16 research outputs found
Theoretical and Numerical Investigation of Liquid-Gas Interface Location of Capillary Driven Flow During the Time Throughout Circular Microchannels
The main aim of this study is to find the best, most rapid, and the most
accurate numerical method to find the liquid-gas interface of capillary driven
flow during the time in circular Microchannels by using COMSOL Multiphysics
software. Capillary driven flow by eliminating micropumps or any physical
pressure gradient generators can make the microfluidic devices cheaper and more
usable. Hence, by using this two-phase flow, the final costs of lots of
microfluidic devices and lab-on-a-chip can significantly be decreased and help
them to be commercialized. The first step to employing the capillary flow in
these devices is the simulation of this flow inside the microchannels. One of
the most common and valid software for this work is COMSOL Multiphysics; this
fact reveals the importance of this study. In this research study, simulation
results obtained by using two possible numerical methods in this software, for
capillary flows of water and ethanol in two different circular microchannels,
verified and compared with four other methods, which verified experimentally
before. Finally, the most accurate and time-saving numerical method of this
software will be specified. This appropriate technique can contribute to
simulate microfluidic and lab-on-a-chip devices, which are made of different
mechanical and electrical parts, in COMSOL Multiphysics software by choosing
the best method.Comment: 7 pages, 13 figures, 7 tables, 2017 5th International Conference on
Robotics and Mechatronics (ICROM
Correlation of dysoxia metabolism markers with trauma scoring systems in multiple trauma patients admitted to the emergency department: A cross-sectional observational study
Background: All the trauma scoring systems (TSSs) have some limitations, and none is useful for patient monitoring. Recently, investigators have tried to modify the TSSs to improve their use. Aims: This study was conducted to determine whether any correlation exists between dysoxia metabolism markers (DMMs), including venous base deficit (BD) and HCO3level with different TSSs. Materials and Methods: In this cross-sectional study, all multiple trauma patients admitted to the emergency department were eligible. Blood samples for venous blood gas analysis were taken at the onset of resuscitation process. TSSs, including trauma index (TI), abbreviated injury score (AIS), Injury Severity Score (ISS), Revised Trauma Score (RTS), and Trauma Score-ISS (TRISS), were calculated for the patients. Spearman's rank correlation coefficient test was applied to find the association between the independent variables. Results: A total of 285 patients with a mean age of 33.37 ñ 15.29 fulfilled the inclusion criteria, of which, 211 cases (74.0) were male. Statistical analysis revealed that there was a correlation between TI and HCO3level (P = 0.0001, r = 0.37) and also TI and BD (P = 0.0001, r = 0.47). Furthermore, there was an indirect correlation between AIS and ISS with HCO3and BD levels and the direct correlation between RTS and TRISS with HCO3and BD levels. Conclusion: It is likely that there is a statistical correlation, although weak, between TSSs with DMMs, including HCO3and BD level
Fabrication and verification of a single aligned nanofibre gas sensor based on nonâcontact direct writing method
Abstract In this letter, the nonâcontact direct writing method for producing single aligned fibre utilizing polyvinylpyrrolidone (PVP) polymer has been explored. It has been shown that with the help of this method, nanofibres can be created in a controlled manner with designed structures. This form of nanofibres is being studied with the goal of using it in carbon monoxide (CO) gas sensors. The temperature required for the annealing operation was 500°C, and finally the authors obtained nanofibres with diameter of 200 nm. In addition, a simulation technique built on the Monte Carlo method has also been introduced. It is shown that this simulation method is compatible with the experimental results with reasonable accuracy. The results showed that the authors have a correlation of about 0.934 between experimental results obtained in 30 ppb of CO gas and its simulation data
Fabrication of Pd Doped WO3 Nanofiber as Hydrogen Sensor
Pd doped WO3 fibers were synthesized by electro-spinning. The sol gel method was employed to prepare peroxopolytungstic acid (P-PTA). Palladium chloride and Polyvinyl pyrrolidone (PVP) was dissolved in the sol Pd:WO3 = 10% molar ratio. The prepared sol was loaded into a syringe connected to a high voltage of 18.3 kV and electrospun fibers were collected on the alumina substrates. Scanning electron microscope (SEM), X-ray powder diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) techniques were used to analyze the crystal structure and chemical composition of the fibers after heat treatment at 500 °C. Resistance-sensing measurements exhibited a sensitivity of about 30 at 500 ppm hydrogen in air, and the response and recovery times were about 20 and 30 s, respectively, at 300 °C. Hydrogen gas sensing mechanism of the sensor was also studied
Detection of retinal capillary nonperfusion in fundus fluorescein angiogram of diabetic retinopathy
Introduction: Retinal capillary nonperfusion
(CNP) is one of the retinal vascular diseases in diabetic retinopathy
(DR) patients. As there is no comprehensive detection technique to
recognize CNP areas, we proposed a different method for computing
detection of ischemic retina, non-perfused (NP) regions, in fundus
fluorescein angiogram (FFA) images.
Methods: Whilst major vessels appear as
ridges, non-perfused areas are usually observed as ponds that are
surrounded by healthy capillaries in FFA images. A new technique using
homomorphic filtering to correct light illumination and detect the ponds
surrounded in healthy capillaries on FFA images was designed and
applied on DR fundus images. These images were acquired from the
diabetic patients who had referred to the Nikookari hospital and were
diagnosed for diabetic retinopathy during one year. Our strategy was
screening the whole image with a fixed window size, which is small
enough to enclose areas with identified topographic characteristics. To
discard false nominees, we also performed a thresholding operation on
the screen and marked images. To validate its performance we applied our
detection algorithm on 41 FFA diabetic retinopathy fundus images in
which the CNP areas were manually delineated by three clinical experts.
Results: Lesions were found as smooth regions
with very high uniformity, low entropy, and small intensity variations
in FFA images. The results of automated detection method were compared
with manually marked CNP areas so achieved sensitivity of 81%,
specificity of 78%, and accuracy of 91%.The result was present as a
Receiver operating character (ROC) curve, which has an area under the
curve (AUC) of 0.796 with 95% confidence intervals.
Conclusion: This technique introduced a new
automated detection algorithm to recognize non-perfusion lesions on FFA.
This has potential to assist detecting and managing of ischemic retina
and may be incorporated into automated grading diabetic retinopathy
structures
Developed wearable miniature sensor to diagnose initial perturbations of cardiorespiratory system
The progress of microelectromechanical systems tends to fabricate miniature motion sensors that can be used for various purposes of biomedical systems, particularly on-body applications. A miniature wireless sensor is developed that not only monitors heartbeat and respiration rate based on chest movements but also identifies initial problems in the cardiorespiratory system, presenting a healthy measure defined based on height and length of the normal distribution of respiration rate and heartbeat. The obtained results of various tests are compared with two commercial sensors consisting of electrocardiogram sensor as well as belt sensor of respiration rate as a reference (gold standard), showing that the root-mean-square errors obtain <2.27 beats/min for a heartbeat and 0.93 breaths/min for respiration rate. In addition, the standard deviation of the errors reaches <1.26 and 0.63 for heartbeat and respiration rates, separately. According to the outcome results, the sensor can be considered an appropriate candidate for in-home health monitoring, particularly early detection of cardiovascular system problems
Assessment of human gait after total knee arthroplasty by dynamic time warping algorithm
Abstract Today, the elderly population is increasing, and there are many drawbacks for them, especially defects in their knee joints which lead to improper gait. To solve this problem, their knee joint can be replaced with knee arthroplasty. In this letter, level of improvement in the human gait before and after total knee arthroplasty (TKA) surgery is investigated using the dynamic time warping (DTW) algorithm. For this purpose, several volunteers who have problems with their knees are incorporated in a test before and after TKA surgery. Then, the data of gait analysis is collected and the data is compared with a reference using the DTW algorithm. The outcome results illustrate an improvement of 89%â97% by the proposed algorithm after TKA surgery. Therefore, patients can see improvement with high accuracy and very fast that result in more use this technique in TKR surgery
Intensity modulation of UV light in gas sensor array to discriminate several analytes at room temperature
Abstract In this study, a gas sensor array along with intensity modulation of UV light was utilized to discriminate several gases at room temperature. The sensor array was consisted of two interdigitated microelectrodes and TiO2 nanofibres were electrospun on them and calcined at 540°C for 90 min. One of these sensors was coated by 2ânm Pt using the DC sputtering method and the other one remained uncoated. In each experiment, the sensor array was located at a distance of 30 mm from a 365ânm UV LED. For intensity modulation of UV light, a staircase waveform voltage was applied to the UV LED. The voltage was included of three voltage steps and the measured powers at a distance of 30 mm from the UVâLED were about 450, 560, and 680 ”W/cm2, respectively. Analytes including acetone, ethanol, methanol, 2âpropanol, and carbon monoxide (CO) at various concentrations ranging from 50 to 500 ppm were examined. Threeâdimensional Principal Component Analysis mapping was successfully used for the segregation of all examined gases. The examinations revealed that using sensor array along with intensity modulation of UV light is an effective method for discrimination of several analytes at room temperature
Very late effects of postoperative atrial fibrillation on outcome of coronary artery bypass graft surgery
Background: Atrial fibrillation (AF) after coronary artery bypass graft (CABG) is a common complication with potentially higher risk of adverse outcome and prolonged hospital stay.
Objective: To determine the impact of postoperative AF (POAF) on long-term outcome in a large cohort of patients who underwent CABG.
Patients and Methods: We conducted an observational cohort study of 989 patients who underwent isolated CABG with more than 5-year follow-up. Patient divided in two groups: patients with and without POAF.
Results: In this study, atrial fibrillation developed after CABG in 156 patients (15.8%). Patients with POAF were generally older (P = 0.001) and presented more often with comorbidities including congestive heart failure (P = 0.001), hypertension (P = 0.001), peripheral vascular disease (P = 0.001), hyperlipidemia (P = 0.009), and renal failure (P = 0.001). Five-year mortality was observed in 23 (2.3%) patients. Patients with POAF had higher five-year mortality rate than those without POAF. Multivariate logistic analysis showed that AF after surgery has a strong effect on mortality (HR, 3.3; 95% CI, 0.04-10.8, P = 0.04) and morbidity rates (HR, 4.0; 95% CI, 2.35-6.96, P = 0.001).
Conclusions: Postoperative atrial fibrillation strongly predicts higher long-term mortality and morbidity following coronary artery bypass graft