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1.
The effects of four pesticides (three herbicides, atrazine, paraquat, glyphosate, and an insecticide, carbaryl) on the activity and kinetics of an invertase (from yeast), a urease (from jack bean) and an acid phosphatase (from potato) were investigated. Glyphosate and paraquat showed a marked activation effect on invertase activity. From the dependence of Vmax and Km parameters on pesticide concentrations, a mixed-type activation mechanism was suggested. The kinetic behaviour of urease and acid phosphatase appeared to be uninfluenced by both pesticides. Methanol, used as solvent for both carbaryl and atrazine, inhibited invertase, urease and acid phosphatase with, respectively, competitive, non-competitive and uncompetitive mechanisms. The extent of the inhibition was different, as estimated by the values of the inhibition constant K1. An additional inhibition effect of urease and invertase activities was achieved in the presence of carbaryl, whereas no influence was detected on the activity and kinetics of acid phosphatase. Finally, atrazine was shown to alter the kinetics of the enzymes only at higher concentrations.  相似文献   
2.
Extremely halophilic archaea (EHA) might play an important role in salted fish production. So far, limited information has been available on the effect of EHA and salt concentration on the safety and quality characteristics of salted anchovies. Eight Halobacterium salinarum strains were isolated from different sea salt samples and subjected to phenotypic and genotypic characterization. The strains were then inoculated into fresh salt before addition to anchovies. A total of 18 experimental productions were performed. The inoculated trials showed the lowest counts of undesired microorganisms. In particular, salted anchovies produced with Hbt. salinarum H11 showed the lowest histamine concentration as well as the highest sensory scores. Differences in terms of volatile organic compounds (VOCs) were estimated among trials. Furthermore, multivariate analysis showed that experimental production performed with a reduced amount of salt (175 g of sea salt per kg of anchovies) did not affect the final quality of salted anchovies. The strain Hbt. salinarum H11 produced salted anchovies with well-appreciated organoleptic features. Thus, the addition of EHA and the use of a lower amount of sea salt might represent a valuable alternative to the traditional method for production of salted anchovies.  相似文献   
3.
Adsorption–desorption characteristics of 2,4-dichlorophenoxyacetic acid (2,4-D) on pure montmorillonite and synthetic chlorite-like complexes [Al(OH)x-montmorillonite complexes, obtained by coating montmorillonite surfaces with different amounts of Al(OH)x] were investigated. The equilibrium adsorption of 2,4-D was described by both Langmuir and Freundlich type isotherms. The extent of adsorption as well as the type of interaction between adsorbate and adsorbent was affected by the nature of incubation buffer and the charge characteristics of supports. At pH 5·6 and in acetate buffer, 2,4-D was negatively adsorbed by montmorillonite and herbicide adsorption capacity increased with increasing amounts of Al(OH)x species loaded on montmorillonite surfaces. When adsorption experiments were performed at the same pH but in phosphate buffer, strong reductions of both the amount of adsorbed pesticide and its affinity for the adsorbents were measured. Evidently, phosphate anions competed strongly with 2,4-D anions for the sorption site on chlorite-like complexes. Furthermore, desorption tests revealed that a large amount (about 60%) of the pesticide was firmly bound to the clay and was not removed even after repeated washings or 24 h exposure to desorption solution. Both electrostatic interactions between the negative COO- moieties of 2,4-D and the positive sites on clays, and ligand exchanges of COO- groups with -OH or water at the clay surface were probably involved in the adsorption process. ©1997 SCI  相似文献   
4.
The molecular changes of organic matter in a cultivated soil after compost amendments was followed by off-line-pyrolysis-TMAH GC-MS. Thermochemolysis of soil and compost provided a detailed molecular characterization of soil organic matter (SOM) by releasing a large amount of different molecules mainly derived from plant biopolymers such as lignin, waxes and bio-polyesters. No significant differences were found before and after 1 year of cultivation in the pyrolytic products released by control soil, which were mainly fatty acids, oxidized forms of lignins, and minor amounts of microbial bio-products and biopolyesters derivatives. Conversely, significant qualitative and quantitative variations were found in the molecular characteristics of SOM between control and compost-amended soils after 1 year of cultivation. Increasing amounts and diversified components of fatty acids, n -alkanes and various biopolyesters derivatives such as hydroxy-alkanoic and alkandioic acids were found in the compost-amended soil. These results indicate that a significant amount of exogenous compost-derived organic molecules were incorporated into SOM after 1 year of cultivation. The organic structural indexes derived from these results indicated direct inputs of undecomposed lignin residues and hydrocarbon waxes from compost material. When compared with the control soil, small but significant amounts of plant biomarkers, such as cyclic di- and triterpenes derivatives, were found only in the compost-amended soil. These findings suggest that the molecular changes of SOM brought about by amendment with biomass residues can be followed by using thermochemolysis of bulk soil samples.  相似文献   
5.
Chemically stable di- and triacetyl derivatives of the natural o-diphenol antioxidant hydroxytyrosol were synthesized, and their chemical and biological antioxidant activities were assessed in comparison with that of the native synthetic compound. The chemical antioxidant activity of the selected compounds was evaluated by measuring the ferric reducing antioxidant power (FRAP). The data clearly indicate that, as expected, the hydroxytyrosol analogues, modified in the o-diphenolic ring, are devoid of any chemical antioxidant activity. On the contrary, both acetyl derivatives, at micromolar concentrations, equally protect against tert-butylhydroperoxide-induced oxidative damages in Caco-2 cells and human erythrocytes. This paper for the first time reports that chemically stable hydroxytyrosol acetyl derivatives, although devoid of chemical antioxidant activity, are as effective as the parent compound in protecting human cells from oxidative stress-induced cytotoxicity, after metabolization by esterases at the intestinal level, suggesting their possible utilization in either nutritional (functional food), cosmetic, or pharmaceutical preparations.  相似文献   
6.
The cultivation of tomato, and other Solanaceae, is of major importance for European agriculture. The revival of the Mediterranean diet is helping to bring back to the tables of European peoples many Solanaceae, and particularly tomato. The European and International demand for processed tomato products has sharply increased the interest given to this culture. Nevertheless tomato is a plant strongly infested by insect pests. This paper presents the state of the art concerning the spread of the invasive Gelechiidae moth, Tuta absoluta (Meyrick) in Italy, along with data on surveying strategies to monitor the insect at regional level.  相似文献   
7.
A hydroxytyrosol triacetyl derivative was very efficiently produced as a highly pure stabilized antioxidant compound by a short treatment of olive mill waste water (OMWW) organic extracts, rich in hydroxytyrosol, with an acetylating mixture composed of HClO4-SiO2 and Ac2O (Chakborti and Gulhane reaction), in mild and safe conditions. A successive single step of middle pressure liquid chromatography (MPLC) purification of the reaction product was performed, with an overall yield of 35.6%. (This process, including both the Chakborti and Gulhane reaction and the MPLC purification, is protected by an international patent under PCT/IT2005/000781.) The o-diphenol triacetyl derivative was also produced by direct reaction of hydroxytyrosol, previously purified by MPLC, with HClO4-SiO2 and Ac2O, with an overall yield of 29.5%. A further procedure for the production of the hydroxytyrosol triacetyl derivative was consistent with the direct treatment of raw OMWW with the acetylating agent and a single step of MPLC purification, with an overall yield of 27.6%. The purified natural triacetylhydroxytyrosol confirmed the same strong protective effects against the oxidative stress in human cells as the corresponding synthetic compound, likely because of the biochemical activation of the acetyl derivative into the active parent hydroxytyrosol by esterases. We therefore propose the utilization of OMWW for recovering hydroxytyrosol as a natural antioxidant in a chemically stabilized form, with a good yield, which can be potentially used as a nontoxic functional component in nutritional, pharmaceutical, and cosmetic preparations.  相似文献   
8.
The influence of air-drying on dehydrogenase, invertase, -glucosidase, urease, phosphatase, arylsulphatase and phenoloxidase activities was measured in three soils affected by anthropogenic activities and in control soils sampled from neighbouring areas. The air-drying changed enzyme activity, but the behaviour was neither site-specific nor enzyme-sensitive. Canonical discriminant analysis of enzymatic activities of both moist fresh and air-dried samples was able to discriminate between altered and unaltered soils irrespective of the site. Numerical alteration indices were developed as a linear function of the seven enzyme activities and the one obtained from fresh sample data was more successful. Air-drying apparently alters in unpredictable ways enzyme activities of soils, which could lead to misinterpretation of results.  相似文献   
9.
Psychrophilic microorganisms have successfully colonized all permanently cold environments from the deep sea to mountain and polar regions. The ability of an organism to survive and grow in cryoenviroments depends on a number of adaptive strategies aimed at maintaining vital cellular functions at subzero temperatures, which include the structural modifications of the membrane. To understand the role of the membrane in the adaptation, it is necessary to characterize the cell-wall components, such as the lipopolysaccharides, that represent the major constituent of the outer membrane. The aim of this study was to investigate the structure of the carbohydrate backbone of the lipooligosaccharide (LOS) isolated from the cold-adapted Psychrobacter arcticus 273-4. The strain, isolated from a 20,000-to-30,000-year-old continuously frozen permafrost in Siberia, was cultivated at 4 °C. The LOS was isolated from dry cells and analyzed by means of chemical methods. In particular, it was degraded either by mild acid hydrolysis or by hydrazinolysis and investigated in detail by 1H and 13C NMR spectroscopy and by ESI FT-ICR mass spectrometry. The oligosaccharide was characterized by the substitution of the heptose residue, usually linked to Kdo in the inner core, with a glucose, and for the unusual presence of N-acetylmuramic acid.  相似文献   
10.
Epithrix hirtipennis Melsh. is a relatively new insect pest in South Europe on tobacco. Observations reported here on its biology and behaviour differ in some pattern from those in the North American population. For the control of TFB (Tabac Flea Beetle) big amount of chemical insecticides are used, consequently there is a requirement for alternative methods. Experiments were carried out withB. thuringiensis ssp. kurstaki and ssp.tenebrionis, Beauveria bassiana, Steinernema carpocapsae andHeterorhabditis sp. in laboratory, semifield and field conditions. The results show that in summertime against the adults by help ofBac. thur. tenebrionis in principle a successful biological control ofE. hirtipennis seems to be possible.  相似文献   
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