Magnetic-field-controlled spin fluctuations and quantum criticality in Sr3_3Ru2_2O7_7

When the transition temperature of a continuous phase transition is tuned to absolute zero, new ordered phases and physical behaviour emerge in the vicinity of the resulting quantum critical point. Sr$_3$Ru$_2$O$_7$ can be tuned through quantum criticality with magnetic field at low temperature. Near its critical field $B$$_c$ it displays the hallmark $T$-linear resistivity and a $T$log(1/$T$) electronic heat capacity behaviour of strange metals. However, these behaviours have not been related to any critical fluctuations. Here we use inelastic neutron scattering to reveal the presence of collective spin fluctuations whose relaxation time and strength show a nearly singular variation with magnetic field as $B$$_c$ is approached. The large increase in the electronic heat capacity and entropy near $B$$_c$ can be understood quantitatively in terms of the scattering of conduction electrons by these spin-fluctuations. On entering the spin-density-wave ordered phase present near $B$$_c$, the fluctuations become stronger suggesting that the order is stabilised through an “order-by-disorder” mechanism

Global patient outcomes after elective surgery: prospective cohort study in 27 low-, middle- and high-income countries.

BACKGROUND: As global initiatives increase patient access to surgical treatments, there remains a need to understand the adverse effects of surgery and define appropriate levels of perioperative care. METHODS: We designed a prospective international 7-day cohort study of outcomes following elective adult inpatient surgery in 27 countries. The primary outcome was in-hospital complications. Secondary outcomes were death following a complication (failure to rescue) and death in hospital. Process measures were admission to critical care immediately after surgery or to treat a complication and duration of hospital stay. A single definition of critical care was used for all countries. RESULTS: A total of 474 hospitals in 19 high-, 7 middle- and 1 low-income country were included in the primary analysis. Data included 44 814 patients with a median hospital stay of 4 (range 2-7) days. A total of 7508 patients (16.8%) developed one or more postoperative complication and 207 died (0.5%). The overall mortality among patients who developed complications was 2.8%. Mortality following complications ranged from 2.4% for pulmonary embolism to 43.9% for cardiac arrest. A total of 4360 (9.7%) patients were admitted to a critical care unit as routine immediately after surgery, of whom 2198 (50.4%) developed a complication, with 105 (2.4%) deaths. A total of 1233 patients (16.4%) were admitted to a critical care unit to treat complications, with 119 (9.7%) deaths. Despite lower baseline risk, outcomes were similar in low- and middle-income compared with high-income countries. CONCLUSIONS: Poor patient outcomes are common after inpatient surgery. Global initiatives to increase access to surgical treatments should also address the need for safe perioperative care. STUDY REGISTRATION: ISRCTN5181700

Sustainable development and technology transfer opportunities in the Sudan

We report an observation of two-dimensional incommensurate magnetic fluctuations in the layered metallic perovskite Sr3Ru2O7. The wave vectors where the magnetic fluctuations are strongest are different from those observed in the superconducting single layer ruthenate Sr2RuO4 and appear to be determined by Fermi surface nesting. No antiferromagnetic ordering is observed for temperatures down to 1.5 K. For temperatures Tgreater than or similar to20 K, the fluctuations become predominately ferromagnetic. Our inelastic neutron scattering measurements provide concrete evidence of the coexistence of competing interactions in Sr3Ru2O7 and of the low-energy scale of the fluctuations

Metamagnetic Transition and Low-Energy Spin Density Fluctuations in Sr₃Ru₂O₇

The magnetic properties of the bilayer ruthenate Sr3Ru2O7 as investigated by neutron scattering are reviewed. No long range magnetic order is observed down to 40 mK, but instead a metamagnetic transition which is induced by a moderate magnetic field at low temperatures. In zero field, the spectrum of the spin fluctuations reveals that at low temperature the magnetic correlations in this material are antiferromagnetic in nature. The wavevectors at which the signal is strongest are incommensurate and appear to be determined by Fermi surface nesting. The low energy scale of the fluctuations suggests that they are intimately related to the metamagnetic transition.</p