A new mathematical approach to finding global solutions of the magnetic structure determination problem

Determination of magnetic structure is an important analytical procedure utilized in various fields ranging from fundamental condensed-matter physics and chemistry to advanced manufacturing. It is typically performed using a neutron diffraction technique; however, finding global solutions of the magnetic structure optimization problem represents a significant challenge. Generally, it is not possible to mathematically prove that the obtained magnetic structure is a truly global solution and that no solution exists when no acceptable structure is found. In this study, the global optimization technique called semidefinite relaxation of quadratic optimization, which has attracted much interest in the field of applied mathematics, is proposed to use as a new analytical method for the determination of magnetic structure, followed by the application of polarized neutron diffraction data. This mathematical approach allows avoiding spurious local solutions, decreasing the amount of time required to find a tentative solution and finding multiple solutions when they exist.

The nature of spin excitations in the one-third magnetization plateau phase of Ba3CoSb2O9

Magnetization plateaus in quantum magnets—where bosonic quasiparticles crystallize into emergent spin superlattices—are spectacular yet simple examples of collective quantum phenomena escaping classical description. While magnetization plateaus have been observed in a number of spin-1/2 antiferromagnets, the description of their magnetic excitations remains an open theoretical and experimental challenge. Here, we investigate the dynamical properties of the triangular-lattice spin-1/2 antiferromagnet Ba₃CoSb₂O₉ in its one-third magnetization plateau phase using a combination of nonlinear spin-wave theory and neutron scattering measurements. The agreement between our theoretical treatment and the experimental data demonstrates that magnons behave semiclassically in the plateau in spite of the purely quantum origin of the underlying magnetic structure. This allows for a quantitative determination of Ba₃CoSb₂O₉ exchange parameters. We discuss the implication of our results to the deviations from semiclassical behavior observed in zero-field spin dynamics of the same material and conclude they must have an intrinsic origin.

Frustrated magnetic materials attract significant interest because their properties can become dominated by quantum fluctuations. Here the authors show that excitations in the plateau phase of a quantum magnet can be understood semiclassically even though the ground state involves strong quantum effects.

Study protocol for the G-SPIRIT trial: a randomised, placebo-controlled, double-blinded phase III trial of granulocyte colony-stimulating factor-mediated neuroprotection for acute spinal cord injury

INTRODUCTION

Granulocyte colony-stimulating factor (G-CSF) is generally used for neutropaenia. Previous experimental studies revealed that G-CSF promoted neurological recovery after spinal cord injury (SCI). Next, we moved to early phase of clinical trials. In a phase I/IIa trial, no adverse events were observed. Next, we conducted a non-randomised, non-blinded, comparative trial, which suggested the efficacy of G-CSF for promoting neurological recovery. Based on those results, we are now performing a phase III trial.

METHODS AND ANALYSIS

The objective of this study is to evaluate the efficacy of G-CSF for acute SCI. The study design is a prospective, multicentre, randomised, double-blinded, placebo-controlled comparative study. The current trial includes cervical SCI (severity of American Spinal Injury Association (ASIA) Impairment Scale B/C) within 48 hours after injury. Patients are randomly assigned to G-CSF and placebo groups. The G-CSF group is administered 400 µg/m²/day×5 days of G-CSF in normal saline via intravenous infusion for 5 consecutive days. The placebo group is similarly administered a placebo. Our primary endpoint is changes in ASIA motor scores from baseline to 3 months. Each group includes 44 patients (88 total patients).

ETHICS AND DISSEMINATION

The study will be conducted according to the principles of the World Medical Association Declaration of Helsinki and in accordance with the Japanese Medical Research Involving Human Subjects Act and other guidelines, regulations and Acts. Results of the clinical study will be submitted to the head of the respective clinical study site as a report after conclusion of the clinical study by the sponsor-investigator. Even if the results are not favourable despite conducting the clinical study properly, the data will be published as a paper.

TRIAL REGISTRATION NUMBER

UMIN000018752.

Assessment of the risk of low bone mineral density in premenopausal Japanese female patients with systemic lupus erythematosus

Background

The aim of this study was to assess the relationships between clinical parameters and bone mineral density (BMD) in Japanese female patients with systemic lupus erythematosus (SLE).

Methods

A total of female 136 SLE patients without menopause were retrospectively assessed to identify associations between age, disease duration, body mass index (BMI), glucocorticoid usage and disease activity and BMD based on the treatment with or without bisphosphonate. There were 71 patients treated with bisphosphonate (bisphosphonate group) and 65 patients without (non-bisphosphonate group). We evaluated the impact of age, disease duration, BMI, serologic SLE markers, glucocorticoid use on BMD of the anterior-posterior (AP) and lateral lumbar spine, total hip and femoral neck using univariate and multivariate linear regression analyses of both bisphosphonate and non-bisphosphonate groups.

Results

Multivariate linear regression analyses showed that in non-bisphosphonate group disease duration was negatively associated with BMD of AP spine and femoral neck, whereas in bisphosphonate group these negative associations were not present. However, multivariate linear regression analyses showed a significant relationship between BMI and BMD of the AP spine, femoral neck and total hip, regardless of bisphosphonate treatment.

Conclusions

Bisphosphonate treatment eliminated the negative relationships between disease duration and the BMD of the spine and hip. AP spine and hip BMD in patients with SLE depend on BMI, regardless of bisphosphonate use. SLE serologic markers and glucocorticoid use were not negatively associated with generalized bone loss. SLE patients with low BMI have a high risk of generalized bone loss, and should be assessed and treated to prevent osteoporosis even before menopause.

Magnetic Frustration Driven by Itinerancy in Spinel CoV2O4

Localized spins and itinerant electrons rarely coexist in geometrically-frustrated spinel lattices. They exhibit a complex interplay between localized spins and itinerant electrons. In this paper, we study the origin of the unusual spin structure of the spinel CoV₂O₄, which stands at the crossover from insulating to itinerant behavior using the first principle calculation and neutron diffraction measurement. In contrast to the expected paramagnetism, localized spins supported by enhanced exchange couplings are frustrated by the effects of delocalized electrons. This frustration produces a non-collinear spin state even without orbital orderings and may be responsible for macroscopic spin-glass behavior. Competing phases can be uncovered by external perturbations such as pressure or magnetic field, which enhances the frustration.

The age, breed and sex pattern of diagnosis for veterinary care in insured cats in Japan

OBJECTIVES

To estimate the annual prevalence of different diagnostic categories by age, breed and sex in insured cats in Japan for which veterinary care claims had been made, and to identify if there is a pattern in these host factors.

MATERIALS AND METHODS

Data from 48,187 cats insured for veterinary care in Japan in the period from April 2012 to March 2013 comprising 26,003 males and 22,184 females were analysed to calculate the annual prevalence of 18 diagnostic categories of disease by age, breed and sex.

RESULTS

The prevalence was highest for urinary system disorders (12·2% for males and 10·0% for females), followed by digestive disorders (11·6% for males and 10·7% for females) and dermatological diseases (8·7% for males and 9·0% for females). The male cats had a higher prevalence than female cats for most diagnostic categories. The prevalence of cardiovascular, urinary, endocrine and neoplastic disorders increased with age; infectious and parasitic diseases had high prevalence at young ages, and the prevalence of respiratory, musculoskeletal disorders and injuries had bimodal peaks. Dermatological disorders had a high prevalence at all ages. A large variation in prevalence was observed between breeds for otic, dermatological, dental and cardiovascular disorders.

CLINICAL SIGNIFICANCE

The findings can be used to increase awareness of patterns of health disorders in different categories of cat.

Live imaging of extracellular signal-regulated kinase and protein kinase A activities during thrombus formation in mice expressing biosensors based on Förster resonance energy transfer

Essentials Spatiotemporal regulation of protein kinases during thrombus formation remains elusive in vivo. Activities of protein kinases were live imaged in mouse platelets at laser-ablated arterioles. Protein kinase A was activated in the dislodging platelets at the downstream side of the thrombus. Extracellular signal-regulated kinase was activated at the core of contracting platelet aggregates.

SUMMARY

Background The dynamic features of thrombus formation have been visualized by conventional video widefield microscopy or confocal microscopy in live mice. However, owing to technical limitations, the precise spatiotemporal regulation of intracellular signaling molecule activities, which have been extensively studied in vitro, remains elusive in vivo. Objectives To visualize, by the use of two-photon excitation microscopy of transgenic mice expressing Förster resonance energy transfer (FRET) biosensors for extracellular signal-regulated kinase (ERK) and protein kinase A (PKA), ERK and PKA activities during thrombus formation in laser-injured subcutaneous arterioles. Results When a core of densely packed platelets had developed, ERK activity was increased from the basal region close to the injured arterioles. PKA was activated at the downstream side of an unstable shell overlaying the core of platelets. Intravenous administration of a MEK inhibitor, PD0325901, suppressed platelet tethering and dislodged platelet aggregates, indicating that ERK activity is indispensable for both initiation and maintenance of the thrombus. A cAMP analog, dbcAMP, inhibited platelet tethering but failed to dislodge the preformed platelet aggregates, suggesting that PKA can antagonize thrombus formation only in the early phase. Conclusion In vivo imaging of transgenic mice expressing FRET biosensors will open a new opportunity to visualize the spatiotemporal changes in signaling molecule activities not only during thrombus formation but also in other hematologic disorders.

Spin glass behavior in frustrated quantum spin system CuAl2O4 with a possible orbital liquid state

CuAl₂O₄ is a normal spinel oxide having quantum spin, S  =  1/2 for Cu²⁺. It is a rather unique feature that the Cu²⁺ ions of CuAl₂O₄ sit at a tetrahedral position, not like the usual octahedral position for many oxides. At low temperatures, it exhibits all the thermodynamic evidence of a quantum spin glass. For example, the polycrystalline CuAl₂O₄ shows a cusp centered at ~2 K in the low-field dc magnetization data and a clear frequency dependence in the ac magnetic susceptibility while it displays logarithmic relaxation behavior in a time dependence of the magnetization. At the same time, there is a peak at ~2.3 K in the heat capacity, which shifts towards a higher temperature with magnetic fields. On the other hand, there is no evidence of new superlattice peaks in the high-resolution neutron powder diffraction data when cooled from 40 to 0.4 K. This implies that there is no long-ranged magnetic order down to 0.4 K, thus confirming a spin glass-like ground state for CuAl₂O₄. Interestingly, there is no sign of structural distortion either although Cu²⁺ is a Jahn-Teller active ion. Thus, we claim that an orbital liquid state is the most likely ground state in CuAl₂O₄. Of further interest, it also exhibits a large frustration parameter, f  =  |θ _CW/T _m| ~ 67, one of the largest values reported for spinel oxides. Our observations suggest that CuAl₂O₄ should be a rare example of a frustrated quantum spin glass with a good candidate for an orbital liquid state.