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We report a theoretical study of the magnetic profiles of vortex pairs in dipolar coupling thin Ni 80 Fe 20 (Permalloy Py™) elliptical nanocylinders. We show that the external magnetic field route can control the magnetic phases at remanence. Although the isolated nanocylinder forms one vortex in the remanence, in the presence of another, the dipolar interaction can induce a vortex pair in each nanocylinder. Moreover, our results show that we can adjust the two pairs of the magnetic vortex via the external magnetic field route. For the major-axis route, the pair of magnetic vortices in a nanocylinder is entirely antiparallel to the pair of magnetic vortices in the other nanocylinder. In contrast, both nanocylinders' pairs of magnetic vortices are completely parallel for the minor-axis route at remanence. In this case, the magnetic patterns are the same in both nanocylinders. As an application, we present the results for a pair of identical and coaxial Py elliptical (245 × 405 × 25 nm 3) nanocylinders separated by a nonmagnetic spacer of 50 nm. [ABSTRACT FROM AUTHOR]

Mining tailings have a strong presence of heavy metals in their composition, and these elements may be associated with the evolution and spread of antimicrobial resistance. The objective of this work was to analyze studies that describe the relationship between bacteria recovered from sites impacted by mining tailings resulting from the collapse of the Fundão and Córrego do Feijão Mine dams and the development of antimicrobial resistance. This is an integrative literature review, using the PubMed, VHL, Science Direct, and Web of Science databases, and the descriptors "antimicrobial resistance", "heavy metal", "dam" and "Brazil" (English) and "resistência antimicrobiana", "metal pesado", "barragem" and "Brasil" (Portuguese). Six articles were selected, four referring to the Fundão dam and two to the Córrego do Feijão Mine. All works suggested that environmental contamination by heavy metals, resulting from mining waste released after the dams collapsed, favored the appearance of antimicrobial resistance genes, that is, they are related to the selective pressure exerted by heavy metals. Disasters such as these raise questions about the interface of antimicrobial resistance in environments that have heavy metals as contaminants, the knowledge of which is of great relevance since antimicrobial resistance is a serious public health problem. [ABSTRACT FROM AUTHOR]

We report a theoretical study of the magnetic profiles of vortex pairs of dipolar coupled Fe nanocylinders. We consider pairs of identical and coaxial 21 nm height Fe circular nanocylinders with the diameter values ranging from 81 nm to 129 nm. We show that, even though each isolated nanocylinder holds a vortex at remanence, the dipolar interaction may inhibit the formation of vortices for small values of the nanocylinders' distance. For moderate values of the nanocylinders' distance, the formation of opposite chirality vortex pairs is favored. We show that the vortex locations, the vortex pair magnetic pattern, and the dipolar field and local field profiles may be tailored using moderate external field values along preparation routes parallel and perpendicular to the Fe uniaxial anisotropy easy axis. [ABSTRACT FROM AUTHOR]

We optimize the spring constants |$k^{i,j}$| (stiffness) of circular spring-mass systems with nearest-neighbour (NN) and next-nearest-neighbour (NNN) springs only. In this optimization problem, such systems are also subjected to damping and periodic external forces. The function to be minimized is the average ratio of the square norm of the on-site internal forces (response) to the square norm of the external on-site forces (input). Under the average of this response/input ratio is meant the average over time and over all configurations of external forces. As main result, it is established that the optimum stiffness matrix converges to the discrete and periodic bi-Laplacian operator as the size |$n$| of the system increases. Such a result is obtained under the following assumptions: (a) the system has the natural mode shape (eigenvector) of alternating |$1$| s and |$-1$| s; and (b) the (external) forcing frequency is at least |$1.095$| times higher than the highest natural frequency. It is remarkable that this optimum stiffness matrix exhibits negative stiffness for the springs linking NNN point masses. More specifically, as |$n$| increases, |$0> k^{i,i+2} \, \, = \, \, - \tfrac{1}{4} \, k^{i,i+1}$| is the relation between the optimum NNN spring constant and the optimum NN spring constant. Such systems illustrate that the introduction of negative stiffness springs in some specific positions does in fact reduce the average response/input ratio. Numerical tables illustrating the main result are given. [ABSTRACT FROM AUTHOR]

Background: Bulls are of great importance in the productive chain and for this reason they should have a good semen quality. There is no doubt that sperm morphology is very important to bull fertility, although little is known about how exactly the abnormal morphologies may affect sperm functions. Objectives: To detail the morphological description of the aplastic midpiece defect (AMD), as well as to understand its consequences for male fertility based on membrane and acrosome status, mitochondrial membrane potential and DNA integrity parameters. Materials and methods: The bulls were divided into two groups: control, consisting of satisfactory potential breeders (n = 3); and AMD, consisting of unsatisfactory potential breeders with a high percentage of AMD (n = 3). Bulls were evaluated by the breeding soundness evaluation; five ejaculates were collected from each animal and analyzed by flow cytometry. Results: Spermatozoa from AMD group exhibited lower sperm motility and vigor (p < 0.05). In addition, it also exhibited lower mitochondrial membrane potential (p < 0.05), a higher percentage of spermatozoa with DNA fragmentation (p < 0.05), lower acrosome and plasma membrane integrity (p < 0.05), and higher lipid bilayer sperm membrane disorganization (p < 0.05) in comparison with control bulls. Discussion: These findings may be due to oxidative stress and a reduction of the energy production capacity in addition to an alteration in the structural composition of the sperm cell. Moreover, semen with a high percentage of AMD may also be undergoing apoptosis. Conclusion: Bulls with a high percentage of AMD in their semen are not suitable for reproduction. Furthermore, it suggests there is a putative genetic basis for this sperm defect. [ABSTRACT FROM AUTHOR]

We report a theoretical study of dipolar effects on the switching current density of soft ferromagnetic elliptical nanoelements. Relevant changes on the critical current value are found according to the orientation of the magnetization and the spin polarization with the major axis. We show that the critical current density may be reduced by as much as 92% for thin nanoelements magnetized along the minor axis direction, using in-plane spin polarization parallel to the magnetization. [ABSTRACT FROM AUTHOR]

A series of new Ni(II) complexes of general formula Ni{ZNO} Br (2a‐i) (ZNO = phenoxy/naphthoxy‐imine with pendant N‐ and O‐donor groups) were prepared and characterized by elemental analysis, IR spectroscopy, ESI‐HRMS, and by X‐ray crystallography for 2e. In the solid state, 2e features a monomeric structure with κ3 coordination of the monoanionic naphthoxy‐imine‐quinoline ligand onto the nickel center. Upon activation with MAO, both classes of nickel catalysts were able to produce selectively 1‐butene (81.5–92.1 wt%) with turnover frequencies (TOFs) varying from 3,100 to 24,300 mol(C2H4) mol (Ni)−1 h−1. Nickel precatalysts bearing phenoxy‐imine ligands were much more active than its naphthoxy analogous under the same conditions. The use of a mixture of cocatalysts (MAO/TMA or MAO/TiBA) resulted in poor activities; however the presence of TiBA in the milieu led to a significant improvement on selectivity for 1‐hexene (25.5 wt%). Under optimized conditions ([Ni] = 10 μmol, 30 °C, oligomerization time = 5 min, 20 bar ethylene, [Al]/[Ni] = 600), precatalyst 2c led to TOF = 59,900 mol(C2H4) mol(Ni)−1 h−1 and selectivity for 1‐butene of 89.5 wt%. [ABSTRACT FROM AUTHOR]

We report a theoretical investigation of the equilibrium pattern and the spectra of head-to-head and Neel domain walls of flat Fe and Py stripes, exchange coupled with a vicinal antiferromagnetic substrate. We show that the domain wall excitation spectrum is tunable by the strength of the interface field. Furthermore, strong interface coupling favors localized wall excitations. [ABSTRACT FROM AUTHOR]

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