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Objectives: To develop and evaluate a multiplanar radiomics model based on cranial ultrasound (CUS) to predict white matter injury (WMI) in premature infants and explore its correlation with neurodevelopment. Methods: We retrospectively reviewed 267 premature infants. The radiomics features were extracted from five standard sections of CUS. The Spearman's correlation coefficient combined with the least absolute shrinkage and selection operator (LASSO) was applied to select features and build radiomics signature, and a multiplanar radiomics model was constructed based on the radiomics signature of five planes. The performance of the model was evaluated using the area under the receiver operating characteristic curve (AUC). Infants with WMI were re‐examined by ultrasound at 2 and 4 weeks after birth, and the recovery degree of WMI was evaluated using multiplanar radiomics. The relationship between WMI and the recovery degree and neurodevelopment was analyzed. Results: The AUC of the multiplanar radiomics in the training and validation sets were 0.94 and 0.91, respectively. The neurodevelopmental function scores in infants with WMI were significantly lower than those in healthy preterm infants and full‐term newborns (P <.001). There were statistically significant differences in the neurodevelopmental function scores of infants between the 2‐ and 4‐week lesion disappearance and 4‐week lesion persistence (P <.001). Conclusions: The multiplanar radiomics model showed a good performance in predicting the WMI of premature infants. It can not only provide objective and accurate results but also dynamically monitor the degree of recovery of WMI to predict the prognosis of premature infants. [ABSTRACT FROM AUTHOR]

The gas mixture CO2–O2 has been considered as an insulation and arc-quenching medium in gas-insulated switchgears. In this paper, the dielectric breakdown properties of CO2–O2 mixtures at different O2 concentrations and gas pressures were studied theoretically by considering ion kinetics in a spatial–temporal growth avalanche model. A kinetic scheme that includes all the main reactions likely to occur in CO2–O2 mixtures is presented. An improved method to calculate the dielectric strength of the gas mixture is developed, based on an avalanche model that considers both spatial growth and temporal processes. Next, the reaction rates of ionization, attachment, detachment and ion conversion, the effective ionization Townsend coefficient αeff/N, and reduced critical electric field strength (E/N)cr in CO2–O2 mixtures at different mixing ratios and gas pressures are analyzed in detail. Finally, a pulsed Townsend experiment is performed to verify the validity and accuracy of the calculation method. Based on this, one detachment reaction rate is modified to yield more accurate results. Better consistency between the results and the experimental values supports the validity of the kinetic system, reaction rates, and the improved calculation method. [ABSTRACT FROM AUTHOR]

Recently, C4F7N mixtures have attracted attention as a promising SF6 alternative due to their low global warming potential and excellent electrical performance. In this study, we introduce a newly built experimental setup for pulsed Townsend measurements as well as the physical model for the acquisition of electron swarm parameters. The effective ionization rate coefficients, electron drift velocity, and density-normalized longitudinal diffusion coefficients in C4F7N and its mixtures with CO2 and N2 were obtained. The reduced critical electric field for pure C4F7N at 100 Pa is determined to be 1002 Td, while it decreases with increasing pressure because of the effect of ion kinetics during the discharge process. C4F7N shows good synergism with CO2 and N2. To have a dielectric strength equivalent to that of SF6, the mixing ratio of C4F7N in its mixtures with CO2 and N2 should be 18% and 12%, respectively. The results provide fundamental data for modeling discharges in C4F7N and its mixtures. [ABSTRACT FROM AUTHOR]

The perfluoronitrile C4F7N is considered a promising SF6-alternative in high-voltage gas-insulated apparatus, thanks to its high dielectric strength and low global warming potential. However, a complete and consistent set of electron-neutral collision cross-sections of C4F7N is still lacking, which hinders relevant plasma modeling. In this contribution, the available electron-neutral collision cross-sections of C4F7N are first compiled and assessed. The initial cross-sections are adjusted iteratively by the electron swarm method to determine a complete and self-consistent cross-section set of C4F7N for the first time. The set is validated by a systematic comparison of electron swarm parameters between Boltzmann equation analysis and experimental measurements in pure C4F7N as well as C4F7N/N2 and C4F7N/Ar mixtures. The proposed cross-section set of C4F7N will be made available to the community in the LXCat database. It will be of particular importance for applications with an emphasis on the discharge mechanisms of this novel gas. [ABSTRACT FROM AUTHOR]

C4F7N and C5F10O are the most promising SF6 alternatives as eco-friendly insulating gaseous mediums in electrical engineering. It is necessary to clarify their electrical stability and decomposition mechanisms. In this work, we first introduced our experimental results for decomposition products of C4F7N/CO2 and C5F10O/synthetic air mixtures under partial discharge and spark discharge conditions. Then, we performed ab initio molecular dynamics (AIMD) simulations on the typical decomposition products. The simulations were performed under standard electron impact mass spectrometry (EI-MS); thus, the statistical results of the mass spectra were compared with those of the experimentally obtained standard mass spectra from the NIST database. The AIMD simulation method in simulating the electron-induced ionization process was verified and found to be reliable. Finally, the calculations were also performed for C4F7N and C5F10O with incident electron energies of 20 eV and 70 eV, respectively. The dominant pathway for both gases is the formation of CF3+ with the fracture of the C–C bond. The AIMD simulation is able to predict the decomposition channels after electron-impact ionization without any preconceived knowledge of fragmentation pathways, which provides a novel insight into understanding the decomposition mechanisms of C4F7N and C5F10O under different discharge conditions with different energies. [ABSTRACT FROM AUTHOR]

Iso-C4 perfluoronitrile (C4F7N) is one of the most promising alternatives to SF6 for use in power equipment, such as high-voltage circuit breakers, due to its excellent electrical properties and environmentally friendly characteristics. The use of SF6 is being reduced because of its high global warming potential. To describe the physical and chemical processes occurring in the arc plasma in circuit breakers, both local thermodynamic equilibrium (LTE) and nonlocal chemical equilibrium (LCE) conditions have to be considered. The plasma composition of the arc core region can be calculated under the assumption of LTE by the method of minimization of the Gibbs free energy. The plasma composition of the arc boundary region or during the arc ignition period is not in LTE or LCE, so the use of a chemical kinetic model that considers the effects of the energy barrier in chemical reactions is required. Calculations for both conditions are presented for C4F7N. To develop the chemical kinetic model, the complete decomposition pathway and transition states were first reexamined and further developed. Based on the decomposition pathway, the rate constants of reactions were obtained according to the variational transition state theory method. The results obtained for the two cases provide a reference for the systematic understanding of the decomposition characteristics of C4F7N gas and for related engineering applications. [ABSTRACT FROM AUTHOR]

Teleseismic primary (P) to secondary (S) converted waves recorded on the INDEPTH III seismic array have been used to detect lithospheric-scale deformation structures of the central Tibetan Plateau from the central Lhasa terrane to the central Qiangtang terrane. A south-dipping crustal converter is seen from the upper crust near the 500-km-long metamorphic core complex exposures in the Qiangtang terrane to the lower crust near the Bangong-Nujiang suture. At deeper depths, a southeast-dipping mantle converter is seen extending from ~50 km north of the Bangong-Nujiang suture at the depth of the Moho, to a depth of ~180 km, ~100 km south of the Bangong-Nujiang suture. We found the observations to be most consistent with a model of lithospheric deformation involving (1) southward subduction of the Tibetan lithospheric mantle along the Bangong-Nujiang suture and (2) thickening of the central Tibetan crust through a thick-skinned, crustal accretionary thrust-wedge structure in response to the India's collision with Asia. Keywords: receiver function, lithospheric structure, continental collision, Tibetan Plateau.

Recently, the C4F7N/CO2 mixture has been highly considered as a promising SF6 alternative due to its low greenhouse effect and excellent electrical performance. Apart from its dielectric strength and arc-quenching capability, the decomposition characteristics of C4F7N/CO2 also play an important role in its future applications in gas-insulated electrical equipment. Therefore, decomposition experiments of the C4F7N/CO2 mixture were carried out under multiple AC discharge breakdowns by using a needle-to-plate electrode configuration. The compositions of the gas mixture before and after breakdowns were detected by using a gas chromatography-mass spectrometer. The results show that a trace amount of C3HF7 exists in the C4F7N product; the decomposition of the C4F7N/CO2 mixture mainly produces CO, CF4, CO2, C2F4, C2F6, C3F8, CF3CN, C3F6, C4F6, C4F10, C2F5CN, C2N2, HCN, C2F3CN, and HF. As the number of breakdowns increases, the content of most decomposition products increases significantly, while the content of C3HF7 decreases. The possible formation pathways of the decomposition products were determined, and the corresponding reaction enthalpies were calculated by quantum chemistry calculation. Relevant results not only reveal the decomposition characteristics of C4F7N/CO2 under AC breakdowns but also help us to better understand the corresponding physicochemical mechanisms, which will provide a good reference for stable operation and safe maintenance in applications. [ABSTRACT FROM AUTHOR]

• Interaction between C4F7N and ZnO surface is stronger that on Zn surface. • The CN group shows a strong activity on the ZnO surface. • Activation energy of C 4 F 7 N dissociation on ZnO surface is higher than on Cu and Al. • Zinc shows potentials to be anti-corrosion material when using C 4 F 7 N. Recently, C 4 F 7 N has been considered as one of the most promising candidates to replace SF 6 due to its excellent insulation performance and environmental-friendly property. Metal zinc is widely used as a coating material in gas-insulated electrical equipment. However, its compatibility with C 4 F 7 N has never been explored before. In this paper, the adsorption properties of C 4 F 7 N on Zn(0 0 0 1) and ZnO(1 0 1 ¯ 0) surfaces were theoretically studied by a first-principles calculation. Adsorption energy, total charge transfer, density of states, and electron density difference were calculated to evaluate the compatibility of C 4 F 7 N with Zn and ZnO. The results demonstrated that the interaction between C 4 F 7 N and ZnO(1 0 1 ¯ 0) is stronger than that of Zn(0 0 0 1). The dissociation pathway of C 4 F 7 N after adsorption on the ZnO(1 0 1 ¯ 0) surface was also determined, which shows that ZnO(1 0 1 ¯ 0) has a catalytic effect on the decomposition process of C 4 F 7 N. Compared with Al(1 1 1) and Cu(1 1 1), the dissociation of C 4 F 7 N on ZnO(1 0 1 ¯ 0) has a higher energy barrier, indicating that the reaction is more difficult to occur. As a result, Zn and ZnO have certain compatibility with C 4 F 7 N, which was also verified by experiments. Therefore, we infer that Zn shows potentials to be used as anti-corrosion coating in C 4 F 7 N gas-insulated electrical equipment. [ABSTRACT FROM AUTHOR]

C 4 F 7 N and C 5 F 10 O are the most promising SF 6 alternatives as eco-friendly insulating gaseous mediums in electrical engineering. It is necessary to clarify their electrical stability and decomposition mechanisms. In this work, we first introduced our experimental results for decomposition products of C 4 F 7 N/CO 2 and C 5 F 10 O/synthetic air mixtures under partial discharge and spark discharge conditions. Then, we performed ab initio molecular dynamics (AIMD) simulations on the typical decomposition products. The simulations were performed under standard electron impact mass spectrometry (EI-MS); thus, the statistical results of the mass spectra were compared with those of the experimentally obtained standard mass spectra from the NIST database. The AIMD simulation method in simulating the electron-induced ionization process was verified and found to be reliable. Finally, the calculations were also performed for C 4 F 7 N and C 5 F 10 O with incident electron energies of 20 eV and 70 eV, respectively. The dominant pathway for both gases is the formation of CF 3 + with the fracture of the C-C bond. The AIMD simulation is able to predict the decomposition channels after electron-impact ionization without any preconceived knowledge of fragmentation pathways, which provides a novel insight into understanding the decomposition mechanisms of C 4 F 7 N and C 5 F 10 O under different discharge conditions with different energies.