MicroRNAs(miRNAs)have been demonstrated to control chicken skeletal muscle growth,however,the potential function of the miR-181-5p family in chicken myogenesis remains largely unknown.Here,our study identified the two...MicroRNAs(miRNAs)have been demonstrated to control chicken skeletal muscle growth,however,the potential function of the miR-181-5p family in chicken myogenesis remains largely unknown.Here,our study identified the two chicken(Gallus gallus;Gga)miR-181-5p family members widely expressed in various tissues,specifically miR-181a-5p and miR-181b-5p.Besides,the breast muscles of fast-growing broilers expressed higher levels of miR-181a-5p and miR-181b-5p than those of slow-growing layers.Functionally,miR-181a-5p and miR-181b-5p both promote the expression level of myogenic factors including myogenin(MyoG),myogenic differentiation 1(MyoD1),and myosin heavy chain(MyHC),meanwhile accelerating the myotube formation of skeletal muscle satellite cells(SMSCs).Mechanistically,miR-181a-5p and miR-181b-5p directly bind to the 3′untranslated region(UTR)of the transforming growth factor beta receptor 1(TGFBR1)mRNA,further reducing the expression of TGFBR1.TGFBR1 is a key Transforming growth factor beta(TGF-β)signaling transduction receptor and had a negative function in muscle cell differentiation.Furthermore,knockdown of TGFBR1 facilitated the expression of chicken myogenic factors,boosted myotube formation,and decreased the SMAD family member 2/3(SMAD2/3)phosphorylation in chicken SMSCs.SMAD2/3 are downstream of TGF-βsignaling,and miR-181a-5p and miR-181b-5p could reduce the expression of TGFBR1 to further diminish the SMAD2/3 phosphorylation.Our findings revealed that the miR-181-5p family targets TGFBR1 to break the TGF-βsignaling transduction,which resulted in promoting chicken skeletal muscle development.展开更多
AIM To elucidate the mechanism of patchouli alcohol(PA) in treatment of rat models of diarrhea-predominant irritable bowel syndrome(IBS-D).METHODS We studied the effects of PA on colonic spontaneous motility using its...AIM To elucidate the mechanism of patchouli alcohol(PA) in treatment of rat models of diarrhea-predominant irritable bowel syndrome(IBS-D).METHODS We studied the effects of PA on colonic spontaneous motility using its cumulative log concentration(3 × 10^(-7) mol/L to 1 × 10^(-4)mol/L). We then determined the responses of the proximal and distal colon segments of rats to the folowing stimuli:(1) carbachol(1 × 10^(-9) mol/L to 1 × 10^(-5) mol/L);(2) neurotransmitter antagonists including N~ω-nitro-l-arginine methyl ester hydrochloride(10μmol/L) and(1 R~*, 2 S~*)-4-[2-Iodo-6-(methylamino)-9 Hpurin-9-yl]-2-(phosphonooxy)bicyclo[3.1.0]hexane-1-methanol dihydrogen phosphate ester tetraammonium salt(1 μmol/L);(3) agonist α,β-methyleneadenosine 5′-triphosphate trisodium salt(100 μmol/L); and(4) single KCl doses(120 mmol/L). The effects of blockers against antagonist responses were also assessed by pretreatment with PA(100 μmol/L) for 1 min. Electrical-field stimulation(40 V, 2-30 Hz, 0.5 ms pulse duration, and 10 s) was performed to observe nonadrenergic, noncholinergic neurotransmitter release in IBS-D rat colon. The ATP level of Kreb's solution was also determined.RESULTS PA exerted a concentration-dependent inhibitory effect on the spontaneous contraction of the colonic longitudinal smooth muscle, and the half maximal effective concentration(EC_(50)) was 41.9 μmol/L. In comparison with the KCl-treated IBS-D group, the contractile response(mg contractions) in the PA + KCl-treated IBS-D group(11.87 ± 3.34) was significantly decreased in the peak tension(P < 0.01). Compared with CCh-treated IBS-D rat colon, the cholinergic contractile response of IBS-D rat colonic smooth muscle(EC_(50) = 0.94 μmol/L) was significantly decreased by PA(EC_(50) = 37.43 μmol/L)(P < 0.05). Lack of nitrergic neurotransmitter release in stress-induced IBS-D rats showed contraction effects on colonic smooth muscle. Pretreatment with PA resulted in inhibitory effect on l-NAME-induced(10 μmol/L) contraction(P < 0.05). ATP might not be the main neurotransmitter involved in inhibitory effects of PA in the colonic relaxation of stressinduced IBS-D rats.CONCLUSION PA application may serve as a new therapeutic approach for IBS-D.展开更多
Temperature and freeze-thaw events are two key factors controlling litter decomposition in cold biomes.Predicted global warming and changes in freeze-thaw cycles therefore may directly or indirectly impact litter deco...Temperature and freeze-thaw events are two key factors controlling litter decomposition in cold biomes.Predicted global warming and changes in freeze-thaw cycles therefore may directly or indirectly impact litter decomposition in those ecosystems. Here, we conducted a2-year-long litter decomposition experiment along an elevational gradient from 3000 to 3600 m to determine the potential effects of litter quality, climate warming and freeze-thaw on the mass losses of three litter types [dragon spruce（Picea asperata Mast.）, red birch（Betula albosinensis Burk.）, and minjiang fir（Abies faxoniana Rehd. et Wild）]. Marked differences in mass loss were observed among the litter types and sampling dates. Decay constant（k） values of red birch were significantly higher than those of the needle litters. However, mass losses between elevations did not differ significantly for any litter type.During the winter, lost mass contributed 18.3-28.8 % of the net loss rates of the first year. Statistical analysis showed that the relationships between mass loss and litter chemistry or their ratios varied with decomposition periods. Our results indicated that short-term field incubations could overestimate the k value of litter decomposition.Considerable mass was lost from subalpine forest litters during the wintertime. Potential future warming may not affect the litter decomposition in the subalpine forest ecosystems of eastern Tibetan Plateau.展开更多
This study presents a simple technique for strengthening the adhesive-bond strength between aluminium(Al)substrate and carbon fibre reinforced polymer(CFRP) utilising resin pre-coating(RPC) with carbon nanotubes(CNTs)...This study presents a simple technique for strengthening the adhesive-bond strength between aluminium(Al)substrate and carbon fibre reinforced polymer(CFRP) utilising resin pre-coating(RPC) with carbon nanotubes(CNTs). The CNT-containing RPC solution with 90 wt% acetone and 10 wt% resin(without hardener) was applied onto Al substrates, where micro-/nano-vertical channels had been created by chemical or mechanical surface treatments to accommodate CNTs. RPC was able to fill all micro-/nano-cavities over the Al substrate surface, then CNTs were pulled into those vertical micro-channels by the capillary action generated from acetone evaporation.Normal epoxy adhesive(resin + hardener) was applied after the CNT-containing RPC treatment. CNTs bridging across the interface between the adhesive joint and Al substrate and sealing of micro-/nano-cavities by RPC effectively enhanced the interfacial shear bond strength between the Al substrate and CFRP by 30–100%depending on the Al substrate surface profiles. Al substrates with two different chemical treatments were compared in this study for the effectiveness of CNT interfacial reinforcement. Results from a steel substrate after sandblasting were also included for comparison.展开更多
Nitrogen deposition has a considerable impact on biogeochemical cycling in terrestrial ecosystems.However,how litter production and element return respond to N addition remains poorly understood in nitrogen-rich subtr...Nitrogen deposition has a considerable impact on biogeochemical cycling in terrestrial ecosystems.However,how litter production and element return respond to N addition remains poorly understood in nitrogen-rich subtropical regions.In this study,a 4-year nitrogen addition experiment explored its eff ects on foliar litter production and carbon,nitrogen and phosphorus in a subtropical Michelia wilsonii forest.A clear seasonal pattern in foliar litterfall was observed,regardless of nitrogen treatments,with a peak in spring and a smaller one in autumn.Foliar litter increased with increasing nitrogen but did not aff ect litter carbon concentrations and often decreased nitrogen and phosphorous concentrations.The eff ect of nitrogen addition was dependent on time(month/year).Carbon,nitrogen and phosphorous return showed similar bimodal seasonal patterns.Nitrogen addition increased carbon and nitrogen return but did not aff ect phosphorous.Our results suggest that the addition of nitrogen stimulates carbon and nutrient return via litterfall.展开更多
To test the effectiveness of N_(2) and CO_(2) in preventing coal from spontaneously combusting,researchers used an adiabatic oxidation apparatus to conduct an experiment with different temperature starting points.Non-...To test the effectiveness of N_(2) and CO_(2) in preventing coal from spontaneously combusting,researchers used an adiabatic oxidation apparatus to conduct an experiment with different temperature starting points.Non-adsorbed helium(He)was used as a reference gas,and coal and oxygen concentration temperature variations were analyzed after inerting.The results showed that He had the best cooling effect,N_(2) was second,and CO_(2) was the worst.At 70℃and 110℃,the impact of different gases on reducing oxygen concentration and the cooling effect was the same.However,at the starting temperature of 150℃,CO_(2) was less effective in lowering oxygen concentration at the later stage than He and N_(2).N_(2) and CO_(2) can prolong the flame retardation time of inert gas and reduce oxygen displacement with an initial temperature increase.When the starting temperature is the same,N_(2) injection cools coal samples and replaces oxygen more effectively than CO_(2) injection.The flame retardancy of inert gas is the combined result of the cooling effect of inert gas and the replacement of oxygen.These findings are essential for using inert flame retardant technology in the goaf.展开更多
Atmospheric pressure fuctuation is one of the most important factors afecting the climate environment and gas emission in the fre area.To obtain the infuence rule of the surface atmospheric pressure change on the gas ...Atmospheric pressure fuctuation is one of the most important factors afecting the climate environment and gas emission in the fre area.To obtain the infuence rule of the surface atmospheric pressure change on the gas sampling and abnormal emission in the mine closed goaf,the No.1 coal mine in Dananhu was taken as the research object.Using Fourier transform and Fisher harmonic analysis and other statistical methods,the infuence of the periodic variation of atmospheric pressure on the gas leakage and outfow in the closed goaf was studied.The results showed that there were three atmospheric pressure periods of 15.2 d,1 d and 182.2 d,and the probability was greater than 95%.The time period with the highest number of atmospheric pressure peaks was 7:00–8:00,which accounted for 20.2%of total occurrence number in a day.And the time periods with the highest number of atmospheric pressure trough were 2:00,15:00 and 16:00,accounting for 27.4%.The peak-to-trough transition time was mainly concentrated around 6 h,and the diurnal variation curve of atmospheric pressure was mainly bimodal.The atmospheric pressure change rate was mostly concentrated in 10–50 Pa/h.It was determined that the distance that the gas sampling pipe was pre-laid into the inner side of the closed wall should be greater than 44.4 m,and the CO concentration and atmospheric pressure in the closed goaf were both periodic and negative with atmospheric pressure.The research results have important guiding signifcance for the monitoring,early warning and environmental protection of the goaf.展开更多
The dynamics of litter nitrogen (N) and phosphorus (P) release could be affected by soil fauna and environmental conditions. The objective of the present study was to investigate the effects of soil fauna on the dynam...The dynamics of litter nitrogen (N) and phosphorus (P) release could be affected by soil fauna and environmental conditions. The objective of the present study was to investigate the effects of soil fauna on the dynamics of N and P during foliar litter decomposition in three types of ecosystems (i.e., montane forest, ecotone, and dry valley) along an elevation gradient. A field experiment using litterbags with two different mesh sizes (0.04 and 3 mm) was conducted from November 2013 to October 2014. Nitrogen and P release rates in decomposing foliar litter from fir (Abies faxoniana) and birch (Betula albosinensis) in montane forest, oak (Quercus baronii) and cypress (Cupressus chengiana) in ecotone, and cypress and clovershrub (Campylotropis macrocarpa) in dry valley were investigated in the upper reaches of the Yangtze River. Soil fauna strongly affected N and P release across different decomposition periods and ecosystem types. The average release rate of N mediated by soil fauna across the entire year was higher in the dry valley (15.6–37.3%) than in the montane forest (0.5–6.4%) and the ecotone (- 3.7–4.9%). The effects of soil fauna on P release rate were manifest in both the montane forest and the dry valley. Moreover, the impacts of soil fauna can vary substantially among different decomposition periods. Our results indicated that soil fauna can significantly affect N and P release during litter decomposition. The N release rate mediated by fauna was likely to be more sensitive to the effects of plant species (i.e., initial litter chemical traits), while the P release rate mediated by soil fauna might be subject to the effects of local-scale environmental factors (e.g., temperature) to a greater extent.展开更多
Coal dust explosion accidents often cause substantial property damage and casualties and frequently involve nano-sized coal dust.In order to study the impact of nano-sized coal on coal dust and methane–coal dust expl...Coal dust explosion accidents often cause substantial property damage and casualties and frequently involve nano-sized coal dust.In order to study the impact of nano-sized coal on coal dust and methane–coal dust explosions,a pipe test apparatus was used to analyze the explosion pressure characteristics of five types of micro-nano particle dusts(800 nm,1200 nm,45μm,60μm,and 75μm)at five concentrations(100 g/m3,250 g/m3,500 g/m3,750 g/m3,and 1000 g/m3).The explosion pressure characteristics were closely related to the coal dust particle size and concentration.The maximum explosion pressure,maximum rate of pressure rise,and deflagration index for nano-sized coal dust were larger than for its micro-sized counterpart,indicating that a nano-sized coal dust explosion is more dangerous.The highest deflagration index Kst for coal dust was 13.97 MPa/(m·s),indicating weak explosibility.When 7%methane was added to the air,the maximum deflagration index Kst for methane–coal dust was 42.62 MPa/(m·s),indicating very strong explosibility.This indicates that adding methane to the coal dust mixture substantially increased the hazard grade.展开更多
Background:The terminal branch orders of plant root systems are increasingly known as an ephemeral module.This concept is crucial to recognize belowground processes.However,it is unknown if root modules still exist af...Background:The terminal branch orders of plant root systems are increasingly known as an ephemeral module.This concept is crucial to recognize belowground processes.However,it is unknown if root modules still exist after they die?Methods:The decomposition patterns of the first five root orders were observed for 3 years using a branch-order classification,a litter-bag method and sequential sampling in a common subalpine tree species(Picea asperata)of southwestern China.Results:Two root modules were observed during the 3-year incubation.Among the first five branch orders,the first three order roots exhibited temporal patterns of mass loss,nutrients and stoichiometry distinct from their woody mother roots throughout the experimental period.This study,for the first time,reported the decomposition pattern of each individual root order and found a similar decomposition dynamic among ephemeral root branches in a forest tree species.Conclusions:Results from this study suggest that root modules may also exist after death,while more data are needed for confirmation.The findings may further advance our understanding of architecture-associated functional heterogeneity in the fine-root system and also improve our ability to predict belowground processes.展开更多
Background:Soil fungi play crucial roles in ecosystem functions.However,how snow cover change associated with winter warming affects soil fungal communities remains unclear in the Tibetan forest.Methods:We conducted a...Background:Soil fungi play crucial roles in ecosystem functions.However,how snow cover change associated with winter warming affects soil fungal communities remains unclear in the Tibetan forest.Methods:We conducted a snow manipulation experiment to explore immediate and legacy effects of snow exclusion on soil fungal community diversity and composition in a spruce forest on the eastern Tibetan Plateau.Soil fungal communities were performed by the high throughput sequencing of gene-fragments.Results:Ascomycota and Basidiomycota were the two dominant fungal phyla and Archaeorhizomyces,Aspergillus and Amanita were the three most common genera across seasons and snow manipulations.Snow exclusion did not affect the diversity and structure of soil fungal community in both snow-covered and snow-free seasons.However,the relative abundance of some fungal communities was different among seasons.Soil fungal groups were correlated with environmental factors(i.e.,temperature and moisture)and soil biochemical variables(i.e.,ammonium and enzyme).Conclusions:These results suggest that the season-driven variations had stronger impacts on soil fungal community than short-term snow cover change.Such findings may have important implications for soil microbial processes in Tibetan forests experiencing significant decreases in snowfall.展开更多
It was found that phosphorylation of small peptide could improve the sensitivity in mass spectrometry. Density functional theory calculations showed that the energy for the protonation of N-(O,O'-dimethyl) phospho...It was found that phosphorylation of small peptide could improve the sensitivity in mass spectrometry. Density functional theory calculations showed that the energy for the protonation of N-(O,O'-dimethyl) phosphoryl glycylglycine is lower than that of glycylglycine. These could help to understanding the experimental results.展开更多
OBJECTIVE To explore the mechanism of G_(αi) and G_(βγ) subunits on dexmedetomidine(DMED)-induced sedation.METHODS Kunming mice were randomly placed into three groups(DMED group,DMED+dbcAMP/rolipram/gallein/M119 gr...OBJECTIVE To explore the mechanism of G_(αi) and G_(βγ) subunits on dexmedetomidine(DMED)-induced sedation.METHODS Kunming mice were randomly placed into three groups(DMED group,DMED+dbcAMP/rolipram/gallein/M119 group,dbcAMP/rolipram/gallein/M119 group) to explore the regulation of dbcAMP/rolipram/gallein/M119 on DMED-induced sedation by establishing loss of righting reflex(LORR) model.DbcAMP/rolipram was intracerebroventricular injected and gallein/M119 was intraperitoneal injected 15 min before DMED intravenous injection.In CHO-α2 A-AR cells,after administration of DMED/gallein/M119,the regulation on the cAMP accumulation stimulated by Forskolin(FSK) was detected,so was the intracellular calcium ion concentration([Ca2 + ]i.The levels of pERK/pCREB were detected by Western Blot to explore the key signal molecules involved in DMED-induced sedation.RESULTS The ED50 of DMED-induced LORR(200.0 nmol·kg^(-1)) was increased to 375.0 or433.3 nmol·kg^(-1) by pre-treatment with cAMP analog dbcAMP(50 nmol/5μl per mouse) or phosphodies.terase 4 inhibitor rolipram(100 nmol/5μl per mouse).In addition,the ED50 of DMED-induced LORR was decreased to 113.6 or 136.5 nmol·kg^(-1) when pre-treated with G_(βγ) subunits inhibitor M119(100 mg·kg^(-1))or gallein(100 mg·kg^(-1)) respectively.Administration of dbcAMP,rolipram,gallein or M119 alone had little effect on LORR of mice.Gallein(10 μmol·L^(-1)) significantly inhibited forskolin-stimulated cAMP accumu.lation in CHO-α2A-AR cells.Compared with G_(βγ) subunits inhibitors or DMED alone,[Ca^(2+)]i and pERK1/2 significantly increased after co-administration of G_(βγ) subunits inhibitors with DMED.DbcAMP(5 μmol·L^(-1))or rolipram(5 μmol·L^(-1)) alone had little effect on ERK1/2 phosphorylation,but decreased DMEDinduced ERK1/2 phosphorylation after co-administration with DMED.G_(βγ) subunit inhibitors treatment increased DMED-induced phosphorylation of CREB,whereas dbcAMP or rolipram had little effect on pCREB induced by DMED.CONCLUSION G_(βγ) subunits might inhibit DMED-induced sedation through cAMP and pERK1/2 pathway,which was opposite to G_(αi) subuint.展开更多
The bio-mimic reactions of N-phosphoryl amino acids are very important in the study of many biochemical processes. The difference of reactivity between a-COOH and b-COOH in phosphoryl aspartic acid was studied by the...The bio-mimic reactions of N-phosphoryl amino acids are very important in the study of many biochemical processes. The difference of reactivity between a-COOH and b-COOH in phosphoryl aspartic acid was studied by theoretical study (Hartree-Fock and Density Functional methods) in this paper. The intermediates II containing five-membered ring were more stable than III with six-membered ring. While for intermediates III, the isomers with six-membered ring in apical-equatorial spanning arrangement were more stable than those with di-equatorial spanning arrangement. At B3LYP/6-31G** level, it was shown that transition states IV and V involving a-COOH or b-COOH group had energy barriers of DE = 58.67 kJmol-1 and 103.94 kJmol-1, respectively. These results were in agreement with the experimental data. So the a-COOH group was involved in form of the intramolecular penta-coordinate phosphoric-carboxylic mixed anhydride intermediates, but not b-COOH group.展开更多
Using the correlation between the radiance or Doppler velocity and the extrapolated magnetic field, we determined the emission heights of a set of solar transition region lines in an equatorial coronal hole and in the...Using the correlation between the radiance or Doppler velocity and the extrapolated magnetic field, we determined the emission heights of a set of solar transition region lines in an equatorial coronal hole and in the surrounding quiet Sun region. We found that for all of the six lower-transition-region lines, the emission height is about 4-5 Mm in the equatorial coronal hole, and around 2 Mm in the quiet Sun region. This result confirms the previous findings that plasma with different temperature can coexist at the same layer of transition region. In the quiet Sun region, the emission height of the upper-transition-region line Ne VIII is almost the same that of the lower-transition-region line, but in the coronal hole, it is twice as high. This difference reveals that the outflow of Ne VIII is a signature of solar wind in the coronal hole and is just a mass supply to the large loops in the quiet Sun.展开更多
Human mesenchymal stem cells(hMSCs)were labeled with Dotarem or(Gd-DOTA)2-EM7(EM7Gd2)via electroporation(EP).Cellular transmission electron microscopy(TEM)reveals free distribution of Gd agents and formation of EM7Gd...Human mesenchymal stem cells(hMSCs)were labeled with Dotarem or(Gd-DOTA)2-EM7(EM7Gd2)via electroporation(EP).Cellular transmission electron microscopy(TEM)reveals free distribution of Gd agents and formation of EM7Gd2 clusters in the cytosol.Cellular magnetic resonance imaging(MRI)reveals that the free Gd agents induce MRI signal enhancement effect due to its fast exocytosis and subsequent interaction with intercellular water molecules.The EM7Gd2 clusters exhibits a longer intracellular retention time and induce a persistent MRI signal reduction effect.The cellular MRI results are interpreted by taking into account both T1 and T2 relaxation rates and their correlation with cellular binding structures of Dotarem and EM7Gd2.展开更多
Double helix DNAs become intertwined around one another during replication and recombination.Here we used magnetic tweezers to make braided DNA molecules and measured their torques under various catenations(Ca)at forc...Double helix DNAs become intertwined around one another during replication and recombination.Here we used magnetic tweezers to make braided DNA molecules and measured their torques under various catenations(Ca)at forces ranging from 0.3 to 8 pN.Images of braided DNA constructs under tensions were captured by scanning electron microscopy which showed major and minor grooves of DNAs and plectonemes of the braids.When the two DNA molecules were braided,the extension decreased as the catenation increased from 0 to 50 turns.We used a thermodynamic Maxwell relation to deduce the torque by integrating the change in the braid extension as a function of the force.The torque increased with the catenation,force and intertether distance until the catenation reached a buckling point.Under the condition of 2 pN force and Ca=20,the torque was computed to be 31,21 and 15 pN nm for the braids of which the intertether distances were 54%,31%and 26%of the DNA contour length,respectively.At an 8.03 pN holding force,the torque was computed to be 76 pN nm as the catenation increased from 0 to 30 turns,or as the catenation density varied from 0 to 0.053.The torque reached a plateau when the catenation increased above 20,indicating formation of braid-plectonemes.The twist modulus increased with the catenation prior to reaching a peak.Before reaching the peak,the moduli were higher than those of a single twisted DNA under the same catenation and applied force.Our experimental data agrees well with the calculation results by a recently developed semiflexible polymer model.Our measurements of the nonlinear torque of the braid establish new fundamental properties of DNA intertwining,which is key to understanding DNA replication and gene expression.The speaker will also introduce briefly other projects in the Xiao group including direct measurements of theforce spectrum of single unlabeled proteins such as adhesive nano-fibers for biofilm,the screening of integrin-targeted peptides drugs by single cell approaches,and the micromechanical approach for determining the survival rate of stem cells.展开更多
Root chemistry varies with tree species and root diameter but little information is available about Tibetan forest species. The root chemistry of three root diameter classes (fine: 0–2 mm, medium: 2–5 mm, coarse: 5...Root chemistry varies with tree species and root diameter but little information is available about Tibetan forest species. The root chemistry of three root diameter classes (fine: 0–2 mm, medium: 2–5 mm, coarse: 5–10 mm) of three subalpine species (Abies faxoniana Rehd. and Wild, Picea asperata Mast., and Betula albosinensis Burkill) were investigated. Carbon concentrations, and carbon/nitrogen and carbon/phosphorus ratios increased but nitrogen, phosphorus and nitrogen/phosphorus ratios decreased with increasing root diameter. The roots of the conifers had higher carbon levels, and higher carbon/nitrogen and carbon/phosphorus ratios than birch roots. The opposite was found with nitrogen and phosphorus levels and nitrogen/phosphorus ratios. Lignin concentrations decreased but cellulose concentrations increased with greater root diameters. The results indicate that diameter-associated variations in root chemistry may regulate their contribution to detrital pools which has important implications for below-ground carbon and nutrient cycles in these subalpine forests.展开更多
Background:Deadwood and the associated epixylic vegetation influence nutrient cycles in forest ecosystems.Open canopies strongly regulate deadwood decomposition and disrupt epixylic vegetation on logs.However,it is un...Background:Deadwood and the associated epixylic vegetation influence nutrient cycles in forest ecosystems.Open canopies strongly regulate deadwood decomposition and disrupt epixylic vegetation on logs.However,it is unclear how the forest canopy density and epixylic vegetation growth affect the nutrient concentrations in deadwood.Methods:We measured the concentrations of nitrogen(N),phosphorus(P),potassium(K),calcium(Ca),sodium(Na),magnesium(Mg),and manganese(Mn)in experimentally exposed decaying logs placed in gaps,at the edge of gaps,and under the closed canopy during a four-year decomposition experiment in a Subalpine Faxon fir forest(Abies fargesii var.faxoniana)on the eastern Qinghai-Tibetan Plateau,China.To assess the effect of the epixylic vegetation,we experimentally removed it from half of the logs used in the study.Results:Under open canopy conditions in the gap and at the edge,the concentrations for most of the nutrients in the bark and the highly decayed wood were lower than under the closed canopy.The effect of the epixylic treatment on nutrient concentrations for all but K and Na in barks varied with the decay classes.Significantly lower concentrations of N,P,Ca,and Mn following the removal of epixylic vegetation were observed in the wood of decay class IV.Epixylic vegetation significantly increased most nutrient concentrations for decaying barks and wood under open canopy conditions.In contrast,epixylic vegetation had no or minimal effects under the closed canopy.Conclusions:Forest canopy density and epixylic vegetation significantly alter the nutrient concentrations in decaying logs.Open canopies likely accelerate the rate of nutrient cycling between the epixylic vegetation and decaying logs in subalpine forests.展开更多
基金supported by the National Key Research and Development Program of China(2022YFF10002020)Sichuan Science and Technology Program,China(2021YFYZ0007 and 2021YFYZ0031).
文摘MicroRNAs(miRNAs)have been demonstrated to control chicken skeletal muscle growth,however,the potential function of the miR-181-5p family in chicken myogenesis remains largely unknown.Here,our study identified the two chicken(Gallus gallus;Gga)miR-181-5p family members widely expressed in various tissues,specifically miR-181a-5p and miR-181b-5p.Besides,the breast muscles of fast-growing broilers expressed higher levels of miR-181a-5p and miR-181b-5p than those of slow-growing layers.Functionally,miR-181a-5p and miR-181b-5p both promote the expression level of myogenic factors including myogenin(MyoG),myogenic differentiation 1(MyoD1),and myosin heavy chain(MyHC),meanwhile accelerating the myotube formation of skeletal muscle satellite cells(SMSCs).Mechanistically,miR-181a-5p and miR-181b-5p directly bind to the 3′untranslated region(UTR)of the transforming growth factor beta receptor 1(TGFBR1)mRNA,further reducing the expression of TGFBR1.TGFBR1 is a key Transforming growth factor beta(TGF-β)signaling transduction receptor and had a negative function in muscle cell differentiation.Furthermore,knockdown of TGFBR1 facilitated the expression of chicken myogenic factors,boosted myotube formation,and decreased the SMAD family member 2/3(SMAD2/3)phosphorylation in chicken SMSCs.SMAD2/3 are downstream of TGF-βsignaling,and miR-181a-5p and miR-181b-5p could reduce the expression of TGFBR1 to further diminish the SMAD2/3 phosphorylation.Our findings revealed that the miR-181-5p family targets TGFBR1 to break the TGF-βsignaling transduction,which resulted in promoting chicken skeletal muscle development.
基金Supported by the National Natural Science Foundation of China,No.81573715Natural Science Foundation of Guangdong Province,China,No.2015A030313348Science and Technology Program of Guangzhou,China,No.201510010257
文摘AIM To elucidate the mechanism of patchouli alcohol(PA) in treatment of rat models of diarrhea-predominant irritable bowel syndrome(IBS-D).METHODS We studied the effects of PA on colonic spontaneous motility using its cumulative log concentration(3 × 10^(-7) mol/L to 1 × 10^(-4)mol/L). We then determined the responses of the proximal and distal colon segments of rats to the folowing stimuli:(1) carbachol(1 × 10^(-9) mol/L to 1 × 10^(-5) mol/L);(2) neurotransmitter antagonists including N~ω-nitro-l-arginine methyl ester hydrochloride(10μmol/L) and(1 R~*, 2 S~*)-4-[2-Iodo-6-(methylamino)-9 Hpurin-9-yl]-2-(phosphonooxy)bicyclo[3.1.0]hexane-1-methanol dihydrogen phosphate ester tetraammonium salt(1 μmol/L);(3) agonist α,β-methyleneadenosine 5′-triphosphate trisodium salt(100 μmol/L); and(4) single KCl doses(120 mmol/L). The effects of blockers against antagonist responses were also assessed by pretreatment with PA(100 μmol/L) for 1 min. Electrical-field stimulation(40 V, 2-30 Hz, 0.5 ms pulse duration, and 10 s) was performed to observe nonadrenergic, noncholinergic neurotransmitter release in IBS-D rat colon. The ATP level of Kreb's solution was also determined.RESULTS PA exerted a concentration-dependent inhibitory effect on the spontaneous contraction of the colonic longitudinal smooth muscle, and the half maximal effective concentration(EC_(50)) was 41.9 μmol/L. In comparison with the KCl-treated IBS-D group, the contractile response(mg contractions) in the PA + KCl-treated IBS-D group(11.87 ± 3.34) was significantly decreased in the peak tension(P < 0.01). Compared with CCh-treated IBS-D rat colon, the cholinergic contractile response of IBS-D rat colonic smooth muscle(EC_(50) = 0.94 μmol/L) was significantly decreased by PA(EC_(50) = 37.43 μmol/L)(P < 0.05). Lack of nitrergic neurotransmitter release in stress-induced IBS-D rats showed contraction effects on colonic smooth muscle. Pretreatment with PA resulted in inhibitory effect on l-NAME-induced(10 μmol/L) contraction(P < 0.05). ATP might not be the main neurotransmitter involved in inhibitory effects of PA in the colonic relaxation of stressinduced IBS-D rats.CONCLUSION PA application may serve as a new therapeutic approach for IBS-D.
基金supported by the National Natural Science Foundation of China(3157044531570601+2 种基金31500509 and31570605)Postdoctoral Science Foundation of China(2013M540714 and 2014T70880)Collaborative Innovation Center of Ecological Security in the Upper Reaches of Yangze River
文摘Temperature and freeze-thaw events are two key factors controlling litter decomposition in cold biomes.Predicted global warming and changes in freeze-thaw cycles therefore may directly or indirectly impact litter decomposition in those ecosystems. Here, we conducted a2-year-long litter decomposition experiment along an elevational gradient from 3000 to 3600 m to determine the potential effects of litter quality, climate warming and freeze-thaw on the mass losses of three litter types [dragon spruce（Picea asperata Mast.）, red birch（Betula albosinensis Burk.）, and minjiang fir（Abies faxoniana Rehd. et Wild）]. Marked differences in mass loss were observed among the litter types and sampling dates. Decay constant（k） values of red birch were significantly higher than those of the needle litters. However, mass losses between elevations did not differ significantly for any litter type.During the winter, lost mass contributed 18.3-28.8 % of the net loss rates of the first year. Statistical analysis showed that the relationships between mass loss and litter chemistry or their ratios varied with decomposition periods. Our results indicated that short-term field incubations could overestimate the k value of litter decomposition.Considerable mass was lost from subalpine forest litters during the wintertime. Potential future warming may not affect the litter decomposition in the subalpine forest ecosystems of eastern Tibetan Plateau.
基金Chang’an University of China for a visiting professor grant (2018-2020) for research collaboration between Chang’an University and University of Western Australia。
文摘This study presents a simple technique for strengthening the adhesive-bond strength between aluminium(Al)substrate and carbon fibre reinforced polymer(CFRP) utilising resin pre-coating(RPC) with carbon nanotubes(CNTs). The CNT-containing RPC solution with 90 wt% acetone and 10 wt% resin(without hardener) was applied onto Al substrates, where micro-/nano-vertical channels had been created by chemical or mechanical surface treatments to accommodate CNTs. RPC was able to fill all micro-/nano-cavities over the Al substrate surface, then CNTs were pulled into those vertical micro-channels by the capillary action generated from acetone evaporation.Normal epoxy adhesive(resin + hardener) was applied after the CNT-containing RPC treatment. CNTs bridging across the interface between the adhesive joint and Al substrate and sealing of micro-/nano-cavities by RPC effectively enhanced the interfacial shear bond strength between the Al substrate and CFRP by 30–100%depending on the Al substrate surface profiles. Al substrates with two different chemical treatments were compared in this study for the effectiveness of CNT interfacial reinforcement. Results from a steel substrate after sandblasting were also included for comparison.
基金supported by the National Natural Science Foundation of China(grants 32071745,32001165,31901295 and 31800519)the Program of Sichuan Excellent Youth Sci-Tech Foundation(2020JDJQ0052)+1 种基金the Applied Basic Research Program of Sichuan of China(2021YJ0340)the National Key Research and Development Program of China(2016YFC0502505 and 2017YFC0505003).
文摘Nitrogen deposition has a considerable impact on biogeochemical cycling in terrestrial ecosystems.However,how litter production and element return respond to N addition remains poorly understood in nitrogen-rich subtropical regions.In this study,a 4-year nitrogen addition experiment explored its eff ects on foliar litter production and carbon,nitrogen and phosphorus in a subtropical Michelia wilsonii forest.A clear seasonal pattern in foliar litterfall was observed,regardless of nitrogen treatments,with a peak in spring and a smaller one in autumn.Foliar litter increased with increasing nitrogen but did not aff ect litter carbon concentrations and often decreased nitrogen and phosphorous concentrations.The eff ect of nitrogen addition was dependent on time(month/year).Carbon,nitrogen and phosphorous return showed similar bimodal seasonal patterns.Nitrogen addition increased carbon and nitrogen return but did not aff ect phosphorous.Our results suggest that the addition of nitrogen stimulates carbon and nutrient return via litterfall.
基金support was received from the National Natural Science Foundation of China(52074156).
文摘To test the effectiveness of N_(2) and CO_(2) in preventing coal from spontaneously combusting,researchers used an adiabatic oxidation apparatus to conduct an experiment with different temperature starting points.Non-adsorbed helium(He)was used as a reference gas,and coal and oxygen concentration temperature variations were analyzed after inerting.The results showed that He had the best cooling effect,N_(2) was second,and CO_(2) was the worst.At 70℃and 110℃,the impact of different gases on reducing oxygen concentration and the cooling effect was the same.However,at the starting temperature of 150℃,CO_(2) was less effective in lowering oxygen concentration at the later stage than He and N_(2).N_(2) and CO_(2) can prolong the flame retardation time of inert gas and reduce oxygen displacement with an initial temperature increase.When the starting temperature is the same,N_(2) injection cools coal samples and replaces oxygen more effectively than CO_(2) injection.The flame retardancy of inert gas is the combined result of the cooling effect of inert gas and the replacement of oxygen.These findings are essential for using inert flame retardant technology in the goaf.
基金This work was financially sponsored by the National Natural Science Foundation of China(51864045,51804161,52074156 and 51804355)And Central University Basic Scientifc Research Business Expenses Special Funds(2023ZKPYAQ03).
文摘Atmospheric pressure fuctuation is one of the most important factors afecting the climate environment and gas emission in the fre area.To obtain the infuence rule of the surface atmospheric pressure change on the gas sampling and abnormal emission in the mine closed goaf,the No.1 coal mine in Dananhu was taken as the research object.Using Fourier transform and Fisher harmonic analysis and other statistical methods,the infuence of the periodic variation of atmospheric pressure on the gas leakage and outfow in the closed goaf was studied.The results showed that there were three atmospheric pressure periods of 15.2 d,1 d and 182.2 d,and the probability was greater than 95%.The time period with the highest number of atmospheric pressure peaks was 7:00–8:00,which accounted for 20.2%of total occurrence number in a day.And the time periods with the highest number of atmospheric pressure trough were 2:00,15:00 and 16:00,accounting for 27.4%.The peak-to-trough transition time was mainly concentrated around 6 h,and the diurnal variation curve of atmospheric pressure was mainly bimodal.The atmospheric pressure change rate was mostly concentrated in 10–50 Pa/h.It was determined that the distance that the gas sampling pipe was pre-laid into the inner side of the closed wall should be greater than 44.4 m,and the CO concentration and atmospheric pressure in the closed goaf were both periodic and negative with atmospheric pressure.The research results have important guiding signifcance for the monitoring,early warning and environmental protection of the goaf.
基金financially supported by the National Natural Science Foundation of China(31670526,31622018,31570445 and 31500509)the Doctoral Scientific Fund Project of the Ministry of Education of China(20135103110002)
文摘The dynamics of litter nitrogen (N) and phosphorus (P) release could be affected by soil fauna and environmental conditions. The objective of the present study was to investigate the effects of soil fauna on the dynamics of N and P during foliar litter decomposition in three types of ecosystems (i.e., montane forest, ecotone, and dry valley) along an elevation gradient. A field experiment using litterbags with two different mesh sizes (0.04 and 3 mm) was conducted from November 2013 to October 2014. Nitrogen and P release rates in decomposing foliar litter from fir (Abies faxoniana) and birch (Betula albosinensis) in montane forest, oak (Quercus baronii) and cypress (Cupressus chengiana) in ecotone, and cypress and clovershrub (Campylotropis macrocarpa) in dry valley were investigated in the upper reaches of the Yangtze River. Soil fauna strongly affected N and P release across different decomposition periods and ecosystem types. The average release rate of N mediated by soil fauna across the entire year was higher in the dry valley (15.6–37.3%) than in the montane forest (0.5–6.4%) and the ecotone (- 3.7–4.9%). The effects of soil fauna on P release rate were manifest in both the montane forest and the dry valley. Moreover, the impacts of soil fauna can vary substantially among different decomposition periods. Our results indicated that soil fauna can significantly affect N and P release during litter decomposition. The N release rate mediated by fauna was likely to be more sensitive to the effects of plant species (i.e., initial litter chemical traits), while the P release rate mediated by soil fauna might be subject to the effects of local-scale environmental factors (e.g., temperature) to a greater extent.
基金This research was supported by the National Key Research and Development Program of China(2016YFC0801800)the National Nature Science Foundation of China(51774291,51864045).
文摘Coal dust explosion accidents often cause substantial property damage and casualties and frequently involve nano-sized coal dust.In order to study the impact of nano-sized coal on coal dust and methane–coal dust explosions,a pipe test apparatus was used to analyze the explosion pressure characteristics of five types of micro-nano particle dusts(800 nm,1200 nm,45μm,60μm,and 75μm)at five concentrations(100 g/m3,250 g/m3,500 g/m3,750 g/m3,and 1000 g/m3).The explosion pressure characteristics were closely related to the coal dust particle size and concentration.The maximum explosion pressure,maximum rate of pressure rise,and deflagration index for nano-sized coal dust were larger than for its micro-sized counterpart,indicating that a nano-sized coal dust explosion is more dangerous.The highest deflagration index Kst for coal dust was 13.97 MPa/(m·s),indicating weak explosibility.When 7%methane was added to the air,the maximum deflagration index Kst for methane–coal dust was 42.62 MPa/(m·s),indicating very strong explosibility.This indicates that adding methane to the coal dust mixture substantially increased the hazard grade.
基金funded by the National Natural Science Foundation of China(Nos.32071745,31870602,31800519 and 31901295)Program of Sichuan Excellent Youth Sci-Tech Foundation(No.2020JDJQ0052)the National Key Research and Development Program of China(Nos.2016YFC0502505and 2017YFC0505003)。
文摘Background:The terminal branch orders of plant root systems are increasingly known as an ephemeral module.This concept is crucial to recognize belowground processes.However,it is unknown if root modules still exist after they die?Methods:The decomposition patterns of the first five root orders were observed for 3 years using a branch-order classification,a litter-bag method and sequential sampling in a common subalpine tree species(Picea asperata)of southwestern China.Results:Two root modules were observed during the 3-year incubation.Among the first five branch orders,the first three order roots exhibited temporal patterns of mass loss,nutrients and stoichiometry distinct from their woody mother roots throughout the experimental period.This study,for the first time,reported the decomposition pattern of each individual root order and found a similar decomposition dynamic among ephemeral root branches in a forest tree species.Conclusions:Results from this study suggest that root modules may also exist after death,while more data are needed for confirmation.The findings may further advance our understanding of architecture-associated functional heterogeneity in the fine-root system and also improve our ability to predict belowground processes.
基金funded by the National Natural Science Foundation of China(Nos.31700542,32071745,31870602,31800519 and 31901295)Program of Sichuan Excellent Youth Sci-Tech Foundation(No.2020JDJQ0052)the National Key Research and Development Program of China(Nos.2016YFC0502505 and 2017YFC0505003)。
文摘Background:Soil fungi play crucial roles in ecosystem functions.However,how snow cover change associated with winter warming affects soil fungal communities remains unclear in the Tibetan forest.Methods:We conducted a snow manipulation experiment to explore immediate and legacy effects of snow exclusion on soil fungal community diversity and composition in a spruce forest on the eastern Tibetan Plateau.Soil fungal communities were performed by the high throughput sequencing of gene-fragments.Results:Ascomycota and Basidiomycota were the two dominant fungal phyla and Archaeorhizomyces,Aspergillus and Amanita were the three most common genera across seasons and snow manipulations.Snow exclusion did not affect the diversity and structure of soil fungal community in both snow-covered and snow-free seasons.However,the relative abundance of some fungal communities was different among seasons.Soil fungal groups were correlated with environmental factors(i.e.,temperature and moisture)and soil biochemical variables(i.e.,ammonium and enzyme).Conclusions:These results suggest that the season-driven variations had stronger impacts on soil fungal community than short-term snow cover change.Such findings may have important implications for soil microbial processes in Tibetan forests experiencing significant decreases in snowfall.
基金The authors thank the National Natural Science Foundation of China(No.39870415)the Ministry of Science and Technology of China,the Education Ministry of China and Tsinghua University for financial suport.
文摘It was found that phosphorylation of small peptide could improve the sensitivity in mass spectrometry. Density functional theory calculations showed that the energy for the protonation of N-(O,O'-dimethyl) phosphoryl glycylglycine is lower than that of glycylglycine. These could help to understanding the experimental results.
文摘OBJECTIVE To explore the mechanism of G_(αi) and G_(βγ) subunits on dexmedetomidine(DMED)-induced sedation.METHODS Kunming mice were randomly placed into three groups(DMED group,DMED+dbcAMP/rolipram/gallein/M119 group,dbcAMP/rolipram/gallein/M119 group) to explore the regulation of dbcAMP/rolipram/gallein/M119 on DMED-induced sedation by establishing loss of righting reflex(LORR) model.DbcAMP/rolipram was intracerebroventricular injected and gallein/M119 was intraperitoneal injected 15 min before DMED intravenous injection.In CHO-α2 A-AR cells,after administration of DMED/gallein/M119,the regulation on the cAMP accumulation stimulated by Forskolin(FSK) was detected,so was the intracellular calcium ion concentration([Ca2 + ]i.The levels of pERK/pCREB were detected by Western Blot to explore the key signal molecules involved in DMED-induced sedation.RESULTS The ED50 of DMED-induced LORR(200.0 nmol·kg^(-1)) was increased to 375.0 or433.3 nmol·kg^(-1) by pre-treatment with cAMP analog dbcAMP(50 nmol/5μl per mouse) or phosphodies.terase 4 inhibitor rolipram(100 nmol/5μl per mouse).In addition,the ED50 of DMED-induced LORR was decreased to 113.6 or 136.5 nmol·kg^(-1) when pre-treated with G_(βγ) subunits inhibitor M119(100 mg·kg^(-1))or gallein(100 mg·kg^(-1)) respectively.Administration of dbcAMP,rolipram,gallein or M119 alone had little effect on LORR of mice.Gallein(10 μmol·L^(-1)) significantly inhibited forskolin-stimulated cAMP accumu.lation in CHO-α2A-AR cells.Compared with G_(βγ) subunits inhibitors or DMED alone,[Ca^(2+)]i and pERK1/2 significantly increased after co-administration of G_(βγ) subunits inhibitors with DMED.DbcAMP(5 μmol·L^(-1))or rolipram(5 μmol·L^(-1)) alone had little effect on ERK1/2 phosphorylation,but decreased DMEDinduced ERK1/2 phosphorylation after co-administration with DMED.G_(βγ) subunit inhibitors treatment increased DMED-induced phosphorylation of CREB,whereas dbcAMP or rolipram had little effect on pCREB induced by DMED.CONCLUSION G_(βγ) subunits might inhibit DMED-induced sedation through cAMP and pERK1/2 pathway,which was opposite to G_(αi) subuint.
基金the National Natural Science Foundation of China (No. 29802006) the Teaching and Research Award Program for Outstanding Young Teachers in Higher Education Institutions of MOE P.R.C. and Tsinghua University.
文摘The bio-mimic reactions of N-phosphoryl amino acids are very important in the study of many biochemical processes. The difference of reactivity between a-COOH and b-COOH in phosphoryl aspartic acid was studied by theoretical study (Hartree-Fock and Density Functional methods) in this paper. The intermediates II containing five-membered ring were more stable than III with six-membered ring. While for intermediates III, the isomers with six-membered ring in apical-equatorial spanning arrangement were more stable than those with di-equatorial spanning arrangement. At B3LYP/6-31G** level, it was shown that transition states IV and V involving a-COOH or b-COOH group had energy barriers of DE = 58.67 kJmol-1 and 103.94 kJmol-1, respectively. These results were in agreement with the experimental data. So the a-COOH group was involved in form of the intramolecular penta-coordinate phosphoric-carboxylic mixed anhydride intermediates, but not b-COOH group.
基金Hui Tian, Jian-Sen He, Bo Tan, and Shuo Yao are supported by the National Natural Science Foundation of China under Grants 40574078, 40336053 and40436015by the Beijing Education Project XK100010404+4 种基金the foundation Major Project of National Basic Research, under contract 2006CB806305Hui Tian is also supported by China Scholarship Council for his stay in the Max-Planck-Institut fr Sonnen system for schung in GermanyLi-Dong Xia is supported by the National Natural Science Foundation of China under Grant 40574064the Programme for New Century Excellent Talents in University (NCET)supported by DLR, CNES, NASA, and the ESA PRODEX programme (Swiss contribution).
文摘Using the correlation between the radiance or Doppler velocity and the extrapolated magnetic field, we determined the emission heights of a set of solar transition region lines in an equatorial coronal hole and in the surrounding quiet Sun region. We found that for all of the six lower-transition-region lines, the emission height is about 4-5 Mm in the equatorial coronal hole, and around 2 Mm in the quiet Sun region. This result confirms the previous findings that plasma with different temperature can coexist at the same layer of transition region. In the quiet Sun region, the emission height of the upper-transition-region line Ne VIII is almost the same that of the lower-transition-region line, but in the coronal hole, it is twice as high. This difference reveals that the outflow of Ne VIII is a signature of solar wind in the coronal hole and is just a mass supply to the large loops in the quiet Sun.
基金the Natural Science Foundation of China(21673281,31870982)a National Key R&D Program from MOST of China(2017YFA0104301).
文摘Human mesenchymal stem cells(hMSCs)were labeled with Dotarem or(Gd-DOTA)2-EM7(EM7Gd2)via electroporation(EP).Cellular transmission electron microscopy(TEM)reveals free distribution of Gd agents and formation of EM7Gd2 clusters in the cytosol.Cellular magnetic resonance imaging(MRI)reveals that the free Gd agents induce MRI signal enhancement effect due to its fast exocytosis and subsequent interaction with intercellular water molecules.The EM7Gd2 clusters exhibits a longer intracellular retention time and induce a persistent MRI signal reduction effect.The cellular MRI results are interpreted by taking into account both T1 and T2 relaxation rates and their correlation with cellular binding structures of Dotarem and EM7Gd2.
基金supported by the National Science Foundation of China ( 11772133, 11372116)the Fundamental Research Funds for the Central Universities ( HUST 0118012051)supported by the NIH through grants ( R01-GM105847,U54-CA193419)
文摘Double helix DNAs become intertwined around one another during replication and recombination.Here we used magnetic tweezers to make braided DNA molecules and measured their torques under various catenations(Ca)at forces ranging from 0.3 to 8 pN.Images of braided DNA constructs under tensions were captured by scanning electron microscopy which showed major and minor grooves of DNAs and plectonemes of the braids.When the two DNA molecules were braided,the extension decreased as the catenation increased from 0 to 50 turns.We used a thermodynamic Maxwell relation to deduce the torque by integrating the change in the braid extension as a function of the force.The torque increased with the catenation,force and intertether distance until the catenation reached a buckling point.Under the condition of 2 pN force and Ca=20,the torque was computed to be 31,21 and 15 pN nm for the braids of which the intertether distances were 54%,31%and 26%of the DNA contour length,respectively.At an 8.03 pN holding force,the torque was computed to be 76 pN nm as the catenation increased from 0 to 30 turns,or as the catenation density varied from 0 to 0.053.The torque reached a plateau when the catenation increased above 20,indicating formation of braid-plectonemes.The twist modulus increased with the catenation prior to reaching a peak.Before reaching the peak,the moduli were higher than those of a single twisted DNA under the same catenation and applied force.Our experimental data agrees well with the calculation results by a recently developed semiflexible polymer model.Our measurements of the nonlinear torque of the braid establish new fundamental properties of DNA intertwining,which is key to understanding DNA replication and gene expression.The speaker will also introduce briefly other projects in the Xiao group including direct measurements of theforce spectrum of single unlabeled proteins such as adhesive nano-fibers for biofilm,the screening of integrin-targeted peptides drugs by single cell approaches,and the micromechanical approach for determining the survival rate of stem cells.
基金supported by the National Key Research and Development Program of China(2016YFC0502505 and2017YFC0505003)the National Natural Science Foundation of China(31570601 and 31500509 and 31700542)the Key Program of Sichuan Education Department(17ZA0321)
文摘Root chemistry varies with tree species and root diameter but little information is available about Tibetan forest species. The root chemistry of three root diameter classes (fine: 0–2 mm, medium: 2–5 mm, coarse: 5–10 mm) of three subalpine species (Abies faxoniana Rehd. and Wild, Picea asperata Mast., and Betula albosinensis Burkill) were investigated. Carbon concentrations, and carbon/nitrogen and carbon/phosphorus ratios increased but nitrogen, phosphorus and nitrogen/phosphorus ratios decreased with increasing root diameter. The roots of the conifers had higher carbon levels, and higher carbon/nitrogen and carbon/phosphorus ratios than birch roots. The opposite was found with nitrogen and phosphorus levels and nitrogen/phosphorus ratios. Lignin concentrations decreased but cellulose concentrations increased with greater root diameters. The results indicate that diameter-associated variations in root chemistry may regulate their contribution to detrital pools which has important implications for below-ground carbon and nutrient cycles in these subalpine forests.
基金jointly funded by the following grants:The National Natural Science Foundation of China(Nos.32071554,31870602,31901295)the National Key R&D Program of China(No.2017YFC0503906)the Program of Sichuan Excellent Youth Sci-Tech Foundation(No.2020JDJQ0052).
文摘Background:Deadwood and the associated epixylic vegetation influence nutrient cycles in forest ecosystems.Open canopies strongly regulate deadwood decomposition and disrupt epixylic vegetation on logs.However,it is unclear how the forest canopy density and epixylic vegetation growth affect the nutrient concentrations in deadwood.Methods:We measured the concentrations of nitrogen(N),phosphorus(P),potassium(K),calcium(Ca),sodium(Na),magnesium(Mg),and manganese(Mn)in experimentally exposed decaying logs placed in gaps,at the edge of gaps,and under the closed canopy during a four-year decomposition experiment in a Subalpine Faxon fir forest(Abies fargesii var.faxoniana)on the eastern Qinghai-Tibetan Plateau,China.To assess the effect of the epixylic vegetation,we experimentally removed it from half of the logs used in the study.Results:Under open canopy conditions in the gap and at the edge,the concentrations for most of the nutrients in the bark and the highly decayed wood were lower than under the closed canopy.The effect of the epixylic treatment on nutrient concentrations for all but K and Na in barks varied with the decay classes.Significantly lower concentrations of N,P,Ca,and Mn following the removal of epixylic vegetation were observed in the wood of decay class IV.Epixylic vegetation significantly increased most nutrient concentrations for decaying barks and wood under open canopy conditions.In contrast,epixylic vegetation had no or minimal effects under the closed canopy.Conclusions:Forest canopy density and epixylic vegetation significantly alter the nutrient concentrations in decaying logs.Open canopies likely accelerate the rate of nutrient cycling between the epixylic vegetation and decaying logs in subalpine forests.
