Comparative Gas Exchange of Ulmus crassifolia (Cedar Elm, Ulmaceae) and Ungnadia speciosa (Mexican Buckey, Sapindaceae) at Ambient and Elevated Levels of Light, CO2 and Temperature

Ulmus crassifolia Nutt. (Cedar elm, Ulmaceae) is a tree found in central and east Texas, northern Mexico, east to Florida, and north to southern Missouri and Oklahoma. Ungnadia speciosa Endl. (Mexican-buckeye, Sapindaceae) is a shrub or small tree found in woodlands and savannas of central and western Texas, southern New Mexico and northern Mexico. In central Texas, both species are found in Juniperus ashei/Quercus virginiana woodlands or savannas or also at low density in inter-canopy grassland gaps or patches. Environmental conditions in this area are stressful because of shallow soils, high summer temperatures, and inconsistent low rainfall. Currently, both species have a low density in these areas, and Ulmus crassifolia is usually a tree, while Ungnadia speciosa is a woody understory shrub. This study suggests U. crassifolia and U. speciosa are tolerant or intermediate species, with juveniles starting in shade. Maximum photosynthetic rate (Amax), dark respiration (Rd), intercellular CO2, light saturation (Lsp) and water use efficiency significantly increased when light levels and CO2 concentrations were elevated for both species, but not when temperatures were elevated. Stomatal conductance decreased when the CO2 concentration doubled, but there were few effects from elevated temperature. These findings suggest that U. speciosa and U. crassifolia should be more common and imply that they will have a higher density in a future high CO2 environment.

Physiological plasticity in eucalyptus clones in the vegetative stage contributes to drought tolerance

With the expansion of eucalyptus crops to areas with severe water limitations,physiological studies involving eucalyptus clones to identify those that are tolerant to water stress become important.The objective of this study was to assess morphological and physiological responses by eucalyptus clones subjected to drought stress and rehydration.The experiment consisted of three eucalyptus clones:VC865,I224 and I144 and two water regimes:control and water stress followed by rehydration,with six replicates.Leaf water potential,gas exchange,maximum quantum efficiency of photo systemⅡand plant height and stem diameter were evaluated under drought stress and rehydration.After6 d of rehydration,the number of leaves,leaf area and dry mass of root,leaf,stem and their total were evaluated.All clones showed intense reduction of gas exchange during the drought stress period,and only VC865 and 1144 showed rapid recovery with 3 d of rehydration.Clone 1224 showed greater reduction in height,stem diameter,number of leaves,water potential at midday(Ψ_(w)_(Midday)),and maximum quantum efficiency of photosystemⅡ(F_(v)/F_(m)).Clones VC865and T144 showed lower reductions inΨ_(wMidday)and F_(v)/F_(m) under stress.VC865 had lower reductions in leaf number,leaf area and higher leaf dry mass,while clone I144 had higher height and lower reduction in root dry mass under.Both these clones showed higher water use efficiency with 3d of rehydration.These different phenotypic plasticities gave the clones VC865 and 1144 efficient mechanisms of acclimatization to stress and more drought tolerance,enhancing their greater capacity for recovery after stress,which allowed lower dry mass reduction.Clone 1224,however,was more susceptible to drought stress,undergoing greater physiological damage with only partial recovery during rehydration.

The interplay between leaf water potential and osmotic adjustment on photosynthetic and growth parameters of tropical dry forest trees

Mimosa tenuiflora and Piptadenia stipulacea are commonly accepted as drought-tolerant species but little is known about their response to drought followed by rehydration.Therefore,the interplay between leaf water potential and osmotic adjustment on photo synthetic and growth parameters of these species was examined.A greenhouse study was conducted in a split-plot design with two water conditions in the main plots(control;drought followed by rehydration),and eight sampling times in the subplots(1,4and 7 days of drought,and 1,3,6,12,and 17 days of rehydration).Plant water status and biochemical changes were assessed as well as leaf gas exchange and subsequent growth.Under drought stress,both species maintained a low leaf water potential throughout the day by accumulating compatible solutes,thus allowing a rapid and full recovery of water status when rehydrated.Although these plants minimized water loss by closing their stomata,neither showed stomatal limitations to photosynthesis.The inhibition of this process during drought was possibly related to mesophyll limitations as well as to a reversible downregulation of photo systems,along with adjustments of their stoichiometry.Water deficits also triggered morphological adaptations at the whole plant level,leading to reduced growth,mainly of the shoots in M.tenuiflora and the roots in P.stipulacea.

Effects of water stress on growth phenology photosynthesis and leaf water potential in Stipagrostis ciliata(Desf.)De Winter in North Africa

Stipagrostis ciliata(Desf.)De Winter is a pastoral C4 grass grown in arid regions.This research work focused on assessing the growth of S.ciliata accessions derived from two different climate regions(a wet arid region in the Bou Hedma National Park in the central and southern part of Tunisia(coded as WA),and a dry arid region from the Matmata Mountain in the south of Tunisia(coded as DA))under water stress conditions.Specifically,the study aimed to investigate the phenological and physiological responses of potted S.ciliata seedlings under different water treatments:T_(1)(200 mm/a),T_(2)(150 mm/a),T_(3)(100 mm/a)and T_(4)(50 mm/a).Growth phenology,net photosynthesis(Pn),stomatal conductance(gs),midday leaf water potential(Ψmd),predawn leaf water potential(Ψpd),soil water content(SWC)and soil water potential(Ψs)were observed during the water stress cycle(from December 2016 to November 2017).The obtained results showed that the highest growth potential of the two accessions(WA and DA)was recorded under treatment T_(1).The two accessions responded differently and significantly to water stress.Photosynthetic parameters,such as Pn and gs,decreased sharply under treatments T_(2),T_(3)and T_(4)compared to treatment T_(1).The higher water stress increased the R/S ratio(the ratio of root dry biomass to shoot dry biomass),with values of 1.29 and 2.74 under treatment T_(4)for accessions WA and DA,respectively.Principal component analysis(PCA)was applied,and the separation of S.ciliata accessions on the first two axes of PCA(PC1 and PC2)suggested that accession DA was detected in the negative extremity of PC1 and PC2 under treatments T_(1)and T_(2).This accession was characterized by a high number of spikes.For treatments T_(3)and T_(4),both accessions were detected in the negative extremity of PC1 and PC2.They were characterized by a high root dry biomass.Therefore,S.ciliata accessions responded to water stress by displaying significant changes in their behaviours.Accession WA from the Bou Hedma National Park(wet arid region)showed higher drought tolerance than accession DA from the Matmata Mountain(dry arid region).S.ciliata exhibits a significant adaptation capacity for water limitation and may be an important species for ecosystem restoration.

Technologies and studies of gas exchange in two-stroke aircraft piston engine:A review

The in-cylinder gas exchange process is crucial to the power performance of two-stroke aircraft piston engines,which is easily influenced by complex factors such as high-altitude performance variation and in-cylinder flow characteristics.This paper reviews the development history and characteristics of gas exchange types,as well as the current state of theory and the validation methods of gas exchange technology,while also discusses the trends of cutting-edge technologies in the field.This paper provides a theoretical foundation for the optimization and engineering design of gas exchange systems and,more importantly,points out that the innovation of gas exchange types,the modification of theoretical models,and the technology of variable airflow organization are the key future research directions in this field.

Shade and sapling size influence restoration of Araucaria angustifolia

Toward improving reforestation of Brazilian pine(Araucaria angustifolia),two contrasting sapling sizes in either full sun or in the shade of a mixed plantation and the effect of opening the canopy were evaluated for survival,growth,gas exchange,photosynthetic pigments,and leaf anatomy 18 months after being planted.At 23 months after planting,a partial opening was made in the canopy in the mixed plantation,then the saplings were evaluated again after 2 months for the same morphophysiological traits.After 18 months,saplings planted in the full sun had higher survival,growth,pigments,and photosynthesis compared to the shaded saplings.Large saplings had higher survival and growth compared to the small ones.Shaded leaves were thinner and little differentiation of palisade parenchyma and hypodermis.After opening of the canopy,photo synthetically active radiation was 10 times higher,and the saplings quickly grew in height due to increased photosynthesis.Thus,although the species can tolerate shade,growth in the shade is limited.We recommend that for reforestation purposes of Brazilian pine,large saplings should be selected and planted in the open for better development.

Systemic regulation of photosynthetic function in maize plants at graining stage under a vertically heterogeneous light environment

To cope with a highly heterogeneous light environment,photosynthesis in plants can be regulated systemically.Currently,the majority of studies are carried out with various plants during the vegetative growth period.As the reproductive sink improves photosynthesis,we wondered how photosynthesis is systemically regulated at the reproductive stage under a vertically heterogeneous light environment in the field.Therefore,changes of light intensity within canopy,chlorophyll content,gas exchange,and chlorophyll a fluorescence transient were carefully investigated at the graining stage of maize under various planting densities.In this study,a high planting density of maize drastically reduced the light intensities in the lower canopy,and increased the difference in vertical light distribution within the canopy.With the increase of vertical heterogeneity,chlorophyll content,light-saturated photosynthetic rate and the quantum yield of electron transport in the ear leaf(EL) and the fourth leaf below the ear(FLBE) were decreased gradually,and the ranges of declines in these parameters were larger at FLBE than those at EL.Leaves in the lower canopy were shaded artificially to further test these results.Partial shading(PS) resulted in a vertically heterogeneous light environment and enhanced the differences in photosynthetic characteristics between EL and FLBE.Removing the tassel and top leaves(RTL) not only improved the vertical light distribution within the canopy,but also reduced the differences in photosynthetic characteristics between the two leaves.Taken together,these results demonstrated that maize plants could enhance the vertical heterogeneity of their photosynthetic function to adapt to their light environment;slight changes of the photosynthetic function in EL at the graining stage under a vertically heterogeneous light environment indicated that the systemic regulation of photosynthesis is weak at the graining stage.

Effects of chemical sterilization of the culture media,porous membranes and luminosity on in vitro culture of Eucalyptus grandis×Eucalyptus urophylla

Hybrid combinations of Eucalyptus have increased due to expansion of plantations into unconventional areas and to the search for higher quality timber.However,most of these species have difficulties surviving in vitro cultivation.Active chlorine and sealing systems are often used to reduce contamination and increase gas exchange.The aim of the present study is to evaluate the establishment,multiplication,elongation and adventitious rooting of E.grandis × E.urophylla.Two clones(C1 and C2) and four active chlorine concentrations(0.000%,0.001%,0.003%,and 0.005%) were tested in the establishment and multiplication phases.Three sealing forms(W/M,1/M and 3/M) and the same four active chlorine concentrations were applied to the elongation phase.Two luminosities(dark and light)and three sealings(W/M,1/M and 3/M) were tested during adventitious rooting.Active chlorine concentration of0.005% led to the lowest fungal contamination rate and to the highest in vitro establishment.Active chlorine concentration of 0.003% resulted in the greatest length and highest number of shoots per explant in the multiplication phase.There were no phytotoxicity problems and the quality of plants grown in an environment with active chlorine was maintained in comparison with those grown in an autoclave.The increase in gas exchange in ventilation systems had a positive impact on the in vitro growth and development of plants.

Early stage nonclinical pulmonary disorder in COVID-19 may present asymptomatic and fuel the contagion

Evidence shows that pulmonary problems in coronavirus disease 2019(COVID-19)may set off from vascular injury that progresses to physiological disturbances through a compromised gas exchange,following an infection with the severe acute respiratory syndrome coronavirus 2.In this process,inefficient gas exchange in the alveolar could precipitate silent nonclinical hypoxemia.Unfortunately,patients with“silent hypoxemia”do not necessarily experience any breathing difficulty(dyspnea)at the early stage of COVID-19 while the disease progresses.As a result,several asymptomatic,presymptomatic and patients with mild symptoms may escape quarantine measure and thus continue to spread the virus through contacts.Therefore,early diagnosis of“silent hypoxemia“,which attracts no clinical warnings,could be an important diagnostic measure to prevent acute respiratory distress syndrome from the risk of pulmonary failure among the presymptomatic and as a screening tool in the asymptomatic who are hitherto potential spreaders of the virus.

Chlorophyll Fluorescence, Photosynthetic and Morphological Characteristics of Waterlogged Sesame Seedlings

Two sesame accessions, ZZM2541 and Ezhi-2, with different tolerance to waterlogging were selected, and the seedlings at the 4-true leaf stage were treated by waterlogging for 48 h. Growth parameters were evaluated 1 d before the beginning of waterlogging and on the 3^(rd)day after the removal of waterlogging(DARW). Morphological characteristics of root and chlorophyll fuorescence were measured on the 3^(rd)DARW and leaf gas exchange was measured on the zero, 3^(rd)and 15^(th) DARW. Results showed that sesame accessions ZZM2541 and Ezhi-2 responded to waterlogging in considerably different performance. The stress induced leaf chlorosis and abscission and slowed growth of plant height in both accessions, but symptom occurred seriously in the susceptive Ezhi-2. In the more tolerant ZZM2541, plentiful of adventitious roots formed above the level.All of the average values of maximum fuorescence yield(F_m), quantum efficiency of open PSII centres(F_v/F_m), initial fluorescence(F_v/F_0) and chlorophyll content(Chl) decreased at the 4-true leaf stage in both accessions after suffering to the stress.The decreases of F_m, F_v/F_0 and Chl were more pronounced in Ezhi-2 than in ZZM2541. Less reductions of mean photosynthetic rate(Pn), transpiration rate(Tr), and stomatal conductance(gs) were observed in the leaves of waterlogged ZZM2541 than in waterlogged Ezhi-2(compared to controls), and the leaves of Ezhi-2 showed a higher water use efficiency(WUE) after the removal of waterlogging. Based on the results, it was concluded that the tolerance to waterlogging of ZZM2541 appears to depend on a combination of photosynthetic characteristics responses and morphological adaption.

Ecophysiological acclimatization to cyclic water stress in Eucalyptus

Drought is considered the main environmental factor limiting productivity in eucalyptus plantations in Brazil. However, recent studies have reported that exposure to water deficit conditions enables plants to respond to subsequent stresses. Thus, this study investigates the ecophysiological acclimatization of eucalyptus clones submitted to recurrent water deficit cycles. Eucalyptus seedlings were submitted to three recurrent water deficit cycles and anatomical, morphological and physiological changes were analyzed. The results were:(1) Eucalyptus seedlings responded to water deficits by directing carbohydrates to root and stem growth;(2) Size and number of stomata were reduced;(3) Stomatal conductance decreased which allowed the plants to reduce water losses through transpiration,increasing instantaneous water use efficiency;(4) The relationship between gas exchanges and available water contents allowed the seedlings to uptake the retained soil water athigher tensions;and,(5) Physiological recovery from subsequent water deficits became faster. As a result of these changes, the eucalyptus seedlings recovered from the same degree of water stress more rapidly.

Critical effects on the photosynthetic efficiency and stem sap flow of poplar in the Yellow River Delta in response to soil water

To explore the critical relationships of photosynthetic efficiency and stem sap flow to soil moisture,two-year-old poplar saplings were selected and a packaged stem sap flow gauge,based on the stem-heat balance method,and a CIRAS-2 portable photosynthesis system were used.The results show that photosynthetic rates(P_(n)),transpiration rates(T_(r)),instantaneous water use efficiency(WUE)and the stem sap flow increased initially and then decreased with decreasing soil water,but their critical values were different.The turning point of relative soil water content(W_(r))from stomatal limitation to nonstomatal limitation of P_(n)was 42%,and the water compensation point of P_(n)was 13%.Water saturation points of P_(n)and T_(r)were 64%and 56%,respectively,and the WUE was 71%.With increasing soil water,the apparent quantum yield(AQY),light saturation point(LSP)and maximum net photosynthetic rate(P_(n)max)increased first and then decreased,while the light compensation point(LCP)decreased first and then increased.When W_(r)was 64%,LCP reached a lower value of 30.7µmol m^(-2)s^(-1),and AQY a higher value of 0.044,indicating that poplar had a strong ability to utilize weak light.When W_(r)was 74%,LSP reached its highest point at 1138.3µmol·m^(-2)s^(-1),indicating that poplar had the widest light ecological amplitude and the highest light utilization efficiency.Stem sap flow and daily sap flow reached the highest value(1679.7 g d^(-1))at W_(r)values of 56%and 64%,respectively,and then declined with increasing or decreasing W_(r),indicating that soil moisture significantly affected the transpiration water-consumption of poplar.Soil water was divided into six threshold grades by critical values to maintain photosynthetic efficiency at different levels,and a W_(r)of 64-71%was classified to be at the level of high productivity and high efficiency.In this range,poplar had high photosynthetic capacity and efficient physiological characteristics for water consumption.The saplings had characteristics of water tolerance and were not drought resistant.Full attention should be given to the soil water environment in the Yellow River Delta when planting Populus.

Resilience of oilseed rape plants to drought stress after exogenous application of AM1,an ABA-mimicking ligand

AM1(ABA-mimicking ligand)is a newly identified signaling molecule for plants during drought tolerance.To investigate the potential role of AM1 in response of rapeseed to drought stress,we conducted experiments by growing rapeseed plants under different levels of drought stress with or without applying AM1 or ABA in a rain shelter.The results indicated that drought significantly inhibited rapeseed growth by damaging the photosyn-thesis system,increasing active oxygen accumulation,destroying the oxidative system,and worsening membrane lipid peroxidation.Exogenously applied AM1 and ABA both relieved the damage to rapeseed that was induced by drought stress.Compared with the drought-treated rapeseed,the AM1 treatment significantly improved plant height,number of greelp leaves,root collar thickness,leaf area,dry matter weight,and root cap ratios of rapeseed.In addition,Pn,Gs,Ci,Tr were significantly increased by the AM1 treatment.The AM1 treatment also alleviated the drought induced reductions in Fv/Fm,ΦPSII,qN and ETR;induced an increase in NPQ;and resulted in decreased active oxygen accumulation and membrane lipid peroxidation.Although the ABA treatment relieved photosynthetic fluorescence and antioxidation system parameters to some extent,the effect was inferior to AM1 treatment.Yield under AM1 treatment was higher than that under ABA treatment but was still far lower than that of normal water supply control.In summary,AM1 is functionally similar to ABA in terms of drought relief and regulation,moreover has a better effect.

Photosynthetic characteristics of cotton are enhaneed by altering the timing of mulch film removal

Background:The photosynthetic parameters of cotton plants may be modified by the timing of film removal during their growing period.This study was undertaken during 2015-2017 in Xinjiang,China,to determine to what extent the film mulching removal time,1 and 10 days before the first irrigation and 1 day before the second irrigation after seedling emergence,influenced cotton's photosynthetic characteristics.The control group(CK)was film-mulched throughout the growth stages.Results:The results suggested the following:(1)Removing mulching-film within 50 days since seedling emergence had adverse effects on soil temperature and moisture.(2)Film-removal before the first or second irrigation after emergence improved the net photosynthetic rate in cotton's later flowering stage and its transpiration rate in mid and later flowed ng stages while enhancing the actual electron transport rate(ETR)and maximum electron transfer rate(ETRmax)between cotton photosystems I and II.(3)Film-removal treatment also increased cotton plants'toleranee to high irradiation after emergence,the trend was more pronounced in the early flowering stage in wetter years.(4)Leaf area index(LAI)of cotton was reduced in the film-removal treatment for which the least accumulation of dry matter occurred in a drought year(i.e.,2015).(5)Film removal caused a yield decrease in the dry year(2015),and the earlier the film was removed,the more seriously the yield decreased.Removing mulching film before the second irrigation could increase the yield of XLZ42 in the rainy year(2016)and the normal rainfall year(2017).Early film removal can in crease the yield of XLZ45 in the rainy year(2016).Conclusions:Collectively,our stud/s experimental results indicate that applying mulch film removal at an appropriate,targeted time after seedling emerge nee had no adverse effects on soil moisture and temperature,and improved the photosy nthetic performance of cotton,thus in creased cotton yield and fiber quality,but no significant difference was reached.

Gas Exchange Mechanism of High Frequency Ventilation:A Brief Narrative Review and Prospect

The high frequency ventilation(HFV)can well support the breathing of respiratory patient with 20%-40%of normal tidal volume.Now as a therapy of rescue ventilation when conversional ventilation failed,the HFV has been applied in the treatments of severe patients with acute respiratory failure(ARF),acute respiratory distress syndrome(ARDS),etc.However,the gas exchange mechanism(GEM)of HFV is still not fully understood by researchers.In this paper,the GEM of HFV is reviewed to track the studies in the last decades and prospect for the next likely studies.And inspired by previous studies,the GEM of HFV is suggested to be continually developed with various hypotheses which will be testified in simulation,experiment and clinic trail.One of the significant measures is to study the GEM of HFV under the cross-disciplinary integration of medicine and engineering.Fully understanding the GEM can theoretically support and expand the applications of HFV,and is helpful in investigating the potential indications and contraindications of HFV.

Piston mechanism of interaction of non-linear geomechanical and physicochemical gas exchange and mass transfer processes in coal-bearing rocks

The article focuses on a theoretical and experimental framework for the quantification of interaction between nonlinear geomechnical and physicochemical processes in high-stress coal-bearing rock mass during mining under high seismic risk due to large-scale blasting and earthquakes,as well as because of structural and temperature effects.The tests were aimed to examine and study comprehensively the piston mechanism of gas exchange and mass transfer processes,revealed recently at the Institute of Mining,SB RAS,as well as to explain the fact that the earthquake-induced low-velocity(quasi-meter range)pendulum waves(velocity to 1 m/s and frequency of 0.5–5 Hz)could stimulate an increase in the gas content in coal mines.In order to perform laboratory investigation at the Institute of Mining SB RAS,special-purpose stand for analyzing gas exchange and mass transfer processes in coal-bearing geomaterials under various thermodynamic conditions(P,V,T)and gas composition was constructed in cooperation with the Institute of Semiconductors Physics SB RAS.Matching of air flow rate with compression pressures allowed to obtain relations showing that air flow rate increases at the uncertain time interval under the increasing of the compression pressure.The same measurements was carried out with another gases such as Hydrogen H_(2),Helium He,methane CH_(4),carbon dioxide CO_(2) and carbon oxide CO.The laboratory tests aimed to detailed investigation of the previously revealed“piston mechanism”of gas exchange and mass transfer processes in the coal specimens and their quantitative description in terms of theory of the pendulum waves were carried in the first time.Consequently,there are some arguments for the testing of the opportunity of quantitative description of the“piston mechanism”related to gas exchange and mass transfer processes in the scale of coal mines.It is relevant when pendulum waves induced by powerful earthquakes and technical blasting reaches the mine.

Precipitation regulates plant gas exchange and its long-term response to climate change in a temperate grassland

Aims Climate change largely impacts ecosystem carbon and water cycles by changing plant gas exchange,which may further cause positive or negative feedback to global climate change.However,long-term global change manipulative experiments are seldom conducted to reveal plant ecophysiological responses to climatic warming and altered precipitation regimes.Methods An 8-year field experiment with both warming and increased precipitation was conducted in a temperate grassland in northern China.We measured leaf gas exchange rates(including plant photosynthesis,transpiration and instantaneous water use efficiency[WUE])of two dominant plant species(Stipa sareptana var.krylovii and Agropyron cristatum)from 2005 to 2012(except 2006 and 2010)and those of other six species from 2011 to 2012.Important Findings Increased precipitation significantly stimulated plant photosynthetic rates(A)by 29.5%and 19.9%and transpiration rates(E)by 42.2%and 51.2%for both dominant species S.sareptana var.krylovii and A.cristatum,respectively,across the 8 years.Similarly,A and E of the six plant functional types were all stimulated by increased precipitation in 2011 and 2012.As the balance of A and E,the instantaneous WUEs of different plant species had species-specific responses to increased precipitation.In contrast,neither warming nor its interaction with increased precipitation significantly affected plant leaf gas exchange rates.Furthermore,A and E of the two dominant species and their response magnitudes to water treatments positively correlated with rainfall amount in July across years.We did not find any significant difference between the short-term versus long-term responses of plant photosynthesis,suggesting the flexibility of leaf gas exchange under climate change.The results suggest that changing precipitation rather than global warming plays a prominent role in determining production of this grassland in the context of climate change.

Conformation Changes of Enkephalin in Coordination with Pb^(2+) Investigated by Gas Phase Hydrogen/Deuterium Exchange Mass Spectrometry Combined with Theoretical Calculations

In this study, the effects of lead ions(Pb^(2+)) on the conformations of leucine encephalin(LE) and methionine encephalin(ME) in gas phase were studied using hydrogen/deuterium exchange mass spectrometry(HDX-MS) and quantum chemistry theoretical calculations at the molecular level. The HDX-MS result revealed that the complexes with the monovalent compounds [LE+Pb–H]+ and [ME+Pb–H]+had a 1:1 stoichiometric ratio, and different HDX reactivates were observed in a follow of [ME+H]+>[LE+H]+>[LE+Pb–H]+> [ME+Pb–H]+. Combining the collision-induced dissociation energies of the complexes and their HDX results, it was found that the more stable the complex, the harder it was for HDX. In addition, the favo-rable conformations of the complexes were obtained by theoretical calculations, revealing that the similar coordination type with diffe-rent bond lengths was obtained. Then, the proton affinity(PA) values of the optimized complexes were calculated to interpret the HDX observations, indicating that the higher the PA values, the more difficult it was for HDX. Overall, the experiments and theoretical calculations revealed that Pb^(2+) could induce conformational changes of LE and ME, and generate ME into a more rigid conformation than LE. The results will prompt further fundamental investigations on the conformational properties of LE/ME in coordination with Pb^(2+).

Advanced hemocompatible polyethersulfone composite artificial lung membrane with efficient CO_(2)/O_(2)exchange channel constructed by modified carbon nanotubes network

Artificial lung membranes as the core module of the extracorporeal membrane oxygenation technology(ECMO)execute the function of extracorporeal blood-gas barrier accomplishing CO_(2)/O_(2)exchange with blood.However,the unsatisfactory hemocompatibility and difficulty in functionalization are the promi-nent challenges faced by current artificial lung membrane materials.In this study,polyethersulfone(PES)composite membranes with self-anticoagulant property and high gas exchange efficient are fabricated by blending PES matrix with poly(vinylamine)(PVAm)modified carboxylic carbon nanotubes(mCNTs)and citrate-based poly(octamethylene-citrate)(POC)pre-polymers.The mCNTs construct specific gas transfer channels within the composite membranes to enhance the gas permeability,while the POC pre-polymers provide anticoagulant property based on the chelation to blood Ca^(2+)and the inactivation effect to in-trinsic coagulation factors.Importantly,directed by the actual ECMO gas exchange mode,we design a gas-liquid convectional circulation device that could evaluate gas exchange efficiency for the composite membranes under mimetic ECMO state.Therefore,this strategy not only proposes a new design method of advanced artificial lung membranes to solve the practical challenges in the current ECMO technology,but also establishes a scientific testing method to evaluate the gas exchange performance for new-type artificial lung membrane materials in the future.

Is COVID-19 different from other causes of acute respiratory distresssyndrome?

Coronavirus disease 2019(COVID-19)pneumonia can lead to acute hypoxemic respiratory failure.When mechanical ventilation is needed,almost all patients with COVID-19 pneumonia meet the criteria for acute respiratorydistress syndrome(ARDS).The question of the specificities of COVID-19-associated ARDS compared to othercauses of ARDS is of utmost importance,as it may justify changes in ventilatory strategies.This review aims todescribe the pathophysiology of COVID-19-associated ARDS and discusses whether specific ventilatory strategiesare required in these patients.