Physical activity, overweight and central adiposity in Swedish children and adolescents: the European Youth Heart Study

BACKGROUND: The aim of this work was to study the associations of physical activity (PA) and other factors predisposing to overweight, with overweight and central adiposity in children and adolescents. METHODS: A total of 557 Swedish children (9.5 +/- 0.3 y) and 517 adolescents (15.6 +/- 0.4 y) from the European Youth Heart Study participated in this study. Logistic regression analyses were used to examine the associations of PA, as measured by accelerometry, and other determinants (i.e. television viewing, birth weight, maternal educational level and parental overweight) with total and central adiposity. Body mass index and waist circumference cut-off values proposed by the IOTF and the Bogalusa Heart Study (i.e. waist measures for predicting risk factors clustering, hereinafter called high-risk waist circumference), respectively, were used. Fatness was estimated from skinfold thicknesses and dichotomized using the 85th sex- and age-specific percentile (high/low). RESULTS: Children and adolescents who had a low level (first tertile) of vigorous PA, were more likely to be overweight (including obesity) and to have a high-risk waist circumference, than those with a high level (third tertile) of vigorous PA. Similarly, those subjects who had a low or middle level (second tertile) of total PA were more likely to be overweight than those who had a high level of total PA. Among the PA variables, only vigorous PA was associated with high total fatness. Birth weight and television viewing, were also associated with higher odds of having a high-risk waist circumference, but these associations were attenuated once either total or vigorous PA variable was included in the model. Those subjects who had two overweight parents were more likely to be overweight and to have a high-risk waist circumference independently of PA variables, compared to those whose parents were not overweight. CONCLUSION: Low levels of total PA and especially vigorous PA may play an important role in the development of overweight and excess of central adiposity in children and adolescents, independently of a number of factors such as television viewing and birth weight. In addition, the data suggest that the association between television viewing and central fat deposition could be attenuated if enough vigorous PA is accumulated. Longitudinal and intervention studies are needed to confirm these findings.This study was supported by grants from the Stockholm County Council. FBO and JRR were supported by grants from the Consejo Superior de Deportes (109/UPB31/03, 13/UPB20/04), Ministerio de Educación y Ciencia de España (AP2003-2128, AP2004-2745), EU DG Sanco, project ALPHA (2006120), and the Margit and Folke Pehrzon Foundation

A History of Spike-Timing-Dependent Plasticity

How learning and memory is achieved in the brain is a central question in neuroscience. Key to today’s research into information storage in the brain is the concept of synaptic plasticity, a notion that has been heavily influenced by Hebb's (1949) postulate. Hebb conjectured that repeatedly and persistently co-active cells should increase connective strength among populations of interconnected neurons as a means of storing a memory trace, also known as an engram. Hebb certainly was not the first to make such a conjecture, as we show in this history. Nevertheless, literally thousands of studies into the classical frequency-dependent paradigm of cellular learning rules were directly inspired by the Hebbian postulate. But in more recent years, a novel concept in cellular learning has emerged, where temporal order instead of frequency is emphasized. This new learning paradigm – known as spike-timing-dependent plasticity (STDP) – has rapidly gained tremendous interest, perhaps because of its combination of elegant simplicity, biological plausibility, and computational power. But what are the roots of today’s STDP concept? Here, we discuss several centuries of diverse thinking, beginning with philosophers such as Aristotle, Locke, and Ribot, traversing, e.g., Lugaro’s plasticità and Rosenblatt’s perceptron, and culminating with the discovery of STDP. We highlight interactions between theoretical and experimental fields, showing how discoveries sometimes occurred in parallel, seemingly without much knowledge of the other field, and sometimes via concrete back-and-forth communication. We point out where the future directions may lie, which includes interneuron STDP, the functional impact of STDP, its mechanisms and its neuromodulatory regulation, and the linking of STDP to the developmental formation and continuous plasticity of neuronal networks

Highly Nonrandom Features of Synaptic Connectivity in Local Cortical Circuits

How different is local cortical circuitry from a random network? To answer this question, we probed synaptic connections with several hundred simultaneous quadruple whole-cell recordings from layer 5 pyramidal neurons in the rat visual cortex. Analysis of this dataset revealed several nonrandom features in synaptic connectivity. We confirmed previous reports that bidirectional connections are more common than expected in a random network. We found that several highly clustered three-neuron connectivity patterns are overrepresented, suggesting that connections tend to cluster together. We also analyzed synaptic connection strength as defined by the peak excitatory postsynaptic potential amplitude. We found that the distribution of synaptic connection strength differs significantly from the Poisson distribution and can be fitted by a lognormal distribution. Such a distribution has a heavier tail and implies that synaptic weight is concentrated among few synaptic connections. In addition, the strengths of synaptic connections sharing pre- or postsynaptic neurons are correlated, implying that strong connections are even more clustered than the weak ones. Therefore, the local cortical network structure can be viewed as a skeleton of stronger connections in a sea of weaker ones. Such a skeleton is likely to play an important role in network dynamics and should be investigated further

Bi(2223) Ag sheathed tape Ic and exponent n characterisation and modelling under DC applied magnetic field

We use a dual channel digital lock-in to perform electrical measurement of AC losses at power frequencies. A DC magnetic field between 2 and 400 mT is applied with a varying angle from parallel to perpendicular to the tape surface, thus having a complete view of the loss behavior under DC applied field. Furthermore, the same experimental layout is used to acquire time series of current and voltage across the sample. Using a triangular input current, we measure and average the voltage, which then is fitted to a power law (I/Ic)^n. The measurements are repeated for the mentioned magnetic field and angle domain to give the dependencies of Ic and n with magnetic field and angle. For device modeling purposes, we can then express a phenomenological law giving Ic and n as a function of the applied magnetic field's intensity and direction

Parametrised Preisach Modelling of Hysteresis in High Temperature Superconductors

We present a parametrised Preisach-type model that describes the hysteresis exhibited by the high temperature superconductors (HTSC); hysteresis is the main cause for losses in the subcritical domain. The parametrised model, in combination with electrical measurements, is independent of geometry, number of filaments and other physical measures, and is identified by a novel method that uses electrical lock-in (loss) measurement technique, which greatly enhances the signal to noise ratio. Identification results from measurements on Bi-2223 multi-filamentary tapes are presented. We have further derived exact models for the hysteretic losses in strip and elliptic geometry strips, where the energy losses were calculated by Norris. The paper contains analysis of the Preisach Model, of its losses and of the suggested parametrisation

Enhancement of power system transient stability using superconducting fault current limiters

Transient stability investigations consist of studying the rotor oscillations of generators (electro-mechanic oscillations, 0.1-2 Hz) after the occurrence of a fault of large amplitude, e.g. short circuit. The goal is to indicate if the generators are capable to stay synchronous after a fault has occurred. The fault duration is one of the most important factors to be determined. In fact, the shorter the fault, the more the maintaining of synchronisation can be guaranteed. Now in case of a fault, a fault current limiter has an extremely fast current transition in comparison to electro-mechanic time constants. This implies a quasi-instantaneous elimination of the fault through a limitation of the current and consequently a better ability to maintain the synchronisation of the system. We recall that in a classic system, the elimination of a fault, by opening a circuit breaker, is carried out in two or three cycles in the best case. We have here studied a simple, radial electric network configuration with a machine and an infinite network. The study covers simulations of a fault that can occur in a network and the consequences of the recovery time of the fault current limiter

Svensk Dagfjärilsövervakning, årsrapport för 2017

Detta är den åttonde årsrapporten från Svensk Dagfjärilsövervakning, ett nationellt miljö-övervakningsprogram som koordineras av Lunds universitet på uppdrag av Naturvårdsverket sedan 2010. Svensk Dagfjärilsövervakning är ett samarbete mellan Sveriges Entomologiska Förening, Naturvårdsverket, Lunds universitet, Sveriges lantbruksuniversitet och Länsstyrelserna. Verksamheten möjliggörs av frivilliga landet runt som mellan den 1 april och 30 september räknar fjärilar. Räkningen sker med en gemensam, systematisk metodik och fördelas på 3-7 inventeringstillfällen under säsongen. Det finns två olika sätt att övervaka, dels punktlokaler som är områden med 25 m radie som bevakas i 15 min per besök, dels slingor som är 0,5-3 km långa rutter som man inventerar i lugn promenadtakt. Genom att övervakningen upprepas inom säsongen och över flera år är det möjligt att skatta hur fjärilsfaunan förändras i antal och artsammansättning. Det åttonde årets övervakning har resulterat i rapporter från 192 slingor och 286 punktlokaler. Slingorna och punkterna är spridda över hela landet, från Beddingestrand i söder till Vuollerim i norr. Antalet rapportörer under 2017 har varit 283 och Svensk Dagfjärilsövervakning har räknat in 64 322 fjärilar av 93 arter. I medeltal har det setts 10,7 arter per punktlokal och 16,1 arter per slinga. För varje funnen fjärilsart redovisar rapporten 2017 års observationer som ett totalantal, en utbredningskarta och figur över de veckor då arten påträffats. Talrikaste arterna 2017 var i tur och ordning luktgräsfjäril, citronfjäril och slåttergräsfjäril. Trender i antal mellan 2010 och 2017 har skattats med hjälp av analysverktyget TRIM för 86 dagfjärils- och bastardsvärmararter. Av dessa minskade 19 arter jämfört med 2010, 15 arter ökade, 8 arter var stabila, medan övriga arter varierade så pass mycket att trenderna är osäkra. Sammanvägda index, så kallade miljöindikatorer har räknats fram för 1) de tolv arter som ingår i den europeiska miljöindikatorn för gräsmarksfjärilar, 2) de tjugo vanligaste fjärilsarterna, 3) fjärilar i jordbruksmiljöer, samt 4) fjärilar i skogsmarker. Miljöindikatorerna för gräsmarksfjärilar och skogsfjärilar är stabila under perioden 2010-2017. Trenderna för miljöindikatorerna för de 20 vanligaste dagfjärilarna och fjärilar i jordbruksmiljöer är att dessa grupper minskar måttligt men signifikant under perioden