Nonreciprocal Phonon Propagation in a Metallic Chiral Magnet.

The phonon magnetochiral effect (MChE) is the nonreciprocal acoustic and thermal transports of phonons caused by the simultaneous breaking of the mirror and time-reversal symmetries. So far, the phonon MChE has been observed only in a ferrimagnetic insulator Cu_{2}OSeO_{3}, where the nonreciprocal response disappears above the Curie temperature of 58 K. Here, we study the nonreciprocal acoustic properties of a room-temperature ferromagnet Co_{9}Zn_{9}Mn_{2} for unveiling the phonon MChE close to room temperature. Surprisingly, the nonreciprocity in this metallic compound is enhanced at higher temperatures and observed up to 250 K. This clear contrast between insulating Cu_{2}OSeO_{3} and metallic Co_{9}Zn_{9}Mn_{2} suggests that metallic magnets have a mechanism to enhance the nonreciprocity at higher temperatures. From the ultrasound and microwave-spectroscopy experiments, we conclude that the magnitude of the phonon MChE of Co_{9}Zn_{9}Mn_{2} mostly depends on the Gilbert damping, which increases at low temperatures and hinders the magnon-phonon hybridization. Our results suggest that the phonon nonreciprocity could be further enhanced by engineering the magnon band of materials.

Magnetically Hidden State on the Ground Floor of the Magnetic Devil's Staircase.

We investigated the low-temperature and high-field thermodynamic and ultrasonic properties of SrCu_{2}(BO_{3})_{2}, which exhibits various plateaux in its magnetization curve above 27 T, called a magnetic Devil's staircase. The results of the present study confirm that magnetic crystallization, the first step of the staircase, occurs above 27 T as a first-order transition accompanied by a sharp singularity in heat capacity C_{p} and a kink in the elastic constant. In addition, we observe a thermodynamic anomaly at lower fields around 26 T, which has not been previously detected by any magnetic probes. At low temperatures, this magnetically hidden state has a large entropy and does not exhibit Schottky-type gapped behavior, which suggests the existence of low-energy collective excitations. Based on our observations and theoretical predictions, we propose that magnetic quadrupoles form a spin-nematic state around 26 T as a hidden state on the ground floor of the magnetic Devil's staircase.

Evaluating the impact of de-escalating antimicrobial therapy in burn patients: a retrospective cohort study.

Antimicrobials should be used appropriately to minimise the risk of resistant strains arising in association with overuse. De-escalation of antimicrobial therapy is one strategy used to ensure appropriate use, but its safety and efficacy in burn patients are unclear. The aim of this study was to evaluate the safety and efficacy of de-escalation therapy for treating infections in burn patients. This retrospective cohort study investigated patients admitted to our intensive care unit with burns and treated for infection between October 1, 2013, and September 30, 2020. Patients were classified into a de-escalation group (Group D) comprising patients treated with empiric antimicrobial therapy followed by de-escalation and a non-de-escalation group (Group ND) comprising patients who did not undergo de-escalation. Characteristics and outcomes were compared between groups. Forty-three patients met the inclusion criteria, including 15 patients in Group D and 28 patients in Group ND. Bacterial species commonly detected in these patients were Corynebacterium spp. (17.3%), Pseudomonas aeruginosa (16.1%), and Staphylococcus aureus (9.6%) . No inter-group difference was seen in 28-day mortality (6.7% vs 21.4%, p =0.391). Multidrug-resistant strains were detected significantly less frequently in Group D (13.0%) than in Group ND (26.1%, p =0.003). De-escalation was associated with use of two or more antimicrobials as empiric antimicrobial therapy. As the use of de-escalation in infection treatment did not impact 28-day mortality, de-escalation might be safe for treating infections in burn patients.

Anisotropic Fully Gapped Superconductivity Possibly Mediated by Charge Fluctuations in a Nondimeric Organic Complex.

We investigate low-temperature electronic properties of the nondimeric organic superconductor ß^{''}-(ET)_{4}[(H_{3}O)Ga(C_{2}O_{4})_{3}]PhNO_{2}. By examining ultrasonic properties, charge disproportionation (CD) without magnetic field dependence is detected below T_{CD}∼8 K just above the superconducting critical temperature T_{c}∼6 K. From quantum oscillations in high fields, we find variation in the Fermi surface and mass enhancement induced by the CD. Heat capacity studies elucidate that the superconducting gap function is fully gapped in the Fermi surface, but anisotropic with fourfold symmetry. We point out that the pairing mechanism of the superconductivity is possibly dominated by charge fluctuations.

Quantum Critical Dynamics of a Heisenberg-Ising Chain in a Longitudinal Field: Many-Body Strings versus Fractional Excitations.

We report a high-resolution terahertz spectroscopic study of quantum spin dynamics in the antiferromagnetic Heisenberg-Ising spin-chain compound BaCo_{2}V_{2}O_{8} as a function of temperature and longitudinal magnetic field. Confined spinon excitations are observed in an antiferromagnetic phase below T_{N}≃5.5 K. In a field-induced gapless phase above B_{c}=3.8 T, we identify many-body string excitations as well as low-energy fractional psinon or antipsinon excitations by comparing to Bethe ansatz calculations. In the vicinity of B_{c}, the high-energy string excitations are found to have a dominant contribution to the spin dynamics as compared with the fractional excitations.

Unconventional Field-Induced Spin Gap in an S=1/2 Chiral Staggered Chain.

We investigate the low-temperature magnetic properties of the molecule-based chiral spin chain [Cu(pym)(H_{2}O)_{4}]SiF_{6}·H_{2}O (pym=pyrimidine). Electron-spin resonance, magnetometry and heat capacity measurements reveal the presence of staggered g tensors, a rich low-temperature excitation spectrum, a staggered susceptibility, and a spin gap that opens on the application of a magnetic field. These phenomena are reminiscent of those previously observed in nonchiral staggered chains, which are explicable within the sine-Gordon quantum-field theory. In the present case, however, although the sine-Gordon model accounts well for the form of the temperature dependence of the heat capacity, the size of the gap and its measured linear field dependence do not fit with the sine-Gordon theory as it stands. We propose that the differences arise due to additional terms in the Hamiltonian resulting from the chiral structure of [Cu(pym)(H_{2}O)_{4}]SiF_{6}·H_{2}O, particularly a uniform Dzyaloshinskii-Moriya coupling and a fourfold periodic staggered field.

Quantum Criticality of an Ising-like Spin-1/2 Antiferromagnetic Chain in a Transverse Magnetic Field.

We report on magnetization, sound-velocity, and magnetocaloric-effect measurements of the Ising-like spin-1/2 antiferromagnetic chain system BaCo_{2}V_{2}O_{8} as a function of temperature down to 1.3 K and an applied transverse magnetic field up to 60 T. While across the Néel temperature of T_{N}∼5 K anomalies in magnetization and sound velocity confirm the antiferromagnetic ordering transition, at the lowest temperature the field-dependent measurements reveal a sharp softening of sound velocity v(B) and a clear minimum of temperature T(B) at B_{⊥}^{c,3D}=21.4 T, indicating the suppression of the antiferromagnetic order. At higher fields, the T(B) curve shows a broad minimum at B_{⊥}^{c}=40 T, accompanied by a broad minimum in the sound velocity and a saturationlike magnetization. These features signal a quantum phase transition, which is further characterized by the divergent behavior of the Grüneisen parameter Γ_{B}∝(B-B_{⊥}^{c})^{-1}. By contrast, around the critical field, the Grüneisen parameter converges as temperature decreases, pointing to a quantum critical point of the one-dimensional transverse-field Ising model.

Radio frequency electrical resistance measurement under destructive pulsed magnetic fields.

We developed a resistance measurement using radio frequency reflection to investigate the electrical transport characteristics under destructive pulsed magnetic fields above 100 T. A sample stage consisting of a homemade flexible printed circuit reduced the noise caused by the induced voltage from the pulsed magnetic fields, improving the accuracy of the measurements of the reflected waves. From the obtained reflectance data, the absolute value of the magnetoresistance was successfully determined by analyzing the phase with admittance charts. These developments enable more accurate and comprehensive measurements of electrical resistance in pulsed magnetic fields.

Unveiling new quantum phases in the Shastry-Sutherland compound SrCu2(BO3)2 up to the saturation magnetic field.

Under magnetic fields, quantum magnets often undergo exotic phase transitions with various kinds of order. The discovery of a sequence of fractional magnetization plateaus in the Shastry-Sutherland compound SrCu2(BO3)2 has played a central role in the high-field research on quantum materials, but so far this system could only be probed up to half the saturation value of the magnetization. Here, we report the first experimental and theoretical investigation of this compound up to the saturation magnetic field of 140 T and beyond. Using ultrasound and magnetostriction techniques combined with extensive tensor-network calculations (iPEPS), several spin-supersolid phases are revealed between the 1/2 plateau and saturation (1/1 plateau). Quite remarkably, the sound velocity of the 1/2 plateau exhibits a drastic decrease of -50%, related to the tetragonal-to-orthorhombic instability of the checkerboard-type magnon crystal. The unveiled nature of this paradigmatic quantum system is a new milestone for exploring exotic quantum states of matter emerging in extreme conditions.

Dimensional reduction and incommensurate dynamic correlations in the [Formula: see text] triangular-lattice antiferromagnet Ca3ReO5Cl2.

The observation of spinon excitations in the [Formula: see text] triangular antiferromagnet Ca3ReO5Cl2 reveals a quasi-one-dimensional (1D) nature of magnetic correlations, in spite of the nominally 2D magnetic structure. This phenomenon is known as frustration-induced dimensional reduction. Here, we present high-field electron spin resonance spectroscopy and magnetization studies of Ca3ReO5Cl2, allowing us not only to refine spin-Hamiltonian parameters, but also to investigate peculiarities of its low-energy spin dynamics. We argue that the presence of the uniform Dzyaloshinskii-Moriya interaction (DMI) shifts the spinon continuum in momentum space and, as a result, opens a zero-field gap at the Γ point. We observed this gap directly. The shift is found to be consistent with the structural modulation in the ordered state, suggesting this material as a perfect model triangular-lattice system, where a pure DMI-spiral ground state can be realized.

Thermal transport and strong mass renormalization in NiCl2-4SC(NH2)2.

Several quantum paramagnets exhibit magnetic-field-induced quantum phase transitions to an antiferromagnetic state that exists for H c1 ≤ H ≤ H c2. For some of these compounds, there is a significant asymmetry between the low- and high-field transitions. We present specific heat and thermal conductivity measurements in NiCl2-4SC(NH2)2, together with calculations which show that the asymmetry is caused by a strong mass renormalization due to quantum fluctuations for H ≤ H c1 that are absent for H ≥ H c2. We argue that the enigmatic lack of asymmetry in thermal conductivity is due to a concomitant renormalization of the impurity scattering.

Higher magnetic-field generation by a mass-loaded single-turn coil.

Single-turn coil (STC) technique is a convenient way to generate ultrahigh magnetic fields of more than 100 T. During the field generation, the STC explosively destructs outward due to the Maxwell stress and Joule heating. Unfortunately, the STC does not work at its full potential because it has already expanded when the maximum magnetic field is reached. Here, we propose an easy way to delay the expansion and increase the maximum field by using a mass-loaded STC. By loading clay on the STC, the field profile drastically changes, and the maximum field increases by 4%. This method offers access to higher magnetic fields for physical property measurements.

Nuclear magnetic resonance measurements in dynamically controlled field pulse.

We present the architecture of the versatile nuclear magnetic resonance (NMR) spectrometer with software-defined radio technology and its application to the dynamically controlled pulsed magnetic fields. The pulse-field technology is the only solution to access magnetic fields greater than 50 T, but the NMR experiment in the pulsed magnetic field was difficult because of the continuously changing field strength. The dynamically controlled field pulse allows us to perform NMR experiment in a quasi-steady field condition by creating a constant magnetic field for a short time around the peak of the field pulse. We confirmed the reproducibility of the field pulses using the NMR spectroscopy as a high precision magnetometer. With the highly reproducible field strength, we succeeded in measuring the nuclear spin-lattice relaxation rate 1/T1, which had never been measured by the pulse-field NMR experiment without dynamic field control. We also implement the NMR spectrum measurement with both the frequency-sweep and field-sweep modes and discuss the appropriate choices of these modes depending on the magnetic properties of the sample to be measured. This development, with further improvement at a long-duration field pulse, will innovate the microscopic measurement in extremely high magnetic fields.

High-field phase diagram of Ni3V2O8studied by specific heat and magnetocaloric effect measurements.

TheH-Tphase diagram of Ni3V2O8is very rich and remains puzzling in a high magnetic field range. Through the state-of-the-art specific heat measurement in pulsed high field to 35 T and magnetocaloric effect measurement up to 45 T, we successfully construct the high-field phase diagram of Ni3V2O8for fields applied along thebaxis. The phase boundaries are corrected for previous results by magnetization and magneto-optical measurements. The resulting phase diagram shows that the high temperature incommensurate (HTI) phase develops well to high fields and low temperatures. In addition to the early reported C', C, low temperature incommensurate (LTI) and HTI phases, we explore a new magnetic ordered phase called HF1 in fields of 10-30 T. A multicritical point is also observed at 6 K and 8 T. Furthermore, the specific heat data reveal enhancements of the anomalies at ∼4 K, probably associated with a strong spin-lattice coupling in this frustrated multiferroic material.

Ultrasound measurement technique for the single-turn-coil magnets.

Ultrasound is a powerful means to study numerous phenomena of condensed-matter physics as acoustic waves couple strongly to structural, magnetic, orbital, and charge degrees of freedom. In this paper, we present such a technique combined with single-turn coils (STCs) that generate magnetic fields beyond 100 T with the typical pulse duration of 6 µs. As a benchmark of this technique, the ultrasound results for MnCr2S4, Cu6[Si6O18]·6H2O, and liquid oxygen are shown. The resolution for the relative sound-velocity change in the STC is estimated as Δv/v ∼ 10-3, which is sufficient to study various field-induced phase transitions and critical phenomena.

Field-induced Bose-Einstein condensation of triplons up to 8 K in Sr3Cr2O8.

Single crystals of the spin dimer system Sr(3)Cr(2)O(8) have been grown for the first time. Magnetization, heat capacity, and magnetocaloric effect data up to 65 T reveal magnetic order between applied fields of H(c1) approximately 30.4 T and H(c2) approximately 62 T. This field-induced order persists up to T(c)(max) approximately 8 K at H approximately 44 T, the highest observed in any quantum magnet where H(c2) is experimentally accessible. We fit the temperature-field phase diagram boundary close to H(c1) using the expression T(c) = A(H-H(c1))(nu). The exponent nu = 0.65(2), obtained at temperatures much smaller than T(c)(max), is that of the 3D Bose-Einstein condensate (BEC) universality class. This finding strongly suggests that Sr(3)Cr(2)O(8) is a new realization of a triplon BEC where the universal regimes corresponding to both H(c1) and H(c2) are accessible at (4)He temperatures.

Viscosity measurements in pulsed magnetic fields by using a quartz-crystal microbalance.

Viscosity measurements in combination with pulsed magnetic fields are developed by use of a quartz-crystal microbalance (QCM). When the QCM is immersed in liquid, the resonant frequency, f0, and the quality factor, Q, of the QCM change depending on (ρη)0.5, where ρ is the mass density and η the viscosity. During the magnetic-field pulse, f0 and Q of the QCM are simultaneously measured by a ringdown technique. The typical resolution of (ρη)0.5 is 0.5%. As a benchmark, the viscosity of liquid oxygen is measured up to 55 T.

Molecular cloning and characterization of a novel human STE20-like kinase, hSLK.

We have cloned a human counterpart to a guinea pig STE20-like kinase cDNA, designated human SLK (hSLK), from a human lung carcinomatous cell line A549 cDNA library. hSLK cDNA encodes a novel 1204 amino acid serine/threonine kinase for which the kinase domain located at the N-terminus shares considerable homology to that of the STE20-like kinase family. The C-terminal domain of hSLK includes both the coiled-coil structure and four Pro/Glu/Ser/Thr-rich (PEST) sequences, but not the GTPase-binding domain (GBD) that is characteristic of the p21-activated kinase (PAK) family, polyproline consensus binding sites, or the Leu-rich domain seen in the group I germinal center kinases (GCKs). Northern blot analysis indicated that hSLK was ubiquitously expressed. hSLK overexpressed in COS-7 cells phosphorylates itself as well as myelin basic protein used as a substrate. On the other hand, hSLK cannot activate any of the three well-characterized mitogen-activated protein kinase MAPK (ERK, JNK/SAPK and p38) pathways. Moreover, hSLK kinase activity is not upregulated by constitutive active forms of GTPases (RasV12, RacV12 and Cdc42V12). These structural and functional properties indicate that hSLK should be considered to be a new member of group II GCKs.

Molecular cloning of 25-hydroxyvitamin D-3 24-hydroxylase (Cyp-24) from mouse kidney: its inducibility by vitamin D-3.

A cDNA encoding a 25-hydroxyvitamin D-3 24-hydroxylase, Cyp-24, has been isolated from mouse kidney cDNA library by hybridization screening. Mouse Cyp-24, coding for 514 amino acid residues, shared 82.1 and 94.7% amino acid identity with human and rat CYP24s, respectively. Among mouse organs examined, Cyp-24 mRNA could be detected in the kidney. When mice were treated with vitamin D-3, Cyp-24 mRNA was induced in the kidney.

Mouse cytochrome P-450 linked ferredoxin: its cDNA cloning and inducibility by dibutyryladenosine 3',5'-cyclic monophosphate and forskolin.

Two full-length cDNAs (F1-1 and F41-1) complementary to mouse kidney mRNA coding for cytochrome P-450 (P450) linked ferredoxin were isolated and completely sequenced. The coding sequences between F1-1 and F41-1 were identical. However, the 3' untranslated regions of F1-1 and F41-1 were 228 and 27 bases long due to the presence of alternative polyadenylation sites, respectively. The deduced amino acid sequence of mouse cytochrome P-450 linked ferredoxin showed 92.5, 75.0, 71.2 and 71.0% identities with those of rat, human, pig and bovine cytochrome P-450 linked ferredoxin, respectively. The cytochrome P-450 linked ferredoxin mRNA was detected in adrenal, kidney and ovary among the organs examined. The treatment of Y-1 cells with dibutyryladenosine 3',5'-cyclic monophosphate or forskolin induced the transcript of cytochrome P-450 linked ferredoxin mRNA.