We develop a model Hamiltonian to treat anomalous Hall conductivity in dilute magnetic semiconductor (DMS) of type (III, Mn, V) considering the impurity potentials (potential due to interaction of spin of carriers wit...We develop a model Hamiltonian to treat anomalous Hall conductivity in dilute magnetic semiconductor (DMS) of type (III, Mn, V) considering the impurity potentials (potential due to interaction of spin of carriers with localized spin of dopant (Mn) and coulomb like potential). Using equation of motion in Green function together with Quantum Kubo-formula of conductivity, the anomalous Hall conductivity is calculated as function of spin-orbit coupling, exchange field and carrier polarization. The calculated result shows that at low impurity concentration, the interplay between spin polarization of carriers, spin-orbit coupling and exchange fields is crucial for existence of anomalous Hall conductivity. The monotonic increment of anomalous Hall conductivity with exchange field is observed for strong spin-orbit coupling limit. In weak spin-orbit coupling limit, the magnitude of anomalous Hall conductivity increases parabolically with the spin-orbit coupling. Our results provide an important basis for understanding the interplay between the spin polarization, spin-orbit coupling, and exchange field on anomalous Hall conductivity at low impurity concentration. The findings are also a key step to realize dissipationless quantum transport without external magnetic field.展开更多
Developing new polymeric semiconductors with excellent device performance is essential for organic electronics. Herein, we synthesized two new thiazoloisoindigo(Tz II)-based polymers, namely, P(Tz II-d Th-d Th) and P(...Developing new polymeric semiconductors with excellent device performance is essential for organic electronics. Herein, we synthesized two new thiazoloisoindigo(Tz II)-based polymers, namely, P(Tz II-d Th-d Th) and P(Tz II-d Th-d Tz), by copolymerizing thiophene-flanked Tz II with bithiophene and bithiazole, respectively. Owing to the more electron-deficient nature of bithiazole than bithiophene, P(Tz II-d Th-d Tz)possesses deeper LUMO/HOMO levels of-3.45/-5.47 e V than P(Tz II-d Th-d Th)(-3.34/-5.32 e V). The organic field-effect transistor(OFET) devices based on P(Tz II-d Th-d Th) exhibited p-type behaviors with an average hole mobility value as high as 1.43 cm^(2)·V^(-1)·s^(-1), while P(Tz II-d Th-d Tz)showed typical ambipolar characteristics with average hole and electron mobilities of 0.38 and 0.56 cm^(2)·V^(-1)·s^(-1). In addition, we compared the performances of both polymers with other Tz II-based polymers reported in our previous work, and showed that the charge carrier polarity can be manipulated by adjusting the number of the thiophene units between the acceptor unit. As the increase of the number of thiophene rings,charge carrier polarity shifts from electron-dominated ambipolar transport to hole-dominated ambipolar transport and then to unipolar hole transport in OFETs, which provides an effective molecular design strategy for further optimization of polymer OFET performance.展开更多
Polar auxin transport plays a divergent role in plant growth and developmental processes including rootand embryo development, vascular pattern formation and cell elongation. Recently isolated Arabidopsispin gene fami...Polar auxin transport plays a divergent role in plant growth and developmental processes including rootand embryo development, vascular pattern formation and cell elongation. Recently isolated Arabidopsispin gene family was believed to encode a component of auxin efflux carrier (Galweiler et al, 1998). Basedon the Arabidopsis pin1 sequence we have isolated a Brassica juncea cDNA (designated Bjpinl), whichencoded a 70-kDa putative auxin efflux carrier. Deduced BjPIN1 shared 65% identities at protein level withAtPIN1 and was highly homologous to other putative PIN proteins of Arabidopsis (with highest homologyto AtPIN3). Hydrophobic analysis showed similar structures between BjPIN1 and AtPIN proteins. Presenceof 6 exons (varying in size between 65 bp and 1229 bp) and 5 introns (sizes between 89 bp and 463 bp)in the genomic fragment was revealed by comparing the genomic and cDNA sequences. Northern blotanalysis indicated that Bjpinl was expressed in most of the tissues tested, with a relatively higher levelof transcript in flowers and a lower level in root tissues. Promoter-reporter gene fusion studies furtherrevealed the expression of Bjpinl in the mature pollen grains, young seeds, root tip, leaf vascular tissue andtrace bundle, stem epidermis, cortex and vascular cells. BjPIN1 was localized on the plasma membraneas demonstrated through fusion expression of green fluorescent protein (GFP). Auxin efflux carrier activitywas elevated in transgenic Arabidopsis expressing BjPIN1.展开更多
Based on the sequence information of Arabidopsis PIN1, two cDNAs encoding PIN homologues fromBrassica juncea, Bjpin2 and Bjpin3, were isolated through cDNA library screening. Bjpin2 and Bjpin3encoded proteins containi...Based on the sequence information of Arabidopsis PIN1, two cDNAs encoding PIN homologues fromBrassica juncea, Bjpin2 and Bjpin3, were isolated through cDNA library screening. Bjpin2 and Bjpin3encoded proteins containing 640 and 635 amino acid residues, respectively, which shared 97.5% identities witheach other and were highly homologous to Arabidopsis PIN1, PIN2 and other putative PIN proteins. BjPIN2and BjPIN3 had similar structures as AtPIN proteins. Northern blot analysis indicated that Bjpin2 wasexpressed in stem, leaf and floral tissues, while Bjpin3 was expressed predominantly in stem and hypocotyls.Two promoter fragments of pin genes, Bjpin-X and Bjpin-Z, were isolated by 'genome walking' techniqueusing primers at 5'-end of pin cDNA. Promoter-gus fusion studies revealed the GUS activities driven byBjpin-X were at internal side of xylem and petal; while those driven by Bjpin-Z were detected at leaf vein,epidermal cell and cortex of stem, vascular tissues and anther. Results of the pin genes with differentexpression patterns in B. juncea suggested the presence of a gene family.展开更多
Polar auxin transport plays a divergent role in plant growth and developmental processes including root and embryo development,vascular pattern formation and cell elongation.Recently isolated Arabidopsis pin gene fami...Polar auxin transport plays a divergent role in plant growth and developmental processes including root and embryo development,vascular pattern formation and cell elongation.Recently isolated Arabidopsis pin gene family was believed to encode a component of auxin efflux carrier(Galweiler et al,1998).Based on the Arabidopsis pin1 sequence we have isolated a Brassica juncea cDNA (designated Bipin1),which encoded a 70-kDa putative auxin efflux carrier.Deduced BjPIN1 shared 65% identities at protein level with AtPIN1 and was highly homologous to other putative PIN proteins of Arabidopsis(with highest homology to AtPIN3).Hydrophobic analysis showed similar structures between BjPIN1 and AtPIN proteins.Presence of 6 exons(varying in size between 65 bp and 1229 bp )and 5 introns (sizes between 89 bp and 463 bp)in the genomic fragment was revealed by comparing the genomic and cDNA sequences.Northern blot analysis indicated that Bjpin1 was expressed in most of the tissues tested,with a relatively higher level of transcript in flowers and a lower level in root tissues.Promoter-reporter gene fusion studies further revealed the expression of Bjpin1 in the mature pollen grains,young seeds, root tip,leaf vascular tissue and trace bundle,stem epidermis,cortex and vascular cells.BjPIN1 was localized on the plasma membrane as demonstrated through fusion expression of green fluorescent protein(GFP).Auxin efflux carrier activity was elevated in transgenic Arabidopsis expressing BjPIN1.展开更多
A multiuser Ultra Wide Band (UWB) channel suffers seriously from realistic impairments. Among this, multipath fading and interferences, such as Multiple Access Interference (MAI) and Inter Symbol Interference (ISI), t...A multiuser Ultra Wide Band (UWB) channel suffers seriously from realistic impairments. Among this, multipath fading and interferences, such as Multiple Access Interference (MAI) and Inter Symbol Interference (ISI), that significantly degrade the system performance. In this paper, a polar coding technique, originally developed by Arikan, is suggested to enhance the BER performance of indoor UWB based Orthogonal Frequency Division Multiplexing (OFDM) communications. Moreover, Interleave Division Multiple Access (IDMA) scheme has been considered for multiuser detection depending on the turbo type Chip-By-Chip (CBC) iterative detection strategy. Three different models as Symmetric Alpha Stable (SαS), Laplace model and Gaussian Mixture Model (GMM), have been introduced for approximating the interferences which are more realistic for UWB system. The performance of the proposed Polar-coded IDMA OFDM-based UWB system is investigated under UWB channel models proposed by IEEE 802.15.3a working group and compared with Low Density Parity Check (LDPC)-coded IDMA OFDM-based UWB system in terms of BER performance and complexity under the studied noise models. Simulation results show that the complexity of the proposed polar-coded system is much lower than LDPC-coded system with minor performance degradation. Furthermore, the proposed polar-coded system is robust against noise and interferences in UWB indoor environment and gains a significant performance improvement by about 5 dB compared with un-coded IDMA-OFDM-UWB system under the studied noise models.展开更多
Based on the sequence information of Arabidopsis PIN1,two cDNAs encoding PIN homologues from Brassica juncea,Bjpin2 and Bjpin3,were isolated through cDNA library screening.Bjpin2 and Bjpin3 encoded proteins containing...Based on the sequence information of Arabidopsis PIN1,two cDNAs encoding PIN homologues from Brassica juncea,Bjpin2 and Bjpin3,were isolated through cDNA library screening.Bjpin2 and Bjpin3 encoded proteins containing 640 and 635 amino acid residues,respectively,which shared 97.5% identities with each other and were highly homologus to Arabidopsis PIN1,PIN2 and other putative PIN proteins.BjPIN2 and BjPIN3 had similar structures as AtPIN proteins.Northern blot analysis indicated that Bjpin2 was expressed in stem,leaf and floral tissues, while Bjpin3 was expressed predominantly in stem and hypocotyls.Two promoter fragments of pin genes,Bjpin-X and Bjpin-Z ,were isolated by 'genome walkin' technique using primers at 5'-end of pin cDNA.Promoter-gus fusion studies revealed the GUS activities driven by Bjpin-X were at internal side of xylem and petal;while those driven by Bjpin-Z were detected at leaf vein, epidermal cell and cortex of stem,vascular tissues and anther.Results of the pin genes with different expression patterns in B.juncea suggested the presence of a gene family.展开更多
Taking into account ultra-fast carrier dynamics, this paper models 640 Gbit/s wavelength conversion scheme based on nonlinear polarization rotation (NPR) in a single semiconductor optical amplifier (SOA) and inves...Taking into account ultra-fast carrier dynamics, this paper models 640 Gbit/s wavelength conversion scheme based on nonlinear polarization rotation (NPR) in a single semiconductor optical amplifier (SOA) and investigates the performance of this kind of wavelength conversion scheme in detail. In this model, two carrier temperature equations are introduced to substitute two energy density equations, which reduce the complexity of calculation in comparison with the previous model. The temporary gain and phase shift dynamics induced by ultra-short optical pulses are numerically simulated and the simulated results are qualitatively in good agreement with reported experimental results. Simulated results show that non-inverted and inverted 640 Gbit/s wavelength conversions based on NPR are achieved with clear open eye diagrams. To further investigate the performance of the non-inverted wavelength conversion scheme, the dependence of output extinction ratio (ER) on some key parameters used in simulation is illustrated. Furthermore, simulated analyses show that high performance non-inverted wavelength conversion based on NPR can be achieved by using a red-shifted filtering scheme.展开更多
Most of the schemes for generating isolated attosecond pulses(IAP) are sensitive to the carrier-envelope phase(CEP)of the driving lasers. We propose a scheme for generating IAP using two-color counter-rotating cir...Most of the schemes for generating isolated attosecond pulses(IAP) are sensitive to the carrier-envelope phase(CEP)of the driving lasers. We propose a scheme for generating IAP using two-color counter-rotating circularly polarized(TCCRCP) laser pulses. The results demonstrate that the dependence of the IAP generation on CEP stability is largely reduced in this scheme. IAP can be generated at most of CEPs. Therefore, the experiment requirements become lower.展开更多
We have demonstrated the first carrier density model for AlGaN channel with AlN buffer using spontaneous and piezoelectric polarization comparison with experimental and theoretical results. From the results we proved ...We have demonstrated the first carrier density model for AlGaN channel with AlN buffer using spontaneous and piezoelectric polarization comparison with experimental and theoretical results. From the results we proved that the formation of 2DEG in undoped structure relied both on spontaneous and piezoelectric polarization. The electron distribution of Al concentration (0 < x < 0.5) was measured for both AlGaN channel and barrier. Barrier thickness assumed between 20 and 25 nm for validating the experimental results. The carrier concentration was observed at the specific interface of the N- and Ga-face by assuming x1, x2 = 0. The model results are verified with previously reported experimental data.展开更多
文摘We develop a model Hamiltonian to treat anomalous Hall conductivity in dilute magnetic semiconductor (DMS) of type (III, Mn, V) considering the impurity potentials (potential due to interaction of spin of carriers with localized spin of dopant (Mn) and coulomb like potential). Using equation of motion in Green function together with Quantum Kubo-formula of conductivity, the anomalous Hall conductivity is calculated as function of spin-orbit coupling, exchange field and carrier polarization. The calculated result shows that at low impurity concentration, the interplay between spin polarization of carriers, spin-orbit coupling and exchange fields is crucial for existence of anomalous Hall conductivity. The monotonic increment of anomalous Hall conductivity with exchange field is observed for strong spin-orbit coupling limit. In weak spin-orbit coupling limit, the magnitude of anomalous Hall conductivity increases parabolically with the spin-orbit coupling. Our results provide an important basis for understanding the interplay between the spin polarization, spin-orbit coupling, and exchange field on anomalous Hall conductivity at low impurity concentration. The findings are also a key step to realize dissipationless quantum transport without external magnetic field.
基金supported by the National Natural Science Foundation of China (Nos.22102086 and 22075105)the start-up funding from Jianghan University。
文摘Developing new polymeric semiconductors with excellent device performance is essential for organic electronics. Herein, we synthesized two new thiazoloisoindigo(Tz II)-based polymers, namely, P(Tz II-d Th-d Th) and P(Tz II-d Th-d Tz), by copolymerizing thiophene-flanked Tz II with bithiophene and bithiazole, respectively. Owing to the more electron-deficient nature of bithiazole than bithiophene, P(Tz II-d Th-d Tz)possesses deeper LUMO/HOMO levels of-3.45/-5.47 e V than P(Tz II-d Th-d Th)(-3.34/-5.32 e V). The organic field-effect transistor(OFET) devices based on P(Tz II-d Th-d Th) exhibited p-type behaviors with an average hole mobility value as high as 1.43 cm^(2)·V^(-1)·s^(-1), while P(Tz II-d Th-d Tz)showed typical ambipolar characteristics with average hole and electron mobilities of 0.38 and 0.56 cm^(2)·V^(-1)·s^(-1). In addition, we compared the performances of both polymers with other Tz II-based polymers reported in our previous work, and showed that the charge carrier polarity can be manipulated by adjusting the number of the thiophene units between the acceptor unit. As the increase of the number of thiophene rings,charge carrier polarity shifts from electron-dominated ambipolar transport to hole-dominated ambipolar transport and then to unipolar hole transport in OFETs, which provides an effective molecular design strategy for further optimization of polymer OFET performance.
基金Studies were supported by "the National NaturalScience Foundation of China, No. 30070073", StateKey Project of Basic Research, No. G199901l604"and "National Natural Science Foundation of Pan-Deng". We thank Dr. Charles Brearley and JianXu for hel
文摘Polar auxin transport plays a divergent role in plant growth and developmental processes including rootand embryo development, vascular pattern formation and cell elongation. Recently isolated Arabidopsispin gene family was believed to encode a component of auxin efflux carrier (Galweiler et al, 1998). Basedon the Arabidopsis pin1 sequence we have isolated a Brassica juncea cDNA (designated Bjpinl), whichencoded a 70-kDa putative auxin efflux carrier. Deduced BjPIN1 shared 65% identities at protein level withAtPIN1 and was highly homologous to other putative PIN proteins of Arabidopsis (with highest homologyto AtPIN3). Hydrophobic analysis showed similar structures between BjPIN1 and AtPIN proteins. Presenceof 6 exons (varying in size between 65 bp and 1229 bp) and 5 introns (sizes between 89 bp and 463 bp)in the genomic fragment was revealed by comparing the genomic and cDNA sequences. Northern blotanalysis indicated that Bjpinl was expressed in most of the tissues tested, with a relatively higher levelof transcript in flowers and a lower level in root tissues. Promoter-reporter gene fusion studies furtherrevealed the expression of Bjpinl in the mature pollen grains, young seeds, root tip, leaf vascular tissue andtrace bundle, stem epidermis, cortex and vascular cells. BjPIN1 was localized on the plasma membraneas demonstrated through fusion expression of green fluorescent protein (GFP). Auxin efflux carrier activitywas elevated in transgenic Arabidopsis expressing BjPIN1.
文摘Based on the sequence information of Arabidopsis PIN1, two cDNAs encoding PIN homologues fromBrassica juncea, Bjpin2 and Bjpin3, were isolated through cDNA library screening. Bjpin2 and Bjpin3encoded proteins containing 640 and 635 amino acid residues, respectively, which shared 97.5% identities witheach other and were highly homologous to Arabidopsis PIN1, PIN2 and other putative PIN proteins. BjPIN2and BjPIN3 had similar structures as AtPIN proteins. Northern blot analysis indicated that Bjpin2 wasexpressed in stem, leaf and floral tissues, while Bjpin3 was expressed predominantly in stem and hypocotyls.Two promoter fragments of pin genes, Bjpin-X and Bjpin-Z, were isolated by 'genome walking' techniqueusing primers at 5'-end of pin cDNA. Promoter-gus fusion studies revealed the GUS activities driven byBjpin-X were at internal side of xylem and petal; while those driven by Bjpin-Z were detected at leaf vein,epidermal cell and cortex of stem, vascular tissues and anther. Results of the pin genes with differentexpression patterns in B. juncea suggested the presence of a gene family.
基金Studies were supported by 'the National Natural
Science Foundation of China, No. 30070073', State
Key Project of Basic Research, No. G199901l604'and 'National Natural Science Foundation of Pan-
Deng'. We thank Dr. Charles Brearley and Jian
Xu for hel
文摘Polar auxin transport plays a divergent role in plant growth and developmental processes including root and embryo development,vascular pattern formation and cell elongation.Recently isolated Arabidopsis pin gene family was believed to encode a component of auxin efflux carrier(Galweiler et al,1998).Based on the Arabidopsis pin1 sequence we have isolated a Brassica juncea cDNA (designated Bipin1),which encoded a 70-kDa putative auxin efflux carrier.Deduced BjPIN1 shared 65% identities at protein level with AtPIN1 and was highly homologous to other putative PIN proteins of Arabidopsis(with highest homology to AtPIN3).Hydrophobic analysis showed similar structures between BjPIN1 and AtPIN proteins.Presence of 6 exons(varying in size between 65 bp and 1229 bp )and 5 introns (sizes between 89 bp and 463 bp)in the genomic fragment was revealed by comparing the genomic and cDNA sequences.Northern blot analysis indicated that Bjpin1 was expressed in most of the tissues tested,with a relatively higher level of transcript in flowers and a lower level in root tissues.Promoter-reporter gene fusion studies further revealed the expression of Bjpin1 in the mature pollen grains,young seeds, root tip,leaf vascular tissue and trace bundle,stem epidermis,cortex and vascular cells.BjPIN1 was localized on the plasma membrane as demonstrated through fusion expression of green fluorescent protein(GFP).Auxin efflux carrier activity was elevated in transgenic Arabidopsis expressing BjPIN1.
文摘A multiuser Ultra Wide Band (UWB) channel suffers seriously from realistic impairments. Among this, multipath fading and interferences, such as Multiple Access Interference (MAI) and Inter Symbol Interference (ISI), that significantly degrade the system performance. In this paper, a polar coding technique, originally developed by Arikan, is suggested to enhance the BER performance of indoor UWB based Orthogonal Frequency Division Multiplexing (OFDM) communications. Moreover, Interleave Division Multiple Access (IDMA) scheme has been considered for multiuser detection depending on the turbo type Chip-By-Chip (CBC) iterative detection strategy. Three different models as Symmetric Alpha Stable (SαS), Laplace model and Gaussian Mixture Model (GMM), have been introduced for approximating the interferences which are more realistic for UWB system. The performance of the proposed Polar-coded IDMA OFDM-based UWB system is investigated under UWB channel models proposed by IEEE 802.15.3a working group and compared with Low Density Parity Check (LDPC)-coded IDMA OFDM-based UWB system in terms of BER performance and complexity under the studied noise models. Simulation results show that the complexity of the proposed polar-coded system is much lower than LDPC-coded system with minor performance degradation. Furthermore, the proposed polar-coded system is robust against noise and interferences in UWB indoor environment and gains a significant performance improvement by about 5 dB compared with un-coded IDMA-OFDM-UWB system under the studied noise models.
基金Studies were supported by the National NaturalSciences Foundation of China (No. 30070073, 95-Yu-29-7) and State Key Project of Basic Research (No.G1999011604). We greatly thank Dr. K1aus Palme for providing the Atpinl nucleotide sequences.
文摘Based on the sequence information of Arabidopsis PIN1,two cDNAs encoding PIN homologues from Brassica juncea,Bjpin2 and Bjpin3,were isolated through cDNA library screening.Bjpin2 and Bjpin3 encoded proteins containing 640 and 635 amino acid residues,respectively,which shared 97.5% identities with each other and were highly homologus to Arabidopsis PIN1,PIN2 and other putative PIN proteins.BjPIN2 and BjPIN3 had similar structures as AtPIN proteins.Northern blot analysis indicated that Bjpin2 was expressed in stem,leaf and floral tissues, while Bjpin3 was expressed predominantly in stem and hypocotyls.Two promoter fragments of pin genes,Bjpin-X and Bjpin-Z ,were isolated by 'genome walkin' technique using primers at 5'-end of pin cDNA.Promoter-gus fusion studies revealed the GUS activities driven by Bjpin-X were at internal side of xylem and petal;while those driven by Bjpin-Z were detected at leaf vein, epidermal cell and cortex of stem,vascular tissues and anther.Results of the pin genes with different expression patterns in B.juncea suggested the presence of a gene family.
基金Project supported by the Ministry of Education of China(Grant Nos105036 and NCET-04-0116)
文摘Taking into account ultra-fast carrier dynamics, this paper models 640 Gbit/s wavelength conversion scheme based on nonlinear polarization rotation (NPR) in a single semiconductor optical amplifier (SOA) and investigates the performance of this kind of wavelength conversion scheme in detail. In this model, two carrier temperature equations are introduced to substitute two energy density equations, which reduce the complexity of calculation in comparison with the previous model. The temporary gain and phase shift dynamics induced by ultra-short optical pulses are numerically simulated and the simulated results are qualitatively in good agreement with reported experimental results. Simulated results show that non-inverted and inverted 640 Gbit/s wavelength conversions based on NPR are achieved with clear open eye diagrams. To further investigate the performance of the non-inverted wavelength conversion scheme, the dependence of output extinction ratio (ER) on some key parameters used in simulation is illustrated. Furthermore, simulated analyses show that high performance non-inverted wavelength conversion based on NPR can be achieved by using a red-shifted filtering scheme.
基金Project supported by the National Natural Science Foundation of China(Grants Nos.61690223,11561121002,61521093,11227902,11404356,and 11574332)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB16)
文摘Most of the schemes for generating isolated attosecond pulses(IAP) are sensitive to the carrier-envelope phase(CEP)of the driving lasers. We propose a scheme for generating IAP using two-color counter-rotating circularly polarized(TCCRCP) laser pulses. The results demonstrate that the dependence of the IAP generation on CEP stability is largely reduced in this scheme. IAP can be generated at most of CEPs. Therefore, the experiment requirements become lower.
文摘We have demonstrated the first carrier density model for AlGaN channel with AlN buffer using spontaneous and piezoelectric polarization comparison with experimental and theoretical results. From the results we proved that the formation of 2DEG in undoped structure relied both on spontaneous and piezoelectric polarization. The electron distribution of Al concentration (0 < x < 0.5) was measured for both AlGaN channel and barrier. Barrier thickness assumed between 20 and 25 nm for validating the experimental results. The carrier concentration was observed at the specific interface of the N- and Ga-face by assuming x1, x2 = 0. The model results are verified with previously reported experimental data.