1,243 research outputs found
Early N-terminal pro-B-type natriuretic peptide is associated with cardiac complications and function during pregnancy in congenital heart disease
Background: Elevated N-terminal pro-B-type natriuretic peptide (NT-proBNP) levels at 20 weeks’ gestation predict adverse cardiovascular (CV) complications during pregnancy in women with congenital heart disease (CHD). To improve early risk assessment in these women, we investigated the predictive value of first-trimester NT-proBNP for CV complications and its association with ventricular function during pregnancy. Methods: Pregnant women with CHD, previously enrolled in a prospective national study or evaluated by an identical protocol, were included. Clinical data, echocardiographic evaluation and NT-proBNP measurements were obtained at 12, 20 and 32 weeks’ gestation. Elevated NT-proBNP was defined as > 235 pg/ml (95th percentile reference value of healthy pregnant women in the literature). Results: We examined 126 females (mean age 29 years). Elevated NT-proBNP at 12 weeks was associated with CV complications (n = 7, 5.6%, odds ratio 10.9, p = 0.004). Arrhythmias were the most common complication (71%). The negative predictive value of low NT-proBNP to exclude CV complications was 97.2%. In women with CV complications, NT-proBNP levels remained high throughout pregnancy, while a decrease was seen in women without CV complications (p < 0.001 for interaction between group and time). At 12 weeks, higher NT-proBNP levels were associated with impaired subpulmonary ventricular function (p < 0.001) and also with a decline in subpulmonary ventricular function later in pregnancy (p = 0.012). Conclusions: In this study, first-trimester NT-proBNP levels were associated with adverse CV complications and a decline in subpulmonary ventricular function later in pregnancy in women with CHD. Early NT-proBNP evaluation is useful for tailored care in pregnant women with CHD
Anomalous superconducting state gap size versus Tc behavior in underdoped Bi_2Sr_2Ca_1-xDy_xCu_2O_8+d
We report angle-resolved photoemission spectroscopy measurements of the
excitation gap in underdoped superconducting thin films of
Bi_2Sr_2Ca_{1-x}Dy_xCu_2O_{8+d}. As Tc is reduced by a factor of 2 by
underdoping, the superconducting state gap \Delta does not fall proportionally,
but instead stays constant or increases slightly, in violation of the BCS
mean-field theory result. The different doping dependences of \Delta and kT_c
indicate that they represent different energy scales. The measurements also
show that \Delta is highly anisotropic and consistent with a d_{x^2-y^2} order
parameter, as in previous studies of samples with higher dopings. However, in
these underdoped samples, the anisotropic gap persists well above T_c. The
existence of a normal state gap is related to the failure of \Delta to scale
with T_c in theoretical models that predict pairing without phase coherence
above T_c.Comment: 10 pages, 4 postscript figures, revtex forma
Isotope effects in underdoped cuprate superconductors: a quantum phenomenon
We show that the unusual doping dependence of the isotope effects on
transition temperature and zero temperature in - plane penetration depth
naturally follows from the doping driven 3D-2D crossover, the 2D quantum
superconductor to insulator transition (QSI) in the underdoped limit and the
change of the relative doping concentration upon isotope substitution. Close to
the QSI transition both, the isotope coefficient of transition temperature and
penetration depth approach the coefficient of the relative dopant
concentration, and its divergence sets the scale. These predictions are fully
consistent with the experimental data and imply that close to the underdoped
limit the unusual isotope effect on transition temperature and penetration
depth uncovers critical phenomena associated with the quantum superconductor to
insulator transition in two dimensions.Comment: 6 pages, 3 figure
Quality of life after esophageal replacement in children
Purpose: Assessing quality of life (QoL) after esophageal replacement (ER) for long gap esophageal atresia (LGEA). Methods: All patients after ER for LGEA with gastric pull-up (GPU n = 9) or jejunum interposition (JI n = 14) at the University Medical Center Groningen and Utrecht (1985–2007) were included. QoL was assessed with 1) gastrointestinal-related QoL using the Gastrointestinal Quality of Life Index (GIQLI)), 2) general QoL (Child Health questionnaire CHF87-BREF (children)/World Health Organization questionnaire WHOQOL-BREF (adults)), and 3) health-related QoL (HRQoL) (TNO AZL TACQoL/TAAQoL). Association of morbidity (heartburn, dysphagia, dyspnea on exertion, recurrent cough) and (HR)QoL was evaluated. Results: Six patients after GPU (75%) and eight patients after JI (57%) responded to the questionnaires (mean age 15.7, SD 5.9, 12 male, two female). Mean gastrointestinal, general and health-related QoL total scores of the patients were comparable to healthy controls. However, young adults reported a worse physical functioning (p = 0.02) but better social functioning compared to peers (p = 0.01). Morbidity was not associated with significant differences in (HR)QoL. Conclusions: With the current validated QoL most patients after ER with GPU and JI for LGEA have normal generic and disease specific QoL scores. Postoperative morbidity does not seem to influence (HR)QoL. Type of Study: Prognosis Study. Level of evidence: III
High-Tc Superconductivity and Antiferromagnetism in Multilayered Copper Oxides - A New Paradigm of Superconducting Mechanism -
High-temperature superconductivity (HTSC) in copper oxides emerges on a
layered CuO2 plane when an antiferromagnetic Mott insulator is doped with
mobile hole carriers. We review extensive studies of multilayered copper oxides
by site-selective nuclear magnetic resonance (NMR), which have uncovered the
intrinsic phase diagram of antiferromagnetism (AFM) and HTSC for a
disorder-free CuO2 plane with hole carriers. We present our experimental
findings such as the existence of the AFM metallic state in doped Mott
insulators, the uniformly mixed phase of AFM and HTSC, and the emergence of
d-wave SC with a maximum Tc just outside a critical carrier density, at which
the AFM moment on a CuO2 plane disappears. These results can be accounted for
by the Mott physics based on the t-J model. The superexchange interaction J_in
among spins plays a vital role as a glue for Cooper pairs or mobile
spin-singlet pairs, in contrast to the phonon-mediated attractive interaction
among electrons established in the Bardeen-Cooper-Schrieffer (BCS) theory. We
remark that the attractive interaction for raising the of HTSC up to
temperatures as high as 160 K is the large J_in (~0.12 eV), which binds
electrons of opposite spins to be on neighboring sites, and that there are no
bosonic glues. It is the Coulomb repulsive interaction U(> 6 eV) among Cu-3d
electrons that plays a central role in the physics behind high-Tc phenomena. A
new paradigm of the SC mechanism opens to strongly correlated electron matter.Comment: 20 pages, 25 figures, Special topics "Recent Developments in
Superconductivity" in J. Phys. Soc. Jpn., Published December 26, 201
Quantum Correlations in NMR systems
In conventional NMR experiments, the Zeeman energy gaps of the nuclear spin
ensembles are much lower than their thermal energies, and accordingly exhibit
tiny polarizations. Generally such low-purity quantum states are devoid of
quantum entanglement. However, there exist certain nonclassical correlations
which can be observed even in such systems. In this chapter, we discuss three
such quantum correlations, namely, quantum contextuality, Leggett-Garg temporal
correlations, and quantum discord. In each case, we provide a brief theoretical
background and then describe some results from NMR experiments.Comment: 21 pages, 7 figure
Calcium scoring using 64-slice MDCT, dual source CT and EBT: a comparative phantom study
Purpose Assessment of calcium scoring (Ca-scoring) on a 64-slice multi-detector computed tomography (MDCT) scanner, a dual-source computed tomography (DSCT) scanner and an electron beam tomography (EBT) scanner with a moving cardiac phantom as a function of heart rate, slice thickness and calcium density. Methods and materials Three artificial arteries with inserted calcifications of different sizes and densities were scanned at rest (0 beats per minute) and at 50–110 beats per minute (bpm) with an interval of 10 bpm using 64-slice MDCT, DSCT and EBT. Images were reconstructed with a slice thickness of 0.6 and 3.0 mm. Agatston score, volume score and equivalent mass score were determined for each artery. A cardiac motion susceptibility (CMS) index was introduced to assess the susceptibility of Ca-scoring to heart rate. In addition, a difference (Δ) index was introduced to assess the difference of absolute Ca-scoring on MDCT and DSCT with EBT. Results Ca-score is relatively constant up to 60 bpm and starts to decrease or increase above 70 bpm, depending on scoring method, calcification density and slice thickness. EBT showed the least susceptibility to cardiac motion with the smallest average CMS-index (2.5). The average CMS-index of 64-slice MDCT (9.0) is approximately 2.5 times the average CMS-index of DSCT (3.6). The use of a smaller slice thickness decreases the CMS-index for both CT-modalities. The Δ-index for DSCT at 0.6 mm (53.2) is approximately 30% lower than the Δ-index for 64-slice MDCT at 0.6 mm (72.0). The Δ-indexes at 3.0 mm are approximately equal for both modalities (96.9 and 102.0 for 64-slice MDCT and DSCT respectively). Conclusion Ca-scoring is influenced by heart rate, slice thickness and modality used. Ca-scoring on DSCT is approximately 50% less susceptible to cardiac motion as 64-slice MDCT. DSCT offers a better approximation of absolute calcium score on EBT than 64-slice MDCT when using a smaller slice thickness. A smaller slice thickness reduces the susceptibility to cardiac motion and reduces the difference between CT-data and EBT-data. The best approximation of EBT on CT is found for DSCT with a slice thickness of 0.6 mm
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