Retraction: Computational fluid dynamics modeling of the millisecond methane steam reforming in microchannel reactors for hydrogen production.

[This retracts the article DOI: 10.1039/C8RA04440F.].

An MRI-Based Radiomic Nomogram for Discrimination Between Malignant and Benign Sinonasal Tumors.

BACKGROUND: Preoperative discrimination between malignant and benign sinonasal tumors is important for treatment plan selection. PURPOSE: To build and validate a radiomic nomogram for preoperative discrimination between malignant and benign sinonasal tumors. STUDY TYPE: Retrospective. POPULATION: In all, 197 patients with histopathologically confirmed 84 benign and 113 malignant sinonasal tumors. FIELD STRENGTH/SEQUENCES: Fast-spin-echo (FSE) T1 -weighted and fat-suppressed FSE T2 -weighted imaging on a 1.5T and 3.0T MRI. ASSESSMENT: T1 and fat-suppressed T2 -weighted images were selected for feature extraction. The least absolute shrinkage selection operator (LASSO) algorithm was applied to establish a radiomic score. Multivariate logistic regression analysis was applied to determine independent risk factors, and the radiomic score was combined to build a radiomic nomogram. The nomogram was assessed in a training dataset (n = 138/3.0T MRI) and tested in a validation dataset (n = 59/1.5T MRI). STATISTICAL TESTS: Independent t-test or Wilcoxon's test, chi-square-test, or Fisher's-test, univariate analysis, LASSO, multivariate logistic regression analysis, area under the curve (AUC), Hosmer-Lemeshow test, decision curve, and the Delong test. RESULTS: In the validation dataset, the radiomic nomogram could differentiate benign from malignant sinonasal tumors with an AUC of 0.91. There was no significant difference in AUC between the combined radiomic score and radiomic nomogram (P > 0.05), and the radiomic nomogram showed a relatively higher AUC than the combined radiomic score. There was a significant difference in AUC between each two of the following models (the radiomic nomogram vs. the clinical model, all P < 0.001; the combined radiomic score vs. the clinical model, P = 0.0252 and 0.0035, respectively, in the training and validation datasets). The radiomic nomogram outperformed the radiomic scores and clinical model. DATA CONCLUSION: The radiomic nomogram combining the clinical model and radiomic score is a simple, effective, and reliable method for patient risk stratification. LEVEL OF EVIDENCE: 4 TECHNICAL EFFICACY STAGE: 2.

Compact Steam-Methane Reforming for the Production of Hydrogen in Continuous Flow Microreactor Systems.

The implementation of fuel cell deployment requires efficient conversion of fuels into hydrogen in a distributed energy system. Fortunately, continuous flow and microreactor technology provide unique opportunities for the portable production of hydrogen. This study focuses on determining the operation space for a thermally integrated methane reforming system, thereby providing a theoretical basis for the design and optimization of such systems. The steam-methane reforming over rhodium coupled with methane combustion over platinum in a thermally integrated microchannel reactor arranged with rectangular-shaped protuberances was studied numerically in order to improve its operability and stability. Computational fluid dynamic simulations were carried out with detailed reaction mechanisms to identify conditions for the maximum hydrogen yield and the highest output power. Various operating lines were presented, and various performance metrics were evaluated accordingly. The results indicated that the efficient production of hydrogen is made possible through improving transport performance for highly active catalysts. The flow disturbance elements designed for the reactor are of great benefit to intensification of the reforming process. There exists a trade-off between fuel utilization and output power. Autothermal operation advantages from improved transport performance in small physical dimensions were demonstrated for the system, but careful thermal management is always necessary to ensure its efficient and stable operation. The thermal conductivity of the wall separating the exothermic and endothermic reactions plays a significant role in determining the performance of the system. Highly active catalysts are required to intensify the overall reforming process and to achieve efficient thermal management. Adjustment of fluid velocities can serve as a convenient means to achieve efficient operation of the system.

Retracted Article: Computational fluid dynamics modeling of the millisecond methane steam reforming in microchannel reactors for hydrogen production.

Methane steam reforming coupled with methane catalytic combustion in microchannel reactors for the production of hydrogen was investigated by means of computational fluid dynamics. Special emphasis is placed on developing general guidelines for the design of integrated micro-chemical systems for the rapid production of hydrogen. Important design issues, specifically heat and mass transfer, catalyst, dimension, and flow arrangement, were explored. The relative importance of different transport phenomena was quantitatively evaluated, and some strategies for intensifying the reforming process were proposed. The results highlighted the importance of process intensification in achieving the rapid production of hydrogen. High heat and mass transfer rates derived from miniaturization of the chemical system are insufficient for process intensification. Improvement of the reforming catalyst is also essential. The efficiency of heat exchange can be improved greatly if the reactor dimension is properly designed. Thermal management is required to improve the reliability of the integrated system. Co-current heat exchange improves the thermal uniformity in the system. The catalyst loading is a key factor determining reactor performance, and must be carefully designed. Finally, engineering maps were constructed to achieve the desired power output, and favorable operating conditions for the rapid production of hydrogen were identified.

A review of the interfacial characteristics of polymer nanocomposites containing carbon nanotubes.

This paper provides an overview of recent advances in research on the interfacial characteristics of carbon nanotube-polymer nanocomposites. The state of knowledge about the chemical functionalization of carbon nanotubes as well as the interaction at the interface between the carbon nanotube and the polymer matrix is presented. The primary focus of this paper is on identifying the fundamental relationship between nanocomposite properties and interfacial characteristics. The progress, remaining challenges, and future directions of research are discussed. The latest developments of both microscopy and scattering techniques are reviewed, and their respective strengths and limitations are briefly discussed. The main methods available for the chemical functionalization of carbon nanotubes are summarized, and particular interest is given to evaluation of their advantages and disadvantages. The critical issues related to the interaction at the interface are discussed, and the important techniques for improving the properties of carbon nanotube-polymer nanocomposites are introduced. Additionally, the mechanism responsible for the interfacial interaction at the molecular level is briefly described. Furthermore, the mechanical, electrical, and thermal properties of the nanocomposites are discussed separately, and their influencing factors are briefly introduced. Finally, the current challenges and opportunities for efficiently translating the remarkable properties of carbon nanotubes to polymer matrices are summarized in the hopes of facilitating the development of this emerging area. Potential topics of oncoming focus are highlighted, and several suggestions concerning future research needs are also presented.