Based on pollen data from 30 sequences reviewed here, we reconstruct the spatial and temporal variations in temperature and in aridity that occurred during the Holocene in the Altai Mountains and the ...surrounding areas (i.e., the examined area). The synthesized regionally-averaged temperature-index curves from low-elevation regions show that the climate was consistently warming from ~12,000 to ~9000 cal. yr BP and has experienced a gradual cooling trend since ~9000 cal. yr BP. It means that the Holocene temperature trend in low-elevation regions of the examined area has sensitively responded to variations in the total solar irradiance. The synthesized regionally-averaged aridity-index curve exhibits a persistent wetting trend during the Holocene in low-elevation regions. The deduced Holocene precipitation-index variations suggest that the Holocene wetting trend resulted from a combined effect of temperature decreasing and precipitation increasing. The Holocene precipitation increase seems to be associated with the Holocene AMO-like (i.e., Atlantic centennial oscillations) events in the North Atlantic Ocean. However, the early-Holocene variations of temperature and aridity in high-elevation regions were significantly deviated from the variations in low-elevation regions and this deviation was probably a result of permafrost thawing at higher elevations.
•Temperature index in low-elevation regions has sensitively responded to variations in total solar irradiance;•Aridity index exhibits a wetting trend in low-elevation regions;•Wetting trend resulted from a combined effect of temperature decreasing and precipitation increasing;•Early-Holocene temperature and aridity in high-elevation region were affected by permafrost thawing.
Based on pollen data of 274 samples from a 550-cm core at Kelashazi Peat in the southern Altai Mountains within China, we reconstructed the Holocene vegetation dynamics and climatic change. The ...pollen assemblages and the associated biome scores indicate that the vegetation in Kelashazi valley was dominated by alpine meadows during the early Holocene (before ~8.2 cal. kyr BP) and by taiga forests in the middle Holocene (~8.2-~5.6 cal. kyr BP) that was followed by an expansion of alpine meadows (~5.6-~3.2 cal. kyr BP). The pollen-based temperature index-indicated thermal maximum lasting from ~8.0 to ~5.6 cal. kyr BP was consistent with temperature stack for 60–30°N and the later onset warming at Kelashazi Peat was associated with the cooling influence of remnant ice sheets in the early Holocene. The pollen-based increasing moisture index curve from Kelashazi Peat is in a good agreement with the synthesized decreasing aridity index curve in low-elevation regions of the Altai Mountains and the surrounding areas during the data-overlapping period between ~12.0 and ~3.2 cal. kyr BP. The Holocene wetting trend at Kelashazi Peat might have resulted not only from the increasing trend of NAO-related winter precipitation but also from the increasing trend of AMO-modulated summer precipitation.
•Holocene vegetation and climate changes was reconstructed in the southern Altai Mountains.•Thermal maximum was consistent with temperature stack for 60–30°N.•Moisture reconstruction is consistent with synthesized Holocene aridity index in low-elevation regions.•Holocene wetting trend have resulted from the increasing trends of NAO-related winter precipitation and AMO-related summer precipitation.
A model of coupled molecular biochemical oscillators is proposed to study non-equilibrium thermodynamics of synchronization. Under general considerations, we find that chemical interactions within an ...ensemble of autonomous oscillators break detailed balance and thus cost energy. This extra energy cost, in addition to the energy dissipated for driving each individual oscillator, is necessary to power the coupling interactions such as oscillator–oscillator exchange reactions, which are responsible for correcting the phase error in each individual noisy oscillator with respect to the collective oscillation of the whole ensemble. By solving the steady-state distribution of the many-oscillator system analytically and numerically, we show that the system reaches its synchronized state through a non-equilibrium phase transition as energy dissipation increases. The critical energy dissipation per period depends on both the frequency and strength of the exchange reaction, which reveals an optimal (efficient) design for achieving maximum synchronization with a fixed energy budget. We apply our general theory to the Kai system in the cyanobacterial circadian clock and predict a relationship between the KaiC ATPase activity and synchronization of the KaiC hexamers. The theoretical framework established here can be extended to study thermodynamics of collective behaviours in other non-equilibrium active systems.The energy cost for the synchronization of biochemical oscillators is determined under general conditions. This framework reveals a relationship between the KaiC ATPase activity and the synchronization of the KaiC hexamers.
High nucleation density diamond films were grown on silicon substrates with a high-density nano-diamond suspension crystal seed. By keeping other parameters constant and varying the amounts of oxygen ...and nitrogen added, diamond films were grown using MPCVD equipment. The composition, structure, and properties of the diamond films were characterized using X-ray diffraction, Raman spectroscopy, and scanning electron microscopy. The results show that the average grain size of samples grown with added oxygen and nitrogen as assisting gases significantly decreased, exhibiting improved crystallinity and fewer defects. However, there was a certain increase in the relative content of graphite, along with the presence of trans-polyacetylene. Furthermore, as the ratio of oxygen to nitrogen increased, the samples exhibited better crystallinity, fewer defects, and overall higher growth quality. The relative content of graphite initially increased, then decreased, and increased again.
•High nucleation density diamond films were grown on silicon substrates with a high-density nano-diamond suspension crystal seed.•The results show that the average grain size of samples grown with added oxygen and nitrogen as assisting gases significantly decreased, exhibiting improved crystallinity and fewer defects.•However, there was a certain increase in the relative content of graphite, along with the presence of trans-polyacetylene.•Furthermore, as the ratio of oxygen to nitrogen increased, the samples exhibited better crystallinity, fewer defects, and overall higher growth quality.•The relative content of graphite initially increased, then decreased, and increased again.
A wideband mono‐cone antenna is proposed. Evolution from a top‐loaded mono‐cone, the top plate is etched by two rings and loaded by an array of resistors and inductors. This design improves impedance ...matching properties in the low frequency range while maintaining a compact size. An equivalent circuit modal is built for assisting the antenna design. A prototype is fabricated and measured for verification. The antenna operates in the frequency band of 118–1100 MHz with |S11|≤‐10 dB and the fluctuation of omni‐directional radiation pattern ≤ 2.5 dB. The occupied area of the antenna is 0.24 λL × 0.24 λL × 0.06 λL, which is attractive for use on aircraft.
Abstract
Oxygen evolution reaction catalysts capable of working efficiently in acidic media are highly demanded for the commercialization of proton exchange membrane water electrolysis. Herein, we ...report a Zn-doped RuO
2
nanowire array electrocatalyst with outstanding catalytic performance for the oxygen evolution reaction under acidic conditions. Overpotentials as low as 173, 304, and 373 mV are achieved at 10, 500, and 1000 mA cm
−2
, respectively, with robust stability reaching to 1000 h at 10 mA cm
−2
. Experimental and theoretical investigations establish a clear synergistic effect of Zn dopants and oxygen vacancies on regulating the binding configurations of oxygenated adsorbates on the active centers, which then enables an alternative Ru−Zn dual-site oxide path of the reaction. Due to the change of reaction pathways, the energy barrier of rate-determining step is reduced, and the over-oxidation of Ru active sites is alleviated. As a result, the catalytic activity and stability are significantly enhanced.
The north-south migration of prevailing westerly system shapes the seasonality of modern precipitation in Arid Central Asia (ACA). The temperate continental climate with warm-season precipitation ...dominates the northern ACA and the Mediterranean climate with cold-season precipitation dominates the southern ACA. However, the north-south contrasts of precipitation/moisture for longer time scales remain unknown. In this study, we quantitatively reconstructed the precipitation sequence covering the past ~14.4 cal. kyr BP based on pollen data obtained from Shayan loess section in southern ACA using MAT (Modern Analogue Technique) method. Our reconstruction shows that the precipitation had an increasing trend from ~14.4 to ~8.2 cal. kyr BP and a decreasing trend from ~8.2 to ~1.5 cal. kyr BP with the past 1500 years being characterized by an averagely high precipitation. The precipitation trend in southern ACA was rather different from that in northern ACA where the precipitation has increased more or less constantly since the late deglaciation. The contrast between southern and northern ACA appears to have been associated with the south-north migration of westerlies that was accompanied with alterations of NAO (North Atlantic Oscillation) phases and also with changes in strengths of Siberian High and ENSO (El Nino-southern Oscillation).
•Pollen-based precipitation since ~14.4 cal. kyr BP was reconstructed using MAT method in southern ACA .•Last-deglacial precipitation trend in southern ACA was different from that in northern ACA.•Contrast between southern and northern ACA is associated with the westerlies, NAO phases, Siberian High and ENSO.
This study reconstructed the vegetation dynamics and associated climate change of the past ~4100 years based on the pollen data from a short peat core (i.e., KLSZ-2) in Kelashazi Peat (48.12°N, ...88.37°E, 2422 m a.s.l.) in the Altai Mountains. The reconstructed vegetation and climate were then stacked with those from a longer peat core (i.e., KLSZ-1) to evaluate the vegetation dynamics and associated climate change of the entire Holocene and to examine the δ13Ccellulose- and δ18Ocellulose-based temperature reconstructions in the same peat. This study shows that vegetation in Kelashazi valley was dominated by alpine meadows before ~8200 cal. yr BP, by taiga forests at ~8200-~5600 cal. yr BP, and by an expansion of alpine meadows since ~5600 cal. yr BP. This study also examined the vegetation dynamics and associated climate in the context of the entire Altai Mountains and the surrounding areas. Our examination suggests that the forest expansion in high elevations was initiated when the temperature reached a threshold level during the early Holocene, and the forest expansion in low elevations (i.e., below the down treeline) was initiated when the moisture reached a threshold level during the middle Holocene or even late Holocene. It is also notable that the forest expansion at low elevations appears to have been longitude-dependent, i.e., time transgressive eastward. A possible mechanism to explain the longitude-dependency is that a gradual shrinking trend of the Siberian High linked to the Holocene increase in winter insolation allowed the domination of the water vapor-enriched Westerlies to gradually encroach eastward.
•Late Holocene vegetation changes were reconstructed in the southern Altai Mountains.•Holocene forest expansion at high elevations was initiated by threshold-level temperature.•Holocene forest expansion at low elevations was initiated by threshold-level moisture.•Forest expansion at low elevations appears longitude-dependent.
In this study, the pea protein isolates were mixed with l-cysteine and then extruded under the temperature of 169 °C and a moisture content of 54% conditions. The effect of l-cysteine (0, 0.03, 0.06, ...0.09, 0.12, 0.15% (w/w)) addition on the functional and structural properties of texturized pea protein was studied. The results showed that water holding capacity descended but oil holding capacity and nitrogen solubility index increased since the hydrophobic group of pea protein was exposed during the high-moisture extrusion. l-cysteine significantly affected the textural properties and fibrous degree of texturized pea protein by changing the cross-linking effect on the disulfide bonds between pea protein molecules. However, l-cysteine would have a negative effect on the fibrous structure when the addition amount exceeded 0.09%. The unstable α-helical structure in the protein secondary structure was transformed into a relatively stable β-sheet by fourier transform infrared spectroscopy. The content of sulfhydryl group decreased due to oxidation reaction during extrusion, which was conducive to the formation of disulfide bond, and the protein rearranged to form a more robust new chemical cross-linking in the die. The extruded pea protein had a dense structure, and the lamellar fiber orientation was obvious according to the observation of scanning electron microscope. It was expected to provide a reference for the development and utilization of pea protein, broaden the research of pea protein high-moisture extrusion technology, and improve the quality of extruded pea protein.
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•l-cysteine modified pea protein isolate in high moisture extrusion.•Excessive L-cysteine (>0.09%) addition would have a negative effect on the functional properties and fibrous structure.•The fiber structure formation mechanism of l-cysteine modified-pea protein isolate was characterized from multi-scale.
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