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Recent studies have shown that a rich variety of exotic physical phenomena can emerge from the presence of electronic flat bands. Using first‐principles calculations, here a monolayered Ca2C possesses a relatively flat band near the Fermi level, and across the whole Brillouin zone is predicted. Next, the weak d0 ferromagnetism in Ca2C is substantially enhanced by a proximity‐coupled electride monolayer of Ca2N is shown. The enhanced magnetism can be attributed to the straightening of the flat band caused by the charge transfer to the electride, while the flattening is tied to the magic ratio of three between the σ and π channels of the effective C─C coupling strength. More surprisingly, even though each of the constituent systems is topologically trivial, the Ca2C/Ca2N heterobilayer is empowered with nontrivial band topology, characterized by a high Chern number tunable by the magnetization orientation or lateral strain. These findings provide a new platform for realizing intriguing magnetic topological metals in 2D materials. [ABSTRACT FROM AUTHOR]

This study investigates the relationship between financial constraints and corporate fraud commission and its detection and the moderating role of short selling using a partial observable bivariate probit model. First, financially constrained corporations are more likely to commit fraud and their fraudulent behaviours are less likely to be detected. Second, short selling has an interesting effect on corporate fraud. On the one hand, short selling has a direct restraining effect on corporate fraud commission and increases the likelihood of corporate fraud detection. On the other hand, short selling plays a moderating role in the relationship between financial constraints and corporate fraud. This study contributes to the corporate fraud literature by analysing the factors influencing corporate fraud and provides theoretical support for regulators and managers in monitoring fraudulent behaviour. [ABSTRACT FROM AUTHOR]

Chinese timber bamboo (Phyllostachys vivax McClure) has been successfully introduced to the coastal belt of eastern China. However, the mechanisms of nutrient uptake and antioxidative protection of P. vivax in response to salinity adaptation in coastal areas remains unclear. P. vivax forests were studied in their native and coastal transplantation sites within the coastal belt of China. In particular, nutrient allocation, anti‐oxidative enzyme activities, biomass accumulation, water contents, water potentials, and root system morphologies vs. microstructures were evaluated in plants from the two sites. Plant morphology adapted to the coastal saline soils by increasing root/shoot ratios and the length of large diameter rhizome, increasing vascular numbers, and lightening epidermal cells within rhizomes. The ratio of Ca2+/Na+ increased, while K+/Na+, Mg2+/Na+ decreased after transplanted to the coastal sites. Nitrogen nutrient contents were significantly positive correlated with plant growth characteristics of P. vivax. The Mg2+, Na+, and Ca2+ concentrations contributed more significantly to differences among organs, while N, Mg2+, Na+, and Ca2+ contents contributed more to root systems. The activities of superoxide dismutase (SOD), peroxidase (POD), and ascorbate peroxidase (APX) decreased, while the levels of glutathione (GSH) and ascorbic acid (AsA) increased in belowground tissues. In contrast, catalase (CAT) activities and protein contents were similar among plants of both sites. The contributions of CAT and proteins were higher for the principal components explaining variation among different organs, while the contributions of APX, CAT, POD, and proteins were higher for root systems. Core Ideas: P. vivax adapt to salinity by morphological and structural changes.Morphological changes are closely related to the absorption and distribution of nutrients.Antioxidative emzymes indirectly affected P. vivax growth. [ABSTRACT FROM AUTHOR]

This study extends the classical model to focus on a firm's optimal investment and endogenous payout strategies when a manager has time‐inconsistent preferences, which we describe by a quasi‐hyperbolic discount function. We attempt to reveal the impacts of time‐inconsistency on liquidation, external financing, credit lines, and risk management. The extended model predicts that the time‐inconsistent manager tends to (a) pay out cash to shareholders earlier by lowering the dividend payment, which causes the firm to hold less cash reserves and raise less equity; (b) invest less in the high cash and engage in much less costly asset sales in the low cash; and (c) choose not to hedge earlier than a time‐consistent counterpart. In addition, our model also shows that the manager's time‐inconsistent preferences decrease firm value and the marginal value of cash. These results highlight that corporate decisions, including payouts, cash holdings, investment, external financing, and even risk management strategies, are highly dependent on the manager's time‐inconsistent preferences. [ABSTRACT FROM AUTHOR]

The intergranular corrosion behaviour and corrosion mechanism of 6082 aluminium alloy subjected to different homogenisation processes were investigated. The results show that with increasing homogenisation temperature and/or time, the amount of corrosion product, Al(OH)3, and the thickness of its layer gradually increase, the corrosion current density decreases, and the corrosion resistance increases. In addition, the corrosion current density of the forged alloy is much smaller than that of the extruded alloy, and thus, the forged alloy is more resistant to corrosion. Two kinds of secondary phase particles, Si and AlMnFeSi, are homogeneously distributed within the plastic deformation flow lines of the alloy. When the boundary between the secondary phase Si particles and the matrix is in contact with the corrosive agent, the matrix dissolves first and initiates the formation of corrosion cracks, as the matrix serves as an anode and the Si particles serve as a cathode in the micro‐galvanic cell configuration. Moreover, the corrosion cracks develop into networks upon electrochemical corrosive coupling between the β″‐Mg2Si precipitates and the precipitate‐free zone (PFZ) located along the grain boundaries. [ABSTRACT FROM AUTHOR]

Purpose The schemes of multi-source interior computed tomography ( CT) have shown promise for ultra-fast, organ-oriented, and low-dose dynamic imaging. Besides forward scattering, x-ray cross scattering from multiple x-ray sources activated simultaneously can further degrade image quality. Here, we investigate the overall x-ray scattering artifact in a recently proposed multi-source interior CT architecture, and present two methods for scatter correction. Methods Compared to single-source global CT, scattering in multi-source interior CT architecture is affected by two new factors: cross scattering from simultaneously activated multiple x-ray sources and region-of-interest ( ROI) oriented interior CT mode. The scatter artifact in the multi-source interior CT architecture was evaluated through both numerical simulation and physical experimentation, and compared to that from conventional single-source global CT. Monte Carlo simulation was conducted with a modified numerical CATphan® 600 phantom. Physical experiments were performed in an in-house developed CT imaging platform with a custom-built phantom. The simulation and experiments were carried out on the single-source CT architecture and the multi-source CT architecture, respectively in the global CT mode and the interior CT mode for comparison. To correct the scattering artifact, two new methods were presented. The first is a beam-stopper-array ( BSA)-based method, which enables an online correction of forward scattering and cross scattering simultaneously. The second is a source-trigger-sequence ( STS)-based method dedicated to cross-scatter correction. It enables on-the-fly measurements of the cross scattering signals at a few pre-selected views. The CT image quality was quantitatively evaluated in terms of contrast-to-noise ratio ( CNR) and CT number deviation before and after the scatter correction. Results X-ray cross scattering degraded image quality in both the simulation and experiments. Before the scatter correction, the multi-source interior CT mode yielded a reduction of CNR at the ROIs by up to 68.5% and 50.7% in the simulation and experiments, respectively. The stationary BSA-based method significantly improved CNR and CT number accuracy in the images from multi-source interior CT mode, by reducing the negative effects from both forward scattering and cross scattering. The STS-based method enabled multi-source interior CT mode to provide comparable image quality to that with the single-source interior CT mode, by correcting the artifact from cross scattering. The remaining forward scattering artifact can be corrected with the fast adaptive scatter kernel superposition ( FASKS) technique. With the proposed scatter correction methods, the CT number error at the ROIs was reduced to less than 37 HU in both simulation and experiments, respectively. Conclusions Cross scattering, in addition to forward scattering, can cause significant image quality degradation in the multi-source interior CT architecture. However, image quality can be significantly improved with the proposed scatter correction methods. [ABSTRACT FROM AUTHOR]

Purpose: Microbeam radiation therapy (MRT) is defined as the use of parallel, microplanar x-ray beams with an energy spectrum between 50 and 300 keV for cancer treatment and brain radiosurgery. Up until now, the possibilities of MRT have mainly been studied using synchrotron sources due to their high flux (100s Gy/s) and approximately parallel x-ray paths. The authors have proposed a compact x-ray based MRT system capable of delivering MRT dose distributions at a high dose rate. This system would employ carbon nanotube (CNT) field emission technology to create an x-ray source array that surrounds the target of irradiation. Using such a geometry, multiple collimators would shape the irradiation from this array into multiple microbeams that would then overlap or interlace in the target region. This pilot study demonstrates the feasibility of attaining a high dose rate and parallel microbeam beams using such a system. Methods: The microbeam dose distribution was generated by our CNT micro-CT scanner (100 µm focal spot) and a custom-made microbeam collimator. An alignment assembly was fabricated and attached to the scanner in order to collimate and superimpose beams coming from different gantry positions. The MRT dose distribution was measured using two orthogonal radiochromic films embedded inside a cylindrical phantom. This target was irradiated with microbeams incident from 44 different gantry angles to simulate an array of x-ray sources as in the proposed compact CNT-based MRT system. Finally, phantom translation in a direction perpendicular to the microplanar beams was used to simulate the use of multiple parallel microbeams. Results: Microbeams delivered from 44 gantry angles were superimposed to form a singlemicrobeam dose distribution in the phantom with a FWHM of 300 µm (calculated value was 290 µm). Also, during the multiple beam simulation, a peak to valley dose ratio of ~10 was found when the phantom translation distance was roughly 4x the beam width. The first prototype CNT-based x-ray tube dedicated to the development of compact MRT technology development was proposed and planned based on the preliminary experimental results presented here and the previous corresponding Monte Carlo simulations. Conclusions: The authors have demonstrated the feasibility of creating microbeam dose distributions at a high dose rate using a proposed compact MRT system. The flexibility of CNT field emission x-ray sources could possibly bring compact and low cost MRT devices to the larger research community and assist in the translational research of this promising new approach to radiation therapy. [ABSTRACT FROM AUTHOR]

Purpose: The size of field-of-view (FOV) of a microcomputed tomography (CT) system can be increased by offsetting the detector. The increased FOV is beneficial in many applications. All prior investigations, however, have been focused to the case in which the increased FOV after offset-detector acquisition can cover the transaxial extent of an object fully. Here, the authors studied a new problem where the FOV of a micro-CT system, although increased after offset-detector acquisition, still covers an interior region-of-interest (ROI) within the object. Methods: An interior-ROI-oriented micro-CT scan with an offset detector poses a difficult reconstruction problem, which is caused by both detector offset and projection truncation. Using the projection completion techniques, the authors first extended three previous reconstruction methods from offset-detector micro-CT to offset-detector interior micro-CT. The authors then proposed a novel method which combines two of the extended methods using a frequency split technique. The authors tested the four methods with phantom simulations at 9.4%, 18.8%, 28.2%, and 37.6% detector offset. The authors also applied these methods to physical phantom datasets acquired at the same amounts of detector offset from a customized micro-CT system. Results: When the detector offset was small, all reconstruction methods showed good image quality. At large detector offset, the three extended methods gave either visible shading artifacts or high deviation of pixel value, while the authors' proposed method demonstrated no visible artifacts and minimal deviation of pixel value in both the numerical simulations and physical experiments. Conclusions: For an interior micro-CT with an offset detector, the three extended reconstruction methods can perform well at a small detector offset but show strong artifacts at a large detector offset. When the detector offset is large, the authors' proposed reconstruction method can outperform the three extended reconstruction methods by suppressing artifacts and maintaining pixel values. [ABSTRACT FROM AUTHOR]

The long-term performance stability of organic solar cells (OSCs), as well as their high power-conversion efficiency, is necessary for their practical use. A stable OSC with the structure of ITO/buffer/donor/acceptor/cathode is presented. A thin layer of MoO3-doped PTCDA (molar ratio 1:1) is adopted as the buffer in CuPc/C60 organic heterojunction photovoltaic (PV) solar cells, resulting in four to five times longer lifetime. The CT complex of buffer layer plays a decisive role in improving the stability and abnormal efficiency changes. [ABSTRACT FROM AUTHOR]

Purpose: Carbon nanotube (CNT) based field emission x-ray source technology has recently been investigated for diagnostic imaging applications because of its attractive characteristics including electronic programmability, fast switching, distributed source, and multiplexing. The purpose of this article is to demonstrate the potential of this technology for high-resolution prospective-gated cardiac micro-CT imaging. Methods: A dynamic cone-beam micro-CT scanner was constructed using a rotating gantry, a stationary mouse bed, a flat-panel detector, and a sealed CNT based microfocus x-ray source. The compact single-beam CNT x-ray source was operated at 50 KVp and 2 mA anode current with 100 μm×100 μm effective focal spot size. Using an intravenously administered iodinated blood-pool contrast agent, prospective cardiac and respiratory-gated micro-CT images of beating mouse hearts were obtained from ten anesthetized free-breathing mice in their natural position. Four-dimensional cardiac images were also obtained by gating the image acquisition to different phases in the cardiac cycle. Results: High-resolution CT images of beating mouse hearts were obtained at 15 ms temporal resolution and 6.2 lp/mm spatial resolution at 10% of system MTF. The images were reconstructed at 76 μm isotropic voxel size. The data acquisition time for two cardiac phases was 44±9 min. The CT values observed within the ventricles and the ventricle wall were 455±49 and 120±48 HU, respectively. The entrance dose for the acquisition of a single phase of the cardiac cycle was 0.10 Gy. Conclusions: A high-resolution dynamic micro-CT scanner was developed from a compact CNT microfocus x-ray source and its feasibility for prospective-gated cardiac micro-CT imaging of free-breathing mice under their natural position was demonstrated. [ABSTRACT FROM AUTHOR]