New type of phenolic resin: Curing reaction of phenol‐novolac based benzoxazine with bisoxazoline or epoxy resin using latent curing agent and the properties of the cured resin

In this study, we aimed to reduce the cure time, and to lower the cure temperature of the benzoxazine compound. Therefore, curing reaction of benzoxazine with bisoxazoline or epoxy resin using the latent curing agent and the properties of the cured resins were investigated. The cure behavior of benzoxazine with bisoxazoline or epoxy resin using the latent curing agent was monitored by differential scanning calorimetry and measurements for storage modulus (G′). The properties of the cured resin were estimated by mechanical properties, electrical insulation, water resistance, heat resistance, and flame resistance. As a result, it was confirmed that by using the latent curing agent, cure time of benzoxazine and bisoxazoline or epoxy resin was reduced, and cure temperature was lowered. And it was found that the curing reaction using phenol‐novolac based benzoxazine (Na) as the benzoxazine compound could proceed more rapidly than that using bisphenol‐A based benzoxazine (Ba) as the benzoxazine compound. However, the cured resins from Ba and bisoxazoline or epoxy resin using the latent curing agent showed good heat resistance, flame resistance, and mechanical properties compared with those from Na and bisoxazoline or epoxy resin using the latent curing agent. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Temperature dependences of piezoelectric properties of vanadium substituted SrBi2Nb2O9 ceramics with grain orientation

The temperature dependence of the piezoelectric properties of vanadium substituted strontium bismuth niobate, SrBi₂Nb_1.95V_0.05O₉ (SBNV) ceramics, were investigated in various vibration modes. The effects of grain orientation in SBNV ceramics on the piezoelectric properties were also studied by the hot-forging (HF) method. The anisotropy of the piezoelectric properties of each vibration mode was confirmed by observing the grain orientation. In particular, HF-SBNV ceramics of the (33) and (15) modes showed excellent piezoelectric properties with relatively high mechanical quality factors, Q_m (2200, 4600), and high electrical quality factors, Q_{e max} (66.0, 21.6), respectively. In addition, HF-SBNV ceramics showed low temperature coefficients of resonance frequency TC-f_r (−16.5, −27.0). HF-SBNV ceramics are considered to be superior candidates for the lead-free piezoelectric application of ceramic resonators.     

1H NMR,thermal, and conductivity studies on PVAc based gel polymer electrolytes

The lithium‐ion conducting gel polymer electrolytes (GPE), PVAc‐DMF‐LiClO₄ of various compositions have been prepared by solution casting technique. ¹H NMR results reveal the existence of DMF in the gel polymer electrolytes at ambient temperature. Structure and surface morphology characterization have been studied by X‐ray diffraction analysis (XRD) and scanning electron microscopy (SEM) measurements. Thermal and conductivity behavior of polymer‐ and plasticizer‐salt complexes have been studied by differential scanning calorimetry (DSC), TG/DTA, and impedance spectroscopy results. XRD and SEM analyses indicate the amorphous nature of the gel polymer‐salt complex. DSC measurements show a decrease in T_g with the increase in DMF concentrations. The thermal stability of the PVAc : DMF : LiClO₄ gel polymer electrolytes has been found to be in the range of (30–60°C). The dc conductivity of gel polymer electrolytes, obtained from impedance spectra, has been found to vary between 7.6 × 10^?7 and 4.1 × 10^?4 S cm^?1 at 303 K depending on the concentration of DMF (10–20 wt %) in the polymer electrolytes. The temperature dependence of conductivity of the polymer electrolyte complexes appears to obey the VTF behavior. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Thermal stability and crystallisation of a Zr55Cu30Al10Ni5 bulk metallic glass studied by in situ ultrasonic echography

An original in situ ultrasonic echography technique was used to study the thermal stability and crystallisation of a Zr₅₅Cu₃₀Al₁₀Ni₅ bulk metallic glass between RT and 630 °C. Changes in Young's modulus with temperature were reported allowing to study the supercooled-liquid state and the crystallisation process. Investigations of viscoelastic properties gave information on the correlation factor (hierarchically correlated motion theory) and three distinct crystallisation stages were observed. Their kinetics were studied using Voigt's and Reuss' approximations for a two-phase material and comparisons with the Johnson–Mehl–Avrami–Kolmogorov theory allowed us to consider a mixed surface/internal nucleation for the first stage and a surface nucleation for the two last stages.     

Effect of strain rate on compressive behavior of a Pd40Ni40P20 bulk metallic glass

Mechanical deformation of Pd₄₀Ni₄₀P₂₀ was characterized in compression over a wide strain rate range (3.3×10⁻⁵ to 2×10³ s⁻¹) at room temperature. The compression sample fractured with a shear plane inclined 42 degree with respect to the loading axis, in contrast to 56 degree for the case of tension. This suggests the yielding of the material deviates from the classical von Mises yield criterion, but follows the Mohr-Coulomb yield criterion. Fracture stress as well as strain was found to decrease with increasing applied strain rate. The compressive stress (1.74 GPa) was also found to be higher than the tensile fracture stress at a quasi-static strain rate. Close examination of the stress–strain curves revealed that localized shear might have occurred at a compressive stress of about 1.4 GPa, much lower than the “apparent” yield stress of 1.74 GPa. However, the stress of 1.4 GPa for shear band initiation is almost the same as the fracture stress measured at a dynamic strain rate of 5×10² s⁻¹. These results suggested that the fracture of a bulk metallic glass is sensitive to the applied loading rate.     

Evolution of long-period stacking ordered structures on annealing as-cast Mg85Y9Zn6 alloy ingot observed by synchrotron radiation small-angle scattering

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Pleiotropic Effects of Sodium-Glucose Cotransporter-2 Inhibitors: Renoprotective Mechanisms beyond Glycemic Control

Diabetes mellitus is a major cause of chronic kidney disease and end-stage renal disease. However, the management of chronic kidney disease, particularly diabetes, requires vast improvements. Recently, sodium-glucose cotransporter-2 (SGLT2) inhibitors, originally developed for the treatment of diabetes, have been shown to protect against kidney injury via glycemic control, as well as various other mechanisms, including blood pressure and hemodynamic regulation, protection from lipotoxicity, and uric acid control. As such, regulation of these mechanisms is recommended as an effective multidisciplinary approach for the treatment of diabetic patients with kidney disease. Thus, SGLT2 inhibitors are expected to become key drugs for treating diabetic kidney disease. This review summarizes the recent clinical evidence pertaining to SGLT2 inhibitors as well as the mechanisms underlying their renoprotective effects. Hence, the information contained herein will advance the current understanding regarding the pleiotropic effects of SGLT2 inhibitors, while promoting future research in the field.     

Calcium aluminate cement in castable alumina: From hydrate bonding to the in situ formation of calcium hexaluminate

Calcium hexaluminate (CA₆) is an intrinsically densification-resistant material, therefore, its porous structures are key materials for applications as high-temperature thermal insulators. This article reports on the combination of calcined alumina and calcium aluminate cement (CAC) in castable aqueous suspensions for the in situ production of porous CA₆. The CAC content (10–34 vol%) and the curing conditions ensure structural integrity prior to sintering and maximize the development of hydrated phases. Changes in physical properties, crystalline phases, and microstructure were investigated after isothermal treatments (120–1500 °C), and three sequential porogenic events were observed. The hydration of CAC preserved the water-derived pores (up to 120 °C), and the dehydroxylation of CAC hydrates (250–700 °C) generated inter-particles pores. Moreover, the in situ expansive formation of CA₂ and CA₆ (900–1500 °C) hindered densification and generated intra-particle pores. Such events differed from those observed with other CaO sources, and resulted in significantly higher pores content and lower thermal conductivity.     

Molecular modeling of single polypeptide chain of calcium-binding protein p26olf from dimeric S100B()

P26olf from olfactory tissue of frog, which may be involvedin olfactory transduction or adaptation, is a Ca²⁺-binding proteinwith 217 amino acids. The p26olf molecule contains two homologousparts consisting of the N-terminal half with amino acids 1–109and the C-terminal half with amino acids 110–217. Eachhalf resembles S100 protein with about 100 amino acids and containstwo helix–loop–helix Ca²⁺-binding structural motifsknown as EF-hands: a normal EF-hand at the C-terminus and apseudo EF-hand at the N-terminus. Multiple alignment of thetwo S100-like domains of p26olf with 18 S100 proteins indicatedthat the C-terminal putative EF-hand of each domain containsa four-residue insertion when compared with the typical EF-handmotifs in the S100 protein, while the N-terminal EF-hand ishomologous to its pseudo EF-hand. We constructed a three-dimensionalmodel of the p26olf molecule based on results of the multiplealignment and NMR structures of dimeric S100B(ßß)in the Ca²⁺-free state. The predicted structure of the p26olfsingle polypeptide chain satisfactorily adopts a folding patternremarkably similar to dimeric S100B(ßß). Each domainof p26olf consists of a unicornate-type four-helix bundle andthey interact with each other in an antiparallel manner formingan X-type four-helix bundle between the two domains. The twoS100-like domains of p26olf are linked by a loop with no sterichindrance, suggesting that this loop might play an importantrole in the function of p26olf. The circular dichroism spectraldata support the predicted structure of p26olf and indicatethat Ca²⁺-dependent conformational changes occur. Since theC-terminal putative EF-hand of each domain fully keeps the helix–loop–helixmotif having a longer Ca²⁺-binding loop, regardless of the four-residueinsertion, we propose that it is a new, novel EF-hand, althoughit is unclear whether this EF-hand binds Ca²⁺. P26olf is a newmember of the S100 protein family.