Electric field driven quantum phase transition between band insulator and topological insulator

We demonstrate theoretically that electric field can drive a quantum phase transition between band insulator to topological insulator in CdTe/HgCdTe/CdTe quantum wells. The numerical results suggest that the electric field could be used as a switch to turn on or off the topological insulator phase, and temperature can affect significantly the phase diagram for different gate voltage and compositions. Our theoretical results provide us an efficient way to manipulate the quantum phase of HgTe quantum wells.Comment: 4 pages, 4 figure

D'yakonov-Perel' spin relaxation in InSb/AlInSb quantum wells

We investigate theoretically the D'yakonov-Perel' spin relaxation time by solving the eight-band Kane model and Poisson equation self-consistently. Our results show distinct behavior with the single-band model due to the anomalous spin-orbit interactions in narrow band-gap semiconductors, and agree well with the experiment values reported in recent experiment (K. L. Litvinenko, et al., New J. Phys. \textbf{8}, 49 (2006)). We find a strong resonant enhancement of the spin relaxation time appears for spin align along [$1\bar{1}0$] at a certain electron density at 4 K. This resonant peak is smeared out with increasing the temperature.Comment: 4 pages, 4 figure

Identification and characterization of a MBP isoform specific to hypothalamus in orange-spotted grouper (Epinephelus coioides)

Myelin basic protein (MBP), as a major component of the myelin sheath, has been revealed to play an important role informing and maintaining myelin structure in vertebrate nervous system. In teleost, hypothalamus is an instinctive brain center and plays significant roles in many physiological functions, such as energy metabolism, growth, reproduction, and stress response. In comparison with other MBP identified in vertebrates, a smallest MBP is cloned and identified from the orange-spotted grouper hypothalamic cDNA plasmid library in this study. RT-PCR analysis and Western blot detection indicate that the EcMBP is specific to hypothalamus, and expresses mainly in the tuberal hypothalamus in adult grouper. Immunofluorescence localization suggests that EcMBP should be expressed by oligodendrocytes, and the expressing cells should be concentrated in hypothalamus and the area surrounding hypothalamus, such as NPOpc, VC, DP, NLTm, and NDLI The studies on EcMBP expression pattern and developmental behaviour in the brains of grouper embryos and larvae reveal that the EcMBP-expressing cells are only limited in a defined set of cells on the border of hypothalamus, and suggest that the EcMBP-expressing cells might be a subpopulation of oliaodendrocyte progenitor cells. This study not only identifies a smallest MBP isoform specific to hypothalamus that can be used as a molecular marker of oligodendrocytes in fish, but also provides new insights for MBP evolution and cellular distribution. (C) 2007 Elsevier B.V.. All rights reserved.Myelin basic protein (MBP), as a major component of the myelin sheath, has been revealed to play an important role informing and maintaining myelin structure in vertebrate nervous system. In teleost, hypothalamus is an instinctive brain center and plays significant roles in many physiological functions, such as energy metabolism, growth, reproduction, and stress response. In comparison with other MBP identified in vertebrates, a smallest MBP is cloned and identified from the orange-spotted grouper hypothalamic cDNA plasmid library in this study. RT-PCR analysis and Western blot detection indicate that the EcMBP is specific to hypothalamus, and expresses mainly in the tuberal hypothalamus in adult grouper. Immunofluorescence localization suggests that EcMBP should be expressed by oligodendrocytes, and the expressing cells should be concentrated in hypothalamus and the area surrounding hypothalamus, such as NPOpc, VC, DP, NLTm, and NDLI The studies on EcMBP expression pattern and developmental behaviour in the brains of grouper embryos and larvae reveal that the EcMBP-expressing cells are only limited in a defined set of cells on the border of hypothalamus, and suggest that the EcMBP-expressing cells might be a subpopulation of oliaodendrocyte progenitor cells. This study not only identifies a smallest MBP isoform specific to hypothalamus that can be used as a molecular marker of oligodendrocytes in fish, but also provides new insights for MBP evolution and cellular distribution. (C) 2007 Elsevier B.V.. All rights reserved

Wavelength tuning in GaAsAlGaAs quantum wells by InAs submonolayer insertion

Wavelength tuning of exciton emissions has been achieved simply by inserting an InAs submonolayer at the centre of GaAs quantum wells during molecular beam epitaxy growth. Photoluminescence measurements show that the emission energy can be effectively tuned from the quantum-well-determined energy down to less than the band gap of GaAs, depending on the well width as well as the InAs layer thickness. Using the effective-mass approximation, the tuning effect can be well predicted theoretically The results reported here may provide an alternative way to tune the wavelength in optoelectronic devices

Infection of Myxobolus turpisrotundus sp n. in allogynogenetic gibel carp, Carassius auratus gibelio (Bloch), with revision of Myxobolus rotundus (s. l.) Nemeczek reported from C-auratus auratus (L.)

Infection of a Myxobolus species, previously identified as Myxobolus rotundus, was detected in 182 of 7892 (2.31%) allogynogenetic gibel carp, Carassius auratus gibelio, in a closed pond culture system in China. Morphological and molecular data showed that this myxosporean is a different species from M. rotundus parasitizing Abramis brama in Europe and is thus designated as a new species, Myxobolus turpisrotundus. M. rotundus (s.l.) ex C. auratusauratus is a synonym of M. turpisrotundus. Plasmodia of M. turpisrotundus develop in the subepidermal tissues of the body surface resulting in an unaesthetic appearance and causing severe economic losses. Prevalence of infection with the myxosporean plasmodia varied seasonally, increasing in winter and decreasing in spring. Prevalence was positively correlated to host size, but no host sex-specificity was found. No infection was observed in other fish species (grass carp, bighead carp and yellow catfish) reared in the same pond, suggesting that the parasite has a relatively strict host specificity. Plasmodia grew gradually as the parasite developed, and reached up to a maximum 5.6 mm in diameter. Plasmodia ruptured naturally to release the mature spores and host fish completely recovered with no mortality. Release of spores and regeneration of lesions were not correlated with water temperature. Histology showed that plasmodia developed sub-epidermally, and that the wall of the plasmodia was composed of a multiple complex structure, including layers of fibroblasts, a collagenous membrane, melanophores and a layer of cup-like cells of unknown derivation and function. The cup-like cells are in direct contact with pre-sporogonic stages located in the peripheral parts of the large plasmodia. No severe host inflammatory response was seen

Chlorophyll a fluorescence responses of Haloxylon ammodendron seedlings subjected to progressive saline stress in the Tarim desert highway ecological shelterbelt

In order to assess the long-term impacts of saline groundwater irrigation to Haloxylon ammodendron, one of the main shrubs in the Tarim desert highway ecological shelterbelt, we irrigated the H. ammodendron seedlings with progressive saline groundwater (3-30 g L-1, simulation environment in the Tarim desert highway ecological shelterbelt) and investigated the diurnal variations of chlorophyll a (Chl a) fluorescence parameters, such as maximal quantum yield of photosystem II (PSII) photochemistry (F-v/F-m), quantum yield of photochemical energy conversion in PSII (Y-II), the apparent rate of electron transport at the PSII level (ETR), photochemical quenching coefficient (q(P)), non-photochemical quenching (NPQ), quantum yield of nonregulated non-photochemical energy loss in PSII (Y-NO) and quantum yield of regulated non-photochemical energy loss in PSII (Y-II), at approximately 2-h intervals. F-v/F-m with 5 g L-1 (S2) was lower than that with 2 g L-1 (S1) but a little higher than 20 g L-1 (S5), respectively. Under the low light [photosyntheticallyactive radiation (PAR) a parts per thousand currency sign 250 mu mol m(-2) s(-1), at 08:00, 10:00 and 20:00 h of the local time], S1 kept the lowest Y-II and the highest Y-NPQ; while under the high light (PAR a parts per thousand yen 1500 mu mol m(-2) s(-1)), the Y-II performed S1 &gt; S2 &gt; S5, and the reverse Y-NPQ; under mild light (250 mu mol m(t-2) s(-1) a parts per thousand currency sign PAR a parts per thousand currency sign 1500 mu mol m(-2) s(-1)), S1 remained the highest Y-II, no matter the light and the salinity, the similar Y-NO almost occurred basically. The results showed that the sand-binding plant H. ammodendron could regulate its energy-utilizing strategies. The S2 might be the most suitable salinity of the irrigation water for H. ammodendron in the Tarim desert highway ecological shelterbelt in the northwest of China. </div

Clonal diversity and genealogical relationships of gibel carp in four hatcheries

To conserve and utilize the genetic pool of gynogenetic gibel carp (Carassius auratus gibelio), the Fangzheng and Qihe stock hatcheries have been established in China. However, little information is available on the amount of genetic variation within and between these populations. In this study, clonal diversity in 101 fish from these two stock hatcheries and 35 fish from two other hatcheries in Wuhan and Pengze respectively was analysed for variation in serum transferrin. Thirteen clones were found in Fangzheng and Qihe, of which 12 were novel. Six clones were specific to Fangzheng and three specific to Qihe, whereas four were shared among the Fangzheng and Qihe fish. To obtain more knowledge on genetic diversity and genealogical relationships within gibel carp, the complete mitochondrial DNA (mtDNA) control region (similar to 920 bp) was sequenced in 64 individuals representing all 14 clones identified in the four hatcheries. Differences in the mtDNA sequences varied remarkably among hatcheries, with the Fangzheng and Qihe lines demonstrating high diversity and Wuhan and Pengze showing no variation. The Fangzheng and Qihe lines might represent two distinct matrilineal sources. One of the Qihe samples carried the haplotype shared by a most widely cultivated Fangzheng clone, indicating that a Fangzheng clone escaped from cultivated ponds and moved into the Qihe hatchery. Four Fangzheng samples clustered within the lineage formed mainly by Qihe samples, most likely reflecting historical gene flow from Qihe to Fangzheng. It is suggested that clones in Wuhan originated from Fangzheng, consistent with their introduction history, supporting the hypothesis that gibel carp in Pengze were domesticated from individuals in the Fangzheng hatchery.To conserve and utilize the genetic pool of gynogenetic gibel carp (Carassius auratus gibelio), the Fangzheng and Qihe stock hatcheries have been established in China. However, little information is available on the amount of genetic variation within and between these populations. In this study, clonal diversity in 101 fish from these two stock hatcheries and 35 fish from two other hatcheries in Wuhan and Pengze respectively was analysed for variation in serum transferrin. Thirteen clones were found in Fangzheng and Qihe, of which 12 were novel. Six clones were specific to Fangzheng and three specific to Qihe, whereas four were shared among the Fangzheng and Qihe fish. To obtain more knowledge on genetic diversity and genealogical relationships within gibel carp, the complete mitochondrial DNA (mtDNA) control region (similar to 920 bp) was sequenced in 64 individuals representing all 14 clones identified in the four hatcheries. Differences in the mtDNA sequences varied remarkably among hatcheries, with the Fangzheng and Qihe lines demonstrating high diversity and Wuhan and Pengze showing no variation. The Fangzheng and Qihe lines might represent two distinct matrilineal sources. One of the Qihe samples carried the haplotype shared by a most widely cultivated Fangzheng clone, indicating that a Fangzheng clone escaped from cultivated ponds and moved into the Qihe hatchery. Four Fangzheng samples clustered within the lineage formed mainly by Qihe samples, most likely reflecting historical gene flow from Qihe to Fangzheng. It is suggested that clones in Wuhan originated from Fangzheng, consistent with their introduction history, supporting the hypothesis that gibel carp in Pengze were domesticated from individuals in the Fangzheng hatchery

Isolation and characterization of polymorphic microsatellite loci in Wuchang bream (Megalobrama amblycephala)

Wuchang bream (Megalobrama amblycephala) is an economically important fish in China. From a (GT)(13)-enriched genomic library, 20 microsatellites were developed. Nine of these 20 loci were polymorphic in a test population with allele numbers ranging from two to four, and the observed and expected heterozygosities ranging from 0.2609 to 0.7826 and from 0.3739 to 0.7546, respectively. In the cross-species amplifications, six of these nine loci were also polymorphic in white amur bream (Parabramis pekinensis). These polymorphic microsatellite loci are potentially useful for population genetics of Wuchang bream and its closely related species.Wuchang bream (Megalobrama amblycephala) is an economically important fish in China. From a (GT)(13)-enriched genomic library, 20 microsatellites were developed. Nine of these 20 loci were polymorphic in a test population with allele numbers ranging from two to four, and the observed and expected heterozygosities ranging from 0.2609 to 0.7826 and from 0.3739 to 0.7546, respectively. In the cross-species amplifications, six of these nine loci were also polymorphic in white amur bream (Parabramis pekinensis). These polymorphic microsatellite loci are potentially useful for population genetics of Wuchang bream and its closely related species