柴油机双卷流燃烧室内外室燃油匹配分析

为了分析双卷流燃烧室内室燃油质量分数对发动机性能的影响,研究了双卷流燃烧室最佳的内室燃油质量分数范围。首先利用AVL Fire软件仿真计算不同油束夹角下双卷流燃烧室内室燃油质量分数变化,分析内室燃油质量分数变化对发动机的动力性和排放性能的影响,发现内室燃油质量分数约为10%~20%时,发动机指示功率较高,碳烟排放较低。然后总结归纳了内室燃油质量分数随喷油提前角和转速变化的规律。转速增大,内室燃油质量分数减小;喷油提前角增大,内室燃油质量分数增大。研究表明转速提高时,适当增加喷油提前角可以保证内室燃油质量分数处于较优值,使柴油机取得较佳性能。该研究可为双卷流燃烧系统的燃油匹配提供参考。     

Rapid detection of tetracyclines and their 4-epimer derivatives from poultry meat with bioluminescent biosensor bacteria

Tetracycline (TC) specific luminescent bacterial biosensors were used in a rapid TC residue assay sensitized to meet the EU maximum residue limit (MRL) for TC residues in poultry muscle tissue (100 microg kg(-1)) by membrane-permeabilizing and chelating agents polymyxin B and EDTA. Sensitivities of 5 ng g(-1) for doxycycline, 7.5 ng g(-1) for chlortetracycline, and 25 ng g(-1) for tetracycline and oxytetracycline were reached. Except for doxycycline, the MRLs of these tetracyclines include their 4-epimer metabolites. In the biosensor assay, all four 4-epimers showed induction capacity and antimicrobial activity, and antimicrobial activity was also observed in the inhibition assay, although with lower efficiency than that of the corresponding parent compound in both assays. The biosensor assay is an inexpensive and rapid high-throughput screening method for the detection of 4-epimer TC residues along with their parent compounds.     

Kinetic and Removal Mechanisms of Ethylbenzene from Contaminated Solutions by Chitin and Chitosan

In this study, the efficiency of chitin and chitosan toward the removal of ethylbenzene from aqueous solutions was investigated. Batch adsorption experiments of ethylbenzene-contaminated waters (5?C200 mg/L) were carried out to evaluate the removal performance. Ethylbenzene uptake was determined from the changes in concentration, as the residual concentration was measured by gas chromatography with mass spectroscopy. The results indicated that the adsorption of ethylbenzene by chitin and chitosan were in agreement with the Langmuir isotherm, for two parameters model, and Redlich?CPeterson isotherm, for three parameters model. A maximum removal percentage of 65% of ethylbenzene can be achieved using chitosan as adsorbent material. The adsorption capacity of ethylbenzene followed the order chitosan?>?chitin. The pseudo-second order rate model described best the adsorption kinetics of ethylbenzene for the two selected adsorbents. The kinetic studies also revealed that the pore diffusion is not the only rate controlling step in the removal of ethylbenzene. Overall, the study demonstrated that chitosan is a potential adsorbent for the removal of ethylbenzene at concentrations as high as 200 mg/L.     

Relationship between antibacterial activity of (+)-catechin derivatives and their interaction with a model membrane

(+)-Catechin derivatives with different alkyl chain lengths were synthesized from (+)-catechin and various straight chain alkylaldehydes in the presence of methyl mercaptan, and their antibacterial activities against Gram-positive bacteria were evaluated. The antibacterial activity increased markedly with elongation of the alkyl chain lengths of the derivatives and reached a maximum at a chain of four to seven carbons. Subsequently, interaction of the (+)-catechin derivatives with a model membrane using liposome was investigated. The derivatives with a chain of three carbons or more were found to have very strong affinity for the membrane. The injury action of the derivatives against the membrane was examined with liposome in which calcein was enclosed as a fluorescent indicator. The leakage was observed in the derivatives with chain lengths of four carbons or more. Particularly the derivatives with chains longer than five carbons are considered to destroy the liposome membrane judging from the degree of the fluorescent leakage. These results implied that the lipophilicity and disrupting ability of the (+)-catechin derivatives to the liposome membrane participate in their antibacterial activity.     

Acetylene reduction by bacteria isolated from the rhizosphere of wheat

An asymbiotic bacillus possessing N₂-ase activity and capable of growth on low-N media was consistently isolated from the rhizosphere of a chromosome substitution line of spring wheat in which a pair of chromosomes 5D from the cultivar Rescue had been substituted for those of ‘Cadet’. None of the bacilli were isolated from either of the two parent cultivars, Rescue and Cadet, or from the corresponding substitution line involving a homoeologous chromosome 5B. Maximum C₂H₂ reduction to C₂H₄ by pure culture isolates was found to occur at a partial pressure of 0.2 atm C₂H₂. C₂H₂ reduction was diminished in the presence of O₂ and nearly ceased at a partial pressure of 0.08 atm O₂.The data presented suggest that altering the genetics of the wheat plant can change the root environment to favor the establishment of bacilli that exhibit N₂-ase activity in pure culture.     

选用解磷菌剂改善缺磷土壤磷素的有效性

山西省大部分土壤为石灰性土壤,耕地土壤缺磷较严重,施入土壤的化学磷肥极易被固定,为了提高缺磷土壤磷素的有效性,分离筛选的B2和B67菌株研制的解磷菌剂(后称菌剂),首先接种到以磷酸三钙为唯一磷源的培养基中,液体速效磷含量比CK提高12.92倍和9.18倍,然后又接种到其它典型缺磷土壤中,可使土壤速效磷含量较CK增加1.35~3.04倍,且发现其溶磷效果和液体的pH值有关,也与土壤磷酸酶活性和有效活菌数相关,而且菌剂在提高土壤速效磷含量的同时,也提高了土壤速效钾的含量。另外菌剂在缺磷的盆栽和大田试验中取得相同效果,除显著提高土壤速效磷含量,培肥土壤外,同时还有改善作物农艺性状,提高作物产量的功效。     

产脂肽菌株发酵生物有机肥的生物防治与促生作用研究

选取对番茄青枯菌有明显抑制作用的产脂肽菌株XZ-173,与有机肥混合发酵制成生物有机肥。通过温室盆栽试验,评价了该生物有机肥对番茄青枯病的防治效果及对番茄的促生效用。结果表明,生物有机肥能够显著降低青枯病发病率,相对防效达56.8%。与施用化肥和未添加XZ-173的有机肥处理相比,施用该生物有机肥能显著提高番茄植株叶绿素含量、番茄地上部和地下部生物量、根际土壤细菌和放线菌数量,显著降低根际土壤中真菌数量。生物有机肥的有益效果使其在作物种植中具有广阔的应用前景。     

Quantitation of the hydroxycinnamic acid derivatives and the glycosides of flavonols and flavones by UV absorbance after identification by LC-MS

A general approach was developed to quantify hydroxycinnamic acid derivatives and the glycosides of flavonols and flavones using UV molar relative response factors (MRRFs). More than 90 standards were analyzed by LC-MS and divided into five groups based on the λ(max) of their band I absorbance profiles. For each group, a commercially available standard was chosen as the group reference standard. Response factors were determined for each standard in each group as purchased (MRRF) and, when possible, after vacuum drying (MRRF(D)). The MRRF(D) values for 17 compounds whose λ(max) values fell within ±2 nm of the group reference standard were 1.01 ± 0.03. MRRF values for compounds whose λ(max) values fell within ±10 nm of the group reference standard were 0.96 ± 0.13. Group reference standards were used to quantify 44 compounds in Chinese lettuce, red onion, and white tea. This approach allows quantitation of numerous compounds for which there are no standards.     

Study of bacteria from manganese concretions. Precipitation of manganese by whole cells and cell-free extracts of isolated bacteria

A microbiological examination of manganese concretions which were found in an alfisol soil of West Peloponnese, Greece, is presented. Two new Mn²⁺ oxidizing bacteria identified as Pseudomonas sp. nov. (E₁) and Citrobacter freundii (E₄) were isolated from the core of the concretions. The Mn²⁺ oxidizing activity of the isolates was demonstrated on solidified media. The quantitative determination of Mn²⁺ precipitation was performed by activation analysis and atomic absorption spectrophotometry. The mechanism of Mn²⁺ precipitation was studied using whole cell, and cell-free extracts of both bacteria; a precipitation of 50% and 70%, respectively, occurred without any change in the pH. The precipitation of Mn²⁺ depended on the concentration of the whole cells and of the cell-free extracts and was independent of the presence of Mn during the growth of the cultures. The activity of cell-free extracts is heat sensitive and inhibited by HgCl₂.The porosity of the concretions and the presence of amorphous manganese oxides in them, together with the morphology and physiology of the bacteria isolated from the core of them, present good evidence that those bacteria play an important role in the formation of the examined concretions.     

Contributions by fungi and bacteria to aggregate stability of cultivated soils

Stability changes during ageing (sterile) or incubation (non-sterile) of both natural field aggregates and remoulded aggregates from five soils were studied for periods up to 30 days. Growth of fungal hyphae, estimated by ergosterol measurement, corresponded to temporary stability increases in both types of aggregates during the first 15 days. Thereafter, fungal hyphae disappeared and were replaced by actinomycetes and bacteria. Increased stability due to entanglement by hyphae was comparable to that due to thixotropy in remoulded aggregates. Bacterial growth accompanied the fall in stability associated with fungal decline, but had little direct effect in stabilizing soil aggregates. Destruction of polysaccharides by periodate oxidation greatly diminished aggregate stability. The role of bacterial polysaccharides in soil aggregate stability is discussed.     

Utilization of organic materials in soil aggregates by bacteria and fungi

Cultures of six fungi and two bacteria were added to samples of aggregates in which either ¹⁴C-labelled glucose or starch was thoroughly distributed in macro- and micropores or in control samples where the labelled substrates were added to the preformed aggregates and considered to be mainly in macropores. The release of ¹⁴CO₂ was monitored over a 24-day incubation.In the control samples with substrates mainly in macropores, the bacteria were as active as fungi in releasing ¹⁴CO₂ from both soils. When the substrates were distributed in macro- and micropores in aggregates made from a fine sandy loam, the fungi were more efficient than bacteria in releasing ¹⁴CO₂. This was not the case in a self-mulching clay.The initial flush of ¹⁴CO₂ released during incubation of the amended fine sandy loam was due mainly to fungi, which were followed by a secondary bacterial population. The change in populations occurred simultaneously with a step in the cumulative ¹⁴CO₂ release curve thought to be due to the utilization of all the labelled substrate added, followed by renewed respiration as the secondary population flourished. The results presented fit well with an efficiency of C assimilation by micro-organism in soil of about 60%.     

Root exudation of sorghum and utilization of exudates by nitrogen-fixing bacteria

Qualitative differences in the soluble exudates of seedlings of different sorghum (Sorghum bicolor) genotypes were demonstrated by variation in growth of diazotrophic bacteria in exudate-containing media. Isolates varied in their ability to utilize the exudate from a given genotype. Variation in the amounts of soluble carbon exuded by axenically grown seedlings of the different genotypes was also observed. However, the variation in plant-associated acetylene reduction activity of one strain, Azospirillum lipoferum 4ABL, did not reflect the variation in exudation of soluble organic carbon, nor the variation in ability of the isolate to utilize the exudates in semi-solid media.     

Assessment on the fermentability of xylooligosaccharides from rice husks by probiotic bacteria

Liquors from rice husk autohydrolysis, containing xylooligosaccharides (XOS), other saccharides, and nonsaccharide compounds, were refined by membrane processing to increase the proportion of substituted XOS in refined liquors. XOS were assayed for composition and degree of polymerization (DP) distribution and hydrolyzed with commercial enzymes for obtaining XOS with DP in the range of 2-6. Nanofiltered, hydrolyzed liquors were subjected to ion exchange processing to yield a final product containing monosaccharides, XOS (accounting for 55.6% of the nonvolatile solutes), and other nonvolatile compounds. The solution obtained after enzymatic hydrolysis with commercial xylanases (in which 82.8% of XOS were in the DP range of 2-6) was examined as a medium for promoting the growth of Bifidobacterium adolescentis CECT 5781, B. longum CECT 4503, B. infantis CECT 4551, and B. breve CECT 4839. The growth rate of B. adolescentis (0.58 h(-1)) was higher than the ones determined for B. longum, B. infantis, and B. breve (0.37, 0.30, and 0.40 h(-1), respectively). The percentage of total XOS consumption by B. adolescentis was 77% after 24 h, the highest percentage of utilization corresponding to xylotriose (90%), followed by xylobiose (84%), xylotetraose (83%), and xylopentaose (71%).     

硅酸盐细菌肥有效活菌的确认与判定

把硅酸盐细菌培制成菌肥 ,施于土壤中 ,具有多方面的综合功效 ,因此它是菌肥中有发展前途的一种。近几年来 ,多种微生物肥料在我国已由研究转入应用阶段 ,因而对其质量的监控就显得尤为重要 ,而有效活菌数是菌肥质量好坏的关键指标之一 ,虽然 NY2 2 7- 94微生物肥料标准对一些菌肥有效活菌数的测定用平板计数法作了规定 ,但其对平板上菌落的辨认、菌的染色确认及有效活菌数的判定方法未做具体说明 ,笔者根据近年检测实践 ,对硅酸盐细菌肥有效活菌数的测定在这方面作了较多实践。1　菌落的辨认按 NY2 2 7- 94微生物肥料标准方法操作 ,将菌…     

Profiling the chlorogenic acids and other caffeic acid derivatives of herbal chrysanthemum by LC-MSn

Four samples of herbal chrysanthemum have been profiled qualitatively by LC-MS5 to identify their component chlorogenic acids and partially characterize other caffeic acid derivatives. The chlorogenic acids were minor components, and the four samples varied markedly in profile. Three p-coumaroylquinic acids, three feruloylquinic acids, four caffeoylquinic acids, six dicaffeoylquinic acids, and two tricaffeoylquinic acids were detected, 13 for the first time from this source. Partial characterization of minor components suggested the presence of five caffeoyl-hexose esters and caffeic acid-4-beta-d-glucose that have not previously been reported from this source, and eight caffeoylquinic acid glycosides and 16 dicaffeoylquinic acid glycosides that have not previously been reported in nature. Succinic acid-containing chlorogenic acids and chlorogenic acids based on epi-quinic acid, previously reported in Chrysanthemum spp., were not detected in these samples.     

Growth rate of bacteria is affected by soil texture and extraction procedure

Effects of soil texture on the extraction efficiency of bacteria from soils and on biosynthetic activity of the extracted bacteria were studied. Bacterial extracts were prepared from three soils of different texture by homogenization (ultrasonication and mixing) or by homogenization-centrifugation at different speeds. Bacterial biosynthetic activity was estimated using thymidine and leucine incorporation techniques. In each step of the extraction procedure, a higher extractability of bacteria was obtained in finer soils than in coarse soil. Also cell-specific growth rates of bacteria were higher in the finer soils than in the coarse soil. However, in all soils, the extracted bacteria always had significantly lower cell-specific thymidine and leucine incorporation rates than the bacteria in soil slurries and thus did not represent so well the bacterial growth in the original soils. The total declines in cell-specific incorporation rates caused by the extraction were larger in fine soil (96-98%) than in coarse soil (90%), but bacteria in the coarse soil were more responsive to only minor intervention. The homogenization-centrifugation method eliminated the differences in bacterial biosynthesis found when working with soil slurries. Therefore, we recommend using of soil slurries or, optionally, soil suspensions to compare bacterial biosynthetic activity among soils of different textures.     

Biotransformation of PCBs by plants and bacteria – consequences of plant-microbe interactions

Plant-microbial interactions within rhizosphere can evolve beneficial effect on degradation or increased accumulation of organic and inorganic contaminants. Our study shows the possibility of additional metabolic interactions between bacteria and plants in contaminated environment on level of their intermediates and their transformation. On example of model contaminants – PCBs, we give more detailed information about abilities of biological systems to metabolise original xenobiotics and also their intermediates and products. The enzymes of bacterial biphenyl operon were able to metabolise intermediates of plant PCB transformation namely 2-chloro-4-hydroxy biphenyl (2Cl-4OHBP) and 3-chloro-4-hydroxybiphenyl (3Cl-4OHBP). In case of other tested hydroxylated chlorobiphenyls the mode of oxygenation as well as the stability of the metabolites produced, greatly differed depending on the type of substituents. Similarly plant cells were able to metabolize, in limited extent, bacterial products of PCB degradation – chlorobenzoates (CBAs). From the four tested plant species tobacco, horseradish, nightshade and alfalfa showed significant transformation abilities only horseradish and black nightshade. Both metabolized in 2 weeks more than 90% of 2-chlorobenzoate and 20–40% of 2,3-; 2,4-; 2,5- and 2,6-dichlorobenzoates.     

壳聚糖及UV-C处理对长山药冷害和品质的影响

为探讨壳聚糖及UV-C处理对贮藏过程中长山药冷害和品质的影响,以长山药为试验材料,采用不同浓度的壳聚糖及不同剂量的UV-C照射处理长山药块茎,对比分析长山药的冷害指数、可溶性固形物、丙二醛(MDA)、相对电导率、抗氧化酶类活性等指标的变化。结果表明,维持长山药块茎品质的壳聚糖最佳浓度为1.0%,UV-C最佳照射剂量为6 KJ·m^-2。此条件下,壳聚糖、UV-C、壳聚糖+UV-C处理都能有效降低长山药块茎的冷害指数,抑制其MDA含量和相对电导率的升高,保护膜结构的完整性,显著降低了多酚氧化酶(PPO)活性,还可以保持较高的可溶性固形物含量和过氧化物酶(POD)活性,说明这3种处理均可控制长山药冷害的发生,延长块茎的贮藏期,其中以壳聚糖+UV-C处理效果最佳。本研究结果为减缓采后长山药冷害提供了一定的理论依据。     

Effects of plant growth-promoting bacteria on the phytoremediation of cadmium-contaminated soil by sunflower

This paper describes the effect of plant growth-promoting bacteria on sunflower growth and its phytoremediation efficiency under Cd-contaminated soils. Four levels of bacteria inoculation (non-inoculation, inoculation by Bacillus safensis, Kocuria rosea and co-inoculation by Bacillus safensis+Kocuria rosea) and four Cd concentrations (0, 50, 100 and 150 mg Cd per kg soil) were arranged as factorial experiment based on a completely randomized design (CRD). Results showed that Cd significantly decreased growth by decreasing the shoot and root length and biomass (p < 0.01). In addition, Cd dramatically decreases photosynthetic pigments, Fe transport to shoot and Zn uptake (p < 0.01). Bacterial inoculation increased Fe and Zn uptake by plants, Cd concentration in the aboveground part of plants and Cd uptake by the enhancement of Cd concentration in plant tissue and biomass production. Results showed that the highest shoot Cd uptake was ?observed in ?inoculated plants by Bacillus safensis at Cd100 (20.35 mg pot^?1). However, in average of Cd treatments, the performance of co-inoculation in Cd uptake (13.04 mg pot^?1) was better than singular inoculation (10.68 and 12.58 mg pot^?1 for Bacillus safensis and Kocuria rosea, respectively). Results revealed that bacterial inoculation increased the Cd uptake performance in shoot and total biomass by 30% and 25%, respectively.