Improving the barrier character of polylactide/phenoxy immiscible blend using poly(lactide‐co‐ɛ‐caprolactone) block copolymer as a compatibilizer

The improvement of the barrier character of polylactide by the addition of poly(hydroxy ether) of bisphenol A (Phenoxy) and poly(lactide‐co ‐?‐caprolactone) copolymer that acts as a compatibilizer is studied. First, differential scanning calorimetry, Fourier transformed infrared spectroscopy, and scanning electron microscopy show that the addition of the copolymer allows to obtain a miscible ternary system. The permeability of polylactide to water vapor, oxygen, and carbon dioxide is enhanced with the addition of phenoxy but better improvement in its barrier character is obtained with the addition of the compatibilizer. The effects of different factors such as miscibility, glass transition temperature, and crystallinity on the transport properties are analyzed. Several permeability prediction models for heterogeneous systems have been applied obtaining quite good results for water vapor and oxygen permeability. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 45396.     

Solid‐state polymerization and characterization of a copolyamide based on adipic acid, 1,4‐butanediamine,and 2,5‐furandicarboxylic acid

2,5‐Furandicarboxylic acid (FDCA) is a promising biobased alternative material to terephthalic acid. In this study, three types of poly(butylene adipamide) (PA‐4,6) containing 10, 20, and 30 mol % of poly(butylene‐2,5‐furandicarboxylamide) (PA‐4,F) were synthesized through consecutive prepolymerization and solid‐state polymerization (SSP). The incorporation of a 10 mol % PA‐4,F component into PA‐4,6 resulted in slight increases in the intrinsic viscosity (IV) and glass‐transition temperature (T_g) after 12 h of SSP at 220 °C. When the SSP temperature and reaction time increased, IV increased proportionally. The highest IV value of 0.75 was obtained by 48 h of SSP at 240 °C, whereas increases in the PA‐4,F content to 20 and 30 mol % gave rise to decreases in IV, T_g, and melting temperature; this interrupted the increase in SSP temperature. The thermal decomposition temperature of the PA‐4,F‐incorporated polyamide was lower than that with PA‐4,6 because of the lower thermal stability of the FDCA component. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43391.     

Slow-Release of Curcumin Induced by Core–Shell Mesoporous Silica Nanoparticles (MSNs) Modified MIL-100(Fe) Composite

As a biocompatible porous material, bio-MOF is a very promising material as a carrier for hydrophobic drugs, including curcumin. However, the stability of bio-MOF against water and humidity still needs to be improved; therefore, surface modifications are required. This study aims to modify the MIL-100(Fe)-based bio-MOF through core–shell architecture by employing mesoporous silica nanoparticles (MSNs or SiO₂) for improving the stability and performance of MIL-100(Fe) to provide a slow-release feature of curcumin. The composites were synthesized via sonochemistry-assisted or mechanochemistry-assisted green protocol to form core–shell structure of MIL-100(Fe)@SiO₂ (Composite-1) or SiO₂@MIL-100(Fe) (Composite-2). Structural, textural, and morphological analyses, including XRD, FTIR, SEM, TEM, and N₂ adsorption–desorption, are discussed in this study to evaluate the composite formation. BET surface area of the MIL-100(Fe) decreased from 1197.45 m²/g to 565.63 and 823.70 m²/g after forming composite-1 and composite-2 with SiO₂. The loading capacity, however, just increased slightly up to 97.89% after the modification. The presence of SiO₂ as shell (composite-1) protects the MIL-100(Fe) from degradation under the acidic condition at pH 5.8 and can maintain the slow-release of curcumin. In contrast, the presence of SiO₂ as core (composite-2) induces the sustained release due to faster degradation of MIL-100(Fe) in acidic condition. Both composites serve as a model for either sustained release or delayed release drug delivery systems.

     

Relation of plasma oestriol to changes in blood pressure in pregnant patients with hypertension

Serial plasma oestriol levels were determined by radioimmunoassay in 24 patients with severe hypertension in pregnancy. No significant correlation could be found between plasma oestriol and percentage change in diastolic blood pressure. It seems unlikely that hypotensive therapy significantly improves fetoplacental function.     

Switching dynamics of IGBTs in soft-switching converters

Next generation of power semiconductor devices will be designed and optimized to meet the specific application requirements. Mixed-mode simulations are used to study the carrier dynamics in punch-through and nonpunch-through Insulated Gate Bipolar Transistor (IGBT) structures during soft- and hard-switching conditions. The simulation results are shown to qualitatively predict the measured bump in the tail current with varying output dv/dt conditions and excessive forward conduction voltage under varying di/dt conditions. A new physical effect termed “conductivity modulation lag” is shown to occur during turn-on under soft-switching conditions. This mechanism is caused by the fact that minority carrier injection into the base of the bipolar transistor significantly lags behind the rate at which drift region conductivity can be modulated. The proposed phenomenon leads to an inductive effect that results in dynamic voltage saturation during turn-on and causes excessive forward voltage drop     

The need for a processual view of inter-organizational systems adoption

In order to sustain competitiveness, companies need to adopt electronic commerce (EC) enabled inter-organizational systems (IOS) to improve the efficiencies of entire supply chains. Adoption of IOS by companies, however, has proved difficult since such systems span organizational boundaries. Understanding IOS adoption is hampered by a lack of theory that can capture the complexity involved in IOS adoption since previous studies mostly employ the factor approach. In this paper, using Efficient Consumer Response as an example of an EC-enabled IOS, we demonstrate that the acknowledgement of the inter-organizational context of these systems naturally introduces the need for the processual approach and different notions of causality. We also show how the factor and the processual approaches to theorizing IOS adoption can be used in a complementary way.     

Tracing the development of teacher knowledge in a design seminar: Integrating content,pedagogy and technology

Effective technology integration for teaching subject matter requires knowledge not just of content, technology and pedagogy, but also of their relationship to each other. Building on Schulman’s [Schulman, L. S. (1987). Knowledge and teaching: foundations for a new reform. Harvard Educational Review, 57(1), 1–22] concept of pedagogical content knowledge, we introduce a framework for conceptualizing Technological Pedagogical Content Knowledge—TPCK [Mishra, P., Koehler, M.J., (in press). Technological pedagogical content knowledge: A new framework for teacher knowledge. Teachers College Record]. We report the results of a semester-long investigation of the development of TPCK during a faculty development design seminar, whereby faculty members worked together with masters students to develop online courses. Quantitative discourse analysis of 15 weeks of field notes for two of the design teams show participants moved from considering technology, pedagogy and content as being independent constructs towards a richer conception that emphasized connections among the three knowledge bases. Our analyses suggests that developing TPCK is a multigenerational process, involving the development of deeper understandings of the complex web of relationships between content, pedagogy and technology and the contexts in which they function. Pedagogic, pragmatic, theoretical, and methodological contributions are discussed.     

Heat Transfer in Coiled Square Tubes for Laminar Flow of Slurry of Microencapsulated Phase Change Material

Passive heat transfer enhancement using a slurry of microencapsulated phase-change material (MEPCM) flowing in a laminar regime through a coiled duct of square cross section was evaluated. The phase-change material is n-octadecane. The flow behavior and heat transfer performance of water and MEPCM suspensions in various configurations (conical spiral, in-plane spiral, and helical spiral) of coiled tubes of square cross section was investigated. The results are compared with those for water as the base fluid flowing through a straight tube. A computational fluid dynamics (CFD) approach is used to simulate the laminar flow of water with MEPCM suspension in these geometries. The liquid suspension properties are expressed as functions of the volumetric concentration of MEPCM particles and the temperature. Improved heat transfer performance was obtained as the concentration of MEPCM suspension increased from 1 to 10%. However, the overall performance in terms of the pumping power consumed for unit heat transferred worsened.     

Analysis of a model for pH-sensitive hydrogels

A mathematical model comprising conservation of mass, momentum, and ions for a hydrogel subject to alterations of the solution pH is derived, analyzed, validated and presented. Good agreement between model predictions and their experimental counterpart are achieved. To gain a physical insight into the deformation behavior of the pH-sensitive hydrogel, a scaling analysis coupled with a parametric study is carried out for key physical and operational parameters. The results suggest the significance of initial fixed-charge density, solution ionic strength, Poisson ratio and Young modulus in determining swelling degree of the hydrogel. In addition, it is noted that changes in acid dissociation constant and temperature lead to a notable shift in equilibrium swelling curves. Permeability and size of the hydrogel were found to significantly affect the deformation kinetics: A hydrogel with higher permeability and/or smaller size exhibits faster deformation. These findings and the characteristic scales could provide important guidelines in designing systems utilizing pH-sensitive hydrogels.     

Investigating information and communication technology-enabled national development as a multi-level social process

Are centralised or decentralised strategies more suitable to address a developing nation's socio-economic challenges through information and communication technology (ICT)? We respond to this long-standing question by conceptualising ICT-enabled national development as a multi-level social process and by drawing on empirical findings from a natural experiment set in the context of health information system projects in Indonesia. Our study demonstrates that successful ICT-enabled national development is not contingent on pursuing one strategy or the other but on how micro-level actors interpret, and subsequently respond to, these strategies and the local changes they trigger. Our findings indicate that centralisation and decentralisation are complementary rather than competing strategies to ICT-enabled national development because, if integrated into a hybrid strategy, decentralisation enables local communities to achieve national development outcomes commonly attributed to centralisation. As such, our work provides empirical evidence, explanations and new theoretical insight into the wider ‘centralisation versus decentralisation’ debate, while also outlining avenues for future research and guidelines for policymakers.