Increase In Growth Velocity Research Articles

Microstructural and Mechanical-Property Manipulation through Rapid Dendrite Growth and Undercooling in an Fe-based Multinary Alloy.

Rapid dendrite growth in single- or dual-phase multicomponent alloys can be manipulated to improve the mechanical properties of such metallic materials. Rapid growth of (αFe) dendrites was realized in an undercooled Fe-5Ni-5Mo-5Ge-5Co (wt.%) multinary alloy using the glass fluxing method. The relationship between rapid dendrite growth and the micro-/nano-mechanical properties of the alloy was investigated by analyzing the grain refinement and microstructural evolution resulting from the rapid dendrite growth. It was found that (αFe) dendrites grow sluggishly within a low but wide undercooling range. Once the undercooling exceeds 250 K, the dendritic growth velocity increases steeply until reaching a plateau of 31.8 ms−1. The increase in the alloy Vickers microhardness with increasing dendritic growth velocity results from the hardening effects of increased grain/phase boundaries due to the grain refinement, the more homogeneous distribution of the second phase along the boundaries, and the more uniform distribution of solutes with increased contents inside the grain, as verified also by nanohardness maps. Once the dendritic growth velocity exceeds ~8 ms−1, the rate of Vickers microhardness increase slows down significantly with a further increase in dendritic growth velocity, owing to the microstructural transition of the (αFe) phase from a trunk-dendrite to an equiaxed-grain microstructure.

Rapid solidification morphologies in Ni3Ge: Spherulites, dendrites and dense-branched fractal structures

Single-phase β-Ni3Ge has been rapidly solidified via drop-tube processing. At low cooling rates (850–300 μm diameter particles, 700–2800 K s−1) the dominant solidification morphology, revealed after etching, is that of isolated spherulites in an otherwise featureless matrix. At higher cooling rates (300–75 μm diameter particles, 2800–25,000 K s−1) the dominant solidification morphology is that of dendrites, again imbedded within a featureless matrix. As the cooling rate increases towards the higher end of this range the dendrites display non-orthogonal side-branching and tip splitting. At the highest cooling rates studied (<75 μm diameter particles, >25,000 K s−1), dense-branched fractal structures are observed. Selected area diffraction analysis in the TEM reveals the spherulites and dendrites are a disordered variant of β-Ni3Ge, whilst the featureless matrix is the ordered variant of the same compound. We postulate that the spherulites and dendrites are the rapid solidification morphology and that the ordered, featureless matrix grew more slowly post-recalescence. Spherulites are most likely the result of kinetically limited growth, switching to thermal dendrites as the growth velocity increases. It is extremely uncommon to observe such a wide range of morphologies as a function of cooling rate in a single material.

Microstructural Evolution and Mechanical Properties in Directionally Solidified Sn–10.2 Sb Peritectic Alloy at a Constant Temperature Gradient

The Sn–10.2 Sb (mass fraction) peritectic alloy was prepared using a vacuum melting furnace and a hot filling furnace. The samples were directionally solidified upwards at steady state conditions with a constant temperature gradient (G=4.5±0.2 K. mm-1) under different growth velocities (V=13.3–266.7 µm. s-1) in a Bridgman-type directional solidification apparatus. The effects of the growth velocity (V) on the dendritic spacings were investigated. Primary dendrite arm spacing (PDAS) of α phase in directionally solidified Sn–10.2 Sb peritectic alloy was measured on the longitudinal and transverse sections of 4 mm diameter cylindrical samples. Secondary dendrite arm spacing (SDAS) was measured on the longitudinal section. The experimental results show that the measured PDAS (λ1L, λ1T) and SDAS (λ2) decrease with increasing growth velocity. The dependence of PDAS, SDAS, microhardness (HV) and compressive strength (σc) on the growth velocity were determined by using a linear regression analysis. The experimental results were compared with the previous experimental results and the results of the experimental models.

Concomitant occurrence of Turner syndrome and growth hormone deficiency.

Turner syndrome (TS) is a genetic disorder in phenotypic females that has characteristic physical features and presents as partial or complete absence of the second sex chromosome. Growth hormone deficiency (GHD) is a condition caused by insufficient release of growth hormone from the pituitary gland. The concomitant occurrence of TS and GHD is rare and has not yet been reported in Korea. Here we report 2 cases of TS and GHD. In case 1, GHD was initially diagnosed. Karyotyping was performed because of the presence of the typical phenotype and poor response to growth hormone therapy, which revealed 45,X/45,X+mar. The patient showed increased growth velocity after the growth hormone dose was increased. In case 2, a growth hormone provocation test and chromosomal analysis were performed simultaneously because of decreased growth velocity and the typical TS phenotype, which showed GHD and a mosaic karyotype of 45,X/46,XX. The patient showed spontaneous pubertal development. In female patients with short stature, it is important to perform a throughout physical examination and test for hormonal and chromosomal abnormalities because diagnostic accuracy is important for treatment and prognosis.

Modeling the growth of an altered layer in mineral weathering

A stochastic reaction-diffusion model on a lattice is introduced to describe the growth kinetics of an altered layer in the weathering of a mineral. Particles R represent H2O that permanently fills the outer surface and diffuse on M (mineral) and A (altered) sites with coefficients DM and DA, respectively. The transformation M+R→A occurs with rate r, representing the irreversible formation of the altered material in a region of molecular size, viz. the lattice site of size a. These assumptions agree with predictions of the interfacial dissolution–reprecipitation mechanism, although the model does not describe the chemistry of dissolution reactions or precipitation processes. Scaling concepts are used to distinguish kinetic regimes and their crossovers, and are supported by simulation results. In the short time reactive regime, the thickness of the altered layer increases linearly in time and filling of that layer by particles R is high. In the long time diffusive regime, the altered layer thickness grows as DAt1/2. Modeling of single crystals require very small values of DM, which produces atomically narrow interfaces between the altered material and the mineral and absence of R in the latter, in agreement with recent experimental results. If r<DM/a2, an interface of thickness lAM∼DM/r1/2 is found, with subsurface fluid penetration and increased growth velocity of the altered layer by a factor lAM/a, but no fluid in the bulk mineral. Estimates of the order of magnitude of transformation rates and of diffusion coefficients are obtained by application of the model to some recently studied systems: calcite dissolution, labradorite weathering, and silicate glass weathering. Effects of dissolution of the altered layer are analyzed. Significant differences between the model and leached layer theories are discussed.

Massive pericardial effusion and short stature caused by autoimmune hypothyroidism in a 9-year-old girl.

A 9-year-, 11-month-old girl was brought to the Emergency Department for sudden dyspnea caused by massive pericardial effusion. In addition to relative bradycardia despite impending cardiac tamponade, short stature, overweight, and hypercholesterolemia were clues for suspected hypothyroidism. During thyroxine supplementation, catch-up growth was incomplete by rapid skeletal maturation. The use of short-term growth hormone showed increased growth velocity. In conclusion, primary hypothyroidism should be included in the etiologic evaluation of pericardial effusion, especially when it is associated with relative bradycardia. Additional growth promoting therapy should be considered for incomplete catch-up growth in prolonged hypothyroidism during thyroxine supplementation.

Enhanced Nutrient Supply to Very Low Birth Weight Infants is Associated with Improved White Matter Maturation and Head Growth

Background: Extrauterine growth restriction is common among very low birth weight infants (VLBW, BW <1,500 g). Optimal postnatal nutrient supply is essential to limit growth restriction and ensure adequate growth and neurodevelopment. Objectives: We compared an enhanced postnatal nutrient supply to a standard supply and evaluated the effects on growth velocity, head circumference growth and cerebral maturation - the latter by magnetic resonance diffusion tensor imaging (DTI). We hypothesized increased growth velocity, head circumference growth and decreased mean diffusivity (MD) in cerebral white matter (WM) areas, suggesting improved cerebral maturation among infants on the enhanced nutrient supply. Methods: In this randomized controlled trial, infants on the enhanced nutrient supply received increased amounts of energy, protein, fat, essential fatty acids and vitamin A until discharge. DTI was performed close to term equivalent age. Outcomes were growth velocity, head circumference growth and WM mean diffusivity. Results: Among the 50 included infants, 14 in the intervention group and 11 controls underwent a successful DTI. Infants on the enhanced diet achieved improved growth velocity (16.5 vs. 13.8 g/kg/day, p = 0.01) and increased head circumference (Δz score: 0.24 vs. -0.12, p = 0.15). A significantly lower MD was seen in a large WM area such as the superior longitudinal fasciculi (1.19 × 10^-3 vs. 1.24 × 10^-3 mm²/s, p = 0.04, adjusted for age when scanned). Conclusions: Enhanced nutrient supply to VLBW infants is associated with improved growth velocity, increased head circumference growth and decreased regional WM mean diffusivity, suggesting improved maturation of cerebral connective tracts.

Formula feeding for late-preterm infants

Preterm birth interrupts physiological foetal development, leading to various degrees of immaturity according to the gestational age at which the infant is born [1]. Since 2005, the imprecise definition of “near-term” infants has been replaced with “late-preterm”, which includes infants born between 340/7 and 366/7 weeks of gestation [2]. Late-preterm infants are at higher risk than term infants of developing medical complications that result in higher rates of mortality and morbidity [3], including thermal instability, respiratory problems, hypoglycaemia, jaundice, and feeding problems. Breastfeeding is the first nutritional choice for all infants, especially for those born preterm. The establishment of successful breastfeeding in late-preterm infants is usually problematic, as late-preterm infants can be sleepier, have less muscular strength and more difficulty with latch, suck and swallow than term infants [4]. For this reason, health-care providers should implement specific strategies aimed at anticipate, identify promptly, and manage breastfeeding problems that the late-preterm infant and mother can experience. However, when exclusive breastfeeding does not guarantee adequate nutrition, supplements might be advisable. Nutritional requirements of late-preterm infants are currently derived from speculations on foetal growth and requirements of preterm and term infants, while specific data on nutritional needs of this population are scarce. There is currently no consensus on whether late-preterm infants would benefit most of a high-protein diet, such as that proposed for “micropreterm” infants [5], or of a low-protein diet, such as that recommended for full-term infants. Some studies suggest that the provision of extra protein and energy could reduce weight loss and increase growth velocity [6], thus decreasing the risk for dehydration and hospital readmission. However, it is important to note that growth rate during late gestation decreases dramatically, and it is likely that protein and energy requirements for infants born during this period wouldn’t be as high as those of very preterm infants [7]. Current guidelines recommend the supplementation with essential nutrients also for late-preterm infants. Actually, it has been shown that supplementation with LC-PUFAs improves visual acuity and cognitive development in infants 30-37 weeks gestation [8]. The best nutritional approach to late-preterm infants still needs to be determined. Human milk’s benefits are undoubted; however, caregivers have to adequately support the establishment of successful breastfeeding and also identify those cases where some supplementation is needed. Further studies will have to clarify whether all late-preterm infants, or only a subgroup such as small-for-gestational-age infants, could benefit from formulas with high energy and protein content.

Determining the Effects of Growth Velocity on Microstructure and Mechanical Properties of Ti-47Al Alloy using Electromagnetic Confinement and Directional Solidification

Directionally solidified Ti-47Al samples without contamination were obtained by the electromagnetic confinement and directional solidification technique. With increasing growth velocity, the solid/liquid interface was changed from cellular to dendritic. The grain boundary turned vague, and the lamellae within the grains became distorted. When the growth velocity increased to 200 μm/s, some γ phases and α phases appeared in local region owing to the enrichment of Al solute. The columnar grain size (λ), interdendritic spacing (λ 1), and interlamellar spacing (λ L) were measured, and the effects of growth velocity on these parameters were discussed. As the growth velocity increased, both the microhardness and the 0.2% offset compression yield stress increased continuously. However, the value of yield stress decreased slightly when the growth velocity increased to 200 μm/s, which resulted from the appearance of γ phases.

Effects of levothyroxine on growth hormone (gh) sensitivity in children with idiopathic short stature

BackgroundThe possible relationship between the circulating concentrations of T4 and GH sensitivity has not been elucidated. ObjectiveThe aim of this study is to evaluate the effect of levothyroxine supplementation on GH sensitivity in prepubertal boys with idiopathic short stature (ISS). MethodsWe selected 28 prepubertal boys with ISS (mean age 8.2±0.5years) and free T4 (Ft4) concentrations between the 3rd and the 25th percentiles (Ft4: 0.8–1.5ng/dl). They were randomly divided into two groups: Group A received thyroid supplementation (1–3μg/kg/day) for 120days, and Group B received placebo for the same period. To evaluate GH sensitivity, an IGF-I generation test (GH: 33μg/kg/day sc for 3days) was performed in both groups: under basal conditions, and after 120days of levothyroxine supplementation (or placebo). ResultsAfter thyroid supplementation, Group A had higher Ft4 concentrations compared with Group B (2.14±0.06 vs 1.48±0.06ng/dl, p=0.01), their growth velocity was significantly higher (2.3±0.1 vs 1.5±0.2cm/4months), and they exhibited a greater increase in IGF-I after GH administration (Group A: 32.5±3.8% vs Group B 17.3±2.6%). ConclusionSupplementation with levothyroxine for 120days promotes an increase in growth velocity, and a greater IGF-I response to short-term GH administration in prepubertal boys with ISS and low-normal thyroid hormone concentrations.

EB1 Accelerates Two Conformational Transitions Important for Microtubule Maturation and Dynamics

SummaryBackgroundThe dynamic properties of microtubules depend on complex nanoscale structural rearrangements in their end regions. Members of the EB1 and XMAP215 protein families interact autonomously with microtubule ends. EB1 recruits several other proteins to growing microtubule ends and has seemingly antagonistic effects on microtubule dynamics: it induces catastrophes, and it increases growth velocity, as does the polymerase XMAP215.ResultsUsing a combination of in vitro reconstitution, time-lapse fluorescence microscopy, and subpixel-precision image analysis and convolved model fitting, we have studied the effects of EB1 on conformational transitions in growing microtubule ends and on the time course of catastrophes. EB1 density distributions at growing microtubule ends reveal two consecutive conformational transitions in the microtubule end region, which have growth-velocity-independent kinetics. EB1 binds to the microtubule after the first and before the second conformational transition has occurred, positioning it several tens of nanometers behind XMAP215, which binds to the extreme microtubule end. EB1 binding accelerates conformational maturation in the microtubule, most likely by promoting lateral protofilament interactions and by accelerating reactions of the guanosine triphosphate (GTP) hydrolysis cycle. The microtubule maturation time is directly linked to the duration of a growth pause just before microtubule depolymerization, indicating an important role of the maturation time for the control of dynamic instability.ConclusionsThese activities establish EB1 as a microtubule maturation factor and provide a mechanistic explanation for its effects on microtubule growth and catastrophe frequency, which cause microtubules to be more dynamic.

Growth Hormone Deficiency and Lysinuric Protein Intolerance: Case Report and Review of the Literature.

Lysinuric protein intolerance (LPI; MIM# 222700) is a rare metabolic disorder caused by a defective cationic amino acids (CAA) membrane transport leading to decreased circulating plasma CAA levels and resulting in dysfunction of the urea cycle. Short stature is commonly observed in children with LPI and has been associated with protein malnutrition. A correlation between LPI and growth hormone deficiency (GHD) has also been postulated because of the known interaction between the AA arginine, ornithine, and lysine and growth hormone (GH) secretion. Our report describes a case of GHD in an LPI patient, who has not presented a significant increase in growth velocity with recombinant-human GH (rhGH) therapy, suggesting some possible pathogenic mechanisms of growth failure. The proband was a 6-year-old boy, diagnosed as suffering from LPI, erythrophagocytosis (HP) in bone marrow, and short stature. Two GH provocative tests revealed GHD. The patient started rhGH therapy and a controlled-protein diet initially with supplementation of oral arginine and then of citrulline. At 3-year follow-up, no significant increase in growth velocity and in insulin-like growth factor-1 (IGF-1) levels was observed. Inadequate nutrition and low plasmatic levels of arginine, ornithine, lysine, and HP may have contributed to his poor growth. Our case suggests that growth failure in patients with GHD and LPI treated with rhGH could have a complex and multifactorial pathogenesis. Persistently low plasmatic levels of lysine, arginine, and ornithine, associated with dietary protein and caloric restriction and systemic inflammation, could determine a defect in coupling GH to IGF-1 production explaining why GH replacement therapy is not able to significantly improve growth impairment. We hypothesize that a better understanding of growth failure pathophysiology in these patients could lead to the development of more rational strategies to treat short stature in patients with LPI.

Evidence for an extended transition in growth orientation and novel dendritic seaweed structures in undercooled Cu–8.9 wt%Ni

A melt encasement (fluxing) technique has been used to systematically study the microstructural development and velocity–undercooling relationship of a Cu–8.9wt%Ni alloy at undercoolings up to 235K. A complex series of microstructural transitions have been identified with increasing undercooling. At the lowest undercoolings a 〈100〉 type dendritic structure gives way to an equiaxed grain structure, consistent with the low undercooling region of grain refinement observed in many alloys. At intermediate undercoolings, dendritic growth returns, consisting of dendrites of mixed 〈100〉 and 〈111〉 character. Within this region, 8-fold growth is first observed at low undercoolings, indicating the dominance of 〈100〉 character. As undercooling is increased, 〈111〉 character begins to dominate and a switch to 6-fold growth is observed. It is believed that this is an extended transition region between 〈100〉 and 〈111〉 dendrite growth, the competing anisotropies of which are giving rise to a novel form of dendritic seaweed, characterised by its containment within a diverging split primary dendrite branch. At higher undercoolings it is suggested that a transition to fully 〈111〉 oriented dendritic growth occurs, accompanied by a rapid increase in growth velocity with further increases in undercooling. At the highest undercooling achieved, a microstructure of both small equiaxed grains, and large elongated grains with dendritic seaweed substructure, is observed. It is thought that this may be an intermediate structure in the spontaneous grain refinement process, in which case the growth of dendritic seaweed appears to play some part.

Effect of recombinant human growth hormone on changes in height, bone mineral density, and body composition over 1–2 years in children with Hurler or Hunter syndrome

Patients with Hurler or Hunter syndrome typically have moderate to severe growth deficiencies despite therapy with allogeneic hematopoietic stem cell transplantation and/or enzyme replacement therapy. It is unknown whether treatment with recombinant human growth hormone (hGH) can improve growth in these children. The objectives of this study were to determine the effects of hGH on growth, bone mineral density (BMD), and body composition in children with Hurler or Hunter syndrome enrolled in a longitudinal observational study. The difference in annual change in outcomes between hGH treated and untreated subjects was estimated by longitudinal regression models that adjusted for age, Tanner stage, and sex where appropriate. We report on 23 participants who completed at least 2 annual study visits (10 [43%] treated with hGH): Hurler syndrome (n=13) average age of 9.8±3.1years (range 5.3–13.6years; 54% female) and Hunter syndrome (n=10) average age of 12.0±2.7years (range 7.0–17.0years; 0% female). As a group, children with Hurler or Hunter syndrome treated with hGH had no difference in annual change in height (growth velocity) compared to those untreated with hGH. Growth velocity in hGH treated individuals ranged from −0.4 to 8.1cm/year and from 0.3 to 6.6cm/year in the untreated individuals. Among children with Hunter syndrome, 100% (N=4) of those treated but only 50% of those untreated with hGH had an annual increase in height standard deviation score (SDS). Of the individuals treated with hGH, those with GHD had a trend towards higher annualized growth velocity compared to those without GHD (6.5±1.9cm/year vs. 3.5±2.1cm/year; p=.050). Children treated with hGH had greater annual gains in BMD and lean body mass. In conclusion, although as a group we found no significant difference in growth between individuals treated versus not treated with hGH, individual response was highly variable and we are unable to predict who will respond to treatment. Thus, a trial of hGH may be appropriate in children with Hurler or Hunter syndrome, severe short stature, and growth failure. However, efficacy of hGH therapy should be evaluated after 1year and discontinued if there is no increase in growth velocity or height SDS. Finally, the long-term benefits of changes in body composition with hGH treatment in this population are unknown.

A review on vitamin d deficiency treatment in pediatric patients.

Vitamin D is essential for calcium absorption and for maintaining bone health in the pediatric population. Vitamin D deficiency may develop from nutritional deficiencies, malabsorption, enzyme-inducing medications, and many other etiologies. It may present as hypocalcemia before bone demineralization at periods of increased growth velocity (infancy and adolescence) because the increased calcium demand of the body cannot be met. In children, inadequate concentrations of vitamin D may cause rickets and/or symptomatic hypocalcemia, such as seizures or tetany. In this review, we will discuss the pharmacology behind vitamin D supplementation, laboratory assessments of vitamin D status, current literature concerning vitamin D supplementation, and various supplementation options for the treatment of vitamin D deficiency in the pediatric population.

Clinical, biochemical, and genetic analysis of two Korean patients with Trichorhinophalangeal syndrome type I and growth hormone deficiency

Tricho-rhino-phalangeal syndrome type I (TRPSI) is a rare autosomal dominant hereditary disorder characterized by sparse hair, bulbous nose, long philtrum, thin upper lip, and skeletal abnormalities including cone-shaped epiphyses, shortening of the phalanges, and short stature. TRPSI is caused by mutations in the TRPS1 gene. Herein, we report two Korean cases of TRPSI. Although both patients (a 17-year-old-female and a 14-year-old male) had typical clinical findings, Patient 1 had an additional growth hormone (GH) deficiency. Treatment with recombinant human growth hormone (rhGH) 0.7 IU/kg/week led to an increase in growth velocity. Over 10 years of GH therapy, the mean growth velocity was 5.7 ± 0.9 cm/year. However, the patient 2 did not show apparent GH deficiency by GH stimulation test, had a poor response with rhGH therapy and GH therapy was discontinued after 6 months. Upon genetic analysis of the TRPS1 gene, two mutations were found. Patient 1 had a heterozygous mutation c.2520dupT (p.Arg841LysfsX3) which had not been previously reported. Patient 2 had a known nonsense mutation c.1630C>T (p.Arg544X). In summary, we were the first to report Korean patients with mutation of TRPS1.

A pilot study on the effect of three hydrocortisone dosing regimen on 17 hydroxyprogesterone levels in patients with congenital adrenal hyperplasia

The 2004 Newborn Screening Act has saved a lot of Filipinos from Congenital Adrenal Hyperplasia (CAH). The increase in the number of patients living with CAH challenges us to find the optimal steroid replacement therapy. In the Philippines, there is no locally published data on this. The objectives of the paper are to compare the effect of different hydrocortisone dosing regimen on the 17 hydroxyprogesterone (17 OHP) levels of patients with CAH and to report adverse effects. The pilot study is a single-blinded randomized control trial comparing the 17 OHP levels of infants with CAH given higher evening hydrocortisone dose (HED), higher morning hydrocortisone dose (HMD) and equal hydrocortisone dose (EHD) who consulted in a tertiary hospital from January 2011 to July 2011. Nine patients completed the study (3 males and 6 females) with mean age of 16 (+11) months. One patient was randomized to HMD, 5 to HED and 3 to EHD. A marginally significant difference (p-value=0.0515) in the 17 OHP levels was observed between treatment groups. Adverse effects included increased BMI with concomitant presence of cushingoid facies in 33% (3/9) of the patients and an increased growth velocity in one patient in the HED group. A significant difference was observed between treatment groups. The decrease in 17OHP was best appreciated in the EHD group but no definitive conclusion can be made on the optimal treatment schedule due to the small sample size. It is recommended that a larger study be done on newly diagnosed neonates with CAH using 525 patients (11 for HMD, 257 for HED and 257 for EHD) and ACTH levels be included in the outcome measures. Also, the use of oral steroids available in the country such as Prednisone or Dexamethasone as an alternative treatment be investigated.

Pubertal Growth and Serum Testosterone and Estradiol Levels in Boys

Background/Aims: To study serum testosterone and estradiol in healthy boys in relation to growth during puberty up to peak height velocity (PHV). Methods: Growth velocity was analyzed through testosterone (n = 41) and 17β-estradiol (n = 37) 24-hour profiles in a dose-response model. Participants were 26 healthy boys admitted for short or tall stature or participating as healthy volunteers at the Queen Silvia Children's Hospital. Other inclusion criteria included the following: gestational age 37-42 weeks, birth weight and length >-2 standard deviation score (SDS) and prepubertal height and weight within ±3 SDS. Testosterone was measured using a modified radioimmunoassay (RIA) with a detection limit of 0.03 nmol/l. Estradiol was determined using an ultrasensitive extraction RIA with a detection limit 4 pmol/l. A sixth-grade polynomial was fitted to each child's growth data, giving growth velocity and age at PHV. Results: Growth velocity increased by 50% from prepubertal growth to PHV at a morning testosterone level of 3.1 nmol/l (95% confidence interval 2.4-4.2), EC₅₀. The corresponding EC₅₀ of 17β-estradiol was 6.5 pmol/l (3.2-13). Boys approaching PHV (<4% remaining) had morning testosterone levels >10 nmol/l and 17β-estradiol >9 pmol/l. Conclusion: Observed early puberty/initial mid puberty morning testosterone levels of 2.4-4.2 nmol/l are associated with a 50% increase in growth velocity from prepubertal growth to PHV in healthy boys.

Low maternal education is associated with increased growth velocity in the first year of life and in early childhood: the ABCD study

The objective of this study is first to examine the relation of maternal education and growth velocity during the first year of life and early childhood (1-5 years). The second objective is to determine the potential explanatory role of standardized birth weight, maternal smoking during pregnancy, maternal prepregnancy body mass index (BMI), and infant feeding practice in this relation. We used longitudinal growth data of 1,684 participants with Dutch ethnicity participating in a population-based cohort study (Amsterdam Born Children and their Development study). Growth velocity of weight and of weight-for-length were calculated by subtracting the weight and weight-for-length standard deviation scores (SDS), respectively of two time periods. In the first year of life, children with low-educated mothers had an increase in SDS of 0.26 (95 % confidence interval (CI) 0.08-0.45) for weight compared to children with high-educated mothers. In early childhood, children with low-educated mothers had a 0.27 SDS (95 % CI 0.11-0.42) increase for weight-for-length, compared to children with high-educated mothers. Using path analysis, these inequalities could partly be explained by maternal smoking, duration of breastfeeding, maternal age, and maternal BMI. Children with low-educated mothers had an increased weight gain during the first year of life and an increased weight-for-length gain in early childhood compared to children with high-educated mothers. Although underlying mechanisms were not completely clarified, an optimal duration of breastfeeding, cessation of maternal smoking, and reduction of maternal BMI seem to reduce these educational inequalities in early growth and possible adverse consequences of accelerated growth.

Effects of Strontium, Magnesium Addition, Temperature Gradient, and Growth Velocity on Al–Si Eutectic Growth in a Unidirectionally-solidified Al–13 wt% Si Alloy

Al–Si eutectic growth mechanism was investigated in a directionally-solidified Al–13 wt% Si alloy with different strontium (Sr) and magnesium (Mg) additions, growth velocities and temperature gradients. Macro- and micro-scale metallographic analyses revealed that addition level of Sr and Mg, temperature gradient and growth velocity are important factors affecting stability of solidifying Al–Si eutectic front and the final morphology of eutectic grains in the solidified Al–13 wt% Si alloys. By varying (tailoring) these factors, a variety of eutectic grain structures and morphologies such as planar front, cellular structure, a mix of cellular and columnar, or equiaxed dendrites, can be obtained. Increasing temperature gradient, reducing growth velocity, or decreasing Sr and Mg contents is beneficial to stabilizing planar growth front of eutectic grains, which is qualitatively in accordance with constitutional supercooling criterion for binary eutectic growth. In contrast, adding more Sr and Mg, increasing growth velocity, or decreasing temperature gradient produces large constitutional supercooling, leading to columnar-equiaxed transition (CET) of eutectic structure, which can be interpreted on the basis of Hunt's Model. It is also found that both solute concentration and solidification variables have significant impact not only on eutectic growth, but also on gas porosity formation.