Increased circulating insulin-like growth factor-1 in late-onset Alzheimer's disease

Background: Insulin-like growth factor (IGF)-1 has been implicated in the pathogenesis of Alzheimer's disease ( AD). Methods: We compared the level of circulating total and bioavailable IGF-1, by simultaneous measurements of IGF-1 and IGF binding protein ( IGFBP)-3, between 87 patients diagnosed with AD and 126 age and sex matched control subjects without cognitive impairment. Blood samples were collected and IGF-1 and IGFBP-3 measured by ELISA. Subjects were also genotyped for apolipoprotein E. Results: Total circulating IGF-1 levels were significantly raised in the AD group as compared to the control group (p = 0.022). There was no significant difference in the circulating level of IGFBP-3 between the two groups. When the IGF-1 levels were ratioed against IGFBP-3 levels as an indicator of unbound, bioavailable circulating IGF-1, there was a significant increase in the molar IGF-1:IGFBP-3 ratio in the AD subjects (0.181 +/- 0.006) as compared to the controls (0.156 +/- 0.004) (p < 0.001). Logistic regression analysis revealed that an increase in the IGF-1: IGFBP-3 molar ratio increased the risk of AD significantly. Conclusion: The results of increased total and free circulating IGF-1 support the hypothesis that in its early stages late-onset AD reflects a state of resistance to IGF-1

Solutions in Self-Dual Gravity Constructed Via Chiral Equations

The chiral model for self-dual gravity given by Husain in the context of the chiral equations approach is discussed. A Lie algebra corresponding to a finite dimensional subgroup of the group of symplectic diffeomorphisms is found, and then use for expanding the Lie algebra valued connections associated with the chiral model. The self-dual metric can be explicitly given in terms of harmonic maps and in terms of a basis of this subalgebra.Comment: Plain Latex, 13 Pages, major revisions of style in the above proof, several Comments added. Version to appear in Physical Review

Stability and Shapes of Cellular Profiles in Directional Solidification: Expansion and Matching Methods

Wetensch. publicatieFaculteit der Wiskunde en Natuurwetenschappe

Indications of microscopic solvability from counting arguments

FWN – Publicaties zonder aanstelling Universiteit Leide

Problematic social media use in childhood and adolescence.

At the time of writing, about 4.59 billion people use social media with many adolescents using their social media accounts across a myriad of applications and platforms. According to recent statistics, in 2022 individuals spent an average of 151 minutes on social media each day, illustrating the global relevance of social media (Dixon, 2022a,b). One of the pressing questions, internationally, is whether social media use is harmful and/or addictive. This question is of particular importance because many teenagers - and younger adolescents - spend considerable time on these platforms, which have increasingly become an integral part of their lives. Moreover, considering lifespan development, adolescents may be particularly vulnerable to specific features and advertisements shown to them on social media platforms. Growing prevalence of poor mental health in young people has led to recent recommendations in the United States to routinely screen for anxiety in 8-18 year olds, and for depression and suicide risk for adolescents between 12-18 years of age (US Preventive Services Task Force et al., 2022 a,b) - the conditions often accompanying problematic social media use. The present work not only provides insights into the current state of the literature but provides also recommendations. [Abstract copyright: Copyright © 2024 The Author(s). Published by Elsevier Ltd.. All rights reserved.

Damage Spreading During Domain Growth

We study damage spreading in models of two-dimensional systems undergoing first order phase transitions. We consider several models from the same non-conserved order parameter universality class, and find unexpected differences between them. An exact solution of the Ohta-Jasnow-Kawasaki model yields the damage growth law $D \sim t^{\phi}$, where $\phi = t^{d/4}$ in $d$ dimensions. In contrast, time-dependent Ginzburg-Landau simulations and Ising simulations in $d= 2$ using heat-bath dynamics show power-law growth, but with an exponent of approximately $0.36$, independent of the system sizes studied. In marked contrast, Metropolis dynamics shows damage growing via $\phi \sim 1$, although the damage difference grows as $t^{0.4}$. PACS: 64.60.-i, 05.50.+qComment: 4 pags of revtex3 + 3 postscript files appended as a compressed and uuencoded file. UIB940320

Citizen Desires, Policy Outcomes, and Community Control

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68810/2/10.1177_107808747200800107.pd

Domain Growth and Finite-Size-Scaling in the Kinetic Ising Model

This paper describes the application of finite-size scaling concepts to domain growth in systems with a non-conserved order parameter. A finite-size scaling ansatz for the time-dependent order parameter distribution function is proposed, and tested with extensive Monte-Carlo simulations of domain growth in the 2-D spin-flip kinetic Ising model. The scaling properties of the distribution functions serve to elucidate the configurational self-similarity that underlies the dynamic scaling picture. Moreover, it is demonstrated that the application of finite-size-scaling techniques facilitates the accurate determination of the bulk growth exponent even in the presence of strong finite-size effects, the scale and character of which are graphically exposed by the order parameter distribution function. In addition it is found that one commonly used measure of domain size--the scaled second moment of the magnetisation distribution--belies the full extent of these finite-size effects.Comment: 13 pages, Latex. Figures available on request. Rep #9401

Early stage scaling in phase ordering kinetics

A global analysis of the scaling behaviour of a system with a scalar order parameter quenched to zero temperature is obtained by numerical simulation of the Ginzburg-Landau equation with conserved and non conserved order parameter. A rich structure emerges, characterized by early and asymptotic scaling regimes, separated by a crossover. The interplay among different dynamical behaviours is investigated by varying the parameters of the quench and can be interpreted as due to the competition of different dynamical fixed points.Comment: 21 pages, latex, 7 figures available upon request from [email protected]

Dynamic scaling and quasi-ordered states in the two dimensional Swift-Hohenberg equation

The process of pattern formation in the two dimensional Swift-Hohenberg equation is examined through numerical and analytic methods. Dynamic scaling relationships are developed for the collective ordering of convective rolls in the limit of infinite aspect ratio. The stationary solutions are shown to be strongly influenced by the strength of noise. Stationary states for small and large noise strengths appear to be quasi-ordered and disordered respectively. The dynamics of ordering from an initially inhomogeneous state is very slow in the former case and fast in the latter. Both numerical and analytic calculations indicate that the slow dynamics can be characterized by a simple scaling relationship, with a characteristic dynamic exponent of $1/4$ in the intermediate time regime