Two- and three-body dissociation dynamics of temporary negative ion NF3(-).

Dissociation dynamics of temporary negative ion NF3(-) formed in the low-energy (0.5 to 4.5 eV) electron attachment is investigated by the anion velocity slice imaging spectroscopy. The kinetic and angular distributions of the F(-) fragment indicate that this fragment is produced via two distinctly different dissociation channels, namely, two-body and three-body fragmentations, at the higher electron attachment energies. The anisotropic distributions of the fast F(-) ions are interpreted as the two-body dissociations relevant to the (2)E resonant state of NF3(-), whereas the slow F(-) can be produced via various three-body dissociations with the products of NF(X (3)Σ(-)) + F + F(-), NF(b (1)Σ(+)) + F + F(-), or N + F2 + F(-), depending on the electron attachment energy.

Hydrophobicity Tailoring of Ferric Covalent Organic Framework/MXene Nanosheets for High-Efficiency Nitrogen Electroreduction to Ammonia.

Electrocatalytic nitrogen reduction reaction (NRR) represents a promising sustainable approach for NH3 synthesis. However, the poor NRR performance of electrocatalysts is a great challenge at this stage, mainly owing to their low activity and the competitive hydrogen evolution reaction (HER). Herein, 2D ferric covalent organic framework/MXene (COF-Fe/MXene) nanosheets with controllable hydrophobic behaviors are successfully prepared via a multiple-in-one synthetic strategy. The boosting hydrophobicity of COF-Fe/MXene can effectively repel water molecules to inhibit the HER for enhanced NRR performances. By virtue of the ultrathin nanostructure, well-defined single Fe sites, nitrogen enrichment effect, and high hydrophobicity, the 1H,1H,2H,2H-perfluorodecanethiol modified COF-Fe/MXene hybrid shows a NH3 yield of 41.8 µg h-1 mgcat. -1 and a Faradaic efficiency of 43.1% at -0.5 V versus RHE in a 0.1 m Na2 SO4 water solution, which are vastly superior to the known Fe-based catalysts and even to the noble metal catalysts. This work provides a universal strategy to design and synthesis of non-precious metal electrocatalysts for high-efficiency N2 reduction to NH3 .

Communication: Imaging the indirect dissociation dynamics of temporary negative ion: N2O- → N2 + O-.

We reported an imaging study of the dissociation dynamics of temporary negative ion N(2)O(-) formed in the low-energy electron attachment, e(-) + N(2)O → N(2)O(-) → N(2) + O(-). With the help of ab initio molecular dynamics calculations, the evolution of momentum distributions of the O(-) fragment in terms of the electron attachment energy is identified as the result of a competition between two distinctly different indirect pathways, namely, climbing over and bypassing the energy ridge after the molecular structure bending. These two pathways prefer leaving the N(2) fragment at the high vibrational and rotational states, respectively.

Incorporating Fullerenes in Nanoscale Metal-Organic Matrixes: An Ultrasensitive Platform for Impedimetric Aptasensing of Tobramycin.

The rational design and preparation of available fullerene@metal-organic matrix hybrid materials are of profound significance in electrochemical biosensing applications due to their unique photoelectric properties. In this work, C60@UiO-66-NH2 nanocomposites serve as greatly promising materials to modify electrodes and fix aptamers, resulting in a remarkable electrochemical aptasensor for impedimetric sensing of tobramycin (TOB). Nanoscale composites have preferable electroactivity and small particle size with more exposed functional sites, such as Zr(IV) and -NH2, to immobilize aptamers for enhanced detection performance. As we know, most of the electrochemical impedance aptasensors require a long time to complete the detection process, but this prepared biosensor shows the rapid quantitative identification of target TOB within 4 min. This work expands the synthesis of functional fullerene@metal-organic matrix hybrid materials in electrochemical biosensing applications.

A covalent organic framework nanosheet-based electrochemical aptasensor with sensitive detection performance.

The development of covalent organic framework nanosheet (COF NS) is becoming a vitally important research field by reason of its high permeability, ordered structure, high utilization of functional site, favourable dispersability and large aspect ratio, resulting in their widespread applications in separation, catalysis, sensing and optical device. In this work, a Tp-Bpy COF NS was prepared via an interfacial synthesis of 2,4,6-triformylphloroglucinol (Tp) and 5,5'-diamino-2,2'-bipyridine (Bpy), which has film morphology, high surface area, large pore, excellent stability and various functional site. It was utilized as a functional material to immobilize aptamers for constructing a sensitive electrochemical aptasensor. Compared with bulk Tp-Bpy COF, Tp-Bpy COF NS can significantly enhance the biosensing performance toward ultra-trace tobramycin. This work is benefit for the exploration of COF NSs and their electrochemical aptasensors in biosensing applications.

Recent advances in metal/covalent organic framework-based electrochemical aptasensors for biosensing applications.

The booming development of novel porous materials, metal-organic frameworks (MOFs) and covalent-organic frameworks (COFs) has been attracting a lot of attention due to their designabilities, diversities, and extensive applications. MOFs and COFs provide a new potential opportunity and platform to fabricate electrochemical aptasensors for biosensing applications. Compared to other traditional materials, MOF/COF-based electrochemical biosensors can appreciably amplify the electrochemical response signals to improve the sensing performance. Herein, we provide a comprehensive overview of MOF/COF-based electrochemical aptasensors for monitoring different ultra-trace analytes (e.g. antibiotics, pesticides, and cancer markers). This review systematically discusses the classification of electrochemical aptasensors based on various functional materials, including pure MOFs, MOF/conductive composites, metal nanoparticle/MOF composites, pure COFs, COFs/conductive composites, and other hybrid materials. Furthermore, some typical MOF/COF-based electrochemical aptasensors in the recognition of specific targets are described in detail to improve and guide further research for biosensing applications.

The variations of surface wetness recorded by multi-proxies in Yuanchi peatland of the Changbai Mountains from 1962 to 2008.

Surface wetness of Yuanchi peatland in the Changbai Mountains were reconstructed by comprehensive analysis on plant residue, testate amoeba and humification, using the age-depth model established with AMS 14C and 137Cs dating methods. The response of surface wetness to climate change was addressed. Results showed that plant residues in the top 50 cm of peat sequence were dominated by mosses. Detrended correspondence analysis (DCA) of plant residue revealed that axis 1 of DCA biplot might represent mire surface wetness (MSW). MSW from 1962 to 2008 as indicated by axis 1 scores of DCA on plant residue were compared with depths to water table derived by testate amoebae-DWT transfer function and humification measurements, and the results showed that the trends of MSW reconstructed by three proxies were largely consistent. They were wetter MSW from 40-50 cm (1962 to 1975), 27-40 cm (fluctuating from wet to dry from 1975 to 1987), and 0-27 cm (drier from 1987 to 2008). Compared with instrumental data from nearby Erdao weather station, the reconstructed MSW was basically consistent with temperature change in this period. The decreases of MSW occurred when mean summer temperature and mean annual temperature were higher than long-term mean value. Our results suggest that the variability in MSW in the recent 46 years predominantly responded weakening of effective precipitation induced by increasing temperature.

[Responses of the germinability of Sphagnum spores in peat to drainage in Baijianghe Peatland, China]. / 白江河泥炭地泥炭藓孢子萌发力对排水的响应.

Drainage severely changes the environment and ecological process in peatlands, but how does it affect the germinability of Sphagnum spores in peat remains unclear. In this study, we took two peat cores from a near-pristine stand dominated by Sphagnum and a drained stand dominated by dwarf shrubs in Baijianghe Peatland in the Changbai Mountains as experimental materials. Those peat cores were cut into slices. Physicochemical characteristics were measured while Sphagnum spores from each slice were extracted to count spore density and test spore germinability. After dating and determining relationship between peat depth and age, we tried to figure out the mechanism underlying the responses of Sphagnum spore germinability to drainage. The average number of spores in the near-pristine stand was slightly higher than that in the drained stand. There was no difference in average spore germinability between the two stands. The drained stand showed higher peat bulk density, total carbon and total nitrogen relative to the near-pristine stand. Upper peat core showed no significant difference in spore accumulation rate between the two stands after drainage (in 1987), with lower average spore germinability (34%) in the near-pristine stand relative to the drained stand (72%). For the whole peat cores, C/N was positively correlated with spore ger-minability in the near-pristine stand while total carbon, pH and burial time were negatively correlated with spore germinability in the drained stand. The drainage 30 years ago had limited effect on spore accumulation, but improved germinability of spores in shallow peat by changing physicochemical properties of peat due to accelerating decomposition, and thus reduced the persistence of spore bank. This may reduce the persistent regeneration potential of Sphagnum after catastrophic distur-bances.

Impacts of transportation and meteorological factors on the transmission of COVID-19.

The ongoing pandemic of 2019 novel coronavirus disease (COVID-19) is challenging global public health response system. We aim to identify the risk factors for the transmission of COVID-19 using data on mainland China. We estimated attack rate (AR) at county level. Logistic regression was used to explore the role of transportation in the nationwide spread. Generalized additive model and stratified linear mixed-effects model were developed to identify the effects of multiple meteorological factors on local transmission. The ARs in affected counties ranged from 0.6 to 9750.4 per million persons, with a median of 8.8. The counties being intersected by railways, freeways, national highways or having airports had significantly higher risk for COVID-19 with adjusted odds ratios (ORs) of 1.40 (p = 0.001), 2.07 (p < 0.001), 1.31 (p = 0.04), and 1.70 (p < 0.001), respectively. The higher AR of COVID-19 was significantly associated with lower average temperature, moderate cumulative precipitation and higher wind speed. Significant pairwise interactions were found among above three meteorological factors with higher risk of COVID-19 under low temperature and moderate precipitation. Warm areas can also be in higher risk of the disease with the increasing wind speed. In conclusion, transportation and meteorological factors may play important roles in the transmission of COVID-19 in mainland China, and could be integrated in consideration by public health alarm systems to better prevent the disease.

Positive/negative ion velocity mapping apparatus for electron-molecule reactions.

In molecular dissociative ionization by electron collisions and dissociative electron attachment to molecule, the respective positively and negatively charged fragments are the important products. A compact ion velocity mapping apparatus is developed for the angular distribution measurements of the positive or negative fragments produced in the electron-molecule reactions. This apparatus consists of a pulsed electron gun, a set of ion velocity mapping optic lenses, a two-dimensional position detector including two pieces of micro-channel plates, and a phosphor screen, and a charge-coupled-device camera for data acquisition. The positive and negative ion detections can be simply realized by changing the voltage polarity of ion optics and detector. Velocity sliced images can be directly recorded using a narrow voltage pulse applied on the rear micro-channel plate. The efficient performance of this system is evaluated by measuring the angular distribution of O(-) from the electron attachments to NO at 7.3 and 8.3 eV and O(+) from the electron collision with CO at 40.0 eV.

Multilevel binomial logistic prediction model for malignant pulmonary nodules based on texture features of CT image.

PURPOSE: To introduce multilevel binomial logistic prediction model-based computer-aided diagnostic (CAD) method of small solitary pulmonary nodules (SPNs) diagnosis by combining patient and image characteristics by textural features of CT image. MATERIALS AND METHODS: Describe fourteen gray level co-occurrence matrix textural features obtained from 2171 benign and malignant small solitary pulmonary nodules, which belongs to 185 patients. Multilevel binomial logistic model is applied to gain these initial insights. RESULTS: Five texture features, including Inertia, Entropy, Correlation, Difference-mean, Sum-Entropy, and age of patients own aggregating character on patient-level, which are statistically different (P<0.05) between benign and malignant small solitary pulmonary nodules. CONCLUSION: Some gray level co-occurrence matrix textural features are efficiently descriptive features of CT image of small solitary pulmonary nodules, which can profit diagnosis of earlier period lung cancer if combined patient-level characteristics to some extent.

[Research advances on interactions among bryophytes].

This paper summarized the present research status and advances on the intra- and interspecific positive interaction, intra- and inter-specific competition, niche, and coexistence of bryophytes. Bryophytes are generally the dominant plants in harsh environments, and there is a trade-off between their water retention and light and nutrient resource availability. Because of the lesser importance of competition in harsh environments, the positive interaction among bryophytes is common, but the intra- and inter-specific competition among bryophytes and the competition between bryophytes and vascular plants are not rare. Competition hierarchy may exist among some bryophytes, but often changes with environments. In the process of bryophyte community formation, the random process, nature of colonization, and difference in regeneration strategy can result in the niche overlap and coexistence of bryophytes, and the niche differentiation resulted from competition is also one of the mechanisms for bryophytes coexistence. Bryophytes should not be simply classified as stress tolerated-ruderal life history strategists, and competition is still one of important factors for constructing some bryophyte communities and vegetations co-existed by bryophytes and vascular plants.

[Niches of seven bryophyte species in Hani peat land of Changbai Mountains].

Based on field investigation and by using Levins and Pianka formula, the niches of seven bryophyte species in Hani Peatland of Changbai Mountains were studied. The results showed that the average niche breadth in nine environmental factors (total nitrogen, total phosphorous, K+ and Ca2+ in peat, pH,and electrical conductivity of surface water, tree coverage, shrub coverage, and depth to water table) of the seven species decreased in the order of Aulacomnium palustre > Sphagnum fallax > S. magellanicum > S. capillifolium = Polytrichum juniperinum > S. palustre > S. fuiscum. S. fuscum tended to be niche-specific species, while A. palustre tended to be niche-general species. Among the nine environmental factors, surface water electrical conductivity had the highest mean overlap value, while depth to water table, tree coverage, surface water pH, and shrub coverage had the lowest one, being the main environmental factors affecting the distribution of bryophytes. Most bryophyte species differentiated in their niches in the factors of depth to water table, tree coverage, surface water pH, and shrub coverage; while a few bryophyte species had higher overlap value in all of the test environmental factors due to their collaboration relationships in water use. This higher overlap value could offer indirect evidence of interspecific competition of bryophytes.