10 research outputs found
Representative elementary volume (REV) of cementitious materials from three-dimensional pore structure analysis
No full textThe representative elementary volume (REV) is a fundamental property of a material, but no direct measurements exist for cementitious materials. In this paper, the REV of cement pastes with supplementary cementitious materials (GGBS, PFA, SF) was determined by analysing the three-dimensional pore structure (> 0.2 μm) using laser scanning confocal microscopy (LSCM). The effect of axial distortion inherent to LSCM on 3D pore structure was also investigated. A range of 3D pore parameters was measured using skeletonisation, maximal ball and random walker algorithms. Results show that axial distortion has insignificant effects on most parameters except Euler connectivity, average pore and throat volumes and directional diffusion tortuosities. Most pore parameters become independent of sampling volume at ≈ 603 μm3 except diffusion tortuosities and formation factor. The REV for porosity calculated based on a statistical approach at eight realisations and 5% relative error was found to be ≈ 1003 μm3
DropAdjust: infusion flow regulator: Design and development of a precise and accurate manually controlled over-line flow regulator for gravity-driven infusion
No full textWorldwide 70-90% of hospitalised patients receive intravenous infusion at some stage during their stay. In many situations, a high degree of infusion accuracy is essential as deviation from the intended dose can quickly become dangerous and moreover costly. Electronic infusion pumps provide the most accurate way of infusion, but they require programming and frequent maintenance. Furthermore, they are unsuitable for austere environments, costly, and could even become scarce in times of a pandemic. Gravity infusion combined with a drop counter could pose an interesting alternative. However, this method appears to be inaccurate over time and setting an accurate flow rate is challenging. The typically used flow regulator, a roller clamp, is the cause of these complications. This study aimed to design and develop a precise and accurate manually controlled over-line flow regulator for gravity-driven infusion. The design process consisted out of three design phases: analysis, synthesis and evaluation. During the analysis, the design requirements were set up. The synthesis phase consisted of generating a morphological overview and several pincher experiments. A pincher is used to clamp the tubing to regulate the flow rate. Then, promising partial solutions were selected, and through rapid prototyping, a final design and prototype were developed. In the evaluation phase, the flow regulator prototype was evaluated based on the set requirements. The developed DropAdjust prototype demonstrated a major performance increase in terms of mean flow rate accuracy and regulation control compared to the roller clamp. In conclusion, the DropAdjust satisfies all tested design criteria and outperformed the roller clamp in terms of accuracy and precision. Moreover, it even showed a mean flow rate accuracy error comparable to the infusion pumps. Thus, the DropAdjust combined with a drop counter provides a more affordable and accessible alternative to the infusion pumps. The prototype is already practice-ready, but several steps are still needed to realise a market-ready device. For instance, conducting endurance tests and acquiring injection moulding advice from an experienced specialist are advised. Also, additional tests are necessary to verify its safety and functionality to qualify for a CE marking.Mechanical Engineering | BioMechanical Desig
Microscopy techniques for determining water–cement (w/c) ratio in hardened concrete: A round-robin assessment
No full textWater to cement (w/c) ratio is usually the most important parameter specified in concrete design and is sometimes the subject of dispute when a shortfall in concrete strength or durability is an issue. However, determination of w/c ratio in hardened concrete by testing is very difficult once the concrete has set. This paper presents the results from an inter-laboratory round-robin study organised by the Applied Petrography Group to evaluate and compare microscopy methods for measuring w/c ratio in hardened concrete. Five concrete prisms with w/c ratios ranging from 0.35 to 0.55, but otherwise identical in mix design were prepared independently and distributed to 11 participating petrographic laboratories across Europe. Participants used a range of methods routine to their laboratory and these are broadly divided into visual assessment, measurement of fluorescent intensity and quantitative backscattered electron microscopy. Some participants determined w/c ratio using more than one method or operator. Consequently, 100 individual w/c ratio determinations were collected, representing the largest study of its type ever undertaken. The majority (81%) of the results are accurate to within ± 0.1 of the target mix w/c ratios, 58% come to within ± 0.05 and 37% are within ± 0.025. The study shows that microscopy-based methods are more accurate and reliable compared to the BS 1881-124 physicochemical method for determining w/c ratio. The practical significance, potential sources of errors and limitations are discussed with the view to inform future applications.Materials and Environmen
Design and functional testing of a novel blood pulse wave velocity sensor
No full textThe multiphotodiode array (MPA) is a novel transmission photoplethysmography (PPG) sensor to measure pulse wave velocity (PWV) in the finger. To validate the MPA, a setup was built to generate a red laser dot traveling over the MPA with known and constant scanning velocities. These scanning velocities were chosen to include speeds at least twice as high as those found in the normal range of PWV in healthy populations and were set at 12.9, 25.8, 36, or 46.7 m/s. The aim of this study was to verify the functionality of the MPA: performing local noninvasive PWV measurements. To illustrate the applicability of the MPA in clinical practice, an in vivo pilot study was conducted using the flow-mediated dilation (FMD) technique. The in vitro accuracy of the MPA was ±0.2%, 0.3%, 0.5%, and 0.6% at the applied scanning velocities. The MPA can measure PWVs with a maximum deviation of 3.0%. The in vivo pilot study showed a PWV before the FMD of 1.1±0.2 m/s. These results suggest that this novel MPA can reliably and accurately measure PWV within clinically relevant ranges and even well beyond.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Medical Instruments & Bio-Inspired Technolog
Measuring pulse wave velocity with a novel, simple sensor on the finger tip: A feasibility study in healthy volunteers
No full textObjective: The speed of pressure pulses traveling through the blood, the pulse wave velocity (PWV), is a metric that provides substantial information about the passive and active elasticity of the blood vessels. Therefore, PWV is a valuable parameter in the diagnosis of cardiovascular and vessel-related neurological diseases. The purpose of this study was to investigate whether a novel, simple, easy-to-use, photoplethysmography-based Multi Photodiode Array (MPA) provides PWV measurements that agree with measurements done with more complicated and harder-to-use systems currently used in clinical practice. Methods: An often-used vascular perturbation that changes the conduit artery vasomotor tone during reactive hyperemia was imposed on thirty healthy volunteers. The MPA was used alongside and its results compared to those of a commonly used measurement device, the Biopac-system, during flow-mediated dilation (FMD). This way it was investigated if measurements with these systems, measuring over two different, but partly overlapping vessel trajectories agree. Results: The baseline absolute PWV values were significantly lower for the MPA as compared to the Biopac-system. Additionally, Bland-Altman plots and Pearson's correlation tests suggested good agreement between the two PWV measurement techniques during the FMD. Conclusion: Measuring PWV with the MPA in clinical practice is feasible and provides reliable data. Significance: The MPA may substantially simplify PWV measurements and may enable long-term PWV monitoring as long as one is aware of the relation between PWV and the vascular trajectory over which it is measured.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Medical Instruments & Bio-Inspired Technolog
Comparison between pulse wave velocities measured using Complior and measured using Biopac
No full textArterial stiffness is a reliable prognostic parameter for cardiovascular diseases. The effect of change in arterial stiffness can be measured by the change of the pulse wave velocity (PWV). The Complior system is widely used to measure PWV between the carotid and radial arteries by means of piezoelectric clips placed around the neck and the wrist. The Biopac system is an easier to use alternative that uses ECG and simple optical sensors to measure the PWV between the heart and the fingertips, and thus extends a bit more to the peripheral vasculature compared to the Complior system. The goal of this study was to test under various conditions to what extent these systems provide comparable and correlating values. 25 Healthy volunteers, 20–30 years old, were measured in four sequential position: sitting, lying, standing and sitting. The results showed that the Biopac system measured consistently and significantly lower PWV values than the Complior system, for all positions. Correlation values and Bland–Altman plots showed that despite the difference in PWV magnitudes obtained by the two systems the measurements did agree well. Which implies that as long as the differences in PWV magnitudes are taken into account, either system could be used to measure PWV changes over time. However, when basing diagnosis on absolute PWV values, one should be very much aware of how the PWV was measured and with what system.Medical Instruments & Bio-Inspired Technolog
3D imaging techniques for characterising microcracks in cement-based materials
No full textConcrete inherently contains pores and microcracks that can adversely impact its mechanical properties and long-term durability. However, characterising microcracks is difficult due to their complex, multiscale and three-dimensional (3D) nature. This paper presents an evaluation of 3D imaging techniques for characterising microcracks induced by different mechanisms. Seven cement pastes, mortars and concretes subjected to drying shrinkage, autogenous shrinkage and freeze-thaw cycles were investigated using focused ion beam nanotomography (FIB-nt), broad ion beam serial section tomography (BIB-SST), laser scanning confocal microscopy (LSCM) combined with serial sectioning and X-ray microtomography (µCT). The study shows that the characteristics of microcracks vary significantly depending on exposure conditions. Yet there is no single technique that can capture the entire size range of microcracks from sub to tens of µm within a sufficiently representative sampling volume. The achievable image volume and resolution, and the advantages and disadvantages of each technique are compared and discussed.M.J. Mac acknowledges the funding from the European Union Seventh Framework Programme under grant agreement 264448. We thank Dr. Trifon Trifonov from Universitat Politècnica de Catalunya (UPC) and Dr. Lidija Korat from the Slovenian National Building and Civil Engineering Institute (ZAG) for their assistance with the Zeiss Neon 40 cross beam and the Xradia MicroXCT-400 respectively. We also thank the Natural History Museum, Zeiss (Cambridge, UK) and FEI (Houston, USA) for providing X-ray μCT scans with the Metris X-Tek HMX ST 225, Xradia 520 Versa and Helican microCT respectively.Peer ReviewedPostprint (author's final draft
Increasing accuracy of pulse transit time measurements by automated elimination of distorted photoplethysmography waves
No full textPhotoplethysmography (PPG) is a widely available non-invasive optical technique to visualize pressure pulse waves (PWs). Pulse transit time (PTT) is a physiological parameter that is often derived from calculations on ECG and PPG signals and is based on tightly defined characteristics of the PW shape. PPG signals are sensitive to artefacts. Coughing or movement of the subject can affect PW shapes that much that the PWs become unsuitable for further analysis. The aim of this study was to develop an algorithm that automatically and objectively eliminates unsuitable PWs. In order to develop a proper algorithm for eliminating unsuitable PWs, a literature study was conducted. Next, a ‘7Step PW-Filter’ algorithm was developed that applies seven criteria to determine whether a PW matches the characteristics required to allow PTT calculation. To validate whether the ‘7Step PW-Filter’ eliminates only and all unsuitable PWs, its elimination results were compared to the outcome of manual elimination of unsuitable PWs. The ‘7Step PW-Filter’ had a sensitivity of 96.3% and a specificity of 99.3%. The overall accuracy of the ‘7Step PW-Filter’ for detection of unsuitable PWs was 99.3%. Compared to manual elimination, using the ‘7Step PW-Filter’ reduces PW elimination times from hours to minutes and helps to increase the validity, reliability and reproducibility of PTT data.</p
Correction to: A combination of herbal compound (SPTC) along with exercise or metformin more efficiently alleviated diabetic complications through down-regulation of stress oxidative pathway upon activating Nrf2-Keap1 axis in AGE rich diet-induced type 2 diabetic mice (Nutrition & Metabolism, (2021), 18, 1, (14), 10.1186/s12986-021-00543-6)
No full textFollowing the publication of the original article 1, the authors identified an error in the funding note. Incorrect funding note: A part of this research was funded partially by NIMAD (National Institute for Medical Research Development) no. 971130. © 2021, The Author(s)
A combination of herbal compound (SPTC) along with exercise or metformin more efficiently alleviated diabetic complications through down-regulation of stress oxidative pathway upon activating Nrf2-Keap1 axis in AGE rich diet-induced type 2 diabetic mice
No full textBackground: SPTC is a mix of four herbal components (Salvia officinalis, Panax ginseng, Trigonella foenum-graeceum, and Cinnamomum zeylanicum) which might be prevented the development of AGE rich diet-induced diabetic complication and liver injury through activated the nuclear factor erythroid-2-related-factor-2 (Nrf2) pathway. Nrf2, as a master regulator of antioxidant response elements by activating cytoprotective genes expression, is decreased oxidative stress that associated with hyperglycemia and increases insulin sensitivity. the aim of this study was to assess whether the combination therapy of SPTC along with exercise or metformin moderate oxidative stress related liver injurie with more favorable effects in the treatment of AGE rich diet-induced type 2 diabetic mice. Methods: We induced diabetes in C57BL/6 mice by AGE using a diet supplementation and limitation of physical activity. After 16 weeks of intervention, AGE fed mice were compared to control mice. Diabetic mice were assigned into seven experimental groups (each group; n = 5): diabetic mice, diabetic mice treated with SPTC (130 mg/kg), diabetic mice treated with Salvia Officinalis (65 mg/kg), diabetic mice treated with metformin (300 mg/kg), diabetic mice with endurance exercise training, diabetic mice treated with SPTC + metformin (130/300 mg/kg), diabetic mice treated with SPTC + exercise training. Results: SPTC + exercise and SPTC + metformin reduced diabetic complications like gain weight, water and calorie intake, blood glucose, insulin, and GLUT4 content more efficiently than each treatment. These combinations improved oxidative stress hemostasis by activating the Nrf2 signaling pathway and attenuating keap1 protein more significantly. Conclusion: Eventually, combined treatment of SPTC with exercise or metformin as a novel approach had more beneficial effects to prevent the development of diabetes and oxidative stress associated with hyperglycemia. Figure not available: see fulltext. © 2021, The Author(s)
