Yuntao Zhang

© 2016 Elsevier B.V.The evaporative-cooling roof is a popular passive energy conservation technique. This article presents a novel approach for modelling and analysing the influence of evaporation on roof thermal performance. A multivariate nonlinear model was developed for the prediction of the evaporation rate from porous tile. A computer program was then developed based on the one-dimensional roof unsteady heat transfer theory. Finally, the computer program and hourly weather data of Guangzhou, China, were used to analyse the impacts of evaporation and slope orientation on roof thermal performance. Evaporation beginning at 11:00 can reduce the external surface temperatures of a horizontal roof and 30°-inclined east-sloping and west-sloping roofs by up to 11.3, 10.7, and 9.8 °C, respectively, from those of a non-evaporative roof. This, in turn, can reduce the peak-hour internal surface heat flux. Additionally, with the horizontal roof, the reduction in the peak-hour heat flux can be doubled if the evaporative layer is frequently replenished with water.

© 2015 American Chemical Society.Near-infrared dye-sensitized upconversion nanoparticles can broaden the absorption range and boost upconversion efficiency of UCNPs. Here, we achieved significantly enhanced upconversion luminescence in dye-sensitized core/active shell UCNPs via the doping of ytterbium ions in the UCNP shell, which bridged the energy transfer from the dye to the UCNP core. As a result, we synergized the two most practical upconversion booster effectors to amplify upconversion efficiency. We demonstrated two biomedical applications using these UCNPs. By using dye-sensitized core/active shell UCNP embedded poly polymer implantable systems, we successfully shifted the optogenetic neuron excitation window to a biocompatible and deep tissue penetrable 800 nm wavelength. Furthermore, UCNPs were water-solubilized with Pluronic F127 with high upconversion efficiency and can be imaged in a mouse model.

Topological insulators nanowires are an emerging class of structures, promising both novel quantum effects and potential applications in low-power electronics, thermoelectrics and spintronics. However, investigating the electronic states of TI NWs is complicated, due to their small lateral size, especially at room temperature. Here, we perform scanning probe based nanoscale imaging to resolve the local surface potential landscapes of Bi 2 Te 3 nanowires at 300 K. We found equipotential rings around the NWs perimeter that we attribute to azimuthal 1D modes. Along the NW axis, these modes are altered, forming potential ripples in the local density of states, due to intrinsic disturbances. Potential mapping of electrically biased NWs enabled us to accurately determine their conductivity which was found to increase with the decrease of NW diameter, consistent with surface dominated transport. Our results demonstrate that TI NWs can pave the way to both exotic quantum states and novel electronic devices.

© 2016 American Chemical Society.Layered transition metal chalcogenides with large spin orbit coupling have recently sparked much interest due to their potential applications for electronic, optoelectronic, spintronics, and valleytronics. However, most current understanding of the electronic structure near band valleys in momentum space is based on either theoretical investigations or optical measurements, leaving the detailed band structure elusive. For example, the exact position of the conduction band valley of bulk MoS2 remains controversial. Here, using angle-resolved photoemission spectroscopy with submicron spatial resolution, we systematically imaged the conduction/valence band structure evolution across representative chalcogenides MoS2, WS2, and WSe2, as well as the thickness dependent electronic structure from bulk to the monolayer limit. These results establish a solid basis to understand the underlying valley physics of these materials, and also provide a link between chalcogenide electronic band structure and their physical properties for potential valleytronics applications.

© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, WeinheimSuperconductivity in monolayer niobium diselenide on bilayer graphene is studied by electrical transport. Monolayer NbSe2 is grown on bilayer graphene by molecular beam epitaxy and capped with a selenium film to avoid degradation in air. The selenium capped samples have TC = 1.9 K. In situ measurements down to 4 K in ultrahigh vacuum show that the effect of the selenium layer on the transport is negligible. The superconducting transition and upper critical fields in air exposed and selenium capped samples are compared. Schematic of monolayer NbSe2/bilayer graphene with selenium capping layer and electrical contacts.

© 2016 American Physical Society.The nematic state, where a system is translationally invariant but breaks rotational symmetry, has drawn great attention recently due to the experimental observations of such a state in both cuprates and iron-based superconductors. The origin of nematicity and its possible tie to the pairing mechanism of high-Tc, however, still remain controversial. Here, we study the electronic structure of a multilayer FeSe film using angle-resolved photoemission spectroscopy. The band reconstruction in the nematic state is clearly delineated. We find that the energy splitting between dxz and dyz bands shows a nonmonotonic distribution in momentum space. From the Brillouin zone center to the Brillouin zone corner, the magnitude of splitting first decreases, then increases, and finally reaches the maximum value of ∼70 meV. Moreover, besides the dxz and dyz bands, band splitting was also observed on the dxy bands with a comparable energy scale around 45 meV. Our results suggest that the electronic anisotropy in the nematic state cannot be explained by a simple on-site ferro-orbital order. Instead, strong anisotropy exists in the hopping of all dxz,dyz, and dxy orbitals, the origin of which holds the key to a microscopic understanding of the nematicity in iron-based superconductors.

© 2016 American Chemical Society.High quality WSe2 films have been grown on bilayer graphene with layer-by-layer control of thickness using molecular beam epitaxy. The combination of angle-resolved photoemission, scanning tunneling microscopy/spectroscopy, and optical absorption measurements reveal the atomic and electronic structures evolution and optical response of WSe2/BLG. We observe that a bilayer of WSe2 is a direct bandgap semiconductor, when integrated in a BLG-based heterostructure, thus shifting the direct-indirect band gap crossover to trilayer WSe2. In the monolayer limit, WSe2 shows a spin-splitting of 475 meV in the valence band at the K point, the largest value observed among all the MX2 materials. The exciton binding energy of monolayer-WSe2/BLG is found to be 0.21 eV, a value that is orders of magnitude larger than that of conventional three-dimensional semiconductors, yet small as compared to other two-dimensional transition metal dichalcogennides semiconductors. Finally, our finding regarding the overall modification of the electronic structure by an alkali metal surface electron doping opens a route to further control the electronic properties of TMDCs.

© 2016, American Society for Biochemistry and Molecular Biology Inc. All rights reserved.Glycyl-tRNA synthetase is the enzyme that covalently links glycine to cognate tRNA for translation. It is of great research interest because of its nonconserved quaternary structures, unique species-specific aminoacylation properties, and noncanonical functions in neurological diseases, but none of these is fully understood. We report two crystal structures of human GlyRS variants, in the free form and in complex with tRNAGly respectively, and reveal new aspects of the glycylation mechanism. We discover that insertion 3 differs considerably in conformation in catalysis and that it acts like a "switch" and fully opens to allow tRNA to bind in a cross-subunit fashion. The flexibility of the protein is supported by molecular dynamics simulation, as well as enzymatic activity assays. The biophysical and biochemical studies suggest that human GlyRS may utilize its flexibility for both the traditional function and alternative functions.

© 2016 Macmillan Publishers Limited.Layered transition metal dichalcogenides are ideal systems for exploring the effects of dimensionality on correlated electronic phases such as charge density wave order and superconductivity. In bulk NbSe 2 a CDW sets in at T CDW = 33 K and superconductivity sets in at T c = 7.2 K. Below T c these electronic states coexist but their microscopic formation mechanisms remain controversial. Here we present an electronic characterization study of a single two-dimensional layer of NbSe 2 by means of low-temperature scanning tunnelling microscopy/spectroscopy, angle-resolved photoemission spectroscopy, and electrical transport measurements. We demonstrate that 3 × 3 CDW order in NbSe 2 remains intact in two dimensions. Superconductivity also still remains in the 2D limit, but its onset temperature is depressed to 1.9 K. Our STS measurements at 5 K reveal a CDW gap of= 4 meV at the Fermi energy, which is accessible by means of STS owing to the removal of bands crossing the Fermi level for a single layer. Our observations are consistent with the simplified electronic structure of single-layer NbSe 2, thus providing insight into CDW formation and superconductivity in this model strongly correlated system.

© 2015 American Physical Society.The level of electronic correlation has been one of the key questions in understanding the nature of superconductivity. Among the iron-based superconductors, the iron chalcogenide family exhibits the strongest electron correlations. To gauge the correlation strength, we performed a systematic angle-resolved photoemission spectroscopy study on the iron chalcogenide series Fe1+ySexTe1-x, a model system with the simplest structure. Our measurement reveals an incoherent-to-coherent crossover in the electronic structure as the selenium ratio increases and the system evolves from a weakly localized to a more itinerant state. Furthermore, we found that the effective mass of bands dominated by the dxy orbital character significantly decreases with increasing selenium ratio, as compared to the dxz/dyz orbital-dominated bands. The orbital-dependent change in the correlation level agrees with theoretical calculations on the band structure renormalization, and may help to understand the onset of superconductivity in Fe1+ySexTe1-x.

Resistance to anoikis, or apoptosis triggered by detachment from the extracellular matrix, lengthens the survival of malignant cells, facilitating reattachment and colonization of secondary sites. To examine the molecular mechanisms underlying resistance to anoikis in human oral squamous cell carcinoma cells, we cultured human squamous carcinoma cells in suspension on plates coated with poly-2-hydroxyethyl methacrylate, which blocks access to the ECM. Cells in suspension that formed multicellular aggregates had significantly lower levels of apoptosis than single cells. Aggregates, but not single cells, had high levels of fibronectin. Preincubation with a cyclic arginine-glycine-aspartic acid peptide or fibronectin-blocking antibody significantly increased anoikis. Single cells had markedly lower expression of the integrin αv receptor than aggregates. Blocking αv function with a blocking antibody or by transfection with an antisense oligonucleotide increased apoptosis and inhibited aggregation. In single cells but not aggregates, phosphorylation of the integrin-associated focal adhesion kinase at tyrosine 397 was reduced, and p53 levels were increased. Apoptosis was increased by blocking FAK with an antisense oligonucleotide and reduced by blocking p53. These findings show that SCC cells escape suspension-induced anoikis by forming multicellular aggregates that avail themselves of fibronectin survival signals mediated by integrin αv. Single cells in suspension that do not form aggregates undergo anoikis because of decreased FAK phosphorylation and increased p53 levels. Thus, SCC cells appear to use neighboring cells and the ECM molecule FN to promote the metastatic phenotype.

Ultra-high isotropic resolution imaging of retinal structures was made possible with an adaptive optics system using dual deformable mirrors and a Fourier-domain optical coherence tomography system with correction for longitudinal chromatic aberration. This system was used to image microscopic retinal structures of healthy as well as diseased retinas in vivo. The improved resolution and contrast enhanced visualization of morphological structures in the retina can be clearly seen. The benefits of this instrument are apparent from comparison of new images with those acquired using a previous generation AO-OCT instrument. Big change in the appearance of speckle field can be observed as well. Additionally, further improvements in volumetric data acquisition and image representation will be discussed. This includes creation of large Field of View AO-OCT volume from multiple sub-volumes and its visualization. Also techniques and results of reducing speckle contrast by averaging multiple B-scans will be presented.

© 2015 American Institute of Chemical Engineers.Current lithium-ion batteries are predicted to be unable to provide the specific energy required to meet the ever-increasing demands of rapidly emerging technologies. Due to a high theoretical specific capacity of 1675 mAh/g, sulfur has gained much attention as a promising positive electrode material for high specific energy rechargeable batteries. Although the lithium/sulfur cell has been studied for many years and continues to receive much attention today as an alternative power source for zero-emission vehicles and advanced electronic devices, the realization of this novel cell's promise as a commercial product has yet to be successful. The major problems with sulfur electrodes involve: the dissolution of sulfur and the resulting diffusion of dissolved polysulfides and the deposition of insulating products on both the negative and the positive electrodes. These solid deposits can physically block the electrode reaction sites, thus passivating the electrode surfaces. Another important problem is the large volume change that occurs with the conversion of S to Li 2 S. It is important to understand that the performance of Li/S cells is hampered by linked chemical and mechanical degradations and both degradation mechanisms must be correctly alleviated in order to markedly improve current-technology Li/S cells. In this study, improved cycling performance via the reactive functional groups on graphene oxide to successfully immobilize sulfur and lithium polysulfides during operation has been demonstrated. The use of a new electrolyte and binder leads to improved cell performance in terms of high-rate capability and good reversibility, yielding at least 800 cycles have also been demonstrated.

Oxidative stress has been implicated in cardiac arrhythmia, although a causal relationship remains undefined. We have recently demonstrated a marked up-regulation of NADPH oxidase isoform 4 in patients with atrial fibrillation, which is accompanied by overproduction of reactive oxygen species. In this study, we investigated the impact on the cardiac phenotype of NOX4 overexpression in zebrafish. One-cell stage embryos were injected with NOX4 RNA prior to video recording of a GFP-labeled beating heart in real time at 24-31 h post-fertilization. Intriguingly, NOX4 embryos developed cardiac arrhythmia that is characterized by irregular heartbeats. When quantitatively analyzed by an established LQ-1 program, the NOX4 embryos displayed much more variable beat-to-beat intervals. Both the phenotype and the increased ROS in NOX4 embryos were attenuated by NOX4 morpholino co-injection, treatments of the embryos with polyethylene glycol-conjugated superoxide dismutase, or NOX4 inhibitors fulvene-5, 6-dimethylaminofulvene, and proton sponge blue. Injection of NOX4-P437H mutant RNA had no effect on the cardiac phenotype or ROS production. In addition, phosphorylation of calcium/cal-modulin-dependent protein kinase II was increased in NOX4 embryos but diminished by polyethylene glycol-conjugated superoxide dismutase, whereas its inhibitor KN93 or AIP abolished the arrhythmic phenotype. Taken together, our data for the first time uncover a novel pathway that underlies the development of cardiac arrhythmia, namely NOX4 activation, subsequent NOX4-specific NADPH-driven ROS production, and redox-sensitive CaMKII activation. These findings may ultimately lead to novel therapeutics targeting cardiac arrhythmia. © 2014 by The American Society for Biochemistry and Molecular Biology, Inc.

Lithium/sulfur cells are receiving significant attention as an alternative power source for zero-emission vehicles and advanced electronic devices due to the very high theoretical specific capacity of the sulfur cathode. However, the poor cycle life and rate capability have remained a grand challenge, preventing the practical application of this attractive technology. Here, we report that a Li/S cell employing a cetyltrimethyl ammonium bromide -modified sulfur-graphene oxide nanocomposite cathode can be discharged at rates as high as 6C and charged at rates as high as 3C while still maintaining high specific capacity, with a long cycle life exceeding 1500 cycles and an extremely low decay rate, perhaps the best performance demonstrated so far for a Li/S cell. The initial estimated cell-level specific energy of our cell was ∼500 W·h/kg, which is much higher than that of current Li-ion cells. Even after 1500 cycles, we demonstrate a very high specific capacity, which corresponds to ∼414 mA·h/g of electrode: still higher than state-of-the-art Li-ion cells. Moreover, these Li/S cells with lithium metal electrodes can be cycled with an excellent Coulombic efficiency of 96.3% after 1500 cycles, which was enabled by our new formulation of the ionic liquid-based electrolyte. The performance we demonstrate herein suggests that Li/S cells may already be suitable for high-power applications such as power tools. Li/S cells may now provide a substantial opportunity for the development of zero-emission vehicles with a driving range similar to that of gasoline vehicles. © 2013 American Chemical Society.

Previous research has consistently demonstrated the importance of parents' expectations and adolescents' expectations on adolescents' academic achievement. Less is known, however, about the reciprocal relationships among these constructs. To address this issue, we analyzed two waves of data from the National Education Longitudinal Study of 1988 using longitudinal cross-lagged path models. The sample consisted of 14,376 students. Results indicated that there was a reciprocal relationship between parents' expectations and adolescents' expectations. Moreover, there was a reciprocal relationship between expectations and adolescents' academic achievement. Multiple-group analyses of gender and ethnicity revealed that the effects of parents' expectations on students' expectations were stronger among males than among females. With respect to ethnic differences, the effects of adolescents' expectations were weakest on parents' expectations among African Americans as compared to the other ethnic groups. Implications of these findings are discussed. © 2010 The Author.

Frontotemporal dementia and Alzheimers disease are sometimes difficult to differentiate clinically because of overlapping symptoms. Using diffusion tensor imaging measurements of fractional anisotropy can be useful in distinguishing the different patterns of white matter degradation between the two dementias. In this study, we performed MRI scans in a 4 Tesla MRI machine including T1-weighted structural images and diffusion tensor images in 18 patients with FTD, 18 patients with Alzheimers disease and 19 cognitively normal controls. FA was measured selectively in specific fibre tracts as well as globally in a voxel-by-voxel analysis. Patients with FTD were associated with reductions of FA in frontal and temporal regions including the anterior corpus callosum, bilateral anterior, descending cingulum tracts, and uncinate tracts, compared to controls. Patients with Alzheimers disease were associated with reductions of FA in parietal, temporal and frontal regions including the left anterior and posterior cingulum tracts, bilateral descending cingulum tracts and left uncinate tracts compared to controls. When compared with Alzheimers disease, FTD was associated with greater reductions of FA in frontal brain regions, whereas no region in Alzheimers disease showed greater reductions of FA when compared to FTD. In conclusion, the regional patterns of anisotropy reduction in FTD and Alzheimers disease compared to controls suggest a characteristic distribution of white matter degradation in each disease. Moreover, the white matter degradation seems to be more prominent in FTD than in Alzheimers disease. Taken together, the results suggest that white matter degradation measured with DTI may improve the diagnostic differentiation between FTD and Alzheimers disease.

Background: Endothelins are paracrine peptides with growth-promoting and vasoactive functions for a variety of cell types. Elevated activation of the endothelin signaling pathway induces cell proliferation and/or survival and is implicated in a variety of malignancies. Increased endothelin 1 was described in solar lentigines in previous reports, raising the possibility that the endothelin pathway may be of significance in keratinocyte proliferation-related disorders. However, detailed investigation on endothelins in skin malignancies is lacking. Objectives: This study aims to survey the expression of endothelins and their receptors in keratinocyte-derived benign and malignant tumors of the skin and to test the effects of endothelin inhibitors on the growth and survival of cultured keratinocytes. Methods: Quantitative polymerase chain reaction was used to measure the level of gene transcription of three endothelins and two endothelin receptors. The genes with significant messenger ribonucleic acid expression abnormalities were confirmed with immunohistochemical analysis to examine expression differences at the protein levels. To analyze the effect of endothelin inhibitors on the keratinocyte growth and survival, keratinocytes were cultured in the presence of various concentrations of endothelin inhibitors and subjected to tetrazolium bromide assay to quantify the cell numbers over time. Results: ET-1 mRNA was found to be significantly up-regulated in seborrheic keratosis and basal cell carcinoma. However, no significant expression increase was found in actinic keratosis, Bowen's disease, or squamous cell carcinoma. Immunohistochemical analysis of ET-1 peptide confirmed increased expression. In cultured keratinocytes, peptide inhibitors of the endothelin pathway resulted in a marked reduction in cell survival. Conclusion: The endothelin signaling pathway, especially ET-1, is activated in basoloid keratinocyte neoplasms of the skin, such as basal cell carcinoma and seborrheic keratosis. Blockade of this pathway can reduce cell survival in vitro. Therefore, endothelin inhibitors potentially offer a novel method for the treatment of some keratinocyte-derived skin tumors.

© 2016 IOP Publishing Ltd.Few-layer thick MoSe2 and WSe2 possess non-trivial spin textures with sizable spin splitting due to the inversion symmetry breaking embedded in the crystal structure and strong spin-orbit coupling. We report a spin-resolved photoemission study of MoSe2 and WSe2 thin film samples epitaxially grown on a bilayer graphene substrate. We only found spin polarization in the single-and trilayer samples-not in the bilayer sample-mostly along the out-of-plane direction of the sample surface. The measured spin polarization is found to be strongly dependent on the light polarization as well as the measurement geometry, which reveals intricate coupling between the spin and orbital degrees of freedom in this class of material.