5,201 research outputs found

    Nonlinear growth generates age changes in the moments of the frequency distribution: the example of height in puberty

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    Higher moments of the frequency distribution of child height and weight change with age, particularly during puberty, though why is not known. Our aims were to confirm that height skewness and kurtosis change with age during puberty, to devise a model to explain why, and to test the model by analyzing the data longitudinally. Heights of 3245 Christ's Hospital School boys born during 1927-1956 were measured twice termly from 9 to 20 years (n = 129 508). Treating the data as independent, the mean, standard deviation (SD), skewness, and kurtosis were calculated in 40 age groups and plotted as functions of age t. The data were also analyzed longitudinally using the nonlinear random-effects growth model H( t) = h( t - epsilon) + alpha, with H( t) the cross-sectional data, h( t) the individual mean curve, and epsilon and alpha subject-specific random effects reflecting variability in age and height at peak height velocity (PHV). Mean height increased monotonically with age, while the SD, skewness, and kurtosis changed cyclically with, respectively, 1, 2, and 3 turning points. Surprisingly, their age curves corresponded closely in shape to the first, second, and third derivatives of the mean height curve. The growth model expanded as a Taylor series in e predicted such a pattern, and the longitudinal analysis showed that adjusting for age at PHV on a multiplicative scale largely removed the trends in the higher moments. A nonlinear growth process where subjects grow at different rates, such as in puberty, generates cyclical changes in the higher moments of the frequency distribution

    Effects of concentric vs eccentric loading on cardiovascular variables and ECG

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    There is a paucity of information concerning the cardiovascular responses and adaptations to strength training. Limited evidence suggest that which particular type of resistance exercise could be more tolerable as well as potentially safer for people with cardiac diseases or impairments. So, the aim of study was to determine and compare the effect of concentric and eccentric loading on cardiovascular variables and ECG.20 Young healthy students (mean age 20 ± 4 years) participated and were randomly divided into two groups- Experimental & Control. Pre & Post training readings were taken for following Parameters –Heart Rate, Blood Pressure, Mean Arterial Pressure, Rate Pressure Product and ECG. At first testing bout, participants performed concentric exercises (at 75% of 10 RM). Participants returned 10 days after the first session to perform exercises using the eccentric contraction type. Related‘t’ test and one way ANOVA was applied for statistical analysis between groups. Cardiovascular measures collected from subjects were significantly lower during eccentric than during concentric bouts in all subjects (p<0.01) and ECG showed no significant changes after both training protocols (p>0.05). So, it can be concluded that since eccentric exercise produces less cardiopulmonary demands so are more suitable for persons with low exercise tolerance, who are at the risk of adverse cardiopulmonary events and for improving and maintaining cardiac fitness.Keywords: Eccentric Exercise, Concentric Exercise, ECG, Cardiopulmonary demands, Young population

    More security or less insecurity

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    We depart from the conventional quest for ‘Completely Secure Systems’ and ask ‘How can we be more Secure’. We draw heavily from the evolution of the Theory of Justice and the arguments against the institutional approach to Justice. Central to our argument is the identification of redressable insecurity, or weak links. Our contention is that secure systems engineering is not really about building perfectly secure systems but about redressing manifest insecurities.Final Accepted Versio

    Altered expression of the voltage-gated calcium channel subunit α2δ-1: a comparison between two experimental models of epilepsy and a sensory nerve ligation model of neuropathic pain.

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    The auxiliary α2δ-1 subunit of voltage-gated calcium channels is up-regulated in dorsal root ganglion neurons following peripheral somatosensory nerve damage, in several animal models of neuropathic pain. The α2δ-1 protein has a mainly presynaptic localization, where it is associated with the calcium channels involved in neurotransmitter release. Relevant to the present study, α2δ-1 has been shown to be the therapeutic target of the gabapentinoid drugs in their alleviation of neuropathic pain. These drugs are also used in the treatment of certain epilepsies. In this study we therefore examined whether the level or distribution of α2δ-1 was altered in the hippocampus following experimental induction of epileptic seizures in rats, using both the kainic acid model of human temporal lobe epilepsy, in which status epilepticus is induced, and the tetanus toxin model in which status epilepticus is not involved. The main finding of this study is that we did not identify somatic overexpression of α2δ-1 in hippocampal neurons in either of the epilepsy models, unlike the upregulation of α2δ-1 that occurs following peripheral nerve damage to both somatosensory and motor neurons. However, we did observe local reorganisation of α2δ-1 immunostaining in the hippocampus only in the kainic acid model, where it was associated with areas of neuronal cell loss, as indicated by absence of NeuN immunostaining, dendritic loss, as identified by areas where microtubule-associated protein-2 immunostaining was missing, and reactive gliosis, determined by regions of strong OX42 staining

    Supraclavicularis proprius muscle associated with supraclavicular nerve entrapment

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    Entrapment neuropathy of the supraclavicular nerve is rare and, when it occurs, is usually attributable to branching of the nerve into narrow bony clavicular canals. We describe another mechanism for entrapment of this nerve with the aberrant muscle; supraclavicularis being found during the routine dissection of an embalmed 82-year-old cadaver. Our report details a unique location for this rare muscular variation whereby the muscle fibres originated posteriorly on the medial aspect of the clavicle before forming a muscular arch over the supraclavicular nerve and passing laterally towards the trapezius and acromion. We recommend that in clinical instances of otherwise unexplained unilateral clavicular pain or tenderness, nerve compression from the supraclavicularis muscle must be borne in mind.
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