Mechanism Of Early Growth Research Articles

Effect of anodizing on high cycle fatigue behaviour of cast AlSi8Mg-T6 alloy

The work investigates the effect of anodizing on the high cycle fatigue behaviour of a high-quality cast Aluminium (AlSi8Mg-T6) alloy. Tensile and fatigue tests are carried out on both non-anodized and anodized specimens in order to highlight the differences in tensile and fatigue responses. In addition, roughness measurements, fracture surfaces analyses, metallography, instrumented micro-indentation and scanning electron microscope (SEM) inspections are performed in order to investigate the interplay between the presence of an anodic layer and the fatigue life of anodized specimens.It is demonstrated that, after anodizing, AlSi8Mg-T6 specimens shows a deterioration of the fatigue performance at medium–low stress amplitudes (130 and 110 MPa). In addition, fracture surface analysis reveals that the presence of the anodic layer modifies the fatigue crack initiation and early growth mechanisms. The manuscript paves the way for an accurate fatigue design of anodized, cast AlSix components.

Molecular dynamics of C–S–H production in graphene oxide environment

Abstract The process of calcium silicate hydrate (C–S–H) generation in graphene oxide (GO) nanoslits was investigated via molecular dynamics simulations using the structural polymerization reaction of silica chains in the synthesis of silica gels. The structural evolution of C–S–H, radial distribution functions, chemical components, and distribution of Q n units in the system were analyzed to investigate the influence of GO on the early growth mechanism of C–S–H and compare the structural differences of C–S–H in the presence and absence of GO. The results showed that the proportion of silicon atoms bonded to bridge-site oxygen atoms in the C–S–H structure increased in the presence of oxygen-containing graphene groups. Ion adsorption in the GO surface layer led to an increase in the degree of polymerization of C–S–H. The nucleation and templating effects of GO were confirmed, revealing the intrinsic mechanism for the formation of GO-modified reinforced cementitious materials.

Transcriptomic profile of leg muscle during early growth and development in Haiyang yellow chicken.

Skeletal muscle growth and development from embryo to adult consists of a series of carefully regulated changes in gene expression. This study aimed to identify candidate genes involved in chicken growth and development and to investigate the potential regulatory mechanisms of early growth in Haiyang yellow chicken. RNA sequencing was used to compare the transcriptomes of chicken muscle tissues at four developmental stages. In total, 6150 differentially expressed genes (DEGs) (fold change 2; false discovery rate (FDR) 0.05) were detected by pairwise comparison in female chickens. Functional analysis showed that the DEGs were mainly involved in the processes of muscle growth and development and cell differentiation. Many of the DEGs, such as MSTN, MYOD1, MYF6, MYF5, and IGF1, were related to chicken growth and development. The Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis showed that the DEGs were significantly enriched in four pathways related to growth and development: extracellular matrix (ECM)–receptor interaction, focal adhesion, tight junction, and insulin signalling pathways. A total of 42 DEGs assigned to these pathways are potential candidate genes for inducing the differences in growth among the four development stages, such as MYH1A, EGF, MYLK2, MYLK4, and LAMB3. This study identified a range of genes and several pathways that may be involved in regulating early growth.

The Paths of Small Fatigue Cracks in High-Strength Steels Initiated from Inclusions and Small Defects

Abstract In fatigue, the early growth mechanisms, paths, and rates of the microstructurally small cracks are not well known. Growth of subsurface—undetected—cracks cannot be monitored in real time, and postfracture fractography is complicated because of the statistical nature of local microstructure. Furthermore, hammering or sliding often damages the fracture surface before the test is stopped. We addressed this challenge with two approaches. This paper deals with fractographic details connected to local microstructure obtained by milling and imaging with a focused ion beam in a scanning electron microscope (SEM). The results provided input such as crack growth on adjacent planes and their coalescence, as well as formation of the “optically dark areas” that play a key role in the early growth and initiation of small cracks in fatigue. A subset of data consisting of eleven 100Cr6 bearing steel specimens loaded at the same stress amplitude, with fatigue lives (Nf) in the range of 10·106 < Nf < 650·106 loading cycles are studied and discussed. The second test series revealed that very early initiation and crack arrest are typical for small notches in the 34CrNiMo6 QT steel. The relation of crack path and microstructure, along with their connection to the optically dark area, is discussed.

Papillary Ductal Plugging is a Mechanism for Early Stone Retention in Brushite Stone Disease.

Mechanisms of early stone retention in the kidney are under studied and poorly understood. To date attachment via Randall's plaque is the only widely accepted theory in this regard, which is best described in idiopathic calcium oxalate stone formers. Brushite stone formers are known to have distinct papillary morphology relative to calcium oxalate stone formers. As such we sought to determine whether stone attachment mechanisms in such patients may be similarly unique. Patients undergoing percutaneous and or ureteroscopic procedures for stone removal consented to endoscopic renal papillary examination and individual stone collection. Each removed stone was processed using micro computerized tomography to assess the 3-dimensional microstructure and the minerals contained, and search for common structural features indicative of novel mechanisms of early growth and attachment to renal tissue. A total of 25 intact brushite stones were removed from 8 patients and analyzed. Video confirmed attachment of 13 of the 25 stones with the remainder believed to have been accidently dislodged during the procedure. Microscopic examination by light and computerized tomography failed to show evidence of Randall's plaque associated with any stone containing brushite. Conversely each brushite stone demonstrated microstructural evidence of having grown attached to a ductal plug formed of apatite. Three-dimensional analysis of small brushite stones suggests overgrowth on ductal apatite plugs as a mechanism of early stone growth and retention. Such findings represent what is to our knowledge the initial supporting evidence for a novel mechanism of stone formation which has previously been hypothesized but never verified.

Transcriptomic profile of leg muscle during early growth in chicken.

The early growth pattern, especially the age of peak growth, of broilers affects the time to market and slaughter weight, which in turn affect the profitability of the poultry industry. However, the underlying mechanisms regulating chicken growth and development have rarely been studied. This study aimed to identify candidate genes involved in chicken growth and investigated the potential regulatory mechanisms of early growth in chicken. RNA sequencing was applied to compare the transcriptomes of chicken muscle tissues at three developmental stages during early growth. In total, 978 differentially expressed genes (DEGs) (fold change ≥ 2; false discovery rate < 0.05) were detected by pairwise comparison. Functional analysis showed that the DEGs are mainly involved in the processes of cell growth, muscle development, and cellular activities (such as junction, migration, assembly, differentiation, and proliferation). Many of the DEGs are well known to be related to chicken growth, such as MYOD1, GH, IGF2BP2, IGFBP3, SMYD1, CEBPB, FGF2, and IGFBP5. KEGG pathway analysis identified that the DEGs were significantly enriched in five pathways (P < 0.1) related to growth and development: extracellular matrix–receptor interaction, focal adhesion, tight junction, insulin signaling pathway, and regulation of the actin cytoskeleton. A total of 42 DEGs assigned to these pathways are potential candidate genes inducing the difference in growth among the three developmental stages, such as MYH10, FGF2, FGF16, FN1, CFL2, MAPK9, IRS1, PHKA1, PHKB, and PHKG1. Thus, our study identified a series of genes and several pathways that may participate in the regulation of early growth in chicken. These results should serve as an important resource revealing the molecular basis of chicken growth and development.

Studies of early growth mechanisms of hydroxyapatite on single crystalline rutile: a model system for bioactive surfaces

Previous studies have shown that crystalline titanium oxide is in vitro bioactive and that there are differences in the HA formation mechanism depending on the crystalline direction of the titanium oxide surface. In the present study, the early adsorption of calcium and phosphate ions on three different surface directions of the single-crystal rutile TiO(2) substrate has been investigated. A crucial step in the nucleation of HA is believed to be the adsorption of Ca(2+) and PO(4)(3-) from phosphate buffer solutions. The (001), (100) and (110) single crystalline rutile surfaces were soaked in phosphate buffer saline solution for 10 min, 1 h and 24 h at 37°C. The surfaces were then analyzed using time-of-flight secondary ion mass spectrometry (TOF-SIMS) and X-ray photoelectron spectroscopy (XPS). The results show that the adsorption of Ca(2+) and PO(4)(3-) is faster on the (001) and (100) surfaces than on the (110) surface. This study also shows that TOF-SIMS can be used as a tool to better understand the adsorption of calcium and phosphate ions and the growth mechanism of HA. This knowledge could be used to tailor new bioactive surfaces for better biological reaction.

Analysis of the early growth mechanisms during the chemical deposition of CdS thin films by spectroscopic ellipsometry

Chemically deposited CdS thin films were analyzed in this work by means of the spectroscopic ellipsometry technique. The CdS thin films were deposited from an ammonia-free process at short durations in order to obtain information about the layer microstructure and kinetic growth process. We found that the conditions of the ammonia-free reaction solution promote the ion-by-ion deposition process at the early growth stages yielding a compact, high refraction index and highly crystalline oriented CdS layers. Using a concentration of 1.82 mg/ml of cadmium in the reaction solution, the resulting films possess a double layer microstructure which consists of an inner compact layer and an external porous one. The inner layer is developed during the first 15 min of deposition time and it reaches a thickness around of 80 nm. After this time and on this inner layer of CdS, it grows an external porous layer whose thickness increases with the deposition time. The formation of the CdS compact layer at the early stages is related with the ion-by-ion growth mechanism. The subsequent CdS porous layer is formed during the cluster-by-cluster growth stage at longer deposition times. By reducing the cadmium concentration in reaction solution down to 0.76 mg/ml, maintaining constant molar ratio concentrations of Cd/complexing and Cd/thiourea, the chemically deposited CdS films develop only the inner compact layer with a thickness of about 80 nm after 35 min of deposition time.

Atmospheric sulphuric acid and aerosol formation: implications from atmospheric measurements for nucleation and early growth mechanisms

Abstract. We have investigated the formation and early growth of atmospheric secondary aerosol particles building on atmospheric measurements. The measurements were part of the QUEST 2 campaign which took place in spring 2003 in Hyytiälä (Finland). During the campaign numerous aerosol particle formation events occurred of which 15 were accompanied by gaseous sulphuric acid measurements. Our detailed analysis of these 15 events is focussed on nucleation and early growth (to a diameter of 3 nm) of fresh particles. It revealed that new particle formation seems to be a function of the gaseous sulphuric acid concentration to the power from one to two when the time delay between the sulphuric acid and particle number concentration is taken into account. From the time delay the growth rates of freshly nucleated particles from 1 nm to 3 nm were determined. The mean growth rate was 1.2 nm/h and it was clearly correlated with the gaseous sulphuric acid concentration. We tested two nucleation mechanisms – recently proposed cluster activation and kinetic type nucleation – as possible candidates to explain the observed dependences, and determined experimental nucleation coefficients. We found that some events are dominated by the activation mechanism and some by the kinetic mechanism. Inferred coefficients for the two nucleation mechanisms are the same order of magnitude as chemical reaction coefficients in the gas phase and they correlate with the product of gaseous sulphuric acid and ammonia concentrations. This indicates that besides gaseous sulphuric acid also ammonia has a role in nucleation.

A microstructural study of transparent metal oxide gas barrier films

The relationship between the microstructure and the water vapour transmission rates of aluminium oxide and aluminium coatings deposited by magnetron sputtering on polyethylene terephthalate have been investigated. The gas barrier properties of the films have been measured as a function of temperature and a range of techniques used to characterize the coatings including atomic force microscopy, which also provided information on the early growth mechanism. It was found that the Al/PET film showed a better water vapour barrier than the AlOx/PET although the activation energy for water vapour permeation was the same for both. We propose that the interaction of water with the barrier coating plays a significant part in determining the observed gas barrier performance.

Nasal capsule shape changes following septopremaxillary ligament resection in a chimpanzee animal model.

Recent human data suggest a relationship between the disruption of the septopremaxillary ligament (SPL) attachment and lack of anterior midfacial growth in cleft lip and palate (CLP) individuals. Early SPL resection in chimpanzees resulted in premaxillary growth deficits through 1200 days. Since the SPL is also continuous with the nasal bones, the present study was undertaken to investigate compensatory nasal capsule shape changes following SPL resection in a chimpanzee animal model. The study used 17 chimpanzees (Pan troglodytes): seven unoperated controls, five sham surgical controls, and five animals with early (average 144 days) SPL resection. Lateral head x-ray films and dental study models were collected quarterly and landmarks representing boundaries of the nasal capsule were identified. Mean nasal capsule polyhedrons were constructed from linear measurements at 200, 600, and 1000 days. In animals with SPL resection, the nasal capsule appeared truncated, shortened anteroposteriorly, and nasion was displaced posteriorly compared to controls by 600 days. Tensor biometric analysis of the growth/shape changes of the nasal capsule triangles revealed no significant differences across age in SPL resection animals while significant (p less than .05) age-related changes were noted in both control groups. Results showed that early SPL resection resulted in maintaining the neonatal nasal capsule morphology in the chimpanzee and suggested that such early growth mechanisms may be operating in complete CLP individuals as well. These data support the concept of early re-establishment of the SPL in primary nasolabial cleft repair to facilitate midfacial and nasal capsule growth.

Nasal Capsule Shape Changes Following Septopremaxillary Ligament Resection in a Chimpanzee Animal Model

Recent human data suggest a relationship between the disruption of the septopremaxillary ligament (SPL) attachment and lack of anterior midfacial growth in cleft lip and palate (CLP) individuals. Early SPL resection in chimpanzees resulted in premaxillary growth deficits through 1200 days. Since the SPL is also continuous with the nasal bones, the present study was undertaken to investigate compensatory nasal capsule shape changes following SPL resection in a chimpanzee animal model. The study used 17 chimpanzees (Pan troglodytes): seven unoperated controls, five sham surgical controls, and five animals with early (average 144 days) SPL resection. Lateral head x-ray films and dental study models were collected quarterly and landmarks representing boundaries of the nasal capsule were identified. Mean nasal capsule polyhedrons were constructed from linear measurements at 200, 600, and 1000 days. In animals with SPL resection, the nasal capsule appeared truncated, shortened anteroposteriorly, and nasion was displaced posteriorly compared to controls by 600 days. Tensor biometric analysis of the growth/shape changes of the nasal capsule triangles revealed no significant differences across age in SPL resection animals while significant (p less than .05) age-related changes were noted in both control groups. Results showed that early SPL resection resulted in maintaining the neonatal nasal capsule morphology in the chimpanzee and suggested that such early growth mechanisms may be operating in complete CLP individuals as well. These data support the concept of early re-establishment of the SPL in primary nasolabial cleft repair to facilitate midfacial and nasal capsule growth.

Initiation and early growth mechanisms of corrosion fatigue cracks in stainless steels

The mechanism of corrosion fatigue crack initiation in stainless steels was examined in both air and chloride solutions. For a tempered martensitic, a duplex and a soft martensitic steel it is shown that the decrease of the fatigue strength from the value measured in air to that measured in corrosive environments depends primarily upon the stability of the protective film. If the passivity is stable, cracks are found to originate almost exclusively at oxide inclusions. Cracking or debonding were found to occur. For the duplex steel in the vicinity of the inclusion there were pronounced emerging persistent slip bands. They cause localized corrosion attack, thus allowing cracks to be formed more easily. If pitting is superposed, crack nucleation always occurs at the base of the pit. Pit formation and growth rate are accelerated by cyclic loading.

Planet formation: Mechanism of early growth

Experiments in vacuum (approx. 0.5 to 1 mbar) and in air quantify mechanics of collisions, rebound, and fragmentation at low velocities (1–50 m/sec), under the conditions usually postulated for the preplanetary environment in the primitive solar nebula. Such collisions have been little studied experimentally. Contrary to widespread assumptions, accretionary growth of the largest meteoroid- and asteroid-sized bodies in a given swarm results spontaneously from the simple mechanics of these collisions, without other ad hoc sticking mechanisms. The smaller bodies in the swarm are less likely to grow. Granular surfaces form, either by gravitational collapse of dust swarms or by rapid formation of regolith surfaces on solid planetesimals; these surfaces strongly promote further growth by retarding rebound. Growth of large bodies increases modal collision velocities, causing fragmentation of smaller bodies and eventual production of interstellar dust as a by-product planetesimal interactions.