Magnetic and structural quantum phase transitions in CeCu6-xAux are independent

The heavy-fermion compound CeCu$_{6-x}$Au$_x$ has become a model system for unconventional magnetic quantum criticality. For small Au concentrations $0 \leq x < 0.16$, the compound undergoes a structural transition from orthorhombic to monoclinic crystal symmetry at a temperature $T_{s}$ with $T_{s} \rightarrow 0$ for $x \approx 0.15$. Antiferromagnetic order sets in close to $x \approx 0.1$. To shed light on the interplay between quantum critical magnetic and structural fluctuations we performed neutron-scattering and thermodynamic measurements on samples with $0 \leq x\leq 0.3$. The resulting phase diagram shows that the antiferromagnetic and monoclinic phase coexist in a tiny Au concentration range between $x\approx 0.1$ and $0.15$. The application of hydrostatic and chemical pressure allows to clearly separate the transitions from each other and to explore a possible effect of the structural transition on the magnetic quantum critical behavior. Our measurements demonstrate that at low temperatures the unconventional quantum criticality exclusively arises from magnetic fluctuations and is not affected by the monoclinic distortion.Comment: 5 pages, 3 figure

Divergent thermal expansion and Grüneisen ratio in a quadrupolar Kondo metal

We report on the low-temperature thermal expansion and magnetostriction of the single-impurity quadrupolar Kondo candidate Y1−xPrxIr2Zn20. In the dilute limit, we find a quadrupolar strain that possesses a singular dependence on temperature T, ɛu∼H2log(1/T), for a small but finite magnetic field H. Together with the previously reported anomalous specific heat C, this implies a quadrupolar Grüneisen ratio Γu=∂Tɛu/C∼H2/[T2log(1/T)] whose divergence for finite H is consistent with the scenario of a quadrupolar Kondo effect. In addition, we find a singular behavior of the isotropic strain ɛB in zero magnetic field resulting in a divergence of both the volume thermal expansion and the volume Grüneisen parameter. We speculate that this behavior might be also induced by putative Kondo correlations via elastic anharmonicities or static strain disorder

Frustrated magnet for adiabatic demagnetization cooling to milli-Kelvin temperatures

Generation of very low temperatures has been crucially important for applications and fundamental research, as low-temperature quantum coherence enables operation of quantum computers and formation of exotic quantum states, such as superfluidity and superconductivity. One of the major techniques to reach milli-Kelvin temperatures is adiabatic demagnetization refrigeration (ADR). This method uses almost non-interacting magnetic moments of paramagnetic salts where large distances suppress interactions between the magnetic ions. The large spatial separations are facilitated by water molecules, with a drawback of reduced stability of the material. Here, we show that an H$_2$O-free frustrated magnet KBaYb(BO$_3$)$_2$ can be ideal refrigerant for ADR, achieving at least 22\,mK upon demagnetization under adiabatic conditions. Compared to conventional refrigerants, KBaYb(BO$_3)_2$ does not degrade even under high temperatures and ultra-high vacuum conditions. Further, its frustrated magnetic network and structural randomness enable cooling to temperatures several times lower than the energy scale of magnetic interactions, which is the main limiting factor for the base temperature of conventional refrigerants.Comment: accepted for publication in Communications Material

A microstructured fiber with defined borosilicate regions to produce a radial micronozzle array for nanoelectrospray ionization

This work highlights the possibility of using microstructured fibres with predefined doped regions to produce functional microstructures at a fibre facet with differential chemical etching. A specially designed silica microstructured fibre (MSF) that possesses specific boron-doped silica regions was fabricated for the purpose of generating a radial micronozzle array. The MSF was drawn from a preform comprising pure silica capillaries surrounded by boron-doped silica rods. Different etching rates of the boron-doped and silica regions at the fiber facet produces raised nozzles where the silica capillaries were placed. Fabrication parameters were explored in relation to the fidelity and protrusion length of the nozzle. Using etching alone, the nozzle protrusion length was limited, and the inner diameter of the channels in the array is expanded. However with the addition of a protective water counter flow, nozzle protrusion is increased to 60 μm with a limited increase in hole diameter. The radial micronozzle array generated nine individual electrosprays which were characterized using spray current measurements and related to theoretical prediction. Signal enhancement for the higher charge state ions for two peptides showed a substantial signal enhancement compared to conventional emitter technology.Y. Fu, S. Morency, K. Bachus, D. Simon, T. Hutama, G. T. T. Gibson, Y. Messaddeq and R. D. Oleschu

Thermodynamic perspective on the field-induced behavior of α\alpha-RuCl3_3

Measurements of the magnetic Gr\"uneisen parameter ($\Gamma_B$) and specific heat on the Kitaev material candidate $\alpha$-RuCl$_3$ are used to access in-plane field- and temperature-dependence of the entropy up to 12 T and down to 1 K. No signatures corresponding to phase transitions are detected beyond the boundary of the magnetically ordered region, but only a shoulder-like anomaly in $\Gamma_B$, involving an entropy increment as small as $10^{-5} R\log 2$. These observations put into question the presence of a thermodynamic phase transition between the purported quantum spin liquid and the field-polarized state of $\alpha$-RuCl$_3$. We show theoretically that at low temperatures $\Gamma_B$ is sensitive to crossings in the lowest excitations within gapped phases, and identify the measured shoulder-like anomaly as being of such origin. Exact diagonalization calculations demonstrate that the shoulder-like anomaly can be reproduced in extended Kitaev models that gain proximity to an additional phase at finite field without entering it. We discuss manifestations of this proximity in other measurements.Comment: published version (incl. Supplemental Material

Relation between eating evoked by lateral hypothalamic stimulation and tail pinch in different rat strains

The similarity between the behaviors evoked by tail pinch (TP) and electrical stimulation of the lateral hypothalamus (ESLH) has been noted by many investigators. Evidence is presented for a possible inverse relationship between the probability that ESLH would evoke eating and the readiness to eat in response to TP in six different rat populations (High and Low lines of the LC1 and LC2 Hebrew University Strains, Sprague--Dawley, and Long--Evans). Discussion of these results emphasizes differences in intensity between ESLH and TP stimulation and differences in emotionality among rat populations.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/24047/1/0000296.pd

Characterization and Engineering Properties of Dry and Ponded Class-F Fly Ash

Characterization studies conducted on Class-F fly-ash specimens gathered from different producers in the southeastern United States confirm general trends reported for fly ash worldwide. Additional tests and detailed analyses explain the spread in specific gravity (interparticle porosity cenospheres), highlight the tendency to segregation and layering, and show marked ferromagnetism. Furthermore, data show that early diagenetic cementation—within days after wetting—hinders densification and produces a fabric that is prone to collapse. New procedures are specifically developed to diagnose and characterize early diagenesis, including (1) pH measurements as an indicator of diagenetic potential, (2) test protocols to assess early diagenesis using oedometer tests and shear-wave velocity, and (3) procedures to determine realizable unit weights as reference values for the analyses of contractive or dilative tendencies and instability. In the absence of early diagenetic cementation, dilative fly-ash behavior is expected in the upper ≈20  m under monotonic shear loading. Flow instability may follow the failure of the containment structure if the ponded ash is saturated and has experienced hindered densification

Efficacy of Dapagliflozin According to Geographic Location of Patients With Heart Failure

Background: Because clinical characteristics and prognosis vary by geographic region in patients with heart failure (HF), the response to treatment may also vary. A previous report suggested that the efficacy of sodium-glucose cotransporter-2 inhibitor efficacy in heart failure with reduced ejection fraction (HFrEF) may be modified by region. Objectives: The goal of this study was to examine the efficacy and safety of dapagliflozin in patients with HF according to geographic region. Methods: We conducted a patient-level pooled analysis of the DAPA-HF (Dapagliflozin and Prevention of Adverse Outcomes in Heart Failure) and DELIVER (Dapagliflozin Evaluation to Improve the Lives of Patients with Preserved Ejection Fraction Heart Failure) trials, which evaluated the effects of dapagliflozin in HFrEF and heart failure with mildly reduced ejection fraction (HFmrEF)/heart failure with preserved ejection fraction (HFpEF), respectively. The primary outcome was the composite of worsening HF or cardiovascular death. Results: Among 11,007 patients, 5,159 (46.9%) were enrolled in Europe, 1,528 (13.9%) in North America, 1,998 (18.2%) in South America, and 2,322 (21.1%) in Asia. The rate of the primary outcome (per 100 person-years) was higher in North America (13.9 [95% CI: 12.5-15.4]) than in other regions: Europe 10.8 (95% CI: 10.1-11.5), South America 10.0 (95% CI: 9.0-11.1), and Asia 10.5 (95% CI: 9.5-11.5). The benefit of dapagliflozin on the primary outcome was not modified by region: dapagliflozin vs placebo HR: Europe, 0.85 (95% CI: 0.75-0.96); North America, 0.75 (95% CI: 0.61-0.93); South America, 0.72 (95% CI: 0.58-0.89); and Asia, 0.74 (95% CI: 0.61-0.91) (P interaction = 0.40). This was the same when evaluated separately for HFrEF (P interaction = 0.39) and HFmrEF/HFpEF (P interaction = 0.84). Patients in North America discontinued randomized treatment more frequently than did those elsewhere (placebo discontinuation: 21.8% in North America vs 6.4% in South America), but discontinuation rates did not differ between placebo and dapagliflozin by region. Conclusions: The efficacy and safety of dapagliflozin were consistent across global regions despite geographic differences in patient characteristics, background treatment, and event rates.</p

Magnetic frustration in a metallic fcc lattice

Magnetic frustration in metals is scarce and hard to pinpoint, but exciting due to the possibility of the emergence of fascinating novel phases. The cubic intermetallic compound HoInCu$_4$ with all holmium atoms on an fcc lattice, exhibits partial magnetic frustration, yielding a ground state where half of the Ho moments remain without long-range order, as evidenced by our neutron scattering experiments. The substitution of In with Cd results in HoCdCu$_4$ in a full breakdown of magnetic frustration. Consequently we found a fully ordered magnetic structure in our neutron diffraction experiments. These findings are in agreement with the local energy scales and crystal electric field excitations, which we determined from specific heat and inelastic neutron scattering data. The electronic density of states for the itinerant bands acts as tuning parameter for the ratio between nearest-neighbor and next-nearest-neighbor interactions and thus for magnetic frustration