Modal Frustration and Periodicity Breaking in Artificial Spin Ice

open7sìHere, an artificial spin ice lattice is introduced that exhibits unique Ising and non-Ising behavior under specific field switching protocols because of the inclusion of coupled nanomagnets into the unit cell. In the Ising regime, a magnetic switching mechanism that generates a uni- or bimodal distribution of states dependent on the alignment of the field is demonstrated with respect to the lattice unit cell. In addition, a method for generating a plethora of randomly distributed energy states across the lattice, consisting of Ising and Landau states, is investigated through magnetic force microscopy and micromagnetic modeling. It is demonstrated that the dispersed energy distribution across the lattice is a result of the intrinsic design and can be finely tuned through control of the incident angle of a critical field. The present manuscript explores a complex frustrated environment beyond the 16-vertex Ising model for the development of novel logic-based technologies.openPuttock, Robert; Manzin, Alessandra; Neu, Volker; Garcia-Sanchez, Felipe; Fernandez Scarioni, Alexander; Schumacher, Hans W; Kazakova, OlgaPuttock, Robert; Manzin, Alessandra; Neu, Volker; Garcia-Sanchez, Felipe; Fernandez Scarioni, Alexander; Schumacher, Hans W; Kazakova, Olg

Modal Frustration and Periodicity Breaking in Artificial Spin Ice

Here, an artificial spin ice lattice is introduced that exhibits unique Ising and non-Ising behavior under specific field switching protocols because of the inclusion of coupled nanomagnets into the unit cell. In the Ising regime, a magnetic switching mechanism that generates a uni- or bimodal distribution of states dependent on the alignment of the field is demonstrated with respect to the lattice unit cell. In addition, a method for generating a plethora of randomly distributed energy states across the lattice, consisting of Ising and Landau states, is investigated through magnetic force microscopy and micromagnetic modeling. It is demonstrated that the dispersed energy distribution across the lattice is a result of the intrinsic design and can be finely tuned through control of the incident angle of a critical field. The present manuscript explores a complex frustrated environment beyond the 16-vertex Ising model for the development of novel logic-based technologies

The Epistemology of “Epistemology Naturalized”

Quine's “Epistemology Naturalized” has become part of the canon in epistemology and excited a widespread revival of interest in naturalism. Yet the status accorded the essay is ironic, since both friends and foes of philosophical naturalism deny that Quine makes a plausible case that the methods of naturalism can accommodate the problems of epistemology

Large-Scale Molecular Dynamics Simulation of CoulombClusters: A Finite-Temperature Analysis

Thermal behavior of Coulomb clusters in a three dimensional confining potential is investigated by molecular dynamics simulations for system sizes of 1,000 to 20,288 ions. The specific heat of the system of shell-structured 20,000 ions is peaked almost at the same temperature as the system of bcc-structured 20,288 ions with much sharper structure for the latter. The diffusion coefficient and the peak to valley ratio of the two-dimensional pair distribution function on the outermost shell are obtained both as a function of temperature. The rotational movement of each shell in the system of 104 ions is observed

Coordinated Supervisory Control of Multi-Terminal HVDC Grids: a Model Predictive Control Approach

A coordinated supervisory control scheme for future multi-terminal High-Voltage Direct-Current (HVDC) grids is proposed. The purpose is to supervise the grid and take appropriate actions to ensure power balance and prevent or remove voltage or current limit violations. First, using DC current and voltage measurements, the power references of the various Voltage Sources Converters (VSC) are updated according to participation factors. Next, the setpoints of the converters are smoothly adjusted to track those power references, while avoiding or correcting limit violations. The latter function resorts to Model Predictive Control and a sensitivity model of the system. The efficiency of the proposed scheme has been tested through dynamic simulations of a five-terminal HVDC grid interconnecting two asynchronous AC areas and a wind farm

Lunar subsurface investigated from correlation of seismic noise.

International audienceBy correlating seismic noise recorded by four sensors placed on the Moon during the Apollo 17 mission, we have retrieved a well-defined dispersed Rayleigh wave pulse. Inversion of its group velocity provides new constraints on the lunar subsurface structure. The estimated ”signal-to-noise” ratio (SNR) of the retrieved Rayleigh wavetrain is strongly dependent on solar illumination, effectively making solar heating a source of seismic noise on the Moon. This result suggests that in future planetary missions it is feasible to extract information on the internal structure of extraterrestrial objects by correlating seismic noise even when natural quakes are absent

Precise tuning of the Curie temperature of (Ga,Mn)As-based magnetic semiconductors by hole compensation: Support for valence-band ferromagnetism

For the prototype diluted ferromagnetic semiconductor (Ga,Mn)As, there is a fundamental concern about the electronic states near the Fermi level, i.e., whether the Fermi level resides in a well-separated impurity band derived from Mn doping (impurity-band model) or in the valence band that is already merged with the Mn-derived impurity band (valence-band model). We investigate this question by carefully shifting the Fermi level by means of carrier compensation. We use helium-ion implantation, a standard industry technology, to precisely compensate the hole doping of GaAs-based diluted ferromagnetic semiconductors while keeping the Mn concentration constant. We monitor the change of Curie temperature (TC) and conductivity. For a broad range of samples including (Ga,Mn)As and (Ga,Mn)(As,P) with various Mn and P concentrations, we observe a smooth decrease of TC with carrier compensation over a wide temperature range while the conduction is changed from metallic to insulating. The existence of TC below 10 K is also confirmed in heavily compensated samples. Our experimental results are naturally explained within the valence-band picture

Histopathological evaluation of endometrial curettage in cases of abnormal uterine bleeding and its correlation with age of patient

Background: Abnormal uterine bleeding (AUB) is defined as a pattern of bleeding that does not correspond with the duration, amount and frequency of the flow of a normal menstrual cycle. The cause of AUB varies according to the age, endometrial response to hormones and its variations and other structural lesions. Endometrial sampling by endometrium curettage is safe and easy technique and its histopathological analysis is considered the gold standard for diagnosis of the etiology of AUB. Aims and objective was to evaluate the spectrum of endometrial histology in cases of AUB, to find out age wise incidence of AUB, and to find out age wise incidence of various histological pattern of endometrium in AUB.Methods: An observational study was conducted on dilatation and curettage material which were obtained from 110 women with a complaint of AUB attending the gynecology outpatient department (OPD) at tertiary care hospital, Rajkot, Gujarat during one year (August 2020 to July 2021).Results: Maximum number of cases of AUB were noted in the age group of (31-40) years (44 cases, 40%). Most common observed histopathological pattern in this study was normal cyclical patterns including proliferative endometrium (34.5%) and secretory endometrium (21%).Conclusions: Histopathological evaluation of endometrium is indicated in women over the age of 35 years presenting with AUB to rule out preneoplastic lesions and malignancies