Twisted topology and Bipolar Non-Hermitian Skin Effect induced by long-range asymmetric coupling

We investigate the twisted topology of the complex eigenspectrum of a one-dimensional non-Hermitian system under the influence of long-range unidirectional coupling. Unlike the complex energy spectrum of the conventional Hatano-Nelson chain, which takes the form of a single loop with a topological winding index of a definite sign, the introduction of long-range unidirectional hopping results in the creation of multiple twisted loops. These twisted loops exhibit opposite signs of the topological winding index, which correlate to alternating clockwise and anticlockwise energy windings. The simultaneous presence of both signs of the winding index translates into a bipolar non-Hermitian skin effect (NHSE), which challenges the conventional wisdom that the NHSE localization is dependent on the direction of the dominant nearest-neighbor interactions. In this bipolar NHSE, the exponents of the complex energy eigenvectors corresponding to clockwise and anti-clockwise windings, lie inside and outside of the complex unit circle, respectively. Interestingly, at the intersections of oppositely oriented energy loops where the sign of the topological winding index flips, the energy becomes real-valued, leading to a suppression of the NHSE. This marks the emergence of Bloch-like contact points, where both the bipolar NHSE and the traditional NHSE vanish. Based on the non-Hermitian model we provide analytical insights into the effects of long-range unidirectional coupling to the winding topology of its complex energy spectra and their broader implications for the field of condensed matter physics.Comment: 11 pages, 3 figure

Impedance responses and size-dependent resonances in topolectrical circuits via the method of images

Resonances in an electric circuit occur when capacitive and inductive components are present together. Such resonances appear in admittance measurements depending on the circuit's parameters and the driving AC frequency. In this study, we analyze the impedance characteristics of nontrivial topolectrical circuits such as one- and two-dimensional Su-Schrieffer-Heeger circuits and reveal that size-dependent anomalous impedance resonances inevitably arise in finite $LC$ circuits. Through the \textit{method of images}, we study how resonance modes in a multi-dimensional circuit array can be nontrivially modified by the reflection and interference of current from the structure and boundaries of the lattice. We derive analytic expressions for the impedance across two corner nodes of various lattice networks with homogeneous and heterogeneous circuit elements. We also derive the irregular dependency of the impedance resonance on the lattice size, and provide integral and dimensionally-reduced expressions for the impedance in three dimensions and above.Comment: 24 pages, 10 figure

The Saudi National Mental Health Survey: Survey instrument and field procedures

ObjectivesTo present an overview of the survey and field procedures developed for the Saudi National Mental Health Survey (SNMHS).MethodsThe SNMHS is a face- to- face community epidemiological survey of DSM- IV mental disorders in a nationally representative sample of the household population in the Kingdom of Saudi Arabia (KSA) (n = 4,004). The SNMHS was implemented as part of the WHO World Mental Health (WMH) Survey Initiative. WMH carries out coordinated psychiatric epidemiological surveys in countries throughout the world using standardized procedures designed to provide valid cross- national comparative data on prevalence and correlates of common mental disorders. However, these procedures need to be adapted to the unique experiences in each country. We focus here on the adaptations made for the SNMHS.ResultsModifications were needed to several interview sections and expansions were needed to address issues of special policy importance in KSA. Several special field implementation challenges also had to be addressed because of the need for female interviewers to travel with male escorts and for respondents to be interviewed by interviewers of the same gender.ConclusionsThoughtful revisions led to a high- quality field implementation in the SNMHS.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/162792/2/mpr1830.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/162792/1/mpr1830_am.pd

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

The James Webb Space Telescope Mission

Twenty-six years ago a small committee report, building on earlier studies, expounded a compelling and poetic vision for the future of astronomy, calling for an infrared-optimized space telescope with an aperture of at least $4m$. With the support of their governments in the US, Europe, and Canada, 20,000 people realized that vision as the $6.5m$ James Webb Space Telescope. A generation of astronomers will celebrate their accomplishments for the life of the mission, potentially as long as 20 years, and beyond. This report and the scientific discoveries that follow are extended thank-you notes to the 20,000 team members. The telescope is working perfectly, with much better image quality than expected. In this and accompanying papers, we give a brief history, describe the observatory, outline its objectives and current observing program, and discuss the inventions and people who made it possible. We cite detailed reports on the design and the measured performance on orbit.Comment: Accepted by PASP for the special issue on The James Webb Space Telescope Overview, 29 pages, 4 figure

Phonon transport in two-dimensional silicon thin film: influence of film width and boundary conditions on temperature distribution

Radiative phonon transport in two-dimensional silicon thin film is considered and equivalent equilibrium temperature is analyzed for different boundary conditions at the film faces. The influence of the film thickness on phonon transport is also examined and limiting film thickness for two-dimensional phonon transport is demonstrated. It is found that the two-dimensional phonon transport reduces to one-dimensional transport for the film width more than or equal to the twice of the thickness of the silicon film. Equivalent equilibrium temperature predicted, agrees well with the previous findings