The fatty acid composition of the temperate calcareous marine sponge Leuconia johnstoni Carter 1871 (Calcaronea, Calcarea) was characterized for the first time in specimens collected off the Brittany coast of
France over four years from October 2005 to September 2008. Forty-one fatty acids (FA) with chain lengths ranging from C14 to C22 were identified as fatty methyl esters (FAME) and N-acyl pyrrolidide (NAP) derivatives by gas chromatography–mass spectrometry (GC–MS). Twenty-two saturated fatty acids (SFA)
were identified accounting for 52.1–59.0% of the total FA and dimethylacetals (DMA). In addition, among the SFA, we noticed
the presence of numerous methyl-branched iso and anteiso FA, suggesting a large number of associated bacteria within L. johnstoni. Thirteen monounsaturated fatty acids (MUFA, 28.0–36.0% of total FA + DMA) were also identified as well as six polyunsaturated
fatty acids (PUFA, 4.0–8.2%). A noticeable DMA was detected at a high level, particularly in September 2008 (11.8%), indicating
the presence of plasmalogens in this sponge species. This calcareous sponge lacked the non-methylene-interrupted FA (NMI FA)
with a Δ5,9 system typical of siliceous Demosponges and Hexactinellids. The occurrence of the unusual 8,13-octadecadienoic
acid was reported for the first time as a minor PUFA in a calcareous sponge. The major FA, representing 20–25% of this sponge
FA, was identified as the new 2-methyl-13-icosenoic acid from mass spectra of its methyl ester and its corresponding N-acyl pyrrolidide derivatives as well as a dimethyl disulfide adduct. 相似文献
An addition of boron largely increases the ductility in polycrystalline high-temperature Co–Re alloys. Therefore, the effect of boron on the alloy structural characteristics is of high importance for the stability of the matrix at operational temperatures. Volume fractions of ε (hexagonal close-packed—hcp), γ (face-centered cubic—fcc) and σ (Cr2Re3 type) phases were measured at ambient and high temperatures (up to 1500 °C) for a boron-containing Co–17Re–23Cr alloy using neutron diffraction. The matrix phase undergoes an allotropic transformation from ε to γ structure at high temperatures, similar to pure cobalt and to the previously investigated, more complex Co–17Re–23Cr–1.2Ta–2.6C alloy. It was determined in this study that the transformation temperature depends on the boron content (0–1000 wt. ppm). Nevertheless, the transformation temperature did not change monotonically with the increase in the boron content but reached a minimum at approximately 200 ppm of boron. A probable reason is the interplay between the amount of boron in the matrix and the amount of σ phase, which binds hcp-stabilizing elements (Cr and Re). Moreover, borides were identified in alloys with high boron content. 相似文献
The knowledge of the steady-state stress for plastic deformation as a function of temperature and strain rate is essential for hot-forming superconducting material into commercially useful shapes. In this paper, results are presented on the experimental determination of the rheology of fully dense polycrystalline Y1Ba2Cu3O7−x superconducting material at temperatures ranging from 750° to 950°C and strain rates of 10−4, 10−5, and 10−6 s−1. The data are best fitted by a power law: ε(s−1)=8.9 × 10−17. (s−1) σ2.5 (Pa) exp [−2.01 × 105(J·mol−1)|RT]. X-ray analysis shows that the superconducting material retains its phase composition after nearly 70% total strain of the sample. A strong anisotropy in the resistivity of the deformed samples is observed because of the development of a preferred orientation of the a or b axis of Y1Ba2Cu3O7−x orthorhombic perovskite single crystals perpendicular to the principal maximum compressive stress. 相似文献
Hydrothermal treatment of a mixture of nickel chloride, silicic acid and sodium hydroxide at a relatively low temperature, 250 °C and pressure, 10 MPa gave a 1:1 nickel phyllosilicate, [Ni3Si2O5(OH)4] composed exclusively of hollow, open ended, multiwall nanotubular particles, up to 200 nm in length. No other phases, in particular no silicate platelets were seen. Previous reports on the hydrothermal preparation of tubular nickel phyllosilicate emphasized the need for high temperatures and pressures (ca 400 °C and 70 MPa), with lower temperature giving mostly small thin plate-like products. The tubular particles obtained also had larger outer diameters, 25–30 nm, and larger inner hollow cores, about 10 nm in diameter than nickel silicate nanotubes prepared at high temperatures and pressures. The XRD pattern of the product matched that of pecoraite, the nickel analogue of the tubular magnesium silicate mineral chrysotile. N2-sorptometry showed the product was mesoporous with a broad range of pore sizes centred around 170 Å, and a BET surface area of 110 m2/g. 相似文献
Mutations within the glucocorticoid receptor (GR) gene locus lead to glucocorticoid resistance which is characterized by several clinical symptoms such as adrenal gland hyperplasia and salt-sensitive hypertension, although the underlying mechanisms are still unknown. We studied GR haploinsufficient (GR+/−) Sprague Dawley rats which, on a standard diet, showed significantly increased plasma aldosterone and corticosterone levels and an adrenocortex hyperplasia accompanied by a normal systolic blood pressure. Following a high salt diet, these rats developed salt-sensitive hypertension and maintained elevated enzyme-soluble epoxide hydrolase (sEH) in adrenal glands, while sEH was significantly decreased in wild-type rats. Furthermore, GR+/− rats showed dysregulation of the equilibrated linoleic and arachidonic acid pathways, with a significant increase of less active metabolites such as 8,9-DiHETrE. In Sprague Dawley rats, GR haploinsufficiency induced steroid disturbances, which provoked hypertension only in combination with high salt intake, which was accompanied by disturbances in sEH and fatty acid metabolism. Our results suggest that sEH inhibition could be a potential target to treat hypertension in patients with GR haploinsufficiency. 相似文献
The interaction of the nucleocapsid NCp7 of the human immunodeficiency virus type 1 (HIV-1) Gag polyprotein with the RNA packaging signal Psi ensures specific encapsidation of the dimeric full length viral genome into nascent virus particles. Being an essential step in the HIV-1 replication cycle, specific genome encapsidation represents a promising target for therapeutic intervention. We previously selected peptides binding to HIV-1 Psi-RNA or stem loops (SL) thereof by phage display. Herein, we describe synthesis of peptide variants of the consensus HWWPWW motif on membrane supports to optimize Psi-RNA binding. The optimized peptide, psi-pepB, was characterized in detail with respect to its conformation and binding properties for the SL3 of the Psi packaging signal by NMR and tryptophan fluorescence quenching. Functional analysis revealed that psi-pepB caused a strong reduction of virus release by infected cells as monitored by reduced transduction efficiencies, capsid p24 antigen levels, and electron microscopy. Thus, this peptide shows antiviral activity and could serve as a lead compound to develop new drugs targeting HIV-1. 相似文献
This work describes a model of the biodegradation of phenol carried out by aerobic granules. These granules were obtained by culturing an activated sludge supernatant in a sequencing batch reactor fed with a synthetic waste water and subsequently, by acclimation to phenol (100 mg/L). The kinetics of phenol biodegradation by the aerobic granules was investigated over a wide range of initial phenol concentrations (40–1112 mg/L) in shake‐flask cultures. A Haldane‐type model was adjusted to the experimental results, which depicts successfully the phenol biodegradation profiles in the entire range of initial concentrations studied by using only one set of parameters. It is our view that the proposed model could contribute to the knowledge about the ability of aerobic granular systems to biodegrade toxic, inhibitory compounds such as phenol. 相似文献
Within the framework of Cahn’s pioneering theory of spinodal decomposition, the effect of the epitaxial stress on the stability of a binary alloy solid solution against infinitesimal compositional fluctuations is revisited. It is shown that the elastic energy term due to a coherent lattice mismatch with a substrate modifies the linearised diffusion equation. This term is particularly high when size effects between the two constituents are strong. It is then necessary to take into account anharmonic terms in the expression of the elastic energy. From the modified diffusion equation, a new spinodal curve, called the epitaxial coherent spinodal, may be calculated for different substrate lattice parameters. The results of the model are compared with recent experiments on coherently grown (001) Au–Ni alloys. A modulated structure has been evidenced upon annealing which is in good agreement with our calculations.
Résumé
Dans le cadre de la théorie de la décomposition spinodale développèe par Cahn, nous présentons l’effet des contraintes épitaxiales sur la stabilitéd’une solution solide d’alliage binaire soumise ádes fluctuations de compostion infinitésimales. Les contraintes induites par l’épitaxie cohérente sur un substrat ayant un paramètre de maille différent de celui de la solution solide considérée sont àl’origine d’un terme d’énergie élastique dont il faut tenir compte dans l’équation de diffusion. Ce terme devient particulièrement important lorsque les effets de taille entre les deux constituants sont grands. Nous montrons qu’il est alors nécessaire de considérer dans l’expression de l’énergie élastique les termes anharmoniques. Une nouvelle spinodale, appelée spinodale cohérente épitaxiale, peut être calculée pour différentes valeurs du paramètre de maille du substrat. Les calculs sont comparés avec les résulats expérimentaux obtenus sur des alliages Au–Ni (001) élaborés de manière cohérente. Une structure modulée a étémise en evidence au cours de recuits, ce qui est en accord avec les résultats du modèle. 相似文献
A semi-empirical nonlinear model of moisture content and wet-milling quality degradation in com drying is established. The model uncertainty is expressed as a relative error level which includes a pre-specified percentage of experimental data. An optimal control strategy for batch drying is determined which maximizes the dryer throughput, while simultaneously satisfying two quality constraints on the final state: achieving specified moisture content and wet-milling quality levels. Taking into account the model uncertainty results in a conservative but less efficient control strategy. The performance - robustness compromise is discussed. 相似文献
Based on theorical analysis of existing models and on experimental observations, a model that allows us to connect the permeate flux tothe intrinsic separation factor takingaccount of the termsof the minimal and maximalseparation factors, was established. The experiments covering a large range of permeate flux (from several 10?9 μL/m 2.s) to several 10.3 mL/(m 2.s)) permit us todetermine the values of maximal seaparation and minimal separation, as well as the solute transport parameterr for the solutions of sodiumchloride and sodium sulfate. 相似文献