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131.
Seasonal variations of methane fluxes from an unvegetated tidal freshwater mudflat (Hammersmith Creek, GA) 总被引:1,自引:0,他引:1
Wetlands are estimated to contribute nearly 40 % of global annual methane (CH4) emissions to the atmosphere. However, because CH4 fluxes from these systems vary spatially, seasonally, and by wetland type, there is a large uncertainty associated with scaling up the CH4 flux from these environments. We monitored seasonal patterns of CH4 cycling from tidal mudflat wetland sediments adjacent to a vegetated freshwater wetland in coastal Georgia between 2008 and 2009. CH4 emissions were significantly correlated with CH4 production and sediment saturation state with respect to CH4 but not with temperature. CH4 cycling displayed distinct seasonal patterns. Winter months were characterized by low CH4 production and emissions. During the spring, summer and fall, CH4 fluxes exceeded CH4 production in the top 40 cm. Comparison of CH4 sources and sinks in conjunction with the interpretation of CH4 concentration profiles using a 1D reactive transport model indicated that CH4 delivered via lateral tidal pumping likely provided additional CH4 to the upper sediment column. Seasonally high CH4 ebullition rates reflected increased CH4 production and decreased CH4 solubility. The annual CH4 flux was estimated to be on the order of 10 mol CH4 m?2 y?1 which is 2–4 times the global average for wetland CH4 emissions. Thus, even though tidal freshwater mudflats are of limited spatial extent, these environments may serve as globally significant sources of CH4 to the atmosphere. This study highlights the importance of these dynamic environments to the global CH4 cycle and their relevance to climate change. 相似文献
132.
Influence of temperature and humidity on the survival of Monilinia fructicola conidia on stone fruits and inert surfaces 下载免费PDF全文
M. Bernat J. Segarra J.A. Navas‐Cortés C. Casals R. Torres N. Teixidó J. Usall 《The Annals of applied biology》2018,173(1):63-70
The survival of the fungus Monilinia fructicola on fruit and inert surfaces at different temperatures (range: 0–30°C) and relative humidity (RH) (range: 60–100%) was investigated. M. fructicola conidia survived better on fruit than on inert surfaces. The viability reduction rate at 20°C and 60% RH was 1.2 and 5.8 days?1 on fruit and inert surfaces, respectively. Overall, on fruit surfaces, conidia viability was reduced at high temperatures and was longer at higher RH than at lower RH; in contrast, on inert surfaces, conidia viability was longer at only low temperatures. On fruit surfaces, at 0°C and 100% RH, conidia survived up to 35 days, and at 30°C and 60% RH, conidia survived up to 7 days. However, on inert surfaces at 20°C and 30°C, conidia lost their viability after 48 and 24 h, respectively. These results suggest that M. fructicola can remain viable in cold rooms for over 30 days on fruit surfaces or over 25 days on inert surfaces. Furthermore, under the orchard conditions during the growing season, conidia may remain viable for only 2–3 days on immature fruit surfaces before conidia will be unable to penetrate the host. 相似文献
133.
134.
E Mestres J. Balanà C. Segarra A. Prevosti L. Serra 《Journal of Zoological Systematics and Evolutionary Research》1994,32(2):108-116
The Western Mediterranean populations of D. subobscura have a very similar chromosomal inversion polymorphism to the American colonizing populations, with the exception of the O5 inversion. This inversion, which is found in appreciable frequencies in colonizing populations and is distributed according to a significant latitudinal cline, both in North and South America, has never been reported in that Palearctic region. Therefore, an analysis of the distribution of this inversion, along a latitudinal cline, has been carried out in Europe. The O Chromosome inversion polymorphism has been studied in seven populations: Gävle and Lilla Edet (Sweden), Gesten (Denmark), Ter-Apel (Holland) and Crézy, Aizenay and Taulé (France). The O5 inversion was only detected in three populations and in low frequencies: Gävle (3.7%), Lilla Edet (1.8 %) and Taulé (1.2 %). However, none of these three populations has all the inversions found in the American populations. The clinal distribution of some O chromosomal arrangements has also been studied according to latitude and the temporal changes of this polymorphism. 相似文献
135.
Sixteen species ofLongitarsus have been chromosomally surveyed, showing a continuous range of even numbers from 2n=26 to 2n=32 chromosomes. Among the total of twenty-three known species, about 40% display a 14+Xy male karyotypic formula, the possible modal and most primitive one for the genus. The current taxonomy of species groupings is in good agreement with the chromosome numbers in some cases, but not in others. Also, there is no interrelationship between chromosome numbers and foodplant selection. The number of large bivalents at metaphase I is generally negatively correlated with the diploid value, suggesting the possible role of centric fusions coupled to shifts in the amount of chromatin as the main chromosomal changes in the evolution ofLongitarsus. The karyotypes of a few studied species are composed of metacentric chromosomes, some of them of rather large size, and a minute y-chromosome. A possible example of polymorphism for the chromosome number inL. nigrofasciatus is reported and briefly discussed. 相似文献
136.
Bonjoch J Diaba F Puigbó G Solé D Segarra V Santamaría L Beleta J Ryder H Palacios JM 《Bioorganic & medicinal chemistry》1999,7(12):695-2897
The synthesis of an azaspirocyclic analogue of FR901483, phosphate 2, is described based on the implementation of a key 5-endo aminocyclization promoted by iodine for direct functionalization of the 1-azaspiro[4.5]decane ring at the C-3 atom. Compound 2 has no inhibitory activity in the cell proliferation assays reported. 相似文献
137.
Martínez A Gutiérrez-de-Terán H Brea J Raviña E Loza MI Cadavid MI Sanz F Vidal B Segarra V Sotelo E 《Bioorganic & medicinal chemistry》2008,16(4):2103-2113
A collection of 25 2-(2'-furyl)-1,2,4-triazolo[1,5-a]quinoxalines incorporating different substitution patterns at position 4 have been synthesized and their binding affinity towards human adenosine receptors (hA(1), hA(2A), hA(2B) and hA(3)) was determined. The biological data show that several potent at hA(1), but lightly selective, adenosine ligands were identified. Moreover, these results confirmed the hypothesis that the structural modifications carried out on the 4-position of the tricyclic system produces a remarkable modification of the adenosine receptorial profile. A 3D-QSAR modelling study (GRIND/ALMOND methodology) performed on the hA(1) data gave further support to the pharmacological results, and it is presented as a useful tool for the future design of ligands with better pharmacological profiles. 相似文献
138.
Stefanachi A Brea JM Cadavid MI Centeno NB Esteve C Loza MI Martinez A Nieto R Raviña E Sanz F Segarra V Sotelo E Vidal B Carotti A 《Bioorganic & medicinal chemistry》2008,16(6):2852-2869
A large series of piperazin-, piperidin- and tetrahydroisoquinolinamides of 4-(1,3-dialkyl-9-deazaxanthin-8-yl)phenoxyacetic acid were prepared through conventional or multiple parallel syntheses and evaluated for their binding affinity at the recombinant human adenosine receptors, chiefly at the hA(2B) and hA(2A) receptor subtypes. Several ligands endowed with high binding affinity at hA(2B) receptors, excellent selectivity over hA(2A) and hA(3) and a significant, but lower, selectivity over hA(1) were identified. Among them, piperazinamide derivatives 23 and 52, and piperidinamide derivative 69 proved highly potent at hA(2B) (K(i)=11, 2 and 5.5 nM, respectively) and selective towards hA(2A) (hA(2A)/hA(2B) SI=912, 159 and 630, respectively), hA(3) (hA(3)/hA(2B) SI=>100, 3090 and >180, respectively) and hA(1) (hA(1)/hA(2B) SI=>100, 44 and 120, respectively), SI being the selectivity index. A number of selected ligands tested in functional assays in vitro showed very interesting antagonist activities and efficacies at both A(2A) and A(2B) receptor subtypes, with pA(2) values close to the corresponding pK(i)s. Structure-affinity and structure-selectivity relationships suggested that the binding potency at the hA(2B) receptor may be increased by lipophilic substituents at the N4-position of piperazinamides and that an ortho-methoxy substituent at the 8-phenyl ring and alkyl groups at N1 larger than the ones at N3, in the 9-deazaxanthine ring, may strongly enhance the hA(2A)/hA(2B) SI. 相似文献
139.
Differentiation of Muller''s Chromosomal Elements D and E in the Obscura Group of Drosophila 总被引:1,自引:2,他引:1 下载免费PDF全文
Twenty-two markers located on Muller's elements D or E have been mapped by in situ hybridization in six species of the obscura group of Drosophila and in D. melanogaster. The obscura species can be grouped into a Palearctic cluster (D. subobscura, D. madeirensis and D. guanche) and a Nearctic one (D. pseudoobscura, D. persimilis and D. miranda). Eleven of the probes contain known genes: E74, Acp70A, Est5, hsp28/23, hsp83, emc, hsp70, Xdh, Acph-1, Cec and rp49. The remaining probes are recombinant phages isolated from a D. subobscura genomic library. All these markers hybridize to the putative homologous chromosome or chromosomal arm of elements D and E. Thus, these elements have conserved their genic content during species divergence. Chromosomal homologies proposed previously for each element among the species of the same cluster have been compared with the present results. The distribution of markers within each element has changed considerably as inferred from pairwise comparisons of obscura species included in the two different clusters. Only chromosomal segments defined by closely linked markers have been conserved: one such segment has been detected in element D and three in element E between D. subobscura and D. pseudoobscura. 相似文献