The band gap problem: the accuracy of the Wien2k code confronted

This paper is a continuation of our detailed study [Phys. Rev. B 86, 195106 (2012)] of the performance of the recently proposed modified Becke-Jonhson potential (mBJLDA) within the known Wien2k code. From the 41 semiconductors that we have considered in our previous paper to compute the band gap value, we selected 27 for which we found low temperature experimental data in order to pinpoint the relative situation of the newly proposed Wien2k(mBJLDA) method as compared to other methods in the literature. We found that the GWA gives the most accurate predictions. The Wien2k (mBJLDA) code is slightly less precise, in general. The Hybrid functionals are less accurate, on the overall. The GWA is definitely the most precise existing method nowadays. In 88% of the semiconductors considered the error was less than 10%. Both, the GWA and the mBJLDA potential, reproduce the band gap of 15 of the 27 semiconductors considered with a 5% error or less. An extra factor to be taken into account is the computational cost. If one would seek for precision without taking this factor into account, the GWA is the method to use. If one would prefer to sacrifice a little the precision obtained against the savings in computational cost, the empirical mBJLDA potential seems to be the appropriate method. We include a graph that compares directly the performance of the best three methods, according to our analysis, for each of the 27 semiconductors studied. The situation is encouraging but the problem is not yet a closed issue.Comment: 8 pages, 1 figur

Unstable and elusive superconductors

We briefly review earlier and report original experimental results in the context of metastable or possible superconducting materials. We show that applied electric field induces conducting state in Copper Chloride (CuCl) whose characteristics resemble behavior of sliding charge-density-wave(s) (CDW). We discuss whether the sliding CDW or collective transport of similar ordered charge phase(s) may account for the problem of "high-temperature superconductivity" observed in this and other materials, including Cadmium Sulfide (CdS), metal-ammonia solutions, polymers, amorphous carbon and tungsten oxides. We also discuss a local superconductivity that occurs at the surface of graphite and amorphous carbon under deposition of foreign atoms/molecules.Comment: Invited review article published in a special edition on Superconducting Materials in honor of the 95th birthday year of Ted Geballe, edited by M. B. Maple, J. Hirsch, and F. Marsigli

Design of a Broadband Amplifier for High Speed Applications

This paper provides comprehensive insight into the design approach followed for an amplifier dedicated to high speed base band signals. To demonstrate the methodology, an amplifier consisting of nine PHEMT cascode cells within a distributed amplifier topology was designed. The resulting frequency response is 40 GHz at the 3-dB point, and the output voltage for a 43 Gbps eye diagram is 7.3 Vpp at the chip terminal

Demographics and Outcomes of Pulmonary Hypertension Patients in United States Emergency Departments

Introduction: Pulmonary hypertension (PH) is a common, yet under-diagnosed, contributor to morbidity and mortality. Our objective was to characterize the prevalence of PH among adult patients presenting to United States (US) emergency departments (ED) and to identify demographic patterns and outcomes of PH patients in the ED.Methods: We analyzed the Nationwide Emergency Department Sample (NEDS) database, with a focus on ED patients aged 18 years and older, with any International Classification of Diseases, Clinical Modification (ICD)-9-CM or ICD-10-CM diagnosis code for PH from 2011 to 2015. The primary outcome was inpatient, all-cause mortality. The secondary outcomes were hospital admission rates and hospital length of stay (LOS).Results: From 2011 to 2015, in a sample of 121,503,743 ED visits, representing a weighted estimate of 545,500,486 US ED visits, patients with a diagnosis of PH accounted for 0.78% (95% confidence interval [CI], 0.75- 0.80%) of all US ED visits. Of the PH visits, 86.9% were admitted to the hospital, compared to 16.3% for all other ED visits (P <0.001). Likewise, hospital LOS and hospital-based mortality were higher in the PH group than for other ED patients (e.g., inpatient mortality 4.5% vs 2.6%, P < 0.001) with an adjusted odds ratio (aOR) of 1.34 (95% CI, 1.31–1.37). Age had the strongest association with mortality, with an aOR of 10.6 for PH patients over 80 years (95% CI, 10.06–11.22), compared to a reference of ages 18 to 30 years.Conclusion: In this nationally representative sample, presentations by patients with PH were relatively common, accounting for nearly 0.8% of US ED visits. Patients with PH were significantly more likely to be admitted to the hospital than all other patients, had longer hospital LOS, and increased risk of inpatient mortality

Nitrification-denitrification in WSP: a mechanism for permanent nitrogen removal in maturation ponds

A pilot-scale primary maturation pond was spiked with 15N-labelled ammonia (15NH4Cl) and 15N labelled nitrite (Na15NO2), in order to improve current understanding of the dynamics of inorganic nitrogen transformations and removal in WSP systems. Stable isotope analysis of δ15N showed that nitrification could be considered as an intermediate step in WSP, which is masked by simultaneous denitrification, under conditions of low algal activity. Molecular microbiology analysis showed that denitrification can be considered a feasible mechanism for permanent nitrogen removal in WSP, which may be supported either by ammonia-oxidising bacteria (AOB) or by methanotrophs, in addition to nitrite-oxidising bacteria (NOB). However, the relative supremacy of the denitrification process over other nitrogen removal mechanisms (e.g., biological uptake) depends upon phytoplanktonic activity