共查询到20条相似文献,搜索用时 15 毫秒
1.
Arnaud L Lognay G Verscheure M Leenaers L Gaspar C Haubruge E 《Journal of chemical ecology》2002,28(3):523-532
Flour beetles are cosmopolitan and common pests in grain stores and flour mills. Their ability to exploit a wide variety of stored products has contributed to their status as major pests of stored food. Although it was previously reported that the same aggregation pheromone, 4,8-dimethyldecanal (DMD), is shared by three flour beetles species (Tribolium castaneum, T. confusum, and T. freemani), the volatiles released by the other Tribolium species associated with stored products have not yet been examined. In the present study, the volatiles produced by males and females of eight Tribolium species were examined by solid phase microextraction (SPME). SPME samples were analyzed by gas chromatography coupled to mass spectrometry (GC-MS). Experiments were conducted to identify volatiles emitted by the adults of different Tribolium species and to determine whether DMD is a common aggregation pheromone. We observed that DMD is not a common pheromone of the eight species tested, but is common to T. castaneum, T. confusum, T. freemani, and T. madens. Two other volatiles were detected, 1-pentadecene, which is shown here to be a common semiochemical of flour beetles, and 1,6-pentadecadiene, which was detected in five species (T. audax, T. brevicornis, T. destructor, T. freemani, and T. madens). 相似文献
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The theory of a steady ignition wave in a multicomponent mixture of a gas and magnesium particles, which is nonequilibrium in terms of phase velocities, is developed. Conditions where the action of a shock wave on a cloud of particles leads to their ignition or regular heating are determined. Qualitatively different types of behavior of the temperatures of dispersed and gas phases behind the front of the leading shock wave are found. A significant role of interphase friction at the early stages of development of the thermal explosion is demonstrated. Verification of the model is performed on the basis of experimental data on the dependence of the induction period of the oxidation reaction in the cloud of particles on the shock–wave Mach number. It is shown that the numerical data obtained within the framework of the equilibrium and nonequilibrium (in terms of phase velocities) models are in good agreement for small–size particles. 相似文献
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An effect of a NiO additive on the combustion and structure formation in a Ni–Al–W system in self-propagating high-temperature synthesis (SHS) is under study. The stages of the combustion of compositions containing a NiO high-energy additive are shown. The interaction of W particles with Ni–Al melts during SHS results in the formation of globular decoration of particles on the basis of solid solutions of tungsten on the particle surface. This effect is observed only in compositions with an equimolar mixture of Ni–Al. With an NiO additive content in the initial sample more than 1 at.%, the globular decoration on the unreacted W particle surface does not occur. This effect can be associated with changes in the combustion temperature, deviation of the NiAl phase in the direction of a larger content of Ni, and the influence of oxide phases on diffusion processes. 相似文献
5.
The chemical and ecological function of cross-attraction of Piezodorus hybneri (Pentatomidae) to the Riptortus clavatus (Alydidae) pheromone (a mixture of three components) was studied. In a field attraction test using traps with synthetic pheromone components, P. hybneri was attracted to (E)-2-hexenyl (E)-2-hexenoate, a component of the R. clavatus pheromone. Other components had neither an additive nor a synergistic effect on the attraction of P. hybneri. Neither (E)-2-hexenyl (E)-2-hexenoate nor other components of the R. clavatus pheromone were detected in volatiles or whole-body extracts of P. hybneri adults by gas chromatographic analysis. In addition, (E)-2-hexenyl (E)-2-hexenoate could not be found in volatiles of soybean plants. Therefore, it appears that P. hybneri responds to a component of the R. clavatus pheromone that is not emitted by P. hybneri itself. We discuss this interspecific pheromone cross-attraction of the soybean bug and hypothesize that P. hybneri utilizes the pheromone of its competitor as a kairomone for host location. 相似文献
6.
Jaime M. Ross Lars Olson Giuseppe Coppotelli 《International journal of molecular sciences》2015,16(8):19458-19476
Mitochondrial dysfunction and impairment of the ubiquitin proteasome system have been described as two hallmarks of the ageing process. Additionally, both systems have been implicated in the etiopathogenesis of many age-related diseases, particularly neurodegenerative disorders, such as Alzheimer’s and Parkinson’s disease. Interestingly, these two systems are closely interconnected, with the ubiquitin proteasome system maintaining mitochondrial homeostasis by regulating organelle dynamics, the proteome, and mitophagy, and mitochondrial dysfunction impairing cellular protein homeostasis by oxidative damage. Here, we review the current literature and argue that the interplay of the two systems should be considered in order to better understand the cellular dysfunction observed in ageing and age-related diseases. Such an approach may provide valuable insights into molecular mechanisms underlying the ageing process, and further discovery of treatments to counteract ageing and its associated diseases. Furthermore, we provide a hypothetical model for the heterogeneity described among individuals during ageing. 相似文献
7.
Shiyin Li Jiangpeng Zhu Guoxiang Wang Lixiao Ni Yong Zhang Christopher T. Green 《Chemical Engineering Communications》2013,200(6):799-805
This study explores the removal rate of nitrobenzene (NB) using a new gas–liquid–liquid (G–L–L) three-phase ozone-loaded system consisting of a gaseous ozone, an aqueous solvent phase, and a fluorinated solvent phase (perfluorodecalin, or FDC). The removal rate of NB was quantified in relation to six factors including (1) initial pH, (2) initial NB dosage, (3) gaseous ozone dosage, (4) free radical scavenger, (5) FDC pre-aerated gaseous ozone, and (6) reuse of FDC. NB removal rate is positively affected by the first three of these factors. Compared with the conventional gas–liquid (water) (G–L) two-phase ozonation system, the free radical scavenger (tertiary butyl alcohol) has much less influence on the removal rate of NB in the G–L–L system. The FDC-loaded ozone acts as an ozone reservoir and serves as the main reactive phase in the G–L–L three-phase system. The reuse of FDC has little influence on the removal rate of NB. These experimental results suggest that the oxidation efficiency of ozonation in the G–L–L three-phase system is better than that in the conventional G–L two-phase system. 相似文献
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The effects of particulate matter on environment and public health have been widely studied in recent years. In spite of the presence of numerous studies about this topic there is no agreement on the relative importance of the particles' size and origin with respect to health effects among researchers. Nevertheless, air quality standards are moving, as the epidemiological attention, towards greater focus on the smaller particles. The most reliable method used in measuring particulate matter (PM) is the gravimetric method since it directly measures PM concentration, guaranteeing an effective traceability to international standards. This technique, however, neglects the possibility to correlate short term intraday atmospheric parameter variations that can influence ambient particle concentration and size distribution as well as human activity patterns. Besides, a continuous method to determine PM concentrations through the measurement of the number size distribution is the system constituted by a Scanning Mobility Particle Sizer (SMPS) and an Aerodynamic Particle Sizer (APS). In this article, the evaluation of the uncertainty budget in measuring PM through the SMPS–APS system, as well as a metrological comparison with the gravimetric reference method in order to analyze the compatibility, was carried out and applied with reference to an experimental campaign developed in a rural site. This choice allowed to assume the hypothesis of spherical particle morphology. The average PM10, PM2.5, and PM1 uncertainties obtained for the SMPS–APS system are equal to 27%, 29%, and 31%, respectively. Here the principle influence parameter is the particle density that has to be directly measured with low uncertainty in order to reduce the PM uncertainty. 相似文献
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Muhammad Shahzad Kamal Abdullah Saad Sultan Usamah A. Al-Mubaiyedh Ibnelwaleed A. Hussien Martial Pabon 《Journal of surfactants and detergents》2014,17(5):985-993
Thermal stability and rheological properties of a novel surfactant–polymer system containing non‐ionic ethoxylated fluorocarbon surfactant was evaluated. A copolymer of acrylamide (AM) and 2‐acrylamido‐2‐methylpropane sulfonic acid (AMPS) was used. Thermal stability and surfactant structural changes after aging at 100 °C were evaluated using TGA, 1H NMR, 13C NMR, 19F NMR and FTIR. The surfactant was compatible with AM–AMPS copolymer and synthetic sea water. No precipitation of surfactant was observed in sea water. The surfactant was found to be thermally stable at 100 °C and no structural changes were detected after exposure to this temperature. Rheological properties of the surfactant–polymer (SP) system were measured in a high pressure rheometer. The effects of surfactant concentration, temperature, polymer concentration and salinity on rheological properties were studied for several SP solutions. At low temperature (50 °C), the viscosity initially increased slightly with the addition of the surfactant, then decreased at high surfactant concentration. At a high temperature (90 °C), an increase in the viscosity with the increase in surfactant concentration was not observed. Overall, the influence of the fluorocarbon surfactant on the viscosity of SP system was weak particularly at high temperatures and high shear rate. Salts present in sea water reduced the viscosity of the polymer due to a charge shielding effect. However, the surfactant was found to be thermally stable in the presence of salts. 相似文献
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Augusto Marcos da Silva Hofmann Cristina Benincá Valesca Kotovicz Everton Fernando Zanoelo 《Journal of the American Oil Chemists' Society》2012,89(10):1929-1938
Drying and cooling are preparatory operations typically applied in the soybean processing industry to reduce the moisture content and temperature of the flakes fed to the extractor. Although these parameters are important for a safe and optimal process of extraction, limited or even inexistent schemes for their control are available. To deal with this problem, the current investigation suggests the use of a PID controller to manipulate the speed of the conveyor belt in order to keep the temperature of the flakes in the discharge of the dryer–cooler close to 61 °C without exceeding the acceptable outlet moisture content range from 9.9 to 12.3 % dry basis (d.b.). Closed-loop responses for the controlled variables when considering simultaneous arbitrary disturbances on operating conditions confirmed the reliability of the current control strategy. A dynamic model represented by a system of two partial differential equations obtained by energy and mass balances for the solute in the bed was used as a virtual conveyor-belt dryer-cooler. Its consistency was checked by a comparison between experimental and calculated results for moisture content and temperature at the exit of a size-scale dryer–cooler of soybean flakes at typical industrial operating conditions. The ISE technique and the simplex method of optimization were used to tune the set of PID parameters in which process control was stable. 相似文献
11.
Mohsen Mohsen-Nia Hamid Modarress Hamid Reza Nabavi 《Journal of the American Oil Chemists' Society》2008,85(10):973-978
Vegetable oils can be deacidified by liquid–liquid extraction based on differences in polarity between triglycerides and fatty
acids and differences in solubility. Information on the equilibrium between the phases of such systems is important for designing
separation processes. The present paper reports experimental data for the extraction of fatty acid from soybean oil by (ethanol + water)
as a mixed-solvent for system of soybean oil + oleic acid + ethanol + water at 30 °C at different water contents. The liquid–liquid
equilibrium data of the systems were used to obtain interaction parameters in the universal quasi-chemical theory (UNIQUAC)
activity coefficient model. These parameters can be used to predict equilibrium data of ternary and quaternary systems. The
deviations between experimental and calculated compositions in both phases for each system using this model were calculated.
The distribution coefficients and the selectivity factors of solvents for extraction of fatty acid from oil at 30 °C were
calculated. Increasing of the water content as the co-solvent decreased the distribution coefficients and increased the selectivity
factors of mixed-solvents, therefore considering the economical and practical aspects the optimum water content may be used
for extracting oleic acid from soybean oil. We concluded that (ethanol + water) as a mixed-solvent can be used for extracting
fatty acids from edible oils in a normal temperature. 相似文献
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1 INTRODUCTION The development of IC-technology requires large size Si wafer and Czochralski (Cz) process has domi-nated the production of single crystals for most of the materials used in the microelectronic industry. It was reported that the melt flow is stable when the wafer diameter is small. Converged solutions were obtained by using a laminar model. For example, Xiao and Derby[1] simulated the flow of oxide melt at Grashof number Gr =2.54×105, Oshima et al.[2] simulated the flo… 相似文献
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Atle Wibe Anna-Karin Borg-Karlson Monika Persson Torbjörn Norin Hanna Mustaparta 《Journal of chemical ecology》1998,24(2):273-287
The enantiomeric composition of seven monoterpene hydrocarbons in headspace volatiles of spruce sawdust and seedlings (Picea abies), pine seedlings (Pinus sylvestris), and branches of juniper (Juniperus communis) was determined by gas chromatographic separation on a -Cyclodextrin column. For the six monoterpenes, -pinene, camphene, -pinene, sabinene, limonene, and -phellandrene, both enantiomers were present, whereas for 3-carene only the (+)-configuration was found. The amount of each enantiomer varied considerably both in relation to total amount of all of them, and for the six pairs also in relation to the opposite enantiomer. One olfactory receptor neuron in the pine weevil (Hylobius abietis) showed a strong response to -pinene when stimulated with all four headspace materials via a GC equipped with a DB-WAX column. The same neuron was subsequently tested with repeated stimulations via the GC effluent containing the (+)- or (–)-enantiomer. A marked better response to (+)- than to (–)--pinene was elicited. Another olfactory receptor neuron that responded strongly to limonene when stimulated with the spruce volatiles was tested for enantiomers of limonene. This neuron responded more strongly to (–)- than to (+)-limonene, when stimulated alternately with each of the limonene enantiomers. Discrimination between enantiomers by plant olfactory receptor neurons suggests that the enantiomeric ratios of volatile compounds may be important in host location by the pine weevil. 相似文献
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Valeria Mezzanotte Manuela Anzano Elena Collina Francesca Alice Marazzi Marina Lasagni 《Polycyclic Aromatic Compounds》2016,36(3):213-228
PAH (Polycyclic Aromatic Hydrocarbons) analyses were carried out on samples from two Wastewater Treatment Plants (WWTPs) in Lombardy, similar for treatment sequences but fed on different influents: industrial component accounts for 70% at Alto Seveso plant while it is absent in Nosedo plant. Sampling concerned the influent and the effluent from activated sludge reactor and the final effluent after disinfection (ozonation for Alto Seveso and peracetic acid treatment for Nosedo). The concentrations of total PAHs were 5.3 ± 4.0 μg L?1 and 2.4 ± 1.3 μg L?1 in Alto Seveso and Nosedo influent, respectively. The lowest molecular weight PAHs had the highest concentrations in both plants; acenaphthene and naphthalene were the most important components in the influent to Alto Seveso and Nosedo WWTPs, respectively. The higher molecular weight compounds had the lowest concentrations and benzo(g,h,i)perylene and dibenzo(a,h)anthracene were never detected. Most of the PAH load entered biological treatment in dissolved form. For both plants PAHs were mostly removed in the biological section (96.5% and 89.5% for Alto Seveso and Nosedo, respectively), while disinfection had a minor role. Peracetic acid (Nosedo) seemed more efficient than ozone (Alto Seveso) in the removal of PAHs (4.18% and 0.89%, respectively). It is now necessary to confirm this result by using the same effluent for the two disinfection treatments. 相似文献
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Serena Bisagni Benjamin Summers Selin Kara Rajni Hatti-Kaul Gideon Grogan Gashaw Mamo Frank Hollmann 《Topics in Catalysis》2014,57(5):366-375
Baeyer–Villiger monooxygenases (BVMOs) are valuable enzymes for specific oxyfunctionalization chemistry. They catalyze the oxidation of ketones to esters, but are also capable of oxidizing other chemical functions, namely aldehydes and heteroatoms such as sulfur, nitrogen, selenium and boron. The oxidation specificity and enantioselectivity of a newly characterized BVMO (BVMO4) from a strain of Dietzia towards sulfide- and aldehyde substrates have been studied. BVMO4 could react with sulfides containing an aromatic group. The presence of a substituent on the aromatic group was tolerated when they were in the meta- and para position and the oxidations yielded predominantly the (R)-sulfoxides. Similarly, BVMO4 displayed a higher activity for aldehydes containing a phenyl group, but long aliphatic aldehydes, namely octanal and decanal, were also accepted as substrate by this enzyme. The major oxidation products of the aldehyde substrates were the respective carboxylic acids in contrast to formate ester that was obtained in most of the previous reports. The Baeyer–Villiger oxidation of the substrate 2-phenylpropionaldehyde was studied in further detail and the corresponding acid product was obtained with good regio- and enantioselectivity. This is a unique feature for BVMO4 and is of great interest for further exploration of an alternative biocatalytic process. 相似文献
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N. N. Khimich E. L. Aleksandrova V. Ya. Goikhman L. A. Koptelova 《Glass Physics and Chemistry》2003,29(4):401-405
The possibility of synthesizing a series of nanohybrids in the Cu+ organic complex–SiO2 system (with different contents of the organic component) by the sol–gel method is analyzed. It is shown that the organic component at a content of 10% provides optimum conditions for the formation of a nanocomposite in this system. The photophysical properties of the nanocomposites synthesized are investigated, and the photosensitivity and quantum yield of charge carrier photogeneration are determined. 相似文献
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Stephanie Kraft Lisa Buchenauer Tobias Polte 《International journal of molecular sciences》2021,22(22)
Fungi represent one of the most diverse and abundant eukaryotes on earth. The interplay between mold exposure and the host immune system is still not fully elucidated. Literature research focusing on up-to-date publications is providing a heterogenous picture of evidence and opinions regarding the role of mold and mycotoxins in the development of immune diseases. While the induction of allergic immune responses by molds is generally acknowledged, other direct health effects like the toxic mold syndrome are controversially discussed. However, recent observations indicate a particular importance of mold/mycotoxin exposure in individuals with pre-existing dysregulation of the immune system, due to exacerbation of underlying pathophysiology including allergic and non-allergic chronic inflammatory diseases, autoimmune disorders, and even human immunodeficiency virus (HIV) disease progression. In this review, we focus on the impact of mycotoxins regarding their impact on disease progression in pre-existing immune dysregulation. This is complemented by experimental in vivo and in vitro findings to present cellular and molecular modes of action. Furthermore, we discuss hypothetical mechanisms of action, where evidence is missing since much remains to be discovered. 相似文献
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The research was directed at establishing the dependence of the disperse composition of particles of TiCl4–Al(i-C4H9)3 catalytically active precipitate, and their activity and molecular weight characteristics of polybutadiene formed in their presence on the length of sections and the confuser diameter of the tubular turbulent apparatus of diffuser–confuser design used to prepare a catalytic system in turbulent flows. An approach that combines methods of computational fluid dynamics (ANSYS Workbench 17.1 platform) and formal kinetics, and solves inverse problems of kinetics has been used to solve the stated problem. The following required dependences were established based on numerical experiments on the models developed using this approach: (1) the hydrodynamics of the process of dispersing particles of TiCl4–Al(i-C4H9)3 catalytically active precipitate in a tubular turbulent apparatus with diffuser–confuser design, and (2) macrokinetics of butadiene polymerization on the particles of TiCl4–Al(i-C4H9)3 catalytically active precipitate dispersed in turbulent flows (batch reactor, the solvent was toluene, and the temperature of the process was 25°С). 相似文献