Focused Ultrasound for Dermal Applications.

Focused ultrasound (FUS) is emerging as one of the most promising, non-invasive treatment techniques. The advancement of transducer technology has paved the way for dermatological applications. A comprehensive review is presented for healthcare practitioners and researchers, summarizing the effect of various operational parameters on the injury zone produced by ultrasound beams for various dermatological applications, which include skin tightening, fat reduction, hyperpigmentation and cancer treatment. In this article, we aim to highlight the efficient operational parameters of FUS to enhance pain relief during surgery and its affordability for skin treatment. Finally, a prospective future technique for efficient FUS is discussed.

Biocompatible Polymer for Self-Humidification.

Lung supportive devices (LSDs) have been extensively utilized in treating patients diagnosed with various respiratory disorders. However, these devices can cause moisture depletion in the upper airway by interfering with the natural lubrication and air conditioning process. To remedy this, current technologies implement heated humidification processes, which are bulky, costly, and nonfriendly. However, it has been demonstrated that in a breath cycle, the amount of water vapor in the exhaled air is of a similar quantity to the amount needed to humidify the inhaled air. This research proposes to trap the moisture from exhaled air and reuse it during inhalation by developing a state-of-the-art hydrophilic/hydrophobic polymer tuned to deliver this purpose. Using the atom transfer radical polymerization (ATRP) method, a substrate was successfully created by incorporating poly (N-isopropyl acrylamide) (PNIPAM) onto cotton. The fabricated material exhibited a water vapor release rate of 24.2 ± 1.054%/min at 32 °C, indicating its ability to humidify the inhaled air effectively. These findings highlight the potential of the developed material as a promising solution for applications requiring rapid moisture recovery.

Aneurysm Rupture Prediction Based on Strain Energy-CFD Modelling.

This paper presents a Patient-Specific Aneurysm Model (PSAM) analyzed using Computational Fluid Dynamics (CFD). The PSAM combines the energy strain function and stress-strain relationship of the dilated vessel wall to predict the rupture of aneurysms. This predictive model is developed by analyzing ultrasound images acquired with a 6-9 MHz Doppler transducer, which provides real-time data on the arterial deformations. The patient-specific cyclic loading on the PSAM is extrapolated from the strain energy function developed using historical stress-strain relationships. Multivariant factors are proposed to locate points of arterial weakening that precede rupture. Biaxial tensile tests are used to calculate the material properties of the artery wall, enabling the observation of the time-dependent material response in wall rupture formation. In this way, correlations between the wall deformation and tissue failure mode can predict the aneurysm's propensity to rupture. This method can be embedded within the ultrasound measures used to diagnose potential AAA ruptures.

Intraluminal Thrombus Characteristics in AAA Patients: Non-Invasive Diagnosis Using CFD.

Abdominal aortic aneurysms (AAA) continue to pose a high mortality risk despite advances in medical imaging and surgery. Intraluminal thrombus (ILT) is detected in most AAAs and may critically impact their development. Therefore, understanding ILT deposition and growth is of practical importance. To assist in managing these patients, the scientific community has been researching the relationship between intraluminal thrombus (ILT) and hemodynamic parameters wall shear stress (WSS) derivatives. This study analyzed three patient-specific AAA models reconstructed from CT scans using computational fluid dynamics (CFD) simulations and a pulsatile non-Newtonian blood flow model. The co-localization and relationship between WSS-based hemodynamic parameters and ILT deposition were examined. The results show that ILT tends to occur in regions of low velocity and time-averaged WSS (TAWSS) and high oscillation shear index (OSI), endothelial cell activation potential (ECAP), and relative residence time (RRT) values. ILT deposition areas were found in regions of low TAWSS and high OSI independently of the nature of flow near the wall characterized by transversal WSS (TransWSS). A new approach is suggested which is based on the estimation of CFD-based WSS indices specifically in the thinnest and thickest ILT areas of AAA patients; this approach is promising and supports the effectiveness of CFD as a decision-making tool for clinicians. Further research with a larger patient cohort and follow-up data are needed to confirm these findings.

Non-invasive diagnostics of blockage growth in the descending aorta-computational approach.

Atherosclerosis causes blockages to the main arteries such as the aorta preventing blood flow from delivering oxygen to the organs. Non-invasive diagnosis of these blockages is difficult, particularly in primary healthcare. In this paper, the effect of arterial blockage development and growth is investigated at the descending aorta on some possible non-invasive assessment parameters including the blood pressure waveform, wall shear stress (WSS), time-average WSS (TAWSS) and the oscillation shear index (OSI). Blockage severity growth is introduced in a simulation model as 25%, 35%, 50% and 65% stenosis at the descending aorta based on specific healthy control aorta data clinically obtained. A 3D aorta model with invasive pulsatile waveforms (blood flow and pressure) is used in the CFD simulation. Blockage severity is assessed by using blood pressure measurements at the left subclavian artery. An arterial blockage growth more than 35% of the lumen diameter significantly affects the pressure. A strong correlation is also observed between the ascending aorta pressure values, pressure at the left subclavian artery and the relative residence time (RRT). An increase of RRT downstream from the stenosis indicates a 35% stenosis at the descending aorta which results in high systolic and diastolic pressure readings. The findings of this study could be further extended by transferring the waveform reading from the left subclavian artery to the brachial artery.

Did You Just Cough? Visualization of Vapor Diffusion in an Office Using Computational Fluid Dynamics Analysis.

Awareness of indoor air quality (IAQ) in crowded places such as schools and offices has increased since 2020 due to the COVID-19 pandemic. In addition, countries' shifting away from containment and towards living with COVID-19 is expected to increase demand for risk mitigation via air-purification devices. In this work, we use Computational Fluid Dynamics (CFD) analysis to investigate the impact of adding an air-purification technology on airflow in an enclosed space. We model a Polyester Filter and UV light (PFUV) dehumidifier in an office with two occupants: one infected with an airborne infectious disease, such as COVID-19; and the other uninfected. We compare three cases where the infected occupant coughs: with no device, and with the device at two different orientations. We construct a CFD model using ANSYS® 2021 Fluent and the Discrete Phase Model (DPM) for the particle treatment. Thermal comfort is assessed using the Testo 400 IAQ and comfort kit. We find that both the device operation and the placement alter the airflow contours, significantly reducing the potential for the uninfected occupant to inhale the vapour expelled by the infected occupant, potentially impacting the likelihood of disease transmission. The device improved thermal comfort measured by Predicted Mean Vote (PMV), Predicted Percentage Dissatisfied (PPD).

Terrain Perception Using Wearable Parrot-Inspired Companion Robot, KiliRo.

Research indicates that deaths due to fall incidents are the second leading cause of unintentional injury deaths in the world. Death by fall due to a person texting or talking on mobile phones while walking, impaired vision, unexpected terrain changes, low balance, weakness, and chronic conditions has increased drastically over the past few decades. Particularly, unexpected terrain changes would many times lead to severe injuries and sometimes death even in healthy individuals. To tackle this problem, a warning system to alert the person of the imminent danger of a fall can be developed. This paper describes a solution for such a warning system used in our bio-inspired wearable pet robot, KiliRo. It is a terrain perception system used to classify the terrain based on visual features obtained from processing the images captured by a camera and notify the wearer of terrain changes while walking. The parrot-inspired KiliRo robot can twist its head and the camera up to 180 degrees to obtain visual feedback for classification. Feature extraction is followed by K-nearest neighbor for terrain classification. Experiments were conducted to establish the efficacy and validity of the proposed approach in classifying terrain changes. The results indicate an accuracy of over 95% across five terrain types, namely pedestrian pathway, road, grass, interior, and staircase.

Prediction of upper airway dryness and optimal continuous positive airway pressure conditions.

Continuous positive airway pressure is the most effective long-term treatment for obstructive sleep apnoea, which is a sleeping disorder characterized by pauses in breathing during sleep. It introduces pressurized atmospheric air into the respiratory system in order to maintain open airways without blockage. Some continuous positive airway pressure devices incorporate a convective heat transfer humidifier to overcome dryness. However, many side effects, including the unacceptable excess of water droplets in the air supply line, have been reported and improvements are essential for better patient's comfort and acceptance of the therapy. The excess of water droplets is attributed to the qualitative rather than the quantitative approach of determining the rise in temperature and humidity of the inspired air. Therefore, a human upper airway mathematical model is developed to predict the heat and water transfer variation between normal breathing and continuous positive airway pressure conditions and determine the optimal input temperature and relative humidity in the continuous positive airway pressure humidifier.

Effect of continuous positive airway pressure treatment on permeability, inflammation and mucus production of human epithelial cells.

Continuous positive airway pressure (CPAP) therapy is the gold standard treatment for obstructive sleep apnoea, which affects millions of people worldwide. However, this therapy normally results in symptoms such as dryness, sneezing, rhinorrhoea, post-nasal drip, nasal congestion and epistaxis in the upper airways. Using bronchial epithelial (Calu-3) and nasal epithelial (RPMI 2650) cells in an in vitro respiratory model, this study, for the first time, investigates the effect of CPAP positive pressure on the human respiratory epithelial mechanisms that regulate upper airways lubrication characteristics. To understand how the epithelium and mucus are affected by this therapy, several parameters were determined before and after positive pressure application. This work demonstrates that the positive pressure not only compresses the cells, but also reduces their permeability and mucus secretion rate, thus drying the airway surface liquid layer and altering the mucus/water ratio. It is also observed that the respiratory epithelia is equally inflamed without or with external humidification during CPAP application. These findings clearly identify the causes of the side-effects reported by patients under CPAP therapy.

Effect of hair removal on solar UV transmission into skin and implications for melanoma skin cancer development.

Melanoma is the severest type of skin cancer. As distinct from many other cancer types, the incidence of melanoma has been increasing steadily over the last century. Discovering new risk factors of melanoma will not only raise public awareness but also potentially contribute to the improvement of skin cancer protection in the future. Nowadays, the tendency of shaving skin hair is becoming increasingly popular for aesthetic purposes. However, human hair serves several functions, one of which is ultraviolet (UV) protection for the skin. What is more, stem cells found in the follicles of hair could be the origin of melanoma upon exposure to ultraviolet radiation. Therefore, it is of interest to investigate the effect of shaving on solar UV transmission in the skin. To achieve that, two groups of skin models are constructed in TracePro software: one with unaltered hair and one with shaved hair. The UV transport in the models is simulated using the Monte Carlo method and the absorptions in the stem cells layer are compared. It is found that shaving will increase the UV transmission to the follicular stem cells to a certain degree. More specifically, shaving limbs will generally increase the solar UV transmission from about 5% to 20% in the UV wavelength range.

Contribution of Human Hair in Solar UV Transmission in Skin: Implications for Melanoma Development.

Melanoma is the deadliest type of skin cancer with its prevalence on the rise. Recently, the melanocyte stem cells in hair follicles have been identified as the possible origin of melanoma upon exposure to ultraviolet radiation (UVR) through skin. It is hypothesized that colourless vellus hair (predominant in childhood) can serve as an alternative pathway in transmitting these ultraviolet (UV) photons to the stem cells. To investigate this, we have used the CRAIC microspectrophotometer to investigate the optical properties of 'vellus-like' hairs and terminal hairs of different colours using UV-VIS-NIR light sources. It was found that the average attenuation coefficient of 'vellus-like' hair is significantly lower than that of terminal hair in the UVA (p < 0.0001) and UVB (p < 0.001) wavelength ranges. Next, the optical properties of hairs are applied to simulations for examining their influence on UV transmission into the skin. The results show that the presence of vellus hair would increase the solar UV transmission to the melanocyte stem cell layer significantly. The findings explain why children are particularly vulnerable to sun exposure and the positive correlation found between the incidence of melanoma in adults' bodies and the number of vellus hairs in these areas.

Stretchable and sensitive sensor based on carbon nanotubes/polymer composite with serpentine shapes via molding technique.

With the rapid development of wearable devices in recent years, stretchable strain sensors based on electrically conductive composites have attracted a great deal of attention owing to their good stretchability and piezoresistivity. However, due to the intrinsic restriction of these types of composites, the conventional stretchable strain sensors cannot do well in all aspect of sensing performance. A stretchable strain sensor based on carbon nanotubes/poly(dimethylsiloxane) composite with the serpentine shape was devised and fabricated. The sensor was readily manufactured through a molding technique. Not only can this sensor distinguish tension strain from transverse or longitudinal direction, but also exhibits good linearity of response to tensile strain. In terms of sensitivity, hysteresis and response time, the stretchable strain sensor showed significant performance. The sensing performance of this proposed stretchable sensor has been demonstrated to be good in this work and it also shows a good prospect for utilization in multifunctional wearable devices.

Simulation of UV power absorbed by follicular stem cells during sun exposure and possible implications for melanoma development.

The incidence of melanoma in children is extremely rare. However, there is convincing evidence supporting a higher risk of developing melanoma in individuals who have experienced excessive sun exposure during their childhood. A possible explanation for this phenomenon is that prior to puberty, the melanocyte stem cells in the bulge region of hair follicles are much shallower in the dermis, resulting in their increased vulnerability to sun exposure. To validate this hypothesis, a Monte Carlo simulation of light transport is applied to quantify the dose of solar UV power absorbed in the stem-cell layers at different depths in both child and adult skins. The simulated results suggest that the stem cells in vellus hair follicles would absorb over 250 times higher UV photons than those in the terminal hair follicles. Due to the thinner epidermis in child skin, the stem cells in vellus hair follicles absorb about 1.9 and 3.2 times greater ultraviolet A and ultraviolet B, respectively, than those in adult skin. These findings provide a possible explanation to why children are particularly vulnerable to sun exposure.

Review of human hair optical properties in possible relation to melanoma development.

Immigration and epidemiological studies provide evidence indicating the correlation of high ultraviolet exposure during childhood and increased risks of melanoma in later life. While the explanation of this phenomenon has not been found in the skin, a class of hair has been hypothesized to be involved in this process by transmitting sufficient ultraviolet rays along the hair shaft to possibly cause damage to the stem cells in the hair follicle, ultimately resulting in melanoma in later life. First, the anatomy of hair and its possible contribution to melanoma development, and the tissue optical properties are briefly introduced to provide the necessary background. This paper emphasizes on the review of the experimental studies of the optical properties of human hair, which include the sample preparation, measurement techniques, results, and statistical analysis. The Monte Carlo photon simulation of human hair is next outlined. Finally, current knowledge of the optical studies of hair is discussed in the light of their possible contribution to melanoma development; the necessary future work needed to support this hypothesis is suggested.

A pilot study on the biomechanical assessment of obstructive sleep apnea pre and post bariatric surgery.

Obesity is a major risk factor for obstructive sleep apnea patients. In obese patients the severity of this risk can be reduced by bariatric surgery. This pilot study investigates the perioperative effects of bariatric surgery on obstructive sleep apnea and on the physical and biomechanical characteristics of the upper airway. Polysomnography and computer tomography data for 10 morbid obese patients promoted for bariatric surgery were conducted before surgery and at 6 and 12 months postoperatively for assessment of the oropharyngeal anatomy, and subsequent three-dimensional modelling of the airway. Mean values for the apnea/hypopnea index and body mass index significantly reduced after surgery. To combine the effect of changes in the upper airway volume and body mass index, a new volume body mass index is introduced. This index increases with a successful bariatric surgery. Although bariatric surgery leads to an effective weight reduction for all age groups, for obstructive sleep apnea patients it may be effective for middle age, less effective for 50-60 years, and further less effective for patients over the age of 60 years.

Manufacturing the Gas Diffusion Layer for PEM Fuel Cell Using a Novel 3D Printing Technique and Critical Assessment of the Challenges Encountered.

The conventional gas diffusion layer (GDL) of polymer electrolyte membrane (PEM) fuel cells incorporates a carbon-based substrate, which suffers from electrochemical oxidation as well as mechanical degradation, resulting in reduced durability and performance. In addition, it involves a complex manufacturing process to produce it. The proposed technique aims to resolve both these issues by an advanced 3D printing technique, namely selective laser sintering (SLS). In the proposed work, polyamide (PA) is used as the base powder and titanium metal powder is added at an optimised level to enhance the electrical conductivity, thermal, and mechanical properties. The application of selective laser sintering to fabricate a robust gas diffusion substrate for PEM fuel cell applications is quite novel and is attempted here for the first time.

Accuracy of Cuff-Measured Blood Pressure: Systematic Reviews and Meta-Analyses.

BACKGROUND: Hypertension (HTN) is the single greatest cardiovascular risk factor worldwide. HTN management is usually guided by brachial cuff blood pressure (BP), but questions have been raised regarding accuracy. OBJECTIVES: This comprehensive analysis determined the accuracy of cuff BP and the consequent effect on BP classification compared with intra-arterial BP reference standards. METHODS: Three individual participant data meta-analyses were conducted among studies (from the 1950s to 2016) that measured intra-arterial aortic BP, intra-arterial brachial BP, and cuff BP. RESULTS: A total of 74 studies with 3,073 participants were included. Intra-arterial brachial systolic blood pressure (SBP) was higher than aortic values (8.0 mm Hg; 95% confidence interval [CI]: 5.9 to 10.1 mm Hg; p < 0.0001) and intra-arterial brachial diastolic BP was lower than aortic values (-1.0 mm Hg; 95% CI: -2.0 to -0.1 mm Hg; p = 0.038). Cuff BP underestimated intra-arterial brachial SBP (-5.7 mm Hg; 95% CI: -8.0 to -3.5 mm Hg; p < 0.0001) but overestimated intra-arterial diastolic BP (5.5 mm Hg; 95% CI: 3.5 to 7.5 mm Hg; p < 0.0001). Cuff and intra-arterial aortic SBP showed a small mean difference (0.3 mm Hg; 95% CI: -1.5 to 2.1 mm Hg; p = 0.77) but poor agreement (mean absolute difference 8.0 mm Hg; 95% CI: 7.1 to 8.9 mm Hg). Concordance between BP classification using the Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure cuff BP (normal, pre-HTN, and HTN stages 1 and 2) compared with intra-arterial brachial BP was 60%, 50%, 53%, and 80%, and using intra-arterial aortic BP was 79%, 57%, 52%, and 76%, respectively. Using revised intra-arterial thresholds based on cuff BP percentile rank, concordance between BP classification using cuff BP compared with intra-arterial brachial BP was 71%, 66%, 52%, and 76%, and using intra-arterial aortic BP was 74%, 61%, 56%, and 65%, respectively. CONCLUSIONS: Cuff BP has variable accuracy for measuring either brachial or aortic intra-arterial BP, and this adversely influences correct BP classification. These findings indicate that stronger accuracy standards for BP devices may improve cardiovascular risk management.

Prestretched airway smooth muscle response to length oscillation.

Airway smooth muscle (ASM) hyperconstriction is the cause of many respiratory diseases including asthma. In vitro testing has demonstrated that the active forces of ASM are reduced by length oscillation (LO) mimicking tidal breathing. In a previous study, we demonstrated that this force reduction can be further enhanced when superimposing oscillations (with certain frequencies and amplitudes) on this LO In contrast, it has been reported that pressurizing the lung may help in relieving asthmatic airway constrictions. Ultimately, this pressurizing stretches the ASM and may disturb the acto-myosin cross-bridges in a manner similar to LO; however, it is of a static rather than dynamic nature. This research investigates the effect of combining both prestretch- and LO-applications on contracted porcine ASM Isolated porcine ASM relaxation was tested with a 0.56%, 2%, or 4% stretch of its reference length (Lref) in addition to LO These oscillations are composed of a main wave mimicking the normal breathing (frequency of 0.33 Hz and amplitude of 4% Lref) and superimposed oscillations (frequencies of 20, 30, 40, 60 and 80 Hz and amplitude of 1% Lref). The oscillations were maintained for 10 min. The results demonstrate that a prestretch of 0.56% and 2% Lref does enhance the contracted ASM relaxation at certain superimposed length oscillations frequencies while of 4% Lref does not.

Reducing upper airway collapse at lower continuous positive airway titration pressure.

During respiration, upper airway (UA) collapse occurs when the forces generated from the negative UA pressures exceed the forces produced by the UA muscles; which leads to loose soft tissue at the back of the mouth. At predetermined titration pressure, the Continuous Positive Airway Pressure (CPAP) normally provides a continuous pressurized and humidified air to prevent airway collapse. However, high titration pressures are not always tolerated by patients and may lead to damaging effects including stroke symptoms for cardiovascular disease patients. This paper hypothesizes that superimposed pressure oscillation can modulate the loose tissue and allow unblocking the upper airway passages to help reduce the required titration pressure. Using MRI scans, this paper investigates the effects of using pressure oscillations superimposed on the CPAP to keep the airway open at lower pressure distributions inside the upper airway and consequently increase the patients' comfort and reduce their rejection to the CPAP.

Assessing abdominal aorta narrowing using computational fluid dynamics.

This paper investigates the effect of developing arterial blockage at the abdominal aorta on the blood pressure waves at an externally accessible location suitable for invasive measurements such as the brachial and the femoral arteries. Arterial blockages are created surgically within the abdominal aorta of healthy Wistar rats to create narrowing resemblance conditions. Blood pressure is measured using a catheter inserted into the right femoral artery. Measurements are taken at the baseline healthy condition as well as at four different severities (20, 50, 80 and 100 %) of arterial blockage. In vivo and in vitro measurements of the lumen diameter and wall thickness are taken using magnetic resonance imaging and microscopic techniques, respectively. These data are used to validate a 3D computational fluid dynamics model which is developed to generalize the outcomes of this work and to determine the arterial stress and strain under the blockage conditions. This work indicates that an arterial blockage in excess of 20 % of the lumen diameter significantly influences the pressure wave and reduces the systolic blood pressure at the right femoral artery. High wall shear stresses and low circumferential strains are also generated at the blockage site.