One-step Real-time Food Quality Analysis by Simultaneous DSC–FTIR Microspectroscopy

This review discusses an analytical technique that combines differential scanning calorimetry and Fourier-transform infrared (DSC–FTIR) microspectroscopy, which simulates the accelerated stability test and detects decomposition products simultaneously in real time. We show that the DSC–FTIR technique is a fast, simple and powerful analytical tool with applications in food sciences. This technique has been applied successfully to the simultaneous investigation of: encapsulated squid oil stability; the dehydration and intramolecular condensation of sweetener (aspartame); the dehydration, rehydration and solidification of trehalose; and online monitoring of the Maillard reaction for glucose (Glc)/asparagine (Asn) in the solid state. This technique delivers rapid and appropriate interpretations with food science applications.     

Simulation of mixed convection in a vertical channel containing discrete porous-covering heat blocks

A numerical investigation is made of fully developed laminar mixed convection in a vertical channel with multiple porous-covered heated blocks on one channel wall. The Brinkman–Forchheimer-Extended Darcy model with the Boussinesq approximation is used to characterize the flowfield inside the porous region. Solution of the coupled governing equations for the fluid/porous/solid composite system is obtained by utilizing control volume method through the use of a stream function-vorticity approach. The dependence of streamlines, isotherms, and local and overall mean Nusselt numbers on the governing parameters, such as the Darcy number, Reynolds number, Grashof number, effective conductivity ratio, and geometric parameter, is documented in detail. The results show that the strength and extent of recirculating flow induced by porous-covering block make significant changes in the cooling of block heater, especially on block back faces.     

New host copolymers containing pendant triphenylamine and carbazole for efficient green phosphorescent OLEDs

A series of vinyl copolymers (P1-P6) containing pendant hole-transporting triphenylamine (11-88 mol%) and carbazole chromophores were synthesized by radical copolymerization to investigate the influence of triphenylamine groups upon optoelectronic properties. The copolymers were readily soluble in common organic solvents and their weight-average molecular weights (M_ws) were between 1.41 × 10⁴ and 2.24 × 10⁴. They exhibited moderate thermal stability with T_d = 402-432 °C at 5% weight loss. The emission spectra (both PL and EL) of the blends [P1-P6 with 4 wt% Ir(ppy)₃] showed dominant green emission (517 nm) attributed to Ir(ppy)₃ due to efficient energy transfer from P1-P6 to Ir(ppy)₃. The HOMO levels of P1-P6, estimated from onset oxidation potentials in cyclic voltammeter, were −5.42 to −5.18 eV, which are much higher than −5.8 eV of conventional poly(9-vinylcarbazole) (PVK) host owing to high hole-affinity of the triphenylamine groups. The optoelectronic performances of phosphorescent EL devices, using P1-P6 as hosts and Ir(ppy)₃ as dopant (ITO/PEDOT:PSS/P1-P6:Ir(ppy)₃ (4 wt%):PBD (40 wt%)/BCP/Ca/Al), were greatly improved relative to that of PVK. The best performance was obtained with P4 device, in which the maximum luminance and luminance efficiency were 11?501 cd/m² and 10.6 cd/A, respectively.     

Improvement of the proton exchange membrane fuel cell (PEMFC) performance at low-humidity conditions by adding hygroscopic γ-Al2O3 particles into the catalyst layer

In this study, hygroscopic γ-alumina particles were added into the catalyst layer of membrane electrode assemblies (MEAs) to improve the wettability and performance of PEMFC at low-humidity conditions. Hygroscopic γ-alumina particles with a BET surface area of 442 m² g⁻¹ and an average pore diameter of 9 nm were synthesized by a three-step sol–gel procedure. Uniform Pt/C/γ-alumina catalyst ink was prepared by utilizing an ultrasonic method, and then sprayed on commercial hydrophobic carbon clothes to serve as the catalyst layer. The water contact angles of the catalyst layer with various amounts of γ-alumina additions 0%, 10%, 20% and 40% were measured to be 136°, 109°, 79° and 0°, respectively. Effect of adding γ-alumina particles into the catalyst layer on the single cell performance was investigated under different temperatures of the electrode humidifier. The increased wettability of the cathode catalyst layer with γ-alumina addition reduced the cell performance due to water flooding, which demonstrates the hygroscopic characteristic of γ-alumina particles. On the other hand, when the γ-alumina particles were added into the anode catalyst layer, it was found that the MEA with 10% γ-alumina addition had the highest current density at anode humidifier temperatures ranging from 25 to 55 °C. Nevertheless, the MEA with 40% γ-alumina addition into the anode catalyst layer showed the lowest current density because of the high electrical resistance of the catalyst layer and the water flooding in the anode caused by excess water absorption. The increased wettability of the anode catalyst layer by an appropriate amount of γ-alumina additions also enhances the water adsorption of the anode due to back diffusion.     

Copolymers containing pendant styryltriphenylamine and carbazole groups: Synthesis, optical, electrochemical properties and its blend with Ir(ppy)3

A series of vinyl copolymers (PVKST12-PVKST91) and homoploymer PVST containing pendant hole-transporting 4-(4-oxystyryl)triphenylamine (12-100 mol%) and carbazole chromophores were synthesized by radical copolymerization and employed as host for Ir(ppy)₃ phosphor to tune emission color. They were characterized using the ¹H NMR, FT-IR, absorption and photoluminescence spectra, elemental analysis, GPC, cyclic voltammetric and thermal analysis (DSC, TGA). Their weight-average molecular weights (M_w) and decomposition temperatures (T_d) were 1.46-5.68 × 10⁴ and 356-399 °C, respectively. The HOMO levels of PVKST12-PVKST91 and PVST, estimated from the onset oxidation potentials in cyclic voltammograms, were −5.40 to −5.14 eV, which are much higher than −5.8 eV of the conventional host poly(9-vinylcarbazole) (PVK) owing to high hole-affinity of the 4-(4-oxystyryl)triphenylamine groups. Therefore, copolymers PVKST are effective in reducing hole-injection barrier between the PEDOT:PSS and emitting layer. Electroluminescent devices [ITO/PEDOT:PSS/PVKST:Ir(ppy)₃:PBD/BCP/Ca/Al] using the hole-transporting PVKST as host were fabricated to tune the emission color. Their EL spectra showed a major emission at 515 nm and a minor peak at 435 nm attributed to Ir(ppy)₃ and 4-(4-oxystyryl)triphenylamine, respectively. The C.I.E. 1931 coordinates shift from (0.29, 0.61) for PVK to (0.33, 0.42) for PVST with an increase in 4-(4-oxystyryl)triphenylamine content.     

Phase Separation of Poly(ether sulfone imide) Modified Epoxy Resins

Amine terminated poly(ether sulfone imide) (PESI) with various imide and ethersulfone contents but similar polymer molecular weights were blended with diglycidyletherbisphenol-A (DGEBA) and cured with diaminodiphenylsulfone (DDS). The imide group, a tertiary amine, is a catalyst of the curing reaction of DGEBA with DDS, but it is poorly compatible with uncured epoxy resin. The ethersulfone group is not a catalyst of the curing reaction of DGEBA with DDS, but it has a similar chemical structure as DDS and is compatible with epoxy resin while it is at a low degree of curing. Since PESIs used in this study had similar molecular weights, increasing imide content of PESI would reduce ethersulfone content. The influence of imide and ethersulfone contents of PESI on the phase separation and curing reaction of DGEBA/DDS/PESI blend was investigated using differential scanning calorimetry (DSC), time-resolved light scattering (TRLS), and polarized optical microscopy (POM). Though the imide group has a catalysis effect on the curing reaction of DGEBA with DDS, however, its poor compatibility with epoxy resin retards the curing reaction. Our experimental results revealed the morphology of the cured blends and the curing behavior was a compromise result of catalysis and compatibility of PESI with epoxy resin.     

Influence of Bi2O3 flux in the structural and photoluminescence properties of SrAl2O4:Eu2+ phosphors

SrAl₂O₄:Eu²⁺ phosphors with various content of Bi₂O₃ flux were synthesized and analyzed. It was observed that the crystallinity and the particle size of the phosphors were increased with the addition of Bi₂O₃ flux. These phenomena are considered to be caused via the melting of the Bi₂O₃ flux particles during the synthesis of the phosphors. The melted Bi₂O₃ flux increased the mobility and homogeneity of solid reactants, thereby enhancing the photoluminescence intensity of the phosphors. SrAl₂O₄:Eu²⁺ phosphors with Bi₂O₃ as the flux exhibited a broad green emission with a peak at 520 nm. The highest photoluminescence emission intensity was observed when 5 mol% Bi₂O₃ flux was added into the phosphors. The emission is due to 4f⁶5d→4f⁷ (⁸S_7/2) transitions of the Eu²⁺ ions. Moreover, Bi₂O₃ flux extended the application of the ultraviolet excited phosphors toward the blue-light excited phosphors. Nevertheless, the influence of Bi₂O₃ on the afterglow and the emission color of SrAl₂O₄:Eu²⁺ phosphors were not significant. This research indicated that Bi₂O₃ flux is effective flux for synthesizing SrAl₂O₄:Eu²⁺ phosphors.     

Endoplasmic Reticulum Stress Contributed to Dipyridamole-Induced Impaired Autophagic Flux and Glioma Apoptosis

Elevation of intracellular cAMP levels has been implicated in glioma cell proliferation inhibition, differentiation, and apoptosis. Inhibition of phosphodiesterase is a way to elevate intracellular cAMP levels. The present study aimed to investigate the anti-glioma potential of dipyridamole, an inhibitor of phosphodiesterase. Upon treatment with dipyridamole, human U87 glioma cells decreased cell viability, clonogenic colonization, migration, and invasion, along with Noxa upregulation, Endoplasmic Reticulum (ER) stress, impaired autophagic flux, Yes-associated Protein 1 (YAP1) phosphorylation, and YAP1 reduction. Pharmacological and genetic studies revealed the ability of dipyridamole to initiate Noxa-guided apoptosis through ER stress. Additionally, the current study further identified the biochemical role of YAP1 in communicating with ER stress and autophagy under situations of dipyridamole treatment. YAP1 promoted autophagy and protected glioma cells from dipyridamole-induced apoptotic cell death. Dipyridamole impaired autophagic flux and rendered glioma cells more vulnerable to apoptotic cell death through ER stress-inhibitable YAP1/autophagy axis. The overall cellular changes caused by dipyridamole appeared to ensure a successful completion of apoptosis. Dipyridamole also duplicated the biochemical changes and apoptosis in glioma T98G cells. Since dipyridamole has additional biochemical and pharmacological properties, further research centered on the anti-glioma mechanisms of dipyridamole is still needed.     

Essential secret image sharing scheme with different importance of shadows

In (k, n) secret image sharing (SIS), a scheme encrypts a secret image into n shadow images. Any k or more shadow images can be collaborated together to reveal the secret image. Most of the previous SIS schemes don’t distinguish the importance of shadows. However, in some application environments, some participants are accorded special privileges due to their status or importance. Thus, some shadows may be more important than others. In this paper, we consider the (t, s, k, n) essential SIS (ESIS) scheme. All n shadows are classified into s essential shadows and (n–s) non-essential shadows. When reconstructing the secret image, the (t, s, k, n)-ESIS scheme needs k shadows, which should include at least t essential shadows.