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Showing papers by "Tsinghua University published in 2011"


Proceedings Article
01 Jan 2011
TL;DR: The design of Kaldi is described, a free, open-source toolkit for speech recognition research that provides a speech recognition system based on finite-state automata together with detailed documentation and a comprehensive set of scripts for building complete recognition systems.
Abstract: We describe the design of Kaldi, a free, open-source toolkit for speech recognition research. Kaldi provides a speech recognition system based on finite-state automata (using the freely available OpenFst), together with detailed documentation and a comprehensive set of scripts for building complete recognition systems. Kaldi is written is C++, and the core library supports modeling of arbitrary phonetic-context sizes, acoustic modeling with subspace Gaussian mixture models (SGMM) as well as standard Gaussian mixture models, together with all commonly used linear and affine transforms. Kaldi is released under the Apache License v2.0, which is highly nonrestrictive, making it suitable for a wide community of users.

5,857 citations


Journal ArticleDOI
TL;DR: Density functional theory calculations show that the high catalytic activity correlates with the partially vacant 5d orbitals of the positively charged, high-valent Pt atoms, which help to reduce both the CO adsorption energy and the activation barriers for CO oxidation.
Abstract: Platinum-based heterogeneous catalysts are critical to many important commercial chemical processes, but their efficiency is extremely low on a per metal atom basis, because only the surface active-site atoms are used. Catalysts with single-atom dispersions are thus highly desirable to maximize atom efficiency, but making them is challenging. Here we report the synthesis of a single-atom catalyst that consists of only isolated single Pt atoms anchored to the surfaces of iron oxide nanocrystallites. This single-atom catalyst has extremely high atom efficiency and shows excellent stability and high activity for both CO oxidation and preferential oxidation of CO in H-2. Density functional theory calculations show that the high catalytic activity correlates with the partially vacant 5d orbitals of the positively charged, high-valent Pt atoms, which help to reduce both the CO adsorption energy and the activation barriers for CO oxidation.

4,446 citations


Proceedings ArticleDOI
20 Jun 2011
TL;DR: This work proposes a regional contrast based saliency extraction algorithm, which simultaneously evaluates global contrast differences and spatial coherence, and consistently outperformed existing saliency detection methods.
Abstract: Automatic estimation of salient object regions across images, without any prior assumption or knowledge of the contents of the corresponding scenes, enhances many computer vision and computer graphics applications. We introduce a regional contrast based salient object detection algorithm, which simultaneously evaluates global contrast differences and spatial weighted coherence scores. The proposed algorithm is simple, efficient, naturally multi-scale, and produces full-resolution, high-quality saliency maps. These saliency maps are further used to initialize a novel iterative version of GrabCut, namely SaliencyCut, for high quality unsupervised salient object segmentation. We extensively evaluated our algorithm using traditional salient object detection datasets, as well as a more challenging Internet image dataset. Our experimental results demonstrate that our algorithm consistently outperforms 15 existing salient object detection and segmentation methods, yielding higher precision and better recall rates. We also show that our algorithm can be used to efficiently extract salient object masks from Internet images, enabling effective sketch-based image retrieval (SBIR) via simple shape comparisons. Despite such noisy internet images, where the saliency regions are ambiguous, our saliency guided image retrieval achieves a superior retrieval rate compared with state-of-the-art SBIR methods, and additionally provides important target object region information.

3,653 citations


Journal ArticleDOI
TL;DR: An asymmetric supercapacitor with high energy density has been developed successfully using graphene/MnO2 composite as positive electrode and activated carbon nanofibers (ACN) as negative electrode in a neutral aqueous Na2SO4 electrolyte as mentioned in this paper.
Abstract: Asymmetric supercapacitor with high energy density has been developed successfully using graphene/MnO2 composite as positive electrode and activated carbon nanofibers (ACN) as negative electrode in a neutral aqueous Na2SO4 electrolyte. Due to the high capacitances and excellent rate performances of graphene/MnO2 and ACN, as well as the synergistic effects of the two electrodes, such asymmetric cell exhibits superior electrochemical performances. An optimized asymmetric supercapacitor can be cycled reversibly in the voltage range of 0–1.8 V, and exhibits maximum energy density of 51.1 Wh kg−1, which is much higher than that of MnO2//DWNT cell (29.1 Wh kg−1). Additionally, graphene/MnO2//ACN asymmetric supercapacitor exhibits excellent cycling durability, with 97% specific capacitance retained even after 1000 cycles. These encouraging results show great potential in developing energy storage devices with high energy and power densities for practical applications.

1,768 citations


Journal ArticleDOI
TL;DR: Graphene, a one-atom layer of graphite, possesses a unique two-dimensional (2D) structure, high conductivity and charge carrier mobility, huge specific surface area, high transparency and great mechanical strength as mentioned in this paper.
Abstract: Graphene, a one-atom layer of graphite, possesses a unique two-dimensional (2D) structure, high conductivity and charge carrier mobility, huge specific surface area, high transparency and great mechanical strength. Thus, it is expected to be an ideal material for energy storage and conversion. During the past several years, a variety of graphene based materials (GBMs) have been successfully prepared and applied in supercapacitors, lithium ion batteries, water splitting, electrocatalysts for fuel cells, and solar cells. In this review, we will summarize the recent advances in the synthesis and applications of GBMs in these energy related systems. The challenges and prospects of graphene based new energy materials are also discussed.

1,750 citations


Journal ArticleDOI
TL;DR: This paper systematically reviews the recent modeling developments for estimating the RUL and focuses on statistical data driven approaches which rely only on available past observed data and statistical models.

1,667 citations


Journal ArticleDOI
TL;DR: This Review tries to summarize what remarkable progress in multiferroic magnetoelectric composite systems has been achieved in most recent few years, with emphasis on thin films; and to describe unsolved issues and new device applications which can be controlled both electrically and magnetically.
Abstract: Multiferroic magnetoelectric composite systems such as ferromagnetic-ferroelectric heterostructures have recently attracted an ever-increasing interest and provoked a great number of research activities, driven by profound physics from coupling between ferroelectric and magnetic orders, as well as potential applications in novel multifunctional devices, such as sensors, transducers, memories, and spintronics. In this Review, we try to summarize what remarkable progress in multiferroic magnetoelectric composite systems has been achieved in most recent few years, with emphasis on thin films; and to describe unsolved issues and new device applications which can be controlled both electrically and magnetically.

1,642 citations


Journal ArticleDOI
TL;DR: To facilitate the application of graphene in nanodevices and to effectively tune the bandgap of graphenes, a promising approach is to convert the 2D graphene sheets into 0D graphene quantum dots (GQDs).
Abstract: Graphene, the two-dimensional (2D) single-atom carbon sheet, has attracted tremendous research interest due to its large surface area, high carrier transport mobility, superior mechanical fl exibility and excellent thermal/chemical stability. [ 1 ] In particular, its high transport mobility [ 2 , 3 ] and environmentally friendly nature meet important requirements in the fabrication of optoelectronic devices. Apart from the conducting fi lm [ 4 , 5 ] and transparent anode [ 6 ] developed previously, its high mobility renders it a promising alternative as an electron-accepting material for photovoltaic device applications. However, the easy aggregation and the poor dispersion of 2D graphene sheets in common solvents limit its application in such devices. Although effort has been made to prepare solution-processable functionalized graphenes (SPFGs), [ 7 ] the non-uniform size and shape, on a scale of several hundred nanometers and even micrometers of SPFGs, remain big challenges for the fabrication of highperformance photovoltaic cells with active layer thicknesses of only nanometer scale. To facilitate the application of graphene in nanodevices and to effectively tune the bandgap of graphenes, a promising approach is to convert the 2D graphene sheets into 0D graphene quantum dots (GQDs). Apart from unique electron transportation properties, [ 8 ] new phenomena from GQDs associated with quantum confi nement and edge effects are expected. [ 9 ] QDs are important for various applications in bioimaging, [ 10 ] lasing, [ 11 ]

1,456 citations



Journal ArticleDOI
TL;DR: The early years of this period were chronicled in the Quarkonium Working Group (QWG) CERN Yellow Report (YR) in 2004, which presented a comprehensive review of the status of the field at that time and provided specific recommendations for further progress as mentioned in this paper.
Abstract: A golden age for heavy-quarkonium physics dawned a decade ago, initiated by the confluence of exciting advances in quantum chromodynamics (QCD) and an explosion of related experimental activity. The early years of this period were chronicled in the Quarkonium Working Group (QWG) CERN Yellow Report (YR) in 2004, which presented a comprehensive review of the status of the field at that time and provided specific recommendations for further progress. However, the broad spectrum of subsequent breakthroughs, surprises, and continuing puzzles could only be partially anticipated. Since the release of the YR, the BESII program concluded only to give birth to BESIII; the B-factories and CLEO-c flourished; quarkonium production and polarization measurements at HERA and the Tevatron matured; and heavy-ion collisions at RHIC have opened a window on the deconfinement regime. All these experiments leave legacies of quality, precision, and unsolved mysteries for quarkonium physics, and therefore beg for continuing investigations at BESIII, the LHC, RHIC, FAIR, the Super Flavor and/or Tau-Charm factories, JLab, the ILC, and beyond. The list of newly found conventional states expanded to include h(c)(1P), chi(c2)(2P), B-c(+), and eta(b)(1S). In addition, the unexpected and still-fascinating X(3872) has been joined by more than a dozen other charmonium- and bottomonium-like "XYZ" states that appear to lie outside the quark model. Many of these still need experimental confirmation. The plethora of new states unleashed a flood of theoretical investigations into new forms of matter such as quark-gluon hybrids, mesonic molecules, and tetraquarks. Measurements of the spectroscopy, decays, production, and in-medium behavior of c (c) over bar, b (b) over bar, and b (c) over bar bound states have been shown to validate some theoretical approaches to QCD and highlight lack of quantitative success for others. Lattice QCD has grown from a tool with computational possibilities to an industrial-strength effort now dependent more on insight and innovation than pure computational power. New effective field theories for the description of quarkonium in different regimes have been developed and brought to a high degree of sophistication, thus enabling precise and solid theoretical predictions. Many expected decays and transitions have either been measured with precision or for the first time, but the confusing patterns of decays, both above and below open-flavor thresholds, endure and have deepened. The intriguing details of quarkonium suppression in heavy-ion collisions that have emerged from RHIC have elevated the importance of separating hot- and cold-nuclear-matter effects in quark-gluon plasma studies. This review systematically addresses all these matters and concludes by prioritizing directions for ongoing and future efforts.

1,354 citations


Journal ArticleDOI
TL;DR: This review selectively analyzes current advances in the field of graphene bioapplications, and focuses on the biofunctionalization of graphene for biological applications, fluorescence-resonance-energy-transfer-based biosensor development by using graphene or graphene-based nanomaterials, and the investigation of grapheneor graphene- based nanommaterials for living cell studies.

Journal ArticleDOI
TL;DR: Graphene hybridized ZnO photocatalyst showed enhanced photocatalytic activity for the degradation of organic dye, which was attributed to the high migration efficiency of photo-induced electrons and the inhibited charge carriers recombination due to the electronic interaction between ZnOs and graphene.
Abstract: Graphene hybridized with ZnO could produce an efficient photocatalyst. The ZnO nanoparticles were firstly coated with an appropriate amount of graphene oxide, the graphene oxide was then in situ reduced to form the ZnO/graphene composite. Graphene hybridized ZnO photocatalyst showed enhanced photocatalytic activity for the degradation of organic dye. The degree of photocatalytic activity enhancement strongly depended on the coverage of graphene on the surface of ZnO nanoparticles. The sample of 2 wt% graphene hybridized ZnO showed the highest photocatalytic activity, which was about 4 times as that of pristine ZnO. The enhancement of photocatalytic activity was attributed to the high migration efficiency of photo-induced electrons and the inhibited charge carriers recombination due to the electronic interaction between ZnO and graphene. The electronic interaction was systematically studied and confirmed by the photoelectrochemical measurements.

Journal ArticleDOI
TL;DR: This system is used to record spatial properties of cat brain activity in vivo, including sleep spindles, single-trial visual evoked responses and electrographic seizures, and it is found that seizures may manifest as recurrent spiral waves that propagate in the neocortex.
Abstract: Arrays of electrodes for recording and stimulating the brain are used throughout clinical medicine and basic neuroscience research, yet are unable to sample large areas of the brain while maintaining high spatial resolution because of the need to individually wire each passive sensor at the electrode-tissue interface. To overcome this constraint, we developed new devices that integrate ultrathin and flexible silicon nanomembrane transistors into the electrode array, enabling new dense arrays of thousands of amplified and multiplexed sensors that are connected using fewer wires. We used this system to record spatial properties of cat brain activity in vivo, including sleep spindles, single-trial visual evoked responses and electrographic seizures. We found that seizures may manifest as recurrent spiral waves that propagate in the neocortex. The developments reported here herald a new generation of diagnostic and therapeutic brain-machine interface devices.

Journal ArticleDOI
TL;DR: In this paper, a series of high-entropy alloys with different Al and Ti contents were designed, and their phase and microstructure were investigated, the adhesive wear behavior and mechanism were also studied and compared with the conventional wear-resistant steels SUJ2 and SKH51.

Journal ArticleDOI
TL;DR: In this article, a ZnO photocatalyst was hybridized with graphite-like C3N4 via a monolayer-dispersed method, and the photocurrent of C 3N4/ZnO was enhanced by 5 times under UV irradiation and a photocurrent under visible light irradiation.
Abstract: A ZnO photocatalyst was hybridized with graphite-like C3N4via a monolayer-dispersed method. After hybridization with C3N4, the photocurrent of ZnO was enhanced by 5 times under UV irradiation and a photocurrent under visible light irradiation was observed. The photocatalytic activity of C3N4/ZnO under UV irradiation was increased by 3.5 times, the visible light photocatalytic activity was generated and the photocorrosion of ZnO was suppressed completely after ZnO was hybridized with C3N4. The enhancement in performance and photocorrosion inhibition under UV irradiation was induced by the high separation efficiency of photoinduced holes from ZnO to the HOMO of C3N4. Under visible light irradiation, the electron excited from the HOMO to the LUMO of C3N4 could directly inject into the CB of ZnO, making C3N4/ZnO present visible light photocatalytic activity. The optimum synergetic effect of C3N4/ZnO was found at a weight ratio of 3%, which corresponded to a monolayer dispersion of C3N4 on the surface of ZnO.

Journal ArticleDOI
TL;DR: This review highlights the recent progress in the chemical synthesis of bimetallic NCs and the control over morphology, size, composition, and structure of bimodal NCs as well as the exploration of their properties and applications.
Abstract: Bimetallic nanocrystals (NCs) with core/shell, heterostructure, or inter-metallic and alloyed structures are emerging as more important materials than monometallic NCs They are expected to display not only a combination of the properties associated with two distinct metals, but also new properties and capabilities due to a synergy between the two metals More importantly, bimetallic NCs usually show composition-dependent surface structure and atomic segregation behavior, and therefore more interesting applied potentials in various fields including electronics, engineering, and catalysis Compared with monometallic NCs, preparation of bimetallic NCs is much more complicated and difficult to be achieved In recent years, researchers from many groups have made great efforts in this area This review highlights the recent progress in the chemical synthesis of bimetallic NCs The control over morphology, size, composition, and structure of bimetallic NCs as well as the exploration of their properties and applications are discussed

Journal ArticleDOI
TL;DR: In this progress report, the recent advancements in the studies of the composites of CCG and small molecules, polymers, inorganic nanoparticles or other carbon nanomaterials are reviewed.
Abstract: Graphene, a one-atom layer of graphite, possesses a unique two-dimensional structure and excellent mechanical, thermal, and electrical properties. Thus, it has been regarded as an important component for making various functional composite materials. Graphene can be prepared through physical, chemical and electrochemical approaches. Among them, chemical methods were tested to be effective for producing chemically converted graphene (CCG) from various precursors (such as graphite, carbon nanotubes, and polymers) in large scale and at low costs. Therefore, CCG is more suitable for synthesizing high-performance graphene based composites. In this progress report, we review the recent advancements in the studies of the composites of CCG and small molecules, polymers, inorganic nanoparticles or other carbon nanomaterials. The methodology for preparing CCG and its composites has been summarized. The applications of CCG-based functional composite materials are also discussed.

Journal ArticleDOI
TL;DR: In this article, the properties of butanol are compared with the conventional gasoline, diesel fuel, and some widely used biofuels, i.e. methanol, ethanol, biodiesel.
Abstract: Butanol is a very competitive renewable biofuel for use in internal combustion engines given its many advantages. In this review, the properties of butanol are compared with the conventional gasoline, diesel fuel, and some widely used biofuels, i.e. methanol, ethanol, biodiesel. The comparison of fuel properties indicates that n-butanol has the potential to overcome the drawbacks brought by low-carbon alcohols or biodiesel. Then, the development of butanol production is reviewed and various methods for increasing fermentative butanol production are introduced in detailed, i.e. metabolic engineering of the Clostridia, advanced fermentation technique. The most costive part of the fermentation is the substrate, so methods involved in renewed substrates are also mentioned. Next, the applications of butanol as a biofuel are summarized from three aspects: (1) fundamental combustion experiments in some well-defined burning reactors; (2) a substitute for gasoline in spark ignition engine; (3) a substitute for diesel fuel in compression ignition engine. These studies demonstrate that butanol, as a potential second generation biofuel, is a better alternative for the gasoline or diesel fuel, from the viewpoints of combustion characteristics, engine performance, and exhaust emissions. However, butanol has not been intensively studied when compared to ethanol or biodiesel, for which considerable numbers of reports are available. Finally, some challenges and future research directions are outlined in the last section of this review.

Journal ArticleDOI
25 Jan 2011-ACS Nano
TL;DR: This work demonstrates a green and facile approach to the synthesis of graphene nanosheets based on Fe reduction of exfoliated graphite oxide, resulting in a substantial removal of oxygen functionalities of thegraphite oxide.
Abstract: The synthesis of graphene nanosheets from graphite oxide typically involves harmful chemical reductants that are undesirable for most practical applications of graphene. Here, we demonstrate a green and facile approach to the synthesis of graphene nanosheets based on Fe reduction of exfoliated graphite oxide, resulting in a substantial removal of oxygen functionalities of the graphite oxide. More interestingly, the resulting graphene nanosheets with residual Fe show a high adsorption capacity of 111.62 mg/g for methylene blue at room temperature, as well as easy magnetic separation from the solution. This approach offers a potential for cost-effective, environmentally friendly, and large-scale production of graphene nanosheets.

Journal ArticleDOI
J. Abadie1, B. P. Abbott1, R. Abbott1, T. D. Abbott2  +611 moreInstitutions (63)
TL;DR: In this paper, the authors demonstrate the squeezed-light enhancement of GEO600, which will be the GW observatory operated by the LIGO Scientific Collaboration in its search for GWs for the next 3-4 years.
Abstract: Around the globe several observatories are seeking the first direct detection of gravitational waves (GWs). These waves are predicted by Einstein’s general theory of relativity1 and are generated, for example, by black-hole binary systems2. Present GW detectors are Michelson-type kilometre-scale laser interferometers measuring the distance changes between mirrors suspended in vacuum. The sensitivity of these detectors at frequencies above several hundred hertz is limited by the vacuum (zero-point) fluctuations of the electromagnetic field. A quantum technology—the injection of squeezed light3—offers a solution to this problem. Here we demonstrate the squeezed-light enhancement of GEO 600, which will be the GW observatory operated by the LIGO Scientific Collaboration in its search for GWs for the next 3–4 years. GEO 600 now operates with its best ever sensitivity, which proves the usefulness of quantum entanglement and the qualification of squeezed light as a key technology for future GW astronomy4.

Journal ArticleDOI
TL;DR: In this article, the observed luminosity functions (LFs) of supernovae are derived from the Lick Observatory Supernova Search (LOSS) data, and a complete sample is constructed, and the observed (uncorrected for host-galaxy extinction) luminosity function (LF) of SNe are derived.
Abstract: This is the second paper of a series in which we present new measurements of the observed rates of supernovae (SNe) in the local Universe, determined from the Lick Observatory Supernova Search (LOSS). In this paper, a complete SN sample is constructed, and the observed (uncorrected for host-galaxy extinction) luminosity functions (LFs) of SNe are derived. These LFs solve two issues that have plagued previous rate calculations for nearby SNe: the luminosity distribution of SNe and the host-galaxy extinction. We select a volume-limited sample of 175 SNe, collect photometry for every object, and fit a family of light curves to constrain the peak magnitudes and light-curve shapes. The volume-limited LFs show that they are not well represented by a Gaussian distribution. There are notable differences in the LFs for galaxies of different Hubble types (especially for SNe Ia). We derive the observed fractions for the different subclasses in a complete SN sample, and find significant fractions of SNe II-L (10%), IIb (12%), and IIn (9%) in the SN II sample. Furthermore, we derive the LFs and the observed fractions of different SN subclasses in a magnitudelimited survey with different observation intervals, and find that the LFs are enhanced at the high-luminosity end and appear more “standard” with smaller scatter, and that the LFs and fractions of SNe do not change significantly when the observation interval is shorter than 10 d. We also discuss the LFs in different galaxy sizes and inclinations, and for different SN subclasses. Some notable results are that there is not a strong correlation between the SN LFs and the host-galaxy size, but there might be a preference for SNe IIn to occur in small, late-type spiral galaxies. The LFs in different inclination bins do not provide strong evidence for extreme extinction in highly inclined galaxies, though the sample is still small. The LFs of different SN subclasses show significant differences. We also find that SNe Ibc and IIb come from more luminous galaxies than SNe II-P, while SNe IIn come from less luminous galaxies, suggesting a possible metallicity effect. The limitations and applications of our LFs are also discussed.

Journal ArticleDOI
28 Mar 2011-ACS Nano
TL;DR: Using density functional theory coupled with Boltzmann transport equation with relaxation time approximation, the electronic structure is investigated and the charge mobility for a new carbon allotrope, the graphdiyne for both the sheet and nanoribbons is predicted.
Abstract: Using density functional theory coupled with Boltzmann transport equation with relaxation time approximation, we investigate the electronic structure and predict the charge mobility for a new carbon allotrope, the graphdiyne for both the sheet and nanoribbons. It is shown that the graphdiyne sheet is a semiconductor with a band gap of 0.46 eV. The calculated in-plane intrinsic electron mobility can reach the order of 10(5) cm(2)/(V s) at room temperature, while the hole mobility is about an order of magnitude lower.

Journal ArticleDOI
TL;DR: In this paper, two types of low-temperature catalysts, the metal oxide catalyst and metal exchanged zeolite catalyst, were reviewed for selective catalytic reduction of NO x with ammonia (NH 3 -SCR) especially at temperature below 200°C.

Journal ArticleDOI
Chun Chen1, Bin Zhao1
TL;DR: In this article, the authors provide an up-to-date revision for both experiment and modeling on relationship between indoor and outdoor particles, using three different parameters: indoor/outdoor (I/O) ratio, infiltration factor and penetration factor.

Journal ArticleDOI
TL;DR: A review of recent advances in electrode material and a configuration of both the anode and cathode in MFCs are provided and the modification methods for the anodic electrode are summarized.

Journal ArticleDOI
TL;DR: This paper reports a new approach which makes use of embedded nitrogen and carbon atoms in metal substrate to prepare nitrogen-doped graphene (NG), and provides not only a better control over the doping density but also a potential advantage to precisely control the solid dopants at desired locations to achieve patterned doping.
Abstract: Graphene is the two-dimensional crystalline form of carbon whose extraordinary charge carrier mobility and other unique features hold great promise for nanoscale electronics. [ 1 ] Because graphene has no bandgap, however, its electrical conductivity cannot be completely controlled like classical semiconductor. Theoretical and experimental studies on graphene doping show the possibility of opening the bandgap and modulating conducting types by substituting carbon atoms with foreign atoms. [ 2 ] Graphene is easily p-doped by adsorbates like physisorbed oxygen molecules, but complementary doping (both n-type and p-type doping) is essential for functional device applications like complementary metal-oxidesemiconductor (CMOS) circuits. [ 3 ] Recently, a number of approaches have been proposed to synthesize nitrogen-doped graphene (NG), such as chemical vapor deposition (CVD), [ 2 a, 4 ] arc-discharge, [ 2 b, 5 ] and post treatments. [ 6 ] Here, we report a new approach which makes use of embedded nitrogen and carbon atoms in metal substrate to prepare NG. As doping is accompanied with the combination of carbon atoms into graphene during annealing process, N atoms can be substitutionally doped into the graphene lattice. Our method provides not only a better control over the doping density but also a potential advantage to precisely control the solid dopants at desired locations to achieve patterned doping. Our approach for NG synthesis is actually the enthusiastic utilization of the very common segregation phenomenon to turn the trace amount of carbon and nitrogen dissolved in bulk metals into NG. [ 7 ] Metals usually contain a trace amount of carbon impurities, which could be brought into evaporated metal fi lm during the electron beam deposition process. [7a, 8 ]

Journal ArticleDOI
TL;DR: A novel fluorescence resonance energy transfer method for nonenzymatic glucose determination has been developed by using the glucose-modified LaF(3):Ce(3+)/Tb(3+) nanocrystals and a simple and sensitive FRET biosensor for avidin is developed.
Abstract: Because of the potential applications of lanthanide-doped nanocrystals in display devices, optical communication, solid-state lasers, catalysis, and biological labeling, the controlled synthesis of these new nanomaterials has sparked considerable interest. Nanosized phosphorescent or optoelectronic devices usually exhibit novel properties, depending on their structures, shapes, and sizes, such as tunable wavelengths, rapid responses, and high efficiencies. Thus, the development of facile synthetic methods towards high-quality lanthanide-doped nanocrystals with uniform size and shape appears to be of key importance both for the exploration of their materials properties and for potential applications.This Account focuses on the recent development in our laboratory of the synthesis and applications of lanthanide-doped nanocrystals. Since 2005, when we proposed a general strategy for nanocrystal synthesis via a liquid−solid−solution process, a range of monodisperse and colloidal lanthanide-doped fluoride, oxi...

Journal ArticleDOI
TL;DR: In this paper, the authors classify possible quantum phases for one-dimensional matrix product states, which represent well the class of 1D gapped ground states, and find that in the absence of any symmetry all states are equivalent to trivial product states.
Abstract: Quantum many-body systems divide into a variety of phases with very different physical properties. The questions of what kinds of phases exist and how to identify them seem hard, especially for strongly interacting systems. Here we make an attempt to answer these questions for gapped interacting quantum spin systems whose ground states are short-range correlated. Based on the local unitary equivalence relation between short-range-correlated states in the same phase, we classify possible quantum phases for one-dimensional (1D) matrix product states, which represent well the class of 1D gapped ground states. We find that in the absence of any symmetry all states are equivalent to trivial product states, which means that there is no topological order in 1D. However, if a certain symmetry is required, many phases exist with different symmetry-protected topological orders. The symmetric local unitary equivalence relation also allows us to obtain some simple results for quantum phases in higher dimensions when some symmetries are present.

Journal ArticleDOI
01 Sep 2011-Mbio
TL;DR: A novel random matrix theory (RMT)-based conceptual framework is described to discern phylogenetic molecular ecological networks of microbial communities based on high-throughput metagenomic sequencing data, among the first to document that the network interactions among different phylogenetic populations in soil microbial communities were substantially changed by a global change such as an elevated CO2 level.
Abstract: Understanding the interactions among different species and their responses to environmental changes, such as ele- vated atmospheric concentrations of CO2, is a central goal in ecology but is poorly understood in microbial ecology. Here we describe a novel random matrix theory (RMT)-based conceptual framework to discern phylogenetic molecular ecological net- works using metagenomic sequencing data of 16S rRNA genes from grassland soil microbial communities, which were sampled from a long-term free-air CO2enrichment experimental facility at the Cedar Creek Ecosystem Science Reserve in Minnesota. Our experimental results demonstrated that an RMT-based network approach is very useful in delineating phylogenetic molecu- lar ecological networks of microbial communities based on high-throughput metagenomic sequencing data. The structure of the identified networks under ambient and elevated CO 2levels was substantially different in terms of overall network topology, net- work composition, node overlap, module preservation, module-based higher-order organization, topological roles of individual nodes, and network hubs, suggesting that the network interactions among different phylogenetic groups/populations were markedly changed. Also, the changes in network structure were significantly correlated with soil carbon and nitrogen contents, indicating the potential importance of network interactions in ecosystem functioning. In addition, based on network topology, microbial populations potentially most important to community structure and ecosystem functioning can be discerned. The novel approach described in this study is important not only for research on biodiversity, microbial ecology, and systems micro- biology but also for microbial community studies in human health, global change, and environmental management. IMPORTANCE The interactions among different microbial populations in a community play critical roles in determining ecosys- tem functioning, but very little is known about the network interactions in a microbial community, owing to the lack of appro- priate experimental data and computational analytic tools. High-throughput metagenomic technologies can rapidly produce a massive amount of data, but one of the greatest difficulties is deciding how to extract, analyze, synthesize, and transform such a vast amount of information into biological knowledge. This study provides a novel conceptual framework to identify microbial interactions and key populations based on high-throughput metagenomic sequencing data. This study is among thefirst to doc- ument that the network interactions among different phylogenetic populations in soil microbial communities were substantially changed by a global change such as an elevated CO2level. The framework developed will allow microbiologists to address re- search questions which could not be approached previously, and hence, it could represent a new direction in microbial ecology research.

Journal ArticleDOI
TL;DR: It is speculated that the JA-induced degradation of Jaz proteins abolishes the interactions of JAZ proteins with bHLH and MYB factors, allowing the transcriptional function of WD-repeat/bHLH/MYB complexes, which subsequently activate respective downstream signal cascades to modulate anthocyanin accumulation and trichome initiation.
Abstract: Jasmonates (JAs) mediate plant responses to insect attack, wounding, pathogen infection, stress, and UV damage and regulate plant fertility, anthocyanin accumulation, trichome formation, and many other plant developmental processes. Arabidopsis thaliana Jasmonate ZIM-domain (JAZ) proteins, substrates of the CORONATINE INSENSITIVE1 (COI1)–based SCF COI1 complex, negatively regulate these plant responses. Little is known about the molecular mechanism for JA regulation of anthocyanin accumulation and trichome initiation. In this study, we revealed that JAZ proteins interact with bHLH (Transparent Testa8, Glabra3 [GL3], and Enhancer of Glabra3 [EGL3]) and R2R3 MYB transcription factors (MYB75 and Glabra1), essential components of WD-repeat/bHLH/MYB transcriptional complexes, to repress JA-regulated anthocyanin accumulation and trichome initiation. Genetic and physiological evidence showed that JA regulates WD-repeat/bHLH/MYB complex-mediated anthocyanin accumulation and trichome initiation in a COI1 -dependent manner. Overexpression of the MYB transcription factor MYB75 and bHLH factors ( GL3 and EGL3 ) restored anthocyanin accumulation and trichome initiation in the coi1 mutant, respectively. We speculate that the JA-induced degradation of JAZ proteins abolishes the interactions of JAZ proteins with bHLH and MYB factors, allowing the transcriptional function of WD-repeat/bHLH/MYB complexes, which subsequently activate respective downstream signal cascades to modulate anthocyanin accumulation and trichome initiation.