Online dynamic cardiac imaging based on the elastic-net model

Purpose: The purpose of this work was to develop an online dynamic cardiac MRI model to reconstruct image frames from partial acquisition of the Cartesian k-space data, which utilizes structural knowledge of consecutive image frames. Materials and methods: Using an elastic-net model, the proposed algorithm reconstructs dynamic images using both L and L norm operations. The L norm enforces the sparsity of the frame difference, while the L norm with motion-adaptive weights catches the internal structure of frame differences. Unlike other online methods such as the Kalman filter (KF) technique, the new model requires no assumption of Gaussian noise, and can faithfully reconstruct the dynamic images within a compressive sensing framework. Results: The proposed method was evaluated using simulated dynamic phantoms with 40 frames of images (128 × 128) and a cardiac MRI cine of 25 frames (256 × 256). Both results showed that the new model offered a better performance than the online KF method in depicting simulated phantom and cardiac dynamics. Conclusion: It is concluded that the proposed imaging model can be used to capture a large variety of objects in motion from highly under-sampled k-space data, and being particularly useful for improving temporal resolution of cardiac MRI

Numerical Simulation of 50 mm 316L Steel Joint of EBW and Its Experimental Validation

The 316L thick plate electron beam welding (EBW) has been widely used in fusion test reactor manufacturing. Therefore, the numerical simulation of the 50 mm 316L austenitic stainless steel by two heat sources and experimental on microstructure and residual stress have been studied in this article. In the simulation study, the traditional heat source model (3D Gaussian heat source) and composite heat source (double ellipsoid heat source superimposed on the 3D Gaussian heat source) were proposed to simulate the welding of local joint. Weld cross-section, temperature curve, and residual stress after welding obtained by simulations were investigated. The experimental study involved residual stress tests and microstructure analysis. It turned out that the result of the composite heat source was closer to the actual joint. The residual stress distribution of simulation was validated and in accordance with experimental measurement. Moreover, the microstructures were studied by electro backscattered diffraction (EBSD) and compared with the temperature curve. The formation mechanism of microstructural heterogeneity was caused mainly by different thermal cycles at different positions of the thick plate. The top of the joint was more prone to stress concentration

A systematic review and meta-analysis of long noncoding RNA linc-UBC1 expression and prognosis and clinicopathological phenotypes in human cancers

AbstractAccording to previous studies, linc-UBC1 is abnormally expressed in various human tumours. Nonetheless, the clinical significance and mechanism of linc-UBC1 in cancer remains unclear. In our present analysis, we wanted to explore the specific role of linc-UBC1 in malignant tumours by integrating all of the relevant literature and subsequently elucidating the relationship between linc-UBC1 expression level and clinical characteristics of cancers. An elaborate database search of PubMed, Embase, Wanfang Data, Web of Science, Ovid, Medline, Cochrane Library and PMC was carried out up to 8 August 2019. We further applied the pooled odds ratio (OR) and hazard ratio (HR) to evaluate OS. After filtering by strict criteria, 11 studies containing 1017 cases were included in this analysis. Our results implied that high expression of linc-UBC1 was obviously related to poor OS in cancer (HR =1.735, 95% 1.348–2.235, p < .001 random effects model). Analogously, the data revealed that high expression of linc-UBC1 was highly correlated with lymph node metastasis (OR = 2.912, 95% CI: 2.056–4.125, p < .001 fix effects model) and high tumour stage (OR = 2.678, 95% CI: 1.859–3.857, p < .001 fix effects model). In summary, linc-UBC1 overexpression is associated with poor OS and advanced tumour stage and could be used as a novel prognostic biomarker in various cancers

Wavelength-Dependent Solar N2 Fixation into Ammonia and Nitrate in Pure Water

Solar-driven N2 fixation using a photocatalyst in water presents a promising alternative to the traditional Haber-Bosch process in terms of both energy efficiency and environmental concern. At present, the product of solar N2 fixation is either NH4+ or NO3-. Few reports described the simultaneous formation of ammonia (NH4+) and nitrate (NO3-) by a photocatalytic reaction and the related mechanism. In this work, we report a strategy to photocatalytically fix nitrogen through simultaneous reduction and oxidation to produce NH4+ and NO3- by W18O49 nanowires in pure water. The underlying mechanism of wavelength-dependent N2 fixation in the presence of surface defects is proposed, with an emphasis on oxygen vacancies that not only facilitate the activation and dissociation of N2 but also improve light absorption and the separation of the photoexcited carriers. Both NH4+ and NO3- can be produced in pure water under a simulated solar light and even till the wavelength reaching 730 nm. The maximum quantum efficiency reaches 9% at 365 nm. Theoretical calculation reveals that disproportionation reaction of the N2 molecule is more energetically favorable than either reduction or oxidation alone. It is worth noting that the molar fraction of NH4+ in the total product (NH4+ plus NO3-) shows an inverted volcano shape from 365 nm to 730 nm. The increased fraction of NO3- from 365 nm to around 427 nm results from the competition between the oxygen evolution reaction (OER) at W sites without oxygen vacancies and the N2 oxidation reaction (NOR) at oxygen vacancy sites, which is driven by the intrinsically delocalized photoexcited holes. From 427 nm to 730 nm, NOR is energetically restricted due to its higher equilibrium potential than that of OER, accompanied by the localized photoexcited holes on oxygen vacancies. Full disproportionation of N2 is achieved within a range of wavelength from ~427 nm to ~515 nm. This work presents a rational strategy to efficiently utilize the photoexcited carriers and optimize the photocatalyst for practical nitrogen fixation

Revealing the aging process of solid electrolyte interphase on SiOx anode

Abstract As one of the most promising alternatives to graphite negative electrodes, silicon oxide (SiO x ) has been hindered by its fast capacity fading. Solid electrolyte interphase (SEI) aging on silicon SiO x has been recognized as the most critical yet least understood facet. Herein, leveraging 3D focused ion beam-scanning electron microscopy (FIB-SEM) tomographic imaging, we reveal an exceptionally characteristic SEI microstructure with an incompact inner region and a dense outer region, which overturns the prevailing belief that SEIs are homogeneous structure and reveals the SEI evolution process. Through combining nanoprobe and electron energy loss spectroscopy (EELS), it is also discovered that the electronic conductivity of thick SEI relies on the percolation network within composed of conductive agents (e.g., carbon black particles), which are embedded into the SEI upon its growth. Therefore, the free growth of SEI will gradually attenuate this electron percolation network, thereby causing capacity decay of SiO x . Based on these findings, a proof-of-concept strategy is adopted to mechanically restrict the SEI growth via applying a confining layer on top of the electrode. Through shedding light on the fundamental understanding of SEI aging for SiO x anodes, this work could potentially inspire viable improving strategies in the future

Temperature Effect on Co-Based Catalysts in Oxygen Evolution Reaction

Oxygen evolution reaction (OER), as the critical step in splitting water, is a thermodynamically “up-hill” process and requires highly efficient catalysts to run. Arrhenius’ law suggests that the higher temperature, the faster the reaction rate, so that a larger OER current density can be achieved at a lower η. Herein, we report an abnormal temperature effect on the performance of Co-based catalysts, e.g., Co₃O₄, Li₂CoSiO₄, and Fe-doped Co­(OH)_<i>x</i>, in OER in alkaline electrolytes. The OER performance reached a maximum when the temperature increased to 65 °C, and the OER performance declined when the temperature became higher. The mechanism was investigated by using Co₃O₄ as a model sample, and we propose that at an optimal temperature (around 55–65 °C) the main rate-determining step changes from OH^– adsorption dominant to a mixed mode and both the adsorption and the cleavage of the OH group can be rate-determining, which leads to the fastest kinetics