Releasing antiferromagnetic skyrmions from local magnetic-anisotropy defects.

Lattice defects may work as a kind of apparatus for catching topological excitations, preventing their escape. So, the problem of removing skyrmions from eventual local defects in magnetic materials must be closely related to new technologies such as skyrmionic. Here, we examine the conditions for drawing a skyrmion from a magnetic impurity in a two-dimensional antiferromagnetic system by applying spin-polarized currents (SPC). Two types of impurities are investigated (local easy-axis and easy-plane anisotropy defects). Also, two methods to release the skyrmion with SPC are explored. In principle, our results could be qualitatively relevant to any other type of lattice defect.

Flat scalp melanoma dermoscopic and reflectance confocal microscopy features correspond to histopathologic type and lesion location.

BACKGROUND: Dermoscopy and Reflectance Confocal Microscopy (RCM) features of scalp melanoma according to lesion location and histopathology have not been fully investigated. OBJECTIVES: To reveal dermoscopic and RCM features of scalp melanoma according to lesion location and histopathology. METHODS: We retrospectively retrieved images of suspicious, atypical excised, flat melanocytic lesions of the scalp, assessed on dermoscopy and RCM at five centres, from June 2007 to April 2020. Lesions were classified according to histopathological diagnoses of nevi, lentigo maligna melanoma (LM/LMM) or superficial spreading melanoma (SSM). Clinical, dermoscopic and RCM images were evaluated; LM/LMM and SSM subtypes were compared through multivariate analysis. RESULTS: Two hundred forty-seven lesions were included. In situ melanomas were mostly LM (81.3%), while invasive melanomas were mostly SSM (75.8%). Male sex, baldness and chronic sun-damaged skin were associated with all types of melanomas and in particular with LM/LMM. LMs were mostly located in the vertex area and SSM in the frontal (OR: 8.8; P < 0.05, CI 95%) and temporal (OR: 16.7; P < 0.005, CI 95%) areas. The dermoscopy presence of pseudo-network, pigmented rhomboidal structures, obliterated hair follicles and annular-granular pattern were associated with LM diagnoses, whereas bluish-white veil was more typical of SSM. Observations on RCM of atypical roundish and dendritic cells in the epidermis were associated with SSM (42.4%) and dendritic cells with LM (62.5%) diagnoses. Folliculotropism on RCM was confirmed as a typical sign of LM. CONCLUSIONS: Flat scalp melanomas reveal specific dermoscopic and RCM features according to histopathologic type and scalp location.

Scattering modes of skyrmions in a bilayer system with ferromagnetic coupling.

Magnetic skyrmions are quasiparticle-like textures that are topologically different from a single domain magnetization state. Their topological protection, combined with the low current density needed to move them, make these objects relevant to be used as information storage structures. In such a context, the analysis of the interactions between skyrmions is interesting and relevant for future applications. In this work, through micromagnetic simulations and numerical calculations, we studied the interaction between two skyrmions living on different parallel ferromagnetic racetracks connected by an exchange-like interaction. The upper and lower racetracks are separated by a height offset and the interaction between the upper and the lower skyrmion is analyzed in terms of the magnetic and geometrical parameters. Three states are predicted, as a function of these parameters: scattered or free skyrmions, bound skymions, and annihilated skyrmions. Our results, presented in a phase diagram, demonstrate that even in the case here called free skyrmions, there is a small and brief interaction when both are close enough, but the skyrmion in the top layer does not drag the skyrmion in the bottom layer. For bound skyrmions, both keep linked during larger times. In the latter case, there are strong changes in the velocity of the skyrmions induced by the effect of a higher effective mass when both are coupled.

Magnus-force induced skyrmion-antiskyrmion coupling in inhomogeneous racetrack.

In this paper we investigate a magnetic racetrack consisting of a junction of three materials with different properties. Indeed, this magnetic system is composed by two distinct regions (racetracks) connected by a thin interface: the first region (termed sector 1) has isotropic in-plane magnetic chirality and supports skyrmion (S) excitations while the second (sector 3) has anisotropic chirality and consequently supports antiskyrmions (A). The interface, which would be a third region (sector 2, connecting sectors 1 and 3) located in the central part of the racetrack, is an easy-axis Heisenberg ferromagnetic material. The topological structures S and A are put in motion by applying a spin-polarized current. Under certain conditions, we show that the skyrmion and the antiskyrmion created in their respective sectors are simultaneously impelled to the interface (due to the Magnus force) to apparently become a unique object (a skyrmion-antiskyrmion pair or SAP). After glued by sector 2, the skyrmion and the antiskyrmion move together (as a SAP) along the direction of the applied current. It is also shown that such an engineered racetrack can support a sequence of several SAP structures in motion, forming a current.

Effects of magnetic monopoles charge on the cracking reversal processes in artificial square ices.

In this paper we perform nanofabrication of square artificial spin ices with different lattice parameters, in order to investigate the roles of vertex excitation on the features of the system. In particular, the character of magnetic charge distribution asymmetry on the vertices are observed under magnetic hysteresis loop experiments. We then compare our results with simulation using an emergent Hamiltonian containing objects such as magnetic monopoles and dipoles in the vertices of the array (instead of the usual Hamiltonian based on the dipolar interactions among the magnetic nanoislands). All possible interactions between these objects are considered (monopole-monopole, monopole-dipole and dipole-dipole). Using realistic parameters we observe very good match between experiments and theory, which allow us to better understand the system dynamics in function of monopole charge intensity.

A simpler potentiometric method for histamine assessment in blood sera.

Histamine intolerance results from a disequilibrium of accumulated histamine and the capacity for histamine degradation. An impaired histamine degradation based on reduced DAO activity and the resulting histamine excess may cause numerous symptoms mimicking an allergic reaction. For that, the determination of histamine in blood or in food products has great importance to identify risk factors. A new histamine-selective electrode is proposed using cucurbit[6]uril (CB[6]), as ionophore, in the analysis of biological samples. The selection of this smart supramolecular organic framework was based on its apparent stability constant of histamine-CB[6] (log ß) of 4.33. The optimized electrode based on a polymeric membrane (PVC) combines the histamine-selective ionophore with 2-nitrophenyl octyl ether as solvent mediator and potassium tetrakis(4-chlorophenyl)borate as anionic additive. Furthermore, multi-walled carbon nanotubes particles were included in the membrane composition to partly lower the detection limit of the method, while improving stability and lowering the response drift (± 4 mV). The electrodes showed a rapid response (≃ 13 s) in the pH operational range of 2.7-5.4, with a Nernstian slope of 30.9 ± 1.2 mV/dec, a detection limit of (3.00 ± 0.61) × 10-7 mol/L, and a lower limit of the linear range of (3.00 ± 0.00) × 10-7 mol/L. After miniaturization, the electrode was used as a detector in a sequential-injection lab-on-valve flow setup. The optimized flow conditions were achieved for sample injection volumes of 197 µL propelled towards the cell under detection, at a flow rate of 30 µL/s during 100 s, making the analysis of 30 samples per hour possible. The developed system was used to analyze spiked blood serum samples previously cleaned by using solid-phase extraction. The sample pretreatment of the serum samples using Oasis MCX cartridges showed outstanding efficiency for histamine determination. The recovery values for three different levels of histamine concentration (1 × 10-4 mol/L, 1 × 10-5 mol/L, and 1 × 10-6 mol/L) were (97 ± 6)%, (103 ± 1)%, and (118 ± 9)%, respectively, showing that this method was suitable for biological samples.

Antiferromagnetic skyrmions overcoming obstacles in a racetrack.

Topological objects interacting with lattice defects is an important topic in condensed matter physics. In this paper, we would like to explore the ballistic trajectory of an antiferromagnetic skyrmion in a racetrack to study processes such as collisions of skyrmions and holes in the magnetic sample. The skyrmion is impelled against the hole-obstacle by means of a spin polarized current. Depending on the skyrmion velocity (associated to the strength of the applied current) and the type of collision (frontal or lateral), it will be captured, scattered or completely destroyed by the hole. In some cases, this obstacle can shift the skyrmion center from a straight line to another one, and it appears as an effective way of manipulating skyrmion trajectories and dynamics.

Approaches to mimic the complexity of the skeletal mesenchymal stem/stromal cell niche in vitro.

Mesenchymal stem/stromal cells (MSCs) are an essential element of most modern tissue engineering and regenerative medicine approaches due to their multipotency and immunoregulatory functions. Despite the prospective value of MSCs for the clinics, the stem cells community is questioning their developmental origin, in vivo localization, identification, and regenerative potential after several years of far-reaching research in the field. Although several major progresses have been made in mimicking the complexity of the MSC niche in vitro, there is need for comprehensive studies of fundamental mechanisms triggered by microenvironmental cues before moving to regenerative medicine cell therapy applications. The present comprehensive review extensively discusses the microenvironmental cues that influence MSC phenotype and function in health and disease - including cellular, chemical and physical interactions. The most recent and relevant illustrative examples of novel bioengineering approaches to mimic biological, chemical, and mechanical microenvironmental signals present in the native MSC niche are summarized, with special emphasis on the forefront techniques to achieve bio-chemical complexity and dynamic cultures. In particular, the skeletal MSC niche and applications focusing on the bone regenerative potential of MSC are addressed. The aim of the review was to recognize the limitations of the current MSC niche in vitro models and to identify potential opportunities to fill the bridge between fundamental science and clinical application of MSCs.

Experimental and theoretical evidences for the ice regime in planar artificial spin ices.

In this work, we explore a kind of geometrical effect in the thermodynamics of artificial spin ices (ASI). In general, such artificial materials are athermal. Here, We demonstrate that geometrically driven dynamics in ASI can open up the panorama of exploring distinct ground states and thermally magnetic monopole excitations. It is shown that a particular ASI lattice will provide a richer thermodynamics with nanomagnet spins experiencing less restriction to flip precisely in a kind of rhombic lattice. This can be observed by analysis of only three types of rectangular artificial spin ices (RASI). Denoting the horizontal and vertical lattice spacings by [Formula: see text] and [Formula: see text], respectively, then, a RASI material can be described by its aspect ratio [Formula: see text]. The rhombic lattice emerges when [Formula: see text]. So, by comparing the impact of thermal effects on the spin flips in these three appropriate different RASI arrays, it is possible to find a system very close to the ice regime.

Inpatient Dermatology Consultations in Renal Transplant Recipients. / Interconsulta hospitalaria en dermatología en una unidad de transplante renal.

BACKGROUND: Renal transplant recipients (RTR), which are an increasing population, frequently suffer from post-transplant dermatological complications. Despite the well-established role of dermatologists in the outpatient care of these patients, no previous studies were found concerning dermatology consultations for hospitalized RTR. OBJECTIVES: To investigate the epidemiology of dermatological conditions presented by RTR during hospitalization and assess the impact of dermatology consultations performed in the hospital setting. METHODS: Dermatology consultations requested for RTR admitted at a kidney transplantation referral hospital in Brazil over 36 consecutive months were retrospectively included. RESULTS: 176 consultations were included. Infectious dermatoses prevailed (52.3%), followed by inflammatory diseases (14.2%), neoplasms (12.5%) and drug reactions (8.5%). Diagnostic agreement between requesting and consulting teams was 38.1%. Most consultations were motivated by common dermatological conditions, unrelated to admission diagnosis. There were some differences in comparison to previous studies including general inpatients, such as: larger proportion of infectious dermatoses and neoplasms, smaller proportion of inflammatory diseases, higher percentage of patients submitted to skin biopsy, smaller proportion of consultations managed with a single visit and higher probability of a systemic treatment being recommended in this population. CONCLUSION: Hospitalized RTR present distinct dermatological epidemiology and higher level of complexity, when compared to studies including general inpatients. Dermatology interventions during hospitalization may be beneficial in the multidisciplinary care of these patients, either contributing to the investigation of systemic conditions or providing relief for cutaneous comorbidities.

Realization of Rectangular Artificial Spin Ice and Direct Observation of High Energy Topology.

In this work, we have constructed and experimentally investigated frustrated arrays of dipoles forming two-dimensional artificial spin ices with different lattice parameters (rectangular arrays with horizontal and vertical lattice spacings denoted by a and b respectively). Arrays with three different aspect ratios γ = a/b = [Formula: see text], [Formula: see text] and [Formula: see text] are studied. Theoretical calculations of low-energy demagnetized configurations for these same parameters are also presented. Experimental data for demagnetized samples confirm most of the theoretical results. However, the highest energy topology (doubly-charged monopoles) does not emerge in our theoretical model, while they are seen in experiments for large enough γ. Our results also insinuate that the string tension connecting two magnetic monopoles in a pair vanishes in rectangular lattices with a critical ratio γ = γ c = [Formula: see text], supporting previous theoretical predictions.

Effects of second neighbor interactions on skyrmion lattices in chiral magnets.

In this paper we investigate the influences of the second neighbor interactions on a skyrmion lattice in two-dimensional chiral magnets. Such a system contains the exchange and the Dzyaloshinskii-Moriya for the spin interactions and therefore, we analyse three situations: firstly, the second neighbor interaction is present only in the exchange coupling; secondly, it is present only in the Dzyaloshinskii-Moriya coupling. Finally, the second neighbor interactions are present in both exchange and Dzyaloshinskii-Moriya couplings. We show that such effects cause important modifications to the helical and skyrmion phases when an external magnetic field is applied.

Interrelationship Between Organizational and Relational Aspects and the Return-to-Work Process: A Case Study with Nursing Professionals at a Teaching Hospital in Brazil.

Introduction The process of returning to work, especially for individuals with labor restrictions, impacts work teams and interferes with the labor reinsertion process. In this study, we aimed to understand the impact of these situations on a nursing team from both organizational and relational perspectives. Methods We conducted a qualitative research study at a university hospital in the municipality of São Paulo using three strategies: documentary analysis; semi-structured interviews with pairs of workers returning to a labor situation; and a focus group with nursing managers. Results Medical leaves of absence overburden the employees who remain working. Regarding the return to work, the participants reported both positive and negative aspects. One positive aspect reported was that those who return to work contribute to the division of labor, generating solidarity and cooperation. The negative aspects reported were related to the return of workers with labor restrictions who do not fully resume their activities, consequently generating conflicts within the work teams that interfere with the reintegration processes. The supervisors reported difficulties reorganizing work on a broad scale and assessing the workers' diagnoses and symptoms and the workers themselves in terms of the necessity of their leaves and the validity of their labor restrictions. Conclusion The organization of labor and social relationships among peers and supervisors is a significant contributor to the success or failure of the work reintegration process and therefore should be considered. We aimed to address this issue by highlighting the complexity of the return-to-work process among health workers.

Investigation of ferromagnetic resonance and magnetoresistance in anti-spin ice structures.

In this work, we report experimental and theoretical investigations performed in anti-spin ice structures, composed by square lattice of elongated antidots, patterned in nickel thin film. The magnetic vortex crystal state was obtained by micromagnetic simulation as the ground state magnetization, which arises due to the magnetic stray field at the antidot edges inducing chirality in the magnetization of platters among antidots. Ferromagnetic resonance (FMR) and magnetoresistance (MR) measurements were utilized to investigate the vortex crystal magnetization dynamics and magnetoelectric response. By using FMR, it was possible to detect the spin wave modes and vortex crystal resonance, in good agreement with dynamic micromagnetic simulation results. The vortex crystal magnetization configuration and its response to the external magnetic field, were used to explain the isotropic MR behaviour observed.

Emergence and mobility of monopoles in a unidirectional arrangement of magnetic nanoislands.

Magnetricity, the magnetic equivalent of electricity, was recently verified experimentally for the first time. Indeed, like the stream of electric charges that produces electric current, emergent magnetic monopoles have been observed to roam freely in geometrically frustrated magnets known as spin ice. However, such phenomena demand extreme physical conditions, say, a single spin ice crystal has to be cooled to very low temperature, around 0.36 K. Candidates to overcome this difficulty are their artificial analogues, the so-called artificial spin ices. Here, we demonstrate that a specific unidirectional arrangement of nanoislands yields a peculiar system where magnetic monopoles emerge and are constrained to move along aligned dipoles, providing an ordered flow of magnetic charges at room temperature.

Order and thermalized dynamics in Heisenberg-like square and Kagomé spin ices.

Thermodynamic properties of a spin ice model on a Kagomé lattice are obtained from dynamic simulations and compared with properties in square lattice spin ice. The model assumes three-component Heisenberg-like dipoles of an array of planar magnetic islands situated on a Kagomé lattice. Ising variables are avoided. The island dipoles interact via long-range dipolar interactions and are restricted in their motion due to local shape anisotropies. We define various order parameters and obtain them and thermodynamic properties from the dynamics of the system via a Langevin equation, solved by the Heun algorithm. Generally, a slow cooling from high to low temperature does not lead to a particular state of order, even for a set of coupling parameters that gives well thermalized states and dynamics. At very low temperature, however, square ice is more likely to reach states near the ground state than Kagomé ice, for the same island coupling parameters.

Evaluation of textile dye degradation due to the combined action of enzyme horseradish peroxidase and hydrogen peroxide.

The kinetic parameters of the oxidant action of the combination of enzyme horseradish peroxidase (HRP) with hydrogen peroxide in the degradation of methylene blue dye were investigated. Twenty-one percent of color removal was obtained at pH 5.0 and temperature of 30 °C. Under these conditions, the kinetic parameters K m and V max of enzymatic reactions were determined for hydrogen peroxide in the absence of methylene blue dye (K m = 17.3 mM; V max = 1.97 mM/min) and in the presence of methylene blue dye (K m = 0.27 mM, V max = 0.29 µM/min). By means of analysis of phosphorescence, the presence of reactive oxygen species was detected in the form of singlet oxygen through the redox reaction between HRP and hydrogen peroxide. The existence of this reactive species is directly dependent on the concentration of hydrogen peroxide in the aqueous solution.

Renal evaluation in women with preeclampsia.

BACKGROUND/AIMS: Preeclampsia (PE) is a cause of glomerulopathy worldwide. Urinary retinol-binding protein (RBP) is a marker of proximal tubular dysfunction, albuminuria is an endothelial injury marker, urine protein:creatinine ratio (PCR) may have a predictive value for renal disease later in life, and, recently, podocyturia has been proposed as a sensitive tool in pregnancy, but it needs to be tested. The aim of this study was to evaluate renal involvement in PE and healthy pregnancy. METHODS: Case-control study with 39 pregnant women assessed after 20 weeks of gestation (25 in the control group, CG, and 14 in the PE group) by performing urinary tests. RESULTS: Mean (±SD) age and gestational age of the CG were 26.9 ± 6.4 years and 37.1 ± 5.0 weeks, and of the PE group 26.4 ± 6.9 years and 30.6 ± 5.6 weeks, respectively (p = 0.001). Mean (±SD) urinary RBP (p = 0.017), albuminuria (p = 0.002), and urinary albumin concentration (UAC) ratio (p = 0.006) of the CG were 0.4 ± 0.7 mg/l, 7.3 ± 6.9 mg/l, and 8.2 ± 6.7 mg/g and of the PE group 2.0 ± 4.4 mg/l, 2,267.4 ± 2,130.8 mg/l (p = 0.002), and 3,778.9 ± 4,296.6 mg/g (p = 0.006), respectively. Mean (±SD) urine PCR in the PE group was 6.7 ± 6.1 g/g (p < 0.001). No statistical differences were found between podocyturia in the CG and PE group (p = 0.258). CONCLUSIONS: Urinary RBP, PCR, albuminuria, and UAC ratio were elevated in the PE group in comparison to the CG. Podocyturia did not predict PE.

Magnetic anisotropy of elongated thin ferromagnetic nano-islands for artificial spin ice arrays.

The energetics of thin elongated ferromagnetic nano-islands is considered for some different shapes, aspect ratios and applied magnetic field directions. These nano-island particles are important for artificial spin ice materials. For low temperature, the magnetic internal energy of an individual particle is evaluated numerically as a function of the direction of a particle's net magnetization. This leads to estimations of effective anisotropy constants for (1) the easy axis along the particle's long direction, and (2) the hard axis along the particle's thin direction. A spin relaxation algorithm together with fast Fourier transform for the demagnetization field is used to solve the micromagnetics problem for a thin system. The magnetic hysteresis is also found. The results indicate some possibilities for controlling the equilibrium and dynamics in spin ice materials by using different island geometries.