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A Combined Computational and Experimental Analysis of PLA and PCL Hybrid Nanocomposites 3D Printed Scaffolds for Bone Regeneration. Biomedicines 2024; 12:261. [PMID: 38397863 PMCID: PMC10886521 DOI: 10.3390/biomedicines12020261] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2023] [Revised: 01/12/2024] [Accepted: 01/16/2024] [Indexed: 02/25/2024] Open
Abstract
A combined computational and experimental study of 3D-printed scaffolds made from hybrid nanocomposite materials for potential applications in bone tissue engineering is presented. Polycaprolactone (PCL) and polylactic acid (PLA), enhanced with chitosan (CS) and multiwalled carbon nanotubes (MWCNTs), were investigated in respect of their mechanical characteristics and responses in fluidic environments. A novel scaffold geometry was designed, considering the requirements of cellular proliferation and mechanical properties. Specimens with the same dimensions and porosity of 45% were studied to fully describe and understand the yielding behavior. Mechanical testing indicated higher apparent moduli in the PLA-based scaffolds, while compressive strength decreased with CS/MWCNTs reinforcement due to nanoscale challenges in 3D printing. Mechanical modeling revealed lower stresses in the PLA scaffolds, attributed to the molecular mass of the filler. Despite modeling challenges, adjustments improved simulation accuracy, aligning well with experimental values. Material and reinforcement choices significantly influenced responses to mechanical loads, emphasizing optimal structural robustness. Computational fluid dynamics emphasized the significance of scaffold permeability and wall shear stress in influencing bone tissue growth. For an inlet velocity of 0.1 mm/s, the permeability value was estimated at 4.41 × 10-9 m2, which is in the acceptable range close to human natural bone permeability. The average wall shear stress (WSS) value that indicates the mechanical stimuli produced by cells was calculated to be 2.48 mPa, which is within the range of the reported literature values for promoting a higher proliferation rate and improving osteogenic differentiation. Overall, a holistic approach was utilized to achieve a delicate balance between structural robustness and optimal fluidic conditions, in order to enhance the overall performance of scaffolds in tissue engineering applications.
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A computational and experimental mechanical study of nanocomposites for 3D printed scaffolds with a new geometry. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2023; 2023:1-4. [PMID: 38082818 DOI: 10.1109/embc40787.2023.10340382] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/18/2023]
Abstract
We present a combined study of the mechanical properties of 3D printed scaffolds made by nanocomposite materials based on polycaprolactone (PCL). The geometry and dimensions of the three different systems is the same. Τhe porosity is 50% for all systems. Distributions of von-Mises strains and stresses, and total deformations were obtained through Finite Element Analysis (FEA) for a maximum amount of force applied, in a compressive numerical experiment. Also compressive experiments were performed for both raw and 3D nanoconposite scaffolds.
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SAFETRANS: a system for 3D visibility estimation and cloud cover detection. APPLIED OPTICS 2023; 62:4600-4608. [PMID: 37707157 DOI: 10.1364/ao.483122] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/09/2022] [Accepted: 03/16/2023] [Indexed: 09/15/2023]
Abstract
The estimation of visibility is of significant importance in aviation safety and forms part of the measurements routinely collected in real time to provide safety guidelines and decisions. Our work concerns the creation and implementation of a lidar-based visibility estimation system as part of the SAFETRANS research program. We created a reproducible system to (1) support standard airport equipment, (2) serve simultaneously as a visibility meter and a ceilometer reporting on cloud cover, (3) offer increased accuracy and improved capabilities compared to standardized equipment currently in use while (4) requiring minimal user training to function. This work presents the visibility estimation and cloud cover algorithms and subsequently reports on results of field tests in a number of Greek airports under various atmospheric conditions.
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An Impact Localization Solution Using Embedded Intelligence-Methodology and Experimental Verification via a Resource-Constrained IoT Device. SENSORS (BASEL, SWITZERLAND) 2023; 23:896. [PMID: 36679690 PMCID: PMC9860581 DOI: 10.3390/s23020896] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/09/2022] [Revised: 01/08/2023] [Accepted: 01/10/2023] [Indexed: 06/17/2023]
Abstract
Recent advances both in hardware and software have facilitated the embedded intelligence (EI) research field, and enabled machine learning and decision-making integration in resource-scarce IoT devices and systems, realizing "conscious" and self-explanatory objects (smart objects). In the context of the broad use of WSNs in advanced IoT applications, this is the first work to provide an extreme-edge system, to address structural health monitoring (SHM) on polymethyl methacrylate (PPMA) thin-plate. To the best of our knowledge, state-of-the-art solutions primarily utilize impact positioning methods based on the time of arrival of the stress wave, while in the last decade machine learning data analysis has been performed, by more expensive and resource-abundant equipment than general/development purpose IoT devices, both for the collection and the inference stages of the monitoring system. In contrast to the existing systems, we propose a methodology and a system, implemented by a low-cost device, with the benefit of performing an online and on-device impact localization service from an agnostic perspective, regarding the material and the sensors' location (as none of those attributes are used). Thus, a design of experiments and the corresponding methodology to build an experimental time-series dataset for impact detection and localization is proposed, using ceramic piezoelectric transducers (PZTs). The system is excited with a steel ball, varying the height from which it is released. Based on TinyML technology for embedding intelligence in low-power devices, we implement and validate random forest and shallow neural network models to localize in real-time (less than 400 ms latency) any occurring impacts on the structure, achieving higher than 90% accuracy.
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Primary MSCs for Personalized Medicine: Ethical Challenges, Isolation and Biocompatibility Evaluation of 3D Electrospun and Printed Scaffolds. Biomedicines 2022; 10:biomedicines10071563. [PMID: 35884868 PMCID: PMC9313419 DOI: 10.3390/biomedicines10071563] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2022] [Revised: 06/24/2022] [Accepted: 06/27/2022] [Indexed: 11/17/2022] Open
Abstract
Autologous cell therapy uses patients’ own cells to deliver precise and ideal treatment through a personalized medicine approach. Isolation of patients’ cells from residual tissue extracted during surgery involves specific planning and lab steps. In the present manuscript, a path from isolation to in vitro research with human mesenchymal stem cells (MSCs) obtained from residual bone tissues is described as performed by a medical unit in collaboration with a research center. Ethical issues have been addressed by formulating appropriate harvesting protocols according to European regulations. Samples were collected from 19 patients; 10 of them were viable and after processing resulted in MSCs. MSCs were further differentiated in osteoblasts to investigate the biocompatibility of several 3D scaffolds produced by electrospinning and 3D printing technologies; traditional orthopedic titanium and nanostructured titanium substrates were also tested. 3D printed scaffolds proved superior compared to other substrates, enabling significantly improved response in osteoblast cells, indicating that their biomimetic structure and properties make them suitable for synthetic tissue engineering. The present research is a proof of concept that describes the process of primary stem cells isolation for in vitro research and opens avenues for the development of personalized cell platforms in the case of patients with orthopedic trauma. The demonstration model has promising perspectives in personalized medicine practices.
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Pathophysiological alterations of left ventricular myocardial systolic function during normal pregnancy assessed by speckle tracking echocardiography: a prospective cohort echocardiography study. Eur Heart J Cardiovasc Imaging 2022. [DOI: 10.1093/ehjci/jeab289.163] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Abstract
Funding Acknowledgements
Type of funding sources: None.
Introduction
Pregnancy induces a variety of haemodynamic and morphological changes, leading to the amplification of cardiac pumping function. These changes do not cause any significant left ventricular (LV) dysfunction by using conventional echocardiographic indices, but it is not fully elucidated whether subclinical or/and reversible myocardial dysfunction is provoked during pregnancy. Two-dimensional speckle tracking echocardiography (2D-STE) can detect subclinical myocardial dysfunction even when conventional echocardiography reveal LV normal ejection fraction (LVEF).Purpose: The aim of this study was to evaluate whether LV systolic performance is impaired during normal low risk pregnancy by using both conventional 2D and 3D echo indices and 2D-STE. Materials and methods: One hundred and twelve consecutive pregnant women without any history of heart disease were prospectively recruited. They underwent serial echocardiographic evaluation in each pregnancy trimester (1st: 8th-12th week, 2nd: 22th-26th week, 3rd: 32-36th week) and 6 months after delivery (time indicated as 4). LV dimensions, relative wall thickness (RWT), 2D-LVEF, 3D-LVEF, systolic S wave from Tissue Doppler Imaging, LV global longitudinal strain (LVGLS), LV global circumferential strain (LVGCS) and LV-twist were measured and compared to 31 nulliparous women of similar age, who served as a control group (c).Results: Progressive eccentric LV hypertrophy was observed during pregnancy, which was subsided postpartum (p1-2 = 0.08, p2-3= 0.002, p3-4 = 0.001, p1-3 < 0.001, p1-4= 0.789), while no significant change in LV dimensions was found. 2D-LVEF, 3D-LVEF and S wave values were not significantly different among the three trimesters, postpartum and controls. LVGLS progressively decreased during pregnancy (1st:-21.71 ± 2.13%, 2nd: -21.20 ± 2.30%, 3rd: -19.82 ± 2.10%,4th: -21.81 ± 2.05%, c: -21.71 ± 2.2[E1]%,overall p < 0,001 ) and returned to normal during puerperium. No significant difference was noted in LVGCS (1st: -18.08 ± 5.54%, 2nd: -18.57 ± 3.41%, 3rd: -18.20 ± 3.33%,4th: -17.95 ± 3.39%,c: -18.8 ± 2.2% , p > 0.3). LV-Twist was significantly higher in the 1st trimester compared to controls (p= 0.04) and remained constantly high during the rest of the pregnancy and puerperium (1st:13.80 ± 5.09°, 2nd :13.46 ± 5.35°, 3rd:13.58 ± 4.32°, 4th:13.37 ± 4.26°, c: 11.5 ± 4.3°, ).Conclusion: Left ventricular subclinical dysfunction seems to occur in the longitudinal axis even in low risk individuals with normal pregnancy. Increased torsional movement of the heart seems to counterbalance the temporal impairment of longitudinal systolic function.
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Biventricular myocardial function in Covid-19 recovered patients assessed by speckle tracking echocardiography: a prospective cohort echocardiography study. Eur Heart J Cardiovasc Imaging 2022. [PMCID: PMC9383374 DOI: 10.1093/ehjci/jeab289.255] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Funding Acknowledgements Type of funding sources: None. Introduction Although severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes respiratory disease and affects primarily the lungs, it may also lead to cardiovascular complications and late manifestations like myocarditis, arrhythmias and myocardial damage. Nevertheless, it is not clear whether cardiovascular involvement remains after Covid-19 recovery. Two-dimensional speckle tracking echocardiography (2D-STE) can detect subclinical myocardial dysfunction, if present, and has been widely used for left (LV) and right (RV) ventricular function assessment in several clinical conditions. Purpose The aim of our study was to evaluate prospectively myocardial systolic function and hence cardiac involvement in patients after the recovery from Covid-19, using 2D-STE. Methods 100 Covid-19 recovered patients with preserved left ventricular ejection fraction (LVEF), were prospectively recruited from March 2021 until June 2021 at the General hospital of Korinthos and at the General hospital of Elefsina, "Thriassio". Based upon clinical manifestation of the disease, they were divided into two groups, those with mild symptoms, who were treated ambulant and those with respiratory insufficiency who were hospitalized. Conventional echo parameters as wells as LV global longitudinal strain (LVGLS), regional strain of all LV walls and right ventricular global longitudinal strain (RVGLS) were measured in all patients and compared to controls. Results The mean time of performed echo examination of all patients was 33.28 ± 9.4 days after the initial confirmed covid-19 infection diagnosis. Although overall LV systolic function expressed by EF was normal and similar to controls, LVGLS was found to be significantly lower in Covid-19 recovered patients in compare to controls (-18.47±-2.4 vs -21.07±-1.76% respectively, p < 0.0001). More specifically, it seemed that especially the lateral wall longitudinal strain (LATLS) and posterior wall longitudinal strain (POSTLS) were significantly reduced in all patients compared to controls (-17.77±-3.48 vs -20.97±-2.86% respectively, p < 0.0001 for LATLS and -19.52±-5.3 vs -22.23±-2.65% respectively, p = 0.01 for POSTLS). RVGLS was found significantly diminished only in the hospitalized group of Covid-19 recovered patients, compared to controls (-21.29±-5.58 vs -26.03±-4.55% respectively, p < 0.0001). Conclusions LVGLS is affected in almost all individuals after covid-19 infection independently of the infection severity, with LATLS being the most sensitive marker of LV impairment and with POSTLS to follow. RV shows impaired GLS only in severely ill patients highlighting RVGLS as a helpful tool of prognosis. Recovered patients from Covid-19 infection have to be monitored for a long time, since the duration and evolution of these lesions is unknown, and the term "long covid disease" might also include the cardiac function.
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Left ventricular diastolic function during pregnancy: insights from conventional and speckle tracking echo parameters. Eur Heart J 2021. [DOI: 10.1093/eurheartj/ehab724.0100] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Abstract
Introduction
Profound changes occur in the cardiovascular system during pregnancy, regarding to induce cardiac pumping function. Although LV systolic and diastolic function have been thoroughly studied using conventional indices, speckle tracking parameters of cardiac function are not well described.
Purpose
The aim of our study was to evaluate the LV diastolic function during an uncomplicated pregnancy using both traditional and newer speckle tracking parameters.
Methods
We prospectively enrolled 40 consecutive pregnant women in whom serial echocardiographic evaluation was performed in each pregnancy trimester (1st: 8th–12th week, 2nd: 22th–26th week, 3rd: 32–36th week) and 6 months after delivery. Mitral inflow velocities (E, A), mitral annulus TDI velocities (E', A'), ratio E/A and E/E' and untwisting velocity rate were measured after cautious selection of studies with legible images in.
Results
The peak E transmitral inflow velocity during early diastole decreased significantly during pregnancy especially between 2nd and 3rd trimester and increased again postpartum (p1-2=0.475, p2-3<0.05 p3-4<0.05). The peak A flow velocity during atrial contraction did not change significantly during pregnancy (p1-2=0.333, p2-3=0.952, p3-4=0.989). As a result, E/A ratio was decreasing as pregnancy was advancing (p1-2=0.964, p2-3<0.05, p3-4=0.240). TDI E' early diastolic velocity was decreased especially in the 3rd trimester and recovered postpartum (p1-2=0.138, p2-3<0.01, p3-4<0.01) while E/E' ratio was increased especially in the 2nd trimester (p1-2<0.05, p2-3=0.572, p3-4=0.021, p1-4=0.383) and also recovered postpartum. Peak untwisting velocity rate demontrated a progressive decrease during pregnancy, although not statistically significant. There was a trend towards recovery in the puerperium (p1-2=0.072, p2-3=0.679, p3-4=0.052, p1-4=0.929) (Table 1).
Conclusion
Our study demonstrated that diastolic function seems to be impaired during an uncomplicated pregnancy. However all the conventional and newer speckle tracking indices of diastolic function remain in normal range. Postpartum appears to be a recovery process in all parameters.
Funding Acknowledgement
Type of funding sources: None.
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On the Multi-Functional Behavior of Graphene-Based Nano-Reinforced Polymers. MATERIALS 2021; 14:ma14195828. [PMID: 34640226 PMCID: PMC8510086 DOI: 10.3390/ma14195828] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/05/2021] [Revised: 09/29/2021] [Accepted: 09/30/2021] [Indexed: 11/25/2022]
Abstract
The objective of the present study is the assessment of the impact performance and the concluded thermal conductivity of epoxy resin reinforced by layered Graphene Nano-Platelets (GNPs). The two types of used GNPs have different average thicknesses, <4 nm for Type 1 and 9–12 nm for Type 2. Graphene-based polymers containing different GNP loading contents (0.5, 1, 5, 10, 15 wt.%) were developed by using the three-roll mill technique. Thermo-mechanical (Tg), impact tests and thermal conductivity measurements were performed to evaluate the effect of GNPs content and type on the final properties of nano-reinforced polymers. According to the results, thinner GNPs were proven to be more promising in all studied properties when compared to thicker GNPs of the same weight content. More specifically, the glass transition temperature of nano-reinforced polymers remained almost unaffected by the GNPs inclusion. Regarding the impact tests, it was found that the impact resistance of the doped materials increased up to 50% when 0.5 wt.% Type 1 GNPs were incorporated within the polymer. Finally, the thermal conductivity of doped polymers with 15 wt.% GNPs showed a 130% enhancement over the reference material.
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Gradient 3D Printed PLA Scaffolds on Biomedical Titanium: Mechanical Evaluation and Biocompatibility. Polymers (Basel) 2021; 13:polym13050682. [PMID: 33668285 PMCID: PMC7956550 DOI: 10.3390/polym13050682] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2021] [Revised: 02/18/2021] [Accepted: 02/19/2021] [Indexed: 12/14/2022] Open
Abstract
The goal of the present investigation was to find a solution to crucial engineering aspects related to the elaboration of multi-layered tissue-biomimicking composites. 3D printing technology was used to manufacture single-layered and gradient multi-layered 3D porous scaffolds made of poly-lactic acid (PLA). The scaffolds manufacturing process was optimized after adjusting key printing parameters. The scaffolds with 60 μm side length (square-shaped pores) showed increased stiffness values comparing to the other specimens. A silicone adhesive has been further used to join biomedical titanium plates, and the PLA scaffolds; in addition, titania nanotubes (TNTs were produced on the titanium for improved adhesion. The titanium-PLA scaffold single lap joints were evaluated in micro-tensile testing. The electrochemical processing of the titanium surface resulted in a 248% increase of the ultimate strength in the overlap area for dry specimens and 40% increase for specimens immersed in simulated body fluid. Finally, the biocompatibility of the produced scaffolds was evaluated with primary cell populations obtained after isolation from bone residual tissue. The manufactured scaffolds present promising features for applications in orthopedic implantology and are worth further.
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Tissue doppler imaging of left atrial appendage during transoesophageal echocardiography predicts successful cardioversion in patients with atrial fibrillation. Eur Heart J Cardiovasc Imaging 2021. [DOI: 10.1093/ehjci/jeaa356.102] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Abstract
Funding Acknowledgements
Type of funding sources: None.
Introduction
Restoration of sinus rhythm in patients with atrial fibrillation (AF) prevents from thromboembolic events, decreases the risk for cardiomyopathy and improves quality of life.
Purpose
This study aimed to determine whether Tissue Doppler Imaging (TDI) during transesophageal echo (TEE) could predict successful electrical cardioversion (CV) of AF lasting more than 48 hours but less than 6 months.
Methods
One hundred patients, 74 men and 26 women of mean age 64.7 ± 9.8 years old with non-valvular AF were included. Pulse wave (PW) Doppler velocities as well as TDI velocities of the medial and lateral walls of the left atrial appendage (LAA) were recorded during TEE before cardioversion. Synchronized electrical cardioversion was occurred within 12 hours after TEE using 100-200 Joules. We also evaluated LA size and the global strain of LAA.
Results
Sinus rhythm restoration was succeeded in 80% of patients and maintained until discharge, 48 hours later. TDI velocities > 8cm/s were correlated with successful cardioversion (sensitivity 70% and specificity 63%) and were more predictive compared to PW Doppler velocities of > 40cm/s. TDI recordings at the medial LAA wall were more accurate, with less artefacts and better positioning of the sample volume. Global longitudinal strain was not significantly correlated with CV outcome.
Conclusion
Our results indicate that TDI velocities of the LAA walls more than 8cm/s could be used as a cut-off value predicting successful cardioversion of AF.
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Fabrication and Characterization of Polyetherimide Electrospun Scaffolds Modified with Graphene Nano-Platelets and Hydroxyapatite Nano-Particles. Int J Mol Sci 2020; 21:E583. [PMID: 31963248 PMCID: PMC7014066 DOI: 10.3390/ijms21020583] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2019] [Revised: 01/10/2020] [Accepted: 01/13/2020] [Indexed: 02/07/2023] Open
Abstract
Solution electrospinning process (SEP) is a versatile technique for generating non-woven fibrous materials intended to a wide range of applications. One of them is the production of fibrous and porous scaffolds aiming to mimic bone tissue, as artificial extracellular matrices (ECM). In the present work, pure and nano-modified electrospun polyetherimide (PEI) scaffolds have been successfully fabricated. The nano-modified ones include (a) graphene nano-platelets (GNPs), (b) hydroxyapatite (HAP), and (c) mixture of both. After fabrication, the morphological characteristics of these scaffolds were revealed by using scanning electron (SEM) and transmission electron (TEM) microscopies, while porosity and mean fiber diameter were also calculated. In parallel, contact angle experiments were conducted so that the hydrophilicity level of these materials to be determined. Finally, the mechanical performance of the fabricated scaffolds was investigated by conducting uniaxial tensile tests. Ιn future work, the fabricated scaffolds will be further utilized for investigation as potential candidate materials for cell culture with perspective in orthopedic applications.
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Effect of water aging on the mechanical properties of flax fiber/bio‐based resin composites. J Appl Polym Sci 2019. [DOI: 10.1002/app.48787] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Graphene Nanoplatelet- and Hydroxyapatite-Doped Supramolecular Electrospun Fibers as Potential Materials for Tissue Engineering and Cell Culture. Int J Mol Sci 2019; 20:ijms20071674. [PMID: 30987205 PMCID: PMC6480389 DOI: 10.3390/ijms20071674] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2019] [Revised: 03/19/2019] [Accepted: 04/01/2019] [Indexed: 01/20/2023] Open
Abstract
Porous and fibrous artificial extracellular matrices (ECM) called scaffolds are considered to be promising avenues of research in the field of biomedical engineering, including tissue fabrication through cell culture. The current work deals with the fabrication of new matrix-type scaffolds through electrospinning, in order to support future three-dimensional tissue formation. The selected material for the fabrication of these scaffolds was a supramolecular polymer (SP) that is based on ureiodypyrimidone hydrogen bonding units (UPy). More precisely, pure SP and modified electrospun scaffolds with (a) graphene nanoplatelets (GNPs), (b) hydroxyapatite (HA), and (c) a mixture of both were fabricated for the needs of the current study. The aim of this work is to engineer and to characterize SP electrospun scaffolds (with and without fillers) and study whether the introduction of the fillers improve the physical and mechanical properties of them. The obtained results indicate that doping the SP scaffolds with GNPs led to improved apparent mechanical properties while HA seems to slightly deteriorate them. For all cases, doping provided thinner fibers with a more hydrophilic surface. Taking together, these types of SP scaffolds can be further studied as potential candidate for cell culture.
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Assessing the Damage Tolerance of Out of Autoclave Manufactured Carbon Fibre Reinforced Polymers Modified with Multi-Walled Carbon Nanotubes. MATERIALS 2019; 12:ma12071080. [PMID: 30986932 PMCID: PMC6479945 DOI: 10.3390/ma12071080] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/20/2019] [Revised: 03/27/2019] [Accepted: 03/29/2019] [Indexed: 11/16/2022]
Abstract
The present study aims to investigate the influence of multi-walled carbon nanotubes (MWCNTs) on the damage tolerance after impact (CAI) of the development of Out of Autoclave (OoA) carbon fibre reinforced polymer (CFRP) laminates. The introduction of MWCNTs into the structure of CFRPs has been succeeded by adding carbon nanotube-enriched sizing agent for the pre-treatment of the fibre preform and using an in-house developed methodology that can be easily scaled up. The modified CFRPs laminates with 1.5 wt.% MWCNTs were subjected to low velocity impact at three impact energy levels (8, 15 and 30 J) and directly compared with the unmodified laminates. In terms of the CFRPs impact performance, compressive strength of nanomodified composites was improved for all energy levels compared to the reference material. The test results obtained from C-scan analysis of nano-modified specimens showed that the delamination area after the impact is mainly reduced, without the degradation of compressive strength and stiffness, indicating a potential improvement of damage tolerance compared to the reference material. SEM analysis of fracture surfaces revealed the additional energy dissipation mechanisms; pulled-out carbon nanotubes which is the main reason for the improved damage tolerance of the multifunctional composites.
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Healing of carbon fiber reinforced plastics by Diels–Alder based polymers: Effects of healing agent concentration and curing cycle. J Appl Polym Sci 2019. [DOI: 10.1002/app.47478] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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‘Vamo’: Introducing a low-cost reusable 3D printed video laryngoscope. TRENDS IN ANAESTHESIA AND CRITICAL CARE 2018. [DOI: 10.1016/j.tacc.2018.09.035] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Preparation of polyvinylpyrrolidone-based polymer electrolytes and their application by in-situ gelation in dye-sensitized solar cells. Electrochim Acta 2018. [DOI: 10.1016/j.electacta.2018.03.194] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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A comparative study between epoxy/Titania micro‐ and nanoparticulate composites thermal and mechanical behavior by means of particle–matrix interphase considerations. POLYM ENG SCI 2017. [DOI: 10.1002/pen.24668] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Poster Session 4The imaging examination and quality assessmentP957Economic impact analysis and quality performance of working with cardiovascular sonographers in high-volume echocardiography laboratoryP958Feasibility of temporal super resolution enhancement of echocardiographic images to diagnose cardiac DiseasesP959Remote medical diagnostician project - Achievements and limitation in tele-echocardiographyP960Right atrial remodeling and galectin-3 are associated with functional capacity in patients with pulmonary arterial hypertensionP961Interatrial electromechanical delay assessed by tissue doppler imaging can separate adults with prehypertension from healthy normotensive controlsP962Preliminary results of an extensive echocardiographic pacemaker optimization protocol for cardiac resynchronization therapyP963Left ventricular global and regional myocardial function in patients with double orifice mitral valve after radical correction on atrioventricular septal defectP964Improving quantitation of left ventricular ejection fraction in a tertiary echocardiography lab - marrying (or merging) guidelines and new technologyP965Echocardiographic evaluation of cardiac function and hemodynamics during LVAD-based resuscitation from cardiac arrest - a porcine studyP966Systolic excursion of the right ventricular outflow tract as a marker of right ventricular dysfunctionP967The impact of the new 2016 ASE/EACVI recommendations in the prevalence and grades of diastolic dysfunction: an analysis from the general populationP968Differential microRNA-21 and microRNA-133 gene expression levels in peripheral blood mononuclear cells from patients with heart failure with preserved ejection fractionP969CMR evaluation of cardiac thrombi and masses by T1 and T2 mapping : an observational studyP970Effect of coronary artery ectasia on left ventricular deformation mechanics. A 2D Speckle Tracking Echocardiography studyP971Diagnostic performance of stress Echo, SPECT, PET, stress CMR, CTCA, CTP and FFRCT for the assessment of CAD versus invasive FFR: a metaanalysisP972Utility of early assessment of myocardial mechanics in STEMI patients treated by primary percutaneous coronary intervention to predict major adverse cardiac events during the first 12 months of folloP973Role of left atrial reservoir in the prediction of increased left ventricular filling pressures in patients with ST-segment elevation myocardial infarctionP974Does the left ventricle ejection fraction improves the Grace risk score accuracy? P975Can we predict significant coronary stenosis using regional strain analysis in non-ST elevation acute coronary syndrome?P976Persistence of pulmonary hypertension after transcatheter aortic valve replacement: incidence and prognostic impactP977Global longitudinal strain is an independent predictor of all cause mortality in patients with severe aortic valve stenosis undergoing valve replacement or treated conservativallyP978Contribution of left ventricular diastolic dysfunction and myocardial fibrosis to pulmonary hypertension in severe aortic stenosisP979Left atrial dysfunction as a determinant of pulmonary hypertension in patients with isolated severe aortic stenosis and preserved left ventricular ejection fractionP980Intraprocedural monitoring protocol using routine transthoracic echocardiography with backup transesophageal probe in transcatheter aortic valve replacement: a single center experience. Eur Heart J Cardiovasc Imaging 2016. [DOI: 10.1093/ehjci/jew260] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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Association of lipid profile with serum PON1 concentration in patients with chronic kidney disease. Ren Fail 2016; 38:1601-1606. [DOI: 10.3109/0886022x.2016.1144031] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
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Mode II fracture toughening and healing of composites using supramolecular polymer interlayers. EXPRESS POLYM LETT 2016. [DOI: 10.3144/expresspolymlett.2016.85] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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Poster session 3The imaging examinationP646Simulator-based testing of skill in transthoracic echoP647Clinical and echocardiographic characteristics of isolated left ventricular non-compactionP648Appropriate use criteria of transthoracic echocardiography and its clinical impact in an aged populationAnatomy and physiology of the heart and great vesselsP649Prevalence and determinants of exercise oscillatory ventilation in the EUROEX trial populationAssessment of diameters, volumes and massP650Left atrial remodeling after percutaneous left atrial appendage closureP651Global atrial performance with tyrosine kinase inhibitors in metastatic renal cell carcinomaP652Early right ventricular response to cardiac resynchronization therapy: impact on clinical outcomesP653Parameters of speckle-tracking echocardiography and biomechanical values of a dilative ascending aortaAssessments of haemodynamicsP654Right atrial hemodynamics in infants and children: observations from 3-dimensional echocardiography derived right atrial volumesAssessment of systolic functionP655One-point carotid wave intensity predicts cardiac mortality in patients with congestive heart failure and reduced ejection fractionP656Persistence of cardiac remodeling in adolescents with previous fetal growth restrictionP6572D speckle tracking-derived left ventricle global longitudinal strain and left ventricular dysfunction stages: a useful discriminator in moderate-to-severe aortic regurgitationP658Global longitudinal strain and strain rate in type two diabetes patients with chronic heart failure: relevance to circulating osteoprotegerinP659Analysis of left ventricular function in patients before and after surgical and interventional mitral valve therapyP660Left ventricular end-diastolic volume is complementary with global longitudinal strain for the prediction of left ventricular ejection fraction in echocardiographic daily practiceP661Left ventricular assist device, right ventricle function, and selection bias: the light side of the moonP662Assessment of right ventricular function in patients with anterior ST elevation myocardial infarction; a 2-d speckle tracking studyP663Right ventricular systolic function assessment in sickle cell anaemia using echocardiographyAssessment of diastolic functionP664Prognostic value of transthoracic cardiopulmonary ultrasound in cardiac surgery intensive care unitP665Comparative efficacy of renin-angiotensin system modulators on prognosis, right heart and left atrial parameters in patients with chronic heart failure and preserved left ventricular systolic functionP666Left atrial volume index is the most significant diastolic functional parameter of hemodynamic burden as measured by NT-proBNP in acute myocardial infarctionP667Preventive echocardiographic screening. preliminary dataP668Assessment of the atrial electromechanical delay and the mechanical functions of the left atrium in patients with diabetes mellitus type IIschemic heart diseaseP669Coronary flow velocity reserve by echocardiography as a measure of microvascular function: feasibility, reproducibility and agreement with PET in overweight patients with coronary artery diseaseP670Influence of cardiovascular risk in the occurrence of events in patients with negative stress echocardiographyP671Prevalence of transmural myocardial infarction and viable myocardium in chronic total occlusion (CTO) patientsP672The impact of the interleukin 6 receptor antagonist tocilizumab on mircovascular dysfunction after non st elevation myocardial infarction assessed by coronary flow reserve from a randomized studyP673Impact of manual thrombus aspiration on left ventricular remodeling: the echocardiographic substudy of the randomized Physiologic Assessment of Thrombus Aspirtion in patients with ST-segment ElevatioP674Acute heart failure in STEMI patients treated with primary percutaneous coronary intervention is related to transmural circumferential myocardial strainP675Long-term prognostic value of infarct size as assessed by cardiac magnetic resonance imaging after a first st-segment elevation myocardial infarctionHeart valve DiseasesP676Prognostic value of LV global longitudinal strain in aortic stenosis with preserved LV ejection fractionP677Importance of longitudinal dyssynchrony in low flow low gradient severe aortic stenosis patients undergoing dobutamine stress echocardiography. a multicenter study (on behalf of the HAVEC group)P678Predictive value of left ventricular longitudinal strain by 2D Speckle Tracking echocardiography, in asymptomatic patients with severe aortic stenosis and preserved ejection fractionP679Clinical and echocardiographic characteristics of the flow-gradient patterns in patients with severe aortic stenosis and preserved left ventricular ejection fractionP6802D and 3D speckle tracking assessment of left ventricular function in severe aortic stenosis, a step further from biplane ejection fractionP681Functional evaluation in aortic stenosis: determinant of exercise capacityP682Left ventricular mechanics: novel tools to evaluate left ventricular function in patients with primary mitral regurgitationP683Plasma B-type natriuretic peptide level in patients with isolated rheumatic mitral stenosisP684Quantitative assessment of severity in aortic regurgitation and the influence of elastic proprieties of thoracic aortaP685Characterization of chronic aortic and mitral regurgitation using cardiovascular magnetic resonanceP686Functional mitral regurgitation: a warning sign of underlying left ventricular systolic dysfunction in heart failure with preserved ejection fraction.P687Secondary mitral valve tenting in primary degenerative prolapse quantified by three-dimensional echocardiography predicts regurgitation recurrence after mitral valve repairP688Advanced heart failure with reduced ejection fraction and severe mitral insufficiency compensate with a higher oxygen peripheral extraction to a reduced cardiac output vs oxygen uptake response to maxP689Predictors of acute procedural success after percutaneous mitraclip implantation in patients with moderate-to-severe or severe mitral regurgitation and reduced ejection fractionP690The value of transvalvular gradients obtained by transthoracic echocardiography in estimation of severe paravalvular leakage in patients with mitral prosthetic valvesP691Characteristics of infective endocarditis in a non tertiary hospitalP692Infective endocarditis: predictors of severity in a 3-year retrospective analysisP693New echocardiographic predictors of early recurrent mitral functional regurgitation after mitraclip implantationP694Transesophageal echocardiography can be reliably used for the allocation of patients with severe aortic stenosis for tras-catheter aortic valve implantationP695Annular sizing for transcatheter aortic valve selection. A comparison between computed tomography and 3D echocardiographyP696Association between aortic dilatation, mitral valve prolapse and atrial septal aneurysm: first descriptive study.CardiomyopathiesP698Cardiac resynchronization therapy by multipoint pacing improves the acute response of left ventricular mechanics and fluid dynamics: a three-dimensional and particle image velocimetry echo studyP699Long-term natural history of right ventricular function in dilated cardiomyopathy: innocent bystander or leading actor?P700Right to left ventricular interdependence at rest and during exercise assessed by the ratio between pulmonary systolic to diastolic time in heart failure reduced ejection fractionP701Exercise strain imaging demonstrates impaired right ventricular contractile reserve in patients with hypertrophic cardiomyopathyP702Prevalence of overt left ventricular dysfunction (burn-out phase) in a portuguese population of hypertrophic cardiomyopathy, a multicentre studyP703Systolic and diastolic myocardial mechanics in hypertrophic cardiomyopathy and their link to the extent of hypertrophy, replacement fibrosis and interstitial fibrosisP704Multimodality imaging and genotype-phenotype associations in a cohort of patients with hypertrophic cardiomyopathy studied by next generation sequencing and cardiac magnetic resonanceP705Sudden cardiac death risk assessment in apical hypertrophic cardiomyopathy: do we need to add MRI to the equation?P706Prognostic value of left ventricular ejection fraction, proBNP, exercise capacity, and NYHA functional class in patients with left ventricular non-compaction cardiomyopathyP707The anti-hypertrophic microRNAs miR-1, miR-133a and miR-26b and their relationship to left ventricular hypertrophy in patients with essential hypertensionP708Prevalence of left ventricular systolic dysfunction in a portuguese population of left ventricular non-compaction cardiomyopathy, a multicentre studyP709Assessment of systolic and diastolic features in light chain amyloidosis: an echocardiographic and cardiac magnetic resonance studyP710Morbid obesity-associated hypertension identifies bariatric surgery best responders: Clinical and echocardiographic follow up studyP711Echocardiographic markera for overhydration in patients under haemodialysisP712Gender aspects of right ventricular size and function in clinically stable heart transplant patientsP713Evidence of cardiac stem cells from the left ventricular apical tip in patients undergone LVAD implant: a comparative strain-ultrastructural studySystemic diseases and other conditionsP714Speckle tracking assessment of right ventricular function is superior for differentiation of pressure versus volume overloaded right ventricleP715Prognostic value of pulmonary arterial pressure: analysis in a large dataset of timely matched non-invasive and invasive assessmentsP716Effect of the glucagon-like peptide-1 analogue liraglutide on left ventricular diastolic and systolic function in patients with type 2 diabetes: a randomised, single-blinded, crossover pilot studyP717Tissue doppler evaluation of left ventricular functions, left atrial mechanical functions and atrial electromechanical delay in juvenile idiopathic arthritisP718Echocardiographic detection of subclinical left ventricular dysfunction in patients with rheumatoid arthritisP719Left ventricular strain values are unaffected by intense training: a longitudinal, speckle-tracking studyP720Diastolic left ventricular function in autosomal dominant polycystic kidney disease: a matched-cohort, speckle-tracking echocardiographic studyP721Relationship between adiponectin level and left ventricular mass and functionP722Left atrial function is impaired in patients with multiple sclerosisMasses, tumors and sources of embolismP723Paradoxical embolization to the brain in patients with acute pulmonary embolism and confirmed patent foramen ovale with bidirectional shunt, results of prospective monitoringP724Following the European Society of Cardiology proposed echocardiographic algorithm in elective patients with clinical suspicion of infective endocarditis: diagnostic yield and prognostic implicationsP725Metastatic cardiac18F-FDG uptake in patients with malignancy: comparison with echocardiographic findingsDiseases of the aortaP726Echocardiographic measurements of aortic pulse wave velocity correlate well with invasive methodP727Assessment of increase in aortic and carotid intimal medial thickness in adolescent type 1 diabetic patientsStress echocardiographyP728Determinants and prognostic significance of heart rate variability in renal transplant candidates undergoing dobutamine stress echocardiographyP729Pattern of cardiac output vs O2 uptake ratio during maximal exercise in heart failure with reduced ejection fraction: pathophysiological insightsP730Prognostic value and predictive factors of cardiac events in patients with normal exercise echocardiographyP731Right ventricular mechanics during exercise echocardiography: normal values, feasibility and reproducibility of conventional and new right ventricular function parametersP732The added value of exercise-echo in heart failure patients: assessing dynamic changes in extravascular lung waterP733Applicability of appropriate use criteria of exercise stress echocardiography in real-life practice: what have we improved with new documents?Transesophageal echocardiographyP7343D-TEE guidance in percutaneous mitral valve interventions correcting mitral regurgitationContrast echocardiographyP735Pulmonary transit time by contrast enhanced ultrasound as parameter for cardiac performance: a comparison with magnetic resonance imaging and NT-ProBNPReal-time three-dimensional TEEP736Optimal parameter selection for anisotropic diffusion denoising filters applied to aortic valve 4d echocardiographsP737Left ventricle systolic function in non-alcoholic cirrhotic candidates for liver transplantation: a three-dimensional speckle-tracking echocardiography studyTissue Doppler and speckle trackingP738Optimizing speckle tracking echocardiography strain measurements in infants: an in-vitro phantom studyP739Usefulness of vascular mechanics in aortic degenerative valve disease to estimate prognosis: a two dimensional speckle tracking studyP740Vascular mechanics in aortic degenerative valve disease: a two dimensional speckle-tracking echocardiography studyP741Statins and vascular load in aortic valve disease patients, a speckle tracking echocardiography studyP742Is Left Bundle Branch Block only an electrocardiographic abnormality? Study of LV function by 2D speckle tracking in patients with normal ejection fractionP743Dominant inheritance of global longitudinal strain in a population of healthy and hypertensive twinsP744Mechanical differences of left atria in paroxysmal atrial fibrillation: A speckle-tracking study.P745Different distribution of myocardial deformation between hypertrophic cardiomyopathy and aortic stenosisP746Left atrial mechanics in patients with chronic renal failure. Incremental value for atrial fibrillation predictionP747Subclinical myocardial dysfunction in cancer patients: is there a direct effect of tumour growth?P748The abnormal global longitudinal strain predicts significant circumflex artery disease in low risk acute coronary syndromeP7493D-Speckle tracking echocardiography for assessing ventricular funcion and infarct size in young patients after acute coronary syndromeP750Evaluation of left ventricular dyssynchrony by echocardiograhy in patients with type 2 diabetes mellitus without clinically evident cardiac diseaseP751Differences in myocardial function between peritoneal dialysis and hemodialysis patients: insights from speckle tracking echoP752Appraisal of left atrium changes in hypertensive heart disease: insights from a speckle tracking studyP753Left ventricular rotational behavior in hypertensive patients: Two dimensional speckle tracking imaging studyComputed Tomography & Nuclear CardiologyP754Effectiveness of adaptive statistical iterative reconstruction of 64-slice dual-energy ct pulmonary angiography in the patients with reduced iodine load: comparison with standard ct pulmonary angiograP755Clinical prediction model to inconclusive result assessed by coronary computed tomography angiography. Eur Heart J Cardiovasc Imaging 2015. [DOI: 10.1093/ehjci/jev277] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Poster session Thursday 12 December - AM: 12/12/2013, 08:30-12:30 * Location: Poster area. Eur Heart J Cardiovasc Imaging 2013. [DOI: 10.1093/ehjci/jet203] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Poster session Wednesday 11 December all day display: 11/12/2013, 09:30-16:00 * Location: Poster area. Eur Heart J Cardiovasc Imaging 2013. [DOI: 10.1093/ehjci/jet202] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Early impairment of left atrial systolic function measured by 2D speckle tracking echocardiography in patients with diabetes and hypertension. Eur Heart J 2013. [DOI: 10.1093/eurheartj/eht310.p5662] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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Right heart deformation mechanics in patients with pulmonary hypertension. Eur Heart J 2013. [DOI: 10.1093/eurheartj/eht307.p325] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Sensing strain and damage in polyurethane/MWCNT nano-composite foams using electrical measurements. EXPRESS POLYM LETT 2013. [DOI: 10.3144/expresspolymlett.2013.4] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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Poster Session Wednesday 5 December all day Display * Determinants of left ventricular performance. Eur Heart J Cardiovasc Imaging 2012. [DOI: 10.1093/ehjci/jes248] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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Lipid abnormalities and oxidized LDL in chronic kidney disease patients on hemodialysis and peritoneal dialysis. Ren Fail 2011; 34:160-4. [PMID: 22172020 DOI: 10.3109/0886022x.2011.641515] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Dyslipoproteinemia and oxidative modification of low-density lipoprotein (oxLDL) contribute to the development of oxidative stress and atherosclerosis in chronic kidney disease (CKD). On the contrary, high-density lipoprotein cholesterol (HDL-C), especially HDL3-C subtype, has protective effect against oxidative damage. There is limited evidence referring HDL-C subclass levels in patients on dialysis. This study was designed to compare lipid abnormalities and oxLDL levels in hemodialysis (HD) and peritoneal dialysis (PD) patients. Serum lipids, HDL subclasses, and oxLDL were measured in 55 patients with CKD-stage 5 (31 patients on HD and 24 patients on PD) and in 21 normal controls (NC). The results showed that in dialysis patients, triglycerides were higher than in controls (p < 0.0001) and HDL-C was significantly lower (p < 0.0001). The HDL2-C subclass concentration did not differ significantly between patients and controls, while HDL3-C was lower in patients (11 ± 0.5 mg/dL) than in NC (23 ± 1, p < 0.0001). oxLDL levels were markedly increased in patients (1.92 ± 0.29 mg/L) compared to NC (0.22 ± 0.05, p < 0.0001). Patients on PD had higher levels of cholesterol (p < 0.001) and apolipoprotein B (p < 0.05) than patients on HD. However, HDL-C, HDL-C subclasses, and oxLDL concentrations did not differ significantly between PD and HD patients. It is concluded that patients with CKD have a nearly 10-fold elevation of oxLDL compared with NC. Patients on PD have differences in the lipid profile compared with patients on HD; however, both modalities seem to possess similar potential to atherosclerosis development.
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Wavelet analysis of head acceleration response under dirac excitation for early oedema detection. J Biomech Eng 2008; 130:021017. [PMID: 18412504 DOI: 10.1115/1.2903432] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The present work deals with the application of an innovative in-house developed wavelet-based methodology for the analysis of the acceleration responses of a human head complex model as a simulated diffused oedema progresses. The human head complex has been modeled as a structure consisting of three confocal prolate spheroids, whereas the three defined regions by the system of spheroids, from the outside to the inside, represent the scull, the region of cerebrospinal fluid, and the brain tissue. A Dirac-like pulse has been used to excite the human head complex model and the acceleration response of the system has been calculated and analyzed via the wavelet-based methodology. For the purpose of the present analysis, a wave propagation commercial finite element code, LS-DYNA 3D, has been used. The progressive diffused oedema was modeled via consecutive increases in brain volume accompanied by a decrease in brain density. It was shown that even a small increase in brain volume (at the level of 0.5%) can be identified by the effect it has on the vibration characteristics of the human head complex. More precisely, it was found that for some of the wavelet decomposition levels, the energy content changes monotonically as the brain volume increases, thus providing a useful index of monitoring an oncoming brain oedema before any brain damage appears due to uncontrolled intracranial hypertension. For the purpose of the present work and for the levels of brain volume increase considered in the present analysis, no pressure increase was assumed into the cranial vault and, associatively, no brain compliance variation.
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A new method for the early diagnosis of brain edema/brain swelling. An experimental study in rabbits. J Biomech 2006; 39:2958-65. [PMID: 16413930 DOI: 10.1016/j.jbiomech.2005.11.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2005] [Accepted: 10/22/2005] [Indexed: 12/01/2022]
Abstract
The aim of the present work is to develop a non-destructive, non-invasive technique for the early diagnosis of an oncoming brain edema based on the variation of vibration characteristics of the head system (i.e. eigenfrequency spectrum and modal damping). Besides the theoretical model that supports the basic principle, the proposed technique has been verified experimentally in animal tests. The advantage of such an approach is that the relative information is available well in advance an increase of intracranial pressure is detected. The uncontrolled intracranial hypertension is associated with increased mortality or vegetative state in head trauma. Traumatic lesions located on temporal lobe render particularly impeding the transtendorial herniation. From the medical point of view, intracranial pressure (ICP) monitoring represents an effective way for early consideration of neurological decompensation in various neurosurgical conditions particularly in the head-injured setting. However, the use of ICP monitoring is not an effective way of brain edema detection, since ICP increase very often causes irreversible problems to the patient's brain. Therefore, the determination of an earlier, less invasive and more sensitive indicator of the oncoming intracranial hypertension and of the impeding neurological deterioration is of profound importance. The present work aims at experimental verification of both eigenfrequency shifting and modal damping increase of the spectral response of the head system of rabbits, wherever a mass increase in the content of cranial shell appears. The conducted analysis concludes that the eigenfrequency spectrum and its modal damping characteristics are sufficiently sensitive parameters in order to characterize mass increase in the cranial shell. Therefore the combination of both the above parameters could be used with confidence for the early diagnosis of brain edema.
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Abstract
A cadaveric biomechanical study was performed to investigate the fracture energy absorbed by strips of bone from the proximal femur in relation to age and gender, under impact loading conditions. Four groups (young male, young female, old male, old female) of four cadaveric proximal femurs were used in each case. Four bone strips were taken from the neck and four from the subtrochanteric area and these were tested under dynamic-impact conditions using the Charpy impact test. The fracture energy was calculated as the energy needed to achieve fracture per unit area, and expressed in J/m2. Bone specimens from young males are significantly tougher under impact conditions to those of females (p = 0.001), whereas between the old male and female groups, fracture energy does not significantly differ (p = 0.165). There was also significant difference (p < 0.0005) between the young and the old groups in both genders. The fracture energy absorption of the subtrochanteric area compared to that of the femoral neck for the same group of age and gender is in general slightly higher for all groups. In conclusion, gender in the young age group played a significant role in bone resistance in breaking whereas in the older age group it played a less important role.
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Abstract
OBJECTIVE This study examines viscoelastic properties of the 'unaffected' tibial condyle in unicompartmental osteoarthritic knees, in order to determine whether to preserve it or not in knee replacement operations. DESIGN The viscoelastic properties of longitudinal strips of cartilage and subchondral bone from osteoarthritic and healthy knees were studied. METHODS Nine medial compartment osteoarthritic and nine cadaveric knees, all age- and gender-matched, were studied. Samples from polyethylene and methacrylate cement were also obtained and all then tested in the DMA (Dynamic Mechanical Analysis) testing apparatus. The dynamic modulus of elasticity (E(dyn)) and the loss factor (tan delta) were measured. RESULTS The medial compartment in osteoarthritic knees had lost its viscoelastic properties, having a significantly higher E(dyn) compared to the lateral one, and lower values of loss factor. In healthy knees there was no significant difference (p=0.18) in viscoelastic properties between both compartments and with the unaffected side of the osteoarthritic knee. Polyethylene and cement appear to have a high modulus of elasticity compared to both the healthy and the osteoarthritic knees. CONCLUSIONS The 'unaffected' (lateral) tibial condyles in medial compartment osteoarthritic knees seem to preserve their viscoelastic properties; it is worth considering a hemiarthroplasty. The significant modulus of elasticity difference between the condyles-polyethylene-cement results in different deformation in the interface between them and induces micromotion and loosening.
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Abstract
We investigated the strain pattern developed in the anterior and posterior part of the fixed patella during knee motion. Eight fresh cadaver knees were used but two were excluded because of non reliable measurements due to misplacement of gauges. Two strain gauges were bonded in the midline of the anterior and two in the posterior surface of the patella. Threaded steel rods were cemented into the intramedullary femoral and tibial canals. The knee was placed on a special device. The quadriceps tendon was gripped and a 4.5 kg weight was attached to the tibial rod 16.5 cm distal to the joint line. Ten flexion/extension cycles were performed before testing. Initially the intact patella was tested. A transverse osteotomy was performed before being stabilized by the AO recommended tension band technique. The knee was retested again as above. Finally an additional circular wire was passed around the patella and the knee was tested again under the same loading configuration. The intact patella showed weak tensile strain on the anterior and compressive strain on the posterior surface through the range of knee motion. Tension band fixation produced weak tensile strains in the first few degrees of flexion and then weak compressive strains in the posterior surface. The presence of the additional circular wire significantly increased the compressive strain. The classical tension band is highly effective for the fixation of the fractured patella but is improved by an additional circular wire.
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Abstract
In order to investigate the ideal position in which the wrist should be immobilized during scaphoid fracture, treatment the strains which are developed in the carpal scaphoid for various wrist positions has been recorded in cadaveric wrists, using strain gauges. The data obtained shows that during radial deviation with neutral or slight palmar flexion of the wrist the waist of the scaphoid tends to compress because of the development of strong compressive strains, while the strain development parallel to the fracture site that tends to shift the scaphoid waist is minimum. This position seems to be the best for stable scaphoid fracture immobilization.
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Brain eigenfrequency shifting as a sensitive index of cerebral compliance in an experimental model of epidural hematoma in the rabbit: preliminary study. Crit Care Med 1999; 27:978-84. [PMID: 10362423 DOI: 10.1097/00003246-199905000-00040] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
OBJECTIVE To verify brain eigenfrequency shifting after the occurrence of a lesion producing mass effect into the cranial vault. DESIGN Experimental animal study. SETTING Laboratory of experimental surgery affiliated with a university critical care department. SUBJECTS Six adult male New Zealand white rabbits. INTERVENTIONS A Camino ICP monitor was placed in the parenchyma, and a 5-Fr balloon-tipped catheter and accelerometer were placed into the epidural space. MEASUREMENTS Before and after the introduction of successive 0.1-mL increments of autologous blood into the balloon, intracranial pressure (ICP) was recorded along with the accelerometer signal obtained during free vibration of the skull triggered by a calibrated hammer. Fast Fourier transformation of the digitized signal provided the eigenfrequency spectrum. The eigenfrequency showing the sharpest decrease after the initial 0.1-mL volume addition was considered as the best frequency, and its variation in response to subsequent 0.1-mL increments represents the brain eigenfrequency shifting. MAIN RESULTS Brain eigenfrequency shifting to lower values occurs for small blood volume increments (up to 0.2 mL). When volume addition becomes >0.3 mL, brain eigenfrequency shifting to higher values is exhibited. The decrease in best frequency after the initial introduction of 0.1 mL is statistically significant (p = .003), in a range of volume in which no significant intracranial pressure difference appears. The respective variation of ICP is explained using a quadratic curve. For volumes of 0 to 0.1 mL, the change in ICP is not statistically significant (p = .08). CONCLUSIONS Changes of the brain's physical characteristics by mass addition in the cranial vault can be expressed by brain eigenfrequency shifting. The method seems advantageous because it reliably detects mass additions at low levels where no ICP change occurs. Additionally, it provides serial measurements, and it is less invasive than the currently used methods for intracranial compliance.
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Rigid or sliding plate. A mechanical evaluation of osteotomy fixation in sheep. Clin Orthop Relat Res 1999:244-9. [PMID: 9973997] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Fracture fixation using rigid plates leads to direct bone union, but it also may lead to complications because of stress protection osteopenia. This study aims to compare the mechanical characteristics restored during the callus formation after an osteotomy is fixed with two types of internal plate fixation. Twenty-four adult female sheep were divided randomly into three groups of eight each, which were euthanized at 2, 4, and 6 months after operation. Half of them had their osteotomized radius fixed with a seven hole dynamic compression plate, whereas in the remainder a sliding plate was used. The sliding plate consists of two halves connected together in such a way as to permit axial sliding of the one within the other, thus allowing cyclic axial load transfer at the fracture site. Bone strips obtained from the healthy (control) and the surgically treated side were subjected to four-point bending tests. The effective modulus of elasticity, ultimate bending strength, and energy absorption to fracture (toughness) were calculated. All parameters were restored more quickly in the sliding plate group, but there was no statistically significant difference observed at 6 months when all the osteotomies were united completely. Thus, the sliding plate, by allowing axial loading at the fracture site, led to a faster callus maturation and hence bony union, which, hopefully, will permit earlier full weightbearing and functional recovery of the injured limb.
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Abstract
Plate fixation depends mainly on the holding power of the screws. In the present study the pattern of screw loosening was investigated. Thirty-two adult female sheep divided into four groups were used. A mid-diaphyseal transverse osteotomy was made on the right radius of each animal, and then plated on the anterior (tension) surface. Half of each group were plated using a standard narrow 7-hole AO Dynamic Compression Plate (DCP), whereas in the remaining animals a 6-hole newly designed sliding plate (SP) was applied. The required torque of tightening intraoperatively, as well as for releasing the screws after killing the animals was recorded with a tension-calibrated screwdriver. The pattern of loosening was similar for all the screws and the three phases could be recognized. An initial loosening was observed 1 month after the operation. A slow recovery of the torque was measured from the second month onwards, becoming highest by the fourth month after the operation, whereas a slow decrease in torque was observed from the fourth to the sixth month. In the SP group, the overall loosening was much lower than the DCP group (P < 0.05), whereas there was no difference in the loosening between the proximally placed screws and the distally placed ones (P > 0.05) for both plates.
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Comparative study of callus performance achieved by rigid and sliding plate osteosynthesis based upon dynamic mechanical analysis. J Med Eng Technol 1994; 18:61-6. [PMID: 8064832 DOI: 10.3109/03091909409030230] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Operative management of long bone fractures is considered to be the treatment of choice all over the world. This could be achieved either by intramedullary nailing or plating. The former allows delivery of stresses into the fracture site, but it requires a well-equipped operating theatre and an experienced surgeon who is, unfortunately, continuously exposed to radiation. On the other hand, plates could easily be applied in every orthopaedic clinic, but the existing ones are rigid and protect the fracture site from stresses to which it is ordinarily exposed. Recently, various experimental attempts have been made to provide plates which allow partial loading on the fracture site and enhance callus formation (secondary fracture healing). Bearing that in mind, a two-part sliding plate (SP) has been developed at the Orthopaedic Clinic of Patras University, which allows intermittent loading into the fracture site. Both the conventional AO rigid plate and SP were applied to osteotomized sheep radii. The dynamic properties of the callus were estimated with its two dynamic mechanical characteristics (dynamic modulus of elasticity and the relative loss factor), whereas its static properties (strength) were evaluated by measuring the ultimate bending strength. A superiority of callus produced by the sliding plate was observed concerning all the parameters under consideration.
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45
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[The child's age, a problem for starting an orthodontic treatment]. ODONTOSTOMATOLOGIKE PROODOS 1985; 39:105-14. [PMID: 3939438] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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46
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[Pseudoprognathism of the mandible and its treatment with functional appliances]. ODONTOSTOMATOLOGIKE PROODOS 1985; 39:57-64. [PMID: 3939435] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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