Scaling determination of the nonlinear I-V characteristics for 2D superconducting networks

It is shown from computer simulations that the current-voltage ($I$-$V$) characteristics for the two-dimensional XY model with resistively-shunted Josephson junction dynamics and Monte Carlo dynamics obeys a finite-size scaling form from which the nonlinear $I$-$V$ exponent $a$ can be determined to good precision. This determination supports the conclusion $a=z+1$, where $z$ is the dynamic critical exponent. The results are discussed in the light of the contrary conclusion reached by Tang and Chen [Phys. Rev. B {\bf 67}, 024508 (2003)] and the possibility of a breakdown of scaling suggested by Bormann [Phys. Rev. Lett. {\bf 78}, 4324 (1997)].Comment: 6 pages, to appear in PR

Langevin Simulations of Two Dimensional Vortex Fluctuations: Anomalous Dynamics and a New IVIV-exponent

The dynamics of two dimensional (2D) vortex fluctuations are investigated through simulations of the 2D Coulomb gas model in which vortices are represented by soft disks with logarithmic interactions. The simulations trongly support a recent suggestion that 2D vortex fluctuations obey an intrinsic anomalous dynamics manifested in a long range 1/t-tail in the vortex correlations. A new non-linear IV-exponent a, which is different from the commonly used AHNS exponent, a_AHNS and is given by a = 2a_AHNS - 3, is confirmed by the simulations. The results are discussed in the context of earlier simulations, experiments and a phenomenological description.Comment: Submitted to PRB, RevTeX format, 28 pages and 13 figures, figures in postscript format are available at http://www.tp.umu.se/~holmlund/papers.htm

Current-voltage characteristics of the two-dimensional XY model with Monte Carlo dynamics

Current-voltage characteristics and the linear resistance of the two-dimensional XY model with and without external uniform current driving are studied by Monte Carlo simulations. We apply the standard finite-size scaling analysis to get the dynamic critical exponent $z$ at various temperatures. From the comparison with the resistively-shunted junction dynamics, it is concluded that $z$ is universal in the sense that it does not depend on details of dynamics. This comparison also leads to the quantification of the time in the Monte Carlo dynamic simulation.Comment: 5 pages in two columns including 5 figures, to appear in PR

Vortex dynamics for two-dimensional XY models

Two-dimensional XY models with resistively shunted junction (RSJ) dynamics and time dependent Ginzburg-Landau (TDGL) dynamics are simulated and it is verified that the vortex response is well described by the Minnhagen phenomenology for both types of dynamics. Evidence is presented supporting that the dynamical critical exponent $z$ in the low-temperature phase is given by the scaling prediction (expressed in terms of the Coulomb gas temperature $T^{CG}$ and the vortex renormalization given by the dielectric constant $\tilde\epsilon$) $z=1/\tilde{\epsilon}T^{CG}-2\geq 2$ both for RSJ and TDGL and that the nonlinear IV exponent a is given by a=z+1 in the low-temperature phase. The results are discussed and compared with the results of other recent papers and the importance of the boundary conditions is emphasized.Comment: 21 pages including 15 figures, final versio

Magnetic-field dependence of dynamical vortex response in two-dimensional Josephson junction arrays and superconducting films

The dynamical vortex response of a two-dimensional array of the resistively shunted Josephson junctions in a perpendicular magnetic field is inferred from simulations. It is found that, as the magnetic field is increased at a fixed temperature, the response crosses over from normal to anomalous, and that this crossover can be characterized by a single dimensionless parameter. It is described how this crossover should be reflected in measurements of the complex impedance for Josephson junction arrays and superconducting films.Comment: 4 pages including 5 figures in two columns, final versio

Iron status in early childhood is modified by diet, sex and growth : Secondary analysis of a randomized controlled vitamin D trial

Background & aims: During early childhood the risk of iron deficiency (ID) is high. Serum ferritin serves as a marker of iron status. We explored prevalence of ID and iron deficiency anemia (IDA), and identified determinants of iron status in infants and toddlers. Methods: We performed a secondary analysis of the Vitamin D intervention in infants (VIDI) study in Finnish healthy term infants. According to study protocol, at 12- and 24-months of age iron status, growth and dietary intakes were evaluated. ID was defined as serum ferritin Results: ID prevalence increased from 14% in infants to 20% in toddlers. IDA prevalence was 3% at both time points. In infants, ID and IDA were more common in boys than in girls (19% vs. 9%, p = 0.001 and 5% vs. 1%, p = 0.039) but no sex-difference in toddlers was observed. Of infants, 30% had daily iron intake below average requirement of 5 mg/day. Higher daily iron intake per body weight (mg/kg) independently associated with higher infant serum ferritin (B (95% CI) 0.30 (0.04, 0.56), p = 0.026). Correlation between iron intake and ferritin was stronger in infants with ID than in infants without ID. Breastfeeding was more common (63% vs. 35%, p < 0.001) among ID infants than in infants without ID. In toddlers, frequent consumption of milk products independently associated with lower ferritin (B (95% CI) -0.03 (-0.05, -0.01), p = 0.001). Consumption of meat and fish associated with better iron status. Serum ferritin at both time points associated with duration of gestation and growth. The association of growth and ferritin was age-dependent in boys, while in girls, faster growth associated consistently with lower ferritin. Conclusions: In Northern European healthy infants and toddlers ID is common. The intake of iron remains below recommendations and food consumption and iron intake associate with iron status. Further studies are warranted to assess significance of ID on child development and clinical health outcomes. (C) 2021 The Authors. Published by Elsevier Ltd.Peer reviewe

The Effects of Vitamin D Supplementation During Infancy on Growth During the First 2 Years of Life

Context: The relationship between maternal and infant vitamin D and early childhood growth remains inadequately understood. Objective: This work aimed to investigate how maternal and child 25-hydroxyvitamin D (25[OH]D) and vitamin D supplementation affect growth during the first 2 years of life. Methods: A randomized, double-blinded, single-center intervention study was conducted from pregnancy until offspring age 2 years. Altogether 812 term-born children with complete data were recruited at a maternity hospital. Children received daily vitamin D-3 supplementation of 10 mu g (group 10) or 30 mu g (group 30) from age 2 weeks to 2 years. Anthropometry and growth rate were measured at age 1 and 2 years. Results: Toddlers born to mothers with pregnancy 25(OH)D greater than 125 nmol/L were at 2 years lighter and thinner than the reference group with 25(OH)D of 50 to 74.9 nmol/L (P .053), but group 30 had slower growth in length and head circumference between 6 months and 1 year (P 121 nmol/L) were shorter (mean difference 0.2 SD score [SDS], P = .021), lighter (mean difference 0.4 SDS, P = .001), and thinner (in length-adjusted weight) (mean difference 0.4 SDS, P = .003) compared with the lowest quartile (< 81.2 nmol/L). Conclusion: Vitamin D and early childhood growth may have an inverse U-shaped relationship.Peer reviewe

Collagen X Biomarker (CXM), Linear Growth, and Bone Development in a Vitamin D Intervention Study in Infants

Publisher Copyright: © 2022 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).Collagen X biomarker (CXM) is suggested to be a biomarker of linear growth velocity. However, early childhood data are limited. This study examines the relationship of CXM to the linear growth rate and bone development, including the possible modifying effects of vitamin D supplementation. We analyzed a cohort of 276 term-born children participating in the Vitamin D Intervention in Infants (VIDI) study. Infants received 10 μg/d (group-10) or 30 μg/d (group-30) vitamin D3 supplementation for the first 2 years of life. CXM and length were measured at 12 and 24 months of age. Tibial bone mineral content (BMC), volumetric bone mineral density (vBMD), cross-sectional area (CSA), polar moment of inertia (PMI), and periosteal circumference (PsC) were measured using peripheral quantitative computed tomography (pQCT) at 12 and 24 months. We calculated linear growth as length velocity (cm/year) and the growth rate in length (SD unit). The mean (SD) CXM values were 40.2 (17.4) ng/mL at 12 months and 38.1 (12.0) ng/mL at 24 months of age (p = 0.12). CXM associated with linear growth during the 2-year follow-up (p = 0.041) but not with bone (p = 0.53). Infants in group-30 in the highest tertile of CXM exhibited an accelerated mean growth rate in length compared with the intermediate tertile (mean difference [95% CI] −0.50 [−0.98, −0.01] SD unit, p = 0.044) but not in the group-10 (p = 0.062) at 12 months. Linear association of CXM and growth rate until 12 months was weak, but at 24 months CXM associated with both length velocity (B for 1 increment of √CXM [95% CI] 0.32 [0.12, 0.52] cm/yr, p = 0.002) and growth rate in length (0.20 [0.08, 0.32] SD unit, p = 0.002). To conclude, CXM may not reliably reflect linear growth from birth to 12 months of age, but its correlation with growth velocity improves during the second year of life.Peer reviewe

Charge Transport in the Dense Two-Dimensional Coulomb Gas

The dynamics of a globally neutral system of diffusing Coulomb charges in two dimensions, driven by an applied electric field, is studied in a wide temperature range around the Berezinskii-Kosterlitz-Thouless transition. I argue that the commonly accepted ``free particle drift'' mechanism of charge transport in this system is limited to relatively low particle densities. For higher densities, I propose a modified picture involving collective ``partner transfer'' between bound pairs. The new picture provides a natural explanation for recent experimental and numerical findings which deviate from standard theory. It also clarifies the origin of dynamical scaling in this context.Comment: 4 pages, RevTeX, 2 eps figures included; some typos corrected, final version to be published in Phys. Rev. Let

Maternal vitamin D status, gestational diabetes and infant birth size

Background: Maternal vitamin D status has been associated with both gestational diabetes mellitus (GDM) and fetal growth restriction, however, the evidence is inconsistent. In Finland, maternal vitamin D status has improved considerably due to national health policies. Our objective was to compare maternal 25-hydroxy vitamin D concentrations [25(OH)D] between mothers with and without GDM, and to investigate if an association existed between maternal vitamin D concentration and infant birth size. Methods: This cross-sectional study included 723 mother-child pairs. Mothers were of Caucasian origin, and infants were born at term with normal birth weight. GDM diagnosis and birth size were obtained from medical records. Maternal 25(OH)D was determined on average at 11 weeks of gestation in pregnancy and in umbilical cord blood (UCB) at birth. Results: GDM was observed in 81 of the 723 women (11%). Of the study population, 97% were vitamin D sufficient [25(OH)D >= 50 nmol/L]. There was no difference in pregnancy 25(OH)D concentration between GDM and non-GDM mothers (82 vs 82 nmol/L, P = 0.99). Regression analysis confirmed no association between oral glucose tolerance test results and maternal 25(OH)D (P > 0.53). Regarding the birth size, mothers with optimal pregnancy 25(OH)D (>= 80 nmol/L) had heavier newborns than those with suboptimal pregnancy 25(OH)D (P = 0.010). However, mothers with optimal UCB 25(OH) D had newborns with smaller head circumference than those with suboptimal 25(OH)D (P = 0.003), which was further confirmed as a linear association (P = 0.024). Conclusions: Maternal vitamin D concentration was similar in mothers with and without GDM in a mostly vitamin D sufficient population. Associations between maternal vitamin D status and birth size were inconsistent. A sufficient maternal vitamin D status, specified as 25(OH)D above 50 nmol/L, may be a threshold above which the physiological requirements of pregnancy are achieved.Peer reviewe