Synthesis of Covalently Modified Energetic Graphene Oxide/CuO Composites with Enhanced Catalytic Performance for Thermal Decomposition of Ammonium Perchlorate.

In this study, a new covalently modified energetic graphene oxide (CMGO) was synthesized by introducing the energetic component 4-amino-1,2,4-triazole on GO sheets through valence bond bonding. The morphology and structure of CMGO were studied by scanning electron microscopy, energy-dispersive spectroscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray diffractometry, and X-ray photoelectron spectroscopy, and the results showed that CMGO was successfully synthesized. Then, CMGO/CuO was prepared by loading nano-CuO onto CMGO sheets using an ultrasonic dispersion method. Furthermore, the catalytic effect of CMGO/CuO on the thermal decomposition of ammonium perchlorate (AP) was investigated using differential scanning calorimetric technique and thermogravimetric analysis. The results revealed that the high decomposition temperature TH and Gibbs free energy ΔG⧧ of the CMGO/CuO/AP composite decreased by 93.9 °C and 15.3 kJ/mol compared with those of raw AP, respectively. The CMGO/CuO composite exhibited more significant catalytic effect on the thermal decomposition of AP than GO/CuO, and the heat release Q of CMGO/CuO/AP was greatly increased from 132.9 to 1428.5 J/g with 5 wt % CMGO/CuO. The above results demonstrated that CMGO/CuO is an excellent composite energetic combustion catalyst, which is expected to be widely used in composite propellants.

College students' learning stress, psychological resilience and learning burnout: status quo and coping strategies.

BACKGROUND: The relationships of college students' learning stress, psychological resilience and learning burnout remain unclear. We aimed to investigate the status quo and relationship of college students' learning stress, psychological resilience and learning burnout, to provide insights to the management and nursing care of college students. METHODS: From September 1 to October 31, 2022, students in our college were selected by stratified cluster sampling and underwent survey with the learning stress scale, college students' learning burnout scale and the psychological resilience scale of college students. RESULTS: A total of 1680 college students were surveyed in this study. The score of learning burnout was positively correlated with the score of learning stress (r = 0.69), and negatively correlated with the score of psychological resilience (r = 0.59), and the score of learning stress was negatively correlated with the score of psychological resilience (r = 0.61). Learning pressure was correlated with the age(r=-0.60) and monthly family income(r=-0.56), the burnout was correlated with the monthly family income(r=-0.61), and psychological resilience was correlated with the age(r = 0.66) (all P < 0.05). Psychological resilience played an intermediary role in the prediction of learning burnout by learning stress, with an total intermediary role of-0.48, accounting for 75.94% of the total effect. CONCLUSIONS: Psychological resilience is the mediating variable of the influence of learning stress on learning burnout. College managers should take various effective measures to improve college students' psychological resilience to reduce college students' learning burnout.

[The measurements of the similarity of dynamic brain functional network].

Brain functional network changes over time along with the process of brain development, disease, and aging. However, most of the available measurements for evaluation of the difference (or similarity) between the individual brain functional networks are for charactering static networks, which do not work with the dynamic characteristics of the brain networks that typically involve a long-span and large-scale evolution over the time. The current study proposes an index for measuring the similarity of dynamic brain networks, named as dynamic network similarity (DNS). It measures the similarity by combining the "evolutional" and "structural" properties of the dynamic network. Four sets of simulated dynamic networks with different evolutional and structural properties (varying amplitude of changes, trend of changes, distribution of connectivity strength, range of connectivity strength) were generated to validate the performance of DNS. In addition, real world imaging datasets, acquired from 13 stroke patients who were treated by transcranial direct current stimulation (tDCS), were used to further validate the proposed method and compared with the traditional similarity measurements that were developed for static network similarity. The results showed that DNS was significantly correlated with the varying amplitude of changes, trend of changes, distribution of connectivity strength and range of connectivity strength of the dynamic networks. DNS was able to appropriately measure the significant similarity of the dynamics of network changes over the time for the patients before and after the tDCS treatments. However, the traditional methods failed, which showed significantly differences between the data before and after the tDCS treatments. The experiment results demonstrate that DNS may robustly measure the similarity of evolutional and structural properties of dynamic networks. The new method appears to be superior to the traditional methods in that the new one is capable of assessing the temporal similarity of dynamic functional imaging data.

A novel fully immersive virtual reality environment for upper extremity rehabilitation in patients with stroke.

Given the rising incidence of stroke, several technology-driven methods for rehabilitation have recently been developed. Virtual reality (VR) is a promising therapeutic technology among them. We recently developed a neuroscientifically grounded VR system to aid recovery of motor function poststroke. The developed system provides unilateral and bilateral upper extremity (UE) training in a fully immersive virtual environment that may stimulate and activate mirror neurons (MNs) in the brain necessary for UE rehabilitation. Twenty-three participants were randomized to a VR group (n = 12) to receive VR intervention (8 h within 2 weeks) plus 8-h occupational therapy (OT) or a control group (n = 11) to receive time-matched OT alone. Treatment effects on motor recovery and cortical reorganization were investigated using the Barthel Index (BI), Fugl-Meyer Upper Extremity (FM-UE), and resting-state fMRI. Both groups significantly improved BI (P < 0.05), reflecting the recovery of UE motor function. The VR group revealed significant improvements on FM-UE scores (P < 0.05) than the control group. Neural activity increased after the intervention, particularly in the brain areas implicating MNs, such as in the primary motor cortex. Overall, results suggested that using a neuroscientifically grounded VR system might offer additional benefits for UE rehabilitation in patients receiving OT.

Proactive Motor Functional Recovery Following Immersive Virtual Reality-Based Limb Mirroring Therapy in Patients with Subacute Stroke.

Virtual reality (VR) is considered to be a promising therapeutic technology for the rehabilitation of upper extremities (UEs) post-stroke. Recently, we designed and then implemented a neuroscientifically grounded VR protocol for the rehabilitation of patients with stroke. The system provides unilateral and bilateral limb mirroring exercises in a fully immersive virtual environment that may stimulate and activate the mirror neuron system in the brain to help patients for their rehabilitation. Twelve patients with subacute stroke underwent the newly implemented VR treatment in addition to conventional rehabilitation for 8 consecutive weekdays. The treatment effect on brain reorganization and motor function was investigated using resting-state fMRI (rs-fMRI) and the Fugl-Meyer assessment for Upper Extremity (FM-UE), respectively. Fifteen healthy controls (HCs) also underwent rs-fMRI scanning one time. The study finally obtained usable data from 8 patients and 13 HCs. After the intervention, patients demonstrated significant improvement in their FM-UE scores (p values < 0.042). Voxel-wise functional connectivity (FC) analysis based on the rs-fMRI data found that HCs showed widespread bilateral FC patterns associated with the dominant hemispheric primary motor cortex (M1). However, the FC patterns in patients revealed intra-hemispheric association with the ipsilesional M1 seed and this association became visible in the contra-hemisphere after the intervention. Moreover, the change of FC values between the bilateral M1 was significantly correlated with the changes in FM-UE scores (p values < 0.037). We conclude that unilateral and bilateral limb mirroring exercise in an immersive virtual environment may enhance cortical reorganization and lead to improved motor function.

IQGAP2 Inhibits Migration and Invasion of Gastric Cancer Cells via Elevating SHIP2 Phosphatase Activity.

Previous studies have shown reduced expression of Src homology 2-containing inositol 5-phosphatase 2 (SHIP2) and its tumor-suppressive role in gastric cancer (GC). However, the precise role of SHIP2 in the migration and invasion of GC cells remains unclear. Here, an IQ motif containing the GTPase-activating protein 2 (IQGAP2) as a SHIP2 binding partner, was screened and identified by co-immunoprecipitation and mass spectrometry studies. While IQGAP2 ubiquitously expressed in GC cells, IQGAP2 and SHIP2 co-localized in the cytoplasm of GC cells, and this physical association was confirmed by the binding of IQGAP2 to PRD and SAM domains of SHIP2. The knockdown of either SHIP2 or IQGAP2 promoted cell migration and invasion by inhibiting SHIP2 phosphatase activity, activating Akt and subsequently increasing epithelial-mesenchymal transition (EMT). Furthermore, knockdown of IQGAP2 in SHIP2-overexpressing GC cells reversed the inhibition of cell migration and invasion by SHIP2 induction, which was associated with the suppression of elevated SHIP2 phosphatase activity. Moreover, the deletion of PRD and SAM domains of SHIP2 abrogated the interaction and restored cell migration and invasion. Collectively, these results indicate that IQGAP2 interacts with SHIP2, leading to the increment of SHIP2 phosphatase activity, and thereby inhibiting the migration and invasion of GC cells via the inactivation of Akt and reduction in EMT.

Spheroidization of Nickel Powder and Coating with Carbon Layer through Laser Heating.

We developed a simple and efficient process, laser heating of nickel powder in ethanol, to produce carbon-encapsulated nickel microspheres. Long-pulse-width laser heated nickel powder suspended in pure ethanol into liquid droplets. In turn, the latter droplets became sphere-like, pyrolyzed surrounding ethanol and dissolved the produced carbon atoms. Because of their lower solubility in solid nickel, excess carbon atoms were then expelled from the metal core after solidification, thus forming graphite-like shells on the laser-modified Ni spheres. Hence, after pyrolysis the transformation of carbon was found to follow the dissolution-precipitation mechanism. The produced carbon-encapsulated nickel microspheres exhibited higher oxidation resistance compared with the initial nickel powder, while keeping their magnetic properties essentially unchanged.

Structure-property relationships of energetic nitrogen-rich salts composed of triaminoguanidinium or ammonium cation and tetrazole-based anions.

Density functional theory and volume-based thermodynamics calculations have been performed to study the crystal densities, heats of formation (HOFs), energetic properties, and thermodynamics of formation for a series of ionic salts composed of triaminoguanidinium or ammonium cations and tetrazole-based anions. Substitution with --NF2, --CH2NF2, --CF2NF2, or --C(NO2)2NF2 groups increased the densities of the salts. The densities of the tetrazole-based salts are affected not only by different substituents but also by different cations. The --CN or --N3 groups are effective substituents for increasing the HOFs of the salts. The triaminoguanidinium cation is more effective than the ammonium cation for increasing the HOF of the tetrazole-based salts. Substitution with --NO2, --NF2, or --C(NO2)2NF2 groups enhances the explosive properties of the salts. The thermodynamics of formation of the salts reveal that all of the tetrazole-based salts with the triaminoguanidinium or ammonium cation could be synthesized using the proposed reactions. Our calculated methods provide a straightforward and inexpensive route for screening a large number of potentially energetic ionic salts.

Prediction of the properties and thermodynamics of formation for energetic nitrogen-rich salts composed of triaminoguanidinium cation and 5-nitroiminotetrazolate-based anions.

Density functional theory and volume-based thermodynamics calculations were performed to study the effects of different substituents and linkages on the densities, heats of formation (HOFs), energetic properties, and thermodynamics of formation for a series of energetic nitrogen-rich salts composed of triaminoguanidinium cation and 5-nitroiminotetrazolate anions. The results show that the -NO(2), -NF(2), or -N(3) group is an effective substituent for increasing the densities of the 5-nitroiminotetrazolate salts, whereas the effects of the bridge groups on the density are coupled with those of the substituents. The substitution of the group -NH(2), -NO(2), -NF(2), -N(3), or the nitrogen bridge is helpful for increasing the HOFs of the salts. The calculated energetic properties indicate that the -NO(2), -NF(2), -N(3), or -N=N- group is an effective structural unit for improving the detonation performance for salts. The thermodynamics of formation of the salts show that all the salts may be synthesized easily by the proposed reactions. The structure-property relationships provide basic information for the molecular design of novel high-energy salts.