1/3 magnetization plateau and frustrated ferrimagnetism in a sodium iron phosphite

AT was supported by the Federal Ministry for Education and Research through the Sofja Kovalevskaya Award of Alexander von Humboldt Foundation. This work was supported in part by Russian Foundation for Basic Research grants 14-02-00111, 14-02-00245, 16-02-00021, from the Ministry of Education and Science of the Russian Federation in the framework of Increase Competitiveness Program of NUST «MISiS» (№ К2-2015-075 and № K4-2015-020) and by Act 211 of the Government of Russian Federation, agreement № 02.A03.21.0006. EAZ, JW and RK acknowledge support by the Excellence Initiative of the German Federal Government and States. PL thanks EPSRC (EP/K503162/1) for partial support of a studentship to IM and the Leverhulme Trust for the award of a post-doctoral fellowship (RPG-2013-343) to LC. SK is grateful for the funding by SSP1458 of the DFG.The sodium-iron phosphite NaFe3(HPO3)2(H2PO3)6 is studied by ac-magnetic susceptibility, pulsed-field magnetization, specific heat, and high-frequency electron spin resonance (HF-ESR) measurements combined with Mössbauer spectroscopy and density-functional calculations. We show that this compound develops ferrimagnetic order below TC = 9.5 K and reveals a magnetization plateau at 1/3-saturation. The plateau extends to Bc ~ 8 T, whereas above Bc the magnetization increases linearly until reaching saturation at Bs ~ 27 T. The Mössbauer spectroscopy reveals two magnetically non-equivalent iron sites with the 2:1 ratio. The HF-ESR spectra are consistent with a two-sublattice ferrimagnet and additionally pinpoint weak magnetic anisotropy as well as short-range spin order that persists well above TC. The ferrimagnetic order in the title compound is stabilized by a network of purely antiferromagnetic exchange interactions. The spin lattice comprises layers coinciding with the crystallographic (10-1) planes, with stronger couplings Ji ~ 1.5 K within the layers and weaker couplings Ji = 0.3−0.4 K between the layers. Both intralayer and interlayer couplings are frustrated. The ensuing ferrimagnetic order arises from a subtle interplay of the frustrated but nonequivalent exchange couplings.PostprintPostprintPeer reviewe

Induced hyperlipaemia and immune challenge in locusts

Injections of immunogens, such as β-1,3-glucan or lipopolysaccharide (LPS), bring about a marked hyperlipaemia with associated changes in lipophorins and apolipophorin-III in the haemolymph of Locusta migratoria. These changes are similar to those observed after injection of adipokinetic hormone (AKH). The possibility that endogenous AKH is released as part of the response to these immunogens is investigated using passive immunisation against AKH-I, and measurement of AKH-I titre in the haemolymph after injection of immunogens. The data presented show that, despite the similarity of the changes brought about by the presence of immunogens in the haemolymph to those brought about by AKH, there is no release of endogenous AKH after injection of laminarin or LPS. A direct effect of the immunogens on release of neutral lipids by the fat body cannot be demonstrated in vitro, and the mechanism by which hyperlipaemia is induced during immune challenge remains uncertain

‘I learned to accept every part of myself’: the transformative impact of a theatre-based sexual health and HIV prevention programme

Theatre-based interventions have been used in health promotion activities among young people to address HIV and sexual health. In this study, we explored the experience of undergraduate student performers participating in a theatre-based HIV prevention and sexual health education intervention for high school students in the USA. Undergraduate students enrolled in a credit-bearing course to learn about HIV and sexual health, participatory theatre and health education techniques. We analysed students’ reflective essays written throughout the semester to identify any changes and the intervention processes that promoted these changes. Students experienced five interrelated forms of transformation: (1) increased knowledge about HIV and sexual health; (2) changes in attitude and communication about sex; (3) artistic growth; (4) emotional growth; and (5) clarification of career goals and future plans. Intervention processes that contributed to these transformations included improvisation, guided writing exercises, the creation of a close-knit cohesive group, and interactions with a group of HIV-positive speakers. Theatre-based, peer-led sexual health programmes can provide a transformative experience for undergraduate student performers. The transformative effects are linked to specific activities and processes of the intervention and require examination in future research

Prevention for substance-using HIV-positive young people: telephone and in-person delivery

HIV risky behaviors and health practices were examined among young people living with HIV (YPLH) in Los Angeles, San Francisco, and New York over 15 months in response to receiving a preventive intervention. YPLH aged 16 to 29 years (n = 175; 26% black and 42% Latino; 69% gay men) were randomly assigned to a 3-module intervention totaling 18 sessions delivered by telephone, in person, or a delayed-intervention condition. Intention-to-treat analyses found that the in-person intervention resulted in a significantly higher proportion of sexual acts protected by condoms overall and with HIV-seronegative partners. Pre- and postanalyses of YPLH in the delayed-intervention condition alone found that YPLH tended to have fewer sexual partners, used fewer drugs, reported less emotional distress, and decreased their use of antiretroviral therapies. Prevention programs can be delivered in alternative formats while retaining efficacy. When YPLH are using hard drugs, drug treatment may be needed before delivery of preventive interventions

‘I learned to accept every part of myself’: the transformative impact of a theatre-based sexual health and HIV prevention programme

Theatre-based interventions have been used in health promotion activities among young people to address HIV and sexual health. In this study, we explored the experience of undergraduate student performers participating in a theatre-based HIV prevention and sexual health education intervention for high school students in the USA. Undergraduate students enrolled in a credit-bearing course to learn about HIV and sexual health, participatory theatre and health education techniques. We analysed students’ reflective essays written throughout the semester to identify any changes and the intervention processes that promoted these changes. Students experienced five interrelated forms of transformation: (1) increased knowledge about HIV and sexual health; (2) changes in attitude and communication about sex; (3) artistic growth; (4) emotional growth; and (5) clarification of career goals and future plans. Intervention processes that contributed to these transformations included improvisation, guided writing exercises, the creation of a close-knit cohesive group, and interactions with a group of HIV-positive speakers. Theatre-based, peer-led sexual health programmes can provide a transformative experience for undergraduate student performers. The transformative effects are linked to specific activities and processes of the intervention and require examination in future research

Thermodynamic properties, electron spin resonance and underlying spin model in Cu3Y(SeO3)2O2Cl

The collaboration between the University of St Andrews and Moscow State University was funded by a Royal Society International Exchanges grant, in collaboration with the RFBR (12-03-92604). P.L. and L.C. also thank the Leverhulme Trust (Award RPG-2013-343).We report a detailed study of the magnetic properties of the buckled kagome compound Cu3Y(SeO3)2O2Cl using heat capacity, magnetization, powder neutron diffraction, electron spin resonance and first-principles calculations. The crystal structure is confirmed to be isotypic with the mineral francisite, with orthorhombic space group symmetry Pmmn throughout the temperature range 5 – 300 K. Magnetization, heat capacity and neutron diffraction confirm long range magnetic order below TN = 35 K. The electron spin resonance spectra reveal the presence of two modes corresponding to two different crystallographic Cu positions. The principal g-values of the g-tensor of Cu(1) sites were found to be g1 = 2.18(4), g2 = 2.10(6) and g3 = 2.05(9), while the effective g-factor of Cu(2) sites is almost isotropic and is on average g = 2.09(5). At low temperatures, Cu3Y(SeO3)2O2Cl undergoes a metamagnetic transition, with a critical field BC = 2.6 T at 2 K, due to the suppression of the inter-plane exchange interactions and saturates in modest magnetic field, BS ≤8 T. The first-principles calculations allow an estimation of both intra-plane and inter-plane exchange interactions. The weakness of the inter-plane exchange interaction results in low values of the critical fields for the metamagnetic transition, while the competition between intra-plane exchange interactions of different signs results in a similarly low value of the saturation field.PostprintPeer reviewe