Structural, magnetic, and luminescent properties of NaGdF4:Nd3+@Fe3O4nanocomposites.

The diverse applications of nanomaterials, and their rapidly increasing demand, have spurred the development of novel multifunctional materials. As such, this study aimed to synthesize and characterize a magneto-luminescent nanocomposite, composed of magnetite and fluorescent quantum dots (NaGdF4:Nd3+@Fe3O4). Nanomaterial synthesis was accomplished through solvothermal and co-precipitation methods. Stable nanoparticles (NPs) with a zeta potential of -19.57 ± 0.42 mV, and a size of 4.55 ± 1.44 nm were obtained. The crystalline structure of the NPs, verified via x-ray diffraction, affirmed the hexagonal pattern of the NaGdF4:Nd3+NPs and the inverse spinel pattern of Fe3O4NPs. In the diffraction pattern of the NaGdF4:Nd3+@Fe3O4NPs, only the phase pertaining to the Fe3O4NPs was identified, indicating their influence on the nanocomposite. Magnetic measurements revealed the superparamagnetic behavior of the material. Photoluminescence spectra of NaGdF4:Nd3+and NaGdF4:Nd3+@Fe3O4NPs verified the luminescent emission around 1060 nm; a feature of the radiative transitions of Nd3+ions. Based on the assessed characteristics, the nanocomposite's multifunctionality was confirmed, positioning the material for potential use in various fields, such as biomedicine.

Twisted graphene superlattices: resonating valence bond states and magnetic properties.

Resonating valence bond (RVB) states are fundamental for understanding quantum spin liquids in two-dimensional (2D) systems. The RVB state is a collective phenomenon in which spins are uncoupled. 2D lattices such as triangular, honeycomb, and dice lattices were investigated using the Hubbard model and exact diagonalization method. We analyzed the total spin, spin-spin correlation functions, local magnetic moments, and spin and charge gaps as a function of on-site Coulomb repulsion, electron concentration, and electronic hopping parameters. Phase diagrams showed that RVB states can live in half-filled and hole-doped anisotropic triangular lattices. We found two types of RVB states: one in the honeycomb sublattice and the other in the centered hexagons in the triangular lattices. Owing to the novel discovery of exotic magnetic ordering in triangular moiré patterns in twisted bilayer graphene and transition metal dichalcogenide systems, our results provide physical insights into the onset of magnetism and possible spin liquid states in these layered materials.

Human radiation for medicine, spiritism and hypnosis in Argentina: scientific controversies around vital radiations (1880-1930).

In the mid-nineteenth century, magnetic theories penetrated other recognized medical practices in Argentina in order to rationalize their procedures, in a culture that accepted and validated magnetism as a positive science. At the start of the twentieth century, mesmerists created a society, published books and journals, and carried out a large welfare programme; there were public lectures, and magnetic treatment for spiritualists and the general public, emphasizing the therapeutic properties of mesmerism. Magnetologists/mesmerists measured vital radiation and built devices using sensitive objects as 'physical' evidence of it. There was an interest in acquiring and using artefacts to measure human radiation useful in medicine. Magnetic practices survived until the end of the 1920s, when they lost importance.

Ground-state phase diagram and universality of sequential topological valence-bond-solid quantum transitions in a mixed tetramer chain.

The ground-state ordering of a quantum mixed-spin Heisenberg tetramer chain composed of an alternate sequence ofs = 1 andS=3/2dimers is studied in detail as a function of two considered exchange interactions ascribed to similar and dissimilar spin pairs. At zero magnetic field, the ferrimagnetic mixed spin-(1, 1, 3/2, 3/2) Heisenberg tetramer chain displays, depending on a mutual interplay between two considered exchange interactions, three distinct gapped valence-bond-solid phases separated by gap-closing quantum critical points. Using density-matrix renormalization group calculations we construct the full ground-state phase diagram as a function of the interaction ratio and magnetic field, which exhibits besides three gapped valence-bond-solid phases special Kosterlitz-Thouless and topological quantum critical points. A tangential finite-size scaling analysis is employed to obtain precise estimates of the zero-field valence-bond-solid transitions and unveil their common logarithmic correction to a power-law scaling of the correlation length.

Synthesis of Iron Oxides and Influence on Final Sizes and Distribution in Bacterial Cellulose Applications.

Iron oxide nanoparticles have been investigated due to their suitable characteristics for diverse applications in the fields of biomedicine, electronics, water or wastewater treatment and sensors. Maghemite, magnetite and hematite are the most widely studied iron oxide particles and have ferrimagnetic characteristics. When very small, however, these particles have superparamagnetic properties and are called superparamagnetic iron oxide nanoparticles (SPIONs). Several methods are used for the production of these particles, such as coprecipitation, thermal decomposition and microemulsion. However, the variables of the different types of synthesis must be assessed to achieve greater control over the particles produced. In some studies, it is possible to compare the influence of variations in the factors for production with each of these methods. Thus, researchers use different adaptations of synthesis based on each objective and type of application. With coprecipitation, it is possible to obtain smaller, more uniform particles with adjustments in temperature, pH and the types of reagents used in the process. With thermal decomposition, greater control is needed over the time, temperature and proportion of surfactants and organic and aqueous phases in order to produce smaller particles and a narrower size distribution. With the microemulsion process, the control of the confinement of the micelles formed during synthesis through the proportions of surfactant and oil makes the final particles smaller and less dispersed. These nanoparticles can be used as additives for the creation of new materials, such as magnetic bacterial cellulose, which has different innovative applications. Composites that have SPIONs, which are produced with greater rigour with regards to their size and distribution, have superparamagnetic properties and can be used in medical applications, whereas materials containing larger particles have ferromagnetic applications. To arrive at a particular particle with specific characteristics, researchers must be attentive to both the mechanism selected and the production variables to ensure greater quality and control of the materials produced.

The Effects of Uniform and Nonuniform Magnetic Fields in Plant Growth: A Meta-Analysis Approach.

Magnetic field (MF) effects have been reported in plants' growth, seed germination, gene expression, and water consumption. Accordingly, magnetic treatments have been proposed as a sustainable alternative to improve yields. Nevertheless, a comprehensive quantitative assessment is needed to understand whether their effects are general, species-specific, or dependent on the experimental setting. We conducted a multilevel meta-analysis of 45 articles that studied 29 different plant species. A positive and neutral effect of a nonuniform MF was found on fresh weight and germination rate, respectively. A significant association was found between a uniform MF and germination. These results suggest that MFs improve plant growth. However, the effects are highly dependent on the experimental setting. This opens exciting questions about the biophysical mechanisms underlying the perception and transduction of this environmental cue and about the possible translation to agricultural practices. © 2023 Bioelectromagnetics Society.

Electronic and magnetic properties of TATA-DNA sequence driven by chemical functionalization.

The TATA box is a promoter sequence able to interact directly with the components of the basal transcription initiation machinery. We investigate the changes in the electronic and magnetic properties of a TATA-DNA sequence when functionalized with different chemical groups; using the first-principles density functional theory specifically, the TATA-DNA sequences were functionalized with methyl groups (CH3 , methylation), amino groups (NH2 , amination), imine groups (NH, imination), chloroamine groups (NCl2 , chloramination), H-adatom (hydrogenation), and Cl-adatom (chlorination). The functional groups were anchored at nitrogen atoms from adenine and oxygen atoms from thymine at sites pointed as reactive regions. We demonstrated that chemical functionalization induces significant changes in charge transfer, hydrogen bond distance, and hydrogen bond energy. The hydrogenation and imination increased the hydrogen bond energy. Results also revealed that the chemical functionalization of DNA molecules exhibit a ferromagnetic ground state, reaching magnetization up to 4.665 µB and complex magnetic ordering. We further demonstrated that the functionalization could induce tautomerism (proton migration in the base pair systems). The present study provides a theoretical basis for understanding the functionalization further into DNA molecules and visualizing possible future applications.

Deciphering Electronic and Structural Effects in Copper Corrole/Graphene Hybrids.

Non-covalent hybrid materials based on graphene and A3 -type copper corrole complexes were computationally investigated. The corroles complexes contain strong electron-withdrawing fluorinated substituents at the meso positions. Our results show that the non-innocent character of corrole moiety modulates the structural, electronic, and magnetic properties once the hybrid systems are held. The graphene-corrole hybrids displayed outstanding stability via the interplay of dispersion and electrostatic driving forces, while graphene act as an electron reservoir. The hybrid structures exposed an intriguing magneto-chemical performance, compared to the isolated counterparts, that evidenced how structural and electronic effects contributed to the magnetic response for both ferromagnetic and antiferromagnetic cases. Directional spin polarization and spin transfer from the corrole to the graphene surface participate in the amplification. Finally, there are relations between the spin transfer, the magnetic response, and the copper distorted ligand field, offering exciting hints about modulating the magnetic response. Therefore, this work shows that copper corroles emerged as versatile building blocks for graphene hybrid materials, especially in applications requiring a magnetic response.

Skyrmion-skyrmion interaction induced by itinerant electrons in a ferromagnetic strip.

Magnetic skyrmions are promising spin textures for building next-generation magnetic memories and spintronic devices. Nevertheless, one of the major challenges in realizing skyrmion-based devices is the stabilization of ordered arrays of these spin textures in different geometries. Here we numerically study the skyrmion-skyrmion interaction potential that arises due to the dynamics of itinerant electrons coupled to the magnetic texture in a ferromagnetic background with racetrack geometry. We consider different topological textures (ferromagnetic (FM) and antiferromagnetic (AFM)), namely: skyrmions, antiskyrmions and biskyrmions. We show that at low electron filling, for sufficiently short separation, the skyrmions strongly couple each other yielding a bound-state bound by electronic dynamics. However, when the filling is increased, the interaction potential energy presents local minima at specific values of the skyrmion-skyrmion distance. Each of these local minima corresponds to energetically stable positions of skyrmions which are 'protected' by well-defined energy barriers. By inspecting the local charge density, we find that in the case of AFM skyrmions, the local antiferromagnetic nature prevents electronic penetration into the core, allowing the AFM skyrmions to be seen as infinite potential barriers for electrons.

Impacto de rehabilitación física y sistema súper inductivo generando magnetismo en fractura postquirúrgica de tobillo: Reporte de caso / Impact of physical rehabilitation and super inductive system by generating magnetism in postsurgical ankle fracture: A case report

Las fracturas pueden producir impotencia funcional, deformidad, hematoma, entumecimiento, dolor y cosquilleo. Muchas requieren cirugía y rehabilitación física por personal calificado y equipos adecuados. El objetivo de este estudio fue aplicar la rehabilitación física y el sistema súper inductivo de alta intensidad como tratamiento en fractura postquirúrgica. La paciente de 46 años, sufre caída de propia altura fracturándose la tibia y peroné derechos, confirmado el diagnóstico, se le realiza la reducción abierta más fijación interna, recibe el alta con férula suropédica que se retira seis semanas después, inicia marcha con apoyo parcial progresivo con incremento de dolor eva 6/10, limitación de la movilidad y edema bimaleolar. La radiografía muestra solución de continuidad del maléolo tibial con material de osteosíntesis. Recibe propuesta terapéutica no invasiva, suspensión de la carga, rehabilitación física por cinco semanas más sistema súper inductivo de alta intensidad tres veces por semana. A la valoración radiográfica de tobillo derecho postero anterior, lateral, y oblicua, presenta reducción correcta del maléolo tibial, la flexión, extensión, inversión y eversión son valorables sin dolor ni edema. Se puede concluir que la rehabilitación y el sistema súper inductivo de alta intensidad con campos electromagnéticos de alta potencia, sí bioestimula la reparación ósea, también acelera el plazo de osteosíntesis con reducción del dolor logrando la recuperación funcional en la paciente.

Fractures can cause functional impotence, deformity, bruising, numbness, pain, and tingling. Many require surgery and physical rehabilitation provided by qualified personnel and adequate equipment. The objetive of this study was to apply physical rehabilitation and high intensity super inductive system as a treatment for postsurgical fracture. A 46-year-old woman suffered a fall from her own height, fracturing the right tibia and fibula, and, an open reduction plus internal fixation was performed, afer confirming the diagnosis. She wadischarged with a south-pedic splint, which was removed 6 weeks later the patient, began to walk with progressive partial support with 6/10 increased eva pain, limitation of mobility and bimalleolar edema. e radiograph shows a solution of continuity of the tibial malleolus with osteosynthesis material. She receives a non-invasive therapeutic proposal, suspension of the load, physical rehabilitation for 5 weeks, and a high intensity super inductive system 3 times a week. Radiographic evaluation of the right ankle anterior, lateral, and oblique shows correct reduction of the tibial malleolus. Flexion, extension, inversion and eversion are assessable without pain or edema. Rehabilitation and high intensity super inductive system with high power electromagnetic fields, biostimulate bone repair and accelerates bone treatment, relieving pain. It can be concluded that the rehabilitation and the high-intensity super-inductive system with high-power electromagnetic fields, biostimulates bone repair, and accelerates the osteosynthesis period with pain reduction, achieving functional recovery of the patient.

A 140-year record of environmental changes in São Sebastião, Brazil.

Over the past two centuries, coastal and estuarine areas have experienced environmental stress due to rapid population growth, leading to higher demand, overexploitation, habitat transformation, and pollution, which have severe consequences on the overall ecosystem and human health. This work aims to understand historical perspectives of such environmental stress in a coastal area of São Sebastião city in the São Paulo State of Brazil, which has witnessed rapid changes in land use over the past 60-70 years. We collected eleven surface sediments and one 64 cm long core from the shallow water depth sector of the São Sebastião Channel (SSC), adjacent to the Araçá Bay region. Sediments were dominantly composed of terrestrial siliciclastic material carrying signatures of both local inputs (i.e., weathered granitic and gneissic rocks of Serra do Mar Mountain ranges) and Plata Plume sediments brought by Brazilian coastal currents. Low sediment accumulation (avg. = 0.10 cm yr-1) between 1880 and 1947 showed a stable environment followed by an abrupt increase in sedimentation (avg. = 0.84 cm yr-1) from 1947 to 2017. This approximate eight-fold increase in sedimentation after 1947 marked significant anthropogenic changes in the region, which is coincidental with major changes in land use through the construction of the port of São Sebastião (1930s) and BR-101 Highway (1980s). While recent surface sediments showed no pollution of heavy metals, anthropogenic Zn enrichment was found between 1880 and 2000. Zn enrichment was from the combined sources, e.g., agriculture activities, domestic sewage, and possibly Zn coated ship paints. Our study also indicates that planned future expansion of São Sebastião port may further increase the sedimentation rate in SSC and impact the ecosystem of Araçá Bay and SSC.

Machine Learning Study of the Magnetic Ordering in 2D Materials.

Magnetic materials have been applied in a large variety of technologies, from data storage to quantum devices. The development of two-dimensional (2D) materials has opened new arenas for magnetic compounds, even when classical theories discourage their examination. Here we propose a machine-learning-based strategy to predict and understand magnetic ordering in 2D materials. This strategy couples the prediction of the existence of magnetism in 2D materials using a random forest and the Shapley additive explanations method with material maps defined by atomic features predicting the magnetic ordering (ferromagnetic or antiferromagnetic). While the random forest model predicts magnetism with an accuracy of 86%, the material maps obtained by the sure independence screening and sparsifying method have an accuracy of ∼90% in predicting the magnetic ordering. Our model indicates that 3d transition metals, halides, and structural clusters with regular transition-metal sublattices have a positive contribution in the total weight deciding the existence of magnetism in 2D compounds. This behavior is associated with the competition between crystal field and exchange splitting. The machine learning model also indicates that the atomic spin orbit coupling (SOC) is a determinant feature for the identification of the patterns separating ferro- from antiferromagnetic order. The proposed strategy is used to identify novel 2D magnetic compounds that, together with the fundamental trends in the chemical and structural space, pave novel routes for experimental exploration.

Effect of structural variation on enzymatic activity in tetranuclear (Cu4) clusters with defective cubane core.

The stimulus to the modeling of enzyme functioning sites comes from their potential to give insight into the natural enzyme's mechanistic pathways, ascertain the role of that different metal ion in the active site and construct better catalysts motivated by nature. The presence of metal ion leads to the activation of molecular oxygen in the metalloenzymes. The metalloenzymes such as the catechol oxidase (CO) enzyme that oxidizes the catechol to corresponding quinones which eventually protect damage tissues from plant and pathogen. Thus, the design and characterization of catalysts used as selectively and efficiently oxidation reactions have grown to be unique challenges for modern inorganic chemists. In this work, two novel tetranuclear complexes (1 and 2) have been synthesized in excellent yield. The complexes were characterized using various spectroscopic techniques such as FTIR, UV-Visible and PXRD pattern. The structure of 1 and 2 was elucidated by SC-XRD (single crystal X-ray diffraction) analysis. The magnetic study reveals the presence of the antiferromagnetic nature of 1 and 2. Both 1 and 2 shows a very good catecholase-like activity by oxidizing the catechol to analogous quinone in methanolic solution. Thus, a structure-activity relationship can further help us design other substituted tetranuclear complexes with enhanced catecholase like activity.Communicated by Ramaswamy H. Sarma.

Crystal structure and magnetic study of the complex salt [RuCp(PTA)2-µ-CN-1κC:2κN-RuCp(PTA)2][Re(NO)Br4(EtOH)0.5(MeOH)0.5].

A new RuII-ReII complex salt, µ-cyanido-κ2 C:N-bis-[(η5-cyclo-penta-dien-yl)bis(3,5,7-tri-aza-phosphaadamantane-κP)ruthenium(II)] tetra-bromido-(ethanol/methanol-κO)nitrosylrhenate(II), [Ru(CN)(C5H5)2(C6H12N3P)4][ReBr4(NO)(CH4O)0.5(C2H6O)0.5] or [RuCp(PTA)2-µ-CN-1κC:2κ2 N-RuCp(PTA)2][Re(NO)Br4(EtOH)0.5(MeOH)0.5] (PTA = 3,5,7-tri-aza-phosphaadaman-tane) was obtained and characterized by single-crystal X-ray diffraction, elemental analysis and infrared spectroscopy. The title salt was obtained by liquid-liquid diffusion of methanol/DMSO solutions of (NBu4)[Re(NO)Br4(EtOH)] and [(PTA)2CpRu-µ-CN-1κC:2κ2 N-RuCp(PTA)2](CF3SO3). The RuII and ReII independent moieties correspond to a binuclear and mononuclear complex ion, respectively. A deep geometrical parameter analysis was performed, and no significant differences were found with earlier reports containing similar mol-ecules. The magnetic properties were investigated in the temperature range 2.0-300 K, and the complex behaves as a quasi-magnetically isolated spin doublet with weak anti-ferromagnetic inter-actions.

Nanomagnetic approach applied to microalgae biomass harvesting: advances, gaps, and perspectives.

Microalgae biomass is a versatile option for a myriad of purposes, as it does not require farmable land for cultivation and due of its high CO2 fixation efficiency during growth. However, biomass harvesting is considered a bottleneck in the process because of its high cost. Magnetic harvesting is a promising method on account of its low cost, high harvesting speed, and efficiency, which can be used to improve the results of other harvesting methods. Here, we present the state of the art of the magnetic harvesting method. Detailed approaches involving different nanomaterials are described, including types, route of synthesis, and functionalization, variables that interfere with harvesting, and recycling methods of nanoparticles and medium. In addition to discussing the overall perspectives of the method, we provide a guideline for future research.

Directional locking and the influence of obstacle density on skyrmion dynamics in triangular and honeycomb arrays.

We numerically examine the dynamics of a single skyrmion driven over triangular and honeycomb obstacle arrays at zero temperature. The skyrmion Hall angleθsk, defined as the angle between the applied external drive and the direction of the skyrmion motion, increases in quantized steps or continuously as a function of the applied drive. For the obstacle arrays studied in this work, the skyrmion exhibits two main directional locking angles ofθsk= -30° and -60°. We show that these directions are privileged due to the obstacle landscape symmetry, and coincide with channels along which the skyrmion may move with few or no obstacle collisions. Here we investigate how changes in the obstacle density can modify the skyrmion Hall angles and cause some dynamic phases to appear or grow while other phases vanish. This interesting behavior can be used to guide skyrmions along designated trajectories via regions with different obstacle densities. For fixed obstacle densities, we investigate the evolution of the lockedθsk= -30° and -60° phases as a function of the Magnus force, and discuss possibilities for switching between these phases using topological selection.

Role of Surfaces in the Magnetic and Ozone Gas-Sensing Properties of ZnFe2O4 Nanoparticles: Theoretical and Experimental Insights.

The magnetic properties and ozone (O3) gas-sensing activity of zinc ferrite (ZnFe2O4) nanoparticles (NPs) were discussed by the combination of the results acquired by experimental procedures and density functional theory simulations. The ZnFe2O4 NPs were synthesized via the microwave-assisted hydrothermal method by varying the reaction time in order to obtain ZnFe2O4 NPs with different exposed surfaces and evaluate the influence on its properties. Regardless of the reaction time employed in the synthesis, the zero-field-cooled and field-cooled magnetization measurements showed superparamagnetic ZnFe2O4 NPs with an average blocking temperature of 12 K. The (100), (110), (111), and (311) surfaces were computationally modeled, displaying the different undercoordinated surfaces. The good sensing activity of ZnFe2O4 NPs was discussed in relation to the presence of the (110) surface, which exhibited low (-0.69 eV) adsorption enthalpy, promoting reversibility and preventing the saturation of the sensor surface. Finally, the O3 gas-sensing mechanism could be explained based on the conduction changes of the ZnFe2O4 surface and the increase in the height of the electron-depletion layer upon exposure toward the target gas. The results obtained allowed us to propose a mechanism for understanding the relationship between the morphological changes and the magnetic and O3 gas-sensing properties of ZnFe2O4 NPs.

A versatile X-ray phase retarder for lock-in XMCD measurements.

X-ray magnetic circular dichroism (XMCD) is a technique commonly used to probe magnetic properties of materials with element and orbital selectivity, which requires the use of circularly polarized (CP) X-rays. It is possible to accomplish XMCD experiments with fixed CP and alternating the magnetic field orientation, but most reliable data are obtained when alternating the magnetization orientation and the polarization between right and left helicities. A versatile strategy has been developed to perform XMCD experiments using a hard X-ray quarter-wave plate, at both polychromatic dispersive and conventional monochromatic optics, in combination with synchronous data acquisition. The switching frequency waveform is fed into a lock-in amplifier to detect and amplify the XMCD signal. The results on a reference sample demonstrate an improvement in data quality and acquisition time. The instrumentation successfully generated 98% of CP X-rays switching the beam helicity at 13 Hz, with the possibility of faster helicity switching once it is installed at the new Brazilian fourth-generation source, SIRIUS.

Pluralismo e dissensão: o magnetismo animal em debate no Portugal de meados de Oitocentos / Pluralism and dissent: animal magnetism in debate in Portugal in the mid-nineteenth century

Resumo Em meados do século XIX, em Portugal, discutiu-se, com relativa intensidade, medicina e sistemas médicos alternativos e complementares, quer na imprensa periódica especializada, quer em alguns jornais de cunho generalista. Desses sistemas médicos, que emergiram com vigor no Portugal do Romantismo, um parece ter gerado especial debate: o magnetismo animal. O presente artigo, em perspectiva comparada, visa resgatar o alcance histórico desse sistema clínico, analisando a curiosidade popular e especializada em torno dessa terapia. Finalmente, contextualizar-se-ão as querelas literárias e institucionais que o magnetismo animal desencadeou no período.

Abstract In mid-nineteenth century Portugal, alternative and complementary medical systems and medicine were discussed with relative intensity in the specialized press and in some mainstream newspapers. One of these medical systems, which gained ground during Portugal's romantic era, seems to have sparked particular debate: animal magnetism. A comparative approach is taken to review the historical scope of this healing system, analyzing popular and specialized curiosity regarding this therapy. Finally, the literary and institutional disagreements that animal magnetism unleashed during the period are contextualized.

Biotransformation of cladribine by a magnetic immobilizated biocatalyst of Lactobacillus animalis.

A stable biocatalyst with magnetic properties based on immobilized Lactobacillus animalis ATCC 35,046 to obtain 2-chloroadenine-2'-deoxyriboside, known as cladribine, is reported for the first time. This nucleoside analogue is an antitumor agent used in the treatment of a wide variety of types of leukemia. In this study, an eco-compatible and alternative bioprocess to obtain cladribine was developed. Product conversion was close to 90% at 2 h in optimized nonconventional reaction media. The microscale biosynthesis of the compound of interest afforded a total productivity close to 370 mg/L/h in the presence of DMSO, and it was stable at least for 30 days in storage conditions.