Previous studies have shown that malappo...

Computational fluid dynamics is a non-invasive in silico tool, useful for a detailed analysis of blood flow through the cardiovascular system, especially in coronary flow. The accuracy of numerical results is strongly dependent on the grid used for geometry meshing. A fine mesh is supposed to provide accurate data useful for medical applications in...

The present study investigated the possibilities and feasibility of drug targeting for an arterial bifurcation lesion to influence the host healing response. A micrometer sized iron particle was used only to model the magnetic carrier in the experimental investigation (not intended for clinical use), to demonstrate the feasibility of the particle t...

Magnetic targeting is a non-invasive strategy to improve treatment efficacy for graft intimal hyperplasia (the leading cause of the arterial bypass graft failure). The present study aims are to investigate the possibility of MPs retention in the bypass graft anastomosis region where IH are developed after surgical intervention and quantify the part...

Long-term efficacy of coronary artery bypass graft surgery (CABG) is affected by graft failure, mainly attributable to the development of intimal hyperplasia (IH) at the site of the distal anatomosis. IH is triggered by presence of disturbed blood flow patterns and altered hemodynamics in the region of the anastomosis. Several factors contribute to...

Bypass graft patency is strongly influenced by geometric parameters such as anastomosis angle or the presence of competitive flow. Low values of Wall Shear Stress are associated to regions with flow disturbance, a main cause for intimal hyperplasia development and therefore graft failure. This paper analyzes the influence of anastomosis angle and c...

The steady flow in an anatomically realistic human carotid bifurcation was simulated numerically. Main parameters such as wall shear stress (WSS), velocity profiles and pressure distributions are investigated in the carotid artery, namely in bifurcation and sinusoidal enlargement regions. Flow in the carotid sinus is dominated by a single secondary...

Stent deployment alters the geometric flow boundary conditions, due to the protrusion of stent struts into the flow stream. The flow field in the vicinity of the stent wires demonstrated the presence of the stagnation zones. The pressure falls rapidly both of the investigated geometries. Downstream to the stenosis throat and the stented segment res...

The long-term success of arterial bypass surgery is often limited by the progression of intimal hyperplasia at the anastomosis between the graft and the native artery. The experimental models were manufactured from glass tubing with a constant internal diameter of 8 mm, fashioned into a straight confguration and helical confguration. The aim of thi...

Bypass graft failure is mainly caused by intimal hyperplasia (IH) that occurs at the graft anastomosis after coronary artery bypass grafting (CABG) surgery. It has been shown that local hemodynamics influences the process of IH initiation and progression. A main concern at this type of surgery is to increase the graft patency, respectively to impro...

Local hemodynamic factors are known affect the natural history of the restenosis critically after coronary stenting of atherosclerosis. Stent-induced flows disturbance magnitude dependent directly on the strut design. The impact of flow alterations around struts vary as the strut geometrical parameters change. Our results provide data regarding the...

Tortuous saphenous vein graft (SVG) hemodynamics was investigated using computational fluid dynamics (CFD) techniques. Computed tomography (CT) technology is used for non-invasive bypass graft assessment 7 days after surgery. CT investigation shown two regions with severe shape remodelling first is an elbow type contortion and second is a severe cu...

Vascular corrosion casting was used for detailed three-dimensional (3D) morphological examination of the normal placental microcirculation. This paper is focused on blood flow dynamics in the branching microvessels of the human placenta. The 3D computational analysis of fetal blood flow in the placenta was performed on simple branching networks of...

This paper analyses the influence of helical turn numbers to helicity values and axial velocity profile at the outlet sections of constant circular cross-section helical tubes. Five different tubes with one, two, four, six and eight turns and constant total length and amplitude, were considered for analyses in steady and laminar conditions at three...

Optimal graft design has been an objective of many researchers in order to find correlations between hemodynamics and graft failure. The character of complex vortex structures created in the area between the heel and occluded section depends on the flow parameters (for the case of straight graft). We can identify two vortices in the symmetry plane...

Luminally protruding struts alter blood flow, creating areas of recirculation, separation, and stagnation. The impact of flow alterations around struts vary as the strut geometrical parameters change. We quantified the influence of the luminal flow alterations due to the presence of the stent struts by performing two-dimensional numerical simulatio...

Local hemodynamic factors are known affect the natural history of the restenosis critically after coronary stenting of atherosclerosis. Stent-induced flows disturbance magnitude dependent directly on the strut design. Strut shape, strut thickness and the distance between consecutive struts have been associated clinically with the with post-interven...

The placenta handles the exchange of oxygen and nutrients from the mother to the fetus. Normal placentation and placental development are critical for a successful pregnancy. In this study, the placenta is obtained from normal pregnancy and of normal vaginal delivery. The polymeric cast of the fetal vasculature of the full-term placenta is used to...

Tortuous saphenous vein graft (SVG) hemodynamics was investigated using computational fluid dynamics (CFD) techniques. Computed tomography (CT) technology is used for noninvasive bypass graft assessment seven days after surgery. CT investigation shows two regions with severe shape remodeling, one is an angle type contortion and the other one is a s...

Optimal graft design has been an objective of many researchers to find correlations between hemodynamics and graft failure. Compared to planar grafts, the helical graft configurations improve hemodynamic performance including the promotion of flow mixing and reduction of flow stagnation regions. In order to evaluate the advantages and disadvantages...

Effects of serial stenosis on coronary hemodynamics are investigated in the human right coronary artery (RCA) by blood flow analysis. The 3D reconstruction of the geometry of the stenosed coronary artery uses the multislice computerized tomography serial images method. Results of the numerical analysis present the hemodynamic characteristics of the...

Aorto-coronary by-pass graft anastomosis geometry is complex, which causes strong secondary flow formation inside the region. Critical flow regions (recirculation regions and particle deposition) inside to the anastomosis zone are found in the current model. Experimental results show high secondary flow along the occluded artery and good fluid mixi...

By-pass graft failure is mainly caused by progressive intimal hyperplasia at graft anastomosis and restenosis. A helical graft induces a swirl flow pattern at the outlet section of the graft, and that can reduce the effects that cause the graft failure. This paper analyses the efficiency of helical geometries in terms of helicity and vorticity. Twe...

In the present work, numerical analysis is performed in a helically sinuous tube with circular cross-section and a finite pitch under laminar flow conditions. The evolution of flows in three helically sinuous tubes at Re = 500 was studied taking into account the effects of torsion and curvature. Results show that in terms of axial velocity, the cur...

Carcinoma of the Fallopian tube is the least frequent tumor of the female genital tract. The diagnosis is difficult but could be made more frequently if the causes of abnormal bleeding were thoroughly investigated by means of cytology and endometrial curettage. Treatment is by resection of the tumor, total hysterectomy, and bilateral salpingo-oopho...

We investigated the flow field within a rigid-walled numerical model of 30°, 45°, and 60° degree bypass graft in order to attempt to identify different type of vortices developed in distal part of the bypass graft. In steady laminar flow, the presence of branching generates a secondary flow in the form of a pair of counter-rotating symmetrical vort...

In this study, effects of serial stenosis on coronary hemodynamics were investigated in the human right coronary artery (RCA) using blood flow analysis. A 3-D model of a serial stenosed RCA was reconstructed based on multislice computerized tomography images. Numerical analysis examined the effect of multiple serial stenoses on the hemodynamic char...

The long-term success of arterial bypass surgery is often limited by the progression of intimal hyperplasia at the anastomosis between the graft and the native artery. The experimental models were manufactured from glass tubing with constant internal diameter of 8 mm, fashioned into a straight configuration and helical configuration. The aim of thi...

The paper focuses on numerical analysis of hydrodynamic behavior in a discharge cone from a swirling flow generator when is operated at lower runner speeds. The swirl generator is used in laboratory instead of a turbine model in order to investigate different swirling flow configurations into a straight draft tube. The purpose for reducing the spee...

This study is devoted to the three-dimensional numerical simulation of developing secondary flows of Newtonian fluid through a curved circular duct. The numerical simulations produced for different Dean numbers show clearly the presence of two steady Dean vortices. Therefore, results confirm that helical flow constitutes an important flow signature...

Curved channel flows and branching of fluid flow are used in many industrial applications to provide compactness and high heat and mass-transfer rates so as to enhance mixing in laminar flow regimes. Branchings of fluid flow are extremely common throughout the human body and involve various complex geometrical configurations and flow conditions ass...

Coronary angiogram (CA) is the gold standard diagnostic tool for coronary artery stenosis. Restenosis after balloon angioplasty is the major limitation of the technique. The goal of the paper is to evaluate the way in which the wall shear stress (WSS) distribution is affected by the blood flow evolution during the cardiac cycle in re-stenosed arter...

The purpose of this paper was to investigate the hemodynamic parameters associated with the blood flow in failed coronary venous bypass grafts using a computational fluid dynamics (CFD) technique. A narrowed section creates bypass graft constriction and disturbed flow. This change of the flow direction alters significantly the local hemodynamic par...

Atherosclerosis creating a constriction can significantly alter the local blood flow dynamics. From a biological aspect, the changes that take place in the flow have a profound effect on the structure and function of the arterial wall and the development of the disease. The purpose of this paper was to non-invasively assess hemodynamic parameters s...

The placenta is responsible for the exchange of oxygen and nutrients from the mother to the fetus. Normal placentation and placental development are critical for a successful pregnancy. In this study the placenta are obtained from normal pregnancy and of normal vaginal delivery (age: 31 years old, parity 1, and gestation 38 weeks). After the delive...

Cavitating flows are notoriously complex because they are highly turbulent and unsteady flows involving two species (liquid/vapor) with a large density difference. These features pose a unique challenge to numerical modeling works. The study briefly reviews the methodology curently employed for industrial cavitating flow simulations using the two-p...

The paper presents a numerical simulation and analysis of the flow inside a poppet valve. First, the single-phase (liquid) flow is investigated, and an original model is introduced for quantitatively describing the vortex flow. Since an atmospheric outlet pressure produces large negative absolute pressure regions, a two-phase (cavitating) flow anal...

Blood flow analysis of the human right coronary artery (RCA) has been carried out to investigate the effects of serial stenosis on coronary hemodynamics. A 3-D model of a serial stenosed RCA was reconstructed based on multislice computerized tomography images. A velocity waveform in the proximal RCA and a pressure waveform in the distal RCA of a pa...

The purpose of this paper was to investigate the hemodynamic parameters associated to the blood flow in failed coronary venous bypass graft using computational fluid dynamics (CFD) technique. Narrowed section creates bypass graft constriction. This change of the flow direction alters significantly the local hemodynamic parameters. In this paper, a...

Nuchal umbilical cord (NUC) is a possible complication of pregnancy which can be associated with adverse perinatal outcome. A retrospective study was done at the County Emergency Hospital Timisoara, Romania, between January 2009 and December 2010 and included cases with NUC at the time of delivery. Outcome variable related to the mothers and newbor...

The purpose of this paper was to non-invasively assess hemodynamic parameters such as mass flow, wall shear stress, pressure drop and particle depositions with computational fluid dynamics (CFD) in the multiple stenosed right coronary artery – RCA using patient-specific data from computed tomography (CT) angiography, and their utilization in clinic...

The purpose of this paper was to non-invasively assess hemodynamic parameters such as mass flow, wall shear stress, pressure drop and particle depositions with computational fluid dynamics (CFD) in the multiple stenosed right coronary artery – RCA using patient-specific data from computed tomography (CT) angiography, and their utilization in clinic...

An investigation of unsteady flows in a three-dimensional bypass model was carried out for Newtonian fluid analogue to blood. The flow conditions considered are of relevance to hemodynamical applications and the localization of coronary diseases, and the main objective was to quantify the accuracy of the predictions and to provide benchmark data th...

The paper presents the authors ongoing efforts to develop a robust and efficient numerical methodology, and the associated expert software, for analysis, design and optimization of hydrofoil cascades. We developed, so far, a Finite Element solver with streamfunction formulation for incompressible, inviscid and irrotational cascade flow, using a mod...

The resistance to flow through a stenosis caused by viscous friction, flow separation, turbulence, and eddies at the site of the stenosis results in energy loss. Energy loss produces pressure loss distal to the stenosis and thus a pressure gradient across the narrowed segment. Assessment of shear stress, along with percent stenosis, in arterial les...

Accurate fluid mechanics models are important tools for predicting the flow field in the coronary artery for understanding the relationship between hemodynamics and the initiation and progression of atherosclerosis. The purpose of this paper is to asses non-invasively hemodynamic parameters such as disturbed flows, pressure distribution and wall sh...

This study focuses on the Achard turbine, a French concept of vertical axis, cross-flow, marine current turbine module. The main advantage of such turbines is their modularity: similar modules can be superposed on the same vertical axis, to form towers, with lengths adapted to marine or river current depths, at different locations. A marine or rive...

The present investigation concentrates on one particular problem related to fluid mechanics: namely, the description of disturbed flow fields in the coronary atherosclerosis. Atherosclerosis creating a constriction can significantly alter the local blood flow dynamics. From a biological aspect, the changes that take place in the flow have a profoun...

Transient three-dimensional laminar incompressible flow with rigid wall has been solved with a commercial 3D finite-volume numerical code. Instantaneous velocity vector and wall shear stress vector fields illustrate strong disturbed flow patterns. Implications of elevated surface contours of hemodynamic wall parameters, disturbed flows, and particl...

A simple hydropower farm model, equipped with 3 Achard turbine modules, aligned on the same row or put in staggered positions, has been built at 1:5 scale, to be tested in water channel. The 2D numerical modelling of the unsteady flow inside that farm model has been performed with COMSOL Multiphysics, using the k-\epsilon turbulence model, in order...

Objective: In this work we describe the complexity of the blood flow using a time dependent analysis, to determine the effects of aneurysm asymmetry,wall shear stress (WSS) distribution and vortex dynamics inside to the aneurysm body. Methods: To produce a realistic three-dimensional model of a patient's anatomy, CT-datasets were acquired by a four...

Objetive: The purpose of this paper was to non-invasively assess hemodynamic parameters such as mass flow, all hear stress, and wall pressure with computational fluid dynamics (CFD) in venous bypass graft using patient-specific data from computed tomography (CT) angiography. Methods: Narrowed venous bypass graft creating a constriction can signific...

In order to determine the optimal arrangement of vertical axis cross-flow marine current turbines within hydropower farms, an innovative, simplified, 2D numerical model was developed. It is based on the interaction between incident flow and turbine blades and was implemented in COMSOL Multiphysics. The new approach proved to save a lot of computati...

New and renewable energy sources are important in order to guarantee a sustainable power production in the future. Practically all hydraulic turbines that are presently used for hydropower generation have been developed for installation in water dams across streams. This conventional design is the most economical and energy efficient for river hydr...

In order to determine some optimal (or near optimal) horizontal arrangement of vertical axis cross-flow marine current turbines within hydropower farms, an innovative, simplified, 2D numerical model was developed. It is based on the interaction between incident flow and turbine blades and was implemented in COMSOL Multiphysics. The new approach pro...

Poster presented at the 2nd International Conference on Ocean Energy ICOE 2008, October 15-17, Brest, France

In order to determine some optimal (or near optimal) horizontal arrangement of vertical axis cross-flow marine current turbines within hydropower farms, an innovative, simplified, 2D numerical model was developed. It is based on the interaction between incident flow and turbine blades and was implemented in COMSOL Multiphysics. The new approach pro...