Bone marrow-derived mesenchymal stem cells (BMSCs) have been shown to promote the regeneration of injured peripheral nerves. Pulsed electromagnetic field (PEMF) reportedly promotes the proliferation and neuronal d...Bone marrow-derived mesenchymal stem cells (BMSCs) have been shown to promote the regeneration of injured peripheral nerves. Pulsed electromagnetic field (PEMF) reportedly promotes the proliferation and neuronal differentiation of BMSCs. Low-frequency PEMF can induce the neuronal differentiation of BMSCs in the absence of nerve growth factors. This study was designed to investigate the effects of low-frequency PEMF pretreatment on the proliferation and function of BMSCs and the effects of low-frequency PEMF pre-treated BMSCs on the regeneration of injured peripheral nerve using in vitro and in vivo experiments.In in vitro experiments, quantitative DNA analysis was performed to determine the proliferation of BMSCs, and reverse transcription-polymerase chain reaction was performed to detect S100 (Schwann cell marker), glial fibrillary acidic protein (astrocyte marker), and brain-derived neurotrophic factor and nerve growth factor (neurotrophic factors) mRNA expression. In the in vivo experiments, rat models of crush-injured mental nerve established using clamp method were randomly injected with low-frequency PEMF pretreated BMSCs, unpretreated BMSCs or PBS at the injury site (1 × 106 cells). DiI-labeled BMSCs injected at the injury site were counted under the fluorescence microscope to determine cell survival. One or two weeks after cell injection, functional recovery of the injured nerve was assessed using the sensory test with von Frey filaments. Two weeks after cell injection, axonal regeneration was evaluated using histomorphometric analysis and retrograde labeling of trigeminal ganglion neurons. In vitro experiment results revealed that low-frequency PEMF pretreated BMSCs proliferated faster and had greater mRNA expression of growth factors than unpretreated BMSCs. In vivo experiment results revealed that compared with injection of unpretreated BMSCs, injection of low-frequency PEMF pretreated BMSCs led to higher myelinated axon count and axon density and more DiI-labeled neurons in the trigeminal ganglia, contributing to rapider functional recovery of injured mental nerve. These findings suggest that low-frequency PEMF pretreatment is a promising approach to enhance the efficacy of cell therapy for peripheral nerve injury repair.展开更多
BACKGROUND: The postoperative recovery of nerve function in patients with peripheral nerve injury is always an important problem to solve after treatment. The electric stimulation induced electromagnetic field can no...BACKGROUND: The postoperative recovery of nerve function in patients with peripheral nerve injury is always an important problem to solve after treatment. The electric stimulation induced electromagnetic field can nourish nerve, postpone muscular atrophy, and help the postoperative neuromuscular function. OBJECTIVE: To observe the effects of low-frequency pulse percutaneous electric stimulation on the functional recovery of postoperative patients with peripheral nerve injury, and quantitatively evaluate the results of electromyogram (EMG) examination before and after treatment. DESIGN : A retrospective case analysis SETTING: The Sixth People's Hospital affiliated to Shanghai Jiaotong University PARTICIPANTS: Nineteen postoperative inpatients with peripheral nerve injury were selected from the De- partment of Orthopaedics, the Sixth People's Hospital affiliated to Shanghai Jiaotong University from June 2005 to January 2006, including 13 males and 6 females aged 24-62 years with an average of 36 years old. There were 3 cases of brachial plexus nerve injury, 3 of median nerve injury, 7 of radial nerve injury, 3 of ul- nar nerve injury and 3 of common peroneal nerve injury, and all the patients received probing nerve fiber restoration. Their main preoperative manifestations were dennervation, pain in limbs, motor and sensory disturbances. All the 19 patients were informed with the therapeutic program and items for evaluation. METHODS: ① Low-frequency pulse percutaneous electric stimulation apparatus: The patients were given electric stimulation with the TERESA cantata instrument (TERESA-0, Shanghai Teresa Health Technology, Co., Ltd.). The patients were stimulated with symmetric square waves of 1-111 Hz, and the intensity was 1.2-5.0 mA, and it was gradually adjusted according to the recovered conditions of neural regeneration following the principle that the intensity was strong enough and the patients felt no obvious upset. They were treated for 4- 24 weeks, 10-30 minutes for each time, 1-3 times a day, and 6 weeks as a course. ② EMG examination was applied to evaluate the recoveries of recruitment, motor conduction velocity (MCV) and sensory conduction velocity (SCV) before and after treatment. The patients were examined with the EMG apparatus (DIS- A2000C, Danmark) before and after the treatment of percutaneous electric stimulation. ③Standards for evaluating the effects included cured (complete recovery of motor functions, muscle strength of grade 5, no abnormality in EMG examination), obviously effective [general recovery of motor function, muscle strength of grade 4, no or a few denervation potentials, motor conduction velocity (MCV) and sensory conduction velocity (SCV)], improved (partial recovery of motor function, muscle strength of grade 3, denervation potentials and reinneration potentials, slowed MCV and SCV, invalid (no obvious changes of motor function). MAIN OUTCOME MEASURES: ① Ameliorated degree of the nerve function of the postoperative patients with peripheral nerve injury treated with percutaneous electric stimulation; ② Changes of EMG examination before and after treatment. RESULTS: All the 19 postoperative patients with peripheral nerve injury were involved in the analysis of results. ① Comparison of nerve function before and after treatment in 19 patients with peripheral nerve injury of different sites: For the patients with radial nerve injury (n=7), the nerve functions all completely recovered after 8-week treatment, and the cured and obvious rate was 100% (7/7); For the patients with brachial plexus nerve injury (n=3), 1 case had no obvious improvement, and the cured and obvious rate was 67% (2/3); For the patients with common peroneal nerve injury (n=3), the extension of foot dorsum generally recovered in 1 case of nerve contusion after 4-week treatment, and the cured and obvious rate was 67% (2/3); For the patients with median nerve injury (n=3), muscle strength was obviously recovered, and the cured and obvious rate was 100% (3/3); For the patients with ulnar nerve injury (n=3), 1 case only had recovery of partial senses, and the cured and obvious rate was 67% (2/3). Totally 9 cases were cured, 7 were obviously effective, 1 was improved, and only 2 were invalid. After 4 courses, the cured rate of damaged nerve function after four courses was 47% (9/19), and effective rate was 89% (17/19).② Comparison of EMG examination before and after treatment: Before and after percutaneous electric stimulation, he effective rates of recruitment, MCV and SCV were 89% (17/19), 58% (11/19), 47% (9/19) respectively, and there were extremely obvious differences (P〈 0.01). CONCLUSION: ①Low-frequency pulse percutaneous electric stimulation can improve the nerve function of postoperative patients with peripheral nerve injury of different sites, especially that the injuries of radial nerve and median nerve recover more obviously. ②Percutaneous electric stimulation can ameliorate the indexes of EMG examination, especially the recruitment, in postoperative patients with peripheral nerve injury.展开更多
BACKGROUND: Electromagnetic radiation can influence dopamine (DA) synthesis in brain tissues or ceils, but electromagnetic frequencies, intensities, and radiation time can produce different effects. In addition, th...BACKGROUND: Electromagnetic radiation can influence dopamine (DA) synthesis in brain tissues or ceils, but electromagnetic frequencies, intensities, and radiation time can produce different effects. In addition, the signal pathway by which electromagnetic radiation influences DA synthesis remains controversial. OBJECTIVE: To determine tyrosine hydroxylase (TH) expression in PC12 cells and DA levels in cell culture media after different periods of low-frequency pulsed electric field (LF-PEF) stimulation, and to determine how LF-PEF signaling stimulates TH synthesis using inhibitors. DESIGN, TIME AND SETTING: A parallel, controlled, cell experiment was performed at the Laboratory of Cell Biology, School of Life Science, East China Normal University, between January and October 2006. MATERIALS: PC12 cells were purchased from the Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, China. Nerve growth factor was purchased from PeproTech, USA. The protein kinase A inhibitor, H-89, and mitogen-activated protein kinase kinase inhibitor, U0126, were purchased from Sigma, USA. METHODS: (1) Following routine culture in Dulbecco's modified eagle medium, primary PC12 cells were stimulated under LF-PEF (pulse frequency 50.Hz, pulse width 20 μs, peak field strength 1 V/m) for 5, 10, 15, 20, and 30 minutes. (2) Inhibitors (H-89 or U0126, 1 μmol/L) were added 30 minutes before LF-PEF stimulation for 10 minutes. MAIN OUTCOME MEASURES: (1) TH expression was determined by Western blot in PC12 cells at 0.5, 1,2, 3, and 4 days after LF-PEF stimulation. Similarly, DA was measured by high-performance liquid chromatography in media at 2, 3, 4, or 5 days after LF-PEE (2) TH expression was detected 1 day after H-89 or U0126 treatment and LF-PEE RESULTS: (1) Short-term LF-PEF stimulation (5 and 10 minutes) increased TH expression and media DA levels after short-term culture (2 days) (P 〈 0.01), but both parameters decreased with longer culture (3 4 days) (P 〈 0.01). Long-term LF-PEF stimulation (15, 20, or 30 minutes) decreased TH and DA synthesis, followed by a rapid increase (P 〈 0.01). (2) H89 could completely inhibit TH expression in PC12 cells stimulated by LF-PEF for 10 minutes, while the inhibition rate of U0126 was 53.2%. CONCLUSION: Short-term LF-PEF first promotes then inhibits, while long-term LF-PEF first inhibits then promotes, TH and DA synthesis. LF-PEF stimulation regulates TH expression primarily by activating protein kinase A to regulate DA synthesis.展开更多
In this paper, the generalized nonlinear Schrodinger equation (GNLSE) is solved by an adaptive split-step Fourier method (ASSFM). It is found that ASSFM must be used to solve GNLSE to ensure precision when the sol...In this paper, the generalized nonlinear Schrodinger equation (GNLSE) is solved by an adaptive split-step Fourier method (ASSFM). It is found that ASSFM must be used to solve GNLSE to ensure precision when the soliton selffrequency shift is remarkable and the photonic crystal fibre (PCF) parameters vary with the frequency considerably. The precision of numerical simulation by using ASSFM is higher than that by using split-step Fourier method in the process of laser pulse propagation in PCFs due to the fact that the variation of fibre parameters with the peak frequency in the pulse spectrum can be taken into account fully.展开更多
The paper presents a general retention formula for supercritical fluid chromatography at finite concentration. A new chromatographic rate theory based on the fugacities of solutes instead of concentrations is develope...The paper presents a general retention formula for supercritical fluid chromatography at finite concentration. A new chromatographic rate theory based on the fugacities of solutes instead of concentrations is developed, thus relieving the restrictions of linear isothermal distribution and infinite dilution. An expression for retention values of a N component system including solvent is obtained by combining the rate theory with the mass balance equation of solutes in chromatography. It is shown that there are N-1 characteristic retention peaks for N components and the retention time can be calculated directly from the equilibrium properties of the components in both mobile phase and stationary phase at the given conditions. The theory can be reduced to the well known formula for infinite dilution and to the result of step-pulse theory in gas chromatography under low pressure at finite concentration. Supercritical fluid chromatography may eventually prove itself to be a useful reseach tool in the field of phase equilibrium and thermodynamic properties of supercritical fluid system.展开更多
Aim To analyze dynamic failure of aerospace strutures subjected lateral impulsive loading. Methods Structures were modeled as rigid-perfectly plastic free-free stepped beams. Basic equations of motion un set up f...Aim To analyze dynamic failure of aerospace strutures subjected lateral impulsive loading. Methods Structures were modeled as rigid-perfectly plastic free-free stepped beams. Basic equations of motion un set up for analysis. Results Final pat deformation and rigid motion solutions were determined for a uniform impulsive loading. The critical rupture conditions for a space shuttle and a missile were obtained. Conclusion Failure is possible for aerospace structures under a uniform impulsive loading, but it is mere difficult in space.展开更多
The two characteristics of near-fault ground motions, i.e., the forward directivity effect and permanent displacement effect, result in long period and large velocity pulse in the velocity time history and large step ...The two characteristics of near-fault ground motions, i.e., the forward directivity effect and permanent displacement effect, result in long period and large velocity pulse in the velocity time history and large step pulse in the displacement time history. Considering the two effects, a simple expression of continuous function for equivalent velocity pulse time history is presented in this paper. The equivalent pulse model, in which the pulse period, peak velocity and pulse shape are described by five parameters, is highly advantageous to fit and simulate the pulse-type velocity time history. The equivalent pulse model comprises only one low-frequency component while the high-frequency component of a pulse-type earthquake record cannot be considered. Based on 28 records of 11 earthquakes, the pulse frequency of pulse-type records is generally less than 1 Hz. Therefore the low-frequency component and high-frequency component are simulated respectively and combined them together to generate a pulse-type ground motion.展开更多
A novel efficient circuit for Ultra-WideBand(UWB) balanced sub-nanosecond monocycle pulse generation is presented.The pulse generator employs wideband bipolar transistor,step recovery diodes,Schottky diodes,and simple...A novel efficient circuit for Ultra-WideBand(UWB) balanced sub-nanosecond monocycle pulse generation is presented.The pulse generator employs wideband bipolar transistor,step recovery diodes,Schottky diodes,and simple charging and discharging circuitry.Simple transient analysis and design of the circuit are presented along with their operating principle.The pulse generator produces truly balanced monocycle pulse with 500 ps pulse-width and 800 mV peak voltage.The generated monocycle pulse also has very symmetrical positive and negative portions and low ringing level.The presented pulse generator can be used as both a transmitter feeding UWB balanced antennas without broadband baluns and a balanced switching pulse generator that used in UWB receiver.展开更多
The propagation along oz of pulsed sound waves made of sequences of elementary unit pulses U (sin τ) where U is the unit step function and τ = kz -ωt is analyzed using the expansion of U (sin τ) and of the Dirac d...The propagation along oz of pulsed sound waves made of sequences of elementary unit pulses U (sin τ) where U is the unit step function and τ = kz -ωt is analyzed using the expansion of U (sin τ) and of the Dirac distribution δ (sin τ) in terms of τ-nπ where n is an integer. Their properties and how these pulsed sound waves could be generated are discussed.展开更多
Starting from the extended nonlinear Schrodinger equation in which the self-steepening effect is included, the evolution and the splitting processes of continuous optical wave whose amplitude is perturbed into time re...Starting from the extended nonlinear Schrodinger equation in which the self-steepening effect is included, the evolution and the splitting processes of continuous optical wave whose amplitude is perturbed into time related ultra-short optical pulse trains in an optical fibre are numerically simulated by adopting the split-step Fourier algorithm. The results show that the self-steepening effect can cause the characteristic of the pulse trains to vary with time, which is different from the self-steepening-free case where the generated pulse trains consist of single pulses which are identical in width, intensity, and interval, namely when pulses move a certain distance, they turn into the pulse trains within a certain time range. Moreover, each single pulse may split into several sub-pulses. And as time goes on, the number of the sub-pulses will decrease gradually and the pulse width and the pulse intensity will change too. With the increase of the self-steepening parameter, the distance needed to generate time-dependent pulse trains will shorten. In addition, for a large self-steepening parameter and at the distance where more sub-pulses appear, the corresponding frequency spectra of pulse trains are also wider.展开更多
This paper proposes a new type of pulse launcher that applies the principle of linear motors. The stator, viz. gun barrel, of the launcher has a new structure of one segment of iron core consisting of 3 staggered lami...This paper proposes a new type of pulse launcher that applies the principle of linear motors. The stator, viz. gun barrel, of the launcher has a new structure of one segment of iron core consisting of 3 staggered laminations. This structure is helpful in advancing the thrust force per volume. Based on introducing the structure and the working principles, this paper resolves the electromagnetic thrusting force and performs mechanical analysis and experiments on the sample launcher. The research shows that this launcher is simple and brushless structure with brief controlling.展开更多
针对传统Buck变换器受最小占空比限制的影响,无法适用于高降压比场合的问题,提出了一种新型无变压器高降压DC-DC变换器。首先,详细地分析了所提变换器的工作模态和开关时序。其次,在控制层面,该变换器应用交错式脉宽调制的开关模式,不...针对传统Buck变换器受最小占空比限制的影响,无法适用于高降压比场合的问题,提出了一种新型无变压器高降压DC-DC变换器。首先,详细地分析了所提变换器的工作模态和开关时序。其次,在控制层面,该变换器应用交错式脉宽调制的开关模式,不但增加了其带载能力,还极大减少了元器件的电压应力。对新型高降压比变换器的工作过程进行分析,同时在理论上进行了参数设计。最后,搭建500/26 V 430 W的样机进行实验,实验结果充分证明了理论的正确性和可行性。展开更多
In the high speed target environment,there exists serious Doppler effect in the low pulse repetition frequency(LPRF) modulated frequency stepped frequency(MFSF) radar signal.The velocity range of the target is lar...In the high speed target environment,there exists serious Doppler effect in the low pulse repetition frequency(LPRF) modulated frequency stepped frequency(MFSF) radar signal.The velocity range of the target is large and the velocity is high ambiguous,so the single method is difficult to satisfy the velocity measurement requirement.For this problem,a novel method is presented,it is a combination of cross-correlation inner frame velocity measurement and range-Doppler coupling velocity measurement.The cross-correlation inner frame method,overcoming the low Doppler tolerance of the cross-correlation between frames,can obtain the coarse velocity of the high speed target,and then the precision velocity can be obtained with the range-Doppler coupling method.The simulation results confirm the method is effective,and also it is well real-time and easy to the project application.展开更多
基金supported by a grant of the Korea Health Technology R & D Project through the Korea Health Industry Development Institute(KHIDI)funded by the Ministry of Health&Welfare,Republic of Korea(grant number:HI15C1535)
文摘Bone marrow-derived mesenchymal stem cells (BMSCs) have been shown to promote the regeneration of injured peripheral nerves. Pulsed electromagnetic field (PEMF) reportedly promotes the proliferation and neuronal differentiation of BMSCs. Low-frequency PEMF can induce the neuronal differentiation of BMSCs in the absence of nerve growth factors. This study was designed to investigate the effects of low-frequency PEMF pretreatment on the proliferation and function of BMSCs and the effects of low-frequency PEMF pre-treated BMSCs on the regeneration of injured peripheral nerve using in vitro and in vivo experiments.In in vitro experiments, quantitative DNA analysis was performed to determine the proliferation of BMSCs, and reverse transcription-polymerase chain reaction was performed to detect S100 (Schwann cell marker), glial fibrillary acidic protein (astrocyte marker), and brain-derived neurotrophic factor and nerve growth factor (neurotrophic factors) mRNA expression. In the in vivo experiments, rat models of crush-injured mental nerve established using clamp method were randomly injected with low-frequency PEMF pretreated BMSCs, unpretreated BMSCs or PBS at the injury site (1 × 106 cells). DiI-labeled BMSCs injected at the injury site were counted under the fluorescence microscope to determine cell survival. One or two weeks after cell injection, functional recovery of the injured nerve was assessed using the sensory test with von Frey filaments. Two weeks after cell injection, axonal regeneration was evaluated using histomorphometric analysis and retrograde labeling of trigeminal ganglion neurons. In vitro experiment results revealed that low-frequency PEMF pretreated BMSCs proliferated faster and had greater mRNA expression of growth factors than unpretreated BMSCs. In vivo experiment results revealed that compared with injection of unpretreated BMSCs, injection of low-frequency PEMF pretreated BMSCs led to higher myelinated axon count and axon density and more DiI-labeled neurons in the trigeminal ganglia, contributing to rapider functional recovery of injured mental nerve. These findings suggest that low-frequency PEMF pretreatment is a promising approach to enhance the efficacy of cell therapy for peripheral nerve injury repair.
基金grants from Sci-entific Research Fund of theMinistry of Health, No.20040801 Shanghai Ris-ing-Star Program of Technologi-cal Committee, No.05QMX1438
文摘BACKGROUND: The postoperative recovery of nerve function in patients with peripheral nerve injury is always an important problem to solve after treatment. The electric stimulation induced electromagnetic field can nourish nerve, postpone muscular atrophy, and help the postoperative neuromuscular function. OBJECTIVE: To observe the effects of low-frequency pulse percutaneous electric stimulation on the functional recovery of postoperative patients with peripheral nerve injury, and quantitatively evaluate the results of electromyogram (EMG) examination before and after treatment. DESIGN : A retrospective case analysis SETTING: The Sixth People's Hospital affiliated to Shanghai Jiaotong University PARTICIPANTS: Nineteen postoperative inpatients with peripheral nerve injury were selected from the De- partment of Orthopaedics, the Sixth People's Hospital affiliated to Shanghai Jiaotong University from June 2005 to January 2006, including 13 males and 6 females aged 24-62 years with an average of 36 years old. There were 3 cases of brachial plexus nerve injury, 3 of median nerve injury, 7 of radial nerve injury, 3 of ul- nar nerve injury and 3 of common peroneal nerve injury, and all the patients received probing nerve fiber restoration. Their main preoperative manifestations were dennervation, pain in limbs, motor and sensory disturbances. All the 19 patients were informed with the therapeutic program and items for evaluation. METHODS: ① Low-frequency pulse percutaneous electric stimulation apparatus: The patients were given electric stimulation with the TERESA cantata instrument (TERESA-0, Shanghai Teresa Health Technology, Co., Ltd.). The patients were stimulated with symmetric square waves of 1-111 Hz, and the intensity was 1.2-5.0 mA, and it was gradually adjusted according to the recovered conditions of neural regeneration following the principle that the intensity was strong enough and the patients felt no obvious upset. They were treated for 4- 24 weeks, 10-30 minutes for each time, 1-3 times a day, and 6 weeks as a course. ② EMG examination was applied to evaluate the recoveries of recruitment, motor conduction velocity (MCV) and sensory conduction velocity (SCV) before and after treatment. The patients were examined with the EMG apparatus (DIS- A2000C, Danmark) before and after the treatment of percutaneous electric stimulation. ③Standards for evaluating the effects included cured (complete recovery of motor functions, muscle strength of grade 5, no abnormality in EMG examination), obviously effective [general recovery of motor function, muscle strength of grade 4, no or a few denervation potentials, motor conduction velocity (MCV) and sensory conduction velocity (SCV)], improved (partial recovery of motor function, muscle strength of grade 3, denervation potentials and reinneration potentials, slowed MCV and SCV, invalid (no obvious changes of motor function). MAIN OUTCOME MEASURES: ① Ameliorated degree of the nerve function of the postoperative patients with peripheral nerve injury treated with percutaneous electric stimulation; ② Changes of EMG examination before and after treatment. RESULTS: All the 19 postoperative patients with peripheral nerve injury were involved in the analysis of results. ① Comparison of nerve function before and after treatment in 19 patients with peripheral nerve injury of different sites: For the patients with radial nerve injury (n=7), the nerve functions all completely recovered after 8-week treatment, and the cured and obvious rate was 100% (7/7); For the patients with brachial plexus nerve injury (n=3), 1 case had no obvious improvement, and the cured and obvious rate was 67% (2/3); For the patients with common peroneal nerve injury (n=3), the extension of foot dorsum generally recovered in 1 case of nerve contusion after 4-week treatment, and the cured and obvious rate was 67% (2/3); For the patients with median nerve injury (n=3), muscle strength was obviously recovered, and the cured and obvious rate was 100% (3/3); For the patients with ulnar nerve injury (n=3), 1 case only had recovery of partial senses, and the cured and obvious rate was 67% (2/3). Totally 9 cases were cured, 7 were obviously effective, 1 was improved, and only 2 were invalid. After 4 courses, the cured rate of damaged nerve function after four courses was 47% (9/19), and effective rate was 89% (17/19).② Comparison of EMG examination before and after treatment: Before and after percutaneous electric stimulation, he effective rates of recruitment, MCV and SCV were 89% (17/19), 58% (11/19), 47% (9/19) respectively, and there were extremely obvious differences (P〈 0.01). CONCLUSION: ①Low-frequency pulse percutaneous electric stimulation can improve the nerve function of postoperative patients with peripheral nerve injury of different sites, especially that the injuries of radial nerve and median nerve recover more obviously. ②Percutaneous electric stimulation can ameliorate the indexes of EMG examination, especially the recruitment, in postoperative patients with peripheral nerve injury.
基金the National Natural Science Foundation of China,No.50677022
文摘BACKGROUND: Electromagnetic radiation can influence dopamine (DA) synthesis in brain tissues or ceils, but electromagnetic frequencies, intensities, and radiation time can produce different effects. In addition, the signal pathway by which electromagnetic radiation influences DA synthesis remains controversial. OBJECTIVE: To determine tyrosine hydroxylase (TH) expression in PC12 cells and DA levels in cell culture media after different periods of low-frequency pulsed electric field (LF-PEF) stimulation, and to determine how LF-PEF signaling stimulates TH synthesis using inhibitors. DESIGN, TIME AND SETTING: A parallel, controlled, cell experiment was performed at the Laboratory of Cell Biology, School of Life Science, East China Normal University, between January and October 2006. MATERIALS: PC12 cells were purchased from the Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, China. Nerve growth factor was purchased from PeproTech, USA. The protein kinase A inhibitor, H-89, and mitogen-activated protein kinase kinase inhibitor, U0126, were purchased from Sigma, USA. METHODS: (1) Following routine culture in Dulbecco's modified eagle medium, primary PC12 cells were stimulated under LF-PEF (pulse frequency 50.Hz, pulse width 20 μs, peak field strength 1 V/m) for 5, 10, 15, 20, and 30 minutes. (2) Inhibitors (H-89 or U0126, 1 μmol/L) were added 30 minutes before LF-PEF stimulation for 10 minutes. MAIN OUTCOME MEASURES: (1) TH expression was determined by Western blot in PC12 cells at 0.5, 1,2, 3, and 4 days after LF-PEF stimulation. Similarly, DA was measured by high-performance liquid chromatography in media at 2, 3, 4, or 5 days after LF-PEE (2) TH expression was detected 1 day after H-89 or U0126 treatment and LF-PEE RESULTS: (1) Short-term LF-PEF stimulation (5 and 10 minutes) increased TH expression and media DA levels after short-term culture (2 days) (P 〈 0.01), but both parameters decreased with longer culture (3 4 days) (P 〈 0.01). Long-term LF-PEF stimulation (15, 20, or 30 minutes) decreased TH and DA synthesis, followed by a rapid increase (P 〈 0.01). (2) H89 could completely inhibit TH expression in PC12 cells stimulated by LF-PEF for 10 minutes, while the inhibition rate of U0126 was 53.2%. CONCLUSION: Short-term LF-PEF first promotes then inhibits, while long-term LF-PEF first inhibits then promotes, TH and DA synthesis. LF-PEF stimulation regulates TH expression primarily by activating protein kinase A to regulate DA synthesis.
文摘In this paper, the generalized nonlinear Schrodinger equation (GNLSE) is solved by an adaptive split-step Fourier method (ASSFM). It is found that ASSFM must be used to solve GNLSE to ensure precision when the soliton selffrequency shift is remarkable and the photonic crystal fibre (PCF) parameters vary with the frequency considerably. The precision of numerical simulation by using ASSFM is higher than that by using split-step Fourier method in the process of laser pulse propagation in PCFs due to the fact that the variation of fibre parameters with the peak frequency in the pulse spectrum can be taken into account fully.
文摘The paper presents a general retention formula for supercritical fluid chromatography at finite concentration. A new chromatographic rate theory based on the fugacities of solutes instead of concentrations is developed, thus relieving the restrictions of linear isothermal distribution and infinite dilution. An expression for retention values of a N component system including solvent is obtained by combining the rate theory with the mass balance equation of solutes in chromatography. It is shown that there are N-1 characteristic retention peaks for N components and the retention time can be calculated directly from the equilibrium properties of the components in both mobile phase and stationary phase at the given conditions. The theory can be reduced to the well known formula for infinite dilution and to the result of step-pulse theory in gas chromatography under low pressure at finite concentration. Supercritical fluid chromatography may eventually prove itself to be a useful reseach tool in the field of phase equilibrium and thermodynamic properties of supercritical fluid system.
文摘Aim To analyze dynamic failure of aerospace strutures subjected lateral impulsive loading. Methods Structures were modeled as rigid-perfectly plastic free-free stepped beams. Basic equations of motion un set up for analysis. Results Final pat deformation and rigid motion solutions were determined for a uniform impulsive loading. The critical rupture conditions for a space shuttle and a missile were obtained. Conclusion Failure is possible for aerospace structures under a uniform impulsive loading, but it is mere difficult in space.
基金National Natural Science Foundation of China (50478063)
文摘The two characteristics of near-fault ground motions, i.e., the forward directivity effect and permanent displacement effect, result in long period and large velocity pulse in the velocity time history and large step pulse in the displacement time history. Considering the two effects, a simple expression of continuous function for equivalent velocity pulse time history is presented in this paper. The equivalent pulse model, in which the pulse period, peak velocity and pulse shape are described by five parameters, is highly advantageous to fit and simulate the pulse-type velocity time history. The equivalent pulse model comprises only one low-frequency component while the high-frequency component of a pulse-type earthquake record cannot be considered. Based on 28 records of 11 earthquakes, the pulse frequency of pulse-type records is generally less than 1 Hz. Therefore the low-frequency component and high-frequency component are simulated respectively and combined them together to generate a pulse-type ground motion.
文摘A novel efficient circuit for Ultra-WideBand(UWB) balanced sub-nanosecond monocycle pulse generation is presented.The pulse generator employs wideband bipolar transistor,step recovery diodes,Schottky diodes,and simple charging and discharging circuitry.Simple transient analysis and design of the circuit are presented along with their operating principle.The pulse generator produces truly balanced monocycle pulse with 500 ps pulse-width and 800 mV peak voltage.The generated monocycle pulse also has very symmetrical positive and negative portions and low ringing level.The presented pulse generator can be used as both a transmitter feeding UWB balanced antennas without broadband baluns and a balanced switching pulse generator that used in UWB receiver.
文摘The propagation along oz of pulsed sound waves made of sequences of elementary unit pulses U (sin τ) where U is the unit step function and τ = kz -ωt is analyzed using the expansion of U (sin τ) and of the Dirac distribution δ (sin τ) in terms of τ-nπ where n is an integer. Their properties and how these pulsed sound waves could be generated are discussed.
基金supported by Key Program of Natural Science Foundation of Educational Commission of Sichuan Province, China (GrantNo 2006A124)the Fundamental Application Research Project of the Department of Science and Technology of Sichuan Province,China (Grant No 05JY029-084)the Foundation of Science and Technology Development of Chengdu University of Information Technology, China (Grant No KYTZ20060604)
文摘Starting from the extended nonlinear Schrodinger equation in which the self-steepening effect is included, the evolution and the splitting processes of continuous optical wave whose amplitude is perturbed into time related ultra-short optical pulse trains in an optical fibre are numerically simulated by adopting the split-step Fourier algorithm. The results show that the self-steepening effect can cause the characteristic of the pulse trains to vary with time, which is different from the self-steepening-free case where the generated pulse trains consist of single pulses which are identical in width, intensity, and interval, namely when pulses move a certain distance, they turn into the pulse trains within a certain time range. Moreover, each single pulse may split into several sub-pulses. And as time goes on, the number of the sub-pulses will decrease gradually and the pulse width and the pulse intensity will change too. With the increase of the self-steepening parameter, the distance needed to generate time-dependent pulse trains will shorten. In addition, for a large self-steepening parameter and at the distance where more sub-pulses appear, the corresponding frequency spectra of pulse trains are also wider.
文摘This paper proposes a new type of pulse launcher that applies the principle of linear motors. The stator, viz. gun barrel, of the launcher has a new structure of one segment of iron core consisting of 3 staggered laminations. This structure is helpful in advancing the thrust force per volume. Based on introducing the structure and the working principles, this paper resolves the electromagnetic thrusting force and performs mechanical analysis and experiments on the sample launcher. The research shows that this launcher is simple and brushless structure with brief controlling.
文摘针对传统Buck变换器受最小占空比限制的影响,无法适用于高降压比场合的问题,提出了一种新型无变压器高降压DC-DC变换器。首先,详细地分析了所提变换器的工作模态和开关时序。其次,在控制层面,该变换器应用交错式脉宽调制的开关模式,不但增加了其带载能力,还极大减少了元器件的电压应力。对新型高降压比变换器的工作过程进行分析,同时在理论上进行了参数设计。最后,搭建500/26 V 430 W的样机进行实验,实验结果充分证明了理论的正确性和可行性。
文摘In the high speed target environment,there exists serious Doppler effect in the low pulse repetition frequency(LPRF) modulated frequency stepped frequency(MFSF) radar signal.The velocity range of the target is large and the velocity is high ambiguous,so the single method is difficult to satisfy the velocity measurement requirement.For this problem,a novel method is presented,it is a combination of cross-correlation inner frame velocity measurement and range-Doppler coupling velocity measurement.The cross-correlation inner frame method,overcoming the low Doppler tolerance of the cross-correlation between frames,can obtain the coarse velocity of the high speed target,and then the precision velocity can be obtained with the range-Doppler coupling method.The simulation results confirm the method is effective,and also it is well real-time and easy to the project application.