Physical and mechanical characterisation of 3D-printed porous titanium for biomedical applications

The elastic modulus of metallic orthopaedic implants is typically 6–12 times greater than cortical bone, causing stress shielding: over time, bone atrophies through decreased mechanical strain, which can lead to fracture at the implantation site. Introducing pores into an implant will lower the modulus significantly. Three dimensional printing (3DP) is capable of producing parts with dual porosity features: micropores by process (residual pores from binder burnout) and macropores by design via a computer aided design model. Titanium was chosen due to its excellent biocompatibility, superior corrosion resistance, durability, osteointegration capability, relatively low elastic modulus, and high strength to weight ratio. The mechanical and physical properties of 3DP titanium were studied and compared to the properties of bone. The mechanical and physical properties were tailored by varying the binder (polyvinyl alcohol) content and the sintering temperature of the titanium samples. The fabricated titanium samples had a porosity of 32.2–53.4 % and a compressive modulus of 0.86–2.48 GPa, within the range of cancellous bone modulus. Other physical and mechanical properties were investigated including fracture strength, density, fracture toughness, hardness and surface roughness. The correlation between the porous 3DP titanium-bulk modulus ratio and porosity was also quantified.     

A simple colorimetric determination of the free amino groups in water soluble chitin derivatives using genipin

A colorimetric method for quantitative measurement of free amino groups of water soluble chitin derivatives is described. The method utilizes genipin as a natural and specific reagent for determining the concentration of free amino groups in samples of water soluble chitin derivatives. The blue color adduct (complex) formed during genipin reaction with free amino groups was measured at about 589 nm and Beer-Lambert’s law obeyed over the concentration range of 50 to 300 mg/L. Parameters of analytical conditions were considered and kept constant during the experimental procedure. Highly acetylated water soluble chitin derivatives can be differentiated from water soluble chitosan using this genipin method. The colorimetric method with genipin was proved to be a rapid and efficient technique to determine the free amino groups in water soluble chitin derivatives. This method can also be applied for the detection of the enzymatic activity of chitindeacetylase.     

Molecular Sieve Materials: Their Synthesis,Properties, and Characterizations

An overview of the history and development of molecular sieve materials since their discovery and commercialization is presented. The evolutionary changes in their composition, sorptive and catalytic properties, surface selectivity, and stability characteristics are emphasized.     

Comparison between the design of experiments and simulation in the three-phase distillation in a sieve tray column for glycerine dehydration

Design of experiments (DOE) is a value scientific approach used to understand the processes in a better way and to determine how the inputs affect the response(s). In this work, this method has been applied to study the behavior of the three-phase distillation in a sieve tray column, through the effects of the process and geometrical variables. The experimental values were compared with predicted values obtained by simulation using the equilibrium and nonequilibrium models. Three-phase distillation has been used for glycerine dehydration using toluene as entrainer, in order to avoid the glycerol degradation by distillation at atmospheric pressure. The best conditions found were: vapor flow rate of toluene = 23.5 kg/h, feed flow rate = 2.2 kg/h and feed concentration = 50 wt% glycerol, using the layout L₄ with fractional hole area = 0.04 and weir height = 70 mm. The nonequilibrium model based on Eckert and Vanek's approach (2001) and Chen–Chuang's correlation (1993) have been used to estimate the binary coefficients of mass transport. The predicted values obtained by the experimental model and by the nonequilibrium model have represented the behavior of the dehydration in the sieve tray column studied. Both models underpinned the experimental results obtained for this column.     

Improving the cleanability of melamine‐formaldehyde‐based decorative laminates

Decorative laminates based on melamine formaldehyde (MF) resin impregnated papers are used at great extent for surface finishing of engineered wood that is used for furniture, kitchen, and working surfaces, flooring and exterior cladding. In all these applications, optically flawless appearance is a major issue. The work described here is focused on enhancing the cleanability and antifingerprint properties of smooth, matt surface‐finished melamine‐coated particleboards for furniture fronts, without at the same time changing or deteriorating other important surface parameters such as hardness, roughness or gloss. In order to adjust the surface polarity of a low pressure melamine film, novel interface‐active macromolecular compounds were prepared and tested for their suitability as an antifingerprint additive. Two hydroxy‐functional surfactants (polydimethysiloxane, PDMS‐OH and perfluoroether, PF‐OH) were oxidized under mild conditions to the corresponding aldehydes (PDMS‐CHO and PF‐CHO) using a pyridinium chlorochromate catalyst. With the most promising oxidized polymeric additive, PDMS‐CHO, the contact angles against water, n‐hexadecane, and squalene increased from 79.8°, 26.3° and 31.4° for the pure MF surface to 108.5°, 54.8°, and 59.3°, respectively, for the modified MF surfaces. While for the laminated MF surface based on the oxidized fluoroether the gloss values were much higher than required, for the surfaces based on oxidized polydimethylsiloxane the technological values as well as the lower gloss values were in agreement with the requirements and showed much improved surface cleanability, as was also confirmed by colorimetric measurements. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40964.     

Distribution,sources, and behavior of trace elements in the Clinton River Watershed,Michigan

The Clinton River watershed near Detroit, Michigan, USA was separated in six different land uses: agricultural, residential, mixed industrial and residential, downstream industrial, Clinton River Spillway, and Lake St. Clair, utilizing As, Cd, Cu, Ni, Pb, and Zn contents of the sediment that has median values of 3, 0.3, 15, 14, 13, and 57 mg kg^− 1, respectively. However, trace element concentrations in the lower Clinton River rivaled those in the most contaminated watersheds of the world. Enrichment factors and principal component analysis (PCA) separated trace elements into 2 categories: anthropogenic (Cd, Cu, Ni, Pb, and Zn) and geogenic (Al, As, Ca, Fe, K, Mg, TOC) sources. PCA linked agricultural, residential, and mixed industrial and residential land uses to anthropogenic Cd, Cu, Ni, Pb, and Zn, and lake sediments to geogenic elements, organic matter and clay contents. The downstream industrial zone has a unique source signature. Trace element concentrations varied with land use. The upper Clinton River (> 20 km from mouth; residential land use; median concentrations up to 25 mg kg^− 1) appeared to meet delisting criteria. Partitioning was also land use and element specific with: (1) exchangeable fraction (up to 94% of total) related to road salt and mobile chloride complex formation; (2) carbonate-bound fraction (up to 100%) resulting from Ca substitution or adsorption; (3) presence of immobile (hydr)oxide-bound fraction (up to 90%) instead of potentially mobile organic matter and sulphide-bound fraction (up to 20%); and (4) residual fraction (up to 65%) originating from geogenic and/or anthropogenic sources.     

Does Centralising Global Account Management Activities in Response to International Retailers Pay Off?

• This study provides insights into how manufacturers adopt their Global Account Management (GAM) activities in response to the increasing expansion of retailers. Specifically, we focus on the manufacturers?? central coordination of two types of GAM activities: strategic and tactical activities.
• We analyse the manufacturers?? associations with international retailers and with GAM effectiveness and efficiency by using data from 172 manufacturers. Moreover, we consider the suppliers?? dependence on their key retail accounts to be an important moderator within the consumer goods sector.
• In particular, manufacturers respond to the centralisation of the retailers?? purchasing activities by centralising strategic GAM activities, such as customer strategy, information processing, or price systems. Additionally, manufacturers respond even stronger by centralising tactical activities, such as category management, marketing, or logistics. Although the centralisation of strategic activities drives GAM effectiveness and efficiency, the centralisation of tactical activities does not. This finding might be explained by the specific context of manufacturer-retailer relations. Finally, we find that, although the decision to centralise GAM activities pays off, the benefits are contingent on the particular type of GAM activity and the level of customer dependency.

     

Starch characterization of different blue maize varieties

Maize shows a significant genetic diversity, giving origin to a great number of varieties, hybrids, and genotypes. Recently, the pigmented corn varieties have received increased interest because of their anthocyanin contents. Although starch is the major component of the pigmented corn, only a few studies have been conducted on this constituent. The aim of this work was to evaluate the physicochemical properties and structural characteristics of starch isolated from six blue maize varieties grown in Mexico. The apparent amylose content ranged between 23.3 and 33.9%. The blue maize starches had an A‐type X‐ray diffraction pattern with similar crystallinity levels. Different gelatinization temperatures and enthalpy values were recorded, exhibiting different retrogradation tendencies (between 36.9 and 60.1%). The pasting parameters showed that the pasting temperature varied between 74.7 and 84.1°C, the maximum peak viscosity between 83.2 and 111.2 RVU units, and the setback viscosity between 26 and 38 RVU units. Structural differences were observed in the degree of branching, molar mass, and gyration radius. In view of their different physicochemical and structural characteristics, each of the blue maize starch varieties studied could have their own specific applications.     

Field performance and nutritive value of a new forage sorghum variety ‘Pnina’ recently developed in Israel

A new forage sorghum entitled Pnina was developed in Israel. Pnina, harvested at early milk (EM) and hard dough (HD) stages of maturity, was compared with commercial sorghum variety FS‐5 and a sorghum BMR/Sudan hybrid Nutriplus. Plants grew during summer and were irrigated with 190 mm water. Pnina was semi‐dwarf (1.35 m height) and absolutely resistant to lodging. The tall varieties FS‐5 and Nutriplus suffered at HD from high lodging. Pnina was more leafy than Nutriplus and FS‐5. The dry matter (DM) content of FS‐5 and Nutriplus were at EM below the level recommended for ensilage and elevated slightly at HD, whereas DM content of Pnina was higher. Crop yields of all varieties at HD were similar and ranged between 13.3 and 14.7 t ha^?1 DM. Dry matter losses during ensilage and silage pH were similar in the three varieties at HD. In vitro DM digestibility of HD silages ranged between 62.5 and 67.1%. Neutral detergent fiber (NDF) content was higher in Pnina silages. Yields of digestible silage per hectare, were similar in the three varieties harvested at HD (8.4 to 8.8 t ha^?1 DM); however, yield of digestible NDF per hectare was higher in Pnina. Data suggest that the new variety Pnina may have field advantage over the other varieties of this study. Copyright © 2005 Society of Chemical Industry     

Behavior of load transfer in functionalized carbon nanotube/epoxy nanocomposites

This paper presents the correlation between the functional groups, interfacial microstructure and behavior of load transfer in carbon nanotube (CNT)/epoxy nanocomposites. Nanocomposites consisting of epoxy and CNTs with/without functionalities (amino and epoxide groups) are prepared and characterized to evaluate the CNT-matrix interactions based on strain-sensitive Raman spectroscopy. The results show that nanocomposites filled with functionalized CNTs exhibit a noticeable G′-band shift in tension while those containing pristine CNTs have a marginal shift, suggesting a more efficient load transfer between the epoxy matrix and functionalized CNTs. An interesting observation is that the slope of the G′-band shifts can be either positive or negative, depending on the functional groups on CNTs and the interfacial structures created between the functionalized CNTs and polymer matrix. The mechanisms behind this observation are discussed with reference to fractography and thermo-mechanical properties of nanocomposites.