Structural Role of Strontium Oxide in Modified Silicate Glasses

In the composition range of x= 0-15 mol%, glasses in the system 24.5Na2O.24.5CaO.6P2O5.xSrO.(45-x)SiO2 have been studied. The glasses are transparent and have an amorphous network structure when they are as prepared. Heat treated glasses, on the other hand, are transformed into opaque white glass ceramics with a highly crystalline network structure. The main well-formed crystalline species in material bioactivity were apatite (calcium phosphate, Ca3(PO4)2, wollastonite (calcium silicate, CaSiO3), and strontium calcium phosphate [Ca2Sr(PO4)2. Increasing SrO improves material crystallite and increases the host glass matrix's hardness. The modification of the apatit Ca(PO3)2 to involve Sr ions inducing Ca2Sr (PO4)2 apatite one is thought to be the cause of the change in XRD spectra, 31P NMR chemical shift, and hardness number as SrO increases. These species help to improve material properties and hardness.

Using Carbomer-Based Hydrogels for Control the Release Rate of Diclofenac Sodium: Preparation and In Vitro Evaluation

The aim of the current research work was to prepare Car934-g-poly(acrylic acid) hydrogels by the free-radical polymerization technique. Various concentrations of carbopol, acrylic acid and ethylene glycol dimethacrylate were employed for the fabrication of Car934-g-poly(acrylic acid) hydrogels. Fourier-transform infrared spectroscopy (FTIR), Thermogravimetric analysis (TGA), Differential scanning calorimetry (DSC), Scanning electron microscope (SEM) and Powder X-ray diffractometry (PXRD) studies were performed to know the structural arrangement, thermal stability, physical appearance and amorphous network of developed hydrogels. FTIR analysis revealed that carbopol reacted with acrylic acid during the process of polymerization and confirmed the grafting of acrylic acid over the backbone of carbopol. TGA and DSC studies showed that developed hydrogels were thermally stable. Surface morphology was analyzed by SEM, which confirmed a porous network of hydrogels. PXRD analysis indicated that crystallinity of the drug was reduced by the amorphous network of hydrogels. Furthermore, swelling studies for all developed hydrogels were performed at both media, i.e., pH 1.2 and 7.4, and higher swelling was exhibited at pH 7.4. Sol–gel analysis was performed to evaluate the soluble unreacted part of the fabricated hydrogels. Similarly, an in-vitro study was conducted for all hydrogel formulations at both acidic (pH 1.2) and basic (pH 7.4) mediums, and a greater drug release was observed at pH 7.4. Different kinetics such as zero-order, first-order, the Higuchi model and the Korsmeyer–Peppas model were applied to know the mechanism of release order of drugs from the hydrogels.

In-Situ Synthesis and Characterization of Nanocomposites in the Si-Ti-N and Si-Ti-C Systems

The pyrolysis (1000 °C) of a liquid poly(vinylmethyl-co-methyl)silazane modified by tetrakis(dimethylamido)titanium in flowing ammonia, nitrogen and argon followed by the annealing (1000–1800 °C) of as-pyrolyzed ceramic powders have been investigated in detail. We first provide a comprehensive mechanistic study of the polymer-to-ceramic conversion based on TG experiments coupled with in-situ mass spectrometry and ex-situ solid-state NMR and FTIR spectroscopies of both the chemically modified polymer and the pyrolysis intermediates. The pyrolysis leads to X-ray amorphous materials with chemical bonding and ceramic yields controlled by the nature of the atmosphere. Then, the structural evolution of the amorphous network of ammonia-, nitrogen- and argon-treated ceramics has been studied above 1000 °C under nitrogen and argon by X-ray diffraction and electron microscopy. HRTEM images coupled with XRD confirm the formation of nanocomposites after annealing at 1400 °C. Their unique nanostructural feature appears to be the result of both the molecular origin of the materials and the nature of the atmosphere used during pyrolysis. Samples are composed of an amorphous Si-based ceramic matrix in which TiNxCy nanocrystals (x + y = 1) are homogeneously formed “in situ” in the matrix during the process and evolve toward fully crystallized compounds as TiN/Si3N4, TiNxCy (x + y = 1)/SiC and TiC/SiC nanocomposites after annealing to 1800 °C as a function of the atmosphere.

Micromechanically informed reaction-induced damage and fracture in polymers due to oxidation

High temperature oxidation in polymers is a complex phenomenon, driven by the coupled diffusion-reaction process, causing changes in the amorphous network structure and resulting in property degradation. Prolonged oxidation in polymers results in the formation of a coarse, oxide layer on the outer surface and induces spontaneous cracking inside the material. In this paper, we present a chemical reaction-driven evolving network theory coupled with phase-field fracture to describe the effect of oxidation in polymers across different length scales. The theory considers the coupling between oxygen diffusion, chemical reactions, large deformation of polymers, and phase-field fracture in a thermodynamically consistent way. Guided by the statistical mechanics, the network theory has been introduced to model the reaction induced chain scissions and crosslinking events causing significant changes in the three-dimensional network structure. Further, these microscale events have been considered as the reason behind macroscopic mechanical property degradation, namely oxidative embrittlement. Finally the network theory is coupled with a phase-field fracture model to capture the macroscale damage and fracture in the polymer under stress-coupled oxidation conditions. We derive the specific constitutive forms for all the physical-chemical processes based on the thermodynamic inequality conditions, and numerically implement the theory in finite elements by writing ABAQUS user-defined element (UEL) subroutine. To present the model's capability, numerical examples with standard fracture geometries have been studied. The simulation results have demonstrated the model's capability of predicting the effect of oxidative aging on the polymer's response.

Neologising misogyny: Urban Dictionary’s folksonomies of sexual abuse

Web 2.0 has facilitated a particularly toxic brand of digital men’s rights activism, collectively known as the Manosphere. This amorphous network of online publics is noted for its virulent anti-feminism, extreme misogyny and synergies with the alt-right. Early manifestations of this phenomenon were confined largely to 4/Chan, Reddit and numerous alt-right forums. More recently, however, this rhetoric has become increasingly evident in Urban Dictionary. This article presents the findings of a machine-learning and manual analysis of Urban Dictionary’s entries relating to sex and gender, to assess the extent to which the Manosphere’s discourses of extreme misogyny and anti-feminism are working their way into everyday vernacular contexts. It also considers the sociolinguistic and gender-political implications of algorithmic and linguistic capitalism, concluding that Urban Dictionary is less a dictionary than it is a platform of folksonomies, which may exert a disproportionate and toxic influence on online discourses related to gender and sexuality.

Investigation of γ ray shielding, structural and dissolution rate studies of alkali based bismuth borate glass systems with MoO3 added

Bi2O3–B2O3–Li2O–K2O–MoO3 glass system has been synthesized using melt-quenching technique. γ ray shielding properties have been evaluated in terms of mass attenuation coefficient at photon energies 356, 662 and 1173 keV. These shielding parameters are also compared with standard nuclear radiation shielding material “barite concrete” at the same photon energies. Most of our prepared samples show better γ ray shielding properties as compared to barite concrete at the same photon energies. Density, molar volume, XRD, FTIR and Raman studies have been employed to study the structural properties of the prepared glass system. Different structural groups such as [BO3], [BO4], [MoO4] and [MoO6] have been detected in the amorphous network. The presence of non-bridging oxygens, bridging oxygens and change of coordination number has been discussed. The optical absorption spectra are recorded in the wavelength range 200–800 nm and optical band gap is calculated which has shown strong dependence on Bi2O3/B2O3 ratio. The samples have also been tested for their durability by measuring dissolution rate properties using distilled water at 90°C. It has been concluded that increase in the content of Bi2O3 in the composition improves durability and γ ray shielding properties of the samples.

Metakaolinite Phosphate Cementitious Matrix: Inorganic Polymer Obtained by Acidic Activation

This work aims to study an aluminosilicate phosphate cementitious matrix. The cementitious matrix was studied on paste samples. The synthesis of metakaolinite phosphate cement (MKPC) was investigated using calorimetric techniques. A systematic study was performed by emphasizing a broad range of Al/P molar ratios, covering the different behavior of the material to the extremes, as well as the optimum composition. X-ray diffraction and scanning electron microscopy revealed that the final structure was mainly an amorphous network, albeit with some non-reacted phases. The compressive strength was studied on mortars using a cement/sand ratio of 1:3. MKPC specimens with Al/P ratios close to 1/1 showed optimal behavior. MKPCs with Al/P ratios above 1/1 were characterized by high porosity and low strength, whereas MKPCs with Al/P < 1 contained an excess of phosphates. The influence of the Al/P molar ratio on compressive strength was also studied, reaching a maximum of 68 MPa for the optimum composition. Based on the results, MKPC may be a promising candidate for construction purposes.

Prediction of amorphous structure and stability of P-N and N-CO extended solids under pressure

ABSTRACTThe amorphous structures of poly-CO, P-N and N-CO extended solids at high pressures were predicted using density functional theory (DFT) and evolutionary algorithms employing variable and fixed concentrations of components methods. Compression of random network of poly-CO up to 45 GPa results in elimination of small rings of the amorphous network. The amorphous structure with stoichiometry N9P was found to be dynamically stable (no imaginary frequencies in phonon-dispersion curve), stable relative transformation to solid nitrogen and phosphorus, but metastable according to convex hull calculations. The amorphous structure of the N-CO extended solid was obtained with various concentrations of N atoms under isotropic compression up to 50 GPa and release of pressure down to 5 GPa calculated using DFT. The higher concentration of CO is found to be favourable for stabilization of an amorphous covalent N-C-O network consisting of chains and a cage of the network. Upon lowering the pressure and decomposition of the compressed extended solid, atoms are disconnected first from the ends of polymeric chains, while rings of random network are sustained almost intact. Results of a calculated Raman spectra are compared with available experimental results.

Charles Dickens and the ‘Dark Corners’ of Children’s Literature

The time is right to consider anew the ways in which Dickens anticipated, participated in, and critiqued the vast mediascape of Victorian children’s literature. In order to do so, we must continue to challenge our enduring bias that children’s literature does not possess the dialogic register of other genres. Dickens, for one, knew better: though he often tells his readers that children’s literature is a ‘nursery of fancy’ that socializes and humanizes through its ‘bright little books’, he shows a world in which children’s literature is an amorphous network of ‘dark corners’, often governed by ruthless, working-class bodies. Dickens’s fiction and journalism reveal his awareness of children’s literature’s growing currency in economic, cultural, and aesthetic terms. This chapter focuses on the years 1849–54, when Dickens’s child production matched his literary production, and when he was sharply attuned to children’s reading materials.