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Linear Growth Rate (linear + growth_rate)
Selected AbstractsLinear stability analysis of flow in a periodically grooved channelINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 6 2003T. Adachi1 Abstract We have conducted the linear stability analysis of flow in a channel with periodically grooved parts by using the spectral element method. The channel is composed of parallel plates with rectangular grooves on one side in a streamwise direction. The flow field is assumed to be two-dimensional and fully developed. At a relatively small Reynolds number, the flow is in a steady-state, whereas a self-sustained oscillatory flow occurs at a critical Reynolds number as a result of Hopf bifurcation due to an oscillatory instability mode. In order to evaluate the critical Reynolds number, the linear stability theory is applied to the complex laminar flow in the periodically grooved channel by constituting the generalized eigenvalue problem of matrix form using a penalty-function method. The critical Reynolds number can be determined by the sign of a linear growth rate of the eigenvalues. It is found that the bifurcation occurs due to the oscillatory instability mode which has a period two times as long as the channel period. Copyright © 2003 John Wiley & Sons, Ltd. [source] Positive Linear Growth and Bone Responses to Growth Hormone Treatment in Children With Types III and IV Osteogenesis Imperfecta: High Predictive Value of the Carboxyterminal Propeptide of Type I Procollagen,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 2 2003Joan C Marini MD Abstract Extreme short stature is a cardinal feature of severe osteogenesis imperfecta (OI), types III and IV. We conducted a treatment trial of growth hormone in children with OI and followed linear growth velocity, bone metabolism markers, histomorphometrics, and vertebral bone density. Twenty-six children with types III and IV OI, ages 4.5,12 years, were treated with recombinant growth hormone (rGH), 0.1,0.2 IU/kg per day for 6 days/week, for at least 1 year. Length, insulin-like growth factor (IGF-I), insulin-like growth factor binding protein (IGFBP-3), bone metabolic markers, and vertebral bone density by DXA were evaluated at 6-month intervals. An iliac crest biopsy was obtained at baseline and 12 months. Approximately one-half of the treated OI children sustained a 50% or more increase in linear growth over their baseline growth rate. Most responders (10 of 14) had moderate type IV OI. All participants had positive IGF-I, IGFBP-3, osteocalcin, and bone-specific alkaline phosphatase responses. Only the linear growth responders had a significant increase in vertebral DXA z-score and a significant decrease in long bone fractures. After 1 year of treatment, responders' iliac crest biopsy showed significant increases in cancellous bone volume, trabecular number, and bone formation rate. Responders were distinguished from nonresponders by higher baseline carboxyterminal propeptide (PICP) values (p < 0.05), suggesting they have an intrinsically higher capacity for collagen production. The results show that growth hormone can cause a sustained increase in the linear growth rate of children with OI, despite the abnormal collagen in their bone matrix. In the first year of treatment, growth responders achieve increased bone formation rate and density, and decreased fracture rates. The baseline plasma concentration of PICP was an excellent predictor of positive response. [source] Anti-inflammatory pharmacotherapy for wheezing in preschool childrenPEDIATRIC PULMONOLOGY, Issue 5 2007Athanasios G. Kaditis MD Abstract Accumulating evidence indicates that there are at least two phenotypes of wheezing in preschool years with distinct natural history. Frequent wheezing in the first 3 years of life with risk factors for asthma (e.g., eczema, maternal asthma) predicts symptoms in older age, while infrequent viral-associated wheezing without risk factors for asthma has a benign prognosis. This systematic review summarizes evidence on the use of anti-inflammatory medications in preschool children with wheezing. Literature search was performed using Medline and the Cochrane Library. Retrieved articles were critically appraised. Episodic use of high-dose inhaled corticosteroids (>1,600 mcg/day of beclomethasone) may ameliorate severity of intermittent viral-associated wheezing. Maintenance inhaled corticosteroids can control symptoms in children with frequent wheezing associated with risk factors for asthma. Inhaled corticosteroids do not alter the natural history of wheezing even when started early in life and could have a negative impact on linear growth rate. Short courses of oral corticosteroids have been proposed as an effective measure to control exacerbations of symptoms although there is little evidence supporting their use. Some studies support the administration of non-steroidal anti-inflammatory medications (leukotriene pathway modifiers, cromones, methylxanthines) for mild frequent wheezing. Maintenance inhaled corticosteroids is the most effective measure for controlling frequent wheezing in preschool children, especially when accompanied by risk factors for asthma. This treatment does not affect the natural history of wheezing, although deceleration of linear growth rate is the most commonly recognized systemic adverse effect. Pediatr Pulmonol. 2007; 42:407,420. © 2007 Wiley-Liss, Inc. [source] The influence of stratospheric potential vorticity on baroclinic instabilityTHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 644 2009L. A. Smy Abstract This article examines the dynamical coupling between the stratosphere and troposphere by considering the effect of direct perturbations to stratospheric potential vorticity on the evolution of midlatitude baroclinic instability in a simple extension of an Eady model. A simulation in which stratospheric potential vorticity is exactly zero is used as a control case, and both zonally symmetric and asymmetric perturbations to the stratospheric potential vorticity are then considered, the former representative of a strong polar vortex, the latter representative of the stratospheric state following a major sudden warming. Both types of stratospheric perturbation result in significant changes to the synoptic-scale evolution of surface temperature, as well as to zonally and globally averaged tropospheric quantities. In the case of a zonally symmetric perturbation, the linear growth rate of all unstable modes decreases with increasing perturbation amplitude. Initial growth rates in cases with significant asymmetric perturbations are also weaker than those of the control case, but final eddy kinetic energy values are much larger due to the growth of low zonal wavenumbers triggered by the initial stratospheric perturbation. A comparison of the zonally symmetric and asymmetric perturbations gives some insight into the possible influence of pre- or post-sudden-warming conditions on tropospheric evolution. Copyright © 2009 Royal Meteorological Society [source] Genotype,phenotype relationships in an investigation of the role of proteases in abdominal aortic aneurysm expansionBRITISH JOURNAL OF SURGERY (NOW INCLUDES EUROPEAN JOURNAL OF SURGERY), Issue 11 2005P. Eriksson Background: The aim of the study was to investigate the effect of functional polymorphisms in promoters of matrix metalloproteinase (MMP) 2, MMP-3, MMP-9, MMP-12 and plasminogen activator inhibitor (PAI) 1 genes on the growth rate of small abdominal aortic aneurysms (AAA). Methods: Some 455 individuals with a small AAA (4·0,5·5 cm) were monitored for aneurysm growth by ultrasonography (mean follow-up 2·6 years). They also provided a DNA sample for analysis of the ,1306 C > T, ,1171 5A > 6A, ,1562 C > T, ,82 A > G and ,675 4G > 5G alleles of MMP-2, MMP-3, MMP-9, MMP-12 and PAI-1, respectively. Mean linear AAA growth rates were calculated by flexible modelling; the sample size was sufficient to detect variants that influenced the growth rate by 25 per cent. Results: For MMP-2, MMP-9 and MMP-12 genotypes, growth rates were similar to the mean linear growth rate of 3·08 mm per year. For MMP-3, growth rates were 3·05 (for 5A5A), 3·19 (for 5A6A) and 2·90 (for 6A6A) mm per year. For PAI-1, patients with 4G4G, 4G5G and 5G5G genotypes had growth rates of 3·18, 2·92 and 3·47 mm per year, respectively, for aneurysms with a baseline diameter of 45·1, 44·6 and 46·2 mm. The increased growth rate for patients with PAI-1 5G5G genotype was not statistically significant (P = 0·061), although these patients had the lowest plasma PAI-1 concentrations (P = 0·018). Conclusion: There was no evidence that any specific MMP polymorphism had a clinically significant effect on AAA expansion. The plasminogen system may have a small but clinically significant role in AAA development. Much larger studies would be needed to evaluate genes of smaller effect. Copyright © 2005 British Journal of Surgery Society Ltd. Published by John Wiley & Sons, Ltd. [source] | ||||||||||