Objective: It is well known that residual cortical cerebral blood flow plays a pivotal role in the pathophysiology of cerebral ischemia and can influence the outcome of recanalization therapy. This ...study examined the impact of residual cortical cerebral blood flow on the neuroprotective efficacy of human albumin in a rat transient cerebral ischemia model.
Methods: Sprague-Dawley rats were subjected to 2 hour middle cerebral artery occlusion. According to different magnitudes of residual cortical cerebral blood flow during cerebral ischemia, rats were divided into three groups: Group I, cerebral blood flow <25% of the baseline; Group II, cerebral blood flow between 25 and 50% of the baseline; Group III, cerebral blood flow >50% of the baseline. The infarct volume and brain swelling were observed after 48 hours of reperfusion. Neurological scores and motor function were also evaluated.
Results: After 2 days of reperfusion, human albumin therapy significantly (p<0.01) reduced total infarct volume and improved the neurological and motor function compared with the stroke group only in Group II. In Group I and in Group III, whether human albumin was administered or not, rats in Group I always showed a poor outcome and rats in Group III always showed an excellent outcome.
Conclusion: Our study suggests that human albumin has neuroprotection in acute stroke treatment only within a magnitude range of residual cortical cerebral blood flow during ischemia.
Grazing exclusion using fences is a key policy being applied by the Chinese government to rehabilitate degraded grasslands on the Tibetan Plateau (TP) and elsewhere. However, there is a limited ...understanding of the effects of grazing exclusion on alpine ecosystem functions and services and its impacts on herders’ livelihoods. Our meta-analyses and questionnaire-based surveys revealed that grazing exclusion with fences was effective in promoting aboveground vegetation growth for up to four years in degraded alpine meadows and for up to eight years in the alpine steppes of the TP. Longer-term fencing did not bring any ecological and economic benefits. We also found that fencing hindered wildlife movement, increased grazing pressure in unfenced areas, lowered the satisfaction of herders, and rendered substantial financial costs to both regional and national governments. We recommend that traditional free grazing should be encouraged if applicable, short-term fencing (for 4–8 years) should be adopted in severely degraded grasslands, and fencing should be avoided in key wildlife habitat areas, especially the protected large mammal species.
•The key soot dynamics processes affecting the SVF were studied.•NH3 addition inhibits the soot formation in the ethylene laminar diffusion flame.•NH3 addition reduces soot inception, surface growth ...and oxidation rate.•The inhibited surface growth caused by NH3 dominates the inhibition of soot formation.•The inhibition of the HACA reaction is the main reason for the reduced soot formation.
Ammonia, as an alternative fuel, is attracting unprecedented attention due to the absence of CO2 emission during its combustion. Effects of ammonia co-firing on soot formation in ethylene laminar diffusion flames have been studied in the first part of this series of papers, addressing the soot volume fraction change and reaction kinetics of gaseous soot precursors. This paper further investigates the effect of ammonia on evolution behaviors of soot particle, namely soot inception, growth and oxidation in the ethylene co-flow diffusion flame. The soot volume fraction (SVF) and spatial distribution in flames without/with ammonia addition (5 and 20 vol%) were measured using laser-induced incandescence (LII) method. A newly constructed C2H4/NH3/PAHs kinetic model consisting of 163 components and 1018 reactions and the CoFlame codes dedicated to simulating laminar co-flow diffusion flame coupled with fixed sectional soot particle model were used to model the flames and soot inception, surface growth, and oxidation processes in them. Numerical results well captured the experimental observation on both peak SVF and flame height, and confirmed that ammonia inhibited the soot formation in the flame, showing a peak SVF decrease of 2–4 % per 1 % ammonia addition. The numerical results revealed that the ammonia addition inhibited all soot inception, surface growth via HACA (hydrogen-abstraction-acetylene-addition) and PAH condensation, and oxidation via OH/O2 processes. Most importantly, inhibition of HACA reactions induced by ammonia was identified as the main reason for reducing soot formation. Kinetic analysis revealed that adding ammonia created a new pathway to consume H radical while decreasing the rate of H radical-generating reactions, leading to a decrease in H radical and ultimately a reduction in the HACA reaction rate.
The morphological characteristics and nanostructure of soot particles in pure n-heptane (C7H16) and n-heptane/ammonia co-flow diffusion flames were analyzed and compared using thermophoretic sampling ...and transmission electron microscopy (TEM) observation combining with quantitative image information extraction methods. The results showed that the overall formation and evolution of soot particles in NH3-doped n-heptane flames along the flame centerline were similar with that without NH3-doping. However, compared to n-heptane flame, the peak average diameter of primary soot particles and the peak gyration radius of soot aggregates in NH3-doped flames were reduced by about 45% and 37%, respectively, which indicated that the growth of both primary soot particles via surface reaction/condensation and soot aggregates via coagulation were significantly decreased. Meanwhile, the fractal dimension of soot aggregates was lower with NH3 addition as the structure of soot aggregates was looser and tended to be more chain-like. After NH3 doping, the peak average fringe length inside soot particles was decreased by 13%, and the inter-fringe spacing and tortuosity of soot were increased by 8% and 3%, respectively. This represented a more disordered microcrystal structure and lower degree of graphitization of soot particles, meaningfully indicating a higher oxidation reactivity.
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•The morphological characteristics and nanostructure of soot in n-heptane/ammonia flames were first studied.•Ammonia addition reduced the size of both primary soot particles and soot aggregates.•The structure of soot aggregates was looser and tended to be more chain-like after ammonia blending.•The microcrystal structure of soot particles might be more disordered and easier to be oxidized with ammonia addition.
Sodium‐ion batteries (SIBs) with fast‐charge capability and long lifespan could be applied in various sustainable energy storage systems, from personal devices to grid storage. Inspired by the ...disordered Rubik's cube, here, we report that the high‐entropy (HE) concept can lead to a very substantial improvement in the sodium storage properties of hexacyanoferrate (HCF). An example of HE‐HCF has been synthesized as a proof of concept, which has achieved impressive cycling stability over 50 000 cycles and an outstanding fast‐charging capability up to 75 C. Remarkable air stability and all‐climate performance are observed. Its quasi‐zero‐strain reaction mechanism and high sodium diffusion coefficient have been measured and analyzed by multiple in situ techniques and density functional theory calculations. This strategy provides new insights into the development of advanced electrodes and provides the opportunity to tune electrochemical performance by tailoring the atomic composition.
Sodium‐ion batteries with fast‐charge capability and long lifespan could be applied in various sustainable energy storage systems, from personal devices to grid storage. Inspired by the disordered Rubik's cube, herein, Peng et al. report that the high‐entropy concept can lead to a very substantial improvement in the sodium storage properties of hexacyanoferrate. which has achieved impressive cycling stability over 50 000 cycles
Growth of dendrites, the low plating/stripping efficiency of Zn anodes, and the high freezing point of aqueous electrolytes hinder the practical application of aqueous Zn‐ion batteries. Here, a ...zwitterionic osmolyte‐based molecular crowding electrolyte is presented, by adding betaine (Bet, a by‐product from beet plant) to the aqueous electrolyte, to solve the abovementioned problems. Substantive verification tests, density functional theory calculations, and ab initio molecular dynamics simulations consistently reveal that side reactions and growth of Zn dendrites are restrained because Bet can break Zn2+ solvation and regulate oriented 2D Zn2+ deposition. The Bet/ZnSO4 electrolyte enables superior reversibility in a Zn–Cu half‐cell to achieve a high Coulombic efficiency >99.9% for 900 cycles (≈1800 h), and dendrite‐free Zn plating/stripping in Zn–Zn cells for 4235 h at 0.5 mA cm−2 and 0.5 mAh cm−2. Furthermore, a high concentration of Bet lowers the freezing point of the electrolyte to −92 °C via the molecular‐crowding effect, which ensures the stable operation of the aqueous batteries at −30 °C. This innovative concept of such a molecular crowding electrolyte will inject new vitality into the development of multifunctional aqueous electrolytes.
A molecular crowding electrolyte is developed for aqueous Zn‐ion batteries. Betaine in the electrolyte can regulate the solvation sheath of Zn2+ and adsorb on the Zn anode to guide the dendrite‐free deposition of Zn2+. A high concentration of betaine breaks the H‐bond between H2O, which keeps the Zn anode stable in a wide temperature range from −30 to 60 °C.
Co-firing ammonia in coal-fired utility boilers is a promising de-carbon technical route for power stations, yet currently, there is still no information on how co-firing ammonia would affect the ...release and conversion of volatiles. Here, coal pellets were burned with/without ammonia co-firing on a flat-flame burner facility in both fuel-lean and -rich conditions. Detailed information on time-resolved evolution of volatile flame, size evolution of soot particles in flame, and changes in their physiochemical structures was obtained. It was observed that co-firing ammonia promoted devolatilization of coal and release of volatiles, leading to an earlier ignition moment in both fuel-lean and -rich conditions. In the flame, massive soot particles were formed from volatiles, and co-firing ammonia affected the conversion of volatiles into soot and changed the flame radiation properties. Interestingly, both the number density of all soot and size of primary soot particles increased after co-firing ammonia in fuel-lean conditions (by 2.5 times and ∼10 nm, respectively), while they decreased in fuel-rich conditions. In fuel-lean conditions, co-firing ammonia promoted inception and surface growth of soot due to competitive consumption of O2 and increased flame temperature, while in fuel-rich conditions, these effects were offset by partial consumption of soot precursors by forming nitrogen-containing species. Furthermore, when ammonia was co-fired, fringe length, tortuosity, and especially inter-fringe spacing of soot increased slightly, indicating that particles formed in co-firing flames might show higher oxidation reactivity than those formed without ammonia co-firing.
TiO2‐based materials are considered to be the promising anodes of sodium‐ion batteries (NIBs) because of their high safety and good stability. However, their low specific capacity and high safety ...operating voltage plateau impose a severe challenge for high energy density batteries. Herein, interconnected micro‐sheets consisting of carbon nanotubes and sulfur doped TiO2 (CNT/S‐TiO2) are synthesized via an ultrasonic process and subsequent calcination, enabling the fabrication of high‐performance material. The utilization of SWCNT overcomes the structure instabilities during electrode preparation of thick electrodes. The incorporation of SWCNT and sulfur dopants in the CNT/S‐TiO2 composite not only enhances conductivity but also improves ion transport dynamics, resulting in rapid charge delivery and high specific capacity at the thick electrode level. Consequently, CNT/S‐TiO2 demonstrates excellent rate performance (from 0.3 to 15 C, with 72.4% capacity retention) and long cycling stability (10000 cycles at a load of 1.96 mg cm−2). More importantly, the high S‐TiO2 content (90%) in the thick electrode (21.2 mg cm−2) achieves a high areal capacity retention of 3.4 mA h cm−2 after 100 cycles, which surpasses the actual application requirements.
To meet the demand for high areal capacity of TiO2‐based anodes in sodium‐ion batteries, it is particularly important to establish thick electrodes. The hierarchical structure of CNT/S‐TiO2 micro‐sheet greatly enhances the mass conductivity of the electrode. Thick electrodes made of CNT/S‐TiO2 show better ion transport capability, while ensuring fast electron transport.
Over the last century, anthropogenic activities have increased nitrogen (N) deposition considerably, which significantly affects ecosystem processes and has the potential to induce N saturation in ...the future. The continuous increase in N deposition may cause a non-linear response in soil respiration (Rs), an important component of carbon (C) cycling. However, little is known about N saturation threshold of soil respiration. In this study, we conducted coordinated experiments in four grassland types across northern China with four N addition levels to explore patterns in the Rs saturation threshold. Our results showed that an Rs saturation threshold generally exists in grassland ecosystems in response to N addition gradients. The N saturation threshold of Rs occurred at an average rate of 50 kg N ha⁻¹ yr⁻¹, but varied widely with grassland type; the N saturation threshold occurred at rates of 100, 50, 50, and 25 kg N ha⁻¹ - yr⁻¹ in the alpine meadow, meadow steppe, typical steppe, and desert steppe, respectively. Autotrophic respiration (Ra) and heterotrophic respiration (Rh) responded to N addition gradients differently. Ra increased initially and became saturated at a rate of 50 kg N ha⁻¹ yr⁻¹ and declined thereafter. In contrast, Rh decreased monotonically after N addition. Structural equation models further confirmed that the effects of N addition gradients on Rs were primarily determined by the non-linear response of belowground biomass. Interestingly, the compiled global dataset showed that the N saturation threshold of Rs increased with precipitation and soil moisture. These findings indicate that the stimulating effect of N deposition on Rs and Ra might diminish with increasing N deposition in the future, especially in dry grassland ecosystems.
•Coal was burned in low O2 (∼6.7%) atmosphere formed via gas fuel combustion.•Soot micromorphology and graphitization degree evolution in flame was characterized.•Oxidation reactivity of the soot ...changed non-linearly along the flame centerline.•Soot reactivity was controlled by firstly graphitization and then aggregate size.
Combustion experiments of a bituminous coal were performed on a flat-flame burner that provided a realistic low-O2 combustion atmosphere. Soot samplings were performed via both thermophoresis and dilution-filtering sampling methods along the flame centerline. The morphology, size, fractional- and nanostructure evolution, and especially the detailed oxidation characteristics of soot of different maturities in flame were comprehensively characterized. Results showed that liquidus tar was formed in the flame bottom which acted as soot precursor, and a direct evidence was obtained that the solid soot particles in the coal flame were mostly derived from the liquidous tar via carbonization. In the nanostructure of the mature soot particles, both of fullerenic, amorphous and diamond phases were detected, indicating a multiple nucleation process during the soot formation in coal flame. Furthermore, it was found that soot in the bright flame core was more difficult to be oxidized than the soot upstream and downstream it. And finally based on the Raman spectrum and particle micromorphology analysis, the non-linear change of the oxidation reactivity of the soot along the flame centerline was revealed to be controlled firstly by the gradual graphitization with increasing of the flame temperature and then by the change of soot aggregate size.
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