More Like this

1. Micro-calcifications predict plaque vulnerability and initiate rupture of the fibrous cap

   Corti A ; Dinh A ; De Paolis A ; Aikawa E ; Weinbaum S ; Cardoso L. ( April 2022 , 48th Annual Northeast Bioengineering Conference (NEBEC 2022))

   Introduction: The mechanical stability of an atheroma fibrous cap (FC) is a crucial factor for the risk of heart attack or stroke in asymptomatic vulnerable plaques. Common determinants of plaque vulnerability are the cap thickness and the presence of micro-calcifications (µCalcs). Higher local stresses have been linked to thin caps(<65µm) and, more recently, our lab demonstrated how µCalcs can potentially initiate cap rupture [1-3]. When combined, these two factors can compromise to a greater extent the stability of the plaque. On this basis, we quantitatively analyzed both individual and combined effects of key determinants of plaque rupture using a tissue damage model on idealized atherosclerotic arteries. Our results were then tested against a diseased human coronary sample. Methods: We performed 28 finite element simulations on three-dimensional idealized atherosclerotic arteries and a human coronary sample. The idealized models present 10% lumen narrowing and 1.25 remodeling index (RI)(Fig.1A). The FC thickness values that we considered were of 50, 100, 150 and 200µm. The human coronary presents a RI=1.31, with 31% lumen occlusion and a 140µm-thick cap(Fig.1B). The human model is based on 6.7μm high-resolution microcomputed tomography (HR-μCT) images. The µCalc has a diameter of 15µm and each artery was expanded up tomore »a systolic pressure of 120mmHg. Layer-specific material properties were de-fined by the HGO model coupled with the hyperelastic failure description proposed by Volokh et al. [4] to repli-cate the rupture of the FC. We considered a max. princi-pal stress for rupture of 545kPa[5]. The lipid core and the µCalc were considered as elastic materials (Ecore = 5kPa, νcore = 0.49; EµCalc= 18,000 kPa, νµCalc=0.3). To obtain a detailed analysis of the cap stresses and rupture progres-sion, a sub-modeling approach was implemented using ABAQUS (Dassault Systemes, v.2019) (Fig. 1). Results: We investigated the quantitative effect of cap thickness and µCalc by simulating tissue failure and de-riving a vulnerability index (VI) for each risk factor. The VI coefficient was defined as the peak cap stress (PCS) normalized by the threshold stress for rupture (545kPa). The relationship between the risk factors and VI was de-termined by deriving the Pearson’s correlation coefficient (PCC) followed by one-tailed t-test (SPSS, IBM, v.25). The null hypothesis was rejected if p<0.05. The presence of the µCalc is the factor that manifests the greater impact on cap stability, leading to at least a 2.5-fold increase in VI and tissue rupture regardless of cap thickness (Fig.2A,B). One µCalc in the cap is the first predictor of vulnerability, with PCCµCalc=0.59 and pµCalc=0.001. Our results also confirm the substantial in-fluence of cap thickness, with an exponential increase in stresses as the cap becomes thinner. The 50µm cap is the only phenotype that ruptures without µCalc (Fig2A). The human sample exhibits PCS levels that are close to the idealized case with 150µm cap and it doesn’t rupture in the absence of the µCalc (PCShuman=233kPa, PCSideal= 252kPa). Conversely, the phenotypes with the µCalc showed an increase in VI of about 2.5 and reached rup-ture under the same blood pressure regime. Conclusions: Our results clearly show the multifactorial nature of plaque vulnerability and the significance of micro-calcifications on the cap mechanical stability. The presence of a μCalc strongly amplifies the stresses in the surrounding tissue, and it can provoke tissue failure even in thick caps that would otherwise be classified as stable. Clearly, plaque phenotypes with a thin cap and μCalcs in the tissue represent the most vulnerable condition. Finally, these observations are well validated by the case of the human atherosclerotic segment, which closely compares to its corresponding idealized model. The novel imple-mentation of the tissue damage description and the defi-nition of a vulnerability index allow one to quantitatively analyze the individual and combined contribution of key determinants of cap rupture, which precedes the for-mation of a thrombus and myocardial infarction.« less
2. Mechanical Performance of Latex and Nitrile Medical Exam Gloves Under Repeated Soap and Water Treatment

   https://doi.org/10.5281/zenodo.51126  

   Jonathan Patterson, Samuel A. ( July 2021 , American journal of advanced research)

   The human cost of the COVID-19 pandemic has taken a great toll, and led, around the globe, to a shortage in personal protective equipment (PPE) such as medical exam gloves. To face this shortage and keep themselves and patients safe, many front-line healthcare providers have been overextending the life of PPE. Though not ideal, one pragmatic solution often used is the practice of sanitization and extended use of existing PPE. The data produced by these experiments should help determine an acceptable reusability window of PPE in a working environment, by which the effective use time may be extended and justified. The effect of repeated sanitization, using soap and water, on the mechanical performance was investigated for latex and nitrile elastomeric medical exam gloves. Tensile tests were performed for various manufacturer brands commonly used in the United States (Glovepak Europa, Polymed and Sempersure) and India (Surgiglove). Tensile test samples were prepared for each studied glove and treatment combination. Nitrile gloves were observed to be more uniformly affected by the application of soap and water sanitization than latex gloves. Glovepak Europa nitrile gloves saw significant changes (p≤0.001) in elastic modulus after 5, 10 and 20 treatments losing 31.5%, 42.7% and 49.7%, respectively.more »Sempersure nitrile gloves also saw significant changes (p≤0.05) in elastic modulus at 5, 10 and 20 treatments losing 44.2%, 34.3% and 45.9%, respectively. Surgiglove nitrile gloves saw a significant loss in elastic modulus of 42.0% (p≤0.001) after 10 treatments. Surgiglove powder free latex showed no significant (p>0.05) change after 10 or 20 repeated treatments using soap and water. Polymed powder free latex showed no significant (p>0.05) change after 10 treatments, but did show a significant (p≤0.05) decrease in elastic modulus by 24.2% after 5 treatments and 25.5% after 20 treatments. Surgiglove powdered latex showed a significant (p≤0.05) increase in elastic modulus by 19.9% after 5 treatments and 15.8% after 10 treatments, while showing no significant (p>0.05) change at 20 treatments. Due to the consistent significant degradation after five repetitions, use of soap and water may not be an adequate sanitization procedure for nitrile gloves, since it would potentially induce premature failure. The latex gloves showed no clear pattern and the results were inconclusive.« less
3. Microfluidic Synthesis of Elastomeric Microparticles: A Case Study in Catalysis of Palladium-Mediated Cross-Coupling

   Bennett, Jeffrey A ; Genzer, Jan ; Abolhasani, Milad ( October 2018 , 2018 AIChE Annual Meeting)

   Metal-mediated cross-coupling reactions offer organic chemists a wide array of stereo- and chemically-selective reactions with broad applications in fine chemical and pharmaceutical synthesis.1 Current batch-based synthesis methods are beginning to be replaced with flow chemistry strategies to take advantage of the improved consistency and process control methods offered by continuous flow systems.2,3 Most cross-coupling chemistries still encounter several issues in flow using homogeneous catalysis, including expensive catalyst recovery and air sensitivity due to the chemical nature of the catalyst ligands.1 To mitigate some of these issues, a ligand-free heterogeneous catalysis reaction was developed using palladium (Pd) loaded into a polymeric network of a silicone elastomer, poly(hydromethylsiloxane) (PHMS), that is not air sensitive and can be used with mild reaction solvents (ethanol and water).4 In this work we present a novel method of producing soft catalytic microparticles using a multiphase flow-focusing microreactor and demonstrate their application for continuous Suzuki-Miyaura cross-coupling reactions. The catalytic microparticles are produced in a coaxial glass capillary-based 3D flow-focusing microreactor. The microreactor consists of two precursors, a cross-linking catalyst in toluene and a mixture of the PHMS polymer and a divinyl cross-linker. The dispersed phase containing the polymer, cross-linker, and cross-linking catalyst is continuously mixed and thenmore »formed into microdroplets by the continuous phase of water and surfactant (sodium dodecyl sulfate) introduced in a counter-flow configuration. Elastomeric microdroplets with a diameter ranging between 50 to 300 micron are produced at 25 to 250 Hz with a size polydispersity less than 3% in single stream production. The physicochemical properties of the elastomeric microparticles such as particle swelling/softness can be tuned using the ratio of cross-linker to polymer as well as the ratio of polymer mixture to solvent during the particle formation. Swelling in toluene can be tuned up to 400% of the initial particle volume by reducing the concentration of cross-linker in the mixture and increasing the ratio of polymer to solvent during production.5 After the particles are produced and collected, they are transferred into toluene containing palladium acetate, allowing the particles to incorporate the palladium into the polymer network and then reduce the palladium to Pd0 with the Si-H functionality present on the PHMS backbones. After the reduction, the Pd-loaded particles can be washed and dried for storage or switched into an ethanol/water solution for loading into a micro-packed bed reactor (µ-PBR) for continuous organic synthesis. The in-situ reduction of Pd within the PHMS microparticles was confirmed using energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS) and focused ion beam-SEM, and TEM techniques. In the next step, we used the developed µ-PBR to conduct continuous organic synthesis of 4-phenyltoluene by Suzuki-Miyaura cross-coupling of 4-iodotoluene and phenylboronic acid using potassium carbonate as the base. Catalyst leaching was determined to only occur at sub ppm concentrations even at high solvent flow rates after 24 h of continuous run using inductively coupled plasma mass spectrometry (ICP-MS). The developed µ-PBR using the elastomeric microparticles is an important initial step towards the development of highly-efficient and green continuous manufacturing technologies in the pharma industry. In addition, the developed elastomeric microparticle synthesis technique can be utilized for the development of a library of other chemically cross-linkable polymer/cross-linker pairs for applications in organic synthesis, targeted drug delivery, cell encapsulation, or biomedical imaging. References 1. Ruiz-Castillo P, Buchwald SL. Applications of Palladium-Catalyzed C-N Cross-Coupling Reactions. Chem Rev. 2016;116(19):12564-12649. 2. Adamo A, Beingessner RL, Behnam M, et al. On-demand continuous-flow production of pharmaceuticals in a compact, reconfigurable system. Science. 2016;352(6281):61 LP-67. 3. Jensen KF. Flow Chemistry — Microreaction Technology Comes of Age. 2017;63(3). 4. Stibingerova I, Voltrova S, Kocova S, Lindale M, Srogl J. Modular Approach to Heterogenous Catalysis. Manipulation of Cross-Coupling Catalyst Activity. Org Lett. 2016;18(2):312-315. 5. Bennett JA, Kristof AJ, Vasudevan V, Genzer J, Srogl J, Abolhasani M. Microfluidic synthesis of elastomeric microparticles: A case study in catalysis of palladium-mediated cross-coupling. AIChE J. 2018;0(0):1-10.« less
4. Mechanical and electrical properties of MWCNT/PP films and structural health monitoring of GF/PP joints

   Li, W. ; Palardy, G. ( November 2021 , SPE Automotive Composites Conference & Exhibition)

   Online repository: https://speautomotive.com/acce-conference/2021-acce-papers-and-program-guides/ and also on: arXiv:2204.00909. Abstract: While welding of thermoplastic composites (TPCs) is a promising rivetless method to reduce weight, higher confidence in joints’ structural integrity and failure prediction must be achieved for widespread use in industry. In this work, we present an innovative study on damage detection for ultrasonically welded TPC joints with multi-walled carbon nanotubes (MWCNTs) and embedded buckypaper films. MWCNTs show promise for structural health monitoring (SHM) of composite joints, assembled by adhesive bonding or fusion bonding, through electrical resistance changes. This study focuses on investigating multifunctional films and their suitability for ultrasonic welding (USW) of TPCs, using two approaches: 1) MWCNT-filled polypropylene (PP) nanocomposites prepared via solvent dispersion, and 2) high conductivity MWCNT buckypaper embedded between PP films by hot pressing. Nanocomposite formulations containing 5 wt% and 10 wt% MWCNTs were synthesized using solvent dispersion method, followed by compression molding to manufacture films. The effect of MWCNT concentration on electrical and dynamic mechanical behavior of multifunctional films was examined with a Sourcemeter and Dynamic Mechanical Analyzer, and a comparison was made between 5 - 20 wt% MWCNT/PP films based on previous research. Glass fiber/polypropylene (GF/PP) composite joints were ultrasonically welded in a single lapmore »shear configuration using buckypaper and MWCNT/PP films. Furthermore, electrical resistance measurements were carried out for joints under bending loads. It was observed that 15 wt% and 20 wt% MWCNT/PP films had higher stability and sensitivity for resistance response than embedded buckypaper and films with low MWCNT contents, demonstrating their suitability for USW and potential for SHM.« less
5. Prototyping of Superhydrophobic Surfaces from Structure-Tunable Micropillar Arrays Using Visible Light Photocuring

   https://doi.org/10.1002/adem.201801150  

   Li, Hansheng ; Chen, Fu-Hao ; Biria, Saeid ; Hosein, Ian D. ( January 2019 , Advanced Engineering Materials)

   A new approach is reported to fabricate micropillar arrays on transparent surfaces by employing the light‐induced self‐writing technique. A periodic array of microscale optical beams is transmitted through a thin film of photo‐crosslinking acrylate resin. Each beam undergoes self‐lensing associated to photopolymerization‐induced changes in the refractive index of the medium, which counters the beam's natural tendency to diverge over space. As a result, a microscale pillar grows along each beam's propagation path. Concurrent, parallel self‐writing of micropillars leads to the prototyping of micropillar‐based arrays, with the capability to precisely vary the pillar diameter and inter‐spacing. The arrays are spray coated with a thin layer of polytetrafluoroethylene (PTFE) nanoparticles to create large‐area superhydrophobic surfaces with water contact angles greater than 150° and low contact angle hysteresis. High transparency is achieved over the entire range of micropillar arrays explored. The arrays are also mechanically durable and robust against abrasion. This is a scalable, straightforward approach toward structure‐tunable micropillar arrays for functional surfaces and anti‐wetting applications.