Quenching experiments were performed at different cooling rates under non-directional solidification by differential thermal analysis, and the morphologic variation of primary phase, phase transition temperature and h...Quenching experiments were performed at different cooling rates under non-directional solidification by differential thermal analysis, and the morphologic variation of primary phase, phase transition temperature and hardness change at the same quenching temperature were investigated. The experimental results show that, with the gradual decrease of the cooling rate from 25 K/min, the morphology of ferrite starts to transform experiencing the dendrite, radial pattern, Widmanstatten-like and wire-net. Sample starts to present the Widmanstatten-like microstructure at 10 K/min which does not exist at higher or lower cooling rates, and this microstructure is detrimental to the mechanical property. Except 10 K/min, the hardness decreases with decreasing cooling rate.展开更多
No-bake resin-bonded sand is commonly used in casting production.However,its air pollution is relatively serious,especially in the molding and pouring process.For this reason,it is necessary to study the gas evolution...No-bake resin-bonded sand is commonly used in casting production.However,its air pollution is relatively serious,especially in the molding and pouring process.For this reason,it is necessary to study the gas evolution characteristics of no-bake resin-bonded sand from room temperature to high temperatures,and not only the amount of gaseous products,but also the composition of the gaseous products.No-bake furan resin-bonded sand(#1),phenolic urethane no-bake resin-bonded sand(#2),and alkaline phenolic no-bake resin-bonded sand(#3)are the three most common no-bake resin-bonded sands in casting.The gas evolution volume and rate of these three no-bake resin-bonded sands were studied.Thermogravimetry-mass spectrometer(TG-MS),headspace-gas chromatography/mass spectrometer(HS-GC/MS),and pyrolysis-gas chromatography/mass spectrometer(PY-GC/MS)were used to measure the composition of the gaseous products emitted from binders at room temperature and high temperatures.The differences between formaldehyde,heterocyclic aromatic compounds(HAC),monocyclic aromatic hydrocarbons(MAH),and polycyclic aromatic hydrocarbons(PAHs)gaseous products from the three types of no-bake resin-bonded sands during the molding and casting process were compared.From the perspective of environmental protection,alkaline phenolic no-bake resin-bonded sand and no-bake furan resin-bonded sand are better than phenolic urethane no-bake resin-bonded sand.展开更多
Two wheat cultivars (Triticum aestivum L.) were used to evaluate the effects ofpost-anthesis severe water deficit (SD) on starch content and granule size distribution and their relations with ethylene and spermidi...Two wheat cultivars (Triticum aestivum L.) were used to evaluate the effects ofpost-anthesis severe water deficit (SD) on starch content and granule size distribution and their relations with ethylene and spermidine (Spd). Comparison to the well-watered (WW) treatment, SD led to lower Spd and higher 1-aminocylopropane-l-carboxylic acid (ACC) concentrations and ethylene evolution rate (EER) in grains at the critical stage of forming starch granules. Application of Spd or aminoethoxyvinylglycine (AVG) significantly reduced ACC concentration and EER and increased Spd concentration, while ethephon or methylglyoxal-bis (MGBG) had an opposite impact. The volume and surface area distribution of starch granules showed a bimodal curve, while the number distribution exhibited a unimodal curve. SD caused a marked drop in grain weight, grain number and starch content, also led to a significant reduction in the proportion (both by volume and by surface area) of B-type starch granules (〈10 Ixm), with an increase in those of A-type starch granules (〉10 ~tm). Application of Spd or AVG increased the proportion (both by volume and by surface area) of B-type starch granules under SD. Correlation analysis suggested that ethylene and Spd showed an antagonism relation in the formation of B-type granules. These results suggested that it would be good for the formation of B-type starch granules to have the physiological traits of higher Spd and lower ACC concentrations and ethylene emission under SD.展开更多
Dwarf Water Lilies Nymphoides aquatica(J.F.Gmel)Kuntze have floating and submerged leaves.Some submerged aquatic vascular plants have a form of CAM(Crassulacean Acid Metabolism)called Submerged Aquatic Macrophyte(SAM)...Dwarf Water Lilies Nymphoides aquatica(J.F.Gmel)Kuntze have floating and submerged leaves.Some submerged aquatic vascular plants have a form of CAM(Crassulacean Acid Metabolism)called Submerged Aquatic Macrophyte(SAM)metabolism.Blue-diode based PAM technology was used to measure the Photosynthetic Oxygen Evolution Rate(POER:1O_(2)≡4e^(-)).Optimum Irradiance(E_(opt)),maximum POER(POER_(max))and quantum efficiency(α_(0))all vary on a diurnal cycle.The shape of the POER vs.E curves is different in seedling,submerged and surface leaves.Both E_(opt) and POER_(max) are very low in seedling leaves(E_(opt)≈104μmol photon m^(-2) s^(-1),PPFD;POER_(max)≈4.95µmol O_(2) g^(-1) Chl a s^(-1)),intermediate in mature submerged leaves(E_(opt)≈419µmol photon m^(-2) s^(-1) PPFD,POER_(max)≈38.1µmol O_(2) g^(-1) Chl a s^(-1))and very high in surface leaves(E_(opt)≈923µmol photon m^(-2) s^(-1) PPFD,POER_(max)≈76.1µmol O_(2) g^(-1) Chl a s^(-1)).Leaf titratable acid(C4 acid pool)is too small(≈20 to 50 mol H+m^(-3))to support substantial SAM metabolism.Gross daily photosynthesis of surface leaves is≈3.71 g C m^(-2) d^(-1) in full sun and as much as 1.4 gC m^(-2) d^(-1) in shaded submerged leaves.There is midday inhibition of photosynthesis.展开更多
Lake Qinghai is located in the northeastern margin of qinghai-tibet plateau.It’s very sensitive to climate change.Through the research of modern sedimentary environmental change in Lake Qinghai,We expect to gain the ...Lake Qinghai is located in the northeastern margin of qinghai-tibet plateau.It’s very sensitive to climate change.Through the research of modern sedimentary environmental change in Lake Qinghai,We expect to gain the information about its response to global environmental change.Our study collected three sedimentary columns of Lake Qinghai in the northwestern,Column samples’length展开更多
Analysis of protein sequences from Mycobacterium tuberculosis H37Rv (Mtb H37Rv) was performed to identify homopeptide repeat- containing proteins (HRCPs). Functional annotation of the HRCPs showed that they are pr...Analysis of protein sequences from Mycobacterium tuberculosis H37Rv (Mtb H37Rv) was performed to identify homopeptide repeat- containing proteins (HRCPs). Functional annotation of the HRCPs showed that they are preferentially involved in cellular metabolism. Furthermore, these homopeptide repeats might play some specific roles in protein-protein interaction. Repeat length differences among Bacteria, Archaea and Eukaryotes were calculated in order to identify the conservation of the repeats in these divergent kingdoms. From the results, it was evident that these repeats have a higher degree of conservation in Bacteria and Archaea than in Eukaryotes. In addi- tion, there seems to be a direct correlation between the repeat length difference and the degree of divergence between the species. Our study supports the hypothesis that the presence of homopeptide repeats influences the rate of evolution of the protein sequences in which they are embedded. Thus, homopeptide repeat may have structural, functional and evolutionary implications on proteins.展开更多
The determinative view of mutation penetrance is a fundamental assumption for the building of molecular evolutionary theory:individuals in the population with the same genotype have the same fitness effect.Since this ...The determinative view of mutation penetrance is a fundamental assumption for the building of molecular evolutionary theory:individuals in the population with the same genotype have the same fitness effect.Since this view has been constantly challenged by experimental evidence,it is desirable to examine to what extent violation of this view could affect our under-standing of molecular evolution.To this end,the author formulated a new theory of molecular evolution under a random model of penetrance:for any individual with the same mutational genotype,the coefficient of selection is a random variable.It follows that,in addition to the conventional Ne-genetic drift(Ne is the effective population size),the variance of penetrance among individuals(ε^(2))represents a new type of genetic drift,coined by theε^(2)-genetic drift.It has been demonstrated that these two genetic drifts together provided new insights on the nearly neutral evolution:the evolutionary rate is inversely related to the log-of-Ne when theε^(2)-genetic drift is nontrivial.This log-of-Ne feature ofε^(2)-genetic drift did explain well why the dN/dS ratio(the nonsynonymous rate to the synonymous rate)in humans is only as twofold as that in mice,while the effective population size(Ne)of mice is about two-magnitude larger than that of humans.It was estimated that,for the first time,the variance of random penetrance in mammalian genes was approximatelyε^(2)≈5.89×10^(-3).展开更多
The molecular phylogenetics of the Lepidoptera (butterflies and moths) is well studied, but that of Trichoptera (caddisflies), the sister clade of Lepidoptera, is less studied. The PCR primer libraries developed f...The molecular phylogenetics of the Lepidoptera (butterflies and moths) is well studied, but that of Trichoptera (caddisflies), the sister clade of Lepidoptera, is less studied. The PCR primer libraries developed for lepidopteran phylogenetics might work in Trichoptera. DNA from 8 caddisfly species (Asynarchus nigriculus (Banks, 1908), Grammotaulius lorettae Denning, 1941, Hesperophylax occidentalis (Banks, 1908), Limnephilus externus Hagen, 1861, Limnephilus picturatus McLachlan, 1875, Limnephilus secludens Banks, 1914, Limnephilus sublunatus Provancher, 1877 and Agrypnia deflata (Milne, 1931)) was used to screen for amplification. 107 primer pairs for 45 nuclear and 3 mitochondrial genes were tested. Primers for 1 new gene (40S ribosomalprotein $2 (RPS2)) and 8 genes previously used in Trichopteran phylogenetics were recovered (16S rRNA, 18S rRNA, carbamoyl-phosphate synthetase (CAD), cytoehrome oxidase I (CO1), cytochrome oxidase 11 (COIl), elongation factor-1 alpha (EF-1 alpha), isoeitrate dehydrogenase (IDH), and RNA polymerase-II (POL-I1)). New primer pairs extended the genomic region sampled for many genes. Evolution rates among loci varied by 2 orders of magnitude. Differences among evolution rates and modes of inheritance offer flexible tools for resolving phylogenetic questions and examining genome evolution in the Trichoptera. Screening libraries of PCR primers is a useful approach for identifying PCR primers in related taxa with limited molecular genetic resources.展开更多
基金Funded by the National Natural Science Foundation of China(No.2010DFB70630)
文摘Quenching experiments were performed at different cooling rates under non-directional solidification by differential thermal analysis, and the morphologic variation of primary phase, phase transition temperature and hardness change at the same quenching temperature were investigated. The experimental results show that, with the gradual decrease of the cooling rate from 25 K/min, the morphology of ferrite starts to transform experiencing the dendrite, radial pattern, Widmanstatten-like and wire-net. Sample starts to present the Widmanstatten-like microstructure at 10 K/min which does not exist at higher or lower cooling rates, and this microstructure is detrimental to the mechanical property. Except 10 K/min, the hardness decreases with decreasing cooling rate.
基金financially supported by the National Natural Science Foundation of China (Grant Nos. U1808216, 51905188)the National Key R&D Program of China (Grant No. 2020YFB1710100)
文摘No-bake resin-bonded sand is commonly used in casting production.However,its air pollution is relatively serious,especially in the molding and pouring process.For this reason,it is necessary to study the gas evolution characteristics of no-bake resin-bonded sand from room temperature to high temperatures,and not only the amount of gaseous products,but also the composition of the gaseous products.No-bake furan resin-bonded sand(#1),phenolic urethane no-bake resin-bonded sand(#2),and alkaline phenolic no-bake resin-bonded sand(#3)are the three most common no-bake resin-bonded sands in casting.The gas evolution volume and rate of these three no-bake resin-bonded sands were studied.Thermogravimetry-mass spectrometer(TG-MS),headspace-gas chromatography/mass spectrometer(HS-GC/MS),and pyrolysis-gas chromatography/mass spectrometer(PY-GC/MS)were used to measure the composition of the gaseous products emitted from binders at room temperature and high temperatures.The differences between formaldehyde,heterocyclic aromatic compounds(HAC),monocyclic aromatic hydrocarbons(MAH),and polycyclic aromatic hydrocarbons(PAHs)gaseous products from the three types of no-bake resin-bonded sands during the molding and casting process were compared.From the perspective of environmental protection,alkaline phenolic no-bake resin-bonded sand and no-bake furan resin-bonded sand are better than phenolic urethane no-bake resin-bonded sand.
基金the National Natural Science Foundation of China(31271661,30871477)the National Basic Research Program of China(2009CB118602)+1 种基金the Special Fund for Agro-Scientific Research in the Public Interest of China(201203100)the Key Technologies R&D Program of China during the 12th Five-Year Plan period(2012BAD04B05)
文摘Two wheat cultivars (Triticum aestivum L.) were used to evaluate the effects ofpost-anthesis severe water deficit (SD) on starch content and granule size distribution and their relations with ethylene and spermidine (Spd). Comparison to the well-watered (WW) treatment, SD led to lower Spd and higher 1-aminocylopropane-l-carboxylic acid (ACC) concentrations and ethylene evolution rate (EER) in grains at the critical stage of forming starch granules. Application of Spd or aminoethoxyvinylglycine (AVG) significantly reduced ACC concentration and EER and increased Spd concentration, while ethephon or methylglyoxal-bis (MGBG) had an opposite impact. The volume and surface area distribution of starch granules showed a bimodal curve, while the number distribution exhibited a unimodal curve. SD caused a marked drop in grain weight, grain number and starch content, also led to a significant reduction in the proportion (both by volume and by surface area) of B-type starch granules (〈10 Ixm), with an increase in those of A-type starch granules (〉10 ~tm). Application of Spd or AVG increased the proportion (both by volume and by surface area) of B-type starch granules under SD. Correlation analysis suggested that ethylene and Spd showed an antagonism relation in the formation of B-type granules. These results suggested that it would be good for the formation of B-type starch granules to have the physiological traits of higher Spd and lower ACC concentrations and ethylene emission under SD.
文摘Dwarf Water Lilies Nymphoides aquatica(J.F.Gmel)Kuntze have floating and submerged leaves.Some submerged aquatic vascular plants have a form of CAM(Crassulacean Acid Metabolism)called Submerged Aquatic Macrophyte(SAM)metabolism.Blue-diode based PAM technology was used to measure the Photosynthetic Oxygen Evolution Rate(POER:1O_(2)≡4e^(-)).Optimum Irradiance(E_(opt)),maximum POER(POER_(max))and quantum efficiency(α_(0))all vary on a diurnal cycle.The shape of the POER vs.E curves is different in seedling,submerged and surface leaves.Both E_(opt) and POER_(max) are very low in seedling leaves(E_(opt)≈104μmol photon m^(-2) s^(-1),PPFD;POER_(max)≈4.95µmol O_(2) g^(-1) Chl a s^(-1)),intermediate in mature submerged leaves(E_(opt)≈419µmol photon m^(-2) s^(-1) PPFD,POER_(max)≈38.1µmol O_(2) g^(-1) Chl a s^(-1))and very high in surface leaves(E_(opt)≈923µmol photon m^(-2) s^(-1) PPFD,POER_(max)≈76.1µmol O_(2) g^(-1) Chl a s^(-1)).Leaf titratable acid(C4 acid pool)is too small(≈20 to 50 mol H+m^(-3))to support substantial SAM metabolism.Gross daily photosynthesis of surface leaves is≈3.71 g C m^(-2) d^(-1) in full sun and as much as 1.4 gC m^(-2) d^(-1) in shaded submerged leaves.There is midday inhibition of photosynthesis.
文摘Lake Qinghai is located in the northeastern margin of qinghai-tibet plateau.It’s very sensitive to climate change.Through the research of modern sedimentary environmental change in Lake Qinghai,We expect to gain the information about its response to global environmental change.Our study collected three sedimentary columns of Lake Qinghai in the northwestern,Column samples’length
基金supported and funded by the Department of Information Technology(DIT),Government of India(Grant No.MITO-088)
文摘Analysis of protein sequences from Mycobacterium tuberculosis H37Rv (Mtb H37Rv) was performed to identify homopeptide repeat- containing proteins (HRCPs). Functional annotation of the HRCPs showed that they are preferentially involved in cellular metabolism. Furthermore, these homopeptide repeats might play some specific roles in protein-protein interaction. Repeat length differences among Bacteria, Archaea and Eukaryotes were calculated in order to identify the conservation of the repeats in these divergent kingdoms. From the results, it was evident that these repeats have a higher degree of conservation in Bacteria and Archaea than in Eukaryotes. In addi- tion, there seems to be a direct correlation between the repeat length difference and the degree of divergence between the species. Our study supports the hypothesis that the presence of homopeptide repeats influences the rate of evolution of the protein sequences in which they are embedded. Thus, homopeptide repeat may have structural, functional and evolutionary implications on proteins.
基金supported by the fund from Iowa State University.
文摘The determinative view of mutation penetrance is a fundamental assumption for the building of molecular evolutionary theory:individuals in the population with the same genotype have the same fitness effect.Since this view has been constantly challenged by experimental evidence,it is desirable to examine to what extent violation of this view could affect our under-standing of molecular evolution.To this end,the author formulated a new theory of molecular evolution under a random model of penetrance:for any individual with the same mutational genotype,the coefficient of selection is a random variable.It follows that,in addition to the conventional Ne-genetic drift(Ne is the effective population size),the variance of penetrance among individuals(ε^(2))represents a new type of genetic drift,coined by theε^(2)-genetic drift.It has been demonstrated that these two genetic drifts together provided new insights on the nearly neutral evolution:the evolutionary rate is inversely related to the log-of-Ne when theε^(2)-genetic drift is nontrivial.This log-of-Ne feature ofε^(2)-genetic drift did explain well why the dN/dS ratio(the nonsynonymous rate to the synonymous rate)in humans is only as twofold as that in mice,while the effective population size(Ne)of mice is about two-magnitude larger than that of humans.It was estimated that,for the first time,the variance of random penetrance in mammalian genes was approximatelyε^(2)≈5.89×10^(-3).
基金provided by a University of Manitoba Graduate Fellowshipthe University of Manitoba Research Grants Program+3 种基金the Field Work Support Program of the Faculty of Science at the University of Manitobaa Rocky Mountain Biological Laboratory Research Fellowshipan NSERC Discovery Grant RGPIN386337-2011a Canada Foundation for Innovation Award
文摘The molecular phylogenetics of the Lepidoptera (butterflies and moths) is well studied, but that of Trichoptera (caddisflies), the sister clade of Lepidoptera, is less studied. The PCR primer libraries developed for lepidopteran phylogenetics might work in Trichoptera. DNA from 8 caddisfly species (Asynarchus nigriculus (Banks, 1908), Grammotaulius lorettae Denning, 1941, Hesperophylax occidentalis (Banks, 1908), Limnephilus externus Hagen, 1861, Limnephilus picturatus McLachlan, 1875, Limnephilus secludens Banks, 1914, Limnephilus sublunatus Provancher, 1877 and Agrypnia deflata (Milne, 1931)) was used to screen for amplification. 107 primer pairs for 45 nuclear and 3 mitochondrial genes were tested. Primers for 1 new gene (40S ribosomalprotein $2 (RPS2)) and 8 genes previously used in Trichopteran phylogenetics were recovered (16S rRNA, 18S rRNA, carbamoyl-phosphate synthetase (CAD), cytoehrome oxidase I (CO1), cytochrome oxidase 11 (COIl), elongation factor-1 alpha (EF-1 alpha), isoeitrate dehydrogenase (IDH), and RNA polymerase-II (POL-I1)). New primer pairs extended the genomic region sampled for many genes. Evolution rates among loci varied by 2 orders of magnitude. Differences among evolution rates and modes of inheritance offer flexible tools for resolving phylogenetic questions and examining genome evolution in the Trichoptera. Screening libraries of PCR primers is a useful approach for identifying PCR primers in related taxa with limited molecular genetic resources.