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Graphite nitrogen, pyridine nitrogen and pyrrole nitrogen are the main nitrogen types in nitrogen-doped graphene materials. In order to investigate the mechanism of the oxygen reduction activity of nitrogen-doped graphene, several models of nitrogen-doped graphene with different nitrogen contents and different nitrogen types are developed. The nitrogen content is varied from 1.3 at% to 7.8 at%, and the adsorption energy is calculated according to the established models, then the band gaps are analyzed through the optimization results, so as to compare the magnitude of the conductivity. Finally, the oxygen reduction activity of graphite nitrogen-doped graphene (GNG) is found to be better than pyridine nitrogen-doped graphene (PDNG) and pyrrole nitrogen-doped graphene (PLNG) when the nitrogen content is lower than 2.6 at%, and the oxygen reduction activity of PDNG is the best when the nitrogen content was higher than 2.6 at%.

Quantitative reconstruction of regional paleotemperature is the key to understanding temperature change and its driving mechanisms. In this study, 133 phytolith samples were collected as proxy indicators from lacustrine sediments of the Zhunzhahanjilin (ZZH) profile in the hinterland of the Badain Jaran Desert, China. The phytolith samples were then analyzed to quantitatively reconstruct the Holocene paleotemperature at the millennial scale. Based on accelerator mass spectrometry (AMS), 14C dates and an ordered clustering method were used to divide the phytoliths into five assemblage zones with environmental significance. The quantitative reconstruction results indicated that the paleotemperature in the Badain Jaran Desert was relatively high during the early Holocene (11,040–8,200 cal a BP), and the average paleotemperature was approximately 9.5°C. This may have led to increased melt water near the surrounding area and recharged the lakes in the Badain Jaran Desert, resulting in the expansion of the lakes during the early Holocene. The average paleotemperature during the middle Holocene (8,200–3,100 cal a BP) was approximately 7.9°C. This period was warm and the environment was humid, with extensive precipitation from summer monsoons and low evaporation leading to higher water levels in the lakes. The paleotemperature decreased during the late Holocene (3,100 cal a BP to the present), and lakes retreated or dried up because of the decreased summer monsoon rains. The Holocene paleotemperature in the Badain Jaran Desert may have been related to July insolation in the Northern Hemisphere and had a range of impacts on the hydrological cycle in this arid region.

The performance of LiDAR with single-photon avalanche diode (SPAD) detectors can degrade seriously when a shortage of photons occurs in adverse environments. It is desirable for SPAD LiDAR to accumulate enough photons so that reliable target detection is maintained under such conditions. It is proposed in this letter to adopt random laser-emitting schemes, such as stochastic pulse position modulation (SPPM), to have more laser pulses illuminated on targets to increase reflected photons. Accordingly, at the receiver side, a novel method, namely multi-start-multi-stop (MSMS), is proposed to work with SPPM to generate histograms for further processing of target detection and ranging. Theoretical analysis and experiments show that the SPPM+MSMS LiDAR can produce, with far less integration time, signal levels comparable to that of conventional LiDAR.

Additional file 1: Table S1. The primers for genes used in real-time qPCR analysis.

Background Soil salinization is becoming an increasingly serious problem worldwide, resulting in cultivated land loss and desertification, as well as having a serious impact on agriculture and the economy. The indoleamine melatonin (N-acetyl-5-methoxytryptamine) has a wide array of biological roles in plants, including acting as an auxin analog and an antioxidant. Previous studies have shown that exogenous melatonin application alleviates the salt-induced growth inhibition in non-halophyte plants; however, to our knowledge, melatonin effects have not been examined on halophytes, and it is unclear whether melatonin provides similar protection to salt-exposed halophytic plants. Results We exposed the halophyte Limonium bicolor to salt stress (300 mM) and concomitantly treated the plants with 5 μM melatonin to examine the effect of melatonin on salt tolerance. Exogenous melatonin treatment promoted the growth of L. bicolor under salt stress, as reflected by increasing its fresh weight and leaf area. This increased growth was caused by an increase in net photosynthetic rate and water use efficiency. Treatment of salt-stressed L. bicolor seedlings with 5 μM melatonin also enhanced the activities of antioxidants (superoxide dismutase [SOD], peroxidase [POD], catalase [CAT], and ascorbate peroxidase [APX]), while significantly decreasing the contents of hydrogen peroxide (H2O2), superoxide anion (O2•−), and malondialdehyde (MDA). To screen for L. bicolor genes involved in the above physiological processes, high-throughput RNA sequencing was conducted. A gene ontology enrichment analysis indicated that genes related to photosynthesis, reactive oxygen species scavenging, the auxin-dependent signaling pathway and mitogen-activated protein kinase (MAPK) were highly expressed under melatonin treatment. These data indicated that melatonin improved photosynthesis, decreased reactive oxygen species (ROS) and activated MAPK-mediated antioxidant responses, triggering a downstream MAPK cascade that upregulated the expression of antioxidant-related genes. Thus, melatonin improves the salt tolerance of L. bicolor by increasing photosynthesis and improving cellular redox homeostasis under salt stress. Conclusions Our results showed that melatonin can upregulate the expression of genes related to photosynthesis, reactive oxygen species scavenging and mitogen-activated protein kinase (MAPK) of L. bicolor under salt stress, which can improve photosynthesis and antioxidant enzyme activities. Thus melatonin can promote the growth of the species and maintain the homeostasis of reactive oxygen species to alleviate salt stress.

Vertical water transport plays an important role in the development and maintenance of lakes in arid zones. However, previous study of this phenomenon has focused mainly on the effects of regional precipitation, rather than effects of groundwater recharge, on arid-zone environmental change. We selected a sedimentary profile from a seasonal lake basin located in the hinterland of the Badain Jaran Desert, northwestern China, to assess the Holocene environmental evolution of this region and its response to climate change. Our results show that peat deposition from 11 to 10 ka indicates humidification after Younger Dryas (YD) event; the lake sediment and lower EM2 and lower principal component analysis (PCA)-1 scores indicate relative more humid environment from 10 to 7.8 ka; the lake sediment and higher EM2 and higher PCA-1 scores indicate most humid environment from 7.8 to 5.8 ka; the transition from lacustrine facies to limnetic facies and increasing salinity indicate drying trend from 5.8 to 2.5 ka; the aeolian sand sediment and lowest EM2 and lowest PCA-1 scores indicate driest environment from 2.5 to 0.8 ka; and lacustrine facies and finest grain size indicate relative humid environment during the ‘Little Ice Age’ period. The environment was relative humid in early Holocene, most Humid in mid-Holocene, and dry in mid-late Holocene. The moisture pattern in the hinterland of the Badain Jaran Desert was synchronous with that in the northeastern of Tibetan Plateau, which implies that the groundwater recharge lake was dominated by the intensity of groundwater recharge from monsoon margin area, especially the northeastern of Tibetan Plateau. As a record from groundwater recharge lake without runoff, our study provides the groundwater output quantity record from northeastern of Tibetan Plateau and would benefit the environment change research and regional water resources allocation around the Tibetan Plateau.

Light detection and ranging (LiDAR) is considered as an essential part of the sensor package for future star technologies such as Advanced Driver Assistance Systems (ADAS) and Simultaneous Localization and Mapping (SLAM). Meanwhile, Single-Photon Avalanche Diode (SPAD) is a very attractive choice as light detectors in LiDARs because of its high sensitivity. LiDARs often need to work in adversary environments such as fog, rain, snow or haze; therefore, advanced signal processing is needed to overcome those difficulties. It is potentially very helpful if LiDAR signal processing can take into considerations of properties of SPADs used as photon detectors. In this paper, three special phenomena associated with specific properties of SPADs are described, and ways of exploiting phenomena for improving the performance of signal detection are explained. Preliminary simulation and/or experiment results are also provided to illustrate the potentials of these approaches.

The studies of surface dilational rheology are important to detent the nature of adsorption film and the properties of foam. In this paper, the adsorption and dilational rheological properties of branched cationic surfactant hexadecanol polyoxyethylene(3) glycidyl ether ammonium chloride (C16G(EO)3PC) at the air-water interface in the absence and presence of electrolyte (NaCl) were investigated by drop shape analysis. The results show that the surface adsorption layer of C16G(EO)3PC behaves elastic in nature with high value up to 90 mN/m, which indicates that the slow relaxation process plays a main role because of the re-arrangement of long branched alkyl chain. The addition of NaCl will enhance diffusion-exchange process and accelerate the formation of film and decreases dilational elasticity obviously. At low NaCl concentration, the in-film slow relaxation process dominates the nature of film, dilational viscosity decreases with an increase of oscillating frequency. By adding more NaCl, diffusion-exchange process plays the crucial role and dilational viscosity increase as a function of frequency. Moreover, viscosity at high NaCl concentration shows larger value under higher oscillating frequency, indicating the contributions of fast diffusion-exchange process. The elastic adsorption film becomes to be viscoelastic by adding electrolyte.

The landslides often due to the rainfall and the excavation inside. Although both of them could influenced the stability of the slope, in the different combination of the condition of rainfall and excavation. The results would make a big difference from condition. The analysis results of Finite Element Method have a large difference with the actual situation, especially in the large deformation and landslide. Therefore, we use the Distinct Element Method to simulate and analysis the collapse of Zengziya in Chongqing. We collect different parameters to simulate the changed conditions of the combination of rainfall, half excavation and whole excavation. Then we will get the data of displacement of the rock and the stress redistribution of the slope. By the analysis of the those data, and the comparison from the field situation, we will draw a conclusion that the main factors of the landslides is the rainfall, and the excavation sometimes can simulate the landslides. At last, our research results can make some help of the practical engineering.

The Cr/Nd:GLSAG crystal were grown by Czochralski method, its structure and luminescence properties were studied, which show that the luminescence properties of Nd3+ ions were improved by co-doping Cr3+ ions and adjusted by mixed garnet.

Zinc one of the key elements that influence human genetic health, was selectively determined in this paper. In the area of metal elements determination in body fluid, most samples used in the study are blood, plasma and saliva. No literature about genetic fluid determination has been found so far. In this paper the preparation of samples, volume of samples and determination parameters were investigated. An easy reliable method of determining zinc in semen and liquor folliculi was established. The recoveries are 92.0%-107.6%, the detection limit is 0.002 mg x L(-1) and the relative standard deviations (RSD) (n = 5) are 1.3%-10.0%.

5 at%Yb3+:YNbO4 crystal is grown by Czochralski(CZ) method. Its transmission and emission spectra are measured. The absorption peaks are located at 933, 955, 974 and 1003 nm with their corresponding absorbtion cross section values 0.7310-20, 1.8510-20, 0.8610-20 and 0.4410-20 cm2; and the FWHM of 955 nm absorbtion peak is 17 nm. Its emission band centered at 1020 nm with the FWHM is 41 nm, which is over three times that of Yb3+:YAG crystal. The emission cross section values of 955, 974, 1005, 1021 and 1030 nm peaks are calculated to be 0.6910-20, 0.8610-20, 1.8110-20, 1.1110-20 and 0.5710-20 cm2, respectively, and the biggest one is comparable to that of Yb3+:YAG crystal. The laser parameters of 5 at% Yb3+:YNbO4 crystal are evaluated and the results suggest that it is a potential all-solid-state pumped laser crystal in tunable and ultrafast lasers field.

A method to compute the numerical derivative of eigenvalues of parameterized crystal field Hamiltonian matrix is given, based on the numerical derivatives the general iteration methods such as Levenberg–Marquardt, Newton method, and so on, can be used to solve crystal field parameters by fitting to experimental energy levels. With the numerical eigenvalue derivative, a detailed iteration algorithm to compute crystal field parameters by fitting experimental energy levels has also been described. This method is used to compute the crystal parameters of Yb3+ in Sc2O3 crystal, which is prepared by a co-precipitation method and whose structure was refined by Rietveld method. By fitting on the parameters of a simple overlap model of crystal field, the results show that the new method can fit the crystal field energy splitting with fast convergence and good stability.

15at.%Yb3+:Gd2SiO5 crystal with a size of30 mm75 mm is grown by the Czochralski method, and its lattice parameters, atom coordinates and temperature factors are determined by the full-profile Rietveld refinement method. Its spectral parameters of oscillator strength, line strength, transition probability, energy lifetime and integral emission cross-section for Yb3+2F7/22F5/2 transition are calculated using the absorption spectraum. And the laser performance evaluation shows that this crystal is a potential laser crystal with relatively high threshold, and could be used as a medium of tunable or ultra-fast laser pumped by high-power laser diode.