Frustration and Glasslike Character in RIn1- xMn xO3 (R = Tb, Dy, Gd).

We bring together ac susceptibility and dc magnetization to uncover the rich magnetic field-temperature behavior of a series of rare earth indium oxides, RInO3 (R = Tb, Dy, and Gd). The degree of frustration is much larger than expected, particularly in TbInO3, and the ground states are glasslike with antiferromagnetic tendencies. The activation energy for spin reorientation is low. Chemical substitution with Mn3+ ions to form TbIn1- xMn xO3 ( x ≤ 0.01) relieves much of the frustration that characterizes the parent compound and slightly enhances the short-range antiferromagnetic order. The phase diagrams developed from this work reveal the rich competition between spin orders and provide an opportunity to compare the dynamics in the RInO3 and Mn-substituted systems. These structure-property relations may be useful for understanding magnetism in other geometrically frustrated multiferroics.

Elucidating the mechanism of multiferroicity in (NH4)3Cr(O2)4 and its tailoring by alkali metal substitution.

The antiferromagnetic Cr(V) peroxychromates, M(3)Cr(O(2))(4), M = K, Rb, and Cs, become ferroelectric when mixed with NH(4)(+), but the underlying mechanism is not understood. Our dielectric relaxation, Raman scattering, and high-frequency EPR measurements on the M(3-x)(NH(4))(x)Cr(O(2))(4) family clarify this mechanism. At 295 K, (NH(4))(3)Cr(O(2))(4) is tetragonal (I42m), with the NH(4)(+) ions occupying two distinctly different sites, N1 and N2. A ferroelectric transition at T(c1) = 250 K is revealed by λ-type anomalies in C(p) and dielectric constant, and lowering of symmetry to Cmc2(1). Below T(c1), the N1 sites lose their tetrahedral symmetry and thus polarization develops. Raman detection of translational modes involving the NH(4)(+) ions around 193 cm(-1) supports this model. EPR around T(c1) revealed that the [Cr(O(2))(4)](3-) ions reorient by about 10°. A minor peak at T(c2) ≈ 207 K is attributed to a short-range ordering that culminates in a long-range, structural order at T(c3) ≈ 137 K. At T(c3), the symmetry is lowered to P1 with significant changes in the cell parameters. Rb(+) and Cs(+) substitutions that block the N1 and N2 sites selectively show that T(c1) is related to the torsional motion of the N1 site, while T(c2) and T(c3) are governed by the motional slowing down of the N2 site. These data show that the multiferroic behavior of this family is governed by the rotational and translational dynamics of the NH(4)(+) ions and is tunable by their controlled substitutions. Relevance to other classes of possible multiferroics is pointed out.

M(3-x)(NH4)(x)CrO8 (M = Na, K, Rb, Cs): a new family of Cr5+-based magnetic ferroelectrics.

Upon consideration of the hydrogen-bonding properties of the NH(4)(+) cation, we synthesized a new class of compounds, M(3-x)(NH(4))(x)CrO(8) (M = Na, K, Rb, Cs). These magnetic compounds with the simple 3d(1) ground state become ferroelectric. X-ray studies confirmed that the phase transition involves a symmetry change from I42m to Cmc2(1) to P1. The transition temperature depends linearly on the composition variable x. The transitions are of the order-disorder type, with N-H···O bonding playing the central role in the mechanism. Extension of this idea to the introduction of ferroelectricity in several other classes of materials is suggested.

The BTLA and PD-1 signaling pathways independently regulate the proliferation and cytotoxicity of human peripheral blood γδ T cells.

BACKGROUND: B- and T-lymphocyte attenuator (BTLA) and programmed cell death-1 (PD-1) inhibit γδ T cell homeostasis and activation. This study aimed to determine whether BTLA and PD-1 signaling pathways were convergent or independent in human peripheral blood γδ T cells. Herein we demonstrate that the signalings of BTLA and PD-1 regulated proliferation and cytotoxicity of human γδ T cells, respectively. METHODS: Human peripheral blood γδ T cells were cultured with inactivated Jurkat cells in the presence of interleukin-2 and zoledronate (Zol) for 14 days. Flow cytometry was performed to evaluate the phenotypes and functions of γδ T cells. RESULTS: The proliferation of the γδ T cells was increased when PBMCs were cocultured with inactivated herpes virus entry mediator (HVEM)low Jurkat cells. The cytotoxicity of the expanded γδ T cells was not affected by coculture with inactivated HVEMlow Jurkat cells and was further increased in the presence of anti-PD-L1 mAb. These results suggest that the inactivation of the BTLA signaling pathway during expansion could help produce more γδ T cells without compromising γδ T cell function. The inhibition of BTLA or PD-1 signaling repressed phosphorylation of the src homology region 2-containing protein tyrosine phosphatase 2 and increased the phosphorylation of protein kinase B in γδ T cells. However, there were no synergistic or additive effects by a combination of BTLA and PD-1 blockade. CONCLUSION: These results suggest that BTLA signaling is crucial in regulating γδ T cell proliferation and function and that the BTLA and PD-1 signaling pathways act independently on the proliferation and cytotoxicity of human peripheral γδ T cells.

Changes in hormone levels of participants in a 622-km ultramarathon race based on distance and recovery period.

BACKGROUND: Runners who participate in endurance sports such as marathons or ultramarathons have superior physical capabilities and health benefits compared to others. However, they may suffer long-term effects of the negative physiological changes during long-distance running. This study aimed to examine the effects of an ultramarathon on hormone levels, and the associated risks. METHODS: Ten participants who completed a 622-km ultramarathon were included. Blood was collected prerace, at the 300-km mark, the 622-km mark, and on the 3rd day of recovery (RD3) and the 6th day of recovery (RD6) and analyzed for human growth hormone (HGH), cortisol, beta-endorphin, serotonin, testosterone, luteinizing hormone (LH), and follicle stimulating hormone (FSH) levels. RESULTS: HGH and beta-endorphin showed the highest increase at the 300-km mark compared to prerace levels, with recovery on RD3 and RD6, respectively. LH, cortisol, and serotonin showed the highest levels of increase at the 622-km mark, with recovery on RD6 for LH, and RD3 for cortisol and serotonin. FSH showed the highest level of decrease at both 300-km and 622-km marks compared to prerace levels, with recovery on RD3. Testosterone decreased the most at the 300-km mark compared to the prerace level and this decrease was below the normal levels; however, it recovered to normal levels on RD3. CONCLUSIONS: Hormone levels after the 622-km ultramarathon were within their normal ranges, except for testosterone. However, all the hormones recovered to prerace levels on RD3 or RD6. This study showed that running ultramarathons does not cause abnormal hormone levels.

A new organic superconductor, beta-(BDA-TTP)2GaCl4 [BDA-TTP = 2,5-(1,3-dithian-2-ylidene)-1,3,4,6-tetrathiapentalene].

The preparation, crystal structure and physical properties of beta-(BDA-TTP)2GaCl4 has been investigated; the salt exhibits superconductivity at 3.1 K (onset) under a hydrostatic pressure of 7.6 kbar.