Investigations into the molecular-level adhesion characteristics of hydroxyapatite-coated and anodized titanium surfaces using the molecular orbital approach

It has been established that the adhesion of cells on to the surfaces of orthopaedic implants depends on the ability of the surfaces to accommodate protein molecules. Hydroxyapatite coating and anodizing are the most common methods to make TiAl6V4 implants (Ti) more biocompatible. In this paper Spartan 02, a molecular dynamics software, is used to analyze and predict the bonding characteristics of Extra cellular matrix protein sequence arginine-glycine-aspartic acid (RGD) on a Hyrdoxyapatite (HA) coated Ti and an anodized Ti surface based on the property of its constituent atoms, their polarity (net electrostatic charge, Qr), the energies of the molecular orbital E_HOMO (energy of the highest occupied molecular orbital), and E_LUMO (energy of the lowest unoccupied molecular orbital). The results show favourable criterion for formation of bonding between the HOMO orbital of the HA coated and anodized surfaces and LUMO orbital of the glycine strand from the RGD unit. The mechanism of bonding of individual atoms to form primary calcium oxide compounds is likely only in the case of HA coated surfaces . The surface texture of the anodized Ti with inherent porosities appear more responsible for the adsorption of proteins on to them by mechanical interlocking than the formation of any intermediate calcium oxide compounds.     

Layer‐by‐Layer Growth of Multicomponent Colloidal Crystals Over Large Areas

Self‐assembly of different sized colloidal particles into multicomponent crystals results in novel material properties compared to the properties of the individual components alone. The formation of binary and, for the first time, ternary colloidal crystals through a simple and inexpensive confined‐area evaporation‐induced layer‐by‐layer (LBL) assembly method is reported. The proposed method produces high quality multicomponent colloidal crystal films over a broad range of particle size‐ratios and large surface areas (cm²) from silica/polystyrene colloidal suspensions of low concentration. By adjusting the size‐ratio and concentration of the colloidal particles, complex crystals of tunable stoichiometries are fabricated and their structural characteristics are further confirmed with reported crystal analogues. In addition, complex structures form as a result of the interplay of the template layer effect, the surface forces exerted by the meniscus of the drying liquid, the space filling principle, and entropic forces. Thus, this LBL approach is a versatile way to grow colloidal crystals with binary, ternary, or more complex structures.     

User‐Friendly Universal and Durable Subcellular‐Scaled Template for Protein Binding: Application to Single‐Cell Patterning

A new method for subcellular‐sized protein patterning on a SiOx substrate is demonstrated by dip‐pen nanolithography printed aldehyde‐terminated alkylsilane template. The aldehyde‐silane template is stable and durable; for example, subcellular scaled IgG protein array can be obtained using one‐year old aldehyde‐silane template. Moreover, single cell patterning is successfully carried out by extracellular material (ECM) protein microarray and nanoarray fabricated on an aldehyde‐silane template. With more than half of chance, single‐ or double‐cells are successfully attached on fibronectin protein nanoarrays in 21 × 21 μm ² (7 × 7 dot array) and 42 × 42 μm² (14 × 14 dot array). The fibronectin nanoarray with small area (21 × 21 μm²) shows the more rate of single cell attachment. Therefore, it is also demonstrated that cell patterning can be controlled by adjusting the nanostructure of ECM materials.     

Effect of Polymer Form and its Consolidation on Mechanical Properties and Quality of Glass/PBT Composites

The aim of this study was to understand the role of the processing in determining the mechanical properties of glass fibre reinforced polybutylene terephthalate composites (Glass/PBT). Unidirectional (UD) composite laminates were manufactured by the vacuum consolidation technique using three different material systems included in this study; Glass/CBT (CBT160 powder based resin), Glass/PBT (prepreg tapes), and Glass/PBT (commingled yarns). The different types of thermoplastic polymer resin systems used for the manufacturing of the composite UD laminate dictate the differences in final mechanical properties which were evaluated by through compression, flexural and short beam transverse bending tests. Microscopy was used to evaluate the quality of the processed laminates, and fractography was used to characterize the observed failure modes. The study provides an improved understanding of the relationships between processing methods, resin characteristics, and mechanical performance of thermoplastic resin composite materials.     

Immersion and TOFD (I-TOFD): A Novel Combination for Examination of Lower Thicknesses

Time of flight diffraction (TOFD) is a well-developed ultrasonic non-destructive testing (NDT) technique which has been applied successfully for accurate sizing of defects in thick sections. Codes of practice such as ASME now permit TOFD for routine examination as an alternative to radiography for thick weldments. However, examination of thinner sections by TOFD has its limitations. The main limitation is that as the thickness of the specimen reduces, the lateral wave, diffracted wave and the back wall echo merge together and it is very difficult to identify and size the discontinuity. Also, the size of conventional transducers limits the required probe separation. Limited success has been obtained internationally through the application of miniature probes and software for extending TOFD to lower thicknesses. In these cases, the minimum thickness that has been examined is 7 mm. A new methodology based on a simple and novel combination of TOFD and the immersion technique has been proposed by the authors that successfully extends the application of TOFD to thinner sections down to 3 mm. Immersion coupling provides a delay line, the necessary angles and probe separation making it possible to examine the thin components successfully. This paper highlights the results of detailed experimental investigations on immersion TOFD and its successful application for the evaluation of welds in hexcan used for encapsulating nuclear fuel pins.     

Assessment of Sensitization in AISI 304 Stainless Steel by Nonlinear Ultrasonic Method

A nonlinear ultrasonic technique has been developed to evaluate sensitization in Type 304 stainless steel.In order to achieve diferent degree of sensitization(DOS),specimens have been subjected to heat treatment at 675℃ at varying soaking time(0.5,1.0,2.0,3.0 and 4.0 h).Heat treated specimens were subjected to intergranular corrosion tests as per ASTM standards A262 and G108.Sensitization in longer soaked material has been confirmed through ditch microstructures,cracks on the bend tested specimens and higher degree of sensitization.Nonlinear ultrasonic studies showed variation in the nonlinearity parameter with soaking time which also confirms sensitization.A good correlation was observed between the degree of sensitization measured by the electrochemical potentiokinetic reactivation test and the ultrasonic nonlinearity parameter.This study clearly demonstrated that nonlinear ultrasonic technique can be used as a potential technique for non-destructive characterization of sensitization in austenitic stainless steel.     

Feed Restriction Modulates Growth,Gut Morphology and Gene Expression in Zebrafish

A reduction in daily caloric or nutrient intake has been observed to promote health benefits in mammals and other vertebrates. Feed Restriction (FR), whereby the overall food intake of the organism is reduced, has been explored as a method to improve metabolic and immune health, as well as to optimize productivity in farming. However, less is known regarding the molecular and physiological consequences of FR. Using the model organism, Danio rerio, we investigated the impact of a short-term (month-long) FR on growth, gut morphology and gene expression. Our data suggest that FR has minimal effects on the average growth rates, but it may affect weight and size heterogeneity in a sex-dependent manner. In the gut, we observed a significant reduction in gut circumference and generally lower mucosal heights, whereas other parameters remained unchanged. Gene Ontology (GO), EuKaryotic Orthologous Groups (KOG), and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis identified numerous metabolic, reproductive, and immune response pathways that were affected by FR. These results broaden our understanding of FR and contribute towards growing knowledge of its effects on vertebrate health.     

Characterisation of heterogeneous microstructure in large forged products using nonlinear ultrasonic method

ABSTRACT

A comparative study between the ultrasonic attenuation and the nonlinearity is presented for the characterisation of microstructure in large dimension forgings. Results are provided for two austenitic stainless steel forgings of AISI type 304L with a diameter 200?mm, where microscopic observations reveal abnormal grain growth near the surface of one of the forgings. Frequency dependence of the nonlinearity parameter is used to discern variations in grain size in these forgings more precisely than attenuation measurements. The distribution of grain size is shown to have a significant influence on the nonlinearity parameter. Relative changes in the nonlinearity parameter with applied frequency were correlative with the microstructural variations in both the forgings.