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Multi-scale predictive models for the shock sensitivity of energetic materials connect energy localization ("hotspots") in the microstructure to macro-scale detonation phenomena. Calculations of hotspot ignition and growth rely on models for chemical reaction rates expressed in Arrhenius forms; these chemical kinetic models, therefore, are foundational to the construction of physics-based, simulation-derived meso-informed closure (reactive burn) models. However, even for commonly used energetic materials (e.g., HMX in this paper) there are a wide variety of reaction rate models available. These available reaction rate models produce reaction time scales that vary by several orders of magnitude. From a multi-scale modeling standpoint, it is important to determine which model best represents the reactive response of the material. In this paper, we examine three global Arrhenius-form rate models that span the range of reaction time scales, namely, the Tarver 3-equation, the Henson 1-equation, and the Menikoff 1-equation models. They are employed in a meso-informed ignition and growth model which allows for connecting meso-scale hotspot dynamics to macro-scale shock-to-detonation transition. The ability of the three reaction models to reproduce experimentally observed sensitivity is assessed by comparing the predicted criticality envelope (Walker–Wasley curve) with experimental data for pressed HMX Class V microstructures. The results provide a guideline for model developers on the plausible range of time-to-ignition that are produced by physically correct Arrhenius rate models for HMX. [ABSTRACT FROM AUTHOR]

Reactive burn models for heterogeneous energetic materials (EMs) must account for chemistry as well as microstructure to predict shock-to-detonation transition (SDT). Upon shock loading, the collapse of individual voids leads to ignition of hotspots, which then grow and interact to consume the surrounding material. The sub-grid dynamics of shock-void interactions and hotspot development are transmitted to macro-scale SDT calculations in the form of a global reactive "burn model." This paper presents a physically evocative model, called meso-informed sub-grid source terms for energy localization (MISSEL), to close the macro-scale governing equations for calculating SDT. The model parameters are explicitly related to four measurable physical quantities: two depending on the microstructure (the porosity ϕ and average pore size D ¯ v o i d ), one depending on shock–microstructure interaction (the fraction of critical voids ξ c r ), and the other depending on the chemistry (the burn front velocity V h s ). These quantities are individually quantifiable using a small number of rather inexpensive meso-scale simulations. As constructed, the model overcomes the following problems that hinder the development of meso-informed burn models: (1) the opacity of more sophisticated surrogate/machine-learning approaches for bridging meso- and macro-scales, (2) the rather large number of high-resolution mesoscale simulations necessary to train machine-learning algorithms, and (3) the need for calibration of many free parameters that appear in phenomenological burn models. The model is tested against experimental data on James curves for a specific class of pressed 1,3,5,7-tetranitro-1,3,5,7-tetrazoctane materials. The simple, evocative, and fast-to-construct MISSEL model suggests a route to develop frameworks for physics-informed, simulation-derived meso-informed burn models. [ABSTRACT FROM AUTHOR]

Amaranthus tricolor L. is a plant of significant botanical diversity and richness. In recent years, it has emerged as a versatile medicinal plant material, with numerous studies highlighting its considerable pharmacological effects. This study provides a comprehensive micromorphological and phytochemical characterization of A. tricolor. The study uses the Ciuley method, a rigorous and scientific approach that has been improved and modified by the Faculty of Pharmacy, University of Medicine and Pharmacy at Ho Chi Minh City, Vietnam. The results, based on A. tricolor collected in District 8, Ho Chi Minh City, Vietnam, were consistent with descriptions published in previous studies. The herbal powder contained distinctive microscopic constituents such as reticulate vessel elements, scalariform vessel elements, and spherical and cuboidal calcium oxalate crystals. The phytochemical characterization revealed the presence of various chemical groups in A. tricolor, including lipids, carotenoids, triterpenoids, flavonoids, tannins, saponins, organic acids, reducing agents, and polyuronic compounds. The macroscopic, microscopic, and chemical characteristics of A. tricolor are crucial for its medicinal use. Macroscopic studies ensure accurate botanical identification, while microscopic analysis reveals internal structures that improve quality control. Chemical characterization identifies active compounds responsible for the documented pharmacological effects. This comprehensive understanding enhances the efficacy, safety, and therapeutic potential of A. tricolor, supporting its optimal use in herbal medicine and paving the way for discovering new therapeutic agents. [ABSTRACT FROM AUTHOR]

Heterogeneous energetic materials (EMs) contain microstructural defects such as voids, cracks, interfaces, and delaminated zones. Under shock loading, these defects offer potential sites for energy localization, i.e., hotspot formation. In a porous EM, the collapse of one void can generate propagating blast waves and hotspots that can influence the hotspot phenomena at neighboring voids. Such void–void interactions must be accounted for in predictive multi-scale models for the reactive response of a porous EM. To infuse such meso-scale phenomena into a multi-scale framework, a meso-informed ignition and growth model (MES-IG) has been developed, where the influence of void–void interactions is incorporated into the overall reaction rate through a function, f v − v . Previously, MES-IG was applied to predict the sensitivity and reactive response of EM, where f v − v was assumed to be a function of the overall sample porosity alone. This paper performs a deeper analysis to model the strong dependency of f v − v on other factors, such as void size and shock strength. The improved model for void–void interactions produces good agreement with direct numerical simulations of the HE microstructures and, thus, advances the predictive capability of multi-scale models of the shock response and sensitivity of EM. [ABSTRACT FROM AUTHOR]

Head-to-head comparisons of multiple experimental observations and numerical simulations on a deconstructed plastic-bonded explosive consisting of an octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine crystal embedded in a polymeric binder with a 4 ns duration 20 GPa input shock are presented. Hot spots observed in high-resolution direct numerical simulations are compared with micro-scale shock-induced reactions visualized using nanosecond microscope imaging and optical pyrometry. Despite the challenges and limitations of both the experimental and simulation techniques, an agreement is obtained on many of the observed features of hot spot evolution, e.g., (1) the magnitude and time variation of temperatures in the hot spots, (2) the time to fully consume the crystals (∼100 ns) of size (100–300 μm) employed in this study, and (3) the locations of hot spot initiation and growth. Three different mechanisms of hot spot formation are indicated by simulations: (1) high-temperature hot spots formed by pore collapse, (2) lower temperature hot spots initiated at the polymer–crystal interface near corners and asperities, and (3) high-temperature reaction waves leading to fast consumption of the energetic crystal. This first attempt at a head-to-head comparison between experiments and simulations not only provides new insight but also highlights efforts needed to bring models and experiments into closer alignment, in particular, highlighting the importance of distinctly three-dimensional and multiple mechanisms of the hot spot ignition and growth. [ABSTRACT FROM AUTHOR]

Meso-scale simulations of pressed energetic materials are performed using synthetic microstructures generated using deep feature representation, a deep convolutional neural network-based approach. Synthetic microstructures are shown to mimic real microstructures in the statistical representation of global and local features of micro-morphology for three different classes of pressed HMX with distinctive micro-structural characteristics. Direct numerical simulations of shock-loaded synthetic microstructures are performed to calculate the meso-scale reaction rates. For all three classes, the synthetic microstructures capture the effect of morphological uncertainties of real microstructures on the response to shock loading. The calculated reaction rates for different classes also compare well with those of the corresponding real microstructures. Thus, the article demonstrates that machine-generated ensembles of synthetic microstructures can be employed to derive structure–property–performance linkages of a wide class of real pressed energetic materials. The ability to manipulate the synthetic microstructures using deep learning-based approaches then provides an opportunity for material designers to develop and manufacture pressed energetic materials that can yield targeted performance. [ABSTRACT FROM AUTHOR]

Carotenoids are widely researched due to their correlation with the mitigation of severe illnesses such as cancer, cardiovascular disease, and macular degeneration, which points out the critical significance of natural pigments. Carotenoid production from microorganisms has many advantages compared to plants or algae because of its rapid growth rate, cost-effectiveness, and independence from geographical factors. The genus Rhodosporidium, specifically the species Rhodosporidium toruloides, is renowned for generating carotenoid-rich biomass in biotechnology. However, the quantity and composition of carotenoid products obtained highly depend on the specific medium and culture conditions. In this research, carotenoid extraction by combining DMSO and acetone can result in high efficiency. Furthermore, the fermentation medium for R. toruloides was successfully optimized with affordable ingredients, including glucose, NaCl, H2O2, KH2PO4, MgSO4.7H2O, NH4Cl2, Na2HPO4, and yeast extract. The reassessment of the optimal model revealed strong compatibility between the predictive and experimental models regarding dry biomass and carotenoid content. The low residual glucose amount ultimately revealed adequate glucose consumption as a substrate for growth and carotenoid production. [ABSTRACT FROM AUTHOR]

Polymer films show the best versatility, low cost, and permeability in packaging purpose. On the contrary, these synthetic materials have a lengthy environmental half-life, cannot be broken down by natural microbes, and increase the formation of solid waste. The synthetic polymer polyvinyl alcohol (PVA) is completely dissolves in water and harmless. It has several uses, including controlled medication delivery systems, polymers recycling, film creation, and packaging. Using PVA and crystalline nanocellulose (CNC) as raw materials, PVA/CNC nanofiber membranes were prepared by solvent casting. Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM), Water vapor permeability (WVP), thermogravimetric analysis (TGA), and tensile strength were used to describe the characteristics of the film. The tensile strength of the PVA/CNC composite film improved significantly: with 2 % CNC content, the tensile strength 157.6 % increase compared to original PVA. The WVP of PVA markedly reduced 32.4 % after adding 4 % CNC. These properties are suitable for applications in various technologies such as food and packaging. [ABSTRACT FROM AUTHOR]

Glutathione (GSH) degradation plays an essential role in GSH homeostasis, which regulates cell survival, especially in cancer cells. Among human GSH degradation enzymes, the ChaC2 enzyme acts on GSH to form 5-l-oxoproline and Cys-Gly specifically in the cytosol. Here, we report the crystal structures of ChaC2 in two different conformations and compare the structural features with other known γ-glutamylcyclotransferase enzymes. The unique flexible loop of ChaC2 seems to function as a gate to achieve specificity for GSH binding and regulate the constant GSH degradation rate. Structural and biochemical analyses of ChaC2 revealed that Glu74 and Glu83 play crucial roles in directing the conformation of the enzyme and in modulating the enzyme activity. Based on a docking study of GSH to ChaC2 and binding assays, we propose a substrate-binding mode and catalytic mechanism. We also found that overexpression of ChaC2, but not mutants that inhibit activity of ChaC2, significantly promoted breast cancer cell proliferation, suggesting that the GSH degradation by ChaC2 affects the growth of breast cancer cells. Our structural and functional analyses of ChaC2 will contribute to the development of inhibitors for the ChaC family, which could effectively regulate the progression of GSH degradation-related cancers. [ABSTRACT FROM AUTHOR]

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