Search

Magnetically induced heterogeneous catalysis has been attracting attention due to its high energy efficiency and flexibility for dynamic reactor control. Iron wool is a commercial, low-cost, and versatile heating agent, which has been used in several magnetic catalysis studies, but its heating properties have never been investigated. Here, the properties of three types of Fe wool were studied using optical and electronic microscopy, x-ray diffraction, and measurements of both heating power and high-frequency hysteresis loops. The effects of strand width, packing, and magnetic field amplitude and frequency were studied. A maximum specific absorption rate (SAR) around 700 W/g under a rms field of 47.4 mT at 93 kHz was measured for the larger width Fe wool. High-frequency hysteresis loops were used to quantify the contribution of hysteresis losses and eddy currents to total heating. Eddy currents contribute 65%–90% to the global heating depending on the strand width. Coating the wool with SiO2 and Ni has negative effects on the SAR but none on hysteresis losses. It is interpreted as originating from the cut-off of inter-wire eddy currents due to the insulating (SiO2, oxidized Ni) nature of the coating. Last, it was found that adding more Fe wool in a given volume mostly decreases the SAR. This effect could be not only due to the absorption and/or screening of the field by surface strands but also due to magnetic interactions. The results described in this work give insights into the magnetic heating of microscale magnetic materials and optimize their use for heterogeneous catalysis. [ABSTRACT FROM AUTHOR]

Background: There are limited evidence-based guidelines to predict which osteochondritis dissecans (OCD) lesions will heal with nonoperative treatment., Purpose: To train a set of classification algorithms to predict nonoperative OCD healing while identifying new clinically meaningful predictors., Study Design: Case-control study; Level of evidence, 3., Methods: Patients with OCD of the knee with open physes undergoing nonoperative management were prospectively queried from the Research on OCD of the Knee (ROCK) cohort (https://kneeocd.org) in April 2022. Patients were included if they met the study criteria for nonoperative treatment success or failure. Nonoperative treatment success was defined as complete healing on magnetic resonance imaging (MRI) and total return to sports participation. Failure was defined as the crossover from nonoperative management to surgery at any point at or beyond the 3-month follow-up. If a patient did not meet one of these criteria, they were not included. Normalized lesion size, lesion location, patient characteristics, and symptoms were used as clinically relevant predictors., Results: A total of 64 patients were included, of whom 24 (37.5%) patients successfully healed with nonoperative management. Multivariate logistic regression revealed that a 1% increase in normalized lesion width was associated with an increase in the likelihood of nonoperative failure (odds ratio [OR], 1.41 [95% CI, 1.17-1.81]; P < .01). By contrast, lesions in the posterior sagittal zone (OR, 0.08 [95% CI, 0.009-0.43]; P < .01) or the medial-most coronal zone (for lesions of the medial femoral) and lateral-most coronal zone (for lesions of the lateral femoral condyle) on MRI (OR, 0.05 [95% CI, 0.004-0.44]; P < .01) were associated with a decrease in the likelihood of nonoperative treatment failure. Support vector machines had a cross-validated area under the receiver operating characteristic curve of 0.89 and a classification accuracy of 83.3%., Conclusion: Lesion location in the posterior aspect of the condyle on sagittal MRI and lesion location in the medial-most or lateral-most locations on coronal MRI were identified as statistically significant predictors of increased nonoperative treatment success on multivariate analysis. Machine learning models can predict which OCD lesions will heal with nonoperative management with superior accuracy compared with previously published models., Competing Interests: One or more of the authors has declared the following potential conflict of interest or source of funding: M.T. has received hospitality payments from Aesculap Biologics. M.D.M. has received education payments from Kairos Surgical. K.G.S. has received education payments from Evolution Surgical and hospitality payments from Arthrex. AOSSM checks author disclosures against the Open Payments Database (OPD). AOSSM has not conducted an independent investigation on the OPD and disclaims any liability or responsibility relating thereto., (© The Author(s) 2024.)

Core-shell nanocomposites made of iron oxide core (IO NPs) coated with mesoporous silica (MS) shells are promising theranostic agents. While the core is being used as an efficient heating nanoagent under alternating magnetic field (AMF) and near infra-red (NIR) light and as a suitable contrast agent for magnetic resonance imaging (MRI), the MS shell is particularly relevant to ensure colloidal stability in a biological buffer and to transport a variety of therapeutics. However, a major challenge with such inorganic nanostructures is the design of adjustable silica structures, especially with tunable large pores which would be useful, for instance, for the delivery of large therapeutic biomolecule loading and further sustained release. Furthermore, the effect of tailoring a porous silica structure on the magneto- or photothermal dissipation still remains poorly investigated. In this work, we undertake an in-depth investigation of the growth of stellate mesoporous silica (STMS) shells around IO NPs cores and of their micro/mesoporous features respectively through time-lapse and in situ liquid phase transmission electron microscopy (LPTEM) and detailed nitrogen isotherm adsorption studies. We found here that the STMS shell features (thickness, pore size, surface area) can be finely tuned by simply controlling the sol-gel reaction time, affording a novel range of IO@STMS core@shell NPs. Finally, regarding the responses under alternating magnetic fields and NIR light which are evaluated as a function of the silica structure, IO@STMS NPs having a tunable silica shell structure are shown to be efficient as T 2 -weighted MRI agents and as heating agents for magneto- and photoinduced hyperthermia. Furthermore, such IO@STMS are found to display anti-cancer effects in pancreatic cancer cells under magnetic fields (both alternating and rotating).

The origin of cell death in the magnetomechanical actuation of cells induced by magnetic nanoparticle motion under low-frequency magnetic fields is still elusive. Here, a miniaturized electromagnet fitted under a confocal microscope is used to observe in real time cells specifically targeted by superparamagnetic nanoparticles and exposed to a low-frequency rotating magnetic field. Our analysis reveals that the lysosome membrane is permeabilized in only a few minutes after the start of magnetic field application, concomitant with lysosome movements toward the nucleus. Those events are associated with disorganization of the tubulin microtubule network and a change in cell morphology. This miniaturized electromagnet will allow a deeper insight into the physical, molecular, and biological process occurring during the magnetomechanical actuation of magnetic nanoparticles.