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TiO2 nanomaterials with platelet or nanosheet morphologies can offer improved properties for photocatalytic applications, but established methods to produce them typically require structure-directing agents since anatase-phase TiO2 does not have a layered structure. In the present work, the preparation of TiO2 nanosheets by the chemical oxidation of TiS2 nanosheets is demonstrated. Electrochemical exfoliation of bulk TiS2 into TiS2 nanosheets, followed by the hydrothermal treatment at 180 °C for 14 h is performed. The results show that polycrystalline TiO2 nanosheets with the anatase structure are formed, and that the nanosheet morphology can still be maintained after the hydrothermal treatment. The TiO2 nanosheets show good photocatalytic activity for the degradation of methylene blue, but the performance is negatively affected by the residual carbon black that was needed in the TiS2 electrode to enable electrochemical exfoliation. These results show that conversion of TiS2 nanosheets to TiO2 nanosheets is a promising synthetic strategy but highlights how the interfacial properties of the obtained materials could be affected by ancillary components in the preparation method.
In the paper, we focus on atom diffusion behavior in Ni-based superalloys, which have important applications in the aero-industry. Specifically, the expressions of the key physical parameter – transition rate (jump rate) in the diffusion can be given from the diffusion theory in solids and the kinetic Monte Carlo (KMC) method, respectively. The transition rate controls the diffusion process and is directly related to the energy of vacancy formation and the energy of migration of atom from density functional theory (DFT). Moreover, from the KMC calculations, the diffusion coefficients for Ni and Al atoms in the γ phase (Ni matrix) and the γʹ phase (intermetallic compound Ni3Al) of the superalloy have been obtained. We propose a strategy of time stepping to deal with the multi-time scale issues. In addition, the influence of temperature and Al concentration on diffusion in dilute alloys is also reported.
In this short note, we study a relation between the tensor product of matrices and a multilinear map defined by the optimal operator. In this particular case, the linear transform (mediating morphism) hidden in the abstract definition of the general tensor product can be determined explicitly.
The role of diffusion tensor tractography (DTT) has become increasingly important in the preoperative mapping of brain white matter. Recently, functional magnetic resonance imaging (fMRI) driven DTT has provided the ability to evaluate the spatial relationship between the corticospinal tract (CST) and motor resection tumor boundaries. The main objective of this study was improvement of the preoperative assessment of the CST in patients with gliomas involving the motor cortical areas.
Seventeen patients with gliomas involving motor cortical areas underwent 3 dimensions (3D) T1-weighted imaging for anatomical referencing, using both fMRI and diffusion tensor imaging (DTI). We used the fast-marching tractography (FMT) algorithm to define the 3D connectivity maps within the whole brain using seed points selected in the white matter adjacent to the location of fMRI activation. The target region of interest (ROI) was placed in the cerebral peduncle. Karnofsky performance status (KPS) scores were evaluated for each patient before and after surgery.
The CST of a total seventeen patients were successfully tracked by choosing seed and target ROI on the path of the fibers. What is more, DTT can indicate preoperatively the possibility for total glioma removal or the maximum extent of surgical resection. The postoperative average KPS score for the seventeen patients enrolled increased by more than 10 points.
Incorporation of fMRI driven DTT showed a maximum benefit in surgical treatment of gliomas. Our study of the assessment precision should enhance the accuracy of glioma operations with a resulting improvement in postoperative patient outcome.
Spermatogenesis is a process in adult male mammals supported by spermatogonial stem cells (SSCs). The cultivation of SSCs has potential value, for example for the treatment of male infertility or spermatogonial transplantation. Testicular interstitial fluid was added to culture medium to a final concentration of 5, 10, 20, 30 or 40%, in order to investigate its effects on proliferation of mouse SSCs in vitro, Alkaline phosphatase (AKP) assay, reverse transcription polymerase chain reaction (RT-PCR) analysis and indirect immunofluorescence of cells were performed to identify SSCs, and the proliferation rate and diameters of the SSCs colonies were measured. The results showed that the optimal addition of testicular interstitial fluid to culture medium was 30%. When medium supplemented with 30% testicular interstitial fluid was used to culture mouse SSCs, the optimum proliferation rate and diameter of the cell colonies were 72.53% and 249 μm, respectively, after 8 days in culture, values that were significant higher than those found for other groups (P < 0.05). In conclusion, proliferation of mouse SSCs could be promoted significantly by supplementation of the culture medium with 30% testicular interstitial fluid. More research is needed to evaluate and understand the precise physiological role of testicular interstitial fluid during cultivation of SSCs.
With exceptional carrier mobilities, mechanical strength, and optical transparency, graphene is a leading material for next-generation electronic devices. However, for most applications, graphene will need to be integrated with other materials, which motivates efforts to understand and tune its surface chemistry. In particular, the modification of graphene via organic functionalization holds promise for tuning the electronic properties of graphene, controlling interfaces with other materials, and tailoring surface chemical reactivity. Toward these ends, this article reviews recent work from our laboratory on noncovalent and covalent organic functionalization of graphene. Using ultrahigh vacuum scanning tunneling microscopy (UHV STM), the molecular ordering and electronic properties of organic adlayers on graphene are characterized at the molecular scale. In addition, UHV STM is employed to nanopattern these organic layers with sub-5 nm resolution, thus providing a pathway for producing graphene-based heteromolecular nanostructures.
Transgenes integrated into mammalian cells are silenced rapidly. This phenomenon correlates with repressed chromatin structure marked by histone hypoacetylation. This study investigated the effect of trichostatin A (TSA; a histone-deacetylase inhibitor) on EGFP expression in transfected cells and embryonic development after somatic cell nuclear transfer (SCNT). Porcine adult fibroblasts were transfected with a pEGFP-C1 vector. Then transfected cells, donor cells for SCNT, were pretreated with TSA, with the untreated cells being used as the control. Expression of EGFP in donor cells and reconstructed embryos was detected when exposed to blue light. Results showed that the percentage of EGFP-positive cells significantly increased when the transfected cells were treated with TSA and the increased expression of EGFP was sustained to at least the morula stage. In addition, the cytotoxic effect of TSA on the transfected cells was dose dependent. In conclusion, TSA can rescue the silenced EGFP gene. Even after transferring the TSA-treated cells to enucleated recipient oocytes, TSA retained the ability to rescue a silenced EGFP gene. In addition, TSA had an impact on cell proliferation.
Amplified fragment length polymorphism (AFLP) markers linked to the stem nematode resistance gene were developed in sweet potato (Ipomoea batatas (L.) Lam.). Using bulked segregant analysis (BSA), 800 AFLP primer combinations were screened in the resistant and susceptible bulked DNA from the 186 progeny of an F1 single-cross population of Xu781 (resistant parent)×Xushu18 (susceptible parent), and 245 of these AFLP primers showed polymorphic bands between resistant and susceptible DNA. Primer combinations detecting polymorphism between the two bulks were used to screen the parents and eight individuals from each of the bulks. The results showed that E2M23 and E33M20 produced a specific band of about 500 bp and 200 bp in length, respectively, in the resistant plants but not in the susceptible plants, suggesting that the markers named E2M23500 and E33M20200 linked to a gene for stem nematode resistance. Amplified analysis of the 186 F1 individuals indicated that the genetic distance between these two markers and the stem nematode resistance gene was 6.9 cM and 11.1 cM, respectively, measured with Mapmaker 3.0. These two AFLP markers were used to identify ten sweet potato varieties planted widely in China and the results were consistent with those of conventional resistance identification, indicating that the two markers can be used in molecular marker-assisted breeding for stem nematode resistance in the sweet potato.
Twins could play a crucial role in our understanding of genetic contributions to numerous etiologically complex disorders. In China, although adult twins are relatively rare, twins will become increasingly available due to increasing twin birth rates. Thus, child twin data will be a valuable resource to contribute to the field of child and adolescent psychopathology. The first twin database of children aged from 6 to 16 was established in Chongqing, R.P., China. In this article, we will discuss our experiences in establishing the twin database, completed in three steps — the first step being to search and identify twins, the second being to keep contact with the twins and the final being to seek cooperation with the twin families, and its future prospects. Our twin database has proven to be an efficient method for the investigation and data collection of twin children in China. The results of our present study suggest that the inclusion of twin information in the residence registration of the public security bureaus in the future may ensure a smooth run of research based on the demographic resources. We propose that school networks may be adopted as the preferred method of collection of twin records for future studies.
The localization of heat shock protein 70 (HSP70) and HSP70 mRNA in the heart, liver, lung, kidney, spleen, thymus and cloacal bursa in broilers that were heat stressed for 6 h was conducted using immunohistochemistry and in situ hybridization techniques. Positive HSP70 mRNA signals were detected in the liver and lung, especially in the vessel walls. A weak presence was found in the myocardial cells. No significant signals were observed in spleen, thymus and cloacal bursa. HSP70 was observed in the vessel walls of all investigated broiler tissues. Localizations of HSP70 and HSP70 mRNA suggest that HSP70 could be correlated with cardiovascular function.
Medium-chain-length polyhydroxyalkanoates (mcl-PHAs) belong to the group of microbial polyesters. The key enzyme for mcl-PHA biosynthesis is type II PHA synthase. The gene phaC2 encoding type II PHA synthase was placed under the control of psbA-pro and psbA-ter of rice (Oryza sativa) to construct a phaC2 cassette, which was ligated with the screening marker gene aadA cassette (prrn–aadA–TpsbA-ter). These recombined fragments were cloned between the plastid rbcL and accD genes for targeting to the large single copy region of the chloroplast genome. A chloroplast transformation vector, pTC2, was constructed and introduced into the tobacco (Nicotiana tobacum) chloroplast genome by particle bombardment. PCR and Southern blot analysis confirmed stable integration of phaC2 into the chloroplast genomes of T0 and T1 transgenic plants, and T1 transgenic plants exhibited homoplasmy. The expression of phaC2 at transcription level was detected by reverse transcriptase–polymerase chain reaction (RT-PCR). Recombinant transgenes in the tobacco chloroplast genome were maternally inherited and were not transmitted via pollen when out-crossed with untransformed female plants. To our knowledge, this is the first report on the stable transformation of phaC2 encoding type II PHA synthase in tobacco via chloroplast genetic engineering.
The period from March to mid April, when oriental armyworm Mythimna separata (Walker) moths migrate from South China to Central China over several nights, is an important window of time in annual armyworm population increase. The presence of nectar sources along the pathway of the migratory population is a prerequisite for moths to reach target habitats and lay eggs. Using flowering periods and geographic distributions, the major spring nectar plants suitable for M. separata moths were identified from among 102 species/varieties of apicultural nectar plants. The nectar plants proposed as important to M. separata include milk vetch Astragalus sinicus L., rape Brassica napa L. and six other species. Spearman's rank correlation analyses were conducted between the annual population size of M. separata and the acreages of milk vetch and rape in the daily stopover areas for migrating populations of M. separata during 1950–1979. The Spearman's coefficient between milk vetch and M. separata was 0.6259 and the correlation was highly significant (P<0.001). Further regression analysis with data from 1950–1979 and from 1980–1992 also revealed a close relationship between annual acreage of damaged crops/wheat and acreage of milk vetch. These results strongly suggest that the unprecedented enlargement in the geographic distribution of milk vetch from Central China into South China was the key factor in the frequent severe oriental armyworm outbreaks that occurred during 1966–1977. This is thought to be the first report in the world that reveals the key role of nectar sources in long distance, regional scale, migration of moths. The argument for the key role of milk vetch is supported by the simultaneous decline in the level of damage inflicted by M. separata and the acreage of milk vetch after 1980.
A glacier system is regarded as the ensemble of many glaciers sharing the same region, influenced by a similar climate and organized by certain intrinsic laws. It can be either ‘sensitive’ or ‘steady’. On the basis of the structure of the glacier system and the nature of the equilibrium-line altitudes at the steady state, functional models of a glacier system responding to climate warming were established, using the Kotlyakov–Krenke equation relating annual glacier ablation and mean summer temperature and the glacier system’s median size. The modeling results under the climatic scenarios with a rate of temperature increase of 0.01, 0.03 and 0.05 K a-1 indicate that by the end of this century the glacial area of China will be reduced by –14%, –40%and –60% respectively. However, model results show distinct differences between the sensitive glacier system and the steady glacier system.
Maturation of porcine oocytes was examined after oocytes were cooled at the germinal vesicle stage. Cumulus-oocyte complexes (COCs) collected from medium-sized follicles were cooled at 24 °C or 4 °C for 5, 30 or 120 min in a solution with or without 1.5 M dimethylsulfoxide (DMSO). After rewarming, COCs were cultured in maturation medium at 39 °C, 5% CO2 in air for 44 h. Meiotic spindle organisation (by immunostaining and confocal microscopy), nuclear maturation (by orcein staining) and cytoplasmic maturation (by intracellular glutathione assay) of oocytes were examined after maturation. When COCs were cooled at 24 °C for various times in the medium without DMSO, a tendency to decreased spindle formation, nuclear maturation and cytoplasmic maturation was observed, but there was no statistical difference compared with controls. Addition of DMSO during cooling inhibited subsequent nuclear maturation and spindle formation. When COCs were cooled at 4 °C, both nuclear and cytoplasmic maturation as well as spindle formation were inhibited in most oocytes in a time-dependent manner. DMSO during cooling did not have any beneficial effect on subsequent oocyte maturation and spindle formation. These results suggest that porcine oocytes are very sensitive to a drop in the temperature before exposure to culture. Cooling oocytes before maturation inhibits their subsequent spindle organisation, nuclear and cytoplasmic maturation. Addition of DMSO to the cooling solution did not protect porcine oocytes from cooling-induced damage.
We will present results for an Al0.24Ga0.76As/GaAs diffused multiple quantum well with five periods of 100/100 Å thick well/barrier layers grown in between Al0.24Ga0.76As guiding layers and cladded on top by a 1 μm thick p-Al0.44Ga0.56As layer and on the bottom by an n-Al0.44Ga0.56As layer of equal thickness, on a n+-GaAs buffer layer and n+-GaAs substrate. Vacancy enhanced QW diffusion is employed where a 2000 Å thick layer of SiO2 is deposited on top of the diffused multiple quantum well structure. Photoluminescence measurement and photovoltage measurement at room temperature show that after rapid thermal annealing for 30 sec at 1000 °C to 1040 °C, a bandgap shift of 30 nm is obtained for the exciton edge. Further, this technique is applied to a ridge waveguide laser structure to make two windows for high power output up to 36 mW. This device shows that the diffusion process may have practical applications.
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