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1.
Among a variety of lipases tested, that obtained from Candida antarctica (SP 435) induced enantioselective hydrolysis of trifluoroethyl 5,5,5-trifluoro-4-(3'-indolyl)-3-thiapentanoate (1c). The selectivity could be increased by optimizing the reaction conditions. Thus, good selectivity was achieved (E = 37) in a buffer containing 10% dichloroethane. In order to improve the optical yields, a sequential kinetic resolution was utilized for the preparative-scale enantioselective hydrolysis of 1c using SP 435. Hydrolysis of trifluoroethyl 6,6,6-trifluoro-5-(3'-indolyl)-4-thiahexanoate (2c) with the lipase of Pseudomonas aeruginosa (LIP) in a buffer containing 20% tert-amyl alcohol at 25 degrees C gave excellent selectivity (E=357). 相似文献
2.
The activity of fresh deposits of methoprene, fenoxycarb and diflubenzuron against F 1 progeny of Rhyzopertha dominica on maize and paddy was compared with that on wheat, at two equilibrium relative humidities. There were differences between slopes of log concentration-probit (lc-p) lines for different compounds, and for the same compound on different grains. Judging by values of the IC 99.9, i.e. the concentration which inhibited progeny production by 99.9%, the order of activity against F 1 progeny on different grains was: methoprene, wheat and paddy > maize; fenoxycarb, wheat > paddy > maize; diflubenzuron, wheat and maize > paddy. Equilibrium relative humidity (e.r.h.) had no consistent effect on activity—at 90% e.r.h., the IC 50 of fenoxycarb on wheat was reduced and the IC 50 of diflubenzuron on maize was increased compared with 70% e.r.h., and other treatments were unaffected. The efficacy of these compounds on maize and paddy against F1 and F2 progeny was evaluated during 48 weeks storage at 30°C, 70% r.h. The resolved S isomer of methoprene was also included. Slopes of lc-p lines were greater against the F2 than against the F1, particularly using diflubenzuron on paddy, with corresponding smaller values of the IC99.9. Equally effective concentrations did not decline systematically over 48 weeks. Minimum effective application rates were judged as the concentrations that prevented living F2 progeny in at least 2 of 3 replicates. Estimates for 48 weeks protection on maize were: methoprene, 2 mg kg−1; S-methoprene, 1 mg kg−1; fenoxycarb, 10 mg kg−1; and diflubenzuron, 5 mg kg−1. Corresponding estimates on paddy were 0.15 mg kg−1, 0.05 mg kg−1, 5 mg kg−1, and 5 mg kg−1. 相似文献
3.
Explants of tuber, meristem and vines from three widely cultivated yam species in Jamaica— D cayenensis, D rotundata and D trifida—were examined for their responses to mineral media strength, inorganic ammonium and growth regulator supplements. Tuber pieces (5mm 3) showed some positive growth responses but did not produce in-vitro plantlets on all the media tested. Meristem tips of D trifida grew rapidly on basal media (BM) supplemented with either 0.1 mglitre ?1 6-benzylamino purine (BAP) and 0.01 mg litre ?1indole butyric acid or 0.2 mg litre ?1 BAP and 1.0 mg litre ?1 naphthalene acetic acid (NAA) producing plantlets by 28 weeks. The nodal explants grew rapidly with plantlets obtained from all the cultivars within 4 weeks. Use of young, vigorously growing vines of 8 weeks or less, as explant source, gave low contamination levels (16–25%) in culture when sterilised for 30 min in 200 g litre ?1 NaOCl in the case of D trifida and 300 g litre ?1 NaOCl in the case of D cayenesis prior to culturing. Initiation of growth was optimal when explants were taken from monopodial vines grown in October or January and placed on BM supplemented with 0.5 mg litre ?1 BAP (BM0.5BAP). Addition of 0.5 mg litre ?1 kinetin to the BM or 0.05 mg litre ?1 NAA to BM0.5BAP depressed shoot production, while 5.0 mg litre ?1 kinetin increased swelling of the nodal region in explants from sympodial shoots and from vines grown in March. The results suggest that nodal segments excised from young, fast growing vines of these species are the best explant source for the purpose of commercial micropropagation. 相似文献
4.
The residue dynamics of plant growth regulators (PGR) forchlorfenuron (CPPU), 6-benzylaminopurine (6-BA), gibberellic acid (GA 3) and ethephon in grape are presented, corresponding to their field applications at recommended and double doses. Random samples were collected from each treated and control plot at regular time intervals. The optimised sample preparation technique involves extraction of 10 g homogenised sample with 20 ml methanol (+1% formic acid) and measurement by LC–MS/MS multiple reaction monitoring, offering limit of quantification ?0.0025 μg/g for all except ethephon with LOQ of 0.005 μg/g. The recoveries at LOQ and above were 84.8–109.5%. Residue dissipation of all the PGRs followed non-linear two-compartment first + first-order kinetics. CPPU, 6-BA and ethephon residues dissipated with preharvest intervals (PHIs) of 33.5, 12 and 32 days at recommended dose with no PHI applicable for GA 3. The PHIs successfully minimised residue problems as observed from survey results of traceable field samples. 相似文献
5.
Sewage treatment plant (STP) effluents are likely a major source of contamination for PBDEs, especially in the receiving water bodies of local aquatic environments surrounding the location of these discharges. Congeners of the pentaBDE mixture, 2,2,',4,4'-tetrabromodiphenyl ether (BDE47), 2,2,',4,4',5-pentabromodiphenyl ether (BDE99), 2,2,',4,4',6-pentabromodiphenyl ether (BDE100), 2,2,',4,4',5,5'-hexabromodiphenyl ether (BDE153), and 2,2,',4,4',5,6'-hexabromodiphenyl ether (BDE154), are of great environmental concern in North America due to their persistence, potential for bioaccumulation, and >97% use of the global production of the mixture in the region. Detailed characterization of the distribution of eight PBDE congeners (2,4,4'-tribromoDE (BDE28) and BDE47, 99, 100, 138, 153, 154, and 183) was carried out at five sites along the treatment process at an activated sludge-type secondary treatment municipal STP facility. PentaBDE mixture congeners, sigma5PBDE (sum of BDE47, 99, 100, 153, and 154) accounted for >98% of the total (sigma 8) PBDE concentration at all sites, with over 80% of the composition being BDE47 and BDE99. Presence of dissolved organic matter affected the mobility of PBDEs during the initial stages of the treatment process. About 9% of the influent mass of sigma5PBDE to the facility is estimated to be discharged into the Little River (leading to the Detroit River) with the final effluent, resulting in an estimated mass loading of approximately 0.7 kg/year. The total mass loading of sigma5PBDE to the Detroit River is expected to be much larger as effluent from this facility accounts for <10% of the total STP discharges to the river. 相似文献
6.
Electric energy plays an important role in reducing the thawing time and accelerating the entire thawing process. Corona wind speed was increased by increasing the applied voltage and current, which were 0.87 ± 0.19, 1.22 ± 0.19, 1.49 ± 0.13 m/s under 8, 10, 12 kV with 3, 5, 10 μA; 1.01 ± 0.12, 1.24 ± 0.17, 1.49 ± 0.10 m/s under − 8, − 10, − 12 kV with 5, 9, 14.5 μA. The models T1, T2, and T3 were designed to study the effects of current, corona wind and electric field on thawing, respectively. T1: a thin stainless-steel sheet covered the top of stainless-steel box with 10 g frozen distilled water; T2: a plastic sheet was placed under the stainless-steel box; T3: a plastic sheet covered the top of plastic box. Electric field alone cannot affect thawing time, which could be maximally reduced by 1/2 compared to that of air thawing. Industrial relevanceWe have studied HVEF thawing for several years because of its many advantages, such as the quick thawing of frozen meat with little energy consumption and good post-thawing quality. The mechanism of HVEF thawing and the reduction of the thawing time, which are important for the industrial application of new technology from principle to design, must be clarified. Meanwhile, this emerging technology will be beneficial for the food-thawing field. 相似文献
8.
The aim of this work was to study the microstructure of vacuum-packed salmon fillets superchilled in an impingement freezer at −30 °C (air temperature) and 227 W/m 2 K (surface heat transfer coefficient, SHTC) for 2.1 min prior to storage at a superchilling storage temperature of −1.7 ± 0.3 °C for 28 days. The microstructure of vacuum-packed salmon fillets were analysed at the surface, mid-centre and centre layers. Significant differences were observed between the ice crystals formed at the surface, mid-centre and centre layers. The size of ice crystals at the centre of the superchilled fillets was 3 times larger than those at the surface layer. Significant differences were observed between the size of ice crystals formed during the superchilling process and following storage. The results further indicated that, after temperature equalisation (1 day of storage) the growth of the intracellular ice crystal was not significant at ( P < 0.05) at any storage time. 相似文献
9.
采用点滴法分别测定了12种药剂对斜纹夜蛾3龄幼虫及9种药剂对5龄幼虫的毒力,比较了不同龄期幼虫对6种药剂敏感性的差异,还测定了9种药剂对甜菜夜蛾4龄幼虫的毒力。结果表明几种药剂对斜纹夜蛾3龄幼虫的毒力大小顺序为甲维盐>茚虫威>定虫隆>毒死蜱>辛硫磷>氟虫脲>虫酰肼>丙溴磷>硫丹>多杀菌素>顺式氯氟氰菊酯>氟虫腈。对5龄幼虫的毒力大小顺序为甲维盐>溴虫腈>茚虫威>灭多威>高效氟氯氰菊酯>毒死蜱>丙溴磷>辛硫磷>硫丹。斜纹夜蛾大龄幼虫对毒力高的药剂更敏感,小龄幼虫对毒力低的药剂较敏感。溴虫腈、氟虫脲对甜菜夜蛾4龄幼虫的毒力最高,但该虫对辛硫磷、丙溴磷、毒死蜱和硫丹表现不敏感。溴虫腈、茚虫威和甲胺基阿维菌素苯甲酸盐是防治上述两种害虫的高效药剂。 相似文献
10.
The volume recovery, product quality and process economics of Rubberwood sawmilling using the conventional live sawing process and the saw dry and rip (SDR) process is described. The results showed that the SDR process, together with high temperature drying resulted in higher volume recovery and product quality compared to the conventional live sawing process. 相似文献
11.
Residues of the pesticides azoxystrobin, fenhexamid and pyrimethanil were determined in strawberry after field treatment. The effect of 'home' washing with tap water and a commercially available vegetable detergent on residue levels was also studied. After treatment, azoxystrobin and pyrimethanil residues on strawberry were on average 0.55 and 2.98 mg kg -1, respectively, values below the maximum residue level (MRL) fixed by the European Union (2.0 and 5 mg kg -1, respectively), while fenhexamid residues were on average 2.99 mg kg -1, which is very close to the MRL of 3.0 mg kg -1, but some samples were over the MRL. Thereafter, all residues declined, with a half-life of about 8 days (azoxystrobin and fenhexamid) and 4.8 days (pyrimethanil). Washing the fruit with tap water reduced the residues of azoxystrobin and fenhexamid but did not affect pyrimethanil residues. Finally, when fruits were washed with a commercial detergent, greater amounts were removed (about 45% of azoxystrobin and pyrimethanil and 60% of fenhexamid). 相似文献
12.
在常量施肥的基础上,苗期和大田期叶面喷施或穴施快大液肥,能改善烟叶生长状况,促使烟苗生长健壮,烟株根系发达,生长旺盛,开片良好,烟叶产量,均价,产值有不同程度的提高;烟叶钾含量增加,含氮化合物下降,刺激性减小,香气增加。 相似文献
13.
Polybrominated diphenyl ethers (PBDEs), polybrominated biphenyls (PBBs), and polychlorinated naphthalenes (PCNs) were quantified in blubber biopsy samples collected from free-ranging male and female killer whales (Orcinus orca) belonging to three distinct communities (southern residents, northern residents, and transients) from the northeastern Pacific Ocean. High concentrations of sigmaPBDE were observed in male southern residents (942+/-582 ng/g Iw), male and female transients (1015+/-605 and 885+/-706 ng/g Iw, respectively), and male and female northern residents (203+/-116 and 415+/-676 ng/g Iw, respectively). Because of large variation within sample groups, sigmaPBDE levels generally did not differ statistically with the exception of male northern residents, which had lower sigmaPBDE concentrations than male southern residents, male transients, and female transients, perhaps reflecting the consumption of less contaminated prey items. Male transient killer whales, which consume high trophic level prey including other cetaceans and occasionally spend time near populated areas, had sigmaPBDE concentrations approximately equal to southern residents. No significant age-related relationships were observed for sigmaPBDE concentrations. sigmaPBDE concentrations were approximately 1-3 orders of magnitude greater than those of sigmaPBB (3.0-31 ng/g Iw) and sigmaPCN (20-167 ng/g Iw) measured in a subset of samples, suggesting that PBDEs may represent a contaminant class of concern in these marine mammals. 相似文献
14.
A gas-chromatographic method is described for determination of residues of butocarboxime (Drawin), its structural isomer aldicarb (Temik), and their toxic sulfoxide and sulfone metabolites. These compounds were determined intact, by gas chromatography employing a thermionic specific detector (TSD). Breakdown of these relatively thermally unstable compounds was avoided by lowering the inlet temperature to 150 degrees C, by keeping column temperature as low as possible, and by using a low-load liquid phase (2% of OV-17 on Gas-Chrom Q). These compounds were determined in enriched extracts of samples of tomatoes and apples and also in the leaves of citrus and cotton. The method is suitable for the separation, differentiation and determination of the two isomers and their metabolites at an enrichment level of 0.1 micrograms/g of fresh weight. The results were confirmed by gas chromatography--chemical-ionization mass-spectrometry. 相似文献
15.
The popularity of "preservative-free" foods among consumers has stimulated rapid growth of processed meats manufactured without sodium nitrite. The objective of this study was to quantify the potential for Clostridium perfringens growth in commercially available processed meats manufactured without the direct addition of nitrite or nitrate. Commercial brands of naturally cured, no-nitrate-or-nitrite-added frankfurters (10 samples), hams (7 samples), and bacon (9 samples) were obtained from retail stores and challenged with a three-strain inoculation (5 log CFU/g) of C. perfringens. Reduced inhibition (P < 0.05) was observed in seven brands of frankfurters, six brands of hams, and four brands of bacon when compared with each respective sodium nitrite-added control. In naturally cured and truly uncured commercial frankfurters, growth over time was approximately 4.7 log, while conventionally cured frankfurters exhibited growth at 1.7 log. Naturally cured ham and bacon products exhibited growth at 4.8 and 3.4 log, respectively, while their conventionally cured counterparts exhibited growth at 2.6 and 2.3 log, respectively. These products also demonstrated variation in growth response. The results indicate that commercially available natural/organic naturally cured meats have more potential for growth of this pathogen than do conventionally cured products. Natural and organic processed meats may require additional protective measures in order to consistently provide the level of safety from bacterial pathogens achieved by conventionally cured meat products, and which is expected by consumers. 相似文献
16.
Although geotextiles are increasingly employed in stormwater infiltration basins, their influence on the flow and transfer of contaminants, such as heavy metals, has not been fully investigated. Leaching column experiments were conducted to characterize the flow and transfer of three heavy metals (zinc, lead, and cadmium) in a calcareous soil with and without geotextiles under steady-state flow and close to saturation forthe soil. The influence of geotextiles was characterized for two types of geotextiles (needlepunched and thermosealed) and for two different initial saturation degrees for the needlepunched geotextile. The main results showed that, when placed wet, the needlepunched geotextile had no influence. When placed dry, it homogenized the flow in its surroundings and thus allowed better contact between heavy metals and the reactive soil, resulting in an increase of their retention. The thermosealed geotextile, placed dry, homogenized the flow and increased retention over a larger area, resulting in optimal global retention. In conclusion, geotextiles could be used in infiltration basins, provided that their effect on both flow and heavy metal retention is optimized by appropriate design--choice of geotextiles--and appropriate monitoring--control of hydric conditions. 相似文献
17.
Administration of 1000 ppm alpha-HCH, 600 ppm beta-HCH and greater than or equal to 125 ppm gamma-HCH to rats caused a growth retardation. alpha-HCH and beta-HCH led to livermass enlargement. beta-HCH caused a decrease of absolute brain-mass. In case of alpha-HCH and gamma-HCH fat tissue, kidneys and adrenals had a high burden in residues. Fat tissue and adrenals had high residues of beta-HCH. The level of HCH-residues during the test period was gamma much less than beta less than alpha. The results are discussed taking into account the contradictory knowledge from literature. 相似文献
18.
This study describes for the first time the spatial and temporal distribution of a growth factor and its receptors in uteri and conceptuses of a marsupial species during the peri-gastrulation period. Uteri (gravid and non-gravid) and blastocysts from 40 female stripe-faced dunnarts (Sminthopsis macroura) were collected over the peri-gastrula period (days 6.0-8.5) and stained immunohistochemically for transforming growth factor beta2 (TGFbeta2) and its receptors, TbetaRI and TbetaRII, to determine possible roles for TGFbeta2 in marsupial embryonic development. The events that occurred during the period examined included the appearance and proliferation of hypoblast and mesoderm, primitive streak and node formation, and early neurulation. Differences in TGFbeta2 quantities between gravid and non-gravid uteri reflect differences in uterine morphology, indicating a role for TGFbeta2 in endometrial remodelling. In blastocysts, large quantities of all three proteins in the trophectoderm during the node stage coincide with both blastocyst expansion before implantation and the appearance of multinucleated cells, indicating that TGFbeta2 plays a role in conceptus elongation and trophectoderm differentiation. In contrast, lack of TbetaRII in blastocysts during hypoblast formation and proliferation negates any role for TGFbeta2 in these processes, as both receptors are required for a response to TGFbeta2. High concentrations of TGFbeta2 but low concentrations of TbetaRII in blastocysts during early primitive streak formation indicate that paracrinal embryo-maternal signalling may be occurring, as blastocysts cannot respond to TGFbeta2 at this stage, but uteri could. A similar situation, but reversed, also occurs during primitive node formation. 相似文献
19.
European Journal of Wood and Wood Products - This paper investigated the impact of microwave-assisted drying on the energy consumption, drying rate, surface temperature, drying time, static bending... 相似文献
20.
评述了日本氧化镁、氢氧化镁生产应用和研究开发动向。包括生产厂家、装置能力和消耗构成以及近期研发活动。 相似文献
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