Nature of Correlated Motion of Electrons in the Parent Cobaltate Superconductors

Recently discovered class of cobaltate superconductors (Na0.3CoO2.nH2O) is a novel realization of interacting quantum electron systems in a triangular network with low-energy degrees of freedom. We employ angle-resolved photoemission spectroscopy to uncover the nature of microscopic electron motion in the parent superconductors for the first time. Results reveal a large hole-like Fermi surface (consistent with Luttinger theorem) generated by the crossing of super-heavy quasiparticles. The measured quasiparticle parameters collectively suggest a two orders of magnitude departure from the conventional Bardeen-Cooper-Schrieffer electron dynamics paradigm and unveils cobaltates as a rather hidden class of relatively high temperature superconductors.Comment: 5 pages, 4 figures, 1 tabl

The effect of door-to-balloon delay in primary percutaneous coronary intervention on clinical outcomes of STEMI: a systematic review and meta-analysis protocol

BACKGROUND: Acute myocardial infarction (AMI) is a medical emergency in which sudden occlusion of coronary artery(ies) results in ischemia and necrosis of the cardiac tissues. Reperfusion therapies that aim at reopening the occluded artery remain the mainstay of treatment for AMI. Primary percutaneous coronary intervention (PCI), which enables the restoration of blood flow by reopening the occluded artery(ies) via a catheter with an inflatable balloon, is currently the preferred treatment for AMI with ST segment elevation (STEMI). The door-to-balloon (D2B) delay refers to the time interval counting from the arrival of a patient with STEMI at a hospital to the time of the balloon inflation (or stent deployment) that reopens the occluded artery(ies). Reducing this delay in primary PCI is thought to be an important strategy toward achieving better patient outcomes. Unfortunately, significant reduction of D2B delay in the USA over the last decade has not been shown to be associated with improved STEMI mortality. It has been suggested that the lack of impact could be due to the expanding use of primary PCI in STEMI as well as the survival cohort effect, leading to a shift toward a higher risk population receiving the procedure. Others have suggested that reduction in D2B delay may not be as impactful as expected, given that it only represents a small fraction of the total ischemic time. Although most existing evidence have pointed to the presence of a beneficial effect of shorter D2B delay, some inconsistencies however exist. This study aims to synthesize available evidence in order to answer the following questions: (1) what is the overall effect of D2B delay on clinical outcomes in patients with STEMI treated with primary PCI? (2) What factors explain the differences of the effect estimates among the studies? (3) What are the important strength and limitation of the existing body of evidence? METHOD: We will search PubMed/MEDLINE, EMBASE, ClinicalTrials.gov, WHO International Clinical Trials Registry, CINAHL Database, and the Cochrane Library using a predefined search strategy. Other sources of literature will include proceedings from the European Society of Cardiology, the American College of Cardiology, the American Heart Association, the EUROPCR, and the ProQuest Dissertations and Theses Database. We will include data from observational studies (case-control and cohort study design) and randomized control trials (that have investigated the relationship of D2B time and clinical outcome(s) in an adult (older than 18) STEMI population). Mortality (cardiac related and all-cause) and incidence heart failure (HF) have been prioritized as the primary outcomes. All eligible studies will be assessed for risk of bias using the Risk Of Bias in Non-randomized Studies - of Interventions tool. The Grading of Recommendations, Assessment, and Evaluation (GRADE) framework will be used to report the quality of evidence and strength of recommendations. We will proceed to analyze the data quantitatively if the pre-specified conditions are satisfied. DISCUSSION: Recent discussion on the negative findings of improved D2B delay over time being unrelated to better STEMI outcomes at the population level has reminded us of an important knowledge gap we have on this domain. This systematic review will serve to address some of these key questions not previously examined. Answers to these questions could clarify the controversies and offer empirical support for or against the suggested hypotheses. SYSTEMATIC REVIEW REGISTRATION: PROSPERO CRD42015026069 ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s13643-016-0304-7) contains supplementary material, which is available to authorized users

Retrofit of water network with regeneration using water pinch analysis

This paper presents the development of a new systematic technique for the retrofit of water network with regeneration based on water pinch analysis. The procedure consists of two parts: retrofit targeting and design for a water network with regeneration unit(s). In the targeting stage, retrofit targets (utility savings and capital investment) were determined for a range of process parameters (total flowrate and/or outlet concentration of the regeneration unit) to obtain a savings versus investment curve. Next, the existing water network was re-designed to meet the chosen targets. A case study on paper making process was used to demonstrate the new methodology

Risk factors for complications after colonic stent insertion for large bowel obstruction

This journal suppl. entitled: DDW 2014 ASGE Program and AbstractsBACKGROUND: Colonic stenting is proven to be an effective means in relieving malignant large bowel obstruction. However, severe complication such as perforation of bowel and subsequently fecal peritonitis can occur after successful of insertion of colonic stent. While colonic stenting is practiced more widely, concern also arises as a result of reports on increased complication rate from this procedure ...postprin

Possible singlet to triplet pairing transition in NaxCoO2 H2O

We present precise measurements of the upper critical field (Hc2) in the recently discovered cobalt oxide superconductor. We have found that the critical field has an unusual temperature dependence; namely, there is an abrupt change of the slope of Hc2(T) in a weak field regime. In order to explain this result we have derived and solved Gor'kov equations on a triangular lattice. Our experimental results may be interpreted in terms of the field-induced transition from singlet to triplet superconductivity.Comment: 6 pages, 5 figures, revte

Magnetic and Metal-Insulator Transitions in beta-Na0.5CoO2 and gamma-K0.5CoO2 -NMR and Neutron Diffraction Studies-

Co-oxides beta-Na0.5CoO2 and gamma-K0.5CoO2 have been prepared by the Na de-intercalation from alpha-NaCoO2 and by the floating-zone method, respectively. It has been found that successive phase transitions take place at temperatures Tc1 and Tc2 in both systems. The appearance of the internal magnetic field at Tc1 with decreasing temperature T indicates that the antiferromagnetic order exists at T < Tc1, as in gamma-Na0.5CoO2. For beta-Na0.5CoO2, the transition temperatures and the NMR parameters determined from the data taken for magnetically ordered state are similar to those of gamma-Na0.5CoO2, indicating that the difference of the stacking ways of the CoO2 layers between these systems do not significantly affect their physical properties. For gamma-K0.5CoO2, the quantitative difference of the physical quantities are found from those of beta- and gamma-Na0.5CoO2. The difference between the values of Tci (i = 1 and 2) of these systems might be explained by considering the distance between CoO2 layers.Comment: 8 pages, 14 figures, 1 Tabl

Fermi surface and quasiparticle dynamics of Na(x)CoO2 {x=0.7} investigated by Angle-Resolved Photoemission Spectroscopy

We present an angle-resolved photoemission study of Na0.7CoO2, the host cobaltate of the NaxCoO2.yH2O series. Our results show a large hexagonal-like hole-type Fermi surface, an extremely narrow strongly renormalized quasiparticle band and a small Fermi velocity. Along the Gamma to M high symmetry line, the quasiparticle band crosses the Fermi level from M toward Gamma consistent with a negative sign of effective single-particle hopping (t ): t is estimated to be about 8 meV which is on the order of exchange coupling J in this system. This suggests that t ~ J ~ 10 meV is an important energy scale in the system. Quasiparticles are well defined only in the T-linear resistivity regime. Small single particle hopping and unconventional quasiparticle dynamics may have implications for understanding the unusual behavior of this new class of compounds.Comment: Revised text, Added Figs, Submitted to PR

Coupling between electronic and structural degrees of freedom in the triangular lattice conductor NaxCoO2

The determination by powder neutron diffraction of the ambient temperature crystal structures of compounds in the NaxCoO2 family, for 0.3 < x <= 1.0, is reported. The structures consist of triangular CoO2 layers with Na ions distributed in intervening charge reservoir layers. The shapes of the CoO6 octahedra that make up the CoO2 layers are found to be critically dependent on the electron count and on the distribution of the Na ions in the intervening layers, where two types of Na sites are available. Correlation of the shapes of cobalt-oxygen octahedra, the Na ion positions, and the electronic phase diagram in NaxCoO2 is made, showing how structural and electronic degrees of freedom can be coupled in electrically conducting triangular lattice systems.Comment: 15 pages, 1 tables, 6 figures Submitted to Physical Review