Showing papers by "National Tsing Hua University published in 2010"

Transition-metal phosphors with cyclometalating ligands: fundamentals and applications

Abstract: One goal of this critical review is to provide advanced methodologies for systematic preparation of transition-metal based phosphors that show latent applications in the field of organic light emitting diodes (OLEDs). We are therefore reviewing various types of cyclometalating chelates for which the favorable metal–chelate bonding interaction, on the one hand, makes the resulting phosphorescent complexes highly emissive in both fluid and solid states at room temperature. On the other hand, fine adjustment of ligand-centered π–π* electronic transitions allows tuning of emission wavelength across the whole visible spectrum. The cyclometalating chelates are then classified according to types of cyclometalating groups, i.e. either aromatic C–H or azolic N–H fragment, and the adjacent donor fragment involved in the formation of metallacycles; the latter is an N-containing heterocycle, N-heterocyclic (NHC) carbene fragment or even diphenylphosphino group. These cyclometalating ligands are capable to react with heavy transition-metal elements, namely: Ru(II), Os(II), Ir(III) and Pt(II), to afford a variety of highly emissive phosphors, for which the photophysical properties as a function of chelate or metal characteristics are systematically discussed. Using Ir(III) complexes as examples, the C^N chelates possessing both C–H site and N-heterocyclic donor group are essential for obtaining phosphors with emission ranging from sky-blue to saturated red, while the N^N chelates such as 2-pyridyl-C-linked azolates are found useful for serving as true-blue chromophores due to their increased ligand-centered π–π* energy gap. Lastly, the remaining NHC carbene and benzyl phosphine chelates are highly desirable to serve as ancillary chelates in localizing the electronic transition between the metal and remaining lower energy chromophoric chelates. As for the potential opto-electronic applications, many of them exhibit remarkable performance data, which are convincing to pave a broad avenue for further development of all types of phosphorescent displays and illumination devices (94 references).

The size of the proton

Abstract: Considering that the proton is a basic subatomic component of all ordinary matter — as well as being ubiquitous in its solo role as the hydrogen ion H+ — there are some surprising gaps in our knowledge of its structure and behaviour. A collaborative project to determine the root-mean-square charge radius of the proton to better than the 1% accuracy of the current 'best' value suggests that those knowledge gaps may be greater than was thought. The new determination comes from a technically challenging spectroscopic experiment — the measurement of the Lamb shift (the energy difference between a specific pair of energy states) in 'muonic hydrogen', an exotic atom in which the electron is replaced by its heavier twin, the muon. The result is unexpected: a charge radius about 4% smaller than the previous value. The discrepancy remains unexplained. Possible implications are that the value of the most accurately determined fundamental constant, the Rydberg constant, will need to be revised — or that the validity of quantum electrodynamics theory is called into question. Here, a technically challenging spectroscopic experiment is described: the measurement of the muonic Lamb shift. The results lead to a new determination of the charge radius of the proton. The new value is 5.0 standard deviations smaller than the previous world average, a large discrepancy that remains unexplained. Possible implications of the new finding are that the value of the Rydberg constant will need to be revised, or that the validity of quantum electrodynamics theory is called into question. The proton is the primary building block of the visible Universe, but many of its properties—such as its charge radius and its anomalous magnetic moment—are not well understood. The root-mean-square charge radius, rp, has been determined with an accuracy of 2 per cent (at best) by electron–proton scattering experiments1,2. The present most accurate value of rp (with an uncertainty of 1 per cent) is given by the CODATA compilation of physical constants3. This value is based mainly on precision spectroscopy of atomic hydrogen4,5,6,7 and calculations of bound-state quantum electrodynamics (QED; refs 8, 9). The accuracy of rp as deduced from electron–proton scattering limits the testing of bound-state QED in atomic hydrogen as well as the determination of the Rydberg constant (currently the most accurately measured fundamental physical constant3). An attractive means to improve the accuracy in the measurement of rp is provided by muonic hydrogen (a proton orbited by a negative muon); its much smaller Bohr radius compared to ordinary atomic hydrogen causes enhancement of effects related to the finite size of the proton. In particular, the Lamb shift10 (the energy difference between the 2S1/2 and 2P1/2 states) is affected by as much as 2 per cent. Here we use pulsed laser spectroscopy to measure a muonic Lamb shift of 49,881.88(76) GHz. On the basis of present calculations11,12,13,14,15 of fine and hyperfine splittings and QED terms, we find rp = 0.84184(67) fm, which differs by 5.0 standard deviations from the CODATA value3 of 0.8768(69) fm. Our result implies that either the Rydberg constant has to be shifted by −110 kHz/c (4.9 standard deviations), or the calculations of the QED effects in atomic hydrogen or muonic hydrogen atoms are insufficient.

A Cost-Effective Supercapacitor Material of Ultrahigh Specific Capacitances: Spinel Nickel Cobaltite Aerogels from an Epoxide-Driven Sol–Gel Process

Abstract: Adv. Mater. 2010, 22, 347–351 2010 WILEY-VCH Verlag Gm The ever worsening energy depletion and global warming issues call for not only urgent development of clean alternative energies and emission control of global warming gases, but also more advanced energy storage and management devices. Supercapacitors, offering transient but extremely high powers, are probably the most important next generation energy storage device. To boost the specific capacitance of supercapacitors, the specific surface area of the electrode materials needs to be as high as possible to promote the electric double-layer capacitances and to accommodate a large amount of superficial electroactive species to participate in faradaic redox reactions. In addition, suitable pore sizes, 2–5 nm, of the porous electrode materials are critical to ease the mass transfer of electrolytes within the pores for fast redox reactions and double-layer charging/discharging. Aerogels are a class of mesoporous materials possessing highly specific surface areas and porosities, from which promising applications in a wide range of areas have been investigated. They are composed of 3D networks of nanoparticles with an average pore size of several nanometers, adjustably falling within the optimal pore sizes of 2–5 nm. Consequently, aerogels are a promising candidate for supercapacitor applications. As to the electrode material, electroactive materials possessing multiple oxidation states/structures that enable rich redox reactions for pseudocapacitance generation are desirable for supercapacitors. Transition metal oxides are such a class of materials that have drawn extensive and intensive research attention in recent years. Among them, RuO2 is themost prominent one with a specific capacitance as high as 1580F g , probably the highest ever reported. The commercialization of RuO2 based supercapacitors, however, is not promising because of the high cost and rareness of Ru. Spinel nickel cobaltite (NiCo2O4) is a low-cost, environmentally friendly transition metal oxide, which has been employed in electrocatalytic water splitting (oxygen evolution) and lithium ion batteries. Its application in supercapacitors, however, received much less attention. Nickel cobaltite has been reported to possess a much better electronic conductivity, at least two orders of magnitude higher, and higher electrochemical activity than those of nickel oxides and cobalt oxides. It is expected to offer richer redox reactions, including contributions from both nickel and cobalt ions, than the two corresponding single component oxides and is a potential cost-effective alternative for RuO2. Based on the above considerations, one would expect nickel cobaltite aerogels, with anticipated good electronic conductivity, low diffusion resistance to protons/cations, easy electrolyte penetration, and high electroactive areas to be a promising candidate for the construction of next-generation, ultrahighperformance supercapacitors. Traditionally, aerogels are prepared with sol–gel processes by taking corresponding alkoxides as the precursors. Alkoxides are generally expensive and sensitive to moisture and heat, requiring careful handling. Recently, to tackle these drawbacks, the epoxide synthetic route, enabling the use of low-cost and stable metal salts as the precursors, was successfully developed to prepare metal oxide aerogels. In this work, we reported the first successful preparation of nickel cobaltite aerogels with the epoxide-driven sol–gel process. The effects of the post-gel-drying calcination temperature on the critical properties of the product aerogels were investigated. At a starting Ni/Co ratio of 0.5 and a post-gel-drying calcination temperature of 200 8C, an optimal combination of composition, crystallinity, specific surface area, pore volume, and pore size was achieved to afford the nickel cobaltite aerogels that showed an extremely high-specific capacitance of 1400 F g 1 under a mass loading of 0.4 mg cm 2 at a sweep rate of 25mV s 1 within a potential window of 0.04 to 0.52V in a 1 M NaOH solution. The excellent reversibility and cycle stability of the product aerogels were also demonstrated. A stoichiometric mixture of nickel and cobalt chlorides was used as the precursor for the preparation of the nickel cobaltite aerogels. After the gel is dried in supercritical carbon dioxide, a post-gel-drying calcination is generally required to acquire preferred composition and/or better crystallinity of the products. The post-gel-drying calcination temperature is thus an important processing parameter to be studied. For referring convenience, we term the product aerogels as Ni–Co–O–T, with Tdenoting the calcination temperature. The T block is omitted for as-prepared samples. Also, for comparison purposes, NiO and Co3O4 aerogels were prepared, termed as Ni–O–T and Co–O–T, respectively. Figure 1a shows the X-ray diffraction (XRD) patterns of the as-prepared product aerogels and those samples calcined at 200 and 300 8C. Surprisingly, nickel cobaltite was formed even at the as-prepared condition. The diffraction peak located at the 2u value

A Highly Efficient Universal Bipolar Host for Blue, Green, and Red Phosphorescent OLEDs

Abstract: In thedesignofhighlyefficientphosphorescentdevices,theselectionofa proper material for each layer is of great importance. Inparticular, the choice of host material for the phosphorescentdopant in the emitting layer fundamentally affects the efficiencyof energy transfer from the host to the dopant. In general, toprevent back energy transfer from a dopant to the host, the hostmatrix should have a larger triplet energy gap (E

In vivo imaging and toxicity assessments of fluorescent nanodiamonds in Caenorhabditis elegans.

Abstract: Nanoscale carbon materials hold great promise for biotechnological and biomedical applications. Fluorescent nanodiamond (FND) is a recent new addition to members of the nanocarbon family. Here, we report long-term in vivo imaging of FNDs in Caenorhabditis elegans (C. elegans) and explore the nano-biointeractions between this novel nanomaterial and the model organism. FNDs are introduced into wild-type C. elegans by either feeding them with colloidal FND solution or microinjecting FND suspension into the gonads of the worms. On feeding, bare FNDs stay in the intestinal lumen, while FNDs conjugated with biomolecules (such as dextran and bovine serum albumin) are absorbed into the intestinal cells. On microinjection, FNDs are dispersed in the gonad and delivered to the embryos and eventually into the hatched larvae in the next generation. The toxicity assessments, performed by employing longevity and reproductive potential as physiological indicators and measuring stress responses with use of reporter genes,...

Dynamic regulation of mitochondrial fission through modification of the dynamin-related protein Drp1

Abstract: Mitochondria in cells comprise a tubulovesicular network shaped continuously by complementary fission and fusion events. The mammalian Drp1 protein plays a key role in fission, while Mfn1, Mfn2, and OPA1 are required for fusion. Shifts in the balance between these opposing processes can occur rapidly, indicating that modifications to these proteins may regulate mitochondrial membrane dynamics. We highlight posttranslational modifications of the mitochondrial fission protein Drp1, for which these regulatory mechanisms are best characterized. This dynamin-related GTPase undergoes a number of steps to mediate mitochondrial fission, including translocation from cytoplasm to the mitochondrial outer membrane, higher-order assembly into spirals, GTP hydrolysis associated with a conformational change and membrane deformation, and ultimately disassembly. Many of these steps may be influenced by covalent modification of Drp1. We discuss the dynamic nature of Drp1 modifications and how they contribute not only to the normal regulation of mitochondrial division, but also to neuropathologic processes.

To Explain or To Predict

Abstract: Statistical modeling is a powerful tool for developing and testing theories by way of causal explanation, prediction, and description. In many disciplines there is near-exclusive use of statistical modeling for causal explanation and the assumption that models with high explanatory power are inherently of high predictive power. Conflation between explanation and prediction is common, yet the distinction must be understood for progressing scientific knowledge. While this distinction has been recognized in the philosophy of science, the statistical literature lacks a thorough discussion of the many differences that arise in the process of modeling for an explanatory versus a predictive goal. The purpose of this paper is to clarify the distinction between explanatory and predictive modeling, to discuss its sources, and to reveal the practical implications of the distinction to each step in the modeling process.

Ultrathin compound semiconductor on insulator layers for high-performance nanoscale transistors

Abstract: Compound semiconductor materials such as gallium arsenide and indium arsenide have outstanding electronic properties, but are costly to process and cannot, on their own, compete with silicon when it comes to low-cost fabrication. But as the relentless miniaturization of silicon electronics is reaching its limits, an alternative route of enhanced device performance is becoming more attractive: the integration of compound semiconductors within silicon. Ali Javey and colleagues now present a promising new concept to integrate ultrathin layers of single-crystal indium arsenide on silicon-based substrates with an epitaxial transfer method, a technique borrowed from large-area optoelectronics. With this technique, involving the use of an elastomeric stamp to lift off indium arsenide nanowires and transfer them to a silicon-based substrate, the authors fabricate thin film transistors with excellent device performance. A potential route to enhancing the performance of electronic devices is to integrate compound semiconductors, which have superior electronic properties, within silicon, which is cheap to process. These authors present a promising new concept to integrate ultrathin layers of single-crystal indium arsenide on silicon-based substrates with an epitaxial transfer method borrowed from large-area optoelectronics. With this technique, the authors fabricate thin-film transistors with excellent device performance. Over the past several years, the inherent scaling limitations of silicon (Si) electron devices have fuelled the exploration of alternative semiconductors, with high carrier mobility, to further enhance device performance1,2,3,4,5,6,7,8. In particular, compound semiconductors heterogeneously integrated on Si substrates have been actively studied7,9,10: such devices combine the high mobility of III–V semiconductors and the well established, low-cost processing of Si technology. This integration, however, presents significant challenges. Conventionally, heteroepitaxial growth of complex multilayers on Si has been explored9,11,12,13—but besides complexity, high defect densities and junction leakage currents present limitations in this approach. Motivated by this challenge, here we use an epitaxial transfer method for the integration of ultrathin layers of single-crystal InAs on Si/SiO2 substrates. As a parallel with silicon-on-insulator (SOI) technology14, we use ‘XOI’ to represent our compound semiconductor-on-insulator platform. Through experiments and simulation, the electrical properties of InAs XOI transistors are explored, elucidating the critical role of quantum confinement in the transport properties of ultrathin XOI layers. Importantly, a high-quality InAs/dielectric interface is obtained by the use of a novel thermally grown interfacial InAsO x layer (~1 nm thick). The fabricated field-effect transistors exhibit a peak transconductance of ~1.6 mS µm−1 at a drain–source voltage of 0.5 V, with an on/off current ratio of greater than 10,000.

Preparation of Covalently Functionalized Graphene Using Residual Oxygen-Containing Functional Groups

Abstract: When fabricated by thermal exfoliation, graphene can be covalently functionalized more easily by applying a direct ring-opening reaction between the residual epoxide functional groups on the graphene and the amine-bearing molecules. Investigation by X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and transmission electron microscopy (TEM) all confirm that these molecules were covalently grafted to the surface of graphene. The resulting dispersion in an organic solvent demonstrated a long-term homogeneous stability of the products. Furthermore, comparison with traditional free radical functionalization shows the extent of the defects characterized by TEM and Raman spectroscopy and reveals that direct functionalization enables graphene to be covalently functionalized on the surface without causing any further damage to the surface structure. Thermogravmetric analysis (TGA) shows that the nondestroyed graphene structure provides greater thermal stability not only for the grafted molecules but als...

Direct Growth of Aligned Zinc Oxide Nanorods on Paper Substrates for Low‐Cost Flexible Electronics

Abstract: www.MaterialsViews.com C O M M U Direct Growth of Aligned Zinc Oxide Nanorods on Paper Substrates for Low-Cost Flexible Electronics N IC A By Afsal Manekkathodi , Ming-Yen Lu , Chun Wen Wang , and Lih-Juann Chen * IO N Contemporary science and technology are hoping to revolutionize modern society with soft portable electronic devices, such as rollup displays, wearable devices, electronic paper, chip smart cards, and basic components in various devices. Research is actively focused on using paper or paper-like substrates for basic electronics components, which make excellent alternative substrates with exceptional technological attributes and commercial perspectives for the many substrates available. [ 1–10 ] The innovative techniques and strategies that are required for these fl exible paper-like platforms are just beginning to emerge from research laboratories in the form of realistic prototypes and have yet to be commercialized. Various electronic devices have already been realized, such as electronic paper displays (EPDs), [ 2 ] printed circuit boards, [ 3 ] thin fi lm transistors (TFTs), [ 4 – 6 ] active-matrix organic light-emitting diodes (AMOLEDs), [ 7 ] paper batteries, [ 8 ]

Au Nanocube-Directed Fabrication of Au-Pd Core-Shell Nanocrystals with Tetrahexahedral, Concave Octahedral, and Octahedral Structures and Their Electrocatalytic Activity

Abstract: In this study, we have successfully developed a facile method for the high-yield fabrication of Au-Pd core-shell heterostructures with an unusual tetrahexahedral (THH) morphology using Au nanocubes as the structure-directing cores. The lattice orientations of the Au nanocubes match those of the Pd shells. Structural analysis establishes that the THH nanocrystals are bounded by high-index {730} facets. A substantial lattice mismatch between Au and Pd, oxidative etching in the presence of chloride and oxygen, the use of cetyltrimethylammonium chloride (CTAC) surfactant, and the reaction temperature (30-60 °C) were identified to be key factors facilitating the formation of the THH core-shell nanocrystals. Intermediate products have also been examined to follow the growth process. By selecting cubic gold cores with sizes of 30-70 nm and varying the volume of the gold core solution used, THH Au-Pd core-shell nanocrystals with continuously adjustable sizes from 56 to 124 nm can be readily obtained. Their UV-vis spectra display progressive red-shifted bands. Interestingly, novel concave octahedral and octahedral Au-Pd core-shell nanocrystals can be prepared by lowering the reaction temperature and prolonging the reaction time. The concave octahedra show depressions on all the {111} faces. Electrocatalytic activity of the three Au-Pd core-shell structures for the oxidation of ethanol has been investigated. The THH nanocrystals with entirely high-index {730} facets were found to exhibit the best electrocatalytic activity. These size-tunable THH Au-Pd core-shell nanocrystals may be valuable for catalyzing other organic reactions.

Finite-time future singularities in modified Gauss–Bonnet and ℱ(R,G) gravity and singularity avoidance

Abstract: We study all four types of finite-time future singularities emerging in the late-time accelerating (effective quintessence/phantom) era from ℱ(R,G)-gravity, where R and G are the Ricci scalar and the Gauss–Bonnet invariant, respectively. As an explicit example of ℱ(R,G)-gravity, we also investigate modified Gauss–Bonnet gravity, so-called F(G)-gravity. In particular, we reconstruct the F(G)-gravity and ℱ(R,G)-gravity models where accelerating cosmologies realizing the finite-time future singularities emerge. Furthermore, we discuss a possible way to cure the finite-time future singularities in F(G)-gravity and ℱ(R,G)-gravity by taking into account higher-order curvature corrections. The example of non-singular realistic modified Gauss–Bonnet gravity is presented. It turns out that adding such non-singular modified gravity to singular Dark Energy makes the combined theory a non-singular one as well.

Engineering the isobutanol biosynthetic pathway in Escherichia coli by comparison of three aldehyde reductase/alcohol dehydrogenase genes

Abstract: Biofuels synthesized from renewable resources are of increasing interest because of global energy and environmental problems. We have previously demonstrated production of higher alcohols from Escherichia coli using a 2-keto acid-based pathway. Here, we have compared the effect of various alcohol dehydrogenases (ADH) for the last step of the isobutanol production. E. coli has the yqhD gene which encodes a broad-range ADH. Isobutanol production significantly decreased with the deletion of yqhD, suggesting that the yqhD gene on the genome contributed to isobutanol production. The adh genes of two bacteria and one yeast were also compared in E. coli harboring the isobutanol synthesis pathway. Overexpression of yqhD or adhA in E. coli showed better production than ADH2, a result confirmed by activity measurements with isobutyraldehyde.

Evolution, genomic analysis, and reconstruction of isobutanol tolerance in Escherichia coli

Abstract: Escherichia coli has been engineered to produce isobutanol, with titers reaching greater than the toxicity level. However, the specific effects of isobutanol on the cell have never been fully understood. Here, we aim to identify genotype–phenotype relationships in isobutanol response. An isobutanol-tolerant mutant was isolated with serial transfers. Using whole-genome sequencing followed by gene repair and knockout, we identified five mutations (acrA, gatY, tnaA, yhbJ, and marCRAB) that were primarily responsible for the increased isobutanol tolerance. We successfully reconstructed the tolerance phenotype by combining deletions of these five loci, and identified glucosamine-6-phosphate as an important metabolite for isobutanol tolerance, which presumably enhanced membrane synthesis. The isobutanol-tolerant mutants also show increased tolerance to n-butanol and 2-methyl-1-butanol, but showed no improvement in ethanol tolerance and higher sensitivity to hexane and chloramphenicol than the parental strain. These results suggest that C4, C5 alcohol stress impacts the cell differently compared with the general solvent or antibiotic stresses. Interestingly, improved isobutanol tolerance did not increase the final titer of isobutanol production.

Phylogenetic diversity measures based on Hill numbers.

Abstract: We propose a parametric class of phylogenetic diversity (PD) measures that are sensitive to both species abundance and species taxonomic or phylogenetic distances. This work extends the conventiona...

Seed-mediated synthesis of gold nanocrystals with systematic shape evolution from cubic to trisoctahedral and rhombic dodecahedral structures.

Abstract: We report a seed-mediated synthesis method for the preparation of gold nanocrystals with systematic shape evolution from truncated cubic to cubic, trisoctahedral, and rhombic dodecahedral structures in aqueous solution for the first time. Nanocrystals with transitional morphologies were also synthesized. The combination of using cetyltrimethylammonium chloride (CTAC) surfactant and a very small amount of NaBr to control the bromide concentration in the growth solution was found to be critical to the formation of nanocubes. Variation in the volume of ascorbic acid added to the growth solution enabled the fine control of nanocrystal morphology. Nanocubes and rhombic dodecahedra with controlled sizes of 30-75 nm were prepared by adjusting the volume of the seed solution added to the growth solution. They can self-assemble into ordered packing structures on substrates because of their uniform sizes. XRD, TEM, and UV-vis absorption characterization of the different products synthesized have been performed. By increasing the bromide concentration 5-fold that used to make the nanocubes, unusual right bipyramids of gold bounded by six {100} faces were produced. The high product purity and excellent size control of this facile synthetic approach should make these novel gold nanostructures be readily available for a wide range of studies.

Trypsin-induced proteome alteration during cell subculture in mammalian cells

Abstract: It is essential to subculture the cells once cultured cells reach confluence. For this, trypsin is frequently applied to dissociate adhesive cells from the substratum. However, due to the proteolytic activity of trypsin, cell surface proteins are often cleaved, which leads to dysregulation of the cell functions. In this study, a triplicate 2D-DIGE strategy has been performed to monitor trypsin-induced proteome alterations. The differentially expressed spots were identified by MALDI-TOF MS and validated by immunoblotting. 36 proteins are found to be differentially expressed in cells treated with trypsin, and proteins that are known to regulate cell metabolism, growth regulation, mitochondrial electron transportation and cell adhesion are down-regulated and proteins that regulate cell apoptosis are up-regulated after trypsin treatment. Further study shows that bcl-2 is down-regulated, p53 and p21 are both up-regulated after trypsinization. In summary, this is the first report that uses the proteomic approach to thoroughly study trypsin-induced cell physiological changes and provides researchers in carrying out their experimental design.

EGFR Promotes Lung Tumorigenesis by Activating miR-7 through a Ras/ERK/Myc Pathway That Targets the Ets2 Transcriptional Repressor ERF

Abstract: MicroRNAs (miRNA) mediate distinct gene regulatory pathways triggered by epidermal growth factor receptor (EGFR) activation, which occurs commonly in lung cancers with poor prognosis. In this study, we report the discovery and mechanistic characterization of the miRNA miR-7 as an oncogenic "oncomiR" and its role as a key mediator of EGFR signaling in lung cancer cells. EGFR activation or ectopic expression of Ras as well as c-Myc stimulated miR-7 expression in an extracellular signal-regulated kinase (ERK)-dependent manner, suggesting that EGFR induces miR-7 expression through a Ras/ERK/Myc pathway. In support of this likelihood, c-Myc bound to the miR-7 promoter and enhanced its activity. Ectopic miR-7 promoted cell growth and tumor formation in lung cancer cells, significantly increasing the mortality of nude mice hosts, which were orthotopically implanted with lung cancers. Quantitative proteomic analysis revealed that miR-7 decreased levels of the Ets2 transcriptional repression factor ERF, the coding sequence of which was found to contain a miR-7 complementary sequence. Indeed, ectopic miR-7 inhibited production of ERF messages with a wild-type but not a silently mutated coding sequence, and ectopic miR-7 rescued growth arrest produced by wild-type but not mutated ERF. Together, these results identified that ERF is a direct target of miR-7 in lung cancer. Our findings suggest that miR-7 may act as an important modulator of EGFR-mediated oncogenesis, with potential applications as a novel prognostic biomarker and therapeutic target in lung cancer.

Evidence and solution of over-RESET problem for HfO X based resistive memory with sub-ns switching speed and high endurance

Abstract: The memory performances of the HfO X based bipolar resistive memory, including switching speed and memory reliability, are greatly improved in this work. Record high switching speed down to 300 ps is achieved. The cycling test shed a clear light on the wearing behavior of resistance states, and the correlation between over-RESET phenomenon and the worn low resistance state in the devices is discussed. The modified bottom electrode is proposed for the memory device to maintain the memory window and to endure resistive switching up to 1010 cycles.