Search results for: distal radius

Authors: Sandrieli Afornali, Adriano Keijiro Maeda, Renato Fedatto Beraldo, Carlos Alberto Mattozo, Ricardo Nascimento Brito

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BACKGROUND: The most used variety in hydrocephalus treatment is the ventriculoperitoneal shunt (VPS). However, it may fails in 20 to 70% of cases. It makes necessary to have alternative cavities for the implantation of the distal catheter. Ventriculo-atrial shunting (VAS) is described as the second option. To our knowledge, there are 121 reported cases of VGB shunt in children until 2020 and a highly variable success rate, from 25 to 100%, with an average of 63% of patients presenting good long-term results. Our goal is to evaluate the epidemiological profile of patients submitted to ventriculo-gallbladder (VGB) shunt and, through a review of literature, to compare our results with others series. METHODS: a retrospective cross-sectional observational study of a case series of nine patients. The medical records of all patients were reviewed, who underwent VGB shunt at the Hospital Pequeno Príncipe from Curitiba, Paraná, Brazil, from January 2014 to October 2022. The inclusion criteria were: patients under 17 years of age with hydrocephalus of any etiology, currently using or prior to VGB shunt. RESULTS: There were 6 (66,7%) male and 3 (33,3%) female. The average age of 73.6 months or 6.1 years at the time of surgery. They were submitted on average 5.1 VPS reviews previous to VGB shunt. Five (55,5%) had complications of VGB shunt: infection (11.1%), atony (11.1%), hypodrainage due to kinking the distal catheter in the solution (11.1%) and ventriculoenteric fistula (22.2%); all these patients were cured at surgical reapproach, and in 2 of them the VGB shunt was reimplanted. Two patients died (22.2%), and five (55,5%) patients maintained the use of VGB shunt in the follow-up period; and in 4 (44.4%) there was never need for review. CONCLUSION: VGB shunt tends to be underestimated because it is still unconventional and little publicized in literature. Our article shows a lower risk of death and similar risk of complications when compared to others altenatives shunts. We emphasize VGB shunt as a safe procedure to be the second option when VPS fails or has contraindications.

Keywords: hydrocephalus, ventricular-gallbladder shunt, VGB shunt, VPS, ventriculoperitoneal shunt, ventriculoatrial shunt

Procedia PDF Downloads 72

Authors: Laila Salah Seada, Ashraf Ibrahim, Fawaz Al Rashid, Ihab Abdo, Hassan Kasim, Waleed Al Mansi, Saud Al Shabli

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Background and Objectives: Colorectal carcinoma is increasing among both men and women worldwide. It has a multifactorial etiology including genetic factors, environmental factors and inflammatory conditions of the digestive tract. A clinicopathologic assessment of colorectal carcinoma in Hail region is done, considering any changing patterns in two 5-year periods from 2005-2009 (A) and from 2012 to 2017 (B). All data had been retrieved from histopathology files of King Khalid Hospital, Hail. Results: During period (A), 75 cases were diagnosed as colorectal carcinoma. Male patients comprised 56/75 (74.7%) of the study, with a mean age of 58.4 (36-97), while females were 19/75 (25.3%) with a mean age of 50.3(30-85) and the difference was significant (p = 0.05). M:F ratio was 2.9:1. Most common histological type was adenocarcioma in 68/75 (90.7%) patients mostly well differentiated in 44/68 (64.7%). Mucinous neoplasms comprised only 7/75 (9.3%) of cases and tended to have a higher stage (p = 0.04). During period (B), 115 cases were diagnosed with an increase of 53.3% in number of cases than period (A). Male to female ratio also decreased to 1.35:1, females being 44.83% more affected. Adenocarcinoma remained the prevalent type (93.9%), while mucinous type was still rare (5.2%). No distal metastases found at time of presentation. Localization of tumors was rectosigmoid in group (A) in 41.4%, which increased to 56.6% in group (B), with an increase of 15.2%. Iliocecal location also decreased from 8% to 3.5%, being 56.25% less. Other proximal areas of the colon were decreased by 25.75%, from 53.9% in group (A) to 40% in group (B). Conclusion: Colorectal carcinoma in Hail region has increased by 53.3% in the past 5 years, with more females being diagnosed. Localization has also shifted distally by 15.2%. These findings are different from Western world patterns which experienced a decrease in incidence and proximal shift of the colon cancer localization. This might be due to better diagnostic tools, population awareness of the disease, as well as changing of life style and/or food habits in the region.

Keywords: colorectal cancer, Hail Region, changing pattern, distal shift

Procedia PDF Downloads 208

Authors: Abdulwhab Alotaibi, Abdullah Alzahrani, Ziyad Bokhari, Abdulelah Alghamdi

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First described in 1975 by Dr. Miller, Medical dressings are uncommon but possible cause of hand digital ischemia due the tourniquet-like effect. The incident of this complication has been reported across wide range of age-groups, yet it seems like that the pediatric population are specifically vulnerable. Multiple dressing types were reported to have caused ischemic injury, such as elastic wrap, tubular gauze, and self-adherent dressings. We present a case of medical dressing induced digital ischemia in patient with Congenital insensitivity to pain and anhidrosis (CIPA), which further challenge the discovery of the condition. An 8-year-old girl known case of CIPA. Brought by her mother to the ER after nail bed injury, which she managed by application of elastic wrap that was left for 24 hours. When the mother found out she immediately removed the elastic band, and noticed the fingertip was black and cold with tense bullae. The color then changed later when she arrived to the ER to dark purple with bluish discoloration on the tip. On examination there was well demarcated tense bullae on the distal right fifth finger. Neurovascular intact, pulse oximetry on distal digit 100%, capillary refill time was delayed. She was seen under Plastic surgery and conservative management recommended, and patient was discharged with safety netting. Two days later the patient came as follow-up visit at which her condition demonstrated significant improvement, the bullae has since ruptured leaving behind sloughed skin, capillary refill and pulse oximetry were both within normal limits, sensory function couldn’t be assessed but her motor function and ROM were normal, topical bacitracin and bandage dressings were applied for the eroded skin. Patient was scheduled for a follow-up in 2 weeks. Preventatively it’s advisable to avoid the commonly implicated dressings such as elastic, tubular gauze or self-adherent wraps in hand or digital injuries when possible, but in cases where the use of these dressings is of necessity the appropriate precautions must be taken, Dr. Makarewich proposed the following 5 measures to help minimize the incidence of the injury: 1-Unwrapping 12 inches of the dressing before rolling the injured finger. 2-Wrapping from distal to proximal with minimal tension to avoid vascular embarrassment. 3-The use of 5-25 inch to overlap the entire wrap. 4-Maintaining light pressure over the wrap to allow adherence of the dressing. 5-Minimization of the number of layers used to wrap the affected digit. Also assessing the capillary refill after the application can help in determining the patency of the supplying blood vessels. It’s also important to selectively determine if the patient is a candidate for conservative management, as tailored approach can help in maximizing the positive outcomes for our patients.

Keywords: congenital insensitivity to pain, digital ischemia, medical dressing, conservative management

Procedia PDF Downloads 63

Authors: Mehmet Erdi Korkmaz, Mustafa Günay

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Nowadays, grinding is frequently replaced with hard turning for reducing set up time and higher accuracy. This paper focused on mathematical modeling of average surface roughness (Ra) in hard turning of AISI L2 grade (DIN 1.2210) cold work tool steel with ceramic tools. The steel was hardened to 60±1 HRC after the heat treatment process. Cutting speed, feed rate, depth of cut and tool nose radius was chosen as the cutting conditions. The uncoated ceramic cutting tools were used in the machining experiments. The machining experiments were performed according to Taguchi L27 orthogonal array on CNC lathe. Ra values were calculated by averaging three roughness values obtained from three different points of machined surface. The influences of cutting conditions on surface roughness were evaluated as statistical and experimental. The analysis of variance (ANOVA) with 95% confidence level was applied for statistical analysis of experimental results. Finally, mathematical models were developed using the artificial neural networks (ANN). ANOVA results show that feed rate is the dominant factor affecting surface roughness, followed by tool nose radius and cutting speed.

Keywords: ANN, hard turning, DIN 1.2210, surface roughness, Taguchi method

Procedia PDF Downloads 371

Authors: Mehdi Boukri, Mohammed Naboussi Farsi, Mounir Naili, Omar Amellal, Mohamed Belazougui, Ahmed Mebarki, Nabila Guessoum, Brahim Mezazigh, Mounir Ait-Belkacem, Nacim Yousfi, Mohamed Bouaoud, Ikram Boukal, Aboubakr Fettar, Asma Souki

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The seismic risk to which the urban centres are more and more exposed became a world concern. A co-operation on an international scale is necessary for an exchange of information and experiments for the prevention and the installation of action plans in the countries prone to this phenomenon. For that, the 1990s was designated as 'International Decade for Natural Disaster Reduction (IDNDR)' by the United Nations, whose interest was to promote the capacity to resist the various natural, industrial and environmental disasters. Within this framework, it was launched in 1996, the RADIUS project (Risk Assessment Tools for Diagnosis of Urban Areas Against Seismic Disaster), whose the main objective is to mitigate seismic risk in developing countries, through the development of a simple and fast methodological and operational approach, allowing to evaluate the vulnerability as well as the socio-economic losses, by probable earthquake scenarios in the exposed urban areas. In this paper, we will present the adaptation and application of this methodology to the Algerian context for the seismic risk evaluation in urban areas potentially exposed to earthquakes. This application consists to perform an earthquake scenario in the urban centre of Constantine city, located at the North-East of Algeria, which will allow the building seismic damage estimation of this city. For that, an inventory of 30706 building units was carried out by the National Earthquake Engineering Research Centre (CGS). These buildings were digitized in a data base which comprises their technical information by using a Geographical Information system (GIS), and then they were classified according to the RADIUS methodology. The study area was subdivided into 228 meshes of 500m on side and Ten (10) sectors of which each one contains a group of meshes. The results of this earthquake scenario highlights that the ratio of likely damage is about 23%. This severe damage results from the high concentration of old buildings and unfavourable soil conditions. This simulation of the probable seismic damage of the building and the GIS damage maps generated provide a predictive evaluation of the damage which can occur by a potential earthquake near to Constantine city. These theoretical forecasts are important for decision makers in order to take the adequate preventive measures and to develop suitable strategies, prevention and emergency management plans to reduce these losses. They can also help to take the adequate emergency measures in the most impacted areas in the early hours and days after an earthquake occurrence.

Keywords: seismic risk, mitigation, RADIUS, urban areas, Algeria, earthquake scenario, Constantine

Procedia PDF Downloads 262

Authors: Barry Hojjatie

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Uniaxial (e.g., three-point bending) and biaxial flexure tests are used frequently for determining the strength of ceramics. It is generally believed that the biaxial test has an advantage as compared to uniaxial test because it produces a state of pure tension on the lower surface of the specimen and the maximum tensile stress, which is usually responsible for crack initiation and failure is unaffected by the edge condition. However, inconsistent strength values have been reported for the same material and testing conditions. The objective of this study was to analyze the strength of dental porcelain materials using the two different test methods and evaluate the main contributions to variability in biaxial testing and to analyze the relative influence of variables such as specimen geometric conditions and loading conditions on calculated strength of porcelain subjected to biaxial testing. Porcelain disks (16 mm dia x 2 mm thick) were subjected to biaxial flexure (pin-on-three-ball), and flexure strength values were calculated. A 3-D finite element model was developed to simulate various biaxial flexure test conditions. Stresses were analyzed for ceramic thickness in the range of 1.0-3.0 mm. For a 2-mm-thick disk subjected to a point load of 200 N, the maximum tensile stress at the lower surface was 180 MPa. This stress decreased to 95, 77, 68, and 59 MPa for the radius of the load values of 0.15, 0.3, 0.6, and 1.0 mm, respectively. Tensile stresses which developed at the top surface near the site of loading were small for the radius of the load ≥ 0.6 mm.

Keywords: ceramis, biaxial, flexure test, uniaxial

Procedia PDF Downloads 155

Authors: Surendra Choudhary, Sapan Tiwari

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The driver has two fundamental duties i) controlling the position of the vehicle along the longitudinal and lateral direction of movement ii) roadway width. Both of these duties are interdependent and are concurrently referred to as two-dimensional driver behavior. One of the main problems facing driver behavior modeling is to identify the parameters for describing the exemplary driving conduct and car maneuver under distinct traffic circumstances. Still, to date, there is no well-accepted theory that can comprehensively model the 2-D driver conduct (longitudinal and lateral). The primary objective of this research is to explore the vehicle's lateral longitudinal behavior in the heterogeneous condition of traffic on horizontal curves as well as the effect of road geometry on dynamic traffic parameters, i.e., car velocity and lateral placement. In this research, with their interrelationship, a thorough assessment of dynamic car parameters, i.e., speed, lateral acceleration, and turn radius. Also, horizontal curve road parameters, i.e., curvature radius, pavement friction, are performed. The dynamic parameters of the various types of car drivers are gathered using a VBOX GPS-based tool with high precision. The connection between dynamic car parameters and curve geometry is created after the removal of noise from the GPS trajectories. The major findings of the research are that car maneuvers with higher than the design limits of speed, acceleration, and lateral deviation on the studied curves of the highway. It can become lethal if the weather changes from dry to wet.

Keywords: geometry, maneuverability, terrain, trajectory, VBOX

Procedia PDF Downloads 143

Authors: A. I. O. Zaid

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Deep drawing is considered to be the most widely used sheet metal forming processes among the particularly in automobile and aircraft industries. It is widely used for manufacturing a large number of the body and spare parts. In its simplest form it may be defined as a secondary forming process by which a sheet metal is formed into a cylinder or alike by subjecting the sheet to compressive force through a punch with a flat end of the same geometry as the required shape of the cylinder end while it is held by a blank holder which hinders its movement but does not stop it. The punch and die profile radii play In this paper, the effects of punch and die profile radii on the autographic record, the minimum thickness strain location where the cracks normally start and cause the fracture, the maximum deep drawing force and the total consumed work in the drawing flat ended cylindrical brass cups are investigated. Five punches and five dies each having different profile radii were manufactured for this investigation. Furthermore, their effect on the quality of the drawn cups is also presented and discussed. It was found that the die profile radius has more effect on the maximum drawing force and the total consumed work than the punch profile radius.

Keywords: punch and die profile radii, deep drawing process, maximum drawing force, total consumed work, quality of produced parts, flat ended cylindrical brass cups

Procedia PDF Downloads 339

Authors: Belkheir Noura, Rabah Kerfah, Boumehani Abdellah

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The influence of solidity variations on the aerodynamic performance of H type vertical axis wind turbine is studied in this paper. The wind turbine model used in this paper is the three-blade wind turbine with the symmetrical airfoil, NACA0021. The length of the chord is 0.265m. Numerical investigations were implemented for the different solidity by changing the radius and blade number. A two-dimensional model of the wind turbine is employed. The approach a Reynolds-Averaged Navier–Stokes equations, completed by the K- ώ SST turbulence model, is used. Motion mesh model capability of a computational fluid dynamics (CFD) solver is used. For each value of the solidity, the aerodynamics performances and the characteristics of the flow field are studied at several values of the tip speed ratio, λ = 0.5 to λ = 3, with an incoming wind speed of 8 m/s. The results show that increasing the number of blades will reduce the maximum value of the power coefficient of the wind turbine. Also, for the VAWT with a lower solidity can obtain the maximum Cp at a high tip speed ratio. The effects of changing the radius and blade number on aerodynamic performance are almost the same. Finally, for the validation, experimental data from the literature and computational results were compared. In conclusion, to study the influence of the solidity in the performances of the wind turbine is to provide the reference for the design of H type vertical axis wind turbines.

Keywords: wind energy, darrieus h type vertical axis wind turbine, computational fluid dynamic, solidity

Procedia PDF Downloads 93

Authors: Amit Kumar Baghel, Sisir Kumar Nayak

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The proposed metamaterial design help to increase the radiation efficiency at 2.9 GHz by reducing the side and back lobes by making the phase difference of the waves emerging from the phase center of the horn antenna same after passing through metamaterial array. The unit cell of the metamaterial is having concentric ring structure made of copper of 0.035 mm thickness on both sides of FR4 sheet. The inner ring diameter is kept as 3 mm, and the outer ring diameters are changed according to the path and tramission phase difference of the unit cell from the phase center of the antenna in both the horizontal and vertical direction, i.e., in x- and y-axis. In this case, the ring radius varies from 3.19 mm to 6.99 mm with the respective S21 phase difference of -62.25° to -124.64°. The total phase difference can be calculated by adding the path difference of the respective unit cell in the array to the phase difference of S21. Taking one of the unit cell as the reference, the total phase difference between the reference unit cell and other cells must be integer multiple of 360°. The variation of transmission coefficient S21 with the ring radius is greater than -6 dB. The array having 5 x 5 unit cell is kept inside the pyramidal horn antenna (L X B X H = 295.451 x 384.233 x 298.66 mm3) at a distance of 36.68 mm from the waveguide throat. There is an improvement in side lobe level in E-plane by 14.6 dB when the array is used. The front to back lobe ration is increased by 1 dB by using the array. The proposed antenna with metamaterial array can be used in beam shaping for wireless power transfer applications.

Keywords: metamaterial, side lobe level, front to back ratio, beam forming

Procedia PDF Downloads 274

Authors: Saleh O. Allehabi, V. A. Dzubaa, V. V. Flambaum, Jiguang Li, A. V. Afanasjev, S. E. Agbemava

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Recently developed versions of the configuration method for open shells, configuration interaction with perturbation theory (CIPT), and configuration interaction with many-body perturbation theory (CI+MBPT) techniques are used to study the electronic structure of Er, Fm, and No atoms. Excitation energies of odd states connected to the even ground state by electric dipole transitions, the corresponding transition rates, isotope shift, hyperfine structure, ionization potentials, and static scalar polarizabilities are calculated. The way of extracting parameters of nuclear charge distribution beyond nuclear root mean square (RMS) radius, e.g., a parameter of quadrupole deformation β, is demonstrated. In nuclei with spin > 1/2, parameter β is extracted from the quadrupole hyperfine structure. With zero nuclear spin or spin 1/2, it is impossible since quadrupole zero, so a different method was developed. The measurements of at least two atomic transitions are needed to disentangle the contributions of the changes in deformation and nuclear RMS radius into field isotopic shift. This is important for testing nuclear theory and for searching for the hypothetical island of stability. Fm and No are heavy elements approaching the superheavy region, for which the experimental data are very poor, only seven lines for the Fm element and one line for the No element. Since Er and Fm have similar electronic structures, calculations for Er serve as a guide to the accuracy of the calculations. Twenty-eight new levels of Fm atom are reported.

Keywords: atomic spectra, electronic transitions, isotope effect, electron correlation calculations for atoms

Procedia PDF Downloads 155

Authors: Souad Mouzaoui, Bahia Djerdjouri

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Oxidative stress is one of the main factors involved in the onset and chronicity of inflammatory bowel disease (IBD). In this study, we investigated the beneficial effects of a potent natural antioxidant, curcumin (Cur) on colitis and mitochondrial dysfunction in trinitrobenzene sulfonic acid (TNBS)-induced colitis in mice. Rectal instillation of the chemical irritant TNBS (30 mg kg-1) induced the disruption of distal colonic architecture and a massive inflammatory cells influx to the mucosa and submucosa layers. Under these conditions, daily administration of Cur (25 mg kg-1) efficiently decreased colitis scores in the inflamed distal colon by reducing leukocyte infiltrate as attested by reduced myeloperoxidase (MPO) activity. Moreover, the levels of nitrite, an end product of inducible NO synthase activity (iNOS) and malonyl dialdehyde (MDA), a marker of lipid peroxidation increased in a time depending manner in response to TNBS challenge. Conversely, the markers of the antioxidant pool, reduced glutathione (GSH) and catalase activity (CAT) were drastically reduced. Cur attenuated oxidative stress markers and partially restored CAT and GSH levels. Moreover, our results expanded the effect of Cur on TNBS-induced colonic mitochondrial dysfunction. In fact, TNBS induced mitochondrial swelling and lipids peroxidation. These events reflected in the opening of mitochondrial transition pore and could be an initial indication in the cascade process leading to cell death. TNBS inhibited also mitochondrial respiratory activity, caused overproduction of mitochondrial superoxide anion (O2-.) and reduced level of mitochondrial GSH. Nevertheless, Cur reduced the extent of mitochondrial oxidative stress induced by TNBS and restored colonic mitochondrial function. In conclusion, our results showed the critical role of oxidative stress in TNBS-induced colitis. They highlight the role of colonic mitochondrial dysfunction induced by TNBS, as a potential source of oxidative damages. Due to its potent antioxidant properties, Cur opens a promising therapeutic approach against oxidative inflammation in IBD.

Keywords: colitis, curcumin, mitochondria, oxidative stress, TNBS

Procedia PDF Downloads 253

Authors: B. Engel, H. Hassan

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Rotary draw bending is a method which is being used in tube forming. In the tube bending process, the neutral axis moves towards the inner arc and the wall thickness distribution changes for tube’s cross section. Thinning takes place in the outer arc of the tube (extrados) due to the stretching of the material, whereas thickening occurs in the inner arc of the tube (intrados) due to the comparison of the material. The calculations of the wall thickness distribution, neutral axis shifting, and strain distribution have not been accurate enough, so far. The previous model (the geometrical model) describes the neutral axis shifting and wall thickness distribution. The geometrical of the tube, bending radius and bending angle are considered in the geometrical model, while the influence of the material properties of the tube forming are ignored. The advanced model is a modification of the previous model using material properties that depends on the correction factor. The correction factor is a purely empirically determined factor. The advanced model was compared with the Finite element simulation (FE simulation) using a different bending factor (Bf=bending radius/ diameter of the tube), wall thickness (Wf=diameter of the tube/ wall thickness), and material properties (strain hardening exponent). Finite element model of rotary draw bending has been performed in PAM-TUBE program (version: 2012). Results from the advanced model resemble the FE simulation and the experimental test.

Keywords: rotary draw bending, material properties, neutral axis shifting, wall thickness distribution

Procedia PDF Downloads 397

Authors: Hsin-Chieh Lee, Fen-Ling Kuo, Jui-Chi Lin

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Background: Upper extremity functional impairment that occurs after stroke includes hemiplegia, synergy movement, muscle hypertonicity, and somatosensory impairment, which result in inefficient and inaccurate movement. Robot-assisted rehabilitation is an intensive training approach that is effective in sensorimotor and hand function recovery. However, these systems mostly focused on the proximal part of the upper limb rather than the distal part. The device used in our study was Gloreha Sinfonia, which focuses on the distal part of the upper limb and uses a dynamic support system to facilitate the whole limb function. The objective of this study was to investigate the effects of robot-assisted therapy (RT) with Gloreha device on sensorimotor, and ADLs in patients with stroke. Method: Patients with stroke (N=25) participated AB or BA (A = 12 RT sessions and B = 12 conventional therapy (CT) sessions) for 6 weeks (60 min at each session, twice a week), with 1-month break for washout period. The performance of the patients was assessed by a blinded assessor at 4 time points (pretest 1, posttest 1, pretest 2, posttest 2) which including the Fugl–Meyer Assessment-upper extremity (FMA-UE), box and block test, electromyography of the extensor digitorum communis (EDC) and brachioradialis, a grip dynamometer for motor evaluation; Semmes–Weinstein hand monofilament and Revision of the Nottingham Sensory Assessment for sensory evaluation; and the Modified Barthel Index (MBI) for assessing the ADL ability. Result: RT group significantly improved FMA-UE proximal scores (p = 0.038), FMA-UE total scores (p = 0.046), and MBI (p = 0.030). The EDC exhibited higher efficiency during the small block grasping task in the RT group than in the CT group (p = 0.050). Conclusions: RT with the Gloreha device might lead to beneficial effects on arm motor function, ADL ability, and EDC muscle recruitment efficacy in patients with subacute to chronic stroke.

Keywords: activities of daily living, hand function, robotic rehabilitation, stroke

Procedia PDF Downloads 118

Authors: Arash M. Shahidi, Tilak Dias, Gayani K. Nandasiri

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While graduated compression is the foundation of treatment and management of many medical complications such as leg ulcer, varicose veins, and lymphedema, monitoring the interface pressure has been conducted using different sensors that operate based on diverse approaches. The variations existed from the pressure readings collected using different interface pressure measurement systems would cause difficulties in taking a decision regarding the compression therapy. It is crucial to acknowledge the differences existing between direct and indirect pressure measurement systems while considering the commercially available systems such as AMI, Picopress and OPM which are under direct measurements systems, and HATRA (BSI), HOSY (RAL-GZ) and FlexiForce which comes under the indirect measurement system. Furthermore, Piezo-resistive sensors (Flexiforce) can measure the changes in resistance corresponding to the applied force on the sensing area. Direct pressure measuring systems are capable of measuring interface pressure on the three-dimensional states, while the indirect pressure measuring systems stretch the fabric in the two-dimensional direction and extrapolate pressure from surface tension measured on the device and neglect the vital factor which is the radius of curvature. In this study, a leg mannequin of known dimensions is selected with a knitted class 3 compression stocking. It has been decided to evaluate the data collected from different available systems (AMI, PicoPress, FlexiForce, and HATRA) and compare the results. The results showed a discrepancy between Hatra, AMI, Picopress, and Flexiforce against the pressure standard used to generate class 3 compression stocking. As predicted a higher pressure value with direct interface measuring systems were monitored against HATRA due to the effect of the radius of curvature.

Keywords: AMI, FlexiForce, graduated compression, HATRA, interface pressure, PicoPress

Procedia PDF Downloads 352

Authors: Scott M. Black, Craig Maclean, Pauline Hall Barrientos, Konstantinos Ritos, Asimina Kazakidi

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Aortic aneurysms and dissections are leading causes of death in cardiovascular disease. Both inevitably lead to hemodynamic instability without surgical intervention in the form of vascular stent-graft deployment. An accurate description of the aortic geometry and blood flow in patient-specific cases is vital for treatment planning and long-term success of such grafts, as they must generate physiological branch perfusion and in-stent hemodynamics. The aim of this study was to create patient-specific computational fluid dynamics (CFD) models through a multi-modality, multi-dimensional approach with boundary condition optimization to predict branch flow rates and in-stent hemodynamics in custom stent-graft configurations. Three-dimensional (3D) thoracoabdominal aortae were reconstructed from four-dimensional flow-magnetic resonance imaging (4D Flow-MRI) and computed tomography (CT) medical images. The former employed a novel approach to generate and enhance vessel lumen contrast via through-plane velocity at discrete, user defined cardiac time steps post-hoc. To produce patient-specific boundary conditions (BCs), the aortic geometry was reduced to a one-dimensional (1D) model. Thereafter, a zero-dimensional (0D) 3-Element Windkessel model (3EWM) was coupled to each terminal branch to represent the distal vasculature. In this coupled 0D-1D model, the 3EWM parameters were optimized to yield branch flow waveforms which are representative of the 4D Flow-MRI-derived in-vivo data. Thereafter, a 0D-3D CFD model was created, utilizing the optimized 3EWM BCs and a 4D Flow-MRI-obtained inlet velocity profile. A sensitivity analysis on the effects of stent-graft configuration and BC parameters was then undertaken using multiple stent-graft configurations and a range of distal vasculature conditions. 4D Flow-MRI granted unparalleled visualization of blood flow throughout the cardiac cycle in both the pre- and postsurgical states. Segmentation and reconstruction of healthy and stented regions from retrospective 4D Flow-MRI images also generated 3D models with geometries which were successfully validated against their CT-derived counterparts. 0D-1D coupling efficiently captured branch flow and pressure waveforms, while 0D-3D models also enabled 3D flow visualization and quantification of clinically relevant hemodynamic parameters for in-stent thrombosis and graft limb occlusion. It was apparent that changes in 3EWM BC parameters had a pronounced effect on perfusion distribution and near-wall hemodynamics. Results show that the 3EWM parameters could be iteratively changed to simulate a range of graft limb diameters and distal vasculature conditions for a given stent-graft to determine the optimal configuration prior to surgery. To conclude, this study outlined a methodology to aid in the prediction post-surgical branch perfusion and in-stent hemodynamics in patient specific cases for the implementation of custom stent-grafts.

Keywords: 4D flow-MRI, computational fluid dynamics, vascular stent-grafts, windkessel

Procedia PDF Downloads 181

Authors: Pulakesh Das, Mukunda Dev Behera, Manchiraju Sri Ramachandra Murthy

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Large numbers of people living in and around the Hindu Kush Himalaya (HKH) region, depends on this diverse mountainous region for ecosystem services. Following the global trend, this region also experiencing rapid population growth, and demand for timber and agriculture land. The eight countries sharing the HKH region have different forest resources utilization and conservation policies that exert varying forces in the forest ecosystem. This created a variable spatial as well altitudinal gradient in rate of deforestation and corresponding forest patch fragmentation. The quantitative relationship between fragmentation and demography has not been established before for HKH vis-à-vis along elevation gradient. This current study was carried out to attribute the overall and different nature in landscape fragmentations along the altitudinal gradient with the demography of each sharing countries. We have used the tree canopy cover data derived from Landsat data to analyze the deforestation and afforestation rate, and corresponding landscape fragmentation observed during 2000 – 2010. Area-weighted mean radius of gyration (AMN radius of gyration) was computed owing to its advantage as spatial indicator of fragmentation over non-spatial fragmentation indices. Using the subtraction method, the change in fragmentation was computed during 2000 – 2010. Using the tree canopy cover data as a surrogate of forest cover, highest forest loss was observed in Myanmar followed by China, India, Bangladesh, Nepal, Pakistan, Bhutan, and Afghanistan. However, the sequence of fragmentation was different after the maximum fragmentation observed in Myanmar followed by India, China, Bangladesh, and Bhutan; whereas increase in fragmentation was seen following the sequence of as Nepal, Pakistan, and Afghanistan. Using SRTM-derived DEM, we observed higher rate of fragmentation up to 2400m that corroborated with high human population for the year 2000 and 2010. To derive the nature of fragmentation along the altitudinal gradients, the Statistica software was used, where the user defined function was utilized for regression applying the Gauss-Newton estimation method with 50 iterations. We observed overall logarithmic decrease in fragmentation change (area-weighted mean radius of gyration), forest cover loss and population growth during 2000-2010 along the elevation gradient with very high R2 values (i.e., 0.889, 0.895, 0.944 respectively). The observed negative logarithmic function with the major contribution in the initial elevation gradients suggest to gap filling afforestation in the lower altitudes to enhance the forest patch connectivity. Our finding on the pattern of forest fragmentation and human population across the elevation gradient in HKH region will have policy level implication for different nations and would help in characterizing hotspots of change. Availability of free satellite derived data products on forest cover and DEM, grid-data on demography, and utility of geospatial tools helped in quick evaluation of the forest fragmentation vis-a-vis human impact pattern along the elevation gradient in HKH.

Keywords: area-weighted mean radius of gyration, fragmentation, human impact, tree canopy cover

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Authors: G. Roshan Deen, J. S. Pedersen

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Temperature-responsive poly(N-isopropyl acrylamide) PNIPAM microgels crosslinked with a new hydrophobic chemical crosslinker was prepared by surfactant-mediated precipitation emulsion polymerization. The temperature-responsive property of the microgel and the influence of the crosslinker on the swelling behaviour was studied systematically by light scattering and small-angle X-ray scattering (SAXS). The radius of gyration (Rg) and the hydrodynamic radius (Rh) of the microgels decreased with increase in temperature due to the volume phase transition from a swollen to a collapsed state. The ratio of Rg/Rh below the transition temperature was lower than that of hard-spheres due to the lower crosslinking density of the microgels. The SAXS data was analysed by a model in which the microgels were modelled as core-shell particles with a graded interface. The model at intermediate temperatures included a central core and a more diffuse outer layer describing pending polymer chains with a low crosslinking density. In the fully swollen state, the microgels were modelled with a single component with a broad graded surface. In the collapsed state they were modelled as homogeneous and relatively compact particles. The polymer volume fraction inside the microgel was also derived based on the model and was found to increase with increase in temperature as a result of collapse of the microgel to compact particles. The polymer volume fraction in the core of the microgel in the collapsed state was about 60% which is higher than that of similar microgels crosslinked with hydrophilic and flexible cross-linkers.

Keywords: microgels, SAXS, hydrophobic crosslinker, light scattering

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Authors: Won Yeol Choi, Sangmo Kang

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The propulsion of a bacterial flagellum in a viscous fluid has attracted many interests in the field of biological hydrodynamics, but remains yet fully understood and thus still a challenging problem. In this study, therefore, we have numerically investigated the flow around a steadily rotating micro-sized spring to further understand such bacterial flagellum propulsion. Note that a bacterium gains thrust (propulsive force) by rotating the flagellum connected to the body through a bio motor to move forward. For the investigation, we convert the spring model from the micro scale to the macro scale using a similitude law (scale law) and perform simulations on the converted macro-scale model using a commercial software package, CFX v13 (ANSYS). To scrutinize the propulsion characteristics of the flagellum through the simulations, we make parameter studies by changing some flow parameters, such as the pitch, helical radius and rotational speed of the spring and the Reynolds number (or fluid viscosity), expected to affect the thrust force experienced by the rotating spring. Results show that the propulsion characteristics depend strongly on the parameters mentioned above. It is observed that the forward thrust increases in a linear fashion with either of the rotational speed or the fluid viscosity. In addition, the thrust is directly proportional to square of the helical radius and but the thrust force is increased and then decreased based on the peak value to the pitch. Finally, we also present the appropriate flow and pressure fields visualized to support the observations.

Keywords: fluid viscosity, hydrodynamics, similitude, propulsive force

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Authors: Samaneh Nabavi, Hadi Shirzad, Somayeh Khanjani, Shirin Jalili

Abstract:

Quantum dots (QDs) are semiconductor nanocrystals that exhibit intrinsic optical and electrical properties that are size dependent due to the quantum confinement effect. Quantum confinement is brought about by the fact that in bulk semiconductor material the electronic structure consists of continuous bands, and that as the size of the semiconductor material decreases its radius becomes less than the Bohr exciton radius (the distance between the electron and electron-hole) and discrete energy levels result. As a result QDs have a broad absorption range and a narrow emission which correlates to the band gap energy (E), and hence QD size. QDs can thus be tuned to give the desired wavelength of fluorescence emission.Due to their unique properties, QDs have attracted considerable attention in different scientific areas. Also, they have been considered for forensic applications in recent years. The ability of QDs to fluoresce up to 20 times brighter than available fluorescent dyes makes them an attractive nanomaterial for enhancing the visualization of latent fingermarks, or poorly developed fingermarks. Furthermore, the potential applications of QDs in the detection of nitroaromatic explosives, such as TNT, based on directive fluorescence quenching of QDs, electron transfer quenching process or fluorescence resonance energy transfer have been paid to attention. DNA analysis is associated tightly with forensic applications in molecular diagnostics. The amount of DNA acquired at a criminal site is inherently limited. This limited amount of human DNA has to be quantified accurately after the process of DNA extraction. Accordingly, highly sensitive detection of human genomic DNA is an essential issue for forensic study. QDs have also a variety of advantages as an emission probe in forensic DNA quantification.

Keywords: forensic science, quantum dots, DNA typing, explosive sensor, fingermark analysis

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Authors: Mauricio Plaza, Willian Aperador

Abstract:

Hip disarticulation is an amputation through the hip joint capsule, removing the entire lower extremity, with a closure of the remaining musculature over the exposed acetabulum. Tumors of the distal and proximal femur were treated by total femur resection; a hip disarticulation sometimes is a performance for massive trauma with crush injuries to the lower extremity. This article discusses the design a system for rehabilitation of a patient with bilateral hip disarticulations. The prosthetics designed allowed the patient to do natural gait suspended between parallel articulate crutches with the body weight support between the crutches. The care of this patient was a challenge due to bilateral amputations at such a high level and the special needs of a patient mobility.

Keywords: amputation, prosthesis, mobility, hemipelvectomy

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Authors: Adae Amoako, Daniel Montero, Peter Murray, George Pujalte

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We present a case of a 42-year-old, right-handed Caucasian male who presented to a medical orthopedics clinic with left wrist pain. The patient indicated that the pain started two months prior to the visit. He could only remember helping a friend move furniture prior to the onset of pain. Examination of the left wrist showed limited extension compared to the right. There was clicking with flexion and extension of the wrist on the dorsal aspect. Mild tenderness was noticed over the distal radioulnar joint. There was ulnar and radial deviation on provocation. Initial 4-view x-rays of the left wrist showed mild radiocarpal and scapho-trapezium-trapezoid (ST-T) osteoarthritis, with subchondral cysts seen in the lunate and scaphoid, with no obvious fractures. The patient was initially put in a wrist brace and diclofenac topical gel was prescribed for pain control, as a patient could not take non-steroidal anti-inflammatory drugs (NSAIDs) due to gastritis. Despite diclofenac topical gel use and bracing, symptoms remained, and a steroid injection with 1 mL of lidocaine with 10 mg of triamcinolone acetonide was performed under fluoroscopy. He obtained some relief but after 3 months, the injection had to be repeated. On 2-month follow up after the initial evaluation, symptoms persisted. Magnetic resonance imaging (MRI) was obtained which showed an abnormal T1 hypodense signal involving the proximal pole of the scaphoid and articular collapse proximally of the scaphoid, with marked irregularity of the overlying cartilage, suggesting a remote injury, findings consistent with avascular necrosis of the proximal pole of the scaphoid. A month after that, the patient had the left proximal pole of the scaphoid debrided and an intercompartmental supraretinacular artery vascularized. Pedicle bone graft reconstruction of the proximal pole of the left scaphoid was done. A non-vascularized autograft from the left radius was also applied. He was put in a thumb spica cast with the interphalangeal joint free for 6 weeks. On 6-week follow-up after surgery, the patient was healing well and could make a composite fist with his left hand. The diagnosis of Preiser’s disease is primarily based on radiological findings. Due to the fact that necrosis happens over a period of time, most AVNs are diagnosed at the late stages of the disease. There appear to be no specific guidelines on the management AVN of the scaphoid. In the past, immobilization and arthroscopic debridement had been used. Radial osteotomy has also been tried. Vascularized bone grafts have also been used to treat Preiser’s disease. In our patient, we used three of these treatment modalities, starting with conservative management with topical NSAIDS and immobilization, then debridement with vascularized bone grafts.

Keywords: wrist pain, avascular necrosis of the scaphoid, Preiser’s disease, vascularized bone grafts

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Authors: Quoc Ngoc Phan, Hieu Van Nguyen, Minh Hong Nguyen

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This study presents an integrated approach using Mercury Injection Capillary Pressure (MICP) and petrographic analysis to assess the seal quality of the inter-bedded shale formations which are considered the intra-formation top seals of hydrocarbon bearing zones in Green Dragon structure. Based on the hydrocarbon column height (HCH) at leak point derived from capillary pressure data, four seal types were identified. Furthermore, the results of scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis were interpreted to clarify the influence of clay minerals on seal capacity. The result of the study indicated that the inter-bedded shale formations are the good sealing quality with a majority of analyzed samples ranked type A and B seals in the sample set. Both seal types occurred mainly in mudstones with pore radius estimated less than 0.251 µm. Overall, type A and B seals contained a large amount of authigenic clay minerals such as illite, chlorite which showed the complexity of morphological arrangement in pore space. Conversely, the least common seal type C and D were presented in moderately compacted sandstones with more open pore radius. It is noticeable that there was a reduction of illite and chlorite in clay mineral fraction of these seal type. It is expected that the integrated analysis approach using Mercury Injection Capillary Pressure and petrographic data employed in this study can be applied to assess the sealing quality of future well sites in Green Dragon or other structures.

Keywords: seal capacity, hydrocarbon height column, seal type, SEM, XRD

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Authors: Yang Shen, Yongpan Cheng, Jinliang Xu

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The effective blade cooling is of great significance for improving the performance of turbine. The mist cooling emerges as the promising way compared with the transitional single-phase cooling. In the mist cooling, the injected droplet will evaporate rapidly, and cool down the blade surface due to the absorbed latent heat, hence the lifetime for evaporating droplet becomes critical for design of cooling passages for the blade. So far there have been extensive studies on the droplet evaporation, but usually the isothermal model is applied for most of the studies. Actually the surface cooling effect can affect the droplet evaporation greatly, it can prolong the droplet evaporation lifetime significantly. In our study, a new theoretical model for sessile droplet evaporation with surface cooling effect is built up in toroidal coordinate. Three evaporation modes are analyzed during the evaporation lifetime, include “Constant Contact Radius”(CCR) mode、“Constant Contact Angle”(CCA) mode and “stick-slip”(SS) mode. The dimensionless number E0 is introduced to indicate the strength of the evaporative cooling, it is defined based on the thermal properties of the liquid and the atmosphere. Our model can predict accurately the lifetime of evaporation by validating with available experimental data. Then the temporal variation of droplet volume, contact angle and contact radius are presented under CCR, CCA and SS mode, the following conclusions are obtained. 1) The larger the dimensionless number E0, the longer the lifetime of three evaporation cases is; 2) The droplet volume over time still follows “2/3 power law” in the CCA mode, as in the isothermal model without the cooling effect; 3) In the “SS” mode, the large transition contact angle can reduce the evaporation time in CCR mode, and increase the time in CCA mode, the overall lifetime will be increased; 4) The correction factor for predicting instantaneous volume of the droplet is derived to predict the droplet life time accurately. These findings may be of great significance to explore the dynamics and heat transfer of sessile droplet evaporation.

Keywords: blade cooling, droplet evaporation, lifetime, theoretical analysis

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Authors: Samuel Abraham Berhane, Lingbing Bu

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This paper presents the spatiotemporal variability of aerosols, clouds, and precipitation within the major cities in Eritrea and it investigates the relationship between aerosols, clouds, and precipitation concerning the presence of aerosols over the study region. In Eritrea, inadequate water supplies will have both direct and indirect adverse impacts on sustainable development in areas such as health, agriculture, energy, communication, and transport. Besides, there exists a gap in the knowledge on suitable and potential areas for cloud seeding. Further, the inadequate understanding of aerosol-cloud-precipitation (ACP) interactions limits the success of weather modification aimed at improving freshwater sources, storage, and recycling. Spatiotemporal variability of aerosols, clouds, and precipitation involve spatial and time series analysis based on trend and anomaly analysis. To find the relationship between aerosols and clouds, a correlation coefficient is used. The spatiotemporal analysis showed larger variations of aerosols within the last two decades, especially in Assab, indicating that aerosol optical depth (AOD) has increased over the surrounding Red Sea region. Rainfall was significantly low but AOD was significantly high during the 2011 monsoon season. Precipitation was high during 2007 over most parts of Eritrea. The correlation coefficient between AOD and rainfall was negative over Asmara and Nakfa. Cloud effective radius (CER) and cloud optical thickness (COT) exhibited a negative correlation with AOD over Nakfa within the June–July–August (JJA) season. The hybrid single-particle Lagrangian integrated trajectory (HYSPLIT) model that is used to find the path and origin of the air mass of the study region showed that the majority of aerosols made their way to the study region via the westerly and the southwesterly winds.

Keywords: aerosol-cloud-precipitation, aerosol optical depth, cloud effective radius, cloud optical thickness, HYSPLIT

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Authors: M. Benlebna, B. Serier, B. Bachir Bouiadjra, S. Khalkhal

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This study focuses on the mechanical behavior of a dental prosthesis subjected to dynamic loads chewing. It covers a three-dimensional analysis by the finite element method, the level of distribution of equivalent stresses induced in the bone between the implants (depending on the number of implants). The studied structure, consisting of a braced, implant and mandibular bone is subjected to dynamic loading of variable amplitude in three directions corrono-apical, mesial-distal and bucco-lingual. These efforts simulate those of mastication. We show that compared to the implantation of a single implant, implantology using two implants promotes the weakening of the bones. This weakness is all the more likely that the implants are located in close proximity to one another.

Keywords: stress, bone, dental implant, distribution, stress levels, dynamic, effort, interaction, prosthesis

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Authors: E. Gopi, E. Devaindran

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Objective: Non-operative management of blunt splenic trauma have started to overtake the traditional splenectomy in recent years across the grade of splenic injury. The two main non-operative methods are observation and angioembolisation. However, the post management convalescence in these groups are still being investigated. The study attempts to quantify the clinical indicators among the two in particular complications, mortalities, conversions to operative management and duration of inpatient stay. Methodology: A systematic search was done via PUBMED, MEDLINE, and EMBASE. A total of 639 articles identified and subsequently 68 articles were identified post duplicates, full text, and inclusion and exclusion criteria. Main exclusions were non-English articles without English translation, pure observational or angioembolisation articles of which no comparison data could be identified and articles looking into pure hemodynamically unstable patients. Results: 24 non randomized controlled trial, 5 clinical control trial and 39 retrospective studies analyzing a total of 23700 patients with blunt splenic trauma. Discrepancies in data were noted in the group who had observational management versus angioembolisation in particular as data was compared among the classes of splenic rupture, the protocol of management in different centers, availability of angiogram suite, and the study design. Further variability was also noted in the angioembolisation arm as the preference for treatment differs between distal versus proximal splenic artery involvement. Overall the cumulative mortality in both observational and angioembolisation group were similar, 2.78% and 5.97% respectively. The cause of death however is not directly attributed to the management itself but rather patient comorbidities, other associated injuries and conversions to splenectomy leading to post splenectomy complications. The cumulative morbidity among each group appears to be same approximately 12% in observational versus 15% in angioembolisation. However, the type of complications varies with the observational group having higher rates of inpatient stay and intrabdominal hematoma infection and angioembolisation group developing more splenic infarcts and bleeds. There were significant disparity in reporting the actual data on duration of inpatient stay and complications to allow a statistically significant quantitative analysis to be done, 15 articles however are currently being considered. Conclusions: Observational management appears to be much effective in managing lower grade splenic trauma (grade 1 and 2) where else angioembolisation appears to play a bigger role in intermediate grades (grade 3-4) in ensuring splenic function preservation. Care has to be taken however in the angioembolisation group in view of distal splenic infarct group compromising splenic function. The cumulated data of 15 articles are now being considered for a meta-analysis.

Keywords: blunt splenic trauma, conservative, non-operative, angioembolisation

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Authors: Karthikeyan M., Paul M. J.

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This abstract describes a case of central pancreatectomy (CP) for a 50-year-old woman with a neuroendocrine tumor in the mid-body of the pancreas. CP, a parenchyma-sparing surgical option, preserves the distal pancreas and spleen, reducing the risk of pancreatic endocrine and exocrine insufficiency compared to traditional resections. The patient, initially misdiagnosed with transient ischemic attack, presented with hypoglycemic symptoms and was found to have a pancreatic lesion. Post-operative results were positive, with a reduction in pancreatic drain volume and normalization of blood sugar levels. This case highlights CP's efficacy in treating centrally located pancreatic lesions while maintaining pancreatic function.

Keywords: central pancreatectomy without anastomosis, no endocrine deficiency on follow-op, less post-op hospital stay, less post-op complications

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Authors: Gintare Judzentyte

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The present research is aimed to discuss semantics and pragmatics of spatial deictics (deictic adverbs of place and demonstrative pronouns) in the Baltic languages: in spoken Lithuanian and in spoken Latvian. The following objectives have been identified to achieve the aim: 1) to determine the usage of adverbs of place in spoken Lithuanian and Latvian and to verify their meanings in face-to-face communication; 2) to determine the usage of demonstrative pronouns in spoken Lithuanian and Latvian and to verify their meanings in face-to-face communication; 3) to compare the systems between the two spoken languages and to identify the main tendencies. As meanings of demonstratives (adverbs of place and demonstrative pronouns) are context-bound, it is necessary to verify their usage in spontaneous interaction. Besides, deictic gestures play a very important role in face-to-face communication. Therefore, an experimental method is necessary to collect the data. Video material representing spoken Lithuanian and spoken Latvian was recorded by means of the method of a qualitative interview (a semi-structured interview: an empirical research is all about asking right questions). The collected material was transcribed and evaluated taking into account several approaches: 1) physical distance (location of the referent, visual accessibility of the referent); 2) deictic gestures (the combination of language and gesture is especially characteristic of the exophoric use); 3) representation of mental spaces in physical space (a speaker sometimes wishes to mark something that is psychically close as psychologically distant and vice versa). The research of the collected data revealed that in face-to-face communication the participants choose deictic adverbs of place instead of demonstrative pronouns to locate/identify entities in situations where the demonstrative pronouns would be expected in spoken Lithuanian and in spoken Latvian. The analysis showed that visual accessibility of the referent is very important in face-to-face communication, but the main criterion while localizing objects and entities is the need for contrast: lith. čia ‘here’, šis ‘this’, latv. šeit ‘here’, šis ‘this’ usually identify distant entities and are used instead of distal demonstratives (lith. ten ‘there’, tas ‘that’, latv. tur ‘there’, tas ‘that’), because the referred objects/subjects contrast to further entities. Furthermore, the interlocutors in examples from a spontaneously situated interaction usually extend their space and can refer to a ‘distal’ object/subject with a ‘proximal’ demonstrative based on the psychological choice. As the research of the spoken Baltic languages confirmed, the choice of spatial deictics in face-to-face communication is strongly effected by a complex of criteria. Although there are some main tendencies, the exact meaning of spatial deictics in the spoken Baltic languages is revealed and is relevant only in a certain context.

Keywords: Baltic languages, face-to-face communication, pragmatics, semantics, spatial deictics

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Authors: Qianhui Li, Christoph H. Bruecker

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Atherosclerotic plaques are typically found where flow separation and variations of shear stress occur. Although helical flow patterns and flow separations have been recorded in the aorta, their relation has not been clearly clarified and especially in the condition of artificial heart valve prostheses. Therefore, an experimental study is performed to investigate the hemodynamic performance of different mechanical heart valves (MHVs), i.e. the SJM Regent bileaflet mechanical heart valve (BMHV) and the Lapeyre-Triflo FURTIVA trileaflet mechanical heart valve (TMHV), in a transparent model of the human aorta under a physiological pulsatile right-hand helical flow condition. A typical systolic flow profile is applied in the pulse-duplicator to generate a physiological pulsatile flow which thereafter flows past an axial turbine blade structure to imitate the right-hand helical flow induced in the left ventricle. High-speed particle image velocimetry (PIV) measurements are used to map the flow evolution. A circular open orifice nozzle inserted in the valve plane as the reference configuration initially replaces the valve under investigation to understand the hemodynamic effects of the entered helical flow structure on the flow evolution in the aortic arch. Flow field analysis of the open orifice nozzle configuration illuminates the helical flow effectively delays the flow separation at the inner radius wall of the aortic arch. The comparison of the flow evolution for different MHVs shows that the BMHV works like a flow straightener which re-configures the helical flow pattern into three parallel jets (two side-orifice jets and the central orifice jet) while the TMHV preserves the helical flow structure and therefore prevent the flow separation at the inner radius wall of the aortic arch. Therefore the TMHV is of better hemodynamic performance and reduces the pressure loss.

Keywords: flow separation, helical aortic flow, mechanical heart valve, particle image velocimetry

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