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1.
In this work, a CL-20/DNB cocrystal explosive model was established and six different kinds of fluoropolymers, i.e., PVDF, PCTFE, F2311, F2312, F2313 and F2314 were added into the (1 0 0), (0 1 0), (0 0 1) crystal orientations to obtain the corresponding polymer bonded explosives (PBXs). The influence of fluoropolymers on PBX properties (energetic property, stability and mechanical properties) was investigated and evaluated using molecular dynamics (MD) methods. The results reveal a decrease in engineering moduli, an increase in Cauchy pressure (i.e., rigidity and stiffness is lessened), and an increase in plastic properties and ductility, thus indicating that the fluoropolymers have a beneficial influence on the mechanical properties of PBXs. Of all the PBXs models tested, the mechanical properties of CL-20/DNB/F2311 were the best. Binding energies show that CL-20/DNB/F2311 has the highest intermolecular interaction energy and best compatibility and stability. Therefore, F2311 is the most suitable fluoropolymer for PBXs. The mechanical properties and binding energies of the three crystal orientations vary in the order (0 1 0)?>?(0 0 1)?>?(1 0 0), i.e., the mechanical properties of the (0 1 0) crystal orientation are best, and this is the most stable crystal orientation. Detonation performance results show that the density and detonation parameters of PBXs are lower than those of the pure CL-20 and CL-20/DNB cocrystal explosive. The power and energetic performance of PBXs are thus weakened; however, these PBXs still have excellent detonation performance and are very promising. The results and conclusions provide some helpful guidance and novel instructions for the design and manufacture of PBXs. 相似文献
2.
Jijun Xiao Wei Zhu Xiufang Ma Heming Xiao Hui Huang Jinshan Li 《Molecular simulation》2013,39(8):775-779
The ‘insert’ model for β-octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX)-based polymer-bonded explosive (PBX) was proposed for finding the relation of temperatures with mechanical properties. This model was simulated by using molecular dynamics models. The elastic constants and the effective moduli were calculated with static analysis method. Cauchy pressure was also calculated. It is found that the rigidity is weakened and the ductibility is improved by adding a small amount of F2311 in the crystalline HMX. The rigidity is also weakened with increasing temperature. However, the ductibility of HMX/F2311 PBX changes as a parabola with increasing temperature duo to the enhancement of F2311 molecular chain movement and simultaneously the increment of high energy conformation ratio in this molecular chain, i.e. the increment of the molecular chain rigidity. 相似文献
3.
Eukaryotic vacuolar H+-ATPases (V-ATPases) are related to the F0F1-ATPases of chloroplasts and mitochondria and are believed to be organized into peripheral and integral membrane complexes. Vacuolar membranes isolated from purified carrot (Daucus carota) root vacuoles were observed to be coated with F1-like particles after negative staining with phosphotungstic acid. The F1-like particles formed typical “ball and stalk” structures, about 9.4 nm in diameter and 13.6 nm in height. The head portion frequently had a characteristic bifurcation or cleft at the apex and appeared to be composed of subunits. Such “V1” complexes were frequently associated with smaller stalked particles emerging near the base. In contrast, negatively-stained carrot mitochondrial F1 complexes averaged 8.7 nm in diameter and 11.7 nm in height. The head groups of the mitochondrial F1s were nearly always spherical, and had no other smaller structures associated with them. The V1 complexes of carrot are thus similar in form to the V1 complexes of Neurospora (Bowman et al. J. Biol. Chem. 264 (1989) 15606–15612). 相似文献
4.
G.A. Collins K.M. Johnston T.T. Martinez M.J.A. Walker 《Prostaglandins & other lipid mediators》1979,18(4):591-603
Prostaglandins are antiarrhythmic in a variety of situations including ischaemic arrhythmias, but the mechanisms involved are not known. In view of this, the protective actions of prostaglandins A2, E2, F1α, F2β, and I2 against abnormalities of beating induced in cultured heart cells were investigated. Abnormalities of beating were induced in single cells by a variety of agents including ouabain, Ca++, K+, dinitrophenol (DNP), and toxic material from the jellyfish
. Abnormalities were assessed in terms of rate, rate range, subjective arrhythmic behaviour and percent cells beating. The prostaglandins (at 10−7-10−5 M) were added with the arrhythmogenic agent to test for their ability to modify agent-induced beating abnormalities and were compared with lidocaine and quinidine. Prostaglandins alone had minimal direct effects on the cells and only minimally reduced responses to arrhythmogenic agents. The most protective prostaglandins, PGE2 and PGF1α, tended to normalise beating behaviour most noticeably in DNP-treated cells, unlike lidocaine and quinidine which were effective against Ca++-induced changes while worsening those of K+. Thus, a general ability to protect disturbed cardiac cells is not seen with high concentrations of prostaglandins. 相似文献
5.
The guanidine hydrochloride-induced reversible unfolding transitions at 4 °C of the β2 subunit of tryptophan synthetase (l-serine hydrolyase (adding indole) EC. 4.2.1.20) and of its two proteolytic fragments, F1 and F2, are compared. The unfolding of the β2 subunit shows a multistate behaviour, as judged by circular dichroism and fluorescence measurements. When isolated, the two fragments have different stabilities. Within β2, the region corresponding to the large fragment, F1 behaves as the corresponding isolated fragment, and no stabilization arising from the interaction with the complementary fragment can be detected. The same behaviour is suggested for the small fragment, F2. These results lead to the apparent conclusion that, at least under these experimental conditions, the interactions between domains do not contribute greatly to the energetics of the folding process of the large β2 protein. 相似文献
6.
V. D. Patil M. V. S. Reddy Y. S. Nerkar 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1994,89(2-3):293-296
The efficiency of early generation selection for yield and related characters in safflower (Carthamus tinctorius L.) was studied in the F2, F3 and F4 generations. Twenty-five F2 progenies derived from various crosses were studied. In the F2 generation, number of capitula per plant (CNSP), number of seeds per capitulum (SPSP), test weight (SWSP), and seed yield (SYSP) were the criteria used for single plant selection. The analysis of variance showed significant differences for all of the characters in the F2, F3, and F4 generations. The analysis of variance in each of the selection classes showed highly significant genotypic differences. A large number of selections in the CNSP and SYSP classes showed greater yield than the check variety. In each class the mean for that particular character showed a positive shift. The observed F3 and F4 means for seed yield per plant was higher in SYSP, indicating the effectiveness of single plant selection for yield. Correlated response showed that selection for number of capitula per plant was effective for improvement of yield. 相似文献
7.
J. N. Sachan B. Singh 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1986,71(4):644-647
Summary Gene effects, and interactions, and associations between days-to-flower initiation and maturity, number of secondary branches and siliquae per plant, and 1,000-seed weight and yield per plant were studied in a cross of Indian mustard (Brassica juncea (L.) Czern & Coss) using the parents and F1, F2, F3, B1, B2, B11, B12, B21, B22, B1S, B2S, B1F1, B2F1, B1bip, B2bip, F2P1, F2F1, and F2bip generations. A linked digenic model was adequate for all characters studied. According to this model, the main effects, additive and interactions between linked pairs of genes, were present in varying proportions for days-to-flower initiation and maturity and number of siliquae per plant. The contribution of linked epistatic effects, however, was much greater than that of additive effects. Dominance effects contributed significantly to the inheritance of days-to-flower initiation. Duplicate epistasis was observed for all traits except 1,000-seed weight where epistasis was of the complementary type. A complete association among the genes of similar effect (increasing or decreasing) was observed for number of secondary branches and siliquae, and yield per plant. Coupling phase linkage was observed for days-to-flower initiation whereas repulsion phase linkage was observed for daysto-maturity and 1,000-seed weight. 相似文献
8.
E. A. Mudrik T. A. Kashentseva K. A. Postelnykh G. V. Nosachenko D. V. Politov 《Russian Journal of Genetics》2014,50(11):1192-1199
Eight variable microsatellite loci were analyzed in terms of studying the genetic structure of different generations of a captive population of a rare endemic Russian species, the Siberian crane (Grus leucogeranus Pallas). It was shown that the founding population of natural origin (15 birds) is characterized by high genetic diversity (N A = 6.625, H O = 0.767, H E = 0.731) and a lack of relatedness (R = ?0.079). In the total sample of descendents of the founders (122 individuals from generations F1, F1/F2, F1/F3, F2, F2/F3), this characteristic level of genetic variation is being maintained; however, we observed a decrease in allelic richness in some generations (F1/F2, F1/F3, F2). We found a low level of relatedness in the sample of descendents of the founders (F1, F1/F2, F1/F3), while the relatedness was maximal (R = 0.302) in the descendents of the breeders of the first generation. A small sample of breeders related to each other of generations F1 and F2 (eight birds) does not represent the entire gene pool of the founders of the Siberian Crane captive population. In view of this, we discuss the need to form a new genetically heterogeneous generation of breeders that would also include Siberian Cranes from the almost extinct Western Siberian population. 相似文献
9.
Ricardo Alcántara-de la Cruz Douglas Silva Parreira Francisco Andreas Rodríguez Dimaté Lorena Duarte Batista Rafael Coelho Ribeiro José Cola Zanuncio 《Journal of Asia》2021,24(2):64-67
Bioactivity of nine essential oils (EOs) was studied on Anagasta kuehniella eggs in relation to the longevity of females, parasitism and emergence rates and sex ratio in the generations parental, F1 and F2 of Trichogramma galloi in comparison to a trade formulation of Azadirachta indica. There was no F1 and F2 progeny with Zingiber officinale being the most harmful. The greatest reductions in the parasitism rates (57, 43 and 28%) in the parental generation was caused by Allium sativum, Carapa guianensis and A. indica, respectively. In addition, A. sativum reduced the longevity (4.7 days) in the parental generation and emergence (33%) of F1. Tested EOs did not affect the sex ratio in the generations F1 and F2 and emergence in the F2. Allium sativum and Z. officinale were non-selective to T. galloi; while A. indica, C. guianensis and P. nigrum oils may compromise the progeny; therefore, their use must be avoided. Citrus sinensis, Mentha piperita, Origanum vulgare, Syzygium aromaticum and Thymus vulgare were selective to T. galloi, and these EOs are promising for IPM programs. 相似文献
10.
M. Roostaei S. A. Mohammadi A. Amri E. Majidi M. Nachit R. Haghparast 《Russian Journal of Plant Physiology》2011,58(2):351-358
The usefulness of fluorescence parameters as drought tolerance selection criteria for winter bread wheat in the highlands
of Iran was studied. A population of 142 recombinant inbred lines, derived from a cross between two common wheat varieties,
Azar2 (winter type) and 87Zhong291 (facultative type), was used to analyze the correlation between grain yield and chlorophyll
fluorescence parameters at the grain-filling stage under drought stress and supplementary irrigation conditions during 2006–2007
and 2007–2008 seasons at Maragheh experiment station of the Dryland Agricultural Research Institute (DARI) using a RCBD with
three replications. The results showed significant differences among the lines in the grain yield and all fluorescence parameters
under rainfed and irrigation conditions. The values of chlorophyll content, F
0, F
m, F
v, F
v/F
m, LWP, YPEC, NPQ, and PI in the drought-tolerant genotypes were significantly higher than those in drought-sensitive genotypes
under drought stress. Significant differences were observed between slope coefficients under drought, but not under supplementary
irrigation conditions except NPQ (P = 5%). It was concluded that chlorophyll content, F
0, F
m, F
v, F
v/F
m, LWP, YPEC, NPQ, and PI could be used as additional indicators in screening wheat germplasm for drought tolerance. 相似文献
11.
One-year old sweet almond (Prunus dulcis) seedlings were submitted to four levels of salt stress induced by NaCl, namely 0.3, 0.5, 0.7, and 1.0 S m−1. Effects of salt stress on a range of chlorophyll (Chl) fluorescence parameters (Chl FPs) and Chl contents were investigated
in order to establish an eco-physiological characterization of P. dulcis to salinity. Salt stress promoted an increase in F0, Fs, and F0/Fm and a decrease in Fm, F′m, Fv/Fm, qP, ΔF/F′m, Fv/F0, and UQF(rel), in almost all Chl fluorescence yields (FY) and FPs due to its adverse effect on activity of photosystem 2. No significant
changes were observed for quenchings qN, NPQ, and qN(rel). The contents of Chl a and b and their ratio were also significantly reduced at increased salt stress. In general, adverse salinity effects became significant
when the electric conductivity of the nutrient solution (ECn) exceeded 0.3 S m−1. The most sensitive salt stress indicators were Fv/F0 and Chl a content, and they are thus best used for early salt detection in P. dulcis. Monitoring of a simple Chl FY, such as F0, also gave a good indication of induced salt stress due to the significant correlations observed between the different Chl
FYs and FPs. Even essential Chl FYs, like F0, Fm, F′m, and Fs, and mutually independent Chl FPs, like Fv/F0 and qP, were strongly correlated with each other. 相似文献
12.
Cuttings of five Populus alba clones (S18 F1-26, Al29 F8-35, J3 F1-4, GU1 F16-36, PO9 F21-88), Populus euphratica, and Populus×euramericana (I-214) were submitted during 45 d to regular watering with NaCl solutions of electrical conductivity of 7 and 14 dS m−1. Chlorophyll a fluorescence in response to the salinity stress was assessed, using F0 and Fv/Fm. Differences in reaction to the salt were found in P. alba clones, F0 and Fv/Fm being the fluorescence parameters used to check out this stress. Minimal constant fluorescence of dark-adapted plants (F0) showed a better correlation with the disease index exhibited by plants and also with salinity dose than the parameter Fv/Fm. Some of the P. alba clones showed the same behaviour, assessed through fluorescence parameters, as P. euphratica, which was previously defined as salt tolerant, while the rest exhibited the same characteristics as I-214, which was very
sensitive. 相似文献
13.
Halogenated vinyl cysteine conjugates, which are potent, specific nephrotoxins, have been chemically synthesized from both chlorotrifluoroethylene (CTFE) and trichloroethylene (TCE) but have not been shown to be formed in a biological system. The vinyl cysteine conjugates are stable, but rapidly activated and degraded enzymatically with the release of pyruvate. Increased concentrations of pyruvate after incubation with CTFE may be an indirect index of the formation and bioactivation of a vinyl cysteine conjugate of CTFE. Incubation of CTFE with 10,000 x g rat liver and kidney supernatants resulted in 60 and 100 nmole/mg/hr increases in pyruvate concentration with concomitant depletion of endogenous glutathione. A renal cortex brush border preparation high in C-S lyase activity but deficient in cytosolic transferases did not generate pyruvate during incubation with CTFE. The evidence presented suggests that halogenated vinyl cysteine conjugates are formed by conjugation of the halogenated ethylene with glutathione which subsequently degrades to form the cysteine conjugate. 相似文献
14.
Pollinator preference may influence the origin and dynamics of plant hybrid zones. Natural hybrid populations between the red‐flowered Iris fulva and the blue‐flowered Iris brevicaulis are found in southern Louisiana. The genetic structure of these populations reflects a lack of intermediate genotypes. We observed pollinator behaviour in an experimental array with five plants each of I. fulva, I. brevicaulis, their F1, and the first backcross generation in each direction, to obtain data on flower type preferences and transitions between flower types. The most abundant visitors were Ruby‐throated Hummingbirds (Archilochus colubris) and workers of the bumblebee Bombus pennsylvanicus. Hummingbirds visited I. fulva twice as often as I. brevicaulis and visited hybrids at intermediate frequencies. Bumblebee workers preferred the purple‐flowered F1s and visited plants of I. fulva and the backcross to I. fulva more often than I. brevicaulis and its backcross. Overall, F1 flowers were visited most frequently. Both hummingbirds and bumblebees visited nearest neighbours in almost 80% of the interplant movements. This meant that a majority of movements were between different flower types, rather than between plants of the same type. Findings from the present study suggest that pollinator preference is not a major causal factor for the lack of intermediate genotypes in natural iris hybrid populations. Instead, pollinator behaviour in our array promoted mixed mating between flower types belonging to different pollination syndromes. However, owing to predominant nearest‐neighbour visitation, the spatial distribution of parental and hybrid genotypes (in concert with pollinator behaviour) will have a strong influence on mating patterns and thus the genotypic structure and evolution of Louisiana iris hybrid zones. 相似文献
15.
Microsatellite DNA Polymorphism in Intensely Enhanced Populations of Sea Trout (Salmo trutta) in the Southern Baltic 总被引:1,自引:0,他引:1
Sea trout (Salmo trutta) is an anadromous form of brown trout, a commercially important salmonid species in Europe. Stocking has been used to compensate for the decrease of natural populations and maintenance of fishery and angling catches. Over 1.5 million smolts and 4.5 million alevins are released to Polish coastal rivers each year. Variation at 7 microsatellite loci (Ssa197, Ssa171, Ssa85, Str15, Str73, Str591, and Str543) was used to study genetic polymorphism of spawners returning to 6 rivers. Application of distance method for comparison of pairs of populations based on number of different alleles (F
ST) revealed significant differences between Vistula and Wieprza, and Parseta as well as between Drweca and Wieprza, and Slupia. The level of heterozygosity was similar between most of the studied sea trout populations; considerable differences were found only for Str591. Differences in frequencies of a few alleles between populations were observed. An exact test of sample differentiation based on allele frequencies confirmed lack of significance of differentiation between the 6 pairs of populations (F
ST and R
ST). No admixture was observed in the studied populations. Possible effects of stocking on the genetic polymorphism of the sea trout populations in wild with implications for biotechnology are discussed. 相似文献
16.
Quantification of coenzymes and related compounds from methanogens was performed in extracts obtained from whole cells with aqueous ethanol at 80°C. By means of high-performance liquid chromatography the following compounds could be detected and quantified in extracts from Methanobacterium thermoautotrophicum: coenzyme MF430, the prosthetic group of methylcoenzyme M reductase, F560, an oxidation product of this compound, coenzyme F420, F342, methanopterin, and carboxytetrahydromethanopterin, previously known as YFC. Coenzyme MF430, coenzyme F420, and methanopterin could be determined in extracts from Methanosarcina barkeri. Structural differences were noticed between the coenzymes from the methanogenic bacteria studied. 相似文献
17.
Synopsis In aquaria and in ponds crosses were made between two closely related allopatric forms of ninespine stickleback of the genus Pungitius (P. pungitius and P. platygaster). There were no ethological isolation mechanisms; F1, F2 and F3 hybrids are fertile; experimental hybrid stocks as well as backcrosses maintain themselves for at least three generations. F1 hybrids are readily distinguishable from parental forms by a combination of morphological characters; F2 hybrids grown in the north near the Arctic circle, are morphologically similar to P. pungitius. The southern form P. platygaster does not survive in northern conditions; eggs of the northern form P. pungitius die at a temperature of 28°C, normal for the spawning of the southern form. By 9 out of 19 studied morphological characters there are distinctions between the two forms. Therefore, ecologically and morphologically the two forms have diverged rather significantly. On the other hand, ethologically and genetically (as judged by the absence of postmating isolating mechanisms) the forms have diverged only slightly. As a result, the differences between the two forms are considered not to exceed the subspecies or at least semispecies rank.In recent years, due to a disturbance of the ranges of both these forms in Eurasia, a tendency for a secondary contact between P. pungitius and P. platygaster appeared in the basins of the rivers Volga and Irtysh. In the immediate future the two forms are expected to come into contact. From our data we predict possible introgressive hybridization between the northern and sourthern forms in natural conditions. 相似文献
18.
High yield and stable transformation of the unicellular green alga Acetabularia by microinjection of SV40 DNA and pSV2neo 总被引:3,自引:0,他引:3
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SV40 DNA and pSV2neo were microinjected into isolated nuclei of Acetabularia mediterranea. The injected nuclei were implanted into anucleate cell fragments of the same species. Such combinations not only survived but also formed progeny. The F1, F2 and F3 generations of these combinations were analyzed. In the case of SV40-treated cells T-antigen was expressed and accumulated in the nuclei of all three generations studied as shown by indirect immunofluorescence. Nuclear exchange experiments revealed expression of the T-antigen only if a transformed nucleus but not if only a transformed cytoplasm was involved. Transformation by pSV2neo, a chimeric gene with a selectable marker was demonstrated by the induction of G-418 resistance as well as immunofluorescence. Genomic DNA was isolated from gametes, originating in cysts from the F1, F2 and F3 generations of injected cells, and subjected to Southern analysis. These experiments demonstrated that both types of DNA are integrated into the host genome. 相似文献
19.
One of the major effects of fluoride on oral bacteria is a reduction in acid tolerance, and presumably also in cariogenicity. The reduction appears to involve transport of protons across the cell membrane by the weak acid HF to dissipate the pH gradient, and also direct inhibition of the F1F0, proton-translocating ATPases of the organisms, especially for Streptococcus mutans. This direct inhibition by fluoride was found to be dependent on aluminum. The dependence on aluminum was indicated by the protection against fluoride inhibition afforded by the Al-chelator deferoxamine and by loss of protection after addition of umolar levels of Al3+, which were not inhibitory for the enzyme in the absence of fluoride. The F1 form of the enzyme dissociated from the cell membrane previously had been found to be resistant to fluoride in comparison with the F1F0 membrane-associated form. However, this difference appeared to depend on less aluminum in the F1 preparation in that the sensitivity of the F1 enzyme to fluoride could be increased by addition of umolar levels of Al3+. The effects of Al on fluoride inhibition were apparent when enzyme activity was assayed in terms of phosphate release from ATP or with an ATP-regenerating system containing phosphoenolpyruvate, pyruvate kinase, NADH and lactic dehydrogenase. Also, Be2+ but not other metal cations, e.g. Co2+, Fe2+, Fe3+, Mn2, Sn2+, and Zn2+, served to sensitize the enzyme to fluoride inhibition. The differences in sensitivities of enzymes isolated from various oral bacteria found previously appeared also to be related to differences in levels of Al. Even the fluoride-resistant enzyme of isolated membranes of Lactobacillus casei ATCC 4646 could be rendered fluoride-sensitive through addition of Al3+. Thus, the F1F0 ATPases of oral bacteria were similar to E1E2 ATPases of eukaryotes in being inhibited by Al-F complexes, and the inhibition presumably involved formation of ADP-Al-F
inf3
sup-
complexes during catalysis at the active sites of the enzymes. 相似文献
20.
Hybridization studies have been carried out with Typha angustifolia, T. latifolia, T. shuttleworthii and T. minima. All combinations, except those with T. minima, were successful. The hybrid has been obtained after 5 attempts involving hundreds of pollinations. The pollen proteins of the parental as well as the F1 generation have been examined by isoelectrofocusing (IEF). The proteins from each species and each hybrid form displayed a distinct and constant pattern. The pollen protein profile thus represents a new, quite easily accessible character by which F1 hybrids between the species studied can be unequivocally identified, whereas the morphological criteria described in the literature to distinguish intermediate forms is insufficient for this purpose. 相似文献