The unexplored role of alkali and alkaline earth elements (ALAEs) on the structure, processing, and biological effects of bioactive glasses.

Bioactive glass has been employed in several medical applications since its inception in 1969. The compositions of these materials have been investigated extensively with emphasis on glass network formers, therapeutic transition metals, and glass network modifiers. Through these experiments, several commercial and experimental compositions have been developed with varying chemical durability, induced physiological responses, and hydroxyapatite forming abilities.

A Methodology for Calculating Inhalation Dose to Public Health Personnel Exposed to Material Resuspended from Evacuees Following the Detonation of a Fission Device.

Following a nuclear fission event, there likely would be a large number of contaminated persons who would seek assistance at community reception centers to be established outside the affected area. This paper provides a methodology for calculating inhalation doses to public health and other response personnel at such facilities who would be receiving and assisting potentially contaminated persons from whom particles can be resuspended. Three hypothetical facilities were considered: the Base Case is a rather small room with no forced air ventilation.

Aqueous Stability of Metal-Organic Frameworks Using ReaxFF-Based Metadynamics Simulations.

Aqueous stability is a critical property for the application of metal-organic framework (MOF) materials in humid conditions. The sampling of the free energy surface for a water reaction is challenging due to a lack of a reactive force field. Here, we developed a ReaxFF force field for simulating the reaction of zeolitic imidazole frameworks (ZIFs) with water.

Trends and perspectives on the commercialization of bioactive glasses.

At least 25 bioactive glass (BG) medical devices have been approved for clinical use by global regulatory agencies. Diverse applications include monolithic implants, bone void fillers, dentin hypersensitivity agents, wound dressing, and cancer therapeutics. The morphology and delivery systems of bioactive glasses have evolved dramatically since the first devices based on 45S5 Bioglass®.

Gelatin and Bioactive Glass Composites for Tissue Engineering: A Review.

Nano-/micron-sized bioactive glass (BG) particles are attractive candidates for both soft and hard tissue engineering. They can chemically bond to the host tissues, enhance new tissue formation, activate cell proliferation, stimulate the genetic expression of proteins, and trigger unique anti-bacterial, anti-inflammatory, and anti-cancer functionalities. Recently, composites based on biopolymers and BG particles have been developed with various state-of-the-art techniques for tissue engineering.

Modeling Oxygen Tricluster Formation in Calcium Aluminosilicate Supercooled Liquids and Glasses.

Calcium aluminosilicate glasses have technological importance for a variety of industrial applications. However, the short-range structure of this glass system remains widely debated regarding the formation of oxygen triclusters. It is argued that triclusters are observed in high percentages within molecular dynamics simulations because of the high melting temperatures and correspondingly high fictive temperatures.

Impact of dynamic stretching exponent on the correlation between liquid fragility and nonexponentiality at the glass transition.

The presence of large scatter in linear response data has cast doubt on the existence of an inverse correlation between liquid fragility and nonexponentiality, as originally proposed by Böhmer(19934201). We present a model for the temperature dependence of the stretching exponent based on the Mauro-Yue-Ellison-Gupta-Allan model for supercooled liquid viscosity and discuss the factors impacting the relationship between fragility and the stretching exponent at the glass transition. The proposed model exhibits distinct advantages over previous models in terms of interpretability and limit behaviors for the temperature dependence.

Mixed metal node effect in zeolitic imidazolate frameworks.

We synthesized two series of bimetallic (zinc and cobalt) zeolitic imidazolate frameworks (ZIF-62) under different solvothermal conditions. It is found that the structure of the derived ZIF crystals is highly sensitive to synthesis conditions. One series possesses the standard ZIF-62 structure, whereas the other has a mixed structure composed of both the standard structure and an unknown one.

Advancing the Mechanical Performance of Glasses: Perspectives and Challenges.

Glasses are materials that lack a crystalline microstructure and long-range atomic order. Instead, they feature heterogeneity and disorder on superstructural scales, which have profound consequences for their elastic response, material strength, fracture toughness, and the characteristics of dynamic fracture. These structure-property relations present a rich field of study in fundamental glass physics and are also becoming increasingly important in the design of modern materials with improved mechanical performance.

Theory of structural relaxation in glass from the thermodynamics of irreversible processes.

This work proposes a fundamental thermodynamic description of structural relaxation in glasses by establishing a link between the Prony series solution to volume relaxation derived from the principles of irreversible thermodynamics and asymmetric Lévy stable distribution of relaxation rates. Additionally, it is shown that the bulk viscosity of glass, and not the shear viscosity, is the transport coefficient governing structural relaxation. We also report the distribution of relaxation times and energy barrier heights underpinning stretched exponential relaxation.

Atomistic Mechanisms of Thermal Transformation in a Zr-Metal Organic Framework, MIL-140C.

To understand the mechanisms responsible for thermal decomposition of a Zr-MOF (MIL-140C), we perform atomistic-scale molecular dynamics (MD) simulations and discuss the simulation data in comparison with the TEM images obtained for the decomposed Zr-MOF. First, we introduce the ReaxFF parameters suitable for the Zr/C/H/O chemistry and then apply them to investigate the thermal stability and morphological changes in the MIL-140C during heating. Based on the performed simulations we propose an atomic mechanism for the collapse of the MIL-140C and the molecular pathways for carbon monoxide formation, the main product of the MIL-140C thermal degradation.

Mixed Alkali Effect in Silicate Glass Structure: Viewpoint of Si Nuclear Magnetic Resonance and Statistical Mechanics.

The mixed alkali effect in glasses is the deviation from linear property changes when alkali cations are mixed. The extent of this effect and its structural origin remain topics of interest. In this work, we use a statistical mechanics approach to predict the composition-structure relationship in mixed modifier NaO-KO-SiO glasses.

Why does BO suppress nepheline (NaAlSiO) crystallization in sodium aluminosilicate glasses?

The uncontrolled growth of nepheline (NaAlSiO4) crystals during the manufacturing of sodium aluminosilicate glasses via the fusion draw or float techniques and during the vitrification of some of the sodium- and alumina-rich nuclear waste glasses is a well-known problem. The addition of B2O3 to suppress the crystallization in these glasses is well documented in the literature. Another advantage of B2O3 is that it lowers the viscosity of the glass melt and, if incorporated in its trigonal coordination state, will improve the intrinsic damage resistance of the final glass product.

Predicting Ionic Diffusion in Glass from Its Relaxation Behavior.

In low-viscosity liquids, diffusion is inversely related to viscosity via the Stokes-Einstein relation. However, the Stokes-Einstein relation breaks down near the glass transition as the supercooled liquid transitions into the non-ergodic glassy state. The nonequilibrium viscosity of glass is governed by the liquid-state viscous properties, namely, the glass transition temperature and the fragility.

Relating structural disorder and melting in complex mixed ligand zeolitic imidazolate framework glasses.

We report the formation of zeolitic imidazolate framework glasses incorporating three organic linkers, from their corresponding novel crystalline structures [Zn(Im2-x-ybImxmbImy)]. Structure-property relationships between chemical compositions and thermal properties are analysed, in addition to the effect on the nanoscale porosity of the glasses formed. A probabilistic model is used to explain melting and the glass transition temperatures of the obtained glasses and link to the nanoscale structural disorder of their crystalline starting structures.

Glass-activated regeneration of volumetric muscle loss.

Volumetric muscle loss (VML) resulting from injuries to skeletal muscles has profound consequences in healthcare. Current VML treatment based on the use of soft materials including biopolymers and decellularized extracellular matrix (dECM) is challenging due to their incapability of stimulating the formation of satellite cells (SCs), muscle stem cells, which are required for muscle regeneration. Additional stem cells and/or growth factors have to be incorporated in these constructs for improved efficacy.

Radiation exposures from the beneficial use of alumina production residue.

Estimates of radiation exposure are developed over the life cycle of beneficial use in cement of an alumina production residue (APR) waste pile. The life cycle includes radiation exposures that might be experienced by industrial workers involved in excavation and transport of the residue to cement plants, industrial workers at the cement plants, construction workers making use of the cement, members of the public who might be in the proximity of the cement products, and disposal of the cement at the end of its useful life. The results indicate that it is not reasonably likely for exposures related to beneficial use of APR waste in cement to exceed the acceptance criteria delineated in current radiation protection standards for workers and members of the general public.

Mechanical properties of bioactive glasses, ceramics, glass-ceramics and composites: State-of-the-art review and future challenges.

The repair and restoration of bone defects in orthopaedic and dental surgery remains a major challenge despite advances in surgical procedures and post-operative treatments. Bioactive glasses, ceramics, glass-ceramics and composites show considerable potential for such applications as they can promote bone tissue regeneration. This paper presents an overview of the mechanical properties of various bioactive materials, which have the potential for bone regeneration.

Statistical Mechanical Model of Topological Fluctuations and the Intermediate Phase in Binary Phosphate Glasses.

Glasses are topologically disordered materials with varying degrees of fluctuations in structure and topology. This study links statistical mechanics and topological constraint theory to quantify the degree of topological fluctuations in binary phosphate glasses. Because fluctuations are a potential mechanism enabling self-organization, we investigated the ability of phosphate glasses to adapt their topology to mitigate localized stresses, e.

Topological Origins of the Mixed Alkali Effect in Glass.

The mixed alkali effect, the deviation from expected linear property changes when alkali ions are mixed in a glass, remains a point of contention in the glass community. While several earlier models have been proposed to explain mixed alkali effects on ionic motion, models based on or containing discussion of structural aspects of mixed-alkali glasses remain rare by comparison. However, the transition-range viscosity depression effect is many orders in magnitude for mixed-alkali glasses, and the original observation of the effect (then known as the Thermometer Effect) concerned the highly anomalous temperature dependence of stress and structural relaxation time constants.

Topological Control of Water Reactivity on Glass Surfaces: Evidence of a Chemically Stable Intermediate Phase.

Glass surfaces are of considerable interest due to their disproportionately large influence on the performance of glass articles in many applications. However, the behavior of glass surfaces has proven difficult to model and predict due to their complex structure and interactions with the environment. Here, the effects of glass network topology on the surface reactivity of glasses have been investigated using reactive and nonreactive force field-based molecular dynamics simulations as well as density functional theory.

Understanding Glass through Differential Scanning Calorimetry.

Differential scanning calorimetry (DSC) is a powerful tool to address some of the most challenging issues in glass science and technology, such as the nonequilibrium nature of the glassy state and the detailed thermodynamics and kinetics of glass-forming systems during glass transition, relaxation, rejuvenation, polyamorphic transition, and crystallization. The utility of the DSC technique spans across all glass-forming chemistries, including oxide, chalcogenide, metallic, and organic systems, as well as recently discovered metal-organic framework glass-forming systems. Here we present a comprehensive review of the many applications of DSC in glass science with focus on glass transition, relaxation, polyamorphism, and crystallization phenomena.