Hemodynamic performance evaluation of neonatal ECMO double lumen cannula using fluid-structure interaction

Extra corporeal membrane oxygenation (ECMO) is an artificial oxygenation facility, employed in situations of cardio-pulmonary failure. Some diseases i.e., acute respiratory distress syndrome, pulmonary hypertension, corona virus disease (COVID-19) etc. affect oxygenation performance of the lungs thus requiring the need of artificial oxygenation. Critical care teams used ECMO technique during the COVID-19 pandemic to support the heart and lungs of COVID-19 patients who had an acute respiratory or cardiac failure. Double Lumen Cannula (DLC) is one of the most critical components of ECMO as it resides inside the patient and, connects patient with external oxygenation circuit. DLC facilitates delivery and drainage of blood from the patient's body. DLC is characterized by delicate balance of internal and external flows inside a limited space of the right atrium (RA). An optimal performance of the DLC necessitates structural stability under biological and hemodynamic loads, a fact that has been overlooked by previously published studies. In the past, many researchers experimentally and computationally investigated the hemodynamic performance of DLC by employing Eulerian approach, which evaluate instantaneous blood damage without considering blood shear exposure history (qualitative assessment only). The present study is an attempt to address the aforementioned limitations of the previous studies by employing Lagrangian (quantitative assessment) and incorporating the effect of fluid-structure interaction (FSI) to study the hemodynamic performance of neonatal DLC. The study was performed by solving three-dimensional continuity, momentum, and structural mechanics equation(s) by numerical methods for the blood flow through neonatal DLC. A two-way coupled FSI analysis was performed to analyze the effect of DLC structural deformation on its hemodynamic performance. Results show that the return lumen was the most critical section with maximum pressure drop, velocity, shear stresses, and blood damage. Recirculation and residence time of blood in the right atrium (RA) increases with increasing blood flow rates. Considering the structural deformation has led to higher blood damage inside the DLC-atrium system. Maximum Von-Mises stress was present on the side edges of the return lumen that showed direct proportionality with the blood flow rate.

Fabrication of Low-Cost Resistance Temperature Detectors and Micro-Heaters by Electrohydrodynamic Printing

EHD printing is an advanced deposition technology that is commonly utilized for the direct manufacture of electrical devices. In this study, meander-type resistive electrodes consisting of silver nanoparticles were printed directly on rigid glass and flexible polyethylene terephthalate (PET) substrates. High-resolution patterns of ≈50 µm linewidth were successfully printed on untreated surfaces utilizing a bigger nozzle of 100 µm inner diameter after improving the experimental settings. The manufactured electrodes were evaluated and used as Resistance Temperature Detectors (RTDs) and micro-heaters in a systematic manner. The temperature sensors performed well, with a Temperature Coefficient of Resistivity (TCRs) of 11.5 ×10-3/°C and 13.3 ×10-3/°C, for glass and PET substrates, respectively, throughout a wide temperature range of 100 °C and 90 °C. Furthermore, the RTDs had a quick response and recovery time, as well as minimal hysteresis. The electrodes' measured sensitivities as micro-heaters were 3.3 °C/V for glass and 6.8 °C/V for PET substrates, respectively. The RTDs were utilized for signal conditioning in a Wheatstone bridge circuit with a self-heating temperature of less than 1 °C as a practical demonstration. The micro-heaters have a lot of potential in the field of soft wearable electronics for biomedical applications, while the extremely sensitive RTDs have a lot of potential in industrial situations for temperature monitoring.

Analysis of Passive Mixing in a Serpentine Microchannel with Sinusoidal Side Walls

Sample mixing is difficult in microfluidic devices because of laminar flow. Micromixers are designed to ensure the optimal use of miniaturized devices. The present study aims to design a chaotic-advection-based passive micromixer with enhanced mixing efficiency. A serpentine-shaped microchannel with sinusoidal side walls was designed, and three cases, with amplitude to wavelength (A/λ) ratios of 0.1, 0.15, and 0.2 were investigated. Numerical simulations were conducted using the Navier⁻Stokes equations, to determine the flow field. The flow was then coupled with the convection⁻diffusion equation to obtain the species concentration distribution. The mixing performance of sinusoidal walled channels was compared with that of a simple serpentine channel for Reynolds numbers ranging from 0.1 to 50. Secondary flows were observed at high Reynolds numbers that mixed the fluid streams. These flows were dominant in the proposed sinusoidal walled channels, thereby showing better mixing performance than the simple serpentine channel at similar or less mixing cost. Higher mixing efficiency was obtained by increasing the A/λ ratio.

Comparative study of ligand binding during the postsynthetic stabilization of metal oxide nanoparticles

In the absence of stabilizers in the reaction medium, the nonaqueous synthesis of metal oxide nanoparticles usually results in agglomerated products. Stabilization is however often possible in a postsynthetic treatment, involving the addition of organic ligands that coordinate to the nanoparticle surface. The ligands are commonly expected to chemisorb via functional groups; however, we have recently shown that also weakly and unspecifically interacting ligands can lead to stabilization. Here, we present detailed investigations on the stabilization, comparing the binding of weakly coordinating ligands to a system with strongly and selectively binding stabilizers and additionally exploring the effect of ligand chain length. Although in all cases stabilization and disintegration of agglomerates to the primary particle level are achieved, strong differences are observed with respect to the processes at the particle surface. Moreover, these processes are shown to be more complex than simple ligand adsorption and need to be understood for proper design and choice of stabilizers.

Artificial neural networks for blur identification and restoration of nonlinearly degraded images

In this paper, an image restoration algorithm is proposed to identify noncausal blur function. Image degradation processes include both linear and nonlinear phenomena. A neural network model combining an adaptive auto-associative network with a random Gaussian process is proposed to restore the blurred image and blur function simultaneously. The noisy and blurred images are modeled as continuous associative networks, whereas auto-associative part determines the image model coefficients and the hetero-associative part determines the blur function of the system. The self-organization like structure provides the potential solution of the blind image restoration problem. The estimation and restoration are implemented by using an iterative gradient based algorithm to minimize the error function.

Reconstruction of thumb in traumatic or congenital loss

Reconstruction of thumb after traumatic or congenital loss in 17 cases is reported. Cases were divided into three groups according to the level of thumb loss. There were two cases in distal zone, seven in middle and eight in proximal zone. Thirteen cases were traumatic in origin and four had congenital loss. Different reconstruction procedures were used at each level. Osteoplastic reconstruction for the middle zone and index finger pollicization for proximal thumb loss are considered to be most useful methods of thumb reconstruction if microsurgical facilities are not available.

Transfer of latissimus dorsi muscle as myocutaneous flap

Latissimus dorsi muscle can be transferred as a muscle flap, myocutaneous flap or as a functioning muscle. It can also be used as free muscle or myocutaneous flap. Its long vascular pedicle makes it possible to rotate this muscle through a wide arc of rotation covering neck and upper extremity. It is a large muscle with extensive area and is ideally suited to cover large areas of skin defect. We are reporting eight cases of latissimus dorsi transfer as a myocutaneous flap to cover the skin defects in neck, axilla and upper extremity. Two cases were post-burn and five post-traumatic. One defect was secondary to excision of a large neurofibroma in the area of elbow. Most of the defects at donar sites could be closed primarily. There was only a partial marginal necrosis of transferred tissue in one case. Based upon the knowledge of its vascular anatomy, part of the muscle can be used for transfer which makes the flap less bulky and it can be tailored exactly to the primary defect.

Hypothenar skin grafts for fingertip reconstruction

Full-thickness skin grafts from the hypothenar area were used to reconstruct 25 digits in a group of 20 patients. The results were evaluated objectively and subjectively at an average of 9.5 months after operation for sensibility, durability, and appearance. Eighty-six percent of the patients had two-point discrimination of 10 mm or less, with one half of them having two-point discrimination of less than 6 mm. All patients had good protective coverage and no ulcer formation. All patients could differentiate between coarse and smooth texture, although only one third had texture discrimination equal to that of normal digits. None of the patients complained of hypersensitivity. The donor site was cosmetically acceptable in all cases. The use of hypothenar full-thickness grafts provides an acceptable method for fingertip reconstruction, particularly in instances of palmar and lateral pulp loss in which there is insufficient tissue available for local advancement.