Coupled effects of climate change and human activities on vegetation dynamics in the Southwestern Alpine Canyon Region of China

The driving effects of climate change and human activities on vegetation change have always been a focal point of research.However,the coupling mechanisms of these driving factors across different temporal and spatial scales remain controversial.The Southwestern Alpine Canyon Region of China(SACR),as an ecologically fragile area,is highly sensitive to the impacts of climate change and human activities.This study constructed a vegetation cover dataset for the SACR based on the Enhanced Vegetation Index(EVI)from 2000 to 2020.Spatial autocorrelation,Theil-Sen trend,and Mann-Kendall tests were used to analyze the spatiotemporal characteristics of vegetation cover changes.The main drivers of spatial heterogeneity in vegetation cover were identified using the optimal parameter geographic detector,and an improved residual analysis model was employed to quantify the relative contributions of climate change and human activities to interannual vegetation cover changes.The main findings are as follows:Spatially,vegetation cover exceeds 60%in most areas,especially in the southern part of the study area.However,the border area between Linzhi and Changdu exhibits lower vegetation cover.Climate factors are the primary drivers of spatial heterogeneity in vegetation cover,with temperature having the most significant influence,as indicated by its q-value,which far exceeds that of other factors.Additionally,the interaction q-value between the two factors significantly increases,showing a relationship of bivariate enhancement and nonlinear enhancement.In terms of temporal changes,vegetation cover shows an overall improving trend from 2000 to 2020,with significant increases observed in 68.93%of the study area.Among these,human activities are the main factors driving vegetation cover change,with a relative contribution rate of 41.31%,while climate change and residual factors contribute 35.66%and 23.53%,respectively.By thoroughly exploring the coupled mechanisms of vegetation change,this study provides important references for the sustainable management and conservation of the vegetation ecosystem in the SACR.

Solar energy‐driven C−H activation of methanol for direct C−C coupling to ethylene glycol with high stability by nitrogen doped tantalum oxide

Direct photocatalytic coupling of methanol to ethylene glycol(EG)is highly attractive.The reported photocatalysts for this reaction are all metal sulfide semiconductors,which may suffer from photocorrosion and have low stability.Thus,the development of non‐sulfide photocatalysts for efficient photocatalytic coupling of methanol to EG and H2 with high stability is urgent but extremely challenging.Herein,the first metal oxide photocatalyst,tantalum‐based semiconductor,is reported for preferential activation of C−H bond within methanol to form hydroxymethyl radical(•CH_(2)OH)and subsequent C−C coupling to EG.Compared with other metal oxide photocatalysts,such as TiO2,ZnO,WO_(3),Nb_(2)O_(5),tantalum oxide(Ta_(2)O_(5))is unique in that it can realize the selective photocatalytic coupling of methanol to EG.The co‐catalyst free nitrogen doped tantalum oxide(2%N‐Ta_(2)O_(5))shows an EG formation rate as high as 4.0 mmol gcat−1 h−1,about 9 times higher than that of Ta_(2)O_(5),with a selectivity higher than 70%.The high charge separation ability of nitrogen doped tantalum oxide plays a key role in its high activity for EG production.This catalyst also shows excellent stability longer than 160 h,which has not been achieved over the reported metal sulfide photocatalysts.Tantalum‐based photocatalyst is an environmentally friendly and highly stable candidate for photocatalytic coupling of methanol to EG.

Ultrasonic Activation of Suzuki and Hiyama Cross-Coupling Reactions Catalyzed by Palladium

The coupling reaction of aryl bromide and aryl boronic acid in water/DMF as solvent was studied using a palladium-complex as a catalyst in the presence of ultrasound at room temperature. The effect on the reaction of a base and a solvent was also studied with and without ultrasound and was found to increase the speed of the reaction. In this regard, we propose reaction mechanisms that could explain the results obtained.

Effect of activated carbon support on CS_2 removal over coupling catalysts

Supported coupling catalysts for CS2 removal were prepared with different activated carbons originated from wood,coconut shell and coal as supports,and their catalytic activities for CS2 removal were tested at ambient temperature.The textural and surface properties of the activated carbons were characterized by nitrogen adsorption,temperature-programmed desorption（TPD）and Boehm titration.The activated carbon support with meso-and macropores,and oxygen-functional groups performs higher CS2 removal ability at ambient temperature.The effects of flow rate,CS2 inlet concentration,temperature and relative humidity on CS2 removal were also investigated.High efficient removal is obtained at temperature of 50-C,space velocity of 2000 h-1,inlet CS2 concentration of 500 mgS/m3 and relative humidity of 20%with the breakthrough sulfur capacity up to 4.3 gS/gCat and working sulfur capacity up to 7 gS/gCat.

Physico-Chemical Properties and Enzyme Activities of the Arable Soils in Lhasa,Tibet,China

An understanding of the physical,chemical,and biological properties of a soil provides a basis for soil use and management.This paper reports the major physico-chemical properties and enzyme activities of the soils of Lhasa's main arable lands and the factors that influence these soil properties.Composite and core samples were taken from the three main arable soil types(alluvial soil,subalpine arable steppe soil,and subalpine arable meadow soil) and were analysed using standard methods.The bulk density and the ventilation porosity ratio of the soils were close to the recommended values for arable lands,and the dominant soil texture was sandy.The soil moisture release rates were arable steppe soil > alluvial soil > arable meadow soil.Soil organic matter content,Cation-Exchange Capacity(CEC),total and available nitrogen content,and catalase activity of the arable meadow soil were higher than those of the alluvial and the arable steppe soils,while soil pH in the arable meadow was lower.Most of the measured properties did not show a significant variance among these three soils.However,the measured indices(apart from the total potassium) indicate that there are notable differences among the three types of soil.The results implied that the utilisation patterns of the arable soil or human activities,such as tillage practices and fertiliser applications,have a substantialeffect on the soil properties in this region.Our results suggest that the cultivation practices in the region have apparently positive impact on the soil organic matter,nutrient contents and bulk density probably due to the sound fertiliser management such as the applications of farmyard manure and chemical fertilisers.However,intense cultivation practices lowered the activity of most soil enzymes.The results demonstrate that the choice of soil management strategy had a significant impact on the soil physicochemical and biological properties in the region studied.

Influence of alkali metal doping on surface properties and catalytic activity/selectivity of CaO catalysts in oxidative coupling of methane

Surface properties （viz. surface area, basicity/base strength distribution, and crystal phases） of alkali metal doped CaO （alkali metal/Ca= 0.1 and 0.4） catalysts and their catalytic activity/selectivity in oxidative coupling of methane （OCM） to higher hydrocarbons at different reaction conditions （viz. temperature, 700 and 750 ℃; CH4/O2 ratio, 4.0 and 8.0 and space velocity, 5140-20550 cm^3 ·g^-1·h^-1） have been investigated. The influence of catalyst calcination temperature on the activity/selectivity has also been investigated. The surface properties （viz. surface area, basicity/base strength distribution） and catalytic activity/selectivity of the alkali metal doped CaO catalysts are strongly influenced by the alkali metal promoter and its concentration in the alkali metal doped CaO catalysts. An addition of alkali metal promoter to CaO results in a large decrease in the surface area but a large increase in the surface basicity （strong basic sites） and the C2＋ selectivity and yield of the catalysts in the OCM process. The activity and selectivity are strongly influenced by the catalyst calcination temperature. No direct relationship between surface basicity and catalytic activity/selectivity has been observed. Among the alkali metal doped CaO catalysts, Na-CaO （Na/Ca = 0.1, before calcination） catalyst （calcined at 750 ℃）, showed best performance （C2＋ selectivity of 68.8% with 24.7% methane conversion）, whereas the poorest performance was shown by the Rb-CaO catalyst in the OCM process.

INVESTIGATION OF ACTIVE CONTROL FOR DYNAMIC STABILITY OF HELICOPTER ROTOR－BODY COUPLING

A study is conducted on the feasibility of helicopter ground and air resonanceby using actively controlled tabs mounted at the trailing edge of an aerofoil. A method isdeveloped to obtain the optimal feedback control law through constructing a referencemodel according to requirements of stability levels in the modal space. The effects of rotorspeed and length and location of tabs on the control law are analyzed, and it is found possible that a controller can be designed into constant feedback gain against rotor speed andto feed back only to the dominant system states to eliminate the unstable range of rotorspeed.

Coupling Strength and System Size Induce Firing Activity of Globally Coupled Neural Network

We investigate how firing activity of globally coupled neural network depends on the coupling strength C and system size N. Network elements are described by space-clamped FitzHugh- Nagumo （SCFHN） neurons with the values of parameters at which no firing activity occurs. It is found that for a given appropriate coupling strength, there is an intermediate range of system size where the firing activity of globally coupled SCFHN neural network is induced and enhanced. On the other hand, for a given intermediate system size level, there exists an optimal value of coupling strength such that the intensity of firing activity reaches its maximum. These phenomena imply that the coupling strength and system size play a vital role in firing activity of neural network.

Simulation Study of Passive Rod Diffusion in Active Bath:Nonmonotonic Length Dependence and Abnormal Translation-Rotation Coupling

Diffusion of tracer particles in active bath has attracted extensive attention in recent years.So far,most studies have considered isotropic spherical tracer particles,while the diffusion of anisotropic particles has rarely been involved.Here we investigate the diffusion dynamics of a rigid rod tracer in a bath of active particles by using Langevin dynamics simulations in a two-dimensional space.Particular attention is paid to how the translation(rotation)diffusion coefficient D_(T)(D_(R))change with the length of rod L and active strength Fa.In all cases,we find that rod exhibits superdiffusion behavior in a short time scale and returns to normal diffusion in the long time limit.Both D_(T) and D_(R) increase with Fa,but interestingly,a nonmonotonic dependence of D_(T)(D_(R))on the rod length has been observed.We have also studied the translation-rotation coupling of rod,and interestingly,a negative translation-rotation coupling is observed,indicating that rod diffuses more slowly in the parallel direction compared to that in the perpendicular direction,a counterintuitive phenomenon that would not exist in an equilibrium counterpart system.Moreover,this anomalous(diffusion)behavior is reentrant with the increase of Fa,suggesting two competitive roles played by the active feature of bath particles.

Active oxygen center in oxidative coupling of methane on La_(2)O_(3) catalyst

La_(2)O_(3) catalyzed oxidative coupling of methane(OCM) is a promising process that converts methane directly to valuable C_(2)(ethylene and ethane) products. Our online MS transient study results indicate that pristine surface without carbonate species demonstrates a higher selectivity to C_(2) products, and a lower light-off temperature as well. Further study is focused on carbonate-free La_(2)O_(3) catalyst surface for identification of active oxygen species associated with such products behavior. XPS reveals unique oxygen species with O 1 s binding energy of 531.5 e V correlated with OCM catalytic activity and carbonates removal. However, indicated thermal stability of this species is much higher than the surface peroxide or superoxide structures proposed by earlier computation models. Motivated by experimental results,DFT calculations reveal a new more stable peroxide structure, formed at the subsurface hexacoordinate lattice oxygen sites, with energy 2.18 e V lower than the previous models. The new model of subsurface peroxide provides a perspective for understanding of methyl radicals formation and C_(2) products selectivity in OCM over La_(2)O_(3) catalyst.

Boosting Electrochemical Urea Synthesis via Constructing Ordered Pd–Zn Active Pair

Electrochemical co-reduction of nitrate(NO_(3)^(-))and carbon dioxide(CO_(2))has been widely regarded as a promising route to produce urea under ambient conditions,however the yield rate of urea has remained limited.Here,we report an atomically ordered intermetallic pallium-zinc(PdZn)electrocatalyst comprising a high density of PdZn pairs for boosting urea electrosynthesis.It is found that Pd and Zn are responsible for the adsorption and activation of NO_(3)^(-)and CO_(2),respectively,and thus the co-adsorption and co-activation NO_(3)^(-)and CO_(2) are achieved in ordered PdZn pairs.More importantly,the ordered and well-defined PdZn pairs provide a dual-site geometric structure conducive to the key C-N coupling with a low kinetical barrier,as demonstrated on both operando measurements and theoretical calculations.Consequently,the PdZn electrocatalyst displays excellent performance for the co-reduction to generate urea with a maximum urea Faradaic efficiency of 62.78%and a urea yield rate of 1274.42μg mg^(-1) h^(-1),and the latter is 1.5-fold larger than disordered pairs in PdZn alloys.This work paves new pathways to boost urea electrosynthesis via constructing ordered dual-metal pairs.

Pinacol Coupling Reactions Catalyzed by Active Zinc

Pinacol coupling reactions catalyzed by active zinc revealed high activity and extensive suitability. The efficiency of the reaction was improved apparently owing to decreasing reductive potential of zinc. In addition, the results indicated that the zinc activity has a direct relation to the coupling reactivity compared to untreated zinc or other general active zinc.

Physico-Chemical Quality of Lake Kyoga at Selected Landing Sites and Anthropogenic Activities

Lake Kyoga, one of the great African lakes in Uganda is facing an increasing pressure from human activities yet there is limited information on water quality of the lake. Therefore this study determined selected physico-chemical parameters of Lake Kyoga at some landing sites (Kayei, Acholi inn, Waitumba, Masindi port) and anthropogenic activities (boat dock, waste site, garden, fishing). The parameters included temperature, pH, water flow rate, dissolved oxygen (DO), nitrite (NO2-) and phosphate (PO4-P). The American Public Health Association (APHA) and Water Watch Australia protocols, standard meters, Merck’s rapid test kits and timing of a float were used to measure the parameters. The results showed that the mean temperature, pH, DO, and PO4-P significantly (p 2- levels were within the EPA drinking water guideline of 0.5 mg/l. The orthophosphates (PO4-P) were highest in the waste sites (0.35 mg/l), followed by gardens (0.24 mg/l) and least in the fishing areas (0.12 mg/l). However, phosphates in the form of P2O5 were higher than the EPA standard value (0.5 mg/l) at Kayei (0.55 mg/l) and Acholi inn (0.55 mg/l) landing sites as well as at waste sites (0.80 mg/l) and gardens (0.55 mg/l) pointing to high nutrient (phosphorus) input at these sites. The high concentrations of nitrites in Lake Kyoga at the investigated anthropogenic activities and landing sites plus phosphate amounts close to waste sites and gardens including Kayei and Acholi inn landing sites call for vigilance in protection of Lake Kyoga through optimized planning. Hence, National Environment Management Authority should ensure proper sewage management in Lake Kyoga catchment to avoid discharge of untreated sewage into the lake. The authority should also regulate waste dumping and cultivation around the lake so as to reduce nutrient (phosphorus) enrichment.

Chronic Immune Activation and Sexual Exposure among HIV Serodiscordant Couples in Senegal

Purpose: In Sub-Saharan Africa, an important proportion of incident HIV cases occur among heterosexual serodiscordant couples (HSDC) but the majority of HIV negative partners can remain seronegative. These are called HIV-exposed seronegative (HESN). We aimed to compare immune activation (IA) levels between HESN, their HIV infected counterparts (HIV+ partners) and HIV unexposed uninfected individuals (HIV-neg Controls) and to evaluate the association between sexual exposure to HIV (SEHIV) and IA. Methods: We conducted a cross-sectional study in Dakar, Senegal on 148 participants recruited between November 2013 and February 2014: 40 HIV-neg Controls, 54 HESN and 54 HIV+ Partners. SEHIV was evaluated individually using questionnaires. IA level was measured by plasma level of β2-microglobulin (β2m). Logistic regression was used to estimate odds ratios (OR) and 95% confidence intervals (CI) for the different associations. Results: The median levels of β2m were 1.57 mg/l (IQR: 1.37 - 1.77), 2.14 mg/l (IQR: 1.76 - 2.43) and 2.24 mg/l (IQR: 1.80 - 3.17) for HIV-neg Controls, HESN and HIV+ partners, respectively. After adjustment, HESN had similar levels of IA with HIV+ partners but significantly higher than that of HIV-neg Controls (adjusted OR = 6.28;95% CI: [2.19 - 18.00]). The association between IA and SEHIV was evaluated in the HIV negative individuals. High frequency of SEHIV was associated with a β2m > 2.2 mg/l (OR = 6.56;95% CI: [1.71 - 25.21]);significantly more than median cut off value of >1.81 mg/l. Conclusions: Our study shows that, despite being uninfected with HIV, HESN individuals show a high level of IA, which was depended on the level of SEHIV.

Research on main circuit parameter coupling relationship of single-phase shunt active power filter

There is a certain coupling relationship among the main circuit parameters of a single-phase shunt active power filter(SAPF),which has a great influence on the reasonable selection of various parameter values.By analyzing the calculation methods of the inductance of alternating current(AC)side and the voltage and capacitance values of direct current(DC)side in the existing single/three-phase SAPF main circuit,a specific single-phase SAPF circuit parameter analytical expression was obtained.Aiming at the coupling relationship among the variables in the resulting expression,the model was optimized and analyzed in MATLAB,and a complete set of parameters design scheme was obtained,which ensure the comprehensive optimization target of the post-harmonic content below 2% is compensated under a specific load.The simulation and experimental procedures verify the correctness of the selected parameters.

Multiple Emulsions Able to Be Used for Oral Administration of Active Pharmaceutical Ingredients: Physico-Chemical Parameters Study of Different Phases

Multiple emulsions are of great therapeutic interest especially in the administration of medicines which can be inactivated by digestive enzymes;moreover the researches of formulation not being often easy, a control of the different phases physicochemical parameters would be of great interest in rapid formulations and at low cost. When formulating emulsions, the preliminary tests, also known as formulation tests, constitute a step which can be long and expensive because of the quantity of reagents that can be used. A rigorous methodology could thus be of great interest, which is at the aim of our study which consists of evaluating the physico-chemical parameters of different phases used to make thus multiple emulsions. In our study, physico-chemical parameters such as conductivity, pH, density, viscosity, and surface tension have been studied by direct measurement using equipment and also by means of suitable mounting. The results showed that the pH and the surface tension have an important role in the prediction of the stability of emulsions, these latter must be of the same order of magnitude. For all phases conductivity does not have too much interest apart from helping to determine the type of the emulsion.

Microwave-activated Coupling Reaction on Polyethylene Glycol

The two-step Sonogashira coupling reaction took place rapidly under microwave activation conditions. PEG bound substrates acted as PTC and polymer support as well. Its yields are 80~90% and the products are in high purity.

Mechanistic Study of Palladium-Catalyzed Oxidative C-H/C-H Coupling of Polyfluoroarenes with Simple Arenes

Pd-catalyzed oxidative C-H/C-H coupling reaction is an emerging type of C-H acti- vation reaction, which attracts great interests because both reaction partners do not re- quire pre-functionalization. In the present study, we employed DFT methods to investigate the mechanism of Pd（OAc）2-catalyzed oxidative C-H/C-H coupling of pentafluoroben-zene with benzene. Four possible pathways were examined in the C-H activation part： path A benzene-pentafluorobenzene mechanism （C-H activation of benzene occurs before the C-H activation of pentafluorobenzene）, path B pentafluorobenzene-benzene mechanism （C-H activation of benzene occurs after the C-H activation of pentafluorobenzene）, path C benzene-pentafluorophenylsilver mechanism （C-H activation of benzene and subsequent transmetalation with pentafiuorophenyl silver complex）, path D pentafiuorophenylsilver- benzene mechanism （transmetalation with pentafluorophenyl silver complex and subsequent C-H activation of benzene）. Based on the calculations, the sequences of two C-H activation steps are found to be different in the oxidative couplings of same substrates （i. e. pentafiu- orobenzene and benzene） in different catalytic systems, where the additive Ag salts played a determinant role. In the absence of Ag salts, the energetically favored pathway is path B （i.e. the C-H activation of pentafluorobenzene takes place before the C-H cleavage of benzene）. In contrast, with the aid of Ag salts, the coordination of pentafluorophenylsilver to Pd center could occur easily with a subsequent C-H activation of benzene in the second step, and the second step significantly raises the whole reaction barrier. Alternatively, in the presence of Ag salts, the kinetically preferred mechanism is path C （i. e. the C-H activation of benzene takes place in the first step followed by transmetalation with pentafluorophenyl- silver complex）, which is similar to path A. The calculations are consistent with the H/D exchange experiment and kinetic isotope effects. Thus the present study not only offers a deeper understanding of oxidative C-H/C-H coupling reaction, but also provides helpful insights to further development of more efficient and selective oxidative C-H/C-H coupling reactions.

The Ocean-Atmosphere Coupled Regimes and East Asian Winter Monsoon (EAWM) Activity

In this paper, ocean-atmosphere coupled regimes are identified on the basis of SVD analysis, cluster analysis and composite analysis. The coupled regimes in cold seasons are identified as the clusters of the ocean-atmosphere coupled states in a low dimensional phase space spanned by the first four SVD modes. Three coupled regimes are found. The first two coupled regimes reflect the ENSO episodes and the accompanying PNA patterns. The third regime, i.e., EAWM regime, is characterized by the strong EAWM activity and the specific SST anomaly. The composite analysis gives further evidences to the identification of EAWM regime and also demonstrates the dynamical process of its formation. The anomaly pattern of the tropical Pacific SSTA in the strong EAWM year differs significantly from that of the La Nina year.

Modulation of spontaneous activities in chronically compressed dorsal root ganglion neurons in rats by sympathetic efferent activation

Objective: To study sympathetic-sensory coupling in chronically compressed dorsal root ganglion (DRG) neurons in rats. Methods: In chronically compressed DRG model, the spontaneous activity of single fiber from the injured DRG neuron was recorded, and lumbar sympathetic trunk was electrical stimulated to study the sympathetic modulation of spontaneous activities in injured DRG neurons. Results: Fifty-seven percent of spontaneous active neurons of injured DRG responded to sympathetic stimulation. The responses included simple excitation, excitation followed by inhibition and simple inhibition. The responses enhanced with the increase of sympathetic stimulation time. The responses to sympathetic stimula- tion could be blocked by intravenously injection of phentolamine, a-adrenorecepor antagonist. Fifty-three percent of injured DRG responded to norepinephrine (NE). The responses to NE were similar to those induced by sympathetic stimulation. Conclusion: Sympathetic-sensory coupling is virtually present in chronic compressed DRG neurons. NE released from sympathetic nerve terminals acts on a-adrenorecepor to influence spontaneous activities of injured DRG neurons.