Simultaneous fractionation of multiple classes of polyphenols from honeybush tea using solid-phase extraction

The structural diversity of polyphenols and the inherent limitations of current extraction techniques pose a challenge to extract polyphenols using a simple and green method. Hence, in this study, a method was developed to simultaneously fractionate multiple classes of polyphenols by only varying ethanol-water solutions. Honeybush tea, which is rich in polyphenols, was selected as a model for this study. Solvent extraction followed by solid-phase extraction (SPE) was developed to obtain a polyphenol-rich fraction from six honeybush samples. Based on a gradient elution programme (10%, 30%, 50%, 70% and 90% (v/v) ethanol-water solution) of SPE, the Strata X cartridge showed a better recovery of most targeted polyphenols under 0.9 mL of the drying volume and 1 mL min⁻¹ of the dispensing speed. The elution programme for fractionating most polyphenols was as follows: single elution with 50% ethanol, followed by twice elution with 70% ethanol. The antioxidant capacity was used to analyse the differences among the polyphenol-rich fractions from six honeybush samples. Principal component analysis (PCA) revealed that unfermented C. genistoides (GG) has the greatest antioxidant capacity among the honeybush species studied. Additionally, mangiferin, isomangiferin and vicenin-2 were the main contributors to the antioxidant capacity in six honeybush fractions according to the correlation study.     

The changes of chemical composition of microencapsulated roselle (Hibiscus sabdariffa L.) seed oil by co-extrusion during accelerated storage

Roselle seed oil (RSO) is an underutilised seed oil, which is having beneficial properties to humans. Microencapsulation of vegetables and seed oil is an alternative to preserve these properties and deliver them to the human diet. In this study, microencapsulation of RSO was performed using co-extrusion technology and 1.5% w/w sodium alginate solution with 1.5% w/w high methoxyl pectin as the wall materials. Results showed that the microencapsulation efficiency was high (95.68 ± 1.95%) and the microencapsulation indeed preserved the content of unsaturated fatty acids, phytosterols, and tocopherols. During an accelerated storage condition at 65 °C for 24 days, most of these properties remained high for the first six storage days, including tocopherol which preserved high γ-tocopherol. Worth noting that the microencapsulated RSO (MRSO) was particularly effective in preserving the total unsaturated fatty acids (especially C18:1 and C18:2), even during the 24th day of storage. The total unsaturated fatty acids retained by MRSO were significantly (P < 0.05) higher (70 ± 0.4%) than the RSO (65.6 ± 1.6%). In short, microencapsulation was effective in preserving the RSO properties.     

Nitrogen-doped graphene-supported zinc sulfide nanorods as efficient Pt-free for visible-light photocatalytic hydrogen production

Nitrogen-doped graphene-ZnS composite (NG-ZnS) was synthesized by thermal treatment of graphene-ZnS composite (G-ZnS) in NH₃ medium. In the second step, the as-synthesized samples were deposited on indium tin oxide glass (ITO) by electrophoretic deposition for photocatalytic hydrogen evolution reaction. The as-prepared NG-ZnS-modified ITO electrode displayed excellent photocatalytic activity, rapid transient photocurrent response, superior stability and high recyclability compared to the pure ZnS and G-ZnS-modified ITO electrode due to the synergy between the photocatalytic activity of ZnS nanorods and the large surface area and high conductivity of N-graphene.     

Targeted Delivery of Anesthetic Agents to Bone Tissues using Conductive Microneedles Enhanced Iontophoresis for Painless Dental Anesthesia

Pain management during dental procedures is a cornerstone for successful daily practice. In current practice, the traditional needle and syringe injection is used to administer local anesthesia. However, the appearance of long needles and the pain associated with it often leads to dental anxiety deterring timely interventions. Microneedles (MNs) have emerged as a minimally invasive alternative to hypodermic needles and shown to be effective in transdermal drug delivery applications. In this article, the potential use of MNs for local anesthesia delivery in dentistry is explored. The development of a novel conductive MN array that can be used in combination with iontophoresis technique to achieve drug penetration through the oral mucosa and the underlying bone tissue is presented. The conductive MN array plays a dual-role, creating micro-conduits and lowering the resistance of the oral mucosa. The reduced tissue resistance further enhances the application of a low-voltage current that is able to direct and accelerate the drug molecules to target the sensory nerves supplying teeth. The successful delivery of lidocaine using this new strategy in a clinically relevant rabbit incisor model is shown to be as effective as the current gold standard.     

Estimating wall deflections in deep excavations using Bayesian neural networks

In this study, a neural network algorithm has been used to model the soil-structure interaction behavior of deep excavations in clays. The hybrid evolutionary Bayesian back-propagation (EBBP) neural network was used in this study and utilizes the genetic algorithms and gradient descent method to determine the optimal parameters within a Bayesian framework to regularize the complexity of learning and to statistically reflect the uncertainty in data. The EBBP analysis was carried out on an extensive database of braced excavation performance from finite element analyses. Additional parametric studies indicate that the model gives logical and consistent trends. Back-analyses of some instrumented case histories from the literature also indicate that the trained neural network model gives reasonable predictions in comparison to the actual measured values. The trained model can serve as a simple and reliable prediction tool to enable estimates of maximum wall deflection for preliminary design of braced excavations in clay. The model is able to take into consideration various factors such as the wall stiffness, support stiffness, the in-situ stress state, non-homogeneous soil conditions, and the variation of soil properties with depth. An added advantage of this approach is that it provides meaningful error bars for the model predictions.     

Investigating the client-related rework in building projects: The case of Singapore

Rework has become one of the most common concerns in construction projects. This study aims to investigate the client-related rework (CRR) in Singapore-based building projects. To achieve the objectives, a literature review and questionnaire survey was conducted and data were collected from 381 projects performed by 51 companies. The results confirmed that the client contributed most to rework. 41 of the 51 companies (80.4%) experienced CRR, and 226 of the 381 projects (59.3%) experienced CRR, which increased project cost by 7.1% and caused 3.3 weeks' delay on the average. Additionally, “replacement of materials by the client” was the cause with the highest frequency of occurrence, while “change of plans or scope by the client” contributed most to CRR and exerted most impact on project cost, schedule and quality performance. This study expands the literature and provides an in-depth understanding of the CRR in Singapore for both practitioners and researchers.     

Total factor productivity growth accounting in the construction industry of Singapore

Total factor productivity (TFP) determines long‐term economic growth and is a comprehensive industry‐level productivity measure. This paper proposes Jorgenson's method as an appropriate TFP measurement for the construction industry. The method is less restrictive than the conventional Chau's approach, as it does not impose the Hick Neutral Technical Change assumption. Jorgenson's method is then applied to estimate TFP growth in the construction industry of Singapore over 1984–1998. TFP growth is found down by 1.53% per annum over this period, indicating that the performance of TFP in the construction industry lags behind the rest of economy. TFP growth is also found to be fluctuating over time and tends to move in tandem with the construction business cycle.

As a monitor of progress towards TFP achievement, factors influencing TFP growth in the construction industry of Singapore over 1984–1997 are identified. Seven factors are found to be significantly related to TFP growth. Among them, economies of scale, R&D by the industry, investment allowance granted and labour unions are leading contributors to TFP growth; while foreign worker, construction accidents and pre‐cast are major hampers.

The general methodology presented in this study can be applied to other countries. Future studies are required to find appropriate indicators for factors unquantified.     

Mechanical reinforcement of polyethylene using n‐alkyl group‐functionalized multiwalled carbon nanotubes: Effect of alkyl group carbon chain length and density

Polyethylene (PE) is one of the most produced synthetic resins in the world. Functionalized multiwalled carbon nanotube (MWCNT) is a potential nanoscale filler to realize the next generation strong and multifunctional PE composites. We demonstrate that MWCNTs grafted with short n‐alkyl groups are effective nanofillers for mechanical reinforcement of PE composites. At 1 wt% filler loading, the yield stress and Young's modulus improve significantly up to 54 and 63% compared with neat PE, respectively. Among ductile properties, tensile strength increases up to 30%; ultimate strain is preserved; and toughness increases up to 33%. More important, we show that short n‐alkyl groups can be grafted on MWCNTs much easier than long chain polymers. Further, we find that alkyl groups of C14–C18 chains have the optimum length for reinforcement. The optimum density of grafted alkyl groups is around 0.390–0.423 μmol/mg when the C14 alkyl groups are used. Overall, the results manifest that MWCNTs grafted with n‐alkyl groups with suitable length and density are efficient nanoscale fillers for high‐performance PE composites. POLYM. ENG. SCI., 54:336–344, 2014. © 2013 Society of Plastics Engineers