Fabrication and Actuation of Magnetic Shape-Memory Materials

Soft actuators are deformable materials that change their dimensions and/or shape in response to external stimuli. Among the various stimuli, remote magnetic fields are one of the most attractive forms of actuation, due to their ease of use, fast response and safety in biological systems. Composites of magnetic particles with polymer matrices are the most common material for magnetic soft actuators. In this paper, we demonstrate the fabrication and actuation of magnetic shape-memory materials based on hydrogels containing field-structured magnetic particles. These actuators are formed by placing the pregel dispersion into a mold of the desired on-field shape and exposing this to a homogeneous magnetic field until the gel point is reached. At this point the material may be removed from the mold and fully gelled in the desired off-field shape. The resultant magnetic shape-memory material then transitions between these two shapes when subjected to successive cycles of a homogeneous magnetic field, acting as a large deformation actuator. For actuators that are planar in the off-field state, this can result in significant bending to return to the on-field state. In addition, it is possible to make shape-memory materials that twist under the application of a magnetic field. For these torsional actuators, both experimental and theoretical results are given.Departamento de Física AplicadaGrupo FQM144Ministerio de Ciencia, Innovación y UniversidadesAgencia Estatal de InvestigaciónDeutsche Forschungsgemeinschaft (DFG

Melatonin-doped polymeric nanoparticles induce high crystalline apatite formation in root dentin

This work was funded by the Ministry of Economy and Competitiveness and European Regional Development Fund( MINECO/AEI/FEDER/UE) Project number PID2020-114694RBI00. Funding for open access charge: University of Granada / CBUA.Objective. To investigate the effect of novel polymeric nanoparticles (NPs) doped with melatonin (ML) on nano-hardness, crystallinity and ultrastructure of the formed hydroxyapatite after endodontic treatment. Methods. Undoped-NPs and ML-doped NPs (ML-NPs) were tested at radicular dentin, after 24 h and 6 m. A control group without NPs was included. Radicular cervical and apical dentin surfaces were studied by nano-hardness measurements, X-ray diffraction and transmission electron microscopy. Mean and standard deviation were analyzed by ANOVA and StudentNewman-Keuls multiple comparisons (p < 0.05). Results. Cervical dentin treated with undoped NPs maintained its nano-hardness values after 6 m of storage being [24 h: 0.29 (0.01); 6 m: 0.30 (0.02) GPa], but it decreased at apical dentin [24 h: 0.36 (0.01); 6 m: 0.28 (0.02) GPa]. When ML-NPs were used, nano-hardness was similar over time [24h: 0.31 (0.02); 6 m: 0.28 (0.03) GPa], at apical dentin. Root dentin treated with ML-NPs produced, in general, high crystallinity of new minerals and thicker crystals than those produced in the rest of the groups. After 6 m, crystals became organized in randomly oriented polyhedral, square polygonal block-like apatite or drop-like apatite polycrystalline lattices when ML-NPs were used. Undoped NPs generated poor crystallinity, with preferred orientation of small crystallite and increased microstrain. Significance. New polycrystalline formations encountered in dentin treated with ML-NPs may produce structural dentin stability and high mechanical performance at the root. The decrease of mechanical properties over time in dentin treated without NPs indicates scarce remineralization potential, dentin demineralization and further potential degradation. The amorphous stage may provide high hydroxyapatite solubility and remineralizing activity.Ministry of Economy and Competitiveness and European Regional Development Fund( MINECO/AEI/FEDER/UE) PID2020-114694RB-I00University of Granada/CBU

Magnetorheology of alginate ferrogels

Magnetorheological (MR) effect is a phenomenon typical of suspensions of magnetizable particles in a liquid carrier, characterized by strong changes of their mechanical properties in response to applied magnetic fields. Its origin is on the migration of magnetized particles and their aggregation into chain-like structures. However, for ferrogels, consisting of dispersions of magnetic particles in a polymer matrix, migration of particles is hindered by the elastic forces of the polymer network, preventing from strong MR effect. Interestingly, we demonstrate in this manuscript that strong MR effect in robustly cross-linked polymer ferrogels is still possible. Experimental results showed enhancement of the storage modulus of more than one order of magnitude for alginate ferrogels containing less than about 10 vol.% of iron particles under moderate magnetic fields. The differential feature of these ferrogels is that, instead of individual particles, the disperse phase consisted of large clusters of iron microparticles homogeneously distributed within the polymer networks. These clusters of magnetic particles were formed at the stage of the preparation of the ferrogels and their presence within the polymer networks had two main consequences. First, the volume fraction of clusters was considerably larger than this of individual particles, resulting in a larger effective volume fraction of solids. Second, since the force of magnetic attraction between magnetic bodies is roughly proportional to the cube of the body size, the existence of such clusters favored inter-cluster interaction under a magnetic field and the appearance of strong MR effect. On this basis, we demonstrated by theoretical modeling that the strong MR effect displayed by the alginate ferrogels of the present work can be quantitatively explained by assuming the existence of large, roughly spherical particle aggregates formed at the stage of the preparation of the ferrogels. Our theoretical model provides a reasonable quantitative prediction of the experimental resultsThis study was supported by project FIS2017-85954-R (Ministerio de Economía, Industria y Competitividad, MINECO, and Agencia Estatal de Investigación, AEI, Spain, cofunded by Fondo Europeo de Desarrollo Regional, FEDER, European Union). CGV acknowledges financial support by Ministerio de Ciencia, Innovación y Universidades and University of Granada, Spain, for her FPU17/00491 grant. AZ is grateful to the Program of the Ministry of Education and Science of the Russian Federation, projects 02.A03.21.0006, 3.1438.2017/4.6, and 3.5214.2017/6.7 and the Russian Fund of Basic Researches, project 18-08-0017

Expected Performance of the ATLAS Experiment - Detector, Trigger and Physics

A detailed study is presented of the expected performance of the ATLAS detector. The reconstruction of tracks, leptons, photons, missing energy and jets is investigated, together with the performance of b-tagging and the trigger. The physics potential for a variety of interesting physics processes, within the Standard Model and beyond, is examined. The study comprises a series of notes based on simulations of the detector and physics processes, with particular emphasis given to the data expected from the first years of operation of the LHC at CERN

ICAR: endoscopic skull‐base surgery

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The Helicobacter pylori Genome Project : insights into H. pylori population structure from analysis of a worldwide collection of complete genomes

Helicobacter pylori, a dominant member of the gastric microbiota, shares co-evolutionary history with humans. This has led to the development of genetically distinct H. pylori subpopulations associated with the geographic origin of the host and with differential gastric disease risk. Here, we provide insights into H. pylori population structure as a part of the Helicobacter pylori Genome Project (HpGP), a multi-disciplinary initiative aimed at elucidating H. pylori pathogenesis and identifying new therapeutic targets. We collected 1011 well-characterized clinical strains from 50 countries and generated high-quality genome sequences. We analysed core genome diversity and population structure of the HpGP dataset and 255 worldwide reference genomes to outline the ancestral contribution to Eurasian, African, and American populations. We found evidence of substantial contribution of population hpNorthAsia and subpopulation hspUral in Northern European H. pylori. The genomes of H. pylori isolated from northern and southern Indigenous Americans differed in that bacteria isolated in northern Indigenous communities were more similar to North Asian H. pylori while the southern had higher relatedness to hpEastAsia. Notably, we also found a highly clonal yet geographically dispersed North American subpopulation, which is negative for the cag pathogenicity island, and present in 7% of sequenced US genomes. We expect the HpGP dataset and the corresponding strains to become a major asset for H. pylori genomics

Protein crystals as a template for in situ formation of magnetite nanoparticles

Resumen del trabajo presentado a XXXIX Reunión Bienal de la Real Sociedad Española de Química, celebrada en Zaragoza del 25 al 29 de junio de 2023.Crystallisation in confned spaces is a widespread phenomenon in nature. Many processes like frost heave, biomineralisation (bones and seashells), growth of salt and ice crystals in the pores of masonry happen not in a bulk, but in limited volumes. Reducing the volume of the system infuences not only the probability of nucleation, but also the kinetic. As the results, in reduced volumes become possible stabilisation of metastable polymorphs, formation of crystals with preferred orientations, modifcation of morphology, etc. One of the most fascinating cases of crystallisation in confned spaces – formation of magnetite nanoparticles inside magnetotactic bacteria. The particles have unusual morphologies, homogeneous size and superparamagnetic properties. The control of the magnetite nanoparticles formation could be explained by a combination of physical and chemicals factors in which nucleation and growth of magnetite crystals is performed in confned vesicles (magnetosomes) modulated by the interaction with different proteins.bIn this work, we imitate this type of control over the precipitation of magnetite using channels of cross-linked protein crystals (CLPCs). CLPCs with different pore size and amino acid decoration were used to study their infuence on the magnetite precipitation. We obtained gradient distribution of nanoparticles with a narrow size distribution of around 2nm independently of the channel diameter size of the CLPCs. But the pores size infuenced the stabilisation of the Fe-rich phase. In case of lysozyme (the smallest pore size), the amorphous metastable intermediates of magnetite were stabilised, while in glucose isomerase crystals, the amorphous phase were recrystallised into the crystalline state of magnetite. Our results demonstrate control in the size and stability of those Fe-rich nanoparticles and the potential use of the CLPCs as excellent scaffolds to study the crystallisation in confnement.Peer reviewe

Alginate Hydrogels Reinforced by Dehydration under Stress—Application to a Soft Magnetic Actuator

We investigated the effect of partial dehydration under mechanical stress in the properties of alginate hydrogels. For this aim, we characterized the mechanical properties of the hydrogels under tensile and shear stress, as well as their swelling behavior, macroscopic appearance, and microscopic structure. We found that the processes of dehydration under a mechanical stress were irreversible with fully rehydration being impossible. What is more, these processes gave rise to an enhancement of the mechanical robustness of the hydrogels beyond the effect due to the increase in polymer concentration caused by dehydration. Finally, we analyzed the applicability of these results to alginate-based magnetic hydrogel grippers that bended in response to an applied magnetic field. Remarkably, our study demonstrated that the dehydration of the magnetic hydrogels under compression facilitated their bending response

Effect of functionalized PHEMA micro- and nano-particles on the viscoelastic properties of fibrin-agarose biomaterials.

Two types of PHEMA-based particles, exhibiting either carboxyl or tertiary ammine functional groups, were incorporated to fibrin-agarose (FA) hydrogels, and the effect of the addition of these synthetic particles on the viscoelastic and microstructural properties of the biomaterials was evaluated. Experimental results indicated that the incorporation of both types of polymeric particles to FA scaffolds was able to improve the biomechanical properties of the biomaterials under steady state and oscillatory shear stresses, resulting in scaffolds characterized by higher values of the storage, loss, and shear moduli. In addition, the microstructural evaluation of the scaffolds showed that the nanoparticles exhibiting carboxyl functional groups were homogeneously distributed across the fibrous network of the hydrogels. The addition of both types of artificial polymeric particles was able to enhance the viscoelastic properties of the FA hydrogels, allowing the biomaterials to reach levels of mechanical consistency under shear stresses in the same range of some human native soft tissues, which could allow these biomaterials to be used as scaffolds for new tissue engineering applications. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 738-745, 2018