Non-magnetic ion site disorder effects on the quantum magnetism of a spin-1/2 equilateral triangular lattice antiferromagnet.

With the motivation to study how non-magnetic ion site disorder affects the quantum magnetism of Ba3CoSb2O9, a spin-1/2 equilateral triangular lattice antiferromagnet, we performed DC and AC susceptibility, specific heat, elastic and inelastic neutron scattering measurements on single crystalline samples of Ba2.87Sr0.13CoSb2O9with Sr doping on non-magnetic Ba2+ion sites. The results show that Ba2.87Sr0.13CoSb2O9exhibits (i) a two-step magnetic transition at 2.7 K and 3.3 K, respectively; (ii) a possible canted 120 degree spin structure at zero field with reduced ordered moment as 1.24µB/Co; (iii) a series of spin state transitions for bothH∥ab-plane andH∥c-axis. ForH∥ab-plane, the magnetization plateau feature related to the up-up-down phase is significantly suppressed; (iv) an inelastic neutron scattering spectrum with only one gapped mode at zero field, which splits to one gapless and one gapped mode at 9 T. All these features are distinctly different from those observed for the parent compound Ba3CoSb2O9, which demonstrates that the non-magnetic ion site disorder (the Sr doping) plays a complex role on the magnetic properties beyond the conventionally expected randomization of the exchange interactions. We propose the additional effects including the enhancement of quantum spin fluctuations and introduction of a possible spatial anisotropy through the local structural distortions.

Survival of itinerant excitations and quantum spin state transitions in YbMgGaO4 with chemical disorder.

A recent focus of quantum spin liquid (QSL) studies is how disorder/randomness in a QSL candidate affects its true magnetic ground state. The ultimate question is whether the QSL survives disorder or the disorder leads to a "spin-liquid-like" state, such as the proposed random-singlet (RS) state. Since disorder is a standard feature of most QSL candidates, this question represents a major challenge for QSL candidates. YbMgGaO4, a triangular lattice antiferromagnet with effective spin-1/2 Yb3+ions, is an ideal system to address this question, since it shows no long-range magnetic ordering with Mg/Ga site disorder. Despite the intensive study, it remains unresolved as to whether YbMgGaO4 is a QSL or in the RS state. Here, through ultralow-temperature thermal conductivity and magnetic torque measurements, plus specific heat and DC magnetization data, we observed a residual κ0/T term and series of quantum spin state transitions in the zero temperature limit for YbMgGaO4. These observations strongly suggest that a QSL state with itinerant excitations and quantum spin fluctuations survives disorder in YbMgGaO4.

Dual Orbital Degeneracy Lifting in a Strongly Correlated Electron System.

The local structure of NaTiSi_{2}O_{6} is examined across its Ti-dimerization orbital-assisted Peierls transition at 210 K. An atomic pair distribution function approach evidences local symmetry breaking preexisting far above the transition. The analysis unravels that, on warming, the dimers evolve into a short range orbital degeneracy lifted (ODL) state of dual orbital character, persisting up to at least 490 K. The ODL state is correlated over the length scale spanning ∼6 sites of the Ti zigzag chains. Results imply that the ODL phenomenology extends to strongly correlated electron systems.

Magnetic ordering in the Ising antiferromagnetic pyrochlore Nd2ScNbO7.

The question of structural disorder and its effects on magnetism is relevant to a number of spin liquid candidate materials. Although commonly thought of as a route to spin glass behaviour, here we describe a system in which the structural disorder results in long-range antiferromagnetic order due to local symmetry breaking. Nd2ScNbO7is shown to have a dispersionless gapped excitation observed in other neodymium pyrochlores belowTN= 0.37 K through polarized and inelastic neutron scattering. However the dispersing spin waves are not observed. This excited mode is shown to occur in only 14(2)% of the neodymium ions through spectroscopy and is consistent with total scattering measurements as well as the magnitude of the dynamic moment 0.26(2)µB. The remaining magnetic species order completely into the all-in all-out Ising antiferromagnetic structure. This can be seen as a result of local symmetry breaking due disordered Sc+3and Nb+5ions about theA-site. From this work, it has been established thatB-site disorder restores the dipole-like behaviour of the Nd+3ions compared to the Nd2B2O7parent series.

Orbital competition of Mn3+ and V3+ ions in Mn1+x V2-x O4.

The structural and magnetic properties of Mn1+x V2-x O4 (0 < x ⩽ 1) have been investigated by the heat capacity, magnetization, x-ray diffraction and neutron diffraction measurements, and a phase diagram of temperature versus composition was built up. For x ⩽ 0.3, a cubic-to-tetragonal (c > a) phase transition was observed. For x > 0.3, the system maintained the tetragonal lattice. Although the collinear and noncollinear magnetic transitions of V3+ ions were obtained in all compositions, the canting angles between the V3+ ions decreased with Mn3+-doping, and the ordering of the Mn3+ ions was only observed as x > 0.4. In order to study the dynamics of the ground state, the first principles simulation was applied to analyze not only the orbital effects of Mn2+, Mn3+, and V3+ ions, but also the related exchange energies.

Dynamical ground state in the XY pyrochlore Yb2GaSbO7.

The magnetic ground state of the pyrochlore Yb2GaSbO7 has remained an enigma for nearly a decade. The persistent spin fluctuations observed by muon spin relaxation measurements at low temperatures have not been adequately explained for this material using existing theories for quantum magnetism. Here we report on the synthesis and characterisation of Yb2GaSbO7 to elucidate the central physics at play. Through DC and AC magnetic susceptibility, heat capacity, and neutron scattering experiments, we observe evidence for a dynamical ground state that makes Yb2GaSbO7 a promising candidate for disorder-induced spin-liquid or spin-singlet behaviour. This state is quite fragile, being tuned to a splayed ferromagnet in a modest magnetic field µ0Hc∼1.5T.

Possible itinerant excitations and quantum spin state transitions in the effective spin-1/2 triangular-lattice antiferromagnet Na2BaCo(PO4)2.

The most fascinating feature of certain two-dimensional (2D) gapless quantum spin liquid (QSL) is that their spinon excitations behave like the fermionic carriers of a paramagnetic metal. The spinon Fermi surface is then expected to produce a linear increase of the thermal conductivity with temperature that should manifest via a residual value (κ0/T) in the zero-temperature limit. However, this linear in T behavior has been reported for very few QSL candidates. Here, we studied the ultralow-temperature thermal conductivity of an effective spin-1/2 triangular QSL candidate Na2BaCo(PO4)2, which has an antiferromagnetic order at very low temperature (TN ~ 148 mK), and observed a finite κ0/T extrapolated from the data above TN. Moreover, while approaching zero temperature, it exhibits series of quantum spin state transitions with applied field along the c axis. These observations indicate that Na2BaCo(PO4)2 possibly behaves as a gapless QSL with itinerant spin excitations above TN and its strong quantum spin fluctuations persist below TN.

Unraveling the Topological Phase of ZrTe_{5} via Magnetoinfrared Spectroscopy.

For materials near the phase boundary between weak and strong topological insulators (TIs), their band topology depends on the band alignment, with the inverted (normal) band corresponding to the strong (weak) TI phase. Here, taking the anisotropic transition-metal pentatelluride ZrTe_{5} as an example, we show that the band inversion manifests itself as a second extremum (band gap) in the layer stacking direction, which can be probed experimentally via magnetoinfrared spectroscopy. Specifically, we find that the band anisotropy of ZrTe_{5} features a slow dispersion in the layer stacking direction, along with an additional set of optical transitions from a band gap next to the Brillouin zone center. Our work identifies ZrTe_{5} as a strong TI at liquid helium temperature and provides a new perspective in determining band inversion in layered topological materials.

[Effects of dexmedetomidine on cerebral oxygen saturation and postoperative revival period in elderly patients with ovarian cancer].

Objective: To observe the effects of dexmedetomidine on cerebral oxygen saturation and postoperative recovery in elderly patients with ovarian cancer. Methods: Sixty elderly patients with ovarian cancer were randomly divided into two groups. Both groups were given total intravenous anesthesia. Patients in group D were given a loading dosage of dexmedetomidine 0.5 µg/kg, followed by continuous infusion 0.2 µg·kg(-1)·h(-1) until 30 minutes before the end of operation. Group C were given normal saline at the same time. The cerebral oxygen saturation was observed and recorded before anaesthesia (T0), an hour after operation (T1), the end of operation (T2) and 30 min after tracheal extubation (T3). The time of extubation and adverse reactions such as restlessness, shivering and respiratory inhibition were observed in both groups. Results: There was no significant difference in cerebral oxygen saturation between the two groups at different time points (P>0.05), and the degree of restlessness and its incidence in group D were lower than those in group C, and the adverse reactions such as shivering were lower (P<0.05). Conclusion: Dexmedetomidine has no obvious effect on cerebral oxygen saturation in elderly patients with ovarian cancer. It can effectively prevent and reduce postoperative restlessness, does not affect recovery time, and has fewer adverse reactions.

A study on related factors of hemodynamic depression in carotid artery stenting.

OBJECTIVE: To investigate the pathogenesis and related factors of carotid artery stenting (CAS) related to hemodynamic depression (HD). PATIENTS AND METHODS: 433 CAS patients were admitted to our hospital and were selected from Jan 2013 to Jun 2016. We set up the HD diagnostic criteria for CAS and observed the whole morphology of vessels to classify carotid atherosclerotic plaques. We analyzed cerebral angiography and placed temporary cardiac pacemaker via femoral vein in order to prepare carotid artery stenting. We determined the general situation of HD after CAS according to the results. RESULTS: 38 patients received temporary placement of cardiac temporary pacemakers, and 241 patients (59.80%) developed HD. 403 patients were divided into HD group and non HD group and results suggested there was no significant difference between the two groups except for diabetes (p>0.05). Also, bilateral carotid stenting was performed in 26 patients (6.45%), and the HD group was significantly higher than that in non HD group (p<0.05). HD group had 31 MACCE cases, and non HD group had 2 MACCE cases. There was no occurrence of adverse cardiovascular events in this study. CONCLUSIONS: Cardiac temporary pacemaker may be one of the effective approaches to improve HD after CAS and reduce perioperative MACCE.

Author Correction: The nature of spin excitations in the one-third magnetization plateau phase of Ba3CoSb2O9.

The original version of this Article omitted the following from the Acknowledgements: 'J. Ma's primary affiliation is Shanghai Jiao Tong University.' This has been corrected in both the PDF and HTML versions of the Article.

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.

Tunable Quantum Spin Liquidity in the 1/6th-Filled Breathing Kagome Lattice.

We present measurements on a series of materials, Li_{2}In_{1-x}Sc_{x}Mo_{3}O_{8}, that can be described as a 1/6th-filled breathing kagome lattice. Substituting Sc for In generates chemical pressure which alters the breathing parameter nonmonotonically. Muon spin rotation experiments show that this chemical pressure tunes the system from antiferromagnetic long range order to a quantum spin liquid phase. A strong correlation with the breathing parameter implies that it is the dominant parameter controlling the level of magnetic frustration, with increased kagome symmetry generating the quantum spin liquid phase. Magnetic susceptibility measurements suggest that this is related to distinct types of charge order induced by changes in lattice symmetry, in line with the theory of Chen et al. [Phys. Rev. B 93, 245134 (2016)PRBMDO2469-995010.1103/PhysRevB.93.245134]. The specific heat for samples at intermediate Sc concentration, which have the minimum breathing parameter, show consistency with the predicted U(1) quantum spin liquid.

Field-Driven Quantum Criticality in the Spinel Magnet ZnCr_{2}Se_{4}.

We report detailed dc and ac magnetic susceptibilities, specific heat, and thermal conductivity measurements on the frustrated magnet ZnCr_{2}Se_{4}. At low temperatures, with an increasing magnetic field, this spinel material goes through a series of spin state transitions from the helix spin state to the spiral spin state and then to the fully polarized state. Our results indicate a direct quantum phase transition from the spiral spin state to the fully polarized state. As the system approaches the quantum criticality, we find strong quantum fluctuations of the spins with behaviors such as an unconventional T^{2}-dependent specific heat and temperature-independent mean free path for the thermal transport. We complete the full phase diagram of ZnCr_{2}Se_{4} under the external magnetic field and propose the possibility of frustrated quantum criticality with extended densities of critical modes to account for the unusual low-energy excitations in the vicinity of the criticality. Our results reveal that ZnCr_{2}Se_{4} is a rare example of a 3D magnet exhibiting a field-driven quantum criticality with unconventional properties.

The protective effect of lidocaine on lipopolysaccharide-induced acute lung injury in rats through NF-κB and p38 MAPK signaling pathway and excessive inflammatory responses.

OBJECTIVE: Acute lung injury is a severe disease with a high rate of mortality, leading to more important illness. We aimed at exploring the protective role and potential mechanisms of lidocaine on lipopolysaccharide (LPS)-induced acute lung injury (ALI). MATERIALS AND METHODS: Sprague Dawley (SD) rats were randomly assigned to control group receiving 0.9% saline solution, LPS group treated with 4 mg/kg LPS i.p., LPS + lidocaine(treated with 4 mg/kg LPS i.p. followed by giving 1 mg/kg, 3 mg/kg, 5 mg/kg of lidocaine i.v.). Lung specimens and the bronchoalveolar lavage fluid (BALF) were collected for histopathological examination and biochemical analyze 12 h after LPS induction. The cytokines expression of TNF-α, IL-6 and MCP-1 was measured by ELISA. In addition, the malondialdehyde (MDA) content, the activities of total antioxidant capacity (T-AOC) and superoxide dismutase (SOD) in lung tissues were also detected using ELISA. The protein expressions of p38, p-p38, p65, p-p65 and IκB were analyzed by Western blot. RESULTS: The results indicated that after lidocaine treatment was able to decrease significantly wet-to-dry (W/D) ratio and ameliorate the histopathologic damage. Additionally, total protein content and the number of leukocytes in BALF significantly decreased. ELISA result indicated that the levels of TNF-α, IL-6 and MCP-1 in BALF were markedly suppressed. Meanwhile, the activities of T-AOC and SOD in lung tissues significantly increased, while the content of MDA significantly decreased after treatment with lidocaine. Moreover, Western blot suggested that lidocaine inhibited phosphorylation of NF-κB p65 and p38 MAPK. CONCLUSIONS: Therefore, lidocaine could ameliorate the LPS-induced lung injury via NF-κB/p38 MAPK signaling and excessive inflammatory responses, providing a potential for becoming the anti-inflammatory agent against lung injury.

Evidence for negative thermal expansion in the superconducting precursor phase SmFeAsO.

The fluorine-doped rare-earth iron oxypnictide series SmFeAsO1-x F x (0 [Formula: see text] 0.10) was investigated with high resolution powder x-ray scattering. In agreement with previous studies (Margadonna et al 2009 Phys. Rev. B. 79 014503), the parent compound SmFeAsO exhibits a tetragonal-to-orthorhombic structural distortion at [Formula: see text] = 130 K which is rapidly suppressed by [Formula: see text] 0.10 deep within the superconducting dome. The change in unit cell symmetry is followed by a previously unreported magnetoelastic distortion at 120 K. The temperature dependence of the thermal expansion coefficient [Formula: see text] reveals a rich phase diagram for SmFeAsO: (i) a global minimum at 125 K corresponds to the opening of a spin-density wave instability as measured by pump-probe femtosecond spectroscopy (Mertelj et al 2010 Phys. Rev. B 81 224504) whilst (ii) a global maximum at 110 K corresponds to magnetic ordering of the Sm and Fe sublattices as measured by magnetic x-ray scattering (Nandi et al 2011 Phys. Rev. B 84 055419). At much lower temperatures than [Formula: see text], SmFeAsO exhibits a significant negative thermal expansion on the order of -40 ppm · K-1 in contrast to the behaviour of other rare-earth oxypnictides such as PrFeAsO (Kimber et al 2008 Phys. Rev. B 78 140503) and the actinide oxypnictide NpFeAsO (Klimczuk et al 2012 Phys. Rev. B 85 174506) where the onset of [Formula: see text] 0 only appears in the vicinity of magnetic ordering. Correlating this feature with the temperature and doping dependence of the resistivity and the unit cell parameters, we interpret the negative thermal expansion as being indicative of the possible condensation of itinerant electrons accompanying the opening of a SDW gap, consistent with transport measurements (Tropeano et al 2009 Supercond. Sci. Technol. 22 034004).

Blood-derived amyloid-ß protein induces Alzheimer's disease pathologies.

The amyloid-ß protein (Aß) protein plays a pivotal role in the pathogenesis of Alzheimer's disease (AD). It is believed that Aß deposited in the brain originates from the brain tissue itself. However, Aß is generated in both brain and peripheral tissues. Whether circulating Aß contributes to brain AD-type pathologies remains largely unknown. In this study, using a model of parabiosis between APPswe/PS1dE9 transgenic AD mice and their wild-type littermates, we observed that the human Aß originated from transgenic AD model mice entered the circulation and accumulated in the brains of wild-type mice, and formed cerebral amyloid angiopathy and Aß plaques after a 12-month period of parabiosis. AD-type pathologies related to the Aß accumulation including tau hyperphosphorylation, neurodegeneration, neuroinflammation and microhemorrhage were found in the brains of the parabiotic wild-type mice. More importantly, hippocampal CA1 long-term potentiation was markedly impaired in parabiotic wild-type mice. To the best of our knowledge, our study is the first to reveal that blood-derived Aß can enter the brain, form the Aß-related pathologies and induce functional deficits of neurons. Our study provides novel insight into AD pathogenesis and provides evidence that supports the development of therapies for AD by targeting Aß metabolism in both the brain and the periphery.

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.

[Clinical application of oxycodone combined with dexmedetomidine in percutaneous ultrasound-guided radiofrequency ablation of hepatocellular carcinomas].

Objective: To explore the effects of oxycodone combined with dexmedetomidine in percutaneous ultrasound-guided radiofrequency ablation of hepatocellular carcinomas. Methods: Sixty patients who underwent percutaneous ultrasound-guided radiofrequency ablation of hepatocellular carcinomas were randomly divided into fentanyl group (group A) and oxycodone group( group B), with 30 patients in each group. Patients in group A were injected with fentanyl (2 µg/kg), and patients in group B were injected with oxycodone (0.2 mg/kg). All the patients were injected with dexmedetomidine, with a loading dose of 0.5 µg/kg for 10 minutes and a continuous infusion rate of 0.2 µg·kg(-1)·h(-1) until the end of the operation. The changes of heart rate (HR), mean arterial pressure (MAP), pulse oxygen saturation (SPO(2)) and bispectral index (BIS) were monitored at different time points: time when patients entering the operating room (T0), the beginning of operation (T1), 10 minutes after operation (T2), the end of operation (T3), 15 minutes after the end of operation (T4). The incidence of side effects (nausea and vomiting, respiratory depression and body movements) was assessed. The visual analogue scale (VAS) scores were also recorded at T0, T3 and an hour postoperatively. Results: Five patients of Group A had the body movements during the operation, and it was improved after injecting with fentanyl 2 µg/kg. Compared with T0, HR in two groups decreased significantly at T2 (P<0.05). At each time point, the difference of MAP, HR, SPO(2) and BIS was not statistically significant in two groups. The incidence of Nausea and vomiting, body movements was lower in group B than that in group A(P<0.05). The VAS scores were lower in group B than that in group A at T3 and an hour postoperatively (P<0.05). Conclusion: The combination of oxycodone and dexmedetomidine can be used safely and effectively in percutaneous ultrasound-guided radiofrequency ablation of hepatocellular carcinomas, and it shows more effective analgesia and less side-effects.