Influence of microwave irradiation on thermal properties of PVA and PVA/graphene nanocomposites

Journal of Thermal Analysis and Calorimetry - This article discusses the effect of microwave irradiation on the thermal properties of poly(vinyl alcohol)/graphene nanocomposites, prepared using a...     

Controlled preparation of aluminum borate powders for the development of defect-related phosphors for warm white LED lighting

The optimization of the elaboration conditions of a new family of highly emissive white phosphors based on glassy yttrium aluminum borates (g-YAB) compositions is presented. Their preparation from solutions is based on the polymeric precursor method (modified Pechini process), involving non-toxic and low cost precursors. The resulting resins were first dried at moderate temperatures followed by two-step annealing treatments of the obtain powders under controlled atmospheres: a first pyrolysis under nitrogen followed by a calcination under oxygen. This favored the gradual oxidation of organic moieties coming from starting materials, avoiding uncontrolled self-combustion reactions, which generate localized hot spots. This prevented phase segregations and the formation of pyrolytic carbon or carbonates, which are strongly detrimental to the luminescence properties. Thus, coupled chemical analyses and luminescence characterizations showed the high chemical homogeneity of the resulting powders and their intense emissions in the whole visible range. These emissions can be tuned from blue to warm white by adjusting the calcination temperature that is an important advantage for the development of LED devices. We showed that impurities of monovalent and divalent cations act as quenching emission centers for these phosphors. Therefore, by increasing the purity grade, we significantly enhanced the PL emissions leading to high internal quantum yields (80–90%). Finally, cathodoluminescence emissions showed the homogeneous dispersion of emitting centers in the g-YAB matrix.     

Optically stimulated luminescence in Ag doped Li2B4O7 single crystal and its sensitivity to neutron detection and dosimetry in OSL mode

Optically stimulated luminescence (OSL) measurements have been carried out on single crystals of Ag doped Li₂B₄O₇ (LTB:Ag) after exposure to various nuclear radiations. The time integrated OSL intensity is found to be linear in the range from 0.1 Gy to 500 Gy. Fading of the OSL signal was found to be around 36% in 48 h. The presence of ⁶Li and ¹⁰B has been gainfully utilized to measure doses of thermal neutrons. Further, the large difference between the wavelength of the stimulation source (∼460 nm) and emission from the LTB:Ag at 270 nm has enhanced the signal-to-noise ratio in a simple OSL set-up with suitable filters. The high sensitivity of the LTB:Ag to thermal neutrons will be useful in variety of applications including personal dosimetry in mixed-fields and imaging devices for neutron radiography.     

Thermoluminescence characterization of newly developed Cu-doped lithium tetraborate materials

This work reports the thermoluminescence characterization of newly synthesized Li₂B₄O₇ (LTB) and LTB:Cu materials of single crystal and glassy structure. The following basic properties were investigated: glow curve, dose response, fading, reproducibility and batch uniformity. The Cu doped samples and the non-doped single crystal gave TL response, while the non-doped glassy LTB did not up to 10 kGy. LTB:Cu single crystals showed promising properties. Their glow curve consists of two well separated peaks (at 165 °C and 270 °C) in the 50–350 °C temperature region. The sensitivity of this material is about 5 times higher than that of the TLD-100. The most attractive feature of these LTB:Cu single crystals is their linear dose response in a very wide range: from 0.3 mGy to 10 kGy. Unfortunately this material is sensitive to light; the fading of irradiated samples is very quick in daylight, but at room temperature and kept in dark the fading of the 270 °C peak is less than 6%.     

Assessment of Growth Factors,Cytokines, and Cellular Markers in Saliva of Patients with Trigeminal Neuralgia

We proposed to perform a comparative analysis of growth factors, cytokines, and chemokine receptors on the salivary cells in the saliva obtained from trigeminal neuralgia (TN) and normal subjects. Saliva was collected from TN and healthy subjects. Salivary cells were isolated by centrifugation. The expression of the cell surface marker was analyzed by flow cytometry. A cytometric bead array was done to measure the levels of cytokines and growth factors on the flow cytometer. Saliva from TN subjects showed lower growth factor levels of Angiopoietin-2, bFGF, HGF, SCF, TGF-α, and VEGF and higher cytokine levels of IL-1β, TNF-α, CCL2, IL-17A, IL-6, and CXCL8, as well as higher expression levels of chemokine receptors CCR1 (CD191), CR3 (CD11b), CCR2 (CD192), CXCR5 (CD185), and CCR5 (CD196) in the cells from TN saliva. A certain set of cytokines and growth factors in the saliva, as well as chemokine receptors on salivary cells, could be a useful tool in the diagnostics and prognostics of trigeminal neuralgia. Trigeminal neuralgia is one of the significant pathological conditions in the class of chronic diseases around the world. Many targeted approaches are being tried by various research groups to utilize the information of the inflammatory microenvironment to resolve the pathology of chronic TN.     

Molecular docking of phenolic compounds and screening of antioxidant and antidiabetic potential of Olea europaea L. Ethanolic leaves extract

Oxidative stress has a crucial role in diabetic pathophysiology, therefore consuming naturally derived antioxidants as a remedial target. This study examines the naturally occurring antioxidant and antidiabetic of Olea europaea L. ethanolic leaves extract. Olea europaea L. leaves were macerated (OLE) by using absolute ethanol. Phytochemical and physiochemical analysis of OLE was screened using standard methods. The antioxidant effects were examined by DPPH (1, 1-diphenyl-2-picrylhydrazil) radical scavenging assay. In vitro antidiabetic was assayed by α-amylase enzyme inhibition study. Ethanolic extraction of OLE by maceration technique, 10% yield. Loss on drying, foreign organic matters and total ash value of OLE showed 2%, 0.2% and 16.5%, respectively. Phytochemical test on OLE confirmed saponin, flavonoid, glycoside, tannin, phenol and carbohydrate presences. The total phenolic and flavonoid contents of OLE is 490 mg GAE/g and 855 mg RUE/g of extract, respectively. OLE (IC₅₀ 38.37 ± 0.26 µg/ml) showed functional DPPH scavenging assay comparable to ascorbic acid (IC₅₀ 30.37 ± 0.17 µg/ml). In the alpha-amylase inhibitory activity, Acarbose showed an IC₅₀ value of 20.06 ± 0.19 µg/ml, while OLE portrayed an IC₅₀ value of 37.99 ± 0.15 µg/ml. The kinetic studies revealed that all samples at high concentrations reacted within a very short time, and a steady state was reached almost immediately. The lowest concentration showed slow kinetic behaviour implied longer periods before the constant state was reached. Molecular docking studies evidenced that most of the phenolic compounds of OLE interact with the active site of Human pancreatic α-amylase through the hydrogen bonding and hydrophobic interaction confirming the alpha-amylase inhibitory effect. The results suggest that Olea europaea L. has been a conceivable natural bioactive source as an antioxidant and an antidiabetic agent.     

Vibrational and thermodynamic properties of orthorhombic CaSnO3 from DFT and DFPT calculations

Density functional theory (DFT) and density functional perturbation theory (DFPT) calculations were used to investigate the vibrational and thermodynamic properties of orthorhombic stannate CaSnO₃ compound. Our approach was based on the generalized gradient approximation with dispersion correction (GGA+D), considering the norm-conserved pseudopotentials. The phonon dispersion relation as well as theoretical peaks of the infrared (IR) and Raman spectrum in the frequency range of 100–800 cm⁻¹ was analyzed and assigned. The thermodynamic potentials and the specific heat at constant volume of the CaSnO₃ compound are also calculated, whose dependence with the temperature are discussed.