Strain control of a bandwidth-driven spin reorientation in Ca3Ru2O7.

The layered-ruthenate family of materials possess an intricate interplay of structural, electronic and magnetic degrees of freedom that yields a plethora of delicately balanced ground states. This is exemplified by Ca3Ru2O7, which hosts a coupled transition in which the lattice parameters jump, the Fermi surface partially gaps and the spins undergo a 90∘ in-plane reorientation. Here, we show how the transition is driven by a lattice strain that tunes the electronic bandwidth. We apply uniaxial stress to single crystals of Ca3Ru2O7, using neutron and resonant x-ray scattering to simultaneously probe the structural and magnetic responses. These measurements demonstrate that the transition can be driven by externally induced strain, stimulating the development of a theoretical model in which an internal strain is generated self-consistently to lower the electronic energy. We understand the strain to act by modifying tilts and rotations of the RuO6 octahedra, which directly influences the nearest-neighbour hopping. Our results offer a blueprint for uncovering the driving force behind coupled phase transitions, as well as a route to controlling them.

Guiding antiferromagnetic transitions in Ca[Formula: see text]RuO[Formula: see text].

Understanding and controlling the transition between antiferromagnetic states having different symmetry content with respect to time-inversion and space-group operations are fundamental challenges for the design of magnetic phases with topologically nontrivial character. Here, we consider a paradigmatic antiferromagnetic oxide insulator, Ca[Formula: see text]RuO[Formula: see text], with symmetrically distinct magnetic ground states and unveil a novel path to guide the transition between them. The magnetic changeover results from structural and orbital reconstruction at the transition metal site that in turn arise as a consequence of substitutional doping. By means of resonant X-ray diffraction we track the evolution of the structural, magnetic, and orbital degrees of freedom for Mn doped Ca[Formula: see text]RuO[Formula: see text] to demonstrate the mechanisms which drive the antiferromagnetic transition. While our analysis focuses on a specific case of substitution, we show that any perturbation that can impact in a similar way on the crystal structure, by reconstructing the induced spin-orbital exchange, is able to drive the antiferromagnetic reorganization.

High-pressure developments for resonant X-ray scattering experiments at I16.

An experimental setup to perform high-pressure resonant X-ray scattering (RXS) experiments at low temperature on I16 at Diamond Light Source is presented. The setup consists of a membrane-driven diamond anvil cell, a panoramic dome and an optical system that allows pressure to be measured in situ using the ruby fluorescence method. The membrane cell, inspired by the Merrill-Bassett design, presents an asymmetric layout in order to operate in a back-scattering geometry, with a panoramic aperture of 100° in the top and a bottom half dedicated to the regulation and measurement of pressure. It is specially designed to be mounted on the cold finger of a 4 K closed-cycle cryostat and actuated at low-temperature by pumping helium into the gas membrane. The main parts of the body are machined from a CuBe alloy (BERYLCO 25) and, when assembled, it presents an approximate height of 20-21 mm and fits into a 57 mm diameter. This system allows different materials to be probed using RXS in a range of temperatures between 30 and 300 K and has been tested up to 20 GPa using anvils with a culet diameter of 500 µm under quasi-cryogenic conditions. Detailed descriptions of different parts of the setup, operation and the developed methodology are provided here, along with some preliminary experimental results.

Local magnetism, magnetic order and spin freezing in the 'nonmetallic metal' FeCrAs.

We present the results of x-ray scattering and muon-spin relaxation ([Formula: see text]SR) measurements on the iron-pnictide compound FeCrAs. Polarized non-resonant magnetic x-ray scattering results reveal the 120° periodicity expected from the suggested three-fold symmetric, non-collinear antiferromagnetic structure. [Formula: see text]SR measurements indicate a magnetically ordered phase throughout the bulk of the material below [Formula: see text] K. There are signs of fluctuating magnetism in a narrow range of temperatures above [Formula: see text] involving low-energy excitations, while at temperatures well below [Formula: see text] behaviour characteristic of freezing of dynamics is observed, likely reflecting the effect of disorder in our polycrystalline sample. Using density functional theory we propose a distinct muon stopping site in this compound and assess the degree of distortion induced by the implanted muon.

Role of defects in determining the magnetic ground state of ytterbium titanate.

Pyrochlore systems are ideally suited to the exploration of geometrical frustration in three dimensions, and their rich phenomenology encompasses topological order and fractional excitations. Classical spin ices provide the first context in which it is possible to control emergent magnetic monopoles, and anisotropic exchange leads to even richer behaviour associated with large quantum fluctuations. Whether the magnetic ground state of Yb2Ti2O7 is a quantum spin liquid or a ferromagnetic phase induced by a Higgs transition appears to be sample dependent. Here we have determined the role of structural defects on the magnetic ground state via the diffuse scattering of neutrons. We find that oxygen vacancies stabilise the spin liquid phase and the stuffing of Ti sites by Yb suppresses it. Samples in which the oxygen vacancies have been eliminated by annealing in oxygen exhibit a transition to a ferromagnetic phase, and this is the true magnetic ground state.

Diffusion mechanism in the sodium-ion battery material sodium cobaltate.

High performance batteries based on the movement of Li ions in Li x CoO2 have made possible a revolution in mobile electronic technology, from laptops to mobile phones. However, the scarcity of Li and the demand for energy storage for renewables has led to intense interest in Na-ion batteries, including structurally-related Na x CoO2. Here we have determined the diffusion mechanism for Na0.8CoO2 using diffuse x-ray scattering, quasi-elastic neutron scattering and ab-initio molecular dynamics simulations, and we find that the sodium ordering provides diffusion pathways and governs the diffusion rate. Above T ~ 290 K the so-called partially disordered stripe superstructure provides channels for quasi-1D diffusion, and melting of the sodium ordering leads to 2D superionic diffusion above T ~ 370 K. We obtain quantitative agreement between our microscopic study of the hopping mechanism and bulk self-diffusion measurements. Our approach can be applied widely to other Na- or Li-ion battery materials.

Vacancy defects and monopole dynamics in oxygen-deficient pyrochlores.

The idea of magnetic monopoles in spin ice has enjoyed much success at intermediate temperatures, but at low temperatures a description in terms of monopole dynamics alone is insufficient. Recently, numerical simulations were used to argue that magnetic impurities account for this discrepancy by introducing a magnetic equivalent of residual resistance in the system. Here we propose that oxygen deficiency is the leading cause of magnetic impurities in as-grown samples, and we determine the defect structure and magnetism in Y2Ti2O7-δ using diffuse neutron scattering and magnetization measurements. These defects are eliminated by oxygen annealing. The introduction of oxygen vacancies causes Ti(4+) to transform to magnetic Ti(3+) with quenched orbital magnetism, but the concentration is anomalously low. In the spin-ice material Dy2Ti2O7 we find that the same oxygen-vacancy defects suppress moments on neighbouring rare-earth sites, and that these magnetic distortions markedly slow down the long-time monopole dynamics at sub-Kelvin temperatures.

Suppression of thermal conductivity by rattling modes in thermoelectric sodium cobaltate.

The need for both high electrical conductivity and low thermal conductivity creates a design conflict for thermoelectric systems, leading to the consideration of materials with complicated crystal structures. Rattling of ions in cages results in low thermal conductivity, but understanding the mechanism through studies of the phonon dispersion using momentum-resolved spectroscopy is made difficult by the complexity of the unit cells. We have performed inelastic X-ray and neutron scattering experiments that are in remarkable agreement with our first-principles density-functional calculations of the phonon dispersion for thermoelectric Na(0.8)CoO2, which has a large-period superstructure. We have directly observed an Einstein-like rattling mode at low energy, involving large anharmonic displacements of the sodium ions inside multi-vacancy clusters. These rattling modes suppress the thermal conductivity by a factor of six compared with vacancy-free NaCoO2. Our results will guide the design of the next generation of materials for applications in solid-state refrigerators and power recovery.

Improvement in cognitive function after right temporal arteriovenous malformation excision.

A patient is presented in whom right temporal AVM excision led to improved cognitive function. Neuropsychological assessment showed a significant postoperative improvement in Performance IQ (p = < 0.05), Full Scale IQ (p = < 0.05), and clinically in visual memory (p = < 0.10). Reversal of vascular steal may lead to increases in cognitive function. We recommend that patients undergoing AVM excision have a complete neuropsychological evaluation.

Effects of relaxin on matrix remodeling enzyme activity of cultured equine ovarian stromal cells.

Relaxin participates in extracellular matrix (ECM) remodeling in many reproductive organs, including the ovary, by regulating proteolytic enzyme activity. Accumulated evidence indicates this action of relaxin is involved in ovarian follicle development and ovulation. Equine follicles are embedded in cortex that is at the center of the ovary and they must expand/emigrate to the fossa, the only site in the ovary for ovulation. Due to the tremendous expansion of the follicle in this species, we hypothesized that ovarian stromal remodeling would be extensive. Therefore, cultured equine ovarian stromal cell (EOSC) lines were obtained from stroma at the apex of large follicles and the effects of relaxin on gelatinases A and B, tissue inhibitors of matrix metalloproteinases (TIMPs), plasminogen activators (PAs) and PA inhibitor-1 (PAI-1) activities were assessed. Our results showed that equine relaxin increased the activity of total gelatinase A (both pro forms and mature forms) and latent progelatinase B present in conditioned medium, latent progelatinase A present in cell extracts, and TIMP-1 and TIMP-2 present in conditioned medium. This study also revealed that equine relaxin increased the urokinase-type PA activity in conditioned medium and cell extracts, tissue-type PA activity in ECM and PAI-1 activity in conditioned medium. These results suggest that relaxin may contribute to equine follicle growth and migration, and facilitate ovulation by modulating the degradation of ECM in ovarian stromal tissue.

A retrospective study to assess the results of CT-directed peri-neural root infiltration in a cohort of 56 patients with low back pain and sciatica.

Fifty-six patients with low back pain and sciatica following radiological investigation were found to have abnormalities at multiple levels, more than one of which could be responsible for the clinical picture or at a single level, which correlated poorly with the clinical findings. Thirty-four patients had a diagnostic peri-neural root infiltration to clarify whether surgery would be appropriate. Evaluation of the technique was by reduction in analgesia. Eighteen patients have had surgery, 14 with a successful, two a moderate and two a poor outcome. Four patients have been denied and two are awaiting an operation. Ten patients referred for a diagnostic procedure deferred surgery in favour of a therapeutic course. Of 22 patients referred directly for a therapeutic course, 15 had a successful, three a moderate and four a poor result. CT-directed peri-radicular root infiltration is a useful adjunct in the management of low back pain and sciatica.

Intra-operative localisation of skull base tumours. A case report using the ISG viewing wand in the management of trigeminal neuroma.

Deep-seated skull base tumours provide as much a challenge to the surgeons' skills of localisation as to his technical abilities during the resection. These lesions are frequently inaccessible and lie adjacent to vital structures requiring extensive cerebral retraction for adequate exposure and direct visualisation. The ISG viewing wand is a newly developed image guidance system to aid direction of the operative approach and localisation of intracerebral pathology. We discuss its use in the management of a trigeminal neuroma.

Production of gelatinases and tissue inhibitors of matrix metalloproteinases by equine ovarian stromal cells In vitro.

Matrix metalloproteinases (MMPs) and tissue inhibitors of MMPs (TIMPs) play very important roles in extracellular matrix (ECM) remodeling in ovarian follicle growth and ovulation. Equine follicles are embedded in cortex that is at the center of the ovary, and they must expand/emigrate to the fossa, the only site in the ovary for ovulation. Therefore, equine ovarian stromal cells (EOSC) are probably involved in ECM remodeling during follicle growth. This study examined whether cultured EOSC synthesize gelatinases and TIMPs, molecules essential for ECM remodeling in other systems. Results showed that cultured EOSC (passage 3-8) had a fibroblast-like morphology and were positive for alpha-smooth muscle actin and type I procollagen by immunostaining. Gelatinase A (MMP-2), gelatinase B (MMP-9), TIMP-1, and TIMP-2 were present in EOSC-conditioned medium, and TIMP-3 in ECM of EOSC. Transforming growth factor beta significantly stimulated the activity of gelatinases A and B and TIMP-1 in conditioned medium from EOSC (p < 0.05). Phorbol 12-myristate 13-acetate also significantly stimulated the activity of gelatinases A and B and TIMP-1 in conditioned medium and of TIMP-3 in ECM (p < 0.05). Our results suggest that EOSC produce important components of the ECM remodeling machinery and, therefore, may play a role in the ECM remodeling during follicle growth in this species.

Expression and localization of relaxin in the ovary of the mare.

Immunoreactive, chromatographic and molecular techniques were used to study the expression of relaxin in mare ovaries at different stages of the oestrous cycle. Relaxin in follicular fluid ranged from 1.6 to 2.5, from 1.4 to 5.2, from 1.2 to 6.7 and from 1.0 to 3.5 ng ml-1 in small (< or = 2 cm), medium (> 2 < or = 3 cm), medium-large (> 3 < or = 4 cm) and large (> 4 cm) follicles, respectively, and total content of fluid relaxin per follicle increased (P < 0.05) with follicular size. When subjected to reverse phase HPLC analysis, follicular fluid yielded absorbance profiles corresponding closely to those of purified relaxin, and immunoreactive peaks in follicular fluid fractions measured by radioimmunoassay matched peaks of the relaxin standard. While relaxin was localized immunocytochemically to granulosa and theca cells of preovulatory follicles, northern blot and reverse transcriptase-PCR followed by Southern blot analysis failed to detect a relaxin transcript in these tissues. A single relaxin transcript (428 bp) corresponding to mRNA encoding relaxin was identified in early, mid- and late stage corpora lutea but not in corpora haemorrhagica or albicantia. Northern blot analysis revealed a weakly expressed 1 kb transcript in total cellular RNA from mature corpora lutea. In situ hybridization studies localized the mRNA to the large luteal cells of mature corpora lutea and relaxin protein was detected by immunocytochemistry in the same tissue. This is the first report demonstrating relaxin in the equine ovary and its expression by luteal cells, thereby suggesting a role for relaxin in follicular or corpus luteum function in cyclic mares.

Hemifacial spasm: a prospective long-term follow up of 83 cases treated by microvascular decompression at two neurosurgical centres in the United Kingdom.

OBJECTIVE: To evaluate the use of microvascular decompression (MVD) for the treatment of hemifacial spasm (HFS). METHODS: Eighty three patients with HFS who underwent MVD via a suboccipital craniectomy are presented. RESULTS: Seventy two out of seventy eight patients available for follow up remained free of any spasms at a mean follow up period of eight years. Two patients continued to have minor intermittent muscle twitches and three had recurrence of HFS. One patient's operation was not completed. Twenty had a transient complication and eight were left with permanent postoperative deficits, the commonest being unilateral sensorineural deafness. Seventy one patients declared themselves satisfied with the procedure. A causative vessel was found on the root exit zone of the seventh cranial nerve in 81 patients. CONCLUSION: The procedure seems to provide lasting relief for most patients. The correct operative technique is essential if complications are to be avoided.

Partial complementary deoxyribonucleic acid cloning of equine relaxin messenger ribonucleic acid, and its localization within the equine placenta.

To determine the site of relaxin gene expression in equine placentae, a set of degenerate oligonucleotide primers was made according to the published amino acid sequence of the A- and B-chain of equine relaxin (eRXN). Total cellular RNA (tcRNA) from equine placentae at about 120 and 300 days of pregnancy was subjected to reverse transcriptase-polymerase chain reaction (RT-PCR) with use of these primers. A single amplification product of approximately 430 bp was detected in each case by agarose gel electrophoresis. The PCR product was ligated into Bluescript plasmid and sequenced to confirm the identity of the clone as an eRXN cDNA fragment. Nucleic acid sequence analysis revealed a 428-bp eRXN cDNA fragment encoding for parts of the A- and B-chain and the connecting peptide (109 residues). Northern analysis of tcRNA from placentae of 120 and 300 days of pregnancy was carried out with use of antisense digoxigenin-labeled cRNA generated from the cDNA clone, and a single transcript of approximately 1 kb was detected. In situ hybridization on placental tissue at 120 and uteroplacental tissue at 300 days of pregnancy indicated that only the fetal trophoblastic cells expressed eRXN mRNA transcripts. The identity of these cells was confirmed by their positive staining with an antibody specific for equine trophoblast (cell surface) protein. Relaxin peptide was also detected immunohistochemically in samples of the same placental tissues. This is the first report of the nucleic acid sequence of eRXN. The study identified fetal trophoblast cells as the site of eRXN mRNA expression and protein secretion in the equine placenta.

Rapid increase in relaxin gene expression in early pregnancy in the pig.

Relaxin mRNA concentrations in porcine corpora lutea were examined during the peri-implantation period and throughout pregnancy using Northern and slot blot analysis. Total RNA was extracted from corpora lutea obtained from pigs of known breeding dates and pregnancy was confirmed by embryo recovery. A 32P-labelled porcine relaxin cDNA probe identified the 1.0 kilobase relaxin transcript. Slot blots were subsequently used to quantify relaxin mRNA concentrations. Relaxin mRNA was detectable in the corpus luteum of the regular cycle and was also present at similar low levels in corpora lutea of days 10, 11 and 12 of pregnancy. In corpora lutea from day 16 of pregnancy onwards 100-fold greater quantities of relaxin mRNA were observed. The intensity remained similar in samples between days 16 and 102 of pregnancy. These studies indicate that elevated relaxin gene expression commences very early in pregnancy and is first detectable in the peri-implantation period.