Enhancement of piezomagnetic response of highly magnetostrictive rare earth‐iron alloys at kHz frequencies

The effects of Al and Si additions on the frequency response of highly magnetostrictive Tb–Dy–Fe alloys have been studied. These elements reduced the electrical conductivity of the material, thereby increasing the depth of penetration of acmagnetic fields and extending the operational frequency range. Complex permeability measurements were made on doped and undoped polycrystalline samples with the objective of studying the improvement in energy conversion efficiency at kilohertz frequencies as a result of the alloying additions. The resulting complex permeability was compared with the values for single crystal specimens of Tb0.3Dy0.7Fe1.92 at a range of frequencies from 10 Hz to 50 kHz

Magnetostrictive materials and method for improving AC characteristics in same

The present invention provides Terfenol-D alloys (“doped” Terfenol) having optimized performances under the condition of time-dependent magnetic fields. In one embodiment, performance is optimized by lowering the conductivity of Terfenol, thereby improving the frequency response. This can be achieved through addition of Group III or IV elements, such as Si and Al. Addition of these types of elements provides scattering sites for conduction electrons, thereby increasing resistivity by 125% which leads to an average increase in penetration depth of 80% at 1 kHz and an increase in energy conversion efficiency of 55%. The permeability of doped Terfenol remains constant over a wider frequency range as compared with undoped Terfenol. These results demonstrate that adding impurities, such as Si and Al, are effective in improving the ac characteristics of Terfenol. A magnetoelastic Grüneisen parameter, γme, has also been derived from the thermodynamic equations of state, and provides another means by which to characterize the coupling efficiency in magnetostrictive materials on a more fundamental basis.</p

Enhancement of piezomagnetic response of highly magnetostrictive rare earth‐iron alloys at kHz frequencies

The effects of Al and Si additions on the frequency response of highly magnetostrictive Tb–Dy–Fe alloys have been studied. These elements reduced the electrical conductivity of the material, thereby increasing the depth of penetration of acmagnetic fields and extending the operational frequency range. Complex permeability measurements were made on doped and undoped polycrystalline samples with the objective of studying the improvement in energy conversion efficiency at kilohertz frequencies as a result of the alloying additions. The resulting complex permeability was compared with the values for single crystal specimens of Tb0.3Dy0.7Fe1.92 at a range of frequencies from 10 Hz to 50 kHz.The following article appeared in Journal of Applied Physics 79 (1996): 6219 and may be found at http://dx.doi.org/10.1063/1.362076.</p

Specialized Tfh cell subsets driving type-1 and type-21 humoral responses in lymphoid tissue

Effective antibody responses are essential to generate protective humoral immunity. Different inflammatory signals polarize T cells towards appropriate effector phenotypes during an infection or immunization. Th1 and Th2 cells have been associated with the polarization of humoral responses. However, T follicular helper cells (Tfh) have a unique ability to access the B cell follicle and support the germinal center (GC) responses by providing B cell help. We investigated the specialization of Tfh cells induced under type-1 and type-2 conditions. We first studied homogenous Tfh cell populations generated by adoptively transferred TCR-transgenic T cells in mice immunized with type-1 and type-2 adjuvants. Using a machine learning approach, we established a gene expression signature that discriminates Tfh cells polarized towards type-1 and type-2 response, defined as Tfh1 and Tfh2 cells. The distinct signatures of Tfh1 and Tfh2 cells were validated against datasets of Tfh cells induced following lymphocytic choriomeningitis virus (LCMV) or helminth infection. We generated single-cell and spatial transcriptomics datasets to dissect the heterogeneity of Tfh cells and their localization under the two immunizing conditions. Besides a distinct specialization of GC Tfh cells under the two immunizations and in different regions of the lymph nodes, we found a population of Gzmk+ Tfh cells specific for type-1 conditions. In human individuals, we could equally identify CMV-specific Tfh cells that expressed Gzmk. Our results show that Tfh cells acquire a specialized function under distinct types of immune responses and with particular properties within the B cell follicle and the GC

Centrality dependence of the charged-particle multiplicity density at mid-rapidity in Pb-Pb collisions at sNN\sqrt{s_{NN}} = 2.76 TeV

The centrality dependence of the charged-particle multiplicity density at mid-rapidity in Pb-Pb collisions at $\sqrt{s_{NN}}$ = 2.76 TeV is presented. The charged-particle density normalized per participating nucleon pair increases by about a factor 2 from peripheral (70-80%) to central (0-5%) collisions. The centrality dependence is found to be similar to that observed at lower collision energies. The data are compared with models based on different mechanisms for particle production in nuclear collisions.The centrality dependence of the charged-particle multiplicity density at mid-rapidity in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 2.76 TeV is presented. The charged-particle density normalized per participating nucleon pair increases by about a factor 2 from peripheral (70-80%) to central (0-5%) collisions. The centrality dependence is found to be similar to that observed at lower collision energies. The data are compared with models based on different mechanisms for particle production in nuclear collisions