A novel InGaAs/InAlAs coupled quantum well structure is proposed for large field-induced refracti... more A novel InGaAs/InAlAs coupled quantum well structure is proposed for large field-induced refractive index change with low absorption loss. In the case of low applied electric field of 15 kV/cm and low absorption loss ('alpha' <= 100 cm^(-1)), a large field-induced refractive index change (for transverse electric (TE) mode, 'Delta' n = 0.012; for transverse magnetic (TM) mode, 'Delta' n
A novel coupled quantum well structure --- quasi-symmetric coupled quantum well (QSCQW) is propos... more A novel coupled quantum well structure --- quasi-symmetric coupled quantum well (QSCQW) is proposed. In the case of low applied electric field (F = 25 kV/cm) and low absorption loss (? ~ 100 cm^(-1)), a large field-induced refractive index change (for TE mode, ?n = 0.0106; for TM mode, ?n = 0.0115) is obtained in QSCQW structure at operating wavelength
We designed and experimentally reported modified potential InGaAs/InAlAs coupled quantum wells. I... more We designed and experimentally reported modified potential InGaAs/InAlAs coupled quantum wells. In this structure, a large blue shift of the absorption edge of more than 35 meV is obtained at a reverse bias of -4 V. This predicts that a large negative electrorefractive index change can be achieved at longer wavelength region of the absorption edge.
Based on a two-energy-level system, we analyse the changing ground eigenenergies of symmetric GaA... more Based on a two-energy-level system, we analyse the changing ground eigenenergies of symmetric GaAs/AlxGa1−x As coupled quantum wells in the presence of an applied electric field. From the theoretical analysis for symmetric coupled quantum well, we find the advantages and disadvantages when it is applied to travelling wave modulator. Hence the conception of quasi-symmetric coupled quantum wells is put forward.
This paper presents a series resonant soft switching capacitor charging power supply (CCPS) based... more This paper presents a series resonant soft switching capacitor charging power supply (CCPS) based on three-level inverter topology. It has two work modes including full voltage mode (FVM) and half voltage mode (HVM). It can be used to change the charging speed of CCPS. It also can be used in the particular scenes that need higher charging voltage precision.
Optoelectronic Materials and Devices for Optical Communications, 2005
From the theoretical analysis for symmetric coupled quantum well,. A novel coupled quantum well s... more From the theoretical analysis for symmetric coupled quantum well,. A novel coupled quantum well structure with low driving electric-field, low absorption loss and large field-induced refractive index change at 1.55 µm is put forward.
Molecular and chemical neuropathology / sponsored by the International Society for Neurochemistry and the World Federation of Neurology and research groups on neurochemistry and cerebrospinal fluid, 1992
In the present study the acute effect of intravenous aluminum chloride (1 mg/kg) on choline acety... more In the present study the acute effect of intravenous aluminum chloride (1 mg/kg) on choline acetyltransferase (ChAT) and acetylcholinesterase (AChE) activities of rats was investigated. Aluminum was found to cross the blood-brain barrier (BBB) as indicated by the detection of aluminum in the cerebrospinal fluid (CSF) 30 min after femoral vein injection. Two hours following aluminum injection, ChAT activity in the basal forebrain and hippocampus was significantly reduced by 30% and 22%, respectively, whereas no change was observed in the caudate nuclei. On the other hand, AChE activity was significantly increased by 45% in the caudate nuclei, whereas little change was observed in other brain areas. This report demonstrates that rapid transport of Al across the BBB, and the acute nature of Al neurotoxicity in rats.
The Journal of Steroid Biochemistry and Molecular Biology, 1995
Autoregulation of glucocorticoid receptor (GR) concentration in vivo may be an important determin... more Autoregulation of glucocorticoid receptor (GR) concentration in vivo may be an important determinant of steroid sensitivity. The dynamics of GR regulation were assessed and compared to regulation of tyrosine aminotransferase (TAT) expression in liver tissue taken from rats treated with a single 50 mg/kg i.v. dose of methylprednisolone. Plasma methylprednisolone concentrations were determined by HPLC analysis. Receptor and TAT message levels were determined by quantitative Northern hybridization. Methylprednisolone plasma kinetics showed a half-life of 0.6 h. Receptor occupancy occurred rapidly and cytosolic GR reappeared over 2-12 h. TAT activity rose between 2 and 6h and then dissipated. Reduction in receptor mRNA levels occurred very rapidly, being detectable by 30 rain following steroid administration. A down-regulated steady-state in GR message expression was reached by 2 h post-injection, and was maintained throughout the 18 h examined in this study. Comparison of methylprednisolone kinetics demonstrated that down-regulation was maintained long after drug was eliminated. In contrast, TAT message induction occurred with a sharp peak; maximal induction occurred between 5-6 h and return to baseline at approx. 8-10 h post-induction. Thi,~ study shows that unlike TAT induction, GR message repression in vivo does not require continual presence of hormone.
Proceedings of the National Academy of Sciences, 1996
The differentiation of small intestinal epithelial cells may require stimulation by microenvironm... more The differentiation of small intestinal epithelial cells may require stimulation by microenvironmental factors in vivo. In this study, the effects of mesenchymal and luminal elements in nonmalignant epithelial cells isolated from the human fetus were studied in vitro. Enterocytes from the human fetus were cultured and microenvironmental factors were added in stages, each stage more closely approximating the microenvironment in vivo. Four stages were examined: epithelial cells derived on plastic from intestinal culture and grown as a cell clone, the same cells grown on connective tissue support, primary epithelial explants grown on fibroblasts with a laminin base, and primary epithelial explants grown on fibroblasts and laminin with n-butyrate added to the incubation medium. The epithelial cell clone dedifferentiated when grown on plastic; however, the cells expressed cytokeratins and villin as evidence of their epithelial cell origin. Human connective tissue matrix from Engelbreth-Holm-Swarm sarcoma cells (Matrigel) modulated their phenotype: alkaline phosphatase activity increased, microvilli developed on their apical surface, and the profile of insulin-like growth factor binding proteins resembled that secreted by differentiated enterocytes. Epithelial cells taken directly from the
We design and experimentally report strain-compensated InGaAs/InAlAs coupled quantum wells with m... more We design and experimentally report strain-compensated InGaAs/InAlAs coupled quantum wells with modified potential. At a lower applied electric field (F=50 kV/cm), the calculated blueshift of the lowest excitonic peak is 40.6 meV. In the room-temperature photocurrent experiments, a maximum upward shift of the apparent peak position of more than 35 meV is observed with an external reverse bias of -4 V. Furthermore, a lower absorption loss (alpha=9.8 cm(-1)) and a large negative refractive index change (Deltan=-0.0095) are obtained at 1.55 mum. This indicates that the strain-compensated InGaAs/InAlAs coupled quantum wells with modified potential have a great potential for application to reflection type electro-optical switches.
Journal of Pharmacokinetics and Biopharmaceutics, 1995
A third-generation pharmacok&etic/pharmacodynanffc model was proposed for receptor/genemediated c... more A third-generation pharmacok&etic/pharmacodynanffc model was proposed for receptor/genemediated cortieosteroid effects. The roles of the messenger RNA (mRNA) for" the glucocorticoid receptor (GR) Or hepatic GR down-regulation and the mRNA for" hepatic tyrosine aminotransferase (TAT) #Muctiou by methylprednisolone (MPL) were exam#led. Male adrenaleetomized Wistar rats received 50 mg/kg MPL iv. Blood and liver' samples were collected at various tone pohas for a period of 18 hr. Plasma concentrations of MPL, fi'ee hepatic cytosolie GR densities, GR mRNA, TAT mRNA, and TAT activities m liver" were determined. Plasma MPL profile was biexponential with a term#ral t~._, of 0.57 hr. Free hepatic GR density rapidly disappeared fi'om cytoplasm after the MPL dose and then slow O, returned to about 60% of starting level after 16 hr. Meanwhile, GR mRNA level fell to 45% of baseline with#r 2 hr postdos#rg, and remained at that level for at least 18 hr. The GR down-regulation of GR mRNA and protein turnover rate were modeled. The TAT mRNA began to increase at about 2 hr, reached a max#num at about 5 hr, and declined to baseline by 14 hr. TAT #rduetion followed a similar pattern, except the induction was delayed about 0.5 hr. Pharmacodynamic parameters were obtained by fitt#rg seven differential equations in a piecewise fashion. The cascade of cortieosteroid steps were modeled by a series of #rductions for steroid-receptor-DNA complex, two intermediate transit eomparmlents, TAT mRNA, and TA T aetivity. Results indicate that GR mRNA and TA T mRNA are major controlling .factor's for the receptor/gene-mediated effects of eorticosteroids.
0 Male Fixher rats received 0.1 mgkg (bolus) of elemental aluminum as the sulfate salt via the po... more 0 Male Fixher rats received 0.1 mgkg (bolus) of elemental aluminum as the sulfate salt via the portal (n = 4) or systemic (n = 4) route of administration. Blood and bile were serially sampled over an 8-h period, postadministration. Aluminum was determined by flameless atomic absorption spectrophotometry. Blood aluminum concentrations declined in a monoexponential fashion, with half-lives of 0.7 h (portal) and 1.08 h (systemic) (p < 0.05). The corresponding systemic clearances were 48.9 f 10.6 and 35.1 -t 3.64 mU(h kg) (p < 0.05). The systemic availability following portal administration was 0.66, indicating a significant "first-pass" effect. Biliary aluminum recovery (9'0 dose) was negli-
We propose a novel coupled quantum well structure, i.e. a quasi-symmetric coupled quantum well (Q... more We propose a novel coupled quantum well structure, i.e. a quasi-symmetric coupled quantum well (QSCQW). Based on the demands of optical switching devices for quantum well materials, the QSCQW configuration is further optimized. Consequently, in the case of low applied electric field 25 kV/cm and low absorption loss 100 cm-1, a large field-induced refractive index change (for TE mode, n = 0.0106; for TM mode, n = 0.0115) is obtained in the QSCQW structure at the operation wavelength 1550 nm. The value is in one or two order of magnitude larger than that in a rectangular quantum well and about 50% larger than that of five-step asymmetric coupled quantum well structure under the same working conditions. The refractive index change obtained with the optimized QSCQW under so low absorption loss and applied electric field is very attractive for semiconductor optical switching devices. This manifests that the QSCQW structure has a great potential for applications in ultra-fast and low-voltage optical switches and in travelling wave modulators.
A potent, long-lasting form of interferon R-2a mono-pegylated with a 40 kilodalton branched poly-... more A potent, long-lasting form of interferon R-2a mono-pegylated with a 40 kilodalton branched poly-(ethylene glycol) was designed, synthesized, and characterized. Mono-pegylated interferon R-2a was comprised of four major positional isomers involving Lys 31 , Lys 121 , Lys 131 , and Lys 134 of interferon. The in vitro anti-viral activity of pegylated interferon R-2a was found to be only 7% of the original activity. In contrast, the in vivo antitumor activity was severalfold enhanced compared to interferon R-2a. Pegylated interferon R-2a showed no immunogenicity in mice. After subcutaneous injection of pegylated interferon R-2a, a 70-fold increase in serum half-life and a 50-fold increase in mean plasma residence time concomitant with sustained serum concentrations were observed relative to interferon R-2a. These preclinical results suggest a significantly enhanced human pharmacological profile for pegylated interferon R-2a. Results of Phase II/III hepatitis C clinical trials in humans confirmed the superior efficacy of pegylated interferon R-2a compared to unmodified interferon R-2a.
An Ehresmann connection on a constrained state bundle defined by nonlinear differential constrain... more An Ehresmann connection on a constrained state bundle defined by nonlinear differential constraints is constructed for nonlinear nonholonomic systems. A set of differential constraints is integrable if and only if the curvature of the Ehresmann connection vanishes. Based on a geometric interpretation of d-delta commutation relations in constrained dynamics given in this paper, the complete integrability conditions for the differential
A novel InGaAs/InAlAs coupled quantum well structure is proposed for large field-induced refracti... more A novel InGaAs/InAlAs coupled quantum well structure is proposed for large field-induced refractive index change with low absorption loss. In the case of low applied electric field of 15 kV/cm and low absorption loss ('alpha' <= 100 cm^(-1)), a large field-induced refractive index change (for transverse electric (TE) mode, 'Delta' n = 0.012; for transverse magnetic (TM) mode, 'Delta' n
A novel coupled quantum well structure --- quasi-symmetric coupled quantum well (QSCQW) is propos... more A novel coupled quantum well structure --- quasi-symmetric coupled quantum well (QSCQW) is proposed. In the case of low applied electric field (F = 25 kV/cm) and low absorption loss (? ~ 100 cm^(-1)), a large field-induced refractive index change (for TE mode, ?n = 0.0106; for TM mode, ?n = 0.0115) is obtained in QSCQW structure at operating wavelength
We designed and experimentally reported modified potential InGaAs/InAlAs coupled quantum wells. I... more We designed and experimentally reported modified potential InGaAs/InAlAs coupled quantum wells. In this structure, a large blue shift of the absorption edge of more than 35 meV is obtained at a reverse bias of -4 V. This predicts that a large negative electrorefractive index change can be achieved at longer wavelength region of the absorption edge.
Based on a two-energy-level system, we analyse the changing ground eigenenergies of symmetric GaA... more Based on a two-energy-level system, we analyse the changing ground eigenenergies of symmetric GaAs/AlxGa1−x As coupled quantum wells in the presence of an applied electric field. From the theoretical analysis for symmetric coupled quantum well, we find the advantages and disadvantages when it is applied to travelling wave modulator. Hence the conception of quasi-symmetric coupled quantum wells is put forward.
This paper presents a series resonant soft switching capacitor charging power supply (CCPS) based... more This paper presents a series resonant soft switching capacitor charging power supply (CCPS) based on three-level inverter topology. It has two work modes including full voltage mode (FVM) and half voltage mode (HVM). It can be used to change the charging speed of CCPS. It also can be used in the particular scenes that need higher charging voltage precision.
Optoelectronic Materials and Devices for Optical Communications, 2005
From the theoretical analysis for symmetric coupled quantum well,. A novel coupled quantum well s... more From the theoretical analysis for symmetric coupled quantum well,. A novel coupled quantum well structure with low driving electric-field, low absorption loss and large field-induced refractive index change at 1.55 µm is put forward.
Molecular and chemical neuropathology / sponsored by the International Society for Neurochemistry and the World Federation of Neurology and research groups on neurochemistry and cerebrospinal fluid, 1992
In the present study the acute effect of intravenous aluminum chloride (1 mg/kg) on choline acety... more In the present study the acute effect of intravenous aluminum chloride (1 mg/kg) on choline acetyltransferase (ChAT) and acetylcholinesterase (AChE) activities of rats was investigated. Aluminum was found to cross the blood-brain barrier (BBB) as indicated by the detection of aluminum in the cerebrospinal fluid (CSF) 30 min after femoral vein injection. Two hours following aluminum injection, ChAT activity in the basal forebrain and hippocampus was significantly reduced by 30% and 22%, respectively, whereas no change was observed in the caudate nuclei. On the other hand, AChE activity was significantly increased by 45% in the caudate nuclei, whereas little change was observed in other brain areas. This report demonstrates that rapid transport of Al across the BBB, and the acute nature of Al neurotoxicity in rats.
The Journal of Steroid Biochemistry and Molecular Biology, 1995
Autoregulation of glucocorticoid receptor (GR) concentration in vivo may be an important determin... more Autoregulation of glucocorticoid receptor (GR) concentration in vivo may be an important determinant of steroid sensitivity. The dynamics of GR regulation were assessed and compared to regulation of tyrosine aminotransferase (TAT) expression in liver tissue taken from rats treated with a single 50 mg/kg i.v. dose of methylprednisolone. Plasma methylprednisolone concentrations were determined by HPLC analysis. Receptor and TAT message levels were determined by quantitative Northern hybridization. Methylprednisolone plasma kinetics showed a half-life of 0.6 h. Receptor occupancy occurred rapidly and cytosolic GR reappeared over 2-12 h. TAT activity rose between 2 and 6h and then dissipated. Reduction in receptor mRNA levels occurred very rapidly, being detectable by 30 rain following steroid administration. A down-regulated steady-state in GR message expression was reached by 2 h post-injection, and was maintained throughout the 18 h examined in this study. Comparison of methylprednisolone kinetics demonstrated that down-regulation was maintained long after drug was eliminated. In contrast, TAT message induction occurred with a sharp peak; maximal induction occurred between 5-6 h and return to baseline at approx. 8-10 h post-induction. Thi,~ study shows that unlike TAT induction, GR message repression in vivo does not require continual presence of hormone.
Proceedings of the National Academy of Sciences, 1996
The differentiation of small intestinal epithelial cells may require stimulation by microenvironm... more The differentiation of small intestinal epithelial cells may require stimulation by microenvironmental factors in vivo. In this study, the effects of mesenchymal and luminal elements in nonmalignant epithelial cells isolated from the human fetus were studied in vitro. Enterocytes from the human fetus were cultured and microenvironmental factors were added in stages, each stage more closely approximating the microenvironment in vivo. Four stages were examined: epithelial cells derived on plastic from intestinal culture and grown as a cell clone, the same cells grown on connective tissue support, primary epithelial explants grown on fibroblasts with a laminin base, and primary epithelial explants grown on fibroblasts and laminin with n-butyrate added to the incubation medium. The epithelial cell clone dedifferentiated when grown on plastic; however, the cells expressed cytokeratins and villin as evidence of their epithelial cell origin. Human connective tissue matrix from Engelbreth-Holm-Swarm sarcoma cells (Matrigel) modulated their phenotype: alkaline phosphatase activity increased, microvilli developed on their apical surface, and the profile of insulin-like growth factor binding proteins resembled that secreted by differentiated enterocytes. Epithelial cells taken directly from the
We design and experimentally report strain-compensated InGaAs/InAlAs coupled quantum wells with m... more We design and experimentally report strain-compensated InGaAs/InAlAs coupled quantum wells with modified potential. At a lower applied electric field (F=50 kV/cm), the calculated blueshift of the lowest excitonic peak is 40.6 meV. In the room-temperature photocurrent experiments, a maximum upward shift of the apparent peak position of more than 35 meV is observed with an external reverse bias of -4 V. Furthermore, a lower absorption loss (alpha=9.8 cm(-1)) and a large negative refractive index change (Deltan=-0.0095) are obtained at 1.55 mum. This indicates that the strain-compensated InGaAs/InAlAs coupled quantum wells with modified potential have a great potential for application to reflection type electro-optical switches.
Journal of Pharmacokinetics and Biopharmaceutics, 1995
A third-generation pharmacok&etic/pharmacodynanffc model was proposed for receptor/genemediated c... more A third-generation pharmacok&etic/pharmacodynanffc model was proposed for receptor/genemediated cortieosteroid effects. The roles of the messenger RNA (mRNA) for" the glucocorticoid receptor (GR) Or hepatic GR down-regulation and the mRNA for" hepatic tyrosine aminotransferase (TAT) #Muctiou by methylprednisolone (MPL) were exam#led. Male adrenaleetomized Wistar rats received 50 mg/kg MPL iv. Blood and liver' samples were collected at various tone pohas for a period of 18 hr. Plasma concentrations of MPL, fi'ee hepatic cytosolie GR densities, GR mRNA, TAT mRNA, and TAT activities m liver" were determined. Plasma MPL profile was biexponential with a term#ral t~._, of 0.57 hr. Free hepatic GR density rapidly disappeared fi'om cytoplasm after the MPL dose and then slow O, returned to about 60% of starting level after 16 hr. Meanwhile, GR mRNA level fell to 45% of baseline with#r 2 hr postdos#rg, and remained at that level for at least 18 hr. The GR down-regulation of GR mRNA and protein turnover rate were modeled. The TAT mRNA began to increase at about 2 hr, reached a max#num at about 5 hr, and declined to baseline by 14 hr. TAT #rduetion followed a similar pattern, except the induction was delayed about 0.5 hr. Pharmacodynamic parameters were obtained by fitt#rg seven differential equations in a piecewise fashion. The cascade of cortieosteroid steps were modeled by a series of #rductions for steroid-receptor-DNA complex, two intermediate transit eomparmlents, TAT mRNA, and TA T aetivity. Results indicate that GR mRNA and TA T mRNA are major controlling .factor's for the receptor/gene-mediated effects of eorticosteroids.
0 Male Fixher rats received 0.1 mgkg (bolus) of elemental aluminum as the sulfate salt via the po... more 0 Male Fixher rats received 0.1 mgkg (bolus) of elemental aluminum as the sulfate salt via the portal (n = 4) or systemic (n = 4) route of administration. Blood and bile were serially sampled over an 8-h period, postadministration. Aluminum was determined by flameless atomic absorption spectrophotometry. Blood aluminum concentrations declined in a monoexponential fashion, with half-lives of 0.7 h (portal) and 1.08 h (systemic) (p < 0.05). The corresponding systemic clearances were 48.9 f 10.6 and 35.1 -t 3.64 mU(h kg) (p < 0.05). The systemic availability following portal administration was 0.66, indicating a significant "first-pass" effect. Biliary aluminum recovery (9'0 dose) was negli-
We propose a novel coupled quantum well structure, i.e. a quasi-symmetric coupled quantum well (Q... more We propose a novel coupled quantum well structure, i.e. a quasi-symmetric coupled quantum well (QSCQW). Based on the demands of optical switching devices for quantum well materials, the QSCQW configuration is further optimized. Consequently, in the case of low applied electric field 25 kV/cm and low absorption loss 100 cm-1, a large field-induced refractive index change (for TE mode, n = 0.0106; for TM mode, n = 0.0115) is obtained in the QSCQW structure at the operation wavelength 1550 nm. The value is in one or two order of magnitude larger than that in a rectangular quantum well and about 50% larger than that of five-step asymmetric coupled quantum well structure under the same working conditions. The refractive index change obtained with the optimized QSCQW under so low absorption loss and applied electric field is very attractive for semiconductor optical switching devices. This manifests that the QSCQW structure has a great potential for applications in ultra-fast and low-voltage optical switches and in travelling wave modulators.
A potent, long-lasting form of interferon R-2a mono-pegylated with a 40 kilodalton branched poly-... more A potent, long-lasting form of interferon R-2a mono-pegylated with a 40 kilodalton branched poly-(ethylene glycol) was designed, synthesized, and characterized. Mono-pegylated interferon R-2a was comprised of four major positional isomers involving Lys 31 , Lys 121 , Lys 131 , and Lys 134 of interferon. The in vitro anti-viral activity of pegylated interferon R-2a was found to be only 7% of the original activity. In contrast, the in vivo antitumor activity was severalfold enhanced compared to interferon R-2a. Pegylated interferon R-2a showed no immunogenicity in mice. After subcutaneous injection of pegylated interferon R-2a, a 70-fold increase in serum half-life and a 50-fold increase in mean plasma residence time concomitant with sustained serum concentrations were observed relative to interferon R-2a. These preclinical results suggest a significantly enhanced human pharmacological profile for pegylated interferon R-2a. Results of Phase II/III hepatitis C clinical trials in humans confirmed the superior efficacy of pegylated interferon R-2a compared to unmodified interferon R-2a.
An Ehresmann connection on a constrained state bundle defined by nonlinear differential constrain... more An Ehresmann connection on a constrained state bundle defined by nonlinear differential constraints is constructed for nonlinear nonholonomic systems. A set of differential constraints is integrable if and only if the curvature of the Ehresmann connection vanishes. Based on a geometric interpretation of d-delta commutation relations in constrained dynamics given in this paper, the complete integrability conditions for the differential
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Papers by Zhi-xin Xu