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To solve SiC machining processes problems such as low processing efficiency, surface/subsurface damage, and machining tool wear, a femtosecond-laser-aided machining process was studied. In this paper, the diamond-machinability and removal mechanism of SiC-modified layer during femtosecond-laser-aided machining process are evaluated at the nanoscale using molecular dynamics. The results show that micro/nano structures in the modified layer significantly influence the material removal process, and SiC surface structures effectively improve the removal efficiency and reduce subsurface damage depth. The surface micro/nano structures introduced by femtosecond laser scanning improve the diamond-machinability of mono-crystalline SiC. [ABSTRACT FROM AUTHOR]

Abstract In this study, the influence mechanism of the coupling effect on the material removal process of SiC in nanoscale condition is investigated using the molecular dynamics method. The geometrical characteristics of a machined surface and the damage distribution under a coupling effect are analyzed. The influence law of the coupling effect on surface/subsurface features is also presented. According to the analysis results, the repeated and interference scratches with multi-abrasives, large-area machined surface morphology, and damage distribution are analyzed. This study is significant in understanding the removal mechanism of SiC during the grinding process at the nanoscale. [ABSTRACT FROM AUTHOR]

Highlights • Strain rate effect and heat effect exist simultaneously and interact with each other. • Subsurface damage depth does not change monotonously with the cutting speed. • Cutting speed directly affects the distribution of dislocations in subsurface region. • Thermal softening effect under high strain rate determines trend of the stress. Abstract To study the influence of strain rate and heat effect on the removal behavior of SiC, the dislocation nucleation/propagation, amorphization and abrasive wear behavior are analyzed in detail according to the mechanical response and temperature distribution in the machining region at different strain rate. The strain rate effect and the thermal softening effect directly affect the material removal amount and form of the subsurface damage. The study found that when the cutting speed reaches 50 m/s, the maximum material removal amount can be obtained. When the cutting speed reaches 150 m/s, the depth of the damaged layer reaches over 6 times of the residual processing depth. There is a large difference in the influence of the strain rate effect caused by the change in velocity on different types of dislocations. The stress component, scratch hardness, and hydrostatic pressure in the machining direction are continuously reduced as the cutting speed increases, and the thermal softening effect caused by the cutting heat is the main factor leading to this phenomenon. Abrasive wear behavior is the result of the coupling action of impact effect and grinding heat. When the cutting speed is 50 m/s, the minimum wear loss can be obtained. [ABSTRACT FROM AUTHOR]

Background: The management of metastatic cancer remains a major challenge in cancer therapy worldwide. The targeted delivery of chemotherapeutic drugs through rationally designed formulations is one potential therapeutic option. Notably, excipient-free nanodispersions that are entirely composed of pharmaceutically active molecules have been evaluated as promising candidates for the next generation of drug formulations. Formulated from the self-assembly of drug molecules, these nanodispersions enable the safe and effective delivery of therapeutic drugs to local disease lesions. Here, we developed a novel and green approach for preparing nanoparticles via the self-assembly of rhein (RHE) and doxorubicin (DOX) molecules, named RHE/DOX nanoparticles (RD NPs); this assembly was associated with the interaction force and did not involve any organic solvents. Results: According to molecular dynamics (MD) simulations, DOX molecules tend to assemble around RHE molecules through intermolecular forces. This intermolecular retention of DOX was further improved by the nanosizing effect of RD NPs. Compared to free DOX, RD NPs exerted a slightly stronger inhibitory effect on 4T1 cells in the scratch healing assay. As a dual drug-loaded nanoformulation, the efficacy of RD NPs against tumor cells in vitro was synergistically enhanced. Compared to free DOX, the combination of DOX and RHE in nanoparticles exerted a synergistic effect with a combination index (CI) value of 0.51 and showed a stronger ability to induce cell apoptosis. Furthermore, the RD NP treatment not only effectively suppressed primary tumor growth but also significantly inhibited tumor metastasis both in vitro and in vivo, with a better safety profile. Conclusions: The generation of pure nanodrugs via a self-assembly approach might hold promise for the development of more efficient and novel excipient-free nanodispersions, particularly for two small molecular antitumor drugs that potentially exert synergistic antiproliferative effects on metastatic breast cancer. [ABSTRACT FROM AUTHOR]

• The deformation mechanism type of 3C-SiC can be controlled simply by cutting mode. • Edge-forward mode is beneficial to improving the machinability of SiC. • The deformation mechanism of 3C-SiC is the result of compound action. Nanoscale structures have attracted a lot of attention in various fields in recent years. Tip-based nanomanufacturing (TBN) process has proven to be a promising technique for fabrication of nanostructures on single crystal SiC. This study investigates the deformation and removal mechanism of SiC under different scratching directions in TBN process by molecular dynamics (MD) simulations. By analyzing the dislocation glide motion and the phase transformation mechanism of SiC, the deformation type that occurs during TBN process was found to be principally the sliding motion of the primary slip system (recoverable elastic slip motion and dislocation glide motion) and the phase transformation (amorphization and sp3 → sp2-like structure transition). This study also shows that the deformation mechanism of SiC during processing is controllable and can be achieved by simply changing the feed direction. The results in this paper can provide direct guidance for the processing of nanogrooves in SiC materials. [ABSTRACT FROM AUTHOR]

As an important third-generation semiconductor material, the micro-deformation and removal mechanism of 6H-SiC at the atomic scale are vital for obtaining ultra-smooth and damage-free surface with atomic steps. Due to the difficulties in directly observing the surface/subsurface of nanomachining region by current experimental means, molecular dynamics method is used to study the atomic-scale details in nanomachining process, such as dislocation slip motion, phase transition, and material separation mechanism. The influence of crystallography-induced anisotropy on the slip deformation and nanometric machinability of 6H-SiC is emphatically investigated. This study contributes significantly to the understanding of micro-deformation and nanomachining process of 6H-SiC. [ABSTRACT FROM AUTHOR]

The effect of microstructure on the deformation mechanism and diamond-machinability of hot-pressed SiC during grinding process is studied. Similar to single-crystal SiC, amorphization, dislocation slip motion, and lattice distortion also occurs in the deformation process of multi-phase SiC ceramics. Other deformation mechanisms related to the microstructure of SiC ceramics, such as intergranular slip motion and grain fragmentation, have decisive influence on diamond-machinability of this material. When the average grain size is lower than 10 nm, there is a significant weakening of scratch hardness. Intergranular slip motions and grain fragmentation can effectively improve the processing efficiency. Therefore, in view of fabrication technology of SiC ceramics, reducing the grain size at nanoscale can improve the diamond-machinability of hot-pressed SiC and favorable for obtaining high-efficiency and high-precision surface processing effectiveness. [ABSTRACT FROM AUTHOR]

[Display omitted] • EGCG as a co-former applied to co-amorphous systems (CAMs) was first reported. • Such CAMs showed good physical stability either under dry or 75% RH conditions. • The dissolution rate of such CAMs was improved significantly compared to model drugs. • The bioavailability of such CAMs has markedly increased in C max and AUC 0-t compared to model drugs. • The molecular mechanisms of CAMs formation were miscibility, hydrogen bonds and π-π interactions. Co-amorphous strategy has been extensively investigated to improve the dissolution of hydrophobic drugs. Here, epigallocatechin-3-gallate (EGCG) was exploited as a co-former in co-amorphous systems based on its unique structure including phenyl rings, phenolic hydroxyl groups and the galloyl moiety. Two model BCS class II drugs, simvastatin (SIM) and nifedipine (NIF), were selected to be co-amorphized with EGCG. All drug-EGCG systems at three molar ratios became amorphous by the means of spray drying and showed high physically stable either under dry condition and 75 % RH at 40 °C or under dry conditions at 25 °C. The optimal feed molar ratios of both EGCG based co-amorphous systems fabricated were determined to be three, under which the significant increases were obtained in the maximum apparent concentrations of 4.90-fold for SIM at 1 h and 106.03-fold for NIF at 0.25 h compared to crystalline drugs by non-sink dissolution studies. The underlying molecular mechanisms of two co-amorphous systems formation were involved in molecular miscibility, hydrogen bonds and π-π stacking interactions unraveled by means of DSC, FTIR and molecular dynamics simulations. More to the point, oral pharmacokinetic studies in rats demonstrated that co-amorphous SIM-EGCG and NIF-EGCG systems at 1:3 have a significant increase in C max of 1.81- and 5.69-fold, and AUC 0-24h of 1.62- and 4.57-fold compared with those of corresponding crystalline drugs, respectively. In conclusion, EGCG is proved to be a promising co-former in co-amorphous systems. [ABSTRACT FROM AUTHOR]

[Display omitted] • Excipient-free nanoparticle of glycoside assembled with aglycone was firstly reported. • The AUC 0-∞ of GA for such DDS markedly increased compared to hydrophobic GA API. • Increased absorption was involved in improvement of solubility/dissolution in vitro. Natural aglycones, a major ingredient accompanied by glycosides in plants, have played an important role in the treatment of various diseases. However, their bioavailability is limited by their poor water solubility. In contrast to previous efforts that required the use of new exotic materials which may raise concerns about biocompatibility, we report the first case of excipient-free nanodispersions in which an insoluble glycyrrhetinic acid (GA) assembled with its amphiphilic parent drug diammonium glycyrrhizinate (DG) into water-dispersible nanodispersions (130.8 nm for particle size and 91.74% for encapsulation efficiency). This strategy largely increased GA's water apparent solubility by hundreds of times to 549.0 μg/mL with a high cumulative dissolution percentage in vitro greater than 80% in 5 min. The study on the formation mechanism showed that the OH, C-O and C=O group stretching peaks shifted in the FTIR spectra of GA-DG nanodispersions, while the COOH peak (δ COOH 12.19 ppm) disappeared in the 1H NMR spectrum of GA-DG nanodispersions, indicating that carboxyl groups on GA may interact with the hydroxyl groups of DG in solution. Molecular dynamics simulations suggested that both hydrophobic interactions and hydrogen-bond interactions contribute to the coassembly of GA and DG molecules in aqueous solution. Oral pharmacokinetic studies in rats demonstrated that such nanodispersions have a significant increase in C max and AUC 0-t of 2.45- and 3.45-fold compared with those for GA, respectively. Therefore, this strategy, employing amphiphilic glycosides as excipients to prepare nanodispersions, not using new materials, paves the way for the further application of hydrophobic aglycone drugs. [ABSTRACT FROM AUTHOR]

Highlights: [•] Molecular dynamics simulation is employed to study the nanoindentation process of Cu50Zr50 amorphous alloy. [•] Shear transformation zones constantly migrate and grow during the indentation process. [•] The effects of indentation depth, loading speed, indenter radius, temperature on material properties are investigated. [•] The hardness is slightly larger when considering the adhesion interaction between indenter and substrate, while the elastic modulus is not significantly affected. [Copyright &y& Elsevier]