Magnetic field

We present a catalog of 3339 hot emission-line stars (ELSs) identified from 451 695 O, B and A type spectra, provided by LAMOST Data Release 5 (DR5). We developed an automated Python routine that identified 5437 spectra having a peak between 6561 and 6568 Å. False detections and bad spectra were removed, leaving 4138 good emission-line spectra of 3339 unique ELSs. We re-estimated the spectral types of 3307 spectra as the LAMOST Stellar Parameter Pipeline (LASP) did not provide accurate spectral types for these emission-line spectra. As Herbig Ae/Be stars exhibit higher excess in near-infrared and mid-infrared wavelengths than classical Ae/Be stars, we relied on 2MASS and WISE photometry to distinguish them. Finally, we report 1089 classical Be, 233 classical Ae and 56 Herbig Ae/Be stars identified from LAMOST DR5. In addition, 928 B[em]/A[em] stars and 240 CAe/CBe potential candidates are identified. From our sample of 3339 hot ELSs, 2716 ELSs identified in this work do not have any...

This work presents a simple design for a mobile single-sided nuclear magnetic resonance (NMR) apparatus with a relatively homogeneous static magnetic field (B(0)) distribution. In the proposed design, the B(0) magnetic field of the apparatus is synthesized using only two permanent magnet blocks, i.e., a cube (main) magnet and a small shim magnet placed above the main magnet. The magnetic flux of the shim magnet partially cancels out that of the main magnet, subsequently creating a smooth B(0) profile above the shim magnet where low-resolution NMR experiments are performed. Compared with many previously published designs, this straightforward design simplifies the construction of the apparatus and simultaneously generates a B(0) field parallel to the apparatus surface, allowing the use of a simple loop-type radiofrequency (RF) coil. Additionally, an apparatus prototype is constructed according to the proposed design. Weighing only 1.8 kg, the constructed apparatus has a compact struc...

In this article, we study a problem on propagation of coupled porosity,  fluid concentration flux, and temperature waves. We use a model formulated in previous papers for porous media saturated by a fluid flow, in the framework of non-equilibrium thermodynamics. We derive three modes of propagation in the one-dimensional and perfect isotropic case, and then we test the validity of the model. The waves propagation velocities are represented in diagrams as functions of the wave number. The derived results have applications in technological sectors  such as seismology, medical sciences, geology and nanotechnology. For more information see https://ejde.math.txstate.edu/Volumes/2021/88/abstr.html

We study the motion of charged particles around Schwarzschild black holes immersed in external (i) asymptotically uniform, (ii) dipolar, and (iii) parabolic-like magnetic fields. The effect of the different magnetic-field configurations on the position of innermost stable circular orbits (ISCOs) for test-charged particles is analyzed. Furthermore, we investigated frequencies of radial and vertical oscillations of the charged particles along their stable circular orbits together with the Keplerian one. As an astrophysical application, we explore quasiperiodic oscillations (QPOs) observed in microquasars sourced by black hole candidates in the frame of the relativistic precession (RP) model. In order to obtain constraints on the values of the magnetic parameter and black hole mass for the microquasars GRO J1655-40 and GRS 1915-105, we use the method so-called $$\chi ^2$$ χ 2 in the Bayesian approach. Also, we get constraints on the magnetic field around the black hole in the microquas...

The intensity and excitation energy is chosen for different materials to probe different regions and excitations concentrations in the sample. The intensity of the PL signal provides information on the quality of surfaces and interfaces. Also, information on the electronic bands structure and the SC Energy gap can be obtained, as well as thermodynamics quantities such as temperature. For this experiment we just compared the photoluminescence (PL) spectra of AlGaAs/GaAs quantum wells (QWs) with different well widths (100 Å and 85 Å) and InAs/GaAs quantum dots (QD) structures as well as the theoretical aspects were covered. The sample are held in a cryostat and excited by a Helium-Neon laser. The emitted light is then captured by an optical fiber plugged to a spectrometer The optical fibre is plugged to a spectrometer equipped with a CCD detector, driven by a computer allowing us to acquire data. And this was used to avoid interaction between charge carriers and thermally excited ph...

We calculate the most probable reaction paths for thermally induced magnetization reversal of a nanomagnet under the influence of spin transfer torque. The presence of the spin transfer torque implies that the standard reaction rate theory of Kramers cannot be used since the dynamics no longer shows detailed balance and so the magnetization reversals are nonequilibrium transitions. Thin film nanomagnets with a biaxial anisotropy, a shape anisotropy that leads to in-plane magnetization with a preferred axis in the plane, are considered. The reaction pathways and rates are computed using geometrical Minimum Action Method. Our results indicate that the transition state has an out-of-plane magnetization component, in contrast to the case without an applied spin transfer torque.

The influence of the gravity and magnetic field on the propagation of Rayleigh wave in a prestressed inhomogeneous, orthotropic elastic solid medium has been discussed. The method of separation of variable has been used to find the frequency equations for the surface waves. The obtained dispersion equations are in agreement with the classical results when gravity, magnetic field, non-homogeneity and initial stress are neglected

This paper deals with the propagation of magnetoelastic torsional waves in nonhomogeneous viscoelastic cylindrically aeolotropic material. The elastic constants and non-homogeneity in density of the material are in the form i¤ij ij i€½ C rand i² i² i€½ r respectively, where Cij i²0, are constants; r is radius vector; l and m are any integers. Frequency equation in each case has been derived and the graphs have been plotted showing the effect of variation of elastic constants and the presence of magnetic field. It is observed that the torsional elastic waves in a viscoelastic solid body propagating under the influence of a superimposed magnetic field can be different significantly from that of those propagating in the absence of a magnetic field. The numerical calculations have been presented graphically by using MATLAB.