Mapping topological order in coordinate space

The organization of the electrons in the ground state is classified by means of topological invariants, defined as global properties of the wavefunction. Here we address the Chern number of a two-dimensional insulator and we show that the corresponding topological order can be mapped by means of a "topological marker", defined in \r-space, and which may vary in different regions of the same sample. Notably, this applies equally well to periodic and open boundary conditions. Simulations over a model Hamiltonian validate our theory

Orbital Magnetization in Insulators: Bulk vs. Surface

The orbital magnetic moment of a finite piece of matter is expressed in terms of the one-body density matrix as a simple trace. We address a macroscopic system, insulating in the bulk, and we show that its orbital moment is the sum of a bulk term and a surface term, both extensive. The latter only occurs when the transverse conductivity is nonzero and owes to conducting surface states. Simulations on a model Hamiltonian validate our theory

How disorder affects the Berry-phase anomalous Hall conductivity: A reciprocal-space analysis

Under the terms of the Creative Commons Attribution License 3.0 (CC-BY).The anomalous Hall conductivity of “dirty” ferromagnetic metals is dominated by a Berry-phase contribution which is usually interpreted as an intrinsic property of the Bloch electrons in the pristine crystal. In this work we evaluate the geometric Hall current directly from the electronic ground state with disorder and then recast it as an integral over the crystalline Brillouin zone. The integrand is an effective k-space Berry curvature, obtained by unfolding the Berry curvature from the small Brillouin zone of a large supercell. Therein, disorder yields a net extrinsic Hall contribution, which we argue is related to the elusive side-jump effect. As an example, we unfold the first-principles Berry curvature of an ordered Fe3Co alloy from the original fcc-lattice Brillouin zone onto a bcc-lattice zone with four times the volume. Comparison with the virtual-crystal Berry curvature clearly reveals the symmetry-breaking effects of the substitutional Co atoms.This work was supported by Grants No. MAT2012-33720 from the Ministerio de Economía y Competitividad (Spain), No. CIG-303602 from the European Commission, and ONR Grant No. N00014-12-1-1041 (USA).Peer Reviewe

Distinctive diffusive properties of swimming planktonic copepods in different environmental conditions

Suspensions of small planktonic copepods represent a special category in the realm of active matter, as their size falls within the range of colloids, while their motion is so complex that it cannot be rationalized according to basic models of self-propelled particles. Indeed, the wide range of individual variability and swimming patterns resemble the behaviour of much larger animals. By analysing hundreds of three-dimensional trajectories of the planktonic copepod Clausocalanus furcatus, we investigate the possibility of detecting how the motion of this species is affected by different external conditions, such as the presence of food and the effect of gravity. While this goal is hardly achievable by direct inspection of single organism trajectories, we show that this is possible by focussing on simple average metrics commonly used to characterize colloidal suspensions, such as the mean square displacement and the dynamic correlation functions. We find that the presence of food leads to the onset of a clear localization that separates a short-time ballistic from a long-time diffusive regime. Such a benchmark reflects the tendency of C. furcatus to remain temporally feeding in a limited space and disappears when food is absent. Localization is clearly evident in the horizontal plane, but is negligible in the vertical direction, due to the effect of gravity. Our results suggest that simple average descriptors may provide concise and useful information on the swimming properties of planktonic copepods, even though single organism behaviour is strongly heterogeneous

Linestrength ratio spectroscopy as a new primary thermometer for redefined Kelvin dissemination

Experimental methods for primary thermometry, after Kelvin unit redefinition on May 2019, become based on a known value of the Boltzmann constant rather than by measuring temperature with respect to a reference point. In this frame, we propose Linestrength Ratio Thermometry (LRT) as a candidate method for primary thermometry in the 9-700 K temperature range. Temperature accuracies at the ppm level are prospected for LRT applied to optical transitions of the CO molecule in the range 80-700 K and of a rare-earth-doped crystal in the 9-100 K one. Future implementations of this technique can contribute to measure the calibration- discrepancies in the ITS-90 metrological scale of thermodynamic temperature which can have a measurable impact in applications ranging from fundamental-physics to meteorology and climatology

Hydroxytyrosol, an olive oil phenolic compound, inhibits cyclooxygenase-2 transcription in phorbol--ester-treated human mocytes

Introduction: Inflammation plays a critical role in atherosclerotic plaque development and instability. Cyclooxygenase(COX)-2 is a key mediator of inflammation. It is up-regulated in activated monocytes and macrophages of human atherosclerotic lesions. The extra-virgin olive oil is a source of bioactive compounds which can be responsible of Mediterranean diet athero-protective effect. Aim of the study was to examine the effects of hydroxytyrosol (HT), a phenolic compound from olives and extra-virgin olive oil, on COX-2 expression in phorbol-ester stimulated monocytic-macrophagic cells and to explore the mechanisms involved. Methods: U937 monocytoid cells were pre-treated with HT (0-10 micromol/L) for 60 min before stimulation with 20 nmol/L phorbol myristate acetate (PMA) in RPMI 1640 medium with 5%SFB for 20 h. Cell supernatants were then tested for the release of PGE2 by EIA kit and cell extracts were analysed for COX-2 expression by Western blot analysis. COX-2 mRNA was investigated by semi-quantitative RT-PCR and COX-2 promoter activity was assessed by transient transfection of full length and partially deleted or mutagenized COX-2 promoter constructs. Results: Stimulation of U937 cells with 20 nmol/L PMA for 20 h caused a marked increase in the production of prostaglandin(PG) E2. This effect was inhibited by 1 micromol/L HT both in PMA-treated U937 (by about 25%) and even more in U937 derived-macrophages (> 40%). Pre-treatment of U937 cells with 0.1-10 micromol/L HT reduced PMA-induced COX-2 protein and mRNA in a concentration dependent manner with a 30% reduction already at 1 mmol/L (p<0.01). HT inhibitory effect was isoform specific given that the constitutive COX-1 expression was not affected. In transient transfection assay, HT reduced PMA-induced COX-2 promoter activity of full length construct. Transient transfections utilizing COX-2 promoter deletion constructs and COX-2 promoter constructs, in which specific enhancer elements were mutagenized, indicated that the effects of HT were, at least in part, mediated via NF-kB elements. Conclusions: HT inhibited PGE2 release and COX-2 expression in phorbol-ester-stimulated monocytes and U937-derived macrophages. These data provide new insight into the anti-inflammatory properties of HT and may contribute to explain the cardiovascular protection by specific components of Mediterranean diets

Totally percutaneous valve replacement for severe aortic regurgitation in a degenerating bioprosthesis

Recently, the feasibility and safety of percutaneous aortic valve replacement (PAVR) has been reported in the treatment of degenerative aortic valve stenosis in patients at high-risk for surgical aortic valve replacement (AVR).1 However, so far this therapy has been limited to patients with severe stenosis of the native valve. We report the case of a patient with severe aortic regurgitation owing to bioprosthesis dysfunction who was successfully treated by implantation of a CoreValve (CoreValve Inc, Irvine. Calif) prosthesis with a totally percutaneous approach

Day-surgery inguinal hernia repair in the elderly: single centre experience

BACKGROUND: Inguinal hernioplasty is well established as a day-surgery procedure, our purpose is to assess the safeness of this approach in elderly patients. METHODS: A total of 292 inguinal hernioplasty were performed between June 2009 and February 2013. Patients were divided into 3 groups depending on the age and postoperative complications were compared in these groups. RESULTS: Despite of a large number of higher risk (ASA 3-4) patients and a higher rate of comorbidity in older patients, unplanned admission postoperative, symptoms and complications were comparable with those for the younger patients. CONCLUSIONS: Ambulatory surgery is feasible also in older patients. Age, comorbidity and higher ASA risk should not be a barrier to elective day surgery