Co-doping with boron and nitrogen impurities in T-carbon

Previously, Ren et al. [Chem. Phys. 518, 69–73, 2019] reported the failure of Boron-Nitrogen (B-N) co-doping as inter B-N bond in T-carbon. In present work, a B-N atom pair is introduced in T-carbon as p-n co-dopant to substitute two carbon atoms in the same carbon tetrahedron and form an intra B-N bond. The stability of this doping system is verified from energy, lattice dynamic, and thermodynamic aspects. According to our B3PW calculations, B-N impurities in this situation can reduce the band gap of T-carbon from 2.95 eV to 2.55 eV, making this material to be a promising photocatalyst. Through the study of its transport properties, we can also conclude that B-N co-doping cannot improve the thermoelectric performance of T-carbon.Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART

Retinal Fundus Image Registration via Vascular Structure Graph Matching

Motivated by the observation that a retinal fundus image may contain some unique geometric structures within its vascular trees which can be utilized for feature matching, in this paper, we proposed a graph-based registration framework called GM-ICP to align pairwise retinal images. First, the retinal vessels are automatically detected and represented as vascular structure graphs. A graph matching is then performed to find global correspondences between vascular bifurcations. Finally, a revised ICP algorithm incorporating with quadratic transformation model is used at fine level to register vessel shape models. In order to eliminate the incorrect matches from global correspondence set obtained via graph matching, we proposed a structure-based sample consensus (STRUCT-SAC) algorithm. The advantages of our approach are threefold: (1) global optimum solution can be achieved with graph matching; (2) our method is invariant to linear geometric transformations; and (3) heavy local feature descriptors are not required. The effectiveness of our method is demonstrated by the experiments with 48 pairs retinal images collected from clinical patients

Effect of Glomus intraradices on root morphology, biomass production and phosphorous use efficiency of Chinese fir seedlings under low phosphorus stress

IntroductionAvailable phosphorus (P) scarcity in the highly weathered soils of the subtropical forests in southern China is a serious concern. To ensure whether inoculation of arbuscular mycorrhizal fungi (AMF) with Chinese fir (Cunninghamia lanceolata) under low P stress conditions could promote its growth and P utilization capacity, an indoor pot simulation experiment was carried out with the different P supply treatments and Chinese fir seedlings as the tested material.MethodsThe experiment had two P supply treatments, no P supply (P0, 0 mmol·L-1 KH2PO4) and normal P supply (P1, 1.0 mmol·L-1 KH2PO4). The seedling in each P supply treatment was inoculated with Glomus intraradices (Gi), a widespread species of AMF in the natural environment, and with no AMF inoculation as a control treatment (CK). The Gi infection rate in the root system, root cortex tissue dissolution rate, root morphological indexes and biomass, whole plant P use efficiency, and root P use efficiency of Chinese fir were determined under different treatment conditions.Results and DiscussionThe results showed that P0 treatment significantly increased the Gi infection rate (p< 0.05). After inoculating AMF with different P supply treatments, the root cortex tissue dissolution rate was considerably enhanced. In contrast, the Chinese fir’s root length and surface area were reduced; however, the root volume did not change significantly. The average root diameter in the P0 treatment and inoculated with AMF was significantly more prominent than in the uninoculated treatment (p< 0.05). The root biomass and root-to-shoot ratio at different P supply treatments were significantly higher in the Gi infection treatment than in the CK group. Under different P supply treatments, root inoculation with Gi promoted root P use efficiency and whole plant P use efficiency. In conclusion, low P stress condition promoted the colonization of AMF in the root system, increased the dissolution of root cortex tissue, root volume, and the average diameter, and promoted root biomass accumulation and P use efficiency

First integral method for an oscillator system

In this article, we consider the nonlinear Duffing-van der Pol-type oscillator system by means of the first integral method. This system has physical relevance as a model in certain flow-induced structural vibration problems, which includes the van der Pol oscillator and the damped Duffing oscillator etc as particular cases. Firstly, we apply the Division Theorem for two variables in the complex domain, which is based on the ring theory of commutative algebra, to explore a quasi-polynomial first integral to an equivalent autonomous system. Then, through solving an algebraic system we derive the first integral of the Duffing-van der Pol-type oscillator system under certain parametric condition

Spatial-Temporal Pattern and Driving Factors of Carbon Efficiency in China: Evidence from Panel Data of Urban Governance

The improvement in city-level carbon efficiency (CE) is crucial for China to achieve its CO2 emission targets. Based on the panel data from 2003 to 2017, total factor CE values of 283 prefecture-level cities were measured using the super-efficiency SBM model. Through the exploratory spatial data analysis (ESDA), we found that the average city-level CE from 2003 to 2017 showed a “W”-type growth trend. Additionally, there are significant spatial heterogeneity and spatial dependency characteristics of city-level CE. The results of local spatial correlation analysis showed that the Low–Low clusters are distributed in all cities of Shanxi and Northern Shaanxi, and gradually expand to Inner Mongolia, Gansu, Ningxia, and Hebei over time, and the High–High clusters are mainly located in the southeast coastal cities and central and eastern Sichuan. High–Low clusters are generally scattered in cities with relatively superior political–economic status in Northeast China, North China, and Northwest China, and gradually concentrated in North China during 2003–2017. Additionally, the dynamic spatial econometric model was employed to investigate the influencing factors of CE, and we found that the city-level CE has the characteristic of path dependence on time. Factors such as industrial structure upgrading and environmental regulation have significant improvement effects on city-level CE, while technological progress, financial development, energy intensity, and government intervention can significantly inhibit city-level CE. Compared with short-term effects, the long-term effects are insignificant with higher absolute values, indicating the long-term persistence and gradual strengthening characteristics of driving factors on city-level CE; however, the acting long-term mechanism has not been formed. Additionally, the regional spillover effect of driving factors on CE is more significant in the short term. Based on the empirical results, some policy implications for cities to improve CE are proposed

Smartphone-Based Quantitative Detection of Ochratoxin A in Wheat via a Lateral Flow Assay

Ochratoxin A (OTA) poses a severe health risk to livestock along the food chain. Moreover, according to the International Agency for Research on Cancer, it is also categorized as being possibly carcinogenic to humans. The lack of intelligent point-of-care test (POCT) methods restricts its early detection and prevention. This work establishes a smartphone-enabled point-of-care test for OTA detection via a fluorescent lateral flow assay within 6 min. By using a smartphone and portable reader, the assay allows for the recording and sharing of the detection results in a cloud database. This intelligent POCT provided (iPOCT) a linearity range of 0.1–3.0 ng/mL and a limit of detection (LOD) of 0.02 ng/mL (0.32 µg/kg in wheat). By spiking OTA in blank wheat samples, the recoveries were 89.1–120.4%, with a relative standard deviation (RSD) between 3.9–9.1%. The repeatability and reproducibility were 94.2–101.7% and 94.6–103.4%, respectively. This work provides a promising intelligent POCT method for food safety

Supported Ionic Liquid Silica as Curing Agent for Epoxy Composites with Improved Mechanical and Thermal Properties

The present study aims to improve the mechanical properties of epoxy composite by incorporating supported ionic liquid silica (IL-silica). The IL-silica not only showed improved interfacial interaction and reinforcement, but also served as cure agent of epoxy composites. The differential scanning calorimetry analysis revealed that epoxy composites could be successfully cured with IL-silica without any routine curing agents. IL-silica/epoxy composites presented higher mechanical and thermal properties compared with epoxy composite containing un-functionalized silica (u-silica). The dynamic mechanical analysis showed that the storage modulus of composites significantly increased with the addition of IL-silica in comparison to that with added u-silica, as well as the variation of Tg parameter. The incorporation of IL-silica simultaneously enhanced the tensile strength, toughness, and thermal stability of the epoxy composites. The considerable improvements in mechanical and thermal properties are ascribed to the improved dispersion of IL-silica and the enhanced interfacial interactions between epoxy matrix and IL-silica by strong covalent bonding, which results in an effective load transfer

Dielectric relaxation of alkyl chains in graphite oxide and n-alkylammonium halides

The dynamic of n-alkylammonium halides and n-alkylammonium cations (n = 12, 14, 16, 18) intercalated in graphite oxide (GO) have been investigated with complex impedance spectroscopy. X-ray diffraction, X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, elemental analysis and thermogravimetry served to characterize the materials. The intercalated alkylammonium cations distributes as monolayers (when n = 12, 14 or 16) or bilayers (when n = 18), with their long axis parallel to GO layers, and with cations of headgroups bonded ionically to C-O- groups of GO; backbones of the confined molecules remain free. All halides and intercalation compounds suffer dielectric loss at low temperature. Arrhenius plots of the thermal dependence of the loss peaks, which are asymmetric, produce apparent activation energies that rise with increasing n. Ngai’s correlated-state model helps to correct for effects of dipole-dipole interaction, leading to virtually identical values for actual activation energy of 110 meV ± 5%; the values are also almost the same as the barrier energy for internal rotation in the alkyl macromolecule. We conclude that the relaxation of the alkylammonium cations arises not from C3 reorientation of the CH3 at its headgroup, but from small-angle wobbling around its major axis, an intrinsic motion