Emergent symmetry in a low-dimensional superconductor on the edge of Mottness

Upon cooling, condensed-matter systems typically transition into states of lower symmetry. The converse-i.e., the emergence of higher symmetry at lower temperatures-is extremely rare. In this work, we show how an unusually isotropic magnetoresistance in the highly anisotropic, one-dimensional conductor Li0.9Mo6O17 and its temperature dependence can be interpreted as a renormalization group (RG) flow toward a so-called separatrix. This approach is equivalent to an emergent symmetry in the system. The existence of two distinct ground states, Mott insulator and superconductor, can then be traced back to two opposing RG trajectories. By establishing a direct link between quantum field theory and an experimentally measurable quantity, we uncover a path through which emergent symmetry might be identified in other candidate materials.

Secondary prevention in diabetic and nondiabetic coronary heart disease patients: Insights from the German subset of the hospital arm of the EUROASPIRE IV and V surveys

BACKGROUND

Patients with coronary heart disease (CHD) with and without diabetes mellitus have an increased risk of recurrent events requiring multifactorial secondary prevention of cardiovascular risk factors. We compared prevalences of cardiovascular risk factors and its determinants including lifestyle, pharmacotherapy and diabetes mellitus among patients with chronic CHD examined within the fourth and fifth EUROASPIRE surveys (EA-IV, 2012-13; and EA-V, 2016-17) in Germany.

METHODS

The EA initiative iteratively conducts European-wide multicenter surveys investigating the quality of secondary prevention in chronic CHD patients aged 18 to 79 years. The data collection in Germany was performed during a comprehensive baseline visit at study centers in Würzburg (EA-IV, EA-V), Halle (EA-V), and Tübingen (EA-V).

RESULTS

384 EA-V participants (median age 69.0 years, 81.3% male) and 536 EA-IV participants (median age 68.7 years, 82.3% male) were examined. Comparing EA-IV and EA-V, no relevant differences in risk factor prevalence and lifestyle changes were observed with the exception of lower LDL cholesterol levels in EA-V. Prevalence of unrecognized diabetes was significantly lower in EA-V as compared to EA-IV (11.8% vs. 19.6%) while the proportion of prediabetes was similarly high in the remaining population (62.1% vs. 61.0%).

CONCLUSION

Between 2012 and 2017, a modest decrease in LDL cholesterol levels was observed, while no differences in blood pressure control and body weight were apparent in chronic CHD patients in Germany. Although the prevalence of unrecognized diabetes decreased in the later study period, the proportion of normoglycemic patients was low. As pharmacotherapy appeared fairly well implemented, stronger efforts towards lifestyle interventions, mental health programs and cardiac rehabilitation might help to improve risk factor profiles in chronic CHD patients.

Negative Thermal Expansion in the Plateau State of a Magnetically Frustrated Spinel

We report on negative thermal expansion (NTE) in the high-field, half-magnetization plateau phase of the frustrated magnetic insulator CdCr_{2}O_{4}. Using dilatometry, we precisely map the phase diagram at fields of up to 30 T and identify a strong NTE associated with the collinear half-magnetization plateau for B>27  T. The resulting phase diagram is compared with a microscopic theory for spin-lattice coupling, and the origin of the NTE is identified as a large negative change in magnetization with temperature, coming from a nearly localized band of spin excitations in the plateau phase. These results provide useful guidelines for the discovery of new NTE materials.

Electron-Hole Tunneling Revealed by Quantum Oscillations in the Nodal-Line Semimetal HfSiS

We report a study of quantum oscillations in the high-field magnetoresistance of the nodal-line semimetal HfSiS. In the presence of a magnetic field up to 31 T parallel to the c axis, we observe quantum oscillations originating both from orbits of individual electron and hole pockets, and from magnetic breakdown between these pockets. In particular, we reveal a breakdown orbit enclosing one electron and one hole pocket in the form of a "figure of eight," which is a manifestation of Klein tunneling in momentum space, although in a regime of partial transmission due to the finite separation between the pockets. The observed very strong dependence of the oscillation amplitude on the field angle and the cyclotron masses of the orbits are in agreement with the theoretical predictions for this novel tunneling phenomenon.

The world's smallest capacitive dilatometer, for high-resolution thermal expansion and magnetostriction in high magnetic fields

For the characterization of novel quantum phases of matter, it is often required to study materials under multi-extreme conditions, in particular down to very low temperatures and in very high magnetic fields. We developed the world's smallest high-resolution capacitive dilatometer suitable for temperatures down to 10 mK and usage in high magnetic fields up to 37.5 T. Despite the extreme miniaturization, the capacitive dilatometer can resolve length changes down to 0.01 Å. This is an unprecedented resolution in a capacitive dilatometer of this compact size. Many cryogenic devices have limited space. Due to the extremely reduced cell size (3 cm³, 12 g), implementation or new applications in many of these sample space lacking devices are now possible. As an important example, the minute device can now be rotated in any standard cryostat, including dilution refrigerators or the commercial physical property measurement system. The present super compact design provides also for high resolution thermal expansion and magnetostriction measurements in a 15.2 mm diameter tube, enabling its use in the 32 mm bore, 37.5 T Bitter magnet at the High Field Magnet Laboratory in Nijmegen down to a temperature of 300 mK.

Linear Magnetoresistance in a Quasifree Two-Dimensional Electron Gas in an Ultrahigh Mobility GaAs Quantum Well

We report a high-field magnetotransport study of an ultrahigh mobility (μ[over ¯]≈25×10^{6}  cm^{2} V^{-1} s^{-1}) n-type GaAs quantum well. We observe a strikingly large linear magnetoresistance (LMR) up to 33 T with a magnitude of order 10^{5}% onto which quantum oscillations become superimposed in the quantum Hall regime at low temperature. LMR is very often invoked as evidence for exotic quasiparticles in new materials such as the topological semimetals, though its origin remains controversial. The observation of such a LMR in the "simplest system"-with a free electronlike band structure and a nearly defect-free environment-excludes most of the possible exotic explanations for the appearance of a LMR and rather points to density fluctuations as the primary origin of the phenomenon. Both, the featureless LMR at high T and the quantum oscillations at low T follow the empirical resistance rule which states that the longitudinal conductance is directly related to the derivative of the transversal (Hall) conductance multiplied by the magnetic field and a constant factor α that remains unchanged over the entire temperature range. Only at low temperatures, small deviations from this resistance rule are observed beyond ν=1 that likely originate from a different transport mechanism for the composite fermions.

[Survey regarding the treatment of malignant middle cerebral artery infarction in German hospitals]

BACKGROUND

There are a variety of intensive care therapies in the treatment of malignant middle cerebral artery infarction (MMI) besides hemicraniectomy (HC), the only treatment with proven efficacy. It is, however, not known how HC and conservative treatments are utilized in German hospitals, Furthermore, data on the care-situation of patients with MMI in Germany is scarce.

METHODS

An anonymous questionnaire was sent to 297 neurological and 133 neurosurgical hospitals in Germany.

RESULTS

The Response rate was 24,7%. Most respondents indicated personal experience in the treatment of MMI (83,3%). HC is usually performed early on site (83,3%). Indication to HC is confirmed on a high level of hierarchy and profession using clinical and radiological criteria in 78,2% of hospitals. Inherent standardized treatment protocols are established in 70,8% of hospitals. Patients are treated on an intensive care unit in 74,5% of hospitals after DHC and in 42,5% of hospitals under non-surgical treatment. Intracranial pressure monitoring is not performed on a regular basis. Differing opinions were observed concerning diagnosis and treatment of MMI without recognizable consensus.

CONCLUSION

Basically, structural requirements for the treatment of MMI exist in the participating hospitals. Heterogeneity in the treatment of MMI is striking. The implementation of treatment protocols and adherence to guidelines are desirable steps to optimize treatment.

Three-month stroke outcome: the European Registers of Stroke (EROS) investigators

BACKGROUND

Contemporaneous data on variations in outcome after first-ever-lifetime stroke between European populations are lacking. We compared differences in case fatality rates, functional outcome, and living conditions 3 months after stroke within the European Registers of Stroke Collaboration.

METHODS

Population-based stroke registers were established in France (Dijon), Italy (Sesto Fiorentino), Lithuania (Kaunas), the United Kingdom (London), Spain (Menorca), and Poland (Warsaw). All patients with first-ever-lifetime stroke of all age groups from the source population (1,087,048 inhabitants) were included. Data collection took part between 2004 and 2006. The study investigated population variations in outcome at 3 months (death, institutionalization due to stroke, or Barthel Index below 12 points) using multivariable logistic regression analyses adjusted for age, sex, stroke severity, stroke subtype, and comorbidities.

RESULTS

A total of 2,034 patients with first-ever-lifetime stroke were included. Median age was 73 years, 52% were female. The mean weighted cumulative risk of death was 21.8% (95% confidence interval 20.0 to 23.6) with a 3-fold variation across populations. The weighted proportion of poor outcome was 41.3% (95% confidence interval 39.0 to 43.7) with a 2-fold variation across populations.

CONCLUSION

More than 40% of patients had a poor outcome, defined as being dead, dependent, or institutionalized 3 months after stroke. Substantial outcome variations were found between populations that were explained by case mix variables in this analysis, yet a trend toward a higher risk of poor outcome was present in Kaunas.

Microwave zero-resistance states in a bilayer electron system

Magnetotransport measurements on a high-mobility electron bilayer system formed in a wide GaAs quantum well reveal vanishing dissipative resistance under continuous microwave irradiation. Profound zero-resistance states (ZRS) appear even in the presence of additional intersubband scattering of electrons. We study the dependence of photoresistance on frequency, microwave power, and temperature. Experimental results are compared with a theory demonstrating that the conditions for absolute negative resistivity correlate with the appearance of ZRS.

[General automated documentation and performance data on the surgical intensive care unit--the theoretical concept of the Regensburg Surgical University Clinic]

Documentation is becoming an ever more time-consuming task due to the need to document increasing ICU productivity, quality management and cost-assessment data. Automatic charting of on-line monitoring data, therapeutic-device data, clinical laboratory data, microbiological data, radiological data and other data reduces documentation time significantly. One of the major advantages of PDMS in the SICU is the quality of the documentation and with better documentation the therapist is able to improve the quality of care. Not only the physician, but also nurses and physiotherapists are able to benefit from these advantages. Our concept, SURGIC (Department of Surgery, University Regensburg, Germany, Intensive Care), stands for: widely automated documentation, work orientation, including physicians, nurses' and physiotherapists' tasks, minimal dataset for simple use and perfect overview, costs assessments, scientific dataset, SICU PDMS as a part of the clinical information system, and professional support by a software-house is necessary.