The necessity for understanding normal human cognitive processes and behavior, and themechanisrns which result in dysfunction in these processes are dependant on utilization of a suitable animal model. In order to dev...The necessity for understanding normal human cognitive processes and behavior, and themechanisrns which result in dysfunction in these processes are dependant on utilization of a suitable animal model. In order to develop pharmaceutical agents to alleviate mental disturbances and enable the individual to cope within the norms of society, it is incumbent upon investigators to choose a species in which pharmacokinetic principles are established and resemble those of hurnans. The choice of rats in cognition research studies has specific advantages in that these anirnals possess similar pharrnacodynamic parameters to hurnans. Further advantages include availability, low cost, ease of breeding, maintenance and an extensive literature database which enable comparisons to present findings. However, there are substantial differences in the perforrnance of various rat strains in tasks of learning, memory, attention, and responses to stress or drugs. In addition to rat strain, quantity of thed also exerts profound consequences on animal behavior. The aim of this review is to demonstrate that there are differences in the central nervous systern responsivencess of rat strains to chemicals and these could be related to factors such as source of supplier, type and quantity of feed, or season of the year. It is also evident that the genotype differs amongst strains and this may be responsible for the observed differences in CNS sensitivity to chemicals. Strain differences must be identified and taken into consideration in interpretation of assessrnent of neurobehavioural functions. It is also incumbent upon the investigators to utilize healthy (diet-controlled) animal models.展开更多
We investigate the Fano factor in a strained armchair and zigzag graphene nanoribbon nanodevice under the effect of ac field in a wide range of frequencies at different temperatures （10？K–70？K）. This nanodevice i...We investigate the Fano factor in a strained armchair and zigzag graphene nanoribbon nanodevice under the effect of ac field in a wide range of frequencies at different temperatures （10？K–70？K）. This nanodevice is modeled as follows： a graphene nanoribbon is connected to two metallic leads. These two metallic leads operate as a source and a drain. The conducting substance is the gate electrode in this three-terminal nanodevice. Another metallic gate is used to govern the electrostatics and the switching of the graphene nanoribbon channel. The substances at the graphene nanoribbon/metal contact are controlled by the back gate. The photon-assisted tunneling probability is deduced by solving the Dirac eigenvalue differential equation in which the Fano factor is expressed in terms of this tunneling probability. The results show that for the investigated nanodevice, the Fano factor decreases as the frequency of the induced ac field increases, while it increases as the temperature increases. In general, the Fano factors for both strained armchair and zigzag graphene nanoribbons are different. This is due to the effect of the uniaxial strain. It is shown that the band structure parameters of graphene nanoribbons at the energy gap, the C–C bond length, the hopping integral, the Fermi energy and the width are modulated by uniaxial strain. This research gives us a promise of the present nanodevice being used for digital nanoelectronics and sensors.展开更多
In this paper, we review various types of graphene-based strain sensors. Graphene is a monolayer of carbon atoms, which exhibits prominent electrical and mechanical properties and can be a good candidate in compact st...In this paper, we review various types of graphene-based strain sensors. Graphene is a monolayer of carbon atoms, which exhibits prominent electrical and mechanical properties and can be a good candidate in compact strain sensor ap- plications. However, a perfect graphene is robust and has a low piezoresistive sensitivity. So scientists have been driven to increase the sensitivity using different kinds of methods since the first graphene-based strain sensor was reported. We give a comprehensive review of graphene-based strain sensors with different structures and mechanisms. It is obvious that graphene offers some advantages and has potential for the strain sensor application in the near future.展开更多
In 2004, China＇s digital seismic observation network project began to deploy 40 sets YRY-4 four-component borehole strainmeters in order to monitor earthquake preparation process. The paper describes observed solid t...In 2004, China＇s digital seismic observation network project began to deploy 40 sets YRY-4 four-component borehole strainmeters in order to monitor earthquake preparation process. The paper describes observed solid tidal strain discreteness and tidal factor anisotropy, analyzes the reliability of observational data and discusses the cause for this phenomenon. After getting rid of interferences, the network, in two years practice, has observed several pre-seismic strain anomalies at stations close to epicenters especially in the Wenchuan Ms8.0 megaquake. It shows that this borehole strainmeter network is capable of monitoring seismogenic process.展开更多
Aim Understanding the response of mesenchymal stem cells （MSCs） to mechanical strain and their consequent gene expression patterns will broaden our knowledge of the mechanobiology of distraction osteogenesis. Method...Aim Understanding the response of mesenchymal stem cells （MSCs） to mechanical strain and their consequent gene expression patterns will broaden our knowledge of the mechanobiology of distraction osteogenesis. Methodology In this study, a single period of cyclic mechanical stretch （0.5 Hz, 2,000 με） was performed on rat bone marrow MSCs. Cellular proliferation and alkaline phosphatase （ALP） activity was examined. The mRNA expression of six bone-related genes （Ets-1, bFGF, IGF-Ⅱ, TGF-β, Cbfal and ALP） was detected using real-time quantitative RT-PCR. Results The results showed that mechanical strain can promote MSCs proliferation, increase ALP activity, and up-regulate the expression of these genes. A significant increase in Ets-1 expression was detected immediately after mechanical stimulation, but Cbfal expression became elevated later. The temporal expression pattem of ALP coincided perfectly with Cbfal. Conclusion The results of this study suggest that mechanical strain may act as a stimulator to induce differentiation of MSCs into osteoblasts, and that these bone-related genes may play different roles in the response of MSCs to mechanical stimulation.展开更多
The strain accumulation state in crustal interior and its migration trend can be inverted from observational data of earth tide tilts.In China,large earthquakes frequently occur in the border area between Yunnan and S...The strain accumulation state in crustal interior and its migration trend can be inverted from observational data of earth tide tilts.In China,large earthquakes frequently occur in the border area between Yunnan and Sichuan Provinces.Using the observational data for years from 7 stations in this area,γ(the amplitude factor of earth tide tilts)values that characterize the strain accumulation state in crustal interior have been inverted in this paper.It has been found out that,Ms】5 events in the area often occur when γreaches an anomaly value.Using the time-space collocational stereomodelling the migration trend of strain accumulation can be determined to make a prediction for the probable location of a forthcoming earthquake in the area.展开更多
First the deviator strain energy is introduced, then the problem of plane-crack critical growth was discussed, a path independent line integral J* was defined, furthermore its conservation was proved strictly. As appl...First the deviator strain energy is introduced, then the problem of plane-crack critical growth was discussed, a path independent line integral J* was defined, furthermore its conservation was proved strictly. As application examples, Mode-I stress intensity factors of cracked beams were obtained with present approach. The results are shown to agree well with those available in the open literature.展开更多
Environmental pollution with petroleum and petrochemical products such as diesel and used oils has been recognized as one of the most serious current problem in the world, especially in developing countries. These pet...Environmental pollution with petroleum and petrochemical products such as diesel and used oils has been recognized as one of the most serious current problem in the world, especially in developing countries. These petrochemical products devastate the soil, surface and underground waters and alter the microbial population at the polluted sites. Thus, the present work aims to optimize the biodegradation of diesel and two used oils (SAE 40 and SAE 50) by bacterial strains namely Acinetobacter S2 and Pseudomonas S7 using either nutrient factors (yeast extract, peptone or trace elements) or surfactants (tween 80 or Sodium Dodecyl Sulfate: SDS). The strains are incubated alone or together with the used oils or diesel supplemented or not with nutrient factors or surfactants for 14, 28, 42 and 56 days, respectively. For all the incubation period, the hydrocarbons degradation rates are determined by gravimetric assay. The results obtained show that nutrient factors increase significantly SAE 50 used oil biodegradation (p = 0.009). Similarly, tween 80 increases SAE 50 and SAE 40 used oils biodegradation but not diesel one. The results also show a significant difference between biodegradation rates at 14, 28, 42 and 56 days for all the hydro-carbons tested (p Acinetobacter S2 and Pseudomonas S7 increases the degradation over the one of the strains alone.展开更多
The large deformation of incompressible rubber cylinder under inner pressure is ana- lyzed by a kind of new rubber materials strain energy function.The theory formulation for the dis- placement and stress is presented...The large deformation of incompressible rubber cylinder under inner pressure is ana- lyzed by a kind of new rubber materials strain energy function.The theory formulation for the dis- placement and stress is presented.The penalty finite element formulation is established in order to ana- lyze nonlinear rubber materials,and the results of finite element method agree well with theoretical ones.A new method for controlling the calculating stability and convergence rates is put forward.The selection of the appropriate penalty factor and its influence on calculated results are discussed.展开更多
This work analyzes the quality of crustal tilt and strain observations during 2014, which were acquired from 269 sets of ground tiltmeters and 212 sets of strainmeters. In terms of data quality, the water tube tiltmet...This work analyzes the quality of crustal tilt and strain observations during 2014, which were acquired from 269 sets of ground tiltmeters and 212 sets of strainmeters. In terms of data quality, the water tube tiltmeters presented the highest rate of excellent quality,approximately 91%, and the pendulum tiltmeters and ground strainmeters yielded rates of81% and 78%, respectively. This means that a total of 380 sets of instruments produced high-quality observational data suitable for scientific investigations and analyses.展开更多
Two improvements have been made on the calculation of plastic strain ratio (r value) in BCC monocrystals by considering the differences in the critical shear stresses among the three slip systems and the rotation of c...Two improvements have been made on the calculation of plastic strain ratio (r value) in BCC monocrystals by considering the differences in the critical shear stresses among the three slip systems and the rotation of crystal lattice. It is found that the results calculated by the improved method are more rational.展开更多
Based on strain signals, a new time-domain methodology for detecting the beam local damage has been developed. The pseudo strain energy density （PSED） is defined and used to build two major damage indexes, the avera...Based on strain signals, a new time-domain methodology for detecting the beam local damage has been developed. The pseudo strain energy density （PSED） is defined and used to build two major damage indexes, the average pseudo strain energy density （APSED） and the average pseudo strain energy density rate （APSEDR）. Probability and mathematical statistics are utilized to derive a standardized damage index. Furthermore, by applying the analytic relation between the strain energy release rate and the stress intensity factor, an analytic solution of crack depth is derived. For the dynamic strain signals, the wavelet packet transform is used to pre-process measured data. Finally, a numerical simulation indicates that this method can effectively identify the damage location and its absolute severity.展开更多
文摘The necessity for understanding normal human cognitive processes and behavior, and themechanisrns which result in dysfunction in these processes are dependant on utilization of a suitable animal model. In order to develop pharmaceutical agents to alleviate mental disturbances and enable the individual to cope within the norms of society, it is incumbent upon investigators to choose a species in which pharmacokinetic principles are established and resemble those of hurnans. The choice of rats in cognition research studies has specific advantages in that these anirnals possess similar pharrnacodynamic parameters to hurnans. Further advantages include availability, low cost, ease of breeding, maintenance and an extensive literature database which enable comparisons to present findings. However, there are substantial differences in the perforrnance of various rat strains in tasks of learning, memory, attention, and responses to stress or drugs. In addition to rat strain, quantity of thed also exerts profound consequences on animal behavior. The aim of this review is to demonstrate that there are differences in the central nervous systern responsivencess of rat strains to chemicals and these could be related to factors such as source of supplier, type and quantity of feed, or season of the year. It is also evident that the genotype differs amongst strains and this may be responsible for the observed differences in CNS sensitivity to chemicals. Strain differences must be identified and taken into consideration in interpretation of assessrnent of neurobehavioural functions. It is also incumbent upon the investigators to utilize healthy (diet-controlled) animal models.
文摘We investigate the Fano factor in a strained armchair and zigzag graphene nanoribbon nanodevice under the effect of ac field in a wide range of frequencies at different temperatures （10？K–70？K）. This nanodevice is modeled as follows： a graphene nanoribbon is connected to two metallic leads. These two metallic leads operate as a source and a drain. The conducting substance is the gate electrode in this three-terminal nanodevice. Another metallic gate is used to govern the electrostatics and the switching of the graphene nanoribbon channel. The substances at the graphene nanoribbon/metal contact are controlled by the back gate. The photon-assisted tunneling probability is deduced by solving the Dirac eigenvalue differential equation in which the Fano factor is expressed in terms of this tunneling probability. The results show that for the investigated nanodevice, the Fano factor decreases as the frequency of the induced ac field increases, while it increases as the temperature increases. In general, the Fano factors for both strained armchair and zigzag graphene nanoribbons are different. This is due to the effect of the uniaxial strain. It is shown that the band structure parameters of graphene nanoribbons at the energy gap, the C–C bond length, the hopping integral, the Fermi energy and the width are modulated by uniaxial strain. This research gives us a promise of the present nanodevice being used for digital nanoelectronics and sensors.
基金Project supported by the National Basic Research Program of China (Grant No. 2013CB934500)the National Natural Science Foundation of China (Grant No. 91223204)
文摘In this paper, we review various types of graphene-based strain sensors. Graphene is a monolayer of carbon atoms, which exhibits prominent electrical and mechanical properties and can be a good candidate in compact strain sensor ap- plications. However, a perfect graphene is robust and has a low piezoresistive sensitivity. So scientists have been driven to increase the sensitivity using different kinds of methods since the first graphene-based strain sensor was reported. We give a comprehensive review of graphene-based strain sensors with different structures and mechanisms. It is obvious that graphene offers some advantages and has potential for the strain sensor application in the near future.
基金supported by National Science Commission of China(No.1978-002)China Earthquake Administration(No.1982-220)
文摘In 2004, China＇s digital seismic observation network project began to deploy 40 sets YRY-4 four-component borehole strainmeters in order to monitor earthquake preparation process. The paper describes observed solid tidal strain discreteness and tidal factor anisotropy, analyzes the reliability of observational data and discusses the cause for this phenomenon. After getting rid of interferences, the network, in two years practice, has observed several pre-seismic strain anomalies at stations close to epicenters especially in the Wenchuan Ms8.0 megaquake. It shows that this borehole strainmeter network is capable of monitoring seismogenic process.
基金supported by grants from the National Nature Science Foundation of China (No. 30772454)Science and Technology Bureau of Sichuan Province (No. 2006z09-013)
文摘Aim Understanding the response of mesenchymal stem cells （MSCs） to mechanical strain and their consequent gene expression patterns will broaden our knowledge of the mechanobiology of distraction osteogenesis. Methodology In this study, a single period of cyclic mechanical stretch （0.5 Hz, 2,000 με） was performed on rat bone marrow MSCs. Cellular proliferation and alkaline phosphatase （ALP） activity was examined. The mRNA expression of six bone-related genes （Ets-1, bFGF, IGF-Ⅱ, TGF-β, Cbfal and ALP） was detected using real-time quantitative RT-PCR. Results The results showed that mechanical strain can promote MSCs proliferation, increase ALP activity, and up-regulate the expression of these genes. A significant increase in Ets-1 expression was detected immediately after mechanical stimulation, but Cbfal expression became elevated later. The temporal expression pattem of ALP coincided perfectly with Cbfal. Conclusion The results of this study suggest that mechanical strain may act as a stimulator to induce differentiation of MSCs into osteoblasts, and that these bone-related genes may play different roles in the response of MSCs to mechanical stimulation.
文摘The strain accumulation state in crustal interior and its migration trend can be inverted from observational data of earth tide tilts.In China,large earthquakes frequently occur in the border area between Yunnan and Sichuan Provinces.Using the observational data for years from 7 stations in this area,γ(the amplitude factor of earth tide tilts)values that characterize the strain accumulation state in crustal interior have been inverted in this paper.It has been found out that,Ms】5 events in the area often occur when γreaches an anomaly value.Using the time-space collocational stereomodelling the migration trend of strain accumulation can be determined to make a prediction for the probable location of a forthcoming earthquake in the area.
文摘First the deviator strain energy is introduced, then the problem of plane-crack critical growth was discussed, a path independent line integral J* was defined, furthermore its conservation was proved strictly. As application examples, Mode-I stress intensity factors of cracked beams were obtained with present approach. The results are shown to agree well with those available in the open literature.
文摘Environmental pollution with petroleum and petrochemical products such as diesel and used oils has been recognized as one of the most serious current problem in the world, especially in developing countries. These petrochemical products devastate the soil, surface and underground waters and alter the microbial population at the polluted sites. Thus, the present work aims to optimize the biodegradation of diesel and two used oils (SAE 40 and SAE 50) by bacterial strains namely Acinetobacter S2 and Pseudomonas S7 using either nutrient factors (yeast extract, peptone or trace elements) or surfactants (tween 80 or Sodium Dodecyl Sulfate: SDS). The strains are incubated alone or together with the used oils or diesel supplemented or not with nutrient factors or surfactants for 14, 28, 42 and 56 days, respectively. For all the incubation period, the hydrocarbons degradation rates are determined by gravimetric assay. The results obtained show that nutrient factors increase significantly SAE 50 used oil biodegradation (p = 0.009). Similarly, tween 80 increases SAE 50 and SAE 40 used oils biodegradation but not diesel one. The results also show a significant difference between biodegradation rates at 14, 28, 42 and 56 days for all the hydro-carbons tested (p Acinetobacter S2 and Pseudomonas S7 increases the degradation over the one of the strains alone.
文摘The large deformation of incompressible rubber cylinder under inner pressure is ana- lyzed by a kind of new rubber materials strain energy function.The theory formulation for the dis- placement and stress is presented.The penalty finite element formulation is established in order to ana- lyze nonlinear rubber materials,and the results of finite element method agree well with theoretical ones.A new method for controlling the calculating stability and convergence rates is put forward.The selection of the appropriate penalty factor and its influence on calculated results are discussed.
基金supported by Special Foundation of Earthquake Science(201408006)Director Foundation of Institute of Seismology,China Earthquake Administration(201516214)
文摘This work analyzes the quality of crustal tilt and strain observations during 2014, which were acquired from 269 sets of ground tiltmeters and 212 sets of strainmeters. In terms of data quality, the water tube tiltmeters presented the highest rate of excellent quality,approximately 91%, and the pendulum tiltmeters and ground strainmeters yielded rates of81% and 78%, respectively. This means that a total of 380 sets of instruments produced high-quality observational data suitable for scientific investigations and analyses.
文摘Two improvements have been made on the calculation of plastic strain ratio (r value) in BCC monocrystals by considering the differences in the critical shear stresses among the three slip systems and the rotation of crystal lattice. It is found that the results calculated by the improved method are more rational.
基金The National Natural Science Foundation of China (Nos.50778077 and 50608036)
文摘Based on strain signals, a new time-domain methodology for detecting the beam local damage has been developed. The pseudo strain energy density （PSED） is defined and used to build two major damage indexes, the average pseudo strain energy density （APSED） and the average pseudo strain energy density rate （APSEDR）. Probability and mathematical statistics are utilized to derive a standardized damage index. Furthermore, by applying the analytic relation between the strain energy release rate and the stress intensity factor, an analytic solution of crack depth is derived. For the dynamic strain signals, the wavelet packet transform is used to pre-process measured data. Finally, a numerical simulation indicates that this method can effectively identify the damage location and its absolute severity.
