Probing into the theory of impact sensitivity: propelling the understanding of phonon-vibron coupling coefficients.

The determination of impact sensitivity of energetic materials traditionally relies on expensive and safety-challenged experimental means. This has instigated a shift towards scientific computations to gain insights into and predict the impact response of energetic materials. In this study, we refine the phonon-vibron coupling coefficients ζ in energetic materials subjected to impact loading, building upon the foundation of the phonon up-pumping model. Considering the full range of interactions between high-order phonon overtones and molecular vibrational frequencies, this is a pivotal element for accurately determining phonon-vibron coupling coefficients ζ. This new coupling coefficient ζ relies exclusively on phonon and molecular vibrational frequencies within the range of 0-700 cm-1. Following a regression analysis involving ζ and impact sensitivity (H50) of 45 molecular nitroexplosives, we reassessed the numerical values of damping factors, establishing a = 2.5 and b = 35. This coefficient is found to be a secondary factor in determining sensitivity, secondary to the rate of decomposition propagation and thermodynamic factor (heat of explosion). Furthermore, the relationship between phonon-vibron coupling coefficients ζ and impact sensitivity was studied in 16 energetic crystalline materials and eight nitrogen-rich energetic salts. It was observed that as the phonon-vibron coupling coefficient increases, the tendency for reduced impact sensitivity H50 still exists.

Molecular Structures, Dipole Moments, and Electronic Properties of ß-HMX under External Electric Field from First-Principles Calculations.

In order to investigate the impact of an external electric field on the sensitivity of ß-HMX explosives, we employ first-principles calculations to determine the molecular structure, dipole moment, and electronic properties of both ß-HMX crystals and individual ß-HMX molecules under varying electric fields. When the external electric field is increasing along the [100], [010], and [001] crystallographic directions of ß-HMX, the calculation results indicate that an increase in the bond length (N1-N3/N1'-N3') of the triggering bond, an increase in the main Qnitro (N3, N3') value, an increase in the minimum surface electrostatic potential, and a decrease in band gap all contribute to a reduction in its stability. Among these directions, the [010] direction exhibits the highest sensitivity, which can be attributed to the significantly smaller effective mass along the [010] direction compared with the [001] and [100] directions. Moreover, the application of an external electric field along the Y direction of the coordinate system on individual ß-HMX molecules reveals that the strong polarization effect induced by the electric field enhances the decomposition of the N1-N3 bonds. In addition, due to the periodic potential energy of ß-HXM crystal, the polarization effect of ß-HMX crystal caused by an external electric field is much smaller than that of a single ß-HXM molecule.

Ca2+ Regulates Autophagy Through CaMKKß/AMPK/mTOR Signaling Pathway in Mechanical Spinal cord Injury: An in vitro Study.

Spinal cord injury (SCI), resulting in damage of the normal structure and function of the spinal cord, would do great harm to patients, physically and psychologically. The mechanism of SCI is very complex. At present, lots of studies have reported that autophagy was involved in the secondary injury process of SCI, and several researchers also found that calcium ions (Ca2+) played an important role in SCI by regulating necrosis, autophagy, or apoptosis. However, to our best of knowledge, no studies have linked the spinal cord mechanical injury, intracellular Ca2+, and autophagy in series. In this study, we have established an in vitro model of SCI using neural cells from fetal rats to explore the relationship among them, and found that mechanical injury could promote the intracellular Ca2+ concentration, and the increased Ca2+ level activated autophagy through the CaMKKß/AMPK/mTOR pathway. Additionally, we found that apoptosis was also involved in this pathway. Thus, our study provides new insights into the specific mechanisms of SCI and may open up new avenues for the treatment of SCI.

Triggering the mechanism of the initial reaction of energetic materials under pressure based on Raman intensity analysis.

The Raman intensity and other stoichiometric calculations of nitromethane (NM) and 2-nitrimino-5-nitro-hexahydro-1,3,5-triazine (NNHT) have been made by using first-principles density functional theory. We propose a method to judge the initial reaction mechanism of NM and NNHT under pressure based on the Raman intensity. Both the resulting NM and NNHT undergo hydrogen transfer and conventional trigger bond cleavage. And the results obtained from the Raman peak intensities infer a reaction path that is not inferior to the traditional C-NO2 and N-NO2 bond cleavage, thus verifying our results.

Atomic mean square displacement study of the bond breaking mechanism of energetic materials before explosive initiation.

Understanding and predicting the bond breaking mechanism of energetic materials before explosion initiation is one of the huge challenges in explosion science. By means of the mean square displacement of the atom from the equilibrium position and theoretical bond breaking tensile change of the chemical bond, we establish a new criterion to judge whether the chemical bond is broken. Further, α-RDX is used as the verification object to verify the accuracy of this model. We obtained an initial decomposition temperature of 434-513 K for α-RDX at 0 GPa, and the initial bond breaking type was N-NO2. Finally, based on this model, we discussed in detail the breaking of chemical bonds of solid nitromethane near the detonation pressure. We think that the high temperature and high pressure caused by the shock wave may break all the chemical bonds of nitromethane near the detonation pressure.

A simulation study on the phase transition behavior of solid nitrogen under extreme conditions.

There are numerous examples of materials that exhibit interesting phenomena at extremely low temperatures, but the difficulty of obtaining absolute zero at high pressure in experiments is sometimes a hurdle to reveal the exact explanation of these low temperature phenomena. Based on the calculations of the phonon spectrum and Gibbs free energy of α-N2 and γ-N2 under different pressures, we found that solid nitrogen at 0 K showed a re-entrant phase transition under continuously increasing pressure. The extremely low temperature in this pressure range turned out to be the main external condition for inducing phase transition as well as phase reversal.

Theoretical study on the correlation between the structure, excess energy, surface energy, electronic structure, nitro charge, and friction sensitivity of N,N'-dinitroethylenediamine (EDNA).

The sensitivity of energetic materials along different crystal directions is not the same and is anisotropic. In order to explore the difference in friction sensitivity of different surfaces, we calculated the structure, excess energy, surface energy, electronic structure, and the nitro group along (1 1 1), (1 1 0), (1 0 1), (0 1 1), (0 0 1), (0 1 0), and (1 0 0) surfaces of EDNA based on density functional theory. The analysis results showed that relative to other surfaces, the (0 0 1) surface has the shortest N-N average bond length, largest N-N average bond population, smallest excess energy and surface energy, widest band gap, and the largest nitro group charge value, which indicates that the (0 0 1) surface has the lowest friction sensitivity compared to other surfaces. Furthermore, the conclusions obtained by analyzing the excess energy are consistent with the results of the N-N bond length and bond population, band gap, and nitro charge. Therefore, we conclude that the friction sensitivity of different surfaces of EDNA can be evaluated using excess energy.

Initial Decomposition of DATB Induced by an External Electric Field.

1,3-Diamino-2,4,6-trinitrobenzene (DATB), a nitro aromatic explosive with excellent properties, can be detonated by an electric field. Using first-principles calculation, we have investigated the initial decomposition of DATB under an electric field. In the realm of electric fields, the rotation of the nitro group around the benzene ring will cause deformation of the DATB structure. Furthermore, when an electric field is applied along the [100] or [001] direction, the C4-N10/C2-N8 bonds initiate decomposition due to electron excitation. On the contrary, the electric field along the [010] direction has a weak influence on DATB. These, together with electronic structures and infrared spectroscopy, give us a visual perspective of the energy transfer and the decomposition caused by C-N bond breaking.

Doping effects on the antibonding states and carriers of two-dimensional PC6.

The absence of a bandgap in pristine graphene severely restricts its application, and there is high demand for other novel two-dimensional (2D) materials. PC6 has recently emerged as a promising 2D material with a direct band gap and ultrahigh carrier mobility. In light of the remarkable properties of an intrinsic PC6 monolayer, it would be intriguing to find out whether a doped PC6 monolayer displays properties superior to the pure system. In this study, we have performed density functional theory calculations to understand the doping effects of both P-site and C-site substitution in PC6 and, for the first time, we discovered doping-related impurity-level anomalies in this system. We successfully explained why no donor or acceptor defect states exist in the band structures of XP-PC6 (X = C, Ge, Sn, O, S, Se, or Te). In group-IV-substituted systems, these dopant states hybridize with host states near the Fermi level rather than act as acceptors, which is deemed to be a potential way to tune the mobility of PC6. In the case of group-VI substitution, the underlying mechanism relating to doping anomalies arises from excess electrons occupying antibonding states.

The effect of pressure on the structural, electronic and vibrational properties of solid carbon dioxide phases.

The structural, electronic and vibrational properties of solid carbon dioxide phases (I, II, III, and IV) under high pressure are studied using first-principles calculations. The calculated structural parameters are in good agreement with the experimental values. The third-order Birch-Murnaghan equation of state is fitted, and the corresponding parameters are obtained. We obtained the phase boundary points of each phase and plotted the phase diagram of solid carbon dioxide. The influence of pressure on the band structure and density of states is studied. The vibrational properties of the four phases of carbon dioxide were studied in detail, and the infrared and Raman spectra of the four phases were obtained. It can be seen from the calculated spectrum that the number and frequency of vibration peaks are in good agreement with the experimental values. And, we also analyze the influence of pressure on the frequency of vibration mode.

Multifunctionalized Gold Sub-Nanometer Particles for Sensitizing Radiotherapy against Glioblastoma.

Glioblastoma is the most common lethal malignant intracranial tumor with a low 5-year survival rate. Currently, the maximal safe surgical resection, followed by high-dose radiotherapy (RT), is a standard treatment for glioblastoma. However, high-dose radiation to the brain is associated with brain injury and results in a high fatality rate. Here, integrated pharmaceutics (named D-iGSNPs) composed of gold sub-nanometer particles (GSNPs), blood-brain barrier (BBB) penetration peptide iRGD, and cell cycle regulator α-difluoromethylornithine is designed. In both simulated BBB and orthotopic murine GL261 glioblastoma models, D-iGSNPs are proved to have a beneficial effect on the BBB penetration and tumor targeting. Meanwhile, data from cell and animal experiments reveal that D-iGSNPs are able to sensitize RT. More importantly, the synergy of D-iGSNPs with low-dose RT can exhibit an almost equal therapeutic effect with that of high-dose RT. This study demonstrates the therapeutic advantages of D-iGSNPs in boosting RT, and may provide a facile approach to update the current treatment of glioblastoma.

Explanation for the conductivity difference of half-Heusler transparent conductors via ionization energy.

To further understand the less-studied half-Heusler transparent conductors, we have considered four 18-electron ABX compounds (TaIrGe, TaIrSn, ZrIrSb, and TiIrSb) to focus on their carrier effective masses and ionization energies. The novelty of this work lies in two aspects: (i) we discover that hole-killer defects are more likely to form in TaIrGe than in ZrIrSb, which leads to a lower concentration of the holes in TaIrGe. This is the fundamental reason for the conductivity of TaIrGe being much lower than that of ZrIrSb; (ii) we propose that the hole effective mass near the sub-valence band maximum (Sub-VBM) could be used to forecast the potential transport performance of the materials. The obtained results show that the transport performance of TaIrGe & TaIrSn is potentially more promising than that of TiIrSb and ZrIrSb. Besides, this work firstly studies the mechanical properties of the considered ABX compounds, offering strong evidence that TaIrGe, TaIrSn, ZrIrSb, and TiIrSb could be potentially flexible and ductile TCMs.

Judging the phase transition pressure of the unknown parent phase if the resulting state is known.

In high-pressure phase transition experiments, the crystal structure of the intermediate phase in some phase transitions is difficult to successfully measure due to the limitations of the experimental conditions. The absence of crystal structure data for the intermediate phase also makes it difficult to calculate the pressure point from the intermediate phase to the new phase by the traditional thermodynamic criterion in theoretical simulations. The Conch Criterion is employed by us to successfully verify the phase transition points by observing the reverse shifts of the DOS (electron density of states) curves for the new phase of Cu2S, PbS, PbSe and PbTe, which breaks through the constraints of the traditional criterion and realizes tracing the source of the phase transition in theoretical calculations.

Formation of new lymphatic vessels in glioma: An immunohistochemical analysis.

We investigated the distribution and formation of new lymphatic vessels in gliomas. Specimens from seven glioma cases were analyzed by immunohistochemical staining for CD34, lymphatic endothelial hyaluronic acid receptor 1 (LYVE-1), prospero-related homeobox 1 (Prox1), nestin, and hypoxia-inducible factor 1α (HIF-1α). Three types of vessels were observed in glioma specimens: LYVE-1+ lymphatic vessels, CD34+ blood vessels, and LYVE-1+ /CD34+ blood vessels. Prox1+ /LYVE-1+ cells were distributed in some lymphatic vessels as well as among vascular endothelial cells and glioma cells. Nestin+ cells were scattered throughout the gliomas, and some lymphatic cells also expressed nestin. HIF-1α+ Prox1+ cells were widely distributed within the glioma specimens. The present immunohistochemical analysis revealed upregulation of Prox1 and HIF-1α in some glioma tissues as well as the differentiation of nestin+ tumor stem cells into LYVE-1+ lymphatic vessels.

A new criterion for the prediction of solid-state phase transition in TMDs.

The classical thermodynamic criterion for phase transition predicts whether the phase transition will occur according to whether the nth derivative of the state parameter is discontinuous, and the continuity verification of multi-order derivatives increases the difficulty and complexity of judgment for phase transition to a certain extent. Based on the reverse shifts of the DOS curves near the Fermi level, we propose a new criterion for solid-state phase transition named Conch Criterion, which has been verified in the TMD system. The new criterion can observe the occurrence of phase transition from another perspective besides the thermodynamic properties while mutually confirming the thermodynamic criterion.

Influences of S, Se, Te and Po substitutions on structural, electronic and optical properties of hexagonal CuAlO2 using GGA and B3LYP functionals.

The effects of X-doping (X = S, Se, Te and Po) on the structural, electronic and optical properties of hexagonal CuAlO2 were studied using first-principles density functional theory. The calculated results showed the obtained lattice constants to increase with increasing atomic number, and the X-doping to be energetically more favorable under Al-rich conditions. The calculated electronic properties showed decreased bandgaps with increasing atomic number, which was due to the better covalent hybridizations after sulfuration doping. The enhanced covalency was further confirmed by calculating the Mulliken atomic populations and bond populations. The density of states indicated the increase of the contribution to antibonding from the X-p states to be a benefit for p-type conductivity. Moreover, the X-doping induced a red shift of the absorption edge.

Predicting the thermal decomposition temperature of energetic materials from a simple model.

CONTEXT: The key factor in designing heat-resistant energetic materials is their thermal sensitivity. Further research and prediction of thermal sensitivity remains a great challenge for us. This study is based on first-principles calculations and establishes a theoretical model, which comprehensively considers band gap, density of states, and Young's modulus to obtain a empirical parameter Ψ. A quantitative relationship was established between the new parameter and the thermal decomposition temperature. The value of Ψ is calculated for 10 energetic materials and is found to have a strong correlation with the experimental thermal decomposition temperature. This further proves the reliability of our model. Specifically, the larger the value of Ψ, the higher the thermal decomposition temperature, and the more stable the energetic material will be. Therefore, to some extent, we can use the new parameter Ψ calculated by the model to predict thermal sensitivity. METHODS: Based on first-principles, this paper used the Cambridge Serial Total Energy Package (CASTEP) module of Materials Studio (MS) for calculations. The Perdew-Burke-Ernzerhof (PBE) functionals in Generalized Gradient Approximation (GGA) method as well as the Grimme dispersion correction was used in this paper.

Molecular dynamics simulation of sensitivity of HMX, FOX-7, and TATB crystals.

METHODS: This study used molecular dynamics (MD) to simulate three materials (HMX, FOX-7, and TATB) under the NVT ensemble. Six temperatures (100 K, 200 K, 300 K, 400 K, 500 K, and 600 K) were simulated. In addition, the trigger bond lengths, energy bands, and density of states of three materials were obtained at different temperatures and compared with the calculated results at 0 K. CONTEXT: The results indicate that the trigger bond lengths of the three materials are very close to the experimental values. Overall, the maximum and average bond lengths of the trigger bonds increase with increasing temperature. The band gap value decreases with increasing temperature. The changes in trigger bond length and band gap value are consistent with the experimental fact that sensitivity increases with increasing temperature. And Eg > 1 eV is consistently found within the temperature range of 0-600 K, indicating that all three materials are non-metallic compounds.

Identification and bioinformatics analysis of genes associated with pyroptosis in spinal cord injury of rat and mouse.

The mechanism of spinal cord injury (SCI) is highly complex, and an increasing number of studies have indicated the involvement of pyroptosis in the physiological and pathological processes of secondary SCI. However, there is limited bioinformatics research on pyroptosis-related genes (PRGs) in SCI. This study aims to identify and validate differentially expressed PRGs in the GEO database, perform bioinformatics analysis, and construct regulatory networks to explore potential regulatory mechanisms and therapeutic targets for SCI. We obtained high-throughput sequencing datasets of SCI in rats and mice from the GEO database. Differential analysis was conducted using the "limma" package in R to identify differentially expressed genes (DEGs). These genes were then intersected with previously reported PRGs, resulting in a set of PRGs in SCI. GO and KEGG enrichment analyses, as well as correlation analysis, were performed on the PRGs in both rat and mouse models of SCI. Additionally, a protein-protein interaction (PPI) network was constructed using the STRING website to examine the relationships between proteins. Hub genes were identified using Cytoscape software, and the intersection of the top 5 hub genes in rats and mice were selected for subsequent experimentally validated. Furthermore, a competing endogenous RNA (ceRNA) network was constructed to explore potential regulatory mechanisms. The gene expression profiles of GSE93249, GSE133093, GSE138637, GSE174549, GSE45376, GSE171441_3d and GSE171441_35d were selected in this study. We identified 10 and 12 PRGs in rats and mice datasets respectively. Six common DEGs were identified in the intersection of rats and mice PRGs. Enrichment analysis of these DEGs indicated that GO analysis was mainly focused on inflammation-related factors, while KEGG analysis showed that the most genes were enriched on the NOD-like receptor signaling pathway. We constructed a ceRNA regulatory network that consisted of five important PRGs, as well as 24 miRNAs and 34 lncRNAs. This network revealed potential regulatory mechanisms. Additionally, the three hub genes obtained from the intersection were validated in the rat model, showing high expression of PRGs in SCI. Pyroptosis is involved in secondary SCI and may play a significant role in its pathogenesis. The regulatory mechanisms associated with pyroptosis deserve further in-depth research.

[Fusion of melanoma cells using a modified phytohaemagglutinin-ECM830 fusion method].

OBJECTIVE: To study melanoma cell fusion and find a highly efficient fusion method for tumor cells. METHODS: Melanoma cells were labeled with green fluorescent protein and red fluorescent protein, respectively, and fused by a modified phytohaemagglutinin (PHA)-ECM830 fusion method. Melanoma fusion cells were selected by the fluorescence activated cell sorting. DNA content was determined by propidium iodide staining. RESULTS: Melanoma cells were labeled with green fluorescent protein and red fluorescent protein markers and successfully fused through PHA-ECM830 fusion method. The fusion efficiency (7.18%) was much higher compared with ECM830 electricfusion method (0.50%). Melanoma fusion cells were successfully obtained by the fluorescence activated cell sorting.DNA content was doubled in melanoma fusion cells compared to B16-F10 melanoma cells. The proliferation rate of melanoma fusion cells was significantly decreased in vitro and in vivo. CONCLUSIONS: We successfully obtained the melanoma fusion cells by the improved PHA-ECM830 fusion method. The proliferation rate of melanoma fusion cells dramatically decreases.