18 research outputs found

    Current density maps, magnetizability, and nuclear magnetic shielding tensors of bis-heteropentalenes. II. Furo-furan Isomers

    Get PDF
    Magnetic susceptibility and nuclear magnetic shielding at the nuclei of bis-heteropentalenes formed by two furan units ([2,3-b], [3,2-b], [3,4-b], and [3,4-c] isomers) have been computed by several approximated techniques and a large Gaussian basis set to achieve near Hartree–Fock estimates. Ab initio models of the ring currents induced by a magnetic field normal to the molecular plane were obtained for the three isomeric systems of higher symmetry, showing that the π electrons give rise to intense diamagnetic circulation. The π currents are responsible for enhanced magnetic anisotropy and strong out-of-plane proton deshielding. The theoretical findings are used to build up a “diatropicity matrix” for two fused five-membered heterocyclic [email protected] ; [email protected]

    Method specific Cholesky decomposition : Coulomb and exchange energies

    Get PDF
    We present a novel approach to the calculation of the Coulomb and exchange contributions to the total electronic energy in self consistent field and density functional theory. The numerical procedure is based on the Cholesky decomposition and involves decomposition of specific Hadamard product matrices that enter the energy expression. In this way, we determine an auxiliary basis and obtain a dramatic reduction in size as compared to the resolution of identity (RI) method. Although the auxiliary basis is determined from the energy expression, we have complete control of the errors in the gradient or Fock matrix. Another important advantage of this method specific Cholesky decomposition is that the exchange energy and Fock matrix can be evaluated with a linear scaling effort contrary to the RI method or standard Cholesky decomposition of the two-electron integral matrix. The methods presented show the same scaling properties as the so-called local density fitting methods, but with full error [email protected]

    COVID-19-Related Thrombotic and Bleeding Events in Adults With Congenital Heart Disease.

    Get PDF
    BACKGROUND Altered coagulation is a striking feature of COVID-19. Adult patients with congenital heart disease (ACHD) are prone to thromboembolic (TE) and bleeding complications. OBJECTIVES The purpose of this study was to investigate the prevalence and risk factors for COVID-19 TE/bleeding complications in ACHD patients. METHODS COVID-19-positive ACHD patients were included between May 2020 and November 2021. TE events included ischemic cerebrovascular accident, systemic and pulmonary embolism, deep venous thrombosis, myocardial infarction, and intracardiac thrombosis. Major bleeding included cases with hemoglobin drop >2 g/dl, involvement of critical sites, or fatal bleeding. Severe infection was defined as need for intensive care unit, endotracheal intubation, renal replacement therapy, extracorporeal membrane oxygenation, or death. Patients with TE/bleeding were compared to those without events. Factors associated with TE/bleeding were determined using logistic regression. RESULTS Of 1,988 patients (age 32 [IQR: 25-42] years, 47% male, 59 ACHD centers), 30 (1.5%) had significant TE/bleeding: 12 TE events, 12 major bleeds, and 6 with both TE and bleeding. Patients with TE/bleeding had higher in-hospital mortality compared to the remainder cohort (33% vs 1.7%; P < 0.0001) and were in more advanced physiological stage (P = 0.032) and NYHA functional class (P = 0.01), had lower baseline oxygen saturation (P = 0.0001), and more frequently had a history of atrial arrhythmia (P < 0.0001), previous hospitalization for heart failure (P < 0.0007), and were more likely hospitalized for COVID-19 (P < 0.0001). By multivariable logistic regression, prior anticoagulation (OR: 4.92; 95% CI: 2-11.76; P = 0.0003), cardiac injury (OR: 5.34; 95% CI: 1.98-14.76; P = 0.0009), and severe COVID-19 (OR: 17.39; 95% CI: 6.67-45.32; P < 0.0001) were independently associated with increased risk of TE/bleeding complications. CONCLUSIONS ACHD patients with TE/bleeding during COVID-19 infection have a higher in-hospital mortality from the illness. Risk of coagulation disorders is related to severe COVID-19, cardiac injury during infection, and use of anticoagulants

    Todas as criaturas do mundo: a arte dos mapas como elemento de orientação geográfica

    Get PDF
    Vague in the outlines and abounding in figures of real or fabulous creatures, the iconography of medieval maps played a significant role in helping users to recognize lands that were virtually unknown to Christendom. In a world with no reliable latitudes and longitudes, the land contours, inhabitants and even certain elements of fauna and flora could become variables of utmost importance for geographic orientation. Notwithstanding the higher levels of precision achieved in their efforts to represent geographic space, the considerable advancements made in latitude determination, and their continuous pursuit of a practical method for the establishment of longitudes, the cartographers of the Age of Discoveries still went to the trouble of depicting notable elements - whether real or imaginary - to help travelers get their bearings around different regions of the globe. As the presence of Europeans continued to expand and an authentic scientific revolution took place in the 17th century, the lengthy notes and eye¿catching representations of nature and local inhabitants soon lost their utility as points of reference on 17th-century maps to become mere accessories of aesthetic and commercial value. The advent of the 18th century consolidated, once and for all, the transformation of such illustrations into essentially decorative elements with no other relevant role to play in mapmaking. In addition to decreasing in number, the figures became more stylized and moved to the borders of the maps as ornamental motifs. Although they often maintained some sort of relation with the geographic space depicted on the map, the motifs chosen could also constitute a rather independent element. In fact, allegories, compositions with a variety of mythological figures, and historical representations were often used to underscore the power of certain political agents

    Erratum: “Density-functional and electron correlated study of five linear birefringences—Kerr, Cotton–Mouton, Buckingham, Jones and magnetoelectric—in gaseous benzene” J. Chem. Phys. 121, 8814 2004; “Density-functional study of electric and magnetic properties of hexafluorobenzene in the vapor phase” J. Chem. Phys. 122, 234314 2005; and “A computational study of some electric and magnetic properties of gaseous BF3 and BCl3” J. Chem. Phys. 123, 114307 2005

    No full text
    Erratum: “Density-functional and electron correlated study of five linear birefringences—Kerr, Cotton–Mouton, Buckingham, Jones and magnetoelectric—in gaseous benzene” †J. Chem. Phys. 121, 8814 „2004…‡; “Density-functional study of electric and magnetic properties of hexafluorobenzene in the vapor phase” †J. Chem. Phys. 122, 234314 „2005…‡; and “A computational study of some electric and magnetic properties of gaseous BF3 and BCl3” †J. Chem. Phys. 123, 114307 „2005…

    Do oceano dos clássicos aos mares dos impérios: transformações cartográficas do Atlântico sul

    No full text
    This article explores the various place-names given to the geographic localities in the South Atlantic by European cartographers in the 16th and 17th centuries. Despite of the fact that representation of continental space seem to have been more common in mapmaking at the time than the depiction of oceans and seas, oceanic waters often received particular names - regional seas - depending on the coastline in combination to the classical names. A series of connections can be established between this fact and the process of consolidation of slave trading and competition between empires
    corecore