中低渗油藏调驱用纳米聚合物微球的稳定性能评价

本文针对纳米微球调剖的要求,通过分散稳定实验和粒径的电镜分析对三种反相微乳液制备的微球进行了筛选,并对选定的MG-50型微球进行热稳定性实验和剪切稳定性实验。结果表明,MG-50型微球在地层水和注入水中长期分散稳定,22 d粒径膨胀倍数高达7倍,分布范围大;0.3%MG-50微球乳液注入低渗透填砂管在85℃放置三个月封堵率仍在75%以上,但是强度下降,易破碎;流变性测量表明该乳液剪切变稀, 结合Darcy公式和Poiseuille定律计算了体系不同速率下注入低渗岩心的剪切速率,结果显示剪切速率对的阻力系数影响不大,即该体系有较好的抗剪切作用。     

Cultivation-Induced Effects on the Organic Matter in Degraded Southern African Soils

We studied quantitative and qualitative changes in soil organic matter (SOM) due to different land uses (reference woodland versus cultivated) on six soils from Tanzania (Mkindo and Mafiga), Zimbabwe (Domboshawa and Chickwaka), and South Africa (Hertzog and Guquka). Structural characteristics of the humic acids (HAs) were measured by Curie-point pyrolysis–gas chromatography/mass spectrometry (P_y–GC/MS) and solid-state ¹³C nuclear magnetic resonance (CPMAS ¹³C NMR) spectroscopy. Significant changes in concentration and composition of SOM were observed between land uses. Losses of organic carbon after cultivation ranged from 35% to 50%. Virgin soils showed large proportions of colloidal humus fractions: humic acids (HAs) and fulvic acids (FAs) but negligible amounts of not-yet decomposed organic residues. The change in land use produced a contrasting effect on the composition of the HAs: a noteworthy “alkyl enhancement” in Mkindo soil and “alkyl depletion” in Chikwaka and to a lesser extent in Domwoshawa. The remaining soils displayed only minor alterations.     

Selection of Variovorax paradoxus-like bacteria in the mycosphere and the role of fungal-released compounds

At two occasions (2004 and 2006), a similar cluster of culturable bacteria was found to be selected in the mycosphere of the basidiomycetous fungus Laccaria proxima (Agaricales, Tricholomataceae) in the field. The bacteria, identified as related to Variovorax paradoxus, comprised 7.3-9% of the total culturable bacterial community in the L. proxima mycosphere, but were not found in corresponding bulk soil (<0.3%). One strain, denoted HB44, was selected in order to unravel the basis of the V. paradoxus mycosphere competence in in vitro experiments with the former Laccaria laccata, which was recently reclassified as Lyophyllum sp. strain Karsten (Agaricales, Tricholomataceae). In liquid culture experiments, L. strain Karsten was shown to be an avid producer of glycerol, next to acetate and formate, which constituted the most abundant carbonaceous compounds released. Strain HB44 was able to grow avidly at the expense of the glycerol liberated by the fungus, as evidenced by proton NMR analysis of the fungal exudates in the medium before and after bacterial growth. In sterilized field soil, strain HB44 survived significantly better in the presence than in the absence of L. strain Karsten. Addition of a glycerol series to the sterilized soil (without the fungus) resulted in the persistence or growth of strain HB44, but only if the pH of this soil was previously set at 5.5. Thus, we provide evidence for the contention that tricholomataceous fungi can create specific niches in soil for the V. paradoxus-related strain HB44 and that glycerol may be a main carbon source that drives the selection of this organism.     

Isotope-edited nuclear magnetic resonance: novel methodologies for investigating metabolism

While the use of NMR and stable isotopes in metabolism studies is hardly new, it is only recently that isotope-edited NMR spectroscopy has been applied in kinetic studies of glyphosate metabolism of soil microbes. NMR can detect multiple species simultaneously and non-destructively, yielding valuable information on structural identification of metabolites. T riple R esonance I sotope ED ited spectroscopy (TRIED), [²H]NMR, and [²H–¹³C] INEPT (I nsensitive N ucleus E nhancement through P olarization T ransfer) are three isotope-edited techniques which have been used in combination to examine the microbial degradation of glyphosate (N-phosphonomethylglycine). Using ¹³C- and ¹⁵N-labeled glyphosate, TRIED can detect multiple metabolites in crude matrices at submicrogram levels, an improvement over earlier techniques where milligrams were needed. It can detect 500 nanograms of ¹³C–¹⁵N-labeled compound in a crude sample (1 : 1400 mass ratio), only a few hours work being required. [²H]NMR and [²H–¹³C]INEPT were also used as complementary techniques to further examine metabolites whose ¹³C–¹⁵N bond has been cleaved. The three-isotope-edited methods produced results consistent with both radioactivity and HPLC analyses. Accordingly, we are able to detect minute levels of metabolites in the presence of complex mixtures, minimizing the costs and time of sample purification. ©1999 Society of Chemical Industry     

Production of Induced Secondary Metabolites by a Co-Culture of Sponge-Associated Actinomycetes,Actinokineospora sp. EG49 and Nocardiopsis sp. RV163

Two sponge-derived actinomycetes, Actinokineospora sp. EG49 and Nocardiopsis sp. RV163, were grown in co-culture and the presence of induced metabolites monitored by ¹H NMR. Ten known compounds, including angucycline, diketopiperazine and β-carboline derivatives 1–10, were isolated from the EtOAc extracts of Actinokineospora sp. EG49 and Nocardiopsis sp. RV163. Co-cultivation of Actinokineospora sp. EG49 and Nocardiopsis sp. RV163 induced the biosynthesis of three natural products that were not detected in the single culture of either microorganism, namely N-(2-hydroxyphenyl)-acetamide (11), 1,6-dihydroxyphenazine (12) and 5a,6,11a,12-tetrahydro-5a,11a-dimethyl[1,4]benzoxazino[3,2-b][1,4]benzoxazine (13a). When tested for biological activity against a range of bacteria and parasites, only the phenazine 12 was active against Bacillus sp. P25, Trypanosoma brucei and interestingly, against Actinokineospora sp. EG49. These findings highlight the co-cultivation approach as an effective strategy to access the bioactive secondary metabolites hidden in the genomes of marine actinomycetes.     

Qualitative modifications of humic acid-like and core-humic acid-like during high-rate composting of pig faeces amended with wheat straw

Humic acid-like (HA-like) and core-humic acid-like (core-HA-like) were characterized during the high-rate composting process by CP-MAS ¹³C NMR, pyrolysis-gas chromatography (GC)/mass spectrometry (MS), and elemental analysis. Results obtained indicated that humification proceeded through a relative concentration of aromatic fractions due to the faster degradation of the O-alkyl and alkyl fractions. Core-HA-like, after purification of the parent material, showed a large reduction of the O-alkyl fraction in terms of HA-like. We concluded that HA-like consisted of refractory organic molecules, such as lignin and biopolymers, which formed a stable structure (core-HA-like) coated with degradable material associated with the core by weak physical association, ether or ester bounds.     

Pretreatment of partially delignified hybrid poplar for biofuels production: Characterization of organosolv hemicelluloses

In this study, extraction of hemicelluloses from the carbohydrate-enriched residues was successfully carried out with organic solvent and the residue was used for bio-based energy production. The chemical composition and physico-chemical properties of six hemicelluloses released were elucidated by a combination of sugar analysis, molecular determination, Fourier transform infrared, and ¹H, ¹³C and 2D-HSQC NMR spectroscopy. The results showed that the successful treatments resulted in a fractionation of the native hemicelluloses. The sugar analysis indicated that xylose (47.14-56.91%) was found to be the major sugar components and small amounts of glucose (14.1-19.06%) and mannose (12.41-18.09%) were also observed in these hemicellulosic fractions. Further studies by NMR spectroscopy exhibited that the acetylated hemicellulosic fraction had a main structure of (1 → 4)-linked β-d-xylopyranosyl backbone with 4-O-methyl-α-d-glucuronic acid as a side chain and a minor structure of linear β-(1 → 4)-linked glucomannans. Furthermore, these hemicelluloses possessed a low substituted degree which was beneficial for enzymatic saccharification.     

Molecular mobility in model dough systems studied by time-domain nuclear magnetic resonance spectroscopy

The microscopic distribution and dynamic state of water and molecular mobility in various model systems are investigated using time-domain NMR spectroscopy. Starch and gluten showed different continuous distribution populations in T₂₁ (μsec range, obtained from One pulse experiments) and T₂₂ (msec range, obtained from CPMG experiments) proving that starch and gluten have different water dynamics and molecular mobility. A starch/gluten mixture (76:12, w/w) and wheat flour dough exhibited similar patterns indicating that water and molecular mobilities in dough tended to be more representative of interactions with starch than gluten, even though both water–starch and water–gluten interactions are occurring in wheat flour dough. Increasing the water content did not influence the continuous distribution pattern of T₂₁ but affected the relative amount of each fraction in T₂₁ (i.e. an increase of the more mobile fraction and a decrease of the less mobile fraction with increasing moisture). Added water has an important role in the more mobile fraction but not in the less mobile fraction, which is in μs range. This indicates that model food systems contain multiple microstructural domains with various water and molecular mobilities that show correspondingly different water dynamics. Therefore, the dispersion of various relaxation time constants helped identify the distribution of independent microstructural domains. The manipulation of the composition of the model food system influences the water dynamics and molecular mobility and provides a basis for the application of the microstructural domain concept to real food systems.