Yi Zhang

© 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.

© 2015 Macmillan Publishers Limited. All rights reserved.A single molecular layer of titanium diselenide is a promising material for advanced electronics beyond graphene - a strong focus of current research. Such molecular layers are at the quantum limit of device miniaturization and can show enhanced electronic effects not realizable in thick films. We show that single-layer TiSe2 exhibits a charge density wave transition at critical temperature TC =232±5 K, which is higher than the bulk TC =200±5 K. Angle-resolved photoemission spectroscopy measurements reveal a small absolute bandgap at room temperature, which grows wider with decreasing temperature T below TC in conjunction with the emergence of ordering. The results are rationalized in terms of first-principles calculations, symmetry breaking and phonon entropy effects. The observed Bardeen-Cooper-Schrieffer behaviour of the gap implies a mean-field CDW order in the single layer and an anisotropic CDW order in the bulk.

Although activated spinal cord glia contribute importantly to neuropathic pain, how nerve injury activates glia remains controversial. It has recently been proposed, on the basis of genetic approaches, that toll-like receptor 4 may be a key receptor for initiating microglial activation following L5 spinal nerve injury. The present studies extend this idea pharmacologically by showing that TLR4 is key for maintaining neuropathic pain following sciatic nerve chronic constriction injury. Established neuropathic pain was reversed by intrathecally delivered TLR4 receptor antagonists derived from lipopolysaccharide. Additionally, -naltrexone, -naloxone, and -naloxone, which we show here to be TLR4 antagonists in vitro on both stably transfected HEK293-TLR4 and microglial cell lines, suppressed neuropathic pain with complete reversal upon chronic infusion. Immunohistochemical analyses of spinal cords following chronic infusion revealed suppression of CCI-induced microglial activation by -naloxone and -naloxone, paralleling reversal of neuropathic pain. Together, these CCI data support the conclusion that neuron-to-glia signaling through TLR4 is important not only for initiating neuropathic pain, as suggested previously, but also for maintaining established neuropathic pain. Furthermore, these studies suggest that the novel TLR4 antagonists -naloxone and -naloxone can each fully reverse established neuropathic pain upon multi-day administration. This finding with -naloxone is of potential clinical relevance. This is because -naloxone is an antagonist that is inactive at the -opioid selective receptors on neurons that produce analgesia. Thus, these data suggest that -opioid antagonists such as -naloxone may be useful clinically to suppress glial activation, yet -opioid agonists suppress pain.

This thesis argues that works of yangbanxi (model theatre) are not mere relics of Maoist propaganda but contested battlegrounds where cultural and communicative memory collide and interpenetrate. It addresses a critical gap in yangbanxi studies by examining the overlooked role of their proliferating remakes, which have rarely been analysed as examples of memory politics. Building on Jan Assmann's concept of the 'gloating gap' (2011), I investigate how the Chinese Communist Party's mechanisms of ideological reproduction recalibrate revolutionary memory, and how artists, even under constraint, exercise creative agency. Understanding remakes as palimpsests that retain traces of previous inscriptions while layering new meanings, the thesis explores how revolutionary memory is overwitten rather than replaced. Instead of tracing a linear retreat of state power, I examine how yangbanxi remakes reflect shifting boundaries of permissible expression under varying degrees of Party involvement. This analysis unfolds within a discursive environment shaped by democratic centralism, where dissent may only circulate indirectly (berry, 2004). I begin with early remakes under the state-led assimilation of ethnic minorities into Han Chinese revolutionary culture, focusing on the Uyghur Qizil Chiragh (1975), where language recording and dramaturgical shifts both serve assimilationist aims and enable vernacular resistance. Next, I examine postmillenial commercial remakes, analysing Tsui Hark's The Taking of Tiger Mountain (2014), which grafts class-struggle tropes onto genre hybridity and diasporic framings. Then I turn to non-state performance through Wen Hui's Hong (2016), an avant-garde reinterpretation of The Red Detachment of Women, developed from archival and bodily memory. Through my practice-led interventions, I explore how adaptive performance resists retraumatization through Brechtian and absurdist strategies. Across these sites, I argue that the mnemonic friction between the ideological archetype and its mutable iterations destabilizes Party efforts to sustain a hegemonic narrative and offer insights into how revolutionary histories are remembered, embodied, and contested.

Digital transformation has reshaped corporate strategy, increasing technological complexity and strategic uncertainty. Traditional corporate governance research, which emphasizes monitoring and control, provides limited explanation of how boards influence strategic adaptation in digitally intensive environments. This study develops a conceptual framework linking corporate governance and strategic management through board digital capability. Integrating agency theory, resource dependence theory, and upper echelons theory, the framework identifies three mechanisms—monitoring enhancement, resource provision, and cognitive framing—through which board digital capability shapes strategic adaptability and digital transformation. The study advances propositions suggesting that technologically competent boards improve strategic alignment, innovation orientation, and long-term competitiveness, particularly in high-technology industries. By reconceptualizing boards as strategic enablers rather than purely monitoring bodies, this research bridges governance and strategy scholarship and offers a capability-based perspective on corporate governance in the digital era.

The effect of authentic leadership and leader competency on employee job performance has received growing attention in the past decades; however, few studies have simultaneously integrated these two leadership perspectives. We have thus developed a mediated moderation model to test the interactive effect of authentic leadership and competency on followers’ job performance through work engagement. Based on a sample of 248 subordinate–supervisor pairs, hierarchical regression analyses reveal that authentic leadership positively relates to followers’ task performance and organizational citizenship behavior ; leader competency moderates the relationship between authentic leadership and OCB; and followers’ work engagement mediates the main effect of authentic leadership and the interactive effect of authentic leadership and competency on followers’ task performance and OCB. All the three results are consistent with our hypotheses.

© The Author 2016.Topological quantum materials represent a new class of matter with both exotic physical phenomena and novel application potentials. Many Heusler compounds, which exhibit rich emergent properties such as unusual magnetism, superconductivity and heavy fermion behaviour, have been predicted to host non-trivial topological electronic structures. The coexistence of topological order and other unusual properties makes Heusler materials ideal platform to search for new topological quantum phases. By carrying out angle-resolved photoemission spectroscopy and ab initio calculations on rare-earth half-Heusler compounds LnPtBi, we directly observe the unusual topological surface states on these materials, establishing them as first members with non-trivial topological electronic structure in this class of materials. Moreover, as LnPtBi compounds are non-centrosymmetric superconductors, our discovery further highlights them as promising candidates of topological superconductors.

To better determine the history of modern birds, we performed a genome-scale phylogenetic analysis of 48 species representing all orders of Neoaves using phylogenomic methods created to handle genome-scale data.We recovered a highly resolved tree that confirms previously controversial sister or close relationships.We identified the first divergence in Neoaves, two groups we named Passerea and Columbea, representing independent lineages of diverse and convergently evolved land and water bird species. Among Passerea, we infer the common ancestor of core landbirds to have been an apex predator and confirm independent gains of vocal learning. Among Columbea, we identify pigeons and flamingoes as belonging to sister clades. Even with whole genomes, some of the earliest branches in Neoaves proved challenging to resolve, which was best explained by massive protein-coding sequence convergence and high levels of incomplete lineage sorting that occurred during a rapid radiation after the Cretaceous-Paleogene mass extinction event about 66 million years ago.

© 2013 Author. Nonlinear all-X-ray signals that involve large core-atom separation compared to the X-ray wavelengths may not be described by the dipole approximation since they contain additional phase factors. Expressions for the rotationally averaged 2D X-ray photon echo signals from randomly oriented systems that take this positiondependent phase into account for arbitrary ratio between the core separation and the resonant wavelength are presented. Application is made to the Se K-edge of a selenium dipeptide system.

Most MRI studies of Alzheimer's disease and frontotemporal dementia have assessed structural, perfusion and diffusion abnormalities separately while ignoring the relationships across imaging modalities. This paper aimed to assess brain gray and white matter abnormalities jointly to elucidate differences in abnormal MRI patterns between the diseases. Twenty AD, 20 FTD patients, and 21 healthy control subjects were imaged using a 4Tesla MRI. GM loss and GM hypoperfusion were measured using high-resolution T1 and arterial spin labeling MRI. WM degradation was measured with diffusion tensor imaging. Using a new analytical approach, the study found greater WM degenerations in FTD than AD at mild abnormality levels. Furthermore, the GM loss and WM degeneration exceeded the reduced perfusion in FTD whereas, in AD, structural and functional damages were similar. Joint assessments of multimodal MRI have potential value to provide new imaging markers for improved differential diagnoses between FTD and AD. Copyright © 2011 Yu Zhang et al.

© 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 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.

© 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.