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101.
As a novel bionic analytical technique, an electronic nose, inspired by the mechanism of the biological olfactory system and integrated with modern sensing technology, electronic technology and pattern recognition technology, has been widely used in many areas. Moreover, recent basic research findings in biological olfaction combined with computational neuroscience promote its development both in methodology and application. In this review, the basic information processing principle of biological olfaction and artificial olfaction are summarized and compared, and four olfactory models and their applications to electronic noses are presented. Finally, a chaotic olfactory neural network is detailed and the utilization of several biologically oriented learning rules and its spatiotemporal dynamic propties for electronic noses are discussed. The integration of various phenomena and their mechanisms for biological olfaction into an electronic nose context for information processing will not only make them more bionic, but also perform better than conventional methods. However, many problems still remain, which should be solved by further cooperation between theorists and engineers. Supported by the National Creative Research Groups Science Foundation of China (Grant No. 60421002) and National Basic Research Programme of China (Grant No. 2004CB720302)  相似文献   
102.
The laminar burning velocity of iso-butanol-air mixtures was measured under different initial pressures, initial temperatures and equivalence ratios using high-speed schlieren photography and outwardly propagation flame in a constant volume combustion bomb. Based on the analysis of stretched flame propagation speed and stretch rate, the laminar burning velocities and Markstein lengths of iso-butanol-air flames are obtained. In accordance, with photos of flame, an analysis of flame stability and the influencing factors is carried out. The results show that the laminar burning velocity is decreased with the increase of initial pressure and is increased with the increase of initial temperature. The maximum value of laminar burning velocity is presented at the equivalence ratio of 1.2. The Markstein length is decreased with the increase of equivalence ratio. For specified equivalence ratio, the Markstein length is decreased with the increase of initial temperature and initial pressure. Thus, the flame instability is increased with the increase of equivalence ratio, initial temperature and initial pressure.  相似文献   
103.
This paper presents a 40000-year-long high-resolution mangrove record from sediments of Core 18300, 18302 and 18323 on the continental shelf of the southern South China Sea and reconstructs the coastline changes on Sunda Shelf since the last 40000 years. In the period Marine Isotope 3, the old Sunda Shelf had low sea level, and it was partly exposed. Flourishing vegetations grew on the exposed old land. Mangroves developed along the coastline. On the Last Glacial Maximum, the sea level dropped greatly, coastline moved from inner shelf to outer shelf, the Old Sunda Land exposed further, and the lowering sea level induced the gradual disappearing of mangroves from the inner Sunda Shelf to the outer Sunda Shelf. And pioneer vegetation ferns covered the broadly exposed old land immediately. At the time of the last Deglaciation, sea level rose greatly, the coastline moved to the sea and the Sunda Shelf was drown again. Mangroves were emergent again from outer shelf to inner shelf and developed quickly.  相似文献   
104.
This paper divides the process of rainfall redistribution into four levels in vegetation restored region of gully in arid-hot valley of Jinshajiang River. These levels include arbor interception, litter interception, soil interception and surface runoff. The results showed that the maximum of interception was 8.10 mm, the mean interception was 4.53 mm, the maximum of interception rate was 56.10 % and the mean interception rate was 32.63 %.When the rainfall is over 20 mm, the interception rate descends rapidly along with the rainfall increasing. The maximum of water-holding content of litter was 8.14-20.33 t/hm^2, the mean of which is 12.52 t/hm^2 and the maximum of water-holding content was over two times of it own weight. The rainfall of litter interception was 150.24 mm, accounted for the rainfall income 24.48%.The maximum water-holding capacity of soil achieves 2 198.54 t/hm^2, but that of the barren land is 1 825.60 t/hm^2. The rainfall of soil interception was 219.87 mm, accounted for the rainfall income 35.82%. The surface runoff of vegetation restored region was 43.41 mm, accounted for 7.07% of the rainfall income, but the surface runoff of non-forest land was 413,24 mm, accounts for 70.26% of the rainfall income.The surface runoff of the planted forest community was by 63.19% lower than that of the non-forest land. Through the interception of the forest land that reduced the soil erosion effectively, good hydrology effect was obtained.  相似文献   
105.
Is there a decline in marine phytoplankton?   总被引:1,自引:0,他引:1  
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106.
RNA interference-mediated inhibition of Hepatitis B Virus replication   总被引:1,自引:0,他引:1  
Persistent and recurrent infection of hepatitis B virus (HBV) represents one of the most common and severe viral infections of humans, and has caused a formidable health problem in the affected countries. Currently used antiviral drugs have a very limited success on controlling HBV replication and infection. RNA interference (RNAi), a process by which double-stranded RNA (dsRNA) directs sequence-specific degradation of target mRNA in mammalian and plant cells, has recently been used to knockdown gene expression in various species. In this study, we sought to determine whether RNAi-mediated silencing of HBV viral gene expression could lead to the effective inhibition of HBV replication. We first developed RNAi vectors that expressed small interfering RNA (siRNA) and targeted the HBV core or surface gene sequence. Our results demonstrated that these specific siRNAs efficiently reduced the levels of corresponding viral RNAs and proteins, and thus suppressed viral replication. Treatment with siRNA gave the greatest reduction in the levels of HBsAg (92%) and in HBeAg (85%) respectively in the cultured cell medium. Our findings further demonstrated that the RNAi-mediated antiviral effect was sequence-specific and dose-dependent. Therefore, our findings strongly suggest that RNAi-mediated silencing of HBV viral genes could effectively inhibit the replication of HBV, hence RNAi-based strategy should be further explored as a more efficacious antiviral therapy of HBV infection.  相似文献   
107.
The amount and biodegradability of dissolved organic carbon (DOC) in forest floors can contribute to carbon sequestration in soils and the release of CO 2-C from soil to the atmosphere.There is only limited knowledge about the biodegradation of DOC in soil extracts and leachates due to the limitations inherent in degradation experiments.Differences in the biodegradation of DOC were studied in forest soil extracts using cold and hot water and 4 mmol/L CaCl 2 solution and in soil leachates sampled under different conditions over a wide range of DOC concentrations.From these results,we developed a simple and rapid method for determining the biodegradable organic C in forest floors.The hot water extracts and CaCl 2 extracts after CH 3 Cl fumigation contained higher concentrations of biodegradable organic C than the cold water extracts and CaCl 2 extracts before fumigation,with rapid DOC degradation occurring 24-48 h after incubation with an inoculum,followed by slow DOC degradation till 120-168 h into the incubation.During a 7-d incubation with an inoculum,the variation in DOC degradation in the different soil extracts was consistent with the change in special UV absorbance at 254 nm.Relatively higher levels of biodegradable organic C were detected in soil leachates from the forest canopy than in forest gaps between April and October 2008 (P <0.05).Relatively lower concentrations of DOC and biodegradable organic C were observed in soil leachates from N-fertilized plots during the growing season compared with the control,with the exception of the plot treated with KNO 3 at a rate of 45 kg N ha 1 a 1.Around 77.4% to 96.3% of the variability in the biodegradable organic C concentrations in the forest floors could be accounted for by the initial DOC concentration and UV absorbance at 254 nm.Compared with the conventional inoculum incubation method,the method of analyzing UV absorbance at 254 nm is less time consuming and requires a much smaller sample volume.The results suggest that the regression models obtained using the initial DOC concentration and UV absorbance can provide a rapid,simple and reliable method for determining the biodegradable organic C content,especially in field studies involving relatively large numbers of samples.  相似文献   
108.
Pitting corrosion of 316L stainless steel in NaCl solution was investigated by means of staircase potential electrochemical impedance spectroscopy (SPEIS). The investigation focused on the transition of stainless steel from the passive state to pitting corrosion. Based on the evolution of electrical parameters of the equivalent electrical circuit, it is suggested that the most probable mechanism of pit creation is the film breaking model. The result demonstrates that staircase potential electrochemical impedance spectroscopy is an effective method for the investigation of pitting corrosion.  相似文献   
109.
Cold fronts occur in northern East Asia during winter and spring.After cold frontal passage,airflow is downward and accompa-nying strong winds fluctuate significantly;this is termed wind gusts.Analysis of observation data shows that wind gust structure has coherent characteristics.This is important for entrainment of spring dust storms into the upper boundary layer,where they are transported great distances.The Lattice Boltzmann Method(LBM) is a computational fluid technique based on the Boltzmann transport equation.The LBM has been used to study complex motion such as turbulence,because it describes motion at the micro level.In this paper,Large eddy simulation is introduced in the LBM,enabling simulation of turbulent flow in the atmospheric boundary layer.The formation and development of wind gusts are simulated,and a coherent structure with a combination of wave and vortex is obtained.This explains the mechanism of soil erosion and sand entrainment by the coherent structure of wind gusts.  相似文献   
110.
This paper further investigates cluster synchronization in a complex dynamical network with two-cluster. Each cluster contains a number of identical dynamical systems, however, the subsystems composing the two clusters can be different, i.e., the individual dynamical system in one cluster can differ from that in the other cluster. Complete synchronization within each cluster is possible only if each node from one cluster receives the same input from nodes in other cluster. In this case, the stability condition of one-cluster synchronization is known to contain two terms: the first accounts for the contribution of the inner-cluster coupling structure while the second is simply an extra linear term, which can be deduced by the "same-input" condition. Applying the connection graph stability method, the authors obtain an upper bound of input strength for one cluster if the first account is known, by which the synchronizability of cluster can be scaled. For different clusters, there are different upper bound of input strength by virtue of different dynamics and the corresponding cluster structure. Moreover, two illustrative examples are presented and the numerical simulations coincide with the theoretical analysis.  相似文献   
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