Different feeding techniques of microstrip patch antennas with different spiral defected ground structures are presented in this paper. The investigated structures illustrate some merits in designing multi-electromagn...Different feeding techniques of microstrip patch antennas with different spiral defected ground structures are presented in this paper. The investigated structures illustrate some merits in designing multi-electromagnetic band-gap structures by adjusting the capacitance and changing the inductance through varying the width and length of spiral defected ground structure. Then by applying the three different spirals shapes (one, two and four arms) as the ground plane of microstrip patch antenna with different feeding techniques to create multi or ultra wide-band, improve the antenna gain and reduce the antenna size, it is found that the four arms spiral defected ground structure of microstrip patch antenna with offset feed gives good performance, electrical size reduction to about 75% as compared to the original patch size and ultra-wide bandwidth extends from 2 GHz up to 12 GHz with ?8 dB impedance bandwidth.展开更多
BACKGROUND： Induced differentiation strategies and cytochemical properties of human embryonic stem ceils （hESCs） have been investigated. However, the electrophysiological functions of tyrosine hydroxylase （TH）-po...BACKGROUND： Induced differentiation strategies and cytochemical properties of human embryonic stem ceils （hESCs） have been investigated. However, the electrophysiological functions of tyrosine hydroxylase （TH）-positive cells dedved from hESCs remain unclear. OBJECTIVE： To investigate the differentiation efficiency of TH-positive cells from hESCs in vitro using modified four-step culture methods, including embryoid body formation, and to examine the functional characteristics of the differentiated TH-positive cells using electrophysiological techniques. DESIGN, TIME AND SETTING： Neuroelectrophysiology was performed at the Reproductive Medicine Center and Stem Cell Research Center, Peking University Third Hospital, and the Neuroscience Research Institute and Department of Neurobiology, Peking University, from September 2004 to August 2008. MATERIALS： The hESC line, PKU-1.1, a monoclonal cell line derived from a pre-implantation human blastocyst in the Reproductive Medical Center of Peking University Third Hospital. The patch clamp recording system was provided by the Neuroscience Research Institute and Department of Neurobiology, Peking University. METHODS： The hESC line was induced to differentiate into TH-positive cells in vitro using a modified four-step culture method, including the formation of embryoid body, as well as the presence of sonic hedgehog and fibroblast growth factor 8. The cell karyotype was assessed by G-banding karyotype analysis techniques and specific markers were detected immunocytochemically. Whole-cell configuration was obtained after obtaining a tight seal of over 1 GΩ. Ionic currents were detected by holding the cells at -70 mV and stepping to test voltages between -80 and 40 mV in 10-mV increments in voltage-clamp configuration. MAIN OUTCOME MEASURES： We measured the cell karyotype, specific cell markers, and the electrophysiological properties of the voltage-gated ion channels on the cell membrane of TH-positive dopaminergic cells differentiated from our hESCs line in vitro. RESULTS： The differentiated cells had a consistent appearance, and the majority of cells （〉 90%） expressed TH and β-tubulion, as well as the neural progenitor marker, nestino Cell karyotype analysis demonstrated that all of the hESCs had a stable and normal karyotype （46, XX） after differentiation. In addition, patch clamp recording showed that the 10 recorded TH-positive cells exhibited a fast inward current when the test voltage depolarized to -30 mV, and a delayed outward current when the test voltage depolarized to -10 mV. The peak of inward current was obtained at voltage between 10 mV and 0 mV, while the peak of outward current was obtained at 40 mV. The average peak of inward current density was （ -50.05 ± 15.50） pA/pF, and the average peak of outward current density was （41.98 ± 13.55） pA/pE CONCLUSION： More than 90% of the differentiated hESC-derived cells induced by the modified four-step culture method exhibit dopaminergic neuronal properties, including general electrophysiological functional properties, such as functional potassium and sodium channels.展开更多
The electrophysiological properties of potassium ion channels are regarded as a basic index for determining the functional differentiation of neural stem cells. In this study, neural stem cells from the hippocampus of...The electrophysiological properties of potassium ion channels are regarded as a basic index for determining the functional differentiation of neural stem cells. In this study, neural stem cells from the hippocampus of newborn rats were induced to differentiate with neurotrophic growth factor, and the electrophysiological properties of the voltage-gated potassium ion channels were observed. Immunofluorescence staining showed that the rapidly proliferating neural stem cells formed spheres in vitro that expressed high levels of nestin. The differentiated neurons were shown to express neuron-specific enolase. Flow cytometric analysis revealed that the neural stem cells were actively dividing and the percentage of cells in the S ＋ G2/M phase was high. However, the ratio of cells in the S ＋ G2/M phase decreased obviously as differentiation proceeded. Whole-cell patch-clamp re- cordings revealed apparent changes in potassium ion currents as the neurons differentiated. The potassium ion currents consisted of one transient outward potassium ion current and one delayed rectifier potassium ion current, which were blocked by 4-aminopyridine and tetraethylammonium, respectively. The experimental findings indicate that neural stem cells from newborn rat hippo- campus could be cultured and induced to differentiate into functional neurons under defined condi- tions in vitro. The differentiated neurons expressed two types of outward potassium ion cur＇ents similar to those of mature neurons in vivo.展开更多
BACKGROUND： A combination of basic fibroblast growth factor （bFGF）, platelet-derived growth factor （PDGF）, human heregulin-beta-1, beta-mercaptoethanol retinoic acid and forskolin has been reported to induce the ...BACKGROUND： A combination of basic fibroblast growth factor （bFGF）, platelet-derived growth factor （PDGF）, human heregulin-beta-1, beta-mercaptoethanol retinoic acid and forskolin has been reported to induce the differentiation of rat bone marrow stromal cells into myelinating Schwann-like cells. OBJECTIVE： To investigate the inducing effects of a combination of bFGF, PDGF, human heregulin-beta-1, beta-mercaptoethanol retinoic acid and forskolin on neural stem cell differentiation by one- and two-step methods. DESIGN, TIME AND SETTING： A cytobiology experiment was performed at the Department of Histology and Embryology, Medical School of Nantong University, and Jiangsu Province Key Laboratory of Neuroregeneration, China, between August 2005 and January 2007. MATERIALS： A total of 30 healthy Sprague Dawley rat embryos at gestational days 14-16 were selected, bFGF, PDGF, human heregulin-beta-t, beta-mercaptoethanol, retinoic acid, and forskolin were purchased from Sigma, USA. METHODS： Passage 3 rat neural stem cells were cultured by a one-step method in serum-free medium plus 10 ng/m/bFGF, 5 ng/mL PDGF, 200 ng/mL heregulin-beta-1,35 ng/mL all-trans retinoic acid, and 5 pmol/L forskolin or by a two-step method in serum-free medium plus 35 ng/m/ all-trans retinoic acid for 72 hours, followed by serum-free medium plus 10 ng/mL bFGF, 5 ng/mL PDGF, 200 ng/mL heregulin-beta-t and 5 μmol/L forskolin. The control condition consisted of 10% fetal bovine serum alone or 20 ng/mL bFGF alone. MAIN OUTCOME MEASURES： Differentiated cells were identified by immunocytochemical staining for microtubule associate protein-2 （MAP2） and St 00 protein. Geometric parameters and sodium ion currents of the differentiated cells were measured by image analysis and whole-cell patch-clamp techniques, respectively. RESULTS： Compared with the two-step culture method, neuronal-like cells exhibited longer processes and a similar appearance to mature neurons using the one-step method. The percentage of MAP2 positive cells induced by the one-step method was significantly greater than the serum-alone group （P 〈 0.05）. Furthermore, the MAP2 positive cells induced by the one-step method had greater surface areas, cell body perimeters, and longer process than cells induced by serum-alone and bFGF-alone （P 〈 0.05）. There were no significant differences in these parameters between the one-step and two-step methods （P 〉 0.05）. In addition, 80% of the induced neuronal-like cells from the one-step method and 20% from the two-step method displayed inwardly-evoked currents. CONCLUSION： The combination of bFGF, PDGF, human heregulin-beta-t, beta-mercaptoethanol retinoic acid and forskolin successfully induced neuronal differentiation from neural stem cells, with the one-step induction being more effective than the two-step method.展开更多
The band gap structures by arranging hybrid shunted piezoelectric materialswith resistance inductive （RL） circuit and negative impedance converter （NIC） closely and at in- tervals are presented. The theoretical mo...The band gap structures by arranging hybrid shunted piezoelectric materialswith resistance inductive （RL） circuit and negative impedance converter （NIC） closely and at in- tervals are presented. The theoretical model is built using transfer matrix method. Then the MATLAB computing language is utilized to simulate the band gap structures. Meanwhile, the effects of the resistance, inductance and capacitance on the local resonant gap are studied. By comparing different combinations of resistance, inductance and capacitance as well as different arrangement of circuits, a 13 kHz band gap is reached under the effect of arranging hybrid pe- riodic shunted piezoelectric patches at intervals and the stability of the system is also analyzed. It is proved that utilizing hybrid shunted piezoelectric patches would have a clear impact on the band gap structure of phononic crystal rods. Moreover, the band gap would be clearly enlarged by arranging hybrid piezoelectric patches at intervals.展开更多
This paper reviewed the concept,formation and function of gap and developed a new concept,canopy rift.It refers to the small 1-25m 2 rift in the canopy caused by the different distribution pattern of the canopy specie...This paper reviewed the concept,formation and function of gap and developed a new concept,canopy rift.It refers to the small 1-25m 2 rift in the canopy caused by the different distribution pattern of the canopy species or breakage,standing death and treefall.Canopy gap,mainly caused by small scale disturbances including natural disturbance regime and human disturbance regime,is an important phase in the forest regeneration cycle.It plays a leading role in the formation and maintenance of the patches mosaic structure in a forest community.Corresponding to the three phases of the forest regeneration cycle,patches can be classified into three types:gap phase,building phase and mature forest.Many factors may contribute to the maintenance of biodiversity.Here we divided them into ① intrinsic factors,mainly including the biological and ecological characteristics of the species and ② external factors,the heterogeneity of habitat.The formation of gaps leads to the diversification of micro environment,and changes the type and magnitude of understory.Gap impacts the forest micro environment,community structure and dynamic process.Gap causes different status of renewal between pioneer species and climax species,and generates the patch which is the different in the constitute of woods,population dynamic and growing speed.It leads to the diversity of community difference and species component,which is the difference of species between community patches.Gap is of great significance in enhancing and maintaining species diversity for it may enhance habitat heterogeneity.展开更多
文摘Different feeding techniques of microstrip patch antennas with different spiral defected ground structures are presented in this paper. The investigated structures illustrate some merits in designing multi-electromagnetic band-gap structures by adjusting the capacitance and changing the inductance through varying the width and length of spiral defected ground structure. Then by applying the three different spirals shapes (one, two and four arms) as the ground plane of microstrip patch antenna with different feeding techniques to create multi or ultra wide-band, improve the antenna gain and reduce the antenna size, it is found that the four arms spiral defected ground structure of microstrip patch antenna with offset feed gives good performance, electrical size reduction to about 75% as compared to the original patch size and ultra-wide bandwidth extends from 2 GHz up to 12 GHz with ?8 dB impedance bandwidth.
基金the National Natural Science Foundation of China, No. 30672239
文摘BACKGROUND： Induced differentiation strategies and cytochemical properties of human embryonic stem ceils （hESCs） have been investigated. However, the electrophysiological functions of tyrosine hydroxylase （TH）-positive cells dedved from hESCs remain unclear. OBJECTIVE： To investigate the differentiation efficiency of TH-positive cells from hESCs in vitro using modified four-step culture methods, including embryoid body formation, and to examine the functional characteristics of the differentiated TH-positive cells using electrophysiological techniques. DESIGN, TIME AND SETTING： Neuroelectrophysiology was performed at the Reproductive Medicine Center and Stem Cell Research Center, Peking University Third Hospital, and the Neuroscience Research Institute and Department of Neurobiology, Peking University, from September 2004 to August 2008. MATERIALS： The hESC line, PKU-1.1, a monoclonal cell line derived from a pre-implantation human blastocyst in the Reproductive Medical Center of Peking University Third Hospital. The patch clamp recording system was provided by the Neuroscience Research Institute and Department of Neurobiology, Peking University. METHODS： The hESC line was induced to differentiate into TH-positive cells in vitro using a modified four-step culture method, including the formation of embryoid body, as well as the presence of sonic hedgehog and fibroblast growth factor 8. The cell karyotype was assessed by G-banding karyotype analysis techniques and specific markers were detected immunocytochemically. Whole-cell configuration was obtained after obtaining a tight seal of over 1 GΩ. Ionic currents were detected by holding the cells at -70 mV and stepping to test voltages between -80 and 40 mV in 10-mV increments in voltage-clamp configuration. MAIN OUTCOME MEASURES： We measured the cell karyotype, specific cell markers, and the electrophysiological properties of the voltage-gated ion channels on the cell membrane of TH-positive dopaminergic cells differentiated from our hESCs line in vitro. RESULTS： The differentiated cells had a consistent appearance, and the majority of cells （〉 90%） expressed TH and β-tubulion, as well as the neural progenitor marker, nestino Cell karyotype analysis demonstrated that all of the hESCs had a stable and normal karyotype （46, XX） after differentiation. In addition, patch clamp recording showed that the 10 recorded TH-positive cells exhibited a fast inward current when the test voltage depolarized to -30 mV, and a delayed outward current when the test voltage depolarized to -10 mV. The peak of inward current was obtained at voltage between 10 mV and 0 mV, while the peak of outward current was obtained at 40 mV. The average peak of inward current density was （ -50.05 ± 15.50） pA/pF, and the average peak of outward current density was （41.98 ± 13.55） pA/pE CONCLUSION： More than 90% of the differentiated hESC-derived cells induced by the modified four-step culture method exhibit dopaminergic neuronal properties, including general electrophysiological functional properties, such as functional potassium and sodium channels.
基金supported by the National Natural Science Foundation of China,No.31000514the Scientific Research Project for Talent with High Education of Xinxiang Medical University,No.2007502002
文摘The electrophysiological properties of potassium ion channels are regarded as a basic index for determining the functional differentiation of neural stem cells. In this study, neural stem cells from the hippocampus of newborn rats were induced to differentiate with neurotrophic growth factor, and the electrophysiological properties of the voltage-gated potassium ion channels were observed. Immunofluorescence staining showed that the rapidly proliferating neural stem cells formed spheres in vitro that expressed high levels of nestin. The differentiated neurons were shown to express neuron-specific enolase. Flow cytometric analysis revealed that the neural stem cells were actively dividing and the percentage of cells in the S ＋ G2/M phase was high. However, the ratio of cells in the S ＋ G2/M phase decreased obviously as differentiation proceeded. Whole-cell patch-clamp re- cordings revealed apparent changes in potassium ion currents as the neurons differentiated. The potassium ion currents consisted of one transient outward potassium ion current and one delayed rectifier potassium ion current, which were blocked by 4-aminopyridine and tetraethylammonium, respectively. The experimental findings indicate that neural stem cells from newborn rat hippo- campus could be cultured and induced to differentiate into functional neurons under defined condi- tions in vitro. The differentiated neurons expressed two types of outward potassium ion cur＇ents similar to those of mature neurons in vivo.
基金the National Natural Science Foundation of China,No.30870643Natural Science Foundation of Jiangsu Province,No. BK2002036
文摘BACKGROUND： A combination of basic fibroblast growth factor （bFGF）, platelet-derived growth factor （PDGF）, human heregulin-beta-1, beta-mercaptoethanol retinoic acid and forskolin has been reported to induce the differentiation of rat bone marrow stromal cells into myelinating Schwann-like cells. OBJECTIVE： To investigate the inducing effects of a combination of bFGF, PDGF, human heregulin-beta-1, beta-mercaptoethanol retinoic acid and forskolin on neural stem cell differentiation by one- and two-step methods. DESIGN, TIME AND SETTING： A cytobiology experiment was performed at the Department of Histology and Embryology, Medical School of Nantong University, and Jiangsu Province Key Laboratory of Neuroregeneration, China, between August 2005 and January 2007. MATERIALS： A total of 30 healthy Sprague Dawley rat embryos at gestational days 14-16 were selected, bFGF, PDGF, human heregulin-beta-t, beta-mercaptoethanol, retinoic acid, and forskolin were purchased from Sigma, USA. METHODS： Passage 3 rat neural stem cells were cultured by a one-step method in serum-free medium plus 10 ng/m/bFGF, 5 ng/mL PDGF, 200 ng/mL heregulin-beta-1,35 ng/mL all-trans retinoic acid, and 5 pmol/L forskolin or by a two-step method in serum-free medium plus 35 ng/m/ all-trans retinoic acid for 72 hours, followed by serum-free medium plus 10 ng/mL bFGF, 5 ng/mL PDGF, 200 ng/mL heregulin-beta-t and 5 μmol/L forskolin. The control condition consisted of 10% fetal bovine serum alone or 20 ng/mL bFGF alone. MAIN OUTCOME MEASURES： Differentiated cells were identified by immunocytochemical staining for microtubule associate protein-2 （MAP2） and St 00 protein. Geometric parameters and sodium ion currents of the differentiated cells were measured by image analysis and whole-cell patch-clamp techniques, respectively. RESULTS： Compared with the two-step culture method, neuronal-like cells exhibited longer processes and a similar appearance to mature neurons using the one-step method. The percentage of MAP2 positive cells induced by the one-step method was significantly greater than the serum-alone group （P 〈 0.05）. Furthermore, the MAP2 positive cells induced by the one-step method had greater surface areas, cell body perimeters, and longer process than cells induced by serum-alone and bFGF-alone （P 〈 0.05）. There were no significant differences in these parameters between the one-step and two-step methods （P 〉 0.05）. In addition, 80% of the induced neuronal-like cells from the one-step method and 20% from the two-step method displayed inwardly-evoked currents. CONCLUSION： The combination of bFGF, PDGF, human heregulin-beta-t, beta-mercaptoethanol retinoic acid and forskolin successfully induced neuronal differentiation from neural stem cells, with the one-step induction being more effective than the two-step method.
基金supported by the National Natural Science Foundation of China(11202056)the Fundamental Research Funds for the Central Universities(HEUCFQ20150305)
文摘The band gap structures by arranging hybrid shunted piezoelectric materialswith resistance inductive （RL） circuit and negative impedance converter （NIC） closely and at in- tervals are presented. The theoretical model is built using transfer matrix method. Then the MATLAB computing language is utilized to simulate the band gap structures. Meanwhile, the effects of the resistance, inductance and capacitance on the local resonant gap are studied. By comparing different combinations of resistance, inductance and capacitance as well as different arrangement of circuits, a 13 kHz band gap is reached under the effect of arranging hybrid pe- riodic shunted piezoelectric patches at intervals and the stability of the system is also analyzed. It is proved that utilizing hybrid shunted piezoelectric patches would have a clear impact on the band gap structure of phononic crystal rods. Moreover, the band gap would be clearly enlarged by arranging hybrid piezoelectric patches at intervals.
文摘This paper reviewed the concept,formation and function of gap and developed a new concept,canopy rift.It refers to the small 1-25m 2 rift in the canopy caused by the different distribution pattern of the canopy species or breakage,standing death and treefall.Canopy gap,mainly caused by small scale disturbances including natural disturbance regime and human disturbance regime,is an important phase in the forest regeneration cycle.It plays a leading role in the formation and maintenance of the patches mosaic structure in a forest community.Corresponding to the three phases of the forest regeneration cycle,patches can be classified into three types:gap phase,building phase and mature forest.Many factors may contribute to the maintenance of biodiversity.Here we divided them into ① intrinsic factors,mainly including the biological and ecological characteristics of the species and ② external factors,the heterogeneity of habitat.The formation of gaps leads to the diversification of micro environment,and changes the type and magnitude of understory.Gap impacts the forest micro environment,community structure and dynamic process.Gap causes different status of renewal between pioneer species and climax species,and generates the patch which is the different in the constitute of woods,population dynamic and growing speed.It leads to the diversity of community difference and species component,which is the difference of species between community patches.Gap is of great significance in enhancing and maintaining species diversity for it may enhance habitat heterogeneity.
