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N-terminal pro-brain natriuretic peptide has an established role in the diagnosis and prognosis of heart failure. In Fontan patients, this peptide is often increased, but its diagnostic value in this particular non-physiologic, univentricular circulation is unclear. We investigated whether N-terminal pro-brain natriuretic peptide represents ventricular function or other key variables in Fontan patients.
Methods and results:
Ninety-five consecutive Fontan patients ≥10 years old who attended the outpatient clinic of the Center for Congenital Heart Diseases in 2012–2013 were included. Time since Fontan completion was 16 ± 9 years. Median N-terminal pro-brain natriuretic peptide was 114 (61–264) ng/l and was higher than gender-and age-dependent normal values in 54% of the patients. Peptide Z-scores were higher in patients in NYHA class III/IV compared to those in class I/II, but did not correlate with ventricular function assessed by MRI and echocardiography, nor with peak exercise capacity. Instead, peptide Z-scores significantly correlated with follow-up duration after Fontan completion (p < 0.001), right ventricular morphology (p = 0.004), indexed ventricular mass (p = 0.001), and inferior caval vein diameter (p < 0.001) (adjusted R2 = 0.615).
N-terminal pro-brain natriuretic peptide levels in Fontan patients correlate with functional class, but do not necessarily indicate ventricular dysfunction. Increased peptide levels were associated with a longer existence of the Fontan circulation, morphologic ventricular characteristics, and signs of increased systemic venous congestion. Since the latter are known to be key determinants of the performance of the Fontan circulation, these findings suggest increase in N-terminal pro-brain natriuretic peptide levels to indicate attrition of the Fontan circulation, independent of ventricular function.
Elastic modulus and residual stress in freestanding ultrathin films (<100 nm) are characterized using bilayer cantilevers. The cantilevers comprise a test film and a well-characterized reference material (SU-8). When released from the substrate, residual stresses in the bilayer cantilever cause it to deflect with measurable curvatures, allowing the determination of both stiffness and residual stress of the test film. The technique does not require sophisticated mechanical test equipment and serves as a useful metrology tool for characterizing coatings immediately after fabrication in a clean room assembly line. The measured biaxial modulus and residual strain of 75 nm copper films are 211 ± 19 GPa and (7.05 ± 0.22) × 10−3, respectively. Additional experiments on the freestanding structures yield a mean Young’s modulus of 115 GPa. These properties are in close agreement with those measured from additional residual stress–driven structures developed on the same coatings by the authors.
The idea of the separation of powers has been subjected to criticism and competition ever since it first came to be during the upheaval of the English Civil War in the 1640s. Since then, it has been dismissed as often as its virtues have been extolled. In recent years the case has once again been stated that the idea of the separation of powers has lost its significance in a globalised world, with a power constellation in which the distinctions between different types of ‘powers’ have blurred and even so-called constituted power holders have become more and more diffuse. Yet even its fiercest opponents cannot deny that the idea of the separation of powers as a theory of government has, in the words of M.J.C. Vile, ‘in modern times, been the most significant, both intellectually and in terms of its influence upon institutional structures’.
Vile's classic description of what he calls the ‘pure doctrine’ of the separation of powers offers us an extensive, but still useful definition to serve as a backdrop for the historical development and practical implementations of this idea: ‘It is essential for the establishment and maintenance of political liberty that the government be divided into three branches or departments, the legislature, the executive, and the judiciary . To each of these three branches there is a corresponding identifiable function of government, legislative, executive, or judicial. Each branch of the government must be confined to the exercise of its own function and not allowed to encroach upon the functions of the other branches. Furthermore, the persons who compose these three agencies of government must be kept separate and distinct (…). In this way each of the branches will be a check to the others and no single group of people will be able to control the machinery of the state.’
The lineage of this idea, which for better or for worse has been prominently featured in western thinking on constitution and government for over three-and-a-half centuries, can be traced back to Greek antiquity where, in the works of Aristotle, among others, rudimentary concepts of differentiated governmental functions are distinguished. These do not, however, fully match later notions of a tripartite division of legislative, executive and judicial power, if only because the law, once created, was considered to be more or less fixed.