Microstructural modelling of hard-magnetic soft materials: Dipole-dipole interactions versus Zeeman effect

Hard-magnetic soft materials are a class of magneto-active polymers (MAPs) where the fillers are composed of hard-magnetic (magnetised) particles. These materials present complex magneto-mechanical couplings, which require the development of modelling frameworks in understanding their responses at the very beginning of conceptualisation and design. Most of the current constitutive approaches available in the literature for hard-magnetic MAPs do not consider dipole–dipole interactions of the embedded particles. However, such interactions among the magnetised particles generate internal forces within the composite that need to be balanced by mechanical stress from the polymeric matrix networks. This fact may imply an initial stretch of the polymeric network and suggests that such dipole–dipole interactions may be important during the MAP deformation process. To address these crucial points, in this contribution, we propose a novel constitutive model relating microstructural characteristics of hard-magnetic MAPs. The model accounts for polymeric network pre-stretch, dipole–dipole interactions, Zeeman effect as well as viscous mechanisms which are formulated on the finite deformation theory. The results obtained herein highlight the importance of accounting for the dipole–dipole interactions and the polymeric network pre-stretch to understand the complex magneto-mechanically coupled behaviour of hard-magnetic MAPs.The authors acknowledge support from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (grant agreement No. 947723, project 4D-BIOMAP). D.G.G. acknowledges support from the Talent Attraction, Spain grant (CM 2018-2018-T2/IND-9992) from the Comunidad de Madrid, Spain. M. H. acknowledges the funding through an EPSRC, United Kingdom Impact Acceleration Award (EP/R511614/1)

A microstructural-based approach to model magneto-viscoelastic materials at finite strains

Magneto-active polymers (MAPs) consist of a polymeric matrix filled with magnetisable particles. MAPsmay change their mechanical properties (i.e., stiffness) and/or mechanical deformation upon the applica-tion of an external magnetic stimulus. Mechanical responses of MAPs can be understood as the combinedcontributions of both polymeric matrix and magnetic particles. Moreover, the magnetic response isdefined by the interaction between magnetisable particles and the external field. Common approachesto model MAPs are based on phenomenological continuum models, which are able to predict theirmagneto-mechanical behaviour but sometimes failed to illustrate specific features of the underlying phy-sics. To better understand the magneto-mechanical responses of MAPs and guide their design and man-ufacturing processes, this contribution presents a novel continuum constitutive model originated from amicrostructural basis. The model is formulated within a finite deformation framework and accounts forviscous (rate) dependences and magneto-mechanical coupling. After the formulations, the model is cal-ibrated with a set of experimental data. The model is validated with a wide range of experimental datathat show its predictability. Such a microstructurally-motivated finite strain model will help in designingMAPs with complex three-dimensional microstructures.The authors acknowledge the financial support of the mobility internship for researchers of Carlos III University of Madrid (Spain) (“Programa propio de investigacion - Convocatoria 2020 movilidada”) that facilitates a research visit of the first author to Zienkiewicz Centre for Computational Engineering (ZCCE) at Swansea University, UK. DGG acknowledges support from Programa de Apoyo a la Realizacion de Proyectos Interdiscisplinares de I+D para Jovenes Investigadores de la Universidad Carlos III de Madrid and Comunidad de Madrid (project: BIOMASKIN), support from the Talent Attraction grant (CM 2018-2018-T2/IND-9992) from the Comunidad de Madrid, and support from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement No. 947723). MH acknowledges the funding through an EPSRC Impact Acceleration Award (2020-2021)

Lung Rest During Extracorporeal Membrane Oxygenation for Neonatal Respiratory Failure-Practice Variations and Outcomes.

OBJECTIVE: Describe practice variations in ventilator strategies used for lung rest during extracorporeal membrane oxygenation for respiratory failure in neonates, and assess the potential impact of various lung rest strategies on the duration of extracorporeal membrane oxygenation and the duration of mechanical ventilation after decannulation. DATA SOURCES: Retrospective cohort analysis from the Extracorporeal Life Support Organization registry database during the years 2008-2013. STUDY SELECTION: All extracorporeal membrane oxygenation runs for infants less than or equal to 30 days of life for pulmonary reasons were included. DATA EXTRACTION: Ventilator type and ventilator settings used for lung rest at 24 hours after extracorporeal membrane oxygenation initiation were obtained. DATA SYNTHESIS: A total of 3,040 cases met inclusion criteria. Conventional mechanical ventilation was used for lung rest in 88% of cases and high frequency ventilation was used in 12%. In the conventional mechanical ventilation group, 32% used positive end-expiratory pressure strategy of 4-6 cm H2O (low), 22% used 7-9 cm H2O (mid), and 43% used 10-12 cm H2O (high). High frequency ventilation was associated with an increased mean (SEM) hours of extracorporeal membrane oxygenation (150.2 [0.05] vs 125 [0.02]; p \u3c 0.001) and an increased mean (SEM) hours of mechanical ventilation after decannulation (135 [0.09] vs 100.2 [0.03]; p = 0.002), compared with conventional mechanical ventilation among survivors. Within the conventional mechanical ventilation group, use of higher positive end-expiratory pressure was associated with a decreased mean (SEM) hours of extracorporeal membrane oxygenation (high vs low: 136 [1.06] vs 156 [1.06], p = 0.001; mid vs low: 141 [1.06] vs 156 [1.06]; p = 0.04) but increased duration of mechanical ventilation after decannulation in the high positive end-expiratory pressure group compared with low positive end-expiratory pressure (p = 0.04) among survivors. CONCLUSIONS: Wide practice variation exists with regard to ventilator settings used for lung rest during neonatal respiratory extracorporeal membrane oxygenation. Use of high frequency ventilation when compared with conventional mechanical ventilation and use of low positive end-expiratory pressure strategy when compared with mid positive end-expiratory pressure and high positive end-expiratory pressure strategy is associated with longer duration of extracorporeal membrane oxygenation. Further research to provide evidence to drive optimization of pulmonary management during neonatal respiratory extracorporeal membrane oxygenation is warranted

Chapter 2.2: 3-D Topo Surface Visualization of Metal Ion Anti-Buffering: An Unexpected Behavior in Metal–Ligand Complexation Systems

Diluting a system that contains metal complexes can sometimes cause surprises. This chapter describes “metal ion anti-buffering”, a situation in which free metal ion concentrations rapidly increase as system dilution drives dissociation. It only occurs under excess free ligand conditions when a solution is dominated by higher stoichiometry complexes. The Law of Mass Action is used to provide a mathematical justification for the phenomenon. A Cu2+-ethylenediamine mixture exhibits this phenomenon when excess free ethylenediamine (en) is present. For example, it occurs when diluting a solution containing a four-fold excess of en over Cu2+. As this mixture is diluted by a factor of ~5600, the modeled free Cu2+ concentration shows a ~470-fold increase. Taken together, this is 2.5 million times higher than dilution of the system would yield in other circumstances. Included are experimental data confirming anti-buffering in the Cu2+-en system. Many other metal-ligand systems can display this behavior. Four additional examples are illustrated including an amino acid under physiological pHs. Anti-Buffering TOPOS, a downloadable Excel workbook in a supplemental file, allows readers to simulate this behavior for many metal-ligand systems. A PowerPoint lecture and teaching materials are also provided, suitable for inclusion in upper division and graduate courses in analytical chemistry, biochemistry and geochemistry.https://scholarworks.umt.edu/topos/1005/thumbnail.jp

Reactivity of [Re\u3csub\u3e2\u3c/sub\u3e(CO)\u3csub\u3e8\u3c/sub\u3e(MeCN)\u3csub\u3e2\u3c/sub\u3e] with Thiazoles: Hydrido Bridged Dirhenium Compounds Bearing Thiazoles in Different Coordination Modes

Reactions of the labile compound [Re2(CO)8(MeCN)2] with thiazole and 4-methylthiazole in refluxing benzene afforded the new compounds [Re2(CO)7{μ-2,3-η2-C3H(R)NS}{η1-NC3H2(4-R)S}(μ-H)] (1, R = H; 2, R = CH3), [Re2(CO)6{μ-2,3-η2-C3H(R)NS}{η1-NC3H2(4-R)S}2(μ-H)] (3, R = H; 4, R = CH3) and fac-[Re(CO)3(Cl){η1-NC3H2(4-R)S}2] (5, R = H; 6, R = CH3). Compounds 1 and 2 contain two rhenium atoms, one bridging thiazolide ligand, coordinated through the C(2) and N atoms and a η1-thiazole ligand coordinated through the nitrogen atom to the same Re as the thiazolide nitrogen. Compounds 3 and 4 contain a Re2(CO)6 group with one bridging thiazolide ligand coordinated through the C(2) and N atoms and two N-coordinated η1-thiazole ligands, each coordinated to one Re atom. A hydride ligand, formed by oxidative-addition of C(2)–H bond of the ligand, bridges Re–Re bond opposite the thiazolide ligand in compounds 1–4. Compound 5 contains a single rhenium atom with three carbonyl ligands, two N-coordinated η1-thiazole ligands and a terminal Cl ligand. Treatment of both 1 and 2 with 5 equiv. of thiazole and 4-methylthiazole in the presence of Me3NO in refluxing benzene afforded 3 and 4, respectively. Further activation of the coordinated η1-thiazole ligands in 1–4 is, however, unsuccessful and results only nonspecific decomposition. The single-crystal XRD structures of 1–5 are reported

Modeling and Analysis of Unmanned Aerial Vehicle System Leveraging Systems Modeling Language (SysML)

The use of unmanned aerial vehicles (UAVs) has seen a significant increase over time in several industries such as defense, healthcare, and agriculture to name a few. Their affordability has made it possible for industries to venture and invest in UAVs for both research and commercial purposes. In spite of their recent popularity; there remain a number of difficulties in the design representation of UAVs, including low image analysis, high cost, and time consumption. In addition, it is challenging to represent systems of systems that require multiple UAVs to work in cooperation, sharing resources, and complementing other assets on the ground or in the air. As a means of compensating for these difficulties; in this study; we use a model-based systems engineering (MBSE) approach, in which standardized diagrams are used to model and design different systems and subsystems of UAVs. SysML is widely used to support the design and analysis of many different kinds of systems and ensures consistency between the design of the system and its documentation through the use of an object-oriented model. In addition, SysML supports the modeling of both hardware and software, which will ease the representation of both the system’s architecture and flow of information. The following paper will follow the Magic Grid methodology to model a UAV system across the SysML four pillars and integration of SysML model with external script-based simulation tools, namely, MATLAB and OpenMDAO. These pillars are expressed within standard diagram views to describe the structural, behavior, requirements, and parametric aspect of the UAV. Finally, the paper will demonstrate how to utilize the simulation capability of the SysML model to verify a functional requirement

Additions to the Fruit Fly Fauna (Diptera: Tephritidae: Dacinae) of Bangladesh, with a Key to the Species

Five species of Bactrocera are reported to occur in Bangladesh for the first time. The species previously recorded as B. nigrofemoralis is actually B. nigrifacia. An illustrated key to the nineteen species known to occur in the country, plus B. nigrofemoralis, is provided

A Preliminary Survey of the Fruit Flies (Diptera: Tephritidae: Dacinae) of Bangladesh

Thirteen species of Bactrocera and one species of Dacus were collected during field surveys in Bangladesh, including eight new country records, for a total of fifteen species confirmed to occur in the country. Color variation in Bangladesh B. dorsalis is similar to that observed in B. invadens in Africa and Sri Lanka

Tetranuclear Group 7/8 Mixed-Metal and Open Trinuclear Group 7 Metal Carbonyl Clusters Bearing Bridging 2-mercapto-1-methylimidazole Ligands

The reactivity of group 7 metal dinuclear carbonyl complexes [M2(CO)6(μ-SN2C4H5)2] (1, M = Re; 2, M = Mn) toward group 8 metal trinuclear carbonyl clusters were examined. Reactions of 1 and 2 with [Os3(CO)10(NCMe)2] in refluxing benzene furnished the tetranuclear mixed-metal clusters [Os3Re(CO)13(μ3-SN2C4H5)] (3) and [Os3Mn(CO)13(μ3-SN2C4H5)] (4), respectively. Similar treatment of 1 and 2 with Ru3(CO)12 yielded the ruthenium analogs [Ru3Re(CO)13(μ3-SN2C4H5)] (5), and [Ru3Mn(CO)13(μ3-SN2C4H5)] (6), but in the case of 2 a secondary product [Mn3(CO)10(μ-Cl)(μ3-SN2C4H5)2] (7) was also formed. Compounds 3–6 have a butterfly core of four metal atoms with the M (Mn or Re) at a wingtip of the butterfly and containing a noncrystallographic mirror plane of symmetry. This result provides a potential method for the synthesis of a series of new group 7/8 mixed metal complexes containing a bifunctional heterocyclic ligand. Compound 7 is a unique example of a 54-electron trimanganese complex having bridging 2-mercapto-1-methylimidazolate and chloride ligands. Interestingly, the reaction of 1 with Fe3(CO)12 at 70–75 °C furnished the tri- and dirhenium complexes [Re3(CO)10(μ-H)(μ3-SN2C4H5)2] (8) and [Re2(CO)6(N2C4H5)(μ-SN2C4H5)2] (9), respectively instead of the expected formation of the mixed-metal clusters. The former is an interesting example of a 52-electron trirhenium-hydridic complex containing bridging 2-mercapto-1-methylimidazolate ligand, while the latter can be viewed as a 1-methylimidazole adduct of 1. No mixed Fe–Re complexes were produced in this reaction. The molecular structures of the new compounds 3–5 and 7–9 were established by single-crystal X-ray diffraction analyses and the DFT studies of compounds 5, 7 and 8 are reported

Role of GSH and Iron-Sulfur Glutaredoxins in Iron Metabolism—Review

Glutathione (GSH) was initially identified and characterized for its redox properties and later for its contributions to detoxification reactions. Over the past decade, however, the essential contributions of glutathione to cellular iron metabolism have come more and more into focus. GSH is indispensable in mitochondrial iron-sulfur (FeS) cluster biosynthesis, primarily by co-ligating FeS clusters as a cofactor of the CGFS-type (class II) glutaredoxins (Grxs). GSH is required for the export of the yet to be defined FeS precursor from the mitochondria to the cytosol. In the cytosol, it is an essential cofactor, again of the multi-domain CGFS-type Grxs, master players in cellular iron and FeS trafficking. In this review, we summarize the recent advances and progress in this field. The most urgent open questions are discussed, such as the role of GSH in the export of FeS precursors from mitochondria, the physiological roles of the CGFS-type Grx interactions with BolA-like proteins and the cluster transfer between Grxs and recipient proteins